ST2 suppresses IL-6 production via the inhibition of IkappaB degradation induced by the LPS signal in THP-1 cells.

LPS induces the production of inflammatory cytokines via the stimulation of Toll-like receptors. In this study, we demonstrated that a soluble secreted form of the ST2 gene product (ST2), a member of the interleukin-1 receptor family, suppressed the production of IL-6 in an LPS-stimulated human monocytic leukemia cell line, THP-1. Immunofluorescence confocal microscopy revealed the binding of ST2 to the surface of the THP-1 cells, in which ST2 led to decreased binding of nuclear factor-kappaB to the IL-6 promoter. Furthermore, the degradation of IkappaB in the cytoplasm after LPS stimulation was reduced by pretreatment with ST2. These results demonstrated that ST2 negatively regulates LPS-induced IL-6 production via the inhibition of IkappaB degradation in THP-1 cells.