Publications by authors named "Mengru Bai"

11 Publications

  • Page 1 of 1

Downregulation of glucose-6-phosphatase expression contributes to fluoxetine-induced hepatic steatosis.

J Appl Toxicol 2021 Aug 12;41(8):1232-1240. Epub 2020 Nov 12.

Institute of Pharmaceutical Analysis and Drug Metabolism, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.

Fluoxetine is a first-line selective serotonin reuptake inhibitor widely applied for the treatment of depression; however, it induces abnormal hepatic lipid metabolism. Considering decreased expression or function of glucose-6-phosphatase (G6Pase), a key enzyme in gluconeogenesis, or the upregulation of fatty acid uptake, causes hepatic lipid accumulation. The aim of this study was to elucidate whether G6Pase regulation and fatty acid uptake alteration contribute to fluoxetine-induced abnormal hepatic lipid metabolism. Our study revealed that 8-week oral administration of fluoxetine dose-dependently increased hepatic triglyceride, causing hepatic steatosis. Concomitantly, the expression of G6Pase in mouse livers and primary mouse hepatocytes (PMHs) was downregulated in a concentration-dependent manner. Furthermore, fluoxetine increased the concentrations of glucose-6-phosphate (G6Pase substrate) and acetyl CoA (the substrate for de novo lipogenesis) in mouse livers. Additionally, fluoxetine also induced lipid accumulation and downregulated G6Pase expression in HepG2 cells. However, the uptake of green fluorescent fatty acid (BODIPY™ FL C16) in PMHs was not changed after fluoxetine treatment, indicating that fluoxetine-induced hepatic steatosis was not associated with fatty acid uptake alteration. In conclusion, fluoxetine downregulated hepatic G6Pase expression, subsequently enhanced the transformation of glucose to lipid, and ultimately resulted in hepatic steatosis, but with no impact on fatty acid uptake.
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http://dx.doi.org/10.1002/jat.4109DOI Listing
August 2021

Downregulation of OCTN2 by cytokines plays an important role in the progression of inflammatory bowel disease.

Biochem Pharmacol 2020 08 21;178:114115. Epub 2020 Jun 21.

Laboratory of Drug Metabolism and Pharmaceutical Analysis, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China. Electronic address:

Inflammatory bowel diseases (IBD) are characterized by chronic relapsing disorders of the gastrointestinal tract. OCTN2 (SLC22A5) and its substrate l-carnitine (l-Car) play crucial roles in maintaining normal intestinal function. An aim of this study was to delineate the expression alteration of OCTN2 in IBD and its underlying mechanism. We also investigated the impact of OCTN2 on IBD progression and the possibility of improving IBD through OCTN2 regulation. Our results showed decreased OCTN2 expression levels and l-Car content in inflamed colon tissues of IBD patients and mice, which negatively correlated with the degree of colonic inflammation in IBD mice. Mixed proinflammatory cytokines TNF-α, IL-1β and IFNγ downregulated the expression of OCTN2 and subsequently reduced the l-Car content through PPARγ/RXRα pathways in FHC cells. OCTN2 silencing reduced the proliferation rate of the colon cells, whereas OCTN2 overexpression increased the proliferation rate. Furthermore, the ability of PPARγ agonist, luteolin, to increase OCTN2 expression resulted in the alleviation of colonic inflammatory responses. In conclusion, OCTN2 was downregulated in IBD by proinflammatory cytokines via the PPARγ/RXRα pathways, which reduced l-Car concentration and subsequently induced IBD deterioration. Upregulation of OCTN2 by the PPARγ agonist alleviated colonic inflammation. Our findings suggest that, OCTN2 may serve as a therapeutic target for IBD therapy.
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http://dx.doi.org/10.1016/j.bcp.2020.114115DOI Listing
August 2020

Up-regulation of hepatic fatty acid transporters and inhibition/down-regulation of hepatic OCTN2 contribute to olanzapine-induced liver steatosis.

Toxicol Lett 2019 Nov 19;316:183-193. Epub 2019 Aug 19.

