Aim: Stress-activated signaling pathways responsible for hepatic ischemia reperfusion injury and their modulation by protective interventions are widely unknown. Preconditioning of rat livers with Atrial Natriuretic Peptide (ANP) attenuates ischemia reperfusion injury (Gerbes et al. Hepatology 1998, 28:1309-1317). Since ANP has recently been shown to be a regulator of the p38 MAPK pathway in endothelial cells (Kiemer et al. Circ Res 2002, 90:874-881), aim of this study was to investigate activities of MAPK during ischemia and reperfusion and effects of ANP on MAPK.
Methods: Rat livers were perfused with KH-buffer in the presence or absence of ANP for 20 min, kept in cold UW solution for 24 h, and reperfused for up to 120 min. Activities of p38 MAPK and JNK was determined by in vitro phosphorylation assays using MBP and c-jun as substrates. After SDS/PAGE electrophoresis, gels were quantified by phosphorimaging.
Results: Activity of p38 MAPK in control organs decreased in the course of ischemia and reperfusion by 85%, whereas ANP increased p38 activity by up to 30-fold. JNK activation of control livers increased in the course of ischemia and reperfusion by up to three-fold. This increase in JNK activity was slightly elevated in ANP preconditioned organs.
Conclusion: This work represents a systematic investigation of MAPK activation during liver ischemia and reperfusion. Employing ANP, for the first time a pharmacological approach to modulate these central signal transduction molecules is presented.