Identification of a functional leukocyte-type NADPH oxidase in human endothelial cells :a potential atherogenic source of reactive oxygen species

Total flavone of flowers of Abelmoschus manihot (L.) Medic inhibits the expression of adhesion molecules in primary mesenteric arterial endothelial cells and ameliorates dextran sodium sulphate-induced ulcerative colitis in mice

BACKGROUND

Flowers of Abelmoschus manihot (L.) medic (AM) is a traditional Chinese medicine used to treat chronic nephritis, nephrotic syndrome, diabetic nephropathy, and colonic inflammation.

PURPOSE

This study aimed to explore the influence of the total flavone of AM flowers (TFA) on acute ulcerative colitis (UC) and the potential underlying mechanism.

METHODS

Efficacy of TFA (30, 60, 120 mg/kg) on UC was evaluated in a dextran sodium sulphate (DSS)-induced colonic inflammatory mouse model by analyzing disease activity index (DAI), histopathological score, colon length, and cytokine expression. Expression levels of critical adhesion molecules and nuclear factor kappa B (NF-κB) were examined by qRT-PCR, Western blotting, or immunofluorescence labeling. Myeloperoxidase activity was examined using ELISA. In vitro THP-1 adhesion assay was used to evaluate monocyte adhesion.

RESULTS

TFA significantly reduced DAI score, prevented colon shortening, and ameliorated histological injuries of colons in DSS-treated mice. TFA inhibited the expression of cytokines (IL-1β and TNF-α) and adhesion molecules (ICAM-1, VCAM-1, and MAdCAM-1) in colon tissues of DSS mice. In vitro studies on mesenteric arterial endothelial cells (MAECs) showed that TFA attenuated TNF-α-induced upregulation of ICAM-1, VCAM-1, and MAdCAM-1, as well as THP-1 cell adhesion to MAECs. TFA also suppressed the phosphorylation and nuclear translocation of NF-κB in MAECs.

CONCLUSION

TFA efficaciously ameliorates UC possibly by inhibiting monocyte adhesion through blocking TNF-α-induced NF-κB activation, which in turn suppresses the upregulation of adhesive molecules in colon endothelial cells. Inhibiting the expression of adhesion molecule in MAECs may represent a useful strategy for therapeutic development to treat UC, with TFA being a safe and efficacious therapeutic agent.

Biological active ingredients of Astragali Radix and its mechanisms in treating cardiovascular and cerebrovascular diseases

BACKGROUND

With the rising age of the global population, the incidence rate of cardiovascular and cerebrovascular diseases (CCVDs) is increasing, which causes serious public health burden. The efforts for new therapeutic approaches are still being sought since the treatment effects of existing therapies are not quite satisfactory. Chinese traditional medicine proved to be very efficient in the treatment of CCVDs. Well described and established in Chinese medicine, Astragali Radix, has been commonly administered in the prophylaxis and cure of CCVDs for thousands of years.

PURPOSE

This review summarized the action mode and mechanisms of Astragali Radix phytochemicals on CCVDs, hoping to provide valuable information for the future application, development and improvement of Astragali Radix as well as CCVDs treatment.

METHODS

A plenty of literature on biological active ingredients of Astragali Radix used for CCVDs treatment were retrieved from online electronic PubMed and Web of Science databases.

RESULTS

This review highlighted the effects of five main active components in Astragali Radix including astragaloside Ⅳ, cycloastragenol, astragalus polysaccharide, calycosin-7-O-β-d-glucoside, and calycosin on CCVDs. The mechanisms mainly involved anti-oxidative damage, anti-inflammatory, and antiapoptotic through signaling pathways such as PI3K/Akt, Nrf2/HO-1, and TLR4/NF-κB pathway. In addition, the majority active constituents in AR have no obvious toxic side effects.

CONCLUSION

The main active components of Astragali Radix, especially AS-IV, have been extensively summarized. It has been proved that Astragali Radix has obvious therapeutic effects on various CCVDs, including myocardial and cerebral ischemia, hypertension, atherosclerosis, cardiac hypertrophy, chronic heart failure. CAG possesses anti-ischemia activity without toxicity, indicating a worthy of further development. However, high-quality clinical and pharmacokinetic studies are required to validate the current studies.

Smilax china leaf extracts suppress pro-inflammatory adhesion response in human umbilical vein endothelial cells and proliferation of HeLa cells

Objective: The objective of this study was to investigate the anti-inflammatory and anticancer effects of the leaves of Smilax china.Methodology: The aqueous extract was examined for its anti-inflammatory effects on tumour necrosis factor (TNF)-α-induced inflammation in HUVECs whereas the aqueous (water), ethyl acetate (EA), butanol (B) and methylene chloride (MC) extracts were examined for their anticancer effect on HeLa cells.Results: The aqueous extract suppressed the (TNF)-α-induced expression of ICAM-1, VCAM-1 and TNF-R1 and attenuated the expression of MCP-1, MMP-9, NF-kB and IFN-γ. The MC extract suppressed the proliferation of HeLa cells at all doses employed (50, 150, and 300 µg/ml). The EA extract demonstrated appreciable anti-proliferative effect whereas the BuOH extract demonstrated mild anti-proliferative activity. The aqueous extract did not show any significant anti-proliferative effect. None of the extracts were toxic to the normal cells (HUVECs).Conclusion: Smilax china leaf extracts possess significant anti-inflammatory and anticancer effects.

NADPH oxidase in the vasculature: Expression, regulation and signalling pathways; role in normal cardiovascular physiology and its dysregulation in hypertension

The last 20-25 years have seen an explosion of interest in the role of NADPH oxidase (NOX) in cardiovascular function and disease. In vascular smooth muscle and endothelium, NOX generates reactive oxygen species (ROS) that act as second messengers, contributing to the control of normal vascular function. NOX activity is altered in response to a variety of stimuli, including G-protein coupled receptor agonists, growth-factors, perfusion pressure, flow and hypoxia. NOX-derived ROS are involved in smooth muscle constriction, endothelium-dependent relaxation and smooth muscle growth, proliferation and migration, thus contributing to the fine-tuning of blood flow, arterial wall thickness and vascular resistance. Through reversible oxidative modification of target proteins, ROS regulate the activity of protein tyrosine phosphatases, kinases, G proteins, ion channels, cytoskeletal proteins and transcription factors. There is now considerable, but somewhat contradictory evidence that NOX contributes to the pathogenesis of hypertension through oxidative stress. Specific NOX isoforms have been implicated in endothelial dysfunction, hyper-contractility and vascular remodelling in various animal models of hypertension, pulmonary hypertension and pulmonary arterial hypertension, but also have potential protective effects, particularly NOX4. This review explores the multiplicity of NOX function in the healthy vasculature and the evidence for and against targeting NOX for antihypertensive therapy.

Role of the Balance of Akt and MAPK Pathways in the Exercise-Regulated Phenotype Switching in Spontaneously Hypertensive Rats

The mechanisms regulating vascular smooth muscle cell (VSMC) phenotype switching and the critical signal modulation affecting the VSMCs remain controversial. Physical exercise acts as an effective drug in preventing elevated blood pressure and improving vascular function. This study was designed to explore the influence of aerobic exercise on the suppression of VSMC phenotype switching by balancing of the Akt, also known as PKB (protein kinase B) and mitogen-activated protein kinase (MAPK) signaling pathways. Spontaneously hypertensive rats (SHRs) and normotensive rats were subjected to exercise treatment before measuring the vascular morphological and structural performances. Exercise induced reverse expression of VSMC protein markers (α-SM-actin, calponin, and osteopontin (OPN)) in spontaneously hypertensive rats. It is noteworthy that the low expression of phosphorylated Akt significantly decreased the expression of VSMC contractile phenotype markers (α-SM-actin and calponin) and increased the expression of the VSMC synthetic phenotype marker (OPN). However, the MAPK signal pathway exerts an opposite effect. VSMCs and whole vessels were treated by inhibitors, namely the p-Akt inhibitor, p-ERK inhibitor, and p-p38 MAPK inhibitors. VSMC phenotype markers were reversed. It is important to note that a significant reverse regulatory relationship was observed between the expression levels of MAPK and the contractile markers in both normotensive and spontaneously hypertensive rats. We demonstrate that aerobic exercise regulates the VSMC phenotype switching by balancing the Akt and MAPK signaling pathways in SHRs.

