The mitochondrial generation of hydrogen peroxide. General properties and effect of hyperbaric oxygen

Factors affecting liver mitochondrial hydrogen peroxide emission

Mitochondria are key cellular sources of reactive oxygen species (ROS) and contain at least 12 known sites on multiple enzymes that convert molecular oxygen to superoxide and hydrogen peroxide (H₂O₂). Quantitation of site-specific ROS emission is critical to understand the relative contribution of different sites and the pathophysiologic importance of mitochondrial ROS. However, factors that affect mitochondrial ROS emission are not well understood. We characterized and optimized conditions for maximal total and site-specific H₂O₂ emission during oxidation of standard substrates and probed the source of the high H₂O₂ emission in unenergized rainbow trout liver mitochondria. We found that mitochondrial H₂O₂ emission capacity depended on the substrate being oxidized, mitochondrial protein concentration, and composition of the ROS detection system. Contrary to our expectation, addition of exogenous superoxide dismutase reduced H₂O₂ emission. Titration of conventional mitochondrial electron transfer system (ETS) inhibitors over a range of conditions revealed that one size does not fit all; inhibitor concentrations evoking maximal responses varied with substrate and were moderated by the presence of other inhibitors. Moreover, the efficacy of suppressors of electron leak (S1QEL1.1 and S3QEL2) was low and depended on the substrate being oxidized. We found that H₂O₂ emission in unenergized rainbow trout liver mitochondria was suppressed by GKT136901 suggesting that it is associated with NADPH oxidase activity. We conclude that optimization of assay conditions is critical for quantitation of maximal H₂O₂ emission and would facilitate more valid comparisons of mitochondrial total and site-specific H₂O₂ emission capacities between studies, tissues, and species.

Photobiomodulation intervention improves oxidative, inflammatory, and morphological parameters of skeletal muscle in cirrhotic Wistar rats

Photobiomodulation (PBM) might be an intervention method to mitigate sarcopenia in cirrhotic patients. Given the lack of research on this issue, the goal of this study was to evaluate possible beneficial effects of PBM on the structural and functional properties of skeletal muscle from cirrhotic rats. Cirrhosis was induced by secondary bile duct ligation (BDL). Wistar rats were randomized into four groups: sham-operated control (Sham), Sham + PBM, BDL, and BDL + PBM. After cirrhosis induction, a dose of PBM (1 J; 100mW; 10 s; 880 nm; 6 × per week) was applied to each quadriceps, from the 15th to the 45th day after surgery. The locomotor ability was performed using an open-field task. The muscle structure was analyzed using histological methods. Cell damage was also evaluated assessing oxidative stress and DNA damage markers, and IL-1β pro-inflammatory interleukin by immunohistochemical analysis. An increase in the number of crossings was observed in the BDL + PBM group in relation to BDL. The BDL group showed muscle atrophy and increased IL-1β in relation to Sham, while in the BDL + PBM group, the fiber muscle was restructured and there was a decrease of IL-1 β. TBARS increased in the liver and muscle tissues in the BDL group and decreased it in the BDL + PBM group. SOD increased while CAT decreased in the BDL + PBM group in relation to the BDL group. No genotoxic or mutagenic effect was observed for PBM treatment. PBM improved the locomotion and the morphology of the muscle fibers, decreasing oxidative stress and inflammation, without causing DNA damage in cirrhotic rats.

Commentary on "Production of superoxide radicals and hydrogen peroxide by NADH-ubiquinone reductase and ubiquinol-cytochrome c reductase from beef-heart mitochondria"

On Production of superoxide radicals and hydrogen peroxide by NADH-ubiquinone reductase and ubiquinol-cytochrome c reductase from beef-heart mitochondria (Arch Biochem Biophys (1977) 180, 248-257) reviews early work that influenced future studies on the mitochondrial production of superoxide anion and hydrogen peroxide.

BODIPY-based rapid response fluorescence probe for sensing and bioimaging endogenous superoxide anion in living cells

The superoxide anion radical (O₂^-), a pernicious ROS in living cells, has long been recognized as an important cell signaling molecule involved in numerous physiological and pathological processes, including innate immunity and metabolic homeostasis. Here, we developed a new bodipy-based fluorescent probe for monitoring O₂^- based on the selective cleavage of phosphate bond in BODIPY-T by O₂^-, producing a high-brightness fluorescent BODIPY-COOH. The probe exhibits excellent selectivity for O₂^- with little interference from other ROS species. Fluorescence imaging of RAW264.7 cells also demonstrated successful detection of endogenous O₂^- changes in living cells, indicating that BODIPY-T is a potential probe for the diagnosis and study of the corresponding diseases.

Cytochrome c Oxidase Inhibition by ATP Decreases Mitochondrial ROS Production

This study addresses the eventual consequence of cytochrome c oxidase (CytOx) inhibition by ATP at high ATP/ADP ratio in isolated rat heart mitochondria. Earlier, it has been demonstrated that the mechanism of allosteric ATP inhibition of CytOx is one of the key regulations of mitochondrial functions. It is relevant that aiming to maintain a high ATP/ADP ratio for the measurement of CytOx activity effectuating the enzymatic inhibition as well as mitochondrial respiration, optimal concentration of mitochondria is critically important. Likewise, only at this concentration, were the differences in ΔΨ_m and ROS concentrations measured under various conditions significant. Moreover, when CytOx activity was inhibited in the presence of ATP, mitochondrial respiration and ΔΨ_m both remained static, while the ROS production was markedly decreased. Consubstantial results were found when the electron transport chain was inhibited by antimycin A, letting only CytOx remain functional to support the energy production. This seems to corroborate that the decrease in mitochondrial ROS production is solely the effect of ATP binding to CytOx which results in static respiration as well as membrane potential.

Toxicity, Anti-Inflammatory, and Antioxidant Activities of Cubiu (Solanum sessiliflorum) and Its Interaction with Magnetic Field in the Skin Wound Healing

Cubiu, an Amazonian fruit, is widely used as food and popular treatment for pathologies that present an inflammatory pattern, such as skin wound healing. However, there is still no confirmation in the scientific literature about the safety profile, as well as the anti-inflammatory, antioxidant, and healing actions of cubiu. This study is divided into two experimental protocols using Wistar rats. Thus, the first objective (protocol 1) of this study was to evaluate the toxicity of an oral administration of cubiu extract at different doses for 28 days. The macroscopic and microscopic analyses of the liver and kidney were performed, and the following analysis was determined in plasma: glutamic oxaloacetic transaminase, glutamic pyruvic transaminase, gamma-glutamyl transpeptidase, glucose, triglycerides, total cholesterol, urea, creatinine, and uric acid. After, we conducted the second protocol aimed to establish the potential antioxidant and anti-inflammatory capacity of cubiu and its interaction with magnetic field in skin wound healing. On days 3, 7, and 14 of treatment, skin and blood samples were collected and analyzed: the oxidative stress biomarkers (reactive substances to thiobarbituric acid, nonprotein thiols, superoxide dismutase, catalase, and glutathione S-transferase), myeloperoxidase enzymatic activity, and cytokines levels (interleukin 1, interleukin 6, interleukin 10, and tumor necrosis factor-alpha). The cubiu has shown to be safe and nontoxic. Both cubiu and magnetic field promoted decreased levels of proinflammatory and prooxidant biomarkers (interleukin 1, interleukin 6, tumor necrosis factor-alpha, and reactive substances to thiobarbituric acid), as well as increased levels of anti-inflammatory and antioxidant biomarkers (interleukin 10, nonprotein thiols, and superoxide dismutase), with greater potential when treatments are used in association. Thus, cubiu promotes antioxidant and anti-inflammatory action in skin wound healing, while also improving results of the conventional treatment for skin healing (magnetic field) when used in association.

