Nitric oxide is the primary mediator of cytotoxicity induced by GSH depletion in neuronal cells

Mangiferin: A natural bioactive immunomodulating glucosylxanthone with potential against cancer and rheumatoid arthritis

Mangiferin is a naturally occurring glucosylxanthone that has shown promising immunomodulatory effects. It is generally isolated from the leaves, peels, bark, and kernels of Mangifera indica Linn. Mangiferin is like a miraculous natural bioactive molecule that has an immunomodulatory function that makes it a potential therapeutic candidate for the treatment of rheumatoid arthritis (RA) and cancer. The anticancer activity of mangiferin acts by blocking NF-κB, as well as regulating the β-catenin, EMT, MMP9, MMP2, LDH, ROS, and NO, and also by the activation of macrophages. It has no cytotoxic effect on grown chondrocytes and lowers matrix metalloproteinase levels. Additionally, it has a potent proapoptotic impact on synoviocytes. The precise molecular mechanism of action of mangiferin on RA and malignancies is still unknown. This comprehensive review elaborates on the immunomodulatory effect of mangiferin and its anticancer and anti-RA activity. This also explained the total synthesis of mangiferin and its in vitro and in vivo screening models.

Biliary atresia: insights into mechanisms using a toxic model of the disease including Wnt and Hippo signaling pathways and microtubules

BACKGROUND

Mechanisms underlying bile duct injury in biliary atresia (BA) remain unclear and mechanisms of bile duct repair are unknown. This study aimed to explore the roles of microtubule instability and Wnt and Hippo signaling pathways in a biliatresone-induced BA model.

METHODS

Using primary murine neonatal cholangiocytes in both 2D and 3D cultures, and ex-vivo extra hepatic bile ducts (EHBD) which also has peri-cholangiocyte area, we analyzed injury and recovery processes. Injury was induced by the toxin biliatresone and recovery was induced by toxin wash-out.

RESULTS

Microtubule stabilizer paclitaxel prevented biliatresone-induced injury, both to cholangiocytes as well as reduced periductal αSMA stain, this process is mediated by decreased glutathione levels. RhoU and Wnt11 (Wnt signaling) and Pard6g and Amotl1 (Hippo signaling) are involved in both injury and recovery processes, with the latter acting upstream to Wnt signaling.

CONCLUSIONS

Early stages of biliatresone-induced EHBD injury in cholangiocytes and periductal structures are reversible. Wnt and Hippo signaling pathways play crucial roles in injury and recovery, providing insights into BA injury mechanisms and potential recovery avenues.

IMPACT

Microtubule stabilization prevents cholangiocyte injury and lumen obstruction in a toxic model of biliary atresia (biliatresone induced). Early stages of biliatresone-induced injury, affecting both cholangiocytes and periductal structures, are reversible. Both Wnt and Hippo signaling pathways play a crucial role in bile duct injury and recovery, with a noted interplay between the two. Understanding mechanisms of cholangiocyte recovery is imperative to unveil potential therapeutic avenues.

Neuroprotective effects of cordycepin inhibit glutamate-induced apoptosis in hippocampal neurons

Glutamate is a neurotransmitter that can cause excitatory neurotoxicity when its extracellular concentration is too high, leading to disrupted calcium balance and increased production of reactive oxygen species (ROS). Cordycepin, a nucleoside adenosine derivative, has been shown to protect against excitatory neurotoxicity induced by glutamate. To investigate its potential neuroprotective effects, the present study employed fluorescence detection and spectrophotometry techniques to analyze primary hippocampal-cultured neurons. The results showed that glutamate toxicity reduced hippocampal neuron viability, increased ROS production, and increased intracellular calcium levels. Additionally, glutamate-induced cytotoxicity activated acetylcholinesterase and decreased glutathione levels. However, cordycepin inhibited glutamate-induced cell death, improved cell viability, reduced ROS production, and lowered Ca2+ levels. It also inhibited acetylcholinesterase activation and increased glutathione levels. This study suggests that cordycepin can protect against glutamate-induced neuronal injury in cell models, and this effect was inhibited by adenosine A1 receptor blockers, indicating that its neuroprotective effect is achieved through activation of the adenosine A1 receptor.

Adenosine Improves Mitochondrial Function and Biogenesis in Friedreich's Ataxia Fibroblasts Following L-Buthionine Sulfoximine-Induced Oxidative Stress

Adenosine is a nucleoside that is widely distributed in the central nervous system and acts as a central excitatory and inhibitory neurotransmitter in the brain. The protective role of adenosine in different pathological conditions and neurodegenerative diseases is mainly mediated by adenosine receptors. However, its potential role in mitigating the deleterious effects of oxidative stress in Friedreich's ataxia (FRDA) remains poorly understood. We aimed to investigate the protective effects of adenosine against mitochondrial dysfunction and impaired mitochondrial biogenesis in L-buthionine sulfoximine (BSO)-induced oxidative stress in dermal fibroblasts derived from an FRDA patient. The FRDA fibroblasts were pre-treated with adenosine for 2 h, followed by 12.50 mM BSO to induce oxidative stress. Cells in medium without any treatments or pre-treated with 5 µM idebenone served as the negative and positive controls, respectively. Cell viability, mitochondrial membrane potential (MMP), aconitase activity, adenosine triphosphate (ATP) level, mitochondrial biogenesis, and associated gene expressions were assessed. We observed disruption of mitochondrial function and biogenesis and alteration in gene expression patterns in BSO-treated FRDA fibroblasts. Pre-treatment with adenosine ranging from 0-600 µM restored MMP, promoted ATP production and mitochondrial biogenesis, and modulated the expression of key metabolic genes, namely nuclear respiratory factor 1 (NRF1), transcription factor A, mitochondrial (TFAM), and NFE2-like bZIP transcription factor 2 (NFE2L2). Our study demonstrated that adenosine targeted mitochondrial defects in FRDA, contributing to improved mitochondrial function and biogenesis, leading to cellular iron homeostasis. Therefore, we suggest a possible therapeutic role for adenosine in FRDA.

In Vitro Toxicological Investigation and Risk Assessment of E-Cigarette Aerosols Based on a Novel Solvent-Free Extraction Method

Cigarettes, potentially safer alternatives to combustible cigarettes, have been reported to increase the health risk for long-term users, so accumulating information about their potential toxicity is of great concern. However, toxicological evaluations of e-cigarette aerosols are limited, which may be attributed to the lack of a simple and efficient extraction method. Here, we developed a high-speed centrifugal method for extracting e-cigarette aerosol collected mass (ACM) and prepared ACM samples of 26 representative e-cigarettes, and 10 samples were further selected based on their cytotoxicity for systematic toxicological assessments. The average extraction efficiency of ACM, primary aerosol components, and typical carbonyls exceeded 85%. The toxicological evaluation showed that the IC₅₀ value range of e-cigarettes for cytotoxicity was 2-52 mg/mL ACM, all e-cigarettes can induce the risk of DNA damage, mitochondrial depolarization, and c-Jun-related signal disturbances; most e-cigarettes significantly caused disturbance of oxidative stress balance. E-cigarettes with higher cytotoxicity appeared to cause a higher degree of damage, while no e-cigarette promoted mutagenicity and cytochrome c release. The toxicity difference among e-cigarettes using nicotine equivalent was significantly lower than that of ACM. This study provides a novel extraction method and a comprehensive in vitro toxicity risk profile of e-cigarette aerosols.

