Discovery of GSK2795039, a Novel Small Molecule NADPH Oxidase 2 Inhibitor

Activation of receptor-independent fluid-phase pinocytosis promotes foamy monocyte formation in atherosclerotic mice

Atherosclerotic cardiovascular disease (ASCVD) is the leading cause of death worldwide. Clinical and experimental data demonstrated that circulating monocytes internalize plasma lipoproteins and become lipid-laden foamy cells in hypercholesterolemic subjects. This study was designed to identify the endocytic mechanisms responsible for foamy monocyte formation, perform functional and transcriptomic analysis of foamy and non-foamy monocytes relevant to ASCVD, and characterize specific monocyte subsets isolated from the circulation of normocholesterolemic controls and hypercholesterolemic patients. We hypothesized that activation of fluid-phase macropinocytosis contributes to foamy monocyte formation in vitro and in hypercholesterolemic mice in vivo. High resolution scanning electron microscopy (SEM) and quantification of FITC/TRITC-dextran internalization demonstrated macropinocytosis stimulation in human (THP-1) and wild type murine monocytes. Stimulation of macropinocytosis induced foamy monocyte formation in the presence of unmodified, native LDL (nLDL) and oxidized LDL (ox-LDL) in vitro. Genetic blockade of macropinocytosis (LysMCre+ Nhe1f/f) inhibited foamy monocyte formation in hypercholesterolemic mice in vivo and attenuated monocyte adhesion to atherosclerotic aortas ex vivo. Mechanistic studies identified NADPH oxidase 2 (Nox2)-derived superoxide anion (O2⋅-) as an important downstream signaling molecule stimulating macropinocytosis in monocytes. qRT-PCR identified CD36 as a major scavenger receptor that increases in response to lipid loading in monocytes and deletion of CD36 (Cd36-/-) inhibited foamy monocyte formation in hypercholesterolemic mice. Bulk RNA-sequencing characterized transcriptional differences between non-foamy and foamy monocytes versus macrophages. Finally, flow cytometry analysis of CD14 and CD16 expression demonstrated a significant increase in intermediate monocytes in hypercholesterolemic patients compared to normocholesterolemic controls. These results provide novel insights into the mechanisms of foamy monocyte formation and potentially identify new therapeutic targets for the treatment of atherosclerosis.

NOX2 in Alzheimer's and Parkinson's disease

Alzheimer's Disease (AD), and related dementias, represent a growing concern for the worldwide population given the increased numbers of people of advanced age. Marked by significant degradation of neurological tissues and critical processes, in addition to more specific factors such as the presence of amyloid plaques and neurofibrillary tangles in AD, robust discussion is ongoing regarding the precise mechanisms by which these diseases arise. One of the major interests in recent years has been the contribution of reactive oxygen species (ROS) and, particularly, the contribution of the ROS-generating NADPH Oxidase proteins. NADPH Oxidase 2 (NOX2), the prototypical member of the family, represents a particularly interesting target for study given its close association with vascular and inflammatory processes in all tissues, including the brain, and the association of these processes with AD development and progression. In this review, we discuss the most relevant and recent work regarding the contribution of NOX2 to AD progression in neuronal, microglial, and cerebrovascular signaling. Furthermore, we will discuss the most promising NOX2-targeted therapeutics for potential AD management and treatment.

Timing, initiation and function: An in-depth exploration of the interaction network among neutrophil extracellular traps related genes in acute pancreatitis

BACKGROUND

Exogenous inhibition of neutrophil extracellular traps (NETs) was believed to alleviate acute pancreatitis (AP). This study aimed to comprehensively explore the key biological behavior of NETs including timing and pathogenesis in AP by integrating of single cell RNA sequencing(scRNA-seq) and bulk RNA-seq.

METHODS

Differentially expressed NETs-related genes and the hub genes of NETs were screened by bulk RNA-seq. ScRNA-seq was used to identify the cell types in pancreas of AP mice and to depict the transcriptomic maps in neutrophils. The mouse AP models were build to verify the timing of initiation of NETs and underlying pathogenesis of damage on pancreas acinar cells.

RESULTS

Tlr4 and Ccl3 were screened for hub genes by bulk RNA-seq. The trajectory analysis of neutrophils showed that high expression of Ccl3, Cybb and Padi4 can be observed in the middle stage during AP. Macrophages might be essential in the biological behavior of neutrophils and NETs. Through animal models, we presented that extensive NETs structures were formed at mid-stage of inflammation, accompanied by more serious pancreas and lung damage. NETs might promote necroptosis and macrophage infiltration in AP, and the damage on pancreatic injury could be regulated by Tlr4 pathway. Ccl3 was considered to recruit neutrophils and promote NETs formation.

CONCLUSION

The findings explored the underlying timing and pathogenesis of NETs in AP for the first time, which provided gene targets for further studies.

TRPM2 channels are essential for regulation of cytokine production in lung interstitial macrophages

Interstitial macrophages (IMs) are essential for organ homeostasis, inflammation, and autonomous immune response in lung tissues, which are achieved through polarization to a pro-inflammatory M1 and an M2 state for tissue repair. Their remote parenchymal localization and low counts, however, are limiting factors for their isolation and molecular characterization of their specific role during tissue inflammation. We isolated viable murine IMs in sufficient quantities by coculturing them with stromal cells and analyzed mRNA expression patterns of transient receptor potential (TRP) channels in naïve and M1 polarized IMs after application of lipopolysaccharide (LPS) and interferon γ. M-RNAs for the second member of the melastatin family of TRP channels, TRPM2, were upregulated in the M1 state and functional channels were identified by their characteristic currents induced by ADP-ribose, its specific activator. Most interestingly, cytokine production and secretion of interleukin-1α (IL-1α), IL-6 and tumor necrosis factor-α in M1 polarized but TRPM2-deficient IMs was significantly enhanced compared to WT cells. Activation of TRPM2 channels by ADP-ribose (ADPR) released from mitochondria by ROS-produced H2O2 significantly increases plasma membrane depolarization, which inhibits production of reactive oxygen species by NADPH oxidases and reduces cytokine production and secretion in a negative feedback loop. Therefore, TRPM2 channels are essential for the regulation of cytokine production in M1-polarized murine IMs. Specific activation of these channels may promote an anti-inflammatory phenotype and prevent a harmful cytokine storm often observed in COVID-19 patients.

Type-I IFNs induce GBPs and lysosomal defense in hepatocytes to control malaria

Plasmodium parasites undergo development and replication within the hepatocytes before infecting the erythrocytes and initiating clinical malaria. Although type-I interferons (IFNs) are known to hinder Plasmodium infection within the liver, the underlying mechanisms remain unclear. Here, we describe two IFN-I-driven hepatocyte antimicrobial programs controlling liver-stage malaria. First, oxidative defense by NADPH oxidases 2 and 4 triggers a pathway of lysosomal fusion with the parasitophorous vacuole (PV) to help clear Plasmodium . Second, guanylate-binding protein (GBP) 1 disruption of the PV activates caspase-1 inflammasome, inducing pyroptosis to remove the infected host cells. Remarkably, both human and mouse hepatocytes enlist these cell-autonomous immune programs to eliminate Plasmodium ; their pharmacologic or genetic inhibition led to profound malarial susceptibility, and are essential in vivo . In addition to identifying the IFN-I-mediated cell-autonomous immune circuits controlling Plasmodium infection in the hepatocytes, this study extends our understanding of how non-immune cells are integral to protective immunity against malaria.

Leishmania infantum exploits the anti-ferroptosis effects of Nrf2 to escape cell death in macrophages

Macrophages are major host cells for the protozoan Leishmania parasite. Depending on their activation state, they either contribute to the detection and elimination of Leishmania spp. or promote parasite resilience. Here, we report that the activation of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) in macrophages plays a pivotal role in the progression of Leishmania infantum infection by controlling inflammation and redox balance of macrophages. We also highlight the involvement of the NOX2/reactive oxygen species (ROS) axis in early Nrf2 activation and, subsequently, prostaglandin E2 (PGE2)/EP2r signaling in the sustenance of Nrf2 activation upon infection. Moreover, we establish a ferroptosis-like process within macrophages as a cell death program of L. infantum and the protective effect of Nrf2 in macrophages against L. infantum death. Altogether, these results identify Nrf2 as a critical factor for the susceptibility of L. infantum infection, highlighting Nrf2 as a promising pharmacological target for the development of therapeutic approaches for the treatment of visceral leishmaniasis.