Oxidative Stress and Assisted Reproduction: A Comprehensive Review of Its Pathophysiological Role and Strategies for Optimizing Embryo Culture Environment

Oxidative stress (OS) due to an imbalance between reactive oxygen species (ROS) and antioxidants has been established as an important factor that can negatively affect the outcomes of assisted reproductive techniques (ARTs). Excess ROS exert their pathological effects through damage to cellular lipids, organelles, and DNA, alteration of enzymatic function, and apoptosis. ROS can be produced intracellularly, from immature sperm, oocytes, and embryos. Additionally, several external factors may induce high ROS production in the ART setup, including atmospheric oxygen, CO2 incubators, consumables, visible light, temperature, humidity, volatile organic compounds, and culture media additives. Pathological amounts of ROS can also be generated during the cryopreservation-thawing process of gametes or embryos. Generally, these factors can act at any stage during ART, from gamete preparation to embryo development, till the blastocyst stage. In this review, we discuss the in vitro conditions and environmental factors responsible for the induction of OS in an ART setting. In addition, we describe the effects of OS on gametes and embryos. Furthermore, we highlight strategies to ameliorate the impact of OS during the whole human embryo culture period, from gametes to blastocyst stage.

Role of mitochondrial reactive oxygen species in homeostasis regulation

Mitochondria are the main source of reactive oxygen species (ROS) in cells. Early studies have shown that mitochondrial reactive oxygen species (mROS) are related to the occurrence and adverse outcomes of many diseases, and are thus regarded as an important risk factor that threaten human health. Recently, increasing evidence has shown that mROS are very important for an organism’s homeostasis. mROS can regulate a variety of signaling pathways and activate the adaptation and protection behaviors of an organism under stress. In addition, mROS also regulate important physiological processes, such as cell proliferation, differentiation, aging, and apoptosis. Herein, we review the mechanisms of production, transformation, and clearance of mROS and their biological roles in different physiological processes.

Metabolic response of Mercenaria mercenaria under heat and hypoxia stress by widely targeted metabolomic approach

In the context of global climatic changes, marine organisms have been exposed to environmental stressors including heat and hypoxia. This calls for the design of multi-stressors to uncover the impact of oceanic factors on aquatic organisms. So far, little is known about the metabolic response of marine organisms, especially bivalves, to the combined effects of heat and hypoxia. In this study, we employed widely targeted metabolomic analysis to study the metabolic response of gills in hard clam, a heat- and hypoxia-tolerant bivalve. A total of 810 metabolites were identified. Results showed that the heat group (HT) and heat plus hypoxia group (HL) had a higher number of differential metabolites than the hypoxia group (LO). Glycolysis was affected by the heat and heat plus hypoxia stress. Moreover, anaerobic metabolic biomarkers were accumulated marking the onset of anaerobic metabolism. Environmental stresses may affect Tricarboxylic acid (TCA) cycle. Accumulation of carnitine and glycerophospholipid may promote fatty acid β oxidation and maintain cell membrane stability, respectively. The high content of oxidized lipids (i.e., Leukotriene) in HL and HT groups implied that the organisms were under ROS stress. The significantly differential metabolites of organic osmolytes and vitamins might relieve ROS stress. Moreover, accumulation of thermoprotective osmolytes (monosaccharide, Trimethylamine N-oxide (TMAO)) accumulation was helpful to maintain protein homeostasis. This investigation provided new insights into the adaptation mechanisms of hard clam to heat, hypoxia and combined stress at the metabolite level and highlighted the roles of molecules and protectants.

Metabolic Reprogramming, Gut Dysbiosis, and Nutrition Intervention in Canine Heart Disease

This review provides a state-of-the-art overview on recent advances in systems biology in canine cardiac disease, with a focus on our current understanding of bioenergetics and amino acid metabolism in myxomatous mitral valve disease (MMVD). Cross-species comparison is drawn to highlight the similarities between human and canine heart diseases. The adult mammalian heart exhibits a remarkable metabolic flexibility and shifts its energy substrate preference according to different physiological and pathological conditions. The failing heart suffers up to 40% ATP deficit and is compared to an engine running out of fuel. Bioenergetics and metabolic readaptations are among the major research topics in cardiac research today. Myocardial energy metabolism consists of three interconnected components: substrate utilization, oxidative phosphorylation, and ATP transport and utilization. Any disruption or uncoupling of these processes can result in deranged energy metabolism leading to heart failure (HF). The review describes the changes occurring in each of the three components of energy metabolism in MMVD and HF. It also provides an overview on the changes in circulating and myocardial glutathione, taurine, carnitines, branched-chain amino acid catabolism and tryptophan metabolic pathways. In addition, the review summarizes the potential role of the gut microbiome in MMVD and HF. As our knowledge and understanding in these molecular and metabolic processes increase, it becomes possible to use nutrition to address these changes and to slow the progression of the common heart diseases in dogs.

Production of reactive oxygen species and involvement of bioprotectants during anhydrobiosis in the tardigrade Paramacrobiotus spatialis

Water unavailability is an abiotic stress causing unfavourable conditions for life. Nevertheless, some animals evolved anhydrobiosis, a strategy allowing for the reversible organism dehydration and suspension of metabolism as a direct response to habitat desiccation. Anhydrobiotic animals undergo biochemical changes synthesizing bioprotectants to help combat desiccation stresses. One stress is the generation of reactive oxygen species (ROS). In this study, the eutardigrade Paramacrobiotus spatialis was used to investigate the occurrence of ROS associated with the desiccation process. We observed that the production of ROS significantly increases as a function of time spent in anhydrobiosis and represents a direct demonstration of oxidative stress in tardigrades. The degree of involvement of bioprotectants, including those combating ROS, in the P. spatialis was evaluated by perturbing their gene functions using RNA interference and assessing the successful recovery of animals after desiccation/rehydration. Targeting the glutathione peroxidase gene compromised survival during drying and rehydration, providing evidence for the role of the gene in desiccation tolerance. Targeting genes encoding glutathione reductase and catalase indicated that these molecules play roles during rehydration. Our study also confirms the involvement of aquaporins 3 and 10 during rehydration. Therefore, desiccation tolerance depends on the synergistic action of many different molecules working together.

Blueberry extract improves redox balance and functional parameters in the right ventricle from rats with pulmonary arterial hypertension

PURPOSE

Pulmonary arterial hypertension (PAH) is a disease characterized by increased pulmonary vascular resistance and right ventricle (RV) failure. In this context, oxidative stress is an essential element contributing to PAH's pathophysiology. Thus, blueberry (BB), which has a high antioxidant capacity, emerges as a natural therapeutic approach in PAH. This work evaluated the effect of BB extract on redox balance in RV in a PAH's animal model.

METHODS

Male Wistar rats (200 ± 20 g) (n = 72) were randomized into eight groups: control (CTR); monocrotaline (MCT); CTR and MCT treated at doses of 50, 100, and 200 mg/kg BB. PAH was induced by administration of MCT (60 mg/kg, intraperitoneal). Rats were treated with BB orally for 5 weeks (2 weeks before monocrotaline and 3 weeks after monocrotaline injection). On day 35, rats were submitted to echocardiography and catheterization, then euthanasia and RV harvesting for biochemical analyses.

RESULTS

RV hypertrophy, observed in the MCT groups, was reduced with BB treatment. MCT elevated RV systolic pressure and pressure/time derivatives, while the intervention with BB decreased these parameters. PAH decreased RV output and pulmonary artery outflow acceleration/ejection time ratio, while increased RV diameters, parameters restored by BB treatment. Animals from the MCT group showed elevated lipid peroxidation and NADPH oxidase activity, outcomes attenuated in animals treated with BB, which also led to increased catalase activity.

CONCLUSION

Treatment with BB partially mitigated PAH, which could be associated with improvement of RV redox state. Such findings constitute an advance in the investigation of the role of BB extract in chronic progressive cardiovascular diseases that involve the redox balance, such as PAH.

The Role of Sphingolipid Signaling in Oxidative Lung Injury and Pathogenesis of Bronchopulmonary Dysplasia

Premature infants are born with developing lungs burdened by surfactant deficiency and a dearth of antioxidant defense systems. Survival rate of such infants has significantly improved due to advances in care involving mechanical ventilation and oxygen supplementation. However, a significant subset of such survivors develops the chronic lung disease, Bronchopulmonary dysplasia (BPD), characterized by enlarged, simplified alveoli and deformed airways. Among a host of factors contributing to the pathogenesis is oxidative damage induced by exposure of the developing lungs to hyperoxia. Recent data indicate that hyperoxia induces aberrant sphingolipid signaling, leading to mitochondrial dysfunction and abnormal reactive oxygen species (ROS) formation (ROS). The role of sphingolipids such as ceramides and sphingosine 1-phosphate (S1P), in the development of BPD emerged in the last decade. Both ceramide and S1P are elevated in tracheal aspirates of premature infants of <32 weeks gestational age developing BPD. This was faithfully reflected in the murine models of hyperoxia and BPD, where there is an increased expression of sphingolipid metabolites both in lung tissue and bronchoalveolar lavage. Treatment of neonatal pups with a sphingosine kinase1 specific inhibitor, PF543, resulted in protection against BPD as neonates, accompanied by improved lung function and reduced airway remodeling as adults. This was accompanied by reduced mitochondrial ROS formation. S1P receptor1 induced by hyperoxia also aggravates BPD, revealing another potential druggable target in this pathway for BPD. In this review we aim to provide a detailed description on the role played by sphingolipid signaling in hyperoxia induced lung injury and BPD.

