Mitochondrial glutathione: features, regulation and role in disease

Relevance of the antioxidant properties of methotrexate and doxycycline to their treatment of cardiovascular disease

Many medications exhibit clinical benefits that are unrelated to their primary therapeutic uses. In many cases, the mechanisms underpinning these pleotropic effects are unknown. Two commonly prescribed medications that exhibit pleotropic benefits in cardiovascular disease and other diseases associated with chronic inflammation are methotrexate (MTX) and doxycycline (DOX). The vast majority of cardiovascular disease is associated with atherosclerosis. Because atherosclerosis is a chronic inflammatory disease, possible mechanisms by which MTX and DOX reduce inflammation have been investigated. Interestingly, the primary structure of both of these medications contain aromatic phenolic rings, which resemble polyphenols that are known to possess antioxidant activity. Inflammation and oxidative stress are intimately related. Inflammation promotes oxidative stress, which in turn leads to further inflammation; in this way, oxidative stress and inflammation can establish a self-perpetuating cycle. It has been shown that MTX and DOX act as antioxidants and are capable of scavenging free radicals and the reactive oxygen species (ROS) superoxide (O₂^-). Furthermore, both MTX and DOX inhibit the formation of malondialdehyde acetaldehyde (MAA) adducts, products of oxidative stress and lipid peroxidation. Importantly, MAA-adducts are highly immunogenic and initiate inflammatory responses; thereby, fueling the cycle of inflammation and oxidative stress that results in chronic inflammation. Thus, reducing the formation of MAA-adducts may ameliorate inflammation that leads to ROS production and in this way, break the self-sustaining cycle of oxidative stress and inflammation. It is possible that the under-recognized antioxidant properties of these medications may be a mechanism by which they and other medications provide pleotropic benefit in the treatment of chronic inflammatory disease.

A Novel HDL-Mimetic Peptide HM-10/10 Protects RPE and Photoreceptors in Murine Models of Retinal Degeneration

Age-related macular degeneration (AMD) is a leading cause of blindness in the developed world. The retinal pigment epithelium (RPE) is a critical site of pathology in AMD. Oxidative stress plays a key role in the development of AMD. We generated a chimeric high-density lipoprotein (HDL), mimetic peptide named HM-10/10, with anti-oxidant properties and investigated its potential for the treatment of retinal disease using cell culture and animal models of RPE and photoreceptor (PR) degeneration. Treatment with HM-10/10 peptide prevented human fetal RPE cell death caused by tert-Butyl hydroperoxide (tBH)-induced oxidative stress and sodium iodate (NaIO₃), which causes RPE atrophy and is a model of geographic atrophy in mice. We also show that HM-10/10 peptide ameliorated photoreceptor cell death and significantly improved retinal function in a mouse model of N-methyl-N-nitrosourea (MNU)-induced PR degeneration. Our results demonstrate that HM-10/10 protects RPE and retina from oxidant injury and can serve as a potential therapeutic agent for the treatment of retinal degeneration.

A Redox-Switchable Colorimetric Probe for "Naked-Eye" Detection of Hypochlorous Acid and Glutathione

We report the development of a new colorimetric probe (L-ol) for investigations of the redox process regulated by hypochlorous acid (HOCl) and glutathione (GSH). The HOCl/GSH redox-switching cycle process was investigated in detail by UV-vis absorption spectroscopy, colorimetric analysis assay and high-resolution mass spectrometry (HRMS). The switchable absorbance responses were attributed to the HOCl-induced oxidation of the p-methoxyphenol unit to the benzoquinone derivative (L-one) and sequential reduction of L-one to hydroquinone (L-ol’) by GSH. In phosphate-buffered saline (PBS) buffer, the absorbance of L-ol at 619 nm underwent a remarkable bathochromic-shift, accompanied by a color change from pale yellow to blue in the presence of HOCl. With further addition of GSH, the absorbance of L-one exclusively recovered to the original level. Meanwhile, the blue-colored solution returned to the naive pale yellow color in the presence of GSH. The detection limits for HOCl and GSH were calculated to be 6.3 and 96 nM according to the IUPAC criteria. Furthermore, L-ol-loaded chromatography plates have been prepared and successfully applied to visualize and quantitatively analyze HOCl in several natural waters.

Promotion of mitochondrial protection by naringenin in methylglyoxal-treated SH-SY5Y cells: Involvement of the Nrf2/GSH axis

Disruption of the mitochondrial function has been associated with redox impairment and triggering of cell death in nucleated human cells, as observed in several diseases. The administration of chemicals that would prevent mitochondrial dysfunction is an attractive strategy in cases of neurodegeneration, cardiovascular diseases, and metabolic disorders. Methylglyoxal (MG) is a dicarbonyl compound that exhibits an important role as a mitochondrial toxicant in neurodegenerative diseases (such as Alzheimer's disease and Parkinson's disease) and diabetes mellitus. On the other hand, naringenin (NGN; C₁₅H₁₂O₅) is a natural antioxidant that also presents anti-inflammatory effects in mammalian cells. In this context, we have evaluated whether and how NGN would be able to prevent the mitochondria-related bioenergetics and redox dysfunctions induced by MG in the human neuroblastoma SH-SY5Y cells. The cells were pretreated (for 2 h) with NGN (at 10-80 μM) and then challenged with MG at 500 μM for 24 h. NGN significantly attenuated the effects of MG on the mitochondrial function and redox environment in this experimental model. Moreover, NGN prevented the MG-triggered mitochondria-related cell death in SH-SY5Y cells. Nonetheless, the inhibition of the synthesis of glutathione (GSH, a major non-enzymatic antioxidant) suppressed the promotion of mitochondrial protection by NGN in MG-treated cells. We also found that the synthesis of GSH was induced by NGN through a mechanism associated with the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2). Therefore, NGN caused mitochondrial protection by an Nrf2/GSH-dependent manner in SH-SY5Y cells exposed to MG.

Slc25a36 modulates pluripotency of mouse embryonic stem cells by regulating mitochondrial function and glutathione level

Mitochondria play a central role in the maintenance of the naive state of embryonic stem cells. Many details of the mechanism remain to be fully elucidated. Solute carrier family 25 member 36 (Slc25a36) might regulate mitochondrial function through transporting pyrimidine nucleotides for mtDNA/RNA synthesis. Its physical role in this process remains unknown; however, Slc25a36 was recently found to be highly expressed in naive mouse embryonic stem cells (mESCs). Here, the function of Slc25a36 was characterized as a maintenance factor of mESCs pluripotency. Slc25a36 deficiency (via knockdown) has been demonstrated to result in mitochondrial dysfunction, which induces the differentiation of mESCs. The expression of key pluripotency markers (Pou5f1, Sox2, Nanog, and Utf1) decreased, while that of key TE genes (Cdx2, Gata3, and Hand1) increased. Cdx2-positive cells emerged in Slc25a36-deficient colonies under trophoblast stem cell culture conditions. As a result of Slc25a36 deficiency, mtDNA of knockdown cells declined, leading to impaired mitochondria with swollen morphology, decreased mitochondrial membrane potential, and low numbers. The key transcription regulators of mitochondrial biogenesis also decreased. These results indicate that mitochondrial dysfunction leads to an inability to support the pluripotency maintenance. Moreover, down-regulated glutathione metabolism and up-regulated focal adhesion reinforced and stabilized the process of differentiation by separately enhancing OCT4 degradation and promoting cell spread. This study improves the understanding of the function of Slc25a36, as well as the relationship of mitochondrial function with naive pluripotency maintenance and stem cell fate decision.

Reactive oxygen species are involved in eosinophil extracellular traps release and in airway inflammation in asthma

In asthma, there are high levels of inflammatory mediators, reactive oxygen species (ROS), and eosinophil extracellular traps (EETs) formation in airway. Here, we attempted to investigate the ROS involvement in EETs release and airway inflammation in OVA-challenged mice. Before the intranasal challenge with ovalbumin (OVA), animals were treated with two ROS inhibitors, N-acetylcysteine (NAC) or diphenyleneiodonium (DPI). We showed that NAC treatment reduced inflammatory cells in lung. DPI and NAC treatments reduced eosinophil peroxidase (EPO), goblet cells hyperplasia, proinflammatory cytokines, NFκB p65 immunocontent, and oxidative stress in lung. However, only the NAC treatment improved mitochondrial energy metabolism. Moreover, the treatments with DPI and NAC reduced EETs release in airway. This is the first study to show that ROS are needed for EETs formation in asthma. Based on our results, NAC and DPI treatments can be an interesting alternative for reducing airway inflammation, mitochondrial damage, and EETs release in asthma.

