An interplay of NOX1-derived ROS and oxygen determines the spermatogonial stem cell self-renewal efficiency under hypoxia.

Reactive oxygen species (ROS) produced by NADPH1 oxidase 1 (NOX1) are thought to drive spermatogonial stem cell (SSC) self-renewal through feed-forward production of ROS by the ROS-BCL6B-NOX1 pathway. Here we report the critical role of oxygen on ROS-induced self-renewal. Cultured SSCs proliferated poorly and lacked BCL6B expression under hypoxia despite increase in mitochondria-derived ROS. Due to lack of ROS amplification under hypoxia, NOX1-derived ROS were significantly reduced, and Nox1-deficient SSCs proliferated poorly under hypoxia but normally under normoxia. NOX1-derived ROS also influenced hypoxic response in vivo because Nox1-deficient undifferentiated spermatogonia showed significantly reduced expression of HIF1A, a master transcription factor for hypoxic response. Hypoxia-induced poor proliferation occurred despite activation of MYC and suppression of CDKN1A by HIF1A, whose deficiency exacerbated self-renewal efficiency. Impaired proliferation of Nox1- or Hif1a-deficient SSCs under hypoxia was rescued by Cdkn1a depletion. Consistent with these observations, Cdkn1a-deficient SSCs proliferated actively only under hypoxia but not under normoxia. On the other hand, chemical suppression of mitochondria-derived ROS or Top1mt mitochondria-specific topoisomerase deficiency did not influence SSC fate, suggesting that NOX1-derived ROS play a more important role in SSCs than mitochondria-derived ROS. These results underscore the importance of ROS origin and oxygen tension on SSC self-renewal.

Glutamine protects mouse spermatogonial stem cells against NOX1-derived ROS for sustaining self-renewal division in vitro.

Reactive oxygen species (ROS) are generated from NADPH oxidases and mitochondria; they are generally harmful for stem cells. Spermatogonial stem cells (SSCs) are unique among tissue-stem cells because they undergo ROS-dependent self-renewal via NOX1 activation. However, the mechanism by which SSCs are protected from ROS remains unknown. Here, we demonstrate a crucial role for Gln in ROS protection using cultured SSCs derived from immature testes. Measurements of amino acids required for SSC cultures revealed the indispensable role of Gln in SSC survival. Gln induced Myc expression to drive SSC self-renewal in vitro, whereas Gln deprivation triggered Trp53-dependent apoptosis and impaired SSC activity. However, apoptosis was attenuated in cultured SSCs that lacked NOX1. In contrast, cultured SSCs lacking Top1mt mitochondria-specific topoisomerase exhibited poor mitochondrial ROS production and underwent apoptosis. Gln deprivation reduced glutathione production; supra-molar Asn supplementation allowed offspring production from SSCs cultured without Gln. Therefore, Gln ensures ROS-dependent SSC-self-renewal by providing protection against NOX1 and inducing Myc.

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 ß-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 affects the development of autism-like behaviors in a maternal immune activation model.

Autism spectrum disorder (ASD) is a neurodevelopmental disorder caused by genetic and environmental factors. Among the environmental factors, maternal infection is known as one of the principal risk factors for ASD. On the other hand, postmortem studies suggested the relationship of oxidative stress with ASD etiology. However, the role of oxidative stress in the development of ASD remains unclear. Here, we report the involvement of NOX1/NADPH oxidase, an enzyme generating reactive oxygen species (ROS), in behavioral and anatomical abnormalities in a maternal immune activation (MIA) model. In the MIA model of gestational polyinosinic-polycytidylic acid (poly(I:C)) exposure, increased serum levels of IL-6 were observed in both wild-type (WT) and Nox1-deficient mice (Nox1KO). Following the comparable induction of MIA in the two genotypes, impairment of social preference and defects in motor coordination were observed in WT offspring but not in offspring deficient in Nox1. MIA up-regulated NOX1 mRNA in the cerebral cortex and cerebellum of the fetus but not in the adult offspring. Although the development of cortical neurons was unaffected by MIA in either genotype, the dropout of Purkinje cells in lobule VII of MIA-affected offspring was significantly ameliorated in Nox1KO. Taken together, these results suggested that NOX1/NADPH oxidase plays an essential role in some behavioral phenotypes observed in ASD, possibly by promoting the loss of Purkinje cells in the cerebellum.

