Changes in expression and immunolocalization of protein associated with toxic bile salts-induced apoptosis in rat hepatocytes

Cholestatic liver injury results from the accumulation of toxic bile salts within the liver. The aim of the present study was to examine the temporal changes in expression and immunolocalization of protein associated with apoptosis in cholestatic rat liver. Rats were anesthetized and cholestasis was induced by double ligation of the common bile duct and sectioning between the ligatures. The animals were euthanized at day 3 and at weeks 1, 2, 4, and 6 after bile duct ligation (BDL). Apoptotic cell death was increased fivefold after 3 days of BDL, decreased over 2 weeks, and remained constant thereafter as has been demonstrated by TUNEL staining. Western blot analysis for Bax, Bcl-2, cytochrome c, and p53 were performed. Results show that total cellular Bax protein was increased 3 days after BDL and decreased over time thereafter. We observed the translocation of Bax to mitochondria and subsequent release of cytochrome c. According to our immunohistochemical data, nuclear p53 increased 3 days after BDL, but cytoplasmic sequestration of p53 was observed after 1 week. The expression of c-Myc was inhibited by 3 days, but increased at later stages following BDL. Bcl-2 was increased over time in BDL rats. Our data suggest toxic bile salts-induced hepatocellular apoptosis is related to differential expression of Bcl-2 family member protein and release of cytochrome c. Cellular localization of p53 plays an important role in apoptotic death of hepatocytes in BDL rats.