Publications by authors named "Senthil K Venugopal"

21 Publications

  • Page 1 of 1

Augmenter of liver regeneration enhances cell proliferation through the microRNA-26a/Akt/cyclin D1 pathway in hepatic cells.

Hepatol Res 2019 Nov 25;49(11):1341-1352. Epub 2019 Jul 25.

Faculty of Life Sciences and Biotechnology, South Asian University, Akbar Bhawan, Chanakyapuri, New Delhi, India.

Aim: Hepatocytes can proliferate and regenerate when injured by toxins, viral infections, and so on. Augmenter of liver regeneration (ALR) is a key regulator of liver regeneration, but the mechanism is unknown. The role of ALR in other cell types is not known. In the present study, we investigated the relationship between microRNA (miRNA)-26a and ALR in the Huh7 cell line and adipose tissue-derived mesenchymal cells from chronic liver disease patients and healthy individuals.

Methods: Huh7 cells were transfected independently with ALR and miRNA-26a expression vectors, and their effects on cell proliferation, the expression of miRNA-26a, and activation of the phosphatase and tensin homolog and Akt signaling pathways were determined. The experiments were repeated on mesenchymal stem cells derived from healthy individuals and chronic liver disease patients to see whether the observations can be replicated in primary cells.

Results: Overexpression of ALR or miRNA-26a resulted in an increase of the phosphorylation of Akt and cyclin D1 expression, whereas it resulted in decreased levels of p-GSK-3β and phosphatase and tensin homolog in Huh7 cells. The inhibition of ALR expression by ALR siRNA or anti-miR-26a decreased the Akt/cyclin D1 signaling pathway, leading to decreased proliferation. Mesenchymal stem cells isolated from the chronic liver disease patients had a higher ALR expression, while the mesenchymal stem cells isolated from healthy volunteers responded to the growth factor treatments for increased ALR expression. It was found that there was a significant increase in miRNA-26a expression and proliferation.

Conclusions: These data clearly showed that ALR induced the expression of miRNA-26a, which downregulated phosphatase and tensin homolog, resulting in an increased p-Akt/cyclin D1 pathway and enhanced proliferation in hepatic cells.
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http://dx.doi.org/10.1111/hepr.13404DOI Listing
November 2019

Butyrate inhibits HBV replication and HBV-induced hepatoma cell proliferation via modulating SIRT-1/Ac-p53 regulatory axis.

Mol Carcinog 2019 04 19;58(4):524-532. Epub 2018 Dec 19.

Molecular Medicine Laboratory, Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, India.

Butyrate, a histone deacetylase inhibitor, has several therapeutic applications, including cancer. However, the effect of butyrate in HBV replication is not known so far. It was hypothesized that butyrate might inhibit HBV replication and host cell proliferation via SIRT-1. It was found that the increased expression of SIRT-1 in Hep G2.2.15 cells (HBV expressing cells) than Hep G2 cells. Next the expression of SIRT-1 and Acetylated p53 (Ac-p53) were measured in the liver biopsy samples of chronic hepatitis B (CHB) patients with high viral load and compared to CHB patients with low viral load and found that there was a high SIRT-1 expression and a low Ac-p53 levels in CHB patients with high viral load compared to CHB patients with low viral load. Incubation of butyrate inhibited SIRT-1 expression and cell proliferation. Inhibition of SIRT-1 by butyrate or SIRT-1 siRNA increased the levels of Ac-p53. The elevated Ac-p53 decreased p-akt, cyclin D1, and thereby inhibited cell proliferation. Incubation of butyrate with Hep G2.2.15 cells also inhibited HBx protein expression, HBV-DNA and hepatitis B surface antigen (HBsAg). Taken together, the data showed that butyrate inhibited HBV replication and cell proliferation by inhibiting SIRT-1 expression in hepatoma cells.
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http://dx.doi.org/10.1002/mc.22946DOI Listing
April 2019

Oxidative stress plays a key role in butyrate-mediated autophagy via Akt/mTOR pathway in hepatoma cells.

Chem Biol Interact 2017 Aug 12;273:99-106. Epub 2017 Jun 12.

Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, India. Electronic address:

Hepatocellular Carcinoma (HCC) is one of the most aggressive forms of cancer, responsible for a number of deaths in humans. Butyrate, one of the short chain fatty acids produced by the gut microbiota during anaerobic fermentation, was shown to be beneficial for inhibiting cancer growth. In this study, we showed that sodium butyrate induced autophagy via reactive oxygen species (ROS) in hepatoma cells. Butyrate (0-6 mM) incubation significantly increased intracellular ROS levels (45.2% compared to control), which in turn inhibited phosphorylation of akt and mTOR, leading to the upregulation of autophagic proteins, such as beclin 1, ATG 5, LC3-II, followed by the increased autophagosome formation (34.4% compared to control cells). Addition of a known antioxidant, N-acetyl cysteine (NAC), reversed these butyrate-induced ROS and autophagy. It was also found that butyrate-induced ROS enhanced MAPK activation, which was inhibited by NAC. In conclusion, our data showed that butyrate induced ROS, which in turn induced autophagy via inhibition of akt/mTOR pathway. Hence, butyrate could be considered as a potential candidate for HCC treatment.
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http://dx.doi.org/10.1016/j.cbi.2017.06.001DOI Listing
August 2017

Butyrate induces ROS-mediated apoptosis by modulating miR-22/SIRT-1 pathway in hepatic cancer cells.

Redox Biol 2017 08 7;12:340-349. Epub 2017 Mar 7.

Faculty of Life Sciences and Biotechnology, South Asian University, Chanakyapuri, New Delhi, India. Electronic address:

Butyrate is one of the short chain fatty acids, produced by the gut microbiota during anaerobic fermentation of dietary fibres. It has been shown that it can inhibit tumor progression via suppressing histone deacetylase and can induce apoptosis in cancer cells. However, the comprehensive pathway by which butyrate mediates apoptosis and growth arrest in cancer cells still remains unclear. In this study, the role of miR-22 in butyrate-mediated ROS release and induction of apoptosis was determined in hepatic cells. Intracellular expression of miR-22 was increased when the Huh 7 cells were incubated with sodium butyrate. Over-expression of miR-22 or addition of sodium butyrate inhibited SIRT-1 expression and enhanced the ROS production. Incubation of cells with anti-miR-22 reversed the effects of butyrate. Butyrate induced apoptosis via ROS production, cytochrome c release and activation of caspase-3, whereas addition of N-acetyl cysteine or anti-miR-22 reversed these butyrate-induced effects. Furthermore, sodium butyrate inhibited cell growth and proliferation, whereas anti-miR-22 inhibited these butyrate-mediated changes. The expression of PTEN and gsk-3 was found to be increased while p-akt and β-catenin expression was decreased significantly by butyrate. These data showed that butyrate modulated both apoptosis and proliferation via miR-22 expression in hepatic cells.
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http://dx.doi.org/10.1016/j.redox.2017.03.006DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5350572PMC
August 2017

Circulating microRNAs: Possible role as non-invasive diagnostic biomarkers in liver disease.

Clin Res Hepatol Gastroenterol 2017 Sep 9;41(4):370-377. Epub 2016 Dec 9.

Faculty of Life Science and Biotechnology, South Asian University, Akbar Bhawan, Chanakyapuri, 110021 New Delhi, India. Electronic address:

Liver is the central organ for metabolism and the hepatocytes metabolize several drugs, hepatotoxins, alcohol, etc. Continuous exposure of the hepatocytes to these toxins result in various chronic diseases, such as alcoholic liver disease, non-alcoholic fatty liver disease, viral hepatitis and hepatocellular carcinoma. Although several diagnostic methods, such as serum markers, liver biopsy or imaging studies are currently available, most of these are either invasive or detect the disease at advanced stages. Hence, there is a need for new molecular markers that can be used for early detection of the disease. MicroRNAs (miRNAs) are naturally occurring, 20-22 nucleotide long, non-coding RNA molecules that regulate the gene expression at post-transcriptional levels, thereby modulating various biological functions. Their expression is deregulated under pathological conditions, and recent studies showed that they are secreted and can be detected in various body fluids. Since the cellular changes occur at earlier stages of the disease, detecting miRNAs in the body fluids could make them as potential novel biomarkers. Albeit, the difficulties in standardization procedures, cost and availability should be addressed before using them in the clinical arena. This review highlights the possible role of secreted miRNAs to use as early non-invasive diagnostic markers for liver disease.
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http://dx.doi.org/10.1016/j.clinre.2016.11.001DOI Listing
September 2017

Humic acid inhibits HBV-induced autophagosome formation and induces apoptosis in HBV-transfected Hep G2 cells.

