Low-Dose Blue Light (420 nm) Reduces Metabolic Activity and Inhibits Proliferation of Human Dermal Fibroblasts

Hypertrophic scarring in burn wounds is caused by overactive fibroblasts and myofibroblasts. Blue light reveals wavelength- and dose-dependent antibacterial and antiproliferative effects and may serve as a therapeutic option against wound infection and fibrotic conditions. Therefore, we evaluated in this study the effects of single and multiple irradiations with blue light at 420 nm (BL(420)) on the intracellular ATP concentration, and on the viability and proliferation of the human skin fibroblast (HDFs). In addition, possible BL(420)-induced effects on the catalase expression and differentiation were assessed by immunocytochemical staining and western blot analyses. Furthermore, we used RNA-seq analyses to identify BL(420)-affected genes. We found that BL(420) induced toxicity in HDFs (up to 83%; 180 J/cm(2)). A low dose of 20 J/cm(2) reduced the ATP concentration by ~50%. Multiple irradiations (4 × 20 J/cm(2)) inhibited proliferation without visible toxicity and reduced catalase protein expression by ~37% without affecting differentiation. The expression of about 300 genes was significantly altered. Many downregulated genes have functions in cell division/mitosis. BL(420) can strongly influence the fibroblast physiology and has potential in wound therapy. However, it is important to consider the possible toxic and antiproliferative effects, which could potentially lead to impaired wound healing and reduced scar breaking strength.