S-nitrosylation of mixed lineage kinase 3 contributes to its activation after cerebral ischemia

Disrupting PIAS3-mediated SUMOylation of MLK3 ameliorates poststroke neuronal damage and deficits in cognitive and sensorimotor behaviors

Activated small ubiquitin-like modifiers (SUMOs) have been implicated in neuropathological processes following ischemic stroke. However, the target proteins of SUMOylation and their contribution to neuronal injury remain to be elucidated. MLK3 (mixed-lineage kinase 3), a member of the mitogen-activated protein kinase kinase kinase (MAPKKK) family, is a critical regulator of neuronal lesions following cerebral ischemia. Here, we found that SUMOylation of MLK3 increases in both global and focal ischemic rodent models and primary neuronal models of oxygen and glucose deprivation (OGD). SUMO1 conjugation at the Lys401 site of MLK3 promoted its activation, stimulated its downstream p38/c-Jun N-terminal kinase (JNK) cascades, and led to cell apoptosis. The interaction of MLK3 with PIAS3, a SUMO ligase, was elevated following ischemia and reperfusion. The PINIT domain of PIAS3 was involved in direct interactions with MLK3. Overexpression of the PINIT domain of PIAS3 disrupted the MLK3-PIAS3 interaction, inhibited SUMOylation of MLK3, suppressed downstream signaling, and reduced cell apoptosis and neurite damage. In rodent ischemic models, the overexpression of the PINIT domain reduced brain lesions and alleviated deficits in learning, memory, and sensorimotor functions. Our findings demonstrate that brain ischemia-induced MLK3 SUMOylation by PIAS3 is a potential target against poststroke neuronal lesions and behavioral impairments.

Targeting the Cysteine Redox Proteome in Parkinson's Disease: The Role of Glutathione Precursors and Beyond

Encouraging recent data on the molecular pathways underlying aging have identified variants and expansions of genes associated with DNA replication and repair, telomere and stem cell maintenance, regulation of the redox microenvironment, and intercellular communication. In addition, cell rejuvenation requires silencing some transcription factors and the activation of pluripotency, indicating that hidden molecular networks must integrate and synchronize all these cellular mechanisms. Therefore, in addition to gene sequence expansions and variations associated with senescence, the optimization of transcriptional regulation and protein crosstalk is essential. The protein cysteinome is crucial in cellular regulation and plays unexpected roles in the aging of complex organisms, which show cumulative somatic mutations, telomere attrition, epigenetic modifications, and oxidative dysregulation, culminating in cellular senescence. The cysteine thiol groups are highly redox-active, allowing high functional versatility as structural disulfides, redox-active disulfides, active-site nucleophiles, proton donors, and metal ligands to participate in multiple regulatory sites in proteins. Also, antioxidant systems control diverse cellular functions, including the transcription machinery, which partially depends on the catalytically active cysteines that can reduce disulfide bonds in numerous target proteins, driving their biological integration. Since we have previously proposed a fundamental role of cysteine-mediated redox deregulation in neurodegeneration, we suggest that cellular rejuvenation of the cysteine redox proteome using GSH precursors, like N-acetyl-cysteine, is an underestimated multitarget therapeutic approach that would be particularly beneficial in Parkinson's disease.

Effect of S-Nitrosylation of RIP3 Induced by Cerebral Ischemia on its Downstream Signaling Pathway

OBJECTIVES

Our preliminary experiments indicate that receptor-interacting protein 3 (RIP3) is S-nitrosylated and contributes to its autophosphorylation (activation) after 3 h of rat brain ischemia/reperfusion mediated by activation of the N-methyl-D-aspartate receptor (NMDAR)-dependent neuronal NO synthase (nNOS) and is involved in the process of neuronal injury. Here, we will to demonstrate whether S-nitrosylation of RIP3 facilitates the activation of the downstream signaling pathway and finally exacerbates ischemic neuron death.

MATERIALS AND METHODS

Adult male Sprague-Dawley rat transient brain ischemia/reperfusion and cortical neurons oxygen and glucose deprivation (OGD)/reoxygenation models were performed. The hippocampal CA1 regions or cultured cells were homogenized and the cytosolic fraction were collected as tissue samples. Coimmunoprecipitation and western blot analysis were carried out for detecting phosphorylation of RIP1 and mixed lineage kinase-like domains (MLKL) and the Cleaved-Caspase8 (Cl-Caspase8). The activities of Glycogen phosphorylase (PYGL), Glutamate-ammonia ligase (GLUL) and Glutamate dehydrogenase (GLUD1) were detected with ultraviolet absorption method.

RESULTS

This study showed that active RIP3 could phosphorylate RIP1 and MLKL through its kinase activity, promote the conversion of Caspase8 to active Cl-Caspase8, enhance the activities of PYGL, GLUL and GLUD1, and finally aggravate neuronal injury in cerebral ischemia/reperfusion. The inhibition of RIP3 S-nitrosylation inhibited the phosphorylation of RIP1 and MLKL, inhibited the activities of Caspase8, PYGL, GLUL, and GLUD1, and alleviated neuronal damage in cerebral ischemia/reperfusion.

CONCLUSIONS

S-nitrosylation of RIP3 increased RIP1 and MLKL phosphorylation levels, Cl-Caspase8 content and PYGL, GLUL and GLUD1 activities and aggravated neuronal damage during cerebral ischemia/reperfusion and regulating the S-nitrosylation of RIP3 and its downstream signaling pathway might be a therapeutic target for stroke.

Roles of Nitric Oxide in Brain Ischemia and Reperfusion

Brain ischemia and reperfusion (I/R) is one of the most severe clinical manifestations of ischemic stroke, placing a significant burden on both individuals and society. The only FDA-approved clinical treatment for ischemic stroke is tissue plasminogen activator (t-PA), which rapidly restores cerebral blood flow but can have severe side effects. The complex pathological process of brain I/R has been well-established in the past few years, including energy metabolism disorders, cellular acidosis, doubling of the synthesis or release of excitotoxic amino acids, intracellular calcium homeostasis, free radical production, and activation of apoptotic genes. Recently, accumulating evidence has shown that NO may be strongly related to brain I/R and involved in complex pathological processes. This review focuses on the role of endogenous NO in pathological processes in brain I/R, including neuronal cell death and blood brain barrier disruption, to explore how NO impacts specific signaling cascades and contributes to brain I/R injury. Moreover, NO can rapidly react with superoxide to produce peroxynitrite, which may also mediate brain I/R injury, which is discussed here. Finally, we reveal several therapeutic approaches strongly associated with NO and discuss their potential as a clinical treatment for ischemic stroke.

