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R M Burch

Publications and source records attributed to R M Burch.

At least 55 records · Page 3Linked to original sources
PubMed1991

Evidence that cultured airway smooth muscle cells contain bradykinin B2 and B3 receptors.

We examined bradykinin-induced 45Ca2+ efflux and prostaglandin synthesis in guinea pig tracheal smooth muscle cells maintained in tissue culture. We also studied the effects of a B1 receptor agonist and antagonist, a B2 receptor antagonist, and the cyclooxygenase inhibitor indomethacin. In cultured smooth muscle cells, bradykinin (0.1 nM to 10 microM) stimulated efflux of 45Ca2+ and induced the synthesis of prostaglandin E2 and the prostacyclin metabolite 6-keto-prostaglandin F1 alpha. DesArg9-bradykinin, a B1 receptor agonist, had no effect on 45Ca2+ efflux or prostaglandin synthesis, and no responses to bradykinin were unaffected by the B1 receptor antagonist desArg9-[Leu8]-bradykinin. Indomethacin (1 microM) abolished bradykinin-induced prostaglandin synthesis but was without effect on 45Ca2+ efflux. NPC 567 (DArg[Hyp3,DPhe7]-bradykinin), a B2 receptor antagonist, had no effect on bradykinin-induced 45Ca2+ efflux, but abolished prostaglandin synthesis. Unlike in membranes prepared freshly from guinea pig tracheal smooth muscle, the B2 receptor antagonist inhibited completely (Ki, 12 nM) binding of [3H]-bradykinin to membranes prepared from cultured tracheal smooth cells. These data suggest that tracheal smooth muscle cells, maintained in culture, express B2 receptors that mediate bradykinin-induced prostaglandin synthesis. The observation that bradykinin-induced efflux of calcium ions was unaffected by B1 or B2 antagonists provides further evidence that airway smooth muscle may contain a novel B3 receptor.

Animals↗
PubMed1991

Oligonucleotides antisense to the interleukin 1 receptor mRNA block the effects of interleukin 1 in cultured murine and human fibroblasts and in mice.

Phosphodiester and phosphorothioate oligodeoxynucleotides (18 mers) were constructed antisense to sequences of the recently cloned murine and human IL-1 receptors. Murine antisense oligonucleotides inhibited IL-1-stimulated PGE2 synthesis by murine fibroblasts in culture in a time (days) and concentration-dependent (3 microM-30 microM) fashion. Murine sense oligonucleotide and an oligonucleotide antisense to human IL-1 receptor were without effect. Moreover, murine antisense oligonucleotides did not affect tumor necrosis factor- or bradykinin-stimulated PGE2 synthesis by murine fibroblasts. Similarly, antisense oligonucleotides to the human, but not the murine, IL-1 receptor inhibited IL-1-stimulated PGE2 synthesis by cultured human fibroblasts. The attenuation of the cellular response to IL-1 caused by the antisense oligonucleotides correlated with a loss in cell surface receptors for IL-1, without any change in the number of bradykinin receptors on these cells. When antisense oligonucleotides were encapsulated in liposomes, they blocked completely the appearance of newly synthesized IL-1 receptors and IL-1-stimulated PGE2 synthesis. In mice, subcutaneous injection with an oligonucleotide antisense to the murine IL-1 receptor markedly inhibited the infiltration of neutrophils in response to subsequent injection of IL-1. These data suggest that antisense oligodeoxynucleotides may share a role in the design of antiinflammatory therapeutics.

Animals↗
PubMed1991

Mass ligand binding screening for receptor antagonists: prototype new drugs and blind alleys.

The ligand binding assay is a powerful tool in the search for antagonists for novel receptors, and for identification of novel classes of antagonists for well-known receptors. Ligand binding mass screening can be adapted for very high throughput. In order for mass screening to be useful, it is necessary to strictly define the binding characteristics for a compound to be considered a putative receptor antagonist. In practice, we have found that synthetic pursuit of a compound with a Ki of greater than or equal to 1 microM is likely to lead down a blind alley unless very good evidence for specificity is available. Even potent competitors for binding should be thoroughly evaluated in assays of biological activity before a synthetic program is initiated in earnest.

Animals↗
PubMed1990

Arachidonic acid metabolism in fibroblasts from patients with peroxisomal diseases: response to interleukin 1.

