Adenovirus-mediated gene transfer transiently corrects the chloride transport defect in nasal epithelia of patients with cystic fibrosis

To evaluate the potential of direct transfer of cystic fibrosis transmembrane conductance regulator (CFTR) cDNA for the treatment of cystic fibrosis (CF), we administered an E1-deficient adenovirus, encoding CFTR, to a defined area of nasal airway epithelium of three individuals with CF. This treatment corrected the Cl- transport defect that is characteristic of CF-affected epithelia. After treatment, there was a decrease in the elevated basal transepithelial voltage, and the normal response to a cAMP agonist was restored. We found no evidence of viral replication or virus-associated adverse effects, even at the highest dose tested (25 MOI). These data represent a small step in achieving long-term improvement of CF lung function by gene therapy.

Beta-adrenergic agonists increase lung liquid clearance in anesthetized sheep

We did experiments to determine whether beta-adrenergic agonists increase lung liquid clearance in anesthetized ventilated adult sheep and, if so, whether the increase is mediated by beta receptors and what mechanism is involved. We instilled 100 ml of autologous serum either alone or with a beta-adrenergic agonist (terbutaline, 10(-5) M, or epinephrine, 5.5 X 10(-6) M) into one lower lobe. After 4 h both terbutaline and epinephrine increased lung liquid clearance. The increase in lung liquid clearance was inhibited when propranolol (a beta blocker) or amiloride (a sodium channel blocker) was added to the terbutaline. Increased clearance was not explained by changes in pulmonary hemodynamics, pulmonary blood flow, or lung lymph flow. We conclude that beta-adrenergic agonists increase lung liquid clearance in anesthetized intact adult sheep. This increase is mediated through beta receptors and probably depends on increased active transport of sodium across the alveolar barrier.

Tolerance to the nonbronchodilator effects of inhaled beta 2-agonists in asthma

BACKGROUND

Tolerance to the direct bronchodilator effects of beta 2-agonists does not appear to occur in asthma. However, it is not known whether this is true for the nonbronchodilator effects of these agents, which protect the airways against bronchoconstrictive stimuli.

METHODS

We investigated whether tolerance develops to the protective effect of inhaled terbutaline on airway responsiveness to the bronchoconstrictors methacholine (which acts directly on airway smooth muscle) and AMP (which acts indirectly by stimulating the release of mediators from mast cells) during sustained treatment with terbutaline. In a randomized, double-blind, crossover study, 12 patients with mild asthma each inhaled a single dose of terbutaline (500 micrograms) or placebo before a challenge with a series of doubling doses of inhaled methacholine or AMP, before and after treatment for seven days with 500 micrograms of terbutaline four times daily or placebo.

RESULTS

Before the seven days of treatment with terbutaline, a single dose of terbutaline reduced airway responsiveness to methacholine by 2.7 doubling doses (95 percent confidence interval, 1.9 to 3.5), but it had an even greater protective effect against AMP, reducing airway responsiveness by 3.8 doubling doses (95 percent confidence interval, 2.7 to 4.9; P less than 0.001). After seven days of treatment with terbutaline, the protective effect of terbutaline against methacholine decreased to 2.2 doubling doses (95 percent confidence interval, 1.3 to 3.0; P = 0.04), and that against AMP decreased even more, to 1.7 doubling doses (95 percent confidence interval, 1.1 to 2.4; P less than 0.001). By contrast, the bronchodilator response to terbutaline was unchanged during seven days of treatment with this agent.

CONCLUSIONS

We observed tolerance to the nonbronchodilator actions of the inhaled beta 2-agonist terbutaline in patients with mild asthma, an effect that may be more pronounced in mast cells than in bronchial smooth muscle. This property of beta-agonists may constitute a drawback to their regular use in patients with asthma.

Bronchodilator action of inhaled nitric oxide in guinea pigs

The effects of inhaling nitric oxide (NO) on airway mechanics were studied in anesthetized and mechanically ventilated guinea pigs. In animals without induced bronchoconstriction, breathing 300 ppm NO decreased baseline pulmonary resistance (RL) from 0.138 +/- 0.004 (mean +/- SE) to 0.125 +/- 0.002 cmH2O/ml.s (P less than 0.05). When an intravenous infusion of methacholine (3.5-12 micrograms/kg.min) was used to increase RL from 0.143 +/- 0.008 to 0.474 +/- 0.041 cmH2O/ml.s (P less than 0.05), inhalation of 5-300 ppm NO-containing gas mixtures produced a dose-related, rapid, consistent, and reversible reduction of RL and an increase of dynamic lung compliance. The onset of bronchodilation was rapid, beginning within 30 s after commencing inhalation. An inhaled NO concentration of 15.0 +/- 2.1 ppm was required to reduce RL by 50% of the induced bronchoconstriction. Inhalation of 100 ppm NO for 1 h did not produce tolerance to its bronchodilator effect nor did it induce substantial methemoglobinemia (less than 2%). The bronchodilating effects of NO were additive with the effects of inhaled terbutaline, irrespective of the sequence of NO and terbutaline administration. Inhaling aerosol generated from S-nitroso-N-acetylpenicillamine also induced a rapid and profound decrease of RL from 0.453 +/- 0.022 to 0.287 +/- 0.022 cmH2O/ml.s, which lasted for over 15 min in guinea pigs broncho-constricted with methacholine. Our results indicate that low levels of inhaled gaseous NO, or an aerosolized NO-releasing compound are potent bronchodilators in guinea pigs.

