Guidelines for measuring reactive oxygen species and oxidative damage in cells and in vivo

Swimming against ALS: How to model disease in zebrafish for pathophysiological and behavioral studies

Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease that leads to progressive disability and motor impairment. Existing therapies provide modest improvements in patient survival, raising a need for new treatments for ALS. Zebrafish is a promising model animal for translational and fundamental research in ALS - it is an experimentally tractable vertebrate, with high homology to humans and an ample experimental toolbox. These advantages allow high-throughput study of behavioral and pathophysiological phenotypes. The last decade saw an increased interest in modelling ALS in zebrafish, leading to the current abundance and variety of available methods and models. Additionally, the rise of gene editing techniques and toxin combination studies has created novel opportunities for ALS studies in zebrafish. In this review, we address the relevance of zebrafish as a model animal for ALS studies, the strategies for model induction and key phenotypical evaluation. Furthermore, we discuss established and emerging zebrafish models of ALS, analyzing their validity, including their potential for drug testing, and highlighting research opportunities in this area.

Defining the nuanced nature of redox biology in post-traumatic stress disorder

Post-traumatic stress disorder (PTSD) is a mental health disorder that arises after experiencing or witnessing a traumatic event. Despite affecting around 7% of the population, there are currently no definitive biological signatures or biomarkers used in the diagnosis of PTSD. Thus, the search for clinically relevant and reproducible biomarkers has been a major focus of the field. With significant advances of large-scale multi-omic studies that include genomic, proteomic, and metabolomic data, promising findings have been made, but the field still has fallen short. Amongst the possible biomarkers examined, one area is often overlooked, understudied, or inappropriately investigated: the field of redox biology. Redox molecules are free radical and/or reactive species that are generated as a consequence of the necessity of electron movement for life. These reactive molecules, too, are essential for life, but in excess are denoted as "oxidative stress" and often associated with many diseases. The few studies that have examined redox biology parameters have often utilized outdated and nonspecific methods, as well as have reported confounding results, which has made it difficult to conclude the role for redox in PTSD. Herein, we provide a foundation of how redox biology may underlie diseases like PTSD, critically examine redox studies of PTSD, and provide future directions the field can implement to enhance standardization, reproducibility, and accuracy of redox assessments for the use of diagnosis, prognosis, and therapy of this debilitating mental health disorder.

1,2,4,5-Tetrazine-tethered probes for fluorogenically imaging superoxide in live cells with ultrahigh specificity

Superoxide (O₂^·-) is the primary reactive oxygen species in mammal cells. Detecting superoxide is crucial for understanding redox signaling but remains challenging. Herein, we introduce a class of activity-based sensing probes. The probes utilize 1,2,4,5-tetrazine as a superoxide-responsive trigger, which can be modularly tethered to various fluorophores to tune probe sensitivity and emission color. These probes afford ultra-specific and ultra-fluorogenic responses towards superoxide, and enable multiplexed imaging of various cellular superoxide levels in an organelle-resolved way. Notably, the probes reveal the aberrant superoxide generation in the pathology of myocardial ischemia/reperfusion injury, and facilitate the establishment of a high-content screening pipeline for mediators of superoxide homeostasis. One such identified mediator, coprostanone, is shown to effectively ameliorating oxidative stress-induced injury in mice with myocardial ischemia/reperfusion injury. Collectively, these results showcase the potential of 1,2,4,5-tetrazine-tethered probes as versatile tools to monitor superoxide in a range of pathophysiological settings.

Protective Effect of Ergothioneine against 7-Ketocholesterol-Induced Mitochondrial Damage in hCMEC/D3 Human Brain Endothelial Cells

Recent findings have suggested that the natural compound ergothioneine (ET), which is synthesised by certain fungi and bacteria, has considerable cytoprotective potential. We previously demonstrated the anti-inflammatory effects of ET on 7-ketocholesterol (7KC)-induced endothelial injury in human blood-brain barrier endothelial cells (hCMEC/D3). 7KC is an oxidised form of cholesterol present in atheromatous plaques and the sera of patients with hypercholesterolaemia and diabetes mellitus. The aim of this study was to elucidate the protective effect of ET on 7KC-induced mitochondrial damage. Exposure of human brain endothelial cells to 7KC led to a loss of cell viability, together with an increase in intracellular free calcium levels, increased cellular and mitochondrial reactive oxygen species, a decrease in mitochondrial membrane potential, reductions in ATP levels, and increases in mRNA expression of TFAM, Nrf2, IL-1β, IL-6 and IL-8. These effects were significantly decreased by ET. Protective effects of ET were diminished when endothelial cells were coincubated with verapamil hydrochloride (VHCL), a nonspecific inhibitor of the ET transporter OCTN1 (SLC22A4). This outcome demonstrates that ET-mediated protection against 7KC-induced mitochondrial damage occurred intracellularly and not through direct interaction with 7KC. OCTN1 mRNA expression itself was significantly increased in endothelial cells after 7KC treatment, consistent with the notion that stress and injury may increase ET uptake. Our results indicate that ET can protect against 7KC-induced mitochondrial injury in brain endothelial cells.

Review on Carbon Dot-Based Fluorescent Detection of Biothiols

Biothiols, such as cysteine (Cys), homocysteine (Hcy), and glutathione (GSH), play a vital role in gene expression, maintaining redox homeostasis, reducing damages caused by free radicals/toxins, etc. Likewise, abnormal levels of biothiols can lead to severe diseases, such as Alzheimer's disease (AD), neurotoxicity, hair depigmentation, liver/skin damage, etc. To quantify the biothiols in a biological system, numerous low-toxic probes, such as fluorescent quantum dots, emissive organic probes, composited nanomaterials, etc., have been reported with real-time applications. Among these fluorescent probes, carbon-dots (CDs) have become attractive for biothiols quantification because of advantages of easy synthesis, nano-size, crystalline properties, low-toxicity, and real-time applicability. A CDs-based biothiols assay can be achieved by fluorescent "Turn-On" and "Turn-Off" responses via direct binding, metal complex-mediated detection, composite enhanced interaction, reaction-based reports, and so forth. To date, the availability of a review focused on fluorescent CDs-based biothiols detection with information on recent trends, mechanistic aspects, linear ranges, LODs, and real applications is lacking, which allows us to deliver this comprehensive review. This review delivers valuable information on reported carbon-dots-based biothiols assays, the underlying mechanism, their applications, probe/CDs selection, sensory requirement, merits, limitations, and future scopes.

Evaluation of oxidative damage to biomolecules and inflammation in patients with urea cycle disorders

Urea cycle disorders (UCD) are inborn errors of metabolism that occur due to a loss of function in enzymes and transporters involved in the urea cycle, causing an intoxication by hyperammonemia and accumulation of metabolites. Patients can develop hepatic encephalopathy (HE), severe neurological and motor disabilities, and often death. The mechanisms involved in the pathophysiology of UCD are many and complex, but there are strong indications that oxidative stress and inflammation are present, being responsible for at least part of the cellular damage that occurs in these diseases. The aim of this study was to evaluate oxidative and nitrosative damage and inflammation in UCD, to better understand the pathophysiology mechanisms of these diseases. We evaluated the nitrite and nitrate content, thiobarbituric acid-reactive substances (TBARS), carbonyl protein content and a panel of cytokines in plasma sample of 14 patients. The UCD patients group consisted of individuals affected with ornithine transcarbamylase deficiency (n = 8), carbamoyl phosphate synthetase deficiency (n = 2), argininosuccinate synthetase deficiency (n = 2); arginase 1 deficiency (n = 1) and argininosuccinate lyase deficiency (n = 1). Patients mean age at diagnosis was 5.25 ± 9.86 years-old and mean concentrations were compared with healthy individuals of matched age and gender. We found a significant reduction in nitrogen reactive species in patients when compared to controls. TBARS was increased in patients, indicating lipid peroxidation. To evaluate protein oxidative damage in UCD, the carbonyl content was measured, and the results also demonstrated an increase in this biomarker. Finally, we found that UCD patients have enhanced concentrations of cytokines, with pro-inflammatory interleukins IL-6, IL-8, interferon-γ and TNF-α, and anti-inflammatory IL-10 being increased when compared to the control group. In conclusion, our results demonstrate that oxidative stress and inflammation occurs in UCD and probably contribute to the severe brain damage present in patients.

