Effect Of Nitric Oxide Treatment Research Articles

Revealing the specific regulations of nitric oxide on the postharvest ripening and senescence of bitter melon fruit

Bitter melon fruit is susceptible to yellowing, softening, and rotting under room-temperature storage conditions, resulting in reduced commercial value. Nitric oxide (NO) is an important signaling molecule and plays a crucial role in regulating the fruit postharvest quality. In this study, we investigated the effects of NO treatment on changes in sensory and firmness of bitter melon fruit during postharvest storage. Moreover, transcriptomic, metabolomic, and proteomic analyses were performed to elucidate the regulatory mechanisms through which NO treatment delays the ripening and senescence of bitter melon fruit. Our results show that differentially expressed genes (DEGs) were involved in fruit texture (CSLE, β-Gal, and PME), plant hormone signal transduction (ACS, JAR4, and AUX28), and fruit flavor and aroma (SUS2, LOX, and GDH2). In addition, proteins differentially abundant were associated with fruit texture (PLY, PME, and PGA) and plant hormone signal transduction (PBL15, JAR1, and PYL9). Moreover, NO significantly increased the abundance of key enzymes involved in the phenylpropanoid biosynthetic pathway, thus enhancing the disease resistance and alleviating softening of bitter melon fruit. Finally, differential metabolites mainly included phenolic acids, terpenoids, and flavonoids. These results provide a theoretical basis for further studies on the physiological changes associated with postharvest ripening and senescence of bitter melon fruit.

Effect of nitric oxide treatment on pork meat quality, microstructure, and total bacterial count during postmortem aging

In this paper, the potential effect of nitric oxide (NO) on improving the fresh meat quality of pork was primarily investigated by treatment of longissimus thoracis (LT) with 0, 20, 40, 60, 80 μL/L NO gas within 6 h post-slaughter. After the NO treatments were completed, the pork chops were vacuum-packaged and stored at 4 °C for 1, 4, and 7 d. Compared with the control group, NO treatment enhanced ultimate pH and a* value, and decreased the total bacterial count. The meat treated with 40 and 60 μL/L NO presented higher water holding capacity (WHC), lower shear force and meat hardness with more unconsolidated muscle cell structure. Though 80 μL/L NO treatment achieved better color and microbial attributes, it had a negative effect on WHC and tenderness. Our data suggest that NO treatment is able to improve pork meat quality in a dose-dependent manner.

Effects of nitric oxide treatment on lignin biosynthesis and texture properties at wound sites of muskmelons

Lignin is an important component of the healing tissue in fruits. In this study, we treated muskmelon (Cucumis melo L. cv. “Manao”) fruit with exogenous nitric oxide (NO) donor sodium nitroprusside (SNP) to observe and analyze its effect on lignin synthesis and accumulation during healing. Results showed that SNP treatment enhanced the contents of endogenous NO and H2O2, increased the activities of phenylalanine ammonia lyase, cinnamate 4 hydroxylase, cinnamyl alcohol dehydrogenase, and peroxidase, and raised the contents of sinapyl alcohol, coniferyl alcohol, coumaryl alcohol, and lignin. SNP augmented the hardness of the healing tissue and decreased its resilience, springiness, and cohesiveness. In addition, SNP treatment effectively reduced the weight loss and disease index of wounded muskmelons. All these results suggest that lignin metabolism mediated by NO play a crucial role in wound healing of muskmelons.

Effects of nitric oxide treatment on flavour compounds and antioxidant enzyme activities of button mushroom (Agaricus bisporus) during storage

Abstract Button mushroom (Agaricus bisporus) is sold well for its unique flavour and nutritional benefits. However, the mushroom flavour deteriorates quickly during storage because of its delicate structure and high moisture. In this study, the effects of nitric oxide (NO) application on flavour compounds and antioxidant enzyme activities of stored button mushrooms were investigated. The button mushrooms were immersed in the NO donor sodium nitroprusside (15 μmol/L) for 3 min and then stored under the condition of 4 °C, 90% relative humidity for 12 days. Results showed that the treated mushrooms have reduced weight loss rate, uniform white colour, and higher firmness during storage. Compared to the control, the ketones, alcohols, esters, and aldehydes in the NO-treated button mushroom increased sharply at 3 days of storage and then showed a continuing decline trend, except ester compounds which reached the peak value at 6 days of storage. In addition, NO treatment increased the total phenolics and catalase activity and inhibited the polyphenol oxidase activity in the stored button mushroom. These results indicated that NO treatment is an alternative storage technology to enhance antioxidant capacity and maintain flavour and consumer acceptance of stored button mushroom.

