Phorbol myristate acetate-induced release of granule enzymes from human neutrophils: inhibition by the calcium antagonist, 8-(N,N-diethylamino)-octyl 3,4,5-trimethoxybenzoate hydrochloride

Quercus infectoria galls possess antioxidant activity and abrogates oxidative stress-induced functional alterations in murine macrophages

The present study reports the antioxidant activity of ethanolic extract of Quercus infectoria galls. The antioxidant potency of galls was investigated employing several established in vitro model systems. Their protective efficacy on oxidative modulation of murine macrophages was also explored. Gall extract was found to contain a large amount of polyphenols and possess a potent reducing power. HPTLC analysis of the extract suggested it to contain 19.925% tannic acid (TA) and 8.75% gallic acid (GA). The extract potently scavenged free radicals including DPPH (IC(50)~0.5 microg/ml), ABTS (IC(50)~1 microg/ml), hydrogen peroxide (H(2)O(2)) (IC(50)~2.6 microg/ml) and hydroxyl (*OH) radicals (IC(50)~6 microg/ml). Gall extract also chelated metal ions and inhibited Fe(3+) -ascorbate-induced oxidation of protein and peroxidation of lipids. Exposure of rat peritoneal macrophages to tertiary butyl hydroperoxide (tBOOH) induced oxidative stress in them and altered their phagocytic functions. These macrophages showed elevated secretion of lysosomal hydrolases, and attenuated phagocytosis and respiratory burst. Activity of macrophage mannose receptor (MR) also diminished following oxidant exposure. Pretreatment of macrophages with gall extract preserved antioxidant armory near to control values and significantly protected against all the investigated functional mutilations. MTT assay revealed gall extract to enhance percent survival of tBOOH exposed macrophages. These results indicate that Q. infectoria galls possess potent antioxidant activity, when tested both in chemical as well as biological models.

Bradykinin-induced chloride conductance in murine proximal tubule epithelial cells

Despite the recognized role of bradykinin (BK)-induced calcium and chloride conductance in regulating salt transport in the kidney, the signaling pathway involved has not been well examined. Patch clamp of murine proximal tubule (TKPTS) cells revealed that BK (10 nM) produced an increase in an outwardly rectifying current from a basal level of 2.9 +/- 0.6 to 13.8 +/- 1.1 pA/pF following addition of BK (n = 8; p < 0.001). The shift in reversal potential seen with BK on changing the intracellular solution to 152 mM chloride and significant inhibition of the current by 100 microM 4,4'-di-isothiocyanato-stilbene-2,2'-disulphonic acid (DIDS) suggested that BK activated a chloride current. BK-induced current was blocked by B2 receptor antagonist but not by B1 antagonist or pertussis toxin indicating that the current was mediated by B2 receptors possibly through Gq activation. TMB-8 completely blocked the BK-calcium rise in fura-2 studies but did not block the BK-chloride response indicating that BK-mediated chloride current is calcium-independent. BK-induced current was dependent on phospholipase C (PLC) since U73122, a PLC-beta blocker (10 microM) blocked it completely. Furthermore, chloride conductance was not modulated by bisindolylmaleimide, an inhibitor of protein kinase C (PKC), but was enhanced by dibutyryl cAMP. We conclude that BK-induced rise in chloride current is mediated by B2 receptors and dependent on PLC activation but not dependent on calcium rise. Furthermore, the current can be modulated by cAMP but not PKC.

Antiinflammatory flavonoids from Artocarpus heterophyllus and Artocarpus communis

The antiinflammatory activities of the isolated flavonoids, including cycloartomunin (1), cyclomorusin (2), dihydrocycloartomunin (3), dihydroisocycloartomunin (4), cudraflavone A (5), cyclocommunin (6), and artomunoxanthone (7), and cycloheterohyllin (8), artonins A (9) and B (10), artocarpanone (11), artocarpanone A (12), and heteroflavanones A (13), B (14), and C (15) from Artocarpus communis and A. heterophyllus, were assessed in vitro by determining their inhibitory effects on the chemical mediators released from mast cells, neutrophils, and macrophages. Compound 4 significantly inhibited the release of beta-glucuronidase and histamine from rat peritoneal mast cells stimulated with P-methoxy-N-methylphenethylamine (compound 48/80). Compound 11 significantly inhibited the release of lysozyme from rat neutrophils stimulated with formyl-Met-Leu-Phe (fMLP). Compounds 8, 10, and 11 significantly inhibited superoxide anion formation in fMLP-stimulated rat neutrophils while compounds 2, 3, 5, and 6 evoked the stimulation of superoxide anion generation. Compound 11 exhibited significant inhibitory effect on NO production and iNOS protein expression in RAW 264.7 cells. The potent inhibitory effect of compound 11 on NO production in lipopolysaccharide (LPS)-activated macrophages, probably through the suppression of iNOS protein expression.

Mechanism of bradykinin-induced Ca2+ mobilization in murine proximal tubule epithelial cells

Despite the recognized physiological role of bradykinin (BK) in the kidney in maintaining glomerular and tubule function and its role in pathological states such as endotoxemia, diabetes, and other diseases, relatively little is known about the mechanisms by which BK can impact kidney function. Furthermore, the signaling of BK receptors in the murine nephron has not been fully characterized. The present studies were undertaken to examine BK-stimulated Ca(2+) signaling using Fura-2 in the murine proximal tubule epithelial cell line TKPTS. BK produced a concentration-dependent rise in intracellular Ca(2+) ([Ca(2+)])(i) (pEC(50) = 8.39 +/- 0.04). Selective antagonists showed the rise in [Ca(2+)](i) was mediated through B2 receptors. The rise in [Ca(2+)](i) was rapid and reversible and was maximally stimulated at 1 microM (697 +/- 70 nM above basal level of 115 +/- 6 nM). Studies with thapsigargin and EGTA showed Ca(2+) mobilization was dependent on two events: release and influx. Both U73122 (1-[6-[[17-beta-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]hexyl]-1H-pyrrole-2,5-dione) [a phospholipase C (PLC) inhibitor] and genistein (a tyrosine kinase inhibitor) partially inhibited BK-stimulated rise in [Ca(2+)](i). When combined, both agents produced a further decrease, suggesting multiple pathways for PLC activation may be involved. The ability of Ni(2+) to inhibit influx indicated the activation of a Ca(2+) release-activated channel (CRAC). Ca(2+) mobilization did not seem to be affected by cyclic nucleotides or protein kinase C. In summary, the TKPTS murine proximal tubule cell line expresses functional B2 receptors linked to Ca(2+) mobilization that is dependent on phospholipase C and activation of CRAC.

