Mechanism and application of ß-adrenoceptor blockers in soft tissue wound healing.

Soft tissue damage stimulates sympathetic nerves to release large amounts of catecholamine hormones which bind to ß-adrenergic receptors (ß-ARs) on the cell membrane surface. It activates the downstream effector molecules and impairs soft tissue wound healing. ß-blockers specifically inhibit ß-ARs activation in acute/chronic skin lesions and ulcerative hemangiomas. They also accelerate soft tissue wound healing by shortening the duration of inflammation, speeding keratinocyte migration and reepithelialization, promoting wound contraction and angiogenesis, and inhibiting bacterial virulence effects. In addition, ß-blockers shorten wound healing periods in patients with severe thermal damage by reducing the hypermetabolic response. While ß-blockers promote/inhibit corneal epithelial cell regeneration and restores limbal stem/progenitor cells function, it could well accelerate/delay corneal wound healing. Given these meaningful effects, a growing number of studies are focused on examining the efficacy and safety of ß-blockers in soft tissue wound repair, including acute and chronic wounds, severe thermal damage, ulcerated infantile hemangioma, corneal wounds, and other soft tissue disorders. However, an intensive investigation on their acting mechanisms is imperatively needed. The purpose of this article is to summerize the roles of ß-blockers in soft tissue wound healing and explore their clinical applications.

25-hydroxycholesterol triggers antioxidant signaling in mouse atria.

Oxysterol, 25-hydroxycholesterol (25HC), is a potent regulator of immune reactions, its synthesis greatly increases by macrophages during inflammation. We hypothesize that 25HC can have cardioprotective effects by limiting consequences of excessive ß-adrenoceptor (ßAR) stimulation, particularly reactive oxygen species (ROS) production, in mouse atria. Isoproterenol, a ßAR agonist, increased extra- and intracellular levels of ROS. This enhancement of ROS production was suppressed by NADPH oxidase antagonists as well as 25HC. Inhibition of ß3ARs, Gi protein and protein kinase Cε prevented the effect of 25HC on isoproterenol-dependent ROS synthesis. Furthermore, 25HC suppressed isoproterenol-induced lipid peroxidation and mitochondrial ROS generation as well as ROS-dependent component of positive inotropic response to isoproterenol. Additionally, 25HC decreased mitochondrial ROS production and lipid peroxidation induced by antimycin A, a mitochondrial poison. Thus, 25HC exerts antioxidant properties alleviating mitochondrial dysfunction-induced and ßAR-dependent cardiac oxidative damage. In the latter case, 25HC can act via signaling mechanism engaging ß3ARs, Gi protein and protein kinase Cε.

Analyses of the onset mechanisms of cardio-stimulatory action by aciclovir.

Cardio-stimulatory actions of aciclovir have been considered to primarily depend on the sympathetically-mediated reflex resulting from its hypotensive effect. To further clarify onset mechanisms of the cardio-stimulatory actions, we initially studied them using isoflurane-anesthetized dogs under thorough ß1-adrenoceptor blockade with atenolol (1 mg/kg, i.v.) (n = 4). Aciclovir (20 mg/kg/10 min, i.v.) decreased mean arterial blood pressure by 10 mmHg, whereas it increased heart rate by 10 bpm and maximum upstroke velocity of ventricular pressure by 928 mmHg/s, and shortened AH interval by 2 ms, indicating that cardio-stimulatory actions were not totally abolished by ß1-adrenoceptor blockade. Then, unknown mechanisms of cardio-stimulatory action were explored. Since aciclovir has a similar chemical structure to theophylline, in silico molecular docking simulation was performed, indicating aciclovir as well as theophylline possesses strong likelihood of interactions with phosphodiesterase 1A, 1C and 3A. Indeed, aciclovir inhibited phosphodiesterase 1A derived from the bovine heart (n = 4), moreover it exerted positive chronotropic action on the atrial tissue preparation of rats along with an increase of tissue cyclic AMP concentration (n = 4). These results indicate that cardio-stimulatory actions of aciclovir could result from not only hypotension-induced, reflex-mediated increase of sympathetic tone but also its inhibitory effects on phosphodiesterase in the heart.

Adrenoceptor Expression and Function in the Endocrine Pancreas.

