ALA-PDT elicits oxidative damage and apoptosis in UVB-induced premature senescence of human skin fibroblasts

- ALA-PDT induced oxidative damage and apoptosis in photoaged fibroblasts.
- ALA-PDT decreased proliferative activity in photoaged fibroblasts.
- ALA-PDT effects were positively correlated with ALA incubation time and red laser dose.
- Antioxidant reduced oxidative damage and apoptosis caused by ALA-PDT.
- Shortened ALA incubation time and the use of antioxidants can reduce side effects.

Background5-Aminolevulinic acid photodynamic therapy (ALA-PDT) has been used for the treatment of skin photoaging. It can significantly improve the appearance of fine lines, dotted pigmentation, and roughness of photoaged skin. However, the mechanisms by which ALA-PDT yields rejuvenating effects on photoaged skin have not been well elucidated. Thus, in this study we explored the effects of ALA-PDT in photoaged fibroblasts.MethodsWe established a stress-induced premature senescence (SIPS) model by repeated exposures of human dermal fibroblasts (HDFs) to ultraviolet B (UVB) irradiation. Cells were irradiated by red light laser at 635 nm wavelength (50 mW/cm2). Intracellular protoporphyrin IX (PpIX) was detected by confocal microscopy. Intracellular reactive oxygen species (ROS) level and mitochondrial membrane potential (MMP) change were detected by fluorescence microscopy and flow cytometry. Morphological changes were observed by optical microscopy. Proliferative activity was measured by a cell counting kit-8 (CCK-8). Cell apoptosis was detected by fluorescence microscopy using Hoechst staining and flow cytometry using annexin V/propidium Iodide double staining.ResultsIntracellular PpIX fluorescence in UVB-induced premature senescent HDFs (UVB-SIPS-HDFs) reached the highest intensity after incubation with 1.00 mmol/L ALA for 6 h (P < 0.05). Compared with control group, intracellular ROS level, MMP, and apoptotic rate were increased (P < 0.05) and proliferative activity was decreased (P < 0.05) in UVB-SIPS-HDFs treated with ALA-PDT, which were positively correlated to ALA incubation time and red light laser dose.ConclusionOur study demonstrated that ALA-PDT elicits oxidative damage and apoptosis in photoaged fibroblasts in vitro, which may be the basis for the rejuvenating effects on photoaged skin.