Nox1 Deficiency Research Articles

Nox1-based NADPH oxidase regulates the Par protein complex activity to control cell polarization.

Cell migration is essential for many biological and pathological processes. Establishing cell polarity with a trailing edge and forming a single lamellipodium at the leading edge of the cell is crucial for efficient directional cell migration and is a hallmark of mesenchymal cell motility. Lamellipodia formation is regulated by spatial-temporal activation of the small GTPases Rac and Cdc42at the front edge, and RhoA at the rear end. At a molecular level, partitioning-defective (Par) protein complex comprising Par3, Par6, and atypical Protein Kinase (aPKC isoforms ζ and λ/ι) regulates front-rear axis polarization. At the front edge, integrin clustering activates Cdc42, prompting the formation of Par3/Par6/aPKC complexes to modulate MTOC positioning and microtubule stabilization. Consequently, the Par3/Par6/aPKC complex recruits Rac1-GEF Tiam to activate Rac1, leading to lamellipodium formation. At the rear end, RhoA-ROCK phosphorylates Par3 disrupting its interaction with Tiam and inactivating Rac1. RhoA activity at the rear end allows the formation of focal adhesions and stress fibers necessary to generate the traction forces that allow cell movement. Nox1-based NADPH oxidase is necessary for PDGF-induced migration in vitro and in vivo for many cell types, including fibroblasts and smooth muscle cells. Here, we report that Nox1-deficient cells failed to acquire a normal front-to-rear polarity, polarize MTOC, and form a single lamellipodium. Instead, these cells form multiple protrusions that accumulate Par3 and active Tiam. The exogenous addition of H2O2 rescues this phenotype and is associated with the hyperactivation of Par3, Tiam, and Rac1. Mechanistically, Nox1 deficiency induces the inactivation of PP2A phosphatase, leading to increased activation of aPKC. These results were validated in Nox1y/- primary mouse aortic smooth muscle cells (MASMCs), which also showed PP2A inactivation after PDGF-BB stimulation consistent with exacerbated activation of aPKC. Moreover, we evaluated the physiological relevance of this signaling pathway using a femoral artery wire injury model to generate neointimal hyperplasia. Nox1y/- mice showed increased staining for the inactive form of PP2A and increased signal for active aPKC, suggesting that PP2A and aPKC activities might contribute to reducing neointima formation observed in the arteries of Nox1y/- mice.

NOX1/NADPH Oxidase Promotes Synaptic Facilitation Induced by Repeated D2 Receptor Stimulation: Involvement in Behavioral Repetition.

Repetitive behavior is a widely observed neuropsychiatric symptom. Abnormal dopaminergic signaling in the striatum is one of the factors associated with behavioral repetition; however, the molecular mechanisms underlying the induction of repetitive behavior remain unclear. Here, we demonstrated that the NOX1 isoform of the superoxide-producing enzyme NADPH oxidase regulated repetitive behavior in mice by facilitating excitatory synaptic inputs in the central striatum (CS). In male C57Bl/6J mice, repeated stimulation of D2 receptors induced abnormal behavioral repetition and perseverative behavior. Nox1 deficiency or acute pharmacological inhibition of NOX1 significantly shortened repeated D2 receptor stimulation-induced repetitive behavior without affecting motor responses to a single D2 receptor stimulation. Among brain regions, Nox1 showed enriched expression in the striatum, and repeated dopamine D2 receptor stimulation further increased Nox1 expression levels in the CS, but not in the dorsal striatum. Electrophysiological analyses revealed that repeated D2 receptor stimulation facilitated excitatory inputs in the CS indirect pathway medium spiny neurons (iMSNs), and this effect was suppressed by the genetic deletion or pharmacological inhibition of NOX1. Nox1 deficiency potentiated protein tyrosine phosphatase activity and attenuated the accumulation of activated Src kinase, which is required for the synaptic potentiation in CS iMSNs. Inhibition of NOX1 or β-arrestin in the CS was sufficient to ameliorate repetitive behavior. Striatal-specific Nox1 knockdown also ameliorated repetitive and perseverative behavior. Collectively, these results indicate that NOX1 acts as an enhancer of synaptic facilitation in CS iMSNs and plays a key role in the molecular link between abnormal dopamine signaling and behavioral repetition and perseveration.SIGNIFICANCE STATEMENT Behavioral repetition is a form of compulsivity, which is one of the core symptoms of psychiatric disorders, such as obsessive-compulsive disorder. Perseveration is also a hallmark of such disorders. Both clinical and animal studies suggest important roles of abnormal dopaminergic signaling and striatal hyperactivity in compulsivity; however, the precise molecular link between them remains unclear. Here, we demonstrated the contribution of NOX1 to behavioral repetition induced by repeated stimulation of D2 receptors. Repeated stimulation of D2 receptors upregulated Nox1 mRNA in a striatal subregion-specific manner. The upregulated NOX1 promoted striatal synaptic facilitation in iMSNs by enhancing phosphorylation signaling. These results provide a novel mechanism for D2 receptor-mediated excitatory synaptic facilitation and indicate the therapeutic potential of NOX1 inhibition in compulsivity.

