NADPH oxidase (NOX) isoforms are inhibited by celastrol with a dual mode of action

Specnuezhenide: Comprehensive review of pharmacology, pharmacokinetics and ethnomedicinal uses

BACKGROUND

Specnuezhenide (SPN) is a bioactive iridoid terpenoid compound mainly found in Ligustri Lucidi Fructus (LLF), that has a broad spectrum of pharmacological effects, including anti-neoplastic, hepatoprotective, anti-aging, anti-inflammatory, immune-modulatory properties.

PURPOSE

The present review provides a comprehensive summary of natural medicinal plants, traditional Chinese medicine compounds containing SPN, and their corresponding pharmacological mechanisms.

METHODS

Using several globally recognized databases such as Web of Science, Google Scholar, PubMed, ScienceDirect, Wiley, ACS, Springer, and CNKI until December 2024, A comprehensive literature search and analysis was carried out with the keywords "Specnuezhenide", " Pharmacology ", "Pharmacokinetics" and " Chinese herbal compound".

RESULTS

The results indicated that SPN is present in a diverse range of plants, including LLF, Osmanthus fragrans seeds and Naked barley. SPN plays an anti-inflammatory role by regulating the NF-κB and MAPK signaling pathways, down-regulating the expression of TNF-α, IL-1β, IL-6 and other cytokines. Furthermore, many Chinese herbal compounds have been found to contain SPN, such as treatment of spleen and kidney deficiency of compound Shenhua tablet, treatment of liver-kidney Yin deficiency of Er Zhi Wan, treatment of pulmonray abscess of Qidongning and treatment of stagnation of QI due to depression of the liver of Shuganzhi Tablet. SPN is primarily distributed in the stomach, intestine, and liver. However, due to its limited absorption in the gastrointestinal tract and low blood concentration, its bioavailability is significantly reduced.

CONCLUSIONS

Thereby, SPN holds immense potential in the prevention and treatment of liver, lung and kidney complications. This review intends to provide a novel insight for further development of SPN, hoping to reveal the potential of SPN and necessity of further studies in this field.

Antioxidant Metabolism Pathways in Vitamins, Polyphenols, and Selenium: Parallels and Divergences

Free radicals (FRs) are unstable molecules that cause reactive stress (RS), an imbalance between reactive oxygen and nitrogen species in the body and its ability to neutralize them. These species are generated by both internal and external factors and can damage cellular lipids, proteins, and DNA. Antioxidants prevent or slow down the oxidation process by interrupting the transfer of electrons between substances and reactive agents. This is particularly important at the cellular level because oxidation reactions lead to the formation of FR and contribute to various diseases. As we age, RS accumulates and leads to organ dysfunction and age-related disorders. Polyphenols; vitamins A, C, and E; and selenoproteins possess antioxidant properties and may have a role in preventing and treating certain human diseases associated with RS. In this review, we explore the current evidence on the potential benefits of dietary supplementation and investigate the intricate connection between SIRT1, a crucial regulator of aging and longevity; the transcription factor NRF2; and polyphenols, vitamins, and selenium. Finally, we discuss the positive effects of antioxidant molecules, such as reducing RS, and their potential in slowing down several diseases.

The Association between NADPH Oxidase 2 (NOX2) and Drug Resistance in Cancer

NADPH oxidase, as a major source of intracellular reactive oxygen species (ROS), assumes an important role in the immune response and oxidative stress response of the body. NADPH oxidase 2 (NOX2) is the first and most representative member of the NADPH oxidase family, and its effects on the development of tumor cells are gaining more and more attention. Our previous study suggested that NCF4 polymorphism in p40phox, a key subunit of NOX2, affected the outcome of diffuse large B-cell lymphoma patients treated with rituximab. It hypothesized that NOX2-mediated ROS could enhance the cytotoxic effects of some anti-tumor drugs in favor of patients with tumors. Several reviews have summarized the role of NOX2 and its congeners-mediated ROS in anti-tumor therapy, but few studies focused on the relationship between the expression of NOX2 and anti-tumor drug resistance. In this article, we systematically introduced the NOX family, represented by NOX2, and a classification of the latest inhibitors and agonists of NOX2. It will help researchers to have a more rational and objective understanding of the dual role of NOX2 in tumor drug resistance and is expected to provide new ideas for oncology treatment and overcoming drug resistance in cancer.

Neuronal NADPH oxidase is required for neurite regeneration of Aplysia bag cell neurons

NADPH oxidase (Nox), a major source of reactive oxygen species (ROS), is involved in neurodegeneration after injury and disease. Nox is expressed in both neuronal and non-neuronal cells and contributes to an elevated ROS level after injury. Contrary to the well-known damaging effect of Nox-derived ROS in neurodegeneration, recently a physiological role of Nox in nervous system development including neurogenesis, neuronal polarity, and axonal growth has been revealed. Here, we tested a role for neuronal Nox in neurite regeneration following mechanical transection in cultured Aplysia bag cell neurons. Using a novel hydrogen peroxide (H2 O2 )-sensing dye, 5'-(p-borophenyl)-2'-pyridylthiazole pinacol ester (BPPT), we found that H2 O2 levels are elevated in regenerating growth cones following injury. Redistribution of Nox2 and p40phox in the growth cone central domain suggests Nox2 activation after injury. Inhibiting Nox with the pan-Nox inhibitor celastrol reduced neurite regeneration rate. Pharmacological inhibition of Nox is correlated with reduced activation of Src2 tyrosine kinase and F-actin content in the growth cone. Taken together, these findings suggest that Nox-derived ROS regulate neurite regeneration following injury through Src2-mediated regulation of actin organization in Aplysia growth cones.

VEO-IBD NOX1 variant highlights a structural region essential for NOX/DUOX catalytic activity

Inflammatory bowel diseases (IBD) are chronic intestinal disorders that result from an inappropriate inflammatory response to the microbiota in genetically susceptible individuals, often triggered by environmental stressors. Part of this response is the persistent inflammation and tissue injury associated with deficiency or excess of reactive oxygen species (ROS). The NADPH oxidase NOX1 is highly expressed in the intestinal epithelium, and inactivating NOX1 missense mutations are considered a risk factor for developing very early onset IBD. Albeit NOX1 has been linked to wound healing and host defence, many questions remain about its role in intestinal homeostasis and acute inflammatory conditions. Here, we used in vivo imaging in combination with inhibitor studies and germ-free conditions to conclusively identify NOX1 as essential superoxide generator for microbiota-dependent peroxynitrite production in homeostasis and during early endotoxemia. NOX1 loss-of-function variants cannot support peroxynitrite production, suggesting that the gut barrier is persistently weakened in these patients. One of the loss-of-function NOX1 variants, NOX1 p. Asn122His, features replacement of an asparagine residue located in a highly conserved HxxxHxxN motif. Modelling the NOX1-p22phox complex revealed near the distal heme an internal pocket restricted by His119 and Asn122 that is part of the oxygen reduction site. Functional studies in several human NADPH oxidases show that substitution of asparagine with amino acids with larger side chains is not tolerated, while smaller side chains can support catalytic activity. Thus, we identified a previously unrecognized structural feature required for the electron transfer mechanism in human NADPH oxidases.

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.

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.

Structure, Activation, and Regulation of NOX2: At the Crossroad between the Innate Immunity and Oxidative Stress-Mediated Pathologies

Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) is a multisubunit enzyme complex that participates in the generation of superoxide or hydrogen peroxide (H₂O₂) and plays a key role in several biological functions. Among seven known NOX isoforms, NOX2 was the first identified in phagocytes but is also expressed in several other cell types including endothelial cells, platelets, microglia, neurons, and muscle cells. NOX2 has been assigned multiple roles in regulating many aspects of innate and adaptive immunity, and human and mouse models of NOX2 genetic deletion highlighted this key role. On the other side, NOX2 hyperactivation is involved in the pathogenesis of several diseases with different etiologies but all are characterized by an increase in oxidative stress and inflammatory process. From this point of view, the modulation of NOX2 represents an important therapeutic strategy aimed at reducing the damage associated with its hyperactivation. Although pharmacological strategies to selectively modulate NOX2 are implemented thanks to new biotechnologies, this field of research remains to be explored. Therefore, in this review, we analyzed the role of NOX2 at the crossroads between immunity and pathologies mediated by its hyperactivation. We described (1) the mechanisms of activation and regulation, (2) human, mouse, and cellular models studied to understand the role of NOX2 as an enzyme of innate immunity, (3) some of the pathologies associated with its hyperactivation, and (4) the inhibitory strategies, with reference to the most recent discoveries.

