Ischemia increases detectable endothelial nitric oxide synthase in rat and human myocardium

Oxidative Stress and Arginine/Nitric Oxide Pathway in Red Blood Cells Derived from Patients with Prediabetes

The effects of the oral glucose tolerance test (OGTT) on red blood cells (RBCs) have not been thoroughly investigated, although it is known that the ingestion of 75 g of glucose during OGTT results in a systemic state of inflammation and oxidative stress. Therefore, we evaluated the effect of OGTT on oxidative stress and L-arginine/Nitric Oxide (L-Arg/NO) metabolic pathway in RBCs obtained from patients with prediabetes. Blood samples were collected from all participants before (T0) and at 10 (T1), 20 (T2), 30 (T3), 60 (T4), 90 (T5), 120 (T6), 150 (T7), and 180 (T8) minutes after glucose loading. Results showed a significant increase in oxidative stress status characterized by a rise in the GSSG/GSH ratio at T4 and T6 that increased in parallel with a reduction of NO production in RBCs. In addition, in this time frame, increased exposure of phosphatidylserine on RBCs membrane was observed. These metabolic modifications were rescued at T8, together with an increase in activated RBC NO synthase expression. These findings provide a possible explanation of the phenomena occurring after glucose loading and suggest that, even in the early stages of diabetes, it may be important to avoid acute variations in glycemia in order to prevent diabetic complications.

Effects of Remote Ischaemic Preconditioning on the Internal Thoracic Artery Nitric Oxide Synthase Isoforms in Patients Undergoing Coronary Artery Bypass Grafting

Remote ischaemic preconditioning (RIPC) is a medical procedure that consists of repeated brief periods of transient ischaemia and reperfusion of distant organs (limbs) with the ability to provide internal organ protection from ischaemia. Even though RIPC has been successfully applied in patients with myocardial infarction during coronary revascularization (surgery/percutaneous angioplasty), the underlying molecular mechanisms are yet to be clarified. Thus, our study aimed to determine the role of nitric oxide synthase (NOS) isoforms in RIPC-induced protection (3 × 5 min of forearm ischaemia with 5 min of reperfusion) of arterial graft in patients undergoing urgent coronary artery bypass grafting (CABG). We examined RIPC effects on specific expression and immunolocalization of three NOS isoforms — endothelial (eNOS), inducible (iNOS) and neuronal (nNOS) in patients’ internal thoracic artery (ITA) used as a graft. We found that the application of RIPC protocol leads to an increased protein expression of eNOS, which was further confirmed with strong eNOS immunopositivity, especially in the endothelium and smooth muscle cells of ITA. The same analysis of two other NOS isoforms, iNOS and nNOS, showed no significant differences between patients undergoing CABG with or without RIPC. Our results demonstrate RIPC-induced upregulation of eNOS in human ITA, pointing to its significance in achieving protective phenotype on a systemic level with important implications for graft patency.

Nebivolol compared with metoprolol for erectile function in males undergoing coronary artery bypass graft

OBJECTIVE

The aim of this study was to evaluate erectile function in males undergoing coronary artery bypass graft (CABG) while on two different adrenoceptor beta-blocker regimens, namely nebivolol and metoprolol. We hypothesize that the negative effects of cardiopulmonary bypass on erectile function may be possibly attenuated by preferring a vasodilating selective β1-blocker, nebivolol, to metoprolol as an anti-ischemic and antiarrhythmic agent in males undergoing CABG.

METHODS

This randomized, double-blind, prospective clinical study was conducted in patients scheduled for CABG surgery between February 2012 and June 2014. A total of 60 consecutive patients who met inclusion criteria were randomized and divided into the following two groups: N group, which received 5 mg of nebivolol orally for 2 weeks before surgery plus 12 weeks after surgery or M group, which received 50 mg of metoprolol orally for the same period. All patients were evaluated by the erectile function domain of the International Index of Erectile Function-5 (IIEF-5) at the time of admission (before starting the beta-blocker) and 3 months after surgery.

RESULTS

In the metoprolol group, the mean IIEF-5 score decreased significantly from a baseline of 15.2±5.8 to 12.9±5.8 (p<0.001), but in the nebivolol group, this difference was not significant (from a baseline 12.9±5.5 to 12.4±5.5, p=0.053). In all patients, the mean IIEF-5 score decreased significantly from a baseline of 14.0±5.7 to 12.6±5.6 (p<0.001).

CONCLUSION

Although erectile function in males undergoing CABG surgery decreases when metoprolol is used, nebivolol exerts protective effects on erectile function against the disruptive effects of cardiopulmonary bypass in patients undergoing CABG.

Nitric oxide synthase regulation of cardiac excitation-contraction coupling in health and disease

Significant advances in our understanding of the ability of nitric oxide synthases (NOS) to modulate cardiac function have provided key insights into the role NOS play in the regulation of excitation-contraction (EC) coupling in health and disease. Through both cGMP-dependent and cGMP-independent (e.g. S-nitrosylation) mechanisms, NOS have the ability to alter intracellular Ca(2+) handling and the myofilament response to Ca(2+), thereby impacting the systolic and diastolic performance of the myocardium. Findings from experiments using nitric oxide (NO) donors and NOS inhibition or gene deletion clearly implicate dysfunctional NOS as a critical contributor to many cardiovascular disease states. However, studies to date have only partially addressed NOS isoform-specific effects and, more importantly, how subcellular localization of NOS influences ion channels involved in myocardial EC coupling and excitability. In this review, we focus on the contribution of each NOS isoform to cardiac dysfunction and on the role of uncoupled NOS activity in common cardiac disease states, including heart failure, diabetic cardiomyopathy, ischemia/reperfusion injury and atrial fibrillation. We also review evidence that clearly indicates the importance of NO in cardioprotection. This article is part of a Special Issue entitled "Redox Signalling in the Cardiovascular System".

Phosphorylation of myocardial eNOS is altered in patients suffering from type 2 diabetes

The present study investigated whether endothelial nitric oxide synthase (eNOS) activation may be dysregulated in cardiac tissue of patients suffering from type 2 diabetes (T2D). We performed immunohistochemical measurements of translocated eNOS activation as well as eNOS phosphorylation at Ser1177, Thr495, Ser 635, Ser114, and of the protein kinase B (Akt) in isolated right atrial trabeculae of patients undergoing cardiac bypass or valve surgery with (n = 12, 68.1 ± 2.5 yr) and without T2D (n = 12, 64.7 ± 2.7 yr). In addition, we investigated oxidative (8-isoprostane) and nitrosative stress markers (nitrotyrosine) as well as the effect of pharmacological stimulation of angiotensin (AT)-receptors on eNOS-phosphorylation. Translocation-dependent eNOS activation was similar in both groups. The same holds true for eNOS phosphorylation at Ser114. eNOS phosphorylation at Ser635 was significantly increased, whereas eNOS phosphorylation of Ser1177 was significantly decreased in the diabetic group paralleled by a decrease in phosphorylation of Akt and Thr495. These alterations were accompanied by a significant decrease in nitrotyrosine. After application of angiotensin II (10 μM, 2 min) for investigation of the AT-receptor-dependent eNOS stimulation, we did not find differences between the increases in eNOS Ser1177-phosphorylation in the nondiabetic (+39.7 ± 23.5%) and in the diabetic group (32.22 ± 11.45%). A simultaneous increase in Akt phosphorylation could not be observed. The present study indicates that T2D goes along with a decrease in eNOS phosphorylation at Ser1177 under basal conditions in cardiac tissue. Whether this may be attributed to the insulin resistance of cardiac muscle has to be further investigated. Receptor-stimulated eNOS activation still works at least for angiotensin II-dependent eNOS activation.

Influence of intermittent hypoxia interval training on exercise-dependent erythrocyte NOS activation and blood pressure in diabetic patients

NOS-activation in erythrocytes (eryNOS) is impaired in patients suffering from type 2 diabetes. We investigated the effect of physical exercise on eryNOS activation and whether 6 week hypoxia interval training may alter this process. Male patients with diabetes mellitus type 2 (NIDDM, n = 12; age, 61.3 ± 8.4 years; BMI, 29.8 ± 3.7 kg/m2) underwent physical exercise training before and after 6 week hypoxia interval training. Training was conducted 4 times per week for 90 min at 15.4–12.7 Vol% of inspired oxygen. Vital parameters were recorded. Before hypoxia intervention, eryNOS phosphorylation at serine1177decreased significantly during exercise (basal 17.4 ± 12.0 compared with exercise 8.4 ± 9.2 arbitrary grey values (arGV); P < 0.05). After 6 weeks of hypoxia intervention, eryNOS–pSer1177(2.2 ± 2.5 arGV) was significantly lower at baseline. Ergometry showed an increase (7.6 ± 3.0 arGV; P < 0.05) followed by a decrease to almost baseline levels after 30 min (3.8 ± 1.5 arGV). Maximal exercise capacity and O2-uptake ([Formula: see text]  max) increased significantly. The effects were independent from exercise-induced elevation of blood pressure. Exercise-dependent eryNOS phosphorylation at serine1177was increased similar to that described for the endothelium in diabetic patients. EryNOS dysregulation was partially restored after intermittent hypoxia training.

