Gaseous Signaling Molecule Nitric Oxide Research Articles

S-nitrosylation of the transcription factor MYB30 facilitates nitric oxide-promoted seed germination in Arabidopsis.

The gaseous signaling molecule nitric oxide (NO) plays an important role in breaking seed dormancy. NO induces a decrease in abscisic acid (ABA) content by transcriptionally activating its catabolic enzyme, the ABA 8'-hydroxylase CYP707A2. However, the underlying mechanism of this process remains unclear. Here, we report that the transcription factor MYB30 plays a critical role in NO-induced seed germination in Arabidopsis (Arabidopsis thaliana). MYB30 loss-of-function attenuates NO-mediated seed dormancy breaking. MYB30 triggers a NO-induced decrease in ABA content during germination by directly promoting CYP707A2 expression. NO induces S-nitrosylation at Cys-49 of MYB30 and enhances its transcriptional activity. Conversely, the ABA receptors PYRABACTIN RESISTANCE1 (PYR1)/PYR1-LIKE (PYL)/REGULATORY COMPONENTS OF ABA RECEPTORS (RCAR) interact with MYB30 and repress its transcriptional activity. ABA promotes the interaction between PYL4 and MYB30, whereas S-nitrosylation releases the PYL4-mediated inhibition of MYB30 by interfering with the PYL4-MYB30 interaction. Genetic analysis showed that MYB30 functions downstream of PYLs during seed dormancy and germination in response to NO. Furthermore, MYB30 mutation significantly represses the reduced dormancy phenotype and the enhanced CYP707A2 expression of the pyr1 pyl1 pyl2 pyl4 quadruple mutant. Our findings reveal that S-nitrosylation of MYB30 precisely regulates the balance of seed dormancy and germination, providing insights into the underlying mechanism of NO-promoted seed germination.

Molecular Mechanisms of Nitric Oxide (NO) Signaling and Reactive Oxygen Species (ROS) Homeostasis during Abiotic Stresses in Plants.

Abiotic stressors, such as drought, heavy metals, and high salinity, are causing huge crop losses worldwide. These abiotic stressors are expected to become more extreme, less predictable, and more widespread in the near future. With the rapidly growing human population and changing global climate conditions, it is critical to prevent global crop losses to meet the increasing demand for food and other crop products. The reactive gaseous signaling molecule nitric oxide (NO) is involved in numerous plant developmental processes as well as plant responses to various abiotic stresses through its interactions with various molecules. Together, these interactions lead to the homeostasis of reactive oxygen species (ROS), proline and glutathione biosynthesis, post-translational modifications such as S-nitrosylation, and modulation of gene and protein expression. Exogenous application of various NO donors positively mitigates the negative effects of various abiotic stressors. In view of the multidimensional role of this signaling molecule, research over the past decade has investigated its potential in alleviating the deleterious effects of various abiotic stressors, particularly in ROS homeostasis. In this review, we highlight the recent molecular and physiological advances that provide insights into the functional role of NO in mediating various abiotic stress responses in plants.

The Emerging Roles of the Gaseous Signaling Molecules NO, H2S, and CO in the Regulation of Stem Cells.

Stem cell technology can be used in tissue engineering and regenerative medicine to transplant stem cells of somatic, embryonic, or induced pluripotent origin, which have tremendous potential for the treatment of currently incurable diseases. Stem cells can maintain their stemness through their self-renewal capability while promoting tissue repair and regeneration through differentiation into various target tissue cells. These two major processes of stem cell biology are precisely regulated via extracellular and intracellular signals. Gaseous signaling molecules have recently been identified to play important roles in both physiology and pathophysiology, and inhalable nitric oxide (iNO) has even been applied as a therapeutic agent. Compared with chemical formulations, these molecules have lower molecular weights and are more likely to pass through the blood-brain barrier and between cells. Nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), three major gaseous signaling molecules involved in biological functions, are emerging as regulators of stem cell processes such as self-renewal, differentiation, survival, anti-apoptotic effects, proliferation, and immune rejection. Although many reviews concerning the roles of gaseous signaling molecules in different diseases or systems are available, few have focused on the roles of these molecules in the regulation of stem cells. Therefore, the aim of this paper is to systematically review the current literature on the functions and mechanisms of the gaseous signaling molecules NO, H2S, and CO in different types of stem cells and to summarize the effects of these molecules on stem cell biology and in therapy.

