Epigenetic regulation mechanism of DNA methylation and miRNAs on the expression of the ALOX5AP gene in patients with ischemic stroke

5-lipoxygenase-activating protein (FLAP), encoded by the arachidonate 5-lipoxygenase-activating protein (ALOX5AP) gene, can adjust the biogenesis of proinflammatory leukotrienes to increase the adhesion and permeability of the vascular internal wall. Moreover, it participates in the process of atherosclerosis and is closely associated with ischemic stroke (IS). Accumulating evidence has shown that the expression levels of the ALOX5AP gene are upregulated in patients with IS. However, the mechanism of ALOX5AP action in IS remain elusive. The present study hypothesized that epigenetic regulation, including DNA methylation and microRNA (miR/miRNA) regulation, affects the expression levels of the ALOX5AP gene. Therefore, 200 patients with a first diagnosis of acute IS and 200 healthy control subjects were enrolled in the present study. Initially, the mRNA expression levels of the ALOX5AP gene were examined by reverse transcription-quantitative PCR. It was found that the mRNA levels of ALOX5AP gene in the IS group were significantly higher compared with controls (P<0.05). Subsequently, the methylation status of 17 CpG sites located in the promoter region of ALOX5AP was assessed by MethyTarget sequencing. However, the levels of methylation exhibited no significant differences between IS and control groups (P>0.05). Moreover, the expression levels of miR-335 and miR-495 were examined as two potential miRNAs targeting the ALOX5AP gene. The expression levels of miR-335 and miR-495 in the IS group were significantly lower compared with the control group (P<0.05). Finally, the luciferase assay results indicated that the luciferase activity of the experimental group following co-transfection of miRNA mimic and wild-type reporter gene plasmid was significantly lower compared with the other experimental groups (P<0.05), suggesting that miR-335 and miR-495 could specifically bind to the 3'-untranslated region of the ALOX5AP gene, thereby downregulating its expression. The present study provided preliminary evidence demonstrating that epigenetic regulation affects the expression of the ALOX5AP gene in patients with IS.