D-4F, an apoA-1 mimetic, decreases airway hyperresponsiveness, inflammation, and oxidative stress in a murine model of asthma.

Asthma is characterized by oxidative stress and inflammation of the airways. Although proinflammatory lipids are involved in asthma, therapies targeting them remain lacking. Ac-DWFKAFYDKVAEKFKEAFNH(2) (4F) is an apolipoprotein (apo)A-I mimetic that has been shown to preferentially bind oxidized lipids and improve HDL function. The objective of the present study was to determine the effects of 4F on oxidative stress, inflammation, and airway resistance in an established murine model of asthma. We show here that ovalbumin (OVA)-sensitization increased airway hyperresponsiveness, eosinophil recruitment, and collagen deposition in lungs of C57BL/6J mice by a mechanism that could be reduced by 4F. OVA sensitization induced marked increases in transforming growth factor (TGF)ß-1, fibroblast specific protein (FSP)-1, anti-T15 autoantibody staining, and modest increases in 4-hydroxynonenal (4-HNE) Michael's adducts in lungs of OVA-sensitized mice. 4F decreased TGFß-1, FSP-1, anti-T15 autoantibody, and 4-HNE adducts in the lungs of the OVA-sensitized mice. Eosinophil peroxidase (EPO) activity in bronchial alveolar lavage fluid (BALF), peripheral eosinophil counts, total IgE, and proinflammatory HDL (p-HDL) were all increased in OVA-sensitized mice. 4F decreased BALF EPO activity, eosinophil counts, total IgE, and p-HDL in these mice. These data indicate that 4F reduces pulmonary inflammation and airway resistance in an experimental murine model of asthma by decreasing oxidative stress.

Agonist-dependent generation of lipoxins from rat basophilic leukemia cell (RBL-1).

Incubation of RBL-1 cells in the presence of 15-HPETE and various agonists generated lipoxins and several isomers. Addition of either A23187, fMLP or PMA modulated the number of isomers and amount of lipoxins produced. Administration of A23187 yielded the largest amount of product (5.3 +/- 1.6 micrograms per 10(8) cells) and generated a total of six and three isomers of LXA4 and B4, respectively. This was 2-fold greater than fMLP, which produced a total of two isomers of LXA4 and LXB4. Addition of PMA generated only LXA4 (0.68 +/- 0.26 micrograms). This is similar to the control receiving only 15-HPETE. Biologically derived LXA4 (3 nM) isolated from RBL-1 incubations contracted a rat tail artery preparation to 12% of the maximum induced by phenylephrine (0.125 microM), whereas LXA4 standard (3 nM) elicited 17.6% of the maximum contraction. These results indicate that RBL-1 cells can utilize exogenous 15-HPETE to generate biologically active lipoxins. Further, the yield and isomers of lipoxins can be modified by different agonists.

Triglyceride-lowering effect of dietary vitamin E in streptozocin-induced diabetic rats. Increased lipoprotein lipase activity in livers of diabetic rats fed high dietary vitamin E.

High vitamin E supplementation in the diets of streptozocin-induced diabetic rats eliminates accumulation of lipid peroxides in the plasma and the liver, returns the plasma triglycerides toward normal levels, and increases the activity of lipoprotein lipase. Vitamin E has no effect on the levels of insulin or glucose. These findings suggest that vitamin E increases the total hepatic triglyceride lipase activity by increasing the lipoprotein lipase activity possibly by protecting the membrane-bound lipase against peroxidative damage.

Inhibition of adrenal cell aldosterone synthesis by endogenous nitric oxide release.

