Inhibitory effects of various drugs on phorbol myristate acetate and n-formyl methionyl leucyl phenylalanine induced O2- production in polymorphonuclear leukocytes

Efficacy of azelastine nasal spray in the treatment of vasomotor (perennial nonallergic) rhinitis

BACKGROUND

Azelastine hydrochloride is an antihistamine with anti-inflammatory properties that is available in the United States in a nasal spray formulation for the treatment of seasonal allergic rhinitis. Vasomotor (perennial nonallergic) rhinitis (VMR) is a noninfectious, chronic rhinitis usually not associated with inflammatory cell infiltration.

OBJECTIVE

Two multicenter, randomized, double-blind, placebo-controlled, parallel-group clinical trials were conducted to determine whether patients with symptoms of VMR (rhinorrhea, sneezing, postnasal drip, and nasal congestion) could be effectively treated with azelastine nasal spray.

METHODS

All of the patients who participated in the trials had a diagnosis of VMR, symptoms for at least 1 year, negative skin tests for a mixed panel of seasonal and perennial allergens, and a nasal cytology examination negative for eosinophils. After a 1-week, single-blind, placebo lead-in period, patients who met the symptom severity qualification criteria were randomized to receive either azelastine nasal spray (two sprays per nostril twice daily, 1.1 mg/day) or placebo nasal spray for 21 days. Patients recorded the severity of their VMR symptoms on diary cards each morning and evening of the trial using a four-point symptom rating scale (0 = none to 3 = severe). The primary efficacy variable was the overall reduction from baseline in the total vasomotor rhinitis symptom score (TVRSS) over the 21-day, double-blind treatment period.

RESULTS

In both studies, azelastine nasal spray significantly (study 1, P = .002; study 2, P = .005) reduced the TVRSS from baseline when compared with placebo. Significant improvement was observed within the first week and improvement in all symptoms favored treatment with azelastine nasal spray. No serious or unexpected adverse events were reported in either study. Bitter taste (19% vs 2%) was the only adverse experience that occurred with a statistically significantly greater incidence in the azelastine group than in the placebo group.

CONCLUSIONS

This is the first demonstration of the efficacy of an antihistamine in the therapy of VMR in two double-blind, placebo-controlled clinical trials.

Management of allergic rhinitis with a combination antihistamine/anti-inflammatory agent

Azelastine nasal spray is a topical antihistamine treatment for the symptoms of seasonal allergic rhinitis. Besides histamine antagonism, azelastine affects other chemical mediators of the inflammatory response including leukotrienes and kinins. This article reviews and discusses the antihistaminic and anti-inflammatory properties of azelastine and the results of pharmacokinetic studies and controlled clinical trials.

An evaluation of the efficacy and safety of azelastine in patients with chronic asthma. Azelastine-Asthma Study Group

BACKGROUND

Azelastine, an oral nonsteroidal, antiinflammatory drug with a good safety profile, has demonstrated relief of symptoms in patients with asthma.

OBJECTIVE

The study was designed to evaluate the efficacy and safety of azelastine, a novel antiallergy compound, in patients with asthma who required maintenance therapy.

METHODS

During this 16-week, double-blind, randomized, parallel-group study, patients received orally administered azelastine (4 mg twice daily), albuterol sulfate (4 mg twice daily), or placebo.

RESULTS

Overall, patients in the azelastine group used 2.5 times less backup medication (p = 0.024) for relief of their asthma symptoms than patients in the placebo group. Reductions in asthma symptoms in the azelastine group were also noted throughout the double-blind treatment period. Moreover, the azelastine group had statistically significant improvements in FEV1 after the first dose of medication. The only notable adverse experiences in the azelastine group were alterations in taste perception and a small mean increase in body weight.

CONCLUSION

Oral administration of azelastine to patients with asthma resulted in overall improvement in airway function while reducing the requirement for adjunctive antiasthma medications.

