Inhibition of reactive oxygen species by Lovastatin downregulates vascular endothelial growth factor expression and ameliorates blood-retinal barrier breakdown in db/db mice: role of NADPH oxidase 4

OBJECTIVE

Oxidative stress is a key pathogenic factor in diabetic retinopathy. We previously showed that lovastatin mitigates blood-retinal barrier (BRB) breakdown in db/db mice. The purpose of this study is to determine the mechanisms underlying the salutary effects of lovastatin in diabetic retinopathy.

RESEARCH DESIGN AND METHODS

Expression of NADPH oxidase (Nox) 4, vascular endothelial growth factor (VEGF), and hypoxia-inducible factor (HIF)-1alpha; production of reactive oxygen species (ROS); and retinal vascular permeability were measured in cultured retinal capillary endothelial cells (RCECs) and in db/db mice treated with lovastatin.

RESULTS

Expressions of Nox4 and VEGF were significantly increased in retinas of db/db mice and reduced by lovastatin treatment. In cultured RCECs, hypoxia and high glucose upregulated mRNA and protein expression of Nox4, ROS generation, and VEGF level. These changes were abrogated by pretreatment with lovastatin or NADPH oxidase inhibitor diphenyleneiodonium chloride. Overexpression of Nox4 increased basal level of ROS generation, HIF-1alpha, and VEGF expression in RCECs. In contrast, blockade of Nox4 activity using adenovirus-expressing dominant-negative Nox4 abolished hypoxia- and high-glucose-induced ROS production and VEGF expression. Moreover, inhibition of Nox4 attenuated hypoxia-induced upregulation of HIF-1alpha and high-glucose-elicited phosphorylation of STAT3. Finally, depletion of Nox4 by adenovirus-delivered Nox4 small interfering RNA significantly decreased retinal NADPH oxidase activity and VEGF expression and reduced retinal vascular premeability in db/db mice.

CONCLUSIONS

Activation of Nox4 plays an important role in high-glucose- and hypoxia-mediated VEGF expression and diabetes-induced BRB breakdown. Inhibition of Nox4, at least in part, contributes to the protective effects of lovastatin in diabetic retinopathy.

[cDNA cloning and expression characterization of three regulatory subunits of NADPH oxidase within cytoplasm from mandarin fish, Siniperca chuatsi]

The phagocyte NADPH oxidase plays a crucial role in host defense against invading microorganisms by catalyzing the formation of reactive oxygen species, which is the precursor of a variety of microbicidal oxidants such as hydrogen peroxide (H2O2). In the present study, full-length cDNAs of three regulatory subunits of NADPH oxidase, including p40phox, p47phox, p67phox were cloned from head kidney of mandarin fish utilizing the reverse transcription polymerase chain reaction and rapid amplification of cDNA ends. Sequence analysis showed that the full length cDNA of p40phox is 1 406 nt, containing a 1 050 nt open reading frames that encodes a 349 amino acid protein, the full length cDNA of p47phox is 1 686 nt, containing a 1 209 nt open reading frames that encodes a 402 amino acid protein, the full length cDNA of p40phox is 2 185 nt, containing a 1 488 nt open reading frames that encodes a 495 amino acid protein. Semi-quantitative RT-PCR analyses from various tissues indicated that mRNAs of the three subunits can be detected in the blood, brain, heart, spleen, kidney and thymus, but their expression intensity are different in tissues. Stimulating the mandarin fish with formalin killed Flavobacterium columnare G4 significantly up-regulated the expression of p40phox in blood and head kidney; and p47phox in head kidney and spleen; and p67phox in blood, head kidney and spleen. The results suggested that mandarin NADPH oxidase was involved in the immune responses against bacteria.

Activation of mineralocorticoid receptors by exogenous glucocorticoids and the development of cardiovascular inflammatory responses in adrenalectomized rats

