Cloning of two human thyroid cDNAs encoding new members of the NADPH oxidase family

The role of DUOXA2 in the clinical diagnosis of paediatric congenital hypothyroidism

Background: Congenital hypothyroidism (CH) is a common metabolic disorder in children that can impact growth and neurodevelopment, particularly during infancy and early childhood. DUOXA2, a DUOX maturation factor, plays a crucial role in the maturation and activation of dual oxidase DUOX2 (a member of the NADPH oxidase family). DUOX2 can correctly migrate to the plasma membrane from the endoplasmic reticulum (ER) with the help of DUOXA2, and the two proteins together form a stable complex that promotes hydrogen peroxide (H2O2) generation in the synthesis of thyroid hormones. Genetic alterations in DUOXA2 lead to defects function of DUOX2 protein causing inherited CH.

Objectives: This review discusses the relationship between DUOXA2 and CH, including the pathogenic mechanisms of CH in children caused by DUOXA2 mutations and the possibility or promise of DUOXA2 gene screening as a diagnostic marker for CH in the clinic.

Methods: The review synthesizes current research on the biological role of DUOXA2 and DUOX2 in thyroid hormone synthesis, the molecular impact of DUOXA2 mutations, and the clinical implications of genetic screening for CH.

Results: Mutations in DUOXA2 disrupt this process of H2O2 generation in the synthesis of thyroid hormones , leading to inherited CH. Early identification through DUOXA2 gene screening could improve diagnostic accuracy, which facilitates early intervention and personalized treatment.

Conclusions: DUOXA2 gene screening holds promise for enhancing diagnostic accuracy in CH. However, it cannot be used as a sole diagnostic indicator, and to optimize diagnostic sensitivity, it should be combined with the screening of other relevant genetic mutations and diagnostic tools. Further research is needed to refine screening protocols and explore therapeutic options.

Neonatal microbiota colonization primes maturation of goblet cell-mediated protection in the pre-weaning colon

Regulated host-microbe interactions are a critical aspect of lifelong health. Colonic goblet cells protect from microorganisms via the generation of a mucus barrier structure. Bacteria-sensing sentinel goblet cells provide secondary protection by orchestrating mucus secretion when microbes breach the mucus barrier. Mucus deficiencies in germ-free mice implicate a role for the microbiota in programming barrier generation, but its natural ontogeny remains undefined. We now investigate the mucus barrier and sentinel goblet cell development in relation to postnatal colonization. Combined in vivo and ex vivo analyses demonstrate rapid and sequential microbiota-dependent development of these primary and secondary goblet cell protective functions, with dynamic changes in mucus processing dependent on innate immune signaling via MyD88 and development of functional sentinel goblet cells dependent on the NADPH/dual oxidase family member Duox2. Our findings identify new mechanisms of microbiota-goblet cell regulatory interaction and highlight the critical importance of the pre-weaning period for the normal development of protective systems that are key legislators of host-microbiota interaction.

Dual oxidase is essential for moulting, hatching and feeding in the brown planthopper

Dual oxidase (Duox) is well-known for its role in immunity and tyrosine cross-linking activity across various biological processes from mammals to holometabolous insects. Nevertheless, its function in hemimetabolous insects remains poorly understood. In this study, we explored the physiological roles of the Duox gene in a hemimetabolous insect, the brown planthopper, one of the most devastating rice pests. A comprehensive analysis of the spatiotemporal expression pattern of the Duox gene was conducted. RNA interference (RNAi)-mediated silencing of the Duox gene led to moulting defects in nymphs, wing abnormalities and impaired feeding in adults and reduced hatchability in eggs. Additionally, Duox knockdown significantly reduced hydrogen peroxide (H2O2) levels in premoulting nymphs and female ovaries. These findings highlight the indispensable role of Duox in moulting, hatching, wing expansion and feeding behaviours in the brown planthopper, shedding light on the relationship between H2O2 production and cuticle structural stability.

Reactive oxygen species in tendon injury and repair

Reactive oxygen species (ROS) are chemical moieties that in physiological concentrations serve as fast-acting signaling molecules important for cellular homeostasis. However, their excess either due to overproduction or inability of the antioxidant system to inactivate them results in oxidative stress, contributing to cellular dysfunction and tissue damage. In tendons, which are hypovascular, hypocellular, and composed predominantly of extracellular matrix (ECM), particularly collagen I, ROS likely play a dual role: regulating cellular processes such as inflammation, proliferation, and ECM remodeling under physiological conditions, while contributing to tendinopathy and impaired healing when dysregulated. This review explores the sources of ROS in tendons, including NADPH oxidases and mitochondria, and their role in key processes such as tissue adaptation to mechanical load and injury repair, also in systemic conditions such as diabetes. In addition, we integrate the emerging perspective that calcium signaling-mediated by mechanically activated ion channels-plays a central role in tendon mechanotransduction under daily mechanical loads. We propose that mechanical overuse (overload) may lead to hyperactivation of calcium channels, resulting in chronically elevated intracellular calcium levels that amplify ROS production and oxidative stress. Although direct evidence linking calcium channel hyperactivity, intracellular calcium dysregulation, and ROS generation under overload conditions is currently circumstantial, this review aims to highlight these connections and identify them as critical avenues for future research. By framing ROS within the context of both adaptive and maladaptive responses to mechanical load, this review provides a comprehensive synthesis of redox biology in tendon injury and repair, paving the way for future work, including development of therapeutic strategies targeting ROS and calcium signaling to enhance tendon recovery and resilience.

Design of Benzyl-triazolopyrimidine-Based NADPH Oxidase Inhibitors Leads to the Discovery of a Potent Dual Covalent NOX2/MAOB Inhibitor

NADPH oxidases (NOXs) are enzymes dedicated to reactive oxygen species (ROS) production and are implicated in cancer, neuroinflammation, and neurodegenerative diseases. VAS2870 is a covalent inhibitor of mainly NOX2 and NOX5. It alkylates a conserved active-site cysteine, blocking productive substrate binding. To enhance potency and selectivity toward NOXs, we conducted some chemical modifications, leading to the discovery of compound 9a that preferentially inhibits NOX2 with an IC50 of 0.155 μM, and only upon its preactivation. We found that 9a, bearing a pargyline moiety, is also able to selectively inhibit MAOB over MAOA (465-fold) with an IC50 of 0.182 μM, being the first-in-class dual NOX2/MAOB covalent inhibitor. Tested in the BV2 microglia neuroinflammation model, 9a decreased ROS production and downregulated proinflammatory cytokines as iNOS, IL-1β, and IL-6 expression more efficiently than the single target inhibitors (rasagiline for MAOB and VAS2870 for NOXs) but also, more importantly, than their combination.

Exploring the potential regulation of DUOX in thyroid hormone‑autophagy signaling via IGF‑1 in the skeletal muscle (Review)

Dual oxidases (DUOX) are enzymes that have the main function in producing reactive oxygen species (ROS) in various tissues. DUOX also play an important role in the synthesis of H2O2, which is essential for the production of thyroid hormone. Thyroid hormones can influence the process of muscle development through direct stimulation of ROS, 5' AMP-activated protein kinase (AMPK) and mTOR and indirect effect autophagy and the insulin-like growth factor 1 (IGF-1) pathway. IGF-1 signaling controls autophagy in two ways: Inhibiting autophagy through activation of the PI3K/AKT/mTOR/MAPK pathway and promoting mitophagy through the nuclear factor erythroid 2-related factor 2-binding receptor Bcl2/adenovirus E1B 19 kDa protein-interacting protein 3. Thyroid hormone deficiency caused by the absence of DUOX should be considered because it might have a significant effect on the growth of skeletal muscle. The effect of DUOX regulation on thyroid hormone autophagy via IGF-1 in skeletal muscle has not been well investigated. The present review discussed the regulatory interactions between DUOX, thyroid hormone, IGF-1 and autophagy, which can influence skeletal muscle development.

