Abstract:

Objective

To investigate the effects and mechanisms of ten-eleven translocation methylcytosine dioxygenase 2 （TET2） on hypoxia-induced injury in human umbilical vein endothelial cells（HUVECs）.

Methods

Human umbilical vein endothelial cells （HUVECs） were treated as follows：HUVECs treated with normal saline under normoxia were defined as the Norm-C group； HUVECs treated with thrombin under normoxia were defined as the Norm-M group； HUVECs treated with normal saline under hypoxia were defined as the Hypo-M group； HUVECs treated with hypoxia and thrombin were also defined as the Hypo-M group. Additionally，HUVECs treated with hypoxia，thrombin，and an adenovirus empty vector without TET2 were defined as the empty vector group； HUVECs treated with hypoxia，thrombin，and a recombinant adenovirus carrying the TET2 gene were defined as the AdTET2 group； HUVECs treated with hypoxia，thrombin，and H₂O₂ were defined as the H₂O₂ group； HUVECs treated with hypoxia，thrombin，a recombinant adenovirus carrying the TET2 gene，and H₂O₂ were defined as the AdTET2+H₂O₂ group. The ultrastructure of the cells was observed，and the levels of tissue plasminogen activator （t-PA），thrombomodulin （TM），vascular endothelial growth factor （VEGF），vascular cell adhesion molecule （VCAM），von Willebrand factor（vWF），plasminogen activator inhibitor-1 （PAI-1），reactive oxygen species （ROS），superoxide dismutase（SOD），and malondialdehyde （MDA） were monitored.

Results

Compared with the Norm-C group，the Hypo-C group exhibited swollen and vacuolated organelles in the cytoplasm，but the cell membranes remained intact.In contrast，the Norm-M and Hypo-M groups showed ruptured cell membranes and cytoplasmic leakage. In the Hypo-M group，the levels of t-PA （2.03±0.04） ng/ml，TM （1.04±0.06）ng/ml，SOD activity （12.97±1.79）U/mg，and TET2 mRNA （0.45±0.04） were lower than those in the Norm-C group t-PA （3.29±0.25）ng/ml，TM （1.45±0.11）ng/ml，SOD activity （19.66±2.15）U/mg，TET2 mRNA （1.00±0.07）. Conversely，the levels of VEGF （435.03±18.27） pg/ml，VCAM （74.14±4.47）ng/ml，vWF （87.22±6.57）ng/ml，PAI-1（12.32±0.28）pg/ml，ROS （81 911.90±3 011.78），and MDA （0.87±0.10） nmol/mg were higher in the Hypo-M group than in the Norm-C group VEGF （328.55±21.02）pg/ml，VCAM （56.74±3.95）ng/ml，vWF（66.27±4.91）ng/ml，PAI-1 （8.07±0.43）pg/ml，ROS （46 424.60±2 040.93），MDA（0.55±0.06）nmol/mg.Compared with the model group or the empty vector group，the AdTET2 group showed increased levels of t-PA，TM，and SOD activity，while VEGF，VCAM，vWF，PAI-1，ROS，and MDA were decreased. In the AdTET2+H₂O₂ group，the levels of TM and t-PA were higher than those in the H₂O₂ group，while VEGF，VCAM，vWF，PAI-1，ROS，and MDA were lower than those in the H₂O₂ group.

Conclusion

Hypoxia and thrombin induce injury in HUVECs，while overexpression of TET2 alleviates oxidative stress and exerts a protective effect.

Key words: Ten-eleven translocation methylcytosine dioxygenase 2, Oxidative stress, Endothelial cell injury, Venous thromboembolism, High altitude hypoxia