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Pieper GM, Siebeneich W, Olds CL, Felix CC, Del Soldato P. Vascular protective actions of a nitric oxide aspirin analog in both in vitro and in vivo models of diabetes mellitus. Free Radic Biol Med 2002; 32:1143-56. [PMID: 12031899 DOI: 10.1016/s0891-5849(02)00832-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
BACKGROUND Defective endothelium-dependent relaxation is observed in experimental and human diabetes mellitus. The nature of this defect is not fully understood but may involve decreased nitric oxide (NO) bioactivity due to enhanced production of reactive oxygen species (ROS). In this paper, we examine the benefits and actions of a novel NO-donating, antioxidant called 2-acetoxybenzoic acid 2-(2-nitrooxymethyl) phenyl ester, and denoted as NCX4016, on NO-mediated endothelium-dependent relaxation in normal arteries exposed to acute elevations in glucose or in arteries derived from chronic diabetic animals. MATERIAL AND METHODS Intrinsic free radical scavenging by NO-NSAIDs in solution were evaluated using electron paramagnetic resonance (EPR) spectroscopy and spin trapping with 5,5-dimethyl-1-pyrroline-N-oxide (DMPO). In acute studies, normal rat aortas were exposed in tissue culture for 18 h to 5.5 mM or 40 mM in the presence or absence of NCX4016, a NO-donating NSAID unrelated to aspirin (NCX2216) or aspirin. Vascular reactivity of thoracic aortic rings to endothelium-dependent relaxation to acetylcholine in vitro was determined. For chronic hyperglycemia, diabetes was induced in rats by intravenous injection with streptozotocin. Vascular reactivity of thoracic aortic rings to endothelium-dependent relaxation to acetylcholine in vitro was determined after 8 wks in untreated animals or animals chronically-treated with NCX4016. Antioxidant efficacy in vivo was determined by measurement of plasma isoprostanes and by nuclear binding activity of NF-kappaB in nuclear fractions of aortae. RESULTS Incubation with NCX4016 and NCX2216 produced a concentration-dependent inhibition of DMPO-OH formation indicating scavenging of hydroxyl radicals (HO(*)). In contrast, little efficacy to scavenge superoxide anion radicals was noted. Acute incubation of normal arteries with elevated glucose concentration caused inhibition of normal relaxation to acetylcholine. This impairment was prevented by co-incubation with NCX4106 but not by mannitol, the parent compound (aspirin) or by NCX2216. In addition, chronic treatment with NCX4016 prevented the development of defective endothelium-dependent relaxation to acetylcholine. This protection did not occur as a result to any changes in blood glucose concentration or hemoglobin glycation. Treatment with NCX4016 did decrease the elevation in plasma isoprostanes and normalized the diabetes-induced increase in NF-kappaB binding activity in nuclear fractions derived from aortic tissue. CONCLUSIONS Collectively, these studies suggest that antioxidant interventions using NO-donating NSAIDs may provide an important novel therapeutic strategy to protect the diabetic endothelium.
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MESH Headings
- Acetylcholine/pharmacology
- Animals
- Anti-Inflammatory Agents, Non-Steroidal/pharmacology
- Anti-Inflammatory Agents, Non-Steroidal/therapeutic use
- Aorta, Thoracic/drug effects
- Aspirin/analogs & derivatives
- Aspirin/pharmacology
- Aspirin/therapeutic use
- Diabetes Mellitus, Experimental/drug therapy
- Diabetes Mellitus, Experimental/metabolism
- Electron Spin Resonance Spectroscopy
- Electrophoretic Mobility Shift Assay
- Endothelium, Vascular/drug effects
- Endothelium, Vascular/metabolism
- Free Radical Scavengers/pharmacology
- Free Radical Scavengers/therapeutic use
- Gene Expression/drug effects
- Glucose/metabolism
- Glucose/pharmacology
- Hydroxyl Radical/metabolism
- Hyperglycemia/drug therapy
- Hyperglycemia/metabolism
- Isoprostanes/metabolism
- Muscle Relaxation/drug effects
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/metabolism
- NF-kappa B/metabolism
- Nitric Oxide/metabolism
- Norepinephrine/pharmacology
- Rats
- Rats, Sprague-Dawley
- Superoxides/metabolism
- Vasodilation/drug effects
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Affiliation(s)
- Galen M Pieper
- Division of Transplant Surgery, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
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52
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Kersten JR, Toller WG, Tessmer JP, Pagel PS, Warltier DC. Hyperglycemia reduces coronary collateral blood flow through a nitric oxide-mediated mechanism. Am J Physiol Heart Circ Physiol 2001; 281:H2097-104. [PMID: 11668071 DOI: 10.1152/ajpheart.2001.281.5.h2097] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
We tested the hypothesis that hyperglycemia alters retrograde coronary collateral blood flow by a nitric oxide-mediated mechanism in a canine Ameriod constrictor model of enhanced collateral development. Administration of 15% dextrose to increase blood glucose concentration to 400 or 600 mg/dl decreased retrograde blood flow through the left anterior descending coronary artery to 78 +/- 9 and 82 +/- 8% of baseline values, respectively. In contrast, saline or L-arginine (400 mg x kg(-1) x h(-1)) had no effect on retrograde flow. Coronary hypoperfusion and 1 h of reperfusion decreased retrograde blood flow similarly in saline- or L-arginine-treated dogs (76 +/- 11 and 89 +/- 4% of baseline, respectively), but these decreases were more pronounced in hyperglycemic dogs (47 +/- 10%). L-arginine prevented decreases in retrograde coronary collateral blood flow during hyperglycemia (100 +/- 5 and 95 +/- 6% of baseline at blood glucose concentrations of 400 and 600 mg/dl, respectively) and after coronary hypoperfusion and reperfusion (84 +/- 14%). The results suggest that hyperglycemia decreases retrograde coronary collateral blood flow by adversely affecting nitric oxide availability.
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Affiliation(s)
- J R Kersten
- Department of Anesthesiology, Medical College of Wisconsin, Milwaukee 53226, USA.
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53
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Minhas S, Cartledge J, Eardley I. The pathophysiological role of prostaglandins in penile erection. Expert Opin Pharmacother 2001; 2:799-811. [PMID: 11336623 DOI: 10.1517/14656566.2.5.799] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Penile erection is a complex haemodynamic event and relaxation of the vascular smooth muscle of the penis is fundamental to this process. This is primarily mediated by nitric oxide (NO) produced from non-adrenergic non-cholinergic (NANC) nerves and the endothelium surrounding the corporal sinusoids. However, corporal tissue has been shown to produce a number of other vasoactive factors, including prostaglandins (PGs), which appear to not only have diverse physiological effects, but are also able to modulate the effects of other neurotransmitters, including NO.
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Affiliation(s)
- S Minhas
- Pyrah Department of Urology, St James's University Hospital, Leeds, UK
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54
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Brodsky SV, Morrishow AM, Dharia N, Gross SS, Goligorsky MS. Glucose scavenging of nitric oxide. Am J Physiol Renal Physiol 2001; 280:F480-6. [PMID: 11181410 DOI: 10.1152/ajprenal.2001.280.3.f480] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Endothelial dysfunction accompanies suboptimal glucose control in patients with diabetes mellitus. A hallmark of endothelial dysfunction is a deficiency in production or bioavailability of vascular nitric oxide (NO). Here we demonstrate that acute exposure of human endothelial cells to glucose, at levels found in plasma of diabetic patients, results in a significant blunting of NO responses to the endothelial nitric oxide synthase (eNOS) agonists bradykinin and A-23187. Monitoring of NO generation by purified recombinant bovine eNOS in vitro, using amperometric electrochemical detection and an NO-selective porphyrinic microelectrode, showed that glucose causes a progressive and concentration-dependent attenuation of detectable NO. Addition of glucose to pure NO solutions similarly elicited a sharp decrease in NO concentration, indicating that glucose promotes NO loss. Electrospray ionization-tandem mass spectrometry, using negative ion monitoring, directly demonstrated the occurrence of a covalent reaction involving unitary addition of NO (or a derived species) to glucose. Collectively, our findings reveal that hyperglycemia promotes the chemical inactivation of NO; this glucose-mediated NO loss may directly contribute to hypertension and endothelial dysfunction in diabetic patients.
