Homologs of gp91phox: cloning and tissue expression of Nox3, Nox4, and Nox5

NADPH-oxidases as potential pharmacological targets for thrombosis and depression comorbidity

There is a complex interrelationship between the nervous system and the cardiovascular system. Comorbidities of cardiovascular diseases (CVD) with mental disorders, and vice versa, are prevalent. Adults with mental disorders such as anxiety and depression have a higher risk of developing CVD, and people with CVD have an increased risk of being diagnosed with mental disorders. Oxidative stress is one of the many pathways associated with the pathophysiology of brain and cardiovascular disease. Nicotinamide adenine dinucleotide phosphate oxidase (NOX) is one of the major generators of reactive oxygen species (ROS) in mammalian cells, as it is the enzyme that specifically produces superoxide. This review summarizes recent findings on the consequences of NOX activation in thrombosis and depression. It also discusses the therapeutic effects and pharmacological strategies of NOX inhibitors in CVD and brain disorders. A better comprehension of these processes could facilitate the development of new therapeutic approaches for the prevention and treatment of the comorbidity of thrombosis and depression.

Myricetin Induces Ferroptosis and Inhibits Gastric Cancer Progression by Targeting NOX4

Ferroptosis holds great potential as a therapeutic approach for gastric cancer (GC), a prevalent and deadly malignant tumor associated with high rates of incidence and mortality. Myricetin, well-known for its multifaceted biomedical attributes, particularly its anticancer properties, has yet to be thoroughly investigated regarding its involvement in ferroptosis. The aim of this research was to elucidate the impact of myricetin on ferroptosis in GC progression. The present study observed that myricetin could trigger ferroptosis in GC cells by enhancing malondialdehyde production and Fe2+ accumulation while suppressing glutathione levels. Mechanistically, myricetin directly interacted with NADPH oxidase 4 (NOX4), influencing its stability by inhibiting its ubiquitin degradation. Moreover, myricetin regulated the inhibition of ferroptosis induced by Helicobacter pylori cytotoxin-associated gene A (CagA) through the NOX4/NRF2/GPX4 pathway. In vivo experiments demonstrated that myricetin treatment significantly inhibited the growth of subcutaneous tumors in BALB/c nude mice. It was accompanied by increased NOX4 expression in tumor tissue and suppression of the NRF2/GPX4 antioxidant pathway. Therefore, this research underscores myricetin as a novel inducer of ferroptosis in GC cells through its interaction with NOX4. It is a promising candidate for GC treatment.

NADPH Oxidase 3: Beyond the Inner Ear

Reactive oxygen species (ROS) were formerly known as mere byproducts of metabolism with damaging effects on cellular structures. The discovery and description of NADPH oxidases (Nox) as a whole enzyme family that only produce this harmful group of molecules was surprising. After intensive research, seven Nox isoforms were discovered, described and extensively studied. Among them, the NADPH oxidase 3 is the perhaps most underrated Nox isoform, since it was firstly discovered in the inner ear. This stigma of Nox3 as "being only expressed in the inner ear" was also used by me several times. Therefore, the question arose whether this sentence is still valid or even usable. To this end, this review solely focuses on Nox3 and summarizes its discovery, the structural components, the activating and regulating factors, the expression in cells, tissues and organs, as well as the beneficial and detrimental effects of Nox3-mediated ROS production on body functions. Furthermore, the involvement of Nox3-derived ROS in diseases progression and, accordingly, as a potential target for disease treatment, will be discussed.

Angiotensin II acts through Rac1 to upregulate pendrin: role of NADPH oxidase

Angiotensin II increases apical plasma membrane pendrin abundance and function. This study explored the role of the small GTPase Rac1 in the regulation of pendrin by angiotensin II. To do this, we generated intercalated cell (IC) Rac1 knockout mice and observed that IC Rac1 gene ablation reduced the relative abundance of pendrin in the apical region of intercalated cells in angiotensin II-treated mice but not vehicle-treated mice. Similarly, the Rac1 inhibitor EHT 1864 reduced apical pendrin abundance in angiotensin II-treated mice, through a mechanism that does not require aldosterone. This IC angiotensin II-Rac1 signaling cascade modulates pendrin subcellular distribution without significantly changing actin organization. However, NADPH oxidase inhibition with APX 115 reduced apical pendrin abundance in vivo in angiotensin II-treated mice. Moreover, superoxide dismutase mimetics reduced Cl- absorption in angiotensin II-treated cortical collecting ducts perfused in vitro. Since Rac1 is an NADPH subunit, Rac1 may modulate pendrin through NADPH oxidase-mediated reactive oxygen species production. Because pendrin gene ablation blunts the pressor response to angiotensin II, we asked if pendrin blunts the angiotensin II-induced increase in kidney superoxide. Although kidney superoxide was similar in vehicle-treated wild-type and pendrin knockout mice, it was lower in angiotensin II-treated pendrin-null kidneys than in wild-type kidneys. We conclude that angiotensin II acts through Rac1, independently of aldosterone, to increase apical pendrin abundance. Rac1 may stimulate pendrin, at least partly, through NADPH oxidase. This increase in pendrin abundance contributes to the increment in blood pressure and kidney superoxide content seen in angiotensin II-treated mice.NEW & NOTEWORTHY This study defines a new signaling mechanism by which angiotensin II modulates oxidative stress and blood pressure.

Placental cartography of NADPH oxidase (NOX) family proteins: Involvement in the pathophysiology of preeclampsia

The placenta is an essential organ for fetal development. During the first trimester, it undergoes dramatic changes as it develops in an environment poor in oxygen (around 2-3%). From about 10 gestational weeks, oxygen levels increase to 8% in the intervillous chamber. These changes are accompanied by modulation of the activity of NADPH oxidase, a major source of production of reactive oxygen species in the first trimester of pregnancy. The NOX complex is composed of seven different proteins (NOX1-5 and DUOX1-2) whose placental involvements during physiological and pathological pregnancies are largely unknown. The aim of the study was to produce a cartography of NOX family proteins, in terms of RNA, protein expression, and localization during physiological pregnancy and in the case of preeclampsia (PE), in a cohort of early-onset PE (n = 11) and late-onset PE (n = 7) cases. NOX family proteins were mainly expressed in trophoblastic cells (NOX4-5, DUOX1) and modulated during physiological pregnancy. NOX4 underwent an unexpected and hitherto unreported nuclear translocation at term. In the case of PE, two groups stood out: NOX1-3, superoxide producers, were down-regulated (p < 0.05) while NOX4-DUOX1, hydrogen peroxide producers, were up-regulated (p < 0.05), compared to the control group. Mapping of placental NOX will constitute a reference and guide for future investigations concerning its involvement in the pathophysiology of PE.

A novel monoclonal antibody reveals the enrichment of NADPH oxidase 5 in human splenic endothelial cells

Members of the NOX/DUOX family of NADPH oxidases are responsible for regulated ROS production in diverse cells and tissues. Detection of NOX/DUOX proteins at the protein level remains an important challenge in the field. Here we report the development and characterization of a novel anti-NOX5 monoclonal antibody, which recognizes the human NOX5 protein in both Western blot, immunocytochemistry, and histochemistry applications. With the help of the antibody we could successfully detect both heterologously and endogenously expressed NOX5 in mammalian cells. Furthermore, we could also detect NOX5 protein in the human spleen, testis, and ovary. Immunohistochemical studies on human testis revealed that NOX5 localized to spermatogenic cells. This expression pattern was also supported by the result of in silico analysis of single-cell RNA sequencing data that indicated that NOX5 protein is present in developing spermatids and spermatocytes. Mature spermatozoa, however, did not contain detectable NOX5. In the human ovary, both immunostaining and single-cell RNA sequencing suggest that NOX5 is expressed in interstitial fibroblasts and theca cells. We also analyzed vascular cells for the presence of NOX5 and we found that NOX5 expression is a fairly specific feature of splenic endothelial cells.

NADPH Oxidases: From Molecular Mechanisms to Current Inhibitors

NADPH oxidases (NOXs) form a family of electron-transporting membrane enzymes whose main function is reactive oxygen species (ROS) generation. Strong evidence suggests that ROS produced by NOX enzymes are major contributors to oxidative damage under pathologic conditions. Therefore, blocking the undesirable actions of these enzymes is a therapeutic strategy for treating various pathological disorders, such as cardiovascular diseases, inflammation, and cancer. To date, identification of selective NOX inhibitors is quite challenging, precluding a pharmacologic demonstration of NOX as therapeutic targets in vivo. The aim of this Perspective is to furnish an updated outlook about the small-molecule NOX inhibitors described over the last two decades. Structures, activities, and in vitro/in vivo specificity are discussed, as well as the main biological assays used.

