Nicotinamide adenine dinucleotide phosphate reduced oxidase 5 (Nox5) regulation by angiotensin II and endothelin-1 is mediated via calcium/calmodulin-dependent, rac-1-independent pathways in human endothelial cells.

RATIONALE: Although Nox5 (Nox2 homolog) has been identified in the vasculature, its regulation and functional significance remain unclear. OBJECTIVES: We sought to test whether vasoactive agents regulate Nox5 through Ca(2+)/calmodulin-dependent processes and whether Ca(2+)-sensitive Nox5, associated with Rac-1, generates superoxide (O(2)(*-)) and activates growth and inflammatory responses via mitogen-activated protein kinases in human endothelial cells (ECs). METHODS AND RESULTS: Cultured ECs, exposed to angiotensin II (Ang II) and endothelin (ET)-1 in the absence and presence of diltiazem (Ca(2+) channel blocker), calmidazolium (calmodulin inhibitor), and EHT1864 (Rac-1 inhibitor), were studied. Nox5 was downregulated with small interfering RNA. Ang II and ET-1 increased Nox5 expression (mRNA and protein). Effects were inhibited by actinomycin D and cycloheximide and blunted by diltiazem, calmidazolium and low extracellular Ca(2+) ([Ca(2+)](e)). Ang II and ET-1 activated NADPH oxidase, an effect blocked by low [Ca(2+)](e), but not by EHT1864. Nox5 knockdown abrogated agonist-stimulated O(2)(*-) production and inhibited phosphorylation of extracellular signal-regulated kinase (ERK)1/2, but not p38 MAPK (mitogen-activated protein kinase) or SAPK/JNK (stress-activated protein kinase/c-Jun N-terminal kinase). Nox5 small interfering RNA blunted Ang II-induced, but not ET-1-induced, upregulation of proliferating-cell nuclear antigen and vascular cell adhesion molecule-1, important in growth and inflammation. CONCLUSIONS: Human ECs possess functionally active Nox5, regulated by Ang II and ET-1 through Ca(2+)/calmodulin-dependent, Rac-1-independent mechanisms. Nox5 activation by Ang II and ET-1 induces ROS generation and ERK1/2 phosphorylation. Nox5 is involved in ERK1/2-regulated growth and inflammatory signaling by Ang II but not by ET-1. We elucidate novel mechanisms whereby vasoactive peptides regulate Nox5 in human ECs and demonstrate differential Nox5-mediated functional responses by Ang II and ET-1. Such phenomena link Ca(2+)/calmodulin to Nox5 signaling, potentially important in the regulation of endothelial function by Ang II and ET-1.

Bile acid reflux contributes to development of esophageal adenocarcinoma via activation of phosphatidylinositol-specific phospholipase Cgamma2 and NADPH oxidase NOX5-S.

Gastroesophageal reflux disease complicated by Barrett's esophagus (BE) is a major risk factor for esophageal adenocarcinoma (EA). However, the mechanisms of the progression from BE to EA are not fully understood. Besides acid reflux, bile acid reflux may also play an important role in the progression from BE to EA. In this study, we examined the role of phosphatidylinositol-specific phospholipase C (PI-PLC) and a novel NADPH oxidase NOX5-S in bile acid-induced increase in cell proliferation. We found that taurodeoxycholic acid (TDCA) significantly increased NOX5-S expression, hydrogen peroxide (H(2)O(2)) production, and cell proliferation in EA cells. The TDCA-induced increase in cell proliferation was significantly reduced by U73122, an inhibitor of PI-PLC. PI-PLCbeta1, PI-PLCbeta3, PI-PLCbeta4, PI-PLCgamma1, and PI-PLCgamma2, but not PI-PLCbeta2 and PI-PLCdelta1, were detectable in FLO cells by Western blot analysis. Knockdown of PI-PLCgamma2 or extracellular signal-regulated kinase (ERK) 2 mitogen-activated protein (MAP) kinase with small interfering RNAs (siRNA) significantly decreased TDCA-induced NOX5-S expression, H(2)O(2) production, and cell proliferation. In contrast, knockdown of PI-PLCbeta1, PI-PLCbeta3, PI-PLCbeta4, PI-PLCgamma1, or ERK1 MAP kinase had no significant effect. TDCA significantly increased ERK2 phosphorylation, an increase that was reduced by U73122 or PI-PLCgamma2 siRNA. We conclude that TDCA-induced increase in NOX5-S expression and cell proliferation may depend on sequential activation of PI-PLCgamma2 and ERK2 MAP kinase in EA cells. It is possible that bile acid reflux present in patients with BE may increase reactive oxygen species production and cell proliferation via activation of PI-PLCgamma2, ERK2 MAP kinase, and NADPH oxidase NOX5-S, thereby contributing to the development of EA.

