Possible role of calmodulin in the control of histamine release from human basophil leukocytes

Trifluoperazine enhancement of Ca2+-dependent inactivation of L-type Ca2+ currents in Helix aspersa neurons

The effects of trifluoperazine hydrochloride (TFP), a calmodulin antagonist, on L-type Ca2+ currents (L-type ICa2+) and their Ca(2+)-dependent inactivation, were studied in identified Helix aspersa neurons, using two microelectrode voltage clamp. Changes in [Ca2+]i were measured in unclamped fura-2 loaded neurons. Bath applied TFP produced a reversible and dose-dependent reduction in amplitude of L-type ICa2+ (IC50 = 28 microM). Using a double-pulse protocol, we found that TFP enhances the efficacy of Ca(2+)-dependent inactivation of L-type ICa2+. Trifluoperazine sulfoxide (50 microM), a TFP derivative with low calmodulin-antagonist activity, did not have any effects on either amplitude or inactivation of L-type ICa2+. TFP (20 microM) increased basal [Ca2+]i from 147 +/- 37 nM to 650 +/- 40 nM (N = 7). The increase in [Ca2+]i was prevented by removal of external Ca2+ and curtailed by depletion of caffeine-sensitive intracellular Ca2+ stores. Since TFP may also block protein kinase C (PKC), we tested the effect of a PKC activator (12-C-tetradecanoyl-phorbol-13-acetate) on L-type Ca2+ currents. This compound produced an increase in L-type ICa2+ without enhancing Ca(2+)-dependent inactivation. The results show that 1) TFP reduces L-type ICa2+ while enhancing the efficacy of Ca(2+)-dependent inactivation. 2) TFP produces an increase in basal [Ca2+]i which may contribute to the enhancement of Ca(2+)-dependent inactivation. 3) PKC up-regulates L-type ICa2+ without altering the efficacy of Ca(2+)-dependent inactivation. 4) The TFP effects cannot be attributed to its action as PKC blocker.

Contribution of cAMP to the inhibitory effect of non-steroidal anti-inflammatory drugs in rat uterine smooth muscle

1. The effect of the non-steroidal anti-inflammatory drugs naproxen, mefenamic acid, phenylbutazone, piroxicam and tolmetin on the vanadate (0.3 mM)-induced tonic contraction, as well as the modifications of these effects by the G-protein inhibitor pertussis toxin, and the inhibitors of protein kinase A, Rp-cAMPS (Rp-Adenosine 3',5'-cyclic monophosphothioate triethylamine salt) and protein kinase C, H-7 [1(5-isoquinolynilsulfonyl)-2-methyl-piperazine], have been assayed to study the possible nature of intracellular mediators contributing to the inhibitory effects of NSAIDs in rat uterine smooth muscle incubated in medium lacking calcium plus EDTA. The effect of phorbol 12,13-dibutyrate on vanadate contraction and its modification with H-7 has also been examined. 2. Naproxen (6-600 microM), mefenamic acid (6-300 microM), phenylbutazone (6-300 microM), piroxicam (6-600 microM) and tolmetin (6-600 microM) produced concentration-dependent relaxation of vanadate-induced tonic contraction. The potency order, in accordance with their respective IC50 values was: phenylbutazone > or = mefenamic acid > or = naproxen > tolmetin > or = piroxicam. 3. The relaxant effects of naproxen, phenylbutazone, piroxicam and tolmetin were significantly antagonized with pertussis toxin (50 ng ml-1), Rp-cAMPS (100 microM) and H-7 (1 microM). However, the effect of mefenamic acid was unmodified by the three drugs. This suggests that the effect of mefenamic acid and other NSAIDs occur by different mechanisms. 4. Phorbol 12,13-dibutyrate relaxed the vanadate contraction but the maximal relaxation achieved (54.8 +/- 8.3%, n = 4) was lower than those induced with the NSAIDs. On the other hand, H-7 (1 microM) did not modify the relaxant effect of phorbol 12,13-dibutyrate. This suggests that H-7 behaves as a PKA, but not a PKC inhibitor, under the present experimental conditions. 5. The relaxation by naproxen, phenylbutazone, piroxicam and tolmetin is presumably produced by increasing cAMP because the effects of these are antagonized with Rp-cAMPS and H-7, and by pertussis-toxin-sensitive mechanisms.