Pre-storage nitric oxide treatment enhances chilling tolerance of zucchini fruit (Cucurbita pepo L.) by S-nitrosylation of proteins and modulation of the antioxidant response

Abstract Nitric oxide (NO), a major signalling molecule with various physiological functions in plants, participates in many responses to abiotic disorders such as cold stress. Chilling injury (CI) is the most costly postharvest problem in zucchini fruit (Cucurbita pepo L.), since it diminishes market acceptability and shelf life. This study investigates the effect of NO treatment on zucchini fruit during postharvest cold storage. Fruit were dipped in an aqueous solution of sodium nitroprusside (SNP; 25, 100, and 500 μM) as a NO donor and in potassium ferricyanide (a structural analogue of SNP) and distilled water, both used as controls and responding the same during postharvest cold storage. The results showed that the application of 25 μM SNP treatment reduced weight loss and CI in zucchini fruit during cold storage. S-nitrosylated proteins detected in the exocarp of NO-treated fruit were more abundant than in non-treated fruit. The application of SNP improved the quality of zucchini fruit stored at 4 °C, with a reduction of weight loss, electrolyte leakage, content of malondialdehyde and H2O2, and delayed loss of firmness during cold storage. NO-treated fruit showed a higher activity of superoxide dismutase, ascorbate peroxidase, glutathione reductase, and phenylalanine ammonia lyase during the first days of cold storage. Total antioxidant capacity was higher in the NO-treated fruit during the first days of cold storage, supported also by higher concentrations of phenols. NO appeared to play a regulatory role in the antioxidant balance in zucchini fruit, maintaining the cellular redox homeostasis and thus modulating ROS toxicity, thereby improving fruit quality during cold conservation.

Exogenous nitric oxide fumigation promoted the emission of volatile organic compounds in peach fruit during shelf life after long-term cold storage

Cold temperature is a common method to store peach after harvest. While long-term cold storage leads to the occurrence of chilling injury and loss of volatile organic compounds (VOCs) after transferring peach to shelf life. Nitric oxide (NO) treatment has been proven to alleviate peach chilling injury. However, the effect of NO treatment on peach VOCs during cold storage plus shelf life is still unknown. In this study, 10 μL L−1 NO was used to fumigate peach before 4 °C cold storage. After cold storage for 21 days, peach were transferred to 20 °C for 3 days to simulate shelf life. Results showed that NO treatment promoted the emission of main VOCs including C6 aldehydes, C6 alcohols, straight-chain esters and lactones after cold storage, supported by the changes of fatty acids and genes expression of PpFADs, PpLOXs, PpHPL, PpADH, PpAATs and PpACXs. Besides, NO also alleviated the occurrence of chilling injury and promoted the recovery of respiration rate and ethylene production during shelf life. In conclusion, treatment with NO effectively prevented the loss of VOCs when transferring peach from cold temperature to shelf life in “Xiahui 6” peach and the possible mechanisms were discussed.

