Exogenous Nitric Oxide Donor Research Articles

Trial of the cerebral perfusion response to sodium nitrite infusion in patients with acute subarachnoid haemorrhage using arterial spin labelling MRI

Aneurysmal subarachnoid haemorrhage (SAH) is a devastating subset of stroke. One of the major determinants of outcome is an evolving multifactorial injury occurring in the first 72 hours, known as early brain injury. Reduced nitric oxide (NO) bioavailability and an associated disruption to cerebral perfusion is believed to play an important role in this process. We sought to explore this relationship, by examining the effect on cerebral perfusion of the in vivo manipulation of NO levels using an exogenous NO donor (sodium nitrite).We performed a double blind placebo controlled randomised experimental medicine study of the cerebral perfusion response to sodium nitrite infusion during the early brain injury period in 15 low grade (World Federation of Neurosurgeons grade 1–2) SAH patients. Patients were randomly assigned to receive sodium nitrite at 10 mcg/kg/min or saline placebo. Assessment occurred following endovascular aneurysm occlusion, mean time after ictus 66h (range 34–90h). Cerebral perfusion was quantified before infusion commencement and after 3 hours, using multi-post labelling delay (multi-PLD) vessel encoded pseudocontinuous arterial spin labelling (VEPCASL) magnetic resonance imaging (MRI).Administration of sodium nitrite was associated with a significant increase in average grey matter cerebral perfusion. Group level voxelwise analysis identified that increased perfusion occurred within regions of the brain known to exhibit enhanced vulnerability to injury. These findings highlight the role of impaired NO bioavailability in the pathophysiology of early brain injury.

Exploring the Effects of Nitric Oxide and Reactive Oxygen Species on Buffalo Sperm Quality: A Comprehensive Review

Buffalo reproduction plays a vital role in the livestock industry, where sperm quality is a critical determinant of successful fertilization and overall fertility. Nitric oxide (NO) and reactive oxygen species (ROS) are key regulators of various physiological processes, including sperm function. However, their dual role in modulating sperm quality is complex, as both excessive and insufficient levels can lead to detrimental effects. This review explores the intricate balance between NO, ROS and sperm quality in buffalo, emphasizing the molecular mechanisms underlying these interactions. NO is a signaling molecule involved in the regulation of sperm motility, capacitation and acrosome reaction, but its overproduction can result in nitrosative stress, impairing sperm function. Similarly, ROS, at physiological levels, are essential for sperm capacitation and acrosome reaction, yet an imbalance towards oxidative stress can lead to lipid peroxidation, DNA fragmentation and reduced sperm viability. This review also delves into the role of exogenous NO donors, such as sodium nitroprusside (SNP), in modulating NO and ROS levels, and their consequent impact on sperm quality. The dual effects of NO and ROS on buffalo sperm highlight the importance of maintaining an optimal redox balance to preserve sperm integrity and functionality. In conclusion, understanding the molecular pathways through which NO and ROS influence sperm quality is crucial for developing targeted strategies to enhance reproductive outcomes in buffalo. Future research should focus on identifying biomarkers of oxidative stress and evaluating the potential of antioxidant therapies to mitigate the adverse effects of NO and ROS, ultimately improving buffalo fertility.

Metabolomic Profiling and Biological Investigation of the Marine Sponge-Derived Fungus Aspergillus sp. SYPUF29 in Response to NO Condition.

Marine-derived fungi are assuming an increasingly central role in the search for natural leading compounds with unique chemical structures and diverse pharmacological properties. However, some gene clusters are not expressed under laboratory conditions. In this study, we have found that a marine-derived fungus Aspergillus sp. SYPUF29 would survive well by adding an exogenous nitric oxide donor (sodium nitroprusside, SNP) and nitric oxide synthetase inhibitor (L-NG-nitroarginine methyl ester, L-NAME) in culture conditions. Moreover, using the LC-MS/MS, we initially assessed and characterized the difference in metabolites of Aspergillus sp. SYPUF29 with or without an additional source of nitrogen. We have found that the metabolic pathway of Arginine and proline metabolism pathways was highly enriched, which was conducive to the accumulation of alkaloids and nitrogen-containing compounds after adding an additional source of nitrogen in the cultivated condition. Additionally, the in vitro anti-neuroinflammatory study showed that the extracts after SNP and L-NAME were administrated can potently inhibit LPS-induced NO-releasing of BV2 cells with lower IC50 value than without nitric oxide. Further Western blotting assays have demonstrated that the mechanism of these extracts was associated with the TLR4 signaling pathway. Additionally, the chemical investigation was conducted and led to nine compounds (SF1-SF9) from AS1; and six of them belonged to alkaloids and nitrogen-containing compounds (SF1-SF6), of which SF1, SF2, and SF8 exhibited stronger activities than the positive control, and showed potential to develop the inhibitors of neuroinflammation.

