Inhibition Of Β-adrenergic Receptors Research Articles

A fixed 20:1 combination of cafedrine/theodrenaline increases cytosolic Ca2+ concentration in human tracheal epithelial cells via ryanodine receptor-mediated Ca2+ release

Mucociliary clearance is a pivotal physiological mechanism that protects the lung by cleaning the airways from pollution and colonization, thereby preventing infection. Ciliary function is influenced by various signal transduction cascades, and Ca2+ represents a key second messenger. A fixed 20:1 combination of cafedrine and theodrenaline has been widely used to treat perioperative hypotension and emergency hypotensive states since the 1960s; however, its effect on the intracellular Ca2+ concentration ([Ca2+]i) of respiratory epithelium remains unknown. Therefore, human tracheal epithelial cells were exposed to the clinically applied 20:1 mixture of cafedrine/theodrenaline and the individual substances separately. [Ca2+]i was assessed by FURA-2 340/380 fluorescence ratio. Pharmacological inhibitors were applied to elucidate relevant signal transduction cascades, and reverse transcription polymerase chain reaction (RT-PCR) was performed on murine tracheal epithelium to analyze ryanodine receptor (RyR) subtype expression. All three pharmacological preparations instantaneously induced a steep increase in [Ca2+]i that quickly returned to its baseline value despite the persistence of each substance. Peak [Ca2+]i following the administration of 20:1 cafedrine/theodrenaline, cafedrine alone, and theodrenaline alone increased in a dose-dependent manner, with median effective concentrations of 0.35 mM (7.32 mM cafedrine and 0.35 mM theodrenaline), 3.14 mM, and 3.45 mM, respectively. When extracellular Ca2+ influx was inhibited using a Ca2+-free buffer solution, the peak [Ca2+]i following the administration of cafedrine alone and theodrenaline alone were reduced but not abolished. No alteration in [Ca2+]i compared with baseline [Ca2+]i was observed during β-adrenergic receptor inhibition. Depletion of caffeine-sensitive stores and inhibition of RyR, but not IP3 receptors, completely abolished any increase in [Ca2+]i. However, [Ca2+]i still increased following the depletion of mitochondrial Ca2+ stores using 2,4-dinitrophenol. RT-PCR revealed RyR-2 and RyR-3 expression on murine tracheal epithelium. Although our experiments showed that cafedrine/theodrenaline, cafedrine alone, or theodrenaline alone release Ca2+ from intracellular stores through mechanisms that are exclusively triggered by β-adrenergic receptor stimulation, which most probably lead to RyR activation, clinical plasma concentrations are considerably lower than those used in our experiments to elicit an increase in [Ca2+]i; therefore, further studies are needed to evaluate the ability of cafedrine/theodrenaline to alter mucociliary clearance in clinical practice.

A 20:1 synergetic mixture of cafedrine/theodrenaline accelerates particle transport velocity in murine tracheal epithelium via IP3 receptor-associated calcium release.

Background: Mucociliary clearance is a pivotal physiological mechanism that protects the lung by ridding the lower airways of pollution and colonization by pathogens, thereby preventing infections. The fixed 20:1 combination of cafedrine and theodrenaline has been used to treat perioperative hypotension or hypotensive states due to emergency situations since the 1960s. Because mucociliary clearance is impaired during mechanical ventilation and critical illness, the present study aimed to evaluate the influence of cafedrine/theodrenaline on mucociliary clearance. Material and Methods: The particle transport velocity (PTV) of murine trachea preparations was measured as a surrogate for mucociliary clearance under the influence of cafedrine/theodrenaline, cafedrine alone, and theodrenaline alone. Inhibitory substances were applied to elucidate relevant signal transduction cascades. Results: All three applications of the combination of cafedrine/theodrenaline, cafedrine alone, or theodrenaline alone induced a sharp increase in PTV in a concentration-dependent manner with median effective concentrations of 0.46µM (consisting of 9.6µM cafedrine and 0.46µM theodrenaline), 408 and 4μM, respectively. The signal transduction cascades were similar for the effects of both cafedrine and theodrenaline at the murine respiratory epithelium. While PTV remained at its baseline value after non-selective inhibition of β-adrenergic receptors and selective inhibition of β1 receptors, cafedrine/theodrenaline, cafedrine alone, or theodrenaline alone increased PTV despite the inhibition of the protein kinase A. However, IP3 receptor activation was found to be the pivotal mechanism leading to the increase in murine PTV, which was abolished when IP3 receptors were inhibited. Depleting intracellular calcium stores with caffeine confirmed calcium as another crucial messenger altering the PTV after the application of cafedrine/theodrenaline. Discussion: Cafedrine/theodrenaline, cafedrine alone, and theodrenaline alone exert their effects via IP3 receptor-associated calcium release that is ultimately triggered by β1-adrenergic receptor stimulation. Synergistic effects at the β1-adrenergic receptor are highly relevant to alter the PTV of the respiratory epithelium at clinically relevant concentrations. Further investigations are needed to assess the value of cafedrine/theodrenaline-mediated alterations in mucociliary function in clinical practice.