Adrenal zona glomerulosa (ZG) cells do not contain nitric oxide (NO) synthase (NOS). We conferred endothelial NOS activity onto adrenal ZG cells through transduction with a recombinant adenovirus encoding the endothelial NOS gene (AdeNOS) to determine the effect of endogenous NO on aldosterone synthesis. A 135-kDa protein band immunoreactive to anti-endothelial NOS antibody was observed in Western blots of AdeNOS-transduced ZG cells but not in control cells or cells transduced with adenovirus encoding the beta-galactosidase gene (AdbetaGal). Nitrate/nitrite production in AdeNOS-transduced ZG cells increased from 0.15+/-0.01 to 0.27+/-0.01 micromol/L after stimulation with 1 nmol/L angiotensin II. The treatment of AdeNOS-transduced cells with 30 micromol/L L-nitro-arginine decreased angiotensin II-stimulated nitrite production from 0.27+/-0. 01 to 0.17+/-0.01 micromol/L. Basal and angiotensin II-stimulated nitrite production was not increased in AdbetaGal-transduced or control cells. AdeNOS-transduced cells demonstrated diaminofluorescein-2 diacetate fluorescence, which was blocked by pretreatment with L-nitro-arginine. Angiotensin II-stimulated aldosterone synthesis decreased from 5123+/-177 pg/mL in AdbetaGal-transduced ZG cells to 72+/-27 pg/mL in AdeNOS-transduced cells. Treatment with the NOS inhibitor thiocitrulline (30 micromol/L) increased angiotensin II-stimulated aldosterone synthesis to 2158+/-45 pg/mL after AdeNOS transduction. These data demonstrate that adenovirus-mediated gene transfer of eNOS in ZG cells results in the expression of active endothelial NOS enzyme and that this endogenous NO production by ZG cells decreases aldosterone synthesis.

Superoxide anion formation from lucigenin: an electron spin resonance spin-trapping study.

Lucigenin (LC2+) is frequently used as a superoxide probe. To detect superoxide, lucigenin must be reduced to the lucigenin cation radical (LC.+). We show, using the phosphorylated spin trap 5-diethoxyphosphoryl-5-methyl-1-pyrroline N-oxide (DEPMPO), that lucigenin stimulates NADPH-dependent superoxide production by endothelial nitric oxide synthase (eNOS). The formation of the DEPMPO-superoxide adduct is calcium/calmodulin independent. DEPMPO-superoxide adduct formation is inhibited by diphenyleneiodonium and is abolished by superoxide dismutase. It is likely that eNOS/NADPH can reduce lucigenin to LC.+ which reduces oxygen to superoxide. Consequently, lucigenin cannot be used to measure superoxide formation.

Chronic myocardial hypoxia increases nitric oxide synthase and decreases caveolin-3.

Nitric oxide synthase (NOS) is believed to play an important role in protecting the myocardium against ischemia. Chronic hypoxia from birth increases NOS activity in the myocardium resulting in enhanced nitric oxide production and increased resistance to ischemia. We examined the effects of chronic hypoxia on NOS gene and protein expression and on NOS protein association with caveolin-3. Rabbits were raised from birth in a normoxic (F(I)O(2) = 0.21) or a hypoxic (F(I)O(2) = 0.12) environment for 9 d, and then the hearts were isolated. Ribonuclease protection assays revealed that chronic hypoxia did not alter NOS transcript levels for NOS1, NOS2, or NOS3. The most abundant transcript was NOS3. Western analysis revealed NOS3 was the only isoform detected. Immunoblots of NOS3 immunoprecipitates showed that chronic hypoxia increases NOS3 protein by 2.0 +/- 0.4-fold and decreases the amount of caveolin-3 that can be coprecipitated with NOS3 by 5.5 +/- 0.9-fold. Immunoblots of normoxic and hypoxic hearts showed that chronic hypoxia decreases the amount of caveolin-3 in heart homogenates by 2. 2 +/- 0.5-fold. These data suggest that a decrease in caveolin-3 plays a role in the mechanisms by which chronic hypoxia increases NOS3 activity in the myocardium.

Electron spin resonance spin-trapping detection of superoxide generated by neuronal nitric oxide synthase.