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.

Clioquinol inhibits dopamine-ß-hydroxylase secretion and noradrenaline synthesis by affecting the redox status of ATOX1 and copper transport in human neuroblastoma SH-SY5Y cells.

Clioquinol (5-chloro-7-indo-8-quinolinol), a chelator and ionophore of copper/zinc, was extensively used as an amebicide to treat indigestion and diarrhea in the mid-1900s. However, it was withdrawn from the market in Japan because its use was epidemiologically linked to an increase in the incidence of subacute myelo-optic neuropathy (SMON). SMON is characterized by the subacute onset of sensory and motor disturbances in the lower extremities with occasional visual impairments, which are preceded by abdominal symptoms. Although pathological studies demonstrated axonopathy of the spinal cord and optic nerves, the underlying mechanisms of clioquinol toxicity have not been elucidated in detail. In the present study, a reporter assay revealed that clioquinol (20-50 µM) activated metal response element-dependent transcription in human neuroblastoma SH-SY5Y cells. Clioquinol significantly increased the cellular level of zinc within 1 h, suggesting zinc influx due to its ionophore effects. On the other hand, clioquinol (20-50 µM) significantly increased the cellular level of copper within 24 h. Clioquinol (50 µM) induced the oxidation of the copper chaperone antioxidant 1 (ATOX1), suggesting its inactivation and inhibition of copper transport. The secretion of dopamine-ß-hydroxylase (DBH) and lysyl oxidase, both of which are copper-dependent enzymes, was altered by clioquinol (20-50 µM). Noradrenaline levels were reduced by clioquinol (20-50 µM). Disruption of the ATOX1 gene suppressed the secretion of DBH. This study suggested that the disturbance of cellular copper transport by the inactivation of ATOX1 is one of the mechanisms involved in clioquinol-induced neurotoxicity in SMON.

Depressive-Like Behaviors Are Regulated by NOX1/NADPH Oxidase by Redox Modification of NMDA Receptor 1.

Involvement of reactive oxygen species (ROS) has been suggested in the development of psychiatric disorders. NOX1 is a nonphagocytic form of NADPH oxidase whose expression in the nervous system is negligible compared with other NOX isoforms. However, NOX1-derived ROS increase inflammatory pain and tolerance to opioid analgesia. To clarify the role of NOX1 in the brain, we examined depressive-like behaviors in mice deficient in Nox1 (Nox1-/Y). Depressive-like behaviors induced by chronic social defeat stress or administration of corticosterone (CORT) were significantly ameliorated in Nox1-/Y Generation of ROS was significantly elevated in the prefrontal cortex (PFC) of mice administrated with CORT, while NOX1 mRNA was upregulated only in the ventral tegmental area (VTA) among brain areas responsible for emotional behaviors. Delivery of miRNA against NOX1 to VTA restored CORT-induced depressive-like behaviors in wild-type (WT) littermates. Administration of CORT to WT, but not to Nox1-/Y, significantly reduced transcript levels of brain-derived neurotrophic factor (bdnf), with a concomitant increase in DNA methylation of the promoter regions in bdnf Delivery of miRNA against NOX1 to VTA restored the level of BDNF mRNA in WT PFC. Redox proteome analyses demonstrated that NMDA receptor 1 (NR1) was among the molecules redox regulated by NOX1. In cultured cortical neurons, hydrogen peroxide significantly suppressed NMDA-induced upregulation of BDNF transcripts in NR1-expressing cells but not in cells harboring mutant NR1 (C744A). Together, these findings suggest a key role of NOX1 in depressive-like behaviors through NR1-mediated epigenetic modification of bdnf in the mesoprefrontal projection.SIGNIFICANCE STATEMENT NADPH oxidase is a source of reactive oxygen species (ROS) that have been implicated in the pathogenesis of various neurological disorders. We presently showed the involvement of a nonphagocytic type of NADPH oxidase, NOX1, in major depressive disorders, including behavioral, biochemical, and anatomical changes in mice. The oxidation of NR1 by NOX1-derived ROS was demonstrated in prefrontal cortex (PFC), which may be causally linked to the downregulation of BDNF, promoting depressive-like behaviors. Given that NOX1 is upregulated only in VTA but not in PFC, mesocortical projections appear to play a crucial role in NOX1-dependent depressive-like behaviors. Our study is the first to present the potential molecular mechanism underlying the development of major depression through the NOX1-induced oxidation of NR1 and epigenetic modification of bdnf.

