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At least 1,333 records · Page 74Linked to original sources
PubMed1987

Human neutrophil activation with interleukin-1. A role for intracellular calcium and arachidonic acid lipoxygenation.

Human monocyte-derived interleukin-1 (IL-1) stimulated the selective extracellular release of cytoplasmic granule-associated elastase from human neutrophils. Although extracellular calcium (Ca2+) enhances but is not required for the expression of granule exocytosis, IL-1 did induce the mobilization of previously sequestered intracellular Ca2+ as measured with the highly selective fluorescent Ca2+ indicator, Quin 2. Further, IL-1 stimulated the mobilization of cell membrane-associated Ca2+ as monitored by a decrease in fluorescence of chlorotetracycline (CTC)-loaded neutrophils. W-7, a calmodulin antagonist, and TMB-8[8(N,N-diethylamino)-octyl-(3,4,5-trimethoxy)benzoate hydrochloride], an intracellular Ca2+ antagonist, inhibited the Quin 2 fluorescent response by neutrophils to IL-1. TPCK (N-alpha-p-tosyl-L-lysine chloromethylketone), a serine protease inhibitor, suppressed IL-1-induced Quin 2 and CTC fluorescence. Exposure of neutrophils to IL-1 resulted in a concentration-dependent production of the 5-lipoxygenase product, LTB4 [5(S),12(R)-dihydroxy-6,14-cis-8,10-trans-eicosatetraenoic acid] which was enhanced in the presence of arachidonic acid (AA). LTB4 production by IL-1-activated neutrophils was suppressed by the lipoxygenase inhibitors nordihydroguaiaretic acid (NDGA) and piriprost potassium [6,9,deepoxy-6,9-(phenylimino)-delta 6,8-prostaglandin l1], and a cyclooxygenase/lipoxygenase inhibitor, 5,8,11,14-eicosatetraynoic acid (ETYA), whereas a cyclooxygenase inhibitor, flurbiprofen, was inactive. These data indicate that cytosolic free Ca2+ ([Ca2+]i) and a metabolite(s) of AA lipoxygenation mediate granule exocytosis elicited with IL-1.

5,8,11,14-Eicosatetraynoic Acid↗
PubMed1978

The use of short-term tests to measure the preventive action of reducing agents on formation and activation of carcinogenic nitroso compounds.

The effect of reducing agents on the nitrosation of methylguanidine (MG) and on the in vitro activation of dimethylnitrosamine (DMN) was examined by measuring DNA-repair synthesis (unscheduled incorporation of [3h]TdR), shifts in alkaline sucrose gradients, frequency of chromosome aberrations, and clone-forming capacity of cultured human fibroblasts. The reducing agents examined were sodium ascorbate, cysteine, cysteamine, and propyl gallate. Since the short-term bioassays used can be quantitated, it has become relatively easy to detect the inhibitory action of reducing compounds on the nitrosation reaction of MG and metabolic activation (with S-9 preparation) of the precarcinogen DMN, to measure their effective dose range, and to establish the most effective ratios between inhibitory agent and reactant. The results indicate that DNA-repair synthesis is a suitable short-term test for studying the numerous combinations and premutations between several carcinogenic or non-carcinogenic agents, and for estimating the capacity of inhibitory agents to affect formation and activation of chemical carcinogens.

Adolescent↗
PubMed1989

Role of cell calcium in alpha-1 adrenergic receptor control of arachidonic acid release from brown adipocytes.

Exposure of brown fat cells to phenylephrine, an agonist of alpha-1 adrenergic receptors, activates a phospholipase A2 which releases arachidonic acid. Since receptor activation of phospholipase A2 requires calcium, experiments were undertaken to define more precisely the role played by calcium in the regulation of enzyme activity. In this study, adipocytes were loaded with the fluorescent calcium chelator quin2 in order to buffer intracellular calcium and block receptor stimulated changes in its concentration. When quin2 loaded adipocytes were incubated in buffer containing 0.10 mM calcium, the ability of phenylephrine to stimulate release of arachidonic acid was severely reduced. At an intracellular quin2 concentration of 6.6 mM stimulated arachidonic acid release was inhibited by more than 50% and at 13 mM it was completely blocked. In contrast, phenylephrine stimulation of inositol phosphate accumulation was unaffected by quin2. Quin2 also did not affect the liberation of arachidonic acid in response to exogenous phospholipase C, A23187 or forskolin. The intracellular calcium antagonist TMB-8 also inhibited phenylephrine-stimulation of arachidonic acid release and this effect was reversed by ionomycin. Basal phospholipase A2 activity was increased by introduction of high calcium concentrations into cells rendered permeable with digitonin, but phenylephrine still caused a further increase in enzyme activity. These findings show a selective inhibition of phenylephrine activation of phospholipase A2 by either the chelation of intracellular calcium with quin2 or by the calcium antagonist TMB-8 and suggest an essential role for intracellular calcium in alpha adrenergic stimulation of enzyme activity. However, because phenylephrine still stimulates enzyme activity in cells rendered permeable with digitonin, we suggest that the action of phenylephrine cannot be attributed solely to changes in intracellular calcium.