Celastrol: The new dawn in the treatment of vascular remodeling diseases

Evidence is mounting that abnormal vascular remodeling leads to many cardiovascular diseases (CVDs). This suggests that vascular remodeling can be a crucial target for the prevention and treatment of CVDs. Recently, celastrol, an active ingredient of the broadly used Chinese herb Tripterygium wilfordii Hook F, has attracted extensive interest for its proven potential to improve vascular remodeling. Substantial evidence has shown that celastrol improves vascular remodeling by ameliorating inflammation, hyperproliferation, and migration of vascular smooth muscle cells, vascular calcification, endothelial dysfunction, extracellular matrix remodeling, and angiogenesis. Moreover, numerous reports have proven the positive effects of celastrol and its therapeutic promise in treating vascular remodeling diseases such as hypertension, atherosclerosis, and pulmonary artery hypertension. The present review summarizes and discusses the molecular mechanism of celastrol regulating vascular remodeling and provides preclinical proof for future clinical applications of celastrol.

Celastrol assuages oxygen-glucose deprivation and reoxygenation-induced damage in human brain microvascular endothelial cells through the circDLGAP4/miR-6085/GDF11 pathway

The effect of Celastrol on cerebral ischemia-reperfusion remains unknown. The study aims to explore the role of circular RNA DLGAP4 (circDLGAP4) in cerebral ischemia-reperfusion and the underlying mechanism. Ischemia-reperfusion (I/R) injury of human brain microvascular endothelial cells (HBMECs) was induced by oxygen-glucose deprivation and reoxygenation (OGD/R). Reverse transcription quantitative real-time PCR (RT-qPCR) and western blotting analysis were performed to detect the expression of circDLGAP4, microRNA-6085 (miR-6085), growth differentiation factor 11 (GDF11), B-cell lymphoma-2 (BCL2) and BCL2-associated x protein (BAX). Cell viability, proliferation, and apoptosis were analyzed by cell counting kit-8, 5-Ethynyl-2'-deoxyuridine and flow cytometry analysis. Oxidative stress was analyzed by evaluating the levels of Malondialdehyde (MDA) and Reactive Oxygen Species (ROS) and the activity of Superoxide Dismutase (SOD). The associations among circDLGAP4, miR-6085 and GDF11 were identified by dual-luciferase reporter, RNA immunoprecipitation (RIP) and RNA pull-down assays. Celastrol reduced OGD/R-induced inhibition of circDLGAP4 expression in HBMECs. Celastrol treatment protected HBMECs from OGD/R-induced cell proliferation inhibition and apoptosis and oxidative stress promotion; however, circDLGAP4 depletion attenuated these effects. CircDLGAP4 acted as a sponge for miR-6085, and miR-6085 mimics restored circDLGAP4-mediated effects in OGD/R-stimulated HBMECs. In addition, GDF11 was identified as a targte of miR-6085, and participated in the regulation of miR-6085 to OGD/R-induced HBMEC damage. Further, circDLGAP4 absence inhibited GDF11 expression by interacting with miR-6085 under Celastrol treatment. Celastrol ameliorated OGD/R-induced HBMEC apoptosis and oxidative stress by circDLGAP4/miR-6085/GDF11 pathway, supporting the use of Celastrol as a therapeutic agent for cerebral infarction.

Advances in the study of nicotinamide adenine dinucleotide phosphate oxidase in myocardial remodeling

Myocardial remodeling is a key pathophysiological basis of heart failure, which seriously threatens human health and causes a severe economic burden worldwide. During chronic stress, the heart undergoes myocardial remodeling, mainly manifested by cardiomyocyte hypertrophy, apoptosis, interstitial fibrosis, chamber enlargement, and cardiac dysfunction. The NADPH oxidase family (NOXs) are multisubunit transmembrane enzyme complexes involved in the generation of redox signals. Studies have shown that NOXs are highly expressed in the heart and are involved in the pathological development process of myocardial remodeling, which influences the development of heart failure. This review summarizes the progress of research on the pathophysiological processes related to the regulation of myocardial remodeling by NOXs, suggesting that NOXs-dependent regulatory mechanisms of myocardial remodeling are promising new therapeutic targets for the treatment of heart failure.

Celastrol: A Promising Agent Fighting against Cardiovascular Diseases

Cardiovascular diseases (CVD) are leading causes of morbidity and mortality worldwide; therefore, seeking effective therapeutics to reduce the global burden of CVD has become increasingly urgent. Celastrol, a bioactive compound isolated from the roots of the plant Tripterygium wilfordii (TW), has been attracting increasing research attention in recent years, as it exerts cardiovascular treatment benefits targeting both CVD and their associated risk factors. Substantial evidence has revealed a protective role of celastrol against a broad spectrum of CVD including obesity, diabetes, atherosclerosis, cerebrovascular injury, calcific aortic valve disease and heart failure through complicated and interlinked mechanisms such as direct protection against cardiomyocyte hypertrophy and death, and indirect action on oxidation and inflammation. This review will mainly summarize the beneficial effects of celastrol against CVD, largely based on in vitro and in vivo preclinical studies, and the potential underlying mechanisms. We will also briefly discuss celastrol’s pharmacokinetic limitations, which hamper its further clinical applications, and prospective future directions.

Role of oxidative stress in calcific aortic valve disease and its therapeutic implications

Calcific aortic valve disease (CAVD) is the end result of active cellular processes that lead to the progressive fibrosis and calcification of aortic valve leaflets. In western populations, CAVD is a significant cause of cardiovascular morbidity and mortality, and in the absence of effective drugs, it will likely represent an increasing disease burden as populations age. As there are currently no pharmacological therapies available for preventing, treating, or slowing the development of CAVD, understanding the mechanisms underlying the initiation and progression of the disease is important for identifying novel therapeutic targets. Recent evidence has emerged of an important causative role for reactive oxygen species (ROS)-mediated oxidative stress in the pathophysiology of CAVD, inducing the differentiation of valve interstitial cells into myofibroblasts and then osteoblasts. In this review, we focus on the roles and sources of ROS driving CAVD and consider their potential as novel therapeutic targets for this debilitating condition.

Reactive Oxygen Species in Cardiovascular Calcification: Role of Medicinal Plants

Cardiovascular calcification, including vascular calcification and calcific aortic valve disease (CAVD), is a serious worldwide health problem, especially in older adults. The mechanisms underlying cardiovascular calcifications are complex and multifactorial. An increase in reactive oxygen species (ROS) and oxidative stress play important roles in the initiation and development of cardiovascular calcification. This mini-review summarizes the recent evidence that supports the association of ROS with vascular calcification and CAVD and discusses the role of medicinal plants for the prevention and treatment of cardiovascular calcification.

Celastrol attenuates the remodeling of pulmonary vascular and right ventricular in monocrotaline-induced pulmonary arterial hypertension in rats

BACKGROUND

Pulmonary arterial hypertension is a progressive angio-proliferative disease associated with high morbidity and mortality rates. Although the histopathology of pulmonary arterial hypertension is well described, its therapeutic option remains unsatisfactory. This study investigated the effect of celastrol treatment on right ventricular dysfunction, remodeling, and pulmonary vascular remodeling in pulmonary arterial hypertension rats as well as its possible mechanisms.

METHODS

Pulmonary arterial hypertension was induced in male Sprague-Dawley rats by a single subcutaneously injection of monocrotaline. After daily delivery of celastrol (1 mg/kg) or vehicle via intraperitoneal injection for 4 weeks, the effects of celastrol on right ventricular function, fibrosis, and pulmonary vascular remodeling were assessed. The infiltration of macrophages, the expression of inflammatory cytokines, including MCP-1, IL-1β, IL-6, and IL-10, and the expression of NF-κB signaling pathway-associated proteins, IκBα, p-IKKα/β and p65 were further detected. Finally, the effect of celastrol on human pulmonary artery smooth cells proliferation under hypoxia was studied in vitro.

