*NO, RSNO, ONOO-, NO+, *NOO, NOx--dynamic regulation of oxidant scavenging, nitric oxide stores, and cyclic GMP-independent cell signaling

Molecular mechanisms and highly functional development for stress tolerance of the yeast Saccharomyces cerevisiae

In response to environmental stress, microorganisms adapt to drastic changes while exerting cellular functions by controlling gene expression, metabolic pathways, enzyme activities, and protein-protein interactions. Microbial cells that undergo a fermentation process are subjected to stresses, such as high temperature, freezing, drying, changes in pH and osmotic pressure, and organic solvents. Combinations of these stresses that continue over long terms often inhibit cells' growth and lead to their death, markedly limiting the useful functions of microorganisms (eg their fermentation ability). Thus, high stress tolerance of cells is required to improve productivity and add value to fermented/brewed foods and biofuels. This review focuses on stress tolerance mechanisms, including l-proline/l-arginine metabolism, ubiquitin system, and transcription factors, and the functional development of the yeast Saccharomyces cerevisiae, which has been used not only in basic science as a model of higher eukaryotes but also in fermentation processes for making alcoholic beverages, food products, and bioethanol.

Research progress of hydrogen sulfide in Alzheimer's disease from laboratory to hospital: a narrative review

Alzheimer's disease is a neurodegenerative disease that mainly occurs in old age and early stages. Its main manifestations are memory impairment, aphasia, apraxia, loss of identity, abstract thinking and impairment of computing power, personality and behavior changes, etc. At present, the treatment of Alzheimer's disease only stays on reducing the disease and delaying the development, which is also a difficult problem to overcome in clinical practice. Hydrogen sulfide, as a third gaseous signal molecule after carbon monoxide and nitrogen monoxide, has become very popular in recent years. It shows very promising prospects in the Alzheimer's disease model. It can protect the nerve function and prevent the progress of the disease by affecting the amyloid precursor protein metabolism, anti-apoptosis, anti-inflammatory, and antioxidant pathways. Therefore, this article summarizes the relevant basic and clinical research of hydrogen sulfide in Alzheimer's disease, and discusses its progress and findings and mechanism characteristics.

The Role of Nitric Oxide in Cancer: Master Regulator or NOt?

Nitric oxide (NO) is a key player in both the development and suppression of tumourigenesis depending on the source and concentration of NO. In this review, we discuss the mechanisms by which NO induces DNA damage, influences the DNA damage repair response, and subsequently modulates cell cycle arrest. In some circumstances, NO induces cell cycle arrest and apoptosis protecting against tumourigenesis. NO in other scenarios can cause a delay in cell cycle progression, allowing for aberrant DNA repair that promotes the accumulation of mutations and tumour heterogeneity. Within the tumour microenvironment, low to moderate levels of NO derived from tumour and endothelial cells can activate angiogenesis and epithelial-to-mesenchymal transition, promoting an aggressive phenotype. In contrast, high levels of NO derived from inducible nitric oxide synthase (iNOS) expressing M1 and Th1 polarised macrophages and lymphocytes may exert an anti-tumour effect protecting against cancer. It is important to note that the existing evidence on immunomodulation is mainly based on murine iNOS studies which produce higher fluxes of NO than human iNOS. Finally, we discuss different strategies to target NO related pathways therapeutically. Collectively, we present a picture of NO as a master regulator of cancer development and progression.

Nitric Oxide Signalling in Yeast

Nitric oxide (NO) is a cellular signalling molecule widely conserved among organisms, including microorganisms such as bacteria, yeasts, and fungi, and higher eukaryotes such as plants and mammals. NO is mainly produced by the activities of NO synthase (NOS) or nitrite reductase (NIR). There are several NO detoxification systems, including NO dioxygenase (NOD) and S-nitrosoglutathione reductase (GSNOR). NO homeostasis, based on the balance between NO synthesis and degradation, is important for regulating its physiological functions, since an excess of NO causes nitrosative stress due to the high reactivity of NO and NO-derived compounds. In yeast, NO may be involved in stress responses, but the role of NO and the mechanism underlying NO signalling are poorly understood due to the lack of mammalian NOS orthologs in the yeast genome. NOS and NIR activities have been observed in yeast cells, but the gene-encoding NOS and the mechanism by which NO production is catalysed by NIR remain unclear. On the other hand, yeast cells employ NOD and GSNOR to maintain intracellular redox balance following endogenous NO production, treatment with exogenous NO, or exposure to environmental stresses. This article reviews NO metabolism (synthesis, degradation) and its regulation in yeast. The physiological roles of NO in yeast, including the oxidative stress response, are also discussed. Such investigations into NO signalling are essential for understanding how NO modulates the genetics and physiology of yeast. In addition to being responsible for the pathology and pharmacology of various degenerative diseases, NO signalling may be a potential target for the construction and engineering of industrial yeast strains.