β-amyloid decreases detectable endothelial nitric oxide synthase in human erythrocytes: a role for membrane acetylcholinesterase

Until few years ago, many studies of Alzheimer's disease investigated the effects of this syndrome in the central nervous system. Only recently, the detection of amyloid beta peptide (Aβ) in the blood has evidenced the necessity to extend studies on extraneuronal cells, particularly on erythrocytes. Aβ is also present in brain capillaries, where it interacts with the erythrocytes, inducing several metabolic and functional alterations. Recently, functionally active endothelial type nitric oxide synthase (eNOS) was discovered in human erythrocytes. The goal of the present study was to evidence the effect of Aβ on erythrocyte eNOS. We found that Aβ following to 24-h exposure causes a decrease in the immune staining of erythrocyte eNOS. Concurrently, Aβ alters erythrocyte cell morphology, decreases nitrites and nitrates levels, and affects membrane acetylcholinesterase activity. Propidium, an acetylcholinesterase inhibitor, was able to reverse the effects elicited by Aβ. These events could contribute to the vascular alterations associated with Alzheimer's disease disease.

eNOS phosphorylation and translocation are altered in male but not female mice by increased activation of the Gαq protein

Little is known about sex-dependent physiological and pathophysiological differences in cardiac endothelial nitric oxide synthase (eNOS) expression and activation. Therefore, we investigated cardiac morphology and eNOS protein expression, including its translocation-dependent activation and phosphorylation, in cardiac tissue of male and female wild-type mice and transgenic heart-failure mice having a cardiac-specific, 5-fold overexpression of the Gαq protein. In addition, we measured calcineurin protein expression. Heart-to-body weight ratio was increased in Gαq mice. Female wild-type mice showed higher eNOS protein expression and activation (translocation and phosphorylation) than did wild-type males. In cardiac tissue of Gαq mice, these sex-dependent differences remained or were enhanced. Protein expression of the catalytic subunit calcineurin A, which has been shown to dephosphorylate eNOS, was higher in wild-type males than in wild-type females. These differences were increased in the Gαq mice model. We conclude that sex differences exist in cardiac eNOS protein expression and phosphorylation. Increased activation of the Gαq protein appears to alter eNOS protein expression and phosphorylation only in males.

Biochemical Detection of cGMP From Past to Present: An Overview

Cyclic guanosine monophosphate (cGMP), generated via the guanylate cyclase (GC)-catalyzed conversion from GTP, is unequivocally recognized as crucial second messenger, intimately involved in the regulation of a broad range of physiological processes such as long term potentiation, blood pressure regulation, or platelet aggregation (for review: Hobbs 2000). Since its first identification in rat urine by Ashman and co-workers (1963), various approaches have been conceived and established to quantify cGMP in biological samples, or to detect cGMP as the reaction product of enzymatic assays, allowing the determination of kinetic parameters. These approaches have evolved from laborious handling of small numbers of samples with average sensitivity to highly developed biochemical detection assays allowing the processing of very large numbers of samples. The present article focuses upon the history of biochemical cGMP detection from the pioneering work of the early years to the actual state-of-the-art approaches for the detection of this important biological messenger.

Intensive exercise induces changes of endothelial nitric oxide synthase pattern in human erythrocytes

The synthesis of nitric oxide (NO) in the circulation has been attributed exclusively to the vascular endothelium, especially to endothelial cells. Recently, it has been demonstrated that red blood cells (RBCs) express the endothelial NOS isoform (eNOS). In addition, RBCs have been assumed to metabolize large quantities of NO due to their high content of hemoglobin. In addition to its known action on endothelial cells, NO seems to possess cardiovascular effects via regulation of RBC deformability. To get a better understanding of the question whether RBCs endothelial NOS (eNOS) is affected by intensive exercise undertaken by elite athletes, the present study aimed to investigate eNOS content, activated eNOS, phosphorylation states of eNOS (eNOSSer(116), eNOSSer(1177), eNOSThr(495)) and nitrotyrosine in erythrocytes of international-class field hockey players following a two-day long intensive training camp. Blood samples were taken before and immediately after the training camp. The athletes were required to complete at least two training sessions per day. The results showed that eNOS content, activated eNOS, eNOSSer(1177), and nitrotyrosine were significantly (p<0.05) down-regulated after the training camp. In contrast, eNOSSer(116), and eNOSThr(495) did not show significant changes, although eNOSThr(495) (p=0.081) tended to decrease. Hemoglobin and hematocrit were significantly decreased after training camp. In conclusion, this study gains new insights into a possible down-regulation of eNOS and NO production in human RBCs following high intensity exercises. It can be speculated that the reduction of eNOS and the combined reduction of eNOS activity influence erythrocyte deformability and lead subsequently to a rheological impairment.

Effects of the beta3-adrenergic agonist BRL 37344 on endothelial nitric oxide synthase phosphorylation and force of contraction in human failing myocardium

BACKGROUND

In nonfailing myocardium, beta(3)-adrenergic signaling causes a decrease in contractility via endothelial nitric oxide synthase (eNOS) activation and nitric oxide (NO) release. This study investigates the hypothesis that beta(3)-adrenergic signaling undergoes alterations in failing myocardium.

METHODS

We compared eNOS- and beta(3)-adrenoceptor expression using Western blot analysis in human nonfailing myocardium versus failing myocardium. With the use of immunohistochemistry, we investigated the distribution of the beta(3)-adrenoceptor protein and eNOS translocation and phosphorylation under basal conditions. beta(3)-adrenergic, eNOS activation, and inotropy were measured in failing myocardium using BRL37344 (BRL, a beta(3)-adrenoceptor agonist).

RESULTS

beta(3)-adrenoceptor expression was increased in failing myocardium. Under basal conditions, Akt- and eNOS(Ser1177) phosphorylation were reduced in failing myocardium. During stimulation with BRL in failing myocardium, a further dephosphorylation of eNOS(Ser1177) and Akt was observed, whereas eNOS(Ser114) phosphorylation was increased. These results suggest a deactivation of eNOS via beta(3)-adrenergic stimulation. Nevertheless, BRL decreased contractility in failing myocardium, but this effect was not observed in the presence of the NO blocker L-NMA. In failing myocardium, the beta(3)-adrenoceptor was predominantly expressed in endothelial cells. In the cardiomyocytes, the beta(3)-adrenoceptor was mainly located at the intercalated disks.

CONCLUSION

In failing cardiomyocytes, beta(3)-adrenergic stimulation seems to deactivate rather than activate eNOS. At the same time, beta(3)-adrenergic stimulation induced a NO-dependent negative inotropic effect. Because beta(3)-adrenoceptors are expressed mainly in the endothelium in failing myocardium, our observations suggest a paracrine-negative inotropic effect via NO liberation from the cardiac endothelial cells.

Functional role of HSP90 complexes with endothelial nitric-oxide synthase (eNOS) and calpain on nitric oxide generation in endothelial cells

Although several reports have indicated that eNOS is a highly sensitive calpain substrate, the occurrence of a concomitant Ca(2+)-dependent activation of the synthase and of the protease has never been analyzed in specific direct experiments. In this study, we have explored in vivo how eNOS can undergo Ca(2+)-dependent translocation and activation, protected against degradation by activated calpain. Here we demonstrate that following a brief exposure to Ca(2+)-loading, the cytosolic eNOS-HSP90 complex recruits calpain in a form in which the chaperone and the synthase are almost completely resistant to digestion by the protease. Furthermore, in the presence of the HSP90 inhibitor geldanamycin, a significant decrease in NO production and an extensive degradation of eNOS protein occurs, indicating that dissociation from membranes and association with the chaperone is correlated to the protection of the synthase. Experiments with isolated membrane preparations confirm the primary role of HSP90 in dissociation of eNOS from caveolae. Prolonged exposure of cells to Ca(2+)-loading resulted in an extensive degradation of both eNOS and HSP90, accompanied by a large suppression of NO production. We propose that the protective effect exerted by HSP90 on eNOS degradation mediated by calpain represents a novel and critical mechanism that assures the reversibility of the intracellular trafficking and activation of the synthase.

Effects ofl-arginine andl-NAME on chronic partial bladder outlet obstruction in rabbit

Nitric oxide (NO) is synthesized from l-arginine by nitric oxide synthase (NOS). NOS can be inhibited by NG-nitro-l-arginine methyl ester (l-NAME) and stimulated by supplementing the diet with l-arginine. The aim of this study was to investigate the influence of NOS activity on the response of rabbits to chronic partial bladder outlet obstruction (PBOO). Surgical PBOOs (2 and 8 wk) were performed on male New Zealand White rabbits. Before obstruction, one-third of the animals were premedicated for 7 days with l-NAME and another third with l-arginine. The results are summarized as follows. First, bladder weight after 8-wk PBOO was significantly lower in animals treated with l-arginine compared with both untreated and rabbits treated with l-NAME. Second, contractile function decreased progressively with PBOO duration. However, after 8 wk of PBOO, the l-arginine group had significantly greater contractile function compared with the no-treatment group, and the l-NAME group had significantly lower contractile function compared with the no-treatment group. Third, at 8 wk following PBOO, the level of protein oxidation and nitration was lowest for the l-arginine group and highest in the l-NAME group. These studies clearly demonstrated that increasing blood flow by stimulating NOS significantly protected the bladder from PBOO dysfunctions, whereas inhibiting blood flow by l-NAME enhanced the dysfunctions mediated by PBOO.

