Effect of limonene and sobrerol on monocrotaline-induced lung alterations and pulmonary hypertension.

The effects of two monocyclic monoterpenes, limonene and sobrerol, known as inhibitors of farnesyltransferase activity, were studied on monocrotaline (MCT)-induced lung injury, pulmonary hypertension and right ventricular hypertrophy in male Wistar rats. After 14 days, pulmonary arterial pressure values and the right ventricle to left ventricle plus septum weight ratios, RV/(LV + S), were markedly increased in rats subcutaneously injected with MCT (60 mg/kg). Limonene and sobrerol, administered daily at the oral dose of 400 mg/rat, markedly decreased the MCT-induced alterations. After treatment for 21 days, limonene still prevented pulmonary hypertension and the increase in RV/(LV + S). Both monoterpenes also reduced the increase in pulmonary arterial media thickness, the development of interstitial fibrosis and the increase in the number of macrophages in intra-alveolar spaces and of lymphocytes around the pulmonary veins. The present data indicate that treatment of rats with inhibitors of farnesyltransferase, like limonene and sobrerol, regulate the development of pulmonary hypertension.

Effect of long-term infusion of platelet-activating factor on pulmonary responsiveness and morphology in the guinea-pig.

The effect of chronic administration of platelet-activating factor (PAF) on airway reactivity, cell recruitment and lung morphology in the guinea-pig has been investigated. Alzet osmotic minipumps delivering either PAF (7.2 mg/kg/14 days) in 0.25% (w/v) bovine serum albumin in saline (saline-BSA), acetylcholine or saline-BSA alone were implanted s.c. in the neck region of guinea-pigs and connected to the jugular vein. In some experiments, implanted and non-implanted animals were treated daily with the PAF antagonist, BN 52021 (15 mg/kg, twice a day, p.o.). On day 15 after minipump implantation, the animals were anesthetized with urethane (1.2 g/kg, i.p.) and tracheal cannula was inserted for mechanical ventilation. Pulmonary inflation pressure (PIP) was monitored and airway responsiveness was assessed by administration of increasing doses of histamine (0.2-100 micrograms/kg, i.v.). As compared to saline-BSA-treated or non-implanted guinea-pigs, chronic treatment of the animals with PAF induced a significant (p less than 0.01) increase in airway response. No significant change in airway responsiveness was observed following chronic acetylcholine administration. In contrast, regardless of the treatment of the animals, no change in the threshold dose of histamine inducing alteration in PIP was noted, suggesting that PAF induces bronchopulmonary hyperreactivity rather than hyperresponsiveness. In addition, no significant difference was observed in the in vitro responsiveness to histamine of lung parenchymal strips from animals having received PAF or saline-BSA.(ABSTRACT TRUNCATED AT 250 WORDS)

Bronchopulmonary and vascular effect of endothelin in the guinea-pig.

Intravenous (i.v.) injection of endothelin in the anesthetized and ventilated guinea-pig induced a dose-dependent increase in pulmonary inflation pressure. The 1 nmol/kg dose rapidly enhanced pulmonary inflation pressure, reaching a peak at 30 s, as well as produced a marked and sustained increase in mean arterial blood pressure. A maximal increase in arterial blood pressure was observed 4 min after the injection of 1 nmol/kg endothelin and remained at a plateau for 20 min. The increase in pulmonary inflation pressure induced by endothelin was significantly enhanced by treatment of the guinea-pigs with propranolol (1 mg/kg i.v.). In contrast to what was observed in untreated guinea pigs, the injection of 1 nmol/kg endothelin in propranolol-treated animals produced within 2 min an irreversible and dramatic decrease in mean arterial blood pressure with a further decline for up to 90 min. The increase in pulmonary inflation pressure induced by 0.5 nmol/kg endothelin was also potentiated significantly in propranolol-treated guinea-pigs as compared to untreated animals. Endothelin 0.5 nmol/kg caused only a transient and non-significant increase in mean arterial blood pressure in both propranolol-treated and untreated animals. Injection of endothelin (40, 120 and 400 pmol) via the pulmonary artery into isolated guinea-pig lungs evoked significant increases in pulmonary inflation pressure and perfusion pressure accompanied by the dose-dependent release of TXB2 but, in contrast, no release of histamine. The in vitro effect of endothelin on pulmonary inflation pressure and perfusion pressure was potentiated when propranolol (1 microM) was added to the perfusion medium. These results demonstrate that the bronchopulmonary effects of endothelin are, at least in part, dissociated from the vascular action of the peptide.