Augmented neutrophil extracellular traps formation promotes atherosclerosis development in socially defeated apoE-/- mice.

Depression is an independent risk factor of cardiovascular disease (CVD); however, the causal association remains undefined. We exposed mice to repeated social defeat (RSD) to precipitate depressive-like behaviors, and investigated the effects on atherosclerosis. Eight-week-old male apoE-/- mice were exposed to RSD by housing with a larger CD-1 mouse in a shared home cage. They were subjected to vigorous physical contact daily for 10 consecutive days and fed a high-cholesterol diet (HCD) for 6 weeks. The social interaction ratio and immobility time showed dramatic social avoidance before and after HCD feeding. Defeated mice showed higher increase in atherosclerotic lesion areas in the aortic root and entire aorta than control mice. Mean blood pressure and lipid profile were equivalent in both groups. While Ly-6G- and Mac3-positive areas in the aortic root were comparable between the groups, citrullinated histone H3 (Cit-H3)- and myeloperoxidase (MPO)-positive areas, markers of neutrophil extracellular traps (NETs), were significantly increased in the defeated mice. Treatment with DNase I completely diminished the exaggerated atherosclerosis. The proportion of peripheral blood polymorphonuclear myeloid-derived suppressor cells (PMN-MDSC), but not of inflammatory monocytes, was markedly increased. Moreover, in vitro NETs formation from bone marrow (BM) PMN-MDSC was markedly augmented, accompanied by higher expression of Nox2 gene and reactive oxygen species. Our findings demonstrate that exposure to RSD promotes atherosclerosis by augmenting NETs formation within the plaque. This provides new insight into the underlying mechanism of depression-related CVD.

NOX1/NADPH Oxidase Expressed in Colonic Macrophages Contributes to the Pathogenesis of Colonic Inflammation in Trinitrobenzene Sulfonic Acid-Induced Murine Colitis.

NOX1/NADPH oxidase, a nonphagocytic isoform of reactive oxygen species-producing enzymes, is highly expressed in the colon, but the physiologic and pathophysiologic roles of this isoform are not fully understood. The present study investigated the role of NOX1 in the development of colonic inflammation in a trinitrobenzene sulfonic acid (TNBS)-induced murine colitis model. Intrarectal injection of TNBS caused severe colitis accompanied by body weight loss, diarrhea, and increased myeloperoxidase (MPO) activity in wild-type (WT) mice. In contrast, the severity of colitis was significantly attenuated in NOX1-deficient (NOX1KO) mice (the inhibitions of macroscopic damage score, body weight loss, diarrhea score, and MPO activity were 73.1%, 36.8%, 83.3%, and 98.4%, respectively). TNBS-induced upregulation of inflammatory cytokines (tumor necrosis factor (TNF)-α and interleukin (IL)-1ß), chemokines (CXCL1 and CXLC2), and inducible nitric oxide synthase (iNOS) was also significantly less in NOX1KO than in WT mice (the inhibitions were 100.8%, 89.0%, 63.5%, 96.7%, and 97.1%, respectively). Expression of NOX1 mRNA was detected not only in the lamina propria but also in peritoneal macrophages isolated from WT mice. Increased expression of TNF-α, IL-1ß, and iNOS in peritoneal macrophages exposed to lipopolysaccharide was significantly attenuated in macrophages isolated from NOX1KO mice (68.1%, 67.0%, and 79.3% inhibition, respectively). These findings suggest that NOX1/NADPH oxidase plays an important role in the pathogenesis of TNBS-induced colonic inflammation via upregulation of inflammatory cytokines, chemokines, and iNOS. NOX1 in colonic macrophages may become a potential target in pharmacologic intervention for inflammatory bowel disease.

