Assembly and regulation of NADPH oxidase and nitric oxide synthase

Nitric oxide, chronic iron and copper overloads and regulation of redox homeostasis in rat liver

Iron [Fe(II)] and copper [Cu(II)] ions produced liver oxidative stress and damage, and as a consequence, changes in the antioxidant protection. The objective of this work is to evaluate whether control of redox homeostasis in chronic overload of Fe(II) and Cu(II) is associated with nitric oxide (NO) and antioxidant enzymes protection in liver. Male Sprague-Dawley rats of 80-90 g received the standard diet ad libitum and drinking water supplemented with either 1.0 g/L of ferrous chloride (0.1% w/v, n = 24) or 0.5 g/L cupric sulfate (0.05% w/v, n = 24) for 42 days. The activities of the enzymes involved in the control of cellular redox homeostasis, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx), were determined by spectrophotometric methods, and NO production was determined by the determination of nitrite levels in liver. Chronic overload with Fe(II) and Cu(II) led to a significant increase of NO production while hampering the activity of NADPH oxidase. Meanwhile, the animals supplemented with Fe(II) showed a decrease in SOD and Gpx activities in liver homogenates with respect to baseline activity after 7 days of treatment, whereas the rats which received Cu(II) showed an increased SOD and catalase activity after 28 and 7 days of chronic overload. Further research is required to understand whether the modulation of the activity of these enzymes upon Cu and Fe overload is involved in a common toxic pathway or may serve to control the steady state of oxidant species related to redox signaling pathways.

Actovegin® reduces PMA-induced inflammation on human cells

Purpose

The effect of Actovegin® was investigated on PMA- and LPS-induced human peripheral blood mononuclear cells (PBMCs).

Methods

PBMCs (1 × 10⁶ cells/ml) from five blood donors (2 f, 3 m; 45–55 years) were grown in medium and exposed to Actovegin® in the presence or absence of PMA or LPS. Supernatants were collected to assess the concentration of cytokines (TNF-α, IL-1beta, IL-6 and IL-10). The reactive oxygen species (ROS) were assessed by a ROS-Glo^TM H₂O₂ assay.

Results

Stimulation of cells by PMA or LPS (without Actovegin®) significantly increased the secretion of IL-1beta, IL-6, IL-10 and TNF-α from PBMCs, compared to controls. Pre-treatment of cells with Actovegin® (1, 5, 25, 125 µg/ml) plus PMA significantly decreased the secretion of IL-1beta from PBMCs, compared to controls (PMA without Actovegin®). In contrast, addition of Actovegin® (1, 5, 25, 125 and 250 µg/ml) plus LPS did not alter the IL-1beta production, compared to controls (LPS without Actovegin®). TNF-α, IL-6 and IL-10 do not contribute to the reduction of inflammatory reactions with Actovegin®.

Conclusions

Actovegin® can reduce the PMA-induced IL-1beta release and the ROS production from PBMCs. These findings may help to explain the clinically known positive effects of Actovegin® on athletic injuries with inflammatory responses (e.g., muscle injuries, tendinopathies).

The natural phenolic compounds as modulators of NADPH oxidases in hypertension

BACKGROUND

Hypertension is a major public health problem worldwide. It is an important risk factor for other cardiovascular diseases such as coronary artery disease, stroke, heart failure, atrial fibrillation, peripheral vascular disease, chronic kidney disease, and atherosclerosis.

PURPOSE

There is strong evidence that excess ROS-derived NADPH oxidase (NOX) is an important agent in hypertension. It augments blood pressure in the presence of other pro-hypertensive factors such as angiotensin II (Ang II), an important and potent regulator of cardiovascular NADPH oxidase, activates NOX via AT1 receptors. NADPH oxidase, a multi-subunit complex enzyme, is considered as a key source of ROS production in the vasculature. The activation of this enzyme is needed for assembling Rac-1, p^40phox, p^47phox and p^67phox subunits. Since, hypertensive patients need to control blood pressure for their entire life and because drugs and other chemicals often induce adverse effects, the use of natural phenolic compounds which are less toxic and potentially beneficial may be good avenues of addition research in our understand of the underlying mechanism involved in hypertension. This review focused on several natural phenolic compounds as berberine, thymoquinone, catechin, celastrol, apocynin, resveratrol, curcumin, hesperidine and G-hesperidine, and quercetin which are NOX inhibitors. In addition, structure activity relationship of these compounds eventually as the most inhibitors was discussed.

METHODS

This comprehensive review is based on pertinent papers by a selective search using relevant keywords that was collected using online search engines and databases such as ScienceDirect, Scopus and PubMed. The literature mainly focusing on natural products with therapeutic efficacies against hypertension via experimental models both in vitro and in vivo was identified.

RESULTS

It has been observed that these natural compounds prevent NADPH oxidase expression and ROS production while increasing NO bioavailability. It have been reported that they improve hypertension due to formation of a stable radical with ROS-derived NADPH oxidase and preventing the assembly of NOX subunites.

CONCLUSION

It is clear that natural phenolic compounds have some potential inhibitory effect on NADPH oxidase activity. In comparison to other phenolic plant compounds, the structural variability of the flavonoids should off different impacts on oxidative stress in hypertension including inhibition of nadph oxidase and direct scavenging of free radicals.

Timing of umbilical cord blood derived mesenchymal stem cells transplantation determines therapeutic efficacy in the neonatal hyperoxic lung injury

Intratracheal transplantation of human umbilical cord blood (UCB)-derived mesenchymal stem cells (MSCs) attenuates the hyperoxia-induced neonatal lung injury. The aim of this study was to optimize the timing of MSCs transplantation. Newborn Sprague-Dawley rats were randomly exposed to hyperoxia (90% for 2 weeks and 60% for 1 week) or normoxia after birth for 21 days. Human UCB-derived MSCs (5×10(5) cells) were delivered intratracheally early at postnatal day (P) 3 (HT3), late at P10 (HT10) or combined early+late at P3+10 (HT3+10). Hyperoxia-induced increase in mortality, TUNEL positive cells, ED1 positive alveolar macrophages, myeloperoxidase activity and collagen levels, retarded growth and reduced alveolarization as evidenced by increased mean linear intercept and mean alveolar volume were significantly better attenuated in both HT3 and HT3+10 than in HT10. Hyperoxia-induced up-regulation of both cytosolic and membrane p47(phox) indicative of oxidative stress, and increased inflammatory markers such as tumor necrosis factor-α, interleukin (IL) -1α, IL-1β, IL-6, and transforming growth factor-β measured by ELISA, and tissue inhibitor of metalloproteinase-1, CXCL7, RANTES, L-selectin and soluble intercellular adhesion molecule-1 measured by protein array were consistently more attenuated in both HT3 and HT3+10 than in HT10. Hyperoxia-induced decrease in hepatocyte growth factor and vascular endothelial growth factor was significantly up-regulated in both HT3 and HT3+10, but not in HT10. In summary, intratracheal transplantation of human UCB derived MSCs time-dependently attenuated hyperoxia-induced lung injury in neonatal rats, showing significant protection only in the early but not in the late phase of inflammation. There were no synergies with combined early+late MSCs transplantation.