NOX1/NADPH oxidase is involved in the LPS-induced exacerbation of collagen-induced arthritis

We investigate as yet an unidentified role of NOX1, a non-phagocytic isoform of the superoxide-generating NADPH oxidase, in immune responses using Nox1-knockout mice (Nox1-KO). The transcripts of NOX1 was expressed in lymphoid tissues, including the spleen, thymus, bone marrow, and inguinal lymphoid nodes. When antibody production after ovalbumin (OVA) immunization was examined, no significant differences were observed in serum anti-OVA IgG levels between wild-type mice (WT) and Nox1-KO. In the experimental asthma, the infiltration of eosinophils and the Th2 cytokine response after the induction of asthma with OVA were similar between the two genotypes. However, the severity and incidence of experimental collagen-induced arthritis (CIA) following the administration of a low dose of endotoxin (LPS) were significantly lower in Nox1-KO. While neither serum levels of autoantibodies nor in vitro cytokine responses were affected by Nox1 deficiency, NOX1 mRNA levels in the spleen significantly increased after the LPS challenge. Among the spleen cells, remarkable LPS-induced upregulation of NOX1 was demonstrated in both CD11b+ monocytes/macrophages and CD11c+ dendritic cells, suggesting that LPS-inducible NOX1 in monocytes/macrophages/dendritic cells may modulate the development of experimental CIA. Therapeutic targeting of NOX1 may therefore control the onset and/or severity of arthritis which is exacerbated by bacterial infection.

NOX1/NADPH oxidase accelerates the onset of experimental arthritis

The critical role of phagocytic NOX2/NADPH oxidase in bacterial killing is well-known. However, the involvement of NOX1 isoform in immune responses has not been clarified. As NOX1 mRNA is expressed in such lymphoid tissues as spleen, thymus, bone marrow, and inguinal lymphoid nodes, we examined the role of NOX1 in experimental animal models using Nox1-deficient mice (Nox1-KO). When antibody production after ovalbumin (OVA) immunization was examined, no significant differences were observed in serum anti OVA IgG levels between wild-type mice (WT) and Nox1-KO. In the experimental asthma, the infiltration of eosinophils and the Th2 cytokine response after the induction of asthma with OVA were similar between the two genotypes. However, the severity and incidence of experimental collagen-induced arthritis (CIA) following the administration of a low dose of endotoxin (LPS) were significantly lower in Nox1-KO. While neither serum levels of autoantibodies nor in vitro cytokine responses following immunization with collagen were affected by Nox1 deficiency, NOX1 mRNA levels in the spleen significantly increased after the LPS challenge. Among the spleen cells, remarkable LPS-induced upregulation of NOX1 was demonstrated in both CD11b+ monocytes/macrophages and CD11c+ dendritic cells. The LPS-inducible NOX1 in monocytes/macrophages/dendritic cells may modulate the development of experimental CIA, providing a novel insight into the function of NOX1 in specific immune responses.