A Zeb1/MtCK1 metabolic axis controls osteoclast activation and skeletal remodeling

Osteoclasts are bone-resorbing polykaryons responsible for skeletal remodeling during health and disease. Coincident with their differentiation from myeloid precursors, osteoclasts undergo extensive transcriptional and metabolic reprogramming in order to acquire the cellular machinery necessary to demineralize bone and digest its interwoven extracellular matrix. While attempting to identify new regulatory molecules critical to bone resorption, we discovered that murine and human osteoclast differentiation is accompanied by the expression of Zeb1, a zinc-finger transcriptional repressor whose role in normal development is most frequently linked to the control of epithelial-mesenchymal programs. However, following targeting, we find that Zeb1 serves as an unexpected regulator of osteoclast energy metabolism. In vivo, Zeb1-null osteoclasts assume a hyperactivated state, markedly decreasing bone density due to excessive resorptive activity. Mechanistically, Zeb1 acts in a rheostat-like fashion to modulate murine and human osteoclast activity by transcriptionally repressing an ATP-buffering enzyme, mitochondrial creatine kinase 1 (MtCK1), thereby controlling the phosphocreatine energy shuttle and mitochondrial respiration. Together, these studies identify a novel Zeb1/MtCK1 axis that exerts metabolic control over bone resorption in vitro and in vivo.

Multi-omic screening of invasive GBM cells in engineered biomaterials and patient biopsies reveals targetable transsulfuration pathway alterations

While the poor prognosis of glioblastoma arises from the invasion of a subset of tumor cells, little is known of the metabolic alterations within these cells that fuel invasion. We integrated spatially addressable hydrogel biomaterial platforms, patient site-directed biopsies, and multi-omics analyses to define metabolic drivers of invasive glioblastoma cells. Metabolomics and lipidomics revealed elevations in the redox buffers cystathionine, hexosylceramides, and glucosyl ceramides in the invasive front of both hydrogel-cultured tumors and patient site-directed biopsies, with immunofluorescence indicating elevated reactive oxygen species (ROS) markers in invasive cells. Transcriptomics confirmed upregulation of ROS-producing and response genes at the invasive front in both hydrogel models and patient tumors. Amongst oncologic ROS, hydrogen peroxide specifically promoted glioblastoma invasion in 3D hydrogel spheroid cultures. A CRISPR metabolic gene screen revealed cystathionine gamma lyase (CTH), which converts cystathionine to the non-essential amino acid cysteine in the transsulfuration pathway, to be essential for glioblastoma invasion. Correspondingly, supplementing CTH knockdown cells with exogenous cysteine rescued invasion. Pharmacologic CTH inhibition suppressed glioblastoma invasion, while CTH knockdown slowed glioblastoma invasion in vivo. Our studies highlight the importance of ROS metabolism in invasive glioblastoma cells and support further exploration of the transsulfuration pathway as a mechanistic and therapeutic target.

Ubiquinone deficiency drives reverse electron transport to disrupt hepatic metabolic homeostasis in obesity

Mitochondrial reactive oxygen species (mROS) are central to physiology. While excess mROS production has been associated with several disease states, its precise sources, regulation, and mechanism of generation in vivo remain unknown, limiting translational efforts. Here we show that in obesity, hepatic ubiquinone (Q) synthesis is impaired, which raises the QH 2 /Q ratio, driving excessive mROS production via reverse electron transport (RET) from site I Q in complex I. Using multiple complementary genetic and pharmacological models in vivo we demonstrated that RET is critical for metabolic health. In patients with steatosis, the hepatic Q biosynthetic program is also suppressed, and the QH 2 /Q ratio positively correlates with disease severity. Our data identify a highly selective mechanism for pathological mROS production in obesity, which can be targeted to protect metabolic homeostasis.

Iron overload modulates follicular microenvironment via ROS/HIF-1α/FSHR signaling

Iron is essential for the health of reproductive system, and women with iron overload suffer from ovarian dysfunction and lack effective treatment in fertility preservation. However, the underlying mechanism of the detrimental effects of iron overload on ovarian function remains ambiguous. Here, we confirmed the excess iron in the circumjacent follicle near endometriomas, which negatively impacted the oocyte development in the affected ovaries. Further, by integrating cell line and chronic iron overload mice model, we demonstrated that iron overload can function as a ROS inducer to amplify mitochondria damage, which significantly elevated the release of cytochrome C and ultimately induced the apoptosis of granular cells. Besides, for the first time, our findings revealed that disruption of HIF-1α/FSHR/CYP19A1 signaling was critical for decreased estrogen synthesis of granular cells in response to iron overload, which can lead to apparent oocyte maldevelopment and subfertility. Overall. this study uncovered that iron overload modulated the follicular microenvironment and generated a deleterious effect on female infertility via ROS/HIF-1α/FSHR signaling. These results might provide potential implications for future clinical risk management of patients with endometrioma and hemopathy.

Role of human HSPE1 for OPA1 processing independent of HSPD1

The human mtHSP60/HSPD1-mtHSP10/HSPE1 system prevents protein misfolding and maintains proteostasis in the mitochondrial matrix. Altered activities of this chaperonin system have been implicated in human diseases, such as cancer and neurodegeneration. However, how defects in HSPD1 and HSPE1 affect mitochondrial structure and dynamics remains elusive. In the current study, we address this fundamental question in a human cell line, HEK293T. We found that the depletion of HSPD1 or HSPE1 results in fragmentation of mitochondria, suggesting a decrease in mitochondrial fusion. Supporting this notion, HSPE1 depletion led to proteolytic inactivation of OPA1, a dynamin-related GTPase that fuses the mitochondrial membrane. This OPA1 inactivation was mediated by a stress-activated metalloprotease, OMA1. In contrast, HSPD1 depletion did not induce OMA1 activation or OPA1 cleavage. These data suggest that HSPE1 controls mitochondrial morphology through a mechanism separate from its chaperonin activity.

The "ON-OFF" Switching Response of Reactive Oxygen Species in Acute Normobaric Hypoxia: Preliminary Outcome

Exposure to acute normobaric hypoxia (NH) elicits reactive oxygen species (ROS) accumulation, whose production kinetics and oxidative damage were here investigated. Nine subjects were monitored while breathing an NH mixture (0.125 F_IO₂ in air, about 4100 m) and during recovery with room air. ROS production was assessed by Electron Paramagnetic Resonance in capillary blood. Total antioxidant capacity, lipid peroxidation (TBARS and 8-iso-PFG2α), protein oxidation (PC) and DNA oxidation (8-OH-dG) were measured in plasma and/or urine. The ROS production rate (μmol·min^-1) was monitored (5, 15, 30, 60, 120, 240 and 300 min). A production peak (+50%) was reached at 4 h. The on-transient kinetics, exponentially fitted (t_1/2 = 30 min r² = 0.995), were ascribable to the low O₂ tension transition and the mirror-like related SpO₂ decrease: 15 min: -12%; 60 min: -18%. The exposure did not seem to affect the prooxidant/antioxidant balance. Significant increases in PC (+88%) and 8-OH-dG (+67%) at 4 h in TBARS (+33%) one hour after hypoxia offset were also observed. General malaise was described by most of the subjects. Under acute NH, ROS production and oxidative damage resulted in time and SpO₂-dependent reversible phenomena. The experimental model could be suitable for evaluating the acclimatation level, a key element in the context of mountain rescues in relation to technical/medical workers who have not had enough time for acclimatization-as, for example, during helicopter flights.

