Natural course of the impairment of endothelium-dependent relaxations after balloon endothelium removal in porcine coronary arteries. Possible dysfunction of a pertussis toxin-sensitive G protein

Kidney allograft infarction associated with transplant renal artery stenosis in a COVID-19 kidney transplant recipient

Kidney allograft infarction is rare, but an urgent condition that requires prompt intervention to avoid allograft loss. Renal artery thrombosis is the leading cause of infarction. Apart from traditional risk factors for thrombosis, emerging SARS-CoV-2 predisposes patients to thrombotic diseases both in arterial and venous vasculatures. We report a case of kidney transplant recipient with known transplant renal artery stenosis (TRAS) status post angioplasty with severe COVID-19, complicated by oliguric acute kidney injury requiring continuous renal replacement therapy (CRRT). She did not have a history of thromboembolic disease. The hospital course was complicated by new-onset atrial and ventricular fibrillation and cardiac arrest requiring multiple rounds of cardiopulmonary resuscitation. She had no signs of renal recovery, and an abdominal CT scan showed evidence of allograft infarcts. She underwent an allograft nephrectomy. Pathology revealed diffuse thrombotic microangiopathy involving glomeruli, arterioles, and arteries associated with diffuse cortical infarction with negative SARS-CoV-2 immunostain and in situ hybridization. This is the first case of kidney allograft infarct with a history of TRAS in a COVID-19 patient. Underlying TRAS and COVID-19-associated thrombosis in this patient are unique and likely play a key role in allograft infarction from arterial thrombosis. Recognizing risk factors and early therapy for allograft infarction may improve transplant outcomes.

The effects of stenting on coronary endothelium from a molecular biological view: Time for improvement?

Coronary artery stenting following balloon angioplasty represents the gold standard in revascularization of coronary artery stenoses. However, stent deployment as well as percutaneous transluminal coronary angioplasty (PTCA) alone causes severe injury of vascular endothelium. The damaged endothelium is intrinsically repaired by locally derived endothelial cells and by circulating endothelial progenitor cells from the blood, leading to re‐population of the denuded regions within several weeks to months. However, the process of re‐endothelialization is often incomplete or dysfunctional, promoting in‐stent thrombosis and restenosis. The molecular and biomechanical mechanisms that influence the process of re‐endothelialization in stented segments are incompletely understood. Once the endothelium is restored, endothelial function might still be impaired. Several strategies have been followed to improve endothelial function after coronary stenting. In this review, the effects of stenting on coronary endothelium are outlined and current and future strategies to improve endothelial function after stent deployment are discussed.

In Development-A New Paradigm for Understanding Vascular Disease

Under physiological conditions, the arterial endothelium exerts a powerful protective influence to maintain vascular homeostasis. However, during the development of vascular disease, these protective activities are lost, and dysfunctional endothelial cells actually promote disease pathogenesis. Numerous investigations have analyzed the characteristics of dysfunctional endothelium with a view to understanding the processes responsible for the dysfunction and to determining their role in vascular pathology. This review adopts an alternate approach: reviewing the mechanisms that contribute to the initial formation of a healthy protective endothelium and on how those mechanisms may be disrupted, precipitating the appearance of dysfunctional endothelial cells and the progression of vascular disease. This approach, which highlights the role of endothelial adherens junctions and vascular endothelial-cadherin in endothelial maturation and endothelial dysfunction, provides new insight into the remarkable biology of this important cell layer and its role in vascular protection and vascular disease.

Nitric Oxide: From Good to Bad

This essay summarizes a lecture presented on October 19th, 2017, during the 58th Annual Meeting of the Japanese College of Angiology in Nagoya, Japan. The lecture summarizes several instances where the absence of relaxations of isolated blood vessels in response to endothelium-dependent vasodilator agonists, which cause activation of endothelial nitric oxide synthase (eNOS) and consequent production of endothelium-derived nitric oxide (NO) and stimulation of soluble guanylyl cyclase (sGC) in underlying vascular smooth muscle, or hypoxia are curtailed or reversed to endothelium-dependent contractions. Chosen examples include selective dysfunction of eNOS activation in regenerated endothelial cells, unresponsiveness of vascular smooth muscle cells to NO during subarachnoid hemorrhage, and biased activation of sGC in vascular smooth muscle cells during acute exposure to hypoxia. The main message of this essay is that absence, blunting, or reversal of endothelium-dependent relaxations in response to vasodilator agonists cannot necessarily be interpreted as a sign of endothelial dysfunction. (This is a review article based on the invited lecture of the 58th Annual Meeting of Japanese College of Angiology.)

The inhibitory effects of polysaccharide peptides (PsP) of Ganoderma lucidum against atherosclerosis in rats with dyslipidemia

Background

Atherosclerosis occurs as a result of low-density lipoprotein (LDL) deposits oxidation. Endothelial dysfunction is an early process of atherosclerosis. Restoring endothelial lining back to normal by endothelial progenitor cells (EPCs) is critical for slowing or reversing vascular disease progression. Oxidative stress from hydrogen peroxide (H₂O₂) is increased in dyslipidemia so that antioxidant agent is required to prevent destruction of blood vessels.

Objectives

This study aims to report Ganoderma lucidum polysaccharide peptide (PsP) effects in atherogenic process by measuring H₂O₂ level, IL-10 level, and EPC number in blood serum, and also intima-media thickness of aorta in dyslipidemia Wistar rat model by giving them a hypercholesterol diet (HCD).

Materials and methods

The study was an experimental in vivo post-test with control group design. Thirty-five Wistar rats (Rattus norwegicus) were divided into five groups (normal diet group, HCD group, and hypercholesterol groups that received 50 mg/kg, 150 mg/kg, and 300 mg/kg bodyweight PsP).

Results

Each treatment group showed significant results for the administration of PsP using the one-way analysis of variance test (p<0.050) for the reduction of H₂O₂ (p = 0.003), levels of IL-10 (p = 0.027), number of EPC in the blood serum (p = 0.011), and the intima-media thickness of the aorta (p = 0.000). PsP from G. lucidum is a potent antioxidant and may prevent atherogenesis process in patients with dyslipidemia.

Conclusions

The optimum doses of PsP in this study is 300 mg/kg bodyweight. Further studies are required to determine the antioxidant effects of PsP G. lucidum and its benefits in the management of dyslipidemia.

