SIRT1 CONTROLS ACETAMINOPHEN HEPATOTOXICITY BY MODULATING INFLAMMATION AND OXIDATIVE STRESS

AIMS: Sirtuin 1 (SIRT1) is a key player in liver physiology and a therapeutic target against hepatic inflammation. We evaluated the role of SIRT1 in the pro-inflammatory context and oxidative stress during acetaminophen (APAP)-mediated hepatotoxicity.

RESULTS: SIRT1 protein levels decreased in human and mouse livers following APAP overdose. SIRT1-Tg mice maintained higher levels of SIRT1 upon APAP injection than wild-type mice and were protected against hepatotoxicity by modulation of antioxidant systems and restrained inflammatory responses, with decreased oxidative stress, pro-inflammatory cytokine mRNA levels, nuclear factor kappa B (NFκB) signaling, and cell death. Mouse hepatocytes stimulated with conditioned medium of APAP-treated macrophages (APAP-CM) showed decreased SIRT1 levels; an effect mimicked by interleukin 1β (IL1β), an activator of NFκB. This negative modulation was abolished by neutralizing IL1β in APAP-CM or silencing p65-NFκB in hepatocytes. APAP-CM of macrophages from SIRT1-Tg mice failed to downregulate SIRT1 protein levels in hepatocytes. In vivo administration of the NFκB inhibitor BAY 11-7082 preserved SIRT1 levels and protected from APAP-mediated hepatotoxicity.

INNOVATION: Our work evidenced the unique role of SIRT1 in APAP hepatoprotection by targeting oxidative stress and inflammation.

CONCLUSION: SIRT1 protein levels are downregulated by IL1β/NFκB signaling in APAP hepatotoxicity, resulting in inflammation and oxidative stress. Thus, maintenance of SIRT1 during APAP overdose by inhibiting NFκB might be clinically relevant. Rebound Track: This work was rejected during standard peer review and rescued by Rebound Peer Review (Antioxid Redox Signal 16:293-296, 2012) with the following serving as open reviewers: Rafael de Cabo, Joaquim Ros, Kalervo Hiltunen, Neil Kaplowitz.