Akihiro Aioi
Development Laboratory, SEPTEM-SOKEN Co., Ltd.,
Ryuta Muromoto
Department of Immunology, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo
Tadashi Matsuda
Department of Immunology, Faculty of Pharmaceutical Sciences, Hokkaido University, Sapporo

[Abstract]
Similar to extracellular lipids, the cornified envelope, which is a structure formed beneath the plasma membrane, contributes to the skin barrier function as a scaffold for extracellular lipids. Therefore, in this study, we focused on transglutaminase 1 (TGM1) which is the key enzyme for formation of the cornified envelope. The objectives of this study were to identify compounds that could upregulate the expression of TGM1 and evaluate their underlying action mechanisms. Expression of the transient receptor potential channel vanilloid subfamily member 4 (TRPV4) at the mRNA and protein levels was estimated by PCR and western blotting. Effects of baicalein and Salvia officinalis (SO) extract on TGM1 mRNA expression were measured by PCR. The involvement of TRPV4 in TGM1 mRNA expression was evaluated by the inhibition and silencing of TRPV4. TRPV4 was expressed in HaCaT cells. Baicalein and SO extract upregulated TGM1 mRNA expression in HaCaT cells. However, inhibition and silencing of TRPV4 abrogated the effects of baicalein and SO extract. Baicalein and SO extract upregulated the expression of TGM1 mRNA via the activation of TRPV4, suggesting that it may improve the skin barrier function by enhancing cornified envelope formation.