Publications by authors named "Marcelo G Roma"

55 Publications

Erratum to: Drug-Induced Vanishing Bile Duct Syndrome: From Pathogenesis to Diagnosis and Therapeutics.

Semin Liver Dis 2021 Aug 29;41(3):e1. Epub 2021 Jun 29.

Instituto de Fisiología Experimental (CONICET-UNR), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina.

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http://dx.doi.org/10.1055/s-0041-1732497DOI Listing
August 2021

Drug-Induced Vanishing Bile Duct Syndrome: From Pathogenesis to Diagnosis and Therapeutics.

Semin Liver Dis 2021 Aug 15;41(3):331-348. Epub 2021 Jun 15.

Instituto de Fisiología Experimental (CONICET-UNR), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina.

The most concerned issue in the context of drug/herb-induced chronic cholestasis is vanishing bile duct syndrome. The progressive destruction of intrahepatic bile ducts leading to ductopenia is usually not dose dependent, and has a delayed onset that should be suspected when abnormal serum cholestasis enzyme levels persist despite drug withdrawal. Immune-mediated cholangiocyte injury, direct cholangiocyte damage by drugs or their metabolites once in bile, and sustained exposure to toxic bile salts when biliary epithelium protective defenses are impaired are the main mechanisms of cholangiolar damage. Current therapeutic alternatives are scarce and have not shown consistent beneficial effects so far. This review will summarize the current literature on the main diagnostic tools of ductopenia and its histological features, and the differential diagnostic with other ductopenic diseases. In addition, pathomechanisms will be addressed, as well as the connection between them and the supportive and curative strategies for ductopenia management.
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http://dx.doi.org/10.1055/s-0041-1729972DOI Listing
August 2021

Spironolactone ameliorates lipopolysaccharide-induced cholestasis in rats by improving Mrp2 function: Role of transcriptional and post-transcriptional mechanisms.

Life Sci 2020 Oct 27;259:118352. Epub 2020 Aug 27.

Institute of Experimental Physiology (IFISE), Faculty of Biochemical and Pharmaceutical Sciences of the National University of Rosario, 2000 Rosario, Argentina. Electronic address:

Aims: Lipopolysaccharide (LPS) induces inflammatory cholestasis by impairing expression, localization, and function of carriers involved in bile formation, e.g. bile salt export pump (Bsep) and multidrug resistance-associated protein 2 (Mrp2). A specific therapy against this disease is still lacking. Therefore, we evaluated the anticholestatic effects of spironolactone (SL), a PXR ligand that regulates bile salt homeostasis, up-regulates Mrp2, and bears anti-inflammatory properties.

Main Methods: Male Wistar rats were divided into four groups: Control, SL (83.3 mg/kg/day of SL, i.p., for 3 days), LPS (2.5 mg/kg/day, i.p., at 8 am of the last 2 days, and 1.5 mg/kg/day at 8 pm of the last day), and SL + LPS. Biliary and plasma parameters and the expression, function, and localization of Mrp2 and Bsep were evaluated.

Key Findings: SL partially prevented LPS-induced drop of basal bile flow by normalizing the bile salt-independent fraction of bile flow (BSIBF), via improvement of glutathione output. This was due to a recovery in Mrp2 transport function, the major canalicular glutathione transporter, estimated by monitoring the output of its exogenously administered substrate dibromosulfophthalein. SL counteracted the LPS-induced downregulation of Mrp2, but not that of Bsep, at both mRNA and protein levels. LPS induced endocytic internalization of both transporters, visualized by immunofluorescence followed by confocal microscopy, and SL partially prevented this relocalization. SL did not prevent the increase in IL-1β, IL-6, and TNF-α plasma levels.

Significance: SL prevents the impairment in Mrp2 expression and localization, and the resulting recovery of Mrp2 function normalizes the BSIBF by improving glutathione excretion.
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http://dx.doi.org/10.1016/j.lfs.2020.118352DOI Listing
October 2020

HGF induces protective effects in α-naphthylisothiocyanate-induced intrahepatic cholestasis by counteracting oxidative stress.

Biochem Pharmacol 2020 04 16;174:113812. Epub 2020 Jan 16.

Departmento de Ciencias de la Salud, Universidad Autónoma Metropolitana, Unidad Iztapalapa, Ciudad de México, Mexico; Unidad de Medicina Traslacional, Instituto Nacional de Cardiología Ignacio Chávez, Ciudad de México, Mexico. Electronic address:

Cholestasis is a clinical syndrome common to a large number of hepatopathies, in which either bile production or its transit through the biliary tract is impaired due to functional or obstructive causes; the consequent intracellular retention of toxic biliary constituents generates parenchyma damage, largely via oxidative stress-mediated mechanisms. Hepatocyte growth factor (HGF) and its receptor c-Met represent one of the main systems for liver repair damage and defense against hepatotoxic factors, leading to an antioxidant and repair response. In this study, we evaluated the capability of HGF to counteract the damage caused by the model cholestatic agent, α-naphthyl isothiocyanate (ANIT). HGF had clear anti-cholestatic effects, as apparent from the improvement in both bile flow and liver function test. Histology examination revealed a significant reduction of injured areas. HGF also preserved the tight-junctional structure. These anticholestatic effects were associated with the induction of basolateral efflux ABC transporters, which facilitates extrusion of toxic biliary compounds and its further alternative depuration via urine. The biliary epithelium seems to have been also preserved, as suggested by normalization in serum GGT levels, CFTR expression and cholangyocyte primary cilium structure our results clearly show for the first time that HGF protects the liver from a cholestatic injury.
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http://dx.doi.org/10.1016/j.bcp.2020.113812DOI Listing
April 2020

Anticholestatic mechanisms of ursodeoxycholic acid in lipopolysaccharide-induced cholestasis.

Biochem Pharmacol 2019 10 13;168:48-56. Epub 2019 Jun 13.

Institute of Experimental Physiology (IFISE), Faculty of Biochemical and Pharmaceutical Sciences of the National University of Rosario, 2000 Rosario, Argentina. Electronic address:

Lipopolysaccharide (LPS) from Gram (-) bacteria induces inflammatory cholestasis by impairing the expression/localization of transporters involved in bile formation (e.g., Bsep, Mrp2). Therapeutic options for this disease are lacking. Ursodeoxycholic acid (UDCA) is the first choice therapy in cholestasis, but its anticholestatic efficacy in this hepatopathy remains to be evaluated. To asses it, male Wistar rats received UDCA for 5 days (25 mg/Kg/day, i.p.) with or without LPS, administered at 8 a.m. of the last 2 days (4 mg/Kg/day, i.p.), plus half of this dose at 8 p.m. of the last day. Then, plasma alkaline phosphatase (ALP), bile flow, basal and taurocholate-stimulated bile acid output, total glutathione output, and total/plasma membrane liver protein expression of Bsep and Mrp2 by confocal microscopy were assessed. mRNA levels of both transporters were assessed by Real-Time PCR. Plasma pro-inflammatory cytokines (IL-6 and TNF-α) were measured by ELISA. Our results showed that UDCA attenuated LPS-induced ALP plasma release and the impairment in the excretion of the Bsep substrate, taurocholate. This was associated with an improved Bsep expression at both mRNA and protein levels, and by an improved localization of Bsep in plasma membrane. UDCA failed to reduce the increase in plasma pro-inflammatory cytokines induced by LPS and Mrp2 expression/function. In conclusion, UDCA protects the hepatocyte against the damaging effect of bile acids accumulated by the LPS-induced secretory failure. This involved an enhanced synthesis of Bsep and an improved membrane stability of the newly synthesized transporters.
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http://dx.doi.org/10.1016/j.bcp.2019.06.009DOI Listing
October 2019

Adaptive downregulation of Cl-/HCO3- exchange activity in rat hepatocytes under experimental obstructive cholestasis.