Role of Flavohemoglobins in the Development and Aflatoxin Biosynthesis of Aspergillus flavus.

Aspergillus flavus is notorious for contaminating food with its secondary metabolite-highly carcinogenic aflatoxins. In this study, we found that exogenous nitric oxide (NO) donor could influence aflatoxin production in A. flavus. Flavohemoglobins (FHbs) are vital functional units in maintaining nitric oxide (NO) homeostasis and are crucial for normal cell function. To investigate whether endogenous NO changes affect aflatoxin biosynthesis, two FHbs, FHbA and FHbB, were identified in this study. FHbA was confirmed as the main protein to maintain NO homeostasis, as its absence led to a significant increase in intracellular NO levels and heightened sensitivity to SNP stress. Dramatically, FHbA deletion retarded aflatoxin production. In addition, FHbA played important roles in mycelial growth, conidial germination, and sclerotial development, and response to oxidative stress and high-temperature stress. Although FHbB did not significantly impact the cellular NO level, it was also involved in sclerotial development, aflatoxin synthesis, and stress response. Our findings provide a new perspective for studying the regulatory mechanism of the development and secondary mechanism in A. flavus.

Development of a Peroral Dosage Form of a Nitrosyl Iron Complex with Thiosulfate Ligands, an Exogenous Nitric Oxide (NO) Donor

Development of a Peroral Dosage Form of a Nitrosyl Iron Complex with Thiosulfate Ligands, an Exogenous Nitric Oxide (NO) Donor

Advanced age and reduced hyaluronan synthesis impair glycocalyx integrity resulting in endothelial dysfunction

The glycocalyx (GC) is a densely structured, gel-like matrix that coats the inner lining of the vascular endothelium. The GC plays a pivotal role in regulating the integrity of the vascular endothelium, primarily through mechano-sensing and -transducing shear stress, while also preserving endothelial barrier function. With advancing age, the GC deteriorates concomitantly with its essential constituent, hyaluronan (HA), which may lead to endothelial dysfunction. Therefore, we hypothesized that advanced age and reduced HA synthesis alone or together will impair GC integrity resulting in endothelial dysfunction. We have generated a tamoxifen-inducible, endothelial cell-specific, knockout mouse model of a hyaluronan producing enzyme, hyaluronan synthase 2 (HAS2), in young (4-6 mo) and old (22-23 mo, n=9-12/group). HAS2 mRNA expression in carotid endothelial cell lysates were reduced by ~47% in endothelial cell HAS2 knockout (ecHAS2KO) vs wildtype (ecHAS2WT, p=0.004) after tamoxifen treatment. The perfused boundary region (PBR), indicative of GC barrier function, was evaluated in vivo in the mesenteric microcirculation. The PBR was significantly impaired with aging (young vs old ecHAS2WT, p=0.047) and genotype (young ecHAS2WT vs KO, p=0.012) but there was no additive effect of aging and genotype (old ecHAS2WT vs KO, p=0.989). Subsequently, GC thickness was determined by measuring the depth of GC collapsed by leukocyte passage through the mesenteric segments. GC thickness was diminished by ~53% with aging (young vs old ecHAS2WT, p<0.0001) and ~59% with genotype (young ecHAS2WT vs KO, p<0.0001) but there was no synergistic effect of aging and genotype (old ecHAS2WT vs KO, p=0.893). Mechano-sensing and -transducing properties of the GC were assessed using ex vivo flow-induced vasodilation in isolated carotid arteries with and without the intra-luminal infusion of HA degrading enzyme, hyaluronidase (HYAL). Flow-induced vasodilation was diminished with aging (young vs old ecHAS2WT, p<0.0001) but this age-related decline was dampened with HYAL (p=0.212). The vasodilatory response to flow was reduced with genotype (young ecHAS2WT vs KO, p<0.0001) but this effect was weakened with HYAL (p=0.953). There was no augmentative effect of aging and genotype with and without HYAL (all p≥0.883). Acetylcholine induced endothelium-dependent dilation (EDD), a measure of endothelial function, was examined ex vivo in isolated mesenteric arteries. The maximal EDD was diminished by ~23% with aging (young vs old ecHAS2WT, p=0.04) but not genotype (young ecHAS2WT vs KO, p=0.962). There was an additive reduction in maximal EDD by ~46% with aging and genotype (old ecHAS2KO vs WT, p=0.021). Endothelium-independent dilation in response to sodium nitroprusside, an exogenous nitric oxide donor, was not different across groups with either aging, genotype, or both (ALL p>0.05). In conclusion, aging and reduced HA synthesis independently impaired GC integrity. As a result, mechano-sensing and -transducing property of GC was disturbed and further diminished by HYAL activity. In addition, endothelial function was impaired with aging and further exacerbated after a reduction in HA synthesis. Funded in part by awards from National Institutes of Health Awards R01 AG060395, R01 AG077751, R01 AG076748, T32 HL007576, T32 HL139451, Veteran's Affairs Merit Review Award I01 BX004492 and Nora Eccles Treadwell Foundation. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Influence of diimine bidentate ligand in the nitrosyl and nitro terpyridine ruthenium complex on the HSA/DNA interaction and antiviral activity

