Nitric Oxide Precursor Research Articles

Photodissociation Dynamics of Nitric Oxide from N-Acetylcysteine- or N-Acetylpenicillamine-bound Roussin's Red Ester.

The photochemical release of nitric oxide (NO) from a NO precursor is advantageous in terms of spatial, temporal, and dosage control of NO delivery to target sites. To realize full control of the quantitative NO administration from photoactivated NO precursors, it is necessary to have detailed dynamical information on the photodissociation of NO from NO precursors. We synthesized two new water-soluble Roussin’s red esters (RREs), [Fe2(μ-N-acetylcysteine)2(NO)4] and [Fe2(μ-N-acetylpenicillamine)2(NO)4], which have five times longer lifetime than the well-known [Fe2(μ-cysteine)2(NO)4]. The photodissociation dynamics of NO from these RREs in water were investigated over a broad time range from 0.3 ps to 10 μs after excitation at 310 and 400 nm using femtosecond time-resolved infrared (IR) spectroscopy. When these RREs are excited, they either release one NO, producing a radical species deficient in one NO (R), [Fe2(μ-RS)2(NO)3], or relax into the ground state without photodeligation via an electronically excited intermediate state (M). R appears immediately after photoexcitation, suggesting that one NO is photodissociated faster than 0.3 ps. A certain fraction of R undergoes geminate recombination (GR) with NO with a time constant of 7–9 ps, while the remaining R competitively binds to the solvent. Solvent-bound R eventually bimolecularly recombines with NO with a rate constant of (1.3–1.6) × 108 M–1 s–1. For a given RRE molecule, the fractional yield of M (0.62–0.76) depends on the excitation wavelength (λex); however, the relaxation time of M (6 ± 1 ns) is independent of λex. Although the primary quantum yield of NO photodissociation (Φ1) was found to be 0.24–0.38, the final yield of NO suitable for other reactions (Φ2) was reduced to 0.14–0.29 due to the picosecond GR of the dissociated NO with R. Detailed photoexcitation dynamics of RRE can be utilized in the quantitative control of NO administration at a specific site and time, promoting pin-point usage of NO in chemistry and biology. We demonstrate that femtosecond IR spectroscopy combined with quantum chemical calculations is a powerful method for obtaining detailed dynamic information on photoactivated NO precursors such as Φ1 and Φ2, the GR yield, and secondary reactions of the nascent photoproducts, which are essential information for the design of efficient photoactivated NO precursors and their quantitative utilization.

Arginase-1 Released into CSF After Aneurysmal Subarachnoid Hemorrhage Decreases Arginine/Ornithine Ratio: a Novel Prognostic Biomarker

We hypothesized that the enzyme arginase-1 is released into the cerebrospinal fluid (CSF) during red blood cell lysis and contributes to dysregulated metabolism of the nitric oxide (NO) precursor L-arginine during aneurysmal subarachnoid hemorrhage (SAH). This prospective case–control study included 43 patients with aneurysmal SAH and ventricular drainage for clinical reasons. Longitudinal CSF samples (99) were obtained in the course of SAH. Patients were dichotomized regarding the occurrence of cerebral vasospasm syndrome (CVS) (N = 19). Arginase-1 and the amino acids L-arginine and L-ornithine were quantified in CSF. Outcome assessments included delayed cerebral ischemia (DCI) and functional status after 3 months using the modified Rankin Scale (mRS). Arginase-1 was released into the CSF of SAH patients whereas this enzyme was undetectable in controls. Compared to patients without CVS, arginase-1 levels were higher in CVS patients until day 14 after clinical event. The well-known surrogate parameter for arginase acitivity, the L-arginine to L-ornithine ratio (Arg/Orn), correlated with CSF arginase-1 levels. Arg/Orn was reduced in patients with CVS from disease onset (days 1–3, p = 0.0009) until day 14. Logistic regression analysis of early Arg/Orn was predictive for CVS (p = 0.008) and DCI (p = 0.035), independent of age, Hunt and Hess grade, and intraventricular blood. Arg/Orn < 2.71 at disease onset predicted CVS with a sensitivity of 86.7% and specificity of 72.2%. Arg/Orn ≥ 2.71 predicted excellent functional outcome. We propose a novel mechanism contributing to NO deprivation during SAH: arginase-1 is released from erythrocytes into the CSF, leading to L-arginine consumption and reduced NO bioavailability. Furthermore, Arg/Orn is a robust predictor for occurrence of CVS, DCI, and functional outcome 3 months after aneurysmal SAH. Our data provide a novel prognostic biomarker and may contribute to the development of novel therapeutic strategies in SAH. Clinical Trial Registration-URL: http://www.drks.de. Unique identifier: DRKS00015293, date of registration: 13.09.2018.