Targeting NADPH Oxidase as an Approach for Diabetic Bladder Dysfunction

Diabetic bladder dysfunction (DBD) is the most prevalent complication of diabetes mellitus (DM), affecting >50% of all patients. Currently, no specific treatment is available for this condition. In the early stages of DBD, patients typically complain of frequent urination and often have difficulty sensing when their bladders are full. Over time, bladder function deteriorates to a decompensated state in which incontinence develops. Based on studies of diabetic changes in the eye, kidney, heart, and nerves, it is now recognized that DM causes tissue damage by altering redox signaling in target organs. NADPH oxidase (NOX), whose sole function is the production of reactive oxygen species (ROS), plays a pivotal role in other well-known and bothersome diabetic complications. However, there is a substantial gap in understanding how NOX controls bladder function in health and the impact of NOX on DBD. The current review provides a thorough overview of the various NOX isoforms and their roles in bladder function and discusses the importance of further investigating the role of NOXs as a key contributor to DBD pathogenesis, either as a trigger and/or an effector and potentially as a target.

Downregulation of IL-8 and IL-10 by LRRC8A Inhibition through the NOX2-Nrf2-CEBPB Transcriptional Axis in THP-1-Derived M2 Macrophages

M2-polarized, tumor-associated macrophages (TAMs) produce pro-tumorigenic and angiogenic mediators, such as interleukin-8 (IL-8) and IL-10. Leucine-rich repeat-containing protein 8 members (LRRC8s) form volume-regulated anion channels and play an important role in macrophage functions by regulating cytokine and chemokine production. We herein examined the role of LRRC8A in IL-8 and IL-10 expression in THP-1-differentiated M2-like macrophages (M2-MACs), which are a useful tool for investigating TAMs. In M2-MACs, the pharmacological inhibition of LRRC8A led to hyperpolarizing responses after a transient depolarization phase, followed by a slight elevation in the intracellular concentration of Ca2+. Both the small interfering RNA-mediated and pharmacological inhibition of LRRC8A repressed the transcriptional expression of IL-8 and IL-10, resulting in a significant reduction in their secretion. The inhibition of LRRC8A decreased the nuclear translocation of phosphorylated nuclear factor-erythroid 2-related factor 2 (Nrf2), while the activation of Nrf2 reversed the LRRC8A inhibition-induced transcriptional repression of IL-8 and IL-10 in M2-MACs. We identified the CCAAT/enhancer-binding protein isoform B, CEBPB, as a downstream target of Nrf2 signaling in M2-MACs. Moreover, among several upstream candidates, the inhibition of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2) suppressed the Nrf2-CEBPB transcriptional axis in M2-MACs. Collectively, the present results indicate that the inhibition of LRRC8A repressed IL-8 and IL-10 transcription in M2-MACs through the NOX2-Nrf2-CEBPB axis and suggest that LRRC8A inhibitors suppress the IL-10-mediated evasion of tumor immune surveillance and IL-8-mediated metastasis and neovascularization in TAMs.

Human Neutrophils Couple Nitric Oxide Production and Extracellular Trap Formation in Allergic Asthma

Rationale: Nitric oxide (NO) is increased in the airways and serum of patients with allergic asthma, suggesting an important role in asthma. NO production has been widely attributed to the canonical inducible NO synthase. Much effort has been made to inhibit this enzyme, with two outcomes: no asthma improvement and partial NO reduction, suggesting the involvement of an inducible NO synthase-independent source. Objectives: Neutrophils produce NO under inflammatory conditions, and their role in asthma has been overlooked. The present study analyzes their possible role as sources of NO. Methods: Our hypothesis was tested in 99 allergic patients with intermittent bronchial asthma and 26 healthy donors. NO production by blood and sputum neutrophils in response to allergens, anti-IgE, and anti-IgE receptor antibodies was assessed by Griess reagent, flow cytometry, and confocal microscopy. The formation of extracellular traps (ETs) as a possible consequence of NO production was quantified by Western blot and confocal microscopy, and reactive oxygen species were assessed with luminol-enhanced chemiluminescence. Measurements and Main Results: Among blood and sputum granulocytes from patients with allergic asthma, only neutrophils produce NO by an IgE-dependent mechanism. This production is independent of NO synthase, but dependent on a reaction between L-arginine and reactive oxygen species from NOX2 (NADPH oxidase). NO and ETosis are induced in parallel, and NO amplifies ET formation, which is a key mediator in asthma. Conclusions: Our findings reveal a novel role of neutrophils as the unique allergen/IgE-dependent NO source in allergic asthma, enhancing ET formation. These results suggest that NO produced by neutrophils needs further consideration in the treatment of allergic asthma.

Eccentric contraction increases hydrogen peroxide levels and alters gene expression through Nox2 in skeletal muscle of male mice

Hydrogen peroxide (H2O2) is one of the key signaling factors regulating skeletal muscle adaptation to muscle contractions. Eccentric (ECC) and concentric (CONC) contractions drive different muscle adaptations with ECC resulting in greater changes. The present investigation tested the hypothesis that ECC produces higher cytosolic and mitochondrial H2O2 concentrations [H2O2] and alters gene expression more than CONC. Cytosolic and mitochondrial H2O2-sensitive fluorescent proteins, HyPer7 and MLS-HyPer7, were expressed in the anterior tibialis muscle of C57BL6J male mice. Before and for 60 min after either CONC or ECC (100 Hz, 50 contractions), [H2O2]cyto and [H2O2]mito were measured by in vivo fluorescence microscopy. RNA sequencing was performed in control (noncontracted), CONC, and ECC muscles to identify genes impacted by the contractions. [H2O2]cyto immediately after ECC was greater than after CONC (CONC: +6%, ECC: +11% vs. rest, P < 0.05) and remained higher for at least 60 min into recovery. In contrast, the elevation of [H2O2]mito was independent of the contraction modes (time; P < 0.0042, contraction mode; P = 0.4965). The impact of ECC on [H2O2]cyto was abolished by NADPH oxidase 2 (Nox2) inhibition (GSK2795039). Differentially expressed genes were not present after CONC or ECC + GSK but were found after ECC and were enriched for vascular development and apoptosis-related genes, among others. In conclusion, in mouse anterior tibialis, ECC, but not CONC, evokes a pronounced cytosolic H2O2 response, caused by Nox2, that is mechanistically linked to gene expression modifications.NEW & NOTEWORTHY This in vivo model successfully characterized the effects of eccentric (ECC) and concentric (CONC) contractions on cytosolic and mitochondrial [H2O2] in mouse skeletal muscle. Compared with CONC, ECC induced higher and more sustained [H2O2]cyto-an effect that was abolished by Nox2 inhibition. ECC-induced [H2O2]cyto elevations were requisite for altered gene expression.

In vivo upstream factors of mouse hepatotoxic mechanism with sustained hepatic glutathione depletion: Acetaminophen metabolite-erythrocyte adducts and splenic macrophage-generated reactive oxygen species

Investigation of acetaminophen (APAP)-induced liver damage recently indicated the significance of phagocytic NADPH oxidase (NOX)-derived reactive oxygen species (ROS) and ferroptosis in the liver. Here, we focused on phagocytosis by iron-containing erythrocyte-devouring splenic macrophages and explored upstream factors of known APAP hepatotoxic mechanisms in vivo. Splenectomy did not alter hepatic cytochrome P450 (CYP) 2E1 activity or hepatic glutathione (GSH) content. APAP injection into splenectomized mice almost completely suppressed increases in plasma alanine aminotransferase levels and centrilobular hepatic necrosis showing the spleen to be a critical tissue in APAP-induced liver damage. Hepatic GSH was recovered to approximately 50 % content at 8 h. In non-splenectomized mice, liver damage was dramatically suppressed by a sensitive redox probe (DCFH-DA), macrophage-depleting clodronate (CL), and a NOX2 inhibitor. APAP treatment resulted in markedly stronger fluorescence intensity from DCFH-DA due to excessive ROS around splenic macrophages, which was lost upon co-treatment with a CYP inhibitor and CL. Deformed erythrocytes disappeared in mice co-treated with DCFH-DA, CL, the NOX2 inhibitor, and the CYP inhibitor. Simultaneously, these four compounds significantly improved APAP-depleted GSH levels. The CYP inhibitor also prevented the formation of APAP-cell adducts in the blood and spleen. In the spleen, CL co-treatment markedly reduced the number of adducts. Splenic ferrous iron levels were significantly elevated by APAP. Therefore, we demonstrated that splenic macrophages devoured APAP metabolite-erythrocyte adducts and subsequently splenic macrophage-related ROS caused sustained hepatic GSH depletion and excessive erythrocyte deformation around 7 h. Our data indicate in vivo upstream factors of known APAP hepatotoxic mechanisms.

