Study On Cytokines And DNA Methylation Of Active Pulmonary Tuberculosis

Pulmonary tuberculosis (PTB) is a chronic inflammatory disease caused by Mycobacterium tuberculosis (M.tb). M.tb infection can be controlled life-long in most infected individuals, however, a minority of cases (5～10%) could develop to active tuberculosis. The host immune system plays an important role in the development and control of disease.Biomarkers are objective characteristics that indicate pathogenic progress, providing information about disease status, risk of progression and response to treatment. Current research is paid much attentions on finding biomarkers from the host and the pathogen. Our previous study supported that IL-6, CCL1 and CXCL9 markedly expressed in peripheral of patients. In this study, we tested a broad range of serum cytokines and chemokines to pulmonary tuberculosis patients compared to latency patients and healthy controls. Moreover, the cohort of close-contacts of tuberculosis patients was follow-up studied every six months. Our results found that CXCL12, CCL1, and TNF-a were significantly expressed a higher level in plasma of tuberculosis patients. Moreover, the cytokine of CXCL12 and IFN-y were markedly increased in patient’s close-contact at the time point when disease occurred. T cell-mediated immunity against tuberculosis, including cytokine production, could be regulated by several mechanisms. As reported, DNA methylation may be involved in influencing the host immunity and cytokine production. Via Infinium Human Methylation 450 Bead Chips assay, we compared the methylation situation of host genes between tuberculosis patients and health controls. Results indicated that tuberculosis patients associated an aberrant hypomethylation compared to healthy controls, totally 1,234 genes (90.4% of differentially methylated genes) are demethylation and 136 genes (9.6%) are hypermethylation. Moreover, these significant genes closely related to functions of inflammatory response, B cell differentiation and positive regulation of NF-κB cascade by Gene Ontology analysis. Meanwhile, CXCL12 was selected and detected the methylation status by bisulfite sequencing PCR sequencing in tuberculosis patients and healthy controls. The level of DNA methylation from 415bp of the up-stream of transcription starting site exhibited significant lo w level of of methylation rate, in particularly the-194bp site presented a significant lower methylation rate compared to the healthy controls. Moreover, a negative correlation was found between the methylation rate of-194bp site and the serum level of CXCL12 in patients.In summary, a profile of cytokines, including CXCL12, CCL1 and TNF-a markedly expressed in tuberculosis patients. By genome-wide DNA methylation examination, we found a profound hypomethylation situation exits in tuberculosis patients compared with the healthy controls, which is worthy of investigating the mechanism underlying DNA methylation and aberrant immune response.