Characterization of YM-58483/BTP2, a novel store-operated Ca2+ entry blocker, on T cell-mediated immune responses in vivo.

YM-58483/BTP2 is a blocker of store-operated Ca2+ entry (SOCE), which regulates the activation of non-excitable cells such as lymphocytes. YM-58483 has been reported to inhibit cytokine production and proliferation in T cells, and to be useful as a probable medicinal candidate for treatment of bronchial asthma. The present study investigated the pharmacological profile and therapeutic potential of YM-58483 in relation to cell-mediated immune responses. In the mouse graft-versus-host disease (GVHD) model, YM-58483 (1-30 mg/kg, p.o.) and cyclosporine A (1-30 mg/kg, p.o.) inhibited donor anti-host cytotoxic T lymphocyte (CTL) activity and IFN-gamma production, and also reduced the number of donor T cells, especially donor CD8+ T cells, in the spleen. YM-58483 and cyclosporine A inhibited T cell proliferation in a one-way mixed lymphocyte reaction (MLR) with IC50 values of 330 and 12.7 nM, respectively. Additionally, YM-58483 (1-10 mg/kg, p.o.) and cyclosporine A (2, 10 mg/kg, p.o.) inhibited the sheep red blood cell (SRBC)-induced delayed type hypersensitivity (DTH) response. These results suggest that the inhibition of SOCE leads to the prevention of antigen-induced T cell responses, which participate in autoimmune diseases such as autoimmune hepatitis and rheumatoid arthritis.

YM-341619 suppresses the differentiation of spleen T cells into Th2 cells in vitro, eosinophilia, and airway hyperresponsiveness in rat allergic models.

T helper (Th) 2 cells play a central role in the pathogenesis of allergic diseases such as allergic asthma, atopic dermatitis, and allergic rhinitis. We have found that YM-341619 hydrochloride, which suppressed IL-4-induced STAT6-dependent reporter gene expression, inhibited the differentiation of mouse spleen T cells into Th2 cells in vitro. YM-341619 suppressed the production of IL-4 and the expression of GATA-3 mRNA, a Th2 transcription factor, in T cells cultured with anti-CD3 antibody and anti-CD28 antibody in the presence of IL-4. In contrast, the production of IFN-gamma and the expression of T-bet mRNA, a Th1 transcription factor, in T cells cultured with anti-CD3 antibody in the presence of IL-12, were not effected by YM-341619. Orally administered YM-341619 (0.003-0.03 mg/kg) reduced the plasma IgE level of DNP-Ascaris-sensitized rats, but not the IgG(2a) level. YM-341619 suppressed IL-4 and IL-13 production in the splenocytes of these DNP-Ascaris-sensitized rats without augmenting IFN-gamma production. YM-341619 also dose-dependently suppressed eosinophil accumulation in the lung (0.003-3 mg/kg, p.o.) and airway hyperresponsiveness (0.3-3 mg/kg, p.o.) induced by repeated exposure to ovalbumin in ovalbumin-sensitized rats. These results suggest that YM-341619 has the ability to suppress allergen-induced Th2 responses by selectively inhibiting the differentiation of CD4(+) T cells into the Th2 subset.

The suppressive effects of YM-58483/BTP-2, a store-operated Ca2+ entry blocker, on inflammatory mediator release in vitro and airway responses in vivo.

YM-58483/BTP-2, 4-methyl-4'-[3,5-bis(trifluoromethyl)-1H-pyrazol-1-yl]-1,2,3-thiadiazole-5-carboxanilide, blocks the store-operated Ca2+ entry (SOCE) that mediates the activation of non-excitable cells. This study investigated the pharmacological profile and therapeutic potential of YM-58483 as anti-asthma drug. YM-58483 inhibited DNP antigen-induced histamine release from and leukotrienes (LTs) production in IgE-primed RBL-2H3 cells, a rat basophilic leukemia cell line, with IC50 values of 460 and 310 nM, respectively. Prednisolone did not inhibit either of these responses. YM-58483 also inhibited phytohemagglutinin-P (PHA)-stimulated IL-5 and IL-13 production in human peripheral blood cells with IC50 values of 125 and 148 nM, respectively, which is approximately 5 times less potent than prednisolone. YM-58483 (30 mg/kg, p.o.) significantly suppressed ovalbumin (OVA)-induced bronchoconstriction in OVA-sensitized guinea pigs, whereas prednisolone did not. YM-58483 (3-30 mg/kg, p.o.) and prednisolone (100mg/kg, p.o.) both significantly and completely suppressed airway hyperresponsiveness (AHR) caused by OVA exposure. Since YM-58483 inhibits two major characteristic symptoms of bronchial asthma, namely bronchoconstriction and AHR via the suppression of inflammatory mediator and cytokine production, SOCE inhibition is a potential approach for treatment.

YM-58483, a selective CRAC channel inhibitor, prevents antigen-induced airway eosinophilia and late phase asthmatic responses via Th2 cytokine inhibition in animal models.

T cells play a regulatory role in the pathogenesis of various immune and allergic diseases, including human asthma. Recently, it was reported that a pyrazole derivative, YM-58483 (BTP2), potently inhibits Ca(2+) release-activated Ca(2+) (CRAC) channels and interleukin (IL)-2 production in T cells. We investigated the effects of YM-58483 on T helper type 2 (Th2) cytokine production in vitro and antigen-induced airway asthmatic responses in vivo. YM-58483 inhibited IL-4 and IL-5 production in a conalbumine-stimulated murine Th2 T cell clone (D10.G4.1), and IL-5 production in phytohemagglutinin-stimulated human whole blood cells with IC(50) values comparable to those reported for its CRAC channel inhibition (around 100 nM). YM-58483 inhibited antigen-induced eosinophil infiltration into airways, and decreased IL-4 and cysteinyl-leukotrienes content in inflammatory airways induced in actively sensitized Brown Norway rats. Furthermore, orally administered YM-58483 prevented antigen-induced late phase asthmatic bronchoconstriction and eosinophil infiltration in actively sensitized guinea pigs. These data suggest that the inhibition of Ca(2+) influx through CRAC channel leads to the prevention of antigen-induced airway inflammation, probably via the inhibition of Th2 cytokine production and inflammatory mediators release. YM-58483 may therefore be useful for treating airway inflammation in bronchial asthma.