Activation of the mineralocorticoid receptor (MR) in the context of a high salt intake produces cardiovascular inflammation plus cardiac fibrosis and failure. Inactivation of vascular 11beta-hydroxysteroid dehydrogenase type 2 activity in intact animals by carbenoxolone (CBX) produces a similar pathology, presumably reflecting coronary vascular MR activation by endogenous glucocorticoids. To test this hypothesis, we have used adrenalectomized rats, without endogenous corticosteroids, and examined the consequences of corticosterone (CORT) replacement on a series of cardiovascular disease parameters. Uninephrectomized adrenalectomized Sprague Dawley rats given 1% NaCl/0.3% KCl to drink were treated for 8 d as follows: control; 20 mg deoxycorticosterone (DOC); 2 mg/d CORT; 2.5 mg/d CBX; CORT plus CBX (CORT/CBX); and CORT/CBX plus 100 mg/kg.d eplerenone. Markers of cardiac oxidative stress (p22(phox) and NOX4 mRNA) were up-regulated in the DOC and CORT/CBX groups; in contrast, inflammatory cell infiltration was increased and endothelial nitric oxide synthase down-regulated by CORT as well as by DOC and CORT/CBX. In the kidney, connective tissue growth factor mRNA levels were increased by DOC and CORT/CBX; in contrast, DOC had no effect on mRNA levels for channel inducing factor or endothelin 3, which were elevated only by CORT/CBX. All changes noted were reversed by eplerenone. Rats given 10-fold lower CORT (0.2 mg/d) with or without CBX showed no change in any parameter. These results suggest that there exist distinct but overlapping ligand-specific MR-mediated tissue responses to a classic mineralocorticoid (DOC) and to the glucocorticoid CORT, in the presence and absence of CBX to block vascular 11beta-hydroxysteroid dehydrogenase type 2.

Cigarette smoke particle-phase extract induces HO-1 expression in human tracheal smooth muscle cells: role of the c-Src/NADPH oxidase/MAPK/Nrf2 signaling pathway

Heme oxygenase-1 (HO-1) is known as an oxidative stress protein that is up-regulated by various stimuli. HO-1 has been shown to protect cells against oxidative damage. Cigarette smoke is a potential inflammatory mediator that causes chronic obstructive pulmonary disease and asthma. In this study, we report that cigarette smoke particle-phase extract (CSPE) is an inducer of HO-1 expression mediated through various signaling pathways in human tracheal smooth muscle cells (HTSMCs). CSPE-induced HO-1 protein, mRNA expression, and promoter activity were attenuated by pretreatment with a ROS scavenger (N-acetyl-l-cysteine) and inhibitors of c-Src (PP1), NADPH oxidase [diphenylene iodonium chloride (DPI) and apocynin (APO)], MEK1/2 (U0126), p38 MAPK (SB202190), and JNK1/2 (SP600125) or transfection with siRNAs for Src, p47(phox), NOX2, p42, p38, JNK2, or NF-E2-related factor 2 (Nrf2). CSPE-stimulated translocation of p47(phox) and Nrf2, ROS production, and NADPH oxidase activity was attenuated by transfection with siRNAs for Src, p47(phox), and NOX2 or pretreatment with PP1, DPI, or APO. Furthermore, CSPE-induced NOX2, c-Src, and p47(phox) complex formation was revealed by immunoprecipitation using an anti-NOX2, anti-p47(phox), or anti-c-Src Ab followed by Western blot against anti-NOX2, anti-p47(phox), or anti-c-Src Abs. These results demonstrate that CSPE-induced ROS generation is mediated through a c-Src/NADPH oxidase/MAPK pathway and in turn initiates the activation of Nrf2 and ultimately induces HO-1 expression in HTSMCs.

Nox1 is involved in p53 deacetylation and suppression of its transcriptional activity and apoptosis

HIPK2 is a stress-induced kinase and a transcriptional corepressor that functionally cooperates with p53 to suppress cancer. Activation of the p53 proapoptotic function requires a cascade of phosphorylations and acetylations, and HIPK2 takes part in both modifications in that it phosphorylates p53 Ser46 and induces p53 Lys382 acetylation. Here, to further investigate the role of HIPK2 in p53 activation, we started with the finding that HIPK2 inhibition upregulated Nox1, a homolog of the catalytic subunit of the superoxide-generating NADPH oxidase, involved in tumor progression and ROS production. We found that Nox1 inhibited p53 Lys382 acetylation, which is a target of SIRT1 deacetylase, and impaired p53 proapoptotic transcriptional activity. By the use of either small interfering RNAs to target SIRT1 or the SIRT1 inhibitor nicotinamide we found that Nox1-dependent inhibition of p53 transcriptional activity was SIRT1-dependent. Thus, Nox1 was unable to inhibit p53 when coexpressed with a SIRT1 deacetylase-defective mutant (SIRT1HY), suggesting a link between Nox1 and SIRT1 activity. Finally, recovery of HIPK2 function downregulated Nox1 expression with rescue of p53 Lys382 acetylation and p53 activity. Together, our findings indicate that Nox1 upregulation may activate SIRT1 and inhibit p53 and that Lys382 is important for p53 proapoptotic function.

