Roles and mechanisms of complement 5a and complement 5a receptor in palmitic acid induced microglia inflammation / 实用医学杂志

Objective To observe the effect of complement 5a receptor(C5aR)antagonist(PMX53)and palmitic acid(PA)on the inflammatory reaction of microglia,and to investigate the roles and mechanisms of com-plement C5a-C5aR in PA induced microglia inflammation.Methods Microglia from one day old mice was collect-ed,purified and identified by primary culture and immunohistochemical staining,and then was randomly divided into three groups including PA group,PA+PMX53 group and control group.The expressions of tumor necrosis factor-α(TNF-α),Iba-1 and ERK1/2 were determined by ELISA,Western blot and QT-PCR.Results In PA group, the levels of Iba-1 and TNF-α were higher significantly than the control group(P<0.001).Similarly,the levels of ERK1/2 mRNA(P = 0.005 6)and p-ERK1/2 protein(P < 0.001)in the PA group were higher significantly than that in control group in spite of no difference in ERK1/2 protein in all groups. However,the levels of Iba-1,p-ERK1/2 protein,ERK1/2 mRNA and TNF-α in the PA+PMX53 group were significantly lower than that in the PA group(P<0.001),although there was no difference in ERK1/2 protein in all groups.Conclusions C5a receptor antagonist suppresses inflammatory reaction of microglia induced byPA,suggesting that C5a-C5aR-ERK may par-ticipate in the inflammation of microglia induced byPA. Therefore,C5a receptor antagonist may protect the brain tissues from inflammation-induced damage.

Increased expression of C5aR is associated with reduced Tregs in chronic graft-versus-host disease / 中国病理生理杂志

AIM:To investigate the expression and potential role of complement 5a receptor (C5aR) in chro-nic graft-versus-host disease (cGVHD).METHODS:The expression of C5aR on lymphocytes and the frequency of CD4+CD25+ Foxp3+ regulatory T cells (Tregs) in 20 cGVHD patients and 9 healthy donors was detected by flow cytometry.The correlation between the expression of C5aR and the percentage of Tregs in the cGVHD patients was analyzed.In addition, the splenocytes from the mice were cultured in vitro, and stimulated these splenocytes with recombinant mouse C5a protein (rmC5a).The peripheral blood mononuclear cells (PBMCs) from cGVHD patients were cultured in vitro, which was inhibited by C5aR antagonist (C5aRA).The frequency of Tregs in these splenocytes and the PBMCs were evaluated by flow cytometry.RESULTS:The expression of C5aR on the lymphocytes was significantly increased in the cGVHD patients compared with the healthy donors, while the percentage of Tregs was markedly lower in the cGVHD patients.The expression of C5aR was negatively correlated with the percentage of Tregs.Furthermore, the development of Tregs was suppressed by rmC5a stimulation, but was promoted by C5aRA in vitro.CONCLUSION:C5aR elevation is associated with Treg reduction in cGVHD, indicating that C5aR may play a potential role in suppressing Tregs, resulting in the incidence of cGVHD.

Yersinia enterocolitica Exploits Signal Crosstalk between Complement 5a Receptor and Toll-like Receptor 1/2 and 4 to Avoid the Bacterial Clearance in M cells

In the intestinal mucosal surface, microfold cells (M cells) are the representative gateway for the uptake of luminal antigens. At the same time, M cells are the primary infection site for pathogens invading mucosal surface for their infection. Although it is well recognized that many mucosal pathogens exploit the M cells for their infection, the mechanism to infect M cells utilized by pathogens is not clearly understood yet. In this study, we found that M cells expressing complement 5a (C5a) receptor (C5aR) also express Toll-like receptor (TLR) 1/2 and TLR4. Infection of Yersinia enterocolitica, an M cell-invading pathogen, synergistically regulated cyclic adenosine monophosphate-dependent protein kinase A (cAMP-PKA) signaling which are involved in signal crosstalk between C5aR and TLRs. In addition, Y. enterocolitica infection into M cells was enhanced by C5a treatment and this enhancement was abrogated by C5a antagonist treatment. Finally, Y. enterocolitica infection into M cells was unsuccessful in C5aR knock-out mice. Collectively, we suggest that exploit the crosstalk between C5aR and TLR signaling is one of infection mechanisms utilized by mucosal pathogens to infect M cells.

Mucosal Immune System and M Cell-targeting Strategies for Oral Mucosal Vaccination

Vaccination is one of the most effective methods available to prevent infectious diseases. Mucosa, which are exposed to heavy loads of commensal and pathogenic microorganisms, are one of the first areas where infections are established, and therefore have frontline status in immunity, making mucosa ideal sites for vaccine application. Moreover, vaccination through the mucosal immune system could induce effective systemic immune responses together with mucosal immunity in contrast to parenteral vaccination, which is a poor inducer of effective immunity at mucosal surfaces. Among mucosal vaccines, oral mucosal vaccines have the advantages of ease and low cost of vaccine administration. The oral mucosal immune system, however, is generally recognized as poorly immunogenic due to the frequent induction of tolerance against orally-introduced antigens. Consequently, a prerequisite for successful mucosal vaccination is that the orally introduced antigen should be transported across the mucosal surface into the mucosa-associated lymphoid tissue (MALT). In particular, M cells are responsible for antigen uptake into MALT, and the rapid and effective transcytotic activity of M cells makes them an attractive target for mucosal vaccine delivery, although simple transport of the antigen into M cells does not guarantee the induction of specific immune responses. Consequently, development of mucosal vaccine adjuvants based on an understanding of the biology of M cells has attracted much research interest. Here, we review the characteristics of the oral mucosal immune system and delineate strategies to design effective oral mucosal vaccines with an emphasis on mucosal vaccine adjuvants.