Different activation of the endothelial L-arginine and cyclooxygenase pathway in the human internal mammary artery and saphenous vein

Superficial temporal artery interposition bypass for the treatment of complex intracranial aneurysms: Flexible and creative options for flow preservation bypass

PURPOSE

Flow-preservation bypass is a treatment option for complex intracranial aneurysms (IAs) that cannot be managed with microsurgical clipping or endovascular treatment. Various bypass methods are available, including interposition grafts such as the radial artery or saphenous vein. Size discrepancy, invasiveness, and procedure complexity must be considered when using interposition grafts. We describe our experience of treating complex IAs using a superficial temporal artery (STA) interposition bypass.

METHODS

We retrospectively reviewed the medical records and operative videos of all patients who were treated for complex IAs at our center from January 2009 to December 2021 using cerebral revascularization. Clinical, radiological, and surgical findings of the cases that underwent STA interposition bypass were investigated.

RESULTS

Seventy-six bypass procedures were performed of which seven (9.2%) complex IAs were managed using STA interposition bypass. Of these 5 cases were of anterior cerebral artery, 1 of middle cerebral artery, and 1 of posterior inferior cerebellar artery aneurysm. There were no postoperative ischemic complications. Revision surgery for postoperative pseudomeningocele was performed in one case. The long-term bypass patency rate was 85.7% (6 out of 7) and good long-term aneurysm control was achieved in all cases, with a mean follow-up of 64 months.

CONCLUSIONS

When treating complex IAs, creative revascularization strategies are needed in selective cases for favorable outcomes. STA interposition graft bypass which can reduce the size discrepancy between the donor and recipient may be a less invasive, flexible, and practical option for treating complex IAs.

Multi-Omics Profiling of Human Endothelial Cells from the Coronary Artery and Internal Thoracic Artery Reveals Molecular but Not Functional Heterogeneity

Major adverse cardiovascular events occurring upon coronary artery bypass graft surgery are typically accompanied by endothelial dysfunction. Total arterial revascularisation, which employs both left and right internal thoracic arteries instead of the saphenous vein to create a bypass, is associated with better mid- and long-term outcomes. We suggested that molecular profiles of human coronary artery endothelial cells (HCAECs) and human internal mammary artery endothelial cells (HITAECs) are coherent in terms of transcriptomic and proteomic signatures, which were then investigated by RNA sequencing and ultra-high performance liquid chromatography-mass spectrometry, respectively. Both HCAECs and HITAECs overexpressed molecules responsible for the synthesis of extracellular matrix (ECM) components, basement membrane assembly, cell-ECM adhesion, organisation of intercellular junctions, and secretion of extracellular vesicles. HCAECs were characterised by higher enrichment with molecular signatures of basement membrane construction, collagen biosynthesis and folding, and formation of intercellular junctions, whilst HITAECs were notable for augmented pro-inflammatory signaling, intensive synthesis of proteins and nitrogen compounds, and enhanced ribosome biogenesis. Despite HCAECs and HITAECs showing a certain degree of molecular heterogeneity, no specific markers at the protein level have been identified. Coherence of differentially expressed molecular categories in HCAECs and HITAECs suggests synergistic interactions between these ECs in a bypass surgery scenario.

Left Internal Mammary Artery as an Endocrine Organ: Insights Into Graft Biology and Long-term Impact Following Coronary Artery Bypass Grafting

The left internal mammary artery (LIMA) is considered the criterion standard vessel for use in coronary artery bypass grafting. In recent decades, countless studies have documented its superiority over other arterial and venous coronary artery bypass grafting conduits, although the full mechanisms for this superiority remain unknown. A growing body of literature has unveiled the importance of extracellular vesicles known as exosomes in cardiovascular signaling and various pathologic states. In this review, we briefly compare the clinical longevity of the LIMA relative to other conduits, explore the effects of varying grafting techniques on clinical and angiographic outcomes, and provide physiologic insights into graft function on a cellular and molecular level. Finally, we explore exosome signaling as it pertains to atherosclerosis in support of the LIMA as an "endocrine organ."

Venous endothelial function in cardiovascular disease

The essential role of the endothelium in vascular homeostasis is associated with the release of endothelium-dependent relaxing and contractile factors (EDRF and EDCF, respectively). Different from arteries, where these factors are widely studied, the vasoactive factors derived from the venous endothelium have been given less attention. There is evidence for a role of the nitric oxide (NO), endothelium-dependent hyperpolarization (EDH) mechanism, and cyclooxygenase (COX)-derived metabolites as EDRFs; while the EDCFs need to be better evaluated since no consensus has been reached about their identity in venous vessels. The imbalance between the synthesis, bioavailability, and/or action of EDRFs and/or EDCFs results in a pathological process known as endothelial dysfunction, which leads to reduced vasodilation and/or increased vasoconstriction. In the venous system, endothelial dysfunction is relevant since reduced venodilation may increase venous tone and decrease venous compliance, thus enhancing mean circulatory filling pressure, which maintains or modify cardiac workload contributing to the etiology of cardiovascular diseases. Interestingly, some alterations in venous function appear at the early stages (or even before) the establishment of these diseases. However, if the venous endothelium dysfunction is involved in these alterations is not yet fully understood and requires further studies. In this sense, the present study aims to review the current knowledge on venous endothelial function and dysfunction, and the general state of the venous tone in two important cardiovascular diseases of high incidence and morbimortality worldwide: hypertension and heart failure.

Acute dietary nitrate supplementation does not change venous volume and compliance in healthy young adults

In this randomized single-blind, placebo-controlled, crossover study, we investigated the influence of inorganic nitrate (NO₃^-) supplementation on venous volume and compliance in the resting forearm and calf. Twenty healthy young adults were assigned to receive an NO₃^--rich beverage (beetroot juice [BRJ]: 140 mL; ~8 mmol NO₃^-) or an NO₃^¯-depleted control beverage (prune juice [CON]: 166 mL; < 0.01 mmol NO₃^-). Two hours after consuming the allocated beverage, each participant rested in the supine position for 20 min. Cuffs were then placed around the right upper arm and right thigh, inflated to 60 mmHg for 8 min, and then decreased to 0 mmHg at a rate of 1 mmHg/s. During inflation and deflation of cuff pressure, changes in venous volume in the forearm and calf were measured by venous occlusion plethysmography. Venous compliance was calculated as the numerical derivative of the cuff pressure‒venous volume curve in the limbs. The plasma NO₃^- concentration was elevated by intake of BRJ (before, 15.5 ± 5.8 µM; after, 572.0 ± 116.1 µM, P < 0.05) but not by CON (before, 14.8 ± 7.2 µM; after, 15.3 ± 7.4 µM, P > 0.05). On the other hand, there was no significant difference in venous volume or compliance in the forearm or calf between BRJ and CON. These findings suggest that although acute inorganic NO₃^- supplementation may enhance the activity of nitric oxide (NO) via NO₃^- → nitrite → NO pathway, it does not influence venous volume or compliance in the limbs in healthy young adults.

Endothelium-dependent contraction: The non-classical action of endothelial prostacyclin, its underlying mechanisms, and implications

Although commonly thought to produce prostacyclin (prostaglandin I₂ ; PGI₂ ) that evokes vasodilatation and protects vessels from the development of diseases, the endothelial cyclooxygenase (COX)-mediated metabolism has also been found to release substance(s) called endothelium-derived contracting factor(s) (EDCF) that causes endothelium-dependent contraction and implicates in endothelial dysfunction of disease conditions. Various mechanisms have been proposed for the process; however, the major endothelial COX metabolite PGI₂ , which has been classically considered to activate the I prostanoid receptor (IP) that mediates vasodilatation and opposes the effects of thromboxane (Tx) A₂ produced by COX in platelets, emerges as a major EDCF in health and disease conditions. Our recent studies from genetically altered mice further suggest that vasomotor reactions to PGI₂ are collectively modulated by IP, the vasoconstrictor Tx-prostanoid receptor (TP; the prototype receptor of TxA₂ ) and E prostanoid receptor-3 (EP3; a vasoconstrictor receptor of PGE₂ ) although with differences in potency and efficacy; a contraction to PGI₂ reflects activities of TP and/or EP3 outweighing that of the concurrently activated IP. Here, we discuss the history of endothelium-dependent contraction, evidences that support the above hypothesis, proposed mechanisms for the varied reactions to endothelial PGI₂ synthesis as well as the relation of its dilator activity to the effect of another NO-independent vasodilator mechanism, the endothelium-derived hyperpolarizing factor. Also, we address the possible pathological and therapeutic implications as well as questions remaining to be resolved or limitations of our above findings obtained from genetically altered mouse models.