RESULTS

Rats with pulmonary arterial hypertension had decreased right ventricular function, increased right ventricular fibrosis and pulmonary arteries with interstitial thickening and prominent media hypertrophy. Treatment with celastrol improved right ventricular function, attenuated right ventricular fibrosis and pulmonary vascular remodeling. Significantly decreased macrophage infiltration, reduced levels of pro-inflammatory cytokines, increased level of anti-inflammatory cytokine and inhibited NF-κB signaling pathway were observed in the lung tissues of rats treated with celastrol. Moreover, celastrol significantly suppressed the proliferation of human pulmonary artery smooth cells under hypoxia.

CONCLUSIONS

We showed that in rats with pulmonary arterial hypertension, celastrol could improve right ventricular function, attenuate right ventricular and pulmonary vascular remodeling, and inhibit human pulmonary artery smooth cells proliferation under hypoxia. Suppression of the nuclear factor-κB (NF-κB) signaling pathway may be a part of the protective mechanism.

Astragalus mongholicus Bunge Water Extract Exhibits Anti-inflammatory Effects in Human Neutrophils and Alleviates Imiquimod-Induced Psoriasis-Like Skin Inflammation in Mice

Neutrophils are the primary immune cells in innate immunity, which are related to various inflammatory diseases. Astragalus mongholicus Bunge is a Chinese medicinal herb used to treat various oxidative stress-related inflammatory diseases. However, there are limited studies that elucidate the effects of Astragalus mongholicus Bunge in human neutrophils. In this study, we used isolated human neutrophils activated by various stimulants to investigate the anti-inflammatory effects of Astragalus mongholicus Bunge water extract (AWE). Cell-free assays were used to examine free radicals scavenging capabilities on superoxide anion, reactive oxygen species (ROS), and nitrogen-centered radicals. Imiquimod (IMQ) induced psoriasis-like skin inflammation mouse model was used for investigating anti-psoriatic effects. We found that AWE inhibited superoxide anion production, ROS generation, and elastase release in human neutrophils, which exhibiting a direct anti-neutrophil effect. Moreover, AWE exerted a ROS scavenging ability in the 2,2’-Azobis (2-amidinopropane) dihydrochloride assay, but not superoxide anion in the xanthine/xanthine oxidase assay, suggesting that AWE exhibited anti-oxidation and anti-inflammatory capabilities by both scavenging ROS and by directly inhibiting neutrophil activation. AWE also reduced CD11b expression and adhesion to endothelial cells in activated human neutrophils. Meanwhile, in mice with psoriasis-like skin inflammation, administration of topical AWE reduced both the affected area and the severity index score. It inhibited neutrophil infiltration, myeloperoxidase release, ROS-induced damage, and skin proliferation. In summary, AWE exhibited direct anti-inflammatory effects by inhibiting neutrophil activation and anti-psoriatic effects in mice with IMQ-induced psoriasis-like skin inflammation. Therefore, AWE could potentially be a pharmaceutical Chinese herbal medicine to inhibit neutrophilic inflammation for anti-psoriasis.

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.

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 Therapeutic Potential of Celastrol in Central Nervous System Disorders: Highlights from In Vitro and In Vivo Approaches

Celastrol, the most abundant compound derived from the root of Tripterygium wilfordii, largely used in traditional Chinese medicine, has shown preclinical and clinical efficacy for a broad range of disorders, acting via numerous mechanisms, including the induction of the expression of several neuroprotective factors, the inhibition of cellular apoptosis, and the decrease of reactive oxygen species (ROS). Given the crucial implication of these pathways in the pathogenesis of Central Nervous System disorders, both in vitro and in vivo studies have focused their attention on the possible use of this compound in these diseases. However, although most of the available studies have reported significant neuroprotective effects of celastrol in cellular and animal models of these pathological conditions, some of these data could not be replicated. This review aims to discuss current in vitro and in vivo lines of evidence on the therapeutic potential of celastrol in neurodegenerative diseases, including Alzheimer’s and Parkinson’s diseases, amyotrophic lateral sclerosis, Huntington’s disease, multiple sclerosis, and cadmium-induced neurodegeneration, as well as in psychiatric disorders, such as psychosis and depression. In vitro and in vivo studies focused on celastrol effects in cerebral ischemia, ischemic stroke, traumatic brain injury, and epilepsy are also described.

A small molecule inhibitor of Nox2 and Nox4 improves contractile function after ischemia-reperfusion in the mouse heart

The NADPH oxidase enzymes Nox2 and 4, are important generators of Reactive oxygen species (ROS). These enzymes are abundantly expressed in cardiomyocytes and have been implicated in ischemia-reperfusion injury. Previous attempts with full inhibition of their activity using genetically modified animals have shown variable results, suggesting that a selective and graded inhibition could be a more relevant approach. We have, using chemical library screening, identified a new compound (GLX481304) which inhibits Nox 2 and 4 (with IC50 values of 1.25 µM) without general antioxidant effects or inhibitory effects on Nox 1. The compound inhibits ROS production in isolated mouse cardiomyocytes and improves cardiomyocyte contractility and contraction of whole retrogradely (Langendorff) perfused hearts after a global ischemia period. We conclude that a pharmacological and partial inhibition of ROS production by inhibition of Nox 2 and 4 is beneficial for recovery after ischemia reperfusion and might be a promising venue for treatment of ischemic injury to the heart.

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.

Modeling Virus-Induced Inflammation in Zebrafish: A Balance Between Infection Control and Excessive Inflammation

The inflammatory response to viral infection in humans is a dynamic process with complex cell interactions that are governed by the immune system and influenced by both host and viral factors. Due to this complexity, the relative contributions of the virus and host factors are best studied in vivo using animal models. In this review, we describe how the zebrafish (Danio rerio) has been used as a powerful model to study host-virus interactions and inflammation by combining robust forward and reverse genetic tools with in vivo imaging of transparent embryos and larvae. The innate immune system has an essential role in the initial inflammatory response to viral infection. Focused studies of the innate immune response to viral infection are possible using the zebrafish model as there is a 4-6 week timeframe during development where they have a functional innate immune system dominated by neutrophils and macrophages. During this timeframe, zebrafish lack a functional adaptive immune system, so it is possible to study the innate immune response in isolation. Sequencing of the zebrafish genome has revealed significant genetic conservation with the human genome, and multiple studies have revealed both functional conservation of genes, including those critical to host cell infection and host cell inflammatory response. In addition to studying several fish viruses, zebrafish infection models have been developed for several human viruses, including influenza A, noroviruses, chikungunya, Zika, dengue, herpes simplex virus type 1, Sindbis, and hepatitis C virus. The development of these diverse viral infection models, coupled with the inherent strengths of the zebrafish model, particularly as it relates to our understanding of macrophage and neutrophil biology, offers opportunities for far more intensive studies aimed at understanding conserved host responses to viral infection. In this context, we review aspects relating to the evolution of innate immunity, including the evolution of viral pattern recognition receptors, interferons and interferon receptors, and non-coding RNAs.

Functional relevance of Gedunin as a bona fide ligand of NADPH oxidase 5 and ROS scavenger: An in silico and in vitro assessment in a hyperglycemic RBC model

Clinical evidence suggests that type 2 diabetes therapy can greatly benefit from the suppression of reactive oxygen species generation and the activation or restoration of cellular antioxidant mechanisms. In human, NADPH oxidase (NOX) is the main producer of reactive oxygen species (ROS) that supress the activity of endogenous antioxidant enzymes. In the present study, the antioxidant potential of Gedunin was studied. In silico findings reveal its strong binding affinity with NOX5 C terminal HSP90 binding site that disrupts NOX5 stability and its ability to generate ROS, leading to restoration antioxidant enzymes activities. It was found that Gedunin suppressed hyperglycaemia induced oxidative stress in an in vitro RBC model and markedly reversed glucose induced changes including haemoglobin glycosylation and lipid peroxidation. A significant restoration of activities of cellular antioxidant enzymes; superoxide dismutase, catalase and glutathione peroxidase in the presence of Gedunin revealed its ability to reduce oxidative stress. These results substantiated Gedunin as a bona fide inhibitor of human NOX5 and a ROS scavenging antioxidant with promising therapeutic attributes including its natural origin and inhibition of multiple diabetic targets.

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In silico study reveals Gedunin as a bonafied ligand of human NOX5.

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Gedunin binds at NADPH oxidase C terminal HSP90 binding site and inhibits ROS formation.

