Blue light induces autophagy imbalance and DNA damage repair disorders in keratinocytes by inhibiting the PI3K/AKT signaling pathway through ITGB3

Melasma is a common pigmented skin disorder that has garnered significant attention due to its severe impact on appearance. Blue light (BL) is a crucial exogenous trigger for melasma, but the specific mechanisms that mediate damage to keratinocytes (KCs) remain unclear. This study aimed to investigate the molecular mechanisms underlying BL-induced KCs damage and its role in melasma. Melasma lesions and paired normal skin tissues were collected for the detection of relevant indicators. HaCaT cells were irradiated with BL to establish an in vitro injury model. Western blotting, RT‒qPCR and immunofluorescence were used to detect the expression of mRNA and proteins related to autophagy, DNA damage repair and related signaling pathways, respectively. An alkaline comet assay and a DCFH-DA probe were used to evaluate DNA damage and ROS levels, respectively. ELISA was performed to detect the expression of inflammatory factors. The PI3K/AKT activator 740 Y-P, the ROS inhibitor NAC, and ITGB3 overexpression/knockdown were used to validate the involved roles. Melasma lesion tissues exhibited significant autophagy imbalance and abnormal DNA damage repair in KCs, characterized by increases in the LC3II/I ratio and Beclin‑1, LC3B, and γH2AX expression and decreased p62, BRCA1, RAD51, ATM, and ATR expression. BL irradiation induced ROS accumulation in normal skin tissues and HaCaT cells, leading to similar autophagy abnormalities, DNA damage repair defects, and inflammatory responses. Concurrently, BL irradiation significantly reduced the p-PI3K/PI3K and p-AKT/AKT ratios, which indicated the inhibition of the PI3K/AKT signaling pathway. Treatment with 740 Y-P ameliorated the BL-induced damage phenotypes. Further studies revealed that ITGB3 expression was downregulated in melasma lesion tissues and BL-irradiated HaCaT cells. NAC treatment or ITGB3 overexpression upregulated ITGB3 expression, activated the PI3K/AKT pathway, and improved BL-induced damage phenotypes, whereas ITGB3 knockdown partially attenuated the protective effects of NAC. BL promotes KCs autophagy dysregulation, DNA damage accumulation, and inflammatory responses by inducing ROS accumulation, downregulating ITGB3 expression, and inhibiting PI3K/AKT signaling pathway activation.