Differentiation of cardiac chronotropic and inotropic effects of beta-adrenoceptor agonists

The relative inotropic and chronotropic activity of beta-adrenoceptor agonists was studied in the noradrenaline-depleted, anaesthetized cat. Terbutaline, a selective beta2-adrenoceptor agonist, gave at a certain dose a more pronounced chronotropic than inotropic response, while a new beta1-selective adrenoceptor agonist (-)-H 80/62 produced the same degree of chronotropic and inotropic stimulation. The results indicate that there is some difference between the beta-adrenoceptors in the sinus node mediating chronotropic stimulation and beta-adrenoceptors in the ventricular myocardium mediating stimulation of the contractile force. It has been shown that there are both beta1- and beta2-adrenoceptors in the heart (Carlsson et al., 1972). In the light of this finding it is hypothetized that there are differences in the relative distribution of beta1- and beta2-adrenoceptors in the sinus node and in the myocardium. Athough beta1 is the predominant type of beta-adrenoceptor in both regions, the beta1:beta2 concentration ratio seems to be higher in the myocardium, than in the sinus node.

Alveolar fluid clearance in the resected human lung

Although the mechanisms responsible for alveolar liquid clearance have been studied in several species, there has not been any information regarding the effect of ion transport agonists or antagonists on alveolar liquid clearance in the human lung. Therefore, we studied alveolar liquid clearance in the recently resected human lung from patients who underwent surgery for lung cancer. A test solution of 40 ml of isosmolar albumin solution was instilled into one segment of a resected lobe within 10 min of resection. Because protein leaves the air spaces very slowly, the concentration of alveolar protein over 4 h was used to quantify alveolar liquid clearance. Basal alveolar liquid clearance was 12 +/- 2% over 4 h. Amiloride (10(-5) M), an inhibitor of apical Na+ uptake, and ouabain (10(-3) M), an inhibitor of Na,K-ATPase activity, reduced alveolar liquid clearance by 40 and 49%, respectively (p < 0.005). Terbutaline (10(-3) or 10(-4) M) doubled alveolar liquid clearance to 28 +/- 9% over 4 h (p < 0.05). Propranolol (10(-4) M) and amiloride (10(-5) M) inhibited the terbutaline-induced increase in alveolar liquid clearance. In conclusion, (1) alveolar liquid clearance in the human lung can be markedly reduced by inhibition of apical sodium channel uptake or Na,K-ATPase activity, and (2) beta-adrenergic stimulation markedly increases the rate of alveolar liquid clearance in the resected human lung without pulmonary perfusion.

Noradrenergic signaling in the wakeful state inhibits microglial surveillance and synaptic plasticity in the mouse visual cortex

Microglia are the brain's resident innate immune cells and also have a role in synaptic plasticity. Microglial processes continuously survey the brain parenchyma, interact with synaptic elements and maintain tissue homeostasis. However, the mechanisms that control surveillance and its role in synaptic plasticity are poorly understood. Microglial dynamics in vivo have been primarily studied in anesthetized animals. Here we report that microglial surveillance and injury response are reduced in awake mice as compared to anesthetized mice, suggesting that arousal state modulates microglial function. Pharmacologic stimulation of β2-adrenergic receptors recapitulated these observations and disrupted experience-dependent plasticity, and these effects required the presence of β2-adrenergic receptors in microglia. These results indicate that microglial roles in surveillance and synaptic plasticity in the mouse brain are modulated by noradrenergic tone fluctuations between arousal states and emphasize the need to understand the effect of disruptions of adrenergic signaling in neurodevelopment and neuropathology.

