Programmed Death Ligand-1 on Microglia Regulates Th1 Differentiation via Nitric Oxide in Experimental Autoimmune Encephalomyelitis

Microglia are considered to be potential anti- gen-presenting cells and have the ability to present antigen under pathological conditions. Nevertheless, whether and how microglia are involved in immune regulation are lar- gely unknown. Here, we investigated the suppressive activity of microglia during experimental autoimmune encephalomyelitis （EAE） induced by myelin oligodendro- cyte glycoprotein, with the goal of understanding their role in regulating the T cell reaction. Using flow cytometric analysis, we found that microglia were characterized by increased cell number and up-regulated programmed death ligand-1 （PD-L1） at the peak phase of EAE. Meanwhile, both the CD4＋ T cells and microglia that infiltrated the central nervous system expressed higher levels of PD1, the receptor for PD-L1, accompanied by a decline of Thl cells. In an ex vivo co-culture system, microglia from EAE mice inhibited the proliferation of antigen-specific CD4＋ T cells and the differentiation of Thl cells, and this was significantly inhibited by PD-L 1 blockade. Further, microglia suppressed Thl cells via nitric oxide （NO）, the production of which was dependent on PD-L1. Thus, these data suggest a scenario in which microglia are involved in the regulation of EAE by suppressing Thl-cell differenti- ation via the PD-L1-NO pathway.

Bifidobacteria DNA Induces Murine Macrophages Activation in vitro

Previous studies have shown that oligodeoxynucleotides containing unmethylated CpG motifs were used as adjuvants for immunoregulation and immune response. This study was to explore the activation effects of Bifidobacteria DNA containing unmethylated CpG motifs （CpG DNA） on murine macrophage J774A.1 cells. The genomic DNA of Bifidobacteria was extracted and purified, and the methylation degree of CpG motifs was tested. The phagocytic ability of the macrophages was detected by flow cytometry. The cytokines （IL-1β, IL-6, IL-12p40 and TNF-α） levels in the culture supernatants of Bifidobacteria DNA treated J774A.1 cells were assayed by ELISA. The content of nitric oxide （NO） was detected by Griess reagent. After treated with Bifidobacteria DNA for 24h, Nile Red stain increased in J774A.1 macrophage, which suggested that the lipid metabolism increased in the macrophages. The phagocytic ability and levels of NO and cytokines of IL-1β, IL-6, IL-12p40 and TNF-α were significantly higher than PBS group and CT DNA group. The results indicated that Bifidobacteria DNA could activate murine macrophages J774A.1, which could provide scientific basis for the research and application of microorganism DNA preparation. Cellular ＆ Molecular Immunology. 2005;2（6）：473-478.

MEF2C promotes M1 macrophage polarization and Th1 responses

The polarization of macrophages to the M1 or M2 phenotype has a pivotal role in inflammation and host defense;however,the underlying molecular mechanism remains unclear.Here,we show that myocyte enhancer factor 2 C(MEF2C)is essential for regulating M1 macrophage polarization in response to infection and inflammation.Global gene expression analysis demonstrated that MEF2C deficiency in macrophages downregulated the expression of M1 phenotypic markers and upregulated the expression of M2 phenotypic markers.MEF2C significantly promoted the expression of interleukin-12 p35 subunit(Il12a)and interleukin-12 p40 subunit(Il12b).Myeloid-specific Mef2c-knockout mice showed reduced IL-12 production and impaired Th1 responses,which led to susceptibility to Listeria monocytogenes infection and protected against DSS-induced IBD in vivo.Mechanistically,we showed that MEF2C directly activated the transcription of Il12a and Il12b.These findings reveal a new function of MEF2C in macrophage polarization and Th1 responses and identify MEF2C as a potential target for therapeutic intervention in inflammatory and autoimmune diseases.

Strontium ranelate incorporated 3D porous sulfonated PEEK simulating MC3T3-E1 cell differentiation

Polyetheretherketone(PEEK)has been used as an implant material because it has similar mechani-cal properties to natural bone.However,inferior osseointegration and bioinertness hamper the clinical application of PEEK.In this study,the surfaces of sulfonated three-dimensional(3D)PEEK porous structures were loaded with different concentrations of strontium ranelate,a compound commonly used in the treatment or prevention of osteoporosis by promoting bone formation and inhibiting bone resorption.Field-emission scanning electron microscopy was used to characterize the topography of the structures,elemental carbon,oxygen and strontium contents were mea-sured by X-ray photoelectron spectroscopy,and surface zeta potentials and water-contact angle were also measured.The results indicated that strontium ranelate was successfully loaded onto the 3D porous structures.In vitro cellular results showed that strontium ranelate-treated sulfonated PEEK(SP-SR)strengthened the adhesion of MC3T3-E1 cells.The activity of alkaline phosphatase,collagen secretion and extracellular matrix mineralization deposition of MC3T3-E1 cells were also improved on the surface of SP-SR.These results indicate that SP-SR could serve a new implant candidate for surgical treatment.