Hepatocyte Nicotinamide Adenine Dinucleotide Phosphate Reduced Oxidase 4 Regulates Stress Signaling, Fibrosis, and Insulin Sensitivity During Development of Steatohepatitis in Mice.

BACKGROUND & AIMS: Reactive oxidative species (ROS) are believed to be involved in the progression of nonalcoholic steatohepatitis (NASH). However, little is known about the sources of ROS in hepatocytes or their role in disease progression. We studied the effects of nicotinamide adenine dinucleotide phosphate reduced oxidase 4 (NOX4) in liver tissues from patients with NASH and mice with steatohepatitis. METHODS: Liver biopsy samples were obtained from 5 patients with NASH, as well as 4 patients with simple steatosis and 5 patients without steatosis (controls) from the University of California, Davis Cancer Center Biorepository. Mice with hepatocyte-specific deletion of NOX4 (NOX4(hepKO)) and NOX4(floxp+/+) C57BL/6 mice (controls) were given fast-food diets (supplemented with high-fructose corn syrup) or choline-deficient l-amino acid defined diets to induce steatohepatitis, or control diets, for 20 weeks. A separate group of mice were given the NOX4 inhibitor (GKT137831). Liver tissues were collected and immunoblot analyses were performed determine levels of NOX4, markers of inflammation and fibrosis, double-stranded RNA-activated protein kinase, and phospho-eIF-2α kinase-mediated stress signaling pathways. We performed hyperinsulinemic-euglycemic clamp studies and immunoprecipitation analyses to determine the oxidation and phosphatase activity of PP1C. RESULTS: Levels of NOX4 were increased in patients with NASH compared with controls. Hepatocyte-specific deletion of NOX4 reduced oxidative stress, lipid peroxidation, and liver fibrosis in mice with diet-induced steatohepatitis. A small molecule inhibitor of NOX4 reduced liver inflammation and fibrosis and increased insulin sensitivity in mice with diet-induced steatohepatitis. In primary hepatocytes, NOX4 reduced the activity of the phosphatase PP1C, prolonging activation of double-stranded RNA-activated protein kinase and phosphorylation of extracellular signal-regulated kinase-mediated stress signaling. Mice with hepatocyte-specific deletion of NOX4 and mice given GKT137831 had increased insulin sensitivity. CONCLUSIONS: NOX4 regulates oxidative stress in the liver and its levels are increased in patients with NASH and mice with diet-induced steatohepatitis. Inhibitors of NOX4 reduce liver inflammation and fibrosis and increase insulin sensitivity, and might be developed for treatment of NASH.

Deficiency of NOX1/nicotinamide adenine dinucleotide phosphate, reduced form oxidase leads to pulmonary vascular remodeling.

