Effect of suppressive sequences to inflammatory response induced by bacterial DNA CpG motif - a basic research on SIRS therapy.

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CpG motifs that frequently appear in bacterial DNA are recognized by mammalian immune system as danger signal to the host and induce immune responses. Mammalian DNA suppresses CpG-induced immune responses. Based on the observation, Yamada et al. and Klieg et al. independently designed suppressive sequences. They extensively studied the nature of this suppression, taking therapeutic application of the novel suppressive sequences into scope. Oligodeoxynucleotides (ODN) with suppressive sequences inhibited IL-6 and IL-12 production by CpG motifs in a dose dependent manner in mouse RAW cells. IgM production, proliferation and the production of IL-6 and IL-12 were also inhibited by suppressive ODN in RPMI 8227 human B cell line in vitro. In vivo study showed that suppressive ODN significantly inhibited CpG-induced pulmonary inflammation, including the production of pro-inflammatory cytokines TNF-, IL-6 chemokines MIP-2 and KC, and mobilization of neutrophils into alveolar spaces as was reported by Yamada, et al. NO is important gaseous mediator of pulmonary inflammation. Immuno-fluorescence assay and RT-PCR showed ODN sup decreased iNOS expression induced by CpG motifs. IL-12 is a key cytokine that switches Th2 immune response to Th1 response. Inhibition of IL-12 production by suppressive ODN was thus studied. Both RT-PCR and luciferase assay for IL-12 p40 showed that suppressive ODN blocked IL-12 mRNA induction. Their findings were confirmed by our observations. CpG motifs cause several diseases such as arthritis, meningitis SLF, and systemic inflammatory response syndrome; SIRS. Suppressive ODN we tested in this study may have therapeutic potency.