Differential distribution of beta-adrenergic receptor subtypes in blood vessels of knockout mice lacking beta(1)- or beta(2)-adrenergic receptors

β2-adrenoceptors kick osteoarthritis - Time to rethink prevention and therapy

Although, during the past decades, substantial advances emerged in identifying major local and systemic factors contributing to initiation and progression of osteoarthritis (OA), some neuroendocrine mechanisms are still not understood or even neglected when thinking about novel therapeutic options. One of which is the sympathetic nervous system that exhibits various OA-promoting effects in different tissues of the joint. Interestingly, the β2-adrenoceptor (AR) mediates the majority of these effects as demonstrated by several in vitro, in vivo as well as in clinical studies. This review article does not only summarize studies of the past two decades demonstrating that the β2-AR plays an OA-promoting role in different tissues of the joint but also aims to encourage the reader to think about next-level research to discover novel and innovative preventive and/or therapeutic strategies targeting the β2-AR in OA.

Fetoplacental vascular effects of maternal adrenergic antihypertensive and cardioprotective medications in pregnancy

Maternal cardiovascular diseases, including hypertension and cardiac conditions, are associated with poor fetal outcomes. A range of adrenergic antihypertensive and cardioprotective medications are often prescribed to pregnant women to reduce major maternal complications during pregnancy. Although these treatments are not considered teratogenic, they may have detrimental effects on fetal growth and development, as they cross the fetoplacental barrier, and may contribute to placental vascular dysregulation. Medication risk assessment sheets do not include specific advice to clinicians and women regarding the safety of these therapies for use in pregnancy and the potential off-target effects of adrenergic medications on fetal growth have not been rigorously conducted. Little is known of their effects on the fetoplacental vasculature. There is also a dearth of knowledge on adrenergic receptor activation and signalling within the endothelium and vascular smooth muscle cells of the human placenta, a vital organ in the maintenance of adequate blood flow to satisfy fetal growth and development. The fetoplacental circulation, absent of sympathetic innervation, and unique in its reliance on endocrine, paracrine and autocrine influence in the regulation of vascular tone, appears vulnerable to dysregulation by adrenergic antihypertensive and cardioprotective medications compared with the adult peripheral circulation. This semi-systematic review focuses on fetoplacental vascular expression of adrenergic receptors, associated cell signalling mechanisms and predictive consequences of receptor activation/deactivation by antihypertensive and cardioprotective medications.

Sympathetic Nervous System and Atherosclerosis

Atherosclerosis is characterized by the narrowing of the arterial lumen due to subendothelial lipid accumulation, with hypercholesterolemia being a major risk factor. Despite the recent advances in effective lipid-lowering therapies, atherosclerosis remains the leading cause of mortality globally, highlighting the need for additional therapeutic strategies. Accumulating evidence suggests that the sympathetic nervous system plays an important role in atherosclerosis. In this article, we reviewed the sympathetic innervation in the vasculature, norepinephrine synthesis and metabolism, sympathetic activity measurement, and common signaling pathways of sympathetic activation. The focus of this paper was to review the effectiveness of pharmacological antagonists or agonists of adrenoceptors (α1, α2, β1, β2, and β3) and renal denervation on atherosclerosis. All five types of adrenoceptors are present in arterial blood vessels. α1 blockers inhibit atherosclerosis but increase the risk of heart failure while α2 agonism may protect against atherosclerosis and newer generations of β blockers and β3 agonists are promising therapies against atherosclerosis; however, new randomized controlled trials are warranted to investigate the effectiveness of these therapies in atherosclerosis inhibition and cardiovascular risk reduction in the future. The role of renal denervation in atherosclerosis inhibition in humans is yet to be established.

Myocardial infarction and oxidative damage in animal models: objective and expectations from the application of cysteine derivatives

Reactive oxygen species (ROS) and associated oxidative stress are the main contributors to pathophysiological changes following myocardial infarction (MI), which is the principal cause of death from cardiovascular disease. The glutathione (GSH)/glutathione peroxidase (GPx) system appears to be the main and most active cardiac antioxidant mechanism. Hence, enhancement of the myocardial GSH system might have protective effects in the setting of MI. It follows that by increasing antioxidant capacity, the heart will be able to reduce the damage associated with MI and even prevent/weaken the occurrence of oxidative stress, which is highly ranked among the factors responsible for the occurrence of acute MI. For these reasons, the primary goal of future investigations should be to address the effects of different antioxidative compounds and especially cysteine derivatives like N-acetyl cysteine (NAC) and L-2-oxothiazolidine-4-carboxylic acid (OTC) as precursors responsible for the enhancement of the GSH-related antioxidant system's capacity. It is assumed that this will lay down the basis for elucidation of the mechanisms throughout which applicable doses of OTC will manifest a potentially positive impact in the reduction of adverse effects of acute MI. The inclusion of OTC in the models for prediction of the distribution of oxygen in infarcted animal hearts can help to upgrade existing computational models. Such a model would be based on computational geometries of the heart, but the inclusion of biochemical redox features in addition to angiogenic therapy, despite improvement of the post-infarcted oxygenated outcome could enhance the accuracy of the predictive values of oxygenation.

Pulmonary hypertension associated with cardiopulmonary bypass and cardiac surgery

BACKGROUND AND AIM

Pulmonary hypertension (PH) is frequently associated with cardiovascular surgery and is a common complication that has been observed after surgery utilizing cardiopulmonary bypass (CPB). The purpose of this review is to explain the characteristics of PH, the mechanisms of PH induced by cardiac surgery and CPB, treatments for postoperative PH, and future directions in treating PH induced by cardiac surgery and CPB using up-to-date findings.

METHODS

The PubMed database was utilized to find published articles.

RESULTS

There are many mechanisms that contribute to PH after cardiac surgery and CPB which involve pulmonary vasomotor dysfunction, cyclooxygenase, the thromboxane A2 and prostacyclin pathway, the nitric oxide pathway, inflammation, and oxidative stress. Furthermore, there are several effective treatments for postoperative PH within different types of cardiac surgery.

CONCLUSIONS

By possessing a deep understanding of the mechanisms that contribute to PH after cardiac surgery and CPB, researchers can develop treatments for clinicians to use which target the mechanisms of PH and ultimately reduce and/or eliminate postoperative PH. Additionally, learning about the most up-to-date studies regarding treatments can allow clinicians to choose the best treatments for patients who are undergoing cardiac surgery and CPB.

