Role of oxidative stress in angiotensin-II mediated contraction of human conduit arteries in patients with cardiovascular disease

Mechanisms involved in nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox)-derived reactive oxygen species (ROS) modulation of muscle function in human and dog bladders

Roles of redox signaling in bladder function is still under investigation. We explored the physiological role of reactive oxygen species (ROS) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) in regulating bladder function in humans and dogs. Mucosa-denuded bladder smooth muscle strips obtained from 7 human organ donors and 4 normal dogs were mounted in muscle baths, and trains of electrical field stimulation (EFS) applied for 20 minutes at 90-second intervals. Subsets of strips were incubated with hydrogen peroxide (H2O2), angiotensin II (Ang II; Nox activator), apocynin (inhibitor of Noxs and ROS scavenger), or ZD7155 (specific inhibitor of angiotensin type 1 (AT1) receptor) for 20 minutes in continued EFS trains. Subsets treated with inhibitors were then treated with H2O2 or Ang II. In human and dog bladders, the ROS, H2O2 (100μM), caused contractions and enhanced EFS-induced contractions. Apocynin (100μM) attenuated EFS-induced strip contractions in both species; subsequent treatment with H2O2 restored strip activity. In human bladders, Ang II (1μM) did not enhance EFS-induced contractions yet caused direct strip contractions. In dog bladders, Ang II enhanced both EFS-induced and direct contractions. Ang II also partially restored EFS-induced contractions attenuated by prior apocynin treatment. In both species, treatment with ZD7155 (10μM) inhibited EFS-induced activity; subsequent treatment with Ang II did not restore strip activity. Collectively, these data provide evidence that ROS can modulate bladder function without exogenous stimuli. Since inflammation is associated with oxidative damage, the effects of Ang II on bladder smooth muscle function may have pathologic implications.

Daily blueberry consumption improves blood pressure and arterial stiffness in postmenopausal women with pre- and stage 1-hypertension: a randomized, double-blind, placebo-controlled clinical trial

BACKGROUND

Postmenopausal women have a high prevalence of hypertension and often develop arterial stiffness thereby increasing cardiovascular disease risk. Although antihypertensive drug therapies exist, increasing numbers of people prefer natural therapies. In vivo studies and a limited number of clinical studies have demonstrated the antihypertensive and vascular-protective effects of blueberries.

OBJECTIVE

To examine the effects of daily blueberry consumption for 8 weeks on blood pressure and arterial stiffness in postmenopausal women with pre- and stage 1-hypertension.

DESIGN

This was an 8-week, randomized, double-blind, placebo-controlled clinical trial.

PARTICIPANTS/SETTING

Forty-eight postmenopausal women with pre- and stage 1-hypertension recruited from the greater Tallahassee, FL, area participated.

INTERVENTION

Participants were randomly assigned to receive either 22 g freeze-dried blueberry powder or 22 g control powder.

MAIN OUTCOME MEASURES

Resting brachial systolic and diastolic blood pressures were evaluated and arterial stiffness was assessed using carotid-femoral pulse wave velocity and brachial-ankle pulse wave velocity. C-reactive protein, nitric oxide, and superoxide dismutase were measured at baseline, 4 weeks, and 8 weeks.

STATISTICAL ANALYSES PERFORMED

Statistical analysis was performed using a split plot model of repeated measures analysis of variance.

RESULTS

After 8 weeks, systolic blood pressure and diastolic blood pressure (131±17 mm Hg [P<0.05] and 75±9 mm Hg [P<0.01], respectively) and brachial-ankle pulse wave velocity (1,401±122 cm/second; P<0.01) were significantly lower than baseline levels (138±14 mm Hg, 80±7 mm Hg, and 1,498±179 cm/second, respectively), with significant (P<0.05) group×time interactions in the blueberry powder group, whereas there were no changes in the group receiving the control powder. Nitric oxide levels were greater (15.35±11.16 μmol/L; P<0.01) in the blueberry powder group at 8 weeks compared with baseline values (9.11±7.95 μmol/L), whereas there were no changes in the control group.

CONCLUSIONS

Daily blueberry consumption may reduce blood pressure and arterial stiffness, which may be due, in part, to increased nitric oxide production.

