Nitric oxide signaling and nitrosative stress in neurons: role for S-nitrosylation

Nuclear GAPDH in cortical microglia mediates cellular stress-induced cognitive inflexibility

We report a mechanism that underlies stress-induced cognitive inflexibility at the molecular level. In a mouse model under subacute cellular stress in which deficits in rule shifting tasks were elicited, the nuclear glyceraldehyde dehydrogenase (N-GAPDH) cascade was activated specifically in microglia in the prelimbic cortex. The cognitive deficits were normalized with a pharmacological intervention with a compound (the RR compound) that selectively blocked the initiation of N-GAPDH cascade without affecting glycolytic activity. The normalization was also observed with a microglia-specific genetic intervention targeting the N-GAPDH cascade. At the mechanistic levels, the microglial secretion of High-Mobility Group Box (HMGB), which is known to bind with and regulate the NMDA-type glutamate receptors, was elevated. Consequently, the hyperactivation of the prelimbic layer 5 excitatory neurons, a neural substrate for cognitive inflexibility, was also observed. The upregulation of the microglial HMGB signaling and neuronal hyperactivation were normalized by the pharmacological and microglia-specific genetic interventions. Taken together, we show a pivotal role of cortical microglia and microglia-neuron interaction in stress-induced cognitive inflexibility. We underscore the N-GAPDH cascade in microglia, which causally mediates stress-induced cognitive alteration.

"NO" Time in Fear Response: Possible Implication of Nitric-Oxide-Related Mechanisms in PTSD

Post-traumatic stress disorder (PTSD) is a psychiatric condition characterized by persistent fear responses and altered neurotransmitter functioning due to traumatic experiences. Stress predominantly affects glutamate, a neurotransmitter crucial for synaptic plasticity and memory formation. Activation of the N-Methyl-D-Aspartate glutamate receptors (NMDAR) can trigger the formation of a complex comprising postsynaptic density protein-95 (PSD95), the neuronal nitric oxide synthase (nNOS), and its adaptor protein (NOS1AP). This complex is pivotal in activating nNOS and nitric oxide (NO) production, which, in turn, activates downstream pathways that modulate neuronal signaling, including synaptic plasticity/transmission, inflammation, and cell death. The involvement of nNOS and NOS1AP in the susceptibility of PTSD and its comorbidities has been widely shown. Therefore, understanding the interplay between stress, fear, and NO is essential for comprehending the maintenance and progression of PTSD, since NO is involved in fear acquisition and extinction processes. Moreover, NO induces post-translational modifications (PTMs), including S-nitrosylation and nitration, which alter protein function and structure for intracellular signaling. Although evidence suggests that NO influences synaptic plasticity and memory processing, the specific role of PTMs in the pathophysiology of PTSD remains unclear. This review highlights pathways modulated by NO that could be relevant to stress and PTSD.

Mechanical activation of vagal afferents involves opposing cation and TREK1 currents and NO regulation

Vagal afferents convey signals of mechanical stimulation in the gut to the brain, which is essential for the regulation of food intake. However, ion channels sensing mechanical stimuli are not fully understood. This study aimed to examine the ionic currents activated by mechanical stimulation and a possible neuro-modulatory role of nitric oxide on vagal afferents. Nodose neuronal currents and potentials, and intestinal afferent firing by mechanical stimulation were measured by whole-cell patch clamp, and in vitro afferent recording, respectively. Osmotically activated cation and two-pore domain K+ currents were identified in nodose neurons. The membrane potential displayed a biphasic change under hypotonic stimulation. Cation channel-mediated depolarization was followed by a hyperpolarization mediated by K+ channels. The latter was inhibited by l-methionine (TREK1 channel inhibitor) and l-NNA (nitric oxide synthase inhibitor). Correspondingly, mechanical stimulation activated opposing cation and TREK1 currents. NOS inhibition decreased TREK1 currents and potentiated jejunal afferent nerve firing induced by mechanical stimuli. This study suggested a novel activation mechanism of ion channels underlying adaptation under mechanical distension in vagal afferent neurons. The guts' ability to perceive mechanical stimuli is vital in determining how it responds to food intake. The mechanosensation through ion channels could initiate and control gut function.

Calcium Supplementation on Glucose Tolerance, Oxidative Stress, and Reproductive Outcomes of Diabetic Rats and Their Offspring

Diabetes mellitus increases the risk of obstetric complications, morbidity, and infant mortality. Controlled nutritional therapy with micronutrients has been employed. However, the effect of calcium (Ca2+) supplementation on diabetic pregnancy is unclear. We aimed to evaluate whether diabetic rats supplemented with Ca2+ during pregnancy present better glucose tolerance, redox status, embryonic and fetal development, newborn weight, and the prooxidant and antioxidant balance of male and female pups. For this, newborn rats received the beta-cytotoxic drug streptozotocin for inducing diabetes on the day of birth. In adulthood, these rats were mated and treated with Ca2+ twice a day from day 0 to day 20 of pregnancy. On day 17, the pregnant rats were submitted to the oral glucose tolerance test (OGTT). At the end of pregnancy, they were anesthetized and killed to collect blood and pancreas samples. The uterine horns were exposed for an evaluation of maternal reproductive outcomes and embryofetal development, and the offspring's liver samples were collected for redox status measurement. Nondiabetic and diabetic rats supplemented with Ca2+ showed no influence on glucose tolerance, redox status, insulin synthesis, serum calcium levels, and embryofetal losses. The reduced rate of newborns classified as adequate for gestational age (AGA) and higher rates of LGA (large) and small (LGA) newborns and higher -SH and GSH-Px antioxidant activities in female pups were observed in diabetic dams, regardless of supplementation. Thus, maternal supplementation caused no improvement in glucose tolerance, oxidative stress biomarkers, embryofetal growth and development, and antioxidants in pups from diabetic mothers.

Taurine, an essential β-amino acid insulates against ketamine-induced experimental psychosis by enhancement of cholinergic neurotransmission, inhibition of oxidative/nitrergic imbalances, and suppression of COX-2/iNOS immunoreactions in mice

Cholinergic, oxidative, nitrergic alterations, and neuroinflammation are some key neuropathological features common in schizophrenia disease. They involve complex biological processes that alter normal behavior. The present treatments used in the management of the disorder remain ineffective together with some serious side effects as one of their setbacks. Taurine is a naturally occurring essential β-amino acid reported to elicit antipsychotic property in first episode psychosis in clinical setting, thus require preclinical investigation. Hence, we set out to investigate the effects of taurine in the prevention and reversal of ketamine-induced psychotic-like behaviors and the associated putative neurobiological mechanisms underlying its effects. Adult male Swiss mice were sheared into three separate cohorts of experiments (n = 7): drug alone, preventive and reversal studies. Treatments consisted of saline (10 mL/kg/p.o./day), taurine (50 and 100 mg/kg/p.o./day) and risperidone (0.5 mg/kg/p.o./day) with concomitant ketamine (20 mg/kg/i.p./day) injections between days 8-14, or 14 days entirely. Behavioral hyperactivity, despair, cognitive impairment, and catalepsy were measured. Brain oxidative/nitrergic imbalance, immunoreactivity (COX-2 and iNOS), and cholinergic markers were determined in the striatum, prefrontal-cortex, and hippocampus. Taurine abates ketamine-mediated psychotic-like episodes without cataleptogenic potential. Taurine attenuated ketamine-induced decrease in glutathione, superoxide-dismutase and catalase levels in the striatum, prefrontal-cortex and hippocampus. Also, taurine prevented and reversed ketamine-mediated elevation of malondialdehyde, nitrite contents, acetylcholinesterase activity, and suppressed COX-2 and iNOS expressions in a brain-region dependent manner. Conclusively, taurine insulates against ketamine-mediated psychotic phenotype by normalizing brain central cholinergic neurotransmissions, oxidative, nitrergic and suppression of immunoreactive proteins in mice brains.