Resilience of the Internal Mammary Artery to Atherogenesis: Shifting From Risk to Resistance to Address Unmet Needs

Fueled by the global surge in aging, atherosclerotic cardiovascular disease reached pandemic dimensions putting affected individuals at enhanced risk of myocardial infarction, stroke, and premature death. Atherosclerosis is a systemic disease driven by a wide spectrum of factors, including cholesterol, pressure, and disturbed flow. Although all arterial beds encounter a similar atherogenic milieu, the development of atheromatous lesions occurs discontinuously across the vascular system. Indeed, the internal mammary artery possesses unique biological properties that confer protection to intimal growth and atherosclerotic plaque formation, thus making it a conduit of choice for coronary artery bypass grafting. Its endothelium abundantly expresses nitric oxide synthase and shows accentuated nitric oxide release, while its vascular smooth muscle cells exhibit reduced tissue factor expression, high tPA (tissue-type plasminogen activator) production and blunted migration and proliferation, which may collectively mitigate intimal thickening and ultimately the evolution of atheromatous plaques. We aim here to provide insights into the anatomy, physiology, cellular, and molecular aspects of the internal mammary artery thereby elucidating its remarkable resistance to atherogenesis. We propose a change in perspective from risk to resilience to decipher mechanisms of atheroresistance and eventually identification of novel therapeutic targets presently not addressed by currently available remedies.

Endothelial cyclooxygenase-1 paradoxically drives local vasoconstriction and atherogenesis despite underpinning prostacyclin generation

Endothelial cyclooxygenase-1-derived prostanoids, including prostacyclin, have clear cardioprotective roles associated with their anti-thrombotic potential but have also been suggested to have paradoxical pathological activities within arteries. To date it has not been possible to test the importance of this because no models have been available that separate vascular cyclooxygenase-1 products from those generated elsewhere. Here, we have used unique endothelial-specific cyclooxygenase-1 knockout mice to show that endothelial cyclooxygenase-1 produces both protective and pathological products. Functionally, however, the overall effect of these was to drive pathological responses in the context of both vasoconstriction in vitro and the development of atherosclerosis and vascular inflammation in vivo. These data provide the first demonstration of a pathological role for the vascular cyclooxygenase-1 pathway, highlighting its potential as a therapeutic target. They also emphasize that, across biology, the role of prostanoids is not always predictable due to unique balances of context, products, and receptors.

Dipyridamole Potentiates the Endothelium-Dependent and -Independent Vasomotion in Isolated Human Small Arteries

Background

To investigate the effects of dipyridamole, a drug with phosphodiesterase-, adenosine reuptake-inhibiting, and prostacyclin-stimulating activity on the biological actions of nitric oxide, 30 norepinephrine-precontracted subcutaneous arterioles were prepared from specimens removed during surgery.

Methods and Results

Specimens were mounted on a myograph and relaxed through either acetylcholine, a muscarinic agonist that stimulates endothelial nitric oxide production, or sodium nitroprusside, an endothelium-independent vasodilator. Studies were performed under control conditions and after dipyridamole which potentiated in a concentration-dependent manner the vasorelaxation induced both by acetylcholine and sodium nitroprusside, indicating an endothelium-independent mechanism of action. The contribution of nitric oxide to the relaxation produced by acetylcholine was confirmed by N-monomethyl-L-arginine, a nitric oxide synthase inhibitor. In contrast, indomethacin, a cyclo-oxygenase inhibitor, was ineffective, indicating that prostacyclin stimulation could not explain the effect of dipyridamole. CGS 21680 C, an A2-selective adenosine receptor agonist insensitive to tissue deaminase, did not influence the relaxations induced by acetylcholine, suggesting that interference with adenosine metabolism was not implicated in the potentiating action of dipyridamole.

Conclusion

Dipyridamole potentiated the vasorelaxing effect of acetylcholine and sodium nitroprusside in human subcutaneous arterioles; neither prostacyclin stimulation nor A2adenosine receptor stimulation could explain this effect. The data are consistent with an increase in intracellular cyclic 3’ 5'-guanosine monophosphate levels secondary to the phosphodiesterase-inhibiting properties of the drug.

Association between vegetable consumption and calf venous compliance in healthy young adults

BACKGROUND

Venous compliance decreases with aging and/or physical inactivity, which is thought to be involved partly in the pathogenesis of cardiovascular disease such as hypertension. This suggests that it is important to maintain high venous compliance from a young age in order to prevent cardiovascular disease. Both nutrient and exercise could play an important role in the improvement and maintenance of vascular health. Indeed, habitual endurance exercise is known to improve the venous compliance, although little is known about the effect of diet on venous compliance. Considering that higher consumption of vegetables could contribute to the arterial vascular health and the decreased blood pressure, it is hypothesized that venous compliance may be greater as vegetable intake is higher. Thus, the purpose of this study was to clarify the association between vegetable intake and venous compliance in healthy young adults.

METHODS

Dietary intake was assessed in 94 subjects (male: n = 44, female: n = 50) using a self-administered diet history questionnaire (DHQ). Intakes of nutrients and food groups that were obtained from the DHQ were adjusted according to total energy intake using the residual method. Based on the adjusted intake of food groups, total vegetable intake was calculated as the sum of green/yellow and white vegetables consumed. Calf volume was measured using venous occlusion plethysmography with a cuff deflation protocol. Calf venous compliance was calculated as the numerical derivative of the cuff pressure-calf volume curve. In addition, circulatory responses (heart rate and systolic and diastolic blood pressure) at resting and maximal oxygen uptake were assessed in all subjects.

RESULTS

Mean value of total vegetables intake was 162.2 ± 98.2 g/day. Simple linear regression analysis showed that greater venous compliance was significantly associated with higher total vegetable consumption (r = 0.260, P = 0.011) and green/yellow vegetable intake (r = 0.351, P = 0.001) but not white vegetable intake (r = 0.013, P = 0.902). These significant associations did not change in the multivariate linear regression models which were adjusted by sex and maximal oxygen uptake.

CONCLUSION

These findings suggest that higher consumption of vegetables, especially of the green/yellow vegetables, may be associated with greater venous compliance in young healthy adults.

Graft Occlusion and Graft Size Changes in Complex Internal Carotid Artery Aneurysm Treated by Extracranial to Intracranial Bypass Using High-Flow Grafts with Therapeutic Internal Carotid Artery Occlusion

BACKGROUND

Although the extracranial-to-intracranial high-flow bypass (EC-IC HFB) continues to be indispensable for complex aneurysms, the risk factors for the graft occlusion and whether the graft size changes after the bypass have not been well established.

OBJECTIVE

To evaluate the risk factors for the graft occlusion and to confirm whether graft diameters changed over time.

METHODS

The data of 75 patients who suffered from complex internal carotid artery (ICA) aneurysms and were treated by EC-IC HFB using radial artery graft (RAG) or saphenous vein graft (SVG) with therapeutic ICA occlusion were evaluated. Clinical and radiological characteristics were compared in patients with and without the graft occlusion by the log-rank test. Graft diameters measured preoperatively, postoperatively, at 6 months, and at 1 year were compared by paired t-test.

RESULTS

During a follow-up period (median 26.2 months), graft occlusions were seen in 4 patients (5.3%), and these were the SVGs. Only SVG was related to graft occlusion (P < .001). There was a significant increase with time in RAG diameters (preoperative, 3.1 ± 0.41 mm; postoperative, 3.6 ± 0.65 mm; 6 months, 4.3 ± 1.0 mm; 1 year, 4.4 ± 1.0 mm), while there were no significant diameter changes in SVGs.