Sympathetic improvement of cancer vaccine efficacy

ABSTRACT The link between stress, other psychological factors and response to cancer, or even the cancer incidence and metastasis, is well established. The inhibition of β-Adrenergic receptors (β-AR) using β-blockers was demonstrated to have an inhibitory effect on cancer recurrence. Direct effects on the stress-induced suppression of anti-tumor immune responses were also shown. In a recent issue of Cancer Immunology Research, Daher and colleagues studied the molecular mechanism behind this protective effect in the context of cancer vaccination. They provided evidence that the β-AR signaling affected the priming of naïve CD8 + T cells in their myeloma model, rather than effector CD8 + T cells which downregulated the expression of β-AR after activation and became insensitive to such signaling. Blocking the β-adrenergic signaling during vaccination led to increased expansion and effector functions of antigen-specific CD8 + T cells and reduced tumor growth. This has implications for the clinical use of β-blockers as adjuvants to enhance cancer vaccination and other types of immunotherapy.

Endothelium-independent and calcium channel-dependent relaxation of the porcine cerebral artery by different species and strains of turmeric

ObjectiveTo clarify the underlying mechanism of turmeric, which is traditionally used as a medicinal plant for the treatment of cardiovascular disorders, such as hypertension, and palpitations. MethodsMethanol extracts of different turmeric were used. A tissue-organ-bath system was used to investigate the vasoactive effects of methanol extracts from 5 kinds of turmeric on isolated porcine basilar arteries. The arterial rings were suspended in physiological solution that was maintained at 37 °C temperature with a continuous supply of 95% O2 and 5% CO2. ResultsAll turmeric extracts (20–800 μg/mL) induced concentration-dependent relaxation of the isolated porcine basilar artery pre-contracted with U46619 (1-5 × 10−9 M) in arterial rings with or without endothelium. There were no significant differences in the relaxation induced by different turmeric or between the endothelium-intact and denuded arteries. In depolarized, Ca2+-free medium, the turmeric extracts inhibited CaCl2-induced contractions and caused a concentration-dependent rightward shift of the response curves. In addition, propranolol (a non-specific β-adrenoceptor antagonist) slightly inhibited the relaxation induced by turmeric. In contrast, Nω-nitro-l-arginine, indomethacin, tetraethylammonium, glibenclamide and 4-aminopyridine did not affect turmeric-induced relaxation. ConclusionThese results demonstrated that turmeric induced endothelium-independent relaxation of the porcine basilar artery, which may be due to the inhibition of extracellular and intracellular Ca2+ receptors and the partial inhibition of β-adrenergic receptors in vascular smooth muscle cells.

β-Adrenergic receptor inhibition affects cerebral glucose metabolism, motor performance, and inflammatory response after traumatic brain injury