Effect of azelastine on airway hyperresponsiveness mediated by stimulated macrophages

The effect of the anti-allergic drug azelastine, 4-(p-chlorobenzyl)-2-(hexahydro-1-methyl-1H-azepine-4-yl)-1-(2H)-phth alazione), on airway hyperresponsiveness induced by immunologically stimulated pulmonary alveolar macrophages was investigated in canine bronchial segments under isometric conditions in vitro. Macrophages stimulated with anti-dinitrophenyl immunoglobulin E (IgE) antibody and dinitrophenyl-human serum albumin potentiated the contractile responses to electrical field stimulation at all frequencies, an effect that was abolished by azelastine (3 x 10(-5) M). In contrast, azelastine had no effect on the potentiation of the contractile responses to electrical stimulation by U46619, a thromboxane A2 mimetic. The IgE-mediated release of thromboxane A2 from macrophages was inhibited by azelastine in a concentration-dependent fashion, the maximal decrease and the concentration required to produce a half-maximal effect being 84 +/- 6% (P < 0.001) and 16 microM, respectively. These results suggest that azelastine may attenuate macrophage-induced parasympathetic airway hyperresponsiveness through an inhibition of the release of thromboxane A2.

The effect of histamine on the oxidative burst of HL60 cells before and after exposure to reactive oxygen species

During an inflammation neutrophils are stimulated to produce reactive oxygen species (ROS). These ROS induce the release of histamine from mast cells, which are also present at the inflammation site. In this study dibutyryl cAMP differentiated HL60 cells are used as a model for human neutrophils. The effect of histamine on formyl-methionyl-leucyl-phenylalanine (fmlp) stimulated cells is examined. Except for histamine also an accumulation of ROS takes place at the inflammation site and we investigated if ROS can influence the response of the stimulated HL60 cells. It is found that 10(-3) M histamine can inhibit the fmlp induced superoxide anion radical production. This occurs partly via an H2 receptor because H2 antagonists like famotidine, mifentidine and ranitidine could partially antagonize this effect of histamine. When HL60 cells are exposed to hydrogen peroxide or hypochlorous acid (20 min), an increased fmlp response is found while the inhibiting effect of histamine remains unchanged.

In vitro inhibition, by loratadine and descarboxyethoxyloratadine, of histamine release from human basophils, and of histamine release and intracellular calcium fluxes in rat basophilic leukemia cells (RBL-2H3)

The effect of the H1-antihistamine drug loratadine and its active metabolite descarboxyethoxyloratadine upon histamine release was examined on anti-immunoglobulin E (IgE) triggered human basophils and 2,4-dinitrophenyl (DNP) triggered rat basophilic leukemia (RBL-2H3) cells. In both experimental systems, dose-dependent inhibition of histamine release was observed at descarboxyethoxyloratadine and loratadine doses above 2 and 7 microM, respectively. In the RBL-2H3 experimental system, inhibition by loratadine increased when the concentration of extracellular Ca2+ was reduced from 1.8 to 0.45 mM. We further investigated the effect of loratadine and descarboxyethoxyloratadine on the increase in cytosolic calcium concentration (Ca2+)i, an early step in biochemical events leading to exocytosis. The effect of these two drugs upon (Ca2+)i changes was measured using the fluorescent probe fura-2 loaded into RBL-2H3 cells passively sensitized with DNP-specific IgE. Both drugs inhibited, in a dose-dependent manner (2.5-25 microM), the (Ca2+)i rise induced by DNP-BSA challenge in sensitized RBL cells, a process observed in both the presence and absence of extracellular Ca2+. Loratadine also inhibited the Mn2+ influx into these cells, thus reflecting the Ca2+ influx. These results suggest that loratadine and descarboxyethoxyloratadine impair the increase in (Ca2+)i following cell activation by decreasing both the influx of extracellular Ca2+ and the release of Ca2+ from intracellular stores.