NOX1 Regulates Collective and Planktonic Cell Migration: Insights From Patients With Pediatric-Onset IBD and NOX1 Deficiency.

Genetic defects of pediatric-onset inflammatory bowel disease (IBD) provide critical insights into molecular factors controlling intestinal homeostasis. NOX1 has been recently recognized as a major source of reactive oxygen species (ROS) in human colonic epithelial cells. Here we assessed the functional consequences of human NOX1 deficiency with respect to wound healing and epithelial migration by studying pediatric IBD patients presenting with a stop-gain mutation in NOX1. Functional characterization of the NOX1 variant included ROS generation, wound healing, 2-dimensional collective chemotactic migration, single-cell planktonic migration in heterologous cell lines, and RNA scope and immunohistochemistry of paraffin-embedded patient tissue samples. Using exome sequencing, we identified a stop-gain mutation in NOX1 (c.160C>T, p.54R>*) in patients with pediatric-onset IBD. Our studies confirmed that loss-of-function of NOX1 causes abrogated ROS activity, but they also provided novel mechanistic insights into human NOX1 deficiency. Cells that were NOX1-mutant showed impaired wound healing and attenuated 2-dimensional collective chemotactic migration. High-resolution microscopy of the migrating cell edge revealed a reduced density of filopodial protrusions with altered focal adhesions in NOX1-deficient cells, accompanied by reduced phosphorylation of p190A. Assessment of single-cell planktonic migration toward an epidermal growth factor gradient showed that NOX1 deficiency is associated with altered migration dynamics with loss of directionality and altered cell-cell interactions. Our studies on pediatric-onset IBD patients with a rare sequence variant in NOX1 highlight that human NOX1 is involved in regulating wound healing by altering epithelial cytoskeletal dynamics at the leading edge and directing cell migration.

Leptin Replacement Therapy Improves Endothelial Function and Vascular Inflammation in a Mouse Model of Acquired Lipodystrophy Associated with Antiretroviral Treatment by Regulating Nox1‐Derived ROS and C‐C Chemokine Receptor Type 5

