BACKGROUND: Heart failure is a rising epidemic in cardiovascular disease. A hallmark of heart failure pathologies is excessive and cumulative DNA damage, leading to an increased and accelerated cardiac cellular senescence. We aimed to investigate the role of DNA breaks in inducing inflammation leading to adverse remodeling, premature senescence, and cardiac dysfunction leading to onset of heart failure.
METHODS AND RESULTS: A) in vivo Animal model: Heart-focused IR (using XRad225Cx from PXi) on adult Sprague Dawley rats; 4-5 per group; dose: 0, 15, 30, 45 Gy (endpoint 12 weeks post-IR). Serial echocardiogram and blood collection, P/V measurements at endpoint calculated; whole heart harvest analysis done. B) in vitro experiments: Primary cardiomyocytes from adult rat hearts; human derived cardiac AC16 cell line; UVB ionizing radiation; protein extraction, western blot probing; RNA extraction and gene expression analysis; immunofluorescence staining and microscopy. Results: DNA damage response, as illustrated by XRCC1 protein expression, is upregulated in multiple heart injury/failure models (TAC, MI, aging) and differ depending on cell stage and/or age (in vitro proliferative vs differentiated AC16 cells). Using in vitro ionizing radiation (UVB 5, 10 mJ/cm2 dose) exposure alters cardiomyocyte morphology, as illustrated by α-actinin immunostaining, and activates innate inflammation and senescence, as illustrated by western blot probes and immunostaining of cGAS, STING, p16 and other relevant proteins. We demonstrate using heart-focused ionizing radiation a novel technique to induce aging related DNA damage and onset of diastolic heart dysfunction. Serial echo data show significant increase in E/A ratios at 8-week and 12-week post heart irradiation of 30 and 45 Gy (E/A > 2.0). We show pressure/volume analysis supporting the echo data (~ 50% decrease in dPdt min, 2-fold increase in Tau measurement and significant [p < 0.01] increase in End diastolic pressure, and no significant change in End systolic pressure). Using an experimental inhibitor compound targeting cytosolic DNA sensor cGAS, we show attenuation of cardiac remodeling and expression of senescence markers.
CONCLUSION: We present here a novel technique to induce accelerated aging of the heart, specifically leading to a diastolic dysfunction heart failure model. We elucidate the molecular pathway originating from the onset of DNA damage accumulation, leading to activation of specialized innate immunity proteins that ultimately upregulate inflammation and senescence. We demonstrate how DNA damage contributes to cardiomyocyte remodeling and cardiac dysfunction. Taken together, we uncover and connect key interactions between multiple pathways converging towards heart failure, and provide evidence for a novel therapeutic drug targeting cardiac aging.