Nebivolol induces eNOS activation and NO-liberation in murine corpus cavernosum

Erectile function is critically dependent upon the activation of the endothelial nitric oxide synthase (eNOS) in the smooth muscle cells of penile corpus cavernosum tissue. Nebivolol is a beta(1)-selective beta-adrenoceptor blocker (beta-ARB) with additional vasodilating properties, which have been attributed to eNOS-activation. Our study investigated whether nebivolol is able to increase eNOS activity in erectile tissue. Murine penile tissue was incubated in an organ bath under control conditions and in the presence of nebivolol or metoprolol. Immunofluorescence staining was performed using specific antibodies against eNOS-activation or eNOS-serine 1177 phosphorylation. Corpus cavernosum smooth muscle tissue was identified using a smooth muscle actin antibody. In addition, slices of murine erectile tissue were incubated with diaminofluorescein (DAF), a specific fluorescence marker for NO-liberation. Under control conditions and after application of metoprolol, we observed a small eNOS-activation and serine 1177-phosphorylation in murine corpus cavernosum tissue. A significant increase in eNOS-activation and serine 1177-phosphorylation of eNOS was observed only in the presence of nebivolol (10 muM). These alterations of the eNOS protein induced after application of nebivolol were associated with a time-dependent increase in DAF fluorescence in murine erectile tissue. We conclude that beta-adrenoceptor blockers differentially influence erectile tissue. Since cardiovascular diseases are often associated with the development of erectile dysfunction, the nebivolol-induced eNOS-activation in corpus cavernosum may be beneficial when treating patients suffering from cardiovascular disease.

CD151 gene delivery activates PI3K/Akt pathway and promotes neovascularization after myocardial infarction in rats

Our previous study showed that CD151 promotes neovascularization and improves blood perfusion in a rat hindlimb ischemia model. In this study, we investigated whether CD151 promotes neovascularization and improves ventricular function after myocardial infarction in rats and the mechanisms involved. Rats were subjected to sham surgery or coronary artery ligation. We used rAAV for direct delivery of the human CD151 gene into the rat myocardium. At 4 weeks after coronary artery ligation, human CD151 mRNA was detected using RT-PCR. Measurement of capillary density was evaluated using immunostaining for von Willebrand factor, and hemodynamic variables and physiological parameters were monitored. Western blot analysis for CD151, PI3K, phosphor-Akt, total Akt, phosphor-eNOS, and total eNOS was performed. In addition, we also observed the effect of CD151 on the expression of VEGF using Western blot analysis. CD151 gene delivery could increase the expression of CD151 at gene and protein levels. Overexpression of CD151 could increase the number of microvessels in the ischemic myocardium and significantly improved the hemodynamic variables after myocardial infarction. In addition, CD151 could activate the PI3K pathway, including activation of Akt and eNOS, but did not affect the expression of VEGF. This study suggested that CD151 could promote neovascularization and improve ventricular function after myocardial infarction in rats. The mechanism may be that CD151 can activate the PI3K pathway and promote neovascularization via the PI3K pathway, without affecting ischemia-induced VEGF expression.

Increased cerebral and renal endothelial nitric oxide synthase gene expression after cardiopulmonary bypass in the rat

OBJECTIVE

Hemodilution and endothelial nitric oxide synthase genetic polymorphism may contribute to cerebral and renal injury after cardiopulmonary bypass. This study tested the hypothesis that cardiopulmonary bypass and anemia stimulate an increase in cerebral and renal endothelial nitric oxide synthase gene expression in an experimental model of cardiopulmonary bypass.

METHODS

Anesthetized rats underwent a sham procedure without cardiopulmonary bypass (sham, n = 5), normothermic bypass for 1 hour (CPB, n = 7), or bypass plus hemodilutional anemia (CPB anemia, n = 9). After 24 hours of recovery, RNA was extracted from the cerebral cortex, renal cortex, and renal medulla. Quantitative reverse transcriptase polymerase chain reaction was used to assess endothelial nitric oxide synthase messenger RNA levels in brain and kidney tissues.

RESULTS

The hemoglobin concentration of anemic CPB rats was significantly lower than that of nonanemic rats on bypass (64 +/- 5 vs 99 +/- 8 g x L(-1), P < .001). Cerebral cortical endothelial nitric oxide synthase messenger RNA levels were increased after cardiopulmonary bypass relative to those of the sham group (11.2 +/- 4.2 vs 6.3 +/- 1.5 fg, P = .031), without a further increase in anemic rats. Renal medullary endothelial nitric oxide synthase messenger RNA levels were significantly higher in the CPB anemia group than in the sham and CPB groups (7.1 +/- 4.4 fg vs 1.8 +/- 0.4 fg vs 3.0 +/- 0.6 fg, P < .001). Renal cortical endothelial nitric oxide synthase messenger RNA levels did not change significantly.

CONCLUSIONS

Normothermic cardiopulmonary bypass was associated with higher endothelial nitric oxide synthase messenger RNA levels in kidney and brain than was the sham procedure 24 hours after cardiopulmonary bypass. Anemia accentuated the increase in renal medullary, but not cerebral cortical, endothelial nitric oxide synthase expression. These data provide an approach for exploring potential mechanisms by which endothelial nitric oxide synthase may contribute to renal and cerebral dysfunction after cardiopulmonary bypass and anemia.

Effect of Thawing on Nitric Oxide Synthase III and Apoptotic Markers in Cryopreserved Human Allografts

BACKGROUND

Previous investigations suggested apoptosis as a contributing factor to early failure of allograft heart valves. As myocardial apoptosis may be induced by nitric oxide (NO) release, this study investigated NO synthase [NOS-III] activation and apoptosis induction in human cryopreserved allografts during the thawing process.

METHODS

Frozen myocardial tissue from ten human allograft heart valves, unsuitable for implantation, was submitted to the following conditions: (1) thawing in paraformaldehyde (Control), thawing according to the standard clinical protocol (Standard), standard-thawing with addition of the NOS-inhibitor N-omega-nitro-l-arginine (L-NA; Standard-LNA), and standard thawing with the NOS-stimulator angiotensin II (Standard-AT-II). Cryo-thin sections were investigated by immunostaining for activated NOS-III, cyclic guanosine monophosphate (cGMP), activated caspase-3, and poly-ADP-ribose polymerase (PARP). Quantitative analyses was performed by television densitometry.

RESULTS

For activated NOS-III, gray unit values were significantly higher in the Standard and Standard-AT-II group than in the Control and Standard-LNA groups (p < 0.001). Gray unit values for cGMP, a downstream NO-signal-pathway molecule, showed results grossly corresponding to NOS-III activation. Activated caspase-3 and PARP showed high levels of expression in all groups with no significant differences.

CONCLUSIONS

Significant activation of NOS-III and subsequent NO-cGMP signal pathway occurs in human cryopreserved allografts during the thawing process and can be significantly reduced by a NOS-III inhibitor administered during thawing. Activation of the apoptosis pathway is also present after thawing, which was not correlated to NOS-III activation. Further experimental investigation focused on the time course and mechanisms of apoptosis and NOS-III activation are required to evaluate NOS and(or) apoptosis inhibitors as therapeutic strategies for improved allograft preservation.

β3-Adrenergic eNOS stimulation in left ventricular murine myocardium

This study investigates mechanisms underlying β3-adrenergic activation of the endothelial nitric oxide synthase (eNOS) in myocardial tissue of wild-type (WT) and β3-adrenoceptor knockout (β3-KNO) mice, in the absence and presence of BRL 37344 (BRL), the preferential β3-adrenoceptor selective agonist. Nitric oxide (NO)-liberation was measured after the application of BRL (10 µmol/L), using fluorescence dye diaminofluorescein (DAF), in left ventricular cardiac preparations. Phosphorylation of eNOSSer1177, eNOSThr495, eNOSSer114, and eNOS translocation, and alterations of 8-isoprostaglandin F2α (a parameter for reactive oxygen radical generation), after application of BRL (10 µmol/L), were studied using immunohistochemical stainings in isolated, electrically stimulated (1 Hz) right atrial (RA) and left ventricular (LV) myocardium. An increased NO release after BRL application (10 µmol/L) was observed in the RA and LV myocardial tissue of WT mice, but not in β3-KNO mice. This NO liberation in WT mice was paralleled by an increased eNOSSer1177, but not eNOSThr495, phosphorylation. A cytosolic eNOS translocation was observed after the application of BRL (10 µmol/L) only in the RA myocardial tissue of WT mice. A BRL (10 µmol/L)-dependent increase in eNOSSer114 phosphorylation was observed only in the LV myocardial tissue of WT mice; this was paralleled by an increase in 8-isoprostaglandin F2α. In murine myocardium, 3 β3-adrenoceptor-dependent activation pathways for eNOS exist (i.e., a translocation and phosphorylation of eNOSSer1177 and eNOSSer114). These pathways are used in a regional-dependent manner. β3-adrenergic oxygen-derived free radical production might be important in situations of enhanced β3-adrenoceptor activation, as has been described in human heart failure.