Targeting the Substrate for Atrial Fibrillation: JACC Review Topic of the Week

The identification of the pulmonary veins as a trigger source for atrial fibrillation (AF) has established pulmonary vein isolation (PVI) as a key target for AF ablation. However, PVI alone does not prevent recurrent AF in many patients, and numerous additional ablation strategies have failed to improve on PVI outcomes. This therapeutic limitation may be due, in part, to a failure to identify and intervene specifically on the pro-fibrillatory substrate within the atria and pulmonary veins. In this review paper, we highlight several emerging approaches with clinical potential that target atrial cardiomyopathy-the underlying anatomic, electrical, and/or autonomic disease affecting the atrium-in various stages of practice and investigation. In particular, we consider the evolving roles of risk factor modification, targeting of epicardial adipose tissue, tissue fibrosis, oxidative stress, and the inflammasome, along with aggressive early anti-AF therapy in AF management. Attention to combatting substrate development promises to improve outcomes in AF.

Bioenergetic and excitotoxic determinants of cofilactin rod formation

Cofilactin rods (CARs), which are 1:1 aggregates of cofilin-1 and actin, lead to neurite loss in ischemic stroke and other disorders. The biochemical pathways driving CAR formation are well-established, but how these pathways are engaged under ischemic conditions is less clear. Brain ischemia produces both ATP depletion and glutamate excitotoxicity, both of which have been shown to drive CAR formation in other settings. Here, we show that CARs are formed in cultured neurons exposed to ischemia-like conditions: oxygen-glucose deprivation (OGD), glutamate, or oxidative stress. Of these conditions, only OGD produced significant ATP depletion, showing that ATP depletion is not required for CAR formation. Moreover, the OGD-induced CAR formation was blocked by the glutamate receptor antagonists MK-801 and kynurenic acid; the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitors GSK2795039 and apocynin; as well as an ROS scavenger. The findings identify a biochemical pathway leading from OGD to CAR formation in which the glutamate release induced by energy failure leads to activation of neuronal glutamate receptors, which in turn activates NADPH oxidase to generate oxidative stress and CARs.

Impact of Surgery-Induced Myeloid-derived Suppressor Cells and the NOX2/ROS Axis on Postoperative Survival in Human Pancreatic Cancer

Preclinical studies imply that surgery triggers inflammation that may entail tumor outgrowth and metastasis. The potential impact of surgery-induced inflammation in human pancreatic cancer is insufficiently explored. This study included 17 patients with periampullary cancer [pancreatic ductal adenocarcinoma (PDAC) n = 14, ampullary carcinoma n = 2, cholangiocarcinoma n = 1] undergoing major pancreatic cancer surgery with curative intent. We analyzed the potential impact of preoperative and postoperative immune phenotypes and function on postoperative survival with >30 months follow-up. The surgery entailed prompt expansion of monocytic myeloid-derived suppressor cells (M-MDSC) that generated NOX2-derived reactive oxygen species (ROS). Strong induction of immunosuppressive M-MDSC after surgery predicted poor postoperative survival and coincided with reduced functionality of circulating natural killer (NK) cells. The negative impact of surgery-induced M-MDSC on survival remained significant in separate analysis of patients with PDAC. M-MDSC-like cells isolated from patients after surgery significantly suppressed NK cell function ex vivo, which was reversed by inhibition of NOX2-derived ROS. High NOX2 subunit expression within resected tumors from patients with PDAC correlated with poor survival whereas high expression of markers of cytotoxic cells associated with longer survival. The surgery-induced myeloid inflammation was recapitulated in vivo in a murine model of NK cell-dependent metastasis. Surgical stress thus induced systemic accumulation of M-MDSC-like cells and promoted metastasis of NK cell-sensitive tumor cells. Genetic or pharmacologic suppression of NOX2 reduced surgery-induced inflammation and distant metastasis in this model. We propose that NOX2-derived ROS generated by surgery-induced M-MDSC may be targeted for improved outcome after pancreatic cancer surgery.

SIGNIFICANCE

Pancreatic cancer surgery triggered pronounced accumulation of NOX2+ myeloid-derived suppressor cells that inhibited NK cell function and negatively prognosticated postoperative patient survival. We propose the targeting of M-MDSC as a conceivable strategy to reduce postoperative immunosuppression in pancreatic cancer.

Eugenol Inhibits Neutrophils Myeloperoxidase In Vitro and Attenuates LPS-Induced Lung Inflammation in Mice

Eugenol (Eug) is a polyphenol extracted from the essential oil of Syzygium aromaticum (L.) Merr. and Perry (Myrtaceae). The health benefits of eugenol in human diseases were proved in several studies. This work aims to evaluate the effect of eugenol on lung inflammatory disorders. For this, using human neutrophils, the antioxidant activity of eugenol was investigated in vitro. Furthermore, a model of LPS-induced lung injury in mice was used to study the anti-inflammatory effect of eugenol in vivo. Results showed that eugenol inhibits luminol-amplified chemiluminescence of resting neutrophils and after stimulation with N-formyl-methionyl-leucyl-phenylalanine (fMLF) peptide or phorbol myristate acetate (PMA). This effect was dose dependent and was significant from a low concentration of 0.1 µg/mL. Furthermore, eugenol inhibited myeloperoxidase (MPO) activity without affecting its degranulation. Eugenol has no scavenging effect on hydrogen peroxide (H2O2) and superoxide anion (O2-). Pretreatment of mice with eugenol prior to the administration of intra-tracheal LPS significantly reduced neutrophil accumulation in the bronchoalveolar lavage fluid (BALF) and decreased total proteins concentration. Moreover, eugenol clearly inhibited the activity of matrix metalloproteinases MMP-2 (21%) and MMP-9 (28%), stimulated by LPS administration. These results suggest that the anti-inflammatory effect of eugenol against the LPS-induced lung inflammation could be exerted via inhibiting myeloperoxidase and metalloproteinases activity. Thus, eugenol could be a promising molecule for the treatment of lung inflammatory diseases.

GKT137831 and hydrogen peroxide increase the release of 6-nitrodopamine from the human umbilical artery, rat-isolated right atrium, and rat-isolated vas deferens

Introduction: The human umbilical artery (HUA), rat-isolated right atrium, and rat-isolated vas deferens present a basal release of 6-nitrodopamine (6-ND). The basal release of 6-ND from these tissues was significantly decreased (but not abolished) when the tissues were pre-incubated with Nω-nitro-L-arginine methyl ester (L-NAME). Methods: In this study, the effect of the pharmacological modulation of the redox environment on the basal release of 6-ND was investigated. The basal release of 6-ND was measured using Liquid chromatography with tandem mass spectrometry (LC-MS/MS). Results and Discussion: Pre-incubation (30 min) of the tissues with GKT137831 (1 μM) caused a significant increase in the basal release of 6-ND from all tissues. In the HUA, pre-incubation with diphenyleneiodonium (DPI) (100 μM) also caused significant increases in the basal release of 6-ND. Preincubation of the HUA with hydrogen peroxide (H2O2) (100 μM) increased 6-ND basal release, whereas pre-incubation with catalase (1,000 U/mL) significantly decreased it. Pre-incubation of the HUA with superoxide dismutase (SOD) (250 U/mL; 30 min) also significantly increased the basal release of 6-ND. Preincubation of the HUA with either allopurinol (100 μM) or uric acid (1 mM) had no effect on the basal release of 6-ND. Pre-treatment of the HUA with L-NAME (100 μM) prevented the increase in the basal release of 6-ND induced by GKT137831, diphenyleneiodonium, and H2O2. The results obtained indicate a major role of endogenous H2O2 and peroxidases as modulators of 6- ND biosynthesis/release and a lack of peroxynitrite contribution.

Effect fraction of Bletilla striata (Thunb.) Reichb.f. alleviates LPS-induced acute lung injury by inhibiting p47phox/NOX2 and promoting the Nrf2/HO-1 signaling pathway

BACKGROUND & AIMS

The effect fraction of Bletilla striata (Thunb.) Reichb.f. (EFBS), a phenolic-rich extract, has significant protective effects on lipopolysaccharide (LPS)-induced acute lung injury (ALI), but its composition and molecular mechanisms are unclear. This study elucidated its chemical composition and possible protective mechanisms against LPS-induced ALI from an antioxidant perspective.