Advances in Selenium and Related Compounds Inhibiting Multi-Organ Fibrosis

Selenium (Se), a critically essential trace element, plays a crucial role in diverse physiological processes within the human body, such as oxidative stress response, inflammation regulation, apoptosis, and lipid metabolism. Organ fibrosis, a pathological condition caused by various factors, has become a significant global health issue. Numerous studies have demonstrated the substantial impact of Se on fibrotic diseases. This review delves into the latest research advancements in Se and Se-related biological agents for alleviating fibrosis in the heart, liver, lungs, and kidneys, detailing their mechanisms of action within fibrotic pathways. Additionally, the article summa-rizes some of the anti-fibrotic drugs currently in clinical trials for the aforementioned organ fibroses.

Delineating the NOX-Mediated Promising Therapeutic Strategies for the Management of Various Cardiovascular Disorders: A Comprehensive Review

Cardiovascular disorders (CVDs) are reported to occur with very high rates of incidence and exhibit high morbidity and mortality rates across the globe. Therefore, research is focused on searching for novel therapeutic targets involving multiple pathophysiological mechanisms. Oxidative stress plays a critical role in the development and progression of various CVDs, such as hypertension, pulmonary hypertension, heart failure, arrhythmia, atherosclerosis, ischemia- reperfusion injury, and myocardial infarction. Among multiple pathways generating reactive oxygen species (ROS), Nicotinamide adenine dinucleotide phosphate (NADPH) oxidases of the NOX family as the major source of ROS generation and plays an intricate role in the development and progression of CVDs. Therefore, exploring the role of different NADPH oxidase isoforms in various cardiovascular pathologies has attracted attention to current cardiovascular research. Focusing on NADPH oxidases to reduce oxidative stress in managing diverse CVDs may offer unique therapeutic approaches to prevent and treat various heart conditions. The current review article highlights the role of different NADPH oxidase isoforms in the pathophysiology of various CVDs. Moreover, the focus is also to emphasize different experimental studies that utilized various NADPH oxidase isoform modulators to manage other disorders. The present review article considers new avenues for researchers/scientists working in the field of cardiovascular pharmacology utilizing NADPH oxidase isoform modulators.

"β-glucan signalling stimulates NOX-2 dependent autophagy and LC-3 associated autophagy (LAP) pathway"

β-Glucan, a complex polysaccharide derived from fungal and yeast cell walls, plays a crucial role in modulating immune responses through their interaction with receptors such as Dectin-1 and Complement receptor 3 (CR-3). This review provides an in-depth analysis of the molecular mechanisms by which β-glucans activate receptor-mediated signalling pathways, focusing particularly on the LC3-associated phagocytosis (LAP) and autophagy pathways. Hence, we explore how β-glucan receptor engagement stimulates NADPH oxidase 2 (NOX-2), leading to the intracellular production of significant level of reactive oxygen species (ROS) essential for both conventional autophagy and LAP. While significant progress has been made in elucidation of downstream signaling by glucans, the regulation of phago-lysosomal maturation and antigen presentation during LAP induction still remains less explored. This review aims to provide a comprehensive overview of these pathways and their regulation by β-glucans. By consolidating the current knowledge, we seek to highlight how these mechanisms can be leveraged for therapeutic applications, particularly in the context of tuberculosis (TB) management, where β-glucans could serve as host-directed adjuvant therapies to combat drug-resistant strains. Despite major advancements in this field, currently key research gaps still persist, including detailed molecular interactions between β-glucan receptors and NOX-2 and the translation of these findings to in-vivo models and clinical investigations. This review underscores the need for further research to explore the therapeutic potential of β-glucans in managing not only tuberculosis but also other diseases such as cancer, cardiovascular conditions, and metabolic disorders.

Newborn Genetic Screening Improves the Screening Efficiency for Congenital Hypothyroidism: A Prospective Multicenter Study in China

Newborn congenital hypothyroidism (CH) screening has been widely used worldwide. The objective of this study was to evaluate the effectiveness of applying biochemical and gene panel sequencing as screening tests for CH and to analyze the mutation spectrum of CH in China. Newborns were prospectively recruited from eight hospitals in China between February and December 2021. Clinical characteristics were collected. Second-generation sequencing was used to detect four CH-related genes, and the genetic patterns of the pathogenic genes were analyzed. We analyzed the relationship between genotype and biochemical phenotype. A total of 29,601 newborns were screened for CH. Gene panel sequencing identified 18 patients, including 10 patients affected by biochemically and genetically screened disorders and 8 patients affected by solely genetically screened disorders. The predictive positive value of genetic screening was 34.62%, which was much greater than that of biochemical screening alone (17.99%). A total of 94 cases of congenital thyroid dysfunction were confirmed by biochemical and genetic screening, including 30 CHs and 64 isolated hyperthyrotropinemia (HTT), with an incidence of 1/987 for CH and 1/463 for HTT, and a total incidence of 1/315 for hypothyroidism. The incidence rate and number of patients in Jinan were the highest, and the incidence rates in Shijiazhuang and Shanghai were the lowest. The gene mutation rate in this study was 19.1%, mainly DUOX2 mutation. The most common variant of DUOX2 was c.1588A>T(p.Lys530*). There was only a difference in sFT4 between groups with gene mutations and those without mutations. Genetic screening is a supplement to biochemical screening. Combining biochemical screening with genetic screening is useful for improving screening efficiency. The incidence of CH in China according to a multicenter study of nearly 30,000 NBS surveys was 1/315. DUOX2 gene mutations are commonly detected in these patients.

The NADPH oxidases DUOX1 and DUOX2 are sorted to the apical plasma membrane in epithelial cells via their respective maturation factors DUOXA1 and DUOXA2

The membrane-integrated NADPH oxidases DUOX1 and DUOX2 are recruited to the apical plasma membrane in epithelial cells to release hydrogen peroxide, thereby playing crucial roles in various functions such as thyroid hormone synthesis and host defense. However, it has remained unknown about the molecular mechanism for apical sorting of DUOX1 and DUOX2. Here we show that DUOX1 and DUOX2 are correctly sorted to the apical membrane via the membrane-spanning DUOX maturation proteins DUOXA1 and DUOXA2, respectively, when co-expressed in MDCK epithelial cells. Impairment of N-glycosylation of DUOXA1 results in mistargeting of DUOX1 to the basolateral membrane. Similar to DUOX1 complexed with the glycosylation-defective DUOXA1, the naturally non-glycosylated oxidase NOX5, which forms a homo-oligomer, is targeted basolaterally. On the other hand, a mutant DUOXA2 deficient in N-glycosylation is less stable than the wild-type protein but still capable of recruiting DUOX2 to the apical membrane, whereas DUOX2 is missorted to the basolateral membrane when paired with DUOXA1. These findings indicate that DUOXA2 is crucial but its N-glycosylation is dispensable for DUOX2 apical recruitment; instead, its C-terminal region seems to be involved. Thus, apical sorting of DUOX1 and DUOX2 is likely regulated in a distinct manner by their respective partners DUOXA1 and DUOXA2.

