Compartmentalization of redox signaling through NADPH oxidase-derived ROS

New insights on the regulators and inhibitors of RhoA-ROCK signalling in Parkinson's disease

A multifaceted and widely prevalent neurodegenerative disease, Parkinson's disease (PD) is typified by the loss of dopaminergic neurons in the midbrain. The discovery of novel treatment(s) that can reverse or halt the course of the disease progression along with identifying the most reliable biomarker(s) in PD remains the crucial concern. RhoA in its active state has been demonstrated to interact with three distinct domains located in the central coiled-coil region of ROCK. RhoA appears to activate effectors most frequently by breaking the intramolecular autoinhibitory connections, which releases functional domains from the effector protein. Additionally, RhoA is highly expressed in the nervous system and it acts as a central molecule for its several downstream effector proteins in multiple signalling pathways both in neurons and glial cells. Mitochondrial dysfunction, vesicle transport malfunction and aggregation of α-Synuclein, a presynaptic neuronal protein genetically and neuropathologically associated with PD. While the RhoA-ROCK signalling pathway appears to have a significant role in PD symptoms, suggesting it could be a promising target for therapeutic interventions. Thus, this review article addresses the potential involvement of the RhoA-ROCK signalling system in the pathophysiology of neurodegenerative illnesses, with an emphasis on its biology and function. We also provide an overview of the state of research on RhoA regulation and its downstream biological activities, focusing on the role of RhoA signalling in neurodegenerative illnesses and the potential benefits of RhoA inhibition as a treatment for neurodegeneration.

Reactive oxygen species and oxidative stress in acute pancreatitis: Pathogenesis and new therapeutic interventions

Acute pancreatitis (AP) is a common acute gastrointestinal disorder affecting approximately 20% of patients with systemic inflammatory responses that may cause pancreatic and peripancreatic fat necrosis. This condition often progresses to multiple organ failure, significantly increasing morbidity and mortality. Oxidative stress, characterized by an imbalance between the body's reactive oxygen species (ROS) and antioxidants, activates the inflammatory signaling pathways. Although the pathogenesis of AP is not fully understood, ROS are increasingly recognized as critical in the disease's progression and development. Modulating the oxidative stress pathway has shown efficacy in mitigating the progression of AP. Despite numerous basic studies examining this pathway, comprehensive reviews of recent research remain sparse. This systematic review offers an in-depth examination of the critical role of oxidative stress in the pathogenesis and progression of AP and evaluates the therapeutic potential of antioxidant interventions in its management.

Dynamics of intracellular and intercellular redox communication

Cell and organ metabolism is organized through various signaling mechanisms, including redox, Ca2+, kinase and electrochemical pathways. Redox signaling operates at multiple levels, from interactions between individual molecules in their microenvironment to communication among subcellular organelles, single cells, organs, and the entire organism. Redox communication is a dynamic and ongoing spatiotemporal process. This article focuses on hydrogen peroxide (H2O2), a key second messenger that targets redox-active protein cysteine thiolates. H2O2 gradients across cell membranes are controlled by peroxiporins, specialized aquaporins. Redox-active endosomes, known as redoxosomes, form at the plasma membrane. Cell-to-cell redox communication involves direct contacts, such as per gap junctions that connect cells for transfer of molecules via connexons. Moreover, signaling occurs through the release of redox-active molecules and enzymes into the surrounding space, as well as through various types of extracellular vesicles (EVs) that transport these signals to nearby or distant target cells.

Exercise-induced adaptations to homeostasis of reactive oxygen species in skeletal muscle

Reactive oxygen species are generated by multiple mechanisms during contractile activity in exercising skeletal muscle and are recognised to play a role in signaling adaptations to the contractions. The sources of the superoxide and hydrogen peroxide generated are now relatively well understood but how the resulting low concentrations of hydrogen peroxide induce activation of multiple signaling pathways remains obscure. Several theories are presented together with accumulating evidence that 2-Cys peroxiredoxins may play a role of "effector" proteins in mediating the signaling actions of hydrogen peroxide. Identification of the mechanisms underlying these pathways offers the potential in the longer term for development of novel interventions to maintain exercise responses in the elderly with the potential to maintain muscle mass and function and consequent quality of life.

Suppression of JNK pathway protects neurons from oxidative injury via attenuating parthanatos in glutamate-treated HT22 neurons

Oxidative stress causes diverse neurological disorders. Parthanatos is a type of programmed cell death, characterised by strong activation of poly (ADP-ribose) (PAR) polymerase-1 (PARP-1), PAR polymer accumulation, and nuclear translocation of apoptosis-inducing factor (AIF), and is involved in cellular oxidative injury. Signalling by c-Jun-N-terminal protein kinase (JNK) is activated by reactive oxygen species (ROS), and this also contributes to ROS production. However, the exact relationship between JNK signalling and parthanatos in neurological disorders triggered by oxidative stress is unclear. In this study, glutamate-treated HT22 neurons were used to investigate whether the signalling by JNK contributes a regulatory role to parthanatos in oxidative stress-related neurological disease. JNK signalling was activated in glutamate-treated HT22 neurons, demonstrated via upregulation of p-JNK levels. Pre-treatment with SP600125 markedly inhibited JNK signalling, increased cell viability, and significantly reversed PARP-1 overproduction, PAR polymer accumulation, and nuclear AIF translocation. In addition, inhibition of JNK signalling severely reduced the production of both intracellular ROS and mitochondria superoxide. This study indicated that parthanatos in glutamate-treated HT22 neurons could be suppressed by JNK signalling inhibition. JNK activation participated in parthanatos via an increase in intracellular ROS levels.

The transcription factor LBD10 sustains pollen tube growth and integrity by modulating reactive oxygen species homeostasis via the regulation of flavonol biosynthesis in Arabidopsis

Reproduction in angiosperms relies on the precise growth of pollen tubes, facilitating the delivery of sperm cells to the ovule for double fertilization. LATERAL ORGAN BOUNDARIES DOMAIN10 (LBD10), a plant-specific transcription factor, plays a pivotal role in Arabidopsis pollen development. Here, we uncovered LBD10's function in sustaining pollen tube growth and integrity. The lbd10 mutant exhibited elevated levels of reactive oxygen species (ROS) and hydrogen peroxide (H2O2) in both pollen grains and tubes, leading to compromised pollen tube growth. The inhibition of ROS synthesis and scavenging of excess ROS with an antioxidant treatment each alleviated these defects in lbd10. The lbd10 mutant displayed reduced flavonol accumulation in both pollen grains and tubes. All the altered phenotypes of lbd10 were complemented by expressing LBD10 under its native promoter. Exogenous application of flavonoids recused the defects in pollen tube growth and integrity in lbd10, along with reducing the excess levels of ROS and H2O2. LBD10 directly binds the promoters of key flavonol biosynthesis genes in chromatin and promotes reporter gene expression in Arabidopsis mesophyll protoplasts. Our findings indicate that LBD10 modulates ROS homeostasis by transcriptionally activating genes crucial for flavonol biosynthesis, thereby maintaining pollen tube growth and integrity.

The Interplay between Mechanoregulation and ROS in Heart Physiology, Disease, and Regeneration

Cardiovascular diseases are currently the most common cause of death in developed countries. Due to lifestyle and environmental factors, this problem is only expected to increase in the future. Reactive oxygen species (ROS) are a key player in the onset of cardiovascular diseases but also have important functions in healthy cardiac tissue. Here, the interplay between ROS generation and cardiac mechanical forces is shown, and the state of the art and a perspective on future directions are discussed. To this end, an overview of what is currently known regarding ROS and mechanosignaling at a subcellular level is first given. There the role of ROS in mechanosignaling as well as the interplay between both factors in specific organelles is emphasized. The consequences at a larger scale across the population of heart cells are then discussed. Subsequently, the roles of ROS in embryogenesis, pathogenesis, and aging are further discussed, exemplifying some aspects of mechanoregulation. Finally, different models that are currently in use are discussed to study the topics above.