The leaves of Scutellaria baicalensis Georgi attenuate brain aging in D-galactose-induced rats via regulating glutamate metabolism and Nrf2 signaling pathway

The present study aimed to evaluate the anti-aging effect of the leaves of Scutellaria baicalensis Georgi (LSBG) and investigate its mechanisms. For this purpose, SD rats were received D-galactose (D-gal) subcutaneously (0.3 g/kg) and LSBG intragastrically (0.4 g/kg or 0.8 g/kg) for 7 weeks. Behavior tests were conducted to evaluate the cognitive function of all rats. Results showed that memory impairment was reversed by LSBG. Then, metabolomics of the cortex and hippocampus were used to investigate the potential mechanisms. 21 metabolites in the cortex and 22 metabolites in the hippocampus of aging rats were altered, respectively. Additionally, results showed that the content of key metabolites and activities of enzymes in glutamate metabolism and its downstream metabolism (glutathione metabolism) could be regulated by the LSBG. Additionally, proteins in the Nrf2 signaling pathway were analyzed by western blot. And the protein expression levels of Nrf2, GCLC, HO-1, NQO-1 were significantly regulated by the LSBG in the cortex and hippocampus. Above all, the anti-aging effects of the LSBG were involved in regulating the glutamate metabolism and Nrf2 signaling pathway.

1-Nitropyrene exposure induces mitochondria dysfunction and impairs oocyte maturation in mice

Oocyte quality is essential for a successful pregnancy. 1-Nitropyrene (1-NP) is a widely distributed pollutant in the environment and is well-known for its mutagenicity and carcinogenicity. However, whether 1-NP has toxic effects on mammalian oocyte quality remains unknown. In the present study, we focused on the effect of 1-NP on oocyte maturation using mouse oocytes as an in vitro model. Our study showed that 1-NP exposure disrupted the meiotic spindle assembly and caused chromosome misalignment, further impaired first polar body extrusion, and significantly decreased the fertilization capability in mouse oocytes. Further investigation showed that the mitochondrial membrane potential (MMP) and ATP levels were decreased, and the expression of genes encoding components of the mitochondrial respiratory chain was inhibited in 1-NP exposed oocytes. Meanwhile, 1-NP exposure increased the levels of reactive oxygen species (ROS), inhibited the expression of genes encoding antioxidant enzymes, and increased the frequency of early apoptotic oocytes. Overall, our data suggest that 1-NP exposure disrupts mitochondrial function and intracellular redox balance, ultimately impairing oocyte maturation. These findings reveal the adverse effect of 1-NP exposure on oocyte quality.

BK Polyomavirus Activates HSF1 Stimulating Human Kidney Hek293 Cell Proliferation

Objectives

Some DNA viruses, such as BKPyV, are capable of inducing neoplastic transformation in human tissues through still unclear mechanisms. The goal of this study is to investigate the carcinogenic potential of BK polyomavirus (BKPyV) in human embryonic kidney 293 (Hek293) cells, dissecting the molecular mechanism that determines the neoplastic transformation.

Materials and Methods

BKPyV, isolated from urine samples of infected patients, was used to infect monolayers of Hek293 cells. Subsequently, intracellular redox changes, GSH/GSSH concentration by HPLC, and reactive oxygen/nitrogen species (ROS/RNS) production were monitored. Moreover, to understand the signaling pathway underlying the neoplastic transformation, the redox-sensitive HFS1-Hsp27 molecular axis was examined using the flavonoid quercetin and polishort hairpin RNA technologies.

Results

The data obtained show that while BKPyV replication is closely linked to the transcription factor p53, the increase in Hek293 cell proliferation is due to the activation of the signaling pathway mediated by HSF1-Hsp27. In fact, its inhibition blocks viral replication and cell growth, respectively.

Conclusions

The HSF1-Hsp27 signaling pathway is involved in BKPyV infection and cellular replication and its activation, which could be involved in cell transformation.

Imbalanced GSH/ROS and sequential cell death

Reactive oxygen species (ROS) are produced in cells during metabolic processes. Excessive intracellular ROS may react with large biomolecules, such as DNA, RNA, proteins, and small biomolecules, that is, glutathione (GSH) and unsaturated fatty acids. GSH has physiological functions, including free radical scavenging, anti-oxidation, and electrophile elimination. The disruption of ROS/GSH balance results in the deleterious oxidation and chemical modification of biomacromolecules, which eventually leads to cell-cycle arrest and proliferation inhibition, and even induces cell death. Imbalanced ROS/GSH may result from a direct increase of ROS, consumption of GSH, intracellular oxidoreductase interference, or thioredoxin activity reduction. Some chemicals including arsenic trioxide (ATO), pyrogallol (PG), and carbobenzoxy-Leu-Leu-leucinal (MG132) could also disrupt the balance of GSH and ROS. This article reviews the occurrence and consequences of the imbalance between GSH and ROS and introduces factors responsible for the disruption of cellular ROS and GSH balance, resulting in cell death. "GSH" and "ROS" were used as keywords to search the relevant literaturess.

Oleuropein Aglycone Peracetylated (3,4-DHPEA-EA(P)) Attenuates H2O2-Mediated Cytotoxicity in C2C12 Myocytes via Inactivation of p-JNK/p-c-Jun Signaling Pathway

Oleuropein, a glycosylated secoiridoid present in olive leaves, is known to be an important antioxidant phenolic compound. We studied the antioxidant effect of low doses of oleuropein aglycone (3,4-DHPEA-EA) and oleuropein aglycone peracetylated (3,4-DHPEA-EA(P)) in murine C2C12 myocytes treated with hydrogen peroxide (H₂O₂). Both compounds were used at a concentration of 10 μM and were able to inhibit cell death induced by the H₂O₂ treatment, with 3,4-DHPEA-EA(P) being more. Under our experimental conditions, H₂O₂ efficiently induced the phosphorylated-active form of JNK and of its downstream target c-Jun. We demonstrated, by Western blot analysis, that 3,4-DHPEA-EA(P) was efficient in inhibiting the phospho-active form of JNK. This data suggests that the growth arrest and cell death of C2C12 proceeds via the JNK/c-Jun pathway. Moreover, we demonstrated that 3,4-DHPEA-EA(P) affects the myogenesis of C2C12 cells; because MyoD mRNA levels and the differentiation process are restored with 3,4-DHPEA-EA(P) after treatment. Overall, the results indicate that 3,4-DHPEA-EA(P) prevents ROS-mediated degenerative process by functioning as an efficient antioxidant.

