The mechanism of 5-aminolevulinic acid-photodynamic therapy pretreatment repressing keloid fibroblast proliferation and invasion by mediating forkhead box protein O6 (FoxO6) antioxidant stress

Objective: Keloid is a kind of disfiguring pathological scarring specific to human skin. For various cutaneous and internal tumours, 5-aminolevulinic acid-photodynamic therapy (5-ALA-PDT) is a curative choice, and we explored its mechanism on keloid fibroblast (KFB) proliferation and invasion via regulating forkhead box protein O6 (FoxO6) antioxidant stress. Methods: Human keloid fibroblasts (HKFs) were cultured in vitro, treated with 5-ALA-PDT and simultaneously transfected with overexpression plasmid (oe-FoxO6). HKF proliferation, invasion, apoptosis and cell cycle were assessed by CCK-8/Transwell/TUNEL/flow cytometry assays. The protein levels of Bax, Bcl-2, FoxO6, Cyclin D1, Cyclin A1 and Cyclin B1 were determined by Western blot. SOD and CAT activities, and MDA and ROS levels were examined using the kits. Results: Pretreatment of 5-ALA-PDT prominently inhibited the proliferation of HKFs, up-regulated Bax level, down-regulated Bcl-2 level, promoted HKF apoptosis, and notably inhibited HKF invasion. 5-ALA-PDT treatment decreased the expression of FoxO6 protein, promoted oxidative stress in HKFs, up-regulated ROS and MDA levels in HKFs and reduced SOD and CAT antioxidant enzyme activities. In addition, 5-ALA-PDT pretreatment increased the level of cell cycle-associated protein Cyclin D1, decreased the levels of Cyclin A1 and Cyclin B1, and accelerated cell cycle arrest in the G₀/G₁ phase of HKFs. Overexpression of FoxO6 partially annulled the promoting effects of 5-ALA-PDT on G₀/G₁ phase cell cycle arrest and oxidative stress in HKFs and enhanced cell proliferation and invasion. Conclusion: 5-ALA-PDT limited HKF proliferation and invasion by down-regulating the expression of FoxO6.