The role of reactive oxygen species in the regulation of the blood-brain barrier

The blood-brain barrier (BBB) regulates the exchange of metabolites and cells between the blood and brain, and maintains central nervous system homeostasis. Various factors affect BBB barrier functions, including reactive oxygen species (ROS). ROS can act as stressors, damaging biological molecules, but they also serve as secondary messengers in intracellular signaling cascades during redox signaling. The impact of ROS on the BBB has been observed in multiple sclerosis, stroke, trauma, and other neurological disorders, making blocking ROS generation a promising therapeutic strategy for BBB dysfunction. However, it is important to consider ROS generation during normal BBB functioning for signaling purposes. This review summarizes data on proteins expressed by BBB cells that can be targets of redox signaling or oxidative stress. It also provides examples of signaling molecules whose impact may cause ROS generation in the BBB, as well as discusses the most common diseases associated with BBB dysfunction and excessive ROS generation, open questions that arise in the study of this problem, and possible ways to overcome them.

FRBM Mini REVIEW: Chemogenetic approaches to probe redox dysregulation in heart failure

Chemogenetics refers to experimental methods that use novel recombinant proteins that can be dynamically and uniquely regulated by specific biochemicals. Chemogenetic approaches allow the precise manipulation of cellular signaling to delineate the molecular pathways involved in both physiological and pathological disease states. Approaches utilizing yeast d-amino acid oxidase (DAAO) enable manipulation of intracellular redox metabolism through generation of hydrogen peroxide in the presence of d-amino acids and have led to the development of new and informative animal models to characterize the impact of oxidative stress in heart failure and neurodegeneration. These chemogenetic models, in which DAAO expression is regulated by different tissue-specific promoters, have led to a range of cardiac phenotypes. This review discusses chemogenetic approaches to manipulate oxidative stress in models of heart failure. These approaches provide new insights into the relationships between redox metabolism and normal and pathologic states in the heart, as well as in other diseases characterized by oxidative stress.

Translocator protein (18 kDa) (Tspo) in the retina and implications for ocular diseases

Translocator protein (18 kDa) (Tspo), formerly known as peripheral benzodiazepine receptor is a highly conserved transmembrane protein primarily located in the outer mitochondrial membrane. In the central nervous system (CNS), especially in glia cells, Tspo is upregulated upon inflammation. Consequently, Tspo was used as a tool for diagnostic in vivo imaging of neuroinflammation in the brain and as a potential therapeutic target. Several synthetic Tspo ligands have been explored as immunomodulatory and neuroprotective therapy approaches. Although the function of Tspo and how its ligands exert these beneficial effects is not fully clear, it became a research topic of interest, especially in ocular diseases in the past few years. This review summarizes state-of-the-art knowledge of Tspo expression and its proposed functions in different cells of the retina including microglia, retinal pigment epithelium and Müller cells. Tspo is involved in cytokine signaling, oxidative stress and reactive oxygen species production, calcium signaling, neurosteroid synthesis, energy metabolism, and cholesterol efflux. We also highlight recent developments in preclinical models targeting Tspo and summarize the relevance of Tspo biology for ocular and retinal diseases. We conclude that glial upregulation of Tspo in different ocular pathologies and the use of Tspo ligands as promising therapeutic approaches in preclinical studies underline the importance of Tspo as a potential disease-modifying protein.

Redox active plant phenolic, acetosyringone, for electrogenetic signaling

Redox is a unique, programmable modality capable of bridging communication between biology and electronics. Previous studies have shown that the E. coli redox-responsive OxyRS regulon can be re-wired to accept electrochemically generated hydrogen peroxide (H2O2) as an inducer of gene expression. Here we report that the redox-active phenolic plant signaling molecule acetosyringone (AS) can also induce gene expression from the OxyRS regulon. AS must be oxidized, however, as the reduced state present under normal conditions cannot induce gene expression. Thus, AS serves as a "pro-signaling molecule" that can be activated by its oxidation-in our case by application of oxidizing potential to an electrode. We show that the OxyRS regulon is not induced electrochemically if the imposed electrode potential is in the mid-physiological range. Electronically sliding the applied potential to either oxidative or reductive extremes induces this regulon but through different mechanisms: reduction of O2 to form H2O2 or oxidation of AS. Fundamentally, this work reinforces the emerging concept that redox signaling depends more on molecular activities than molecular structure. From an applications perspective, the creation of an electronically programmed "pro-signal" dramatically expands the toolbox for electronic control of biological responses in microbes, including in complex environments, cell-based materials, and biomanufacturing.

The Pathogenesis of Pancreatitis and the Role of Autophagy

The pathogenesis of acute and chronic pancreatitis has recently evolved as new findings demonstrate a complex mechanism operating through various pathways. In this review, the current evidence indicating that several mechanisms act in concert to induce and perpetuate pancreatitis were presented. As autophagy is now considered a fundamental mechanism in the pathophysiology of both acute and chronic pancreatitis, the fundamentals of the autophagy pathway were discussed to allow for a better understanding of the pathophysiological mechanisms of pancreatitis. The various aspects of pathogenesis, including trypsinogen activation, ER stress and mitochondrial dysfunction, the implications of inflammation, and macrophage involvement in innate immunity, as well as the significance of pancreatic stellate cells in the development of fibrosis, were also analyzed. Recent findings on exosomes and the miRNA regulatory role were also presented. Finally, the role of autophagy in the protection and aggravation of pancreatitis and possible therapeutic implications were reviewed.

HyPer as a tool to determine the reductive activity in cellular compartments

A multitude of cellular metabolic and regulatory processes rely on controlled thiol reduction and oxidation mechanisms. Due to our aerobic environment, research preferentially focuses on oxidation processes, leading to limited tools tailored for investigating cellular reduction. Here, we advocate for repurposing HyPer1, initially designed as a fluorescent probe for H2O2 levels, as a tool to measure the reductive power in various cellular compartments. The response of HyPer1 depends on kinetics between thiol oxidation and reduction in its OxyR sensing domain. Here, we focused on the reduction half-reaction of HyPer1. We showed that HyPer1 primarily relies on Trx/TrxR-mediated reduction in the cytosol and nucleus, characterized by a second order rate constant of 5.8 × 102 M-1s-1. On the other hand, within the mitochondria, HyPer1 is predominantly reduced by glutathione (GSH). The GSH-mediated reduction rate constant is 1.8 M-1s-1. Using human leukemia K-562 cells after a brief oxidative exposure, we quantified the compartmentalized Trx/TrxR and GSH-dependent reductive activity using HyPer1. Notably, the recovery period for mitochondrial HyPer1 was twice as long compared to cytosolic and nuclear HyPer1. After exploring various human cells, we revealed a potent cytosolic Trx/TrxR pathway, particularly pronounced in cancer cell lines such as K-562 and HeLa. In conclusion, our study demonstrates that HyPer1 can be harnessed as a robust tool for assessing compartmentalized reduction activity in cells following oxidative stress.

Ras3 in Bombyx mori with antiviral function against B. mori nucleopolyhedrovirus

Bombyx mori ras protein3 (BmRas3) is a small molecular protein in the GTPase superfamily, which has the activity of binding guanosine nucleotides and GTP enzymes. It acts as a molecular switch by coupling extracellular signal to different cellular response through the conversion between Ras-GTP conformation and Ras-GDP conformation, thus regulating signal pathways responsible for cell growth, migration, adhesion, survival and differentiation. However, few studies have been done on Ras3 in silkworm, and its function and mechanism are unclear. In this study, we found that the overexpression of BmRas3 inhibited the infection of BmNPV(B. mori nucleopolyhedrovirus), while knockdown of BmRas3 could promote the infection of BmNPV. In addition, after the BmRas3 in silkworm larvae was knockdown, the anti-BmNPV ability of silkworm decreased and the survival rate of silkworm was affected. Additionly in the cells with BmRas3 overexpression, the transcription level of BmMapkk6 、BmP38、BmJNK、BmERK1/2 and BmERK5 were significantly increased after BmNPV infection, and the transcript levels of BmMapkk6、BmP38、BmJNK、BmERK1/2 and BmERK5 were also inhibited to varying degrees This is the first report on the antiviral effect of BmRas3 in silkworm, which provides a new direction for further study on the anti-BmNPV mechanism of silkworm and screening and cultivation of anti-BmNPV silkworm strain.

