Nitric oxide stimulates type IV MSHA pilus retraction in Vibrio cholerae via activation of the phosphodiesterase CdpA.

Bacteria use surface appendages called type IV pili to perform diverse activities including DNA uptake, twitching motility, and attachment to surfaces. The dynamic extension and retraction of pili are often required for these activities, but the stimuli that regulate these dynamics remain poorly characterized. To address this question, we study the bacterial pathogen Vibrio cholerae, which uses mannose-sensitive hemagglutinin (MSHA) pili to attach to surfaces in aquatic environments as the first step in biofilm formation. Here, we use a combination of genetic and cell biological approaches to describe a regulatory pathway that allows V. cholerae to rapidly abort biofilm formation. Specifically, we show that V. cholerae cells retract MSHA pili and detach from a surface in a diffusion-limited, enclosed environment. This response is dependent on the phosphodiesterase CdpA, which decreases intracellular levels of cyclic-di-GMP to induce MSHA pilus retraction. CdpA contains a putative nitric oxide (NO)-sensing NosP domain, and we demonstrate that NO is necessary and sufficient to stimulate CdpA-dependent detachment. Thus, we hypothesize that the endogenous production of NO (or an NO-like molecule) in V. cholerae stimulates the retraction of MSHA pili. These results extend our understanding of how environmental cues can be integrated into the complex regulatory pathways that control pilus dynamic activity and attachment in bacterial species.

Gestational intermittent hypoxia induces endothelial dysfunction and hypertension in pregnant rats: role of endothelin type B receptor†.

Obstructive sleep apnea is a recognized risk factor for gestational hypertension, yet the exact mechanism behind this association remains unclear. Here, we tested the hypothesis that intermittent hypoxia, a hallmark of obstructive sleep apnea, induces gestational hypertension through perturbed endothelin-1 signaling. Pregnant Sprague-Dawley rats were subjected to normoxia (control), mild intermittent hypoxia (10.5% O2), or severe intermittent hypoxia (6.5% O2) from gestational days 10-21. Blood pressure was monitored. Plasma was collected and mesenteric arteries were isolated for myograph and protein analyses. The mild and severe intermittent hypoxia groups demonstrated elevated blood pressure, reduced plasma nitrate/nitrite, and unchanged endothelin-1 levels compared to the control group. Western blot analysis revealed decreased expression of endothelin type B receptor and phosphorylated endothelial nitric oxide synthase, while the levels of endothelin type A receptor and total endothelial nitric oxide synthase remained unchanged following intermittent hypoxia exposure. The contractile responses to potassium chloride, phenylephrine, and endothelin-1 were unaffected in endothelium-denuded arteries from mild and severe intermittent hypoxia rats. However, mild and severe intermittent hypoxia rats exhibited impaired endothelium-dependent vasorelaxation responses to endothelin type B receptor agonist IRL-1620 and acetylcholine compared to controls. Endothelium denudation abolished IRL-1620-induced vasorelaxation, supporting the involvement of endothelium in endothelin type B receptor-mediated relaxation. Treatment with IRL-1620 during intermittent hypoxia exposure significantly attenuated intermittent hypoxia-induced hypertension in pregnant rats. This was associated with elevated circulating nitrate/nitrite levels, enhanced endothelin type B receptor expression, increased endothelial nitric oxide synthase activation, and improved vasodilation responses. Our data suggested that intermittent hypoxia exposure during gestation increases blood pressure in pregnant rats by suppressing endothelin type B receptor-mediated signaling, providing a molecular mechanism linking intermittent hypoxia and gestational hypertension.

Liquid plasma promotes angiogenesis through upregulation of endothelial nitric oxide synthase-induced extracellular matrix metabolism: potential applications of liquid plasma for vascular injuries.

