Effect Of Intermittent High Glucose On Human Umbilical Vein Endothelial Cells And The Protective Effect Of Allopurinol

ObjectivesTo observe the injury on human umbilical vein endothelial cell (HUVEC) induced by intermittent high glucose in vitro, study the protective effect of allopurinol on injured vascular endothelial cell (VEC), and discuss its mechanism.Methods1. The injury effect of high glucose and intermittent high glucose on VEC. The experiment was divided into seven groups:A. Normal control (added5.5mol/LGlu constantly); B.7.8mmol/LGlu group (added7.8mmol/LGlu constantly); C.5.5mmol/L/7.8mmol/LGlu group (added5.5mmol/L or7.8mmol/LGlu alternately in every24h); D.14.5mmol/LGlu group (added14.5mmol/LGLU constantly); E.5.5mmol/L/14.5mmol/L Glu group (added5.5mmol/L or14.5mmol/LGlu alternately in every24h); F.20mmol/LGlu group (added20mmol/LGlu constantly); G.5.5mmol/L/20mmol/LGlu group (added5.5mmol/L or20mmol/LGlu alternately in every24h). The sample in each group was incubated with HUVEC for5days respectively, and then MTT for each group was measured. The contents of malondialdehyde (MDA), superoxide dismutase (SOD), intercellular adhesive-1(ICAM-1) and apoptosis rate in cell supernatant for normal control, high glucose and intermittent high glucose group were measured. And the cell morphology was observed by microscopy.2. The protective effect of allopurinol on injury of HUVEC induced by high glucose and intermittent high glucose. The experiment was divided into three groups:(1). Normal control;(2) Allopurinol protective group (Concentrations were0.1mmol/L,0.2mmol/L and0.3mmol/L respectively);(3) VitamineC positive control group (Concentration was100mg/L). Allopurinol and vitamine Cwith differentconcentrations were incubated with HUVEC for5hours firstly. Then,5.5mmol/L/20mmol/L high glucose was added intermittently to induce injury. The content of MDA, SOD, NO, ICAM-1and apoptosis rate in cell supernatant for each group was measured.Results1. Intermittent high glucose and constant high glucose all can result in apoptotic morphological changes of HUVECs. The apoptosis rate in intermittent high glucose group was higher than constant high glucose group (P<0.05). There was no significant difference on the apoptosis rate between5.5or7.8mmol/L glucose group and control group (P>0.05). Compared with the control group, the content of SOD and NO in culture of intermittent high glucose and constant high glucose group waslower(P<0.05), decrease in the intermittent high glucose group was the most significantly (P<0.05). The content of MDA and ICAM-1in culture of intermittent high glucose and constant high glucose group was higher than control group (P<0.05). But the most increased was in intermittent high glucose group (P<0.05).2. The apoptosis rate in allopurinol drug-protective group (0.1mmol/L,0.2mmol/L and0.3mmol/L) was lower than5.5mmol/L/20mmol/L intermittent high glucose group, in which0.3mmol/L was more significant (P<0.01); The contents of SOD and NO in culture of this group were increased more than5.5mmol/L/20mmol/L intermittent high glucose group, in which0.3mmol/L allopurinol group was more significant (P<0.01). The content of MDA and ICAM-1in culture of drug-protective group was lower than intermittent high glucose group, which showed a concentration dependent manner in a certain concentration range(0.05mmol/L-0.2mmol/L)(P<0.05). Conclusion:1. High glucose and intermittent high glucose all have an injury effect on VEC, and intermittent high glucose group is more easily to accelerate the apoptosis of HUVEC than constant high glucose group.2. The mechanism of injury on endothelial cell induced by intermittent high glucose more severe in vitro may be the levels of oxidative stress (OS) increased, inflammatory reaction aggravated and apoptosis rate increased under the intermittent high glucose environment.3. Allopurinol has a protective effect on the injury of HUVEC induced by high glucose and intermittent high glucose that shows a concentration dependent manner.4. The mechanism of protective effect of allopurinol on the injury of HUVEC induced by high glucose and intermittent high glucose includes inhibition of oxidative stress, inflammation and apoptosis.