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PubMed2007

Chronic administration of genistein improves endothelial dysfunction in spontaneously hypertensive rats: involvement of eNOS, caveolin and calmodulin expression and NADPH oxidase activity.

The soya-derived phytoestrogen genistein has been suggested to be protective in cardiovascular diseases. In the present study, we have analysed whether chronic oral genistein might influence endothelial function in male SHRs (spontaneously hypertensive rats) via ERs (oestrogen receptors), changes in eNOS (endothelial NO synthase) activity and vascular O(2)(-) (superoxide) production. Rats (23-weeks old) were divided into the following groups: WKY (Wistar-Kyoto)-vehicle, SHR-vehicle, WKY-genistein (10 mg.kg(-1) of body weight.day(-1)); SHR-genistein; SHR-genistein-faslodex (ICI 182780; 2.5 mg.kg(-1) of body weight.day(-1)). Vascular expression of eNOS, caveolin-1 and calmodulin-1 were analysed by Western blotting, eNOS activity by conversion of [(3)H]arginine into L-[(3)H]citrulline and O(2)(-) production by chemoluminescence of lucigenin. In SHRs, after 5 weeks of treatment, genistein reduced systolic blood pressure and enhanced endothelium-dependent aortic relaxation to acetylcholine, but had no effect on the vasodilator responses to sodium nitroprusside. Compared with WKY rats, SHRs had up-regulated eNOS and down-regulated caveolin-1 and calmodulin-1 expression, increased NADPH-induced O(2)(-) production, but reduced eNOS activity. Genistein increased aortic calmodulin-1 protein abundance and eNOS activity, and reduced NADPH-induced O(2)(-) production in SHRs. The pure ERalpha and ERbeta antagonist faslodex did not modify any of the changes induced by genistein in SHRs, suggesting that these effects are unrelated to ER stimulation. In conclusion, genistein reduced the elevated blood pressure and endothelial dysfunction in SHRs. This latter effect appears to be related to increased eNOS activity associated with increased calmodulin-1 expression and decreased O(2)(-) generation.

Animals↗

PubMed1987

Pulmonary endothelial dysfunction induced by unilateral as compared to bilateral thoracic irradiation in rats.

Rats were sacrificed 2 months after a single dose of 10-30 Gy of 60Co gamma rays delivered to either a right unilateral or a bilateral thoracic port. Four indices of lung endothelial function were measured: the activities of angiotensin-converting enzyme (ACE) and plasminogen activator (PLA) and the production of prostacyclin (PGI2) and thromboxane (TXA2). The number of macrophages recovered by bronchoalveolar lavage (BAL) and the degree of right ventricular hypertrophy (an index of pulmonary hypertension) also were determined. Right lung ACE and PLA activity decreased linearly, and PGI2 and TXA2 production increased linearly with increasing radiation dose. The response curves for right unilateral and bilateral thoracic irradiation were not significantly different. In contrast, bilateral irradiation was more toxic than unilateral, since rats exposed to the former exhibited decreased body weight, an increased incidence of pleural effusions, an increase in the number of macrophages recovered by BAL, and right ventricular hypertrophy. These data demonstrate that pulmonary endothelial dysfunction induced by hemithorax irradiation represents a direct response of the endothelium to radiation injury and is not secondary to other phenomena such as shunting of function to the shielded lung.

Animals↗

PubMed2006

Impaired cerebral CO2 vasoreactivity: association with endothelial dysfunction.