N-Acetyl-Cysteine: Modulating the Cysteine Redox Proteome in Neurodegenerative Diseases

In the last twenty years, significant progress in understanding the pathophysiology of age-associated neurodegenerative diseases has been made. However, the prevention and treatment of these diseases remain without clinically significant therapeutic advancement. While we still hope for some potential genetic therapeutic approaches, the current reality is far from substantial progress. With this state of the issue, emphasis should be placed on early diagnosis and prompt intervention in patients with increased risk of neurodegenerative diseases to slow down their progression, poor prognosis, and decreasing quality of life. Accordingly, it is urgent to implement interventions addressing the psychosocial and biochemical disturbances we know are central in managing the evolution of these disorders. Genomic and proteomic studies have shown the high molecular intricacy in neurodegenerative diseases, involving a broad spectrum of cellular pathways underlying disease progression. Recent investigations indicate that the dysregulation of the sensitive-cysteine proteome may be a concurrent pathogenic mechanism contributing to the pathophysiology of major neurodegenerative diseases, opening new therapeutic opportunities. Considering the incidence and prevalence of these disorders and their already significant burden in Western societies, they will become a real pandemic in the following decades. Therefore, we propose large-scale investigations, in selected groups of people over 40 years of age with decreased blood glutathione levels, comorbidities, and/or mild cognitive impairment, to evaluate supplementation of the diet with low doses of N-acetyl-cysteine, a promising and well-tolerated therapeutic agent suitable for long-term use.

The emerging roles of nitric oxide in ferroptosis and pyroptosis of tumor cells

Tumor cells can develop resistance to cell death which is divided into necrosis and programmed cell death (PCD). PCD, including apoptosis, autophagy, ferroptosis, pyroptosis, and necroptosis. Ferroptosis and pyroptosis, two new forms of cell death, have gradually been of interest to researchers. Boosting ferroptosis and pyroptosis of tumor cells could be a potential cancer therapy. Nitric oxide (NO) is a ubiquitous, lipophilic, highly diffusible, free-radical signaling molecule that plays various roles in tumorigenesis. In addition, NO also has regulatory mechanisms through S-nitrosylation that do not depend on the classic NO/sGC/cGMP signaling. The current tumor treatment strategy for NO is to promote cell death through promoting S-nitrosylation-induced apoptosis while multiple drawbacks dampen this tumor therapy. However, numerous studies have suggested that suppression of NO is perceived to active ferroptosis and pyroptosis, which could be a better anti-tumor treatment. In this review, ferroptosis and pyroptosis are described in detail. We summarize that NO influences ferroptosis and pyroptosis and infer that S-nitrosylation mediates ferroptosis- and pyroptosis-related signaling pathways. It could be a potential cancer therapy different from NO-induced apoptosis of tumor cells. Finally, the information shows the drugs that manipulate endogenous production and exogenous delivery of NO to modulate the levels of S-nitrosylation.

Nitrosative Stress and Human Disease: Therapeutic Potential of Denitrosylation

Proteins dynamically contribute towards maintaining cellular homeostasis. Posttranslational modification regulates the function of target proteins through their immediate activation, sudden inhibition, or permanent degradation. Among numerous protein modifications, protein nitrosation and its functional relevance have emerged. Nitrosation generally initiates nitric oxide (NO) production in association with NO synthase. NO is conjugated to free thiol in the cysteine side chain (S-nitrosylation) and is propagated via the transnitrosylation mechanism. S-nitrosylation is a signaling pathway frequently involved in physiologic regulation. NO forms peroxynitrite in excessive oxidation conditions and induces tyrosine nitration, which is quite stable and is considered irreversible. Two main reducing systems are attributed to denitrosylation: glutathione and thioredoxin (TRX). Glutathione captures NO from S-nitrosylated protein and forms S-nitrosoglutathione (GSNO). The intracellular reducing system catalyzes GSNO into GSH again. TRX can remove NO-like glutathione and break down the disulfide bridge. Although NO is usually beneficial in the basal context, cumulative stress from chronic inflammation or oxidative insult produces a large amount of NO, which induces atypical protein nitrosation. Herein, we (1) provide a brief introduction to the nitrosation and denitrosylation processes, (2) discuss nitrosation-associated human diseases, and (3) discuss a possible denitrosylation strategy and its therapeutic applications.

Pretreatment with S-Nitrosoglutathione Attenuates Septic Acute Kidney Injury in Rats by Inhibiting Inflammation, Oxidation, and Apoptosis

Objective

We aimed to investigate the protective effect of s-nitrosoglutathione (SNG) pretreatment on acute kidney injury (AKI) in septic rats.

Methods

We constructed a rat model of sepsis by cecal ligation and puncture and observed the survival of the rats. We obtained kidney and blood samples from rats, observed the pathological damage to the kidney tissues, and evaluated kidney function and the expression levels of inflammatory factors. We also detected the expression of induced nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in the kidneys by immunohistochemistry and evaluated the apoptosis of kidney tubular epithelial cells (KTEC) by TUNEL.

Results

Pretreatment with SNG significantly reduced the mortality of septic rats, attenuated kidney pathological damage, and decreased the levels of serum creatinine, plasma neutrophil gelatinase-associated lipocalin, and plasma kidney injury molecule-1. Moreover, SNG pretreatment decreased the levels of TNF-α and IL-1β in serum and kidney and reduced the expressions of NO, iNOS, PGE2, and COX-2 in the kidneys. Furthermore, pretreatment with SNG significantly reduced the apoptotic rate of KTEC and decreased the levels of caspase-3 and Bax mRNA, but increased the level of Bcl-2 mRNA.

Conclusion

Pretreatment with SNG has a protective effect on AKI in septic rats, and the specific mechanisms are related to inhibition of inflammation, oxidation, and apoptosis.

Neuroprotective Effects of a Novel Inhibitor of c-Jun N-Terminal Kinase in the Rat Model of Transient Focal Cerebral Ischemia

A novel specific inhibitor of c-Jun N-terminal kinase, 11H-indeno[1,2-b]quinoxalin-11-one oxime sodium salt (IQ-1S), has a high affinity to JNK3 compared to JNK1/JNK2. The aim of this work was to study the mechanisms of neuroprotective activity of IQ-1S in the models of reversible focal cerebral ischemia (FCI) in Wistar rats. The animals were administered with an intraperitoneal injection of IQ-1S (5 and 25 mg/kg) or citicoline (500 mg/kg). Administration of IQ-1S exerted a pronounced dose-dependent neuroprotective effect, not inferior to the effects of citicoline. Administration of IQ-1S at doses of 5 and 25 mg/kg reduced the infarct size by 20% and 50%, respectively, 48 h after FCI, whereas administration of citicoline reduced the infarct size by 34%. The administration of IQ-1S was associated with a faster amelioration of neurological status. Control rats showed a 2.0-fold increase in phospho-c-Jun levels in the hippocampus compared to the corresponding values in sham-operated rats 4 h after FCI. Administration of IQ-1S at a dose of 25 mg/kg reduced JNK-dependent phosphorylation of c-Jun by 20%. Our findings suggest that IQ-1S inhibits JNK enzymatic activity in the hippocampus and protects against stroke injury when administered in the therapeutic and prophylactic regimen in the rat model of FCI.

