Cyclosporin A blocks bile acid synthesis in cultured hepatocytes by specific inhibition of chenodeoxycholic acid synthesis.
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ABSTRACT:
SUBMITTER: Princen HM
PROVIDER: S-EPMC1150079 | biostudies-other | 1991 Apr
REPOSITORIES: biostudies-other
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Project description:The bile salt export pump (BSEP) is responsible for the export of bile acid from hepatocytes. Impaired transcellular transport of bile acids in hepatocytes with mutations in BSEP causes cholestasis. Compensatory mechanisms to regulate the intracellular bile acid concentration in human hepatocytes with BSEP deficiency remain unclear. To define pathways that prevent cytotoxic accumulation of bile acid in hepatocytes, we developed a human induced pluripotent stem cell-based model of isogenic BSEP-deficient hepatocytes in a Transwell culture system. Induced hepatocytes (i-Heps) exhibited defects in the apical export of bile acids but maintained a low intracellular bile acid concentration by inducing basolateral export. Modeling the autoregulation of bile acids on hepatocytes, we found that BSEP-deficient i-Heps suppressed de novo bile acid synthesis using the FXR pathway via basolateral uptake and export without apical export. These observations inform the development of therapeutic targets to reduce the overall bile acid pool in patients with BSEP deficiency.
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Project description:Transporter-mediated alterations in bile acid disposition may have significant toxicological implications. Current methods to predict interactions are limited by the interplay of multiple transporters, absence of protein in the experimental system, and inaccurate estimates of inhibitor concentrations. An integrated approach was developed to predict altered bile acid disposition due to inhibition of multiple transporters using the model bile acid taurocholate (TCA). TCA pharmacokinetic parameters were estimated by mechanistic modeling using sandwich-cultured human hepatocyte data with protein in the medium. Uptake, basolateral efflux, and biliary clearance estimates were 0.63, 0.034, and 0.074 mL/min/g liver, respectively. Cellular total TCA concentrations (Ct,Cells) were selected as the model output based on sensitivity analysis. Monte Carlo simulations of TCA Ct,Cells in the presence of model inhibitors (telmisartan and bosentan) were performed using inhibition constants for TCA transporters and inhibitor concentrations, including cellular total inhibitor concentrations ([I]t,cell) or unbound concentrations, and cytosolic total or unbound concentrations. For telmisartan, the model prediction was accurate with an average fold error (AFE) of 0.99-1.0 when unbound inhibitor concentration ([I]u) was used; accuracy dropped when total inhibitor concentration ([I]t) was used. For bosentan, AFE was 1.2-1.3 using either [I]u or [I]t This difference was evaluated by sensitivity analysis of the cellular unbound fraction of inhibitor (fu,cell,inhibitor), which revealed higher sensitivity of fu,cell,inhibitor for predicting TCA Ct,Cells when inhibitors exhibited larger ([I]t,cell/IC50) values. In conclusion, this study demonstrated the applicability of a framework to predict hepatocellular bile acid concentrations due to drug-mediated inhibition of transporters using mechanistic modeling and cytosolic or cellular unbound concentrations.
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Project description:Addition of foetal-bovine serum to rat hepatocytes cultured in Williams E medium resulted in improved maintenance of bile-acid-synthetic capacity and cholesterol 7 alpha-hydroxylase activity as compared with cultures supplemented with rat or newborn-bovine serum or cultures in a hormonally defined serum-free medium. Minimally, 5% (v/v) foetal-bovine serum was necessary to maintain these liver-specific functions. Serum factor(s) responsible for these effects were not dialysable or associated with lipoproteins, but were removed by charcoal extraction.
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Project description:Bile acids (BAs) are detergents essential for intestinal absorption of lipids. Disruption of BA homeostasis can lead to severe liver damage. BA metabolism is therefore under strict regulation by sophisticated feedback mechanisms. The hormone-like protein Fibroblast growth factor 19 (FGF19) is essential for maintaining BA homeostasis by down regulating BA synthesis. Here, the impact of both FGF19 and chenodeoxycholic acid (CDCA) on primary human hepatocytes was investigated and a possible autocrine/paracrine function of FGF19 in regulation of BA synthesis evaluated. Primary human hepatocytes were treated with CDCA, recombinant FGF19 or conditioned medium containing endogenously produced FGF19. RNA sequencing revealed that treatment with CDCA causes deregulation of transcripts involved in BA metabolism, whereas treatment with FGF19 had minor effects. CDCA increased FGF19 mRNA expression within 1 h. We detected secretion of the resulting FGF19 protein into medium, mimicking in vivo observations. Furthermore, medium enriched with endogenously produced FGF19 reduced BA synthesis by down regulating CYP7A1 gene expression. However, following knockdown of FGF19, CDCA still independently decreased BA synthesis, presumably through the regulatory protein small heterodimer partner (SHP). In summary, we show that in primary human hepatocytes CDCA regulates BA synthesis in an FGF19-independent manner.
