Immunomodulatory effect of the antiasthma Chinese herbal formula MSSM-002 on TH2 cells

Abstract

Background: T(H)2 cytokines play a central role in the pathogenesis of allergic asthma. We previously showed that the "antiasthma" Chinese herbal formula MSSM-002 exhibited therapeutic effects on established allergic airway responses in a murine model of allergic asthma. However, the mechanisms underlying these effects are largely unknown.

Objective: The objective of this study was to determine whether and how MSSM-002 modulates an established T(H)2 response and whether the actions of MSSM-002 on T(H)2 cell differs from corticosteroids.

Methods: T(H)2 polarized splenocytes (T(H)2-SPCs) from mice with antigen-induced airway hyperresponsiveness and T(H)2 cloned cells, D10 G4.1 (D10), were cultured in the presence or absence of antigen with or without MSSM-002 and dexamethasone, and the proliferative responses and cytokine profiles were determined. Apoptosis and T(H)2 transcription factor GATA-3 expression and binding to IL-4 gene promoter and V(A) enhancer in MSSM-002-treated D10 cells were also determined.

Results: MSSM-002 significantly decreased antigen-induced proliferation and IL-4 and IL-5 production but increased IFN-gamma production by T(H)2-SPCs, whereas dexamethasone suppressed IFN-gamma as well as IL-4 and IL-5. Anti-IL-12 antibody, although abrogating MSSM-002 induction of IFN-gamma, had no significant effect on MSSM-002 suppression of IL-4 and IL-5 secretion. MSSM-002 also suppressed T(H)2 cytokine secretion by D10 cells, and in contrast to dexamethasone, MSSM-002 did not induce apoptosis of D10 cells. MSSM-002 markedly suppressed GATA-3 mRNA and protein expression and the binding to IL-4 gene promoter and V(A) enhancer in D10 cells.

Conclusion: MSSM-002, in contrast to the overall suppression of T cells by dexamethasone, exhibits immunomodulatory actions on T(H)2 cells caused, at least partially, by downregulation of GATA-3.