Effect of aspirin on high glucose-induced senescence of endothelial cells

Background Endothelial cell senescence is accelerated under high glucose condition, which may contribute to the vascular complications in the diabetics, tt has been proved that aspirin has multiple cytoprotective effects. This study aimed to investigate the effect of aspirin on high glucose-induced endothelial cell senescence and its possible mechanism. Methods Human umbilical venous endothelial cells were cultured in Dulbecco＇s modified Eagle＇s medium （DMEM） with different treatments including the normal glucose （5.5 mmol/L）, high glucose （33 mmol/L） and aspirin （0.01-1.00 mmol/L） with high glucose. And 300 umol/L L-NAME was added to the culture medium when needed. After 48 hours, SA-13-gal staining was used to evaluate the senescence. Total nitric oxide （NO） production and NO synthase （NOS） activity were measured using Griess reaction and molecular probes of 3-amino-4-aminomethyl-2＇, 7＇- difluorescein, diacetate. The level of intracellular reactive oxygen species was monitored by flow cytometry using 2＇, 7＇-dichlorofluorescein diacetate. Endothelial NOS （eNOS）, caveolin-1 protein expressions and caveolin-1/eNOS interaction were analyzed by immunoblotting and immunoprecipitation respectively. Asymmetric dimethylarginine （ADMA） concentration was determined by high-performance liquid chromatography. Results Exposure to 33 mmol/L glucose for 48 hours significantly increased the number of SA-13-gal positive cells. Co-incubation with aspirin markedly inhibited SA-13-gal activity dose-dependently. Aspirin increased NOS activity with eNOS protein expression unchanged and increased NO levels and alleviated oxidative stress. Consistent with these findings, caveolin-1 expression, caveolin-1/eNOS interaction and ADMA accumulation were also decreased. All the inhibitory effects of aspirin on senescence were completely obliterated by L-NAME, the NOS inhibitor. Conclusion The anti-senescent effects of aspirin are fulfilled by increasing NO production via the up-regulation of NOS activity and preventing caveolin-1 expression, caveolin-1/eNOS interaction and ADMA accumulation.

Globular adiponectin protects human umbilical vein endothelial cells against apoptosis through adiponectin receptor 1/adenosine monophosphate-activated protein kinase pathway

Background Endothelial dysfunction is a key event in the onset and progression of atherosclerosis in diabetic patients. Apoptosis may lead to endothelial dysfunction and contribute to vascular complications. However, no study has addressed apoptosis in human umbilical vein endothelial cells （HUVECs） induced by an intermittent high-glucose media and its association with adiponectin receptor 1 （adipoR1）, adipoR2, or adenosine monophosphate （AMP）-activated protein kinase （AMPK）. Methods HUVECs were cultured in continuous normal glucose （5.5 mmol/L）, continuous high glucose （25 mmol/L）, alternating normal and high glucose and mannitol. In the alternating normal and high-glucose media, HUVECs were treated under different conditions. First, cells were transfected with the adipoRl-specific small-interfering RNA （siRNA） and then stimulated with globular adiponectin （gAD）. Second, cells were cultured in both gAD and the AMPK activator 5-aminoimidazole-4-carboxamide-l-13-D-ribofuranoside （AICAR）. Third, cells were cultured in the AMPK inhibitor adenine-9-13-D-arabino-furanoside （araA）, gAD, and in AICAR. Results HUVEC apoptosis increased more significantly in an intermittent high-glucose medium than in a constant high-glucose medium. HUVEC apoptosis induced by an intermittent high-glucose medium was inhibited when the cells were pretreated with 3 pg/ml gAD, which rapidly activated AMPK and adipoR1 in HUVECs. However, adipoR2 was not activated. Conclusions We found that adipoR1, not adipoR2, is involved in mediating intermittent high-concentration glucose- evoked apoptosis in endothelial cells, gAD activated AMPK through adipoR1, leads to the partial inhibition of HUVEC apoptosis. A fluctuating glucose medium is more harmful than a constant high-glucose medium to endothelial cells.