Targeting the Main Sources of Reactive Oxygen Species Production: Possible Therapeutic Implications in Chronic Pain

Humans have long been combating chronic pain. In clinical practice, opioids are firstchoice analgesics, but long-term use of these drugs can lead to serious adverse reactions. Finding new, safe and effective pain relievers that are useful treatments for chronic pain is an urgent medical need. Based on accumulating evidence from numerous studies, excess reactive oxygen species (ROS) contribute to the development and maintenance of chronic pain. Some antioxidants are potentially beneficial analgesics in the clinic, but ROS-dependent pathways are completely inhibited only by scavenging ROS directly targeting cellular or subcellular sites. Unfortunately, current antioxidant treatments do not achieve this effect. Furthermore, some antioxidants interfere with physiological redox signaling pathways and fail to reverse oxidative damage. Therefore, the key upstream processes and mechanisms of ROS production that lead to chronic pain in vivo must be identified to discover potential therapeutic targets related to the pathways that control ROS production in vivo. In this review, we summarize the sites and pathways involved in analgesia based on the three main mechanisms by which ROS are generated in vivo, discuss the preclinical evidence for the therapeutic potential of targeting these pathways in chronic pain, note the shortcomings of current research and highlight possible future research directions to provide new targets and evidence for the development of clinical analgesics.

Radiotherapy-associated Sensorineural Hearing Loss in Pediatric Oncology Patients

During the radiotherapeutic treatment of pediatric oncology patients, they would be at a latent risk of developing ionizing radiation-induced ototoxicity when the cochlea or auditory nerve is located within the radiation field. Sensorineural hearing loss (SNHL) is an irreversible late complication of radiotherapy, and its incidence depends on various factors such as the patient's hearing sensitivity, total radiation dose to the cochlea, radiotherapy fractionation regimen, age and chemoradiation. Importantly, this complication exhibits serious challenges to adult survivors of childhood cancer, as it has been linked to impairments in academic achievement, psychosocial development, independent living skills, and employment in the survivor population. Therefore, early detection and proper management can alleviate academic, speech, language, social, and psychological morbidity arising from hearing deficits. In the present review, we have addressed issues such as underlying mechanisms of radiation-induced SNHL, audiometric findings of pediatric cancer patients treated with radiotherapy, and management and protection measures against radiation-induced ototoxicity.

Systematic analysis of apoptosis-related genes in the prognosis of lung squamous cell carcinoma: a combined single-cell RNA sequencing study

Background

Lung squamous cell carcinoma (LUSC) has a poor prognosis and lacks appropriate diagnostic and treatment strategies. Apoptosis dysregulation is associated with tumor occurrence and drug resistance, but the prognostic value of apoptosis-related genes (ARGs) in LUSC remains unclear.

Methods

Using univariate Cox regression, least absolute shrinkage and selection operator (LASSO) regression, and multivariate Cox regression analysis based on differentially expressed ARGs, we constructed an ARG-related prognostic model for LUSC survival rates. We conducted correlation analysis of prognostic ARGs by incorporating the dataset of normal lung tissue from the Genotype-Tissue Expression (GTEx) database. We then constructed a risk model, and the predictive ability of the model was evaluated using receiver operating characteristic (ROC) curve analysis. Non-small cell lung cancer (NSCLC) single-cell RNA sequencing (scRNA-seq) data were downloaded from the Gene Expression Omnibus (GEO) database. Subsequently, these data were subjected to single-cell analysis. Cell subgroups were determined and annotated by dimensionality reduction clustering, and the cell subgroups in disease development were identified via pseudotemporal analysis with the Monocle 2 algorithm.

Results

We identified four significantly prognostic ARGs and constructed a stable prognostic risk model. Kaplan-Meier curve analysis showed that the high-risk group had a poorer prognosis (P<0.05). Furthermore, the ROC analysis of 3-, 5- and 7-year survival rates confirmed that the model had good predictive value for patients with LUSC. Single-cell RNA sequencing showed the prognostic ARGS were enriched in epithelial cells, smooth muscle cells, and T cells. Pseudotime analysis was used to infer the differentiation process and time sequence of cells.

Conclusions

This study identified ARGs that are associated with prognosis in LUSC, and a risk model based on these prognostic genes was constructed that could accurately predict the prognosis of LUSC. Single-cell sequencing analysis provided new insights into the cellular-level development of tumors. These findings provide more guidance for the diagnosis and treatment of patients with LUSC.

Androgen receptor contributes to repairing DNA damage induced by inflammation and oxidative stress in prostate cancer

Background

Androgen deprivation therapy remains the first-line therapy option for prostate cancer, mostly resulting in the transition of the disease to a castration-resistant state. The lack of androgen signaling during therapy affects various cellular processes, which sometimes paradoxically contributes to cancer progression. As androgen receptor (AR) signaling is known to contribute to oxidative stress regulation, loss of AR may also affect DNA damage level and the response mechanism in oxidant and inflammatory conditions of the prostate tumor microenvironment. Therefore, this study aimed to investigate the role of AR and AR-regulated tumor suppressor NKX3.1 upon oxidative stress-induced DNA damage response (DDR) in the inflammatory tumor microenvironment of the prostate.

Materials and methods

Intracellular reactive oxygen species (ROS) level was induced by either inflammatory conditioned media obtained from lipopolysaccharide-induced macrophages or oxidants and measured by dichlorodihydrofluorescein diacetate. In addition to this, DNA damage was subsequently quantified by counting gH2AX foci using an immunofluorescence-based Aklides platform. Altered expression of proteins function in DDR detected by western blotting.

Results

Cellular levels of ROS and ROS-induced DNA double-strand break damage were analyzed in the absence and presence of AR signaling upon treatment of prostate cancer cells by either oxidants or inflammatory microenvironment exposure. The results showed that AR suppresses intracellular ROS and contributes to DNA damage recognition under oxidant conditions. Besides, increased DNA damage due to loss of NKX3.1 under inflammatory conditions was alleviated by its overexpression. Moreover, the activation of the DDR mediators caused by AR and NKX3.1 activation in androgen-responsive and castration-resistant prostate cancer cells indicated that the androgen receptor function is essential both in controlling oxidative stress and in activating the ROS-induced DDR.

Conclusion

Taken together, it is concluded that the regulatory function of androgen receptor signaling has a vital function in the balance between antioxidant response and DDR activation.

Transient receptor potential vanilloid 4 (TRPV4) in neutrophils enhances myocardial ischemia/reperfusion injury

The Ca2+-permeable TRPV4 cation channel is expressed in neutrophils and contributes to myocardial ischemia/reperfusion injury. Here we tested the hypotheses that TRPV4 promotes neutrophil activation and subsequently aggregates myocardial ischemia/reperfusion injury. TRPV4 protein was confirmed in neutrophils, and its function was assessed by the current and intracellular Ca2+ concentration elevations evoked by TRPV4 agonists. Furthermore, TRPV4 agonists dose-dependently promoted migration toward fMLP, reactive oxygen species production, and myeloperoxidase release, which were prevented by pretreatment with a selective TRPV4 antagonist, in neutrophils from TRPV4 knockout mice, Ca2+-free medium, or BAPTA-AM + Ca2+-free medium. Blockade of TRPV4 also inhibited the effects of commonly used neutrophil activators fMLP and PMA. Mechanically, TRPV4 regulated neutrophil activation, particularly reactive oxygen species production, by affecting PKCα, P38, and AKT via Ca2+ signaling. In addition, isolated hearts infused with neutrophils from wild-type mice showed additional myocardial ischemia/reperfusion injuries but not those infused with TRPV4 knockout. Our study reveals that TRPV4-mediated neutrophil activation enhances myocardial ischemia/reperfusion injury, and it might be a novel therapeutic target for myocardial ischemia/reperfusion injury and other neutrophil-mediated inflammatory diseases.

GPX3 expression was down-regulated but positively correlated with poor outcome in human cancers

Introduction

Cancer is a crucial public health problem and one of the leading causes of death worldwide. Previous studies have suggested that GPX3 may be involved in cancer metastasis and chemotherapy resistance. However, how GPX3 affects cancer patients' outcomes and the underlying mechanism remains unclear.