OBJECTIVE: Involvement of reactive oxygen species derived from nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) oxidase has been documented in the development of hypoxia-induced model of pulmonary arterial hypertension (PAH). Because the PAH-like phenotype was demonstrated in mice deficient in Nox1 gene (Nox1(-/Y)) raised under normoxia, the aim of this study was to clarify how the lack of NOX1/NADPH oxidase could lead to pulmonary pathology. APPROACH AND RESULTS: Spontaneous enlargement and hypertrophy of the right ventricle, accompanied by hypertrophy of pulmonary vessels, were demonstrated in Nox1(-/Y) 9 to 18 weeks old. Because an increased number of α-smooth muscle actin-positive vessels were observed in Nox1(-/Y), pulmonary arterial smooth muscle cells (PASMCs) were isolated and characterized by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling staining. In Nox1(-/Y) PASMCs, the number of apoptotic cells was significantly reduced without any change in the expression of endothelin-1, and hypoxia-inducible factors HIF-1α and HIF-2α, factors implicated in the pathogenesis of PAH. A significant decrease in a voltage-dependent K(+) channel, Kv1.5 protein, and an increase in intracellular potassium levels were demonstrated in Nox1(-/Y) PASMCs. When a rescue study was performed in Nox1(-/Y) crossed with transgenic mice overexpressing rat Nox1 gene, impaired apoptosis and the level of Kv1.5 protein in PASMCs were almost completely recovered in Nox1(-/Y) harboring the Nox1 transgene. CONCLUSIONS: These findings suggest a critical role for NOX1 in cellular apoptosis by regulating Kv1.5 and intracellular potassium levels. Because dysfunction of Kv1.5 is among the features demonstrated in PAH, inactivation of NOX1/NADPH oxidase may be a causative factor for pulmonary vascular remodeling associated with PAH.

A protective role of Nox1/NADPH oxidase in a mouse model with hypoxia-induced bradycardia.

Although it has been reported that endotoxin-induced expression of Nox1 in the heart contributes to apoptosis in cardiomyocytes, functional role of Nox1 at the physiological expression level has not been elucidated. The aim of this study was to clarify the role of Nox1 under a hypoxic condition using wild-type (WT, Nox1(+/Y)) and Nox1-deficient (Nox1(-/Y)) mice. ECG recordings from anesthetized mice revealed that Nox1(-/Y) mice were more sensitive to hypoxia, resulting in bradycardia, compared to WT mice. Atrial and ventricular electrocardiograms recorded from Langendorff-perfused hearts revealed that hypoxic perfusion more rapidly decreased heart rate in Nox1(-/Y) hearts compared with WT hearts. Sinus node recovery times measured under a hypoxic condition were prolonged more markedly in the Nox1(-/Y) hearts. Sinoatrial node dysfunction of Nox1(-/Y) hearts during hypoxia was ameriolated by the pre-treatment with the Ca(2+) channel blocker nifedipine or the K(+) channel opener pinacidil. Spontaneous action potentials were recorded from enzymatically-isolated sinoatrial node (SAN) cells under a hypoxic condition. There was no significant difference in the elapsed times from the commencement of hypoxia to asystole between WT and Nox1(-/Y) SAN cells. These findings suggest that Nox1 may have a protective effect against hypoxia-induced SAN dysfunction.

ROS-generating oxidases Nox1 and Nox4 contribute to oncogenic Ras-induced premature senescence.

Activated oncogenes induce premature cellular senescence, a permanent state of proliferative arrest in primary rodent and human fibroblasts. Recent studies suggest that generation of reactive oxygen species (ROS) is involved in oncogenic Ras-induced premature senescence. However, the signaling mechanism controlling this oxidant-mediated irreversible growth arrest is not fully understood. Here, we show that through the Ras/MEK pathway, Ras oncogene up-regulated the expression of superoxide-generating oxidases, Nox1 in rat REF52 cells and Nox4 in primary human lung TIG-3 cells, leading to an increase in intracellular level of ROS. Ablation of Nox1 and Nox4 by small interfering RNAs (siRNAs) blocked the RasV12 senescent phenotype including ß-galactosidase activity, growth arrest and accumulation of tumor suppressors such as p53 and p16Ink4a. This suggests that Nox-generated ROS transduce senescence signals by activating the p53 and p16Ink4a pathway. Furthermore, Nox1 and Nox4 siRNAs inhibited both Ras-induced DNA damage response and p38MAPK activation, whereas overexpression of Nox1 and Nox4 alone was able to induce senescence. The involvement of Nox1 in Ras-induced senescence was also confirmed with embryonic fibroblasts derived from Nox1 knockout mice. Together, these findings suggest that Nox1- and Nox4-generated ROS play an important role in Ras-induced premature senescence, which may involve DNA damage response and p38MAPK signaling pathways.