Dynein Coordinates β2-Adrenoceptor-Mediated Relaxation in Normotensive and Hypertensive Rat Mesenteric Arteries

BACKGROUND

The voltage-gated potassium channel (Kv)7.4 and Kv7.5 channels contribute to the β-adrenoceptor-mediated vasodilatation. In arteries from hypertensive rodents, the Kv7.4 channel is downregulated and function attenuated, which contributes to the reduced β-adrenoceptor-mediated vasodilatation observed in these arteries. Recently, we showed that disruption of the microtubule network, with colchicine, or inhibition of the microtubule motor protein, dynein, with ciliobrevin D, enhanced the membrane abundance and function of Kv7.4 channels in rat mesenteric arteries. This study aimed to determine whether these pharmacological compounds can improve Kv7.4 function in third-order mesenteric arteries from the spontaneously hypertensive rat, thereby restoring the β-adrenoceptor-mediated vasodilatation.

METHODS

Wire and intravital myography was performed on normotensive and hypertensive male rat mesenteric arteries and immunostaining was performed on isolated smooth muscle cells from the same arteries.

RESULTS

Using wire and intravital microscopy, we show that ciliobrevin D enhanced the β-adrenoceptor-mediated vasodilatation by isoprenaline. This effect was inhibited partially by the Kv7 channel blocker linopirdine and was dependent on an increased functional contribution of the β2-adrenoceptor to the isoprenaline-mediated relaxation. In mesenteric arteries from the spontaneously hypertensive rat, ciliobrevin D and colchicine both improved the isoprenaline-mediated vasorelaxation and relaxation to the Kv7.2 -7.5 activator, ML213. Immunostaining confirmed ciliobrevin D enhanced the membrane abundance of Kv7.4. As well as an increase in the function of Kv7.4, the functional changes were associated with an increase in the contribution of β2-adrenoceptor following isoprenaline treatment. Immunostaining experiments showed ciliobrevin D prevented isoprenaline-mediated internalizationof the β2-adrenoceptor.

CONCLUSIONS

Overall, these data show that colchicine and ciliobrevin D can induce a β2-adrenoceptor-mediated vasodilatation in arteries from the spontaneously hypertensive rat as well as reinstating Kv7.4 channel function.

Involvement of β-adrenoceptors in the cardiovascular responses induced by selective adenosine A2A and A2B receptor agonists

A_2A and A_2B adenosine receptors produce regionally selective regulation of vascular tone and elicit differing effects on mean arterial pressure (MAP), whilst inducing tachycardia. The tachycardia induced by the stimulation of A_2A or A_2B receptors has been suggested to be mediated by a reflex increase in sympathetic activity. Here, we have investigated the role of β₁ - and β₂ -adrenoceptors in mediating the different cardiovascular responses to selective A_2A and A_2B receptor stimulation. Hemodynamic variables were measured in conscious male Sprague-Dawley rats (350-450 g) via pulsed Doppler flowmetry. The effect of intravenous infusion (3 min per dose) of the A_2A -selective agonist CGS 21680 (0.1, 0.3, 1.0 µg.kg^-1 .min^-1 ) or the A_2B -selective agonist BAY 60-6583 (4.0, 13.3, 40.0 µg.kg^-1 .min^-1 ) in the absence or following pre-treatment with the non-selective β-antagonist propranolol (1.0 mg.kg^-1 ), the selective β₁ -antagonist CGP 20712A (200 µg.kg^-1 ), or the selective β₂ -antagonist ICI 118,551 (2.0 mg.kg^-1 ) was investigated (maintenance doses also administered). CGP 20712A and propranolol significantly reduced the tachycardic response to CGS 21680, with no change in the effect on MAP. ICI 118,551 increased BAY 60-6583-mediated renal and mesenteric flows, but did not affect the heart rate response. CGP 20712A attenuated the BAY 60-6583-induced tachycardia. These data imply a direct stimulation of the sympathetic activity via cardiac β₁ -adrenoceptors as a mechanism for the A_2A - and A_2B -induced tachycardia. However, the regionally selective effects of A_2B agonists on vascular conductance were independent of sympathetic activity and may be exploitable for the treatment of acute kidney injury and mesenteric ischemia.

The effect of the long-term inhibition of hydrogen sulfide production on the reactivity of the cardiovascular system in Wistar rats

In this study, we investigated the blood pressure responses of the peripheral bed in vivo after chronic hydrogen sulphide (H2S) inhibition combined with acute nitric oxide (NO) deficiency. We also evaluated the role of endogenously produced H2S in the vasoactive responses of large- and medium-sized arteries in vitro. Changes in integrated blood pressure responses were measured after chronic inhibition of cystathionine-γ-lyase, an enzyme involved in H2S synthesis, with DL-propargylglycine (PPG), and acute inhibition of NO-synthase with nonspecific L-NG-nitro arginine methyl ester (L-NAME), and vasoactive responses of the thoracic aorta (TA) and mesenteric artery (MA) were investigated after acute incubation with PPG. We confirmed that chronic H2S deficiency had no effect on blood pressure, heart trophycity, noradrenaline and H2S donor vasoactive responses but induced renal hypertrophy and decrease in acetylcholine-induced hypotensive and L-NAME-induced hypertensive responses. Acute H2S deficiency led to an increase in basal tone (MA) or active tone (TA), whereas endothelium-dependent vasorelaxation remained unaffected. Long-term administration of PPG revealed a role of endogenous H2S in the bioavailability of endothelial NO in peripheral arteries. When both H2S and NO were lacking, the activation of H2S-independent compensatory mechanisms plays an important role in maintaining the vasodilator responses of the cardiovascular system.

Increased β-adrenergic stimulation augments vascular smooth muscle cell calcification via PKA/CREB signalling

In chronic kidney disease (CKD), hyperphosphatemia promotes medial vascular calcification, a process augmented by osteogenic transdifferentiation of vascular smooth muscle cells (VSMCs). VSMC function is regulated by sympathetic innervation, and these cells express α- and β-adrenergic receptors. The present study explored the effects of β2-adrenergic stimulation by isoproterenol on VSMC calcification. Experiments were performed in primary human aortic VSMCs treated with isoproterenol during control or high phosphate conditions. As a result, isoproterenol dose dependently up-regulated the expression of osteogenic markers core-binding factor α-1 (CBFA1) and tissue-nonspecific alkaline phosphatase (ALPL) in VSMCs. Furthermore, prolonged isoproterenol exposure augmented phosphate-induced calcification of VSMCs. Isoproterenol increased the activation of PKA and CREB, while knockdown of the PKA catalytic subunit α (PRKACA) or of CREB1 genes was able to suppress the pro-calcific effects of isoproterenol in VSMCs. β2-adrenergic receptor silencing or inhibition with the selective antagonist ICI 118,551 blocked isoproterenol-induced osteogenic signalling in VSMCs. The present observations imply a pro-calcific effect of β2-adrenergic overstimulation in VSMCs, which is mediated, at least partly, by PKA/CREB signalling. These observations may support a link between sympathetic overactivity in CKD and vascular calcification.

