Upregulation of Aldose Reductase mRNA by Hyperglycemia in Claf Pulmonary Artery Endothelial Cells

Nam, Sang Yiup; Oh, Jung Hyun; Park, Jin Chul; Yoon, Ji Sung; Won, Kyu Chang; Lee, Chan Woo; Cho, Ihn Ho; Lee, Choong Ki; Lee, In Kyu; Lee, Hyoung Woo

Abstract

BACKGROUND: Hyperglycemia is thought to be an important etiologic factor in the development of diabetic macro- and microangiopathies. Several theories have been proposed to explain why diabetic patients are at an increased risk for such vascular disorders. In uncontrolled diabetes, excess glucose causes a glycation of various proteins, an increase in oxidative stress, an increase in DAG or PKC and an increase in polyol pathway. And, it has been proposed that hyperglycemia leads to the dysfunction or damage of endothelial cells through the activation of cellular aldose reductase(polyol pathway). METHODS: To verify this hypothesis, we quantitated AR(Aldose reductase) activity and mRNA in CPAE(Calf pulmonary artery endothelial) cell under normal and high ambient glucose levels in the culture medium. The time course of AR mRNA expression after exposure of CPAE cells to 22mM glucose was determined using PCR quantitative analysis. RESULTS: AR mRNA levels began to increase at 6h after glucose exposure, reached a maximum at 24h (about 2.3 fold increase), and then gradually decreased. Aldose reductase activity was found to strongly correlate with aldose reductase mRNA expression after cells were exposed to 22mM glucose. In contrast, aldose reductase mRNA expression at 24h after glucose exposure decreased following exposure to 50mM glucose. By testing other osmolytes, we also examined whether the AR activity is specific for glucose. There was an increase in AR activity only after the addition of 20mM mannitol to the medium. CONCLUSION: These observations suggest that hyperglycemia could induce the overexpression of aldose reductase mRNA in cultured CPAE cells and this could be an important step in the pathogenesis of diabetic complications.