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Affiliation(s)
- S V Brodsky
- Program in Biomedical Engineering, Department of Medicine, State University of New York, Stony Brook, NY 11794-8152, USA
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55
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McCarty MF. Up-regulation of endothelial nitric oxide activity as a central strategy for prevention of ischemic stroke - just say NO to stroke! Med Hypotheses 2000; 55:386-403. [PMID: 11058418 DOI: 10.1054/mehy.2000.1075] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Nitric oxide (NO) produced by the endothelium of cerebral arterioles is an important mediator of endothelium-dependent vasodilation (EDV), and also helps to prevent thrombosis and vascular remodeling. A number of risk factors for ischemic stroke are associated with impaired EDV, and this defect is usually at least partially attributable to a decrease in the production and/or stability of NO. These risk factors include hypertension, high-sodium diets, homocysteine, diabetes, visceral obesity, and aging. Conversely, many measures which may provide protection from ischemic stroke - such as ample dietary intakes of potassium, arginine, fish oil, and selenium - can have a favorable impact on EDV. Protection afforded by exercise training, estrogen replacement, statin drugs, green tea polyphenols, and cruciferous vegetables may reflect increased expression of the endothelial NO synthase. IGF-I activity stimulates endothelial NO production, and conceivably is a mediator of the protection associated with higher-protein diets in Japanese epidemiology and in hypertensive rats. These considerations prompt the conclusion that modulation of NO availability is a crucial determinant of risk for ischemic stroke. Multifactorial strategies for promoting effective cerebrovascular NO activity, complemented by measures that stabilize platelets and moderate blood viscosity, should minimize risk for ischemic stroke and help maintain vigorous cerebral perfusion into ripe old age. The possibility that such measures will also diminish risk for Alzheimer's disease, and slow the normal age-related decline in mental acuity, merits consideration. A limited amount of ecologic epidemiology suggests that both stroke and senile dementia may be extremely rare in cultures still consuming traditional unsalted whole-food diets. Other lines of evidence suggest that promotion of endothelial NO activity may decrease risk for age-related macular degeneration.
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Affiliation(s)
- M F McCarty
- Pantox Laboratories, San Diego, California 92109, USA
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56
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Vallejo S, Angulo J, Peiró C, Cercas E, Sánchez-Ferrer A, Nevado J, Llergo JL, Rodríguez-Mañas L, Sánchez-Ferrer CF. Treatment with acarbose may improve endothelial dysfunction in streptozotocin-induced diabetic rats. J Cardiovasc Pharmacol 2000; 36:255-62. [PMID: 10942169 DOI: 10.1097/00005344-200008000-00017] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
We sought to determine whether a single reduction of hyperglycemia and those derivatives from nonenzymatic protein glycosylation may be effective in reducing the development of diabetic endothelial dysfunction. Therefore, we investigated how acarbose, an inhibitor of intestinal alpha-glucosidase that reduce hyperglycemia by lowering glucose absorption, may prevent the impairment of acetylcholine (ACh)-induced endothelium-dependent relaxations observed in isolated vascular segments from untreated streptozotocin-induced diabetic rats. When administered after diabetes induction, 10 mg/kg acarbose decreased modestly the enhancement of blood glucose and glycosylated hemoglobin (HbA1c) levels, but not those of advanced glycosylation end products (AGEs). This effect was linked to a partial improvement of ACh-induced responses both in conductance vessels, such as aortic segments, and resistance vasculature, like mesenteric microvessels. When acarbose was introduced after 6 weeks of untreated diabetes, blood glucose, HbA1c, and AGE levels were not affected and endothelial dysfunction remained unchanged in mesenteric microvessels, whereas a small improvement was observed in aortic segments. The addition of 100 U/ml superoxide dismutase enhanced the impaired relaxations to values similar to vessels from nondiabetic rats, indicating a main role for superoxide anions in diabetes-induced endothelial dysfunction. We conclude that hyperglycemia itself or elevated HbA1c, but not plasma AGEs, are related to enhanced oxidative stress and to the impairment of endothelium function associated to diabetes. This process can be partially prevented by reducing glucose absorption with acarbose.
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Affiliation(s)
- S Vallejo
- Unidad de Investigación y Servicio de Geriatría, Hospital Universitario de Getafe, Spain
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57
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Hucks D, Ward JPT. Critical dependence of the NO-mediated component of cyclic AMP-induced vasorelaxation on extracellular L-arginine in pulmonary arteries of the rat. Br J Pharmacol 2000; 130:997-1004. [PMID: 10882383 PMCID: PMC1572160 DOI: 10.1038/sj.bjp.0703399] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
A component of isoprenaline-mediated vasorelaxation in pulmonary arteries is mediated by nitric oxide (NO). We examined the effects of physiological concentrations (</=400 microM) of L-arginine on isoprenaline-induced relaxation in rat pulmonary arteries, and following inhibition of L-arginine uptake with L-lysine. In addition, we examined the role of the endothelium, and whether L-arginine affected acetylcholine (ACh)-induced relaxation. Isoprenaline-induced relaxation was potentiated by 400 microM L-arginine in pulmonary arteries; maximum relaxation was increased from 83+/-4% of initial tone to 94+/-4% (P<0.05). L-lysine (10 mM) not only abolished the potentiation by L-arginine, but suppressed relaxation compared to control (70+/-4%, P<0.05), even in the absence of L-arginine added to the bath. Blockade of NO synthase with 100 microM L-NMMA or removal of the endothelium inhibited isoprenaline-induced relaxation to the same extent as L-lysine, and under these conditions the presence or absence of 400 microM L-arginine made no difference. L-lysine had no additional effect when applied in combination with L-NMMA. The effect of extracellular L-arginine was concentration dependent, with an apparent EC(50) of approximately 1-7 microM. Relaxation to the membrane permeant cyclic AMP analogue CPT cyclic AMP was also potentiated by L-arginine and inhibited by L-lysine. There was however no difference in relaxation induced by acetylcholine (ACh) in the presence of L-arginine or L-lysine, and isoprenaline-induced relaxation of mesenteric arteries was unaffected by L-arginine or L-lysine. These results strongly suggest that extracellular L-arginine is critically important for development of the NO- and endothelium-dependent component of cyclic AMP-induced vasorelaxation in rat pulmonary arteries, but is not required for ACh-induced relaxation. As the apparent EC(50) for this effect is in the low micromolar range it is likely to be fully activated in vivo, as plasma L-arginine is >150 microM.
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Affiliation(s)
- D Hucks
- Department of Respiratory Medicine and Allergy, Guy's, King's and St Thomas' School of Medicine, King's College London, Guy's Campus, London SE1 9RT
| | - J P T Ward
- Department of Respiratory Medicine and Allergy, Guy's, King's and St Thomas' School of Medicine, King's College London, Guy's Campus, London SE1 9RT
- Author for correspondence:
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58
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Bagg W, Whalley GA, Sathu A, Gamble G, Sharpe N, Braatvedt GD. The effect of acute hyperglycaemia on brachial artery flow mediated dilatation in normal volunteers. AUSTRALIAN AND NEW ZEALAND JOURNAL OF MEDICINE 2000; 30:344-50. [PMID: 10914752 DOI: 10.1111/j.1445-5994.2000.tb00836.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
BACKGROUND Endothelial function is known to be abnormal in patients with diabetes and acute hyperglycaemia may play an aetiological role. AIMS The aim of this randomised controlled study was to determine if acute systemic hyperglycaemia impairs endothelial function in normal subjects. METHODS Endothelial function was assessed by the change in brachial artery diameter in response to forearm ischaemia using B-mode ultrasound in ten healthy subjects (eight male) aged 19-35 years. Brachial artery blood flow velocity and diameter were measured before and after five minutes of forearm ischaemia. Measurements were performed in the supine position after an overnight fast, before and after 60 minute infusions of 0.9% saline or 10% dextrose. Measurements were made on two separate occasions at least 24 hours apart, and subjects were randomised to saline first or dextrose first. The largest diameter measured after ischaemia was divided by the resting arterial diameter to calculate percent dilatation of the artery from baseline, and is reported as flow-mediated dilatation (FMD). RESULTS Dextrose infusion resulted in a significant rise in mean (SD) serum glucose 5.2 (0.1) to 9.2 (0.3) mmol/L and insulin concentration 6.3 (1.4) to 20.6 (3.7) mU/L p<0.002. Brachial artery blood flow velocity and diameter increased significantly from baseline after ischaemia (p<0.002). Mean FMD (SEM) before and after infusion were not, however, significantly different (p=0.4) (pre-saline 7.3 [1.0]%, post saline 5.2 [1.5]% and predextrose 8.1 [2.0]%, post dextrose 5.9 [1.7]%). CONCLUSIONS These data suggest that acute hyperglycaemia does not impair FMD in normal subjects.
