Increased inactivation of nitric oxide is involved in impaired coronary flow reserve in heart failure

H2O2 Mediates VEGF- and Flow-Induced Dilations of Coronary Arterioles in Early Type 1 Diabetes: Role of Vascular Arginase and PI3K-Linked eNOS Uncoupling

In diabetes, the enzyme arginase is upregulated, which may compete with endothelial nitric oxide (NO) synthase (eNOS) for their common substrate L-arginine and compromise NO-mediated vasodilation. However, this eNOS uncoupling can lead to superoxide production and possibly vasodilator hydrogen peroxide (H₂O₂) formation to compensate for NO deficiency. This hypothesis was tested in coronary arterioles isolated from pigs with 2-week diabetes after streptozocin injection. The NO-mediated vasodilation induced by flow and VEGF was abolished by NOS inhibitor L-NAME and phosphoinositide 3-kinase (PI3K) inhibitor wortmannin but was not affected by arginase inhibitor N^ω-hydroxy-nor-L-arginine (nor-NOHA) or H₂O₂ scavenger catalase in control pigs. With diabetes, this vasodilation was partially blunted, and the remaining vasodilation was abolished by catalase and wortmannin. Administration of L-arginine or nor-NOHA restored flow-induced vasodilation in an L-NAME sensitive manner. Diabetes did not alter vascular superoxide dismutase 1, catalase, and glutathione peroxidase mRNA levels. This study demonstrates that endothelium-dependent NO-mediated coronary arteriolar dilation is partially compromised in early type 1 diabetes by reducing eNOS substrate L-arginine via arginase activation. It appears that upregulated arginase contributes to endothelial NO deficiency in early diabetes, but production of H₂O₂ during PI3K-linked eNOS uncoupling likely compensates for and masks this disturbance.

Efficacy of the monocarbonyl curcumin analog C66 in the reduction of diabetes-associated cardiovascular and kidney complications

Curcumin is a polyphenolic compound derived from turmeric that has potential beneficial properties for cardiovascular and renal diseases and is relatively safe and inexpensive. However, the application of curcumin is rather problematic due to its chemical instability and low bioavailability. The experimental results showed improved chemical stability and potent pharmacokinetics of one of its analogs – (2E,6E)-2,6-bis[(2-trifluoromethyl)benzylidene]cyclohexanone (C66). There are several advantages of C66, like its synthetic accessibility, structural simplicity, improved chemical stability (in vitro and in vivo), presence of two reactive electrophilic centers, and good electron-accepting capacity. Considering these characteristics, we reviewed the literature on the application of C66 in resolving diabetes-associated cardiovascular and renal complications in animal models. We also summarized the mechanisms by which C66 is preventing the release of pro-oxidative and pro-inflammatory molecules in the priming and in activation stage of cardiomyopathy, renal fibrosis, and diabetic nephropathy. The cardiovascular protective effect of C66 against diabetes-induced oxidative damage is Nrf2 mediated but mainly dependent on JNK2. In general, C66 causes inhibition of JNK2, which reduces cardiac inflammation, fibrosis, oxidative stress, and apoptosis in the settings of diabetic cardiomyopathy. C66 exerts a powerful antifibrotic effect by reducing inflammation-related factors (MCP-1, NF-κB, TNF-α, IL-1β, COX-2, and CAV-1) and inducing the expression of anti-inflammatory factors (HO-1 and NEDD4), as well as targeting TGF-β/SMADs, MAPK/ERK, and PPAR-γ pathways in animal models of diabetic nephropathy. Based on the available evidence, C66 is becoming a promising drug candidate for improving cardiovascular and renal health.

