The effect of an oral leukotriene antagonist, ONO-1078, on allergen-induced immediate bronchoconstriction in asthmatic subjects.

BACKGROUND: Cysteinyl leukotrienes are potent contractile agonists for airway smooth muscle. To examine the relative role of cysteinyl leukotrienes in immediate airway obstruction in human subjects with asthma after allergen challenge, we investigated the effect of ONO-1078, a potent receptor antagonist of cysteinyl leukotrienes, on the response. METHODS: ONO-1078 and an inactive placebo, in 150-mg capsule form, were administered every 12 hours for 1 week, in a double-blind, cross-over fashion. To examine the effect on the early part of the response, total respiratory resistance (Rrs) was continuously evaluated for 10 minutes after the start of a 1-minute exposure to an appropriate concentration of allergen. Rrs and FEV1.0 were estimated every 10 minutes for 60 minutes after the exposure. RESULTS: ONO-1078 significantly reduced percent changes in Rrs and FEV1.0 from 20 to 60 minutes after the exposure, as well as percent maximum changes in these indices, although the treatment did not alter the time from the start of allergen exposure to the beginning of elevation of Rrs, the time from the start to the point at which total respiratory conductance decreased by 35% from its baseline value, or percent changes in Rrs or FEV1.0 10 minutes after the exposure. CONCLUSIONS: Therefore, we conclude that cysteinyl leukotrienes primarily mediate a later part of immediate airway obstruction after allergen exposure.

[Effect of thromboxane A2 synthetase inhibitor (OKY-046) on leukotriene C4-induced airway hyperresponsiveness in guinea pigs].

In this study, we investigated the effects of peroral (p.o.) administration of a thromboxane A2 (TXA2) synthetase inhibitor, OKY-046, on the airway hyperresponsiveness (AHR) in guinea pigs induced by intravenous administration of leukotriene C4 (LTC4). A 3 micrograms/kg/hr LTC4 infusion induced airway wall thickening (AWT) and AHR to 1.8 and 3.6 micrograms/kg histamine bolus shot. OKY-046 100 mg/kg p.o. partially inhibited the AHR induced by LTC4 without inhibition of AWT. Previously, we have reported that LTC4-induced AHR was partially inhibited, to the same exert as by OKY-046, by TXA2 receptor antagonists, ONO-NT-126 and ONO-8809. These data suggest that intravenous administration of LTC4 generates TXA2, and TXA2 augments LTC4-induced AHR partially in guinea pigs.

Effect of a new leukotriene receptor antagonist, ONO-1078, on human bronchial smooth muscle in vitro.

Peptide leukotrienes (LT) have been postulated to play a major role in the etiology of bronchial asthma. The present study investigated the effect of a new peptide LT receptor antagonist, ONO-1078, on isolated human bronchial smooth muscle in vitro. Helical strips of bronchi were suspended in the organ baths filled with 37 degrees C Krebs solution and mechanical responses were recorded isometrically. ONO-1078 produced dose-dependent relaxations, which suggested that the spontaneous basal tone was in part mediated by LT. ONO-1078 caused dose-dependent relaxations of the tissues which were precontracted with LTC4 or LTD4 (3 x 10(-8) M). Pretreatment of bronchi with ONO-1078 (10(-8) M, 10(-7) M) significantly inhibited dose-dependent contractions induced by LTC4 and LTD4. ONO-1078 (10(-6) M) also significantly reduced the antigen-induced contractions in bronchi passively sensitized with atopic serum from mite-allergic patients. Moreover the combination of an H1-receptor antagonist, diphenhydramine (10(-5) M), and ONO-1078 (10(-6) M) completely abolished the antigen-induced contractions. The present findings demonstrate that ONO-1078 is a potent antagonist of exogenous and endogenous LT in the human airway. The selective LT antagonist such as ONO-1078 may be valuable in the therapy of allergic asthma.

Role of leukotrienes in airway hyperresponsiveness in guinea-pigs.