NADPH Oxidases in Neurodegenerative Disorders: Mechanisms and Therapeutic Opportunities

Significance: The nicotinamide adenine dinucleotide phosphate oxidase (NOX) enzyme family, located in the central nervous system, is recognized as a source of reactive oxygen species (ROS) in the brain. Despite its importance in cellular processes, excessive ROS generation leads to cell death and is involved in the pathogenesis of neurodegenerative disorders. Recent advances: NOX enzymes contribute to the development of neurodegenerative diseases, such as Parkinson's disease (PD), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and stroke, highlighting their potential as targets for future therapeutic development. This review will discuss NOX's contribution and therapeutic targeting potential in neurodegenerative diseases, focusing on PD, AD, ALS, and stroke. Critical issues: Homeostatic and physiological levels of ROS are crucial for regulating several processes, such as development, memory, neuronal signaling, and vascular homeostasis. However, NOX-mediated excessive ROS generation is deeply involved in the damage of DNA, proteins, and lipids, leading to cell death in the pathogenesis of a wide range of diseases, namely neurodegenerative diseases. Future directions: It is essential to understand the role of NOX homologs in neurodegenerative disorders and the pathological mechanisms undergoing neurodegeneration mediated by increased levels of ROS. This further knowledge will allow the development of new specific NOX inhibitors and their application for neurodegenerative disease therapeutics. Antioxid. Redox Signal. 41, 522-541.

Neonatal microbiota colonization drives maturation of primary and secondary goblet cell mediated protection in the pre-weaning colon

In the distal colon, mucus secreting goblet cells primarily confer protection from luminal microorganisms via generation of a sterile inner mucus layer barrier structure. Bacteria-sensing sentinel goblet cells provide a secondary defensive mechanism that orchestrates mucus secretion in response to microbes that breach the mucus barrier. Previous reports have identified mucus barrier deficiencies in adult germ-free mice, thus implicating a fundamental role for the microbiota in programming mucus barrier generation. In this study, we have investigated the natural neonatal development of the mucus barrier and sentinel goblet cell-dependent secretory responses upon postnatal colonization. Combined in vivo and ex vivo analyses of pre- and post-weaning colonic mucus barrier and sentinel goblet cell maturation demonstrated a sequential microbiota-dependent development of these primary and secondary goblet cell-intrinsic protective functions, with dynamic changes in mucus processing dependent on innate immune signalling via MyD88, and development of functional sentinel goblet cells dependent on the NADPH/Dual oxidase family member Duox2. Our findings therefore identify new mechanisms of microbiota-goblet cell regulatory interaction and highlight the critical importance of the pre-weaning period for the normal development of colonic barrier function.

Research progress on the role of reactive oxygen species in the initiation, development and treatment of breast cancer

According to international cancer data, breast cancer (BC) is the leading type of cancer in women. Although significant progress has been made in treating BC, metastasis and drug resistance continue to be the primary causes of mortality for many patients. Reactive oxygen species (ROS) play a dual role in vivo: normal levels can maintain the body's normal physiological function; however, high levels of ROS below the toxicity threshold can lead to mtDNA damage, activation of proto-oncogenes, and inhibition of tumor suppressor genes, which are important causes of BC. Differences in the production and regulation of ROS in different BC subtypes have important implications for the development and treatment of BC. ROS can also serve as an important intracellular signal transduction factor by affecting the antioxidant system, activating MAPK and PI3K/AKT, and other signal pathways to regulate cell cycle and change the relationship between cells and the activity of metalloproteinases, which significantly impacts the metastasis of BC. Hypoxia in the BC microenvironment increases ROS production levels, thereby inducing the expression of hypoxia inducible factor-1α (HIF-1α) and forming "ROS- HIF-1α-ROS" cycle that exacerbates BC development. Many anti-BC therapies generate sufficient toxic ROS to promote cancer cell apoptosis, but because the basal level of ROS in BC cells exceeds that of normal cells, this leads to up-regulation of the antioxidant system, drug efflux, and apoptosis inhibition, rendering BC cells resistant to the drug. ROS crosstalks with tumor vessels and stromal cells in the microenvironment, increasing invasiveness and drug resistance in BC.

X-ray structure and enzymatic study of a bacterial NADPH oxidase highlight the activation mechanism of eukaryotic NOX

NADPH oxidases (NOX) are transmembrane proteins, widely spread in eukaryotes and prokaryotes, that produce reactive oxygen species (ROS). Eukaryotes use the ROS products for innate immune defense and signaling in critical (patho)physiological processes. Despite the recent structures of human NOX isoforms, the activation of electron transfer remains incompletely understood. SpNOX, a homolog from Streptococcus pneumoniae, can serves as a robust model for exploring electron transfers in the NOX family thanks to its constitutive activity. Crystal structures of SpNOX full-length and dehydrogenase (DH) domain constructs are revealed here. The isolated DH domain acts as a flavin reductase, and both constructs use either NADPH or NADH as substrate. Our findings suggest that hydride transfer from NAD(P)H to FAD is the rate-limiting step in electron transfer. We identify significance of F397 in nicotinamide access to flavin isoalloxazine and confirm flavin binding contributions from both DH and Transmembrane (TM) domains. Comparison with related enzymes suggests that distal access to heme may influence the final electron acceptor, while the relative position of DH and TM does not necessarily correlate with activity, contrary to previous suggestions. It rather suggests requirement of an internal rearrangement, within the DH domain, to switch from a resting to an active state. Thus, SpNOX appears to be a good model of active NOX2, which allows us to propose an explanation for NOX2's requirement for activation.

Dual oxidase 2 (duox 2) participates in the intestinal antibacterial innate immune responses of Procambarus clarkii by regulating ROS levels

Dual oxidase (Duox) a member of the nicotinamide adenine dinucleotide phosphate oxidase (NOX) family can induce the production of reactive oxygen species (ROS). In vertebrates, the duox gene was indicated to be associated with the mucosal immunity. The roles of the duox gene in invertebrates were mainly studied in insects for the function of maintaining intestinal flora balance. In recent years, some studies have reported that Duox is involved in regulating the production of ROS and plays an important role in defending against the intestinal pathogen infection. However, the molecular mechanism has not been fully illuminated. In this study, a duox 2 involved in the production of H2O2 was identified for the first time in P. clarkii. Mature Pc-Duox 2 is a 7-transmembrane protein molecule that includes PHD, FAD, and NAD domains. Pc-duox 2 was mainly expressed in hemocytes and intestinal tissue. Its expression levels were obviously upregulated after intramuscular or oral infection with V. harveyi. In the RNAi assay, the upregulated trends of H2O2 and total ROS levels in crayfish intestine were significantly suppressed when Pc-duox 2 was knocked down. Compared with the slightly affected SOD activity, the upregulated CAT activity was suppressed more obviously in the crayfish intestine. Furthermore, Pc-duox 2 had an important effect on the maintenance of the structural stability of crayfish the intestine. Further research revealed that the knockdown of Pc-duox 2 could cause an obvious suppression in the upregulated levels of Toll signalling pathway-related genes, including Pc-toll 1, Pc-toll 3, Pc-dorsal, Pc-ALF 5, Pc-crustin 1, and Pc-lysozyme. Ultimately, these changes triggered the accelerated death of crayfish. Overall, we speculated that Pc-duox 2 played an important role in antibacterial innate immunity in the crayfish intestine by regulating the total ROS level.

Functional studies associate novel DUOX2 gene variants detected in heterozygosity to Crohn's disease

PURPOSE

Crohn's disease is a chronic gastrointestinal inflammatory disease with possible extraintestinal symptoms. There are predisposing genetic factors and even monogenic variants of the disorder. One of the possible genetic factors are variants of the DUOX2 gene. The protein product of the DUOX2 gene is a dual oxidase enzyme producing H2O2 in the bowel. Reduced H2O2 levels impact mucosal homeostasis and contribute to the development of inflammatory bowel disease. Thus far, only 19 patients with IBD with the DUOX2 variants have been described.

