The beta-adrenoceptor of the human lymphocyte and human lung parenchyma

Ageing and the Autonomic Nervous System

The vertebrate nervous system is divided into central (CNS) and peripheral (PNS) components. In turn, the PNS is divided into the autonomic (ANS) and enteric (ENS) nervous systems. Ageing implicates time-related changes to anatomy and physiology in reducing organismal fitness. In the case of the CNS, there exists substantial experimental evidence of the effects of age on individual neuronal and glial function. Although many such changes have yet to be experimentally observed in the PNS, there is considerable evidence of the role of ageing in the decline of ANS function over time. As such, this chapter will argue that the ANS constitutes a paradigm for the physiological consequences of ageing, as well as for their clinical implications.

Autonomic regulation of T-lymphocytes: Implications in cardiovascular disease

The nervous and immune systems both serve as essential assessors and regulators of physiological function. Recently, there has been a great interest in how the nervous and immune systems interact to modulate both physiological and pathological states. In particular, the autonomic nervous system has a direct line of communication with immune cells anatomically, and moreover, immune cells possess receptors for autonomic neurotransmitters. This circumstantial evidence is suggestive of a functional interplay between the two systems, and extensive research over the past few decades has demonstrated neurotransmitters such as the catecholamines (i.e. dopamine, norepinephrine, and epinephrine) and acetylcholine have potent immunomodulating properties. Furthermore, immune cells, particularly T-lymphocytes, have now been found to express the cellular machinery for both the synthesis and degradation of neurotransmitters, which suggests the ability for both autocrine and paracrine signaling from these cells independent of the nervous system. The details underlying the functional interplay of this complex network of neuroimmune communication are still unclear, but this crosstalk is suggestive of significant implications on the pathogenesis of a number of autonomic-dysregulated and inflammation-mediated diseases. In particular, it is widely accepted that numerous forms of cardiovascular diseases possess imbalanced autonomic tone as well as altered T-lymphocyte function, but a paucity of literature exists discussing the direct role of neurotransmitters in shaping the inflammatory microenvironment during the progression or therapeutic management of these diseases. This review seeks to provide a fundamental framework for this autonomic neuroimmune interaction within T-lymphocytes, as well as the implications this may have in cardiovascular diseases.

Autonomic nervous system and immune system interactions

The present review assesses the current state of literature defining integrative autonomic-immune physiological processing, focusing on studies that have employed electrophysiological, pharmacological, molecular biological, and central nervous system experimental approaches. Central autonomic neural networks are informed of peripheral immune status via numerous communicating pathways, including neural and non-neural. Cytokines and other immune factors affect the level of activity and responsivity of discharges in sympathetic and parasympathetic nerves innervating diverse targets. Multiple levels of the neuraxis contribute to cytokine-induced changes in efferent parasympathetic and sympathetic nerve outflows, leading to modulation of peripheral immune responses. The functionality of local sympathoimmune interactions depends on the microenvironment created by diverse signaling mechanisms involving integration between sympathetic nervous system neurotransmitters and neuromodulators; specific adrenergic receptors; and the presence or absence of immune cells, cytokines, and bacteria. Functional mechanisms contributing to the cholinergic anti-inflammatory pathway likely involve novel cholinergic-adrenergic interactions at peripheral sites, including autonomic ganglion and lymphoid targets. Immune cells express adrenergic and nicotinic receptors. Neurotransmitters released by sympathetic and parasympathetic nerve endings bind to their respective receptors located on the surface of immune cells and initiate immune-modulatory responses. Both sympathetic and parasympathetic arms of the autonomic nervous system are instrumental in orchestrating neuroimmune processes, although additional studies are required to understand dynamic and complex adrenergic-cholinergic interactions. Further understanding of regulatory mechanisms linking the sympathetic nervous, parasympathetic nervous, and immune systems is critical for understanding relationships between chronic disease development and immune-associated changes in autonomic nervous system function.

Adrenergic regulation of IgE involves modulation of CD23 and ADAM10 expression on exosomes

Soluble CD23 plays a role in the positive regulation of an IgE response. Engagement of the β2 adrenergic receptor (β2AR) on a B cell is known to enhance the level of both soluble CD23 and IgE, although the mechanism by which this occurs is not completely understood. In this study, we report that, in comparison with a CD40 ligand/IL-4-primed murine B cell alone, β2AR engagement on a primed B cell increased gene expression of a disintegrin and metalloproteinase (ADAM)10, which is the primary sheddase of CD23, as well as protein expression of both CD23 and ADAM10, in a protein kinase A- and p38 MAPK-dependent manner, and promoted the localization of these proteins to exosomes as early as 2 d after priming, as determined by both Western blot and flow cytometry and confirmed by electron microscopy. In comparison with isolated exosomes released from primed B cells alone, the transfer of exosomes released from β2AR agonist-exposed primed B cells to cultures of recipient primed B cells resulted in an increase in the level of IgE produced per cell, without affecting the number of cells producing IgE, as determined by ELISPOT. These effects still occurred when a β2AR antagonist was added along with the transfer to block residual agonist, and they failed to occur when exosomes were isolated from β2AR-deficient B cells. These findings suggest that the mechanism responsible for mediating the β2AR-induced increase in IgE involves a shuttling of the β2AR-induced increase in CD23 and ADAM10 proteins to exosomes that subsequently mediate an increase in IgE.

Sympathetic modulation of immunity: relevance to disease

Optimal host defense against pathogens requires cross-talk between the nervous and immune systems. This paper reviews sympathetic-immune interaction, one major communication pathway, and its importance for health and disease. Sympathetic innervation of primary and secondary immune organs is described, as well as evidence for neurotransmission with cells of the immune system as targets. Most research thus far has focused on neural-immune modulation in secondary lymphoid organs, has revealed complex sympathetic modulation resulting in both potentiation and inhibition of immune functions. SNS-immune interaction may enhance immune readiness during disease- or injury-induced 'fight' responses. Research also indicate that dysregulation of the SNS can significantly affect the progression of immune-mediated diseases. However, a better understanding of neural-immune interactions is needed to develop strategies for treatment of immune-mediated diseases that are designed to return homeostasis and restore normal functioning neural-immune networks.

