Significance of nitric oxide synthases: Lessons from triple nitric oxide synthases null mice

Evaluation of the anti-inflammatory effect of 1,4-dihydropyridine derivatives

INTRODUCTION

Inflammation is a physiological event that protects the organism against different factors that lead to loss of tissue homeostasis. Dihydropyridine (DHP) derivatives are heterocyclic compounds known for their different biological activities, including anti-inflammatory activities.

OBJECTIVE

To evaluate the anti-inflammatory activity of 1,4-dihydropyridine (1,4-DHP) derivatives using anti-inflammatory models in vitro, in RAW264.7 cells induced by lipopolysaccharide (LPS) and in vivo using the acute lung injury (ALI) model in mice.

RESULTS

Fifteen compounds derived from 1,4-DHP were tested in RAW264.7 cells for their cytotoxic effect and cell viability. Thereafter, only the six compounds that showed the highest cell viability were tested for the production or inhibition of the pro-inflammatory cytokine interleukin 6 (IL-6). The best compound (compound 4) was tested for its anti-inflammatory effects in vitro and in vivo, showing inhibition of nitric oxide (NO), pro-inflammatory cytokines, increased phagocytic activity, and an increase in IL-10 in vitro. In in vivo tests, compound 4 also reduces the levels of NO, myeloperoxidase (MPO) activity, leukocyte migration, and exudation, as well as reducing the levels of tumor necrosis factor-alpha (TNF-α) and IL-6 and preventing the loss in the lung architecture.

CONCLUSION

This compound showed important anti-inflammatory activity, with a significant ability to reduce the production of pro-inflammatory mediators and increase the phagocytic activity of macrophages and anti-inflammatory mediator secretion (IL-10). These findings led us to hypothesize that this compound can repolarize the macrophage response to an anti-inflammatory profile (M2). Moreover, it was also able to maintain its anti-inflammatory activity in vivo experiments.

Alleviated cerebral infarction in male mice lacking all nitric oxide synthase isoforms after middle cerebral artery occlusion

PURPOSE

The role of the nitric oxide synthases (NOSs) system in cerebral infarction has been examined in pharmacological studies with non-selective NOSs inhibitors. However, due to the non-specificity of the non-selective NOSs inhibitors, its role remains to be fully elucidated. We addressed this issue in mice in which neuronal, inducible, and endothelial NOS isoforms were completely disrupted.

METHODS AND RESULTS

We newly generated mice lacking all three NOSs by crossbreeding each single NOS-/- mouse. In the male, cerebral infarct size at 24 h after middle cerebral artery occlusion (MCAO) was significantly smaller in the triple n/i/eNOSs-/- genotype as compared with wild-type genotype. Neurological deficit score and mortality rate were also significantly lower in the triple n/i/eNOSs-/- than in the WT genotype. In contrast, in the female, there was no significant difference in the cerebral infarct size in the two genotypes. In the male triple n/i/eNOSs-/- genotype, orchiectomy significantly increased the cerebral infarct size, and in the orchiectomized male triple n/i/eNOSs-/- genotype, treatment with testosterone significantly reduced it. Cyclopaedic and quantitative comparisons of mRNA expression levels in cerebral infarct lesions between the male wild-type and triple n/i/eNOSs-/- genotypes at 1 h after MCAO revealed significant involvements of decreased oxidative stress and mitigated mitochondrial dysfunction in the alleviated cerebral infarction in the male triple n/i/eNOSs-/- genotype.

CONCLUSIONS

These results provide the first evidence that the NOSs system exerts a deleterious effect against acute ischemic brain injury in the male.

The pivotal role of neuronal nitric oxide synthase in the release of 6-nitrodopamine from mouse isolated vas deferens

6-Nitrodopamine (6-ND) is released from rat and human vas deferens and is considered a major mediator of both tissues contractility. The contractions induced by 6-ND are selectively blocked by both tricyclic antidepressants and α1-adrenoceptor antagonists. Endothelial nitric oxide synthase (eNOS) is the major isoform responsible for 6-ND release in mouse isolated heart, however the origin of 6-ND in the vas deferens is unknown. Here it was investigated by LC-MS/MS the basal release of 6-ND from isolated vas deferens obtained from control, eNOS-/-, nNOS-/-, and iNOS-/- mice. In addition, it was evaluated in vitro vas deferens contractility following electric field stimulation (EFS). Basal release of 6-ND was significantly reduced in nNOS-/- mice compared to control mice, but not decreased when the vas deferens were obtained from either eNOS-/- or iNOS-/- mice. Pre-incubation of the vas deferens with tetrodotoxin (1 μM) significantly reduced the basal release of 6-ND from control, eNOS-/-, and iNOS-/- mice but had no effect on the basal release of 6-ND from nNOS-/- mice. EFS-induced frequency-dependent contractions of the vas deferens, which were significantly reduced when the tissues obtained from control, eNOS-/- and iNOS-/- mice, were pre-incubated with l-NAME, but unaltered when the vas deferens was obtained from nNOS-/- mice. In addition, the EFS-induced contractions were significantly smaller when the vas deferens were obtained from nNOS-/- mice. The results clearly demonstrate that nNOS is the main NO isoform responsible for 6-ND release in mouse vas deferens and reinforces the concept of 6-ND as a major modulator of vas deferens contractility.

The importance of the endothelial nitric oxide synthase on the release of 6-nitrodopamine from mouse isolated atria and ventricles and their role on chronotropism

6-nitrodopamine (6-ND) is released from rat isolated atria, where it acts as a potent positive chronotropic agent. The release of 6-ND from rat isolated atria and ventricles is significantly reduced when pre-incubated with l-NAME, and the release was not affected by tetrodotoxin pre-treatment, indicating that in the heart, the origin of 6-ND is not neurogenic. Since l-NAME inhibits all three isoforms of NO synthase, it was investigated the basal release of 6-ND from isolated atria and ventricles from nNOS-/-, iNOS-/- and eNOS-/- mice of either sex. The release of 6-ND was measured by LC-MS/MS. There were no significant differences in the 6-ND basal release from isolated atria and ventricles from male control mice, as compared to female control mice. The 6-ND release from atria obtained from eNOS-/- mice was significantly reduced when compared to atria obtained from control mice. The 6-ND release in nNOS-/- mice was not significantly different compared to control animals whereas the 6-ND release from atria obtained from iNOS-/- mice was significantly higher when compared to control group. Incubation of the isolated atria with l-NAME caused a significant decrease in the basal atrial rate of control, nNOS-/-, and iNOS-/- mice, but not in eNOS-/- mice. The results clearly indicate that eNOS is the isoform responsible for the synthesis of 6-ND in the mice isolated atria and ventricles and supports the concept that 6-ND is the major mechanism by which endogenous NO modulates heart rate.