| S-EPMC7937932 | biostudies-literature
Project description:Hepatocellular accumulation of bile acids due to inhibition of the canalicular bile salt export pump (BSEP/ABCB11) is one proposed mechanism of drug-induced liver injury (DILI). Some hepatotoxic compounds also are potent inhibitors of bile acid uptake by Na(+)-dependent taurocholate cotransporting polypeptide (NTCP/SLC10A1). This study used a cassette dosing approach in rat and human sandwich-cultured hepatocytes (SCH) to determine whether known or suspected hepatotoxic drugs inhibit bile acid transport individually or in combination. [(3)H]-Taurocholate served as the NTCP/BSEP probe substrate. Individually, cyclosporin A and rifampin decreased taurocholate in vitro biliary clearance (Cl(biliary)) and biliary excretion index (BEI) by more than 20% in rat SCH, suggesting that these drugs primarily inhibited canalicular efflux. In contrast, ampicillin, carbenicillin, cloxacillin, nafcillin, oxacillin, carbamazepine, pioglitazone, and troglitazone decreased the in vitro Cl(biliary) by more than 20% with no notable change in BEI, suggesting that these drugs primarily inhibited taurocholate uptake. Cassette dosing (n=2-4 compounds per cassette) in rat SCH yielded similar findings, and results in human SCH were consistent with rat SCH. In summary, cassette dosing in SCH is a useful in vitro approach to identify compounds that inhibit the hepatic uptake and/or excretion of bile acids, which may cause DILI.
| S-EPMC3129609 | biostudies-literature
Project description:Caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), COVID-19 is a virus-induced inflammatory disease of the airways and lungs that leads to severe multi-organ damage and death. Here we show that cellular lipid synthesis is required for SARS-CoV-2 replication and offers an opportunity for pharmacological intervention. Screening a short-hairpin RNA sublibrary that targets metabolic genes, we identified genes that either inhibit or promote SARS-CoV-2 viral infection, including two key candidate genes, ACACA and FASN, which operate in the same lipid synthesis pathway. We further screened and identified several potent inhibitors of fatty acid synthase (encoded by FASN), including the US Food and Drug Administration-approved anti-obesity drug orlistat, and found that it inhibits in vitro replication of SARS-CoV-2 variants, including more contagious new variants, such as Delta. In a mouse model of SARS-CoV-2 infection (K18-hACE2 transgenic mice), injections of orlistat resulted in lower SARS-CoV-2 viral levels in the lung, reduced lung pathology and increased mouse survival. Our findings identify fatty acid synthase inhibitors as drug candidates for the prevention and treatment of COVID-19 by inhibiting SARS-CoV-2 replication. Clinical trials are needed to evaluate the efficacy of repurposing fatty acid synthase inhibitors for severe COVID-19 in humans.
| S-EPMC8475461 | biostudies-literature
Project description:This SuperSeries is composed of the SubSeries listed below.
2024-10-09 | GSE279099 | GEO
Project description:Elobixibat is a minimally absorbed ileal bile acid (BA) transporter (IBAT) inhibitor in development against chronic constipation (CC) and constipation-predominant Irritable Bowel Syndrome (IBS-C). CC is associated with an increased risk for cardiovascular disease and type2 diabetes mellitus. The objectives of this study were to evaluate metabolic effects of elobixibat. Effects on plasma lipids and BA synthesis were evaluated utilizing a 4-week, placebo-controlled study in patients with dyslipidemia while changes of glucagon-like peptide-1 (GLP-1) by elobixibat was assayed in samples from a 14 day high-dose elobixibat study in patients with CC.Thirty-six dyslipidemic patients, 21 females, mean age 63 years, were randomized to 2.5 mg or 5 mg elobixibat or placebo once daily for four weeks. The primary endpoint was the change in low density lipoprotein (LDL) cholesterol. Secondary endpoints included other lipid parameters and serum 7?-hydroxy-4-cholesten-3-one (C4), a marker of BA (bile acid) synthesis. Another study, in 36 patients with CC treated with high dose elobixibat; 15 mg or 20 mg/day or placebo for 14 days, was evaluated for changes in GLP-1.In the dyslipidemia study LDL cholesterol was reduced by 7.4 % (p?=?0.044), and the LDL/HDL ratio was decreased by 18 % (p?=?0.004). Serum C4 increased, indicating that BA synthesis was induced. No serious adverse events were recorded. In the CC study, GLP-1 increased significantly in both the 15 mg (20.7?±?2.4 pmol/L; p?=?0.03) and the 20 mg group (25.6?±?4.9 pmol/L; p?=?0.02).Elobixibat reduces LDL cholesterol and LDL/HDL ratio and increase circulating peak GLP-1 levels, the latter in line with increased intestinal BA mediated responses in humans.ClinicalTrial.gov: NCT01069783 and NCT01038687 .