Mitochondrial function and abnormalities implicated in the pathogenesis of ASD

Mitochondria are the powerhouse that generate over 90% of the ATP produced in cells. In addition to its role in energy production, the mitochondrion also plays a major role in carbohydrate, fatty acid, amino acid and nucleotide metabolism, programmed cell death (apoptosis), generation of and protection against reactive oxygen species (ROS), immune response, regulation of intracellular calcium ion levels and even maintenance of gut microbiota. With its essential role in bio-energetic as well as non-energetic biological processes, it is not surprising that proper cellular, tissue and organ function is dependent upon proper mitochondrial function. Accordingly, mitochondrial dysfunction has been shown to be directly linked to a variety of medical disorders, particularly neuromuscular disorders and increasing evidence has linked mitochondrial dysfunction to neurodegenerative and neurodevelopmental disorders such as Alzheimer's Disease (AD), Parkinson's Disease (PD), Rett Syndrome (RS) and Autism Spectrum Disorders (ASD). Over the last 40 years there has been a dramatic increase in the diagnosis of ASD and, more recently, an increasing body of evidence indicates that mitochondrial dysfunction plays an important role in ASD development. In this review, the latest evidence linking mitochondrial dysfunction and abnormalities in mitochondrial DNA (mtDNA) to the pathogenesis of autism will be presented. This review will also summarize the results of several recent `approaches used for improving mitochondrial function that may lead to new therapeutic approaches to managing and/or treating ASD.

Autophagy accounts for approximately one-third of mitochondrial protein turnover and is protein selective

The destruction of mitochondria through macroautophagy (autophagy) has been recognised as a major route of mitochondrial protein degradation since its discovery more than 50 years ago, but fundamental questions remain unanswered. First, how much mitochondrial protein turnover occurs through auto-phagy? Mitochondrial proteins are also degraded by nonautophagic mechanisms, and the proportion of mitochondrial protein turnover that occurs through autophagy is still unknown. Second, does auto-phagy degrade mitochondrial proteins uniformly or selectively? Autophagy was originally thought to degrade all mitochondrial proteins at the same rate, but recent work suggests that mitochondrial autophagy may be protein selective. To investigate these questions, we used a proteomics-based approach in the fruit fly Drosophila melanogaster, comparing mitochondrial protein turnover rates in autophagy-deficient Atg7 mutants and controls. We found that ~35% of mitochondrial protein turnover occurred via autophagy. Similar analyses using parkin mutants revealed that parkin-dependent mitophagy accounted for ~25% of mitochondrial protein turnover, suggesting that most mitochondrial autophagy specifically eliminates dysfunctional mitochondria. We also found that our results were incompatible with uniform autophagic turnover of mitochondrial proteins and consistent with protein-selective autophagy. In particular, the autophagic turnover rates of individual mitochondrial proteins varied widely, and only a small amount of the variation could be attributed to tissue differences in mitochondrial composition and autophagy rate. Furthermore, analyses comparing autophagy-deficient and control human fibroblasts revealed diverse autophagy-dependent turnover rates even in homogeneous cells. In summary, our work indicates that autophagy acts selectively on mitochondrial proteins, and that most mitochondrial protein turnover occurs through non-autophagic processes. Abbreviations: Atg5: Autophagy-related 5 (Drosophila); ATG5: autophagy related 5 (human); Atg7: Autophagy-related 7 (Drosophila); ATG7: autophagy related 7 (human); DNA: deoxyribonucleic acid; ER: endoplasmic reticulum; GFP: green fluorescent protein; MS: mass spectrometry; park: parkin (Drosophila); Pink1: PTEN-induced putative kinase 1 (Drosophila); PINK1: PTEN-induced kinase 1 (human); PRKN: parkin RBR E3 ubiquitin protein ligase (human); RNA: ribonucleic acid; SD: standard deviation; Ub: ubiquitin/ubiquitinated; WT: wild-type; YME1L: YME1 like ATPase (Drosophila); YME1L1: YME1 like 1 ATPase (human).

Age-related loss of mitochondrial glutathione exacerbates menadione-induced inhibition of Complex I

The role of mitochondrial GSH (mGSH) in the enhanced age-related susceptibility to xenobiotic toxicity is not well defined. We determined mGSH status and indices of mitochondrial bioenergetics in hepatocytes from young and old F344 rats treated with 300 μM menadione, a concentration that causes 50% cell death in old. At this concentration, mGSH was significantly lost only in hepatocytes from old rats, and with near total depletion due to lower basal mGSH in aged cells. In old hepatocytes, menadione caused mitochondrial membrane potential to collapse, as well as significant deficits in maximal O₂ consumption and respiratory reserve capacity, indicators of cellular bioenergetic resiliency. Further examination revealed that the menadione-mediated loss of respiratory reserve capacity in aged hepatocytes was from significant inhibition of Complex I activity and increased proton leak, for which an increase in Complex II activity was not able to compensate. These data demonstrate an age-related increase in mitochondrial susceptibility to a redox-cycling challenge, particularly in regards to Complex I activity, and provide a plausible mechanism to link this vulnerability to mGSH perturbations.

Characterization and Regulation of Carrier Proteins of Mitochondrial Glutathione Uptake in Human Retinal Pigment Epithelium Cells

Purpose

To characterize two mitochondrial membrane transporters 2-oxoglutarate (OGC) and dicarboxylate (DIC) in human RPE (hRPE) and to elucidate their role in the regulation of mitochondrial glutathione (mGSH) uptake and cell death in oxidative stress.

Methods

The localization of OGC and DIC proteins in confluent hRPE, polarized hRPE monolayers and mouse retina was assessed by immunoblotting and confocal microscopy. Time- and dose-dependent expression of the two carriers were determined after treatment of hRPE with H2O2, phenyl succinate (PS), and butyl malonate (BM), respectively, for 24 hours. The effect of inhibition of OGC and DIC on apoptosis (TUNEL), mGSH, and mtDNA was determined. Silencing of OGC by siRNA knockdown on RPE cell death was studied. Kinetics of caspase 3/7 activation with OGC and DIC inhibitors and effect of cotreatment with glutathione monoethyl ester (GSH-MEE) was determined using the IncuCyte live cell imaging.

Results

OGC and DIC are expressed in hRPE mitochondria and exhibited a time- and dose-dependent decrease with stress. Pharmacologic inhibition caused a decrease in OGC and DIC in mitochondria without changes in mtDNA and resulted in increased apoptosis and mGSH depletion. GSH-MEE prevented apoptosis through restoration of mGSH. OGC siRNA exacerbated apoptotic cell death in stressed RPE which was inhibited by increased mGSH from GSH-MEE cotreatment.

Conclusions

Characterization and mechanism of action of two carrier proteins of mGSH uptake in RPE are reported. Regulation of OGC and DIC will be of value in devising therapeutic strategies for retinal disorders such as AMD.

Protective role of l-glutamic acid and l-cysteine in mitigation the chlorpyrifos-induced oxidative stress in rats

Exposure to the organophosphorus insecticide chlorpyrifos (CPF) can lead to oxidative stress. The aim of this work was to investigate and compare the protective effects of amino acids (l-glutamic acid (l-Glu) and l-cysteine (L-Cys) alone or in combination) for the purpose of suppression and mitigation of CPF-induced oxidative stress in rats. Rats were divided into five groups: CPF, CPF/L-Glu, CPF/L-Glu and l-Cys, CPF/L-Cys, control. The level of GSH and the activities of glutathione-related enzymes were determined. The content of lipid peroxidation products was also monitored. The obtained results suggest that level of GSH and activity of GSH-related enzymes was significantly inhibited by CPF. l-Glu and l-Cys were able to prevent CPF-induced oxidative stress. In rats treated with amino acids, we observed less significant or no changes in studied parameters. It was established that the above-mentioned amino acids, administered alone and in their combination, can mitigate and suppress CPF-induced oxidative stress. The most significant mitigation effect was found in rats treated with l-Glu only.

Clozapine attenuates mitochondrial burdens and abnormal behaviors elicited by phencyclidine in mice via inhibition of p47 phox; Possible involvements of phosphoinositide 3-kinase/Akt signaling

BACKGROUND

Oxidative stress and mitochondrial dysfunction have been implicated in the pathophysiology of schizophrenia.

AIMS

We investigated whether antipsychotic clozapine modulates nicotinamide adenine dinucleotide phosphate oxidase and mitochondrial burdens induced by phencyclidine in mice.

METHODS

We examined the effect of clozapine on nicotinamide adenine dinucleotide phosphate oxidase activation, mitochondrial burdens (i.e. oxidative stress and mitochondrial dysfunction), and activities of enzymatic antioxidant in the prefrontal cortex, and subsequent abnormal behaviors induced by repeated treatment with phencyclidine. p47 ^phox Knockout mice and LY294002, a phosphoinositide 3-kinase inhibitor, were employed to elucidate the pharmacological mechanism of clozapine.

