Sex specific effects of the fatty acid amide hydrolase inhibitor URB597 on memory and brain β2-adrenergic and D1-dopamine receptors

An increasing body of evidence shows significant sex differences in the mammalian brain in multiple behaviours and psychiatric and neurological diseases and as well as that the endocannabinoid system may differ between males and females. In this study we investigated sex differences in working, short-term and long-term memory and the expression of β₂-adrenergic and D1- and D2-receptors in the mPFC and hippocampus, brain regions that are involved in stress response and memory modulation in rats exposed to the chronic unpredictable stress (CUS) and the potential beneficial effects of the chronic fatty acid amide hydrolase inhibitor URB597 treatment. Chronically stressed male rats had an improvement of working memory, while stressed females showed very low object-recognition abilities. On the other hand, animals of both sexes exhibited long-term memory impairment. Our results showed that CUS decreased the expression of β₂-adrenoceptors in the mPFC and D1 receptors in the mPFC and hippocampus of male rats and decreased β₂-adrenoceptors and D1- receptors in the hippocampus of female. URB597 treatment had a positive effect on the short-term memory of stressed animals of both sexes whereas failed to restore long-term memory and did not affect the protein levels β2-adrenoceptors and D1 receptors in the hippocampus of CUS female rats. The present results support that endocannabinoids induced long-term memory and neurochemical alternations which are sex dependent, suggesting sex specific treatment strategies of mental disorders.

Downregulation of connexin43 potentiates noradrenaline-induced expression of brain-derived neurotrophic factor in primary cultured cortical astrocytes

Decreased expression of brain-derived neurotrophic factor (BDNF) is involved in the pathology of depressive disorders. Astrocytes produce BDNF following antidepressant treatment or stimulation of adrenergic receptors. Connexin43 (Cx43) is mainly expressed in central nervous system astrocytes and its expression is downregulated in patients with major depression. How changes in Cx43 expression affect astrocyte function, including BDNF production, is poorly understood. The current study examined the effect of Cx43 knockdown on BDNF expression in cultured cortical astrocytes after stimulation of adrenergic receptors. The expression of Cx43 in rat primary cultured cortical astrocytes was downregulated with RNA interference. Levels of messenger RNAs (mRNAs) or proteins were measured by real-time PCR and western blotting, respectively. Knockdown of Cx43 potentiated noradrenaline (NA)-induced expression of BDNF mRNA in cultured astrocytes. NA treatment induced proBDNF protein expression in astrocytes transfected with small interfering RNA (siRNA) targeting Cx43, but not with control siRNA. This potentiation was mediated by the Src tyrosine kinase-extracellular signal-regulated kinase (ERK) pathway through stimulation of adrenergic α1 and β receptors. Furthermore, the Gq/11 protein-Src-ERK pathway and the G-protein coupled receptor kinase 2-Src-ERK pathway were involved in α1 and β adrenergic receptor-mediated potentiation of BDNF mRNA expression, respectively. The current studies demonstrate a novel mechanism of BDNF expression in cortical astrocytes mediated by Cx43, in which downregulation of Cx43 increases, through adrenergic receptors, the expression of BDNF. The current findings indicate a potentially novel mechanism of action of antidepressants, via regulation of astrocytic Cx43 expression and subsequent BDNF expression.

Rosuvastatin Reduces L-Type Ca2+ Current and Alters Contractile Function in Cardiac Myocytes via Modulation of β-Adrenergic Receptor Signaling

Rosuvastatin is one of the most used statins to lower plasma cholesterol levels. Although previous studies have reported remarkable cardiovascular effects of rosuvastatin (RSV), the mechanisms of these effects are largely unknown. In this study, we investigated the acute effects of RSV on L-type Ca2+ currents and contractile function of ventricular myocytes under basal conditions and during β-adrenergic stimulation. The effects of RSV were investigated in freshly isolated adult rat ventricular myocytes. L-type Ca+2 currents and myocyte contractility were recorded using patch-clamp amplifier and sarcomere length detection system. All experimental recordings were performed at 36 ± 1 °C. L-type Ca+2 currents were significantly reduced with the administration of 1 μM RSV (~ 24%) and this reduction in Ca2+ currents was observed at almost all potential ranges applied. Suppression of L-type Ca2+ current by RSV was prevented by adenylyl cyclase (AC) and protein kinase A (PKA) inhibitors SQ 22536 and KT5720, respectively. However, inhibition of Rho-associated kinases (ROCKs) by Y-27632 or nitric oxide synthase (NOS) by L-NAME failed to circumvent the inhibitory effect of RSV. Finally, we examined the effect of RSV during β-adrenergic receptor stimulation by isoproterenol and observed that RSV significantly suppresses the β-adrenergic responses in both L-type Ca2+ currents and contraction parameters. In conclusion, RSV modulates the β-adrenergic signaling cascade and thereby mimics the impact of β-adrenergic receptor blockers in adult ventricular myocytes through modulation of the AC-cAMP-PKA pathway.

Characterization and functional analysis of a β-adrenergic-like octopamine receptor from the oriental armyworm (Mythimna separata Walker)

The β-adrenergic-like octopamine receptor (OA2B2), which binds the biogenic amine octopamine, belongs to the class of G-protein coupled receptors and significantly regulates many physiological and behavioral processes in insects. In this study, the putative open reading frame sequence of the MsOA2B2 gene in Mythimna separata was cloned, the full-length complementary DNA was 1191 bp and it encoded a 396-amino acid protein (GenBank accession number MN822800). Orthologous sequence alignment, phylogenetic tree analysis, and protein sequence analysis all showed that the cloned receptor belongs to the OA2B2 protein family. Real-time quantitative polymerase chain reaction of spatial and temporal expression analysis revealed that the MsOAB2 gene was expressed in all developmental stages of M. separata and was most abundant in egg stages and second and fourth instars compared with other developmental stages, while the expression level during the pupal stage was much lower than that at the other stages. Further analysis with sixth instar M. separata larvae showed that the MsOA2B2 gene was expressed 1.81 times higher in the head than in integument and gut tissues. Dietary ingestion of dsMsOA2B2 significantly reduced the messenger RNA level of MsOA2B2 and decreased mortality following amitraz treatment. This study provides both a pharmacological characterization and the gene expression patterns of OA2B2 in M. separata, facilitating further research for insecticides using MsOA2B2 as a target.

Choosing among β-blockers in heart failure patients according to β-receptors' location and functions in the cardiopulmonary system

Several large clinical trials showed a favorable effect of β-blocker treatment in patients with chronic heart failure (HF) as regards overall mortality, cardiovascular mortality, and hospitalizations. Indeed, the use of β-blockers is strongly recommended by current international guidelines, and it remains a cornerstone in the pharmacological treatment of HF. Although different types of β-blockers are currently approved for HF therapy, possible criteria to choose the best β-blocking agent according to HF patients' characteristics and to β-receptors' location and functions in the cardiopulmonary system are still lacking. In such a context, a growing body of literature shows remarkable differences between β-blocker types (β1-selective blockers versus β1-β2 blockers) with respect to alveolar-capillary gas diffusion and chemoreceptor response in HF patients, both factors able to impact on quality of life and, most likely, on prognosis. This review suggests an original algorithm for choosing among the currently available β-blocking agents based on the knowledge of cardiopulmonary pathophysiology. Particularly, starting from lung physiology and from some experimental models, it focuses on the mechanisms underlying lung mechanics, chemoreceptors, and alveolar-capillary unit impairment in HF. This paper also remarks the significant benefit deriving from the correct use of the different β-blockers in HF patients through a brief overview of the most important clinical trials.