Reactive oxygen species-upregulating nanomedicines towards enhanced cancer therapy

Reactive oxygen species (ROS) play a crucial role in physiological and pathological processes, emerging as a therapeutic target in cancer. Owing to the high concentration of ROS in solid tumor tissues, ROS-based treatments, such as photodynamic therapy and chemodynamic therapy, and ROS-responsive drug delivery systems have been widely explored to powerfully and specifically suppress tumors. However, their anticancer efficacy is still hampered by the heterogeneous ROS levels, and thus comprehensively upregulating the ROS levels in tumor tissues can ensure an enhanced therapeutic effect, which can further sensitize and/or synergize with other therapies to inhibit tumor growth and metastasis. Herein, we review the recently emerging drug delivery strategies and technologies for increasing the H₂O₂, ˙OH, ¹O₂, and ˙O₂^- concentrations in cancer cells, including the efficient delivery of natural enzymes, nanozymes, small molecular biological molecules, and nanoscale Fenton-reagents and semiconductors and neutralization of intracellular antioxidant substances and localized input of mechanical and electromagnetic waves (such as ultrasound, near infrared light, microwaves, and X-rays). The applications of these ROS-upregulating nanosystems in enhancing and synergizing cancer therapies including chemotherapy, chemodynamic therapy, phototherapy, and immunotherapy are surveyed. In addition, we discuss the challenges of ROS-upregulating systems and the prospects for future studies.

Early Detection Is the Best Prevention-Characterization of Oxidative Stress in Diabetes Mellitus and Its Consequences on the Cardiovascular System

Previous studies demonstrated an important role of oxidative stress in the pathogenesis of cardiovascular disease (CVD) in diabetic patients due to hyperglycemia. CVD remains the leading cause of premature death in the western world. Therefore, diabetes mellitus-associated oxidative stress and subsequent inflammation should be recognized at the earliest possible stage to start with the appropriate treatment before the onset of the cardiovascular sequelae such as arterial hypertension or coronary artery disease (CAD). The pathophysiology comprises increased reactive oxygen and nitrogen species (RONS) production by enzymatic and non-enzymatic sources, e.g., mitochondria, an uncoupled nitric oxide synthase, xanthine oxidase, and the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX). Considering that RONS originate from different cellular mechanisms in separate cellular compartments, adequate, sensitive, and compartment-specific methods for their quantification are crucial for early detection. In this review, we provide an overview of these methods with important information for early, appropriate, and effective treatment of these patients and their cardiovascular sequelae.

Translational molecular imaging and drug development in Parkinson's disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder that primarily affects elderly people and constitutes a major source of disability worldwide. Notably, the neuropathological hallmarks of PD include nigrostriatal loss and the formation of intracellular inclusion bodies containing misfolded α-synuclein protein aggregates. Cardinal motor symptoms, which include tremor, rigidity and bradykinesia, can effectively be managed with dopaminergic therapy for years following symptom onset. Nonetheless, patients ultimately develop symptoms that no longer fully respond to dopaminergic treatment. Attempts to discover disease-modifying agents have increasingly been supported by translational molecular imaging concepts, targeting the most prominent pathological hallmark of PD, α-synuclein accumulation, as well as other molecular pathways that contribute to the pathophysiology of PD. Indeed, molecular imaging modalities such as positron emission tomography (PET) and single-photon emission computed tomography (SPECT) can be leveraged to study parkinsonism not only in animal models but also in living patients. For instance, mitochondrial dysfunction can be assessed with probes that target the mitochondrial complex I (MC-I), while nigrostriatal degeneration is typically evaluated with probes designed to non-invasively quantify dopaminergic nerve loss. In addition to dopaminergic imaging, serotonin transporter and N-methyl-D-aspartate (NMDA) receptor probes are increasingly used as research tools to better understand the complexity of neurotransmitter dysregulation in PD. Non-invasive quantification of neuroinflammatory processes is mainly conducted by targeting the translocator protein 18 kDa (TSPO) on activated microglia using established imaging agents. Despite the overwhelming involvement of the brain and brainstem, the pathophysiology of PD is not restricted to the central nervous system (CNS). In fact, PD also affects various peripheral organs such as the heart and gastrointestinal tract - primarily via autonomic dysfunction. As such, research into peripheral biomarkers has taken advantage of cardiac autonomic denervation in PD, allowing the differential diagnosis between PD and multiple system atrophy with probes that visualize sympathetic nerve terminals in the myocardium. Further, α-synuclein has recently gained attention as a potential peripheral biomarker in PD. This review discusses breakthrough discoveries that have led to the contemporary molecular concepts of PD pathophysiology and how they can be harnessed to develop effective imaging probes and therapeutic agents. Further, we will shed light on potential future trends, thereby focusing on potential novel diagnostic tracers and disease-modifying therapeutic interventions.

Protein Susceptibility to Peroxidation by 4-Hydroxynonenal in Hereditary Hemochromatosis

Iron overload caused by hereditary hemochromatosis (HH) increases free reactive oxygen species that, in turn, induce lipid peroxidation. Its 4-hydroxynonenal (HNE) by-product is a well-established marker of lipid peroxidation since it reacts with accessible proteins with deleterious consequences. Indeed, elevated levels of HNE are often detected in a wide variety of human diseases related to oxidative stress. Here, we evaluated HNE-modified proteins in the membrane of erythrocytes from HH patients and in organs of Hfe^-/- male and female mice, a mouse model of HH. For this purpose, we used one- and two-dimensional gel electrophoresis, immunoblotting and MALDI-TOF/TOF analysis. We identified cytoskeletal membrane proteins and membrane receptors of erythrocytes bound to HNE exclusively in HH patients. Furthermore, kidney and brain of Hfe^-/- mice contained more HNE-adducted protein than healthy controls. Our results identified main HNE-modified proteins suggesting that HH favours preferred protein targets for oxidation by HNE.

Neurotoxic A1 astrocytes promote neuronal ferroptosis via CXCL10/CXCR3 axis in epilepsy

Epilepsy is a common neurological disorder with a complex etiology. Ferroptosis, a new form of programmed cell death, is characterized by the accumulation of lipid peroxides and associated with seizures. However, the underlying mechanism of ferroptosis in epilepsy remains elusive. Here, we found that GPX4-GSH-dependent neuronal ferroptosis was detected in epileptic mice, which was attenuated with ferroptosis inhibitors. Moreover, activated neurotoxic A1 astrocytes facilitated seizure-related neuronal ferroptosis in epileptic brains. Inhibition of ferroptosis blocked A1 astrocyte-induced neurotoxicity. A1 astrocyte-secreted CXCL10 enhanced STAT3 phosphorylation but suppressed SLC7A11 in neurons via CXCR3, leading to ferroptosis-associated lipid peroxidation in a GPX4-dependent manner. This was in line with clinical findings, showing a significant correlation between neuronal ferroptosis and A1 astrocytes in epileptic patients. In summary, the present data show that A1 astrocyte-induced neuronal ferroptosis contributes to the pathogenesis of epilepsy, which offers a novel therapeutic target for precision medicine.