Intratracheal Transplantation of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells Dose-Dependently Attenuates Hyperoxia-Induced Lung Injury in Neonatal Rats

Intratracheal transplantation of human umbilical cord blood (UCB)-derived mesenchymal stem cells (MSCs) attenuates the hyperoxia-induced neonatal lung injury. The aim of this preclinical translation study was to optimize the dose of human UCB-derived MSCs in attenuating hyperoxia-induced lung injury in newborn rats. Newborn Sprague-Dawley rats were randomly exposed to hyperoxia (95% oxygen) or normoxia after birth for 14 days. Three different doses of human UCB-derived MSCs, 5 × 103 (HT1), 5 × 104 (HT2), and 5 × 105 (HT3), were delivered intratracheally at postnatal day (P) 5. At P14, lungs were harvested for analyses including morphometry for alveolarization, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling (TUNEL) staining, myeoloperoxidase activity, mRNA level of tumor necross factor-α (TNF-α), interleukin-1β (IL-1β), IL-6, and transforming growth factor-β (TGF-β), human glyceradehyde-3-phosphate dehydrogenase (GAPDH), and p47 phox, and collagen levels. Increases in TUNEL-positive cells were attenuated in all transplantation groups. However, hyperoxia-induced lung injuries, such as reduced alveolarization, as evidenced by increased mean linear intercept and mean alveolar volume, and increased collagen levels were significantly attenuated in both HT2 and HT3, but not in HT1, with better attenuation in HT3 than in HT2. Dose-dependent human GAPDH expression, indicative of the presence of human RNA in lung tissue, was observed only in the transplantation groups, with higher expression in HT3 than in HT2, and higher expression in HT2 than in HT1. Hyperoxia-induced inflammatory responses such as increased myeloperoxidase acitivity, mRNA levels of TNF-α, IL-1β, IL-6, and TGF-β of the lung tissue, and upregulation of both cytosolic and membrane p47 phox, indicative of oxidative stress, were significantly attenuated in both HT2 and HT3 but not in HT1. These results demonstrate that intratracheal transplantation of human UCB-derived MSCs with appropriate doses may attenuate hyperoxia-induced lung injury through active involvement of these cells in modulating host inflammatory responses and oxidative stress in neonatal rats.

Granulocyte colony stimulating factor attenuates hyperoxia-induced lung injury by down-modulating inflammatory responses in neonatal rats

PURPOSE

Granulocyte colony stimulating factor (G-CSF) has been known to increase neutrophil production and have anti-inflammatory properties, but the effect of G-CSF on pulmonary system is in controversy. We investigated whether G-CSF treatment could attenuate hyperoxia-induced lung injury, and whether this protective effect is mediated by the down-modulation of inflammatory responses in a neonatal rat model.

MATERIALS AND METHODS

Newborn Sprague-Dawley rats (Orient Co., Seoul, Korea) were subjected to 14 days of hyperoxia (90% oxygen) beginning within 10 h after birth. G-CSF (20 μg/kg) was administered intraperitoneally on the fourth, fifth, and sixth postnatal days.

RESULTS

This treatment significantly improved hyperoxia-induced reduction in body weight gain and lung pathology such as increased mean linear intercept, mean alveolar volume, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling positive cells. Hyperoxia- induced activation of nicotinamide adenine dinucleotide phosphate oxidase, which is responsible for superoxide anion production, as evidenced by upregulation and membrane translocation of p67(phox) was significantly attenuated after G-CSF treatment, as were inflammatory responses such as increased myeloperoxidase activity and mRNA expression of transforming growth factor-β. However, the attenuation of other proinflammatory cytokines such as tumor necrosis factor-α and interleukin- 6 was not significant.

CONCLUSION

In sum, G-CSF treatment significantly attenuated hyperoxia-induced lung injury by down-modulating the inflammatory responses in neonatal rats.

Nitrite reduction: a ubiquitous function from a pre-aerobic past

In eukaryotes, small amounts of nitrite confer cytoprotection against ischemia/reperfusion-related tissue damage in vivo, possibly via reduction to nitric oxide (NO) and inhibition of mitochondrial function. Several hemeproteins are involved in this protective mechanism, starting with deoxyhemoglobin, which is capable of reducing nitrite. In facultative aerobic bacteria, such as Pseudomonas aeruginosa, nitrite is reduced to NO by specialized heme-containing enzymes called cd(1) nitrite reductases. The details of their catalytic mechanism are summarized below, together with a hypothesis on the biological role of the unusual d(1)-heme, which, in the reduced state, shows unique properties (very high affinity for nitrite and exceptionally fast dissociation of NO). Our results support the idea that the nitrite-based reactions of contemporary eukaryotes are a vestige of earlier bacterial biochemical pathways. The evidence that nitrite reductase activities of enzymes with different cellular roles and biochemical features still exist today highlights the importance of nitrite in cellular homeostasis.

Reactive oxygen species modulate growth of cerebral aneurysms: a study using the free radical scavenger edaravone and p47phox(-/-) mice

Cerebral aneurysm (CA) is a relatively common disease and can cause a catastrophic subarachnoid hemorrhage with a high mortality and morbidity rate. Despite its clinical and social importance, the detailed mechanism of CA formation remains to be elucidated, resulting in the absence of effective medical treatment against CAs. Recent studies revealed that chronic inflammation in arterial walls by hemodynamic force is implicated in CA formation. Reactive oxygen species (ROS) are a major mediator of inflammation and actively participate in the pathogenesis of various vascular diseases. In the present study, we first assessed the expression of ROS-producing and -eliminating genes in CA walls by immunohistochemistry and RT-PCR analysis. The ROS-producing gene, p47phox, was upregulated in infiltrating macrophages and medial smooth muscle cells in arterial walls. Upregulated ROS-producing genes and suppressed ROS-eliminating genes suggested that ROS overproduction occurred in aneurysmal walls. In situ superoxide imaging by dihydroethidium, which showed ROS overproduction in aneurysmal walls, confirmed this hypothesis. Edaravone, a powerful free radical scavenger, effectively inhibited CA formation by suppressing inflammation-related gene expression in aneurysmal walls. Furthermore, CA formation was markedly inhibited by p47phox deletion in mice and was accompanied by decreased inflammation in aneurysmal walls. These data suggested the active participation of ROS and p47phox in CA formation and the therapeutic potential of an ROS-eliminating agent against CA formation.

Alpha-phenyl-N-tert-butylnitrone attenuates hyperoxia-induced lung injury by down-modulating inflammation in neonatal rats

This study was done to determine whether alpha -phenyl-N-tert-butylnitrone (PBN), a spin-trapping agent possessing significant anti-inflammatory capabilities, could attenuate hyperoxia-induced lung injury, and if so, whether this protective effect is mediated by the down-modulation of inflammation in neonatal rats. Newborn Sprague-Dawley rat pups were subjected to 14 days of hyperoxia (> 90% oxygen) within 10 hours after birth. PBN treatment, given 100 mg/kg intraperitoneally daily throughout the experiment, significantly attenuated hyperoxia-induced lung pathology, such as decreased radial alveolar count, increased mean linear intercept, and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling-positive cells. Hyperoxia-induced activation of nicotinamide adenine dinucleotide phosphate oxidase that is responsible for superoxide anion production, as evidenced by up-regulation and membrane translocation of p67phox, and the inflammatory responses, such as increased mRNA expression of tumor necrosis factor-alpha, interleukin-6, and transforming growth factor-beta, were also significantly attenuated with PBN treatment. In summary, a spin-trapping agent PBN significantly attenuated hyperoxia-induced lung injury by down-regulating the inflammatory responses in neonatal rats.

A novel biofuel cell harvesting energy from activated human macrophages

Macrophage phagocytosis activates NADPH oxidase, an electron transport system in the plasma membrane. This study examined the feasibility of utilizing electrons transferred through the plasma membrane via NADPH oxidase to run a biofuel cell. THP-1 human monocytic cells were chemically stimulated to differentiate into macrophages. Further they were activated to induce a phagocytic response. During differentiation, cells became adherent to a plain gold electrode which was used as anode in a two-compartment fuel cell system. The current production in the fuel cell always corresponded to the NADPH oxidase activity, which was evaluated by the amount of superoxide anion produced upon stimulation in combination with the expression levels of the different NADPH oxidase subunits in cells. Moreover, our results of different inhibitory tests let us conclude that (i) the current observed in the fuel cell originates from NADPH oxidase in activated macrophages and (ii) there are multiple electron transport pathways from the cells to the electrode. One pathway involves superoxide anions produced upon stimulation, additional not yet identified electron transport occurs independently of superoxide anions.This type of novel biofuel cell driven by living human cells may eventually develop into a battery replacement for small medical devices.