Ultra-Endurance Associated With Moderate Exercise in Rats Induces Cerebellar Oxidative Stress and Impairs Reactive GFAP Isoform Profile

Ultra-endurance (UE) race has been associated with brain metabolic changes, but it is still unknown which regions are vulnerable. This study investigated whether high-volume training in rodents, even under moderate intensity, can induce cerebellar oxidative and inflammatory status. Forty-five adult rats were divided into six groups according to a training period, followed or not by an exhaustion test (ET) that simulated UE: control (C), control + ET (C-ET), moderate-volume (MV) training and MV-ET, high-volume training (HV) and HV-ET. The training period was 30 (MV) and 90 (HV) min/day, 5 times/week for 3 months as a continuous running on a treadmill at a maximum velocity of 12 m/min. After 24 h, the ET was performed at 50% maximum velocities up to the animals refused to run, and then serum lactate levels were evaluated. Serum and cerebellar homogenates were obtained 24 h after ET. Serum creatine kinase (CK), lactate dehydrogenase (LDH), and corticosterone levels were assessed. Lipid peroxidation (LP), nitric oxide (NO), Interleukin 1β (IL-1β), and GFAP proteins, reduced and oxidized glutathione (GSH and GSSG) levels, superoxide dismutase (SOD) and catalase (CAT) activities were quantified in the cerebellum. Serum lactate concentrations were lower in MV-ET (∼20%) and HV-ET (∼40%) compared to the C-ET group. CK and corticosterone levels were increased more than ∼ twofold by HV training compared to control. ET increased CK levels in MV-ET vs. MV group (P = 0.026). HV induced higher LP levels (∼40%), but an additive effect of ET was only seen in the MV-ET group (P = 0.02). SOD activity was higher in all trained groups vs. C and C-ET (P < 0.05). CAT activity, however, was intensified only in the MV group (P < 0.02). The 50 kDa GFAP levels were enhanced in C-ET and MV-ET vs. respective controls, while 42 kDa (∼40%) and 39 kDa (∼26%) isoform levels were reduced. In the HV-ET group, the 50 KDa isoform amount was reduced ∼40-60% compared to the other groups and the 39 KDa isoform, increased sevenfold. LDH levels, GSH/GSSG ratio, and NO production were not modified. ET elevated IL-1β levels in the CT and MV groups. Data shows that cerebellar resilience to oxidative damage may be maintained under moderate-volume training, but it is reduced by UE running. High-volume training per se provoked systemic metabolic changes, cerebellar lipid peroxidation, and unbalanced enzymatic antioxidant resource. UE after high-volume training modified the GFAP isoform profile suggesting impaired astrocyte reactivity in the cerebellum.

Supplementation with a putative calorie restriction mimetic micronutrient blend increases glutathione concentrations and improves neuroenergetics in brain of healthy middle-aged men and women

BACKGROUND

Caloric restriction (CR) without micronutrient deficiency has been shown to increase both lifespan and healthspan. In animals, CR has been demonstrated to increase glutathione (GSH), a neuroprotective antioxidant, in the brain and preserve brain mitochondrial function by altering neuroenergetics. In humans it has been associated with improvements in mood states and cognitive function. However, most CR studies have employed a 30-60% reduction in calories which is likely too stringent for most people to adhere to long-term. Thus, there is an unmet need for nutritional supplements which can mimic the biological effects of CR, without the need for calorie limitations.

AIM

The purpose of the present randomized, placebo-controlled clinical trial was to use Proton (¹H) Magnetic Resonance Spectroscopic (MRS) measurements to determine non-invasively whether a blend of micronutrients, a putative CR mimetic, positively modulates metabolites related to neuroprotection and neuroenergetics in the brain.

METHODS

Healthy middle-aged men and women (N = 63 [33 women]; age: 40-60 years) were randomized in a double-blind manner to 6 weeks supplementation with either the putative CR mimetic or placebo. At baseline and 6 weeks, subjects underwent MRS at 3 T to investigate changes in brain chemistry, including the neurometabolites: GSH, Glutamate (Glu), Glutamine (Gln) and N-Acetylaspartate (NAA).

RESULTS

GSH, a marker of antioxidant and cellular redox status, increased in the brain of participants in the supplement group. The supplement group also showed an increase in the Glu/Gln ratio, a marker of excitatory neurotransmission and bioenergetics. A trend for an increase in NAA/H₂O, a marker of neuronal integrity, was observed in females in the supplement group.

CONCLUSIONS

The present study reveals that 6-weeks daily supplementation with a micronutrient blend elicits positive changes in brain neurochemistry. This is the first study to demonstrate that a putative CR mimetic increases brain GSH concentrations and improves neuroprotection and neuroenergetics in the brain of healthy humans. This study was registered at www.clinicaltrials.gov as NCT02439983.

Extrahepatic cholangiocyte obstruction is mediated by decreased glutathione, Wnt and Notch signaling pathways in a toxic model of biliary atresia

Biliary atresia is a neonatal liver disease with extrahepatic bile duct obstruction and progressive liver fibrosis. The etiology and pathogenesis of the disease are unknown. We previously identified a plant toxin, biliatresone, responsible for biliary atresia in naturally-occurring animal models, that causes cholangiocyte destruction in in-vitro models. Decreases in reduced glutathione (GSH) mimic the effects of biliatresone, and agents that replenish cellular GSH ameliorate the effects of the toxin. The goals of this study were to define signaling pathways downstream of biliatresone that lead to cholangiocyte destruction and to determine their relationship to GSH. Using cholangiocyte culture and 3D cholangiocyte spheroid cultures, we found that biliatresone and decreases in GSH upregulated RhoU/Wrch1, a Wnt signaling family member, which then mediated an increase in Hey2 in the NOTCH signaling pathway, causing downregulation of the transcription factor Sox17. When these genes were up- or down-regulated, the biliatresone effect on spheroids was phenocopied, resulting in lumen obstruction. Biopsies of patients with biliary atresia demonstrated increased RhoU/Wrch1 and Hey2 expression in cholangiocytes. We present a novel pathway of cholangiocyte injury in a model of biliary atresia, which is relevant to human BA and may suggest potential future therapeutics.

Glutathione and Nitric Oxide: Key Team Players in Use and Disuse of Skeletal Muscle

Glutathione (GSH) is the main non-enzymatic antioxidant playing an important role in detoxification, signal transduction by modulation of protein thiols redox status and direct scavenging of radicals. The latter function is not only performed against reactive oxygen species (ROS) but GSH also has a fundamental role in buffering nitric oxide (NO), a physiologically-produced molecule having-multifaceted functions. The efficient rate of GSH synthesis and high levels of GSH-dependent enzymes are characteristic features of healthy skeletal muscle where, besides the canonical functions, it is also involved in muscle contraction regulation. Moreover, NO production in skeletal muscle is a direct consequence of contractile activity and influences several metabolic myocyte pathways under both physiological and pathological conditions. In this review, we will consider the homeostasis and intersection of GSH with NO and then we will restrict the discussion on their role in processes related to skeletal muscle function and degeneration.

Origin and pathophysiology of protein carbonylation, nitration and chlorination in age-related brain diseases and aging

Non-enzymatic protein modifications occur inevitably in all living systems. Products of such modifications accumulate during aging of cells and organisms and may contribute to their age-related functional deterioration. This review presents the formation of irreversible protein modifications such as carbonylation, nitration and chlorination, modifications by 4-hydroxynonenal, removal of modified proteins and accumulation of these protein modifications during aging of humans and model organisms, and their enhanced accumulation in age-related brain diseases.

Xyloketal derivative C53N protects against mild traumatic brain injury in mice

Purpose

Mild traumatic brain injury (mTBI), the most common type of TBI, can result in prolonged cognitive impairment, mood disorders, and behavioral problems. Reducing oxidative stress and inflammation can rescue the neurons from mTBI-induced cell death. Xyloketal B, a natural product from mangrove fungus, has shown good antioxidative and neuroprotective effects in several disease models. Here, we investigated the potential protection afforded by a xyloketal derivative, C53N, in a closed-skull mTBI model.

