p47phox participates in activation of RelA in endothelial cells

Phytochemical Composition, Anti-Inflammatory and ER Stress-Reducing Potential of Sambucus ebulus L. Fruit Extract

Sambucus ebulus L. (SE) fruits are used for their immunostimulation, hematopoietic and antiviral potential. Recently, we focused on analyzing the mechanism underlying SE fruit aqueous extract's (FAE) immunomodulation and anti-inflammatory activities, with attention to its endoplasmic reticulum (ER) stress-reducing potential. J774A.1 macrophages were treated with SE FAE alone or in conditions of lipopolysaccharides (LPS) stimulation. Using GC-MS and LC-MS/MS, its phytochemical composition was analyzed. To measure transcription and protein levels, we used qPCR and Western blot, respectively. The prevailing phytochemicals in SE FAE were hydroxycinnamic acids, proanthocyanidins and anthocyanins. The content of some amino acids, organic acids, alcohols, fatty acids and esters were newly reported. Extracts exerted an immunostimulation potential by stimulating IL-6, TNFα, Ccl2, COX2 and iNOS transcription, without inducing ER stress. SE FAE suppressed the LPS-induced transcription of inflammation related genes (IL-1β, IL-6, TNFα, Ccl2, Icam-1, Fabp4, COX2, iNOS, Noxo1, IL-1ra, Sirt-1) and reduced the protein levels of iNOS, peIF2α, ATF6α and CHOP. The effects were comparable to that of salicylic acid. SE suppresses LPS-stimulated inflammatory markers on the transcription and translation levels. Targeting ER stress is possibly another mechanism underlying its anti-inflammatory potential. These findings reveal the potential of SE fruits as a beneficial therapeutic of inflammation and ER stress-related pathological conditions.

RNA-Seq analysis in giant pandas reveals the differential expression of multiple genes involved in cataract formation

BACKGROUND

The giant panda (Ailuropoda melanoleuca) is an endangered mammalian species native to China. Fewer than 2500 giant pandas are known to exist, many of which are bred in captivity as a means to preserve and repopulate the species. Like other captive mammals, giant pandas acquire age-related cataracts, reducing their quality of life. Recent comparative genome-wide methylation analysis revealed 110 differentially methylated genes associated with cataract formation including six also associated with the formation of age-related cataracts in humans.

RESULTS

To investigate the pathological pathway in greater detail, here we used RNA-Seq analysis to investigate the differential expression profiles of genes in three giant pandas with cataracts and three healthy controls. We identified more than 700 differentially expressed genes, 29 of which were selected for further analysis based on their low q-value. We found that many of the genes encoded regulatory and signaling proteins associated with the control of cell growth, migration, differentiation and apoptosis, supporting previous research indicating a key role for apoptosis in cataract formation.

CONCLUSION

The identification of genes involved in the formation of age-related cataracts could facilitate the development of predictive markers, preventative measures and even new therapies to improve the life of captive animals.

Role of NADPH oxidase NOX5-S, NF-κB, and DNMT1 in acid-induced p16 hypermethylation in Barrett's cells

Inactivation of tumor suppressor genes via promoter hypermethylation may play an important role in the progression from Barrett's esophagus (BE) to esophageal adenocarcinoma (EA). We have previously shown that acid-induced p16 gene promoter hypermethylation may depend on activation of NADPH oxidase NOX5-S in BAR-T cells and OE33 EA cells. DNA methyltransferase 1 (DNMT1) is known to participate in maintaining established patterns of DNA methylation in dividing cells and may play an important role in the development of cancer. Therefore, we examined whether DNMT1 is involved in acid-induced p16 gene promoter hypermethylation in BAR-T cells. We found that the acid significantly increased p16 gene promoter methylation, decreased p16 mRNA, and increased cell proliferation, effects that may depend on activation of DNMT1 in BAR-T cells. DNMT1 is overexpressed in EA cells FLO and OE33 and EA tissues. Acid treatment upregulated DNMT1 mRNA expression and increased DNMT1 promoter activity. Acid-induced increases in DNMT1 mRNA expression and promoter activity were significantly decreased by knockdown of NOX5-S and NF-κB1 p50. Conversely, overexpression of NOX5-S, p50, or p65 significantly increased DNMT1 promoter activity. Knockdown of NOX5-S significantly decreased the acid-induced increase in luciferase activity in cells transfected with pNFκB-Luc. An NF-κB binding element GGGGTATCCC was identified in the DNMT1 gene promoter. We conclude that the acid-induced increase in p16 gene promoter methylation, downregulation of p16 mRNA, and increase in cell proliferation may depend on activation of DNMT1 in BAR-T cells. Acid-induced DNMT1 expression may depend on sequential activation of NOX5-S and NF-κB1 p50.