Nitric oxide (NO) acts in different physiological processes, such as blood pressure control, antiparasitic activities, neurotransmission, and antitumor action. Among the exogenous NO donors, ruthenium nitrosyl/nitro complexes are potential candidates for prodrugs, due to their physicochemical properties, such as thermal and physiological pH stability. In this work, we proposed the synthesis and physical characterization of the new nitro terpyridine ruthenium (II) complexes of the type [RuII(L)(NO2)(tpy)]PF6 where tpy = 2,2':6′,2″-terpyridine; L = 3,4-diaminobenzoic acid (bdq) or o-phenylenediamine (bd) and evaluation of influence of diimine bidentate ligand NH.NHq-R (R = H or COOH) in the HSA/DNA interaction as well as antiviral activity. The interactions between HSA and new nitro complexes [RuII(L)(NO2)(tpy)]+ were evaluated. The Ka values for the HSA–[RuII(bdq)(NO2)(tpy)]+ is 10 times bigger than HSA–[RuII(bd)(NO2)(tpy)]+. The sites of interaction between HSA and the complexes via synchronous fluorescence suppression indicate that the [RuII(bdq)(NO2)(tpy)]+ is found close to the Trp-241 residue, while the [RuII(bd)(NO2)(tpy)]+ complex is close to Tyr residues. The interaction with fish sperm fs-DNA using direct spectrophotometric titration (Kb) and ethidium bromide replacement (KSV and Kapp) showed weak interaction in the system fs-DNA-[RuII(bdq)(NO)(tpy)]+. Furthermore, fs-DNA–[RuII(bd)(NO2)(tpy)]+ and fs-DNA–[RuII(bd)(NO)(tpy)]3+ system showed higher intercalation constant. Circular dichroism spectra for fs-DNA–[RuII(bd)(NO2)(tpy)]+ and fs-DNA–[RuII(bd)(NO)(tpy)]3+, suggest semi-intercalative accompanied by major groove binding interaction modes. The [RuII(bd)(NO2)(tpy)]+ and [RuII(bd)(NO)(tpy)]3+ inhibit replication of Zika and Chikungunya viruses based in the nitric oxide release under S-nitrosylation reaction with cysteine viral.

Nitric oxide-induced lipophagic defects contribute to testosterone deficiency in rats with spinal cord injury.

