Cholestasis and Regulation of Genes Related to Drug Metabolism and Biliary Transport in Rat Liver Following Treatment with Cyclosporine A and Sirolimus (Rapamycin)

Abstract

Cyclosporine A and sirolimus are used alone or in combination as immunosuppressants in organ transplantation. To elucidate hepatic side effects, we examined hepatic mRNA of proteins involved in biliary and hepatocellular transport of drugs, formation of glutathione (GSH) and drug metabolising cytochrome P-450 enzymes (CYPs) in rats treated orally for 2 weeks with cyclosporine A (15 mg/kg/day), sirolimus (0.4 mg/kg/day), their combination (same doses), or vehicle. Liver function tests (alanine aminotransferase, alkaline phosphatase, g-glutamyl transferase and bilirubin) in blood were then analysed as were hepatic mRNA levels of canalicular transport proteins (Mrp2, Bsep, Mdr1b and Mdr2), sinusoidal transport proteins (Ntcp, Oatp1 and Oatp2), GSH related enzymes (g-glutamylcysteine synthetase light (GCSlc) and heavy (GCShc) chain subunits and glutathione-S-transferase) and CYPs (CYP3A9, CYP1A2, CYP2E1 and CYP2BI/ II). Cyclosporine A caused moderate cholestatic changes in liver enzymes, which was synergistically exacerbated by sirolimus. The data suggest that the underlying mechanisms behind cholestasis were not totally identical in the different treatment regimens. Cholestasis secondary to cyclosporine A could be related to reduction in mRNA expression of GSH synthesising enzymes and Mrp2, leading to reduced protection against oxidative stress and reduced bile acid-independent bile flow. After sirolimus treatment, Mrp2 mRNA was also reduced together with reduced levels of most CYPs and increased Oatp2, possibly leading to accumulation of toxic metabolites in the hepatocytes. The enhanced cholestatic effect of the combination treatment could be related to reduced GSH synthesising enzymes and even more pronounced reduction in Mrp2 mRNA and increase of Oatp2 mRNA.

A phase II pilot study of tacrolimus/sirolimus GVHD prophylaxis for sibling donor hematopoietic stem cell transplantation using 3 conditioning regimens

“…29 We observed higher tacrolimus levels in Bu/Cy compared with Flu/Mel, but not with TBI/VP16 (as shown in Table 3). The tacrolimus levels were not significantly associated with TMA in our univariate analysis; thus, it is unlikely that the increased risk of TMA in Bu/Cy was attributable to the tacrolimus levels.…”

Sirolimus is associated with veno-occlusive disease of the liver after myeloablative allogeneic stem cell transplantation

“…In animal models, sirolimus exposure decreases hepatic glutathione production. 39 The use of targeted oral dosing of busulfan or the use of the intravenous preparation of busulfan, with more reliable pharmacokinetics, may be associated with a lower incidence of VOD. 40,41 With an increased rate of VOD in the Cy/TBI cohort without a decrement in overall survival, there must be a compensatory decrease in non-VOD TRM or relapse rates when sirolimus is used, since the rate of mortality after VOD diagnosis was no different between groups.…”

Effect of Disease Pathologies on Transporter Expression and Function

“…Several studies have shown that drug transport is disrupted during liver diseases, leading to adverse drug reactions . A reduction in biliary excretion is a primary mechanism responsible for altered drug disposition and pharmacokinetics .…”