PLoS One 2019 21;14(2):e0212215. Epub 2019 Feb 21.

Instituto de Fisiología Experimental (IFISE)-Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas-Universidad Nacional de Rosario, Rosario, Argentina.

In obstructive cholestasis, there is an integral adaptive response aimed to diminish the bile flow and minimize the injury of bile ducts caused by increased intraluminal pressure and harmful levels of bile salts and bilirrubin. Canalicular bicarbonate secretion, driven by the anion exchanger 2 (AE2), is an influential determinant of the canalicular bile salt-independent bile flow. In this work, we ascertained whether AE2 expression and/or activity is reduced in hepatocytes from rats with common bile duct ligation (BDL), as part of the adaptive response to cholestasis. After 4 days of BDL, we found that neither AE2 mRNA expression (measured by quantitative real-time PCR) nor total levels of AE2 protein (assessed by western blot) were modified in freshly isolated hepatocytes. However, BDL led to a decrease in the expression of AE2 protein in plasma membrane fraction as compared with SHAM control. Additionally, AE2 activity (JOH-, mmol/L/min), measured in primary cultured hepatocytes from BDL and SHAM rats, was decreased in the BDL group versus the control group (1.9 ± 0.3 vs. 3.1 ± 0.2, p<0.005). cAMP-stimulated AE2 activity, however, was not different between SHAM and BDL groups (3.7 ± 0.3 vs. 3.5 ± 0.3), suggesting that cAMP stimulated insertion into the canalicular membrane of AE2-containing intracellular vesicles, that had remained abnormally internalized after BDL. In conclusion, our results point to the existence of a novel adaptive mechanism in cholestasis aimed to reduce biliary pressure, in which AE2 internalization in hepatocytes might result in decreased canalicular HCO3- output and decreased bile flow.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0212215PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6383990PMC
November 2019

Cholangiocyte death in ductopenic cholestatic cholangiopathies: Mechanistic basis and emerging therapeutic strategies.

Life Sci 2019 Feb 2;218:324-339. Epub 2019 Jan 2.

Instituto de Fisiología Experimental (IFISE-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Suipacha 570, 2000 Rosario, Argentina. Electronic address:

Among hepatic diseases, cholestatic ductopenic cholangiopathies are poorly studied, and they are rarely given the importance they deserve, especially considering their high incidence in clinical practice. Although cholestatic ductopenic cholangiopathies have different etiologies and pathogenesis, all have the same target (the cholangiocyte) and similar mechanistic basis of cell death. Cholestatic cholangiopathies are characterized, predominantly, by obstructive or functional damage in the biliary epithelium, resulting in an imbalance between proliferation and cholangiocellular death; this leads to the progressive disappearance of bile ducts, as has been shown to occur in primary sclerosing cholangitis, primary biliary cholangitis, low-phospholipid-associated cholelithiasis syndrome, cystic fibrosis-related liver disease, and drug-induced ductopenia, among other biliary disorders. This review summarizes the features of the more common ductopenic syndromes and the cellular mechanisms involved in cholengiocellular death, with focus on the main forms of cholangiocyte death described so far, namely apoptosis, autophagy, necrosis, and necroptosis. It also emphasizes the importance to study in depth the molecular mechanisms of cholengiocyte death to make possible to counteract them with therapeutic purposes. These therapeutic strategies are limited in number and efficacy at present, and this is why it is important to find complementary, safe strategies to stimulate cholangiocellular proliferation in order favor bile duct replenishment as well. Successful in finding appropriate treatments would prevent the patient from having liver transplantation as the only therapeutic alternative.
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http://dx.doi.org/10.1016/j.lfs.2018.12.044DOI Listing
February 2019

Heme oxygenase-1 induction by hemin prevents oxidative stress-induced acute cholestasis in the rat.

Clin Sci (Lond) 2019 01 11;133(1):117-134. Epub 2019 Jan 11.

Instituto de Fisiología Experimental (IFISE-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas (U.N.R.), Rosario, Argentina

We previously demonstrated in and models that physiological concentrations of unconjugated bilirubin (BR) prevent oxidative stress (OS)-induced hepatocanalicular dysfunction and cholestasis. Here, we aimed to ascertain, in the whole rat, whether a similar cholestatic OS injury can be counteracted by heme oxygenase-1 (HO-1) induction that consequently elevates endogenous BR levels. This was achieved through the administration of hemin, an inducer of HO-1, the rate-limiting step in BR generation. We found that BR peaked between 6 and 8 h after hemin administration. During this time period, HO-1 induction fully prevented the pro-oxidant -butylhydroperoxide (BuOOH)-induced drop in bile flow, and in the biliary excretion of bile salts and glutathione, the two main driving forces of bile flow; this was associated with preservation of the membrane localization of their respective canalicular transporters, bile salt export pump (Bsep) and multidrug resistance-associated protein 2 (Mrp2), which are otherwise endocytosed by OS. HO-1 induction counteracted the oxidation of intracellular proteins and membrane lipids induced by BuOOH, and fully prevented the increase in the oxidized-to-total glutathione (GSHt) ratio, a sensitive parameter of hepatocellular OS. Compensatory elevations of the activity of the antioxidant enzymes catalase (CAT) and superoxide dismutase (SOD) were also prevented. We conclude that HO-1 induction protects the liver from acute oxidative injury, thus preventing consequent cholestasis. This reveals an important role for the induction of HO-1 and the consequently elevated levels of BR in preserving biliary secretory function under OS conditions, thus representing a novel therapeutic tool to limit the cholestatic injury that bears an oxidative background.
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http://dx.doi.org/10.1042/CS20180675DOI Listing
January 2019

Molecular pathways of nonalcoholic fatty liver disease development and progression.

Cell Mol Life Sci 2019 Jan 20;76(1):99-128. Epub 2018 Oct 20.

Instituto de Fisiología Experimental (IFISE-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Suipacha 570, 2000, Rosario, Argentina.

Nonalcoholic fatty liver disease (NAFLD) is a main hepatic manifestation of metabolic syndrome. It represents a wide spectrum of histopathological abnormalities ranging from simple steatosis to nonalcoholic steatohepatitis (NASH) with or without fibrosis and, eventually, cirrhosis and hepatocellular carcinoma. While hepatic simple steatosis seems to be a rather benign manifestation of hepatic triglyceride accumulation, the buildup of highly toxic free fatty acids associated with insulin resistance-induced massive free fatty acid mobilization from adipose tissue and the increased de novo hepatic fatty acid synthesis from glucose acts as the "first hit" for NAFLD development. NAFLD progression seems to involve the occurrence of "parallel, multiple-hit" injuries, such as oxidative stress-induced mitochondrial dysfunction, endoplasmic reticulum stress, endotoxin-induced, TLR4-dependent release of inflammatory cytokines, and iron overload, among many others. These deleterious factors are responsible for the triggering of a number of signaling cascades leading to inflammation, cell death, and fibrosis, the hallmarks of NASH. This review is aimed at integrating the overwhelming progress made in the characterization of the physiopathological mechanisms of NAFLD at a molecular level, to better understand the factor influencing the initiation and progression of the disease.
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http://dx.doi.org/10.1007/s00018-018-2947-0DOI Listing
January 2019

Review article: drug-induced liver injury in the context of nonalcoholic fatty liver disease - a physiopathological and clinical integrated view.

