Luisa Daffonchio

Effectiveness of carbocysteine lysine salt monohydrate on models of airway inflammation and hyperresponsiveness.

We investigated the possible effects of the mucoactive drug Carbocysteine lysine salt monohydrate (CLS.H2O) on experimentally-induced airway inflammation and hyperresponsiveness. CLS.H2O given by the oral route (300 mg kg(-1)) significantly reduced neutrophil infiltration into the airway lumen induced by intratracheal injection of IL-1 beta in rats. In addition, CLS.H2O inhibited dose-dependently (100-300 mg kg(-1) p.o.) the formation of pleural exudate and leukocyte recruitment induced by intrapleural injection of carrageenan in rats. Because of the close interaction between the inflammatory process and the development of airway hyperresponsiveness we also tested CLS.H2O on cigarette-smoke-induced inflammation and hyperreactivity in anaesthetized guinea-pigs. The drug, given either by oral (300 mg kg(-1)) or aerosol route (30-100 mg ml(-1)), was able to reduce the increase in airway responsiveness induced by smoke and the associated cell recruitment detected in the bronchoalveolar lavage (BAL) fluids. These results suggest that CLS.H2O can exert an anti-inflammatory action in addition to its mucoregulatory activity. The anti-inflammatory and anti-hyperreactivity effect of the drug within the airways may be of advantage in the treatment of inflammatory lung diseases where mucus secretion together with airway inflammation and hyperreactivity contribute to airway obstruction.

Defibrotide, an antithrombotic substance which prevents myocardial contracture in ischemic rabbit heart

Defibrotide, a polydeoxyribonucleotide obtained from mammalian lungs, reduced in a dose-dependent fashion the ischemic contracture due to low perfusion (0.2 ml/min) of isovolumic left heart of rabbit and abolished the irregular rhythm of the heart, thereby restoring the cardiomechanical activity upon reperfusion (20 ml/min). Defibrotide stimulated the release of PG-like material from the heart in a dose-dependent manner without modifying the basal contractility. Both PGE2 and PGI2 (10 ng/ml) have an antiischemic activity on this preparation as shown by the partial reduction of the ischemic contracture and by the improvement of heart contractility upon reperfusion. Indomethacin infusion (1 microgram/ml) completely removed both the antiischemic activity of Defibrotide (400 micrograms/ml) and its ability to increase the generation of prostaglandins in the rabbit heart. These results suggest that Defibrotide has a beneficial influence on ischemic rabbit heart through an increase in prostaglandin synthesis. However other mechanisms not necessarily related to prostaglandin generation, such as a direct effect on membrane function deactivation and mitochondrial Ca2+ overload, should be considered in explaining the antiischemic activity of Defibrotide in the rabbit heart.

Airway hyperreactivity induced by active cigarette smoke exposure in guinea-pigs: possible role of sensory neuropeptides

Exposure to cigarette smoke is associated with increased airway responsiveness to different stimuli, both in human and animal studies. However, the mechanisms involved in the pathogenesis of smoke-induced airway hyperreactivity are less clear. We investigated the development of airway hyperreactivity induced by active cigarette smoke exposure in anaesthetised guinea-pigs and the possible mechanisms involved. Active inhalation of cigarette smoke (15 s/min for 10 min) potentiated the broncho-contractile effect of acetylcholine (Ach), indicating the occurrence of airway hyperreactivity. This phenomenon appeared within 5 min and lasted up to 50 min after smoke exposure. Smoke induced airway hyperreactivity was a non-specific phenomenon, involving an enhanced responsiveness to both Ach and histamine (Hist). Recruitment of proinflammatory cells into the airway lumen, as revealed by the analysis of bronchoalveolar lavage fluid, paralleled the development of the hyperreactive phenomenon, suggesting a relationship between the inflammatory reaction and the genesis of smoke-induced airway hyperreactivity. Cervical bilateral vagotomy did not modify either the degree and the time-course of smoke induced airway hyperreactivity. Moreover, atropine treatment did not affect the increase in Hist response due to smoke inhalation. On the other hand, depletion of substance P due to capsaicin pretreatment almost completely prevented the capacity of cigarette smoke to potentiate Ach induced bronchoconstriction. Cyclo-oxygenase inhibition, by indomethacin pretreatment, reduced the time course of the hyperreactivity induced by smoke inhalation. Our results clearly demonstrate the occurrence of airway hyperreactivity triggered by active cigarette smoke exposure. Moreover, the data obtained suggest a predominant role for substance P and related peptides in the pathogenesis of smoke induced increase in airway responsiveness.

Airway hyperreactivity follows anaphylactic microshock in anaesthetized guinea-pigs.