The sympathetic nervous system plays an important role in the regulation of endocrine pancreatic function, most importantly insulin release. Among the nine adrenoceptor (AR) subtypes, the α2A-AR appears to be the subtype most abundantly expressed in the human pancreas. While α2- and ß-AR have opposing effects, the net response to sympathetic stimulation is inhibition of insulin secretion mediated by α2-AR located in the plasma membrane of pancreatic ß cells. This inhibition may be present physiologically as evidenced by increased insulin secretion in healthy and diabetic humans and animals in response to α2-AR antagonists, a finding that was confirmed in all studies. Based on such data and on an association of an α2A-AR polymorphism, that increases receptor expression levels, with an elevated risk for diabetes, increased α2A-AR signaling in the pancreatic ß cells has been proposed as a risk factor for the development of type 2 diabetes. Thus, the α2A-AR was proposed as a drug target for the treatment of some forms of type 2 diabetes. Drug research and development programs leveraging this mechanism have reached the clinical stage, but none have resulted in an approved medicine due to a limited efficacy. While ß-AR agonists can increase circulating insulin levels in vivo, it remains controversial whether this includes a direct effect on ß cells or occurs secondary to general metabolic effects. Therefore, the regulation of endocrine pancreatic function is physiologically interesting but may be of limited therapeutic relevance.

Adrenoceptors: Receptors, Ligands and Their Clinical Uses, Molecular Pharmacology and Assays.

The nine G protein-coupled adrenoceptor subtypes are where the endogenous catecholamines adrenaline and noradrenaline interact with cells. Since they are important therapeutic targets, over a century of effort has been put into developing drugs that modify their activity. This chapter provides an outline of how we have arrived at current knowledge of the receptors, their physiological roles and the methods used to develop ligands. Initial studies in vivo and in vitro with isolated organs and tissues progressed to cell-based techniques and the use of cloned adrenoceptor subtypes together with high-throughput assays that allow close examination of receptors and their signalling pathways. The crystal structures of many of the adrenoceptor subtypes have now been determined opening up new possibilities for drug development.

Mitochondrial damage in a Takotsubo syndrome-like mouse model mediated by activation of ß-adrenoceptor-Hippo signaling pathway.

Takotsubo syndrome (TTS) is characterized by short-term contractile dysfunction with its mechanism undefined. We showed that activation of cardiac Hippo pathway mediates mitochondrial dysfunction and that stimulation of ß-adrenoceptors (ßAR) activates Hippo pathway. Here, we investigated the role of ßAR-Hippo signaling in mediating mitochondrial dysfunction in isoproterenol (Iso)-induced TTS-like mouse model. Elderly postmenopausal female mice were administered with Iso (1.25 mg/kg/h for 23 h). Cardiac function was determined by serially echocardiography. At days 1 and 7 post-Iso exposure, mitochondrial ultrastructure and function were examined by electron microscopy and various assays. Alterations in cardiac Hippo pathway and effects of genetic inactivation of Hippo kinase (Mst1) on mitochondrial damage and dysfunction in the acute phase of TTS were investigated. Isoproterenol exposure induced acute increase in biomarkers of cardiac damage and ventricular contractile dysfunction and dilation. At day 1 post-Iso, we observed extensive abnormalities in mitochondrial ultrastructure, downregulation of mitochondrial marker proteins, and mitochondrial dysfunction evidenced by lower ATP content, increased lipid droplets, higher contents of lactate, and augmented reactive oxygen species (ROS). All changes were reversed by day 7. ßAR stimulation led to activation of cardiac Hippo pathway with enhanced expression of Hippo kinase Mst1 and inhibitory YAP phosphorylation, as well as reduced nuclear YAP-TEAD1 interaction. In mice with cardiac expression of inactive mutant Mst1 gene, acute mitochondrial damage and dysfunction were mitigated. Stimulation of cardiac ßAR activates Hippo pathway that mediates mitochondrial dysfunction with energy insufficiency and enhanced ROS, promoting acute but short-term ventricular dysfunction.NEW & NOTEWORTHY Takotsubo syndrome (TTS) is featured by activation of sympatho-ß-adrenoceptor (ßAR) system leading to acute loss of ventricular contractile performance. However, the molecular mechanism remains undefined. We demonstrated, in an isoproterenol-induced murine TTS-like model, extensive mitochondrial damage, metabolic dysfunction, and downregulated mitochondrial marker proteins, changes temporarily associated with cardiac dysfunction. Mechanistically, stimulation of ßAR activated Hippo signaling pathway and genetic inactivation of Mst1 kinase ameliorated mitochondrial damage and metabolic dysfunction at the acute phase of TTS.

