miR-146a Polymorphism Influences Levels of miR-146a, IRAK-1, and TRAF-6 in Young Patients with Coronary Artery Disease

Modulation of nuclear factor KappaB (NF-kappa B) activation may play a role in regulating inflammatory conditions associated with coronary artery disease (CAD). MicroRNA-146a (miR-146a) primarily targets interleukin-1 receptor-associated kinase 1 (IRAK-1) and tumour necrosis factor receptor associated factor 6 (TRAF-6), which results in inhibition of NF-kappa B via the TLR pathway. This study investigated the influence of the miR-146a GC rs2910164 on miR-146a expression in young South African Indians with CAD. CAD patients and controls were genotyped by PCR-RFLP and miRNA-146a levels were measured by qPCR. IRAK-1, TRAF-6 and NF-kappa B expression was determined by Western blot. No differences in genotypic frequency was found (GG: 45 vs. 47 %, GC: 46 vs. 41 %, CC: 9 vs. 12 %) in controls and patients respectively (odds ratio = 1.025; 95 % confidence interval 0.6782-1.550; p = 0.9164). Significantly higher levels of miR-146a was associated with CAD patients with the CC genotype (6.25-fold increase relative to controls and patients with the wildtype variant, p < 0.0001). Significantly lower levels of IRAK-1 (0.38 +/- A 0.02; p = 0.0072) and TRAF-6 (0.44 +/- A 0.02; p = 0.0146) was found in CAD patients with the CC genotype. The lowest levels of NF-kappa B and C-reactive protein were found in patients with the homozygous C allele compared to the heterozygous GC and wildtype variants. We propose a role for miR-146a in TLR signalling through a negative feedback mechanism involving the attenuation of NF-kappa B by down-regulation of IRAK-1 and TRAF-6. Our observations implicate miR-146a as a target for lowering inflammation in CAD patients.