Deciphering the role of GFPT2 in radiation-induced cardiovascular disease - Project Summary/Abstract Radiation-induced heart disease affects 15-30% of cancer patients who undergo radiation therapy (RT) to the chest and encompasses a broad range of cardiovascular disease (CVD) with potentially profound prognostic implications. Despite its impact, the exact causes of RICVD remain uncertain, and limited preventive treatments are available. Addressing this gap is an urgent requirement. Ionizing radiation (IR) has been shown to promote a persistent senescence-associated secretory phenotype (SASP) in myeloid cells, which plays a key role in the development of CVD. IR-induced SASP and accumulating senescent myeloid cells in tissues can trigger prolonged inflammation, but the mechanisms by which IR induces SASP remain unclear. Our long-term goals are to determine the fundamental mechanisms contributing to RICVD, identify patients at high risk for RICVD, and establish novel therapeutic approaches. It has become evident that glutamate metabolism plays a key role in promoting the survival of senescent cells and SASP induction. We conducted a metabolite profiling and found that both glutamate (Glu) and amino sugar metabolisms were upregulated in human monocyte-derived macrophages from patients with RICVD compared to those from non-RICVD patients. Glutamine-fructose-6-phosphate transaminase 2 (GFPT2) is a crucial enzyme that upregulates both glutamate and amino sugar (a precursor of glycosaminoglycan (GAGs)); our preliminary data showed that GFPT2 is acetylated at K17 and K254, which stabilizes GFPT2 expression after IR, and that this acetylation is regulated by NAD+-dependent sirtuin 6 ( SIRT6) deactivation. We hypothesize that IR-induced telomeric DNA damage initiates a positive feedback loop in which PARP activation leads to TOP2 degradation via TOP2- PARylation. The sustained TOP2 reduction stabilizes GFPT2 by deactivating SIRT6 and upregulating acetylation, promoting Glu/amino sugar/GAGs, SASP, and thus RICVD. We will test our hypothesis by pursuing the following three specific aims: In Aim 1, we will Investigate the role of the PARP-TOP2β positive feedback loop in provoking Glu and GAGs and subsequent SASP after IR in vitro. In Aim 2, we will determine how SIRT6 deactivation-mediated GFPT2 acetylation/stabilization and subsequent Glu/GAGs contribute to the persistent induction of SASP following IR in vitro . In Aim 3, we will determine the role of PARP1-TOP2β and Glu/GAGs in IR-induced atherosclerosis and atrial fibrillation (AF) in an in vivo setting. By elucidating the role of the PARP-TOP2β axis and NAD+-dependent GFPT2 acetylation/stabilization and its subsequent impact on Glu metabolism and SASP induction, this study a/GAGsims to enhance our understanding of the mechanisms underlying the persistent induction of SASP after radiation in myeloid cells. Additionally, the investigation of GFPT2 activation and Glu/amino sugar/GAG’s regulatory role may provide insights into therapeutic strategies for mitigating RICVD.