METHODS

Here we present a case report of an adolescent female diagnosed at eleven years of age with IBD that was subsequently reclassified as Crohn's disease. She was treated with immunosuppressants and biological therapy but experienced additional complications. Her peripheral blood lymphocyte DNA was studied using massive parallel sequencing. Detected variants were functionally studied.

RESULTS

Whole exome sequencing found two novel DUOX2 gene variants: a de novo variant c.3646C>T; p.R1216W and a maternally inherited variant c.3391G>A; p.A1131T which were initially classified as variants of unknown significance. However, follow-up functional studies demonstrated that both DUOX2 variants led to impaired H2O2 generation, which led to their reclassification to the likely pathogenic class according to the ACMG.net. Therefore, we conclude that these variants are causative for the disease.

CONCLUSIONS

Identifying novel variants in patients with Crohn's disease and their families is important for precision medicine approaches and understanding of the pathogenesis of likely "monogenic" rare forms of inflammatory bowel disease.

Monogenic Disorders of ROS Production and the Primary Anti-Oxidative Defense

Oxidative stress, characterized by an imbalance between the production of reactive oxygen species (ROS) and the cellular anti-oxidant defense mechanisms, plays a critical role in the pathogenesis of various human diseases. Redox metabolism, comprising a network of enzymes and genes, serves as a crucial regulator of ROS levels and maintains cellular homeostasis. This review provides an overview of the most important human genes encoding for proteins involved in ROS generation, ROS detoxification, and production of reduced nicotinamide adenine dinucleotide phosphate (NADPH), and the genetic disorders that lead to dysregulation of these vital processes. Insights gained from studies on inherited monogenic metabolic diseases provide valuable basic understanding of redox metabolism and signaling, and they also help to unravel the underlying pathomechanisms that contribute to prevalent chronic disorders like cardiovascular disease, neurodegeneration, and cancer.

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.

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.

Nox4 as a novel therapeutic target for diabetic vascular complications

Diabetic vascular complications can affect both microvascular and macrovascular. Diabetic microvascular complications, such as diabetic nephropathy, diabetic retinopathy, diabetic neuropathy, and diabetic cardiomyopathy, are believed to be caused by oxidative stress. The Nox family of NADPH oxidases is a significant source of reactive oxygen species and plays a crucial role in regulating redox signaling, particularly in response to high glucose and diabetes mellitus. This review aims to provide an overview of the current knowledge about the role of Nox4 and its regulatory mechanisms in diabetic microangiopathies. Especially, the latest novel advances in the upregulation of Nox4 that aggravate various cell types within diabetic kidney disease will be highlighted. Interestingly, this review also presents the mechanisms by which Nox4 regulates diabetic microangiopathy from novel perspectives such as epigenetics. Besides, we emphasize Nox4 as a therapeutic target for treating microvascular complications of diabetes and summarize drugs, inhibitors, and dietary components targeting Nox4 as important therapeutic measures in preventing and treating diabetic microangiopathy. Additionally, this review also sums up the evidence related to Nox4 and diabetic macroangiopathy.

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.

The Effect of Long-Term Inorganic Iodine on Intrathyroidal Iodothyronine Content and Gene Expression in Mice with Graves' Hyperthyroidism

Background: The main molecular mechanism underlying acute suppression of iodine organification in normal thyroids after an excessive iodine load, that is, the Wolff-Chaikoff effect, is assumed to be suppression of iodine oxidation and iodothyronine synthesis. However, the mechanism underlying chronic antithyroid action of inorganic iodine in Graves' disease is not fully understood. Using a mouse model of Graves' hyperthyroidism, we examined changes in iodothyronine content and gene expression profiles in the thyroid glands after inorganic iodine loading. Materials and Methods: Graves' hyperthyroidism was induced and maintained in BALB/c mice by repeated immunizations of recombinant adenovirus expressing the human thyrotropin (TSH) receptor A-subunit. Hyperthyroid mice were left untreated (GD-C; n = 8) or treated with inorganic iodine for 12 weeks (GD-NaI; n = 8). We used unimmunized BALB/c mice as a control group (n = 10). In each mouse, serum thyroxine (T4) levels were measured with enzyme-linked immunosorbent assay (ELISA) at 4-week intervals. The intrathyroidal iodothyronine content and gene expression levels were, respectively, evaluated by mass spectrometry and RNA sequencing (RNA-seq) at the end of the experimental period. Results: Serum T4 levels in the GD-C group remained higher than in the control group, whereas those in the GD-NaI group declined to normal levels during the experimental period. Intrathyroidal triiodothyronine (T3), reverse T3 (rT3), and T4 contents in the GD-C group were higher than the control group, and rT3 and T4 were further increased in the GD-NaI group. The observed alterations in iodothyronine levels in the thyroid and sera may be explained by altered expression levels of genes for iodothyronine biosynthetic molecules, their transporter, and deiodinases. Conclusion: In this mouse model of hyperthyroidism, higher intrathyroidal accumulation of T4 and reduced gene expression data of iodothyronine transporters in the GD-NaI group suggest that chronic antithyroid action of iodine in Graves' disease involves suppression of hormone secretion.

The Role of Macula Densa Nitric Oxide Synthase 1 Beta Splice Variant in Modulating Tubuloglomerular Feedback

Abnormalities in renal electrolyte and water excretion may result in inappropriate salt and water retention, which facilitates the development and maintenance of hypertension, as well as acid-base and electrolyte disorders. A key mechanism by which the kidney regulates renal hemodynamics and electrolyte excretion is via tubuloglomerular feedback (TGF), an intrarenal negative feedback between tubules and arterioles. TGF is initiated by an increase of NaCl delivery at the macula densa cells. The increased NaCl activates luminal Na-K-2Cl cotransporter (NKCC2) of the macula densa cells, which leads to activation of several intracellular processes followed by the production of paracrine signals that ultimately result in a constriction of the afferent arteriole and a tonic inhibition of single nephron glomerular filtration rate. Neuronal nitric oxide (NOS1) is highly expressed in the macula densa. NOS1β is the major splice variant and accounts for most of NO generation by the macula densa, which inhibits TGF response. Macula densa NOS1β-mediated modulation of TGF responses plays an essential role in control of sodium excretion, volume and electrolyte hemostasis, and blood pressure. In this article, we describe the mechanisms that regulate macula densa-derived NO and their effect on TGF response in physiologic and pathologic conditions. © 2023 American Physiological Society. Compr Physiol 13:4215-4229, 2023.

MicroRNAs in the Regulation of NADPH Oxidases in Vascular Diabetic and Ischemic Pathologies: A Case for Alternate Inhibitory Strategies?

Since their discovery in the vasculature, different NADPH oxidase (NOX) isoforms have been associated with numerous complex vascular processes such as endothelial dysfunction, vascular inflammation, arterial remodeling, and dyslipidemia. In turn, these often underlie cardiovascular and metabolic pathologies including diabetes mellitus type II, cardiomyopathy, systemic and pulmonary hypertension and atherosclerosis. Increasing attention has been directed toward miRNA involvement in type II diabetes mellitus and its cardiovascular and metabolic co-morbidities in the search for predictive and stratifying biomarkers and therapeutic targets. Owing to the challenges of generating isoform-selective NOX inhibitors (NOXi), the development of specific NOXis suitable for therapeutic purposes has been hindered. In that vein, differential regulation of specific NOX isoforms by a particular miRNA or combina-tion thereof could at some point become a reasonable approach for therapeutic targeting under some circumstances. Whereas administration of miRNAs chronically, or even acutely, to patients poses its own set of difficulties, miRNA-mediated regulation of NOXs in the vasculature is worth surveying. In this review, a distinct focus on the role of miRNAs in the regulation of NOXs was made in the context of type II diabetes mellitus and ischemic injury models.