Antioxidant Roles of SGLT2 Inhibitors in the Kidney

The reduction-oxidation (redox) system consists of the coupling and coordination of various electron gradients that are generated thanks to serial reduction-oxidation enzymatic reactions. These reactions happen in every cell and produce radical oxidants that can be mainly classified into reactive oxygen species (ROS) and reactive nitrogen species (RNS). ROS and RNS modulate cell-signaling pathways and cellular processes fundamental to normal cell function. However, overproduction of oxidative species can lead to oxidative stress (OS) that is pathological. Oxidative stress is a main contributor to diabetic kidney disease (DKD) onset. In the kidney, the proximal tubular cells require a high energy supply to reabsorb proteins, metabolites, ions, and water. In a diabetic milieu, glucose-induced toxicity promotes oxidative stress and mitochondrial dysfunction, impairing tubular function. Increased glucose level in urine and ROS enhance the activity of sodium/glucose co-transporter type 2 (SGLT2), which in turn exacerbates OS. SGLT2 inhibitors have demonstrated clear cardiovascular benefits in DKD which may be in part ascribed to the generation of a beneficial equilibrium between oxidant and antioxidant mechanisms.

Antioxidant Paradox in Male Infertility: 'A Blind Eye' on Inflammation

The pathophysiology of male infertility involves various interlinked endogenous pathways. About 50% of the cases of infertility in men are idiopathic, and oxidative stress (OS) reportedly serves as a central mechanism in impairing male fertility parameters. The endogenous antioxidant system operates to conserve the seminal redox homeostasis required for normal male reproduction. OS strikes when a generation of seminal reactive oxygen species (ROS) overwhelms endogenous antioxidant capacity. Thus, antioxidant treatment finds remarkable relevance in the case of idiopathic male infertility or subfertility. However, due to lack of proper detection of OS in male infertility, use of antioxidant(s) in some cases may be arbitrary or lead to overuse and induction of 'reductive stress'. Moreover, inflammation is closely linked to OS and may establish a vicious loop that is capable of disruption to male reproductive tissues. The result is exaggeration of cellular damage and disruption of male reproductive tissues. Therefore, limitations of antioxidant therapy in treating male infertility are the failure in the selection of specific treatments targeting inflammation and OS simultaneously, two of the core mechanisms of male infertility. The present review aims to elucidate the antioxidant paradox in male infertility treatment, from the viewpoints of both induction of reductive stress as well as overlooking the inflammatory consequences.

Current views in chronic obstructive pulmonary disease pathogenesis and management

Chronic obstructive pulmonary disease (COPD) is a progressive lung dysfunction caused mainly by inhaling toxic particles and cigarette smoking (CS). The continuous exposure to ruinous molecules can lead to abnormal inflammatory responses, permanent damages to the respiratory system, and irreversible pathological changes. Other factors, such as genetics and aging, influence the development of COPD. In the last decade, accumulating evidence suggested that mitochondrial alteration, including mitochondrial DNA damage, increased mitochondrial reactive oxygen species (ROS), abnormal autophagy, and apoptosis, have been implicated in the pathogenesis of COPD. The alteration can also extend to epigenetics, namely DNA methylation, histone modification, and non-coding RNA. This review will discuss the recent progressions in COPD pathology, pathophysiology, and molecular pathways. More focus will be shed on mitochondrial and epigenetic variations related to COPD development and the role of nanomedicine as a potential tool for the prevention and treatment of this disease.

Behavioral, Oxidative, and Biochemical Effects of Omega-3 on an Ovariectomized Rat Model of Menopause

OBJECTIVES

Menopause induces changes in neuronal transmission, leading to anxiety and depression. Changes in the brain's glutamate levels cause psychological behavior in postmenopausal women. Omega-3 has been studied to improve some of these behaviors.

METHODS

Twenty-four female Wistar rats were divided into four groups: sham-operated treated with water (SO-W), sham-operated treated with omega-3 (SO-O), ovariectomized (OVX) treated with water (OVX-W), and bilateral OVX treated with omega-3 (OVX-O). These treatments were performed for 20 days via gavage, before and after surgery, totaling 40 days.

RESULTS

In the forced swimming, elevated plus-maze, and open field tests to assess behaviors, such as depression and anxiety, omega-3 improved these behaviors in both treated groups. The levels of thiobarbituric acid reactive substances (TBARS) in the brain were not different between the groups; however, there was a significant decrease in the catalase activity in the SO-O group compared with the SO-W group (P < 0.05). The glutamate level in the cerebrospinal fluid (CSF) was elevated in the SO-O group (P < 0.001) but not in the OVX-W or OVX-O groups.

CONCLUSIONS

These results bring novel data when related to the glutamatergic system in the SO-O group. This has suggested that the action mechanism of omega-3 was not dependent on glutamate levels in the CSF of the OVX group, but it played a regulatory role in the sham-operated animals. To confirm this, more studies are needed to explore this field when relating to the estrogen and glutamate receptor changes in specific brain regions.

Effects of Hyperoxia on Aging Biomarkers: A Systematic Review

The effects of short-term hyperoxia on age-related diseases and aging biomarkers have been reported in animal and human experiments using different protocols; however, the findings of the studies remain conflicting. In this systematic review, we summarized the existing reports in the effects of short-term hyperoxia on age-related diseases, hypoxia-inducible factor 1α (HIF-1α), and other oxygen-sensitive transcription factors relevant to aging, telomere length, cellular senescence, and its side effects. This review was done as described in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. A systematic search was done in PubMed, Google Scholar, and Cochrane Library and from the references of selected articles to identify relevant studies until May 2021. Of the total 1,699 identified studies, 17 were included in this review. Most of the studies have shown significant effects of short-term hyperoxia on age-related diseases and aging biomarkers. The findings of the studies suggest the potential benefits of short-term hyperoxia in several clinical applications such as for patients undergoing stressful operations, restoration of cognitive function, and the treatment of severe traumatic brain injury. Short-term hyperoxia has significant effects in upregulation or downregulation of transcription factors relevant to aging such as HIF-1α, nuclear factor kappa-light-chain-enhancer of activated B-cells (NF-kB), and nuclear factor (erythroid-derived 2)-like 2 (NRF2) among others. Short-term hyperoxia also has significant effects to increase antioxidant enzymes, and increase telomere length and clearance of senescent cells. Some of the studies have also reported adverse consequences including mitochondrial DNA damage and nuclear cataract formation depending on the dose and duration of oxygen exposure. In conclusion, short-term hyperoxia could be a feasible treatment option to treat age-related disease and to slow aging because of its ability to increase antioxidant enzymes, significantly increase telomere length and clearance of senescent cells, and improve cognitive function, among others. The reported side effects of hyperoxia vary depending on the dose and duration of exposure. Therefore, it seems that additional studies for better understanding the beneficial effects of short-term hyperoxia and for minimizing side effects are necessary for optimal clinical application.

Oxidative Stress and Toxicity in Reproductive Biology and Medicine: A Comprehensive Update on Male Infertility Volume II - Conclusion

Infertility is a globally under-recognized public health problem significantly impacting individual health and socioeconomics affecting millions of couples. The reasons for infertility are manifold and not only include many couples decision to postpone having children but also diseases (e.g., diabetes, infections, or varicocele), lifestyle (e.g., obesity), and environmental factors (e.g., bisphenol A, DTT or dioxin). In the pathology of many causes of infertility, oxidative stress plays a significant role as reactive oxygen species (ROS) exert significant detrimental effects. On the other hand, a small amount of ROS is essential to trigger physiological events such as capacitation. Therefore, a fine balance between oxidation and reduction has to be maintained. Apart from treating the underlying disease or correcting the cause of the infertility, oxidative stress can be treated by antioxidant supplementation. Since plants and their extracts contain numerous phytochemicals which exhibit antioxidant activity, many people tend to use herbal products. Alternatively, isolated antioxidants such as vitamin C or E are also used. However, when using purified antioxidants, it is essential that the redox balance is maintained to avoid a "reductive stress" situation, which is as harmful as oxidative stress.