NIR-II Responsive Hydrogel as an Angiogenesis Inhibition Agent for Tumor Microenvironment Reprogramming.

Regulation of angiogenesis is a great challenge for effective anticancer therapy. Generally, anti-angiogenic therapies are focused on inhibition of inducers involved in pro-angiogenic communication pathways. Despite the great potential of anti-angiogenic therapy, engineering efficient angiogenesis inhibition agents (AIAs) is still a formidable challenge, since most anti-angiogenic therapies are limited due to the cancer recurrence via compensatory expression of different angiogenic mediators. Herein, we present a new strategy of near-infrared-II (NIR-II) responsive hydrogel AIAs, constructed by incorporation of nitric oxide (NO) precursor (BNN6) and 2D WO2.9 nanosheets within hydrogel (WB@hydrogel). Because of the defect/2D engineering, the bandgap of the WO2.9 nanosheets narrows, which extends the absorption to the NIR-II region. It offers a favorable NIR-II controlled manner for NO generation through irradiation time and light intensity. The continuous supply of NO can activate the expression of wild-type p53 protein and further reverse the transcriptional expression of pro- and anti-angiogenic factors of the tumor microenvironment (TME), subsequently alternating pro-angiogenic TME to anti-angiogenic TME. In the murine tumor model, this method achieved high tumor growth inhibition (TGI) rate and excellent anti-recurrence efficiency.

Modulatory Effects of L-Arginine on Methylxanthine-Induced Cardiotoxicity in Rats: A Differential Role for Nitric Oxide (NO)

Methylxanthines are potent bronchodilators used in obstructive airway disease like COPD and bronchial asthma, but the narrow therapeutic index and resultant adverse effect profile have restricted their use. Novel beneficial effects and modes of action are now being proposed for these pharmacoeconomically viable agents. Cardiotoxicity is a prominent adverse effect of methylxanthone and thus we investigated possible mechanisms for such toxicity with an aim to devise ameliorative strategies for counteracting such undesirable effects. In view of the cardioprotective role of nitric oxide (NO) and NO mimetics, the present study investigated the possible modulatory role of L-arginine, a NO precursor, in theophylline induced cardiotoxicity in rats, with a view to exploring strategies for facilitating the safe use of this drug. The methylxanthine, aminophylline induced cardiotoxic effects like increased heart rat, raised mean BP, inverted T-waves and prolonged QTc interval (in ECG). These were accompanied by increased levels of cardiac biomarkers like Troponin-I, CPK-MB, and ADMA. Oxidative stress markers like MDA were elevated whereas, antioxidant defence markers like GSH and SOD were suppressed. Co-administration of L-arginine (with aminophylline) had dose-related effects on cardiac function (heart rate, mean BP, ECG changes) and cardiospecific biomarkers (TnI, CPK-MB, ADMA) - the lower dose being protective whereas the higher dose potentiating some of the cardiac effects and cardiospecific/oxidative stress biomarker levels. The results indicate a biphasic involvement of NO in the cardiotoxic effect of theophylline and suggests possible interactions of NO with reactive oxygen species during such modulations of cardiotoxicity.

GTP Cyclohydrolase I as a Potential Drug Target: New Insights into Its Allosteric Modulation via Normal Mode Analysis.