Antiinflammatory evaluation of alcoholic extract of galls of Quercus infectoria

Galls of Quercus infectoria Olivier (Fagaceae) possess pleiotropic therapeutic activities, with particular efficacy against inflammatory diseases. The present study was undertaken to evaluate the effect of alcoholic extract of Q. infectoria galls on various in vivo and in vitro experimental models of inflammation. Oral administration of gall extract significantly inhibited carrageenan, histamine, serotonin and prostaglandin E2 (PGE2) induced paw oedemas, while topical application of gall extract inhibited phorbol-12-myristate-13-acetate (PMA) induced ear inflammation. The extract also inhibited various functions of macrophages and neutrophils relevant to the inflammatory response. In vitro exposure of rat peritoneal macrophages to gall extract ameliorated lipopolysaccharide (LPS) stimulated PGE2 and nitric oxide (NO) production and PMA stimulated superoxide (O2*-) production in a dose dependent manner. Gall extract also scavenged NO and O2*-. Probing into mechanism of NO inhibition in macrophages revealed gall extract to ameliorate the induction of inducible NO synthase (iNOS), respectively without any inhibitory effect on its catalytic activities even at higher concentrations. Gall extract also significantly inhibited formyl-Met-Leu-Phe (fMLP) stimulated degranulation in neutrophils. These results suggest that alcoholic extract of galls of Q. infectoria exerts in vivo antiinflammatory activity after oral or topical administration and also has the ability to prevent the production of some inflammatory mediators.

Inhibition of cyclic GMP formation and aggregation inDictyosteliumby the intracellular Ca2+antagonist TMB-8

Aggregation in Dictyostelium discoideum was shown in previous studies employing EGTA to require Ca2+, but the intra- or extracellular site of action of this ion and its role in chemotaxis were not determined [1]. In this investigation we show that the intracellular Ca2+ immobilising agent TMB-8 does not affect binding of the signalling nucleotide, cAMP, to the cell surface receptors but abolishes the rapid accumulation of intracellular cGMP and subsequent chemotactic aggregation. We infer that movement of Ca2+ from membrane-bound stores is triggered by binding of cAMP to the cell-surface receptor and that this plays a primary role in stimulating cGMP formation and chemotaxis.

Determination of the oxidative burst chemiluminescent response of avian and murine-derived macrophages versus corresponding cell lines in relation to stimulation with Salmonella serotypes

In contrast to mammalian systems, avian species lack a resident or harvestable macrophage population in the abdominal exudate. Peritoneal macrophages in the chicken can be elicited if an inflammatory agent such as sephadex is injected. This study examines the kinetics of different macrophage populations, derived by different methods of isolation and from different hosts, with respect to the elicited oxidative burst upon infection with host-adapted Salmonella serotypes. The nature of the oxidative burst elicited by murine and avian-derived and cell line macrophages was determined after stimulation with phorbol myristate (PMA), zymosan A, and Salmonella serotypes. Both murine and chicken peritoneal macrophages, chicken blood monocytes and corresponding cell lines, J774A.1 and HD-11, were unable to produce a detectable chemiluminescent (CL) response after interaction with Salmonella using the luminescent probe luminol. However, both PMA and zymosan A induced a CL response in all cell types, with PMA eliciting a higher and earlier peak response (pkH) than zymosan A. Lucigenin-enhanced CL in both murine and chicken macrophages was achieved with PMA, zymosan A and Salmonella serotypes. In this case, zymosan A induced higher responses than PMA. In the peritoneal macrophages of both hosts, there were no significant differences in the oxidative burst induced by the different Salmonella serotypes. However, the J774A.1 (murine) cells demonstrated significant differences, with S. enterica serotype Choleraesuis (S. choleraesuis and S. gallinarum producing the highest response. In the HD-11 (chicken) cells, S. choleraesuis and S. dublin elicited the higher CL. With both cell lines, S. abortusovis failed to induce an appreciable CL response. In these experiments it was demonstrated that oxidative burst was not detectable in monocytes/macrophage populations using luminol, which suggests a link to the lack of a myeloperoxidase system in these cells. Lucigenin-enhanced CL appeared independent from the myeloperoxidase system, indicating production of another oxidative species compared with luminol. No discernable effect of host specificity with regard to Salmonella serotype and respective host was seen in host-derived or cell line macrophages, and cell line macrophages displayed altered functional characteristics with regard to oxidative burst in comparison with their primary counterparts.

Bioactive constituents of the roots of Cynanchum atratum

A novel biphenylneolignan, 2,6,2',6'-tetramethoxy-4,4'-bis(2,3-epoxy-1-hydroxypropyl)biphenyl (1), and two new glycosides named atratoglaucosides A (2) and B (3), were isolated from the roots of Cynanchum atratum, and their structures were determined on the basis of chemical and spectroscopic evidence. The aglycons of 2 and 3 were identified as glaucogenin C and 7-desoxyneocynapanogenin A, a new disecopregnane. A known compound, glaucogenin C 3-O-beta-D-cymaropyranosyl-(1-->4)-alpha-L-diginopyranosyl-(1-->4)-beta-D-thevetopyranoside (4), isolated from the same source, showed a significant cytotoxic effect against 212 cells. This substance also gave a significant inhibitory effect on TNF-alpha (tumor necrosis factor-alpha) formation from the RAW 264.7 mouse macrophage-like cell line stimulated with LPS (lipopolysaccharide) and on the N9 microglial cell line stimulated with LPS/IFN-gamma (interferon-gamma).

New lignan glycosides with potent antiinflammatory effect, isolated from Justicia ciliata

Two new lignan glycosides, 4-O-[alpha-L-arabinopyranosyl-(1' "-->2' ')-beta-D-xylopyranosyl-(1' " '-->5' ')-beta-D-apiofuranosyl]diphyllin (1), named ciliatoside A (1), and 4-O-¿[beta-D-apiofuranosyl-(1' " "-->3' ")-alpha-L-arabinopyranosyl-(1' "-->2' ')][beta-D-xylopyranosyl-(1' " '-->5' ')]-beta-D-apiofuranosyl¿diphyllin (2), named ciliatoside B (2), were isolated from the whole plant of Justicia ciliata. The structures of 1 and 2 were determined by spectral and chemical methods. Compounds 1 and 2 strongly inhibited the accumulation of NO(2)(-) in lipopolysaccharide-stimulated RAW 264.7 cells in a concentration-dependent manner with IC(50) values of 27.1 +/- 1.6 and 29.4 +/- 1.4 microM, respectively.

Synthesis and anti-inflammatory effect of chalcones

The process of degranulation of mast cells and neutrophils contributes to inflammatory disorders. Activation of microglial cells and macrophages is believed to be involved in inflammatory, infectious and degenerative diseases of the CNS. Combining the potent inhibition of chemical mediators released by the degranulation of mast cells or neutrophils and from the activated microglial cells or macrophages, would lead to a promising anti-inflammatory agent for the treatment of peripheral and central inflammation. A series of chalcone derivatives have been reported to have potent anti-inflammatory activity. In an effort to continually develop potent anti-inflammatory agents, novel series of chalcones, 2'-hydroxy- and 2',5'-dihydroxychalcones were synthesized and their inhibitory effects on the activation of mast cells, neutrophils, microglial cells and macrophages were evaluated in-vitro. The chalcones were prepared by Claisen-Schmidt condensation of appropriate acetophenones with an appropriate aromatic aldehyde. The alkoxychalcones were prepared with appropriate hydroxychalcones and alkyl iodide and the dihydroxychalcones were prepared by hydrogenation of an appropriate chalcone with Pd/C. Almost all of the hydroxychalcones exhibited potent inhibitory effects on the release of beta-glucuronidase and lysozyme from rat neutrophils stimulated with formyl-Met-Leu-Phe/cytochalasin B (fMLP/CB). Of the hydroxychalcones, compound 1 was the most potent inhibitor of the release of beta-glucuronidase (IC50=1.6+/-0.2 microM) and lysozyme (IC50=1.4+/-0.2 microM) from rat neutrophils stimulated with fMLP/CB. Almost all of the 2',5'-dialkoxychalcones exhibited potent inhibitory effects on nitric oxide (NO) formation from murine microglial cell lines N9 stimulated with lipopolysaccharide (LPS). Of these, compound 11 showed the greatest effect (IC50=0.7+/-0.06 microM). The present results demonstrated that most of the chalcone derivatives have an anti-inflammatory effect. The inhibitory effects of dialkoxychalcones, 10-12 on inflammation are probably not due to the inhibition of mast cells and neutrophil degranulation, but are mediated through the suppression of NO formation from N9 cells.