Nitric oxide affects cisplatin cytotoxicity oppositely in A2780 and A2780-CDDP cells via the connexin32/gap junction

Chemoresistance is a main obstacle in ovarian cancer therapy and new treatment strategies and further information regarding the mechanism of the medication cisplatin are urgently needed. Nitric oxide has a critical role in modulating the activity of chemotherapeutic drugs. Our previous work showed that connexin32 contributed to cisplatin resistance. However, whether nitric oxide is involved in connexin32-mediated cisplatin resistance remains unknown. In this study, using A2780 and A2780 cisplatin-resistant cells, we found that S-nitroso-N-acetyl-penicillamine, a nitric oxide donor, attenuated cisplatin toxicity by decreasing gap junctions in A2780 cells. Enhancement of gap junctions using retinoic acid reversed the effects of S-nitroso-N-acetyl-penicillamine on cisplatin toxicity. In A2780 cisplatin-resistant cells, however, S-nitroso-N-acetyl-penicillamine enhanced cisplatin toxicity by decreasing connexin32 expression. Downregulation of connexin32 expression by small interfering RNA exacerbated the effects of S-nitroso-N-acetyl-penicillamine on cisplatin cytotoxicity and upregulation of connexin32 expression by pcDNA transfection reversed the effects of S-nitroso-N-acetyl-penicillamine on cisplatin cytotoxicity. Our study suggests for the first time that combining cisplatin with nitric oxide in clinical therapies for ovarian cancer should be avoided before cisplatin resistance emerges. The present study provides a productive area of further study for increasing the efficacy of cisplatin by combining cisplatin with the specific inhibitors or enhancers of nitric oxide in clinical treatment.

Hederagenin Attenuates Cerebral Ischaemia/Reperfusion Injury by Regulating MLK3 Signalling

Cerebral ischaemia/reperfusion (CI/R) injury is a major challenge due to the lack of effective neuroprotective drugs. Hederagenin (HE) is the aglycone part of saponins extracted from Hedera helix Linné that has exhibited anti-apoptotic and anti-inflammatory effects; however, the role of HE in CI/R has not been elucidated. In this study, mice were intraperitoneally (i.p.) injected with HE (26.5, 53, or 106 μmol/kg body weight) for 3 days after middle cerebral artery occlusion (MCAO). Neural function and brain infarct volume were evaluated. HE treatment attenuated CI/R-induced apoptosis and inflammatory cytokine expression within the infarcted areas. HE treatment also decreased the activation of the MLK3 signalling pathway, which potentiates CI/R damage via the MAPK and NFκB pathways. Due to HE's safety profile, it has potential to be used for the clinical treatment of ischaemic stroke.

Nitric oxide, a communicator between tumor cells and endothelial cells, mediates the anti-tumor effects of Marsdenia Tenacissima Extract (MTE)

ETHNOPHARMACOLOGICAL RELEVANCE

Marsdenia tenacissima (Roxb.) Wight & Arn is a well-known traditional Chinese medicine for treating cancer. The anti-tumor effects of the water soluble component of M. tenacissima (MTE, M. Tenacissima Extract) have been intensely studied. However, the roles of microenvironmental cells in mediating the anti-tumor actions of MTE remain to be defined.

AIM OF THE STUDY

To determine the roles of nitric oxide (NO) released by endothelial cells (ECs), an important component of tumor microenvironment, in regulating the anti-cancer effects of MTE, and to explore the underlying mechanisms.

MATERIALS AND METHODS

Co-culture system of ECs and A549 non-small cell lung cancer (NSCLC) cells was established for determining the interactions of ECs and lung cancer cells. Nitro-L-arginine methyl ester hydrochloride (L-NAME) was used to inhibit the production of NO. Cell viability was examined using cell counting kit 8 and 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT) assay. NO assay and Western blot were used to determine the involved signaling pathway. Primary lung microenvironmental cells (PLMCs) were cultured to examine the roles of NO released from the lung microenvironment in regulating the anti-cancer effects of MTE. A subcutaneous xenograft model was established to determine the involvement of NO in effects of MTE against NSCLCs in vivo.

RESULTS

In the co-culture system of ECs and A549 NSCLC cells, MTE (30 mg/mL) treatment reduced viability of lung cancer cells. However, when L-NAME (a nitric oxide synthase (NOS) inhibitor, 300 μM) was introduced into the co-culture system, the NSCLC-inhibiting effects of MTE were significantly suppressed. By contrast, addition of L-NAME (300 μM) did not affect the anti-cancer efficiency of MTE when ECs were not present. Mechanistically, MTE enhanced endothelial production of NO via stimulating PKA-endothelial nitric oxide synthase (eNOS) signaling. Elevated levels of NO inhibited proliferation and promoted apoptosis of the A549 NSCLC cells. Importantly, PKA-eNOS-NO signaling was effective in mediating the anti-cancer effects of MTE, when lung cancer cells were co-cultured with PLMCs. Finally, oral administration of MTE to the subcutaneous xenograft mice significantly suppressed tumor growth, while elevated NO productions. Plasma NO was also revealed to be negatively correlated with the tumor weight.

CONCLUSIONS

ECs significantly contributed to anti-cancer effects of MTE by elevating production of NO, in a PKA-dependent manner. The present study revealed a novel anti-cancer mechanism of MTE through regulating the function of ECs, an important component of tumor microenvironment.

Inhibition of HDAC4 Attenuated JNK/c-Jun-Dependent Neuronal Apoptosis and Early Brain Injury Following Subarachnoid Hemorrhage by Transcriptionally Suppressing MKK7

The c-Jun N-terminal kinase (JNK)/c-Jun cascade-dependent neuronal apoptosis has been identified as a central element for early brain injury (EBI) following subarachnoid hemorrhage (SAH), but the molecular mechanisms underlying this process are still thoroughly undefined to date. In this study, we found that pan-histone deacetylase (HDAC) inhibition by TSA, SAHA, VPA, and M344 led to a remarkable decrease in the phosphorylation of JNK and c-Jun, concomitant with a significant abrogation of apoptosis caused by potassium deprivation in cultured cerebellar granule neurons (CGNs). Further investigation showed that these effects resulted from HDAC inhibition-induced transcriptional suppression of MKK7, a well-known upstream kinase of JNK. Using small interference RNAs (siRNAs) to silence the respective HDAC members, HDAC4 was screened to be required for MKK7 transcription and JNK/c-Jun activation. LMK235, a specific HDAC4 inhibitor, dose-dependently suppressed MKK7 transcription and JNK/c-Jun activity. Functionally, HDAC4 inhibition via knockdown or LMK235 significantly rescued CGN apoptosis induced by potassium deprivation. Moreover, administration of LMK235 remarkably ameliorated the EBI process in SAH rats, associated with an obvious reduction in MKK7 transcription, JNK/c-Jun activity, and neuronal apoptosis. Collectively, the findings provide new insights into the molecular mechanism of neuronal apoptosis regarding HDAC4 in the selective regulation of MKK7 transcription and JNK/c-Jun activity. HDAC4 inhibition could be a potential alternative to prevent MKK7/JNK/c-Jun axis-mediated nervous disorders, including SAH-caused EBI.

S-nitrosoglutathione protects lipopolysaccharide-induced acute kidney injury by inhibiting toll-like receptor 4-nuclear factor-κB signal pathway

OBJECTIVES

To investigate the therapeutic effects and mechanisms of S-nitrosoglutathione (SNG) on acute kidney injury (AKI) induced by lipopolysaccharide (LPS).

METHODS

We established an AKI model by intraperitoneal administration of LPS in mice and LPS-induced human kidney (HK-2) cells in vitro. We obtained the kidney tissues from mice for histopathological examination, examined inflammatory cytokines by enzyme-linked immunosorbent assay and measured the expression levels of toll-like receptor 4-nuclear factor-κB (TLR4-NF-κB) signal pathway-related proteins by Western blotting.