Guanosine triphosphate (GTP) cyclohydrolase I (GCH1) catalyzes the conversion of GTP into dihydroneopterin triphosphate (DHNP). DHNP is the first intermediate of the folate de novo biosynthesis pathway in prokaryotic and lower eukaryotic microorganisms and the tetrahydrobiopterin (BH4) biosynthesis pathway in higher eukaryotes. The de novo folate biosynthesis provides essential cofactors for DNA replication, cell division, and synthesis of key amino acids in rapidly replicating pathogen cells, such as Plasmodium falciparum (P. falciparum), a causative agent of malaria. In eukaryotes, the product of the BH4 biosynthesis pathway is essential for the production of nitric oxide and several neurotransmitter precursors. An increased copy number of the malaria parasite P. falciparum GCH1 gene has been reported to influence antimalarial antifolate drug resistance evolution, whereas mutations in the human GCH1 are associated with neuropathic and inflammatory pain disorders. Thus, GCH1 stands as an important and attractive drug target for developing therapeutics. The GCH1 intrinsic dynamics that modulate its activity remains unclear, and key sites that exert allosteric effects across the structure are yet to be elucidated. This study employed the anisotropic network model to analyze the intrinsic motions of the GCH1 structure alone and in complex with its regulatory partner protein. We showed that the GCH1 tunnel-gating mechanism is regulated by a global shear motion and an outward expansion of the central five-helix bundle. We further identified hotspot residues within sites of structural significance for the GCH1 intrinsic allosteric modulation. The obtained results can provide a solid starting point to design novel antineuropathic treatments for humans and novel antimalarial drugs against the malaria parasite P. falciparum GCH1 enzyme.

Serum L-arginine and endogenous methylarginine concentrations predict irritable bowel syndrome in adults: Anested case-control study.

Background & AimsNitric oxide, a major inhibitory nonadrenergic, noncholinergic neurotransmitter that relaxes smooth muscle, may be implicated in the pathophysiology of visceral hypersensitivity in irritable bowel syndrome (IBS). Impaired bioavailability of the nitric oxide precursor molecule L‐arginine and higher concentrations of methylarginines (endogenous inhibitors of nitric oxide synthesis) are known to impair nitric oxide synthesis in numerous gastrointestinal cell types. We therefore examined serum concentrations of L‐arginine and the methylarginines in a nested case‐control study, to assess whether these factors are associated with adult IBS.MethodsData on clinical characteristics, methylarginines, and L‐arginine (measured using LC‐MS/MS) were collected from a random population‐based cohort of Australian adults (median age = 64 years; IQR = 60–70). Cases of IBS, defined according to Rome III criteria (N = 156), and controls (N = 332) were identified from within the cohort at the 5‐year follow‐up.ResultsIn adjusted logistic regression analyses, L‐arginine, asymmetric dimethylarginine, symmetric dimethylarginine, L‐arginine/asymmetric dimethylarginine ratio, and Kessler‐10 psychological distress scores were significantly associated with IBS (p > 0.05). Similar results were found for IBS subtypes. Higher serum L‐arginine concentration had the strongest association with IBS diagnosis, with an odds ratio of 9.03 for those with serum L‐arginine at the 75th (84 μmol/L) versus 25th (46 μmol/L) percentile (95% CI: 5.99–13.62). L‐arginine had the best discriminative ability with a bias‐adjusted area under the receiver operator characteristic curve of 0.859.ConclusionsHigher serum concentrations of L‐arginine and endogenous methylarginines are strongly associated with IBS in adults.