Clioquinol increases the expression of VGF, a neuropeptide precursor, through induction of c-Fos expression.

Clioquinol was used extensively in the mid-1900s as an amebicide to treat indigestion and diarrhea. It was eventually withdrawn from the market because it was linked to subacute myelo-optic neuropathy (SMON) in Japan. However, the pathogenesis of SMON has not yet been elucidated in detail. As reported previously, we performed a global analysis on human neuroblastoma cells using DNA chips. The global analysis and quantitative PCR demonstrated that the mRNA level of VGF (nonacronymic), the precursor of neuropeptides involved in pain reactions, was significantly increased when SH-SY5Y and IMR-32 neuroblastoma cells were treated with clioquinol. Promoter analyses in SH-SY5Y cells revealed that a region responsive to clioquinol exists between -1381 and -1349 of the human VGF gene, which contains an activator protein (AP)-1 site-like sequence. The introduction of mutations at this site significantly reduced clioquinol-induced transcriptional activation. Clioquinol induced the expression of the AP-1 family transcription factors, c-Jun and c-Fos. Electrophoresis mobility shift assays demonstrated that c-Jun and c-Fos could bind to the AP-1 site at -1374/-1368 in SH-SY5Y cells treated with clioquinol. RNA interference against c-Fos significantly suppressed clioquinol-induced VGF mRNA expression. These results suggest that the clioquinol-induced expression of c-Fos mediates the induction of VGF expression.

Role of hepatocyte-derived IL-7 in maintenance of intrahepatic NKT cells and T cells and development of B cells in fetal liver.

The liver contains a variety of resident immune cells, such as NK cells, NKT cells, T cells, macrophages, and dendritic cells. However, little is known about how IL-7, which is produced by hepatocytes, functions locally in development and maintenance of liver immune cells. To address this question, we established IL-7-floxed mice and crossed them with albumin promoter-driven Cre (Alb-Cre) transgenic mice to establish conditional knockout of IL-7 in hepatocytes. The levels of IL-7 transcripts were reduced 10-fold in hepatocyte fraction. We found that the absolute numbers of NKT and T cells were significantly decreased in adult liver of IL-7(f/f) Alb-Cre mice compared with IL-7(f/f) control mice. In contrast, NK cells, dendritic cells, and B cells were unchanged in the IL-7(f/f) Alb-Cre liver. The number of Vα14(+) invariant NKT cells was significantly reduced in liver, but not in thymus and spleen, of IL-7(f/f) Alb-Cre mice. Furthermore, B cell development was impaired in perinatal liver of IL-7(f/f) Alb-Cre mice. This study demonstrates that hepatocyte-derived IL-7 plays an indispensable role in maintenance of NKT and T cells in adult liver and development of B cells in fetal liver, and suggests that hepatocytes provide a unique IL-7 niche for intrahepatic lymphocytes.

A crucial role for Nox 1 in redox-dependent regulation of Wnt-ß-catenin signaling.