Males with acute spinal cord injury (SCI) frequently exhibit testosterone deficiency and reproductive dysfunction. While such incidence rates are high in chronic patients, the underlying mechanisms remain elusive. Herein, we generated a rat SCI model, which recapitulated complications in human males, including low testosterone levels and spermatogenic disorders. Proteomics analyses showed that the differentially expressed proteins were mostly enriched in lipid metabolism and steroid metabolism and biosynthesis. In SCI rats, we observed that testicular nitric oxide (NO) levels were elevated and lipid droplet-autophagosome co-localization in testicular interstitial cells was decreased. We hypothesized that NO impaired lipophagy in Leydig cells (LCs) to disrupt testosterone biosynthesis and spermatogenesis. As postulated, exogenous NO donor (S-nitroso-N-acetylpenicillamine (SNAP)) treatment markedly raised NO levels and disturbed lipophagy via the AMPK/mTOR/ULK1 pathway, and ultimately impaired testosterone production in mouse LCs. However, such alterations were not fully observed when cells were treated with an endogenous NO donor (L-arginine), suggesting that mouse LCs were devoid of an endogenous NO-production system. Alternatively, activated (M1) macrophages were predominant NO sources, as inducible NO synthase inhibition attenuated lipophagic defects and testosterone insufficiency in LCs in a macrophage-LC co-culture system. In scavenging NO (2-4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (CPTIO)) we effectively restored lipophagy and testosterone levels both in vitro and in vivo, and importantly, spermatogenesis in vivo. Autophagy activation by LYN-1604 also promoted lipid degradation and testosterone synthesis. In summary, we showed that NO-disrupted-lipophagy caused testosterone deficiency following SCI, and NO clearance or autophagy activation could be effective in preventing reproductive dysfunction in males with SCI.

Three-Step Depletion Strategy of Glutathione: Tunable Metal-Organic-Framework-Engineered Nanozymes for Driving Oxidative/Nitrative Stress to Maximize Ferroptosis Therapy.

Ferroptosis is a novel type of nonapoptotic programmed cell death involving the accumulation of lipid peroxidation (LPO) to a lethal threshold. Herein, we propose tunable zeolitic imidazolate framework (ZIFs)-engineered biodegradable nanozymes for ferroptosis mediated by both reactive oxygen species (ROS) and nitrogen species (RNS). l-Arginine is utilized as an exogenous nitric oxide donor and loaded into hollow ZIFs@MnO2 artificial nanozymes, which are formed by etching ZIFs with potassium permanganate and simultaneously generating a MnO2 shell in situ. The constructed nanozymes with multienzyme-like activities including peroxidase, oxidase, and catalase can release satisfactory ROS and RNS through a cascade reaction, consequently promoting the accumulation of LPO. Furthermore, it can improve the efficiency of ferroptosis through a three-step strategy of glutathione (GSH) depletion; that is, the outer MnO2 layer consumes GSH under slightly acidic conditions and RNS downregulates SLC7A11 and glutathione reductase, thus directly inhibiting GSH biosynthesis and indirectly preventing GSH regeneration.

Photosynthetic adaptation mechanisms of waterlogged wheat (Triticum aestivum) at flowering under exogenous nitric oxide donor application

AbstractThe effects of nitric oxide (NO) on the photosynthetic adaptation mechanisms of wheat plants in waterlogging during the flowering stage are poorly understood. Field and pot experiments using two cultivars were conducted with three treatments: waterlogging (WL), waterlogging plus NO donor sodium nitroprusside (WLsnp), and adequate water (CK). The results indicated that the WLsnp and CK treatments exhibited significantly higher 1000‐kernel weight and yield than the WL treatment because of high photosynthetic potential(P<0.05). We found that the photosynthetic performance, including photosynthetic rate (Pn), stomatal conductance (gs), mesophyll conductance (gm), carbon dioxide concentration at the carboxylation site (Cc), maximum carboxylation rate (Vcmax), maximum electron transfer rate (Jmax), actual electron transfer rate (J), actual PSII efficiency (ΦPSII) and potential maximum efficiency in PSII (Fv/Fm), was significantly improved in the WLsnp treatment compared to the WL treatment, both during waterlogging and after de‐waterlogging. Little difference was observed in the photosynthetic performance between the WLsnp and CK treatments during waterlogging for cultivar YM15 and after de‐waterlogging for cultivar YM24. Further analysis indicated that gs, gm and J were identified as key physiological indicators that synergistically regulate Pn of waterlogged wheat plants. Overall, the improvement of wheat's waterlogging resistance capacity after spraying NO is mainly related to high gs, great gm, and high J.