BACKGROUND: Applications of nonthermal plasma have expanded beyond the biomedical field to include antibacterial, anti-inflammatory, wound healing, and tissue regeneration. Plasma enhances epithelial cell repair; however, the potential damage to deep tissues and vascular structures remains under investigation. RESULT: This study assessed whether liquid plasma (LP) increased nitric oxide (NO) production in human umbilical vein endothelial cells by modulating endothelial NO synthase (eNOS) phosphorylation and potential signaling pathways. First, we developed a liquid plasma product and confirmed the angiogenic effect of LP using the Matrigel plug assay. We found that the NO content increased in plasma-treated water. NO in plasma-treated water promoted cell migration and angiogenesis in scratch and tube formation assays via vascular endothelial growth factor mRNA expression. In addition to endothelial cell proliferation and migration, LP influenced extracellular matrix metabolism and matrix metalloproteinase activity. These effects were abolished by treatment with NG-L-monomethyl arginine, a specific inhibitor of NO synthase. Furthermore, we investigated the signaling pathways mediating the phosphorylation and activation of eNOS in LP-treated cells and the role of LKB1-adenosine monophosphate-activated protein kinase in signaling. Downregulation of adenosine monophosphate-activated protein kinase by siRNA partially inhibited LP-induced eNOS phosphorylation, angiogenesis, and migration. CONCLUSION: The present study suggests that LP treatment may be a novel strategy for promoting angiogenesis in vascular damage. Video Abstract.

Exploring the power of nitric oxide and nanotechnology for prolonging postharvest shelf-life and enhancing fruit quality.

Nitric oxide (NO) is a versatile signaling molecule that plays a crucial role in regulating postharvest fruit quality. The utilization of NO donors to elevate endogenous NO levels and induce NO-mediated responses represents a promising strategy for extending fruit shelf-life after harvest. However, the effectiveness of NO treatment is influenced by various factors, including formulation and application methods. In this review, we investigate the impact of NO supply on different fruits, aiming to prolong postharvest shelf-life and enhance fruit quality. Furthermore, we delve into the underlying mechanisms of NO action, particularly its interactions with ethylene and reactive oxygen species (ROS). Excitingly, we also highlight the emerging field of nanotechnology in postharvest applications, discussing the use of nanoparticles as a novel approach for achieving sustained release of NO and enhancing its effects. By harnessing the potential of nanotechnology, our review is a starting point to help identify gaps and future directions in this important, emerging field.

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.

Nitric Oxide-Releasing Porous Coating with Antibacterial Activity and Blood Compatibility.

Nitric oxide (NO)-releasing coating is promising to enhance the biocompatibility of medical devices. In this study, polyurethane (PU) and S-nitrosated keratin (KSNO) were dissolved with dimethyl sulfoxide (DMSO) and tetrahydrofuran (THF) to prepare a coating solution. This solution is facile to form a porous coating on various substrates based on solvent-evaporation-induced phase separation (SEIPS). The coating could continuously release NO up to 200 h in the presence of ascorbic acid (Asc). In addition, the coating could accelerate endothelialization by promoting the viability of human umbilical vein endothelial cells (HUVECs) while inhibiting the proliferation of human umbilical artery smooth muscle cells (HUASMCs). Furthermore, the coating had good antibacterial activity and blood compatibility. Taken together, this universal coating provides wider potential applications in the field of cardiovascular implants.

Effects of elevated levels of intracellular nitric oxide on Pseudomonas aeruginosa biofilm in chronic skin wound and slow-killing infection models.

Nitric oxide (NO), produced through the denitrification pathway, regulates biofilm dynamics through the quorum sensing system in Pseudomonas aeruginosa. NO stimulates P. aeruginosa biofilm dispersal by enhancing phosphodiesterase activity to decrease cyclic di-GMP levels. In a chronic skin wound model containing a mature biofilm, the gene expression of nirS, encoding nitrite reductase to produce NO, was low, leading to reduced intracellular NO levels. Although low-dose NO induces biofilm dispersion, it is unknown whether it influences the formation of P. aeruginosa biofilms in chronic skin wounds. In this study, a P. aeruginosa PAO1 strain with overexpressed nirS was established to investigate NO effects on P. aeruginosa biofilm formation in an ex vivo chronic skin wound model and unravel the underlying molecular mechanisms. Elevated intracellular NO levels altered the biofilm structure in the wound model by inhibiting the expression of quorum sensing-related genes, which was different from an in vitro model. In Caenorhabditis elegans as a slow-killing infection model, elevated intracellular NO levels increased worms' lifespan by 18%. Worms that fed on the nirS-overexpressed PAO1 strain for 4 h had complete tissue, whereas worms that fed on empty plasmid-containing PAO1 had biofilms on their body, causing severe damage to the head and tail. Thus, elevated intracellular NO levels can inhibit P. aeruginosa biofilm growth in chronic skin wounds and reduce pathogenicity to the host. Targeting NO is a potential approach to control biofilm growth in chronic skin wounds wherein P. aeruginosa biofilms are a persistent problem.