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Gedunin reverses hemoglobin glycosylation, lipid peroxidation and restores activity of cellular antioxidant enzymes.

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Gedunin exhibits antioxidant property with dual mode of action: as an ROS scavenger and NOX5 inhibitor.

Neuronal NADPH oxidase 2 regulates growth cone guidance downstream of slit2/robo2

NADPH oxidases (Nox) are membrane-bound multi-subunit protein complexes producing reactive oxygen species (ROS) that regulate many cellular processes. Emerging evidence suggests that Nox-derived ROS also control neuronal development and axonal outgrowth. However, whether Nox act downstream of receptors for axonal growth and guidance cues is presently unknown. To answer this question, we cultured retinal ganglion cells (RGCs) derived from zebrafish embryos and exposed these neurons to netrin-1, slit2, and brain-derived neurotrophic factor (BDNF). To test the role of Nox in cue-mediated growth and guidance, we either pharmacologically inhibited Nox or investigated neurons from mutant fish that are deficient in Nox2. We found that slit2-mediated growth cone collapse, and axonal retraction were eliminated by Nox inhibition. Though we did not see an effect of either BDNF or netrin-1 on growth rates, growth in the presence of netrin-1 was reduced by Nox inhibition. Furthermore, attractive and repulsive growth cone turning in response to gradients of BDNF, netrin-1, and slit2, respectively, were eliminated when Nox was inhibited in vitro. ROS biosensor imaging showed that slit2 treatment increased growth cone hydrogen peroxide levels via mechanisms involving Nox2 activation. We also investigated the possible relationship between Nox2 and slit2/Robo2 signaling in vivo. astray/nox2 double heterozygote larvae exhibited decreased area of tectal innervation as compared to individual heterozygotes, suggesting both Nox2 and Robo2 are required for establishment of retinotectal connections. Our results provide evidence that Nox2 acts downstream of slit2/Robo2 by mediating growth and guidance of developing zebrafish RGC neurons.

Maraviroc, celastrol and azelastine alter Chlamydia trachomatis development in HeLa cells

Introduction . Chlamydia trachomatis (Ct) is an obligate intracellular bacterium, causing a range of diseases in humans. Interactions between chlamydiae and antibiotics have been extensively studied in the past.Hypothesis/Gap statement: Chlamydial interactions with non-antibiotic drugs have received less attention and warrant further investigations. We hypothesized that selected cytokine inhibitors would alter Ct growth characteristics in HeLa cells.Aim. To investigate potential interactions between selected cytokine inhibitors and Ct development in vitro.Methodology. The CCR5 receptor antagonist maraviroc (Mara; clinically used as HIV treatment), the triterpenoid celastrol (Cel; used in traditional Chinese medicine) and the histamine H1 receptor antagonist azelastine (Az; clinically used to treat allergic rhinitis and conjunctivitis) were used in a genital in vitro model of Ct serovar E infecting human adenocarcinoma cells (HeLa).Results. Initial analyses revealed no cytotoxicity of Mara up to 20 µM, Cel up to 1 µM and Az up to 20 µM. Mara exposure (1, 5, 10 and 20 µM) elicited a reduction of chlamydial inclusion numbers, while 10 µM reduced chlamydial infectivity. Cel 1 µM, as well as 10 and 20 µM Az, reduced chlamydial inclusion size, number and infectivity. Morphological immunofluorescence and ultrastructural analysis indicated that exposure to 20 µM Az disrupted chlamydial inclusion structure. Immunofluorescence evaluation of Cel-incubated inclusions showed reduced inclusion sizes whilst Mara incubation had no effect on inclusion morphology. Recovery assays demonstrated incomplete recovery of chlamydial infectivity and formation of structures resembling typical chlamydial inclusions upon Az removal.Conclusion. These observations indicate that distinct mechanisms might be involved in potential interactions of the drugs evaluated herein and highlight the need for continued investigation of the interaction of commonly used drugs with Chlamydia and its host.

Postnatal Antioxidant and Anti-inflammatory Treatments Prevent Early Ketamine-Induced Cortical Dysfunctions in Adult Mice

Early brain insult, interfering with its maturation, may result in psychotic-like disturbances in adult life. Redox dysfunctions and neuroinflammation contribute to long-term psychiatric consequences due to neurodevelopmental abnormalities. Here, we investigated the effects of early pharmacological modulation of the redox and inflammatory states, through celastrol, and indomethacin administration, on reactive oxygen species (ROS) amount, levels of malondialdehyde (MDA) and antioxidant enzymes (superoxide dismutase 1, SOD1, glutathione, GSH, and catalase, CAT), as well as of pro-inflammatory cytokines (tumor necrosis factor-alpha, TNF-α, interleukin-6, IL-6, and interleukin-1 beta, IL-1β), in the prefrontal cortex of adult mice exposed to a neurotoxic insult, i.e. ketamine administration, in postnatal life. Early celastrol or indomethacin prevented ketamine-induced elevations in cortical ROS production. MDA levels in ketamine-treated mice, also administered with celastrol, were comparable with the control ones. Indomethacin also prevented the increase in lipid peroxidation following early ketamine administration. Whereas no significant differences were detected in SOD1, GSH, and CAT levels between ketamine and saline-administered mice, celastrol elevated the cortical amount of these antioxidant enzymes and the same effect was induced by indomethacin per se. Both celastrol and indomethacin prevented ketamine-induced enhancement in TNF-α and IL-1β levels, however, they had no effects on increased IL-6 amount resulting from ketamine exposure in postnatal life. In conclusion, our data suggest that an early increase in cortical ROS scavenging and reduction of lipid peroxidation, via the enhancement of antioxidant defense, together with inhibition of neuroinflammation, may represent a therapeutic opportunity against psychotic-like disturbances resulting, later in life, from the effects of a neurotoxic insult on the developing brain.

Molecular insights of NADPH oxidases and its pathological consequences

Reactive oxygen species (ROS), formed by the partial reduction of oxygen, were for a long time considered to be a byproduct of cellular metabolism. Since, increase in cellular levels of ROS results in oxidative stress leading to damage of nucleic acids, proteins, and lipids resulting in numerous pathological conditions; ROS was considered a bane for aerobic species. Hence, the discovery of NADPH oxidases (NOX), an enzyme family that specifically generates ROS as its prime product came as a surprise to redox biologists. NOX family proteins participate in various cellular functions including cell proliferation and differentiation, regulation of genes and protein expression, apoptosis, and host defence immunological response. Balanced expression and activation of NOX with subsequent production of ROS are critically important to regulate various genes and proteins to maintain homeostasis of the cell. However, dysregulation of NOX activation leading to enhanced ROS levels is associated with various pathophysiologies including diabetes, cardiovascular diseases, neurodegenerative diseases, ageing, atherosclerosis, and cancer. Although our current knowledge on NOX signifies its importance in the normal functioning of various cellular pathways; yet the choice of ROS producing enzymes which can tip the scale from homeostasis toward damage, as mediators of biological functions remain an oddity. Though the role of NOX in maintaining normal cellular functions is now deemed essential, yet its dysregulation leading to catastrophic events cannot be denied. Hence, this review focuses on the involvement of NOX enzymes in various pathological conditions imploring them as possible targets for therapies. SIGNIFICANCE OF THE STUDY: The NOXs are multi-subunit enzymes that generate ROS as a prime product. NOX generated ROS are usually regulated by various molecular factors and play a vital role in different physiological processes. The dysregulation of NOX activity is associated with pathological consequences. Recently, the dynamic proximity of NOX enzymes with different molecular signatures of pathologies has been studied extensively. It is essential to identify the precise role of NOX machinery in its niche during the progression of pathology. Although inhibition of NOX could be a promising approach for therapeutic interventions, it is critical to expand the current understanding of NOX's dynamicity and shed light on their molecular partners and regulators.