Characterization of the galactono-1,4-lactone dehydrogenase from pepper fruits and its modulation in the ascorbate biosynthesis. Role of nitric oxide

Pepper fruit is one of the highest vitamin C sources of plant origin for our diet. In plants, ascorbic acid is mainly synthesized through the L-galactose pathway, being the L-galactono-1,4-lactone dehydrogenase (GalLDH) the last step. Using pepper fruits, the full GalLDH gene was cloned and the protein molecular characterization accomplished. GalLDH protein sequence (586 residues) showed a 37 amino acids signal peptide at the N-terminus, characteristic of mitochondria. The hydrophobic analysis of the mature protein displayed one transmembrane helix comprising 20 amino acids at the N-terminus. By using a polyclonal antibody raised against a GalLDH internal sequence and immunoblotting analysis, a 56kDa polypeptide cross-reacted with pepper fruit samples. Using leaves, flowers, stems and fruits, the expression of GalLDH by qRT-PCR and the enzyme activity were analyzed, and results indicate that GalLDH is a key player in the physiology of pepper plants, being possibly involved in the processes which undertake the transport of ascorbate among different organs.We also report that an NO (nitric oxide)-enriched atmosphere enhanced ascorbate content in pepper fruits about 40% parallel to increased GalLDH gene expression and enzyme activity. This is the first report on the stimulating effect of NO treatment on the vitamin C concentration in plants. Accordingly, the modulation by NO of GalLDH was addressed. In vitro enzymatic assays of GalLDH were performed in the presence of SIN-1 (peroxynitrite donor) and S-nitrosoglutahione (NO donor). Combined results of in vivo NO treatment and in vitro assays showed that NO provoked the regulation of GalLDH at transcriptional and post-transcriptional levels, but not post-translational modifications through nitration or S-nitrosylation events promoted by reactive nitrogen species (RNS) took place. These results suggest that this modulation point of the ascorbate biosynthesis could be potentially used for biotechnological purposes to increase the vitamin C levels in pepper fruits.

Effect of nitric oxide treatment on chilling injury, antioxidant enzymes and expression of the CmCBF1 and CmCBF3 genes in cold-stored Hami melon (Cucumis melo L.) fruit

Short-term exposure to a low concentration of nitric oxide (NO) treatment can prevent or alleviate chilling injury (CI), and extend the postharvest life of various fresh fruits and vegetables. However no research on this topic has been reported for Hami melon fruit. In this study, Hami melon fruit were pre-treated with 60μL/L NO for 3h at 25°C, and then stored at 1±0.5°C with a relative humidity (RH) of 75–80% for 49d. The results showed that NO treatment effectively decreased the CI index and CI incidence, reduced the increases in membrane permeability and malondialdehyde (MDA) content, inhibited superoxide anion (O2−) production rates, reduced H2O2 content, and sustained higher activity of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) in the rind of Hami melon fruit during storage at 1±0.5°C. C-repeat/dehydration responsive element (CRT/DRE)-binding factors (CBFs) are the best-characterized transcription factors controlling cold-responsive gene expression and cold acclimation. To investigate the molecular regulation of cold resistance by NO treatment in Hami melon fruit, a 639-bp CmCBF1 gene and a 615-bp CmCBF3 gene were identified, and the effect NO on the expression of CmCBF1 and CmCBF3 was measured by RT-qPCR. The results showed that the expression of CmCBF1 and CmCBF3 were induced, the expression of the CmCBF1 and CmCBF3 in NO treated fruit was significantly higher than in control fruit during storage at 1±0.5°C. These results indicate that NO treatment can alleviate and delay CI in cold-stored Hami melon fruit via enhancing the activities of antioxidant enzymes and up-regulating the expression of CmCBF1 and CmCBF3.

Effect of nitric oxide on biochemical and antioxidant properties of pomegranate fruit cv. Shishe-kab during cold storage

Pomegranate is a subtropical fruit that is widely consumed as fresh fruit and juice, however, its postharvest life is limited mainly due to storage disorders. The aim of this study was to determine the effect of nitric oxide (NO) on antioxidant activity and quality attributes of pomegranate fruit. The fruits were dipped for two minutes into different NO concentrations (0, 30, 100, 300 or 1000 µM). Then, the fruits were stored in cold room at 5 °C and RH 85%. After 90 days storage, changes in chilling injury, electrolyte leakage, titratable acidity (TA), total soluble solids (TSS), pH, antioxidant activity and total anthocyanin were evaluated. The results showed that 1000 µM NO application resulted in significant decrease in electrolyte leakage and TSS and maintained antioxidant activity and total anthocyanin in pomegranate fruit. However, no significant effect of NO treatment was observed on TA and chilling injury index. In conclusion, postharvest application of NO may be a promising method for maintaining quality of pomegranate fruit during cold storage.