The effect of isovitexin on lipopolysaccharide-induced renal injury and inflammation by induction of protective autophagy

Chronic kidney disease (CKD) is a systemic inflammatory syndrome that includes tubulointerstitial inflammation. Lipopolysaccharide (LPS), the outer membrane of Gram-negative bacteria, can increase reactive oxygen species production (ROS) that triggers cell inflammation. Isovitexin (IV) is a flavone that has the potential for anticancer, antioxidant, and anti-inflammatory. This study aimed to hypothesize that IV inhibited LPS-induced renal injury in vitro and in vivo. In vitro study, IV prevented LPS-induced ROS production and increased cell viability on SV40-MES-13 cells. Additionally, IV ameliorated mitochondrial membrane potential, downregulated inflammation and pyroptosis factors on LPS treatment. We found that LPS treatment reduced the expression of autophagy, however, this effect was reversed by IV. In vivo study, the renal injury model in C57BL/6 mice cotreatment with IV was examined. In addition, IV decreased LPS-induced glomerular atrophy and reduced inflammation-related cytokines releases. Further showed that IV could significantly reduce LPS-induced inflammation and pyroptosis factors in mice. Under the immunostaining, increased fluorescence of LC3 autophagy-related protein was recovered by IV. In summary, IV ameliorated renal injury, inflammation and increased protected autophagy by anti-ROS production, anti-inflammation, and anti-pyroptosis. In the future, the safety of isovitexin as a novel perspective for CKD patients should be evaluated in further clinical studies.

Commentary: On the merit of an early contributor of the "Preparation for Oxidative Stress" (POS) theory

This commentary acknowledges the contributions of the Ukrainian biologist, Dr. Volodymyr Lushchak, to the understanding of the physiological adaptive strategy called "Preparation for Oxidative Stress" (POS). In the 1990s, various studies revealed that activities of antioxidant enzymes rose in animals under hypometabolic conditions. These timely observations allowed scientists to propose that this increase could prepare animals for reoxygenation events following the release of oxygen restriction, but in doing so, would trigger oxidative damage, hence the use of the term "preparation". Over next 25 years, the phenomenon was described in detail in more than one hundred studies of animals under conditions of aestivation, hypoxia/anoxia, freezing, severe dehydration, ultraviolet exposure, air exposure of water-breathing animals, salinity stress, and others. The POS phenomenon remained without a mechanistic explanation until 2013, when it was proposed that a small increase in oxyradical formation during hypoxia exposure (in hypoxia-tolerant animals) could activate redox-sensitive transcription factors that, in turn, would initiate transcription and translation of antioxidant enzymes. Dr. Lushchak, who studied goldfish under severe hypoxia in the 1990s, had actually proposed the increased production of oxyradicals under this condition and concluded that it would lead to an upregulation of antioxidant enzymes, the hallmark of the POS strategy. However, his research partner at the time, Dr. Hermes-Lima, thought the idea did not have sufficient evidence to support it and recommended the removal of this explanation. In those days, the main line of thinking was that increased oxyradical formation under hypoxia was "impossible". So, as it turns out, the ideas of Dr. Lushchak were well ahead of his time. It then took >10 years before the biochemical and molecular mechanisms responsible for triggering the POS response were clarified. In the present article, this fascinating history is described to highlight Dr. Lushchak's contributions and insights about the POS theory.

Tryptophan Metabolism Acts as a New Anti-Ferroptotic Pathway to Mediate Tumor Growth

Emerging evidence reveals that amino acid metabolism plays an important role in ferroptotic cell death. The conversion of methionine to cysteine is well known to protect tumour cells from ferroptosis upon cysteine starvation through transamination. However, whether amino acids-produced metabolites participate in ferroptosis independent of the cysteine pathway is largely unknown. Here, the authors show that the tryptophan metabolites serotonin (5-HT) and 3-hydroxyanthranilic acid (3-HA) remarkably facilitate tumour cells to escape from ferroptosis distinct from cysteine-mediated ferroptosis inhibition. Mechanistically, both 5-HT and 3-HA act as potent radical trapping antioxidants (RTA) to eliminate lipid peroxidation, thereby inhibiting ferroptotic cell death. Monoamine oxidase A (MAOA) markedly abrogates the protective effect of 5-HT via degrading 5-HT. Deficiency of MAOA renders cancer cells resistant to ferroptosis upon 5-HT treatment. Kynureninase (KYNU), which is essential for 3-HA production, confers cells resistant to ferroptotic cell death, whereas 3-hydroxyanthranilate 3,4-dioxygenase (HAAO) significantly blocks 3-HA mediated ferroptosis inhibition by consuming 3-HA. In addition, the expression level of HAAO is positively correlated with lipid peroxidation and clinical outcome. Together, the findings demonstrate that tryptophan metabolism works as a new anti-ferroptotic pathway to promote tumour growth, and targeting this pathway will be a promising therapeutic approach for cancer treatment.

An improved method for the detection of myeloperoxidase chlorinating activity in biological systems using the redox probe hydroethidine

Conversion of the redox probe hydroethidine (HE) to 2-chloroethidium (2-Cl-E⁺) by myeloperoxidase (MPO)-derived hypochlorous acid (HOCl) provides comparable specificity and superior sensitivity to measurement of 3-chlorotyrosine (3-Cl-Tyr), the gold standard biomarker for MPO chlorinating activity in biological systems. However, a limitation of the former method is the complex mixture of products formed by the reaction of HE with reagent HOCl, coupled with the difficult purification of 2-Cl-E⁺ from this mixture for analytical purposes. This limitation prompted us to test whether 2-Cl-E⁺ could be formed by reaction of HE with the strong and widely used chlorinating agent, N-chlorosuccinimide (NCS). Unexpectedly, such reaction yielded 2-chlorohydroethidine (2-Cl-HE) as the major product in addition to 2-Cl-E⁺, as assessed by high performance liquid chromatography (HPLC), mass spectrometry (MS), and nuclear magnetic resonance (NMR). 2-Cl-HE was also observed to be the major chlorination product formed from HE with both reagent and enzymatically generated HOCl, just as it was formed ex vivo in different healthy and diseased mouse and human tissues upon incubation with glucose/glucose oxidase to generate a flux of hydrogen peroxide (H₂O₂). Quantification of 2-Cl-HE plus 2-Cl-E⁺ improved the sensitivity of the HE-based method compared with measurement of only 2-Cl-E⁺. Moreover, 2-chlorodimidium (2-Cl-D⁺) was developed as a practical internal standard instead of the previously used internal standard, deuterated 2-Cl-E⁺ (d₅-2-Cl-E⁺). Overall, the present study describes an improved method for the detection of MPO/chlorinating activity in biological systems of health and disease.

Transcriptional Insights of Oxidative Stress and Extracellular Traps in Lung Tissues of Fatal COVID-19 Cases

Neutrophil extracellular traps (NETs) and oxidative stress are considered to be beneficial in the innate immune defense against pathogens. However, defective clearance of NETs in the lung of acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-infected patients could lead to severe respiratory syndrome infection, the so-called coronavirus disease 2019 (COVID-19). To elucidate the pathways that are related to NETs within the pathophysiology of COVID-19, we utilized RNA sequencing (RNA-seq) as well as immunofluorescence and immunohistochemistry methods. RNA-seq analysis provided evidence for increased oxidative stress and the activation of viral-related signaling pathways in post-mortem lungs of COVID-19 patients compared to control donors. Moreover, an excess of neutrophil infiltration and NET formation were detected in the patients' lungs, where the extracellular DNA was oxidized and co-localized with neutrophil granule protein myeloperoxidase (MPO). Interestingly, staining of the lipid peroxidation marker 4-hydroxynonenal (4-HNE) depicted high colocalization with NETs and was correlated with the neutrophil infiltration of the lung tissues, suggesting that it could serve as a suitable marker for the identification of NETs and the severity of the disease. Moreover, local inhalation therapy to reduce the excess lipid oxidation and NETs in the lungs of severely infected patients might be useful to ameliorate their clinical conditions.