Highly active antiretroviral therapy (HAART) has been used at suppressing HIV replication, as a side effect HAART promotes lipodystrophy, which is a metabolic disorder characterized by an abnormal adipose tissue distribution, reduced leptin plasma levels and vascular complications. Leptin replacement therapy (LRT) is currently used to treat metabolic dysfunctions in patients diagnosed with congenital lipodystrophy. Here, we sought to investigate whether LRT restores vascular function and reduces inflammation in mice treated with the antiretroviral agent, ritonavir. Four weeks of ritonavir reduced body weight [control (C): 28.4±0.5 vs. Rit: 24.4 ± 0.2g*, *P<0.05], fat mass (C: 10 ± 0.4 vs. Rit: 4.5 ± 0.9 %*, *P<0.05) and leptin plasma levels (C: 4.7 ± 0.05 vs. Rit: 2.0 ± 0.36 ng/mL*, *P<0.05) confirming that it induces acquired lipodystrophy. Acquired lipodystrophy impaired endothelial function, increased plasma lipid peroxidation and vascular H2O2, and ROS producing enzymes (Nox1 and NoxA1). Furthermore, acquired lipodystrophy was associated with vascular inflammation characterized by elevation of NLRP3, Caspase‐1, IL‐1β, MCP‐1, F4/80, CCR5 and CCL5 gene expression. ROS scavenging via tempol (SOD mimetic, 100 μmol/l) or GKT771 (Nox1 inhibitor, 10 μmol/l) restored endothelial function. LRT (10μg/day/7 days, osmotic mini‐pump), at the end of the 3‐week ritonavir, restored endothelial function, reduced vascular oxidative stress and Nox1 and NOXA1 gene expression and vascular inflammation. Nox1 deficiency (Nox1−/−) protected mice from acquired lipodystrophy‐induced endothelial dysfunction and reduced inflammatory markers including CCR5 and CCL5. In order to analyze whether vascular inflammation is occurring via CCR5/CCL5, we induced lipodystrophy in CCR5 deficient mice (CCR5−/−). These mice were protected from acquired lipodystrophy‐induced endothelial dysfunction and vascular inflammation. Moreover, deleting endothelial leptin signaling via specific deletion of leptin receptor (LepR) in endothelial cells (LepR−/−EC mice) promoted endothelial dysfunction, which was reverted by pre‐incubating aortic rings with Nox1 inhibitor (GKT771) in vitro and increased inflammatory markers. Furthermore, LepR−/−EC mice were resistant to the vascular protective effects of LRT. Taken all together, LRT restores endothelial function and reduces vascular inflammation in acquired lipodystrophy associated with HAART via endothelium dependent reduction in Nox1‐derived ROS and CCR5/CCL5. Taken together these data support a key role for endothelial leptin signaling in the control of vascular tone and inflammation and suggest that LRT could represent a potential new avenue for the treatment of vascular diseases associated with acquired lipodystrophy.Support or Funding InformationWork supported by 17POST33410363 and 1K99HL140139‐01A1 to TBN and 1R01HL13030101 to EJ.BdC.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Abstract 008: Leptin Treatment Attenuates Vascular Dysfunction and Inflammation in Mouse Model(s) of Acquired Lipodystrophy via Reducing Nox1-derived Ros

Although extremely efficient at suppressing HIV replication, highly active antiretroviral therapy (HAART) induces lipodystrophy, a metabolic disorder characterized by an abnormal adipose tissue distribution, reduced leptin levels and vascular dysfunction. Leptin replacement therapy (LRT) is currently used to improve metabolic function in patients suffering from congenital lipodystrophy. Here, we analyzed whether LRT restores vascular function and inflammation in mice treated with the antiretroviral agent, ritonavir (Rit). Four weeks of Rit reduced body weight [control (C): 28.4±0.5 vs. Rit: 24.4±0.2g*, *P<0.05] and fat mass (C: 10±1 vs. Rit: 6.5±1 %*) confirming that it induces lipodystrophy. Rit impaired aortic endothelial function [Relaxation to acetylcholine: C: 74±4 vs. Rit: 21±15%*), increased ROS producing enzymes (NOX1 and NOXA1), induced vascular inflammation (increased IL-1β, MCP-1, GATA Binding Protein 3 and INF-γ gene expression) and increased TBARS levels. ROS scavenging via tempol or GKT137117, (Nox1/4 inhibitor) pre-incubation blunted endothelial dysfunction. LRT (10μg/day/7 days, osmotic mini-pump), at the end of the 3-week Rit, restored endothelial function, reduced Nox1 and NOXA1 gene expression and vascular inflammation. NOX1 deficiency in Nox1 KO mice protected mice from Rit-induced endothelial dysfunction and vascular inflammation. Increasing endothelial leptin sensitivity via specific deletion of protein tyrosine phosphatase 1B (Ptp1b) in endothelial cells ( Ptp1b-/-EC mice) protected mice from Rit-induced endothelial dysfunction and reduced Nox1 and NOXA1 gene expression, and vascular inflammation. To address the relevance of these observations to other forms of acquired lipodystrophy, experiments were repeated in mice in which lipodystrophy was induced at 8 week of age, by the deletion of Bscl2, a gene involved in adipocyte maturation. Bscl2 deletion reduced fat mass, and induced endothelial dysfunction via ROS-mediated mechanisms. Again, LRT reverted endothelial dysfunction by downregulating Nox1 expression. All together, these data presents leptin as a key regulator of endothelial oxidative stress level and as a potential avenue for the treatment vascular disease.