Methods

Sequencing data and clinical data from TCGA, GTEx, HPA, and CPTAC were used to explore the relationship between GPX3 expression and clinical features. Immunoinfiltration scores were used to assess the relationship between GPX3 and the tumor immune microenvironment. Functional enrichment analysis was used to predict the role of GPX3 in tumors. Gene mutation frequency, methylation level, and histone modification were used to predict the GPX3 expression regulation method. Breast, ovarian, colon, and gastric cancer cells were used to investigate the relationship between GPX3 expression and cancer cell metastasis, proliferation, and chemotherapy sensitivity.

Results

GPX3 is down-regulated in various tumor tissues, and GPX3 expression level can be used as a marker for cancer diagnosis. However, GPX3 expression is associated with higher stage and lymph node metastasis, as well as poorer prognosis. GPX3 is closely related to thyroid function and antioxidant function, and its expression may be regulated by epigenetic inheritance such as methylation modification or histone modification. In vitro experiments, GPX3 expression is associated with cancer cell sensitivity to oxidant and platinum-based chemotherapy and is involved in tumor metastasis in oxidative environments.

Discussion

We explored the relationship between GPX3 and clinical features, immune infiltration characteristics, migration and metastasis, and chemotherapy sensitivities of human cancers. We further investigated the potential genetic and epigenetic regulation of GPX3 in cancer. Our results suggested that GPX3 plays a complicated role in the tumor microenvironment, simultaneously promoting metastasis and chemotherapy resistance in human cancers.

Critical Role of Aquaporins in Cancer: Focus on Hematological Malignancies

Simple Summary

Aquaporins are proteins able to regulate the transfer of water and other small substances such as ions, glycerol, urea, and hydrogen peroxide across cellular membranes. AQPs provide for a huge variety of physiological phenomena; their alteration provokes several types of pathologies including cancer and hematological malignancies. Our review presents data revealing the possibility of employing aquaporins as biomarkers in patients with hematological malignancies and evaluates the possibility that interfering with the expression of aquaporins could represent an effective treatment for hematological malignancies.

Abstract

Aquaporins are transmembrane molecules regulating the transfer of water and other compounds such as ions, glycerol, urea, and hydrogen peroxide. Their alteration has been reported in several conditions such as cancer. Tumor progression might be enhanced by aquaporins in modifying tumor angiogenesis, cell volume adaptation, proteases activity, cell–matrix adhesions, actin cytoskeleton, epithelial–mesenchymal transitions, and acting on several signaling pathways facilitating cancer progression. Close connections have also been identified between the aquaporins and hematological malignancies. However, it is difficult to identify a unique action exerted by aquaporins in different hemopathies, and each aquaporin has specific effects that vary according to the class of aquaporin examined and to the different neoplastic cells. However, the expression of aquaporins is altered in cell cultures and in patients with acute and chronic myeloid leukemia, in lymphoproliferative diseases and in multiple myeloma, and the different expression of aquaporins seems to be able to influence the efficacy of treatment and could have a prognostic significance, as greater expression of aquaporins is correlated to improved overall survival in leukemia patients. Finally, we assessed the possibility that modifying the aquaporin expression using aquaporin-targeting regulators, specific monoclonal antibodies, and even aquaporin gene transfer could represent an effective therapy of hematological malignancies.

NADPH oxidase 2 activity in Parkinson's disease

Mitochondrial dysfunction and oxidative stress are strongly implicated in Parkinson's disease (PD) pathogenesis and there is evidence that mitochondrially-generated superoxide can activate NADPH oxidase 2 (NOX2). Although NOX2 has been examined in the context of PD, most attention has focused on glial NOX2, and the role of neuronal NOX2 in PD remains to be defined. Additionally, pharmacological NOX2 inhibitors have typically lacked specificity. Here we devised and validated a proximity ligation assay for NOX2 activity and demonstrated that in human PD and two animal models thereof, both neuronal and microglial NOX2 are highly active in substantia nigra under chronic conditions. However, in acute and sub-acute PD models, we observed neuronal, but not microglial NOX2 activation, suggesting that neuronal NOX2 may play a primary role in the early stages of the disease. Aberrant NOX2 activity is responsible for the formation of oxidative stress-related post-translational modifications of α-synuclein, and impaired mitochondrial protein import in vitro in primary ventral midbrain neuronal cultures and in vivo in nigrostriatal neurons in rats. In a rat model, administration of a brain-penetrant, highly specific NOX2 inhibitor prevented NOX2 activation in nigrostriatal neurons and its downstream effects in vivo, such as activation of leucine-rich repeat kinase 2 (LRRK2). We conclude that NOX2 is an important enzyme that contributes to progressive oxidative damage which in turn can lead to α-synuclein accumulation, mitochondrial protein import impairment, and LRRK2 activation. In this context, NOX2 inhibitors hold potential as a disease-modifying therapy in PD.

Upregulation of Nox4 induces a pro-survival Nrf2 response in cancer-associated fibroblasts that promotes tumorigenesis and metastasis, in part via Birc5 induction

BACKGROUND

A pro-oxidant enzyme, NADPH oxidase 4 (Nox4) has been reported to be a critical downstream effector of TGFβ-induced myofibroblast transformation during fibrosis. While there are a small number of studies suggesting an oncogenic role of Nox4 derived from activated fibroblasts, direct evidence linking this pro-oxidant to the tumor-supporting CAF phenotype and the mechanisms involved are lacking, particularly in breast cancer.

METHODS

We targeted Nox4 in breast patient-derived CAFs via siRNA-mediated knockdown or administration of a pharmaceutical inhibitor (GKT137831). We also determine primary tumor growth and metastasis of implanted tumor cells using a stable Nox4-/- syngeneic mouse model. Autophagic flux of CAFs was assessed using a tandem fluorescent-tagged ptfl-LC3 plasmid via confocal microscopy analysis and determination of the expression level of autophagy markers (beclin-1 and LC3B). Nox4 overexpressing CAFs depend on the Nrf2 (nuclear factor-erythroid factor 2-related factor 2) pathway for survival. We then determined the dependency of Nox4-overexpressing CAFs on the Nrf2-mediated adaptive stress response pathway for survival. Furthermore, we investigated the involvement of Birc5 on CAF phenotype (viability and collagen contraction activity) as well as the expression level of CAF markers, FAP and αSMA.

CONCLUSIONS

We found that deletion of stroma Nox4 and pharmaceutically targeting its activity with GKT137831 significantly inhibited orthotopic tumor growth and metastasis of implanted E0771 and 4T1 murine mammary carcinoma cell lines in mice. More importantly, we found a significant upregulation of Nox4 expression in CAFs isolated from human breast tumors versus normal mammary fibroblasts (RMFs). Our in situ RNA hybridization analysis for Nox4 transcription on a human breast tumor microarray further support a role of this pro-oxidant in the stroma of breast carcinomas. In addition, we found that Nox4 promotes autophagy in CAFs. Moreover, we found that Nox4 promoted survival of CAFs via activation of Nrf2, a master regulator of oxidative stress response. We have further shown Birc5 is involved as a downstream modulator of Nrf2-mediated pro-survival phenotype. Together these studies indicate a role of redox signaling via the Nox4-Nrf2 pathway in tumorigenesis and metastasis of breast cancer cells by promoting autophagy and survival of CAFs.

Self-Sustained Regulation or Self-Perpetuating Dysregulation: ROS-dependent HIF-YAP-Notch Signaling as a Double-Edged Sword on Stem Cell Physiology and Tumorigenesis

Organ development, homeostasis, and repair often rely on bidirectional, self-organized cell-niche interactions, through which cells select cell fate, such as stem cell self-renewal and differentiation. The niche contains multiplexed chemical and mechanical factors. How cells interpret niche structural information such as the 3D topology of organs and integrate with multiplexed mechano-chemical signals is an open and active research field. Among all the niche factors, reactive oxygen species (ROS) have recently gained growing interest. Once considered harmful, ROS are now recognized as an important niche factor in the regulation of tissue mechanics and topology through, for example, the HIF-YAP-Notch signaling pathways. These pathways are not only involved in the regulation of stem cell physiology but also associated with inflammation, neurological disorder, aging, tumorigenesis, and the regulation of the immune checkpoint molecule PD-L1. Positive feedback circuits have been identified in the interplay of ROS and HIF-YAP-Notch signaling, leading to the possibility that under aberrant conditions, self-organized, ROS-dependent physiological regulations can be switched to self-perpetuating dysregulation, making ROS a double-edged sword at the interface of stem cell physiology and tumorigenesis. In this review, we discuss the recent findings on how ROS and tissue mechanics affect YAP-HIF-Notch-PD-L1 signaling, hoping that the knowledge can be used to design strategies for stem cell-based and ROS-targeting therapy and tissue engineering.

