Objective: To screen the differentially expressed micro ribonucleic acids (miRNAs) in the serum of coronary atherosclerosis patients, and to investigate their possible mechanisms of action.
Patients and methods: The differentially expressed serum miRNAs were screened from 3 coronary artery disease (CAD) patients and 3 healthy controls using miRNA expression profiles, which were verified using low-throughput quantitative Reverse Transcription-Polymerase Chain Reaction (RT-qPCR) assay. 60 apolipoprotein E (ApoE)-/- mice were divided into model group, agomir-126 group, agomir-control (con) group, and antagomir-126 group using a random number table. They were fed with high-fat diets (21% fat and 0.15% cholesterol) ad libitum for 15 weeks to establish the mouse model of CAD. Then, hematoxylin and eosin (HE) staining was applied to detect the impact of miR-126 expression level on the tissue morphology in the thoracic aortic region. The influences of miR-126 expression level on the secretion levels of tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and IL-10 were determined via enzyme-linked immunosorbent assay (ELISA). Western blotting assay was performed to examine the effects of miR-126 expression level on the expression levels of nuclear factor-kappa B (NF-κB) and vascular cell adhesion molecule-1 (VACM-1) in the tissues of the thoracic aortic region of the mice. The correlation between miR-126 expression level and sphingosine-1-phosphate receptor 2 (S1PR2) in the serum of CAD patients and animal models was analyzed by the Pearson correlation coefficient method. The targets of miR-126 were predicted using the bioinformatics method, and the direct targets were verified through investigations. Western blotting assay and ELISA were adopted to detect the impacts of miR-126 expression level on the expression and secretion levels of TNF-α, IL-1β, and IL-10 in S1P + oxidized low-density lipoprotein (ox-LDL)-induced human umbilical vein endothelial cells (HUVECs). Lentivirus-small hairpin RNA (shRNA) was utilized to knock down the expression level of S1RP2 to determine whether miR-126 affected the increase in the inflammation level in S1P + ox-LDL-induced HUVECs by targeting S1RP2.
Results: Compared with those in control group, 4 miRNAs (miR-126, miR-206, miR-4297, and miR-3646) in the serum of CAD patients exhibited the most significant expression differences, which increased by 6.72, 7.11, 13.57, and 21.22 times, respectively. The verification results of low-throughput RT-qPCR assay indicated that there were remarkable changes in the expression levels of the 4 selected miRNAs with differential expressions in comparison with those in control group, displaying statistically significant differences (p<0.01). The results of HE staining manifested that the coronary atherosclerotic plaques were reduced markedly in agomir-126 group, while notably more coronary atherosclerotic plaques were formed in the thoracic aortic region in antagomir-126 group. Meanwhile, the elevated expression level of miR-126 evidently lowered the expressions of serum TNF-α and IL-1β, but significantly increased the expression of IL-10 in the mouse model of CAD. According to the analysis results of the Pearson correlation coefficient method, the miR-126 expression level was negatively correlated with S1PR2 expression level in the serum of both CAD patients and animal models (r=-0.6123, r=-5.37). It was shown in bioinformatics prediction and luciferase reporter gene assay that miR-126 negatively regulated the S1PR2 expression by targeting the 3' untranslated region (UTR) of S1PR2 messenger RNA (mRNA). In the in vitro inflammation model, the increased expression level of miR-126 could relieve the inflammation in cells induced by S1P + ox-LDL. Based on the results of both Western blotting assay and ELISA, the differences in the expression and secretion levels of TNF-α, IL-1β, and IL-10, as well as the expression levels of signaling molecules of the NF-κB signaling pathway, in the cells were not statistically significant among miR-126 mimic treatment group, sh-S1PR2 group, and miR-126 mimic + sh-S1PR2 group, indicating that miR-126 affects the inflammation level in HUVECs by targeting S1PR2.
Conclusions: MiR-126 represses the progression of coronary atherosclerosis in the mice by binding to S1PR2. The results of this research may propose a new mechanism of miR-126 in exerting its therapeutic effects and possess potential value for the treatment of CAD in the future.