Exogenous Hydrogen Peroxide Induces Lipid Raft-Mediated STAT-6 Activation in T Cells

Background/Aims: CD4+ T cells are a critical component of the adaptive immune response. While the mechanisms controlling the differentiation of the Th1, Th17, and regulatory T cell subsets from naïve CD4+ T cells are well described, the factors that induce Th2 differentiation are still largely unknown. Methods: The effects of treatment with exogenous H ₂ O ₂ on STAT-6 phosphorylation and activation in T cells were examined by immunoblotting, immunofluorescence and gel shift assay. Anti-CD3 antibody and methyl-β-cyclodextrin were utilized to induce lipid raft assembly and to investigate the involvement of lipid rafts, respectively. Results: Jurkat and EL-4 T cells that were exposed to H ₂ O ₂ showed rapid and strong STAT-6 phosphorylation, and the extent of STAT-6 phosphorylation was enhanced by co-treatment with anti-CD3 antibody. The effect of H ₂ O ₂ on STAT-6 phosphorylation and translocation was inhibited by disruption of lipid rafts. STAT-6 activation in response to H ₂ O ₂ treatment regulated IL-4 gene expression, and this response was strengthened by treatment with anti-CD3. Conclusion: Our results indicate that reactive oxygen species such as H ₂ O ₂ can act on upstream and initiating factors for activation of STAT-6 in T cells and contribute to formation of a positive feedback loop between STAT-6 and IL-4 in the Th2 differentiation process.