NOS is a ubiquitous enzyme that has an oxygenase and reductase activity. NOS reduces electron acceptors, at the reductase domain, by a one-electron mechanism that is not inhibited by SOD. One example of this activity is the direct reduction of ferricytochrome c by nNOS. Redox cycling electron acceptors (EA in Scheme 1), such as lucigenin and NBT, are reduced by NOS to generate an intermediate radical (EAred). This radical can then be reoxidized to the parent compound by oxygen, and in the process generate superoxide. Consequently, both NBT and lucigenin will enhance NADPH-dependent superoxide generation in the presence of flavoprotein reductases such as NOS. The artificial generation of superoxide from lucigenin and NBT is a major pitfall in the use of these compounds as superoxide probes. We conclude that the use of ESR spin-trapping techniques, although not free of problems, is a viable technique for the detection and quantification of superoxide in systems containing nNOS.

Effect of dietary vitamin E on the production of platelet 12-hydroxyeicosatetraenoic acid (12-HETE).

Collagen and thrombin challenged platelets from vitamin E-deficient rabbits generated significantly more 12-HETE when compared to the platelets from vitamin E-supplemented rabbits. Similarly, conversion of arachidonic acid to 12-HETE was increased in platelets from vitamin E-deficient rabbits. These data show that vitamin E plays a role not only in deacylation of platelet phospholipids but also in the lipoxygenase mediated reactions.

Adaptation to chronic hypoxia confers tolerance to subsequent myocardial ischemia by increased nitric oxide production.

Chronic exposure to hypoxia from birth increased the tolerance of the rabbit heart to subsequent ischemia compared with age-matched normoxic controls. The nitric oxide donor GSNO increased recovery of post-ischemic function in normoxic hearts to values not different from hypoxic controls, but had no effect on hypoxic hearts. The nitric oxide synthase inhibitors L-NAME and L-NMA abolished the cardioprotective effect of hypoxia. Message and catalytic activity for constitutive nitric oxide synthase as well as nitrite, nitrate, and cGMP levels were elevated in hypoxic hearts. Inducible nitric oxide synthase was not detected in normoxic or chronically hypoxic hearts. Increased tolerance to ischemia in rabbit hearts adapted to chronic hypoxia is associated with increased expression of constitutive nitric oxide synthase.

Endothelial cell perturbation and low-density lipoprotein. Quantitative autoradiography.

The focal entry and accumulation of LDL within the arterial wall of the normal animal may represent an early stage in the development of the atherosclerotic plaque. Concentrations of LDL 10 to 100 times normal medial concentrations might be difficult to clear from the arterial wall, permitting accumulation of lipid. Elevated LDL concentrations, in proximity to smooth muscle cells, appear to stimulate SMC proliferation. High LDL concentrations might also enhance mononuclear cell adhesion to endothelium. Since LDL has a high affinity for heparin and heparin for growth factors, LDL accumulation may be a mechanism for the concentration of such materials in the intima. The observation of markedly enhanced macromolecular permeability foci could be related to several potential mechanisms of initiation of atherosclerosis. This observation is of particular note when the focal occurrence of atherosclerosis is considered. Although atherosclerosis is seen as a generalized thickening of the intima, it is the focal narrowing of the lumen that is often responsible for the stenosis which produces symptoms such as angina or myocardial infarction.

Protein kinase B/Akt activates c-Jun NH(2)-terminal kinase by increasing NO production in response to shear stress.