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Affiliation(s)
- W Bagg
- Department of Medicine, University of Auckland, Auckland Hospital, Grafton, NZ.
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59
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Keegan A, Jack AM, Cotter MA, Cameron NE. Effects of aldose reductase inhibition on responses of the corpus cavernosum and mesenteric vascular bed of diabetic rats. J Cardiovasc Pharmacol 2000; 35:606-13. [PMID: 10774792 DOI: 10.1097/00005344-200004000-00014] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
We examined the effects of 2 months of streptozotocin-induced diabetes mellitus in rats on relaxation and contraction of corpus cavernosum and the mesenteric vascular bed in vitro. A further diabetic group was treated from diabetes induction with 10 mg/kg/day of the aldose reductase inhibitor, WAY121509. For corpus cavernosum, maximal acetylcholine-induced relaxation was 35.5% reduced (p < 0.001) by diabetes, and this deficit was completely prevented by WAY121509 treatment. Neither diabetes nor treatment affected contractile responses to field stimulation of noradrenergic nerves; however, nonadrenergic noncholinergic nerve relaxation responses were 32.9% decreased by diabetes and WAY 121509 attenuated this by 84% (p < 0.001). For the mesenteric vascular bed, diabetes depressed maximal endothelium-dependent vasodilation to acetylcholine by 25.2% (p < 0.001), and this was partially (50.6%; p < 0.01) prevented by WAY121509. Nitric oxide synthase blockade revealed endothelium-derived hyperpolarising factor-mediated vasodilation to acetylcholine that was 73.5% (p < 0.001) depressed by diabetes; WAY121509 provided partial (43.4%; p < 0.001) protection. Neither diabetes nor treatment affected endothelium-independent vasorelaxation to the nitric oxide donor, sodium nitroprusside, in corpus cavernosum or mesenteric vessels. Thus the data show protective effects of WAY121509 on nitric oxide-mediated cavernosal vasorelaxation responses and on mesenteric endothelium-derived hyperpolarising factor responses. Together these findings could account for the beneficial effects of aldose reductase inhibition on diabetic complications in experimental models.
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Affiliation(s)
- A Keegan
- Department of Biomedical Sciences, University of Aberdeen, Scotland
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60
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Abstract
The balance of penile smooth muscle tone is finely controlled, with contractile factors acting in opposition to relaxant factors. The principal agents in this process are undoubtedly noradrenaline and nitric oxide. Prostaglandins probably have a crucial role in the 'fine tuning' of corporal smooth muscle tone. Their effects on control mechanisms in the healthy penis are more likely to be modulatory rather than direct.
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Affiliation(s)
- S Minhas
- Pyrah Department of Urology, St James's University Hospital, Leeds, UK
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61
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62
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Lash JM, Nase GP, Bohlen HG. Acute hyperglycemia depresses arteriolar NO formation in skeletal muscle. THE AMERICAN JOURNAL OF PHYSIOLOGY 1999; 277:H1513-20. [PMID: 10516190 DOI: 10.1152/ajpheart.1999.277.4.h1513] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In the rat intestinal and cerebral microvasculatures, acute D-glucose hyperglycemia suppresses endothelium-dependent dilation to ACh without affecting endothelium-independent dilation to nitroprusside. This study determined whether acute hyperglycemia suppressed arteriolar wall nitric oxide concentration ([NO]) at rest or during ACh stimulation and inhibited nitroprusside-, ACh- or contraction-induced dilation of rat spinotrapezius arterioles. Vascular responses were measured before and after 1 h of topical 300 mg/100 ml D-glucose; arteriolar [NO] was measured with NO-sensitive microelectrodes. Arteriolar dilation to ACh was not significantly altered after superfusion of 300 mg/100 ml D-glucose. However, after hyperglycemia, arteriolar [NO] was not increased by ACh, compared with a 300 nM increase attained during normoglycemia. Arteriolar dilation to submaximal nitroprusside and muscle contractions was enhanced by hyperglycemia. These results indicated that in the rat spinotrapezius muscle, acute hyperglycemia suppressed arteriolar NO production while simultaneously augmenting vascular smooth muscle responsiveness to nitroprusside, presumably through cGMP-mediated mechanisms. In effect, this may have allowed ACh- and muscle contraction-induced vasodilation to be maintained during hyperglycemia despite an impaired NO system.
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Affiliation(s)
- J M Lash
- Department of Physiology, Indiana University School of Medicine, Indianapolis, Indiana 46202, USA
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63
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Terata K, Coppey LJ, Davidson EP, Dunlap JA, Gutterman DD, Yorek MA. Acetylcholine-induced arteriolar dilation is reduced in streptozotocin-induced diabetic rats with motor nerve dysfunction. Br J Pharmacol 1999; 128:837-43. [PMID: 10516670 PMCID: PMC1571695 DOI: 10.1038/sj.bjp.0702856] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
1. Diabetes mellitus produces marked abnormalities in motor nerve conduction, but the mechanism is not clear. In the present study we hypothesized that in the streptozotocin (STZ)-induced diabetic rat impaired vasodilator function is associated with reduced endoneural blood flow (EBF) which may contribute to nerve dysfunction. 2. We examined whether diabetes-induced reductions in sciatic nerve conduction velocity and EBF were associated with impaired endothelium-dependent dilation in adjacent arterioles. We measured motor nerve conduction velocity (MNCV) in the sciatic nerve using a non-invasive procedure, and sciatic nerve nutritive blood flow using microelectrode polarography and hydrogen clearance. In vitro videomicroscopy was used to quantify arteriolar diameter responses to dilator agonists in arterioles overlying the sciatic nerve. 3. MNCV and EBF in 4-week-STZ-induced diabetic rats were decreased by 22% and 49% respectively. Arterioles were constricted with U46619 and dilation to acetylcholine (ACh), aprikalim, or sodium nitroprusside (SNP) examined. All agonists elicited dose-dependent dilation in control and diabetic rats, although ACh-induced dilation was significantly reduced in diabetic rats. Treating vessels from normal or diabetic rats with indomethacin (INDO) alone did not significantly affect ACh-induced relaxation. However, ACh-induced vasodilation was significantly reduced by treatment with KCl or Nomega-nitro-L-arginine (LNNA) alone. Combining LNNA and KCl further reduced ACh-induced dilation in these vessels. 4. Diabetes causes vasodilator dysfunction in a microvascular bed that provides circulation to the sciatic nerve. These studies imply that ACh-induced dilation in these vessels is mediated by multiple mechanisms that may include the endothelial-dependent production of nitric oxide and endothelial-derived hyperpolarizing factor. This impaired vascular response is associated with neural dysfunction.
