Objectives To explore the influence of constant or intermittent high glucose on human umbilical vein endothelial cells (HUVECs), and the effects of tetramethylpyrazine (TMP) on HUVECs exposed to constant or intermittent high glucose.
Methods HUVECs were incubated for 8 days in media containing different glucose concentrations: 5.56 mmol/l (normal glucose), 25 mmol/l (constant high glucose), or a daily alternating 5.56 or 25 mmol/l glucose (intermittent high glucose). Meanwhile, drug intervention was performed in different glucose conditions with TMP at concentrations of 500 μmol/L, 100 μmol/L and 20 μmol/L. Then cell viability was measured by MTT method, cell membrane damage was determined by lactate dehydrogenase (LDH) leakage, and Nitric oxide (NO), endothelin-1 (ET-1), soluble intercellular adhesion molecule-1 (sICAM-1) and tumour necrosis factor-α (TNF-α) concentrations in the cell culture supernatant were measured. The activities of superoxide dismutase (SOD), nitric oxide synthetase (NOS) and the contents of malondialdehyde (MDA) in the cell lysate were examined by enzyme method or spectrophotometry.
Results The HUVECs viability and LDH leakage were no significance difference in different glucose culture conditions with or without TMP. Compared with constant high glucose or intermittent high glucose group, 500 μmol/L and 100 μmol/L TMP could significantly decreased the increased MDA, ET-1, TNF-α and sICAM-1 levels induced by constant high glucose or intermittent high glucose (P < 0.05 or P < 0.01), while obviously increased the decreased SOD, NOS and NO levels (P < 0.05 or P < 0.01).
Conclusions Both intermittent and constant high glucose could impair vascular endothelial function, while TMP can partially reverse this impairment, which may take effect by alleviating oxidative stress, reducing inflammatory reaction and cell adhesion molecule.