Materials and methods

Skulls of mice were thinned to 20–30 µm thickness, following which they were subjected to a slight compression injury to induce mTBI. One hour after TBI, mice were intraperitoneally injected with C53N, which was solubilized in 0.5% dimethyl sulfoxide in saline. In vivo two-photon laser scanning microscopy was used to image cell death in injured parenchyma in each mouse over a 12-hour period (at 1, 3, 6, and 12 hours). Water content and oxidation index, together with pathological analysis of glial reactivity, were assessed at 24 hours to determine the effect of C53N on mTBI.

Results

Cell death, oxidative stress, and glial reactivity increased in mTBI mice compared with sham-injured mice. Treatment with 40 or 100 mg/kg C53N 1 hour after mTBI significantly attenuated oxidative stress and glial reactivity and reduced parenchymal cell death at the acute phase after mTBI.

Conclusion

The present study highlights the therapeutic potential of the xyloketal derivative C53N for pharmacological intervention in mTBI.

S-nitrosylation drives cell senescence and aging in mammals by controlling mitochondrial dynamics and mitophagy

S-nitrosylation, a prototypic redox-based posttranslational modification, is frequently dysregulated in disease. S-nitrosoglutathione reductase (GSNOR) regulates protein S-nitrosylation by functioning as a protein denitrosylase. Deficiency of GSNOR results in tumorigenesis and disrupts cellular homeostasis broadly, including metabolic, cardiovascular, and immune function. Here, we demonstrate that GSNOR expression decreases in primary cells undergoing senescence, as well as in mice and humans during their life span. In stark contrast, exceptionally long-lived individuals maintain GSNOR levels. We also show that GSNOR deficiency promotes mitochondrial nitrosative stress, including excessive S-nitrosylation of Drp1 and Parkin, thereby impairing mitochondrial dynamics and mitophagy. Our findings implicate GSNOR in mammalian longevity, suggest a molecular link between protein S-nitrosylation and mitochondria quality control in aging, and provide a redox-based perspective on aging with direct therapeutic implications.

Adipose triglyceride lipase decrement affects skeletal muscle homeostasis during aging through FAs-PPARα-PGC-1α antioxidant response

During aging skeletal muscle shows an accumulation of oxidative damage as well as intramyocellular lipid droplets (IMLDs). However, although the impact of these modifications on muscle tissue physiology is well established, the direct effectors critical for their occurrence are poorly understood. Here we show that during aging the main lipase of triacylglycerols, ATGL, significantly declines in gastrocnemius and its downregulation in C2C12 myoblast leads to the accumulation of lipid droplets. Indeed, we observed an increase of oxidative damage to proteins in terms of carbonylation, S-nitrosylation and ubiquitination that is dependent on a defective antioxidant cell response mediated by ATGL-PPARα-PGC-1α. Overall our findings describe a pivotal role for ATGL in the antioxidant/anti-inflammatory response of muscle cells highlighting this lipase as a therapeutic target for fighting the progressive decline in skeletal muscle mass and strength.

Taurine treatment prevents derangement of the hepatic γ-glutamyl cycle and methylglyoxal metabolism in a mouse model of classical homocystinuria: regulatory crosstalk between thiol and sulfinic acid metabolism

Cystathionine β-synthase-deficient homocystinuria (HCU) is a poorly understood, life-threatening inborn error of sulfur metabolism. Analysis of hepatic glutathione (GSH) metabolism in a mouse model of HCU demonstrated significant depletion of cysteine, GSH, and GSH disulfide independent of the block in trans-sulfuration compared with wild-type controls. HCU induced the expression of the catalytic and regulatory subunits of γ-glutamyl ligase, GSH synthase (GS), γ-glutamyl transpeptidase 1, 5-oxoprolinase (OPLAH), and the GSH-dependent methylglyoxal detoxification enzyme, glyoxalase-1. Multiple components of the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-mediated antioxidant-response regulatory axis were induced without any detectable activation of Nrf2. Metabolomic analysis revealed the accumulation of multiple γ-glutamyl amino acids and that plasma ophthalmate levels could serve as a noninvasive marker for hepatic redox stress. Neither cysteine, nor betaine treatment was able to reverse the observed enzyme inductions. Taurine treatment normalized the expression levels of γ-glutamyl ligase C/M, GS, OPLAH, and glyoxalase-1, and reversed HCU-induced deficits in protein glutathionylation by acting to double GSH levels relative to controls. Collectively, our data indicate that the perturbation of the γ-glutamyl cycle could contribute to multiple sequelae in HCU and that taurine has significant therapeutic potential for both HCU and other diseases for which GSH depletion is a critical pathogenic factor.-Maclean, K. N., Jiang, H., Aivazidis, S., Kim, E., Shearn, C. T., Harris, P. S., Petersen, D. R., Allen, R. H., Stabler, S. P., Roede, J. R. Taurine treatment prevents derangement of the hepatic γ-glutamyl cycle and methylglyoxal metabolism in a mouse model of classical homocystinuria: regulatory crosstalk between thiol and sulfinic acid metabolism.

A systematic review of p53 regulation of oxidative stress in skeletal muscle

Background: p53 is a tumor suppressor protein involved in regulating a wide array of signaling pathways. The role of p53 in the cell is determined by the type of imposed oxidative stress, its intensity and duration. The last decade of research has unravelled a dual nature in the function of p53 in mediating the oxidative stress burden. However, this is dependent on the specific properties of the applied stress and thus requires further analysis.

Methods: A systematic review was performed following an electronic search of Pubmed, Google Scholar, and ScienceDirect databases. Articles published in the English language between January 1, 1990 and March 1, 2017 were identified and isolated based on the analysis of p53 in skeletal muscle in both animal and cell culture models.

Results: Literature was categorized according to the modality of imposed oxidative stress including exercise, diet modification, exogenous oxidizing agents, tissue manipulation, irradiation, and hypoxia. With low to moderate levels of oxidative stress, p53 is involved in activating pathways that increase time for cell repair, such as cell cycle arrest and autophagy, to enhance cell survival. However, with greater levels of stress intensity and duration, such as with irradiation, hypoxia, and oxidizing agents, the role of p53 switches to facilitate increased cellular stress levels by initiating DNA fragmentation to induce apoptosis, thereby preventing aberrant cell proliferation.

Conclusion: Current evidence confirms that p53 acts as a threshold regulator of cellular homeostasis. Therefore, within each modality, the intensity and duration are parameters of the oxidative stressor that must be analyzed to determine the role p53 plays in regulating signaling pathways to maintain cellular health and function in skeletal muscle.