Influence of epithelial removal on the antihistaminic activity of azelastine in the guinea-pig airway smooth muscles

The influence of epithelial removal on the antihistaminic activity of azelastine in the guinea-pig isolated cervical trachea and main bronchus was examined. In both preparations with an intact epithelium, histamine produced a concentration-dependent contraction, but its potency (pD2) and contractility (Emax) were significantly higher in the main bronchus than in the cervical trachea. Epithelial removal from these preparations significantly increased the pD2 values in both tracheal and bronchial preparation, while the Emax value was significantly increased only in the cervical trachea. When these preparations were pretreated with azelastine (20 or 200 nM), concentration-response curves for histamine shifted downward, but were not influenced by the presence of an intact epithelium. Neither concentration of azelastine significantly modified the contractile responsiveness of tracheal and bronchial preparations to carbachol or neurokinin A. These results indicate that azelastine selectively antagonizes the histamine-induced contraction of the guinea-pig airway smooth muscles with or without an intact epithelium.

Effect of mammalian lignans on fMLP-induced oxidative bursts in human polymorphonuclear leucocytes

We examined the effects of mammalian lignans, enterolactone, prestegane B and 2,3-dibenzylbutane-1,4-diol (DBB) on superoxide production and luminol-dependent chemiluminescence (LCL) response in human polymorphonuclear leucocytes (PMNs). The three lignans had no direct effect on the responses of human PMNs. DBB and prestegane B enhanced the superoxide production and LCL response induced by formylmethionyl-leucyl-phenylalanine (fMLP), but enterolactone inhibited fMLP-induced effects. The effects of DBB were stronger than those of prestegane B and the effects of DBB were inhibited by bromophenacyl bromide, mepacrine, N-(6-aminophenyl)-5-chloro-1-naphthalene, sulphonamide and trifluoroperazine, but not by gossypol, nordihydroguaretic acid, indomethacin, staurosporine, 1-(5-isoquinolinesulphonyl)-2-methylpiperazine dihydrochloride or (R,S)-2-methoxy-3-(octadecyl-carbamoyloxy)-propyl-2-(2-thiazoli o)-ethylphosphate. These results suggest that DBB primes the responses of human PMNs, and the priming effect is caused by the activation of phospholipase A2--and Ca(2+)-calmodulin-pathways, but not by the activation of lipoxygenase, cyclo-oxygenase and protein kinase C or by the release of platelet activating factor.

Seasonal variations of nasal resistance in allergic rhinitis and environmental pollen counts. II: Efficacy of preseasonal therapy

We gave Mao-bushi-saishin-to, a Chinese blended medicine, and azelastine to an adult patient with hay fever due to Japanese cedar pollen and measured nasal resistance and ambient floating pollen counts throughout the time of Japanese cedar pollination in separated years. In the patient Mao-bushi-saishin-to was effective against preseasonal increases in nasal airway resistance but could not control severe episodes of allergic rhinitis caused by high dose exposure to Japanese cedar pollen and also perhaps caused by a priming effect. Azelastine inhibited both pre- and post-seasonal increases in nasal airway resistance but not only on high pollen counts days.

The effect of azelastine on the early allergic response

To study the effect of azelastine on the immediate reaction to nasal allergen challenge, we performed a double blind, placebo-controlled cross-over clinical trial. Thirteen subjects with seasonal allergic rhinitis underwent nasal challenge with antigen 4 hr after a single oral 2 mg dose of azelastine. The response was monitored by counting the number of sneezes and by measuring the levels of histamine, prostaglandin D2, immunoreactive sulphidopeptide leukotrienes, kinis and TAME-esterase activity in recovered nasal lavages. After a single dose of azelastine, there was a significant reduction in sneezing (10 vs 2, P = 0.01) and in the median levels of recovered TAME-esterase activity (63.1 vs 17.5 c.p.m. x 10(-3), P = 0.01), immunoreactive sulphidopeptide leukotrienes (7.5 vs 2.1 ng/ml, P = 0.03) and kinins (1370 vs 251 pg/ml, P = 0.03), with no significant reduction in the median levels of histamine (3.7 vs 1.2 ng/ml, P = 0.2) and prostaglandin D2 (70 vs 70 pg/ml, P = 0.2) compared to placebo (numbers represent total increase over diluent challenge). These results suggest that azelastine does not inhibit mast cell activation but affects the consequences of released histamine, namely sneezing, increased vascular permeability and the generation of kinins. The results further suggest that other cells, in addition to mast cells, might be responsible for the generation of leukotrienes during the early allergic response, and that azelastine reduces their ability to generate this mediator or that inhibition of leukotriene release from mast cells occurs at lower drug concentrations.

