Extract of Scutellaria baicalensis induces semaphorin 3A production in human epidermal keratinocytes

Abstract

In a disease-state-dependent manner, the histamine-resistant itch in dry skin-based skin diseases such as atopic dermatitis (AD) and xerosis is mainly due to hyperinnervation in the epidermis. Semaphorin 3A (Sema3A) is a nerve repulsion factor expressed in keratinocytes and it suppresses nerve fiber elongation in the epidermis. Our previous studies have shown that Sema3A ointment inhibits epidermal hyperinnervation and scratching behavior and improves dermatitis scores in AD model mice. Therefore, we consider Sema3A as a key therapeutic target for improving histamine-resistant itch in AD and xerosis. This study was designed to screen a library of herbal plant extracts to discover compounds with potential to induce Sema3A in normal human epidermal keratinocytes (NHEKs) using a reporter gene assay, so that positive samples were found. Among the positive samples, only the extract of S. baicalensis was found to consistently increase Sema3A levels in cultured NHEKs in assays using quantitative real-time PCR and ELISA. In evaluation of reconstituted human epidermis models, the level of Sema3A protein in culture supernatants significantly increased by application of the extract of S. baicalensis. In addition, we investigated which components in the extract of S. baicalensis contributed to Sema3A induction and found that baicalin and baicalein markedly increased the relative luciferase activity, and that baicalein had higher induction activity than baicalin. Thus, these findings suggest that S. baicalensis extract and its compounds, baicalin and baicalein, may be promising candidates for improving histamine-resistant itch via the induction of Sema3A expression in epidermal keratinocytes.

Induction of Semaphorin 3A by Resveratrol and Pinostilbene via Activation of the AHR-NRF2 Axis in Human Keratinocytes

“…Although few reports on the treatment of AD with SEMA3A in humans have been published, one report described that the topical application of SEMA3A protein improved pruritus and disease activity in an AD mouse model [ 18 ]. It has also been reported that baicalein, a component of Chinese herbal medicines, increases SEMA3A expression in human keratinocytes [ 19 ]. However, to the best of our knowledge, no reports on topical agents that increase SEMA3A expression have been published, and the mechanism by which SEMA3A is regulated remains unclear.…”