Adrenoceptors in the Lower Urinary Tract.

Adrenoceptors importantly contribute to the physiological regulation of lower urinary tract (LUT) function and have become a target of several clinically successful treatments for major LUT diseases. In the bladder dome, ß-adrenoceptor subtypes are found in multiple cell types and mediate relaxation of detrusor smooth muscle, perhaps partly indirectly by acting on afferent nerves and cells of the mucosa. ß3-adrenoceptor agonists such as mirabegron and vibegron are used to treat overactive bladder syndrome. In the bladder trigone and urethra, α1-adrenoceptors cause contraction and thereby physiologically contribute to bladder outlet resistance. α1-adrenoceptors in the prostate also cause contraction and pathophysiologically elevate bladder outlet resistance leading to voiding dysfunction in benign prostatic hyperplasia. α1-adrenoceptor antagonist such as tamsulosin is widely used as a first-line option to treat LUT symptoms in men, but it remains unclear to which extent and how smooth muscle relaxation contributes to symptom relief.

Subcellular Compartmentalization of Cyclic Adenosine Monophosphate in Heart Failure and Inotropic Pharmacology.

Cyclic adenosine monophosphate (cAMP) is a second messenger downstream of many G-protein coupled receptors, including the ß1-adrenoceptor, which is the target of many clinically used inotropic agents. When the Gαs subunit of a heterotrimeric G-protein is activated, it causes a localized elevation of cAMP. The significance of the spatial distribution of the elevation in cAMP is increasingly recognized, as is the disturbance of these microdomains in diseased states. Herein, the spatial compartmentalization of inotropic signaling is explored, including from internalized receptors.

Ractopamine residues in meat might reduce the risk of type 2 diabetes.

Background: The overall prevalence of diabetes in the world has risen substantially in the past several decades, so have complications and mortalities associated with it. Aim: Prevention strategies for diabetes thus become an urgent public health need for reducing the burden of diabetes. Methods: Ractopamine, a ß1/2-adrenergic receptor agonist, has been approved for use in finishing swine, cattle, and turkey in countries where meat exporting brings tremendous economic benefits. This leanness enhancer is recently found to be a full agonist at trace amine-associated receptor 1 also. A thorough literature review was performed to assess possible effects of ractopamine on glucose metabolism. Results: Activating ß-adrenoceptor could lead to glucose-lowering effects independent of insulin while activation on trace amine-associated receptor 1 induces an incretin-like signaling on insulin-secreting pancreatic ß-cells. Conclusion: Accordingly, it is hypothesized that long-term consuming meat containing ractopamine might lower the risk of type 2 diabetes.

Agonists in the Extended Conformation Stabilize the Active State of ß-Adrenoceptors.

In this study, we conducted a comparative analysis of the structure of agonists and antagonists of transmembrane (TM) ß-adrenoceptors (ß-ARs) and their interactions with the ß-ARs and proposed the mechanism of receptor activation. A characteristic feature of agonist and antagonist molecules is the presence of a hydrophobic head (most often, one or two aromatic rings) and a tail with a positively charged amino group. All ß-adrenergic agonists have two carbon atoms between the aromatic ring of the head and the nitrogen atom of the amino group. In antagonist molecules, this fragment can be either reduced or increased to four atoms due to the additional carbon and oxygen atoms. The agonist head, as a rule, has two H-bond donors or acceptors in the para- and meta-positions of the aromatic rings, while in the antagonist heads, these donors/acceptors are absent or located in other positions. Analysis of known three-dimensional structures of ß-AR complexes with agonists showed that the agonist head forms two H-bonds with the TM5 helix, and the tail forms an ionic bond with the D3.32 residue of the TM3 helix and one or two H-bonds with the TM7 helix. The tail of the antagonist can form similar bonds, but the interaction between the head and the TM5 helix is much weaker. As a result of these interactions, the agonist molecule acquires an extended "strained string" conformation, in contrast to the antagonist molecule, which has a longer, bended, and flexible tail. The "strained string" of the agonist interacts with the TM6 helix (primarily with the W6.48 residue) and turns it, which leads to the opening of the G protein-binding site on the intracellular side of the receptor, while flexible and larger antagonist molecules do not have the same effect on the receptor.