Stereochemistry and biological activities of constituents from Cynanchum taiwanianum

The stereochemistry of new acetophenones, cynandione B-D (2-4), isolated from Cynanchum taiwanianum, elucidated by computer modelling calculation and NOESY spectrum. It establishes the absolute configurations of cynandiones B-D (2-4) as 7R; 7"S, 7S; 7"S and 7R; 7"R, respectively. Cynandione B (2) strongly inhibited the release of beta-glucuronidase and lysozyme in formyl-methionyl-leucyl-phenylalanine (fMLP)-stimulated rat neutrophils in a concentration-dependent manner with IC50 values of 1.5 +/- 0.2 and 1.6 +/- 0.2 microM, respectively. 2,5-Dihydroxyacetophenone (6) strongly inhibited the aggregation of washed rabbit platelets induced by arachidonic acid in a concentration-dependent manner with an IC50 value of about 4.8 microM. In human citrated platelet-rich plasma, 2,5-dihydroxyacetophenone (6) inhibited the secondary phase, but not the primary phase, of aggregation induced by adrenaline and ADP. These results suggest that the antiplatelet effect of 2,5-dihydroxyacetophenone (6) is due to inhibition of the formation of thromboxane A2.

Synthesis and anti-inflammatory effect of chalcones and related compounds

PURPOSE

Mast cell and neutrophil degranulations are the important players in inflammatory disorders. Combined with potent inhibition of chemical mediators released from mast cells and neutrophil degranulations, it could be a promising anti-inflammatory agent. 2',5'-Dihydroxychalcone has been reported as a potent chemical mediator and cyclooxygenase inhibitor. In an effort to continually develop potent anti-inflammatory agents, a novel series of chalcone, 2'- and 3'-hydroxychalcones, 2',5'-dihydroxychalcones and flavanones were continually synthesized to evaluate their inhibitory effects on the activation of mast cells and neutrophils and the inhibitory effect on phlogist-induced hind-paw edema in mice.

METHODS

A series of chalcones and related compounds were prepared by Claisen-Schmidt condensation of appropriate acetophenones with appropriate aromatic aldehyde and the anti-inflammatory activities of these synthetic compounds were studied on inhibitory effects on the activation of mast cells and neutrophils.

RESULTS

Some chalcones showed strong inhibitory effects on the release of beta-glucuronidase and histamine from rat peritoneal mast cells stimulated with compound 48/80. Almost all chalcones and 4'-hydroxyflavanone exhibited potent inhibitory effects on the release of beta-glucuronidase and lysozyme from rat neutrophils stimulated with formyl-Met-Leu-Phe (fMLP). Some chalcones showed potent inhibitory effects on superoxide formation of rat neutrophils stimulated with fMLP/cytochalasin B (CB) or phorbol myristate acetate (PMA). 2',3-Dihydroxy-, 2',5'-dihydroxy-4-chloro-, and 2',5'-dihydroxychalcone showed remarkable inhibitory effects on hind-paw edema induced by polymyxin B in normal as well as in adrenalectomized mice.

CONCLUSIONS

These results indicated that the anti-inflammatory effects of these compounds were mediated, at least partly, through the suppression of chemical mediators released from mast cells and neutrophils.

2',5'-Dihydroxychalcone as a potent chemical mediator and cyclooxygenase inhibitor

Eleven chalcone derivatives have been tested for their inhibitory effects on platelet aggregation in rabbit platelet suspension and the activation of mast cells and neutrophils. Arachidonic acid-induced platelet aggregation was potently inhibited by almost all the compounds and some also had a potent inhibitory effect on collagen-induced platelet aggregation and cyclooxygenase. Some hydroxychalcone derivatives showed strong inhibitory effects on the release of beta-glucuronidase and lysozyme, and on superoxide formation by rat neutrophils stimulated with the peptide fMet-Leu-Phe (fMLP). We found that the anti-inflammatory effect of 2',5'-dihydroxychalcone was greater than that of trifluoperazine. 2'5'-Dihydroxy and 2',3,4,5'-tetrahydroxyl chalcones, even at low concentration (50 microM), tested in platelet-rich plasma from man almost completely inhibited secondary aggregation induced by adrenaline. These results suggest that the anti-platelet effects of the chalcones are mainly a result of inhibition of thromboxane formation.

Volume regulation and the efflux of amino acids from cells in incubated slices of rat cerebral cortex. II. Dependence on Ca2+ ions

The efflux of gamma-aminoisobutyric acid (GABA) and L-glutamate from pre-loaded cells in rat cerebral cortical slices has been studied during interventions designed to affect the availability of intracellular Ca2+ during hyposmotic swelling and membrane depolarization due to raised extracellular K+. Calmodulin-dependent acceleration of amino acid efflux in hyposmotic media, with cell swelling less than would be predicted on the basis of perfect osmometric behaviour (see Ref. [1]), was unaffected by Ca-ionophore in the presence of external Ca2+ or by the omission of external Ca2+, but was suppressed by pre-exposure of slices to thapsigargin (2 microM), which is reported to deplete cytosolic Ca2+, and by TMB-8 (0.5 mM), which blocks release of Ca2+ from internal stores. TMB-8 also led to significant cell swelling. The effects of TMB-8 were reversed by Ca-ionophore. Raised external K+ (54 mM) led to accelerated amino acid efflux which required calmodulin activation and was blocked by (i) omission of external Ca2+, (ii) the voltage-sensitive Ca2+ channel blocker nifedipine (1 microM), (iii) the anion transport inhibitor DIDS (25 microM for GABA, 100 microM for L-glutamate, see Ref. [1]), and (iv) the -SH group acetylator N-ethylmaleimide. TMB-8 was without effect in high K+ media. These results suggest that while enhanced amino acids efflux probably occurs through the same population of Ca/calmodulin-dependent, DIDS-sensitive pathways following hyposmotic shock or membrane depolarization, the source of Ca2+ ions required for the activation of these pathways may depend upon which of these acceleratory stimuli is applied.