Autoregulation and Autoinhibition of the Main NO Synthase Isoforms (Brief Review)

Nitric oxide (II) (NO) is the most important mediator of a wide range of physiological and pathophysiological processes. It is synthesized by NO synthases (NOSs), which have three main isoforms differing from each other in terms of activation and inhibition features, levels of NO production, subcellular localization, etc. At the same time, all isoforms are structurally very similar, and these differences are determined by NOS autoregulatory elements. The article presents an analysis of the autoregulatory and autoinhibitory mechanisms of the NOS reductase domain that determine differences in the productivity of isoforms, as well as their dependence on the concentration of Ca2+ ions. The main regulatory elements in NOS that modulate the electron transfer from flavin to heme include calmodulin (CaM), an autoinhibitory insert (AI), and the C-terminal tail (C-tail). Hydrophobic interactions of CaM with the surface of the NOS oxidase domain are assumed to facilitate electron transfer from flavin mononucleotide (FMN). CaM binding causes a change in the inter-domain distances, a shift of AI and the C-tail, and, as a result, a decrease in their inhibitory effect. CaM also shifts the conformational equilibrium of the reductase domain towards more open conformations, reduces the lifetime of conformations, their stereometric distribution, and accelerates the flow of electrons through the reductase domain. The AI element, apparently, induces a conformational change that hinders electron transfer within the reductase domain, similar to the hinge domain in cytochrome P450. Together with CaM, the C-tail regulates the electron flow between flavins, the distance and relative orientation of isoalloxane rings, and also modulates the electron flow from FMN to the terminal acceptor. Together with the C-tail, AI also predetermines the dependence of neuronal and endothelial forms of NOS on the concentration of Ca2+ ions, and the C-tail length affects differences in the productivity of NO synthesis. The inhibitory effect of the C-tail is likely to be reduced by CaM binding due to the C-tail shift due to the electrostatic repulsive forces of the negatively charged phosphate and aspartate residues. The autoregulatory elements of NOS require further study, since the mechanisms of their interaction are complex and multidirectional, and hence provide a wide range of characteristics of the observed isoforms.

Delivery of nitric oxide with a pH-responsive nanocarrier for the treatment of renal fibrosis

Fibrosis is an excessive accumulation of extracellular matrix (ECM) that may cause severe organ dysfunction. Nitric oxide (NO), a multifunctional gaseous signaling molecule, may inhibit fibrosis, and delivery of NO may serve as a potential antifibrotic strategy. However, major limitations in the application of NO to treat fibrotic diseases include its nonspecificity, short half-life and low availability in fibrotic tissue. Herein, we aimed to develop a stimuli-responsive drug carrier to deliver NO to halt kidney fibrosis. We manufactured a nanoparticle (NP) composed of pH-sensitive poly[2-(diisopropylamino)ethyl methacrylate (PDPA) polymers to encapsulate a NO donor, a dinitrosyl iron complex (DNIC; [Fe₂(μ-SEt)₂(NO)₄]). The NPs were stable at physiological pH 7.4 but disintegrated at pH 4.0-6.0. The NPs showed significant cytotoxicity to cultured human myofibroblasts and were able to inhibit the activation of myofibroblasts, as indicated by a lower expression level of α-smooth muscle actin and the synthesis of a major ECM component, collagen I, in cultured human myofibroblasts. When given to mice treated with unilateral ureteral ligation/obstruction (UUO) to induce kidney fibrosis, these NPs remained in blood at a stable concentration for as long as 24 h and might enter the fibrotic kidneys to suppress myofibroblast activation and collagen I production, leading to a 70% reduction in the fibrotic area. In summary, our strategy to assemble a NO donor, the iron nitrosyl complex DNIC, into pH-responsive NPs proves effective in treating renal fibrosis and warrants further investigation for its therapeutic potential.

Low levels of nitric oxide promotes heme maturation into several hemeproteins and is also therapeutic

Nitric oxide (NO) is a signal molecule and plays a critical role in the regulation of vascular tone, displays anti-platelet and anti-inflammatory properties. While our earlier and current studies found that low NO doses trigger a rapid heme insertion into immature heme-free soluble guanylyl cyclase β subunit (apo-sGCβ), resulting in a mature sGC-αβ heterodimer, more recent evidence suggests that low NO doses can also trigger heme-maturation of hemoglobin and myoglobin. This low NO phenomena was not only limited to sGC and the globins, but was also found to occur in all three nitric oxide synthases (iNOS, nNOS and eNOS) and Myeloperoxidase (MPO). Interestingly high NO doses were inhibitory to heme-insertion for these hemeproteins, suggesting that NO has a dose-dependent dual effect as it can act both ways to induce or inhibit heme-maturation of key hemeproteins. While low NO stimulated heme-insertion of globins required the presence of the NO-sGC-cGMP signal pathway, iNOS heme-maturation also required the presence of an active sGC. These effects of low NO were significantly diminished in the tissues of double (n/eNOS^−/−) and triple (n/i/eNOS^−/−) NOS knock out mice where lung sGC was found be heme-free and the myoglobin or hemoglobin from the heart/lungs were found be low in heme, suggesting that loss of endogenous NO globally impacts the whole animal and that this impact of low NO is both essential and physiologically relevant for hemeprotein maturation. Effects of low NO were also found to be protective against ischemia reperfusion injury on an ex vivo lung perfusion (EVLP) system prior to lung transplant, which further suggests that low NO levels are also therapeutic.

•

Low levels of NO enable heme-maturation of the globins by a process that required an NO triggered heme-insertion into sGCβ.

•This effect of low NO was also found to occur for all three nitric oxide synthases (NOSs) and Myeloperoxidase (MPO).

•Tissues from n/eNOS^−/− and n/i/eNOS^−/− knock out mice had low heme levels in the globins, while sGC was largely heme-free.

•Low NO at ppm levels also manifests itself as a therapy during ischemic reperfusion injury of lungs on the EVLP.

Endothelial Dysfunction in Heart Failure With Preserved Ejection Fraction: What are the Experimental Proofs?

Heart failure with preserved ejection fraction (HFpEF) has been recognized as the greatest single unmet need in cardiovascular medicine. Indeed, the morbi-mortality of HFpEF is high and as the population ages and the comorbidities increase, so considerably does the prevalence of HFpEF. However, HFpEF pathophysiology is still poorly understood and therapeutic targets are missing. An unifying, but untested, theory of the pathophysiology of HFpEF, proposed in 2013, suggests that cardiovascular risk factors lead to a systemic inflammation, which triggers endothelial cells (EC) and coronary microvascular dysfunction. This cardiac small vessel disease is proposed to be responsible for cardiac wall stiffening and diastolic dysfunction. This paradigm is based on the fact that microvascular dysfunction is highly prevalent in HFpEF patients. More specifically, HFpEF patients have been shown to have decreased cardiac microvascular density, systemic endothelial dysfunction and a lower mean coronary flow reserve. Importantly, impaired coronary microvascular function has been associated with the severity of HF. This review discusses evidence supporting the causal role of endothelial dysfunction in the pathophysiology of HFpEF in human and experimental models.

Modulation of Insulin Resistance, Dyslipidemia and Serum Metabolome in iNOS Knockout Mice following Treatment with Nitrite, Metformin, Pioglitazone, and a Combination of Ampicillin and Neomycin

Oxidative and nitrosative stress plays a pivotal role in the incidence of metabolic disorders. Studies from this lab and others in iNOS-/- mice have demonstrated occurrence of insulin resistance (IR), hyperglycemia and dyslipidemia highlighting the importance of optimal redox balance. The present study evaluates role of nitrite, L-arginine, antidiabetics (metformin, pioglitazone) and antibiotics (ampicillin-neomycin combination, metronidazole) on metabolic perturbations observed in iNOS-/- mice. The animals were monitored for glucose tolerance (IPGTT), IR (insulin, HOMA-IR, QUICKI), circulating lipids and serum metabolomics (LC-MS). Hyperglycemia, hyperinsulinemia and IR were rescued by nitrite, antidiabetics, and antibiotics treatments in iNOS-/- mice. Glucose intolerance was improved with nitrite, metformin and pioglitazone treatment, while ampicillin-neomycin combination normalised the glucose utilization in iNOS-/- mice. Increased serum phosphatidylethanolamine lipids in iNOS-/- mice were reversed by metformin, pioglitazone and ampicillin-neomycin; dyslipidemia was however marginally improved by nitrite treatment. The metabolic improvements were associated with changes in selected serum metabolites-purines, ceramide, 10-hydroxydecanoate, glucosaminate, diosmetin, sebacic acid, 3-nitrotyrosine and cysteamine. Bacterial metabolites-hippurate, indole-3-ethanol; IR marker-aminoadipate and oxidative stress marker-ophthalmate were reduced by pioglitazone and ampicillin-neomycin, but not by nitrite and metformin treatment. Results obtained in the present study suggest a crucial role of gut microbiota in the metabolic perturbations observed in iNOS-/- mice.

