M2 macrophages promote PKM2 production in fibroblasts to alleviate UVB-induced photoaging.

Ultraviolet radiation is a major factor in causing skin aging. Compared to younger individuals, older adults exhibit a significant imbalance in the M1/M2 macrophage ratio, with an elevated proportion of M1 macrophages, but little is known about the role of macrophages in skin aging. Here, we report the critical role of M2 macrophages and PKM2 in preventing fibroblast photoaging. UVB-treated photoaged fibroblasts showed a reduction in PKM2. Compared to M1 macrophages, treatment with M2 macrophage significantly alleviated this photoaging and enhanced PKM2 synthesis in fibroblasts. Mechanistically, this is due to the secretion of CCL1 by M2 macrophages, which acts on the CCR8 receptor on the cell surface, promoting PKM2 production in photoaged fibroblasts. This further activates the TGF-β1/Smad2 pathway, thereby reducing cellular aging. This provides a potential strategy for the treatment of skin photoaging.