Mechanisms of conditioned immunomodulation

This article presents some recent work from our laboratory indicating that multiple physiological systems play a role in conditioned immunomodulation. The first study shows that naltrexone, but not N-methylnaltrexone, blocks the suppressive effects of an aversive conditioned stimulus on Con-A-induced proliferation and natural killer cell activity of splenic lymphocytes. This finding indicates that central opioid activity is involved in the conditioned effects. The second study shows that the beta-adrenergic antagonists atenolol and ICI-118,551 block of the suppressive effects of an aversive conditioned stimulus on Con-A-induced proliferation, but have no effect on natural killer cell activity. This result indicates the involvement of the adrenergic system in a subset of the conditioned effects. Collectively, these experiments provide evidence that both the opioid system and the sympathetic nervous system are involved in conditioned immunomodulatory changes elicited by an aversive conditioned stimulus.

The role of adrenoceptor-mediated signals in the modulation of lymphocyte function

Adrenoceptors are heterotrimeric glycoproteins that bind specific endogenous ligands, such as the sympathetic neurotransmitter norepinephrine and the neurohormone epinephrine. Ligand binding to an adrenoceptor expressed on the cell surface initiates a cascade of biochemical and molecular responses inside the cell that lead to a change in cellular activity. Initially, the stimulation of an adrenoceptor directly activates G proteins that stimulate enzymes to induce the production of second messengers. The cascade continues as the second messengers activate serine/threonine protein kinases, resulting in either an inhibition or enhancement of cellular activity. The resulting changes in cellular activity are mediated by changes in gene expression that are induced by the phosphorylation of specific transcription factors. Adrenoceptor subtypes are expressed by both T and B lymphocytes. The aim of this review is to summarize and discuss the results from the many studies that have examined the role of adrenoceptor-mediated intracellular signals in the modulation of lymphocyte function. Another aim of this review is to discuss how these studies have advanced our understanding of the mechanisms by which the sympathetic nervous system transmits information to both T and B lymphocytes to maintain immune homeostasis.

Decreased beta 2-adrenoceptor density and decreased isoproterenol induced c-AMP increase in juvenile type I diabetes mellitus: an additional cause of severe hypoglycaemia in childhood diabetes?

Little is known about the receptor and post receptor mechanisms of sympathoadrenal signal transmission in type I diabetes mellitus. Therefore, we examined the maximum binding of granulocyte beta 2-adrenoceptors and the in vitro c-AMP accumulation in lymphocytes of 24 children and adolescents with diabetes mellitus and 14 similarly aged healthy subjects. The number of high affinity beta 2-adrenoceptors on granulocytes correlated significantly with unstimulated (r = 0.6, P < 0.004) and with isoproterenol stimulated c-AMP values in lymphocytes (r = 0.68, P < 0.0007) showing the proportional changes of beta 2-adrenoceptors and c-AMP in two different cells. The number of beta 2-adrenoceptors on granulocytes was significantly reduced in diabetic as compared to healthy children (median 1397, range 599-3405 vs. 2205, 825-3200 beta 2-adrenoceptors per granulocyte, P = 0.014). Moreover, the percentage in vitro stimulation of c-AMP by isoproterenol in lymphocytes was significantly reduced in diabetic children as compared to healthy individuals (120%, 39%-278% vs. 225%, 66%-500%, P = 0.012). These results indicate a decreased sympathoadrenergic signal transmission in peripheral blood cells as a model for the liver probably contributing to severe hypoglycaemia in diabetic children.

Evidence for the involvement of β-adrenergic receptors in conditioned immunomodulation

This study investigates the role of beta-adrenergic receptors in the immunomodulatory effects of a conditioned aversive stimulus (CS). A CS is an environmental event that is not inherently aversive, but acquires aversive properties through pairings with a stimulus such as electric shock. This study evaluated the effects of administration of the beta 1-receptor selective antagonist atenolol, and the beta 2-receptor antagonist ICI 118,551 on conditioned immune alterations. Administration of either antagonist prior to presentation of the CS resulted in a dose-dependent attenuation of the CS-induced suppression of splenic T-cell proliferative response to concanavalin A, phytohemagglutinin, and the combination of ionomycin/phorbol-myristate-acetate. Furthermore, both antagonists dose-dependently attenuated the CS-induced suppression of gamma-interferon production by concanavalin-A (ConA)-stimulated splenocytes. In contrast, neither antagonist significantly attenuated the CS-induced suppression of the B-cell mitogenic response to LPS, interleukin-2 production, natural killer cell activity, or mitogenic responsiveness of blood lymphocytes. Thus it is likely that multiple mechanisms are involved in CS-induced immune alterations and these results clearly implicate beta 1 and beta 2-adrenergic receptors in a subset of immunomodulatory effects.

The inhibitory effect of nebulized albuterol on the early and late asthmatic reactions and increase in airway responsiveness provoked by inhaled allergen in asthma

It is widely held that inhaled beta 2-adrenoceptor agonists inhibit the early asthmatic response (EAR) but not the late response (LAR) or attendant increase in bronchial responsiveness. In this study of 10 atopic asthmatic subjects, we have investigated the effects of a high dose of nebulized albuterol (2.5 mg) on the allergen-provoked EAR, LAR, and increase in histamine responsiveness. In a randomized blinded fashion, study subjects inhaled the following combinations: albuterol followed 10 min later by allergen, placebo followed by allergen, albuterol followed by saline (albuterol, placebo, and control study periods, respectively). Airway caliber was measured as FEV1 and followed at regular intervals for 7.5 h postallergen. Bronchial responsiveness to histamine was measured and recorded as the PC20 value before and at 1.5, 3.5, 5.5, and 7.5 h after allergen or control challenge. During the placebo study period, allergen challenge caused mean 29.6 +/- 6.4 and 24.4 +/- 6.4% falls in FEV1 at 20 min and 7.5 h, respectively (both p less than 0.05), and a progressive decrease in PC20 amounting to a geometric mean of 1.9 doubling dilutions at 7.5 h (p less than 0.05). Albuterol followed by allergen resulted in a 13.1 +/- 2.2% increase in FEV1 prior to allergen followed by abolition of the EAR and inhibition of the LAR with only a 9.2 +/- 3.5% fall in FEV1 at 7.5 h, significantly different from that of placebo at 7.5 h (p = 0.048). Similarly, PC20 histamine fell by only 0.64 doubling dilutions at 7.5 h, not significantly different from baseline values but different from placebo values (p = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Neopterin quantification in acute severe asthma