The purpose of this study was to evaluate how β-adrenergic receptor inhibition after traumatic brain injury (TBI) alters changes in early cerebral glucose metabolism and motor performance, as well as cerebral cytokine and heat shock protein (HSP) expression. Mouse cerebral glucose metabolism was measured by microPET fluorodeoxyglucose uptake and converted into standardized uptake values (SUV). Four groups of C57/Bl6 mice (wild type [WT]) were initially evaluated: sham or TBI, followed by tail vein injection of either saline or a nonselective β-adrenergic receptor inhibitor (propranolol, 4 mg/kg). Then motor performance, cerebral cytokine, and HSP70 expression were studied at 12 hours and 24 hours after sham injury or TBI in WT mice treated with saline or propranolol and in β1-adrenergic/β2-adrenergic receptor knockout (BARKO) mice treated with saline. Cerebral glucose metabolism was significantly reduced after TBI (mean SUV TBI, 1.63 vs. sham 1.97, p < 0.01) and propranolol attenuated this reduction (mean SUV propranolol, 1.89 vs. saline 1.63, p < 0.01). Both propranolol and BARKO reduced motor deficits at 24 hours after injury, but only BARKO had an effect at 12 hours after injury. TBI WT mice treated with saline performed worse than propranolol mice at 24 hours after injury on rotarod (23 vs. 44 seconds, p < 0.01) and rearing (130 vs. 338 events, p = 0.01) results. At 24 hours after injury, sham BARKO and TBI BARKO mice were similar on rotarod (21 vs. 19 seconds, p = 0.53), ambulatory testing (2,891 vs. 2,274 events, p = 0.14), and rearing (129 vs. 64 events, p = 0.09) results. Interleukin 1β expression was affected by BARKO and propranolol after TBI; attenuation of interleukin 6 and increased HSP70 expression were noted only with BARKO. β-adrenergic receptor inhibition affects cerebral glucose metabolism, motor performance, as well as cerebral cytokine and HSP expression after TBI.

Propranolol Inhibition of β-Adrenergic Receptor Does Not Suppress Pathologic Neovascularization in Oxygen-Induced Retinopathy

Retinopathy of prematurity (ROP) is a leading cause of blindness in children and is, in its most severe form, characterized by uncontrolled growth of vision-threatening pathologic vessels. Propranolol, a nonselective β-adrenergic receptor blocker, was reported to protect against pathologic retinal neovascularization in a mouse model of oxygen-induced retinopathy (OIR). Based on this single animal study using nonstandard evaluation of retinopathy, clinical trials are currently ongoing to evaluate propranolol treatment in stage 2 ROP patients who tend to experience spontaneous disease regression and are at low risk of blindness. Because these ROP patients are vulnerable premature infants who are still in a fragile state of incomplete development, the efficacy of propranolol treatment in retinopathy needs to be evaluated thoroughly in preclinical animal models of retinopathy and potential benefits weighed against potential adverse effects. Retinopathy was induced by exposing neonatal mice to 75% oxygen from postnatal day (P) 7 to P12. Three routes of propranolol treatment were assessed from P12 to P16: oral gavage, intraperitoneal injection, or subcutaneous injection, with doses varying between 2 and 60 mg/kg/day. At P17, retinal flatmounts were stained with isolectin and quantified with a standard protocol to measure vasoobliteration and pathologic neovascularization. Retinal gene expression was analyzed with qRT-PCR using RNA isolated from retinas of control and propranolol-treated pups. None of the treatment approaches at any dose of propranolol (up to 60 mg/kg/day) were effective in preventing the development of retinopathy in a mouse model of OIR, evaluated using standard techniques. Propranolol treatment also did not change retinal expression of angiogenic factors including vascular endothelial growth factor. Propranolol treatment via three routes and up to 30 times the standard human dose failed to suppress retinopathy development in mice. These data bring into question whether propranolol through inhibition of β-adrenergic receptors is an appropriate therapeutic approach for treating ROP.

Spasmolytic Effects of Aqueous Extract of Mixture from Aframomumum Melegueta (K Schum) – Citrus Aurantifolia (Christm and Panzer) on Isolated Trachea from Rat

The spasmolytic properties of the aqueous extract of Aframomum melegueta (K Schum) and Citrus aurantifolia (Christm and Panzer) (AMCA) mixture were tested on isolated rat trachea. Inhibition of the contraction was observed the in presence of the AMCA (EC 50 = 1.80 ± 0.48 mg/mL) after a pre contraction of the trachea by acetylcholine (10⁻⁵ M). With propranolol (10⁻⁶ M), the spasmolytic activity of the mixture was inhibited and the concentration-response curve shifted to the right. The EC50 value was then 2.60 ± 0.41 mg/mL. AMCA also inhibited contraction induced by KCl (4.10⁻² M) with EC50 value = 1.86 ± 0.65 mg/mL. These results clearly show the relaxing effect of the aqueous extract on the isolated rat trachea. This effect involved some β-adrenergic receptor inhibition.