Abbreviations: Acadl: acyl-CoA dehydrogenase, long chain; Acadm: acyl-CoA dehydrogenase, C-4 to C-12 straight chain; AIF: apoptosis-inducing factor; Akt: protein kinase B (PKB); AMPK: AMP-activated protein kinase; ATF-4: activating transcription factor 4; ATM: ATM serine/threonine kinase; Bax: BCL2 associated X, apoptosis regulator; Bcl-2: B cell Leukemia/Lymphoma 2 apoptosis regulator; Bhlhe40: basic helix-loop-helix family member e40; BH3: Borane; Bim: bcl-2 interacting mediator of cell death; Bok: Bcl-2 related ovarian killer; COX-IV: cytochrome c oxidase IV; cGMP: Cyclic guanosine monophosphate; c-myc: proto-oncogene protein; Cpt1b: carnitine palmitoyltransferase 1B; Dr5: death receptor 5; eNOS: endothelial nitric oxide synthase; ERK: extracellular regulated MAP kinase; Fas: Fas Cell surface death receptor; FDXR: Ferredoxin Reductase; FOXO3a: forkhead box O3; Gadd45a: growth arrest and DNA damage-inducible 45 alpha; GLS2: glutaminase 2; GLUT 1 and 4: glucose transporter 1(endothelial) and 4 (skeletal muscle); GSH: Glutathione; Hes1: hes family bHLH transcription factor 1; Hey1: hes related family bHLH transcription factor with YRPW motif 1; HIFI-α: hypoxia-inducible factor 1, α-subunit; HK2: Hexokinase 2; HSP70: Heat Shock Protein 70; H₂O₂: Hydrogen Peroxide; Id2: inhibitor of DNA-binding 2; IGF-1-BP3: Insulin-like growth factor binding protein 3; IL-1β: Interleukin 1 beta; iNOS: inducible nitric oxide synthase; IRS-1: Insulin receptor substrate 1; JNK: c-Jun N-terminal kinases; LY-83583: 6-anilino-5,8-quinolinedione; inhibitor of soluble guanylate cyclase and of cGMP production; Mdm 2/ 4: Mouse double minute 2 homolog (mouse) Mdm4 (humans); mtDNA: mitochondrial DNA; MURF1: Muscle RING-finger protein-1; MyoD: Myogenic differentiation 1; MyoG: myogenin; Nanog: Nanog homeobox; NF-kB: Nuclear factor-κB; NO: nitric oxide; NoxA: phorbol-12-myristate-13-acetate-induced protein 1 (Pmaip1); NRF-1: nuclear respiratory factor 1; Nrf2: Nuclear factor erythroid 2-related factor 2; P21: Cdkn1a cyclin-dependent kinase inhibitor 1A (P21); P38 MAPK: mitogen-activated protein kinases; p53R2: p53 inducible ribonucleotide reductase gene; P66Shc: src homology 2 domain-containing transforming protein C1; PERP: p53 apoptosis effector related to PMP-22; PGC-1α: Peroxisome proliferator-activated receptor gamma coactivator 1-alpha; PGM: phosphoglucomutase; PI3K: Phosphatidylinositol-4,5-bisphosphate 3-kinase; PKCβ: protein kinase c beta; PTEN: phosphatase and tensin homolog; PTIO: 2-phenyl-4, 4, 5, 5,-tetramethylimidazoline-1-oxyl 3-oxide (PTIO) has been used as a nitric oxide (NO) scavenger; Puma: The p53 upregulated modulator of apoptosis; PW1: paternally expressed 3 (Peg3); RNS: Reactive nitrogen species; SIRT1: sirtuin 1; SCO2: cytochrome c oxidase assembly protein; SOD2: superoxide dismutase 2; Tfam: transcription factor A mitochondrial; TIGAR: Trp53 induced glycolysis repulatory phosphatase; TNF-a: tumor necrosis factor a; TRAF2: TNF receptor associated factor 2; TRAIL: type II transmembrane protein.

Altered S-nitrosylation of p53 is responsible for impaired antioxidant response in skeletal muscle during aging

p53 transcriptional activity has been proposed to regulate both homeostasis and sarcopenia of skeletal muscle during aging. However, the exact molecular function of p53 remains to be clearly defined. We demonstrated a requirement of nuclear p53 S-nitrosylation in inducing a nitric oxide/PGC-1α-mediated antioxidant pathway in skeletal muscle. Importantly, mutant form of p53-DNA binding domain (C124S) did not undergo nuclear S-nitrosylation and failed in inducing the expression of antioxidant genes (i.e. SOD2 and GCLC). Moreover, we found that during aging the nuclear S-nitrosylation of p53 significantly declines in gastrocnemius/soleus leading to an impairment of redox homeostasis of skeletal muscle. We suggested that decreased level of nuclear neuronal nitric oxide synthase (nNOS)/Syntrophin complex, which we observed during aging, could be responsible for impaired nuclear S-nitrosylation. Taken together, our data indicate that altered S-nitrosylation of p53 during aging could be a contributing factor of sarcopenia condition and of other skeletal muscle pathologies associated with oxidative/nitrosative stress.

N-Methyl-D aspartate receptor-mediated effect on glucose transporter-3 levels of high glucose exposed-SH-SY5Y dopaminergic neurons

High glucose and insulin lead to neuronal insulin resistance. Glucose transport into the neurons is achieved by regulatory induction of surface glucose transporter-3 (GLUT3) instead of the insulin. N-methyl-D aspartate (NMDA) receptor activity increases GLUT3 expression. This study explored whether an endogenous NMDA receptor antagonist, kynurenic acid (KynA) affects the neuronal cell viability at high glucose concentrations. SH-SY5Y neuroblastoma cells were exposed to 150-250 mg/dL glucose and 40 μU/mL insulin. In KynA and N-nitro-l-arginine methyl ester (L-NAME) supplemented cultures, oxidative stress, mitochondrial metabolic activity (MTT), nitric oxide as nitrite+nitrate (NOx) and GLUT3 were determined at the end of 24 and 48-h incubation periods. Viable cells were counted by trypan blue dye. High glucose-exposed SH-SY5Y cells showed two-times more GLUT3 expression at second 24-h period. While GLUT3-stimulated glucose transport and oxidative stress was increased, total mitochondrial metabolic activity was significantly reduced. Insulin supplementation to high glucose decreased NOx synthesis and GLUT3 levels, in contrast oxidative stress increased three-fold. KynA significantly reduced oxidative stress, and increased MTT by regulating NOx production and GLUT3 expression. KynA is a noteworthy compound, as an endogenous, specific NMDA receptor antagonist; it significantly reduces oxidative stress, while increasing cell viability at high glucose and insulin concentrations.

The toxin biliatresone causes mouse extrahepatic cholangiocyte damage and fibrosis through decreased glutathione and SOX17

Biliary atresia, the most common indication for pediatric liver transplantation, is a fibrotic disease of unknown etiology affecting the extrahepatic bile ducts of newborns. The recently described toxin biliatresone causes lumen obstruction in mouse cholangiocyte spheroids and represents a new model of biliary atresia. The goal of this study was to determine the cellular changes caused by biliatresone in mammalian cells that ultimately lead to biliary atresia and extrahepatic fibrosis. We treated mouse cholangiocytes in three-dimensional (3D) spheroid culture and neonatal extrahepatic duct explants with biliatresone and compounds that regulate glutathione (GSH). We examined the effects of biliatresone on SOX17 levels and determined the effects of Sox17 knockdown on cholangiocytes in 3D culture. We found that biliatresone caused disruption of cholangiocyte apical polarity and loss of monolayer integrity. Spheroids treated with biliatresone had increased permeability as shown by rhodamine efflux within 5 hours compared with untreated spheroids, which retained rhodamine for longer than 12 hours. Neonatal bile duct explants treated with the toxin showed lumen obstruction with increased subepithelial staining for α-smooth muscle actin and collagen, consistent with fibrosis. Biliatresone caused a rapid and transient decrease in GSH, which was both necessary and sufficient to mediate its effects in cholangiocyte spheroid and bile duct explant systems. It also caused a significant decrease in cholangiocyte levels of SOX17, and Sox17 knockdown in cholangiocyte spheroids mimicked the effects of biliatresone.