The effects of carvedilol, metoprolol and propranolol on cisplatin-induced kidney injury.

The ß-adrenoceptor blockers may have anti-oxidant properties or induce ß-arrestin recruitment beyond classical desensitization of receptor/G protein coupling, offering potential therapeutic benefits. Here, we investigated the effects of carvedilol, metoprolol and propranolol in an animal model of cisplatin-induced nephrotoxicity. Rats received the ß-blockers (3 or 12 mg/kg/day) with or without cisplatin, and kidney function was investigated using renal scintigraphy, histopathology, and serum variables. Metoprolol and propranolol as well as low-dose carvedilol did not alter kidney function, per se. Meanwhile, high-dose carvedilol reduced renal accumulation of Technetium-99m (99mTc)-labeled dimercaptosuccinic acid (99mTc-DMSA) without significant effect on other variables. Furthermore, low-dose carvedilol prevented cisplatin-induced reduction of tracer uptake, but high-dose of this drug aggravated the situation. In this regard, both low and high -doses of carvedilol significantly inhibited cisplatin effects on kidney histology, BUN and creatinine levels. Also, high-dose propranolol inhibited cisplatin adverse effects on radiotracer uptake, histological manifestations, BUN and creatinine levels, while metoprolol failed to cause a notable effect. Taken together, carvedilol and high-dose propranolol may offer potential benefits in cisplatin nephrotoxicity.

Beneficial and harmful effects of CB1 and CB2 receptor antagonists on chronotropic and inotropic effects related to atrial ß-adrenoceptor activation in humans and in rats with primary hypertension.

We have previously shown that cannabinoid CB1 and CB2 receptor antagonists, AM251 and AM630, respectively, modulate cardiostimulatory effects of isoprenaline in atria of Wistar rats. The aim of the present study was to examine whether such modulatory effects can also be observed (a) in the human atrium and (b) in spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY). Inotropic effects of isoprenaline and/or CGP12177 (that activate the high- and low-affinity site of ß1 -adrenoceptors, respectively) were examined in paced human atrial trabeculae and rat left atria; chronotropic effects were studied in spontaneously beating right rat atria. AM251 modified cardiostimulatory effects more strongly than AM630. Therefore, AM251 (1 µM) enhanced the chronotropic effect of isoprenaline in WKY and SHR as well as inotropic action of isoprenaline in WKY and in human atria. It also increased the inotropic influence of CGP12177 in SHR. AM630 (1 µM) decreased the inotropic effect of isoprenaline and CGP12177 in WKY, but enhanced the isoprenaline-induced inotropic effect in SHR and human atria. Furthermore, AM251 (0.1 and 3 µM) and AM630 (0.1 µM) reduced the inotropic action of isoprenaline in human atria. In conclusion, cannabinoid receptor antagonists have potentially harmful and beneficial effects through their amplificatory effects on ß-adrenoceptor-mediated positive chronotropic and inotropic actions, respectively.

Propranolol diminished severity of rat EAE by enhancing immunoregulatory/protective properties of spinal cord microglia.

Sympathetic dysfunction is suggested to contribute to development of multiple sclerosis and experimental autoimmune encephalomyelitis (EAE) alike. Considering important role of microglia in development/resolution of neuroinflammation, contribution of noradrenaline, the key sympathetic end-point mediator, in modulation of microglial phenotypic and functional properties in rat EAE model was examined. The study showed that noradrenaline acting in neurocrine and autocrine/paracrine way might influence microglia during EAE. Propranolol treatment over the effector phase moderated EAE course. This was associated with the increased proportion of microglia expressing CX3CR1, the key molecule in their immunomodulatory/neuroprotective action, and upregulation of CX3CR1 downstream Nrf2 gene. This correlated with the increased heme oxygenase-1 (HO-1) expression and phagocytic capacity of microglia, and their phenotypic changes mirrored in increased proportion of CD163- and CD83-expressing cells. The enhanced HO-1 expression was linked with the decreased proportion of microglial cells expressing IL-1ß and IL-23, and possibly IL-6, followed by increased proportion of IL-10-expressing microglia, and downregulated MCP-1/CCL2 expression. Consistently, spinal cord infiltration with blood-borne myeloid and CD4+ T cells, as well as CD4+ T-cell reactivation/proliferation and differentiation into highly pathogenic IL-17+ cells co-producing IFN-γ and GM-CSF were decreased in propranolol-treated rats compared with saline-injected controls. The in vitro investigations of the effects of noradrenaline on microglia showed that noradrenaline through ß-adrenoceptor may influence Nrf2 expression also via CX3CR1-independent route. The study suggests ß-adrenoceptor-mediated neuroinflammation-promoting role of noradrenaline in EAE via modulation of microglial Nrf2 expression, and thereby forms the basis for further translational pharmacological research to improve multiple sclerosis therapy.

