Glucose-induced up-regulation of CD36 mediates oxidative stress and microvascular endothelial cell dysfunction

Abstract

Hyperglycaemia-induced oxidative stress is implicated in the pathogenesis of chronic diabetic complications. Glucose-mediated oxidation of LDL may result in increased oxidative stress and vascular endothelial cell dysfunction via interaction with a cell surface scavenger receptor, CD36. In this study, we investigated the role of CD36 in cultured microvascular endothelial cells (MVECs) and in the heart by using an animal model of chronic diabetes. Cultured MVECs were subjected to varying glucose concentrations and assayed for alteration in CD36 gene expression and protein levels. To assess for oxidised LDL (ox-LDL) uptake, MVECs exposed to low and high glucose were treated with ox-LDL (80 microg/ml), a ligand for CD36. Haem oxygenase-1 (HO-1) and endothelin-1 (ET-1) induction, as well as oxidative stress were determined. The role of glucose-induced CD36 alteration in ox-LDL uptake was also assayed following post-transcriptional CD36 gene silencing. For in vivo studies, CD36 mRNA and oxidative DNA and protein damage were measured in heart tissues of 1-month-old diabetic Sprague-Dawley rats. We found that glucose increased CD36 mRNA and protein levels in MVECs. High levels of glucose also augmented ox-LDL uptake, in association with increasing HO-1 and ET-1 mRNA levels. CD36 gene silencing prevented glucose-induced CD36 alteration, reduced ox-LDL uptake, and prevented HO-1 and ET-1 up-regulation. Similar to in vitro studies, diabetic heart tissues exhibited increased CD36 mRNA levels and increased oxidative DNA and protein damage. Our results provide evidence that up-regulation of CD36 may have a role in increasing oxidative stress in MVECs and the heart in chronic diabetes.