Posttranslational protein modifications by reactive nitrogen and chlorine species and strategies for their prevention and elimination

Proteins are subject to various posttranslational modifications, some of them being undesired from the point of view of metabolic efficiency. Prevention of such modifications is expected to provide new means of therapy of diseases and decelerate the process of aging. In this review, modifications of proteins by reactive nitrogen species and reactive halogen species, is briefly presented and means of prevention of these modifications and their sequelae are discussed, including the denitrase activity and inhibitors of myeloperoxidase.

Activation of calcium signaling through Trpv1 by nNOS and peroxynitrite as a key trigger of skeletal muscle hypertrophy

Skeletal muscle atrophy occurs in aging and pathological conditions, including cancer, diabetes and AIDS. Treatment of atrophy is based on either preventing protein-degradation pathways, which are activated during atrophy, or activating protein-synthesis pathways, which induce muscle hypertrophy. Here we show that neuronal nitric oxide synthase (nNOS) regulates load-induced hypertrophy by activating transient receptor potential cation channel, subfamily V, member 1 (TRPV1). The overload-induced hypertrophy was prevented in nNOS-null mice. nNOS was transiently activated within 3 min after overload. This activation promoted formation of peroxynitrite, a reaction product of nitric oxide with superoxide, which was derived from NADPH oxidase 4 (Nox4). Nitric oxide and peroxynitrite then activated Trpv1, resulting in an increase of intracellular Ca(2+) concentration ([Ca(2+)](i)) that subsequently triggered activation of mammalian target of rapamycin (mTOR). Notably, administration of the TRPV1 agonist capsaicin induced hypertrophy without overload and alleviated unloading- or denervation-induced atrophy. These findings identify nitric oxide, peroxynitrite and [Ca(2+)](i) as the crucial mediators that convert a mechanical load into an intracellular signaling pathway and lead us to suggest that TRPV1 could be a new therapeutic target for treating muscle atrophy.

Mitochondria as a target for the cardioprotective effects of nitric oxide in ischemia-reperfusion injury

During cardiac ischemia-reperfusion (IR) injury, excessive generation of reactive oxygen species (ROS) and overload of Ca(2+) at the mitochondrial level both lead to opening of the mitochondrial permeability transition (PT) pore on reperfusion. This can result in the depletion of ATP, irreversible oxidation of proteins, lipids, and DNA within the cardiomyocyte, and can trigger cell-death pathways. In contrast, mitochondria are also implicated in the cardioprotective signaling processes of ischemic preconditioning (IPC), to prevent IR-related pathology. Nitric oxide (NO*) has emerged as a potent effector molecule for a variety of cardioprotective strategies, including IPC. Whereas NO* is most noted for its activation of the "classic" soluble guanylate cyclase (sGC) signaling pathway, emerging evidence indicates that NO can directly act on mitochondria, independent of the sGC pathway, affording acute cardioprotection against IR injury. These direct effects of NO* on mitochondria are the focus of this review.

Endocannabinoids and reactive nitrogen and oxygen species in neuropathologies

Neuropathologies that affect our population include ischemic stroke and neurodegenerative diseases of immune origin, including multiple sclerosis. The endocannabinoid system in the brain, including agonists anandamide (arachidonyl ethanolamide) and 2-arachidonoylglycerol, and the CB1 and CB2 cannabinoid receptors, has been implicated in the pathophysiology of these disease states, and can be a target for therapeutic interventions. This review concentrates on cellular signal transduction pathways believed to be involved in the cellular damage.

The role of a formaldehyde dehydrogenase-glutathione pathway in protein S-nitrosation in mammalian cells

Intracellular sulfhydryls, both protein and non-protein, are potential targets of nitric oxide-related species. S-Nitrosation of proteins can occur in vivo and can affect their activity. Metabolic pathways that regulate protein S-nitrosation are therefore likely to be biologically important. We now report that formaldehyde dehydrogenase, an enzyme that decomposes S-nitrosoglutathione, can indirectly regulate the level of cellular protein S-nitrosation. Nitrogen oxide donors induced high levels of protein S-nitrosation in HeLa cells and lower levels in Mutatect fibrosarcoma cells, as determined by Saville-Griess assay and Western-dot-blot analysis. Depletion of glutathione by treatment with buthionine sulfoximine markedly increased protein S-nitrosation in both cell lines. Glutathione depletion also increased cytokine-induced S-nitrosation in brain endothelial cells. Formaldehyde dehydrogenase activity was 2-fold higher in Mutatect than in HeLa cells. We downregulated formaldehyde dehydrogenase activity in Mutatect cells by stably expressing antisense RNA and short-interfering RNA. In these cells, both protein S-nitrosation and S-nitrosoglutathione levels were significantly enhanced after exposure to nitrogen oxide donors as compared to parental cells. Overall, a strong inverse correlation between total S-nitrosothiols and formaldehyde dehydrogenase activity was seen. Inhibition of glutathione reductase, the enzyme that converts oxidized to reduced glutathione, by dehydroepiandrosterone similarly increased protein S-nitrosation and S-nitrosoglutathione levels in both cell lines. Our results provide the first evidence that formaldehyde dehydrogenase-dependent decomposition of S-nitrosoglutathione plays a role in protecting against nitrogen oxide-mediated protein S-nitrosation. We propose that formaldehyde dehydrogenase and glutathione reductase participate in a glutathione-dependent metabolic cycle that decreases protein S-nitrosation following exposure of cells to nitric oxide.

Interferon-gamma expression in periventricular leukomalacia in the human brain

Periventricular leukomalacia (PVL), the major lesion underlying cerebral palsy in survivors of prematurity, is characterized by focal periventricular necrosis and diffuse gliosis of immature cerebral white matter. Causal roles have been ascribed to hypoxiaischemia and maternal-fetal infection, leading to cytokine responses, inflammation, and oligodendrocyte cell death. Because interferon-gamma (IFN-gamma) is directly toxic to immature oligodendrocytes, we tested the hypothesis that it is expressed in PVL (N = 13) compared to age-adjusted controls (N = 31) using immunocytochemistry. In PVL, IFN-gamma immunopositive macrophages were clustered in necrotic foci, and IFN-gamma immunopositive reactive astrocytes were present throughout the surrounding white matter (WM). The difference in the number of IFN-gamma immunopositive glial cells/high power field (IFN-gamma score, Grades 0-3) between PVL cases (age-adjusted mean 2.59+/-0.25) and controls (age-adjusted mean 1.39+/-0.16) was significant (p<0.001). In the gliotic WM, the IFN-gamma score correlated with markers for lipid peroxidation, but not nitrative stress. A subset of premyelinating (04+) oligodendrocytes expressed IFN-gamma receptors in PVL and control cases, indicating that these cells are vulnerable to IFN-gamma toxicity via receptor-mediated interactions. In PVL, IFN-gamma produced by macrophages and reactive astrocytes may play a role in cytokine-induced toxicity to premyelinating oligodendrocytes as part of a cytokine response stimulated by ischemia and/or infection.

Uncoupling protein 2 prevents neuronal death including that occurring during seizures: a mechanism for preconditioning

The mitochondrial uncoupling protein (UCP2) is expressed in selected regions of the brain. Here we demonstrate that up-regulation of UCP2 is part of a neuroprotective set of responses to various cellular stresses in vitro and in vivo. PC12 cells, when transfected with UCP2, were protected against free radical-induced cell death. Seizure activity was associated with elevated UCP2 levels and mitochondrial uncoupling activity. In transgenic mice that expressed UCP2 constitutively in the hippocampus before seizure induction, a robust reduction in cell death was seen. Because UCP2 increased mitochondrial number and ATP levels with a parallel decrease in free radical-induced damage, it is reasonable to suggest that mitochondrial UCPs precondition neurons by dissociating cellular energy production from that of free radicals to withstand the harmful effects of cellular stress occurring in a variety of neurodegenerative disorders, including epilepsy.

Epr analysis reveals three tissues responding to endotoxin by increased formation of reactive oxygen and nitrogen species

The excessive formation of reactive oxygen and nitrogen species (RONS) in tissue has been implicated in the development of various diseases. In this study we adopted ex vivo low temperature EPR spectroscopy combined with spin trapping technique to measure local RONS levels in frozen tissue samples. CP-H (1-hydroxy-3-carboxy-pyrrolidine), a new nontoxic spin probe, was used to analyze RONS in vivo. In addition, nitrosyl complexes of hemoglobin were determined to trace nitric oxide released into blood. By this technique we found that RONS formation in tissue of control animals increased in the following order: liver < heart < brain < cerebellum < lung < muscle < blood < ileum < kidney < duodenum < jejunum. We also found that endotoxin challenge, which represents the most common model of septic shock, increased the formation of RONS in rat liver, heart, lung, and blood, but decreased RONS formation in jejunum. We did not find changes in RONS levels in other parts of gut, brain, skeletal muscles, and kidney. Scavenging of RONS by CP-H was accompanied by an increase in blood pressure, indicating that LPS-induced vasodilatation may be due to RONS, but not due to nitric oxide. Experiments with tissue homogenates incubated in vitro with CP-H showed that ONOO(-) and O(2)(*)(-), as well as other not identified RONS, are detectable by CP-H in tissue. In summary, low-temperature EPR combined with CP-H infusion allowed detection of local RONS formation in tissues. Increased formation of RONS in response to endotoxin challenge is organ specific.