Increased Ca2+ sensitivity and protein expression of SERCA 2a in situations of chronic beta3-adrenoceptor deficiency

This study investigated the influence of chronic beta(3)-adrenoceptor deficiency on myocardial function. Therefore, we investigated Ca(2+)-regulatory proteins, SERCA 2a activity, and myofibrillar and mitochondrial function in hearts of wild-type (WT, n=7) and beta(3)-adrenoceptor knockout mice (beta(3)-KNO, n=7). Morphometric heart analysis showed no difference between WT and beta(3)-KNO. No alterations were observed for the protein expression of the ryanodine receptor or phospholamban. However, in beta(3)-KNO mice, protein expression of SERCA 2a and phospholamban phosphorylation were significantly increased. These changes were accompanied by an increased SERCA 2a activity in beta(3)-KNO. Alterations in phospholamban phosphorylation were independent of alterations in beta(1)/beta(2)-adrenoceptor distribution and protein expression of G proteins in beta(3)-KNO. Measurement of myofibrillar Ca(2+) sensitivity showed no difference in the Ca(2+)/force relation for WT and beta(3)-KNO. The same seems to hold true for mitochondrial function since the protein expressions of cytochrome c, uncoupling protein 3 and cytochrome c oxidase subunit IV were similar in WT and beta(3)-KNO. The conclusion is that depression of beta(3)-adrenergic stimulation may modulate the protein expression of SERCA 2a and phospholamban phosphorylation, thereby improving sarcoplasmic reticulum Ca(2+) uptake. Thus, beta(3)-adrenergic depression may be a therapeutic aim in situations of impaired SERCA 2a activity, e.g. for the treatment of heart failure.

ENOS is not activated by nebivolol in human failing myocardium

Nebivolol is a highly selective beta(1)-adrenoceptor blocker with additional vasodilatory properties, which may be due to an endothelial-dependent beta(3)-adrenergic activation of the endothelial nitric oxide synthase (eNOS). beta(3)-adrenergic eNOS activation has been described in human myocardium and is increased in human heart failure. Therefore, this study investigated whether nebivolol may induce an eNOS activation in cardiac tissue. Immunohistochemical stainings were performed using specific antibodies against eNOS translocation and eNOS serine(1177) phosphorylation in rat isolated cardiomyocytes, human right atrial tissue (coronary bypass-operation), left ventricular non-failing (donor hearts) and failing myocardium after application of the beta-adrenoceptor blockers nebivolol, metoprolol and carvedilol, as well as after application of BRL 37344, a specific beta(3)-adrenoceptor agonist. BRL 37344 (10 microM) significantly increased eNOS activity in all investigated tissues (either via translocation or phosphorylation or both). None of the beta-blockers (each 10 microM), including nebivolol, increased either translocation or phosphorylation in any of the investigated tissues. In human failing myocardium, nebivolol (10 microM) decreased eNOS activity. In conclusion, nebivolol shows a tissue-specific eNOS activation. Nebivolol does not activate the endothelial eNOS in end-stage human heart failure and may thus reduce inhibitory effects of NO on myocardial contractility and on oxidative stress formation. This mode of action may be of advantage when treating heart failure patients.

Zur Funktion des β3-Adrenozeptors am Herzen: Signaltransduktion, inotroper Effekt und therapeutischer Ausblick

Beta-adrenergic stimulation is an important regulatory mechanism of cardiac function. Next to beta1- and beta2-adrenoceptors, the expression of a third beta-adrenoceptor population, the beta3-adrenoceptor, has recently been evidenced in the human heart. Stimulation of cardiac beta3-adrenoceptors leads to a decrease in contractility via a release of nitric oxide (NO). In this context, different molecular mechanisms of endothelial nitric oxide synthase (eNOS) activation have been uncovered to occur as a consequence of beta3-adrenergic stimulation. In both nonfailing and failing myocardium, beta3-adrenergic stimulation may have a protective effect against excessive chatecolaminergic stimulation as it occurs during somatic and mental stress and during heart failure. For this reason, the beta3-adrenoceptor is discussed as a possible target for the pharmacological therapy of heart failure.

MECHANISMS UNDERLYING NEBIVOLOL-INDUCED ENDOTHELIAL NITRIC OXIDE SYNTHASE ACTIVATION IN HUMAN UMBILICAL VEIN ENDOTHELIAL CELLS

1. Nebivolol (NEB) has been shown to be a selective blocker of beta1-adrenoceptors with additional vasodilating properties that are mediated, at least in part, by an endothelial-dependent liberation of nitric oxide (NO). In the present study, we investigated the underlying mechanisms of NEB-induced vasodilation. 2. Immunohistochemical staining of endothelial nitric oxide synthase (eNOS) was performed in the absence and presence of NEB in human umbilical vein endothelial cells (HUVEC). In addition, we measured the release of nitric oxide (NO) using diaminofluorescein. Metoprolol (MET) was used for comparison. 3. Nebivolol, but not MET (each at 10 micromol/L), caused a time-dependent increase in NO release from HUVEC, as demonstrated by an increase in DAF fluorescence at 0 versus 10 min (+234 +/- 7 and 55 +/- 22% basal, respectively). Blockade of beta3-adrenoceptors by SR 59230A (1 micromol/L) partially reduced the NEB-induced increase in DAF fluorescence. Complete inhibition of NEB-induced NO liberation was achieved by the simultaneous blockade of beta3-adrenoceptors and oestrogen receptors (with 1 micromol/L ICI 182,780). 4. Application of NEB significantly increased eNOS translocation and serine 1177 phosphorylation of eNOS. However, NEB did not alter eNOS-phosphorylation at threonine 495 and at serine 114. 5. In conclusion, the endothelium-dependent NO liberation induced by NEB is due to stimulation of beta3-adrenoceptors and oestrogen receptors and coincides with eNOS translocation and a phosphorylation at eNOS-serine 1177. These characteristics of NEB may be beneficial not only when treating patients suffering from cardiovascular disease, but may also prevent further deterioration of endothelial dysfunction.

Crataegus Special Extract WS® 1442 Induces an Endothelium-Dependent, NO-mediated Vasorelaxation via eNOS-Phosphorylation at Serine 1177

PURPOSE

This study investigates the influence of WS(R) 1442, a special extract of Crataegus leaves with flowers, on the relaxation of rat aorta and human mammarian artery (coronary bypass patients).

METHODS

Experiments were performed in the presence and absence (mechanical disruption) of endothelium. In addition, we investigated three fractions of WS(R) 1442 (fraction A: lipophilic, containing flavonoids and oligomeric procyanidins (OPC), fraction B: hydrophilic, containing flavonoids and low molecular weight OPC, fraction C: hydrophilic, essentially flavonoid-free and rich in high molecular weight OPC).

RESULTS

WS 1442 induced a concentration-dependent vasodilation in isolated vessel rings that had been precontracted by 10 microM phenylephrine (concentration for halfmaximal relaxation (IC(50)): rat: 15.1 +/- 0.6 microg/ml (n = 7), human: 19.3 +/- 3.4 microg/ml (n = 6)). The maximal vasorelaxation induced after application of 100 microg of WS 1442 was 75.0 +/- 5.7% (rat) and 79.2 +/- 5.8% (human) of the papaverine (0.1 mM)-induced vasodilation. If the experiments were performed in the presence of L-nitroarginine methylester (10 microM, eNOS-inhibition) or after mechanical disruption of the endothelium, no vasorelaxation was observed in the presence of WS 1442. The vasorelaxant properties of WS 1442 were mediated by fraction C. WS 1442 induced an NO-liberation from human coronary artery endothelial cells as measured by diaminofluorescein. WS 1442 induced eNOS-activation was due to a phosphorylation at serine 1177. No eNOS-translocation or phosphorylation at serine 114 or threonine 495 was observed after application of WS 1442.

CONCLUSIONS

It is concluded that WS 1442, induces an endothelium-dependent, NO-mediated vasorelaxation via eNOS phosphorylation at serine 1177.