Pharmacological characterization of adrenergic alpha and beta receptors mediating the vasomotor responses of cerebral arteries in vitro

The adrenergic receptors in the isolated feline middle cerebral artery were characterized pharmacologically using a sensitive system for recording circular contractions in vitro. Epinephrine. norepinephrine, isoproterenol. and phenylephrine contracted the vessel in the mentioned order of potency. Together with the inhibitory patterns obtained with graded doses of piperoxan (reversible competitive inhibition) and dibenamine or phenoxybenzamine (irreversible competitive inhibition), these results showed that the contraction was mediated by alpha receptors. With piperoxan and norepinephrine, the mean value for pA 2 was 7.06 and for K H 1.24 x 10 -7 M. The mean value for K A calculated for norepinephrine before and after partial irreversible blockade of the alpha receptors with phenoxybenzamine was 1.73 x 10 -6 M. The norepinephrine response was not directly proportional to the amount of receptors occupied; ED 50 was reached when only about 11% of the receptors were occupied and the E Am response was obtained when 75% of the receptors were occupied. Dilation was achieved only after an active tonic contraction had been induced (with 5-hydroxytryptamine) in the vessels, and the order of potency was isoproterenol > norepinephrine - epinephrine > terbutaline. Inhibition with INPEA and propranolol was competitive, as confirmed by Arunlakshana-Schild plots, showing that the dilatory response was a beta-receptor effect. The values for pA 2 (8.78 and 9.17) and K H (2.31 x 10 -9 M and 1.77 x 10 -9 M) for propranolol were indistinguishable in tests with terbutaline and isoproterenol, respectively. Comparison of the relative potencies of norepinephrine and epinephrine as well as isoproterenol and terbutaline suggested that the receptors were of the beta 1 type.

Effects of norepinephrine on rat cultured microglial cells that express alpha1, alpha2, beta1 and beta2 adrenergic receptors

Microglial cells rapidly become activated in response to even minor damage of neurons, suggestive of the intimate interactions between neurons and microglial cells. Although mediators for microglia-neuron interactions have not been well identified, neurotransmitters are possible candidates transmitting signals from neurons to microglial cells. Among the neurotransmitters, we focused on the effects of norepinephrine and other adrenergic agonists on the functions of rat cultured microglial cells. Reverse transcriptase polymerase chain reaction studies revealed that microglial cells expressed mRNAs encoding alpha1A, alpha2A, beta1 and beta2 receptors. Norepinephrine and a beta2 adrenergic agonist terbutaline elevated intracellular cAMP level of microglial cells. Norepinephrine, an alpha1 agonist phenylephrine, a beta1 agonist dobutamine and terbutaline suppressed the expressions of mRNAs encoding pro-inflammatory cytokines, interleukin-6 and tumor necrosis factor alpha. Release of tumor necrosis factor alpha and nitric oxide was suppressed by norepinephrine, phenylephrine, dobutamine and terbutaline. An alpha2 agonist clonidine and dobutamine upregulated the expression of mRNA encoding catechol-O-methyl transferase, an important enzyme to degrade norepinephrine. Norepinephrine, dobutamine and terbutaline upregulated the expressions of mRNA encoding 3-phospshoglycerate dehydrogenase, an essential enzyme for synthesis of L-serine and glycine, which are amino acids necessary for neuronal survival. Clonidine upregulated the expression of mRNA encoding an anti-apoptotic factor Bcl-xL. These results suggest that norepinephrine participates in the regulation of brain function at least partly by modulating the functions of microglia.

A pathogenic role of visceral fat beta 3-adrenoceptors in obesity

Increased release of free fatty acids (FFA) from visceral fat cells to the portal venous system may cause several metabolic disturbances in obesity. However, this hypothesis and the underlying mechanism remain to be demonstrated. In this study catecholamine-induced lipid mobilization through lipolysis in omental adipose tissue was investigated in vitro in 25 markedly obese subjects (body mass index range 35-56 kg/m2) undergoing weight reduction surgery and in 19 nonobese subjects (body mass index range 20-28 kg/m2) undergoing cholecystectomy. Release of FFA and glycerol, induced by norepinephrine or adrenergic receptor subtype-specific agonists, were determined in isolated omental fat cells. The obese subjects had higher fat cell volume, blood pressure, plasma insulin levels, blood glucose, plasma triglycerides, and plasma cholesterol than the controls. There was evidence of upper-body fat distribution in the obese group. The rate of FFA and glycerol response to norepinephrine was increased twofold in the cells of obese subjects; no significant reutilization of FFA during catecholamine-induced lipolysis was observed in any of the groups (glycerol/FFA ratio near 1:3). There were no differences in the lipolytic sensitivity to beta 3- or beta 2-adrenoceptor specific agonists between the two groups. However, beta 3-adrenoceptor sensitivity was approximately 50 times enhanced (P = 0.0001), and the coupling efficiency of these receptors was increased from 37 to 56% (P = 0.01) in obesity. Furthermore, the obese subjects demonstrated a sixfold lower alpha 2-adrenoceptor sensitivity (P = 0.04). beta 3-Adrenoceptor sensitivity, but not alpha 2-, beta 1-, or beta 2-adrenoceptor sensitivity, correlated with norepinephrine-induced lipolysis (r = -0.67, P = 0.0001) and fat cell volume (r = -0.71, P = 0.0001). In conclusion, catecholamine-induced rate of FFA mobilization from omental fat cells is accelerated due to elevated rate of lipolysis in obesity, mainly because of an increased beta 3-adrenoceptor function, but partly also because of a decreased alpha 2-adrenoceptor function. This promotes an increased release of FFA to the portal system, which may contribute to the parallel metabolic disturbances observed in upper-body obesity.