Inhibitory effects of phenyltin compounds on stimulus-induced changes in cytosolic free calcium and plasma membrane potential of human neutrophils

To clarify the inhibitory mechanisms by triphenyltin chloride (TPTCl) on superoxide anion formation in neutrophils, the effects of phenyltin compounds [TPTCl, diphenyltin dichloride (DPTCl2) and phenyltin trichloride (MPTCl3) on the increase of cytosolic free calcium and the changes in membrane potential in neutrophils stimulated by n-formyl-methionyl-leucyl-phenylalanine (FMLP) were examined. TPTCl and DPTCl2 concentration dependently inhibited the increase of fluorescence intensity of the dye 3,3'-dipropyl-thiodicarbocyanine iodide [diS-C3-(5)] (membrane potential probe) in neutrophils induced by 0.1 microM FMLP in the presence or absence of extracellular calcium (1.26 mM). TPTCl had a greater inhibitory effect on FMLP-mediated membrane potential change than that of DPTCl2. In the presence of extracellular calcium, TPTCl and DPTCl2 increased intracellular free calcium [( Ca2+]i) of unstimulated fura-2-loaded neutrophils at concentrations from 1.0 to 10 microM TPTCl and from 2.5 to 10 microM DPTCl2. TPTCl and DPTCl2 also increased slightly, in the absence of extracellular calcium, [Ca2+]i without stimulation of FMLP in neutrophils. However, TPTCl and DPTCl2 significantly inhibited the rise of [Ca2+]i in neutrophils stimulated by FMLP at concentrations from 2.5 microM to 10 microM TPTCl and at a concentration of 10 microM DPTCl2 in the absence of extracellular calcium. TPTCl and DPTCl2 significantly inhibited the superoxide anion production by FMLP at concentrations over 2.5 microM in the presence of extracellular calcium. In the absence of extracellular calcium, TPTCl and DPTCl2 also inhibited the superoxide anion production by FMLP at concentrations over 1.5 microM TPTCl and over 5.0 microM DPTCl2.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of chemiluminescence in granulocytes and alveolar macrophages by azelastine

The effect of azelastine, an orally effective antiasthmatic antiallergic drug on the generation of oxygen-derived free radicals in phagocytes was investigated using different chemiluminescence-assays. The chemiluminescence (CL) of both human polymorphonuclear granulocytes (PMNL) and guinea-pig alveolar macrophages (AM) was induced either by phorbol myristate acetate (PMA) or zymosan and amplified either by lucigenin or DMNH (7-dimethylamino-naphthalene-1,2-dicarbonic-acidhydrazide). The inhibitory effect of azelastine was dependent on the inducer employed and the condition and type of cells used. Azelastine reduced PMA-induced CL concentration-dependently in both PMNL (IC30 = 3.9 microM) and AM (IC30 = 9.8 microM). In AM zymosan-induced CL was inhibited 21.7% by 10 microM azelastine, whereas in PMNL it remained unchanged up to 10 microM azelastine. Azelastine has a significantly stronger inhibitory effect (IC30 = 4.2 microM) on oxygen free radical generation in AM primed by fetal calf serum than in unprimed AM. Based on present results it is likely that azelastine inhibits oxygen-derived free radical generation by interaction with protein kinase C.

