In Vitro Investigation of Amyloid-β Hepatobiliary Disposition in Sandwich- Cultured Primary Rat Hepatocytes

Failure in amyloid-beta (A beta) systemic clearance across the liver has been suggested to play a role in A beta brain accumulation and thus to contribute largely to the pathology of Alzheimer's disease (AD). The purpose of this study was to characterize in vitro the transport mechanisms of A beta(40) across the liver using sandwich-cultured primary rat hepatocytes (SCHs) and to determine its biliary clearance (CLbile) and biliary excretion index (BEI%). I-125-A beta(40) BEI% was time dependent and reached steady state at 30 minutes, with an average value of 29.8% and a CLbile of 1.47 ml/min per kilogram of body weight. The role of low-density lipoprotein receptor-related protein1 (LRP1) in mediating the basolateral uptake of I-125-A beta(40) in SCHs was assessed using receptor-associated protein (RAP, 2 mM). A significant reduction in I-125-A beta(40) BEI% and CLbile with RAP was observed, demonstrating a major contribution of LRP1 in mediating hepatic uptake of intact (125I)-A beta(40) via transcytosis. Furthermore, activity studies suggested a lower role of receptor for advanced glycation end products (RAGE) in I-125-A beta(40) hepatic uptake. Verapamil (50 mM) and valspodar (20 mM) significantly reduced I-125-A beta(40) BEI%, indicating a role for P-glycoprotein (P-gp) in the biliary excretion of I-125-Ab beta(40) in SCHs. LRP1-and P-gp-mediated (125I)-A beta(40) biliary excretion was inducible and increased BEI% by 26% after rifampicin pretreatment. In conclusion, our findings demonstrated that besides LRP1, P-gp and, to a lesser extent, RAGE are involved in I-125-A beta(40) hepatobiliary disposition and support the use of enhancement of A beta hepatic clearance via LRP1 and P-gp induction as a novel therapeutic approach for the prevention and treatment of AD.