Regulation of proliferation of skeletal muscle precursor cells by NADPH oxidase

Skeletal muscle precursor cells are adult stem cells located among muscle fibers. Proliferation, migration, and subsequent differentiation of these cells are critical steps in the repair of muscle injury. We document in this study the roles and mechanisms through which the NAPDH oxidase complex regulates muscle precursor cell proliferation. The NADPH oxidase subunits Nox2, Nox4, p22(phox), p47(phox), and p67(phox) were detected in primary human and murine skeletal muscle precursor cells. In human muscle precursor cells, NADPH oxidase-fusion proteins were localized in the cytosolic and membrane compartments of the cell, except for p47(phox), which was detected in the nucleus. In proliferating subconfluent precursor cells, both Nox2 and Nox4 contributed to O(2)(-) production. However, Nox4 expression was significantly attenuated in differentiated myotubes. Proliferation of precursor cells was significantly reduced by antioxidants (N-acetylcysteine and apocynin), inhibition of p22(phox) expression by using siRNA oligonucleotides, and reduction of Nox4 and p47(phox) activities with dominant-negative vectors and siRNA oligonucleotides resulted in attenuation of activities of the Erk1/2, PI-3 kinase/AKT and NFkappaB pathways and significant reduction in cyclin D1 levels. We conclude that NADPH oxidase is expressed in skeletal muscle precursor cells and that its activity plays an important role in promoting proliferation of these cells.

HIV-1 Tat activates dual Nox pathways leading to independent activation of ERK and JNK MAP kinases

Human immunodeficiency virus, type 1 Tat is known to exert pleiotropic effects on the vascular endothelium through mitogen-activated protein (MAP) kinases, although the signaling pathways leading to MAP kinase activation are incompletely understood. We focused on proximal pathways potentially governing downstream MAP kinase activity by Tat. Within 2 min, Tat activated both Ras and Rho GTPases in endothelial cells, leading to ERK phosphorylation by 10 min. Notably, Rac1 was necessary for downstream activation of RhoA and both Rac1 and RhoA acted upstream of the Ras/ERK cassette. Antioxidants and the oxidase inhibitor diphenylene iodonium blocked ERK phosphorylation, but specific interference with the canonical Nox2 oxidase had no effect on ERK. Instead, knock down of the novel oxidase Nox4 completely suppressed Tat-dependent Ras and ERK activation downstream of Rac1 and RhoA. Conversely, interference with Rac1, PAK1, and Nox2 blocked JNK phosphorylation, whereas RhoA(N19) and Nox4 knock down did not. Further, knock down of Nox2, but not Nox4, blocked Tat-induced cytoskeletal rearrangement, whereas knock down of Nox4, but not Nox2, blocked Tat-dependent proliferation. Rac1, therefore, bifurcates Tat signaling, leading to concurrent but separate Nox4-dependent Ras/ERK activation, and Nox2-dependent JNK activation. Tat signaling, therefore, provides an example of Nox-specific differential control of MAP kinase pathways.