Therapeutic potential of NOX inhibitors in neuropsychiatric disorders

RATIONALE

Neuropsychiatric disorders encompass a broad category of medical conditions that include both neurology as well as psychiatry such as major depressive disorder, autism spectrum disorder, bipolar disorder, schizophrenia as well as psychosis.

OBJECTIVE

NADPH-oxidase (NOX), which is the free radical generator, plays a substantial part in oxidative stress in neuropsychiatric disorders. It is thought that elevated oxidative stress as well as neuroinflammation plays a part in the emergence of neuropsychiatric disorders. Including two linked with membranes and four with subunits of cytosol, NOX is a complex of multiple subunits. NOX has been linked to a significant source of reactive oxygen species in the brain. NOX has been shown to control memory processing and neural signaling. However, excessive NOX production has been linked to cardiovascular disorders, CNS degeneration, and neurotoxicity. The increase in NOX leads to the progression of neuropsychiatric disorders.

RESULT

Our review mainly emphasized the characteristics of NOX and its various mechanisms, the modulation of NOX in various neuropsychiatric disorders, and various studies supporting the fact that NOX might be the potential therapeutic target for neuropsychiatric disorders.

CONCLUSION

Here, we summarizes various pharmacological studies involving NOX inhibitors in neuropsychiatric disorders.

A Reappraisal of the Utility of L-012 to Measure Superoxide from Biologically Relevant Sources

The detection of superoxide anion (O2●-) in biological tissues remains challenging. Barriers to convenient and reproducible measurements include expensive equipment, custom probes, and the need for high sensitivity and specificity. The luminol derivative, L-012, has been used to measure O2●- since 1993 with mixed results and concerns over specificity. The goal of this study was to better define the conditions for use and their specificity. We found that L-012 coupled with depolymerized orthovanadate, a relatively impermeable tyrosine phosphatase inhibitor, yielded a highly sensitive approach to detect extracellular O2●-. In O2●- producing HEK-NOX5 cells, orthovanadate increased L-012 luminescence 100-fold. The combination of L-012 and orthovanadate was highly sensitive, stable, scalable, completely reversed by superoxide dismutase, and selective for O2●- generating NOXes versus NOX4, which produces H2O2. Moreover, there was no signal from cells transfected with NOS3 (NO●) and NOS2(ONOO-). To exclude the effects of altered tyrosine phosphorylation, O2●- was detected using non-enzymatic synthesis with phenazine methosulfate and via novel coupling of L-012 with niobium oxalate, which was less active in inducing tyrosine phosphorylation. Overall, our data shows that L-012 coupled with orthovanadate or other periodic group 5 salts yields a reliable, sensitive, and specific approach to measuring extracellular O2●- in biological systems.

Apocynin, an NADPH Oxidase Enzyme Inhibitor, Prevents Amebic Liver Abscess in Hamster

Amebiasis is an intestinal infection caused by Entamoeba histolytica. Amebic liver abscess (ALA) is the most common extraintestinal complication of amebiasis. In animal models of ALA, neutrophils have been shown to be the first cells to come into contact with Entamoeba histolytica during the initial phase of ALA. One of the multiple mechanisms by which neutrophils exhibit amebicidal activity is through reactive oxygen species (ROS) and the enzyme NADPH oxidase (NOX2), which generates and transports electrons to subsequently reduce molecular oxygen into superoxide anion. Previous reports have shown that ROS release in the susceptible animal species (hamster) is mainly stimulated by the pathogen, in turn provoking such an exacerbated inflammatory reaction that it is unable to be controlled and results in the death of the animal model. Apocynin is a natural inhibitor of NADPH oxidase. No information is available on the role of NOX in the evolution of ALA in the hamster, a susceptible model. Our study showed that administration of a selective NADPH oxidase 2 (NOX2) enzyme inhibitor significantly decreases the percentage of ALA, the size of inflammatory foci, the number of neutrophils, and NOX activity indicated by the reduction in superoxide anion (O2-) production. Moreover, in vitro, the apocynin damages amoebae. Our results showed that apocynin administration induces a decrease in the activity of NOX that could favor a decrease in ALA progression.

Renal fibrosis in type 2 cardiorenal syndrome: An update on mechanisms and therapeutic opportunities

Cardiorenal syndrome (CRS) is a state of coexisting heart failure and renal insufficiency in which acute or chronic dysfunction of the heart or kidney lead to acute or chronic dysfunction of the other organ.It was found that renal fibrosis is an important pathological process in the progression of type 2 CRS to end-stage renal disease, and progressive renal impairment accelerates the deterioration of cardiac function and significantly increases the hospitalization and mortality rates of patients. Previous studies have found that Hemodynamic Aiteration, RAAS Overactivation, SNS Dysfunction, Endothelial Dysfunction and Imbalance of natriuretic peptide system contribute to the development of renal disease in the decompensated phase of heart failure, but the exact mechanisms is not clear. Therefore, in this review, we focus on the molecular pathways involved in the development of renal fibrosis due to heart failure and identify the canonical and non-canonical TGF-β signaling pathways and hypoxia-sensing pathways, oxidative stress, endoplasmic reticulum stress, pro-inflammatory cytokines and chemokines as important triggers and regulators of fibrosis development, and summarize the therapeutic approaches for the above signaling pathways, including SB-525334 Sfrp1, DKK1, IMC, rosarostat, 4-PBA, etc. In addition, some potential natural drugs for this disease are also summarized, including SQD4S2, Wogonin, Astragaloside, etc.

The selective NOX4 inhibitor GLX7013159 decreases blood glucose concentrations and human beta-cell apoptotic rates in diabetic NMRI nu/nu mice transplanted with human islets

NADPH oxidase 4 (NOX4) inhibition has been reported to mitigate diabetes-induced beta-cell dysfunction and improve survival in vitro, as well as counteract high-fat diet-induced glucose intolerance in mice. We investigated the antidiabetic effects of the selective NOX4 inhibitor GLX7013159 in vivo in athymic diabetic mice transplanted with human islets over a period of 4 weeks. The GLX7013159-treated mice achieved lower blood glucose and water consumption throughout the treatment period. Furthermore, GLX7013159 treatment resulted in improved insulin and c-peptide levels, better insulin secretion capacity, as well as in greatly reduced apoptotic rates of the insulin-positive human cells, measured as colocalization of insulin and cleaved caspase-3. We conclude that the antidiabetic effects of NOX4 inhibition by GLX7013159 are observed also during a prolonged study period in vivo and are likely to be due to an improved survival and function of the human beta-cells.

New insights in the molecular regulation of the NADPH oxidase 2 activity: Negative modulation by Poldip2

Poldip2 was shown to be involved in oxidative signaling to ensure certain biological functions. It was proposed that, in VSMC, by interaction with the Nox4-associated membrane protein p22^phox, Poldip2 stimulates the level of reactive oxygen species (ROS) production. In vitro, with fractionated membranes from HEK393 cells over-expressing Nox4, we confirmed the up-regulation of NADPH oxidase 4 activity by the recombinant and purified Poldip2. Besides Nox4, the Nox1, Nox2, or Nox3 isoforms are also established partners of the p22^phox protein raising the question of their regulation by Poldip2 and of the effect in cells expressing simultaneously different Nox isoforms. In this study, we have addressed this issue by investigating the potential regulatory role of Poldip2 on NADPH oxidase 2, present in phagocyte cells. Unexpectedly, the effect of Poldip2 on phagocyte NADPH oxidase 2 was opposite to that observed on NADPH oxidase 4. Using membranes from circulating resting neutrophils, the ROS production rate of NADPH oxidase 2 was down-regulated by Poldip2 (2.5-fold). The down-regulation effect could not be correlated to the interaction of Poldip2 with p22^phox but rather, to the interaction of Poldip2 with the p47^phox protein, one of the regulatory proteins of the phagocyte NADPH oxidase. Our results show that the interaction of Poldip2 with p47^phox constitutes a novel regulatory mechanism that can negatively modulate the activity of NADPH oxidase 2 by trapping the so-called "adaptor" subunit of the complex. Poldip2 could act as a tunable switch capable of specifically regulating the activities of NADPH oxidases. This selective regulatory role of Poldip2, positive for Nox4 or negative for Nox2 could orchestrate the level and the type of ROS generated by Nox enzymes in the cells.