TLR activation of the transcription factor XBP1 regulates innate immune responses in macrophages

Sensors of pathogens, such as Toll-like receptors (TLRs), detect microbes to activate transcriptional programs that orchestrate adaptive responses to specific insults. Here we report that TLR4 and TLR2 specifically activated the endoplasmic reticulum (ER) stress sensor kinase IRE1alpha and its downstream target, the transcription factor XBP1. Previously described ER-stress target genes of XBP1 were not induced by TLR signaling. Instead, TLR-activated XBP1 was required for optimal and sustained production of proinflammatory cytokines in macrophages. Consistent with that finding, activation of IRE1alpha by ER stress acted in synergy with TLR activation for cytokine production. Moreover, XBP1 deficiency resulted in a much greater bacterial burden in mice infected with the TLR2-activating human intracellular pathogen Francisella tularensis. Our findings identify an unsuspected critical function for XBP1 in mammalian host defenses.

Cooperative induction of CXCL10 involves NADPH oxidase: Implications for HIV dementia

With the increasing prevalence of HIV-associated neurocognititve disorders (HAND), understanding the mechanisms by which HIV-1 induces neuro-inflammation and subsequent neuronal damage is important. The hallmark features of HIV-encephalitis, the pathological correlate of HIV-associated Dementia (HAD), are gliosis, oxidative stress, chemokine dysregulation, and neuronal damage/death. Since neurons are not infected by HIV-1, the current thinking is that these cells are damaged indirectly by pro-inflammatory chemokines released by activated glial cells. CXCL10 is a neurotoxic chemokine that is upregulated in astroglia activated by HIV-1 Tat, IFN-gamma, and TNF-alpha. In this study we have demonstrated that HIV-1 Tat increases CXCL10 expression in IFN-gamma and TNF-alpha stimulated human astrocytes via NADPH oxidase. We have shown that the treatment of astrocytes with a mixture of Tat and cytokines leads to a respiratory burst that is abrogated by apocynin, an NADPH oxidase inhibitor. Pretreatment of Tat, IFN-gamma, and TNF-alpha stimulated astrocytes with apocynin also resulted in concomitant inhibition of CXCL10 expression. Additionally, apocynin was also able to reduce Tat and cytokine-mediated activation of the corresponding signaling molecules Erk1/2, Jnk, and Akt with a decrease in activation and nuclear translocation of NF-kappaB, important regulators of CXCL10 induction. Understanding the mechanisms involved in reducing both oxidative stress and the release of pro-inflammatory agents could lead to the development of therapeutics aimed at decreasing neuro-inflammation in patients suffering from HAD.

Protection of podocytes from hyperhomocysteinemia-induced injury by deletion of the gp91phox gene

In this study, mice lacking the gp91(phox) gene were used to address the role of NADPH oxidase in hyperhomocysteinemia-induced podocyte injury. It was found that a folate-free diet increased plasma homocysteine levels, but failed to increase O(2)(-) production in the glomeruli from gp91(phox) gene knockout (gp91(-/-)) mice, compared with wild-type (gp91(+/+)) mice. Proteinuria and glomerular damage index (GDI) were significantly lower, whereas the glomerular filtration rate (GFR) was higher in gp91(-/-) than in gp91(+/+) mice when they were on the folate-free diet (urine albumin excretion, 21.23+/-1.88 vs 32.86+/-4.03 microg/24 h; GDI, 1.17+/-0.18 vs 2.59+/-0.49; and GFR, 53.01+/-4.69 vs 40.98+/-1.44 microl/min). Hyperhomocysteinemia-induced decrease in nephrin expression and increase in desmin expression in gp91(+/+) mice were not observed in gp91(-/-) mice. Morphologically, foot process effacement and podocyte loss due to hyperhomocysteinemia were significantly attenuated in gp91(-/-) mice. In in vitro studies of podocytes, homocysteine was found to increase gp91(phox) expression and O2(*)(-) generation, which was substantially inhibited by gp91(phox) siRNA. Functionally, homocysteine-induced decrease in vascular endothelial growth factor-A production was abolished by gp91(phox) siRNA or diphenyleneiodonium, a NADPH oxidase inhibitor. These results suggest that the functional integrity of NADPH oxidase is essential for hyperhomocysteinemia-induced podocyte injury and glomerulosclerosis.