Laminar shear stress activates c-Jun NH(2)-terminal kinase (JNK) by the mechanisms involving both nitric oxide (NO) and phosphatidylinositide 3-kinase (PI3K). Because protein kinase B (Akt), a downstream effector of PI3K, has been shown to phosphorylate and activate endothelial NO synthase, we hypothesized that Akt regulates shear-dependent activation of JNK by stimulating NO production. Here, we examined the role of Akt in shear-dependent NO production and JNK activation by expressing a dominant negative Akt mutant (Akt(AA)) and a constitutively active mutant (Akt(Myr)) in bovine aortic endothelial cells (BAEC). As expected, pretreatment of BAEC with the PI3K inhibitor (wortmannin) prevented shear-dependent stimulation of Akt and NO production. Transient expression of Akt(AA) in BAEC by using a recombinant adenoviral construct inhibited the shear-dependent stimulation of NO production and JNK activation. However, transient expression of Akt(Myr) by using a recombinant adenoviral construct did not induce JNK activation. This is consistent with our previous finding that NO is required, but not sufficient on its own, to activate JNK in response to shear stress. These results and our previous findings strongly suggest that shear stress triggers activation of PI3K, Akt, and endothelial NO synthase, leading to production of NO, which (along with O(2-), which is also produced by shear) activates Ras-JNK pathway. The regulation of Akt, NO, and JNK by shear stress is likely to play a critical role in its antiatherogenic effects.

Production of platelet thromboxane A2 and arterial prostacyclin I2 from hypercholesterolemic rats.

The plasma cholesterol, plasma malonaldehyde (MDA), platelet thromboxane A2 (TXA2) and vascular prostacyclin (PGI2) were measured in male Sprague-Dawley rats fed diets supplemented with cholesterol (1%) and cholic acid (0.5%). For comparisons, measurements were made in rats fed normal diets. The concentration of cholesterol in the plasma of rats had reached a maximum in 1 week of feeding experimental diets. TXA2 production from collagen and thrombin stimulated platelets was significantly decreased in animals fed experimental diets for 1 week. The production of MDA in the plasma of animals fed experimental diets for 8 weeks was significantly lower compared to the animals fed normal diets. There was a small but significant reduction in the formation of PGI2 in rats fed experimental diets for 8 weeks. These data suggest that feeding cholesterol rich diets to rats alters the platelet membrane properties differently from human and rabbit. Furthermore, cholesterol feeding to rats had some damaging effect on the arterial PGI2 synthesis.

Effect of lovastatin on serum lipids in patients with nonfamilial primary hypercholesterolemia.

The effect of lovastatin on serum lipids and its tolerability in patients with non-familial primary hypercholesterolemia (type II-A and type II-B) during a six-month period were evaluated in this open-label study. Thirty-eight patients were enrolled in the study; tolerability was assessed in all 38 patients. Thirty patients completed the study, and the effect of lovastatin on serum lipids in these patients was assessed. Some patients had been treated for hypercholesterolemia with long-term dietary and other non-pharmacologic means before entry into the study. All patients were unresponsive to a six-week program of intensive dietary therapy and other nonpharmacologic treatment to lower their blood cholesterol levels before receiving lovastatin. While maintaining intensive dietary therapy, administration of lovastatin was instituted at a dosage of 20 mg/day, which was increased by 20-mg increments monthly, as necessary, to a maximum of 80 mg/day. In an effort to achieve goal levels of low-density lipoprotein cholesterol (LDL-C), ten patients received a daily dosage of 20 mg, 12 patients received 40 mg, seven patients 60 mg, and one patient 80 mg. Twenty-nine of the 30 patients achieved significant lowering of serum levels of total cholesterol (TC), LDL-C, and apolipoprotein (apo) B-I; this was demonstrated after the first month of therapy with lovastatin and was maintained throughout the six-month treatment period. One patient failed to demonstrate lowering of these serum lipids, despite receiving the maximum recommended dosage of lovastatin of 80 mg/day. Comparative measurements of serum lipids during dietary therapy alone and after six months of diet plus lovastatin therapy were as follows: TC, 289 +/- 5 versus 216 +/- 9 mg/dl (P less than 0.0005); LDL-C, 206 +/- 4 versus 141 +/- 5 mg/dl (P less than 0.0005); and apo B-I, 112 +/- 3 versus 89 +/- 2 mg/dl (P less than 0.0005). Serum levels of very-low-density lipoprotein cholesterol (VLDL-C) and triglycerides decreased slightly during lovastatin therapy, but the changes were not statistically significant. There were slight but statistically insignificant increases in serum levels of high-density lipoprotein cholesterol (HDL-C), apo A-I, and apo A-II.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of redox-active drugs on superoxide generation from nitric oxide synthases: biological and toxicological implications.

