Nitric Oxide

Compensatory mechanisms in myoglobin deficient mice preserve NO homeostasis Publication date: 1 September 2019 Source: Nitric Oxide, Volume 90 Author(s): Ji Won Park, Barbora Piknova, Soumyadeep Dey, Constance T. Noguchi, Alan N. Schechter Abstract The mechanism for nitric oxide (NO) generation from reduction of nitrate (NO3−) and nitrite (NO2−) has gained increasing attention due to the potential beneficial effects of NO in cardiovascular diseases and exercise performance. We have previously shown in rodents that skeletal muscle is the major nitrate reservoir in the body and that exercise enhances the nitrate reduction pathway in the muscle tissue and have proposed that nitrate in muscle originates from diet, the futile cycle of nitric oxide synthase 1 (NOS1) and/or oxidation of NO by oxymyoglobin. In the present study, we tested the hypothesis that lack of myoglobin expression would decrease nitrate levels in skeletal muscle. We observed a modest but significant decrease of nitrate level in skeletal muscle of myoglobin deficient mice compared to littermate control mice (17.3 vs 12.8 nmol/g). In contrast, a NOS inhibitor, L-NAME or a low nitrite/nitrate diet treatment led to more pronounced decreases of nitrate levels in the skeletal muscle of both control and myoglobin deficient mice. Nitrite levels in the skeletal muscle of both types of mice were similar (0.48 vs 0.42 nmol/g). We also analyzed the expression of several proteins that are closely related to NO metabolism to examine the mechanism by which nitrate and nitrite levels are preserved in the absence of myoglobin. Western blot analyses suggest that the protein levels of xanthine oxidoreductase and sialin, a nitrate transporter, both increased in the skeletal muscle of myoglobin deficient mice. These results are compatible with our previously reported model of nitrate production in muscle and suggest that myoglobin deficiency activates compensatory mechanisms to sustain NO homeostasis. Graphical abstract

Effect of nitrite on the electroencephalographic activity in the healthy brain Publication date: 1 September 2019 Source: Nitric Oxide, Volume 90 Author(s): Edit Franko, Martyn Ezra, Douglas C. Crockett, Olivier Joly, Kyle Pattinson Abstract Background Nitrite is a major intravascular store for nitric oxide. The conversion of nitrite to the active nitric oxide occurs mainly under hypoxic conditions to increase blood flow where it is needed the most. The use of nitrite is, therefore, being evaluated widely to reduce the brain injury in conditions resulting in cerebral hypoxia, such as cardiac arrest, ischaemic stroke or subarachnoid haemorrhage. However, as it is still unknown how exogenous nitrite affects the brain activity of healthy individuals, it is difficult to clearly understand how it affects the ischaemic brain. Objective Here we performed a double-blind placebo-controlled crossover study to investigate the effects of nitrite on neural activity in the healthy brain. Methods Twenty-one healthy volunteers were recruited into the study. All participants received a continuous infusion of sodium nitrite (0.6 mg/kg/h) on one occasion and placebo (sodium chloride) on another occasion. Electroencephalogram was recorded before the start and during the infusion. We computed the power spectrum density within the conventional frequency bands (delta, theta, alpha, beta), and the ratio of the power within the alpha and delta bands. We also measured peripheral cardiorespiratory physiology and cerebral blood flow velocities. Results We found no significant effect of nitrite on the power spectrum density in any frequency band. Similarly, the alpha-delta power ratio did not differ between the two conditions. The peripheral cardiorespiratory physiology and middle cerebral artery velocity and associated indices were also unaffected by the nitrite infusion. However, nitrite infusion decreased the mean blood pressure and increased the methaemoglobin concentration in the blood. Conclusion Our study shows that exogenous sodium nitrite does not alter the electrical activity in the healthy brain. This might be because the sodium nitrite is converted to vasoactive nitric oxide in areas of hypoxia, and in the healthy brain there is no significant amount of conversion due to lack of hypoxia. However, this lack of change in the power spectrum density in healthy people emphasises the specificity of the brain's response to nitrite in disease.