Delimitation and functional characterization of the bidirectional THOX-DUOXA promoter regions in thyrocytes

The THOX and DUOXA genes encode components of the oxidative machinery involved in thyroid hormone biosynthesis. Both of these genes are duplicated in mammalian genomes and are positioned in a head-to-head configuration, THOX1 facing DUOXA1 and THOX2 facing DUOXA2, respectively. The intergenic regions in both couples of genes exhibit dissimilar compositions, being highly GC-rich in the case of THOX1-DUOXA1 but not in the other case. In this study we localized precisely the transcription starts of all four genes using the RLM-RACE technique. It revealed that the distance between THOX1 and DUOXA1 transcription units is of about 70bp only, whereas THOX2 and DUOXA2 transcription starts are separated by 170bp. Analysis of these putative promoter regions revealed the presence of several potential binding sites for transcription factor Sp1 within the THOX1-DUOXA1 intergenic space, and of a TATA box and an Inr element in front of DUOXA2 and THOX2 genes, respectively. The putative promoter regions were inserted into a specifically designed vector harbouring two distinct reporter genes facing each other and their activity was investigated in transient transfection experiments in rat thyroid PCCl3 cells. Both regions exhibited bidirectional promoter activity in the assay. Gel shift experiments using extracts obtained from PCCl3 cells demonstrated the existence of at least one functional Sp1 binding site within the THOX1-DUOXA1 promoter. When Sp1 binding was abolished by mutation of the DNA sequence, a clear reduction in promoter activity in both THOX1 and DUOXA1 directions was observed in the functional assay. As these promoter sequences are well conserved in mammalian genomes, it appears very likely that the results we obtained here in the rat may be extended to the other species.

Chronic granulomatous disease

Chronic granulomatous disease (CGD) was first described in the 1950s and has become a paradigm for genetic neutrophil diseases. It is characterized by recurrent infections with a narrow spectrum of bacteria and fungi as well as a common set of inflammatory complications most notably including inflammatory bowel disease. Over the last half century major advances in management have profoundly altered the major clinical issues and the life expectancy of CGD. With X-linked and autosomal recessive forms, it has been an important disease for the development of bone marrow transplantation and gene therapy. Some of the recent developments in infectious syndromes, inflammatory complications, and curative approaches are discussed in this review.

Curcumin reduces angiotensin II-mediated cardiomyocyte growth via LOX-1 inhibition

BACKGROUND

Curcumin, a natural polyphenolic compound, has been shown to reduce cardiomyocyte growth. Angiotensin II type 1 receptor (AT1R) and lectin-like oxidized low density lipoprotein (ox-LDL) receptor-1 (LOX-1) are major stimuli for cardiomyocyte growth via activation of oxidant signals. We postulated that curcumin may reduce Ang II-mediated cardiomyocyte growth via AT1R and LOX-1 inhibition.

METHODS

Adult mouse cardiomyocytes (HL-1) were incubated overnight in serum-free medium, and then treated with solvents or curcumin, the AT1R inhibitor losartan or anti-LOX-1 antibody for 3 hours, and the cells were then stimulated with Ang II. We measured cardiomyocyte growth, and associated intracellular redox signals using reverse transcriptase-polymerase chain reaction and quantitative real-time RT-PCR. We also examined the effect of curcumin on cardiomyocyte biology with forced overexpression of LOX-1 gene.

RESULTS

Curcumin (5-10 microM), losartan, and anti-LOX-1 antibody markedly attenuated Ang II-mediated oxidant stress, and the expression of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and nuclear factor-kappaB (NF-kappaB). Attenuation of redox state by curcumin resulted in abrogation of Ang II-mediated cardiomyocyte growth and atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) genes. Curcumin also reduced Ang II-mediated upregulation of AT1R and LOX-1. The forced upregulation of LOX-1 enhanced the expression of genes for AT1R, ANP, and BNP, and curcumin pretreatment reduced LOX-1 and AT1R expression and LOX-1-mediated increase in hypertrophy markers.

CONCLUSIONS

Curcumin attenuates Ang II-mediated cardiomyocyte growth by inhibiting LOX-1 and AT1R expression and suppressing the heightened intracellular redox state.

Dehydroepiandrosterone sulfate directly activates protein kinase C-beta to increase human neutrophil superoxide generation