Developing a robust, fast and reliable measurement method for the analysis of methylarginine derivatives and related metabolites

Background

Nitric oxide (NO) plays an important role in endothelial homeostasis. Asymmetric dimethyl arginine (ADMA), L-N monomethyl arginine (L-NMMA) and symmetric dimethyl arginine (SDMA), which are derivatives of methylarginine, directly or indirectly reduce NO production. Therefore, these metabolites are an important risk factor for various diseases, including cardiovascular diseases. Numerous methods have been developed for the measurement of methylarginine derivatives, but various difficulties have been encountered. This study aimed to develop a reliable, fast and cost-effective method for the analysis and measurement of methylarginine derivatives (ADMA, SDMA, L-NMMA) and related metabolites (arginine, citrulline, homoarginine, ornithine), and to validate this method according to Clinical and Laboratory Standards Institute (CLSI) protocols.

Methods

For the analysis of ADMA, SDMA, L-NMMA, arginine, homoarginine, citrulline, ornithine, 200 Âµl of serum were precipitated with methanol, and subsequently derivatized with a butanol solution containing 5% acetyl chloride. Butyl derivatives were separated using a C18 reverse phase column with a 5 min run time. Detection of analytes was achieved by utilising the specific fragmentation patterns identified through tandem mass spectrometry.

Results

The method was linear for ADMA, SDMA, L-NMMA, ornithine, arginine, homoarginine and citrulline in the ranges of 0.023–6.0, 0.021–5.5, 0.019–5.0, 0.015–250, 0.015–250, 0.019–5 and 0.015–250 µM, respectively. The inter-assay CV% values for all analytes was less than 9.8%.

Conclusions

Data obtained from method validation studies shows that the developed method is highly sensitive, precise and accurate. Short analysis time, cost-effectiveness, and multiplexed analysis of these metabolites, with the same pretreatment steps, are the main advantages of the method.

Spontaneous pulmonary emphysema in mice lacking all three nitric oxide synthase isoforms

The roles of endogenous nitric oxide (NO) derived from the entire NO synthases (NOSs) system have yet to be fully elucidated. We addressed this issue in mice in which all three NOS isoforms were deleted. Under basal conditions, the triple n/i/eNOSs^−/− mice displayed significantly longer mean alveolar linear intercept length, increased alveolar destructive index, reduced lung elastic fiber content, lower lung field computed tomographic value, and greater end-expiratory lung volume as compared with wild-type (WT) mice. None of single NOS^−/− or double NOSs^−/− genotypes showed such features. These findings were observed in the triple n/i/eNOSs^−/− mice as early as 4 weeks after birth. Cyclopaedic and quantitative comparisons of mRNA expression levels between the lungs of WT and triple n/i/eNOSs^−/− mice by cap analysis of gene expression (CAGE) revealed that mRNA expression levels of three Wnt ligands and ten Wnt/β-catenin signaling components were significantly reduced in the lungs of triple n/i/eNOSs^−/− mice. These results provide the first direct evidence that complete disruption of all three NOS genes results in spontaneous pulmonary emphysema in juvenile mice in vivo possibly through down-regulation of the Wnt/β-catenin signaling pathway, demonstrating a novel preventive role of the endogenous NO/NOS system in the occurrence of pulmonary emphysema.

Endogenous S-nitrosocysteine proteomic inventories identify a core of proteins in heart metabolic pathways

Protein cysteine residues are essential for protein folding, participate in enzymatic catalysis, and coordinate the binding of metal ions to proteins. Enzymatically catalyzed and redox-dependent post-translational modifications of cysteine residues are also critical for signal transduction and regulation of protein function and localization. S-nitrosylation, the addition of a nitric oxide equivalent to a cysteine residue, is a redox-dependent modification. In this study, we curated and analyzed four different studies that employed various chemoselective platforms coupled to mass spectrometry to precisely identify S-nitrosocysteine residues in mouse heart proteins. Collectively 1974 S-nitrosocysteine residues in 761 proteins were identified and 33.4% were identified in two or more studies. A core of 75 S-nitrosocysteine residues in 44 proteins were identified in all four studies. Bioinformatic analysis of each study indicated a significant enrichment of mitochondrial proteins participating in metabolism. Regulatory proteins in glycolysis, TCA cycle, oxidative phosphorylation and ATP production, long chain fatty acid β-oxidation, and ketone and amino acid metabolism constitute the major functional pathways impacted by protein S-nitrosylation. In the cardiovascular system, nitric oxide signaling regulates vasodilation and cardiac muscle contractility. The meta-analysis of the proteomic data supports the hypothesis that nitric oxide signaling via protein S-nitrosylation is also a regulator of cardiomyocyte metabolism that coordinates fuel utilization to maximize ATP production. As such, protein cysteine S-nitrosylation represents a third functional dimension of nitric oxide signaling in the cardiovascular system to ensure optimal cardiac function.

Animal models for diabetes insipidus

The hormone arginine vasopressin (AVP) is a nonapeptide synthesized by hypothalamic magnocellular nuclei and secreted from the posterior pituitary into the bloodstream. It binds to AVP receptor 2 in the kidney to promote the insertion of aquaporin channels (AQP2) and antidiuretic responses. AVP secretion deficits produce central diabetes insipidus (CDI), while renal insensitivity to the antidiuretic effect of AVP causes nephrogenic diabetes insipidus (NDI). Hereditary and acquired forms of CDI and NDI generate hypotonic polyuria, polydipsia, hyperosmolality, and hypernatremia. The AVP mutant (Brattleboro) rat is the principal animal model of hereditary CDI, while neurohypophysectomy, pituitary stalk compression, hypophysectomy, and mediobasal hypothalamic lesions produce acquired CDI. In animals, hereditary NDI is mainly caused by mutations in AVP2R or AQP2 genes, while acquired NDI is most frequently induced by lithium. We report here on the determinants of the intake and excretion of water and mineral salts and on the different types of DI in humans. We then describe the hydromineral characteristics of these animal models and the responses observed after administration of hypertonic NaCl or when they are fed with low-sodium diets. Finally, we report on the effects of drugs such as AVP analogues and/or oxytocin, another neuropeptide that increases sodium excretion in animal models and humans with CDI, and sildenafil, a compound that increases the expression and function of AQP2 channels in animal models and humans with NDI.