KEY FINDINGS

Pretreatment of SNG effectively improved the kidney function, reduced the pathological damage score of kidney in mice and decreased the expression levels of IL-1β, IL-6 and TNF-α in a dose-dependent manner in vivo and in vitro. Furthermore, pretreatment of SNG also repressed TLR4, phosphorylated NF-κB IκBα, IKKβ and p65 expression levels in HK-2 cells induced by LPS.

CONCLUSIONS

S-nitrosoglutathione attenuates the severity of LPS-induced AKI by inhibiting the TLR4-NF-κB signalling pathway and may act as a protective agent for septic AKI.

Protective Effects of a New C-Jun N-terminal Kinase Inhibitor in the Model of Global Cerebral Ischemia in Rats

c-Jun N-terminal kinase (JNK) is activated by various brain insults and is implicated in neuronal injury triggered by reperfusion-induced oxidative stress. Some JNK inhibitors demonstrated neuroprotective potential in various models, including cerebral ischemia/reperfusion injury. The objective of the present work was to study the neuroprotective activity of a new specific JNK inhibitor, IQ-1S (11H-indeno[1,2-b]quinoxalin-11-one oxime sodium salt), in the model of global cerebral ischemia (GCI) in rats compared with citicoline (cytidine-5'-diphosphocholine), a drug approved for the treatment of acute ischemic stroke and to search for pleiotropic mechanisms of neuroprotective effects of IQ-1S. The experiments were performed in a rat model of ischemic stroke with three-vessel occlusion (model of 3VO) affecting the brachiocephalic artery, the left subclavian artery, and the left common carotid artery. After 7-min episode of GCI in rats, 25% of animals died, whereas survived animals had severe neurological deficit at days 1, 3, and 5 after GCI. At day 5 after GCI, we observing massive loss of pyramidal neurons in the hippocampal CA1 area, increase in lipid peroxidation products in the brain tissue, and decrease in local cerebral blood flow (LCBF) in the parietal cortex. Moreover, blood hyperviscosity syndrome and endothelial dysfunction were found after GCI. Administration of IQ-1S (intragastrically at a dose 50 mg/kg daily for 5 days) was associated with neuroprotective effect comparable with the effect of citicoline (intraperitoneal at a dose of 500 mg/kg, daily for 5 days).The neuroprotective effect was accompanied by a decrease in the number of animals with severe neurological deficit, an increase in the number of animals with moderate degree of neurological deficit compared with control GCI group, and an increase in the number of unaltered neurons in the hippocampal CA1 area along with a significant decrease in the number of neurons with irreversible morphological damage. In rats with IQ-1S administration, the LCBF was significantly higher (by 60%) compared with that in the GCI control. Treatment with IQ-1S also decreases blood viscosity and endothelial dysfunction. A concentration-dependent decrease (IC₅₀ = 0.8 ± 0.3 μM) of tone in isolated carotid arterial rings constricted with phenylephrine was observed after IQ-1S application in vitro. We also found that IQ-1S decreased the intensity of the lipid peroxidation in the brain tissue in rats with GCI. 2.2-Diphenyl-1-picrylhydrazyl scavenging for IQ-1S in acetonitrile and acetone exceeded the corresponding values for ionol, a known antioxidant. Overall, these results suggest that the neuroprotective properties of IQ-1S may be mediated by improvement of cerebral microcirculation due to the enhanced vasorelaxation, beneficial effects on blood viscosity, attenuation of the endothelial dysfunction, and antioxidant/antiradical IQ-1S activity.

Vascular endothelial growth factor-modified macrophages accelerate reendothelialization and attenuate neointima formation after arterial injury in atherosclerosis-prone mice

Vascular endothelial growth factor (VEGF) is a promising molecule for cardiovascular diseases therapy. But lack of a targeted delivery system limits its translation into clinical application. This study aimed to develop stably overexpressing VEGF macrophages for targeted VEGF delivery to injured arteries and determine their potential for repairing of the damaged endothelium. Wire-induced carotid artery injury model was established in atherosclerosis-prone mice. It was observed that the VEGF-modified macrophages were recruited to the site of vascular injury and incorporated into new endothelium formation. VEGF-modified macrophages therapy accelerated reendothelialization and attenuated neointima formation. The VEGF protein level in tissues of injured arteries treated with VEGF-modified macrophages was increased. The upregulated C-C chemokine receptor type 5 (CCR5) and unaltered CCR2 protein levels were verified in VEGF-modified macrophages in vitro. Moreover, enhanced nitric oxide (NO) production in the culture medium of VEGF-modified macrophages was demonstrated. Our results indicated that VEGF-modified macrophages acted as vectors of VEGF targeting injured arteries, promoting the repairing directly by incorporating into new endothelium formation and indirectly by secreting sustainable VEGF and producing NO locally. This study represents a novel therapeutic application of targeted cell therapy with VEGF-modified macrophages for cardiovascular diseases.

c-Jun N-Terminal Kinases (JNKs) in Myocardial and Cerebral Ischemia/Reperfusion Injury

In this article, we review the literature regarding the role of c-Jun N-terminal kinases (JNKs) in cerebral and myocardial ischemia/reperfusion injury. Numerous studies demonstrate that JNK-mediated signaling pathways play an essential role in cerebral and myocardial ischemia/reperfusion injury. JNK-associated mechanisms are involved in preconditioning and post-conditioning of the heart and the brain. The literature and our own studies suggest that JNK inhibitors may exert cardioprotective and neuroprotective properties. The effects of modulating the JNK-depending pathways in the brain and the heart are reviewed. Cardioprotective and neuroprotective mechanisms of JNK inhibitors are discussed in detail including synthetic small molecule inhibitors (AS601245, SP600125, IQ-1S, and SR-3306), ion channel inhibitor GsMTx4, JNK-interacting proteins, inhibitors of mixed-lineage kinase (MLK) and MLK-interacting proteins, inhibitors of glutamate receptors, nitric oxide (NO) donors, and anesthetics. The role of JNKs in ischemia/reperfusion injury of the heart in diabetes mellitus is discussed in the context of comorbidities. According to reviewed literature, JNKs represent promising therapeutic targets for protection of the brain and the heart against ischemic stroke and myocardial infarction, respectively. However, different members of the JNK family exert diverse physiological properties which may not allow for systemic administration of non-specific JNK inhibitors for therapeutic purposes. Currently available candidate JNK inhibitors with high therapeutic potential are identified. The further search for selective JNK3 inhibitors remains an important task.