Increased NOX2 expression in astrocytes leads to eNOS uncoupling through dihydrofolate reductase in endothelial cells after subarachnoid hemorrhage

Introduction

Endothelial nitric oxide synthase (eNOS) uncoupling plays a significant role in acute vasoconstriction during early brain injury (EBI) after subarachnoid hemorrhage (SAH). Astrocytes in the neurovascular unit extend their foot processes around endothelia. In our study, we tested the hypothesis that increased nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) expression in astrocytes after SAH leads to eNOS uncoupling.

Methods

We utilized laser speckle contrast imaging for monitoring cortical blood flow changes in mice, nitric oxide (NO) kits to measure the level of NO, and a co-culture system to study the effect of astrocytes on endothelial cells. Moreover, the protein levels were assessed by Western blot and immunofluorescence staining. We used CCK-8 to measure the viability of astrocytes and endothelial cells, and we used the H2O2 kit to measure the H2O2 released from astrocytes. We used GSK2795039 as an inhibitor of NOX2, whereas lentivirus and adeno-associated virus were used for dihydrofolate reductase (DHFR) knockdown in vivo and in vitro.

Results

The expression of NOX2 and the release of H2O2 in astrocytes are increased, which was accompanied by a decrease in endothelial DHFR 12 h after SAH. Moreover, the eNOS monomer/dimer ratio increased, leading to a decrease in NO and acute cerebral ischemia. All of the above were significantly alleviated after the administration of GSK2795039. However, after knocking down DHFR both in vivo and in vitro, the protective effect of GSK2795039 was greatly reversed.

Discussion

The increased level of NOX2 in astrocytes contributes to decreased DHFR in endothelial cells, thus aggravating eNOS uncoupling, which is an essential mechanism underlying acute vasoconstriction after SAH.

Identification of an inhibitor for atherosclerotic enzyme NOX-1 to inhibit ROS production

Background

NOX-1 overexpression has been observed in various studies, persons with diabetes or cardiovascular conditions. NOX-1 orchestrates the disease pathogenesis of various cardiovascular conditions such as atherosclerotic plaque development and is a very crucial biomarker. Therefore, this study was carried out to deduce the three-dimensional modelled structure of NOX-1 using DeepMind AlphaFold-2 to find meaningful insight into the structural biology. Extensive in silico approaches have been used to determine the active pocket, virtually screen large chemical space to identify potential inhibitors. The role of the key amino acid residues was also deduced using alanine scanning mutagenesis contributing to the catalytic process and to the overall stability of NOX-1.

Results

The modelled structure of NOX-1 protein was validated using ERRAT. The ERRAT statistics with 9 amino acids sliding window have shown a confidence score of 96.937%. According to the Ramachandran statistics, 96.60% of the residues lie within the most favoured region, and 2.80% of residues lie in the additionally allowed region, which gives an overall of 99.4% residues in the three quadrants in the plot. GKT-831 which is a referral drug in this study has shown a GOLD interaction score of 62.12 with respect to the lead molecule zinc000059139266 which has shown a higher GOLD score of 78.07. Alanine scanning mutagenesis studies has shown that Phe201, Leu98 and Leu76 are found to be the key interacting residues in hydrophobic interactions. Similarly, Tyr324, Arg287 and Cys73 are major amino acid residues in the hydrogen bond interactions.

Conclusions

NOX-1 overexpression leads to heightened ROS production resulting in catastrophic outcomes. The modelled structure of NOX-1 has a good stereochemistry with respect to Ramachandran plot. The lead molecule zinc000059139266 has shown to have a very high interaction score of 78.07 compared to the referral drug GKT-831 with a score of 62.12. There is an excellent scope for the lead molecule to progress further into in vitro and in vivo studies.

Structure, regulation, and physiological functions of NADPH oxidase 5 (NOX5)

NOX5 is the last member of the NADPH oxidase (NOXs) family to be identified and presents some specific characteristics differing from the rest of the NOXs. It contains four Ca²⁺ binding domains at the N-terminus and its activity is regulated by the intracellular concentration of Ca²⁺. NOX5 generates superoxide (O₂^•-) using NADPH as a substrate, and it modulates functions related to processes in which reactive oxygen species (ROS) are involved. Those functions appear to be detrimental or beneficial depending on the level of ROS produced. For example, the increase in NOX5 activity is related to the development of various oxidative stress-related pathologies such as cancer, cardiovascular, and renal diseases. In this context, pancreatic expression of NOX5 can negatively alter insulin action in high-fat diet-fed transgenic mice. This is consistent with the idea that the expression of NOX5 tends to increase in response to a stimulus or a stressful situation, generally causing a worsening of the pathology. On the other hand, it has also been suggested that it might have a positive role in preparing the body for metabolic stress, for example, by inducing a protective adipose tissue adaptation to the excess of nutrients supplied by a high-fat diet. In this line, its endothelial overexpression can delay lipid accumulation and insulin resistance development in obese transgenic mice by inducing the secretion of IL-6 followed by the expression of thermogenic and lipolytic genes. However, as NOX5 gene is not present in rodents and human NOX5 protein has not been crystallized, its function is still poorly characterized and further extensive research is required.

Host-Derived Cytotoxic Agents in Chronic Inflammation and Disease Progression

At inflammatory sites, cytotoxic agents are released and generated from invading immune cells and damaged tissue cells. The further fate of the inflammation highly depends on the presence of antagonizing principles that are able to inactivate these host-derived cytotoxic agents. As long as the affected tissues are well equipped with ready-to-use protective mechanisms, no damage by cytotoxic agents occurs and resolution of inflammation is initiated. However, long-lasting and severe immune responses can be associated with the decline, exhaustion, or inactivation of selected antagonizing principles. Hence, cytotoxic agents are only partially inactivated and contribute to damage of yet-unperturbed cells. Consequently, a chronic inflammatory process results. In this vicious circle of permanent cell destruction, not only novel cytotoxic elements but also novel alarmins and antigens are liberated from affected cells. In severe cases, very low protection leads to organ failure, sepsis, and septic shock. In this review, the major classes of host-derived cytotoxic agents (reactive species, oxidized heme proteins and free heme, transition metal ions, serine proteases, matrix metalloproteases, and pro-inflammatory peptides), their corresponding protective principles, and resulting implications on the pathogenesis of diseases are highlighted.

Natural Bioactive Compounds Targeting NADPH Oxidase Pathway in Cardiovascular Diseases

Cardiovascular disease (CVD) is the leading cause of death worldwide, in both developed and developing countries. According to the WHO report, the morbidity and mortality caused by CVD will continue to rise with the estimation of death going up to 22.2 million in 2030. NADPH oxidase (NOX)-derived reactive oxygen species (ROS) production induces endothelial nitric oxide synthase (eNOS) uncoupling and mitochondrial dysfunction, resulting in sustained oxidative stress and the development of cardiovascular diseases. Seven distinct members of the family have been identified of which four (namely, NOX1, 2, 4 and 5) may have cardiovascular functions. Currently, the treatment and management plan for patients with CVDs mainly depends on the drugs. However, prolonged use of prescribed drugs may cause adverse drug reactions. Therefore, it is crucial to find alternative treatment options with lesser adverse effects. Natural products have been gaining interest as complementary therapy for CVDs over the past decade due to their wide range of medicinal properties, including antioxidants. These might be due to their potent active ingredients, such as flavonoid and phenolic compounds. Numerous natural compounds have been demonstrated to have advantageous effects on cardiovascular disease via NADPH cascade. This review highlights the potential of natural products targeting NOX-derived ROS generation in treating CVDs. Emphasis is put on the activation of the oxidases, including upstream or downstream signalling events.