Low Nitric Oxide Bioavailability Increases Renin Production in the Collecting Duct

In the kidney, the stimulation of renin production by the collecting duct (CD-renin) contributes to the development of hypertension. The CD is a major nephron segment for the synthesis of nitric oxide (NO), and low NO bioavailability in the renal medulla is associated with hypertension. However, it is unknown whether NO regulates renin production in the CD. To test the hypothesis that low intrarenal NO levels stimulate the production of CD-renin, we first examined renin expression in the distal nephron segments of CD-eNOS deficient mice. In these mice, specific CD-renin immunoreactivity was increased compared to wild-type littermates; however, juxtaglomerular (JG) renin was not altered. To further assess the intracellular mechanisms involved, we then treated M-1 cells with either 1 mM L-NAME (L-arginine analog), an inhibitor of NO synthase activity, or 1 mM NONOate, a NO donor. Both treatments increased intracellular renin protein levels in M-1 cells. However, only the inhibition of NOS with L-NAME stimulated renin synthesis and secretion as reflected by the increase in Ren1C transcript and renin protein levels in the extracellular media, respectively. In addition, NONOate induced a fast mobilization of cGMP and intracellular renin accumulation. These response was partially prevented by guanylyl cyclase inhibition with ODQ (1H-[1,2,4] oxadiazolo[4,3-a]quinoxalin-1]. Accumulation of intracellular renin was blocked by protein kinase G (PKG) and protein kinase C (PKC) inhibitors. Our data indicate that low NO bioavailability increases CD-renin synthesis and secretion, which may contribute to the activation of intrarenal renin angiotensin system.

Systemic Insulin Resistance and Metabolic Perturbations in Chow Fed Inducible Nitric Oxide Synthase Knockout Male Mice: Partial Reversal by Nitrite Supplementation

iNOS, an important mediator of inflammation, has emerged as an important metabolic regulator. There are conflicting observations on the incidence of insulin resistance (IR) due to hyperglycemia/dyslipidemia in iNOS^−/− mice. There are reports that high fat diet (HFD) fed mice exhibited no change, protection, or enhanced susceptibility to IR. Similar observations were also reported for low fat diet (LFD) fed KO mice. In the present study chow fed iNOS^−/− mice were examined for the incidence of IR, and metabolic perturbations, and also for the effect of sodium nitrite supplementation (50 mg/L). In IR-iNOS^−/− mice, we observed significantly higher body weight, BMI, adiposity, blood glucose, HOMA-IR, serum/tissue lipids, glucose intolerance, enhanced gluconeogenesis, and disrupted insulin signaling. Expression of genes involved in hepatic and adipose tissue lipid uptake, synthesis, oxidation, and gluconeogenesis was upregulated with concomitant downregulation of genes for hepatic lipid excretion. Nitrite supplementation restored NO levels, significantly improved systemic IR, glucose tolerance, and also reduced lipid accumulation by rescuing hepatic insulin sensitivity, glucose, and lipid homeostasis. Obesity, gluconeogenesis, and adipose tissue insulin signaling were only partially reversed in nitrite supplemented iNOS^−/− mice. Our results thus demonstrate that nitrite supplementation to iNOS^−/− mice improves insulin sensitivity and metabolic homeostasis, thus further highlighting the metabolic role of iNOS.

Determination of Endothelial Nitric Oxide Synthase Gene Polymorphism and Plasma Asymmetric Dimethyl Arginine Concentrations in Patients with Lung Cancer

Objective

Genetic factors can contribute to both the occurrence and development of lung cancer. This study aimed to investigate endothelial nitric oxide synthase (eNOS) G894T and T-786C polymorphisms and plasma asymmetric dimethylarginine (ADMA) levels of lung cancer patients in comparison with healthy subjects.

Materials and Methods

A total of 200 subjects, 100 patients with lung cancer and 100 healthy volunteers were included in this study. To determine eNOS gene polymorphisms, we collected and analyzed blood samples with polymerase chain reaction (PCR). Plasma ADMA levels were evaluated by high-performance liquid chromatography (HPLC).

Results

The difference in gene polymorphisms between lung cancer patients and healthy controls were insignificant. However, lung cancer patients had statistically significantly higher plasma ADMA levels than healthy controls. The patients and control groups with CC polymorphisms and TT polymorphisms on eNOS T-786C and G894T gene regions had higher plasma ADMA levels. The CC polymorphisms and plasma ADMA levels were higher in patients with small-cell lung cancer compared to those in patients with non-small-cell lung cancer.

Conclusion

Although eNOS gene polymorphisms had no significant difference between lung cancer patients and healthy controls, plasma ADMA levels were higher in lung cancer patients compared to healthy controls. Our study suggests that CC genotypes and elevated plasma ADMA levels might be associated with small-cell lung cancer.

Nitric Oxide in Dental Pulp Tissue: From Molecular Understanding to Clinical Application in Regenerative Endodontic Procedures

Nitric oxide (NO), which is synthesized by the enzyme NO synthase (NOS), is a versatile endogenous molecule with multiple biological effects on many tissues and organs. In dental pulp tissue, NO has been found to play multifaceted roles in regulating physiological activities, inflammation processes, and tissue repair events, such as cell proliferation, neuronal degeneration, angiogenesis, and odontoblastic differentiation. However, there is a deficiency of detailed discussion on the NO-mediated interactions between inflammation and reparative/regenerative responses in wounded dental pulp tissue, which is a central determinant of ultimate clinical outcomes. Thus, the purpose of this review is to outline the current molecular understanding on the roles of Janus-faced molecule NO in dental pulp physiology, inflammation, and reparative activities. Based on this knowledge, advanced physicochemical techniques designed to manipulate the therapeutic potential of NOS and NO production in endodontic regeneration procedures are further discussed. Impact statement The interaction between inflammation and reparative/regenerative responses is very important for regenerative endodontic procedures, which are biologically based approaches intended to replace damaged tissues. Inside dental pulp tissue, endogenous nitric oxide (NO) is generated mainly by immunocompetent cells and dental pulp cells and mediates not only inflammatory/immune activities but also signaling cascades that regulate tissue repair and reconstruction, indicating its involvement in both tissue destruction and regeneration. Thus, it is feasible that NO acts as one of the indicators and modulators in dental pulp repair or regeneration under physiological and pathological conditions.

TRPC Channels in Cardiac Plasticity

The heart flexibly changes its structure in response to changing environments and oxygen/nutrition demands of the body. Increased and decreased mechanical loading induces hypertrophy and atrophy of cardiomyocytes, respectively. In physiological conditions, these structural changes of the heart are reversible. However, chronic stresses such as hypertension or cancer cachexia cause irreversible remodeling of the heart, leading to heart failure. Accumulating evidence indicates that calcium dyshomeostasis and aberrant reactive oxygen species production cause pathological heart remodeling. Canonical transient receptor potential (TRPC) is a nonselective cation channel subfamily whose multimodal activation or modulation of channel activity play important roles in a plethora of cellular physiology. Roles of TRPC channels in cardiac physiology have been reported in pathological cardiac remodeling. In this review, we summarize recent findings regarding the importance of TRPC channels in flexible cardiac remodeling (i.e., cardiac plasticity) in response to environmental stresses and discuss questions that should be addressed in the near future.

l-arginine Supplementation Increased Only Endothelium-Dependent Relaxation in Sprague-Dawley Rats Fed a High-Salt Diet by Enhancing Abdominal Aorta Endothelial Nitric Oxide Synthase Gene Expression

Background

Abnormal vascular reactivity and reduced expression of endothelial nitric oxide synthase (eNOS) gene are hallmark of salt-induced hypertension in rats. Although l-arginine is an established vasodilator, the mechanism by which it modulates vascular reactivity in salt-induced hypertension is not clearly understood.

Objectives

This study was designed to investigate the mechanism by which oral l-arginine supplementation modulates vascular reactivity and eNOS gene expression in Sprague-Dawley rats fed a high-salt diet.