Endostatin, the proteolytic fragment of collagen XVIII, induces vasorelaxation

Collagen XVIII is an important component of the extracellular matrix and is expressed in basement membranes. Its degradation results in the generation of endostatin claimed to possess antiangiogenic activity. To date, only limited knowledge exists with regard to the cellular signaling of this molecule. We show in single-cell measurements using the Ca2+ indicator fura-2 acetoxy methylester (fura-2 AM) and the nitric oxide (NO) indicator 4,5-diaminofluorescein diacetate that application of endostatin (ES) (5 pmol/L, 100 ng/mL) induced Ca2+ spikes and an increase of NO production in human and murine endothelial cells. The NO response was independent of an increase in cytosolic Ca2+ and blocked by the endothelial NO synthase (eNOS) inhibitor NG-nitro-L-arginine methyl ester and by incubation with pertussis toxin known to inhibit G(i/o) proteins. The physiological relevance of this novel signaling pathway of ES was assessed with isometric force measurements in large and small arteries of mouse. Physiological concentrations of ES were found to decrease vascular tone in an endothelium-dependent manner. This occurred via an Arg-Gly-Asp (RGD) peptide-independent pathway through activation of G(i/o) proteins, phosphatidylinositol 3-kinase, Akt, and eNOS. We conclude that the proteolytic matrix fragment ES is a prominent vasorelaxing agent. Because ES is constantly released into the blood, it is a novel regulator of blood pressure and, therefore, represents an interesting pharmacological target.

Hypoxia induces production of nitric oxide and reactive oxygen species in glomus cells of rat carotid body

The carotid body is an arterial chemoreceptor organ that senses arterial pO(2) and pH. Previous studies have indicated that both reactive oxygen species (ROS) and nitric oxide (NO) are important potential mediators that may be involved in the response of the carotid body to hypoxia. However, whether their production by the chemosensitive elements of the carotid body is indeed oxygen-dependent is currently unclear. Thus, we have investigated their production under normoxic (20% O(2)) and hypoxic (1% O(2)) conditions in slice preparations of the rat carotid body by using fluorescent indicators and confocal microscopy. NO-synthesizing enzymes were identified by immunohistochemistry and histochemistry, and the subcellular localization of the NO-sensitive indicator diaminofluorescein was determined by a photoconversion technique and electron microscopy. Glomus cells of the carotid body responded to hypoxia by increases in both ROS and NO production. The hypoxia-induced increase in NO generation required (to a large extent, but not completely) extracellular calcium. Glomus cells were immunoreactive to endothelial NO synthase but not to the neuronal or inducible isoforms. Ultrastructurally, the NO-sensitive indicator was observed in mitochondrial membranes after exposure to hypoxia. The data show that glomus cells respond to exposure to hypoxia by the enhanced production of both ROS and NO. NO production by glomus cells is probably mediated by endothelial NO synthase, which is activated by calcium influx. The presence of NO indicator in mitochondria suggests the hypoxic regulation of mitochondrial function via NO in glomus cells.

The influence of propofol on P-selectin expression and nitric oxide production in re-oxygenated human umbilical vein endothelial cells

BACKGROUND

Reperfusion injury is characterized by free radical production and endothelial inflammation. Neutrophils mediate much of the end-organ injury that occurs, requiring P-selectin-mediated neutrophil-endothelial adhesion, and this is associated with decreased endothelial nitric oxide production. Propofol has antioxidant properties in vitro which might abrogate this inflammation.

METHODS

Cultured human umbilical vein endothelial cells were exposed to 20 h of hypoxia and then returned to normoxic conditions. Cells were treated with saline, Diprivan 5 microg/l or propofol 5 microg/l for 4 h after re-oxygenation and were then examined for P-selectin expression and supernatant nitric oxide concentrations for 24 h. P-selectin was determined by flow cytometry, and culture supernatant nitric oxide was measured as nitrite.

RESULTS

In saline-treated cells, a biphasic increase in P-selectin expression was demonstrated at 30 min (P = 0.01) and 4 h (P = 0.023) after re-oxygenation. Propofol and Diprivan prevented these increases in P-selectin expression (P < 0.05). Four hours after re-oxygenation, propofol decreased endothelial nitric oxide production (P = 0.035).

CONCLUSION

This is the first study to demonstrate an effect of propofol upon endothelial P-selectin expression. Such an effect may be important in situations of reperfusion injury such as cardiac transplantation and coronary artery bypass surgery. We conclude that propofol attenuates re-oxygenation-induced endothelial inflammation in vitro.

Puerarin Induces Angiogenesis in Myocardium of Rat with Myocardial Infarction

Puerarin is a major effective ingredient extracted from the traditional Chinese medicine ge-gen (radix puerariae, RP). Recently, puerarin has been used to treat patients with coronary artery diseases (CAD). However, the mechanisms of puerarin on coronary artery diseases are still not very clear. In this study, we investigated the role of puerarin on angiogenesis in the non-ischemic and ischemic myocardium. We found that puerarin (120, 60 mg/kg, i.p.) could reduce infarct area in the heart of rat with myocardial infarction (MI). Puerarin (120 mg/kg) induced angiogenesis in the non-ischemic and ischemic myocardium, which was one of the mechanisms of curing coronary artery diseases. The gene expression or activation of vascular endothelial growth factor (VEGF), hypoxia-inducible factor 1alpha (HIF-1alpha) and endothelial nitric oxide synthase (eNOS) that correlated with angiogenesis were also induced by puerarin. From these results, we suggested that puerarin may induce therapeutic angiogenesis in myocardium of rat with MI. The mechanism may be that puerarin can induce VEGF and eNOS expression.

eNOS translocation but not eNOS phosphorylation is dependent on intracellular Ca2+ in human atrial myocardium

In endothelial cells, two ways of endothelial nitric oxide (NO) synthase (eNOS) activation are known: 1) translocation and 2) Akt-dependent phosphorylation of the enzyme at Ser(1177) (Ser(1177) eNOS). We have recently shown that agonist-induced Ser(1177) eNOS phosphorylation also occurs in human myocardium (10). In this study, we investigated the Ca(2+) dependency of these two mechanisms in human atrium. Therefore, atrial tissue was obtained from patients who underwent coronary artery bypass operations. In immunohistochemical experiments, the translocated form of eNOS and phosphorylated Ser(1177) eNOS were labeled using specific antibodies. eNOS translocation was measured in the absence and presence of the Ca(2+) chelator BAPTA before and after application of BRL 37344 (BRL), a beta(3)-adrenoceptor agonist that increases eNOS activity (34). In the absence of BAPTA, BRL time dependently increased the staining intensity of translocated eNOS, whereas in the presence of BAPTA, this effect was blunted. In contrast, BRL clearly increased the staining of phosphorylated Ser(1177) eNOS even in the presence of BAPTA. This observation was confirmed using Western blot analysis. Using the NO-sensitive dye diaminofluorescein, we have demonstrated that BRL induced a strong NO release. This effect was completely abolished in the presence of BAPTA but was unaffected by LY-292004, an inhibitor of phosphatidylinositol 3-kinase activity and eNOS phosphorylation. Although Ca(2+) dependent, neither the translocation of eNOS nor NO release was changed by the adenylate cyclase activator forskolin. In conclusion, 1) in human atrial myocardium, BRL-induced eNOS translocation but not Ser(1177) eNOS phosphorylation is dependent on intracellular Ca(2+). 2) In atrial myocardium, eNOS-translocation and not Ser(1177) eNOS phosphorylation is responsible for generating the main amount of NO. 3) Although Ca(2+) dependent, eNOS translocation and NO release could not be mimicked by adenylate cyclase activation as a mediator of beta-adrenergic stimulation.

Phospho-eNOS Ser-114 in human mesenchymal stem cells: Constitutive phosphorylation, nuclear localization and upregulation during mitosis

Activity of endothelial nitric oxide synthase (eNOS) is modulated by protein-protein interaction and phosphorylation at specific serine or threonine residues. Using immunofluorescence analysis we show here that proliferating mesenchymal stem cells (MSCs) derived from human bone marrow exhibit cytosolic and pronounced nuclear localization of eNOS. Examination of phosphorylated eNOS subspecies revealed that eNOS phosphorylated at Ser-114 is heavily enriched in the nucleus, whereas eNOS phosphorylated at Ser-1177 is localized at filamentous structures in the cytosol that are abundant in the perinuclear region. Phosphorylation of eNOS at Ser-114 but not at Ser-1177 was strongly increased in cells shortly before mitosis and decreased to normal level after completed cell division. Double immunofluorescence analysis revealed that subcellular localization of 8-hydroxyguanosine immunoreactivity was overlapping with eNOS phosphorylated at Ser-114 in human MSCs providing evidence that phosphorylation at this residue is linked to the generation of superoxide anions. As expected there was only a weak colocalization between eNOS phosphorylated at Ser-1177 and caveolin-1. Different from many other cell systems, human MSCs accumulate eNOS in the nucleus without an acute stimulus. eNOS constitutively phosphorylated at distinct amino acid residues is targeted to different subcellular compartments pointing to an important role of specific phosphorylation events in the life cycle of proliferating human MSCs.