Conflicting data exist on the role of nitric oxide (NO) in cerebral blood flow (CBF) autoregulation. Previous studies involving human and animal subjects seem to indicate that NO involvement is limited to the CO(2)-dependent mechanism (chemoregulation) and not to the pressure-dependent autoregulation (mechanoregulation). We tested this hypothesis in patients with impaired endothelial function compared with healthy controls. Blood pressure, heart rate, end-tidal Pco(2), CBF velocities (CBFV), forearm blood flow, and reactive hyperemia were assessed in 16 patients with diabetes mellitus and/or hypertension and compared with 12 age- and sex-matched healthy controls. Pressure-dependent autoregulation was determined by escalating doses of phenylephrine. CO(2) vasoreactivity index was extrapolated from individual slopes of mean CBFV during normocapnia, hyperventilation, and CO(2) inhalation. Measurements were repeated after sodium nitroprusside infusion. Indexes of endothelial function, maximal and area under the curve (AUC) of forearm blood flow (FBF) changes, were significantly impaired in patients (maximal flow: 488 +/- 75 vs. 297 +/- 31%; P = 0.01, AUC DeltaFBF: 173 +/- 17 vs. 127 +/- 11; P = 0.03). Patients and controls showed similar changes in cerebrovascular resistance during blood pressure challenges (identical slopes). CO(2) vasoreactivity was impaired in patients compared with controls: 1.19 +/- 0.1 vs. 1.54 +/- 0.1 cm.s(-1).mmHg(-1); P = 0.04. NO donor (sodium nitroprusside) offsets this disparity. These results suggest that patients with endothelial dysfunction have impaired CO(2) vasoreactivity and preserved pressure-dependent autoregulation. This supports our hypothesis that NO is involved in CO(2)-dependent CBF regulation alone. CBFV chemoregulation could therefore be a surrogate of local cerebral endothelial function.

Brain↗

PubMed2000

Does ADMA cause endothelial dysfunction?

Asymmetric dimethylarginine (ADMA) is an endogenous and competitive inhibitor of nitric oxide synthase. Plasma levels of this inhibitor are elevated in patients with atherosclerosis and in those with risk factors for atherosclerosis. In these patients, plasma ADMA levels are correlated with the severity of endothelial dysfunction and atherosclerosis. By inhibiting the production of nitric oxide, ADMA may impair blood flow, accelerate atherogenesis, and interfere with angiogenesis. ADMA may be a novel risk factor for vascular disease.

Amidohydrolases↗

PubMed2005

Consumption of trans fatty acids is related to plasma biomarkers of inflammation and endothelial dysfunction.

Trans fatty acid intake has been associated with a higher risk of cardiovascular disease. The relation is explained only partially by the adverse effect of these fatty acids on the lipid profile. We examined whether trans fatty acid intake could also affect biomarkers of inflammation and endothelial dysfunction including C-reactive protein (CRP), interleukin-6 (IL-6), soluble tumor necrosis factor receptor 2 (sTNFR-2), E-selectin, and soluble cell adhesion molecules (sICAM-1 and sVCAM-1). We conducted a cross-sectional study of 730 women from the Nurses' Health Study I cohort, aged 43-69 y, free of cardiovascular disease, cancer, and diabetes at time of blood draw (1989-1990). Dietary intake was assessed by a validated FFQ in 1986 and 1990. CRP levels were 73% higher among those in the highest quintile of trans fat intake, compared with the lowest quintile. IL-6 levels were 17% higher, sTNFR-2 5%, E-selectin 20%, sICAM-1 10%, and sVCAM-1 levels 10% higher. Trans fatty acid intake was positively related to plasma concentration of CRP (P = 0.009), sTNFR-2 (P = 0.002), E-selectin (P = 0.003), sICAM-1 (P = 0.007), and sVCAM-1 (P = 0.001) in linear regression models after controlling for age, BMI, physical activity, smoking status, alcohol consumption, intake of monounsaturated, polyunsaturated, and saturated fatty acids, and postmenopausal hormone therapy. In conclusion, this study suggests that higher intake of trans fatty acids could adversely affect endothelial function, which might partially explain why the positive relation between trans fat and cardiovascular risk is greater than one would predict based solely on its adverse effects on lipids.

Biomarkers↗

PubMed2002

Raloxifene improves endothelial dysfunction in hypertension by reduced oxidative stress and enhanced nitric oxide production.