Effect of Nitric Oxide on Browning of Stem Tip Explants of Malus sieversii

Browning is a major problem in the tissue culture of woody plants. Previous studies have shown that nitric oxide (NO) plays a role in regulating plant responses to stress, but its effect on browning in the tissue culture of Malus remains unclear. This study aimed to investigate the impact of exogenous NO donor sodium nitroprusside (SNP) on the browning of Malus sieversii stem tip explants. The results demonstrated that the addition of 50 μM SNP significantly reduced explant browning. Further analysis revealed that exogenous NO decreased the browning index (BD) and levels of malondialdehyde (MDA), hydrogen peroxide (H2O2), and superoxide anion radical O2−. Additionally, NO treatment increased the activity of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX). NO treatment also enhanced the activity of phenylalanine ammonia lyase (PAL), which contributed to the accumulation of flavonoids and inhibited the activity of polyphenol oxidase (PPO) and peroxidase (POD), which are key enzymes involved in the browning process. Furthermore, 50 μM SNP significantly promoted the accumulation of non-enzymatic antioxidants such as proline (Pro), soluble sugar (SS), and soluble protein (SP). Therefore, the results suggest that NO is able to counteract excessive reactive oxygen species (ROS) damage by enhancing both the enzymatic and non-enzymatic antioxidant systems, resulting in a reduction in browning in stem tip explants. Consequently, an improvement in the in vitro propagation efficiency of Malus sieversii shoot tip explants can be achieved.

Nitric Oxide-Induced Morphological Changes to Bacteria.

Antimicrobial resistance poses a serious threat to global health, necessitating research for alternative approaches to treating infections. Nitric oxide (NO) is an endogenously produced molecule involved in multiple physiological processes, including the response to pathogens. Herein, we employed microscopy- and fluorescence-based techniques to investigate the effects of NO delivered from exogenous NO donors on the bacterial cell envelopes of pathogens, including resistant strains. Our goal was to assess the role of NO donor architecture (small molecules, oligosaccharides, dendrimers) on bacterial wall degradation to representative Gram-negative bacteria (Klebsiella pneumoniae, Pseudomonas aeruginosa) and Gram-positive bacteria (Staphylococcus aureus, Enterococcus faecium) upon treatment. Depending on the NO donor, bactericidal NO doses spanned 1.5-5.5 mM (total NO released). Transmission electron microscopy of bacteria following NO exposure indicated extensive membrane damage to Gram-negative bacteria with warping of the cellular shape and disruption of the cell wall. Among the small-molecule NO donors, those providing a more extended release (t1/2 = 120 min) resulted in greater damage to Gram-negative bacteria. In contrast, rapid NO release (t1/2 = 24 min) altered neither the morphology nor the roughness of these bacteria. For Gram-positive bacteria, NO treatments did not result in any drastic change to cellular shape or membrane integrity, despite permeation of the cell wall as measured by depolarization assays. The use of positively charged quaternary ammonium (QA)-modified NO-releasing dendrimer proved to be the only NO donor system capable of penetrating the thick peptidoglycan layer of Gram-positive bacteria.

SNP application improves drought tolerance in soybean

As an important bioactive molecule, nitric oxide (NO) can effectively alleviate the effects of drought stress on crops. However, it is still unclear whether it can increase the stress resistance of soybean. Therefore, in this study, our objective was to explore the effect of exogenous NO application on the physiological characteristics of soybean seedlings under drought stress. As test material, two soybean varieties, HN65 and HN44, were used, while sodium nitroprusside (SNP) of 100 μmol L−1, 200 μmol L−1, 500 μmol L−1, 1000 μmol L−1 served as an exogenous NO donor, and PEG-6000 as an osmotic regulator to simulate drought stress. The effects of irrigation with different SNP concentrations for different days on the physiological characteristics of the soybean seedlings under drought conditions were then investigated. The results obtained showed that the activities of antioxidant enzymes, osmotic regulator contents, as well as the abscisic acid and salicylic acid contents of the plant leaves increased with increasing SNP concentration and treatment time. However, we observed that excessively high SNP concentrations decreased the activities of key nitrogen metabolism enzymes significantly. This study provides a theoretical basis for determining a suitable exogenous NO concentration and application duration. It also highlights strategies for exploring the mechanism by which exogenous NO regulates crop drought resistance.

Glyceryl trinitrate-induced blood pressure variability decrease during head-up tilt test predicts vasovagal response.