Sci Rep 2016 10 6;6:34496. Epub 2016 Oct 6.

Faculty of Life Sciences and Biotechnology, South Asian University, Akbar Bhawan Chanakyapuri New Delhi, India.

Hepatitis B Virus (HBV) utilizes several mechanisms to survive in the host cells and one of the main pathways being autophagosome formation. Humic acid (HA), one of the major components of Mineral pitch, is an Ayurvedic medicinal food, commonly used by the people of the Himalayan regions of Nepal and India for various body ailments. We hypothesized that HA could induce cell death and inhibit HBV-induced autophagy in hepatic cells. Incubation of Hep G2.2.1.5 cells (HepG2 cells stably expressing HBV) with HA (100 μM) inhibited both cell proliferation and autophagosome formation significantly, while apoptosis induction was enhanced. Western blot results showed that HA incubation resulted in decreased levels of beclin-1, SIRT-1 and c-myc, while caspase-3 and β-catenin expression were up-regulated. Western blot results showed that HA significantly inhibited the expression of HBx (3-fold with 50 μM and 5-fold with 100 μM) compared to control cells. When HA was incubated with HBx-transfected Hep G2 cells, HBx-induced autophagosome formation and beclin-1 levels were decreased. These data showed that HA induced apoptosis and inhibited HBV-induced autophagosome formation and proliferation in hepatoma cells.
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http://dx.doi.org/10.1038/srep34496DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5052648PMC
October 2016

Mineral pitch induces apoptosis and inhibits proliferation via modulating reactive oxygen species in hepatic cancer cells.

BMC Complement Altern Med 2016 May 27;16:148. Epub 2016 May 27.

Faculty of Life Sciences and Biotechnology, South Asian University, Akbar Bhawan Chanakyapuri, New Delhi, India.

Background: Mineral Pitch (MP) is a dark brown coloured humic matter originating from high altitude rocks. It is an Ayurvedic medicinal food, commonly used by the people of the Himalayan regions of Nepal and India for various body ailments.

Methods: The Huh-7 cells were treated with different concentrations of MP for 24 h, and both apoptosis and proliferation was determined by the TUNEL and MTT assays respectively. The formation of ROS and nitric oxide was analysed by DCFH-DA and Griess reagent respectively. The expression of miRNA-21 and miRNA-22 were checked by the real time PCR. Effect of miRNA-22 on proliferation and c-myc was studied by over-expressing miRNA-22 premiRs in Huh-7 cells.

Results: We found that MP enhanced anti-cancer effects by inducing apoptosis and inhibiting proliferation. MP induced both ROS and NO, upon neutralizing them, there was a partial recovery of apoptosis and proliferation. MP also induced miRNA-22 expression, while miRNA-21 expression was inhibited. Over-expression of miRNA-22 resulted in a significant inhibition of proliferation. miRNA-22 directly targeted c-myc gene, thereby inhibited proliferation. These results clearly show that MP induces its anti-cancer activity by more than one pathway.

Conclusion: The data clearly indicate that MP induced apoptosis via the production of ROS, and inhibited proliferation by inducing miRNA-22 and inhibiting miRNA-21 in Huh-7 cells.
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http://dx.doi.org/10.1186/s12906-016-1131-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4882837PMC
May 2016

Overexpression of microRNA-30a inhibits hepatitis B virus X protein-induced autophagosome formation in hepatic cells.

FEBS J 2015 Mar 13;282(6):1152-63. Epub 2015 Feb 13.

Faculty of Life Sciences and Biotechnology, South Asian University, New Delhi, India.