NADPH Oxidase Inhibition: Preclinical and Clinical Studies in Diabetic Complications

Significance: Oxidative stress plays a critical role in the development and progression of serious micro- and macrovascular complications of diabetes. Nicotinamide adenine dinucleotide phosphate oxidase (NOX)-derived reactive oxygen species (ROS) significantly contribute to oxidative stress-associated inflammatory pathways that lead to tissue damage of different organs, including the kidneys, retina, brain, nerves, and the cardiovascular system. Recent Advances: Preclinical studies, including genetic-modified mouse models or cell culture models, have revealed the role of specific NOX isoforms in different diabetic complications, and suggested them as a promising target for the treatment of these diseases. Critical Issues: In this review, we provide an overview of the role of ROS and oxidative stress in macrovascular complications, such as stroke, myocardial infarction, coronary artery disease, and peripheral vascular disease that are all mainly driven by atherosclerosis, as well as microvascular complications, such as diabetic retinopathy, nephropathy, and neuropathy. We summarize conducted genetic deletion studies of different Nox isoforms as well as pharmacological intervention studies using NOX inhibitors in the context of preclinical as well as clinical research on diabetic complications. Future Directions: We outline the isoforms that are most promising for future clinical trials in the context of micro- and macrovascular complications of diabetes.

The NADPH Oxidase Family and Its Inhibitors

Significance: The oxidative stress, resulting from an imbalance in the production and scavenging of reactive oxygen species (ROS), is known to be involved in the development and progression of several pathologies. The excess of ROS production is often due to an overactivation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX) and for this reason these enzymes became promising therapeutic targets. However, even if NOX are now well characterized, the development of new therapies is limited by the lack of highly isoform-specific inhibitors. Recent Advances: In the past decade, several groups and laboratories have screened thousands of molecules to identify new specific inhibitors with low off-target effects. These works have led to the characterization of several new potent NOX inhibitors; however, their specificity varies a lot depending on the molecules. Critical Issues: Here, we are reviewing more than 25 known NOX inhibitors, focusing mainly on the newly identified ones such as APX-115, NOS31, Phox-I1 and 2, GLX7013114, and GSK2795039. To have a better overall view of these molecules, the inhibitors were classified according to their specificity, from pan-NOX inhibitors to highly isoform-specific ones. We are also presenting the use of these compounds both in vitro and in vivo. Future Directions: Several of these new molecules are potent and very specific inhibitors that could be good candidates for the development of new drugs. Even if the results are very promising, most of these compounds were only validated in vitro or in mice models and further investigations will be required before using them as potential therapies.

Nicotinamide Adenine Dinucleotide Phosphate Oxidase and Neurodegenerative Diseases: Mechanisms and Therapy

Significance: The growing incidence of neurodegenerative diseases significantly impacts the individuals who suffer from these disorders and is a major health concern globally. Although the specific mechanisms of neurodegenerative diseases are still far from being acknowledged, it is becoming clear that oxidative stress and neuroinflammation are critical contributing factors to the progression of neurodegeneration. Thus, it is conceivable that the inhibition of oxidative stress and neuroinflammation may represent promising therapeutic targets for the treatment of neurodegenerative diseases. Recent Advances: Recently, the strategy for neurodegenerative disease therapy has shifted from the use of antioxidants and conventional anti-inflammatory targets to upstream mediators due to the failure of most antioxidants and nonsteroidal anti-inflammatory drugs in clinical trials. Nicotinamide adenine dinucleotide phosphate oxidases (NOXs), a family of superoxide-producing enzyme complexes, have been identified as an upstream factor that controls both oxidative stress and neuroinflammation. Genetic inactivation or pharmacological inhibition of NOX enzymes displays potent neuroprotective effects in a broad spectrum of neurodegenerative disease models. Critical Issues: The detailed mechanisms of how NOX enzymes regulate oxidative stress and neuroinflammation still remain unclear. Moreover, the currently available inhibitors of NOX enzymes exhibit nonspecificity, off-target effects, unsuitable pharmacokinetic properties, and even high toxicity, markedly limiting their potential clinical applications. Future Directions: This review provides novel insights into the roles of NOXs in neurodegenerative pharmacology, and indicates the types of NOX enzyme inhibitors that should be identified and developed as candidates for future applications, which might reveal novel neurodegenerative disease therapies based on NOXs.

Monocyte-Derived Dendritic Cell Differentiation in Inflammatory Arthritis Is Regulated by the JAK/STAT Axis via NADPH Oxidase Regulation

Monocyte-derived Dendritic cells (Mo-DC) are a distinct DC subset, involved in inflammation and infection, they originate from monocytes upon stimulation in the circulation and their activation and function may vary in autoimmune diseases. In this study we investigate the differences in Mo-DC differentiation and function in patients with Rheumatoid (RA) compared to Psoriatic arthritis (PsA). A significant increase in the Mo-DC differentiation marker CD209, paralleled by a corresponding decrease in the monocytic marker CD14, was demonstrated in RA compared to PsA, as early as 1 day post Mo-DC differentiation. RA monocytes ex-vivo were phenotypically different to PsA, displaying a more mature phenotype associated with altered cellular-morphology, early dendrite formation, and a significant increase in the CD40 marker. In addition, SPICE algorithm flow cytometric analysis showed distinct differences in chemokine receptors distribution in HC compared to PsA and RA CD14+ cells in the blood, with increased expression of the chemokine receptors CCR7 and CXCR4 observed in PsA and RA. In addition CD14+ cells at the site of inflammation showed a different chemokine receptor pattern between PsA and RA patients, with higher expression of CXCR3 and CXCR5 in RA when compared to PsA. The early priming observed in RA resulted in monocyte-endocytosis and antigen-uptake mechanisms to be impaired, effects that were not observed in PsA where phagocytosis capacity remained highly functional. Tofacitinib inhibited early Mo-DC differentiation, decreasing both CD209 and CD40 activation markers in RA. Inhibition of Mo-DC differentiation in response to Tofacitinib was mediated via an imbalance in the activation of NADPH-oxidases NOX5 and NOX2. This effect was reversed by NOX5 inhibition, but not NOX2, resulting in suppression of NOX5-dependent ROS production. In conclusion, RA monocytes are already primed ex vivo to become DC, evident by increased expression of activation markers, morphological appearance and impaired endocytosis capacity. Furthermore, we demonstrated for the first time that NOX5 mediates Mo-DC differentiation and function in response to Tofacitinib, which may alter DC functions.

NADPH oxidases: Current aspects and tools

Reactive oxygen species (ROS) have been shown or at least suggested to play an essential role for cellular signaling as second messengers. NADPH oxidases represent a source of controlled ROS formation. Accordingly, understanding the role of individual NADPH oxidases bears potential to interfere with intracellular signaling cascades without disturbing the signaling itself. Many tools have been developed to study or inhibit the functions and roles of the NADPH oxidases. This short review summarizes diseases, potentially associated with NADPH oxidases, genetically modified animals, and inhibitors.

Celastrol attenuates collagen-induced arthritis via inhibiting oxidative stress in rats

The present work aimed to investigate the anti-rheumatism effect and the mechanism of celastrol in collagen-induced arthritis (CIA) rats. The CIA model was established in male Wistar rats by intradermal injection of bovine collagen-II in complete Freund's adjuvant (CFA) at the base of tail. The rats received oral administration of celastrol for 28 days. A variety of indicators, including paw swelling and arthritis scores, were measured for anti-rheumatism effect. Celastrol treatment attenuated paw swelling and arthritis scores in CIA rats. Celastrol improved the spleen and thymus indexes in CIA rats. The increased levels of inflammatory cytokines, such as tumor necrosis factor (TNF)-α, interleukin (IL)-1β, IL-6, and interferon (IFN)-γ, were abolished by celastrol treatment. In addition, the weakened superoxide dismutase (SOD) activity, the increased levels of malondialdehyde (MDA), and superoxide anions, and enhanced NADPH oxidase (Nox) activity were all reversed by celastrol treatment. Nox4 overexpression reversed the attenuating effects of celastrol on paw swelling and arthritis scores in CIA rats. The celastrol-induced improvement in spleen and thymus indexes in CIA rats was inhibited by Nox4 overexpression. Nox4 overexpression reversed the abolishing effects of celastrol on the increases of TNF-α, IL-1β, IL-6, and IFN-γ levels in the serum of CIA rats. These results demonstrated that celastrol improved rheumatism in arthritis via inhibiting oxidative stress.