VAS2870 Inhibits Histamine-Induced Calcium Signaling and vWF Secretion in Human Umbilical Vein Endothelial Cells

In this study, we investigated the effects of NAD(P)H oxidase (NOX) inhibitor VAS2870 (3-benzyl-7-(2-benzoxazolyl)thio-1,2,3-triazolo[4,5-d]pyrimidine) on the histamine-induced elevation of free cytoplasmic calcium concentration ([Ca²⁺]_i) and the secretion of von Willebrand factor (vWF) in human umbilical vein endothelial cells (HUVECs) and on relaxation of rat aorta in response to histamine. At 10 μM concentration, VAS2870 suppressed the [Ca²⁺]_i rise induced by histamine. Inhibition was not competitive, with IC50 3.64 and 3.22 μM at 1 and 100 μM concentrations of histamine, respectively. There was no inhibition of [Ca²⁺]_i elevation by VAS2870 in HUVECs in response to the agonist of type 1 protease-activated receptor SFLLRN. VAS2870 attenuated histamine-induced secretion of vWF and did not inhibit basal secretion. VAS2870 did not change the degree of histamine-induced relaxation of rat aortic rings constricted by norepinephrine. We suggest that NOX inhibitors might be used as a tool for preventing thrombosis induced by histamine release from mast cells without affecting vasorelaxation.

Myeloperoxidase promotes tube formation, triggers ERK1/2 and Akt pathways and is expressed endogenously in endothelial cells

Myeloperoxidase is a member of the mammalian peroxidase family, mainly expressed in the myeloblastic cell lineage. It is considered a major bactericidal agent as it is released in the phagosome where it catalyzes the formation of reactive oxygen species. It is also released in the extracellular spaces including blood where it is absorbed on (lipo)proteins and endothelial cell surface, interfering with endothelial function. We performed RNA sequencing on MPO-treated endothelial cells, analyzed their transcriptome and validated the profile of gene expression by individual qRT-PCR. Some of the induced genes could be grouped in several functional networks, including tubulogenesis, angiogenesis, and blood vessel morphogenesis and development as well as signal transduction pathways associated to these mechanisms. MPO treatment mimicked the effects of VEGF on several signal transduction pathways, such as Akt, ERK or FAK involved in angiogenesis. Accordingly MPO, independently of its enzymatic activity, stimulated tube formation by endothelial cells. RNA interference also pointed at a role of endogenous MPO in tubulogenesis and endothelium wound repair in vitro. These data suggest that MPO, whether from endogenous or exogenous sources, could play a role in angiogenesis and vascular repair in vivo.

Advanced oxidation protein products induce chondrocyte death through a redox-dependent, poly (ADP-ribose) polymerase-1-mediated pathway

This study aimed to investigate the effect of AOPPs on apoptosis in human chondrocytes. Chondrocytes were treated with AOPPs. Cell death, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, reactive oxygen species (ROS) generation, and the expression of apoptotic proteins were detected in vitro. AOPPs levels were detected by colorimetric method. The results in vitro demonstrated that AOPPs induced cell death in human chondrocyte through a redox-dependent pathway, including RAGE-mediated, NADPH oxidase-dependent ROS generation, and poly (ADP-ribose) polymerase-1 (PARP-1) activation. Targeting AOPPs-induced cellular mechanisms might emerge as a promising therapeutic option for patients with RA.

Notoginsenoside R1 attenuates high glucose-induced endothelial damage in rat retinal capillary endothelial cells by modulating the intracellular redox state

The aim of this study was to examine whether Notoginsenoside R1 (NR1) attenuates high glucose-induced cell damage in rat retinal capillary endothelial cells (RCECs) and to explore the mechanisms involved. The exposure of rat RCECs to high concentration of glucose (30 mM) for 72 h led to significant cytotoxicity, including decreased cell viability, reduced mitochondrial DNA copy number, increased lactate dehydrogenase release and elevated apoptosis. NR1, when present in the culture medium, markedly attenuated the high glucose-induced cytotoxicity in rat RCECs. Moreover, high glucose also induced a significant increase in intracellular reactive oxygen species and subsequently increased the activity of NADPH oxidase and poly-ADP (ribose) polymerase, whereas the activity of catalase decreased. The addition of NR1 to the medium significantly reduced the generation of reactive oxygen species, inhibited NADPH oxidase and poly-ADP (ribose) polymerase activities and increased catalase activity in RCECs, accompanied by a reduced cellular nitrotyrosine level. To explore the underlying mechanisms involved, the cellular redox status was monitored. Both the cellular NAD⁺ and NADPH levels decreased significantly in high glucose medium, which resulted in a marked decrease in the NAD⁺/NADH and NADPH/NADP⁺ ratios. High glucose stimulation also enhanced the accumulation of GSSG, maintaining the GSH/GSSG ratio lower than that in the control group with 5.5 mM glucose. When treated with NR1, the cellular NAD⁺, NADPH and GSH concentrations increased, and the ratios of NAD⁺/NADH, NADPH/NADP⁺ and GSH/GSSG increased, similar to the control group. These results demonstrate that NR1 attenuates high glucose-induced cell damage in RCECs. Therefore, NR1 may exert its protective effects via mechanisms that involve changes in the cellular redox state.

Hydrogen Peroxide as a Paracrine Vascular Mediator: Regulation and Signaling Leading to Dysfunction

Numerous studies have demonstrated the ability of a variety of vascular cells, including endothelial cells, smooth muscle cells, and fibroblasts, to produce reactive oxygen species (ROS). Until recently, major emphasis was placed on the production of superoxide anion (O2–) in the vasculature as a result of its ability to directly attenuate the biological activity of endothelium-derived nitric oxide (NO). The short half-life and radius of diffusion of O2– drastically limit the role of this ROS as an important paracrine hormone in vascular biology. On the contrary, in recent years, the O2– metabolite hydrogen peroxide (H2O2) has increasingly been viewed as an important cellular signaling agent in its own right, capable of modulating both contractile and growth-promoting pathways with more far-reaching effects. In this review, we will assess the vascular production of H2O2, its regulation by endogenous scavenger systems, and its ability to activate a variety of vascular signaling pathways, thereby leading to vascular contraction and growth. This discussion will include the ability of H2O2 to (i) Initiate calcium flux as well as (ii) stimulate pathways leading to sensitization of contractile elements to calcium. The latter involves a variety of protein kinases that have also been strongly implicated in vascular hypertrophy. Previous Intensive study has emphasized the ability of NADPH oxidase-derived O2– and H2O2 to activate these pathways in cultured smooth muscle cells. However, growing evidence indicates a considerably more complex array of unique oxidase systems in the endothelium, media, and adventitia that appear to participate in these deleterious effects in a sequential and temporal manner. Taken together, these findings seem consistent with a paracrine effect of H2O2 across the vascular wall.

Advanced oxidation protein products induce apoptosis of human chondrocyte through reactive oxygen species-mediated mitochondrial dysfunction and endoplasmic reticulum stress pathways

Advanced oxidation production products (AOPPs) have been confirmed to accumulate in patients with rheumatoid arthritis (RA). Previous study demonstrated that AOPPs could accelerate cartilage destruction in rabbit arthritis model. However, the effect of AOPP stimulation on apoptosis of human chondrocyte and the underlying mechanisms remains unclear. This study demonstrated that exposure of chondrocyte to AOPPs resulted in cell apoptosis. AOPP stimulation triggered reactive oxygen species (ROS) production, which induced mitochondrial dysfunction and endoplasmic reticulum stress (ER stress) resulted in caspase activation. Furthermore, an antioxidant, N-acetylcysteine, markedly blocked these signals. Our study demonstrated that AOPPs induce apoptosis via ROS-related mitochondria- and ER-dependent signals in human chondrocyte. Targeting AOPP-triggered ROS generation might be as a promising option for patients with RA.

Acid sphingomyelinase inhibition protects mice from lung edema and lethal Staphylococcus aureus sepsis

Pulmonary edema associated with increased vascular permeability is a severe complication of Staphylococcus aureus-induced sepsis and an important cause of human pathology and death. We investigated the role of the mammalian acid sphingomyelinase (Asm)/ceramide system in the development of lung edema caused by S. aureus. Our findings demonstrate that genetic deficiency or pharmacologic inhibition of Asm reduced lung edema in mice infected with S. aureus. The Asm/ceramide system triggered the formation of superoxide, resulting in degradation of tight junction proteins followed by lung edema. Treatment of infected mice with amitriptyline, a potent inhibitor of Asm, protected mice from lung edema caused by S. aureus, but did not reduce systemic bacterial numbers. In turn, treatment with antibiotics reduced bacterial numbers but did not protect mice from lung edema. In contrast, only the combination of antibiotics and amitriptyline inhibited both pulmonary edema and bacteremia protecting mice from lethal sepsis and lung dysfunction suggesting the combination of both drugs as novel treatment option for sepsis.