Short-term hypercaloric diet induces blunted aortic vasoconstriction and enhanced vasorelaxation via increased nitric oxide synthase 3 activity and expression in Dahl salt-sensitive rats

AIM

To elucidate the role of the O(2)(-), H(2)O(2) or NO pathways in aortic angiotensin (Ang)II-induced vasoconstriction in Dahl salt-sensitive (SS) rats compared with control SS-13(BN) rats on a normal or hypercaloric diet.

METHODS

Aortic function was assessed using wire myography in 16-week-old rats maintained on a normal diet or a 4-week hypercaloric diet. Nitric oxide synthase (NOS) activity and expression was determined by the conversion of radio-labelled arginine to citrulline and Western blot analysis respectively.

RESULTS

On normal diet, AngII-induced vasoconstriction was greater in SS than SS-13(BN) rats. Polyethylene glycol superoxide dismutase (PEG-SOD) reduced the aortic AngII response similarly in both strains on normal diet. Catalase blunted, whereas N(ω)-Nitro-L-arginine methyl ester (L-NAME) did not affect the AngII response in SS rats. In SS-13(BN) rats, catalase had no effect and L-NAME enhanced AngII response. On hypercaloric diet, aortic AngII responsiveness was reduced in SS but unaltered in SS-13(BN) rats compared with their normal diet counterparts. PEG-SOD reduced the AngII response in both rats on hypercaloric diet. Catalase treatment did not alter aortic AngII response, while L-NAME increased the response in SS rats on hypercaloric diet. In SS-13(BN) rats on hypercaloric diet, catalase reduced and L-NAME did not alter the AngII response. Furthermore, aortic endothelial-dependent vasorelaxation was increased in SS rats on hypercaloric diet compared with normal diet and aortic NOS3 activity and expression was increased.

CONCLUSION

A short-term hypercaloric diet induces a blunted vasoconstrictive and enhanced vasodilatory phenotype in SS rats, but not in SS-13(BN) rats, via reduced H(2)O(2) and increased NOS3 function.

Human internal thoracic artery grafts exhibit severe morphological and functional damage and spasmic vasomotion due to oxidative stress

Background

The internal thoracic artery (ITA) is the first choice for myocardial revascularization, but atherosclerotic lesions and perioperative vasospasm may still limit its functionality. Oxidative stress via the peroxynitrite – poly-(ADP-ribose) polymerase (PARP) cascade plays an important role in the pathogenesis of impaired vascular tone via endothelial injury. We aimed to investigate and describe the histology, PARP activation and functionality of ITA grafts and to assess the possible beneficial effect of PARP-inhibition.

Material/Methods

ITA specimens from 47 patients (26 men, mean age 66.2±1.7 years) who underwent coronary bypass surgery were processed for histological and immunohistochemical studies for oxidative stress and PARP activation, and were functionally tested with acetylcholine (ACh) and sodium nitroprusside (SNP) with or without PARP inhibition.

Results

The sections showed atherosclerotic alterations and oxidative and nitrosative stress were evidenced by positive 3-nitrotyrosine, 4-hydroxynonenal and PAR stainings. Functionally, 88.1% reacted to K-Krebs, 68.7% exhibited contraction after 1 μM phenylephrine, 29.9% exhibited relaxation to 30 μM Ach, and all precontracted segments relaxed to 30 μM SNP. High amplitude vasomotion was observed in 47.8% of the segments, which could be abolished by the application of 10 μM SNP. Incubation of the preparations with PJ34 did not improve endothelium-dependent vasodilation.

Conclusions

ITA grafts are severely damaged both morphologically and functionally in patients undergoing coronary artery bypass surgery, but PARP inhibition cannot improve their functional characteristics. The topical use of SNP to the ITA during the operation may improve vascular functions by dilating the vessels and eliminating the eventual spasmic vasomotion.