NO-cGMP signaling molecules in cells of the rat molar dentin-pulp complex

By the formation of cyclic guanosine 3',5'-monophosphate (cGMP), nitric oxide (NO)-sensitive enzyme-soluble guanylate cyclase (sGC) plays a receptor role for NO within the NO-cGMP signaling cascade, which is involved in vasodilatation and neurotransmission. The hypothesis that NO-cGMP signaling molecules modulate cells of the dentin-pulp complex was investigated in rat molars by histochemical, immunohistochemical, immuno-ultrastructural, and organ bath techniques. NO synthase (NOS) I-III, the sGC alpha(2)-subunit/beta(1)-subunit, and cGMP were detected in odontoblasts and blood vessels. NOS I, sGC alpha(2), and cGMP were identified in nerve fibers. Treatment of rat molars with the NO donor NONOate (10(-5) M) increased cGMP staining intensities in blood vessels and odontoblasts, while NO synthase inhibitor L-NAME (10(-4) M) attenuated intensity of the reaction products for cGMP, suggesting an effect of endogenous NO on sGC. These correlations of patterns and alterations of cGMP staining intensities after treatment with the NO donor or NO inhibitor might represent an NO-sGC-cGMP signaling-dependent modulation of odontoblasts, blood vessels, and nerve fibers in the dentin-pulp complex.

Role of nitric oxide during coronary endothelial dysfunction after myocardial infarction

This study aimed to investigate whether permanent ischaemia influences subacute vasodilatation responses of non-infarcted rat coronary vasculature, and to characterise these coronary changes. Ischaemia led to a significant impairment of the endothelium-dependent vasodilator response, while coronary vasodilatory capacity remained unaltered. In normal coronary circulation, nitric oxide (NO) and prostanoids contributed to vasodilatation, while basal involvement of endothelium-derived hyperpolarising factor was limited. Vasodilatory impairment following myocardial infarction did not originate from alterations in the prostanoid pathway, and only a slightly increased influence of K+ channels was observed. However, NO-mediated vasodilatation was significantly increased after ischaemia, as also confirmed by higher mRNA and protein levels of iNOS and eNOS. Additionally, the amount of superoxide was enhanced following infarction. We conclude that subacute postinfarction remodeling is accompanied by endothelial dysfunction in non-infarcted coronary arteries. Although the NO-mediated response is increased after ischaemia, its final action is restricted due to the presence of superoxide.

NOSIP and its interacting protein, eNOS, in the rat trachea and lung

Endothelial nitric oxide synthase (eNOS), the major nitric oxide (NO)-generating enzyme of the vasculature, is regulated through multiple interactions with proteins, including caveolin-1, Hsp90, Ca2+-calmodulin, and the recently discovered eNOS-interacting protein, NOSIP. Previous studies indicate that NOSIP may contribute to the intricate regulation of eNOS activity and availability. Because eNOS has been shown to be abundantly expressed in the airways, we determined the expression and cellular localization of NOSIP in rat trachea and lung by RT-PCR and immunohistochemistry and examined the interaction of NOSIP with eNOS in lung by coimmunoprecipitation. In tracheal epithelium and lung, NOSIP mRNA expression was prevalent, as shown by RT-PCR, and the corresponding protein interacted with eNOS, as demonstrated by coimmunoprecipitation. Using immunohistochemistry, we found both NOSIP and eNOS immunoreactivity in ciliated epithelial cells of trachea and bronchi, while Clara cells showed immunoreactivity for NOSIP only. NOSIP and eNOS were present in vascular and bronchial smooth muscle cells of large arteries and airways, whereas endothelial cells, as well as bronchiolar and arteriolar smooth muscle cells, exclusively stained for NOSIP. Our results point to functional role(s) of NOSIP in the control of airway and vascular diameter, mucosal secretion, NO synthesis in ciliated epithelium, and, therefore, of mucociliary and bronchial function.

Mechanisms of beta 3-adrenoceptor-induced eNOS activation in right atrial and left ventricular human myocardium

beta-Adrenoceptors are important modulators of cardiac function. The present study investigated beta(3)-adrenergic eNOS activation in human myocardium. We measured nitric oxide (NO) liberation (diaminofluorescence) and signal transduction (immunohistochemistry, phosphorylation of eNOS(Ser1177), eNOS(Thr495), eNOS(Ser114), Akt/protein kinase B (Akt/PKB), and eNOS translocation) in human right atrial (RA, aortocoronary-bypass OP) and left ventricular nonfailing (LV, rejected donor hearts) myocardium after application of BRL 37344 (BRL), a preferential beta(3)-adrenoceptor agonist. In both RA and LV, BRL (10 microl) induced a liberation of NO. An eNOS activation via translocation was only observed in RA after application of BRL (10 microM). Yet, the NO liberation in both LV and RA was accompanied by phosphorylation of eNOS(Ser1177) and Akt/PKB. BRL-induced eNOS phosphorylation was abolished by LY292004, a blocker of PI-3 kinase. eNOS-Ser(114) phosphorylation was unchanged in RA, but decreased in LV after beta(3)-adrenergic stimulation. BRL did not alter phosphorylation of eNOS(Thr495). In conclusion, receptor-dependent eNOS activation is differentially regulated in the human heart. In the left ventricle, eNOS activation via phosphorylation seems to be of major importance, whereas in human atrial myocardium eNOS translocation is the predominant mechanism induced by beta(3)-adrenergic activation.

A hemodynamic response to intravenous adenovirus vector particles is caused by systemic Kupffer cell-mediated activation of endothelial cells

Intravascular injection of adenoviral vectors may result in a toxic and potentially lethal reaction, the mechanism of which is poorly understood. We noted that mice demonstrated a transient change in behavior that was characterized by inactivity and lethargy within minutes after intravenous injection of relatively low doses of adenoviral vectors (including high-capacity gutless vectors). Moreover, immediately after vector injection a significant drop in blood pressure was measured that most probably was caused by the systemic activation of endothelial cells as monitored by detection of phosphorylated Akt/PKB kinase, activated endothelial nitric oxide synthase (eNOS), and nitrotyrosine. The activation of the endothelium was the result of the interaction of viral particles with Kupffer cells, which are resident macrophages of the liver representing the first line of defense of the innate immune system. Surprisingly, the uptake of vector particles by Kupffer cells not only resulted in their strong activation, but also in their nearly complete disappearance from the liver. Our results suggest that the toxicity of intravenously injected adenoviral vectors may be directly linked to the activation and destruction of Kupffer cells.

N-acetylcysteine prevents reactive oxygen species-mediated myocardial stress in patients undergoing cardiac surgery: results of a randomized, double-blind, placebo-controlled clinical trial

OBJECTIVE

Reactive oxygen species have been shown to contribute to myocardial stress in patients undergoing cardiac surgery, as demonstrated by myocardial 8-iso-prostaglandin-F(2)alpha and nitrotyrosine formation. We hypothesized that the reactive oxygen species scavenger N-acetylcysteine attenuates reactive oxygen species-mediated myocardial stress in patients undergoing cardiac surgery.

METHODS

Forty patients undergoing coronary artery surgery (mean age +/- SD, 66 +/- 9 years; 9 women and 31 men) were randomized to receive either N-acetylcysteine (100 mg/kg into cardiopulmonary bypass prime followed by infusion at 20 mg.kg(-1).h(-1), n = 20) or placebo (n = 20). Patients and clinical staff were blinded to group assignment. Transmural left ventricular biopsy specimens collected before and at the end of cardiopulmonary bypass were subjected to immunocytochemical staining against 8-iso-prostaglandin-F(2)alpha (primary measure) as an indicator for reactive oxygen species-mediated lipid peroxidation and nitrotyrosine (coprimary measure) as a marker for peroxynitrite-mediated tissue injury. Cardiomyocyte staining was quantitatively determined by using densitometry (in gray units). Global left ventricular function was measured on the basis of fractional area of contraction by using transesophageal echocardiography.

RESULTS

Patient characteristics in both groups were comparable. The change in left ventricular cardiomyocyte staining (end of cardiopulmonary bypass--before cardiopulmonary bypass) differed significantly between groups for both primary measures: 8-iso-prostaglandin-F(2)alpha, -1.8 +/- 7.5 gray units (mean +/- SD, N-acetylcysteine group) versus 5.0 +/- 4.1 gray units (placebo group; 95% confidence interval, 2.6-11.0, P =.003); nitrotyrosine, -6.4 +/- 10.0 gray units (N-acetylcysteine group) versus 9.2 +/- 8.4 gray units (placebo group; 95% confidence interval, 9.4-21.7, P <.001). Hemodynamics and clinical outcomes were comparable in both groups.

CONCLUSIONS

Reactive oxygen species scavenging with N-acetylcysteine attenuates myocardial oxidative stress in the hearts of patients subjected to cardiopulmonary bypass and cardioplegic arrest.

