Tannin Inhibits Histamine and SLIGRL-NH2-Induced Itch via TRPV1 and TRPA1 Signaling Pathway

Background: Tannin is a naturally occurring plant polyphenol. Its main characteristic is that it displays anti-oxidant, anti-inflammatory, anti-viral, and anti-proliferative biological activities. However, the mechanism by which tannin impacts itch remains unknown. In the present study, through behavioral analysis and calcium imaging, we examined the mechanism by which tannin reduces histaminergic itch and non-histaminergic itch. Methods: First, we confirmed that tannin inhibited itch in the scratching test with histamine, compound 48/80, and SLIGRL-NH2 treatment. Second, we confirmed that tannin inhibited capsaicin- and AITC-induced calcium responses in primary-cultured DRG neurons. Third, tannin blocked the capsaicin- and AITC-induced calcium responses in TRPV1- and TRPA1-expressing HEK293 cells, respectively. Results: These results reveal that tannin reduced histamine-dependent or independent itching by activating inhibitory signals of TRPV1 and TRPA1. Conclusions: Thus, our findings suggest that tannin may be a promising drug for the treatment of histamine or non-histamine-dependent itch. fetal bovine serum (FBS; Gibco-BRL, USA) and 1% penicillin – streptomycin (Sigma, USA). Transfection was performed with Lipofectamine 2000 (Invitrogen) at 70-80% confluency, and transfected cells were cultured in the culture medium for 48 hours before calcium imaging analysis. TRPV1 plasmid vector or TRPA1 transfected HEK293 cells were provided by Seok bae Oh from Seoul University. variety of blockers and transgenic mice. Our results demonstrated that tannin alleviates histaminergic itch and non-histaminergic itch via inhibitory signaling of TRPV1 and TRPA1.