KEY MESSAGES

Antibiotics are often insufficient to cure S. aureus-induced sepsis. S. aureus induces lung edema via the Asm/ceramide system. Genetic deficiency of Asm inhibits lung dysfunction upon infection with S. aureus. Pharmacologic inhibition of Asm reduces lung edema induced by S. aureus. Antibiotics plus amitriptyline protect mice from lung edema and lethal S. aureus sepsis.

Role of small GTPase protein Rac1 in cardiovascular diseases: development of new selective pharmacological inhibitors

A pathway-based genome-wide association analysis has recently identified Rac1 as one of the biologically important gene in coronary heart diseases. The role of the small GTPase Rac1 in cardiac hypertrophy and atherosclerosis has also been documented in clinical studies with the HMG-CoA reductase inhibitors and in in vitro and in vivo settings using transgenic and knockout mice. Thus, Rac1 has emerged as a new pharmacological target for the treatment of cardiovascular diseases. The activation state of Rac1 depends on the release of guanosine diphosphate and the binding of guanosine triphosphate. This cycling is regulated by the guanine nucleotide exchange factors, as activators, and by the GTPase-activating proteins. Three categories of selective Rac1 inhibitors have been developed affecting different steps of this pathway: antagonists of Rac1-guanine nucleotide exchange factor interaction, allosteric inhibitors of nucleotide binding to Rac1, and antagonists of Rac1-mediated NADPH oxidase activity. These chemical compounds have shown to selectively inhibit Rac1 activation in cultured cell lines without affecting the homologous proteins RhoA and Cdc42. Moreover, pioneer studies have been conducted with Rac1 inhibitors in in vivo experimental models of cardiovascular diseases with encouraging results. The present review summarizes the current knowledge of the role of Rac1 in cardiovascular diseases and the pharmacological approaches that have been developed to selectively inhibit its function.

Astragalus polysaccharides suppress ICAM-1 and VCAM-1 expression in TNF-α-treated human vascular endothelial cells by blocking NF-κB activation

AIM

To investigate the effects Astragalus polysaccharides (APS) on tumor necrosis factor (TNF)-α-induced inflammatory reactions in human umbilical vein endothelial cells (HUVECs) and to elucidate the underlying mechanisms.

METHODS

HUVECs were treated with TNF-α for 24 h. The amounts of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were determined with Western blotting. HUVEC viability and apoptosis were detected using cell viability assay and Hoechst staining, respectively. Reactive oxygen species (ROS) production was measured by DHE staining. Monocyte and HUVEC adhesion assay was used to detect endothelial cell adhesive function. NF-κB activation was detected with immunofluorescence.

RESULTS

TNF-α (1-80 ng/mL) caused dose- and time-dependent increases of ICAM-1 and VCAM-1 expression in HUVECs, accompanied by significant augmentation of IκB phosphorylation and NF-κB translocation into the nuclei. Pretreatment with APS (10 and 50 μg/mL) significantly attenuated TNFα-induced upregulation of ICAM-1 VCAM-1 and NF-κB translocation. Moreover, APS significantly reduced apoptosis, ROS generation and adhesion function damage in TNF-α-treated HUVECs.

CONCLUSION

APS suppresses TNFα-induced adhesion molecule expression by blocking NF-κB signaling and inhibiting ROS generation in HUVECs. The results suggest that APS may be used to treat and prevent endothelial cell injury-related diseases.

[The Fetal Tobacco Syndrome - A statement of the Austrian Societies for General- and Family Medicine (ÖGAM), Gynecology and Obstetrics (ÖGGG), Hygiene, Microbiology and Preventive Medicine (ÖGHMP), Pediatrics and Adolescence Medicine (ÖGKJ) as well as Pneumology (ÖGP)]

Over more than 50 years, the nocuous effects of smoking in pregnancy on the fetus are well known. In the first years of science the focus was primarily on restricted fetal growth while in more recent years over 10.000 studies investigated the incomparably big sum of detrimental effects for the unborn's health. In this statement we want to present the recent scientific findings on this topic. The statement is aimed to show all doctors who treat pregnant women the present situation and evidence. In the beginning we give a short overview about the epidemiological situation in Europe. Then we present step by step the health effects with regards to pathophysiology and clinics. Furthermore the reader will learn about possibilities for smoking cessation in pregnancy. The problem of passive-smoking in pregnancy will be dealt with in a separate chapter. At present there is strong evidence that pregnant smoking has a detrimental effect on birth-weight, placenta-associated disease, stillbirth, sudden infant death syndrome (SIDS), childhood overweight, clefts, lung function, asthma, cardiovascular diseases and mental developmental disorders. These factors can be summarized by the term Fetal Tobacco Syndrome. There is supply for more studies for less investigated health effects. Pregnancy is a chance to stop smoking as most women show a high motivation in this period. Hence doctors of all disciplines should inform pregnant women about the detrimental effects of smoking on their unborn child and show them possibilities for smoking cessation.

Vascular cell adhesion molecule-1 expression and signaling during disease: regulation by reactive oxygen species and antioxidants

The endothelium is immunoregulatory in that inhibiting the function of vascular adhesion molecules blocks leukocyte recruitment and thus tissue inflammation. The function of endothelial cells during leukocyte recruitment is regulated by reactive oxygen species (ROS) and antioxidants. In inflammatory sites and lymph nodes, the endothelium is stimulated to express adhesion molecules that mediate leukocyte binding. Upon leukocyte binding, these adhesion molecules activate endothelial cell signal transduction that then alters endothelial cell shape for the opening of passageways through which leukocytes can migrate. If the stimulation of this opening is blocked, inflammation is blocked. In this review, we focus on the endothelial cell adhesion molecule, vascular cell adhesion molecule-1 (VCAM-1). Expression of VCAM-1 is induced on endothelial cells during inflammatory diseases by several mediators, including ROS. Then, VCAM-1 on the endothelium functions as both a scaffold for leukocyte migration and a trigger of endothelial signaling through NADPH oxidase-generated ROS. These ROS induce signals for the opening of intercellular passageways through which leukocytes migrate. In several inflammatory diseases, inflammation is blocked by inhibition of leukocyte binding to VCAM-1 or by inhibition of VCAM-1 signal transduction. VCAM-1 signal transduction and VCAM-1-dependent inflammation are blocked by antioxidants. Thus, VCAM-1 signaling is a target for intervention by pharmacological agents and by antioxidants during inflammatory diseases. This review discusses ROS and antioxidant functions during activation of VCAM-1 expression and VCAM-1 signaling in inflammatory diseases.

Apocynin attenuates ventilator-induced lung injury in an isolated and perfused rat lung model

RATIONALE

Apocynin suppresses the generation of reactive oxygen species (ROS) that are implicated in ventilator-induced lung injury (VILI). We thus hypothesized that apocynin attenuates VILI.

METHODS

VILI was induced by mechanical ventilation with tidal volume (V(t)) of 15 ml/kg in isolated and perfused rat lung. Apocynin was administered in the perfusate at onset of mechanical ventilation. A group ventilated with low V(t) of 5 ml/kg served as control. Hemodynamics, lung injury indices, inflammatory responses, and activation of apoptotic pathways were determined upon completion of mechanical ventilation.

RESULTS

There was an increase in lung permeability and lung weight gain after mechanical ventilation with high V(t), compared with low V (t). Levels of inflammatory cytokines including interleukin-1β (IL-1β), tumor necrosis factor-alpha (TNF-α), and macrophage inflammatory protein-2 (MIP-2) increased in lung lavage fluids; concentrations of carbonyl, thiobarbituric acid reactive substances, and H(2)O(2) were higher in perfusates and lung lavage fluids, and expression of myeloperoxidase, JNK, p38, and caspase-3 in lung tissue was greater in the high-V(t) than in the low-V(t) group. Administration of apocynin attenuated these inflammatory responses and lung permeability associated with decreased activation of nuclear factor-κB.