A closer look into NADPH oxidase inhibitors: Validation and insight into their mechanism of action

NADPH-oxidases (NOXs) purposefully produce reactive-oxygen-species (ROS) and are found in most kingdoms of life. The seven human NOXs are each characterized by a specific expression profile and a fine regulation to spatio-temporally tune ROS concentration in cells and tissues. One of the best known roles for NOXs is in host protection against pathogens but ROS themselves are important second messengers involved in tissue regeneration and the modulation of pathways that induce and sustain cell proliferation. As such, NOXs are attractive pharmacological targets in immunomodulation, fibrosis and cancer. We have studied an extensive number of available NOX inhibitors, with the specific aim to identify bona fide ligands versus ROS-scavenging molecules. Accordingly, we have established a comprehensive platform of biochemical and biophysical assays. Most of the investigated small molecules revealed ROS-scavenging and/or assay-interfering properties to various degrees. A few compounds, however, were also demonstrated to directly engage one or more NOX enzymes. Diphenylene iodonium was found to react with the NOXs' flavin and heme prosthetic groups to form stable adducts. We also discovered that two compounds, VAS2870 and VAS3947, inhibit NOXs through the covalent alkylation of a cysteine residue. Importantly, the amino acid involved in covalent binding was found to reside in the dehydrogenase domain, where the nicotinamide ring of NADPH is bound. This work can serve as a springboard to guide further development of bona fide ligands with either agonistic or antagonistic properties toward NOXs.

Connexin32 ameliorates renal fibrosis in diabetic mice by promoting K48-linked NADPH oxidase 4 polyubiquitination and degradation

BACKGROUND AND PURPOSE

Nox4 is the major isoform of NADPH oxidase found in the kidney and contributes to the pathogenesis of diabetic nephropathy. However, the molecular mechanisms of increased Nox4 expression induced by hyperglycaemia remain to be elucidated. Here, the role of the connexin32-Nox4 signalling axis in diabetic nephropathy and its related mechanisms were investigated.

EXPERIMENTAL APPROACH

Diabetes was induced in mice by low-dose streptozotocin (STZ) combined with a high-fat diet. Effects of connexin32 on Nox4 expression and on renal function and fibrosis in STZ-induced diabetic mice were investigated using adenovirus-overexpressing connexin32 and connexin32-deficient mice. Interactions between connexin32 and Nox4 were analysed by co-immunoprecipitation and immunofluorescence assays.

KEY RESULTS

Connexin32 was down-regulated in the kidneys of STZ-induced diabetic mice. Overexpression of connexin32 reduced expression of Nox4 and improved renal function and fibrosis in diabetic mice, whereas connexin32 deficiency had opposite effects. Down-regulation of fibronectin expression by connexin32 was not dependent on gap junctional intercellular communication involving connexin32. Connexin32 interacted with Nox4 and reduced the generation of hydrogen peroxide, leading to the down-regulation of fibronectin expression. Mechanistically, connexin32 decreased Nox4 expression by promoting its K48-linked polyubiquitination. Interestingly, Smurf1 overexpression inhibited K48-linked polyubiquitination of Nox4. Furthermore, connexin32 interacted with Smurf1 and inhibited its expression.

CONCLUSION AND IMPLICATIONS

Connexin32 ameliorated renal fibrosis in diabetic mice by promoting K48-linked Nox4 polyubiquitination and degradation via inhibition of Smurf1 expression. Targeting the connexin32-Nox4 signalling axis may contribute to the development of novel treatments for diabetic nephropathy.

Celastrol Alleviates Aortic Valve Calcification Via Inhibition of NADPH Oxidase 2 in Valvular Interstitial Cells

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The reactive oxygen species–generating enzyme Nox2 is up-regulated in the leaflets of both rabbit and human with CAVD.

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Nox2 is markedly induced in cultured porcine AVICs after osteogenic stimulation. Knockdown of endogenous Nox2 substantially suppressed AVIC calcification.

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Celastrol, a natural compound capable of inhibiting Nox2 activity, significantly decreased AVIC calcification in vitro, and mitigated the severity of aortic valve fibrosis, calcification, and stenosis in a rabbit model of CAVD in vivo.

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The protective effects of celastrol may, in part, involve the inhibition of Nox2-mediated glycogen synthase kinase 3 beta/β-catenin pathway.

This study sought to investigate whether reactive oxygen species (ROS)–generating reduced nicotinamide adenine dinucleotide phosphate oxidase 2 (Nox2) contributes to calcific aortic valve disease (CAVD) or whether celastrol, a natural Nox2 inhibitor, may provide potential therapeutic target for CAVD. CAVD is an active and cellular-driven fibrocalcific process characterized by differentiation of aortic valvular interstitial cells (AVICs) toward an osteogenic-like phenotype. ROS levels increase in calcified aortic valves, while the sources of ROS and their roles in the pathogenesis of CAVD are elusive. The roles of Nox2 and the effects of celastrol were studied using cultured porcine AVICs in vitro and a rabbit CAVD model in vivo. Nox2 proteins were significantly upregulated in human aortic valves with CAVD. In vitro, Nox2 was markedly induced upon stimulation of AVICs with osteogenic medium, along with the increases in ROS production and calcium nodule formation. Celastrol significantly decreased calcium deposition of AVICs by 35%, with a reduction of ROS generation. Knockdown of endogenous Nox2 substantially suppressed AVIC calcification by 39%, the inhibitory effect being similar to celastrol treatment. Mechanistically, either celastrol treatment or knockdown of Nox2 significantly inhibited glycogen synthase kinase 3 beta/β-catenin signaling, leading to attenuation of fibrogenic and osteogenic responses of AVICs. In a rabbit CAVD model, administration of celastrol significantly reduced aortic valve ROS production, fibrosis, calcification, and severity of aortic stenosis, with less left ventricular dilatation and better preserved contractile function. Upregulation of Nox2 is critically involved in CAVD. Celastrol is effective to alleviate CAVD, likely through the inhibition of Nox2-mediated glycogen synthase kinase 3 beta/β-catenin pathway in AVICs.

Early Celastrol Administration Prevents Ketamine-Induced Psychotic-Like Behavioral Dysfunctions, Oxidative Stress and IL-10 Reduction in The Cerebellum of Adult Mice

Administration of subanesthetic doses of ketamine during brain maturation represents a tool to mimic an early insult to the central nervous system (CNS). The cerebellum is a key player in psychosis pathogenesis, to which oxidative stress also contributes. Here, we investigated the impact of early celastrol administration on behavioral dysfunctions in adult mice that had received ketamine (30 mg/kg i.p.) at postnatal days (PNDs) 7, 9, and 11. Cerebellar levels of 8-hydroxydeoxyguanosine (8-OHdG), NADPH oxidase (NOX) 1 and NOX2, as well as of the calcium-binding protein parvalbumin (PV), were also assessed. Furthermore, celastrol effects on ketamine-induced alterations of proinflammatory (TNF-α, IL-6 and IL-1β) and anti-inflammatory (IL-10) cytokines in this brain region were evaluated. Early celastrol administration prevented ketamine-induced discrimination index decrease at adulthood. The same was found for locomotor activity elevations and increased close following and allogrooming, whereas no beneficial effects on sniffing impairment were detected. Ketamine increased 8-OHdG in the cerebellum of adult mice, which was also prevented by early celastrol injection. Cerebellar NOX1 levels were enhanced at adulthood following postnatal ketamine exposure. Celastrol per se induced NOX1 decrease in the cerebellum. This effect was more significant in animals that were early administered with ketamine. NOX2 levels did not change. Ketamine administration did not affect PV amount in the cerebellum. TNF-α levels were enhanced in ketamine-treated animals; however, this was not prevented by early celastrol administration. While no changes were observed for IL-6 and IL-1β levels, ketamine determined a reduction of cerebellar IL-10 expression, which was prevented by early celastrol treatment. Our results suggest that NOX inhibition during brain maturation prevents the development of psychotic-like behavioral dysfunctions, as well as the increased cerebellar oxidative stress and the reduction of IL-10 in the same brain region following ketamine exposure in postnatal life. This opens novel neuroprotective opportunities against early detrimental insults occurring during brain development.

Pharmacological characterization of the seven human NOX isoforms and their inhibitors

Background

NADPH oxidases (NOX) are a family of flavoenzymes that catalyze the formation of superoxide anion radical (O₂^•-) and/or hydrogen peroxide (H₂O₂). As major oxidant generators, NOX are associated with oxidative damage in numerous diseases and represent promising drug targets for several pathologies. Various small molecule NOX inhibitors are used in the literature, but their pharmacological characterization is often incomplete in terms of potency, specificity and mode of action.