Adipose Tissue, Brown↗
PubMed2001

Inhibition by costunolide of phorbol ester-induced transcriptional activation of inducible nitric oxide synthase gene in a human monocyte cell line THP-1.

Costunolide, the predominant sesquiterpene lactone in Saussureae radix, has been reported to exhibit potent chemopreventive effects on carcinogenesis. Effects of costunolide on cellular activation induced by a tumor-promoting phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) were investigated using a reporter gene assay which was designed to reflect the promoter activity of the inducible nitric oxide synthase (iNOS) gene in a human monocyte cell line THP-1. iNOS promoter-dependent reporter gene activity was significantly increased by TPA, and the TPA-induced increase of the reporter gene activity was efficiently reduced by costunolide, with an IC50 of approximately 2 microM. The addition of sulfhydryl (SH) compounds effectively abrogated the inhibitory effects of costunolide, suggesting the involvement of its reactivity with SH groups of target proteins and/or thiol-depleting property. The present findings may further explain the cancer-preventive property of costunolide.

Anticarcinogenic Agents↗
PubMed1999

Early copper-induced leakage of K(+) from Arabidopsis seedlings is mediated by ion channels and coupled to citrate efflux.

Copper tolerance among Arabidopsis ecotypes is inversely correlated with long-term K(+) leakage and positively correlated with short-term K(+) leakage (A. Murphy, L. Taiz [1997] New Phytol 136: 211-222). To probe the mechanism of the early phase of K(+) efflux, we tested various channel blockers on copper and peroxide-induced K(+) efflux from seedling roots. The K(+) channel blockers tetraethyl ammonium chloride and 4-aminopyridine (4-AP) both inhibited short-term copper-induced K(+) efflux. In contrast, peroxide-induced K(+) efflux was insensitive to both tetraethyl ammonium chloride and 4-AP. Copper-induced lipid peroxidation exhibited a lag time of 4 h, while peroxide-induced lipid peroxidation began immediately. These results suggest that short-term copper-induced K(+) efflux is mediated by channels, while peroxide-induced K(+) efflux represents leakage through nonspecific lesions in the lipid bilayer. Tracer studies with (86)Rb(+) confirmed that copper promotes K(+) efflux rather than inhibiting K(+) uptake. Short-term K(+) release is electroneutral, since electrophysiological measurements indicated that copper does not cause membrane depolarization. Short-term K(+) efflux was accompanied by citrate release, and copper increased total citrate levels. Since citrate efflux was blocked by 4-AP, K(+) appears to serve as a counterion during copper-induced citrate efflux. As copper but not aluminum selectively induces citrate production and release, it is proposed that copper may inhibit a cytosolic form of aconitase.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1998

Pharmacologic characterization of latex extracts by isolated guinea pig tracheal tissue.

