Haemophilus influenzae induced loss of lung beta-adrenoceptor binding sites and modulation by changes in peripheral catecholaminergic input

The adrenergic system in lymphocytes from children with cystic fibrosis

Several in vivo and in vitro studies have suggested that children suffering from cystic fibrosis (CF) might have a general defect of beta-adrenoceptors on the cell surface which might account for an unbalanced secretory process. In order to investigate if this view holds true, we determined the beta-adrenoceptor density and affinity on lymphocytes by means of radioligand studies using 125-iodo-cyano-pindolol (125-ICYP) in 20 children with CF. Cyclic AMP (cAMP) response was also investigated after specific beta-adrenoceptor stimulation with isoprenaline (IPN) and after direct stimulation of the adenylate cyclase with forskolin in lymphocytes. Children with CF and controls have identical numbers and affinities of beta-adrenoceptors on lymphocytes. The cyclic AMP response was identical in CF- and in age-matched control children regardless whether adenylate cyclase was stimulated directly or via beta-adrenoceptors. In conclusion, the data support the view that no general adrenoceptor or adenylate cyclase defect exists in CF. As several studies have found abnormal reactions to adrenergic stimuli in CF patients, we presume that there is a defect beyond the level of adrenergic receptors and cAMP which remains to be identified.

Membrane fluidity of guinea pig lymphocytes and the dysfunction of the respiratory airway and lymphocyte beta-adrenergic systems of the guinea pig

The beta-adrenergic receptor responsiveness of isolated guinea pig tracheal spirals can be negatively affected by intraperitoneal administration of the Gram-negative bacterium Haemophilus influenzae, four days prior to the experiment. The reduction in tracheal relaxation is accompanied by a decrease in beta-adrenergic receptor binding sites in splenic lymphocyte membranes and by a decrease in the fluidity of these membranes. The H. influenzae-induced dysfunction of both the respiratory airway and lymphocyte beta-adrenergic systems can be mimicked by modulating the amount of linoleic acid in the diet. This linoleic acid induced dysfunction of the beta-adrenergic system is also accompanied by a decrease in the plasma membrane fluidity of the splenic lymphocyte membranes of the guinea pigs. The role for plasma membrane fluidity in asthma is discussed in relation to current concepts for atopy.

Beta adrenoceptor binding and induced relaxation in airway smooth muscle from patients with chronic airflow obstruction

Beta adrenoceptor function in central airway smooth muscle of patients with chronic airflow obstruction was investigated by radioligand binding studies and isoprenaline relaxation experiments. Receptor characteristics were determined in tracheal smooth muscle preparations obtained at necropsy from 12 patients and in bronchial tissue obtained at thoracototomy from 21 patients with chronic airflow obstruction. Receptor characteristics were compared with those obtained in airway tissue preparations from 65 control subjects without chronic airflow obstruction. The number of beta adrenoceptors, their binding affinity for the radioligand [125I]-(-)-cyanopindolol, and the tissue binding characteristics of isoprenaline were similar in tissue from patients with chronic airflow obstruction and from control subjects. Isoprenaline induced relaxation of tracheal smooth muscle without precontraction by methacholine showed slightly (though not significantly) less sensitivity to isoprenaline in patients with chronic airflow obstruction than in control subjects (mean (SEM) pD2--the negative logarithm of the concentration producing 50% relaxation--6.32 (0.16) v 6.62 (0.15)). The same pattern of pD2 values was found in segmental bronchial strips without precontraction by methacholine (chronic airflow obstruction 6.55 (0.27), control 7.14 (0.12)). Isoprenaline relaxation in segmental bronchial strips when contracted maximally was significantly less in the patients with airflow obstruction than in the control subjects (pD2 value 5.99 (0.18) v 6.45 (0.07)). These results suggest that beta adrenoceptors in airway smooth muscle of patients with chronic airflow obstruction are not abnormal in number or in binding affinity but that there is less effective coupling between components of the relaxant system distal to the beta adrenoceptor. The possibility that the reduced isoprenaline sensitivity is a consequence of previous bronchodilator treatment cannot be excluded.