Nitric oxide and cyclic nucleotides participate in the relaxation of diclofenac on rat uterine smooth muscle

1. The effect of diclofenac (10-100 microM) on vanadate-induced contraction of rat uterus in calcium-free buffer containing EDTA and the modification of this response by pertussis toxin (50 micrograms/ml), Rp-cAMPS (10 microM), W-7 (10 and 60 microM), L-NMMA (10 and 100 microM) and D-NMMA (100 microM) has been assessed. The effects of sodium nitroprusside (10 microM-1 mM), 3-morpholinosydnonimine (SIN-1; 0.1-100 microM), 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ; 0.1-100 microM) and 8-BrcGMP (10 microM to 1 mM) on vandate-evoked contraction were also studied. 2. Diclofenac produced dose-dependent relaxation of vanadate (0.3 mM)-induced contraction (EC50:17.3 +/- 1.8 microM, n = 11). This effect was significantly (P < 0.05) reduced by pertussis toxin (EC50: 37.4 +/- 4.5 microM, n = 6) and Rp-cAMPS (EC50:36.3 +/- 3.1 microM, n = 6). 3. The calmodulin inhibitor W-7 (1-100 microM) relaxed, in a concentration-dependent way, the vanadate contraction (EC50:67.0 +/- 18 microM). W-7 (10 and 60 microM) did not modify the relaxation elicited by diclofenac, which suggests that calmodulin inhibition and the increase of cAMP are two different actions of diclofenac. 4. The action of diclofenac was antagonized (P < 0.05) by L-NMMA (100 microM) and ODQ (1 and 100 microM) but not by D-NMMA (100 microM), which suggests the involvement of NO-synthase in this effect. 5. Sodium nitroprusside (1 mM) relaxed the vanadate contraction by only 31.7 +/- 1.04% (n = 7) and SIN-1 by 27.1 +/- 1.2% (n = 6). This suggests that, under the present experimental conditions, both NO donors were ineffective. However, 8-BrcGMP (EC50:327 +/- 71 microM, n = 7) relaxed this contraction up to 58.7 +/- 1.89%. Rp-cAMPS (10 microM) did not modify the 8-BrcGMP effect. Thus, a partial contribution of cGMP to inhibitor effect of drugs on rat uterus was possible. 6. The association between L-NMMA plus ODQ, L-NMMA plus Rp-cAMPS and ODQ plus Rp-cAMPS did not produce more displacement than L-NMMA, Rp-cAMPS or ODQ alone. This suggests the involvement of NO and cyclic nucleotides in the relaxant effect of diclofenac in rat uterus.

Involvement of sodium/calcium exchange in the diclofenac-induced spasmolytic effect on rat uterus

1. The effect of diclofenac (10-100 microM) on rat uterus contraction and its modification by ouabain (0.1 mM), amiloride (0.1 and 1 mM), ouabain (0.1 mM) plus amiloride (1 mM) and the replacement of sodium by choline have been assayed. 2. Diclofenac produces dose-dependent relaxation of vanadate (0.3 mM)-induced contraction (EC50, 17.3 +/- 1.8 microM). This effect is significantly reduced in choline medium (EC50, 49.1 +/- 4.5 microM) and by ouabain in sodium-medium (EC50, 52 +/- 7 microM). 3. Amiloride displaces, in a dose-dependent way, the diclofenac-induced relaxant effect. However, ouabain plus amiloride did not produce a sinergic effect. 4. Our results suggest that diclofenac produces relaxation of vanadate-induced contraction by activation of Na+/Ca(2+)-exchange.

Spasmolytic and calmodulin inhibitory effect of non-steroidal anti-inflammatory drugs in vitro

The effect of several anti-inflammatory drugs (NSAIDs), the calmodulin inhibitor W-7 and cortisol on vanadate-induced tonic contraction and on calmodulin dependent cAMP-phosphodiesterase activity have been assayed. Indomethacin, diclofenac, phenylbutazone, mefenamic acid, naproxen, tolmetin, piroxicam, aspirin and W-7, but not metimazol, produce dose-dependent relaxation of vanadate-induced tonic contraction on isolated rat uterus. Cortisol relaxes the vanadate contraction up to 45%. None of the drugs assayed inhibit the basal activity of phosphodiesterase with concentrations lower than 1 mM. However, indomethacin, diclofenac, phenylbutazone, mefenamic acid, naproxen, piroxicam, aspirin and W-7 inhibit, in a concentration-dependent way, the calmodulin-stimulated activity of phosphodiesterase. The maximum inhibition achieved with tolmetin (1 mM) and cortisol (1 mM) was 38% and 24%, respectively. Metamizol has no effect on basal or/and stimulated phosphodiesterase. This, as far as we know, is the first description of relationship between NSAIDs and calmodulin-dependent processes and our results suggest that the inhibition of calmodulin with NSAIDs may be directly related to their pKa and liposolubility.