METHODS

EFBS was prepared by ethanol extraction, enriched by polyamide column chromatography, and characterized using ultra-performance liquid chromatography/time-of-flight mass spectrometry. The LPS-induced ALI model and the RAW264.7 model were used to evaluate the regulatory effects of EFBS on oxidative stress, and transcriptome analysis was performed to explore its possible molecular mechanism. Then, the pathway by which EFBS regulates oxidative stress was validated through inhibitor intervention, flow cytometry, quantitative PCR, western blotting, and immunofluorescence techniques.

RESULTS

A total of 22 compounds in EFBS were identified. The transcriptome analyses of RAW264.7 cells indicated that EFBS might reduce reactive oxygen species (ROS) production by inhibiting the p47phox/NADPH oxidase 2 (NOX2) pathway and upregulating the nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (HO-1) pathway. Both in vitro and in vivo data confirmed that EFBS significantly inhibited the expression and phosphorylation of p47phox protein, thereby weakening the p47phox/NOX2 pathway and reducing ROS production. EFBS significantly increased the expression of Nrf2 in primary peritoneal macrophages and lung tissue and promoted its nuclear translocation, dose-dependent increase in HO-1 levels, and enhancement of antioxidant activity. In vitro, both Nrf2 and HO-1 inhibitors significantly reduced the scavenging effects of EFBS on ROS, further confirming that EFBS exerts antioxidant effects at least partially by upregulating the Nrf2/HO-1 pathway.

CONCLUSIONS

EFBS contains abundant phenanthrenes and dibenzyl polyphenols, which can reduce ROS production by inhibiting the p47phox/NOX2 pathway and enhance ROS clearance activity by upregulating the Nrf2/HO-1 pathway, thereby exerting regulatory effects on oxidative stress and improving LPS-induced ALI.

Reactive oxygen species augment contractile responses of saphenous artery in 10-15-day-old but not adult rats: Substantial role of NADPH oxidases

Reactive oxygen species (ROS) produced by NADPH oxidases (NOX, a key source of ROS in vascular cells) are involved in the regulation of vascular tone, but this has been explored mainly for adult organisms. Importantly, the mechanisms of vascular tone regulation differ significantly in early postnatal ontogenesis and adulthood, while the vasomotor role of ROS in immature systemic arteries is poorly understood. We tested the hypothesis that the functional contribution of NADPH oxidase-derived ROS to the regulation of peripheral arterial tone is higher in the early postnatal period than in adulthood. We studied saphenous arteries from 10- to 15-day-old ("young") and 3- to 4-month-old ("adult") male rats using lucigenin-enhanced chemiluminescence, quantitative PCR, Western blotting, and isometric myography. We demonstrated that both basal and NADPH-stimulated superoxide anion radical (O2•-) production was significantly higher in the arteries from young in comparison to adult rats. Importantly, pan-inhibitor of NADPH oxidase VAS2870 (10 μM) reduced NADPH-induced O2•- production in arteries of young rats. Saphenous arteries of both young and adult rats demonstrated high levels of Nox2 and Nox4 mRNAs, while Nox1 and Nox3 mRNAs were not detected. The protein contents of NOX2 and NOX4 were significantly higher in arterial tissue of young compared to adult animals. Moreover, VAS2870 (10 μM) had no effect on methoxamine-induced contractile responses of adult arteries but decreased them significantly in young arteries; such effect of VAS2870 persisted after removal of the endothelium. Finally, NOX2 inhibitor GSK2795039 (10 μM), but not NOX1/4 inhibitor GKT137831 (10 μM) weakened methoxamine-induced contractile responses of arteries from young rats. Thus, ROS produced by NOX2 have a pronounced contractile influence in saphenous artery smooth muscle cells of young, but not adult rats, which is associated with the increased vascular content of NOX2 protein at this age.

NADPH oxidase 2 inhibitor GSK2795039 prevents doxorubicin-induced cardiac atrophy by attenuating cardiac sympathetic nerve terminal abnormalities and myocyte autophagy

Doxorubicin is widely used for the treatment of human cancer, but its clinical use is limited by a cumulative dose-dependent cardiotoxicity. However, the mechanism of doxorubicin-induced cardiac atrophy and failure remains to be fully understood. In this study, we tested whether the specific NADPH oxidase 2 (Nox2) inhibitor GSK2795039 attenuates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy, leading to the amelioration of cardiac atrophy and dysfunction in chronic doxorubicin-induced cardiomyopathy. Mice were randomized to receive saline, doxorubicin (2.5 mg/kg, every other day, 6 times) or doxorubicin plus GSK2795039 (2.5 mg/kg, twice a day, 9 weeks). Left ventricular (LV) total wall thickness and LV ejection fraction were decreased in doxorubicin-treated mice compared with saline-treated mice and the decreases were prevented by the treatment of the specific Nox2 inhibitor GSK2795039. The ratio of total heart weight to tibia length and myocyte cross-sectional area were decreased in doxorubicin-treated mice, and the decreases were attenuated by the GSK2795039 treatment. In doxorubicin-treated mice, myocardial Nox2 and 4-hydroxynonenal levels were increased, myocardial expression of GAP43, tyrosine hydroxylase and norepinephrine transporter, markers of sympathetic nerve terminals, was decreased, and these changes were prevented by the GSK2795039 treatment. The ratio of LC3 II/I, a marker of autophagy, and Atg5, Atg12 and Atg12-Atg5 conjugate proteins were increased in doxorubicin-treated mice, and the increases were attenuated by the GSK2795039 treatment. These findings suggest that inhibition of Nox2 by GSK2795039 attenuates cardiac sympathetic nerve terminal abnormalities and myocyte autophagy, thereby ameliorating cardiac atrophy and dysfunction after chronic doxorubicin treatment.

Alternating magnetic fields drive stimulation of gene expression via generation of reactive oxygen species

Magnetogenetics represents a method for remote control of cellular function. Previous work suggests that generation of reactive oxygen species (ROS) initiates downstream signaling. Herein, a chemical biology approach was used to elucidate further the mechanism of radio frequency-alternating magnetic field (RF-AMF) stimulation of a TRPV1-ferritin magnetogenetics platform that leads to Ca2+ flux. RF-AMF stimulation of HEK293T cells expressing TRPV1-ferritin resulted in ∼30% and ∼140% increase in intra- and extracellular ROS levels, respectively. Mutations to specific cysteine residues in TRPV1 responsible for ROS sensitivity eliminated RF-AMF driven Ca2+-dependent transcription of secreted embryonic alkaline phosphatase (SEAP). Using a non-tethered (to TRPV1) ferritin also eliminated RF-AMF driven SEAP production, and using specific inhibitors, ROS-activated TRPV1 signaling involves protein kinase C, NADPH oxidase, and the endoplasmic reticulum. These results suggest ferritin-dependent ROS activation of TRPV1 plays a key role in the initiation of magnetogenetics, and provides relevance for potential applications in medicine and biotechnology.

Nicotinamide adenine dinucleotide phosphate oxidase in pancreatic diseases: Mechanisms and future perspectives

Pancreatitis and pancreatic cancer (PC) stand as the most worrisome ailments affecting the pancreas. Researchers have dedicated efforts to unraveling the mechanisms underlying these diseases, yet their true nature continues to elude their grasp. Within this realm, oxidative stress is often believed to play a causal and contributory role in the development of pancreatitis and PC. Excessive accumulation of reactive oxygen species (ROS) can cause oxidative stress, and the key enzyme responsible for inducing ROS production in cells is nicotinamide adenine dinucleotide phosphate hydrogen oxides (NOX). NOX contribute to pancreatic fibrosis and inflammation by generating ROS that injure acinar cells, activate pancreatic stellate cells, and mediate macrophage polarization. Excessive ROS production occurs during malignant transformation and pancreatic carcinogenesis, creating an oxidative microenvironment that can cause abnormal apoptosis, epithelial to mesenchymal transition and genomic instability. Therefore, understanding the role of NOX in pancreatic diseases contributes to a more in-depth exploration of the exact pathogenesis of these diseases. In this review, we aim to summarize the potential roles of NOX and its mechanism in pancreatic disorders, aiming to provide novel insights into understanding the mechanisms underlying these diseases.

