Protective effect of Thai silk extracts on drug-induced phototoxicity in human epidermal A431 cells and a reconstructed human epidermis model.

Bombyx mori silk extracts, derived from the cocoon degumming process of draw and dye silk in the textile industry, are mainly composed of sericin protein. To add value to the Thai silk extracts, and hence the silk industry, a simple enrichment process was recently developed and the enriched silk extracts were then applied in nano-cosmeceutical products and nano-delivery systems. In this study, the protective effect of Thai silk extracts from three different strains of Bombyx mori on the drug-induced phototoxicity was evaluated in vitro using chlorpromazine (CPZ), a commonly used antipsychotic drug, as a representative phototoxic drug. The human epidermal A431 cell line and reconstructed human epidermis (RhE) model were used as the in vitro skin model. The silk extracts significantly improved the viability of A431 cells after CPZ exposure and ultraviolet A (UVA) irradiation, as shown by the significantly increased CPZ and UVA IC50 values and the decreased proportion of apoptotic cells. The protective effect of these silk extracts against the CPZ-induced UVA-phototoxicity in A431 cells was associated with the attenuation of intracellular oxidative stress via an increased intracellular glutathione level. Likewise, the silk extracts exhibited a protective effect on the CPZ-induced UVA-phototoxicity in the RhE model, in terms of an improved tissue viability and attenuation of the released inflammatory cytokine, interleukin-1α. These findings support the potential usefulness of silk extracts in novel applications, especially in the protection of drug-induced phototoxicity.