Coupling vascular and myocardial inflammatory injury into a common phenotype of cardiovascular dysfunction: systemic inflammation and aging - a mini-review

The rising epidemic of cardiovascular (CV) disease is fuelled by obesity, hypertension and diabetes and, independently and cumulatively, by an aging population. Extensive research identified immunoinflammatory mechanisms as key drivers in the initiation and progression of the disease, from early asymptomatic stages of vascular and myocardial injury leading to the clinically manifest dysfunction and remodeling in advanced stages. Underlying processes include endothelial dysfunction and extracellular matrix restructuration leading to increased vascular stiffness, as well as myocardial remodeling with dilatation and wall thinning. In this, overproduction of tumor necrosis factor-α, amongst others, contributes to generalized CV injury and dysfunction. Moreover, recent insights into the involvement of innate and adaptive immunity in atherosclerosis have shed light on many interesting parallels with chronic systemic inflammatory conditions, such as rheumatoid arthritis, with aggravated inflammation-induced vascular and myocardial injury. Besides, chronologic age has been identified as a potent, independent risk for reduced CV capacity and a plethora of heart diseases, with other modifiable risk factors acting as accelerators. We discuss the available evidence and propose that characterization of inflammatory CV responses might reveal a distinctive CV inflammatory phenotype. A comprehensive noninvasive bio-signature, comprising immunomic biomarkers and integrated noninvasive imaging, may serve as a potential tool in the early diagnosis and prognostication of CV risk.

Chemistry and antihypertensive effects of tempol and other nitroxides

Nitroxides can undergo one- or two-electron reduction reactions to hydroxylamines or oxammonium cations, respectively, which themselves are interconvertible, thereby providing redox metabolic actions. 4-Hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl (tempol) is the most extensively studied nitroxide. It is a cell membrane-permeable amphilite that dismutates superoxide catalytically, facilitates hydrogen peroxide metabolism by catalase-like actions, and limits formation of toxic hydroxyl radicals produced by Fenton reactions. It is broadly effective in detoxifying these reactive oxygen species in cell and animal studies. When administered intravenously to hypertensive rodent models, tempol caused rapid and reversible dose-dependent reductions in blood pressure in 22 of 26 studies. This was accompanied by vasodilation, increased nitric oxide activity, reduced sympathetic nervous system activity at central and peripheral sites, and enhanced potassium channel conductance in blood vessels and neurons. When administered orally or by infusion over days or weeks to hypertensive rodent models, it reduced blood pressure in 59 of 68 studies. This was accompanied by correction of salt sensitivity and endothelial dysfunction and reduced agonist-evoked oxidative stress and contractility of blood vessels, reduced renal vascular resistance, and increased renal tissue oxygen tension. Thus, tempol is broadly effective in reducing blood pressure, whether given by acute intravenous injection or by prolonged administration, in a wide range of rodent models of hypertension.

p38 MAPK contributes to angiotensin II-induced COX-2 expression in aortic fibroblasts from normotensive and hypertensive rats

OBJECTIVE

To investigate the effect of angiotensin II on cyclooxygenase-2 (COX-2) expression in aortic adventitial fibroblasts from normotensive [Wistar-Kyoto (WKY)] rats and spontaneously hypertensive rats (SHRs).

METHODS

Protein expression was determined by western blot, mRNA levels by real-time PCR, transcriptional activity by luciferase assays, superoxide anion (O2*-) production by dihydroethidine fluorescence and prostaglandin E2 by enzyme immunoassay.

RESULTS

Angiotensin II (0.1 micromol/l, 0.5-6 h) time dependently induced COX-2 protein expression, this effect being transient in fibroblasts from WKY rats and maintained over time in SHRs. Angiotensin II effect was abolished by valsartan (1 micromol/l), an angiotensin II type 1 receptor antagonist. Angiotensin II-induced prostaglandin E2 production was reduced by valsartan and the COX-2 inhibitor NS398 (1 micromol/l). Angiotensin II increased O2*- production more in SHR than WKY rats. This increase was reduced by apocynin (30 micromol/l) and allopurinol (10 micromol/l), respective nicotinamide adenine dinucleotide phosphate (NADPH) and xanthine oxidase inhibitors. However, angiotensin II-induced COX-2 expression was unaffected by apocynin, allopurinol, tempol (1 mmol/l) or catalase (1000 U/ml). Angiotensin II (2-30 min) induced p38 mitogen-activated protein kinase (MAPK) phosphorylation, transiently in WKY rats but sustained in SHRs. The p38 inhibitor SB203580 (10 micromol/l) reduced angiotensin II-induced COX-2 protein and mRNA levels. The angiotensin II effect was not prevented by inhibition of mRNA synthesis, and angiotensin II was unable to modulate COX-2 transcriptional activity.