Evaluation of Reactive Oxygen Species Scavenging of Polydopamine with Different Nanostructures

Reactive oxygen species (ROS) play an important role in cellular metabolism and many oxidative stress-related diseases, while excessive accumulation of ROS will lead to genetic changes in cells and promote the occurrence of inflammatory diseases or cell death. Nature-inspired polydopamine (PDA) with tailored nanostructures emerges as an ROS scavenger and is considered as an effective approach to inflammation-related diseases. However, the effects of nanoparticle structure on PDA scavenging efficacy and efficiency remain uncovered. In this work, three typical PDA nanoparticles including solid PDA, mesoporous PDA, and hollow PDA are synthesized, and of which physiochemical properties are characterized. Furthermore, their ROS scavenging performance is investigated by in vitro evaluation of radical removal. Among the three nanoparticles, mesoporous PDA is demonstrated to have the highest scavenging capability, mainly due to its specific surface area. Finally, the study on three in vivo inflammation models is constructed. The results confirm that mesoporous PDA is the most potent scavenger of ROS and more effective in reducing reperfusion injury, improving renal function, and preventing periodontitis progression, respectively. Together with the good biosafety and biocompatibility profiles, PDA nanoparticles, mesoporous PDA in particular, can be a promising avenue of ROS scavenging in fight against the inflammatory diseases.

Addo S, Harris RA, Lucas R, Csányi G. SARS-CoV-2 Spike Protein Stimulates Macropinocytosis in Murine and Human Macrophages via PKC-NADPH Oxidase Signaling

Coronavirus disease 2019 (COVID-19) is an infectious disease caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). While recent studies have demonstrated that SARS-CoV-2 may enter kidney and colon epithelial cells by inducing receptor-independent macropinocytosis, it remains unknown whether this process also occurs in cell types directly relevant to SARS-CoV-2-associated lung pneumonia, such as alveolar epithelial cells and macrophages. The goal of our study was to investigate the ability of SARS-CoV-2 spike protein subunits to stimulate macropinocytosis in human alveolar epithelial cells and primary human and murine macrophages. Flow cytometry analysis of fluid-phase marker internalization demonstrated that SARS-CoV-2 spike protein subunits S1, the receptor-binding domain (RBD) of S1, and S2 stimulate macropinocytosis in both human and murine macrophages in an angiotensin-converting enzyme 2 (ACE2)-independent manner. Pharmacological and genetic inhibition of macropinocytosis substantially decreased spike-protein-induced fluid-phase marker internalization in macrophages both in vitro and in vivo. High-resolution scanning electron microscopy (SEM) imaging confirmed that spike protein subunits promote the formation of membrane ruffles on the dorsal surface of macrophages. Mechanistic studies demonstrated that SARS-CoV-2 spike protein stimulated macropinocytosis via NADPH oxidase 2 (Nox2)-derived reactive oxygen species (ROS) generation. In addition, inhibition of protein kinase C (PKC) and phosphoinositide 3-kinase (PI3K) in macrophages blocked SARS-CoV-2 spike-protein-induced macropinocytosis. To our knowledge, these results demonstrate for the first time that SARS-CoV-2 spike protein subunits stimulate macropinocytosis in macrophages. These results may contribute to a better understanding of SARS-CoV-2 infection and COVID-19 pathogenesis.

Role of Mitochondrial ROS for Calcium Alternans in Atrial Myocytes

Atrial calcium transient (CaT) alternans is defined as beat-to-beat alternations in CaT amplitude and is causally linked to atrial fibrillation (AF). Mitochondria play a significant role in cardiac excitation-contraction coupling and Ca signaling through redox environment regulation. In isolated rabbit atrial myocytes, ROS production is enhanced during CaT alternans, measured by fluorescence microscopy. Exogenous ROS (tert-butyl hydroperoxide) enhanced CaT alternans, whereas ROS scavengers (dithiothreitol, MnTBAP, quercetin, tempol) alleviated CaT alternans. While the inhibition of cellular NADPH oxidases had no effect on CaT alternans, interference with mitochondrial ROS (ROSm) production had profound effects: (1) the superoxide dismutase mimetic MitoTempo diminished CaT alternans and shifted the pacing threshold to higher frequencies; (2) the inhibition of cyt c peroxidase by SS-31, and inhibitors of ROSm production by complexes of the electron transport chain S1QEL1.1 and S3QEL2, decreased the severity of CaT alternans; however (3) the impairment of mitochondrial antioxidant defense by the inhibition of nicotinamide nucleotide transhydrogenase with NBD-Cl and thioredoxin reductase-2 with auranofin enhanced CaT alternans. Our results suggest that intact mitochondrial antioxidant defense provides crucial protection against pro-arrhythmic CaT alternans. Thus, modulating the mitochondrial redox state represents a potential therapeutic approach for alternans-associated arrhythmias, including AF.

Clinical Impact and Mechanisms of Nonatherosclerotic Vascular Aging: The New Kid to Be Blocked

Ischemic cardiovascular disease and stroke remain the leading cause of global morbidity and mortality. During aging, protective mechanisms in the body gradually deteriorate, resulting in functional, structural, and morphologic changes that affect the vascular system. Because atherosclerotic plaques are not always present along with these alterations, we refer to this kind of vascular aging as nonatherosclerotic vascular aging (NAVA). To maintain proper vascular function during NAVA, it is important to preserve intracellular signalling, prevent inflammation, and block the development of senescent cells. Pharmacologic interventions targeting these components are potential therapeutic approaches for NAVA, with a particular emphasis on inflammation and senescence. This review provides an overview of the pathophysiology of vascular aging and explores potential pharmacotherapies that can improve the function of aged vasculature, focusing on NAVA.

NOX-induced oxidative stress is a primary trigger of major neurodegenerative disorders

Neurodegenerative diseases (NDDs) causing cognitive impairment and dementia are difficult to treat due to the lack of understanding of primary initiating factors. Meanwhile, major sporadic NDDs share many risk factors and exhibit similar pathologies in their early stages, indicating the existence of common initiation pathways. Glucose hypometabolism associated with oxidative stress is one such primary, early and shared pathology, and a likely major cause of detrimental disease-associated cascades; targeting this common pathology may therefore be an effective preventative strategy for most sporadic NDDs. However, its exact cause and trigger remain unclear. Recent research suggests that early oxidative stress caused by NADPH oxidase (NOX) activation is a shared initiating mechanism among major sporadic NDDs and could prove to be the long-sought ubiquitous NDD trigger. We focus on two major NDDs - Alzheimer's disease (AD) and Parkinson's disease (PD), as well as on acquired epilepsy which is an increasingly recognized comorbidity in NDDs. We also discuss available data suggesting the relevance of the proposed mechanisms to other NDDs. We delve into the commonalities among these NDDs in neuroinflammation and NOX involvement to identify potential therapeutic targets and gain a deeper understanding of the underlying causes of NDDs.

Targeting NOX2 with Bivalent Small-Molecule p47phox-p22phox Inhibitors

Nicotinamide adenine dinucleotide phosphate oxidase isoform 2 (NOX2) is an enzymatic complex whose function is the regulated generation of reactive oxygen species (ROS). NOX2 activity is central to redox signaling events and antibacterial response, but excessive ROS production by NOX2 leads to oxidative stress and inflammation in a range of diseases. The protein-protein interaction between the NOX2 subunits p47phox and p22phox is essential for NOX2 activation, thus p47phox is a potential drug target. Previously, we identified 2-aminoquinoline as a fragment hit toward p47phoxSH3A-B and converted it to a bivalent small-molecule p47phox-p22phox inhibitor (Ki = 20 μM). Here, we systematically optimized the bivalent compounds by exploring linker types and positioning as well as substituents on the 2-aminoquinoline part and characterized the bivalent binding mode with biophysical methods. We identified several compounds with submicromolar binding affinities and cellular activity and thereby demonstrated that p47phox can be targeted by potent small molecules.

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.

Host-derived reactive oxygen species trigger activation of the Candida albicans transcription regulator Rtg1/3

The signals that denote mammalian host environments and dictate the activation of signaling pathways in human-associated microorganisms are often unknown. The transcription regulator Rtg1/3 in the human fungal pathogen Candida albicans is a crucial determinant of host colonization and pathogenicity. Rtg1/3's activity is controlled, in part, by shuttling the regulator between the cytoplasm and nucleus of the fungus. The host signal(s) that Rtg1/3 respond(s) to, however, have remained unclear. Here we report that neutrophil-derived reactive oxygen species (ROS) direct the subcellular localization of this C. albicans transcription regulator. Upon engulfment of Candida cells by human or mouse neutrophils, the regulator shuttles to the fungal nucleus. Using genetic and chemical approaches to disrupt the neutrophils' oxidative burst, we establish that the oxidants produced by the NOX2 complex-but not the oxidants generated by myeloperoxidase-trigger Rtg1/3's migration to the nucleus. Furthermore, screening a collection of C. albicans kinase deletion mutants, we implicate the MKC1 signaling pathway in the ROS-dependent regulation of Rtg1/3 in this fungus. Finally, we show that Rtg1/3 contributes to C. albicans virulence in the nematode Caenorhabditis elegans in an ROS-dependent manner as the rtg1 and rtg3 mutants display virulence defects in wild-type but not in ROS deficient worms. Our findings establish NOX2-derived ROS as a key signal that directs the activity of the pleiotropic fungal regulator Rtg1/3.