Glyceryl trinitrate (GTN) provoked cardioinhibitory syncope during the head-up tilt test is preceded by a period of disrupted blood pressure variability (BPV). Endogenous nitric oxide (NO) attenuates BPV independently of blood pressure (BP). We hypothesized that exogenous NO donor GTN might decrease BPV during the presyncope period. A decrease in BPV may predict the tilt outcome. We analyzed 29 tilt test recordings of subjects with GTN-induced cardioinhibitory syncope and 30 recordings of negative subjects. A recursive autoregressive model of BPV after GTN was performed; powers of the respiratory (0.15-0.45 Hz) and nonrespiratory frequency (0.01-0.15 Hz) bands were calculated for each of the 20 normalized time periods. The post-GTN relative changes in heart rate, BP, and BPV were calculated. In the syncope group, spectral power of nonrespiratory frequency systolic and diastolic BPV progressively felt for 30% after GTN application and stabilized after 180 s. BP started to fall 240 s after the GTN application. Decrease in nonrespiratory frequency power of diastolic BPV 20 s after GTN administration predicted cardioinhibitory syncope (area under the curve 0.811; 77% sensitivity; 70% specificity; cutoff value > 7%). GTN application during the tilt test attenuates systolic and diastolic nonrespiratory frequency BPV during the presyncope period, independent of BP. A decrease in nonrespiratory frequency diastolic BPV 20 s after GTN application predicts cardioinhibitory syncope with good sensitivity and moderate specificity.

Ascorbate-glutathione cycle and thioredoxin system are involved in nitric oxide alleviating excess nitrate stress in tomato seedlings

ABSTRACT Nitric oxide (NO) plays an important role in plant growth, development, and stress responses. The exogenous NO donor sodium nitroprusside (SNP) increased the plant height, root length, and biomass of tomato seedlings under nitrate stress, especially 100 μM SNP. The reactive oxygen species (ROS) and malondialdehyde (MDA) contents were decreased, while the antioxidant enzyme activities, ascorbate and glutathione contents, and expression of SlTrxh, SlNTRB, SlTpx were increased in tomato after SNP and nitrate stress treatment, compared with nitrate stress. The tomato plants showed shorter root length, more MDA and ROS contents after the NADPH-dependent thioredoxin reductase (NTR) inhibitor Auranofin (ANF) was added, suggesting that ANF inhibited the alleviating effect of NO under nitrate stress. The NO and S-nitrosothiol (SNO) contents and the SlNR transcript levels were decreased and the expression of SlGLB, SlGSNOR was increased after NO and nitrate stress treatment. The S-nitrosylated level in tomato roots was increased after nitrate stress. The SlMDHAR, SlTrxh, and SlNTRB protein were S-nitrosylated after NO and nitrate stress treatment. These results suggested that key enzymes in ascorbate-glutathione cycle and Trx system played an important role in alleviating the effect of NO in tomato seedlings under nitrate stress involving the S-nitrosylation modification.

Specific dilation pattern in placental circulation and the NO/sGC role in preeclampsia placental vessels.

Endothelial functions in controlling blood flow in placental circulation are still unclear. The present study compares vascular dilations between placental circulation and other vessels, as well as between normal and preeclampsia placental vessels. Placental, umbilical, and other vessels (cerebral and mesenteric arteries) were collected from humans, sheep, and rats. Vasodilation was tested by JZ101 and DMT. Q-PCR, Western blot, and Elisa were used for molecular experiments. Endothelium-dependent/derived vasodilators, including acetylcholine, bradykinin, prostacyclin, and histamine, mediated no or minimal dilation in placental circulation, which was different from that in other vessels in sheep and rats. There were lower mRNA expressions of muscarinic receptors, histamine receptors, bradykinin receptor 2, endothelial nitric oxide synthesis (eNOS), and less nitric oxide (NO) in human umbilical vessels when compared with placental vessels. Exogenous NO donors (sodium nitroprusside, SNP) and soluble guanylate cyclase (sGC) activators (Bay41-2272) decreased the baseline of vessel tone in placental circulation in humans, sheep, and rats, but not in other arteries. The sGC inhibitor ODQ suppressed the reduced baseline caused by the SNP. The decreased baseline by SNP or Bay41-2272 was higher in placental vessels than in umbilical vessels, suggesting that the role of NO/sGC is more important in the placenta. NO concentrations in preeclampsia placental vessels were lower than those in control, while no significant change was found in umbilical plasma between the two groups. eNOS expression was similar between normal and preeclampsia placental vessels, but phosphorylated eNOS levels were significantly lower in preeclampsia. Following serotonin, SNP or Bay41-2272-mediated dilations were weaker in preeclampsia placental vessels. The decreased amplitude of SNP- or Bay41-2272 at baseline was smaller in preeclampsia. The decreased amplitudes of ODQ + SNP were comparable between the two groups. Despite higher beta sGC expression, sGC activity in the preeclampsia placenta was lower. This study demonstrated that receptor-mediated endothelium-dependent dilation in placental circulation was significantly weaker than other vessels in various species. The results, showed firstly, that exogenous NO played a role in regulating the baseline tone of placental circulation via sGC. Lower NO production and decreased NO/sGC could be one of the reasons for preeclampsia. The findings contribute to understanding specific features of placental circulation and provide information about preeclampsia in placental vessels.