Increased sensitivity of African American triple negative breast cancer cells to nitric oxide-induced mitochondria-mediated apoptosis.

BackgroundBreast cancer is a complex heterogeneous disease where many distinct subtypes are found. Younger African American (AA) women often present themselves with aggressive form of breast cancer with unique biology which is very difficult to treat. Better understanding the biology of AA breast tumors could lead to development of effective treatment strategies. Our previous studies indicate that AA but not Caucasian (CA) triple negative (TN) breast cancer cells were sensitive to nitrosative stress-induced cell death. In this study, we elucidate possible mechanisms that contribute to nitric oxide (NO)-induced apoptosis in AA TN breast cancer cells.MethodsBreast cancer cells were treated with various concentrations of long-acting NO donor, DETA-NONOate and cell viability was determined by trypan blue exclusion assay. Apoptosis was determined by TUNEL and caspase 3 activity as well as changes in mitochondrial membrane potential. Caspase 3 and Bax cleavage, levels of Cu/Zn superoxide dismutase (SOD) and Mn SOD was assessed by immunoblot analysis. Inhibition of Bax cleavage by Calpain inhibitor, and levels of reactive oxygen species (ROS) as well as SOD activity was measured in NO-induced apoptosis. In vitro and in vivo effect of NO treatment on mammary cancer stem cells (MCSCs) was assessed.Results and discussionNO induced mitocondria-mediated apoptosis in all AA but not in CA TN breast cancer cells. We found significant TUNEL-positive cells, cleavage of Bax and caspase-3 activation as well as depolarization mitochondrial membrane potential only in AA TN breast cancer cells exposed to NO. Inhibition of Bax cleavage and quenching of ROS partially inhibited NO-induced apoptosis in AA TN cells. Increase in ROS coincided with reduction in SOD activity in AA TN breast cancer cells. Furthermore, NO treatment of AA TN breast cancer cells dramatically reduced aldehyde dehydrogenase1 (ALDH1) expressing MCSCs and xenograft formation but not in breast cancer cells from CA origin.ConclusionsEthnic differences in breast tumors dictate a need for tailoring treatment options more suited to the unique biology of the disease.

The use and mechanism of NO to prevent frost damage to flower of apricot

Apricot production is mostly located in areas of Iran, where flowering is damaged by temperatures. Using plant growth regulators to decrease spring frost damage is suggested as a measure to avoid frost damage. The objective of this study was to determine the effects of nitric oxide treatment on avoiding spring frost damage apricot. We evaluated applications of nitric oxide (NO) 0 (control, water only), 10 and 15μM at green tip and pink tip stages of ‘Thokhm Gerdi’ apricot then treated shoots were collected and cutting sections were placed in incubator and subjected to sequential freezing temperature, −1, and −3°C, held for 30min at each temperature. The NO treatment decreased freezing injury, lipid peroxidation and ion leakage percentage for flowers after freezing tests at treatment both stages (especially pink tip stage and −3°C) compared with control. The results showed No application increased significantly proline, inducing sugar, ascorbate peroxidase, superoxide dismutase, catalase, peroxidase enzyme activity and DPPH-radical scavenging activity of flowers. These results showed that NO affects antioxidant capacity of flowers and changes solute content (proline, inducing sugar). Moreover, NO treatment protects apricot flowers from freezing and spring frost damage. So, the present study is the first evidence that nitric oxide effects on avoiding spring frost damage of apricot.