NOX Dependent ROS Generation and Cell Metabolism

Reactive oxygen species (ROS) represent a group of high reactive molecules with dualistic natures since they can induce cytotoxicity or regulate cellular physiology. Among the ROS, the superoxide anion radical (O2·-) is a key redox signaling molecule prominently generated by the NADPH oxidase (NOX) enzyme family and by the mitochondrial electron transport chain. Notably, altered redox balance and deregulated redox signaling are recognized hallmarks of cancer and are involved in malignant progression and resistance to drugs treatment. Since oxidative stress and metabolism of cancer cells are strictly intertwined, in this review, we focus on the emerging roles of NOX enzymes as important modulators of metabolic reprogramming in cancer. The NOX family includes seven isoforms with different activation mechanisms, widely expressed in several tissues. In particular, we dissect the contribute of NOX1, NOX2, and NOX4 enzymes in the modulation of cellular metabolism and highlight their potential role as a new therapeutic target for tumor metabolism rewiring.

Functional interactions between NADPH oxidase 5 and actin

NADPH oxidase 5 (NOX5) is a transmembrane oxidative signaling enzyme which produces superoxide in response to intracellular calcium flux. Increasing evidence indicates that NOX5 is involved in a variety of physiological processes as well as human disease, however, details of NOX5 signaling pathways and targets of NOX5 mediated oxidative modifications remain poorly resolved. Actin dynamics have previously been shown to be modulated by oxidative modification, however, a direct connection to NOX5 expression and activity has not been fully explored. Here we show that NOX5 and actin interact in the cell, and each modulate the activity of the other. Using actin effector molecules jasplakinolide, cytochalasin D and latrunculin A, we show that changes in actin dynamics affect NOX5 superoxide production. In tandem, NOX5 oxidatively modifies actin, and shifts the ratio of filamentous to monomeric actin. Finally, we show that knockdown of NOX5 in the pancreatic cancer cell line PSN-1 impairs cell migration. Together our findings indicate an important link between actin dynamics and oxidative signaling through NOX5.

ROS-triggered endothelial cell death mechanisms: Focus on pyroptosis, parthanatos, and ferroptosis

The endothelium is a single layer of epithelium covering the surface of the vascular system, and it represents a physical barrier between the blood and vessel wall that plays an important role in maintaining intravascular homeostasis. However, endothelial dysfunction or endothelial cell death can cause vascular barrier disruption, vasoconstriction and diastolic dysfunction, vascular smooth muscle cell proliferation and migration, inflammatory responses, and thrombosis, which are closely associated with the progression of several diseases, such as atherosclerosis, hypertension, coronary atherosclerotic heart disease, ischemic stroke, acute lung injury, acute kidney injury, diabetic retinopathy, and Alzheimer's disease. Oxidative stress caused by the overproduction of reactive oxygen species (ROS) is an important mechanism underlying endothelial cell death. Growing evidence suggests that ROS can trigger endothelial cell death in various ways, including pyroptosis, parthanatos, and ferroptosis. Therefore, this review will systematically illustrate the source of ROS in endothelial cells (ECs); reveal the molecular mechanism by which ROS trigger pyroptosis, parthanatos, and ferroptosis in ECs; and provide new ideas for the research and treatment of endothelial dysfunction-related diseases.

Suramin enhances chondrogenic properties by regulating the p67phox/PI3K/AKT/SOX9 signalling pathway

Aims

Autologous chondrocyte implantation (ACI) is a promising treatment for articular cartilage degeneration and injury; however, it requires a large number of human hyaline chondrocytes, which often undergo dedifferentiation during in vitro expansion. This study aimed to investigate the effect of suramin on chondrocyte differentiation and its underlying mechanism.

Methods

Porcine chondrocytes were treated with vehicle or various doses of suramin. The expression of collagen, type II, alpha 1 (COL2A1), aggrecan (ACAN); COL1A1; COL10A1; SRY-box transcription factor 9 (SOX9); nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX); interleukin (IL)-1β; tumour necrosis factor alpha (TNFα); IL-8; and matrix metallopeptidase 13 (MMP-13) in chondrocytes at both messenger RNA (mRNA) and protein levels was determined by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) and western blot. In addition, the supplementation of suramin to redifferentiation medium for the culture of expanded chondrocytes in 3D pellets was evaluated. Glycosaminoglycan (GAG) and collagen production were evaluated by biochemical analyses and immunofluorescence, as well as by immunohistochemistry. The expression of reactive oxygen species (ROS) and NOX activity were assessed by luciferase reporter gene assay, immunofluorescence analysis, and flow cytometry. Mutagenesis analysis, Alcian blue staining, reverse transcriptase polymerase chain reaction (RT-PCR), and western blot assay were used to determine whether p67^phox was involved in suramin-enhanced chondrocyte phenotype maintenance.

Results

Suramin enhanced the COL2A1 and ACAN expression and lowered COL1A1 synthesis. Also, in 3D pellet culture GAG and COL2A1 production was significantly higher in pellets consisting of chondrocytes expanded with suramin compared to controls. Surprisingly, suramin also increased ROS generation, which is largely caused by enhanced NOX (p67^phox) activity and membrane translocation. Overexpression of p67^phox but not p67^phoxAD (deleting amino acid (a.a) 199 to 212) mutant, which does not support ROS production in chondrocytes, significantly enhanced chondrocyte phenotype maintenance, SOX9 expression, and AKT (S473) phosphorylation. Knockdown of p67^phox with its specific short hairpin (sh) RNA (shRNA) abolished the suramin-induced effects. Moreover, when these cells were treated with the phosphoinositide 3-kinase/protein kinase B (PI3K/AKT) inhibitor LY294002 or shRNA of AKT1, p67^phox-induced COL2A1 and ACAN expression was significantly inhibited.

Conclusion

Suramin could redifferentiate dedifferentiated chondrocytes dependent on p67^phox activation, which is mediated by the PI3K/AKT/SOX9 signalling pathway.

Cite this article: Bone Joint Res 2022;11(10):723–738.

NOX4 has the potential to be a biomarker associated with colon cancer ferroptosis and immune infiltration based on bioinformatics analysis

Background

Colon cancer (CC) is a common tumor, but its pathogenesis is still not well understood. Competitive endogenous RNA (ceRNA) theory, ferroptosis and tumor immune infiltration may be the mechanisms of the development of cancer. The purpose of the study is to seek genes connected with both immunity and ferroptosis, and provide important molecular basis for early noninvasive diagnosis and immunotherapy of CC.

Methods

We extracted messenger RNA (mRNA), microRNA (miRNA), and long noncoding RNA (lncRNA) data of CC from The Cancer Genome Atlas database (TCGA), identified the differentially expressed mRNA (DEmRNA), miRNA (DEmiRNA) and lncRNA (DElncRNA), then constructed a ceRNA network. Venn overlap analysis was used to identify genes associated with immunity and ferroptosis in ceRNA network. The expression and prognosis of target genes were analyzed via Gene Expression Profiling Interactive Analysis (GEPIA) and PrognoScan database, and we analysed the related functions and signaling pathways of target genes by enrichment analysis. The correlation between target genes and tumor immune infiltrating was explored by CIBERSORT and spearman correlation analysis. Finally, the expression of target genes was detected via quantitative reverse transcription-PCR (qRT-PCR) in CC and normal colon tissues.

Results

Results showed that there were 4 DElncRNA, 4 DEmiRNA and 126 DEmRNA in ceRNA network. NADPH oxidase 4 protein (NOX4) was a DEmRNA associated with immunity and ferroptosis in ceRNA network. NOX4 was highly expressed in CC and connected with unfavourable prognosis. NOX4 was obviously enriched in pathways connected with carcinogenesis and significantly correlated with six kinds of immune cells. Immune checkpoints and NOX4 spearman correlation analysis showed that the expression of NOX4 was positively related to programmed cell death protein 1 (PD-1)-PDCD1, programmed cell death-Ligand 1 (PD-L1)-CD274 and cytotoxic T-lymphocyte-associated protein 4 (CTLA4).

Conclusions

To conclude, our study suggests that NOX4 is associated with both ferroptosis and tumor immunity, and might be a biomarker associated with the carcinogenesis, prognosis of CC and a potential target of CC immunotherapy.

