ALDH2 contributes to melatonin-induced protection against APP/PS1 mutation-prompted cardiac anomalies through cGAS-STING-TBK1-mediated regulation of mitophagy

Ample clinical evidence suggests a high incidence of cardiovascular events in Alzheimer’s disease(AD),although neither precise etiology nor effective treatment is available.This study was designed to evaluate cardiac function in AD patients and APP/PS1 mutant mice,along with circulating levels of melatonin,mitochondrial aldehyde dehydrogenase(ALDH2)and autophagy.AD patients and APP/PS1 mice displayed cognitive and myocardial deficits,low levels of circulating melatonin,ALDH2 activity,and autophagy,ultrastructural,geometric(cardiac atrophy and interstitial fibrosis)and functional(reduced fractional shortening and cardiomyocyte contraction)anomalies,mitochondrial injury,cytosolic mtDNA buildup,apoptosis,and suppressed autophagy and mitophagy.APP/PS1 mutation downregulated cyclic GMP-AMP synthase(cGAS)and stimulator of interferon genes(STING)levels and TBK1 phosphorylation,while promoting Aβaccumulation.Treatment with melatonin overtly ameliorated unfavorable APP/PS1-induced changes in cardiac geometry and function,apoptosis,mitochondrial integrity,cytosolic mtDNA accumulation(using both immunocytochemistry and qPCR),mitophagy,and cGAS-STING-TBK1 signaling,although these benefits were absent in APP/PS1/ALDH2−/−mice.In vitro evidence indicated that melatonin attenuated APP/PS1-induced suppression of mitophagy and cardiomyocyte function,and the effect was negated by the nonselective melatonin receptor blocker luzindole,inhibitors or RNA interference of cGAS,STING,TBK1,and autophagy.Our data collectively established a correlation among cardiac dysfunction,low levels of melatonin,ALDH2 activity,and autophagy in AD patients,with compelling support in APP/PS1 mice,in which melatonin rescued myopathic changes by promoting cGAS-STING-TBK1 signaling and mitophagy via an ALDH2-dependent mechanism.