To investigate the pathogenic role of cell-mediated immunity (CMI) in acute severe asthma, 10 patients with acute asthma requiring admission to hospital had measurements of serum and urine absolute neopterin and neopterin/creatinine ratios. Serum was collected upon entry to hospital, 24 hr later and at 2 weeks; and urine at 24 hr and at 2 weeks after admission. Comparisons were made with 12 stable asthmatic patients, healthy control subjects, and six renal transplant patients undergoing transplant rejection. In contrast to the renal transplant patients who demonstrated T-lymphocyte-macrophage activation, neopterin concentrations and neopterin/creatinine ratios in both acute and stable asthmatic patients were not elevated. We have not found functional evidence that CMI participates in the pathogenesis of acute severe asthma.

Investigations of the possible glycosylation of monoamine oxidase B from pig leucocytes

Monoamine oxidase B (MAO B) from pig liver has been reported to be a sialoglycoprotein. However, when that enzyme from pig lymphocytes and granulocytes was separated by polyacrylamide gel electrophoresis after labelling with the specific irreversible inhibitor [3H]pargyline, staining with 1-ethyl-2-[3-(1-ethyl-naphtho [1,2d] thiazolin-2-ylidene)-2-methylpropenyl] naphtho [1,2d] thiazolium bromide ("Stains-all") failed to detect the presence of sialic acid residues. Treatment of the enzyme in disrupted lymphocytes and granulocytes, or in mitochondrial fractions prepared from them, with neuraminidase resulted in a decrease in MAO activity. However, after the enzyme was rendered soluble by treatment with octylglucoside, treatment with neuraminidase had no effect on the activity. These results indicate that sialic acid residues are not an intrinsic component of MAO B, although associated material containing such groups appears to affect the activity of the membrane-bound enzyme. The activities of membrane-bound preparations of MAO B from pig lymphocytes and granulocytes were unaffected by treatment with trypsin or beta-chymotrypsin. After the preparations had been rendered soluble by treatment with octylglucoside there was a decrease in the activity on treatment with beta-chymotrypsin, but trypsin treatment had no effect. Thus solubilization resulted in residues sensitive to cleavage by the former enzyme becoming accessible to it. Tryptic and chymotryptic peptides separated from the sodium dodecyl sulphate denatured enzymes by polyacrylamide gel electrophoresis revealed no differences between MAO B prepared from lymphocytes and granulocytes.

Influence of short- and long-term inhalation of salbutamol on lung function and beta 2-adrenoceptors of mononuclear blood cells in asthmatic children

Clinical observations have shown that some asthma patients develop tachyphylaxis to beta-sympathomimetic drugs. As down-regulation of the number of beta-adrenoceptors in different human tissues after exposure to catecholamines and beta-adrenergic drugs is well known, we investigated whether a interrelation exists between beta-adrenoceptor down-regulation and clinically detectable beta-adrenergic subsensitivity during beta-sympathomimetic treatment. The following results were obtained: 1. beta 2-Sympathomimetic inhalation treatment with salbutamol in therapeutic doses led to a significant down-regulation of beta 2-adrenoceptors and consecutive cyclic adenosine monophosphate response to isoprenaline. This effect was already detectable after short-term treatment of 3-7 days in 9 asthmatic children. 2. In the long-term study over 6 months, salbutamol inhalation in 12 asthmatic children led to a significant down-regulation of beta-adrenoceptor binding sites on mononuclear blood cells (MNC) from 1539 +/- 91 to 1115 +/- 99 after 14 days, remaining in this range thereafter. 3. The mean airway resistance (Raw) of these 12 patients decreased significantly within 14 days from 8.1 +/- 0.8 to 5.7 +/- 0.5 cm H2O/l/s to remain stable throughout the 6 months of salbutamol treatment. The differences in Raw before and immediately after inhalation of 0.2 mg salbutamol (2 puffs) were unchanged during the study period. It is concluded, that long-term inhalative treatment with salbutamol over a period of 6 months does not result in refractoriness to beta-adrenergic drugs in the airways of asthmatic children, even though a significant down-regulation of beta 2-receptors on peripheral MNC occurs.

Beta 2-adrenoceptors in human lung and peripheral mononuclear leukocytes of untreated and terbutaline-treated patients

Beta 2-adrenoceptor agonists act against bronchoconstriction by stimulating beta 2-adrenoceptors in bronchial smooth muscle. However, tachyphylaxis has been argued to occur because of beta 2-adrenoceptor down-regulation following therapy with beta 2-adrenergic agents. To investigate receptor alterations, human peripheral mononuclear leukocytes are frequently used, since human lung tissue is not easily available. In order to study whether beta 2-adrenoceptors in MNL reliably reflect the conditions in the human lung tissue, we compared MNL and human lung tissue of 18 patients who had to undergo lung resection. Ten patients were untreated, and eight had bronchodilator therapy prior to therapy with terbutaline because of bronchoconstriction. Both in human lung and MNL, the beta 2-adrenoceptor subpopulation was characterized by competition experiments with the beta 1-selective antagonist CGP 207.12 A and the beta 2-selective antagonist ICI 118.551. In MNL, a significant decrease in the density of beta 2-adrenoceptors was found in treated but not in untreated patients, while the antagonist affinity of the beta 2-adrenoceptors remained unchanged. However, in lung parenchyma, which was obtained at the very same time from the same patients, no down-regulation of the total amount of beta 2-adrenoceptors could be measured. It is concluded that MNLs are a reliable model for studying properties of beta 2-adrenoceptor regulation. However, the hereby obtained results show that MNLs do not reflect the conditions of beta 2-adrenoceptors in human lung tissue. Human lung tissue is found to be less susceptible than human MNL for beta 2-adrenoceptor down-regulation by terbutaline treatment at therapeutic doses.(ABSTRACT TRUNCATED AT 250 WORDS)