A critical evaluation of [ML(ONO)]n+ (M = Fe, Ru, Os) as nitric oxide precursor influenced by spin multiplicity and geometrical parameters (M-O-NO and MO-N-O) for the NO release: A theoretical study

In cell biology, the physiological functions control blood pressure by the production of nitric oxide, and the exploitation of metal complexes such as [ML-ONO] (M = Fe2+, Ru2+, Os2+) has been motivated to study the photolytic liability of NO. The structural and electronic properties of the complexes of 1,4,8,11-tetrakis-(1-methyl-pyridyl)-1,4,8,11-tetraazacyclotetradecane were analyzed theoretically. The results show that β-cleavage of nitrito group in the complex [ML-ONO]n+ (M = Fe, Ru, Os; n = 1 or 2) favors the NO release, and observed the role of spin multiplicity. The M(II)-O-NO angle is associated with the degree of activation of the M(II)O—NO bond, relying on the excitations (S = 1 or S = 2), and it is corelated to the reduction of the bond angle ONO (~133° at S = 0) to ~ 105° at S = 1 or 2, favoring the nitrito β-cleavage for the complexes. This is consistent with orbital energy (dx2-y2) stabilizing the axial M(III)-O bond greater than that in M(II)-O [Fe < Ru ~ Os] as the excitation of singlet to triplet or to quintet prompts the NO delivery according to Gibbs free energy, agreeing with the transition state energy. However, at high spin state like 3/2 or 5/2, irrespective of bond angle M(III)-O-NO or ONO, the bond O-NO was broken spontaneously, resulting relatively a greater bond distance. Natural Transition Orbitals (NTOs), Molecular orbital (MO) Electron density contour on molecular orbital surface were also studied to understand the M-ONO bonding nature, and observed its performance in the TD-DFT electronic spectra.

Nitric Oxide Deficiency in Mitochondrial Disorders: The Utility of Arginine and Citrulline.

Mitochondrial diseases represent a growing list of clinically heterogeneous disorders that are associated with dysfunctional mitochondria and multisystemic manifestations. In spite of a better understanding of the underlying pathophysiological basis of mitochondrial disorders, treatment options remain limited. Over the past two decades, there is growing evidence that patients with mitochondrial disorders have nitric oxide (NO) deficiency due to the limited availability of NO substrates, arginine and citrulline; decreased activity of nitric oxide synthase (NOS); and NO sequestration. Studies evaluating the use of arginine in patients with mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes (MELAS) presenting with stroke-like episodes showed symptomatic improvement after acute administration as well as a reduction in the frequency and severity of stroke-like episodes following chronic use. Citrulline, another NO precursor, was shown through stable isotope studies to result in a greater increase in NO synthesis. Recent studies showed a positive response of arginine and citrulline in other mitochondrial disorders besides MELAS. Randomized-controlled studies with a larger number of patients are warranted to better understand the role of NO deficiency in mitochondrial disorders and the efficacy of NO precursors as treatment modalities in these disorders.

Exogenous arginine enhances the chilling tolerance in postharvest papaya fruit by regulating arginine and proline metabolism

Papaya fruit is easily affected by low temperature, causing chilling injury (CI). In this study, the exogenous arginine was applied in the storage of postharvest papaya fruit and it was found that 0.8 mM arginine treatment significantly alleviated CI of papaya fruit. Arginine treatment promoted the accumulation of polyamines (PAs), which might be ascribed to the increased activities of arginase, arginine decarboxylase (ADC), ornithine decarboxylase (ODC), and S-adenosylmethionine decarboxylase (SAMDC). A higher accumulation of proline was found in arginine-treated papaya fruit, which may be due to increased activity of ornithine-δ-aminotransferase (OAT) and Δ1-pyrroline-5-carboxylate acid synthase (P5CS) and inhibited activity of proline dehydrogenase (PDH). In addition, arginine treatment increased higher nitric oxide synthase (NOS) activity and promoted the generation of nitric oxide (NO). The results of this study indicate that exogenous arginine may improve the chilling tolerance of postharvest papaya fruit by regulating arginine and proline metabolism. Practical applications In recent years, chilling injury of tropical fruits is a significant problem, including papaya. Many studies on polyamine, proline, nitric oxide, and chilling injury of fruits, but arginine, as a common precursor of polyamine, proline, and nitric oxide, are rarely studied, especially in papaya fruit. Our findings demonstrated that the exogenous arginine can regulate endogenous arginine metabolism, induce polyamine, putrescine, and nitric oxide accumulation, and coordinate to alleviate chilling injury of papaya fruit.