Effect of NO Treatment during Shelf Life of ‘Hayward’ Kiwifruit after Storage at Cold Temperature

The effect of nitric oxide (NO) treatment on the quality of kiwifruit, cv. Hayward, was studied at room temperature after cold storage for one or three months at 0°C. Kiwifruits cold-stored for one month were treated with 200 μL·L -1 NO and subsequently transferred to room temperature to monitor quality changes over the course of their shelf life. Weight loss was high in fruits not treated with NO. Ethylene production was delayed for two days by NO treatment, and respiration rate was reduced to less half than that of the control. The kiwifruits stored for three months were treated with N2 and 100, 200, or 500 μL·L -1 NO, or air alone. The highest weight loss was observed in kiwifruit treated with 100 μL·L -1 NO. While ethylene production was high in fruits treated with 100 μL·L -1 NO and without the treatment, it was relatively low in the kiwifruit treated with 200 and 500 µL·L -1 NO. Firmness was abruptly decreased in fruits not treated with NO, while the kiwifruit exposed to 200 μL·L -1 NO maintained the same levelf firmness for 9 days at room temp erature.n addition,rowth of Botrytis cinerea was inhibited by NO as compared with the air and N2 treatments. Our findings indicate that NO can be used effectively for prolonging shelf life and maintaining fruit quality during distribution after cold storage. The optimum NO concentration for cold-stored kiwifruits was found to be 200 μL·L -1 .

Effects of nitric oxide treatment on the cell wall softening related enzymes and several hormones of papaya fruit during storage

Papaya fruits (Carica papaya L. cv 'Sui you 2') harvested with < 5% yellow surface at the blossom end were fumigated with 60 microL/L of nitric oxide for 3 h and then stored at 20 degrees C with 85% relative humility for 20 days. The effects of nitric oxide treatment on ethylene production rate, the activities of cell wall softening related enzymes including polygalacturonase, pectin methyl esterase, pectate lyase and cellulase and the levels of hormones including indole acetic acid, abscisic acid, gibberellin and zeatin riboside were examined. The results showed that papaya fruits treated with nitric oxide had a significantly lower rate of ethylene production and a lesser loss of firmness during storage. A decrease in polygalacturonase, pectin methyl esterase, pectate lyase and cellulase activities was observed in nitric oxide treated fruit. In addition, the contents of indole acetic acid, abscisic acid and zeatin riboside were reduced in nitric oxide treated fruit, but no significant reduction in the level of gibberellin was found. These results indicate that nitric oxide treatment can effectively delay the softening and ripening of papaya fruit, likely via the regulation of cell wall softening related enzymes and certain hormones.

Effect of Nitric Oxide Treatment on Storage Quality and Disease Resistance of Satsuma Mandarin Fruits

The effects of sodium nitroprusside (SNP) treatment on the disease resistance and storage quality of citrus fruits were investigated through inoculation and storage. The results showed that SNP treatment could effectively reduce the disease incidence and lesion diameter of satsuma mandarin inoculated with Colletotrichum gloeosporioides Penz. during storage. Compared with control, weight lose rate degraded, but soluble protein, ascorbic acid (ASA), reducing sugar content and SSC/TA ratio increased in SNP treated fruits. 50 μmol•L-1 SNP treatment had the better effect than 30 and 100 μmol•L-1 SNP treatment.

The role of nitric oxide in tendon healing

Nitric oxide (NO) is a small free radical that is generated by a family of enzymes called the nitric oxide synthases (NOS). There are 3 isoforms of NOS: endothelial NOS (eNOS), brain or neuronal NOS (bNOS), and inducible NOS (iNOS). In experiments performed during the last 20 years, we have shown that NO is induced by all 3 isoforms of NOS after tendon injury and that NOS activity is upregulated in tendinopathy. In normal uninjured tendons, there is very little NOS activity. In injured rat and human tendons, NOS activity was found in healing fibroblasts in a temporal fashion. In animal models, competitive inhibition of NOS resulted in reduced tendon healing, whereas the addition of NO resulted in enhanced tendon healing. In cultured human cells, the addition of NO via chemical means and adenovirus transfection resulted in enhanced collagen synthesis. We performed 3 randomized, double-blinded clinical trials that demonstrated a significant positive beneficial effect of NO treatment on clinical symptoms and function in patients with Achilles tendinopathy, tennis elbow, and supraspinatus tendonitis. NO was delivered via glyceryl trinitrate (GTN) patches. We also conducted a 3-year prospective follow-up that demonstrated significant long-term efficacy of GTN patches in treating noninsertional Achilles tendinopathy. In a 5-year prospective comparison treating lateral epicondylitis, we found no additional benefits of GTN vs placebo at 5 years. The use of a new GTN patch, OrthoDerm, demonstrated no evidence for efficacy in treating chronic lateral epicondylitis.