Aliment Pharmacol Ther 2018 11 7;48(9):892-913. Epub 2018 Sep 7.

Instituto de Fisiología Experimental (IFISE-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina.

Background: Nonalcoholic fatty disease (NAFLD) is the most common liver disease, since it is strongly associated with obesity and metabolic syndrome pandemics. NAFLD may affect drug disposal and has common pathophysiological mechanisms with drug-induced liver injury (DILI); this may predispose to hepatoxicity induced by certain drugs that share these pathophysiological mechanisms. In addition, drugs may trigger fatty liver and inflammation per se by mimicking NAFLD pathophysiological mechanisms.

Aims: To provide a comprehensive update on (a) potential mechanisms whereby certain drugs can be more hepatotoxic in NAFLD patients, (b) the steatogenic effects of drugs, and (c) the mechanism involved in drug-induced steatohepatitis (DISH).

Methods: A language- and date-unrestricted Medline literature search was conducted to identify pertinent basic and clinical studies on the topic.

Results: Drugs can induce macrovesicular steatosis by mimicking NAFLD pathogenic factors, including insulin resistance and imbalance between fat gain and loss. Other forms of hepatic fat accumulation exist, such as microvesicular steatosis and phospholipidosis, and are mostly associated with acute mitochondrial dysfunction and defective lipophagy, respectively. Drug-induced mitochondrial dysfunction is also commonly involved in DISH. Patients with pre-existing NAFLD may be at higher risk of DILI induced by certain drugs, and polypharmacy in obese individuals to treat their comorbidities may be a contributing factor.

Conclusions: The relationship between DILI and NAFLD may be reciprocal: drugs can cause NAFLD by acting as steatogenic factors, and pre-existing NAFLD could be a predisposing condition for certain drugs to cause DILI. Polypharmacy associated with obesity might potentiate the association between this condition and DILI.
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http://dx.doi.org/10.1111/apt.14952DOI Listing
November 2018

Mechanisms of canalicular transporter endocytosis in the cholestatic rat liver.

Biochim Biophys Acta Mol Basis Dis 2018 Apr 31;1864(4 Pt A):1072-1085. Epub 2018 Jan 31.

Instituto de Fisiología Experimental (IFISE) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas - Universidad Nacional de Rosario, Suipacha 570, S2002LRL Rosario, Argentina. Electronic address:

Impaired canalicular secretion due to increased endocytosis and intracellular retention of canalicular transporters such as BSEP and MRP2 is a main, common pathomechanism of cholestasis. Nevertheless, the mechanisms governing this process are unknown. We characterized this process in estradiol 17 β-d-glucuronide (E17G)-induced cholestasis, an experimental model which partially mimics pregnancy-induced cholestasis. Inhibitors of clathrin-mediated endocytosis (CME) such as monodansylcadaverine (MDC) or K depletion, but not the caveolin-mediated endocytosis inhibitors filipin and genistein, prevented E17G-induced endocytosis of BSEP and MRP2, and the associated impairment of activity of these transporters in isolated rat hepatocyte couplets (IRHC). Immunofluorescence and confocal microscopy studies showed that, in E17G-treated IRHC, there was a significant increase in the colocalization of MRP2 with clathrin, AP2, and Rab5, three essential members of the CME machinery. Knockdown of AP2 by siRNA in sandwich-cultured rat hepatocytes completely prevented E17G-induced endocytosis of BSEP and MRP2. MDC significantly prevented this endocytosis, and the impairment of bile flow and biliary secretion of BSEP and MRP2 substrates, in isolated and perfused livers. BSEP and MRP2, which were mostly present in raft (caveolin-enriched) microdomains in control rats, were largely found in non-raft (clathrin-enriched) microdomains in livers from E17G-treated animals, from where they can be readily recruited for CME. In conclusion, our findings show that CME is the mechanism responsible for the internalization of the canalicular transporters BSEP and MRP2 in E17G-induced cholestasis. The shift of these transporters from raft to non-raft microdomains could be a prerequisite for the transporters to be endocytosed under cholestatic conditions.
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http://dx.doi.org/10.1016/j.bbadis.2018.01.015DOI Listing
April 2018

Dynamic Localization of Hepatocellular Transporters: Role in Biliary Excretion and Impairment in Cholestasis.

Curr Med Chem 2019 ;26(7):1113-1154

Instituto de Fisiologia Experimental (IFISE) - Facultad de Ciencias Bioquimicas y Farmaceuticas (CONICET - U.N.R.), S2002LRL, Rosario, Argentina.

Bile flow generation is driven by the vectorial transfer of osmotically active compounds from sinusoidal blood into a confined space, the bile canaliculus. Hence, localization of hepatocellular transporters relevant to bile formation is crucial for bile secretion. Hepatocellular transporters are localized either in the plasma membrane or in recycling endosomes, from where they can be relocated to the plasma membrane on demand, or endocytosed when the demand decreases. The balance between endocytic internalization/ exocytic targeting to/from this recycling compartment is therefore the main determinant of the hepatic capability to generate bile, and to dispose endo- and xenobiotics. Furthermore, the exacerbated endocytic internalization is a common pathomechanisms in both experimental and human cholestasis; this results in bile secretory failure and, eventually, posttranslational transporter downregulation by increased degradation. This review summarizes the proposed structural mechanisms accounting for this pathological condition (e.g., alteration of function, localization or expression of F-actin or F-actin/transporter cross-linking proteins, and switch to membrane microdomains where they can be readily endocytosed), and the mediators implicated (e.g., triggering of "cholestatic" signaling transduction pathways). Lastly, we discussed the efficacy to counteract the cholestatic failure induced by transporter internalization of a number of therapeutic experimental approaches based upon the use of compounds that trigger exocytic targetting of canalicular transporters (e.g., cAMP, tauroursodeoxycholate). This therapeutics may complement treatments aimed to transcriptionally improve transporter expression, by affording proper localization and membrane stability to the de novo synthesized transporters.
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http://dx.doi.org/10.2174/0929867325666171205153204DOI Listing
June 2019

Activation of insulin-like growth factor 1 receptor participates downstream of GPR30 in estradiol-17β-D-glucuronide-induced cholestasis in rats.

Arch Toxicol 2018 Feb 31;92(2):729-744. Epub 2017 Oct 31.

Instituto de Fisiología Experimental (IFISE), Facultad de Ciencias Bioquímicas y Farmacéuticas (CONICET-U.N.R.), Suipacha 570, S2002LRL, Rosario, Argentina.

