Angiotensin receptor type 1 polymorphism A1166C is associated with altered AT1R and miR-155 expression in carotid plaque tissue and development of hypoechoic carotid plaques.

Background and Aims: The principal biologic effects of the renin-angiotensin system are mediated by activation of the AT1R receptor. The microRNA miR-155 regulates AT1R expression, with both its, and AT1R's activity, linked to atherosclerosis. Target sites for miR-155 lie within the 3' UTR of the human AT1R gene, and include the AT1R A1166C polymorphism. Thus far, only levels of circulating miR-155 have been investigated with respect to A1166C genotypes. We hypothesized that the A1166C polymorphism could correlate with different, ultra-sonographically defined plaque phenotypes, as well as with an altered expression of AT1R mRNA and protein in human carotid plaques (CP), and altered expression of miR-155 in patients with advanced atherosclerosis.
Methods: Our study cohort comprised 411 patients with advanced carotid atherosclerosis (298 hyperechoic; 113 hypoechoic plaques). PCR analyses identified A1166C genotypes; quantitative real-time PCR determined AT1R and miR-155 expression levels, with AT1R protein expression evaluated by western blot.
Results: Genotypes containing the C allele bore a significant association with the hypoechoic plaque phenotype (adjusted OR 1.87, 95% CI 1.16-3.00, p = 0.01). The expression of AT1R mRNA and miR-155 were significantly up-regulated in the CPs of CC genotype carriers compared to the AA/AC genotypes (p = 0.032, p = 0.015, respectively). AT1R protein expression was also significantly higher for CC genotypes (p < 0.01).
Conclusion: Our results indicate that the AT1R A1166C polymorphism impacts an ultrasonographically-defined human plaque phenotype, with intra-plaque AT1R and miR-155 expression altered in advanced carotid atherosclerosis. Validation and replication of these data should contribute to an improved personalized therapy with which to prevent carotid atherosclerosis.
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