Transepithelial transport by pulmonary alveolar type II cells in primary culture

Fluid and electrolyte transport by epithelial cells in vitro can be recognized by the ability of cultured cells to form domes and by the electrical properties of monolayer cultures. Pulmonary alveolar epithelial cells are thought to be partially responsible for fluid movement in the fetal lung, but their role in electrolyte transport in the adult lung is not known. We isolated alveolar type II cells from adult rat lung and maintained them on plastic culture dishes alone, on plastic culture dishes coated with an extracellular matrix, and on collagen-coated Millipore filters. Numerous large domes were formed on culture dishes coated with the extracellular matrix; smaller domes were formed on uncoated plastic culture dishes. Sodium butyrate (3 mM) stimulated dome formation. Transmission electron microscopy showed that the epithelial cells had flattened but still retained lamellar inclusions and that the cells were polarized with microvilli on the apical surface facing the culture medium. The electrical properties of the monolayers maintained on collagen-coated Millipore filters were tested in two laboratories. The transepithelial potential differences were 0.7 +/- 0.1 mV (24 filters, seven experiments) and 1.3 +/- 0.1 mV (13 filters, two experiments) apical side negative, and the corresponding resistances were 217 +/- 11 ohm X cm2 and 233 +/- 12 ohm X cm2. Terbutaline (10 microM) produced a biphasic response with a transient decrease and then a sustained increase in potential difference. Amiloride (0.1 mM) completely abolished the potential difference when it was added to the apical side but not when it was added to the basal side, whereas 1 mM ouabain inhibited the potential difference more effectively from the basal side. Thus, type II cells form a polarized epithelium in culture, and these cells actively transport electrolytes in vitro.

Tight monolayers of rat alveolar epithelial cells: bioelectric properties and active sodium transport

Because the pulmonary alveolar epithelium separates air spaces from a fluid-filled compartment, it is expected that this barrier would be highly resistant to the flow of solutes and water. Investigation of alveolar epithelial resistance has been limited due to the complex anatomy of adult mammalian lung. Previous efforts to study isolated alveolar epithelium cultured on porous substrata yielded leaky monolayers. In this study, alveolar epithelial cells isolated from rat lungs and grown on tissue culture-treated Nucleopore filters resulted in tight monolayers with transepithelial resistance greater than 2,000 omega.cm2. Changes in bioelectric properties of these alveolar epithelial monolayers in response to ouabain, amiloride, and terbutaline are consistent with active sodium transport across a polarized barrier. 22Na flux measurements under short-circuit conditions directly confirm net transepithelial absorption of sodium by alveolar epithelial cells in the apical to basolateral direction, comparable to the observed short-circuit current (4.37 microA/cm2). The transport properties of these tight monolayers may be representative of the characteristics of the mammalian alveolar epithelial barrier in vivo.

Capsazepine inhibits cough induced by capsaicin and citric acid but not by hypertonic saline in guinea pigs

Acidic solutions mimick many of the effects of capsaicin (Cap), including pain, bronchoconstriction, cough, and sensory neuropeptide release. Evidence from the use of the Cap antagonist capsazepine suggests that in some cases protons act at the Cap receptor. In the present study, we have investigated whether cough evoked by Cap and citric acid (CA) is mediated specifically via the Cap receptor on airway sensory nerves. We have examined the effects of capsazepine on Cap-, CA-, and hypertonic saline-induced cough and also on CA-induced nasal irritation in awake guinea pigs. Capsazepine was nebulized for 5 min before cough challenges with Cap for 5 min and CA for 10 min. Control animals were pretreated with vehicle alone. Capsazepine (100 microM) inhibited the cough response to 30 microM Cap from 0.77 +/- 0.14 coughs/min in control animals to 0.23 +/- 0.08 coughs/min (P < 0.05) and to 80 microM Cap from 1.4 +/- 0.23 to 0.3 +/- 0.11 coughs/min (P < 0.01). There was no effect, however, of lower concentrations of capsazepine (5 and 10 microM) against Cap-evoked cough. At a concentration of 100 microM, capsazepine also inhibited the coughing induced by 0.25 M CA from 1.8 +/- 0.26 to 0.93 +/- 0.31 coughs/min (P < 0.05) but not that induced by 0.5 M CA. Nasal irritation induced by 0.25 M CA, but not by 0.5 M CA, was also inhibited by capsazepine from 2.47 +/- 0.37 to 0.75 +/- 0.31 nose wipes/min (P < 0.05). This inhibitory effect of capsazepine did not appear to reflect a nonspecific suppression of the cough reflex, since cough evoked by exposure to hypertonic (7%) saline for 10 min was unaffected by pretreatment with capsazepine (100 microM). These data show that capsazepine is a specific inhibitor of Cap- and CA-induced cough in guinea pigs. Moreover, they suggest that low pH stimuli evoke cough and nasal irritation by an action at the Cap receptor, either directly or through the release of an intermediate agent.

