Ataxia‐telangiectasia mutated activation mediates transforming growth factor beta signaling in acetaminophen‐induced liver injury in mice

Acetaminophen (APAP) overdose is associated with increased transforming growth factor beta 1 (TGFβ1) signaling and elevated oxidative stress, which exacerbate DNA damage. TGFβ1 has been shown to regulate ataxia-telangiectasia mutated (ATM) signaling and DNA repair in other cell types. This study investigates the DNA damage response (DDR) during APAP-induced liver injury, focusing on ATM-mediated regulation of TGFβ1 signaling. APAP administration in vitro and in vivo resulted in DNA damage, increased ATM signaling, accumulation of γH2AX, and activation of phosphorylated ataxia telangiectasia mutated (pATM) and phosphorylated checkpoint kinase 2 (pChk2). Pretreatment with an ATM inhibitor, KU55933, attenuated APAP-induced hepatocyte damage and resulted in attenuated mothers against decapentaplegic homolog 2/3 (SMAD2/3) signaling with no changes in activated TGFβ1 levels, suggesting that ATM activation modulates TGFβ1 signaling via post-translational mechanisms. APAP was found to promote transforming growth factor beta receptor 2 (TGFβRII) stabilization through activation of phosphorylated casitas B-lineage lymphoma (p-c-cbl) and subsequent neddylation of TGFβRII, which was attenuated by inhibitors of ATM signaling or neddylation machinery. In conclusion, APAP-induced hepatic DNA damage activates an ATM-mediated response that enhances TGFβ1 signaling through stabilization of TGFβRII, and inhibition of ATM consequently reduces APAP-induced hepatic injury.