Melatonin Ameliorates Hepatic Ferroptosis in NAFLD by Inhibiting ER Stress via the MT2/cAMP/PKA/IRE1 Signaling Pathway

Ferroptosis, an iron-dependent cell death form, has recently been observed in the development of non-alcoholic fatty liver disease (NAFLD).Melatonin (Mel) shows potential benefits for preventing and treating liver diseases.Whether and how Mel ameliorates hepatic ferroptosis in NAFLD is not fully understood.Here we established a mouse model of NAFLD induced by long-term high-fat diet (HFD) feeding.We found that Mel treatment ameliorated global metabolic abnormalities and inhibited the progression of NAFLD in mice.Most importantly, Mel supplementation significantly improved HFD-induced iron homeostasis disorders in the liver, including iron overload and ferritin transport disorders.For another, Mel ameliorated HFD-induced hepatic lipid peroxidation.The recuperative role of exogenous Mel on hepatocyte ferroptosis was also observed in PA-or Erastin-treated HepG2 cells.Mechanistically, MT2, but not MT1, was involved in the effect of Mel.Furthermore, Mel treatment inhibited HFD or Erastin-activated ER stress and activated the PKA/IRE1 signaling pathway.Co-expression of p-PKA and p-IRE1 was enhanced by the MT2 antagonist.Inhibitions of PKA and IRE1 respectively improved hepatocyte ferroptosis, and activations of cAMP/PKA reversed Mel's effect on ferroptosis.Collectively, these findings suggest that exogenous Mel inhibits hepatic ferroptosis in NAFLD by ameliorating ER stress through the MT2/cAMP/PKA/IRE1 pathway, proving that Mel is a promising candidate drug for the treatment of hepatic ferroptosis in NAFLD.