Changthangi Pashmina Goat Genome: Sequencing, Assembly, and Annotation

Pashmina goats produce the world's finest and the most costly animal fiber (Pashmina) with an average fineness of 11-13 microns and have more evolved mechanisms than any known goat breed around the globe. Despite the repute of Pashmina goat for producing the finest and most sought-after animal fiber, meager information is available in the public domain about Pashmina genomics and transcriptomics. Here we present a 2.94 GB genome sequence from a male Changthangi white Pashmina goat. We generated 294.8 GB (>100X coverage) of the whole-genome sequence using the Illumina HiSeq 2500 sequencer. All cleaned reads were mapped to the goat reference genome (2,922,813,246 bp) which covers 97.84% of the genome. The Unaligned reads were used for de novo assembly resulting in a total of 882 MB non-reference contigs. De novo assembly analysis presented in this study provides important insight into the adaptation of Pashmina goats to cold stress and helps enhance our understanding of this complex phenomenon. A comparison of the Pashmina goat genome with a wild goat genome revealed a total of 2,823 high impact single nucleotide variations and small insertions and deletions, which may be associated with the evolution of Pashmina goats. The Pashmina goat genome sequence provided in this study may improve our understanding of complex traits found in Pashmina goats, such as annual fiber cycling, defense mechanism against hypoxic, survival secret in extremely cold conditions, and adaptation to a sparse diet. In addition, the genes identified from de novo assembly could be utilized in differentiating Pashmina fiber from other fibers to avoid falsification at marketing practices.

Activation of AMP kinase ameliorates kidney vascular dysfunction, oxidative stress and inflammation in rodent models of obesity

BACKGROUND AND PURPOSE

Obesity is a risk factor for the development of chronic kidney disease independent of diabetes, hypertension and other co-morbidities. Obesity-associated nephropathy is linked to dysregulation of the cell energy sensor AMP-activated protein kinase (AMPK). We aimed here to assess whether impairment of AMPK activity may cause renal arterial dysfunction in obesity and to evaluate the therapeutic potential of activating renal AMPK.

EXPERIMENTAL APPROACH

Effects of the AMPK activator A769662 were assessed on intrarenal arteries isolated from ob/ob mice and obese Zucker rats and then mounted in microvascular myographs. Superoxide and hydrogen peroxide production were measured by chemiluminescence and fluorescence, respectively, and protein expression was analysed by western blotting.

KEY RESULTS

Endothelium-dependent vasodilation and PI3K/Akt/eNOS pathway were impaired in preglomerular arteries from genetically obese rats and mice, along with impaired arterial AMPK activity and blunted relaxations induced by the AMPK activator A769662. Acute ex vivo exposure to A769662 restored endothelial function and enhanced activity of PI3K/Akt/eNOS pathway in obese rats, whereas in vivo treatment with A769662 improved metabolic state and ameliorated endothelial dysfunction, reduced inflammatory markers and vascular oxidative stress in renal arteries and restored redox balance in renal cortex of obese mice.

CONCLUSION AND IMPLICATIONS

These results demonstrate that AMPK dysregulation underlies obesity-associated kidney vascular dysfunction and activation of AMPK improves metabolic state, protects renal endothelial function and exerts potent vascular antioxidant and anti-inflammatory effects. The beneficial effects of vascular AMPK activation might represent a promising therapeutic approach to the treatment of obesity-related kidney injury.

Adrenergic signalling in osteoarthritis

Adrenoceptors (ARs) mediate the effects of the sympathetic neurotransmitters norepinephrine (NE) and epinephrine (E) in the human body and play a central role in physiologic and pathologic processes. Therefore, ARs have long been recognized as targets for therapeutic agents, especially in the field of cardiovascular medicine. During the past decades, the contribution of the sympathetic nervous system (SNS) and particularly of its major peripheral catecholamine NE to the pathogenesis of osteoarthritis (OA) attracted growing interest. OA is the most common degenerative joint disorder worldwide and a disease of the whole joint. It is characterized by progressive degradation of articular cartilage, synovial inflammation, osteophyte formation, and subchondral bone sclerosis mostly resulting in chronic pain. The subchondral bone marrow, the periosteum, the synovium, the vascular meniscus and numerous tendons and ligaments are innervated by tyrosine hydroxylase-positive (TH+) sympathetic nerve fibers that release NE into the synovial fluid and cells of all abovementioned joint tissues express at least one out of nine AR subtypes. During the past decades, several in vitro studies explored the AR-mediated effects of NE on different cell types in the joint. So far, only a few studies used animal OA models to investigate the contribution of distinct AR subtypes to OA pathogenesis in vivo. This narrative review shortly summarizes the current background knowledge about ARs and their signalling pathways at first. In the second part, we focus on recent findings in the field of NE-induced AR-mediated signalling in different joint tissues during OA pathogenesis and at the end, we will delineate the potential of targeting the adrenergic signalling for OA prevention or treatment. We used the PubMed bibliographic database to search for keywords such as 'joint' or 'cartilage' or 'synovium' or 'bone' and 'osteoarthritis' and/or 'trauma' and 'sympathetic nerve fibers' and/or 'norepinephrine' and 'adrenergic receptors / adrenoceptors' as well as 'adrenergic therapy'.

Clinical value of detecting autoantibodies against β1-, β2,- and α1-adrenergic receptors in carvedilol treatment of patients with heart failure

Objective

To determine the possible association of anti-β₁-adrenergic receptors (anti-β₁-AR), anti-β₂-AR and anti-α₁-AR with carvedilol treatment in patients with heart failure (HF).

Methods

A total of 267 HF patients were prospectively enrolled. Blood samples were measured by an enzyme-linked immunosorbent assay. All of the patients received carvedilol for their HF. Each patient was followed up for six months and their cardiac function was measured.

Results

The final analysis encompassed 137 patients comprising 65 patients with three autoantibodies (positive group) and 72 patients without all three autoantibodies but with one or two autoantibodies (negative group). The frequency and geometric mean titer of anti-β₁-AR, anti-β₂-AR, and anti-α₁-AR were significantly lower in the group without all three autoantibodies after six months of carvedilol treatment (all P < 0.01; from 100% to 57%, 50%, and 49%, respectively; and from 1: 118, 1: 138, and 1: 130 to 1: 72, 1: 61, and 1: 67, respectively). Furthermore, 28 patients in the positive group demonstrated complete ablation of autoantibodies. In addition, left ventricular remodelling and function was significantly improved by the use of carvedilol combined with the standard treatment regime for six months in the positive group (P < 0.01) when compared to the negative group (P < 0.05).