Reductive Stress and Male Infertility

Male infertility research and clinical advances had vast progress in the last few decades. Strong research evidence underpinned the concepts of oxidative stress (OS)-mediated male reproductive disruptions, which bear answers to several cases of idiopathic male infertility. Antioxidant treatment held the prime solution for OS-mediated male infertility. But excess use of antioxidants is challenged by the research breakthrough that reductive stress also predisposes to male infertility, resolutely instituting that any biological extremes of the redox spectrum are deleterious to male fertility. Superfluity of reducing agents may hinder essential oxidation mechanisms, affecting physiological homeostasis. These mechanisms need to be explicated and updated time and again to identify the fine thread between OS-mediated male infertility treatment and induction of reductive stress. This chapter thus presents the evidence-based concepts pertaining to the antioxidants actions to combat OS-induced male infertility, the mechanism of induction of reductive stress and its impact on male reproduction.

Mitophagy in Yeast: Decades of Research

Mitophagy, the selective degradation of mitochondria by autophagy, is one of the most important mechanisms of mitochondrial quality control, and its proper functioning is essential for cellular homeostasis. In this review, we describe the most important milestones achieved during almost 2 decades of research on yeasts, which shed light on the molecular mechanisms, regulation, and role of the Atg32 receptor in this process. We analyze the role of ROS in mitophagy and discuss the physiological roles of mitophagy in unicellular organisms, such as yeast; these roles are very different from those in mammals. Additionally, we discuss some of the different tools available for studying mitophagy.

Pharmacological Modulation of Nrf2/HO-1 Signaling Pathway as a Therapeutic Target of Parkinson's Disease

Parkinson’s disease (PD) is a complex neurodegenerative disorder featuring both motor and nonmotor symptoms associated with a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Oxidative stress (OS) has been implicated in the pathogenesis of PD. Genetic and environmental factors can produce OS, which has been implicated as a core contributor to the initiation and progression of PD through the degeneration of dopaminergic neurons. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates activation of multiple protective genes, including heme oxygenase-1 (HO-1), which protects cells from OS. Nrf2 has also been shown to exert anti-inflammatory effects and modulate both mitochondrial function and biogenesis. Recently, a series of studies have reported that different bioactive compounds were shown to be able to activate Nrf2/antioxidant response element (ARE) and can ameliorate PD-associated neurotoxin, both in animal models and in tissue culture. In this review, we briefly overview the sources of OS and the association between OS and the pathogenesis of PD. Then, we provided a concise overview of Nrf2/ARE pathway and delineated the role played by activation of Nrf2/HO-1 in PD. At last, we expand our discussion to the neuroprotective effects of pharmacological modulation of Nrf2/HO-1 by bioactive compounds and the potential application of Nrf2 activators for the treatment of PD. This review suggests that pharmacological modulation of Nrf2/HO-1 signaling pathway by bioactive compounds is a therapeutic target of PD.

A Review of Potential Novel Glaucoma Therapeutic Options Independent of Intraocular Pressure

Glaucoma, a progressive optic neuropathy characterized by retinal ganglion cell degeneration and visual field loss, is the leading cause of irreversible blindness worldwide. Intraocular pressure (IOP) is presently the only modifiable risk factor demonstrated to slow or halt disease progression; however, glaucomatous damage persists in almost 50% of patients despite significant IOP reduction. Many studies have investigated the non-IOP-related risk factors that contribute to glaucoma progression as well as interventions that can prevent or delay glaucomatous neurodegeneration and preserve vision throughout life, independently of IOP. A vast number of experimental studies have reported effective neuroprotection in glaucoma, and clinical studies are ongoing attempting to provide strong evidence of effectiveness of these interventions. In this review, we look into the current understanding of the pathophysiology of glaucoma and explore the recent advances in non-IOP related strategies for neuroprotection and neuroregeneration in glaucoma.

Environmental toxicant-induced maladaptive mitochondrial changes: A potential unifying mechanism in fatty liver disease?

Occupational and environmental exposures to industrial chemicals are well known to cause hepatotoxicity and liver injury. However, despite extensive evidence showing that exposure can lead to disease, current research approaches and regulatory policies fail to address the possibility that subtle changes caused by low level exposure to chemicals may also enhance preexisting conditions. In recent years, the conceptual understanding of the contribution of environmental chemicals to liver disease has progressed significantly. Mitochondria are often target of toxicity of environmental toxicants resulting in multisystem disorders involving different cells, tissues, and organs. Here, we review persistent maladaptive changes to mitochondria in response to environmental toxicant exposure as a mechanism of hepatotoxicity. With better understanding of the mechanism(s) and risk factors that mediate the initiation and progression of toxicant-induced liver disease, rational targeted therapy can be developed to better predict risk, as well as to treat or prevent this disease.

Targeted antioxidant delivery modulates mitochondrial functions, ameliorates oxidative stress and preserve sperm quality during cryopreservation

Mitochondria are vital organelles with a multifaceted role in cellular bioenergetics, biosynthesis, signaling and calcium homeostasis. During oxidative phosphorylation, sperm mitochondria generate reactive oxygen species (ROS) at physiological levels mediating signaling pathways essential for sperm fertilizing competence. Moreover, sperm subpopulation with active mitochondria is positively associated with sperm motility, chromatin and plasma membrane integrity, and normal morphology. However, the osmotic and thermal stress, and intracellular ice crystal formation generate excess ROS to cause mitochondrial dysfunction, potentiating cryoprotectant-induced calcium overload in the mitochondrial matrix. It further stimulates the opening of mitochondrial permeability transition pores (mPTP) to release pro-apoptotic factors from mitochondria and initiate apoptotic cascade, with a decrease in Mitochondrial Membrane Potential (MMP) and altered sperm functions. To improve the male reproductive potential, it is essential to address challenges in semen cryopreservation, precisely the deleterious effects of oxidative stress on sperm quality. During semen cryopreservation, the supplementation of extended semen with conventional antioxidants is extensively reported. However, the outcomes of supplementation to improve semen quality are inconclusive across different species, which is chiefly attributed to the unknown bioavailability of antioxidants at the primary site of ROS generation, i.e., mitochondria. Increasing evidence suggests that the targeted delivery of antioxidants to sperm mitochondria is superior in mitigating oxidative stress and improving semen freezability than conventional antioxidants. Therefore, the present review comprehensively describes mitochondrial-targeted antioxidants, their mechanism of action and effects of supplementation on improving semen cryopreservation efficiency in different species. Moreover, it also discusses the significance of active mitochondria in determining sperm fertilizing competence, cryopreservation-induced oxidative stress and mitochondrial dysfunction, and its implications on sperm fertility. The potential of mitochondrial-targeted antioxidants to modulate mitochondrial functions and improve semen quality has been reviewed extensively.

Oxidative Stress, Mitochondrial Function and Adaptation to Exercise: New Perspectives in Nutrition

Cells have the ability to adapt to stressful environments as a part of their evolution. Physical exercise induces an increase of a demand for energy that must be met by mitochondria as the main (ATP) provider. However, this process leads to the increase of free radicals and the so-called reactive oxygen species (ROS), which are necessary for the maintenance of cell signaling and homeostasis. In addition, mitochondrial biogenesis is influenced by exercise in continuous crosstalk between the mitochondria and the nuclear genome. Excessive workloads may induce severe mitochondrial stress, resulting in oxidative damage. In this regard, the objective of this work was to provide a general overview of the molecular mechanisms involved in mitochondrial adaptation during exercise and to understand if some nutrients such as antioxidants may be implicated in blunt adaptation and/or an impact on the performance of exercise by different means.