Estradiol-17β-D-glucuronide (E17G), through the activation of different signaling proteins, induces acute endocytic internalization of canalicular transporters in rat, including multidrug resistance-associated protein 2 (Abcc2) and bile salt export pump (Abcb11), generating cholestasis. Insulin-like growth factor 1 receptor (IGF-1R) is a membrane-bound tyrosine kinase receptor that can potentially interact with proteins activated by E17G. The aim of this study was to analyze the potential role of IGF-1R in the effects of E17G in isolated perfused rat liver (IPRL) and isolated rat hepatocyte couplets. In vitro, IGF-1R inhibition by tyrphostin AG1024 (TYR, 100 nM), or its knock-down with siRNA, strongly prevented E17G-induced impairment of Abcc2 and Abcb11 function and localization. The protection by TYR was not additive to that produced by wortmannin (PI3K inhibitor, 100 nM), and both protections share the same dependency on microtubule integrity, suggesting that IGF-1R shared the signaling pathway of PI3K/Akt. Further analysis of the activation of Akt and IGF-1R induced by E17G indicated a sequence of activation GPR30-IGF-1R-PI3K/Akt. In IPRL, an intraportal injection of E17G triggered endocytosis of Abcc2 and Abcb11, and this was accompanied by a sustained decrease in the bile flow and the biliary excretion of Abcc2 and Abcb11 substrates. TYR did not prevent the initial decay, but it greatly accelerated the recovery to normality of these parameters and the reinsertion of transporters into the canalicular membrane. In conclusion, the activation of IGF-1R is a key factor in the alteration of canalicular transporter function and localization induced by E17G, and its activation follows that of GPR30 and precedes that of PI3K/Akt.
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http://dx.doi.org/10.1007/s00204-017-2098-3DOI Listing
February 2018

Mitogen-activated protein kinases are involved in hepatocanalicular dysfunction and cholestasis induced by oxidative stress.

Arch Toxicol 2017 Jun 2;91(6):2391-2403. Epub 2016 Dec 2.

Instituto de Fisiología Experimental (IFISE-CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario (UNR), Suipacha 570, 2000, Rosario, Argentina.

In previous studies, we showed that the pro-oxidant model agent tert-butyl hydroperoxide (tBuOOH) induces alterations in hepatocanalicular secretory function by activating Ca-dependent protein kinase C isoforms (cPKC), via F-actin disorganization followed by endocytic internalization of canalicular transporters relevant to bile formation (Mrp2, Bsep). Since mitogen-activated protein kinases (MAPKs) may be downstream effectors of cPKC, we investigated here the involvement of the MAPKs of the ERK1/2, JNK1/2, and p38 types in these deleterious effects. tBuOOH (100 µM, 15 min) increased the proportion of the active, phosphorylated forms of ERK1/2, JNK1/2, and p38, and panspecific PKC inhibition with bisindolylmaleimide-1 (100 nM) or selective cPKC inhibition with Gö6976 (1 μM) prevented the latter two events. In isolated rat hepatocyte couplets, tBuOOH (100 µM, 15 min) decreased the canalicular vacuolar accumulation of the fluorescent Bsep and Mrp2 substrates, cholylglycylamido fluorescein, and glutathione-methylfluorescein, respectively, and selective inhibitors of ERK1/2 (PD098059), JNK1/2 (SP600125), and p38 (SB203580) partially prevented these alterations. In in situ perfused rat livers, these three MAPK inhibitors prevented tBuOOH (75 µM)-induced impairment of bile flow and the decrease in the biliary output of the Bsep and Mrp2 substrates, taurocholate, and dinitrophenyl-S-glutathione, respectively. The changes in Bsep/Mrp2 and F-actin localization induced by tBuOOH, as assessed by (immuno)fluorescence staining followed by analysis of confocal images, were prevented total or partially by the MAPK inhibitors. We concluded that MAPKs of the ERK1/2, JNK1/2, and p38 types are all involved in cholestasis induced by oxidative stress, by promoting F-actin rearrangement and further endocytic internalization of canalicular transporters critical for bile formation.
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http://dx.doi.org/10.1007/s00204-016-1898-1DOI Listing
June 2017

Cyproterone acetate induces a wide spectrum of acute liver damage including corticosteroid-responsive hepatitis: report of 22 cases.

Liver Int 2016 Feb 16;36(2):302-10. Epub 2015 Jul 16.

Unidad de Hepatología y Servicio de Farmacología Clínica, Instituto de Investigación Biomédica de Málaga-IBIMA, Hospital Universitario Virgen de la Victoria, Universidad de Málaga, Málaga, Spain.

Background & Aims: Cyproterone acetate (CPA), an anti-androgenic drug for prostate cancer, has been associated with drug-induced liver injury (DILI). We aim to expand the knowledge on the spectrum of phenotypes and outcomes of CPA-induced DILI.

Methods: Twenty-two males (70 ± 8 years; range 54-83) developing liver damage as a result of CPA therapy (dose: 150 ± 50 mg/day; range 50-200) were included. Severity index and causality by RUCAM were assessed.

Results: From 1993 to 2013, 22 patients were retrieved. Latency was 163 ± 97 days. Most patients were symptomatic, showing hepatocellular injury (91%) and jaundice. Liver tests at onset were: ALT 18 ± 13 × ULN, ALP 0.7 ± 0.7 × ULN and total serum bilirubin 14 ± 10 mg/dl. International normalized ratio values higher than 1.5 were observed in 14 (66%) patients. Severity was mild in 1 case (4%), moderate in 7 (32%), severe in 11 (50%) and fatal in 3 (14%). Five patients developed ascitis, and four encephalopathy. One patient had a liver injury that resembled autoimmune hepatitis. Eleven (50%) were hospitalized. Nineteen patients recovered after CPA withdrawal, although three required steroid therapy (two of them had high ANA titres). Liver biopsy was performed in seven patients (two hepatocellular collapse, one submassive necrosis, two cholestatic hepatitis, one cirrhosis with iron overload and one autoimmune hepatitis). RUCAM category was 'highly probable' in 19 (86%), 'probable' in 1 (4%), and 'possible' in 2 (9%).

Conclusions: CPA-induced liver injury is severe and can be fatal, and may occasionally resemble autoimmune DILI. The benefit/risk ratio of this drug should be thoroughly assessed in each patient.
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http://dx.doi.org/10.1111/liv.12899DOI Listing
February 2016

EGFR participates downstream of ERα in estradiol-17β-D-glucuronide-induced impairment of Abcc2 function in isolated rat hepatocyte couplets.

Arch Toxicol 2016 Apr 27;90(4):891-903. Epub 2015 Mar 27.

Instituto de Fisiología Experimental (IFISE), Facultad de Ciencias Bioquímicas y Farmacéuticas (CONICET - U.N.R.), Suipacha 570, S2002LRL, Rosario, Argentina.

Estradiol-17β-D-glucuronide (E17G) induces acute endocytic internalization of canalicular transporters, including multidrug resistance-associated protein 2 (Abcc2) in rat, generating cholestasis. Several proteins organized in at least two different signaling pathways are involved in E17G cholestasis: one pathway involves estrogen receptor alpha (ERα), Ca(2+)-dependent protein kinase C and p38-mitogen activated protein kinase, and the other pathway involves GPR30, PKA, phosphoinositide 3-kinase/AKT and extracellular signal-related kinase 1/2. EGF receptor (EGFR) can potentially participate in both pathways since it interacts with GPR30 and ERα. Hence, the aim of this study was to analyze the potential role of this receptor and its downstream effectors, members of the Src family kinases in E17G-induced cholestasis. In vitro, EGFR inhibition by Tyrphostin (Tyr), Cl-387785 or its knockdown with siRNA strongly prevented E17G-induced impairment of Abcc2 function and localization. Activation of EGFR was necessary but not sufficient to impair the canalicular transporter function, whereas the simultaneous activation of EGFR and GPR30 could impair Abcc2 transport. The protection of Tyr was not additive to that produced by the ERα inhibitor ICI neither with that produced by Src kinase inhibitors, suggesting that EGFR shared the signaling pathway of ERα and Src. Further analysis of ERα, EGFR and Src activations induced by E17G, demonstrated that ERα activation precedes that of EGFR and EGFR activation precedes that of Src. In conclusion, activation of EGFR is a key factor in the alteration of canalicular transporter function and localization induced by E17G and it occurs before that of Src and after that of ERα.
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http://dx.doi.org/10.1007/s00204-015-1507-8DOI Listing
April 2016

Challenge of liver disease in systemic lupus erythematosus: Clues for diagnosis and hints for pathogenesis.