| S-EPMC4511433 | biostudies-literature
Project description:Deficiency of multidrug resistance 2 (mdr2), a canalicular phospholipid floppase, leads to excretion of low-phospholipid "toxic" bile causing progressive cholestasis. We hypothesize that pharmacological inhibition of the ileal, apical sodium-dependent bile acid transporter (ASBT), blocks progression of sclerosing cholangitis in mdr2(-/-) mice. Thirty-day-old, female mdr2(-/-) mice were fed high-fat chow containing 0.006% SC-435, a minimally absorbed, potent inhibitor of ASBT, providing, on average, 11 mg/kg/day of compound. Bile acids (BAs) and phospholipids were measured by mass spectrometry. Compared with untreated mdr2(-/-) mice, SC-435 treatment for 14 days increased fecal BA excretion by 8-fold, lowered total BA concentration in liver by 65%, reduced total BA and individual hydrophobic BA concentrations in serum by >98%, and decreased plasma alanine aminotransferase, total bilirubin, and serum alkaline phosphatase levels by 86%, 93%, and 55%, respectively. Liver histology of sclerosing cholangitis improved, and extent of fibrosis decreased concomitant with reduction of hepatic profibrogenic gene expression. Biliary BA concentrations significantly decreased and phospholipids remained low and unchanged with treatment. The phosphatidylcholine (PC)/BA ratio in treated mice corrected toward a ratio of 0.28 found in wild-type mice, indicating decreased bile toxicity. Hepatic RNA sequencing studies revealed up-regulation of putative anti-inflammatory and antifibrogenic genes, including Ppara and Igf1, and down-regulation of several proinflammatory genes, including Ccl2 and Lcn2, implicated in leukocyte recruitment. Flow cytometric analysis revealed significant reduction of frequencies of hepatic CD11b(+) F4/80(+) Kupffer cells and CD11b(+) Gr1(+) neutrophils, accompanied by expansion of anti-inflammatory Ly6C(-) monocytes in treated mdr2(-/-) mice.Inhibition of ASBT reduces BA pool size and retention of hydrophobic BA, favorably alters the biliary PC/BA ratio, profoundly changes the hepatic transcriptome, attenuates recruitment of leukocytes, and abrogates progression of murine sclerosing cholangitis.
| S-EPMC4713368 | biostudies-literature
Project description:ContextAlterations in bile acid (BA) synthesis and transport have the potential to affect multiple metabolic pathways in the pathophysiology of obesity.ObjectiveThe objective of the study was to investigate the effects of obesity on serum fluctuations of BAs and markers of BA synthesis.DesignWe measured BA fluctuations in 11 nonobese and 32 obese subjects and BA transporter expression in liver specimens from 42 individuals and specimens of duodenum, jejunum, ileum, colon, and pancreas from nine individuals.Main outcome measuresWe analyzed serum BAs and markers of BA synthesis after overnight fasting, during a hyperinsulinemic-euglycemic clamp, or a mixed-meal tolerance test and the association of BA transporter expression with body mass index.ResultsBA synthesis markers were 2-fold higher (P < .01) and preferentially 12α-hydroxylated (P < .05) in obese subjects, and both measures were correlated with clamp-derived insulin sensitivity (r = -0.62, P < .0001, and r = -0.39, P = .01, respectively). Insulin infusion acutely reduced serum BAs in nonobese subjects, but this effect was blunted in obese subjects (δBAs -44.2% vs -4.2%, P < .05). The rise in serum BAs postprandially was also relatively blunted in obese subjects (δBAs +402% vs +133%, P < .01). Liver expression of the Na+-taurocholate cotransporting polypeptide and the bile salt export pump were negatively correlated with body mass index (r = -0.37, P = .02, and r = -0.48, P = .001, respectively).ConclusionsObesity is associated with increased BA synthesis, preferential 12α-hydroxylation, and impaired serum BA fluctuations. The findings reveal new pathophysiological aspects of BA action in obesity that may lend themselves to therapeutic targeting in metabolic disease.
| S-EPMC4870845 | biostudies-literature