Redox Control of Signalling Responses to Contractile Activity and Ageing in Skeletal Muscle

Research over almost 40 years has established that reactive oxygen species are generated at different sites in skeletal muscle and that the generation of these species is increased by various forms of exercise. Initially, this was thought to be potentially deleterious to skeletal muscle and other tissues, but more recent data have identified key roles of these species in muscle adaptations to exercise. The aim of this review is to summarise our current understanding of these redox signalling roles of reactive oxygen species in mediating responses of muscle to contractile activity, with a particular focus on the effects of ageing on these processes. In addition, we provide evidence that disruption of the redox status of muscle mitochondria resulting from age-associated denervation of muscle fibres may be an important factor leading to an attenuation of some muscle responses to contractile activity, and we speculate on potential mechanisms involved.

Reactive Oxygen Species Differentially Modulate the Metabolic and Transcriptomic Response of Endothelial Cells

Reactive oxygen species (ROS) are important mediators of both physiological and pathophysiological signal transduction in the cardiovascular system. The effects of ROS on cellular processes depend on the concentration, localization, and duration of exposure. Cellular stress response mechanisms have evolved to mitigate the negative effects of acute oxidative stress. In this study, we investigate the short-term and long-term metabolic and transcriptomic response of human umbilical vein endothelial cells (HUVEC) to different types and concentrations of ROS. To generate intracellular H₂O₂, we utilized a lentiviral chemogenetic approach for overexpression of human D-amino acid oxidase (DAO). DAO converts D-amino acids into their corresponding imino acids and H₂O₂. HUVEC stably overexpressing DAO (DAO-HUVEC) were exposed to D-alanine (3 mM), exogenous H₂O₂ (10 µM or 300 µM), or menadione (5 µM) for various timepoints and subjected to global untargeted metabolomics (LC-MS/MS) and RNAseq by MACE (Massive analysis of cDNA ends). A total of 300 µM H₂O₂ led to pronounced changes on both the metabolic and transcriptomic level. In particular, metabolites linked to redox homeostasis, energy-generating pathways, and nucleotide metabolism were significantly altered. Furthermore, 300 µM H₂O₂ affected genes related to the p53 pathway and cell cycle. In comparison, the effects of menadione and DAO-derived H₂O₂ mainly occurred at gene expression level. Collectively, all types of ROS led to subtle changes in the expression of ribosomal genes. Our results show that different types and concentration of ROS lead to a different metabolic and transcriptomic response in endothelial cells.

Chemogenetic Approaches to Probe Redox Pathways: Implications for Cardiovascular Pharmacology and Toxicology

Chemogenetics refers to experimental systems that dynamically regulate the activity of a recombinant protein by providing or withholding the protein's specific biochemical stimulus. Chemogenetic tools permit precise dynamic control of specific signaling molecules to delineate the roles of those molecules in physiology and disease. Yeast d-amino acid oxidase (DAAO) enables chemogenetic manipulation of intracellular redox balance by generating hydrogen peroxide only in the presence of d-amino acids. Advances in biosensors have allowed the precise quantitation of these signaling molecules. The combination of chemogenetic approaches with biosensor methodologies has opened up new lines of investigation, allowing the analysis of intracellular redox pathways that modulate physiological and pathological cell responses. We anticipate that newly developed transgenic chemogenetic models will permit dynamic modulation of cellularredox balance in diverse cells and tissues and will facilitate the identification and validation of novel therapeutic targets involved in both physiological redox pathways and pathological oxidative stress.

Modulating autophagic flux via ROS-responsive targeted micelles to restore neuronal proteostasis in Alzheimer's disease

Compromised autophagy and defective lysosomal clearance significantly contribute to impaired neuronal proteostasis, which represents a hallmark of Alzheimer's disease (AD) and other age-related neurodegenerative disorders. Growing evidence has implicated that modulating autophagic flux, instead of inducing autophagosome formation alone, would be more reliable to rescue neuronal proteostasis. Concurrently, selectively enhancing drug concentrations in the leision areas, instead of the whole brain, will maximize therapeutic efficacy while reduing non-selective autophagy induction. Herein, we design a ROS-responsive targeted micelle system (TT-NM/Rapa) to enhance the delivery efficiency of rapamycin to neurons in AD lesions guided by the fusion peptide TPL, and facilitate its intracellular release via ROS-mediated disassembly of micelles, thereby maximizing autophagic flux modulating efficacy of rapamycin in neurons. Consequently, it promotes the efficient clearance of intracellular neurotoxic proteins, β-amyloid and hyperphosphorylated tau proteins, and ameliorates memory defects and neuronal damage in 3 × Tg-AD transgenic mice. Our studies demonstrate a promising strategy to restore autophagic flux and improve neuronal proteostasis by rationally-engineered nano-systems for delaying the progression of AD.

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Modulating autophagic flux to restore neuronal proteostasis was proved to be effective in delaying the progression of AD.

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We designed a novel ROS-responsive targeted micelle with superior targetability and desirable cargo release in AD neurons.

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Our designed TPL peptide with high preferentiality to AD lesions showed great promise for developing AD-targeted therapeutics.

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Systematic evaluation of TT-NM/Rapa would provide a rationale for applying rapamycin in neurodegenerative disease treatment.

Idiopathic Pulmonary Comorbidities and Mechanisms

Idiopathic pulmonary fibrosis (IPF) is a disease with an unknown etiology mainly characterized by a progressive decline of lung function due to the scarring of the tissue deep in the lungs. The overall survival after diagnosis remains low between 3 and 5 years. IPF is a heterogeneous disease and much progress has been made in the past decade in understanding the disease mechanisms that contributed to the development of two new drugs, pirfenidone and nintedanib, which improved the therapeutic management of the disease. The understanding of the cofactors and comorbidities of IPF also contributed to improved management of the disease outcome. In the present review, we evaluate scientific evidence which indicates IPF as a risk factor for other diseases based on the complexity of molecular and cellular mechanisms involved in the disease development and of comorbidities. We conclude from the existing literature that while much progress has been made in understating the mechanisms involved in IPF development, further studies are still necessary to fully understand IPF pathogenesis which will contribute to the identification of novel therapeutic targets for IPF management as well as other diseases for which IPF is a major risk factor.

Redox Homeostasis and Regulation in Pluripotent Stem Cells: Uniqueness or Versatility?

Pluripotent stem cells (PSCs) hold great potential both in studies on developmental biology and clinical practice. Mitochondrial metabolism that encompasses pathways that generate ATP and produce ROS significantly differs between PSCs and somatic cells. Correspondingly, for quite a long time it was believed that the redox homeostasis in PSCs is also highly specific due to the hypoxic niche of their origin-within the pre-implantation blastocyst. However, recent research showed that redox parameters of cultivated PSCs have much in common with that of their differentiated progeny cells. Moreover, it has been proven that, similar to somatic cells, maintaining the physiological ROS level is critical for the regulation of PSC identity, proliferation, differentiation, and de-differentiation. In this review, we aimed to summarize the studies of redox metabolism and signaling in PSCs to compare the redox profiles of pluripotent and differentiated somatic cells. We collected evidence that PSCs possess metabolic plasticity and are able to adapt to both hypoxia and normoxia, that pluripotency is not strictly associated with anaerobic conditions, and that cellular redox homeostasis is similar in PSCs and many other somatic cells under in vitro conditions that may be explained by the high conservatism of the redox regulation system.