Effect of Exogenous Nitric Oxide on Enterocytozoon hepatopenaei Copy Numbers and Immunity of Exopalaemon carinicauda

To explore the effect of nitric oxide (NO) on Enterocytozoon hepatopenaei (EHP) invading the shrimp, sodium nitroprusside was used as an exogenous NO donor to investigate the effects of different concentrations (0 μg/L (control group), 0.3 μg/L, 0.6 μg/L, and 0.9 μg/L) of sodium nitroprusside on the EHP copy number and the structure in the hepatopancreas of Exopalaemon carinicauda infected by EHP. The results showed that the EHP copy number in the sodium nitroprusside group was significantly lower than that in the control group, and the hepatopancreas in the sodium nitroprusside injection group had less structure damage than the control group. Additionally, superoxide dismutase (SOD) activity in the control group and 0.3 μg/L groups increased and then decreased, while alkaline phosphatase (AKP) activity decreased and then increased, with the same trend, and, the inducible nitric oxide synthase (iNOS) activity in the haemolymph of the 0.3 μg/L group was significantly higher than that of the control group at 3 days ( P < 0.05 ). The NO content the 0.3 μg/L group was also higher from 1 to 4 days than that in the control group and significantly higher than that in the control group at 3 days ( P < 0.05 ). The injection of NO could reduce the EHP copy number in infected E. carinicauda and slow down the pathological changes in the hepatopancreas structure, which might be related to the increase in NO content.

Salicylic Acid and Jasmonic Acid Increase the Polysaccharide Production of Nostoc flagelliforme via the Regulation of the Intracellular NO Level

To significantly improve the polysaccharide production of Nostoc flagelliforme, a total of 12 chemicals were evaluated for their effects on polysaccharide accumulation. The results showed that salicylic acid and jasmonic acid increased the accumulation of the polysaccharides in N. flagelliforme significantly, by more than 20%. Three polysaccharides, namely control-capsule polysaccharide, salicylic acid-capsule polysaccharide, and jasmonic acid-capsule polysaccharide, were extracted and purified from N. flagelliforme under normal, salicylic acid, and jasmonic acid culture conditions, respectively. Their chemical compositions slightly differed regarding the total sugar and uronic acid contents, with average molecular weights of 2.06 × 103, 2.16 × 103 and 2.04 × 103 kDa, respectively. They presented similar Fourier transform infrared spectra and no significant difference in antioxidant activity. It was revealed that the salicylic acid and jasmonic acid significantly increased the level of nitric oxide. By investigating the effects of the exogenous nitric oxide scavenger and nitric oxide donor on the nitric oxide levels and polysaccharide yield of N. flagelliforme, the results showed that the increase in intracellular nitric oxide levels might be an important factor promoting the accumulation of polysaccharides. These findings provide a theoretical foundation for enhancing the yield of secondary metabolites by regulating the intracellular nitric oxide levels.