The gasotransmitter hydrogen sulfide inhibits transepithelial anion secretion of pregnant mouse endometrial epithelium Publication date: 1 September 2019 Source: Nitric Oxide, Volume 90 Author(s): Jia-Wen Xu, Dong-Dong Gao, Lei Peng, Zhuo-Er Qiu, Li-Jiao Ke, Yun-Xin Zhu, Yi-Lin Zhang, Wen-Liang Zhou Abstract Endometrial epithelium exhibits a robust ion transport activity required for dynamical regulation of uterine fluid environment and thus embryo implantation. However, there still lacks a thorough understanding of the ion transport processes and regulatory mechanism in peri-implantation endometrial epithelium. As a gaseous signaling molecule or gasotransmitter, hydrogen sulfide (H2S) regulates a myriad of cellular and physiological processes in various tissues, including the modulation of ion transport proteins in epithelium. This study aimed to investigate the effects of H2S on ion transport across mouse endometrial epithelium and its possible role in embryo implantation. The existence of endogenous H2S in pregnant mouse uterus was tested by the detection of two key H2S-generating enzymes and measurement of H2S production rate in tissue homogenates. Transepithelial ion transport processes were electrophysiologically assessed in Ussing chambers on early pregnant mouse endometrial epithelial layers, demonstrating that H2S suppressed the anion secretion by blocking cystic fibrosis transmembrane conductance regulator (CFTR). H2S increased intracellular Cl− concentration ([Cl−]i) in mouse endometrial epithelial cells, which was abolished by pretreatment with the CFTR selective inhibitor CFTRinh-172. The cAMP level in mouse endometrial epithelial cells was not affected by H2S, indicating that H2S blocked CFTR in a cAMP-independent way. In vivo study showed that interference with H2S synthesis impaired embryo implantation. In conclusion, our study demonstrated that H2S inhibits the transepithelial anion secretion of early pregnant mouse endometrial epithelium via blockade of CFTR, contributing to the preparation for embryo implantation.

New generation of nitric oxide-releasing porous materials: Assessment of their potential to regulate biological functions Publication date: 1 September 2019 Source: Nitric Oxide, Volume 90 Author(s): Rosana V. Pinto, Ana C. Fernandes, Fernando Antunes, Zhi Lin, João Rocha, João Pires, Moisés L. Pinto Abstract Nitric oxide (NO) presents innumerable biological roles, and its exogenous supplementation for therapeutic purposes has become a necessity. Some nanoporous materials proved to be potential vehicles for NO with high storage capacity. However, there is still a lack of information about their efficiency to release controlled NO and if they are biocompatible and biologically stable. In this work, we address this knowledge gap starting by evaluating the NO release and stability under biological conditions and their toxicity with primary keratinocyte cells. Titanosilicates (ETS-4 and ETS-10 types) and clay-based materials were the materials under study, which have shown in previous studies suitable NO gas adsorption/release rates. ETS-4 proved to be the most promising material, combining good biocompatibility at 180 μg/mL, stability and slower NO release. ETS-10 and ETAS-10 showed the best biocompatibility at the same concentration and, in the case of clay-based materials, CoOS is the least toxic of those tested and the one that releases the highest NO amount. The potentiality of these new NO donors to regulate biological functions was assessed next by controlling the mitochondrial respiration and the cell migration. NO-loaded ETS-4 regulates O2 consumption and cell migration in a dose-dependent manner. For cell migration, a biphasic effect was observed in a narrow range of ETS-4 concentration, with a stimulatory effect becoming inhibitory just by doubling ETS-4 concentration. For the other materials, no effective regulation was achieved, which highlights the relevance of the new assessment presented in this work for nanoporous NO carriers that will pave the way for further developments. Graphical abstract

Nitric oxide releasing two-part creams containing S-nitrosoglutathione and zinc oxide for potential topical antimicrobial applications Publication date: 1 September 2019 Source: Nitric Oxide, Volume 90 Author(s): Joshua C. Doverspike, Yang Zhou, Jianfeng Wu, Xiaojuan Tan, Chuanwu Xi, Mark E. Meyerhoff Abstract Currently, most antimicrobial topical treatments utilize antibiotics to prevent or treat infection at a wound site. However, with the ongoing evolution of multi-drug resistant bacterial strains, there is a high demand for alternative antimicrobial treatments. Nitric oxide (NO) is an endogenous gas molecule with potent antimicrobial activity, which is effective against a wide variety of bacterial strains. In this study, the potential for creating NO releasing creams containing the naturally occurring NO carrier, S-nitrosoglutathione (GSNO), are characterized and evaluated. GSNO is shown to have prolonged stability (>300 days) when mixed and stored within Vaseline at 24 °C. Further, enhanced proliferation of NO from GSNO using zinc oxide nanoparticles (ZnO) is demonstrated. Triggering NO release from the GSNO/Vaseline mixture using a commercial zinc oxide-containing cream exhibits first-order NO release kinetics with the highest %NO release over the first 6 h. Significant killing effects against S. aureus, S. epidermidis, and P. aeruginosa are demonstrated for the GSNO/Vaseline/ZnO cream mixtures in a proportional manner dependent upon the concentration of GSNO in the final mixture. Graphical abstract