1. Repeated aerosolization of leukotriene C4 (LTC4) to guinea-pigs produced leftward shift in their pulmonary resistance (RL) dose-response curves to inhaled acetylcholine (ACh) without increasing the maximum responses. 2. Repeated LTC4 aerosolization did not increase airway eosinophils. 3. The 5-lipoxygenase-activating protein (FLAP) inhibitor, MK-886, prevented the leftward shift in RL dose-response curves to ACh following repeated antigen challenge in guinea-pigs. 4. MK-886 did not inhibit the increased maximal RL produced by repeated antigen challenge, nor inhibit the airway eosinophilia induced by repeated antigen challenge. 5. Our findings suggest that leukotrienes may account for the leftward shift in pulmonary resistance responses caused by antigen but do not cause the airway eosinophilia nor enhanced maximum broncho-constrictor response to antigen.

[Effect of thromboxane A2 (TXA2) antagonists on bronchial hyperresponsiveness induced by intravenous administration of leukotriene C4 (LTC4) in guinea pigs].

Effects of TXA2 antagonists on bronchial hyperresponsiveness induced by intravenous administration of LTC4 in guinea pigs were investigated by measurement of dynamic compliance and dynamic respiratory resistance, using a formula to exclude the effects of changes in airway wall thickness. With the formula, the ratio of bronchial smooth muscle constriction by histamine can be estimated as an index of bronchial hyperresponsiveness to histamine. Administration of LTC4 induced airway wall edema. The ratio of bronchial smooth muscle constriction by histamine was enhanced by the administration of LTC4. TXA2 antagonists, ONO-NT-126 and ONO-8809, inhibited the increased ratio of bronchial smooth muscle constriction of LTC4. On the other hand, the antagonists showed no significant effects on airway wall edema by LTC4. These results suggest TXA2 may play a role in LTC4-induced bronchial hyperresponsiveness to histamine.

Leukotriene C4-induced radioprotection: the role of hypoxia.

Pretreatment of mice with leukotriene C4 (LTC4), a biological mediator that can cause marked contraction of vascular, tracheal, and bronchial smooth muscles, enhances radiation survival. Optimal protection is observed with 10 micrograms LTC4 per mouse (400 micrograms/kg body wt) administered subcutaneously 5 to 10 min prior to irradiation. Pretreatment with 10 micrograms LTC4 increases the LD50/30 from 8.36 Gy in mice receiving saline to 15.7 Gy, providing a dose reduction factor of 1.9. Enhanced survival of mice was observed with doses of 50 micrograms LTD4/mouse, but not with LTE4. Fifteen minutes after administration of 10 micrograms LTC4, the breathing rate is reduced by 33%, the blood paO2 by 20%, the paCO2 by 29%, and the HCO3- by 43%. Whole blood lactate increased by 288% at this same time. The period over which the elevation in blood lactate occurs is similar to the times for optimal radioprotection. These data coupled with the finding that protection was eliminated when irradiation occurred in an enriched oxygen atmosphere indicate that hypoxia plays a role in leukotriene C4-induced animal radiation survival. High-performance liquid chromatography and tissue distribution analyses support a role for an indirect mechanism since the highest levels of LTC4 in the tissues do not correlate with the peak time for radioprotection.

Effect of leukotriene C4 on theophylline disposition in guinea pigs.

The pharmacokinetics of theophylline in acutely ill patients show wide intraindividual variability associated with the severity of clinical status. To investigate the mechanism of this variability, we studied the effects of leukotriene C4 (LTC4)-induced pathophysiologic changes on the disposition of theophylline. The plasma concentration-time profiles were measured after simultaneous intravenous bolus injection of theophylline and antipyrine in guinea pigs. The animals received 5 micrograms/kg of LTC4 intravenously 60 min later. The plasma theophylline concentration 30 min after LTC4 treatment was significantly lower (p less than 0.05) than that of nontreated control animals, whereas the plasma antipyrine concentration at that time was not affected. In addition, the treated animals showed significantly slower declines in plasma concentrations of both drugs (0.0805 +/- 0.0199 and 0.291 +/- 0.020 h-1 for theophylline and antipyrine, respectively, mean +/- SEM) than did controls (0.197 +/- 0.010 and 0.439 +/- 0.028 h-1). Leukotriene C4 treatment also induced moderate bronchoconstriction and metabolic acidosis, increased blood hemoglobin concentration and hematocrit, and decreased concentration of serum proteins. In connection with these changes, the plasma unbound fraction of theophylline increased significantly (p less than 0.001, 94.4 +/- 3.3% in treatment versus 58.2 +/- 4.4% in control), but that of antipyrine was unchanged (94.9 +/- 3.0% in treatment versus 92.1 +/- 0.9% in control). These findings indicated that an increase in the volume of distribution was responsible for the abrupt change in plasma theophylline concentration following LTC4 treatment, and the apparent change in the volume of distribution was estimated as 26.1 +/- 5.6%.(ABSTRACT TRUNCATED AT 250 WORDS)

Do leukotrienes mediate bile acid-induced gastric mucosal injury?