Endothelial dysfunction and vascular disease - a 30th anniversary update

The endothelium can evoke relaxations of the underlying vascular smooth muscle, by releasing vasodilator substances. The best-characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO) which activates soluble guanylyl cyclase in the vascular smooth muscle cells, with the production of cyclic guanosine monophosphate (cGMP) initiating relaxation. The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDH-mediated responses). As regards the latter, hydrogen peroxide (H₂ O₂ ) now appears to play a dominant role. Endothelium-dependent relaxations involve both pertussis toxin-sensitive G_i (e.g. responses to α₂ -adrenergic agonists, serotonin, and thrombin) and pertussis toxin-insensitive G_q (e.g. adenosine diphosphate and bradykinin) coupling proteins. New stimulators (e.g. insulin, adiponectin) of the release of EDRFs have emerged. In recent years, evidence has also accumulated, confirming that the release of NO by the endothelial cell can chronically be upregulated (e.g. by oestrogens, exercise and dietary factors) and downregulated (e.g. oxidative stress, smoking, pollution and oxidized low-density lipoproteins) and that it is reduced with ageing and in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively lose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and EDH, in particular those due to H₂ O₂ ), endothelial cells also can evoke contraction of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factors. Recent evidence confirms that most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells and that prostacyclin plays a key role in such responses. Endothelium-dependent contractions are exacerbated when the production of nitric oxide is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive and diabetic patients. In addition, recent data confirm that the release of endothelin-1 can contribute to endothelial dysfunction and that the peptide appears to be an important contributor to vascular dysfunction. Finally, it has become clear that nitric oxide itself, under certain conditions (e.g. hypoxia), can cause biased activation of soluble guanylyl cyclase leading to the production of cyclic inosine monophosphate (cIMP) rather than cGMP and hence causes contraction rather than relaxation of the underlying vascular smooth muscle.

2014 Williams Harvey Lecture: importance of coronary vasomotion abnormalities-from bench to bedside

Coronary vasomotion abnormalities play important roles in the pathogenesis of ischaemic heart disease, in which endothelial dysfunction and coronary artery spasm are substantially involved. Endothelial vasodilator functions are heterogeneous depending on the vessel size, with relatively greater role of nitric oxide (NO) in conduit arteries and predominant role of endothelium-derived hyperpolarizing factor (EDHF) in resistance arteries, where endothelium-derived hydrogen peroxide serves as an important EDHF. The functions of NO synthases in the endothelium are also heterogeneous with multiple mechanisms involved, accounting for the diverse functions of the endothelium in vasomotor as well as metabolic modulations. Cardiovascular abnormalities and metabolic phenotypes become evident when all three NO synthases are deleted, suggesting the importance of both NO and EDHF. Coronary artery spasm plays important roles in the pathogenesis of a wide range of ischaemic heart disease. The central mechanism of the spasm is hypercontraction of vascular smooth muscle cells (VSMCs), but not endothelial dysfunction, where activation of Rho-kinase, a molecular switch of VSMC contraction, plays a major role through inhibition of myosin light-chain phosphatase. The Rho-kinase pathway is also involved in the pathogenesis of a wide range of cardiovascular diseases and new Rho-kinase inhibitors are under development for various indications. The registry study by the Japanese Coronary Spasm Association has demonstrated many important aspects of vasospastic angina. The ongoing international registry study of vasospastic angina in six nations should elucidate the unknown aspects of the disorder. Coronary vasomotion abnormalities appear to be an important therapeutic target in cardiovascular medicine.

Endothelial dysfunction in an ovine model of collagen-induced arthritis

BACKGROUND

Rheumatoid arthritis (RA) induces systemic inflammation, producing a range of co-morbidities including cardiovascular disease. An early vascular change is endothelial dysfunction, characterized by reduced endothelium-dependent vasodilation. The aim of this study was to assess endothelial function in isolated coronary and digital arteries using an ovine model of collagen-induced RA.

METHODS

Sheep were culled following induction of arthritis, and their endothelial function was compared to that of normal sheep. Paired arterial segments were mounted in a wire myograph and dilated with endothelium-dependent vasodilators [bradykinin, serotonin, carbachol and adenosine diphosphate (ADP); linked to either Gi or Gq signalling pathways] and endothelium-independent dilators (adenosine and sodium nitroprusside) to construct cumulative concentration-response curves.

RESULTS

Coronary arteries from arthritic sheep exhibited a significantly greater EC50 value for bradykinin-induced relaxation compared to non-arthritic controls (2.9 × 10(-8) M for arthritic sheep vs. 8.6 × 10(-9) M for controls). Digital arteries from arthritic sheep also exhibited a significantly greater EC50 for relaxation to ADP and a significant decrease in the carbachol maximal response. Responses to sodium nitroprusside were unchanged in both coronary and digital arteries.

CONCLUSION

Sheep with RA demonstrated attenuated arterial relaxation to endothelium-dependent vasodilators. This may provide a useful model of endothelial dysfunction in chronic inflammatory conditions. The dysfunction did not appear to be associated with one specific G-protein signalling pathway.

Protective effects of histamine on Gq-mediated relaxation in regenerated endothelium

In the porcine coronary artery, regenerated endothelium is dysfunctional as regards the responses to endothelium-dependent agonists. The current study aimed to determine the possible involvement of histamine in such dysfunction. Pigs were treated chronically with pyrilamine (H1 receptor inhibitor, 2 mg·kg−1·day−1) with part of their coronary endothelium and allowed to regenerate for 28 days after balloon denudation. The results showed a reduction in relaxation to bradykinin (Gq protein dependent) only in the pyrilamine-treated group (area under the curve, 269.7 ± 13.4 vs. 142.0 ± 31.0, native endothelium vs. regenerated endothelium) but not in the control group (253.0 ± 22.1 vs. 231.9 ± 29.5, native endothelium vs. regenerated endothelium). The differences in the relaxation to serotonin (Gi protein dependent) between native and regenerated endothelium were not affected by the pyrilamine treatment (control group, 106.3 ± 17.0 vs. 55.61 ± 12.7; and pyrilamine group, 106.0 ± 8.20 vs. 49.30 ± 6.31, native endothelium vs. regenerated endothelium). These findings indicate that during regeneration of the endothelium, the activation of H1 receptors by endogenous histamine may be required to maintain the endothelium-dependent Gq protein-mediated relaxation to bradykinin, suggesting a beneficial role of the monoamine in the process of endothelial regeneration.

Perivascular delivery of neomycin inhibits the activation of NF-κB and MAPK pathways, and prevents neointimal hyperplasia and stenosis after arterial injury

The nuclear transcription factor kappaB (NF-kappaB) is a cytoplasmic dimer that, as the family of mitogen-activated protein kinase (MAPK), can directly regulate the expression of early genes and genes involved in the stress response, following a variety of physiological or pathological stimuli. Both of them stimulate the transcription of many proteins, which are considered important during inflammation. A crucial role has been assigned to these factors in cellular proliferation and in neointimal hyperplasia secondary to the endothelial lesion of arterial vessels. On the other hand, it has been described that neomycin can have an inhibitory function on tumor cell proliferation, through the inhibition of different intracellular pathways of signaling, among them the NF-kappaB and MAPK pathways. Rat common carotid artery was subjected to balloon angioplasty. Neomycin sulfate (18 mg) was applied using pluronic acid gel on the adventitial surface of the injured vessel. MAPK and NF-kappaB activation was quantified after 24 hours with immunohistochemical staining. Neointimal formation was quantified after 14 days with morphometry. Immunohistochemistry results demonstrating MAPK and NF-kappaB activation reveal that both transcription factors are activated in the media of the control vessel wall. In contrast, the immunoreactivity for MAPK and NF-kappaB in the sections obtained from arteries treated with neomycin over 24 hours was insufficient or nonexistent. Treatment with neomycin on adventitia over 14 days in arteries on which angioplasty was performed shows a neointimal index (intimal area/medial area) decrease of 71% in comparison with arteries that were not treated. The adventitial neomycin treatment over 14 days produces a very significant increase (287.5%; p<0.0001) in the arterial luminal circumference in comparison with arteries treated with vehicle. These results support the theory that neomycin plays an important role against neointimal hyperplasia through the inhibition of MAPK and NF-kappaB activation.