Actively sensitized guinea-pigs were challenged with a dose of ovalbumin aerosol (300 micrograms ml-1, 5 s) that caused submaximal bronchoconstriction (anaphylactic microshock). Airway reactivity to i.v. 5-hydroxytryptamine (5-HT), i.v. acetylcholine (ACh) and aerosolised 5-HT was assessed subsequently. In addition, histological studies were carried out to investigate possible pulmonary recruitment of inflammatory cells following anaphylactic microshock. Following antigen challenge, there was a significant (P less than 0.05) increase in airway reactivity. This phenomenon was temporally separated (60-120 min) from the initial anaphylactic bronchoconstriction, but occurred in the absence of detectable lung pathology other than minor epithelial necrosis. Whilst histamine aerosol (100 micrograms ml-1, 5 s) did not induce airway hyperreactivity, pretreatment with the histamine H1 receptor antagonist mepyramine (2 mg kg-1 i.v.) prevented that occurring following antigen challenge. These observations suggest that in the pathogenesis of airway hyperreactivity, mediator release from resident leukocytes is initially more important than pulmonary infiltration of circulating cells. Depletion of a putative epithelium-derived relaxant factor may also play a contributory role. The anaphylactic release of histamine may modulate the release of secondary mediators of airway hyperreactivity.

Interleukin-1β : a possible mediator of lung inflammation and airway hyperreactivity

Interleukin-1 (IL-1), a peptide released from monocytes/macrophages, plays an important role in the inflammatory and immune responses. Airway hyperreactivity and the underlying airway inflammation are common features in asthma pathology. We investigated and characterized the inflammatory alterations induced within the guinea-pig respiratory system by IL-1 beta. Injection of IL-1 beta (1-6 micrograms/animal) into the pleural space resulted in a dose-dependent inflammatory response, as shown by the formation of pleural exudate and leucocyte recruitment. A threshold dose of IL-1 beta (1 micrograms/animal) markedly potentiated the inflammatory reaction triggered by the classical proinflammatory agent croton oil, underlining the amplifying role of IL-1 beta in the inflammatory events. The inflammatory process induced by intrapleural injection of IL-1 beta (6 micrograms/animal) was associated with the development of a hyperreactive phenomenon which involved both the peripheral and large airways. In fact, increased contractile activity of histamine was evident in the tracheas and parenchymal strips isolated from guinea-pigs exposed to IL-1 beta. These results provide evidence for a possible role of IL-1 beta in the genesis of airway inflammation and bronchial hyperreactivity.

Passive cigarette smoke exposure induces airway hyperreactivity to histamine but not to acetylcholine in guinea-pigs

We have investigated the changes in airway reactivity induced in guinea-pigs by passive cigarette smoke exposure. In particular, we studied the development of airway hyperresponsiveness both in vivo and in vitro after passive exposure of the animals to cigarette smoke in a plexiglass box. Passive smoke exposure significantly (p less than 0.01) increased histamine induced bronchoconstriction. The dose-ratio calculated between histamine dose-response curves constructed in control and smoke exposed animals was 2.13 (95% confidence limits: 1.46-3.09). Acetylcholine induced bronchoconstriction was not potentiated after the same smoke exposure, indicating some specificity of the mediators involved in the airway hyperresponsiveness triggered by passive smoke exposure. The airway hyperreactivity induced by smoke exposure was associated with a specific increase in histamine contraction induced in vitro in lung parenchymal strips but not in tracheae or pulmonary arteries. Maximal histamine contraction in parenchymal strips taken from smoke exposed animals was significantly (p less than 0.01) enhanced by approximately 110% when compared to control. There was a significant (p less than 0.01) increase in the number of macrophages and eosinophils in the bronchoalveolar lavage fluid of animals passively exposed to cigarette smoke, but no mucus hypersecretion was evident. Our data demonstrate the occurrence of airway hyperreactivity induced by passive cigarette smoke exposure, which involves increased smooth muscle reactivity and cell recruitment.

Involvement of arachidonic acid metabolites in β-adrenoceptor desensitization: functional and biochemical studies

The prolonged in vitro perfusion of rat lung with isoproterenol (Iso) induced a desensitization of beta-adrenoceptors which was dose- and time-dependent. The decrease in functional responsiveness of rat lung parenchyma to the beta-agonist correlated well with the loss of [3H]dihydroalprenolol ([3H]DHA) binding sites and adenylate cyclase activity after the beta-adrenoceptor desensitization procedure. The cyclooxygenase inhibitor indomethacin prevented the beta-adrenoceptor desensitization as was shown by the restored isoproterenol-induced relaxation in rat lung parenchyma strips and adenylate cyclase activity after the milder desensitization procedure. Inhibition of the arachidonic acid cascade at different levels with different compounds such as BW 755C and betamethasone prevented the desensitization of beta-adrenoceptors. These findings suggest a role for arachidonic acid metabolites in beta-adrenoceptor desensitization. The possible sites of action of arachidonic acid metabolites are also discussed in relation to the inability of indomethacin to prevent the desensitization of beta-adrenoceptors that was induced by the higher Iso concentration used.