CONCLUSIONS

Angiotensin II increases COX-2 expression in aortic fibroblasts through mechanisms including p38 MAPK pathway, independent of reactive oxygen species production and nonmediated by COX-2 transcriptional activity modulation. The sustained angiotensin-induced p38 MAPK activation in SHR cells might be related to the maintained COX-2 expression in this strain.

Superoxide anion mediates angiotensin II-induced potentiation of contractile response to sympathetic stimulation

Angiotensin II is known to potentiate vasoconstriction induced by electrical field stimulation (EFS), but the underlying mechanisms for this potentiation are not fully understood. This study was designed to investigate the role of superoxide anion in the potentiation effects of angiotensin II. Contraction of rat mesenteric arterial segments was induced by perivascular nerve stimulation with EFS, and superoxide production was measured with lucigenin-enhanced chemiluminescence. Extracellular signal-regulated kinase (ERK) phosphorylation was determined in cultured smooth muscle cells with Western blot. Angiotensin II concentration dependently potentiated the contraction of rat mesenteric arteries to EFS, which is frequency-dependent. This potentiation was blunted by an angiotensin AT(1) receptor antagonist (2-ethoxy-1-[[2'-(1H-tetrazol-5-yl)biphenyl-4-yl]methyl]-1H-benzimidazole-7-carboxylic acid, CV-11974), NAD(P)H oxidase inhibitor (apocynin), superoxide dismutase (SOD) and its mimetic tiron, but not affected by angiotensin AT(2) receptor antagonist and inhibitors of xanthine oxidase, cytochrome P450, and cyclooxygenase. Angiotensin II increased superoxide production by mesenteric arteries, which was blunted by angiotensin AT(1) receptor antagonist CV-11974, and NAD(P)H oxidase inhibitor apocynin. Superoxide generating compound pyrogallol mimicked the effects of angiotensin II. Tyrosine kinase inhibitor (tyrphostin A25) and mitogen-activated protein kinase (MAPK)/ERK inhibitors (1,4-diamino-2,3-dicyano-1,4-bis [2-aminophenylthio]butadiene (U 0126)) inhibited angiotensin II- and pyrogallol-induced potentiation of EFS-induced contraction, while inactive forms of these inhibitors did not show any inhibitory effects. In cultured smooth muscle cells from mesenteric arteries, angiotensin II and superoxide similarly induced ERK phosphorylation. These results showed that superoxide mediated angiotensin II-induced potentiation of contractile response to EFS and tyrosine kinase-MAPK/ERK activation was involved.

Role of NADPH oxidase and iNOS in vasoconstrictor responses of vessels from hypertensive and normotensive rats

BACKGROUND AND PURPOSE

To analyse the influence of hypertension in the modulation induced by inducible NOS (iNOS)-derived NO and superoxide anion (O(2) (*-)) of vasoconstrictor responses and the sources of O(2) (*-) implicated.

EXPERIMENTAL APPROACH

Vascular reactivity experiments were performed in segments of aorta from normotensive, Wistar Kyoto (WKY) and spontaneously hypertensive rats (SHR); protein and mRNA expressions were respectively measured by western blot and quantitative reverse transcription-polymerase chain reaction and O(2) (*-) production was evaluated by ethidium fluorescence.

KEY RESULTS

The contractile responses to phenylephrine (1 nM-30 microM) and 5-hydroxytryptamine (0.1-100 microM) were greater in aortic segments from SHR than WKY. The selective iNOS inhibitor, 1400W (10 microM), increased the phenylephrine contraction only in WKY segments; however, iNOS protein and mRNA expressions were greater in aorta from SHR than WKY. Superoxide dismutase (SOD, 150 U ml(-1)) reduced phenylephrine and 5-hydroxytryptamine responses only in aorta from SHR; the NAD(P)H oxidase inhibitor apocynin (0.3 mM) decreased phenylephrine and 5-hydroxytryptamine responses more in vessels from SHR than WKY. Co-incubation with SOD plus 1400W potentiated the phenylephrine and 5-hydroxytryptamine responses more in segments from SHR than WKY. O(2) (*-) production was greater in aorta from SHR than WKY; apocynin abolished this difference.