CONCLUSION

The present study showed that the SVG was related to the graft occlusion and RAGs gradually enlarged. Unless Allen test is negative, RAG may be better to be used as a graft in EC-IC HFB if therapeutic ICA occlusion is needed.

Venous endothelium reactivity to Angiotensin II: A study in primary endothelial cultures of rat vena cava and portal vein

The role of the vascular endothelium in modulating the arterial system has been widely investigated, but poorly explored at the venous site. In the present work, primary cultures of venous endothelium from rat Vena Cava (VC) and Portal Vein (PV) were established, characterized and analyzed according to their growth pattern and ability to produce nitric oxide (NO) and prostanoids (PGF_{2 α} and PGI₂), at basal state and after stimulation with Angiotensin II (Ang II, 1μmol/L). Basal NO was detected in all examined cells in culture. Pre-incubation with Ang II increased NO production in cells from VC (but not in PV cultures), through activation of both AT₁ and AT₂ receptors. Both cultures exhibited detectable levels of PGF_{2 α} at resting conditions, which were similarly enhanced by Ang II. Basal PGI₂ levels were higher in PV, but increased after Ang II treatment in VC, with no further effect on PV cells. We conclude that endothelial cells from VC and PV exhibit important properties and react to Ang II, probably influencing the whole circulatory system. This experimental cell model gives support to further studies concerning intracellular pathways of the venous endothelium, analyzed in separate from the vascular smooth muscle wall.

Circadian Influence on Metabolism and Inflammation in Atherosclerosis

Many aspects of human health and disease display daily rhythmicity. The brain's suprachiasmic nucleus, which interprets recurring external stimuli, and autonomous molecular networks in peripheral cells together, set our biological circadian clock. Disrupted or misaligned circadian rhythms promote multiple pathologies including chronic inflammatory and metabolic diseases such as atherosclerosis. Here, we discuss studies suggesting that circadian fluctuations in the vessel wall and in the circulation contribute to atherogenesis. Data from humans and mice indicate that an impaired molecular clock, disturbed sleep, and shifting light-dark patterns influence leukocyte and lipid supply in the circulation and alter cellular behavior in atherosclerotic lesions. We propose that a better understanding of both local and systemic circadian rhythms in atherosclerosis will enhance clinical management, treatment, and public health policy.

Neuronal nitric oxide synthase-derived hydrogen peroxide effect in grafts used in human coronary bypass surgery

Recently, H₂O₂ has been identified as the endothelium-dependent hyperpolarizing factor (EDHF), which mediates flow-induced dilation in human coronary arteries. Neuronal nitric oxide synthase (nNOS) is expressed in the cardiovascular system and, besides NO, generates H₂O₂ The role of nNOS-derived H₂O₂ in human vessels is so far unknown. The present study was aimed at investigating the relevance of nNOS/H₂O₂ signaling in the human internal mammary artery (IMA) and saphenous vein (SV), the major conduits used in coronary artery bypass grafting. In the IMA, but not in the SV, ACh (acetylcholine)-induced vasodilatation was decreased by selective nNOS inhibition with TRIM or Inhibitor 1, and by catalase, which specifically decomposes H₂O₂ Superoxide dismutase (SOD), which generates H₂O₂ from superoxide, decreased the vasodilator effect of ACh on SV. In the IMA, SOD diminished phenylephrine-induced contraction in endothelium-containing, but not in endothelium-denuded vessels. Importantly, while exogenous H₂O₂ produced vasodilatation in IMA, it constricted SV. ACh increased H₂O₂ production in both sets of vessels. In the IMA, the increase in H₂O₂ was inhibited by catalase and nNOS blockade. In SV, H₂O₂ production was abolished by catalase and reduced by nNOS inhibition. Immunofluorescence experiments showed the presence of nNOS in the vascular endothelium and smooth muscle cells of both the IMA and SV. Together, our results clearly show that H₂O₂ induced endothelium-dependent vascular relaxation in the IMA, whereas, in the SV, H₂O₂ was a vasoconstrictor. Thus, H₂O₂ produced in the coronary circulation may contribute to the susceptibility to accelerated atherosclerosis and progressive failure of the SV used as autogenous graft in coronary bypass surgery.

Endothelium, lipoproteins and atherosclerotic vascular disease

The endothelium modulates vascular tone by releasing nitric oxide, which is a potent vasodilator and inhibitor of platelet aggregation. Together with prostacyclin, the endogenous nitrate nitric oxide has an important protective role in preventing vasospasm and thrombus formation. In addition, the endothelium is a source of contracting factors such as endothelin-1, thromboxane A2 and endoperoxides. Due to its strategic anatomical position, the endothelium is a primary target for injurious stimuli and cardiovascular risk factors. Low density lipoproteins reduce endothelium-dependent relaxation and enhance endothelium- dependent contraction. The same pattern of endothelial dysfunction occurs in hypercholesterolaemia and atherosclerosis. These alterations of endothelial function may contribute to vasospasm, ischaemia and thrombus formation, which are common events in patients with atherosclerotic vascular disease.

Vascular effects of quinapril completely depend on ACE insertion/deletion polymorphism

Introduction

The angiotensin-converting enzyme (ACE) DD-genotype is associated with increased plasma and myocardial ACE-activity. The influence of the ACE insertion/deletion (I/D) polymorphism on the effects of ACE-inhibition on vascular responses has not been previously described.

Materials and methods

In the randomised, double-blind QUinapril On Vascular ACE and Determinants of Ischemia Study (QUO VADIS), 149 patients undergoing coronary bypass surgery were randomised to receive either the ACE inhibitor, quinapril, or placebo. In 82 patients, we obtained ACE-genotype, and measured vascular responses to angiotensin II (Ang II) in left internal mammary arteries.

Results

In the placebo group, the mean maximal vasoconstriction to Ang II was significantly lower in patients with the DD-genotype than in those with the ID/II genotype (36.2±5.11% [n=13] vs. 55.6±4.57% [n=25]; p=0.01). In the quinapril group, the mean maximal vasoconstriction to Ang II was similar [n=8] vs. 57.7±4.07% [n=35]; p=0.85). between DD- and ID/II-genotype (59.6±9.19%

Conclusions

DD-genotype patients showed decreased vascular responses to Ang II but treatment with quinapril completely restored the decreased vascular response in DD-genotype patients to the same level as II/ID-genotype patients, while no effect of quinapril was demonstrated in the II/ID-genotype patients.

Internal thoracic artery: anatomical and biological characteristics revisited

The left internal thoracic artery has become the conduit of choice for coronary artery bypass grafting, due to its superior patency rates at 10 or more years with little or no evidence of atherosclerotic changes. Recent evidence indicates that a second internal thoracic artery graft provides improved results relative to overall survival and major cardiac and cerebrovascular event-free survival, and reduces the need for repeat revascularization. However, the routine use of bilateral internal thoracic arteries is limited due to a perceived higher incidence of deep sternal wound infection. The surgical anatomy, collateral blood supply to the sternum, and biological characteristics of internal thoracic artery conduits are reviewed.

Effects of acute transmural pressure elevation on endothelium-dependent vasodilation in isolated rat mesenteric veins

BACKGROUND/AIMS

The vascular regulatory function of the endothelium can be impaired by increases in transmural pressure (TMP). We tested the hypothesis that increasing TMP impairs the endothelial dilator function of rat mesenteric small veins (MSVs).

METHODS

In PGF2α-preconstricted MSVs, bradykinin (BK), sodium nitroprusside (SNP) and S-Nitroso-N-acetylpenicillamine (SNAP) concentration-response curves were generated at intermediate (6 mm Hg) and high (12 mm Hg) pressures. BK-induced vasodilation was examined in the absence and presence of nitric oxide synthase inhibitor [N(ω)-nitro-L-arginine (L-NNA), 100 µM], cyclooxygenase inhibitor (indomethacin, 1 µM), and large (BKCa, paxilline, 500 nM) and small (SKCa, apamin, 300 nM) conductance Ca(2+)-activated K(+) channel blockers.