Mitochondria-Targeted Compounds to Assess and Improve Human Sperm Function

Significance: Currently 10%-15% of couples in reproductive age face infertility issues. More importantly, male factor contributes to 50% of these cases (either alone or in combination with female causes). Among various reasons, impaired sperm function is the main cause for male infertility. Furthermore, mitochondrial dysfunction and oxidative stress due to increased reactive oxygen species (ROS) production, particularly of mitochondrial origin, are believed to be the main contributors. Recent Advances: Mitochondrial dysfunction, particularly due to increased ROS production, has often been linked to impaired sperm function/quality. For decades, different methods and approaches have been developed to assess mitochondrial features that might correlate with sperm functionality. This connection is now completely accepted, with mitochondrial functionality assessment used more commonly as a readout of sperm functionality. More recently, mitochondria-targeted compounds are on the frontline for both assessment and therapeutic approaches. Critical Issues: In this review, we summarize the current methods for assessing key mitochondrial parameters known to reflect sperm quality as well as therapeutic strategies using mitochondria-targeted antioxidants aiming to improve sperm function in various situations, particularly after sperm cryopreservation. Future Directions: Although more systematic research is needed, mitochondria-targeted compounds definitely represent a promising tool to assess as well as to protect and improve sperm function. Antioxid. Redox Signal. 37, 451-480.

The construction of preclinical evidence for the treatment of liver fibrosis with quercetin: A systematic review and meta-analysis

Quercetin (3,3',4',5,7-pentahydroxyflavone), a flavonoid, is widely found in fruits and vegetables and exerts broad-spectrum pharmacological effects in the liver. Many studies have explored the bioactivity of quercetin in the treatment of liver fibrosis. Hence, through a systematic review and biological mechanism evaluation, this study aimed to construct a body of preclinical evidence for the treatment of liver fibrosis using quercetin. The literature used in this study was mainly obtained from four databases, and the SYRCLE list (10 items) was used to evaluate the quality of the included literature. A meta-analysis of HA, LN, and other indicators was performed via STATA 15.0 software. Subgroup analyses based on animal species and model protocol were performed to further obtain detailed results. Moreover, the therapeutic mechanism of quercetin was summarized in a directed network form based on a comprehensive search of the literature. After screening, a total of 14 articles (comprising 15 studies) involving 254 animals were included. The results from the analysis showed that the corresponding liver function indexes, such as the levels of HA and LN, were significantly improved in the quercetin group compared with the model group, and liver function, such as the levels of AST and ALT, were also improved in the quercetin group. The species- and model-based subgroup analyses of AST and ALT revealed that quercetin exerts a significant effect. The therapeutic mechanism of quercetin was shown to be related to multiple pathways involving anti-inflammatory and antioxidant activities and lipid accumulation, including regulation of the TGF-β, α-SMA, ROS, and P-AMPK pathways. The results showed that quercetin exerts an obvious effect on liver fibrosis, and more prominent improvement effects on liver function and liver fibrosis indicators were obtained with a dose of 5-200 mg during a treatment course ranging from 4 to 8 weeks. Quercetin might be a promising therapeutic for liver fibrosis.

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.

Impact of calcium and reactive oxygen species on human sperm function: Role of NOX5

NOX5 is introduced as a new therapeutic target for infertility treatment. This study aimed to compare the basal and stimulated reactive oxygen species (ROS) production and sperm function in human teratozoospermic (n = 15) and normozoospermic (n = 17) semen samples following calcium overload and NOX5 activation. Washed spermatozoa incubated for 1 h under five various conditions: control group, adding a calcium ionophore A23187, phorbol myristate acetate (PMA), A23187 + PMA, and diphenylene iodonium (DPI) + A23187 + PMA. ROS generation was measured immediately after treatment for 30 min. Motility, viability, acrosome reaction, and apoptosis were evaluated after 1-h incubation. ROS production significantly increased when A23187 or PMA was added to the sperm medium. DPI had suppressive effects on ROS generation. Progressive and total motility significantly decreased following calcium elevation and NOX5 activation, which was somewhat returned by DPI. Necrotic and live cells in teratozoospermia was, respectively, higher and lower than normozoospermia samples. Incubation with A23187 significantly increased the percentage of early and late apoptosis. Teratozoosperm are more vulnerable than normal spermatozoa, and produce more basal and stimulated ROS. It seems that calcium overload induces apoptosis in spermatozoa and loss of viability through MPT pore opening and increased intracellular ROS.

Central role of c-Src in NOX5- mediated redox signalling in vascular smooth muscle cells in human hypertension

AIMS

NOX-derived reactive oxygen species (ROS) are mediators of signalling pathways implicated in vascular smooth muscle cell (VSMC) dysfunction in hypertension. Among the numerous redox-sensitive kinases important in VSMC regulation is c-Src. However, mechanisms linking NOX/ROS to c-Src are unclear, especially in the context of oxidative stress in hypertension. Here, we investigated the role of NOX-induced oxidative stress in VSMCs in human hypertension focusing on NOX5, and explored c-Src, as a putative intermediate connecting NOX5-ROS to downstream effector targets underlying VSMC dysfunction.

METHODS AND RESULTS

VSMC from arteries from normotensive (NT) and hypertensive (HT) subjects were studied. NOX1,2,4,5 expression, ROS generation, oxidation/phosphorylation of signalling molecules, and actin polymerization and migration were assessed in the absence and presence of NOX5 (melittin) and Src (PP2) inhibitors. NOX5 and p22phox-dependent NOXs (NOX1-4) were down-regulated using NOX5 siRNA and p22phox-siRNA approaches. As proof of concept in intact vessels, vascular function was assessed by myography in transgenic mice expressing human NOX5 in a VSMC-specific manner. In HT VSMCs, NOX5 was up-regulated, with associated oxidative stress, hyperoxidation (c-Src, peroxiredoxin, DJ-1), and hyperphosphorylation (c-Src, PKC, ERK1/2, MLC20) of signalling molecules. NOX5 siRNA reduced ROS generation in NT and HT subjects. NOX5 siRNA, but not p22phox-siRNA, blunted c-Src phosphorylation in HT VSMCs. NOX5 siRNA reduced phosphorylation of MLC20 and FAK in NT and HT. In p22phox- silenced HT VSMCs, Ang II-induced phosphorylation of MLC20 was increased, effects blocked by melittin and PP2. NOX5 and c-Src inhibition attenuated actin polymerization and migration in HT VSMCs. In NOX5 transgenic mice, vascular hypercontractilty was decreased by melittin and PP2.

CONCLUSION

We define NOX5/ROS/c-Src as a novel feedforward signalling network in human VSMCs. Amplification of this system in hypertension contributes to VSMC dysfunction. Dampening the NOX5/ROS/c-Src pathway may ameliorate hypertension-associated vascular injury.

NADPH Oxidase 4 (NOX4) in Cancer: Linking Redox Signals to Oncogenic Metabolic Adaptation

Cancer cells can survive and maintain their high proliferation rate in spite of their hypoxic environment by deploying a variety of adaptative mechanisms, one of them being the reorientation of cellular metabolism. A key aspect of this metabolic rewiring is the promotion of the synthesis of antioxidant molecules in order to counter-balance the hypoxia-related elevation of reactive oxygen species (ROS) production and thus combat the onset of cellular oxidative stress. However, opposite to their negative role in the inception of oxidative stress, ROS are also key modulatory components of physiological cellular metabolism. One of the major physiological cellular ROS sources is the NADPH oxidase enzymes (NOX-es). Indeed, NOX-es produce ROS in a tightly regulated manner and control a variety of cellular processes. By contrast, pathologically elevated and unbridled NOX-derived ROS production is linked to diverse cancerogenic processes. In this respect, NOX4, one of the members of the NOX family enzymes, is of particular interest. In fact, NOX4 is closely linked to hypoxia-related signaling and is a regulator of diverse metabolic processes. Furthermore, NOX4 expression and function are altered in a variety of malignancies. The aim of this review is to provide a synopsis of our current knowledge concerning NOX4-related processes in the oncogenic metabolic adaptation of cancer cells.