The effects of theophylline on beta 2-adrenoceptors on polymorphonuclear leukocytes of asthmatic children and juveniles. Increase in receptor density and prevention of agonist-induced down-regulation

The density (Bmax) and affinity (KD) of beta 2-adrenoceptors in polymorphonuclear leukocytes (PMN) were measured in 29 children and juveniles with mild or moderate asthma and in 25 healthy control subjects using the highly specific radioligand (+/-)-125I-cyanopindolol. No significant difference in Bmax was found between asthmatic subjects without medication and the control group. The asthmatic subjects were divided into four different groups by their actual medication: no medication, adrenergics, theophylline, adrenergics plus theophylline. Analysis of variance revealed highly significant differences between these groups for Bmax (P = 0.0016) but not for KD. In asthmatics on adrenergic therapy Bmax was significantly lower (995 +/- 415) than in asthmatics without medication (1660 +/- 521; P = 0.008). In contrast, Bmax in asthmatics on theophylline therapy was significantly higher (2137 +/- 231; P = 0.009) than in the controls. Bmax was average in the group of asthmatics treated with both adrenergics and theophylline (1619 +/- 547). It is concluded that in asthmatic subjects therapy with theophylline increases the density of beta 2-adrenoceptors and partly prevents their down-regulation induced by adrenergic therapy.

Characterization of monoamine oxidase activity present in human granulocytes and lymphocytes

The characterization of monoamine oxidase (MAO) activity in lymphocytes and granulocytes was studied by using cells prepared from human blood. The specific activities of the enzyme towards beta-phenylethylamine (PEA), benzylamine (Bz), tyramine (TYR) and 5-hydroxytryptamine (5-HT) were found to be 5-times higher in lymphocytes than in granulocytes. The absence of the semicarbazide-sensitive amine oxidase (SSAO) was confirmed by the lack of effect of semicarbazide on the benzylamine oxidation. The presence of MAO-B was corroborated by the inhibition of PEA oxidation with nanomolar deprenyl concentrations and by inhibition of TYR oxidation with high clorgyline concentrations, as well as by the simple sigmoid curve obtained in both cases. These results, together with the substrate preferences, suggest that the MAO activity of human granulocytes and lymphocytes is predominantly of the B form. For each fraction the kinetic constants were determined towards PEA, TYR and Bz as substrates. The Km values were similar for both cellular samples, whereas the Vmax values were higher in lymphocytes than in granulocytes. MAO-B was titrated with [3H]pargyline in order to find out the number of active sites. The corresponding molecular concentration, Kcat values and turnover number showed the presence of related enzymes in human granulocytes and lymphocytes.

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.

Adrenoceptors and the lung: their role in health and disease

alpha- and beta-Adrenoceptors have each been divided into two subgroups (alpha 1, alpha 2, beta 1 and beta 2). The basic mechanisms underlying the adrenoceptor/effector coupling are complex and vary for the alpha-, but not for the beta-subpopulations. Adrenoceptors of the bronchi and the lung show a special pattern of distribution and response, ensuring that the airway system works as a functionary unit. Dysfunctions of adrenoceptor-mediated effects have been suggested to contribute to some important paediatric disorders such as hyaline membrane syndrome, wet lung, bronchial asthma, cystic fibrosis, and pertussis. Drugs which act on the adrenergic system influence some of these disorders directly. Further studies applying modern techniques to receptor research are needed in order to clarify the basic mechanisms involved in receptor-mediated lung disorders and the activity of drugs in lung tissue.

Beta-adrenergic receptors of lymphocytes in children with allergic respiratory diseases

The beta-adrenergic receptor binding sites on peripheral lymphocytes in children with bronchial asthma (n = 16) and seasonal allergic rhinitis (n = 8) were examined in comparison with normal controls (n = 18) by means of 124I-cyanopindolol. The number of beta-adrenergic receptors was significantly lower in the asthmatic group (858 +/- 460/lymphocyte) than in the controls (1564 +/- 983/lymphocyte). The value (1891 +/- 1502/lymphocyte in children with allergic rhinitis was slightly higher than that in healthy controls. Of the 24 patients suffering from allergic diseases of the lower or upper airways, the bronchial histamine provocation test was performed in 21; 16 gave positive results, while 5 were negative. No difference in beta-adrenergic receptor count was found between the histamine-positive and negative patients. Neither was there any correlation between the number of beta-adrenergic receptors and the high (16/24) and low (8/24) serum IgE concentrations found in allergic patients. The significant decrease in beta-adrenergic receptor count in asthmatic children lends support to Szentiványi's concept. Further qualitative and quantitative analysis of lymphocyte beta-adrenergic receptors may provide an individual approach to the treatment of bronchial asthma with beta-sympathomimetic drugs.

Effect of serum on isoproterenol-induced cyclic AMP accumulation in human lymphocytes

The effects of autologous serum on basal and isoproterenol (IPR) or prostaglandin E1 (PGE1) stimulated adenosine 3',5' cyclic monophosphate (cAMP) levels were investigated in human lymphocytes. For all blood donors, serum (25% (v/v)) lowered the basal cAMP content. In contrast, the responsiveness of the lymphocyte cAMP accumulation to (-)-IPR was increased. This effect was most clearly demonstrable in bicarbonate buffered incubation medium (40-50% increase of maximal response), but was also seen in phosphate buffered medium (10-20% increase). Serum did not alter the sensitivity of the lymphocytes to IPR. The response to PGE1, which was a considerable more effective stimulator of cAMP accumulation than IPR, was not affected in any consistent way by serum. The results indicate that serum influences the regulation of lymphocyte cAMP and that this effect may partly be exerted at the level of the beta-adrenoceptors.