Methods

Forty-eight weaned male Sprague-Dawley rats of weight range 90 to 110 g were randomly divided into 6 groups of 8 rats per group. Group I was fed normal rat chow ad libitum and served as the Normal Diet group. Group II was fed a diet that contained 8% NaCl. Groups III and IV took normal and high-salt diet, respectively, and then received oral l-arginine supplementation (100 mg/kg/day), while groups V and VI took normal and high-salt diet, respectively, and then were co-administered with both l-arginine and l-nitro-arginine methyl ester (L-NAME; 100 mg/kg/day and 40 mg/kg/day, respectively) orally. At the end of 12-week experimental period, the animals were sacrificed to assess vascular reactivity and gene expression level.

Results

Our results show that high-salt diet significantly reduced (P < .05) endothelium-dependent relaxation response to acetylcholine and qualitatively reduced eNOS gene expression in the abdominal aorta of the rats. However, l-arginine supplementation improved the impaired endothelium-dependent relaxation and nitric oxide level while ameliorating the reduced eNOS gene expressions.

Conclusion

This study suggests that oral supplementation of l-arginine enhances endothelial-dependent relaxation in rats fed a high-salt diet by ameliorating eNOS gene expression in the abdominal aorta of the rats.

Protective Role of Myelocytic Nitric Oxide Synthases against Hypoxic Pulmonary Hypertension in Mice

RATIONALE

Nitric oxide (NO), synthesized by NOSs (NO synthases), plays a role in the development of pulmonary hypertension (PH). However, the role of NO/NOSs in bone marrow (BM) cells in PH remains elusive.

OBJECTIVES

To determine the role of NOSs in BM cells in PH.

METHODS

Experiments were performed on 36 patients with idiopathic pulmonary fibrosis and on wild-type (WT), nNOS (neuronal NOS)^-/-, iNOS (inducible NOS)^-/-, eNOS (endothelial NOS)^-/-, and n/i/eNOSs^-/- mice.

MEASUREMENTS AND MAIN RESULTS

In the patients, there was a significant correlation between higher pulmonary artery systolic pressure and lower nitrite plus nitrate levels in the BAL fluid. In the mice, hypoxia-induced PH deteriorated significantly in the n/i/eNOSs^-/- genotype and, to a lesser extent, in the eNOS^-/- genotype as compared with the WT genotype. In the n/i/eNOSs^-/- genotype exposed to hypoxia, the number of circulating BM-derived vascular smooth muscle progenitor cells was significantly larger, and transplantation of green fluorescent protein-transgenic BM cells revealed the contribution of BM cells to pulmonary vascular remodeling. Importantly, n/i/eNOSs^-/--BM transplantation significantly aggravated hypoxia-induced PH in the WT genotype, and WT-BM transplantation significantly ameliorated hypoxia-induced PH in the n/i/eNOSs^-/- genotype. A total of 69 and 49 mRNAs related to immunity and inflammation, respectively, were significantly upregulated in the lungs of WT genotype mice transplanted with n/i/eNOSs^-/--BM compared with those with WT-BM, suggesting the involvement of immune and inflammatory mechanisms in the exacerbation of hypoxia-induced PH caused by n/i/eNOSs^-/--BM transplantation.

CONCLUSIONS

These results demonstrate that myelocytic n/i/eNOSs play an important protective role in the pathogenesis of PH.

Functional Relationship between Leptin and Nitric Oxide in Metabolism

Leptin, the product of the ob gene, was originally described as a satiety factor, playing a crucial role in the control of body weight. Nevertheless, the wide distribution of leptin receptors in peripheral tissues supports that leptin exerts pleiotropic biological effects, consisting of the modulation of numerous processes including thermogenesis, reproduction, angiogenesis, hematopoiesis, osteogenesis, neuroendocrine, and immune functions as well as arterial pressure control. Nitric oxide (NO) is a free radical synthesized from L-arginine by the action of the NO synthase (NOS) enzyme. Three NOS isoforms have been identified: the neuronal NOS (nNOS) and endothelial NOS (eNOS) constitutive isoforms, and the inducible NOS (iNOS). NO mediates multiple biological effects in a variety of physiological systems such as energy balance, blood pressure, reproduction, immune response, or reproduction. Leptin and NO on their own participate in multiple common physiological processes, with a functional relationship between both factors having been identified. The present review describes the functional relationship between leptin and NO in different physiological processes.

Alterations on a key nephrogenic/cardiogenic gene expression linked to hypertension development

The elevation of blood pressure produces specific organic lesions, including kidney and cardiac damage. On the other hand, cardiovascular disease usually leads to the development of hypertension. Thus, hypertension could be both a cause and a consequence of cardiovascular disease. Previous studies linked the lack of nitric oxide to cardiovascular abnormalities, including hypertension, arteriosclerosis, myocardial infarction, cardiac hypertrophy, diastolic heart failure, and reduced endothelium-derived hyperpolarizing factor responses, with shorter survival. The lack of this gas also leads to renal/cardiac abnormalities. It is widely known that nephrogenic deficiency is a risk factor for kidney disease. Besides, recent evidence suggests that alterations in WT-1, a key nephrogenic factor, could contribute to the development of hypertension. Moreover, some genes involved in the development of hypertension depend on WT-1. This knowledge makes it essential to investigate and understand the mechanisms regulating the expression of these genes during renal/cardiac development, and hypertension. As a consequence, the most in-depth knowledge of the complex aetiopathogenic mechanism responsible for the hypertensive disease will allow us to propose novel therapeutic tools.

Puerarin Reduces Blood Pressure in Spontaneously Hypertensive Rats by Targeting eNOS

Puerarin is an isoflavonoid isolated from the root of Pueraria lobata (Gegen in Chinese) that has been widely used to treat cardiovascular and cerebrovascular diseases in China. Here, we investigated the hypotensive effects and mechanisms of puerarin in spontaneously hypertensive rats. The qPCR array technique was used to determine the expression of hypertension-related genes. Then, the differentially expressed genes were analyzed using the STRING database. The systolic blood pressure and diastolic blood pressure of rats decreased after the administration of puerarin for nine weeks. Puerarin, but not losartan, also slowed the heart rate of rats. NO and cGMP levels were improved by puerarin. Eighteen differentially expressed hypertension-related genes were identified by comparing the model group with the control group and the high-dose puerarin group with the model group. NO and cGMP levels were increased by high-dose puerarin. High-dose puerarin increased the levels of the phosphorylated eNOS protein and decreased AT1 and Cav1 levels. Based on our results, eNOS was a key target in the mechanism by which puerarin reduced blood pressure, and puerarin represents a potential antihypertensive agent.

Hypertension-induced changes in the rat myocardium during the development of cardiac hypertrophy - a comparison between the left and the right ventricle

The hypertrophy of the cardiac muscle is one of the most significant maladaptive mechanisms activated in response to increased workload. It is associated with histological and ultrastructural alterations, changes in the quantitative parameters and the expression of different enzymes. While the structural and functional consequences of systemic hypertension on the left ventricle have been well evaluated, the right ventricle has received less attention. The aim of the present study was to analyse and compare the changes in the left and right ventricle during the development of cardiac hypertrophy initiated by systemic hypertension in different age groups of spontaneously hypertensive rats. Therefore, we studied the histology and ultrastructure of the cells of the myocardium, evaluated the immunohistochemical expression of the enzyme neuronal nitric oxide synthase and conducted a quantitative analysis of several morphometric parameters. We used three groups of spontaneously hypertensive rats. For the quantitative analysis we also used three age groups of age- and weight-matched control animals (normotensive Wistar rats). In both ventricles, we described cardiomyocytic hypertrophy, focal myocytolysis and increased collagen deposition in the interstitial space. Our observations on the ultrastructural level were associated with changes in the cardiomyocytic nuclei, the arrangement, maturity and organisation of the myofibrils, the localisation and ultrastructure of the mitochondria, the development and maturity of the intercalated discs, as well as changes in the components of the interstitium. The immunohistochemical expression of neuronal nitric oxide synthase in the left ventricle was stronger than that in the right ventricle across all age groups. The comparative quantitative analysis revealed that changes in the studied morphometric parameters in the two ventricles occurred disproportionately. In conclusion, the present study characterised the development of cardiac hypertrophy in response to systemic hypertension in both ventricles and demonstrated the involvement of the right ventricle.

