Nuclear NFκB Activity Balances Purine Metabolism in Cellular Senescence

Abstract

Upregulation of nuclear factor {kappa}B (NF{kappa}B) signaling is a hallmark of aging and major cause of age-related chronic inflammation; however, its physiological functions and mechanisms remain unclear. By combining mathematical modeling and experiments, we show that dysfunction of negative feedback regulators of NF{kappa}B, I{kappa}B and A20, alters the NF{kappa}B nuclear dynamics from oscillatory to sustained, promoting cellular senescence by remodeling epigenetic regulation and metabolic landscape. Sustained NF{kappa}B activity by I{kappa}B downregulation enhanced inflammation- and senescence-associated gene expression through increased NF{kappa}B-DNA binding and slowed the cell cycle by upregulating purine catabolism via mTORC2/AKT pathways. Notably, I{kappa}B knockdown combined with A20 overexpression resulted in lower NF{kappa}B amplitude, cytokine expression, and SA-{beta}-gal activity than I{kappa}B knockdown alone. I{kappa}B downregulation is correlated with hypoxanthine phosphoribosyltransferase 1 (HPRT1) expression in the purine salvage pathway in aged mouse hearts. Our study suggests that nuclear NF{kappa}B homeostasis is critical for balancing purine metabolism associated with chronic inflammation and tissue aging.