Low‐level red LED light inhibits hyperkeratinization and inflammation induced by unsaturated fatty acid in an in vitro model mimicking acne

Background and Objective Acne vulgaris is a chronic inflammatory disease of the pilosebaceous units (PSU), associated with increased sebum production, abnormal follicular keratinization (hyperkeratinization), follicular overgrowth of Propionibacterium acnes ( P. acnes ), and increased inflammatory mediator release. Light therapy has attracted medical interests as a safe alternative treatment for acne. Both blue and red light therapies at high doses >10 J/cm 2 have demonstrated marked effects on inflammatory acne lesions. However, few studies have investigated the effects of lower doses of light. The aim of this study is to investigate the biological effects of lower doses of red light at 0.2–1.2 J/cm 2 for acne using an in vitro model previously developed to mimic the inflammation and hyperkeratinization observed clinically in acne. Materials and Methods Human epidermal equivalents were topically exposed to an unsaturated fatty acid, oleic acid (OA), followed by red light‐emitting diode (LED) light treatments (light‐plus‐OA treatments). Endpoints evaluated included the proinflammatory cytokine IL‐1α, epidermal barrier integrity, as measured by transepithelial electrical resistance (TEER), and stratum corneum (SC) thickness to monitor hyperkeratinization. Results OA‐induced IL‐1α release was significantly ( P < 0.05) reduced following red LED light at 0.2, 0.5, and 1.2 J/cm 2 , from 266 ± 11 pg/ml of no‐light‐plus‐OA‐treated (OA treatment without light) controls to 216 ± 9, 231 ± 8, and 212 ± 7 pg/ml, respectively. Histological examination showed that SC thickening following OA treatment was reduced from 43% of total epidermis for no‐light‐plus‐OA treatment to 37% and 38% of total epidermis following 0.5 and 1.1 J/cm 2 red light plus OA treatment, respectively ( P < 0.05). Moreover, 1.1 J/cm 2 red‐light‐plus‐OA treatment improved OA‐induced TEER changes from 29% of baseline for no‐light‐plus‐OA treatment, to 36% of baseline. Conclusion Low level red LED light therapy could provide beneficial effects of anti‐inflammation, normalizing pilosebaceous hyperkeratinization, and improving barrier impairment in Acne vulgaris . Lasers Surg. Med. 50:158–165, 2018. © 2017 Wiley Periodicals, Inc.