Identification of FtpA, a Dps-like protein involved in anti-oxidative stress and virulence in Actinobacillus pleuropneumoniae

Bacteria have evolved a variety of enzymes to eliminate endogenous or host-derived oxidative stress factors. The Dps protein, first identified in Escherichia coli, contains a ferroxidase center and protects bacteria from reactive oxygen species damage. There is a lack of knowledge of the role of Dps-like proteins in bacterial pathogenesis. Actinobacillus pleuropneumoniae causes pleuropneumonia, a respiratory disease of swine. The A. pleuropneumoniae ftpA gene is up-regulated during a shift to anaerobiosis, in biofilms and, as found in this study, also by H₂O₂. An A. pleuropneumoniae ftpA deletion mutant (△ftpA) had increased H₂O₂ sensitivity, less intracellular viability in macrophages, and decreased virulence in a mouse infection model. Expression of ftpA in an E. coli dps mutant restored wild-type resistance to H₂O₂. FtpA possesses a conserved ferritin domain containing a ferroxidase site. Recombinant rFtpA bound and oxidized Fe²⁺ reversibly. Under aerobic conditions, compared with the wild-type strain, the viability of an △ftpA mutant was reduced after extended culture, transition from anaerobic to aerobic conditions, and upon supplementation with Fenton reaction substrates. Under anaerobic conditions, additional H₂O₂ resulted in a more severe growth defect of △ftpA than under aerobic conditions. Therefore, by oxidizing and mineralizing Fe²⁺, FtpA alleviates oxidative damage mediated by intracellular Fenton reactions. Furthermore, by mutational analysis, two residues were confirmed to be critical for Fe²⁺ binding and oxidization, as well as for A. pleuropneumoniae H₂O₂ resistance. Taken together, this study demonstrates that A. pleuropneumoniae FtpA is a Dps-like protein, playing critical roles in oxidative stress resistance and virulence. IMPORTANCE As a ferroxidase, Dps of Escherichia coli can protect bacteria from reactive oxygen species damage, but its role in bacterial pathogenesis has received little attention. In this study, FtpA of the swine respiratory pathogen A. pleuropneumoniae was identified as a new Dps-like protein. It facilitated A. pleuropneumoniae resistance to H₂O₂, survival in macrophages, and infection in vivo. FtpA could bind and oxidize Fe²⁺ through two important residues in its ferroxidase site and protected the bacteria from oxidative damage mediated by the intracellular Fenton reaction. These findings provide new insights into the role of the FtpA-based antioxidant system in the pathogenesis of A. pleuropneumoniae, and the conserved Fe²⁺ binding ligands in Dps/FtpA provide novel drug target candidates for disease prevention.

Mitochondrial Management of Reactive Oxygen Species

Mitochondria in aerobic eukaryotic cells are both the site of energy production and the formation of harmful species, such as radicals and other reactive oxygen species, known as ROS. They contain an efficient antioxidant system, including low-molecular-mass molecules and enzymes that specialize in removing various types of ROS or repairing the oxidative damage of biological molecules. Under normal conditions, ROS production is low, and mitochondria, which are their primary target, are slightly damaged in a similar way to other cellular compartments, since the ROS released by the mitochondria into the cytosol are negligible. As the mitochondrial generation of ROS increases, they can deactivate components of the respiratory chain and enzymes of the Krebs cycle, and mitochondria release a high amount of ROS that damage cellular structures. More recently, the feature of the mitochondrial antioxidant system, which does not specifically deal with intramitochondrial ROS, was discovered. Indeed, the mitochondrial antioxidant system detoxifies exogenous ROS species at the expense of reducing the equivalents generated in mitochondria. Thus, mitochondria are also a sink of ROS. These observations highlight the importance of the mitochondrial antioxidant system, which should be considered in our understanding of ROS-regulated processes. These processes include cell signaling and the progression of metabolic and neurodegenerative disease.

Increased H2O2 levels and p53 stabilization lead to mitochondrial dysfunction in XPC-deficient cells

XPC deficiency is associated with mitochondrial dysfunction, increased mitochondrial H2O2 production and sensitivity to the Complex III inhibitor antimycin A (AA), through a yet unclear mechanism. We found an imbalanced expression of several proteins that participate in important mitochondrial function and increased expression and phosphorylation of the tumor suppressor p53 in Xeroderma pigmentosum complementation group C (XP-C) (XPC-null) cells compared with an isogenic line corrected in locus with wild-type XPC (XPC-wt). Interestingly, inhibition of p53 nuclear import reversed the overexpression of mitochondrial proteins, whereas AA treatment increased p53 expression more strongly in the XP-C cells. However, inhibition of p53 substantially increased XP-C cellular sensitivity to AA treatment, suggesting that p53 is a critical factor mediating the cellular response to mitochondrial stress. On the other hand, treatment with the antioxidant N-acetylcysteine increased glutathione concentration and decreased basal H2O2 production, p53 levels and sensitivity to AA treatment in the XPC-null back to the levels found in XPC-wt cells. Thus, the results suggest a critical role for mitochondrially generated H2O2 in the regulation of p53 expression, which in turn modulates XP-C sensitivity to agents that cause mitochondrial stress.

Cytotoxicity and Mitochondrial Effects of Phenolic and Quinone-Based Mitochondria-Targeted and Untargeted Antioxidants on Human Neuronal and Hepatic Cell Lines: A Comparative Analysis

Mitochondriotropic antioxidants (MC3, MC6.2, MC4 and MC7.2) based on dietary antioxidants and analogs (caffeic, hydrocaffeic, trihydroxyphenylpropanoic and trihydroxycinnamic acids) were developed. In this study, we evaluate and compare the cytotoxicity profile of novel mitochondria-targeted molecules (generally known as MitoCINs) on human HepG2 and differentiated SH-SY5Y cells with the quinone-based mitochondria-targeted antioxidants MitoQ and SkQ1 and with two non-targeted antioxidants, resveratrol and coenzyme Q10 (CoQ10). We further evaluate their effects on mitochondrial membrane potential, cellular oxygen consumption and extracellular acidification rates. Overall, MitoCINs derivatives reduced cell viability at concentrations about six times higher than those observed with MitoQ and SkQ1. A toxicity ranking for both cell lines was produced: MC4 < MC7.2 < MC3 < MC6.2. These results suggest that C-6 carbon linker and the presence of a pyrogallol group result in lower cytotoxicity. MC3 and MC6.2 affected the mitochondrial function more significantly relative to MitoQ, SkQ1, resveratrol and CoQ10, while MC4 and MC7.2 displayed around 100-1000 times less cytotoxicity than SkQ1 and MitoQ. Based on the mitochondrial and cytotoxicity cellular data, MC4 and MC7.2 are proposed as leads that can be optimized to develop safe drug candidates with therapeutic application in mitochondrial oxidative stress-related diseases.

Redox Regulation and Oxidative Stress in Mammalian Oocytes and Embryos Developed In Vivo and In Vitro

Oocytes and preimplantation embryos require careful regulation of the redox environment for optimal development both in vivo and in vitro. Reactive oxygen species (ROS) are generated throughout development as a result of cellular metabolism and enzyme reactions. ROS production can result in (i) oxidative eustress, where ROS are helpful signalling molecules with beneficial physiological functions and where the redox state of the cell is maintained within homeostatic range by a closely coupled system of antioxidants and antioxidant enzymes, or (ii) oxidative distress, where excess ROS are deleterious and impair normal cellular function. in vitro culture of embryos exacerbates ROS production due to a range of issues including culture-medium composition and laboratory culture conditions. This increase in ROS can be detrimental not only to assisted reproductive success rates but can also result in epigenetic and genetic changes in the embryo, resulting in transgenerational effects. This review examines the effects of oxidative stress in the oocyte and preimplantation embryo in both the in vivo and in vitro environment, identifies mechanisms responsible for oxidative stress in the oocyte/embryo in culture and approaches to reduce these problems, and briefly examines the potential impacts on future generations.