Activation of NMDA receptors mediated iron accumulation via modulating iron transporters in Parkinson's disease

Increasing evidence has confirmed that nigral iron accumulation and activation of NMDA receptors (NRs) contribute to the neurodegeneration of dopamine (DA) neurons in Parkinson's disease (PD). Earlier work indicated that activation of NRs participated in iron metabolism in the hippocampus. However, the relationship between activation of NRs and iron accumulation in DA neurons of the substantia nigra in PD was unknown. In this study, our results showed that NRs inhibitors MK-801 and AP5 protected nigrostriatal projection system and reduced nigral iron levels of 6-hydroxydopamine (6-OHDA)-induced PD rats. In vitro studies demonstrated that NMDA treatment increased the expression of iron importer divalent metal transporter 1 (DMT1) and decreased the expression of iron exporter ferropotin 1 (Fpn1), which were dependent on iron regulatory protein 1 (IRP1). This led to increased intracellular iron levels and intensified the decrease in mitochondrial transmembrane potential in MES23.5 dopaminergic neurons. In addition, we reported that MK801 and neuronal nitric oxide synthase inhibitor could antagonize 6-OHDA-induced up-regulation of IRP1 and DMT1 and down-regulation of Fpn1, thus attenuating 6-OHDA-induced iron accumulation in MES23.5 cells. This suggested that 6-OHDA-induced activation of NRs might modulate the expression of DMT1 and Fpn1 via the neuronal nitric oxide synthase-IRP1 pathway.-Xu, H., Liu, X., Xia, J., Yu, T., Qu, Y., Jiang, H., Xie, J., Activation of NMDA receptors mediated iron accumulation via modulating iron transporters in Parkinson's disease.

Effects of Nitric Oxide on Renal Proximal Tubular Na+ Transport

Nitric oxide (NO) has a wide variety of physiological functions in the kidney. Besides the regulatory effects in intrarenal haemodynamics and glomerular microcirculation, in vivo studies reported the diuretic and natriuretic effects of NO. However, opposite results showing the stimulatory effect of NO on Na⁺ reabsorption in the proximal tubule led to an intense debate on its physiological roles. Animal studies have showed the biphasic effect of angiotensin II (Ang II) and the overall inhibitory effect of NO on the activity of proximal tubular Na⁺ transporters, the apical Na⁺/H⁺ exchanger isoform 3, basolateral Na⁺/K⁺ ATPase, and the Na⁺/HCO₃⁻ cotransporter. However, whether these effects could be reproduced in humans remained unclear. Notably, our recent functional analysis of isolated proximal tubules demonstrated that Ang II dose-dependently stimulated human proximal tubular Na⁺ transport through the NO/guanosine 3′,5′-cyclic monophosphate (cGMP) pathway, confirming the human-specific regulation of proximal tubular transport via NO and Ang II. Of particular importance for this newly identified pathway is its possibility of being a human-specific therapeutic target for hypertension. In this review, we focus on NO-mediated regulation of proximal tubular Na⁺ transport, with emphasis on the interaction with individual Na⁺ transporters and the crosstalk with Ang II signalling.

Understanding gene functions and disease mechanisms: Phenotyping pipelines in the German Mouse Clinic

Since decades, model organisms have provided an important approach for understanding the mechanistic basis of human diseases. The German Mouse Clinic (GMC) was the first phenotyping facility that established a collaboration-based platform for phenotype characterization of mouse lines. In order to address individual projects by a tailor-made phenotyping strategy, the GMC advanced in developing a series of pipelines with tests for the analysis of specific disease areas. For a general broad analysis, there is a screening pipeline that covers the key parameters for the most relevant disease areas. For hypothesis-driven phenotypic analyses, there are thirteen additional pipelines with focus on neurological and behavioral disorders, metabolic dysfunction, respiratory system malfunctions, immune-system disorders and imaging techniques. In this article, we give an overview of the pipelines and describe the scientific rationale behind the different test combinations.

The latest advances in the discovery of nitric oxide hybrid drug compounds

INTRODUCTION

There is a great interest in Nitric oxide (NO) within medicinal chemistry since it's involved in human signaling pathways. Prodrugs or hybrid compounds containing NO-donor scaffolds linked to an active compound are valuable, due to their potential for modulating many pathological conditions due to NO's biological properties when released in addition to the native drug. Compounds that selectively inhibit nitric oxide synthase isoforms (NOS) can also increase therapeutic capacity, particularly in the treatment of chronic diseases. However, search for bioactive compounds to efficiently and selectively modulate NO is still a challenge in drug discovery. Areas covered: In this review, the authors highlight the recent advances in the strategies used to discover NO-hybrid derivatives, especially those related to anti-inflammatory, cardiovascular, anticancer and anti-microorganism activities. They also focus on: nitric oxide synthase inhibitors, NO delivery materials and other related activities. Expert opinion: The process of molecular hybridization can be used to obtain NO-releasing compounds that also interact with different targets. The main problem with this approach is to control NO multiple actions in the right biological system. However, the use of NO-releasing groups with many different scaffolds leads to new molecular structures for bioactive compounds, suggesting synergies.

Transgenic overexpression of GTP cyclohydrolase 1 in cardiomyocytes ameliorates post-infarction cardiac remodeling

GTP cyclohydrolase 1 (GCH1) and its product tetrahydrobiopterin play crucial roles in cardiovascular health and disease, yet the exact regulation and role of GCH1 in adverse cardiac remodeling after myocardial infarction are still enigmatic. Here we report that cardiac GCH1 is degraded in remodeled hearts after myocardial infarction, concomitant with increases in the thickness of interventricular septum, interstitial fibrosis, and phosphorylated p38 mitogen-activated protein kinase and decreases in left ventricular anterior wall thickness, cardiac contractility, tetrahydrobiopterin, the dimers of nitric oxide synthase, sarcoplasmic reticulum Ca²⁺ release, and the expression of sarcoplasmic reticulum Ca²⁺ handling proteins. Intriguingly, transgenic overexpression of GCH1 in cardiomyocytes reduces the thickness of interventricular septum and interstitial fibrosis and increases anterior wall thickness and cardiac contractility after infarction. Moreover, we show that GCH1 overexpression decreases phosphorylated p38 mitogen-activated protein kinase and elevates tetrahydrobiopterin levels, the dimerization and phosphorylation of neuronal nitric oxide synthase, sarcoplasmic reticulum Ca²⁺ release, and sarcoplasmic reticulum Ca²⁺ handling proteins in post-infarction remodeled hearts. Our results indicate that the pivotal role of GCH1 overexpression in post-infarction cardiac remodeling is attributable to preservation of neuronal nitric oxide synthase and sarcoplasmic reticulum Ca²⁺ handling proteins, and identify a new therapeutic target for cardiac remodeling after infarction.