A pyrazole derivative potently inhibits lymphocyte Ca2+ influx and cytokine production by facilitating transient receptor potential melastatin 4 channel activity.

3,5-Bis(trifluoromethyl)pyrazole derivative (BTP2) or N-[4-3, 5-bis(trifluromethyl)pyrazol-1-yl]-4-methyl-1,2,3-thiadiazole-5-carboxamide (YM-58483) is an immunosuppressive compound that potently inhibits both Ca2+ influx and interleukin-2 (IL-2) production in lymphocytes. We report here that BTP2 dosedependently enhances transient receptor potential melastatin 4 (TRPM4), a Ca2+-activated nonselective (CAN) cation channel that decreases Ca2+ influx by depolarizing lymphocytes. The effect of BTP2 on TRPM4 occurs at low nanomolar concentrations and is highly specific, because other ion channels in T lymphocytes are not significantly affected, and the major Ca2+ influx pathway in lymphocytes, ICRAC, is blocked only at 100-fold higher concentrations. The efficacy of BTP2 in blocking IL-2 production is reduced approximately 100-fold when preventing TRPM4-mediated membrane depolarization, suggesting that the BTP2-mediated facilitation of TRPM4 channels represents the major mechanism for its immunosuppressive effect. Our results demonstrate that TRPM4 channels represent a previously unrecognized key element in lymphocyte Ca2+ signaling and that their facilitation by BTP2 supports cell membrane depolarization, which reduces the driving force for Ca2+ entry and ultimately causes the potent suppression of cytokine release.

Receptor-mediated regulation of the TRPM7 channel through its endogenous protein kinase domain.

TRPM7 is a ubiquitously expressed and constitutively active divalent cation-selective ion channel, whose basal activity is regulated by intracellular levels of Mg(2+) and Mg.ATP. We have investigated receptor-mediated mechanisms that may actively regulate TRPM7 activity. We here report that TRPM7 currents are suppressed by intracellular GTPgammaS, suggesting the involvement of heterotrimeric G proteins. TRPM7 currents are also inhibited by stimulating endogenous muscarinic receptors, which is mediated by G(i) because the inhibitory effect is blunted by pertussis toxin. Conversely, stimulation of endogenous G(s)-coupled beta-adrenergic receptors potentiates TRPM7 currents, whereas G(q)-coupled thrombin receptors have little effect. Consistent with the involvement of G(s)/G(i) in controlling adenylyl cyclase activity, elevations of intracellular cAMP levels enhance TRPM7 activity and prevent receptor-mediated modulation of TRPM7 activity by muscarinic and adrenergic agonists. This cAMP-dependent effect requires the functional integrity of both protein kinase A (PKA) and the endogenous kinase domain of TRPM7 because cAMP-mediated effects are abolished when treating cells with the PKA inhibitors H89 or KT5720 as well as in cells expressing phosphotransferase-deficient TRPM7 constructs. These mutant channels are also much less susceptible to GTPgammaS-mediated inhibition, suggesting that the main regulatory effect occurs through G(i)- and G(s)-mediated changes in cAMP. Taken together, our results demonstrate that TRPM7 activity is up- and down-regulated through its endogenous kinase in a cAMP- and PKA-dependent manner.

A pyrazole derivative, YM-58483, potently inhibits store-operated sustained Ca2+ influx and IL-2 production in T lymphocytes.

In nonexcitable cells, Ca(2+) entry is mediated predominantly through the store depletion-dependent Ca(2+) channels called store-operated Ca(2+) (SOC) or Ca(2+) release-activated Ca(2+) channels. YM-58483, a pyrazole derivative, inhibited an anti-CD3 mAb-induced sustained Ca(2+) influx in acute T cell leukemia, Jurkat cells. But it did not affect an anti-CD3 mAb-induced transient intracellular Ca(2+) increase in Ca(2+)-free medium, nor anti-CD3 mAb-induced phosphorylation of phospholipase Cgamma1. It was suggested that YM-58483 inhibited Ca(2+) influx through SOC channels without affecting the TCR signal transduction cascade. Furthermore, YM-58483 inhibited thapsigargin-induced sustained Ca(2+) influx with an IC(50) value of 100 nM without affecting membrane potential. YM-58483 inhibited by 30-fold the Ca(2+) influx through SOC channels compared with voltage-operated Ca(2+) channels, while econazole inhibited both SOC channels and voltage-operated Ca(2+) channels with an equivalent range of IC(50) values. YM-58483 potently inhibited IL-2 production and NF-AT-driven promoter activity, but not AP-1-driven promoter activity in Jurkat cells. Moreover, this compound inhibited delayed-type hypersensitivity in mice with an ED(50) of 1.1 mg/kg. Therefore, we concluded that YM-58483 was a novel store-operated Ca(2+) entry blocker and a potent immunomodulator, and could be useful for the treatment of autoimmune diseases and chronic inflammation. Furthermore, YM-58483 would be a candidate for the study of capacitative Ca(2+) entry mechanisms through SOC/CRAC channels and for identification of putative Ca(2+) channel genes.