Modulation of scratching behavior by silencing an endogenous cyclooxygenase-1 gene in the skin through the administration of siRNA.

BACKGROUND RNA interference (RNAi) is rapidly becoming a major tool that is revolutionizing research in the bioscience and biomedical fields. To apply the RNAi technique in vivo, it is crucial to develop appropriate methods of guiding the short interfering RNA (siRNA) molecules to the right tissues and cells. Here, we demonstrate an efficient method for performing gene knockdown in the body skin using the in vivo electro-transduction of siRNA. Using this method, we examined whether the targeted silencing of the cyclooxygenase (COX) gene in the skin could modulate the scratching behavior of an atopic dermatitis mouse model. METHODS NC/Nga mice were used as the atopic dermatitis model. Using our optimized in vivo electroporation conditions, siRNAs were introduced into the skin; the silencing efficiency was then analyzed by Western blotting, measuring the levels of prostaglandins, and immunohistochemistry. The scratching behaviors of the mice were measured using an automatic system. RESULTS Targeted silencing of the COX-1 gene using our in vivo siRNA technique significantly accelerated the scratching behavior of NC/Nga mice, whereas the COX-2 siRNA showed no effect. In addition, the effect of COX-1 siRNA was mimicked by treatment with a COX-1-selective inhibitor (SC-560). CONCLUSIONS We have demonstrated the successful silencing of endogenous gene expression in the skin using the intradermal transfection of unmodified siRNA via electroporation. Using this method, we revealed that COX- 1-mediated prostaglandins may act as endogenous inhibitors of scratching behavior.