Effect of Nitric Oxide Treatment on Storage Quality of Glorious Oranges

Effect of nitric oxide (NO) treatment on storage quality and disease resistance of Glorious oranges was investigated in the experiment. The results showed that NO treatment could effectively reduce disease incidence inoculated with Collletotichum goeosporioides Penz and inhibit the increase of lesion diameter of Glorious oranges during storage. Compared with the control, NO treatment kept higher level of titritable acidity (TA), soluble protein, ascorbic acid (ASA) and reducing sugar, and lower level of weight lose rate and soluble solid concentration (SSC), retarding ripening of fruits.

Effect of nitric oxide treatment on antioxidant responses and psbA gene expression in two wheat cultivars during grain filling stage under drought stress and rewatering

The effect of sodium nitroprusside (SNP; nitric oxide donor) treatment on wheat plant (Triticum aestivum L.) under drought stress during grain filling stage was investigated. When two cultivars wheat plants, Yumai No. 949 and Shanmai No. 5, were drought stressed by PEG for 72 h and rewatered for 48 h, the affections of osmotic dehydration and rehydration on the antioxidant enzymes activities and psbA gene transcriptional abundance were compared. Relative water contents (RWC) decreased markedly after 72 h of PEG stress, along with an obvious decrease in chlorophyll content, increase in SOD, CAT and APX activities, and MDA content as well. Real-time quantitative polymerase chain amplification indicated that drought stress also remarkably inhibited the transcription of psbA gene in photosystem II (PSII). All of these responses could be restored by removing of stress and applying another 48 h of rewatering. The exogenous 0.2 mmol l−1 SNP treatment could significantly alleviate the stress injury and accelerate the progress of recovery. Compared to Yumai No. 949, Shanmai No. 5 had less destroyed plasma membranes, higher RWC and chlorophyll contents, more psbA gene transcriptional abundance during water stress, and rapider recovery to control after rewatering, suggesting not only a better drought resistance but also a better recovery capability after a severe drought stress. The present results also suggested that the application of exogenous SNP could enhance the stress resistance of wheat plant during grain filling stage by increasing antioxidant enzymes activities, as well as protecting important gene transcription in PSII, which were to the benefit of functional recovery from drought stress.

Effects of nitric oxide treatment on active oxygen metabolism and flesh lignification in bamboo shoots

SummaryThe effects of nitric oxide (NO) on active oxygen metabolism and flesh lignification in fresh-cut bamboo shoots (Phyllostachys violascens) were investigated. To determine the optimum concentration of sodium nitroprusside (SNP; a donor of NO) treatment, shoots were treated for 1 h in 0, 0.1, 0.5, or 1.0 mM SNP, then stored in perforated plastic bags for 10 d at 20°C, and 80 – 90% relative humidity. The application of 0.5 mM SNP was most effective in preventing an increase in shoot firmness and allied accumulations of lignin and cellulose. Treatment with 0.5 mM SNP also inhibited the typical, storage-related decreases in shoot superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activities. In addition, SNP treatment reduced the increase in peroxidase (POD) activity in shoots. SNP treatment maintained low levels of production of superoxide anions (O2.–) and hydrogen peroxide (H2O2), while inhibiting the accumulation of malondialdehyde (MDA) and an increase in membrane permeability in shoots. Our results suggest that pre-treatment with 0.5 mM SNP could maintain the balance between the formation and the removal of active oxygen species in bamboo shoots. This appears to delay lipid peroxidation, and thereby prevent the development of flesh lignification and the associated decline in post-harvest shoot quality.

Nitric oxide improves internal iron availability in plants.