Experimental approach

We used cell lines expressing high levels of human NOX isoforms (NOX1-5, DUOX1 and 2) to detect NOX-derived O₂^•- or H₂O₂ using a variety of specific probes. NOX inhibitory activity of diphenylene iodonium (DPI), apocynin, diapocynin, ebselen, GKT136901 and VAS2870 was tested on NOX isoforms in cellular and membrane assays. Additional assays were used to identify potential off target effects, such as antioxidant activity, interference with assays or acute cytotoxicity.

Key results

Cells expressing active NOX isoforms formed O₂^•-, except for DUOX1 and 2, and in all cases activation of NOX isoforms was associated with the detection of extracellular H₂O₂. Among all molecules tested, DPI elicited dose-dependent inhibition of all isoforms in all assays, however all other molecules tested displayed interesting pharmacological characteristics, but did not meet criteria for bona fide NOX inhibitors.

Conclusion

Our findings indicate that experimental results obtained with widely used NOX inhibitors must be carefully interpreted and highlight the challenge of developing reliable pharmacological inhibitors of these key molecular targets.

Activation of nicotinamide adenine dinucleotide phosphate oxidase is the primary trigger of epileptic seizures in rodent models

OBJECTIVE

Despite decades of epilepsy research, 30% of focal epilepsies remain resistant to antiseizure drugs, with effective drug development impeded by lack of understanding on how seizures are initiated. Here, we report the mechanism of seizure onset relevant to most seizures that are characteristic of focal epilepsies.

METHODS

Electric and metabolic network parameters were measured using several seizure models in mouse hippocampal slices and acutely induced seizures in rats in vivo to determine metabolic events occurring at seizure onset.

RESULTS

We show that seizure onset is associated with a rapid release of H₂ O₂ resulting from N-methyl-D-aspartate (NMDA) receptor-mediated activation of nicotinamide adenine dinucleotide phosphate oxidase (NOX). NOX blockade prevented the fast H₂ O₂ release as well as the direct current shift and seizurelike event induction in slices. Similarly, intracerebroventricular injection of NOX antagonists prevented acutely induced seizures in rats.

INTERPRETATION

Our results show that seizures are initiated by NMDA receptor-mediated NOX-induced oxidative stress and can be arrested by NOX inhibition. We introduce a novel use for blood-brain barrier-permeable NOX inhibitor with a significant potential to become the first seizure-specific medication. Thus, targeting NOX may provide a breakthrough treatment for focal epilepsies. ANN NEUROL 2019;85:907-920.

Celastrol attenuates renal injury in diabetic rats via MAPK/NF-κB pathway

The purpose of this study was to investigate the renal protective effect of celastrol on diabetic rats. Furthermore, the mechanism of its action was discussed whether it was related to MAPK/NF-κB signaling pathway. There were a total of 36 rats. Six rats were randomly chosen as the control group. The remaining 30 rats were given 1% streptozotocin intraperitoneal injection (50 mg/kg) and were randomly divided into five groups: the model control group, the low-dose celastrol group, the high-dose celastrol group, the Tripterygium wilfordii polyglycosides group, and the MAPK/NF-κB inhibitor group. After 4 weeks of continuous administration, 24-hr urine volume, urinary protein, blood urea nitrogen, and serum creatinine content were observed, and hematoxylin-eosin (HE) staining of the kidney and liver were evaluated. p38MAPK was designated by immunohistochemical method, and NF-κB p65 in renal tissue was detected by western blotting. Our results showed that celastrol could not only reduce contents of creatinine and urea nitrogen in blood but also reduce excretion of urinary protein in diabetic rats, improve renal pathological injury, and down-regulate the expression of p38MAPK and NF-κB p65. In conclusion, celastrol could protect kidney of diabetic rats by regulating the signal pathway of MAPK/NF-κB, inhibiting inflammation and delaying renal injury.

The natural phenolic compounds as modulators of NADPH oxidases in hypertension

BACKGROUND

Hypertension is a major public health problem worldwide. It is an important risk factor for other cardiovascular diseases such as coronary artery disease, stroke, heart failure, atrial fibrillation, peripheral vascular disease, chronic kidney disease, and atherosclerosis.

PURPOSE

There is strong evidence that excess ROS-derived NADPH oxidase (NOX) is an important agent in hypertension. It augments blood pressure in the presence of other pro-hypertensive factors such as angiotensin II (Ang II), an important and potent regulator of cardiovascular NADPH oxidase, activates NOX via AT1 receptors. NADPH oxidase, a multi-subunit complex enzyme, is considered as a key source of ROS production in the vasculature. The activation of this enzyme is needed for assembling Rac-1, p^40phox, p^47phox and p^67phox subunits. Since, hypertensive patients need to control blood pressure for their entire life and because drugs and other chemicals often induce adverse effects, the use of natural phenolic compounds which are less toxic and potentially beneficial may be good avenues of addition research in our understand of the underlying mechanism involved in hypertension. This review focused on several natural phenolic compounds as berberine, thymoquinone, catechin, celastrol, apocynin, resveratrol, curcumin, hesperidine and G-hesperidine, and quercetin which are NOX inhibitors. In addition, structure activity relationship of these compounds eventually as the most inhibitors was discussed.

METHODS

This comprehensive review is based on pertinent papers by a selective search using relevant keywords that was collected using online search engines and databases such as ScienceDirect, Scopus and PubMed. The literature mainly focusing on natural products with therapeutic efficacies against hypertension via experimental models both in vitro and in vivo was identified.

RESULTS

It has been observed that these natural compounds prevent NADPH oxidase expression and ROS production while increasing NO bioavailability. It have been reported that they improve hypertension due to formation of a stable radical with ROS-derived NADPH oxidase and preventing the assembly of NOX subunites.

CONCLUSION

It is clear that natural phenolic compounds have some potential inhibitory effect on NADPH oxidase activity. In comparison to other phenolic plant compounds, the structural variability of the flavonoids should off different impacts on oxidative stress in hypertension including inhibition of nadph oxidase and direct scavenging of free radicals.

Quantifying Drug Combination Synergy along Potency and Efficacy Axes

Two goals motivate treating diseases with drug combinations: reduce off-target toxicity by minimizing doses (synergistic potency) and improve outcomes by escalating effect (synergistic efficacy). Established drug synergy frameworks obscure such distinction, failing to harness the potential of modern chemical libraries. We therefore developed multi-dimensional synergy of combinations (MuSyC), a formalism based on a generalized, multi-dimensional Hill equation, which decouples synergistic potency and efficacy. In mutant-EGFR-driven lung cancer, MuSyC reveals that combining a mutant-EGFR inhibitor with inhibitors of other kinases may result only in synergistic potency, whereas synergistic efficacy can be achieved by co-targeting mutant-EGFR and epigenetic regulation or microtubule polymerization. In mutant-BRAF melanoma, MuSyC determines whether a molecular correlate of BRAFi insensitivity alters a BRAF inhibitor's potency, efficacy, or both. These findings showcase MuSyC's potential to transform the enterprise of drug-combination screens by precisely guiding translation of combinations toward dose reduction, improved efficacy, or both.

NADPH oxidase 2 inhibitors CPP11G and CPP11H attenuate endothelial cell inflammation & vessel dysfunction and restore mouse hind-limb flow

First described as essential to the phagocytic activity of leukocytes, Nox2-derived ROS have emerged as mediators of a range of cellular and tissue responses across species from salubrious to deleterious consequences. Knowledge of their role in inflammation is limited, however. We postulated that TNFα-induced endothelial reactive oxygen species (ROS) generation and pro-inflammatory signaling would be ameliorated by targeting Nox2. Herein, we in silico-modelled two first-in-class Nox2 inhibitors developed in our laboratory, explored their cellular mechanism of action and tested their efficacy in in vitro and mouse in vivo models of inflammation. Our data show that these inhibitors (CPP11G and CPP11H) disrupted canonical Nox2 organizing factor, p47^phox, translocation to Nox2 in the plasma membrane; and abolished ROS production, markedly attenuated stress-responsive MAPK signaling and downstream AP-1 and NFκB nuclear translocation in human cells. Consequently, cell adhesion molecule expression and monocyte adherence were significantly inhibited by both inhibitors. In vivo, TNFα-induced ROS and inflammation were ameliorated by targeted Nox2 inhibition, which, in turn, improved hind-limb blood flow. These studies identify a proximal role for Nox2 in propagated inflammatory signaling and support therapeutic value of Nox2 inhibitors in inflammatory disease.