Inhibition of β-Adrenergic Receptors Induces a Persistent Deficit in Retrieval of a Cocaine-Associated Memory Providing Protection against Reinstatement

Drug-seeking behavior is maintained by encounters with drug-associated cues. Preventing retrieval of drug-associated memories that these cues provoke would therefore limit relapse susceptibility; however, little is known regarding the mechanisms of retrieval. Here, we show that β-adrenergic receptor activation is necessary for the retrieval of a cocaine-associated memory. Using a conditioned place preference (CPP) procedure, rats were conditioned to associate one chamber, but not another, with cocaine. When administered before a CPP trial, propranolol, but not saline, prevented retrieval of a cocaine-associated CPP. In subsequent drug-free trials, rats previously treated with propranolol continued to show a retrieval deficit, as no CPP was evident. This retrieval deficit was long lasting and robust, as the CPP did not re-emerge during a test for spontaneous recovery 14 days later or reinstate following a priming injection of cocaine. Moreover, the peripheral β-adrenergic receptor antagonist sotalol did not affect retrieval. Thus, retrieval of cocaine-associated memories is mediated by norepinephrine acting at central β-adrenergic receptors. Our findings support the use of propranolol, a commonly prescribed β-blocker, as an adjunct to exposure therapy for the treatment of addiction by preventing retrieval of drug-associated memories during and long after treatment, and by providing protection against relapse.

Beta-Adrenergic Stimulation Contributes to Maintenance of Endothelial Barrier Functions Under Baseline Conditions

cAMP signaling within the endothelium is known to reduce paracellular permeability and to protect against loss of barrier functions under various pathological conditions. Because activation of β-adrenergic receptors elevates cellular cAMP, we tested whether β-adrenergic receptor signaling contributes to the maintenance of baseline endothelial barrier properties. We compared hydraulic conductivity of rat postcapillary venules in vivo with resistance measurements and with reorganization of endothelial adherens junctions in cultured microvascular endothelial cells downstream of β-adrenergic receptor-mediated changes of cAMP levels. Inhibition of β-adrenergic receptors by propranolol increased hydraulic conductivity, reduced both cAMP levels and TER of microvascular endothelial cell monolayers and induced fragmentation of VE-cadherin staining. In contrast, activation by epinephrine both increased cAMP levels and TER and resulted in linearized VE-cadherin distribution, however this was not sufficient to block barrier-destabilization by propranolol. Similarly, PDE inhibition did not prevent propranolol-induced TER reduction and VE-cadherin reorganization whereas increased cAMP formation by AC activation enhanced endothelial barrier functions under baseline conditions and under conditions of propranolol treatment. Our results indicate that generation of cAMP mediated by activation of β-adrenergic receptor signaling contributes to the maintenance of endothelial barrier properties under baseline conditions.

Nitric oxide-mediated vasodilation becomes independent of β-adrenergic receptor activation with increased intensity of hypoxic exercise

Hypoxic vasodilation in skeletal muscle at rest is known to include β-adrenergic receptor-stimulated nitric oxide (NO) release. We previously reported that the augmented skeletal muscle vasodilation during mild hypoxic forearm exercise includes β-adrenergic mechanisms. However, it is unclear whether a β-adrenergic receptor-stimulated NO component exists during hypoxic exercise. We hypothesized that NO-mediated vasodilation becomes independent of β-adrenergic receptor activation with increased exercise intensity during hypoxic exercise. Ten subjects (7 men, 3 women; 23 ± 1 yr) breathed hypoxic gas to titrate arterial O(2) saturation to 80% while remaining normocapnic. Subjects performed two consecutive bouts of incremental rhythmic forearm exercise (10% and 20% of maximum) with local administration (via a brachial artery catheter) of propranolol (β-adrenergic receptor inhibition) alone and with the combination of propranolol and nitric oxide synthase inhibition [N(G)-monomethyl-l-arginine (l-NMMA)] under normoxic and hypoxic conditions. Forearm blood flow (FBF, ml/min; Doppler ultrasound) and blood pressure [mean arterial pressure (MAP), mmHg; brachial artery catheter] were assessed, and forearm vascular conductance (FVC, ml·min(-1)·100 mmHg(-1)) was calculated (FBF/MAP). During propranolol alone, the rise in FVC (Δ from normoxic baseline) due to hypoxic exercise was 217 ± 29 and 415 ± 41 ml·min(-1)·100 mmHg(-1) (10% and 20% of maximum, respectively). Combined propranolol-l-NMMA infusion during hypoxic exercise attenuated ΔFVC at 20% (352 ± 44 ml·min(-1)·100 mmHg(-1); P < 0.001) but not at 10% (202 ± 28 ml·min(-1)·100 mmHg(-1); P = 0.08) of maximum compared with propranolol alone. These data, when integrated with earlier findings, demonstrate that NO contributes to the compensatory vasodilation during mild and moderate hypoxic exercise; a β-adrenergic receptor-stimulated NO component exists during low-intensity hypoxic exercise. However, the source of the NO becomes less dependent on β-adrenergic mechanisms as exercise intensity increases.