World J Hepatol 2014 Jun;6(6):394-409

Fernando Bessone, Natalia Poles, Gastroenterology and Hepatology Department, University of Rosario School of Medicine, Rosario 2000, Argentina.

Systemic lupus erythematosus (SLE) encompass a broad spectrum of liver diseases. We propose here to classify them as follows: (1) immunological comorbilities (overlap syndromes); (2) non-immunological comorbilities associated to SLE; and (3) a putative liver damage induced by SLE itself, referred to as "lupus hepatitis". In the first group, liver injury can be ascribed to overlapping hepatopathies triggered by autoimmune mechanisms other than SLE occurring with higher incidence in the context of lupus (e.g., autoimmune hepatitis, primary biliary cirrhosis). The second group includes non-autoimmune liver diseases, such as esteatosis, hepatitis C, hypercoagulation state-related liver lesions, hyperplasic parenchymal and vascular lesions, porphyria cutanea tarda, and drug-induced hepatotoxicity. Finally, the data in the literature to support the existence of a hepatic disease produced by SLE itself, or the occurrence of a SLE-associated prone condition that increases susceptibility to acquire other liver diseases, is critically discussed. The pathological mechanisms underlying each of these liver disorders are also reviewed. Despite the high heterogeneity in the literature regarding the prevalence of SLE-associated liver diseases and, in most cases, lack of histopathological evidence or clinical studies large enough to support their existence, it is becoming increasingly apparent that liver is an important target of SLE. Consequently, biochemical liver tests should be routinely carried out in SLE patients to discard liver disorders, particularly in those patients chronically exposed to potentially hepatotoxic drugs. Diagnosing liver disease in SLE patients is always challenging, and the systematization of the current information carried out in this review is expected to be of help both to attain a better understanding of pathogenesis and to build an appropriate work-up for diagnosis.
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http://dx.doi.org/10.4254/wjh.v6.i6.394DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4081614PMC
June 2014

Sandwich-cultured rat hepatocytes as an in vitro model to study canalicular transport alterations in cholestasis.

Arch Toxicol 2015 Jun 10;89(6):979-90. Epub 2014 Jun 10.

Instituto de Fisiología Experimental (IFISE) - Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Facultad de Ciencias Bioquímicas y Farmacéuticas - Universidad Nacional de Rosario (UNR), Suipacha 570, S2002LRL, Rosario, Argentina.

At present, it has not been systematically evaluated whether the functional alterations induced by cholestatic compounds in canalicular transporters involved in bile formation can be reproduced in sandwich-cultured rat hepatocytes (SCRHs). Here, we focused on two clinically relevant cholestatic agents, such as estradiol 17β-D-glucuronide (E17G) and taurolithocholate (TLC), also testing the ability of dibutyryl cyclic AMP (DBcAMP) to prevent their effects. SCRHs were incubated with E17G (200 µM) or TLC (2.5 µM) for 30 min, with or without pre-incubation with DBcAMP (10 µM) for 15 min. Then, the increase in glutathione methyl fluorescein (GS-MF)-associated fluorescence inside the canaliculi was monitored by quantitative time-lapse imaging, and Mrp2 transport activity was calculated by measuring the slope of the time-course fluorescence curves during the initial linear phase, which was considered to be the Mrp2-mediated initial transport rate (ITR). E17G and TLC impaired canalicular bile formation, as evidenced by a decrease in both the bile canaliculus volume and the bile canaliculus width, estimated from 3D and 2D confocal images, respectively. These compounds decreased ITR and induced retrieval of Mrp2, a main pathomechanism involved in their cholestatic effects. Finally, DBcAMP prevented these effects, and its well-known choleretic effect was evident from the increase in the canalicular volume/width values; this choleretic effect is associated in part with its capability to increase Mrp2 activity, evidenced here by the increase in ITR of GS-MF. Our study supports the use of SCRHs as an in vitro model useful to quantify canalicular transport function under conditions of cholestasis and choleresis.
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http://dx.doi.org/10.1007/s00204-014-1283-xDOI Listing
June 2015

The Ca²⁺-calmodulin-Ca²⁺/calmodulin-dependent protein kinase II signaling pathway is involved in oxidative stress-induced mitochondrial permeability transition and apoptosis in isolated rat hepatocytes.

Arch Toxicol 2014 Sep 11;88(9):1695-709. Epub 2014 Mar 11.

Instituto de Fisiología Experimental (IFISE), Facultad de Ciencias Bioquímicas y Farmacéuticas, CONICET-Universidad Nacional de Rosario, Suipacha 570, 2000, Rosario, Argentina.

Oxidative stress (OS) is a common event in most hepatopathies, leading to mitochondrial permeability transition pore (MPTP) formation and further exacerbation of both OS from mitochondrial origin and cell death. Intracellular Ca²⁺ increase plays a permissive role in these events, but the underlying mechanisms are poorly known. We examined in primary cultured rat hepatocytes whether the Ca²⁺/calmodulin (CaM)-dependent protein kinase II (CaMKII) signaling pathway is involved in this process, by using tert-butyl hydroperoxide (tBOOH) as a pro-oxidant, model compound. tBOOH (500 μM, 15 min) induced MPTP formation, as assessed by measuring mitochondrial membrane depolarization as a surrogate marker, and increased lipid peroxidation in a cyclosporin A (CsA)-sensitive manner, revealing the involvement of MPTPs in tBOOH-induced radical oxygen species (ROS) formation. Intracellular Ca²⁺ sequestration with BAPTA/AM, CaM blockage with W7 or trifluoperazine, and CaMKII inhibition with KN-62 all fully prevented tBOOH-induced MPTP opening and reduced tBOOH-induced lipid peroxidation to a similar extent to CsA, suggesting that Ca²⁺/CaM/CaMKII signaling pathway fully mediates MPTP-mediated mitochondrial ROS generation. tBOOH-induced apoptosis, as shown by flow cytometry of annexin V/propidium iodide, mitochondrial release of cytochrome c, activation of caspase-3 and increase in the Bax-to-Bcl-xL ratio, and the Ca²⁺/CaM/CaMKII signaling antagonists fully prevented these effects. Intramitochondrial CaM and CaMKII were partially involved in tBOOH-induced MPTP formation, since W7 and KN-62 both attenuated the tBOOH-induced, MPTP-mediated swelling of isolated mitochondria. We concluded that Ca²⁺/CaM/CaMKII signaling pathway is a key mediator of OS-induced MPTP formation and the subsequent exacerbation of OS from mitochondrial origin and apoptotic cell death.
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http://dx.doi.org/10.1007/s00204-014-1219-5DOI Listing
September 2014

Physiological concentrations of unconjugated bilirubin prevent oxidative stress-induced hepatocanalicular dysfunction and cholestasis.

