Cyclosporin A reduces canalicular membrane fluidity and regulates transporter function in rats

Abstract

Changes of the biliary canalicular membrane lipid content can affect membrane fluidity and biliary lipid secretion in rats. The immunosuppressant cyclosporin A is known to cause intrahepatic cholestasis. This study investigated whether cyclosporin A influenced canalicular membrane fluidity by altering membrane phospholipids or transporter expression. In male Sprague-Dawley rats, a bile-duct cannula was inserted to collect bile, and sodium taurocholate was infused (100 nmol/min per 100 g) for 60 min. During steady-state taurocholate infusion, cyclosporin A (20 mg/kg) or vehicle was injected intravenously and then bile was collected for 80 min. After killing the rats, canalicular membrane vesicles were prepared. Expression of canalicular membrane transporters was assessed by Western blotting and canalicular membrane vesicle fluidity was estimated by fluorescence polarization. Cyclosporin A reduced biliary lipid secretion along with a disproportionate reduction of lipids relative to bile acids. Cyclosporin A significantly decreased canalicular membrane fluidity along with an increase of the cholesterol/phospholipid molar ratio. Only expression of the transporter P-glycoprotein was increased by cyclosporin A. Because canalicular membrane transporter expression was largely unchanged by cyclosporin A despite a marked decrease of biliary lipid secretion, transporter activity may partly depend upon canalicular membrane fluidity.

Biliary diseases in heart transplanted patients: a comparison between cyclosporine a versus tacrolimus-based immunosuppression

“…Although there are numerous data about the lithogenic characteristics of a CsA-based immunosuppressive therapy in animal studies [ 2 , 4 - 6 , 12 - 14 ], as well as in transplanted patients [ 1 , 15 ], clinical studies of hepatobiliary complications using Tac, which is similarly metabolized like CsA, are rare. Most animal model studies showed no or only mild lithogenic effects of Tac compared with CsA [ 16 , 17 ].…”

Integrative “-Omics” Analysis in Primary Human Hepatocytes Unravels Persistent Mechanisms of Cyclosporine A-Induced Cholestasis

“…It is a neutral highly lipophilic cyclic peptide and a potent immunosuppressant which has contributed significantly to improvements in organ transplantation but also causes various toxic effects in the kidney and the liver . CsA inhibits biliary bile acid secretion, and inhibition of the secretion of biliary components such as phospholipids, cholesterol, and bilirubin has also been reported. − CsA, a multidrug resistance-1 protein (MDR1) substrate, may cause cholestatic liver injury through a number of mechanisms, , namely, (I) competitive inhibition of ATP-dependent transporters, − (II) inhibition of intrahepatic vesicle transport and targeting of ATP-dependent transporters to the canalicular membrane, ,, and (III) impairment of bile formation partly by increasing canalicular membrane fluidity without affecting the expression of canalicular transporters . Other studies suggest that CsA reduces the expression of glutathione synthesizing enzymes and the canalicular glutathione efflux system, multidrug resistance-associated protein 2 (MRP2), leading to reduced bile acid-independent bile flow …”

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

“…Bsep is correctly localized, its intrinsic transport activity is selectively inhibited. Although an increase in membrane cholesterol could be beneficial because it improves its localization in lipid raft microdomains, excessive cholesterol content decreases J o u r n a l P r e -p r o o f canalicular membrane fluidity [52], a factor thought to influence Bsep transport activity [53,54]; this may explain the somewhat lower Bsep-mediated transport of the exogenously administered TC in the SL alone group (see Fig. 2).…”

“…The 'rigidizing' effect of SL could be particularly detrimental in endotoxemic rats, since LPS per se reduces hepatocellular membrane fluidity by increasing the cellular influx of Ca 2+ [55], an effect that would add to the 'rigidizing' effect of SL itself, which may further decrease plasma membrane fluidity by alternative mechanisms associated with its effect as an aldosterone antagonist or as an estrogen-mimetic compound [46]. Unlike Bsep, circumstantial evidence suggest that Mrp2 transport function is scantily influenced by diminutions of plasma membrane fluidity [54], thus explaining the lack of impairment in DBSP biliary excretion when SL was administered alone (see Fig. 1), and the good relationship between improved localization and enhanced function observed for Mrp2 in SL+LPS co-treated group (see Figs.…”