A newly discovered interference of the central nitrergic system on oxytocin-induced hypophagia in layer-type chickens

Various neurochemical pathways are participating in the regulation of food intake in mammals and birds. Both oxytocin (OT) and nitric oxide (NO) are known as hypophagic agents in birds. This study consisted of 6 experiments and each experiment had 4 groups (ngroup=11, 5-day-old chickens). In all experiments, 3-hour food-deprived (FD3) birds received intracerebroventricular (ICV) injections either control diluent or drug solution. Then the birds had ad libitum access to the food and fresh water and then cumulative food intake (gr) was measured based on the percentage of the body weight (%BW). In experiments 1 to 3, ICV injections of L-arginine (precursor of NO, 200, 400, and 800 nmol), L-NAME (NOS inhibitor, 100, 200, and 400 nmol) and OT (2.5, 5, and 10 µg) were performed respectively. In experiment 4, each group received any ICV injections of L-NAME (100 nmol), OT (10 µg) or a co-injection of L-NAME (100 nmol) and OT (10 µg). In experiment 5, L-arginine (ICV, 200 nmol), OT (10 µg), or L-arginine (200 nmol) and OT (10 µg) were injected to the groups. Experiment 6 was similar to the experiment 5, although the dose of OT was 2.5 µg in all the treatment groups. Results showed that the ICV injection of L-NAME (100 nmol) significantly attenuated hypophagic effect induced by OT (10 µg) (p < 0.05). Findings suggested that NO might mediate the hypophagic effect of OT in FD3 neonatal layer-type chickens.

Endothelial Cell-Derived Tethered Lipid Bilayers Generating Nitric Oxide for Endovascular Implantation.

Engineering an endothelium-mimetic surface has been one of long-lasting topics to develop ideal cardiovascular devices. The aim of the study was to investigate the potential use of a model of lipid bilayers that not only come from membranes extracted from endothelial cells (ECs) but also embedded with a type of organoselenium lipid enabling it to catalyze the generation of nitric oxide (NO). Herein, the titanium-cloaking in lipid bilayers extracted from ECs was prepared to propose a promising idea for the development of endovascular implants. For this purpose, we synthesized and characterized a lipidic molecule containing selenium and verified enough catalytic activity for the NO generation in the presence of S-nitrosothiols (RSNO) as endogenous NO precursors. We demonstrated the fabrication process of tethered lipid bilayers, from membrane extraction to vesicle fusion, and validated the successful formation of the layer and the catalyst insertion. The resulting bilayer presented endothelium-similar properties including the NO generation and cellular interactions. The catalyst inserted into the bilayer provided an unexampled result in the release period and kinetics of NO, likely similar to the native endothelial system. Using three different cells including EC, smooth muscle cell (SMC), and macrophage, it was demonstrated that the membrane responds selectively to each cell in the manner of promotive, suppressive, and nonimmunoreactive, respectively. Taken together, the fundamental study on obtained results not only provides understanding of the kinetics of designed NO catalyst and cellular interactions of reassembled membranes but also suggests very useful data on rational design and development of many vascular implantable devices, even expandable toward to nonvascular biointerfacing devices.

Role of nitric oxide in orthodontic tooth movement (Review).

Nitric oxide (NO) is an ubiquitous signaling molecule that mediates numerous cellular processes associated with cardiovascular, nervous and immune systems. NO also plays an essential role in bone homeostasis regulation. The present review article summarized the effects of NO on bone metabolism during orthodontic tooth movement in order to provide insight into the regulatory role of NO in orthodontic tooth movement. Orthodontic tooth movement is a process in which the periodontal tissue and alveolar bone are reconstructed due to the effect of orthodontic forces. Accumulating evidence has indicated that NO and its downstream signaling molecule, cyclic guanosine monophosphate (cGMP), mediate the mechanical signals during orthodontic-related bone remodeling, and exert complex effects on osteogenesis and osteoclastogenesis. NO has a regulatory effect on the cellular activities and functional states of osteoclasts, osteocytes and periodontal ligament fibroblasts involved in orthodontic tooth movement. Variations of NO synthase (NOS) expression levels and NO production in periodontal tissues or gingival crevicular fluid (GCF) have been found on the tension and compression sides during tooth movement in both orthodontic animal models and patients. Furthermore, NO precursor and NOS inhibitor administration increased and reduced the tooth movement in animal models, respectively. Further research is required in order to further elucidate the underlying mechanisms and the clinical application prospect of NO in orthodontic tooth movement.