Experimental model for the study by chemiluminescence of the activation of isolated equine leucocytes

The activation of human polymorphonuclear leucocytes (the respiratory burst) can be studied by measuring their chemiluminescent response. This technique was adapted to equine leucocytes to investigate the effects of cell number, activator concentration, enhancers of chemiluminescence, pH, temperature and inhibitors. Leucocytes were isolated from citrated blood from healthy horses and chemiluminescence was measured with a Bio-Orbit luminometer sensitive to 900 nm light. The optimal cell density for the maximal chemiluminescent response ranged from 10(6) to 10(7) leucocytes 600 microliters-1. Chemiluminescence increased as a function of temperature, and the concentrations of luminol, lucigenin and phorbol myristate acetate (PMA), and was pH related (optimal pH value = 8.0 for lucigenin and 8.5 for luminol). The inhibition of chemiluminescence by 5 x 10(-5) M azide was 88 per cent for luminol and 37 per cent for lucigenin. Superoxide dismutase (100 IU) totally inhibited the chemiluminescence response. Approximately 30 per cent variability in chemiluminescence was observed under the same assay conditions, depending on the origin of the leucocytes. Based on these results, the conditions selected for the measurement of equine leucocyte chemiluminescence were: 10(6) to 10(7) leucocytes 600 microliters-1, 1 x 10(-6)M PMA, 1 mM luminol or 0.4 mM lucigenin, physiological pH (7.4) and physiological temperature (37.8 degrees C). These conditions were similar to those used for measuring the chemiluminescent response of human leucocytes.

Synthesis and anti-inflammatory effects of xanthone derivatives

Eighteen synthetic xanthone derivatives were tested for their inhibitory effects on the activation of mast cells and neutrophils. 1,3- and 3,5-Dihydroxyxanthone showed strong inhibitory effects on the release of beta-glucuronidase and histamine from rat peritoneal mast cells stimulated with compound 48/80. 1,6-Dihydroxyxanthone and 1,3,8-trihydroxyxanthone showed strong inhibitory effects on the release of beta-glucuronidase, and beta-glucuronidase and lysozyme, respectively, from rat neutrophils stimulated with formyl-Met-Leu-Phe (fMLP). 1,3- and 1,6-Dihydroxyxanthone, 1,3,7-trihydroxyxanthone, and 1,3,5,6-, 2,3,6,7-, and 3,4,5,6-tetrahydroxyxanthone showed potent inhibitory effects on superoxide formation of rat neutrophils stimulated with fMLP. 1,6- and 3,5-Dihydroxyxanthone showed remarkable inhibitory effects on hind-paw oedema induced by polymyxin B in normal as well as in adrenalectomized mice. These data indicated that the anti-inflammatory effect of these compounds is mediated through the suppression of chemical mediators released from mast cell and neutrophil degranulation.

Regulation of immune complexes binding of macrophages by pectic polysaccharide from Bupleurum falcatum L.: pharmacological evidence for the requirement of intracellular calcium/calmodulin on Fc receptor up-regulation by bupleuran 2IIb

The pectic polysaccharide, bupleuran 2IIb, up-regulates Fc-receptor (FcR) expression on peritoneal macrophages in a dose-dependent manner. The intracellular signal transduction by bupleuran 2IIb leading to the expression of FcR was studied. Neither the protein kinase C (PKC) inhibitor, 1-(5-isoquinolinylsulphonyl)-2-methylpiperazine dihydrochloride, nor the structurally distinct PKC antagonist, calphostin C, inhibited bupleuran 2IIb-induced up-regulation of FcR, whereas two direct activators of PKC, L-alpha-1-oleoyl-2-acetyl-sn-3-glycerol and N-(6-phenylhexyl)-5-chloro-1-naphthalenesulphonamide were unable to up-regulate the expression of FcR. The protein kinase A (PKA) inhibitor, N-[2-(methylamino)ethyl]-5-isoquinolinesulphonamide dihydrochloride also did not inhibit bupleuran 2IIb-induced up-regulation of FcR. Fluorescence image analysis using the calcium-sensitive dye, Fura-2, demonstrated that bupleuran 2IIb induced a rapid increase in intracellular levels of calcium (Ca2+). When macrophages were treated with calcium antagonist, 8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate hydrochloride, bupleuran 2IIb-induced up-regulation of FcR was inhibited in a dose-dependent manner. The bupleuran 2IIb-induced up-regulation of FcR was also blocked by two structurally distinct calmodulin antagonists, trifluoperazine and N-(6-aminohexyl)-5-chloro-1-naphthalenesulphonamide hydrochloride. Furthermore, elevation of intracellular Ca2+ using the calcium ionophore, A23187, led to up-regulation of the FcR expression in a dose-dependent manner. These results suggest that bupleuran 2IIb induces the up-regulation of FcR on macrophages by a mechanism dependent on an increase in intracellular Ca2+ followed by activation of the calmodulin, but not by a PKC or PKA pathway.

A histamine derivative increases intracellular calcium mobilization and oxidative metabolism in HL-60 cells

Past work in our laboratory has shown that a derivative of histamine, histamine-trifluoromethyl-toluidide (HTMT), has surprising tissue specificity on lymphocytes and can produce remarkable immunosuppression. This study focuses on the effects of HTMT on Ca2+ mobilization and oxidative metabolism in undifferentiated and DMSO-differentiated HL-60 cells. HTMT caused two phases of increases in intracellular calcium concentrations ([Ca2+]i) in HL-60 cells. The responses were dose dependent, with similar EC50 values (1.7 x 10(-5) M for undifferentiated and 1.5 x 10(-5) M for differentiated cells). The increase in [Ca2+]i in differentiated cells was much greater than in undifferentiated cells. The maximum responses were observed after the undifferentiated cells were incubated with DMSO for 7 days. The increase in [Ca2+]i induced by HTMT in both types of cells was competitively antagonized by high concentrations of histamine but not by classic histamine receptor antagonists (H1, H2, or H3). The inhibitory effects of histamine on [Ca2+]i accumulation in differentiated cells were partially reversed by histamine H2 receptor antagonist ranitidine, whereas in undifferentiated cells, the effects of histamine on Ca2+ mobilization were not affected by ranitidine. Other cAMP elevating agents did not inhibit increases in [Ca2+]i in undifferentiated cells but did affect [Ca2+]i in differentiated cells. The enhanced response in [Ca2+]i mobilization after differentiation of HL-60 cells appeared to be the result of an increase in the expression/function of receptors for HTMT. One interesting feature of this regulation was the fact that cAMP per se did not regulate HTMT induced Ca2+ mobilization in undifferentiated cells but inhibited the mobilization in differentiated cells. HTMT caused the generation of reactive oxygen species in both undifferentiated and differentiated HL-60 cells as measured by chemoluminescence and the levels of generation correlated with the mobilization of [Ca2+]i. In addition, the EC50s for the HTMT induced calcium mobilization and the generation of reactive oxygen species were similar, as was the case for histamine induced inhibition (Ki) in both cell types. The data imply a second messenger role for Ca2+ in HTMT induced neutrophil activation.