CONCLUSIONS

VILI is associated with inflammatory responses including generation of ROS, cytokines, and activation of mitogen-activated protein kinase cascades. Administration of apocynin at onset of mechanical ventilation attenuates inflammatory responses and VILI in the isolated, perfused rat lung model.

Apocynin, a Plant-Derived Drug, Might Be Useful in the Treatment of Myocardial Ischemia Reperfusion Injury in Rat Hearts

Apocynin is a potent and selective inhibitor of the NADPH oxidase-dependent production of ROS by stimulated human PMNs. Apocynin was isolated by activity-guided isolation from Picrorhiza kurroa, and in the years following its discovery it has been used in many laboratories around the world. Reactive oxygen species (ROS) production by activated polymorphonuclear neutrophils (PMNs) plays an important role in many cardiovascular disease states, including myocardial ischemia reperfusion injury. The purpose of this study is to examine the beneficial effects of apocynin on myocardial ischemia reperfusion injury. Myocardial I/R injury was caused by clamping the left anterior descending (LAD) coronary artery for 20 min followed by release of the clamp allowing reperfusion for 1 h. Administration of apocynin i.p. (5mg/kg i.p. 10%DMSO) 15 min after ischemia significantly reduced the: 1) histological evidence of myocardial injury; 2) pro-inflammatory cytokines (TNF-α, IL-1β); 3) adhesion molecules (ICAM-1, P-Selectin); 4) nitrotyrosine formation; 5) NF-kB expression; 6) PAR formation; and 7) apoptosis (Bax, Bcl-2, Fas-L and tunel). Based on these findings we propose that apocynin would be useful in the treatment of various ischemia and reperfusion diseases.

NAD(P)H oxidase-derived reactive oxygen species contribute to age-related impairments of endothelium-dependent dilation in rat soleus feed arteries

We tested the hypothesis that age-related endothelial dysfunction in rat soleus muscle feed arteries (SFA) is mediated in part by NAD(P)H oxidase-derived reactive oxygen species (ROS). SFA from young (4 mo) and old (24 mo) Fischer 344 rats were isolated and cannulated for examination of vasodilator responses to flow and acetylcholine (ACh) in the absence or presence of a superoxide anion (O(2)(-)) scavenger (Tempol; 100 μM) or an NAD(P)H oxidase inhibitor (apocynin; 100 μM). In the absence of inhibitors, flow- and ACh-induced dilations were attenuated in SFA from old rats compared with young rats. Tempol and apocynin improved flow- and ACh-induced dilation in SFA from old rats. In SFA from young rats, Tempol and apocynin had no effect on flow-induced dilation, and apocynin attenuated ACh-induced dilation. To determine the role of hydrogen peroxide (H(2)O(2)), dilator responses were assessed in the absence and presence of catalase (100 U/ml) or PEG-catalase (200 U/ml). Neither H(2)O(2) scavenger altered flow-induced dilation, whereas both H(2)O(2) scavengers blunted ACh-induced dilation in SFA from young rats. In old SFA, catalase improved flow-induced dilation whereas PEG-catalase improved ACh-induced dilation. Compared with young SFA, in response to exogenous H(2)O(2) and NADPH, old rats exhibited blunted dilation and constriction, respectively. Immunoblot analysis revealed that the NAD(P)H oxidase subunit gp91phox protein content was greater in old SFA compared with young. These results suggest that NAD(P)H oxidase-derived reactive oxygen species contribute to impaired endothelium-dependent dilation in old SFA.

Are nicotine replacement therapy, varenicline or bupropion options for pregnant mothers to quit smoking? Effects on the respiratory system of the offspring

Nicotine occurs in tobacco smoke. It is a habit-forming substance and is prescribed by health professionals to assist smokers to quit smoking. It is rapidly absorbed from the lungs of smokers. It crosses the placenta and accumulates in the developing fetus. Nicotine induces formation of oxygen radicals and at the same time also reduces the antioxidant capacity of the lungs. Nicotine and the oxidants cause point mutations in the DNA molecule thereby changing the program that controls lung growth and maintenance of lung structure. The data available indicate that maternal nicotine exposure induces a persistent inhibition of glycolysis and a drastically increased AMP level. These metabolic changes are thought to contribute to the faster aging of the lungs of the offspring of mothers that are exposed to nicotine via the placenta and mother's milk. The lungs of these animals are more susceptible to damage as shown by the gradual deterioration of the lung parenchyma. The rapid metabolic and structural aging of the lungs of the animals exposed to nicotine via the placenta and mother's milk, and thus during phases of lung development characterized by rapid cell division, is likely due to 'programming' induced by nicotine. Since varenicline, a partial nicotine agonist, has basically the same structure as nicotine, and also binds to acetylcholine receptors in competition with nicotine (but with largely the same effect), it is not advisable to use nicotine or varenicline during gestation and lactation. Furthermore, the use of individual vitamin supplements is also not advisable because of the negative impact on the program that controls maintenance of lung structural and functional integrity and aging. A more appropriate smoking cessation program will also include a mixture of antioxidant nutrients such as in tomato juice.

NADPH oxidases 1 and 4 mediate cellular senescence induced by resveratrol in human endothelial cells

Resveratrol is believed to be partially responsible for the French paradox--the low risk of cardiovascular disease despite a high-fat diet in the French population. Recently, resveratrol has also been discussed as a life-span booster in several organisms. Age-related diseases are associated on the cellular level with senescence. We, therefore, hypothesized that resveratrol is vasoprotective by counteracting endothelial cell senescence. Surprisingly, we observed that chronic treatment with resveratrol (10 microM) was prosenescent in primary human endothelial cells. Resveratrol induced elevated reactive oxygen species (ROS) levels that were associated with and causally linked to an accumulation of cells in the S phase of the cell cycle, as measured by flow cytometry. We further show that cell accumulation in S phase leads to increased ROS and finally senescence. Using an siRNA approach, we clearly identified two NADPH oxidases, Nox1 and Nox4, as major targets of resveratrol and primary sources of ROS that act upstream of the observed S-phase accumulation.

Regulation of NADPH oxidase in vascular endothelium: the role of phospholipases, protein kinases, and cytoskeletal proteins

The generation of reactive oxygen species (ROS) in the vasculature plays a major role in the genesis of endothelial cell (EC) activation and barrier function. Of the several potential sources of ROS in the vasculature, the endothelial NADPH oxidase family of proteins is a major contributor of ROS associated with lung inflammation, ischemia/reperfusion injury, sepsis, hyperoxia, and ventilator-associated lung injury. The NADPH oxidase in lung ECs has most of the components found in phagocytic oxidase, and recent studies show the expression of several homologues of Nox proteins in vascular cells. Activation of NADPH oxidase of nonphagocytic vascular cells is complex and involves assembly of the cytosolic (p47(phox), p67(phox), and Rac1) and membrane-associated components (Noxes and p22(phox)). Signaling pathways leading to NADPH oxidase activation are not completely defined; however, they do appear to involve the cytoskeleton and posttranslation modification of the components regulated by protein kinases, protein phosphatases, and phospholipases. Furthermore, several key components regulating NADPH oxidase recruitment, assembly, and activation are enriched in lipid microdomains to form a functional signaling platform. Future studies on temporal and spatial localization of Nox isoforms will provide new insights into the role of NADPH oxidase-derived ROS in the pathobiology of lung diseases.

Mitochondrial H2O2 emission and cellular redox state link excess fat intake to insulin resistance in both rodents and humans

High dietary fat intake leads to insulin resistance in skeletal muscle, and this represents a major risk factor for type 2 diabetes and cardiovascular disease. Mitochondrial dysfunction and oxidative stress have been implicated in the disease process, but the underlying mechanisms are still unknown. Here we show that in skeletal muscle of both rodents and humans, a diet high in fat increases the H(2)O(2)-emitting potential of mitochondria, shifts the cellular redox environment to a more oxidized state, and decreases the redox-buffering capacity in the absence of any change in mitochondrial respiratory function. Furthermore, we show that attenuating mitochondrial H(2)O(2) emission, either by treating rats with a mitochondrial-targeted antioxidant or by genetically engineering the overexpression of catalase in mitochondria of muscle in mice, completely preserves insulin sensitivity despite a high-fat diet. These findings place the etiology of insulin resistance in the context of mitochondrial bioenergetics by demonstrating that mitochondrial H(2)O(2) emission serves as both a gauge of energy balance and a regulator of cellular redox environment, linking intracellular metabolic balance to the control of insulin sensitivity.