Role of a novel bile acid receptor TGR5 in the development of oesophageal adenocarcinoma.

BACKGROUND AND AIMS: Mechanisms of the progression from Barrett's oesophagus to oesophageal adenocarcinoma (OA) are not fully understood. Bile acids may have an important role in this progression. This study aimed at examining the role of NADPH oxidase NOX5-S and a novel bile acid receptor TGR5 in taurodeoxycholic acid (TDCA)-induced increase in cell proliferation. METHODS: Human Barrett's cell line BAR-T and OA cell line FLO were transfected by the Lipofectamine 2000 or Amaxa-Nucleofector-System. mRNAs were measured by real-time PCR. H(2)O(2) was measured by a fluorescent assay. Cell proliferation was determined by measurement of thymidine incorporation. RESULTS: NOX5-S was present in FLO cells. TDCA significantly increased NOX5-S expression, H(2)O(2) production and thymidine incorporation in FLO and BAR-T cells. This increase in thymidine incorporation was significantly reduced by knockdown of NOX5-S. TGR5 mRNA and protein levels were significantly higher in OA tissues than in normal oesophageal mucosa or Barrett's mucosa. Knockdown of TGR5 markedly inhibited TDCA-induced increase in NOX5-S expression, H(2)O(2) production and thymidine incorporation in FLO and BAR-T cells. Overexpression of TGR5 significantly enhanced the effects of TDCA in FLO cells. TGR5 receptors were coupled with Galphaq and Galphai3 proteins, but only Galphaq mediated TDCA-induced increase in NOX5-S expression, H(2)O(2) production and thymidine incorporation in FLO cells. CONCLUSIONS: TDCA-induced increase in cell proliferation depends on upregulation of NOX5-S expression in BAR-T and FLO cells. TDCA-induced NOX5-S expression may be mediated by activation of the TGR5 receptor and Galphaq protein. These data may provide potential targets to prevent and/or treat Barrett's OA.

Chemical sensing using nanostructured polythiophene transistors.

We show that the chemical sensing responses of organic field-effect transistors based on nanostructured regioregular polythiophene are strongly dependent upon the gate biasing field. With different applied gate voltages, the source-drain current response can be different both in sign and magnitude for the same analyte. This implies that multiple competing sensing mechanisms exist at the same time. We propose that the sensing mechanisms for polycrystalline semiconducting polymer thin films are mainly an intragrain effect, which yields a positive response, and a grain boundary effect, which yields a negative response.

STAT5 mediates PAF-induced NADPH oxidase NOX5-S expression in Barrett's esophageal adenocarcinoma cells.

We have shown that NADPH oxidase NOX5-S is overexpressed in Barrett's esophageal adenocarcinoma (EA) cells and may contribute to the progression from Barrett's esophagus (BE) to EA presumably by increasing cell proliferation and decreasing apoptosis (Fu X, Beer DG, Behar J, Wands J, Lambeth D, Cao W. J Biol Chem 281: 20368-20382, 2006). The mechanism(s) of NOX5-S overexpression in EA, however, is not fully understood. In SEG1 EA cells we found that acid treatment significantly increased platelet-activating factor (PAF) production, which in turn markedly increased NOX5-S expression and hydrogen peroxide (H(2)O(2)) production. Knockdown of NOX5-S by NOX5-S small interfering RNA (siRNA) blocked PAF-dependent H(2)O(2) production. PAF-dependent induction of NOX5-S expression and H(2)O(2) production were significantly decreased by the MAPK kinase 1 inhibitor PD-98059, by the cytosolic phospholipase A(2) (cPLA(2)) inhibitor AACOCF3, and by STAT5 downregulation with STAT5 siRNA. PAF significantly increased the phosphorylation of ERK1/2 MAPK, cPLA(2), and STAT5. Using inhibitors, we demonstrated that PAF-induced STAT5 phosphorylation depends on activation of ERK1/2 MAPK and cPLA(2), whereas PAF-induced cPLA(2) phosphorylation was associated with activation of ERK1/2 MAPK. Given that STAT5 bound to the c-sis-inducible element (TTCTGGTAA) of the NOX5-S promoter, overexpression of STAT5 significantly increased NOX5-S promoter activity. We conclude that acid-induced NOX5-S expression and H(2)O(2) production is mediated in part by production of PAF in SEG1 EA cells, and that PAF-induced increase in NOX5-S expression depends on sequential activation of ERK MAP kinases, cPLA(2), and STAT5 in these cells.