CONCLUSION

Biliatresone decreases GSH and SOX17 in mouse cholangiocytes. In 3D cell systems, this leads to cholangiocyte monolayer damage and increased permeability; in extrahepatic bile duct explants, it leads to disruption of the extrahepatic biliary tree and subepithelial fibrosis. This mechanism may be important in understanding human biliary atresia. (Hepatology 2016;64:880-893).

Vitamin E, γ-tocotrienol, Protects Against Buthionine Sulfoximine-Induced Cell Death by Scavenging Free Radicals in SH-SY5Y Neuroblastoma Cells

The induction of reactive oxygen species (ROS) to selectively kill cancer cells is an important feature of radiotherapy and various chemotherapies. Depletion of glutathione can induce apoptosis in cancer cells or sensitize them to anticancer treatments intended to modulate ROS levels. In contrast, antioxidants protect cancer cells from oxidative stress-induced cell death by scavenging ROS. The role of exogenous antioxidants in cancer cells under oxidative insults remains controversial and unclear. This study aimed to identify protective pathways modulated by γ-tocotrienol (γT3), an isomer of vitamin E, in human neuroblastoma SH-SY5Y cells under oxidative stress. Using buthionine sulfoximine (BSO) as an inhibitor of glutathione synthesis, we found that BSO treatment reduced the viability of SH-SY5Y cells. BSO induced cell death by increasing apoptosis, decreased the level of reduced glutathione (GSH), and increased ROS levels in SH-SY5Y cells. Addition of γT3 increased the viability of BSO-treated cells, suppressed apoptosis, and decreased the ROS level induced by BSO, while the GSH level was unaffected. These results suggest that decreasing GSH levels by BSO increased ROS levels, leading to apoptosis in SH-SY5Y cells. γT3 attenuated the BSO-induced cell death by scavenging free radicals.

Involvement of Inositol Biosynthesis and Nitric Oxide in the Mediation of UV-B Induced Oxidative Stress

The involvement of NO-signaling in ultraviolet B (UV-B) induced oxidative stress (OS) in plants is an open question. Inositol biosynthesis contributes to numerous cellular functions, including the regulation of plants tolerance to stress. This work reveals the involvement of inositol-3-phosphate synthase 1 (IPS1), a key enzyme for biosynthesis of myo-inositol and its derivatives, in the response to NO-dependent OS in Arabidopsis. Homozygous mutants deficient for IPS1 (atips1) and wild-type plants were transformed with a reduction- grx1-rogfp2 and used for the dynamic measurement of UV-B-induced and SNP (sodium nitroprusside)-mediated oxidative stresses by confocal microscopy. atips1 mutants displayed greater tissue-specific resistance to the action of UV-B than the wild type. SNP can act both as an oxidant or repairer depending on the applied concentration, but mutant plants were more tolerant than the wild type to nitrosative effects of high concentration of SNP. Additionally, pretreatment with low concentrations of SNP (10, 100 μM) before UV-B irradiation resulted in a tissue-specific protective effect that was enhanced in atips1. We conclude that the interplay between nitric oxide and inositol signaling can be involved in the mediation of UV-B-initiated oxidative stress in the plant cell.

The cellular and genomic response of rat dopaminergic neurons (N27) to coated nanosilver

This study examined if nanosilver (nanoAg) of different sizes and coatings were differentially toxic to oxidative stress-sensitive neurons. N27 rat dopaminergic neurons were exposed (0.5-5 ppm) to a set of nanoAg of different sizes (10nm, 75 nm) and coatings (PVP, citrate) and their physicochemical, cellular and genomic response measured. Both coatings retained their manufactured sizes in culture media, however, the zeta potentials of both sizes of PVP-coated nanoAg were significantly less electronegative than those of their citrate-coated counterparts. Markers of oxidative stress, measured at 0.5-5 ppm exposure concentrations, indicated that caspase 3/7 activity and glutathione levels were significantly increased by both sizes of PVP-coated nanoAg and by the 75 nm citrate-coated nanoAg. Both sizes of PVP-coated nanoAg also increased intra-neuronal nitrite levels and activated ARE/NRF2, a reporter gene for the oxidative stress-protection pathway. Global gene expression on N27 neurons, exposed to 0.5 ppm for 8h, indicated a dominant effect by PVP-coated nanoAg over citrate. The 75 nm PVP-coated material altered 196 genes that were loosely associated with mitochondrial dysfunction. In contrast, the 10nm PVP-coated nanoAg altered 82 genes that were strongly associated with NRF2 oxidative stress pathways. Less that 20% of the affected genes were shared by both sizes of PVP-coated nanoAg. These cellular and genomic findings suggest that PVP-coated nanoAg is more bioactive than citrate-coated nanoAg. Although both sizes of PVP-coated nanoAg altered the genomic expression of N27 neurons along oxidative stress pathways, exposure to the 75 nm nanoAg favored pathways associated with mitochondrial dysfunction, whereas the 10nm PVP-coated nanoAg affected NRF2 neuronal protective pathways.

Glutathione: new roles in redox signaling for an old antioxidant

The physiological roles played by the tripeptide glutathione have greatly advanced over the past decades superimposing the research on free radicals, oxidative stress and, more recently, redox signaling. In particular, GSH is involved in nutrient metabolism, antioxidant defense, and regulation of cellular metabolic functions ranging from gene expression, DNA and protein synthesis to signal transduction, cell proliferation and apoptosis. This review will be focused on the role of GSH in cell signaling by analysing the more recent advancements about its capability to modulate nitroxidative stress, autophagy, and viral infection.

Short time exposure to hydrogen peroxide induces sustained glutathione export from cultured neurons

Hydrogen peroxide is a normal by-product of cellular metabolism that in higher concentrations can cause oxidative stress. Cultured cerebellar granule neurons efficiently disposed of micromolar concentrations of hydrogen peroxide with half-times in the minute range in a process that predominately involved catalase. Application of up to 100 µM hydrogen peroxide did not affect the cell viability for up to 4h, but caused a time- and concentration-dependent increase in the extracellular glutathione (GSH) content that was accompanied by a matching decrease in the cellular GSH content. Hydrogen peroxide at 100 µM stimulated maximally the GSH export from viable neurons, but did not affect GSH export from cultured astrocytes. The peroxide-induced extracellular GSH accumulation from neurons was lowered by 70% in the presence of MK571, an inhibitor of multidrug resistance protein (Mrp) 1. The extracellular GSH content determined after 4h of incubation was already significantly increased after a 5-min exposure of neurons to hydrogen peroxide and became maximal after 15 min of peroxide application. These data demonstrate that just a short exposure of viable cerebellar granule neurons to micromolar concentrations of hydrogen peroxide stimulates a prolonged Mrp1-mediated export of cellular GSH. This process may compromise the antioxidative potential of neurons and increase their sensitivity toward drugs and toxins.