Action of platelet-activating factor (PAF) antagonists on the bronchopulmonary effects of PAF in the guinea-pig.

Intravenous injection of BN 52021 in anesthetized guinea-pigs, 5 min before challenge, inhibited in a dose-dependent fashion with an IC50 of 0.90 mg/kg the bronchoconstriction induced by PAF (60 ng/kg i.v.). However, BN 52021 did not prevent the leukopenia following PAF injection but significantly inhibited the thrombocytopenia induced by PAF. The dioxolan compound, BN 52111, dose-dependently reduced the bronchoconstriction (IC50 = 0.27 mg/kg) and at doses higher than 1 mg/kg partially antagonized the decrease in the number of circulating platelets and leukocytes induced by PAF. BN 52115 also markedly inhibited the bronchoconstriction (IC50 = 0.36 mg/kg) as well as the thrombocytopenia induced by PAF, but was without significant effect on the leukopenia. These results demonstrate that the two dioxolan compounds, BN 52111 and BN 52115, are more potent than BN 52021 in inhibiting the in vivo bronchopulmonary alterations induced by PAF. Since these alterations are related to the activation of platelets by the autacoid, these blood elements are probably the targets of BN 52111 and BN 52115. Injection of PAF (10 and 100 ng) via the pulmonary artery of ventilated and perfused guinea-pig lungs induced dose-dependent increases in pulmonary inflation pressure (PIP) and pulmonary perfusion pressure (PPP), associated with a dose-dependent release of thromboxane B2 (TxB2). Addition of BN 52021, BN 52111 or BN 52115 (0.1, 1 or 10 microM) to the perfusion medium, 15 min before challenge, dose-dependently inhibited the bronchopulmonary effects of PAF. Although BN 52111 was the more potent in inhibiting the PAF-induced increase in PIP, BN 52021 was the more active with respect to the PAF-evoked generation of TxB2, suggesting that the two phenomena are not directly related.

Effect of cyclosporin A and the platelet-activating factor (PAF) antagonist, BN 52021, on PAF- and antigen- induced bronchoconstriction in the guinea-pig.

The effects of the PAF antagonist, BN 52021, and cyclosporin A (CsA), either alone or in combination, on PAF- and antigen- induced bronchoconstriction were investigated in control and passively sensitized guinea-pigs, respectively. Although single administration of CsA alone has no effect on the PAF-induced bronchoconstriction, a marked inhibition of this phenomenon is observed when the drug is given along with an inactive dose of BN 52021. This effect of the association of the two drugs on the bronchoconstriction is also related to an action on the PAF-induced alterations in the number of leukocytes and platelets. In addition, administration of CsA for 48 hrs, which alone does not influence PAF-induced bronchoconstriction, markedly increases the inhibition evoked by BN 52021. Although bolus administration of CsA has no effect on the antigen -induced bronchoconstriction, a marked inhibition of this phenomenon is observed when the drug is given for 2 days. This inhibition by CsA is not further enhanced when the animals are also treated with BN 52021. These results strengthen the hypothesis that PAF and the immune system are involved in the regulation of bronchopulmonary reactions.

Effect of endothelin-1 on blood pressure and bronchopulmonary system of the guinea pig.

The bronchopulmonary and pressor effects of endothelin-1 (ET-1), a newly described vasoconstrictor peptide produced by endothelial cells, were investigated in the guinea pig. Intravenous injection of ET-1 (1 nmol/kg) induced an increase in pulmonary inflation pressure (PIP) as well as an important and sustained increase in arterial blood pressure (BP). Pretreatment of these animals with propranolol (1 mg/kg i.v.), provoked a significant enhancement of the ET-1-induced increase in PIP, accompanied by a dramatic and significant decrease of BP. When administered by aerosol for 1 min, ET-1 (1, 5, or 10 micrograms/ml) induced a dose-dependent increase in PIP that was maximal by 4-5 min, but no significant change of BP. Pretreatment of guinea pigs with propranolol (1 mg/kg), mepyramine (1 mg/kg i.v.), nifedipine (50 mg/kg i.p.), or verapamil (0.3 mg/kg i.v.) did not inhibit the bronchopulmonary response evoked by aerosol administration of 10 micrograms/ml of ET-1. In contrast, pretreatment of the animals with indomethacin (10 mg/kg i.v.) or BN 52021 (10 mg/kg i.v.) significantly reduced the bronchopulmonary response of ET-1 given by aerosol. Injection of ET-1 (0.1, 0.3, and 1 micrograms) into isolated guinea pig lungs caused significant increases in PIP that were accompanied by the release of TxB2 but not histamine. These results demonstrate that ET-1 induces bronchopulmonary alterations in the guinea pig that appear to be dissociated from the systemic vascular effects of the peptide.