BACKGROUND: It has not been completely clarified whether selective estrogen receptor modulators (SERMs) such as raloxifene exert vasoprotective effects similar to those of estrogens. METHODS AND RESULTS: To investigate vascular effects of raloxifene, male spontaneously hypertensive rats were treated for 10 weeks with either raloxifene (10 mg x kg(-1) x d(-1)) or vehicle. Raloxifene improved endothelium-dependent vasodilatation but had no effect on either endothelium-independent vasorelaxation or phenylephrine-induced vasoconstriction. Raloxifene treatment increased the release of NO from the vessel wall by enhanced expression and activity of endothelial NO synthase. Blood pressure reduction after bradykinin infusion was more pronounced in animals treated with SERMs. The production of superoxide in intact aortic segments was decreased by raloxifene treatment. Administration of raloxifene had no effect on the expression of the essential NAD(P)H oxidase subunits p22phox and nox1 in the vasculature but reduced the activity and expression of vascular membrane-bound rac1, a GTPase required for the activation of the NAD(P)H oxidase. Finally, blood pressure levels were significantly decreased in spontaneously hypertensive rats treated with raloxifene. All SERM effects were also detected in healthy age-matched Wistar rats. In cultured rat aortic vascular smooth muscle cells, raloxifene inhibited angiotensin II-induced reactive oxygen species production dependent on estrogen receptor activation. CONCLUSIONS: Raloxifene treatment improves hypertension-induced endothelial dysfunction by increased bioavailability of NO. This is achieved by an increased activity of endothelial NO synthase and by an estrogen receptor-dependent reduction in release of reactive oxygen species from vascular cells. These vascular effects cause a profound blood pressure reduction and lead to decreased vascular damage in male spontaneously hypertensive rats.

Animals↗

PubMedDate not supplied

Endothelial dysfunction in hypertension.

Endothelium can deeply influence vascular tone and structure. The main endothelium derived factor is nitric oxide, which is not only a potent vasodilator but also inhibits platelet aggregation, smooth muscle cell migration and proliferation, monocyte adhesion and adhesion molecule expression, thus protecting the vessel wall against the development of atherosclerosis and thrombosis. In human hypertension, endothelial dysfunction has been documented in peripheral and coronary macro and microcirculation and in renal circulation. Impaired endothelium-dependent vasodilation associated with essential hypertension seems to be a primary phenomenon, since it can be detected in the offspring of essential hypertensive patients, shows no clear correlation with blood pressure value, and is not normalized by the mere reduction of blood pressure. The phenomenon responsible for endothelial alteration in essential hypertensive patients seems to be the activation of an alternative pathway involving cyclooxygenase which reduces NO availability through production of oxidative stress. This alteration in the NO pathway could be the main mechanism through which a dysfunctional endothelium could be a promoter of atherosclerosis and thrombosis in essential hypertension.

Endothelium, Vascular↗

PubMed2005

[Endothelial dysfunction in patients with diabetes: identification, pathogenesis and treatment].

Cardiovascular diseases are the leading cause of morbidity and mortality in people with diabetes. Vascular abnormalities can be observed long before atherosclerosis develops and in sites not usually prone to atherosclerosis. These vascular abnormalities are known to be due to endothelial dysfunctions, one of the most frequent of which is depressed endothelium-dependent dilation. In patients with diabetes, this is mainly linked to decreased bioavailability of nitric oxide. Although inactivation of tetrahydrobiopterin, a co-factor of NO-synthase, may depress nitric oxide production, the latter is more likely due to the inactivation of nitric oxide by superoxide anions: enhanced oxidative stress increases their production in people with diabetes. Moreover, hyperglycemia directly activates oxidative stress, which in turn depresses endothelium-dependent vasodilation. Glycemia and oxidative stress are positively correlated in people with diabetes. However, while depression of endothelium-dependent dilation may be a visible functional manifestation of oxidative stress, the oxidative stress itself is mainly responsible for the cascade of endothelial events that play a key role in development of vascular atherosclerosis and its complications. Especially important among these events are the activation of NF-kappaB and the oxidation of LDL-cholesterol. Although antioxidants provide short-term improvement of endothelial function in humans, all studies of the effectiveness of preventive antioxidant therapy have been disappointing. Control of hyperglycemia thus remains the best way to improve endothelial function and to prevent atherosclerosis and other cardiovascular complications of diabetes.

Antioxidants↗

PubMed2006

Androgen deficiency and endothelial dysfunction in men with end-stage kidney disease receiving maintenance hemodialysis.