Oxidant stress, immune dysregulation, and vascular function in type I diabetes

Although high glucose is an important contributor to diabetic vasculopathies, complications still occur in spite of tight glycemic control, suggesting that some critical event prior to or concurrent with hyperglycemia may contribute to early vascular changes. Utilizing previously published and new experimental evidence, this review will discuss how prior to the hyperglycemic state, an imbalance between oxidants and antioxidants may contribute to early vascular dysfunction and set in motion proinflammatory insults that are further amplified as the diabetes develops. This imbalance results from the resetting of the equilibrium between vessel superoxide/H(2)O(2) production and/or decreased antioxidant defenses. Such an imbalance may cause endothelial dysfunction, characterized by abnormal endothelium-dependent vasoreactivity, as the first sign of blood vessel damage, followed by morphological changes of the vessel wall and inflammation. As such, increased oxidant stress in preglycemic states may be a critically central initiating event that underlies the pathogenesis of life-threatening vascular diseases in autoimmune diabetes. This review focuses on the relationship between oxidative stress, immune dysregulation, and vascular injury in type 1 diabetes, and how the discovery of novel pathways of vascular disease in nonobese diabetic mice may direct future studies in patients with type 1 diabetes.

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.

Specificity in reactive oxidant signaling: think globally, act locally

Although reactive oxidants have long been stigmatized as unwanted metabolic byproducts, the expression of oxidases specifically functioning to produce these same molecules in a regulated fashion is surprisingly pervasive throughout metazoan and plant evolution. Although the involvement of oxidants in many signaling pathways is well documented, the cellular strategies for conferring pathway specificity to such reactive molecules have remained more recondite. Recent studies now suggest that cells may spatially restrict oxidant production to allow microdomain-specific signaling.

NADPH oxidases in cardiovascular health and disease

Increased oxidative stress plays an important role in the pathophysiology of cardiovascular diseases such as hypertension, atherosclerosis, diabetes, cardiac hypertrophy, heart failure, and ischemia-reperfusion. Although several sources of reactive oxygen species (ROS) may be involved, a family of NADPH oxidases appears to be especially important for redox signaling and may be amenable to specific therapeutic targeting. These include the prototypic Nox2 isoform-based NADPH oxidase, which was first characterized in neutrophils, as well as other NADPH oxidases such as Nox1 and Nox4. These Nox isoforms are expressed in a cell- and tissue-specific fashion, are subject to independent activation and regulation, and may subserve distinct functions. This article reviews the potential roles of NADPH oxidases in both cardiovascular physiological processes (such as the regulation of vascular tone and oxygen sensing) and pathophysiological processes such as endothelial dysfunction, inflammation, hypertrophy, apoptosis, migration, angiogenesis, and vascular and cardiac remodeling. The complexity of regulation of NADPH oxidases in these conditions may provide the possibility of targeted therapeutic manipulation in a cell-, tissue- and/or pathway-specific manner at appropriate points in the disease process.

Nox2 and Rac1 regulate H2O2-dependent recruitment of TRAF6 to endosomal interleukin-1 receptor complexes

Reactive oxygen species (ROS) generated by NADPH oxidases (Nox) have been implicated in the regulation of signal transduction. However, the cellular mechanisms that link Nox activation with plasma membrane receptor signaling remain poorly defined. We have found that Nox2-derived ROS influence the formation of an active interleukin-1 (IL-1) receptor complex in the endosomal compartment by directing the H2O2-dependent binding of TRAF6 to the IL-1R1/MyD88 complex. Clearance of both superoxide and H2O2 from within the endosomal compartment significantly abrogated IL-1beta-dependent IKK and NF-kappaB activation. MyD88-dependent endocytosis of IL-1R1 following IL-1beta binding was required for the redox-dependent formation of an active endosomal receptor complex competent for IKK and NF-kappaB activation. Small interfering RNAs to either MyD88 or Rac1 inhibited IL-1beta induction of endosomal superoxide and NF-kappaB activation. However, MyD88 and Rac1 appear to be recruited independently to IL-1R1 following ligand stimulation. In this context, MyD88 binding was required for inducing endocytosis of IL-1R1 following ligand binding, while Rac1 facilitated the recruitment of Nox2 into the endosomal compartment and subsequent redox-dependent recruitment of TRAF6 to the MyD88/IL-1R1 complex. The identification of Nox-active endosomes helps explain how subcellular compartmentalization of redox signals can be used to direct receptor activation from the plasma membrane.