Calcium mobilization and cell proliferation activated by extracellular ATP in human ovarian tumour cells

The effects of ATP on cell proliferation and intracellular calcium concentration ([Ca2+]i) were examined in a human ovarian cancer cell line (OVCAR-3). Micromolar concentrations of ATP promoted a biphasic rise in [Ca2+]i representing a phase with a rapid peak followed by a phase in which the rise was slower and sustained. When the influx of extracellular calcium was blocked by calcium chelation to EGTA, the ATP stimulated rise in [Ca2+]i was rapid and monophasic. Voltage-sensitive calcium channel blockers like nifedipine and verapamil had no effect on the action of ATP while prenylamine totally blocked calcium influx. ATP inclusion in the medium significantly stimulated growth of OVCAR-3 cells. Fetal calf serum (FCS) increased [Ca2+]i with similar biphasic kinetics representing both the entry of extracellular calcium and release of calcium from intracellular stores. FCS also caused a substantial increase in cell growth. From these experiments it was concluded that an increase in [Ca2+]i is obligatory for stimulation of cell growth in OVCAR-3 cells and that this increase probably requires a contribution from the entry of extracellular calcium. The involvement of both pertussis toxin sensitive G-protein and protein kinase C in ATP induced responses was indicated by the data showing interference of the response by pertussis toxin and phorbol-myristate acetate.

Inhibitory effect of 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8) on germination of Bacillus cereus T spores

Effect of 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate hydrochloride (TMB-8), a calcium antagonist, on germination of Bacillus cereus T spores induced by L-alanine and inosine was investigated. TMB-8 had no effect on the germination of heat-activated spores, whereas it inhibited that of nonactivated spores. The TMB-8 inhibitory effect was antagonized competitively by inosine, but not by L-alanine. Addition of Ca2+ reversed the inhibitory effect of TMB-8 in a dose-related fashion. Based on the results, a role of inosine and a site(s) for inhibitory action of TMB-8 in the process leading to the germination of nonactivated spores were discussed.

Characterisation of muscarinic cholinergic receptors in human ovaries, ovarian tumours and tumour cell lines

Using [3H]quinuclidinyl benzilate (QNB) as radioligand, muscarinic cholinergic receptor sites in isolated plasma membrane fractions from human ovarian tumours, cultured tumour cells, and normal ovarian tissue were characterised. QNB binding to all preparations, except from poorly differentiated tumour, was specific, saturable, and of high affinity. In contrast to normal ovaries, benign tumours, well differentiated adenocarcinoma and OVCAR-3 cells, the poorly differentiated adenocarcinoma and SKOV-3 cells completely lacked specific QNB binding. The muscarinic receptor densities and the Kd values in preparation from ovaries, receptor-positive tumours and OVCAR-3 cells were similar. QNB binding was strongly inhibited by the classical muscarinic receptor antagonist atropine, but poorly by the agonist carbachol. In contrast to atropine, inhibition by pirenzepine and AF-DX 116 was relatively low. These data suggest that muscarinic receptors in ovaries and ovarian tumours are of m3 type.

Independent actions of asparagine and high levels of free Ca2+ in the induction of ornithine decarboxylase

During growth stimulation of cells, Ca2+ and amino acids of the A, ASC and N transport systems are important for the induction of ornithine decarboxylase (ODC, L-ornithine carboxylase, EC 4.1.1.17). In order to clarify the relationship between Ca2+ and amino acids, we studied the induction of ODC by asparagine under three different Ca2+ states in H-35 rat hepatoma cells. First, in normal cells, extracellular Ca2+ above 0.1 mM and 10 mM asparagine separately stimulated ODC activity and their effects were approximately additive. In these normal cells, asparagine could act in the absence of medium Ca2+. TMB-8, a sequestered-Ca2+ release antagonist, had no effect on ODC induction whilst the asparagine action is sensitive to treatment with W7, a Ca-calmodulin antagonist, or lanthanum, a Ca2+ antagonist. Secondly, in cells treated with 0.5 mM EGTA in Ca(2+)-free medium, the asparagine action on ODC induction was blocked but the inhibition could be reversed by the addition of Ca2+ to the medium. Thirdly, ionomycin treatment in the absence of medium Ca2+ did not block the asparagine effect. Furthermore, in ionomycin-treated cells, the presence of high levels of medium Ca2+ increased ODC activity, but this increase was additive to, and could not replace, the action of asparagine. Our results indicate that the asparagine action does not depend on an increase of intracellular free-Ca2+.

Human neutrophil response to short-term exposure to F-75 cobalt-based alloy

The effect of biomaterials on the activation of human neutrophils was studied. Human neutrophils were incubated with F-75 cobalt-based alloy or polystyrene microspheres of a nonphagocytosable size with two times total neutrophil plane surface area. Scanning and transmission electron microscope (SEM, TEM), energy dispersive x-ray microanalysis (EDX), and graphite furnace atomic absorption spectroscopy (GFAAS) were used to analyze changes in cellular morphology and metal content. This report presents evidence that human PMNs display morphological changes related to foreign material challenge, including activation on F-75 bead surfaces, pinocytosis of corrosion products, formation of intracellular vacuoles, degranulation, etc. Moreover, when PMNs were present, the corrosion release rate of F-75 increased as much as three times over cell-free controls.

Interferon-gamma induces phosphorylation of multiple small-molecular-weight proteins in U937 cells

This study examines the hypothesis that interferon-gamma (IFN-gamma) induces protein phosphorylation as part of the signal transduction pathway used to activate U937 cells. U937 cells labeled with 32Pi were treated with IFN-gamma, proteins were separated by two-dimensional polyacrylamide gel electrophoresis, and the pattern of protein phosphorylation was determined by autoradiography and computer-assisted two-dimensional densitometry. IFN-gamma (100 U/ml) induced phosphorylation of multiple proteins between 15 and 60 min, and the proteins were all dephosphorylated by 120 min. The pattern of proteins phosphorylated in the presence of ionomycin or PMA differed from that of IFN-gamma. Inhibition of protein kinase C activity by 1-(5-isoquinolinesulfonyl)2-methyl piperazine (H-7), inhibition of calcium-calmodulin-dependent protein kinase by N-(6-aminohexyl)-5-chloro-naphthalenesulfonamide (W-7), and inhibition of calcium redistribution by 8-(diethylamino)-octyl 3,4,5-trimethoxybenzoate hydrochloride (TMB-8) did not inhibit the majority of IFN-gamma-induced protein phosphorylation. These data indicate that IFN-gamma induces protein phosphorylation in U937 cells by activation of a kinase different from, or in addition to, protein kinase C or calcium-calmodulin-dependent kinase.