Leukotrienes C4 and D4 are potent vasoconstrictors and have been proposed as mediators of the severe gastric mucosal injury caused by a variety of necrotizing agents. The purpose of this study was to investigate the role of leukotrienes on the less severe gastric mucosal injury caused by low concentrations of bile acid. Prior to injury with 5 mM acidified taurocholate (pH 1.2), rat stomachs were pretreated with either normal saline, leukotrienes C4 or D4 (10(-6), 10(-8), and 10(-9) M), or SKF-104353 (a leukotriene D4 receptor antagonist 10(-7) M). Injury was assessed by measuring net transmucosal hydrogen ion flux, luminal appearance of DNA, and histologic injury. Topical pretreatment with LTC4 and LTD4 significantly increased bile acid-induced luminal hydrogen ion loss and DNA accumulation in a dose-dependent manner. Leukotriene receptor blockade with SKF-104353 significantly decreased these parameters. Thus, both LTC4 and LTD4 exacerbate the gastric mucosal injury caused by the application of low concentrations of bile acid while leukotriene receptor blockade reduces this injury (corroborated by histologic injury analysis). This study suggests that leukotrienes may be mediators of bile acid-induced gastric mucosal injury.

Urinary excretion of leukotriene E4 and 11-dehydro-thromboxane B2 in response to bronchial provocations with allergen, aspirin, leukotriene D4, and histamine in asthmatics.

In vivo production of thromboxane (TX) A2 and the cysteinyl-containing leukotrienes (LT) C4, D4, and E4 in correlation to airway responses was studied. Bronchial provocation with specific allergen in atopic asthmatics was followed by a significant increase in urinary concentration of immunoreactive LTE4 (34 +/- 6 before versus 56 +/- 7 ng/mmol creatinine after allergen challenge; n = 5) and 11-dehydro-TXB2 (164 +/- 29 versus 238 +/- 25 ng/mmol creatinine). In the presence of the leukotriene-antagonist ICI-204,219, which significantly increased the PD20 for allergen, the increment in urinary excretion of LTE4 was even higher (60 +/- 8 versus 288 +/- 128 ng/mmol creatinine; n = 5). In contrast, provocation with histamine (n = 5) did not provoke release of leukotrienes or thromboxane, nor was inhalation of LTD4 (n = 7) associated with increased urinary concentration of 11-dehydro-TXB2. Furthermore, bronchoconstriction induced by inhalation of lysine-aspirin in aspirin-sensitive asthmatics (n = 4) was followed by increased levels of LTE4 in the urine, whereas the levels of 11-dehydro-TXB2 remained the same. Finally, the basal levels of LTE4 in the urine of nine aspirin-sensitive asthmatics were elevated as compared with 15 other asthmatics (112 +/- 54 versus 38 +/- 20 ng/mmol creatinine; p less than 0.001). The findings support that the cysteinyl-leukotrienes are potential mediators of allergen-induced asthma and that the release of LTE4 and 11-dehydro-TXB2 into the urine appeared to be a direct and dose-dependent effect of the antigen-antibody reaction.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased secretion of glandular-kallikrein in the bronchial washings induced by intravenous injection of leukotriene C4 in guinea-pigs.