Electroacupuncture exerts neuroprotective effects on ischemia/reperfusion injury in JNK knockout mice: the underlying mechanism

Simple regulation of c-Jun N-terminal kinase (JNK) or p38 mitogen-activated protein kinase (MAPK) pathways is not enough to trigger cell apoptosis. However, activation of the stress activated pathway (JNK/p38 MAPK) together with inhibition of the growth factor activated extracellular signal-regulated kinase (ERK) pathway can promote cell apoptosis. We hypothesized that inhibition of the JNK or p38 pro-apoptotic pathway and activating the ERK pathway could be the mechanism of anti-apoptosis following cerebral ischemia/reperfusion injury. To investigate the mechanism of the protective effect of electroacupuncture on cerebral ischemia/reperfusion injury in JNK knockout mice, mouse models of cerebral ischemia/reperfusion injury were established by Longa’s method. Electroacupuncture was conducted at acupoints Chize (LU5), Hegu (LI4), Sanyinjiao (SP6) and Zusanli (ST36) 1.5 hours after ischemia/reperfusion injury for 20 minutes, once a day. The neurological function was evaluated using neurological deficit scores. The expression of phospho-extracellular signal-regulated kinase (p-ERK) and phospho-p38 (p-p38) in JNK knockout mice was detected using double-labeling immunofluorescence and western blot assay. The mRNA expression of ERK and p38 was measured by quantitative real-time polymerase chain reaction. Electroacupuncture improved neurological function, increased the immunoreactivity and relative expression of p-ERK and reduced that of p-p38 in the cerebral cortex and hippocampus on the injured side. Electroacupuncture increased mRNA expression of ERK, but decreased that of p38 in the cerebral cortex and hippocampus on the injured side. In conclusion, electroacupuncture upregulated the protective ERK pathway and inhibited the pro-apoptotic p38 pathway, thereby exerting a neuroprotective effect and improving the neurological function in JNK knockout mice.

The role S-nitrosylation in manganese-induced autophagy dysregulation in SH-SY5Y cells

Overexposure to manganese (Mn) has been known to induce nitrosative stress. The dysregulation of autophagy has implicated in nitric oxide (NO) bioactivity alterations. However, the mechanism of Mn-induced autophagic dysregulation is unclear. The protein of Bcl-2 was considered as a key role that could participate to the autophagy signaling regulation. To further explore whether S-nitrosylation of Bcl-2 involved in Mn-induced autophagy dysregulation, we treated human neuroblastoma (SH-SY5Y) cells with Mn and pretreated cells with 1400 W, a selective iNOS inhibitor. After cells were treated with 400 μM Mn for 24 h, there were significant increases in production of NO, inducible NO synthase (iNOS) activity, the mRNA and protein expressions of iNOS. Interestingly, autophagy was activated after cells were treated with Mn for 0-12 h; while the degradation process of autophagy-lysosome pathway was blocked after cells were treated with Mn for 24 h. Moreover, S-nitrosylated JNK and Bcl-2 also increased and phospho-JNK and phospho-Bcl-2 reduced in Mn-treated cells. Then, the affinity between Bcl-2 and Beclin-1 increased significantly in Mn-treated cells. We used the 1400 W to neutralize Mn-induced nitrosative stress. The results showed that S-nitrosylated JNK and Bcl-2 reduced while their phosphorylation were recovered to some extent. The findings revealed that NO-mediated S-nitrosylation of Bcl-2 directly affected the interaction between Beclin-1 and Bcl-2 leading to autophagy inhibition.

S-Nitrosoglutathione ameliorates acute renal dysfunction in a rat model of lipopolysaccharide-induced sepsis

OBJECTIVE

Sepsis induces an inflammatory response that results in acute renal failure (ARF). The current study is to evaluate the role of S-Nitrosoglutathione (GSNO) in renoprotection from lipopolysaccharide (LPS)-induced sepsis.

METHODS

Rats were divided to three groups. First group received LPS (5 mg/kg body weight), second group was treated with LPS + GSNO (50 μg/kg body weight), and third group was administered with vehicle (saline). They were sacrificed on day 1 and 3 post-LPS injection. Serum levels of nitric oxide (NO), creatinine and blood urea nitrogen (BUN) were analysed. Tissue morphology, T lymphocyte infiltrations, and the expression of inflammatory (TNF-α, iNOS) and anti-inflammatory (IL-10) mediators as well as glutathione (GSH) levels were determined.

KEY FINDING

Lipopolysaccharide significantly decreased body weight and increased cellular T lymphocyte infiltration, caspase-3 and iNOS and decreased PPAR-γ in renal tissue. NO, creatinine and BUN were significantly elevated after LPS challenge, and they significantly decreased after GSNO treatment. TNF-α level was found significantly increased in LPS-treated serum and kidney. GSNO treatment of LPS-challenged rats decreased caspase-3, iNOS, TNF-α, T lymphocyte infiltration and remarkably increased levels of IL-10, PPAR-γ and GSH.

CONCLUSION

GSNO can be used as a renoprotective agent for the treatment of sepsis-induced acute kidney injury.

Neuroprotective Effects of Inhibiting Fyn S-Nitrosylation on Cerebral Ischemia/Reperfusion-Induced Damage to CA1 Hippocampal Neurons

Nitric oxide (NO) can regulate signaling pathways via S-nitrosylation. Fyn can be post-translationally modified in many biological processes. In the present study, using a rat four-vessel-occlusion ischemic model, we aimed to assess whether Fyn could be S-nitrosylated and to evaluate the effects of Fyn S-nitrosylation on brain damage. In vitro, Fyn could be S-nitrosylated by S-nitrosoglutathione (GSNO, an exogenous NO donor), and in vivo, endogenous NO synthesized by NO synthases (NOS) could enhance Fyn S-nitrosylation. Application of GSNO, 7-nitroindazole (7-NI, an inhibitor of neuronal NOS) and hydrogen maleate (MK-801, the N-methyl-d-aspartate receptor (NMDAR) antagonist) could decrease the S-nitrosylation and phosphorylation of Fyn induced by cerebral ischemia/reperfusion (I/R). Cresyl violet staining validated that these compounds exerted neuroprotective effects against the cerebral I/R-induced damage to hippocampal CA1 neurons. Taken together, in this study, we demonstrated that Fyn can be S-nitrosylated both in vitro and in vivo and that inhibiting S-nitrosylation can exert neuroprotective effects against cerebral I/R injury, potentially via NMDAR-mediated mechanisms. These findings may lead to a new field of inquiry to investigate the underlying pathogenesis of stroke and the development of novel treatment strategies.

Inhibition on the S-nitrosylation of MKK4 can protect hippocampal CA1 neurons in rat cerebral ischemia/reperfusion

S-nitrosylation, the nitric oxide-derived post-translational modification of proteins, plays critical roles in various physiological and pathological functions. In this present study, a rat model of cerebral ischemia and reperfusion by four-vessel occlusion was generated to assess MKK4 S-nitrosylation. Immunoprecipitation and immunoblotting were performed to evaluate MKK4 S-nitrosylation and phosphorylation. Neuronal loss was observed using histological detection. These results indicated that endogenous NO promoted the S-nitrosylation of MKK4. However, application of the exogenous NO donor S-nitrosoglutathione (GNSO), an inhibitor of the neuronal nitric oxide synthase 7-nitroindazole (7-NI), and the N-methyl-d-aspartate receptor (NMDAR) antagonist MK801 diminished I/R-induced S-nitrosylation and phosphorylation. These compounds also markedly decreased cerebral I/R-induced degeneration and death of neurons in hippocampal CA1 region in rats. Taken together, we demonstrated for the first time, that cerebral ischemia/reperfusion can induce S-nitrosylation of MKK4. We also found that inhibiting S-nitrosylation and activation of MKK4 resulted in marked decreases in neuronal degeneration and apoptosis, potentially via NMDAR-mediated mechanisms. These findings may lead to a new field of inquiry to investigate the underlying pathogenesis of stoke and the development of novel treatment strategies.