The nitric oxide-cyclic guanosine monophosphate pathway inhibits the bladder ATP release in response to a physiological or pathological stimulus.

The release of ATP from the epithelium of the urinary bladder (urothelium) in response to mechanical/chemical stimuli contributes to the visceral sensation in the micturition reflex. The nitric oxide (NO)‐mediated induction of cyclic guanosine monophosphate (cGMP) has been detected in urothelial cells and may inhibit the micturition reflex. However, the function of the NO‐cGMP pathway in the regulation of urothelial ATP release remains poorly understood in contrast to its effects on smooth muscles or primary afferent nerves. Therefore, we investigated the relevance of the NO‐cGMP pathway to ATP release on the mucosal side in the present study. The administration of l‐arginine (NO precursor) or NOC 12 (NO donor) significantly reduced ATP release to the mucosal side at a physiologically normal urine storage pressure (5 cmH2O). L‐NAME (NO synthase inhibitor) significantly increased the distention‐induced release of ATP. The phosphodiesterase‐5 inhibitor, sildenafil, which increases cGMP levels, inhibited distention‐induced ATP release. Furthermore, sildenafil significantly reduced ATP release in response to the administration of lipopolysaccharide. These results suggest that the NO‐cGMP pathway inhibited urothelial ATP release during the storage phase under both physiological and pathological conditions.

Presence of antioxidants and nitric-oxide precursors in Mimosa pudica extract

Blood pressure lowering effect of Mimosa pudica induced by dieresis was reported earlier. As a diuretic it enhances urine outflow, decreases plasma volume, venous return; and thereby, reduce blood pressure. Besides the diuretic agent, some other blood pressure lowering substance may also be present in Mimosa pudica. Present study was undertaken to reveal the presence of antioxidants and nitrite in Mimosa pudica extract, which may help to reduce blood pressure. Methanolic extract of Mimosa pudica (using 80% methanol) was lyophilised to obtain dried Mimosa pudica Extract (MPE). For Total phenolic content estimation Folin’s method and for estimation of flavonoids, Aluminium chloride method were followed. The radical scavenging and superoxide anion radical scavenging activity were measured following standardised methods. Nitrite content of MPE at different dilutions (10-100 µl in methanol) was measured following standardised procedure keeping sodium nitrite as the standard. Present study noted presence of favonoids and phenolic compounds and also noted antioxidant property in the aforesaid extract that exhibited DPPH+ and superoxide scavenging activities. Besides that, this study also revealed formation of nitrites in the extract of Mimosa pudica in a dose dependent manner. Nitrite is the precursor of nitric oxide (NO). NO is a potent vasodilator that decreases blood pressure. Present study indicated the presence of both antioxidants and nitrites in Mimosa pudica extract; both of which have blood pressure lowering properties indicating it as a blood pressure lowering agent; and helpful in the maintenance of vascular health.

Decreased Expression and Uncoupling of Endothelial Nitric Oxide Synthase in the Cerebral Cortex of Rats with Thioacetamide-Induced Acute Liver Failure.

Acute liver failure (ALF) is associated with deregulated nitric oxide (NO) signaling in the brain, which is one of the key molecular abnormalities leading to the neuropsychiatric disorder called hepatic encephalopathy (HE). This study focuses on the effect of ALF on the relatively unexplored endothelial NOS isoform (eNOS). The cerebral prefrontal cortices of rats with thioacetamide (TAA)-induced ALF showed decreased eNOS expression, which resulted in an overall reduction of NOS activity. ALF also decreased the content of the NOS cofactor, tetrahydro-L-biopterin (BH4), and evoked eNOS uncoupling (reduction of the eNOS dimer/monomer ratio). The addition of the NO precursor L-arginine in the absence of BH4 potentiated ROS accumulation, whereas nonspecific NOS inhibitor L-NAME or EDTA attenuated ROS increase. The ALF-induced decrease of eNOS content and its uncoupling concurred with, and was likely causally related to, both increased brain content of reactive oxidative species (ROS) and decreased cerebral cortical blood flow (CBF) in the same model.