Arch Toxicol 2014 Feb 4;88(2):501-14. Epub 2013 Dec 4.

Facultad de Ciencias Bioquímicas y Farmacéuticas, Instituto de Fisiología Experimental (IFISE-CONICET), U.N.R., Suipacha 570, 2000, Rosario, Argentina.

Bilirubin is an endogenous antioxidant with cytoprotective properties, and several studies highlight its potential in the treatment of pro-oxidant diseases. We demonstrated that oxidative stress (OS), a key feature in most hepatopathies, induces cholestasis by actin cytoskeleton disarrangement and further endocytic internalization of key canalicular transporters, such as the bile salt export pump (Bsep) and the multidrug resistance-associated protein 2 (Mrp2) . Here, we evaluated the capability of physiological concentrations of unconjugated bilirubin (UB) to limit OS and the impairment in biliary secretory function induced by the model pro-oxidant agent, tert-butylhydroperoxide (tBuOOH). UB fully prevented the formation of reactive oxygen species and membrane lipid peroxidation induced by tBuOOH in isolated rat hepatocytes. In the isolated rat hepatocyte couplet model, UB (17.1 μM) prevented the endocytic internalization of Bsep and Mrp2 and the impairment in their secretory function induced by tBuOOH. UB also prevented actin disarrangement, as evaluated by both plasma membrane bleb formation and actin fluorescent staining. Finally, UB prevented tBuOOH-induced cPKC activation. Experiments in isolated perfused rat livers showed that UB prevents the increase in oxidized glutathione biliary excretion and the drop in bile flow and the biliary excretion of specific Bsep and Mrp2 substrates. We conclude that physiological concentrations of UB are sufficient to prevent the biliary secretory failure induced by OS, by counteracting actin disarrangement and the consequent internalization of canalicular transporters relevant to normal bile formation. This reveals an important role for UB in preserving biliary secretory function under OS conditions.
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http://dx.doi.org/10.1007/s00204-013-1143-0DOI Listing
February 2014

G-protein-coupled receptor 30/adenylyl cyclase/protein kinase A pathway is involved in estradiol 17ß-D-glucuronide-induced cholestasis.

Hepatology 2014 Mar 21;59(3):1016-29. Epub 2014 Jan 21.

Instituto de Fisiología Experimental (IFISE), Facultad de Ciencias Bioquímicas y Farmacéuticas (CONICET-U.N.R.), Rosario, Argentina.

Unlabelled: Estradiol-17ß-D-glucuronide (E17G) activates different signaling pathways (e.g., Ca(2+) -dependent protein kinase C, phosphoinositide 3-kinase/protein kinase B, mitogen-activated protein kinases [MAPKs] p38 and extracellular signal-related kinase 1/2, and estrogen receptor alpha) that lead to acute cholestasis in rat liver with retrieval of the canalicular transporters, bile salt export pump (Abcb11) and multidrug resistance-associated protein 2 (Abcc2). E17G shares with nonconjugated estradiol the capacity to activate these pathways. G-protein-coupled receptor 30 (GPR30) is a receptor implicated in nongenomic effects of estradiol, and the aim of this study was to analyze the potential role of this receptor and its downstream effectors in E17G-induced cholestasis. In vitro, GPR30 inhibition by G15 or its knockdown with small interfering RNA strongly prevented E17G-induced impairment of canalicular transporter function and localization. E17G increased cyclic adenosine monophosphate (cAMP) levels, and this increase was blocked by G15, linking GPR30 to adenylyl cyclase (AC). Moreover, AC inhibition totally prevented E17G insult. E17G also increased protein kinase A (PKA) activity, which was blocked by G15 and AC inhibitors, connecting the links of the pathway, GPR30-AC-PKA. PKA inhibition prevented E17G-induced cholestasis, whereas exchange protein activated directly by cyclic nucleotide/MAPK kinase, another cAMP downstream effector, was not implicated in cAMP cholestatic action. In the perfused rat liver model, inhibition of the GPR30-AC-PKA pathway totally prevented E17G-induced alteration in Abcb11 and Abcc2 function and localization.

Conclusion: Activation of GPR30-AC-PKA is a key factor in the alteration of canalicular transporter function and localization induced by E17G. Interaction of E17G with GPR30 may be the first event in the cascade of signaling activation.
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http://dx.doi.org/10.1002/hep.26752DOI Listing
March 2014

Hormonal modulation of hepatic cAMP prevents estradiol 17β-D-glucuronide-induced cholestasis in perfused rat liver.

Dig Dis Sci 2013 Jun 31;58(6):1602-14. Epub 2013 Jan 31.

Instituto de Fisiología Experimental (IFISE), Facultad de Ciencias Bioquímicas y Farmacéuticas (CONICET, U.N.R.), Suipacha 570, S2002LRL, Rosario, Argentina.

Background: Estradiol-17β-D-glucuronide (E17G) induces cholestasis in vivo, endocytic internalization of the canalicular transporters multidrug resistance-associated protein 2 (Abcc2) and bile salt export pump (Abcb11) being a key pathomechanism. Cyclic AMP (cAMP) prevents cholestasis by targeting these transporters back to the canalicular membrane. In hepatocyte couplets, glucagon and salbutamol, both of which increase cAMP, prevented E17G action by stimulating the trafficking of these transporters by different mechanisms, namely: glucagon activates a protein kinase A-dependent pathway, whereas salbutamol activates an exchange-protein activated by cAMP (Epac)-mediated, microtubule-dependent pathway.

Methods: The present study evaluated whether glucagon and salbutamol prevent E17G-induced cholestasis in a more physiological model, i.e., the perfused rat liver (PRL). Additionally, the preventive effect of in vivo alanine administration, which induces pancreatic glucagon secretion, was evaluated.

Results: In PRLs, glucagon and salbutamol prevented E17G-induced decrease in both bile flow and the secretory activity of Abcc2 and Abcb11. Salbutamol prevention fully depended on microtubule integrity. On the other hand, glucagon prevention was microtubule-independent only at early time periods after E17G administration, but it was ultimately affected by the microtubule disrupter colchicine. Cholestasis was associated with endocytic internalization of Abcb11 and Abcc2, the intracellular carriers being partially colocalized with the endosomal marker Rab11a. This effect was completely prevented by salbutamol, whereas some transporter-containing vesicles remained colocalized with Rab11a after glucagon treatment. In vivo, alanine administration increased hepatic cAMP and accelerated the recovery of bile flow and Abcb11/Abcc2 transport function after E17G administration. The initial recovery afforded by alanine was microtubule-independent, but microtubule integrity was required to sustain this protective effect.

Conclusion: We conclude that modulation of cAMP levels either by direct administration of cAMP modulators or by physiological manipulations leadings to hormone-mediated increase of cAMP levels (alanine administration), prevents estrogen-induced cholestasis in models with preserved liver architecture, through mechanisms similar to those arisen from in vitro studies.
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http://dx.doi.org/10.1007/s10620-013-2558-4DOI Listing
June 2013

Sequential activation of classic PKC and estrogen receptor α is involved in estradiol 17ß-D-glucuronide-induced cholestasis.

PLoS One 2012 27;7(11):e50711. Epub 2012 Nov 27.

Instituto de Fisiología Experimental (IFISE), Facultad de Ciencias Bioquímicas y Farmacéuticas (CONICET-U.N.R.), Rosario, Argentina.