Interleukin-1beta induction of NFkappaB is partially regulated by H2O2-mediated activation of NFkappaB-inducing kinase

Reactive oxygen species (ROS) have been demonstrated to act as second messengers in a number of signal transduction pathways, including NFkappaB. However, the mechanism(s) by which ROS regulate NFkappaB remain unclear and controversial. In the present report, we describe a mechanism whereby interleukin-1beta (IL-1beta) stimulation of NFkappaB is partially regulated by H2O2-mediated activation of NIK and subsequent NIK-mediated phosphorylation of IKKalpha. IL-1beta induced H2O2 production in MCF-7 cells and clearance of this ROS through the expression of GPx-1 reduced NFkappaB transcriptional activation by inhibiting NIK-mediated phosphorylation of IKKalpha. Although IKKalpha and IKKbeta were both involved in IL-1beta-mediated activation of NFkappaB, only the IKKalpha-dependent component was modulated by changes in H2O2 levels. Interestingly, in vitro reconstitution experiments demonstrated that NIK was activated by a very narrow range of H2O2 (1-10 microM), whereas higher concentrations (100 microM to 1 mM) inhibited NIK activity. Treatment of cells with the general Ser/Thr phosphatase inhibitor (okadaic acid) lead to activation of NFkappaB and enhanced NIK activity as a IKKalpha kinase, suggesting that ROS may directly regulate NIK through the inhibition of phosphatases. Recruitment of NIK to TRAF6 following IL-1beta stimulation was inhibited by H2O2 clearance and Rac1 siRNA, suggesting that Rac-dependent NADPH oxidase may be a source of ROS required for NIK activation. In summary, our studies have demonstrated that redox regulation of NIK by H2O2 is mechanistically important in IL-1beta induction of NFkappaB activation.

Nitric oxide bioavailability in malaria

Rational development of adjunct or anti-disease therapy for severe Plasmodium falciparum malaria requires cellular and molecular definition of malarial pathogenesis. Nitric oxide (NO) is a potential target for such therapy but its role during malaria is controversial. It has been proposed that NO is produced at high levels to kill Plasmodium parasites, although the unfortunate consequence of elevated NO levels might be impaired neuronal signaling, oxidant damage and red blood cell damage that leads to anemia. In this case, inhibitors of NO production or NO scavengers might be an effective adjunct therapy. However, increasing amounts of evidence support the alternate hypothesis that NO production is limited during malaria. Furthermore, the well-documented NO scavenging by cell-free plasma hemoglobin and superoxide, the levels of which are elevated during malaria, has not been considered. Low NO bioavailability in the vasculature during malaria might contribute to pathologic activation of the immune system, the endothelium and the coagulation system: factors required for malarial pathogenesis. Therefore, restoring NO bioavailability might represent an effective anti-disease therapy.

NF-κB Activation Plays a Role in Superoxide-Mediated Cerebral Endothelial Dysfunction After Hypoxia/Reoxygenation

Background and Purpose— Cerebral vascular injury occurs in response to hypoxia/reoxygenation (H/R). However, the cellular signaling pathways that regulate this event remain unclear. The present study was designed to determine whether reactive oxygen species (ROS) mediate endothelial dysfunction after H/R in cerebral resistance arteries and, if so, the relative contribution of ROS, NADPH oxidase, and a nuclear factor-κB (NF-κB) pathway.

Methods— Arterial diameter and intraluminal pressure were simultaneously measured on rat posterior cerebral arteries (PCA). Superoxide was measured by 5-μmol/L lucigenin-enhanced chemiluminescence.

