The effect of organic amendment on potential mobility and bioavailability of 137Cs and 60Co in tropical soils

In this work the role of organic matter in the potential mobility and bioavailability of 137Cs and 60Co in Brazilian soil was investigated. Radish was cultivated in pots containing the top layer (0-20 cm) of a Histosol, Ferralsol and Nitisol spiked with 137Cs and 60Co. In the case of the Ferralsol and Nitisol samples, besides the control, two different rates of organic amendments were used. In these soils, a sequential extraction protocol was used to identify the main soil compartments that could be responsible for the variation of transfer factor values. Our results indicate that organic amendment could be suggested as a practical countermeasure for 137Cs and 60Co contamination, since it reduces bioavailability of radionuclides and, consequently, soil to plant transfer factor values by almost one order of magnitude in a short period of time.

Soil to plant transfer of 137Cs and 60Co in Ferralsol, Nitisol and Acrisol

In this study, soil to plant transfer factor values were determined for 137Cs and 60Co in radish (Raphanus sativus), maize (Zea mays L.) and cabbage (Brassica oleracea L. var. capitata) growing in gibbsite-, kaolinite- and iron-oxide-rich soils. After 3 years of experiment in lysimeters it was possible to identify the main soil properties able to modify the soil to plant transfer processes, e.g. exchangeable K and pH, for 137Cs, and organic matter for 60Co. Results of sequential chemical extraction were coherent with root uptake and allowed the recognition of the role of iron oxides on 137Cs behaviour and of Mn oxides on 60Co behaviour. This information should provide support for adequate choices of countermeasures to be applied on tropical soils in case of accident or for remediation purposes.

Carboxylated, heteroaryl-substituted chalcones as inhibitors of vascular cell adhesion molecule-1 expression for use in chronic inflammatory diseases

Starting from a simple chalcone template, structure-activity relationship (SAR) studies led to a series of carboxylated, heteroaryl-substituted chalcone derivatives as novel, potent inhibitors of vascular cell adhesion molecule-1 (VCAM-1) expression. Correlations between lipophilicity determined by calculated logP values and inhibitory efficacy were observed among structurally similar compounds of the series. Various substituents were found to be tolerated at several positions of the chalcone backbone as long as the compounds fell into the right range of lipophilicity. The chalcone alpha,beta-unsaturated ketone moiety seemed to be the pharmacophore required for inhibition of VCAM-1 expression. Compound 19 showed significant antiinflammatory effects in a mouse model of allergic inflammation, indicating that this series of compounds might have therapeutic value for human asthma and other inflammatory disorders.

Composted municipal waste effects on chemical properties of a Brazilian soil

The spread of composted municipal waste (CMW) on land can be used for sustainable crop production. Nevertheless, heavy metals availability may be a problem. Therefore, the main objective of this study was to assess the impact of CMW disposal on heavy metal accumulation in soil and plants. The treatments consisted of an untreated plot (control) and four rates of CMW application. All plots were cultivated in succession of carrot, cauliflower, sweet corn, and radish. Cu and Pb significantly accumulated in the topsoil (0-5 cm) with a similar pattern in the depths of 5-10 cm and 10-20 cm. Cauliflower, for Fe and Cu, and radish, for Pb and Cu, had their tissue analysis significantly affected due to the increasing rates of application of CMW. Nevertheless, the levels of accumulation in both, soil and plant, are within permissible limits. The evidences provided by this experiment indicated that heavy metals are less likely to cause problems for the estimation of CMW loadings to Brazilian agricultural land.

Activation of Nrf2/ARE pathway protects endothelial cells from oxidant injury and inhibits inflammatory gene expression

The antioxidant response element (ARE) is a transcriptional control element that mediates expression of a set of antioxidant proteins. NF-E2-related factor 2 (Nrf2) is a transcription factor that activates ARE-containing genes. In endothelial cells, the ARE-mediated genes are upregulated by atheroprotective laminar flow through a Nrf2-dependent mechanism. We tested the hypothesis that activation of ARE-regulated genes via adenovirus-mediated expression of Nrf2 may suppress redox-sensitive inflammatory gene expression. Expression of Nrf2 in human aortic endothelial cells (HAECs) resulted in a marked increase in ARE-driven transcriptional activity and protected HAECs from H2O2-mediated cytotoxicity. Nrf2 suppressed TNF-α-induced monocyte chemoattractant protein (MCP)-1 and VCAM-1 mRNA and protein expression in a dose-dependent manner and inhibited TNF-α-induced monocytic U937 cell adhesion to HAECs. Nrf2 also inhibited IL-1β-induced MCP-1 gene expression in human mesangial cells. Expression of Nrf2 inhibited TNF-α-induced activation of p38 MAP kinase. Furthermore, expression of a constitutively active form of MKK6 (an upstream kinase for p38 MAP kinase) partially reversed Nrf2-mediated inhibition of VCAM-1 expression, suggesting that p38 MAP kinase, at least in part, mediates Nrf2's anti-inflammatory action. In contrast, Nrf2 did not inhibit TNF-α-induced NF-κB activation. These data identify the Nrf2/ARE pathway as an endogenous atheroprotective system for antioxidant protection and suppression of redox-sensitive inflammatory genes, suggesting that targeting the Nrf2/ARE pathway may represent a novel therapeutic approach for the treatment of inflammatory diseases such as atherosclerosis.

AGIX-4207 [2-[4-[[1-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]thio]-1-methylethyl]thio]-2,6-bis(1,1-dimethylethyl)phenoxy]acetic acid], a novel antioxidant and anti-inflammatory compound: cellular and biochemical characterization of antioxidant activity and inhibition of redox-sensitive inflammatory gene expression

The pathogenesis of chronic inflammatory diseases, including rheumatoid arthritis, is regulated, at least in part, by modulation of oxidation-reduction (redox) homeostasis and the expression of redox-sensitive inflammatory genes including adhesion molecules, chemokines, and cytokines. AGIX-4207 [2-[4-[[1-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]thio]-1-methylethyl]thio]-2,6-bis(1,1-dimethylethyl)phenoxy]acetic acid] is a novel, orally active, phenolic antioxidant and anti-inflammatory compound with antirheumatic properties. To elucidate its anti-inflammatory mechanisms, we evaluated AGIX-4207 for a variety of cellular, biochemical, and molecular properties. AGIX-4207 exhibited potent antioxidant activity toward lipid peroxides in vitro and displayed enhanced cellular uptake relative to a structurally related drug, probucol. This resulted in potent inhibition of cellular levels of reactive oxygen species in multiple cell types. AGIX-4207 selectively inhibited tumor necrosis factor (TNF)-alpha-inducible levels of the redox-sensitive genes, vascular cell adhesion molecule-1 and monocyte chemoattractant protein-1, with less inhibition of E-selectin, and no effect on intracellular adhesion molecule-1 expression in endothelial cells. In addition, AGIX-4207 inhibited cytokine-induced levels of monocyte chemoattractant protein-1, interleukin (IL)-6, and IL-8 from endothelial cells and human fibroblast-like synoviocytes as well as lipopolysaccharide-induced release of TNF-alpha, IL-1beta, and IL-6 from human peripheral blood mononuclear cells. AGIX-4207 did not inhibit TNF-alpha-induced nuclear translocation of nuclear factor of the kappa-enhancer in B cells (NF-kappaB), suggesting that the mechanism of action is independent of this redox-sensitive transcription factor. Taken together, these results provide a mechanistic framework for understanding the anti-inflammatory and antirheumatic activity of AGIX-4207 and provide further support for the view that inhibition of redox-sensitive inflammatory gene expression is an attractive approach for the treatment of chronic inflammatory diseases.

Discovery of Novel Phenolic Antioxidants as Inhibitors of Vascular Cell Adhesion Molecule-1 Expression for Use in Chronic Inflammatory Diseases

Vascular cell adhesion molecule-1 (VCAM-1) mediates recruitment of leukocytes to endothelial cells and is implicated in many inflammatory conditions. Since part of the signal transduction pathway that regulates the activation of VCAM-1 expression is redox-sensitive, compounds with antioxidant properties may have inhibitory effects on VCAM-1 expression. Novel phenolic compounds have been designed and synthesized starting from probucol (1). Many of these compounds demonstrated potent inhibitory effects on cytokine-induced VCAM-1 expression and displayed potent antioxidant effects in vitro. Some of these derivatives (4o, 4p, 4w, and 4x) inhibited lipopolysaccharide (LPS)-induced secretion of pro-inflammatory cytokines such as tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), and IL-6 from human peripheral blood mononuclear cells (hPBMCs) in a concentration-dependent manner in vitro and showed antiinflammatory effects in an animal model. Compounds 4ad and 4ae are currently in clinical trials for the treatment of rheumatoid arthritis (RA) and prevention of chronic organ transplant rejection, respectively.