Effects of ß-adrenoceptor activation on haemodynamics during hypoxic stress in rats.

NEW FINDINGS: What is the central question of this study? The acute hypoxic compensatory reaction is based on haemodynamic changes, and ß-adrenoceptors are involved in haemodynamic regulation. What is the role of ß-adrenoceptors in haemodynamics during hypoxic exposure? What is the main finding and its importance? Activation of ß2 -adrenoceptors attenuates the increase in pulmonary artery pressure during hypoxic exposure. This compensatory reaction activated by ß2 -adrenoceptors during hypoxic stress is very important to maintain the activities of normal life. ABSTRACT: The acute hypoxic compensatory reaction is accompanied by haemodynamic changes. We monitored the haemodynamic changes in rats undergoing acute hypoxic stress and applied antagonists of ß-adrenoceptor (ß-ARs) subtypes to reveal the regulatory role of ß-ARs on haemodynamics. Sprague-Dawley rats were randomly divided into control, atenolol (ß1 -AR antagonist), ICI 118,551 (ß2 -AR antagonist) and propranolol (non-selective ß-AR antagonist) groups. Rats were continuously recorded for changes in haemodynamic indexes for 10 min after administration. Then, a hypoxic ventilation experiment [15% O2 , 2200 m a.sl., 582 mmHg (0.765 Pa), PO2 87.3 mmHg; Xining, China] was conducted, and the indexes were monitored for 5 min after induction of hypoxia. Plasma catecholamine concentrations were also measured. We found that, during normoxia, the mean arterial pressure, heart rate, ascending aortic blood flow and pulmonary artery pressure were reduced in the propranolol and atenolol groups. Catecholamine concentrations were increased significantly in the atenolol group compared with the control group. During hypoxia, mean arterial pressure and total peripheral resistance were decreased in the control, propranolol and ICI 118,551 groups. Pulmonary arterial pressure and pulmonary vascular resistance were increased in the propranolol and ICI 118,551 groups. During hypoxia, catecholamine concentrations were increased significantly in the control group, but decreased in ß-AR antagonist groups. In conclusion, the ß2 -AR is involved in regulation of pulmonary haemodynamics in the acute hypoxic compensatory reaction, and the activation of ß2 -ARs attenuates the increase in pulmonary arterial pressure during hypoxic stress. This compensatory reaction activated by ß2 -ARs during hypoxic stress is very important to maintain activities of normal life.

ß-Adrenoceptor regulates contraction and inflammatory cytokine expression of human bladder smooth muscle cells via autophagy under pathological hydrostatic pressure.

AIMS: Abnormal intravesical pressure created by partial bladder outlet obstruction (PBOO) triggered the progression from chronic inflammation to fibrosis, initiating structural and functional alterations of bladder. To elucidate the underlying mechanisms of contraction and inflammatory response, we investigated the isolated human bladder smooth muscle cells (hBSMC) under pathological hydrostatic pressure (HP) mimicking the in vivo PBOO condition. METHODS: hBSMCs were subjected to HP of 200 cm H2 O to explore the contraction and inflammatory cytokine expression of hBSMC treated with ß-adrenoceptors (ADRBs) and/or autophagy signaling pathway agonists and/or antagonists. RESULTS: We showed that pathological HP induced the release of the proinflammatory cytokines, including monocyte chemotactic protein-1, regulated upon activation normal T cell expressed and secreted factor, and interleukin-6. HP downregulated ADRB2 and ADRB3 expression, which was consistent with the results of the PBOO rat model. ADRB2 or autophagy activation repressed pathological HP-induced proinflammatory cytokine production. ADRB2, ADRB3 or autophagy activation ameliorated the HP-enhanced contraction. The increased contraction and autophagy activity by ADRB2 agonist under HP conditions were reversed by pretreatment with antagonists of adenosine monophosphate-activated protein kinase (AMPK). CONCLUSION: The present study provides evidence that the ADRB3 agonist suppresses hBSMC contraction under pathological HP conditions. Moreover, the ADRB2 agonist negatively regulates the contraction and inflammatory response of hBSMCs through AMPK/mTOR-mediated autophagy under pathological HP. These findings provide a theoretical basis for potential therapeutic strategies for patients with PBOO.

