Endoplasmic Reticulum Stress-Induced Upregulation of STARD1 Promotes Acetaminophen-Induced Acute Liver Failure

Background & Aims Acetaminophen (APAP) overdose is a major cause of acute liver failure (ALF). Mitochondrial SH3BP5 (also called SAB) and phosphorylation of c-Jun N-terminal kinase (JNK) mediate the hepatotoxic effects of APAP. We investigated the involvement of steroidogenic acute regulatory protein (STARD1), a mitochondrial cholesterol transporter, in this process and sensitization by valproic acid (VPA), which depletes glutathione and stimulates steroidogenesis. Methods Nonfasted C57BL/6J mice (control) and mice with liver-specific deletion of STARD1 (Stard1ΔHep), SAB (SabΔHep), or JNK1 and JNK2 (Jnk1+2ΔHep) were given VPA with or without APAP. Liver tissues were collected and analyzed by histology and immunohistochemistry and for APAP metabolism, endoplasmic reticulum (ER) stress, and mitochondrial function. Adult human hepatocytes were transplanted into Fah−/−/Rag2−/−/Il2rg−/−/NOD (FRGN) mice to create mice with humanized livers. Results Administration of VPA before administration of APAP increased the severity of liver damage in control mice. The combination of VPA and APAP increased expression of CYP2E1, formation of NAPQI-protein adducts, and depletion of glutathione from liver tissues of control mice, resulting in ER stress and the upregulation of STARD1. Livers from control mice given VPA and APAP accumulated cholesterol in the mitochondria and had sustained mitochondrial depletion of glutathione and mitochondrial dysfunction. Inhibition of ER stress, by administration of tauroursodeoxycholic acid to control mice, prevented upregulation of STARD1 in liver and protected the mice from hepatoxicity following administration of VPA and APAP. Administration of N-acetylcysteine to control mice prevented VPA- and APAP-induced ER stress and liver injury. Stard1ΔHep mice were resistant to induction of ALF by VPA and APAP, despite increased mitochondrial levels of glutathione and phosphorylated JNK; we made similar observations in fasted Stard1ΔHep mice given APAP alone. SabΔHep mice or Jnk1+2ΔHep mice did not develop ALF following administration of VPA and APAP. The ability of VPA to increase the severity of APAP-induced liver damage was observed in FRGN mice with humanized liver. Conclusions In studies of mice, we found that upregulation of STARD1 following ER stress mediates APAP hepatoxicity via SH3BP5 and phosphorylation of JNK1 and JNK2.
We acknowledge the support from grants SAF2014–57674R, SAF-2015–69944R, and SAF2017–85877R from Plan Nacional de I+D, Spain, and by the CIBEREHD; the center grant P50AA011999 Southern California Research Center for ALPD and Cirrhosis funded by National Institute on Alcohol Abuse and Alcoholism/National Institutes of Health (NIH); the NIH R01DK06715 and the USC Research Center for Liver Diseases P30DK485522 Instrumentation (NK), as well as support from AGAUR of the Generalitat de Catalunya SGR-2017–1112, European Cooperation in Science & Technology (COST) ACTION CA17112 Prospective European Drug-Induced Liver Injury Network, and the Fundación BBVA.