Hepatitis B virus (HBV) enters the host and survives by using several mechanisms. One of the ways that HBV survives and replicates in the host cells is by inducing autophagy. Previous reports have shown that microRNA (miRNA)-30a inhibits autophagosome formation in cancer cells. Hence, we hypothesized that overexpression of miRNA-30a could inhibit HBV-induced autophagosome formation in hepatic cells. To study this, both HepG2 cells and HepG2.2.1.5 cells (HBV-expressing stable cell line) were transfected with miRNA-30a, and the cells were collected either for RNA isolation or protein isolation after 72 h of transfection. Beclin-1 expression was significantly higher in untransfected HepG2.2.1.5 cells than in HepG2 cells. Western blots showed that miRNA-30a overexpression resulted in a significant decrease in beclin-1 expression (eight-fold and four-fold in HepG2 and HepG2.2.1.5 cells, respectively) and c-myc expression, whereas the numbers of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL)-positive cells were increased. In contrast, overexpression of HBV X protein (HBx) in HepG2 cells resulted in the enhancement of beclin-1 (six-fold increase as compared with the empty vector-transfected cells) and c-myc expression, whereas the numbers of TUNEL-positive cells were reduced. To confirm these findings, HBx and miRNA-30a were coexpressed in HepG2 cells, and the results showed significant inhibition of autophagosome formation and beclin-1 and c-myc expression, whereas apoptosis increased. These data demonstrate that HBx induces autophagosome formation via beclin-1 expression, whereas miRNA-30a overexpression could successfully inhibit the beclin-1 expression induced by HBx, thereby modulating autophagosome formation in hepatic cells.
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http://dx.doi.org/10.1111/febs.13209DOI Listing
March 2015

miRNA regulation of liver growth after 50% partial hepatectomy and small size grafts in rats.

Transplantation 2011 Feb;91(3):293-9

Department of Internal Medicine, Transplant Research Program, University of California, Davis Medical Center, Sacramento, CA 95817, USA.

Background: The molecular mechanisms underlying the growth of small size grafts and the remaining livers are poorly understood. MicroRNAs (miRNAs) negatively modulate expression of genes that are involved in cellular function and metabolism. The aim of this study is to identify critical miRNA species that modulate the growth of small grafts and the remaining livers after partial hepatectomy (PH).

Methods: Small size graft liver transplantation was performed in rats. Liver tissue was harvested after transplant or PH for the determination of miRNA expression profile, and the data were confirmed by quantitative reverse-transcriptase polymerase chain reaction. The genes involved in cell cycle and proliferation were analyzed by quantitative reverse-transcriptase polymerase chain reaction and immunohistochemical staining.

Results: Compared with control liver, miR_122a, Let_7b, and miR_26a were reduced by more than 90% in 45% volume grafts. In the remaining livers after 50% PH, 30 miRNAs were down-regulated by more than 50%, and among them, miR_22a, miR_26a, miR_30b, Let_7f, and Let_7g were markedly decreased. A negative correlation existed between down-regulated miRNAs and highly up-regulated genes involved in cell cycle and proliferation in the remaining livers. Moreover, overexpression of miR_26a markedly down-regulated cyclin E2 protein levels and significantly decreased proliferation of HepG2 cells.

Conclusion: Down-regulated miRNAs play a pivotal role in promoting the growth of small size grafts and the remaining livers. The negative correlation between down-regulated miRNAs and up-regulated genes suggests that these specific miRNAs participate in the modulation of a growth response in both living donors and small size graft recipients.
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http://dx.doi.org/10.1097/TP.0b013e318204756cDOI Listing
February 2011

Acute liver injury upregulates microRNA-491-5p in mice, and its overexpression sensitizes Hep G2 cells for tumour necrosis factor-alpha-induced apoptosis.

Liver Int 2010 Mar 14;30(3):376-87. Epub 2009 Dec 14.

Department of Internal Medicine: Transplant Research Program, University of California Davis Medical Center, Sacramento, CA 95817, USA.

Background: MicroRNAs (miRNAs) have emerged as novel genetic regulators of cell functions such as proliferation, apoptosis and cancer.

Aims: The aim of this study was to evaluate the role of a specific miRNA in modulating hepatic cell functions.

Methods: C57Bl/6 mice were administered anti-fas receptor antibodies to induce liver cell apoptosis. miRNAs were purified from the liver tissue and evaluated using an miRNA microarray. The role of miRNA-491_5p, which was overexpressed in the model, in modulating hepatic cell functions was evaluated. miRNA-491_5p was overexpressed in Hep G2 cells, followed by the addition of tumour necrosis factor (TNF)-alpha, and induction of apoptosis as well as genes involved in apoptosis pathways were evaluated. The effect of miRNA-491_5p target genes on apoptosis was also analysed by inhibiting their expression by siRNA-induced gene silencing.