Penile erection and cardiovascular function: effects and pathophysiology.

Penile erection (PE) is a hemodynamic event that results from a neuroendocrine process, and it is influenced by the cardiovascular status of the patient. However, it may also modulate an individual's cardiovascular events. The present study provides the mechanisms involved in the association of PE and cardiovascular function. Erection upsurges the cardiac rate, blood pressure, and oxygen uptake. Sex-enhancing strategies, such as phosphodiesterase inhibitors, alprostadil, and testosterone also promote vasodilatation and cardiac performance, thus preventing myocardial infarction. More so, drugs that are used in the treatment of hypertensive heart diseases (such as angiotensin system inhibitors and ß-blockers) facilitate vasodilatation and PE. These associations have been linked with nitric oxide- and testosterone-dependent enhancing effects on the vascular endothelium. In addition, impaired cardiovascular function may negatively impact PE; therefore, impaired PE may be a pointer to cardiovascular pathology. Hence, evaluation of the cardiovascular status of an individual with erectile dysfunction (ED) is essential. Also, employing strategies that are used in maintaining optimal cardiac function may be useful in the management of ED.

Endogenous Nitric Oxide Can Enhance Oxidative Stress Caused by Air Pollutants and Explain Higher Susceptibility of Individuals with Inflammatory Disorders.

Air pollution causes morbidity and excess mortality. In the epithelial lining fluid of the respiratory tract, air pollutants trigger a chemical reaction sequence that causes the formation of noxious hydroxyl radicals that drive oxidative stress. For hitherto unknown reasons, individuals with pre-existing inflammatory disorders are particularly susceptible to air pollution. Through detailed multiphase chemical kinetic analysis, we show that the commonly elevated concentrations of endogenous nitric oxide in diseased individuals can increase the production of hydroxyl radicals via peroxynitrite formation. Our findings offer a molecular rationale of how adverse health effects and oxidative stress caused by air pollutants may be exacerbated by inflammatory disorders.

Nitric oxide and AMF-mediated regulation of soil enzymes activities, cysteine-H2S system and thiol metabolites in mitigating chromium (Cr (VI)) toxicity in pigeonpea genotypes.

Cr (VI) hampers plant growth and yield by reducing essential nutrient uptake as it competes for phosphate and sulfate transporters. Nitric oxide (NO) and mycorrhization play important roles in mitigating Cr (VI) toxicity. Present study aimed to compare the potential of AMF (Arbuscular mycorrhizal fungi)-Rhizoglomus intraradices and NO (0.25 mM) in alleviating Cr (VI) stress (0, 10 and 20 mg/kg) in two differentially tolerant pigeonpea genotypes (Pusa 2001 and AL 201). Cr (VI) toxicity reduced growth, mycorrhizal colonization, nutrient uptake, and overall productivity by inducing reactive oxygen species (ROS) generation, with AL 201 more sensitive than Pusa 2001. NO and AM enhanced activities of soil enzymes, thereby increasing nutrients availability as well as their uptake, with AM more effective than NO. Both amendments reduced oxidative stress and restricted Cr (VI) uptake by increasing the activities of antioxidant and S- assimilatory enzymes, with Pusa 2001 more responsive than AL 201. NO was relatively more efficient in regulating cysteine-H2S system by increasing the activities of biosynthetic enzymes (ATP-sulfurylase (ATPS), O-acetylserine thiol lyase (OASTL), D-cysteine desulfhydrase (DCD) and L-cysteine desulfhydrase (LCD), while AM significantly increased glutathione reductase (GR), γ-glutamylcysteine synthetase (γ-ECS) enzymes activities and resultant glutathione (GSH), phytochelatins (PCs), and non-protein thiols (NP-SH) synthesis. Moreover, co-application of NO and AM proved to be highly beneficial in negating the toxic effects of Cr (VI) due to functional complementarity between them. Study suggested the combined use of NO and AM as a useful strategy in re-establishing pigeonpea plants growing in Cr (VI)-stressed environments.