Latex manufacturing workers are exposed to a heterogeneous aerosol of organic compounds. Previous studies of latex workers involved in glove production indicate that these individuals are at risk of developing respiratory symptoms and impaired lung function. The effect of latex extracts on isolated guinea pig tracheal smooth muscles was studied using latex water-soluble extracts obtained at different stages of the industrial process. Latex extracts were prepared as a 1:10 (w/v) solution. Dose-related contractions of nonsensitized guinea pig trachea were demonstrated using two latex extracts (latex 1 and latex 2). Latex 1 was prepared from the native latex and latex 2 from a processed form of latex which was relatively free of soluble proteins. Pharmacologic studies were performed by pretreating guinea pig tracheal tissue with drugs known to modulate smooth muscle contraction: atropine, indomethacin, pyrilamine, nordihydroguaiacetic acid, acivicin, trimethobenzoic acid and capsaicin. Constrictor effects of the dust extracts were inhibited by a wide variety of these agents. Atropine consistently and strikingly reduced the contractile effects of these extracts. This observation may suggest an interaction of the extracts with parasympathetic nerves or more directly with muscarinic receptors. Inhibition of contraction by blocking other mediators was less effective and varied with the dust extract. Pretreatment with capsaicin did not change the constrictor effects of latex 1 but enhanced the effects of latex 2. Depletion of neuropeptides, however, did not reduce the constrictor effect. We suggest that latex extracts cause dose-related airway smooth muscle constriction by nonimmunological mechanisms involving a variety of airway mediators and possibly cholinergic receptors. This effect is not dependent on the presensitization of guinea pigs.

Animals↗
PubMed1985

Beta adrenergic receptor-stimulated prostaglandin synthesis in the isolated rabbit heart: relationship to extra- and intracellular calcium.

We have investigated the contribution of extra- and intracellular Ca++ and calmodulin to beta adrenergic receptor-stimulated prostaglandin synthesis in the isolated rabbit heart perfused with Krebs-Henseleit buffer. Administration of isoproterenol (100 ng) increased the output of immunoreactive 6-keto-prostaglandin F1 alpha and prostaglandin E2 as well as heart rate and developed tension; the coronary perfusion pressure was reduced. Isoproterenol-induced output of prostaglandins was positively correlated with the extracellular Ca++ concentration (0-5 mM). Infusion of the Ca++ channel blockers diltiazem (22 microM) or nifedipine (0.27 microM) inhibited isoproterenol-stimulated output of prostaglandins and the positive inotropic but not the positive chronotropic effect of the amine. Administration of the intracellular Ca++ antagonists 8-(diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride (23 microM) or ryanodine (1.6 microM) reduced the outflow of prostaglandins and the positive chronotropic and inotropic effect elicited by isoproterenol. The calmodulin inhibitors trifluoperazine (50 microM) or calmidazolium (1 microM) failed to alter isoproterenol-induced output of prostaglandins; trifluoperazine but not calmidazolium reduced the developed tension and coronary perfusion pressure without altering heart rate. The prostaglandin synthesis elicited by arachidonic acid (3 micrograms) was inhibited by indomethacin but not by alterations in extracellular Ca++, Ca++ channel blockers, intracellular Ca++ antagonists or calmodulin inhibitors. These data suggest that activation of beta adrenergic receptors promotes cardiac prostaglandin synthesis and myocardial contractility by increasing the trans-sarcolemmal flux of Ca++, which releases intracellular Ca++.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1980

Production of methanol from aromatic acids by Pseudomonas putida.

When grown at the expense of 3,4,5-trimethoxybenzoic acid, a strain of Pseudomonas putida oxidized this compound and also 3,5-dimethoxy-4-hydroxybenzoic (syringic) and 3,4-dihydroxy-5-methoxybenzoic (3-O-methylgallic) acids; but other hydroxy- or methoxy-benzoic acids were oxidized slowly or not at all. Radioactivity appeared exclusively in carbon dioxide when cells were incubated with [4-methoxyl-14C]trimethoxybenzoic acid, but was found mainly in methanol when[methoxyl-14C]3-O-methylgallic acid was metabolized. The identity of methanol was proved by analyzing the product from [methoxyl-13C]3-O-methylgallic acid by nuclear magnetic resonance spectroscopy and by isolating the labeled 3,5-dinitrobenzoic acid methyl ester, which was examined by mass spectrometry. These results, together with measurements of oxygen consumed in demethylations catalyzed by cell extracts, showed that two methoxyl groups of 3,4,5-trimethoxybenzoate and one of syringate were oxidized to give carbon dioxide and 3-O-methylgallate. This was then metabolized to pyruvate; the other product was presumed to be the 4-methyl ester of oxalacetic acid, for which cell extracts contained an inducible, specific esterase. P. putida did not metabolize the methanol released from this compound by hydrolysis. Support for the proposed reaction sequence was obtained by isolating mutants which, although able to convert 3,4,5-trimethoxybenzoic acid into 3-O-methylgallic acid, were unable to use either compound for growth.