Calcium and potassium are important regulators of barrier homeostasis in murine epidermis

Topical solvent treatment removes lipids from the stratum corneum leading to a marked increase in transepidermal water loss (TEWL). This disturbance stimulates a variety of metabolic changes in the epidermis leading to rapid repair of the barrier defect. Using an immersion system we explored the nature of the signal leading to barrier repair in intact mice. Initial experiments using hypotonic to hypertonic solutions showed that water transit per se was not the crucial signal. However, addition of calcium at concentrations as low as 0.01 mM inhibited barrier repair. Moreover, both verapamil and nifedipine, which block calcium transport into cells, prevented the calcium-induced inhibition of TEWL recovery. Additionally, trifluoroperazine or N-6-aminohexyl-5-chloro-1-naphthalenesulfonamide, which inhibit calmodulin, prevented the calcium-induced inhibition of TEWL recovery. Although these results suggest an important role for calcium in barrier homeostasis, calcium alone was only modestly effective in inhibiting TEWL recovery. Potassium alone (10 mM) and phosphate alone (5 mM) also produced a modest inhibition of barrier repair. Together, however, calcium and potassium produced a synergistic inhibition of barrier repair (control 50% recovery vs. calcium + potassium 0-11% recovery in 2.5 h). Furthermore, in addition to inhibiting TEWL recovery, calcium and potassium also prevented the characteristic increase in 3-hydroxy-3-glutaryl CoA reductase activity that occurs after barrier disruption. Finally, the return of lipids to the stratum corneum was also blocked by calcium and potassium. These results demonstrate that the repair of the epidermal permeability barrier after solvent disruption can be prevented by calcium, potassium, and phosphate. The repair process may be signalled by a decrease in the concentrations of these ions in the upper epidermis resulting from increased water flux leading to passive loss of these ions.

Effect of 2-acetylaminofluorene on intracellular free Ca2+ in isolated rat hepatocytes

The effect of 2-acetylaminofluorene (2-AAF) on the intracellular free Ca2+ ([Ca2+]i) and viability of isolated rat hepatocytes has been investigated using the fluorescent probes quin 2 and propidium iodide respectively. At the highest concentration tested (224 microM), 2-AAF produces an elevation of [Ca2+]i which shows a biphasic profile. A small initial increase is observed during the first 5 min; this is followed by a considerable rise which reaches up to 2.5 times the control value at 15 min. These changes in intracellular calcium are not accompanied by detectable alterations in cell viability. In order to determine the mechanisms by which this effect of 2-AAF takes place, three calcium antagonists, namely verapamil, TMB-8 (8-(diethylamino)-octyl-3,4,5-trimethoxybenzoate) and ruthenium red (RuR), have been used. The results suggest that the first phase is dependent upon internal Ca2+ store mobilization, while the second phase seems to be related to Ca2+ entry from the extracellular space. The data obtained with RuR further indicate that mitochondria may be involved in the perturbation of calcium homeostasis caused by 2-AAF. In addition, in the experiments involving antagonists, no consistent pattern emerges that suggests a close relationship between intracellular Ca2+ levels and cell viability. The present study provides further information on the mechanisms by which these well-known hepatotoxin 2-AAF may interact with liver cells. It also shows that when these cells are exposed to a toxin, short-term changes in [Ca2+]i may not be accompanied by loss of cell viability, and conversely, that changes in cell viability may occur without alterations in [Ca2+]i.

Receptor-mediated increase in cytosolic calcium in LLC-PK1 cells by platelet activating factor and thromboxane A2

Several studies indicate an important role of platelet activating factor (PAF) and thromboxane A2 (TXA2) in glomerular pathophysiology. However, the potential role of PAF or TXA2 in renal tubular pathophysiology has received little attention, and the presence of functional receptors for these autacoids in renal tubular epithelium has not been previously studied. We examined the effects of PAF and the TXA2 analogue, ONO11113, on the cytosolic free calcium concentration [( Ca2+]i) in cultured LLC-PK1 cell line using a fluorescent probe, fura-2. In these cells, the addition of PAF or ONO11113 caused a significant increment in [Ca2+]i in a dose-dependent manner: both agonists (10(-7) M) increased [Ca2+]i from 148 +/- 16 to 288 +/- 39 nM and from 130 +/- 8 to 240 +/- 18 nM, with the values of EC50 for PAF and ONO11113 being 17 +/- 4 and 17 +/- 2 nM, respectively. These effects were both rapid and transient, returning to baseline in two minutes. The effect of PAF was selectively blocked by PAF receptor antagonist BN50730, but not by TXA2 receptor antagonist L657925. Similarly ONO11113 response was abolished by L657925, but not by BN50730. PAF- or ONO11113-challenged cells did not respond to a second addition of the same agent and showed heterologous desensitization to the other agonist. The initial peaks of [Ca2+]i as well as the sustained elevations in [Ca2+]i induced by PAF or ONO11113 were reduced following the chelation of extracellular Ca2+ by 10 mM ethylene glycol-bis(beta-aminomethyl ether)-N,N,N',N'-tetraacetic acid (EGTA).(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the response of bovine and human neutrophils to various stimuli

Elastase release, oxidant production and cytoplasmic Ca2+ fluxes by bovine and human neutrophils were compared using sensitive kinetic assays on a photon-counting spectrofluorometer. The stimulants used were phorbol myristate acetate (PMA), cytochalasin B, zymosan opsonized with bovine complement (bOZ) or human complement (hOZ), calcium ionophore, formyl-methionyl-leucyl-phenylalanine (FMLP) and concanavalin A (Con A). The respiratory burst of bovine and human neutrophils was stimulated by PMA and OZ but not by cytochalasin B, or calcium ionophore. Con A weakly stimulated this response in human neutrophils but not bovine. FMLP stimulated the respiratory burst of human but not bovine neutrophils. For evaluation of elastase release, human neutrophils were pretreated with cytochalasin B for 5 min and then stimulated. Cytochalasin B alone did not stimulate elastase release from human neutrophils. Phorbol myristate acetate, calcium ionophore, hOZ, FMLP and Con A did stimulate human neutrophils pretreated with cytochalasin B to release elastase. Human serum OZ was also able to stimulate elastase release from human neutrophils not pretreated with cytochalasin B. Some bovine neutrophils released elastase in response to cytochalasin B alone. Those bovine neutrophils that did not release elastase in response to cytochalasin B alone released elastase when stimulated with Con A or calcium ionophore after cytochalasin B pretreatment. Bovine neutrophils did not release elastase in response to FMLP or PMA with or without cytochalasin B pretreatment, but did release elastase in response to bOZ alone. Total elastase activity of bovine neutrophils was determined to be about 50 times less than that of human neutrophils. Intracellular calcium fluxes were stimulated in human neutrophils by calcium ionophore, FMLP, hOZ and Con A but not by PMA or cytochalasin B. Bovine neutrophil calcium fluxes were stimulated by calcium ionophore, Con A and bOZ; cytochalasin B also stimulated bovine neutrophils to increase cytoplasmic calcium concentration. Cytoplasmic calcium fluxes were not stimulated in bovine neutrophils by PMA or FMLP. In summary, human and bovine neutrophils respond similarly to calcium ionophore and OZ, but differently to PMA, cytochalasin B, Con A and FMLP.