G protein-coupled receptor kinase 2 regulates mitochondrial bioenergetics and impairs myostatin-mediated autophagy in muscle cells

G protein-coupled receptor kinase 2 (GRK2) is an important protein involved in β-adrenergic receptor desensitization. In addition, studies have shown GRK2 can modulate different metabolic processes in the cell. For instance, GRK2 has been recently shown to promote mitochondrial biogenesis and increase ATP production. However, the role of GRK2 in skeletal muscle and the signaling mechanisms that regulate GRK2 remain poorly understood. Myostatin is a well-known myokine that has been shown to impair mitochondria function. Here, we have assessed the role of myostatin in regulating GRK2 and the subsequent downstream effect of myostatin regulation of GRK2 on mitochondrial respiration in skeletal muscle. Myostatin treatment promoted the loss of GRK2 protein in myoblasts and myotubes in a time- and dose-dependent manner, which we suggest was through enhanced ubiquitin-mediated protein loss, as treatment with proteasome inhibitors partially rescued myostatin-mediated loss of GRK2 protein. To evaluate the effects of GRK2 on mitochondrial respiration, we generated stable myoblast lines that overexpress GRK2. Stable overexpression of GRK2 resulted in increased mitochondrial content and enhanced mitochondrial/oxidative respiration. Interestingly, although overexpression of GRK2 was unable to prevent myostatin-mediated impairment of mitochondrial respiratory function, elevated levels of GRK2 blocked the increased autophagic flux observed following treatment with myostatin. Overall, our data suggest a novel role for GRK2 in regulating mitochondria mass and mitochondrial respiration in skeletal muscle.

Activation of NPRs and UCP1-independent pathway following CB1R antagonist treatment is associated with adipose tissue beiging in fat-fed male dogs

CB1 receptor (CB1R) antagonism improves the deleterious effects of a high-fat diet (HFD) by reducing body fat mass and adipocyte cell size. Previous studies demonstrated that the beneficial effects of the CB1R antagonist rimonabant (RIM) in white adipose tissue (WAT) are partially due to an increase of mitochondria numbers and upregulation thermogenesis markers, suggesting an induction of WAT beiging. However, the molecular mechanism by which CB1R antagonism induces weight loss and WAT beiging is unclear. In this study, we probed for genes associated with beiging and explored longitudinal molecular mechanisms by which the beiging process occurs. HFD dogs received either RIM (HFD+RIM) or placebo (PL) (HFD+PL) for 16 wk. Several genes involved in beiging were increased in HFD+RIM compared with pre-fat, HFD, and HFD+PL. We evaluated lipolysis and its regulators including natriuretic peptide (NP) and its receptors (NPRs), β-1 and β-3 adrenergic receptor (β1R, β3R) genes. These genes were increased in WAT depots, accompanied by an increase in lipolysis in HFD+RIM. In addition, RIM decreased markers of inflammation and increased adiponectin receptors in WAT. We observed a small but significant increase in UCP1; therefore, we evaluated the newly discovered UCP1-independent thermogenesis pathway. We confirmed that SERCA2b and RYR2, the two key genes involved in this pathway, were upregulated in the WAT. Our data suggest that the upregulation of NPRs, β-1R and β-3R, lipolysis, and SERCA2b and RYR2 may be one of the mechanisms by which RIM promotes beiging and overall the improvement of metabolic homeostasis induced by RIM.

Interdependence of hypoxia and β-adrenergic receptor signaling in pulmonary arterial hypertension

The β-adrenergic receptor (βAR) exists in an equilibrium of inactive and active conformational states, which shifts in response to different ligands and results in downstream signaling. In addition to cAMP, βAR signals to hypoxia-inducible factor 1 (HIF-1). We hypothesized that a βAR-active conformation (R**) that leads to HIF-1 is separable from the cAMP-activating conformation (R*) and that pulmonary arterial hypertension (PAH) patients with HIF-biased conformations would not respond to a cAMP agonist. We compared two cAMP agonists, isoproterenol and salbutamol, in vitro. Isoproterenol increased cAMP and HIF-1 activity, while salbutamol increased cAMP and reduced HIF-1. Hypoxia blunted agonist-stimulated cAMP, consistent with receptor equilibrium shifting toward HIF-activating conformations. Similarly, isoproterenol increased HIF-1 and erythropoiesis in mice, while salbutamol decreased erythropoiesis. βAR overexpression in cells increased glycolysis, which was blunted by HIF-1 inhibitors, suggesting increased βAR leads to increased hypoxia-metabolic effects. Because PAH is also characterized by HIF-related glycolytic shift, we dichotomized PAH patients in the Pulmonary Arterial Hypertension Treatment with Carvedilol for Heart Failure trial (NCT01586156) based on right ventricular (RV) glucose uptake to evaluate βAR ligands. Patients with high glucose uptake had more severe disease than those with low uptake. cAMP increased in response to isoproterenol in mononuclear cells from low-uptake patients but not in high-uptake patients' cells. When patients were treated with carvedilol for 1 wk, the low-uptake group decreased RV systolic pressures and pulmonary vascular resistance, but high-uptake patients had no physiologic responses. The findings expand the paradigm of βAR activation and uncover a novel PAH subtype that might benefit from β-blockers.

A requirement for epigenetic modifications during noradrenergic stabilization of heterosynaptic LTP in the hippocampus

Beta-adrenergic receptor (b-AR) activation by noradrenaline (NA) enhances memory formation and long-term potentiation (LTP), a form of synaptic plasticity characterized by an activity-dependent increase in synaptic strength. LTP is believed to be a cellular mechanism for contextual learning and memory. In the mammalian hippocampus, LTP can be observed at multiple synaptic pathways after strong stimulation of a single synaptic pathway. This heterosynaptic LTP is believed to involve synaptic tagging of active synapses and capture of plasticity-related proteins that enable heterosynaptic transfer of persistent potentiation. These processes may permit distinct neural pathways to associate information transmitted by separate, but convergent, synaptic inputs. We had previously shown that transcription and epigenetic modifications were necessary for stabilization of homosynaptic LTP. However, it is unclear whether transfer of LTP to a second, heterosynaptic pathway involves b-ARs signalling to the nucleus. Using electrophysiologic recordings in area CA1 of murine hippocampal slices, we show here that pharmacologically inhibiting b-AR activation, transcription, DNA methyltransferase or histone acetyltransferase activation, prevents stabilization of heterosynaptic LTP. Our data suggest that noradrenergic stabilization of heterosynaptic ("tagged") LTP requires not only transcription, but specifically, DNA methylation and histone acetylation. NA promotes stable heterosynaptic plasticity through engagement of nuclear processes that may contribute to prompt consolidation of short-term memories into resilient long-term memories under conditions when the brain's noradrenergic system is recruited.

Neuropharmacological agents modifying endotoxin-induced changes in mice

A variety of neuropharmacological agents were tested to elucidate how chlorpromazine influenced an endotoxin-induced reaction. The results obtained, particularly with beta-adrenergic blocking agents, reserpine and fusaric acid, suggested that the primary locus of chlorpromazine's action was mediated by peripheral beta-adrenergic receptor blockade. Such a locus is compatible with the low doses of propranolol which suppress the reaction, and with successful treatment of shock with dopamine.

Ghrelin potentiates cardiac reactivity to stress by modulating sympathetic control and beta-adrenergic response

Prior evidence indicates that ghrelin is involved in the integration of cardiovascular functions and behavioral responses. Ghrelin actions are mediated by the growth hormone secretagogue receptor subtype 1a (GHS-R1a), which is expressed in peripheral tissues and central areas involved in the control of cardiovascular responses to stress.

AIMS

In the present study, we assessed the role of ghrelin - GHS-R1a axis in the cardiovascular reactivity to acute emotional stress in rats.

MAIN METHODS AND KEY FINDINGS

Ghrelin potentiated the tachycardia evoked by restraint and air jet stresses, which was reverted by GHS-R1a blockade. Evaluation of the autonomic balance revealed that the sympathetic branch modulates the ghrelin-evoked positive chronotropy. In isolated hearts, the perfusion with ghrelin potentiated the contractile responses caused by stimulation of the beta-adrenergic receptor, without altering the amplitude of the responses evoked by acetylcholine. Experiments in isolated cardiomyocytes revealed that ghrelin amplified the increases in calcium transient changes evoked by isoproterenol.