Institute of Pharmaceutical Analysis and Drug Metabolism, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China. Electronic address:

Olanzapine, a representative of antipsychotics, is a first-line drug for treatment of schizophrenia. However, olanzapine-induced liver steatosis limits its clinical utilization. This study is to explore the mechanism of liver steatosis induced by olanzapine based on the regulation of transporters involved in uptake and oxidation of fatty acids. Our results revealed that 12-week oral administration of olanzapine increased hepatic triglyceride(TG), caused liver steatosis. Our further studies showed that the expression of fatty acid transporter 2(FATP2) and fatty acid binding protein 1(FABP1) were up-regulated in liver of female mice after 12-week olanzapine exposure, as well as in primary mouse hepatocytes treated with olanzapine. Olanzapine treatment also reduced hepatic β-hydroxybutyrate level (indicator of fatty acid β-oxidation), meanwhile, the L-carnitine (L-Car) concentration in liver of olanzapine group was significantly lower than that in control group. Further study demonstrated that both mRNA and protein expression of hepatic OCTN2 (carnitine/organic cation transporter 2) were obviously down-regulated in male mice after 12-week olanzapine treatment. Also, olanzapine markedly inhibited L-Car uptake in MDCK-hOCTN2 cells (1.06 μM of IC), HepG2 cells and primary mouse hepatocytes. Supplementation of L-Car attenuated hepatic TG rise and improved simple steatosis in olanzapine treatment mice. Taken together, up-regulation of FATP2/FABP1 and down-regulation/inhibition of hepatic OCTN2 probably contribute to olanzapine-induced liver steatosis. Supplementation of L-Car is a promising strategy to attenuate olanzapine-induced simple steatosis.
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http://dx.doi.org/10.1016/j.toxlet.2019.08.013DOI Listing
November 2019

Roles of organic anion transporter 2 and equilibrative nucleoside transporter 1 in hepatic disposition and antiviral activity of entecavir during non-pregnancy and pregnancy.

Br J Pharmacol 2019 09 10;176(17):3236-3249. Epub 2019 Jul 10.

Laboratory of Pharmaceutical Analysis and Drug Metabolism, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China.

Background And Purpose: Entecavir (ETV), a first-line antiviral drug against hepatitis B virus (HBV), has the possibility to be used to prevent mother-to-child transmission. The aim of present study was to clarify the mechanism of ETV uptake into hepatocytes and evaluate the alteration of ETV's hepatic distribution during pregnancy.

Experimental Approach: The roles of equilibrative nucleotide transporter (ENT) 1 and organic anion transporter (OAT) 2 in ETV accumulation and anti-HBV efficacy were studied in human ENT1 or OAT2 overexpressed cell models and HepG2.2.15 cells, respectively; meanwhile, the liver-to-plasma ETV concentration ratios in non-pregnant and pregnant mice were measured to evaluate the effect of pregnancy on ETV hepatic distribution.

Key Results: ETV was shown to be a substrate of ENT1 and OAT2. An ENT1 inhibitor significantly decreased the efficacy of ETV in HepG2.2.15 cells, while overexpression of OAT2 increased susceptibility of HBV to ETV. The liver-to-plasma ETV concentration ratios in pregnant mice were sharply reduced; whereas, the absolute concentration of ETV in the liver did not obviously alter in pregnancy. Although oestradiol and progesterone showed a concentration-dependent inhibition on ETV accumulation both in hepatic cell lines and in primary human hepatocytes, a physiologically relevant concentration of oestradiol and progesterone did not affect antiviral activity of ETV.

Conclusions And Implications: OAT2 and ENT1 are the main transporters involved in the hepatic uptake and anti-HBV efficacy of ETV. The concentration of ETV in the liver was not obviously altered during pregnancy, which indicates that dosage adjustment in pregnancy is not necessary.
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http://dx.doi.org/10.1111/bph.14756DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6692639PMC
September 2019

Multiple Drug Transporters Contribute to the Placental Transfer of Emtricitabine.

Antimicrob Agents Chemother 2019 08 25;63(8). Epub 2019 Jul 25.

Women's Hospital, School of Medicine, Zhejiang University, Hangzhou, Zhejiang, China