Sphingosine kinase-1 mediates TNF-α-induced MCP-1 gene expression in endothelial cells: upregulation by oscillatory flow

Atherosclerosis is a focal inflammatory disease and preferentially occurs in areas of low fluid shear stress and oscillatory flow, whereas the risk of atherosclerosis is decreased in regions of high fluid shear stress and steady laminar flow. Sphingosine kinase-1 (SphK1) catalyzes the conversion of sphingosine to sphingosine-1 phosphate (S1P), a sphingolipid metabolite that plays important roles in angiogenesis, inflammation, and cell growth. In the present study, we demonstrated that exposure of human aortic endothelial cells to oscillatory flow (shear stress, ±5 dyn/cm2for 48 h) resulted in a marked increase in SphK1 mRNA levels compared with endothelial cells kept in static culture. In contrast, laminar flow (shear stress, 20 dyn/cm2for 48 h) decreased SphK1 mRNA levels. We further investigated the role of SphK1 in TNF-α-induced expression of inflammatory genes, such as monocyte chemoattractant protein-1 (MCP-1) and VCAM-1 by using small interfering RNA (siRNA) specifically for SphK1. Treatment of endothelial cells with SphK1 siRNA suppressed TNF-α-induced increase in MCP-1 mRNA levels, MCP-1 protein secretion, and activation of p38 MAPK. SphK1 siRNA also inhibited TNF-α-induced cell surface expression of VCAM-1, but not ICAM-1, protein. Exposure of endothelial cells to S1P led to an increase in MCP-1 protein secretion and MCP-1 mRNA levels and activation of NF-κB-mediated transcriptional activity. Treatment of endothelial cells with the p38 MAPK inhibitor SB-203580 suppressed S1P-induced MCP-1 protein secretion. These data suggest that SphK1 mediates TNF-α-induced MCP-1 gene expression through a p38 MAPK-dependent pathway and may participate in oscillatory flow-mediated proinflammatory signaling pathway in the vasculature.

Discovery of novel heteroaryl-substituted chalcones as inhibitors of TNF-α-induced VCAM-1 expression

Novel chalcone derivatives have been discovered as potent inhibitors of TNF-alpha-induced VCAM-1 expression. Thienyl or benzothienyl substitution at the meta-position of ring B helps boost potency while large substitution at the para-position on ring B is detrimental. Various substitutions are tolerated on ring A. A lipophilicity-potency relationship has been observed in several sub-series of compounds.

Selective Inhibition of Endothelial and Monocyte Redox-Sensitive Genes by AGI-1067: A Novel Antioxidant and Anti-Inflammatory Agent

Atherosclerosis is a disease of oxidative stress and inflammation. AGI-1067 [butanedioic acid, mono[4-[[1-[[3,5-bis(1,1-dimethylethyl)-4-,hydroxyphenyl]thio]-1-methylethyl]thio]-2,6-bis (1,1-dimethylethyl)phenyl] ester] is a metabolically stable derivative of, yet pharmacologically distinct from, the antioxidant drug probucol. It is a member of a novel class of orally active, antioxidant, anti-inflammatory compounds termed vascular protectants and exhibits antiatherosclerotic properties in multiple animal models and in humans. To elucidate its antiatherosclerotic mechanisms, we have evaluated several cellular and molecular properties of AGI-1067 in vitro. AGI-1067 exhibited potent lipid peroxide antioxidant activity comparable with probucol yet demonstrated significantly enhanced cellular uptake over that observed with probucol. AGI-1067, but not probucol, inhibited basal levels of reactive oxygen species (ROS) in cultured primary human endothelial cells and both basal and hydrogen peroxide-induced levels of ROS in the promonocytic cell line, U937. Furthermore, AGI-1067 inhibited the inducible expression of the redox-sensitive genes, vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1, in endothelial cells as well as tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1beta, and IL-6 production in peripheral blood mononuclear cells, whereas probucol had no effect. cDNA array hybridization experiments demonstrated that AGI-1067 selectively inhibited the expression of only a subset of TNF-alpha-responsive and nuclear factor-kappaB (NF-kappaB)-inducible genes in endothelial cells. The inhibitory effect of AGI-1067 on inducible VCAM-1 gene expression occurred at the transcriptional level, yet AGI-1067 had no effect on the activation of the redox-sensitive transcription factor NF-kappaB. These studies suggest that the anti-inflammatory and antiatherosclerotic properties of AGI-1067 may be due to selective inhibition of redox-sensitive endothelial and monocyte inflammatory gene expression. These studies provide a molecular basis for understanding the mechanism of action of this new class of therapeutic antiatherosclerotic compounds.

AGI-1067: a multifunctional phenolic antioxidant, lipid modulator, anti-inflammatory and antiatherosclerotic agent

To explore the therapeutic efficacy and potential mechanisms of action of a new class of antiatherosclerotic drugs, AGI-1067 [mono[4-[[1-[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]thio]-1-methylethyl]thio]-2,6-bis(1,1-dimethylethyl)phenyl] ester] (butanedioc acid) was tested in several animal models of atherosclerosis. AGI-1067, a novel phenolic antioxidant, was well tolerated in a 1-year study in hypercholesterolemic cynomolgus monkeys. It lowered low-density lipoprotein cholesterol (LDLc) by 41 and 90% at oral doses of 50 and 150 mg/kg, respectively and increased high-density lipoprotein cholesterol (HDLc) by 107% at the higher dose. In contrast, another phenolic antioxidant, probucol, had a modest LDLc-lowering effect (15% at 250 mg/kg) while decreasing HDLc (37% at 150 mg/kg). Histopathology of the aortas and coronary arteries revealed no atherosclerosis in the AGI-1067 (150 mg/kg) group and minimal-to-moderate atherosclerosis in the vehicle and probucol (150 mg/kg) groups. AGI-1067 also inhibited atherosclerosis in LDL receptor-deficient (LDLr -/-) mice and apolipoprotein E-deficient (ApoE -/-) mice even in the absence of a lipid-lowering effect. In LDLr -/- mice, AGI-1067 reduced aortic atherosclerosis by 49%. In ApoE -/- mice, AGI-1067 reduced atherosclerosis by 25, 41, and 49% in the arch, thoracic, and abdominal regions of the aorta. AGI-1067 also reduced vascular cell adhesion molecule-1 (VCAM-1) and monocyte chemoattractant protein-1 (MCP-1) mRNA levels in lungs of lipopolysaccharide-stimulated mice. At the cellular level, AGI-1067 inhibited tumor necrosis factor-alpha-inducible expression of VCAM-1, MCP-1, and E-selectin in human aortic endothelial cells (IC50 values = 6, 10, and 25 microM, respectively). These data show that AGI-1067 can inhibit atherosclerosis not only via its lipid-lowering effects but also by having direct anti-inflammatory effects on the vessel wall and suggest that it may be a novel therapeutic agent for coronary artery disease.

Chemistry and pharmacology of vascular protectants: a novel approach to the treatment of atherosclerosis and coronary artery disease

This review addresses the role of oxidative stress in the pathology of atherosclerosis and why it is now believed that atherosclerosis is not only a disease of oxidative stress but also of chronic inflammation. Perhaps more importantly, this review also describes the vascular protectant (V-protectant) technology platform originated at AtheroGenics, Inc., from which a series of inhibitory compounds has emerged to treat a number of chronic inflammatory diseases, including atherosclerosis. In atherosclerosis, these drugs not only act as antioxidants, but also as lipid modulators, inhibitors of inflammation, and inhibitors of gene expression. It is also important to understand the basis for considering vascular cell adhesion molecule-1 (VCAM-1) as a reduction-oxidation-sensitive protein, which has a key role in the early phases of atherosclerosis. The review concludes with a description of the design and chemistry of AtheroGenics' lead clinical development compound, AGI-1067, and an analysis of its preclinical in vitro and in vivo profile. AGI-1067 is a novel, potent antioxidant with anti-inflammatory properties. It inhibits gene expression of VCAM-1 and monocyte chemoattractant protein-1, decreases low-density lipoprotein cholesterol levels, and prevents atherosclerosis in a number of animal models. AGI-1067 is currently undergoing clinical trials as an antiatherosclerotic agent.

Laminar flow induction of antioxidant response element-mediated genes in endothelial cells. A novel anti-inflammatory mechanism

Atherosclerotic lesions preferentially develop in areas of the vasculature exposed to nonlaminar blood flow and low fluid shear stress, whereas laminar flow and high fluid shear stress are athero-protective. We have identified a set of genes including NAD(P)H:quinone oxidoreductase-1 (NQO1), heme oxygenase-1 (HO-1), ferritin (heavy and light chains), microsomal epoxide hydrolase, glutathione S-transferase, and gamma-glutamylcysteine synthase, whose expression is induced by exposure to prolonged physiological levels of steady laminar flow (shear stress = 20 dyn/cm(2)) in endothelial cells (EC). These genes contain an antioxidant response element (ARE) or ARE-like transcriptional regulatory sequence in their promoters and generally function to protect cells against oxidant stress. We demonstrate that exposure of EC to laminar flow activates ARE-mediated transcriptional activity. Mutation of the ARE from either the NQO1 or HO-1 promoter abolished laminar flow-induced NQO1 and HO-1 transcriptional activation. Expression of antisense Nrf2 (a transcriptional factor for ARE), a dominant negative Nrf2, or the cytoplasmic inhibitor of Nrf2 (Keap1/INrf2) inhibited laminar flow-induced NQO1 promoter activation in EC. In addition, expression of NQO1 or Nrf2 inhibited tumor necrosis factor-alpha-induced activation of VCAM-1 (vascular cell adhesion molecule-1) gene expression in EC. These data define the ARE as a novel endothelial shear stress response element. Furthermore, laminar flow activation of antioxidant genes via an ARE-dependent transcriptional mechanism may represent a novel athero-protective and anti-inflammatory mechanism in the vasculature.

