MiR-200a mediates protection of thymosin beta 4 in cardiac microvascular endothelial cells as a novel mechanism under hypoxia-reoxygenation injury.

Thymosin beta-4 (Tβ4) is a ubiquitous protein, which has been suggested to regulate multiple cell signal pathways and a variety of cellular functions. However, the role Tβ4 plays in the cardiac microvascular endothelial cells (CMECs) under myocardial ischemia/reperfusion injury (MIRI) is currently unknown. Here we investigated the effects of Tβ4 on hypoxia/reoxygenation (H/R) induced CMECs injury and its potential molecular mechanism. Cultured CMECs were positively identified by flow cytometry using antibody against CD31 and VWF/Factor VIII, which are constitutively expressed on the surface of CMECs. Then the reduced level of Tβ4 was detected in H/R-CMECs by RT-qPCR. In order to determine the effects of Tβ4 on H/R-CMECs, we transfected the overexpression or silence vector of Tβ4 into CMECs under H/R condition. Our results indicated that H/R treatment could reduce proliferation, increased apoptosis, adhesion and ROS production in CMECs, which were attenuated by Tβ4 overexpression or aggravated by Tβ4 silence, implying Tβ4 is able to promote CMECs against H/R-induced cell injury. Furthermore, the microRNA 200a (miR-200a) level was also increased by Tβ4 in H/R-CMECs or reduced by Tβ4 siRNA. To investigated the mechanism of protective effects of Tβ4 on CMECs injury, the miR-200a inhibitor was transfected into H/R-CMECs. The results indicated that inhibition of miR-200a inversed the protection of Tβ4 on H/R-CMECs, specifically including cell proliferation, cell adhesion, cell apoptosis and ROS production, as well as nuclear factor erythroid 2-related factor 2 (Nrf2) nuclear translocation. In conclusion, our results determined that Tβ4 attenuated H/R induced CMECs injury by miR-200a-Nrf2 signaling. This article is protected by copyright. All rights reserved.