SIGNIFICANCE

Taken together, our results indicate that the Ghrelin-GHS-R1a axis potentiates the magnitude of stress-evoked tachycardia by modulating the autonomic nervous system and peripheral mechanisms, strongly relying on the activation of cardiac calcium transient and beta-adrenergic receptors.

Calcium/calmodulin-dependent protein kinase II regulation of IKs during sustained β-adrenergic receptor stimulation

BACKGROUND

Sustained β-adrenergic receptor (β-AR) stimulation causes pathophysiological changes during heart failure (HF), including inhibition of the slow component of the delayed rectifier potassium current (I_Ks). Aberrant calcium handling, including increased activation of calcium/calmodulin-dependent protein kinase II (CaMKII), contributes to arrhythmia development during HF.

OBJECTIVE

The purpose of this study was to investigate CaMKII regulation of KCNQ1 (pore-forming subunit of I_Ks) during sustained β-AR stimulation and associated functional implications on I_Ks.

METHODS

KCNQ1 phosphorylation was assessed using liquid chromatography-tandem mass spectrometry after sustained β-AR stimulation with isoproterenol (ISO). Peptide fragments corresponding to KCNQ1 residues were synthesized to identify CaMKII phosphorylation at the identified sites. Dephosphorylated (alanine) and phosphorylated (aspartic acid) mimics were introduced at identified residues. Whole-cell, voltage-clamp experiments were performed in human endothelial kidney 293 cells coexpressing wild-type or mutant KCNQ1 and KCNE1 (auxiliary subunit) during ISO treatment or lentiviral δCaMKII overexpression.

RESULTS

Novel KCNQ1 carboxy-terminal sites were identified with enhanced phosphorylation during sustained β-AR stimulation at T482 and S484. S484 peptides demonstrated the strongest δCaMKII phosphorylation. Sustained β-AR stimulation reduced I_Ks activation (P = .02 vs control) similar to the phosphorylated mimic (P = .62 vs sustained β-AR). Individual phosphorylated mimics at S484 (P = .04) but not at T482 (P = .17) reduced I_Ks function. Treatment with CN21 (CaMKII inhibitor) reversed the reductions in I_Ks vs CN21-Alanine control (P < .01). δCaMKII overexpression reduced I_Ks similar to ISO treatment in wild type (P < .01) but not in the dephosphorylated S484 mimic (P = .99).

CONCLUSION

CaMKII regulates KCNQ1 at S484 during sustained β-AR stimulation to inhibit I_Ks. The ability of CaMKII to inhibit I_Ks may contribute to arrhythmogenicity during HF.

Increased CD11b+ cells and Interleukin-1 (IL-1) alpha levels during cardiomyopathy induced by chronic adrenergic activation

BACKGROUND

Systemic CD11b+ cells have been associated with several cardiac diseases, such as chronic heart failure.

OBJECTIVES

To assess the levels of circulating CD11b+ cells and pro-inflammatory cytokines in cardiomyopathy induced by chronic adrenergic stimulation.

METHODS

Male Lewis rats were injected with low doses of isoproterenol (isoprel) for 3 months. Cardiac parameters were tested by echocardiography. The percentage of CD11b+ cells was tested by flow cytometry. The levels of inflammatory cytokines in the sera were determined by an inflammation array, and the expression levels of cardiac interleukin-1 (IL-1) receptors were analyzed by real-time polymerase chain reactions. Cardiac fibrosis and inflammation were determined by histological analysis.

RESULTS

Chronic isoprel administration resulted in increased heart rate, cardiac hypertrophy, elevated cardiac peri-vascular fibrosis, reduced fractional shortening, and increased heart weight per body weight ratio compared to control animals. This clinical presentation was associated with accumulation of CD11b+ cells in the spleen with no concomitant cardiac inflammation. Cardiac dysfunction was also associated with elevated sera levels of IL-1 alpha and over expression of cardiac IL-1 receptor type 2.

CONCLUSIONS

CD11b+ systemic levels and IL-1 signaling are associated with cardiomyopathy induced by chronic adrenergic stimulation. Further studies are needed to define the role of systemic immunomodulation in this cardiomyopathy.

Effect of Cortisol on Plasma Lactate Levels following Cortisolinduced Hyperglycaemia in Common African Toad, Bufo regularis

Previous studies in man have shown that cortisol induces hyperglycemia through gluconeogenesis. However,the metabolic substrates involved in cortisol-induced hyperglycemia and the role of adrenergic receptors in lactate productionin toads have not been well studied. This study investigated the effects of adrenergic receptor blockers in cortisol-inducedhyperglycemia and blood lactate levels in the common African toad (Bufo regularis). Each toad was fasted and anaesthetizedwith sodium thiopentone given intraperitoneally (50mg/kg/i.p). The animals (control) received 0.7% amphibian saline whileanimals (untreated) received cortisol intravenously (50µg/kg/i.v). In pre-treatment groups, animals received propanolol (0.5mg/kg/i.v), prazosin (0.2 mg/kg/i.v) and combination of propanolol (0.5mg/kg/i.v) and prazosin (0.2 mg/kg/i.v) respectivelyfollowed by administration of cortisol 50µg/kg/i.v. Thereafter, blood samples were collected for estimation of glucose andlactate using the modified glucose oxidase method and colorimetric method respectively. Cortisol caused significant increase in blood glucose level ((p<0.05) and reduction in blood lactate levels. Pre-treatment with Prazosin (0.2 mg/kg/i.v) causedsignificant (p<0.05) increase in blood glucose level and significant reduction in blood lactate levels while pre-treatment withPropanolol (0.5mg/kg/i.v) abolished cortisol-induced hyperglycemia and caused increase in blood lactate levels comparedwith the untreated group. The combination of both blockers abolished the hyperglycemic effect of cortisol and causedincrease in the blood lactate levels. The results of this study show that cortisol-induced hyperglycemia is a consequent ofgluconeogenesis and mediated through the beta-adrenergic receptors. The results also show that lactate is produced andused as a gluconeogenic substrate to induce cortisol hyperglycemia in the Common African toad bufo regularis. The betaadrenergic receptors are involved in the use of lactate to induce cortisol hyperglycemia in the Common African toad Buforegularis.

Glucocorticoids modulate human brown adipose tissue thermogenesis in vivo

INTRODUCTION

Brown adipose tissue (BAT) is a thermogenic organ with substantial metabolic capacity and has important roles in the maintenance of body weight and metabolism. Regulation of BAT is primarily mediated through the β-adrenoceptor (β-AR) pathway. The in vivo endocrine regulation of this pathway in humans is unknown. The objective of our study was to assess the in vivo BAT temperature responses to acute glucocorticoid administration.

METHODS

We studied 8 healthy male volunteers, not pre-selected for BAT presence or activity and without prior BAT cold-activation, on two occasions, following an infusion with hydrocortisone (0.2mg.kg^-1.min^-1 for 14h) and saline, respectively. Infusions were given in a randomized double-blind order. They underwent assessment of supraclavicular BAT temperature using infrared thermography following a mixed meal, and during β-AR stimulation with isoprenaline (25ng.kg fat-free mass^-1.min^-1 for 60min) in the fasting state.

RESULTS

During hydrocortisone infusion, BAT temperature increased both under fasting basal conditions and during β-AR stimulation. We observed a BAT temperature threshold, which was not exceeded despite maximal β-AR activation. We conclude that BAT thermogenesis is present in humans under near-normal conditions. Glucocorticoids modulate BAT function, representing important physiological endocrine regulation of body temperature at times of acute stress.