Novel phenolic antioxidants as multifunctional inhibitors of inducible VCAM-1 expression for use in atherosclerosis

A series of novel phenolic compounds has been discovered as potent inhibitors of TNF-alpha-inducible expression of vascular cell adhesion molecule-1 (VCAM-1) with concurrent antioxidant and lipid-modulating properties. Optimization of these multifunctional agents led to the identification of 3a (AGI-1067) as a clinical candidate with demonstrated efficacies in animal models of atherosclerosis and hyperlipidemia.

Generic values for soil-to-plant transfer factors of radiocesium

There is a need for soil-to-plant transfer factors of radionuclides that take into account all possible crops on all soil varieties to support dose assessment studies. Because only limited experimental data exist for worldwide soil systems, such values should necessarily have a generic character. This paper describes a generic system for 137Cs, mainly based on a reference soil-to-plant transfer factor which depends solely on soil properties such as nutrient status, exchangeable K-content, pH and moisture content. Crops are divided into crop groups, cereals serving as reference group. The transfer of other crop groups can be calculated by multiplying data for cereals by a conversion factor. Existing data present in the IUR (International Union of Radioecologists) databank and in large part the work of a FAO (Food and Agriculture Organisation)/IAEA(International Atomic Energy Agency)/IUR project on tropical systems provided the basis for the derivation of the conversion factors and reference values.

Pharmacological evidence for tumor necrosis factor as a mediator of allergic inflammation in the airways

Tumor necrosis factor (TNF) has been implicated in the pathophysiology of a number of inflammatory diseases of the lung. Using the TNF receptor fusion protein, Ro 45-2081, our study investigated the involvement of TNF in allergic inflammatory responses in the airways of sensitized guinea pigs and Brown-Norway rats. Sensitized guinea pigs exhibited an enhanced airway reactivity to substance P (1-10 micrograms/kg, i.v.) at 6 hr after antigen challenge which was inhibited (P < .05) by Ro 45-2081 (3 mg/kg, i.p.). Treatment with Ro 45-2081 (1-3 mg/kg, i.p.) dose-dependently inhibited (P < .05) the accumulation of neutrophils and total cells in bronchoalveolar lavage fluid in sensitized guinea pigs examined at 6 and 24 hr postchallenge. Ro 45-2081 (3 mg/kg, i.p.) also significantly (P < .05) reduced the number of eosinophils in bronchoalveolar lavage at both time points whereas a lower dose (1 mg/kg, i.p.) had no effect. Ro 45-2081 (1 or 3 mg/kg, i.p.) abolished antigen-induced microvascular leakage (quantified by tissue content of Evans blue dye) in the trachea and main bronchi in sensitized guinea pigs. In the Brown-Norway rat, Ro 45-2081 (1-3 mg/kg, i.p.) caused a dose-dependent inhibition of neutrophil and eosinophil infiltration into bronchoalveolar lavage fluid at 24 hr after antigen challenge. In both guinea pig and Brown-Norway rat models, treatment with dexamethasone (30 mg/kg, i.p., for guinea pig and 0.3 mg/kg, i.p., for Brown-Norway rat) produced virtually identical results to those obtained with Ro 45-2081. The ability of Ro 45-2081 to inhibit antigen-induced responses in sensitized animals suggests that TNF is a mediator of allergic inflammation in the lung.

Suitability of enalapril as a probe of the dipeptide transporter system: in vitro and in vivo studies

PURPOSE

Previous in situ and in vitro studies indicated that the intestinal absorption of enalapril is a saturable carrier-mediated process via the dipeptide transporter system (DTS); however, the oral absorption of enalapril has not been reported to be a saturable process in vivo. Our objectives were to: 1) evaluate the suitability of enalapril as a probe of the DTS, and 2) compare various experimental models as they pertain to studying the DTS.

METHODS

The in vitro uptake of enalapril by rat intestinal rings and permeability across Caco-2 cells were studied as a function of concentration and in the presence of compounds that are known substrates of the DTS. The effect of enalapril on the uptake of [3H]-glycyl-L-proline (gly-L-pro) by Caco-2 cells was also examined. In vivo studies were conducted in rats (1 to 50 mg/kg) and dogs (0.06 to 6 mg/kg) to evaluate the oral absorption of enalapril over a wide dose range.

RESULTS

In vitro intestinal uptake/permeability of enalapril was not saturable nor inhibited by beta-lactam antibiotics, gly-L-pro, or SQ-29852. Moreover, a 20,000-fold molar excess of enalapril did not inhibit the uptake of [3H]-gly-L-pro by Caco-2 cells. The in vivo studies in rats and dogs did not demonstrate saturable absorption.

CONCLUSIONS

The present in vitro and in vivo results indicated that enalapril is primarily absorbed by a non-saturable, passive diffusion process and it is not a suitable model compound for studying the DTS.

Effects of Ro 47-0203 on endothelin-1 and sarafotoxin S6c-induced contractions of human bronchus and guinea-pig trachea

Endothelin exerts a variety of biological effects in the lung which indicate that this peptide may have a role in the pathophysiology of a number of pulmonary diseases. In this study, the endothelin receptors on the human bronchus were compared with those on the guinea-pig trachea using the novel, non-peptide antagonist Ro 47-0203 (4-tert-butyl-N-[6-(2-hydroxy-ethoxy)-5-(2-methoxy-phenoxy)-2,2' -bipyrimidin-4-yl]-benzenesulphonamide, non-selective for endothelin ETA over endothelin ETB receptor) and the peptide antagonist BQ123 (cyclo(-D-Val-Leu-D-Trp-D-Asp-Pro), endothelin ETA receptor selective). On the human bronchus and guinea-pig trachea, the concentration-effect curve for endothelin-1 was shifted to the right by Ro 47-0203 (100 microM) with concentration ratios of 28.2 +/- 6.8 and 39.5 +/- 13.9, respectively but lower concentrations of the antagonist had no effect. Although the concentration-effect curve for sarafotoxin S6c on the human bronchus was shifted to the right by Ro 47-0203 (30 and 100 microM, concentration ratio: 6.88 +/- 1.72 and 69.7 +/- 17.2, respectively), equivalent degrees of inhibition could be obtained on guinea-pig trachea with lower concentrations of antagonist (10 and 30 microM, concentration ratio: 6.90 +/- 1.58 and 75.8 +/- 14.1 respectively). The lack of effect of BQ123 (10 microM) and the high concentrations of Ro 47-0203 needed to show antagonism indicate that endothelin receptors on both tissues are probably the endothelin ETB subtype. Although the antagonism by Ro 47-0203 is not classically competitive, the greater effect of Ro 47-0203 against sarafotoxin S6c on the guinea-pig trachea may reflect a difference between the endothelin ETB receptors on these tissues.

Inhibition of Sephadex-induced lung injury in the rat by Ro 45-2081, a tumor necrosis factor receptor fusion protein

Tumor necrosis factor (TNF) is an inflammatory cytokine produced by many cell types which may contribute to the pathophysiology of a variety of lung diseases. In this study we have used Ro 45-2081 (a soluble receptor composed of the human p55 TNF receptor and human heavy-chain immunoglobulin G) to explore the role of TNF in the acute inflammatory response in the rat lung to intravenous injection of Sephadex beads. The effects of Ro 45-2081 have also been compared with those of dexamethasone. At 24 and 72 h after Sephadex, there was a significant increase in the total number of leukocytes in bronchoalveolar lavage fluid (BALF). At 24 h, the number of neutrophils comprised around 50% of the total leukocyte number, decreasing to around 10% of total by 72 h. The eosinophil count was maintained at around 10% of the total leukocyte number. Pretreatment with either Ro 45-2081 [1 and 3 mg kg-1, intraperitoneally (i.p.)] or dexamethasone (0.1 and 0.3 mg kg-1, i.p.) inhibited the neutrophilia at 24 h after Sephadex, although Ro 45-2081 had no significant effect on total cell number. At 72 h after Sephadex, Ro 45-2081 (1 and 3 mg kg-1, i.p., daily) significantly reduced the neutrophil influx into BALF but had no inhibitory effect on eosinophil number. In contrast, dexamethasone (0.1 and 0.3 mg kg-1, i.p., daily) virtually abolished the infiltration of neutrophils and eosinophils into BALF. The lack of effect of Ro 45-2081 on eosinophil infiltration into the rat lung and the inhibition caused by dexamethasone suggest that factors other than TNF are involved in this part of the inflammatory response induced by Sephadex. However, the inhibitory effects of Ro 45-2081 show that TNF may play an important role in the recruitment of neutrophils into the lungs of Sephadex-treated rats.

Design and development of a vasoactive intestinal peptide analog as a novel therapeutic for bronchial asthma

Analogs of vasoactive intestinal peptide (VIP) were synthesized and screened as bronchodilators with the ultimate goal of enhancing the potency and extending the duration of action of the native peptide. Several design approaches were applied to the problem. First, the amino acid residues required for receptor binding and activation were identified. A model of the active pharmacophore was developed. With knowledge of the secondary structure (NMR) of the peptide, various analogs were synthesized to stabilize alpha-helical conformations. Having achieved a level of enhanced bronchodilator potency, our approach then concentrated on identification of the sites of proteolytic degradation and synthesis of metabolically-stable analogs. Two primary cleavage sites on the VIP molecule were identified as the amide bonds between Ser25-Ile26 and Thr7-Asp8. This information was used to synthesize cyclic peptides which incorporated disulfide and lactam ring structures. Analog work combined the best multiple-substitution sites with potent cyclic compounds which resulted in identification of a cyclic lead peptide. This compound, Ro 25-1553, exhibited exceptionally high potency, metabolic stability, and a long duration of action and may be an effective therapeutic for the treatment of bronchospastic diseases.