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.

NOX as a Therapeutic Target in Liver Disease

The nicotinamide adenine dinucleotide phosphate hydrogen oxidase (NADPH oxidase or NOX) plays a critical role in the inflammatory response and fibrosis in several organs such as the lungs, pancreas, kidney, liver, and heart. In the liver, NOXs contribute, through the generation of reactive oxygen species (ROS), to hepatic fibrosis by acting through multiple pathways, including hepatic stellate cell activation, proliferation, survival, and migration of hepatic stellate cells; hepatocyte apoptosis, enhancement of fibrogenic mediators, and mediation of an inflammatory cascade in both Kupffer cells and hepatic stellate cells. ROS are overwhelmingly produced during malignant transformation and hepatic carcinogenesis (HCC), creating an oxidative microenvironment that can cause different and various types of cellular stress, including DNA damage, ER stress, cell death of damaged hepatocytes, and oxidative stress. NOX1, NOX2, and NOX4, members of the NADPH oxidase family, have been linked to the production of ROS in the liver. This review will analyze some diseases related to an increase in oxidative stress and its relationship with the NOX family, as well as discuss some therapies proposed to slow down or control the disease's progression.

Structure of the core human NADPH oxidase NOX2

NOX2 is the prototypical member of the NADPH oxidase NOX superfamily and produces superoxide (O₂^•-), a key reactive oxygen species (ROS) that is essential in innate and adaptive immunity. Mutations that lead to deficiency in NOX2 activity correlate with increased susceptibility to bacterial and fungal infections, resulting in chronic granulomatous disease. The core of NOX2 is formed by a heterodimeric transmembrane complex composed of NOX2 (formerly gp91) and p22, but a detailed description of its structural architecture is lacking. Here, we present the structure of the human NOX2 core complex bound to a selective anti-NOX2 antibody fragment. The core complex reveals an intricate extracellular topology of NOX2, a four-transmembrane fold of the p22 subunit, and an extensive transmembrane interface which provides insights into NOX2 assembly and activation. Functional assays uncover an inhibitory activity of the 7G5 antibody mediated by internalization-dependent and internalization-independent mechanisms. Overall, our results provide insights into the NOX2 core complex architecture, disease-causing mutations, and potential avenues for selective NOX2 pharmacological modulation.

NADPH Oxidases in Aortic Aneurysms

Abdominal aortic aneurysms (AAAs) are a progressive dilation of the infrarenal aorta and are characterized by inflammatory cell infiltration, smooth muscle cell migration and proliferation, and degradation of the extracellular matrix. Oxidative stress and the production of reactive oxygen species (ROS) have been shown to play roles in inflammatory cell infiltration, and smooth muscle cell migration and apoptosis in AAAs. In this review, we discuss the principles of nicotinamide adenine dinucleotide phosphate oxidase (NADPH oxidase/NOX) signaling and activation. We also discuss the effects of some of the major mediators of NOX signaling in AAAs. Separately, we also discuss the influence of genetic or pharmacologic inhibitors of NADPH oxidases on experimental pre-clinical AAAs. Experimental evidence suggests that NADPH oxidases may be a promising future therapeutic target for developing pharmacologic treatment strategies for halting AAA progression or rupture prevention in the management of clinical AAAs.

Evolutionary and structural analyses of the NADPH oxidase family in eukaryotes reveal an initial calcium dependency

Reactive oxygen species are unstable molecules generated by the partial reduction of dioxygen. NADPH oxidases are a ubiquitous family of enzymes devoted to ROS production. They fuel an array of physiological roles in different species and are chemically demanding enzymes requiring FAD, NADPH and heme prosthetic groups in addition to either calcium or a various number of cytosolic mediators for activity. These activating partners are exclusive components that partition and distinguish the NOX members from one another. To gain insight into the evolution of these activating mechanisms, and in general in their evolutionary history, we conducted an in-depth phylogenetic analysis of the NADPH oxidase family in eukaryotes. We show that all characterized NOXs share a common ancestor, which comprised a fully formed catalytic unit. Regarding the activation mode, we identified calcium-dependency as the earliest form of NOX regulation. The protein-protein mode of regulation would have evolved more recently by gene-duplication with the concomitant loss of the EF-hands motif region. These more recent events generated the diversely activated NOX systems as observed in extant animals and fungi.

Redox Homeostasis in Thyroid Cancer: Implications in Na+/I- Symporter (NIS) Regulation

Radioiodine therapy (RAI) is a standard and effective therapeutic approach for differentiated thyroid cancers (DTCs) based on the unique capacity for iodide uptake and accumulation of the thyroid gland through the Na⁺/I⁻ symporter (NIS). However, around 5–15% of DTC patients may become refractory to radioiodine, which is associated with a worse prognosis. The loss of RAI avidity due to thyroid cancers is attributed to cell dedifferentiation, resulting in NIS repression by transcriptional and post-transcriptional mechanisms. Targeting the signaling pathways potentially involved in this process to induce de novo iodide uptake in refractory tumors is the rationale of “redifferentiation strategies”. Oxidative stress (OS) results from the imbalance between ROS production and depuration that favors a pro-oxidative environment, resulting from increased ROS production, decreased antioxidant defenses, or both. NIS expression and function are regulated by the cellular redox state in cancer and non-cancer contexts. In addition, OS has been implicated in thyroid tumorigenesis and thyroid cancer cell dedifferentiation. Here, we review the main aspects of redox homeostasis in thyrocytes and discuss potential ROS-dependent mechanisms involved in NIS repression in thyroid cancer.

TGF-β1 Disrupts redox balance in PCCL3 thyroid cell and is sexually dimorphic expressed in rat thyroid gland

Thyroid diseases are more prevalent in women, and this difference seems to be associated with the oxidative stress found in the thyroid of females. Thyroid NADPH Oxidase 4 (NOX4) was shown to respond to estrogen, which can also modulate TGF-β1, a potent stimulator of NOX4. This study aimed to investigate the effects of TGF-β1 on redox homeostasis parameters in the rat thyroid cell PCCL3 and the interrelationship between estrogen and TGF-β1. TGF-β1 treatment increased both intra- and extracellular ROS generation along with NOX4 expression and reduced GPX and catalase activities, extracellular H2O2 scavenging capacity, and reduced thiol content. TGF-β1 mRNA and protein expression are higher in female thyroid glands of rats in comparison to males. Moreover, 17β-estradiol treatment enhanced TGF-β1 mRNA in PCCL3 cells, decreased extracellular bioavailability but did not activate Smad pathway. Our data suggest that higher levels of TGF-β1 in females are potentially related to higher ROS availability which may be associated with the sex disparity in thyroid disorders.

Computational Models on Pathological Redox Signalling Driven by Pregnancy: A Review

Oxidative stress is associated with a myriad of diseases including pregnancy pathologies with long-term cardiovascular repercussions for both the mother and baby. Aberrant redox signalling coupled with deficient antioxidant defence leads to chronic molecular impairment. Abnormal placentation has been considered the primary source for reactive species; however, placental dysfunction has been deemed secondary to maternal cardiovascular maladaptation in pregnancy. While various therapeutic interventions, aimed at combating deregulated oxidative stress during pregnancy have shown promise in experimental models, they often result as inconclusive or detrimental in clinical trials, warranting the need for further research to identify candidates. The strengths and limitations of current experimental methods in redox research are discussed. Assessment of redox status and oxidative stress in experimental models and in clinical practice remains challenging; the state-of-the-art of computational models in this field is presented in this review, comparing static and dynamic models which provide functional information such as protein-protein interactions, as well as the impact of changes in molecular species on the redox-status of the system, respectively. Enhanced knowledge of redox biology in during pregnancy through computational modelling such as generation of Systems Biology Markup Language model which integrates existing models to a larger network in the context of placenta physiology.