Protective effects of phosphodiesterase 2 inhibitor on depression- and anxiety-like behaviors: involvement of antioxidant and anti-apoptotic mechanisms

Stress occurs in everyday life, but the relationship between stress and the onset or development of depression/anxiety remains unknown. Increasing evidence suggests that the impairment of antioxidant defense and the neuronal cell death are important in the process of emotional disorders. Chronic stress impairs the homeostasis of antioxidants/oxidation, which results in the aberrant stimulation of the cell cycle proteins where cGMP-PKG signaling is thought to have an inhibitory role. Phosphodiesterase 2 (PDE2) is linked to cGMP-PKG signaling and highly expressed in the limbic brain regions including hippocampus and amygdala, which may play important roles in the treatment of depression and anxiety. To address the possible effects of PDE2 inhibitors on depression-/anxiety-like behaviors and the underlying mechanisms, Bay 60-7550 (0.75, 1.5 and 3 mg/kg, i.p.) was administered 30 min before chronic stress. The results suggested that Bay 60-7550 not only restored the behavioral changes but also regulated Cu/Zn superoxide dismutase (SOD) levels differentially in hippocampus and amygdala, which were increased in the hippocampus while decreased in the amygdala. It was also significant that Bay 60-7550 regulated the abnormalities of pro- and anti-apoptotic components, such as Bax, Caspase 3 and Bcl-2, and the indicator of PKG signaling characterized by pVASP(ser239), in these two brain regions. The results suggested that Bay 60-7550 is able to alleviate oxidative stress and mediate part of the apoptotic machinery in neuronal cells possibly through SOD-cGMP/PKG-anti-apoptosis signaling and that inhibition of PDE2 may represent a novel therapeutic target for psychiatric disorders, such as depression and anxiety.

The role of nNOS and PGC-1α in skeletal muscle cells

Neuronal nitric oxide synthase (nNOS) and peroxisome proliferator activated receptor γ co-activator 1α (PGC-1α) are two fundamental factors involved in the regulation of skeletal muscle cell metabolism. nNOS exists as several alternatively spliced variants, each having a specific pattern of subcellular localisation. Nitric oxide (NO) functions as a second messenger in signal transduction pathways that lead to the expression of metabolic genes involved in oxidative metabolism, vasodilatation and skeletal muscle contraction. PGC-1α is a transcriptional coactivator and represents a master regulator of mitochondrial biogenesis by promoting the transcription of mitochondrial genes. PGC-1α can be induced during physical exercise, and it plays a key role in coordinating the oxidation of intracellular fatty acids with mitochondrial remodelling. Several lines of evidence demonstrate that NO could act as a key regulator of PGC-1α expression; however, the link between nNOS and PGC-1α in skeletal muscle remains only poorly understood. In this Commentary, we review important metabolic pathways that are governed by nNOS and PGC-1α, and aim to highlight how they might intersect and cooperatively regulate skeletal muscle mitochondrial and lipid energetic metabolism and contraction.

Temporal and spatial increase of reactive nitrogen species in the kainate model of temporal lobe epilepsy

Steady-state levels of reactive oxygen species (ROS) and oxidative damage to cellular macromolecules are increased in the rodent hippocampus during epileptogenesis. However, the role of reactive nitrogen species (RNS) in epileptogenesis remains to be explored. The goal of this study was to determine the spatial and temporal occurrence of RNS i.e. nitric oxide levels in a rat model of temporal lobe epilepsy (TLE). Rats were injected with a single high dose of kainate and monitored by video for behavioral seizures for 6weeks to determine the onset and severity of chronic seizures. RNS and tissue/mitochondrial redox status (glutathione redox couple and coenzyme A:glutathione redox couple) were measured in the hippocampus at 8h, 24h, 48h, 1wk, 3wk and 6wk following kainate to assess the level of reactive species in subcellular compartments. We observed a biphasic increase in RNS levels with a return to control values at the 48h time point. However, both tissue and mitochondrial redox status showed permanent and significant decreases during the entire time course of epilepsy development. 3 nitrotyrosine (3NT) protein adducts were found to gradually increase throughout epileptogenesis, conceivably as a result of the local environment under oxidative and nitrosative stress. Colocalization of 3NT immunostaining with neuron- or astrocyte-specific markers revealed neuron-specific localization of 3NT in hippocampal principal neurons. Persistent and concurrent glutathione oxidation and nitrosative stress occur during epileptogenesis suggesting a favorable environment for posttranslational modifications.

Nuclear recruitment of neuronal nitric-oxide synthase by α-syntrophin is crucial for the induction of mitochondrial biogenesis

Neuronal nitric-oxide synthase (nNOS) has various splicing variants and different subcellular localizations. nNOS can be found also in the nucleus; however, its exact role in this compartment is still not completely defined. In this report, we demonstrate that the PDZ domain allows the recruitment of nNOS to nuclei, thus favoring local NO production, nuclear protein S-nitrosylation, and induction of mitochondrial biogenesis. In particular, overexpression of PDZ-containing nNOS (nNOSα) increases S-nitrosylated CREB with consequent augmented binding on cAMP response element consensus sequence on peroxisome proliferator-activated receptor γ co-activator (PGC)-1α promoter. The resulting PGC-1α induction is accompanied by the expression of mitochondrial genes (e.g., TFAM, MtCO1) and increased mitochondrial mass. Importantly, full active nNOS lacking PDZ domain (nNOSβ) does not localize in nuclei and fails in inducing the expression of PGC-1α. Moreover, we substantiate that the mitochondrial biogenesis normally accompanying myogenesis is associated with nuclear translocation of nNOS. We demonstrate that α-Syntrophin, which resides in nuclei of myocytes, functions as the upstream mediator of nuclear nNOS translocation and nNOS-dependent mitochondrial biogenesis. Overall, our results indicate that altered nNOS splicing and nuclear localization could be contributing factors in human muscular diseases associated with mitochondrial impairment.

Glutathione metabolism and Parkinson's disease

It has been established that oxidative stress, defined as the condition in which the sum of free radicals in a cell exceeds the antioxidant capacity of the cell, contributes to the pathogenesis of Parkinson disease. Glutathione is a ubiquitous thiol tripeptide that acts alone or in concert with enzymes within cells to reduce superoxide radicals, hydroxyl radicals, and peroxynitrites. In this review, we examine the synthesis, metabolism, and functional interactions of glutathione and discuss how these relate to the protection of dopaminergic neurons from oxidative damage and its therapeutic potential in Parkinson disease.

Arginine increases genotoxicity induced by methyl methanesulfonate in human lymphocytes

Nitric oxide (NO) is a free radical that is produced in cells from L-arginine. NO is involved in the physiological control of different tissues, but it can act as a toxic mediator in the cells. In this study we investigated the effect of L-arginine on the genotoxicity induced by methyl methanesulfonate (MMS) in human lymphocytes. Blood was treated with N(G)-nitro-L-arginine methyl ester (L-NAME) as an inhibitor of nitric oxide synthase for finding out the role of NO in this effect. Human whole blood was treated with L-arginine (50, 100 and 250 μM) and/or L-NAME, then it was treated in vitro with MMS after 24 h of culture. The lymphocytes were stimulated by phytohemagglutinin to find out the micronuclei in cytokinesis-blocked binucleated cells. DNA fragmentation of lymphocytes was detected by using a fluorescence microscope after propidium iodide staining. These data showed that arginine increased the frequency of MMS-induced micronuclei in lymphocytes. However, the genotoxicity was decreased by using L-NAME. Arginine and L-NAME have not shown any DNA damage in cultured human lymphocytes. In conclusion, addition of L-arginine to MMS as an alkylating agent caused an increase of DNA damage in human lymphocytes. This enhancement of genotoxicity was reduced by NAME as NO inhibitor. It is thus cleared that an increase of DNA damage by arginine and MMS is related to NO production.

p53 orchestrates the PGC-1α-mediated antioxidant response upon mild redox and metabolic imbalance

AIMS

The transcriptional coactivator peroxisome proliferator-activated receptor-γ coactivator-1 α (PPARGC1A or PGC-1α) is a powerful controller of cell metabolism and assures the balance between the production and the scavenging of pro-oxidant molecules by coordinating mitochondrial biogenesis and the expression of antioxidants. However, even though a huge amount of data referring to the role of PGC-1α is available, the molecular mechanisms of its regulation at the transcriptional level are not completely understood. In the present report, we aim at characterizing whether the decrease of antioxidant glutathione (GSH) modulates PGC-1α expression and its downstream metabolic pathways.