Ro 25-1553: a novel, long-acting vasoactive intestinal peptide agonist. Part I: In vitro and in vivo bronchodilator studies

Ro 25-1553, a cyclic peptide analog of vasoactive intestinal peptide (VIP), was designed to overcome many of the deficiencies inherent in this natural neuropeptide. On isolated guinea pig tracheal smooth muscle, Ro 25-1553 produces concentration-dependent relaxation of contractile responses to a number of different spasmogens. Depending on the contractile stimulus, Ro 25-1553 is 24 to 89 times more potent than VIP as a relaxant of guinea pig trachea. The high potency of Ro 25-1553 extends to studies on isolated, histamine-contracted, human bronchial smooth muscle, where Ro 25-1553 exhibits a 390-fold enhancement over native VIP and is more potent than other bronchodilating drugs, such as the beta 2-adrenoceptor agonists isoproterenol and salbutamol. Ro 25-1553 was shown to displace the radioligand 125I-VIP from rat forebrain membranes with an IC50 value of 4.98 nM, thereby demonstrating that it acts at a VIP receptor. In addition, when tested in a battery of 40 other binding assays (e.g., muscarinic, histamine, LTs, Ca++, TxA2, endothelin, alpha and beta adrenergic, platelet-activating factor, neurokinins, etc.) at concentrations as high as 10 microM, Ro 25-1553 was found to be inactive; thus it appears to be specific for VIP receptors. The potent smooth muscle relaxant activity exhibited in vitro by Ro 25-1553 is also evident after in vivo intratracheal administration or aerosolization of the compound. Pulmonary responses evoked by histamine, leukotriene D4, platelet-activating factor and acetylcholine are inhibited dose-dependently by intratracheally instilled Ro 25-1553 with nearly identical potency (ED50 values ranging from 0.07 micrograms to 0.26 micrograms).(ABSTRACT TRUNCATED AT 250 WORDS)

Ro 25-1553: a novel, long-acting vasoactive intestinal peptide agonist. Part II: Effect on in vitro and in vivo models of pulmonary anaphylaxis

Studies were conducted to compare the effect of native vasoactive intestinal peptide (VIP), Ro 25-1553 (a cyclic peptide analog of VIP) and salbutamol (a beta2-adrenoceptor agonist) on antigen-induced pathophysiological effects in the guinea pig. Ro 25-1553 and salbutamol (0.01-1.0 microM) prevented antigen-induced contractions of the guinea pig trachea in vitro with IC50 values of 0.07 and 0.05 microM, respectively. VIP (0.01-1.0 microM) had no effect on antigen-induced tracheal contractions. Aerosolized Ro 25-1553 and salbutamol were equipotent in preventing antigen-induced increases in guinea pig lung resistance (IC50 value = 0.0001%), whereas aerosolized VIP (0.1%) was ineffective. Ro 25-1553 (0.1-100 micrograms), instilled intratracheally 2 min before the antigen challenge of buffer-perfused lungs from sensitized guinea pigs, produced a dose-dependent inhibition of bronchoconstrictor, vasoconstrictor and edemagenic responses, whereas intratracheal VIP (100 micrograms) had no effect. Intratracheal salbutamol (0.1-100 micrograms) inhibited antigen-induced responses in a manner comparable to Ro 25-1553. Lung inflammation was assessed as leukocyte accumulation in bronchoalveolar lavage fluid after the antigen provocation. Aerosolized antigen-induced bronchoalveolar lavage eosinophilia (13-fold increase over saline controls) at 6 hr after challenge was prevented in a concentration-dependent manner by pretreatment with nebulized Ro 25-1553 and salbutamol, but not by pretreatment with native VIP. These results indicate that Ro 25-1553 suppresses various pathophysiological features associated with pulmonary anaphylaxis and asthma, including airway reactivity, edema formation and granulocyte accumulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Differential antagonism of airway contractile responses to prostaglandin (PG)D2 and 9 alpha, 11 beta-PGF2 by atropine, SK&F 88046 and SQ 29,548 in the guinea pig

PGD2, the predominant prostanoid released from activated human lung mast cells, is metabolized to 9 alpha, 11 beta-PGF2 by an 11-ketoreductase. Both prostanoids contract mammalian airway smooth muscle. In the present study, aerosol administration of PGD2 or 9 alpha, 11 beta-PGF2 (five puffs of 10-50 micrograms/ml) to anesthetized, spontaneously breathing guinea pigs produced significant increases in airway resistance and decreases in dynamic lung compliance. The changes in airway resistance and dynamic lung compliance induced by 50 micrograms/ml were reduced approximately 60% and 25%, respectively, by pretreatment with atropine (1 mg/kg, i.v., -10 min). Pretreatment with the TxA2 receptor antagonist SK&F 88046 (N,N'-bis[7-(3-chlorobenzene aminosulfonyl)-1,2,3,4- tetrahydroisoquinolyl]disulfonylimide) (5 mg/kg, i.v., -10 min), nearly abolished the changes in airway resistance and dynamic lung compliance that were elicited by both agonists. Pretreatment with a TxA2 synthase inhibitor, CGS 13080 (10 mg/kg, i.v., -10 min), had no effect on PGD2- or 9 alpha, 11 beta-PGF2-induced bronchoconstriction, suggesting that these prostanoids did not provoke the release of TxA2. In vitro, PGD2, 9 alpha, 11 beta-PGF2 and a TxA2 mimic, U-44069, produced concentration-dependent contractions of the guinea pig isolated trachea with pD2s of 6.4, 6.0 and 7.2, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

SK&F 104353, a selective leukotriene receptor antagonist, inhibits leukotriene D4- and antigen-induced bronchoconstriction in cynomolgus monkeys

The ability of SK&F 104353 to prevent and reverse leukotriene (LT) D4- and antigen (Ag)-induced bronchoconstriction was examined in anesthetized, spontaneously breathing cynomolgus monkeys. Aerosol administration of LTD4 (10 micrograms/ml; 20 breaths) produced a sustained increase in pulmonary resistance and decrease in dynamic lung compliance. Aerosolized SK&F 104353 (150 breaths, 0.3 or 4.4 mg/ml) administered 15 min prior to LTD4 challenge antagonized these changes in a dose-dependent manner. When given intravenously 6 min after LTD4, SK&F 104353 (5 mg/kg) rapidly and completely reversed the ongoing bronchoconstriction. In mepyramine-pretreated (2 mg/kg i.v.) monkeys sensitive to aerosolized Ascaris suum Ag, intravenously administered SK&F 104353 (5 mg/kg) substantially reversed, but did not abolish, Ag-induced bronchoconstriction when administered 12 min after the Ag challenge. In contrast, SK&F 104353 (5 mg/kg i.v.) did not reverse Ag-induced bronchoconstriction in animals that had not been pretreated with mepyramine. Similar results were obtained when SK&F 104353 (20 mg/kg i.v.) was administered (as a pretreatment) 5 min prior to Ag under these conditions. Thus, SK&F 104353 reduced Ag-induced bronchoconstriction in mepyramine-pretreated monkeys, but had little effect in the absence of mepyramine. The data suggest that LTs, in addition to histamine, play a role in allergic bronchoconstriction in cynomolgus monkeys.

Inflammatory mediators of experimental colitis in rats

Colonic inflammation was induced in rats by intracolonic administration of 0.25 ml of 50% ethanol containing 30 mg of trinitrobenzene sulfonic acid (TNB). Control rats were treated with 0.25 ml of 50% ethanol or with 30 mg of TNB in 0.25 ml of saline. After 24 h, mucosal ulceration and hemorrhage were observed in TNB/ethanol-, 50% ethanol-, and to a lesser extent, in TNB/saline-treated rats. After 1 wk, mucosal damage was completely resolved in the 50% ethanol and TNB/saline-treated rats but the lesions in the TNB/ethanol-treated rats persisted and progressed to a chronic active inflammatory process after 3 wk. Myeloperoxidase activity was significantly elevated in mucosal scrapings from all treatment groups at all time intervals when macroscopic and microscopic mucosal injury was evident. Interleukin-1 was found to be the most sensitive indicator of mucosal inflammation, and its mucosal values correlated with myeloperoxidase activity. Leukotriene B4 was increased in control rats at 1 wk and in TNB/ethanol-treated rats at all time intervals. The maximal increase in leukotriene B4 was observed at 1 wk. Thromboxane B2 generation was reduced while platelet activating factor generation was not increased in TNB/ethanol-treated rats. These results indicate that in this TNB/ethanol model of gut inflammation, myeloperoxidase activity and interleukin-1 are reliable and sensitive indicators of colonic inflammation, and that thromboxane B2 is not involved in the acute lesions, whereas leukotriene B4 appears in the chronic active inflammatory response.