Dehydroepiandrosterone sulfate (DHEAS) is the most abundant steroid in the human circulation and is secreted by the adrenals in an age-dependent fashion, with maximum levels during the third decade and very low levels in old age. DHEAS is considered an inactive metabolite, whereas cleavage of the sulfate group generates dehydroepiandrosterone (DHEA), a crucial sex steroid precursor. However, here we show that DHEAS, but not DHEA, increases superoxide generation in primed human neutrophils in a dose-dependent fashion, thereby impacting on a key bactericidal mechanism. This effect was not prevented by coincubation with androgen and estrogen receptor antagonists but was reversed by the protein kinase C inhibitor Bisindolylmaleimide 1. Moreover, we found that neutrophils are unique among leukocytes in expressing an organic anion-transporting polypeptide D, able to mediate active DHEAS influx transport whereas they did not express steroid sulfatase that activates DHEAS to DHEA. A specific receptor for DHEAS has not yet been identified, but we show that DHEAS directly activated recombinant protein kinase C-beta (PKC-beta) in a cell-free assay. Enhanced PKC-beta activation by DHEAS resulted in increased phosphorylation of p47(phox), a crucial component of the active reduced nicotinamide adenine dinucleotide phosphate complex responsible for neutrophil superoxide generation. Our results demonstrate that PKC-beta acts as an intracellular receptor for DHEAS in human neutrophils, a signaling mechanism entirely distinct from the role of DHEA as sex steroid precursor and with important implications for immunesenescence, which includes reduced neutrophil superoxide generation in response to pathogens.

High resolution melting analysis for gene scanning

High resolution melting is a new method of genotyping and variant scanning that can be seamlessly appended to PCR amplification. Limitations of genotyping by amplicon melting can be addressed by unlabeled probe or snapback primer analysis, all performed without labeled probes. High resolution melting can also be used to scan for rare sequence variants in large genes with multiple exons and is the focus of this article. With the simple addition of a heteroduplex-detecting dye before PCR, high resolution melting is performed without any additions, processing or separation steps. Heterozygous variants are identified by atypical melting curves of a different shape compared to wild-type homozygotes. Homozygous or hemizygous variants are detected by prior mixing with wild-type DNA. Design, optimization, and performance considerations for high resolution scanning assays are presented for rapid turnaround of gene scanning. Design concerns include primer selection and predicting melting profiles in silico. Optimization includes temperature gradient selection of the annealing temperature, random population screening for common variants, and batch preparation of primer plates with robotically deposited and dried primer pairs. Performance includes rapid DNA preparation, PCR, and scanning by high resolution melting that require, in total, only 3h when no variants are present. When variants are detected, they can be identified in an additional 3h by rapid cycle sequencing and capillary electrophoresis. For each step in the protocol, a general overview of principles is provided, followed by an in depth analysis of one example, scanning of CYBB, the gene that is mutated in X-linked chronic granulomatous disease.

NADPH oxidase limits innate immune responses in the lungs in mice

BACKGROUND

Chronic granulomatous disease (CGD), an inherited disorder of the NADPH oxidase in which phagocytes are defective in generating superoxide anion and downstream reactive oxidant intermediates (ROIs), is characterized by recurrent bacterial and fungal infections and by excessive inflammation (e.g., inflammatory bowel disease). The mechanisms by which NADPH oxidase regulates inflammation are not well understood.

METHODOLOGY/PRINCIPAL FINDINGS

We found that NADPH oxidase restrains inflammation by modulating redox-sensitive innate immune pathways. When challenged with either intratracheal zymosan or LPS, NADPH oxidase-deficient p47(phox-/-) mice and gp91(phox)-deficient mice developed exaggerated and progressive lung inflammation, augmented NF-kappaB activation, and elevated downstream pro-inflammatory cytokines (TNF-alpha, IL-17, and G-CSF) compared to wildtype mice. Replacement of functional NADPH oxidase in bone marrow-derived cells restored the normal lung inflammatory response. Studies in vivo and in isolated macrophages demonstrated that in the absence of functional NADPH oxidase, zymosan failed to activate Nrf2, a key redox-sensitive anti-inflammatory regulator. The triterpenoid, CDDO-Im, activated Nrf2 independently of NADPH oxidase and reduced zymosan-induced lung inflammation in CGD mice. Consistent with these findings, zymosan-treated peripheral blood mononuclear cells from X-linked CGD patients showed impaired Nrf2 activity and increased NF-kappaB activation.

CONCLUSIONS/SIGNIFICANCE

These studies support a model in which NADPH oxidase-dependent, redox-mediated signaling is critical for termination of lung inflammation and suggest new potential therapeutic targets for CGD.

[A report of a family with chronic granulomatous disease with a gp91phox disorder]

The chronic granulomatous disease is a primary immunodeficiency with a defect of the phagocytosis process; its main alteration resides in the incapacity of the NADPH oxidase system to produce reactive oxygen species capable of destruct pathogenic organisms such as bacteria, fungus and mycobacteria. Patients are susceptible to severe and mild infections, mainly pneumonias, linfadenitis and gastroenteritis that tend to be repetitive; in addition, they presented granulomatous inflammation and autoimmunity. We presented the case of two brothers with X-linked chronic granulomatous disease with alteration in the sub-unit gp91Phox; heredofamilial background was endogamy and consanguinity. Both patients suffered severe infections, frequent abscesses and a poor growth. Diagnosis was confirmed with nitroblue tetrazolium test. During their evolution, the patients presented also BCGitis, BCGosis and septic shock. They began prophylactic treatment with trimetoprim sulfametoxazole and itraconazole, as well as gamma interferon, with favorable response, presenting a lower amount of infectious episodes, as well as a recovery of their weight and height. The early diagnosis of the patients has improved their prognosis.