Coronary blood flow in heart failure: cause, consequence and bystander

Heart failure is a clinical syndrome where cardiac output is not sufficient to sustain adequate perfusion and normal bodily functions, initially during exercise and in more severe forms also at rest. The two most frequent forms are heart failure of ischemic origin and of non-ischemic origin. In heart failure of ischemic origin, reduced coronary blood flow is causal to cardiac contractile dysfunction, and this is true for stunned and hibernating myocardium, coronary microembolization, myocardial infarction and post-infarct remodeling, possibly also for the takotsubo syndrome. The most frequent form of non-ischemic heart failure is dilated cardiomyopathy, caused by genetic mutations, myocarditis, toxic agents or sustained tachyarrhythmias, where alterations in coronary blood flow result from and contribute to cardiac contractile dysfunction. Hypertrophic cardiomyopathy is caused by genetic mutations but can also result from increased pressure and volume overload (hypertension, valve disease). Heart failure with preserved ejection fraction is characterized by pronounced coronary microvascular dysfunction, the causal contribution of which is however not clear. The present review characterizes the alterations of coronary blood flow which are causes or consequences of heart failure in its different manifestations. Apart from any potentially accompanying coronary atherosclerosis, all heart failure entities share common features of impaired coronary blood flow, but to a different extent: enhanced extravascular compression, impaired nitric oxide-mediated, endothelium-dependent vasodilation and enhanced vasoconstriction to mediators of neurohumoral activation. Impaired coronary blood flow contributes to the progression of heart failure and is thus a valid target for established and novel treatment regimens.

Chronic exposure to tramadol induces cardiac inflammation and endothelial dysfunction in mice

Tramadol is an opioid extensively used to treat moderate to severe pain; however, prolonged therapy is associated with several tissues damage. Chronic use of tramadol was linked to increased hospitalizations due to cardiovascular complications. Limited literature has described the effects of tramadol on the cardiovascular system, so we sought to investigate these actions and elucidate the underlying mechanisms. Mice received tramadol hydrochloride (40 mg/kg body weight) orally for 4 successive weeks. Oxidative stress, inflammation, and cardiac toxicity were assessed. In addition, eNOS expression was evaluated. Our results demonstrated marked histopathological alteration in heart and aortic tissues after exposure to tramadol. Tramadol upregulated the expression of oxidative stress and inflammatory markers in mice heart and aorta, whereas downregulated eNOS expression. Tramadol caused cardiac damage shown by the increase in LDH, Troponin I, and CK-MB activities in serum samples. Overall, these results highlight the risks of tramadol on the cardiovascular system.

Endothelial dysfunction and vascular disease - a 30th anniversary update

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

Inhibition of JNK by novel curcumin analog C66 prevents diabetic cardiomyopathy with a preservation of cardiac metallothionein expression

The development of diabetic cardiomyopathy is attributed to diabetic oxidative stress, which may be related to the mitogen-activated protein kinase (MAPK) c-Jun NH2-terminal kinase (JNK) activation. The present study tested a hypothesis whether the curcumin analog C66 [(2E,6E)-2,6-bis(2-(trifluoromethyl)benzylidene) cyclohexanone] as a potent antioxidant can protect diabetes-induced cardiac functional and pathogenic changes via inhibition of JNK function. Diabetes was induced with a single intraperitoneal injection of streptozotocin in male C57BL/6 mice. Diabetic and age-matched control mice were randomly divided into three groups, each group treated with C66, JNK inhibitor (JNKi, SP600125), or vehicle (1% CMC-Na solution) by gavage at 5 mg/kg every other day for 3 mo. Neither C66 nor JNKi impacted diabetic hyperglycemia and inhibition of body-weight gain, but both significantly prevented diabetes-induced JNK phosphorylation in the heart. Compared with basal line, cardiac function was significantly decreased in diabetic mice at 3 mo of diabetes but not in C66- or JNKi-treated diabetic mice. Cardiac fibrosis, oxidative damage, endoplasmic reticulum stress, and cell apoptosis, examined by Sirius red staining, Western blot, and thiobarbituric acid assay, were also significantly increased in diabetic mice, all which were prevented by C66 or JNKi treatment under diabetic conditions. Cardiac metallothionein expression was significantly decreased in diabetic mice but was almost normal in C66- or JNKi-treated diabetic mice. These results suggest that, like JNKi, C66 is able to prevent diabetic upregulation of JNK function, resulting in a prevention of diabetes-induced cardiac fibrosis, oxidative stress, endoplasmic reticulum stress, and cell death, along with a preservation of cardiac metallothionein expression.