Inhibitory effect of 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) in vascular smooth muscle

The inhibitory effects of 8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate (TMB-8) on vascular smooth muscle contraction and cytosolic Ca2+ level ([Ca2+]i) were examined using isolated rabbit aorta loaded with a fluorescent Ca2+ indicator, fura-2. TMB-8 (100 microM) decreased the high K(+)-induced increase in muscle tension, and [Ca2+]i and 45Ca2+ influx to their respective resting levels. TMB-8 (100 microM) almost completely inhibited the increase in [Ca2+]i and 45Ca2+ influx due to norepinephrine although muscle tension was only partially decreased. A higher concentration of TMB-8 (300 microM) inhibited the remaining portion of the contraction without additional decrease in [Ca2+]i. The inhibitory effect of TMB-8 on high K(+)-induced contraction, but not on the norepinephrine-induced contraction, was antagonized by the increase in external Ca2+ concentrations or by the Ca2+ channel activators, CGP 28,392 and by Bay K8644. In Ca(2+)-free solution, norepinephrine-induced transient increases in [Ca2+]i and muscle tension and 100 microM TMB-8 inhibited these changes. The caffeine-induced transient increases in [Ca2+]i and muscle tension were also inhibited by TMB-8 at concentrations higher than those needed to inhibit the norepinephrine-induced transient changes. In permeabilized smooth muscle, TMB-8 (300 microM) did not inhibit the Ca(2+)-induced contraction. These results suggest that TMB-8 inhibits vascular smooth muscle contractility by inhibiting Ca2+ influx, Ca2+ release and Ca2+ sensitization of contractile elements.

Signal transduction mechanisms of Ia induction in B cells by interleukin 4 and immunoglobulin receptors

Molecular mechanisms of signal transduction through receptors for interleukin 4 (IL-4) are still largely unknown. To elucidate the second messenger(s) of IL-4 action in mature B cells, we performed blocking experiments with inhibitors of various aspects of cellular responses, using Ia-inducing activity of IL-4 as a readout system. In the event, only agents that are shown to inhibit calcium ion (Ca2+) release from intracellular stores, such as 3,4,5-trimethoxybenzoic acid 8-(diethylamino)octyl ester (TMB-8) and ryanodine, could block the IL-4 action in a dose-dependent fashion. These results suggest that the process leading to the final expression of IL-4 action may be mediated, at some point, by the release of Ca2+ from intracellular stores. In the parallel experiments with antiimmunoglobulin (Ig) antibody, we found that amiloride, an inhibitor of Na+/H+ pump, blocks the Ia induction by anti-IgM antibody. Thus the Na+/H+ exchange system activated by anti-Ig antibody may be present in mature B cells.

Role of intracellular calcium in priming of human peripheral blood monocytes by bacterial lipopolysaccharide

To determine the role of intracellular calcium ([Ca2+]i) in the priming of monocytes (M phi) by bacterial lipopolysaccharide (LPS), the membrane expression of two functional proteins and phagocytosis and respiratory burst were examined by microfluorimetry. LPS induced a significant increase in HLA-DR and C3bi receptor (CR3) expression within 2 h of its addition to whole blood. The enhanced expression of both antigens by LPS was dose-dependent, with concentrations as low as 0.1 ng/ml producing a response. The involvement of [Ca2+]i was demonstrated by loading isolated M phi with the intracellular calcium chelator quin-2 or the inhibitor of intracellular calcium redistribution TMB-8 prior to addition of LPS. Both compounds inhibited the LPS-induced increase in HLA-DR and CR3 expression. No role for extracellular calcium, for calcium slow channel flux, or for the calcium-calmodulin complex in LPS priming was demonstrated when LPS was added in the presence of EGTA, trifluperazine (TFP), or verapamil. The addition of the calcium ionophores A23187 or ionomycin failed to increase expression of either antigen. Prior exposure to LPS primed M phi for enhanced phagocytosis and respiratory burst activity. These functions were inhibited by TMB-8, but not by TFP or verapamil. Addition of LPS to isolated M phi increased [Ca2+]i by 23% at 30 sec and 42% at 5 min, as measured by the calcium-sensitive, intracellular probe indo-1. These results suggest that intracellular Ca2+ mobilization is necessary, but not sufficient, for LPS-induced priming of human peripheral blood monocytes.

Ca++ antagonists distinguish different requirements for cAMP-mediated gene expression in the cellular slime mold, Dictyostelium discoideum

Cyclic AMP is essential for the accumulation of many prespore mRNAs and can advance the time of appearance of mRNAs specifically enriched in prestalk cells. Additionally, when late-developing cells are washed free of cAMP, a number of growth phase mRNAs reaccumulate. This reaccumulation can be suppressed by cAMP. These effects of cAMP are all mediated through the cell surface cAMP receptor and can occur under conditions where the receptor-associated adenylate cyclase is inactive, indicating that the initial intracellular transduction event necessary for expression of these mRNAs does not depend upon cAMP synthesis. The dihydropyridine derivatives, nifedipine and nitrendipine, are highly specific Ca++ channel blockers. They are shown here to prevent the influx of Ca++ from the external medium that occurs in response to cAMP binding to the cell surface receptor during development. These two compounds as well as another Ca++ antagonist, 8-N,N-diethylamino)octyl-3,4,5-trimethoxy-benzoate (TMB-8) and a calmodulin inhibitor, N-(6-amino-hexyl)-5-chloro-1-naphthalene sulfonamide (W7), all specifically decrease cAMP-mediated prespore mRNA accumulation in a dose-dependent manner. They also prevent cAMP from suppressing the expression of the growth phase genes. The growth phase mRNAs reaccumulate in cAMP-treated cells in the presence of increasing concentrations of these drugs. By contrast, cAMP induction of the pre-stalk-enriched mRNA is not as significantly affected by these agents. These results raise the possibility that the cell surface cAMP receptor can couple to different signal transduction systems and thereby induce or suppress the expression of different sets of cAMP-regulated genes during development.

Resistance of some capsular serotype D strains of Pasteurella multocida to rabbit polymorphonuclear neutrophil phagocytosis

The mechanism of resistance of Capsular Type D strains of Pasteurella multocida to killing by rabbit polymorphonuclear neutrophils (PMN) was studied using an in vitro assay that differentiates intra- from extracellular bacteria. Two Capsular Type D strains (3761 and 3766), resistant to killing by rabbit PMN, and one Type A strain (R1), susceptible to PMN destruction, were compared. After combining opsonized bacteria and PMN, the Capsular Type D Strains 3761 and 3766 remained extracellular while the Capsular Type A Strain R1 was internalized by PMN. Thus, both Type D strains were resistant to phagocytosis by rabbit PMN.

The effect of calcium channel blockers and calmodulin inhibitors on the macrophage factor-stimulated synthesis of collagenase by rabbit chondrocytes

Macrophages and monocytes secrete a factor(s) which can stimulate the synthesis of collagenase in synovial cells and in chondrocytes. Incubation of rabbit chondrocytes with macrophage conditioned medium (MCM) and with the calcium channel blockers, nifedipine, verapamil or diltiazem (up to 200 microM) had no effect on collagenase synthesis. However, TMB-8 (8-[N,N-diethylamino]-octyl 3,4,5-trimethoxybenzoate hydrochloride), an inhibitor of internal calcium movement, did inhibit the process with an IC50 of approximately 130 microM. The calmodulin antagonists, trifluoperazine, chlorpromazine and calmidazolium (R-24571) were effective inhibitors of the process with IC50's of 40 microM, 18 microM and 3.5 microM, respectively. Collagenase activity itself was not affected by these agents. The data suggests that calmodulin and/or internal calcium movement may play a role in the macrophage factor-stimulated synthesis of collagenase in rabbit chondrocytes.