RESULTS

BK, SNP and SNAP responses were not altered by TMP increases. BK-induced vasodilation was significantly reduced by L-NNA, indomethacin, apamin and paxilline at 6 mm Hg and L-NNA at 12 mm Hg, and was further reduced by coapplication of apamin and/or paxilline with L-NNA compared with responses obtained with either blocker. Endothelium removal completely abolished BK-induced vasodilation.

CONCLUSION

Venous endothelial dilator function is not affected by TMP elevation. BK-induced vasodilation is completely dependent on the presence of functional endothelial cells and mediated in part by nitric oxide, BKCa and SKCa channels, while the participation of prostacyclin may be important at intermediate pressures.

Activated Rho/Rho kinase and modified calcium sensitivity in cryopreserved human saphenous veins

BACKGROUND

We have shown previously that cryopreservation of human internal mammary arteries activates protein kinase C and enhances intracellular Ca(2+) [Ca(2+)](i). We now present evidence that in human saphenous veins (HSV) cryoinjury is associated with activation of the Rho/Rho kinase signaling pathways and enhanced [Ca(2+)](i).

METHODS

HSV were investigated in vitro either unfrozen within 12h after removal or after storage at -196 degrees C in a cryomedium containing 1.8M dimethyl sulfoxide and 0.1M sucrose as cryoprotectant additives.

RESULTS

Cryostorage diminished responses to receptor-mediated contractile agonists such as noradrenaline, 5-HT and endothelin-1 by up to 30% whereas responses to KCl were attenuated by about 50%. Concentration-response curves for CaCl(2) on unfrozen and cryopreserved HSV revealed similar inhibitory activities of both blocking 1,4-dihydropyridine derivatives nifedipine and the (-)-(R) enantiomer of SDZ 202-791 whereas the Ca(2+) channel activating (+)-(S) enantiomer of SDZ 202-791 was 10 times less effective at enhancing contractions to CaCl(2) when tested after cryostorage. These functional effects were reflected by changes in [Ca(2+)](i) as demonstrated by fluorescence of Fluo-3AM loaded veins. The diminished activity of (+)-(S) SDZ 202-791 in cryopreserved HSV was reversed partially when the potassium channel opener pinacidil (1 microM) was present during the freezing/thawing process. Blockade of Rho kinase by HA-1077 proved to be significantly more effective at attenuating contractile responses to both endothelin-1 and KCl after cryostorage.

CONCLUSIONS

Data suggested that cryopreservation modified [Ca(2+)](i) of venous smooth muscle cells (1) through depolarization-induced changes in Ca(2+) influx and (2) through activation of Rho kinase signaling pathways.

Correlation between vascular responsivensss and expression of novel transcripts of the ETA-receptor in human vascular tissue

Alternatively spliced endothelin (ET-1) receptor transcripts have been identified, but their significance to the functional effects of ET-1 has not been established. We have investigated the presence and influence of alternatively spliced ET(A) receptor transcripts on ET-1 mediated contraction of segments of human saphenous vein. The expression of ET(A) receptor transcripts was examined with quantitative reverse transcription-polymerase chain reaction (qPCR) studies, while the response of veins to ET-1 was tested with in vitro organ bath techniques. The expression of four different transcripts for the ET(A) receptor, in which either exon 3 is spliced out (Delta3), exon 4 is spliced out (Delta4), both 3 and 4 spliced out (Delta3,4) and when both exons 2 and 4 (Delta2,4) are spliced out were identified. Functional studies showed that a lack of efficacy and potency of ET-1 is associated with a significantly lower expression of the Delta3,4 transcript. ET(A) receptor antagonism was insurmountable in samples that had lower levels of the Delta3,4 transcript, while samples from patients with higher expression of the Delta3,4 showed surmountable antagonism with BQ123. These results suggest that there is a genetic basis for the variability between individuals for the contractile effect of ET-1 at ET(A) receptors.

The vascular endothelium in hypertension

The vascular endothelium plays a fundamental role in the basal and dynamic regulation of the circulation. Thus, it has a crucial role in the pathogenesis of hypertension. A spectrum of vasoactive substances is synthesised in the endothelium; of these, nitric oxide (NO), prostacyclin (PGI2) and endothelin (ET)-1 are the most important. There is a continuous basal release of NO determining the tone of peripheral blood vessels. Systemic inhibition of NO synthesis or scavenging of NO through oxidative stress causes an increase in arterial blood pressure. Also, the renin-angiotensin-aldosterone system has a major role in hypertension as it has a direct vasoconstrictor effect and important interactions with oxygen free radicals and NO. Prostacyclin, in contrast to NO, does not contribute to the maintenance of basal vascular tone of conduit arteries, but its effect on platelets is most important. ET acts as the natural counterpart to endothelium-derived NO and has an arterial blood pressure-raising effect in man. Anti-hypertensive therapy lowers blood pressure and may influence these different mediators, thus influencing endothelial function. In summary, due to its position between the blood pressure and smooth muscle cells responsible for peripheral resistance, the endothelium is thought to be both victim and offender in arterial hypertension. The delicate balance of endothelium-derived factors is disturbed in hypertension. Specific anti-hypertensive and anti-oxidant treatment is able to restore this balance.

Cellular, molecular and immunological mechanisms in the pathophysiology of vein graft intimal hyperplasia

Coronary artery disease, leading to myocardial infarction and ischaemia, affects millions of persons and is one of the leading causes of morbidity and mortality worldwide. Invasive techniques such as coronary artery bypass grafting are used to alleviate the sequelae of arterial occlusion. Unfortunately, restenosis or occlusion of the grafted conduit occurs over a time frame of months to years with a gradual reduction in patency, especially in vein grafts. The events leading to intimal hyperplasia (IH) formation involve numerous cellular and molecular components. Various cellular elements of the vessel wall are involved as are leucocyte-endothelial interactions that trigger the coagulation cascade leading to localized thrombus formation. Subsequent phenotypic modification of the medial smooth muscle cells and their intimal migration is the basis of the lesion formation that is thought to be propagated by an immune-mediated reaction. Despite intense scrutiny, the pathophysiology of IH remains an enigma. Although several growth factors, cytokines and numerous other biomolecules have been implicated and their relationship to prohyperplasia pathways such as the phosphatidyl-inositol 3-kinase (PI3K)-Akt pathway has been established, many pieces of the puzzle are still missing. An in-depth understanding of early vein graft adaptation and progression is necessary to improve the long-term prognosis and develop more effective therapeutic measures. In this review, we have critically evaluated and summarized the literature to elucidate and interlink the numerous established and emerging factors that play a key role in the development of IH leading to vein graft restenosis.

Absence of histamine-induced nitric oxide release in the human radial artery: implications for vasospasm of coronary artery bypass vessels

Radial artery (RA) bypass grafts can develop severe vasospasm. As histamine is known to induce vasospasm, its effect on RA was assessed compared with the classic bypass vessels internal mammary artery (MA) and saphenous vein (SV). The vessels were examined in organ chambers for isometric tension recording. Histamine induced contractions on baseline; the sensitivity was higher in RA and SV than MA. After precontraction with norepinephrine, histamine did not evoke relaxations of RA but induced relaxations of MA and less of SV at lower concentrations; it induced contractions at higher concentrations, reaching similar levels in all three vessels. Indomethacin did not affect the response of MA and RA but potentiated relaxations and reduced contractions of SV. Endothelium removal, Nω-nitro-l-arginine methyl ester (l-NAME), or the H2-receptor blocker cimetidine did not affect the response of RA, but inhibited relaxations and enhanced contractions in MA and inhibited relaxations in SV; in the latter, only l-NAME enhanced contractions. Real-time PCR detected much lower expression of endothelial H2-receptor in RA than MA or SV. Western blots revealed similar endothelial nitric oxide (NO) synthase expression in all three vessels. Relaxations to acetylcholine were identical in RA and MA. Thus histamine releases NO by activating the endothelial H2-receptor, the expression of which is much lower in RA than MA or SV. H2-receptor activation also releases prostaglandins in SV, partially antagonizing NO. The lack of histamine-induced NO production represents a possible mechanism of RA vasospasm.