Conclusions

Carvedilol treatment significantly decreases frequency and geometric mean titer in patients with all three autoantibodies, even up to complete ablation, and significantly improved cardiac function and remodelling. The effect of carvedilol is probably correlated to the presence of all three autoantibodies.

Vascular tone and angiogenesis modulation by catecholamine coordinated to ruthenium

Catecholamines participate in angiogenesis, an important tumor development process. However, the way catecholamines interact with their receptors has not been completely elucidated, and doubts still remain as to whether these interactions occur between catechol and/or amine sites and particular amino acid residues on the catecholamine receptors. To evaluate how catechol and amine groups contribute to angiogenesis, we immobilized the catechol site through ruthenium ion (Ru) coordination, to obtain species with the general formula [Ru(NH₃)₄(catecholamine-R)]Cl. We then assessed the angiogenic activity of the complexes in a chorioallantoic membrane model (CAM) and examined vascular reactivity and calcium mobilization in rat aortas and vascular cells. [Ru(NH₃)₄(catecholamine-R)]Cl acted as partial agonists and/or antagonists of their respective receptors and induced calcium mobilization. [Ru(NH₃)₄(isoproterenol)]⁺ [Ru(NH₃)₄(noradrenaline)]⁺, and [Ru(NH₃)₄(adrenaline)]⁺ behaved as antiangiogenic complexes, whereas [Ru(NH₃)₄(dopamine)]⁺ proved to be a proangiogenic complex. In conclusion, catecholamines and [Ru(NH₃)₄(catecholamine-R)]Cl can modulate angiogenesis, and catechol group availability can modify the way these complexes impact the vascular tone, suggesting that catecholamines and their receptors interact differently after catecholamine coordination to ruthenium.

Age-dependent changes in electrophysiology and calcium handling: implications for pediatric cardiac research

Rodent models are frequently employed in cardiovascular research, yet our understanding of pediatric cardiac physiology has largely been deduced from more simplified two-dimensional cell studies. Previous studies have shown that postnatal development includes an alteration in the expression of genes and proteins involved in cell coupling, ion channels, and intracellular calcium handling. Accordingly, we hypothesized that postnatal cell maturation is likely to lead to dynamic alterations in whole heart electrophysiology and calcium handling. To test this hypothesis, we employed multiparametric imaging and electrophysiological techniques to quantify developmental changes from neonate to adult. In vivo electrocardiograms were collected to assess changes in heart rate, variability, and atrioventricular conduction (Sprague-Dawley rats). Intact, whole hearts were transferred to a Langendorff-perfusion system for multiparametric imaging (voltage, calcium). Optical mapping was performed in conjunction with an electrophysiology study to assess cardiac dynamics throughout development. Postnatal age was associated with an increase in the heart rate (181 ± 34 vs. 429 ± 13 beats/min), faster atrioventricular conduction (94 ± 13 vs. 46 ± 3 ms), shortened action potentials (APD₈₀: 113 ± 18 vs. 60 ± 17 ms), and decreased ventricular refractoriness (VERP: 157 ± 45 vs. 57 ± 14 ms; neonatal vs. adults, means ± SD, P < 0.05). Calcium handling matured with development, resulting in shortened calcium transient durations (168 ± 18 vs. 117 ± 14 ms) and decreased propensity for calcium transient alternans (160 ± 18- vs. 99 ± 11-ms cycle length threshold; neonatal vs. adults, mean ± SD, P < 0.05). Results of this study can serve as a comprehensive baseline for future studies focused on pediatric disease modeling and/or preclinical testing.NEW & NOTEWORTHY This is the first study to assess cardiac electrophysiology and calcium handling throughout postnatal development, using both in vivo and whole heart models.

Live Imaging and Analysis of Vasoactive Properties of Drugs Using an in-ovo Chicken Embryo Model: Replacing and Reducing Animal Testing

Vasodilation occurs as a result of the relaxation of the smooth muscle cells present in the walls of blood vessels. Various suitable models are available for the analysis of the vasoactive properties of drugs with therapeutic applications. But all these models have limitations, such as ethical issues and high cost. The purpose of this study is to develop an alternative model for studying the vasoactive properties of drugs using an in-ovo chicken embryo model. In the preliminary experiment, we used a well-known vasoconstrictor (adrenaline) and a vasodilator (spermine NoNoate) in the chick embryo area vasculosa and evaluated their concentration-response curve. Adrenaline (10 µM) and spermine NoNoate (10 µM) were administered in different arteries and veins and different positions of the right vitelline artery of the chick embryo. Results showed the middle of the vessel bed of the right vitelline artery having the best vasoactive effect compared to others. Finally, anti-hypertensive drugs, calcium channel blockers, and NOS agonists were administered in the chick embryo area vasculosa to validate the model. Results demonstrate that the chick embryo area vasculosa can be an alternative, robust, and unique in-ovo model for screening of anti-hypertensive drugs in real time.

Low-Dose Adrenaline Reduces Blood Pressure Acutely in Anesthetized Pigs Through a β2-Adrenergic Pathway

Adrenaline (epinephrine) is one of the prime messengers of the fight-or-flight response, favoring the activation of β-adrenergic receptors. Although general vasoconstriction to nonessential tissues is imperative, the vasodilatory effect of β-adrenergic receptor activation contends with this. We aimed to determine the dose-dependent effects of adrenaline on hemodynamics and to test whether adrenaline could lower blood pressure (BP) through a β2-adrenergic pathway. Nineteen Danish landrace pigs were used to pharmacologically probe the hemodynamic effect of adrenaline. Pigs were anesthetized, intubated, and electrocardiogram, systolic BP (SBP), diastolic BP (DBP), and left ventricular pressure (LVP) were monitored continuously. First, we tested the dose-dependent effects of adrenaline (0.01-10 µg/kg). Second, we determined the response to adrenaline (0.3 µg/kg) after atropine, prazosin, and propranolol pretreatment. Finally, we tested the hemodynamic effect of salbutamol in a subset of pigs. All doses of adrenaline increased heart rate, while BP showed a biphasic response: At low doses, adrenaline decreased SBP from 118 ± 3 to 106 ± 4 mm Hg (n = 15; P < 0.05) and DBP from 86 ± 3 to 71 ± 3 (n = 15; P < 0.05), while at high doses, SBP and DBP increased. LVP showed a similar pattern, with a tendency of decreased pressure at low doses, and an increased pressure at high doses (P < 0.05). Pretreatment with autonomic blockers revealed that the increase in BP was due to α-adrenergic activity, while the decrease was due to β-adrenergic activity. In confirmation, β-adrenergic activation through salbutamol showed a similar decrease in SBP, DBP, and LVP. We conclude that adrenaline dose-dependently increases heart rate, while producing a biphasic response in BP with a decrease at low doses and an increase at high doses in an anesthetized, large-animal model.

