The matricellular protein TSP1 promotes human and mouse endothelial cell senescence through CD47 and Nox1

Senescentcells withdraw from the cell cycle and do not proliferate. The prevalence of senescentcompared to normally functioning parenchymal cells increases with age, impairing tissue and organ homeostasis. A contentious principle governing this process has been the redox theory of aging. We linked matricellular protein thrombospondin 1(TSP1) and its receptor CD47to the activation of NADPH oxidase 1 ( Nox1), but not of the other closely related Nox isoforms, and associated oxidative stress, and to senescencein human cells and aged tissue. In human endothelial cells, TSP1 promoted senescenceand attenuated cell cycle progression and proliferation. At the molecular level, TSP1 increased Nox1-dependent generation of reactive oxygen species (ROS), leading to the increased abundance of the transcription factor p53. p53 mediated a DNA damage response that led to senescencethrough Rb and p21 cip , both of which inhibit cell cycle progression. Nox1inhibition blocked the ability of TSP1 to increase p53 nuclear localization and p21 cip abundance and its ability to promote senescence. Mice lacking TSP1 showed decreases in ROS production, p21 cip expression, p53 activity, and aging-induced senescence. Conversely, lung tissue from aging humans displayed increases in the abundance of vascular TSP1, Nox1, p53, and p21 cip . Finally, genetic ablation or pharmacological blockade of Nox1in human endothelial cells attenuated TSP1-mediated ROS generation, restored cell cycle progression, and protected against senescence. Together, our results provide insights into the functional interplay between TSP1 and Nox1in the regulation of endothelial senescenceand suggest potential targets for controlling the aging process at the molecular level.