Correction to "Update on Gaseous Signaling Molecules Nitric Oxide and Hydrogen Sulfide: Strategies to Capture their Functional Activity for Human Therapeutics".

Correction to "Update on Gaseous Signaling Molecules Nitric Oxide and Hydrogen Sulfide: Strategies to Capture their Functional Activity for Human Therapeutics".

Update on Gaseous Signaling Molecules Nitric Oxide and Hydrogen Sulfide: Strategies to Capture their Functional Activity for Human Therapeutics.

Discovery of the production of gaseous molecules, such as nitric oxide and hydrogen sulfide, within the human body began a new concept in cellular signaling. Over the past 30 years, these molecules have been investigated and found to have extremely important beneficial effects in numerous chronic diseases. Gaseous signaling molecules that diffuse in three dimensions apparently contradict the selectivity and specificity afforded by normal ligand receptor binding and activation. This new concept has also created hurdles in the development of safe and efficacious drug therapy based on these molecules. Mechanisms involving formation of more stable intermediates and second messengers allow for new strategies for safe and effective delivery of these molecules for human disease. The purpose of this review is to highlight the biologic effects of nitric oxide and hydrogen sulfide, their seemingly indistinguishable effects, and how these molecules can be safely harnessed for drug development and precursors or substrates administered for human consumption through applied physiology.

Improving risk assessment approaches for chemicals with both endogenous and exogenous exposures

To conduct risk assessments of exogenous chemicals for which there are also endogenous exposures, knowledge of the chemistry and biology of both types of exposures needs to be integrated into problem formulation and carried through to risk characterization. This issue is framed in a risk assessment context, highlighting the importance of quantifying increments of dose from all sources of the same or similar chemicals interacting with biological targets; understanding the influence of endogenous chemical concentrations on disease risk; and assessing total dose to targets in evaluating risk from incremental environmental exposures. Examples of recent assessments illustrate the importance of addressing this issue. Evaluations of data on blood or organ concentrations of ammonia, methanol, formaldehyde, acetaldehyde, and three gaseous signaling molecules (hydrogen sulfide, carbon monoxide, and nitric oxide) provide examples where current data are already informing perspectives on relative exposures at the portal of entry and systemically. To facilitate quality risk assessments of exogenous chemicals with endogenous exposures, a series of specific questions are presented that need to be addressed in systematic review to enhance problem formulation, improve the development of holistic conceptual models, and to facilitate the identification of priority data needs for improving risk assessments.

Revisiting the systemic lipopolysaccharide mediated neuroinflammation: Appraising the effect of l-cysteine mediated hydrogen sulphide on it

The present research was ventured to examine the effect of l-cysteine on neuro-inflammation persuaded by peripheral lipopolysaccharides (LPS, 125 μg/kg, i.p.) administration. No behavioral, biochemical, and inflammatory abnormality was perceived in the brain tissues of experimental animals after LPS administration. l-cysteine precipitated marginal symptoms of toxicity in the brain tissue. Similar pattern of wholesome effect of LPS were perceived when evaluated through the brain tissue fatty acid profile, histopathologically and NF-ĸBP65 protein expression. LPS was unsuccessful to alter the levels of hydrogen sulphide (H2S), cyclooxygenase (COX) and lipoxygenase (LOX) enzyme in brain tissue. LPS afforded significant peripheral toxicity, when figured out through inflammatory markers (COX, LOX), gaseous signaling molecules nitric oxide (NO), H2S, liver toxicity (SGOT, SGPT), and inflammatory transcription factor (NF-ĸBP65) and l-cysteine also provided a momentous protection against the same as well. The study inculcated two major finding, firstly LPS (i.p.) cannot impart inflammatory changes to brain and secondly, l-cysteine can afford peripheral protection against deleterious effect of LPS (i.p.)