Vascular phenotype of amyloid precursor protein-deficient mice

The amyloid precursor protein (APP) is expressed in the blood vessel wall, but the physiological function of APP is not completely understood. Previous studies established that APP has amine oxidase activity responsible for degradation of catecholamines. In the present study, we characterized the vascular phenotype of APP-knockout (APP-/-) mice. We demonstrate that circulating levels of catecholamines are significantly increased in male as compared with female APP-/- mice. Studies of vasomotor function in isolated aortas revealed that contractions to the α1-receptor agonist phenylephrine were significantly reduced in male APP-/- mice but not in females. In addition, contractions to G protein activation with sodium fluoride were reduced exclusively in male APP-/- mice aortas. The endothelium-dependent relaxations to acetylcholine were not affected by the loss of APP in mice of both sexes. Further analysis of the mechanisms underlying endothelium-dependent relaxations revealed that inhibition of cyclooxygenase by indomethacin significantly impaired relaxations to acetylcholine exclusively in male APP-/- mice. Furthermore, acetylcholine-induced production of cyclic guanosine monophosphate (cGMP) was significantly reduced in male APP-/- mice aortas while acetylcholine-induced production of cyclic adenosine monophosphate (cAMP) was enhanced. We concluded that altered vascular reactivity to phenylephrine appears to be in part the result of chronic exposure of male APP-/- aorta to high circulating levels of catecholamines. The mechanisms responsible for the impairment of endothelium-dependent cGMP signaling and adaptive enhancement of endothelium-dependent production of cAMP remain to be defined. NEW & NOTEWORTHY Male amyloid precursor protein (APP)-deficient mice have higher circulating levels of catecholamines as compared with female APP-deficient mice. As a consequence, endothelium-dependent and endothelium-independent vasomotor functions of male APP-deficient mice are significantly altered. Under physiological conditions, expression of APP appears to play an important role in vascular function.

Rat mesenteric small artery neurogenic dilatation is predominantly mediated by β1 -adrenoceptors in vivo

KEY POINTS

The prevailing dogma about neurogenic regulation of vascular tone consists of major vasodilatation caused by CGRP (and possibly substance P) released from sensory-motor nerves and vasoconstriction caused by noradrenaline, ATP and neuropeptode Y release from sympathetic nerves. Most studies on perivascular nerve-mediated vasodilatation are made in vitro. In the present study, we provide evidence indicating that in vivo electrical perivascular nerve stimulation in rat mesenteric small arteries causes a large β1-adrenoceptor-mediated vasodilatation, which contrasts with a smaller vasodilatation caused by endogenous CGRP that is only visible after inhibition of Y1 NPY receptors.

ABSTRACT

Mesenteric arteries are densely innervated and the nerves are important regulators of vascular tone and hence blood pressure and blood flow. Perivascular sensory-motor nerves have been shown to cause vasodilatation in vitro. However, less is known about their function in vivo. Male Wistar rats (10-12 weeks old; n = 72) were anaesthetized with ketamine (3 mg kg^-1 ) and xylazine (0.75 mg kg^-1 ) or pentobarbital (60 mg kg^-1 ). After a laparotomy, a section of second-order mesenteric artery was visualized in an organ bath after minimal removal of perivascular adipose tissue. The effects of electrical field stimulation (EFS) and drugs on artery diameter and blood flow were recorded with intravital microscopy and laser speckle imaging. EFS caused vasodilatation in arteries constricted with 1 μm U46619 in the presence of 140 μm suramin and 1 μm prazosin. The vasodilatation was inhibited by 1 μm tetrodotoxin and 5 μm guanethidine, although not by the 1 μm of the CGRP receptor antagonist BIBN4096bs. In the presence of 0.3 μm Y1 receptor antagonist BIBP3226, BIBN4096bs partly inhibited the vasodilatation. Atenolol at a concentration 1 μm inhibited the vasodilatation, whereas 0.1 μm of the β₂ -adrenoceptor selective antagonist ICI-118,551 had no effect. Increasing the extracellular [K⁺ ] to 20 mm caused vasodilatation but was converted to vasoconstriction in the presence of 1 μm BIBN4096bs, and constriction to 30 mm potassium was potentiated by BIBN4096bs. Atenolol but not BIBN4096bs increased contraction to EFS in the absence of suramin and prazosin. In mesenteric small arteries of anaesthetized rats, EFS failed to stimulate major dilatation via sensory-motor nerves but induced sympathetic β₁ -adrenoceptor-mediated dilatation.

Assessing structural and functional response of murine vasculature to acute β-adrenergic stimulation in vivo during hypothermic and hyperthermic conditions

Background: Because of the importance of adrenoreceptors in regulating the cardiovascular (CV) system and the role of the CV system in thermoregulation, understanding the response to these two stressors is of interest. The purpose of this study was to assess changes of arterial geometry and function in vivo during thermal and β-adrenergic stress induced in mice and quantified by MRI.Methods: Male mice were anesthetized and imaged at 7 T. Anatomical and functional data were acquired from the neck (carotid artery), torso (suprarenal and infrarenal aorta and iliac artery) and periphery (femoral artery). Intravenous dobutamine (tail vein catheter, 40 µg/kg/min, 0.12 mL/h) was used as β-adrenergic stressor. Baseline and dobutamine data were acquired at minimally hypothermic (35 °C) and minimally hyperthermic (38 °C) core temperatures. Cross-sectional vessel area and maximum cyclic strain were measured across the cardiac cycle.Results: Vascular response varied by location and by core temperature. For minimally hypothermic conditions (35 °C), average, maximum and minimum areas decreased with dobutamine only at the suprarenal aorta (avg: -17.9%, max: -13.5%, min: -21.4%). For minimally hyperthermic conditions (38 °C), vessel areas decreased between baseline and dobutamine at the carotid (avg: -19.6%, max: -15.5%, min: -19.3%) and suprarenal aorta (avg: -24.2%, max: -17.4%, min: -17.3%); whereas, only the minimum vessel area decreased for the iliac artery (min: -14.4%). Maximum cyclic strain increased between baseline and dobutamine at the iliac artery for both conditions and at the suprarenal aorta at hyperthermic conditions.Conclusions: At hypothermic conditions, the vessel area response to dobutamine is diminished compared to hyperthermic conditions where the vessel area response mimics normothermic dobutamine conditions. The varied response emphasizes the need to monitor and control body temperature during medical conditions or treatments that may be accompanied by hypothermia, especially when vasoactive agents are used.