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Affiliation(s)
- K Terata
- Veterans Affairs Medical Center, Diabetes Endocrinology Research Center and Department of Internal Medicine, University of Iowa, Iowa City, Indiana, IA, 52246, U.S.A
| | - L J Coppey
- Veterans Affairs Medical Center, Diabetes Endocrinology Research Center and Department of Internal Medicine, University of Iowa, Iowa City, Indiana, IA, 52246, U.S.A
| | - E P Davidson
- Veterans Affairs Medical Center, Diabetes Endocrinology Research Center and Department of Internal Medicine, University of Iowa, Iowa City, Indiana, IA, 52246, U.S.A
| | - J A Dunlap
- Veterans Affairs Medical Center, Diabetes Endocrinology Research Center and Department of Internal Medicine, University of Iowa, Iowa City, Indiana, IA, 52246, U.S.A
| | - D D Gutterman
- Veterans Affairs Medical Center, Diabetes Endocrinology Research Center and Department of Internal Medicine, University of Iowa, Iowa City, Indiana, IA, 52246, U.S.A
| | - M A Yorek
- Veterans Affairs Medical Center, Diabetes Endocrinology Research Center and Department of Internal Medicine, University of Iowa, Iowa City, Indiana, IA, 52246, U.S.A
- Author for correspondence:
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64
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Abstract
Reactive oxygen species (ROS) are elevated by metabolic changes in diabetes, including autoxidation and increased advanced glycation. Endogenous protection by the glutathione redox cycle is also compromised by the competing NADPH requirement of elevated polyol pathway flux. Antioxidant treatment strategies prevent or reverse nerve conduction velocity (NCV) deficits in diabetic rats. These include lipophilic scavengers such as butylated hydroxytoluene, probucol and vitamin E, more hydrophilic agents like alpha-lipoic acid and acetyl cysteine, and transition metal chelators that inhibit autoxidation. In the long-term, elevated ROS cause cumulative damage to neurons and Schwann cells, however, they also have a deleterious effect on nerve blood flow in the short term. This causes endoneurial hypoxia, which is responsible for early NCV deficits. Antioxidant treatment corrects the blood flow deficit and promotes normal endoneurial oxygenation. ROS cause antioxidant-preventable vascular endothelium abnormalities, neutralizing nitric oxide mediated vasodilation and increasing reactivity to vasoconstrictors. Unsaturated fatty acids are a major target for ROS and essential fatty acid metabolism is impaired by diabetes. Gamma-linolenic acid stimulates vasodilator prostanoid production, and there are marked synergistic interactions between gamma-linolenic acid and antioxidants. This has encouraged the development of novel drugs such as ascorbyl-gamma-linolenic acid and gamma-linolenic acid-lipoic acid with enhanced therapeutic potential.
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Affiliation(s)
- N E Cameron
- Department of Biomedical Sciences, University of Aberdeen, Scotland, UK.
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65
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Keegan A, Cotter MA, Cameron NE. Effects of chelator treatment on aorta and corpus cavernosum from diabetic rats. Free Radic Biol Med 1999; 27:536-43. [PMID: 10490273 DOI: 10.1016/s0891-5849(99)00125-2] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Transition-metal catalyzed reactions contribute to oxidative stress, which has been implicated in the pathogenesis of diabetic complications. The aim was to evaluate the effects of treatment with the transition metal chelator trientine on endothelium-dependent relaxation of aorta and corpus cavernosum from streptozotocin-induced diabetes of 8 weeks duration in rats. Effects on cavernosum autonomic innervation were also examined. Diabetes caused a 30.1 +/- 3.8% reduction in maximum aorta endothelium-dependent relaxation to acetylcholine (ACh), which was markedly attenuated (72.7 +/- 10.6%) by trientine treatment. Reversal treatment (4 weeks untreated diabetes, 4 weeks trientine) did not effect endothelium-dependent relaxation compared with aortas from rats with 4 weeks of diabetes, however, there was a 22.5 +/- 6.2% improvement compared with 8 weeks of diabetes. Eight weeks of diabetes caused a 41.5 +/- 6.6% reduction in corpus cavernosum endothelium-dependent maximum relaxation to ACh that was 70.1 +/- 16.9% prevented by trientine. Cavernosum nonadrenergic, noncholinergic (NANC) nerve stimulation caused frequency-dependent relaxation to a maximum of 40.9 +/- 2.4%, which was reduced by diabetes to 24.2 +/- 2.1%. Trientine partially prevented this deficit, maximum relaxation being 31.9 +/- 2.3%. Thus, metal chelator treatment has beneficial effects on aorta and cavernosum endothelium-dependent relaxation and on cavernosum NANC innervation.
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Affiliation(s)
- A Keegan
- Department of Biomedical Sciences, University of Aberdeen, Foresterhill, Scotland, United Kingdom
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66
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García VM, Ochoa JE, Elías MM. Effect of early stage of experimental diabetes on vascular functions in isolated perfused kidneys. JOURNAL OF AUTONOMIC PHARMACOLOGY 1999; 19:97-103. [PMID: 10466942 DOI: 10.1046/j.1365-2680.1999.00122.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The present study investigates the renal vascular responsiveness to vasoactive agents in diabetic rats which present an early stage of renal failure. Adult male Wistar rats were administered alloxan (150 mg kg(-1), s.c.). Seven days later the right kidneys were isolated and perfused. Renal perfusion pressure was measured continuously. Concentration-response curves were plotted for noradrenaline (NA), sodium nitroprusside (SNP) and carbachol. In basal conditions, kidneys from diabetic rats presented a decreased vascular resistance compared with those from control rats. The vasoconstrictor response to NA showed decreased EC50 values in preparations from diabetic rats compared with control ones (EC50 nmols, control: 2.03 +/- 0.44, n = 8; diabetic: 0.84+/-0.18, n = 6, P < 0.05). This enhanced sensitivity to NA could be in line with the decreased glomerular filtration rate and cortical renal plasma flow previously described in vivo in our laboratory (Garcia, Girardi, Ochoa, Torres & Elias, 1998). Vasoconstrictor responses to phenylephrine were not however, different between diabetic and control rat kidneys. This suggests that the increased sensitivity to NA was due to impaired neuronal uptake since phenylephrine is not a substrate for neuronal uptake. After precontraction with phenylephrine, both endothelium-dependent (carbachol) and endothelium independent (SNP) vasodilator agents caused similar response in the preparations taken from the two groups of animals. So, the enhanced sensitivity to NA is not associated with a deficient dilator responsiveness of the renal vasculature. The vasodilator response to carbachol was the same in absence or presence of L-arginine in the perfusate, suggesting no alteration in its availability at this stage of diabetes. Diabetic animals showed increased plasma level of fructosamine and glycosylated haemoglobin (Hb A1c), indicating the presence of early glycated products at this stage of diabetes, which could be involved in a possible structural alteration of the vessels.
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Affiliation(s)
- V M García
- Farmacología. Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, República Argentina
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67
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Renaudin C, Michoud E, Lagarde M, Wiernsperger N. Impaired microvascular responses to acute hyperglycemia in type I diabetic rats. J Diabetes Complications 1999; 13:39-44. [PMID: 10232708 DOI: 10.1016/s1056-8727(98)00018-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Abnormal reactivity of resistance vasculature may induce long-term alterations in regional hemodynamics, contributing to the pathogenesis of diabetic microangiopathy. The purpose of this study was to examine the responses of microvessels to a hyperglycemic episode aimed at mimicking a physiological stimulus such as the postprandial state. This study is the first to report the direct, in situ, visualization of this situation by intravital microscopy in the skeletal muscle of diabetic rat and is particularly interesting as it applies to an iterative, physiological stimulus. The study was conducted in 5-month-old rats, either nondiabetic (ND) or rendered diabetic (D) for 12 weeks (streptozotocin, 60 mg/kg, i.v.). Intravital microscopy was used to examine diameter and vasomotion changes in precapillary arterioles (< 20 microm) in the spinotrapezius muscle of fasted, anesthetized rats, before and up to 60 min after infusion of glucose or isotonic saline. After intravenous glucose infusion, a precapillary arteriolar vasoconstriction associated with an increase in the number of arterioles presenting vasomotion were seen in ND rats. In contrast, no modification in either parameter was observed in D rats. Our results indicate that, microvessels react to acute changes in the metabolic environment such as induced by elevation of plasma glucose. There was a complete loss of reactivity (vasoconstriction and vasomotion) of precapillary arterioles to superimposed hyperglycemia in D rats. According to the "hemodynamic hypothesis", this impaired vasoconstriction could result in hyperperfusion of microvessels and subsequent microvascular damages which might contribute to the development of diabetic microangiopathy.