Iron deficiency impairs chlorophyll biosynthesis and chloroplast development. In leaves, most of the iron must cross several biological membranes to reach the chloroplast. The components involved in the complex internal iron transport are largely unknown. Nitric oxide (NO), a bioactive free radical, can react with transition metals to form metal-nitrosyl complexes. Sodium nitroprusside, an NO donor, completely prevented leaf interveinal chlorosis in maize (Zea mays) plants growing with an iron concentration as low as 10 microM Fe-EDTA in the nutrient solution. S-Nitroso-N-acetylpenicillamine, another NO donor, as well as gaseous NO supply in a translucent chamber were also able to revert the iron deficiency symptoms. A specific NO scavenger, 2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide, blocked the effect of the NO donors. The effect of NO treatment on the photosynthetic apparatus of iron-deficient plants was also studied. Electron micrographs of mesophyll cells from iron-deficient maize plants revealed plastids with few photosynthetic lamellae and rudimentary grana. In contrast, in NO-treated maize plants, mesophyll chloroplast appeared completely developed. NO treatment did not increase iron content in plant organs, when expressed in a fresh matter basis, suggesting that root iron uptake was not enhanced. NO scavengers 2-(4-carboxy-phenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide and methylene blue promoted interveinal chlorosis in iron-replete maize plants (growing in 250 microM Fe-EDTA). Even though results support a role for endogenous NO in iron nutrition, experiments did not establish an essential role. NO was also able to revert the chlorotic phenotype of the iron-inefficient maize mutants yellow stripe1 and yellow stripe3, both impaired in the iron uptake mechanisms. All together, these results support a biological action of NO on the availability and/or delivery of metabolically active iron within the plant.

Inhaled nitric oxide does not prevent endotoxin-induced lung injury in rabbits.

Neutrophils, platelets, and cytokines are thought to play a pivotal role in the pathogenesis of endotoxin-induced lung injury which resembles features of acute respiratory distress syndrome (ARDS). For initiation of this pathological process, neutrophils and platelets are activated and adhere to pulmonary endothelium. Nitric oxide (NO) inhibits adhesion and activation of these cells and decreases the cytokine level in bronchoalveolar lavage (BAL) fluid obtained from patients with ARDS. Limited data are available on the effect of NO treatment before and after endotoxin on the development and advance of ARDS. The aim of the current study was to determine whether NO inhalation prevents acute lung injury. Thirty-two male anaesthetized rabbits were randomly assigned to receive one of four treatments (n = 8 each); Group S-N received saline with nitrogen (N2), Group S-NO received saline infusion with NO (20 p.p.m.) inhalation, Group E-N received an infusion of Escherichia coli endotoxin 100 micrograms/ kg over 60 min with inhalation of N2, and Group E-NO received endotoxin with NO (20 p.p.m.) inhalation. The lungs of the rabbits were ventilated with 40% oxygen until 6 h after the start of endotoxin or saline administration. Haemodynamics and PaO2 were recorded during the ventilation period. After observation, the lung wet-to dry-(W/D) weight ratio, lung mechanics, and cell fraction, activated complements, cytokines, arachidonic acid metabolites, and albumin concentrations in the BAL fluid were measured and analysed. Light microscopic findings were compared among the four groups. Pulmonary hypertension and deterioration of oxygenation by endotoxin were less pronounced in rabbits receiving NO. The lung compliance after endotoxin was similar in Groups E-NO and E-N. The W/D weight ratio and neutrophils and albumin concentrations in the BAL fluid increased in Groups E-NO and E-N. The BAL fluid concentrations of interleukin-8, thromboxane A2, and prostacyclin were similar in the two endotoxin-treated groups. Endotoxin caused extensive morphologic lung damage regardless of NO inhalation. The increase in pulmonary arterial pressure and deterioration of oxygenation were less in endotoxin-exposed rabbits receiving NO inhalation compared with those receiving N2. Accumulation of neutrophils and platelets in the lung, morphological lung damage, and the release of cytokines and prostanoids were observed in the E-NO group. However, we are unable to extrapolate these results directly to the human clinical setting because of the short observation period, the use of only one dose of NO, and the species difference.