Classical and novel pharmacological insights offered by the simple chick cardiomyocyte cell culture model: a valuable teaching aid and a primer for "real" research

The chick embryo cardiomyocyte model of cell culture is a staple technique in many physiology and pharmacology laboratories. Despite the relative simplicity, robustness, and reproducibility inherent in this model, it can be used in a variety of ways to yield important new insights that help facilitate student understanding of underlying physiological and pharmacological concepts as well as, more generally, the scientific method. Using this model, this paper will show real data obtained by undergraduate students in the authors' laboratories. It will first demonstrate classical pharmacological concepts such as full and partial agonism, inverse agonism, and competitive reversible antagonism and then move on to more complex pharmacology involving the characterization of novel receptors in these cells.

Antiarrhythmic Action ofβ-Blockers: Potential Mechanisms

Sympathetic nervous system overactivity has been linked to ventricular tachyarrhythmias and sudden death. It has been hypothesized that the extent and nature of the arrhythmogenic effect of sympathetic stimulation depends on the underlying myocardial substrate, the mechanism of the arrhythmia, and the integrated effects of sympathetic stimulation in the particular individual circumstance. Multiple direct and indirect mechanisms of adrenergic action on the heart may benefit from the known antiarrhythmic actions of β-blocker therapy and other interventions that decrease sympathetic tone. The antiarrhythmic mechanism of β-blockade (and possibly α-blockade) will depend on the specific mechanism of the individual arrhythmia and will differ for those arrhythmias caused by tachycardia and ischemia, those caused by reentry and promoted by decreased conduction velocity and shortened refractoriness, and those caused by early or delayed afterdepolarizations, usually in the context of prolonged action potential duration. Antagonism of cardiac adrenergic activity by β-blockade in particular is the best-established drug therapy to prevent ventricular arrhythmias.

The Relationship Between β-Receptor Sensitivity and Nocturnal Blood Pressure and Heart Rate Recovery in Normotensive People

This study examined the relationship between nocturnal blood pressure (BP) dipping and chronotropic dose25 (CD25) as an indicator of β-adrenergic receptor functioning in normotensive people. In addition, the authors evaluated the influence of β-receptor functioning on heart rate recovery after exercise. The sample consisted of 41 participants (18 men, 23 women). Ambulatory BP monitoring took place in each patient's home. On a separate occasion, β-adrenergic receptor sensitivity was determined by response to isoproterenol infusion. Heart rate (HR) recovery was defined as the change from peak HR to that measured after 1 and 2 minutes of recovery. Relationships between dipping and CD25 were found such that participants with higher CD25 values had less nocturnal decline in systolic BP, diastolic BP, and mean arterial pressure ( r =–0.445, –0.533, –0.510, respectively; p<0.004, 0.001, 0.001, respectively). Heart rate recovery at 1 and 2 minutes after exercise was 28.8 ±5 and 49.9 ±6 beats/minute, respectively. Participants with higher CD25 values had more heart rate decline during the first 2 minutes of recovery ( r =0.407, p<0.008). In addition, heart rate recovery was inversely related to systolic, diastolic, and mean nocturnal blood pressure dipping ( r =–0.348, –0.432, –0.408, respectively, p<0.028, 0.005, 0.009, respectively). Normotensive people with an abnormal circadian pattern of blood pressure may have desensitized β-adrenergic receptors. This desensitization may contribute to blunted nocturnal blood pressure and increased heart rate recovery as measured at 2 minutes following exercise testing.

Flow Cytometric Quantification of Peripheral Blood Cell β-Adrenergic Receptor Density and Urinary Endothelial Cell-Derived Microparticles in Pulmonary Arterial Hypertension

Pulmonary arterial hypertension (PAH) is a heterogeneous disease characterized by severe angiogenic remodeling of the pulmonary artery wall and right ventricular hypertrophy. Thus, there is an increasing need for novel biomarkers to dissect disease heterogeneity, and predict treatment response. Although β-adrenergic receptor (βAR) dysfunction is well documented in left heart disease while endothelial cell-derived microparticles (Ec-MPs) are established biomarkers of angiogenic remodeling, methods for easy large clinical cohort analysis of these biomarkers are currently absent. Here we describe flow cytometric methods for quantification of βAR density on circulating white blood cells (WBC) and Ec-MPs in urine samples that can be used as potential biomarkers of right heart failure in PAH. Biotinylated β-blocker alprenolol was synthesized and validated as a βAR specific probe that was combined with immunophenotyping to quantify βAR density in circulating WBC subsets. Ec-MPs obtained from urine samples were stained for annexin-V and CD144, and analyzed by a micro flow cytometer. Flow cytometric detection of alprenolol showed that βAR density was decreased in most WBC subsets in PAH samples compared to healthy controls. Ec-MPs in urine was increased in PAH compared to controls. Furthermore, there was a direct correlation between Ec-MPs and Tricuspid annular plane systolic excursion (TAPSE) in PAH patients. Therefore, flow cytometric quantification of peripheral blood cell βAR density and urinary Ec-MPs may be useful as potential biomarkers of right ventricular function in PAH.

Persistent Catechol-O-methyltransferase-dependent Pain Is Initiated by Peripheral β-Adrenergic Receptors

BACKGROUND

Patients with chronic pain disorders exhibit increased levels of catecholamines alongside diminished activity of catechol-O-methyltransferase (COMT), an enzyme that metabolizes catecholamines. The authors found that acute pharmacologic inhibition of COMT in rodents produces hypersensitivity to mechanical and thermal stimuli via β-adrenergic receptor (βAR) activation. The contribution of distinct βAR populations to the development of persistent pain linked to abnormalities in catecholamine signaling requires further investigation.

METHODS

Here, the authors sought to determine the contribution of peripheral, spinal, and supraspinal βARs to persistent COMT-dependent pain. They implanted osmotic pumps to deliver the COMT inhibitor OR486 (Tocris, USA) for 2 weeks. Behavioral responses to mechanical and thermal stimuli were evaluated before and every other day after pump implantation. The site of action was evaluated in adrenalectomized rats receiving sustained OR486 or in intact rats receiving sustained βAR antagonists peripherally, spinally, or supraspinally alongside OR486.

RESULTS

The authors found that male (N = 6) and female (N = 6) rats receiving sustained OR486 exhibited decreased paw withdrawal thresholds (control 5.74 ± 0.24 vs. OR486 1.54 ± 0.08, mean ± SEM) and increased paw withdrawal frequency to mechanical stimuli (control 4.80 ± 0.22 vs. OR486 8.10 ± 0.13) and decreased paw withdrawal latency to thermal heat (control 9.69 ± 0.23 vs. OR486 5.91 ± 0.11). In contrast, adrenalectomized rats (N = 12) failed to develop OR486-induced hypersensitivity. Furthermore, peripheral (N = 9), but not spinal (N = 4) or supraspinal (N = 4), administration of the nonselective βAR antagonist propranolol, the β2AR antagonist ICI-118,511, or the β3AR antagonist SR59230A blocked the development of OR486-induced hypersensitivity.

CONCLUSIONS

Peripheral adrenergic input is necessary for the development of persistent COMT-dependent pain, and peripherally-acting βAR antagonists may benefit chronic pain patients.

Prenatal drug exposures sensitize noradrenergic circuits to subsequent disruption by chlorpyrifos

We examined whether nicotine or dexamethasone, common prenatal drug exposures, sensitize the developing brain to chlorpyrifos. We gave nicotine to pregnant rats throughout gestation at a dose (3mg/kg/day) producing plasma levels typical of smokers; offspring were then given chlorpyrifos on postnatal days 1-4, at a dose (1mg/kg) that produces minimally-detectable inhibition of brain cholinesterase activity. In a parallel study, we administered dexamethasone to pregnant rats on gestational days 17-19 at a standard therapeutic dose (0.2mg/kg) used in the management of preterm labor, followed by postnatal chlorpyrifos. We evaluated cerebellar noradrenergic projections, a known target for each agent, and contrasted the effects with those in the cerebral cortex. Either drug augmented the effect of chlorpyrifos, evidenced by deficits in cerebellar β-adrenergic receptors; the receptor effects were not due to increased systemic toxicity or cholinesterase inhibition, nor to altered chlorpyrifos pharmacokinetics. Further, the deficits were not secondary adaptations to presynaptic hyperinnervation/hyperactivity, as there were significant deficits in presynaptic norepinephrine levels that would serve to augment the functional consequence of receptor deficits. The pretreatments also altered development of cerebrocortical noradrenergic circuits, but with a different overall pattern, reflecting the dissimilar developmental stages of the regions at the time of exposure. However, in each case the net effects represented a change in the developmental trajectory of noradrenergic circuits, rather than simply a continuation of an initial injury. Our results point to the ability of prenatal drug exposure to create a subpopulation with heightened vulnerability to environmental neurotoxicants.