Emtricitabine (FTC) is a first-line antiviral drug recommended for the treatment of AIDS during pregnancy. We hypothesized that transporters located in the placenta contribute to FTC transfer across the blood-placenta barrier. BeWo cells, cell models with stable or transient expression of transporter genes, primary human trophoblast cells (PHTCs), and small interfering RNAs (siRNAs) were applied to demonstrate which transporters were involved. FTC accumulation in BeWo cells was reduced markedly by inhibitors of equilibrative nucleoside transporters (ENTs), concentrative nucleoside transporters (CNTs), organic cation transporters (OCTs), and organic cation/carnitine transporter 1 (OCTN1) and increased by inhibitors of breast cancer resistance protein (BCRP) and multidrug resistance-associated proteins (MRPs). ENT1, CNT1, OCTN1, MRP1/2/3, and BCRP, but not ENT2, CNT3, OCTN2, or multidrug resistance protein 1 (MDR1), were found to transport FTC. FTC accumulation in PHTCs was decreased significantly by inhibitors of ENTs and OCTN1. These results suggest that ENT1, CNT1, and OCTN1 probably contribute to FTC uptake from maternal circulation to trophoblasts and that ENT1, CNT1, and MRP1 are likely involved in FTC transport between trophoblasts and fetal blood, whereas BCRP and MRP1/2/3 facilitate FTC transport from trophoblasts to maternal circulation. Coexistence of tenofovir or efavirenz with FTC in the cell medium did not influence FTC accumulation in BeWo cells or PHTCs.
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http://dx.doi.org/10.1128/AAC.00199-19DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6658773PMC
August 2019

Maternal Plasma l-Carnitine Reduction During Pregnancy Is Mainly Attributed to OCTN2-Mediated Placental Uptake and Does Not Result in Maternal Hepatic Fatty Acid -Oxidation Decline.

Drug Metab Dispos 2019 06 27;47(6):582-591. Epub 2019 Mar 27.

Laboratory of Pharmaceutical Analysis and Drug Metabolism, College of Pharmaceutical Sciences (M.B., Y.C., M.C., P.L., Z.M., H.Z., S.Z., H.J.) and Women's Hospital, School of Medicine (Q.Z., D.S., C.Z.), Zhejiang University, Hangzhou, People's Republic of China

l-Carnitine (l-Car) plays a crucial role in fatty acid -oxidation. However, the plasma l-Car concentration in women markedly declines during pregnancy, but the underlying mechanism and its consequences on maternal hepatic -oxidation have not yet been clarified. Our results showed that the plasma l-Car level in mice at gestation day (GD) 18 was significantly lower than that in nonpregnant mice, and the mean fetal-to-maternal plasma l-Car ratio in GD 18 mice was 3.0. Carnitine/organic cation transporter 2 (OCTN2) was highly expressed in mouse and human placenta and upregulated as gestation proceeds in human placenta, whereas expressions of carnitine transporter (CT) 1, CT2, and amino acid transporter B were extremely low. Further study revealed that renal peroxisome proliferator-activated receptor (PPAR) and OCTN2 were downregulated and the renal l-Car level was reduced, whereas the urinary excretion of l-Car was lower in late pregnant mice than in nonpregnant mice. Meanwhile, progesterone (pregnancy-related hormone) downregulated the expression of renal OCTN2 via PPAR-mediated pathway, and inhibited the activity of OCTN2, but estradiol, corticosterone, and cortisol did not. Unexpectedly, the maternal hepatic level of l-Car and -hydroxybutyrate (an indicator of mitochondrial -oxidation), and mRNA levels of several enzymes involved in fatty acid -oxidation in GD 18 mice were higher than that in nonpregnant mice. In conclusion, OCTN2 mediated l-Car transfer across the placenta played a major role in maternal plasma l-Car reduction during pregnancy, which did not subsequently result in maternal hepatic fatty acid -oxidation decrease.
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http://dx.doi.org/10.1124/dmd.119.086439DOI Listing
June 2019

Clozapine-induced reduction of l-carnitine reabsorption via inhibition/down-regulation of renal carnitine/organic cation transporter 2 contributes to liver lipid metabolic disorder in mice.

Toxicol Appl Pharmacol 2019 01 19;363:47-56. Epub 2018 Nov 19.

Laboratory of Pharmaceutical Analysis and Drug Metabolism, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, China. Electronic address:

