Protein Kinase C (PKC) Participates in Acetaminophen Hepatotoxicity Through c-jun-N-terminal Kinase (JNK)-Dependent and -Independent Signaling Pathways

This study examines the role of protein kinase C (PKC) and AMP-activated kinase (AMPK) in acetaminophen (APAP) hepatotoxicity. Treatment of primary mouse hepatocytes with broad-spectrum PKC inhibitors (Ro-31-8245, Go6983), protected against APAP cytotoxicity despite sustained c-jun-N-terminal kinase (JNK) activation. Broad-spectrum PKC inhibitor treatment enhanced p-AMPK levels and AMPK regulated survival-energy pathways including autophagy. AMPK inhibition by compound C or activation using an AMPK activator oppositely modulated APAP cytotoxicity, suggesting that p-AMPK and AMPK regulated energy survival pathways, particularly autophagy, play a critical role in APAP cytotoxicity. Ro-31-8245 treatment in mice up-regulated p-AMPK levels, increased autophagy (i.e., increased LC3-II formation, p62 degradation), and protected against APAP-induced liver injury, even in the presence of sustained JNK activation and translocation to mitochondria. In contrast, treatment of hepatocytes with a classical PKC inhibitor (Go6976) protected against APAP by inhibiting JNK activation. Knockdown of PKC-alpha using antisense (ASO) in mice also protected against APAP-induced liver injury by inhibiting JNK activation. APAP treatment resulted in PKC-alpha translocation to mitochondria and phosphorylation of mitochondrial PKC substrates. JNK 1 and 2 silencing in vivo decreased APAP-induced PKC-alpha translocation to mitochondria, suggesting PKC-alpha and JNK interplay in a feed-forward mechanism to mediate APAP-induced liver injury. Conclusion: PKC-alpha and other PKC(s) regulate death (JNK) and survival (AMPK) proteins, to modulate APAP-induced liver injury. (Hepatology 2014;59:1543-1554)