Cisd2 delays atrial aging via a modulation of calcium homeostasis that mitigates atrial myopathy

Age-associated atrial myopathy results in structural remodeling and a disturbance of atrial conductance. Atrial myopathy often precedes atrial fibrillation (AF) and can facilitate AF progression. However, the molecular mechanism linking aging to atrial deterioration remains elusive. CDGSH iron-sulfur domain-containing protein 2 (CISD2) is a mammalian pro-longevity gene. We used Cisd2 knockout (Cisd2KO) and Cisd2 transgenic (Cisd2TG) mice to investigate pathophysiological mechanisms underlying age-related atrial myopathy. Four findings are pinpointed. Firstly, in both humans and mice, the level of atrial CISD2 declines during natural aging; this correlates with age-associated damage, namely degeneration of intercalated discs, mitochondria, sarcoplasmic reticulum (SR) and myofibrils. Secondly, in Cisd2KO and naturally aged wild-type mice, Cisd2 deficiency causes atrial electrical dysfunction and structural deterioration; conversely, sustained Cisd2 levels protect Cisd2TG mice against age-related atrial myopathy. Thirdly, Cisd2 plays a vital role in maintaining Ca²⁺ homeostasis in atrial cardiomyocytes. Cisd2 deficiency disrupts Ca²⁺ regulation, leading to elevated cytosolic Ca²⁺, reduced SR Ca²⁺, impaired store-operated calcium entry, and mitochondrial Ca²⁺ overload; these compromise mitochondrial function and attenuate antioxidant capability. Finally, transcriptomic analysis reveals that Cisd2 protects the atrium from metabolic reprogramming and preserves into old age a transcriptomic profile resembling a youthful pattern, thereby safeguarding the atrium from age-related injury. This study highlights Cisd2's crucial role in preventing atrial aging and underscores the therapeutic potential of targeting Cisd2 when combating age-associated atrial dysfunction, which may lead to the development of strategies for improving cardiac health in aging populations.