Interactive effects of peptidoleukotrienes and histamine on microvascular permeability and their involvement in experimental cutaneous and conjunctival immediate hypersensitivity

The involvement of peptidoleukotrienes (LTs) in mediating the increase in microvascular permeability associated with experimental cutaneous immediate hypersensitivity was studied by examining the effect of SK&F 104353, a potent and selective LT-antagonist, on the response evoked by graded, intradermal injections of antigen. SK&F 104353, employed at doses that profoundly blocked LTC4, LTD4 and LTE4 responses, significantly reduced the response produced by experimental cutaneous immediate hypersensitivity. The response to the lowest antigen dose (0.1 microgram) was, however, entirely insusceptible to SK&F 104353. The effect of SK&F 104353 was also examined in combination with a pyrilamine-cimetidine dosing regimen sufficient to remove the histaminergic component of cutaneous immediate hypersensitivity. The non-histaminergic component associated with higher antigen doses (10 and 100 micrograms) was significantly reduced but not abolished by SK&F 104353; the non-histaminergic component associated with low antigen doses (0.1 and 1 microgram) was not susceptible to SK&F 104353. Thus, the increase in cutaneous microvascular permeability evoked by immediate hypersensitivity appears to comprise three components: (1) A histaminergic response apparent for all antigen doses; (2) a LT-mediated component which is manifest in response to high antigen doses; (3) a third, unidentified component that is present for the entire antigen dose-range but contributes less to the overall response when high antigen doses are used. A distinct non-histaminergic, non-leukotriene mediated component was not a feature of conjunctival immediate hypersensitivity. SK&F 104353 administered in combinatio with pyrilamine-cimetidine virtually abolished the response with a small residual remaining only for the highest antigen dose. In further contrast to cutaneous immediate hypersensitivity, SK&F 104353 alone was comparatively ineffective in type 1 allergic conjunctivitis. This difference in susceptibility to SK&F 104353 appears to reflect the type of histamine-LTD4 interactive effect on microvascular permeability. Histamine and LTD4 were additive in terms of cutaneous microvascular permeability. In the conjunctiva, histamine and LTD4 appeared mutually exclusive in that the level of response produced by the combination tended not to exceed that of the single component which caused the greater effect.

The bronchopulmonary pharmacology of SK&F 104353 in anesthetized guinea pigs: demonstration of potent and selective antagonism of responses to peptidoleukotrienes

The bronchopulmonary pharmacology of SK&F 104353 [2(S)-hydroxy-3(R)-[2(2-carboxyethyl)thio]-3[2-(8- phenyloctyl)phenyl]-propanoic acid], a potent and selective leukotriene (LT) receptor antagonist in vitro, was assessed in anesthetized, spontaneously breathing guinea pigs. Aerosol administration of SK&F 104353 (5-2000 micrograms/ml x 100 breaths) reduced in a concentration-dependent manner the response to a standard LTD4 challenge (4.33 micrograms/ml x 5 breaths) given 30 min later. Inhalation of a 2000 micrograms/ml solution abolished LTD4-induced bronchoconstriction for at least 2 hr. The i.v. administration of SK&F 104353 10 min before challenge antagonized LTD4-induced bronchoconstriction with an ID50 of 0.55 mumol/kg (0.25 mg/kg). Substantial antagonism of LTD4-induced bronchospasm was observed for at least 60 min after i.v. administration of 5 mumol/kg of SK&F 104353. Infusion of SK&F 104353 at various rates revealed that a steady-state plasma concentration of 0.125 microM (0.06 micrograms/ml) reduced LTD4-induced bronchoconstriction by 60%. In addition to preventing the response to LTD4, i.v. administered SK&F 104353 (10 mumol/kg) rapidly and completely reversed ongoing LTD4-induced bronchoconstriction. SK&F 104353 also was effective when given intraduodenally 1 hr before LTD4 challenge, although the ID50 (32 mumol/kg) was 60-fold greater than the i.v. ID50. Given intragastrically, 100 mumol/kg of SK&F 104353 abolished the response to LTD4 for 1 hr, and reduced the response for 6 hr. SK&F 104353 (20 mumol/kg i.v.) had no effect on the bronchoconstriction induced by aerosolized acetylcholine, histamine or U-44069, but did antagonize the response to LTC4. SK&F 104353 alone did not produce bronchoconstriction when administered by any route or dose.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of putative thromboxane receptor agonists and antagonists on rat small intestinal ion transport

Effects of a thromboxane mimic, U46619, on electrolyte transport were examined in vitro using stripped segments of rat ileal mucosa mounted in Ussing chambers. Addition of U46619 to the serosal bathing solution elicited a transient increase in short-circuit current (Isc) and decrease in transepithelial conductance (Gt). The increase in Isc was accompanied by a transient increase in Cl- secretion and decrease in Na+ absorption. In the steady-state, Isc was not increased whereas Gt remained decreased and Na+ and Cl- absorption were inhibited. Removal of Cl- or pretreatment with serosal and mucosal indomethacin (1 microM) or the thromboxane receptor antagonist, SK&F 88046, added to the serosal bathing solution, inhibited the increase in Isc stimulated by U46619 (apparent KB approximately 8 nM). The effects of U46619 on both Isc and Gt are qualitatively similar to those resulting from stimulation with leukotriene D4. However, the changes in Isc with leukotriene D4 (10 microM) are antagonized by SK&F 88046 only at high concentrations (1-10 microM). In addition, the secretagogues prostaglandin F2 alpha, lys-bradykinin, serotonin and histamine, produce qualitatively similar changes in Isc to those seen with U46619 without altering Gt. With the exception of prostaglandin F2 alpha, the effects of these secretagogues are not inhibited by SK&F 88046 (10 microM). These results indicate that U46619 acts at a thromboxane receptor to stimulate intestinal Cl- secretion and inhibit Na+ and Cl- absorption. These changes are inhibited selectively by the thromboxane receptor antagonist, SK&F 88046.

Effect of sulfidopeptide leukotrienes D4 and E4 on ileal ion transport in vitro in the rat and rabbit

Effects of leukotrienes D4 and E4 (LTD4 and LTE4) on electrolyte transport were examined, employing stripped segments of rat and rabbit ileum mounted in Ussing chambers. Addition of LTD4 or LTE4 to the serosal but not the mucosal bathing solution elicited a transient increase in short-circuit current (Isc) with maximal responses seen at 10(-5) M and 10(-8) M in rat and rabbit respectively and a sustained decrease in transepithelial conductance (Gt) in the rat only. In the rat, Cl replacement, reduction of bathing solution [Ca2+] to 1 microM or pretreatment with 1 microM indomethacin or meclofenamic acid inhibited the LTD4- or LTE4-induced Isc changes with no effect on the decrease in Gt. LTD4 (10 microM) transiently increased net Cl secretion and produced a sustained decrease in both unidirectional and net Na transport and mucosal-to-serosal Cl flux in rat ileum. The decrease in unidirectional Na fluxes is accounted for predominantly by a change in the potential independent flux of Na. These results suggest that the increase in Isc in both rat and rabbit is mediated by arachidonic acid metabolites, whereas the decrease in Gt and net Na absorption in rat ileum is mediated by a cyclooxygenase-independent pathway.

Flushing and haemodynamic responses to vasopressin peptides in the rhesus monkey

1. The mechanism of the flushing, hypotension and tachycardia associated with i.v. administration of desGlyd(CH2)5D-Tyr(Et)VAVP (SK&F 101926; 25 micrograms kg-1) and the selective V2 antidiuretic agonist, desamino-8-D-arginine vasopressin (dDAVP; 3 micrograms kg-1) was studied in ketamine-anaesthetized rhesus monkeys. 2. The flushing associated with SK&F 101926 was reduced by pretreatment with a mast cell stabilizer and by repeated administration of peptide (within 2-4 weeks). A similar desensitization to dDAVP-associated flushing was observed on repeated administration. 3. Treatment with dDAVP also resulted in reduced SK&F 101926-associated flushing. 4. The hypotension associated with SK&F 101926 was not affected by pretreatment with a mast cell stabilizer. A similar degree of hypotension was observed with repeated administration of either SK&F 101926 or dDAVP. 5. The tachycardia associated with SK&F 101926 was reduced by pretreatment with a mast cell stabilizer or repeated administration of SK&F 101926. Repeated administration of dDAVP, however, resulted in an enhanced tachycardia. 6. Indomethacin (5 mg kg-1 i.v.) did not alter the flushing or the hypotension associated with the administration of either SK&F 101926 or dDAVP, but resulted in an enhanced tachycardia to SK&F 101926. 7. Administration of a selective V1 vasopressor antagonist did not result in flushing, hypotension or tachycardia. 8. It was concluded that the flushing response to vasopressin-like peptides in rhesus monkeys may be due to an action on mast cells, whereas the haemodynamic responses are not, but probably involve direct vasodilator actions.