Effect of chromium on the level of IL-12 and IFN-gamma in occupationally exposed workers

Chromium may affect humoral and cellular immunity, acting on T lymphocytes as well as on granulocytes and monocytes cells. Cytokines play an important role in the immune balance. In this study, the level of IL-12 and IFN-gamma were evaluated in the sera and PHA/LPS stimulated culture supernatant of human PBMCs of healthy volunteers and occupationally exposed chromium workers. All the workers were highly exposed to chromium having mean of 104.65+/-77.21 microg/dL (range 23.7-316.8 microg/dL). A suspension of exposed and unexposed human PBMC (0.5x10(6) cells/ml) prepared and cultured in RPMI-1640 supplemented with 10% FCS for 18 h in the presence or absence of LPS (10 ng/ml) which used for stimulation of IL-12 and IFN-gamma. The level of IL-12 and IFN-gamma were evaluated in the sera samples as well as LPS stimulated and unstimulated culture supernatant of h-PBMCs of chromium exposed workers. In these chromium exposed workers the level of IL-12 was 433.66+/-197.49 pg/ml and 983.45+/-330.99 pg/ml in LPS stimulated culture supernatant of normal individuals and highly chromium exposed workers, which was significant (P<0.05). Although the level of IL-12 was (78.61+/-61.03 pg/ml to 146.52+/-46.37 pg/ml) elevated in unstimulated culture supernatant of h-PBMCs of chromium exposed individuals as compared to control, but it was not significant. This observation also suggests that a significant increase in IFN-gamma production in LPS stimulated and unstimulated culture supernatant of h-PBMCs of chromium exposed workers as compared to control. However, IFN-gamma level have a significant positive correlation between blood chromium level (r=0.833, t=6.3872, P 0.05) and exposure time (in years) (r=0.8916, t=8.3540, P 0.05) of the occupationally exposed workers.

Effects of NADPH oxidase inhibitor on diabetic nephropathy in OLETF rats: the role of reducing oxidative stress in its protective property

Diabetic nephropathy is the most serious complication in diabetes mellitus. Oxidative stress via nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and vascular endothelial growth factor (VEGF) pathway play critical roles in the development of diabetic nephropathy. We evaluated the effects of apocynin, NADPH oxidase inhibitor on diabetic nephropathy in a type 2 diabetic rat model. Sixteen Otsuka Long Evans Tokushima Fatty (OLETF) rats and 9 Long Evans Tokushima Otsuka (LETO) were divided into the following three groups: LETO rats (n=9), control OLETF rats (n=7) and apocynin-treated OLETF rats (n=9). We examined body weights, plasma glucose levels, urinary albumin-creatinine ratio (ACR) and protein-creatinine ratio (PCR). At 50 weeks, experimental rats were sacrificed and their kidneys were extracted for hematoxylin eosin stain, immunohistochemical VEGF stain and VEGF mRNA real-time RT-PCR. To examine oxidative stress, we checked 24h urinary 8-OHdG (8-hydroxy-2'-deoxyguanosine) and MDA (malondialdehyde). Urinary protein and albumin excretions were reduced after apocynin treatment, though apocynin could not significantly decrease serum glucose levels. There were improvements of glomerular and mesangial expansion in the apocynin-treated OLETF rats. Apocynin significantly decreased optical density of glomerular VEGF expression in immunohistochemical stain and reduced the concentration of 24h urinary 8-OHdG and MDA. From these results, it was suggested that apocynin may have the potential to protect against diabetic nephropathy via amelioration of oxidative stress.

Nitric oxide, tetrahydrobiopterin, oxidative stress, and endothelial dysfunction in hypertension

Endothelial dysfunction in the setting of cardiovascular risk factors such as hypercholesterolemia, diabetes mellitus, chronic smoking, as well hypertension, is, at least in part, dependent of the production of reactive oxygen species (ROS) and the subsequent decrease in vascular bioavailability of nitric oxide (NO). ROS-producing enzymes involved in increased oxidative stress within vascular tissue include NADPH oxidase, xanthine oxidase, and mitochondrial superoxide producing enzymes. Superoxide produced by the NADPH oxidase may react with NO, thereby stimulating the production of the NO/superoxide reaction product peroxynitrite. Peroxynitrite in turn has been shown to uncouple eNOS, therefore switching an antiatherosclerotic NO producing enzyme to an enzyme that may accelerate the atherosclerotic process by producing superoxide. Increased oxidative stress in the vasculature, however, is not restricted to the endothelium and also occurs within the smooth muscle cell layer. Increased superoxide production has important consequences with respect to signaling by the soluble guanylate cyclase and the cGMP-dependent kinase I, which activity and expression is regulated in a redox-sensitive fashion. The present review will summarize current concepts concerning eNOS uncoupling, with special focus on the role of tetrahydrobiopterin in mediating eNOS uncoupling.

Inhibition of NADPH oxidase prevents advanced glycation end product-mediated damage in diabetic nephropathy through a protein kinase C-alpha-dependent pathway

OBJECTIVE

Excessive production of reactive oxygen species (ROS) via NADPH oxidase has been implicated in the pathogenesis of diabetic nephropathy. Since NADPH oxidase activation is closely linked to other putative pathways, its interaction with changes in protein kinase C (PKC) and increased advanced glycation was examined.

RESEARCH DESIGN AND METHODS

Streptozotocin-induced diabetic or nondiabetic Sprague Dawley rats were followed for 32 weeks, with groups randomized to no treatment or the NADPH oxidase assembly inhibitor apocynin (15 mg . kg(-1) . day(-1); weeks 16-32). Complementary in vitro studies were performed in which primary rat mesangial cells, in the presence and absence of advanced glycation end products (AGEs)-BSA, were treated with either apocynin or the PKC-alpha inhibitor Ro-32-0432. RESULTS; Apocynin attenuated diabetes-associated increases in albuminuria and glomerulosclerosis. Circulating, renal cytosolic, and skin collagen-associated AGE levels in diabetic rats were not reduced by apocynin. Diabetes-induced translocation of PKC, specifically PKC-alpha to renal membranes, was associated with increased NADPH-dependent superoxide production and elevated renal, serum, and urinary vascular endothelial growth factor (VEGF) concentrations. In both diabetic rodents and in AGE-treated mesangial cells, blockade of NADPH oxidase or PKC-alpha attenuated cytosolic superoxide and PKC activation and increased VEGF. Finally, renal extracellular matrix accumulation of fibronectin and collagen IV was decreased by apocynin.

CONCLUSIONS

In the context of these and previous findings by our group, we conclude that activation of NADPH oxidase via phosphorylation of PKC-alpha is downstream of the AGE-receptor for AGE interaction in diabetic renal disease and may provide a novel therapeutic target for diabetic nephropathy.

Pathophysiology, diagnosis and prognostic implications of endothelial dysfunction

Endothelial dysfunction (ED) in the setting of cardiovascular risk factors such as hypercholesterolemia, hypertension, diabetes mellitus, chronic smoking as well as in patients with heart failure has been shown to be at least in part dependent on the production of reactive oxygen species (ROS) such as superoxide and the subsequent decrease in vascular bioavailability of nitric oxide (NO). Methods to quantify endothelial dysfunction include forearm plethysmography, flow-dependent dilation of the brachial artery, finger-pulse plethysmography, pulse curve analysis, and quantitative coronary angiography after intracoronary administration of the endothelium-dependent vasodilator acetylcholine. Superoxide sources include the NADPH oxidase, xanthine oxidase, and mitochondria. Superoxide produced by the NADPH oxidase may react with NO released by the endothelial nitric oxide synthase (eNOS) thereby generating peroxynitrite (ONOO-), leading to eNOS uncoupling and therefore eNOS-mediated superoxide production. The present review will discuss current concepts of how to assess endothelial function, prognostic implications of ED, mechanisms underlying ED with focus on oxidative stress and circulating biomarkers, which have been proposed to indicate endothelial dysfunction and/or damage, respectively.