Endothelial NOX5 Expression Modulates Thermogenesis and Lipolysis in Mice Fed with a High-Fat Diet and 3T3-L1 Adipocytes through an Interleukin-6 Dependent Mechanism

Obesity is a global health issue associated with the development of metabolic syndrome, which correlates with insulin resistance, altered lipid homeostasis, and other pathologies. One of the mechanisms involved in the development of these pathologies is the increased production of reactive oxygen species (ROS). One of the main producers of ROS is the family of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases, among which NOX5 is the most recently discovered member. The aim of the present work is to describe the effect of endothelial NOX5 expression on neighboring adipose tissue in obesity conditions by using two systems. An in vivo model based on NOX5 conditional knock-in mice fed with a high-fat diet and an in vitro model developed with 3T3-L1 adipocytes cultured with conditioned media of endothelial NOX5-expressing bEnd.3 cells, previously treated with glucose and palmitic acid. Endothelial NOX5 expression promoted the expression and activation of specific markers of thermogenesis and lipolysis in the mesenteric and epididymal fat of those mice fed with a high-fat diet. Additionally, the activation of these processes was derived from an increase in IL-6 production as a result of NOX5 activity. Accordingly, 3T3-L1 adipocytes treated with conditioned media of endothelial NOX5-expressing cells, presented higher expression of thermogenic and lipolytic genes. Moreover, endothelial NOX5-expressing bEnd.3 cells previously treated with glucose and palmitic acid also showed interleukin (IL-6) production. Finally, it seems that the increase in IL-6 stimulated the activation of markers of thermogenesis and lipolysis through phosphorylation of STAT3 and AMPK, respectively. In conclusion, in response to obesogenic conditions, endothelial NOX5 activity could promote thermogenesis and lipolysis in the adipose tissue by regulating IL-6 production.

Rho GTPases: Non-canonical regulation by cysteine oxidation

Rho GTPases are critically important and are centrally positioned regulators of the actomyosin cytoskeleton. By influencing the organization and architecture of the cytoskeleton, Rho proteins play prominent roles in many cellular processes including adhesion, migration, intra-cellular transportation, and proliferation. The most important method of Rho GTPase regulation is via the GTPase cycle; however, post-translational modifications (PTMs) also play critical roles in Rho protein regulation. Relative to other PTMs such as lipidation or phosphorylation that have been extensively characterized, protein oxidation is a regulatory PTM that has been poorly studied. Protein oxidation primarily occurs from the reaction of reactive oxygen species (ROS), such as hydrogen peroxide (H₂ O₂ ), with amino acid side chain thiols on cysteine (Cys) and methionine (Met) residues. The versatile redox modifications of cysteine residues exemplify their integral role in cell signalling processes. Here we review prominent members of the Rho GTPase family and discuss how lipidation, phosphorylation, and oxidation on conserved cysteine residues affects their regulation and function.

Molecular Mechanisms of Hypertensive Nephropathy: Renoprotective Effect of Losartan through Hsp70

Hypertensive nephrosclerosis is the second most common cause of end-stage renal disease after diabetes. For years, hypertensive kidney disease has been focused on the afferent arterioles and glomeruli damage and the involvement of the renin angiotensin system (RAS). Nonetheless, in recent years, novel evidence has demonstrated that persistent high blood pressure injures tubular cells, leading to epithelial–mesenchymal transition (EMT) and tubulointerstitial fibrosis. Injury primarily determined at the glomerular level by hypertension causes changes in post-glomerular peritubular capillaries that in turn induce endothelial damage and hypoxia. Microvasculature dysfunction, by inducing hypoxic environment, triggers inflammation, EMT with epithelial cells dedifferentiation and fibrosis. Hypertensive kidney disease also includes podocyte effacement and loss, leading to disruption of the filtration barrier. This review highlights the molecular mechanisms and histologic aspects involved in the pathophysiology of hypertensive kidney disease incorporating knowledge about EMT and tubulointerstitial fibrosis. The role of the Hsp70 chaperone on the angiotensin II–induced EMT after angiotensin II type 1 receptor (AT₁R) blockage, as a possible molecular target for therapeutic strategy against hypertensive renal damage is discussed.

Cadmium-Induced Kidney Injury: Oxidative Damage as a Unifying Mechanism

Cadmium is a nonessential metal that has heavily polluted the environment due to human activities. It can be absorbed into the human body via the gastrointestinal tract, respiratory tract, and the skin, and can cause chronic damage to the kidneys. The main site where cadmium accumulates and causes damage within the nephrons is the proximal tubule. This accumulation can induce dysfunction of the mitochondrial electron transport chain, leading to electron leakage and production of reactive oxygen species (ROS). Cadmium may also impair the function of NADPH oxidase, resulting in another source of ROS. These ROS together can cause oxidative damage to DNA, proteins, and lipids, triggering epithelial cell death and a decline in kidney function. In this article, we also reviewed evidence that the antioxidant power of plant extracts, herbal medicines, and pharmacological agents could ameliorate cadmium-induced kidney injury. Finally, a model of cadmium-induced kidney injury, centering on the notion that oxidative damage is a unifying mechanism of cadmium renal toxicity, is also presented. Given that cadmium exposure is inevitable, further studies using animal models are warranted for a detailed understanding of the mechanism underlying cadmium induced ROS production, and for the identification of more therapeutic targets.

NADPH Oxidases in the Central Nervous System: Regional and Cellular Localization and the Possible Link to Brain Diseases

Significance: The significant role of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) in signal transduction is mediated by the production of reactive oxygen species (ROS), especially in the central nervous system (CNS). The pathogenesis of some neurologic and psychiatric diseases is regulated by ROS, acting as a second messenger or pathogen. Recent Advances: In the CNS, the involvement of Nox-derived ROS has been implicated in the regulation of multiple signals, including cell survival/apoptosis, neuroinflammation, migration, differentiation, proliferation, and synaptic plasticity, as well as the integrity of the blood/brain barrier. In these processes, the intracellular signals mediated by the members of the Nox family vary among different tissues. The present review illuminates the regions and cellular, subcellular localization of Nox isoforms in the brain, the signal transduction, and the role of NOX enzymes in pathophysiology, respectively. Critical Issues: Different signal transduction cascades are coupled to ROS derived from various Nox homologues with varying degrees. Therefore, a critical issue worth noting is the varied role of the homologues of NOX enzymes in different signaling pathways and also they mediate different phenotypes in the diverse pathophysiological condition. This substantiates the effectiveness of selective Nox inhibitors in the CNS. Future Directions: Further investigation to elucidate the role of various homologues of NOX enzymes in acute and chronic brain diseases and signaling mechanisms, and the development of more specific NOX inhibitors for the treatment of CNS disease are urgently needed. Antioxid. Redox Signal. 35, 951-973.

Oxidative Stress Induced by Reactive Oxygen Species (ROS) and NADPH Oxidase 4 (NOX4) in the Pathogenesis of the Fibrotic Process in Systemic Sclerosis: A Promising Therapeutic Target

Numerous clinical and research investigations conducted during the last two decades have implicated excessive oxidative stress caused by high levels of reactive oxygen species (ROS) in the development of the severe and frequently progressive fibrotic process in Systemic Sclerosis (SSc). The role of excessive oxidative stress in SSc pathogenesis has been supported by the demonstration of increased levels of numerous biomarkers, indicative of cellular and molecular oxidative damage in serum, plasma, and other biological fluids from SSc patients, and by the demonstration of elevated production of ROS by various cell types involved in the SSc fibrotic process. However, the precise mechanisms mediating oxidative stress development in SSc and its pathogenetic effects have not been fully elucidated. The participation of the NADPH oxidase NOX4, has been suggested and experimentally supported by the demonstration that SSc dermal fibroblasts display constitutively increased NOX4 expression and that reduction or abrogation of NOX4 effects decreased ROS production and the expression of genes encoding fibrotic proteins. Furthermore, NOX4-stimulated ROS production may be involved in the development of certain endothelial and vascular abnormalities and may even participate in the generation of SSc-specific autoantibodies. Collectively, these observations suggest NOX4 as a novel therapeutic target for SSc.

Reactive Oxygen Species in Acute Lymphoblastic Leukaemia: Reducing Radicals to Refine Responses

Acute lymphoblastic leukaemia (ALL) is the most common cancer diagnosed in children and adolescents. Approximately 70% of patients survive >5-years following diagnosis, however, for those that fail upfront therapies, survival is poor. Reactive oxygen species (ROS) are elevated in a range of cancers and are emerging as significant contributors to the leukaemogenesis of ALL. ROS modulate the function of signalling proteins through oxidation of cysteine residues, as well as promote genomic instability by damaging DNA, to promote chemotherapy resistance. Current therapeutic approaches exploit the pro-oxidant intracellular environment of malignant B and T lymphoblasts to cause irreversible DNA damage and cell death, however these strategies impact normal haematopoiesis and lead to long lasting side-effects. Therapies suppressing ROS production, especially those targeting ROS producing enzymes such as the NADPH oxidases (NOXs), are emerging alternatives to treat cancers and may be exploited to improve the ALL treatment. Here, we discuss the roles that ROS play in normal haematopoiesis and in ALL. We explore the molecular mechanisms underpinning overproduction of ROS in ALL, and their roles in disease progression and drug resistance. Finally, we examine strategies to target ROS production, with a specific focus on the NOX enzymes, to improve the treatment of ALL.