Results: Upregulation of miRNA-491_5p was found in a high-dose anti-fas receptor antibody group. Overexpression of microRNA-491_5p sensitized Hep G2 cells for TNF-alpha-induced apoptosis, and also caused an inhibition of alpha-fetoprotein, (AFP), heat shock protein-90 (hsp-90) and nuclear factor-kappaB (NF-kappaB). Overexpression of miRNA-491_5p or inhibition of AFP and hsp-90 resulted in an increased apoptosis in TNF-alpha-treated Hep G2 cells.

Conclusions: One of the miRNAs that is associated with the acute liver injury mouse model, miRNA-491_5p, sensitizes Hep G2 cells for TNF-alpha-induced apoptosis, at least in part, by inhibiting AFP, hsp-90 and NF-kappaB.
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http://dx.doi.org/10.1111/j.1478-3231.2009.02181.xDOI Listing
March 2010

Liver fibrosis causes downregulation of miRNA-150 and miRNA-194 in hepatic stellate cells, and their overexpression causes decreased stellate cell activation.

Am J Physiol Gastrointest Liver Physiol 2010 Jan 5;298(1):G101-6. Epub 2009 Nov 5.

Dept. of Internal Medicine, Transplant Research Program, 4635 2nd Ave., Research Bldg. I, Rm. 1001, UCDavis Medical Ctr., Sacramento, CA 95817, USA.

Activation of hepatic stellate cells (HSC) results in their proliferation and in the secretion of extracellular matrix (ECM) proteins, which leads to hepatic fibrosis. microRNAs (miRNAs) have been shown to regulate various cell functions, such as proliferation, differentiation, and apoptosis. Hence, we have analyzed the miRNAs that were differentially expressed in HSC isolated from sham-operated and bile duct-ligated rats. Expression of two miRNAs, miRNA-150 and miRNA-194, was reduced in HSC isolated from fibrotic rats compared with sham-operated animals. These two miRNAs were overexpressed in LX-2 cells, and their ability to inhibit cell proliferation, the expression of smooth muscle alpha-actin (SMA), a marker for activation, and collagen type I, a marker for ECM secretion, was determined. Overexpression of these two miRNAs resulted in a significant inhibition of proliferation (P < 0.05) and reduced SMA and collagen I levels compared with either untreated cells or nonspecific miRNA-expressing cells. Next, the protein targets of these two miRNAs were found using bioinformatics approaches. C-myb was found to be a target for miRNA-150, and rac 1 was found to be one of the targets for miRNA-194. Therefore, we studied the expression of these two proteins by overexpressing these two miRNAs in LX-2 cells and found that overexpression of miRNA-150 and miRNA-194 resulted in a significant inhibition of c-myb and rac 1 expression, respectively. We conclude that both miRNA-150 and miRNA-194 inhibit HSC activation and ECM production, at least in part, via inhibition of c-myb and rac 1 expression.
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http://dx.doi.org/10.1152/ajpgi.00220.2009DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2806096PMC
January 2010

A novel small molecule, LAS-0811, inhibits alcohol-induced apoptosis in VL-17A cells.

Biochem Biophys Res Commun 2009 Feb 6;379(4):876-81. Epub 2009 Jan 6.

Department of Internal Medicine, Transplant Research Program, University of California Davis Medical Center, 4635 2nd Ave. Research Building I, Room 1001, Sacramento, CA 95817, USA.

One of the pathways by which alcohol induces hepatocyte apoptosis is via oxidative stress. We screened several chemically-synthesized small molecules and found LAS-0811, which inhibits oxidative stress. In this study, we elucidated its role in inhibiting alcohol-induced apoptosis in hepatocyte-like VL-17A cells. VL-17A cells were pre-incubated with LAS-0811, followed by ethanol incubation. Ethanol-induced reactive oxygen species and apoptosis were significantly inhibited in LAS-0811 pre-treated cells. VL-17A cells were transfected with a reporter (ARE/TK-GFP) plasmid containing green fluorescent protein (GFP) as a reporter gene and the anti-oxidant response element as the promoter. LAS-0811 pre-treatment significantly induced the GFP expression compared to the cells treated with ethanol alone. LAS-0811 induced the activation of nrf2 and enhanced the expression and activity of glutathione peroxidase, one of the downstream targets of nrf2. The results indicate that LAS-0811 protects VL-17A cells against ethanol-induced oxidative stress and apoptosis at least in part via nrf2 activation.
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http://dx.doi.org/10.1016/j.bbrc.2008.12.133DOI Listing
February 2009

Role of MAPK phosphatase-1 in sustained activation of JNK during ethanol-induced apoptosis in hepatocyte-like VL-17A cells.