Molecular determinants of beta-adrenergic signaling to voltage-gated K+ channels in the cerebral circulation

Voltage-gated K⁺ (K_v ) channels are major determinants of membrane potential in vascular smooth muscle cells (VSMCs) and regulate the diameter of small cerebral arteries and arterioles. However, the intracellular structures that govern the expression and function of vascular K_v channels are poorly understood. Scaffolding proteins including postsynaptic density 95 (PSD95) recently were identified in rat cerebral VSMCs. Primarily characterized in neurons, the PSD95 scaffold has more than 50 known binding partners, and it can mediate macromolecular signaling between cell-surface receptors and ion channels. In cerebral arteries, Shaker-type K_v 1 channels appear to associate with the PSD95 molecular scaffold, and PSD95 is required for the normal expression and vasodilator influence of members of this K⁺ channel gene family. Furthermore, recent findings suggest that the β1-subtype adrenergic receptor is expressed in cerebral VSMCs and forms a functional vasodilator complex with K_v 1 channels on the PSD95 scaffold. Activation of β1-subtype adrenergic receptors in VSMCs enables protein kinase A-dependent phosphorylation and opening of K_v 1 channels in the PSD95 complex; the subsequent K⁺ efflux mediates membrane hyperpolarization and vasodilation of small cerebral arteries. Early evidence from other studies suggests that other families of K_v channels and scaffolding proteins are expressed in VSMCs. Future investigations into these macromolecular complexes that modulate the expression and function of K_v channels may reveal unknown signaling cascades that regulate VSMC excitability and provide novel targets for ion channel-based medications to optimize vascular tone.

Molecular pathways of oestrogen receptors and β-adrenergic receptors in cardiac cells: Recognition of their similarities, interactions and therapeutic value

Oestrogen receptors (ERs) and β-adrenergic receptors (βARs) play important roles in the cardiovascular system. Moreover, these receptors are expressed in cardiac myocytes and vascular tissues. Numerous experimental observations support the hypothesis that similarities and interactions exist between the signalling pathways of ERs (ERα, ERβ and GPR30) and βARs (β₁ AR, β₂ AR and β₃ AR). The recently discovered oestrogen receptor GPR30 shares structural features with the βARs, and this forms the basis for the interactions and functional overlap. GPR30 possesses protein kinase A (PKA) phosphorylation sites and PDZ binding motifs and interacts with A-kinase anchoring protein 5 (AKAP5), all of which enable its interaction with the βAR pathways. The interactions between ERs and βARs occur downstream of the G-protein-coupled receptor, through the G_αs and G_αi proteins. This review presents an up-to-date description of ERs and βARs and demonstrates functional synergism and interactions among these receptors in cardiac cells. We explore their signalling cascades and the mechanisms that orchestrate their interactions and propose new perspectives on the signalling patterns for the GPR30 based on its structural resemblance to the βARs. In addition, we explore the relevance of these interactions to cell physiology, drugs (especially β-blockers and calcium channel blockers) and cardioprotection. Furthermore, a receptor-independent mechanism for oestrogen and its influence on the expression of βARs and calcium-handling proteins are discussed. Finally, we highlight promising therapeutic avenues that can be derived from the shared pathways, especially the phosphatidylinositol-3-OH kinase (PI3K/Akt) pathway.

Age-, Gender-, and in Vivo Different Doses of Isoproterenol Modify in Vitro Aortic Vasoreactivity and Circulating VCAM-1

Different human-like cardiomyopathies associated to β-adrenergic stimulation are experimentally modeled in animals through variations in dose, route, and duration of administration of different cardiotoxic drugs. However, associated changes in the vasculature and their relation to systemic inflammation, and the influence of cardiovascular diseases risk factors (gender and age) upon them are seldom analyzed. Here we studied the effect of age and gender on the vasoreactivity of aortas from mice subjected to in vivo repeated β-adrenergic stimulation with different doses of isoproterenol (ISO) in association with circulating inflammatory cytokines. Young (2 months) and old (18 months) male and female mice received 0 (control), 5, 40, 80 or 160 μg/g/d of ISO (7 days, s.c.). IL-1α, IL-4 and vascular cell adhesion molecule-1 (VCAM-1) were quantified in plasma. In vitro, norepinephrine-induced vasoconstriction and acetylcholine-induced relaxation were measured in aortas. No differences in contraction, relaxation, IL-1α, and IL-4 were found between control young males and females. Age decreased contraction in males and relaxation was lower in females and abolished in males. VCAM-1 was higher in young males than in females and increased in old mice. Vasoconstriction in ISO-treated mice results as a bell-shaped curve on contraction in young and old males, with lower values in the latter. In females, ISO-160 increased contraction in young females but decreased it in old females. Vasorelaxation was reduced in ISO-treated young males and females. ISO-80 and 160 reduced vasorelaxation in old females, and intermediate doses relaxed aortas from old males. VCAM-1 was higher in young and old males with ISO-80 and 160; while VCAM-1 was higher only with ISO-160 in old females. Our results demonstrate that repeated β-adrenergic stimulation modifies vascular reactivity depending on gender, age, and dose. Females were less sensitive to alterations in vasoreactivity, and young females required a higher amount of the adrenergic stimuli than old females to show vascular alterations. Changes were independent of IL-1α and IL-4. VCAM-1 only changed in old females stimulated with ISO 160. Our results highlight the relevance of considering and comparing in the same study females and aged organisms to improve the accuracy of applications to clinical studies.

Effect of anaesthetic and choice of neuromuscular blocker on vagal control of heart rate under laboratory animal experimental conditions

Neuromuscular-blocking agents are commonly used in laboratory animal research settings. Due to actions of cholinergic receptors at locations other than the motor end-plate, these agents have a strong propensity to modulate autonomic outflow and may therefore not be desirable in studies examining autonomic function. This study aimed to compare the effect of two non-depolarizing neuromuscular-blocking agents, pancuronium and cisatracurium, on blood pressure, heart rate and non-invasive indices of autonomic function (heart rate variability, systolic blood pressure variability and baroreflex sensitivity) under two different types of anaesthesia in Lewis rats. Pancuronium produced a profound vagolytic response characterized by tachycardia, reduction in heart rate variability and baroreflex sensitivity under urethane anaesthesia, and with minimal effect under isoflurane anaesthesia. Conversely, cisatracurium produced no evidence of vagolytic action under either urethane or isoflurane anaesthesia. Therefore, for studies interested in examining autonomic function, particularly baroreflex or vagal function, neuromuscular blockade would be best achieved using cisatracurium.