Ethnic differences in human lymphocytic cyclic AMP production after isoprenaline stimulation and propranolol blockade

The stimulatory effects of isoprenaline on human lymphocytic cyclic AMP (cAMP) and blockade by propranolol were studied in vitro in healthy Black and White volunteers. Basal levels of lymphocytic cAMP were significantly higher in Blacks than in Whites. Stimulation with isoprenaline caused a dose-related increase in cAMP, which was in concentrations of 10(-9) to 10(-5)M significantly greater in Blacks than in Whites. Blockade by 10(-4)M propranolol did not affect basal cAMP levels significantly, but increases in cAMP levels were significantly smaller in both groups after 10(-9) to 10(-2)M isoprenaline, while differences between cAMP levels in Blacks and Whites were still significant at concentrations 10(-9) to 10(-3)M. The increased cAMP concentration in lymphocytes of Blacks probably reflects a higher degree of beta 2-adrenoceptor activity which could be due to either a greater number and/or greater sensitivity of lymphocytic beta 2-adrenoceptors in Blacks than in Whites.

Ethanol dependent interaction between prostaglandins and lipoxygenase products in human peripheral lymphocytes

The effect of lipoxygenase products, 12-L-HETE and 15-L-HPETE, on cyclic AMP levels in human peripheral lymphocytes was examined in the absence and in the presence of a prostaglandin of the E-type (0.6-3.0 microM) or isoprenaline (33 microM). The studies were performed either in the absence or in the presence of 6 per cent ethanol. For comparison the effect of arachidonic acid and linolenic acid were studied. In the absence of ethanol 12-L-HETE and 15-L-HPETE had no significant effect on cyclic AMP accumulation. However, in the presence of ethanol 12-L-HETE (above 1 microM) inhibited prostaglandin E1 but not isoprenaline induced cyclic AMP accumulation. 15-L-HPETE had a biphasic effect on prostaglandin E2 induced cyclic AMP accumulation. Concentrations below 1 microM stimulated, those above inhibited. Virtually complete inhibition was seen at 15 microM. The two other fatty acids inhibited both prostaglandin E2 and isoprenaline induced cyclic AMP accumulation in the presence, but not in the absence of ethanol. The results show that lipoxygense products have little or no effect on cyclic AMP accumulation in human peripheral lymphocytes unless ethanol is present. In the presence of ethanol both 12-L-HETE and 15-L-HPETE appeared to selectively affect the cyclic AMP accumulation stimulated by PGE.

Effect of exercise on isoprenaline-induced lymphocyte cAMP production in atopic asthmatics and atopic and non-atopic, non-asthmatic subjects

The effect of exercise on isoprenaline-induced cyclic adenosine monophosphate (cAMP) production was studied in peripheral-blood lymphocytes obtained from ten patients with atopic asthma, seven subjects who were atopic but did not have asthma and eight non-atopic, non-asthmatic control subjects. The asthma in the atopic subjects was mild only requiring intermittent treatment with inhaled beta adrenoceptor agonists, none of which were taken in the 48 hr prior to the study. Exercise consisted of a standardized 6-min run on a treadmill sufficient to raise the subject's pulse rate to greater than 160 bpm and respiratory function was measured before and at 5, 10, 15, 20, 30 and 60 min after the test. Blood samples were taken 5 min before and at 10 and 60 min after exercise, lymphocytes were separated by density gradient centrifugation and cAMP measured by a competitive radioimmunoassay. Exercise led to a significant decrease (27%) in the forced expiratory volume in 1 sec (FEV1) in the ten atopic asthmatic subjects but no change (less than 3%) in the non-atopic and atopic non-asthmatics. There was no significant difference in the unstimulated cAMP levels before exercise in the three groups, but stimulation with isoprenaline caused a significantly greater rise in cAMP in the non-atopic, non-asthmatic subjects when compared to both the atopic asthmatics and the atopic subjects without asthma. Exercise led to a significant elevation of cAMP in all three groups of subjects, but the same differences between the groups remained.(ABSTRACT TRUNCATED AT 250 WORDS)

Age-dependency of alpha- and beta-adrenoceptors on thrombocytes and lymphocytes of asthmatic and nonasthmatic children

Among the possible mechanisms which may cause wheezing or asthmatic episodes a genetically determined beta-adrenoceptor blockade and a hyperresponsiveness of alpha-adrenoceptors has been postulated. Evidence to support this hypothesis stems from an increased bronchial sensitivity to beta-blockers, a reduced formation of cyclic AMP in response to beta-adrenergic stimulation and enhanced alpha-adrenergic responses in asthmatic subjects. The recent development of techniques for measuring the specific, high-affinity binding of radiolabeled alpha- and beta-adrenergic antagonists made it possible to study alpha- and beta-adrenoceptors in vitro. Based upon the assumption that a change in the number and/or affinity of adrenergic receptors might be a general phenomenon, we have performed alpha- and beta-receptor binding studies on lymphocytes and platelets from wheezing infants and asthmatic children as well as of infants, children, and adults not suffering from these diseases. Using 125[I]-cyanopindolol (ICYP) and 3[H]-yohimbine (HYOH) as highly specific ligands for alpha- and beta-adrenoceptors, the following results were obtained: Lymphocytes and platelets from control subjects and asthmatics bound similar amounts of ICYP and HYOH and thus showed no differences either in the number or the affinity of alpha- and beta-adrenoceptors. Lymphocytes and platelets of wheezing and nonwheezing infants also bound the same amounts of the radioligands. In asthmatic children receiving 4 X 2 puffs salbutamol beta-adrenoceptors were down-regulated and this may mimic beta-adrenoceptor blockade. When subjects were divided into four categories according to age (0-5, 5-10, 10-20 years, adults) the number of beta-adrenoceptor binding sites showed an age-dependent increase.(ABSTRACT TRUNCATED AT 250 WORDS)

Autacoid and beta-adrenergic agonist modulation of N-formylmethionyl-leucyl-phenylalanine evoked lysosomal enzyme release from human neutrophils

Isoprenaline, histamine and PGE1 inhibit N-formylmethionyl-leucyl-phenylalanine evoked lysosomal enzyme release from human neutrophils. Their effects are dose-dependent and potentiated by 3-isobutyl-1-methylxanthine pretreatment of the cells. The order of activity is PGE1 greater than isoprenaline greater than histamine. The maximum of inhibition afforded by each agonist depends on the amount of the secretory stimulus, since it is higher at lower concentrations of the secretagogue. Isoprenaline effects are competitively antagonized by propranolol and are mimicked by fenoterol and salbutamol. These results suggest that human neutrophil functions are modulated by endogenous control mechanisms, that can also be activated by drugs acting on the same receptors as the endogenous mediators.