S-nitrosylated PARIS Leads to the Sequestration of PGC-1α into Insoluble Deposits in Parkinson's Disease Model

Neuronal accumulation of parkin-interacting substrate (PARIS), a transcriptional repressor of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), has been observed in Parkinson's disease (PD). Herein, we showed that PARIS can be S-nitrosylated at cysteine 265 (C265), and S-nitrosylated PARIS (SNO-PARIS) translocates to the insoluble fraction, leading to the sequestration of PGC-1α into insoluble deposits. The mislocalization of PGC-1α in the insoluble fraction was observed in S-nitrosocysteine-treated PARIS knockout (KO) cells overexpressing PARIS WT but not S-nitrosylation deficient C265S mutant, indicating that insolubility of PGC-1α is SNO-PARIS-dependent. In the sporadic PD model, α-synuclein preformed fibrils (α-syn PFFs)-injected mice, we found an increase in PARIS, SNO-PARIS, and insoluble sequestration of PGC-1α in substantia nigra (SN), resulting in the reduction of mitochondrial DNA copy number and ATP concentration that were restored by N(ω)-nitro-L-arginine methyl ester, a nitric oxide synthase (NOS) inhibitor. To assess the dopaminergic (DA) neuronal toxicity by SNO-PARIS, lentiviral PARIS WT, C265S, and S-nitrosylation mimic C265W was injected into the SN of either PBS- or α-syn PFFs-injected mice. PARIS WT and C265S caused DA neuronal death to a comparable extent, whereas C265W caused more severe DA neuronal loss in PBS-injected mice. Interestingly, there was synergistic DA loss in both lenti-PARIS WT and α-syn PFFs-injected mice, indicating that SNO-PARIS by α-syn PFFs contributes to the DA toxicity in vivo. Moreover, α-syn PFFs-mediated increment of PARIS, SNO-PARIS, DA toxicity, and behavioral deficits were completely nullified in neuronal NOS KO mice, suggesting that modulation of NO can be a therapeutic for α-syn PFFs-mediated neurodegeneration.

Effects of electroconvulsive therapy on nitrosative stress and oxidative DNA damage parameters in patients with a depressive episode

BACKGROUND

Few studies have investigated the relationship between electroconvulsive therapy (ECT) and markers of nitrosative stress and oxidative DNA damage.

OBJECTIVE

The aim of this study is to examine changes in nitrosative stress and oxidative DNA damage in patients with a depressive episode treated with ECT.

METHODS

The current study included 48 patients with a depressive episode treated with ECT and 30 healthy control participants. First, the serum nitrosative stress markers of nitric oxide (NO•), nitric oxide synthase (NOS), and peroxynitrite (ONOO-) and the oxidative DNA damage marker 8-hydroxy-2'-deoxyguanosine (8-OHdG) were compared between the study and control groups. These parameters were also compared pre- and post-treatment for the study group.

RESULTS

NO•, NOS, and ONOO- levels were significantly higher in patients with depressive disorder (DD) than in the control group. NO• and NOS levels significantly decreased in the ECT group after treatment while 8-OHdG levels significantly increased.

CONCLUSIONS

The study findings suggest that ECT may have reduced nitrosative stress levels while increasing oxidative DNA damage. More research is now needed to better understand the issue.KEY POINTSNitrosative stress levels can increase in patients with depressive disorder.Electroconvulsive therapy may reduce nitrosative stress while increasıng oxidative DNA damage.These results suggest that nitrosative stress plays an important role in the mechanism of action of electroconvulsive therapy.

How Cells Deal with the Fluctuating Environment: Autophagy Regulation under Stress in Yeast and Mammalian Systems

Eukaryotic cells frequently experience fluctuations of the external and internal environments, such as changes in nutrient, energy and oxygen sources, and protein folding status, which, after reaching a particular threshold, become a type of stress. Cells develop several ways to deal with these various types of stress to maintain homeostasis and survival. Among the cellular survival mechanisms, autophagy is one of the most critical ways to mediate metabolic adaptation and clearance of damaged organelles. Autophagy is maintained at a basal level under normal growing conditions and gets stimulated by stress through different but connected mechanisms. In this review, we summarize the advances in understanding the autophagy regulation mechanisms under multiple types of stress including nutrient, energy, oxidative, and ER stress in both yeast and mammalian systems.

Pharmacological activities of Asclepias curassavica L. (Apocynaceae) aerial parts

ETHNOPHARMACOLOGICAL RELEVANCE

Asclepias curassavica L. (Apocynaceae) is a perennial shrub used in the folk treatment of parasitism, pain, and inflammation.

AIM OF THE STUDY

This work assessed the antiparasitic, anti-inflammatory, antinociceptive, and sedative effects of an ethanol extract from the aerial parts of Asclepias curassavica (ACE).

MATERIALS AND METHODS

The antiparasitic activity against Trichomonas vaginalis was evaluated using the trypan blue exclusion test. The in vitro anti-inflammatory actions of ACE (1-200 μg/ml) were analyzed using LPS-stimulated primary murine macrophages. The in vivo pharmacological activity of ACE (50-200 mg/kg p.o.) was evaluated using animal models of inflammation (TPA-induced ear edema test and carrageenan-induced paw edema test) and nociception (acetic acid-induced writhing test, formalin-induced licking test, and hot plate test).

RESULTS

ACE showed poor antiparasitic effects against Trichomonas vaginalis (IC₅₀ = 302 μg/ml). ACE increased the production of IL-10 in both in vitro assays (EC₅₀ = 3.2 pg/ml) and in vivo assays (ED₅₀ = 111 mg/kg). ACE showed good antinociceptive actions (ED₅₀ = 158 mg/kg in phase 1 and ED₅₀ = 83 mg/kg in phase 2) in the formalin test. Pre-treatment with naloxone blocked the antinociceptive response induced by ACE. In addition, ACE did not induce sedative effects or motor coordination deficits in mice.

CONCLUSION

Findings showed that the anti-inflammatory activity of ACE is associated with increasing levels of IL-10 in both in vitro and in vivo assays, whereas the antinociceptive effect is associated with the participation of the opioidergic system, without inducing sedation or motor coordination impairment.

Prevention and reversal of ketamine-induced experimental psychosis in mice by the neuroactive flavonoid, hesperidin: The role of oxidative and cholinergic mechanisms

Currently, prevailing evidence have identified cholinergic and oxidative pathways as important therapeutic targets for abating ketamine-induced schizophrenia-like behavior. Thus, this study evaluated the ability of hesperidin, a naturally occurring antioxidant and neuroprotective flavonoid, to prevent and reverse ketamine-induced schizophrenia-like behaviors and changes in cholinergic, oxidative and nitrergic status in mice. Forty-eight male Swiss mice were allotted into the preventive and reversal studies with 4 groups (n = 6) each. In the preventive study, groups 1 and 2 received vehicle (10 mL/kg/p.o./day), while groups 3 and 4 had hesperidin (100 mg/kg/p.o./day) for 14 days, but ketamine (20 mg/kg/i.p./day) was concurrently given to groups 2 and 4 from days 8-14. In the reversal study, groups 1 and 3 received vehicle, groups 2 and 4 were pretreated with ketamine for 14 days. Nevertheless, groups 3 and 4 additionally received hesperidin from days 8-14. Thereafter, schizophrenia-like behavior from exploratory activity, open-field (positive symptoms), Y-maze (cognitive symptoms) and social interaction (negative symptoms) tests were evaluated. Brain levels of oxidative/nitrergic (glutathione, superoxide-dismutase, malondialdehyde and nitrite levels) and cholinergic (acetylcholinesterase activity) markers were measured in the prefrontal-cortex, striatum and hippocampus. Hesperidin prevents and reverses ketamine-induced hyperactivities, social withdrawal and cognitive impairment. Also, hesperidin prevented and reversed ketamine-induced decrease in glutathione and superoxide-dismutase levels in the prefrontal-cortical, striatal and hippocampal brain regions in mice. Consequently, hesperidin attenuated ketamine-induced increase in malondialdehyde, nitrite levels and acetylcholinesterase activities in the prefrontal-cortex, striatum and hippocampus, respectively. The study showed that hesperidin prevents and reverses ketamine-induced schizophrenia-like behavior through inhibition of oxidative/nitrergic stress and acetylcholinesterase activity in mice brains. Therefore, these findings suggest that hesperidin dietary supplementation could provide natural nutritional intervention to protect against epigenetic-induced mental ill-health like schizophrenia, and thus serve as an important agent for nutritional psychiatry.