Results— Hypoxia/reoxygenation selectively inhibited cerebral vasodilation to the endothelium-dependent agonist acetylcholine (Ach) (0.01 to 10 μmol/L) by ≈50%. Impaired vasodilation after H/R was reversed by 2,2,6,6-tetramethylpiperidine- N -oxyl (Tempo) (100 μmol/L), a cell-permeable superoxide dismutase mimetic, and partially by ebselen (10 μmol/L), a peroxynitrite scavenger. H/R-impaired vasodilation to Ach was also preserved by apocynin (1 mmol/L), a specific inhibitor for NADPH oxidase. Correspondingly, H/R significantly increased lucigenin-detectable superoxide, which was reduced by either Tempo or apocynin, but not by allopurinol (10 μmol/L), an inhibitor of xanthine oxidase. Finally, the NF-κB inhibitors helenalin (10 μmol/L) and MG-132 (1 μmol/L) independently antagonized H/R-impaired Ach-induced vasodilation without affecting dilator response to sodium nitroprusside, an endothelium-independent vasodilator.

Conclusions— These results indicate that superoxide mediates cerebral endothelial dysfunction after hypoxia/reoxygenation largely via activation of NADPH oxidase and possibly activation of NF-κB pathway.

p47phox Associates With the Cytoskeleton Through Cortactin in Human Vascular Smooth Muscle Cells

OBJECTIVE

We tested the hypothesis that p47phox associates with the actin cytoskeleton, enabling site-directed activation of NAD(P)H oxidase, and assessed whether these actions influence reactive oxygen species (ROS) generation and signaling by angiotensin II (Ang II) in vascular smooth muscle cells (VSMCs) from human resistance and coronary arteries.

METHODS AND RESULTS

Electroporation of anti-p47phox antibody into VSMCs abrogated Ang II-mediated O2 generation, establishing the requirement for p47phox in this response. Immunfluorescence confocal microscopy demonstrated a cytosolic distribution of p47phox in basal conditions. After Ang II stimulation, p47phox rearranged in a linear fashion, colocalizing with F-actin. Co-immunoprecipitation studies confirmed an association between p47phox and actin and demonstrated an interaction with the actin-binding protein cortactin. Cytoskeletal disruption with cytochalasin prevented p47phox:actin interaction and attenuated ROS formation and p38MAP kinase and Akt phosphorylation by Ang II. Intracellular ROS generation in response to LY83583 (O2 generator) or exogenous H2O2 and Ang II-induced ERK1/2 activation were unaltered by cytochalasin.

CONCLUSIONS

The p47phox:actin interaction, through cortactin, plays an important role in Ang II-mediated site-directed assembly of functionally active NAD(P)H oxidase, ROS generation, and activation of redox-sensitive p38MAP kinase and Akt, but not ERK1/2. These findings demonstrate the importance of an intact actin-cytoskeleton in NAD(P)H oxidase regulation and redox signaling by Ang II in human VSMCs.

Role of the actin cytoskeleton in angiotensin II signaling in human vascular smooth muscle cells