Reversible drug effects on the metabolic activation of polymorphonuclear leukocytes

Polymorphonuclear leukocytes (PMNs) stimulated by the chemotactic peptide formyl-methionyl-leucyl-phenylalanine (FMLP) were effectively inhibited by chlorpromazine (10 microM) and azelastine (20 microM) in terms of superoxide generation, and restored by the addition of dodecylbenzenesulfonic acid (DBS) in a range of concentrations from 20 to 40 microM. The stimulation of superoxide generation by DBS was also inactivated by dodecylamine (DA) but was restored by the subsequent addition of DBS. A dose dependent competitive inhibition and activation of leukocytes was observed between azelastine (10 microM) and DBS (20 microM). The release of arachidonic acid from leukocytes activated by the chemotactic peptide was decreased by DA or chlorpromazine, but could be restored by DBS. The changes in membrane potential of leukocytes as monitored by cyanine dye were also decreased by DA, chlorpromazine or azelastine. These observations indicate that some cationic drugs reversibly inhibit membrane bound enzymes or receptors. The physiological responses of these inhibited PMNs can then be restored by appropriate anionic amphiphiles.

Azelastine. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic potential

Azelastine is an antiallergic agent which demonstrates histamine H1-receptor antagonist activity and also inhibits histamine release from mast cells following antigen and non-antigen stimuli. Azelastine antagonises histamine- and leukotriene-induced bronchospasm in animal studies and reduces airway responsiveness to inhaled antigen or distilled water, and exercise challenge. In comparative studies, orally administered azelastine in doses up to 4 mg/day consistently relieved symptoms in patients with seasonal or perennial rhinitis - comparable to inhaled sodium cromoglycate (cromolyn sodium) 80 mg/day, oral chlorpheniramine (chlorphenamine) and oral terfenadine 120 mg/day. In addition, azelastine administered as an intranasal spray was as effective as oral terfenadine 120 mg/day and intranasal budesonide 0.4 mg/day in alleviating symptoms of rhinitis. Azelastine is also a potent antiasthmatic agent which produces significant and long lasting bronchodilation in patients with bronchial asthma. The drug is superior to placebo and comparable to oral ketotifen 2 mg/day and sustained release theophylline 700 mg/day when administered as a twice daily oral 4 mg dose. Azelastine is generally well tolerated: the most common adverse effects are altered taste perception and drowsiness. Adverse effects are mild and transient and result in withdrawal of treatment in less than 2% of patients. In a comparative study oral azelastine 2 or 4 mg/day produced no more sedation than terfenadine 120 mg/day. Thus, barring unexpected findings with wider clinical use, azelastine offers an effective and well tolerated choice of treatment for patients with allergic rhinitis and/or bronchial asthma, which may be particularly beneficial in patients in whom inhaled drug treatment is contraindicated.

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.

Phospholipase A2 induced airway hyperreactivity to cooling and acetylcholine in rat trachea: pharmacological modulation

1. Rat isolated tracheal smooth muscle preparations respond to phospholipase A2 (PLA2) and phospholipase C (PLC) with contractile responses of highly variable magnitudes. Rat tracheae exposed to PLA2 or PLC for a period of 10-30 min, exhibit airway hyperreactivity (AH) to cooling (10 degrees C), i.e., respond with strong contractile responses. Phospholipase D neither contracted rat tracheae nor induced AH to cooling. 2. PLA2-induced AH to cooling was dependent on the presence of extracellular Ca2+ in the physiological solution. 3. Verapamil, azelastine, diltiazem and TMB-8 (each 10 microM) significantly attenuated PLA2-induced AH. This effect was not shared by nifedipine (10 microM). 4. Bepridil (10 microM), a Ca2+ and calmodulin antagonist, also significantly attenuated AH induced by PLA2. 5. Indomethacin (a cyclo-oxygenase inhibitor), AA-861 (a selective 5-lipoxygenase inhibitor), FPL 55712 (a leukotriene receptor antagonist), methysergide (a 5-hydroxytryptamine D-receptor antagonist) and pyrilamine (a histamine H1-receptor antagonist) exerted little or no effect on PLA2-induced AH to cooling. 6. Atropine significantly attenuated PLA2-induced AH suggesting the participation of acetylcholine. 7. Nordihydroguaiaretic acid (an antioxidant; 5-lipoxygenase inhibitor) and BW 755C (an antioxidant; a dual inhibitor of cyclo-oxygenase and 5-lipoxygenase) significantly attenuated PLA2-induced AH to cooling. 8. In conclusion, these data show that PLA2 (an enzyme involved in the synthesis of Paf-acether, prostaglandins, thromboxanes, leukotrienes, diacylglycerol, superoxide free radicals and lipid peroxides, etc.) induces AH to cooling and acetylcholine in rat trachea. The induction of AH to cooling is dependent on the presence of extracellular Ca2+ and is significantly attenuated by verapamil, diltiazem, bepridil, atropine and azelastine (an antiallergic/antiasthmatic drug).