The relaxant effect of vasoactive intestinal polypeptide in the isolated canine uterine artery: the role of endothelium

The purpose of this study was to examine the effect of vasoactive intestinal polypeptide (VIP) on the uterine artery obtained from non-pregnant dogs. VIP (3 x 10(-9)-3 x 10(-7) M) induced concentration-dependent relaxation in canine uterine arteries with intact endothelium, pre-contracted with 10(-5) M phenylephrine (pEC(50) = 7.52 +/- 0.02, maximal response was 82.19 +/- 2.15%, n = 36). The administration of the cyclooxygenase inhibitor indomethacin (10(-5) M) or 4-aminopyridine (4-AP), a blocker of potassium channels (10(-5) M), did not modify the relaxation induced by VIP. Contrary to this, N(G)-nitro-L-arginine (L-NOARG) (10(-5) M) inhibited relaxation is evoked by VIP. Indomethacin applied with L-NOARG did not provoke further inhibition of VIP-induced relaxation. In the presence of both L-NOARG and L-NOARG + indomethacin, 4-AP led to the further inhibition of VIP-induced relaxation of canine uterine artery. It is concluded that VIP induces endothelium-dependent relaxation of uterine arteries of non-pregnant dogs, which can be entirely explained by the production of nitric oxide (NO) from the endothelial cells. We proposed that when NO synthesis is inhibited, VIP induces further relaxation, independent of the edothelium-derived relaxing factors, probably through activation of K(+) channels.

The effect of glucose and mental stress on cutaneous microvascular endothelial function

Glucose and mental stress, independently, have been found to impair arterial endothelial function (an indicator of vascular health). The present study sought to determine whether the combination of glucose and stress would have a greater effect on microvascular endothelial function than each on its own. To assess endothelial function, surges in skin blood flow (reactive hyperemia), following the release of cuff pressure to the upper arm at 200 mmHg for 5 min, were measured with laser Doppler flowmetry in 40 young, healthy females. Endothelial function did not change significantly following a 5-min mathematics stressor or the consumption of 75 g of glucose. However, the combination of glucose and stress impaired endothelium-dependent dilatation 30 min after glucose consumption. These findings suggest that combinations of vascular risk factors may be more threatening to cardiovascular health than singularly occurring factors.

Ascorbic acid improves impaired venous and arterial endothelium-dependent dilation in smokers

AIM

To compare the acute effects of ascorbic acid on vasodilation of veins and arteries in vivo.

METHODS

Twenty-six healthy non-smokers and 23 healthy moderate smokers were recruited in this study. The dorsal hand vein compliance technique and flow-mediated dilation were used. Dose-response curves to bradykinin and sodium nitroprusside were constructed to test the endothelium-dependent and -independent relaxation before and after acute infusion of ascorbic acid.

RESULTS

Smokers had an impaired venodilation with bradykinin compared with non-smokers (68.3%+/-13.2% vs 93.7%+/-20.1%, respectively; P<0.05). Ascorbic acid administration in the dorsal hand vein significantly increased the venodilation with bradykinin in smokers (68.3%+/-13.2% vs 89.5%+/-6.3% before and after infusion, respectively; P<0.05) but not in non-smokers (93.7%+/-20.1% vs 86.4%+/-12.4% before and after infusion, respectively). Similarly, the arterial response in smokers had an impaired endothelium-dependent dilation compared with that in non-smokers (8.8%+/-2.7% vs 15.2%+/-2.3%, respectively; P<0.05) and ascorbic acid restored this response in smokers (8.8%+/-2.7% vs 18.7%+/-6.5% before and after infusion, respectively; P<0.05), but no difference was seen in non-smokers (15.2%+/-2.3% vs 14.0%+/-4.4% before and after infusion, respectively). The endothelium-independent dilation did not differ in both the groups studied. No important hemodynamic change was detected using the Portapress device.

CONCLUSION

Smokers had impaired endothelium-dependent vasodilation responsiveness in both arterial and venous systems. Ascorbic acid restores this responsiveness in smokers.

The pulmonary biology of isoprostanes

Isoprostanes were first recognized as convenient markers of oxidative stress, but their powerful effects on a variety of cell functions are now also being increasingly appreciated. This is particularly true of the lung, which is comprised of a wide variety of different cell types (smooth muscle, innervation, epithelium, lymphatics, etc.), all of which have been shown to respond to exogenously applied isoprostanes. In this review, we summarize these biological responses in the lung, and also consider the roles that isoprostanes might play in a range of pulmonary clinical disorders.

The pulmonary biology of isoprostanes

Isoprostanes are widely recognized as useful markers of membrane lipid peroxidation. It seems to be less well appreciated, however, that they also elicit important biological responses, even though this was first shown at the same time that they were introduced as markers of oxidative stress. The past several years have seen the list of cells/tissues which are sensitive to isoprostanes grow considerably: in fact, as we summarize here, there is now evidence that essentially every cell type in the lung responds in some pathologically relevant way to isoprostanes. In this sense, they might well be considered as not just markers of oxidative stress and inflammation, but also as a novel group of inflammatory mediators. Moreover, in addition to their pathological effects, we summarize here the evidence which has led us to hypothesize that isoprostanes could play an important role in vascular smooth muscle physiology as "endothelium-derived hyperpolarizing factors."

Prostacyclin release and receptor activation: differential control of human pulmonary venous and arterial tone

1. In human pulmonary vascular preparations, precontracted arteries were more sensitive to the relaxant effect of acetylcholine (ACh) than veins (pD(2) values: 7.25+/-0.08 (n=23) and 5.92+/-0.09 (n=25), respectively). Therefore, the role of prostacyclin (PGI(2)) was explored to examine whether this mediator may be responsible for the difference in relaxation. 2. In the presence of the cyclooxygenase (COX) inhibitor, indomethacin (INDO), the ACh relaxations were reduced in arteries but not in veins. On the contrary, an inhibitor (l-NOARG) of the nitric oxide synthase blocked preferentially the relaxation in veins. 3. A greater release of 6-keto-PGF(1alpha), the stable metabolite of PGI(2), was observed in arterial preparations than in venous preparations when stimulated with either ACh or arachidonic acid (AA). 4. Exogenous PGI(2) produced a reduced relaxant effect in the precontracted vein when compared with the artery. In the presence of the EP(1)-receptor antagonist AH6809, the PGI(2) relaxation of veins was similar to arteries. 5. In veins, AA (0.1 mm) produced a biphasic response, namely, a contraction peak (0.4-0.5 g) followed by a relaxation. These contractions in venous preparations were abolished either in the absence of endothelium or in the presence of INDO or an EP(1)-receptor antagonist (AH6809, SC19220). In the arterial preparations AA induced only relaxations. 6. In both vascular preparations, COX-1 but not the COX-2 protein was detected in microsomal preparations derived from homogenized tissues or freshly isolated endothelial cells. 7. The differential vasorelaxations induced by ACh may be explained, in part, by a more pronounced production and release of PGI(2) in human pulmonary arteries than in the veins. In addition, while PGI(2) induced relaxation by activation of IP-receptors in both types of vessels, a PGI(2) constrictor effect was responsible for masking the relaxation in the veins by activation of the EP(1)-receptor.

Endothelium-dependent Relaxation of Canine Uterine Artery in Response to Acetylcholine: the Possible Involvement of Alternative Pathways

The effect of acetylcholine on the isolated, pre-contracted, uterine artery of non-pregnant dog was investigated. Acetylcholine-induced concentration-dependent relaxation of isolated canine uterine artery with endothelium (pEC50 = 6.48 +/-0.01, n = 37) and was without effect on arterial segments denuded of endothelium. Indomethacin, 4-aminopyridine (10-5 m) and pre-contraction with K+-rich Krebs-Ringer bicarbonate solution had no effect on acetylcholine-induced relaxation. NG-nitro-l-arginine (l-NOARG) (10-5 m) inhibited relaxation evoked by acetylcholine. Indomethacin applied with l-NOARG led to further inhibition of acetylcholine-induced relaxation. In the presence of both l-NOARG and indomethacin, 4-aminopiridine did not provoke further inhibition of acetylcholine-induced relaxation of canine uterine artery. It is concluded that the acetylcholine-induced relaxation of canine uterine artery is probably mediated by endothelial production of nitric oxide (NO). However, if NO-synthase is inhibited, acetylcholine-induced vasorelaxation may be, in part, mediated through activation of cyclooxygenase pathway.