Effects of prolonged treatment with .BETA.-adrenoceptor antagonist, carteolol on systemic and regional hemodynamics in stroke-prone spontaneously hypertensive rats.

The present study was designed to determine the regional hemodynamic effects of prolonged beta-adrenergic receptor inhibition in conscious stroke-prone spontaneously hypertensive rats (SHRSP) using a radioactive microsphere method. When the regional blood flow was compared between 10 and 30 weeks of age, the age-related changes in organ blood flow were observed in several organs, i.e., the reduction of flow rate in kidney, adrenal gland and intestines. The reduction of flow rate in these organs contributes strongly to the age-related rise of total peripheral resistance. Carteolol, a beta-adrenoceptor antagonist, was given at a dose of 10 mg/kg/d from 10 to 30 weeks of age. These animals gained more weight than the untreated control SHRSPs, and heart rate was reduced significantly. Blood pressure was not affected. However, the prolonged treatment with carteolol prevented the age-related reduction of the blood flow rate in the kidney, adrenal gland and intestines. Thus, our findings indicate that carteolol had appreciable and beneficial effects on the maintenance of flow rates in the above organs of SHRSP without any change in blood pressure.

The effects of α- or β-adrenergic receptor agonists and antagonists and calcium entry blockers on the spontaneous vasomotion

The effects of systemic injections of vasoactive substances were studied in the microcirculation of the hamster skin fold window preparation, which can be observed without anesthesia, exposure, and acute surgical procedures. The effects were characterized by the continuous measurement of the diameter of the arterial microvessels ranging from 100 to 8 μm. Power spectrum analysis was utilized to determine the frequency and the amplitude of the fundamental component of spontaneous diameter changes. Epinephrine and norepinephrine increased the frequency of vasomotion and reduced mean diameter at low dosages. Phentolamine reduced the frequency of vasomotion and increased mean diameter. Propranolol increased the frequency of vasomotion and did not significantly change mean diameter. Adenosine and verapamil suppressed vasomotion and increased mean diameter. These results are explained by postulating that low-dosage α-adrenergic receptor stimulation facilitates the spontaneous discharge of smooth muscle cells; β-adrenergic receptor stimulation has the opposite effect, whereas β-adrenergic receptor inhibition also enhances the vasomotor effect. Calcium entry blockers abolish the rhythmic discharge. This explanation of the activity of the various substances supports the hypothesis that the spontaneous vasomotion of the arterial microvessels is related to the intrinsic property of smooth muscle cells.

Effects of histamine-sensitizing factor and cortisol on lymphocyte adenyl cyclase responses

Levels of cyclic adenosime monophosphate (cAMP) in lymphocytes are regulated by β-adrenergic agonists and PGE 1. The effect of these agonists is potentiated by cortisol. Incubation of lymphocytes with histamine-sensitizing factor (HSF) leads to loss of response to epinephrine and PGE 1. The response can be partially restored by cortisol. Incubation of lymphocytes with β-adrenergic antagonists such as propranolol leads to the loss of β-adrenergic agents but not PGE 1 The inhibition by propranolol is not reversed by cortisol. These results suggest that the action of HSF and Bordetella pertussis vaccine is not mediated through the inhibition of β-adrenergic receptors alone.