Intracellular expression of reactive oxygen species-generating NADPH oxidase NOX4 in normal and cancer thyroid tissues

NADPH oxidase 4 (NOX4) belongs to the NOX family that generates reactive oxygen species (ROS). Function and tissue distribution of NOX4 have not yet been entirely clarified. To date, in the thyroid gland, only DUOX1/2 NOX systems have been described. NOX4 mRNA expression, as shown by real-time PCR, was present in normal thyroid tissue, regulated by TSH and significantly increased in differentiated cancer tissues. TSH increased the protein level of NOX4 in human thyroid primary culture and NOX4-dependent ROS generation. NOX4 immunostaining was detected in normal and pathologic thyroid tissues. In normal thyroid tissue, staining was heterogeneous and mostly found in activated columnar thyrocytes but absent in quiescent flat cells. Papillary and follicular thyroid carcinomas displayed more homogeneous staining. The p22(phox) protein that forms a heterodimeric enzyme complex with NOX4 displayed an identical cellular expression pattern and was also positively regulated by TSH. ROS may have various biological effects, depending on the site of production. Intracellular NOX4-p22(phox) localization suggests a role in cytoplasmic redox signaling, in contrast to the DUOX localization at the apical membrane that corresponds to an extracellular H(2)O(2) production. Increased NOX4-p22(phox) in cancer might be related to a higher proliferation rate and tumor progression but a role in the development of tumors has to be further studied and established in the future.

Molecular characterization and expression analysis of BmNOX in two strains of Bombyx mori with contrasting viral resistance phenotype

We recently documented the identification of a 26.5 kDa protein named BmNox in the gut fluid of Nistari strain of Bombyx mori, which possessed antiviral activity against BmNPV in vitro. In this report, we report the characterization of the full-length gene encoding BmNOX and the levels of expression of this gene in select tissues of silkworm larvae from a BmNPV-susceptible and a BmNPV-resistant strain to the defense capability in Bombyx mori larvae challenged with BmNPV. We also evaluated the BmNox expression in various stages of larval life of a resistant and a susceptible strain of Bombyx mori selected from among a panel of strains of silkworm. Nistari, a multivoltine strain of silkworm, expressed BmNOX during all five larval stages, and were highly resistant to BmNPV infection. In sharp contrast, CSR(2), a bivoltine strain, showed weaker expression of BmNOX in the anterior midgut in larval life and was highly susceptible to BmNPV infection. BmNOX is a secretory protein with dual expression in gut fluid and mid gut tissue. BmNOX is expressed heavily in the posterior mid gut, with weaker expression in the fore- and mid-gut regions.

Potential mechanisms of low-sodium diet-induced cardiac disease: superoxide-NO in the heart

RATIONALE

Patients on a low salt (LS) diet have increased mortality.

OBJECTIVE

To determine whether reduction in NO bioactivity may contribute to the LS-induced cardiac dysfunction and mortality.

METHODS AND RESULTS

Adult male mongrel dogs were placed on LS (0.05% sodium chloride) for 2 weeks. Body weight (25.4 + or - 0.4 to 23.6 + or - 0.4 kg), left ventricular systolic pressure (137.0 + or - 3.4 to 124.0 + or - 6.7 mm Hg), and mean aortic pressure (111 + or - 3.1 to 98 + or - 4.3 mm Hg) decreased. Plasma angiotensin II concentration increased (4.4 + or - 0.7 to 14.8 + or - 3.7 pg/mL). Veratrine-induced (5 microg/kg) NO-mediated vasodilation was inhibited by 44% in LS; however, the simultaneous intravenous infusion of ascorbic acid or apocynin acutely and completely reversed this inhibition. In LS heart tissues, lucigenin chemiluminescence was increased 2.3-fold to angiotensin II (10(-8) mol/L), and bradykinin (10(-4) mol/L) induced reduction of myocardial oxygen consumption in vitro was decreased (40 + or - 1.3% to 16 + or - 6.3%) and completely restored by coincubation with tiron, tempol or apocynin. Switching of substrate uptake from free fatty acid to glucose by the heart was observed (free fatty acid: 8.97 + or - 1.39 to 4.53 + or - 1.12 micromol/min; glucose: 1.31 + or - 0.52 to 6.86 + or - 1.78 micromol/min). Western blotting indicated an increase in both p47(phox) (121%) and gp91(phox) (44%) as did RNA microarray analysis (433 genes changed) showed an increase in p47(phox) (1.6-fold) and gp91(phox) (2.0 fold) in the LS heart tissue.

