NAD+ metabolism governs the proinflammatory senescence-associated secretome

Abstract

Cellular senescence is a stable growth arrest that is implicated in tissue ageing and cancer. Senescent cells are characterized by an upregulation of proinflammatory cytokines, which is termed the senescence-associated secretory phenotype (SASP). NAD + metabolism influences both tissue ageing and cancer. However, the role of NAD + metabolism in regulating the SASP is poorly understood. Here we show that nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme of the NAD + salvage pathway, governs the proinflammatory SASP independent of senescence-associated growth arrest. NAMPT is regulated by HMGAs during senescence. The HMGAs/NAMPT/NAD + signaling axis promotes the proinflammatory SASP through enhancing glycolysis and mitochondrial respiration. HMGAs/NAMPT promotes the proinflammatory SASP through NAD + -mediated suppression of AMPK kinase, which suppresses p53-mediated inhibition of p38MAPK to enhance NFκb activity. We conclude that NAD + metabolism governs the proinflammatory SASP. Given the tumor-promoting effects of the proinflammatory SASP, our results suggest that anti-ageing dietary NAD + augmentation should be administered with precision.

Topoisomerase 1 cleavage complex enables pattern recognition and inflammation during senescence

“…Retrovirus and lentivirus infection. Retrovirus production and transduction were performed using Phoenix cells to package the infection viruses (Dr. Gary Nolan, Stanford University) 26 . Lentivirus was produced using the ViraPower kit (Invitrogen) based on the manufacturer's instructions in the 293FT human embryonal kidney cell line by Lipofectamine 2000 transfection (Thermo Fisher, Cat.…”

“…For oncogene-induced senescence, IMR90 cells were infected with retrovirus produced by pBABE-puro-H-RAS G12V (Addgene) at 37°C for 24 h. A second round of infection was performed on the same target cells. Infected cells were drug-selected using 3 μg/ml puromycin 26 . For Etoposide-induced senescence, IMR90 or OVCAR3 cells at~60-70% confluency were treated with 50 μM or 2 μM Etoposide for 48 h. The treated cells were cultured in fresh medium and harvested at day 8.…”

“…SA-β-Gal staining was performed as previously described 26 . Briefly, cells were fixed for 5 min at room temperature in 2% formaldehyde/0.2 glutaraldehyde in PBS.…”

“…Secreted cytokine assay. For cytokine-array analysis, cells were washed once and cultured in serum-free medium for 48 h 26 . Conditioned medium was filtered (0.2 μm) and then subjected to cytokine-array assay using Human Cytokine Array C1 kit (RayBiotech, Cat.…”

The Aging Metabolome—Biomarkers to Hub Metabolites

“…have recently shown that SASP is controlled by NAD + metabolism. [ 48 ] Specifically, the authors showed that the salvage arm of NAD metabolism, which is controlled by the enzyme nicotinamide phosphoribosyl transferase (NAMPT) controls the proinflammatory SASP. Using an oncogene induced senescence model and LC–MS/MS assays, the authors showed that the senescent cells have significantly increased levels of NAD+, and NAMPT mediated synthesis of NAD + (using cells with NAMPT inhibition), and was required for the secretion of SASP factors (IL‐10 and TNF‐α).…”