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Macrophages play an important role in the pathogenesis of chronic colitis. However, it remains unknown how macrophages residing in the colonic lamina propria are regulated. We characterized colonic lamina proprial CD11b-positive cells (CLPMphi). CLPMphi of wild-type mice, but not IL-10-deficient mice, displayed hyporesponsiveness to TLR stimulation in terms of cytokine production and costimulatory molecule expression. We compared CLPMphi gene expression profiles of wild-type mice with IL-10-deficient mice, and identified genes that are selectively expressed in wild-type CLPMphi. These genes included nuclear IkappaB proteins such as Bcl-3 and IkappaBNS. Because Bcl-3 has been shown to specifically inhibit LPS-induced TNF-alpha production, we analyzed the role of IkappaBNS in macrophages. Lentiviral introduction of IkappaBNS resulted in impaired LPS-induced IL-6 production, but not TNF-alpha production in the murine macrophage cell line RAW264.7. IkappaBNS expression led to constitutive and intense DNA binding of NF-kappaB p50/p50 homodimers. IkappaBNS was recruited to the IL-6 promoter, but not to the TNF-alpha promoter, together with p50. Furthermore, small interference RNA-mediated reduction in IkappaBNS expression in RAW264.7 cells resulted in increased LPS-induced production of IL-6, but not TNF-alpha. Thus, IkappaBNS selectively suppresses LPS-induced IL-6 production in macrophages. This study established that nuclear IkappaB proteins differentially regulate LPS-induced inflammatory cytokine production in macrophages.

Background. To assess the contribution of IL-6 signaling to the physiopathology of Crohn's disease, we introduced anti-IL-6 receptor monoclonal antibody to a murine colitis model. Methods. Colitis was induced in C.B-17-scid mice to which were transferred CD45RB[sup high] CD4[sup +] T cells from Balb/c mice. Anti-IL-6 receptor monoclonal antibody or rat IgG was given intraperitoneally after T-cell transfer, followed by weekly injection. Vascular adhesion molecules and inducible nitric oxide synthase were visualized by immunostaining. Cytokine expression was determined by RT-PCR, and apoptotic cells were determined by the TUNEL method. Results. Mice treated with anti-IL-6 receptor monoclonal antibody showed normal growth while controls lost weight. Colitis was improved histologically with reduced infiltration of LFA-1[sup +] monocytes/ macrophages and VLA-4[sup +] T cells. ICAM-1 and VCAM-1 expression in the colonic vascular endothelium was markedly suppressed by the treatment, whereas no significant difference was seen in MAdCAM-1. IFN-γ, TNF-α, and IL-1β mRNAs were markedly reduced, but no difference was observed in the expression of IL-4, IL-10, and TGF-β. Inducible nitric oxide synthase was upregulated in the mucosa of colitic mice and downregulated in the treated mice. Apoptotic cells were very sparse despite massive CD4[sup +] T-cell infiltration in colitic mice, whereas increased apoptosis was seen in the treated mice with an apparently reduced number of T cells. Conclusions. AntiIL-6 receptor monoclonal antibody abrogated murine colitis. It effectively blocked the expression of adhesion molecules, thereby blocking leukocyte recruitment, and increased T-cell apoptosis. These results strongly suggest the therapeutic potential of anti-IL-6 receptor monoclonal antibody for human Crohn's disease. [ABSTRACT FROM AUTHOR]