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Hydroquinone (HQ), is one of the most effective drugs to treat hyperpigmentary disorders, but often causes skin irritation in clinic. Mast cell plays an important role in contact dermatitis and triggering pseudo-allergic reactions via MRGPRX2. Whether HQ induced skin irritant reaction through activating mast cells via MRGPRX2 remains unknown.To investigate the role of mast cells in HQ induced skin irritant reaction and verify whether MRGPRX2 participated in the HQ effect on mast cells which contributed to the pathogenesis of skin irritant reaction.A mouse model of HQ induced skin irritation was established to observe the local and systemic inflammation associated with mast cell receptor MrgprB2. Human mast cell LAD2 were used to verify the effect of HQ on mast cells via MRGPRX2 by knocking down with siRNA.Mast cells were involved in the development of HQ-induced irritant reaction and local inflammation are closely related to mast cell receptor MrgprB2. HQ could activate mast cells via MRGPRX2, causing changes in calcium concentration, degranulation, and release of inflammatory cytokines which lead to skin irritant reaction.HQ induced skin irritant reaction could be skin pseudo-allergic reactions achieved by activating mast cells via MRGPRX2.

Types I and III collagens are the major collagens comprising skin connective tissue. Defects in these collagens lead to diseases of dermal connective tissue and fibre hyperplasia. RNA interference (RNAi) provides a powerful tool to inhibit specific gene expression. In this study, we generated small interfering RNAs (siRNA) expression cassettes (SECs) by polymerase chain reaction (PCR) as a method to quickly screen the efficacy of siRNAs. We then cloned the most efficient SECs into vectors, using a rapid and novel method intrinsic to the design of the SEC, and transfected human skin fibroblasts (HSF) to generate stable lines. We show that the transfection of SECs into HSFs resulted in specific and effective repression of COL1A1 and COL3A1 expression (5.00% and 6.48% of control levels) provided a rapid method for testing candidate siRNA sequences. We report the use of vector-based RNAi to establish stable HSF cell lines with persistent knockdown over at least 30 days (25.21% and 22.12% of control levels). These stably modified HSF cell lines may be used for the study of other types of collagen or proteins of the extracellular matrix (ECM).