BACKGROUND: Mizoribine (MZR) is an imidazole nucleoside isolated from Eupenicillium brefeldianum. MZR is currently in clinical use for patients who have undergone renal transplantation. Therapeutic efficacy of MZR has also been demonstrated in rheumatoid arthritis and lupus nephritis. MZR has been shown to inhibit the proliferation of lymphocytes by interfering with inosine monophosphate dehydrogenase. Since the exact mechanism by which MZR benefits rheumatoid arthritis (RA) is not clear, we investigated the ability of MZR to direct its immunosuppressive influences on other antigen presenting cells, such as macrophages. METHODS: Mouse macrophage RAW264.7 cells were stimulated with lipopolysaccharide in the presence of MZR. To elucidate the mechanism of the therapeutic efficacy in chronic inflammatory diseases, we examined the effects of MZR on the production of pro-inflammatory cytokines, nitric oxide (NO) and prostaglandin E2 (PGE2) in macrophages. RESULTS: MZR dose-dependently decreased the production of nitric oxide and pro- inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukins 1beta (IL-beta) and IL-6 PGE2. Examination of gene expression levels showed that the anti-inflammatory effect correlated with the down-regulation of inducible nitiric oxide synthase expression, cycloxygenase-2 expression and TNF-alpha gene expression. CONCLUSION: In this work, we resulted whether MZR (1.25~10 microgram/ml) inhibited macrophage activation by inhibiting secretion of pro-inflammatory cytokines, NO and PGE2. These findings provide an explanation for the therapeutic efficacy of MZR in chronic inflammation- associated diseases.
Animals ; Antigen-Presenting Cells ; Arthritis, Rheumatoid ; Cytokines* ; Dinoprostone* ; Down-Regulation ; Eupenicillium ; Gene Expression ; Humans ; Inosine Monophosphate ; Interleukin-6 ; Interleukins ; Kidney Transplantation ; Lupus Nephritis ; Lymphocytes ; Macrophage Activation ; Macrophages* ; Mice ; Nitric Oxide ; Oxidoreductases ; Tumor Necrosis Factor-alpha

BACKGROUND: Dendritic cells (DCs) play a critical role not only in the initiation of immune responses, but also in the induction of immune tolerance. In an effort to regulate immune responses through the modulation of antigen presenting cell (APC) function of DCs, we searched for and characterized APC function modulators from natural products. METHODS: DCs were cultured in the presence of propolis components, WP and CP, and then examined for their ability to present exogenous antigen in association with major histocompatibility complexes (MHC). RESULTS: WP and CP inhibited class I MHC-restricted presentation of exogenous antigen (cross-presentation) in a DC cell line, DC2.4 cells, and DCs generated from bone marrow cells with GM-CSF and IL-4. The inhibitory activity of WP and CP appeared to be due not only to inhibition of phagocytic activity of DCs, but also to suppression of expression of MHC molecules on DCs. We also examined the effects of WP and CP on T cells. Interestingly, WP and CP increased IL-2 production from T cells. CONCLUSION: These results demonstrate that WP and CP inhibit MHC-restricted presentation of exogenous antigen through down-regulation of phagocytic activity and suppression of expression of MHC molecules on DCs.
Antigen Presentation ; Biological Products ; Bone Marrow Cells ; Cell Line ; Dendritic Cells* ; Down-Regulation ; Granulocyte-Macrophage Colony-Stimulating Factor ; Immune Tolerance ; Interleukin-2 ; Interleukin-4 ; Major Histocompatibility Complex* ; Propolis* ; T-Lymphocytes