A-FABP and oxidative stress underlie the impairment of endothelium-dependent relaxations to serotonin and the intima-medial thickening in the porcine coronary artery with regenerated endothelium

Experiments were designed to determine the cause of the selective dysfunction of G(i) proteins, characterized by a reduced endothelium-dependent relaxation to serotonin (5-hydroxytryptamine), in coronary arteries lined with regenerated endothelial cells. Part of the endothelium of the left anterior descending coronary artery of female pigs was removed in vivo to induce regeneration. The animals were treated chronically with vehicle (control), apocynin (antioxidant), or BMS309403 (A-FABP inhibitor) for 28 days before functional examination and histological analysis of segments of coronary arteries with native or regenerated endothelium of the same hearts. Isometric tension was recorded in organ chambers and cumulative concentration-relaxation curves obtained in response to endothelium-dependent [serotonin (G(i) protein mediated activation of eNOS) and bradykinin (G(q) protein mediated activation of eNOS)] and independent [detaNONOate (cGMP-mediated), isoproterenol (cAMP-mediated)] vasodilators. The two inhibitors tested did not acutely affect relaxations of preparations with either native or regenerated endothelium. In the chronically treated groups, however, both apocynin and BMS309403 abolished the reduction in relaxation to serotonin in segments covered with regenerated endothelium and prevented the intima-medial thickening caused by endothelial regeneration, without affecting responses to bradykinin or endothelium-independent agonists (detaNONOate and isoproterenol). Thus, inhibition of either oxidative stress or A-FABP likely prevents both the selective dysfunction of G(i) protein mediated relaxation to serotonin and the neointimal thickening resulting from endothelial regeneration.

Regulator of G protein signaling 2 deficiency causes endothelial dysfunction and impaired endothelium-derived hyperpolarizing factor-mediated relaxation by dysregulating Gi/o signaling

Regulator of G protein signaling 2 (RGS2) is a GTPase-activating protein for G(q/11)α and G(i/o)α subunits. RGS2 deficiency is linked to hypertension in mice and humans, although causative mechanisms are not understood. Because endothelial dysfunction and increased peripheral resistance are hallmarks of hypertension, determining whether RGS2 regulates microvascular reactivity may reveal mechanisms relevant to cardiovascular disease. Here we have determined the effects of systemic versus endothelium- or vascular smooth muscle-specific deletion of RGS2 on microvascular contraction and relaxation. Contraction and relaxation of mesenteric resistance arteries were analyzed in response to phenylephrine, sodium nitroprusside, or acetylcholine with or without inhibitors of nitric oxide (NO) synthase or K(+) channels that mediate endothelium-derived hyperpolarizing factor (EDHF)-dependent relaxation. The results showed that deleting RGS2 in vascular smooth muscle had minor effects. Systemic or endothelium-specific deletion of RGS2 strikingly inhibited acetylcholine-evoked relaxation. Endothelium-specific deletion of RGS2 had little effect on NO-dependent relaxation but markedly impaired EDHF-dependent relaxation. Acute, inducible deletion of RGS2 in endothelium did not affect blood pressure significantly. Impaired EDHF-mediated vasodilatation was rescued by blocking G(i/o)α activation with pertussis toxin. These findings indicated that systemic or endothelium-specific RGS2 deficiency causes endothelial dysfunction resulting in impaired EDHF-dependent vasodilatation. RGS2 deficiency enables endothelial G(i/o) activity to inhibit EDHF-dependent relaxation, whereas RGS2 sufficiency facilitates EDHF-evoked relaxation by squelching endothelial G(i/o) activity. Mutation or down-regulation of RGS2 in hypertension patients therefore may contribute to endothelial dysfunction and defective EDHF-dependent relaxation. Blunting G(i/o) signaling might improve endothelial function in such patients.

Chronic administration of BMS309403 improves endothelial function in apolipoprotein E-deficient mice and in cultured human endothelial cells

BACKGROUND AND PURPOSE

Adipocyte fatty acid-binding protein (A-FABP) is up-regulated in regenerated endothelial cells and modulates inflammatory responses in macrophages. Endothelial dysfunction accompanying regeneration is accelerated by hyperlipidaemia. Here, we investigate the contribution of A-FABP to the pathogenesis of endothelial dysfunction in the aorta of apolipoprotein E-deficient (ApoE(-/-) ) mice and in cultured human endothelial cells.

EXPERIMENTAL APPROACH

A-FABP was measured in aortae of ApoE(-/-) mice and human endothelial cells by RT-PCR, immunostaining and immunoblotting. Total and phosphorylated forms of endothelial nitric oxide synthase (eNOS) were measured by immunoblotting. Changes in isometric tension were measured in rings of mice aortae

KEY RESULTS

A-FABP was expressed in aortic endothelium of ApoE(-/-) mice aged 12 weeks and older, but not at 8 weeks or in C57 wild-type mice. Reduced endothelium-dependent relaxations to acetylcholine, UK14304 (selective α(2) -adrenoceptor agonist) and A23187 (calcium ionophore) and decreased protein presence of phosphorylated and total eNOS were observed in aortae of 18 week-old ApoE(-/-) mice compared with age-matched controls. A 6 week treatment with the A-FABP inhibitor, BMS309403, started in 12 week-old mice, improved endothelial function, phosphorylated and total eNOS and reduced plasma triglyceride levels but did not affect endothelium-independent relaxations. The beneficial effect of BMS309403 on UK14304-induced relaxations was attenuated by Pertussis toxin. In cultured human microvascular endothelial cells, lipid-induced A-FABP expression was associated with reduced phosphorylated eNOS and NO production and was reversed by BMS309403.

CONCLUSIONS AND IMPLICATIONS

Elevated expression of A-FABP in endothelial cells contributes to their dysfunction both in vivo and in vitro.

Endothelial dysfunction and vascular disease

The endothelium can evoke relaxations (dilatations) of the underlying vascular smooth muscle, by releasing vasodilator substances. The best characterized endothelium-derived relaxing factor (EDRF) is nitric oxide (NO). The endothelial cells also evoke hyperpolarization of the cell membrane of vascular smooth muscle (endothelium-dependent hyperpolarizations, EDHF-mediated responses). Endothelium-dependent relaxations involve both pertussis toxin-sensitive G(i) (e.g. responses to serotonin and thrombin) and pertussis toxin-insensitive G(q) (e.g. adenosine diphosphate and bradykinin) coupling proteins. The release of NO by the endothelial cell can be up-regulated (e.g. by oestrogens, exercise and dietary factors) and down-regulated (e.g. oxidative stress, smoking and oxidized low-density lipoproteins). It is reduced in the course of vascular disease (e.g. diabetes and hypertension). Arteries covered with regenerated endothelium (e.g. following angioplasty) selectively loose the pertussis toxin-sensitive pathway for NO release which favours vasospasm, thrombosis, penetration of macrophages, cellular growth and the inflammatory reaction leading to atherosclerosis. In addition to the release of NO (and causing endothelium-dependent hyperpolarizations), endothelial cells also can evoke contraction (constriction) of the underlying vascular smooth muscle cells by releasing endothelium-derived contracting factor (EDCF). Most endothelium-dependent acute increases in contractile force are due to the formation of vasoconstrictor prostanoids (endoperoxides and prostacyclin) which activate TP receptors of the vascular smooth muscle cells. EDCF-mediated responses are exacerbated when the production of NO is impaired (e.g. by oxidative stress, ageing, spontaneous hypertension and diabetes). They contribute to the blunting of endothelium-dependent vasodilatations in aged subjects and essential hypertensive patients.

