TRPM8 channel inhibitor AMTB suppresses murine T-cell activation induced by T-cell receptor stimulation, concanavalin A, or external antigen re-stimulation

Transient receptor potential (TRP) channels are a family of non-selective cation channels that are functionally expressed in various organs and cells. Among them, transient receptor potential vanilloid (TRPV) 1 and TRPV4 channels are expressed in T cells, where they serve as Ca²⁺ channels for T-cell receptor signaling [Bertin et al., 2014, Majhi et al., 2015]. Here, we show that not only TRPV1 and TRPV4 channel inhibitors, but also a transient receptor potential melastatin (TRPM) 8 channel inhibitor can suppress murine T-cell activation. Mouse splenic lymphocytes pretreated with N-(3-aminopropyl)-2-[(3-methylphenyl)methoxy]-N-(2-thienylmethyl)benzamide hydrochloride (AMTB), a TRPM8 channel-selective inhibitor, showed significantly reduced IL-2 and IL-6 release from T cells after stimulation with anti-CD3ε/anti-CD28 antibodies or concanavalin A. AMTB also suppressed IL-2 mRNA expression and activation of extracellular signal-regulated kinase 1/2, which is involved in IL-2 production. Further, the increase of CD25 (IL-2 receptor alpha chain) expression after T-cell activation was suppressed by AMTB. TRPM8 channel was expressed in CD4⁺ T cells isolated from splenocytes, and we confirmed that the release of IL-2 from isolated CD4⁺ T cells was significantly suppressed by AMTB. In vitro re-stimulation of splenocytes from external antigen-immunized mice with the same antigen induced IL-2 and IL-6 production, which was significantly suppressed by AMTB. Thus, the TRPM8 channel inhibitor AMTB suppresses T-cell activation induced by various stimulants.