Physiological concentrations of unconjugated bilirubin (UB) prevent oxidative stress (OS)-induced cholestasis in the isolated and perfused rat liver (IPRL)

BASIGLIO C.L.; TOLEDO F.D.; ARRIAGA S.M; BOAGLIO A. C.; OCHOA J. E; SANCHEZ POZZI E. J.; MOTTINO A. D.; ROMA M. G.

Buenos Aires

Congreso; VIII International Congress; 2013

Society for Free Radicals Biology and Medicine-South American Group

we previously showed in isolated rat hepatocyte couplets that OS induces secretory failure by endocytic internalization of canalicular transporters (Bsep and Mrp2), as a consequence of actin cytoskeleton disarrangement. Bilirubin is an endogenous antioxidant, but its role in the prevention of OS-induced cholestasis is uncertain. Here, we evaluated the capacity of UB to limit the alterations in biliary secretory function, using tert-butilhydroperoxide (tBuOOH) in the IPRL model. tBuOOH (75 µM) induced an abrupt increase in the oxidized glutathione-to-total glutathione ratio in bile (+167±28%) and pre-perfusion with UB (17 µM) prevented this phenomenon (p 0,05; n=4). Bile flow sharply dropped after perfusion with tBuOOH (-71±3%), while UB completely prevented this phenomenon (p 0,05; n=5). tBuOOH induced a decrease in biliary excretion of taurocholate (-46±12%) and dinitrophenyl-glutathione (-130±37%), and UB prevented both alterations (p 0,05; n=4). Confocal microscopy studies revealed that tBuOOH produces disruption of actin cytoskeleton as well as endocytic internalization of Bsep and Mrp2, while UB prevented these alterations. We conclude that physiological concentrations of UB counteract the alterations in biliary secretory function induced by OS, by preserving actin cytoskeleton integrity and, consequently, canalicular transporters localization. This would contribute to limit the progression of cholestatic hepatopathies which concur with high levels of OS.