1. Intravenous administration of leukotriene C4 (LTC4) and LTD4 (1-10 nmol kg-1) caused a dose-dependent increase in secretion of glandular-kallikrein in the bronchial washings of guinea-pigs, as measured by cleavage of a synthetic substrate and the formation of kinin. LTC4 was more potent than LTD4 and pilocarpine was much less potent than peptide leukotrienes on a molecular basis. 2. The increases in levels of glandular-kallikrein in the bronchial washings that were induced by LTC4 (3 nmol kg-1, i.v.) were almost completely inhibited by pretreatment with an antagonist of leukotrienes (ONO-1078), with an antagonist of thromboxane (S-1452), with an inhibitor of thromboxane synthetase (OKY-046), with indomethacin, with atropine or with scopolamine. These results indicate that the LTC4-induced increase in levels of glandular-kallikrein may have been mediated by the formation of thromboxane and the release of acetylcholine. 3. The increases in levels of glandular-kallikrein in the bronchial washings induced by STA2 (20 pmol kg-1, i.v.), a stable analogue of thromboxane A2, were completely blocked by pretreatment with atropine, whereas increases induced by pilocarpine (41 mumol kg-1, i.v.) were not blocked by pretreatment with indomethacin, although such increases were inhibited by atropine. This result indicates that secretion of kallikrein stimulated by LTC4 may have been mediated by the successive formation of thromboxane A2 and release of acetylcholine. 4. Intravenous administration of bradykinin (3-30 nmol kg-1) caused a dose-dependent increase in levels of glandular-kallikrein in the bronchial washings. This increase was completely inhibited by pretreatment with atropine, with indomethacin or with an antagonist of thromboxane.5. The increases in levels of glandular-kallikrein in the bronchial washings induced by LTC4 (3 nmol kg'- , i.v.) and pilocarpine (41 flmol kg- 1, i.v.) were significantly inhibited by pretreatment with an antagonist of bradykinin. These results suggest that intravenous LTC4 may increase secretion of glandular-kallikrein via formation of thromboxane A2 and release of acetylcholine in that order, and kinin released by kallikrein may enhance the rate of secretion of glandular-kallikrein.

Increase in the kinin levels in the bronchial washings after intravenous injection of leukotriene C4 in guinea pigs.

In guinea pig plasma, bradykinin (BK) was degraded mainly to des-Arg1-BK by an aminopeptidase-like enzyme, which was inhibited by 2-mercaptoethanol. Besides this degradation, BK was also hydrolyzed by kininase I and kininase II from C-terminal end to des-Arg9-BK, des-Phe8-Arg9-BK and Arg-Pro-Pro-Gly-Phe ([1-5] BK). The formation of des-9-BK was strongly blocked by DL-2-mercaptomethyl-3-guanidinoethylthiopropanoic acid (MGPA) and that of des-8,9-BK and [1-5] BK was inhibited by captopril. When guinea pigs were pretreated with a cocktail of 2-mercaptoethanol, MGPA and captopril, intravenous administration of leukotriene (LT) C4 (10 nmol/kg) caused an increase in the levels of free kinin in the bronchial washings of guinea pigs. This increase was accompanied with the increase in glandular-kallikrein activity, which could be inhibited by aprotinin. As BK is reported to induce both bronchoconstriction and bronchial secretion, the increased free BK induced by LTC4 might enhance the effect of LTC4.

Inhibitory effect of inhalation of a thromboxane synthetase inhibitor on bronchoconstriction induced by aerosolized leukotriene C4 and thromboxane A2 analogue in anesthetized guinea pigs.

Effect of aerosol administration of a thromboxane synthetase inhibitor (OKY-046) on bronchoconstriction induced by aerosol leukotriene C4, histamine and a thromboxane A2 analogue (STA2) was studied in anesthetized, artificially ventilated guinea pigs in order to evaluate the effectiveness of inhalation of OKY-046 on an unfavorable mechanism of secondary release of thromboxane A2. 0.01-1.0 micrograms/ml leukotriene C4, 25-400 micrograms/ml histamine and 0.033-1.0 micrograms/ml STA2 inhaled from an ultrasonic nebulizer developed for small animals caused a dose-dependent increase of pressure at the airway opening (Pao), which is considered to be an index representing bronchial response. Pretreatment of the animals with aerosol OKY-046 (0.035 and 0.35 mg/animal) significantly reduced the airway responses produced by inhalation of leukotriene C4 and STA2, in a dose-dependent manner, while the pretreatment did not affect the histamine dose-response curve. These findings suggest that aerosol leukotriene C4 and STA2 activate thromboxane synthesis in the airway, and inhalation of OKY-046 may be useful for preventing the secondary release of thromboxane A2, which is an unfavorable mechanism in asthma.