Hydrogen peroxide and phosphoinositide metabolites synergistically regulate a cation current to influence neuroendocrine cell bursting

In various neurons, including neuroendocrine cells, non-selective cation channels elicit plateau potentials and persistent firing. Reproduction in the marine snail Aplysia californica is initiated when the neuroendocrine bag cell neurons undergo an afterdischarge, that is, a prolonged period of enhanced excitability and spiking during which egg-laying hormone is released into the blood. The afterdischarge is associated with both the production of hydrogen peroxide (H₂ O₂ ) and activation of phospholipase C (PLC), which hydrolyses phosphatidylinositol-4,5-bisphosphate into diacylglycerol (DAG) and inositol trisphosphate (IP₃ ). We previously demonstrated that H₂ O₂ gates a voltage-dependent cation current and evokes spiking in bag cell neurons. The present study tests if DAG and IP₃ impact the H₂ O₂ -induced current and excitability. In whole-cell voltage-clamped cultured bag cell neurons, bath-application of 1-oleoyl-2-acetyl-sn-glycerol (OAG), a DAG analogue, enhanced the H₂ O₂ -induced current, which was amplified by the inclusion of IP₃ in the pipette. A similar outcome was produced by the PLC activator, N-(3-trifluoromethylphenyl)-2,4,6-trimethylbenzenesulfonamide. In current-clamp, OAG or OAG plus IP₃ , elevated the frequency of H₂ O₂ -induced bursting. PKC is also triggered during the afterdischarge; when PKC was stimulated with phorbol 12-myristate 13-acetate, it caused a voltage-dependent inward current with a reversal potential similar to the H₂ O₂ -induced current. Furthermore, PKC activation followed by H₂ O₂ reduced the onset latency and increased the duration of action potential firing. Finally, inhibiting nicotinamide adenine dinucleotide phosphate oxidase with 3-benzyl-7-(2-benzoxazolyl)thio-1,2,3-triazolo[4,5-d]pyrimidine diminished evoked bursting in isolated bag cell neuron clusters. These results suggest that reactive oxygen species and phosphoinostide metabolites may synergize and contribute to reproductive behaviour by promoting neuroendocrine cell firing. KEY POINTS: Aplysia bag cell neurons secrete reproductive hormone during a lengthy burst of action potentials, known as the afterdischarge. During the afterdischarge, phospholipase C (PLC) hydrolyses phosphatidylinositol-4,5-bisphosphate into diacylglycerol (DAG) and inositol trisphosphate (IP₃ ). Subsequent activation of protein kinase C (PKC) leads to H₂ O₂ production. H₂ O₂ evokes a voltage-dependent inward current and action potential firing. Both a DAG analogue, 1-oleoyl-2-acetyl-sn-glycerol (OAG), and IP₃ enhance the H₂ O₂ -induced current, which is mimicked by the PLC activator, N-(3-trifluoromethylphenyl)-2,4,6-trimethylbenzenesulfonamide. The frequency of H₂ O₂ -evoked afterdischarge-like bursting is augmented by OAG or OAG plus IP₃ . Stimulating PKC with phorbol 12-myristate 13-acetate shortens the latency and increases the duration of H₂ O₂ -induced bursts. The nicotinamide adenine dinucleotide phosphate oxidase inhibitor, 3-benzyl-7-(2-benzoxazolyl)thio-1,2,3-triazolo[4,5-d]pyrimidine, attenuates burst firing in bag cell neuron clusters.

Combination of Trans-Resveratrol and ε-Viniferin Induces a Hepatoprotective Effect in Rats with Severe Acute Liver Failure via Reduction of Oxidative Stress and MMP-9 Expression

Stilbenes are a major grapevine class of phenolic compounds, known for their biological activities, including anti-inflammatory and antioxidant, but never studied in combination. We aimed to evaluate the effect of trans-resveratrol + ε-viniferin as an antioxidant mixture and its role in inflammatory development an in vivo model of severe acute liver failure induced with TAA. Trans-resveratrol + trans-ε-viniferin (5 mg/kg each) was administered to Wistar rats. Resveratrol + ε-viniferin significantly decreased TBARS and SOD activity and restored CAT and GST activities in the treated group. This stilbene combination reduced the expression of TNFα, iNOS, and COX-2, and inhibited MMP-9. The combination of resveratrol + ε-viniferin had a hepatoprotective effect, reducing DNA damage, exhibiting a protective role on the antioxidant pathway by altering SOD, CAT, and GST activities; by downregulating TNFα, COX-2, and iNOS; and upregulating IL-10. Our results suggested that adding viniferin to resveratrol may be more effective in hepatoprotection than resveratrol alone, opening a new perspective on using this stilbene combination in functional diets.

Cofilin1 oxidation links oxidative distress to mitochondrial demise and neuronal cell death

Many cell death pathways, including apoptosis, regulated necrosis, and ferroptosis, are relevant for neuronal cell death and share common mechanisms such as the formation of reactive oxygen species (ROS) and mitochondrial damage. Here, we present the role of the actin-regulating protein cofilin1 in regulating mitochondrial pathways in oxidative neuronal death. Cofilin1 deletion in neuronal HT22 cells exerted increased mitochondrial resilience, assessed by quantification of mitochondrial ROS production, mitochondrial membrane potential, and ATP levels. Further, cofilin1-deficient cells met their energy demand through enhanced glycolysis, whereas control cells were metabolically impaired when challenged by ferroptosis. Further, cofilin1 was confirmed as a key player in glutamate-mediated excitotoxicity and associated mitochondrial damage in primary cortical neurons. Using isolated mitochondria and recombinant cofilin1, we provide a further link to toxicity-related mitochondrial impairment mediated by oxidized cofilin1. Our data revealed that the detrimental impact of cofilin1 on mitochondria depends on the oxidation of cysteine residues at positions 139 and 147. Overall, our findings show that cofilin1 acts as a redox sensor in oxidative cell death pathways of ferroptosis, and also promotes glutamate excitotoxicity. Protective effects by cofilin1 inhibition are particularly attributed to preserved mitochondrial integrity and function. Thus, interfering with the oxidation and pathological activation of cofilin1 may offer an effective therapeutic strategy in neurodegenerative diseases.

Effects of Environmental and Pathological Hypoxia on Male Fertility

Male infertility is a widespread health problem affecting approximately 6%-8% of the male population, and hypoxia may be a causative factor. In mammals, two types of hypoxia are known, including environmental and pathological hypoxia. Studies looking at the effects of hypoxia on male infertility have linked both types of hypoxia to poor sperm quality and pregnancy outcomes. Hypoxia damages testicular seminiferous tubule directly, leading to the disorder of seminiferous epithelium and shedding of spermatogenic cells. Hypoxia can also disrupt the balance between oxidative phosphorylation and glycolysis of spermatogenic cells, resulting in impaired self-renewal and differentiation of spermatogonia, and failure of meiosis. In addition, hypoxia disrupts the secretion of reproductive hormones, causing spermatogenic arrest and erectile dysfunction. The possible mechanisms involved in hypoxia on male reproductive toxicity mainly include excessive ROS mediated oxidative stress, HIF-1α mediated germ cell apoptosis and proliferation inhibition, systematic inflammation and epigenetic changes. In this review, we discuss the correlations between hypoxia and male infertility based on epidemiological, clinical and animal studies and enumerate the hypoxic factors causing male infertility in detail. Demonstration of the causal association between hypoxia and male infertility will provide more options for the treatment of male infertility.

Insulin signaling alters antioxidant capacity in the diabetic heart

Diabetic cardiomyopathy is associated with an increase in oxidative stress. However, antioxidant therapy has shown a limited capacity to mitigate disease pathology. The molecular mechanisms responsible for the modulation of reactive oxygen species (ROS) production and clearance must be better defined. The objective of this study was to determine how insulin affects superoxide radical (O₂^•–) levels. O₂^•– production was evaluated in adult cardiomyocytes isolated from control and Akita (type 1 diabetic) mice by spin-trapping electron paramagnetic resonance spectroscopy. We found that the basal rates of O₂^•– production were comparable in control and Akita cardiomyocytes. However, culturing cardiomyocytes without insulin resulted in a significant increase in O₂^•– production only in the Akita group. In contrast, O₂^•– production was unaffected by high glucose and/or fatty acid supplementation. The increase in O₂^•– was due in part to a decrease in superoxide dismutase (SOD) activity. The PI3K inhibitor, LY294002, decreased Akita SOD activity when insulin was present, indicating that the modulation of antioxidant activity is through insulin signaling. The effect of insulin on mitochondrial O₂^•– production was evaluated in Akita mice that underwent a 1-week treatment of insulin. Mitochondria isolated from insulin-treated Akita mice produced less O₂^•– than vehicle-treated diabetic mice. Quantitative proteomics was performed on whole heart homogenates to determine how insulin affects antioxidant protein expression. Of 29 antioxidant enzymes quantified, thioredoxin 1 was the only one that was significantly enhanced by insulin treatment. In vitro analysis of thioredoxin 1 revealed a previously undescribed capacity of the enzyme to directly scavenge O₂^•–. These findings demonstrate that insulin has a role in mitigating cardiac oxidative stress in diabetes via regulation of endogenous antioxidant activity.