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Affiliation(s)
- C Renaudin
- Diabetic Microangiopathy Research Unit, Lipha-INSERM U 352, Villeurbanne, France
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68
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Patel JM, Martens JR, Li YD, Gelband CH, Raizada MK, Block ER. Angiotensin IV receptor-mediated activation of lung endothelial NOS is associated with vasorelaxation. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 275:L1061-8. [PMID: 9843842 DOI: 10.1152/ajplung.1998.275.6.l1061] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The hexapeptide angiotensin (ANG) IV, a metabolic product of ANG II, has been reported to play a functional role in the regulation of blood flow in extrapulmonary tissues. Here, we demonstrate that ANG IV-specific (AT4) receptors are present in porcine pulmonary arterial endothelial cells (PAECs) and that the binding of ANG IV to AT4 receptors can be blocked by its antagonist divalinal ANG IV but not by the ANG II-, AT1-, and AT2-receptor blockers [Sar1,Ile8]ANG II, losartan, and PD-123177, respectively. ANG IV significantly increased endothelial cell constitutive nitric oxide synthase (ecNOS) activity (P < 0.05) as well as cellular cGMP content (P < 0. 001). Western blot analysis revealed that ecNOS protein expression was comparable in control and ANG IV-stimulated cells. Divalinal ANG IV but not [Sar1,Ile8]ANG II, losartan, or PD-123177 inhibited the ANG II- and ANG IV-stimulated increases in ecNOS activity and cGMP content in PAECs. Incubation in the presence of N-nitro-L-arginine methyl ester (L-NAME) or methylene blue but not of indomethacin significantly diminished ANG IV-stimulated as well as basal levels of cGMP (P < 0.001). Similarly, in situ studies with precontracted porcine pulmonary arterial rings showed that ANG IV caused an endothelium-dependent relaxation that was blocked by L-NAME or methylene blue. Collectively, these results demonstrate that ANG IV binds to AT4 receptors, activates ecNOS by posttranscriptional modulation, stimulates cGMP accumulation in PAECs, and causes pulmonary arterial vasodilation, suggesting that ANG IV plays a role in the regulation of blood flow in the pulmonary circulation.
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Affiliation(s)
- J M Patel
- Research Service, Department of Veterans Affairs Medical Center, University of Florida College of Medicine, Gainesville, Florida 32608-1611, USA
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69
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Johnston GD. Ulster says 'NO'; explosion, resistance and tolerance. Nitric oxide and the actions of organic nitrates. THE ULSTER MEDICAL JOURNAL 1998; 67:79-90. [PMID: 9885543 PMCID: PMC2448994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Affiliation(s)
- G D Johnston
- Department of Therapeutics and Pharmacology, Queens's University of Belfast
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70
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Brands MW, Fitzgerald SM. Acute endothelium-mediated vasodilation is not impaired at the onset of diabetes. Hypertension 1998; 32:541-7. [PMID: 9740623 DOI: 10.1161/01.hyp.32.3.541] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Vascular injury and impaired vascular function are central to the increased mortality associated with diabetes. Hyperglycemia in diabetes has been suggested to play a role in this process, in part by impairing the function of the vascular endothelium. It has been difficult, however, to isolate the direct effect of glucose in both humans and in animal models of diabetes. This was evaluated in the present study in 7 rats that were chronically instrumented with a Transonic flow probe at the iliac bifurcation of the abdominal aorta, a nonoccluding catheter inserted immediately anterior to the flow probe, and a femoral vein catheter. Acute infusions of acetylcholine and sodium nitroprusside (1 and 10 microg/min IA) increased hindquarter blood flow significantly by approximately 27 and 10 mL/min over baseline, respectively, at the high dose. Streptozotocin (70 mg/kg IV) was administered, but normoglycemia was maintained with continuous intravenous insulin infusion to control for potential streptozotocin side effects. Diabetes was induced 5 to 7 days later by stopping the insulin infusion. Hindlimb blood flow (measured 24 hours per day) decreased during the diabetic period and was accompanied by an increase in mean arterial pressure, suggesting a vasoconstrictor response. However, the responses to acetylcholine and sodium nitroprusside were not altered significantly on either day 2 or day 6 of the diabetic period. This suggests that neither endothelium-mediated vasorelaxation nor responsiveness to nitric oxide is impaired during the initial phase of diabetes and that diabetic hyperglycemia does not have a significant, direct effect to impair endothelium-mediated relaxation in insulin-dependent diabetes mellitus. The mechanism for the change in baseline blood flow and its potential influence on endothelial function, however, are not known.
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Affiliation(s)
- M W Brands
- From the Department of Physiology and Biophysics, University of Mississippi Medical Center, Jackson, MS 39216, USA.
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71
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Altan N, Buğdayci G, Tutkun FK, Sancak B, Nazaroğlu NK. The effect of the sulfonylurea glyburide on nitric oxide in streptozotocin-induced diabetic rat. GENERAL PHARMACOLOGY 1998; 31:319-21. [PMID: 9688480 DOI: 10.1016/s0306-3623(97)00430-8] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
1. The interaction between nitric oxide (NO) and superoxide anions has received a great deal of attention. Because NO is rapidly inactivated by superoxide anions, it has been suggested that an enhanced formation of this radical may be involved in the accelerated breakdown of NO. 2. In the present study, we administrated glyburide (glibenclamide) to Streptozotocin-induced diabetic rats and determined the effect of such treatment on serum nitrite+nitrate levels. Serum nitrite+nitrate levels were reduced in diabetic animals (P<0.001). Administration of glyburide to diabetic rats reversed the diabetes-induced changes, suggesting that glyburide may directly increase serum nitrite+nitrate levels.
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Affiliation(s)
- N Altan
- Department of Biochemistry, Faculty of Medicine, University of Gazi, Ankara, Turkey
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72
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Pieper GM. Review of alterations in endothelial nitric oxide production in diabetes: protective role of arginine on endothelial dysfunction. Hypertension 1998; 31:1047-60. [PMID: 9576113 DOI: 10.1161/01.hyp.31.5.1047] [Citation(s) in RCA: 267] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- G M Pieper
- Department of Transplant Surgery, Medical College of Wisconsin, Froedtert Memorial Hospital, Milwaukee 53226, USA.
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73
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Wang HD, Pagano PJ, Du Y, Cayatte AJ, Quinn MT, Brecher P, Cohen RA. Superoxide anion from the adventitia of the rat thoracic aorta inactivates nitric oxide. Circ Res 1998; 82:810-8. [PMID: 9562441 DOI: 10.1161/01.res.82.7.810] [Citation(s) in RCA: 266] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The purpose of this study was to determine whether superoxide anion is produced endogenously in the rat aortic adventitia and whether sufficient superoxide anion is produced to interfere with the response of the rat aorta to nitric oxide. Relaxation was measured in rings of the rat thoracic aorta, which were oriented so that the adventitial or luminal surface could be preferentially exposed to nitric oxide or sodium nitroprusside. To accomplish this, the rings were mounted (1) with the adventitia facing outward, (2) with the adventitia facing inward after inverting, or (3) with the adventitia facing outward after inverting twice (to control for the inverting procedure). The relaxation to nitric oxide, but not to sodium nitroprusside, was less in rings with the adventitia facing outward compared with those in which it faced inward. In contrast, the response to nitric oxide via either surface was similar when extracellular superoxide anion was scavenged with superoxide dismutase. Incubation of rings with nitro blue tetrazolium (NBT) resulted in blue formazan staining of the adventitia, and lucigenin chemiluminescence was significantly greater when detected from the adventitial compared with the intimal aspect of the artery. The reduction of NBT in intact aortic rings was 30+/-2 pmol x min(-1) x mg(-1) and was significantly decreased by superoxide dismutase to 19+/-2 pmol x min(-1) x mg(-1) and by a synthetic superoxide dismutase mimic, Euk-8, to 11+/-2 pmol x min(-1) x mg(-1). The NADPH oxidase inhibitor, diphenyleneiodonium, decreased NBT reduction to 9+/-1 pmol x min(-1) x mg(-1), whereas inhibitors of xanthine oxidase, mitochondrial oxidases, and nitric oxide synthase were ineffective. Immunohistochemical staining indicated the localization of NADPH oxidase proteins gp91phox, p22phox, p47phox, and p67phox almost exclusively in the adventitia of the rat aorta with no substantial staining in the media. These results indicate that NADPH oxidase located in the adventitia of rat thoracic aorta generates sufficient extracellular superoxide anion to constitute a barrier capable of inactivating nitric oxide. This study suggests that adventitial superoxide anion can play a role in the pathophysiology of the arterial wall.