Post-Translational Modification and Subcellular Compartmentalization: Emerging Concepts on the Regulation and Physiopathological Relevance of RhoGTPases

Cells and tissues are continuously exposed to both chemical and physical stimuli and dynamically adapt and respond to this variety of external cues to ensure cellular homeostasis, regulated development and tissue-specific differentiation. Alterations of these pathways promote disease progression-a prominent example being cancer. Rho GTPases are key regulators of the remodeling of cytoskeleton and cell membranes and their coordination and integration with different biological processes, including cell polarization and motility, as well as other signaling networks such as growth signaling and proliferation. Apart from the control of GTP-GDP cycling, Rho GTPase activity is spatially and temporally regulated by post-translation modifications (PTMs) and their assembly onto specific protein complexes, which determine their controlled activity at distinct cellular compartments. Although Rho GTPases were traditionally conceived as targeted from the cytosol to the plasma membrane to exert their activity, recent research demonstrates that active pools of different Rho GTPases also localize to endomembranes and the nucleus. In this review, we discuss how PTM-driven modulation of Rho GTPases provides a versatile mechanism for their compartmentalization and functional regulation. Understanding how the subcellular sorting of active small GTPase pools occurs and what its functional significance is could reveal novel therapeutic opportunities.

Electrochemical Measurements Reveal Reactive Oxygen Species in Stress Granules*

Stress granules (SGs) are membrane-less organelles that assemble in the cytoplasm to organize cellular contents and promote rapid adaptation during stress. To understand how SGs contribute to physiological functions, we used electrochemical measurements to detect electroactive species in SGs. With amperometry, we discovered that reactive oxygen species (ROS) are encapsulated inside arsenite-induced SGs, and H2 O2 is the main species. The release kinetics of H2 O2 from single SGs and the number of H2 O2 molecules were quantified. The discovery that SGs contain ROS implicates them as communicators of the cellular stresses rather than a simple endpoint. This may explain how SGs regulate cellular metabolism and stress responses. This may also help better understand their cytoprotective functions in pathological conditions associated with SGs such as neurodegenerative diseases (NDs), cancers and viral infections.

Pyroptosis and Redox Balance in Kidney Diseases

Significance: Kidney diseases remain a worldwide public health problem resulting in millions of deaths each year; they are characterized by progressive destruction of renal function by sustained inflammation. Pyroptosis is a lytic type of programmed cell death involved in inflammation, as well as a key fibrotic mechanism that is critical in the development of kidney pathology. Pyroptosis is induced by the cleavage of Gasdermins by various caspases and is executed by the insertion of the N-terminal fragment of cleaved Gasdermins into the plasma membrane, creating oligomeric pores and allowing the release of diverse proinflammatory products into the extracellular space. Inflammasomes are multiprotein complexes leading to the activation of caspase-1, which will cleave Gasdermin D, releasing several proinflammatory cytokines; this results in the initiation and amplification of the inflammatory response. Recent Advances: The efficacy of Gasdermin D cleavage is reduced by a change in the redox balance. Recently, several studies have shown that the attenuation of reactive oxygen species (ROS) production induced by antioxidant pathways results in a reduction of renal pyroptosis. In this review, we discuss the role of pyroptosis in the pathogenesis of chronic kidney disease (CKD) and acute kidney disease; summarize the clinical outcomes and different molecular mechanisms leading to Gasdermin activation; and examine studies about the capacity of antioxidants, particularly Nrf2 activators, to ameliorate Gasdermin activity. Future Directions: We illustrate the potential influence of the deregulation of redox balance on inflammasome activity and pyroptosis as a novel therapeutic approach for the treatment of kidney diseases. Antioxid. Redox Signal. 35, 40-60.

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.

Nox2 impairs VEGF-A-induced angiogenesis in placenta via mitochondrial ROS-STAT3 pathway

Aberrant placental angiogenesis is associated with fetal intrauterine growth restriction (IUGR), but the mechanism underlying abnormal placental angiogenesis remains largely unknown. Here, lower vessel density and higher expression of NADPH oxidases 2 (Nox2) were observed in the placentae for low birth weight (LBW) fetuses versus normal birth weight (NBW) fetuses, with a negative correlation between Nox2 and placental vessel density. Moreover, it was revealed for the first time that Nox2 deficiency facilitates angiogenesis in vitro and in vivo, and vascular endothelial growth factor-A (VEGF-A) has an essential role in Nox2-controlled inhibition of angiogenesis in porcine vascular endothelial cells (PVECs). Mechanistically, Nox2 inhibited phospho-signal transducer and activator of transcription 3 (p-STAT3) in the nucleus by inducing the production of mitochondrial reactive oxygen species (ROS). Dual-luciferase assay confirmed that knockdown of Nox2 reduces the expression of VEGF-A in an STAT3 dependent manner. Our results indicate that Nox2 is a potential target for therapy by increasing VEGF-A expression to promote angiogenesis and serves as a prognostic indicator for fetus with IUGR.

NADPH Oxidases: Redox Regulators of Stem Cell Fate and Function

One of the major sources of reactive oxygen species (ROS) generated within stem cells is the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase family of enzymes (NOXs), which are critical determinants of the redox state beside antioxidant defense mechanisms. This balance is involved in another one that regulates stem cell fate: indeed, self-renewal, proliferation, and differentiation are decisive steps for stem cells during embryo development, adult tissue renovation, and cell therapy application. Ex vivo culture-expanded stem cells are being investigated for tissue repair and immune modulation, but events such as aging, senescence, and oxidative stress reduce their ex vivo proliferation, which is crucial for their clinical applications. Here, we review the role of NOX-derived ROS in stem cell biology and functions, focusing on positive and negative effects triggered by the activity of different NOX isoforms. We report recent findings on downstream molecular targets of NOX-ROS signaling that can modulate stem cell homeostasis and lineage commitment and discuss the implications in ex vivo expansion and in vivo engraftment, function, and longevity. This review highlights the role of NOX as a pivotal regulator of several stem cell populations, and we conclude that these aspects have important implications in the clinical utility of stem cells, but further studies on the effects of pharmacological modulation of NOX in human stem cells are imperative.

Size and surface modification of silica nanoparticles affect the severity of lung toxicity by modulating endosomal ROS generation in macrophages

Background

As the application of silica nanomaterials continues to expand, increasing chances of its exposure to the human body and potential harm are anticipated. Although the toxicity of silica nanomaterials is assumed to be affected by their physio-chemical properties, including size and surface functionalization, its molecular mechanisms remain unclear. We hypothesized that analysis of intracellular localization of the particles and subsequent intracellular signaling could reveal a novel determinant of inflammatory response against silica particles with different physico-chemical properties.

Results

We employed a murine intratracheal instillation model of amorphous silica nanoparticles (NPs) exposure to compare their in vivo toxicities in the respiratory system. Pristine silica-NPs of 50 nm diameters (50 nm-plain) induced airway-centered lung injury with marked neutrophilic infiltration. By contrast, instillation of pristine silica particles of a larger diameter (3 μm; 3 μm-plain) significantly reduced the severity of lung injury and neutrophilic infiltration, possibly through attenuated induction of neutrophil chemotactic chemokines including MIP2. Ex vivo analysis of alveolar macrophages as well as in vitro assessment using RAW264.7 cells revealed a remarkably lower cellular uptake of 3 μm-plain particles compared with 50 nm-plain, which is assumed to be the underlying mechanism of attenuated immune response. The severity of lung injury and neutrophilic infiltration was also significantly reduced after intratracheal instillation of silica NPs with an amine surface modification (50 nm-NH₂) when compared with 50 nm-plain. Despite unchanged efficacy in cellular uptake, treatment with 50 nm-NH₂ induced a significantly attenuated immune response in RAW264.7 cells. Assessment of intracellular redox signaling revealed increased reactive oxygen species (ROS) in endosomal compartments of RAW264.7 cells treated with 50 nm-plain when compared with vehicle-treated control. In contrast, augmentation of endosomal ROS signals in cells treated with 50 nm-NH₂ was significantly lower. Moreover, selective inhibition of NADPH oxidase 2 (NOX2) was sufficient to inhibit endosomal ROS bursts and induction of chemokine expressions in cells treated with silica NPs, suggesting the central role of endosomal ROS generated by NOX2 in the regulation of the inflammatory response in macrophages that endocytosed silica NPs.