Protection against Doxorubicin-Induced Cardiotoxicity by Ergothioneine

Background: Anthracyclines such as doxorubicin remain a primary treatment for hematological malignancies and breast cancers. However, cardiotoxicity induced by anthracyclines, possibly leading to heart failure, severely limits their application. The pathological mechanisms of anthracycline-induced cardiac injury are believed to involve iron-overload-mediated formation of reactive oxygen species (ROS), mitochondrial dysfunction, and inflammation. The dietary thione, ergothioneine (ET), is avidly absorbed and accumulated in tissues, including the heart. Amongst other cytoprotective properties, ET was shown to scavenge ROS, decrease proinflammatory mediators, and chelate metal cations, including Fe²⁺, preventing them from partaking in redox activities, and may protect against mitochondrial damage and dysfunction. Plasma ET levels are also strongly correlated to a decreased risk of cardiovascular events in humans, suggesting a cardioprotective role. This evidence highlights ET's potential to counteract anthracycline cardiotoxicity. Methods and Findings: We investigated whether ET supplementation can protect against cardiac dysfunction in mice models of doxorubicin-induced cardiotoxicity and revealed that it had significant protective effects. Moreover, ET administration in a mouse breast cancer model did not exacerbate the growth of the tumor or interfere with the chemotherapeutic efficacy of doxorubicin. Conclusion: These results suggest that ET could be a viable co-therapy to alleviate the cardiotoxic effects of anthracyclines in the treatment of cancers.

Cerebroprotective actions of hydrogen sulfide in the epileptic brain in newborn pigs

BACKGROUND

Neonatal epileptic seizures cause postictal dysregulation of cerebral blood flow. Hydrogen sulfide (H₂S), a mediator with vasodilator and antioxidant properties, is produced in the brain by astrocyte cystathionine β-synthase (CBS). This study investigated whether H₂S improves the cerebral vascular outcome of seizures.

METHODS

Epileptic seizures were induced in newborn pigs using bicuculline. The effects of the CBS inhibitor aminooxyacetate (AOA) and the H₂S donor NaHS on cerebral vascular outcome of seizures were examined in live pigs, cerebral endothelial cells, and cortical astrocytes.

RESULTS

Brain H₂S was elevated during seizures. AOA blocked H₂S and reduced functional hyperemia in the epileptic brain. The endothelium- and astrocyte-dependent vasodilation of pial arterioles was impaired 48 h after seizures suggesting cerebral vascular dysfunction. Systemic NaHS elevated brain H₂S and blocked reactive oxygen species in the epileptic brain and in primary endothelial cells and astrocytes during inflammatory and excitotoxic conditions. Postictal cerebrovascular dysfunction was exaggerated in H₂S-inhibited pigs and minimized in NaHS-treated pigs.

CONCLUSIONS

H₂S elevation in the epileptic brain via activation of CBS contributes to functional hyperemia and exhibits cerebroprotective properties. The H₂S donor NaHS enhances brain antioxidant defense and provides a therapeutic approach for preventing adverse cerebral vascular outcome of neonatal epileptic seizures.

IMPACT

Epileptic seizures in neonates lead to prolonged postictal cerebral vascular dysregulation. The role of hydrogen sulfide (H₂S), a mediator with vasodilator and antioxidant properties, in the epileptic brain has been explored. Astrocytes are major sites of enzymatic H₂S production in the epileptic brain. Postictal cerebral vascular dysfunction is exaggerated when astrocyte H₂S production is pharmacologically inhibited during seizures. Postictal cerebral vascular dysfunction is minimized when the brain H₂S is elevated by systemic administration of NaHS during seizures. NaHS provides a therapeutic approach for improving cerebrovascular outcome of epileptic seizures via a mechanism that involves the antioxidant potential of H₂S.

Urinary 15-F2t-Isoprostane Concentrations in Dogs with Liver Disease

Isoprostanes are stable end products of lipid peroxidation that can be used as markers of oxidative stress. It was previously reported that a cohort of dogs with various liver diseases had increased urinary isoprostane concentrations compared to healthy control (HC) dogs. The aim of this study was to measure and report urinary isoprostane concentrations in dogs with different types of liver diseases. Urine was collected from 21 HC dogs and from 40 dogs with liver disease, including 25 with chronic hepatitis (CH), 7 with steroid hepatopathy (SH), and 8 with a congenital portosystemic shunt (CPSS). In this prospective, observational study, urinary 15-F_2t-isoprostane (F₂-IsoP) concentrations were measured by liquid chromatography/mass spectrometry and normalized to urinary creatinine concentrations. Concentrations were compared between groups using a Kruskal-Wallis test followed by Dunn's multiple comparisons tests. Significance was set at p < 0.05. The median (range) urinary F₂-IsoP to creatinine ratios (ng/mg UCr) were 3.6 (2.2-12.4) for HC dogs, 5.7 (2.4-11.3) for dogs with CH, 4.8 (2.4-8.6) for dogs with SH, and 12.5 (2.9-22.9) for dogs with CPSS. CPSS dogs had significantly higher urinary F₂-IsoP concentrations than HC dogs (p = 0.004), suggesting increased oxidative stress among this cohort.

Chemogenetic emulation of intraneuronal oxidative stress affects synaptic plasticity

Oxidative stress, a state of disrupted redox signaling, reactive oxygen species (ROS) overproduction, and oxidative cell damage, accompanies numerous brain pathologies, including aging-related dementia and Alzheimer's disease, the most common neurodegenerative disorder of the elderly population. However, a causative role of neuronal oxidative stress in the development of aging-related cognitive decline and neurodegeneration remains elusive because of the lack of approaches for modeling isolated oxidative injury in the brain. Here, we present a chemogenetic approach based on the yeast flavoprotein d-amino acid oxidase (DAAO) for the generation of intraneuronal hydrogen peroxide (H₂O₂). To validate this chemogenetic tool, DAAO and HyPer7, an ultrasensitive genetically encoded H₂O₂ biosensor, were targeted to neurons. Changes in the fluorescence of HyPer7 upon treatment of neurons expressing DAAO with d-norvaline (D-Nva), a DAAO substrate, confirmed chemogenetically induced production of intraneuornal H₂O₂. Then, using the verified chemogenetic tool, we emulated isolated intraneuronal oxidative stress in acute brain slices and, using electrophysiological recordings, revealed that it does not alter basal synaptic transmission and the probability of neurotransmitter release from presynaptic terminals but reduces long-term potentiation (LTP). Moreover, treating neurons expressing DAAO with D-Nva via the patch pipette also decreases LTP. This observation indicates that isolated oxidative stress affects synaptic plasticity at single cell level. Our results broaden the toolset for studying normal redox regulation in the brain and elucidating the role of oxidative stress to the pathogenesis of cognitive aging and the early stages of aging-related neurodegenerative diseases. The proposed approach is useful for identification of early markers of neuronal oxidative stress and may be used in screens of potential antioxidants effective against neuronal oxidative injury.