CONCLUSIONS AND IMPLICATIONS

Increased O(2) (*-) formation from NADP(H) oxidase in vessels from hypertensive rats contributes to the vasoconstrictor responses and counteract the increase of NO from iNOS and the consequent modulation of these responses.

The inhibitory effect of leptin on angiotensin II-induced vasoconstriction in vascular smooth muscle cells is mediated via a nitric oxide-dependent mechanism

Leptin inhibits the contractile response induced by angiotensin (Ang) II in vascular smooth muscle cells (VSMCs) of the aorta. We studied in vitro and ex vivo the role of nitric oxide (NO) in the effect of leptin on the Ang II-induced vasoconstriction of the aorta of 10-wk-old Wistar rats. NO and nitric oxide synthase (NOS) activity were assessed by the Griess and (3)H-arginine/citrulline conversion assays, respectively. Stimulation of inducible NOS (iNOS) as well as Janus kinases/signal transducers and activators of transcription (JAK/STAT) and phosphoinositide 3-kinase (PI3K)/Akt signaling pathways were determined by Western blot. The contractile responses to Ang II were evaluated in endothelium-denuded aortic rings using the organ bath system. Changes in intracellular Ca(2+) were measured in VSMCs using fura-2 fluorescence. Leptin significantly (P < or = 0.01) stimulated NO release and NOS activity in VSMCs. Leptin's effect on NO was abolished by the NOS inhibitor, N(G)-monomethyl l-arginine, or the iNOS selective inhibitor L-N(6)-(1-iminoethyl)-lysine. Accordingly, leptin increased iNOS protein expression, with a comparable time course with that of NO production and NOS activity. Leptin also significantly increased STAT3 (P < or = 0.01) and Akt (P < or = 0.001) phosphorylation. Moreover, either the JAK2 inhibitor, AG490, or the PI3K inhibitor, wortmannin, significantly (P < or = 0.05) abrogated the leptin-induced increase in iNOS protein. Finally, both N(G)-monomethyl L-arginine and L-N(6)-(1-iminoethyl)-lysine inhibitors completely blunted (P < or = 0.001) the leptin-mediated inhibition of the Ang II-induced VSMC activation and vasoconstriction. These findings suggest that the endothelium-independent depressor action of leptin is mediated by an increase of NO bioavailability in VSMCs. This process requires the up-regulation of iNOS through mechanisms involving JAK2/STAT3 and PI3K/Akt pathways.

The role of oxidant stress in angiotensin II-mediated contraction of human resistance arteries in the state of health and the presence of cardiovascular disease

BACKGROUND

Angiotensin II is a powerful vasoconstrictor and regulator of cardiovascular growth. Also, it increases formation of reactive oxygen species and contributes to vascular dysfunction. We investigated the role of oxidant stress in contraction of human resistance arteries to angiotensin II, in health and in the presence of cardiovascular disease.

METHODS AND PATIENTS

Studies of isometric contraction to angiotensin II, using human resistance arteries from healthy volunteers and patients, undergoing cardiac revascularization surgery, were performed by the broad-spectrum antioxidant agent vitamin C and superoxide dismutase mimetic TEMPOL. In the presence of vitamin C, the potency and the maximum contractile response were reduced in both patients and healthy volunteers. Addition of TEMPOL caused a decrease in angiotensin II-induced contraction only in the patients' group.

CONCLUSIONS

Our studies provide evidence for the role of oxidant stress in the contractile response of human resistance arteries to angiotensin II. In patients with cardiovascular disease, the superoxide anion may be the major species involved. In healthy subjects, other reactive oxygen species and the redox-independent vasoconstrictor action of angiotensin II predominate.

CONDENSED ABSTRACT

Increased formation of reactive oxygen species, due to angiotensin II, contributes to vascular dysfunction. We determined the oxidative reactivity of human resistance arteries to angiotensin II in healthy subjects and patients, undergoing cardiac revascularization surgery, using the broad-spectrum antioxidant agent, vitamin C, and superoxide dismutase mimetic, TEMPOL. There was a large decrease in potency and maximum of angiotensin II-induced contractile response noted in both groups with the former, while the latter reduced contraction only in the patients' group. Superoxide anion may play a major role in angiotensin II contractions of human resistance arteries in the presence of cardiovascular disease. In healthy subjects, other reactive species and the redox-independent pathways predominate.