Plasma medicine for neuroscience-an introduction

Plasma is an ionized gas. It is typically formed at high temperature. As a result of both the development of low-temperature plasma sources and a better understanding of complex plasma phenomena over the last decade, "plasma medicine" has become a booming interdisciplinary research topic of growing importance that explores enormous opportunities at the interface of chemistry, plasma physics, and biomedical sciences with engineering. This review presents the latest development in plasma medicine in the area of the central nervous system and aims to introduce cutting-edge plasma medicine to clinical and translational medical researchers and practitioners.

Redox modifications in synaptic components as biomarkers of cognitive status, in brain aging and disease

Aging is a natural process that includes several changes that gradually make organisms degenerate and die. Harman's theory proposes that aging is a consequence of the progressive accumulation of oxidative modifications mediated by reactive oxygen/nitrogen species, which plays an essential role in the development and progression of many neurodegenerative diseases. This review will focus on how abnormal redox modifications induced by age impair the functionality of neuronal redox-sensitive proteins involved in axonal elongation and guidance, synaptic plasticity, and intercellular communication. We will discuss post-transcriptional regulation of gene expression by microRNAs as a mechanism that controls the neuronal redox state. Finally, we will discuss how some brain-permeant antioxidants from the diet have a beneficial effect on cognition. Taken together, the evidence revised here indicates that oxidative-driven modifications of specific proteins and changes in microRNA expression may be useful biomarkers for aging and neurodegenerative diseases. Also, some specific antioxidant therapies have undoubtedly beneficial neuroprotective effects when administered in the correct doses, in the ideal formulation combination, and during the appropriate therapeutic window. The use of some antioxidants is, therefore, still poorly explored for the treatment of neurodegenerative diseases such as Alzheimer's disease.

The Axonal Motor Neuropathy-Related HINT1 Protein Is a Zinc- and Calmodulin-Regulated Cysteine SUMO Protease

Aims: Histidine triad nucleotide-binding protein 1 (HINT1) exhibits proapoptotic and tumor-suppressive activity. HINT1 binds to transcription factors such as teneurin1 and to the regulator of G protein signaling 17 (RGS) (Z2) protein, which incorporates the small ubiquitin-like modifier (SUMO), and is implicated in several types of cancer. HINT1 interacts with proteins such as PKCγ and Raf-1 through zinc ions provided by the cysteine-rich domain of RGSZ2 and the coupled neural nitric oxide synthase (nNOS). Recently, a series of HINT1 mutants have been reported to cause human autosomal recessive axonal neuropathy with neuromyotonia (ARAN-NM). However, the specific alteration in the function of HINT1 induced by these mutants remains to be elucidated. Because sumoylation modifies protein association and transcriptional regulation, we investigated whether HINT1 exhibits zinc- and redox-regulated sumoylase activity, which may be altered in those mutants. Results: HINT1 exhibits cysteine protease activity to remove SUMO from a variety of signaling proteins. HINT1 sumoylase activity is blocked by zinc, and it is released by nitric oxide or calcium-activated calmodulin (CaM). HINT1 contains a SUMO-interacting motif (110-116 HIHLHVL) and the catalytic triad Cys84-Asp87-His114 in the C-terminal region. Thus, zinc probably provided by the RGSZ2-nNOS complex may bind to Cys84 to block HINT1 isopeptidase activity. Innovation: To date, HINT1 is the only sumoylase that is regulated by two alternate pathways, redox- and calcium-activated CaM. Conclusion: The 15 human HINT1 mutants reported to cause ARAN-NM exhibited altered sumoylase activity, which may contribute to the onset of this human motor disease.

Glutathione compartmentalization and its role in glutathionylation and other regulatory processes of cellular pathways

Glutathione is considered the major non-protein low molecular weight modulator of redox processes and the most important thiol reducing agent of the cell. The biosynthesis of glutathione occurs in the cytosol from its constituent amino acids, but this tripeptide is also present in the most important cellular districts, such as mitochondria, nucleus, and endoplasmic reticulum, thus playing a central role in several metabolic pathways and cytoprotection mechanisms. Indeed, glutathione is involved in the modulation of various cellular processes and, not by chance, it is a ubiquitous determinant for redox signaling, xenobiotic detoxification, and regulation of cell cycle and death programs. The balance between its concentration and redox state is due to a complex series of interactions between biosynthesis, utilization, degradation, and transport. All these factors are of great importance to understand the significance of cellular redox balance and its relationship with physiological responses and pathological conditions. The purpose of this review is to give an overview on glutathione cellular compartmentalization. Information on its subcellular distribution provides a deeper understanding of glutathione-dependent processes and reflects the importance of compartmentalization in the regulation of specific cellular pathways. © 2018 BioFactors, 45(2):152-168, 2019.

Murrayanine Attenuates Lipopolysaccharide-induced Inflammation and Protects Mice from Sepsis-associated Organ Failure

Murrayanine (MK) is the main compound isolated from Murraya koenigii, an aromatic plant belonging to the Rutaceae family, also known as curry leaf tree. Murrayanine was reported to possess potential antioxidant, antimycobacterial and antifungal effects. However, its effect in sepsis remains unclear. This study was designed to investigate the anti-inflammatory effect of MK using both in vitro and in vivo assay. Results of this study indicated that MK decreased NO, TNF-α and IL-6 production in both lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and murine peritoneal macrophages. Moreover, iNOS and COX-2 protein expression as well as their downstream product, PGE2, was also decreased effectively in RAW 264.7 cells. Furthermore, MK decreased the phosphorylation of IKB and repressed NF-kB activity in LPS-activated RAW 264.7 cells. Additionally, we evaluated MK efficacy in vivo using LPS-induced sepsis, a systemic inflammation model in mice. Administration of MK inhibits pro-inflammatory cytokines (TNF-α and IL-6) secretion; decreases AST, ALT, BUN and CRE level in mouse sera; mitigates lung, liver and kidney injuries; and also increases LPS-challenged mice survival rate. Collectively, our results suggest that MK exerts potential as a new anti-inflammatory and immunosuppressive drug in sepsis treatment.

Anti-inflammatory and anti-oxidative effects of 3-(naphthalen-2-yl(propoxy)methyl)azetidine hydrochloride on β-amyloid-induced microglial activation

We aimed to assess the anti-inflammatory and antioxidative properties of KHG26792, a novel azetidine derivative, in amyloid β (Aβ)-treated primary microglial cells. KHG26792 attenuated the Aβ-induced production of inflammatory mediators such as IL-6, IL-1β, TNF-α, and nitric oxide. The levels of protein oxidation, lipid peroxidation, ROS, and NADHP oxidase enhanced by Aβ were also downregulated by KHG26792 treatment. The effects of KHG26792 against the Aβ-induced increases in inflammatory cytokine levels and oxidative stress were achieved by increasing the phosphorylation of Akt/GSK-3β signaling and by decreasing the Aβ-induced translocation of NF-κB. Our results provide novel insights into the use of KHG26792 as a potential agent against Aβ toxicity, including its role in the reduction of inflammation and oxidative stress. Nevertheless, further investigations of cellular signaling are required to clarify the in vivo effects of KHG26792 against Aβ-induced toxicity.