Conclusions

Our murine model suggested that the pulmonary toxicity of silica NPs depended on their physico-chemical properties through distinct mechanisms. Cellular uptake of larger particles by macrophages decreased, while surface amine modification modulated endosomal ROS signaling via NOX2, both of which are assumed to be involved in mitigating immune response in macrophages and resulting lung injury.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12989-021-00415-0.

Pleiotropic and Potentially Beneficial Effects of Reactive Oxygen Species on the Intracellular Signaling Pathways in Endothelial Cells

Endothelial cells (ECs) are exposed to molecular dioxygen and its derivative reactive oxygen species (ROS). ROS are now well established as important signaling messengers. Excessive production of ROS, however, results in oxidative stress, a significant contributor to the development of numerous diseases. Here, we analyze the experimental data and theoretical concepts concerning positive pro-survival effects of ROS on signaling pathways in endothelial cells (ECs). Our analysis of the available experimental data suggests possible positive roles of ROS in induction of pro-survival pathways, downstream of the G_i-protein-coupled receptors, which mimics insulin signaling and prevention or improvement of the endothelial dysfunction. It is, however, doubtful, whether ROS can contribute to the stabilization of the endothelial barrier.

Oxidative Stress and Hypertension

A link between oxidative stress and hypertension has been firmly established in multiple animal models of hypertension but remains elusive in humans. While initial studies focused on inactivation of nitric oxide by superoxide, our understanding of relevant reactive oxygen species (superoxide, hydrogen peroxide, and peroxynitrite) and how they modify complex signaling pathways to promote hypertension has expanded significantly. In this review, we summarize recent advances in delineating the primary and secondary sources of reactive oxygen species (nicotinamide adenine dinucleotide phosphate oxidases, uncoupled endothelial nitric oxide synthase, endoplasmic reticulum, and mitochondria), the posttranslational oxidative modifications they induce on protein targets important for redox signaling, their interplay with endogenous antioxidant systems, and the role of inflammasome activation and endoplasmic reticular stress in the development of hypertension. We highlight how oxidative stress in different organ systems contributes to hypertension, describe new animal models that have clarified the importance of specific proteins, and discuss clinical studies that shed light on how these processes and pathways are altered in human hypertension. Finally, we focus on the promise of redox proteomics and systems biology to help us fully understand the relationship between ROS and hypertension and their potential for designing and evaluating novel antihypertensive therapies.

Prussian blue nanozyme-mediated nanoscavenger ameliorates acute pancreatitis via inhibiting TLRs/NF-κB signaling pathway

Rationale: Acute pancreatitis (AP) is a serious acute condition affecting the abdomen and shows high morbidity and mortality rates. Its global incidence has increased in recent years. Inflammation and oxidative stress are potential therapeutic targets for AP. This study was conducted to investigate the intrinsic anti-oxidative and anti-inflammatory effects of Prussian blue nanozyme (PBzyme) on AP, along with its underlying mechanism. Methods: Prussian blue nanozymes were prepared by polyvinylpyrrolidone modification method. The effect of PBzyme on inhibiting inflammation and scavenging reactive oxygen species was verified at the cellular level. The efficacy and mechanism of PBzyme for prophylactically treating AP were evaluated using the following methods: serum testing in vivo, histological scoring following hematoxylin and eosin staining, terminal deoxynucleotidyl transferase dUTP nick end labeling fluorescence staining, polymerase chain reaction array, Kyoto Encyclopedia of Genes and Genomes analysis and Western blotting analysis. Results: The synthetic PBzyme showed potent anti-oxidative and anti-inflammatory effects in reducing oxidative stress and alleviating inflammation both in vitro and in vivo in the prophylactic treatment of AP. The prophylactic therapeutic efficacy of PBzyme on AP may involve inhibition of the toll-like receptor/nuclear factor-κB signaling pathway and reactive oxygen species scavenging. Conclusion: The single-component, gram-level mass production, stable intrinsic biological activity, biosafety, and good therapeutic efficacy suggest the potential of PBzyme in the preventive treatment of AP. This study provides a foundation for the clinical application of PBzyme.

On the mechanisms underlying attenuated redox responses to exercise in older individuals: A hypothesis

Responding appropriately to exercise is essential to maintenance of skeletal muscle mass and function at all ages and particularly during aging. Here, a hypothesis is presented that a key component of the inability of skeletal muscle to respond effectively to exercise in aging is a denervation-induced failure of muscle redox signalling. This novel hypothesis proposes that an initial increase in oxidation in muscle mitochondria leads to a paradoxical increase in the reductive state of specific cysteines of signalling proteins in the muscle cytosol that suppresses their ability to respond to normal oxidising redox signals during exercise. The following are presented for consideration:Transient loss of integrity of peripheral motor neurons occurs repeatedly throughout life and is normally rapidly repaired by reinnervation, but this repair process becomes less efficient with aging. Each transient loss of neuromuscular integrity leads to a rapid, large increase in mitochondrial peroxide production in the denervated muscle fibers and in neighbouring muscle fibers. This peroxide may initially act to stimulate axonal sprouting and regeneration, but also stimulates retrograde mitonuclear communication to increase expression of a range of cytoprotective proteins in an attempt to protect the fiber and neighbouring tissues against oxidative damage. The increased peroxide within mitochondria does not lead to an increased cytosolic peroxide, but the increases in adaptive cytoprotective proteins include some located to the muscle cytosol which modify the local cytosol redox environment to induce a more reductive state in key cysteines of specific signalling proteins. Key adaptations of skeletal muscle to exercise involve transient peroxiredoxin oxidation as effectors of redox signalling in the cytosol. This requires sensitive oxidation of key cysteine residues. In aging, the chronic change to a more reductive cytosolic environment prevents the transient oxidation of peroxiredoxin 2 and hence prevents essential adaptations to exercise, thus contributing to loss of muscle mass and function. Experimental approaches suitable for testing the hypothesis are also outlined.

Comparative Genomic and Physiological Analyses of a Superoxide Dismutase Mimetic (SODm-123) for Its Ability to Respond to Oxidative Stress in Tomato Plants

Superoxide dismutases (SODs) are a group of enzymes that have a crucial role in controlling oxidative stress in plants. Here, we synthesized an environmentally friendly SOD mimic, SODm-123, from L-aspartic acid and manganese oxide. SODm-123 showed similar enzymatic activity to Mn-SOD. To gain insights into the role of SODm-123 in oxidative stress tolerance, a series of experiments were conducted to assess the physiological and molecular responses of tomato plants when treated with SODm-123. The results showed that the levels of O₂^-• and H₂O₂ in tomato cells were affected by SODm-123 treatment, indicating that SODm-123 can control oxidative stress like Mn-SOD. The results also exhibited that SODm-123 increased the contents of photosynthetic pigments. However, it was noted that SODm-123 resulted in a reduction in the content of soluble sugar and MDA. These results indicate that SODm-123 promoted the efficiency of photosynthesis by regulating the content of H₂O₂. To further investigate the role of SODm-123 in controlling oxidative stress, a transcriptome analysis was used to identify differentially expressed genes (DEGs) associated with SODm-123 treatment. The results indicated that SODm-123 treatment resulted in 341 differentially expressed genes (DEGs) in treated tomato leaves at 96 h after treatment. Kyoto encyclopedia of genes and genomes (KEGG) revealed that DEGs were involved in pathways such as photosynthetic pigment biosynthesis, ABC transporters, sugar metabolism, and MAPK signaling, which further confirmed a positive role of SODm-123 in improving stress tolerance in plants. Overall, the results of this study suggest that SODm-123 promotes the growth and development of tomato seedlings and therefore can be used as a potential growth-promoting agent for plants.

Reactive Oxygen Species Induced p53 Activation: DNA Damage, Redox Signaling, or Both?