Procaspase-9 induces its cleavage by transnitrosylating XIAP via the Thioredoxin system during cerebral ischemia-reperfusion in rats

Transnitrosylation is an important mechanism by which nitric oxide (NO) modulates cell signaling pathways. For instance, SNO-caspase-3 can transnitrosylate the X-linked inhibitor of apoptosis (XIAP) to enhance apoptosis. XIAP is a potent antagonist of caspase apoptotic activity. Decrease in XIAP activity via nitrosylation results in SNO-XIAP-mediated caspase activation. Considering the functional liaison of procaspase-9 and XIAP, we hypothesized that procaspase-9 nitrosylates XIAP directly. Our data confirmed that cerebral ischemia-reperfusion induced XIAP nitrosylation, procaspase-9 denitrosylation and cleavage. Interestingly, the time courses of the nitrosylation of procaspase-9 and XIAP were negatively correlated, which was more prominent after cerebral ischemia-reperfusion, suggesting a direct interaction. The nitrosylation of XIAP, as well as the denitrosylation and cleavage of procaspase-9, were inhibited by DNCB, TrxR1 AS-ODNs, or TAT-AVPY treatment. Meanwhile, DNCB, TrxR1 AS-ODNs, or TAT-AVPY also inhibited the decrease in hippocampal CA1 neurons induced by ischemia-reperfusion in rats. The denitrosylation and cleavage of procaspase-9 induced by OGD/reoxygenation in SH-SY5Y cells were inhibited when cells were co-transfected with wild-type procaspase-9 and XIAP mutant (C449G). These data suggest that cerebral ischemia-reperfusion induces a transnitrosylation from procaspase-9 to XIAP via the Trx system to consequently cause apoptosis. Additionally, Cys325 is a critical S-nitrosylation site of procaspase-9.

A novel dual NO-donating oxime and c-Jun N-terminal kinase inhibitor protects against cerebral ischemia-reperfusion injury in mice

The c-Jun N-terminal kinase (JNK) has been shown to be an important regulator of neuronal cell death. Previously, we synthesized the sodium salt of 11H-indeno[1,2-b]quinoxalin-11-one (IQ-1S) and demonstrated that it was a high-affinity inhibitor of the JNK family. In the present work, we found that IQ-1S could release nitric oxide (NO) during its enzymatic metabolism by liver microsomes. Moreover, serum nitrite/nitrate concentration in mice increased after intraperitoneal injection of IQ-1S. Because of these dual actions as JNK inhibitor and NO-donor, the therapeutic potential of IQ-1S was evaluated in an animal stroke model. We subjected wild-type C57BL6 mice to focal ischemia (30min) with subsequent reperfusion (48h). Mice were treated with IQ-1S (25mg/kg) suspended in 10% solutol or with vehicle alone 30min before and 24h after middle cerebral artery (MCA) occlusion (MCAO). Using laser-Doppler flowmetry, we monitored cerebral blood flow (CBF) above the MCA during 30min of MCAO provoked by a filament and during the first 30min of subsequent reperfusion. In mice treated with IQ-1S, ischemic and reperfusion values of CBF were not different from vehicle-treated mice. However, IQ-1S treated mice demonstrated markedly reduced neurological deficit and infarct volumes as compared with vehicle-treated mice after 48h of reperfusion. Our results indicate that the novel JNK inhibitor releases NO during its oxidoreductive bioconversion and improves stroke outcome in a mouse model of cerebral reperfusion. We conclude that IQ-1S is a promising dual functional agent for the treatment of cerebral ischemia and reperfusion injury.

A beacon of hope in stroke therapy-Blockade of pathologically activated cellular events in excitotoxic neuronal death as potential neuroprotective strategies

Excitotoxicity, a pathological process caused by over-stimulation of ionotropic glutamate receptors, is a major cause of neuronal loss in acute and chronic neurological conditions such as ischaemic stroke, Alzheimer's and Huntington's diseases. Effective neuroprotective drugs to reduce excitotoxic neuronal loss in patients suffering from these neurological conditions are urgently needed. One avenue to achieve this goal is to clearly define the intracellular events mediating the neurotoxic signals originating from the over-stimulated glutamate receptors in neurons. In this review, we first focus on the key cellular events directing neuronal death but not involved in normal physiological processes in the neurotoxic signalling pathways. These events, referred to as pathologically activated events, are potential targets for the development of neuroprotectant therapeutics. Inhibitors blocking some of the known pathologically activated cellular events have been proven to be effective in reducing stroke-induced brain damage in animal models. Notable examples are inhibitors suppressing the ion channel activity of neurotoxic glutamate receptors and those disrupting interactions of specific cellular proteins occurring only in neurons undergoing excitotoxic cell death. Among them, Tat-NR2B9c and memantine are clinically effective in reducing brain damage caused by some acute and chronic neurological conditions. Our second focus is evaluation of the suitability of the other inhibitors for use as neuroprotective therapeutics. We also discuss the experimental approaches suitable for bridging our knowledge gap in our current understanding of the excitotoxic signalling mechanism in neurons and discovery of new pathologically activated cellular events as potential targets for neuroprotection.

Activating transcription factor 3 SUMOylation is involved in angiotensin II-induced endothelial cell inflammation and dysfunction

Activating transcription factor 3 (ATF3) is an adaptive-response protein induced by various environmental stresses and is implicated in the pathogenesis of many disease states. However, the role of ATF3 SUMOylation in hypertension-induced vascular injury remains poorly understood. Here we investigated the function of ATF3 SUMOylation in vascular endothelial cells (ECs). The expression of ATF3 and small ubiquitin-like modifier 1 (SUMO1) was increased in angiotensin II (Ang II)-induced human umbilical vein endothelial cells (HUVECs). Microscopic analyses further revealed that the expression of ATF3 and SUMO1 is upregulated and colocalized in the endothelium of thoracic aortas from Ang II-induced hypertensive mice. However, Ang II-induced upregulation of ATF3 and SUMO1 in vitro and in vivo was blocked by Ang II type I receptor antagonist olmesartan. Moreover, Ang II induced ATF3 SUMOylation at lysine 42, which is SUMO1 dependent. ATF3 SUMOylation attenuated ATF3 ubiquitination and in turn promoted ATF3 protein stability. ATF3 or SUMO1 knockdown inhibited Ang II-induced expression of inflammatory molecules such as tumor necrosis factor (TNF)-α, interleukin (IL)-6 and IL-8. Wild type ATF3 but not ATF3-K42R (SUMOylation defective mutant) reduced the production of nitric oxide (NO), a key indicator of EC function. Consistently, ginkgolic acid, an inhibitor of SUMOylation, increased NO production in HUVECs and significantly improved vasodilatation of aorta from Ang II-induced hypertensive mice. Our findings demonstrated that ATF3 SUMOylation is involved in Ang II-induced EC inflammation and dysfunction in vitro and in vivo through inhibiting ATF3 ubiquitination and increasing ATF3 protein stability.