Unlabelled: Estradiol 17ß-D-glucuronide (E17G) induces acute cholestasis in rat with endocytic internalization of the canalicular transporters bile salt export pump (Abcb11) and multidrug resistance-associated protein 2 (Abcc2). Classical protein kinase C (cPKC) and PI3K pathways play complementary roles in E17G cholestasis. Since non-conjugated estradiol is capable of activating these pathways via estrogen receptor alpha (ERα), we assessed the participation of this receptor in the cholestatic manifestations of estradiol glucuronidated-metabolite E17G in perfused rat liver (PRL) and in isolated rat hepatocyte couplets (IRHC). In both models, E17G activated ERα. In PRL, E17G maximally decreased bile flow, and the excretions of dinitrophenyl-glutathione, and taurocholate (Abcc2 and Abcb11 substrates, respectively) by 60% approximately; preadministration of ICI 182,780 (ICI, ERα inhibitor) almost totally prevented these decreases. In IRHC, E17G decreased the canalicular vacuolar accumulation of cholyl-glycylamido-fluorescein (Abcb11 substrate) with an IC50 of 91±1 µM. ICI increased the IC50 to 184±1 µM, and similarly prevented the decrease in the canalicular vacuolar accumulation of the Abcc2 substrate, glutathione-methylfluorescein. ICI also completely prevented E17G-induced delocalization of Abcb11 and Abcc2 from the canalicular membrane, both in PRL and IRHC. The role of ERα in canalicular transporter internalization induced by E17G was confirmed in ERα-knocked-down hepatocytes cultured in collagen sandwich. In IRHC, the protection of ICI was additive to that produced by PI3K inhibitor wortmannin but not with that produced by cPKC inhibitor Gö6976, suggesting that ERα shared the signaling pathway of cPKC but not that of PI3K. Further analysis of ERα and cPKC activations induced by E17G, demonstrated that ICI did not affect cPKC activation whereas Gö6976 prevented that of ERα, indicating that cPKC activation precedes that of ERα.

Conclusion: ERα is involved in the biliary secretory failure induced by E17G and its activation follows that of cPKC.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0050711PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3507741PMC
May 2013

ERK1/2 and p38 MAPKs are complementarily involved in estradiol 17ß-D-glucuronide-induced cholestasis: crosstalk with cPKC and PI3K.

PLoS One 2012 14;7(11):e49255. Epub 2012 Nov 14.

Institute of Experimental Physiology, National Scientific and Technical Research Council/National University of Rosario, Rosario, Argentina.

Objective: The endogenous, cholestatic metabolite estradiol 17ß-D-glucuronide (E(2)17G) induces endocytic internalization of the canalicular transporters relevant to bile formation, Bsep and Mrp2. We evaluated here whether MAPKs are involved in this effect.

Design: ERK1/2, JNK1/2, and p38 MAPK activation was assessed by the increase in their phosphorylation status. Hepatocanalicular function was evaluated in isolated rat hepatocyte couplets (IRHCs) by quantifying the apical secretion of fluorescent Bsep and Mrp2 substrates, and in isolated, perfused rat livers (IPRLs), using taurocholate and 2,4-dinitrophenyl-S-glutathione, respectively. Protein kinase participation in E(2)17G-induced secretory failure was assessed by co-administering selective inhibitors. Internalization of Bsep/Mrp2 was assessed by confocal microscopy and image analysis.

Results: E(2)17G activated all kinds of MAPKs. The PI3K inhibitor wortmannin prevented ERK1/2 activation, whereas the cPKC inhibitor Gö6976 prevented p38 activation, suggesting that ERK1/2 and p38 are downstream of PI3K and cPKC, respectively. The p38 inhibitor SB203580 and the ERK1/2 inhibitor PD98059, but not the JNK1/2 inhibitor SP600125, partially prevented E(2)17G-induced changes in transporter activity and localization in IRHCs. p38 and ERK1/2 co-inhibition resulted in additive protection, suggesting complementary involvement of these MAPKs. In IPRLs, E(2)17G induced endocytosis of canalicular transporters and a rapid and sustained decrease in bile flow and biliary excretion of Bsep/Mrp2 substrates. p38 inhibition prevented this initial decay, and the internalization of Bsep/Mrp2. Contrarily, ERK1/2 inhibition accelerated the recovery of biliary secretion and the canalicular reinsertion of Bsep/Mrp2.

Conclusions: cPKC/p38 MAPK and PI3K/ERK1/2 signalling pathways participate complementarily in E(2)17G-induced cholestasis, through internalization and sustained intracellular retention of canalicular transporters, respectively.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0049255PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3498151PMC
May 2013

Localization status of hepatocellular transporters in cholestasis.

Front Biosci (Landmark Ed) 2012 Jan 1;17:1201-18. Epub 2012 Jan 1.

Instituto de Fisiologia Experimental (IFISE), CONICET, Facultad de Ciencias Bioquimicas y Farmaceuticas, Universidad Nacional de Rosario, S2002LRL, Rosario, Argentina.

Vectorial transport of osmotically active solutes from blood into bile is essential for bile flow generation. Therefore, the localization status of hepatocellular transporters involved in this function is critical. These transporters are localized either in the plasma membrane or in an endosomal, submembranous compartment, from where they undergo recycling to the plasma membrane. The balance between exocytic targeting/endocytic internalization from/to this recycling compartment is therefore a chief determinant of the liver capability to secrete bile. Furthermore, its impairment may lead to sustained endocytic internalization, eventually resulting in transporter degradation. Exacerbated internalization of hepatocellular transporters occurs in several experimental models of cholestasis, and also in most human cholestatic liver diseases. This review outlines the possible mechanisms explaining this alteration (e.g., alteration of the organization of actin or actin-transporter linking proteins), and the mediators involved (e.g., activation of "cholestatic" signaling pathways). Finally, several experimental therapeutic approaches based upon the administration of compounds that stimulate exocytic targeting of canalicular transporters (e.g., cAMP, tauroursodeoxycholate) are described with regard to their capability to prevent cholestatic alterations resulting from transporter internalization.
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http://dx.doi.org/10.2741/3981DOI Listing
January 2012

Prevention of estradiol 17beta-D-glucuronide-induced canalicular transporter internalization by hormonal modulation of cAMP in rat hepatocytes.

Mol Biol Cell 2011 Oct 24;22(20):3902-15. Epub 2011 Aug 24.

Instituto de Fisiología Experimental, Facultad de Ciencias Bioquímicas y Farmacéuticas, Consejo Nacional de Investigaciones Científicas y Técnicas, Universidad Nacional de Rosario, S2002LRL Rosario, Argentina.

In estradiol 17β-d-glucuronide (E17G)-induced cholestasis, the canalicular hepatocellular transporters bile salt export pump (Abcb11) and multidrug-resistance associated protein 2 (Abcc2) undergo endocytic internalization. cAMP stimulates the trafficking of transporter-containing vesicles to the apical membrane and is able to prevent internalization of these transporters in estrogen-induced cholestasis. Hepatocyte levels of cAMP are regulated by hormones such as glucagon and adrenaline (via the β2 receptor). We analyzed the effects of glucagon and salbutamol (a β2 adrenergic agonist) on function and localization of Abcb11 and Abcc2 in isolated rat hepatocyte couplets exposed to E17G and compared the mechanistic bases of their effects. Glucagon and salbutamol partially prevented the impairment in Abcb11 and Abcc2 transport capacity. E17G also induced endocytic internalization of Abcb11 and Abcc2, which partially colocalized with the endosomal marker Rab11a. This effect was completely prevented by salbutamol, whereas some transporter-containing vesicles remained internalized and mainly colocalizing with Rab11a in the perinuclear region after incubation with glucagon. Glucagon prevention was dependent on cAMP-dependent protein kinase (PKA) and independent of exchange proteins activated directly by cAMP (Epac) and microtubules. In contrast, salbutamol prevention was PKA independent and Epac/MEK and microtubule dependent. Anticholestatic effects of glucagon and salbutamol were additive in nature. Our results show that increases in cAMP could activate different anticholestatic signaling pathways, depending on the hormonal mediator involved.
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http://dx.doi.org/10.1091/mbc.E11-01-0047DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3192868PMC
October 2011

Ursodeoxycholic acid in cholestasis: linking action mechanisms to therapeutic applications.

