ABSTRACT
MicroRNAs (miRNAs) are genomically encoded non-protein-encoding small RNAs, which negatively regulate target gene expression at post-transcriptional level. The present study aimed to investigate whether disorders of miRNAs system were involved in the pathogenesis of hypertension in spontaneously hypertensive rats (SHR). MiRanda, Target Scan and PicTar were utilized for predictive analysis of miRNAs and target genes. MiR-1, miR-133a, miR-155 and miR-208 were selected as the candidate miRNAs potentially related to blood pressure. The expression levels of miR-1, miR-133a, miR-155 and miR-208 in the aorta of 4-, 8-, 16- and 24-week-old SHR and age-matched Wistar-Kyoto (WKY) rats were detected by real-time RT-PCR. The mRNA levels of angiotensin II receptor type 1 (AGTR1a), angiotensin II receptor associated protein (AGTRAP), divalent metal transporter 1 (DMT1), low-density lipoprotein-related protein 1B (LRP1B), fibroblast growth factor-7 (FGF-7), protocadherin 9 precursor (PCDH9), chloride channel protein 5 (CLCN-5), small conductance calcium activated potassium channel protein 3 (KCNN3) and thyroid hormone receptor associated protein 1 (THRAP1), which were predicted to be target genes of differentially expressed miRNAs, were further detected by real-time RT-PCR. The results obtained showed that the expression levels of miR-1, miR-155 and miR-208 in the aorta were significantly different from those in the heart of WKY rats. The miR-155 level was significantly lower in aorta of 16-week-old SHR than that of age-matched WKY rats (P<0.05), but there was no difference between SHR and WKY rats in other age groups. In addition, miR-155 level was negatively correlated to blood pressure (r=-0.525, P<0.05). Both in WKY rats and SHR, miR-208 was most abundantly expressed in 4-week-old rats, but declined significantly in 8-, 16- and 24-week-old rats (P<0.05). No difference in miR-208 levels was observed between age-matched SHR and WKY rats. Moreover, miR-208 expression in aorta was negatively correlated with blood pressure (r=-0.400, P<0.05) and age (r=-0.684, P<0.0001). Neither miR-1 nor miR-133a was differentially expressed in SHR and WKY rats in different age groups. The mRNA levels of predicted target genes were not correlated to miR-155 or miR-208 levels. These results indicate that miR-155 is less expressed in the aorta of adult SHR compared with that of WKY rats and is negatively correlated with blood pressure, suggesting it is possibly involved in the development and pathologic progress of hypertension. The miR-208 expression in rat aorta declines with aging and it may play a role in the blood vessel development.