ß-Adrenoceptors regulate matrix metalloproteinase expression in human urothelial cells under hydrostatic pressure.

The bladder wall is constantly subjected to intravesical pressure during the filling and voiding cycles. An imbalance between matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) under elevated intravesical pressure contributes to pathological changes in the bladder. To investigate the changes in human urothelial cells (HUCs) under elevated intravesical pressure, this study analyzed the effect of ß-adrenoceptor signaling on the expression of MMPs and TIMPs in HUCs exposed to pathological hydrostatic pressure (HP) (70 cm H2 O) for 6 hours. Quantitative polymerase chain reaction, Western blot analysis, and cell fluorescence staining were used to explore the effect of ß-adrenoceptor signaling on the expression of MMPs and TIMPs in HUCs after agonist and/or antagonist treatment. The expression levels of ß2 - and ß3 -adrenoceptor, MMP1, and MMP2 were greatly downregulated, while the expression of TIMP1 was greatly upregulated. Formoterol and BRL 37344, which are agonists of ß2 - and ß3 -adrenoceptor, respectively, significantly increased MMP1 and MMP2 expression under 70 cm H2 O. As a classic downstream pathway of ß2 - and ß3 -adrenoceptor, protein kinase A (PKA) signaling inhibited MMP1 and MMP2 expression by regulating cAMP response element binding protein (CREB) activity. MMP1 and MMP2 expression in HUCs under 70 cm H2 O was modified by ß2 - and ß3 -adrenoceptor via the PKA/CREB pathway. This outcome suggests that MMPs likely participate in the pathological effects of elevated intravesical pressure. The underlying mechanism of ß2 - and ß3 -adrenoceptor in elevated intravesical pressure was also revealed; this mechanism constitutes a new potential therapeutic target for partial bladder outlet obstruction.

Effects of Catecholamine Metabolites on Beta-Adrenoceptor-Mediated Relaxation of Smooth Muscle: Evaluation in Mouse and Guinea-Pig Trachea and Rat Aorta.

The ß-adrenoceptor (ß-AR)-mediated pharmacological effects of catecholamine (CA) metabolites are not well known. We examined the effects of seven CA metabolites on smooth muscle relaxation in mouse and guinea pig (GP) tracheas and rat thoracic aorta. Among them, metadrenaline (MA) significantly relaxed GP trachea (ß2-AR dominant), even in the presence of clorgiline, a monoamine oxidase-A inhibitor. In mouse trachea (ß1-AR dominant), normetadrenaline (NMA) and MA (10-4 M each) apparently did not affect isoprenaline (ISO)-induced relaxation, but significantly inhibited it in the presence of clorgiline. ISO-induced relaxation was also unaffected by 3,4-dihydroxyphenylglycol (DHPG) (10-4 M), but significant suppression was observed with the addition of 3,5-dinitrocatechol, a catechol-O-methyltransferase inhibitor. In GP trachea, NMA, MA, 3,4-dihydroxymandelic acid (DOMA), and DHPG (10-4 M each) significantly augmented ISO-induced relaxation. However, in the presence of clorgiline plus 3,5-dinitrocatechol, both NMA and MA (10-4 M) significantly suppressed ISO-induced relaxation. DHPG (10-4 M) also significantly suppressed ISO-induced relaxation in the presence of 3,5-dinitrocatechol. In rat thoracic aorta, DHPG (10-4 M) significantly suppressed relaxation induced by CGP-12177 A (a ß3-AR partial agonist) in the presence of 3,5-dinitrocatechol plus propranolol. Our findings indicate that 1) MA may possess ß2-AR agonistic action; 2) NMA and MA augment ß2-AR-mediated tracheal relaxation in the absence of CA metabolic inhibitors, though themselves possessing ß1-, ß2-AR antagonistic action (ß2 > ß1); 3) DHPG exhibits ß1-, ß2-, ß3-AR antagonistic action, and this is particularly marked for ß3-AR. Our observations may help explain some of the pathologies associated with pheochromocytoma, which is characterized by increased CA metabolite levels.