A novel multifunctional microneedle patch for synergistic photothermal- gas therapy against maxillofacial malignant melanoma and associated skin defects.

Considering the high recrudescence and the long-lasting unhealed large-sized wound that affect the aesthetics and cause dysfunction after resection of maxillofacial malignant skin tumors, a groundbreaking strategy is urgently needed. Photothermal therapy (PTT), which has become a complementary treatment of tumors, however, is powerless in tissue defect regeneration. Therefore, a novel multifunctional sodium nitroprusside and Fe2+ ions loaded microneedles (SNP-Fe@MNs) platform was fabricated by accomplishing desirable NIR-responsive photothermal effect while burst releasing nitric oxide (NO) after the ultraviolet radiation for the ablation of melanoma. Moreover, the steady releasing of NO in the long term by the platform can exert its angiogenic effects via upregulating multiple related pathways to promote tissue regeneration. Thus, the therapeutic dilemma caused by postoperative maxillofacial skin malignancies could be conquered through promoting tumor cell apoptosis via synergistic PTT-gas therapy and subsequent regeneration process in one step. The bio-application of SNP-Fe@MNs could be further popularized based on its ideal bioactivity and appealing features as a strategy for synergistic therapy of other tumors occurred in skin.

Photodynamic and nitric oxide therapy-based synergistic antimicrobial nanoplatform: an advanced root canal irrigation system for endodontic bacterial infections.

BACKGROUND: The main issues faced during the treatment of apical periodontitis are the management of bacterial infection and the facilitation of the repair of alveolar bone defects to shorten disease duration. Conventional root canal irrigants are limited in their efficacy and are associated with several side effects. This study introduces a synergistic therapy based on nitric oxide (NO) and antimicrobial photodynamic therapy (aPDT) for the treatment of apical periodontitis. RESULTS: This research developed a multifunctional nanoparticle, CGP, utilizing guanidinylated poly (ethylene glycol)-poly (ε-Caprolactone) polymer as a carrier, internally loaded with the photosensitizer chlorin e6. During root canal irrigation, the guanidino groups on the surface of CGP enabled effective biofilm penetration. These groups undergo oxidation by hydrogen peroxide in the aPDT process, triggering the release of NO without hindering the production of singlet oxygen. The generated NO significantly enhanced the antimicrobial capability and biofilm eradication efficacy of aPDT. Furthermore, CGP not only outperforms conventional aPDT in eradicating biofilms but also effectively promotes the repair of alveolar bone defects post-eradication. Importantly, our findings reveal that CGP exhibits significantly higher biosafety compared to sodium hypochlorite, alongside superior therapeutic efficacy in a rat model of apical periodontitis. CONCLUSIONS: This study demonstrates that CGP, an effective root irrigation system based on aPDT and NO, has a promising application in root canal therapy.

NIR-activated electrospun nanodetonator dressing enhances infected diabetic wound healing with combined photothermal and nitric oxide-based gas therapy.

