Novel inhibitory effects of cardamonin on thromboxane A(2)-induced scratching response: Blocking of G(h)/transglutaminase-2 binding to thromboxane A(2) receptor

Abstract

Alpinia katsumadai is known to suppress thromboxane A(2) (TXA(2)) receptor agonist-induced scratching in mice. The specific components of A. katsumadai responsible for these biological effects, however, are not known. In the present study, we investigated whether cardamonin (CDN), one of major principles of A. katsumadai, has suppressive effects on TXA(2)-induced scratching in mice. Scratching induced by U46619 (the TXA(2) receptor agonist) at a dose of 10 nmol/site was shown to be suppressed by CDN (0.1 nmo1-0.5 nmol/site). Suppression of the U46619-induced scratching response by CDN was found to be unrelated to competition with the ligand at the TXA(2) receptor, since CDN did not suppress [H-3] SQ29548 (the TXA(2) receptor antagonist) binding to TXA(2) receptor. TXA(2) receptor expression in A549, HaCaT, and SH-SY5Y cell lines was examined and determined to be significant in the A549 and SH-SY5Y cell lines. Further, binding of high molecular G protein G(h)/transglutaminase-2 (G(h)/Tgase-2) to TXA(2) receptor was confirmed in the A549 and SH-SY5Y cells by co-immunoprecipitation. CON suppressed the binding of TXA(2) receptor with G(h)/Tgase-2, which also acts as a G protein involved in TXA(2) signaling. These results suggested that CDN suppresses TXA(2) receptor agonist-induced scratching by suppressing TXA(2) signaling, specifically via blocking of the binding of G(h)/Tgase-2 to TXA(2) receptor. (C) 2014 Elsevier Inc. All rights reserved.