Vasodilatory and electrophysiological actions of 8-iso-prostaglandin E2 in porcine coronary artery

We examined the effects of several E-ring and F-ring isoprostanes on mechanical and electrophysiological activity in porcine coronary artery. Several isoprostanes evoked concentration-dependent contractions, with 8-iso-PGE2 being the most potent (-log EC50 of 6.9 +/- 0.1); this excitatory effect has been described in detail elsewhere and was not examined further here. 8-iso-PGE2 evoked dose-dependent relaxations in tissues preconstricted with the thromboxane A2-agonist U46619 (10(-6) M), with a negative log EC50 of 6.0 +/- 0.1 (n = 5). 8-iso-PGE1 and 8-iso-PGF2 beta also evoked relaxations (albeit with lower potency), whereas the other F-ring isoprostanes (8-iso-PGF1 alpha, 8-iso-PGF1 beta, and 8-iso-PGF2 alpha) were largely ineffective in this respect. The potency and efficacy of 8-iso-PGE2 in reversing tone were not dependent upon the concentration of U46619 used to preconstrict the tissues (10(-8) to 10(-6) M), indicating a lack of U46619-induced functional antagonism of these responses. 8-iso-PGE2 was able to completely relax tissues that had been denuded of endothelium (as indicated by loss of responsiveness to bradykinin). 8-iso-PGE2-evoked relaxations were markedly reduced by elevating the K+ equilibrium potential using 30 mM KCl and abolished by 60 mM KCl; they were also sensitive to charybdotoxin (10(-7) M) but not to 4-aminopyridine (1 mM). 8-iso-PGE2 also caused membrane hyperpolarization and augmentation of outward K+ current. We conclude that 8-iso-prostaglandin E2 acts directly on the smooth muscle to increase K+ conductance, leading to membrane hyperpolarization and vasodilation.

Increased calcium buffering in coronary smooth muscle cells from diabetic dyslipidemic pigs

No studies exist concerning the ability of the plasma membrane Ca(2+) pump (PMCA), sarcoplasmic reticulum Ca(2+) pump (SERCA) and Na(+)-Ca(2+) exchanger (NCX) to regulate myoplasmic Ca(2+) (Ca(m)) in vascular smooth muscle cells from diabetic individuals with dyslipidemia. We tested the hypothesis that diabetic dyslipidemia would increase vascular smooth muscle cells to buffer Ca(m). Cells were isolated from the coronary artery of male Yucatan pigs treated for 20 weeks with: (1) a low fat diet (control group); (2) a high fat/cholesterol diet (F group); or (3) alloxan-induced diabetic pigs fed the high fat diet (DF group). The maximum Ca(m) response to a depolarizing 80 mM KCl (80 K) solution was evaluated in the absence and presence of thapsigargin (TSG; inhibits SERCA) and low Na (inhibits NCX). In response to 80 K alone, there was no difference in the Ca(m) response between groups. In the presence of TSG, the 80 K response decreased by 43% in the DF group; TSG did not affect the 80 K response in the control and F groups. When exposed to both TSG and low Na, the 80 K response also decreased by 55% in the DF group. This suggests increased Ca(m) buffering by the PMCA and/or mitochondria in the DF group when SERCA and NCX are inhibited. Compared to the control and F groups, low Na alone elicited a 50% lower Ca(m) amplitude in the DF group, which was reversed with TSG treatment; this suggests that SERCA activity is increased in DF pigs. Western blots also indicated a 7-fold increase in the approximately 115 kDa band density of an anti-SERCA2 antibody in DF compared to control pigs. This is the first report to demonstrate increased Ca(2+) buffering, specifically by SERCA, in vascular smooth muscle cells from diabetic individuals with dyslipidemia.

Differences between angiotensin-converting enzyme inhibition and angiotensin II-AT1 antagonism on angiotensin-mediated responses in human internal mammary arteries

The current study aimed to demonstrate differences between angiotensin (Ang)-converting enzyme (ACE) inhibition and Ang II-AT1 receptor antagonism on full concentration-contraction responses to Ang I. Contraction responses to increasing concentrations of Ang I (1 nM-1 microM) were evaluated in organ baths in the presence of captopril (10 microM-1 mM) with or without a chymase inhibitor (1 microM soybean trypsin inhibitor), or irbesartan (0.1 nM-microM), in internal mammary arteries from 25 patients undergoing coronary bypass surgery. Responses were expressed as a percentage of the control response to 10 microM phenylephrine. Captopril did not change the maximum response to Ang I (control: 46.3 +/- 6.3%, captopril: 43.0 +/- 4.6%). In contrast, 0.1 microM irbesartan completely blocked the maximum response to Ang I (from 45.8 +/- 6.7% to 1.9 +/- 1.9%, p < 0.001). However, addition of soybean trypsin inhibitor to captopril more effectively shifted -log pD2 than captopril alone (0.47 +/- 0.06 vs 0.95 +/- 0.14 log units, p = 0.007). Ang I-mediated effects are much more effectively inhibited by Ang II antagonism than by ACE inhibition. The incomplete effects of captopril on the inhibition of Ang II formation might be caused by alternative Ang II forming enzyme(s), as was demonstrated by the additive effects of soybean trypsin inhibitor added to captopril.

Relaxation by urocortin of human saphenous veins

Urocortin, an endogenous peptide structurally related to corticotropin-releasing factor (CRF), has potent cardiovascular effects, suggesting that it may be of significance in cardiovascular regulation. The objective of this study was to analyse the effects of urocortin and its action mechanisms on human blood vessels. To this, 3 mm long segments from human saphenous veins were prepared for isometric tension recording in an organ bath. In the segments at basal resting tone, urocortin did not produce any effect, but in the segments precontracted with endothelin-1 (1 - 10 nM), urocortin (1 pM - 10 nM) produced concentration-dependent relaxation. This relaxation was not modified by the inhibitor of nitric oxide synthase NG-nitro-L-arginine methyl ester (L-NAME, 100 microM), but it was potentiated by the cyclo-oxygenase inhibitor meclofenamate (10 microM) and it was reduced by the inhibitors of high-conductance Ca2+-dependent potassium channels tetraethylammonium (TEA, 10 mM) and charybdotoxin (100 nM). These results indicate that human saphenous veins are very sensitive to urocortin, which produces vascular relaxation by a mechanism independent of nitric oxide and dependent of high-conductance Ca2+-dependent potassium channels, and that it may be opposed by the release of vasoconstrictor prostanoids. Therefore, urocortin may be of significance for regulation of the venous circulation in humans.

Are endothelium-derived hyperpolarizing and contracting factors isoprostanes?

The endothelium releases many vasoactive substances, including prostacyclin, nitric oxide and endothelin, in addition to several other factors about which little is known. The latter are referred to as 'endothelium-derived hyperpolarizing factors' (EDHFs) and 'endothelium-derived contracting factors' (EDCFs). Although there is much debate about the identities of EDHFs and EDCFs, a prevailing hypothesis is that they are cyclooxygenase-independent metabolites of arachidonic acid and many researchers associate them with free radicals. These properties are shared with isoprostanes. In this article, I compare the properties of EDHFs and EDCFs with those of the isoprostanes and propose novel experiments that might identify isoprostanes as candidate molecules for EDHFs and EDCFs.

