The effect of phentolamine on adenylate cyclase and on isoproterenol stimulation in leukocytes from asthmatic and nonasthmatic subjects

Adrenoceptor responsiveness in bronchial asthma: effect of isoprenaline inhalation on plasma cyclic 3',5'-AMP levels

The effect of isoprenaline inhalation on plasma levels of cyclic AMP has been studied in a group of normal subjects and compared to a group of asthmatics. The normal subjects had a prompt rise in their plasma cyclic AMP level, and when compared to the asthmatic group, had a significantly greater percentage rise in plasma cyclic AMP from the basal levels. The markedly attenuated response to isoprenaline inhalation in the asthmatic group is consistent with the concept that asthmatics have a relative impairment of beta-adrenoceptor function. These results support the in vitro studies demonstrating that lymphocytes from asthmatic subjects incubated with isoprenaline produce less cyclic AMP than those from normal subjects.

Alpha-adrenoceptor blocking drugs in asthma

The effect of alpha-adrenoceptor blocking drug, thymoxamine alone and in combination with isoprenaline, was studied on the specific airways conductance (SGaw) in ten patients with extrinsic asthma. Thymoxamine when given together with isoprenaline produced significantly greater increase in SGaw as compared to improvement achieved with isoprenaline alone. It is suggested that the potentiation of isoprenaline induced bronchodilatation by thymoxamine is mediated by increased cyclic AMP formation in the bronchial smooth muscle.

Beta adrenergic receptor function in depression and the effect of antidepressant drugs

It has been suggested that alterations of monoamine receptor sensitivity in the central nervous system may be associated with some forms of affective illness. It has been observed by several investigators that chronic treatment with antidepressant drugs causes down regulation of NE receptor coupled adenylate cyclase and beta adrenergic receptor binding in rat brain. This observation has led to the suggestion that the therapeutic effects of antidepressant drugs may be related to the changes in the responsivity of beta adrenergic receptors. In order to examine if depressive illness may be associated with altered beta adrenergic function, we studied adenylate cyclase and its responsiveness to norepinephrine and isoproterenol in the leukocytes obtained from patients with psychiatric illness and normal controls as an index of beta adrenergic receptor function. We also studied the effects of antidepressant drugs, in vitro, on isoproterenol sensitive leukocyte adenylate cyclase. We observed that norepinephrine and isoproterenol sensitive leukocyte adenylate cyclase in depressed patients are significantly decreased as compared to normal controls. Our results appear to have been replicated by another group of investigators. We also observed that certain antidepressant drugs potentiate isoproterenol stimulated accumulation of cyclic AMP in human leukocytes. This potentiation was most pronounced in the case of iprindole. These results thus indicated a decreased beta adrenergic receptor function in patients with depressive illness. Whether or not such decreased receptor function is associated with depressive illness or is a manifestation of some other changes unrelated to the illness is not clear. Our results also indicate that some antidepressant drugs may enhance adrenergic transmission by potentiating the effects of neurotransmitters on beta adrenergic receptors.

Virus associated immune and pharmacologic mechanisms in disorders of respiratory and cutaneous atopy

Anaphylaxis represents non-atopic immediate hypersensitivity, whereas manifestations of atopic immediate hypersensitivity include bronchial asthma, hay fever, allergic rhinitis, chronic urticaria, and atopic dermatitis. In spite similar antigen exposure, only a minority of the population shown some form of atopic disease. Atopic disease with its spontaneous pattern of familial occurrence cannot be induced at will.

The exact pathogenesis of atopy is yet to be elucidated. Two theories prevail: 1) atopy is a primary disorder of the immune system with sequelae in the various effector tissues; and 2) a concept of atopy as a primary autonomic imbalance, essentially beta adrenergic in character, with sequelae in effector cells, including those engaged in the production of antibodies. The autonomic imbalance is perceived as caused not by some disorder of the autonomic nervous system itself but by a defector functioning of its effector cells. These two concepts are not mutually exclusive. The IgE antibody, which mediates allergic reactions, is essentially identical with atopic reagin in various animal species.

The beta adrenergic theory regards atopic disorders (i.e., perennial and seasonal allergic rhinitis, bronchial asthma, and atopic dermatitis) not as immunologic diseases but as unique patterns of altered reactivities to a broad spectrum of immunologic, psychic, infectious, chemical and physical stimuli. The antigen-antibody interaction is given the same role as that of a broad category of nonspecific stimuli that function only to trigger the same defective homeostatic mechanism in the various effector cells involved in immediate hypersensitivities. Current evidence favors the possibility that there are inherited and/or acquired multiple abnormalities in the receptor—adenylate cyclase—cyclic AMP system of all effector cells that are critical in the organization of immune reactivities.

Atopic abnormality may be 1) acquired by functional receptor regulatory shifts caused by hormonal changes, infection (viral, bacterial, etc), allergic tissue injury or other event; 2) genetically determined; or 3) caused by autoimmune disease. One, two or all three of these effector mechanisms may be operative in a particular disease.

There is an important relationship between asthma and viral respiratory infection. A history of childhood viral respiratory illness is a risk factor for the development of chronic obstructive airway syndromes in later life. Asthmatic attacks occurred only when the infection produced fever, malaise, cough or coryza. The dominant role of fever in these episodes immediately suggests the profound involvement of adrenergic effector mechanisms. The presence of autoantibodies to beta-adrenoceptors in patients correlated well with a reduced beta—and an increased alpha-adrenergic responsiveness. Virus infections can elicit autoantibody formation.

In patients with atopic dermatitis an increased susceptibility and abnormal host response to viral infections in general. Defective cytotoxic T cells, abnormally functioning macrophages and natural killer cells, a reduced production of IFNα in children, and of IFNγ in atopic patients with food allergy has recently been demonstrated. Lymphocytic cyclic AMP-phosphodiesterase, that destroys cyclic AMP, is increased in atopic dermatitis and in allergic respiratory disease of adults, and this increased activity correlated closely with histamine release from basophils. Peripheral blood leukocytes and lymphocytes in atopic dermatitis have frequently demonstrated impaired beta adrenergic reactivity.

Allergic tissue injury may be initiated by antigen-specific IgE antibodies that combine with Fcε receptors on various cell types and trigger mediator release upon encounter with the antigen. Various noxious agents that are capable of triggering asthma are capable of releasing inflammatory mediators from the same target cells. Accounting only for those pharmacologic mediators where the cell-type has been identified, the spectrum of mediator-storing, synthesizing, or transporting cells includes neutrophil leucocytes, basophilic leucocytes eosinophilic leucocytes; mast cells, “chromaffin-positive” mast cells, enterochromaffin cells, chromaffin cells; platelets, neurosecretory cells and nerve cells that potentially produce all amine-mediators as well as prostaglandins and kinins.

Effect of long-term corticosteroid therapy on monocyte chemotaxis in man

The influence of prednisolone on monocyte chemotactic activity in vitro at prednisolone concentrations comparable with those achieved in man following oral dosage has been investigated. Chemotactic activity of monocytes from each of sixteen normal subjects was suppressed by concentrations of prednisolone as low as 25 ng/ml (suppression of chemotaxis, 20%). Maximal suppression occurred at 100 ng/ml (suppression of chemotaxis, 48%) and no significant increase in suppression was produced by increasing the concentration to 200 ng/ml (suppression of chemotaxis, 53%). In contrast, monocytes isolated from ten patients receiving corticosteroid therapy showed no significant suppression of chemotactic activity when exposed to these concentrations of prednisolone, even though they exhibited a normal ability to respond to a chemotactic stimulus. The lack of suppression of monocyte chemotaxis in patients receiving corticosteroid therapy is unexplained, but may represent a change in the circulating monocyte or lymphocyte populations.