Decreased expression and activity of G-protein-coupled receptor kinases in peripheral blood mononuclear cells of patients with rheumatoid arthritis

Beta2-Adrenergic and chemokine receptor antagonists delay the onset and reduce the severity of joint injury in rheumatoid arthritis. beta2-Adrenergic and chemokine receptors belong to the G-protein-coupled receptor family whose responsiveness is turned off by the G-protein-coupled receptor kinase family (GRK-1 to 6). GRKs phosphorylate receptors in an agonist-dependent manner resulting in receptor/G-protein uncoupling via subsequent binding of arrestin proteins. We assessed the activity of GRKs in lymphocytes of rheumatoid arthritis (RA) patients by rhodopsin phosphorylation. We found a significant decrease in GRK activity in RA subjects that is mirrored by a decrease in GRK-2 protein expression. Moreover, GRK-6 protein expression is reduced in RA patients whereas GRK-5 protein levels were unchanged. In search of an underlying mechanism, we demonstrated that proinflammatory cytokines induce a decrease in GRK-2 protein levels in leukocytes from healthy donors. Since proinflammatory cytokines are abundantly expressed in RA, it may provide an explanation for the decrease in GRK-2 expression and activity in patients. No changes in beta2-adrenergic receptor number and Kd were detected. However, RA patients showed a significantly increased cAMP production and inhibition of TNF-alpha production by beta2-adrenergic stimulation, suggesting that reduced GRK activity is associated with increased sensitivity to beta2-adrenergic activation.

Hypoxia reduces alveolar epithelial sodium and fluid transport in rats: reversal by beta-adrenergic agonist treatment

In cultured alveolar epithelial cells, hypoxia induces a downregulation of the two main Na proteins, the epithelial Na channel (ENaC) and the Na,K-ATPase. However, the in vivo effects of hypoxia on alveolar epithelial transport have not been well studied. Therefore, the objectives of this study were to investigate in an in vivo rat model if hypoxia induces a reduction in vectorial Na and fluid transport across the alveolar epithelium in vivo, and if a change in net fluid transport is associated with modification in the expression and/or activity of Na transport proteins. Rats were exposed to 8% O(2) from 3 to 24 h. Hypoxia induced a progressive decrease in alveolar liquid clearance (ALC) reaching 50% at 24 h, an effect that was related primarily to a decrease in amiloride-sensitive transepithelial Na transport. On RNase protection assay of alveolar type II (ATII) cells isolated immediately after hypoxic exposure, steady state levels of mRNA were increased for alpha-rENaC and beta(1)-Na, K-ATPase, whereas the levels of gamma-rENaC and alpha(1)-Na,K-ATPase were unchanged. On Western blots of ATII cell membranes, alpha-ENaC subunit protein slightly increased, whereas the amount of alpha(1)- and beta(1)-Na,K-ATPase protein were unchanged with hypoxia. Thus, the decrease in transepithelial Na transport was not explained by a parallel change in gene expression or the quantity of transport proteins. Interestingly, hypoxia-induced decrease in ALC was completely reversed by intra-alveolar administration of the beta(2) agonist, terbutaline (10(-4) M). These results suggest that hypoxia-induced decrease in Na transport is not simply related to a downregulation of Na transport proteins but rather to a decrease in Na protein activity by either internalization of the proteins and/or direct alteration of the protein in the membrane. The dramatic increase of ALC with beta(2)-agonist therapy indicates that the decrease of transepithelial Na and fluid transport during hypoxia is rapidly reversible, a finding of major clinical significance.

Interpretation of bronchodilator response in patients with obstructive airways disease. The Dutch Chronic Non-Specific Lung Disease (CNSLD) Study Group

BACKGROUND

There is no agreement on how a bronchodilator response should be expressed. Ideally, the index used should be able to distinguish asthma from chronic obstructive lung disease and be independent of initial FEV1.