Pharmacological inhibition of Ref-1 enhances the therapeutic sensitivity of papillary thyroid carcinoma to vemurafenib

The use of the BRAF inhibitor vemurafenib exhibits drug resistance in the treatment of thyroid cancer (TC), and finding more effective multitarget combination therapies may be an important solution. In the present study, we found strong correlations between Ref-1 high expression and BRAF mutation, lymph node metastasis, and TNM stage. The oxidative stress environment induced by structural activation of BRAF upregulates the expression of Ref-1, which caused intrinsic resistance of PTC to vemurafenib. Combination inhibition of the Ref-1 redox function and BRAF could enhance the antitumor effects of vemurafenib, which was achieved by blocking the action of Ref-1 on BRAF proteins. Furthermore, combination treatment could cause an overload of autophagic flux via excessive AMPK protein activation, causing cell senescence and cell death in vitro. And combined administration of Ref-1 and vemurafenib in vivo suppressed PTC cell growth and metastasis in a cell-based lung metastatic tumor model and xenogeneic subcutaneous tumor model. Collectively, our study provides evidence that Ref-1 upregulation via constitutive activation of BRAF in PTC contributes to intrinsic resistance to vemurafenib. Combined treatment with a Ref-1 redox inhibitor and a BRAF inhibitor could make PTC more sensitive to vemurafenib and enhance the antitumor effects of vemurafenib by further inhibiting the MAPK pathway and activating the excessive autophagy and related senescence process.

Generation of Reactive Oxygen Species (ROS) by Harmful Algal Bloom (HAB)-Forming Phytoplankton and Their Potential Impact on Surrounding Living Organisms

Most marine phytoplankton with relatively high ROS generation rates are categorized as harmful algal bloom (HAB)-forming species, among which Chattonella genera is the highest ROS-producing phytoplankton. In this review, we examined marine microalgae with ROS-producing activities, with focus on Chattonella genera. Several studies suggest that Chattonella produces superoxide via the activities of an enzyme similar to NADPH oxidase located on glycocalyx, a cell surface structure, while hydrogen peroxide is generated inside the cell by different pathways. Additionally, hydroxyl radical has been detected in Chattonella cell suspension. By the physical stimulation, such as passing through between the gill lamellas of fish, the glycocalyx is easily discharged from the flagellate cells and attached on the gill surface, where ROS are continuously produced, which might cause gill tissue damage and fish death. Comparative studies using several strains of Chattonella showed that ROS production rate and ichthyotoxicity of Chattonella is well correlated. Furthermore, significant levels of ROS have been reported in other raphidophytes and dinoflagellates, such as Cochlodinium polykrikoides and Karenia mikimotoi. Chattonella is the most extensively studied phytoplankton in terms of ROS production and its biological functions. Therefore, this review examined the potential ecophysiological roles of extracellular ROS production by marine microalgae in aquatic environment.

miR-199a Downregulation as a Driver of the NOX4/HIF-1α/VEGF-A Pathway in Thyroid and Orbital Adipose Tissues from Graves′ Patients

Graves’ disease (GD) is an autoimmune thyroiditis often associated with Graves’ orbitopathy (GO). GD thyroid and GO orbital fat share high oxidative stress (OS) and hypervascularization. We investigated the metabolic pathways leading to OS and angiogenesis, aiming to further decipher the link between local and systemic GD manifestations. Plasma and thyroid samples were obtained from patients operated on for multinodular goiters (controls) or GD. Orbital fats were from GO or control patients. The NADPH-oxidase-4 (NOX4)/HIF-1α/VEGF-A signaling pathway was investigated by Western blotting and immunostaining. miR-199a family expression was evaluated following quantitative real-time PCR and/or in situ hybridization. In GD thyroids and GO orbital fats, NOX4 was upregulated and correlated with HIF-1α stabilization and VEGF-A overexpression. The biotin assay identified NOX4, HIF-1α and VEGF-A as direct targets of miR-199a-5p in cultured thyrocytes. Interestingly, GD thyroids, GD plasmas and GO orbital fats showed a downregulation of miR-199a-3p/-5p. Our results also highlighted an activation of STAT-3 signaling in GD thyroids and GO orbital fats, a transcription factor known to negatively regulate miR-199a expression. We identified NOX4/HIF-1α/VEGF-A as critical actors in GD and GO. STAT-3-dependent regulation of miR-199a is proposed as a common driver leading to these events in GD thyroids and GO orbital fats.

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.

Cryo-EM: A new dawn in thyroid biology

The thyroid gland accumulates the rare dietary element iodine and incorporates it into iodinated thyroid hormones, utilising several tightly regulated reactions and molecular mechanisms. Thyroid hormones are essential in vertebrates and play a central role in many biological processes, such as development, thermogenesis and growth. The control of these functions is exerted through the binding of hormones to nuclear thyroid hormone receptors that rule the transcription of numerous metabolic genes. Over the last 50 years, thyroid biology has been studied extensively at the cellular and organismal levels, revealing its multiple clinical implications, yet, a complete molecular understanding is still lacking. This includes the atomic structures of crucial pathway components that would be needed to elucidate molecular mechanisms. Here we review the currently known protein structures involved in thyroid hormone synthesis, regulation, transport, and actions. We also highlight targets for future investigations that will significantly benefit from recent advances in macromolecular structure determination by electron cryo-microscopy (cryo-EM). As an example, we demonstrate how cryo-EM was crucial to obtain the structure of the large thyroid hormone precursor protein, thyroglobulin. We discuss modern cryo-EM compared to other structure determination methods and how an integrated structural and cell biological approach will help filling the molecular knowledge gap in our understanding of thyroid hormone metabolism. Together with clinical, cellular and high-throughput 'omics' studies, atomic structures of thyroid components will provide an important framework to map disease mutations and to interpret and predict thyroid phenotypes.

Dual oxidase 1 promotes antiviral innate immunity

Dual oxidase 1 (DUOX1) is an NADPH oxidase that is highly expre-ssed in respiratory epithelial cells and produces H2O2 in the airway lumen. While a line of prior in vitro observations suggested that DUOX1 works in partnership with an airway peroxidase, lactoperoxidase (LPO), to produce antimicrobial hypothiocyanite (OSCN-) in the airways, the in vivo role of DUOX1 in mammalian organisms has remained unproven to date. Here, we show that Duox1 promotes antiviral innate immunity in vivo. Upon influenza airway challenge, Duox1-/- mice have enhanced mortality, morbidity, and impaired lung viral clearance. Duox1 increases the airway levels of several cytokines (IL-1β, IL-2, CCL1, CCL3, CCL11, CCL19, CCL20, CCL27, CXCL5, and CXCL11), contributes to innate immune cell recruitment, and affects epithelial apoptosis in the airways. In primary human tracheobronchial epithelial cells, OSCN- is generated by LPO using DUOX1-derived H2O2 and inactivates several influenza strains in vitro. We also show that OSCN- diminishes influenza replication and viral RNA synthesis in infected host cells that is inhibited by the H2O2 scavenger catalase. Binding of the influenza virus to host cells and viral entry are both reduced by OSCN- in an H2O2-dependent manner in vitro. OSCN- does not affect the neuraminidase activity or morphology of the influenza virus. Overall, this antiviral function of Duox1 identifies an in vivo role of this gene, defines the steps in the infection cycle targeted by OSCN-, and proposes that boosting this mechanism in vivo can have therapeutic potential in treating viral infections.