The role of NADPH oxidases in infectious and inflammatory diseases

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX) are enzymes that generate superoxide or hydrogen peroxide from molecular oxygen utilizing NADPH as an electron donor. There are seven enzymes in the NOX family: NOX1-5 and dual oxidase (DUOX) 1-2. NOX enzymes in humans play important roles in diverse biological functions and vary in expression from tissue to tissue. Importantly, NOX2 is involved in regulating many aspects of innate and adaptive immunity, including regulation of type I interferons, the inflammasome, phagocytosis, antigen processing and presentation, and cell signaling. DUOX1 and DUOX2 play important roles in innate immune defenses at epithelial barriers. This review discusses the role of NOX enzymes in normal physiological processes as well as in disease. NOX enzymes are important in autoimmune diseases like type 1 diabetes and have also been implicated in acute lung injury caused by infection with SARS-CoV-2. Targeting NOX enzymes directly or through scavenging free radicals may be useful therapies for autoimmunity and acute lung injury where oxidative stress contributes to pathology.

Backstage players of fibrosis: NOX4, mTOR, HDAC, and S1P; companions of TGF-β

The fibrotic process could be easily defined as a pathological excess of extracellular matrix deposition, leading to disruption of tissue architecture and eventually loss of function; however, this process involves a complex network of several signal transduction pathways. Virtually almost all organs could be affected by fibrosis, the most affected are the liver, lung, skin, kidney, heart, and eyes; in all of them, the transforming growth factor-beta (TGF-β) has a central role. The canonical and non-canonical signal pathways of TGF-β impact the fibrotic process at the cellular and molecular levels, inducing the epithelial-mesenchymal transition (EMT) and the induction of profibrotic gene expression with the consequent increase in proteins such as alpha-smooth actin (α-SMA), fibronectin, collagen, and other extracellular matrix proteins. Recently, it has been reported that some molecules that have not been typically associated with the fibrotic process, such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 4 (NOX4), mammalian target of rapamycin (mTOR), histone deacetylases (HDAC), and sphingosine-1 phosphate (S1P); are critical in its development. In this review, we describe and discuss the role of these new players of fibrosis and the convergence with TGF-β signaling pathways, unveiling new insights into the panorama of fibrosis that could be useful for future therapeutic targets.

Altered redox homeostasis in steroid-depleted follicles attenuates hCG regulation of follicular events: Cross-talk between endocrine and IGF axis in maturing oocytes

Steroids and insulin-like growth factors (Igfs) are indispensable for folliculogenesis and reproductive fitness in the vertebrate ovary. The intrafollicular redox balance is also of immense importance for ovarian follicles wherein low levels of ROS are being utilized for cell signalling and regulation of gene expression; its excess may interfere with normal physiological processes leading to ovotoxicity. However, the functional relevance of ovarian steroidogenesis in maintaining the follicular microenvironment with coordinated redox homeostasis and intra-ovarian growth factors axis is relatively less understood. Using zebrafish full-grown (FG) ovarian follicles in vitro, our study shows that blocking steroid biosynthesis with anti-steroidal drugs, DL-aminoglutethimide (AG) or Trilostane (Trilo), prevents hCG (LH analogue)-induced StAR expression concomitant with a robust increase in intrafollicular ROS levels. Congruent with heightened intracellular levels of superoxide anions (O₂^•-) and hydrogen peroxide (H₂O₂), priming with AG or Trilo abrogates the transcript abundance of major antioxidant enzyme genes (SOD1, SOD2, and CAT) in hCG-stimulated follicles. Significantly, blocking steroidogenesis attenuates transcript abundance of HSP70 but elevates NOX4 expression potentially through ERα-mediated pathway. Importantly, disrupted redox balance in AG/Trilo pre-incubated FG follicles negatively impacts hCG-mediated activation of PKA/CREB signaling and transcriptional activation of igf ligands. Elevated ROS attenuation of antioxidant defense parameters and impaired endocrine and autocrine/paracrine homeostasis converge upon reduced p34cdc2 (Thr-161) phosphorylation, a reliable marker for MPF activation, and resumption of meiotic G2-M1 transition in hCG-treated follicles. Collectively, altered redox homeostasis in steroid-depleted follicles has a significant negative influence on GTH (LH) regulation of follicular events, specifically Igf synthesis, meiotic maturational competence and ovarian fitness.

Nitric oxide and heme-NO stimulate superoxide production by NADPH oxidase 5

Nitric oxide (NO) is a ubiquitous cell signaling molecule which mediates widespread and diverse processes in the cell. These NO dependent effects often involve activation (e.g. NO binding to the heme group of soluble guanylyl cyclase for cGMP production) or inactivation (e.g. S-nitrosation) of protein targets. We studied the effect of NO and heme-NO on the transmembrane signaling enzyme NADPH oxidase 5 (NOX5), a heme protein which produces superoxide in response to increases in intracellular calcium. We found that treatment with NO donors increases NOX5 activity through heme-dependent effects, and that this effect could be recapitulated by the addition of heme-NO. This work adds to our understanding of NOX5 regulation in the cell but also provides a framework for understanding how NO could cause widespread changes in hemeprotein activity based on different affinities for heme v. heme-NO, and helps explain the opposing roles NO plays in activation and inactivation of hemeprotein targets.

Modulating neuroinflammation in neurodegeneration-related dementia: can microglial toll-like receptors pull the plug?

Neurodegeneration-associated dementia disorders (NADDs), namely Alzheimer and Parkinson diseases, are developed by a significant portion of the elderly population globally. Extensive research has provided critical insights into the molecular basis of the pathological advancements of these diseases, but an efficient curative therapy seems elusive. A common attribute of NADDs is neuroinflammation due to a chronic inflammatory response within the central nervous system (CNS), which is primarily modulated by microglia. This response within the CNS is positively regulated by cytokines, chemokines, secondary messengers or cyclic nucleotides, and free radicals. Microglia mediated immune activation is regulated by a positive feedback loop in NADDs. The present review focuses on evaluating the crosstalk between inflammatory mediators and microglia, which aggravates both the clinical progression and extent of NADDs by forming a persistent chronic inflammatory milieu within the CNS. We also discuss the role of the human gut microbiota and its effect on NADDs as well as the suitability of targeting toll-like receptors for an immunotherapeutic intervention targeting the deflation of an inflamed milieu within the CNS.

Interplay Between Reactive Oxygen/Reactive Nitrogen Species and Metabolism in Vascular Biology and Disease

Reactive oxygen species (ROS; e.g., superoxide [O₂^•-] and hydrogen peroxide [H₂O₂]) and reactive nitrogen species (RNS; e.g., nitric oxide [NO^•]) at the physiological level function as signaling molecules that mediate many biological responses, including cell proliferation, migration, differentiation, and gene expression. By contrast, excess ROS/RNS, a consequence of dysregulated redox homeostasis, is a hallmark of cardiovascular disease. Accumulating evidence suggests that both ROS and RNS regulate various metabolic pathways and enzymes. Recent studies indicate that cells have mechanisms that fine-tune ROS/RNS levels by tight regulation of metabolic pathways, such as glycolysis and oxidative phosphorylation. The ROS/RNS-mediated inhibition of glycolytic pathways promotes metabolic reprogramming away from glycolytic flux toward the oxidative pentose phosphate pathway to generate nicotinamide adenine dinucleotide phosphate (NADPH) for antioxidant defense. This review summarizes our current knowledge of the mechanisms by which ROS/RNS regulate metabolic enzymes and cellular metabolism and how cellular metabolism influences redox homeostasis and the pathogenesis of disease. A full understanding of these mechanisms will be important for the development of new therapeutic strategies to treat diseases associated with dysregulated redox homeostasis and metabolism. Antioxid. Redox Signal. 34, 1319-1354.

Pharmacological intervention in oxidative stress as a therapeutic target in neurological disorders

OBJECTIVES

Oxidative stress is a major cellular burden that triggers reactive oxygen species (ROS) and antioxidants that modulate signalling mechanisms. Byproducts generated from this process govern the brain pathology and functions in various neurological diseases. As oxidative stress remains the key therapeutic target in neurological disease, it is necessary to explore the multiple routes that can significantly repair the damage caused due to ROS and consequently, neurodegenerative disorders (NDDs). Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is the critical player of oxidative stress that can also be used as a therapeutic target to combat NDDs.

