503 Effects of blue light on inflammation and skin barrier recovery following acute perturbation

Abstract

Topically applied Imiquimod has been shown to induce psoriasis-like skin inflammation in mice. The use of larger animals such as rats would enable the use of clinical research techniques. We therefore characterized the psoriasis-like inflammation in the Imiquimod rat model using the technique of dermal Open Flow Microperfusion (dOFM) for sampling of biomarkers in inflamed and healthy skin. Psoriasis-like skin inflammation was induced on a skin test site of Sprague-Dawley rats by applying a daily dose of topical Imiquimod. Half of the animals additionally received a daily dose of oral dexamethasone to prevent the Imiquimod-induced skin inflammation. Skinfold thickness, erythema and scaling of this skin were assessed daily. After 8 days, dermal interstitial fluid was sampled from Imiquimodtreated skin and from untreated skin with dOFM in both groups. The samples were analyzed for forty cytokines and mediators. Topical Imiquimod induced psoriasis-like local skin inflammation in those animals not receiving oral dexamethasone. Skinfold thickness and the scores for erythema and scaling increased significantly over 8 days. The key cytokine for psoriasis inflammation, IL-17A, was only detected in dOFM samples from Imiquimod-treated inflamed skin. The concentrations of several other mediators were significantly different between treated and untreated skin, and different to those in animals that received oral dexamethasone. This study demonstrates the utility of the Imiquimod model in rats for the preclinical testing of novel anti-psoriatic drugs. Moreover, the study demonstrates that dOFM is a valuable tool in preclinical and clinical drug development.

Damaging effects of UVA, blue light, and infrared radiation: in vitro assessment on a reconstructed full-thickness human skin

“…In another reconstructed model with Chinese-origin cells, IL-6 and IL-8 were released after UVA exposure (26), and it has also been shown that IL-8 increases in human skin after UV radiation exposure (28). Regarding blue light, contrarily to our results, one study determined that exposure to blue light did not increase IL-1α levels in the forearms of healthy volunteers, however the doses used were much lower than the doses in our study (29). Also, it is proven that blue light induces IL-1α, IL-6, and IL-8 in NHEK keratinocytes (4).…”