Canonical Wnt signaling critically regulates cell fate and proliferation in developmental stages and adult tissues. Redox regulation through nucleoredoxin (NRX) has recently been identified in canonical Wnt signaling. However, the source of reactive oxygen species (ROS) affecting the redox state of NRX remains elusive. Our principal aim in this study was to investigate whether superoxide-generating NADPH oxidase1 (Nox1) is involved in NRX-regulated Wnt signaling in intestinal and colon epithelial cells. Here, we demonstrate that Wnt treatment of mouse intestinal cells induces production of ROS through Nox1. This Nox1 action is regulated by Rac1 GTPase through Wnt-induced activation of the Rac1 guanine nucleotide exchange factor Vav2 by Src-mediated tyrosine phosphorylation. Nox1-generated ROS oxidize and inactivate NRX, thereby releasing the NRX-dependent suppression of Wnt-ß-catenin signaling through dissociation of NRX from Dvl. Nox1 small-interference RNA inhibits cell response to Wnt, including stabilization of ß-catenin, expression of cyclin D1 and c-Myc via the TCF transcription factor, and accelerated cell proliferation. Nox1 mediates Wnt-induced cell growth in colon cancer cells with the normal Wnt pathway, but not in APC-deficient colon cancer cells, which are constitutively active in Wnt signaling. Together, these results suggest the mediating role of Nox1 in redox-dependent regulation of canonical Wnt-ß-catenin signaling and provide further insight into the regulatory mechanism of the Wnt pathway.

Involvement of NOX1/NADPH oxidase in morphine-induced analgesia and tolerance.

The involvement of reactive oxygen species (ROS) in morphine-induced analgesia and tolerance has been suggested, yet how and where ROS take part in these processes remains largely unknown. Here, we report a novel role for the superoxide-generating enzyme NOX1/NADPH oxidase in the regulation of analgesia and acute analgesic tolerance. In mice lacking Nox1 (Nox1(-/Y)), the magnitude of the analgesia induced by morphine was significantly augmented. More importantly, analgesic tolerance induced by repeated administration of morphine was significantly suppressed compared with that in the littermates, wild-type Nox1(+/Y). In a membrane fraction obtained from the dorsal spinal cord, no difference was observed in morphine-induced [(35)S]GTPγS-binding between the genotypes, whereas morphine-stimulated GTPase activity was significantly attenuated in Nox1(-/Y). At 2 h after morphine administration, a significant decline in [(35)S]GTPγS-binding was observed in Nox1(+/Y) but not in Nox1(-/Y). No difference in the maximal binding and affinity of [(3)H]DAMGO was observed between the genotypes, but the translocation of protein kinase C isoforms to the membrane fraction following morphine administration was almost completely abolished in Nox1(-/Y). Finally, the phosphorylation of RGS9-2 and formation of a complex by Gαi2/RGS9-2 with 14-3-3 found in morphine-treated Nox1(+/Y) were significantly suppressed in Nox1(-/Y). Together, these results suggest that NOX1/NADPH oxidase attenuates the pharmacological effects of opioids by regulating GTPase activity and the phosphorylation of RGS9-2 by protein kinase C. NOX1/NADPH oxidase may thus be a novel target for the development of adjuvant therapy to retain the beneficial effects of morphine.

PPARδ coordinates angiotensin II-induced senescence in vascular smooth muscle cells through PTEN-mediated inhibition of superoxide generation.

Cellular senescence-associated changes in blood vessels have been implicated in aging and age-related cardiovascular disorders. Here, we demonstrate that peroxisome proliferator-activated receptor (PPAR) δ coordinates angiotensin (Ang) II-induced senescence of human vascular smooth muscle cells (VSMCs). Activation of PPARδ by GW501516, a specific ligand for PPARδ, significantly attenuated Ang II-induced generation of superoxides and suppressed senescence of VSMCs. A marked increase in the levels of p53 and p21 induced by Ang II was blunted by the treatment with GW501516. Ligand-activated PPARδ up-regulated expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and suppressed the phosphatidylinositol 3-kinase (PI3K)/Akt pathway. Knockdown of PTEN with siRNA abrogated the effects of PPARδ on cellular senescence, on PI3K/Akt signaling, and on generation of ROS in VSMCs treated with Ang II. Finally, administration of GW501516 to apoE-deficient mice treated with Ang II significantly reduced the number of senescent cells in the aorta, where up-regulation of PTEN with reduced levels of phosphorylated Akt and ROS was demonstrated. Thus, ligand-activated PPARδ confers resistance to Ang II-induced senescence by up-regulation of PTEN and ensuing modulation of the PI3K/Akt signaling to reduce ROS generation in vascular cells.