Diabetic wounds pose a challenge to healing due to increased bacterial susceptibility and poor vascularization. Effective healing requires simultaneous bacterial and biofilm elimination and angiogenesis stimulation. In this study, we incorporated polyaniline (PANI) and S-Nitrosoglutathione (GSNO) into a polyvinyl alcohol, chitosan, and hydroxypropyltrimethyl ammonium chloride chitosan (PVA/CS/HTCC) matrix, creating a versatile wound dressing membrane through electrospinning. The dressing combines the advantages of photothermal antibacterial therapy and nitric oxide gas therapy, exhibiting enduring and effective bactericidal activity and biofilm disruption against methicillin-sensitive Staphylococcus aureus, methicillin-resistant Staphylococcus aureus, and Escherichia coli. Furthermore, the membrane's PTT effect and NO release exhibit significant synergistic activation, enabling a nanodetonator-like burst release of NO through NIR irradiation to disintegrate biofilms. Importantly, the nanofiber sustained a uniform release of nitric oxide, thereby catalyzing angiogenesis and advancing cellular migration. Ultimately, the employment of this membrane dressing culminated in the efficacious amelioration of diabetic-infected wounds in Sprague-Dawley rats, achieving wound closure within a concise duration of 14 days. Upon applying NIR irradiation to the PVA-CS-HTCC-PANI-GSNO nanofiber membrane, it swiftly eradicates bacteria and biofilm within 5 min, enhancing its inherent antibacterial and anti-biofilm properties through the powerful synergistic action of PTT and NO therapy. It also promotes angiogenesis, exhibits excellent biocompatibility, and is easy to use, highlighting its potential in treating diabetic wounds.

The Impact of LY487379 or CDPPB on eNOS Expression in the Mouse Brain and the Effect of Joint Administration of Compounds with NO• Releasers on MK-801- or Scopolamine-Driven Cognitive Dysfunction in Mice.

The role of endothelial nitric oxide synthase (eNOS) in the regulation of a variety of biological processes is well established, and its dysfunction contributes to brain pathologies, including schizophrenia or Alzheimer's disease (AD). Positive allosteric modulators (PAMs) of metabotropic glutamate (mGlu) receptors were shown to be effective procognitive compounds, but little is known about their impact on eNOS expression and stability. Here, we investigated the influence of the acute and chronic administration of LY487379 or CDPPB (mGlu2 and mGlu5 PAMs), on eNOS expression in the mouse brain and the effect of the joint administration of the ligands with nitric oxide (NO) releasers, spermineNONOate or DETANONOate, in different combinations of doses, on MK-801- or scopolamine-induced amnesia in the novel object recognition (NOR) test. Our results indicate that both compounds provoked eNOS monomer formation, and CDPPB at a dose of 5 mg/kg exaggerated the effect of MK-801 or scopolamine. The coadministration of spermineNONOate or DETANONOate enhanced the antiamnesic effect of CDPPB or LY487379. The best activity was observed for ineffective or moderate dose combinations. The results indicate that treatment with mGluR2 and mGluR5 PAMs may be burdened with the risk of promoting eNOS uncoupling through the induction of dimer dissociation. Administration of the lowest possible doses of the compounds with NO• donors, which themselves have procognitive efficacy, may be proposed for the treatment of schizophrenia or AD.

Nitric oxide precipitates catastrophic chromosome fragmentation by bolstering both hydrogen peroxide and Fe(II) Fenton reactants in E. coli.

Immune cells kill invading microbes by producing reactive oxygen and nitrogen species, primarily hydrogen peroxide (H2O2) and nitric oxide (NO). We previously found that NO inhibits catalases in Escherichia coli, stabilizing H2O2 around treated cells and promoting catastrophic chromosome fragmentation via continuous Fenton reactions generating hydroxyl radicals. Indeed, H2O2-alone treatment kills catalase-deficient (katEG) mutants similar to H2O2+NO treatment. However, the Fenton reaction, in addition to H2O2, requires Fe(II), which H2O2 excess instantly converts into Fenton-inert Fe(III). For continuous Fenton when H2O2 is stable, a supply of reduced iron becomes necessary. We show here that this supply is ensured by Fe(II) recruitment from ferritins and Fe(III) reduction by flavin reductase. Our observations also concur with NO-mediated respiration inhibition that drives Fe(III) reduction. We modeled this NO-mediated inhibition via inactivation of ndh and nuo respiratory enzymes responsible for the step of NADH oxidation, which results in increased NADH pools driving flavin reduction. We found that, like the katEG mutant, the ndh nuo double mutant is similarly sensitive to H2O2-alone and H2O2+NO treatments. Moreover, the quadruple katEG ndh nuo mutant lacking both catalases and efficient respiration was rapidly killed by H2O2-alone, but this killing was delayed by NO, rather than potentiated by it. Taken together, we conclude that NO boosts the levels of both H2O2 and Fe(II) Fenton reactants, making continuous hydroxyl-radical production feasible and resulting in irreparable oxidative damage to the chromosome.