Prostaglandin E2 synthesis and eicosanoid biosynthetic enzyme activities (arachidonyl CoA synthetase, cyclooxygenase and phospholipase A2) were measured in dermal fibroblasts from patients with metabolic disorders of peroxisomal origin and compared to those from normal subjects and patients with other metabolic disorders of lipid metabolism. Basal- as well as interleukin 1-stimulated prostaglandin E2 syntheses were higher in fibroblasts from patients with X-linked adrenoleukodystrophy, the Zellweger cerebrohepatorenal syndrome and rhizomelic chondrodysplasia punctata than in normals. Basal cyclooxygenase and phospholipase A2 activities were elevated in most of the peroxisomal disease cells. Cells from patients with adrenomyeloneuropathy, however, had significantly lower cytokine-stimulated cyclooxygenase and phospholipase A2 activities than normals, as well as lower prostaglandin E2 synthesis in response to interleukin 1. The peroxisomal disease lines exhibited dose-response curves to interleukin 1 similar to controls. Receptor-binding analysis indicated that cells from patients with rhizomelic chondrodysplasia punctata expressed 5-times fewer interleukin 1 receptors than normals and the other disease lines. Exaggerated arachidonic acid metabolism in response to interleukin 1 suggests that cells from patients with peroxisomal enzyme defects may be useful in elucidating pathways for arachidonate release and eicosanoid synthesis.

Adrenoleukodystrophy↗
PubMed1990

A bradykinin antagonist inhibits carrageenan edema in rats.

Bradykinin has been implicated in acute inflammatory reactions. Intradermal injection elicits increased vascular permeability and hyperalgesia, and bioassays have suggested increased bradykinin concentration in inflammatory exudates. Poorly specific inhibitors of kallikrein, the enzyme catalyzing formation of bradykinin, inhibit certain acute inflammatory reactions. However, the lack of a specific bradykinin receptor antagonist has made proof of the hypothesis difficult. In this study, we have used the potent, specific bradykinin antagonist DArg[Hyp3DPhe7] bradykinin (NPC 567) as a probe to examine the role of bradykinin in carrageenan-induced edema in the paws of rats. Subplantar injection of carrageenan led to an increase in immunoreactive bradykinin and metabolic product, desArg9bradykinin. NPC 567 inhibited the development of edema in response to carrageenan, to a maximum 65%. Thus, bradykinin appears to be a major mediator of increased vascular permeability in response to carrageenan.

Analgesics↗
PubMed1990

Expression of striatal D1 dopamine receptors coupled to inositol phosphate production and Ca2+ mobilization in Xenopus oocytes.

Expression of central nervous system receptors for dopamine was examined by injection of poly(A)+ RNA (mRNA) from rat striatum into oocytes from Xenopus laevis. Electrophysiological measurements in mRNA-injected oocytes indicated that addition of 100 microM dopamine induced an inward current (40-100 nA) that was consistent with the activation of endogenous Ca2(+)-dependent Cl- channels. This current was also elicited by addition of the selective D1 agonist SKF 38393 but not by the selective D2 agonist quinpirole. Prior addition of the dopaminergic antagonist cis-piflutixol completely abolished dopamine-induced currents but had no effect on currents produced by serotonin. Using 45Ca2+ efflux assays, addition of 100 microM dopamine to injected oocytes stimulated efflux 2- to 3-fold. This increase was mimicked by SKF 38393 and was blocked by the D1-selective antagonist (+)SCH 23390 but not by the D2-selective antagonist domperidone. No increase in 45Ca2+ efflux was seen with 100 microM quinpirole. Size fractionation of striatal mRNA yielded a single peak (2.5-3.0 kilobases) of D1 receptor-mediated 45Ca2+ efflux activity in injected oocytes. In addition, dopamine stimulation of oocytes injected with peak fractions and prelabeled with myo-[3H]inositol caused a 3-fold increase in [3H]inositol 1,4,5-triphosphate [( 3H]InsP3) formation. No effect on [3H]InsP3 production or 45Ca2+ efflux was observed, however, in injected oocytes incubated with 1 mM N6,O2'-dibutyryladenosine 3',5'-cyclic monophosphate. Thus, in addition to D1 receptors that stimulate adenylyl cyclase, rat striatum contains D1 receptors that can couple to InsP3 formation and mobilization of intracellular Ca2+.

Animals↗
PubMed1990

Kinin signal transduction: role of phosphoinositides and eicosanoids.