Allergic responses and subsequent development of airway hyperreactivity to cold provocation in the rat trachea: pharmacological modulation

An in vitro model of airway hyperreactivity to cold provocation was developed. Cold provocation (10 degrees C) alone was not sufficient to cause contraction of rat isolated tracheal smooth muscle preparations. However, following recovery from antigen-induced responses in sensitized rat tracheal segments, cold provocation resulted in marked contractile responses. L-652,731 (a Paf-acether antagonist) and atropine significantly attenuated antigen-induced responses and subsequent development of airway hyperreactivity to cold provocation. Indomethacin augmented allergic responses and subsequent development of airway hyperreactivity to cold challenge. Nordihydroguaiaretic acid, FPL 55712 and theophylline did not exert any effect. The data obtained in this study showed that (i) Paf-acether and acetylcholine may play an important role in the mediation of allergic responses and subsequent development of airway hyperreactivity to cold provocation; (ii) the significant attenuation of antigen-induced airway hyperreactivity to cold provocation by Ca2+ channel blockers (nifedipine, bepridil and TMB-8) suggests an increase in Ca2+ influx/permeability following antigen challenge which appears to be responsible for the development of airway hyperreactivity to cold provocation; and (iii) 5-HT, prostaglandins or thromboxanes and leukotrienes play little or no role in the mediation of allergic responses and subsequent development of airway hyperreactivity to cold exposure in rat trachea.

Effect of azelastine on the intracellular Ca2+ mobilization in guinea pig peritoneal macrophages

Azelastine, an orally effective anti-allergic agent, has been demonstrated to inhibit the release of histamine and leukotrienes. This suggests that azelastine might alter the mobilization of intracellular Ca2+. We have examined the effect of azelastine on the change in intracellular free calcium concentration ([Ca2+])i) in guinea pig peritoneal macrophages induced by platelet activating factor (PAF-acether) or N-formylmethionyl-leucyl-phenylalanine (FMLP) using a fluorescent Ca2+ indicator, fura2. PAF-acether raised [Ca2+]i from 89 +/- 4 to 243 +/- 26 nM (n = 15) within 20 s after addition of PAF-acether in the presence of 2 mM EGTA. This indicates that the stimulation of macrophages by PAF-acether induced intracellular mobilization of Ca2+, and pretreatment with azelastine reduced the PAF-acether-induced increase in [Ca2+]i in a dose-dependent manner (IC50 = 16 microM). Azelastine also inhibited the FMLP-induced increase in [Ca2+]i. Furthermore, PAF-acether and FMLP both caused the release of prostaglandin E2 from macrophages, and pretreatment with azelastine reduced the PGE2 release dose dependently (IC50 = 10 microM). These results suggest that azelastine inhibits the release of Ca2+ from intracellular storage sites induced by PAF-acether or FMLP, and that this effect possibly causes reduction in the release of PGE2 from the cells.