Long-term dietary nitrite and nitrate deficiency causes the metabolic syndrome, endothelial dysfunction and cardiovascular death in mice

AIMS/HYPOTHESIS

Nitric oxide (NO) is synthesised not only from L-arginine by NO synthases (NOSs), but also from its inert metabolites, nitrite and nitrate. Green leafy vegetables are abundant in nitrate, but whether or not a deficiency in dietary nitrite/nitrate spontaneously causes disease remains to be clarified. In this study, we tested our hypothesis that long-term dietary nitrite/nitrate deficiency would induce the metabolic syndrome in mice.

METHODS

To this end, we prepared a low-nitrite/nitrate diet (LND) consisting of an amino acid-based low-nitrite/nitrate chow, in which the contents of L-arginine, fat, carbohydrates, protein and energy were identical with a regular chow, and potable ultrapure water. Nitrite and nitrate were undetectable in both the chow and the water.

RESULTS

Three months of the LND did not affect food or water intake in wild-type C57BL/6J mice compared with a regular diet (RD). However, in comparison with the RD, 3 months of the LND significantly elicited visceral adiposity, dyslipidaemia and glucose intolerance. Eighteen months of the LND significantly provoked increased body weight, hypertension, insulin resistance and impaired endothelium-dependent relaxations to acetylcholine, while 22 months of the LND significantly led to death mainly due to cardiovascular disease, including acute myocardial infarction. These abnormalities were reversed by simultaneous treatment with sodium nitrate, and were significantly associated with endothelial NOS downregulation, adiponectin insufficiency and dysbiosis of the gut microbiota.

CONCLUSIONS/INTERPRETATION

These results provide the first evidence that long-term dietary nitrite/nitrate deficiency gives rise to the metabolic syndrome, endothelial dysfunction and cardiovascular death in mice, indicating a novel pathogenetic role of the exogenous NO production system in the metabolic syndrome and its vascular complications.

Altered glucose and lipid homeostasis in liver and adipose tissue pre-dispose inducible NOS knockout mice to insulin resistance

On the basis of diet induced obesity and KO mice models, nitric oxide is implied to play an important role in the initiation of dyslipidemia induced insulin resistance. However, outcomes using iNOS KO mice have so far remained inconclusive. The present study aimed to assess IR in iNOS KO mice after 5 weeks of LFD feeding by monitoring body composition, energy homeostasis, insulin sensitivity/signaling, nitrite content and gene expressions changes in the tissues. We found that body weight and fat content in KO mice were significantly higher while the respiratory exchange ratio (RER), volume of carbon dioxide (VCO₂), and heat production were lower as compared to WT mice. Furthermore, altered systemic glucose tolerance, tissue insulin signaling, hepatic gluconeogenesis, augmented hepatic lipids, adiposity, as well as gene expression regulating lipid synthesis, catabolism and efflux were evident in iNOS KO mice. Significant reduction in eNOS and nNOS gene expression, hepatic and adipose tissue nitrite content, circulatory nitrite was also observed. Oxygen consumption rate of mitochondrial respiration has remained unaltered in KO mice as measured using extracellular flux analyzer. Our findings establish a link between the NO status with systemic and tissue specific IR in iNOS KO mice at 5 weeks.

Crucial roles of nitric oxide synthases in β-adrenoceptor-mediated bladder relaxation in mice

The specific roles of nitric oxide (NO) synthases (NOSs) in bladder smooth muscle remain to be elucidated. We examined the roles of NOSs in β-adrenoceptor (AR)-mediated bladder relaxation. Male mice (C57BL6) deficient of neuronal NOS [nNOS-knockout (KO)], endothelial NOS (eNOS-KO), neuronal/endothelial NOS (n/eNOS-KO), neuronal/endothelial/inducible NOS (n/e/iNOS-KO), and their controls [wild-type (WT)] were used. Immunohistochemical analysis was performed in the bladder. Then the responses to relaxing agents and the effects of several inhibitors on the relaxing responses were examined in bladder strips precontracted with carbachol. Immunofluorescence staining showed expressions of nNOS and eNOS in the urothelium and smooth muscle of the bladder. Isoproterenol-induced relaxations were significantly reduced in nNOS-KO mice and were further reduced in n/eNOS-KO and n/e/iNOS-KO mice compared with WT mice. The relaxation in n/e/iNOS-KO mice was almost the same as in n/eNOS-KO mice. Inhibition of Ca2+-activated K+ (KCa) channel with charybdotoxin and apamin abolished isoproterenol-induced bladder relaxation in WT mice. Moreover, direct activation of KCa channel with NS1619 caused comparable extent of relaxations among WT, nNOS-KO, and n/eNOS-KO mice. In contrast, NONOate (a NO donor) or hydrogen peroxide (H2O2) (another possible relaxing factor from eNOS) caused minimal relaxations, and catalase (H2O2 scavenger) had no inhibitory effects on isoproterenol-induced relaxations. These results indicate that both nNOS and eNOS are substantially involved in β-AR-mediated bladder relaxations in a NO- or H2O2-independent manner through activation of KCa channels.

Adverse Effect of High-Fat Diet on Metabolic Programming in Offspring Born to a Murine Model of Maternal Hypertension

BACKGROUND

We previously reported that offspring heterozygous mice partially lacking endothelial nitric oxide synthase (eNOS) gene, and born to hypertensive eNOS-/- Knockout mother, are hypertensive. We hypothesized that those offspring when placed on high-fat diet (HFD) will undergo altered metabolic programming increasing their risk for developing metabolic syndrome.

METHODS

eNOS-/-KO and wild-type mice (eNOS+/+WT) were cross-bred to produce heterozygous offspring: maternal heterozygous (Mat, eNOS-/+), born from hypertensive eNOS-/-KO mothers; and paternal heterozygous (Pat, eNOS-/+), born from normotensive WT mothers. Mat, eNOS-/+ and Pat, eNOS-/+ female were allocated to HFD or control diet (CD) until 8 weeks of age. Then a metabolic profile was obtained: weight, glucose/insulin tolerance test (GTT, ITT), systolic blood pressure (SBP), serum fasting levels of insulin, adiponectin, leptin, and a lipid panel.

RESULTS

Weight was not different between all offspring within each diet. GTT curve was higher in Mat, eNOS-/+ vs. Pat, eNOS-/+ offspring on both diet (P < 0.001). In ITT, glucose level at 15 minutes was higher in Mat, eNOS-/+ on HFD. Insulin level was increased in Mat, eNOS-/+ vs. Pat, eNOS-/+ on either diet. SBP was elevated in Mat, eNOS-/+ vs. Pat, eNOS-/+ on CD and was further raised in Mat, eNOS-/+ offspring on HFD (P < 0.001). No other differences were seen except for lower high-density lipoprotein levels in Mat, eNOS-/+ fed HFD (P < 0.003).

CONCLUSIONS

Mat, eNOS-/+ offspring exposed in utero to maternal hypertension and fed HFD postnatally have increased susceptibility for metabolic abnormalities. Thus, maternal HTN is a risk factor for altered fetal metabolic programming.