In vivo imaging of nitric oxide in the male rat brain exposed to a shock wave.

While numerous studies have suggested the involvement of cerebrovascular dysfunction in the pathobiology of blast-induced traumatic brain injury (bTBI), its exact mechanisms and how they affect the outcome of bTBI are not fully understood. Our previous study showed the occurrence of cortical spreading depolarization (CSD) and subsequent long-lasting oligemia/hypoxemia in the rat brain exposed to a laser-induced shock wave (LISW). We hypothesized that this hemodynamic abnormality is associated with shock wave-induced generation of nitric oxide (NO). In this study, to verify this hypothesis, we used an NO-sensitive fluorescence probe, diaminofluorescein-2 diacetate (DAF-2 DA), for real-time in vivo imaging of male Sprague-Dawley rats' brain exposed to a mild-impulse LISW. We observed the most intense fluorescence, indicative of NO production, along the pial arteriolar walls during the period of 10-30 min post-exposure, parallel with CSD occurrence. This post-exposure period also coincided with the early phase of hemodynamic abnormalities. While the changes in arteriolar wall fluorescence measured in rats receiving pharmacological NO synthase inhibition by nitro-L-arginine methyl ester (L-NAME) 24 h before exposure showed a temporal profile similar to that of changes observed in LISW-exposed rats with CSD, their intensity level was considerably lower; this suggests partial involvement of NOS in shock wave-induced NO production. To the best of our knowledge, this is the first real-time in vivo imaging of NO in rat brain, confirming the involvement of NO in shock-wave-induced hemodynamic impairments. Finally, we have outlined the limitations of this study and our future research directions.

Nitric Oxide Attenuates Human Cytomegalovirus Infection yet Disrupts Neural Cell Differentiation and Tissue Organization.

Human cytomegalovirus (HCMV) is a prevalent betaherpesvirus that is asymptomatic in healthy individuals but can cause serious disease in immunocompromised patients. HCMV is also the leading cause of virus-mediated birth defects. Many of these defects manifest within the central nervous system and include microcephaly, sensorineural hearing loss, and cognitive developmental delays. Nitric oxide is a critical effector molecule produced as a component of the innate immune response during infection. Congenitally infected fetal brains show regions of brain damage, including necrotic foci with infiltrating macrophages and microglia, cell types that produce nitric oxide during infection. Using a 3-dimensional cortical organoid model, we demonstrate that nitric oxide inhibits HCMV spread and simultaneously disrupts neural rosette structures, resulting in tissue disorganization. Nitric oxide also attenuates HCMV replication in 2-dimensional cultures of neural progenitor cells (NPCs), a prominent cell type in cortical organoids that differentiate into neurons and glial cells. The multipotency factor SOX2 was decreased during nitric oxide exposure, suggesting that early neural differentiation is affected. Nitric oxide also reduced maximal mitochondrial respiration in both uninfected and infected NPCs. We determined that this reduction likely influences neural differentiation, as neurons (Tuj1+ GFAP- Nestin-) and glial populations (Tuj1- GFAP+ Nestin-) were reduced following differentiation. Our studies indicate a prominent, immunopathogenic role of nitric oxide in promoting developmental defects within the brain despite its antiviral activity during congenital HCMV infection. IMPORTANCE Human cytomegalovirus (HCMV) is the leading cause of virus-mediated congenital birth defects. Congenitally infected infants can have a variety of symptoms manifesting within the central nervous system. The use of 3-dimensional (3-D) cortical organoids to model infection of the fetal brain has advanced the current understanding of development and allowed broader investigation of the mechanisms behind disease. However, the impact of the innate immune molecule nitric oxide during HCMV infection has not been explored in neural cells or cortical 3-D models. Here, we investigated the effect of nitric oxide on cortical development during HCMV infection. We demonstrate that nitric oxide plays an antiviral role during infection yet results in disorganized cortical tissue. Nitric oxide contributes to differentiation defects of neuron and glial cells from neural progenitor cells despite inhibiting viral replication. Our results indicate that immunopathogenic consequences of nitric oxide during congenital infection promote developmental defects that undermine its antiviral activity.