Angiotensin II (Ang II) regulates vascular smooth muscle cell (VSMC) function by activating signaling cascades that promote vasoconstriction, growth, and inflammation. Subcellular mechanisms coordinating these processes are unclear. In the present study, we questioned the role of the actin cytoskeleton in Ang II mediated signaling through mitogen-activated protein (MAP) kinases and reactive oxygen species (ROS) in VSMCs. Human VSMCs were studied. Cells were exposed to Ang II (10–7 mol/L) in the absence and presence of cytochalasin B (10–6 mol/L, 60 min), which disrupts the actin cytoskeleton. Phosphorylation of p38MAP kinase, JNK, and ERK1/2 was assessed by immuno blotting. ROS generation was measured using the fluoroprobe chloromethyl-2',7'-dichlorodihydrofluorescein diacetate (4 µmol/L). Interaction between the cytoskeleton and NADPH oxidase was determined by evaluating the presence of p47phox in the Triton X-100 insoluble membrane fraction. Ang II significantly increased phosphorylation of p38MAP kinase, JNK, and ERK1/2 (two- to threefold above control, p < 0.05). Cytochalasin B pretreatment attenuated p38MAP kinase and JNK effects (p < 0.05) without altering ERK1/2 phosphorylation. ROS formation, which was increased in Ang II stimulated cells, was significantly reduced by cytochalasin B (p < 0.01). p47phox, critically involved in NADPH oxidase activation, colocalized with the actin cytoskeleton in Ang II stimulated cells. Our data demonstrate that Ang II mediated ROS formation and activation of p38MAP kinase and JNK, but not ERK1/2, involves the actin cytoskeleton in VSMCs. In addition, Ang II promotes interaction between actin and p47phox. These data indicate that the cytoskeleton is involved in differential MAP kinase signaling and ROS generation by Ang II in VSMCs. Together, these studies suggest that the cytoskeleton may be a central point of crosstalk in growth- and redox-signaling pathways by Ang II, which may be important in the regulation of VSMC function.Key words: superoxide, NADPH oxidase, p38MAP kinase, JNK, ERK1/2.

Endothelial cell superoxide generation: regulation and relevance for cardiovascular pathophysiology

The endothelial generation of reactive oxygen species (ROS) is important both physiologically and in the pathogenesis of many cardiovascular disorders. ROS generated by endothelial cells include superoxide (O2-*), hydrogen peroxide (H2O2), peroxynitrite (ONOO-*), nitric oxide (NO), and hydroxyl (*OH) radicals. The O2-* radical, the focus of the current review, may have several effects either directly or through the generation of other radicals, e.g., H2O2 and ONOO-*. These effects include 1) rapid inactivation of the potent signaling molecule and endothelium-derived relaxing factor NO, leading to endothelial dysfunction; 2) the mediation of signal transduction leading to altered gene transcription and protein and enzyme activities ("redox signaling"); and 3) oxidative damage. Multiple enzymes can generate O2-*, notably xanthine oxidase, uncoupled NO synthase, and mitochondria. Recent studies indicate that a major source of endothelial O2-* involved in redox signaling is a multicomponent phagocyte-type NADPH oxidase that is subject to specific regulation by stimuli such as oscillatory shear stress, hypoxia, angiotensin II, growth factors, cytokines, and hyperlipidemia. Depending on the level of oxidants generated and the relative balance between pro- and antioxidant pathways, ROS may be involved in cell growth, hypertrophy, apoptosis, endothelial activation, and adhesivity, for example, in diabetes, hypertension, atherosclerosis, heart failure, and ischemia-reperfusion. This article reviews our current knowledge regarding the sources of endothelial ROS generation, their regulation, their involvement in redox signaling, and the relevance of enhanced ROS generation and redox signaling to the pathophysiology of cardiovascular disorders where endothelial activation and dysfunction are implicated.

NADPH oxidase mediates vascular endothelial cadherin phosphorylation and endothelial dysfunction

Vascular endothelial activation is an early step during leukocyte/endothelial adhesion and transendothelial leukocyte migration in inflammatory states. Leukocyte transmigration occurs through intercellular gaps between endothelial cells. Vascular endothelial cadherin (VE-cadherin) is a predominant component of endothelial adherens junctions that regulates intercellular gap formation. We found that tumor necrosis factor (TNF) caused tyrosine phosphorylation of VE-cadherin, separation of lateral cell-cell junctions, and intercellular gap formation in human umbilical vein endothelial cell (HUVEC) monolayers. These events appear to be regulated by intracellular oxidant production through endothelial NAD(P)H (nicotinamide adenine dinucleotide phosphate) oxidase because antioxidants and expression of a transdominant inhibitor of the NADPH oxidase, p67(V204A), effectively blocked the effects of TNF on all 3 parameters of junctional integrity. Antioxidants and p67(V204A) also decreased TNF-induced JNK activation. Dominant-negative JNK abrogated VE-cadherin phosphorylation and junctional separation, suggesting a downstream role for JNK. Finally, adenoviral delivery of the kinase dead PAK1(K298A) decreased TNF-induced JNK activation, VE-cadherin phosphorylation, and lateral junctional separation, consistent with the proposed involvement of PAK1 upstream of the NADPH oxidase. Thus, PAK-1 acts in concert with oxidase during TNF-induced oxidant production and loss of endothelial cell junctional integrity.