Oxidative Stress in Age-Related Neurodegenerative Diseases: An Overview of Recent Tools and Findings

Reactive oxygen species (ROS) have been described to induce a broad range of redox-dependent signaling reactions in physiological conditions. Nevertheless, an excessive accumulation of ROS leads to oxidative stress, which was traditionally considered as detrimental for cells and organisms, due to the oxidative damage they cause to biomolecules. During ageing, elevated ROS levels result in the accumulation of damaged proteins, which may exhibit altered enzymatic function or physical properties (e.g., aggregation propensity). Emerging evidence also highlights the relationship between oxidative stress and age-related pathologies, such as protein misfolding-based neurodegenerative diseases (e.g., Parkinson's (PD), Alzheimer's (AD) and Huntington's (HD) diseases). In this review we aim to introduce the role of oxidative stress in physiology and pathology and then focus on the state-of-the-art techniques available to detect and quantify ROS and oxidized proteins in live cells and in vivo, providing a guide to those aiming to characterize the role of oxidative stress in ageing and neurodegenerative diseases. Lastly, we discuss recently published data on the role of oxidative stress in neurological disorders.

N-acetyloxfenicine strongly induces mitohormesis in mice as well as in insects

Mitohormesis defines the increase in fitness induced by adaptive responses to mild mitochondrial stress. Here, we show that N-acetyloxfenicine (NAO) exerted higher thermotolerance than an endogenous mitohormesis inducer, N-acetyltyrosine (NAT). This activity was not observed in armyworm larvae injected with oxfenicine, suggesting the importance of N-acetylation. NAO-induced hormetic effect was triggered by transient perturbation of mitochondria, which causes a small increase in ROS production and leads to retrograde responses including enhanced expression of antioxidant enzyme genes via activation of FoxO transcription factors. Furthermore, pretreatment with NAO significantly repressed stress-induced peroxidation of lipids in mice and growth of colorectal cancer HCT116 cells that had been transplanted into nude mice. Taken together, NAO is a potent mitohormesis inducer that is similar to NAT in terms of structure and functions.

TrkB agonist N-acetyl serotonin promotes functional recovery after traumatic brain injury by suppressing ferroptosis via the PI3K/Akt/Nrf2/Ferritin H pathway

Ferroptosis is a form of regulated cell death that is mainly triggered by iron-dependent lipid peroxidation. A growing body of evidence suggests that ferroptosis is involved in the pathophysiology of traumatic brain injury (TBI), and tropomyosin-related kinase B (TrkB) deficiency would mediate TBI pathologies. As an agonist of TrkB and an immediate precursor of melatonin, N-acetyl serotonin (NAS) exerts several beneficial effects on TBI, but there is no information regarding the role of NAS in ferroptosis after TBI. Here, we examined the effect of NAS treatment on TBI-induced functional outcomes and ferroptosis. Remarkably, the administration of NAS alleviated TBI-induced neurobehavioral deficits, lesion volume, and neurodegeneration. NAS also rescued TBI-induced mitochondrial shrinkage, the changes in ferroptosis-related molecule expression, and iron accumulation in the ipsilateral cortex. Similar results were obtained with a well-established ferroptosis inhibitor, liproxstatin-1. Furthermore, NAS activated the TrkB/PI3K/Akt/Nrf2 pathway in the mouse model of TBI, while inhibition of PI3K and Nrf2 weakened the protection of NAS against ferroptosis both in vitro and in vivo, suggesting that a possible pathway linking NAS to the action of anti-ferroptosis was TrkB/PI3K/Akt/Nrf2. Given that ferritin H (Fth) is a known transcription target of Nrf2, we then investigated the effects of NAS on neuron-specific Fth knockout (Fth-KO) mice. Strikingly, Fth deletion almost abolished the protective effects of NAS against TBI-induced ferroptosis and synaptic damage, although Fth deletion-induced susceptibility toward ferroptosis after TBI was reversed by an iron chelator, deferoxamine. Taken together, these data indicate that the TrkB agonist NAS treatment appears to improve brain function after TBI by suppressing ferroptosis, at least in part, through activation of the PI3K/Akt/Nrf2/Fth pathway, providing evidence that NAS is likely to be a promising anti-ferroptosis agent for further treatment for TBI.

Different Modes of Mechanism of Gamma-Mangostin and Alpha-Mangostin to Inhibit Cell Migration of Triple-Negative Breast Cancer Cells Concerning CXCR4 Downregulation and ROS Generation

Background

Two mangostin compounds, gamma-mangostin and alpha-mangostin, show anticancer properties through the inhibition of cell proliferation and cell migration. Metastatic triple-negative breast cancer (TNBC) cells, including MDA-MB-231, highly express C-X-C chemokine receptor type 4 (CXCR4) to maintain reactive oxygen species (ROS) and cell migration.

Objectives

This study was performed to analyze and compare different modes of action of γ-mangostin and α-mangostin as antimigratory effects targeted on CXCR4 in MDA-MB-231 as a model of TNBC cell.

Methods

This study investigated the effect of γ-mangostin and α-mangostin using a series of assays, including Cell Counting Kit-8 (CCK-8) assay for cytotoxicity, wound healing assay for migration study, quantitative real-time polymerase chain reaction (qRT-PCR) for gene expression analysis, and flow cytometry for ROS measurement, along with in silico study to observe the binding between the compound and CXCR4.

Results

The findings revealed half maximal inhibitory concentration (IC50) values of 25 and 20 μM for γ-mangostin and α-mangostin in MDA-MB 231 cells, respectively. Moreover, a concentration of 10 μM was used for the migration assay. Both γ-mangostin and α-mangostin significantly suppressed cell migration within 24 hours. The present gene expression studies revealed the downregulation of key migration-associated genes, namely Farp, CXCR4, and LPHN2, upon γ-mangostin treatment but not α-mangostin. Additionally, both γ-mangostin and α-mangostin increased cellular ROS generation, highlighting the same effect of γ-mangostin and α-mangostin ROS elevation to inhibit cancer cell migration. Molecular docking simulations further suggested a potential interaction between γ-mangostin and α-mangostin with CXCR4 in high affinity.

Conclusions

These findings suggest that both γ-mangostin and α-mangostin inhibit breast cancer cell migration and induce cellular ROS levels in MDA-MB-231 cells; notably, γ-mangostin suppresses CXCR4 mRNA expression that might correlate to its activity to inhibit MDA-MB-231 cell migration.

Regulation of Mitochondrial Hydrogen Peroxide Availability by Protein S-glutathionylation

BACKGROUND

It has been four decades since protein S-glutathionylation was proposed to serve as a regulator of cell metabolism. Since then, this redox-sensitive covalent modification has been identified as a cell-wide signaling platform required for embryonic development and regulation of many physiological functions.

SCOPE OF THE REVIEW

Mitochondria use hydrogen peroxide (H₂O₂) as a second messenger, but its availability must be controlled to prevent oxidative distress and promote changes in cell behavior in response to stimuli. Experimental data favor the function of protein S-glutathionylation as a feedback loop for the inhibition of mitochondrial H₂O₂ production.

MAJOR CONCLUSIONS

The glutathione pool redox state is linked to the availability of H₂O₂, making glutathionylation an ideal mechanism for preventing oxidative distress whilst playing a part in desensitizing mitochondrial redox signals.

GENERAL SIGNIFICANCE

The biological significance of glutathionylation is rooted in redox status communication. The present review critically evaluates the experimental evidence supporting its role in negating mitochondrial H₂O₂ production for cell signaling and prevention of electrophilic stress.