Nitric oxide and hormesis.

This present paper provides an assessment of the occurrence of nitric oxide (NO)-induced hormetic-biphasic dose/concentration relationships in biomedical research. A substantial reporting of such NO-induced hormetic effects was identified with particular focus on wound healing, tumor promotion, and sperm biology, including mechanistic assessment and potential for translational applications. Numerous other NO-induced hormetic effects have been reported, but require more development prior to translational applications. The extensive documentation of NO-induced biphasic responses, across numerous organs (e.g., bone, cardiovascular, immune, intestine, and neuronal) and cell types, suggests that NO-induced biological activities are substantially mediated via hormetic processes. These observations are particularly important because broad areas of NO biology are constrained by the quantitative features of the hormetic response. This determines the amplitude and width of the low dose stimulation, affecting numerous biomedical implications, study design features (e.g., number of doses, dose spacing, sample sizes, statistical power), and the potential success of clinical trials.

Reduction in blood pressure following acute dietary nitrate ingestion is correlated with increased red blood cell S-nitrosothiol concentrations.

Dietary nitrate (NO3-) supplementation can enhance nitric oxide (NO) bioavailability and lower blood pressure (BP) in humans. The nitrite concentration ([NO2-]) in the plasma is the most commonly used biomarker of increased NO availability. However, it is unknown to what extent changes in other NO congeners, such as S-nitrosothiols (RSNOs), and in other blood components, such as red blood cells (RBC), also contribute to the BP lowering effects of dietary NO3-. We investigated the correlations between changes in NO biomarkers in different blood compartments and changes in BP variables following acute NO3- ingestion. Resting BP was measured and blood samples were collected at baseline, and at 1, 2, 3, 4 and 24 h following acute beetroot juice (∼12.8 mmol NO3-, ∼11 mg NO3-/kg) ingestion in 20 healthy volunteers. Spearman rank correlation coefficients were determined between the peak individual increases in NO biomarkers (NO3-, NO2-, RSNOs) in plasma, RBC and whole blood, and corresponding decreases in resting BP variables. No significant correlation was observed between increased plasma [NO2-] and reduced BP, but increased RBC [NO2-] was correlated with decreased systolic BP (rs = -0.50, P = 0.03). Notably, increased RBC [RSNOs] was significantly correlated with decreases in systolic (rs = -0.68, P = 0.001), diastolic (rs = -0.59, P = 0.008) and mean arterial pressure (rs = -0.64, P = 0.003). Fisher's z transformation indicated no difference in the strength of the correlations between increases in RBC [NO2-] or [RSNOs] and decreased systolic blood pressure. In conclusion, increased RBC [RSNOs] may be an important mediator of the reduction in resting BP observed following dietary NO3- supplementation.

Gaseous nitric oxide failed to inhibit the replication cycle of SARS-CoV-2 in vitro.

Nitric oxide (NO) has been shown to have antimicrobial activity in vitro and in some in vivo models, while the virucidal activity of NO remains elusive. Some studies using NO donors have suggested that NO could be a potential candidate to treat SARS-CoV infection. The Covid-19 pandemic raised the hypothesis that NO gas might have an impact on Sars-CoV-2 replication cycle and might be considered as a candidate therapy to treat COVID-19. To our knowledge, there are no in vitro preclinical studies demonstrating a virucidal effect of gaseous NO on SARS-CoV-2. This study aims to determine whether gaseous NO has an impact on the replication cycle of SARS-CoV-2 in vitro. To that end, SARS-CoV-2 infected epithelial (VeroE6) and pulmonary (A549-hACE2) cells were treated with repeated doses of gaseous NO at different concentrations known to be efficient against bacteria. Our results show that exposing SARS-CoV-2 infected-cells to NO gas even at high doses (160 ppm, 6 h) does not influence the replication cycle of the virus in vitro. We report here that NO gas has no antiviral properties in vitro on SARS-COV-2. Therefore, there is no rationale for its usage in clinical settings to treat COVID-19 patients for direct antiviral purposes, which does not exclude other potential physiological benefits of this gas.