In vitro effects of aqueous cotton dust extract on leucocyte cyclic adenosine monophosphate levels

Aqueous cotton dust extracts (ACDE) stimulated production of cyclic adenosine monophosphate (cAMP) in normal human peripheral blood mononuclear leucocytes (MNL). This response was not due to prostaglandin production by monocytes or platelets in the cell preparation nor to stimulation of the beta-adrenergic or H2 receptors; however, desensitization experiments indicated that the response may be receptor mediated. The possible involvement of such receptor desensitization in byssinosis pathogenesis is discussed.

Dose-response curves to inhaled beta-adrenoceptor agonists in normal and asthmatic subjects

We have compared bronchodilator dose-response curves to inhaled salbutamol in seven normal and eight asthmatic subjects. In all normal subjects maximal bronchodilatation measured by partial flow volume curves was achieved at a cumulative dose of 110 micrograms. The dose necessary to produce half maximal response (ED50) was 23 +/- 2 micrograms (mean +/- s.e. mean) with a range of 18-28 micrograms. In asthmatic subjects maximal bronchodilatation measured by FEV1 and by maximal flow volume curves was achieved at significantly higher (P less than 0.01) doses of salbutamol with a mean ED50 of 83 +/- 28 micrograms and range of 25-251 micrograms. There was a significant (P less than 0.05) correlation between ED50 and % predicted baseline FEV1. This is more likely to reflect impaired access of drug for airway beta-adrenoceptors than impaired beta-adrenoceptor function in asthma. In five asthmatic subjects dose-response curves to salbutamol and isoprenaline were compared and found to be similar, thus providing no evidence that salbutamol is a partial agonist in vivo, as it appears to be in vitro.

Lymphocyte beta-adrenergic refractoriness induced by theophylline or metaproterenol in healthy and asthmatic subjects

Beta-adrenergic refractoriness was assessed in human lymphocytes following in vivo administration of the beta-adrenergic agonist, metaproterenol, the phosphodiesterase inhibitor, theophylline, or both concomitantly, to normal and asthmatic subjects. In normal subjects both beta-adrenergic receptor number and isoproterenol stimulated cAMP response decreases during therapy with metaproterenol (59 +/- 3; 51 +/- 16% of control, respectively), theophylline (76 +/- 6; 78 +/- 16), or concomitant metaproterenol and theophylline (47 +/- 4; 69 +/- 13). The asthmatic subjects were of two types; one type responding to metaproterenol or theophylline therapy by down regulation of receptor number to zero or near zero values, and a second group of asthmatics insensitive to down regulation of receptor number. The results suggest that the induction of the refractory state is different between asthmatics and non-asthmatics, and that there may be a role for cAMP in the development of beta-adrenergic refractoriness, in vivo.

Physiological regulation of beta-receptors in man

Previous studies have shown that pharmacological doses of agonists can down-regulate beta receptors. We have shown that alteration of catecholamines within the physiological range is associated with modulation of beta receptor density. The stimulus used to alter catecholamine concentrations in vivo was change in sodium intake. In addition, administration of the beta blocker, propranolol, raised beta receptor density and the rise in receptor density was proportional to the pretreatment catecholamine concentrations. It appears that beta receptors in vivo are in a chronic state of down regulation and that this degree of down regulation parallels the catecholamine concentrations.

Comparison of four different beta-adrenoceptor blocking drugs on lymphocyte isoprenaline-stimulated cyclic AMP production

1 The influence of acebutolol, atenolol, pindolol and timolol on human lymphocyte cyclic AMP (cAMP) and its stimulation by isoprenaline in vitro has been studied. 2 Acebutolol and atenolol (10(-8)-10(-6)M) had no significant influence on lymphocyte cAMP levels or on isoprenaline-stimulated increase in cAMP. 3 Pindolol and timolol significantly antagonised the effect of isoprenaline, and pA2 values were calculated to be 8.12 and 8.04 respectively. This suggests that beta 2-adrenoceptors are involved in this phenomenon. 4 Only pindolol produced a significant increase in lymphocyte cAMP, which is consistent with its partial agonist activity.

Regulation of human leukocyte beta receptors by endogenous catecholamines: relationship of leukocyte beta receptor density to the cardiac sensitivity to isoproterenol

High levels of beta receptor agonist have previously been shown to down-regulate beta receptor density on circulating leukocytes in man; however, the factors controlling receptor density under physiological conditions have not previously been defined. To determine whether beta receptor density is normally down-regulated by circulating, physiological levels of catecholamines we have examined the relationship between receptor density and catecholamine levels. Urinary epinephrine and norepinephrine were significantly reciprocally correlated to lymphocyte receptor density. A similar relationship existed between beta receptor density and supine plasma epinephrine, norepinephrine, upright epinephrine, and norepinephrine levels. Change in sodium intake from 10 to 400 meq/d caused a 52% increase in lymphocyte and a 48% increase in polymorphonuclear beta receptor density. The changes in receptor density were accompanied by an increase in the sensitivity to isoproterenol measured as a fall in the dose of isoproterenol required to raise the heart rate by 25 beats per minute. Beta receptor density on both lymphocyte and polymorphonuclear cells was significantly correlated to the cardiac sensitivity to isoproterenol. Propranolol administration resulted in an increase in the density of beta receptors on lymphocyte and polymorphonuclear cells that correlated with the subject's pretreatment catecholamine levels. These findings, therefore, suggest that physiological levels of catecholamines normally down-regulate beta receptors in man and that blockade of this down-regulation by propranolol allows receptor density to increase.

