| Effect of Rig-I on Quantity and Apoptosis of MacrophagesRetinoic acid-inducible gene-I( Rig-I) was originally found in the NB4 cells, one of the Acute Promyelocytic Leukemia(APL) cell line, as being up-regulated in the process of NB4 differentiation induced by all trans-retinoic acid(ATRA). It is generally indentified that Rig-I is one kind of intracellular viral ds RNA sensors which plays an important role in dectecting incoming viral RNA. When being infected with virus, Rig-I dectected virus by its RD structural domain and transmits downstream signaling through MAVS(IPS1/VISA/Cardif), resulting in NF-?B and IRF activation and producing type I interferon and inflammatory cytokines to resist virus invasion. But in our previous study, an unexpected discovery was found that the immune response of Rig-I knock-out(ko) mice is lower and they were easily susceptible to conditional pathogenic bacteria infection. Rig-I-/- mice were easily infected with a commensal bacterium, S. xylosus, in the skin around eyes and neck, due to defects in B cell development and specific Ig G3 immunoglobulin class switch recombination(CSR). In addition, Rig-I knock-out mice were susceptible to colitis, defects in T cell activation and excessive proliferation of granulocyte. These datas indicate that Rig-I plays a critical important role not only in antiviral innate immune responses but also in antibacterial responses. Rig-I knock-out mice were also found to be more easily infected with E. coli as compared to wild type(wt) mice due to decreased phagocytosis of bacterial. It is because the Cdc42/Rac1 activation were impaired in Rig-I knock-out mice and resulted in the inhibition of actin polymerization. Macrophage is an important member of the innate immune defense system. We analyzed the total number, Large peritioneal macrophages(LPM) and small peritoneal macrophages(SPM) quantities and apoptosis of wild type and Rig-I knock-out mice peritoneal macrophage by flow cytometry. Compared to wild type mice, the total number of Rig-I knock-out mice and its subset(LPM and SPM) was lower but the apoptosis was increased. These datas demonstrate that Rig-I plays a critical important role in regulating the quantities of macrophages and is may be a definite link why Rig-I knock-out mice were easily susceptible to conditional pathogenic bacteria infection.Effect of Rig-I on Proliferation, Apoptosis and Function of LPS-induced MacrophagesLipopolysaccharide(LPS), an outer membrane component of Gram negative bacteria, is a potential activator of macrophages. By interacting with the membrane receptor CD14, LPS stimulates innate immune responses.To investigate the biology function and mechanism of Rig-I on LPS-induced macrophages such as proliferation, apoptosis and cytokines secretion. Macrophages(Raw264.7) with Rig-I gene knock-down or overexpression were treated with different doses of LPS for indicated times. The viability was analyzed by CCK8 and apoptosis was measured by flow cytometry. The expression levels of related cytokines were examined by q PCR. The Toll like receptor-4(TLR4) signaling induced by LPS was detected by Western blot. CCK8 and flow cytometry analyses showed that Rig-I promoted the proliferation of macrophages and inhibited LPS-induced apoptosis. q PCR results indicated that Rig-I upregulated the expression of TNF-?, IL-10, IL-1 and IL-6 in macrophage cells. These effects caused by Rig-I were further demonstrated to be due to activation of AKT and its downstream p-38, NF-?B and Bcl-x L. These datas firstly suggested that Rig-I could regulate proliferation, apoptosis and function of LPS-induced macrophages through AKT signaling pathway. |
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