Spirodela polyrhiza extract modulates the activation of atopic dermatitis-related ion channels, Orai1 and TRPV3, and inhibits mast cell degranulation

Abstract

Context: Spirodela polyrhiza (L.) Schleid. (Lemnaceae), Spirodelae Herba (SH), has been known to relieve inflammation, urticaria and skin symptoms including pruritus, eczema and rash. Objective: The effects of SH extract on two calcium ion channels, Orai1 and TRPV3, and their potential as novel therapeutics for atopic dermatitis (AD) were investigated. The regulatory role of Orai1 on mast cell degranulation was evaluated. Materials and methods: The dried leaves of SH were extracted by 70% methanol. Effects of SH extract (100 mu g/mL) in an HEK293T cell line overexpressing human Orai1 or TRPV3 were assessed. Ion channel modulation in transfected HEK293T cells was measured using a conventional whole-cell patch-clamp technique. IgE-antigen complex-stimulated mast cell degranulation was measured by beta-hexosaminidase assay with morphological observation after treatment with 20, 50 and 100 mu g/mL SH extract. Results: SH extract (100 mu g/mL) significantly inhibited Orai1 activity (63.8 +/- 0.97%) in Orai1-STIM1 co-overexpressed HEK293T cells. SH extract significantly increased TRPV3 activity (81.29 +/- 0.05% at 100mV) compared with the positive control 2-APB (100 mu M), which induced full activation. SH extract inhibited degranulation in IgE-antigen complex-stimulated RBL-2H3 mast cells by decreasing beta-hexosaminidase activity (3.14 +/- 0.03, 2.56 +/- 0.12 and 2.29 +/- 0.08 mU/mg, respectively). Conclusion: Our results suggested that SH extract could treat abnormal skin barrier pathologies in AD through modulation of the activities of the calcium ion channels Orai1 and TRPV3 and inhibition of mast cell degranulation. This is the first report of an herbal effect on the modulation of ion channels associated with skin barrier disruption in AD pathogenesis.