Systemic injection of planktonic forms of mammalian-derived nanoparticles alters arterial response to injury in rabbits

Experiments were designed to test the hypothesis that the systemic delivery of planktonic forms of nanoparticles (NPs) derived from calcified, diseased human tissue or bovine blood are transmissible particles that exacerbate arterial response to injury. New Zealand White rabbits in which the endothelium was mechanically removed from one carotid artery were injected intravenously with either saline (control), lipopolysaccharide (LPS; surrogate for subclinical infection), hydroxyapatite crystals (HA; surrogate for NP shell), HA crystals exposed to culture media, or planktonic forms of bovine- or human-derived NPs. Carotid arteries were monitored by ultrasonography for 5 wk and then removed for histological examination. Uninjured arteries from all animals in each group remained patent with a normal anatomy. Injured arteries from 6 of 11 animals injected with human-derived NPs occluded and/or calcified; none of the injured arteries from animals in the other groups occluded (n = 28; P < or = 0.05). Injured arteries of rabbits injected with LPS or HA crystals developed eccentric hyperplasia. Discontinuous internal elastic laminae and thinning media characterized arteries from animals injected with bovine-derived NPs or cultured HA crystals. In conclusion, the systemic administration of planktonic forms of human-derived NPs exacerbated arterial response to injury distinct from that of bovine-derived NPs and other inflammatory agents.

Endothelium-derived hyperpolarizing factor mediated relaxations in pig coronary arteries do not involve Gi/o proteins

AIM

Endothelium-dependent relaxations to certain neurohumoral substances are mediated by pertussis toxin-sensitive Gi/o protein. Our experiments were designed to determine the role, if any, of pertussis toxin-sensitive G-proteins in relaxations attributed to endothelium-derived hyperpolarizing factor (EDHF).

METHODS

Pig coronary arterial rings with endothelia were suspended in organ chambers filled with Krebs-Ringer bicarbonate solution maintained at 37 degrees and continuously aerated with 95%O2 and 5% CO2. Isometric tension was measured during contractions to prostaglandin F2alpha in the presence of indomethacin and N(omega)- nitro-L-arginine methyl ester (L-NAME).

RESULTS

Thrombin, the thrombin receptor- activating peptide SFLLRN, bradykinin, substance P, and calcimycin produced dose-dependent relaxations. These relaxations were not inhibited by prior incubation with pertussis toxin, but were abolished upon the addition of charybdotoxin plus apamin. Relaxations to the alpha2-adrenergic agonist UK14304 and those to serotonin were abolished in the presence of indomethacin and L-NAME.

CONCLUSION

Unlike nitric oxide-mediated relaxations, EDHF-mediated relaxations of pig coronary arteries do not involve pertussis toxin-sensitive pathways and are Gi/o protein independent.

Human-derived nanoparticles and vascular response to injury in rabbit carotid arteries: proof of principle

Self-calcifying, self-replicating nanoparticles have been isolated from calcified human tissues. However, it is unclear if these nanoparticles participate in disease processes. Therefore, this study was designed to preliminarily test the hypothesis that human-derived nanoparticles are causal to arterial disease processes. One carotid artery of 3 kg male rabbits was denuded of endothelium; the contralateral artery remained unoperated as a control. Each rabbit was injected intravenously with either saline, calcified, or decalcified nanoparticles cultured from calcified human arteries or kidney stones. After 35 days, both injured and control arteries were removed for histological examination. Injured arteries from rabbits injected with saline showed minimal, eccentric intimal hyperplasia. Injured arteries from rabbits injected with calcified kidney stone- and arterial-derived nanoparticles occluded, sometimes with canalization. The calcified kidney stone-derived nanoparticles caused calcifications within the occlusion. Responses to injury in rabbits injected with decalcified kidney stone-derived nanoparticles were similar to those observed in saline-injected animals. However, decalcified arterial-derived nanoparticles produced intimal hyperplasia that varied from moderate to occlusion with canalization and calcification. This study offers the first evidence that there may be a causal relationship between human-derived nanoparticles and response to injury including calcification in arteries with damaged endothelium.

Endothelium-derived hyperpolarizing factor in preeclampsia: heterogeneous contribution, mechanisms, and morphological prerequisites

We hypothesized that in preeclampsia (PE), contribution of endothelium-derived hyperpolarizing factor (EDHF) and the mechanism/s of its action differ from that in normal pregnancy (NP). We aimed to assess endothelial function and morphology in arteries from NP and PE with particular focus on EDHF. Arteries (≈200 μm) were dissected from subcutaneous fat biopsies obtained from women undergoing cesarean section. With the use of wire myography, responses to the endothelium-dependent agonist bradykinin (BK) were determined before and after inhibition of pathways relevant to EDHF activity. The overall responses to BK in arteries from PE ( n = 13) and NP ( n = 17) were similar. However, in PE, EDHF-mediated relaxation was reduced ( P < 0.05). All women within the PE group were divided into two subgroups: with more ( group 1) or less ( group 2) than 50% reduction of EDHF-typed responses after 18-α-glycyrrhetinic acid (an inhibitor of myoendothelial gap junctions, MEGJs). The division showed that 1) MEGJs are principally involved when the EDHF contribution is reduced; and 2) when the EDHF contribution is similar to that in NP, the H2O2 and/or cytochrome P-450 epoxygenase products of arachidonic acid (AA), along with MEGJs, confer EDHF-mediated relaxation. In contrast, MEGJs were the main pathway for EDHF in NP. The abundant presence of MEGJs in arteries from NP but deficiency of them in PE was observed using transmission electron microscopy. We conclude that PE is associated with heterogeneous contribution of EDHF, and the mechanism behind EDHF-typed responses is mediated either by MEGJs alone or in combination with H2O2 or cytochrome P-450 epoxygenase metabolites of AA.