OBJECTIVES AND METHODS: Two thirds of men with end-stage kidney disease (ESKD) have serum testosterone levels in the hypogonadal range. We examined if low serum testosterone levels were correlated with measures of endothelial dysfunction in ESKD. Bilateral common carotid artery (CCA) intima-media thickness (IMT) and atherosclerotic plaque occurrence, left ventricular mass index, flow- (FMD) and nitrate-mediated vasodilatation (NMD) of the brachial artery were determined by ultrasound imaging in 100 nondiabetic men with ESKD (50 men exhibited androgen deficiency; serum testosterone concentrations <300 ng/dl). RESULTS: Left-ventricular mass index, CCA diameter, CCA-IMT and atherosclerotic plaque occurrence were all significantly increased in ESKD patients with androgen deficiency compared with patients without androgen deficiency (p < 0.05). Also, FMD and NMD measurements were significantly reduced in the former compared with the latter (p < 0.05). Testosterone levels were inversely correlated with age and duration of hemodialysis therapy (r = -0.44 and r = -0.55; p < 0.001). Testosterone levels were negatively correlated to CCA-IMT and atherosclerotic plaque occurrence in patients with androgen deficiency (r = -0.32, p < 0.003, and r = -0.23, p < 0.04, respectively). FMD and NMD measurements were positively correlated to total (r = 0.65 and r = 0.61; both p < 0.0001) and free (r = 0.52 and r = 0.48; both p < 0.001) testosterone levels in patients with low androgenicity. CONCLUSION: The present results indicated that ESKD patients with androgen deficiency had increased CCA-IMT, atherosclerotic plaque occurrence and reduced FMD and NMD compared with patients without androgen deficiency. Testosterone serum levels were negatively correlated to CCA-IMT and positively correlated to endothelium-dependent vasodilatation in ESKD patients with androgen deficiency.

Adult↗

PubMed1997

Rapid reversal of endothelial dysfunction in hypercholesterolaemic rabbits treated with simvastatin and pravastatin.

1. The main objective of the present study was to verify the speed with which two 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors, simvastatin and pravastatin, could revert endothelial cell dysfunction in hypercholesterolaemic rabbits. An attempt was also made to correlate the plasma cholesterol level and the tissue cholesterol and malondialdehyde (MDA) contents of the aortae with the endothelium-dependent relaxation on the assumption that any endothelial dysfunction could be rapidly and partially reversed, even in the presence of relatively high serum cholesterol levels. 2. Ninety-one male New Zealand white rabbits were randomly assigned to hypercholesterolaemic (control), simvastatin or pravastatin groups. All rabbits were fed a diet supplemented with cholesterol (0.5%) and coconut oil (2%) for 8 weeks. Simvastatin (10 and 20 mg/day) and pravastatin (15 and 30 mg/day) were administered 6, 4 and 2 days before the end of the experiment. At the end of the 8th week, animals were killed and the aortae were removed for histological examination as well as for the measurement of cholesterol and MDA contents and for endothelium-dependent relaxation studies. 3. The results showed that significant improvement in endothelium-dependent relaxation was obtained only with pravastatin and only with 4 or 6 days of administration. In these cases, the cholesterol and MDA contents of the vessel wall were reduced, although no significant changes were observed in plasma total cholesterol. Higher doses of the drugs did not alter these results. 4. We conclude that pravastatin enhances endothelium-dependent relaxation when administered to cholesterol-fed rabbits, probably via an anti-oxidant action. This effect, which was observed to start on the 4th day of drug administration, may represent a new therapeutic approach for the treatment of acute coronary syndromes in hypercholesterolaemic patients.

Animals↗

PubMed2002

Ferric saccharate induces oxygen radical stress and endothelial dysfunction in vivo.

BACKGROUND: Intravenous iron supplementation is used widely in haemodialysis patients. However, nontransferrin-bound iron (NTBI), which increases after intravenous supplementation of ferric saccharate, has been suggested to act as a catalytic agent in oxygen radical formation in vitro and may thus contribute to endothelial impairment in vivo. MATERIALS AND METHODS: In 20 healthy volunteers the effect of 100 mg ferric saccharate infusion was investigated. Vascular ultrasound was used to assess endothelium-dependent vasodilatation at baseline, and 10 and 240 min after ferric saccharate infusion. Whole blood was collected to measure NTBI and in vivo radical formation was assessed by electron spin resonance. A time-control study was performed using saline infusion. RESULTS: Infusion of ferric saccharate induces a greater than fourfold increase in NTBI, as well as a transient, significant (P < 0.01) reduction of flow-mediated dilatation 10 min after infusion of ferric saccharate, when compared with saline. The generation of superoxide in whole blood increased significantly 10 and 240 min after infusion of ferric saccharate by, respectively, 70 and 53%. CONCLUSIONS: Iron infusion at a currently used therapeutic dose for intravenous iron supplementation leads to increased oxygen radical stress and acute endothelial dysfunction.