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Affiliation(s)
- H D Wang
- Robert Dawson Evans Department of Clinical Research, Boston University School of Medicine, Mass 02118, USA
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74
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Zharikov SI, Block ER. Characterization of L-arginine uptake by plasma membrane vesicles isolated from cultured pulmonary artery endothelial cells. BIOCHIMICA ET BIOPHYSICA ACTA 1998; 1369:173-83. [PMID: 9528685 DOI: 10.1016/s0005-2736(97)00191-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
We investigated the mechanisms of [3H]-L-arginine transport via System Y+ using plasma membrane vesicles derived from cultured pulmonary artery endothelial cells. [3H]-L-arginine uptake into plasma membrane vesicles was Na-independent, sensitive to trans-stimulation, unaffected by proton-conducting ionophores, and selectively inhibited by cationic amino acids. Kinetic experiments performed over a wide range of substrate concentrations revealed only one population of L-arginine transporters with Km = 130 microM. To elucidate the driving force for L-arginine transport, we measured [3H]-L-arginine uptake by plasma membrane vesicles at different transmembrane ion gradients. Plasma membrane vesicles accumulated [3H]-L-arginine only when a membrane potential was imposed across the vesicles, and the velocity of uptake was linearly related to the magnitude of the created membrane potential. The presence of potassium ions inside the vesicles was not essential for uptake of L-arginine into vesicles, but it was essential for trans-stimulation of L-arginine transport. [3H]-L-arginine accumulated in plasma membrane vesicles can be released by agents that dissipate transmembrane potassium gradients (e.g. saponin, gramicidin, and nigericin). Diazoxide and pinacidil, activators of K(+)-channels, had no significant effect on [3H]-L-arginine uptake, whereas tetraethylammonium chloride, 4-aminopyridine, and glibenclamide, inhibitors of K(+)-channels, caused decreases in [3H]-L-arginine transport by plasma membrane vesicles. This study demonstrates for the first time a specific role for potassium ions in the mechanism of L-arginine transport, particularly in the phenomenon of trans-stimulation.
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Affiliation(s)
- S I Zharikov
- Research Service, VA Medical Center, Gainesville, FL, USA
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75
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Pieper GM, Adams MB, Roza AM. Pancreatic transplantation reverses endothelial dysfunction in experimental diabetes mellitus. Surgery 1998. [DOI: 10.1016/s0039-6060(98)70233-8] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
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76
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McDonald KK, Zharikov S, Block ER, Kilberg MS. A caveolar complex between the cationic amino acid transporter 1 and endothelial nitric-oxide synthase may explain the "arginine paradox". J Biol Chem 1997; 272:31213-6. [PMID: 9395443 DOI: 10.1074/jbc.272.50.31213] [Citation(s) in RCA: 347] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Immunohistochemistry of porcine pulmonary artery endothelial cells (PAEC) with antibodies specific for caveolin, endothelial nitric-oxide synthase (eNOS), and the arginine transporter (CAT1) demonstrates that all of these proteins co-localize in plasma membrane caveolae. When incubated with solubilized PAEC plasma membrane proteins, eNOS-specific antibody immunoprecipitates CAT1-mediated arginine transport. These results document the existence of a caveolar complex between CAT1 and eNOS in PAEC that provides a mechanism for the directed delivery of substrate arginine to eNOS. Direct transfer of extracellular arginine to membrane-bound eNOS accounts for the "arginine paradox" and explains why caveolar localization of eNOS is required for optimal nitric oxide production by endothelial cells.
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Affiliation(s)
- K K McDonald
- Department of Biochemistry and Molecular Biology and the Center for Structural Biology, University of Florida College of Medicine, Gainesville, Florida 32610-0245, USA
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77
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Cipolla MJ, Porter JM, Osol G. High glucose concentrations dilate cerebral arteries and diminish myogenic tone through an endothelial mechanism. Stroke 1997; 28:405-10; discussion 410-1. [PMID: 9040698 DOI: 10.1161/01.str.28.2.405] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
BACKGROUND AND PURPOSE Diabetes is associated with cerebrovascular disease and impaired autoregulation of cerebral blood flow. The purpose of this study was to determine the effect of acute glucose exposure on basal tone and myogenic reactivity of isolated rat cerebral arteries. METHODS Posterior cerebral arteries (PCAs, n = 38) were dissected from male Wistar rats and mounted on glass cannulas in a system that allowed control of transmural pressure (TMP) and measurement of lumen diameter. Arteries were exposed to various concentrations of glucose, and the amount of basal tone and reactivity to TMP was measured. The effect of elevated glucose on cerebral endothelial modulation of basal tone was determined by mechanical denudation and the use of inhibitors of both nitric oxide and prostaglandin synthesis. RESULTS Arteries exposed to 44 versus 5.5 mmol/L glucose developed significantly less intrinsic tone (percent tone, 2 +/- 1% versus 28 +/- 2%; P < .01) and responded passively to increases in TMP. Preexisting tone present in 5.5 mmol/L glucose was eliminated on exposure to 44 mmol/L glucose, which decreased tone from 30 +/- 5% to 5 +/- 4% (P < .01). Glucose-induced dilations were concentration dependent such that half-maximal responses were obtained at 25 +/- 2 mmol/L. Endothelial removal abolished this effect, and the amount of tone was similar in 5.5 versus 44 mmol/L glucose (percent tone, 46 +/- 6% versus 49 +/- 5%; P > .05), as did inhibition of nitric oxide production with 0.3 mmol/L nitro-L-arginine (percent tone, 52 +/- 4% versus 46 +/- 3%; P > .05); however, blockade of the cyclooxygenase pathway with indomethacin (10(-5) mmol/L) only partially inhibited the dilation to glucose (percent tone, 32 +/- 3% in 5.5 mmol/L versus 12.4 +/- 3% in 44 mmol/L; P < .01). CONCLUSIONS Acute glucose exposure dilates arteries with intrinsic tone and impairs cerebrovascular reactivity to TMP via an endothelium-mediated mechanism that involves nitric oxide and prostaglandins.
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Affiliation(s)
- M J Cipolla
- Department of Surgery, Oregon Health Sciences University, Portland.
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78
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Pieper GM. Divergent actions of chronic insulin treatment in vivo versus acute treatment ex vivo on diabetic-induced endothelial dysfunction. Life Sci 1997; 60:PL371-6. [PMID: 9194692 DOI: 10.1016/s0024-3205(97)00292-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Streptozotocin-induced diabetes is associated with hyperglycemia and hypoinsulinemia. The role of insulin in diabetes-induced endothelial dysfunction is unknown. In the present study, we evaluated the effect of chronic insulin treatment in vivo versus acute insulin administration ex vivo on endothelium-dependent relaxation in aortic rings of the streptozotocin-induced diabetic rat. Relaxation to acetylcholine (but not A23187) was impaired in diabetic compared to control rings. This defect was prevented by chronic insulin treatment but was not reversed by acute insulin administration ex vivo. Thus, endothelial dysfunction in the streptozotocin-induced diabetic rat is specific for the chronic diabetic state and not to vascular toxicity of streptozotocin. Nevertheless, it is apparent that insulin at a physiological concentration does not cause an acute direct effect on facilitating endothelium-dependent relaxation in diabetic blood vessels.