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Insulin decreases ROS production in T1D Akita cardiomyocytes.

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Insulin signaling downstream of PI3K is required for this effect.

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Insulin increases the antioxidant capacity in the Akita heart.

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Trx1 is upregulated by insulin in the Akita heart in vivo.

Spleen tissue changes after restraint stress: effects of aerobic exercise training

Inflammation has been described as a prominent mechanism involved in dysfunctions and diseases evoked by chronic stress. Notably, the spleen is an immune organ controlled by sympathetic and glucocorticoid mechanisms, but the impact of chronic stress in the spleen is not entirely understood. Besides, the impact of aerobic exercise training on the effects of chronic stress in the spleen has never been reported. Therefore, this study aimed to assess the changes caused in the spleen by repeated restraint stress and the effect of aerobic exercise training performed after a period of chronic restraint stress in rats. We identified that daily exposure to restraint stress (120 min per session, for 14 consecutive days) increased corticosterone and noradrenaline content, gene expression of glucocorticoid and β₂-adrenergic receptors, TNF-α and IL-6 levels, and increased pro-oxidant substances in the spleen. Circulating levels of corticosterone were also increased in chronically stressed animals. Exercise training (1 h a day/5 days per week, for 60 days) increased glucocorticoid receptor gene expression, interleukin (IL)-10 and antioxidant mechanisms in the spleen. Exercise also decreased splenic noradrenaline, tumoral necrosis factor (TNF)-α, and IL-6 contents. Lastly, the effects of repeated restraint stress in the spleen were mitigated in animals subjected to aerobic training. Taken together, the results reported in the present study indicate that aerobic exercise training is a relevant non-pharmacological therapeutic approach to dysfunctions in the spleen caused by a period of stress.

Mitochondrial Dysfunction in Diseases, Longevity, and Treatment Resistance: Tuning Mitochondria Function as a Therapeutic Strategy

Mitochondria are very important intracellular organelles because they have various functions. They produce ATP, are involved in cell signaling and cell death, and are a major source of reactive oxygen species (ROS). Mitochondria have their own DNA (mtDNA) and mutation of mtDNA or change the mtDNA copy numbers leads to disease, cancer chemo/radioresistance and aging including longevity. In this review, we discuss the mtDNA mutation, mitochondrial disease, longevity, and importance of mitochondrial dysfunction in cancer first. In the later part, we particularly focus on the role in cancer resistance and the mitochondrial condition such as mtDNA copy number, mitochondrial membrane potential, ROS levels, and ATP production. We suggest a therapeutic strategy employing mitochondrial transplantation (mtTP) for treatment-resistant cancer.

Biomarkers of oxidative stress in the post-embryonic characterization of the neotropical annual killifish

Annual killifish are among the most remarkable extremophile species with the shortest vertebrate life span. Few studies have reported on the oxidative balance throughout their life cycle and its association to the natural aging process of these neotropical animals in a natural environment. We standardized and analyzed physiological markers related to the redox balance of the annual killifish (Cynopoecilus fulgens) throughout the post-embryonic life cycle (enzyme activity of Superoxide Dismutase, Catalase, Glutathione Peroxidase, and Glutathione S-transferase, as well as the determination of the levels of Lipoperoxidation, Carbonylated Proteins, and Total Proteins). We tested the influence of environmental variables on these biomarkers. Individuals were collected, including juveniles, adults, and seniles, in three sampling units around the Parque Nacional da Lagoa do Peixe, located in the Coastal Plain of Rio Grande do Sul. We observed that males and females used different physiological strategies of their redox balance during their life cycle, and their oxidative balance was influenced by their reproductive period and environmental variables (water temperature, abundance of predators, abundance of another sympatric annual killifish species, and abundance of C. fulgens). The population of each temporary pond presented different physiological responses to the adaptation of their life cycle, and there was an influence of environmental component as a modulator of this cycle. Our study offers reference values that will be useful for comparison in future research with short-lived organisms.

Evaluation of lipolysis and toxicological parameters of low-level laser therapy at different wavelengths and doses in the abdominal subcutaneous tissue

Investigate the effects of low-level lasers therapy (LLLT) aiming abdominal lipolysis. Female Wistar rats received applications of LLLT directly in the abdominal skin twice a week (5 weeks). Except the control group (n = 5), animals received treatments with red wavelength 660 nm being (I) R3.3 group (n = 5): 3.3 J/cm², and (II) R5 group (n = 5): 5 J/cm², or infrared wavelength 808 nm being (III) IR3.3 group (n = 5): 3.3 J/cm², and (IV) IR5 group (n = 5): 5 J/cm². Abdominal subcutaneous and liver tissues were evaluated histologically. Levels of thiobarbituric acid reactive substances (TBARS) and catalase (CAT) activity were analyzed in liver tissue. In the peripheral blood aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), high-density lipoprotein (HDL), low-density lipoprotein (LDL), triglycerides, and total cholesterol were investigated. Micronucleus assay was performed in the bone marrow. Except for the IR3.3 group, all treated groups reduced the body weight (p < 0.001). The R5 group reduced the abdominal subcutaneous tissue weight and thickness (p < 0.05), even though all treated groups reduced the number of adipocytes and its size (p < 0.001). No histological changes in the liver. There were no alterations in the triglycerides and LDL levels. The IR5 group increased the total cholesterol levels and decreased the HDL, ALT (both p < 0.05), and AST levels (p < 0.001). The group IR3.3 showed higher levels of ALP (p < 0.01). The R3.3 group increased the TBARS and CAT activity (p < 0.05). No mutagenic effects were found. The red laser treatment at 5 J/cm² led to lipolysis and did not alter the liver's parameters.

Changes of cardiolipin involve in the occurrence and development of mitochondrial dysfunction associated with non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is one of the most common liver diseases, which is often accompanied by mitochondrial dysfunction. Cardiolipin is a special lipid of mitochondrial inner membrane and any change of cardiolipin may cause series of mitochondria-relevant diseases. Changes in cardiolipin content, fatty acid side chain composition after cardiolipin remodeling, and the content of cardiolipin remodeling enzymes play an important role in the occurrence and development of NAFLD-related mitochondrial dysfunction.

Epidermal growth factor receptor and integrins meet redox signaling through P66shc and Rac1

This review examines the concerted role of Epidermal Growth Factor Receptor (EGFR) and integrins in regulating Reactive oxygen species (ROS) production through different signaling pathways. ROS as such are not always deleterious to the cells but they also act as signaling molecules, that regulates numerous indespensible physiological fuctions of life. Many adaptor proteins, particularly Shc and Grb2, are involved in mediating the downstream signaling pathways stimulated by EGFR and integrins. Integrin-induced activation of EGFR and subsequent tyrosine phosphorylation of a class of acceptor sites on EGFR leads to alignment and tyrosine phosphorylation of Shc, PLCγ, the p85 subunit of PI-3 K, and Cbl, followed by activation of the downstream targets Erk and Akt/PKB. Functional interactions between these receptors result in the activation of Rac1 via these adaptor proteins, thereby leading to Reactive Oxygen Species. Both GF and integrin activation can produce oxidants independently, however synergistically there is increased ROS generation, suggesting a mutual cooperation between integrins and GFRs for redox signalling. The ROS produced further promotes feed-forward stimulation of redox signaling events such as MAPK activation and gene expression. This relationship has not been reviewed previously. The literature presented here can have multiple implications, ranging from looking at synergistic effects of integrin and EGFR mediated signaling mechanisms of different proteins to possible therapeutic interventions operated by these two receptors. Furthermore, such mutual redox regulation of crosstalk between EGFR and integrins not only add to the established models of pathological oxidative stress, but also can impart new avenues and opportunities for targeted antioxidant based therapeutics.