Kinins elicit prostaglandin and inositol phosphate production in 3T3 fibroblasts through stimulation of B2 receptors. Prostaglandin synthesis is maximum by 5 min, whereas inositol phosphate production continues for longer than 30 min. Prostaglandin synthesis is stimulated by phospholipase A2, which releases arachidonate from phospholipids, whereas a phosphatidylinositol-specific phospholipase C catalyzes formation of equimolar amounts of inositol phosphate and diacylglycerol. Stimulation of these two second-messenger systems occurs through independent pathways: (a) dexamethasone inhibits prostaglandin formation by inhibiting phospholipase A2, and, to a lesser degree, cyclooxygenase, but is without effect on inositol phosphate production; (b) neomycin inhibits inositol phosphate production without affecting prostaglandin synthesis; (c) phorbol esters inhibit inositol phosphate production while augmenting prostaglandin synthesis; and (d) indomethacin inhibits prostaglandin synthesis but does not affect inositol phosphate production. At later times (greater than 10 min), the two pathways interact. Stimulation with one agonist to increase diacylglycerol results in augmentation of prostaglandin synthesis in response to a second agonist. Inositol phosphates cause release of calcium from intracellular stores. Prostaglandins stimulate (by binding to their own receptors) adenylate cyclase to increase cAMP. Additionally, prostaglandins increase intracellular free calcium by increasing influx of extracellular calcium. Both inositol phosphates and prostaglandins play roles in mitogenesis in these cells.

Animals↗
PubMed1990

Functional expression of B2 bradykinin receptors from Balb/c cell mRNA in Xenopus oocytes.

The murine BALB/c 3T3 fibroblast clone SV-T2 (3T3 cells) expresses receptors for the nonapeptide bradykinin. In these cells, bradykinin stimulates both inositol phosphate (InsP) formation and arachidonic acid release by independently activating phospholipase C and phospholipase A2, respectively. These actions of bradykinin are mediated by a receptor(s) coupled to pertussis toxin-insensitive guanine nucleotide-binding proteins. Bradykinin-stimulated increases in InsP lead to the mobilization of intracellular Ca2+. We examined the expression of 3T3 receptors for bradykinin in oocytes from Xenopus laevis, cells capable of in vitro expression of foreign mRNA for receptors coupled to the mobilization of Ca2+. Poly(A)+ mRNA was prepared from 3T3 cells and expression of receptors for bradykinin was demonstrated by agonist-mediated stimulation of 45Ca2+ efflux from oocytes injected with 50 ng of poly(A)+ RNA. Bradykinin-stimulated efflux of 45Ca2+ was dose dependent (EC50 = 15 nM) and blocked by the specific mixed B1,B2 bradykinin antagonist NPC 567 but not by the B1 antagonist desArg9[Leu8]bradykinin. Size fractionation of 3T3 poly(A)+ RNA on a sucrose gradient demonstrated a single peak of bradykinin-stimulated 45Ca2+ efflux, with an approximate mRNA size of 4.5 kilobases. Bradykinin-stimulated 45Ca2+ efflux in size-fractionated mRNA was clearly separable from response to [Arg]vasopressin at another receptor linked to InsP formation and Ca2+ mobilization in 3T3 cells.

Animals↗
PubMed1989

Diacylglycerol in the synergy of bradykinin and thrombin stimulation of prostaglandin synthesis.

Simultaneous addition of bradykinin and thrombin to 3T3 fibroblasts for 5 min resulted in less than additive stimulation of prostaglandin E2 synthesis. However, if cells were stimulated with either agonist alone, then the other added 15 min later, prostaglandin E2 synthesis was synergistically enhanced. In contrast, if either agonist was added, then prostaglandin E2 synthesis in response to the same agonist assessed 15 min later, synthesis was markedly reduced. Bradykinin and thrombin caused increased diacylglycerol accumulation in the cells, and addition of the diacylglycerol kinase inhibitor R59022 dramatically increased the effects of sequential addition of the agonists. These results suggest that diacylglycerol generated in response to activation of one receptor amplifies the effects of activation of other receptors.

Animals↗
PubMed1989

Bradykinin stimulates tumor necrosis factor and interleukin-1 release from macrophages.

Bradykinin and related kinins have been implicated in the initiation and maintenance of inflammation. Cytokines appear to be the primary mediators of many inflammatory diseases. The potential ability of bradykinin to stimulate release of tumor necrosis factor and interleukin-1 from macrophages was examined. Bradykinin stimulated release of both cytokines from P388-D1 and RAW264.7 murine macrophages. Studies with selective agonists and antagonists suggest that cytokine release is mediated by a B1 kinin receptor.