Effects of the thromboxane receptor antagonist SK&F 88046 in the canine, monkey and human coronary vasculature

U-46619, a stable "functional" thromboxane/endoperoxide receptor agonist, produced potent contractile responses in isolated canine, rhesus monkey and human left circumflex coronary arteries (EC50 = 9.11 x 10(-9)M, 1.98 x 10(-8)M and 3.50 x 10(-9)M, respectively). Canine intrapulmonary veins were also contracted potently by U-46619 (EC50 = 1.22 x 10(-9)M). SK&F 88046, a thromboxane A2 (TxA2) end-organ receptor antagonist, blocked the vasoconstrictor effects of U-46619 in the canine circumflex artery (KB = 1.33 x 10(-8)M), canine intrapulmonary vein (KB = 1.46 x 10(-9)M), monkey circumflex artery (KB = 8.47 x 10(-8)M), and human circumflex artery (KB = 8.49 x 10(-7)M). SK&F 88046 was 10-60 times more potent in the canine and rhesus monkey coronary vasculature than in the human coronary preparations. Intracoronary administration of U-46619 to anesthetized, open chest dogs produced a dose-related decrease in left circumflex coronary artery blood flow which resulted in decreases in left ventricular developed pressure, left ventricular positive and negative dP/dt, ascending aortic blood flow, and an increase in left ventricular end-diastolic pressure. The decrease in coronary blood flow and the hemodynamic changes were either attenuated or completely inhibited by i.v. administration of SK&F 88046 (2.5 mg/kg + 0.05 mg/kg/min or 5.0 mg/kg + 0.1 mg/kg/min). SK&F 88046 was compared to two other TxA2 receptor antagonists in canine isolated intrapulmonary veins. SQ 29,548 was approximately 2-times more potent than SK&F 88046 as an antagonist of U-44619 mediated contractions (KB = 7.0 x 10(-10)M). In contrast, BM 13.177 was 150-fold less potent (KB = 2.19 x 10(-7)M) than SK&F 88046. Thus, the present study demonstrates species variability in response to TxA2 agonists and antagonists and reconfirms the relative importance of species selection in studying these agents.

Beneficial effects of the peptidoleukotriene receptor antagonist, SK&F 104353, on the responses to experimental endotoxemia in the conscious rat

The purpose of this study was to examine the effects of the peptidoleukotriene receptor antagonist, SK&F 104353, on the responses to endotoxin in conscious male Sprague-Dawley rats. Administration of Salmonella enteritidis endotoxin (30 mg/kg i.v.; LD90) resulted in a decrease in the number of circulating platelets, leukopenia, an increase in hematocrit, and 0% survival at 24 hr. Pretreatment with SK&F 104353 (1 mg/kg, i.v. bolus followed by 3 mg/kg/hr, i.v. infusion for 6 hr) 5 min before injection of endotoxin produced steady state plasma drug levels of 1.6 micrograms/ml in naive animals and levels of approximately 3.4 micrograms/ml in endotoxemic animals (P less than 0.05). SK&F 104353 significantly attenuated the endotoxin-induced thrombocytopenia (P less than 0.05) but had no effect on either the endotoxin-induced early leukopenia or late leukocytosis. Additionally, SK&F 104353 significantly reduced the endotoxin-induced hemoconcentration (P less than 0.05) and improved survival to 30% at 48 hr (P less than 0.05). A higher dose of SK&F 104353 (2 mg/kg, i.v. bolus followed by 10 mg/kg/hr, i.v. infusion for 6 hr) did not produce any further benefit. These data indicate clearly the pathophysiologic role of peptidoleukotrienes in endotoxemia and suggest SK&F 104353 could be useful for ameliorating some of the deleterious sequelae associated with this condition.

Prevention and reversal of endotoxin-induced pulmonary hypertension by a leukotriene antagonist

We investigated the role of leukotrienes in endotoxin-induced changes in pulmonary circulation. In six conscious sheep, haemodynamic measurements were obtained for the calculation of pulmonary vascular resistance (PVR), along with measurements of arterial oxygen tension (PaO2), leucocyte count (WBC), thromboxane B2 (TxB2), 6-Keto-PgF1 alpha and PgF2 alpha, before and at predetermined intervals after a 10-min infusion of E. coli endotoxin (0.3 microgram/kg), with and without treatment with the leukotriene receptor antagonist, FPL-57231. Endotoxin caused a biphasic response (i.e., phase I = 0-1 h, phase II = 1.5-4 h), with a mean +/- SE increase in PVR to 415 +/- 112% of baseline during phase I and a lesser increase of 175% (range = 153-199%) of baseline during phase II. Mean +/- SE PaO2 decreased from 86 +/- 4 to 67 +/- 6 mmHg and WBC count decreased from 8.6 +/- 0.6 to 2.8 +/- 0.7 thousand/mm3 during phase I, whereas TxB2 increased from 145 +/- 28 to 3164 +/- 1082 pg/ml, 6-Keto-PgF1 alpha from 129 +/- 14 to 438 +/- 114 pg/ml and PgF2 alpha from 122 +/- 7 to 242 +/- 43 pg/ml. One hour infusion of FPL-57231 (1 mg/kg/min) administered prior to and throughout phase I attenuated the phase I increases in PVR without preventing the increases in TxB2; however, it partly attenuated 6-Keto-PgF1 alpha and enhanced generation of PgF2 alpha during phase I. Discontinuation of FPL-57231 was followed by an exaggerated response of PVR during phase II to an average of 209% of baseline (range = 186-235%).(ABSTRACT TRUNCATED AT 250 WORDS)

Prevention and reversal of endotoxin-induced pulmonary hypertension by a leukotriene antagonist

We investigated the role of leukotrienes in endotoxin-induced changes in pulmonary circulation. In six conscious sheep, haemodynamic measurements were obtained for the calculation of pulmonary vascular resistance (PVR), along with measurements of arterial oxygen tension (PaO2), leucocyte count (WBC), thromboxane B2 (TxB2), 6-Keto-PgF1 alpha and PgF2 alpha, before and at predetermined intervals after a 10-min infusion of E. coli endotoxin (0.3 microgram/kg), with and without treatment with the leukotriene receptor antagonist, FPL-57231. Endotoxin caused a biphasic response (i.e., phase I = 0-1 h, phase II = 1.5-4 h), with a mean +/- SE increase in PVR to 415 +/- 112% of baseline during phase I and a lesser increase of 175% (range = 153-199%) of baseline during phase II. Mean +/- SE PaO2 decreased from 86 +/- 4 to 67 +/- 6 mmHg and WBC count decreased from 8.6 +/- 0.6 to 2.8 +/- 0.7 thousand/mm3 during phase I, whereas TxB2 increased from 145 +/- 28 to 3164 +/- 1082 pg/ml, 6-Keto-PgF1 alpha from 129 +/- 14 to 438 +/- 114 pg/ml and PgF2 alpha from 122 +/- 7 to 242 +/- 43 pg/ml. One hour infusion of FPL-57231 (1 mg/kg/min) administered prior to and throughout phase I attenuated the phase I increases in PVR without preventing the increases in TxB2; however, it partly attenuated 6-Keto-PgF1 alpha and enhanced generation of PgF2 alpha during phase I. Discontinuation of FPL-57231 was followed by an exaggerated response of PVR during phase II to an average of 209% of baseline (range = 186-235%).(ABSTRACT TRUNCATED AT 250 WORDS)

Functional antagonism by salbutamol suggests differences in the relative efficacies and dissociation constants of the peptidoleukotrienes in guinea pig trachea

To assimilate information about the relative efficacies and affinities of the peptidoleukotrienes, the ability of the beta adrenoceptor agonist salbutamol to antagonize functionally contractions produced by leukotrienes (LT)C4, LTD4 and LTE4 was examined in the guinea pig trachea. There was a marked gradation in the sensitivity of LT-induced responses to antagonism by pretreatment with salbutamol (0.01-1.0 microM): LTC4 less than LTD4 less than LTE4. These data suggest marked differences in the receptor reserve for the LTs. However, this postulate is not supported by the finding that the magnitude of the ratio for the estimated dissociation constant, KA, and EC50 values, which provides an indirect measure of the relative receptor reserve, were similar: LTC4 = 4.50, LTD4 = 10.54 and LTE4 = 3.18. Substantial differences were apparent in the estimated KA values: LTC4 = 2.88 nM, LTD4 = 11.8 and LTE4 = 46.4 nM. In the presence of a maximally effective concentration of LTE4 (1 or 10 microM), addition of LTD4 (1 or 10 microM) produced further contraction of the tissue whereas the reverse was not the case. Furthermore, in the presence of salbutamol (70 nM), LTE4 (0.1 microM) produced a 3.6-fold rightward shift in LTD4 concentration-response curves with no effect on the maximum contractile response; a pKB of 7.42 was calculated for LTE4. The results suggest that the large differences in the ability of pretreatment with salbutamol to inhibit contractions produced by LTC4, LTD4 or LTE4 are not attributable solely to corresponding differences in receptor reserve for the individual LTs.(ABSTRACT TRUNCATED AT 250 WORDS)

Characterization of the conjunctival vasopermeability response to leukotrienes and their involvement in immediate hypersensitivity

The microvascular permeability response of the guinea pig conjunctiva to sulfidopeptide leukotrienes (LTs) was quantified as extravasation of radiolabeled bovine serum albumin. The LTs were potent inducers of increased microvascular permeability, with relative potencies LTE4 greater than or equal to LTD4 greater than LTC4. The response to LTs was unaffected by indomethacin or a pyrilamine/cimetidine combination, but the LT antagonists FPL 55712 and SKF 102922 significantly inhibited the response to LTC4, LTD4 and LTE4. In guinea pigs actively sensitized to ovalbumin, topical ocular administration of ovalbumin markedly increased conjunctival microvascular permeability; this response was reduced by approximately 50% following histaminergic blockade by pyrilamine/cimetidine. FPL 55712 and SKF 102922 and the 5-lipoxygenase inhibitor nordihydroguaiaretic acid (NDGA) had no effect on the response to antigen when used alone. However, each agent significantly reduced the non-histaminergic component of the response when given in conjunction with pyrilamine/cimetidine. Thus, it appears that the immediate hypersensitivity response in guinea pig conjunctiva has a possible non-histaminergic component which is at least partly mediated by LTs.