Suppression of endotoxin-induced proinflammatory responses by citrus pectin through blocking LPS signaling pathways

Pectin is composed of complex polysaccharides rich in galactoside residues, and it is most abundant in citrus fruits. Pectin and modified pectin have been found to exhibit anti-mutagenic activity and inhibit cancer metastasis and proliferation, with no evidence of toxicity or other serious side effects. In this study, we investigated the inhibitory effect of pectin at different degrees of esterification (DEs) on the expressions of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in lipopolysaccharide (LPS)-activated macrophages. Western blot and RT-PCR analyses demonstrated that 30% esterified pectin (DE30), DE60 pectin, and DE90 pectin significantly inhibited the protein and mRNA expressions of iNOS and COX-2 in LPS-activated macrophages, and DE90 pectin was the most-potent inhibitor. To clarify the mechanisms involved, DE90 pectin was found to inhibit the phosphorylation of MAPKs and IKK kinase activity. In addition, DE90 pectin inhibited the activation of NF-kappaB and AP-1 by electrophoretic mobility shift assay and transient transfection experiments. Finally, we found that DE90 pectin could bind with LPS, and might result in decreased binding of LPS to its receptor. These results suggest that modulation of iNOS and COX-2 expressions by dietary pectin may be important in cancer chemoprevention and anti-inflammation.

Mechanisms underlying endothelial dysfunction in diabetes mellitus: therapeutic implications

Hyperglycemia is the major causal factor in the development of endothelial dysfunction in patients with diabetes mellitus. Although the mechanisms underlying this phenomenon are likely to be multifactorial, recent in vivo and in vitro studies have indicated a crucial role of the diacylglycerol (DAG)-protein kinase C (PKC) pathway in mediating this phenomenon. PKC may have multiple adverse effects on vascular function, including the activation of superoxide-producing enzymes such as the nicotinamide adenine dinicleotide phosphate (NADPH) oxidase as well as increased expression of a dysfunctional, superoxide-producing, uncoupled endothelial nitric oxide synthase (NOS III). PKC-mediated superoxide production may inactivate nitric oxide (NO) derived from endothelial NOS III, but also may inhibit the activity and/or expression of the NO downstream target, the soluble guanylyl cyclase. Among the different isoforms of PKC, mainly the beta-isoforms have been shown to be activated. Recent studies with selective (isoform-specific) and non-selective PKC inhibitors show that they are able to beneficially influence glucose-induced endothelial dysfunction in experimental animal models as well as in patients, pointing to the therapeutic potential of these compounds in the prevention and treatment of vascular complications of diabetes.

Vascular consequences of endothelial nitric oxide synthase uncoupling for the activity and expression of the soluble guanylyl cyclase and the cGMP-dependent protein kinase

Endothelial dysfunction in the setting of cardiovascular risk factors, such as hypercholesterolemia, hypertension, diabetes mellitus, chronic smoking, as well as in the setting of heart failure, has been shown to be at least partly dependent on the production of reactive oxygen species (ROS), such as the superoxide radical, and the subsequent decrease in vascular bioavailability of nitric oxide (NO). Superoxide-producing enzymes involved in increased oxidative stress within vascular tissue include the NAD(P)H oxidase, the xanthine oxidase, and mitochondrial superoxide-producing enzymes. Superoxide produced by the NADPH oxidase may react with NO released by endothelial nitric oxide synthase (eNOS), thereby generating peroxynitrite. Peroxynitrite in turn has been shown to uncouple eNOS, thereby switching an antiatherosclerotic NO-producing enzyme to an enzyme that may initiate or even accelerate the atherosclerotic process by producing superoxide. Increased oxidative stress in the vasculature, however, is not restricted to the endothelium and has also been demonstrated to occur within the smooth muscle cell layer in the setting of hypercholesterolemia, diabetes mellitus, hypertension, congestive heart failure, and nitrate tolerance. Increased superoxide production by the endothelial and/or smooth muscle cells has important consequences with respect to signaling by the soluble guanylyl cyclase (sGC) and the cGMP-dependent protein kinase I (cGK-I), the activity and expression of which has been shown to be regulated in a redox-sensitive fashion. The present review summarizes current concepts concerning eNOS uncoupling and also focuses on the consequences for downstream signaling with respect to activity and expression of the sGC and cGK-I in various diseases.

Nifedipine protects against overproduction of superoxide anion by monocytes from patients with systemic sclerosis

We have reported previously that dihydropyridine-type calcium-channel antagonists (DTCCA) such as nifedipine decrease plasma markers of oxidative stress damage in systemic sclerosis (SSc). To clarify the cellular basis of these beneficial effects, we investigated the effects in vivo and in vitro of nifedipine on superoxide anion (O₂^•-) production by peripheral blood monocytes. We compared 10 healthy controls with 12 patients with SSc, first after interruption of treatment with DTCCA and second after 2 weeks of treatment with nifedipine (60 mg/day). O₂^•- production by monocytes stimulated with phorbol myristate acetate (PMA) was quantified by the cytochrome c reduction method. We also investigated the effects in vitro of DTCCA on O₂^•- production and protein phosphorylation in healthy monocytes and on protein kinase C (PKC) activity using recombinant PKC. After DTCCA had been washed out, monocytes from patients with SSc produced more O₂^•- than those from controls. Nifedipine treatment considerably decreased O₂^•- production by PMA-stimulated monocytes. Treatment of healthy monocytes with nifedipine in vitro inhibited PMA-induced O₂^•- production and protein phosphorylation in a dose-dependent manner. Finally, nifedipine strongly inhibited the activity of recombinant PKC in vitro. Thus, the oxidative stress damage observed in SSc is consistent with O₂^•- overproduction by primed monocytes. This was decreased by nifedipine treatment both in vivo and in vitro. This beneficial property of nifedipine seems to be mediated by its cellular action and by the inhibition of PKC activity. This supports the hypothesis that this drug could be useful for the treatment of diseases associated with oxidative stress.

Enhanced lung injury and delayed clearance of Pneumocystis carinii in surfactant protein A-deficient mice: attenuation of cytokine responses and reactive oxygen-nitrogen species

Surfactant protein A (SP-A), a member of the collectin family, selectively binds to Pneumocystis carinii and mediates interactions between pathogen and host alveolar macrophages in vitro. To test the hypothesis that mice lacking SP-A have delayed clearance of Pneumocystis organisms and enhanced lung injury, wild-type C57BL/6 (WT) and SP-A-deficient mice (SP-A(-/-)) with or without selective CD4(+)-T-cell depletion were intratracheally inoculated with Pneumocystis organisms. Four weeks later, CD4-depleted SP-A-deficient mice had developed a more severe Pneumocystis infection than CD4-depleted WT (P. carinii pneumonia [PCP] scores of 3 versus 2, respectively). Whereas all non-CD4-depleted WT mice were free of PCP, intact SP-A(-/-) mice also had evidence of increased organism burden. Pneumocystis infection in SP-A-deficient mice was associated histologically with enhanced peribronchial and/or perivascular cellularity (score of 4 versus 2, SP-A(-/-) versus C57BL/6 mice, respectively) and a corresponding increase in bronchoalveolar lavage (BAL) cell counts. Increases in SP-D content, gamma interferon, interleukin-4, interleukin-5, and tumor necrosis factor alpha in BAL fluid occurred but were attenuated in PCP-infected SP-A(-/-) mice compared to WT mice. There were increases in total BAL NO levels in both infected groups, but nitrite levels were higher in SP-A(-/-) mice, indicating a reduction in production of higher oxides of nitrogen that was also reflected in lower levels of 3-nitrotyrosine staining in the SP-A(-/-) group. We conclude that despite increases in inflammatory cells, SP-A-deficient mice infected with P. carinii exhibit an enhanced susceptibility to the organism and attenuated production of proinflammatory cytokines and reactive oxygen-nitrogen species. These data support the concept that SP-A is a local effector molecule in the lung host defense against P. carinii in vivo.