Growth differentiation factor 15 impairs aortic contractile and relaxing function through altered caveolar signaling of the endothelium

Growth differentiation factor 15 (GDF15) is an independent predictor of cardiovascular disease, and increased GDF15 levels have been associated with endothelial dysfunction in selected patients. We therefore investigated whether GDF15 modulates endothelial function in aortas of wild-type (WT) and GDF15 knockout (KO) mice. Vascular contractions to phenylephrine and relaxation to ACh were assessed in aortas obtained from healthy WT and GDF15 KO mice. The effects of GDF15 pretreatment and the involvement of ROS or caveolae were determined. Phenylephrine-induced contractions and ACh-mediated relaxations were similar in WT and GDF15 KO mice. Pretreatment with GDF15 inhibited contraction and relaxation in both groups. Inhibition of contraction by GDF15 was absent in denuded vessels or after blockade of nitric oxide (NO) synthase. Relaxation in WT mice was mediated mainly through NO and an unidentified endothelium-derived hyperpolarizin factor (EDHF), whereas GDF15 KO mice mainly used prostaglandins and EDHF. Pretreatment with GDF15 impaired relaxation in WT mice by decreasing NO; in GDF15 KO mice, this was mediated by decreased action of prostaglandins. Disruption of caveolae resulted in a similar inhibition of vascular responses as GDF15. ROS inhibition did not affect vascular function. In cultured endothelial cells, GDF15 pretreatment caused a dissociation between caveolin-1 and endothelial NO synthase. In conclusion, GDF15 impairs aortic contractile and relaxing function through an endothelium-dependent mechanism involving altered caveolar endothelial NO synthase signaling.

Impaired vasodilation in the pathogenesis of hypertension: focus on nitric oxide, endothelial-derived hyperpolarizing factors, and prostaglandins

Under resting conditions the arterial vasculature exists in a vasoconstricted state referred to as vascular tone. Physiological dilatation in response to increased flow, a function of normal endothelium is necessary to maintain normal blood pressure. Endothelial dysfunction in vascular smooth muscle cells thus results in loss of normal vasorelaxant function and the inability of arteries to appropriately dilate in response to increased blood flow in either a systemic or regional vascular bed, resulting in increased blood pressure, a sequence that may represent a common pathway to hypertension. Normal vasorelaxation is mediated by a number of endothelial systems including nitric oxide (NO), prostaglandins (PGI2 and PGE2), and a family of endothelial-derived hyperpolarizing factors (EDHF). In response to hemodynamic shear stress, endothelium continuously releases NO, EDHF, and PGI2 to provide vasodilatation. EDHF, not a single molecule but rather a group of molecules that includes epoxyeicosatrienoic acids, hydrogen peroxide, carbon monoxide, hydrogen sulfide, C-natriuretic peptide, and K+ itself, causes vasodilatation by activation of vascular smooth muscle cell K+ channels, resulting in hyperpolarization and thus vasorelaxation. The understanding and effective management of blood pressure requires an understanding of both physiologic and pathophysiologic regulation of vascular tone. This review describes molecular mechanisms underlying normal endothelial regulation and pathological states, such as increased oxidative stress, which cause loss of vasorelaxation. Possible pharmacological interventions to restore normal function are suggested.

Endothelial mitochondria and heart disease

The endothelium is vital to the proper functioning in the heart, in particular due to its production of nitric oxide (NO) which regulates vascular tone. Damage to the endothelium contributes to the development of atherosclerosis, and hence to possible myocardial infarction and subsequent heart failure. Like most cells, endothelial cells contain mitochondria, despite their having relatively little dependence on oxidative phosphorylation for ATP production. However, endothelial mitochondria are centrally involved in maintaining the fine regulatory balance between mitochondrial calcium concentration, reactive oxygen species (ROS) production, and NO. This raises the question of whether damage to endothelial mitochondria would have repercussions in terms of the development of heart disease. In fact, increasingly nuanced techniques enabling restricted transgenic expression of antioxidant proteins in mice has demonstrated that mitochondrial ROS do contribute to endothelial damage. New pharmaceutical approaches designed to target protective molecules such as ROS scavengers to the mitochondria promise to be effective in preventing heart disease. As well as protecting cardiomyocytes, these drugs may have the added benefit of preventing damage to the endothelial mitochondria. However, much remains to be done in understanding the contribution that mitochondria make to endothelial function.