Regional differences in the reactivity of guinea-pig airways

Regional differences in the sensitivity of guinea-pig airways to cholinergic and beta-adrenoceptor stimulation as well as Schultz-Dale responses were studied in vitro. Carbachol and isoproterenol produced a 27% and 39% greater response, respectively, in the trachea as compared to the bronchus. Contractions to histamine in tracheal and bronchial tissues were significantly less than those evoked by carbachol (P less than 0.05); however, lung parenchymal strips did not show any difference in maximal contractility to these agonists. Responses to antigen in airways from sensitized guinea-pigs or responses to anaphylactic mediators, LTD4 and PGD2, in normal airways did not show any differences in maximum tissue contractility (trachea and bronchus). Among the airway tissues examined, lung parenchymal strips were more responsive to these mediators as compared to tracheal and bronchial tissues. Threshold and sub-threshold concentrations of LTD4 had no effect on tracheal and bronchial airway contractions to PGD2; however, PGD2-induced contractions of the lung parenchymal strip were significantly inhibited in the presence of LTD4 (P less than 0.0001). Our data suggest that: (1) considerable regional differences exist in the reactivity of guinea-pig airways; (2) the maximum responses of bronchial airways to cholinergic and beta-adrenergic stimuli appear less than that observed in the trachea; (3) small peripheral airways appear more responsive to some mediators of anaphylaxis than are the larger central airways. Therefore, it would appear that the trachea and bronchus are more responsive to cholinergic stimuli, while the lung parenchyma is more responsive to PGD2, LTD4 and also to in vitro anaphylaxis.(ABSTRACT TRUNCATED AT 250 WORDS)

Modulation of arachidonic acid metabolites as potential therapy of asthma

Bronchial asthma is a multifactorial disease characterized by reversible bronchoconstriction, airway hyperreactivity, oedema and excessive mucus production. Present therapy directed against specific mediators has not been overwhelmingly successful. Even though there exists a multiplicity of purported mediators, perhaps the key to better therapy is a vigorous understanding of the arachidonic acid cascade and investigations to modulate specific products of these pathways. Within the cyclooxygenase pathway an interesting scenario might be to effectively antagonize the potent bronchoconstrictive effects of prostaglandin (PG)D2 and its recently identified predominant metabolite, an 11-hydroxyl epimer, 9 alpha,11 beta-PGF2. PGD2 is the major cyclooxygenase product released from sensitized human lung and bronchoalveolar lavage (BAL) mast cells; it possesses a myriad of biological actions relevant to the pathogenesis of asthma. While no specific antagonists of PGD2 or 9 alpha,11 beta-PGF2 have been identified, some preliminary studies have suggested that, perhaps, PGD2 may be interacting, at least in part, with thromboxane receptors. In addition, peroxidation of arachidonic acid catalyzed by 5-lipoxygenase produces the leukotrienes, which are extremely potent bronchoconstrictors as well as oedema and mucus secretagogues. Leukotrienes are primary mast cell mediators which may be the vital link to both early (acute) and late (chronic) asthmatic attacks. Research seeking leukotriene antagonists has been intensive. Leading clinical candidates have emerged from Smith Kline and French, Lilly, Merck-Frosst, ICI-Stuart and other groups. However, we must await the outcome of ongoing clinical trials in asthmatics to determine just how important the leukotrienes really are in the pathogenesis of asthma, allergy and inflammation. Thus, modulation of the effects of products of arachidonic acid metabolism may provide a new and more specific treatment for bronchial asthma.

Pharmacologic profile of SK&F 104353: a novel, potent and selective peptidoleukotriene receptor antagonist in guinea pig and human airways

In this report, we describe the in vitro and in vivo pharmacologic profile of 2(S)-hydroxy-3(R)-[(2-carboxyethyl)thio]-3-[2-(8-phenyloctyl)pheny l]- propanoic acid (SK&F 104353) in guinea pig and human airways. In the isolated guinea pig trachea, SK&F 104353 was a potent, competitive antagonist of leukotriene (LT) D4-induced contractions (pA2 = 8.6). In contrast, SK&F 104353 produced little effect on LTC4 concentration-response curves under conditions where the bioconversion of LTC4 to LTD4 was inhibited. LTE4-induced contractions in guinea pig trachea were sensitive to inhibition by SK&F 104353 (pKB greater than 8.9). SK&F 104353 (10 microM) had no intrinsic contractile activity and was without effect on contractions produced by KCl, histamine, prostaglandin D2, platelet-activating factor or U-44069 in guinea pig trachea. Furthermore, unlike other purported LT antagonists, LT 171883 and FPL 55712, SK&F 104353 (30 microM) did not inhibit cyclic nucleotide phosphodiesterase activity measured in homogenates from canine tracheal smooth muscle. In the isolated human bronchus, SK&F 104353 produced concentration-dependent rightward shifts in LTD4 concentration-response curves and, unlike in guinea pig trachea, was an effective antagonist of LTC4-induced contractions with a pKB of 8.0 to 8.4. This provides further evidence that, in contrast to guinea pig airways, responses produced by LTC4 and LTD4 in human bronchus appear to be mediated via the same LT receptor population. SK&F 104353 was also an effective antagonist of LTE4-induced responses in human bronchus (pKB greater than 8.2).(ABSTRACT TRUNCATED AT 250 WORDS)

Is the guinea pig trachea a good in vitro model of human large and central airways? Comparison on leukotriene-, methacholine-, histamine- and antigen-induced contractions

To analyze comprehensively the relevance of the guinea pig trachea as a model of human large and central airways, the contractile effects of the peptidoleukotrienes (LTs), histamine, methacholine and antigen on guinea pig and human airways were compared in vitro. Although some differences were apparent, LTC4, LTD4, LTE4, histamine and methacholine had comparable EC50 values and elicited similar maximal responses in both guinea pig trachea and human bronchus (second-seventh generation). In the presence of l-serine borate (45 mM), LTC4 concentration-response curves were shifted significantly to the left in guinea pig trachea but not in human bronchus. Furthermore, the LT receptor antagonists (SK&F 102922 and FPL 55712) had similar potencies against LTC4- and LTD4-induced contractions of human bronchus, whereas, in the guinea pig trachea, they were much more effective antagonists of responses produced by LTD4 than those elicited by LTC4. These results provide further evidence that, unlike in human bronchus, LTC4- and LTD4-induced contractions in the guinea pig trachea are mediated via distinct leukotriene receptors. Ovalbumin-induced contractions of actively sensitized guinea pig tracheae exhibited the same profile as anti-immunoglobulin E-induced contractions of the passively sensitized human bronchus. Furthermore, antigen-induced contractions in both the guinea pig trachea and human bronchus possessed a similar sensitivity to inhibition by mepyramine (10 microM) and the LT antagonists (10 microM), added either alone or in combination. These results indicate that the isolated guinea pig trachea is a suitable model of human large and central airways.

Effect of alpha-adrenoceptor stimulation of isolated canine, ferret and guinea pig airways

Functional responses and subtypes of alpha-adrenoceptors in canine trachealis smooth muscle were investigated using the agonists; epinephrine, norepinephrine, SK&F 89748 (alpha 1-selective) and BHT-933 (alpha 2-selective) in the presence of a beta-adrenoceptor antagonist. Tissue contractility to these agonists was in the range of 16 to 46% of the maximum response to serotonin. SK&F 89748 was most effective in canine airways; however, the contractions could be abolished by methysergide. Neither precontraction of the airways by KCl nor degree of beta-adrenoceptor blockade increased the reactivity of SK&F 89748 in this tissue. Reactivity of ferret and guinea pig airways to norepinephrine in the presence of beta-adrenoceptor blockade was insignificant. Responses of guinea pig airways to tyramine was about 1,000-fold less than those observed for vascular smooth muscle. Taken together these data suggest that alpha-adrenoceptors do not have any significance in the pathogenesis of airway hyperreactivity in dog, ferret and guinea pig airways. Moreover, adrenoceptors in guinea pig airways appear to be hormonal beta-adrenoceptors.