In this article, we address the mechanism of superoxide formation from constitutive nitric oxide synthases (NOS). Merits and drawbacks of the various superoxide detection assays are reviewed. One of the most viable techniques for measuring superoxide from NOS is electron spin resonance (ESR) spin-trapping using a novel phosphorylated spin trap. Implications of superoxide and peroxynitrite formation from NOS enzymes in cardiovascular and cerebrovascular disorders are discussed.

Lipid fluidity modulates platelet aggregation and agglutination in vitro.

To determine the effect of altered membrane fluidity on platelet aggregation/agglutination, fresh, washed human platelets were treated with A2C, a cyclopropyl fatty acid ester which is known to enhance mobility of intrinsic membrane bilayer constituents and increase membrane fluidity. Fluorescence polarization studies demonstrated A2C incubation time- and concentration-dependent increases in platelet membrane fluidity (decreased fluorescence anisotropy). Preincubation with A2C was associated with diminished collagen, thrombin and ristocetin-induced platelet aggregation/agglutination. Aggregation/agglutination was diminished by 93 +/- 5% for collagen (0.2 mg/ml), 53 +/- 3% for thrombin (1.0 U/ml) and 85 +/- 9% for ristocetin (1.1 mg/ml). These data suggest that membrane fluidity is involved in the regulation of platelet function.

Chromium (VI) increases endothelial cell expression of ICAM-1 and decreases nitric oxide activity.

Occupational, airborne pollutants, such as heavy metals, are recognized for inducing injury and cytotoxicity. Chromium(VI) is a redox cycling heavy metal that has been strongly implicated in the initiation of cancer. Its proinflammatory effects, however, have not been systematically examined. In our study, we found that potassium dichromate [Cr(VI)] treatment of human umbilical vein endothelial cells (HUVEC) increased intracellular adhesion molecule (ICAM) expression at the message level. ICAM message levels remained elevated for 12-24 hours after exposure and increased with time and concentration. Cr(VI) increased the release of superoxide anion without affecting the ability of endothelial cultures to produce nitric oxide. However, Cr(VI) decreased cGMP in HUVEC, suggesting that the nitric oxide produced was scavenged intracellularly. Cr(VI) also increased nitrotyrosine in HUVEC cultures. These data are consistent with the idea that exposure to Cr(VI) increases the production of superoxide anion, which scavenges nitric oxide to increase the formation of peroxynitrite. The loss in nitric oxide activity and increased formation of peroxynitrite likely enhance endothelial cell expression of ICAM-1. Cr(VI)-induced increases in the adhesive properties of the endothelium may play a critical role in the initiation and progression of tissue injury through increased recruitment of proinflammatory white blood cells.

Attenuated expression of inducible nitric oxide synthase in lung microvascular endothelial cells is associated with an increase in ICAM-1 expression.