Apocynin prevents cyclooxygenase 2 expression in human monocytes through NADPH oxidase and glutathione redox-dependent mechanisms

In the present study we report the preventive effect of apocynin, an active constituent of the Himalayan herb Picrorhiza kurrooa, on cyclooxygenase-2 (Cox-2) synthesis and activity in human adherent monocytes exposed to serum treated zymosan (STZ) and phorbol myristate acetate (PMA). Apocynin markedly decreases the intracellular reduced/oxidized glutathione ratio (GSH/GSSG) and prevents nuclear factor-kappaB (NF-kappaB) activation in stimulated monocytes. Moreover, it reduces intracellular reactive oxygen species (ROS) generation, NADPH oxidase activity in monocyte homogenates and translocation of p47phox subunit in monocyte membranes. p47phox levels are also reduced in lysates of apocynin-treated monocytes. The inhibition of Cox-2 by apocynin is completely abrogated by GSH provision. Results from this study indicate that apocynin inhibits Cox-2 synthesis and activity induced in monocytes by an increased oxidative tone and provide an explanation for the protective effect exerted by this compound in numerous cell and animal models of inflammation. Attenuation of NADPH oxidase derived ROS coupled with GSH/GSSG reduction and suppression of NF-kappaB activation are highlighted as the molecular mechanisms responsible for Cox-2 inhibition.

Human immunodeficiency virus type 1 Tat regulates endothelial cell actin cytoskeletal dynamics through PAK1 activation and oxidant production

Human immunodeficiency virus type 1 Tat exerts prominent angiogenic effects which may lead to a variety of vasculopathic conditions in AIDS patients. Because endothelial cells undergo prominent cytoskeletal rearrangement during angiogenesis, we investigated the specific effects of Tat on the endothelial cell actin cytoskeleton. Glutathione S-transferase (GST)-Tat, at a level of 200 ng/ml (equivalent to 52 ng of Tat/ml), caused stress fiber disassembly, peripheral retraction, and ruffle formation in human umbilical vein endothelial cells (HUVEC) and human lung microvascular endothelial cells. At 600 ng of GST-Tat/ml (157 ng of Tat/ml), actin structures were lost, and severe cytoskeletal collapse occurred. In contrast, GST-Tat harboring mutations within either the cysteine-rich or basic domains exerted minimal effects on the endothelial cytoskeleton. HUVEC expressing a DsRed-Tat fusion protein displayed similar actin rearrangements, followed by actin collapse, whereas neighboring nontransfected cells retained normal actin structures. Because active mutants of p21-activated kinase 1 (PAK1) induce identical changes in actin dynamics, we hypothesized that Tat exerts its cytoskeletal effects through PAK1. GST-Tat activated PAK1 within 5 min, and adenovirus delivery of a kinase-dead PAK1 [PAK1(K298A)] completely prevented cytoskeletal collapse induced by GST-Tat or DsRed-Tat and also blocked downstream activation of c-Jun N-terminal kinase. Further, GST-Tat increased phosphorylation of the NADPH oxidase subunit p47(phox) and caused its rapid redistribution to membrane ruffles. PAK1(K298A) blocked p47(phox) phosphorylation, and interference with NADPH oxidase function through superoxide scavenging or through expression of a transdominant inhibitor, p67(V204A), prevented GST-Tat-induced alterations in the actin cytoskeleton. We conclude that Tat induces actin cytoskeletal rearrangements through PAK1 and downstream activation of the endothelial NADPH oxidase.