P53-dependent miRNAs mediate nitric oxide-induced apoptosis in colonic carcinogenesis

Both miRNAs and nitric oxide (NO) play important roles in colonic inflammation and tumorigenesis. Resistance of colonic epithelial cells to apoptosis may contribute to tumor development. We hypothesized that some miRNAs could increase the resistance of colonic cancer cells to nitric oxide-induced apoptotic cell death. Here we show that NO induced apoptosis and stimulated expression of some miRNAs. Loss of p53 not only blocked NO-induced apoptosis but also dramatically inhibited the expression of NO-related miRNAs, such as miR-34, miR-203, and miR-1301. In addition, blockage of p53-dependent miRNAs significantly reduced NO-induced apoptosis. Furthermore, forced expression of these miRNAs rendered HT-29 cells, which are resistant to apoptosis with mutant p53, more sensitive to NO-induced apoptotic cell death. Most interestingly, in a colitis-associated colon cancer mouse model, the level of miRNAs dropped significantly, accompanied by downregulation of p21, which is a key target gene of p53. In human colorectal cancer samples, the expression of miR-34 significantly correlated with the level of inducible nitric oxide synthase (iNOS). We contend that increased NO production may select cells with low levels of p53-dependent miRNAs which contributes to human colonic carcinogenesis and tumor progression.

Light-evoked S-nitrosylation in the retina

Nitric oxide (NO) synthesis in the retina is triggered by light stimulation. NO has been shown to modulate visual signal processing at multiple sites in the vertebrate retina, via activation of the most sensitive target of NO signaling, soluble guanylate cyclase. NO can also alter protein structure and function and exert biological effects directly by binding to free thiol groups of cysteine residues in a chemical reaction called S-nitrosylation. However, in the central nervous system, including the retina, this reaction has not been considered to be significant under physiological conditions. Here we provide immunohistochemical evidence for extensive S-nitrosylation that takes place in the goldfish and mouse retinas under physiologically relevant light intensities, in an intensity-dependent manner, with a strikingly similar pattern in both species. Pretreatment with N-ethylmaleimide (NEM), which occludes S-nitrosylation, or with 1-(2-trifluromethylphenyl)imidazole (TRIM), an inhibitor of neuronal NO synthase, eliminated the light-evoked increase in S-nitrosylated protein immunofluorescence (SNI) in the retinas of both species. Similarly, light did not increase SNI, above basal levels, in retinas of transgenic mice lacking neuronal NO synthase. Qualitative analysis of the light-adapted mouse retina with mass spectrometry revealed more than 300 proteins that were S-nitrosylated upon illumination, many of which are known to participate directly in retinal signal processing. Our data strongly suggest that in the retina light-evoked NO production leads to extensive S-nitrosylation and that this process is a significant posttranslational modification affecting a wide range of proteins under physiological conditions.

Vitexin protects brain against ischemia/reperfusion injury via modulating mitogen-activated protein kinase and apoptosis signaling in mice

Vitexin is a major bioactive flavonoid compound derived from the dried leaf of hawthorn (Crataegus pinnatifida), a widely used conventional folk medicine in China. Recent studies have shown that vitexin presents neuroprotective effects in vitro. Whether this protective effect applies to the cerebral ischemia/reperfusion (I/R) injury remains elusive. In the present study, we examined the potential neuroprotective effect of vitexin against cerebral I/R injury and underlying mechanisms. A focal cerebral I/R model in male Kunming mice was induced by middle cerebral artery occlusion (MCAO) for 2 h followed by reperfusion for 22 h. The neurological function and infarct volume were assessed by using Long's five-point scale system and triphenyl-tetrazolium chloride (TTC) staining technique, respectively. Neuronal damage was evaluated by histological staining. Extracellular signal-regulated kinases 1/2 (ERK1/2), c-Jun N-terminal kinases (JNK) and p38 phosphorylation, and apoptosis were measured via Western blot at 24 h after reperfusion. As a result, systemic vitexin treatment significantly reduced neurological deficit, cerebral infarct volume and neuronal damage when compared with the I/R group. Western blot analyses revealed that vitexin markedly upregulated p-ERK1/2 and downregulated p-JNK and p-p38. Meanwhile, vitexin increased Bcl-2 expression and suppressed the overexpression of Bax in the I/R injury mice. In conclusion, the results indicate that vitexin protects brain against cerebral I/R injury, and this effect may be regulated by mitogen-activated protein kinase (MAPK) and apoptosis signaling pathways.

Posttranslational modification of Sirt6 activity by peroxynitrite

The mammalian sirtuin 6 (Sirt6) is a site-specific histone deacetylase that regulates chromatin structure and many fundamental biological processes. It inhibits endothelial cell senescence and inflammation, prevents development of cardiac hypertrophy and heart failure, modulates glucose metabolism, and represses tumor growth. The basic molecular mechanisms underlying regulation of Sirt6 enzymatic function are largely unknown. Here we hypothesized that Sirt6 function can be regulated via posttranslational modification, focusing on the role of peroxynitrite, one of the major reactive nitrogen species formed by excessive nitric oxide and superoxide generated during disease processes. We found that incubation of purified recombinant Sirt6 protein with 3-morpholinosydnonimine (SIN-1; a peroxynitrite donor that generates nitric oxide and superoxide simultaneously) increased Sirt6 tyrosine nitration and decreased its intrinsic catalytic activity. Similar results were observed in SIN-1-treated Sirt6, which was overexpressed in HEK293 cells, and in endogenous Sirt6 when human retinal microvascular endothelial cells were treated with SIN-1. To further investigate whether Sirt6 nitration occurs under pathological conditions, we determined Sirt6 nitration and activity in retina using a model of endotoxin-induced retinal inflammation. Our data showed that Sirt6 nitration was increased, whereas its activity was decreased, in this model. With mass spectrometry, we identified that tyrosine 257 in Sirt6 was nitrated after SIN-1 treatment. Mutation of tyrosine 257 to phenylalanine caused loss of Sirt6 activity and abolished SIN-1-induced nitration and decrease in its activity. Mass spectrometry analysis also revealed oxidation of methionine and tryptophan in Sirt6 after SIN-1 treatment. Our results demonstrate a novel regulatory mechanism controlling Sirt6 activity through reactive nitrogen species-mediated posttranslational modification under oxidative and nitrosative stress.

S-nitroso-proteome in poplar leaves in response to acute ozone stress

Protein S-nitrosylation, the covalent binding of nitric oxide (NO) to protein cysteine residues, is one of the main mechanisms of NO signaling in plant and animal cells. Using a combination of the biotin switch assay and label-free LC-MS/MS analysis, we revealed the S-nitroso-proteome of the woody model plant Populus x canescens. Under normal conditions, constitutively S-nitrosylated proteins in poplar leaves and calli comprise all aspects of primary and secondary metabolism. Acute ozone fumigation was applied to elicit ROS-mediated changes of the S-nitroso-proteome. This treatment changed the total nitrite and nitrosothiol contents of poplar leaves and affected the homeostasis of 32 S-nitrosylated proteins. Multivariate data analysis revealed that ozone exposure negatively affected the S-nitrosylation status of leaf proteins: 23 proteins were de-nitrosylated and 9 proteins had increased S-nitrosylation content compared to the control. Phenylalanine ammonia-lyase 2 (log2[ozone/control] = −3.6) and caffeic acid O-methyltransferase (−3.4), key enzymes catalyzing important steps in the phenylpropanoid and subsequent lignin biosynthetic pathways, respectively, were de-nitrosylated upon ozone stress. Measuring the in vivo and in vitro phenylalanine ammonia-lyase activity indicated that the increase of the phenylalanine ammonia-lyase activity in response to acute ozone is partly regulated by de-nitrosylation, which might favor a higher metabolic flux through the phenylpropanoid pathway within minutes after ozone exposure.