Deficiency in Duox2 activity alleviates ileitis in GPx1- and GPx2-knockout mice without affecting apoptosis incidence in the crypt epithelium

Mice deficient in glutathione peroxidase (GPx)-1 and -2 (GPx1-/-GPx2-/- double knockout or DKO mice) develop very-early-onset (VEO) ileocolitis, suggesting that lack of defense against reactive oxygen species (ROS) renders susceptibility to intestinal inflammation. Two members of ROS-generating NADPH oxidase family, NOX1 and DUOX2, are highly inducible in the intestinal epithelium. Previously, we reported that Nox1 deficiency ameliorated the pathology in DKO mice (Nox1-TKO). The role of Duox2 in ileocolitis of the DKO mice is evaluated here in Duoxa-TKO mice by breeding DKO mice with Duoxa-/- mice (Duoxa-TKO), which do not have Duox2 activity. Similar to Nox1-TKO mice, Duoxa-TKO mice no longer have growth retardation, shortened intestine, exfoliation of crypt epithelium, crypt abscesses and depletion of goblet cells manifested in DKO mice by 35 days of age. Unlike Nox1-TKO mice, Duoxa-TKO mice still have rampant crypt apoptosis, elevated proliferation, partial loss of Paneth cells and diminished crypt density. Treating DKO mice with NOX inhibitors (di-2-thienyliodonium/DTI and thioridazine/THZ) and an antioxidant (mitoquinone/MitoQ) significantly reduced gut pathology. Furthermore, in the inflamed human colon, DUOX protein expression is highly elevated in the apical, lateral and perinuclear membrane along the whole length of gland. Taken together, we conclude that exfoliation of crypt epithelium, but not crypt apoptosis, is a major contributor to inflammation. Both Nox1 and Duox2 induce exfoliation of crypt epithelium, but only Nox1 induces apoptosis. NOX1 and DUOX2 may be potential therapeutic targets for treating ileocolitis in human patients suffering inflammatory bowel disease (IBD).

The ROS-generating oxidase Nox1 is required for epithelial restitution following colitis.

Accumulating evidence suggests that reactive oxygen species (ROS) generated by endogenous metabolic enzymes are involved in a variety of intracellular mechanisms. In particular, superoxide-generating NADPH oxidase (Nox) 1 is highly expressed in the colon and has been implicated in physiological and pathophysiological states of colon tissues. However, its role in tissue repair following colitis has not been fully elucidated. Our study using experimental colitis in mice showed that repair of the mucosal layer did not occur in Nox1-deficient mice following dextran sulfate sodium-induced colitis. This was accompanied by inhibition of proliferation, cell survival, migration, and terminal differentiation (generation of goblet cells) of crypt progenitor cells, as determined by histochemical analyses. Furthermore, Nox1 expression as well as ROS production in the colon crypt was increased during the repair process, and Nox1 deficiency suppressed these events. The results suggest that Nox1 promotes colon mucosal wound repair by sustaining the bioactivity of crypt progenitor cells and plays a crucial role in the epithelial restitution in the case of damage associated with colitis.

Nox1in cardiovascular diseases: regulation and pathophysiology.

Since its discovery in 1999, a number of studies have evaluated the role of Nox1 NADPH oxidase in the cardiovascular system. Nox1 is activated in vascular cells in response to several different agonists, with its activity regulated at the transcriptional level as well as by NADPH oxidase complex formation, protein stabilization and post-translational modification. Nox1 has been shown to decrease the bioavailability of nitric oxide, transactivate the epidermal growth factor receptor, induce pro-inflammatory signalling, and promote cell migration and proliferation. Enhanced expression and activity of Nox1 under pathologic conditions results in excessive production of reactive oxygen species and dysregulated cellular function. Indeed, studies using genetic models of Nox1 deficiency or overexpression have revealed roles for Nox1in the pathogenesis of cardiovascular diseases ranging from atherosclerosis to hypertension, restenosis and ischaemia/reperfusion injury. These data suggest that Nox1 is a potential therapeutic target for vascular disease, and drug development efforts are ongoing to identify a specific bioavailable inhibitor of Nox1.