Potential role of the NADPH oxidase NOX1 in the pathogenesis of 5-fluorouracil-induced intestinal mucositis in mice.

Although NADPH oxidase 1 (NOX1) has been shown to be highly expressed in the gastrointestinal tract, the physiological and pathophysiological roles of this enzyme are not yet fully understood. In the present study, we investigated the role of NOX1 in the pathogenesis of intestinal mucositis induced by the cancer chemotherapeutic agent 5-fluorouracil (5-FU) in mice. Intestinal mucositis was induced in Nox1 knockout (Nox1KO) and littermate wild-type (WT) mice via single, daily administration of 5-FU for 5 days. In WT mice, 5-FU caused severe intestinal mucositis characterized by a shortening of villus height, a disruption of crypts, a loss of body weight, and diarrhea. In Nox1KO mice, however, the severity of mucositis was significantly reduced, particularly with respect to crypt disruption. The numbers of apoptotic caspase-3- and caspase-8-activated cells in the intestinal crypt increased 24 h after the first 5-FU administration but were overall significantly lower in Nox1KO than in WT mice. Furthermore, the 5-FU-mediated upregulation of TNF-α, IL-1ß, and NOX1 and the production of reactive oxygen species were significantly attenuated in Nox1KO mice compared with that in WT mice. These findings suggest that NOX1 plays an important role in the pathogenesis of 5-FU-induced intestinal mucositis. NOX1-derived ROS production following administration of 5-FU may promote the apoptotic response through upregulation of inflammatory cytokines.

NOX1/nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) oxidase promotes proliferation of stellate cells and aggravates liver fibrosis induced by bile duct ligation.

UNLABELLED: Among multiple isoforms of nicotinamide adenine dinucleotide phosphate, reduced form (NADPH) oxidase expressed in the liver, the phagocytic NOX2 isoform in hepatic stellate cells (HSCs) has been demonstrated to play a key role in liver fibrogenesis. The aim of this study was to clarify the role of NOX1, a nonphagocytic form of NADPH oxidase, in the development of fibrosis using Nox1-deficient mice (Nox1KO). Liver injury and fibrosis were induced by bile duct ligation (BDL) and carbon tetrachloride in Nox1KO and wildtype littermate mice (WT). Primary HSCs were isolated to characterize the NOX1-induced signaling cascade involved in liver fibrogenesis. Following BDL, a time-dependent increase in NOX1 messenger RNA (mRNA) was demonstrated in WT liver. Compared with those in WT, levels of collagen-1α mRNA and hydroxyproline were significantly suppressed in Nox1KO with a reduced number of activated HSCs and less severe fibrotic lesions. The expression levels of α-smooth muscle actin, a marker of HSCs activation, were similar in cultured HSCs isolated from both genotypes. However, cell proliferation was significantly attenuated in HSCs isolated from Nox1KO. In these cells, the expression of p27(kip1) , a cell cycle suppressor, was significantly up-regulated. Concomitantly, a significant reduction in phosphorylated forms of Akt and forkhead box O (FOXO) 4, a downstream effector of Akt that regulates the transcription of p27(kip1) gene, was demonstrated in Nox1KO. Finally, the level of the oxidized inactivated form of phosphatase and tensin homolog (PTEN), a negative regulator of PI3K/Akt pathway, was significantly attenuated in HSCs of Nox1KO. CONCLUSION: These findings indicate that reactive oxygen species derived from NOX1/NADPH oxidase oxidize and inactivate PTEN to positively regulate the Akt/FOXO4/p27(kip1) signaling pathway. NOX1 may thus promote proliferation of HSCs and accelerate the development of fibrosis following BDL-induced liver injury.