RESULTS

Phencyclidine treatment resulted in an early increase nicotinamide adenine dinucleotide phosphate oxidase activity, membrane translocation of p47 ^phox, interaction between p-Akt and p47 ^phox, and mitochondrial burdens in wild-type mice. Although these increases returned to near control level four days post-phencyclidine, mitochondrial superoxide dismutase and glutathione peroxidase activities were decreased at that time. Clozapine, LY294002, or p47 ^phox knockout significantly ameliorated social withdrawal and recognition memory deficits produced by phencyclidine. Importantly, LY294002 did not significantly alter the effects of clozapine against abnormal behaviors and the interaction between p-Akt and p47 ^phox induced by phencyclidine. Furthermore, neither LY294002 nor clozapine exhibited any additive effects to the protection afforded by p47 ^phox knockout against phencyclidine insult.

CONCLUSION

Our results suggest that p47 ^phox gene mediates phencyclidine-induced mitochondrial burdens and abnormal behaviors, and that the interactive modulation between p47 ^phox and phosphoinositide 3-kinase/Akt is important for the understanding on the pharmacological mechanism of clozapine.

Mitochondrial Oxidative Stress and Antioxidants Balance in Fatty Liver Disease

Fatty liver disease is one of the most prevalent forms of chronic liver disease that encompasses both alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD). Alcoholic steatohepatitis (ASH) and nonalcoholic steatohepatitis (NASH) are intermediate stages of ALD and NAFLD, which can progress to more advanced forms, including cirrhosis and hepatocellular carcinoma. Oxidative stress and particularly alterations in mitochondrial function are thought to play a significant role in both ASH and NASH and recognized to contribute to the generation of reactive oxygen species (ROS), as documented in experimental models. Despite the evidence of ROS generation, the therapeutic efficacy of treatment with antioxidants in patients with fatty liver disease has yielded poor results. Although oxidative stress is considered to be the disequilibrium between ROS and antioxidants, there is evidence that a subtle balance among antioxidants, particularly in mitochondria, is necessary to avoid the generation of ROS and hence oxidative stress. Conclusion: As mitochondria are a major source of ROS, the present review summarizes the role of mitochondrial oxidative stress in ASH and NASH and presents emerging data indicating the need to preserve mitochondrial antioxidant balance as a potential approach for the treatment of human fatty liver disease, which may pave the way for the design of future trials to test the therapeutic role of antioxidants in fatty liver disease.

Real time detection of glutathionse in chemotherapy squamous-cell carcinoma cells of a fluorescent probe

Glutathione (GSH) plays a key role in protecting damage induced by radiation and chemotherapy drugs. Current methods, which quantify GSH level changes by using cellular extraction or being based on redox homeostasis results, are unable to directly measure real time GSH level in live cells. In this article, we utilized a newly designed reversible fluorescent probe to measure GSH in living cells. The image of probe 1 can reveal intracellular GSH location and GSH level changes caused by different chemotherapy drugs in squamous-cell carcinoma cells. The results show that it is the first report with probe 1 that to quantify real-time GSH level changes in the cultured chemotherapy cancer cells and different changes in GSH level that may confer chemotherapy resistance.

Targeting SLC25A10 alleviates improved antioxidant capacity and associated radioresistance of cancer cells induced by chronic-cycling hypoxia

High tumor heterogeneity and increased therapy resistance acquired in a hypoxic tumor microenvironment remain major obstacles to successful radiotherapy. Others and we have shown that adaptation of cancer cells to cycling severe hypoxia and intermittent reoxygenation stress (chronic-cycling hypoxia) increases cellular antioxidant capacity thereby supporting resistance to chemotherapy and radiotherapy. Here we explored the involvement of antioxidant-associated mitochondrial transport-systems for maintenance of redox-homeostasis in adaptation to chronic-cycling hypoxia and associated radioresistance. Genetic or pharmacological inhibition of the mitochondrial dicarboxylate carrier (SLC25A10) or the oxoglutarate-carrier (SLC25A11) increased the cytotoxic effects of ionizing radiation (IR). But only targeting of SLC25A10 was effective in overcoming chronic-cycling hypoxia-induced enhanced death resistance in vitro and in vivo by disturbing increased antioxidant capacity. Furthermore, in silico analysis revealed that overexpression of SLC25A10 but not SLC25A11 is associated with reduced overall survival in lung- and breast-cancer patients. Our study reveals a role of SLC25A10 in supporting both, redox- and energy-homeostasis, ensuring radioresistance of cancer cells with tolerance to chronic-cycling hypoxia thereby proposing a novel strategy to overcome a mechanism of hypoxia-induced therapy resistance with potential clinical relevance regarding decreased patient survival.

Glutathione Reduction of Patulin-Evoked Cytotoxicity in HEK293 Cells by the Prevention of Oxidative Damage and the Mitochondrial Apoptotic Pathway

Patulin (PAT) is a mycotoxin frequently detected in moldy fruits and fruit products. This study investigated the protective role of glutathione (GSH), an antioxidant agent, against PAT-induced cytotoxicity and its potential mechanisms in HEK293 cells. The obtained results showed that the addition of GSH significantly increased cell viability and decreased apoptosis induced by PAT. Additionally, GSH decreased intracellular ROS and mitochondrial ROS overproduction, suppressed the decline of the mitochondrial membrane potential, and maintained cellular ATP contents. GSH prevented the impairment of mitochondrial oxidative-phosphorylation system and, especially, enhanced the mRNA and protein levels of electron-transport-chain complex III (UQCRC2) and complex V (ATP5, ATP6 and ATP8). Furthermore, GSH increased endogenous GSH contents; enhanced the antioxidant-enzyme activities of SOD, CAT, GR, and GPx; and modulated oxidative damage. These results suggest that GSH reduces PAT-induced cytotoxicity via inhibition of oxidative damage and the mitochondrial apoptotic pathway in HEK293 cells.

CFTR prevents neuronal apoptosis following cerebral ischemia reperfusion via regulating mitochondrial oxidative stress

The cystic fibrosis transmembrane conductance regulator (CFTR) is linked to cell apoptosis and abundantly expressed in brain tissue. Mitochondrial oxidative stress plays a key role in activating apoptotic pathway following cerebral ischemia reperfusion (IR) injury. Reduced glutathione (GSH) is exclusively synthesized in cytosol but distributed in mitochondria. In the present study, we investigated whether CFTR affected mitochondrial oxidative stress via regulating GSH and thereby protected neurons against apoptosis following cerebral IR. Brains were subjected to global IR by four-vessel occlusion and CFTR activator forskolin (FSK) was used in vivo. CFTR silence was performed in vitro for neurons by RNA interference. We found that FSK suppressed neuronal apoptosis whereas CFTR silence enhanced neuronal apoptosis. FSK prevented the elevations in reactive oxygen species (ROS) and caspase activities while FSK inhibited the reductions in complex I activity and mitochondrial GSH level following IR. FSK decreased mitochondrial oxidative stress partially and preserved mitochondrial function. On the contrary, CFTR silence exaggerated mitochondrial dysfunction. CFTR loss increased hydrogen peroxide (H₂O₂) level and decreased GSH level in mitochondria. Importantly, we showed that CFTR was located on mitochondrial membrane. GSH transport assay suggested that GSH decrease may be a consequence not a reason for mitochondrial oxidative stress mediated by CFTR disruption. Our results highlight the central role of CFTR in the pathogenesis of cerebral IR injury. CFTR regulates neuronal apoptosis following cerebral IR via mitochondrial oxidative stress-dependent pathway. The mechanism of CFTR-mediated mitochondrial oxidative stress needs further studies. KEY MESSAGES: CFTR activation protects brain tissue against IR-induced apoptosis and oxidative stress. CFTR disruption enhances H₂O₂-induced neuronal apoptosis and CFTR loss leads to mitochondrial oxidative stress. CFTR regulates IR-induced neuronal apoptosis via mitochondrial oxidative stress. CFTR may be a potential therapeutic target to cerebral IR damage.

A novel isoflavone, ME-344, targets the cytoskeleton in acute myeloid leukemia

The isoflavone ME-344 is a potent anti-cancer agent with preclinical and clinical efficacy in solid tumors. Yet, the mechanism of action of ME-344 has not been fully defined and the preclinical efficacy in leukemia has not been established. Therefore, we investigated the anti-leukemic properties and mechanism of action of ME-344. In a panel of 7 leukemia cell lines, ME-344 was cytotoxic with an IC₅₀ in the range of 70–260 nM. In addition, ME-344 was cytotoxic to primary AML patient samples over normal hematopoietic cells. In an OCI-AML2 xenograft model, ME-344 reduced tumor growth by up to 95% of control without evidence of toxicity. Mechanistically, ME-344 increased mitochondrial ROS generation in leukemic cells. However, antioxidant treatment did not rescue cell death, suggesting that ME-344 had additional targets beyond the mitochondria. We demonstrated that ME-344 inhibited tubulin polymerization by interacting with tubulin near the colchicine-binding site. Furthermore, inhibition of tubulin polymerization was functionally important for ME-344 induced death. Finally, we showed that ME-344 synergizes with vinblastine in leukemia cells. Thus, our study demonstrates that ME-344 displays preclinical efficacy in leukemia through a mechanism at least partly related to targeting tubulin polymerization.