The amplified chemiluminescence test to characterize antirheumatic drugs as oxygen radical scavengers

High levels of reactive oxygen species (ROS) are generated by phagocytes involved in host defence and inflammation. Thus, it appears highly desirable to learn more about the potential of antirheumatic drugs to scavenge ROS or to inhibit their enzymatic generation. Amplified chemiluminescence (CL) allows detection of O-2 using lucigenin (LgCL) or H2O2 using luminol (LuCL). A total of 43 compounds have been tested quantitatively in vitro (10(-6) to 10(-4) mol/l) with respect to three test parameters; varying cell-activity, and incubation-time employing two different phagocyte populations (neutrophils/macrophages). The most active compounds with LgCL were the known radical scavengers nordihydroguaiaretic acid (NDGA), N-propyl gallate, superoxide dismutase and chloroquine, the non-steroidal anti-inflammatory drugs (NSAID) benzydamine, timegadine, carprofen, enolicam, the known lipoxygenase inhibitors (e.g. CBS 1108/1114, BW 755C) and glucosaminoglucan polysulfate. Inactive in this system were corticosteroids (prednisolone, dexamethasone) most of the tested NSAID (N = 16/20), most disease modifying drugs (D-penicillamine, levamisole, gold-TM) and the anti-gout drugs (sulfinpyrazone, allopurinol, colchicine). Therefore amplified CL with lucigenin appears to be a rapid, kinetic, reproducible means of pharmacological profiling in vitro new anti-inflammatory drugs for radical scavenger activity.

Antagonism of histamine and leukotrienes by azelastine in isolated guinea pig ileum

The effects of azelastine on histamine- and leukotriene C4 and D4 (LTC4, LTD4)-induced contractile responses in isolated guinea pig ileum were investigated. Following a 2-min contact with the ileum, azelastine produced competitive antagonism of histamine (pA2 = 8.24). Following a 15-min contact, azelastine at 2.5 X 10(-9) M exerted competitive antagonism, but at higher concentrations (10, 40 and 160 X 10(-9) M) it not only shifted histamine concentration-effect curves to the right but also suppressed its maximum. Thus, azelastine exerts a dual (competitive/noncompetitive) antagonism of histamine depending upon the concentration and duration of contact. Azelastine and FPL 55712 (a known LT receptor antagonist) produced concentration-dependent antagonism of LTC4 and LTD4. Azelastine and compound FPL 55712 also exerted concentration-dependent reversal (relaxation) of pre-existing LTC4-induced contractions. In conclusion, the potent H1-histamine and leukotriene receptor blocking activities of azelastine may contribute to its antiasthmatic/antiallergic activities.

Inhibition of leukotriene (SRS-A)-mediated acute lung anaphylaxis by azelastine in guinea pigs

Azelastine hydrochloride, chemically known as 1(2H)-phthalazinone, 4-[(4-chlorophenyl)methyl]-2-(hexahydro-1-methyl-1H-azepine-4-yl)-, monohydrochloride, is a novel, orally effective, long-acting, antiallergic/antiasthmatic agent. The ability of azelastine and selected antiallergic drugs to inhibit SRS-A (leukotriene)-mediated acute lung anaphylaxis in guinea pigs (Konzett-Rossler method) was investigated. Azelastine and ketotifen were administered p.o. 2 and 24 h before antigen challenge; disodium cromoglycate (DSCG) was administered i.v. immediately before antigen challenge. The oral dose of azelastine required to inhibit leukotriene-mediated allergic bronchospasm by 50% (ID50: mg/kg) was 0.063 at 2 h and 0.120 at 24 h. Ketotifen at a dose of 0.05 to 10 mg/kg at 2 and 24 h, p.o., as well as DSCG at a dosage of 0.3 to 10 mg/kg at 0 min, i.v., produced weak, inconsistent and nondose-related antianaphylactic effects. Azelastine is an orally effective and long-acting inhibitor of in vivo synthesis and/or release of leukotrienes.