KE-298 and its active metabolite KE-758 suppress nitric oxide production by murine macrophage cells and peritoneal cells from rats with adjuvant induced arthritis

Objective: To analyze the effects of KE-298 and KE-758 on lipopolysaccharide (LPS) induced nitric oxide (NO) production by the RAW264.7 murine macrophage cell line, and the effect of KE-758 on spontaneous NO production by peritoneal cells from rats with Adjuvant induced arthritis.

Methods: The amount of NO was determined using Griess reagents. The proteins for inducible NO Synthase (iNOS) and cyclooxygenase-2 (COX-2) were detected by Western blot, then mRNA for interferon-beta (IFN)-beta, IFN regulatory factor-1 (IRF-1), and iNOS were detected by RT-PCR. Degradation of iNOS mRNA was analyzed using Northern blot. Nuclear factor-kappa B (NF-kappa B) in nuclear extracts was determined by EMSA. Adjuvant arthritis in rats was induced by inoculating heat killed Mycobacterium butyricum s.c. in the tail.

Results: KE-298 and KE-758 suppressed NO production by LPS activated RAW264.7 cells by inhibiting iNOS gene expression. Neither LPS induced NF-kappa B activation nor degradation of iNOS mRNA was affected by KE-758 treatment. LPS induced IFN-beta and IRF-1 gene expression were markedly suppressed by KE-758. In rats with Adjuvant induced arthritis, enhanced NO and iNOS production by cultured peritoneal cells and the development of arthritis were suppressed by KE-758.

Conclusion: KE-758 suppressed LPS induced iNOS gene expression by murine macrophage cells by inhibiting IFN-beta/IRF-1 expression. The potential of KE-758 to inhibit iNOS production might partly explain its efficacy on Adjuvant induced arthritis in rats.