Metformin reduces the incidence of
cardiovascular diseases, and potential underlying mechanisms of action have been suggested. Here, we investigated the role of
metformin in endothelial cell injury and endothelial-mesenchymal transition (EndMT) induced by
hypoxia. All experiments were performed in human cardiac microvascular endothelial cells (HCMECs). HCMECs were exposed to hypoxic conditions for 24, 48, 72, and 96 hours, and we assessed the cell viability by cell counting kit 8;
metformin (2, 5, 10, and 20 mmol/L) was added to the cells after exposure to the hypoxic conditions for 48 hours. The cells were randomly divided into the control group,
hypoxia group,
hypoxia +
metformin group,
hypoxia + control
small interfering RNA group,
hypoxia + small interfering Prkaa1 (siPrkaa1) group, and
hypoxia + siPrkaa1 +
metformin group. Flow cytometry and cell counting kit 8 were used to monitor apoptosis and assess cell viability. Immunofluorescence staining was used to identify the CD31+/alpha smooth muscle actin+ double-positive cells. Quantitative real-time-PCR and Western blot were used for
mRNA and
protein expression analyses, respectively.
Hypoxia contributed to endothelial
injuries and EndMT of HCMECs in a time-dependent manner, which was mainly manifested as decreases in cell viability, increases in apoptotic rate, and changes in expression of apoptosis-related and EndMT-related mRNAs and
proteins. Furthermore,
metformin could attenuate the
injuries and EndMT caused by
hypoxia. After
metformin treatment, phosphorylated-AMPK (pAMPK) and p-
endothelial nitric oxide synthase expression increased, whereas p-
mammalian target of rapamycin expression decreased. However, results obtained after transfection with siPrkaa1 were in contrast to the results of
metformin treatment. In conclusion,
metformin can attenuate endothelial
injuries and suppress EndMT of HCMECs under hypoxic conditions because of its ability to activate the AMPK pathway, increase p-AMPK/
AMP-activated protein kinase, and inhibit
mammalian target of rapamycin.