Modulation of SIRT1 by IL-1β/NFκB signaling during Acetaminophen-induced hepatotoxicity

Abstract

[Introduction]: The liver is the main organ in charge of drug catabolism and also the major site susceptible to drug injury. Sirtuin 1 (SIRT1), a NAD+-dependent histone deacetylase, is a key player in liver physiology and a therapeutic target against hepatic inflammation. In this study, we evaluated the role of SIRT1 in the pro-inflammatory context and oxidative stress during acetaminophen (APAP)-mediated hepatotoxicity.

[Material and Methods]: SIRT1 expression was analyzed in APAP-induced liver failure in humans and mice. Hepatotoxicity was assessed in wild-type and transgenic mice overexpressing SIRT1 (SIRT1 Tg) poisoned with APAP (300 mg/kg). Raw 264.7 and peritoneal macrophages were treated with APAP and conditioned medium (CM) was added to mouse hepatocytes. siRNA was used to reduce inflammatory mediators in hepatocytes.

[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.

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