Ginsenoside Re protects methamphetamine-induced dopaminergic neurotoxicity in mice via upregulation of dynorphin-mediated κ-opioid receptor and downregulation of substance P-mediated neurokinin 1 receptor

BACKGROUND

We previously reported that ginsenoside Re (GRe) attenuated against methamphetamine (MA)-induced neurotoxicity via anti-inflammatory and antioxidant potentials. We also demonstrated that dynorphin possesses anti-inflammatory and antioxidant potentials against dopaminergic loss, and that balance between dynorphin and substance P is important for dopaminergic neuroprotection. Thus, we examined whether GRe positively affects interactive modulation between dynorphin and substance P against MA neurotoxicity in mice.

METHODS

We examined changes in dynorphin peptide level, prodynorphin mRNA, and substance P mRNA, substance P-immunoreactivity, homeostasis in enzymatic antioxidant system, oxidative parameter, microglial activation, and pro-apoptotic parameter after a neurotoxic dose of MA to clarify the effects of GRe, prodynorphin knockout, pharmacological inhibition of κ-opioid receptor (i.e., nor-binaltorphimine), or neurokinin 1 (NK1) receptor (i.e., L-733,060) against MA insult in mice.

RESULTS

GRe attenuated MA-induced decreases in dynorphin level, prodynorphin mRNA expression in the striatum of wild-type (WT) mice. Prodynorphin knockout potentiated MA-induced dopaminergic toxicity in mice. The imbalance of enzymatic antioxidant system, oxidative burdens, microgliosis, and pro-apoptotic changes led to the dopaminergic neurotoxicity. Neuroprotective effects of GRe were more pronounced in prodynorphin knockout than in WT mice. Nor-binaltorphimine, a κ-opioid receptor antagonist, counteracted against protective effects of GRe. In addition, we found that GRe significantly attenuated MA-induced increases in substance P-immunoreactivity and substance P mRNA expression in the substantia nigra. These increases were more evident in prodynorphin knockout than in WT mice. Although, we observed that substance P-immunoreactivity was co-localized in NeuN-immunreactive neurons, GFAP-immunoreactive astrocytes, and Iba-1-immunoreactive microglia. NK1 receptor antagonist L-733,060 or GRe selectively inhibited microgliosis induced by MA. Furthermore, L-733,060 did not show any additive effects against GRe-mediated protective activity (i.e., antioxidant, antimicroglial, and antiapoptotic effects), indicating that NK1 receptor is one of the molecular targets of GRe.

CONCLUSIONS

Our results suggest that GRe protects MA-induced dopaminergic neurotoxicity via upregulatgion of dynorphin-mediated κ-opioid receptor and downregulation of substance P-mediated NK1 R.

Real-Time Monitoring of Glutathione in Living Cells Reveals that High Glutathione Levels Are Required to Maintain Stem Cell Function

The core functions of stem cells (SCs) are critically regulated by their cellular redox status. Glutathione is the most abundant non-protein thiol functioning as an antioxidant and a redox regulator. However, an investigation into the relationship between glutathione-mediated redox capacity and SC activities is hindered by lack of probe. Here, we demonstrate that cyanoacrylamide-based coumarin derivatives are ratiometric probes suitable for the real-time monitoring of glutathione levels in living SCs. These probes revealed that glutathione levels are heterogeneous among subcellular organelles and among individual cells and show dynamic changes and heterogeneity in repopulating SCs depending on oxidative stress or culture conditions. Importantly, a subpopulation of SCs with high glutathione levels exhibited increased stemness and migration activities in vitro and showed improved therapeutic efficiency in treating asthma. Our results indicate that high glutathione levels are required for maintaining SC functions, and monitoring glutathione dynamics and heterogeneity can advance our understanding of the cellular responses to oxidative stress.

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FreSHtracer is a reversible probe for a fast and ratiometric reaction with GSH

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FreSHtracer and its derivatives enable real-time monitoring of intracellular GSH

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FreSHtracer reports dynamic changes and heterogeneity of GSH level in stem cells

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High GSH levels are required for maintaining functional potency of stem cells

Interspecific variation in brain mitochondrial complex I and II capacity and ROS emission in marine sculpins

Environmental hypoxia presents a metabolic challenge for animals because it inhibits mitochondrial respiration and can lead to the generation of reactive oxygen species (ROS). We investigated the interplay between O2 use for aerobic respiration and ROS generation among sculpin fishes (Cottidae, Actinopterygii) that are known to vary in whole-animal hypoxia tolerance. We hypothesized that mitochondria from hypoxia tolerant sculpins would show more efficient O2 use with a higher phosphorylation efficiency and lower ROS emission. We showed that brain mitochondria from more hypoxia tolerant sculpins had lower complex I and higher complex II flux capacities compared with less hypoxia tolerant sculpins, but these differences were not related to variation in phosphorylation efficiency (ADP/O) or mitochondrial coupling (respiratory control ratio). The hypoxia tolerant sculpin had higher mitochondrial H2O2 emission per O2 consumed (H2O2/O2) under oligomycin-induced state 4 conditions compared to less hypoxia tolerant sculpin. An in vitro redox challenge experiment revealed species differences in how well mitochondria defend their glutathione redox status when challenged with high levels of reduced glutathione, but the redox challenge elicited the same H2O2/O2 in all species. Furthermore, in vitro anoxia-recovery lowered absolute H2O2 emission (H2O2/mg mitochondrial protein) in all species and negatively impacted state 3 respiration rates in some species, but the responses were not related to hypoxia tolerance. Overall, we clearly demonstrate a relationship between hypoxia tolerance and complex I and II flux capacities in sculpins, but the differences in complex flux capacity do not appear to be directly related to variation in ROS metabolism.

Mitochondria and Sex-Specific Cardiac Function

The focus of this chapter is the gender differences in mitochondria in cardiovascular disease. There is broad evidence suggesting that some of the gender differences in cardiovascular outcome may be partially related to differences in mitochondrial biology (Ventura-Clapier R, Moulin M, Piquereau J, Lemaire C, Mericskay M, Veksler V, Garnier A, Clin Sci (Lond) 131(9):803-822, 2017)). Mitochondrial disorders are causally affected by mutations in either nuclear or mitochondrial genes involved in the synthesis of respiratory chain subunits or in their posttranslational control. This can be due to mutations of the mtDNA which are transmitted by the mother or mutations in the nuclear DNA. Because natural selection on mitochondria operates only in females, mutations may have had more deleterious effects in males than in females (Ventura-Clapier R, Moulin M, Piquereau J, Lemaire C, Mericskay M, Veksler V, Garnier A, Clin Sci (Lond) 131(9):803-822, 2017; Camara AK, Lesnefsky EJ, Stowe DF. Antioxid Redox Signal 13(3):279-347, 2010). As mitochondrial mutations can affect all tissues, they are responsible for a large panel of pathologies including neuromuscular disorders, encephalopathies, metabolic disorders, cardiomyopathies, neuropathies, renal dysfunction, etc. Many of these pathologies present sex/gender specificity. Thus, alleviating or preventing mitochondrial dysfunction will contribute to mitigating the severity or progression of the development of diseases. Here, we present evidence for the involvement of mitochondria in the sex specificity of cardiovascular disorders.

The Interrelation between Reactive Oxygen Species and Autophagy in Neurological Disorders

Neurological function deficits due to cerebral ischemia or neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) have long been considered a thorny issue in clinical treatment. Recovery after neurologic impairment is fairly limited, which poses a major threat to health and quality of life. Accumulating evidences support that ROS and autophagy are both implicated in the onset and development of neurological disorders. Notably, oxidative stress triggered by excess of ROS not only puts the brain in a vulnerable state but also enhances the virulence of other pathogenic factors, just like mitochondrial dysfunction, which is described as the culprit of nerve cell damage. Nevertheless, autophagy is proposed as a subtle cellular defense mode against destructive stimulus by timely removal of damaged and cytotoxic substance. Emerging evidence suggests that the interplay of ROS and autophagy may establish a determinant role in the modulation of neuronal homeostasis. However, the underlying regulatory mechanisms are still largely unexplored. This review sets out to afford an overview of the crosstalk between ROS and autophagy and discusses relevant molecular mechanisms in cerebral ischemia, AD, and PD, so as to provide new insights into promising therapeutic targets for the abovementioned neurological conditions.