Chronically impaired endothelial vasoreactivity following oversized endovascular introducer sheath placement in porcine iliac arteries: implications for endovascular therapy

The conventional endovascular aortic aneurysm procedure entails the placement of oversized introducer sheaths in relatively normal ileofemoral arteries to allow the delivery and deployment of endovascular prosthesis. Endoluminal manipulation with passage of oversized endoluminal devices can lead to endothelial denudation, resulting in impaired cellular function. The purpose of this study was to assess the time course of endothelial function with vasoreactivity following oversized endovascular sheath insertion ranging from 1 day to 16 weeks in normal porcine iliac arteries. Following oversized introducer sheath placement in bilateral iliac arteries, vasoreactivity was tested using both endothelium-dependent and -independent vasodilators. Intravascular ultrasonography showed a significant reduction in the luminal area at 12 and 16 weeks. This was similarly supported by morphometric analysis, which showed increased medial thickness with an elevated intima to media ratio at the same time course. Endothelium-dependent relaxation to bradykinin, calcium ionophore A23187, serotonin, and adenosine diphosphate all uniformly displayed attenuated endothelial dysfunction at all time points when compared with the control group. In contrast, endothelium-independent relaxation showed a decreased vasoresponsiveness at 4 weeks. In conclusion, this study underscored the detrimental and chronic endothelial dysfunction in a normal artery caused by oversized introducer sheath placement. Chronically impaired endothelial function may play a role leading to iliofemoral artery thrombosis or late occlusion, which were well-recognized adverse events following endovascular aneurysm procedures. Our study underscores the importance of appropriate patient selection to minimize potential sheath oversize and endograft device miniaturization to avoid vessel wall injury and maintain vasoreactivity.

P2 receptors in atherosclerosis and postangioplasty restenosis

Atherosclerosis is an immunoinflammatory process that involves complex interactions between the vessel wall and blood components and is thought to be initiated by endothelial dysfunction [Ross (Nature 362:801–09, 1993); Fuster et al. (N Engl J Med 326:242–50, 1992); Davies and Woolf (Br Heart J 69:S3–S11, 1993)]. Extracellular nucleotides that are released from a variety of arterial and blood cells [Di Virgilio and Solini (Br J Pharmacol 135:831–42, 2002)] can bind to P2 receptors and modulate proliferation and migration of smooth muscle cells (SMC), which are known to be involved in intimal hyperplasia that accompanies atherosclerosis and postangioplasty restenosis [Lafont et al. (Circ Res 76:996–002, 1995)]. In addition, P2 receptors mediate many other functions including platelet aggregation, leukocyte adherence, and arterial vasomotricity. A direct pathological role of P2 receptors is reinforced by recent evidence showing that upregulation and activation of P2Y₂ receptors in rabbit arteries mediates intimal hyperplasia [Seye et al. (Circulation 106:2720–726, 2002)]. In addition, upregulation of functional P2Y receptors also has been demonstrated in the basilar artery of the rat double-hemorrhage model [Carpenter et al. (Stroke 32:516–22, 2001)] and in coronary artery of diabetic dyslipidemic pigs [Hill et al. (J Vasc Res 38:432–43, 2001)]. It has been proposed that upregulation of P2Y receptors may be a potential diagnostic indicator for the early stages of atherosclerosis [Elmaleh et al. (Proc Natl Acad Sci U S A 95:691–95, 1998)]. Therefore, particular effort must be made to understand the consequences of nucleotide release from cells in the cardiovascular system and the subsequent effects of P2 nucleotide receptor activation in blood vessels, which may reveal novel therapeutic strategies for atherosclerosis and restenosis after angioplasty.

Development of genetically engineered mice lacking all three nitric oxide synthases

Nitric oxide (NO) is produced in almost all tissues and organs, exerting multiple biological actions under both physiological and pathological conditions. NO is synthesized by three different isoforms of NO synthase (NOS): neuronal, inducible, and endothelial NOSs. Due to the substantial compensatory interactions among the NOS isoforms, the ultimate roles of endogenous NO in our body still remain to be fully elucidated. To address this point, we have successfully developed mice in which all three NOS genes are completely disrupted. NOS expression and activities were totally absent in the triply n/i/eNOS(-/-) mice before and after treatment with lipopolysaccharide. While the triply n/i/eNOS(-/-) mice were viable, their survival and fertility rates were markedly reduced as compared with wild-type mice. The phenotypes of those mice that we first noticed were polyuria, polydipsia, and renal unresponsiveness to vasopressin, characteristics consistent with nephrogenic diabetes insipidus. We subsequently observed that in those mice, arteriosclerosis is spontaneously developed with a clustering of cardiovascular risk factors. These results provide the first evidence that the systemic deletion of all three NOSs causes a variety of cardiovascular diseases in mice, demonstrating a critical role of the endogenous NOSs system in maintaining cardiovascular homeostasis.

P2 receptors in atherosclerosis and postangioplasty restenosis

Atherosclerosis is an immunoinflammatory process that involves complex interactions between the vessel wall and blood components and is thought to be initiated by endothelial dysfunction [1-3]. Extracellular nucleotides that are released from a variety of arterial and blood cells [4] can bind to P2 receptors and modulate proliferation and migration of smooth muscle cells (SMC), which is known to be involved in intimal hyperplasia that accompanies atherosclerosis and postangioplasty restenosis [5]. In addition, P2 receptors mediate many other functions, including platelet aggregation, leukocyte adherence, and arterial vasomotoricity. A direct pathological role of P2 receptors is reinforced by recent evidence showing that up-regulation and activation of P2Y(2) receptors in rabbit arteries mediates intimal hyperplasia [6]. In addition, up-regulation of functional P2Y receptors also has been demonstrated in the basilar artery of the rat double-hemorrhage model [7] and in coronary arteries of diabetic dyslipidemic pigs [8]. It has been proposed that up-regulation of P2Y receptors may be a potential diagnostic indicator for the early stages of atherosclerosis [9]. Therefore, particular effort must be made to understand the consequences of nucleotide release from cells in the cardiovascular system and the subsequent effects of P2 nucleotide receptor activation in blood vessels, which may reveal novel therapeutic strategies for atherosclerosis and restenosis after angioplasty.

Endothelial dysfunction: a multifaceted disorder (The Wiggers Award Lecture)

Endothelial cells synthesize and release various factors that regulate angiogenesis, inflammatory responses, hemostasis, as well as vascular tone and permeability. Endothelial dysfunction has been associated with a number of pathophysiological processes. Oxidative stress appears to be a common denominator underlying endothelial dysfunction in cardiovascular diseases. However, depending on the pathology, the vascular bed studied, the stimulant, and additional factors such as age, sex, salt intake, cholesterolemia, glycemia, and hyperhomocysteinemia, the mechanisms underlying the endothelial dysfunction can be markedly different. A reduced bioavailability of nitric oxide (NO), an alteration in the production of prostanoids, including prostacyclin, thromboxane A2, and/or isoprostanes, an impairment of endothelium-dependent hyperpolarization, as well as an increased release of endothelin-1, can individually or in association contribute to endothelial dysfunction. Therapeutic interventions do not necessarily restore a proper endothelial function and, when they do, may improve only part of these variables.

