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Endothelial function, fibrinolysis, and angiotensin-converting enzyme inhibition.

Experimental and clinical studies with angiotensin-converting enzyme (ACE) inhibitors have suggested that these agents may reduce the risk of atherothrombotic events. Recent studies have identified the role of angiotensin II and ACE in the regulation of fibrinolysis. There is now substantial evidence that the renin-angiotensin system (RAS) plays an important role in the regulation of vascular fibrinolytic balance. This recently recognized relationship may contribute to the vasculoprotective effects of ACE inhibitors.

Angiotensin-Converting Enzyme Inhibitors↗

Transforming growth factor-beta(1) restores antiplatelet function of endothelial cells exposed to anoxia-reoxygenation injury.

Transforming growth factor-beta(1) released from platelet alpha-granules may preserve endothelial functions in injured vessels. However, direct evidence is lacking regarding how this cytokine modifies the antithrombotic function of injured endothelial cells. We performed an in vitro study to investigate the effects of transforming growth factor-beta(1) on platelet functions in the presence of cultured endothelial cells exposed to anoxia-reoxygenation injury. Cultured bovine aorta endothelial cells were placed in an anoxic chamber (0.5% O(2), 5% CO(2)) for 60 minutes followed by a 90-minute reoxygenation. Collagen (2 microg/mL)-induced platelet aggregation (10(8) platelets/mL), as determined by impedance aggregometry, was potently inhibited in the presence of control endothelial cells (17.4+/-3.3 Omega) at a concentration of 5x10(4) cells/mL, as compared to their absence (68. 2+/-2.2 Omega). Inhibition of platelet aggregation was attenuated in endothelial cells exposed to anoxia-reoxygenation (54.6+/-2.5 Omega). However, preincubation of endothelial cells with transforming growth factor-beta(1) (1.0 ng/mL) for 16 hours partially recovered the inhibitory capability of platelet aggregation by injured endothelial cells (40.6+/-3.8 Omega). Cell viability, confirmed by a trypan blue dye exclusion test, was similar (93-96%), including control, 1.0 ng/mL transforming growth factor-beta(1)- and/or anoxia-reoxygenation-pretreated cells. The capability of platelet inhibition was restored when the endothelial cells were preincubated for 4 hours or more. Restoration of antiplatelet capacity in endothelial cells by transforming growth factor-beta(1) was suggested to be due to several mechanisms, including an increase in nitric oxide synthase activity, up-regulation of prostacyclin release, and restoration of adenosine triphosphate diphosphohydrolase activity, which was attenuated by anoxia-reoxygenation pretreatment. In summary, transforming growth factor-beta(1) released from activated platelets may play a compensatory role in the preservation of endothelial functions to inhibit platelet activation.

Animals↗

Impaired EDHF-mediated vasodilation and function of endothelial Ca-activated K channels in uremic rats.

BACKGROUND: Chronic renal failure (CRF) is associated with increased cardiovascular morbidity, abnormal arterial tone, and endothelial dysfunction. Ca(2+)-activated K(+)-channels (K(Ca)) are important regulators of endothelial function by controlling endothelial hyperpolarization and thus endothelium-derived hyperpolarizing factor (EDHF)-mediated vasodilations. Here we tested the hypothesis whether an altered function of endothelial K(Ca) and diminished EDHF-mediated vasodilation contribute to the endothelial dysfunction in the rat remnant kidney model of chronic renal failure. METHODS: Functional expression of endothelial K(Ca) currents and endothelium-dependent vasodilations in rat carotid arteries were assessed by using patch-clamp techniques, single-cell reverse transcription-polymerase chain reaction (RT-PCR), and a pressure myograph 8 weeks after either subtotal 5/6 nephrectomy in normotensive or hypertensive, or sham-operated rats. RESULTS: Acetylcholine (ACh)-induced EDHF-mediated vasodilations were present in sham-operated rats, but almost absent in both normotensive 5/6 nephrectomy rats and hypertensive 5/6 nephrectomy rats. In experiments without blocking nitric oxide/prostacyclin synthesis, endothelium-dependent vasodilation to ACh was significantly reduced in both normotensive 5/6 nephrectomy rats and hypertensive 5/6 nephrectomy rats. In sham-operated rats, 1-ethyl-2-benzimidazolinone (1-EBIO), a selective opener of endothelial small and intermediate K(Ca), induced a substantial EDHF-mediated vasodilation, which was greatly reduced in hypertensive 5/6 nephrectomy rats and in normotensive 5/6 nephrectomy rats. In patch-clamp experiments, mean K(Ca) currents were significantly reduced in endothelial cells from hypertensive 5/6 nephrectomy rats and normotensive 5/6 nephrectomy rats when compared to sham-operated rats. Concordantly, single-cell reverse-transcription-polymerase chain reaction (RT-PCR) analysis revealed a greatly reduced frequency of endothelial cells expressing the K(Ca) genes, SKCa3 and IKCa1 in 5/6 nephrectomy rats compared to sham-operated rats. CONCLUSION: Experimental CRF leads to a loss of EDHF-type vasodilation which was caused at least in part by an impaired functional expression of endothelial hyperpolarizing K(Ca). The loss of EDHF-type vasodilation may contribute to endothelial dysfunction and abnormal arterial tone in CRF.