Novel biomarkers of metabolic dysfunction is autism spectrum disorder: potential for biological diagnostic markers

Autism spectrum disorder (ASD) is a neurodevelopmental disorder that is behaviorally defined by social and communication impairments and restricted interests and repetitive behaviors. There is currently no biomarkers that can help in the diagnosis. Several studies suggest that mitochondrial dysfunction is commonly involved in ASD pathophysiology, but standard mitochondrial biomarkers are thought to be very variable. In the present study we examine a wide variety of plasma biomarkers of mitochondrial metabolism and the related abnormalities of oxidative stress and apoptosis in 41 ASD patients assessed for ASD severity using the Childhood Autism Rating Scales and 41 non-related age and sex matched healthy controls. Our findings confirm previous studies indicating abnormal mitochondrial and related biomarkers in children with ASD including pyruvate, creatine kinase, Complex 1, Glutathione S-Transferase, glutathione and Caspase 7. As a novel finding, we report that lactate dehydrogenase is abnormal in children with ASD. We also identified that only the most severe children demonstrated abnormalities in Complex 1 activity and Glutathione S-Transferase. Additionally, we find that several biomarkers could be candidates for differentiating children with ASD and typically developing children, including Caspase 7, gluthatione and Glutathione S-Transferase by themselves and lactate dehydrogenase and Complex I when added to other biomarkers in combination. Caspase 7 was the most discriminating biomarker between ASD patients and healthy controls suggesting its potential use as diagnostic marker for the early recognition of ASD pathophysiology. This study confirms that several mitochondrial biomarkers are abnormal in children with ASD and suggest that certain mitochondrial biomarkers can differentiate between ASD and typically developing children, making them possibly useful as a tool to diagnosis ASD and identify ASD subgroups.

MicroRNA-34a promotes mitochondrial dysfunction-induced apoptosis in human lens epithelial cells by targeting Notch2

Purpose

Human lens epithelial cell (HLEC) apoptosis is a common pathogenic mechanism in age-related cataracts (ARC). While the function of microRNAs (miRNAs) in the eye is beginning to be explored using miRNA expression array, the role of miR-34a in regulating HLEC apoptosis remains unknown and requires further investigation.

Methods

Quantitative reverse-transcript polymerase chain reaction (RT-PCR) was used to determine the expression level of miR-34a in cataractous and control samples. MiR-34a mimics and small interfering RNAs were transfected into SRA01/04. Cell apoptosis and oxidative stress were assessed by flow cytometry. The Dual-Luciferase Reporter Assay System was used to confirm whether miR-34a bound to the 3'-UTR of the target gene and blocked its activity. The potential roles of the identified target genes in apoptosis and mitochondria dysfunction were also evaluated.

Results

The expression of miR-34a increased in lens epithelial samples of ARC compared with the transparent group (cataract 2.41±0.81 vs. control 1.20±0.44, P=0.005). In cultured SRA01/04, miR-34a increased reactive oxygen species production and induced apoptosis (early apoptosis: 45.55%±5.96% vs. 15.85%±4.93%, P<0.01; late apoptosis: 6.10%±2.67% vs. 0.95%±0.42%, P<0.01). Overexpression of miR-34a promoted mitochondria-mediated apoptosis through activation of caspase-9, disruption of the mitochondrial membrane potential, blocking of mitochondrial energy metabolism and enhancement of cytochrome C release. Furthermore, Notch1 and Notch2 were confirmed as putative targets of miR-34a, but only Notch2 was verified as the effector that triggered mitochondria-mediated apoptosis.

Conclusion

MicroRNA-34a is increased in the cataractous lens and triggers mitochondria-mediated apoptosis and oxidative stress by suppressing Notch2.

Multifaceted Roles of Glutathione and Glutathione-Based Systems in Carcinogenesis and Anticancer Drug Resistance

SIGNIFICANCE

Glutathione is the most abundant antioxidant molecule in living organisms and has multiple functions. Intracellular glutathione homeostasis, through its synthesis, consumption, and degradation, is an intricately balanced process. Glutathione levels are often high in tumor cells before treatment, and there is a strong correlation between elevated levels of intracellular glutathione/sustained glutathione-mediated redox activity and resistance to pro-oxidant anticancer therapy. Recent Advances: Ample evidence demonstrates that glutathione and glutathione-based systems are particularly relevant in cancer initiation, progression, and the development of anticancer drug resistance.

CRITICAL ISSUES

This review highlights the multifaceted roles of glutathione and glutathione-based systems in carcinogenesis, anticancer drug resistance, and clinical applications.

FUTURE DIRECTIONS

The evidence summarized here underscores the important role played by glutathione and the glutathione-based systems in carcinogenesis and anticancer drug resistance. Future studies should address mechanistic questions regarding the distinct roles of glutathione in different stages of cancer development and cancer cell death. It will be important to study how metabolic alterations in cancer cells can influence glutathione homeostasis. Sensitive approaches to monitor glutathione dynamics in subcellular compartments will be an indispensible step. Therapeutic perspectives should focus on mechanism-based rational drug combinations that are directed against multiple redox targets using effective, specific, and clinically safe inhibitors. This new strategy is expected to produce a synergistic effect, prevent drug resistance, and diminish doses of single drugs. Antioxid. Redox Signal. 27, 1217-1234.

Ginsenoside Re protects against phencyclidine-induced behavioral changes and mitochondrial dysfunction via interactive modulation of glutathione peroxidase-1 and NADPH oxidase in the dorsolateral cortex of mice

We investigated whether ginsenoside Re (Re) modulates phencyclidine (PCP)-induced sociability deficits and recognition memory impairments to extend our recent finding. We examined the role of GPx-1 gene in the pharmacological activity of Re against mitochondrial dysfunction induced by PCP in the dorsolateral cortex of mice. Since mitochondrial oxidative stress activates NADPH oxidase (PHOX), we applied PHOX inhibitor apocynin for evaluating interactive modulation between GPx-1 and PHOX against PCP neurotoxicity. Sociability deficits and recognition memory impairments induced by PCP were more pronounced in GPx-1 knockout (KO) than in wild type (WT) mice. PCP-induced mitochondrial oxidative stress, mitochondrial dysfunction, and membrane translocation of p47phox were more evident in GPx-1 KO than in WT. Re treatment significantly attenuated PCP-induced neurotoxic changes. Re also significantly attenuated PCP-induced sociability deficits and recognition memory impairments. The attenuation by Re was comparable to that by apocynin. The attenuation was more obvious in GPx-1 KO than in WT. Importantly, apocynin did not show any additional positive effects on the neuroprotective activity of Re, indicating that PHOX is a molecular target for therapeutic activity of Re. Our results suggest that Re requires interactive modulation between GPx activity and PHOX (p47phox) to exhibit neuroprotective potentials against PCP insult.

Reversible Reaction-Based Fluorescent Probe for Real-Time Imaging of Glutathione Dynamics in Mitochondria

We report a mitochondria-specific glutathione (GSH) probe-designated as Mito-RealThiol (MitoRT)-that can monitor in vivo real-time mitochondrial glutathione dynamics, and apply this probe to follow mitochondrial GSH dynamic changes in living cells for the first time. MitoRT can be utilized in confocal microscopy, super-resolution fluorescence imaging, and flow cytometry systems. Using MitoRT, we demonstrate that cells have a high priority to maintain the GSH level in mitochondria compared to the cytosol not only under normal growing conditions but also upon oxidative stress.

Differences in Reperfusion-Induced Mitochondrial Oxidative Stress and Cell Death Between Hippocampal CA1 and CA3 Subfields Are Due to the Mitochondrial Thioredoxin System

AIMS

The susceptibility of CA1 over CA3 to damage from cerebral ischemia may be related to the differences in reactive oxygen species (ROS) production/removal between the two hippocampal subfields. We aimed to measure CA1/CA3 differences in net ROS production in real time in the first 30 min of reperfusion in pyramidal cells. We aimed to determine the underlying cause of the differential vulnerability of CA1 and CA3.

RESULTS

Real-time determinations of mitochondrial H₂O₂ and, independently, glutathione (GSH) redox status from roGFP-based probes in individual pyramidal cells in organotypic hippocampal cultures during oxygen-glucose deprivation (OGD)-reperfusion (RP) demonstrate a significantly more oxidizing environment during RP in CA1 than CA3 mitochondria. Protein levels (immunohistochemistry and Western blots), roGFP2-based probe measurements during controlled mitochondrial production of ROS, and thioredoxin reductase (TrxR) inhibition by auranofin are consistent with a more effective mitochondrial thioredoxin (Trx) system in CA3. Inhibition of TrxR eliminates the differences in redox status and cell death between the regions. Overexpression of cytosolic Trx1 does not influence mitochondrial H₂O₂ production.

INNOVATION

Real-time changes of mitochondrial H₂O₂ and GSH in tissue cultures during early RP, and also during controlled production of superoxide and peroxide, reveal significant differences between CA1 and CA3. The mitochondrial Trx system is responsible for the observed differences during RP as well as for delayed cell death 18 h afterward.

CONCLUSION

Greater mitochondrial Trx efficacy in CA3 pyramidal cells results in less vulnerability to ischemia/reperfusion because of the less oxidizing environment in CA3 mitochondria during RP. Antioxid. Redox Signal. 27, 534-549.