NADPH Oxidases (NOX): An Overview from Discovery, Molecular Mechanisms to Physiology and Pathology

The reactive oxygen species (ROS)-producing enzyme NADPH oxidase (NOX) was first identified in the membrane of phagocytic cells. For many years, its only known role was in immune defense, where its ROS production leads to the destruction of pathogens by the immune cells. NOX from phagocytes catalyzes, via one-electron trans-membrane transfer to molecular oxygen, the production of the superoxide anion. Over the years, six human homologs of the catalytic subunit of the phagocyte NADPH oxidase were found: NOX1, NOX3, NOX4, NOX5, DUOX1, and DUOX2. Together with the NOX2/gp91phox component present in the phagocyte NADPH oxidase assembly itself, the homologs are now referred to as the NOX family of NADPH oxidases. NOX are complex multidomain proteins with varying requirements for assembly with combinations of other proteins for activity. The recent structural insights acquired on both prokaryotic and eukaryotic NOX open new perspectives for the understanding of the molecular mechanisms inherent to NOX regulation and ROS production (superoxide or hydrogen peroxide). This new structural information will certainly inform new investigations of human disease. As specialized ROS producers, NOX enzymes participate in numerous crucial physiological processes, including host defense, the post-translational processing of proteins, cellular signaling, regulation of gene expression, and cell differentiation. These diversities of physiological context will be discussed in this review. We also discuss NOX misregulation, which can contribute to a wide range of severe pathologies, such as atherosclerosis, hypertension, diabetic nephropathy, lung fibrosis, cancer, or neurodegenerative diseases, giving this family of membrane proteins a strong therapeutic interest.

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.

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.

Structure and genetic variants of thyroglobulin: Pathophysiological implications

Thyroglobulin (TG) plays a main role in the biosynthesis of thyroid hormones (TH), and, thus, it is involved in a wide range of vital functions throughout the life cycle of all vertebrates. Deficiency of TH production due to TG genetic variants causes congenital hypothyroidism (CH), with devastating consequences such as intellectual disability and impaired growth if untreated. To this day, 229 variations in the human TG gene have been identified while the 3D structure of TG has recently appeared. Although TG deficiency is thought to be of autosomal recessive inheritance, the introduction of massive sequencing platforms led to the identification of a variety of monoallelic TG variants (combined with mutations in other thyroid gene products) opening new questions regarding the possibility of oligogenic inheritance of the disease. In this review we discuss remarkable advances in the understanding of the TG architecture and the pathophysiology of CH associated with TG defects, providing new insights for the management of congenital disorders as well as counseling benefits for families with a history of TG abnormalities. Moreover, we summarize relevant aspects of TH synthesis within TG and offer an updated analysis of animal and cellular models of TG deficiency for pathophysiological studies of thyroid dyshormonogenesis while highlighting perspectives for new investigations. All in all, even though there has been sustained progress in understanding the role of TG in thyroid pathophysiology during the past 50 years, functional characterization of TG variants remains an important area of study for future advancement in the field.

Downregulation of DUOX1 function contributes to aging-related impairment of innate airway injury responses and accelerated senile emphysema

Aging is associated with a gradual loss of lung function due to increased cellular senescence, decreased regenerative capacity, and impaired innate host defense. One important aspect of innate airway epithelial host defense to nonmicrobial triggers is the secretion of alarmins such as IL-33 and activation of type 2 inflammation, which were previously found to depend on activation of the NADPH oxidase (NOX) homolog DUOX1, and redox-dependent signaling pathways that promote alarmin secretion. Here, we demonstrate that normal aging of C57BL/6J mice resulted in markedly decreased lung innate epithelial type 2 responses to exogenous triggers such as the airborne allergen Dermatophagoides pteronyssinus, which was associated with marked downregulation of DUOX1, as well as DUOX1-mediated redox-dependent signaling. DUOX1 deficiency was also found to accelerate age-related airspace enlargement and decline in lung function but did not consistently affect other features of lung aging such as senescence-associated inflammation. Intriguingly, observations of age-related DUOX1 downregulation and enhanced airspace enlargement due to DUOX1 deficiency in C57BL/6J mice, which lack a functional mitochondrial nicotinamide nucleotide transhydrogenase (NNT), were much less dramatic in C57BL/6NJ mice with normal NNT function, although the latter mice also displayed impaired innate epithelial injury responses with advancing age. Overall, our findings indicate a marked aging-dependent decline in (DUOX1-dependent) innate airway injury responses to external nonmicrobial triggers, but the impact of aging on DUOX1 downregulation and its significance for age-related senile emphysema development was variable between different C57BL6 substrains, possibly related to metabolic alterations due to differences in NNT function.

DUOX1 in mammalian disease pathophysiology

Dual oxidase 1 (DUOX1) is a member of the protein family of nicotinamide adenine dinucleotide phosphate (NADPH) oxidases. DUOX1 has several normal physiological, immunological, and biochemical functions in different parts of the body. Dysregulated oxidative metabolism interferes with various disease pathologies and numerous therapeutic options are based on targeting cellular redox pathways. DUOX1 forms an important enzymatic source of biological oxidants, and DUOX1 expression is frequently dysregulated in various diseases. While this review shortly addresses the biochemical and cellular properties and proposed physiological roles of DUOX1, its main purpose is to summarize the current knowledge with respect to the potential role of DUOX1 enzyme in disease pathology, especially in mammalian organisms. Although DUOX1 is normally prominently expressed in epithelial lineages, it is frequently silenced in epithelial-derived cancers by epigenetic mechanisms. While an abundance of information is available on DUOX1 transcription in different diseases, an increasing number of mechanistic studies indicate a causative relationship between DUOX1 function and disease pathophysiology. Additionally, specific functions of the DUOX1 maturation factor, DUOXA1, will also be addressed. Lastly, urgent and outstanding questions on the field of DUOX1 will be discussed that could provide valuable new diagnostic tools and novel therapeutic options.

The double-edged roles of ROS in cancer prevention and therapy

Reactive oxygen species (ROS) serve as cell signaling molecules generated in oxidative metabolism and are associated with a number of human diseases. The reprogramming of redox metabolism induces abnormal accumulation of ROS in cancer cells. It has been widely accepted that ROS play opposite roles in tumor growth, metastasis and apoptosis according to their different distributions, concentrations and durations in specific subcellular structures. These double-edged roles in cancer progression include the ROS-dependent malignant transformation and the oxidative stress-induced cell death. In this review, we summarize the notable literatures on ROS generation and scavenging, and discuss the related signal transduction networks and corresponding anticancer therapies. There is no doubt that an improved understanding of the sophisticated mechanism of redox biology is imperative to conquer cancer.

Radio-Iodide Treatment: From Molecular Aspects to the Clinical View

Simple Summary

This year marks the 80th commemoration of the first time that radio-iodide treatment (RAI) was used. RAI is one of the most effective targeted internal radiation anticancer therapies ever devised and it has been used for many decades, however, a thorough understanding of the underlying molecular mechanisms involved could greatly improve the success of this therapy. This is an in-depth innovative review focusing on the molecular mechanisms underlying radio-iodide therapy in thyroid cancer and how the alteration of these mechanisms affects the results in the clinic.