Locally administered antiproliferative drugs inhibit hypercontractility to serotonin in balloon-injured pig coronary artery

Although drugs such as sirolimus and paclitaxel are effective in reducing restenosis, their effects on vascular function are often overlooked. In this study, we have examined the effects of local delivery of several anti-restenotic drugs given in vivo after balloon injury on in vitro vascular contraction and relaxation 28 days after injury. Paclitaxel (50 microM), the farnesyl protein transferase inhibitor L744 (25 microM), sirolimus (25 microM) and Van 10/4 (decahydro-1,1,4,7-tetramethyl-1H-cycloprop[e]azulen-4-o-[2-(3-methylpent-2-enoyl)-fucopyranoside]; 25 microM) were delivered to porcine coronary arteries in vivo and the arteries removed 28 days later. Contractions to KCl and 5-hydroxytryptamine (5-HT) and relaxations to calcimycin and 3-morpholinosydnonimine (SIN-1) were measured in control (LCx) and balloon-injured (LAD) rings. In vehicle-infused coronary arteries, contraction to KCl and 5-HT was significantly enhanced 28 days after balloon injury, while the response to calcimycin had recovered fully, indicating endothelial regrowth. The response to SIN-1 was unchanged. None of the four drugs tested had any effect on the enhanced response to KCl 28 days after injury or on recovery of the calcimycin response. The hyper-responsiveness to 5-HT was eliminated by sirolimus, Van 10/4 and L744, but not paclitaxel. This study demonstrates that local drug infusion with structurally different antiproliferative drugs at the time of balloon angioplasty does not affect endothelial recovery and may in some cases prevent hyper-responsiveness to constrictor agents.

Aortic function is compromised in a rat model of polycystic ovary syndrome

BACKGROUND

Arterial mechanical parameters are modified in women with polycystic ovary syndrome (PCOS), before and during pregnancy. This study tested the hypothesis that aortic mechanics and endothelial function are modified in the mifepristone-treated rat model of PCOS.

METHODS

Female rats injected daily with mifepristone or vehicle for 7-9 days were assessed by ultrasound to allow estimation of aortic stiffness index and compliance. The influence of acetylcholine (ACh) and sodium nitroprusside (SNP) on dissected phenylephrine-contracted aortic rings was assessed.

RESULTS

Aortic compliance was reduced by 67% in mifepristone-treated rats versus controls (P<0.05), while stiffness index was increased 2.3-fold (P<0.02). ACh-induced dilation was less in aortic rings from mifepristone-treated rats (P=0.022) and was less sensitive to the nitric oxide (NO) synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME) (P<0.001), while SNP-induced dilation was greater (P=0.001).

CONCLUSIONS

Aortic mechanics in vivo and endothelial function in vitro were consistently perturbed in mifepristone-treated rats. Aortic ring behaviour suggested that NO release was depressed or degradation elevated, with a compensatory increase in NO sensitivity and/or activation of a non-NO-mediated relaxation mechanism. The mifepristone-treated rat is a valid model for investigation of the vascular deficits seen in PCOS.

Combination Therapy with Cerivastatin and Nifedipine Improves Endothelial Dysfunction After Balloon Injury in Porcine Coronary Arteries

HMG-CoA reductase inhibitors and calcium channel blockers have antiatherogenic effects; however, their mechanisms remain to be elucidated. This study examined the effect of cerivastatin and/or nifedipine on the endothelial dysfunction in porcine balloon-injured coronary arteries. Normal male pigs were randomly divided into the following four groups: control, cerivastatin (1 mg/kg/d PO), nifedipine (4 mg/kg/d PO), and their combination (n = 10 each). We started the treatments 3 days before balloon injury in the proximal left coronary arteries and continued for 4 weeks after the procedure. Then, we examined endothelial vasodilator functions ex vivo in organ chambers and in vitro by Western blotting for eNOS expression. Endothelium-dependent relaxations to serotonin, but not those to bradykinin or the calcium ionophore A23187 or endothelium-independent relaxations to sodium nitroprusside, were significantly impaired by balloon injury. The monotherapy with cerivastatin or nifedipine partially improved, and their combination supernormalized the relaxations to serotonin without affecting those to bradykinin or A23187 or endothelium-independent relaxations to sodium nitroprusside. The expression of eNOS was significantly reduced by balloon injury and normalized by the combination therapy. These results indicate that the combination therapy improves endothelial dysfunction after balloon injury, in which the up-regulation of eNOS may be involved.

Injury of the coronary endothelium at implantation increases endothelial dysfunction and intimal hyperplasia after heart transplantation

BACKGROUND

Coronary endothelial dysfunction occurs early after heart transplantation and predicts the development of intimal thickening characteristic of cardiac allograft vasculopathy.

OBJECTIVES

To assess the effects of removal of the endothelium by balloon injury of coronary arteries of allografts without rupture of the internal elastic lamina at the time of implantation and on coronary endothelial dysfunction, and to assess the development of accelerated atherosclerosis after heart transplantation.

METHODS

A porcine model of heterotopic heart transplantation with preoperative immunologic typing, enabling progressive rejection without immunosuppression, was used to study the effect of endothelial removal on these 2 end points. Endothelium-dependent relaxations of epicardial coronary arteries from allografts submitted to endothelial denudation after harvest, arteries from allografts not undergoing denudation, and native coronary arteries were compared 30 days after graft implantation by using standard organ chamber experiments. Intimal thickening was measured by light microscopy with a semiquantitative scale (0 to 4+ grading).

RESULTS

Relaxations to serotonin and to bradykinin were significantly decreased in denuded arteries compared with nondenuded allograft arteries. There was a significant increase in the incidence of severe intimal hyperplasia in denuded arteries compared with nondenuded arteries, which were both significantly increased compared to native coronary arteries.

CONCLUSIONS

Endothelial injury at implantation worsens the endothelial dysfunction as a result of rejection after heart transplantation and compounds the intimal thickening leading to cardic allograft vasculopathy. All efforts should be deployed to maintain a morphologically intact and functional endothelium at the time of graft implantation.

Nitric oxide and angiogenesis in cardiovascular disease

Ischemic heart disease and peripheral artery disease mainly develop as a consequence of atherosclerotic lesion formation. Angiogenesis, the formation of new blood vessels from the preexisting vascular bed, is of paramount importance in the maintenance of vascular integrity both in the repair process of damaged tissue (wound healing) and in the formation of collateral vessels in response to tissue ischemia. Angiogenesis is a complex process that is orchestrated by a multitude of cytokines/chemokines and growth factors. In its broadest sense, angiogenesis cannot be viewed as a single process. It is likely that different mediators are involved in different phases of angiogenesis. Vascular endothelial cells produce nitric oxide (NO), an endothelium-derived labile molecule, which maintains vascular homeostasis and thereby prevents vascular atherosclerotic changes. In patients with ischemic heart disease and peripheral artery disease, the release of endothelium-derived NO is decreased, which plays an important role in the atherosclerotic disease progression. In recent years, endothelium-derived NO has been shown to modulate angiogenesis in vitro and in vivo. In this review, we summarize recent progress in the field of the NO-mediated regulation of postnatal angiogenesis.

