Effect And Mechanism Of IL-21on Secretion Of LPS-Induced Mouse Peritoneal Macrophages

Macrophages are strategically located throughout the body tissues with a widebiology function in host immune responses, such as phagocytosis, pro-inflammation,ingest and process foreign materials, dead cells and debris, immunoregulation,cytokine (e.g. TNF-α, IL-6) and chemokine (e.g. MIP-2, RANTES) secretion. InLPS-stimulated macrophages, two signal pathway are responsible for the regulation ofpro-inflammation cytokines secretion in intracellular, MAPK and NF-κB, which isactivated by Toll-like receptor4. Inducible genes that are known to be transactivatedby NF-κB include, but are not limited to, TNF-α, IL-6, iNOS, IL-1β, IFN-γ, IL-8,IL-12, MIP-2, RANTES in macrophages. LPS stimulition induce the activation of allthree families of MAPKs. Inhibition of any of the three MAPK pathways (JNK, p38MAPK, and ERK) is sufficient to block induction of TNF-α by LPS.IL-21is produced by CD4+T cells as well as by NK T cells，and has pleiotropiceffects on both innate and adaptive immune responses, such as enhanced proliferationof lymphoid cells, increased cytotoxicity of CD8+T cells and natural killer cells, anddifferentiation of B cells into plasma cells, inhibitory antigen-presenting function ofdendritic cells, and increased proapoptotic for B cells and NK cells. It is reported thatstimulating macrophage with IL-21enhanced their capacity of antigen uptake,protease activity, induce antigen-specific CD4+T cell proliferation in dependencefrom the IL-21Ra. Taken together, IL-21plays a previously unrecognized role inmodulating innate and acquired effector mechanisms of murine macrophages.Now that macrophages play an important role in the immune defense, whileIL-21as a key cytokine, play a crucial role in modulating innate and acquired effectormechanisms of murine macrophages. Whether IL-21regulates the secretion cytokineand chemokine in LPS-induced macrophages? If so, which signal pathway is involvedin the regulation of IL-21in LPS-induced macrophages? It has not been reported yet.To investigate the regulatory role of IL-21LPS-induced macrophages, the mRNA levels of TNF-α, IL-1β, IL-6, iNOS in macrophages were detected bysemi-quantitative reverse transcription and polymerase chain reaction, and theconcentration of TNF-α、IL-6in the cell-free supernatants was measured by ELISAduring the different time points after incubated with IL-21(100ng/ml) in the presenceor absence of LPS (100ng/ml) treatment. We further investigated signal transductionmechanisms to determine how IL-21affects in LPS-induced peritoneal macrophages.Our results suggested that IL-21R was expressed in macrophage, andIL-21(100ng/ml) can active normal macrophage, but not lead to inflammation.Compared to LPS group, IL-21treatment significantly inhabited LPS-inducedexpression of iNOS, TNF-α, IL-6, IL-1β in macrophages and/or supernatants. It isshown that IL-21decreased LPS-induced excessive inflammation in macrophage andhad some degree anti-inflammation function. In addition, IL-21clearly inhibited thephosphorylation of ERK, IκBα and NF-κB translocation in LPS-induced macrophages.All results shown that IL-21inhabited LPS-induced expression of iNOS, TNF-α, IL-6in macrophages and/or supernatants is mediated by decreased the phosphorylation ofERK, IκBα and NF-κB translocation, and have a regulate role in activatedmacrophage.