Inhibition of leukotriene D4-induced coronary vasoconstriction by leukotriene antagonists in the anesthetized dog

Anesthetized open-chest dogs were instrumented for the measurement of left circumflex coronary artery (LCX) blood flow and aortic blood flow, systemic arterial blood pressure, heart rate, lead II ECG, left ventricular end-diastolic pressure, left ventricular developed pressure and left ventricular positive and negative dP/dt to study the hemodynamic effects of leukotriene D4 (LTD4) and selective LTD4 antagonists on the coronary vasculature. Administration of LTD4 alone into the LCX (0.625-10 micrograms) produced a dose-dependent decrease in LCX blood flow, dP/dt and aortic blood flow and an increase in left ventricular end-diastolic pressure. Systemic arterial blood pressure, left ventricular developed pressure and heart rate were unchanged by LTD4. During i.v. infusions of the LTD4 antagonists, SK&F 102922 or FPL 55712 (1 mg/kg/min), the dose-dependent decreases in LCX flow, dP/dt and aortic blood flow were blocked whereas the increase in left ventricular end-diastolic pressure remained unchanged. The thromboxane A2 antagonist, SK&F 88046 (5 mg/kg + 0.1 mg/kg/min), which has been reported previously to block the coronary blood flow reducing action of LTC4, had no effect on the LCX blood flow responses to intracoronary LTD4. In a separate study, dogs instrumented in a similar manner were given bolus injections of arginine-vasopressin (1 microgram), the thromboxane A2 mimetic, U-46619 (10 micrograms), LTD4 (10 micrograms), angiotensin II (1 microgram) and prostaglandin F2 alpha (100 micrograms) directly into the LCX to provoke coronary vasoconstriction. SK&F 102922 and FPL 55712 selectively blocked the coronary vasoconstriction produced by LTD4, but had no effect on vasoconstriction produced by the other agonists.(ABSTRACT TRUNCATED AT 250 WORDS)

Enhancement of leukotriene D4-induced contraction of guinea-pig isolated trachea by platelet activating factor

The effect of platelet activating factor (PAF), a potent lipid mediator of inflammation, was examined in the induction of airway hyperreactivity to known mediators of anaphylaxis. Concentration-dependent contractions of the isolated guinea-pig trachea to PAF (10(-7)-10(-5) M) were produced and an EC50 value was found to be 7.5 X 10(-7) M. Pretreatment for 30 min with a known PAF inhibitor, CV-3988 (10(-5) or 10(-4) M), produced significant inhibition of PAF contractions; however, at 10(-6) M, CV-3988 had no effect. In the presence of meclofenamic acid (10(-6) M), the concentration-response curve to PAF was shifted significantly upward and to the left. This potentiation could be reversed by pretreating the tissues with the peptidoleukotriene antagonists, FPL 55712 or SK&F 102922 (10(-5) M). Pretreatment with PAF concentrations having essentially no intrinsic activity (10(-8), 10(-7)) significantly enhanced the contraction of guinea-pig trachea to various concentrations of LTD4 and to certain concentrations of a thromboxane mimic (U-46619). Pretreatment with lyso-PAF failed to potentiate the LTD4 response, while pretreatment with CV-3988 reverse the potentiation by PAF of the lower concentrations of LTD4. However, PAF failed to enhance contractions (with or without the presence of meclofenamic acid) to acetylcholine, histamine, PGD2 or LTC4 (in the presence of serine borate). These results indicate a possible role for PAF as a mediator of airway hyperreactivity.

Endotoxin-induced changes in pulmonary hemodynamics and respiratory mechanics. Role of lipoxygenase and cyclooxygenase products

We investigated the role of leukotrienes and cyclooxygenase products in endotoxin-induced pulmonary vascular and airway changes. In 11 conscious sheep, measurements of pulmonary vascular resistance (PVR), lung resistance (RL), arterial PO2, leukocyte count (WBC), and plasma thromboxane B2 (TxB2), 6-keto-PgF1 alpha and PgF2 alpha were obtained, before and at predetermined intervals after a 10-min infusion of E. coli endotoxin (0.3 microgram/kg). On a separate occasion, 5 sheep received an infusion of the leukotriene end-organ receptor antagonist FPL-57231 (0.7 to 1 mg/kg/min), before and for as long as 4 h after endotoxin infusion; and 6 sheep received a single injection of the cyclooxygenase inhibitor indomethacin (2 mg/kg) 1 h before endotoxin infusion. Endotoxin caused a biphasic response with an increase in mean PVR and RL to 441 and 353% of baseline, respectively, during the early phase (0 to 1 hr), and lesser increases to 168 and 195% of baseline during the late phase (1.5 to 4 h). These changes were associated with mild hypoxemia, marked leukopenia, and marked increases in plasma TxB2, 6-keto-PgF1 alpha and PgF2 alpha. The FPL-57231 completely blocked the endotoxin-induced changes in PVR, RL, and PaO2 during both phases without preventing the increases in TxB2; however, it partly attenuated the increases in 6-keto-PgF1 alpha and enhanced the generation of PgF2 alpha. Indomethacin, which blocked the endotoxin-induced increases in TxB2, 6-keto-PgF1 alpha, PgF2 alpha, and RL, only partly blocked the increase in PVR during the early phase, followed by an exaggerated increase of PVR during the late phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of alpha-adrenergic receptors in cartilaginous and non-cartilaginous human airways

An imbalance between the density of alpha- and beta-adrenergic receptors in airway smooth muscle has been suggested as one of the potential underlying mechanisms of bronchial asthma. Therefore, the present study was conducted to examine the presence and functional behavior of alpha-adrenoceptors in isolated human bronchi and bronchioles. Human airway tissues did not show any spontaneous tone during equilibration in physiological solution. Sensitivity of non-cartilaginous airways (8th generation and smaller) to histamine was approximately 3 times more than cartilaginous (2nd-7th generation) airways. In the presence of beta-adrenoceptor blockade, norepinephrine (3 X 10(-4) M) evoked approximately 14-40% of maximum histamine contraction in cartilaginous and non-cartilaginous airways from three donors. When tone in these tissues was elevated by pretreatment with histamine (10(-5) M), leukotriene D4 (10(-10) M), carbachol (1 X 10(-6) M-3 X 10(-6) M) or KCl (10(-2) M), the sensitivity to norepinephrine was potentiated. Airway tissue from one donor was found to be highly reactive to norepinephrine and the maximum contractions were 118 and 145% of maximum histamine contraction for cartilaginous and non-cartilaginous airways, respectively. Time to reach maximum contraction in cartilaginous airways was 80 min compared to 21 min for non-cartilaginous airways from the same donor. These data suggest that human airways contain contractile alpha-adrenoceptors in addition to relaxant beta-adrenoceptors, which haven been reported previously in the literature. Though activation of alpha-adrenoceptors induces contractions in human airway smooth muscle, the potency of norepinephrine for alpha-adrenoceptors in these airways is low compared to that reported for vascular smooth muscle.

Synthesis and structure-activity relationship studies of a series of 5-aryl-4,6-dithianonanedioic acids and related compounds: a novel class of leukotriene antagonists

A series of 5-alkynyl- and 5-aryl-4,6-dithianonanedioic acids and related compounds has been prepared for evaluation of leukotriene antagonist activity. The alkynyl compounds were prepared by thioacetal exchange from the corresponding acetylenic acetals. The aryl derivatives were synthesized from the appropriate benzaldehydes, most of which were prepared by one of three general routes: Meyers' oxazolin method, a palladium coupling procedure, and a hydroxybenzaldehyde alkylation. The analogues were examined in vitro for their ability to antagonize an LTD4-induced contraction of isolated guinea pig tracheal smooth muscle and to compete with [3H]LTD4 for receptor sites on guinea pig lung membrane. A number of structure-activity relationships have emerged from this study. There is an optimal chain length of 10-12 atoms (or its equivalent) in the lipid tail and two methylenes in the polar region. In the aromatic series, the ortho- and meta-substituted compounds have comparable activity, whereas the para derivatives are inactive. Substitution in the aromatic ring and lipid tail is generally well tolerated, with the terminal phenyl (6) and acetylene (33) analogues having especially good activity. Conformational restriction of either the polar region or lipid tail produced compounds devoid of activity. A number of selected analogues were also evaluated in vivo as antagonists of LTD4-induced bronchoconstriction in the guinea pig. The data established these compounds as a novel class of leukotriene antagonists with potential utility for the treatment of asthma and other immediate hypersensitivity diseases.

The effect of calcium antagonists on histamine and leukotriene-induced tracheal microvascular permeability in the guinea pig

The effects of several calcium antagonists, i.e., nifedipine, verapamil and 8-[N,N-diethylamino]-octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8), were evaluated in situ on agonist-induced increases in permeability of the airway microvasculature in anesthetized guinea pigs. Vascular permeability was measured as tracheal extravascular albumin content by using 125I-bovine serum albumin and the utilization of 51Cr labelled-erythrocytes to correct for blood volume. Intratracheal injections of histamine (1, 10 and 100 micrograms) or leukotriene (LT) D4 (1, 10 and 100 ng) produced dose-dependent increases in extravasated radiolabelled albumin in the trachea. Although histamine produced a greater maximal response than LTD4, the latter provocation was ten times more potent than the former. Nifedipine, a dihydropyridine calcium slow channel blocker, exhibited dose-dependent (30, 100 and 300 micrograms/kg) inhibitory activity against histamine-induced increases in extravascular albumin, while another calcium slow channel blocker, verapamil (100, 300 and 1000 micrograms/kg), exhibited much less activity. TMB-8, a purported intracellular calcium antagonist (1 and 10 mg/kg), was observed to have some inhibitory activity versus histamine. Similar doses of all three calcium antagonists failed to significantly inhibit increases in tracheal microvascular permeability evoked by LTD4. These results suggest that differences in mediator-induced microvascular permeability in the guinea pig trachea are evident depending upon the agonist selected and the pool of calcium utilized.