Overexpression of human NOX1 complex induces genome instability in mammalian cells.

The production of reactive oxygen species (ROS) in mammalian cells is tightly regulated because of their potential to damage macromolecules, including DNA. To investigate possible links between high ROS levels, oxidative DNA damage, and genomic instability in mammalian cells, we established a novel model of chronic oxidative stress by coexpressing the NADPH oxidase human (h) NOX1 gene together with its cofactors NOXO1 and NOXA1. Transfectants of mismatch repair (MMR)-proficient HeLa cells or MMR-defective Msh2(-/-) mouse embryo fibroblasts overexpressing the hNOX1 complex displayed increased intracellular ROS levels. In one HeLa clone in which ROS were particularly elevated, reactive nitrogen species were also increased and nitrated proteins were identified with an anti-3-nitrotyrosine antibody. Overexpression of the hNOX1 complex increased the steady-state levels of DNA 8-oxo-7,8-dihydroguanine and caused a threefold increase in the HPRT mutation rate in HeLa cells. In contrast, additional oxidatively generated damage did not affect the constitutive mutator phenotype of the Msh2(-/-) fibroblasts. Because no significant changes in the expression of several DNA repair enzymes for oxidative DNA damage were identified, we suggest that chronic oxidative stress can saturate the cell's DNA repair capacity and cause significant genomic instability.

NADPH oxidase NOX5-S mediates acid-induced cyclooxygenase-2 expression via activation of NF-kappaB in Barrett's esophageal adenocarcinoma cells.

We have shown that the NADPH oxidase NOX5-S may play an important role in the progression from Barrett's esophagus to esophageal adenocarcinoma (EA) by increasing cell proliferation and decreasing apoptosis. However, the mechanism of the acid-induced NOX5-S-mediated increase in cell proliferation is not known. We found that, in SEG1 EA cells, the acid-induced increase in prostaglandin E2 (PGE2) production was mediated by activation of cyclooxygenase-2 (COX2) but not by COX1. Acid treatment increased intracellular Ca2+, and a blockade of intracellular Ca2+ increase inhibited the acid-induced increase in COX2 expression and PGE2 production. Knockdown of NOX5-S or NF-kappaB1 p50 by their small interfering RNA significantly inhibited acid-induced COX2 expression and PGE2 production in SEG1 cells. Acid treatment significantly decreased IkappaBalpha and increased luciferase activity when SEG1 cells were transfected with an NF-kappaB in vivo activation reporter plasmid, pNF-kappaB-Luc. In a novel Barrett's cell line overexpressing NOX5-S, IkappaBalpha was significantly reduced, and luciferase activity increased when these Barrett's cells were transfected with pNF-kappaB-Luc. Overexpression of NOX5-S in Barrett's cells significantly increased H2O2 production, COX2 expression, PGE2 production, and thymidine incorporation. The increase in thymidine incorporation occurring in NOX5-S-overexpressing Barrett's cells or induced by acid treatment in SEG1 EA cells was significantly decreased by COX2 inhibitors or small interfering RNA. We conclude that acid-induced COX2 expression and PGE2 production depend on an increase in cytosolic Ca2+ and sequential activation of NOX5-S and NF-kappaB in SEG1 cells. COX2-derived PGE2 production may contribute to NOX5-S-mediated cell proliferation in SEG1 cells.

Volatile organic compound detection using nanostructured copolymers.

Regioregular polythiophene-based conductive copolymers with highly crystalline nanostructures are shown to hold considerable promise as the active layer in volatile organic compound (VOC) chemresistor sensors. While the regioregular polythiophene polymer chain provides a charge conduction path, its chemical sensing selectivity and sensitivity can be altered either by incorporating a second polymer to form a block copolymer or by making a random copolymer of polythiophene with different alkyl side chains. The copolymers were exposed to a variety of VOC vapors, and the electrical conductivity of these copolymers increased or decreased depending upon the polymer composition and the specific analytes. Measurements were made at room temperature, and the responses were found to be fast and appeared to be completely reversible. Using various copolymers of polythiophene in a sensor array can provide much better discrimination to various analytes than existing solid state sensors. Our data strongly indicate that several sensing mechanisms are at play simultaneously, and we briefly discuss some of them.

cAMP-response element-binding protein mediates acid-induced NADPH oxidase NOX5-S expression in Barrett esophageal adenocarcinoma cells.