Induction of plasma exudation and inflammatory cell infiltration by leukotriene C4 and leukotriene B4 in mouse peritonitis.

Leukotriene induction of the fluid and cellular phases of the inflammatory response in the mouse was evaluated. Intraperitoneal injection of leukotriene C4 (LTC4 250 ng) led to dye extravasation but not polymorphonuclear leukocyte (PMN) infiltration, whereas injection of leukotriene B4 (LTB4 250 ng), led to PMN infiltration but not dye extravasation. The injection of both leukotrienes did not result in synergy. LTC4 did not appear to induce significant release or formation of chemotactic mediators, but the dye extravasation induced by LTC4 was inhibited by the vasoactive amine antagonist cyproheptadine and not by the eicosanoid inhibitors phenidone or naproxen. The response was markedly inhibited by the cytokine and eicosanoid inhibitors SK&F 86002 and SK&F 104493. PMN infiltration induced by LTB4 was not inhibited by SK&F 86002 or phenidone but was abrogated by colchicine treatment. LTB4 in this model did not appear to cause release or formation of vasoactive mediators. These leukotrienes appeared to be independent, complementary, and sufficient to mount a complete inflammatory response in the mouse.

[The metabolism of peptide leukotrienes in the lung may affect their coronary vasoconstrictive effect in anesthetized dogs].

The deteriorative effect of peptide leukotrienes (LTs) on the coronary circulation are well known. On the other hand, it has been recognized that some of these prostanoids are metabolized in the pulmonary vascular bed. To clarify the influence of the metabolism of LTs in the lung on their effects to the coronary circulation, we compared the changes of coronary circulation parameters by leukotriene D4 (LTD4) and C4 (LTC4) administered (5 mcg/kg) into the right atrium (RA) and the left atrium (LA) in 8 mongrel dogs. After the administration of LTD4 and LTC4, significant reduction of coronary blood flow (LTD4-RA 65.8 +/- 3.4%, LTD4-LA 54.8 +/- 2.3%, LTC4-RA 64.3 +/- 3.9%, LTC4-LA 66.9 +/- 3.7%) and elevation of coronary vascular resistance (LTD4-RA 130.5 +/- 8.2%, LTD4-LA 157.3 +/- 6.1%, LTC4-RA 138.7 +/- 8.0%, LTC4-LA 129.5 +/- 10.1%) were recognized. The effect of LTD4, administered into the left atrium was significantly greater than that administered into the right atrium (p less than 0.05). The difference between right and left atrial administration was not statistically significant, although a tendency for the effect to be greater with right atrial administration than left was recognized. The LTC4 concentration in aortic blood measured by radioimmunoassay was significantly lower in right atrial administration than left (p less than 0.05). These results suggested that LTD4 was metabolized and inactivated in the lung during its passage through the pulmonary circulation, and LTC4 was not only inactivated but also converted to LTD4 and activated in the pulmonary vascular bed.(ABSTRACT TRUNCATED AT 250 WORDS)

Intracarotid infusion of leukotriene C4 selectively increases blood-brain barrier permeability after focal ischemia in rats.

Intracarotid infusions of leukotriene C4 (LTC4) were used to open selectively the blood-brain barrier (BBB) in ischemic tissue after middle cerebral artery (MCA) occlusion in rats. BBB permeability was determined by quantitative autoradiography using [14C]aminoisobutyric acid. Seventy-two hours after MCA occlusion, LTC4 (4 micrograms total dose) infused into the carotid artery ipsilateral to the MCA occlusion selectively increased the unidirectional transfer constant for permeability Ki approximately threefold within core ischemic tissue and tissue adjacent ot the ischemic core. No effect on BBB permeability was seen within nonischemic brain tissue or in ischemic tissue after only 24 h after MCA occlusion. gamma-Glutamyl transpeptidase (gamma-GTP) activity was decreased in capillaries in ischemic tissue at 48 and 72 h after infarction, compared to high gamma-GTP in normal brain capillaries and moderate gamma-GTP in capillaries in the ischemic tissue at 24 h after infarction. These findings suggest that normal brain capillaries resist the vasogenic effects of LTC4. In contrast, LTC4 increases permeability in capillaries of ischemic tissue, where gamma-GTP is decreased. gamma-Glutamyl transpeptidase, an enzyme that inactivates LTC4 to LTD4 and LTE4 to LTF4, may act as an "enzymatic barrier" in normal brain capillaries to leukotrienes.

