Inhibition of Interleukin 10 Transcription Through The SMAD2/3 Signaling Pathway By Ca 2+ -activated K + channel K Ca 3.1 activation in Human T-cell Lymphoma HuT-78 Cells.

The hyperpolarization induced by intermediate-conductance Ca2+ -activated K+ channel (KCa 3.1) activation increases the driving force for Ca2+ influx, which generally promotes cell proliferation, migration, and cytokine production in immunocompetent cells. Interleukin-10 (IL-10) from tumor-infiltrating lymphocytes and macrophages, lymphoma, and carcinoma cells facilitates escape from tumor immune surveillance; however, the role of KCa 3.1 in IL-10 production remains unclear. The objective of the present study is to elucidate the involvement of KCa 3.1 in IL-10 expression and production using the human T-cell lymphoma HuT-78 cells. In HuT-78 cells, IL-10 gene expression and production were significantly reduced by the treatment with the KCa 3.1 activator for 6 hr. Western blotting showed that the protein expression ratio of Phospho-Smad2 (P-Smad2)/Smad2, but not P-Smad3/Smad3 was significantly decreased by the treatment with KCa 3.1 activator in HuT-78 cells. Concomitant with this, the nuclear translocation of P-Smad2 was significantly inhibited by KCa 3.1 activator. Furthermore, the KCa 3.1 activator-induced transcriptional repression of IL-10 disappeared with the pre-treatment with the calmodulin kinase II (CaMKII) inhibitor, KN-62 for 1 hr, and KCa 3.1 activator-induced decreases in the nuclear translocation of P-Smad2 were also prevented by the pre-treatment with KN-62. Taken together, the KCa 3.1 activator-induced transcriptional repression of IL-10 is due to the inhibition of the nuclear translocation of P-Smad2 in HuT-78 cells, resulting in the prevention of P-Smad2/3 complex formation in nuclei, and the activation of CaMKII induced by KCa 3.1 activators suppresses the constitutive activation of P-Smad2/3 in HuT-78 cells. Therefore, KCa 3.1 activators have potential as a therapeutic option to suppress the tumor-promoting activities of IL-10.