PARylation of POLG Mediated by PARP1 Accelerates Ferroptosis-Induced Vascular Calcification via Activating Adora2a/Rap1 Signaling

BACKGROUND: Vascular calcification (VC) is associated with diabetes, chronic kidney disease, and aging. VC is found to be a powerful and independent risk factor for cardiovascular mortality. Vascular smooth muscle cell (VSMC) ferroptosis, a form of cell death, is known to be involved in VC. However, whether VSMC ferroptosis is regulated by posttranslational modifications remains undefined. METHODS: We explored the potential role and mechanism of PARP1 (poly[ADP-ribose] polymerase 1)-mediated poly(ADP-ribosyl)ation (PARylation) in VSMC ferroptosis during VC. Mouse VSMCs were treated with β-glycerophosphate, and Parp1 flox/flox Tagln Cre + calcified mice were generated with AAV9-sh-POLG (DNA polymerase gamma) injected to establish in vitro and in vivo models, respectively. RNA-sequencing analysis was performed to determine the transcriptomic alterations in VSMCs overexpressing POLG and treated with β-glycerophosphate. RESULTS: Both PARP1 expression and PARylation levels were increased in β-glycerophosphate–induced VC, with PARP1 knockdown mitigating VC by improving mitochondrial function and inhibiting the subsequent VSMC ferroptosis. Mechanistically, POLG PARylation levels were increased in calcified VSMCs from PARP1 activation, triggering PARylation-dependent ubiquitination of POLG that resulted in POLG downregulation. This led to mitochondrial dysfunction and Adora2a (adenosine receptor A2A)/Rap1 (Ras-associated protein 1) signaling pathway activation to induce VSMC ferroptosis, which ultimately aggravated VC. CONCLUSIONS: Our study establishes the critical role of PARP1-mediated PARylation-dependent ubiquitination of POLG in VSMC ferroptosis-induced VC. These findings suggest that PARP1 inhibitors could potentially serve as novel therapeutic strategies for VC.