C60 fullerene attenuates muscle force reduction in a rat during fatigue development

C₆₀ fullerene (C₆₀) as a nanocarbon particle, compatible with biological structures, capable of penetrating through cell membranes and effectively scavenging free radicals, is widely used in biomedicine. A protective effect of C₆₀ on the biomechanics of fast (m. gastrocnemius) and slow (m. soleus) muscle contraction in rats and the pro- and antioxidant balance of muscle tissue during the development of muscle fatigue was studied compared to the same effect of the known antioxidant N-acetylcysteine (NAC). C₆₀ and NAC were administered intraperitoneally at doses of 1 and 150 mg kg^-1, respectively, daily for 5 days and 1 h before the start of the experiment. The following quantitative markers of muscle fatigue were used: the force of muscle contraction, the level of accumulation of secondary products of lipid peroxidation (TBARS) and the oxygen metabolite H₂O₂, the activity of first-line antioxidant defense enzymes (superoxide dismutase (SOD) and catalase (CAT)), and the condition of the glutathione system (reduced glutathione (GSH) content and the activity of the glutathione peroxidase (GP_x) enzyme). The analysis of the muscle contraction force dynamics in rats against the background of induced muscle fatigue showed, that the effect of C₆₀, 1 h after drug administration, was (15-17)% more effective on fast muscles than on slow muscles. A further slight increase in the effect of C₆₀ was revealed after 2 h of drug injection, (7-9)% in the case of m. gastrocnemius and (5-6)% in the case of m. soleus. An increase in the effect of using C₆₀ occurred within 4 days (the difference between 4 and 5 days did not exceed (3-5)%) and exceeded the effect of NAC by (32-34)%. The analysis of biochemical parameters in rat muscle tissues showed that long-term application of C₆₀ contributed to their decrease by (10-30)% and (5-20)% in fast and slow muscles, respectively, on the 5th day of the experiment. At the same time, the protective effect of C₆₀ was higher compared to NAC by (28-44)%. The obtained results indicate the prospect of using C₆₀ as a potential protective nano agent to improve the efficiency of skeletal muscle function by modifying the reactive oxygen species-dependent mechanisms that play an important role in the processes of muscle fatigue development.

Impact of Mitochondrial A3243G Heteroplasmy on Mitochondrial Bioenergetics and Dynamics of Directly Reprogrammed MELAS Neurons

The MELAS syndrome primarily affecting the CNS is mainly caused by the m.A3243G mutation. The heteroplasmy in different tissues affects the phenotypic spectrum, yet the impact of various levels of m.A3243G heteroplasmy on CNS remains elusive due to the lack of a proper neuronal model harboring m.A3243G mutation. We generated induced neurons (iNs) through the direct reprogramming of MELAS patients, with derived fibroblasts harboring high (>95%), intermediate (68%), and low (20%) m.A3243G mutation. iNs demonstrated neuronal morphology with neurite outgrowth, branching, and dendritic spines. The heteroplasmy and deficiency of respiratory chain complexes were retained in MELAS iNs. High heteroplasmy elicited the elevation in ROS levels and the disruption of mitochondrial membrane potential. Furthermore, high and intermediate heteroplasmy led to the impairment of mitochondrial bioenergetics and a change in mitochondrial dynamics toward the fission and fragmentation of mitochondria, with a reduction in mitochondrial networks. Moreover, iNs derived from aged individuals manifested with mitochondrial fission. These results help us in understanding the impact of various heteroplasmic levels on mitochondrial bioenergetics and mitochondrial dynamics in neurons as the underlying pathomechanism of neurological manifestations of MELAS syndrome. Furthermore, these findings provide targets for further pharmacological approaches of mitochondrial diseases and validate iNs as a reliable platform for studies in neuronal aspects of aging, neurodegenerative disorders, and mitochondrial diseases.

Activity-Based Sensing for Chemistry-Enabled Biology: Illuminating Principles, Probes, and Prospects for Boronate Reagents for Studying Hydrogen Peroxide

Activity-based sensing (ABS) offers a general approach that exploits chemical reactivity as a method for selective detection and manipulation of biological analytes. Here, we illustrate the value of this chemical platform to enable new biological discovery through a case study in the design and application of ABS reagents for studying hydrogen peroxide (H2O2), a major type of reactive oxygen species (ROS) that regulates a diverse array of vital cellular signaling processes to sustain life. Specifically, we summarize advances in the use of activity-based boronate probes for the detection of H2O2 featuring high molecular selectivity over other ROS, with an emphasis on tailoring designs in chemical structure to promote new biological principles of redox signaling.

Oxidative Stress and Antioxidants-A Critical Review on In Vitro Antioxidant Assays

Antioxidants have been widely studied in the fields of biology, medicine, food, and nutrition sciences. There has been extensive work on developing assays for foods and biological systems. The scientific communities have well-accepted the effectiveness of endogenous antioxidants generated in the body. However, the health efficacy and the possible action of exogenous dietary antioxidants are still questionable. This may be attributed to several factors, including a lack of basic understanding of the interaction of exogenous antioxidants in the body, the lack of agreement of the different antioxidant assays, and the lack of specificity of the assays, which leads to an inability to relate specific dietary antioxidants to health outcomes. Hence, there is significant doubt regarding the relationship between dietary antioxidants to human health. In this review, we documented the variations in the current methodologies, their mechanisms, and the highly varying values for six common food substrates (fruits, vegetables, processed foods, grains, legumes, milk, and dairy-related products). Finally, we discuss the strengths and weaknesses of the antioxidant assays and examine the challenges in correlating the antioxidant activity of foods to human health.

Tiron Has Negative Effects on Osteogenic Differentiation via Mitochondrial Dysfunction in Human Periosteum-Derived Cells

Tiron is a potent antioxidant that counters the pathological effects of reactive oxygen species (ROS) production due to oxidative stress in various cell types. We examined the effects of tiron on mitochondrial function and osteoblastic differentiation in human periosteum-derived cells (hPDCs). Tiron increased mitochondrial activity and decreased senescence-associated β-galactosidase activity in hPDCs; however, it had a detrimental effect on osteoblastic differentiation by reducing alkaline phosphatase (ALP) activity and alizarin red-positive mineralization, regardless of H₂O₂ treatment. Osteoblast-differentiating hPDCs displayed increased ROS production compared with non-differentiating hPDCs, and treatment with tiron reduced ROS production in the differentiating cells. Antioxidants decreased the rates of oxygen consumption and ATP production, which are increased in hPDCs during osteoblastic differentiation. In addition, treatment with tiron reduced the levels of most mitochondrial proteins, which are increased in hPDCs during culture in osteogenic induction medium. These results suggest that tiron exerts negative effects on the osteoblastic differentiation of hPDCs by causing mitochondrial dysfunction.

Redox signaling and metabolism in Alzheimer's disease

Reduction and oxidation reactions are essential for biochemical processes. They are part of metabolic pathways and signal transduction. Reactive oxygen species (ROS) as second messengers and oxidative modifications of cysteinyl (Cys) residues are key to transduce and translate intracellular and intercellular signals. Dysregulation of cellular redox signaling is known as oxidative distress, which has been linked to various pathologies, including neurodegeneration. Alzheimer's disease (AD) is a neurodegenerative pathology linked to both, abnormal amyloid precursor protein (APP) processing, generating Aβ peptide, and Tau hyperphosphorylation and aggregation. Signs of oxidative distress in AD include: increase of ROS (H2O2, O2 •-), decrease of the levels or activities of antioxidant enzymes, abnormal oxidation of macromolecules related to elevated Aβ production, and changes in mitochondrial homeostasis linked to Tau phosphorylation. Interestingly, Cys residues present in APP form disulfide bonds that are important for intermolecular interactions and might be involved in the aggregation of Aβ. Moreover, two Cys residues in some Tau isoforms have been shown to be essential for Tau stabilization and its interaction with microtubules. Future research will show the complexities of Tau, its interactome, and the role that Cys residues play in the progression of AD. The specific modification of cysteinyl residues in redox signaling is also tightly connected to the regulation of various metabolic pathways. Many of these pathways have been found to be altered in AD, even at very early stages. In order to analyze the complex changes and underlying mechanisms, several AD models have been developed, including animal models, 2D and 3D cell culture, and ex-vivo studies of patient samples. The use of these models along with innovative, new redox analysis techniques are key to further understand the importance of the redox component in Alzheimer's disease and the identification of new therapeutic targets in the future.