Naringenin Attenuates H2O2-Induced Mitochondrial Dysfunction by an Nrf2-Dependent Mechanism in SH-SY5Y Cells

Mitochondria are the major site of ATP production in mammalian cells. Furthermore, these organelles are a source and a target of reactive oxygen species (ROS), such as radical anion superoxide (O₂^-·) and hydrogen peroxide (H₂O₂). The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) is the master regulator of the mammalian redox biology and controls the expression of antioxidant and phase II detoxifying enzymes in several cell types. Naringenin (NGN, 5,7-dihydroxy-2-(4-hydroxyphenyl)-2,3-dihydrochromen-4-one), a flavanone, exhibits cytoprotective effects by acting as an antioxidant and anti-inflammatory agent. NGN is a potent activator of Nrf2. Nonetheless, it was not examine yet whether NGN would induce mitochondrial protection in cells under redox stress. Therefore, we investigate here whether Nrf2 would be involved in the mitochondrial protection elicited by NGN in SH-SY5Y cells exposed to H₂O₂. We observed that a pretreatment with NGN at 80 µM for 2 h reduced the levels of lipid peroxidation, protein carbonylation, and protein nitration in the membranes of mitochondria obtained from H₂O₂-treated SH-SY5Y cells. Additionally, NGN prevented the H₂O₂-induced impairment in the function of the enzymes aconitase, α-ketoglutarate dehydrogenase, and succinate dehydrogenase. The activites of the complexes I and V, as well as the production of ATP, were restored by NGN. NGN also suppressed the H₂O₂-induced mitochondria-related apoptosis. Interestingly, NGN promoted an increase in the levels of both total and mitochondrial glutathione (GSH). Silencing of Nrf2 abolished the protective effects induced by NGN. Overall, NGN induced mitochondrial protection by an Nrf2-dependent mechanism in H₂O₂-treated SH-SY5Y cells.

Sulforaphane Promotes Mitochondrial Protection in SH-SY5Y Cells Exposed to Hydrogen Peroxide by an Nrf2-Dependent Mechanism

Sulforaphane (SFN; C₆H₁₁NOS₂) is an isothiocyanate found in cruciferous vegetables, such as broccoli, kale, and radish. SFN exhibits antioxidant, anti-apoptotic, anti-tumor, and anti-inflammatory activities in different cell types. However, it was not previously demonstrated whether and how this natural compound would exert mitochondrial protection experimentally. Therefore, we investigated here the effects of a pretreatment (for 30 min) with SFN at 5 μM on mitochondria obtained from human neuroblastoma SH-SY5Y cells exposed to hydrogen peroxide (H₂O₂) at 300 μM for 24 h. We found that SFN prevented loss of viability in H₂O₂-treated SH-SY5Y cells. Furthermore, SFN decreased lipid peroxidation, protein carbonylation, and protein nitration in mitochondrial membranes of H₂O₂-exposed cells. Importantly, SFN enhanced the levels of both cellular and mitochondrial glutathione (GSH). SFN also suppressed the H₂O₂-mediated inhibition of mitochondrial components involved in the maintenance of the bioenergetics state, such as aconitase, α-ketoglutarate dehydrogenase, and succinate dehydrogenase, as well as complexes I and V. Consequently, SFN prevented the decline induced by H₂O₂ on the levels of ATP in SH-SY5Y cells. Silencing of the nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factor by using small interfering RNA (siRNA) abolished the mitochondrial and cellular protection elicited by SFN. Therefore, SFN abrogated the H₂O₂-induced mitochondrial impairment by an Nrf2-dependent manner.

The Role of Interleukin-18, Oxidative Stress and Metabolic Syndrome in Alzheimer's Disease

The role of interleukins (ILs) and oxidative stress (OS) in precipitating neurodegenerative diseases including sporadic Alzheimer's disease (AD), requires further clarification. In addition to neuropathological hallmarks-extracellular neuritic amyloid-β (Aβ) plaques, neurofibrillary tangles (NFT) containing hyperphosphorylated tau and neuronal loss-chronic inflammation, as well as oxidative and excitotoxic damage, are present in the AD brain. The pathological sequelae and the interaction of these events during the course of AD need further investigation. The brain is particularly sensitive to OS, due to the richness of its peroxidation-sensitive fatty acids, coupled with its high oxygen demand. At the same time, the brain lack robust antioxidant systems. Among the multiple mechanisms and triggers by which OS can accumulate, inflammatory cytokines can sustain oxidative and nitrosative stress, leading eventually to cellular damage. Understanding the consequences of inflammation and OS may clarify the initial events underlying AD, including in interaction with genetic factors. Inflammatory cytokines are potential inducers of aberrant gene expression through transcription factors. Susceptibility disorders for AD, including obesity, type-2 diabetes, cardiovascular diseases and metabolic syndrome have been linked to increases in the proinflammatory cytokine, IL-18, which also regulates multiple AD related proteins. The association of IL-18 with AD and AD-linked medical conditions are reviewed in the article. Such data indicates that an active lifestyle, coupled to a healthy diet can ameliorate inflammation and reduce the risk of sporadic AD.

Glutathione as a Redox Biomarker in Mitochondrial Disease-Implications for Therapy

Technical advances in the ability to measure mitochondrial dysfunction are providing new insights into mitochondrial disease pathogenesis, along with new tools to objectively evaluate the clinical status of mitochondrial disease patients. Glutathione (l-ϒ-glutamyl-l-cysteinylglycine) is the most abundant intracellular thiol, and the intracellular redox state, as reflected by levels of oxidized (GSSG) and reduced (GSH) glutathione, as well as the GSH/GSSG ratio, is considered to be an important indication of cellular health. The ability to quantify mitochondrial dysfunction in an affected patient will not only help with routine care, but also improve rational clinical trial design aimed at developing new therapies. Indeed, because multiple disorders have been associated with either primary or secondary deficiency of the mitochondrial electron transport chain and redox imbalance, developing mitochondrial therapies that have the potential to improve the intracellular glutathione status has been a focus of several clinical trials over the past few years. This review will also discuss potential therapies to increase intracellular glutathione with a focus on EPI-743 (α-tocotrienol quinone), a compound that appears to have the ability to modulate the activity of oxidoreductases, in particular NAD(P)H:quinone oxidoreductase 1.

Membrane Lipid Replacement for chronic illnesses, aging and cancer using oral glycerolphospholipid formulations with fructooligosaccharides to restore phospholipid function in cellular membranes, organelles, cells and tissues

Membrane Lipid Replacement is the use of functional, oral supplements containing mixtures of cell membrane glycerolphospholipids, plus fructooligosaccharides (for protection against oxidative, bile acid and enzymatic damage) and antioxidants, in order to safely replace damaged, oxidized, membrane phospholipids and restore membrane, organelle, cellular and organ function. Defects in cellular and intracellular membranes are characteristic of all chronic medical conditions, including cancer, and normal processes, such as aging. Once the replacement glycerolphospholipids have been ingested, dispersed, complexed and transported, while being protected by fructooligosaccharides and several natural mechanisms, they can be inserted into cell membranes, lipoproteins, lipid globules, lipid droplets, liposomes and other carriers. They are conveyed by the lymphatics and blood circulation to cellular sites where they are endocytosed or incorporated into or transported by cell membranes. Inside cells the glycerolphospholipids can be transferred to various intracellular membranes by lipid globules, liposomes, membrane-membrane contact or by lipid carrier transfer. Eventually they arrive at their membrane destinations due to 'bulk flow' principles, and there they can stimulate the natural removal and replacement of damaged membrane lipids while undergoing further enzymatic alterations. Clinical trials have shown the benefits of Membrane Lipid Replacement in restoring mitochondrial function and reducing fatigue in aged subjects and chronically ill patients. Recently Membrane Lipid Replacement has been used to reduce pain and other symptoms as well as removing hydrophobic chemical contaminants, suggesting that there are additional new uses for this safe, natural medicine supplement. This article is part of a Special Issue entitled: Membrane Lipid Therapy: Drugs Targeting Biomembranes edited by Pablo V. Escribá.

A new H2S-specific near-infrared fluorescence-enhanced probe that can visualize the H2S level in colorectal cancer cells in mice

Near-infrared (NIR) fluorescence-based sensors capable of selective detection of H2S in vivo would be useful tools to understand the mechanisms of diseases. A new NIR fluorescence probe 1 was developed for the detection of endogenous H2S in colorectal cancer cells in mice. 1 displayed an 87-fold fluorescence enhancement at 796 nm (with excitation at 730 nm) when reacted with H2S in a buffer (pH 7.4). 1 was water-soluble, cell-membrane-permeable, had low cytotoxicity and high selectivity and sensitivity for H2S. The properties of 1 enable its use in monitoring endogenous H2S in living cells, tissues, and mice. The bioimaging results indicated that (1) d-Cys could induce endogenous H2S production in living cells and stimulate angiogenesis; (2) tail intravenous injection of 1 into mice generated strong fluorescence in the liver while intraperitoneal injection of d-Cys could further enhance fluorescence in the liver in vivo; (3) importantly, endogenous H2S in colorectal cancer cells (HCT116, HT29) in vitro and in murine tumor models could be quickly and selectively detected by intratumoral injection of 1. These results indicated that our new probe could serve as an efficient tool for the detection of cellular H2S in living animals and even for cancer diagnosis.