Apocynin: molecular aptitudes

Apocynin is a naturally occurring methoxy-substituted catechol, experimentally used as an inhibitor of NADPH-oxidase. It can decrease the production of superoxide (O(2)(-)) from activated neutrophils and macrophages while the ability of phagocytosis remains unaffected. The anti-inflammatory activity of apocynin has been demonstrated in a variety of cell and animal models of inflammation. Apocynin, after metabolic conversion, inhibits the assembly of NADPH-oxidase that is responsible for reactive oxygen species (ROS) production. It is, therefore, extensively used to reveal the role of this enzyme in cell and experimental models. Although some of the ROS serve as signaling molecules in the cells, excessive production is damaging and has been implicated to play an important role in the progression of many disease processes. This is why in many studies apocynin presents a promising potential treatment for some disorders; however, its utility with inflammatory diseases remains to be determined. Since its mode of action is not well defined, we tried to get a more precise insight into the mechanisms by which apocynin exerts its activity. Considering the anti-inflammatory activities of apocynin, we may conclude that this compound definitely deserves further study.

Lipid rafts keep NADPH oxidase in the inactive state in human renal proximal tubule cells

Recent studies have indicated the importance of cholesterol-rich membrane lipid rafts (LRs) in oxidative stress-induced signal transduction. Reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidases, the major sources of reactive oxygen species, are implicated in cardiovascular diseases, including hypertension. We tested the hypothesis that NADPH oxidase subunits and activity are regulated by LRs in human renal proximal tubule cells. We report that a high proportion of p22(phox) and the small GTPase Rac1 are expressed in LRs in human renal proximal tubule cells. The D(1)-like receptor agonist, fenoldopam (1 micromol/L per 20 minutes) dispersed Nox subunits within LRs and non-LRs and decreased oxidase activity (30.7+/-3.3%). In contrast, cholesterol depletion (2% methyl-beta-cyclodextrin [beta CD]) translocated NADPH oxidase subunits out of LRs and increased oxidase activity (154.0+/-10.5% versus control, 103.1+/-3.4%), which was reversed by cholesterol repletion (118.9+/-9.9%). Moreover, NADPH oxidase activation by beta CD (145.5+/-9.0%; control: 98.6+/-1.6%) was also abrogated by the NADPH oxidase inhibitors apocynin (100.4+/-3.2%) and diphenylene iodonium (9.5+/-3.3%). Furthermore, beta CD-induced reactive oxygen species production was reversed by knocking down either Nox2 (81.0+/-5.1% versus beta CD: 162.0+/-2.0%) or Nox4 (108.0+/-10.8% versus beta CD: 152.0+/-9.8%). We have demonstrated for the first time that disruption of LRs results in NADPH oxidase activation that is abolished by antioxidants and silencing of Nox2 or Nox4. Therefore, in human renal proximal tubule cells, LRs maintain NADPH oxidase in an inactive state.

Homocysteine stimulates NADPH oxidase-mediated superoxide production leading to endothelial dysfunction in rats

Elevation of blood homocysteine (Hcy) levels (hyperhomocysteinemia) is a risk factor for cardiovascular disorders. We previously reported that oxidative stress contributed to Hcy-induced inflammatory response in vascular cells. In this study, we investigated whether NADPH oxidase was involved in Hcy-induced superoxide anion accumulation in the aorta, which leads to endothelial dysfunction during hyperhomocysteinemia. Hyperhomocysteinemia was induced in rats fed a high-methionine diet. NADPH oxidase activity and the levels of superoxide and peroxynitrite were markedly increased in aortas isolated from hyperhomocysteinemic rats. Expression of the NADPH oxidase subunit p22phox increased significantly in these aortas. Administration of an NADPH oxidase inhibitor (apocynin) not only attenuated aortic superoxide and peroxynitrite to control levels but also restored endothelium-dependent relaxation in the aortas of hyperhomocysteinemic rats. Transfection of human endothelial cells or vascular smooth muscle cells with p22phox siRNA to inhibit NADPH oxidase activation effectively abolished Hcy-induced superoxide anion production, thus indicating the direct involvement of NADPH oxidase in elevated superoxide generation in vascular cells. Taken together, these results suggest that Hcy-stimulated superoxide anion production in the vascular wall is mediated through the activation of NADPH oxidase, which leads to endothelial dysfunction during hyperhomocysteinemia.

Effects of apocynin and ethanol on intracerebral haemorrhage-induced brain injury in rats

1. In the present study, we investigated whether the administration of apocynin, an NADPH oxidase inhibitor, provided brain protection in a rat model of intracerebral haemorrhage (ICH). 2. Rats were divided into sham, ICH untreated, ICH treated with vehicle (ethanol) and ICH treated with apocynin groups. Intracerebral haemorrhage was induced by collagenase injection. Neurological function, haemorrhage volume and brain oedema were measured 24 h after ICH. 3. Intracerebral haemorrhage caused significant neurological deficit associated with brain oedema. Apocynin (3, 10 and 30 mg/kg) failed to reduce brain injury after ICH. Low dose ethanol (0.2 g/kg) improved neurological function and reduced brain oedema (ICH-vehicle vs ICH-untreated, P < 0.05). 4. In conclusion, apocynin has no neuroprotective effect when administered intraperitoneally after ICH.

Oxidized low density lipoprotein receptor-1 mediates oxidized low density lipoprotein-induced apoptosis in human umbilical vein endothelial cells: Role of reactive oxygen species

Studies have shown that oxidized low density lipoprotein (ox-LDL) elicits both necrotic and apoptotic cell death and several mechanisms have been proposed. Ox-LDL induces reactive oxygen species (ROS), a second messenger that might be involved in apoptosis, formation in different types of cells including endothelial cells (ECs) and smooth muscle cells (SMCs). As lectin-like ox-LDL receptor-1 (LOX-1) was the main receptor for ox-LDL, this study was designed to determine whether the apoptosis induced by ox-LDL was mediated by LOX-1 in cultured human umbilical vein endothelial cells (HUVECs) and whether there is an association between LOX-1 mediated apoptosis and the production of ROS. After exposure to ox-LDL (50,100, and 150 microg/ml for 18 h), HUVECs exhibit typical apoptotic characteristics as determined by transmission electron microscopy and flow cytometry analysis in a dose-dependent pattern. Ox-LDL increases intracellular ROS formation including superoxide anion (O2-) and hydrogen peroxide (H2O2) in a dose-dependent and time-dependent manner. Pretreatment with anti-LOX-1 mAb, Vitamin C, apocynin or catalase significantly reduced ROS production and prevented ox-LDL-induced apoptosis, while indomethacin or allopurinol had no effect. These results suggest that LOX-1 mediates ox-LDL-induced apoptosis in endothelial cells and that ROS production and NADPH oxidase might play an important role in ox-LDL-induced apoptosis.

Nonhematopoietic NADPH oxidase regulation of lung eosinophilia and airway hyperresponsiveness in experimentally induced asthma

Pulmonary eosinophilia is one of the most consistent hallmarks of asthma. Infiltration of eosinophils into the lung in experimental asthma is dependent on the adhesion molecule vascular cell adhesion molecule-1 (VCAM-1) on endothelial cells. Ligation of VCAM-1 activates endothelial cell NADPH oxidase, which is required for VCAM-1-dependent leukocyte migration in vitro. To examine whether endothelial-derived NADPH oxidase modulates eosinophil recruitment in vivo, mice deficient in NADPH oxidase (CYBB mice) were irradiated and received wild-type hematopoietic cells to generate chimeric CYBB mice. In response to ovalbumin (OVA) challenge, the chimeric CYBB mice had increased numbers of eosinophils bound to the endothelium as well as reduced eosinophilia in the lung tissue and bronchoalveolar lavage. This occurred independent of changes in VCAM-1 expression, cytokine/chemokine levels (IL-5, IL-10, IL-13, IFNgamma, or eotaxin), or numbers of T cells, neutrophils, or mononuclear cells in the lavage fluids or lung tissue of OVA-challenged mice. Importantly, the OVA-challenged chimeric CYBB mice had reduced airway hyperresponsiveness (AHR). The AHR in OVA-challenged chimeric CYBB mice was restored by bypassing the endothelium with intratracheal administration of eosinophils. These data suggest that VCAM-1 induction of NADPH oxidase in the endothelium is necessary for the eosinophil recruitment during allergic inflammation. Moreover, these studies provide a basis for targeting VCAM-1-dependent signaling pathways in asthma therapies.