CONCLUSIONS

LS diet induces the activation of the renin-angiotensin system, which increases oxidative stress via the NADPH oxidase and attenuates NO bioavailability in the heart.

Reperfusion and neurovascular dysfunction in stroke: from basic mechanisms to potential strategies for neuroprotection

Effective stroke therapies require recanalization of occluded cerebral blood vessels. However, reperfusion can cause neurovascular injury, leading to cerebral edema, brain hemorrhage, and neuronal death by apoptosis/necrosis. These complications, which result from excess production of reactive oxygen species in mitochondria, significantly limit the benefits of stroke therapies. We have developed a focal stroke model using mice deficient in mitochondrial manganese-superoxide dismutase (SOD2-/+) to investigate neurovascular endothelial damage that occurs during reperfusion. Following focal stroke and reperfusion, SOD2-/+ mice had delayed blood-brain barrier breakdown, associated with activation of matrix metalloproteinase and high brain hemorrhage rates, whereas a decrease in apoptosis and hemorrhage was observed in SOD2 overexpressors. Thus, induction and activation of SOD2 is a novel strategy for neurovascular protection after ischemia/reperfusion. Our recent study identified the signal transducer and activator of transcription 3 (STAT3) as a transcription factor of the mouse SOD2 gene. During reperfusion, activation of STAT3 and its recruitment into the SOD2 gene were blocked, resulting in increased oxidative stress and neuronal apoptosis. In contrast, pharmacological activation of STAT3 induced SOD2 expression, which limits ischemic neuronal death. Our studies point to antioxidant-based neurovascular protective strategies as potential treatments to expand the therapeutic window of currently approved therapies.

The 5A apolipoprotein A-I mimetic peptide displays antiinflammatory and antioxidant properties in vivo and in vitro

OBJECTIVE

The apolipoprotein (apo)A-I mimetic peptide 5A is highly specific for ATP-binding cassette transporter (ABC)A1-mediated cholesterol efflux. We investigated whether the 5A peptide shares other beneficial features of apoA-I, such as protection against inflammation and oxidation. Methods- New Zealand white rabbits received an infusion of apoA-I, reconstituted high-density lipoprotein (HDL) containing apoA-I ([A-I]rHDL), or the 5A peptide complexed with phospholipids (1-palmitoyl-2-linoleoyl phosphatidylcholine [PLPC]), before inserting a collar around the carotid artery. Human coronary artery endothelial cells (HCAECs) were incubated with (A-I)rHDL or 5A/PLPC before stimulation with tumor necrosis factor alpha. Results- ApoA-I, (A-I)rHDL, and 5A/PLPC reduced the collar-mediated increase in (1) endothelial expression of cell adhesion molecules vascular cell adhesion molecule-1 and intercellular adhesion molecule-1; (2) production, as well as the expression of the Nox4 catalytic subunits of the NADPH oxidase; and (3) infiltration of circulating neutrophils into the carotid intima-media. In HCAECs, both 5A/PLPC and (A-I)rHDL inhibited tumor necrosis factor-alpha-induced intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expression, as well as the nuclear factor kappaB signaling cascade and production. The effects of the 5A/PLPC complex were no longer apparent in HCAECs knocked down for ABCA1.

CONCLUSIONS

Like apoA-I, the 5A peptide inhibits acute inflammation and oxidative stress in rabbit carotids and HCAECs. In vitro, the 5A peptide exerts these beneficial effects through interaction with ABCA1.

Phosphoinositide 3-kinase mediates CD40 ligand-induced oxidative stress and endothelial dysfunction via Rac1 and NADPH oxidase 2

OBJECTIVES

CD40 ligand (CD40L) has been implicated as an inducer of reactive oxygen species (ROS) generation in endothelial cells, but definitive evidence for this and the in vivo relevance haves not been demonstrated fully. We thus investigated whether phosphoinositide 3-kinase (PI3K) was linked to ROS generation and endothelial reactivity in response to CD40L.

