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.