KEY FINDINGS

Several antioxidants signalling pathways are found to be associated with oxidative stress and show a protective effect against stressors by increasing the release of various cytoprotective enzymes and also exert anti-inflammatory response against this oxidative damage. These pathways along with antioxidants and reactive species can be the defined targets to eliminate or reduce the harmful effects of neurological diseases.

SUMMARY

Herein, we discussed the underlying mechanism and crucial role of antioxidants in therapeutics together with natural compounds as a pharmacological tool to combat the cellular deformities cascades caused due to oxidative stress.

Mechanism of Gene-Environment Interactions Driving Glial Activation in Parkinson's Diseases

PURPOSE OF REVIEW

Parkinson's disease (PD) is the most prevalent motor disorder and is characterized by loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) region of the brain. Though the pathology of PD is well established, the cause of this neuronal loss is not well understood. Approximately 90% of PD cases are sporadic, and the environment plays a significant role in disease pathogenesis. The etiology of PD is highly complex, with neuroinflammation being one of the most critical factors implicated in PD. However, the signaling mechanisms underlying neuroinflammation and its interaction with environmental factors are unclear.

RECENT FINDINGS

Astroglia and microglia are the two principal cells that play an essential role in maintaining neuronal health in many ways, including through immunological means. Exposure to environmental stressors from various sources affects these glial cells leading to chronic and sustained inflammation. Recent epidemiological studies have identified an interaction among environmental factors and glial genes in Parkinson's disease. Mechanistic studies have shown that exposure to pesticides like rotenone and paraquat, neurotoxic metals like manganese and lead, and even diesel exhaust fumes induce glial activation by regulating various key inflammatory pathways, including the inflammasomes, NOX pathways, and others. This review aims to discuss the recent advances in understanding the mechanism of glial induction in response to environmental stressors and discuss the potential role of gene-environment interaction in driving glial activation.

Targeting Reactive Oxygen Species Metabolism to Induce Myeloma Cell Death

Multiple myeloma (MM) is a common hematological disease characterized by the accumulation of clonal malignant plasma cells in the bone marrow. Over the past two decades, new therapeutic strategies have significantly improved the treatment outcome and patients survival. Nevertheless, most MM patients relapse underlying the need of new therapeutic approaches. Plasma cells are prone to produce large amounts of immunoglobulins causing the production of intracellular ROS. Although adapted to high level of ROS, MM cells die when exposed to drugs increasing ROS production either directly or by inhibiting antioxidant enzymes. In this review, we discuss the efficacy of ROS-generating drugs for inducing MM cell death and counteracting acquired drug resistance specifically toward proteasome inhibitors.

NADPH Oxidase 5 and Melatonin: Involvement in Ram Sperm Capacitation

Reactive oxygen species (ROS) play an essential role in mammalian sperm capacitation. NADPH oxidase 5 (NOX5) has been described as the main source of ROS production in some mammalian spermatozoa, such as human and equine. On the other hand, melatonin can decrease cellular ROS levels and regulates NOX activity in somatic cells. Therefore, the objectives of this work were (1) to identify NOX5 in ram spermatozoa and analyze its possible changes during in vitro capacitation and (2) to investigate the effect of melatonin on NOX5 expression and localization and on superoxide levels in capacitated ram spermatozoa. Protein bands associated with NOX5 were detected by Western blot analysis. Likewise, indirect immunofluorescence (IIF) revealed six different immunotypes for NOX5, which varied throughout in vitro capacitation. Superoxide (O₂^⋅–), evaluated by DHE/Yo-Pro-1, rose after in vitro capacitation and in the presence of the calcium ionophore A23187 but decreased in the presence of the NOX inhibitor GKT136901. GKT also reduced the percentage of capacitated and acrosome-reacted spermatozoa that had increased during incubation in capacitating conditions. The presence of melatonin at micromolar concentrations avoided the increment in O₂^⋅– and the changes in NOX5 immunotypes provoked by capacitation. In conclusion, NOX5 is present in ram spermatozoa and the changes in its distribution, associated with sperm capacitation, can be prevented by melatonin. To this extent, it could imply that melatonin exerts its antioxidant role, at least in part, by modulating NOX5 activity during ram sperm capacitation.

Overexpression of heat shock protein 70 inhibits epithelial-mesenchymal transition and cell migration induced by transforming growth factor-β in A549 cells

Heat shock protein 70 (HSP70) is a key member of the HSP family that contributes to a pre-cancerous environment; however, its role in lung cancer remains poorly understood. The present study used geranylgeranylacetone (GGA) to induce HSP70 expression, and transforming growth factor-β (TGF-β) was used to construct an epithelial-mesenchymal transition (EMT) model by stimulating A549 cells in vitro. Western Blot was performed to detect protein levels of NADPH oxidase 4 (NOX4) and the EMT-associated proteins E-cadherin and vimentin both before and after HSP70 expression. Cell morphological changes were observed, and the effect of HSP70 on cell migration ability was detected via the wound healing. The results demonstrated that GGA at 50 and 200 μmol/L could significantly induce HSP70 expression in A549 cells (P < 0.05). Furthermore, HSP70 induced by 200 μmol/L GGA significantly inhibited the changes of E-cadherin, vimentin, and cell morphology induced by TGF-β (P < 0.05), while HSP70 induced by 50 μmol/L GGA did not. The results of the wound healing assay indicated that 200 μmol/L GGA significantly inhibited A549 cell migration induced by TGF-β. Taken together, the results of the present study demonstrated that overexpression of HSP70 inhibited the TGF-β induced EMT process and changed the cell morphology and migratory ability induced by TGF-β in A549 cells.

Tumor cell metabolism correlates with resistance to gas plasma treatment: The evaluation of three dogmas

Gas plasma is a partially ionized gas increasingly recognized for targeting cancer. Several hypotheses attempt to explain the link between plasma treatment and cytotoxicity in cancer cells, all focusing on cellular membranes that are the first to be exposed to plasma-generated reactive oxygen species (ROS). One proposes high levels of aquaporins, membrane transporters of water and hydrogen peroxide, to mark tumor cell line sensitivity to plasma treatment. A second focuses on membrane-expression of redox-related enzymes such as NADPH oxidases (NOX) that may modify or amplify the effects of plasma-derived ROS, fueling plasma-induced cancer cell death. Another hypothesis is that the decreased cholesterol content of tumor cell membranes sensitizes these to plasma-mediated oxidation and subsequently, cytotoxicity. Screening 33 surface molecules in 36 tumor cell lines in correlation to their sensitivity to plasma treatment, the expression of aquaporins or NOX members could not explain the sensitivity but were rather associated with treatment resistance. Correlation with transporter or enzyme activity was not tested. Analysis of cholesterol content confirmed the proposed positive correlation with treatment resistance. Strikingly, the strongest correlation was found for baseline metabolic activity (Spearman r = 0.76). Altogether, these data suggest tumor cell metabolism as a novel testable hypothesis to explain cancer cell resistance to gas plasma treatment for further elucidating this innovative field's chances and limitations in oncology.

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.

Crosstalk between endoplasmic reticulum stress and oxidative stress: a dynamic duo in multiple myeloma

Under physiological and pathological conditions, cells activate the unfolded protein response (UPR) to deal with the accumulation of unfolded or misfolded proteins in the endoplasmic reticulum. Multiple myeloma (MM) is a hematological malignancy arising from immunoglobulin-secreting plasma cells. MM cells are subject to continual ER stress and highly dependent on the UPR signaling activation due to overproduction of paraproteins. Mounting evidence suggests the close linkage between ER stress and oxidative stress, demonstrated by overlapping signaling pathways and inter-organelle communication pivotal to cell fate decision. Imbalance of intracellular homeostasis can lead to deranged control of cellular functions and engage apoptosis due to mutual activation between ER stress and reactive oxygen species generation through a self-perpetuating cycle. Here, we present accumulating evidence showing the interactive roles of redox homeostasis and proteostasis in MM pathogenesis and drug resistance, which would be helpful in elucidating the still underdefined molecular pathways linking ER stress and oxidative stress in MM. Lastly, we highlight future research directions in the development of anti-myeloma therapy, focusing particularly on targeting redox signaling and ER stress responses.