Consequences of reduced production of NO on vascular reactivity of porcine coronary arteries after angioplasty: importance of EDHF

1 The consequences of the reduced production of nitric oxide (NO) by cells from regenerated endothelium were investigated by measuring membrane potential of smooth muscle cells (SMCs), isometric tension and cyclic nucleotides content in porcine coronary arteries with intimal thickening, four weeks following angioplasty. 2 Under basal conditions, SMCs of coronary arteries with regenerated endothelium were depolarized by 10 mV. This depolarization was associated with 82% decreased level of cGMP without alteration in cAMP. 3 Sodium nitroprusside (SNP, 1 micro M) repolarized SMCs of the previously denuded coronary arteries. This repolarization was abolished by 1H-[1,2,4]-oxadiazolo[4,3-a]quinoxalin-1-one (ODQ, 10 micro M) and not suppressed by glibenclamide (10 micro M), iberiotoxin (IbTX, 100 nM) and the combination of charybdotoxin (ChTX, 40 nM) plus apamin (100 nM). 4 Four-aminopyridine (4-AP, 1-5 mM) generated spontaneous rhythmic activities only in coronary arteries with regenerated endothelium which were abolished by SNP. Nevertheless, 4-AP did not suppress the repolarization induced by SNP. 5 In vascular segments with regenerated endothelium, contracted with prostaglandin F(2alpha) (PGF(2alpha)), relaxation to bradykinin (BK, 30 nM) was unaltered despite a reduced production of cGMP (-70%). Indomethacin (10 micro M) plus N(omega)-nitro-L-arginine (L-NA, 30 micro M) reduced relaxation (-12% and -35% for native and regenerated endothelium, respectively) but did not abolish it. 6 The hyperpolarizations induced by BK were not altered by the presence of indomethacin and L-NA and were unchanged in segments with regenerated endothelium. 7 These data are consistent with a contribution of impairment in NO production to the depolarization of SMCs. Nevertheless, EDHF responses to BK are sufficient to maintain a normal relaxation after angioplasty.

Bradykinin inhibits serum-depletion-induced apoptosis of human vascular endothelial cells by inducing nitric oxide via calcium ion kinetics

Vascular endothelial cells play important roles in atherogenesis, and bradykinin is associated with atherosclerosis. The effect of bradykinin on apoptosis in human umbilical vein endothelial cells (HUVECs) was investigated, with a focus on Ca2+ kinetics and nitric oxide production. In serum-free conditions, the number of apoptotic cells increased in a time-dependent manner, but this increase was inhibited by bradykinin in a dose-dependent manner. The apoptosis inhibited by bradykinin was reduced by nitric oxide inhibitor N(G)-monomethyl-L-arginine (L-NMMA) and consequently restored by combined treatment with L-NMMA and L-arginine. Bradykinin increased influx of extracellular Ca2+, generation of inositol 1,4,5-trisphosphate, and release of Ca2+ from intracellular storage sites, thus increasing the total intracellular Ca2+ concentration ([Ca2+]i). Bradykinin increased nitric oxide production, which was inhibited by L-NMMA and restored by combined treatment with L-NMMA and L-arginine. Sodium nitroprusside (SNP) dose-dependently increased nitric oxide production and inhibited apoptosis; however, 10(-5) M SNP did not inhibit apoptosis. Caspase-3 inhibitor, acetyl-Asp-Met-Gln-Asp-aldehyde, enhanced bradykinin-induced inhibition of apoptosis but did not effect bradykinin-induced nitric oxide production. These findings suggest that bradykinin inhibits serum-depletion-induced apoptosis in HUVECs by enhancing nitric oxide production via an increase in [Ca2+]i.

Differences in endothelial function and morphologic modulation between canine autogenous venous and arterial grafts: endothelium and intimal thickening

BACKGROUND

Late graft failure is still a problem for vascular surgeons. A previous study showed superior patency of arterial grafts compared with venous grafts. In this review we discuss the differences in functional and morphologic modulation of experimental autogenous venous and arterial grafts.

RESULTS

In canine venous grafts, the endothelium of the graft was denuded and recovered within 3 or 4 weeks. In contrast, in arterial grafts, denudation of the endothelium was minimal, and no platelet adherence was observed. Instead, nearly normal intact endothelial cell surface had covered the intima within 3 days after grafting. The histologic findings for arterial grafts thus were quite different from those for venous grafts. Different responses to flow changes between venous and arterial grafts were observed. In the venous grafts, pronounced intimal thickening was associated with impairment of endothelial responses, whereas in the arterial grafts, intact endothelial function and no intimal thickening were observed.

CONCLUSIONS

The intact endothelial function and absence of intimal thickening under the arterial grafts may explain the superior patency of autogenous arterial grafts in comparison with venous grafts.

Coronary artery endothelial protection after local delivery of 17beta-estradiol during balloon angioplasty in a porcine model: a potential new pharmacologic approach to improve endothelial function

OBJECTIVES

The goal of this research was to study the effect of locally delivered 17beta-estradiol (17beta-E) during angioplasty on endothelial function after percutaneous transluminal coronary angioplasty (PTCA) at four weeks.

BACKGROUND

The endothelium plays a major role in the structural and functional integrity of coronary arteries and is damaged by PTCA.

METHODS

Juvenile swine were subjected to PTCA, after which each artery was randomly-assigned to 600-microg 17beta-E delivered locally, an equal volume of vehicle (V) or PTCA alone. After four weeks, the improvement in endothelial function was assessed by angiography using intracoronary acetylcholine (Ach) infusion and by immunohistochemistry.

RESULTS

At 10(-5) mol/l and 10(-4) mol/l Ach, significant vasoconstriction was noted in arteries treated with PTCA alone (p < 0.01 and p < 0.0001, respectively) and with PTCA plus V (p < 0.02 and p < 0.001, respectively). No significant vasoconstrictive response to Ach was observed in arteries treated with PTCA plus 17beta-E. Immunohistochemistry of vessels four weeks after PTCA revealed enhanced re-endothelialization (p < 0.0005) and endothelial nitric-oxide synthase (eNOS) expression (p < 0.0005) in PTCA plus 17beta-E-treated arteries compared with the other two treatment groups. Arteries treated with 17beta-E showed significantly lower neointima formation, which correlated inversely with the extent of re-endothelialization and eNOS expression.

CONCLUSIONS

Locally delivered 17beta-E significantly enhances re-endothelialization and endothelial function after PTCA, possibly by improving the expression of eNOS. Since endothelial dysfunction can promote both restenosis and coronary spasm, local 17beta-E administration is a promising new approach to improve long-term results after PTCA.

Endothelial adrenoceptors

alpha2 -Adrenergic agonists cause endothelium-dependent relaxation in a number of isolated blood vessels. This effect is explained by the activation of endothelial alpha 2 -adrenoceptors linked to nitric oxide synthase by G i -coupling proteins. The endothelial response to alpha 2 -adrenergic agonists is blunted considerably after regeneration of the endothelium and in atherosclerotic arteries. The relaxation of isolated arteries caused by beta-adrenergic agonists is reduced by removal of the endothelium and, in most cases, by inhibitors of the l -arginine nitric oxide pathway. Likewise, in the intact animal and in the human forearm the vasodilatation to beta 2 -adrenergic agonists is blunted by inhibitors of nitric oxide synthase. Whether these findings reflect the presence of functional beta-adrenoceptors on the endothelium remains controversial. Several beta-adrenergic blockers cause endothelium-dependent relaxation in vitro or augment the production of nitric oxide in vivo. However, these responses cannot be attributed to interactions with endothelial beta-adrenoceptors.