Effects of dietary linoleic acid on beta-adrenergic responsiveness of the guinea pig respiratory system

Respiratory autonomic beta-adrenergic receptor function was investigated in isolated tracheal spirals of guinea pigs receiving different diets. Comparison was made between control and Haemophilus influenzae treated animals; this latter group serving as animal model for atopy. The different semi-synthetic diets (35 energy%) varying in their linoleic acid contents (5.85, 11.25 and 22.05 en%), exerted profound effects on membrane fatty acid composition. No influence of these diets on either food intake or growth could be detected. Isoprenaline induced relaxation of guinea pig tracheal spirals was maximal in the dietary group receiving moderate linoleic acid (11.25 en%). Both the addition and the withdrawal of linoleic acid to this diet resulted in a significant impairment of beta-adrenergic receptor function, to the same extent as can be induced by Haemophilus influenzae. The results are discussed in view of current concepts for atopy.

Density and agonist-promoted high and low affinity states of the beta-adrenoceptor on human B- and T-cells

beta-Adrenoceptor binding on peripheral blood mononuclear cells (PBMC) of healthy adult volunteers was investigated using the radioligand 125iodo-cyanopindolol (ICYP). Saturation binding studies were performed with nine different concentrations of ICYP. Receptor density and affinity were calculated by Scatchard plots. Resolution of beta-adrenoceptors into those with high and low affinity state of the beta-adrenoceptor was obtained from inhibition curves with salbutamol using Hofstee plots. Receptor density on enriched B-cells ('B-cells') was two-fold higher than on enriched T-cells ('T-cells') (P less than 0.025). Affinity (KD values) of beta-adrenoceptors did not differ for B- and T-cells. However, when two distinct binding states for beta-adrenoceptor agonists were identified using salbutamol displacement curves, beta-adrenoceptors on T-cells presented more receptors in a high affinity state than those on B-cells (P less than 0.01). Since the ability of an agonist to activate adenylate cyclase is closely correlated with the ratio of low to high affinity states formed in the presence of the agonist, increased intrinsic activity for the beta-adrenoceptor agonist on T-cells may be postulated. In conclusion, determination of the B/T ratio is a prerequisite for interpretation of beta-adrenoceptor changes on peripheral lymphocytes in various diseases.

Involvement of the spleen in the endotoxin-induced deterioration of the respiratory airway and lymphocyte beta-adrenergic systems of the guinea pig

The beta-adrenergic binding sites on splenic lymphocyte membranes of the guinea pig were characterized with the radio-ligand [125I]cyanopindolol and showed a maximal number of binding sites (Bmax) of 125 fmol/mg protein and an affinity (Kd) of 170 pM. The potency of various beta-adrenoceptor antagonists to compete for [125I]cyanopindolol binding suggested that the receptor is of the beta 2 subtype. Endotoxin (1 mg/kg) induced a 35% decrease in the number of beta-adrenergic binding sites on lymphocytes, 4 days after i.p. administration. The reduction in the number of beta-adrenoceptors on the lymphocytes was accompanied by a 30% decrease in the relaxation of isolated guinea pig tracheal spirals to isoprenaline and a 20% reduction in the number of beta-adrenergic binding sites in peripheral lung tissue. The endotoxin-induced deterioration of the beta-adrenergic system in the respiratory airways was completely prevented by splenectomy. It is concluded that the spleen, and or cells or products derived from the spleen, are involved in the changes of the beta-adrenergic system in the respiratory airways and lymphocytes.