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Affiliation(s)
- G M Pieper
- Department of Transplant Surgery, The Medical College of Wisconsin, Milwaukee 53226, U.S.A
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79
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Lindsay RM, Peet RS, Wilkie GS, Rossiter SP, Smith W, Baird JD, Williams BC. In vivo and in vitro evidence of altered nitric oxide metabolism in the spontaneously diabetic, insulin-dependent BB/Edinburgh rat. Br J Pharmacol 1996; 120:1-6. [PMID: 9117082 PMCID: PMC1564340 DOI: 10.1038/sj.bjp.0700862] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
1. Altered vasoreactivity may contribute significantly to the pathogenesis of diabetic vascular complications. This study investigated the effect of (a) insulin-related diabetes, and (b) chronic in vivo administration of N(omega)-nitro-L-arginine ester (L-NAME), a nitric oxide (NO) synthase inhibitor, on mean arterial pressure and in vitro vascular reactivity to noradrenaline in mesenteric arterial bed preparations from spontaneously diabetic, insulin-dependent and treated BB rats, the best animal model of insulin-dependent mellitus (IDDM) currently available. Four groups of animals from the Edinburgh colony (BB/E) of spontaneous diabetic BB rats were studied: age-matched (mean +/- s.e. mean = 156 +/- 2d) non-diabetic (glycated haemoglobin = 3.8 +/- 0.1%) and insulin-treated diabetic (glycated haemoglobin = 6.2 +/- 0.5%; duration of diabetes = 56 +/- 4 d) groups were either L-NAME treated (oral dose = 27 +/- 1 mg kg-1 d-1; duration of treatment from 30 until 153 days of age) or untreated. Although our diabetic BB/E rats do not achieve overall normoglycaemia, individual adjustment of the daily insulin dose administered to every diabetic rat achieves better glycaemic control than previous groups studying altered vascular reactivity and endothelial dysfunction in this animal model of diabetes. 2. Mean arterial pressure (measured directly via indwelling carotid arterial cannulae) was not significantly different between non-diabetic (116 +/- 3 mmHg; n = 10) and diabetic (122 +/- 2 mmHg; n = 12) BB/E rats. L-NAME treatment significantly (P < 0.001) increased mean arterial pressure in both groups (165 +/- 6 mmHg; n = 9 and 142 +/- 4 mmHg; n = 6 respectively) but the degree of hypertension observed in L-NAME-treated diabetic rats was significantly (P < 0.01) attenuated compared to non-diabetic rats treated with L-NAME. 3. Mesenteric arterial bed preparations were cannulated under anesthesia, excised and intralumenally perfused ex vivo with noradrenaline (0.2-20 microM). Basal perfusion pressures were not significantly different in mesentery preparations from non-diabetic (27.0 +/- 2.6 mmHg) and diabetic (27.1 +/- 3.2 mmHg) BB/E rats. There was no significant difference in maximal response above basal perfusion pressure (MAX) or pEC50, defined as the negative log of the agonist concentration required to give 50% of the maximal response above basal perfusion pressure, to noradrenaline in untreated non-diabetic (166 +/- 7 mmHg and 5.74 +/- 0.05 respectively) and diabetic (170 +/- 11 mmHg and 5.59 +/- 0.05) BB/E rats. 4. In vivo treatment of non-diabetic and diabetic BB/E rats with L-NAME had no significant effect on basal perfusion pressure (25.9 +/- 4.3 mmHg and 28.5 +/- 3.9 mmHg respectively). L-NAME treatment in vivo increased (P < 0.001) MAX to noradrenaline of non-diabetic rats (224 +/- 8 mmHg) but did not affect the value for diabetic rats (178 +/- 14 mmHg). L-NAME treatment did not alter after the pEC50 values in either group (5.71 +/- 0.05 and 5.65 +/- 0.05). 5. Consistent with previous studies using vascular preparations from spontaneously diabetic BB rats, mesentery preparations from diabetic BB/E rats (n = 12) exhibited a significantly reduced vasodilator response to acetylcholine (F value = 4.4, P < 0.05) across the concentration range studied compared to non-diabetic BB/E rats (n = 12) although there was no significant difference in maximal relaxation (diabetic 53.1 +/- 4.3% vs non-diabetic 55.7 +/- 5.5%) or pEC50, (diabetic 6.92 +/- 0.25 vs non-diabetic 7.49 +/- 0.22). There was no significant (F value = 0.8, P > 0.1) difference in the response to GTN between preparations from non-diabetic and diabetic rats (maximal relaxation: 49.6 +/- 3.7% vs 48.5 +/- 4.3%; pEC50: 7.84 +/- 0.12 vs 7.89 +/- 0.22 respectively). 6. In conclusion, vascular responsiveness to noradrenaline is not impaired in spontaneously diabetic BB/E rats with significantly better glycaemic control than those used in previous studies. However, following chronic L-NAME treatment, diabetic BB/E rats exhibit attenuated hypertension and an absence of enhanced vascular responsiveness to noradrenaline in vitro compared to similarly treated non-diabetic rats. These results, together with the significantly impaired endothelium-dependent vasodilatation and unchanged endothelium-independent vasodilatation in vitro of preparations from diabetic BB/E rats, are consistent with the hypothesis that functional changes in the synthesis and metabolism of NO (rather than altered vascular responsiveness to NO) occur in diabetes. Our results indicate that good glycaemic control alone is insufficient to prevent these abnormalities in NO availability and further studies to characterize the origin of these changes are necessary.
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Affiliation(s)
- R M Lindsay
- Metabolic Unit, Western General Hospitals NHS Trust, Edinburgh
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80
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Kamata K, Kobayashi T. Changes in superoxide dismutase mRNA expression by streptozotocin-induced diabetes. Br J Pharmacol 1996; 119:583-9. [PMID: 8894182 PMCID: PMC1915697 DOI: 10.1111/j.1476-5381.1996.tb15712.x] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
1. Experiments were designed to investigate the involvement of superoxide anions in the attenuated endothelium-dependent relaxation of the rat aorta from streptozotocin (STZ)-induced diabetic rats. 2. The endothelium-dependent relaxation responses to acetylcholine (ACh, 10(-7) M) in helical strips of the aorta precontracted with noradrenaline (NA, 5 x 10(-3) approximately 3 x 10(-7) M) were significantly decreased in STZ-induced diabetic rats. The recovery phase of the relaxation after single administration of ACh in the STZ-induced diabetic rats was more rapid than those in control vessels. 3. Preincubation of aortic strips with superoxide dismutase (SOD, 60 u ml-1) normalized the recovery phase of the relaxation of diabetic aorta after single administration of ACh, whereas catalase (150 u ml-1) or indomethacin (10(-5) M) had no effects on the relaxation. 4. SOD (180 u ml-1) caused relaxation in NA precontracted aortic strips and the degree of the SOD-induced relaxation was significantly greater in diabetic aorta as compared with age-matched control vessels. 5. When the changes in mRNA expressions of Mn-SOD or Cu-Zn-SOD were observed, Mn-SOD mRNA expression was markedly decreased, and Cu-Zn-SOD was slightly decreased in diabetic aorta. 6. These results suggest that the rapid destruction of NO by superoxide anions may occur in the STZ-induced diabetic rats, and this may be due to a decrease in mRNA expression of Mn-SOD or Cu-Zn-SOD.
