Synergistic injury of the endothelial cells by high glucose and high uric acid through the aldose reductase pathway

Abstract

Objective To find the common target and molecular mechanism of the synergistic injury of the endothelial cell caused by high glucose and high uric acid for prevention from cardiovascular diseases in diabetes patients complicated with hyperuricemia. Methods The human umbilical vein endothelial cell line (HUVEC-C) was treated with high glucose (30 mmol/L, HG), high uric acid (600 μmol/L, UA) or HG plus UA for 48 hours. The activity of aldose reductase (AR) was blocked with alrestatin (10 μmol/L). Real-time quantitative PCR was used for detecting the mRNA expression of endothelial nitric oxide synthase (eNOS) and AR. Western blot was used to detect the expression of reduced nicotinamide adenine dinucleotide phosphate oxidase (NOX)2, NOX4, eNOS and AR proteins. The intracellular activity of ROS was assayed with confocal microscopy. Nitric oxide (NO) concentration was measured with chemiluminescence assay kit. Results Compared with the HG or UA, HG+ UA could significantly reduce not only the mRNA and protein levels of eNOS but also NO production, and increase the intracellular ROS generation in the endothelial cells. HG+ UA also remarkably increased AR mRNA level and protein expression. Furthermore, in the endothelial cells of the HG+ UA group, alrestatin significantly increased the mRNA and protein expression of eNOS as well as the secretion level of NO, while alrestatin obviously down-regulated both the protein expression of NOX4 and the intracellular content of ROS, but had no effects on NOX2. Conclusions In endothelial cells, via the aldose reductase pathway, the hyperglycemia and hyperuricemia synergistically decreased the expression of eNOS and the production of NO, but increased the ROS generation, aggravating the endothelial dysfunction, which could be blocked by inhibition of aldose reductase through down-regulation of NOX4. Key words: High glucose; High uric acid; Endothelial cell; Aldose reductase; Nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4)