METHODS AND RESULTS

CD40L treatment activated PI3K activity by regulating the association between PI3K p85 and the CD40 receptor. CD40L exposure also stimulated the GTPase Rac1, which is known to activate NADPH oxidases, and enhanced ROS formation, whereas PI3K inhibition or depletion by small interfering RNA (siRNA) prevented these responses. Subsequently, PI3K overexpression activated Rac1 and increased ROS generation. These responses were not observed in the presence of inactive Rac1 or siRNA against the NADPH oxidase subunit NOX2. Protein kinase Czeta mediates PI3K-regulated NADPH oxidase activation by promoting cellular p47phox translocation. Importantly, PI3K inhibition prevented CD40L-mediated ROS generation and endothelial dysfunction in a mouse model. In summary, PI3K mediates CD40L-induced ROS production and subsequent endothelial dysfunction.

CONCLUSIONS

Targeting PI3K may provide a new therapeutic approach in diseases associated with oxidative stress and endothelial dysfunction.

Induction of COX-2/PGE(2)/IL-6 is crucial for cigarette smoke extract-induced airway inflammation: Role of TLR4-dependent NADPH oxidase activation

Exposure to cigarette smoke extract (CSE) leads to airway and lung inflammation through an oxidant-antioxidant imbalance. Cyclooxygenase-2 (COX-2) and prostaglandin E(2) (PGE(2)) have been shown to play critical roles in respiratory inflammation. Here, we show that COX-2/PGE(2)/IL-6 induction is dependent on Toll-like receptor 4 (TLR4)/NADPH oxidase signaling in human tracheal smooth muscle cells (HTSMCs). CSE induced COX-2 expression in vitro in HTSMCs and in vivo in the airways of mice. CSE also directly caused an increase in TLR4. Moreover, CSE-regulated COX-2, PGE(2), and IL-6 generation was inhibited by pretreatment with TLR4 Ab; inhibitors of c-Src (PP1), NADPH oxidase (diphenylene iodonium chloride and apocynin), p38 MAPK (SB202190), MEK1/2 (U0126), JNK1/2 (SP600125), and NF-kappaB (helenalin); a ROS scavenger (N-acetyl-l-cysteine); and transfection with siRNA of TLR4, MyD88, TRAF6, Src, p47(phox), p38, p42, JNK2, or p65. CSE-induced leukocyte numbers in BAL fluid were also reduced by pretreatment with these inhibitors. Furthermore, CSE induced p47(phox) translocation and TLR4/MyD88/TRAF6 and c-Src/p47(phox) complex formation. We found that PGE(2) enhanced IL-6 production in HTSMCs and leukocyte count in BAL fluid. In addition, treatment with nicotine could induce COX-2, PGE(2), and IL-6 generation in in vivo and in vitro studies. These results demonstrate that CSE-induced ROS generation was mediated through the TLR4/MyD88/TRAF6/c-Src/NADPH oxidase pathway, in turn initiated the activation of MAPKs and NF-kappaB, and ultimately induced COX-2/PGE(2)/IL-6-dependent airway inflammation.

Total body irradiation causes residual bone marrow injury by induction of persistent oxidative stress in murine hematopoietic stem cells

Ionizing radiation (IR) and/or chemotherapy causes not only acute tissue damage but also late effects including long-term (or residual) bone marrow (BM) injury. The induction of residual BM injury is primarily attributable to the induction of hematopoietic stem cell (HSC) senescence. However, the molecular mechanisms by which IR and/or chemotherapy induces HSC senescence have not been clearly defined, nor has an effective treatment been developed to ameliorate the injury. Thus, we investigated these mechanisms in this study. The results from this study show that exposure of mice to a sublethal dose of total body irradiation (TBI) induced a persistent increase in reactive oxygen species (ROS) production in HSCs only. The induction of chronic oxidative stress in HSCs was associated with sustained increases in oxidative DNA damage, DNA double-strand breaks (DSBs), inhibition of HSC clonogenic function, and induction of HSC senescence but not apoptosis. Treatment of the irradiated mice with N-acetylcysteine after TBI significantly attenuated IR-induced inhibition of HSC clonogenic function and reduction of HSC long-term engraftment after transplantation. The induction of chronic oxidative stress in HSCs by TBI is probably attributable to the up-regulation of NADPH oxidase 4 (NOX4), because irradiated HSCs expressed an increased level of NOX4, and inhibition of NOX activity with diphenylene iodonium but not apocynin significantly reduced TBI-induced increases in ROS production, oxidative DNA damage, and DNA DSBs in HSCs and dramatically improved HSC clonogenic function. These findings provide the foremost direct evidence demonstrating that TBI selectively induces chronic oxidative stress in HSCs at least in part via up-regulation of NOX4, which leads to the induction of HSC senescence and residual BM injury.