Mitigation of gravitropic bending of snapdragon cut flowers through SNP treatment via ROS asymmetry elimination and auxin sensitivity reduction

Snapdragons (Antirrhinum majus L.) are an important fresh-cut flower in the international flower market. During storage and transportation, snapdragons often undergo a gravitropic response that has a substantial adverse effect on their ornamental and market value. The gravitropic response is a complex physiological and biochemical process that is affected by signals such as auxins and reactive oxygen species (ROS). In this study, we found that the pretreatment of exogenous nitric oxide (NO) donor sodium nitroprusside (SNP, 0.2 mM) effectively inhibited the gravitropic bending of snapdragon cut flowers after horizontal placement. The gravitropic stimulus induced higher ROS (O2−∙ and H2O2) accumulation in the lower side compared to the upper side of the bending zone of the control flower stems. Compared to the control, a substantially higher accumulation of ROS was induced through the SNP treatment, correlating with the increased activity of catalase (CAT) and ascorbate peroxidase (APX), as well as the enhanced expression of AmAPX1 and AmCAT1. However, unlike the control, no ROS asymmetric distribution was found for the SNP-treated flowers. Four free auxins, IAA, IBA, ME-IAA and ICA, were detected in the flower stems, among which, only IBA showed asymmetric distribution after the gravitropic stimulus. An IBA content that was approximately 26% higher was detected in the lower side compared to the upper side of the control flower at 2 h, but no difference was found for the SNP-treated flowers. A higher expression of the AmPIN3 gene at the lower sides compared to the upper sides of the control may be correlated with the transient IBA asymmetric distribution. Interestingly, an expression of AmIAA2 and AmSUR50 that was around 2-fold was detected in the lower side compared to the upper side of the control, indicating that higher auxin sensitivity may be induced in the lower side. However, the expression of AmIAA2 and AmSUR50 was reduced by the SNP treatment, implying that high ROS levels may reduce auxin sensitivity. Furthermore, a higher AmExp1 and AmH+–ATPase1 expression in the lower side compared to the upper side was found for the control but not for the SNP-treated flowers, indicating the two genes may be involved in the bending of the flower stems. The above results reveal that SNP treatment eliminates the asymmetric distribution of ROS and reduced auxin sensitivity of snapdragon flower stems, thereby eliminating their asymmetric growth and further inhibiting their gravitropic response.

Repurposing nitric oxide donating drugs in cancer therapy through immune modulation

BackgroundNitric oxide-releasing drugs are used for cardiovascular diseases; however, their effects on the tumor immune microenvironment are less clear. Therefore, this study explored the impact of nitric oxide donors on tumor progression in immune-competent mice.MethodsThe effects of three different nitric oxide-releasing compounds (SNAP, SNP, and ISMN) on tumor growth were studied in tumor-bearing mouse models. Three mouse tumor models were used: B16F1 melanoma and LL2 lung carcinoma in C57BL/6 mice, CT26 colon cancer in BALB/c mice, and LL2 lung carcinoma in NOD/SCID mice. After nitric oxide treatment, splenic cytokines and lymphocytes were analyzed by cytokine array and flow cytometry, and tumor-infiltrating lymphocytes in the TME were analyzed using flow cytometry and single-cell RNA sequencing.ResultsLow doses of three exogenous nitric oxide donors inhibited tumor growth in two immunocompetent mouse models but not in NOD/SCID immunodeficient mice. Low-dose nitric oxide donors increase the levels of splenic cytokines IFN-γ and TNF-α but decrease the levels of cytokines IL-6 and IL-10, suggesting an alteration in Th2 cells. Nitric oxide donors increased the number of CD8+ T cells with activation gene signatures, as indicated by single-cell RNA sequencing. Flow cytometry analysis confirmed an increase in infiltrating CD8+ T cells and dendritic cells. The antitumor effect of nitric oxide donors was abolished by depletion of CD8+ T cells, indicating the requirement for CD8+ T cells. Tumor inhibition correlated with a decrease in a subtype of protumor macrophages and an increase in a subset of Arg1-positive macrophages expressing antitumor gene signatures. The increase in this subset of macrophages was confirmed by flow cytometry analysis. Finally, the combination of low-dose nitric oxide donor and cisplatin induced an additive cancer therapeutic effect in two immunocompetent animal models. The enhanced therapeutic effect was accompanied by an increase in the cells expressing the gene signature of NK cell.ConclusionsLow concentrations of exogenous nitric oxide donors inhibit tumor growth in vivo by regulating T cells and macrophages. CD8+ T cells are essential for antitumor effects. In addition, low-dose nitric oxide donors may be combined with chemotherapeutic drugs in cancer therapy in the future.