Mechanistic role of PDE4/cAMP in the development of HIV‐PI induced FasL mediated hepatotoxicity

Abstract

HIV protease inhibitors (HIV‐PIs) have been successfully used in the anti‐retroviral therapy in the treatment of HIV‐1 infection in the past two decades. Hence it is highly relevant to study the underlying mechanisms in HIV‐PIs induced hepatotoxicity that can negatively impact treatment outcomes. Hence, activation of hepatotoxic Fas/FasL signaling in HIV‐PI induced hepatotoxicity was investigated.Clinically relevant combination of HIV‐PIs [Ritanovir (Rit)+Lopinavir (Lop)] significantly up‐regulated FasL and Fas expression in H4IIE rat hepatoma cell line as well as primary rat hepatocytes. Our recent work showed that PDE4 expression/cAMP metabolism plays a significant role in hepatic inflammation and injury. Hence, we examined the potential role of PDE4 expression in the HIV‐PIs mediated activation of Fas and FasL expression. Commensurate with the increase in FasL and Fas, PDE4 expression was also increased with Rit+Lop treatment. To address the causal role of PDE4 expression, cells were treated with a highly specific PDE4 inhibitor rolipram which markedly inhibited Fas and FasL mRNA and protein expression induced by HIV PIs.Increased PDE4 decreases cellular cAMP levels and downstream cAMP effector molecules (cAMP‐PKA and ‐EPAC). Hence, effect of H‐89 (PKA inhibitor) and ESI‐09 (EPAC inhibitor) was examined in hepatocytes treated with HIV‐PI and rolipram. Both inhibitors significantly reversed the rolipram protective effect leading to re‐expression of Fas and FasL. Overall, this data strongly support and identify a mechanistic role for PDE4 regulated cAMP‐EPAC/PKA in the development of HIV‐PI induced FasL mediated hepatotoxicity.