INCREASED EXPRESSION OF TISSUE PLASMINOGEN-ACTIVATOR AND ITS INHIBITOR AND REDUCED FIBRINOLYTIC POTENTIAL OF HUMAN ENDOTHELIAL-CELLS CULTURED IN ELEVATED GLUCOSE

In diabetic patients, elevated plasma levels of t-PA and PAl-1 accompany impaired fibrinolysis. To identify mechanisms for these abnormalities, we examined whether vascular endothelial cells exposed to high glucose upregulate t-PA and PAl-1 production and whether ambient PA activity is decreased concomitantly. In 17 cultures of human umbilical vein endothelial cells grown to confluency in 30 mM glucose, the t-PA antigen released to the medium in 24 h was (median) 52 ng/10(6) cells (range 10-384) and the PAl-1 antigen was 872 ng/10(6) cells (range 217-2074)-both greater (P < 0.02) than the amounts released by paired control cultures grown in 5 mM glucose-29 ng/10(6) cells (range 7.5-216) and 461 ng/10(6) cells (range 230-3215), respectively. In the presence of high glucose, the steady-state levels of t-PA and PAl-1 mRNAs were increased correspondingly (median 142 and 183% of control, respectively, P < 0.05); high glucose per se and hypertonicity contributed to the upregulation in additive fashion. The PA activity of conditioned medium from cultures exposed to high glucose was 0.4 IU/ml (range 0.2-0.6), which was significantly lower (P < 0.02) than the PA activity of control medium (0.5 IU/ml, range 0.2-0.9). No difference was observed when comparing the PA activities of acidified conditioned media, expected to be depleted of inhibitors. Thus, high glucose coordinately upregulates endothelial t-PA and PAl-1 expression through effects exerted at the pretranslational level and enhanced by even mild degrees of hypertonicity. The decrease in ambient fibrinolytic potential may reflect an overwhelming effect of the increased availability of PAl-1. These findings propose a contributory mechanism for the fibrinolytic abnormalities of diabetes and the thrombotic tendency of the hyperglycemic hyperosmolar state.