Polysulfides (H2Sn) produced from the interaction of hydrogen sulfide (H2S) and nitric oxide (NO) activate TRPA1 channels

Hydrogen sulfide (H2S) exerts synergistic effects with another gaseous signaling molecule nitric oxide (NO) on ion channels and vasculature. However, the mechanism of the synergy is not well understood. Here, we show that the interaction between H2S and NO generates polysulfides (H2Sn), which activate transient receptor potential ankyrin 1 (TRPA1) channels. High performance liquid chromatography with tandem mass spectrometry analysis, along with the imaging of intracellular Ca2+ and H2Sn, showed that H2Sn and their effects were abolished by cyanolysis and by reducing substances such as dithiothreitol (DTT), cysteine, and glutathione (GSH). However, the effects of nitroxyl or nitrosopersulfide, other potential products of H2S and NO interaction, are not affected by cyanolysis or reducing substances. This study demonstrates that H2Sn are products of synergy between H2S and NO and provides a new insight into the signaling mechanisms.

Nitric Oxide Is Involved in Ethylene-Induced Adventitious Rooting in Marigold

The plant hormone ethylene and the gaseous signaling molecule nitric oxide (NO) are involved in numerous plant growth and development processes. However, the mechanisms by which their interaction a...

Unravelling the reactive oxygen and reactive nitrogen signalling networks in plants.

Unravelling the reactive oxygen and reactive nitrogen signalling networks in plants.

Chapter Four - Nitric Oxide Regulation of Adult Neurogenesis

The ubiquitous gaseous signaling molecule nitric oxide participates in the regulation of a variety of physiological and pathological processes, including adult neurogenesis. Adult neurogenesis, or the generation of new neurons in the adult brain, is a restricted event confined to areas with neurogenic capability. Although nitric oxide has been shown to mediate conflicting effects on adult neurogenesis, which may be partly explained by its unique characteristics, more studies are required in order to fully comprehend and appreciate the mechanisms involved. Neuropeptide Y, a neurotransmitter shown to be an important regulator of adult hippocampal neurogenesis, acts through intracellular nitric oxide to induce an increase in neural progenitor cell proliferation.

Mechanistic Studies on the Reaction of Nitrocobalamin with Glutathione: Kinetic evidence for formation of an aquacobalamin intermediate.

The essential but also toxic gaseous signaling molecule nitric oxide is scavenged by the reduced vitamin B12 complex cob(II)alamin. The resulting complex, nitroxylcobalamin (NO--Cbl(III)), is rapidly oxidized to nitrocobalamin (NO2Cbl) in the presence of oxygen; however it is unlikely that nitrocobalamin is itself stable in biological systems. Kinetic studies on the reaction between NO2Cbl and the important intracellular antioxidant, glutathione (GSH), are reported. In this study, a reaction pathway is proposed in which the β-axial ligand of NO2Cbl is first substituted by water to give aquacobalamin (H2OCbl+), which then reacts further with GSH to form glutathionylcobalamin (GSCbl). Independent measurements of the four associated rate constants k1, k-1, k2, and k-2 support the proposed mechanism. These findings provide insight into the fundamental mechanism of ligand substitution reactions of cob(III)alamins with inorganic ligands at the β-axial site.