Gastroesophageal reflux disease complicated by Barrett esophagus (BE) is a major risk factor for esophageal adenocarcinoma (EA). The mechanisms whereby acid reflux may accelerate the progression from BE to EA are not known. We found that NOX1 and NOX5-S were the major isoforms of NADPH oxidase in SEG1-EA cells. The expression of NOX5-S mRNA was significantly higher in these cells than in esophageal squamous epithelial cells. NOX5 mRNA was also significantly higher in Barrett tissues with high grade dysplasia than without dysplasia. Pulsed acid treatment significantly increased H(2)O(2) production in both SEG1-EA cells and BE mucosa, which was blocked by the NADPH oxidase inhibitor apocynin. In SEG1 cells, acid treatment increased mRNA expression of NOX5-S, but not NOX1, and knockdown of NOX5 by NOX5 small interfering RNA abolished acid-induced H(2)O(2) production. In addition, acid treatment increased intracellular Ca(2+) and phosphorylation of cAMP-response element-binding protein (CREB). Acid-induced NOX5-S expression and H(2)O(2) production were significantly inhibited by removal of extracellular Ca(2+) and by knockdown of CREB using CREB small interfering RNA. Two novel CREB-binding elements TGACGAGA and TGACGCTG were identified in the NOX5-S gene promoter. Overexpression of CREB significantly increased NOX5-S promoter activity. Knockdown of NOX5 significantly decreased [(3)H]thymidine incorporation, which was restored by 10(-13) M H(2)O(2). Knockdown of NOX5 also significantly decreased retinoblastoma protein phosphorylation and increased cell apoptosis and caspase-9 expression. In conclusion, in SEG1 EA cells NOX5-S is overexpressed and mediates acid-induced H(2)O(2) production. Acid-induced NOX5-S expression depends on an increase in intracellular Ca(2+) and activation of CREB. NOX5-S contributes to increased cell proliferation and decreased apoptosis.

Nanostructure dependence of field-effect mobility in regioregular poly(3-hexylthiophene) thin film field effect transistors.

Low polydispersity regioregular polythiophenes with number average molecular weights ranging from 2 to 13 kDa were cast under the same conditions from solution to form a series of field effect transistors (FETs). Tapping mode AFM and grazing incidence small-angle X-ray scattering revealed that in all cases the polymers formed regular nanofibrillar morphologies with the width of nanofibrils proportional to the weight average contour length of polymer chains, indicating that conjugated backbones were oriented perpendicular to the nanofibril axes. FET charge carrier mobilities exhibited exponential dependence on nanofibril width, pointing to the decisive role of extended conjugated pathways in charge transport.

Addition of the antioxidant probucol to angiotensin II type I receptor antagonist arrests progressive mesangioproliferative glomerulonephritis in the rat.

Angiotensin II (Ang II) and reactive oxidative species (ROS) that are produced by NADPH oxidase have been implicated in the progression of glomerulonephritis (GN). This study examined the effect of simultaneously interrupting Ang II and ROS with an Ang II receptor blocker (ARB), candesartan, and a free radical scavenger, probucol, in a model of progressive mesangioproliferative GN induced by the injection of anti-Thy-1 antibody into uninephrectomized rats. Nephritic rats were divided into four groups and given daily oral doses of the following: Vehicle, 1% probucol diet, 70 mg/L candesartan in drinking water, and probucol plus candesartan. These treatments lasted until day 56. Vehicle-treated nephritic rats developed progressively elevated proteinuria and glomerulosclerosis. Candesartan kept proteinuria significantly lower than vehicle or probucol. The addition of probucol to candesartan normalized urinary protein excretion. Increases in BP in nephritic rats were lowered by these treatments, except with probucol. It is interesting that both glomerular cell number and glomerulosclerosis were significantly decreased by candesartan and normalized by the addition of probucol. Immunohistochemical studies for TGF-beta1, collagen type I, and fibronectin revealed that the combined treatment abolished glomerular fibrotic findings compared with candesartan. In addition, glomerular expression of NADPH oxidase components and superoxide production suggested that the combined treatment completely eliminated NADPH oxidase-associated ROS production. In conclusion, our study provides the first evidence that the antioxidant probucol, when added to an Ang II receptor blockade, fully arrests proteinuria and disease progression in GN. Furthermore, the data suggest that NADPH oxidase-associated ROS production may play a pivotal role in the progression of GN. The combination of probucol and candesartan may represent a novel route of therapy for patients with progressive GN.

