Targeting the NLRP3 in macrophages contributes to senescence cell clearance in radiation-induced skin injury

The persistent accumulation of senescence cells is one of the characteristics of radiation-induced skin injury (RISI), leading to fibrosis and impaired healing. However, the reasons why these senescence cells are resistant to clearance remain unclear. The mouse RISI model was established using an X-ray generator, and a shield was used to cover all areas except the skin of the right leg or back for protecting surrounding tissue. ScRNA sequencing, immunohistochemistry, immunofluorescence, qPCR, western blot, primary cell co-culture system and fluorescence microsphere phagocytosis assay were performed for the functional and mechanistic investigations. The dynamic changes of senescence cell levels and multiple immune cell levels during RISI were evaluated, we found that macrophages could remove senescence cells from the dermis, and the clearance ability gradually strengthens over time. ScRNA sequencing revealed that macrophages with high senescence clearance capacity exhibited increased NOD-like receptor family pyrin domain-containing 3 (NLRP3) expression compared to those with low senescence clearance capacity. Inhibition or conditional knockout of Nlrp3 in macrophages led to senescence cell clearance dysfunction and impaired healing. Further studies found that interleukin-33 secreted by senescence cells inhibited the expression of NLRP3 in macrophages and their ability to phagocytize senescence cells, especially in the early stages after radiation. In addition, Nocardia rubra cell wall skeleton (Nr-CWS), an approved immunomodulator, was found to activate macrophage NLRP3 expression, reduce senescence cell burden, and accelerate the healing of RISI. This study underscored NLRP3 in macrophages as a critical intervention target for senescence cell immunosurveillance and emphasized Nr-CWS as a potential therapeutic agent for accelerating senescence cell clearance in RISI.