The regulation of cardiac activity by nitric oxide (NO) in the Vietnamese stick insect, Baculum extradentatum

This study examines the role of the unconventional gaseous signaling molecule nitric oxide (NO) on the regulation of heart rate in the Vietnamese stick insect, Baculum extradentatum. Using nicotinamide dinucleotide hydrogen phosphate (NADPH)-diaphorase histochemistry, as well as immunohistochemistry and Western blotting with an antibody against NO synthetase (NOS), we identified the presence of NOS in hemocytes present throughout the lumen of the dorsal vessel. We propose that NO is delivered to heart muscle tissue via hemocytes circulating within the hemolymph. In the present study, stimulation of NO levels by the application of the NO donor MAHMA-NONOate and l-arginine led to a dose-dependent decrease in heart rate. Treatment of tissues with the NOS inhibitor, L-NAME, in equimolar concentrations with l-arginine, led to a recovery of heart rate, without modifying heart rate on its own. Finally guanosine 3′,5′-cyclic monophosphate (cGMP) analog, 8-bromo-cGMP, elicited similar inhibitory effects on stick insect heart rate as did the guanylate cyclase activator, YC-1, and the phosphodiesterase inhibitor, dipyridamole, indicating that cGMP is most likely the second messenger in the stick insect NO signaling pathway. Contrary to the cardioexcitatory effect of NO on other insect hearts, we have found that NO inhibits stick insect heart rate independently from any nervous system input, in a similar inhibitory fashion as that of vertebrate hearts.

Odorant-Dependent Generation of Nitric Oxide in Mammalian Olfactory Sensory Neurons

The gaseous signalling molecule nitric oxide (NO) is involved in various physiological processes including regulation of blood pressure, immunocytotoxicity and neurotransmission. In the mammalian olfactory bulb (OB), NO plays a role in the formation of olfactory memory evoked by pheromones as well as conventional odorants. While NO generated by the neuronal isoform of NO synthase (nNOS) regulates neurogenesis in the olfactory epithelium, NO has not been implicated in olfactory signal transduction. We now show the expression and function of the endothelial isoform of NO synthase (eNOS) in mature olfactory sensory neurons (OSNs) of adult mice. Using NO-sensitive micro electrodes, we show that stimulation liberates NO from isolated wild-type OSNs, but not from OSNs of eNOS deficient mice. Integrated electrophysiological recordings (electro-olfactograms or EOGs) from the olfactory epithelium of these mice show that NO plays a significant role in modulating adaptation. Evidence for the presence of eNOS in mature mammalian OSNs and its involvement in odorant adaptation implicates NO as an important new element involved in olfactory signal transduction. As a diffusible messenger, NO could also have additional functions related to cross adaptation, regeneration, and maintenance of MOE homeostasis.

Mechanisms of Nitric Oxide Interplay with Rho GTPase Family Members in Modulation of Actin Membrane Dynamics in Pericytes and Fibroblasts

Migration of pericytes such as hepatic stellate cells is fundamentally important for diverse biological and pathological processes including tumor invasion and fibrosis. In prototypical migratory cells such as fibroblasts, the small GTPases Rac1 and RhoA govern the assembly of lamellipodia and stress fibers, respectively, cytoskeletal structures that are integral to the cell migration process. The gaseous signaling molecule nitric oxide (NO) influences growth factor chemotactic responses, although this occurs primarily in cell-type-specific ways and through cell biological effects that are poorly characterized. In this study, we use complementary molecular and cell biological approaches to delineate important roles for Rac1, RhoA, and NO in migration of the human hepatic stellate cell line LX2 and primary rat hepatic stellate cells. Both platelet-derived growth factor (PDGF) and Rac1 overexpression drove migration through formation of actin-positive filopodia spikes in LX2 as compared to the formation of lamellipodia in fibroblasts. NO inhibited PDGF- and Rac1-driven migration in LX2 by abrogating filopodia formation and inhibited migration of fibroblasts by attenuating lamellipodial protrusions. Additionally, RhoA conferred resistance to NO inhibition of migration and restored chemotactic responses to PDGF in the absence of functional Rac1 in LX2. In conclusion, these studies identify novel crosstalk between small GTPases, cytoskeletal structures, and NO in pericyte-specific pathways, providing counterbalances in the chemotactic responses to growth factors.

Odorant-evoked nitric oxide signals in the antennal lobe of Manduca sexta.