Ageing, late-onset asthma and the beta-adrenoceptor

Late-onset asthma in old age is a common clinical problem. There are similarities between receptor and post-receptor beta 2-adrenoceptor abnormalities reported in young asthmatics and in elderly normal subjects. Recent evidence lends some support to the idea of the 'aging' beta 2-adrenoceptor as a contributory factor in the development of late-onset asthma, although questions of the validity of the peripheral mononuclear cell model and of receptor tachyphylaxis to intrinsic and extrinsic beta-adrenoceptor agonists remain unresolved. Further work should focus on in vivo studies of airway receptor function and on beta 2-adrenoceptor-mediated pathways other than smooth muscle-related bronchoconstriction.

Decreased mononuclear cell beta-adrenergic receptors in bronchial asthma: parallel studies of lymphocyte and granulocyte desensitization

To assess the interaction of bronchial asthma and beta-agonist drugs, beta-adrenergic receptors were measured in human mixed leukocyte, mononuclear cell, and polymorphonuclear leukocyte cell membranes simultaneously. The densities and affinities of beta-adrenergic receptors were determined, by Scatchard analysis, with a potent beta-antagonist 125I-hydroxybenzylpindolol (125I-HYP) and compared among 12 nonatopic controls (group I), 13 mild asthmatics not taking drugs (group II), and eight asthmatics receiving long-term beta-agonist therapy (group III). Our findings were as follows. (1) Asthmatics not taking drugs (group II) have significantly lower mean mononuclear leukocyte beta-adrenergic receptor density (p less than 0.05) but no significant difference in mean polymorphonuclear leukocyte beta-adrenergic receptor density than the control group. (2) Asthmatics receiving long-term beta-agonist treatment (group III) had significantly lower mean beta-adrenergic receptor density in all three cell fractions (p less than 0.05). (3) Group I and II females had a higher mean beta-adrenergic receptor density in mixed leukocyte and polymorphonuclear cell fractions than males (p less than 0.05). (4) Terbutaline sulfate clearly caused desensitization of beta-adrenergic receptors in human leukocyte membranes in vivo. These results show that beta-adrenergic receptor density is influenced by cell type, beta-adrenergic agonist administration, and sex; they also show that bronchial asthma itself is associated with lower lymphocyte beta-receptor density.

Adrenoceptors: molecular nature and role in atopic diseases

Since Szentivanyi proposed the idea that asthma and other atopic diseases are due to a beta adrenergic defect there has been much interest in the role of the adrenergic receptors in allergy. The radioactive ligand binding techniques developed within the last few years have greatly increased our knowledge concerning the molecular nature of the adrenoceptors and the events following receptor stimulation. The adrenoceptors have shown to be very dynamic structures. Their number and affinity may be altered due to various physiological and pharmacological stimuli. Their role in the pathogenesis of atopic diseases has not been definitely settled, but there seem to be a true beta adrenergic hyporesponsiveness and alpha hyperresponsiveness in asthma. This article briefly describes the radioligand binding technique and summarizes our present knowledge of the nature of the alpha and beta adrenoceptors and their possible role in atopic diseases.

Adrenergic responses of asthmatic and normal subjects to submaximal and maximal work levels

The response of the adrenergic system of asthmatic subjects to exercise and the role of plasma catecholamines in exercise-induced asthma were investigated. Plasma levels of norepinephrine and epinephrine were measured at rest, during and after exercise in 7 asthmatic and 9 matched normal subjects. Exercise-induced bronchospasm occurred in all asthmatic subjects following exercise, while no significant change was observed in the normal subjects. The results showed that plasma levels of norepinephrine and epinephrine at rest and changes that occcurred during and after exercise were similar in both normal and asthmatic subjects. These data suggest that the adrenergic response of asthmatics to the same relative exercise stress as reflected in plasma catecholamine levels does not differ from that of normal subjects. It appears that changes in the circulating catecholamines do not play a significant role in the pathogenesis of exercised-induced asthma.

