PI 3-kinase pathway is responsible for antiapoptotic effects of atrial natriuretic peptide in rat liver transplantation

摘要

AIM:To investigate the in vivo effect of atrial natriureticpeptide(ANP)and its signaling pathway during ortho-topic rat liver transplantation.METHODS:Rats were infused with NaCl,ANP(5 μg/kg),wortmannin(WM,16 μg/kg),or a combination ofboth for 20 min.Livers were stored in UW solution(4°C)for 24 h,transplanted and reperfused.Apoptosis wasexamined by caspase-3 activity and TUNEL staining.Phosphorylation of Akt and Bad was visualized by West-ern blotting and phospho-Akt-localization by confocalmicroscopy.RESULTS:ANP-pretreatment decreased caspase-3activity and TUNEL-positive cells after cold ischemia,indicating antiapoptotic effects of ANP in vivo.The an-tiapoptotic signaling of ANP was most likely caused byphosphorylation of Akt and Bad,since pretreatment withPI 3-kinase inhibitor WM abrogated the ANP-inducedreduction of caspase-3 activity.Interestingly,analysis ofliver tissue by confocal microscopy showed translocationof phosphorylated Akt to the plasma membrane of hepa-tocytes evoked by ANP.CONCLUSION:ANP activates the PI-3-kinase pathwayin the liver in vivo leading to phosphorylation of Bad, an event triggering antiapoptotic signaling cascade inischemic liver.