Histone Deacetylases Enhance Ca(2+)-Activated K(+) Channel K(Ca)3.1 Expression in Murine Inflammatory CD4(+) T Cells

The up-regulated expression of the Ca(2+)-activated K(+) channel K(Ca)3.1 in inflammatory CD4(+) T cells has been implicated in the pathogenesis of inflammatory bowel disease (IBD) through the enhanced production of inflammatory cytokines, such as interferon-γ (IFN-γ). However, the underlying mechanisms have not yet been elucidated. The objective of the present study is to clarify the involvement of histone deacetylases (HDACs) in the up-regulation of K(Ca)3.1 in the CD4(+) T cells of IBD model mice. The expression levels of K(Ca)3.1 and its regulators, such as function-modifying molecules and transcription factors, were quantitated using a real-time polymerase chain reaction (PCR) assay, Western blotting, and depolarization responses, which were induced by the selective K(Ca)3.1 blocker TRAM-34 (1 μM) and were measured using a voltage-sensitive fluorescent dye imaging system. The treatment with 1 μM vorinostat, a pan-HDAC inhibitor, for 24 h repressed the transcriptional expression of K(Ca)3.1 in the splenic CD4(+) T cells of IBD model mice. Accordingly, TRAM-34-induced depolarization responses were significantly reduced. HDAC2 and HDAC3 were significantly up-regulated in the CD4(+) T cells of IBD model mice. The down-regulated expression of K(Ca)3.1 was observed following treatments with the selective inhibitors of HDAC2 and HDAC3. The K(Ca)3.1 K(+) channel regulates inflammatory cytokine production in CD4(+) T cells, mediating epigenetic modifications by HDAC2 and HDAC3.