Clozapine, an atypical antipsychotic drug, is widely utilized for the treatment of schizophrenia; however, clozapine-induced metabolic disorders, such as fatty liver and weight gain, warrant increased attention. Considering the crucial role of l-carnitine (L-Car) in fatty acid oxidation and carnitine/organic cation transporter (OCTN) 2 in renal reabsorption of L-Car, we aimed to study whether clozapine-induced liver lipid metabolic disorder is associated with L-Car dysregulation via inhibition/down-regulation of renal OCTN2. Our results reveal that clozapine inhibits L-Car uptake in MDCK-hOCTN2 cells with an IC value of 1.78 μM. Additionally, clozapine significantly reduces the uptake of L-Car in HK-2 cells, mouse primary cultured proximal tubular (mPCPT) cells and HepG2 cells. Acute (intraperitoneal injection) and 21-day successive oral administration of clozapine at 12.5, 25, and 50 mg/kg to mice resulted in 2-3-fold greater renal excretion of L-Car than in the vehicle group, and the concentration of L-Car in plasma and liver was significantly decreased. Concomitantly, mRNA and protein levels of mOctn2 in the kidney were markedly down regulated. Additionally, 28-day oral administration of clozapine induced increased triglyceride (TG) and total cholesterol (TCHO) levels in mouse livers, while L-Car (40 mg/kg - 1 g/kg) attenuated clozapine-induced liver TG and TCHO increase in a dose-dependent manner. These results indicate that clozapine-induced reduction of L-Car reabsorption via inhibition/down-regulation of renal OCTN2 contributes to liver lipid metabolic disorder. L-Car supplementation is probably an effective strategy to attenuate clozapine-induced abnormal lipid metabolism.
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http://dx.doi.org/10.1016/j.taap.2018.11.007DOI Listing
January 2019

Multiple organic cation transporters contribute to the renal transport of sulpiride.

Biopharm Drug Dispos 2017 Dec 20;38(9):526-534. Epub 2017 Nov 20.

Laboratory of Pharmaceutical Analysis and Drug Metabolism, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang, China.

Sulpiride, a selective dopamine D2 receptor blocker, is used widely for the treatment of schizophrenia, depression and gastric/duodenal ulcers. Because the great majority of sulpiride is positively charged at physiological pH 7.4, and ~70% of the dose recovered in urine is in the unchanged form after human intravenous administration of sulpiride, it is believed that transporters play an important role in the renal excretion of sulpiride. The aim of the present study was to explore which transporters contribute to the renal disposition of sulpiride. The results demonstrated that sulpiride was a substrate of human carnitine/organic cation transporter 1 (hOCTN1) and 2 (hOCTN2), human organic cation transporter 2 (hOCT2), human multidrug and toxin efflux extrusion protein 1 (hMATE1) and 2-K (hMATE2-K). Sulpiride accumulation from the basolateral (BL) to the apical (AP) side in MDCK-hOCT2/pcDNA3.1 cell monolayers was much greater than that in MDCK-hOCT2/hMATE1 cells, and cimetidine dramatically reduced the intracellular accumulation of sulpiride from BL to AP. In addition, the accumulation of sulpiride in mouse primary renal tubular cells (mPRTCs) was markedly reduced by inhibitors of Oct2 and Octns. The results implied that OCTN1, OCTN2, OCT2, MATE1 and MATE2-K probably contributed to the renal transfer of sulpiride, in which OCT2 mediated the uptake of sulpiride from the bloodstream to the proximal tubular cells, while MATEs contributed to the sulpiride efflux from the proximal tubular cells to the renal lumen, and OCTNs participated in both renal secretion and reabsorption.
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http://dx.doi.org/10.1002/bdd.2104DOI Listing
December 2017

Multiple drug transporters mediate the placental transport of sulpiride.

Arch Toxicol 2017 Dec 9;91(12):3873-3884. Epub 2017 Jun 9.

Laboratory of Pharmaceutical Analysis and Drug Metabolism, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, 866 Yuhangtang Road, Hangzhou, 310058, China.

Sulpiride is a typical antipsychotic drug for the treatment of schizophrenia, depression and other psychological disorders. It has been proven that a small amount of sulpiride could cross the human placenta using an ex vivo placental perfusion model. However, the placental transfer mechanism has not been elucidated. Considering the structure of sulpiride, we speculated that the transporters expressed in placenta might be involved in sulpiride uptake across the blood-placenta barrier. The aim of our study was to determine which transporters contributed to the placental transfer of sulpiride. Our results revealed that sulpiride was a substrate of human organic cation transporter (hOCT) 3, human multidrug resistance protein (hMDR) 1 and human breast cancer resistance protein (hBCRP) using transfected cells expressing respective transporters. In addition, the accumulation of sulpiride in BeWo cells (a human choriocarcinoma cell line) was obviously affected by inhibitors of carnitine/organic cation transporter (OCTN) 2, MDR1 and BCRP. The accumulation of sulpiride in primary human trophoblast cells was obviously affected by inhibitors of OCT3, OCTN1 and OCTN2. The above results indicate that hOCTN1 and hOCTN2 likely contribute to the sulpiride uptake from maternal circulation to trophoblast cells, while hMDR1 and hBCRP mediate the efflux from trophoblast cells to maternal circulation, and hOCT3 probably is involved in the bidirectional transport of sulpiride between the placenta and fetal blood.
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http://dx.doi.org/10.1007/s00204-017-2008-8DOI Listing
December 2017

Multiple SLC and ABC Transporters Contribute to the Placental Transfer of Entecavir.

