An Endothelial Storage Granule for Tissue-Type Plasminogen Activator

In previous studies we have shown that, after stimulation by a receptor ligand such as thrombin, tissue-type plasminogen activator (tPA) and von Willebrand factor (vWf) will be acutely released from human umbilical vein endothelial cells (HUVEC). However, the mechanisms involved in the secretion of these two proteins differ in some respects, suggesting that the two proteins may be stored in different secretory granules

Amyloids - A functional coat for microorganisms

Amyloids are filamentous protein structures ~10 nm wide and 0.1–10 µm long that share a structural motif, the cross-β structure. These fibrils are usually associated with degenerative diseases in mammals. However, recent research has shown that these proteins are also expressed on bacterial and fungal cell surfaces. Microbial amyloids are important in mediating mechanical invasion of abiotic and biotic substrates. In animal hosts, evidence indicates that these protein structures also contribute to colonization by activating host proteases that are involved in haemostasis, inflammation and remodelling of the extracellular matrix. Activation of proteases by amyloids is also implicated in modulating blood coagulation, resulting in potentially life-threatening complications.

Acute and chronic effects of oestrogen on endothelial tissue-type plasminogen activator release in postmenopausal women

The capacity of vascular endothelium to locally release tissue-type plasminogen activator (t-PA) represents an important endogenous defence mechanism against intravascular fibrin deposition and thrombosis. We determined the influence of chronic and acute oestrogen administration on endothelial t-PA release in postmenopausal women. Sixty-three healthy postmenopausal women were studied: 31 non-users (age 58 ± 1 years) and 32 users of hormone replacement therapy, including oestrogen alone (ORT: 62 ± 2 years; n = 15) and in combination with progesterone (HRT: 57 ± 1 years; n = 17). Net endothelial t-PA release was determined in vivo, in response to intrabrachial infusions of bradykinin and sodium nitroprusside. To examine the acute effects of oestrogen on endothelial t-PA release, bradykinin and sodium nitroprusside dose-response curves were repeated in the presence of 17 β-oestradiol in 20 of the 31 non-users. Net endothelial release of t-PA was ≈30 % higher (P < 0.01) in women taking ORT (from 2.0 ± 1.0 to 83.6 ± 9.2 ng (100 ml tissue)−1 min−1) compared with those taking HRT (from 1.4 ± 0.4 to 63.5 ± 5.6 ng (100 ml tissue)−1 min−1) and those not taking supplementation (1.0 ± 0.7 to 63.0 ± 4.7 ng (100 ml tissue)−1 min−1). Intra-arterial infusion of 17 β-oestradiol significantly potentiated bradykinin-induced t-PA release. Net endothelial release of t-PA was ≈45 % higher (P < 0.01) after (from 1.0 ± 0.8 to 87.4 ± 9.9 ng (100 ml tissue)−1 min−1) versus before (1.2 ± 0.6 to 60.8 ± 5.6 ng (100 ml tissue)−1 min−1) acute 17 β-oestradiol administration. Our results suggest that oestrogen has a direct modulatory effect on the capacity of the endothelium to release t-PA in healthy postmenopausal women. However, progesterone appears to oppose the favourable influence of oestrogen on endothelial fibrinolytic capacity