Oxidants in the Gas Phase of Cigarette Smoke Pass Through the Lung Alveolar Wall and Raise Systemic Oxidative Stress

Cigarette smoking-induced oxidative stress plays a key role in the pathogenesis of atherosclerosis in smokers. Aqueous cigarette smoke extract (CSE) contains stable oxidants, peroxynitrite-like reactants, which have the ability to oxidize and nitrate low-density lipoprotein (LDL). We examined whether oxidants in CSE can penetrate into the blood through the lung alveolar wall and cause oxidative vascular injury. The oxidants in CSE and sodium peroxynitrite could easily pass through the reconstituted basement membrane. When CSE or sodium peroxynitrite solution was infused into the alveolar air space of an isolated rat lung mounted in tyrosine solution, CSE gradually increased the 3-nitrotyrosine levels in the external tyrosine solution while sodium peroxynitrite caused a rapid increase. CSE did not activate the rat alveolar macrophages. When rats were acutely exposed to the gas phase of cigarette smoke from which tar and nicotine had been removed, both serum levels of 3-nitrotyrosine and 8-hydroxy-2'-deoxyguanine, oxidative stress markers, rapidly increased. Our results demonstrate that relatively stable oxidants in CSE can pass through the pulmonary alveolar wall into the blood and induce systemic oxidative stress, which most likely facilitates oxidative modification of LDL and endothelial dysfunction, explaining early key events in the development of atherosclerosis.

β1 antagonist and β2 agonist, celiprolol, restores the impaired endothelial dependent and independent responses and decreased TNFα in rat with type II diabetes

The effect of beta antagonists in the diabetic vascular lesion is controversial. We investigated the effect of celiprolol hydrochloride, a beta1 antagonist and mild beta2 agonist, on the lesions and function in type II male Otsuka Long-Evans Tokushima Fatty (OLETF) diabetic rats. OLETF rats were fed regular chow with or without atenolol (25 mg/kg/day) or celiprolol (100 mg/kg/day) treatment (group DM, no treatment; group DM-a, atenolol treatment; group DM-c, celiprolol treatment), and treatment was continued for 31 days. Separately, normoglycemic control rats, LETO, were prepared as group C. On day 3, endothelial cells of the right internal carotid artery were removed by balloon injury, and the rats were evaluated 4 weeks after balloon injury. The plasma glucose and lipid levels were unchanged throughout the treatment period. Intimal thickening was observed in the right carotid artery in the DM and DM-a groups; however, little thickening was observed in those of DM-c rats. Acetylcholine-induced NO-dependent relaxation in arteries was improved in DM-c rats compared with DM and DM-a rats (maximum relaxation DM 30.8+/-4.5, DM-a 37.4+/-3.9, DM-c 48.8+/-4.6%, *P<0.05 vs. DM for DM-c rats). Tone-related basal NO release and acetylcholine-induced NO-dependent relaxation in the arteries and plasma NO(x) (sum of NO(2)(-) and NO(3)(-)) were greater in DM-c and C groups than in DM and DM-a groups. The serum TNFalpha levels did not increase in DM-c rats compared with those of the DM or DM-a groups, and were comparable with those of group C.

CONCLUSION

In conclusion, Celiprolol improves endothelial function in the arteries of OLETF rats, and further restore it 4 weeks after endothelial denudation in the arteries of OLETF rats. NO and O(2)(-) may have a role in the important underlying mechanisms by reducing the TNFalpha levels.

Bone Morphogenic Protein-4 Induces Hypertension in Mice

Background— Recent in vitro studies have shown that disturbed flow and oxidative conditions induce the expression of bone morphogenic proteins (BMPs 2 and 4) in cultured endothelial cells. BMPs can stimulate superoxide production and inflammatory responses in endothelial cells, raising the possibility that BMPs may play a role in vascular diseases such as hypertension and atherosclerosis. In this study, we examined the hypothesis that BMP4 would induce hypertension in intact animals by increasing superoxide production from vascular nicotinamide adenine dinucleotide phosphate (NADPH) oxidases and an impairment of vasodilation responses.

Methods and Results— BMP4 infusion by osmotic pumps increased systolic blood pressure in a time- and dose-dependent manner in both C57BL/6 mice (from 101 to 125 mm Hg) and apolipoprotein E–null mice (from 107 to 146 mm Hg) after 4 weeks. Cotreatment with the BMP antagonist noggin or the NADPH oxidase inhibitor apocynin completely blocked the BMP4 effect. In addition, BMP4 infusion stimulated aortic NADPH oxidase activity and impaired vasorelaxation, both of which were prevented either by coinfusing noggin or by treating the isolated aortas with apocynin. BMP4, however, did not cause significant changes in maximum relaxation induced by the endothelium-independent vasodilator nitroglycerin. Remarkably, BMP4 infusion failed to stimulate aortic NADPH oxidases, increase blood pressure, and impair vasodilation responses in p47phox-deficient mice.

Conclusions— These results suggest that BMP4 infusion induces hypertension in mice in a vascular NADPH oxidase–dependent manner and the subsequent endothelial dysfunction. We suggest that BMP4 is a novel mediator of endothelial dysfunction and hypertension and that noggin and its analogs could be used as therapeutic agents for treating vascular diseases.

Gö 6983: A Fast Acting Protein Kinase C Inhibitor that Attenuates Myocardial Ischemia/Reperfusion Injury

Reperfusion injury is characterized by a decrease in endothelial release of nitric oxide within 5 min after reperfusion, increased leukocyte-endothelium interaction, and transmigration of leukocytes into the myocardium, producing cardiac contractile dysfunction. Gö 6983 is a fast acting, lipid soluble, broad spectrum protein kinase C inhibitor. When administered at the beginning of reperfusion, it can restore cardiac function within 5 min and attenuate the deleterious effects associated with acute ischemia/reperfusion. Gö 6983 may offer greater cardioprotection than other broad-spectrum PKC inhibitors in postischemic reperfusion injury because it inhibits PKC(zeta) as well as four other isoforms. The cardioprotection is associated with decreased leukocyte superoxide release and increased endothelial derived nitric oxide from vascular tissue. In vitro studies of human tissue showed that Gö 6983 significantly inhibited antigen-induced superoxide release from leukocytes of patients previously sensitized to tree pollen. In human vascular tissue, Gö 6983 inhibited intracellular Ca(2+) accumulation, suggesting a mechanism for its vasodilator properties. These studies suggest that Gö 6983 would be an effective compound to use in a clinical ischemia/reperfusion setting of organ transplantation and/or cerebral ischemia where inhibiting superoxide release and vasoconstriction in postischemic tissues would allow for better restoration of organ function during reperfusion. However, given the broad-spectrum action of Gö 6983, careful titration of the dose regimen would be recommended to ensure a successful outcome in the setting of organ transplantation and/or cerebral ischemia.

NAD(P)H oxidase contributes to the progression of remote hepatic parenchymal injury and endothelial dysfunction, but not microvascular perfusion deficits

Oxidative stress occurs in remote liver injury, but the origin of the oxidant generation has yet to be thoroughly delineated. Some reports suggest that the source of the distant oxidative stress originates from the site of initial insult [i.e., xanthine oxidase (XO)]; however, it could also be derived from sources such as phagocytic and/or vascular NAD(P)H oxidase (Nox) enzymes. With a murine model of bilateral hindlimb ischemia-reperfusion, we describe here a mechanism for Nox-dependent oxidant production that contributes, at least in part, to remote hepatic parenchymal injury and sinusoidal endothelial cell (SEC) dysfunction. To determine whether Nox enzymes were the source of oxidants, mice were treated immediately after the onset of hindlimb ischemia with specific inhibitors to XO (50 mg/kg ip allopurinol) or Nox (10 mg/kg ip gp91ds-tat and 3 mg/kg ip apocynin). After 1 h of ischemia, hindlimbs were reperfused for either 3 or 6 h. Inhibition of XO failed to provide any improvement in parenchymal injury, SEC dysfunction, neutrophil accumulation, or microvascular dysfunction. In contrast, the inhibition of Nox enzymes prevented the progression (6 h) of parenchymal injury, significantly protected against SEC dysfunction, and completely prevented signs of neutrophil-derived oxidant stress. At the same time, however, inhibition of Nox failed to protect against the early parenchymal injury and microvascular dysfunction at 3 h of reperfusion. These data confirm that microvascular perfusion deficits are not essential for the pathogenesis of remote hepatic parenchymal injury. The data also suggest that Nox enzymes, not XO, are involved in the progression of compromised hepatic parenchymal and endothelial integrity during a systemic inflammatory response.