Current strategies and perspectives for correcting endothelial dysfunction in atherosclerosis

The vascular endothelium synthesizes and releases a spectrum of vasoactive substances such as nitric oxide and endothelin. In atherosclerosis, the delicate balance between endothelium-derived factors is disturbed. Endothelin acts as the natural counterpart to endothelium-derived nitric oxide, which exerts vasodilating, antithrombotic and antiproliferative effects, and inhibits leukocyte adhesion to the vascular wall. Besides its blood pressure increasing effect in man, endothelin also induces vascular and myocardial hypertrophy, which are independent risk factors for cardiovascular morbidity and mortality. The derangement of endothelial function in atherosclerosis is likely to be caused in part by genetic factors, but is also due to cardiovascular risk factors. Endothelial dysfunction in atherosclerosis is crucial for the development of the disease process in the vasculature and is therefore an important therapeutic target. However, the efficacy of pharmacotherapy aimed at an improvement in endothelial function depends on the individual risk factor profile of the patient.

Pathophysiology of vascular endothelium and circulating platelets: implications for coronary revascularisation and treatment

Constant vasodilatation, inhibition of platelet and leukocyte adhesion, and local thrombolysis are the mechanisms through which an intact endothelial layer exerts its protective action on coronary circulation. A loss in these features is not only the first step in the development of atherosclerosis, but also a potent trigger for complications after revascularisation procedures. Percutaneous coronary interventions, particularly in the course of stenting, induce endothelial injury that can last up to months after the procedure. On the other hand, the preservation of endothelial function appears the best feature of arterial versus venous grafts after coronary bypass surgery. An early diagnosis either by invasive or non-invasive techniques has important implications for prognosis, and endothelial dysfunction can be effectively counteracted by medical treatment (ACE inhibitors, statins). Activated circulating platelets are present in the course of coronary artery disease, increasing the risk of thrombotic occlusion and/or plaque regrowth, after both percutaneous and surgical revascularisation. New antiplatelet agents are under development to reduce endothelium-platelet interaction. On the basis of the latest studies, coronary revascularisation should be integrated in a more complete treatment, which would take into account the complex processes involving the underlying atherosclerotic plaque.

Short-term treatment with transdermal nicotine affects the function of canine saphenous veins

Experiments were designed to determine the effects of nicotine treatment on the functions of saphenous veins used for coronary artery bypass grafts in dogs. Dogs received either no treatment or transdermal nicotine for 5 weeks at doses of 11 mg, 22 mg or 44 mg/day. Saphenous veins were removed and suspended for the measurement of isometric force in organ chambers. Endothelium was removed mechanically from some rings. N(G)-mono-methyl-L-arginine (L-NMMA; 10(-4) M) was used to inhibit the production of nitric oxide. Contractions to alpha2-adrenergic stimulation were decreased in veins from dogs treated with a 22-mg/day dose of transdermal nicotine. In addition, endothelium-dependent relaxations to adenosine-diphosphate (10(-8)-10(-4) M) and the calcium ionophore A23,187 (10(-8)-10(-6) M) were decreased in veins from dogs with a 22-mg/day dose and increased in veins from dogs treated with a 44-mg/day dose. These relaxations were inhibited by L-NMMA. Plasma concentrations of oxidized products of nitric oxide were decreased only in dogs treated with 22 mg/day of nicotine. The relaxation of rings without endothelium (direct response on the smooth muscle) to nitric oxide were not altered by nicotine treatment. These results suggest that the short-term treatment of dogs with intermediate (22 mg/day) but not low (11 mg/day) or high (44 mg/day) doses of transdermal nicotine decreases the endothelial function of veins used for coronary artery bypass grafts. Therefore, changes in plasma products of nitric oxide and endothelium-dependent relaxations mediated by nitric oxide are related to the dose of nicotine treatment.

Administration of glutathione in patients with type 2 diabetes mellitus increases the platelet constitutive nitric oxide synthase activity and reduces PAI-1

Several studies suggest that nitric oxide (NO) production is impaired in diabetes mellitus. Reduced levels of NO could contribute to cardiovascular mortality. Furthermore, NO synthesis is impaired in glutathione (GSH)-depleted human umbilical vein endothelial cells and GSH is reduced in patients with type 2 diabetes mellitus (T2DM). We tested the hypothesis that treatment with GSH may improve platelet constitutive NO sinthase (cNOS) activity in patients with T2DM. Fifteen patients with T2DM underwent a treatment with GSH 600 mg/day i.m. for 10 days. With respect to the basal values on the 10th day of treatment, the red blood cell GSH concentration and platelets cNOS increased (1.4+/-0.1 vs 1.9+/-0.1 micromol/10(10) RBC, p<0.001 and 0.7+/-0.1 vs 2.9+/-0.2 fmol x min(-1) x 10(-9) PLTs, p<0.001, respectively) and the plasma PAI-1 levels diminished (81.4+/-3.7 vs 68.7+/-4.0 ng/ml, p<0.002). A negative correlation between the cNOS and the PAI-1 was found on the basal values. After a wash-out of 30 days the values of red blood cell GSH concentration, platelet cNOS activity and PAI-1 Ag returned to the basal levels. These data suggest that the administration of GSH, in patients with T2DM, is able to improve platelet cNOS activity together with a reduction of PAI-1.

Tetrahydrobiopterin improves endothelial function in human saphenous veins

OBJECTIVES

Diminished production of nitric oxide has been linked to saphenous vein endothelial dysfunction. Tetrahydrobiopterin is an obligate cofactor for the oxidation of L -arginine by nitric oxide synthase in the production of nitric oxide by endothelial cells. The objective of the present study was to examine whether the exogenous addition of tetrahydrobiopterin improves endothelial function in saphenous veins from patients undergoing coronary artery bypass graft operations.

METHODS

Vascular segments of saphenous veins were obtained from 17 patients undergoing elective coronary artery bypass grafting, and in vitro endothelium-dependent and endothelium-independent responses to acetylcholine and sodium nitroprusside were assessed. Isometric dose-response curves were constructed in precontracted rings in the presence and absence of tetrahydrobiopterin (0.1 mmol/L) with the use of the organ bath apparatus. The percentages of maximum relaxation and sensitivity were compared between interventions.

RESULTS

Acetylcholine caused dose-dependent endothelium-mediated relaxation in saphenous veins. In the presence of tetrahydrobiopterin, acetylcholine-induced relaxation was significantly augmented (percentage maximum relaxation, 16.8% +/- 2.9% vs control 7.5% +/- 1.8%; P =.003) without an effect on agonist sensitivity. These effects were endothelium-specific because endothelium-independent responses to sodium nitroprusside were preserved.

CONCLUSIONS

These data uncover beneficial effects of acute tetrahydrobiopterin addition on endothelial function in human vessels. Because endothelial dysfunction has been implicated in the development of graft failure, studies aimed at chronic delivery of tetrahydrobiopterin would be useful in determining the contribution of this cofactor toward saphenous vein atherosclerosis.

Endothelium-dependent relaxation in perforating branch of human internal mammary artery

The purpose of the present study was to examine the effect of acetylcholine on perforating branch of the human internal mammary artery (HIMA). Acetylcholine (10(-9)-10(-5)M) induced concentration- and endothelium-dependent relaxation (pEC(50)=7.54+/-0.03, maximal response was 98+/-1.3%) of the precontracted arterial segments. Indomethacin, 4-aminopyridine (10(-5)M) and precontraction with K(+)-rich Krebs-Ringer-bicarbonate solution had no effect on acethylcholine-induced relaxation. N(G)-monomethyl-L-arginine (L-NMMA) (10(-5)M) inhibited relaxation evoked by acetylcholine. Indomethacin applied together with L-NMMA lead to further inhibition of acethylcholine-induced relaxation. Even in the presence of both L-NMMA and indomethacin, 4-aminopyridine had no provoked further inhibition of acetylcholine-induced relaxation of perforating branch of HIMA. It was concluded that the acethylcholine-induced relaxation of isolated perforating branch of HIMA is probably mediated via endothelial production of nitric oxide. However, when NO-synthase is inhibited, acetylcholine-induced vasorelaxation may be, in part, mediated through activation of cyclooxygenase pathway and consequent production and release of prostacyclin or some other cyclooxygenase products.