Enzyme Induction↗
PubMed1993

Inhibition of the activation of hageman factor (factor XII) by eosinophils and eosinophilic constituents.

Several syndromes characterized by striking eosinophilia may be complicated by thrombosis. The experiments described indicate that, paradoxically, eosinophils and certain of their constituents inhibit the activation of Hageman factor (HF, factor XII). In earlier studies, suspensions of mixed types of granulocytes, other nucleated peripheral blood cells, and platelets inhibited activation of Hageman factor by ellagic acid, glass, and sulfatides. After these cells were sedimented by centrifugation, the supernatant fluids were also inhibitory. No attempt had been made earlier to distinguish among different granulocytic species. In the present study, suspensions of eosinophils and the supernatant fluid after eosinophils had been separated by centrifugation inhibited activation of Hageman factor by ellagic acid. The protein concentration of that amount of supernatant fluid that inhibited activation by about half was 16 micrograms/ml, approximately the same as had been described for suspensions of peripheral blood mononuclear cells. Activation of Hageman factor by ellagic acid was also inhibited by certain constituents of eosinophils, including eosinophil peroxidase, eosinophil major basic protein and eosinophil cationic protein. Inhibition was not specific for ellagic acid-induced activation of Hageman factor, as inhibition was also observed with sulfatide-induced activation. Inhibition was presumably related to neutralization of the negative charge of activators of Hageman factor. Thus, bismuth subgallate, a particulate activator of Hageman factor, was no longer effective after it had been exposed to eosinophil cationic protein. The observations reported here raise the question of whether in vivo eosinophils modulate certain of the defense reactions ascribed to Hageman factor.

Blood Proteins↗
PubMed1991

Ca(2+)-independent form of protein kinase C may regulate Na+ transport across frog skin.

Activators of protein kinase C (PKC) stimulate Na+ transport (JNa) across frog skin. We have examined the effect of Ca2+ on PKC stimulation of JNa. Both the phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA) and the diacyl-glycerol sn-1,2-dioctanoylglycerol (DiC8) were used as PKC activators. Blocking Ca2+ entry into the cytosol (either from external or internal stores) reduced the subsequent natriferic effect of the PKC activators. This negative interaction did not simply reflect saturation of activation of the apical Na+ channels, since the stimulations produced by blocking Ca2+ entry and adding cyclic AMP were simply additive. The Ca2+ dependence of the natriferic effect could have reflected either a direct action of cytosolic Ca2+ on PKC or an indirect action on the final receptor site (the Na+ channel). To distinguish between these possibilities, the TPA- and phospholipid-dependent kinase activity of broken-cell preparations was assayed. The kinase activity was not stimulated by physiological levels of Ca2+, and in fact was inhibited at millimolar concentrations of Ca2+. We conclude that the effects of Ca2+ on the natriferic response to PKC activators are indirect. Reducing cytosolic uptake of Ca2+ may have stimulated Na+ transport by a chemical modification of the apical channels observed in other tight epithelia. The usual stimulation of Na+ transport produced by PKC activators in frog skin may reflect the operation of a nonconventional form of PKC. This enzyme is Ca2+ independent and seems related to the nPKC or PKC epsilon observed in other systems.

Amiloride↗
PubMed1995

Sulphasalazine inhibition of thiopurine methyltransferase: possible mechanism for interaction with 6-mercaptopurine and azathioprine.

Thiopurine drugs are used in the treatment of inflammatory bowel disease--as are sulphasalazine and its metabolite 5-aminosalicylic acid (ASA). S-Methylation catalyzed by thiopurine methyltransferase (TPMT) is a major pathway in the metabolism of thiopurines. The hypothesis was tested that TPMT might be inhibited by sulphasalazine or isomers of ASA. Sulphasalazine as well as 3-, 4- and 5-ASA inhibited recombinant human TPMT, with IC50 values of 78, 99, 2600 and 1240 microM, respectively. Kinetic studies demonstrated that the inhibition of TPMT by sulphasalazine and ASA isomers was non-competitive with regard to the thiopurine substrate, 6-MP, and was uncompetitive with regard to the methyl donor for the reaction, S-adenosyl-L-methionine. Our observations raise the possibility of a clinically significant drug-drug interaction in patients treated simultaneously with sulphasalazine and thiopurine drugs.

Aminosalicylic Acids↗