Role of platelet-activating factor (PAF) in the bronchopulmonary alterations and beta-adrenoceptor function induced by endotoxin.

The possibility that PAF is implicated in the alterations of the beta-adrenoceptor function observed during endotoxemia was investigated. Lung parenchymal strips (LPS) from endotoxin-treated guinea-pig demonstrated specific desensitization to low doses of PAF whereas the contractions induced by histamine and leukotriene D4 were slightly affected. In addition, histamine-contracted LPS from endotoxin-injected animals exhibited decreased responsiveness to isoproterenol, a phenomenon not observed with guinea-pigs also treated with the specific PAF antagonist, BN 52021. No alteration of the sensitivity to isoproterenol of LPS preincubated with PAF was noted, suggesting an indirect effect of the autacoid on beta-adrenoceptor function.

Gossypol: a potent inhibitor of PAF-acether- and leukotriene-induced contractions of guinea-pig lung parenchyma strips.

Gossypol, a substance extracted from cotton plants, markedly inhibited the contractile responses of guinea-pig lung parenchyma strips stimulated with leukotriene B4 (LTB4), leukotriene D4 (LTD4) and PAF-acether but not the responses to histamine (except at high concentration). It was slightly less potent than nordihydroguaiaretic acid (NDGA) and a PAF-antagonist (BN 52021). From previously reported effects of gossypol on the cyclooxygenase and lipoxygenases, and on the similarity of the inhibition produced by NDGA and gossypol on the lung parenchyma, it is suggested that the inhibition of the myotropic activity of the lung parenchyma by gossypol is due to interactions with the formation of cyclooxygenase products within the guinea-pig lung.

Interference of the PAF-acether antagonist BN 52021 with passive anaphylaxis in the guinea-pig.

PAF-acether may be involved in anaphylaxis and asthma. We tested the new PAF-acether antagonist BN 52021 against the effects of antigen in passively sensitized guinea-pigs. Bronchoconstriction by ovalbumin administered i.v. (1 mg/kg) or by aerosol (1 or 10 mg/ml for a period of 1 min) was significantly reduced by BN 52021 (1-10 mg/kg), which did not inhibit drop of leukocyte counts after the i.v. challenge. In both cases, when the guinea-pigs were pretreated by propranolol, high amounts of BN 52021 became ineffective against shock. The reduction of the anaphylactic bronchoconstriction, induced by the combination of mepyramine, aspirin and FPL 55712 was not improved by BN 52021. Tested on isolated lung strips from passively sensitized guinea-pig, BN 52021, at a concentration which inhibits PAF-induced contraction (0.1 mM), did not inhibit the anaphylactic contraction triggered by the administration of ovalbumin (10 micrograms/ml) nor the accompanying release of histamine and thromboxane. In contrast, BN 52021 (30 microM) significantly reduced the anaphylactic release of histamine and of thromboxane from perfused lungs of passively sensitized guinea-pigs. The results with the isolated lung strips and the propranolol-treated guinea-pigs in vivo suggest a dissociation between the anti-anaphylactic and the anti-PAF-acether properties of BN 52021.

Characterization of platelet activating factor (PAF)-acether-induced contractions of guinea-pig lung strips by selected inhibitors of arachidonic acid metabolism and by PAF-acether antagonists.

The myotropic activities of PAF-acether, leukotriene B4, leukotriene D4 and histamine were compared on superfused guinea-pig lung parenchymal strip and were shown to have the following order of potency: PAF-acether greater than LTD4 greater than LTB4 greater than histamine. The contractile response of the lung parenchyma to PAF-acether was inhibited by aspirin, imidazole and OKY-046, which suggested that thromboxane A2 might play a mediator role in PAF-induced contractions. Neither an antagonist of leukotriene D4, FPL-55712, nor an antihistamine, mepyramine, had any effect on PAF contractions. The activity of a novel antagonist of PAF-acether, BN 52021, was also studied on superfused lung parenchyma contracted by histamine, leukotriene B4, leukotriene D4 and PAF-acether. This compound was without effect on the histamine response but it slightly reduced the contractions elicited by leukotriene D4 and potentiated those by leukotriene B4. BN 52021 (7.1 X 10(-6) M) inhibited by 63% the contraction induced by 5.7 X 10(-13) M PAF-acether and by 52% that induced by 5.7 X 10(-10) M PAF-acether and kadsurenone (8.4 X 10(-6) M), another PAF-acether antagonist, inhibited the same PAF-induced contractions by 75% and 20% respectively.