Novel NADPH Oxidase-2 Inhibitors as Potential Anti-Inflammatory and Neuroprotective Agents

A family of seven NADPH oxidase enzymes (Nox1-5, Duox1-2) has been implicated in a variety of diseases, including inflammatory lung diseases, neurodegenerative diseases, cardiovascular diseases, and cancer. Here, we report the results of our studies aimed at developing novel brain-permeable Nox2 inhibitors with potential application as neuroprotective agents. Using cell-based assays, we identified a novel Nox2 inhibitor, TG15-132, that prevents PMA-stimulated oxygen consumption and reactive oxygen species (superoxide radical anion and hydrogen peroxide) formation upon acute treatment in differentiated HL60 cells. Long-term treatment with TG15-132 attenuates the induction of genes encoding Nox2 subunits, several inflammatory cytokines, and iNOS in differentiated THP-1 cells. Moreover, TG15-132 shows a relatively long plasma half-life (5.6 h) and excellent brain permeability, with a brain-to-plasma ratio (>5-fold) in rodent models. Additionally, TG15-132 does not cause any toxic effects on vital organs or blood biomarkers of toxicity in mice upon chronic dosing for seven days. We propose that TG15-132 may be used as a Nox2 inhibitor and a potential neuroprotective agent, with possible further structural modifications to increase its potency.

Effects of ROS pathway inhibitors and NADH and FADH2 linked substrates on mitochondrial bioenergetics and ROS emission in the heart and kidney cortex and outer medulla

Mitochondria are major sources of reactive oxygen species (ROS), which play important roles in both physiological and pathological processes. However, the specific contributions of different ROS production and scavenging components in the mitochondria of metabolically active tissues such as heart and kidney cortex and outer medulla (OM) are not well understood. Therefore, the goal of this study was to determine contributions of different ROS production and scavenging components and provide detailed comparisons of mitochondrial respiration, bioenergetics, ROS emission between the heart and kidney cortex and OM using tissues obtained from the same Sprague-Dawley rat under identical conditions and perturbations. Specifically, data were obtained using both NADH-linked substrate pyruvate + malate and FADH2-linked substrate succinate followed by additions of inhibitors of different components of the electron transport chain (ETC) and oxidative phosphorylation (OxPhos) and other ROS production and scavenging systems. Currently, there is limited data available for the mitochondria of kidney cortex and OM, the two major energy-consuming tissues in the body only next to the heart, and scarce quantitative information on the interplay between mitochondrial ROS production and scavenging systems in the three tissues. The findings from this study demonstrate significant differences in mitochondrial respiratory and bioenergetic functions and ROS emission among the three tissues. The results quantify the rates of ROS production from different complexes of the ETC, identify the complexes responsible for variations in mitochondrial membrane depolarization and regulations of ROS production, and quantify the contributions of ROS scavenging enzymes towards overall mitochondrial ROS emission. These findings advance our fundamental knowledge of tissue-specific and substrate-dependent mitochondrial respiratory and bioenergetic functions and ROS emission. This is important given the critical role that excess ROS production, oxidative stress, and mitochondrial dysfunction in the heart and kidney cortex and OM play in the pathogenesis of cardiovascular and renal diseases, including salt-sensitive hypertension.

New NADPH Oxidase 2 Inhibitors Display Potent Activity against Oxidative Stress by Targeting p22phox-p47phox Interactions

NADPH oxidase (NOX2) is responsible for reactive oxygen species (ROS) production in neutrophils and has been recognized as a key mediator in inflammatory and cardiovascular pathologies. Nevertheless, there is a lack of specific NOX2 pharmacological inhibitors. In medicinal chemistry, heterocyclic compounds are essential scaffolds for drug design, and among them, indole is a very versatile pharmacophore. We tested the hypothesis that indole heteroaryl-acrylonitrile derivatives may serve as NOX2 inhibitors by evaluating the capacity of 19 of these molecules to inhibit NOX2-derived ROS production in human neutrophils (HL-60 cells). Of these compounds, C6 and C14 exhibited concentration-dependent inhibition of NOX2 (IC₅₀~1 µM). These molecules also reduced NOX2-derived oxidative stress in cardiomyocytes and prevented cardiac damage induced by ischemia-reperfusion. Compound C6 significantly reduced the membrane translocation of p47^phox, a cytosolic subunit that is required for NOX2 activation. Molecular docking analyses of the binding modes of these molecules with p47^phox indicated that C6 and C14 interact with specific residues in the inner part of the groove of p47^phox, the binding cavity for p22^phox. This combination of methods showed that novel indole heteroaryl acrylonitriles represent interesting lead compounds for developing specific and potent NOX2 inhibitors.

Unlocking the power of NOX2: A comprehensive review on its role in immune regulation

Reactive oxygen species (ROS) are a family of highly reactive molecules with numerous, often pleiotropic functions within the cell and the organism. Due to their potential to destroy biological structures such as membranes, enzymes and organelles, ROS have long been recognized as harmful yet unavoidable by-products of cellular metabolism leading to "oxidative stress" unless counterbalanced by cellular anti-oxidative defense mechanisms. Phagocytes utilize this destructive potential of ROS released in high amounts to defend against invading pathogens. In contrast, a regulated and fine-tuned release of "signaling ROS" (sROS) provides essential intracellular second messengers to modulate central aspects of immunity, including antigen presentation, activation of antigen presenting cells (APC) as well as the APC:T cell interaction during T cell activation. This regulated release of sROS is foremost attributed to the specialized enzyme NADPH-oxidase (NOX) 2 expressed mainly in myeloid cells such as neutrophils, macrophages and dendritic cells (DC). NOX-2-derived sROS are primarily involved in immune regulation and mediate protection against autoimmunity as well as maintenance of self-tolerance. Consequently, deficiencies in NOX2 not only result in primary immune-deficiencies such as Chronic Granulomatous Disease (CGD) but also lead to auto-inflammatory diseases and autoimmunity. A comprehensive understanding of NOX2 activation and regulation will be key for successful pharmaceutical interventions of such ROS-related diseases in the future. In this review, we summarize recent progress regarding immune regulation by NOX2-derived ROS and the consequences of its deregulation on the development of immune disorders.

NOX2 inhibition stabilizes vulnerable plaques by enhancing macrophage efferocytosis via MertK/PI3K/AKT pathway

NADPH oxidases 2 (NOX2) is the main source of ROS in macrophages, which plays a critical role in the formation of atherosclerosis. However, effects of NOX2 inhibition on established vulnerable plaques and the potential role involved remain unclear. The purpose of this study is to investigate the latent mechanism of NOX2-triggered vulnerable plaque development. We generated a vulnerable carotid plaque model induced by carotid branch ligation and renal artery constriction, combined with a high-fat diet in ApoE^-/- mice. NOX2 specific inhibitor, GSK2795039 (10 mg/kg/day by intragastric administration for 8 weeks) significantly prevented vulnerable plaque, evaluated by micro-ultrasound imaging parameters. A profile of less intraplaque hemorrhage detection, increased collagen-lipid ratio, fibrous cap thickness and less necrotic core formation were also found in GSK2795039 treated group. Mechanistically, reduced 4-HNE, in situ lesional apoptosis and enhanced efferocytosis were involved in mice treated with NOX2 inhibitor. Further analysis in mouse macrophages confirmed the role of NOX2 inhibition in enhancing macrophage efferocytosis by regulating the MertK/PI3K/AKT pathway. In summary, our data defined previously few recognized roles of NOX2 in vulnerable plaque pathogenesis and an undescribed NOX2-ROS-MerTK axis acts involved in regulating macrophage efferocytosis in the formation of rupture-prone vulnerable plaques.

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.