New Application of pH-Mediated Acid Stacking Technique for Amphoteric Compounds in Capillary Electrophoresis: Example Assay of Blood Glutathiones

Both reduced and oxidized forms of glutathiones were firstly stacked and detected using pH-mediated acid stacking method, in which glutathiones were stacked as cations and separated as anions. Factors, such as injection time, sweeping time, buffer pH, concentration of sodium chloride in sample matrix, that influenced stacking and separation were systematically studied and optimized. Under the optimum condition, the enhancement factors of ~20 times for both reduced and oxidized forms of glutathiones could be easily obtained within 20 min with satisfied sensitivities (limit of detections were 0.12 and 0.06 μmol/L for reduced and oxidized glutathione, respectively, at signal-to-noise ratio, S/N = 3), linearity range (0.3-300.0 and 0.6-300.0 μmol/L for reduced and oxidized glutathione, respectively), recoveries (>98%) and reproducibilities (relative standard deviation <5.1% for peak height). The proposed method provides an alternation way for assaying of glutathiones, as well as amphoteric compounds, in blood sample.

Molecular mechanisms of apoptosis in hepatocellular carcinoma cells induced by ethanol extracts of Solanum lyratum Thumb through the mitochondrial pathway

AIM

To explore the induction effects and mechanism of Solanum lyratum Thumb (ST) on human hepatocellular carcinoma SMMC-7721 cells through the mitochondrial pathway.

METHODS

The experiments were conducted on three groups: an experimental group (with ST ethanol extracts' concentration being 2.5, 5 and 10 mg/L), a negative control group (with only nutrient solution, 0 mg/L ST ethanol extracts), and a positive control group (2.5 mg/L DDP). The inhibition rate of cell proliferation was checked by using the methyl thiazolyl tetrazolium method, and cell apoptosis was tested by TUNEL method. Furthermore, RT-PCR was used to examine mRNA expression of Fas, FasL, caspase-8, caspase-3, p53 and Bcl-2 genes.

RESULTS

Compared with the negative control group, the inhibition and apoptosis rates of the experimental group with different concentrations of ST extracts on human hepatocellular carcinoma SMMC-7721 cells significantly increased (P < 0.05). Besides, the mRNA expression of FasL and Bcl-2 significantly decreased (P < 0.05) while the mRNA expression of Fas, caspase-8, caspase-3 and p53 increased significantly. When compared with the positive control group, the experimental groups with 5 mg/L ST ethanol extracts showed effects similar to the positive control group.

CONCLUSION

ST ethanol extracts induced the apoptosis of hepatocellular carcinoma SMMC-7721 cells through up-regulated Fas, caspase-8, caspse-3 and p53, and down-regulated FasL and Bcl-2 in the mitochondrial pathway.

Investigating mitochondrial redox state using NADH and NADPH autofluorescence

The redox states of the NAD and NADP pyridine nucleotide pools play critical roles in defining the activity of energy producing pathways, in driving oxidative stress and in maintaining antioxidant defences. Broadly speaking, NAD is primarily engaged in regulating energy-producing catabolic processes, whilst NADP may be involved in both antioxidant defence and free radical generation. Defects in the balance of these pathways are associated with numerous diseases, from diabetes and neurodegenerative disease to heart disease and cancer. As such, a method to assess the abundance and redox state of these separate pools in living tissues would provide invaluable insight into the underlying pathophysiology. Experimentally, the intrinsic fluorescence of the reduced forms of both redox cofactors, NADH and NADPH, has been used for this purpose since the mid-twentieth century. In this review, we outline the modern implementation of these techniques for studying mitochondrial redox state in complex tissue preparations. As the fluorescence spectra of NADH and NADPH are indistinguishable, interpreting the signals resulting from their combined fluorescence, often labelled NAD(P)H, can be complex. We therefore discuss recent studies using fluorescence lifetime imaging microscopy (FLIM) which offer the potential to discriminate between the two separate pools. This technique provides increased metabolic information from cellular autofluorescence in biomedical investigations, offering biochemical insights into the changes in time-resolved NAD(P)H fluorescence signals observed in diseased tissues.

Integrated High-Content Quantification of Intracellular ROS Levels and Mitochondrial Morphofunction

Oxidative stress arises from an imbalance between the production of reactive oxygen species (ROS) and their removal by cellular antioxidant systems. Especially under pathological conditions, mitochondria constitute a relevant source of cellular ROS. These organelles harbor the electron transport chain, bringing electrons in close vicinity to molecular oxygen. Although a full understanding is still lacking, intracellular ROS generation and mitochondrial function are also linked to changes in mitochondrial morphology. To study the intricate relationships between the different factors that govern cellular redox balance in living cells, we have developed a high-content microscopy-based strategy for simultaneous quantification of intracellular ROS levels and mitochondrial morphofunction. Here, we summarize the principles of intracellular ROS generation and removal, and we explain the major considerations for performing quantitative microscopy analyses of ROS and mitochondrial morphofunction in living cells. Next, we describe our workflow, and finally, we illustrate that a multiparametric readout enables the unambiguous classification of chemically perturbed cells as well as laminopathy patient cells.

Mitochondrial calcium uptake underlies ROS generation during aminoglycoside-induced hair cell death

Exposure to aminoglycoside antibiotics can lead to the generation of toxic levels of reactive oxygen species (ROS) within mechanosensory hair cells of the inner ear that have been implicated in hearing and balance disorders. Better understanding of the origin of aminoglycoside-induced ROS could focus the development of therapies aimed at preventing this event. In this work, we used the zebrafish lateral line system to monitor the dynamic behavior of mitochondrial and cytoplasmic oxidation occurring within the same dying hair cell following exposure to aminoglycosides. The increased oxidation observed in both mitochondria and cytoplasm of dying hair cells was highly correlated with mitochondrial calcium uptake. Application of the mitochondrial uniporter inhibitor Ru360 reduced mitochondrial and cytoplasmic oxidation, suggesting that mitochondrial calcium drives ROS generation during aminoglycoside-induced hair cell death. Furthermore, targeting mitochondria with free radical scavengers conferred superior protection against aminoglycoside exposure compared with identical, untargeted scavengers. Our findings suggest that targeted therapies aimed at preventing mitochondrial oxidation have therapeutic potential to ameliorate the toxic effects of aminoglycoside exposure.

A Proteomic Investigation of Hepatic Resistance to Ascaris in a Murine Model

The helminth Ascaris causes ascariasis in both humans and pigs. Humans, especially children, experience significant morbidity including respiratory complications, growth deficits and intestinal obstruction. Given that 800 million people worldwide are infected by Ascaris, this represents a significant global public health concern. The severity of the symptoms and associated morbidity are related to the parasite burden and not all hosts are infected equally. While the pathology of the disease has been extensively examined, our understanding of the molecular mechanisms underlying resistance and susceptibility to this nematode infection is poor. In order to investigate host differences associated with heavy and light parasite burden, an experimental murine model was developed utilising Ascaris-susceptible and -resistant mice strains, C57BL/6J and CBA/Ca, respectively, which experience differential burdens of migratory Ascaris larvae in the host lungs. Previous studies identified the liver as the site where this difference in susceptibility occurs. Using a label free quantitative proteomic approach, we analysed the hepatic proteomes of day four post infection C57BL/6J and CBA/Ca mice with and without Ascaris infection to identify proteins changes potentially linked to both resistance and susceptibility amongst the two strains, respectively. Over 3000 proteins were identified in total and clear intrinsic differences were elucidated between the two strains. These included a higher abundance of mitochondrial proteins, particularly those associated with the oxidative phosphorylation pathway and reactive oxygen species (ROS) production in the relatively resistant CBA/Ca mice. We hypothesise that the increased ROS levels associated with higher levels of mitochondrial activity results in a highly oxidative cellular environment that has a dramatic effect on the nematode’s ability to successfully sustain a parasitic association with its resistant host. Under infection, both strains had increased abundances in proteins associated with the oxidative phosphorylation pathway, as well as the tricarboxylic acid cycle, with respect to their controls, indicating a general stress response to Ascaris infection. Despite the early stage of infection, some immune-associated proteins were identified to be differentially abundant, providing a novel insight into the host response to Ascaris. In general, the susceptible C57BL/6J mice displayed higher abundances in immune-associated proteins, most likely signifying a more active nematode cohort with respect to their CBA/Ca counterparts. The complement component C8a and S100 proteins, S100a8 and S100a9, were highly differentially abundant in both infected strains, signifying a potential innate immune response and the importance of the complement pathway in defence against macroparasite infection. In addition, the signatures of an early adaptive immune response were observed through the presence of proteins, such as plastin-2 and dipeptidyl peptidase 1. A marked decrease in proteins associated with translation was also observed in both C57BL/6J and CBA/Ca mice under infection, indicative of either a general response to Ascaris or a modulatory effect by the nematode itself. Our research provides novel insights into the in vivo host-Ascaris relationship on the molecular level and provides new research perspectives in the development of Ascaris control and treatment strategies.

