Multi‐Omics Analysis Reveals Photodynamic Therapy Ameliorating Skin Photoaging by Improving Cellular Senescence Through Mitohormesis‐Mediated Reduction of Citrate Content

Clinical evidence supports the anti-photoaging efficacy of 5-aminolevulinic acid photodynamic therapy (ALA-PDT), yet its mechanism remains elusive. Paradoxically, ALA-PDT generates reactive oxygen species (ROS), a key mediator of ultraviolet radiation (UVR)-induced photoaging, raising questions about its rejuvenating effects. Here, we employed a multi-omics approach to clarify this paradox. A UVR-induced hairless mouse model of photoaging was treated with ALA-PDT, followed by transcriptomic, proteomic, and metabolomic profiling of skin biopsies. In vitro, fibroblast senescence was induced by UV irradiation to evaluate ALA-PDT's protective effects. Mitochondrial function and citrate (CA) levels were assessed pre- and post-treatment. ALA-PDT significantly ameliorated photoaging phenotypes in mice, with multi-omics data revealing sustained improvements in epidermal structure, extracellular matrix integrity, and immune responses. Key mechanistic findings included ALA-PDT-induced mitohormesis and tricarboxylic acid cycle reprogramming, notably reduced intracellular CA. In vitro, low-dose ALA-PDT downregulated senescence markers and CA content in UV-stressed fibroblasts, concomitant with upregulated mitohormesis markers. These effects were abrogated by inhibiting mitochondrial ROS, suggesting ROS-dependent mitohormetic signaling. Collectively, our data demonstrate that low-dose ALA-PDT alleviates photoaging by mitigating cellular senescence via mitohormesis-mediated CA reduction, offering a novel metabolic intervention strategy for age-related skin disorders.