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.

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.

Acute pressor effect of central angiotensin II is mediated by NAD(P)H-oxidase-dependent production of superoxide in the hypothalamic cardiovascular regulatory nuclei

BACKGROUND

Centrally applied angiotensin II (Ang II) increases sympathetic nervous activity and mean arterial blood pressure (MAP), but the mediation of these effects is not fully understood.

OBJECTIVE

To test the hypothesis that central effects of Ang II are mediated by reduced nicotinamide adenine dinucleotide phosphate [NAD(P)H]-oxidase-dependent production of superoxide in the hypothalamus.

METHODS

Under isoflurane anesthesia, male Sprague-Dawley rats were given an intracerebroventricular infusion of either artificial cerebrospinal fluid or apocynin (4 microg/kg per min), a selective inhibitor for NAD(P)H oxidase, for 30 min, followed by Ang II (20 ng) or carbachol (200 ng), while MAP and heart rate were measured at the femoral artery. At the end of the experiments, hydroethidine, a superoxide-sensitive fluorescent dye, was infused intravenously for 10 min, and superoxide production was assessed in the vasoregulatory hypothalamic nuclei using confocal microscopy.

RESULTS

Ang II elicited a rapid 11 +/- 2-mmHg increase in MAP and a 16 +/- 2-beats/min decrease in heart rate. Apocynin abolished these effects of Ang II in a specific manner, as carbachol-induced increases in MAP were unaffected by the inhibition of NAD(P)H oxidase (MAP increased by 9 +/- 2 and 8 +/- 1 mmHg in the absence and presence of apocynin, respectively). In response to Ang II, apocynin-sensitive production of superoxide increased significantly in the nuclei of the anterior hypothalamus, in the subfornical organ, and in the paraventricular nucleus of the hypothalamus.

CONCLUSION

These findings demonstrate that acute pressor responses of central Ang II are mediated by NAD(P)H-oxidase-dependent production of superoxide in the hypothalamus.

Targeting reactive oxygen species in hypertension

PURPOSE OF REVIEW

Hypertension is a major risk factor for vascular diseases such as stroke, myocardial infarction, and renal microvascular disease. The mechanism by which vascular disease develops is complex, and growing evidence suggests that an increase in reactive oxygen species during hypertension is a major contributing factor. NADPH oxidase, the primary source of reactive oxygen species in the cardiovascular system, is a strong candidate for the development of therapeutic agents to ameliorate hypertension and end-organ damage.

RECENT FINDINGS

Various scavengers and inhibitors of reactive oxygen species have been proposed for use in animal as well as human studies. While many of these agents are effective at lowering tissue reactive oxygen species levels, their specificity is a serious concern. Our laboratory has developed cell-permeant peptidic inhibitors targeting key interactions among the different NAD(P)H oxidase homologues. One of these inhibitors targeting nox2 and p47-phox interaction has proven useful in attenuating target neoplasia and hypertrophy.

SUMMARY

Strategies aimed at specifically inhibiting NAD(P)H oxidase have proven effective in attenuating cardiovascular oxidative stress. The development of new inhibitors targeting novel oxidase homologues appears to hold significant promise for clarifying the physiologic role of these homologues as well as for the development of new antioxidant therapies.

Lysophosphatidylcholine-induced elevation of asymmetric dimethylarginine level by the NADPH oxidase pathway in endothelial cells

Recent studies suggested that endothelium is a main source of reactive oxygen species (ROS) and the major source was via NADPH oxidase pathway. Various stimuli including lysophosphatidylcholine (LPC), a major component of oxidized low-density lipoprotein (ox-LDL), can enhance the activity of NADPH oxidase and lead to a marked ROS generation. Asymmetric dimethylarginine (ADMA) is an endogenous nitric oxide (NO) synthase (NOS) inhibitor, which is synthesized by protein arginine methyltransferase I (PRMT I) and degraded by dimethylarginine dimethylaminohydrolase (DDAH) in endothelial cells. Much evidence showed that ADMA was closely related to endothelial dysfunction. Our previous study showed that LPC elevated ADMA level in endothelial cells via increasing oxidative stress, but the precise cellular mechanism is not defined yet. The present study was to explore the mechanism of NADPH oxidase in LPC-induced elevation of ADMA. In LPC-treated endothelial cells, the ROS production, cell viability, ADMA and NO levels, the activity of DDAH and expression of PRMT I were detected. Treatment with LPC (10 microg/ml) for 24 h markedly increased intracellular ROS production, the expression of PRMT I, level of ADMA, decreased the concentration of NO and the activity of DDAH. These effects were attenuated by diphenyliodonium, the NADPH oxidase inhibitor. In summary, the present results suggested that LPC-induced elevation of ADMA was due to reduction of DDAH activity and the up-regulation of PRMT expression by stimulation of ROS production via NADPH oxidase pathway.

NADPH oxidase is involved in angiotensin II-induced apoptosis in H9C2 cardiac muscle cells: effects of apocynin

Angiotensin II stimulates NADPH oxidase activity in vascular cells. However, it is not fully understood whether angiotensin II, which plays an important role in heart failure, stimulates NADPH oxidase activation and expression in cardiac myocytes. Previous studies have shown that angiotensin II induces myocyte apoptosis, but whether the change is mediated via NADPH oxidase remains to be elucidated. In this study we proposed to determine whether angiotensin II stimulated NADPH oxidase activation and NADPH oxidase subunit p47-phox expression in H9C2 cardiac muscle cells. If so, we would determine whether the NADPH oxidase inhibitor apocynin prevented angiotensin II-induced apoptosis. The results showed that angiotensin II increased NADPH oxidase activity, p47-phox protein and mRNA expression, intracellular reactive oxygen species, and apoptosis in H9C2 cells. Angiotensin II elevated p38 mitogen-activated protein kinase (MAPK) activity, decreased Bcl-2 protein, and increased Bax protein and caspase-3 activity. Apocynin treatment inhibited angiotensin II-induced NADPH oxidase activation and increases in p47-phox expression, intracellular reactive oxygen species, and apoptosis. The effect of apocynin on apoptosis was associated with reduced p38 MAPK activity, increased Bcl-2 protein, and decreased Bax protein and caspase-3 activity. These results suggest that angiotensin II-induced apoptosis is mediated via NADPH oxidase activation probably through p38 MAPK activation, a decrease in Bcl-2 protein, and caspase activation.

Hyperhomocysteinemia, a cardiac metabolic disease: role of nitric oxide and the p22phox subunit of NADPH oxidase

BACKGROUND

Hyperhomocysteinemia (HHcy) is a reliable indicator of cardiovascular disease, in part because of the production of superoxide and scavenging of nitric oxide (NO). The present study assessed the impact of HHcy on the NO-dependent control of cardiac O2 consumption and examined enzymatic sources of superoxide.

METHODS AND RESULTS

Rats and mice were fed methionine in drinking water for 5 to 9 weeks to increase plasma homocysteine, a process that did not cause significant changes in hemodynamic function. The ability of the NO agonists bradykinin and carbachol to reduce myocardial O2 consumption in vitro was impaired by approximately 40% in methionine-fed rats, and this impairment was proportional to their individual plasma homocysteine concentration. However, responses were restored in the presence of ascorbic acid, tempol, and apocynin, which inhibits NADPH oxidase assembly. Western blots showed no difference in Cu/Zn or Mn superoxide dismutase, endothelial NO synthase, or inducible NO synthase protein, but HHcy caused a 100% increase in the p22phox subunit of NADPH oxidase. Western blots with plasma membrane-enriched fractions of cell lysate detected elevated levels of p22phox, p67phox, and rac-1, which indicates increased oxidase assembly. Finally, mice lacking a functional gp91phox subunit of NADPH oxidase demonstrated normal NO-dependent regulation of myocardial O2 consumption after methionine feeding.

CONCLUSIONS

In HHcy, superoxide produced by NADPH oxidase reduces the ability of NO to regulate mitochondrial function in the myocardium. The severity of this effect is proportional to the increase in homocysteine.