Clin Sci (Lond) 2011 Dec;121(12):523-44

Institute of Experimental Physiology (IFISE-CONICET), Faculty of Biochemical and Pharmacautical Sciences, National University of Rosario, Suipacha 570, S2002LRL Rosario, Argentina.

UDCA (ursodeoxycholic acid) is the therapeutic agent most widely used for the treatment of cholestatic hepatopathies. Its use has expanded to other kinds of hepatic diseases, and even to extrahepatic ones. Such versatility is the result of its multiple mechanisms of action. UDCA stabilizes plasma membranes against cytolysis by tensioactive bile acids accumulated in cholestasis. UDCA also halts apoptosis by preventing the formation of mitochondrial pores, membrane recruitment of death receptors and endoplasmic-reticulum stress. In addition, UDCA induces changes in the expression of metabolizing enzymes and transporters that reduce bile acid cytotoxicity and improve renal excretion. Its capability to positively modulate ductular bile flow helps to preserve the integrity of bile ducts. UDCA also prevents the endocytic internalization of canalicular transporters, a common feature in cholestasis. Finally, UDCA has immunomodulatory properties that limit the exacerbated immunological response occurring in autoimmune cholestatic diseases by counteracting the overexpression of MHC antigens and perhaps by limiting the production of cytokines by immunocompetent cells. Owing to this multi-functionality, it is difficult to envisage a substitute for UDCA that combines as many hepatoprotective effects with such efficacy. We predict a long-lasting use of UDCA as the therapeutic agent of choice in cholestasis.
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http://dx.doi.org/10.1042/CS20110184DOI Listing
December 2011

Phosphoinositide 3-kinase/protein kinase B signaling pathway is involved in estradiol 17β-D-glucuronide-induced cholestasis: complementarity with classical protein kinase C.

Hepatology 2010 Oct;52(4):1465-76

Institute of Experimental Physiology, National Scientific and Technical Research Council/University of Rosario, Rosario, Argentina.

Unlabelled: Estradiol 17β-D-glucuronide (E(2)17G) is an endogenous, cholestatic metabolite that induces endocytic internalization of the canalicular transporters relevant to bile secretion: bile salt export pump (Bsep) and multidrug resistance-associated protein 2 (Mrp2). We assessed whether phosphoinositide 3-kinase (PI3K) is involved in E(2)17G-induced cholestasis. E(2)17G activated PI3K according to an assessment of the phosphorylation of the final PI3K effector, protein kinase B (Akt). When the PI3K inhibitor wortmannin (WM) was preadministered to isolated rat hepatocyte couplets (IRHCs), it partially prevented the reduction induced by E(2)17G in the proportion of IRHCs secreting fluorescent Bsep and Mrp2 substrates (cholyl lysyl fluorescein and glutathione methylfluorescein, respectively). 2-Morpholin-4-yl-8-phenylchromen-4-one, another PI3K inhibitor, and an Akt inhibitor (Calbiochem 124005) showed similar protective effects. IRHC immunostaining and confocal microscopy analysis revealed that endocytic internalization of Bsep and Mrp2 induced by E(2)17G was extensively prevented by WM; this effect was fully blocked by the microtubule-disrupting agent colchicine. The protection of WM was additive to that afforded by the classical protein kinase C (cPKC) inhibitor 5,6,7,13-tetrahydro-13-methyl-5-oxo-12H-indolo[2,3-a]pyrrolo[3,4-c]carbazole-12-propanenitrile (Gö6976); this suggested differential and complementary involvement of the PI3K and cPKC signaling pathways in E(2)17G-induced cholestasis. In isolated perfused rat liver, an intraportal injection of E(2)17G triggered endocytosis of Bsep and Mrp2, and this was accompanied by a sustained decrease in the bile flow and the biliary excretion of the Bsep and Mrp2 substrates [(3)H]taurocholate and glutathione until the end of the perfusion period. Unlike Gö6976, WM did not prevent the initial decay, but it greatly accelerated the recovery to normality of these parameters and the reinsertion of Bsep and Mrp2 into the canalicular membrane in a microtubule-dependent manner.

Conclusion: The PI3K/Akt signaling pathway is involved in the biliary secretory failure induced by E(2)17G through sustained internalization of canalicular transporters endocytosed via cPKC.
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http://dx.doi.org/10.1002/hep.23846DOI Listing
October 2010

Tauroursodeoxycholate counteracts hepatocellular lysis induced by tensioactive bile salts by preventing plasma membrane-micelle transition.

Chem Biol Interact 2010 Dec 24;188(3):386-92. Epub 2010 Aug 24.

Instituto de Fisiología Experimental, Rosario, Argentina.

Ursodeoxycholic acid is widely used as a therapeutic agent for the treatment of cholestatic liver diseases. In these hepatopathies, the bile secretory failure produces accumulation of endogenous, tensioactive bile salts, leading to plasma membrane damage and, eventually, hepatocellular lysis. In the present study, we analyzed the capacity of the ursodeoxycholic acid endogenous metabolite, tauroursodeoxycholate (TUDC), to stabilize the hepatocellular plasma membrane against its transition to the micellar phase induced by the tensioactive bile salt taurochenodeoxycholate (TCDC), the main endogenous bile salt accumulated in cholestasis. The disruption of the plasma membrane was evaluated (i) in isolated hepatocytes, through the release of the enzyme lactate dehydrogenase to the incubation medium and (ii) in isolated plasma membranes, through the self-quenching assay of the membranotropic probe octadecylrhodamine B; this assay allows for detergent-induced transition from membrane bilayer to micelle to be monitored. Our results showed that isolated hepatocytes treated with TUDC are more resistant to TCDC-induced cell lysis. When this effect was evaluated in isolated plasma membranes, the TCDC concentration necessary to reach half of the transition from bilayer to micelle was increased by 22% (p<0.05). This difference remained even when TUDC was removed from the incubation medium before adding TCDC, thus indicating that TUDC exerted its effect directly on the plasma membrane. When the same experiments were carried out using the non-ionic detergent TX-100 or the cholesterol-complexing detergent digitonin, no protective effect was observed. In conclusion, TUDC prevents selectively the bilayer to micelle transition of the hepatocellular plasma membrane induced by hydrophobic bile salts that typically build up and accumulate in cholestatic processes. Our results suggest that formation of a complex between negatively charged TUDC and cholesterol in the membrane favours repulsion of negatively charged detergent bile salts, thus providing a basis for the understanding of the TUDC protective effects.
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http://dx.doi.org/10.1016/j.cbi.2010.08.004DOI Listing
December 2010
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