Ethanol consumption alters expression and colocalization of bile salt export pump and multidrug resistance protein 2 in the rat

Abstract

Chronic ethanol consumption elicits detrimental changes of liver metabolism. By employing a 12-week-long feeding regimen, we investigated the effects of chronic ethanol consumption on the expression and localization of bile salt export pump (Bsep), a major canalicular exporter of bile salts, and multidrug resistance protein 2 (Mrp2), a canalicular organic anion transporter, in the rat liver. RT-PCR, confocal immunofluorescence microscopy, immunoblotting, and quantitative colocalization analysis were used to examine their gene and protein expression, and changes in the distribution of antigenic sites. Bsep mRNA was upregulated, while Mrp2 mRNA responded by downregulation. In agreement with mRNA, the expression of Bsep protein increased, while the expression of Mrp2 protein responded with a decrease, suggesting that the expression of both of them is transcriptionally regulated. Confocal immunofluorescence microscopy showed disruption of the colocalization of Bsep and Mrp2 proteins at the hepatocyte canalicular membrane and their relocation intracellularly. Quantitative colocalization analysis of Bsep and Mrp2 proteins revealed a steady decrease in the degree of colocalization and Mrp2 expression, indicating that although the properties of both transporters are affected, Mrp2 is altered more. These findings provide evidence that ethanol alters Bsep and Mrp2 canalicular transporters in the rat liver, at both the mRNA and protein levels. Mrp2 shows deeper involvement. Eight weeks appears to be a critical time point in this process.

Chronic alcohol feeding inhibits physiological and molecular parameters of intestinal and renal riboflavin transport

“…Also, our findings on the inhibition in RF intestinal and renal transport events by chronic alcohol exposure are in contrast to the induction in the activity/ expression of other transporters and channels (2,14,18,46). In summary, our data in the current study show that chronic alcohol exposure leads to impairment in the two important steps involved in the regulation of normal RF body homeostasis, i.e., the entry step at the level of the intestine and the exit step at the level of the kidneys.…”

The Role of the Sodium-Taurocholate Cotransporting Polypeptide (NTCP) and of the Bile Salt Export Pump (BSEP) in Physiology and Pathophysiology of Bile Formation

“…Hypoxia induces a down regulation of Bsep in rat and mouse liver [78,128]. Fatty liver disease in obsese Zucker rats is paralleled by a slight down regulation of Bsep [255], while in fatty livers of chronically ethanol fed rats, Bsep is upregulated at the mRNA and protein level [354]. Taken together, in animal models of liver injury, Bsep is only mildly affected at the expression level but may alter its subcellular localization [92,262].…”

State-of-the-art technologies, current opinions and developments, and novel findings: news from the field of histochemistry and cell biology

“…Besides aVecting bile production (see Zinchuk et al 2007), cholestasis apparently increases permeability of this barrier. Maly and Landmann (2008) investigated the changes in molecular composition of TJ proteins after bile duct ligation and release.…”