Ascaris infection is a significant burden on the people who live in developing countries with infection being linked to poor hygiene and low socio-economic status. The parasite causes a range of symptoms, especially in children, which include both chronic morbidity, such as growth retardation, and acute outcomes, such as intestinal obstruction. Certain people tend to be more heavily infected than others, with those individuals experiencing worse morbidity. The understanding of the difference between susceptible and resistant people is an essential first step in the development of new therapies in order to eliminate this neglected parasitic disease. Using an established mouse model involving a susceptible and resistant strain, we aimed to gain insight into the host-Ascaris interaction at the hepatic interface and elucidate some of the molecular mechanisms potentially involved in resistance. A number of key intrinsic differences were determined between both strains including major differences in mitochondrial and ROS associated processes which may present the nematodes with differing oxidative conditions and explain the failure of the nematode to establish a successful parasitism in the resistant strain. In addition, we resolved signatures of the innate and early adaptive immune response and a major reduction in the proteins associated with translation in both strains under infection. Our findings need to be further explored, but could be the foundation for a better understanding of the mechanisms behind the differential parasite burden and in the future, potential new therapies for control.

Mitochondria, cholesterol and cancer cell metabolism

Given the role of mitochondria in oxygen consumption, metabolism and cell death regulation, alterations in mitochondrial function or dysregulation of cell death pathways contribute to the genesis and progression of cancer. Cancer cells exhibit an array of metabolic transformations induced by mutations leading to gain-of-function of oncogenes and loss-of-function of tumor suppressor genes that include increased glucose consumption, reduced mitochondrial respiration, increased reactive oxygen species generation and cell death resistance, all of which ensure cancer progression. Cholesterol metabolism is disturbed in cancer cells and supports uncontrolled cell growth. In particular, the accumulation of cholesterol in mitochondria emerges as a molecular component that orchestrates some of these metabolic alterations in cancer cells by impairing mitochondrial function. As a consequence, mitochondrial cholesterol loading in cancer cells may contribute, in part, to the Warburg effect stimulating aerobic glycolysis to meet the energetic demand of proliferating cells, while protecting cancer cells against mitochondrial apoptosis due to changes in mitochondrial membrane dynamics. Further understanding the complexity in the metabolic alterations of cancer cells, mediated largely through alterations in mitochondrial function, may pave the way to identify more efficient strategies for cancer treatment involving the use of small molecules targeting mitochondria, cholesterol homeostasis/trafficking and specific metabolic pathways.

Mitochondria-targeted antioxidant mitotempo protects mitochondrial function against amyloid beta toxicity in primary cultured mouse neurons

Mitochondrial defects including excess reactive oxygen species (ROS) production and compromised ATP generation are featured pathology in Alzheimer's disease (AD). Amyloid beta (Aβ)-mediated mitochondrial ROS overproduction disrupts intra-neuronal Redox balance, in turn exacerbating mitochondrial dysfunction leading to neuronal injury. Previous studies have found the beneficial effects of mitochondria-targeted antioxidants in preventing mitochondrial dysfunction and neuronal injury in AD animal and cell models, suggesting that mitochondrial ROS scavengers hold promise for the treatment of this neurological disorder. In this study, we have determined that mitotempo, a novel mitochondria-targeted antioxidant protects mitochondrial function from the toxicity of Aβ in primary cultured neurons. Our results showed that Aβ-promoted mitochondrial superoxide production and neuronal lipid oxidation were significantly suppressed by the application of mitotempo. Moreover, mitotempo also demonstrated protective effects on mitochondrial bioenergetics evidenced by preserved mitochondrial membrane potential, cytochrome c oxidase activity as well as ATP production. In addition, the Aβ-induced mitochondrial DNA (mtDNA) depletion and decreased expression levels of mtDNA replication-related DNA polymerase gamma (DNA pol γ) and Twinkle were substantially mitigated by mitotempo. Therefore, our study suggests that elimination of excess mitochondrial ROS rescues mitochondrial function in Aβ-insulted neruons; and mitotempo has the potential to be a promising therapeutic agent to protect mitochondrial and neuronal function in AD.

Alpha-synuclein-induced oxidative stress correlates with altered superoxide dismutase and glutathione synthesis in human neuroblastoma SH-SY5Y cells

Alpha-synuclein (α-syn) is a major component of Lewy bodies found in sporadic and inherited forms of Parkinson's disease (PD). Mutations in the gene encoding α-syn and duplications and triplications of wild-type (WT) α-syn have been associated with PD. Several mechanisms have been implicated in the degeneration of dopaminergic neurons in PD, including oxidative stress and mitochondrial dysfunction. Here we defined the occurrence of oxidative stress in SH-SY5Y cells overexpressing WT α-syn in a doxycycline (Dox) regulated manner, before and after exposure to iron (500 µM), and determined the changes in proteins involved in the intracellular antioxidant defense system. Data evidenced an increase in caspase-3 activation and diminished reducing capacity of -Dox cells, associated with decreased activity of mitochondria complex I and reduced mitochondrial transcription factor A (TFAM) levels in these cells. Furthermore, total and mitochondrial reactive oxygen species levels were higher under basal conditions in cells overexpressing α-syn (-Dox) and this increase was apparently correlated with diminished levels and activities of SOD1 and SOD2 in -Dox cells. Moreover, both reduced and oxidized glutathione levels were diminished in -Dox cells under basal conditions, concomitantly with decreased activity of GCL and reduced protein levels of GCLc. The effects caused by iron (500 µM) were mostly independent of α-syn expression and triggered different antioxidant responses to possibly counterbalance higher levels of free radicals. Overall, data suggest that overexpression of α-syn modifies the antioxidant capacity of SH-SY5Y cells due to altered activity and protein levels of SOD1 and SOD2, and decreased glutathione pool.

Effects of Antioxidant N-acetylcysteine Against Paraquat-Induced Oxidative Stress in Vital Tissues of Mice

Paraquat (PQ) is a commonly used herbicide that induces oxidative stress via reactive oxygen species (ROS) generation. This study aimed to investigate the effects of the antioxidant N-acetylcysteine (NAC) against PQ-induced oxidative stress in mice. Male Balb/C mice (24) were randomly divided into 4 groups and treated for 3 weeks: 1) control (saline), 2) NAC (0.5% in diet), 3) PQ (20 mg/kg, IP) and 4) combination (PQ + NAC). Afterwards mice were sacrificed and oxidative stress markers were analyzed. Our data showed no significant change in serum antioxidant capacity. PQ enhanced lipid peroxidation (MDA) levels in liver tissue compared to control whereas NAC decreased MDA levels (p<0.05). NAC significantly increased MDA in brain tissue (p<0.05). PQ significantly depleted glutathione (GSH) levels in liver (p=0.001) and brain tissue (p<0.05) but non-significant GSH depletion in lung tissue. NAC counteracted PQ, showing a moderate increase GSH levels in liver and brain tissues. PQ significantly increased 8-oxodeoxyguanosine (8-OH-dG) levels (p<0.05) in liver tissue compared to control without a significant change in brain tissue. NAC treatment ameliorated PQ-induced oxidative DNA damage in the liver tissue. PQ significantly decreased the relative mtDNA amplification and increased the frequency of lesions in liver and brain tissue (p<0.0001), while NAC restored the DNA polymerase activity in liver tissue but not in brain tissue. In conclusion, PQ induced lipid peroxidation, oxidative nuclear DNA and mtDNA damage in liver tissues and depleted liver and brain GSH levels. NAC supplementation ameliorated the PQ-induced oxidative stress response in liver tissue of mice.

Redox Imbalance and Viral Infections in Neurodegenerative Diseases

Reactive oxygen species (ROS) are essential molecules for many physiological functions and act as second messengers in a large variety of tissues. An imbalance in the production and elimination of ROS is associated with human diseases including neurodegenerative disorders. In the last years the notion that neurodegenerative diseases are accompanied by chronic viral infections, which may result in an increase of neurodegenerative diseases progression, emerged. It is known in literature that enhanced viral infection risk, observed during neurodegeneration, is partly due to the increase of ROS accumulation in brain cells. However, the molecular mechanisms of viral infection, occurring during the progression of neurodegeneration, remain unclear. In this review, we discuss the recent knowledge regarding the role of influenza, herpes simplex virus type-1, and retroviruses infection in ROS/RNS-mediated Parkinson's disease (PD), Alzheimer's disease (AD), and amyotrophic lateral sclerosis (ALS).