The nNOS-p38MAPK pathway is mediated by NOS1AP during neuronal death

Neuronal nitric oxide synthase (nNOS) and p38MAPK are strongly implicated in excitotoxicity, a mechanism common to many neurodegenerative conditions, but the intermediary mechanism is unclear. NOS1AP is encoded by a gene recently associated with sudden cardiac death, diabetes-associated complications, and schizophrenia (Arking et al., 2006; Becker et al., 2008; Brzustowicz, 2008; Lehtinen et al., 2008). Here we find it interacts with p38MAPK-activating kinase MKK3. Excitotoxic stimulus induces recruitment of NOS1AP to nNOS in rat cortical neuron culture. Excitotoxic activation of p38MAPK and subsequent neuronal death are reduced by competing with the nNOS:NOS1AP interaction and by knockdown with NOS1AP-targeting siRNAs. We designed a cell-permeable peptide that competes for the unique PDZ domain of nNOS that interacts with NOS1AP. This peptide inhibits NMDA-induced recruitment of NOS1AP to nNOS and in vivo in rat, doubles surviving tissue in a severe model of neonatal hypoxia-ischemia, a major cause of neonatal death and pediatric disability. The highly unusual sequence specificity of the nNOS:NOS1AP interaction and involvement in excitotoxic signaling may provide future opportunities for generation of neuroprotectants with high specificity.

The small GTPase RALA controls c-Jun N-terminal kinase-mediated FOXO activation by regulation of a JIP1 scaffold complex

FOXO (forkhead box O) transcription factors are tumor suppressors and increase the life spans of model organisms. Cellular stress, in particular oxidative stress caused by an increase in levels of reactive oxygen species (ROS), activates FOXOs through JNK-mediated phosphorylation. Importantly, JNK regulation of FOXO is evolutionarily conserved. Here we identified the pathway that mediates ROS-induced JNK-dependent FOXO regulation. Following increased ROS, RALA is activated by the exchange factor RLF (RalGDS-like factor), which is in complex with JIP1 (C-Jun-amino-terminal-interacting protein 1) and JNK. Active RALA consequently regulates assembly and activation of MLK3, MKK4, and JNK onto the JIP1 scaffold. Furthermore, regulation of FOXO by RALA and JIP1 is conserved in C. elegans, where both ral-1 and jip-1 depletion impairs heat shock-induced nuclear translocation of the FOXO orthologue DAF16.

Genistein attenuates ischemic oxidative damage and behavioral deficits via eNOS/Nrf2/HO-1 signaling

Global cerebral ischemia, such as occurs following cardiac arrest, can lead to oxidative stress, hippocampal neuronal cell death, and cognitive defects. The current study examined the potential beneficial effect and underlying mechanisms of post-treatment with the naturally occurring isoflavonic phytoestrogen, genistein, which has been implicated to attenuate oxidative stress. Genistein (1 mg kg(-1)) was administered i.v. 5 min after reperfusion in rats subjected to four-vessel global cerebral ischemia (GCI). The results revealed that genistein exerted significant neuroprotection of hippocampal CA1 neurons following GCI, as evidenced by an increase in NeuN-positive neurons and the decrease in TUNEL-positive neurons. Furthermore, genistein treatment also resulted in significantly improved spatial learning and memory as compared to vehicle control animals. The beneficial effects of genistein appear to be mediated by an increase of phosphorylation/activation of eNOS, with subsequent activation of the antioxidant/detoxification Nrf2/Keap1 transcription system. Along these lines, genistein increased keap1 S-nitrosylation, with a corresponding nuclear accumulation and enhanced DNA binding activity of Nrf2. Genistein also enhanced levels of the Nrf2 downstream antioxidant protein, heme oxygenase (HO)-1, as compared to vehicle control groups. In accordance with its induction of Nrf2 activation, genistein exerted a robust attenuation of oxidative DNA damage and lipid peroxidative damage in hippocampal CA1 neurons after GCI, as measured by immunofluorescence staining of the oxidative stress markers, 8-hydroxy-2-deoxyguanosine (8-OHdG) and 4-Hydroxynonenal (4-HNE). Interestingly, the aforementioned effects of genistein were abolished by pretreatment with L-NAME, an inhibitor of eNOS activation. In conclusion, the results of the study demonstrate that low dose genistein can exert significant antioxidant, neuroprotective, and cognitive-enhancing effects in the hippocampal CA1 region following GCI. Mechanistically, the beneficial effects of genistein appear to be mediated by enhanced eNOS phosphorylation/activation and nitric oxide (NO)-mediated thiol modification of Keap1, with subsequent upregulation of the Nrf2/HO-1 antioxidative signaling pathway and a resultant attenuation of oxidative stress.

Methods for detection and characterization of protein S-nitrosylation

Reversible protein S-nitrosylation, defined as the covalent addition of a nitroso moiety to the reactive thiol group on a cysteine residue, has received increasing recognition as a critical post-translational modification that exerts ubiquitous influence in a wide range of cellular pathways and physiological processes. Due to the lability of the S-NO bond, which is a dynamic modification, and the low abundance of endogenously S-nitrosylated proteins in vivo, unambiguous identification of S-nitrosylated proteins and S-nitrosylation sites remains methodologically challenging. In this review, we summarize recent advancements and the use of state-of-art approaches for the enrichment, systematic identification and quantitation of S-nitrosylation protein targets and their modification sites at the S-nitrosoproteome scale. These advancements have facilitated the global identification of >3000 S-nitrosylated proteins that are associated with wide range of human diseases. These strategies hold promise to site-specifically unravel potential molecular targets and to change S-nitrosylation-based pathophysiology, which may further the understanding of the potential role of S-nitrosylation in diseases.

ATPA induced GluR5-containing kainite receptor S-nitrosylation via activation of GluR5-Gq-PLC-IP(3)R pathway and signalling module GluR5·PSD-95·nNOS

GluR5-containing kainite receptor (GluR5-KAR) plays an important role in the pathophysiology of nervous system diseases, while S-nitrosylation exerts a variety of effects on biological systems. However, the mechanism of GluR5-KAR S-nitrosylation is still unclear up to now. Here our researches found that GluR5-KAR selective agonist ATPA stimulation activated the nonclassical GluR5-KAR-Gq-PLC-IP(3)R pathway and the signalling module GluR5·PSD-95·nNOS (the former is more important), led to Ca(2+) release from intracellular calcium stores endoplasmic reticulum (ER) to cytoplasm and extracellular calcium indrawal, respectively, which further resulted in nNOS activation and GluR5-KAR S-nitrosylation, and then inhibited GluR5-mediated whole-cell current attenuation and induced apoptosis in primary cultured hippocampal neurons. Clarification of the primary mechanisms of GluR5-KAR S-nitrosylation induced by ATPA and identification of critical cysteine for GluR5-2a S-nitrosylation (Cys231 and Cys804) open up a brand-new field for revealing downstream signalling pathway of GluR5-KAR and its molecular characteristics, exploring the pathogenesis of neurological diseases and searching for promising therapies.