Positive interaction between leukotriene C4 and histamine and other mediators on vascular tissues.

The interaction of leukotriene C4 (LTC4) with the contractile activity of histamine (H), serotonin (5HT) and norepinephrine (NE) has been investigated in isolated vascular preparations. Threshold concentration of LTC4 (5 X 10(-9) M) significantly potentiated the vasoconstricting effect of these compounds on guinea-pig pulmonary artery (GPPA). This phenomenon was long-lasting for H since it was still present 40 min after LTC4 had been washed. FPL-55712 (10(-5) M) counteracted the increased H response on GPPA induced by LTC4. Potentiation of H activity due to LTC4 was also observed on guinea-pig thoracic aorta (GPTA) indicating that LTC4-induced hyperreactivity is not a phenomenon restricted to the pulmonary vascular bed. In the experiments carried out in presence of indomethacin (3 X 10(-6) M), LTC4 still potentiated H-induced vasoconstriction on GPPA, however the time course of the phenomenon was significantly shorter than that observed in absence of the cyclooxygenase inhibitor. The contractile activity of H and NE on guinea-pig portal vein (GPPV) was not potentiated by LTC4. These results demonstrate that LTC4 induces hyperreactivity of the arterial vascular tissue to vasoactive compounds and suggest that cysteinyl-leukotrienes may have pathological significance in the hemodynamic changes occurring during anaphylactic reactions. Preliminary experiments carried out on human intralobar pulmonary artery strongly support this hypothesis.

Effectiveness of levodropropizine against cigarette smoke-induced airway hyperreactivity: possible mechanism

We verified the possible effect of the new antitussive drug levodropropizine on airway hyperreactivity and lung inflammation induced by cigarette smoke exposure in anaesthetized guinea-pigs. Levodropropizine, administered by aerosol at 25 mg/ml for 30 s completely prevented smoke induced airway hyperreactivity. The protective effect was early in onset (3 min) and lasted up to 30 min. The same dose of codeine, administered in the form of an aerosol, decreased the increase in airway responsiveness induced by smoke inhalation slightly but not significantly. In parallel with the functional results, levodropropizine also inhibited the recruitment of inflammatory cells triggered by smoke exposure within the airway lumen. When levodropropizine was administered i.v. to anaesthetized guinea-pigs, it reduced the bronchocontractile effect of capsaicin dose-dependently, whereas it was without effect against substance P-induced bronchoconstriction. These data demonstrate the ability of levodropropizine to counteract the hyperreactive phenomenon and the associated inflammatory event induced by cigarette smoke exposure, an effect which might depend on its capacity to modulate the activation of the peptidergic system.

Arachidonic acid metabolites induced β-adrenoceptor densitization in rat lung in vitro

The possible involvement of arachidonic acid (AA) or its metabolites in beta-adrenoceptor desensitization has been studied in rat lung parenchyma both from a functional and a biochemical point of view. In vitro perfusion of rat lungs with AA (3 X 10(-5)M for 20 min) reduced the relaxant effect of isoproterenol (ISO) on lung parenchymal strips, shown by a shift to the right of ISO dose-response curve, similar to that obtained using desensitizing concentration of specific beta-agonist. Moreover, AA treatment reduced the capacity of ISO to stimulate adenylate-cyclase activity, whereas the number of beta-receptor binding sites was not significantly modified. Inhibition of cyclo-oxygenase pathway by indomethacin (INDO) (1.5 X 10(-5)M) prevented both the loss of ISO-relaxing capacity and the decrease of adenylate-cyclase activity induced by AA treatment. In order to support the role of eicosanoids in beta-adrenoceptor desensitization, changes of endogenous free AA levels have also been studied in lung homogenates. Perfusion of rat lung with ISO (10(-6)M for 20 min) decreased by about 50% the levels of free AA and the pretreatment with BW755C (9 X 10(-5)M), a lipo- and cyclo-oxygenase inhibitor, prevented this phenomenon. On the basis of these results, we suggest that the activation of AA cascade is actually involved in beta-adrenoceptor desensitization in lung tissues with a possible interference at the site beyond the drug-receptor interaction.