Protective effect of flavonoids against aging- and lipopolysaccharide-induced cognitive impairment in mice

Flavonoids, naturally occurring polyphenolic compounds, are known to inhibit both lipopolysaccharide (LPS) stimulated tumor necrosis factor alpha and interleukin 6 release which modulate the proinflammatory molecules that have been reported in many progressive neurodegenerative disorders, including Alzheimer's disease (AD), viral and bacterial meningitis, AIDS dementia complex, and stroke. The present experiments were performed to study the possible effects of exogenously administered flavonoids (apigenin-7-glucoside and quercetin) on the cognitive performance in aged and LPS-treated mice (an animal model for AD) using passive avoidance and elevated plus-maze tasks. Aged and LPS-treated mice showed poor retention of memory in step-through passive avoidance and in plus-maze tasks. Chronic administration of the flavonoids apigenin-7-glucoside (5-20 mg/kg i.p.) and quercetin (25-100 mg/kg i.p.) dose dependently reversed the age-induced and LPS-induced retention deficits in both test paradigms. However, flavonoids after chronic administration in young mice did not show any improvement of memory retention in both paradigms. Apigenin-7-glucoside showed more efficacy as compared with quercetin in both models that may be probably due to its greater efficacy to inhibit cyclooxygenase-2 and inducible nitric oxide synthase. Chronic treatment with flavonoids did not alter the locomotor activity in both young and aged mice; however, aged mice showed improvement of performance on Rota-Rod test. The results showed that chronic treatment with flavonoids reverses cognitive deficits in aged and LPS-intoxicated mice which suggests that modulation of cyclooxygenase-2 and inducible nitric synthase by flavonoids may be important in the prevention of memory deficits, one of the symptoms related to AD.

A comparison of reactive oxygen species generation by rat peritoneal macrophages and mast cells using the highly sensitive real-time chemiluminescent probe pholasin: inhibition of antigen-induced mast cell degranulation by macrophage-derived hydrogen peroxide

Mast cells and macrophages live in close proximity in vivo and reciprocally regulate one another's function in various ways. Although activated macrophages possess a powerful reactive oxygen species (ROS) generating system, there is conflicting evidence regarding whether mast cells can produce ROS. We used the highly sensitive real-time chemiluminescent probe Pholasin to examine ROS release by peritoneal macrophages and mast cells isolated from OVA-sensitized rats. Macrophages stimulated with PMA (0.8 microM) or ionomycin (1 microM), but not OVA (1 microg/ml), released high-level ROS, levels of which peaked after 3-7 min and declined to baseline levels within 1 h. Superoxide was identified as the major ROS species induced by PMA but not by ionomycin. In contrast, purified mast cells stimulated with PMA released low-level ROS, which was entirely due to the contaminating (2%) macrophages, and did not release any detectable ROS in response to ionomycin or OVA at concentrations that induced degranulation. Stimulation of mixed cell populations with PMA to induce macrophage ROS release led to 50% inhibition of serotonin release from mast cells stimulated 5 min later with OVA. The PMA-induced inhibitory factor was identified as hydrogen peroxide. In conclusion, activated rat peritoneal macrophages but not mast cells produce ROS, and macrophage-derived hydrogen peroxide inhibits mast cell degranulation. The latter could be an important mechanism whereby phagocytic cells regulate mast cell activation and promote resolution of IgE-mediated inflammation.

Antioxidant and prooxidant activities of alpha-lipoic acid and dihydrolipoic acid

Reactive oxygen (ROS) and nitrogen oxide (RNOS) species are produced as by-products of oxidative metabolism. A major function for ROS and RNOS is immunological host defense. Recent evidence indicate that ROS and RNOS may also function as signaling molecules. However, high levels of ROS and RNOS have been considered to potentially damage cellular macromolecules and have been implicated in the pathogenesis and progression of various chronic diseases. alpha-Lipoic acid and dihydrolipoic acid exhibit direct free radical scavenging properties and as a redox couple, with a low redox potential of -0.32 V, is a strong reductant. Several studies provided evidence that alpha-lipoic acid supplementation decreases oxidative stress and restores reduced levels of other antioxidants in vivo. However, there is also evidence indicating that alpha-lipoic acid and dihydrolipoic acid may exert prooxidant properties in vitro. alpha-Lipoic acid and dihydrolipoic acid were shown to promote the mitochondrial permeability transition in permeabilized hepatocytes and isolated rat liver mitochondria. Dihydrolipoic acid also stimulated superoxide anion production in rat liver mitochondria and submitochondrial particles. alpha-Lipoic acid was recently shown to stimulate glucose uptake into 3T3-L1 adipocytes by increasing intracellular oxidant levels and/or facilitating insulin receptor autophosphorylation presumably by oxidation of critical thiol groups present in the insulin receptor beta-subunit. Whether alpha-lipoic acid and/or dihydrolipoic acid-induced oxidative protein modifications contribute to their versatile effects observed in vivo warrants further investigation.

Blockade of superoxide generation prevents high-affinity immunoglobulin E receptor-mediated release of allergic mediators by rat mast cell line and human basophils

BACKGROUND

Previous studies have shown that rat peritoneal mast cells and mast cell model rat basophilic leukaemia (RBL-2H3) cells generate intracellular reactive oxygen species (ROS) in response to antigen challenge. However, the physiological significance of the burst of ROS is poorly understood.

OBJECTIVE

The present study was undertaken to investigate the role of superoxide anion in mediator release in rat and human cell systems.

METHODS

RBL-2H3 cells were directly stimulated with anti-rat FcepsilonRI alpha-subunit monoclonal antibody (mAb). For the analysis of human cell system, leucocytes were isolated by dextran sedimentation from healthy volunteers or from patients, and challenged either with anti-human FcepsilonRI mAb or with the relevant antigens. Superoxide generation was determined by chemiluminescence-based methods. The releases of histamine and leukotrienes (LT)s were determined by enzyme-linked immunosorben assay (ELISA).

RESULTS

Cross-linking of FcepsilonRI on RBL-2H3 cells or on human leucocytes from healthy donors by the anti-FcepsilonRI mAb resulted in a rapid generation of superoxide anion, as determined by chemiluminescence using superoxide-specific probes. Similarly, leucocytes from patients generated superoxide anion in response to the challenge with the relevant allergen but not with the irrelevant allergen. Furthermore, diphenyleneiodonium (DPI), a well-known inhibitor of flavoenzymes suppressed the superoxide generation and the release of histamine and LTC4 induced by the anti-FcepsilonRI mAb or by allergen in parallel.

CONCLUSION

These results indicate that both RBL-2H3 cells and human basophils generate superoxide anion upon FcepsilonRI cross-linking either by antibody or by allergen challenge and that blockade of the generation prevents the release of allergic mediators. The findings strongly support the role of superoxide generation in the activation of mast cells and basophils under both physiological and pathological conditions. The findings suggest that drugs regulating the superoxide generation have potential therapeutic use for allergic disorders.

Auto-protective redox buffering systems in stimulated macrophages

BACKGROUND

Macrophages, upon encounter with micro-organisms or stimulated by cytokines, produce various effector molecules aimed at destroying the foreign agents and protecting the organism. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are front line molecules exerting strong cytotoxic activities against micro-organisms and many cells, including macrophages themselves. Using cells of the murine macrophage cell line (RAW 264.7) stimulated in vitro with lipopolysaccharide (LPS) and/or interferon (IFN-gamma), which induce strong endogenous NO production, we examined by which mechanisms a fraction of activated macrophages protect themselves from nitrosative stress and manage to escape destruction?

RESULTS

We observed that survivors (10-50% depending on the experiments) had acquired a resistant phenotype being capable to survive when further exposed in vitro to an apoptosis inducing dose of the NO donor compound DETA-NO. These cells expressed an increased steady-state levels of Mn SOD, CuZn SOD and catalase mRNA (130-200%), together with an increased activity of the corresponding enzymes. Intracellular concentration of glutathione was also increased (x 3.5 fold at 6 hours, still maintained x 5.2 fold at 48 hours). Neither mRNA for glutathione peroxydase, gamma-glutamylcysteine synthase and glutathione reductase, nor thioredoxine and thioredoxine reductase, were significantly modified. Additional experiments in which RAW 264.7 cells were stimulated with LPS and/or IFN-gamma in the presence of relatively specific inhibitors of both Mn and Cu/Zn SOD, aminotriazol (ATZ) catalase inhibitor and buthionine sulfoximine (BSO) glutathione inhibitor, showed that inhibiting LPS-induced up-regulation of intracellular redox buffering systems also prevented acquisition of the resistant phenotype.

