Glucose and human vascular endothelial cell ageing
This study examined whether raised extracellular glucose concentrations (through increased oxidative stress) could induce DNA damage and hasten human vascular endothelial cell (HUVEC) senescence.;HUVEC DNA damage was measured using the comet assay. Senescence was detected by beta-Galactosidase staining at pH 6. Telomere lengths and mitochondrial genome copy numbers were obtained through Southern analysis. 8-oxoguanine excision was assessed by a nucleotide incision assay. Western blotting demonstrated Ref-1 and electron transport chain complex IV (subunit I) expression.;DNA damage peaked after four fours of high glucose (HG; 22mM) exposure. This was D-glucose specific and concentration dependent. DNA damage was attenuated by N-acetylcysteine (p < 0.01) and augmented by formamidopyrimidine DNA glycosylase (p <0.05), indicating that HG induced oxidative lesions. DNA damage was associated with premature HUVEC senescence (p = 0.011) and accelerated telomere shortening (p = 0.03). N-acetylcysteine did not prevent telomere attrition. 8-oxoguanine incision and Ref-1 expression decreased during 24-hour HG treatment, suggesting that HG could disrupt the efficiency of oxidative DNA lesion repair. No difference in mitochondrial DNA content in HG exposed HUVECs was found. However, complex IV (subunit I) expression fell in HG conditioned HUVECs ( p = 0.006), implying that HG could affect mitochondrial activity.;This study demonstrates for the first time that elevated glucose concentrations promote oxidative DNA damage in human vascular cells. This leads to accelerated telomere attrition, prompts premature human endothelial cell senescence and may profoundly disturb mitochondrial function. These observations provide a novel mechanism to implicate glucose in accelerated vascular ageing in diabetes.