RESULTS

We found that upon GSH shortage, induced either by its chemical depletion or by metabolic stress (i.e., fasting), p53 binds to the PPARGC1A promoter of both human and mouse genes, and this event is positively related to increased PGC-1α expression. This effect was abrogated by inhibiting nitric oxide (NO) synthase or guanylate cyclase, implicating NO/cGMP signaling in such a process. We show that p53-mediated PGC-1α upregulation is directed to potentiate the antioxidant defense through nuclear factor (erythroid-derived 2)-like2 (NFE2L2)-mediated expression of manganese superoxide dismutase (SOD2) and γ-glutamylcysteine ligase without modulating mitochondrial biogenesis.

INNOVATION AND CONCLUSIONS

We outlined a new NO-dependent signaling axis responsible for survival antioxidant response upon mild metabolic stress (fasting) and/or oxidative imbalance (GSH depletion). Such signaling axis could become the cornerstone for new pharmacological or dietary approaches for improving antioxidant response during ageing and human pathologies associated with oxidative stress.

Glutathione efflux and cell death

SIGNIFICANCE

Glutathione (GSH) depletion is a central signaling event that regulates the activation of cell death pathways. GSH depletion is often taken as a marker of oxidative stress and thus, as a consequence of its antioxidant properties scavenging reactive species of both oxygen and nitrogen (ROS/RNS).

RECENT ADVANCES

There is increasing evidence demonstrating that GSH loss is an active phenomenon regulating the redox signaling events modulating cell death activation and progression.

CRITICAL ISSUES

In this work, we review the role of GSH depletion by its efflux, as an important event regulating alterations in the cellular redox balance during cell death independent from oxidative stress and ROS/RNS formation. We discuss the mechanisms involved in GSH efflux during cell death progression and the redox signaling events by which GSH depletion regulates the activation of the cell death machinery.

FUTURE DIRECTIONS

The evidence summarized here clearly places GSH transport as a central mechanism mediating redox signaling during cell death progression. Future studies should be directed toward identifying the molecular identity of GSH transporters mediating GSH extrusion during cell death, and addressing the lack of sensitive approaches to quantify GSH efflux.

Caloric Restriction and the Nutrient-Sensing PGC-1α in Mitochondrial Homeostasis: New Perspectives in Neurodegeneration

Mitochondrial activity progressively declines during ageing and in many neurodegenerative diseases. Caloric restriction (CR) has been suggested as a dietary intervention that is able to postpone the detrimental aspects of aging as it ameliorates mitochondrial performance. This effect is partially due to increased mitochondrial biogenesis. The nutrient-sensing PGC-1α is a transcriptional coactivator that promotes the expression of mitochondrial genes and is induced by CR. It is believed that many of the mitochondrial and metabolic benefits of CR are due to increased PGC-1α activity. The increase of PGC-1α is also positively linked to neuroprotection and its decrement has been involved in the pathogenesis of many neurodegenerative diseases. This paper aims to summarize the current knowledge about the role of PGC-1α in neuronal homeostasis and the beneficial effects of CR on mitochondrial biogenesis and function. We also discuss how PGC-1α-governed pathways could be used as target for nutritional intervention to prevent neurodegeneration.

Redox regulation of mitochondrial function

Redox-dependent processes influence most cellular functions, such as differentiation, proliferation, and apoptosis. Mitochondria are at the center of these processes, as mitochondria both generate reactive oxygen species (ROS) that drive redox-sensitive events and respond to ROS-mediated changes in the cellular redox state. In this review, we examine the regulation of cellular ROS, their modes of production and removal, and the redox-sensitive targets that are modified by their flux. In particular, we focus on the actions of redox-sensitive targets that alter mitochondrial function and the role of these redox modifications on metabolism, mitochondrial biogenesis, receptor-mediated signaling, and apoptotic pathways. We also consider the role of mitochondria in modulating these pathways, and discuss how redox-dependent events may contribute to pathobiology by altering mitochondrial function.

Elevated skeletal muscle apoptotic signaling following glutathione depletion

Oxidative stress has a well-established role in numerous intracellular signaling pathways, including apoptosis. Glutathione is an important cellular antioxidant and is the most abundant low molecular weight thiol in the cell. Although previous work has shown a link between glutathione and apoptosis, this relationship has not been defined in skeletal muscle. The present investigation examined the effect of glutathione depletion on skeletal muscle apoptotic signaling, and mitochondrial apoptotic-susceptibility. Administration of L: -buthionine-[S,R]-sulfoximine (BSO; 30 mM in drinking water for 10 days) caused glutathione depletion in whole muscle and isolated mitochondria, as well as elevated muscle catalase protein content and reactive oxygen species (ROS) generation. Glutathione depletion was associated with elevated DNA fragmentation, mitochondrial Bax levels, Poly(ADP-ribose) polymerase (PARP) cleavage, and calpain activity; however, caspase-3, -8, and -9 activity were not altered. BSO administration was also associated with higher cytosolic and nuclear protein levels of apoptosis-inducing factor (AIF), but not cytochrome c, second mitochondria-derived activator of caspase (Smac), or endonuclease G (EndoG). In addition, isolated mitochondria from BSO animals demonstrated significantly lower membrane potential, increased Ca(2+)-induced permeability transition pore opening, and greater basal and ROS-induced AIF and cytochrome c release. These results demonstrate that glutathione depletion in skeletal muscle increases caspase-independent signaling, as well as augments mitochondrial-associated apoptotic events to subsequent cell death stimuli.

Glutathione is a crucial guardian of protein integrity in the brain upon nitric oxide imbalance

GSH is mostly considered a non-enzymatic antioxidant that serves for modulating the redox status of protein thiols, detoxification and direct scavenging activity of oxyradicals. Within the cells, GSH has also the role to buffer the flux of nitric oxide (NO), which in the nervous system is physiologically produced being an important neuromodulator and neurotransmitter. However, this role of GSH in modulating NO toxicity is often considered of secondary importance. Recently, we confuted such assumption as we demonstrated that GSH depletion triggers a severe NO imbalance, which is the primary cause of neuronal death. Here we report that even a slight and non-toxic decrease of GSH in brain mice causes protein nitration that is reversed by inhibiting NO production. This evidence indicates that NO imbalance and the associated nitrosative hallmarks observed in neurodegenerative diseases as well as in health ageing are likely the consequence of the progressive decline of GSH.