Adult↗

PubMed2003

Mechanisms of endothelial dysfunction in the metabolic syndrome.

Cardiovascular disease is a leading cause of death and disability in patients with diabetes or metabolic syndrome (MS). The available data suggest that many patients with diabetes or MS already have vascular abnormalities by the time they are diagnosed with their metabolic disorder. Endothelial dysfunction (ED), which is one of the initial steps in the process of vascular disease, is often present in patients with diabetes or MS. Although the precise mechanism(s) by which diabetes or MS causes ED remains to be elucidated, several possibilities exist. Hyperglycemia, hyperinsulinemia, increased oxidative stress, and diabetic dyslipidemia can all contribute to ED individually or in concert with one another. ED in the setting of diabetes or MS can subsequently result in the activation of a variety of pathways that alter vascular function and participate in the process of vascular remodeling and atherosclerosis. Because insulin resistance is the predominant mechanism responsible for various perturbations seen in MS or diabetes, it is essential to develop a therapeutic strategy that can improve insulin sensitivity with the hope that such interventions would reduce the risk of future cardiovascular events.

Diabetes Complications↗

PubMed1999

In vivo endothelial dysfunction characterizes patients with impaired fasting glucose.

OBJECTIVE: The American Diabetes Association has recently defined a new category of abnormal glucose homeostasis called "impaired fasting glucose" (IFG), where glucose levels do not meet the criteria of diabetes but are too high to be considered normal. We determined whether endothelial dysfunction is a characteristic of subjects with IFG. RESEARCH DESIGN AND METHODS: In vivo vasodilatory responses to intra-arterial infusions of endothelium-dependent (acetylcholine [ACh]) and -independent (sodium nitroprusside [SNP]) vasoactive agents were determined in 17 IFG subjects (age 63 +/- 1 years, BMI 26.5 +/- 0.8 kg/m2, serum LDL cholesterol 3.5 +/- 0.2 mmol/l) with fasting plasma glucose levels of 117 +/- 1 mg/dl and in 12 subjects with normal fasting plasma glucose concentrations. RESULTS: The blood-flow response to the low dose of ACh was 46% (5.9 +/- 0.7 vs. 10.9 +/- 1.3 ml.dl-1.min-1, IFG vs. normal, P < 0.01) and to the high dose was 31% (9.1 +/- 1.2 vs. 13.2 +/- 1.5 ml.dl-1.min-1, P < 0.05, respectively) lower in the IFG than in the normal subjects. In contrast, blood-flow responses to both low (7.8 +/- 0.5 vs. 9.0 +/- 0.9 ml.dl-1.min-1, IFG vs. normal, NS) and high (11.6 +/- 1.2 vs. 12.3 +/- 1.3 ml.dl-1.min-1, NS, respectively) doses of SNP were comparable. The ratio of endothelium-dependent to -independent blood flow was 40% lower in the IFG (0.75 +/- 0.1) than in the normal (1.24 +/- 0.1, P < 0.001) subjects. Both fasting plasma glucose (r = -0.48, P < 0.01) and glycosylated hemoglobin (r = -0.42, P < 0.05) were inversely correlated with endothelium-dependent vasodilation but not with other parameters, such as weight, blood pressure, or lipids. CONCLUSIONS: We conclude that vascular dysfunction is associated with abnormal, although nondiabetic, glucose homeostasis.

Acetylcholine↗

PubMed1999

[Endothelial dysfunction in patients with acute coronary syndrome].

Increased vasoconstriction, activation of platelet vessel wall interaction and invasion of monocytes into the subintima as well as vascular smooth muscle cell proliferation play a fundamental role in the pathogenesis of coronary artery disease. Acute coronary syndromes such as myocardial infarction and unstable angina pectoris are characterized by plaque rupture or erosion, activation of platelets and the coagulation system and vasoconstriction. Endothelial dysfunction may be one of the underlying mechanisms linking coronary artery disease and acute coronary syndromes. Both of these are often temporarily limited. Therefore, "non-invasive examination" of endothelial function by venous occlusion plethysmography or high resolution ultrasound might be useful for monitoring high-risk patients.