Mechanisms underlying attenuated contractile response of aortic rings to noradrenaline in fructose-fed mice

We hypothesized that an impairment of endothelial dysfunction and an increased response to alpha-adrenoceptor agonists may occur in fructose-fed, insulin-resistant mice. The aim of the present study was to assess the relationship between endothelial dysfunction and agonist-induced contractile responses in such mice. The acetylcholine-induced relaxation was significantly attenuated in streptozotocin-diabetic and fructose-fed mice. The contractile response to noradrenaline was significantly weaker than the control in fructose-fed but not in streptozotocin-diabetic mice; treatment with N(G)-nitro-L-arginine effectively restored this response. Incubating aortic rings with noradrenaline increased the NO(x) [nitrite (NO(2)(-)) and nitrate (NO(3)(-))] level and this level was significantly higher in fructose-fed mice than in control mice. Clonidine induced a dose-dependent relaxation in aortic rings pre-contracted with prostaglandin F(2alpha) that was completely abolished by N(G)-nitro-L-arginine; this relaxation was markedly enhanced in fructose-fed mice. In both control and fructose-fed mice, the clonidine-induced relaxation was significantly attenuated and the noradrenaline-induced contraction augmented by pertussis toxin. These results suggest that endothelial function is attenuated in both fructose-fed and streptozotocin-diabetic mice. It is suggested that the decreased noradrenaline contractile response in fructose-fed mice (compared to both controls and streptozotocin-diabetic mice) may be due to an increase in nitric oxide formation mediated by endothelial GTP-binding-coupled alpha(2)-adrenoceptors.

Arterial balloon catheter: a new atraumatic device for dilating arterial grafts

BACKGROUND

Harvesting of the internal mammary artery (IMA) for use in myocardial revascularization may result in spasm, which can impair early graft flow. Hydrostatic and mechanical dilatation can exert an intraluminal shear force, causing denudation of the IMA endothelium. A new long balloon dilatation technique (LB) has been developed to mechanically increase IMA diameter and flow without exerting any shear force on the endothelium.

METHODS

Vascular rings of porcine IMA were divided into four groups: no manipulation (control), metal dilators (MD), short balloon (SB), or LB intraluminal dilation. In situ flows after dilation and percentage of intact endothelium after silver nitrate staining were determined. Endothelium-dependent contractions with arachidonic acid, relaxations with acetylcholine, endothelium-independent contractions with norepinephrine, and relaxation with sodium nitroprusside were recorded in organ chamber experiments.

RESULTS

Increases in IMA flows were similar in all dilated groups. Endothelium-independent contractions and relaxations of IMA smooth muscle were unaffected by any type of mechanical dilation. However, endothelium-dependent contractions and relaxations were significantly impaired after MD and SB but preserved after LB dilation compared with control. Silver nitrate staining showed a greater preservation of the endothelial coverage after LB dilation.

CONCLUSIONS

IMA dilatation with the novel arterial LB catheter increases IMA flow and preserves endothelial cell integrity, making it an effective and atraumatic method to relieve IMA spasm before use for coronary artery bypass grafting.

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.

EDHF mediates flow-induced dilation in skeletal muscle arterioles of female eNOS-KO mice

Vasodilation to increases in flow was studied in isolated gracilis muscle arterioles of female endothelial nitric oxide synthase (eNOS)-knockout (KO) and female wild-type (WT) mice. Dilation to flow (0-10 microl/min) was similar in the two groups, yet calculated wall shear stress was significantly greater in arterioles of eNOS-KO than in arterioles of WT mice. Indomethacin, which inhibited flow-induced dilation in vessels of WT mice by approximately 40%, did not affect the responses of eNOS-KO mice, whereas miconazole and 6-(2-proparglyoxyphenyl)hexanoic acid (PPOH) abolished the responses. Basal release of epoxyeicosatrienonic acids from arterioles was inhibited by PPOH. Iberiotoxin eliminated flow-induced dilation in arterioles of eNOS-KO mice but had no effect on arterioles of WT mice. In WT mice, neither N(omega)-nitro-L-arginine methyl ester nor miconazole alone affected flow-induced dilation. Combination of both inhibitors inhibited the responses by approximately 50%. 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) alone inhibited flow-induced dilation by approximately 49%. ODQ + indomethacin eliminated the responses. Thus, in arterioles of female WT mice, nitric oxide and prostaglandins mediate flow-induced dilation. When eNOS is inhibited, endothelium-derived hyperpolarizing factor substitutes for nitric oxide. In female eNOS-KO mice, metabolites of cytochrome P-450, via activation of large-conductance Ca2+-activated K+ channels of smooth muscle, mediate entirely the arteriolar dilation to flow.

Effects of red ginseng upon vascular endothelial function in patients with essential hypertension

This study is to estimate the effect of Korean red ginseng on vascular endothelial cell dysfunction in patients with hypertension. Seventeen patients with hypertension who were divided into ginseng-treated (7) and non-treated (10) groups and 10 normotensive subjects were included. To assess the function of the vascular endothelial cell, changes of forearm blood flow to infusion of acetylcholine, sodium nitroprusside and bradykinin in incremental doses were measured by venous occlusion plethysmography. In the ginseng-treated hypertensive group, forearm blood flows at the highest dose of acetylcholine and bradykinin were significantly higher than those of the non-treated hypertensive group and were not different from those of the control group. In the case of sodium nitroprusside infusion, no significant differences were observed between the control, non-treated and treated groups. In conclusion, Korean red ginseng can improve the vascular endothelial dysfunction in patients with hypertension possibly through increasing synthesis of nitric oxide.

Chronic endothelial dysfunction after oversized coronary balloon angioplasty in pigs: a 12-week follow-up of coronary vasoreactivity in vivo and in vitro

Previous studies have reported the development of vasoconstriction immediately after invasive coronary interventions. Other studies in animals have demonstrated that using oversized balloon angioplasty, vasospasm can be suppressed, even in the presence of endothelial denudation due to important structural alteration in vascular smooth muscle. The regenerated endothelium also appears to be impaired chronically by selective attenuation of in vitro endothelial dependent relaxation related to pertussis toxin-sensitive G proteins. The purpose of this investigation was to verify in vivo and in vitro vasoreactivity to bradykinin (BK) and serotonin (5-hydroxytryptamine; 5-HT) (endothelial dependent agonists) as well as to nitroglycerin (NTG) (exogenous nitric oxide donor) at different times after oversized balloon angioplasty intervention ranging from 1 h to 12 weeks, in normal porcine coronary arteries. BK-induced vasodilatation in vivo was impaired acutely, but it was restored after 4 weeks. Serotonin caused vasoconstriction in vivo that was significantly augmented after 12 weeks. Conversely, endothelium-dependent vasodilatation in vitro to BK and 5-HT remained attenuated during the whole period of follow-up. Finally, relaxation elicited by NTG was reduced in the in vivo experiment until the first week after the procedure. Histological analysis showed severe arterial injury, and complete recovery of endothelial coverage after 4 weeks. In conclusion, this experiment supports evidence for the occurrence of the acute attenuation of vasoresponsiveness and chronic endothelial dysfunction following overstretching coronary balloon angioplasty. Abnormal remodeling associated with the severity of injury may contribute to chronic endothelial dysfunction. Differences found between in vivo and in vitro studies also suggest that multiple endogenous influences present in the former can attenuate the greater endothelial dysfunction demonstrated by endothelial assessment in vitro.