METHODS

Two hundred and seventy four adults (aged 18-60 years) outpatients with obstructive airways disease were studied. Patients were divided into syndrome groups on the basis of a standardised history: asthma (n = 99), asthmatic bronchitis (n = 88), and chronic obstructive lung disease (n = 51); 36 subjects could not be attributed to any subgroup. FEV1 was measured before and 20 minutes after inhalation of 1000 micrograms terbutaline. Different expressions of bronchodilator response (delta FEV1) were compared with respect to their dependence on initial FEV1 and their efficacy in separating subjects with asthma from those with chronic obstructive lung disease. delta FEV1 was expressed as a percentage of initial FEV1 (delta FEV1%init), absolute value (delta FEV1[1]), percentage of predicted FEV1 (delta FEV1%pred), standardised residual (delta SR-FEV1), and percentage of maximal possible increase (delta FEV1%[pred-init]).

RESULTS

delta FEV1%init was more dependent on initial FEV1 (p = -0.405) than delta FEV1[1] (r = -0.145), delta FEV1%pred (r = -0.166), and delta SR-FEV1 (r = -0.127). delta FEV1%[pred-init] reached infinity when initial FEV1 approached predicted levels. delta FEV1%pred had a higher likelihood ratio (1.71) for separating patients with asthma from those with chronic obstructive lung disease than other expressions of bronchodilator response. Asthmatic patients had larger mean bronchodilator responses than patients in other subgroups; this difference was largest for delta SR-FEV1 (F = 9.19) and delta FEV1%pred (F = 9.03); it was much smaller for delta FEV1%init (F = 5.89). Despite significant differences in mean response, there was a large overlap of individual responses between diagnostic subgroups. The bronchodilator response was continuously and unimodally distributed for all expressions.

CONCLUSIONS

delta FEV1%pred appears to be the most useful method of expressing bronchodilator response, both for clinical and for research purposes. Reversibility of airways obstruction in response to a bronchodilator is a continuous variable and not a dichotomous triat. Any cut off level of a "positive" bronchodilator response is therefore arbitrary.

Cardiac adrenoceptors: physiological and pathophysiological relevance

At present, nine adrenoceptor (AR) subtypes have been identified: alpha(1A)-, alpha(1B)-, alpha(1D)-, alpha(2A)-, alpha(2B)-, alpha(2C)-, beta(1)-, beta(2)-, and beta(3)AR. In the human heart, beta(1)- and beta(2)AR are the most powerful physiologic mechanism to acutely increase cardiac performance. Changes in betaAR play an important role in chronic heart failure (CHF). Thus, due to increased sympathetic activity in CHF, betaAR are chronically (over)stimulated, and that results in beta(1)AR desensitization and alterations of down-stream mechanisms. However, several questions remain open: What is the role of beta(2)AR in CHF? What is the role of increases in cardiac G(i)-protein in CHF? Do increases in G-protein-coupled receptor kinase (GRK)s play a role in CHF? Does betaAR-blocker treatment cause its beneficial effects in CHF, at least partly, by reducing GRK-activity? In this review these aspects of cardiac AR pharmacology in CHF are discussed. In addition, new insights into the functional importance of beta(1)- and beta(2)AR gene polymorphisms are discussed. At present it seems that for cardiovascular diseases, betaAR polymorphisms do not play a role as disease-causing genes; however, they might be risk factors, might modify disease, and/or might influence progression of disease. Furthermore, betaAR polymorphisms might influence drug responses. Thus, evidence has accumulated that a beta(1)AR polymorphism (the Arg389Gly beta(1)AR) may affect the response to betaAR-blocker treatment.

Comparison of DNA-lipid complexes and DNA alone for gene transfer to cystic fibrosis airway epithelia in vivo

Cationic lipids show promise as vectors for transfer of CFTR cDNA to airway epithelia of patients with cystic fibrosis (CF). However, previous studies have not compared the effect of DNA-lipid to DNA alone. Recently, we developed a formulation of plasmid encoding CFTR (pCF1-CFTR) and cationic lipid (GL-67:DOPE) that generated greater gene transfer in mouse lung than previously described DNA-lipid vectors. Therefore, we tested the hypothesis that DNA-lipid complexes were more effective than DNA alone at transferring CFTR cDNA to airway epithelia in vivo. We administered complexes of DNA-lipid to one nostril and DNA alone to the other nostril in a randomized, double-blind study. Electrophysiologic measurements showed that DNA-lipid complexes partially corrected the Cl- transport defect. Importantly, the pCF1-CFTR plasmid alone was at least as effective as complexes of DNA with lipid. Measurements of vector-specific CFTR transcripts also showed gene transfer with both DNA-lipid and DNA alone. These results indicate that nonviral vectors can transfer CFTR cDNA to airway epithelia and at least partially restore the Cl- transport defect characteristic of CF. However, improvements in the overall efficacy of gene transfer are required to develop a treatment for CF.