Beta-adrenoceptor density and resolution of high and low affinity state on B- and T-cells in asthmatic and non-asthmatic children

Beta-adrenoceptor binding in lymphocytes of asthmatic and non-asthmatic children and healthy adult volunteers was investigated with the radioligand 125-iodocyanopindolol (ICYP). Binding studies were performed with 4 to 5 different concentrations of ICYP. Receptor density and affinity were calculated by Scatchard plots. Resolution of beta-adrenoceptors into those of high and low affinity state was obtained from inhibition curves with salbutamol using Hofstee plots. Receptor density in B-cell enriched fractions was two to three-fold higher than in T-cells for all patients and volunteers studied (P less than 0.025). No difference in beta-adrenoceptor density on B and T-cells occurred neither in age-matched asthmatic and non-asthmatic children nor in adult volunteers. The affinity of beta-adrenoceptors did not differ for B and T-cells nor for the patients or volunteers studied. However, when two distinct binding states for beta-adrenoceptor agonists were obtained using salbutamol displacement curves it appeared that beta-adrenoceptors on T-cells were at a higher affinity state compared to those on B-cells in asthmatic and non-asthmatic children, as well as in adults. Since the ability of an agonist to activate adenylate cyclase correlates closely with the amount of high affinity receptor state formed in the presence of the agonist, increased intrinsic activity of the beta-adrenoceptor agonist on T-cells may be postulated. In conclusion, age-related control groups and determination of the B/T ratio are necessary for interpretation of beta-adrenoceptor changes in bronchial asthma.

Effects of dietary poly-unsaturated fatty acids on tracheal histaminergic and cholinergic responsiveness in experimental models of bronchial hypersensitivity and hyperreactivity

Respiratory histaminergic and cholinergic receptor function was investigated in isolated tracheal spirals of guinea pigs receiving different diets. Comparison was made between saline treated (controls) and Haemophilus influenzae treated animals in non sensitized conditions, the latter being a model for bronchial hyperreactivity, and in sensitized conditions, being a model for allergen induced bronchial hypersensitivity. The different semi-synthetic diets (35 energy% fat), varying in linoleic acid content (5.85, 11.25 and 22.05 en% fat) and one diet with low linoleic acid (3.55 en%) in which linolenic acid was added additionally (5.30 en%), exerted profound effects on tracheal reactivity to histamine. In sensitized animals the maximal induced histamine contraction was significantly diminished in the dietary group receiving 5.85 en% linoleic acid as compared with the other dietary groups (35% decrease in the H. influenzae-treated, 20-30% decrease in saline treated animals). Results in non-sensitized animals were similar, though less pronounced. No effect on food intake or growth of the animals could be demonstrated during the six week experimental periods. The carbachol induced contraction of the tracheal spirals of sensitized animals receiving low linoleic acid was also significantly decreased as compared to the other dietary groups (30% for saline treated and 20-30% for H. influenzae-treated animals). No difference in carbachol responsiveness could be detected between the different dietary groups under non-sensitized conditions. The results are discussed in view of the current concepts for bronchial hyperreactivity, especially in relation to eicosanoid involvement.

Phagocytosis and metabolism of alveolar macrophages of guinea pigs treated with Haemophilus influenzae

Previously we showed that guinea pig alveolar macrophages (AMs) incubated with serum obtained from Haemophilus influenzae-treated animals had detrimental effects on airway smooth muscle beta-adrenergic receptor function. In the present study the influence of H. influenzae treatment on several functions of guinea pig AMs was examined. Sera obtained from animals 4 days after intraperitoneal administration of H. influenzae or from control guinea pigs possessed similar opsonic capacities. No effects of these sera on hydrogen peroxide release by AMs were observed as compared to the basal hydrogen peroxide release of AMs. Interestingly, stimulation of AMs with serum from control animals resulted in a diminished cyclo-oxygenase product formation, which was potentiated after incubating AMs with serum from H. influenzae-treated guinea pigs. No differences in phagocytic activity of AMs isolated from control or H. influenzae-treated animals were observed. When AMs were incubated with phorbol myristate acetate or zymosan, the cells produced superoxide anion and released hydrogen peroxide. However, the amounts of superoxide and hydrogen peroxide released did not differ between AMs isolated from control or H. influenzae-treated animals.