The role of β-adrenergic receptors and p38MAPK signaling pathways in physiological processes of cardiosphere-derived cells

The effects of β adrenergic receptors (β-ARs) and p38 mitogen-activated protein kinases (MAPK) pathways on cardiosphere-derived cells (CDCs) are largely unknown. This study aimed to investigate the roles of β-ARs and p38MAPK pathways on the proliferation, apoptosis, and differentiation capacity of CDCs. The CDCs were treated with β1-AR blocker (Met group), β2-AR antagonist (ICI group), and p38MAPK inhibitor (SB group), non-selective β-AR blocker (PRO group), and β-AR agonist (ISO group). The viability, apoptotic rate and differentiation status of CDCs were determined by MST-1 assay, flow cytometery, and Western blot, respectively. The CDCs viability significantly reduced in ICI group (all P < 0.05), and SB group had a significant high viability after 48 h treatment (P < 0.05). Compared with control group, all treated groups had a low apoptotic rate. After treatment for 72 h, ISO treatment elevated the expression of Nkx2.5, and could partially or fully attenuate the inhibitory effects of β-AR antagonists and/or p38MAPK inhibitor. A similar overall trend of protein expression levels among all groups could be observed between protein pairs of cTnT and β1-AR as well as c-Kit and β2-AR, respectively. These results suggested that β-ARs and p38MAPK signaling pathways play crucial roles in the proliferation and differentiation of CDCs. Our findings should be helpful for better understanding the molecular mechanism underlying the physiological processes of CDCs.

Pharmacogenetic Associations of β1-Adrenergic Receptor Polymorphisms With Cardiovascular Outcomes in the SPS3 Trial (Secondary Prevention of Small Subcortical Strokes)

BACKGROUND AND PURPOSE

Functional polymorphisms (Ser49Gly and Arg389Gly) in ADRB1 have been associated with cardiovascular and β-blocker response outcomes. Herein we examined associations of these polymorphisms with major adverse cardiovascular events (MACE), with and without stratification by β-blocker treatment in patients with a history of stroke.

METHODS

Nine hundred and twenty-six participants of the SPS3 trial's (Secondary Prevention of Small Subcortical Strokes) genetic substudy with hypertension were included. MACE included stroke, myocardial infarction, and all-cause death. Kaplan-Meier and multivariable Cox regression analyses were used. Because the primary component of MACE was ischemic stroke, we tested the association of Ser49Gly with ischemic stroke among 41 475 individuals of European and African ancestry in the NINDS (National Institute of Neurological Disorders and Stroke) SiGN (Stroke Genetics Network).

RESULTS

MACE was higher in carriers of the Gly49 allele than in those with the Ser49Ser genotype (10.5% versus 5.4%, log-rank P=0.005). Gly49 carrier status was associated with MACE (hazard ratio, 1.62; 95% confidence interval, 1.00-2.68) and ischemic stroke (hazard ratio, 1.81; 95% confidence interval, 1.01-3.23) in SPS3 and with small artery ischemic stroke (odds ratio, 1.14; 95% confidence interval, 1.03-1.26) in SiGN. In SPS3, β-blocker-treated Gly49 carriers had increased MACE versus non-β-blocker-treated individuals and noncarriers (hazard ratio, 2.03; 95% confidence interval, 1.20-3.45). No associations were observed with the Arg389Gly polymorphism.

CONCLUSION

Among individuals with previous small artery ischemic stroke, the ADRB1 Gly49 polymorphism was associated with MACE, particularly small artery ischemic stroke, a risk that may be increased among β-blocker-treated individuals. Further research is needed to define β-blocker benefit among ischemic stroke patients by ADRB1 genotype.

CLINICAL TRIAL REGISTRATION

URL: http://www.clinicaltrials.gov. Unique identifier: NCT00059306.

Low epinephrine levels and selective deficiency of β2-adrenoceptor vasodilation at birth

AIMS

Epinephrine is unique among biogenic catecholamines as a potent agonist of β2-adrenoceptors. The β2-adrenoceptor mediated effects during development might be linked to the increase of epinephrine synthesis. Our purpose was to characterize β-adrenoceptor-mediated relaxation in the aorta of newborn and young rabbits (3 to 4months old), and to relate those responses with the epinephrine content of the adrenal gland.

MAIN METHODS

The epinephrine levels and the tyrosine hydroxylase activity were determined in adrenal glands of newborn and young rabbits. Also, concentration-response curves to phenylephrine (selective α1-adrenoceptor agonist), dobutamine (selective β1-adrenoceptor agonist), terbutaline (selective β2-adrenoceptor agonist), and CL 316243 (selective β3-adrenoceptor agonist) were determined in isolated aortic rings obtained from both groups.

KEY FINDINGS

The adrenal gland content and the plasma concentrations of epinephrine were lower in newborn than in young rabbits. In contrast, the tyrosine hydroxylase activity was higher in newborn than in young rabbits. On the other hand, the maximal response to phenylephrine was lower in newborn than in young rabbits. Terbutaline at concentrations selective for β2-adrenoceptors had no relaxing effects in neonates, in contrast to young rabbits. The potency and the maximal response of neither dobutamine nor CL 316243 were significantly different between the two groups.

SIGNIFICANCE

In rabbits, as well as in humans, β2-adrenoceptor-mediated responses and epinephrine synthesis are both immature at birth. On the other hand, the β1 and β3-adrenoceptor-mediated responses are fully developed. We conclude that epinephrine may influence the development of the β2-adrenoceptor-mediated responses at birth and the rabbit is an excellent model to study these issues.

Stress, metabolism and cancer: integrated pathways contributing to immune suppression

The potential for immune cells to control cancers has been recognized for many decades, but only recently has real excitement begun to spread through the oncology community following clear evidence that therapeutic blockade of specific immune-suppressive mechanisms is enough to make a real difference in survival for patients with several different advanced cancers. However, impressive and encouraging as these new clinical data are, it is clear that more effort should be devoted toward understanding the full spectrum of factors within cancer patients, which have the potential to block or weaken antitumor activity by immune cells. The goal of this brief review is to highlight recent literature revealing interactive stress and metabolic pathways, particularly those mediated by the sympathetic nervous system, which may conspire to block immune cells from unleashing their full killing potential. There is exciting new information regarding the role of neurogenesis by tumors and adrenergic signaling in cancer progression (including metabolic changes associated with cachexia and lipolysis) and in regulation of immune cell function and differentiation. However, much more work is needed to fully understand how the systemic metabolic effects mediated by the brain and nervous system can be targeted for therapeutic efficacy in the setting of immunotherapy and other cancer therapies.