Modulation of nuclear factor-κB signaling and reduction of neural tube defects by quercetin-3-glucoside in embryos of diabetic mice

BACKGROUND

Diabetes mellitus in early pregnancy increases the risk of birth defects in infants. Maternal hyperglycemia stimulates the expression of nitric oxide synthase 2, which can be regulated by transcription factors of the nuclear factor-κB family. Increases in reactive nitrogen species generate intracellular stress conditions, including nitrosative, oxidative, and endoplasmic reticulum stresses, and trigger programmed cell death (or apoptosis) in the neural folds, resulting in neural tube defects in the embryo. Inhibiting nitric oxide synthase 2 can reduce neural tube defects; however, the underlying mechanisms require further delineation. Targeting nitric oxide synthase 2 and associated nitrosative stress using naturally occurring phytochemicals is a potential approach to preventing birth defects in diabetic pregnancies.

OBJECTIVE

This study aims to investigate the effect of quercetin-3-glucoside, a naturally occurring polyphenol flavonoid, in reducing maternal diabetes-induced neural tube defects in an animal model, and to delineate the molecular mechanisms underlying quercetin-3-glucoside action in regulating nitric oxide synthase 2 expression.

STUDY DESIGN

Female mice (C57BL/6) were induced to develop diabetes using streptozotocin before pregnancy. Diabetic pregnant mice were administered quercetin-3-glucoside (100 mg/kg) daily via gavage feeding, introduction of drug to the stomach directly via a feeding needle, during neurulation from embryonic day 6.5-9.5. After treatment at embryonic day 10.5, embryos were collected and examined for the presence of neural tube defects and apoptosis in the neural tube. Expression of nitric oxide synthase 2 and superoxide dismutase 1 (an antioxidative enzyme) was quantified using Western blot assay. Nitrosative, oxidative, and endoplasmic reticulum stress conditions were assessed using specific biomarkers. Expression and posttranslational modification of factors in the nuclear factor-κB system were investigated.

RESULTS

Treatment with quercetin-3-glucoside (suspended in water) significantly decreased neural tube defect rate and apoptosis in the embryos of diabetic mice, compared with those in the water-treated diabetic group (3.1% vs. 24.7%; P < .001). Quercetin-3-glucoside decreased the expression of nitric oxide synthase 2 and nitrosative stress (P < .05). It also increased the levels of superoxide dismutase 1 (P < .05), further increasing the antioxidative capacity of the cells. Quercetin-3-glucoside treatment also alleviated of endoplasmic reticulum stress in the embryos of diabetic mice (P < .05). Quercetin-3-glucoside reduced the levels of p65 (P < .05), a member of the nuclear factor-κB transcription factor family, but augmented the levels of the inhibitor of κBα (P < .05), which suppresses p65 nuclear translocation. In association with these changes, the levels of inhibitor of κB kinase-α and inhibitor of κBα phosphorylation were elevated (P < .05).

CONCLUSION

Quercetin-3-glucoside reduces the neural tube defects rate in the embryos of diabetic dams. Quercetin-3-glucoside suppresses nitric oxide synthase 2 and increases superoxide dismutase 1 expression, leading to alleviation of nitrosative, oxidative, and endoplasmic reticulum stress conditions. Quercetin-3-glucoside may regulate the expression of nitric oxide synthase 2 via modulating the nuclear factor-κB transcription regulation system. Quercetin-3-glucoside, a naturally occurring polyphenol that has high bioavailability and low toxicity, is a promising candidate agent to prevent birth defects in diabetic pregnancies.

Role of Nitric Oxide and Hydrogen Sulfide in Ischemic Stroke and the Emergent Epigenetic Underpinnings

Nitric oxide (NO) and hydrogen sulfide (H₂S) are the key gasotransmitters with an imperious role in the maintenance of cerebrovascular homeostasis. A decline in their levels contributes to endothelial dysfunction that portends ischemic stroke (IS) or cerebral ischemia/reperfusion (CI/R). Nevertheless, their exorbitant production during CI/R is associated with exacerbation of cerebrovascular injury in the post-stroke epoch. NO-producing nitric oxide synthases are implicated in IS pathology and their activity is regulated, inter alia, by various post-translational modifications and chromatin-based mechanisms. These account for heterogeneous alterations in NO production in a disease setting like IS. Interestingly, NO per se has been posited as an endogenous epigenetic modulator. Further, there is compelling evidence for an ingenious crosstalk between NO and H₂S in effecting the canonical (direct) and non-canonical (off-target collateral) functions. In this regard, NO-mediated S-nitrosylation and H₂S-mediated S-sulfhydration of specific reactive thiols in an expanding array of target proteins are the principal modalities mediating the all-pervasive influence of NO and H₂S on cell fate in an ischemic brain. An integrated stress response subsuming unfolded protein response and autophagy to cellular stressors like endoplasmic reticulum stress, in part, is entrenched in such signaling modalities that substantiate the role of NO and H₂S in priming the cells for stress response. The precis presented here provides a comprehension on the multifarious actions of NO and H₂S and their epigenetic underpinnings, their crosstalk in maintenance of cerebrovascular homeostasis, and their "Janus bifrons" effect in IS milieu together with plausible therapeutic implications.

Developmental Alcohol Exposure Impairs Activity-Dependent S-Nitrosylation of NDEL1 for Neuronal Maturation

Neuronal nitric oxide synthase is involved in diverse signaling cascades that regulate neuronal development and functions via S-Nitrosylation-mediated mechanism or the soluble guanylate cyclase (sGC)/cyclic guanosine monophosphate (cGMP) pathway activated by nitric oxide. Although it has been studied extensively in vitro and in invertebrate animals, effects on mammalian brain development and underlying mechanisms remain poorly understood. Here we report that genetic deletion of "Nos1" disrupts dendritic development, whereas pharmacological inhibition of the sGC/cGMP pathway does not alter dendritic growth during cerebral cortex development. Instead, nuclear distribution element-like (NDEL1), a protein that regulates dendritic development, is specifically S-nitrosylated at cysteine 203, thereby accelerating dendritic arborization. This post-translational modification is enhanced by N-methyl-D-aspartate receptor-mediated neuronal activity, the main regulator of dendritic formation. Notably, we found that disruption of S-Nitrosylation of NDEL1 mediates impaired dendritic maturation caused by developmental alcohol exposure, a model of developmental brain abnormalities resulting from maternal alcohol use. These results highlight S-Nitrosylation as a key activity-dependent mechanism underlying neonatal brain maturation and suggest that reduction of S-Nitrosylation of NDEL1 acts as a pathological factor mediating neurodevelopmental abnormalities caused by maternal alcohol exposure.

Design, synthesis and biological assessment of N-adamantyl, substituted adamantyl and noradamantyl phthalimidines for nitrite, TNF-α and angiogenesis inhibitory activities

A library of 15 novel and heretofore uncharacterized adamantyl and noradamantyl phthalimidines was synthesized and evaluated for neuroprotective and anti-angiogenic properties. Phthalimidine treatment in LPS-challenged cells effected reductions in levels of secreted TNF-α and nitrite relative to basal amounts. The primary SAR suggests nitration of adamantyl phthalimidines has marginal effect on TNF-α activity but promotes anti-nitrite activity; thioamide congeners retain anti-nitrite activity but are less effective reducing TNF-α. Site-specific nitration and thioamidation provided phthalimidine 24, effecting an 88.5% drop in nitrite concurrent with only a 4% drop in TNF-α. Notable anti-angiogenesis activity was observed for 20, 21 and 22.

The molecular aspects of oxidative & nitrosative stress and the tryptophan catabolites pathway (TRYCATs) as potential causes of depression

Depression is the most common mental disorder in the world. It is estimated that 350 million people suffer from depression worldwide. Depressive disorders will have become the second most frequent health problem globally by the year 2020, just behind ischemic heart disease. The causes of depressive disorders are not fully known. Previous studies showed that impaired tryptophan catabolites pathway, oxidative and nitrosative stress may play an important role in the pathogenesis of depression. Patients with depression have lower plasma levels of superoxide dismutase and glutathione peroxidise in comparison to controls. Moreover, depressed patients are characterized by decreased plasma levels of zinc, coenzyme Q10, albumin, uric acid, vitamin E and glutathione. Abnormal nitric oxidative production and nitric oxide synthase activity are also associated with depression. A dysfunction of the tryptophan catabolites pathway, indicated by increased levels of tryptophan 2,3-dioxygenase and indoleamine 2,3-dioxygenase, is also involved in the development of depression. Furthermore, increased levels of kynurenine and quinolinic acid might cause depression. Moreover, studies to date indicate that 8-oxyguanine, malondialdehyde, and 8-iso-prostaglandin F2α may serve as possible biomarkers. Additionally, regulation of defective mechanisms may provide a promising direction for the development of new and effective therapies.

[Physiological roles of redox signals in relation to synaptic plasticity and brain functions]

In our classical knowledge, redox molecules, including reactive oxygen species (ROS), nitric oxide (NO) and hydrogen sulfide, are considered to be generated as byproducts of aerobic metabolism and act as harmful oxidants of macromolecules, such as proteins and lipids. On the other hands, recently, expressions of enzymes producing redox molecules are identified and reported to be expressed in wide range of tissues, including brain. Moreover, activities of some of these enzymes are revealed to be regulated by physiological signals (e.g. calcium). These observations suggest that redox molecules act as physiological messengers and have biological functions. Actually, recent studies indicate possible involvement of redox signals in functional modification of proteins essential for synaptic plasticity in cultured cells and acute slice preparations. For example, S-nitrosylation of type 1 ryanodine receptor, an intracellular calcium-release channel, is revealed to be essential for NO-induced calcium release (NICR) and synaptic plasticity in cerebellar Purkinje cells. Further studies on mutant animals deficient in redox-modification site may clarify essential role of redox signals in brain functions in vivo.

Thioredoxin promotes survival signaling events under nitrosative/oxidative stress associated with cancer development

Accumulating mutations may drive cells into the acquisition of abnormal phenotypes that are characteristic of cancer cells. Cancer cells feature profound alterations in proliferation programs that result in a new population of cells that overrides normal tissue construction and maintenance programs. To achieve this goal, cancer cells are endowed with up regulated survival signaling pathways. They also must counteract the cytotoxic effects of high levels of nitric oxide (NO) and of reactive oxygen species (ROS), which are by products of cancer cell growth. Accumulating experimental evidence associates cancer cell survival with their capacity to up-regulate antioxidant systems. Elevated expression of the antioxidant protein thioredoxin-1 (Trx1) has been correlated with cancer development. Trx1 has been characterized as a multifunctional protein, playing different roles in different cell compartments. Trx1 migrates to the nucleus in cells exposed to nitrosative/oxidative stress conditions. Trx1 nuclear migration has been related to the activation of transcription factors associated with cell survival and cell proliferation. There is a direct association between the p21Ras-ERK1/2 MAP Kinases survival signaling pathway and Trx1 nuclear migration under nitrosative stress. The expression of the cytoplasmic protein, the thioredoxin-interacting protein (Txnip), determines the change in Trx1 cellular compartmentalization. The anti-apoptotic actions of Trx1 and its denitrosylase activity occur in the cytoplasm and serve as important regulators of cell survival. Within this context, this review focuses on the participation of Trx1 in cells under nitrosative/oxidative stress in survival signaling pathways associated with cancer development.

The role of S-nitrosoglutathione reductase (GSNOR) in human disease and therapy

S-nitrosoglutathione reductase (GSNOR), or ADH5, is an enzyme in the alcohol dehydrogenase (ADH) family. It is unique when compared to other ADH enzymes in that primary short-chain alcohols are not its principle substrate. GSNOR metabolizes S-nitrosoglutathione (GSNO), S-hydroxymethylglutathione (the spontaneous adduct of formaldehyde and glutathione), and some alcohols. GSNOR modulates reactive nitric oxide (•NO) availability in the cell by catalyzing the breakdown of GSNO, and indirectly regulates S-nitrosothiols (RSNOs) through GSNO-mediated protein S-nitrosation. The dysregulation of GSNOR can significantly alter cellular homeostasis, leading to disease. GSNOR plays an important regulatory role in smooth muscle relaxation, immune function, inflammation, neuronal development and cancer progression, among many other processes. In recent years, the therapeutic inhibition of GSNOR has been investigated to treat asthma, cystic fibrosis and interstitial lung disease (ILD). The direct action of •NO on cellular pathways, as well as the important regulatory role of protein S-nitrosation, is closely tied to GSNOR regulation and defines this enzyme as an important therapeutic target.

Neuroprotective Role of Atractylenolide-I in an In Vitro and In Vivo Model of Parkinson's Disease

Parkinson’s disease (PD) is an age-related neurological disorder characterized by a loss of dopaminergic neurons within the midbrain. Neuroinflammation has been nominated as one of the key pathogenic features of PD. Recently, the inadequate pharmacotherapy and adverse effects of conventional drugs have spurred the development of unconventional medications in the treatment of PD. The purpose of this study is to investigate the anti-neuroinflammatory mechanisms of Atractylenolide-I (ATR-I) in in vivo and in vitro models of PD. Nitrite assay was measured via Griess reaction in lipopolysaccharide (LPS) stimulated BV-2 cells. mRNA and protein levels were determined by a reverse transcription-polymerase chain reaction (RT-PCR) and immunoblot analysis, respectively. Further, flow cytometry, immunocytochemistry, and immunohistochemistry were employed in BV-2 cells and MPTP-intoxicated C57BL6/J mice. Pre-treatment with ATR-I attenuated the inflammatory response in BV-2 cells by abating the nuclear translocation of nuclear factor-κB (NF-κB) and by inducing heme oxygenase-1 (HO-1). The intraperitoneal administration of ATR-I reversed MPTP-induced behavioral deficits, decreased microglial activation, and conferred protection to dopaminergic neurons in the mouse model of PD. Our experimental reports establish the involvement of multiple benevolent molecular events by ATR-I in MPTP-induced toxicity, which may aid in the development of ATR-I as a new therapeutic agent for the treatment of PD.

N-Adamantyl-4-Methylthiazol-2-Amine Attenuates Glutamate-Induced Oxidative Stress and Inflammation in the Brain

In this study, we explored the possible mechanisms underlying the neuroprotective and anti-oxidative effects of N-adamantyl-4-methylthiazol-2-amine (KHG26693) against in vivo glutamate-induced toxicity in the rat cerebral cortex. Our results showed that pretreatment with KHG26693 significantly attenuated glutamate-induced elevation of lipid peroxidation, tumor necrosis factor-α, interferon gamma, IFN-γ, interleukin-1β, nitric oxide, reactive oxygen species, NADPH oxidase, caspase-3, calpain activity, and Bax. Furthermore, KHG26693 pretreatment attenuated key antioxidant parameters such as levels of superoxide dismutase, catalase, glutathione, and glutathione reductase. KHG26693 also attenuated the protein levels of inducible nitric oxide synthase, neuronal nitric oxide synthase, nuclear factor erythroid 2-related factor 2, heme oxygenase-1, and glutamate cysteine ligase catalytic subunit caused by glutamate toxicity. Finally, KHG26693 mitigated glutamate-induced changes in mitochondrial ATP level and cytochrome oxidase c. Thus, KHG26693 functions as neuroprotective and anti-oxidative agent against glutamate-induced toxicity through its antioxidant and anti-inflammatory activities in rat brain at least in part.

Essential Roles of Natural Products and Gaseous Mediators on Neuronal Cell Death or Survival

Although precise cellular and molecular mechanisms underlying neurodegeneration still remain enigmatic, key factors associated with degenerative disorders, such as glutamate toxicity and oxidative stress, have been recently identified. Accordingly, there has been growing interest in examining the effects of exogenous and endogenous molecules on neuroprotection and neurodegeneration. In this paper, we review recent studies on neuroprotective and/or neurodegenerative effects of natural products, such as caffeic acid and chlorogenic acid, and gaseous mediators, including hydrogen sulfide and nitric oxide. Furthermore, possible molecular mechanisms of these molecules in relation to glutamate signals are discussed. Insight into the pathophysiological role of these molecules will make progress in our understanding of molecular mechanisms underlying neurodegenerative diseases, and is expected to lead to potential therapeutic approaches.

Nitrosative Stress, Hypernitrosylation, and Autoimmune Responses to Nitrosylated Proteins: New Pathways in Neuroprogressive Disorders Including Depression and Chronic Fatigue Syndrome

Nitric oxide plays an indispensable role in modulating cellular signaling and redox pathways. This role is mainly effected by the readily reversible nitrosylation of selective protein cysteine thiols. The reversibility and sophistication of this signaling system is enabled and regulated by a number of enzymes which form part of the thioredoxin, glutathione, and pyridoxine antioxidant systems. Increases in nitric oxide levels initially lead to a defensive increase in the number of nitrosylated proteins in an effort to preserve their function. However, in an environment of chronic oxidative and nitrosative stress (O&NS), nitrosylation of crucial cysteine groups within key enzymes of the thioredoxin, glutathione, and pyridoxine systems leads to their inactivation thereby disabling denitrosylation and transnitrosylation and subsequently a state described as "hypernitrosylation." This state leads to the development of pathology in multiple domains such as the inhibition of enzymes of the electron transport chain, decreased mitochondrial function, and altered conformation of proteins and amino acids leading to loss of immune tolerance and development of autoimmunity. Hypernitrosylation also leads to altered function or inactivation of proteins involved in the regulation of apoptosis, autophagy, proteomic degradation, transcription factor activity, immune-inflammatory pathways, energy production, and neural function and survival. Hypernitrosylation, as a consequence of chronically elevated O&NS and activated immune-inflammatory pathways, can explain many characteristic abnormalities observed in neuroprogressive disease including major depression and chronic fatigue syndrome/myalgic encephalomyelitis. In those disorders, increased bacterial translocation may drive hypernitrosylation and autoimmune responses against nitrosylated proteins.

Amelioration of intracellular stress and reduction of neural tube defects in embryos of diabetic mice by phytochemical quercetin

Diabetes mellitus in early pregnancy causes birth defects, including neural tube defects (NTDs). Hyperglycemia increases production of nitric oxide (NO) through NO synthase 2 (Nos2) and reactive oxygen species (ROS), generating nitrosative and oxidative stress conditions in the embryo. The present study aimed to target nitrosative stress using a naturally occurring Nos2 inhibitor, quercetin, to prevent NTDs in the embryos of diabetic mice. Daily administration of quercetin to diabetic pregnant mice during the hyperglycemia-susceptible period of organogenesis significantly reduced NTDs and cell apoptosis in the embryos, compared with those of vehicle-treated diabetic pregnant mice. Using HPLC-coupled ESI-MS/MS, quercetin metabolites, including methylated and sulfonylated derivatives, were detected in the conceptuses. The methylated metabolite, 3-O-methylquercetin, was shown to reduce ROS level in embryonic stem cells cultured in high glucose. Quercetin treatment decreased the levels of Nos2 expression, protein nitrosylation, and protein nitration, alleviating nitrosative stress. Quercetin increased the expression of superoxide dismutase 1 and 2, and reduced the levels of oxidative stress markers. Expression of genes of redox regulating enzymes and DNA damage repair factors was upregulated. Our study demonstrates that quercetin ameliorates intracellular stresses, regulates gene expression, and reduces embryonic malformations in diabetic pregnancy.

Endothelial Nitric Oxide Synthase-Derived Nitric Oxide Prevents Dihydrofolate Reductase Degradation via Promoting S-Nitrosylation

OBJECTIVE

Dihydrofolate reductase (DHFR) is a key protein involved in tetrahydrobiopterin (BH4) regeneration from 7,8-dihydrobiopterin (BH2). Dysfunctional DHFR may induce endothelial nitric oxide (NO) synthase (eNOS) uncoupling resulting in enzyme production of superoxide anions instead of NO. The mechanism by which DHFR is regulated is unknown. Here, we investigate whether eNOS-derived NO maintains DHFR stability.

APPROACH AND RESULTS

DHFR activity, BH4 content, eNOS activity, and S-nitrosylation were assessed in human umbilical vein endothelial cells and in aortas isolated from wild-type and eNOS knockout mice. In human umbilical vein endothelial cells, depletion of intracellular NO by transfection with eNOS-specific siRNA or by the NO scavenger 2-(4-carboxyphenyl)-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (PTIO)-both of which had no effect on DHFR mRNA levels-markedly reduced DHFR protein levels in parallel with increased DHFR polyubiquitination. Supplementation of S-nitroso-l-glutathione (GSNO), a NO donor, or MG132, a potent inhibitor of the 26S proteasome, prevented eNOS silencing and PTIO-induced DHFR reduction in human umbilical vein endothelial cells. PTIO suppressed S-nitrosylation of DHFR, whereas GSNO promoted DHFR S-nitrosylation. Mutational analysis confirmed that cysteine 7 of DHFR was S-nitrosylated. Cysteine 7 S-nitrosylation stabilized DHFR from ubiquitination and degradation. Experiments performed in aortas confirmed that PTIO or eNOS deficiency reduces endothelial DHFR, which can be abolished by MG132 supplementation.

CONCLUSIONS

We conclude that S-nitrosylation of DHFR at cysteine 7 by eNOS-derived NO is crucial for DHFR stability. We also conclude that NO-induced stabilization of DHFR prevents eNOS uncoupling via regeneration of BH4, an essential eNOS cofactor.

N-adamantyl-4-methylthiazol-2-amine suppresses lipopolysaccharide-induced brain inflammation by regulating NF-κB signaling in mice

We report that N-adamantyl-4-methylthiazol-2-amine (KHG26693), a novel thiazole derivative, can prevent lipopolysaccharide (LPS)-induced brain inflammation in mice. In this LPS-induced model of brain inflammation, administration of KHG26693 effectively prevented increases in the levels of IL-1β, TNF-α, prostaglandin E2, malondialdehyde, and nitric oxide, and mitigated reductions in the levels of superoxide dismutase in the hippocampus. KHG26693 also prevented reductions in the levels of hippocampal brain-derived neurotrophic factors. Furthermore, pretreatment with KHG26693 prior to LPS treatment dramatically attenuated the elevation of inducible nitric oxide synthase and cyclooxygenase-2 protein levels. Moreover, pretreatment with KHG26693 significantly suppressed LPS-induced phosphorylation of NF-κB and IκBα through the inactivation of IKKβ. Additionally, KHG26693 caused the downregulation of LPS-induced cystathionine-b-synthase gene expression in the brain. Although the clinical relevance of our findings remains to be determined, our data suggest that KHG26693 might prevent neuronal cell injury via the reduction of inflammation and oxidative stress in the brain.

Antidepressant-like effects induced by NMDA receptor blockade and NO synthesis inhibition in the ventral medial prefrontal cortex of rats exposed to the forced swim test

RATIONALE

Systemic treatment with NMDA receptor (NMDAR) antagonists, inhibitors of neuronal nitric oxide synthase (nNOS) or of soluble guanylyl cyclase (sGC), induce antidepressant-like effects in rats. Increased levels of glutamate and nitric oxide (NO) in the medial prefrontal cortex (MPFC) of stressed animals have been described in the literature. However, the role of the NMDAR-nNOS-sGC pathway of the MPFC in the mediation of forced swim-induced behaviors remains unclear.

OBJECTIVE

The aim of this work was to test the hypothesis that the inhibition of the NMDAR-nNOS-sGC pathway in the ventral MPFC (infralimbic (IL) or prelimbic (PL)) would elicit antidepressant-like effects in the forced swim test (FST).

METHODS

Rats implanted with cannulae aimed at the PL or the IL were exposed to the FST and injected with LY235959 (NMDAR antagonist), NPA (nNOS inhibitor), ODQ (sGC inhibitor), or carboxy-PTIO (NO scavenger). Additional groups received the AMPA antagonist, NBQX, before the effective doses of LY235959 or NPA.

RESULTS

LY235959 administration into PL or IL before the FS pretest produced no effects. Administration of LY235959 (3 and 10 nmol/0.2 μL) after pretest was effective only when administered into the PL. However, the administration of NPA (0.01 nmol/0.2 μL), c-PTIO (1.0 nmol/0.2 μL), and ODQ (1.0 nmol/0.2 μL) into the PL or IL before the FST produced antidepressant-like effects. NBQX blocked the antidepressant-like effect of LY235959 but not of NPA.

CONCLUSION

Blocking NMDAR or NO signaling in the vMPFC, either in the IL or the PL, induces antidepressant-like effects in the rat FST. These effects seemingly occur through independent mechanisms, since NBQX blocked the former effect but not the latter.

Nitric oxide signals postovulatory aging-induced abortive spontaneous egg activation in rats

OBJECTIVE

The aim of this study was to determine whether an increase of intracellular nitric oxide (NO) level signals postovulatory aging-induced abortive spontaneous egg activation (SEA) in rats.

METHODS

Freshly ovulated eggs (arrested at metaphase-II stage; M-II) were cultured in vitro for 3 hours to induce postovulatory egg aging. The morphological changes, inducible nitric oxide synthase (iNOS) expression, NO, cytosolic free Ca(2+), 3',5' cyclic guanosine monophosphate (cGMP), cell division cycle 25B (Cdc25B) and Wee1 levels, specific phosphorylation (pThr-14/Tyr-15) as well as total cyclin-dependent kinases-1 (Cdk1) (PSTAIRE) levels were analyzed.

RESULTS

Postovulatory aging induced generation of NO possibly through an iNOS-mediated pathway. The increase in NO level was associated with augmented cytosolic free Ca(2+) as well as cGMP levels in aged eggs. A significant increase in Wee1 level and decrease of Cdc25B level were observed in aged eggs. An accumulation of phosphorylated Cdk1 (pThr-14/Tyr-15) level was observed in aged eggs, while total Cdk1 (PSTAIR) level remained unchanged.

CONCLUSION

Our study demonstrates that generation of NO through an iNOS-mediated pathway increases cytosolic free Ca2+and cGMP levels. High levels of these signal molecules trigger the accumulation of phosphorylated Cdk1 in aged eggs. Thus, NO signals the accumulation of phosphorylated Cdk1 and induces postovulatory aging-induced abortive SEA in the rat.

Thioredoxin-mimetic peptides as catalysts of S-denitrosylation and anti-nitrosative stress agents

S-nitrosylation, the coupling of a nitric oxide moiety to a reactive cysteine residue to form an S-nitrosothiol (SNO), is an important posttranslational mechanism for regulating protein activity. Growing evidence indicates that hyper-S-nitrosylation may contribute to cellular dysfunction associated with various human diseases. It is also increasingly appreciated that thioredoxin and thioredoxin reductase play significant roles in the cellular catabolism of SNO and protection from nitrosative stress. Here, we investigated the SNO reductase activity and protective effects of thioredoxin-mimetic peptides (TXMs), Ac-Cys-Pro-Cys-amide (CB3) and Ac-Cys-Gly-Pro-Cys-amide (CB4), both under cell-free conditions and in nitrosatively stressed cultured cells. In vitro biochemical analyses revealed that the TXM peptides reduced small-molecule SNO compounds, such as S-nitrosoglutathione (GSNO), and acted as general and efficient protein-denitrosylating agents. In particular, CB3 was found to be a highly potent SNO-metabolizing agent. Notably, CB3 mimicked the activity of thioredoxin by coupling with thioredoxin reductase to enhance GSNO reduction. Moreover, in a cell-free lysate system, both CB3 and CB4 synergized with an NADPH-dependent activity to denitrosylate proteins. Further investigation revealed that the TXM peptides protect the peroxiredoxin-thioredoxin system from SNO-dependent inhibition. Indeed, SNO-inhibited Prx1 was efficiently denitrosylated and reactivated by CB3 or CB4. In addition, CB3 protected thioredoxin reductase from SNO-mediated inactivation both in vitro and in intact cells. Finally, CB3 and CB4 partially rescued human neuroblastoma SH-SY5Y cells and rat insulinoma INS-1 832/13 cells from GSNO-induced growth inhibition. Collectively, the present findings indicate the efficient denitrosylation activity and protective effects of TXM peptides and suggest their potential therapeutic value in treating pathological conditions related to nitrosative stress.

Redox proteomics analysis to decipher the neurobiology of Alzheimer-like neurodegeneration: overlaps in Down's syndrome and Alzheimer's disease brain

Accumulation of oxidative damage is a common feature of neurodegeneration that, together with mitochondrial dysfunction, point to the fact that reactive oxygen species are major contributors to loss of neuronal homoeostasis and cell death. Among several targets of oxidative stress, free-radical-mediated damage to proteins is particularly important in aging and age-related neurodegenerative diseases. In the majority of cases, oxidative-stress-mediated post-translational modifications cause non-reversible modifications of protein structure that consistently lead to impaired function. Redox proteomics methods are powerful tools to unravel the complexity of neurodegeneration, by identifying brain proteins with oxidative post-translational modifications that are detrimental for protein function. The present review discusses the current literature showing evidence of impaired pathways linked to oxidative stress possibly involved in the neurodegenerative process leading to the development of Alzheimer-like dementia. In particular, we focus attention on dysregulated pathways that underlie neurodegeneration in both aging adults with DS (Down's syndrome) and AD (Alzheimer's disease). Since AD pathology is age-dependent in DS and shows similarities with AD, identification of common oxidized proteins by redox proteomics in both DS and AD can improve our understanding of the overlapping mechanisms that lead from normal aging to development of AD. The most relevant proteomics findings highlight that disturbance of protein homoeostasis and energy production are central mechanisms of neurodegeneration and overlap in aging DS and AD. Protein oxidation affects crucial intracellular functions and may be considered a 'leitmotif' of degenerating neurons. Therapeutic strategies aimed at preventing/reducing multiple components of processes leading to accumulation of oxidative damage will be critical in future studies.

dbSNO 2.0: a resource for exploring structural environment, functional and disease association and regulatory network of protein S-nitrosylation

Given the increasing number of proteins reported to be regulated by S-nitrosylation (SNO), it is considered to act, in a manner analogous to phosphorylation, as a pleiotropic regulator that elicits dual effects to regulate diverse pathophysiological processes by altering protein function, stability, and conformation change in various cancers and human disorders. Due to its importance in regulating protein functions and cell signaling, dbSNO (http://dbSNO.mbc.nctu.edu.tw) is extended as a resource for exploring structural environment of SNO substrate sites and regulatory networks of S-nitrosylated proteins. An increasing interest in the structural environment of PTM substrate sites motivated us to map all manually curated SNO peptides (4165 SNO sites within 2277 proteins) to PDB protein entries by sequence identity, which provides the information of spatial amino acid composition, solvent-accessible surface area, spatially neighboring amino acids, and side chain orientation for 298 substrate cysteine residues. Additionally, the annotations of protein molecular functions, biological processes, functional domains and human diseases are integrated to explore the functional and disease associations for S-nitrosoproteome. In this update, users are allowed to search a group of interested proteins/genes and the system reconstructs the SNO regulatory network based on the information of metabolic pathways and protein-protein interactions. Most importantly, an endogenous yet pathophysiological S-nitrosoproteomic dataset from colorectal cancer patients was adopted to demonstrate that dbSNO could discover potential SNO proteins involving in the regulation of NO signaling for cancer pathways.

Role of apoptosis signal-regulating kinase 1 (ASK1) as an activator of the GAPDH-Siah1 stress-signaling cascade

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) plays roles in both energy maintenance, and stress signaling by forming a protein complex with seven in absentia homolog 1 (Siah1). Mechanisms to coordinate its glycolytic and stress cascades are likely to be very important for survival and homeostatic control of any living organism. Here we report that apoptosis signal-regulating kinase 1 (ASK1), a representative stress kinase, interacts with both GAPDH and Siah1 and is likely able to phosphorylate Siah1 at specific amino acid residues (Thr-70/Thr-74 and Thr-235/Thr-239). Phosphorylation of Siah1 by ASK1 triggers GAPDH-Siah1 stress signaling and activates a key downstream target, p300 acetyltransferase in the nucleus. This novel mechanism, together with the established S-nitrosylation/oxidation of GAPDH at Cys-150, provides evidence of how the stress signaling involving GAPDH is finely regulated. In addition, the present results imply crosstalk between the ASK1 and GAPDH-Siah1 stress cascades.

Inflammatory stimuli induce inhibitory S-nitrosylation of the deacetylase SIRT1 to increase acetylation and activation of p53 and p65

Inflammation increases the abundance of inducible nitric oxide synthase (iNOS), leading to enhanced production of nitric oxide (NO), which can modify proteins by S-nitrosylation. Enhanced NO production increases the activities of the transcription factors p53 and nuclear factor κB (NF-κB) in several models of disease-associated inflammation. S-nitrosylation inhibits the activity of the protein deacetylase SIRT1. SIRT1 limits apoptosis and inflammation by deacetylating p53 and p65 (also known as RelA), a subunit of NF-κB. We showed in multiple cultured mammalian cell lines that NO donors or inflammatory stimuli induced S-nitrosylation of SIRT1 within CXXC motifs, which inhibited SIRT1 by disrupting its ability to bind zinc. Inhibition of SIRT1 reduced deacetylation and promoted activation of p53 and p65, leading to apoptosis and increased expression of proinflammatory genes. In rodent models of systemic inflammation, Parkinson's disease, or aging-related muscular atrophy, S-nitrosylation of SIRT1 correlated with increased acetylation of p53 and p65 and activation of p53 and NF-κB target genes, suggesting that S-nitrosylation of SIRT1 may represent a proinflammatory switch common to many diseases and aging.

Impaired metabolic reactivity to oxidative stress in early psychosis patients

Because increasing evidence point to the convergence of environmental and genetic risk factors to drive redox dysregulation in schizophrenia, we aim to clarify whether the metabolic anomalies associated with early psychosis reflect an adaptation to oxidative stress. Metabolomic profiling was performed to characterize the response to oxidative stress in fibroblasts from control individuals (n = 20) and early psychosis patients (n = 30), and in all, 282 metabolites were identified. In addition to the expected redox/antioxidant response, oxidative stress induced a decrease of lysolipid levels in fibroblasts from healthy controls that were largely muted in fibroblasts from patients. Most notably, fibroblasts from patients showed disrupted extracellular matrix- and arginine-related metabolism after oxidative stress, indicating impairments beyond the redox system. Plasma membrane and extracellular matrix, 2 regulators of neuronal activity and plasticity, appeared as particularly susceptible to oxidative stress and thus provide novel mechanistic insights for pathophysiological understanding of early stages of psychosis. Statistically, antipsychotic medication at the time of biopsy was not accounting for these anomalies in the metabolism of patients' fibroblasts, indicating that they might be intrinsic to the disease. Although these results are preliminary and should be confirmed in a larger group of patients, they nevertheless indicate that the metabolic signature of reactivity to oxidative stress may provide reliable early markers of psychosis. Developing protective measures aimed at normalizing the disrupted pathways should prevent the pathological consequences of environmental stressors.

Anti-inflammatory mechanisms of N-adamantyl-4-methylthiazol-2-amine in lipopolysaccharide-stimulated BV-2 microglial cells

The activation of microglia is crucially associated with the neurodegeneration observed in many neuroinflammatory pathologies, such as multiple sclerosis, Parkinson's disease, and Alzheimer's disease. We have examined various thiazole derivatives with the goal of developing new anti-neuroinflammatory drugs. Thiazole derivatives are attractive candidates for drug development, because they are efficiently synthesized and active against a number of disease organisms and conditions, including neurodegenerative disorders. The present study investigated the effects of a new compound, N-adamantyl-4-methylthiazol-2-amine (KHG26693), against lipopolysaccharide (LPS)-induced inflammation in cultured BV-2 microglial cells. KHG26693 suppressed several inflammatory responses in LPS-activated cells, as evidenced by decreased levels of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), hydrogen peroxide (H(2)O(2)), reactive oxygen species (ROS), nitric oxide (NO), and lipid peroxidation. These anti-inflammatory/antioxidative actions occurred as a result of the downregulation of NADPH oxidase (NOX), inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX-2) content, but not as a result of the upregulation of superoxide dismutase (SOD) or catalase activity. The pharmacological properties of KHG26693 were also facilitated via inhibition of both the cluster of differentiation 14 (CD14)/toll-like receptor 4 (TLR4)-dependent nuclear factor kappa B (NF-κB) signaling pathway and extracellular signal-regulated kinase (ERK) phosphorylation. Furthermore, KHG26693 successfully blocked the migration of LPS-activated microglia, most likely by modulating the ERK pathway. Taken together, these results demonstrate that the anti-inflammatory and antioxidative actions of KHG26693 are mediated, at least in part, through the control of microglial activation.

Effects of N-adamantyl-4-methylthiazol-2-amine on hyperglycemia, hyperlipidemia and oxidative stress in streptozotocin-induced diabetic rats

Thiazole derivatives are attractive candidates for drug development because they can be efficiently synthesized and are active against a number of diseases and conditions, including diabetes. In our present study, we investigated the anti-inflammatory and antioxidant properties of N-adamantyl-4-methylthiazol-2-amine (KHG26693), a new thiazole derivative, in a streptozotocin (STZ)-induced model of diabetes mellitus. STZ-induced diabetic rats were intraperitoneally administered KHG26693 (3mg/kg-body weight/day) for 4 weeks. KHG26693 administration significantly decreased blood glucose, triglycerides, and cholesterol and increased insulin. KHG26693 also suppressed several inflammatory responses in STZ-induced diabetic rats, as evidenced by decreased levels of serum tumor necrosis factor-α, interleukin-1β, and nitric oxide. Additionally, KHG26693 significantly modulated hepatic lipid peroxidation, catalase and superoxide dismutase activity, and the nonenzymatic antioxidant status (e.g., vitamins C and E), and reduced the glutathione content. These anti-inflammatory/antioxidative actions occurred as a result of the downregulation of inducible nitric oxide synthase and nuclear factor-kappa B. Taken together, our results suggest that KHG26693 successfully reduces the production of oxidative stress in STZ-induced diabetic rats by regulating the oxidation-reduction system, specifically increasing antioxidant capacity. Furthermore, KHG26693 treatment significantly reverted the key enzymes of glucose metabolism, such as glucokinase, glucose-6-phosphatase, glycogen synthase, glycogen phosphorylase, and fructose-1,6-bisphosphatase, to near-normal levels in liver tissues. These results indicate that KHG26693 normalizes disturbed glucose metabolism by enhancing glucose utilization and decreasing liver glucose production via insulin release, suggesting the possibility of future diabetes treatments.