Elevated Intraluminal Pressure Inhibits Vascular Tissue Plasminogen Activator Secretion and Downregulates Its Gene Expression

Abstract

Abstract-We recently discovered that patients with essential hypertension have a markedly impaired capacity for stimulated release of tissue plasminogen activator (tPA) from vascular endothelium. This defect may reduce the chance of timely spontaneous thrombolysis in case of an atherothrombotic event. We now investigated whether increased intraluminal pressure as such may depress vascular tPA release or downregulate its gene expression. Segments of human umbilical veins were studied in a new computerized vascular perfusion model under steady laminar flow conditions for 3 or 6 hours. Paired segments were perfused at high or physiological intraluminal pressure (40 versus 20 mm Hg) under identical shear stress (10 dyne/cm 2 ). Quantitative immunohistochemical evaluation of cellular tPA immunoreactivity was performed on paraffin-embedded 5-m vascular sections. tPA mRNA in endothelial cells was quantified with reverse transcription real-time TaqMan polymerase chain reaction with GAPDH as endogenous control. Secretion of tPA into perfusion medium was evaluated with SDS-PAGE and Western blotting, followed by densitometric quantification. High-pressure perfusion downregulated tPA gene expression with a 38% decrease in tPA mRNA levels (Pϭ0.01) compared with vessels perfused under normal intraluminal pressure. tPA release into the perfusion medium was markedly suppressed by high pressure (PϽ0.01 ANOVA). The intracellular storage pool of tPA was reduced after 6 but not 3 hours. Thus, elevated intraluminal pressure downregulates tPA gene and protein expression and inhibits its release from the endothelium independently of shear stress. The defective capacity for stimulated tPA release that we demonstrated in patients with essential hypertension might thus be an effect of the elevated intraluminal pressure per se.

Impaired Endothelial Release of Tissue-Type Plasminogen Activator in Patients With Chronic Kidney Disease and Hypertension

“…We recently demonstrated in an ex vivo perfusion model that both tPA synthesis and release from endothelial cells in isolated human conduit vessels was markedly suppressed when intraluminal pressure was elevated to the high physiological range. 4 The intracellular signal transduction pathways mediating the effect of intravascular pressure are, as yet, not fully elucidated, but this observation offers a potential explanation for the observed defective tPA secretory response in patients with high blood pressure.…”

“…We recently showed that the capacity for tPA release is markedly impaired in patients with untreated primary hypertension, 3 and further experimental ex vivo studies indicated that this defect could be because of the elevated intraluminal pressure per se. 4 Chronic kidney disease (CKD) is frequently accompanied by hypertension and also with a markedly increased risk of atherothrombotic complications. 5 The association of CKD with thrombotic events is somewhat puzzling because renal disease is typically associated with increased bleeding tendency due to platelet dysfunction and disturbed plasma coagulation.…”

Stimulated Tissue Plasminogen Activator Release as a Marker of Endothelial Function in Humans

“…Serum from smokers, but not from nonsmokers, reduced substance P-induced t-PA release from cultured endothelial cells, 96 suggesting that a blood-borne mediator may affect endothelial t-PA responses. Using ex vivo human umbilical veins, increased intraluminal pressure decreased t-PA release as well as gene and protein expression, 97 suggesting that raised intraluminal pressure might itself impair t-PA release. Detailed characterization of the path-ways of t-PA secretion and how these are affected by different stimuli will provide a platform for the investigation of the mechanisms of impaired secretion.…”

Evidence for renoprotection by blockade of the renin–angiotensin–aldosterone system in hypertension and diabetes

“…28 Elevated intraluminal pressure can also lead to downregulation of tissue plasminogen activator, a promoter of fibrinolysis/thrombolysis, which is impaired in patients with hypertension. 29 Angiotensin II also increases production of plasminogen activator inhibitor-1, which is both a major inhibitor of fibrinolysis and is antiproteolytic, thus promoting matrix accumulation. 30 Aldosterone independently contributes to renal injury, as well.…”