Human basophil histamine release is differently affected by inhibitors of calmodulin, diacylglycerol kinase and peptidyl prolyl cis-trans isomerase in a secretagogue specific manner

To assess the role of calmodulin in human basophil histamine release, we triggered leukocytes with different secretagogues in the presence of putative inhibitors of calmodulin. Calcium ionophore-induced histamine release was reduced or blocked by calmidazolium, CGS 9343B, felodipine, metofenazate, and Ro 22-4839. H 186/86, a felodipine-related dihydropyridine derivative, blocked A23187-but not ionomycin-triggered histamine release, suggesting a difference in the mode of action of these ionophores. In contrast, leukocyte histamine release triggered by the purported protein kinase C (PKC) activator, 1,2-isopropylidene-3-decanoyl-sn-glycerol (IpOCOC9), was enhanced by calmidazolium, CGS 9349B and metofenazate but not affected by felodipine or Ro 22-4839, whereas the response triggered by 4 beta-phorbol 12-myristate 13-acetate (PMA) was reduced by metofenazate and Ro 22-4839 but not consistently affected by calmidazolium, CGS 9343B or felodipine. The PMA-induced histamine release was enhanced by H 186/86. Anti-IgE- and FMLP-induced responses were either unaffected or slightly enhanced by the examined calmodulin antagonists. In comparison with the calmodulin antagonists, R 59022, an inhibitor of diacylglycerol kinase, failed to reduce calcium ionophore-triggered histamine release, whereas FK506, an inhibitor of peptidyl prolyl cis-trans isomerase (PPI), reduced both anti-IgE- and ionophore-triggered responses. These results indicate that calmodulin constitutes an obligate link in signal transduction pathways leading to human leukocyte histamine release if the trigger is a calcium ionophore but not when responses are induced by anti-IgE, FMLP or PMA; a calmodulin-dependent component may rather balance responses induced by IpOCOC9.(ABSTRACT TRUNCATED AT 250 WORDS)

Anti-inflammatory effect of cyclosporin A on human skin mast cells

We have examined the effects of cyclosporin A (CsA) and cyclosporin H (CsH), which bind with different affinity to cyclophilin, to evaluate the role of this protein in the release of preformed (histamine) and de novo synthesized (prostaglandin D2[PGD2]) mediators of inflammatory reactions from human skin mast cells (HSMC). CsA (2.4-800 nM)-inhibited (5-60%) histamine release from HSMC challenged with anti-IgE. CsA exerted little, if any, inhibitory effect on histamine release from HSMC challenged with compound A23187 and substance P, whereas it completely suppressed A23187-induced histamine release from human basophils. Inhibition of histamine release from HSMC challenged with anti-IgE was extremely rapid and was not abolished by washing (three times) the cells before anti-IgE challenge. CsA (2.4-800 nM) markedly inhibited (25-70%) the de novo synthesis of PGD2 from HSMC challenged with anti-IgE. CsH, which has an extremely low affinity for cyclophilin, had no effect on skin mast-cell mediator release. These data suggest that CsA is a potent anti-inflammatory agent acting on HSMC, presumably by interacting with cyclophilin.

Effects of flavonoids on immune and inflammatory cell functions

No doubt can remain that the flavonoids have profound effects on the function of immune and inflammatory cells as determined by a large number and variety of in vitro and some in vivo observations. That these ubiquitous dietary chemicals may have significant in vivo effects on homeostasis within the immune system and on the behavior of secondary cell systems comprising the inflammatory response seems highly likely but more work is required to strengthen this hypothesis. Ample evidence indicates that selected flavonoids, depending on structure, can affect (usually inhibit) secretory processes, mitogenesis, and cell-cell interactions including possible effects on adhesion molecule expression and function. The possible action of flavonoids on the function of cytoskeletal elements is suggested by their effects on secretory processes. Moreover, evidence indicates that certain flavonoids may affect gene expression and the elaboration and effects of cytokines and cytokine receptors. How all of these effects are mediated is not yet clear but one important mechanism may be the capacity of flavonoids to stimulate or inhibit protein phosphorylation and thereby regulate cell function. Perhaps the counterbalancing effect of cellular protein tyrosine phosphatases will also be found to be affected by flavonoids. Some flavonoid effects can certainly be attributed to their recognized antioxidant and radical scavenging properties. A potential mechanism of action that requires scrutiny, particularly in relation to enzyme inhibition, is the redox activity of appropriately configured flavonoids. Finally, in a number of cell systems it seems that resting cells are not affected significantly by flavonoids but once a cell becomes activated by a physiological stimulus a flavonoid-sensitive substance is generated and interaction of flavonoids with that substance dramatically alters the outcome of the activation process.

Anti-allergic properties of cyclosporin A: inhibition of mediator release from human basophils and rat basophilic leukemia cells (RBL-2H3)

In vitro the immunosuppressive drug cyclosporin A (CS-A) strongly inhibited histamine release from human basophils (HB) and the rat basophilic leukemia cell line (RBL) 2H3. It also inhibited leukotriene release from HB. In HB the IC50 values for inhibition of histamine release induced by Con A, anti-IgE, calcium ionophore A23187 and antigen (mite) were 0.03, 0.12, 0.36 and 2.0 microM, respectively. In fact, these figures underestimate the potency of CS-A, since studies with 3H-CS-A showed substantial adsorption to plastic experimental wares which was inversely proportional to drug concentration. With anti-IgE and A23187, the drug acted promptly when added at the same time as the inducers but, with antigen, inhibition increased with time of pre-incubation. Washing of HB after pre-incubation with CS-A did not remove the drug effect. Inhibition of histamine release was abolished by Ca2+ excess (5 mM). For TPA-induced release, the drug inhibited the Ca2(+)-dependent but not the Ca2(+)-independent component. In Ca2(+)-free conditions, ionophore A23187, which caused little or no histamine release on its own, was able to synergize with TPA in causing release, apparently by mobilizing intracellular Ca2+. CS-A blocked the synergism but not the original TPA effect. CS-A was compared with the calmodulin inhibitors, W7, TFP and ABCNS; all inhibited histamine release. CS-A also potently inhibited IgE-mediated histamine release from RBL-2H3 cells, without affecting their growth or viability.

The effect of azelastine and some other antiasthmatic and antiallergic drugs on calmodulin and protein kinase C

The antiallergic and antiasthmatic drug, azelastine, interacts strongly with calmodulin (but not bovine serum albumin) as determined by an indirect assay; it also moderately inhibited the Ca2+-calmodulin-dependent enzyme bovine brain phosphodiesterase. Ketotifen was less active than azelastine in both assays of calmodulin reactivity and both drugs were less active than the recognized calmodulin inhibitor, W-7. Neither azelastine nor ketotifen had any inhibitory effect on the Ca2+- and phospholipid-dependent protein kinase C. A number of other commonly employed antiallergic and antiasthmatic drugs were essentially inactive in the calmodulin assays and had no or marginal inhibitory effect on protein kinase C.

Pathophysiology of human basophils and mast cells in allergic disorders

Basophil leukocytes and tissue mast cells are inflammatory cells that are found in virtually all human tissues. They appear to be involved in the pathogenesis of such allergic diseases as allergic rhinitis, bronchial asthma, anaphylaxis, atopic and contact dermatitis, chronic urticaria, and hypersensitivity pneumonitis. By releasing a variety of chemical mediators, they could also play a role in the pathophysiology of a wide range of inflammatory disorders of the joints, and of intestine, lung, coronary, and myocardial diseases. Although these two cell types are similar in several aspects, striking differences have also been observed. Moreover, human mast cells from different anatomical sites and within an individual tissue synthesize different mediators and have different release mechanisms. The recent advent of techniques that yield highly purified basophils and mast cells from diverse tissues will probably lead to major advancements in understanding the biochemical and pharmacological mechanisms that control the release process of these cells. The release of mediators from these cells is also controlled by a series of largely undefined biochemical steps that represent the basis of the concept of basophil and mast cell releasability. Alterations of basophil or mast cell releasability have already been detected in patients with allergic rhinitis, bronchial asthma, atopic dermatitis, and chronic urticaria. Taken together, these findings demonstrate that basophils, mast cells, and their chemical mediators play a pivotal role in several inflammatory disorders.

Cyclosporin A inhibits the release of histamine and peptide leukotriene C4 from human lung mast cells

We investigated the effect of cyclosporin A (CsA) on in vitro release of chemical mediators from mast cells purified from human lung tissues. CsA (3 X 10(-2) to 1 microgram/ml) dose-dependently inhibited IgE-mediated release of histamine and peptide leukotriene C4 (LTC4) from human lung mast cells. The same concentrations of CsA also inhibited the release of histamine from lung mast cells challenged with the Ca2+ ionophore A23187. Therefore, CsA in pharmacological concentrations inhibits the IgE- and non-IgE-mediated release of inflammatory mediators from mast cells purified from human lung tissues.