BACKGROUND/PURPOSE: The molecular and cellular events that regulate inflammatory lung injury, a major cause of morbidity in surgical patients, remain unclear. The authors hypothesize that nitric oxide (NO) plays an important role in regulating polymorphonuclear cell (PMN)-induced acute lung injury, and further, that attenuated expression of inducible nitric oxide synthase (iNOS) and therefore decreased production of NO by lung microvascular endothelial cells (LMVEC), accelerates inflammation and injury. METHODS: LMVEC and aortic EC (AEC) from rat and human were stimulated with lipopolysaccharide (LPS) and cytokines; changes in iNOS mRNA expression and iNOS activity were determined. The role of NO in mediating inflammatory responses was evaluated by determining PMN adherence to LMVEC and lung tissue slices in the presence and absence of NOS inhibitors and NO donors. Human LMVEC and AEC were assessed by FACS analysis for ICAM-1 expression, because this is thought to be a critical determinant of PMN adherence. RESULTS: When stimulated with endotoxin and cytokines, rat AEC monolayers express nearly 3-fold more iNOS mRNA than rat LMVEC. The low levels of LMVEC iNOS expression are associated with a 4-fold lower nitrite and nitrate production. Similar trends are seen in human endothelial cells. When iNOS activity was blocked, PMN adherence to tumor necrosis factor alpha (TNFalpha)/LPS-stimulated LMVEC was markedly increased. In contrast, adding a nitric oxide donor to endotoxin/cytokine-stimulated LMVEC monolayers reduced PMN adherence to near background levels. Similar responses were observed in vivo. Human lung microvascular endothelial cells show a substantially increased level of ICAM-1 upregulation when compared with similarly stimulated human aortic macrovascular endothelial cells. CONCLUSIONS: These data indicate that LMVEC express less iNOS and produce less NO than AEC. This lower expression and activity of iNOS in LMVEC may be linked to increased expression of ICAM-1. Because ICAM-1 has been shown to be essential for tight PMN adherence, these data suggest that relatively low iNOS expression in LMVEC may contribute to a propensity for the lung to be injured by activated PMNs.

Oxidized low density lipoprotein increases U937 cell 5-lipoxygenase activity: induction of 5-lipoxygenase activating protein.

This study examines the effects of oxidized low density lipoprotein (ox-LDL) on mononuclear cell arachidonic acid (AA) metabolism. U937 and HL60 cells, employed as models for mononuclear cells and promyelocytic cells, respectively, were exposed to ox-LDL (20 micrograms protein/ml) for 24 hours. HPLC analysis of 1-14C-AA metabolites indicates that ox-LDL increases U937 and HL60 cell production of 15-hydroxyeicosatetraenoic acid (15-HETE) and 5-hydroxyeicosatetraenoic acid (5-HETE). Northern analysis indicates that ox-LDL increases U937 cell FLAP transcript levels 10-times control levels but did not appear to alter 5-lipoxygenase (5-LO) mRNA levels. In contrast, ox-LDL increases HL60 cell transcript levels for FLAP and 5-LO 1.5 times and 10 times control levels, respectively. Thus, we propose that ox-LDL plays an important role in the up-regulation of the 5-LO pathway in mononuclear cells. Such activation may explain, in part, the mechanisms by which ox-LDL promotes atherogenesis.

Atherogenic concentrations of low-density lipoprotein enhance endothelial cell generation of epoxyeicosatrienoic acid products.

To investigate the effects of protracted low-density lipoprotein (LDL) exposure on endothelial cell (EC) epoxyeicosatrienoic acid (EET) generation, human umbilical vein ECs were incubated in atherogenic concentrations of LDL (240 mg cholesterol per deciliter) (LDL-EC). After 4 days' incubation with LDL, EC were stimulated with human thrombin in the presence of 1-[14C]-arachidonic acid. Substantially more EET products were generated by LDL-ECs than by cells not exposed to high levels of LDL (C-EC). Thrombin stimulation caused LDL-EC to produce five- to eightfold more in 14,15-EET, 11,12-EET, 8,9-EET, and 5,6-EET, with 14,15-EET as the major product. This is the first demonstration, to date, that EETs can be induced in EC. Metapyrone (SKF-525A) markedly inhibited EC EET generation, indicating a role for the cytochrome P-450 enzyme system in human EC arachidonic acid metabolism. One EET product, 14,15-EET, has been found to be chemotactic and to promote adhesion of U937 cells, a human monocytic lymphoma cell line, to EC. Thus, protracted exposure to atherogenic LDL concentrations increases the generation of chemotactic and adhesion factors (ie, 14,15-EET) after thrombin stimulation, possibly through the cytochrome P-450 enzyme system.