Catecholamines, cyclic AMP and renin in two contrasting forms of essential hypertension

Essential hypertension (EH) can be subdivided according to the sympathetic and renin activity into two contrasting forms: (1) borderline beta-hyperadrenergic renin hyperresponsive and (2) stable beta-hypoadrenergic renin hyporesponsive EH. These two forms probably represent two expreme poles in the spectrum of EH in which sympathetic and renin hyper- or hyporeactivity cannot be accounted for by catecholamine determinations solely. beta-Adrenergic responsiveness monitored by plasma cyclic AMP determinations revealed plasma cyclic AMP, renin and circulatory hyperresponsiveness to isoproterenol in borderline hyperadrenergic EH while the opposite, cyclic AMP and renin hyporesponsiveness to insulin-induced hypoglycemia have been described in low renin stable EH. The kidney is in the center of the adrenergic abnormality in the two forms of EH with the borderline one excreting into the urine catecholamines not accounted for by their glomerular filtration. Catecholamines solely, however, do not account for the differences in both forms of EH which can probably be attributed to their different beta-adrenergic responsiveness.

Hypothalamic action of adrenoreceptor blocking agents

In cats anaesthetized with pentobarbital sodium, the posterior hypothalamus was superfused and electrically stimulated with a push-pull cannula. The pressor response to stimulation of this hypothalamic area was inhibited when the hypothalamus was superfused with drugs blocking either alpha-adrenoreceptors (piperoxan, tolazoline), or beta-adrenoreceptors--(+/-)-propranolol, (-)-propranolol, practolol, sotalol, metoprolol. (+)-Propranolol and a concentration of procaine equianaesthetic to propranolol were ineffective. During superfusion with tolazoline in the presence of practolol the inhibition was twice as that when the hypothalamus was superfused with either tolazoline or practolol. In another series of experiments the push-pull cannula was inserted into the anterior hypothalamus. The depressor response to stimulation of this area was inhibited by the hypothalamic superfusion with the alpha-adrenoreceptor blocking drugs phentolamine, tolazoline, piperoxan or yohimbine. Hypothalamic superfusion with phenylephrine abolished the inhibitory effect of phentolamine on the depressor response. The results indicate that adrenoreceptors are present in the hypothalamus and that they are involved in blood pressure changes elicited by hypothalamic stimulation.

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone promotes esophageal squamous cell carcinoma growth via beta-adrenoceptors in vitro and in vivo

Cigarette smoke is a risk factor for esophageal squamous cell carcinoma (ESCC). It contains several carcinogens known to initiate and promote tumorigenesis as well as metastasis. The nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is one of the strongest carcinogens in tobacco and our previous studies have shown its proliferation-promoting role in the progression of ESCC. Recently, NNK was identified as an agonist for both beta1- and beta2-adrenoceptors. Thus, we hypothesized that the cancer-promoting effect of NNK was likely mediated through beta-adrenoceptors in ESCC. Therefore, we investigated the comprehensive role of NNK in ESCC in vitro and in vivo, and found that NNK promoted many oncogenic features including ESCC cell proliferation and xenograft tumor growth as well as ESCC cell migration and invasion. Western blotting showed that NNK induced significant up-regulation of phosphorylated ERK1/2, cyclin D1, Bcl-2, and vascular endothelial growth factor as well as down-regulation of Bax. Importantly, the oncogenic effects of NNK in ESCC and the altered protein expression were reversed to some extent by down-regulation of beta1- and beta2-adrenoceptors with the beta2-adrenoceptor showing a greater rescue effect. Taken together, our in vitro and in vivo results demonstrate that NNK plays an oncogenic role in ESCC through beta-adrenoceptors. Furthermore, beta2-adrenoceptor might play a more important role in this process. Our findings might provide a chemoprevention and therapy strategy for cigarette smoke-related ESCC carcinogenesis.

[A case of swelling of salivary gland due to drug treatment for threatened premature labor]

Ritodrine hydrochloride (luteonin), a beta-agonist with predominant effects on beta adrenoreceptors such as those of the uterus, is effective in suppressing premature uterine contractions. This medicine was used in drug treatment in the case of threatened premature labor. A 26-year-old female who complained of acute swelling of the bilateral salivary glands was consulted to our otorhinolaryngological department. The soft swelling of the bilateral parotid and submandibular glands had developed after intravenous administration of ritodrine hydrochloride for treatment of her threatened premature labor. In addition, serum amylase levels were elevated. The swelling of the salivary glands and the elevation of the serum amylase subsided following discontinuation of the ritodrine hydrochloride. In salivary glands, too, the beta-adrenoreceptors exist. Following stimulation of those receptors in those glands increased secretion of amylase occurs. Our findings suggested that beta-stimulation by ritodrine hydrochloride led to the swelling of the salivary glands and the elevation of the serum amylase. To our knowledge, in Japan, our case is the first otorhinolaryngological report of swelling of the salivary glands due to ritodrine hydrochloride. Otolaryngologist should therefore have full knowledge regarding swelling of salivary glands due to ritodrine hydrochloride.

[In vivo testing of new ultrashort-acting β-blockers with the effect on systolic blood pressure and heart rate]

In this experiment, newly synthesized ultrashort-acting blockers of β-adrenergic receptors were tested. Compounds were synthesized at the Department of Chemical Drugs of Pharmaceutical Faculty VFU Brno as esters of aryloxyaminopropanol, thereby gaining a very short half-life in blood plasma. Experiment was conducted in vivo in a rat model. Changes in systolic blood pressure and heart rate were monitored by invasive method in normotensive rats. The values ​​of blood pressure and heart rate were recorded for 20 minutes following the i.v. administration of tested substances or placebo into the jugular vein. In the experiment was tested a series of four substances (2MC2, 2MC2b, 2MC2c, 2MC2d) with different alkyl chain length at a dose of 3.0 mg·kg⁻¹. After evaluation of results was carried out the second part of the experiment, i.e. testing of substances 2MC2c and 2MC2d at a lower dose of 1.0 mg·kg⁻¹. The results show the best effect of 2MC2d, asubstance with longest alkyl chain and highest lipophilicity.

Modulation of β-adrenergic receptor in rat lung after gamma irradiation

OBJECTIVES

To study the effect of γ irradiation on β-adrenergic receptors of the lung.

MATERIALS AND METHODS

Healthy Sprague-Dawley rats were used as an animal model. Cell membrane proteins of lung tissue were harvested after the whole lung received 20 Gy of 60Co γ irradiation. 125I-labeled iodopindolol (125I-IPIN) was used as a ligand of β-adrenergic receptors. The numbers of the β-adrenergic receptors were determined by radioligand-receptor binding assay (RBA). Data were compared with irreversible blockage using antagonist bromoacetylalprenololmenthan (BAAM).

RESULTS

The post-radiation RBA assay showed that the number of β-adrenergic receptors in lung tissue decreased at a steady rate. It decreased to 48% of the normal level at the 15th day after irradiation. At 40 days after radiation the level of β-adrenergic receptors started to increase at a steady rate and reached to the normal level around 70 days after radiation. There were significant differences in receptor synthesis, degradation and regeneration rates between irradiation group and BAMM group.

CONCLUSIONS

The whole lung irradiation could severely affect the levels of β-adrenergic receptors. The potential clinical implications of radiation-induced changes of β-adrenergic receptors warrant further investigation.

