MiR-21-5p protects against ischemic stroke by targeting IL-6R

Ischemic stroke is a brain dysfunction disease caused by vascular obstruction. The expression of many kinds of microRNAs (miRNAs) is related to ischemic stroke. MiRNA has the ability to reduce or save ischemic injury. Therefore, we aimed to explore the protective miRNA in the ischemia-reperfusion process.

The Gene Expression Omnibus (GEO) peripheral RNA sequencing (RNA-seq) datasets of ischemic stroke patients were analyzed to search for differentially expressed miRNAs in the ischemia-reperfusion process. The expression level of miRNA in 60 patients with ischemic stroke and 23 age-matched healthy control inpatients was tested by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The significantly changed miRNAs were verified through comparison of the peripheral blood of healthy people and patients of the hospital. The in-vitro ischemia-reperfusion model was established through oxygen-glucose deprivation (OGD) treated HEMC-1 cells. The cell viabilities and cell apoptosis are detected by 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT) assay and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, respectively. Apoptosis-related proteins including Bcl-2, Bax, caspase-3, and caspase-9 expression levels were verified by western blot. Predict the combination of hsa-miR-21-5p and interleukin-6 receptor (IL-6R) through TargetScan database, clone the 2964-2961 site of IL-6R-3'-untranslated region (3'-UTR), establish IL-6R-3'-UTR and IL-6R-3'-UTR mutant plasmids, copy and clone wild type and mutant IL-6R-3'-UTR into luciferase report vector pGL3 respectively, and detect the activity of luciferase. The expression of hsa-miR-21-5p was regulated by using hsa-miR-21-5p mimic and hsa-miR-21-5p inhibitor.

Through RNA-seq analysis, it was revealed that "hsa-miR-548ar-3p", "hsa-miR-651-5p", "hsa-miR-142-3p", "hsa-miR-21-5p", and "hsa-miR-30e-5p" were notably lower in ischemia patients, and that "hsa-miR-21-5p" was significantly decreased in the peripheral blood of hospital patients. Luciferase assay showed that hsa-miR-21-5p could directly bind to the 3'-UTR of the IL-6R gene and inhibit IL-6R translation; the level of IL-6R was also elevated in patients. In the OGD-treated HMEC-1 cells, overexpressed hsa-miR-21-5p mimic could enhance cell viabilities and decrease cell apoptosis. Moreover, IL-6R overexpression could reduce the protective effects of hsa-miR-21-5p.

In the peripheral blood of ischemia patients, hsa-miR-21-5p is significantly decreased and IL-6R is elevated. The "hsa-miR-21-5p" could bind to the IL-6R gene and suppress IL-6R expression, thus alleviating the damage of OGD treatment in HMEC-1 cells.