Animals↗

PubMed2005

Endothelial dysfunction and cardiovascular risk profile in nonalcoholic fatty liver disease.

Nonalcoholic fatty liver disease (NAFLD) is consistently associated with features of the metabolic syndrome, a condition carrying a high risk of cardiovascular events. We measured the vasodilatory response of the brachial artery in response to ischemia (a test of endothelial function) (FMV) as well as cardiovascular risk profile in 52 NAFLD cases and 28 age- and sex-matched controls. The 10-year risk of coronary events was calculated according to the Framingham equation and the scores derived from the PROCAM study and NCEP-ATPIII proposals. FMV was 6.33% +/- 5.93% in NAFLD versus 12.22% +/- 5.05% in controls (P < .0001), and higher in pure fatty liver (9.93%) compared with nonalcoholic steatohepatitis (4.94%) (P = .010). No differences were observed in flow-independent vasodilation (response to sublingual nitroglycerin). Percent FMV was negatively associated with insulin resistance (homeostasis model assessment) in the whole population (r = -0.243; P = .030). In logistic regression analysis, NAFLD was associated with a percent FMV in the lower tertile (OR, 6.7; 95% CI, 1.26-36.1), after adjustment for age, sex, body mass index, and insulin resistance. Among NAFLD patients, low FMV was associated with nonalcoholic steatohepatitis (adjusted OR, 6.8; 95% CI, 1.2-40.2). The 10-year probability of cardiovascular events was moderately increased in NAFLD, and particularly in nonalcoholic steatohepatitis. In conclusion, our study provides evidence of endothelial dysfunction and increased risk of cardiovascular events in NAFLD. The risk of advanced liver disease is well recognized in NAFLD patients, but the large majority of cases might experience cardiovascular disease in the long term, indirectly limiting the burden of liver failure.

Adult↗

PubMed2000

Dynamic progression of contractile and endothelial dysfunction and infarct extension in the late phase of reperfusion.

BACKGROUND: Myocardial injury during early reperfusion (R) has been well documented. However, the extent and time course of myocardial injury during late R are still unclear. The purpose of this study was to determine the extent of regional contractile and endothelial dysfunction and myocardial blood flow (MBF) defect as well as extension of infarction in association with neutrophil (PMN) actions during R. MATERIALS AND METHODS: A total of 29 dogs underwent a protocol of 1 h LAD ischemia followed by 6, 24, 48, and 72 h of R, respectively. Regional contractile function (sonomicrometry), MBF (colored microspheres), infarct size (triphenyltetrazolium chloride staining), and PMN localization (immunohistochemistry) were determined. RESULTS: Percentage segmental shortening at 6, 24, 48, and 72 h of R was significantly blunted (-1.8 +/- 1.2,* - 0.37 +/- 0. 6,* 0.04 +/- 0.2,* and 5.9 +/- 1.2* vs baseline 17.7 +/- 0.8). MBF (ml/min/g) was attenuated at 24 (0.27 +/- 0.03*), 48 (0.46 +/- 0. 07*), and 72 h of R (0.48 +/- 0.06*) vs 6 h of R (0.65 +/- 0.06). Infarct size increased from 6 (27 +/- 2%) to 24 h of R (41 +/- 2%*) with no further increase at 48 and 72 h of R, consistent with a peak of creatine kinase activity. PMN adherence (mm(2) endothelium) to left anterior descending coronary artery (LAD) segments was increased after 6 h of R (63 +/- 3*) vs nonischemic left circumflex coronary artery (LCX) segments (42 +/- 2) with a peak at 48 h of R (111 +/- 5*). Endothelium-dependent vascular relaxation in the LAD was also blunted at 6, 24, and 48 h of R. Immunostaining revealed CD18-positive PMNs were mainly accumulated in intravascular space during 6 h of R with an increase in migration of PMNs seen at 24 h of R, consistent with a peak of myeloperoxidase release. Myeloperoxidase activity in a given area at risk sample was significantly correlated with infarct extension during the first 24 h of R. CONCLUSIONS: These results provide pathologic evidence for myocardial injury during the extended R and a basis for exploration of interventions designed to limit myocardial injury after ischemia. (*P < 0.05 vs Baseline, 6 h of R and LCX segments.)