Zinc-induced root architectural changes of rhizotron-grown B. napus correlate with a differential nitro-oxidative response Publication date: 1 September 2019 Source: Nitric Oxide, Volume 90 Author(s): Gábor Feigl, Árpád Molnár, Réka Szőllősi, Attila Ördög, Kitti Törőcsik, Dóra Oláh, Attila Bodor, Katalin Perei, Zsuzsanna Kolbert Abstract Roots have a noteworthy plasticity: due to different stress conditions their architecture can change to favour seedling vigour and yield stability. The development of the root system is regulated by a complex and diverse signalling network, which besides hormonal factors, includes reactive oxygen (ROS) - and nitrogen species (RNS). The delicate balance of the endogenous signal system can be affected by various environmental stimuli, such as the excess of essential heavy metals, like zinc (Zn). Zn at low concentration, is able to induce the morphological and physiological adaptation of the root system, but in excess it exerts toxic effects on plants. In this study the effect of a low, growth-inducing, and a high, growth inhibiting Zn concentrations on the early development of Brassica napus (L.) root architecture and the underlying nitro-oxidative mechanisms were studied in a soil-filled rhizotron system. The growth-inhibiting Zn treatment resulted in elevated protein tyrosine nitration due to the imbalance in ROS and RNS homeostasis, however its pattern was not changed compared to the control. This nitro-oxidative stress was accompanied by serious changes in the cell wall composition and decrease in the cell proliferation and viability, due to the high Zn uptake and disturbed microelement homeostasis in the root tips. During the positive root growth response, a tyrosine nitration-pattern reorganisation was observed; there were no substantial changes in ROS and RNS balance and the viability and proliferation of the root tips’ meristematic zone decreased to a lesser extent, as a result of a lower Zn uptake. The obtained results suggest that Zn in different amounts triggers different root growth responses accompanied by distinct changes in the pattern and strength of tyrosine nitration, proposing that nitrosative processes have an important role in the stress-induced root growth responses.

The role of nitric oxide signaling in pulmonary circulation of high- and low-altitude newborn sheep under basal and acute hypoxic conditions Publication date: 1 August 2019 Source: Nitric Oxide, Volume 89 Author(s): Emilio A. Herrera, Germán Ebensperger, Ismael Hernández, Emilia M. Sanhueza, Aníbal J. Llanos, Roberto V. Reyes Abstract Nitric oxide (NO) is the main vasodilator agent that drives the rapid decrease of pulmonary vascular resistance for the respiratory onset during the fetal to neonatal transition. Nevertheless, the enhanced NO generation by the neonatal pulmonary arterial endothelium does not prevent development of hypoxic pulmonary hypertension in species without an evolutionary story at high altitude. Therefore, this study aims to describe the limits of the NO function at high-altitude during neonatal life in the sheep as an animal model without tolerance to perinatal hypoxia. We studied the effect of blockade of NO synthesis with l-NAME in the cardiopulmonary response of lowland (580 m) and highland (3600 m) newborn lambs basally and under an episode of acute hypoxia. We also determined the pulmonary expression of proteins that mediate the actions of the NO vasodilator pathway in the pulmonary vasoactive tone and remodeling. We observed an enhanced nitrergic function in highland lambs under basal conditions, evidenced as a markedly greater increase in basal mean pulmonary arterial pressure (mPAP) and resistance (PVR) under blockade of NO synthesis. Further, acute hypoxic challenge in lowland lambs infused with l-NAME markedly increased their mPAP and PVR to values greater than baseline, whilst in highland animals under NO synthesis blockade, these variables did not show additional increase in response to low PO2. Highland animals showed increased pulmonary RhoA expression, decreased PSer188-RhoA fraction, increased PSer311-p65-NFқβ fraction and up-regulated smooth muscle α-actin, relative to lowland controls. Taken together our data suggest that NO-mediated vasodilation is important to keep a low pulmonary vascular resistance under basal conditions and acute hypoxia at low-altitude. At high-altitude, the enhanced nitrergic signaling partially prevents excessive pulmonary hypertension but does not protect against acute hypoxia. The decreased vasodilator efficacy of nitrergic tone in high altitude lambs could be in part due to increased RhoA signaling that opposes to NO action in the hypoxic pulmonary circulation.

