Association of Chlamydia trachomatis, C. pneumoniae, and IL-6 and IL-8 Gene Alterations With Heart Diseases

Abstract

Atherosclerosis is a progressive disease characterized by chronic inflammation of the arterial walls, associated with genetic and infectious factors. The present study investigated the involvement of <i>Chlamydia trachomatis</i> and <i>Chlamydia pneumoniae</i> infections and immunological markers (C-reactive protein, CRP, TNF-α, IL-6, IL-8, and IL-10) in the process of atherosclerosis. The evaluation included 159 patients for surgical revascularization (CAD) and 71 patients for surgical heart valve disease (HVD) at three hospitals in Belém, Brazil. The control group (CG) comprised 300 healthy individuals. Blood samples collected before surgery were used for antibodies detection (enzyme immunoassay), CRP (immunoturbidimetry) and IL-6 levels (enzyme immunoassay). Tissue fragments (atheroma plaque, heart valve and ascending aorta) were collected during surgery and subjected to qPCR for detection of bacterial DNA. Promoter region polymorphisms of each marker and relative quantification of <i>TNF-</i>α, <i>IL-8</i>, and <i>IL-10</i> gene expression were performed. Demography and social information were similar to the general population involved with both diseases. Antibody prevalence to <i>C. trachomatis</i> was 30.6, 20.3, and 36.7% (in the CAD, HVD, and CG, respectively) and to <i>C. pneumoniae</i> was 83.6, 84.5, and 80.3% (in the CAD, HVD, and CG, respectively). <i>C. trachomatis</i> cryptic plasmid DNA was detected in 7.4% of the samples. Frequency of <i>IL6</i>-174G>C polymorphism was higher in CAD and HVD than in CG regardless of previous exposure to <i>Chlamydia</i>. Previous <i>C. trachomatis</i> infection showed involvement in HVD and CAD. Significant association between disease and previous <i>C. pneumoniae</i> infection was found only among HVD. GG genotype of IL6-174G>C is apparently a risk factor for heart disease, whereas AT genotype of <i>IL8</i>-251A>T was mainly involved in valvulopathies, including patients with prior exposure to <i>C. pneumoniae</i>.