Pharmacological control of the in vivo passive anaphylactic shock by the PAF-acether antagonist compound BN 52021.

BN 52021 antagonized PAF-acether-induced bronchoconstriction (BC) in the guinea-pig and inhibited BC triggered by antigen in passively sensitized animals. The anti-anaphylactic activity was prevented by propranolol and may either result from an additional property of the drug, independent from PAF antagonism or from different PAF-dependent mechanisms with different responsiveness to the various antagonists.

Comparative effects of drugs on leukotrienes-, PAF-acether- and histamine- induced contractions of guinea-pig lung parenchymal strips.

Dose-response curves to leukotrienes B4 (LTB4), D4 (LTD4), PAF-acether and histamine applied as single or cumulative doses are studied on guinea-pig lung parenchymal strips (GPLP). A mole to mole comparison shows that PAF-acether is the most potent agonist, when GPLP contracts maximally to histamine. GPLP possesses specific receptors to histamine, LTD4 and PAF-acether which can be blocked by selective receptors antagonists: mepyramine as antihistaminic, FPL 55712 as anti-SRS-A substance, BN 52021 and kadsurenone as anti-PAF-receptor antagonists; meanwhile, a part of their action is mediated through the release of arachidonate metabolites. Histamine, LTB4, LTD4 and PAF-acether-induced contractions are all dependent on cyclooxygenase. Thromboxane A2 (TXA2) could be one of the cyclooxygenase products involved. A part of contractile effects of LTB4 and LTD4, but not of histamine, is liked to the generation of lipoxygenase metabolites as their contractions are partially inhibited by NDGA and ETYA. Contraction-induced by PAF-acether is reduced in presence of NDGA but not by FPL 55712, which indicates that lipoxygenase products other than peptidoleukotrienes are involved in the PAF-response.

Interference of BN 52021 (ginkgolide B) with the bronchopulmonary effects of PAF-acether in the guinea-pig.

The interaction between the ginkgolide BN 52021 and the effects of PAF-acether on the bronchopulmonary system of the guinea-pig was studied. In pentobarbitone or ethyl carbamate-anaesthetized animals, BN 52021 (1 mg/kg i.v. or 10 mg/kg p.o.) inhibited bronchoconstriction, the hematocrit increase and the accompanying thrombopenia and leukopenia induced by PAF-acether (33-100 ng/kg) and failed to block the bronchoconstriction produced by collagen, arachidonic acid and the tripeptide formyl-Met-Leu-Phe (FMLP). BN 52021, 3 mg/kg, reduced the bronchoconstriction induced by aerosolized PAF-acether. BN 52021, 300 microM, also inhibited the superoxide production by PAF-acether-stimulated alveolar macrophages and failed to reduce the same effects when triggered by FMLP (0.01-1 microM). BN 52021 blocked the formation of thromboxane-triggered by PAF-acether (100 ng) injected into perfused lung, under conditions where the effects of arachidonic acid where not modified. Finally, pretreatment of parenchyma lung strips with BN 52021 (100 microM) partially inhibited the contraction induced by PAF-acether (0.1 microM) and suppressed the accompanying release of thromboxane. BN 52021 is a selective antagonist of the effects of PAF-acether on the bronchopulmonary system and on circulating blood cells of the guinea-pig.

Effect of an extract of Ginkgo biloba on the isolated ileum of the guinea-pig.

1. The effects of an extract of Ginkgo biloba (Gb) were studied using the guinea-pig isolated ileum. 2. Using isometric recording, the dose-response relation for the action of Gb was complex, and at 400 micrograms/ml was reproducibly biphasic--a relaxation followed by a contraction. 3. Droperidol (3 X 10(-7) M - 10(-6) M), cyproheptadine (10(-7) M), and diphenhydramine (10(-7) M) prolonged the relaxation and usually decreased the amplitude of the contraction produced by Gb (400 micrograms/ml), whereas phentolamine, hexamethonium, methysergide, or cimetidine (10(-7) or 10(-6) M) did not affect the response to Gb. 4. The action of Gb on the guinea-pig ileum might involve mechanisms associated with dopamine and/or histamine.