Targeting nitric oxide as a key modulator of sepsis, arthritis and pain Publication date: 1 August 2019 Source: Nitric Oxide, Volume 89 Author(s): Fernando Spiller, Rodrigo Oliveira Formiga, Jonathan Fernandes da Silva Coimbra, Jose Carlos Alves-Filho, Thiago Mattar Cunha, Fernando Queiroz Cunha Abstract Nitric oxide (NO) is produced by enzymatic activity of neuronal (nNOS), endothelial (eNOS), and inducible nitric oxide synthase (iNOS) and modulates a broad spectrum of physiological and pathophysiological conditions. The iNOS isoform is positively regulated at transcriptional level and produces high levels of NO in response to inflammatory mediators and/or to pattern recognition receptor signaling, such as Toll-like receptors. In this review, we compiled the main contributions of our group for understanding of the role of NO in sepsis and arthritis outcome and the peripheral contributions of NO to inflammatory pain development. Although neutrophil iNOS-derived NO is necessary for bacterial killing, systemic production of high levels of NO impairs neutrophil migration to infections through inhibiting neutrophil adhesion on microcirculation and their locomotion. Moreover, neutrophil-derived NO contributes to multiple organ dysfunction in sepsis. In arthritis, NO is chief for bacterial clearance in staphylococcal-induced arthritis; however, it contributes to articular damage and bone mass degradation. NO produced in inflammatory sites also downmodulates pain. The mechanism involved in analgesic effect and inhibition of neutrophil migration is dependent on the activation of the classical sGC/cGMP/PKG pathway. Despite the increasing number of studies performed after the identification of NO as an endothelium-derived relaxing factor, the underlying mechanisms of NO in inflammatory diseases remain unclear.

Nitric oxide and interactions with reactive oxygen species in the development of melanoma, breast, and colon cancer: A redox signaling perspective Publication date: 1 August 2019 Source: Nitric Oxide, Volume 89 Author(s): Hugo P. Monteiro, Elaine G. Rodrigues, Adriana K.C. Amorim Reis, Luiz S. Longo, Fernando T. Ogata, Ana I.S. Moretti, Paulo E. da Costa, Ana C.S. Teodoro, Maytê S. Toledo, Arnold Stern Abstract Cancer development is closely related to chronic inflammation, which is associated with identifiable markers of tumor progression, such as uncontrolled cell proliferation, angiogenesis, genomic instability, chemotherapeutic resistance, and metastases. Redox processes mediated by reactive oxygen species (ROS) and nitric oxide (NO) within the inflammatory tumor microenvironment play an essential role in directly influencing intercellular and intracellular signaling. These reactive species originating in the cancer cell or its microenvironment, mediate the epithelial-mesenchymal transition (EMT) and the mesenchymal-epithelial transition (MET). However, intracellular interactions between NO and ROS must be controlled to prevent cell death. Melanoma, breast, and colon cancer cells have developed a mechanism to survive and adapt to oxidative and nitrosative stress. The mechanism involves a spatial-temporal fine adjustment of the intracellular concentrations of NO and ROS, thereby guaranteeing the successful development of cancer cells. Physiological concentrations of NO and supra physiological concentrations of ROS are prevalent in cancer cells at the primary site. The situation reverses in cancer cells undergoing the EMT prior to being released into the blood stream. Intracellular supra physiological concentrations of NO found in circulating cancer cells endow them with anoikis resistance. When the anoikis-resistant cancer cells arrive at a metastatic site they undergo the MET. Endogenous supra physiological concentrations of ROS and physiological NO concentrations are prevalent in these cells. Understanding tumor progression from the perspective of redox signaling permits the characterization of new markers and approaches to therapy. The synthesis and use of compounds with the capacity of modifying intracellular concentrations of NO and ROS may prove effective in disrupting a redox homeostasis operative in cancer cells.

Delivery of carbon monoxide via halogenated ether anesthetics Publication date: 1 August 2019 Source: Nitric Oxide, Volume 89 Author(s): Christopher P. Hopper, Jakob Wollborn