Evaluation of nitric oxide release in the coronary effluent by a novel EPR technique: A study on isolated rat hearts subjected to cold cardioplegia and reperfusion

Aim of this study was to investigate the cardiac release of nitric oxide (NO) before and after cold cardioplegia by a novel electron paramagnetic resonance (EPR) technique. Isolated rat hearts were perfused for 20 min in a Langendorff apparatus and then subjected to 3 hours potassium-hypotermic cardioplegia, followed by 20 min reperfusion. The coronary effluent was collected in a flask containing ferrous-bis-diethyldithiocarbamate as a spin trap of NO. Since the trapping agent was not delivered to the heart with the perfusion medium, we avoided that an abnormal extraction of NO from the tissue could inhibit its biological activity. The EPR signal was well detectable after equilibration (25.6 +/- 3.0 nmol/L +/- S.E.M.) and significantly increased following perfusion with 10 micromol/L serotonin (41.1 +/- 3.2 nmol/L) or 10 micromol/L nitroprusside (43.5 +/- 2.9 nmol/L). The basal level of NO did not change after reperfusion, but serotonin administration was not able to stimulate its release. Serotonin failure to stimulate NO production was not due to a loss of endothelial NO synthase, since its protein expression was not modified after reperfusion. The perfusion pressure increased by 51% after reperfusion and was quite completely restored following serotonin or nitroprusside treatment, with respect to the non-stimulated equilibration condition. Therefore, we suggest that the coronary spasm following a cold cardioplegic arrest is not due to an impaired production of basal NO and that NO-donors can be effective in relaxing vascular smooth muscle cells.

Localization of NOS-1 in the sarcolemma region of a subpopulation of atrial cardiomyocytes including myoendocrine cells and NOS-3 in vascular and endocardial endothelial cells of the rat heart

Cellular localization patterns of NOS isoforms 1 and 3 (nNOS and eNOS, respectively) in the mammalian heart under basal (non-stimulated) working conditions are still a matter of discussion. Therefore, this issue was reinvestigated in rats using RT-PCR, Western blotting, catalytic histochemistry, immunohistochemistry and image analysis. Tongue and extensor digitorum longus muscles served as positive controls for NOS-1 and NOS-3. RT-PCR revealed NOS-1 mRNA and NOS-3 mRNA in atria and ventricles. Western blotting showed NOS-1 protein in atria and NOS-3 protein in the walls of both heart chambers. Localization of the activity of urea-resistant (and therefore specific) NADPH diaphorase (NADPH-D) and NOS-1 immunohistochemistry showed that NOS-1 is present in the sarcolemma region of a subpopulation of atrial cardiomyocytes but not in working and impulse-conducting cardiomyocytes of atria and ventricles. Atrial natriuretic peptide (ANP) immunohistochemistry revealed that a minority of the NOS-1-expressing atrial cardiomyocytes are myoendocrine cells. eNOS immunostaining was present in endothelial cells of capillaries of the conducting and working myocardium and endocardial cells. Image analysis of the activity of urea-resistant NOS diaphorase showed that NOS-1 activity is lower in the sarcolemma region of atrial cardiomyocytes than in that of tongue and extensor digitorum longus myofibers. These data suggest that, in the non-stimulated rat heart. NOS-1 is expressed in a subpopulation of atrial cardiomyocytes including myoendocrine cells, and that NOS-3 is expressed in the vascular and endocardial endothelium.

Endothelial dysfunction and infarct-size relate to impaired EDHF response in rat experimental chronic heart failure

BACKGROUND

The rat coronary ligation model of chronic heart failure has been extensively used to investigate its pathophysiology including the role of endothelial dysfunction. Inconsistent results have been obtained concerning the role of endothelial dilative mediators nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF).

AIMS

Our aim was to investigate involvement of NO and EDHF in aortic endothelial dysfunction in this model and the influence of individual infarct sizes. Furthermore, we investigated whether it is justified to regard rats that failed to develop large infarct sizes as SHAM controls.

METHODS

We performed coronary ligations and SHAM operations and studied acetylcholine (ACh)-induced relaxations and underlying endothelial mediators in isolated aortic rings 12 weeks after infarction. By then, cardiac and hemodynamic parameters were deteriorated in animals with large myocardial infarctions (large-MI, 35+/-3%), but not those with small myocardial infarctions (small-MI, 5+/-2%).

RESULTS

Large-MI showed decreased ACh-induced relaxation compared to SHAM due to decreased contribution of EDHF which was inversely correlated with individual infarct-size. Interestingly, small-MI showed significantly increased ACh-induced relaxation compared to SHAM due to increased NO contribution.

CONCLUSIONS

Our results suggest that impaired aortic endothelial dilatory function in large-MI is mainly due to an impaired EDHF response and strongly depends on individual infarct-size. In addition, endothelium-dependent relaxation of small-MI rats differed from SHAM, indicating that both groups may not be pooled to serve as controls. These results emphasize the importance of infarct-size and choice of the control group, and may explain inconsistencies in previous studies.

The preferential beta3-adrenoceptor agonist BRL 37344 increases force via beta1-/beta2-adrenoceptors and induces endothelial nitric oxide synthase via beta3-adrenoceptors in human atrial myocardium

1 The present study investigated the effects of the preferential beta(3)-AR agonist BRL 37344 (BRL) on force of contraction (FOC), Ca(2+)-transient and eNOS-activity in human right atrial myocardium. 2 BRL concentration-dependently caused an increase in FOC that was paralleled by an increase in Ca(2+)-transient and a shortening of time to half peak relaxation (T0.5T). These effects were abolished in the presence of propranolol (0.3 micro M). 3 BRL acted as a competitive antagonist towards isoprenaline and in binding experiments it was shown to have a distinct affinity towards beta(1/2)-AR. 4 In immunohistochemical experiments BRL (10 micro M) increased detection of activated eNOS. This effect remained constant in the presence of propranolol (0.3 micro M). 5 BRL increased directly detected NO in DAF-staining experiments. This increase was significantly smaller in the presence of the NO-inhibitor L-NAME. 6 The inotropic effects of BRL were not changed in the presence of L-NMA. 7 These results suggest that the inotropic effects of BRL in human atrium are mediated via beta(1/2)-AR, whereas the increase of atrial eNOS-activity is due to beta(3)- adrenergic stimulation. This increase in eNOS-activity did not influence atrial myocardial contractility. In conclusion, this study shows that beta(3)-adrenergic stimulation is present in human atrium, but may not be functionally as significant as in the left ventricle.

Nitrotyrosine and 8-isoprostane formation indicate free radical-mediated injury in hearts of patients subjected to cardioplegia

OBJECTIVE

Myocardial ischemia and reperfusion induced by cardioplegic arrest subjects the heart to free radical-mediated stress. The purpose of our study was to investigate the effect of cardioplegia-induced ischemia and reperfusion on myocardial formation and distribution of (1) nitrotyrosine as an indicator for peroxynitrite-mediated tissue injury resulting from increased nitric oxide release and (2) 8-isoprostane as an indicator for oxygen-derived free radical-mediated lipid peroxidation.

METHODS

In 10 patients undergoing coronary artery operations (64 +/- 6 [mean +/- SD] years, 3 women and 7 men) subjected to cardiopulmonary bypass and intermittent cold blood cardioplegia, we collected transmural left ventricular biopsy specimens before and at the end of cardiopulmonary bypass. Specimens were cut at 10 micro m and subjected to immunocytochemical staining against the nitric oxide-producing enzyme constitutive nitric oxide synthase, cyclic guanosine monophosphate (intracellular second messenger of nitric oxide), nitrotyrosine, and 8-isoprostane by using polyclonal antibodies. For global left ventricular function determination, we measured the fractional area of contraction using transesophageal echocardiography.

RESULTS

Nitric oxide synthase activity in cardiac myocytes increased from 34 +/- 10 gray units before cardiopulmonary bypass to 47 +/- 12 gray units at the end of bypass (P =.015), and all hearts showed increased cyclic guanosine monophosphate content in both myocytes and endothelial cells at the end of bypass. The number of nitrotyrosine-positive capillaries increased from 36 +/- 29/mm(2) before bypass to 82 +/- 47/mm(2) at the end of bypass (P =.012), and 8-isoprostane-positive capillaries increased from 92 +/- 72/mm(2) before bypass to 209 +/- 108/mm(2) at the end of bypass (P =.005). The fractional area of contraction was 53% +/- 12% before bypass and 56% +/- 12% after bypass (P =.47) but was slightly decreased to 45% +/- 14% at 4 hours after bypass (P =.121).

CONCLUSIONS

Our data show that cardioplegia-induced myocardial ischemia and reperfusion is associated with nitrotyrosine and 8-isoprostane formation mainly in the coronary endothelium, indicating injury mediated by both peroxynitrite and oxygen-derived free radicals. Because nitric oxide synthase activation was accompanied with increased cyclic guanosine monophosphate, these data suggest that direct effects of nitric oxide on cardiac myocytes, as well as nitric oxide-mediated coronary endothelial injury, might contribute to injury associated with cardioplegia and cardiopulmonary bypass.

