Melatonin modulates mitochondrial function and inhibits atherosclerosis progression through NRF2 activation and OPA1 inhibition

BACKGROUND: Atherosclerosis (AS), a major cardiovascular disease, is characterized by chronic inflammation and oxidative stress. Melatonin (MLT) has emerged as a potential therapeutic agent due to its anti-inflammatory and antioxidant properties, although the specific mechanisms underlying its action, especially as far as mitochondrial function in AS is concerned, have yet to be fully elucidated. METHODS: mice were fed a high-fat diet with or without MLT treatment. Aortic tissues were analyzed using hematoxylin and eosin, Masson staining, qPCR, and immunofluorescence. Oxidized low-density lipoprotein-treated RAW264.7 macrophages were assessed for AS progression, mitochondrial function, and oxidative stress using electron microscopy, Seahorse analysis, and molecular docking. RESULTS: MLT treatment significantly reduced atherosclerotic plaque formation, systemic and mitochondrial oxidative stress, and inflammation. MLT treatment was found to enhance mitochondrial function through upregulating the expression of key regulators of mitochondrial biogenesis and the activity of mitochondrial respiratory chain complexes, whereas markers of mitochondrial fusion [for example, optic atrophy protein 1 (OPA1)] were downregulated. Mechanistically, MLT was shown to directly interact with nuclear factor erythroid 2-related factor 2 (NRF2), thereby activating its antioxidant pathway, which in turn regulated mitochondrial function. Additionally, OPA1 was identified as a downstream target of MLT, and its inhibition improved mitochondrial function and reduced inflammation. CONCLUSION: This study is the first to elucidate that MLT synergistically ameliorates mitochondrial dysfunction through dual mechanisms-activating the NRF2 antioxidant pathway and suppressing OPA1-mediated mitochondrial fusion-providing novel therapeutic targets for AS.