Haemophilus influenzae induces a potentiated increase in guinea-pig pulmonary resistance to histamine

The human respiratory pathogen Haemophilus influenzae (H.i.) induced bronchial hyperreactivity to histamine (1.0-8.0 micrograms/100 g b.w. i.v.) in vivo in anaesthetized spontaneously breathing guinea-pigs. This hyperreactivity was caused by a potentiated increase in pulmonary resistance. Decreases in dynamic compliance did not differ. Atropine prevented the potentiation at 1.0 and 2.0 micrograms histamine/100 g b.w. These results show that H.i. induces bronchial hyperreactivity in vivo which is mediated by direct and reflex effects of histamine in the central airways.

Bronchial hyperreactivity to histamine induced by Haemophilus influenzae vaccination

Bronchial hyperreactivity to histamine 4 days following vaccination with the human respiratory pathogen Haemophilus influenzae was tested in two in vivo and one in vitro models. Conscious vaccinated guinea pigs exposed to aerosolized histamine became asphyxial significantly faster than saline-treated controls. Also the bronchoconstriction in anaesthetized guinea pigs as a result of i.v. histamine was significantly potentiated in the H. influenzae pretreated group. Isoprenaline (30 micrograms/kg) partially inhibited the bronchoconstriction. The difference in histamine sensitivity between the two groups however remained. Protection against bronchoconstriction by atropine on the other hand was significantly enhanced in the vaccinated animals. This suggests a hyperreactivity of the parasympathetic, cholinergic pathways as a result of H. influenzae vaccination.

Anterior hypothalamic lesions prevent the endotoxin-induced reduction of beta-adrenoceptor number in guinea pig lung

Bacterial endotoxin (E. coli O111:B4) induces, 4 days after intraperitoneal injection, a 30% reduction of guinea pig lung beta-adrenoceptor number (Bmax). No change in affinity (Kd) for the receptors occurred. Bilateral electrolytic lesions centered in the anterior hypothalamic nucleus prevent this reduction in Bmax and even reverse the reduction into a small increase in beta-adrenoceptor number. Since it is known from the literature data that anterior hypothalamic lesions as well as beta-adrenoceptor stimulants have an inhibitory influence on the immune system, the mechanism by which these lesions inhibit the reduction of beta-adrenoceptor sites after bacterial endotoxin and influence immune functions, may be related.

Haemophilus influenzae and the beta-adrenergic system: a review

Haemophilus influenzae is a bacterium that often can be isolated from the deeper respiratory airways of patients with chronic asthmatic bronchitis. In the present study the effects of H. influenzae vaccination on guinea pig pulmonary beta-adrenoceptor number and function (in vitro and in vivo) have been evaluated. Functioning of beta-adrenoceptors is determined by measuring the beta-mimetic effect of isoprenaline on the inhibition of anaphylactic mediator release and isolated tracheal strip relaxation. The number of beta-adrenoceptor binding sites was measured by means of a 3H-dihydroalprenolol binding assay. Also the mechanism of action underlying the changes in beta-adrenoceptor functioning was evaluated. Furthermore, it was established that the effect on the beta-adrenoceptor system was not specific for H. influenzae and that other respiratory pathogens were also biologically active in this respect.