Vascular nitric oxide: Beyond eNOS

As the first discovered gaseous signaling molecule, nitric oxide (NO) affects a number of cellular processes, including those involving vascular cells. This brief review summarizes the contribution of NO to the regulation of vascular tone and its sources in the blood vessel wall. NO regulates the degree of contraction of vascular smooth muscle cells mainly by stimulating soluble guanylyl cyclase (sGC) to produce cyclic guanosine monophosphate (cGMP), although cGMP-independent signaling [S-nitrosylation of target proteins, activation of sarco/endoplasmic reticulum calcium ATPase (SERCA) or production of cyclic inosine monophosphate (cIMP)] also can be involved. In the blood vessel wall, NO is produced mainly from l-arginine by the enzyme endothelial nitric oxide synthase (eNOS) but it can also be released non-enzymatically from S-nitrosothiols or from nitrate/nitrite. Dysfunction in the production and/or the bioavailability of NO characterizes endothelial dysfunction, which is associated with cardiovascular diseases such as hypertension and atherosclerosis.

Beta1-adrenergic receptor-mediated dilation of rat cerebral artery requires Shaker-type KV1 channels on PSD95 scaffold

Postsynaptic density-95 (PSD95) is a scaffolding protein in cerebral vascular smooth muscle cells (cVSMCs), which binds to Shaker-type K(+) (KV1) channels and facilitates channel opening through phosphorylation by protein kinase A. β1-Adrenergic receptors (β1ARs) also have a binding motif for PSD95. Functional association of β1AR with KV1 channels through PSD95 may represent a novel vasodilator complex in cerebral arteries (CA). We explored whether a β1AR-PSD95-KV1 complex is a determinant of rat CA dilation. RT-PCR and western blots revealed expression of β1AR in CA. Isoproterenol induced a concentration-dependent dilation of isolated, pressurized rat CA that was blocked by the β1AR blocker CGP20712. Cranial window imaging of middle cerebral arterioles in situ showed isoproterenol- and norepinephrine-induced dilation that was blunted by β1AR blockade. Isoproterenol-induced hyperpolarization of cVSMCs in pressurized CA was blocked by CGP20712. Confocal images of cVSMCs immunostained with antibodies against β1AR and PSD95 indicated strong colocalization, and PSD95 co-immunoprecipitated with β1AR in CA lysate. Blockade of KV1 channels, β1AR or disruption of PSD95-KV1 interaction produced similar blunting of isoproterenol-induced dilation in pressurized CA. These findings suggest that PSD95 mediates a vasodilator complex with β1AR and KV1 channels in cVSMCs. This complex may be critical for proper vasodilation in rat CA.

Pathophysiological mechanisms of catecholamine and cocaine-mediated cardiotoxicity

Overactivation of the sympatho-adrenergic system is an essential mechanism providing short-term adaptation to the stressful conditions of critical illnesses. In the same way, the administration of exogenous catecholamines is mandatory to support the failing circulation in acutely ill patients. In contrast to these short-term benefits, prolonged adrenergic stress is detrimental to the cardiovascular system by initiating a series of adverse effects triggering significant cardiotoxicity, whose pathophysiological mechanisms are complex and only partially elucidated. In addition to the development of myocardial oxygen supply/demand imbalance induced by the sustained activation of adrenergic receptors, catecholamines can damage cardiomyocytes by fostering mitochondrial dysfunction, via two main mechanisms. The first one is calcium overload, consecutive to β-adrenergic receptor-mediated activation of protein kinase A and subsequent phosphorylation of multiple Ca(2+)-cycling proteins. The second one is oxidative stress, primarily related to the transformation of catecholamines into "aminochromes," which undergo redox cycling in mitochondria to generate copious amounts of oxygen-derived free radicals. In turn, calcium overload and oxidative stress promote mitochondrial permeability transition and cardiomyocyte cell death, both via the apoptotic and necrotic pathways. Comparable mechanisms of myocardial toxicity, including marked oxidative stress and mitochondrial dysfunction, have been reported with the use of cocaine, a common recreational drug with potent sympathomimetic activity. The aim of the current review is to present in detail the pathophysiological processes underlying the development of catecholamine and cocaine-induced cardiomyopathy, as such conditions may be frequently encountered in the clinical practice of cardiologists and ICU specialists.

Enhanced endothelium-dependent relaxation of rat pulmonary artery following β-adrenergic overstimulation: involvement of the NO/cGMP/VASP pathway

AIMS

The aim of this study was to investigate whether β-adrenoceptor (β-AR) overstimulation induced by in vivo treatment with isoproterenol (ISO) alters vascular reactivity and nitric oxide (NO) production and signaling in pulmonary arteries.

MAIN METHODS

Vehicle or ISO (0.3mgkg(-1)day(-1)) was administered daily to male Wistar rats. After 7days, the jugular vein was cannulated to assess right ventricular (RV) systolic pressure (SP) and end diastolic pressure (EDP). The extralobar pulmonary arteries were isolated to evaluate the relaxation responses, protein expression (Western blot), NO production (diaminofluorescein-2 fluorescence), and cyclic guanosine 3',5'-monophosphate (cGMP) levels (enzyme immunoassay kit).

KEY FINDINGS

ISO treatment induced RV hypertrophy; however, no differences in RV-SP and EDP were observed. The pulmonary arteries from the ISO-treated group showed enhanced relaxation to acetylcholine that was abolished by the NO synthase (NOS) inhibitor N(ω)-nitro-l-arginine methyl ester (l-NAME); whereas relaxation elicited by sodium nitroprusside, ISO, metaproterenol, mirabegron, or KCl was not affected by ISO treatment. ISO-treated rats displayed enhanced endothelial NOS (eNOS) and vasodilator-stimulated phosphoprotein (VASP) expression in the pulmonary arteries, while phosphodiesterase-5 protein expression decreased. ISO treatment increased NO and cGMP levels and did not induce eNOS uncoupling.

SIGNIFICANCE

The present data indicate that β-AR overactivation enhances the endothelium-dependent relaxation of pulmonary arteries. This effect was linked to an increase in eNOS-derived NO production, cGMP formation and VASP content and to a decrease in phosphodiesterase-5 expression. Therefore, elevated NO bioactivity through cGMP/VASP signaling could represent a protective mechanism of β-AR overactivation on pulmonary circulation.

Mechanisms of propranolol action in infantile hemangioma

Infantile hemangioma is a common tumor of infancy. Although most hemangiomas spontaneously regress, treatment is indicated based on complications, risk to organ development and function, and disfigurement. The serendipitous discovery of propranolol, a non-selective β-adrenergic receptor blocker, as an effective means to regress hemangiomas has made this a first-line therapy for hemangioma patients. Propranolol has shown remarkable response rates. There are, however, some adverse effects, which include changes in sleep, acrocyanosis, hypotension, and hypoglycemia. