Effects of personal care product particulates on a murine atopic dermatitis model

Abstract

The pathogenesis of atopic dermatitis (AD) is multifactorial with genetic, immunological, and environmental aspects. Titanium dioxide, polystyrene, and other substances contained in personal care products (PCPs) can aggravate AD, but the definitive effects of PCPs themselves remain to be elucidated. Exogenous environmental stimuli can promote adaptive immunity as one underlying mechanism exacerbating AD, but the responses of innate immunity have not been fully understood. The present research aimed to study whether commercially available PCPs can affect the progress of AD following topical application and the response of group 2 innate lymphoid cells (ILC2s) in the pathologic condition. After eight days of continuous administration on dorsal ear skin of C57BL/6J mice, AD-like symptoms were observed in the MC903 (calcipotriol)-treated mice, with or without PCP particulates. However, a high concentration of PCP+MC903 mitigated the pathology, with milder erythema and edema. Cytokine thymic stromal lymphopoietin and interleukin-4 were also lowered concurrently. Such results suggested frequent application of the PCP conferred transient suppression against MC903-induced pathogenesis. Conversely, higher transepidermal water loss by PCP+MC903 indicated a more compromised skin barrier function. Also, the percentage of ILC2s among ear tissue lymphocytes was higher as reported in AD patients. These results suggest that although the PCP may stimulate ILC2s in the innate immune system, generally it has bifunctional effects that suppress and exacerbate skin immune responses.