CONCLUSIONS

Our data suggest a direct causal relationship between survival of a fraction of macrophages and a up-regulation of key sets of auto-protective intracellular redox buffering systems, occurring simultaneously with modulation of expression of apoptotic molecules of the Bcl2-Bcl-XL/Bax-Bad family.

Nitric oxide and Coxsackievirus B3 myocarditis: differential expression of inducible nitric oxide synthase in mouse heart after infection with virulent or attenuated virus

Increased expression of inducible nitric oxide synthase (iNOS) has been found in inflammatory myocardial disease and increased production of nitric oxide (NO) has both an inhibitory effect on virus replication and a cytotoxic effect on host cells. To investigate the relationship between severity of enteroviral myocarditis and iNOS expression, a characterised murine model was infected with either cardiovirulent or an attenuated Coxsackievirus B3 and myocardial samples were collected on Day 7. The ability of these viruses to induce NOS expression was compared by measurement of iNOS enzyme activity and localisation of iNOS protein or peroxynitrite, a product of excessive NO production. In accordance with previous reports, high expression of iNOS was detected in mice infected with the cardiovirulent virus. The iNOS protein was located mainly in infiltrating macrophages in and around foci of necrotic myofibres where viral genomic RNA was detected. In contrast, the level of iNOS expression was significantly lower in mice infected with the attenuated virus. This correlates with fewer and smaller myocarditic lesions and less infiltrating cells in the heart. iNOS was not detected in mock-infected mice by the above assays. These findings suggest that one mechanism of attenuation may be associated with the reduced ability of the variant to induce NOS expression in the heart. This also confirms a cytotoxic role for NO in the pathogenesis of Coxsackievirus B3-induced myocarditis.

Subtractive screening reveals up-regulation of NADPH oxidase expression in Crohn's disease intestinal macrophages

Macrophages play a central role during the pathogenesis of inflammation. In normal intestinal mucosa surface expression of typical macrophage markers such as CD14, CD16, CD11b or T-cell co-stimulatory molecules such as CD80 or CD86 is low indicating anergy and low pro-inflammatory activity of these cells. During inflammatory bowel disease (IBD) the mucosa is invaded by a population of macrophages displaying these markers, secreting higher cytokine levels and representing an activated cell population. CD33(+) cells (macrophages) were isolated from normal and Crohn's disease mucosa and mRNA was isolated by polyT magnetic beads. A subtractive screening was performed subtracting mRNA from normal macrophages from those of Crohn's disease macrophages. Oxidative burst activity was determined by flow cytometry. Seventy clones were obtained by the subtractive mRNA screening. Sequencing showed > 99% homology to mRNA of monocyte chemoattractant protein-1 (MCP-1) for three clones. Five clones obtained by subtraction revealed > 99% homology to mRNA of cytochrome b (subunit gp91). Differential expression of the cytochrome b subunit gp91 and the cytosolic NADPH oxidase subunit p67 was confirmed by RT-PCR and 'virtual' Northern blots. The fluorescence ratio of stimulated versus unstimulated cells was 0.9 +/- 0.16 in control macrophages indicating a lack of oxidative burst activity. In Crohn's disease this ratio was significantly increased to 1.80 +/- 0.8 (P = 0.004) confirming the molecular data. In conclusion NADPH oxidase mRNA is down-regulated or absent in macrophages from normal mucosa correlating with a lack of oxidative burst activity. In IBD macrophage-oxidative burst activity is increased and NADPH oxidase mRNA induced. Inhibition of NADPH oxidase could be a new therapeutical target in IBD and reduce mucosal tissue damage in active IBD.

Interferon-gamma listericidal action is mediated by novel Rab5a functions at the phagosomal environment

Control and clearance of Listeria monocytogenes infection is an interferon-gamma-dependent process. The listericidal mechanism of action involves activation of NADPH oxidase and inducible nitric-oxide synthase to produce reactive oxygen and nitrogen intermediate radicals, respectively. Recently, we have described in a nonpathogenic model of L. monocytogenes (hemolysin negative mutant strain) that the interferon-gamma-inducible GTPase Rab5a contributed to Listeria destruction in resting macrophages. Here, we report in a pathogenic model of L. monocytogenes (hemolysin-positive strain) that Rab5a plays a central role in Listeria destruction induced by interferon-gamma and within the phagosomal environment. These findings reveal the importance of Rab5a as the responsible factor mediating the listericidal action of interferon-gamma. Active Rab5a causes remodeling of the phagosomal environment, facilitates the translocation of Rac2 to LM phagosomes, and regulates the activity of this GTPase. Rac2 activation and translocation governs the phagocyte NADPH oxidase activity and the consequent reactive oxygen intermediate production that leads to killing of the pathogen.

Activated macrophages migrate to the subcutaneous tumor site via the peritoneum: a novel route of cell trafficking

Spontaneous regression of AK-5 tumor in syngeneic hosts reported earlier involves the interplay of Th1-type cytokines and cell-mediated immunity. Upon subcutaneous transplantation of AK-5 cells, there was accumulation of immune cells in the peritoneum, of which macrophages were the predominant type and were found to be in a hyperactive state. They released macrophage-derived tumoricidal mediators like NO, O2(-), and ONOO(-) which exhibited potent cytotoxic activity against AK-5 cells in vitro. Interestingly, there was a dramatic disappearance of these hyperactive cells from the peritoneal cavity which correlated well with the onset of tumor regression at the subcutaneous site. Direct labeling of these cells in the peritoneum by the tracking dye PKH26 showed their migration to the tumor site. Similarly, frozen tumor sections when scanned under confocal microscope clearly exhibited fluorescent macrophages embedded into the tumor. Immunohistochemical sections of these intratumoral macrophages showed nitrotyrosine residues, indicating their contribution in the free-radical-mediated AK-5 cell death, thereby leading to successful tumor remission. These observations suggest a directional migration of the hyperactivated peritoneal population to the tumor site. We have also confirmed the influx of macrophages and other immune cells into the peritoneum after sc transplantation of Meth A tumor cells in Balb/c mice. Our studies suggest a role for the peritoneal compartment in imparting appropriate stimulus to the immune cells prior to their participation in the antitumor immune response. These studies suggest a novel route of macrophage trafficking via the peritoneum.

Mechanisms underlying endothelial dysfunction in diabetes mellitus

Incubation of endothelial cells in vitro with high concentrations of glucose activates protein kinase C (PKC) and increases nitric oxide synthase (NOS III) gene expression as well as superoxide production. The underlying mechanisms remain unknown. To address this issue in an in vivo model, diabetes was induced with streptozotocin in rats. Streptozotocin treatment led to endothelial dysfunction and increased vascular superoxide production, as assessed by lucigenin- and coelenterazine-derived chemiluminescence. The bioavailability of vascular nitric oxide (as measured by electron spin resonance) was reduced in diabetic aortas, although expression of endothelial NOS III (mRNA and protein) was markedly increased. NOS inhibition with N:(G)-nitro-L-arginine increased superoxide levels in control vessels but reduced them in diabetic vessels, identifying NOS as a superoxide source. Similarly, we found an activation of the NADPH oxidase and a 7-fold increase in gp91(phox) mRNA in diabetic vessels. In vitro PKC inhibition with chelerythrine reduced vascular superoxide in diabetic vessels, whereas it had no effect on superoxide levels in normal vessels. In vivo PKC inhibition with N:-benzoyl-staurosporine did not affect glucose levels in diabetic rats but prevented NOS III gene upregulation and NOS-mediated superoxide production, thereby restoring vascular nitric oxide bioavailability and endothelial function. The reduction of superoxide in vitro by chelerythrine and the normalization of NOS III gene expression and reduction of superoxide in vivo by N:-benzoyl-staurosporine point to a decisive role of PKC in mediating these phenomena and suggest a therapeutic potential of PKC inhibitors in the prevention or treatment of vascular complications of diabetes mellitus. The full text of this article is available at http://www.circresaha.org.

