Abstract
Abstract Background Age-related atrial cardiomyopathy is characterized by conduction disturbance, structural fibrosis as well as cardiac remodeling. Atrial cardiomyopathy promotes the development of atrial fibrillation, which is associated with a 5-fold increase in the risk of stroke. However, the molecular mechanisms underlying age-associated deterioration of atrial function remain unclear. Cisd2 is a mitochondrial outer membrane protein that regulates intracellular calcium homeostasis and mitochondrial integrity. Importantly, Cisd2 is a pro-longevity gene in mammals. Purpose In this study, we investigate the role of Cisd2 in atrial cardiomyopathy during aging. Methods CISD2 expression and atrial conductance were examined in different age human surgical samples. Atrial conductance was assessed and validated by immunofluorescence and Transmission electron microscope in Cisd2 knockout and overexpressing transgenic mice at young and old age. The mitochondrial functions and calcium homeostasis were investigated in the atrial HL-1 cell lines with Cisd2KO or re-expression. Transcriptomic analysis of mice atrial tissues was performed. Results The age-associated decrease of atrial Cisd2 protein, in human and mice, were associated with atrial conductance disturbance and intercalated disc disorganization. Furthermore, Cisd2 deficiency disrupts calcium homeostasis via dysregulation of Serca2a and Stim1 resulting in an increased level of basal cytosolic Ca2+ and mitochondrial Ca2+ overload in HL-1 atrial cardiomyocytes. Most strikingly, in Cisd2 transgenic mice, a persistently high level of Cisd2 is sufficient to delay age-associated atrial myopathy and attenuate age-related atrial structural defects and functional decline. In addition, it results in a younger atrial transcriptome pattern during old age. Conclusions The mitochondrial-associated membrane-bounded CDGSH iron-sulfur domain-containing protein 2 (CISD2) protein regulates cytosolic calcium homeostasis and mitochondrial integrity. Interestingly, an age-dependent decrease of atrial Cisd2 protein has been detected during aging in both humans and mice. Our findings indicate that decreased atrial Cisd2 is one of the causes of atrial myopathy during cardiac aging. A persistently high level of atrial Cisd2 delays atrial myopathy during aging and ameliorates age-related atrial dysfunction.
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