Development of an improved and specific inhibitor of NADPH oxidase 2 to treat traumatic brain injury

NADPH oxidases (NOX's), and the reactive oxygen species (ROS) they produce, play an important role in host defense, thyroid hormone synthesis, apoptosis, gene regulation, angiogenesis and other processes. However, overproduction of ROS by these enzymes is associated with cardiovascular disease, fibrosis, traumatic brain injury (TBI) and other diseases. Structural similarities between NOX's have complicated development of specific inhibitors. Here, we report development of NCATS-SM7270, a small molecule optimized from GSK2795039, that inhibited NOX2 in primary human and mouse granulocytes. NCATS-SM7270 specifically inhibited NOX2 and had reduced inhibitory activity against xanthine oxidase in vitro. We also studied the role of several NOX isoforms during mild TBI (mTBI) and demonstrated that NOX2 and, to a lesser extent, NOX1 deficient mice are protected from mTBI pathology, whereas injury is exacerbated in NOX4 knockouts. Given the pathogenic role played by NOX2 in mTBI, we treated mice transcranially with NCATS-SM7270 after injury and revealed a dose-dependent reduction in mTBI induced cortical cell death. This inhibitor also partially reversed cortical damage observed in NOX4 deficient mice following mTBI. These data demonstrate that NCATS-SM7270 is an improved and specific inhibitor of NOX2 capable of protecting mice from NOX2-dependent cell death associated with mTBI.

Microglial reprogramming by Hv1 antagonism protects neurons from inflammatory and glutamate toxicity

Although the precise mechanisms determining the neurotoxic or neuroprotective activation phenotypes in microglia remain poorly characterized, metabolic changes in these cells appear critical for these processes. As cellular metabolism can be tightly regulated by changes in intracellular pH, we tested whether pharmacological targeting of the microglial voltage-gated proton channel 1 (Hv1), an important regulator of intracellular pH, is critical for activated microglial reprogramming. Using a mouse microglial cell line and mouse primary microglia cultures, either alone, or co-cultured with rat cerebrocortical neurons, we characterized in detail the microglial activation profile in the absence and presence of Hv1 inhibition. We observed that activated microglia neurotoxicity was mainly attributable to the release of tumor necrosis factor alpha, reactive oxygen species, and zinc. Strikingly, pharmacological inhibition of Hv1 largely abrogated inflammatory neurotoxicity not only by reducing the production of cytotoxic mediators but also by promoting neurotrophic molecule production and restraining excessive phagocytic activity. Importantly, the Hv1-sensitive change from a pro-inflammatory to a neuroprotective phenotype was associated with metabolic reprogramming, particularly via a boost in NADH availability and a reduction in lactate. Most critically, Hv1 antagonism not only reduced inflammatory neurotoxicity but also promoted microglia-dependent neuroprotection against a separate excitotoxic injury. Our results strongly suggest that Hv1 blockers may provide an important therapeutic tool against a wide range of inflammatory neurodegenerative disorders.

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

Background

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

Results

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

Conclusions

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

Blockade of ROS production inhibits oncogenic signaling in acute myeloid leukemia and amplifies response to precision therapies

Mutations in the type III receptor tyrosine kinase FLT3 are frequent in patients with acute myeloid leukemia (AML) and are associated with a poor prognosis. AML is characterized by the overproduction of reactive oxygen species (ROS), which can induce cysteine oxidation in redox-sensitive signaling proteins. Here, we sought to characterize the specific pathways affected by ROS in AML by assessing oncogenic signaling in primary AML samples. The oxidation or phosphorylation of signaling proteins that mediate growth and proliferation was increased in samples from patient subtypes with FLT3 mutations. These samples also showed increases in the oxidation of proteins in the ROS-producing Rac/NADPH oxidase-2 (NOX2) complex. Inhibition of NOX2 increased the apoptosis of FLT3-mutant AML cells in response to FLT3 inhibitors. NOX2 inhibition also reduced the phosphorylation and cysteine oxidation of FLT3 in patient-derived xenograft mouse models, suggesting that decreased oxidative stress reduces the oncogenic signaling of FLT3. In mice grafted with FLT3 mutant AML cells, treatment with a NOX2 inhibitor reduced the number of circulating cancer cells, and combining FLT3 and NOX2 inhibitors increased survival to a greater extent than either treatment alone. Together, these data raise the possibility that combining NOX2 and FLT3 inhibitors could improve the treatment of FLT3 mutant AML.

GSK2795039 prevents RIP1-RIP3-MLKL-mediated cardiomyocyte necroptosis in doxorubicin-induced heart failure through inhibition of NADPH oxidase-derived oxidative stress

Doxorubicin (DOX), which is widely used for the treatment of cancer, induces cardiomyopathy associated with NADPH oxidase-derived reactive oxygen species. GSK2795039 is a novel small molecular NADPH oxidase 2 (Nox2) inhibitor. In this study, we investigated whether GSK2795039 prevents receptor-interacting protein kinase 1 (RIP1)-RIP3-mixed lineage kinase domain-like protein (MLKL)-mediated cardiomyocyte necroptosis in DOX-induced heart failure through NADPH oxidase inhibition. Eight-week old mice were randomly divided into 4 groups: control, GSK2795039, DOX and DOX plus GSK2795039. H9C2 cardiomyocytes were treated with DOX and GSK2795039. In DOX-treated mice, the survival rate was reduced, left ventricular (LV) end-systolic dimension was increased and LV fractional shortening was decreased, and these alterations were attenuated by the GSK2795039 treatment. GSK2795039 inhibited not only myocardial NADPH oxidase subunit gp91phox (Nox2) protein, but also p22phox, p47phox and p67phox proteins and prevented oxidative stress 8-hydroxy-2'-deoxyguanosine levels in DOX-treated mice. RIP3 protein and phosphorylated RIP1 (p-RIP1), p-RIP3 and p-MLKL proteins, reflective of their respective kinase activities, markers of necroptosis, were markedly increased in DOX-treated mice, and the increases were prevented by GSK2795039. GSK2795039 prevented the increases in serum lactate dehydrogenase and myocardial fibrosis in DOX-treated mice. Similarly, in DOX-treated cardiomyocytes, GSK2795039 improved cell viability, attenuated apoptosis and necrosis and prevented the increases in p-RIP1, p-RIP3 and p-MLKL expression. In conclusion, GSK2795039 prevents RIP1-RIP3-MLKL-mediated cardiomyocyte necroptosis through inhibition of NADPH oxidase-derived oxidative stress, leading to the improvement of myocardial remodeling and function in DOX-induced heart failure. These findings suggest that GSK2795039 may have implications for the treatment of DOX-induced cardiomyopathy.

A Cyclodiaryliodonium NOX Inhibitor for the Treatment of Pancreatic Cancer via Enzyme-Activatable Targeted Delivery by Sulfated Glycosaminoglycan Derivatives

Pancreatic cancer renders a principal cause of cancer mortalities with a dismal prognosis, lacking sufficiently safe and effective therapeutics. Here, diversified cyclodiaryliodonium (CDAI) NADPH oxidase (NOX) inhibitors are rationally designed with tens of nanomolar optimal growth inhibition, and CD44-targeted delivery is implemented using synthesized sulfated glycosaminoglycan derivatives. The self-assembled nanoparticle-drug conjugate (NDC) enables hyaluronidase-activatable controlled release and facilitates cellular trafficking. NOX inhibition reprograms the metabolic phenotype by simultaneously impairing mitochondrial respiration and glycolysis. Moreover, the NDC selectively diminishes non-mitochondrial reactive oxygen species (ROS) but significantly elevates cytotoxic ROS through mitochondrial membrane depolarization. Transcriptomic profiling reveals perturbed p53, NF-κB, and GnRH signaling pathways interconnected with NOX inhibition. After being validated in patient-derived pancreatic cancer cells, the anticancer efficacy is further verified in xenograft mice bearing heterotopic and orthotopic pancreatic tumors, with extended survival and ameliorated systemic toxicity. It is envisaged that the translation of cyclodiaryliodonium inhibitors with an optimized molecular design can be expedited by enzyme-activatable targeted delivery with improved pharmacokinetic profiles and preserved efficacy.

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.

NOX2 inhibition enables retention of the circadian clock in BV2 microglia and primary macrophages

Introduction

Sustained neuroinflammation is a major contributor to the progression of neurodegenerative diseases such as Alzheimer's (AD) and Parkinson's (PD) diseases. Neuroinflammation, like other cellular processes, is affected by the circadian clock. Microglia, the resident immune cells in the brain, act as major contributors to neuroinflammation and are under the influence of the circadian clock. Microglial responses such as activation, recruitment, and cytokine expression are rhythmic in their response to various stimuli. While the link between circadian rhythms and neuroinflammation is clear, significant gaps remain in our understanding of this complex relationship. To gain a greater understanding of this relationship, the interaction between the microglial circadian clock and the enzyme NADPH Oxidase Isoform 2 (NOX2) was studied; NOX2 is essential for the production of reactive oxygen species (ROS) in oxidative stress, an integral characteristic of neuroinflammation.

Methods

BV2 microglia were examined over circadian time, demonstrating oscillations of the clock genes Per2 and Bmal1 and the NOX2 subunits gp91phox and p47phox.

