Pituitary adenylate cyclase-Activating polypeptides prevent hepatocyte damage by promoting yes-Associated protein in liver ischemia-reperfusion injury

Background. Hepatic ischemia-reperfusion injury (IRI) is a severe complication in liver transplantation, hepatectomy, and hemorrhagic shock. As neuropeptides transmit the regulatory signal between nervous and immune systems communication, our previous study documented that pituitary adenylate cyclase-Activating polypeptides (PACAP) depressed hepatic Toll-like receptor 4 immune response in liver IRI. Methods. Here, we focused on how PACAP suppressed hepatocellular damage and enhanced hepatocyte regeneration in a murine model of partial liver warm IRI. Results. Yes-Associated protein (YAP), a cellular modulator of tissue regeneration, was readily induced in wild type (WT) mouse IR-livers. As its induction was failed in PACAP-deficient livers, PACAP supplement enhanced YAP expression in WT mouse and promoted its nuclear translocation and downstream antioxidative/regenerative genes expression both in vivo and in vitro. Further, verteporfin, a YAP transcriptional inhibitor, abolished PACAP-mediated hepatoprotection significantly. Meanwhile, blockade of protein kinase A (PKA)-CRE-binding protein (CREB) signaling recreated liver damage in PACAP-protected liver as well as impeded stimulation on YAP and its downstream gene expressions. Consistently, inhibition of PKA-CREB decreased PACAP-promoted YAP expression in primary hepatocytes culture, and made them vulnerable to H₂O₂ stress in vitro. In addition, lysophosphatidic acid, another Hippo pathway inhibitor, failed to affect PACAP-mediated hepatoprotection or hepatocellular YAP induction. This implies that PACAP regulated YAP through PKA-CREB pathway at the transcriptional level rather than canonical hippo pathway. Conclusions. Our study discovered the neural modulation of PACAP-YAP axis in hepatic cytoprotection and homeostasis in liver IRI. These reveal a novel insight of neuropeptide PACAP in combating liver IRI in clinical patients.