MnSOD protects against COX1-mediated endothelial dysfunction in chronic heart failure

Endothelial function is impaired by oxidative stress in chronic heart failure (HF). Mechanisms that protect against increases in oxidative stress in HF are not clear. The goal of this study was to determine whether manganese superoxide dismutase (MnSOD) plays a key role in protecting against endothelial dysfunction in HF. Endothelial function and gene expression were examined in aorta from wild-type mice (MnSOD(+/+)) and mice deficient in MnSOD (MnSOD(+/-)) 12 wk after ligation of the left coronary artery (LCA). LCA ligation produced similar size myocardial infarctions in MnSOD(+/+) and MnSOD(+/-) mice and reduced ejection fraction to approximately 20% in both groups. Maximal relaxation in response to acetylcholine was 78 +/- 3% (mean +/- SE) and 66 +/- 8% in sham-operated MnSOD(+/+) and MnSOD(+/-) mice, respectively. Expression of antioxidant enzymes increased in MnSOD(+/+) mice with HF, and maximal relaxation to acetylcholine was slightly impaired (68 +/- 4%). Greater endothelial dysfunction was observed in MnSOD(+/-) mice with HF (46 +/- 5%, P < 0.05), which was significantly improved by polyethylene glycol-catalase but not Tempol. Incubation with the nonspecific cyclooxygenase (COX) inhibitor indomethacin or the COX1 inhibitor valeryl salicylate, but not the COX-2 inhibitor NS-398, significantly improved relaxation to acetylcholine in HF mice (maximum relaxation = 74 +/- 5, 91 +/- 1, and 58 +/- 5%). These data suggest that MnSOD plays a key role in protecting against endothelial dysfunction in HF. A novel mechanism was identified whereby chronic increases in oxidative stress, produced by mitochondrial SOD deficiency, impair vascular function via a hydrogen peroxide-dependent, COX1-dependent, endothelium-derived contracting factor.

Endothelial dysfunction and vascular disease

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

NADPH oxidase contributes to coronary endothelial dysfunction in the failing heart

Increased reactive oxygen species (ROS) produced by the failing heart can react with nitric oxide (NO), thereby decreasing NO bioavailability. This study tested the hypothesis that increased ROS generation contributes to coronary endothelial dysfunction in the failing heart. Congestive heart failure (CHF) was produced in six dogs by ventricular pacing at 240 beats/min for 4 wk. Studies were performed at rest and during treadmill exercise under control conditions and after treatment with the NADPH oxidase inhibitor and antioxidant apocynin (4 mg/kg iv). Apocynin caused no significant changes in heart rate, aortic pressure, left ventricular (LV) systolic pressure, LV end-diastolic pressure, or maximum rate of LV pressure increase at rest or during exercise in normal or CHF dogs. Apocynin caused no change in coronary blood flow (CBF) in normal dogs but increased CBF at rest and during exercise in animals with CHF (P < 0.05). Intracoronary ACh caused dose-dependent increases of CBF that were blunted in CHF. Apocynin had no effect on the response to ACh in normal dogs but augmented the response to ACh in CHF dogs (P < 0.05). The oxidative stress markers nitrotyrosine and 4-hydroxy-2-nonenal were significantly greater in failing than in normal myocardium. Furthermore, coelenterazine chemiluminescence for O(2)(-) was more than twice normal in failing myocardium, and this difference was abolished by apocynin. Western blot analysis of myocardial lysates demonstrated that the p47(phox) and p22(phox) subunits of NADPH were significantly increased in the failing hearts, while real-time PCR demonstrated that Nox2 mRNA was significantly increased. The data indicate that increased ROS generation in the failing heart is associated with coronary endothelial dysfunction and suggest that NADPH oxidase may contribute to this abnormality.

Gene transfer of extracellular superoxide dismutase improves endothelial function in rats with heart failure

