The Role Of PKC In Host Defense Against Mycobacterium Tuberculosis Infection By Macrophages

Tuberculosis is one of infectious diseases with high mortality rate. When the host is attacked by Mycobacterium tuberculosis, macrophages utilize their pattern recognition receptors(PRRs) on the cell surface to recognize the pathogen-associated molecular patterns(PAMPs) of the pathogen. Through a series of signal transduction pathways, macrophages can produce nitric oxide(NO) and inflammatory cytokines,which mediate direct killing or activate adaptive immunity to clear the pathogen.Trehalose-6, 6-dimycolate(TDM) has been isolated as a major glycolipid from the cell wall of pathogenic mycobacteria. Researches indicate that TDM is the most important PAMPs of Mycobacterium tuberculosis. Macrophages can use their cell membrane receptors Mincle and MCL to recognize of TDM in the cell wall of Mycobacterium tuberculosis specifically. Signal transduction occurs through Fc receptor?-chain(FcR?), to recruit spleen tyrosine kinase(Syk). Syk recruitment leads to nuclear factor kappa-light-chain-enhancer of activated B cells(NF-kB) activation through Card9–Bcl10–MALT1 signalosomes. DNA transcription leads to the production of cytokines and chemokines. Activated immune cells aggregate to sites of infection and form granulomas. Release of immune effector molecules ultimately clear Mycobacterium tuberculosis, either by direct killing or activation of the adaptive immune responses.PKC ? is a member of the protein kinase C family. It is a multifunctional enzyme which is involved in diverse cellular signaling pathways and regulation of gene expression. Recently, researchers found that in fungal infections, dendritic cells(DC)can activate PKC ?, and induce Card9-Bcl10 compound formation which leads to phosphorylate of the downstream TAK1. Finally NF-?B Signaling pathways are activated, ultimately resulting in releasing of a large number of cytokines.This research mainly is used PKC? gene knockout mice model. We isolated and cultured bone marrow-derived macrophages in vitro. We stimulated macrophages with TDM analogue trehalose dibehenate(TDB) and compared the production of IL-1?, IL-6and NO at the RNA and protein levels between wild type and PKC?-/- macrophages.Compared with wild-type, PKC? knock out macrophages had a significant decline in the production of IL-1?, IL-6 and NO protein expression after TDB stimulation. RNA transcription of IL-1?, IL-6 and NO also had a dramatic decline in PKC? knock out macrophages. In vivo, we injected TDM into the tail vein of mice. After TDM injection wild-type mice appeared the phenomenon such as anorexia, weight loss and even death.After seven days, we found that the lung volume was increased and formed obvious granuloma of pneumonia in wild-type but not PKC?-/- mice. Compared with mutant mice, inflammatory cytokines production in the lung of wild-type mice increased significantly. On the contrary PKC? knock out mice had no death during the experiment.Mice had no changes in large degree to diet and weight. The size and shape of lung are normal, without formation of pulmonary granulomas.In summary, we conclude that PKC? play an important role in the secretion of inflammatory cytokines by macrophages stimulated with TDB. We also believe that PKC? is involved in TDM-mediated pneumonia granulomas formation.