Hypoxia and beta 2-agonists regulate cell surface expression of the epithelial sodium channel in native alveolar epithelial cells

Alveolar hypoxia may impair sodium-dependent alveolar fluid transport and induce pulmonary edema in rat and human lung, an effect that can be prevented by the inhalation of beta(2)-agonists. To investigate the mechanism of beta(2)-agonist-mediated stimulation of sodium transport under conditions of moderate hypoxia, we examined the effect of terbutaline on epithelial sodium channel (ENaC) expression and activity in cultured rat alveolar epithelial type II cells exposed to 3% O(2) for 24 h. Hypoxia reduced transepithelial sodium current and amiloride-sensitive sodium channel activity without decreasing ENaC subunit mRNA or protein levels. The functional decrease was associated with reduced abundance of ENaC subunits (especially beta and gamma) in the apical membrane of hypoxic cells, as quantified by biotinylation. cAMP stimulation with terbutaline reversed the hypoxia-induced decrease in transepithelial sodium transport by stimulating sodium channel activity and markedly increased the abundance of beta-and gamma-ENaC in the plasma membrane of hypoxic cells. The effect of terbutaline was prevented by brefeldin A, a blocker of anterograde transport. These novel results establish that hypoxia-induced inhibition of amiloride-sensitive sodium channel activity is mediated by decreased apical expression of ENaC subunits and that beta(2)-agonists reverse this effect by enhancing the insertion of ENaC subunits into the membrane of hypoxic alveolar epithelial cells.

Beta2-adrenoceptors facilitating noradrenaline secretion from human vasoconstrictor nerves

Isolated biopsy specimens of human peripheral arteries and veins, preincubated with 3H-(-)- noradrenaline (NA) to label the neural stores of NA, were used to study the Beta-adrenoceptors previously found to increase the secretion of 3H-NA evoked by electrical field stimulation of the adrenergic nerves of this tissue. The increase in nerve stimulation induced secretion of 3H-NA caused by 0.04 muM isoprenaline was prevented by 1 muM propranolol. This beta-blocking drug by itself slightly but significantly depressed the secretion of 3H-NA caused by nerve stimulation in the absence of isoprenaline. While the secretion of 3H-NA was not affected by known beta1-agonists, it was dose-dependently and reversibly increased by two different beta2-agonists. The effect of isoprenaline on 3H-NA secretion was not altered by a selective beta1-antagonist, but strongly reduced or abolished by a beta2-blocking drug. The results indicate that the beta-adrenoceptors involved in the control of NA secretion from the vasoconstrictor nerves of human omental blood vessels are only to a minimal extent stimulated by NA secreted from the nerves, and therefore do probably not mainly serve to mediate local positive feedback control of transmitter secretion; the receptors appear to be beta2 in nature.

Alpha- and beta-adrenergic receptor subtypes properties, distribution and regulation

The effects of catecholamines in the central and peripheral nervous systems appear to be mediated through interactions with 2 major classes of receptor: alpha-adrenoceptors and beta-adrenoceptors. Subtypes of both alpha- and beta-adrenoceptors exist. In the periphery, alpha 1-receptors are located postsynaptically, mediating the excitatory effects of catecholamines at alpha-receptors. alpha 2-Adrenoceptors, on the other hand, are autoreceptors involved in the regulation of noradrenaline (norepinephrine) release. In the central nervous system, both alpha 1- and alpha 2-receptors exist on postsynaptic cells; there are also 2 principal subtypes of beta-adrenoceptors. beta 1-Receptors have a high affinity for both noradrenaline and adrenaline (epinephrine) and are found in the heart, brain, and adipose tissue. beta 2-Receptors have a low affinity for noradrenaline and are involved in mediation of relaxation of vascular and other smooth muscles and in many of the metabolic effects of catecholamines. A variety of effector systems have been implicated in the actions of catecholamines. Most, though not all, of the effects of catecholamines at beta-receptors are mediated through activation of adenyl cyclase and increases in cyclic AMP accumulation. The effects of catecholamines at alpha-receptors generally involve other second messenger systems. Thus, in at least some systems, stimulation of alpha 1-adrenoceptors mediates increases in phosphoinositide breakdown, while alpha 2-adrenoceptors appear to act through inhibition of adenyl cyclase activity. The pharmacological effects of alpha- and beta-adrenoceptors were initially characterised by measuring responses observed in intact preparations. The advent of the use of radioligand binding techniques has allowed direct approaches to the characterisation of receptor properties. The use of radioligands makes it possible to determine the affinities of receptors for specific ligands, and it is possible to determine the density of receptors in a tissue. Finally, in vitro assays serve as a means through which receptors can be followed during solubilisation, isolation, and reconstitution. Several ligands are now available for the study of alpha- and beta-adrenoceptors. In general, relatively selective radioligands are available for the study of alpha-receptors. Thus, 3H-WB 4101 and 3H-prazosin are selective ligands for alpha 1-receptors; the ligand 125I-IBE 2254 also shows high selectivity for alpha 1-receptors. 3H-Yohimbine and 3H-rauwolscine are selective antagonists for the labelling of alpha 2-receptors and 3H-clonidine is a selective agonist used for studying alpha 2-receptors.(ABSTRACT TRUNCATED AT 400 WORDS)