J Biol Chem 2007 Nov 11;282(44):31900-8. Epub 2007 Sep 11.

Department of Internal Medicine, Transplant Research Program, UC Davis Medical Center, Sacramento, California 95817, USA.

Ethanol metabolism plays a central role in activating the mitogen-activated protein kinase (MAPK) cascade leading to inflammation and apoptosis. Sustained activation of c-Jun N-terminal kinase (JNK), one of the MAPKs, has been shown to induce apoptosis in hepatocytes. MAPK phosphatase-1 (MKP-1) has been shown to dephosphorylate MAPKs in several cells. The aim of the study is to evaluate the role of MKP-1 in sustained JNK activation as a mechanism to explain ethanol-induced hepatocyte apoptosis. VL-17A cells (HepG2 cells overexpressing alcohol dehydrogenase and cytochrome P450-2E1) were exposed to ethanol for different time periods. Western blots were performed for MKP-1, phospho-JNK, phosphotyrosine, and protein kinase Cdelta (PKCdelta). Electrophoretic mobility shift assays for AP-1 were performed. Apoptosis was measured by caspase-3 activity assay, TUNEL, and 4',6-diamidino-2-phenylindole staining. Reactive oxygen species were neutralized by overexpressing both superoxide dismutase-3 and catalase genes using lentiviral vectors in VL-17A cells. Ethanol incubation markedly decreased the MKP-1 protein levels to 15% of control levels and was associated with sustained phosphorylation of p46 JNK and p54 JNK, as well as increased apoptosis. VL-17A cells overexpressing superoxide dismutase-3 and catalase, treatment with a tyrosine kinase inhibitor, or incubation of the cells with PKCdelta small interference RNAs significantly inhibited the ethanol-induced MKP-1 degradation and apoptosis. Ethanol-induced oxidative stress enhanced the tyrosine phosphorylation of PKCdelta, which in turn caused the proteasomal degradation of MKP-1, leading to sustained JNK activation and increased apoptosis in VL-17A cells.
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http://dx.doi.org/10.1074/jbc.M703729200DOI Listing
November 2007

Ethanol induces apoptosis in hepatocytes by a pathway involving novel protein kinase C isoforms.

Cell Signal 2007 Nov 27;19(11):2339-50. Epub 2007 Jul 27.

Department of Internal Medicine, Transplant Research Program, University of California, Davis Medical Center, Sacramento, CA 95817, USA.

Unlabelled: Ethanol abuse is one of the major etiologies of cirrhosis. Ethanol has been shown to induce apoptosis via activation of oxidative stress, mitogen-activated protein kinases (MAPK), and tyrosine kinases. However, there is a paucity of data that examine the interplay among these molecules. In the present study we have systematically elucidated the role of novel protein kinase C isoforms (nPKC; PKCdelta and PKCepsilon) in ethanol-induced apoptosis in hepatocytes. Ethanol enhanced membrane translocation of PKCdelta and PKCepsilon, which was associated with the phosphorylation of p38MAPK, p42/44MAPK and JNK1/2, and the nuclear translocation of NF-kappaB and AP-1. This resulted in increased apoptosis in primary rat hepatocytes. Inhibition of both PKCdelta and PKCepsilon resulted in a decreased MAPK activation, decreased nuclear translocation of NF-kappaB and AP-1, and inhibition of apoptosis. In addition, ethanol activated the tyrosine phosphorylation of PKCdelta via tyrosine kinase in hepatocytes. The tyrosine phosphorylated PKCdelta was cleaved by caspase-3 and these fragments were translocated to the nucleus. Inhibition of ethanol-induced oxidative stress blocked the membrane translocation of PKCdelta and PKCepsilon, and the tyrosine phosphorylation of PKCdelta in hepatocytes. Inhibition of oxidative stress, tyrosine kinase or caspase-3 activity caused a decreased nuclear translocation of PKCdelta in response to ethanol, and was associated with less apoptosis.