Beta-adrenoceptor desensitization in rat lung: functional and biochemical aspects

Rat lung parenchymal strips were used to study beta-adrenoceptor desensitization from both a functional and a biochemical point of view. Prolonged "in vitro' exposure of rat lung to the beta-agonist isoproterenol (10(-6) M for 20 min) markedly reduced the antagonistic activity of isoproterenol on carbachol-induced contractions. The loss of responsiveness to isoproterenol was associated with a 33% decrease of the beta-receptor number with concomitant reduction of isoproterenol-stimulated adenylate cyclase activity, whereas the enzyme response to NaF was identical in control and in desensitized rat lung. On the basis of these results obtained by comparing the functional and biochemical aspects of the desensitization process, we suggest that the marked reduction of pharmacological activity of isoproterenol after desensitization was primarily due to the decrease in the number of binding sites. The possible molecular mechanisms underlying desensitization are also discussed.

Antigen sensitization does not alter response of guinea-pig lung strips to noradrenaline

Guinea-pigs were sensitized to ovalbumin by an intraperitoneal injection, followed 3 weeks later by daily aerosol exposure for 4 weeks. Noradrenaline-induced contractions of peripheral lung strips from sensitized and unsensitized guinea-pigs were compared. There were no differences in sensitized or unsensitized strips with respect to maximal tension generated, concentration of noradrenaline for threshold or maximal responses or EC50. These results suggest that any changes in the population of alpha-adrenoceptors consequent upon immunological sensitization did not influence contractile responses to noradrenaline.

Bacterial cell wall components decrease the number of guinea-pig lung beta-adrenoceptors

Infections of the deeper respiratory airways can contribute to the progression of chronic asthmatic bronchitis. In the present report a number of microorganisms affecting the number of beta-adrenoceptors in guinea-pig lung homogenates are described. Haemophilus influenzae, Streptococcus pneumoniae, Bordetella pertussis and Escherichia coli O111B4 induced a significant decrease of the number of beta-adrenoceptors (by approximately 20%). Staphylococcus aureus, influenza A virus and Escherichia coli J5 were not active. These data point to a common factor shared by gram-negative bacilli; i.e. endotoxin. Purified endotoxin of E. coli O111B4 also decreased the number of beta-adrenoceptors, while E. coli J5-LPS did not. This suggests that neutral polysaccharides of bacterial cell walls, especially those in the 'O'-antigenic side chain of gram-negative endotoxins may be responsible for the decrease of beta-adrenoceptor number and therefore contribute to the pathogenesis of chronic asthmatic bronchitis. Intact endotoxin seems to be necessary since neither the isolated lipid nor the polysaccharide part of E. coli O111B4 LPS affected the number of beta-adrenoceptors in the lung.

Involvement of catecholamines in Haemophilus influenzae induced decrease of beta-adrenoceptor function

The deeper airways of patients with asthmatic bronchitis are often infected with Haemophilus influenzae. Vaccination of guinea pigs with H. influenzae resulted in a significant impairment of the isoproterenol induced relaxation of isolated tracheal spirals by approximately 50% 4 days following vaccination. In the present study we further investigated the effects of some drugs affecting catecholamine release on the H. influenzae induced functional desensitization of tracheal spirals. Benserazide, an inhibitor of dopa-decarboxylase, completely prevented the reduction in isoproterenol-induced relaxation after H. influenzae vaccination, while no effect on relaxation of tracheal spirals from control animals was detected. On the other hand, inhibiting the re-uptake of catecholamines with desipramine did not influence the relaxation in the H. influenzae vaccinated tracheal spirals. Treatment of control animals with desipramine however resulted in a decreased relaxation of the isolated spirals by 40%. One day following vaccination with H. influenzae the level of norepinephrine in lung tissue was significantly elevated by 71%, and in plasma by 77%, while after 4 days no significant effects were observed. The spontaneous release of norepinephrine, epinephrine and dopamine of tracheal incubates was increased at days 1 and 4 following vaccination. The release of catecholamines from minced lung incubates of H. influenzae pretreated guinea pigs did not differ from that of controls. On the basis of these results it may be suggested that catecholamine metabolism is changed in lungs from H. influenzae vaccinated animals. Catecholamines, accordingly may play a role in the desensitization of beta-adrenoceptors by H. influenzae.