In situ assessment of the role of the beta 1-, beta 2- and beta 3-adrenoceptors in the control of lipolysis and nutritive blood flow in human subcutaneous adipose tissue

1. The involvement of beta 1-, beta 2- and beta 3-adrenoceptors in the control of lipolysis and nutritive blood flow was investigated in abdominal subcutaneous adipose tissue of healthy young adults by use of an in situ microdialysis technique. 2. Dialysis probes were infused either with isoprenaline (non-selective beta-adrenoceptor agonist), CGP 12,177 (selective beta 3-adrenoceptor agonist having beta 1-/beta 2-antagonist properties), dobutamine (selective beta 1-adrenoceptor agonist) or terbutaline (selective beta 2-adrenoceptor agonist). The recovery of each probe used for perfusion was calculated by an in vivo calibration method. The local blood flow was estimated through the measurement of the escape of ethanol infused simultaneously with the drugs included in the probe. 3. Isoprenaline infusion at 0.01 microM had a weak effect while higher concentrations of isoprenaline (0.1 and 1 microM) caused a rapid, sustained and concentration-dependent increase of glycerol outflow; the maximum increase was 306 +/- 34% with 1 microM. Isoprenaline also increased the nutritive blood flow in adipose tissue; a significant effect appeared at 0.1 microM isoprenaline and was greater at 1 microM. 4. CGP 12,177 (10 and 100 microM) increased the glycerol concentration in the dialysate (128 +/- 8 and 149 +/- 12%, respectively) and nutritive blood flow. Terbutaline and dobutamine (100 microM) both provoked rapid and similar increases in glycerol outflow (252 +/- 18 and 249 +/- 18%, respectively). Both, terbutaline and dobutamine increased nutritive blood flow. 5. It is concluded that beta 1- and beta 2-adrenoceptor subtypes are both mainly involved in the mobilization of lipids and in the control of nutritive blood flow. beta 3-Adrenoceptors play a weaker role in the control of lipolysis and nutritive blood flow in human subcutaneous abdominal adipose tissue.

Clinical interpretation of airway response to a bronchodilator. Epidemiologic considerations

Airways responsiveness to a bronchodilator is frequently measured to assist in determining the cause of respiratory symptoms. Clinically, a greater than 15% improvement in the FEV1 is often used to define the "increased" response indicative of asthma. However, unlike other tests of lung function, reference standards derived from "healthy" members of a general population sample have never been reported. As part of a health survey carried out in Alberta, Canada, 2,609 subjects completed a standardized respiratory symptom questionnaire and had FEV1 measured before and 20 min after inhaling terbutaline sulfate via a 750-ml spacer device. Among asymptomatic never-smoking subjects with a FEV1 greater than 80% of predicted, the upper 95th percentile of bronchodilator response (BDR), when expressed as 100 x (FEV1 postBDR - FEV1 preBDR)/predicted baseline FEV1 averaged 9%. This value remained remarkably stable across gender, age (7 to 75 yr), and height groups, and deviated to 6% only when baseline FEV1 was greater than 120% of predicted. Consistent with other respiratory function variables, in which the upper limit of normal is often defined as the upper 95th percentile, our population-derived reference values provide a conceptual definition of BDR that can easily be applied to define "increased" response in the clinical setting.

Effect of terbutaline on premature labor. A double-blind placebo-controlled study

The effect of terbutaline, a "selective" beta2-receptor stimulator, was compared with that of placebo in 30 patients in premature labor. Treatment consisted of an intravenous infusion for at least 8 hours, and then of subcutaneous injections four times daily for 3 days together with peroral treatment, which was continued until the end of week 36 of pregnancy. In 12 of 15 terbutaline-treated patients (80 per cent) premature labor was arrested beyond the treatment period, compared with three of 15 in the placebo group (20 per cent). This difference is statistically significant (p less than 0.01). No serious side effects were observed. During infusion, there was an increase in maternal heart rate. This was more pronounced in the terbutaline group (30 per cent) than in the placebo group (9 per cent). There were no adverse effects on blood pressure, but fetal tachycardia was observed more frequently in the terbutaline than in the placebo group. The results suggest that terbutaline is a safe, potent, and well-tolerated inhibitor of premature labor.