β stimulator induces upregulation of miR-27a in the rat heart one hour after the injection

MicroRNAs (miRs) are non-coding small RNA containing 18 to 22 nucleotides, that post-transcriptionally regulates mRNA expression. Chronic injection of β stimulator is known to induce cardiac injury and change of miRs expression level in the heart with some pathological changes such as fibrosis, heart failure, myocardial infarction. We investigated the changes in the expression level of miRs in the rat heart one hour after isoproterenol (a β stimulator) injection.

Male Sprague-Dawley rats were assigned into three groups and received subcutaneous injection of normal sarin (NS) or 0.1 mg/kg isoproterenol (ISO-0.1) or 10 mg/kg isoproterenol (ISO-10). After one hour, we collected their heart and plasma. Total RNA was extracted from the left ventricle and used for deep miRNA sequencing. Based on the results of miRNA sequencing, we performed real-time polymerase chain reaction (RT-PCR) using 8 miR primers. Cardiac injury was evaluated by hematoxylin and eosin, and phosphotungstic acid–hematoxylin staining and measuring troponin-I levels in plasma.

Troponin-I was significantly increased in ISO-0.1 and ISO-10 groups, but histological observation did not show any cardiac necrosis. miRNA sequencing identified 14 upregulated miRs and 12 downregulated miRs. Of the 26 miRs, RT-PCR confirmed miR-144-3p/5p and miR-451-5p were decreased, and that 5 miRs (miR-27a-5p, miR-30b-3p, miR-92a-1-5p, miR-132-5p, miR-582-3p) were upregulated.

This study showed that β stimulus causes downregulation of miR-144/451 cluster and increases expression of five 5 miRs in the heart, especially 6.5-fold upregulation of miR-27a-5p as early as one hour after isoproterenol injection. Therefore, these miRs might be good biomarkers for cardiac injury.