Differential effect of beta-adrenergic receptor antagonism in basolateral amygdala on reconsolidation of aversive and appetitive memories associated with morphine in rats

Positive and negative emotional experiences induced by addictive drugs play an important role in the development of dysfunctional drug-related memory, which becomes resistant to extinction and contributes to high rate of relapse. Those memories may undergo a process called reconsolidation that in some cases can be disrupted by pharmacological treatment. The basolateral amygdala (BLA) has been shown to mediate the reconsolidation of drug-related appetitive memory, but its role in withdrawal-related aversive memory remains elusive. The present study used conditioned place preference (CPP) and conditioned place aversion (CPA) paradigms to investigate the role of BLA and its noradrenergic receptors in reconsolidation of morphine-associated emotional memory in rats. We found that inhibition of protein synthesis in BLA disrupted the reconsolidation of morphine CPP (m-CPP) and CPA related to morphine withdrawal (m-CPA). A high dose of the β-noradrenergic receptor antagonist propranolol (3 µg) in BLA-impaired reconsolidation of m-CPA but not m-CPP, whereas a low dose (0.3 µg) was ineffective. In contrast, neither low nor high doses of the α-noradrenergic receptor antagonist phentolamine (1 or 10 µg) blocked the reconsolidation of m-CPP and m-CPA. In addition, infusion of propranolol (3 µg) into nucleus accumbens after retrieval of either m-CPP or m-CPA did not affect its reconsolidation. The findings indicate that appetitive and aversive addictive memories share common neural substrates in BLA, but the specific neurotransmitter mechanism on reconsolidation of morphine-associated negative and positive memories can be dissociable.

β1-Adrenergic receptor blockade extends the life span of Drosophila and long-lived mice

Chronic treatment with β-adrenergic receptor (βAR) agonists increases mortality and morbidity while βAR antagonists (β-blockers) decrease all-cause mortality for those at risk of cardiac disease. Levels of sympathetic nervous system βAR agonists and βAR activity increase with age, and this increase may hasten the development of age-related mortality. Here, we show that β-blockers extend the life span of healthy metazoans. The β-blockers metoprolol and nebivolol, administered in food daily beginning at 12 months of age, significantly increase the mean and median life span of isocalorically fed, male C3B6F1 mice, by 10 and 6.4%, respectively (P < 0.05). Neither drug affected the weight or food intake of the mice, indicating that induced CR is not responsible for these effects, and that energy absorption and utilization are not altered by the drugs. Both β-blockers were investigated to control for their idiosyncratic, off-target effects. Metoprolol and nebivolol extended Drosophila life span, without affecting food intake or locomotion. Thus, βAR antagonists are capable of directly extending the life span of two widely divergent metazoans, suggesting that these effects are phylogenetically highly conserved. Thus, long-term use of β-blockers, which are generally well-tolerated, may enhance the longevity of healthy humans.

Increased β-adrenergic inotropy in ventricular myocardium from Trpm4-/- mice

RATIONALE

The Trpm4 gene has recently been associated with several disorders, including cardiac conduction diseases and Brugada syndrome. Transient receptor potential member 4 (TRPM4) proteins constitute Ca2+ -activated, but Ca2+ -impermeable, nonselective cation channels and are expressed both in atrial and in ventricular cardiomyocytes. The physiological function of TRPM4 in the heart remains, however, incompletely understood.

OBJECTIVE

To establish the role of TRPM4 in cardiac muscle function.

METHODS AND RESULTS

We used TRPM4 knockout mice and performed patch-clamp experiments, membrane potential measurements, microfluorometry, contractility measurements, and in vivo pressure-volume loop analysis. We demonstrate that TRPM4 proteins are functionally present in mouse ventricular myocytes and are activated on Ca2+ -induced Ca2+ release. In Trpm4(-/-) mice, cardiac muscle displays an increased β-adrenergic inotropic response both in vitro and in vivo. Measurements of action potential duration show a significantly decreased time for 50% and 90% repolarization in Trpm4(-/-) ventricular myocytes. We provide evidence that this change in action potential shape leads to an increased driving force for the L-type Ca2+ current during the action potential, which explains the altered contractility of the heart muscle.

CONCLUSIONS

Our results show that functional TRPM4 proteins are novel determinants of the inotropic effect of β-adrenergic stimulation on the ventricular heart muscle.

Use of a three-dimensional virtual environment to teach drug-receptor interactions

Objective. To determine whether using 3-dimensional (3D) technology to teach pharmacy students about the molecular basis of the interactions between drugs and their targets is more effective than traditional lecture using 2-dimensional (2D) graphics.Design. Second-year students enrolled in a 4-year masters of pharmacy program in the United Kingdom were randomly assigned to attend either a 3D or 2D presentation on 3 drug targets, the β-adrenoceptor, the Na(+)-K(+) ATPase, and the nicotinic acetylcholine receptor.Assessment. A test was administered to assess the ability of both groups of students to solve problems that required analysis of molecular interactions in 3D space. The group that participated in the 3D teaching presentation performed significantly better on the test than the group who attended the traditional lecture with 2D graphics. A questionnaire was also administered to solicit students' perceptions about the 3D experience. The majority of students enjoyed the 3D session and agreed that the experience increased their enthusiasm for the course.Conclusions. Viewing a 3D presentation of drug-receptor interactions improved student learning compared to learning from a traditional lecture and 2D graphics.

Improved survival outcomes with the incidental use of beta-blockers among patients with non-small-cell lung cancer treated with definitive radiation therapy

BACKGROUND

Preclinical studies have shown that norepinephrine can directly stimulate tumor cell migration and that this effect is mediated by the beta-adrenergic receptor.

PATIENTS AND METHODS

We retrospectively reviewed 722 patients with non-small-cell lung cancer (NSCLC) who received definitive radiotherapy (RT). A Cox proportional hazard model was utilized to determine the association between beta-blocker intake and locoregional progression-free survival (LRPFS), distant metastasis-free survival (DMFS), disease-free survival (DFS), and overall survival (OS).

RESULTS

In univariate analysis, patients taking beta-blockers (n = 155) had improved DMFS (P < 0.01), DFS (P < 0.01), and OS (P = 0.01), but not LRPFS (P = 0.33) compared with patients not taking beta-blockers (n = 567). In multivariate analysis, beta-blocker intake was associated with a significantly better DMFS [hazard ratio (HR), 0.67; P = 0.01], DFS (HR, 0.74; P = 0.02), and OS (HR, 0.78; P = 0.02) with adjustment for age, Karnofsky performance score, stage, histology type, concurrent chemotherapy, radiation dose, gross tumor volume, hypertension, chronic obstructive pulmonary disease and the use of aspirin. There was no association of beta-blocker use with LRPFS (HR = 0.91, P = 0.63).

CONCLUSION

Beta-blocker use is associated with improved DMFS, DFS, and OS in this large cohort of NSCLC patients. Future prospective trials can validate these retrospective findings and determine whether the length and timing of beta-blocker use influence survival outcomes.

Inhibitory effects of daidzein on intestinal motility in normal and high contractile states

CONTEXT

Daidzein is a naturally occurring compound and has various health benefits. However, its effects on intestinal smooth muscle contractility remain unknown.

AIMS

The present study was to characterize the effects of daidzein on the contractility of isolated jejunal smooth muscle and its underlying mechanisms.

METHODS

Ex vivo assay was selected as the major method to determine the effects of daidzein on the contractility of isolated jejunal smooth muscle fragment (JSMF).

RESULTS

Daidzein (5-160 µmol/L) inhibited the contractility of JSMF in normal contractile state and in a dose-dependent manner. Daidzein also inhibited the contractility of JSMF induced by ACh, histamine, erythromycin and high Ca²⁺, respectively, and decreased charcoal propulsion in the small intestine in vivo. The inhibitory effects of daidzein were partially blocked by phentolamine or propranolol and were abolished in the presence of varapamil or at Ca²⁺-free assay condition. However, the inhibitory effects of daidzein on jejunal contraction were not significantly influenced by nitric oxide (NO) synthase inhibitor L-NG-nitro-arginine (L-NNA). Daidzein was also found to directly inhibit the phosphorylation and Mg²⁺-ATPase activity of smooth muscle myosin.