Abstract

Thyroid radio-iodide therapy (RAI) is one of the oldest known and used targeted therapies. In thyroid cancer, it has been used for more than eight decades and is still being used to improve thyroid tumor treatment to eliminate remnants after thyroid surgery, and tumor metastases. Knowledge at the molecular level of the genes/proteins involved in the process has led to improvements in therapy, both from the point of view of when, how much, and how to use the therapy according to tumor type. The effectiveness of this therapy has spread into other types of targeted therapies, and this has made sodium/iodide symporter (NIS) one of the favorite theragnostic tools. Here we focus on describing the molecular mechanisms involved in radio-iodide therapy and how the alteration of these mechanisms in thyroid tumor progression affects the diagnosis and results of therapy in the clinic. We analyze basic questions when facing treatment, such as: (1) how the incorporation of radioiodine in normal, tumor, and metastatic thyroid cells occurs and how it is regulated; (2) the pros and cons of thyroid hormonal deprivation vs. recombinant human Thyroid Stimulating Hormone (rhTSH) in radioiodine residence time, treatment efficacy, thyroglobulin levels and organification, and its influence on diagnostic imaging tests and metastasis treatment; and (3) the effect of stunning and the possible causes. We discuss the possible incorporation of massive sequencing data into clinical practice, and we conclude with a socioeconomical and clinical vision of the above aspects.

The Transcription Factor NF-κB Mediates Thyrotropin-Stimulated Expression of Thyroid Differentiation Markers

Background: The nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) transcription factor is a key regulator of cell survival, proliferation, and gene expression. Although activation of NF-κB signaling in thyroid follicular cells after thyrotropin (TSH) receptor (TSHR) engagement has been reported, the downstream signaling leading to NF-κB activation remains unexplored. Here, we sought to elucidate the mechanisms that regulate NF-κB signaling activation in response to TSH stimulation. Methods: Fisher rat-derived thyroid cell lines and primary cultures of NF-κB essential modulator (NEMO)-deficient mice thyrocytes were used as models. Signaling pathways leading to the activation of NF-κB were investigated by using chemical inhibitors and phospho-specific antibodies. Luciferase reporter gene assays and site-directed mutagenesis were used to monitor NF-κB-dependent gene transcriptional activity and the expression of thyroid differentiation markers was assessed by reverse transcription quantitative polymerase chain reaction and Western blot, respectively. Chromatin immunoprecipitation (ChIP) was carried out to investigate NF-κB subunit p65 DNA binding, and small interfering RNA (siRNA)-mediated gene knockdown approaches were used for studying gene function. Results: Using thyroid cell lines, we observed that TSH treatment leads to protein kinase C (PKC)-mediated canonical NF-κB p65 subunit nuclear expression. Moreover, TSH stimulation phosphorylated the kinase TAK-1, and its knockdown abolished TSH-induced NF-κB transcriptional activity. TSH induced the transcriptional activity of the NF-κB subunit p65 in a protein kinase A (PKA)-dependent phosphorylation at Ser-276. In addition, p65 phosphorylation at Ser-276 induced acetyl transferase p300 recruitment, leading to its acetylation on Lys-310 and thereby enhancing its transcriptional activity. Evaluation of the role played by NF-κB in thyroid physiology demonstrated that the canonical NF-κB inhibitor BAY 11-7082 reduced TSH-induced expression of thyroid differentiation markers. The involvement of NF-κB signaling in thyroid physiology was confirmed by assessing the TSH-induced gene expression in primary cultures of NEMO-deficient mice thyrocytes. ChIP and the knockdown experiments revealed that p65 is a nuclear effector of TSH actions, inducing the transcripcional expression of thyroid differentiation markers. Conclusions: Taken together, our results point to NF-κB being a pivotal mediator in the TSH-induced thyroid follicular cell differentiation, a relevant finding with potential physiological and pathophysiological implications.

Analysis of Mutation Spectra of 28 Pathogenic Genes Associated With Congenital Hypothyroidism in the Chinese Han Population

PURPOSE

Congenital hypothyroidism (CH) is the most common neonatal endocrine disease; its early detection ensures successful treatment and prevents complications. However, its molecular etiology remains unclear.

METHODS

We used second-generation sequencing to detect 28 pathogenic genes in 15 Chinese Han patients with CH in Shenzhen, China, and analyzed the genetic pattern of the pathogenic genes through their pedigrees. The pathogenicity assessment of gene mutations was performed based on the American College of Medical Genetics and Genomics (ACMG) classification guidelines, inheritance models, and published evidence.

RESULTS

Mutations in several target genes were identified in 14 of 15 patients (93.33%); these mutations were distributed in eight genes (DUOX2, DUOXA2, TPO, TG, TSHR, FOXE1, KDM6A, and POU1F1). DUOX2 exhibited the highest mutation frequency (44%, 11/25), followed by TPO (16%, 4/25) and TG (16%, 4/25). DUOX2 exhibited the highest biallelic mutation (7/15). Eight out of 25 variants verified by the ACMG guidelines were classified as pathogenic (P, category 1) or possibly pathogenic (LP, Type 2), namely six variants of DUOX2, and one variant of TPO and DUOXA2. Five new mutations were detected: one in DUOX2, which was located in the splicing region of mRNA (c.1575-1G>A), three new missense mutants, p.A291T, p.R169W, and p. S1237dup, and one new TPO missense variant c.2012G>T (p.W671L). The main criteria for determining the genotype-phenotype relationship were a diagnostic detection rate of 53.33% (8/15) and combination of three or more gene mutations.

CONCLUSIONS

CH gene mutations in the population may be mainly manifested in genes influencing thyroid hormone synthesis, such as DUOX2 compound heterozygous mutations, which exhibited a high detection rate. The clinical manifestations are diverse, and mainly include transient CH. Therefore, genetic screening is recommended for CH patients to determine the correlation between clinical phenotypes and gene mutations, which will assist in clinical management.

NOX Inhibitors: From Bench to Naxibs to Bedside

Reactive oxygen species (ROS) are ubiquitous metabolic products and important cellular signaling molecules that contribute to several biological functions. Pathophysiology arises when ROS are generated either in excess or in cell types or subcellular locations that normally do not produce ROS or when non-physiological types of ROS (e.g., superoxide instead of hydrogen peroxide) are formed. In the latter scenario, antioxidants were considered as the apparent remedy but, clinically, have consistently failed and even sometimes induced harm. The obvious reason for that is the non-selective ROS scavenging effects of antioxidants which interfere with both qualities of ROS, physiological and pathological. Therefore, it is essential to overcome this "antidote or neutralizer" strategy. We here review the most promising alternative approach by identifying the disease-relevant enzymatic sources of ROS, target these selectively, but leave physiological ROS signaling through other sources intact. Among all ROS sources, NADPH oxidases (NOX1-5 and DUOX1-2) stand out as their sole function is to produce ROS, whereas most other enzymatic sources only produce ROS as a by-product or upon biochemical uncoupling or damage. This qualifies NOXs as the main potential drug-target candidates in diseases associated with dysfunction in ROS signaling. As a reflection of this, the development of several NOX inhibitors has taken place. Recently, the WHO approved a new stem, "naxib," which refers to NADPH oxidase inhibitors, and thereby recognized NOX inhibitors as a new therapeutic class. This has been announced while clinical trials with the first-in-class compound, setanaxib (initially known as GKT137831) had been initiated. We also review the differences between the seven NOX family members in terms of structure and function in health and disease and then focus on the most advanced NOX inhibitors with an exclusive focus on clinically relevant validations and applications. Therapeutically relevant NADPH oxidase isoforms type 1, 2, 4, and 5 (NOX1, NOX2, NOX4, NOX5). Of note, NOX5 is not present in mice and rats and thus pre-clinically less studied. NOX2, formerly termed gp91^phox, has been correlated with many, too many, diseases and is rather relevant as genetic deficiency in chronic granulomatous disease (CGD), treated by gene therapy. Overproduction of ROS through NOX1, NOX4, and NOX5 leads to the indicated diseases states including atherosclerosis (red), a condition where NOX4 is surprisingly protective.