Optimizing Synthetic miRNA Minigene Architecture for Efficient miRNA Hairpin Concatenation and Multi-target Gene Knockdown

Synthetic microRNA (miRNA) minigenes (SMIGs) have a major potential for molecular therapy; however, their optimal architecture still needs to be determined. We have previously optimized the stem structure of miRNA hairpins for efficient gene knockdown. Here, we investigate the overall architecture of SMIGs driven by polymerase II-dependent promoters. When miRNA hairpins were placed directly behind the promoter, gene knockdown was inefficient as compared with constructs containing an intercalated sequence (“spacer”). Spacer sequence was relevant for knockdown efficiency and concatenation potential: GFP-based sequences (even when truncated or including stop codons) were particularly efficient. In contrast, a spacer of similar length based on a CD4 intronic sequence was entirely inefficient. Spacer sequences influenced miRNA steady-state levels without affecting transcript stability. We demonstrate that with an optimized spacer, up to five concatenated hairpins targeting two different genes are efficiently expressed and able to knock down their respective targets. Transplantation of hematopoietic stem cells containing a CCR5 knockdown SMIG demonstrated a sustained in vivo efficacy of our approach. In summary, we have defined features that optimize SMIG efficiency. Based on these results, optimized knockdown of genes of interest, such as the HIV co-receptor CCR5 and the NADPH oxidase subunit p22^phox, was achieved.

Antioxidants and Chronic Obstructive Pulmonary Disease

Antioxidants represent an attractive therapeutic avenue for individuals with chronic obstructive pulmonary disease (COPD). Cigarette smoke, the major cause of COPD, contains very high concentrations of gaseous and soluble oxidants that can directly induce cell injury and death. Furthermore, particulate matter in cigarette smoke activates lung macrophages that subsequently attract neutrophils. Both neutrophils and macrophages from the lungs of cigarette smokers continuously release large amounts of superoxide and hydrogen peroxide through the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex. Once individuals with COPD stop smoking, the neutrophilic inflammation in the airways and lung parenchyma persists, as do the markers of oxidative stress. Several animal models of cigarette smoke-induced injury have provided evidence that various antioxidants may prevent inflammation and morphological changes associated with COPD however, evidence of benefit in patients is less abundant. Although oxidants can inactivate alpha-1 antitrypsin and other protective proteins, damage lung tissue, and increase mucus production, they also are essential for killing pathogens and resolving inflammation. This review will examine the pre-clinical and clinical evidence of a role for antioxidants in the therapy of patients with COPD.

The novel NADPH oxidase 4 selective inhibitor GLX7013114 counteracts human islet cell death in vitro

It has been proposed that pancreatic beta-cell dysfunction in type 2 diabetes is promoted by oxidative stress caused by NADPH oxidase (Nox) over-activity. The aim of the present study was to evaluate the efficacy of novel Nox inhibitors as protective agents against cytokine- or high glucose + palmitate-induced human beta-cell death. The Nox2 protein was present mainly in the cytoplasm and was induced by cytokines. Nox4 protein immunoreactivity, with some nuclear accumulation, was observed in human islet cells, and was not affected by islet culture in the presence of cytokines or high glucose + palmitate. Nox inhibitors with partial or no isoform selectivity (DPI, dapsone, GLX351322, and GLX481372) all reduced ROS production of human islet cells exposed to high glucose + palmitate. This was paralleled by improved viability and reduced caspase 3 activation. The Nox1 selective inhibitor ML171 failed to reduce human islet cell death in response to both cytokines and high glucose + palmitate. The selective Nox2 inhibitor Phox-I2 also failed to protect against cytokines, but protected partially against high glucose + palmitate-induced cellular death. The highly selective Nox4 inhibitor GLX7013114 protected islet cells against both cytokines and high glucose + palmitate. However, as no osmotic control for high glucose was used, we cannot exclude the possibility that the high glucose effect was due to osmosis. It is concluded that Nox4 may participate in stress-induced islet cell death in human islets in vitro. We propose that Nox4 mediates pro-apoptotic effects in intact islets under stressful conditions and that selective Nox4-inhibition may be a therapeutic strategy in type 2 diabetes.

Celastrol as a pentacyclic triterpenoid with chemopreventive properties

Celastrol is a highly investigated anticancer moiety. It is a pentacyclic triterpenoid, isolated several decades ago with promising role in chemoprevention. Celastrol has been found to target multiple proinflammatory, angiogenic and metastatic proteins. Inhibition of these targets results in significant reduction of cancer growth, survival and metastasis. This review summarizes the varied molecular targets of celastrol along with insight into the various recently published clinical, preclinical and industrial patents (2011-2017).

nox2/cybb Deficiency Affects Zebrafish Retinotectal Connectivity

NADPH oxidase (Nox)-derived reactive oxygen species (ROS) have been linked to neuronal polarity, axonal outgrowth, cerebellar development, regeneration of sensory axons, and neuroplasticity. However, the specific roles that individual Nox isoforms play during nervous system development in vivo remain unclear. To address this problem, we investigated the role of Nox activity in the development of retinotectal connections in zebrafish embryos. Zebrafish broadly express four nox genes (nox1, nox2/cybb, nox5, and duox) throughout the CNS during early development. Application of a pan-Nox inhibitor, celastrol, during the time of optic nerve (ON) outgrowth resulted in significant expansion of the ganglion cell layer (GCL), thinning of the ON, and a decrease in retinal axons reaching the optic tectum (OT). With the exception of GCL expansion, these effects were partially ameliorated by the addition of H₂O₂, a key ROS involved in Nox signaling. To address isoform-specific Nox functions, we used CRISPR/Cas9 to generate mutations in each zebrafish nox gene. We found that nox2/cybb chimeric mutants displayed ON thinning and decreased OT innervation. Furthermore, nox2/cybb homozygous mutants (nox2/cybb^-/-) showed significant GCL expansion and mistargeted retinal axons in the OT. Neurite outgrowth from cultured zebrafish retinal ganglion cells was reduced by Nox inhibitors, suggesting a cell-autonomous role for Nox in these neurons. Collectively, our results show that Nox2/Cybb is important for retinotectal development in zebrafish.SIGNIFICANCE STATEMENT Most isoforms of NADPH oxidase (Nox) only produce reactive oxygen species (ROS) when activated by an upstream signal, making them ideal candidates for ROS signaling. Nox enzymes are present in neurons and their activity has been shown to be important for neuronal development and function largely by in vitro studies. However, whether Nox is involved in the development of axons and formation of neuronal connections in vivo has remained unclear. Using mutant zebrafish embryos, this study shows that a specific Nox isoform, Nox2/Cybb, is important for the establishment of axonal connections between retinal ganglion cells and the optic tectum.

NADPH Oxidases and Their Roles in Skin Homeostasis and Carcinogenesis

SIGNIFICANCE

Skin protects the body from dehydration, pathogens, and external mutagens. NADPH oxidases are central components for regulating the cellular redox balance. There is increasing evidence indicating that reactive oxygen species (ROS) generated by members of this enzyme family play important roles in the physiology and pathophysiology of the skin. Recent Advances: NADPH oxidases are active producers of ROS such as superoxide and hydrogen peroxide. Different isoforms are found in virtually all tissues. They play pivotal roles in normal cell homeostasis and in the cellular responses to various stressors. In particular, these enzymes are integral parts of redox-sensitive prosurvival and proapoptotic signaling pathways, in which they act both as effectors and as modulators. However, continuous (re)activation of NADPH oxidases can disturb the redox balance of cells, in the worst-case scenario in a permanent manner. Abnormal NADPH oxidase activity has been associated with a wide spectrum of diseases, as well as with aging and carcinogenesis.

CRITICAL ISSUES

Sunlight with its beneficial and deleterious effects induces the activation of NADPH oxidases in the skin. Evidence for the important roles of this enzyme family in skin cancer and skin aging, as well as in many chronic skin diseases, is now emerging.

FUTURE DIRECTIONS

Understanding the precise roles of NADPH oxidases in normal skin homeostasis, in the cellular responses to solar radiation, and during carcinogenesis will pave the way for their validation as therapeutic targets not only for the prevention and treatment of skin cancers but also for many other skin-related disorders. Antioxid. Redox Signal. 28, 1238-1261.