FAM96A is essential for maintaining organismal energy balance and adipose tissue homeostasis in mice

The iron (Fe) metabolism plays important role in regulating systemic metabolism and obesity development. The Fe inside cells can form iron-sulfur (Fe-S) clusters, which are usually assembled into target proteins with the help of a conserved cluster assembly machinery. Family with sequence similarity 96A (FAM96A; also designated CIAO2A) is a cytosolic Fe-S assembly protein involved in the regulation of cellular Fe homeostasis. However, the biological function of FAM96A in vivo is still incompletely defined. Here, we tested the role of FAM96A in regulating organismal Fe metabolism, which is relevant to obesity and adipose tissue homeostasis. We found that in mice genetically lacking FAM96A globally, intracellular Fe homeostasis was interrupted in both white and brown adipocytes, but the systemic Fe level was normal. FAM96A deficiency led to adipocyte hypertrophy and organismal energy expenditure reduction even under nonobesogenic normal chow diet-fed conditions. Mechanistically, FAM96A deficiency promoted mechanistic target of rapamycin (mTOR) signaling in adipocytes, leading to an elevation of de novo lipogenesis and, therefore, fat mass accumulation. Furthermore, it also caused mitochondrial defects, including defects in mitochondrial number, ultrastructure, redox activity, and metabolic function in brown adipocytes, which are known to be critical for the control of energy balance. Moreover, adipocyte-selective FAM96A knockout partially phenocopied global FAM96A deficiency with adipocyte hypertrophy and organismal energy expenditure defects but the mice were resistant to high-fat diet-induced weight gain. Thus, FAM96A in adipocytes may autonomously act as a critical gatekeeper of organismal energy balance by coupling Fe metabolism to adipose tissue homeostasis.

NAC, NAC, Knockin' on Heaven's door: Interpreting the mechanism of action of N-acetylcysteine in tumor and immune cells

N-acetylcysteine (NAC) has been used as a direct scavenger of reactive oxygen species (hydrogen peroxide, in particular) and an antioxidant in cancer biology and immuno-oncology. NAC is the antioxidant drug most frequently employed in studies using tumor cells, immune cells, and preclinical mouse xenografts. Most studies use redox-active fluorescent probes such as dichlorodihydrofluorescein, hydroethidine, mitochondria-targeted hydroethidine, and proprietary kit-based probes (i.e., CellROX Green and CellROX Red) for intracellular detection of superoxide or hydrogen peroxide. Inhibition of fluorescence by NAC was used as a key experimental observation to support the formation of reactive oxygen species and redox mechanisms proposed for ferroptosis, tumor metastasis, and redox signaling in the tumor microenvironment. Reactive oxygen species such as superoxide and hydrogen peroxide stimulate or abrogate tumor cells and immune cells depending on multiple factors. Understanding the mechanism of antioxidants is crucial for interpretation of the results. Because neither NAC nor the fluorescent probes indicated above react directly with hydrogen peroxide, it is critically important to reinterpret the results to advance our understanding of the mechanism of action of NAC and shed additional mechanistic insight on redox-regulated signaling in tumor biology. To this end, this review is focused on how NAC could affect multiple pathways in cancer cells, including iron signaling, ferroptosis, and the glutathione-dependent antioxidant and redox signaling mechanism, and how NAC could inhibit oxidation of the fluorescent probes through multiple mechanisms.

Mitochondrial signal transduction

The analogy of mitochondria as powerhouses has expired. Mitochondria are living, dynamic, maternally inherited, energy-transforming, biosynthetic, and signaling organelles that actively transduce biological information. We argue that mitochondria are the processor of the cell, and together with the nucleus and other organelles they constitute the mitochondrial information processing system (MIPS). In a three-step process, mitochondria (1) sense and respond to both endogenous and environmental inputs through morphological and functional remodeling; (2) integrate information through dynamic, network-based physical interactions and diffusion mechanisms; and (3) produce output signals that tune the functions of other organelles and systemically regulate physiology. This input-to-output transformation allows mitochondria to transduce metabolic, biochemical, neuroendocrine, and other local or systemic signals that enhance organismal adaptation. An explicit focus on mitochondrial signal transduction emphasizes the role of communication in mitochondrial biology. This framework also opens new avenues to understand how mitochondria mediate inter-organ processes underlying human health.

Redox Status Is the Mainstay of SARS-CoV-2 and Host for Producing Therapeutic Opportunities

Over hundreds of years, humans have faced multiple pandemics and have overcome many of them with scientific advancements. However, the recent coronavirus disease (COVID-19) has challenged the physical, mental, and socioeconomic aspects of human life, which has introduced a general sense of uncertainty among everyone. Although several risk profiles, such as the severity of the disease, infection rate, and treatment strategy, have been investigated, new variants from different parts of the world put humans at risk and require multiple strategies simultaneously to control the spread. Understanding the entire system with respect to the commonly involved or essential mechanisms may be an effective strategy for successful treatment, particularly for COVID-19. Any treatment for COVID-19 may alter the redox profile, which can be an effective complementary method for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry and further replication. Indeed, redox profiles are one of the main barriers that suddenly shift the immune response in favor of COVID-19. Fortunately, several redox components exhibit antiviral and anti-inflammatory activities. However, access to these components as support elements against COVID-19 is limited. Therefore, understanding redox-derived species and their nodes as a common interactome in the system will facilitate the treatment of COVID-19. This review discusses the redox-based perspectives of the entire system during COVID-19 infection, including how redox-based molecules impact the accessibility of SARS-CoV-2 to the host and further replication. Additionally, to demonstrate its feasibility as a viable approach, we discuss the current challenges in redox-based treatment options for COVID-19.

Mitochondrial HSC70-1 Regulates Polar Auxin Transport through ROS Homeostasis in Arabidopsis Roots

Arabidopsis mitochondrial-localized heat shock protein 70-1 (mtHSC70-1) modulates vegetative growth by assisting mitochondrial complex IV assembly and maintaining reactive oxygen species (ROS) homeostasis. In addition, mtHSC70-1 affects embryo development, and this effect is mediated by auxin. However, whether mtHSC70-1 regulates vegetative growth through auxin and knowledge of the link between ROS homeostasis and auxin distribution remain unclear. Here, we found that mtHSC70-1 knockout seedlings (mthsc70-1a) displayed shortened roots, decreased fresh root weight and lateral root number, increased root width and abnormal root morphology. The introduction of the mtHSC70-1 gene into mthsc70-1a restored the growth and development of roots to the level of the wild type. However, sugar and auxin supplementation could not help the mutant roots restore to normal. Moreover, mthsc70-1a seedlings showed a decrease in meristem length and activity, auxin transport carrier (PINs and AUX1) and auxin abundances in root tips. The application of exogenous reducing agents upregulated the levels of PINs in the mutant roots. The introduction of antioxidant enzyme genes (MSD1 or CAT1) into the mthsc70-1a mutant rescued the PIN and local auxin abundances and root growth and development. Taken together, our data suggest that mtHSC70-1 regulates polar auxin transport through ROS homeostasis in Arabidopsis roots.