NADPH oxidase NOX1 is involved in activation of protein kinase C and premature senescence in early stage diabetic kidney

Increased oxidative stress and activation of protein kinase C (PKC) under hyperglycemia have been implicated in the development of diabetic nephropathy. Because reactive oxygen species derived from nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, NOX1 accelerate the translocation of PKC isoforms, NOX1 is postulated to play a causative role in the development of diabetic nephropathy. Hyperglycemia was induced in wild-type and Nox1-deficient mice (KO) by two doses of streptozotocin injection. At 3 weeks after the induction of hyperglycemia, glomeruli and cortical tubules were isolated from kidneys. The mRNA level of Nox1 was significantly upregulated in the renal cortex at 3 weeks of hyperglycemia. Urinary albumin and expression of inflammatory or fibrotic mediators were similarly elevated in diabetic wild-type and KO; however, increases in glomerular volume and mesangial matrix area were attenuated in diabetic KO. Nox1 deficiency significantly reduced the levels of renal thiobarbituric acid-reacting substances and 8-hydroxydeoxyguanosine, membranous translocation of PKCα/β, activity of PKC, and phosphorylation of p38 mitogen-activated protein kinase in the diabetic kidney. Furthermore, increased staining of senescence-associated β-galactosidase in glomeruli and cortical tubules of diabetic mice was significantly suppressed in KO. Whereas the levels of cyclin-dependent kinase inhibitors, p16INK4A and p21Cip1, were equivalent between the genotypes, increased levels of p27Kip1 and γ-H2AX, a biomarker for DNA double-strand breaks, were significantly attenuated in isolated glomeruli and cortical tubules of diabetic KO. Taken together, NOX1 modulates the p38/p27Kip1 signaling pathway by activating PKC and promotes premature senescence in early stage diabetic nephropathy.

NOX1 deficiency in apolipoprotein E-knockout mice is associated with elevated plasma lipids and enhanced atherosclerosis

Nicotinamide adenine dinucleotide phosphate oxidases (NOX) are enzymes that generate reactive oxygen species (ROS). NOX2 activity in the vascular wall is elevated in hypercholesterolemia, and contributes to oxidative stress and atherogenesis. Here we examined the role of another NOX isoform, NOX1, in atherogenesis in apolipoprotein E-knockout (APOE−/−) mice fed a Western diet for 14 weeks. Although NOX1 mRNA expression was unchanged in aortas from APOE−/− versus wild-type mice, expression of the NOX1-specific organizer, NOXO1, was diminished, consistent with an overall reduction in NOX1 activity in APOE−/− mice. To examine the impact of a further reduction in NOX1 activity, APOE−/− mice were crossed with NOX1−/y mice to generate NOX1−/y/APOE−/− double-knockouts. NOX1 deficiency in APOE−/− mice was associated with 30–50% higher plasma very-low-density lipoprotein (VLDL)/LDL and triglyceride levels (P < 0.01). Vascular ROS levels were also elevated by twofold in NOX1−/y/APOE−/− versus APOE−/− mice (P < 0.05), despite no changes in expression of other NOX subunits. Although en face analysis of the descending aorta revealed no differences in plaque area between NOX1−/y/APOE−/− and APOE−/− mice, intimal thickening in the aortic sinus was increased by 40% (P < 0.05) in the double-knockouts. Moreover, NOX1 deficiency was associated with a less stable plaque phenotype; aortic sinus lesions contained 60% less collagen (P < 0.01), 40% less smooth muscle (P < 0.01), and 2.5-fold higher levels of matrix metalloproteinase-9 (P < 0.001) than lesions in APOE−/− mice. Thus, these data, which suggest a protective role for NOX1 against hyperlipidemia and atherosclerosis in APOE−/− mice, highlight the complex and contrasting roles of different NOX isoforms (e.g., NOX2 versus NOX1) in vascular pathology.