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Affiliation(s)
- K Kamata
- Department of Physiology and Morphology, Hoshi University, Tokyo, Japan
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81
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Matsunaga T, Okumura K, Ishizaka H, Tsunoda R, Tayama S, Tabuchi T, Yasue H. Impairment of coronary blood flow regulation by endothelium-derived nitric oxide in dogs with alloxan-induced diabetes. J Cardiovasc Pharmacol 1996; 28:60-7. [PMID: 8797137 DOI: 10.1097/00005344-199607000-00010] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Diabetes mellitus is a major cause of ischemic coronary artery disease. Endothelial dysfunction is implicated in the pathogenesis of diabetic vascular disease. To examine coronary blood flow (CBF) regulation with endothelium-derived nitric oxide (EDNO) in the diabetic state, we compared the effects of both acetylcholine (ACh) and adenosine (Ado) on left circumflex coronary artery (LCX) blood flow in 12 vehicle-treated and 21 dogs made diabetic with alloxan anesthetized with pentobarbital. All dogs were pretreated with aspirin to inhibit endogenous prostaglandins. None of the hemodynamic parameters were significantly different in the two groups. The percent change in coronary vascular resistance (CVR) after ACh (100 ng/kg) infusion was significantly attenuated in diabetic dogs (-56.5 +/- 1.4%) as compared with vehicle-treated dogs (-64.5 +/- 1.2%) (p < 0.01), whereas the effect of Ado (1 microgram/kg) was not different between the two groups (-71.1 +/- 1.5% in vehicle, -67.0 +/- 1.3% in diabetes). After infusion of incremental doses of NG-nitro-L-arginine methyl ester (L-NAME) 10(-5)-10(-3)M, the effect of ACh was progressively inhibited in both groups and was different no longer between the two groups after the maximal dose. L-Arginine (L-ARG), but not D-ARG, significantly restored the effect of ACh in diabetic dogs but did not affect vehicle-treated dogs. The effect of Ado did not change after L- and D-ARG administration. Cu, Zn-superoxide dismutase (Cu, Zn-SOD) had no effect on any of the effects of ACh and Ado in diabetic dogs. Regulation of CBF with EDNO is impaired in dogs with alloxan-induced diabetes, and this impairment is partially restored by L-ARG.
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Affiliation(s)
- T Matsunaga
- Division of Cardiology, Kumamoto University School of Medicine, Japan
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82
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Turner NC, White P. Effects of streptozotocin-induced diabetes on vascular reactivity in genetically hyperinsulinaemic obese Zucker rats. J Cardiovasc Pharmacol 1996; 27:884-90. [PMID: 8761857 DOI: 10.1097/00005344-199606000-00017] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Although the fa/fa Zucker rat shows many of the features of type II diabetes, the absence of consistent cardiovascular complications in this model may be due to the absence of significant hyperglycaemia. We studied the consequences of streptozotocin (STZ)-induced insulin deficiency and hyperglycaemia on vascular reactivity in the fa/fa Zucker rat. Hyperinsulinaemic obese Zucker rats were rendered diabetic by injection of STZ (50-60 mg/kg intraperitoneally, i.p.), and vascular tissue was removed for study 10-12 weeks later. In isolated aorta, there was no difference in the phenylephrine (PE) concentration-response relation between lean and obese control animals, but the concentration-response curve was shifted to the left in diabetic animals, (pD2 7.56 +/- 0.04 in STZ diabetic animals, n = 8; 7.4 +/- 0.04 in obese control, n = 9, p < 0.05). The maximum response was also enhanced in both aorta and perfused mesentery of STZ-treated animals. In contrast, the potency of serotonin (5-HT) in inducing contractions of isolated aorta were enhanced in tissues from obese as compared with lean animals (pD2 6.63 +/- 0.06, n = 9; 6.17 +/- 0.07, n = 7 respectively; p < 0.01) and was attenuated in animals with STZ-induced diabetes (pD2 6.31 +/- 0.09, n = 8, p = 0.05). The differential effects of hyperglycaemia on PE-and 5-HT-induced vasoconstriction suggest that the long-lasting modulation of vasoconstrictor responses induced by increases in blood glucose level may be specific for some agonists.
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Affiliation(s)
- N C Turner
- Department of Vascular Biology, SmithKline Beecham Pharmaceuticals, Frythe, Welwyn, Herts, England
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83
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Archibald V, Cotter MA, Keegan A, Cameron NE. Contraction and relaxation of aortas from diabetic rats: effects of chronic anti-oxidant and aminoguanidine treatments. NAUNYN-SCHMIEDEBERG'S ARCHIVES OF PHARMACOLOGY 1996; 353:584-91. [PMID: 8740154 DOI: 10.1007/bf00169180] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
We examined whether chronic treatment with the free radical scavengers butylated hydroxytoluene (1 g kg-1 day-1) and N-acetyl-L-cysteine (250 mg kg-1 day-1), or the inhibitor of advanced glycosylation reactions, aminoguanidine (1 g kg-1 day-1), could prevent the development of relaxation and contraction abnormalities in aorta from 2 month streptozotocin-diabetic rats. Diabetes caused a 24% deficit in maximal endothelium-dependent relaxation to acetylcholine for phenylephrine precontracted aortas (P < 0.01). This was unaffected by tissue-bath glucose concentration (5.5 or 40 mM), or by addition of 1 mM L-arginine. Butylated hydroxytoluene, N-acetyl-L-cysteine and aminoguanidine treatments gave substantial protection, maximum relaxation remaining in the non-diabetic range. Neither diabetes nor treatment affected endothelium-independent relaxation to glyceryl trinitrate. To test the suggestion that aminoguanidine could act as an inhibitor of constitutive nitric oxide synthase, acute aminoguanidine effects on endothelium-dependent relaxation to acetylcholine were also examined. No inhibition was noted. A modest increase in phenylephrine sensitivity with diabetes (P < 0.05) was unaffected by butylated hydroxytoluene or N-acetyl-L-cysteine, but partially prevented by aminoguanidine (P < 0.05). The data, therefore, provide evidence for the involvement of reactive oxygen species and the advanced glycosylation process particularly for impaired endothelium-dependent relaxation in experimental diabetes.
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Affiliation(s)
- V Archibald
- Department of Biomedical Sciences, University of Aberdeen, Marischal College, Scotland, UK
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84
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Way KJ, Reid JJ. Effect of diabetes and elevated glucose on nitric oxide-mediated neurotransmission in rat anococcygeus muscle. Br J Pharmacol 1995; 115:409-14. [PMID: 7582450 PMCID: PMC1908417 DOI: 10.1111/j.1476-5381.1995.tb16348.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
1. Nitric oxide (NO)-mediated neurotransmission is impaired in anococcygeus muscle from 8-week streptozotocin-induced diabetic rats. This study investigated the effects of insulin treatment, and the duration of diabetes on this impairment. In addition, the effect of in vitro exposure to elevated glucose has been investigated on NO-mediated relaxations, in muscles from untreated rats. 2. Relaxant responses to field stimulation (0.5-5 Hz, 10s train), sodium nitroprusside (SNP; 5 and 10 nM) and NO (1 and 3 microM) were significantly impaired in anococcygeus muscles from 8-week diabetic rats, compared to responses from control rats. Insulin treatment (5 u Lente day-1, s.c.) of diabetic rats prevented the development of this impairment. 3. Consistent with findings in 8-week diabetic rats, relaxation induced by field stimulation, SNP and NO were attenuated in tissues from 2-week and 4-week diabetic rats compared to corresponding control responses, whereas relaxations to papaverine (3 and 10 microM) were not reduced. In contrast, diabetes of 3-days duration did not affect relaxations to field stimulation, SNP or NO. 4. Incubation of anococcygeus muscles from untreated rats in medium containing elevated glucose (44.1 mM) for 6 h, significantly impaired relaxations to field stimulation compared to responses obtained after normal glucose (11.1 mM) incubation. Relaxations to SNP and to NO were not affected by 6 h exposure to elevated glucose. Similarly, incubation in hyperosmolar solutions containing mannose or sucrose for 6 h, impaired relaxations to field stimulation, but not to SNP or NO. 5. The results indicate that the diabetes-induced impairment of NO-mediated neurotransmission in the rat anococcygeus muscle develops between 3 days and 2 weeks after the induction of diabetes with streptozotocin. Prevention of the impairment by insulin treatment suggests that it is specific for the diabetic state. In addition, the impairment may be related to hyperglycaemia and the consequent rise in osmolarity, since in vitro exposure to high glucose as well as to other hyperosmolar media impaired NO-mediated relaxations to field stimulation.
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Affiliation(s)
- K J Way
- Department of Pharmacology, University of Melbourne, Parkville, Victoria, Australia
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