The gaseous signaling molecule nitric oxide (NO) can affect the activities of neurons and neural networks in many different systems. The strong expression of NO synthase (NOS) in the primary synaptic neuropil (the antennal lobe in insects and the olfactory bulb in vertebrates) of the olfactory system of most organisms, and the unique spheroidal geometry of olfactory glomeruli in those neuropils, have led to suggestions that NO signaling is important for processing olfactory information. No direct evidence exists, however, that NO signals are produced in olfactory glomeruli. We investigated the production of NO in the antennal lobe of the moth, Manduca sexta, by using immunocytochemistry and real-time optical imaging with a NO-sensitive fluorescent marker, diaminofluorescein diacetate. We confirmed that NOS was expressed in the axons of olfactory receptor neurons projecting to all glomeruli. Soluble guanylyl cyclase, the best characterized target of NO, was found in a subset of postsynaptic antennal lobe neurons that included projection neurons, a small number of GABA-immunoreactive neurons, and a serotonin-immunoreactive neuron. We found that odorant stimulation evoked NO signals that were reproducible and spatially focused. Different odorants evoked spatially distinct patterns of NO production. Increased concentrations of pheromone and plant odorants caused increases in peak signal intensity. Increased concentrations of plant odorants also evoked a dramatic increase in signal area. The results of these experiments show clearly that odorant stimulation can evoke NO production in the olfactory system. The NO signals produced are likely to play an important role in processing olfactory information.

Caveolae compartmentalization of heme oxygenase-1 in endothelial cells.

The heme oxygenase (HO) and nitric oxide synthase (NOS) enzymes generate the gaseous signaling molecules carbon monoxide (CO) and nitric oxide, respectively. Constitutive NOSs localize to caveolae, and their activities are modulated by caveolin-1. Nothing is known of the localization of the inducible heme oxygenase-1 (HO-1) in plasma membrane caveolae. Thus, we examined the distribution and subcellular localization of HO-1, biliverdin reductase (BVR), and NADPH:cytochrome P450 reductase (NPR) in pulmonary artery endothelial cells. Each of these proteins localized in part to plasma membrane caveolae in endothelial cells. Inducers of HO-1 or overexpression of HO-1 increased the content of this protein in a detergent-resistant fraction containing caveolin-1. Inducible HO activity appeared in plasma membrane, cytosol, and isolated caveolae. In addition, caveolae contained endogenous BVR activity, supporting the same compartmentalization of both enzymes. Caveolin-1 physically interacted with HO-1, as shown by coimmunoprecipitation studies. HO activity dramatically increased in cells expressing caveolin-1 antisense transcripts, suggesting a negative regulatory role for caveolin-1. Conversely, caveolin-1 expression attenuated LPS-inducible HO activity. Since their initial characterization in 1969, HO enzymes have been described as endoplasmic reticulum-associated proteins. We demonstrate for the first time the localization of heme degradation enzymes to plasma membrane caveolae, and present novel evidence that caveolin-1 interacts with and modulates HO activity.

Dark-dependent soluble guanylyl cyclase activity in locust photoreceptor cells

The enzyme soluble guanylyl cyclase (SGC) mediates physiological effects of the gaseous signalling molecule nitric oxide by generating the second messenger molecule cyclic-GMP (cGMP). Here we have demonstrated that SGC is expressed in photoreceptor cells of locust compound eyes. However, stimulation of SGC activity in the eyes was observed only in the dark, indicating that light may cause inhibition of SGC activity in locust photoreceptor cells. Because light causes elevation of cytosolic Ca2+ in insect photoreceptor cells, we investigated the involvement of Ca2+ in mediating the inhibitory effect of light on SGC activity in the locust eye. Light-adapted locust eyes incubated with Ca2+-free physiological saline displayed a similar level of stimulated SGC activity to that normally seen only in dark-adapted eyes. These data indicate for the first time that Ca2+ may regulate SGC activity in cells. Moreover, the dark dependence of SGC activity in the locust eye suggests that SGC and cGMP may participate in dark-adaptation mechanisms in insect photoreceptor cells.