The beta-adrenoreceptor in human lymphocytes

The beta-adrenoreceptors of human lymphocytes were investigated by binding assays using a radiolabelled beta-adrenoreceptor agonist, 3H-hydroxybenzylisoproterenol, in an intact cell system. Intact human lymphocytes had binding sites for the ligand, which seemed to represent physiological beta-adrenoreceptors. Thus, assay of binding of the beta-adrenergic agonist, 3H-HBI, by intact lymphocytes can be used to study beta-adrenoreceptors in human tissue and to elucidate possible beta-adrenoreceptor disorders in human diseases.

Sympathetic innervation of murine thymus and spleen: evidence for a functional link between the nervous and immune systems

Sympathetic innervation was demonstrated in both perivascular and parenchymal regions of murine thymus and spleen. Catecholamine varicosities were associated with mast cells in these areas. The antibody response to sheep red blood cells of 7 week old mice that had been sympathectomized with six-hydroxydopamine (6OHDA) at birth was significantly elevated compared with saline treated controls. Alpha-methyl tyrosine (alpha-MT) and 6OHDA treatment of mice, producing a more complete sympathectomy, showed a significantly enhanced anti-SRBC response with respect to mice treated with alpha-MT or 6OHDA alone. Catecholamine levels in thymus, spleen, and adrenals of both experimental and control mice were measured using liquid chromatography with electrochemical detection (LCEC). The present study suggests that the sympathetic nervous system has a functional role in modulating the humoral immune response in vivo.

Beta-adrenoceptors in human lung, bronchus and lymphocytes

1 The ability of propranolol, metoprolol, acebutolol, atenolol and practolol to reverse the stimulant effect of 10^-5 M isoprenaline on lymphocyte cyclic AMP levels was determined. The ratios of doses required to produce 50% inhibition as compared with propranolol were 1:316 for metoprolol 1:1780 for acebutolol and 1:2820 for atenolol. No ratio could be calculated for practolol as it never produced more than 35% inhibition possibly because of its intrinsic sympathomimetic activity. This rank order of antagonist potencies suggest the lymphocyte β-receptor has β₂ selectivity.

2 For peripheral airway smooth muscle isoprenaline, adrenaline and noradrenaline had relative EC₅₀s of 1:25:9290 respectively in the absence of uptake blockade. However, the EC₅₀s changed to 1:15:82 in the presence of neuronal uptake blockade and x-adrenoceptor blockade. These observations are consistent with β₂ selectivity. Salbutamol behaved as a partial agonist on peripheral airway smooth muscle. It was possible to demonstrate competitive antagonism to isoprenaline. Estimates of the dissociation constant of salbutamol were obtained (6.6 ± 0.02) × 10^-7 M, n=4, mean ± s.e. mean).

3 A novel technique for determining the pA₂ is described which is particularly useful on peripheral airway smooth muscle. Values obtained for propranolol and practolol using this technique were:

propranolol pA₂ 7.83 ± 0.14; slope=0.97 ± 0.05 (n=4),

practolol pA₂ 5.62 ± 0.15; slope=1.17 ± 0.17 (n=4)

These values support the β₂ selectivity suggested by the agonist studies.

4 The cyclic AMP response of lung parenchyma to β-adrenoceptor agonists and antagonists (in the presence of isoprenaline demonstrated β₂ selectivity. Salbutamolol appeared to be a partial agonist when compared with the cyclic AMP response to isoprenaline.

5 The β-adrenoceptors of the lymphocyte, bronchial smooth muscle and lung parenchyma have β₂ selectivity although they differ somewhat quantitatively from each other.

Tachyphylaxis to beta-adrenoceptor agonists in human bronchial smooth muscle: studies in vitro

In studies on human isolated peripheral airway smooth muscle; 1 A concentration dependent beta-adrenoceptor tachyphylaxis was observed to isoprenaline. 2 Cross desensitization to other beta-adrenoceptor agonists was demonstrated. 3 The desensitization was reversible with time. Hydrocortisone appeared to accelerate the recovery from the desensitized state. Low concentration isoprenaline (10(-9) mol l-1) prevented recovery whereas cyclohexamide 1.8 x 10(-4) mol l-1 had no noticeable effect on recovery. Continued occupancy of the receptor appears to prevent recovery. The recovery from the desensitized state does not apparently require synthesis of new proteins. 4 Bronchial wall cyclic AMP response to isoprenaline was attenuated after isoprenaline induced desensitization whereas total phosphodiesterase activity of bronchial wall was not altered by desensitization. Thus by exclusion the adenylate cyclase receptor complex may be altered in human peripheral airway smooth muscle beta-adrenoceptor tachyphylaxis.

Lymphocyte monoamine oxidase activity and chronic schizophrenia

Lymphocyte monoamine oxidase (MAO) activity was assayed in 62 chronic schizophrenic patients, 113 normal volunteers, and 23 first-degree relatives of schizophrenic patients. Mean lymphocyte MAO activity was significantly lower (p < 0.001) in the chronic schizophrenic group than in controls; first-degree relatives had a mean lymphocyte MAO activity midway between the schizophrenics and normals. No relationship was found between lymphocyte MAO activity and sex or age of subjects. When subjects were subgrouped by race, blacks had significantly lower MAO activity than whites (p < 0.001).

