Project Summary/Abstract Premature senescence-triggered vascular diseases (PmSVD) induced by ionizing radiation (IR), as well as Hutchinson-Gilford progeria syndrome (HGPS), are notably characterized by accelerating processes of atherosclerosis (AthS) and coronary artery disease (CAD). Although endothelial dysfunction in PmSVDs is well known, there is a paucity of available treatments to prevent PmSVD-induced CAD; hence, there is an urgent need to fill this gap. Persistent senescence-associated secretory phenotype (PISP), provoked by TL dysfunction, plays a central role in cancer recurrence and resistance, but its regulatory mechanisms and contribution to AthS remain unknown. Our long-term goal is to determine the molecular mechanisms by which PmSVD induces PISP in endothelial cells (ECs) and CAD. PmSVD significantly up-regulated TOP2β degradation via PKCζ activation. The depletion of EC TOP2β instigated PARP activation and PISP; it also accelerated AthS. We showed the critical role of mtROS in PKCζ activation, which is one of the initial steps for the Mt-nucleus feedback loop. Of note, the crucial role of mtROS in both IR and HGPS has been well established. Lastly, by performing IC-MS analysis in both IR and HGPS ECs, we also found that the following 3 metabolite-related pathways were regulated in IR and HGPS ECs in common: 1) nucleotide sugars-glycosaminoglycans (GAGs) and sulfate, 2) glutamate, and 3) NAD+- hydrogen sulfide (H2S). Although the contribution of all 3 metabolites pathways to CAD and aging has been suggested, the exact role and mechanical insights in regulating PmSVD remain largely unknown. We propose the novel hypothesis that PmSVD-induced mtROS activates the PKCζ-TOP2β module, followed by TOP2β degradation, and instigates TL DNA damage. TL DNA damage promotes PARP activation, which induces mt dysfunction and forms an mt-nucleus feedback loop, resulting in persistent metabolites changes, including nucleotide sugars and NAD+-H2S pathways, causing PIS