Results

The BV2 microglial clock exerted significant control over NOX2 expression and inhibition of NOX2 enabled the microglia to retain a functional circadian clock while reducing levels of ROS and inflammatory cytokines. These trends were mirrored in mouse bone marrow-derived primary macrophages.

Conclusions

NOX2 plays a crucial role in the interaction between the circadian clock and the activation of microglia/macrophages into their pro-inflammatory state, which has important implications in the control of neuroinflammation.

ARHGAP15 promotes metastatic colonization in gastric cancer by suppressing RAC1-ROS pathway

The molecular mechanism of tumor metastasis, especially how metastatic tumor cells colonize in a distant site, remains poorly understood. Here we reported that ARHGAP15, a Rho GTPase activating protein, enhanced gastric cancer (GC) metastatic colonization, which was quite different from its reported role as a tumor suppressor gene in other cancers. It was upregulated in metastatic lymph nodes and significantly associated with a poor prognosis. Ectopic expression of ARHGAP15 promoted metastatic colonization of gastric cancer cells in murine lungs and lymph nodes in vivo or protected cells from oxidative-related death in vitro. However, genetic downregulation of ARHGAP15 had the opposite effect. Mechanistically, ARHGAP15 inactivated RAC1 and then decreased intracellular accumulation of reactive oxygen species (ROS), thus enhancing the antioxidant capacity of colonizing tumor cells under oxidative stress. This phenotype could be phenocopied by inhibition of RAC1 or rescued by the introduction of constitutively active RAC1 into cells. Taken together, these findings suggested a novel role of ARHGAP15 in promoting gastric cancer metastasis by quenching ROS through inhibiting RAC1 and its potential value for prognosis estimation and targeted therapy.

Effects of NADPH Oxidase Isoform-2 (NOX2) Inhibition on Behavioral Responses and Neuroinflammation in a Mouse Model of Neuropathic Pain

NADPH oxidase isoform-2 (NOX2) has been implicated in the pathophysiology of neuropathic pain (NP), mostly through the modulation of neuroinflammation. Since it is also accepted that some neuroimmune mechanisms underlying NP are sex-dependent, we aimed to evaluate the effects of early systemic treatment with the NOX2-selective inhibitor (NOX2i) GSK2795039 on behavioral responses and spinal neuroinflammation in spared nerve injury (SNI)-induced NP in male and female mice. Mechanical sensitivity was evaluated with the von Frey test, while general well-being and anxiety-like behavior were assessed with burrowing and light/dark box tests. Spinal microglial activation and cytokines IL-1β, IL-6, and IL-10, as well as macrophage colony-stimulating factor (M-CSF) were evaluated by immunofluorescence and multiplex immunoassay, respectively. NOX2i treatment reduced SNI-induced mechanical hypersensitivity and early SNI-induced microglial activation in both sexes. SNI-females, but not males, showed a transient reduction in burrowing activity. NOX2i treatment did not improve their burrowing activity, but tendentially reduced their anxiety-like behavior. NOX2i marginally decreased IL-6 in females, and increased M-CSF in males. Our findings suggest that NOX2-selective inhibition may be a potential therapeutic strategy for NP in both male and female individuals, with particular interest in females due to its apparent favorable impact in anxiety-like behavior.

Chemical synthesis of a reported p47phox/p22phox inhibitor and characterization of its instability and irreproducible activity

The nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2) multi-subunit complex is a highly abundant and central source of reactive oxygen species. NOX2 is a key enzyme of the innate immune system involved in antibacterial response, but excessive NOX2 activity is involved in oxidative stress and inflammation in many diseases. Inhibition of NOX2 has great potential as a therapeutic strategy. An intriguing pharmacological approach for inhibiting NOX2 is to target the p47phox subunit and thereby block the protein-protein interaction with p22phox, whereby assembling and activation of NOX2 is prevented. However, the shallow binding pocket of p47phox makes it difficult to develop drug-like p47phox/p22phox inhibitors. Recently, the small molecule LMH001 was reported to inhibit the p47phox/p22phox interaction, reduce endothelial NOX2 activity, and protect mice from angiotensin II-induced vascular oxidative stress. These noteworthy results could have significant impact on the field of NOX2 pharmacology, as specific and efficient inhibitors are scarce. Here, we synthesized and tested LMH001 to have it available as a positive control. We established a robust synthetic route for providing LMH001, but subsequently we experienced that LMH001 is chemically unstable in aqueous buffer. In addition, neither LMH001 nor its breakdown products were able to inhibit the p47phox/p22phox interaction in a non-cellular fluorescence polarization assay. However, LHM001 was a weak inhibitor of NOX2 in a functional cell assay, but with same low potency as one of its breakdown products. These findings question the activity and suggested mechanism of LMH001 and constitute important information for other researchers interested in chemical probes for studying NOX2 biology.

Live Imaging in Planarians: Immobilization and Real-Time Visualization of Reactive Oxygen Species

Imaging of living animals allows the study of metabolic processes in relation to cellular structures or larger functional entities. To enable in vivo imaging during long-term time-lapses in planarians, we combined and optimized existing protocols, resulting in an easily reproducible and inexpensive procedure. Immobilization with low-melting-point agarose eliminates the use of anesthetics, avoids interfering with the animal during imaging-functionally or physically-and allows recovering the organisms after the imaging procedure. As an example, we used the immobilization workflow to image the highly dynamic and fast-changing reactive oxygen species (ROS) in living animals. These reactive signaling molecules can only be studied in vivo and mapping their location and dynamics during different physiological conditions is crucial to understand their role in developmental processes and regeneration. In the current protocol, we describe both the immobilization and ROS detection procedure. We used the intensity of the signals together with pharmacological inhibitors to validate the signal specificity and to distinguish it from the autofluorescent nature of the planarian.

NOX2 oxidase inhibitor GSK2795039 possess antiviral activity against H1N1 influenza A virus in vitro and vivo

The continuous zoonotic circulation and reassortment potential of influenza A viruses (IAV) in nature represents an enormous public health threat to humans. Beside vaccination antivirals are needed to efficiently control spreading of the disease. The previous research has shown that NOX2 involved in IAV replication, but the detailed mechanism has not been reported. In the present study we investigated the roles of NOX2 in host inflammatory response and IAV replication using a novel inhibitor GSK2795039. The drug significantly reduced H1N1 virus induced NOX2 activity and ROS release in human lung epithelial cells. The results of time course experiments suggested that GSK2795039 inhibited an early post-entry step of viral infection. Concomitantly, there was a decreased expression of pro-inflammatory cytokines (tumor necrosis factor (TNF)-α, interferon (IFN)-β and interleukin (IL)-6) in NOX2 suppressed cells. In vivo, compared with control groups, suppression of NOX2 improved the survival rate of mice infected with H1N1 virus (42.9% in GSK2795039 treated mice versus >0% of control mice) and viral burden also decreased in the GSK2795039 treated group. Thus, our data demonstrated a critical role for NOX2 in the establishment of H1N1 infection and subsequent inflammatory reactions, which suggest that GSK2795039 may be a potential therapeutic drug for IAV infection.

Selective Pharmacological Inhibition of NOX2 by GSK2795039 Improves Bladder Dysfunction in Cyclophosphamide-Induced Cystitis in Mice

Interstitial cystitis/bladder pain syndrome (IC/BPS) is a chronic inflammatory disease without consistently effective treatment. Among the many mediators implicated in cystitis, the overproduction of reactive oxygen species (ROS) seems to play a key role, although the main source of ROS remains unclear. This study aimed to investigate the contribution of NADPH oxidase (NOX) isoforms in ROS generation and the voiding dysfunction of cyclophosphamide (CYP, 300 mg/Kg, ip, 24 h)-induced cystitis in adult female mice, a well-recognized animal model to study IC/BPS, by using GKT137831 (5 mg/Kg, ip, three times in a 24 h period) or GSK2795039 (5 mg/Kg, ip, three times in a 24 h period) to inhibit NOX1/4 or NOX2, respectively. Our results showed that treatment with GSK2795039 improved the dysfunctional voiding behavior induced by CYP, reduced bladder edema and inflammation, and preserved the urothelial barrier integrity and tight junction occludin expression, besides inhibiting the characteristic vesical pain and bladder superoxide anion generation. In contrast, the NOX1/4 inhibitor GKT137831 had no significant protective effects. Taken together, our in vivo and ex vivo data demonstrate that NOX2 is possibly the main source of ROS observed in cystitis-induced CYP in mice. Therefore, selective inhibition of NOX2 by GSK2795039 may be a promising target for future therapies for IC/BPS.

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.