Studies on leukotriene D4 as an eosinophil chemoattractant.

The effects of LTD4 on eosinophil motility were studied in order to indicate its potential role as an eosinophil chemoattractant. The guinea pig was selected as a suitably sensitive species for in vivo studies. Eosinophil infiltration was quantified by digital image analysis of 6 microns paraffin ocular and cutaneous tissue sections stained by Luna's method. LTD4, applied topically to the ocular surface, caused pronounced eosinophil infiltration into the conjunctival epithelium and was more potent and efficacious than a variety of other putative mediators of allergy. Pretreatment with the LT-antagonist SK&F 104353 (i.v. 1 mg/kg) abolished LTD4-induced eosinophil infiltration into the conjunctiva. Eosinophil infiltration did not occur in other ocular anterior segments structures such as the cornea, iris and ciliary body after either topical application or intracameral injection. LTD4 did not cause eosinophil emigration into skin following intradermal injection, despite causing an increase in cutaneous microvascular permeability at identical doses. These studies indicate that LTD4 may cause eosinophil emigration in vivo according to tissue-dependent regulation.

Multiple mechanisms of xanthine actions on airway reactivity.

Xanthines are effective in the treatment of asthma, but the mechanism of action remains unclear. Pulmonary effects of seven xanthines, exhibiting a range of potencies as cyclic nucleotide phosphodiesterase (PDE) inhibitors and as adenosine antagonists, were investigated in anesthetized and ventilated guinea pigs. The bronchodilator effects of xanthines, determined from reversal of bronchoconstriction induced by aerosols of histamine and carbachol, correlated with their relative potencies as cyclic AMP-PDE inhibitors. The hypotensive effects of xanthines at bronchodilator doses were also consistent with PDE inhibition. Prophylactic effects of xanthines against bronchoconstriction induced by an aerosol of ovalbumin in sensitized guinea pigs, or by aerosols of leukotriene D4 and platelet-activating factor (PAF) in normal guinea pigs, occurred by a mechanism unrelated to bronchodilation and could not be readily attributed to PDE inhibition or adenosine A1/A2 receptor antagonism. There was a close association between inhibition of the responses to antigen and leukotriene D4, suggesting a common mechanism of action, but these effects gave a different profile from inhibition of the response to PAF. In addition, PAF-induced hypotension was unaffected in animals in which PAF-induced bronchoconstriction was inhibited, suggesting a mechanism other than PAF receptor antagonism. These results indicate that the bronchodilator, antiallergic and anti-inflammatory effects of xanthines occur through multiple molecular mechanisms of action, including at least one unknown mechanism. Furthermore, 8-phenyltheophylline produces these prophylactic effects at a dose that does not produce the cardiovascular or emetic side effects associated with xanthines, thereby exhibiting unique characteristics of potential therapeutic importance.

Skin responses to intradermal histamine and leukotrienes C4, D4, and E4 in patients with chronic idiopathic urticaria and in normal subjects.

Mast cell inflammatory mediators, such as histamine, and newly formed compounds, such as the leukotrienes, cause wheal and flare when they are injected intradermally into normal subjects and may therefore play a role in the formation of urticaria. The effects of intradermal injections (50 microliters) of six different concentrations of histamine (range, 3.3 x 10(-4) to 3.3 x 10(-9) mol/L) and the leukotrienes C4, D4, and E4 (range, 2 x 10(-4) to 2 x 10(-9) mol/L) have been compared in 10 normal subjects and in 10 patients with chronic idiopathic urticaria. Wheal-and-flare sizes were measured at timed intervals up to 4 hours, and area under the curve for each response over time was calculated. There were no significant differences in leukotriene-induced responses between groups. Maximum sizes of histamine-induced wheal and flare were similar in each group of subjects. There were, however, significant increases in mean areas under the response curve of histamine wheal and flare in the patients with urticaria (wheal, p less than 0.001; flare, p less than 0.001; analysis of variance). These findings demonstrate a prolongation of skin responses to histamine in patients with urticaria and suggest an impaired clearance of histamine (or other vasoactive agents released by histamine) from the skin of these patients.