Angiotensin II, reactive oxygen species, and Ca2+signaling in afferent arterioles

In afferent arteriolar vascular smooth muscle cells, ANG II induces a rise in cytosolic Ca2+([Ca2+]i) via inositol trisphosphate receptor (IP3R) stimulation and by activation of the adenine diphosphate ribose (ADPR) cyclase to form cyclic ADPR, which sensitizes the ryanodine receptor (RyR) to Ca2+. We hypothesize that ANG II stimulation of NAD(P)H oxidases leads to the formation of superoxide anion (O2−·), which, in turn, activates ADPR cyclase. Afferent arterioles were isolated from rat kidney with the magnetized microsphere and sieving technique and loaded with fura-2 to measure [Ca2+]i. ANG II rapidly increased [Ca2+]iby 124 ± 12 nM. In the presence of apocynin, a specific inhibitor of NAD(P)H oxidase assembly, the [Ca2+]iresponse was reduced to 35 ± 5 nM ( P < 0.01). Tempol, a superoxide dismutase mimetic, did not alter the [Ca2+]iresponse to ANG II at a concentration of 10−4M (99 ± 12 nM), but 10−3M tempol reduced the response to 32 ± 3 nM ( P < 0.01). The addition of nicotinamide, an inhibitor of ADPR cyclase, to apocynin or tempol (10−3M) resulted in no further inhibition. Measurement of superoxide production with the fluorescent probe tempo 9-AC showed that ANG II caused an increase of 48 ± 20 arbitrary units; apocynin or diphenyl iodonium (an inhibitor of flavoprotein oxidases) inhibited the response by 94%. Hydrogen peroxide (H2O2) was studied at physiological (10−7M) and higher concentrations. In the presence of H2O2(10−7M), neither baseline [Ca2+]inor the response to ANG II was altered (125 ± 15 nM), whereas H2O2(10−6and 10−5M) inhibited the [Ca2+]iresponse to ANG II by 35 and 46%, respectively. We conclude that ANG II rapidly activates NAD(P)H oxidases of afferent arterioles, leading to the formation of O2−·, which then stimulates ADPR cyclase to form cADPR. cADPR, by sensitizing the RyR to Ca2+, augments the Ca2+response (calcium-induced calcium release) initiated by activation of the IP3R.

Hypoxic pulmonary hypertension: role of superoxide and NADPH oxidase (gp91phox)

Chronic exposure to low-O2 tension induces pulmonary arterial hypertension (PAH), which is characterized by vascular remodeling and enhanced vasoreactivity. Recent evidence suggests that reactive oxygen species (ROS) may be involved in both processes. In this study, we critically examine the role superoxide and NADPH oxidase plays in the development of chronic hypoxic PAH. Chronic hypoxia (CH; 10% O2 for 3 wk) caused a significant increase in superoxide production in intrapulmonary arteries (IPA) of wild-type (WT) mice as measured by lucigenin-enhanced chemiluminescence. The CH-induced increase in the generation of ROS was obliterated in NADPH oxidase (gp91phox) knockout (KO) mice, suggesting that NADPH oxidase was the major source of ROS. Importantly, pathological changes associated with CH-induced PAH (mean right ventricular pressure, medial wall thickening of small pulmonary arteries, and right heart hypertrophy) were completely abolished in NADPH oxidase (gp91phox) KO mice. CH potentiated vasoconstrictor responses of isolated IPAs to both 5-hydroxytryptamine (5-HT) and the thromboxane mimetic U-46619. Administration of CuZn superoxide dismutase to isolated IPA significantly reduced CH-enhanced superoxide levels and reduced the CH-enhanced vasoconstriction to 5-HT and U-46619. Additionally, CH-enhanced superoxide production and vasoconstrictor activity seen in WT IPAs were markedly reduced in IPAs isolated from NADPH oxidase (gp91phox) KO mice. These results demonstrate a pivotal role for gp91phox-dependent superoxide production in the pathogenesis of CH-induced PAH.

Up-regulation of Akt and eNOS induces vascular smooth muscle cell differentiation in hypertension in vivo

Recent studies have shown that angiotensin II type 1 (AT1) receptor-mediated Akt activation induces vascular smooth muscle cell (VSMC) dedifferentiation in vitro. However, the critical signal transductions affecting the VSMC phenotype remain unclear in vivo. We examined whether signal transduction through AT1 receptor-mediated reactive oxygen species (ROS) could regulate the VSMC phenotype in stroke-prone spontaneously hypertensive rats (SHRSPs). Male SHRSPs were randomized and treated for 6 weeks with a vehicle, an ACE inhibitor cilazapril, or an AT1 receptor antagonist E4177. The 2 drugs showed equipotent effects on the blood pressure, aortic morphology, and collagen deposition. Both drugs also significantly reduced aortic NAD(P)H oxidase activity and p38MAPK and ERK expression, whereas p-Akt, eNOS, and SM2 were significantly increased in SHRSP aortas. Furthermore, E4177 was more effective than cilazapril at inducing VSMC differentiation by reducing NAD(P)H oxidase activity, and up-regulating p-Akt, eNOS, and SM2. Thus, an ACE inhibitor and an AT1 receptor antagonist inhibited VSMC dedifferentiation through inhibition of NAD(P)H oxidase activity and up-regulation of eNOS and Akt in SHRSP aortas, suggesting that in contrast to the in vitro experiments, AT1 receptor-mediated NAD(P)H oxidase-generated ROS, eNOS, and Akt might be crucial determinants for the VSMC phenotype in hypertension in vivo.

NADPH oxidase inhibitor, apocynin, restores the impaired endothelial-dependent and -independent responses and scavenges superoxide anion in rats with type 2 diabetes complicated by NO dysfunction

OBJECTIVE

We investigated the effect of apocynin, an NADPH oxidase inhibitor, in the impairment of vascular responses in Otsuka Long-Evans Tokushima Fatty (OLETF) rats (type 2 diabetic rat model) with or without (w/wo) N-nitro-l-arginine methyl ester treatment.

METHODS

Male OLETF and littermate Long-Evans Tokushima Otsuka (LETO) (28 weeks old) rats were separated as follows: LETO w/wo apocynin (Gp C, Gp C-apo), OLETF w/wo apocynin (Gp DM, Gp DM-apo) and OLETF plus l-nitro arginine acetate ester w/wo apocynin (Gp DMLN, Gp DMLN-apo). Five days after, peritoneal macrophages were stimulated with thioglycolate. Two days after, they were evaluated.

RESULTS

Plasma glucose and lipid levels remained unchanged. Acetylcholine-induced nitric oxide-dependent (NO-dependent) relaxation and nitroglycerin-induced NO-independent relaxation were improved in the Gp DMLN-apo, compared with that in Gp DMLN. Tone-related basal NO release and plasma NO(2) (-) and NO(3) (-) tended to be lower in Gp DM and Gp DMLN groups. The increased amount of superoxide anion released from macrophages in Gp DM and Gp DMLN was restored by apocynin. Intimal thickening was observed in aortae of Gp DM and Gp DMLN animals; however, there was little in aortae of Gp DM-apo and Gp DMLN(-) apo rats. Increased tumour necrosis factor-alpha (TNF-alpha) in the Gp DM and Gp DMLN was also restored by apocynin treatment.

CONCLUSION

Apocynin restores the impairment of endothelial and non-endothelial function in diabetic angiopathy in OLETF without changing plasma glucose and lipid levels. NO and O(2) (-) may play a role in this process by decreasing TNF-alpha levels.

Resveratrol and curcumin reduce the respiratory burst of Chlamydia-primed THP-1 cells

The intracellular bacterium Chlamydia pneumoniae is involved in the inflammation process of atherosclerosis. We previously demonstrated that C. pneumonia infected monocytes (THP-1 cells) responded to stimulation by an increased respiratory burst linked to an increased NADPH oxidase (NOX) activity. We now tested agents acting on the assembly of the NOX subunits or on protein kinase C, a trigger of NOX activity. Apocynin, resveratrol, rutin, quercetin, curcumin, and tocopherols were tested. The cells were pre-incubated with Chlamydia and the agent for 19 h, and then stimulated with phorbol myristate acetate. The NOX activity was monitored by measuring the hydrogen peroxide production. Resveratrol and curcumin (10(-4)-10(-6) M) were better inhibitors than apocynin. alpha-Tocopherol was inactive, and gamma-tocopherol inhibitor at 10(-4) M only. Quercetin was inactive, and rutin a moderate but significant inhibitor. The inhibition by resveratrol was increased by 10(-6) M rutin or quercetin. Resveratrol and curcumin thus appeared to be interesting for atherosclerosis treatment.