Direct comparison of inorganic nitrite and nitrate on vascular dysfunction and oxidative damage in experimental arterial hypertension

Arterial hypertension is one of the major health risk factors leading to coronary artery disease, stroke or peripheral artery disease. Dietary uptake of inorganic nitrite (NO2−) and nitrate (NO3−) via vegetables leads to enhanced vascular NO bioavailability and provides antihypertensive effects. The present study aims to understand the underlying vasoprotective effects of nutritional NO2− and NO3− co-therapy in mice with angiotensin-II (AT-II)-induced arterial hypertension. High-dose AT-II (1 mg/kg/d, 1w, s. c.) was used to induce arterial hypertension in male C57BL/6 mice. Additional inorganic nitrite (7.5 mg/kg/d, p. o.) or nitrate (150 mg/kg/d, p. o.) were administered via the drinking water. Blood pressure (tail-cuff method) and endothelial function (isometric tension) were determined. Oxidative stress and inflammation markers were quantified in aorta, heart, kidney and blood. Co-treatment with inorganic nitrite, but not with nitrate, normalized vascular function, oxidative stress markers and inflammatory pathways in AT-II treated mice. Of note, the highly beneficial effects of nitrite on all parameters and the less pronounced protection by nitrate, as seen by improvement of some parameters, were observed despite no significant increase in plasma nitrite levels by both therapies. Methemoglobin levels tended to be higher upon nitrite/nitrate treatment. Nutritional nitric oxide precursors represent a non-pharmacological treatment option for hypertension that could be applied to the general population (e.g. by eating certain vegetables). The more beneficial effects of inorganic nitrite may rely on superior NO bioactivation and stronger blood pressure lowering effects. Future large-scale clinical studies should investigate whether hypertension and cardiovascular outcome in general can be influenced by dietary inorganic nitrite therapy.

Marching to the Beet: The effect of dietary nitrate supplementation on high altitude exercise performance and adaptation during a military trekking expedition

PurposeThe aim was to investigate the effect of dietary nitrate supplementation (in the form of beetroot juice, BRJ) for 20 days on salivary nitrite (a potential precursor of bioactive nitric oxide), exercise performance and high altitude (HA) acclimatisation in field conditions (hypobaric hypoxia). MethodsThis was a single-blinded randomised control study of 22 healthy adult participants (12 men, 10 women, mean age 28 ± 12 years) across a HA military expedition. Participants were randomised pre-ascent to receive two 70 ml dose per day of either BRJ (~12.5 mmol nitrate per day; n = 11) or non-nitrate calorie matched control (n = 11). Participants ingested supplement doses daily, beginning 3 days prior to departure and continued until the highest sleeping altitude (4800 m) reached on day 17 of the expedition. Data were collected at baseline (44 m altitude), at 2350 m (day 9), 3400 m (day 12) and 4800 m (day 17). ResultsBRJ enhanced the salivary levels of nitrite (p = 0.007). There was a significant decrease in peripheral oxygen saturation and there were increases in heart rate, diastolic blood pressure, and rating of perceived exertion with increasing altitude (p=<0.001). Harvard Step Test fitness scores significantly declined at 4800 m in the control group (p = 0.003) compared with baseline. In contrast, there was no decline in fitness scores at 4800 m compared with baseline (p = 0.26) in the BRJ group. Heart rate recovery speed following exercise at 4800 m was significantly prolonged in the control group (p=<0.01) but was unchanged in the BRJ group (p = 0.61). BRJ did not affect the burden of HA illness (p = 1.00). ConclusionsBRJ increases salivary nitrite levels and ameliorates the decline in fitness at altitude but does not affect the occurrence of HA illness.

