Qiliqiangxin attenuates hypoxia-induced injury in primary rat cardiac microvascular endothelial cells via promoting HIF-1α-dependent glycolysis

Protection of cardiac microvascular endothelial cells (CMECs) against hypoxia injury is an important therapeutic strategy for treating ischaemic cardiovascular disease. In this study, we investigated the effects of qiliqiangxin (QL) on primary rat CMECs exposed to hypoxia and the underlying mechanisms. Rat CMECs were successfully isolated and passaged to the second generation. CMECs that were pre-treated with QL (0.5mg/mL) and/or HIF-1 alpha siRNA were cultured in a three-gas hypoxic incubator chamber (5% CO2, 1% O-2, 94% N-2) for 12 hours. Firstly, we demonstrated that compared with hypoxia group, QL effectively promoted the proliferation while attenuated the apoptosis, improved mitochondrial function and reduced ROS generation in hypoxic CMECs in a HIF-1 alpha-dependent manner. Meanwhile, QL also promoted angiogenesis of CMECs via HIF-1 alpha/VEGF signalling pathway. Moreover, QL improved glucose utilization and metabolism and increased ATP production by up-regulating HIF-1 alpha and a series of glycolysis-relevant enzymes, including glucose transport 1 (GLUT1), hexokinase 2 (HK2), 6-phosphofructokinase 1 (PFK1), pyruvate kinase M2 (PKM2) and lactate dehydrogenase A (LDHA). Our findings indicate that QL can protect CMECs against hypoxia injury via promoting glycolysis in a HIF-1 alpha-dependent manner. Lastly, the results suggested that QL-dependent enhancement of HIF-1 alpha protein expression in hypoxic CMECs was associated with the regulation of AMPK/mTOR/HIF-1 alpha pathway, and we speculated that QL also improved HIF-1 stabilization through down-regulating prolyl hydroxylases 3 (PHD3) expression.