The role of uric acid in protection against peroxynitrite-mediated pathology

Peroxynitrite, the product of the free radicals nitric oxide and superoxide, has been implicated in the pathogenesis of inflammatory CNS disorders. Uric acid, an effective scavenger of peroxynitrite, is a purine metabolite present at high levels in the serum of hominoids relative to lower-order animals due to the functional deletion of urate oxidase. Raising the normally low levels of uric acid in mice is therapeutic for experimental allergic encephalomyelitis, an animal model of multiple sclerosis. This therapeutic activity of uric acid is associated with the inhibition of peroxynitrite-induced tissue damage, blood-CNS barrier permeability changes, and CNS inflammation. Based on these findings we have concluded that peroxynitrite has an important role in promoting enhanced vascular permeability and inflammatory cell extravasation. We hypothesize that higher uric acid levels in hominoids evolved to protect against this process.

Hypoxic vasoconstriction in intact lungs: a role for NADPH oxidase-derived H(2)O(2)?

Hypoxic pulmonary vasoconstriction (HPV) matches lung perfusion with ventilation. Controversy exists whether decreased or increased reactive oxygen species may elicit HPV and from which source such oxygen metabolites are derived. In rabbit lungs, we detected transcripts of a nonphagocytic NADPH oxidase subunit homologous to mitogenic oxidase-1 (Mox1) or NADPH oxidase homolog 1 (NOH-1L). In perfused rabbit lungs, we employed 1) a new NADPH oxidase inhibitor [4-(2-aminoethyl)benzenesulfonyl fluoride (AEBSF; 100-600 microM)] and 2) the superoxide dismutase (SOD) inhibitors diethyldithiocarbamic acid (DETC; 100 microM to 10 mM) and triethylenetetramine (TETA; 1-25 mM). Specificity of these agents for HPV was investigated by comparison with U-46619-induced vasoconstrictions. AEBSF induced a transient increase in pulmonary arterial pressure with increased strength of HPV. Subsequent to this initial response, normoxic pulmonary arterial pressure was not affected and HPV was specifically suppressed. Whereas DETC turned out to act in a nonspecific fashion, TETA suppressed HPV specifically. These findings provide evidence of a role for a nonphagocytic NAD(P)H oxidase with superoxide and SOD-related hydrogen peroxide formation in HPV. Because HPV was inhibited but not mimicked by the inhibitors, increased rather than decreased superoxide and/or hydrogen peroxide formation is suggested as the hypoxia-provoked signaling event.

Diphenyleneiodonium prevents reactive oxygen species generation, tyrosine phosphorylation, and histamine release in RBL-2H3 mast cells

Mast cells play a central role in immediate allergic reactions mediated by immunoglobulin E. It has recently been reported that mast cells generate intracellular reactive oxygen species (ROS) in response to stimulation with divergent physiologically relevant stimulants. However, the physiological role of ROS is poorly understood. Here we demonstrate that mast cell model rat basophilic leukemia (RBL-2H3) cells generate ROS in response to antigen and the calcium-ionophore A23187 via activation of diphenyleneiodonuim (DPI)-sensitive enzyme and that blockade of ROS generation by DPI suppresses histamine release induced by either stimulant. Increased tyrosine phosphorylation of pp125(FAK) and a 77-kDa protein coprecipitating specifically with the kinase occurred in parallel with the secretion, and blockade of ROS generation by DPI also suppressed the tyrosine phosphorylation of both proteins. These findings suggest that ROS generated by a flavoenzyme-dependent mechanism may be involved in histamine release through the pp125(FAK) pathway.

Immune-inflammatory mechanisms in IFNgamma-mediated anti-tumor activity

IFNgamma is a functionally pleiotropic cytokine which shows considerable potency in promoting anti-tumor functions in vivo. Despite limited efficacy when delivered systemically either to experimental animals or patients, IFNgamma appears to play an important and perhaps critical role in directing the development of immune-mediated tumor destruction when expressed within the tumor bed. This has been demonstrated both by use of tumor cells transduced to express IFNgamma and by the use of IL-12 which is able, at least is murine models, to promote an IFNgamma-dependent, T cell mediated anti-tumor response. Recent studies indicate that the therapeutic efficacy of IFNgamma in tumor models depends critically upon the ability of the tumor cells themselves to respond to IFNgamma. Though IFNgamma is able to induce anti-viral activity and has direct anti-proliferative effects on some tumor cell lines, immunomodulatory function also appears to be an important component of its anti-tumor action. This is mediated through the action of several different classes of IFNgamma-inducible gene expression which control antigen processing and presentation, leukocyte trafficking, and indirect tumor cytotoxicity.

Release of hydrogen peroxide by rat type II pneumocytes in the prolonged culture

Type II pneumocytes (T II pneumocytes) produce hydrogen peroxide (H(2)O(2)), which may be potentially dangerous for the lung. These cells in culture differentiate to type I-like pneumocytes and it may reflect the differentiation which follows the injury of alveolar epithelium. This work was undertaken to estimate the H(2)O(2) release by T II pneumocytes, freshly isolated and cultured up to 8 days. The light and electron microscopy evaluation confirmed the differentiation of T II pneumocytes to type I-like cells. The release of H(2)O(2), estimated spectrofluorimetrically as homovanillic acid oxidation product obtained in the presence of horseradish peroxidase, was significantly higher at day 4 (0.63+/-0. 68nmol/mg protein/min, P</=0.02) and 6 (0.46+/-0.31, P</=0.001) compared to fresh cells (0.15+/-0.08). Phorbol esters increased H(2)O(2) release at day 2 (0.39+/-0.22 vs 0.16+/-0.08, P</=0.02) and the inhibition of protein kinase C resulted in the decrease at day 2 (0.14+/-0.06 vs 0.07+/-0.02, P</=0.025), day 6, (0.49+/-0.25 vs 0. 15+/-0.08, P</=0.005) and 8 (0.76+/-0.63 vs 0.23+/-0.29, P</=0.02). Inhibition of intracellular catalase resulted in a significant increase only at day 2 (0.23+/-0.1 vs 0.15+/-0.09, P</=0.05). Inhibition of mitochondrial respiratory chain decreased H(2)O(2) release at day 2 (0.13+/-0.11 vs 0.07+/-0.07, P</=0.002) and 4 (0. 75+/-0.88 vs 0.61+/-0.85, P</=0.002). These results indicate that alveolar epithelium may be a source of potentially dangerous ROS and that the cell differentiation is accompanied by the increase of H(2)O(2) production. Both mitochondrial respiratory chain and membrane-bound NADPH-oxidase may be responsible for the production of H(2)O(2) by T II pneumocytes.

Prenyltransferase inhibitors block superoxide production by pulmonary vascular smooth muscle

We recently showed that the farnesyltransferase inhibitor FTI-277 blocks interleukin 1beta (IL-1beta)-induced nitric oxide production in pulmonary vascular smooth muscle cells (SMC), whereas the geranylgeranyltransferase inhibitor GGTI-298 enhances this effect. Here we show that IL-1beta and platelet-derived growth factor (PDGF) stimulate superoxide production by pulmonary vascular SMC and that this effect is blocked by both FTI-277 and GGTI-298, suggesting that farnesylated and geranylgeranylated proteins are required for superoxide production. We also show that FTI-277 and GGTI-298 block superoxide production stimulated by constitutively active mutant H-Ras. Furthermore, superoxide production by IL-1beta, PDGF factor, and constitutively activated Ras is blocked by diphenyleneiodonium, implicating NAD(P)H oxidase as the generating enzyme. Given the role of oxidant radicals in vascular reactivity and injury, the action of both FTI-277 and GGTI-298 in suppressing superoxide generation by an inflammatory cytokine as well as by a potent smooth muscle mitogen may be therapeutically useful.

