MicroRNA-128 confers protection against cardiac microvascular endothelial cell injury in coronary heart disease via negative regulation of IRS1.

OBJECTIVE: Cardiac microvascular endothelial cells (CMECs) play a critical role in the physiological regulation of coronary blood flow and its dysfunction is associated with myocardium ischemic injury. This study was performed to clarify the effect of microRNA-128 (miR-128) on the CMEC injury in coronary heart disease (CHD) by binding to insulin receptor substrate 1 (IRS1).

METHODS: The rat CMECs were cultured by explant culture method and identified by CD31 immunofluorescence assay. CMECs were treated with homocysteine (Hcy), which underwent stress of CHD, followed by treatment of miR-128 mimics/inhibitors or IRS1 siRNA. Expression of miR-128, IRS1, and vascular endothelial growth factor (VEGF) was determined. The viability, apoptosis, migration ability, and tube formation ability of CMECs were evaluated. The superoxide dismutase (SOD), malondialdehyde (MDA), and reactive oxygen species (ROS) of CMECs were evaluated, respectively.

RESULTS: In rat CMECs, miR-128 was poorly expressed and IRS1 was highly expressed. Notably, miR-128 targeted and negatively regulated IRS1. Additionally, the treatment with Hcy in CMECs led to reduced viability, migration ability, tube formation, VEGF expression, SOD activity as well as increased cell apoptosis, MDA and ROS levels. The experimental results demonstrated that miR-128 mimics and IRS1 siRNA in rat CMECs promoted viability, migration ability, tube formation, VEGF expression, SOD activity, while repressing cell apoptosis, MDA and ROS levels. MiR-128 inhibitors could reverse the tendencies.

CONCLUSION: Collectively, our study provides evidence that miR-128 targeted and negatively regulated IRS1 expression, whereby the functional injury of CMECs induced by Hcy was ameliorated. Furthermore, protection of miR-128 was stimulated by reducing oxidative stress.