Reconsideration of the significance of substrate-level phosphorylation in the citric acid cycle*.

For nearly 50 years, students of metabolism in animals have been taught that a substrate-level phosphorylation in the Krebs citric acid cycle produces GTP that subsequently undergoes a transphosphorylation with ADP catalyzed by nucleoside diphosphate kinase. Research in the past decade has revealed that animals also express an ADP-forming succinate-CoA ligase whose activity exceeds that of the GDP-forming enzyme in some tissues. Here I argue that the primary fate of GTP is unlikely to be transphosphorylation with ADP. Rather, two succinate-CoA ligases with different nucleotide specificities have evolved to better integrate and regulate the central metabolic pathways that involve the citric acid cycle. The products of substrate-level phosphorylation, ATP and/or GTP, may represent a pool of nucleotide that has a different phosphorylation potential than the ATP made by oxidative phosphorylation and may be channeled to meet specific needs within mitochondria and the cell. Further research is needed to determine the applicable mechanisms and how they vary in tissues.

Evaluation of two anti-gp91phox antibodies as immunoprobes for Nox family proteins: mAb 54.1 recognizes recombinant full-length Nox2, Nox3 and the C-terminal domains of Nox1-4 and cross-reacts with GRP 58.

Progress in the study of Nox protein expression has been impeded because of the paucity of immunological probes. The large subunit of human phagocyte flavocytochrome b558 (Cytb), gp91phox, is also the prototype member of the recently discovered family of NADPH oxidase (Nox) proteins. In this study, we have evaluated the use of two anti-gp91phox monoclonal antibodies, 54.1 and CL5, as immunoprobes for Nox family proteins. Sequence alignment of gp91phox with Nox1, Nox3 and Nox4 identified regions of the Nox proteins that correspond to the gp91phox epitopes recognized by mAb 54.1 and CL5. Antibody 54.1 produced positive immunoblots of recombinant C-terminal fragments of these homologous proteins expressed in E. coli. Furthermore, only mAb 54.1 recognized full-length murine and human Nox3 expressed in HEK-293 cells, in immunoblots of alkali-stripped or detergent-solubilized membranes. 54.1 recognized Nox3 expression-specific proteins with Mr 30,000, 50,000, 65,000 and 88,000 for the murine protein and Mr of 38,000-58,000, 90,000, 100,000-130,000 and a broad species of higher than 160,000 for the human protein. We conclude that mAb 54.1 can serve as a probe of Nox3 and possibly other Nox proteins, if precautions are taken to remove GRP 58 and other crossreactive membrane-associated or detergent-insoluble proteins from the sample to be probed.

Expression of two succinyl-CoA synthetases with different nucleotide specificities in mammalian tissues.

For nearly 50 years, succinyl-CoA synthetase in animals was thought to be specific for guanine nucleotides. Recently, we purified and characterized both an ADP-forming succinyl-CoA synthetase from pigeon breast muscle and the GDP-forming enzyme from liver (Johnson, J. D., Muhonen, W. W., and Lambeth, D. O. (1998) J. Biol. Chem. 273, 27573-27579). Using the sequences of the pigeon enzymes as queries in BLAST searches, we obtained genetic evidence that both enzymes are expressed in a wide range of animal species (Johnson, J. D., Mehus, J. G., Tews, K., Milavetz, B. I., and Lambeth, D. O. (1998) J. Biol. Chem. 273, 27580-27586). Here we extend those observations by presenting data from Western and Northern blots and enzymatic assays showing that both proteins are widely expressed in mammals with the relative amounts varying from tissue to tissue. We suggest that both succinyl-CoA synthetases catalyze the reverse reaction in the citric acid cycle in which the ADP-forming enzyme augments ATP production, whereas the GDP-forming enzyme supports GTP-dependent anabolic processes. Widely accepted shuttle mechanisms are invoked to explain how transport of P-enolpyruvate across mitochondrial membranes can transfer high energy phosphate between the cytosol and mitochondrial matrix.