PI3K/Akt signaling pathway is involved in estradiol 17ß-D-glucuronide-induced cholestasis: complementarity with cPKC

BOAGLIO, AC; ZUCCHETTI, AE; SANCHEZ POZZI, EJ; PELLEGRINO, JM; OCHOA, JE; MOTTINO, AD; VORE, M; CROCENZI, FA; ROMA, MG

HEPATOLOGY (BALTIMORE, MD.)

JOHN WILEY & SONS INC

Lugar: New York; Año: 2010 vol. 52 p. 1865 - 1876

0270-9139

Estradiol 17ß-D-glucuronide (E17G) is an endogenous, cholestatic metabolite that induces endocytic internalization of the canalicular transporters relevant to bile secretion Bsep and Mrp2. We assessed here whether PI3K is involved in E217G-induced cholestasis. E217G activated PI3K, as assessed by the phosphorylation of the final PI3K effector Akt. When preadministered to isolated rat hepatocyte couplets (IRHCs), the PI3K inhibitor wortmannin (WM) partially prevented the reduction induced by E217G in the proportion of IRHCs secreting the fluorescent Bsep and Mrp2 substrates cholyllysylfluorescein and glutathionmethylfluorescein, respectively. LY294002, another PI3K inhibitor, and an Akt inhibitor (Calbiochem® #124005) showed similar protective effects. IRHC immunostaining and confocal microscopy analysis revealed that endocytic internalization of Bsep and Mrp2 induced by E217G was extensively prevented by WM; this effect was fully blocked by the microtubule-disrupting agent colchicine. WM protection was additive to that afforded by the cPKC inhibitor Gö6976, suggesting a differential, complementary involvement of PI3K and cPKC signaling pathways in E17G-induced cholestasis. In the isolated perfused rat liver, an intraportal injection of E17G triggered endocytosis of Bsep and Mrp2, accompanied by a sustained decrease in bile flow and the biliary excretion of the Bsep and Mrp2 substrates [3H]taurocholate and glutathione until the end of the perfusion period. Unlike Gö6976, WM did not prevent the initial decay, but greatly accelerated the recovery to normality of these parameters and the reinsertion of Bsep and Mrp2 into the canalicular membrane in a microtubule-dependent manner. Conclusion: PI3K/Akt signaling pathway is involved in the biliary secretory failure induced by E17G by producing a sustained internalization of canalicular transporters endocytosed via cPKC.