Oshima, Junko

Abstract Cellular senescence is a dynamic stress response process that contributes to aging. From initiation to maintanence, senescent cells continuously undergo complex molecular changes and develop an altered transcriptome. Understanding how the molecular architecture of these cells evolves to sustain their non-proliferative state will open new therapeutic avenues to allievate or delay consequences of aging. Seeking to understand these molecular changes, we studied the transcriptomic profiles of endothelial replication-induced senescence and senescence induced by the inflammatory cytokine, TNF-α. The downregulated gene signature of both replicative and TNF-α senescence were highly overlapped: decreasing expression of several genes associated to cell cycle regulation, DNA replication, recombination, repair, chromatin structure, cellular assembly, and organization. We identified multiple targets of p53/p16-pRB-E2F-DREAM that are essential for proliferation, mitotic progression, resolving DNA damage, maintaining chromatin integrity, and DNA synthesis were repressed in senescent cells. Here we provide important molecular link between DREAM repressor complex and senescence, and identify pleothra of p53/p16-pRB-E2F-DREAM targets that controls the stability of the senescenct arrest. We propose stable repression of large number of mitotic genes by p53/p16-pRB-E2F-DREAM pathway contributes to the extended mitotic arrest and permanence of the senescent state.

Abstract Older age and underlying conditions such as diabetes/obesity or immunosuppression are leading host risk factors for developing severe complications from COVID‐19 infection. The pathogenesis of COVID‐19‐related cytokine storm, tissue damage, and fibrosis may be interconnected with fundamental aging processes, including dysregulated immune responses and cellular senescence. Here, we examined effects of key cytokines linked to cellular senescence on expression of SARS‐CoV‐2 viral entry receptors. We found exposure of human umbilical vein endothelial cells (HUVECs) to the inflammatory cytokines, TNF‐α + IFN‐γ or a cocktail of TNF‐α + IFN‐γ + IL‐6, increased expression of ACE2/DPP4, accentuated the pro‐inflammatory senescence‐associated secretory phenotype (SASP), and decreased cellular proliferative capacity, consistent with progression towards a cellular senescence‐like state. IL‐6 by itself failed to induce substantial effects on viral entry receptors or SASP‐related genes, while synergy between TNF‐α and IFN‐γ initiated a positive feedback loop via hyper‐activation of the JAK/STAT1 pathway, causing SASP amplification. Breaking the interactive loop between senescence and cytokine secretion with JAK inhibitor ruxolitinib or antiviral drug remdesivir prevented hyper‐inflammation, normalized SARS‐CoV‐2 entry receptor expression, and restored HUVECs proliferative capacity. This loop appears to underlie cytokine‐mediated viral entry receptor activation and links with senescence and hyper‐inflammation.