DISCUSSION AND CONCLUSION

The results implicated that α- and β-adrenergic receptors were involved in the inhibitory effects produced by daidzein rather than via NO pathway. As a phytoestrogen, daidzein has shown its potential value in relieving the hypercontractility of small intestine.

Vasodilatory mechanisms of beta receptor blockade

Beta-blockers are widely prescribed for the treatment of a variety of cardiovascular pathologies. Compared to traditional beta-adrenergic antagonists, beta-blockers of the new generation exhibit ancillary properties such as vasodilation through different mechanisms. This translates into a more favorable hemodynamic profile. The relative affinities of beta-adrenoreceptor antagonists towards the three beta-adrenoreceptor isotypes matter for predicting their functional impact on vasomotor control. This review will focus on the mechanisms underlying beta-blocker-evoked vasorelaxation with a specific emphasis on agonist properties of beta(3)-adrenergic receptors.

A review of beta antagonist treatment for infantile hemangioma

Infantile hemangiomas are benign vascular neoplasms of childhood that often have implications on development, cosmesis, and comfort. Traditional therapy has involved either observation or corticosteroids, depending on location and size. Recent studies have reported the successful use of beta-adrenergic antagonists in treating infantile hemangiomas. This succinct review discusses the properties and current applications of beta-adrenergic antagonists as well as the established treatments for infantile hemangioma.

Regulation of β-adrenergic control of heart rate by GTP-cyclohydrolase 1 (GCH1) and tetrahydrobiopterin

AIMS

Clinical markers of cardiac autonomic function, such as heart rate and response to exercise, are important predictors of cardiovascular risk. Tetrahydrobiopterin (BH4) is a required cofactor for enzymes with roles in cardiac autonomic function, including tyrosine hydroxylase and nitric oxide synthase. Synthesis of BH4 is regulated by GTP cyclohydrolase I (GTPCH), encoded by GCH1. Recent clinical studies report associations between GCH1 variants and increased heart rate, but the mechanistic importance of GCH1 and BH4 in autonomic function remains unclear. We investigate the effect of BH4 deficiency on the autonomic regulation of heart rate in the hph-1 mouse model of BH4 deficiency.

METHODS AND RESULTS

In the hph-1 mouse, reduced cardiac GCH1 expression, GTPCH enzymatic activity, and BH4 were associated with increased resting heart rate; blood pressure was not different. Exercise training decreased resting heart rate, but hph-1 mice retained a relative tachycardia. Vagal nerve stimulation in vitro induced bradycardia equally in hph-1 and wild-type mice both before and after exercise training. Direct atrial responses to carbamylcholine were equal. In contrast, propranolol treatment normalized the resting tachycardia in vivo. Stellate ganglion stimulation and isoproterenol but not forskolin application in vitro induced a greater tachycardic response in hph-1 mice. β1-adrenoceptor protein was increased as was the cAMP response to isoproterenol stimulation.

CONCLUSION

Reduced GCH1 expression and BH4 deficiency cause tachycardia through enhanced β-adrenergic sensitivity, with no effect on vagal function. GCH1 expression and BH4 are novel determinants of cardiac autonomic regulation that may have important roles in cardiovascular pathophysiology.

AAV6-βARKct gene delivery mediated by molecular cardiac surgery with recirculating delivery (MCARD) in sheep results in robust gene expression and increased adrenergic reserve

OBJECTIVE

Genetic modulation of heart function is a novel therapeutic strategy. We investigated the effect of molecular cardiac surgery with recirculating delivery (MCARD)-mediated carboxyl-terminus of the β-adrenergic receptor kinase (βARKct) gene transfer on cardiac mechanoenergetics and β-adrenoreceptor (βAR) signaling.

METHODS

After baseline measurements, sheep underwent MCARD-mediated delivery of 10(14) genome copies of self-complimentary adeno-associated virus (scAAV6)-βARKct. Four and 8 weeks after MCARD, mechanoenergetic studies using magnetic resonance imaging were performed. Tissues were analyzed with real-time quantitative polymerase chain reaction (RT-qPCR) and Western blotting. βAR density, cyclic adenosine monophosphate levels, and physiologic parameters were evaluated.

RESULTS

There was a significant increase in dP/dt(max) at 4 weeks: 1384 ± 76 versus 1772 ± 182 mm Hg/s; and the increase persisted at 8 weeks in response to isoproterenol (P < .05). Similarly, the magnitude of dP/dt(min) increased at both 4 weeks and 8 weeks with isoproterenol stimulation (P < .05). At 8 weeks, potential energy was conserved, whereas in controls there was a decrease in potential energy (P < .05) in response to isoproterenol. RT-qPCR confirmed robustness of βARKct expression throughout the left ventricle and undetectable expression in extracardiac tissues. Quantitative Western blot data confirmed higher expression of βARKct in the left ventricle: 0.46 ± 0.05 versus 0.00 in lung and liver (P < .05). Survival was 100% and laboratory parameters of major organ function were within normal limits.

CONCLUSIONS

MCARD-mediated βARKct delivery is safe, results in robust cardiac-specific gene expression, enhances cardiac contractility and lusitropy, increases adrenergic reserve, and improves energy utilization efficiency in a preclinical large animal model.

Chronic sympathetic activation promotes downregulation of β-adrenoceptor-mediated effects in the guinea pig heart independently of structural remodeling and systolic dysfunction

It is uncertain if downregulation of β-adrenoceptor signaling pathway is promoted by an enhanced adrenergic tone at an early stage of cardiac disease, or it develops secondary to detrimental local myocardial changes in advanced heart failure. We examined the integrity of β-adrenoceptor signaling pathway upon chronic infusion of isoproterenol, a β-adrenoceptor agonist, at a dose producing no structural left ventricular (LV) remodeling and systolic dysfunction. Subcutaneous isoproterenol infusion (400 μg kg(-1) h(-1) over 16 days) to guinea pigs using osmotic minipumps produced no change in cardiac weights, LV internal dimensions, myocyte cross-sectional area, extent of interstitial fibrosis, and basal contractile function. Isolated, perfused heart preparations from isoproterenol-treated guinea pigs exhibited attenuated responsiveness to acute β-adrenoceptor stimulation, as evidenced by reduced LV developed pressure increase, less shortening of LV epicardial monophasic action potential and effective refractory period, and less myocardial cyclic adenosine monophosphate elevation, in response to isoproterenol exposure, when compared to saline-treated controls. Pharmacological responses to forskolin, an activator of the adenylate cyclase catalytic subunit, were well preserved in isoproterenol-treated hearts. Downregulation of β-adrenoceptor-mediated effects upon chronic isoproterenol infusion was associated with markedly reduced stimulatory G-protein α-subunit (G(sα)) myocardial expression levels. No change in expression levels of β-adrenoceptors, G-protein-coupled receptor kinase 2, inhibitory G-protein α-subunit (G(iα2)), and Ca(v)1.2 and K(v)7.1 ion channels was determined in isoproterenol-treated hearts. We therefore conclude that sustained adrenergic overstimulation may promote downregulation of myocardial β-adrenoceptor-mediated effects independently of structural LV remodeling and systolic failure, an effect attributed to β-adrenoceptor uncoupling from adenylate cyclase due to reduced G(sα)-protein expression.

Evolution of β-blockers: from anti-anginal drugs to ligand-directed signalling

Sir James Black developed β-blockers, one of the most useful groups of drugs in use today. Not only are they being used for their original purpose to treat angina and cardiac arrhythmias, but they are also effective therapeutics for hypertension, cardiac failure, glaucoma, migraine and anxiety. Recent studies suggest that they might also prove useful in diseases as diverse as osteoporosis, cancer and malaria. They have also provided some of the most useful tools for pharmacological research that have underpinned the development of concepts such as receptor subtype selectivity, agonism and inverse agonism, and ligand-directed signalling bias. This article examines how β-blockers have evolved and indicates how they might be used in the future.