Vasoconstrictor effects of iso-prostaglandin F2alpha type-III (8-iso-prostaglandin F2alpha) on human saphenous veins

Free radical generation can initiate the peroxidation of arachidonic acid, resulting in a non-cyclooxygenase-dependent production of bioactive prostaglandin F2-like compounds. We have investigated the effects of iso-prostaglandin F2alpha type III, (iPF2alpha-III, formerly named 8-iso prostaglandin F2alpha) on human saphenous veins, and characterized the underlying mechanisms. In organ baths, the contractile effects of iPF2alpha-III were tested on saphenous vein rings coming from 22 patients. iPF2alpha-III induced concentration-dependent contractions of isolated human saphenous veins. The maximal contraction did not differ significantly from that of prostaglandin F2alpha (PGF2alpha). The pD2 values for iPF2alpha-III, PGF2alpha, endothelin-1 (ET-1), and U46619 (a stable thromboxane A2 mimetic) were 6.31+/-0.12, 5.66+/-0.13, 7.37+/-0.08, and 7.99+/-0.31, respectively (p < 0.001 for U46619 vs. iPF2alpha-III and PGF2alpha; and ET-1 vs. PGF2alpha). Emax values of iPF2alpha-III, PGF2alpha, ET-1, and U46619 were 137.7+/-24.3%, 145.9+/-7.5%, 92.9+/-16.8%, and 238.7+/-23.7%, respectively (p < 0.001 for U46619 vs. iPF2alpha-III, PGF2alpha and ET-1; and for PGF2alpha vs. ET-1). The responses to iPF2alpha-III were inhibited by GR 32191 10(-7) M, a TP-receptor antagonist, without affecting the maximal response (pD2 values were 5.98+/-0.06 in the absence, and 5.22+/-0.05 in the presence of GR32191; p < 0.001). Concentration-effect curves to iPF2alpha-III were not affected by phosphoramidon 10(-5) M (an endothelin converting enzyme inhibitor), BQ123 10(-6) M (a selective ET(A)-receptor antagonist), BQ788 10(-6) M (a selective ET(B)-receptor antagonist), and indomethacin 10(-5) M (a cyclooxygenase inhibitor). Finally, the contractile response of iPF2alpha-III did not involve the release of thromboxane B2 and ET-1, measured using enzyme immunoassays. This study demonstrates that iPF2alpha-III is a vasoconstrictor of human saphenous veins, with a potency fourfold greater than that of PGF2alpha, and 50 times less than that of the thromboxane A2 mimetic, U46619. These effects are mediated at least in part by TP-receptor stimulation, but do not involve thromboxane A2 or ET-1 release.

A T-786-->C mutation in the 5'-flanking region of the endothelial nitric oxide synthase gene and coronary arterial vasomotility

In the endothelium, synthesis of nitric oxide (NO) from the amino acid L-arginine is catalyzed by the endothelial NO synthase (eNOS), and the continuously generated NO serves to maintain basal vascular tone. Recently, we discovered a T-786-->C mutation in the 5'-flanking region of the eNOS gene; this mutation reduced the promoter activity of the eNOS gene and was associated with coronary spasm. We examined the vasomotility of the epicardial coronary artery in subjects with and without T-736-->C mutation. We examined vasomotility in 32 consecutive subjects who were heterozygotes for the T-786-->C mutation and in 68 subjects without the T-786-->C mutation who had equivalent age, sex, and smoking status at the proximal and distal segments of the left descending coronary artery by performing quantitative coronary angiography. In subjects with the mutant allele (-786C allele), basal diameters of proximal and distal segments before intracoronary injection of acetylcholine (ACh) were less than diameters in subjects without the mutant allele (p <0.05), although there was no difference between subjects with and without the mutant allele in the diameters of coronary arteries after isosorbide dinitrate (ISDN) administration. When we compared the changes in diameters, both ACh-induced vasoconstriction and ISDN-induced vasodilatation in subjects with the mutant allele were significantly increased in the proximal (p <0.01, p <0.001, respectively) and distal segments (p <0.03, p <0.01, respectively). Taken together, these findings strongly suggest that the T-786-->C mutation increases the basal tone of the coronary artery, and enhances the response to the constrictor effects of ACh and the dilator effect of ISDN because of reducing the endothelial NO synthesis.

A comparison of primary endothelial cells and endothelial cell lines for studies of immune interactions

The purpose of this study was to assess the suitability of using endothelial cell (EC) lines for studies of endothelial/immune interactions. The immortal human EC lines HMEC-1, ECV304 and EaHy926 were compared to human umbilical vein endothelial cells (HUVEC) for constitutive and induced expression of surface antigens known to be involved in interactions with T cells. These cell lines were also compared to HUVEC in transendothelial migration assays. Flow cytometry was used to measure cell surface expression of platelet/endothelial cell adhesion molecule-1 (PECAM-1), intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), E-selectin, major histocompatibility complex (MHC) class I and MHC class II, CD40, CD95 (fas) and lymphocyte function associated antigen-3 (LFA-3) before and after treatment with the cytokines tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma). Polymerase chain reaction (PCR) was used to detect expression of the MHC class II transactivator. Significant differences were found in the ability to respond to cytokines between HUVEC and the cell lines, the greatest differences being induction of VCAM-1 and E-selectin in response to TNF-alpha and induction of MHC class II antigens in response to IFN-gamma. Thus unlike HUVEC, induction of VCAM-1 and E-selectin was not detectable on EaHy926 and ECV304 and barely detectable on HMEC-1. MHC class II antigens were not induced on ECV304 in response to IFN-gamma and nor was the class II transactivator (CIITA). Unlike HUVEC and the other cell lines, ECV304 were constitutively negative for PECAM-1. Constitutive and induced expression of MHC class I, ICAM-1, LFA/3, CD40 and fas were most conserved between the cell lines and showed little difference to HUVEC. The migration of peripheral blood mononuclear cells (PBMC) through all cell lines was significantly reduced compared to through HUVEC, suggesting that there is a functional difference between the cell lines with regard to interactions with lymphocytes. In conclusion this study has demonstrated significant differences in the ability of endothelial cell lines to respond to cytokines compared to primary HUVEC cultures. In particular ECV304 compares very poorly with HUVEC. Whether these differences are caused by immortalization procedures or reflect heterogeneity of EC arising from different vascular beds is discussed.

alpha(2)-adrenoceptor and NPY receptor-mediated contractions of porcine isolated blood vessels: evidence for involvement of the vascular endothelium

1. Enhanced contractions to the alpha(2)-adrenoceptor agonist UK14304 and neuropeptide Y (NPY) in the porcine ear artery can be uncovered by pharmacological manipulation. The aim of this study was to determine whether similar pharmacological manipulation can uncover enhanced contractions in the porcine splenic artery, and to determine whether the endothelium modulates these responses. 2. UK14304 (0.3 microM) and NPY (0.1 microM) produced small contractions of the porcine splenic artery. After pre-contraction of the tissue with U46619, followed by relaxation with forskolin, the responses to both UK14304 and NPY were enhanced. Enhanced contractions to both UK14304 and NPY were also obtained after relaxation with SNP. These results demonstrate that, as in the porcine ear artery, alpha(2)-adrenoceptors and NPY receptors are able to produce enhanced contractile responses through both adenylyl cyclase-dependent and -independent signal transduction pathways. 3. Removal of the endothelium had no significant effect on responses to UK14304 either alone or in the presence of U46619 and forskolin in the porcine splenic artery. On the other hand, responses to UK14304 after relaxation with SNP were reduced after endothelium-denudation in both the porcine splenic artery and ear artery. Similar results were obtained with NPY in the porcine ear artery. 4. In conclusion, enhanced contractile responses to UK14304 and NPY in the porcine splenic artery can be uncovered using methods similar to those employed in the porcine ear artery. Under certain conditions the responses to both agents are modulated by the endothelium. These data highlight further the similarities in the signal transduction pathways used by both alpha(2)-adrenoceptors and NPY receptors to induce vasoconstriction.