Prostaglandin E2 releases luteinizing hormone-releasing hormone from the female juvenile hypothalamus through a Ca2+-dependent, calmodulin-independent mechanism

Prostaglandin E2 (PGE2) has been implicated as a mediator of norepinephrine-induced luteinizing hormone-releasing hormone (LHRH) release from the hypothalamus. The present experiments were undertaken to examine the hypothesis that mobilization of Ca2+ from intracellular stores and cyclic AMP (cAMP) formation are involved in this effect. Incubation of median eminence (ME) nerve terminals from juvenile rats in Ca2+-free Krebs-Ringer bicarbonate buffer reduced, but failed to prevent the stimulatory effect of PGE2 on LHRH release. None of 5 calmodulin antagonists or a blocker of calmodulin-dependent kinase affected the LHRH response to PGE2. In contrast, inhibition of intracellular Ca2+ mobilization with TMB-8 or dantrolene in Ca2+-free medium prevented the LHRH releasing effect of PGE2. Similarly to PGE2, the stimulatory effect of the Ca2+ ionophore A 23187 on LHRH release was not affected by inhibition of calmodulin activity. This, however, blocked the increase in PGE2 formation induced by the ionophore. PGE2 evoked a dose-related increase in cAMP accumulation in Ca2+-containing medium and this effect was inhibited both by blockers of intracellular Ca2+ mobilization and by calmodulin antagonists. Surprisingly, removal of extracellular Ca2+ increased basal cAMP levels in the incubation medium without affecting LHRH release; PGE2 induced a further increase in cAMP which was prevented by inhibition of intracellular Ca2+ translocation. Stimulation of adenylate cyclase activity with forskolin (F) resulted in similar increases in cAMP levels both in the presence and absence of extracellular Ca2+. However, F failed to evoke LHRH release in Ca2+-free medium. The results indicate that: (a) the stimulatory effect of PGE2 on LHRH release involves mobilization of intracellular Ca2+ but not the participation of calmodulin; (b) the formation of PGE2 itself is calmodulin-dependent; (c) PGE2 stimulates cAMP formation through a calmodulin-dependent mechanism that requires translocation of intracellular (membrane?) Ca2+; (d) the cAMP system of a population of nerve terminals different from that responsive to PGE2 is normally subjected to a Ca2+-dependent inhibitory control; and (e) although PGE2 is a potent stimulator of cAMP formation in the ME and endogenously produced cAMP can induce LHRH release, in the absence of extracellular Ca2+ PGE2 stimulates LHRH release in a cAMP-independent manner.

Effects of TMB-8, a calcium antagonist, on transport properties of the isolated canine tracheal epithelium

The effects of the putative intracellular Ca2+ antagonist, TMB-8 (8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate), on the canine tracheal epithelium were examined. Luminal addition reduced rapidly, but reversibly, the transmucosal potential difference and increased the resistance across the open-circuited epithelium. Under short-circuit conditions, the drug reduced stimulation by prostaglandin E2, forskolin, 8-bromo cyclic AMP, prostaglandin F2 alpha and A23187. Inhibition of prostaglandin E2 responses were accompanied by reversal of net Cl- fluxes produced by the agonist. The effects of TMB-8 were unaffected by increasing Ca2+ in the bathing solutions, and were not mimicked by procaine, nitrendipine, calmidazolium, compound 48/80 or trifluoperazine. W7 did, to a limited extent, produce similar responses, though the drug was more toxic, and the effects were irreversible.

The intracellular calcium antagonist, TMB-8, inhibits prolactin gene expression in GH3 cells

We examined the effects of the drug, TMB-8, which promotes sequestration of intracellular Ca2+, on the ability of extracellular Ca2+ to stimulate prolactin gene expression in GH3 cells. TMB-8 inhibited prolactin mRNA levels in a dose-dependent manner in the concentration range of 2.5-10 microM. Prolactin mRNA levels were increased about 18-fold by the addition of 0.1 mM CaCl2, and about 25-fold by the addition of 0.4 mM CaCl2. Addition of 10 microM TMB-8 reduced these levels to about 4-fold and 7-fold, respectively. At 10 microM TMB-8 did not effect total protein synthesis or the Ca2+-induced aggregation of the cells, indicating a selective inhibition by the drug of prolactin gene expression. Both TMB-8 and the calmodulin inhibitor, calmidazolium, reversed the effects of Ca2+ on prolactin mRNA levels in cells that had been pretreated for 2 days with 0.4 mM CaCl2.

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.

Human polymorphonuclear neutrophil activation with arachidonic acid

The capacity of arachidonic acid (AA) to stimulate granule exocytosis from human polymorphonuclear neutrophils (PMNs) was investigated. AA induced the selected extracellular release of azurophil (myeloperoxidase, lysozyme) and specific (lysozyme, vitamin B12 binding protein) granule constituents from human PMNs in a time- and concentration-dependent manner. Cytochalasin B (CB) enhanced but was not required for PMN activation with AA. Although extracellular calcium had no effect on granule exocytosis, AA did stimulate the mobilization of intracellular sequestered Ca2+ which resulted in an increase in cytosolic-free Ca2+ ([Ca2+]i) as reflected by increased fluorescence of Fura-2-treated cells. AA stimulated Ca2+/phospholipid-dependent protein kinase C (PK-C) activity in PMNs. 4,4'-Diisothiocyano-2,2'-disulphonic acid stilbene (DIDS), an anion channel blocker, caused a concentration-dependent inhibition of granule enzyme release. Activation of PMNs with AA was unaffected by the lipoxygenase/cycle-oxygenase inhibitors, 5,8,11, 14-eicosatetraynoic acid (ETYA) and benoxaprofen, a lipoxygenase inhibitor, 6, 9, deepoxy-6,9-(phenylimino) delta 6,8-prostaglandin 1(1) (piriprost potassium) or a pure cyclo-oxygenase inhibitor, flurbiprofen. These data define the properties of AA as a secretory stimulus for human PMNs.

Contraction of rat thoracic aorta strips induced by phorbol 12-myristate 13-acetate

Phorbol 12-myristate 13-acetate (PMA) induced a slow and progressive increase in tension of rat thoracic aorta strips in the presence of extracellular Ca2+. Complete relaxation could not be obtained in Ca2+-free buffer containing 1 mM ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid (EGTA) and 10(-7) M PMA. In the absence of extracellular Ca2+, PMA (10(-7) M) induced a small but sustained contraction which was not altered by the addition of another 2 mM EGTA and 3 X 10(-5) M verapamil. Papaverine (10(-4) M) relaxed the PMA-induced contraction to the base line, but phentolamine (10(-5) M), cyproheptadine (10(-5) M), atropine (10(-5) M) and tetrodotoxine (10(-6) M) did not change the contraction. Ca2+-depleted muscle strips, prepared by four repeated applications of 10(-7) M norepinephrine in Ca2+-free buffer, were contracted by 10(-7) M PMA, but at a lower maximum tension than nontreated strips. The action of PMA on rat aorta strips in Ca2+-free buffer did not require the presence of the adventitial layer or endothelial cells. These results suggest that PMA may induce activation of protein kinase C and smooth muscle contraction in the absence of extracellular Ca2+, without an increase in myoplasmic Ca2+.