Mammalian intermediate-term memory: new findings in neonate rat

The ability of anisomycin, a translation inhibitor, and actinomycin, a transcription inhibitor to disrupt a cAMP/PKA-dependent odor preference memory in neonate rat was examined. Previous reports in invertebrates had described a novel translation-dependent intermediate-term memory dissected with these inhibitors, but similar effects have not been reported in mammalian memory systems. When anisomycin was infused into the olfactory bulb after the pairing of peppermint odor and the β-adrenoceptor agonist isoproterenol (2mg/kg), short-term memory (1 or 3h) was intact, but intermediate (5h) and long-term (24h) memory was disrupted. When actinomycin was infused, only long-term memory was disrupted. This pattern of results is consistent with that reported in invertebrates for intermediate-term memory and led us to try a lower level of the unconditioned stimulus (isoproterenol) to isolate intermediate-term memory from long-term memory. Pups given a dose of 1.5mg/kg isoproterenol paired with peppermint odor showed memory for peppermint 5h, but not 24h, after training. These observations in the rat pup olfactory system parallel short-, intermediate- and long-term memory characteristics previously described in invertebrates. Odor preference memory in neonate rodents offers a tool to increase our understanding of the properties and mechanisms of multi-phasic memory in mammals.

The β-blocker propranolol affects cAMP-dependent signaling and induces the stress response in Mediterranean mussels, Mytilus galloprovincialis

Widespread occurrence of pharmaceuticals is reported in aquatic systems, posing concerns for the health of aquatic wildlife and a theoretical risk to humans. A recent concept was developed for the identification of highly active compounds amongst the environmental pharmaceuticals, based on their mode of action, the homology between human targets and possible targets in the environment, and the importance of the affected pathway for the target species. In line with this approach, this study investigated whether propranolol (PROP) affects the cAMP-dependent pathway in Mediterranean mussels, Mytilus galloprovincialis. PROP is a prototypical β-adrenoceptor antagonist, and these receptors exist in bivalves and show gross pharmacological properties similar to their mammalian counterparts. PROP also acts as a 5-HT1 receptor antagonist, which is the sole 5-HT receptor reported in bivalves to date. Importantly, β-adrenoceptor and 5HT-1 receptor subtypes are positively and negatively coupled to cAMP-mediated signaling, respectively. PROP was administered as either l-PROP or dl-PROP. A wide range of concentrations was tested including low (0.3, 3 and 30ng/L) and high (300ng/L) environmental ranges, and a concentration 5-fold above the maximum reported environmental level (30,000ng/L). After a 7-day exposure, mussel cAMP levels and PKA activities were significantly reduced in digestive gland, increased in mantle/gonads and unaffected in gills. Similar patterns were observed for the mRNA expression of the ABCB1 gene encoding the membrane transporter P-glycoprotein, hypothesised to be under PKA modulation. The effects on the digestive gland are consistent with PROP blocking β-adrenoceptors. The observed increased cAMP levels in the mantle/gonad tissue support PROP blocking 5-HT1 receptors. Catalase and glutathione-S tranferase were differently affected by PROP in the two tissues. Mussel haemocyte lysosome membrane stability, a sensitive biomarker of animal health status, was concentration-dependently reduced following PROP exposure. Our observations provide evidence for PROP affecting cell signaling in M. galloprovincialis. Moreover, the chemical interacts with specific and evolutionally conserved biochemical pathways for which it was designed. The mode of action of PROP in mussels is related with its therapeutic properties in humans, based upon these conserved human targets. It also induced a stress response, and all these effects were displayed at the lowest concentrations tested.

β-Adrenergic Receptor Subtypes in the Urinary Tract

Within the urinary tract, β-adrenergic receptors (AR) are found largely on smooth muscle cells but are also present, at least in the bladder, in the urothelium and on afferent nerves. Our understanding of β-AR subtype expression and function is hampered by a lack of well-validated tools, particularly with regard to β(3)-AR. Moreover, the β-AR subtypes involved in a specific function may differ between species. In the ureter, β-AR can modulate pacemaker activity and smooth muscle tone involving multiple subtypes. In the human bladder, β-AR promote urine storage. Bladder smooth muscle relaxation primarily involves β(3)-AR, and the agonists selective for this subtype are in clinical development to treat bladder dysfunction. While prostate and urethra also express β-AR, the overall physiological role in these tissues remains unclear.

β-Adrenergic Responsive Induction of Insulin Resistance in Liver of Aging Rats

INTRODUCTION. We previously demonstrated increases in β-adrenergic receptor (β-AR) density in rat liver, in association with increased β-AR-mediated stimulation of glucose output in rat hepatocytes, during senescent aging. We therefore hypothesized that pharmacologic β-adrenergic stimulation might induce insulin resistance and glucose output in liver of aging rats in vivo. METHODS. In this study, pancreatic clamps were performed on young adult (4-month-old) and senescent (24-month-old) Fischer 344 male rats by infusing somatostatin (3 μg/kg/min) at time 0 to inhibit insulin secretion, and then infusing insulin (1 mU/kg/min) to replace basal insulin concentrations. At time 0 rats also received either the β-AR agonist isoproterenol (100 ng/kg/min) or saline (control). After 120 min the insulin infusion rate was increased to 4 mU/kg/min for an additional 120 min. Tritiated glucose was infused throughout the study to measure glucose turnover rates. RESULTS AND CONCLUSION. The results of the pancreatic clamp studies demonstrated that under saline control conditions hepatic glucose production (HGP) was suppressed during hyperinsulinemia in both young and old rats, with a trend toward reduced insulin sensitivity in the older animals. Isoproterenol infusion impaired insulin-induced suppression of HGP in both age groups. The results suggest that β-AR stimulation by isoproterenol increases HGP and acutely induces hepatic insulin resistance in both young and old rats. A similar role for β-adrenergic-mediated hepatic insulin resistance in aging humans would suggest a novel therapeutic target for the treatment or prevention of glucose dysregulation and diabetes developing with advancing age.

Role of serotonin and/or norepinephrine in the MDMA-induced increase in extracellular glucose and glycogenolysis in the rat brain

The acute administration of MDMA has been shown to promote glycogenolysis and increase the extracellular concentration of glucose in the striatum. In the present study the role of serotonergic and/or noradrenergic mechanisms in the MDMA-induced increase in extracellular glucose and glycogenolysis was assessed. The relationship of these responses to the hyperthermia produced by MDMA also was examined. The administration of MDMA (10mg/kg, i.p.) resulted in a significant and sustained increase of 65-100% in the extracellular concentration of glucose in the striatum, as well as in the prefrontal cortex and hippocampus, and a 35% decrease in brain glycogen content. Peripheral blood glucose was modestly increased by 32% after MDMA treatment. Treatment of rats with fluoxetine (10mg/kg, i.p.) significantly attenuated the MDMA-induced increase in extracellular glucose in the striatum but had no effect on MDMA-induced glycogenolysis or hyperthermia. Treatment with prazosin (1mg/kg, i.p.) did not alter the glucose or glycogen responses to MDMA but completely suppressed MDMA-induced hyperthermia. Finally, propranolol (3mg/kg, i.p.) significantly attenuated the MDMA-induced increase in extracellular glucose and glycogenolysis but did not alter MDMA-induced hyperthermia. The present results suggest that MDMA increases extracellular glucose in multiple brain regions, and that this response involves both serotonergic and noradrenergic mechanisms. Furthermore, beta-adrenergic and alpha-adrenergic receptors appear to contribute to MDMA-induced glycogenolysis and hyperthermia, respectively. Finally, hyperthermia, glycogenolysis and elevated extracellular glucose appear to be independent, unrelated responses to acute MDMA administration.