Neuronal nitric oxide synthase in hypertension - an update

Hypertension is a prevalent condition worldwide and is the key risk factor for fatal cardiovascular complications, such as stroke, sudden cardiac death and heart failure. Reduced bioavailability of nitric oxide (NO) in the endothelium is an important precursor for impaired vasodilation and hypertension. In the heart, NO deficiency deteriorates the adverse consequences of pressure-overload and causes cardiac hypertrophy, fibrosis and myocardial infarction which lead to fatal heart failure and sudden cardiac death. Recent consensus is that both endothelial and neuronal nitric oxide synthases (eNOS or NOS3 and nNOS or NOS1) are the constitutive sources of NO in the myocardium. Between the two, nNOS is the predominant isoform of NOS that controls intracellular Ca²⁺ homeostasis, myocyte contraction, relaxation and signaling pathways including nitroso-redox balance. Notably, our recent research indicates that cardiac eNOS protein is reduced but nNOS protein expression and activity are increased in hypertension. Furthermore, nNOS is induced by the interplay between angiotensin II (Ang II) type 1 receptor (AT1R) and Ang II type 2 receptor (AT2R), mediated by NADPH oxidase and reactive oxygen species (ROS)-dependent eNOS activity in cardiac myocytes. nNOS, in turn, protects the heart from pathogenesis via positive lusitropy in hypertension. Soluble guanylate cyclase (sGC)-cGMP/PKG-dependent phosphorylation of myofilament proteins are novel targets of nNOS in hypertensive myocardium. In this short review, we will endeavor to overview new findings of the up-stream and downstream regulation of cardiac nNOS in hypertension, shed light on the underlying mechanisms which may be of therapeutic value in hypertensive cardiomyopathy.

The functional variants of endothelial nitric oxide synthase gene associated with rheumatoid arthritis in Turkish adults

This study aimed to investigate whether functional variants of endothelial nitric oxide synthase (eNOS) gene play any role in rheumatoid arthritis (RA) ethiopathogenesis and treatment in the Turkish population. Because, eNOS variants are responsible for alteration of the NO level in plasma, by reducing/increasing the endothelial NO synthesis. In the study, two eNOS gene variants (G894T and intron 4 VNTR A/B) were examined at extracted DNAs from 65 peripheral blood cell of RA patients. For the control, blood samples obtained from 70 healthy persons were studied. Genotyping of molecular variants was performed by PCR-RFLP and/or PCR technique. The data obtained was compared in itself and response to therapy. We found that "TT genotypic frequency" for the G894T variant was significantly associated with RA with an overall risk of 8.3-fold (p 0.029). No association was identified between intron 4 VNTR A/B variant and RA. At the 6 months, the mean visual analog scale (VAS), health assessment questionnaire (HAQ), and disease activity score for 28 joints (DAS 28) improvement was not significant among groups. Improvement in DAS was significantly better in anti-TNF treatment than disease-modifying antirheumatic drugs (DMARD) treatment treated subgroup. We report for the first time that variants in the eNOS "TT" genotype might be contributed to the increased risk of RA in the Turkish population. These results imply that functional variants of eNOS gene might have an effect on RA patients and response to anti-TNF treatment. In addition, the results suggest that eNOS variants might be associated and affect host susceptibility and/or response to treatment in Turkish RA patients.

Altered Nitric Oxide System in Cardiovascular and Renal Diseases

Nitric oxide (NO) is synthesized by a family of NO synthases (NOS), including neuronal, inducible, and endothelial NOS (n/i/eNOS). NO-mediated effects can be beneficial or harmful depending on the specific risk factors affecting the disease. In hypertension, the vascular relaxation response to acetylcholine is blunted, and that to direct NO donors is maintained. A reduction in the activity of eNOS is mainly responsible for the elevation of blood pressure, and an abnormal expression of iNOS is likely to be related to the progression of vascular dysfunction. While eNOS/nNOS-derived NO is protective against the development of atherosclerosis, iNOS-derived NO may be proatherogenic. eNOS-derived NO may prevent the progression of myocardial infarction. Myocardial ischemia/reperfusion injury is significantly enhanced in eNOS-deficient animals. An important component of heart failure is the loss of coronary vascular eNOS activity. A pressure-overload may cause severer left ventricular hypertrophy and dysfunction in eNOS null mice than in wild-type mice. iNOS-derived NO has detrimental effects on the myocardium. NO plays an important role in regulating the angiogenesis and slowing the interstitial fibrosis of the obstructed kidney. In unilateral ureteral obstruction, the expression of eNOS was decreased in the affected kidney. In triply n/i/eNOS null mice, nephrogenic diabetes insipidus developed along with reduced aquaporin-2 abundance. In chronic kidney disease model of subtotal-nephrectomized rats, treatment with NOS inhibitors decreased systemic NO production and induced left ventricular systolic dysfunction (renocardiac syndrome).

[Exercise-induced shear stress: Physiological basis and clinical impact]

The physiological regulation of vascular function is essential for cardiovascular health and depends on adequate control of molecular mechanisms triggered by endothelial cells in response to mechanical and chemical stimuli induced by blood flow. Endothelial dysfunction is one of the major risk factors for cardiovascular disease, where an imbalance between synthesis of vasodilator and vasoconstrictor molecules is one of its main mechanisms. In this context, the shear stress is one of the most important mechanical stimuli to improve vascular function, due to endothelial mechanotransduction, triggered by stimulation of various endothelial mechanosensors, induce signaling pathways culminating in increased bioavailability of vasodilators molecules such as nitric oxide, that finally trigger the angiogenic mechanisms. These mechanisms allow providing the physiological basis for the effects of exercise on vascular health. In this review it is discussed the molecular mechanisms involved in the vascular response induced by shear stress and its impact in reversing vascular injury associated with the most prevalent cardiovascular disease in our population.

Physiological and pathophysiological reactive oxygen species as probed by EPR spectroscopy: the underutilized research window on muscle ageing

Reactive oxygen and nitrogen species (ROS and RNS) play crucial roles in triggering, mediating and regulating physiological and pathophysiological signal transduction pathways within the cell. Within the cell, ROS efflux is firmly controlled both spatially and temporally, making the study of ROS dynamics a challenging task. Different approaches have been developed for ROS assessment; however, many of these assays are not capable of direct identification or determination of subcellular localization of different ROS. Here we highlight electron paramagnetic resonance (EPR) spectroscopy as a powerful technique that is uniquely capable of addressing questions on ROS dynamics in different biological specimens and cellular compartments. Due to their critical importance in muscle functions and dysfunction, we discuss in some detail spin trapping of various ROS and focus on EPR detection of nitric oxide before highlighting how EPR can be utilized to probe biophysical characteristics of the environment surrounding a given stable radical. Despite the demonstrated ability of EPR spectroscopy to provide unique information on the identity, quantity, dynamics and environment of radical species, its applications in the field of muscle physiology, fatiguing and ageing are disproportionately infrequent. While reviewing the limited examples of successful EPR applications in muscle biology we conclude that the field would greatly benefit from more studies exploring ROS sources and kinetics by spin trapping, protein dynamics by site-directed spin labelling, and membrane dynamics and global redox changes by spin probing EPR approaches.

Vascular nitric oxide: Beyond eNOS

As the first discovered gaseous signaling molecule, nitric oxide (NO) affects a number of cellular processes, including those involving vascular cells. This brief review summarizes the contribution of NO to the regulation of vascular tone and its sources in the blood vessel wall. NO regulates the degree of contraction of vascular smooth muscle cells mainly by stimulating soluble guanylyl cyclase (sGC) to produce cyclic guanosine monophosphate (cGMP), although cGMP-independent signaling [S-nitrosylation of target proteins, activation of sarco/endoplasmic reticulum calcium ATPase (SERCA) or production of cyclic inosine monophosphate (cIMP)] also can be involved. In the blood vessel wall, NO is produced mainly from l-arginine by the enzyme endothelial nitric oxide synthase (eNOS) but it can also be released non-enzymatically from S-nitrosothiols or from nitrate/nitrite. Dysfunction in the production and/or the bioavailability of NO characterizes endothelial dysfunction, which is associated with cardiovascular diseases such as hypertension and atherosclerosis.