Animals↗

PubMed2003

Mechanisms of endothelial dysfunction after ionized radiation: selective impairment of the nitric oxide component of endothelium-dependent vasodilation.

(1) Gamma radiation impairs vascular function, leading to the depression of endothelium-dependent vasodilatation. Loss of the nitric oxide (NO) pathway has been implicated, but little is known about radiation effects on other endothelial mediators. (2) This study investigated the mechanisms of endothelial dysfunction in rabbits subjected to whole-body irradiation from a cobalt(60) source. (3) The endothelium-dependent relaxation of rabbit aorta evoked by acetylcholine (ACh) or A23187 was impaired in a dose-dependent manner by irradiation at 2 Gy or above. Inhibition was evident 9 days post-irradiation and persisted over the 30 day experimental period. (4) Endothelium-independent responses to glyceryl trinitrate (GTN), sodium nitroprusside (SNP) and 3-morpholino-sydnonimine (SIN-1) were suppressed over a similar dose range at 7-9 days post-irradiation, but recovered fully by 30 days post-irradiation. (5) In healthy vessels, ACh-induced relaxation was inhibited by L-N(omega)-nitroarginine (L-NA; 3 x 10(-4) M) and charybdotoxin (10(-8) M) plus apamin (10(-6) M) but resistant to indomethacin, indicating the involvement of NO and endothelium-derived hyperpolarizing factor (EDHF). Supporting this, ACh caused smooth muscle hyperpolarization that was reduced by L-NA and charybdotoxin plus apamin. (6) In irradiated vessels, responses to ACh were insensitive to L-NA but abolished by charybdotoxin plus apamin, indicating selective loss of NO-mediated relaxation. (7) In animals treated shortly after irradiation with the antioxidant, alpha-tocopherol acetate, the NO-dependent relaxation was restored without effect on the EDHF-dependent component. (8) The results imply that radiation selectively impairs the NO pathway as a consequence of oxidative stress, while EDHF is able to maintain endothelium-dependent relaxation at a reduced level.

Animals↗

PubMed2005

Transgenic activation of the kallikrein-kinin system inhibits intramyocardial inflammation, endothelial dysfunction and oxidative stress in experimental diabetic cardiomyopathy.

The mechanisms contributing to diabetic cardiomyopathy, as well as the protective pathways of the kallikrein-kinin-system (KKS), are incompletely understood. In a kallikrein-overexpressing rat model of streptozotocin (STZ)-induced diabetic cardiomyopathy, we investigated the involvement of inflammatory pathways, endothelial dysfunction, and oxidative stress. Six weeks after STZ injection, impairment of left ventricular (LV) function parameters measured by a Millar-tip catheter (peak LV systolic pressure; dP/dtmax; dP/dtmin) was accompanied by a significant increment of ICAM-1 and VCAM-1 (CAMs) expression, as well as of beta2-leukocyte-integrins+ (CD18+, CD11a+, CD11b+) and cytokine (TNF-alpha and IL-1beta)-expressing infiltrates in male Sprague-Dawley (SD-STZ) rats compared with normoglycemic littermates. Furthermore, SD-STZ rats demonstrated a significant impairment of endothelium-dependent relaxation evoked by acetylcholine and significantly increased plasma TBARS (plasma thiobarbituric acid reactive substances) levels as a measure of oxidative stress. These diabetic cardiomyopathy-associated alterations were significantly attenuated (P<0.05) in diabetic transgenic rats expressing the human kallikrein 1 (hKLK1) gene with STZ-induced diabetes. CAMs expression, beta2-leukocyte-integrins+, and cytokine-expressing infiltrates correlated significantly with all evaluated LV function parameters. The multiple protective effects of the KKS in experimental diabetic cardiomyopathy comprise the inhibition of intramyocardial inflammation (CAMs expression, beta2-leukocyte-integrins+ infiltration and cytokine expression), an improvement of endothelium-dependent relaxation and the attenuation of oxidative stress. These insights might have therapeutic implications also for human diabetic cardiomyopathy.

Acetylcholine↗