Improvement of nitric oxide-dependent vasodilatation by HMG-CoA reductase inhibitors through attenuation of endothelial superoxide anion formation

Three 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (HCRIs), atorvastatin, pravastatin, and cerivastatin, inhibited phorbol ester-stimulated superoxide anion (O(2)(-)) formation in endothelium-intact segments of the rat aorta in a time- and concentration-dependent manner (maximum inhibition of 70% after 18 hours at 1 to 10 micromol/L). The HMG-CoA reductase product mevalonic acid (400 micromol/L) reversed the inhibitory effect of the HCRIs, which, conversely, was mimicked by inactivation of p21 Rac with Clostridium sordellii lethal toxin but not by inactivation of p21 Rho with Clostridium botulinum exoenzyme (C3). A mevalonate-sensitive inhibition of phorbol ester-stimulated O(2)(-) formation by atorvastatin was also observed in porcine cultured endothelial cells and in a murine macrophage cell line. In the rat aorta, no effect of the HCRIs on protein kinase C, NADPH oxidase, or superoxide dismutase (SOD) activity and expression was detected, whereas that of endothelial nitric oxide (NO) synthase was enhanced approximately 2-fold. Moreover, exposure of the segments to atorvastatin resulted in a significant improvement of endothelium-dependent NO-mediated relaxation, and this effect was abolished in the presence of SOD. Taken together, these findings suggest that in addition to augmenting endothelial NO synthesis, HCRIs inhibit endothelial O(2)(-) formation by preventing the isoprenylation of p21 Rac, which is critical for the assembly of NADPH oxidase after activation of protein kinase C. The resulting shift in the balance between NO and O(2)(-) in the endothelium improves endothelial function even in healthy blood vessels and therefore may provide a reasonable explanation for the beneficial effects of HCRIs in patients with coronary heart disease in addition to or as an alternative to the reduction in serum LDL cholesterol.

The methanol extract of Spiraea prunifolia var. simpliciflora root inhibits the generation of nitric oxide and superoxide in RAW 264.7 cells

It is well established that nitric oxide (NO) and superoxide radicals play pivotal roles in the pathogenesis of inflammatory diseases and fever. This study is undertaken to address whether the methanol extract of Spiraea prunifolia var. simpliciflora root, a traditional medicine as an antipyretic, modulates the generation of NO and superoxide in IFN-gamma primed or polymyristic acetate (PMA) stimulated RAW 264.7 cells, respectively. The generation of NO as well as the expression of inducible nitric oxide synthase (iNOS) protein from IFN-gamma primed RAW 264.7 cells is markedly decreased by the methanol extract in a dose dependent manner. However, the methanol extract does not affect the viability of RAW 264.7 cells, as assessed by methylthiazol-2-yl-2,5-diphenyl tetrazolium bromide (MTT) assay. In addition, the methanol extract suppresses the generation of superoxide in PMA-stimulated RAW 264.7 cells in a dose and a time dependent manner. Taken together, anti-pyretic effects of Spiraea prunifolia var. simpliciflora root extract could result from direct suppression of NO and decreased superoxide generation.

Cerebrospinal fluid nitric oxide levels in childhood bacterial meningitis

The role of nitric oxide (NO) in childhood bacterial meningitis was investigated by determining the levels of nitrate/nitrite, stable end products of NO metabolism, in cerebrospinal fluid (CSF). Eighteen children with bacterial meningitis and 18 as a control group were included in the study. Mean (+/- SD) CSF nitrate/nitrite levels were 27.6 +/- 26 micromol/l in the bacterial meningitis group and 3.2 +/- 1.8 micromol/l in the control group (p = 0.0005). We found no correlation between CSF nitrate/nitrite levels and CSF white blood cell count (r = 0.22), protein (r = 0.26) or tumour necrosis factor alpha (TNF-alpha) levels (r = 0.046), but a moderate negative correlation between CSF nitrate/nitrite and glucose levels (r = -0.46).

Suppression of inducible cyclooxygenase and inducible nitric oxide synthase by apigenin and related flavonoids in mouse macrophages

Prostaglandins biosynthesis and nitric oxide production have been implicated in the process of carcinogenesis and inflammation. In this study, we investigated the effect of various flavonoids and (-)-epigallocatechin-3-gallate on the activities of inducible cyclooxygenase (COX-2) and inducible nitric oxide synthase (iNOS) in lipopolysaccharide (LPS)-activated RAW 264.7 macrophages. Apigenin, genistein and kaempferol were markedly active inhibitors of transcriptional activation of COX-2, with IC(50) < 15 microM. In addition, apigenin and kaempferol were also markedly active inhibitors of transcriptional activation of iNOS, with IC(50) < 15 microM. Of those compounds tested, apigenin was the most potent inhibitor of transcriptional activation of both COX-2 and iNOS. Western and northern blot analyses demonstrated that apigenin significantly blocked protein and mRNA expression of COX-2 and iNOS in LPS-activated macrophages. Transient transfection experiments showed that LPS caused an approximately 4-fold increase in both COX-2 and iNOS promoter activities, these increments were suppressed by apigenin. Moreover, electrophoretic mobility shift assay (EMSA) experiments indicated that apigenin blocked the LPS-induced activation of nuclear factor-kB (NF-kB). The inhibition of NF-kB activation occurs through the prevention of inhibitor kB (IkB) degradation. Transient transfection experiments also showed that apigenin inhibited NF-kB-dependent transcriptional activity. Finally, we showed that apigenin could inhibit the IkB kinase activity induced by LPS or interferon-gamma. The results of further studies suggest that suppression of transcriptional activation of COX-2 and iNOS by apigenin might mainly be mediated through inhibition of IkB kinase activity. This study suggests that modulation of COX-2 and iNOS by apigenin and related flavonoids may be important in the prevention of carcinogenesis and inflammation.

Chemoreceptor discharges and cytochrome redox changes of the rat carotid body: role of heme ligands

In superfused in vitro rat carotid body, we recorded chemoreceptor discharges and the redox state of cytochromes simultaneously to identify the primary oxygen-sensing protein controlling transmitter release and electrical activity of the carotid sinus nerve. These parameters were tested under the influence of heme ligands such as oxygen, cyanide, 4-(2-aminoethyl)-benzenesulfonyl fluoride, and CO. During stimulation, there was an initial increase in discharge frequency followed by a decline or suppression of activity. Photometric changes lagged and were maintained as nerve activity decreased. Reducing mitochondrial cytochromes by cyanide or prolonged severe hypoxia, suppressed the chemoreceptor discharge. 4-(2-Aminoethyl)-benzenesulfonyl fluoride, a specific inhibitor of the phagocytic cytochrome b(558), also silenced the chemoreceptors after an initial excitation. CO increased the chemoreceptor discharge under normoxia, an effect inhibited by light, when the cytochromes were not reduced. When the discharges were depressed by severe hypoxia, exposure to light excited the chemoreceptors and the cytochromes were reduced. The rapidity of the chemosensory responses to light and lack of effect on dopamine release from type I cells led us to hypothesize that carotid body type I cells and the apposed nerve endings use different mechanisms for oxygen sensing: the nerve endings generate action potentials in association with membrane heme proteins whereas cytosolic heme proteins signal the redox state, releasing modulators or transmitters from type I cells.

Role for NADPH/NADH oxidase in the modulation of vascular tone

The endothelium modulates vascular tone by producing vasodilator and vasconstrictor substances. Of these, the best characterized and potentially most important are nitric oxide (NO.) and O2-.. These small molecules exhibit opposing effects on vascular tone and chemically react with each other in a fashion that negates their individual effects and leads to the production of potentially toxic substances, such as peroxynitrite (ONOO-). These dynamic interactions may likely have important implications, altering not only tissue perfusion but also contributing to the process of atherosclerosis. The precise O2-. source within vascular tissue remains to be determined. Recent work demonstrated that in endothelial cells as well as in vascular smooth muscle cells, a membrane-associated NAD(P)H-dependent oxidase represents the most significant O2-. source. Interestingly, this oxidase is activated upon stimulation with angiotension II, suggesting that under all conditions of an activated circulating and/or local renin-angiotensin system endothelial dysfunction secondary to increased vascular O2-. production is expected.