Acetylcholine↗

Wild artichoke prevents the age-associated loss of vasomotor function.

Endothelial dysfunction, which is more often observed in conduit arteries such as the aorta, carotid, femoral, and brachial arteries, is largely due to alterations in cellular signal transduction initiated by an escalating cycle of damage triggered by oxidative stress. This phenomenon is exacerbated in the elderly, where a progressive loss of vascular endothelial function and concurrent loss of vasomotor control is frequent. In a previous study, we demonstrated that the wild artichoke (Cynara cardunculus) is able to increase the production of the vasorelaxant factor nitric oxide by cultured aortic endothelial cells. We now extended that study to verify (1) the vasorelaxant potential of C. cardunculus on isolated rat aortic rings and (2) whether the vasomodulating properties of C. cardunculus are maintained in vivo, after administration to aged rats. The results demonstrate that the wild artichoke and its main components, namely, luteolin and apigenin, improve aortic relaxation when added to the incubation bath. Moreover, the feeding of wild artichoke [10 mg (kg of polyphenols)(-1) day(-1)] to aged rats significantly restores proper vasomotion, to a degree similar to that observed in young animals. This study provides further justification to the advice to consume wild greens as part of a balanced diet and suggests that close attention should be paid to the diet of the elderly, because it can effectively modulate important parameters of cardiovascular risk.

Aging↗

Expression and function of endothelial Ca(2+)-activated K(+) channels in human mesenteric artery: A single-cell reverse transcriptase-polymerase chain reaction and electrophysiological study in situ.

Ca(2+)-activated K(+) (K(Ca)) channels have been suggested to play a role in the control of endothelial functions such as regulation of vascular tone and cell proliferation. We established a method for single-cell reverse transcriptase-polymerase chain reaction analysis in combination with the patch-clamp technique to characterize K(Ca) channel expression and function in single endothelial cells (ECs) within the endothelial monolayer of intact human mesenteric arteries (MAs) and in disease states. We tested whether endothelial K(Ca) channel expression and function are altered in MAs obtained from patients with colonic adenocarcinoma (CA) compared with those in MAs from non-cancer patients with inactive diverticulitis. Expression of the intermediate-conductance K(Ca) channel (hIK1) was detected in non-cancer and CA patients. In whole-cell patch-clamp measurements, only ECs expressing hIK1 exhibited corresponding K(Ca) currents, whereas respective K(Ca) currents were missing in hIK1-negative ECs. This heterogeneity of hIK1 expression patterns is indicative of a specialized subset of ECs within the endothelial monolayer. In CA patients, compared with non-cancer patients, a 2.5-fold increase in hIK1-expressing ECs per MA was observed (P:<0.05). However, K(Ca) current densities in hIK1-expressing ECs of both groups were similar. In addition to hIK1, expression of the large-conductance K(Ca) channel (hSlo) was detected in single ECs from CA patients. The increased K(Ca) channel expression in CA patients resulted in a 2. 7-fold increase of bradykinin-induced endothelial hyperpolarization compared with controls (P:<0.05). This increased expression and function of K(Ca) channels might indicate an altered functional state of the endothelium in cancer patients and could play a role in tumor angiogenesis.

Adenocarcinoma↗

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