Animals↗
PubMed1989

Interleukin 1 stimulates prostaglandin synthesis and cyclic AMP accumulation in Swiss 3T3 fibroblasts: interactions between two second messenger systems.

Biochemical events elicited by interleukin 1 (IL-1) were studied in Swiss 3T3 fibroblasts. One hour after its addition, IL-1 stimulated synthesis of prostaglandin E2 (PGE2), which continued to accumulate for 4 days. IL-1 also stimulated cAMP accumulation. Indomethacin blocked cAMP accumulation in response to IL-1, suggesting that PGE2 was responsible for the increase. Addition of exogenous PGE2 to indomethacin-treated cells restored cAMP accumulation. IL-1 enhanced thymidine incorporation, and indomethacin attenuated responses to lower concentrations. Thus, PGE2 appeared to play a role in the ability of low concentrations of IL-1 to stimulate thymidine incorporation. PGE2 augmented thymidine incorporation by increasing cAMP accumulation because in the presence of indomethacin addition of exogenous cAMP enhanced thymidine incorporation in response to low concentrations of IL-1. Elevated cAMP further stimulated PGE2 synthesis. Thus, PGE2 and cAMP interacted to potentiate their mutual accumulation. In summary, IL-1 stimulates PGE2 synthesis. PGE2, in turn, stimulates cAMP accumulation which potentiates IL-1-stimulated PGE2 synthesis and thymidine incorporation.

Animals↗
PubMed1989

Tumor necrosis factor causes amplification of arachidonic acid metabolism in response to interleukin 1, bradykinin, and other agonists.

Tumor necrosis factor stimulated prostaglandin E2 synthesis in Swiss 3T3 fibroblasts. Interleukin 1 also stimulated prostaglandin synthesis. Simultaneous addition of tumor necrosis factor and interleukin 1 synergistically stimulated prostaglandin synthesis, even when both growth factors were added at what would be supramaximal concentrations by themselves. Several small peptides and nonpeptides rapidly stimulate prostaglandin synthesis in these cells. Pretreatment with tumor necrosis factor synergistically enhanced prostaglandin synthesis in response to bradykinin, bombesin, thrombin, norepinephrine, and platelet-activating factor. Thus, tumor necrosis factor stimulates prostaglandin synthesis and greatly amplifies prostaglandin synthesis in response to other agonists. This finding may have significance in chronic inflammatory diseases such as rheumatoid arthritis in which several hormones and growth factors may synergistically augment eicosanoid synthesis.

Animals↗
PubMed1989

The kallikrein-kininogen-kinin system in chronic inflammation.

We examined bradykinin's effects on macrophages and fibroblasts, two cell types important in the pathogenesis of chronic inflammation. Bradykinin stimulated release of proteins of 18 kDa from macrophages. These proteins caused increased thymocyte proliferation (interleukin 1, IL-1) and completely inhibited lipoprotein lipase (tumor necrosis factor, TNF). When fibroblasts were incubated with bradykinin, PGE2 synthesis was stimulated. Pretreatment with IL-1 or TNF dramatically amplified bradykinin-stimulated PGE2 synthesis. Thus, bradykinin is involved in a positive feedback loop in which bradykinin activates macrophages to release potent inflammatory cytokines; these in turn amplify responsiveness of bradykinin target tissues.

Chronic Disease↗
PubMed1989

G protein regulation of phospholipase A2.

Many neurotransmitters and hormones activate receptors that are known to be coupled to their effectors by GTP-binding regulatory proteins, G proteins. Activation of many of these same receptors elicits arachidonate release and metabolism. During the past few years, novel experimental techniques have revealed that in many cells arachidonate release is independent of generation of other second messengers, including inositol phosphates, diacylglycerols, and elevation in free intracellular calcium. Much evidence has accumulated to implicate phospholipase A2 as the enzyme catalyzing arachidonate release, and suggesting that this effector enzyme, too, is activated by G proteins. In neural tissues as well as epithelium, endothelium, contractile and connective tissues, and blood cells, G proteins coupled to receptors for a variety of peptide and nonpeptide neurotransmitters and hormones have been shown to directly activate phospholipase A2. In retinal rod outer segments, transducin is the coupling G protein, but the G proteins coupling receptor activation to phospholipase A2 in other cell types is less clear. Some are pertussis toxin-sensitive, whereas others are not, and evidence exists that the ras gene product G protein may also be coupled to and regulate phospholipase A2.