Significance: The p53 tumor suppressor has been dubbed the "guardian of genome" because of its various roles in the response to DNA damage such as DNA damage repair, cell cycle arrest, senescence, and apoptosis, all of which are in place to prevent mutations from being passed on down the lineage. Recent Advances: Reactive oxygen species (ROS), for instance hydrogen peroxide derived from mitochondrial respiration, have long been regarded mainly as a major source of cellular damage to DNA and other macromolecules. Critical Issues: More recently, ROS have been shown to also play important physiological roles as second messengers in so-called redox signaling. It is, therefore, not clear whether the observed activation of p53 by ROS is mediated through the DNA damage response, redox signaling, or both. In this review, we will discuss the similarities and differences between p53 activation in response to DNA damage and redox signaling in terms of upstream signaling and downstream transcriptional program activation. Future Directions: Understanding whether and how DNA damage and redox signaling-dependent p53 activation can be dissected could be useful to develop anti-cancer therapeutic p53-reactivation strategies that do not depend on the induction of DNA damage and the resulting additional mutational load.

Peroxiredoxin 6 mediates protective function of astrocytes in Aβ proteostasis

Background

Disruption of β-amyloid (Aβ) homeostasis is the initial culprit in Alzheimer’s disease (AD) pathogenesis. Astrocytes respond to emerging Aβ plaques by altering their phenotype and function, yet molecular mechanisms governing astrocytic response and their precise role in countering Aβ deposition remain ill-defined. Peroxiredoxin (PRDX) 6 is an enzymatic protein with independent glutathione peroxidase (Gpx) and phospholipase A2 (PLA₂) activities involved in repair of oxidatively damaged cell membrane lipids and cellular signaling. In the CNS, PRDX6 is uniquely expressed by astrocytes and its exact function remains unexplored.

Methods

APPswe/PS1_dE9 AD transgenic mice were once crossed to mice overexpressing wild-type Prdx6 allele or to Prdx6 knock out mice. Aβ pathology and associated neuritic degeneration were assessed in mice aged 10 months. Laser scanning confocal microscopy was used to characterize Aβ plaque morphology and activation of plaque-associated astrocytes and microglia. Effect of Prdx6 gene dose on plaque seeding was assessed in mice aged six months.

Results

We show that hemizygous knock in of the overexpressing Prdx6 transgene in APP_swe/PS1_dE9 AD transgenic mice promotes selective enticement of astrocytes to Aβ plaques and penetration of plaques by astrocytic processes along with increased number and phagocytic activation of periplaque microglia. This effects suppression of nascent plaque seeding and remodeling of mature plaques consequently curtailing brain Aβ load and Aβ-associated neuritic degeneration. Conversely, Prdx6 haplodeficiency attenuates astro- and microglia activation around Aβ plaques promoting Aβ deposition and neuritic degeneration.

Conclusions

We identify here PRDX6 as an important factor regulating response of astrocytes toward Aβ plaques. Demonstration that phagocytic activation of periplaque microglia vary directly with astrocytic PRDX6 expression level implies previously unappreciated astrocyte-guided microglia effect in Aβ proteostasis. Our showing that upregulation of PRDX6 attenuates Aβ pathology may be of therapeutic relevance for AD.

Decoding the role of SOD2 in sickle cell disease

Sickle cell disease (SCD) is an inherited hemoglobinopathy caused by a single point mutation in the β-globin gene. As a consequence, deoxygenated hemoglobin polymerizes triggering red blood cell sickling and hemolysis, vaso-occlusion, and ischemia/reperfusion. Allied to these pathologies is the overproduction of reactive oxygen species driven by hemoglobin Fenton chemistry and peroxidase reactions as well as by secondary activation of vascular oxidases, including NAD(P)H oxidase and xanthine oxidase. In addition, hypoxia, produced by sickle red blood cell occlusion, disrupts mitochondrial metabolism and generates excess superoxide through electron leak from the mitochondrial respiratory chain. Superoxide dismutase 2 (SOD2) is a mitochondrial-specific antioxidant enzyme that dismutates superoxide to hydrogen peroxide, which is then converted to water by catalase and glutathione peroxidase. In SCD, the antioxidant defense system is significantly diminished through decreased expression and activity levels of antioxidant enzymes, including superoxide dismutase, catalase, and glutathione peroxidase. From a translational perspective, genetic variants including a missense variant in SOD2 (valine to alanine at position 16) are present in 45% of people with African ancestry and are associated with increased sickle complications. While it is known that there is an imbalance between oxidative species and antioxidant defenses in SCD, much more investigation is warranted. This review summarizes our current understanding of antioxidant defense systems in SCD, particularly focused on SOD2, and provides insight into challenges and opportunities as the field moves forward.

AGE/RAGE signaling-mediated endoplasmic reticulum stress and future prospects in non-coding RNA therapeutics for diabetic nephropathy

Disturbance of endoplasmic reticulum (ER) homeostasis triggered by the accumulation of unfolded proteins and advanced glycation end-products (AGEs) plays a major role in pathophysiology of diabetic nephropathy. Activation of receptor for AGEs (RAGE) stimulates NADPH oxidase-mediated reactive oxygen species (ROS) production, leading to ER stress, inflammation, glomerular hypertrophy, podocyte injury, and renal fibrosis. A growing body of evidence indicates that non-coding RNAs (ncRNAs) could rescue ER stress and renal inflammation by the epigenetic modification. This review summarizes ncRNA regulation in AGE/RAGE signaling-mediated ER stress, and discusses the opportunities and challenges of ncRNA-loaded extracellular vesicle therapy in diabetic nephropathy.

Oxidative Stress in Cancer

Contingent upon concentration, reactive oxygen species (ROS) influence cancer evolution in apparently contradictory ways, either initiating/stimulating tumorigenesis and supporting transformation/proliferation of cancer cells or causing cell death. To accommodate high ROS levels, tumor cells modify sulfur-based metabolism, NADPH generation, and the activity of antioxidant transcription factors. During initiation, genetic changes enable cell survival under high ROS levels by activating antioxidant transcription factors or increasing NADPH via the pentose phosphate pathway (PPP). During progression and metastasis, tumor cells adapt to oxidative stress by increasing NADPH in various ways, including activation of AMPK, the PPP, and reductive glutamine and folate metabolism.

Oxidative Stress in Cancer

Contingent upon concentration, reactive oxygen species (ROS) influence cancer evolution in apparently contradictory ways, either initiating/stimulating tumorigenesis and supporting transformation/proliferation of cancer cells or causing cell death. To accommodate high ROS levels, tumor cells modify sulfur-based metabolism, NADPH generation, and the activity of antioxidant transcription factors. During initiation, genetic changes enable cell survival under high ROS levels by activating antioxidant transcription factors or increasing NADPH via the pentose phosphate pathway (PPP). During progression and metastasis, tumor cells adapt to oxidative stress by increasing NADPH in various ways, including activation of AMPK, the PPP, and reductive glutamine and folate metabolism.

Cross-Talk between NADPH Oxidase and Mitochondria: Role in ROS Signaling and Angiogenesis

Angiogenesis, a new vessel formation from the pre-existing ones, is essential for embryonic development, wound repair and treatment of ischemic heart and limb diseases. However, dysregulated angiogenesis contributes to various pathologies such as diabetic retinopathy, atherosclerosis and cancer. Reactive oxygen species (ROS) derived from NADPH oxidase (NOX) as well as mitochondria play an important role in promoting the angiogenic switch from quiescent endothelial cells (ECs). However, how highly diffusible ROS produced from different sources and location can communicate with each other to regulate angiogenesis remains unclear. To detect a localized ROS signal in distinct subcellular compartments in real time in situ, compartment-specific genetically encoded redox-sensitive fluorescence biosensors have been developed. Recently, the intercellular communication, “cross-talk”, between ROS derived from NOX and mitochondria, termed “ROS-induced ROS release”, has been proposed as a mechanism for ROS amplification at distinct subcellular compartments, which are essential for activation of redox signaling. This “ROS-induced ROS release” may represent a feed-forward mechanism of localized ROS production to maintain sustained signaling, which can be targeted under pathological conditions with oxidative stress or enhanced to promote therapeutic angiogenesis. In this review, we summarize the recent knowledge regarding the role of the cross-talk between NOX and mitochondria organizing the sustained ROS signaling involved in VEGF signaling, neovascularization and tissue repair.