Drug Metab Dispos 2017 03 6;45(3):269-278. Epub 2017 Jan 6.

Laboratory of Pharmaceutical Analysis and Drug Metabolism, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research, College of Pharmaceutical Sciences, Zhejiang University, Hangzhou, Zhejiang, China (Z.M., X.Y., T.J., M.B., S.Z., H.J.); and Women's Hospital School of Medicine Zhejiang University, Hangzhou, China (C.Z., D.S.)

Entecavir (ETV), a nucleoside analog with high efficacy against hepatitis B virus, is recommended as a first-line antiviral drug for the treatment of chronic hepatitis B. However, scant information is available on the use of ETV in pregnancy. To better understand the safety of ETV in pregnant women, we aimed to demonstrate whether ETV could permeate placental barrier and the underlying mechanism. Our study showed that small amount of ETV could permeate across placenta in mice. ETV accumulation in activated or nonactivated BeWo cells (treated with or without forskolin) was sharply reduced in the presence of 100 µM of adenosine, cytidine, and in Na free medium, indicating that nucleoside transporters possibly mediate the uptake of ETV. Furthermore, ETV was proved to be a substrate of concentrative nucleoside transporter (CNT) 2 and CNT3, of organic cation transporter (OCT) 3, and of breast cancer resistance protein (BCRP) using transfected cells expressing respective transporters. The inhibition of ETV uptake in primary human trophoblast cells further confirmed that equilibrative nucleoside transporter (ENT) 1/2, CNT2/3, OCT3, and organic cation/carnitine transporter (OCTN) 2 might be involved in ETV transfer in human placenta. Therefore, ETV uptake from maternal circulation to trophoblast cells was possibly transported by CNT2/3, ENT1/2, and OCTN2, whereas ETV efflux from trophoblast cells to fetal circulation was mediated by OCT3, and efflux from trophoblast cells to maternal circulation might be mediated by BCRP, multidrug resistance-associated protein 2, and P-glycoprotein. The information obtained in the present study may provide a basis for the use of ETV in pregnancy.
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http://dx.doi.org/10.1124/dmd.116.073304DOI Listing
March 2017

Interaction of six protoberberine alkaloids with human organic cation transporters 1, 2 and 3.

Xenobiotica 2016 2;46(2):175-83. Epub 2015 Jul 2.

a Laboratory of Pharmaceutical Analysis and Drug Metabolism, Zhejiang Province Key Laboratory of Anti-Cancer Drug Research , College of Pharmaceutical Sciences, Zhejiang University , Hangzhou , Zhejiang , P.R. China.

1. Organic cation transporters (OCTs) play an important role in drug safety and efficacy. Protoberberine alkaloids are ubiquitous organic cations or weak bases with remarkable biological actives. This study was to elucidate the potential interaction of alkaloids (coptisine, jatrorrhizine, epiberberine, berberrubine, palmatine and corydaline) with OCTs using Madin-Darby canine kidney (MDCK) cells stably expressing human OCT1, OCT2 and OCT3. 2. All the tested alkaloids significantly inhibited the uptake of MPP(+), a model OCT substrate, in MDCK-hOCTs cells with the IC50 of 0.931-9.65 μM. Additionally, coptisine, jatrorrhizine and epiberberine were substrates of all the hOCTs with the Km of 0.273-5.80 μM, whereas berberrubine was a substrate for hOCT1 and hOCT2, but not for hOCT3, the Km values were 1.27 and 1.66 μM, respectively. The transport capacity of coptisine in MDCK cells expressing the variants of hOCT1-P341L or hOCT2-A270S was significantly higher than that in wild-type (WT) cells with the Clint (Vmax/Km) of 379 ± 7.4 and 433 ± 5.7 μl/mg protein/min, respectively. 3. The above data indicate that the tested alkaloids are potent inhibitors, and coptisine, jatrorrhizine, epiberberine and berberrubine are substrates of hOCT1, hOCT2 and/or hOCT3 with high affinity. In addition, the variants (OCT1-P341L and OCT2-A270S) possess higher transport capacity to coptisine than WT hOCTs.
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http://dx.doi.org/10.3109/00498254.2015.1056283DOI Listing
November 2016
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