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-γ 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 IgG2a level. YM-341619 suppressed IL-4 and IL-13 production in the splenocytes of these DNP–Ascaris-sensitized rats without augmenting IFN-γ 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.