Biased Agonism: The Future (and Present) of Inotropic Support.

Biased agonism, which is the concept that different ligands activate different downstream signalling partners in different ratios to cause different functional effects, is yet to gain appropriate appreciation in the field of inotropic pharmacology. Biased agonism has already proven to be a clinically translatable technology in analgesic pharmacology, but this development is yet to be translated into inotropes. A better appreciation of bias in clinically used inotropes and a focus on bias when developing novel inotropes has the potential to lead to more targeted, personalized, and cleaner inotropes.

ß3-Adrenoceptor agonists inhibit purinergic receptor-mediated contractions of the murine detrusor.

ß3-Adrenoceptor (ß3-AR) agonists are used to treat overactive bladder syndrome; however, their mechanism of action has not been determined. The aims of this study were to compare the effects of ß3-AR agonists on cholinergic versus purinergic receptor-mediated contractions of the detrusor and to examine the mechanisms underlying inhibition of the purinergic responses by ß3-AR agonists. Isometric tension recordings were made from strips of murine detrusor and whole cell current recordings were made from freshly isolated detrusor myocytes using the patch-clamp technique. Transcriptional expression of exchange protein directly activated by cAMP (EPAC) subtypes in detrusor strips was assessed using RT-PCR and real-time quantitative PCR. The ß3-AR agonists BRL37344 and CL316243 (100 nM) inhibited cholinergic nerve-mediated contractions of the detrusor by 19 and 23%, respectively, but did not reduce contractions induced by the cholinergic agonist carbachol (300 nM). In contrast, BRL37344 and CL316243 inhibited purinergic nerve-mediated responses by 55 and 56%, respectively, and decreased the amplitude of contractions induced by the P2X receptor agonist α,ß-methylene ATP by 40 and 45%, respectively. The adenylate cyclase activator forskolin inhibited purinergic responses, and these effects were mimicked by a combination of the PKA activator N6-monobutyryl-cAMP and the EPAC activator 8-pCPT-2'-O-methyl-cAMP-AM (007-AM). Application of ATP (1 µM) evoked reproducible P2X currents in isolated detrusor myocytes voltage-clamped at -60 mV. These responses were reduced in amplitude in the presence of BRL37344 and also by 007-AM. This study demonstrates that ß3-AR agonists reduce postjunctional purinergic responses in the detrusor via a pathway involving activation of the cAMP effector EPAC.

Noradrenaline through ß-adrenoceptor contributes to sexual dimorphism in primary CD4+ T-cell response in DA rat EAE model?

Males exhibit stronger sympathetic nervous system (SNS) activity, but weaker primary CD4+ T-cell (auto)immune responses. To test the role of catecholamines, major end-point SNS mediators, in this dimorphism, influence of propranolol (ß-adrenoceptor blocker) on mitogen/neuroantigen-stimulated CD4+ T cells from female and male EAE rat draining lymph node (dLN) cell cultures was examined. Male rat dLNs exhibited higher noradrenaline concentration and frequency of ß2-adrenoceptor-expressing CD4+ T lymphocytes and antigen presenting cells. Propranolol, irrespective of exogenous noradrenaline presence, more prominently augmented IL-2 production and proliferation of CD4+ lymphocytes in male than female rat dLN cell cultures. In neuroantigen-stimulated dLN cells of both sexes propranolol increased IL-1ß and IL-23/p19 expression and IL-17+ CD4+ cell frequency, but enhanced IL-17 production only in male rat CD4+ lymphocytes, thereby abrogating sexual dimorphism in IL-17 concentration observed in propranolol-free cultures. Thus, ß-adrenoceptor-mediated signalling may contribute to sex bias in rat IL-17-producing cell secretory capacity.