Protective role of endothelial nitric oxide synthase

Nitric oxide is a versatile molecule, with its actions ranging from haemodynamic regulation to anti-proliferative effects on vascular smooth muscle cells. Nitric oxide is produced by the nitric oxide synthases, endothelial NOS (eNOS), neural NOS (nNOS), and inducible NOS (iNOS). Constitutively expressed eNOS produces low concentrations of NO, which is necessary for a good endothelial function and integrity. Endothelial derived NO is often seen as a protective agent in a variety of diseases. This review will focus on the potential protective role of eNOS. We will discuss recent data derived from studies in eNOS knockout mice and other experimental models. Furthermore, the role of eNOS in human diseases is described and possible therapeutic intervention strategies will be discussed.

Parathyroid hormone-related peptide improves contractile function of stunned myocardium in rats and pigs

The effect of synthetic parathyroid hormone (PTH)-related peptide [PTHrP(1-34)] on regional myocardial function was studied in 11 anesthetized pigs. Intracoronary infusion of PTHrP (cumulative dose: 14 +/- 1 microg) decreased coronary resistance to 33 +/- 2% of baseline (P < 0.05) and regional myocardial function to 90 +/- 3% of baseline (not significant). Ischemia-reperfusion alters the activity of several kinases and therefore possibly the myocardial effects of PTHrP. In stunned myocardium, induced by 20-min ischemia and 30-min reperfusion, the dose of PTHrP reducing coronary resistance to a minimum of 29 +/- 2% was decreased to 8 +/- 2 microg (P < 0.05). Regional myocardial function was no longer decreased but increased to 132 +/- 9% (P < 0.05). The increase in regional myocardial function during PTHrP was inversely related to baseline function at 30-min reperfusion in vivo (r = 0.9) as well as in myocytes isolated from stunned pig hearts (r = 0.7). In isolated rat hearts subjected to 30-min global ischemia followed by 30-min reperfusion, blockade of endogenous PTHrP by d-Trp(12)-Tyr(34)-PTH(7-34) attenuated the recovery of left ventricular developed pressure by 30 +/- 14% (P < 0.05). Thus endogenous and exogenous PTHrP impact on the function of stunned myocardium.

Distribution of the novel eNOS-interacting protein NOSIP in the liver, pancreas, and gastrointestinal tract of the rat

BACKGROUND & AIMS

Recently, a yeast 2-hybrid screen served to identify a new endothelial nitric oxide synthase (eNOS)-interacting protein (NOSIP), which causes redistribution of eNOS from the plasma membrane to intracellular compartments and reduces eNOS activity. Its in situ distribution is unknown and is reported here in comparison with that of eNOS and neuronal NOS for the rat gastrointestinal tract.

METHODS

Immunofluorescence was performed on acetone-fixed cryosections by using a polyclonal antiserum raised against a NOSIP-glutathione S-transferase fusion protein; specificity was verified by Western blotting.

RESULTS

Cytoplasmic NOSIP immunoreactivity was observed in endothelial cells of some locations, e.g., the hepatic central vein, but it was mainly observed in the striated esophageal muscle; vascular, gastric, and intestinal smooth muscle; and in interstitial cells of Cajal. Nuclear NOSIP immunoreactivity was more widespread, including some myenteric neurons and several epithelial cell types of esophagus, stomach, pancreas, liver, and gut. This cellular distribution matched with that of its potential binding partner eNOS, as determined by immunohistochemistry and reduced nicotinamide adenine dinucleotide phosphate-diaphorase histochemistry, and eNOS, but not neuronal NOS, could be coimmunoprecipitated with NOSIP from small intestine.

CONCLUSIONS

NOSIP coimmunoprecipitates and is widely codistributed with eNOS in nonvascular cells in the gastrointestinal tract, suggesting an involvement of eNOS/NOSIP in the regulation of gastrointestinal secretion and motility.

The nitric oxide synthase-1 and nitric oxide synthase-3/nitric oxide signalling systems in the heart of wild type mice and mouse mutants

Recently, we have shown that nitric oxide synthase-1 (NOS-1) and thus its product NO are present in the sarcolemma region of a subpopulation of atrial cardiomyocytes in the rat heart. In order to find out whether this newly discovered sarcolemma-associated NOS/NO system represents a general signalling mechanism in the murine rodent heart and whether its properties are comparable to those in skeletal muscle fibres, immunohistochemical and catalytic histochemical methods (including image analysis) were applied to the heart and extensor digitorum longus (EDL) and tongue muscles of wild type and mutant mice. In different strains of wild type mice and NOS-3 knockouts, urea-resistant (and therefore specific) NOS NADPH diaphorase histochemistry and NOS-1 immunohistochemistry revealed that NOS-1 activity and protein were present in the sarcolemma region of a subpopulation of atrial and ventricular working cardiomyocytes, but not in those of the impulse conducting system. Using image analysis, NOS-1 showed similar activities in the sarcolemma region of cardiomyocytes and in EDL type I myofibres. In mdx and NOS-1 knockout mice, NOS-1 was absent from the sarcolemma region of atrial and ventricular cardiomyocytes and of EDL and tongue muscle fibres, whereas NOS-1 was present in the hearts of NOS-3 knockouts. Atrial natriuretic peptide immunohistochemistry identified part of the atrial NOS-1-expressing cardiomyocytes as myoendocrine cells. In mdx mice as well as in NOS-1 - and NOS-3-deficient animals, the peptide was found in greater abundance than in wild type mice. These data suggest that NOS-1 is expressed in a subpopulation of working cardiomyocytes in the murine rodent heart, that the myoendocrine cells may be negatively modulated by NOS-1 - and NOS-3-produced NO, and that the anchoring mechanisms for NOS-1 in these cells (i.e. their confinement to the sarcolemma region) are comparable to those in skeletal muscle fibres.

Preconditioning-mediated neuroprotection: role of nitric oxide, cGMP, and new protein expression

Preconditioning adaptation induced by transient ischemia can increase brain tolerance to oxidative stress, but the underlying neuroprotective mechanisms are not fully understood. Recently, we developed a human brain-derived cell model to investigate preconditioning mechanism in SH-SY5Y neuroblastoma cells.(1) Our results demonstrate that a non-lethal serum deprivation-stress for 2 h (preconditioning stress) enhanced the tolerance to a subsequent lethal oxidative stress (24 h serum deprivation) and also to 1-methyl-4-phenyl-pyridinium (MPP(+)).(2) Two-hour non-lethal preconditioning stress increased the expression of neuronal nitric oxide (NOS1/nNOS) mRNA, Fos, Ref-1, NOS protein, and then nitric oxide (*NO) production. As well as MnSOD expression, the *NO-cGMP-PKG pathway mediated the preconditioning-induced upregulation of antiapoptotic protein Bcl-2 and the downregulation of adaptor protein p66(shc). We also propose that cGMP-mediated preconditioning-induced adaptation against oxidative stress may be due to the synthesis of a new protein, such as thioredoxin (Trx) since the protective effect can be blocked by Trx reductase inhibitor.(3) The antioxidative potency of Trx was approximately 100 and 1,000 times greater than GSNO and GSH, respectively. These results suggest that *NO-cGMP-PKG signaling pathway plays an important role in the preconditioning-induced neuroprotection, and perhaps cardioprotection, against oxidative stress.

Functional interaction of caveolin-1 and eNOS in myocardial capillary endothelium revealed by immunoelectron microscopy

Immunogold labeling on samples of isolated perfused rat hearts embedded by an innovative low-temperature LR White procedure provided detailed insight into the interaction of caveolin-1 and endothelial NOS in myocardial capillary endothelium at the subcellular level. Separately, the localization of caveolin-1 and eNOS at caveolae under steady state conditions was visualized. A double-labeling experiment supported their close co-localization. Short-term bradykinin stimulation caused a detectable dissociation of eNOS from caveolin and its redistribution to different cell compartments, whereas caveolin itself remained stationary at caveolae. Morphometric analysis revealed that more than 80% of detectable eNOS was co-localized with caveolin-1 at caveolae under control conditions. After brief stimulation for 2 min with 10(-7) M bradykinin, only 26% of the eNOS signals were associated with caveolin-1 and randomly distributed over the endothelial cells. After stimulation, eNOS was found at the plasmalemmal and intracellular membranes, freely in the cytoplasm, and at outer mitochondrial membranes.

Nitric oxide synthase expression and function in embryonic and adult cardiomyocytes

Nitric oxide (NO) is an important signalling molecule that plays a relevant role in different cell systems, among them the adult heart. The effects of NO are primarily mediated through modulation of Ca(2+) homeostasis, myofibrillar contractility, and metabolic regulation in cardiomyocytes. Recent evidence also suggests an important role of NO for cardiomyogenesis by modulating proliferation and differentiation and regulating cardiac function. In the embryonic, but also the healthy and diseased, adult mammalian heart, the inducible (iNOS) and the endothelial (eNOS) nitric oxide synthases (NOS) are detected. However, the expression pattern of NO and its function differ during development. Furthermore, under pathophysiological conditions NOS expression can also change and cause impairment of cardiac performance and cytotoxic effects. The present review focuses on the role and function of NO during cardiomyogenesis, the mechanisms responsible for eNOS availability, and the paracrine effects of NO generated by cardiomyocytes.