Conclusion: These results provide a newly-described mechanism by which ethanol induces apoptosis via activation of nPKC isoforms in hepatocytes.
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http://dx.doi.org/10.1016/j.cellsig.2007.07.013DOI Listing
November 2007

Delivery of antioxidative enzyme genes protects against ischemia/reperfusion-induced liver injury in mice.

Liver Transpl 2006 Dec;12(12):1869-79

Transplant Research Institute, University of California, Davis Medical Center, Sacramento, CA 95817, USA.

Hepatic ischemia/reperfusion (I/R) injury is characterized by the generation of reactive oxygen species (ROS), such as superoxide anions and hydrogen peroxide. The aim of this study is to investigate whether antioxidative gene delivery by our polylipid nanoparticles (PLNP) is an effective approach for prevention of the injury. Polyplexes of extracellular superoxide dismutase (EC-SOD) and/or catalase genes were injected via the portal vein 1 day prior to a warm I/R procedure in mice. The effects of the gene delivery were determined 6 hours after starting reperfusion. PLNP-mediated antioxidative gene delivery led to a marked increase in human EC-SOD and catalase gene expression in the liver. Liver superoxide dismutase (SOD) and catalase activity both increased approximately 10-fold. Increased liver superoxide anion levels caused by the I/R procedure were reduced to normal levels by EC-SOD gene delivery. The overexpression of these 2 antioxidative genes significantly suppressed the I/R-induced elevation of serum alanine aminotransferase (ALT) levels, decreased liver malondialdehyde content, restored glutathione reserve, and improved liver histology. In conclusion, EC-SOD or catalase gene delivery by PLNP resulted in high levels of the transgene activity in the liver, and markedly attenuated hepatic I/R injury. The protection is directly associated with elevated antioxidative enzyme activity as the result of the gene delivery. This novel approach may become a potential therapy to improve graft function and survival after liver transplantation.
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http://dx.doi.org/10.1002/lt.21001DOI Listing
December 2006

Development of an in vitro screening assay to test the antiinflammatory properties of dietary supplements and pharmacologic agents.

Clin Chem 2005 Dec 15;51(12):2252-6. Epub 2005 Sep 15.

Laboratory for Atherosclerosis and Metabolic Research, Department of Pathology & Laboratory Medicine, University of California, Davis Medical Center, Sacramento, 95817, USA.

Background: Monocytes and macrophages are critical in atherosclerosis and on stimulation secrete proinflammatory, proatherogenic cytokines such as tumor necrosis factor (TNF)-alpha and interleukin (IL)-1beta, which have been shown to be present in atherosclerotic lesions. The aim of this study was to develop a rapid in vitro screening assay to test the antiinflammatory effects of different compounds.

Methods And Results: THP-1 cells (human monocytic cell line) were stimulated with different concentrations of lipopolysaccharide (LPS; 0 to 1000 microg/L) and for different times (4, 12, and 24 h), and the secretion of proinflammatory cytokines (IL-1, IL-6, and TNF-alpha) was assessed. TNF-alpha secretion was maximum at the lowest LPS concentration (100 microg/L) and at shortest duration of incubation (4 h). Maximum secretion of IL-1beta and IL-6 was achieved at 24 h with higher doses of LPS. Treatment of THP-1 with various test compounds such as dietary supplements (alpha-tocopherol, N-acetylcysteine, catechin and epigallocatechin gallate) as well as pharmacologic agents (statins, peroxisome proliferator-activated receptor-gamma agonists, and an angiotensin II receptor blocker) significantly inhibited LPS-stimulated TNF-alpha release.

Conclusions: The release of TNF-alpha after stimulation of THP-1 cells with LPS is a valid model system to test novel compounds for potential antiinflammatory effects.
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http://dx.doi.org/10.1373/clinchem.2005.056093DOI Listing
December 2005

Hyperglycemia induces monocytic release of interleukin-6 via induction of protein kinase c-{alpha} and -{beta}.

Diabetes 2005 Jan;54(1):85-91

Laboratory for Atherosclerosis and Metabolic Research, the University of California Davis Medical Center, 4635, II Ave., Res. 1 Bldg., Rm. 3000, Sacramento, CA 95817, USA.