Nox1 NADPH oxidase is necessary for late but not early myocardial ischaemic preconditioning

Ischaemic preconditioning (IPC) is an adaptive mechanism that renders the myocardium resistant to injury from subsequent hypoxia. Although reactive oxygen species (ROS) contribute to both the early and late phases of IPC, their enzymatic source and associated signalling events have not yet been understood completely. Our objective was to investigate the role of the Nox1 NADPH oxidase in cardioprotection provided by IPC. Wild-type (WT) and Nox1-deficient mice were treated with three cycles of brief coronary occlusion and reperfusion, followed by prolonged occlusion either immediately (early IPC) or after 24 h (late IPC). Nox1 deficiency had no impact on the cardioprotection afforded by early IPC. In contrast, deficiency of Nox1 during late IPC resulted in a larger infarct size, cardiac remodelling, and increased myocardial apoptosis compared with WT hearts. Furthermore, expression of Nox1 in WT hearts increased in response to late IPC. Deficiency of Nox1 abrogated late IPC-mediated activation of cardiac nuclear factor-κB (NF-κB) and induction of tumour necrosis factor-α (TNF-α) in the heart and circulation. Finally, knockdown of Nox1 in cultured cardiomyocytes prevented TNF-α induction of NF-κB and the protective effect of IPC on hypoxia-induced apoptosis. Our data identify a critical role for Nox1 in late IPC and define a previously unrecognized link between TNF-α and NF-κB in mediating tolerance to myocardial injury. These findings have clinical significance considering the emergence of Nox1 inhibitors for the treatment of cardiovascular disease.

Renal Redox-Sensitive Signaling, but Not Blood Pressure, Is Attenuated by Nox1 Knockout in Angiotensin II–Dependent Chronic Hypertension

We demonstrated previously that, in mice with chronic angiotensin II-dependent hypertension, gp91phox-containing NADPH oxidase is not involved in the development of high blood pressure, despite being important in redox signaling. Here we sought to determine whether a gp91phox homologue, Nox1, may be important in blood pressure elevation and activation of redox-sensitive pathways in a model in which the renin-angiotensin system is chronically upregulated. Nox1-deficient mice and transgenic mice expressing human renin (TTRhRen) were crossed, and 4 genotypes were generated: control, TTRhRen, Nox1-deficient, and TTRhRen Nox1-deficient. Blood pressure and oxidative stress (systemic and renal) were increased in TTRhRen mice (P<0.05). This was associated with increased NADPH oxidase activation. Nox1 deficiency had no effect on the development of hypertension in TTRhRen mice. Phosphorylation of c-Src, mitogen-activated protein kinases, and focal adhesion kinase was significantly increased 2- to 3-fold in kidneys from TTRhRen mice. Activation of c-Src, p38 mitogen-activated protein kinase, c-Jun N-terminal kinase, and focal adhesion kinase but not of extracellular signal regulated kinase 1/2 or extracellular signal regulated kinase 5, was reduced in TTRhRen/Nox1-deficient mice (P<0.05). Expression of procollagen III was increased in TTRhRen and TTRhRen/Nox1-deficient mice versus control mice, whereas vascular cell adhesion molecule-1 was only increased in TTRhRen mice. Our findings demonstrate that, in Nox1-deficient TTRhRen mice, blood pressure is elevated despite reduced NADPH oxidase activation, decreased oxidative stress, and attenuated redox signaling. Our results suggest that Nox1-containing NADPH oxidase plays a key role in the modulation of systemic and renal oxidative stress and redox-dependent signaling but not in the elevation of blood pressure in a model of chronic angiotensin II-dependent hypertension.