Redox-responsive micelles integrating catalytic nanomedicine and selective chemotherapy for effective tumor treatment

Chemotherapy is one of the most conventional modalities for cancer therapy. However, the high multidrug resistance of tumor cells still limited the clinical application of current chemotherapy. Considering the ability of nitric oxide (NO) to modulate potent P-glycoprotein to inhibit multi-drug resistance, a synergistic methodology combining chemotherapy and sustained NO generation is an ideal way to further promote the chemotherapy. Herein, a multi-functional micelle with tumor-selective chemotherapy driven by redox-triggered doxorubicin (DOX) release and drug resistance inhibition based on intracellular NO generation was fabricated for effective tumor treatment. The micelle consists of DOX as core, arginine/glucose oxidase (Arg/GOx) as shell and redox-responsive disulfide bond as a linker, which is denoted as micelle-DOX-Arg-GOx. The Arg serves as the biological precursor of nitric oxide for inhibition of multi-drug resistance to promote chemotherapy and GOx catalyzes glucose to produce hydrogen peroxide (H2O2) for increasing the generation of NO. Moreover, the glucose supply could be simultaneously blocked by the catalytic process, which further enhanced therapeutic efficiency. This micelle requests a tumor-specific microenvironment (a considerable amount of GSH) to perform synergistic therapeutics including chemotherapy, starvation therapy (catalytic medicine), and gas therapy for tumor treatment, which resulted in significant cytotoxicity to tumor tissue.

Citrulline supplementation improves spatial memory in a murine model for Alzheimer's disease

ObjectivesAlzheimer's disease (AD) correlates with the dysfunction of metabolic pathways that translates into neurological symptoms. An arginine deficiency, a precursor of nitric oxide (NO), has been reported for patients with AD. We aimed to evaluate the effect of citrulline oral supplementation on cognitive decline in an AD murine model. MethodsThree-month citrulline or water supplementation was blindly given to male and female wild-type and 3 × Tg mice with AD trained and tested in the Morris water maze. Cerebrospinal fluid and brain tissue were collected. Ultra-performance liquid chromatography was used for arginine determinations and the Griess method for NO. ResultsEight-month-old male 3 × Tg mice with AD supplemented with citrulline performed significantly better in the Morris water maze task. Arginine levels increased in the cerebrospinal fluid although no changes were seen in brain tissue and only a tendency of increase of NO was observed. ConclusionsCitrulline oral administration is a viable treatment for memory improvement in the early stages of AD, pointing to NO as a viable, efficient target for memory dysfunction in AD.

Curcumin relieves mice gastric emptying dysfunction induced by L-arginine and atropine through interstitial cells of Cajal.

Curcumin is natural polyphenol from Curcuma longa rhizomes with several biological properties. Our previous studies demonstrated that curcumin inhibited functional gastric emptying disorders induced by L-arginine, the precursor of nitric oxide (NO), and atropine, an acetylcholine receptor (AChR) blocker. However, the mechanism of action of curcumin remains unclear. In the present study, mouse models of functional gastric emptying disorders induced by L-arginine and atropine were used to examine changes in interstitial cells of Cajal (ICC) and NO- and ACh-mediated regulation of gastrointestinal motility. Curcumin pre-treatment ameliorated the gastric emptying rate in mice treated with L-arginine or atropine (P<0.01). NO content and NO synthase activity significantly increased in the stomachs of L-arginine-treated mice, compared with controls (P<0.01). Acetylcholinesterase activity (P<0.01) and mRNA expression (P<0.01), as well as AChR mRNA levels (P<0.05) significantly decreased following atropine treatment. Moreover, in both models, the levels of c-kit, anoctamin 1 and connexin 43 significantly decreased in the stomach (P<0.01). Conversely, curcumin pre-treatment inhibited the changes induced by L-arginine and atropine (P<0.01 or P<0.05). By affecting the production of exogenous NO, the effects of Ach-AchR and the biomarkers of ICC, curcumin relieves the gastric emptying dysfunction in mice.