Beta adrenergic receptors of polymorphonuclear particulates in bronchial asthma

We have tested the beta adrenergic receptor theory of bronchial asthma by determining the number and affinity of binding sites of the beta adrenergic radioligand [(3)H]dihydroalprenolol (DHA) and the activity of adenylate cyclase in broken cell preparations of polymorphonuclear leukocytes (PMN). We studied 31 control subjects (group 1), 30 asthmatics receiving no systemic adrenergic medication (group 2), and 17 asthmatics receiving adrenergic agonists systemically (group 3). Control subjects and asthmatics taking no adrenergic drugs bound similar amounts of DHA at 0.5 nM and 30 nM DHA and had about 900 binding sites per PMN. In contrast, asthmatics receiving adrenergic agonists had a >70% decrease in their number of DHA binding sites per PMN (254+/-57). In a subset of our three groups of subjects (eight from group 1, six from group 2, and five from group 3) we measured DHA binding at several DHA concentrations and found similar values (0.4-0.7 nM) for the dissociation constant of DHA among these subjects. In further studies we examined the interaction of the agonist (-)-isoproterenol with beta adrenergic receptors in 8 normal subjects and 10 asthmatics not receiving adrenergic medication. We tested the ability of isoproterenol to compete for DHA binding sites and to stimulate adenylate cyclase in sonicates prepared from PMN and examined under identical conditions. The dissociation constants for the competition of isoproterenol for DHA binding sites in normal and asthmatic subjects were virtually identical ( approximately 1.0 muM). In addition, the (activation constant) values for stimulation of adenylate cyclase were similar (0.16-0.19 muM) in the two groups of subjects.Thus, these data suggest that asthma per se is not associated with alteration in either the number or affinity of beta adrenergic receptors in PMN. Our findings indicate that previous reports of abnormal beta adrenergic receptor function in asthmatic patients may in part be explained by prior treatment of such patients with adrenergic agonists. Because the asthmatics who received adrenergic agonists in our study tended to be more ill and to receive additional medication compared to subjects in group 2, we cannot rule out unequivocally that severe asthma may be associated with decreased binding to beta adrenergic receptors. Nevertheless, we conclude that beta adrenergic receptors on PMN from asthmatics are relatively normal unless such patients are treated with adrenergic agonists.

Characterization of the receptor mediating the antianaphylactic effects of beta-adrenoceptor agonists in human lung tissue in vitro

1 The rank order of potency of six beta-adrenoceptor agonists as inhibitors of the anaphylactic release of histamine from fragments of passively sensitized human lung in vitro was (--)-isoprenaline greater than (--) -adrenaline greater than (+/-)-salbutamol greater than (--)-noradrenaline greater than R0363 greater than H133/22. 2 The beta-adrenoceptor antagonists, propranolol, atenolol and H35/25, blocked the response to both (--)-isoprenaline and (+/-)-salbutamol competitively. Each antagonist gave similar pA2 values with both agonists. pA2 values were consistently at the high end of the range expected for interaction at a beta 2-adrenoceptor. 3 Practolol did not antagonize isoprenaline in a competitive manner but was a competitive antagonist of salbutamol with a pA2 at the high end of the range expected for interaction at a beta 2-adrenoceptor. 4 Data obtained with agonists are consistent with the receptor being of the beta 2-subtype. Data obtained with antagonists indicate a consistently higher affinity for the receptor than observed for the beta 2-subtype in other tissues but do not suggest a novel beta-adrenoceptor subtype on the mast cell of the human lung.

Quantitative assessment of bronchial beta-adrenoceptor blockade in man

1. We describe a method for assessing bronchial beta-adrenoceptor blockade quantitatively in man. Specific airway conductance is measured after increasing doses of inhaled salbutamol and the extent to which the dose-response curve is displaced to the right after beta-adrenoceptor blocking drugs is used to assess bronchial beta-adrenoceptor blockade. 2. Salbutamol dose-response curves were plotted for six normal subjects by measuring sGaw 15 min after increasing doses of inhaled salbutamol. Salbutamol produced a 30-70% increase in sGaw. 3. Salbutamol dose response curves were obtained 2 h after oral practolol (100 mg and 200 mg) and oral propranolol (40 mg and 80 mg) on separate days and were displaced to the right. 4. The mean dose ratios for practolol 100 mg and 200 mg were 1.2 and 2.1 and for propranolol 40 mg and 80 mg they were 21 and 61 respectively.

Relation between catecholamine-induced cyclic AMP changes and hyperpolarization in isolated rat sympathetic ganglia

1. The effect of catecholamines on cyclic adenosine 3'5'-monophosphate (cyclic AMP) production in isolated rat superior cervical ganglia has been measured under experimental conditions in which they also produce ganglion hyperpolarization.2. (+/-)Isoprenaline (1 muM) increased cyclic AMP levels by 8-100 times after 15 min incubation at 25 degrees C. Half-maximal stimulation occurred at about 0.03 muM. This was due to stimulation of beta-receptors, since it was prevented by 1 muM-propranolol but not by 1 muM-phentolamine.3. The alpha-agonists phenylephrine (100 muM), dopamine (100 muM) and clonidine (1 muM) did not produce a detectable increase in ganglionic cyclic AMP. Dopamine (100 muM) was also ineffective at 37 degrees C in the presence of 10 mM-theophylline.4. Exogenous cyclic AMP (0.01-1 mM) hyperpolarized the ganglion. This effect was replicated by other adenosine compounds, most effectively by adenosine and by adenosine 5'-monophosphate, and was antagonized by theophylline. Dibutyryl cyclic AMP was weaker than cyclic AMP.5. Neither theophylline nor the non-xanthine phosphodiesterase inhibitor, Ro 20-1724, enhanced the hyperpolarizing actions of noradrenaline or dopamine.6. Since catecholamine-induced hyperpolarization of the isolated rat ganglion is induced via alpha-receptors, whereas cyclic AMP-production is induced via beta-receptors, it is concluded that cyclic AMP is unlikely to mediate the hyperpolarization. The effect of exogenous cyclic AMP may be due to an action on external adenosine-receptors.

Use of exercise challenge to investigate possible tolerance to beta-adrenoceptor stimulation in asthma

The effect of prolonged salbutamol administration on beta-adrenoceptor function in asthma has been examined. Six adult patients received salbutamol tablets (16 mg daily) for between 4 and 20 weeks and six adolescents received salbutamol aerosol (800 microgram daily) for 2--5 weeks. Before and after the treatment period the acute bronchodilator response to inhaled salbutamol and the ability of inhaled salbutamol to protect against exercise-induced asthma were examined. Lymphocyte beta-adrenoceptor function was also measured in the patients on tablet therapy. Inhaled salbutamol was less effective in protecting against exercise-induced asthma at the end of the treatment period in the patients who had received tablet therapy, but otherwise there was no significant change in beta-receptor function of either airways or lymphocytes. This apparent loss of efficacy of inhaled salbutamol in the prevention of exercise-induced asthma in some subjects, even when its acute bronchodilator effect is preserved, might reflect differences in the susceptibility of different beta-adrenoceptors to desensitization after prolonged stimulation: its clinical importance remains uncertain.