Oxidative stress is associated with endothelial dysfunction in heart failure. The goals of this study were to determine whether 1) gene transfer of extracellular superoxide dismutase (ecSOD) reduces levels of superoxide and improves endothelial function in the aorta and mesenteric artery in rats with heart failure, and 2) the heparin-binding domain (HBD) of ecSOD, by which ecSOD binds to cells, is required for protective effects of ecSOD. Seven weeks after coronary ligation, in rats with heart failure and sham-operated rats, we injected adenoviral vectors intravenously that express ecSOD, ecSOD with deletion of the HBD (ecSODΔHBD), or a control vector. Four days after injection of viruses, responses to acetylcholine, ADP, and sodium nitroprusside were examined in rings of the aorta and mesenteric artery. ecSOD bound to endothelium and increased SOD activity in the aorta after gene transfer of ecSOD, not ecSODΔHBD. Gene transfer of ecSOD, but not ecSODΔHBD, reduced levels of superoxide and improved relaxation to acetylcholine and ADP in the aorta and mesenteric artery from rats with heart failure. Improvement of relaxation to acetylcholine in the mesenteric artery from rats with heart failure after gene transfer of ecSOD was mediated in part by hydrogen peroxide. The major finding of this study is that the HBD of ecSOD is necessary for protection against endothelial dysfunction in rats with heart failure. We speculate that a common gene variant in the HBD of ecSOD, which is a risk factor for ischemic heart disease, may be a risk factor for vascular maladaptation and endothelial dysfunction in heart failure.

Contribution of vascular NAD(P)H oxidase to endothelial dysfunction in heart failure and the therapeutic effects of HMG-CoA reductase inhibitor

BACKGROUND

The vascular NAD(P)H oxidase-derived superoxide anion (O(2)-) plays a crucial role in the pathological progression of hypertension and atherosclerosis, and HMG-CoA reductase inhibitors (statins) have vascular antioxidant effects. However, it is unclear whether the vascular NAD(P)H oxidase is involved in the endothelial dysfunction of congestive heart failure (CHF) and whether HMG-CoA reductase inhibitors (statins) exert their vasoprotective effects in CHF. The present study examined both the involvement of vascular NAD(P)H oxidase in endothelial dysfunction in dogs with tachycardia-induced CHF and the therapeutic effect of a statin (pitavastatin).

METHODS AND RESULTS

Femoral blood flow (FBF) responses to acetylcholine was significantly impaired in the CHF group, but were improved by pitavastatin. Vascular O(2)- production, NAD(P)H oxidase activity and Nox4 and p47phox expression were significantly elevated in CHF compared with the normal group. The elevated O(2)-production in the CHF group was suppressed by the NAD(P)H oxidase inhibitor, apocynin, to the normal level. In contrast, neither the gene expression nor the activity of endothelial nitric oxide synthase (eNOS) differed significantly between the normal and CHF groups. However, pitavastatin significantly suppressed O(2)- production, NAD(P)H oxidase activity and Nox4 and p47phox expression and increased eNOS expression and activity compared with the CHF group.

CONCLUSIONS

The activated vascular NAD(P)H oxidase contributes to endothelial dysfunction in CHF, which was partly improved by pitavastatin via its inhibition of NAD(P)H oxidase.

Endothelial dysfunction in congestive heart failure: ACE inhibition vs. angiotensin II antagonism

BACKGROUND

Endothelial dysfunction of the vasculature contributes to the elevated peripheral resistance and reduced myocardial perfusion in congestive heart failure (CHF). The present study systematically investigated the effect of angiotensin II (AT(1))- receptor blockade on vascular superoxide (O(2)(-)) production and endothelial dysfunction.

METHODS AND RESULTS

Vasodilator responses and O(2)(-) production were determined in aortic rings from Wistar rats with experimental CHF 10 weeks after extensive myocardial infarction and compared with sham-operated animals (Sham). Rats were either treated with placebo (P), with the AT(1)-receptor antagonist Irbesartan (50 mg kg(-1) day(-1)) or with the ACE inhibitor Trandolapril (0.3 mg kg(-1) day(-1)). In CHF-P, endothelium-dependent, acetylcholine-induced relaxation was significantly attenuated compared with Sham-P. Chronic treatment with Trandolapril or Irbesartan significantly improved endothelium-dependent relaxation. Aortic O(2)(-) formation was markedly increased in CHF, and was not significantly affected by Trandolapril treatment, while it was reduced by Irbesartan. eNOS expression was reduced in CHF and normalised by both treatments.

CONCLUSION

Endothelial vasomotor function in CHF rats was normalised by long-term treatment with an ACE inhibitor or an AT(1)-antagonist. Reduced aortic eNOS expression was normalised by both treatments, whereas aortic superoxide formation was only reduced by the AT(1)-antagonist Irbesartan.