Animals↗
PubMed1989

Antagonists of B2 bradykinin receptors.

Bradykinin and its active metabolites, produced by kallikreins at their sites of action, potently elicit a variety of biological effects: hypotension, bronchoconstriction, gut and uterine contraction, epithelial secretion in airway, gut, and exocrine glands, vascular permeability, pain, connective tissue proliferation, cytokine release, and eicosanoid formation. These effects are mediated by at least two broad classes of receptors. The most common is the B2 subtype. The availability of competitive antagonists of B2 receptors has provided powerful tools for the study of bradykinin's actions. The significance of kinins in certain human diseases is being explored by using these agents as potential therapeutic agents. Human clinical trials are under way to test the usefulness of bradykinin receptor antagonists to treat symptoms of the common cold and the pain associated with severe burns. Trials are also being comtemplated for use in treatment of asthma.

Airway Resistance↗
PubMed1989

[Arg1-D-Phe7]-substituted bradykinin analogs inhibit bradykinin- and vasopressin-induced contractions of uterine smooth muscle.

The purpose of the present study was to examine the tissue selectivity of several [Arg1-D-Phe7]-substituted analogs of bradykinin. Unlike D-Arg-[Hyp3-D-Phe7]-bradykinin (NPC567), which antagonizes bradykinin-induced contractions both in rat isolated uterus and guinea pig ileum, [D-Nal1-Thi5,8-D-Phe7]-bradykinin (NPC573) was active only in uterine smooth muscle. Binding studies revealed that, unlike several [D-Phe7]-substituted analogs, including NPC567, NPC573 competed with radiolabeled bradykinin neither at receptors in uterus nor ileum. Moreover, no [Arg1-D-Phe7]-substituted analog competed with bradykinin binding in guinea pig ileum, suggesting that these agents, which inhibit uterine but not ileal contractions to bradykinin, may not be bradykinin receptor antagonists. NPC573 inhibited [Arg8]-vasopressin-induced contraction of the uterus more potently than it did bradykinin, although NPC573 (and other [Arg1-D-Phe7]-substituted analogs tested) did not inhibit binding of a vasopressin antagonist either in uterus or liver membranes. We therefore suggest that [Arg1-D-Phe7]-substituted analogs of bradykinin inhibit contractions of uterine smooth muscle by a mechanism other than receptor antagonism. In addition, the tissue selectivity of these agents suggests that the mechanisms underlying bradykinin's contractile effect in uterus are different than in intestinal smooth muscle.

Animals↗
PubMed1989

Evidence for a pulmonary B3 bradykinin receptor.

We have examined pulmonary effects of bradykinin (Bk) in vivo and in vitro in guinea pigs and their potential inhibition by antagonists of Bk B1 and B2 receptors. Bk was a potent bronchoconstrictor in vivo and caused contractions of isolated, epithelium-denuded trachealis. D-Arg[Hyp3,D-Phe7]-Bk (NPC567) and D-arg[Hyp3,Thi5,8,D-Phe7]-Bk (NPC349), B2 receptor antagonists, were weak inhibitors of Bk-induced bronchoconstriction in vivo and were virtually inactive as antagonists of Bk-induced airway smooth muscle contraction. Several other B2 antagonists as well as B1 antagonist, des-Arg9-[Leu8]-Bk, did not inhibit Bk-induced tracheal contraction. The B1 receptor agonist des-Arg9-Bk was without effect on tracheal tone. Tracheal responses to Bk were unaffected by antagonists of muscarinic, histamine, serotonin, and catecholamine receptors. The inability of the antagonists to inhibit Bk is unlikely to be due to their degradation, because NPC567 was only weakly active in the presence of inhibitors of kininase I (EC 3.4.11.2), kininase II (EC 3.4.15.1), and neutral endopeptidase (EC 3.4.24.11). These studies were corroborated by ligand binding experiments in guinea pig and ovine airways. In [3H]Bk binding, the Bk antagonists had no effect in guinea pig trachea, slightly displaced [3H]Bk in ovine trachea, and inhibited approximately 60% of total specific binding in lung. des-Arg9-[Leu8]-Bk and several other agents, including atropine, neurokinin A, substance P, and vasoactive intestinal peptide, had no effect on lung Bk binding. Bk and its analogs were not degraded during the binding assay. These data suggest that pulmonary tissue, particularly in the large airways, contains a novel Bk binding site, a B3 receptor, which may be involved in Bk-induced bronchoconstriction.

Airway Resistance↗