Reactive Oxygen Species (ROS): Key components in Cancer Therapies

Reactive oxygen species (ROS) refer to the highly reactive substances, which contain oxygen radicals. Hypochlorous acid, peroxides, superoxide, singlet oxygen, alpha-oxygen and hydroxyl radicals are the major examples of ROS. Generally, the reduction of oxygen (O2) in molecular form produces superoxide (•O2-) anion. ROS are produced during a variety of biochemical reactions within the cell organelles, such as endoplasmic reticulum, mitochondria and peroxisome. Naturally, ROS are also formed as a byproduct of the normal metabolism of oxygen. The production of ROS can be induced by various factors such as heavy metals, tobacco, smoke, drugs, xenobiotics, pollutants and radiation. From various experimental studies, it is reported that ROS act as either tumor suppressing or tumor promoting agent. The elevated levels of ROS can arrest the growth of tumor through the persistent increase in cell cycle inhibition. The increased level of ROS can induce apoptosis by both intrinsic and extrinsic pathways. ROS are considered to be tumor suppressing agent as the production of ROS is due to the use of most of the chemotherapeutic agents in order to activate the cell death. The cytotoxic effect of ROS provides impetus towards apoptosis, but in higher levels, ROS can cause initiation of malignancy that leads to uncontrolled cell death in cancer cells. Whereas, some species of ROS can influence various activities at the cellular level that include cell proliferation. This review highlights the genesis of ROS within cells by various routes and their role in cancer therapies.

Mild Mitochondrial Uncoupling Decreases Experimental Atherosclerosis, A Proof of Concept

Aim: Atherosclerosis is responsible for high morbidity and mortality rates around the world. Local arterial oxidative stress is involved in all phases of atherosclerosis development. Mitochondria is a relevant source of the oxidants, particularly under certain risky conditions, such as hypercholesterolemia. The aim of this study was to test whether lowering the production of mitochondrial oxidants by induction of a mild uncoupling can reduce atherosclerosis in hypercholesterolemic LDL receptor knockout mice.

Methods: The mice were chronically treated with very low doses of DNP (2,4-dinitrophenol) and metabolic, inflammatory and redox state markers and atherosclerotic lesion sizes were determined.

Results: The DNP treatment did not change the classical atherosclerotic risk markers, such as plasma lipids, glucose homeostasis, and fat mass, as well as systemic inflammatory markers. However, the DNP treatment diminished the production of mitochondrial oxidants, systemic and tissue oxidative damage markers, peritoneal macrophages and aortic rings oxidants generation. Most importantly, development of spontaneous and diet-induced atherosclerosis (lipid and macrophage content) were significantly decreased in the DNP-treated mice. In vitro, DNP treated peritoneal macrophages showed decreased H₂O₂ production, increased anti-inflammatory cytokines gene expression and secretion, increased phagocytic activity, and decreased LDL-cholesterol uptake.

Conclusions: These findings are a proof of concept that activation of mild mitochondrial uncoupling is sufficient to delay the development of atherosclerosis under the conditions of hypercholesterolemia and oxidative stress. These results promote future approaches targeting mitochondria for the prevention or treatment of atherosclerosis.

Oxidative Modifications of RNA and Its Potential Roles in Biosystem

Elevated level of oxidized RNA was detected in vulnerable neurons in Alzheimer patients. Subsequently, several diseases and pathological conditions were reported to be associated with RNA oxidation. In addition to several oxidized derivatives, cross-linking and unique strand breaks are generated by RNA oxidation. With a premise that dysfunctional RNA mediated by oxidation is the pathogenetic molecular mechanism, intensive investigations have revealed the mechanism for translation errors, including premature termination, which gives rise to aberrant polypeptides. To this end, we and others revealed that mRNA oxidation could compromise its translational activity and fidelity. Under certain conditions, oxidized RNA can also induce several signaling pathways, to mediate inflammatory response and induce apoptosis. In this review, we focus on the oxidative modification of RNA and its resulting effect on protein synthesis as well as cell signaling. In addition, we will also discuss the potential roles of enzymatic oxidative modification of RNA in mediating cellular effects.

Beyond mitochondria: Alternative energy-producing pathways from all strata of life

It is well-established that mitochondria are the powerhouses of the cell, producing adenosine triphosphate (ATP), the universal energy currency. However, the most significant strengths of the electron transport chain (ETC), its intricacy and efficiency, are also its greatest downfalls. A reliance on metal complexes (FeS clusters, hemes), lipid moities such as cardiolipin, and cofactors including alpha-lipoic acid and quinones render oxidative phosphorylation vulnerable to environmental toxins, intracellular reactive oxygen species (ROS) and fluctuations in diet. To that effect, it is of interest to note that temporal disruptions in ETC activity in most organisms are rarely fatal, and often a redundant number of failsafes are in place to permit continued ATP production when needed. Here, we highlight the metabolic reconfigurations discovered in organisms ranging from parasitic Entamoeba to bacteria such as pseudomonads and then complex eukaryotic systems that allow these species to adapt to and occasionally thrive in harsh environments. The overarching aim of this review is to demonstrate the plasticity of metabolic networks and recognize that in times of duress, life finds a way.

Reduction of host cell mitochondrial activity as Mycobacterium leprae's strategy to evade host innate immunity

Leprosy is a much-feared incapacitating infectious disease caused by Mycobacterium leprae or M lepromatosis, annually affecting roughly 200,000 people worldwide. During host-pathogen interaction, M leprae subverts the immune response, leading to development of disease. Throughout the last few decades, the impact of energy metabolism on the control of intracellular pathogens and leukocytic differentiation has become more evident. Mitochondria play a key role in regulating newly-discovered immune signaling pathways by controlling redox metabolism and the flow of energy besides activating inflammasome, xenophagy, and apoptosis. Likewise, this organelle, whose origin is probably an alphaproteobacterium, directly controls the intracellular pathogens attempting to invade its niche, a feature conquered at the expense of billions of years of coevolution. In the present review, we discuss the role of reduced host cell mitochondrial activity during M leprae infection and the consequential fates of M leprae and host innate immunity. Conceivably, inhibition of mitochondrial energy metabolism emerges as an overlooked and novel mechanism developed by M leprae to evade xenophagy and the host immune response.

Saccharomyces boulardii modulates oxidative stress and renin angiotensin system attenuating diabetes-induced liver injury in mice

Type 1 diabetes (T1DM) is a chronic disease characterized by hyperglycemia due to a deficiency in endogenous insulin production, resulting from pancreatic beta cell death. Persistent hyperglycemia leads to enhanced oxidative stress and liver injury. Several studies have evaluated the anti-diabetic and protective effects of probiotic strains in animal models. In the present study, we investigated, through histopathological and biochemical analyses, the effects of eight weeks of administration of Saccharomyces boulardii (S. boulardii) yeast on the liver of streptozotocin (STZ) induced diabetic C57BL/6 mice. Our results demonstrated that S. boulardii attenuates hepatocytes hydropic degeneration and hepatic vessels congestion in STZ-induced diabetic mice. The treatment attenuated the oxidative stress in diabetic mice leading to a reduction of carbonylated protein concentration and increased activity of antioxidant enzymes superoxide dismutase and glutathione peroxidase, compared to untreated diabetic animals. The results also show the beneficial influence of S. boulardii in regulating the hepatic concentration of renin angiotensin system (RAS) peptides. Therefore, our results demonstrated that S. boulardii administration to STZ-induced diabetic mice reduces oxidative stress and normalizes the concentration of RAS peptides, supporting the hypothesis that this yeast may have a role as a potential adjunctive therapy to attenuate diabetes-induced liver injury.

Adverse Effects of Heat Stress on the Intestinal Integrity and Function of Pigs and the Mitigation Capacity of Dietary Antioxidants: A Review

Heat stress (HS) significantly affects the performance of pigs by its induced stressors such as inflammation, hypoxia and oxidative stress (OS), which mightily strain the intestinal integrity and function of pigs. As heat stress progresses, several mechanisms in the intestinal epithelium involved in the absorption of nutrients and its protective functions are altered. Changes in these mechanisms are mainly driven by cellular oxidative stress, which promotes disruption of intestinal homeostasis, leading to intestinal permeability, emphasizing intestinal histology and morphology with little possibility of recovering even after exposure to HS. Identification and understanding of these altered mechanisms are crucial for providing appropriate intervention strategies. Therefore, it is this papers' objective to review the important components for intestinal integrity that are negatively affected by HS and its induced stressors. With due consideration to the amelioration of such effects through nutritional intervention, this work will also look into the capability of dietary antioxidants in mitigating such adverse effects and maintaining the intestine's integrity and function upon the pigs' exposure to high environmental temperature.