Comparison of cyclic adenosine monophosphate response of lymphocytes in normal and asthmatic subjects to norepinephrine and salbutamol

Reduced response of beta adrenergic receptors, especially beta-2 receptors, has been suggested as a contributing factor in the etiology of asthma. Cyclic adenosine monophosphate (AMP) production in lymphocytes after exposure to 10(-3) M salbutamol, predominantly a beta-2 receptor stimulant, was significantly less in asthmatic subjects than in normal subjects, while there was no significant difference in cyclic AMP response to 10(-3) M norepinephrine, predominantly a beta-1 receptor stimulant. Both drugs evoked the maximum response at 10(-3) M. The cyclic AMP response to salbutamol of 5 asthmatic subjects being treated with steroids was diminished significantly compared with that of 7 patients not treated with steroids; however, the response to norepinephrine was similar in both groups. The degree of the abnormality in the beta-2 receptor response seems to be related to the severity of the asthma.

Development of "resistance" in beta-adrenergic receptors of asthmatic patients

Complete in vitro dose-response curves for (see article) -isoproterenol (isoprenaline) sulfate showed no functional defects in bronchial muscular beta-adrenergic receptors in three patients with chronic intrinsic asthma, as compared to 60 patients with normal pulmonary function. Complete in vivo dose-response curves for intravenously infused isoproterenol were obtained in eight outpatients with chronic intrinsic asthma to register effects on bronchial muscle (forced expiratory volume in one second), heart rate, blood pressure, and skeletal muscular tremor. The isoproterenol test was performed before and also during oral treatment with a long-acting selective beta-adrenergic stimulator (terbutaline sulfate, 5 mg three times daily). The study was performed over 12 months to avoid seasonal variation in basal levels of obstruction and was concluded by adding inhaled terbutaline (two inhalations four times daily) to oral therapy. No "resistance" developed in bronchial beta-adrenergic receptors during this prolonged treatment. Inhalation therapy in addition to oral therapy improved bronchodilation without causing resistance. Even six inhalations given four times daily (four- to five-hour intervals) did not cause any bronchial resistance; however, resistance developed in skeletal muscles with decreased tremor and in cardiac beta-adrenergic receptors.

Effect of alpha receptor blocking drug, thymoxamine, on allergen induced bronchoconstriction in extrinsic asthma

In ten patients with extrinsic bronchial asthma, allergen provoked bronchospasm was significantly inhibited by the alpha receptor blocking drug thymoxamine given intravenously. In two of these patients thymoxamine by inhalation also effectively inhibited allergen induced bronchoconstriction. It is suggested that thymoxamine may be acting either by increasing intracellular levels of cyclic AMP and thus inhibiting mediator release following allergen challenge or by modifying the airways response to these mediators by altering the bronchomotor tone. The variable responses recorded after allergen challenge in presence of alpha blockade with thymoxamine suggests that the dominant effect is on the bronchomotor tone rather than the mediator release.

Increased adenosine triphosphatase in leukocytes of asthmatic children

Adenosine triphosphatase (ATPase) activities were compared in leukocytes of asthmatic and nonasthmatic children. Both Mg(2+)- and Ca(2+)-dependent ATPase activities were significantly elevated in two membrane fractions (59 to 66%) and in a superntant fraction (68 to 72%) prepared from sonicated leukocytes of asthmatic subjects. Intact cell surface or ecto ATPase was also elevated (67 to 76%) in asthmatic leukocytes. Alternate day glucocorticosteroid therapy was associated with leukocyte ATPase activities intermediate between those for asthmatics not receiving steroids and for nonasthmatic control subjects. Incubation of normal leukocytes with 10(-8) M hydrocortisone or leukocyte membranes with 10(-4)-10(-3) M hydrocortisone in vitro also resulted in decreased ATPase activities. The elevated leukocyte ATPase activities appear to relate to the adrenergic imbalance in asthma previously characterized by reduced beta adrenergic responsiveness of adenylate cyclase and suggest the possibility of more than one enzymatic abnormality intrinsic to the asthmatic condition.