Diabetes confers an increased propensity to atherosclerosis. Inflammation is pivotal in atherogenesis, and diabetes is a proinflammatory state. Interleukin (IL)-6, in addition to inducing the acute-phase response, contributes to insulin resistance. Monocytes from type 2 diabetic patients secrete increased IL-6. The aim of this study was to examine molecular mechanisms for increased IL-6 release from monocytes under hyperglycemia. Monocytic cells (THP-1) were cultured in the presence of 5.5 mmol/l (normal) or 15 mmol/l (high) glucose and mannitol. Secreted IL-6, intracellular IL-6, and IL-6 mRNA were significantly increased with hyperglycemia (P < 0.001). Incubation of cells with inhibitors of reactive oxygen species failed to affect high-glucose-induced IL-6 release. Pan-protein kinase C (PKC) inhibitors significantly decreased high-glucose-induced IL-6 release. A specific inhibitor of p38 mitogen-activated protein kinase (MAPK; SB 202190), but not the extracellular signal-regulated kinase inhibitor PD98059, significantly decreased high-glucose-induced IL-6 release. Furthermore, the PKC-alpha/beta2 inhibitor decreased p38MAPK and the resulting high-glucose-induced IL-6 release. Both antisense oligos to PKC-beta and -alpha as well as small interfering RNA (siRNA) to PKC-alpha and -beta resulted in significantly decreased high-glucose-induced IL-6 release. Nuclear factor-kappaB (NF-kappaB) inhibitors significantly decreased IL-6 mRNA and protein. siRNA to PKC-beta and -alpha also significantly decreased NF-kappaB activity and IL-6 release. The combination was not additive to either siRNA alone, suggesting that they work through a common pathway. Thus, IL-6 release from monocytes under hyperglycemia appears to be mediated via upregulation of PKC, through p38MAPK and NF-kappaB, resulting in increased mRNA and protein for IL-6. Thus, inhibition of PKC-alpha and -beta can ameliorate the proinflammatory state of diabetes.
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http://dx.doi.org/10.2337/diabetes.54.1.85DOI Listing
January 2005

C-reactive protein: risk marker or mediator in atherothrombosis?

Hypertension 2004 Jul 17;44(1):6-11. Epub 2004 May 17.

Laboratory for Atherosclerosis and Metabolic Research, UC Davis Medical Center, 4635 Second Ave, Res 1 Bldg, Rm 3000, Sacramento, Calif 95817, USA.

Inflammation appears to be pivotal in all phases of atherosclerosis from the fatty streak lesion to acute coronary syndromes. An important downstream marker of inflammation is C-reactive protein (CRP). Numerous studies have shown that CRP levels predict cardiovascular disease in apparently healthy individuals. This has resulted in a position statement recommending cutoff levels of CRP <1.0, 1.0 to 3.0, and >3.0 mg/L equating to low, average, and high risk for subsequent cardiovascular disease. More interestingly, much in vitro data have now emerged in support of a role for CRP in atherogenesis. To date, studies largely in endothelial cells, but also in monocyte-macrophages and vascular smooth muscle cells, support a role for CRP in atherogenesis. The proinflammatory, proatherogenic effects of CRP that have been documented in endothelial cells include the following: decreased nitric oxide and prostacyclin and increased endothelin-1, cell adhesion molecules, monocyte chemoattractant protein-1 and interleukin-8, and increased plasminogen activator inhibitor-1. In monocyte-macrophages, CRP induces tissue factor secretion, increases reactive oxygen species and proinflammatory cytokine release, promotes monocyte chemotaxis and adhesion, and increases oxidized low-density lipoprotein uptake. Also, CRP has been shown in vascular smooth muscle cells to increase inducible nitric oxide production, increase NFkappa(b) and mitogen-activated protein kinase activities, and, most importantly, upregulate angiotensin type-1 receptor resulting in increased reactive oxygen species and vascular smooth muscle cell proliferation. Future studies should be directed at delineating the molecular mechanisms for these important in vitro observations. Also, studies should be directed at confirming these findings in animal models and other systems as proof of concept. In conclusion, CRP is a risk marker for cardiovascular disease and, based on future studies, could emerge as a mediator in atherogenesis.
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http://dx.doi.org/10.1161/01.HYP.0000130484.20501.dfDOI Listing
July 2004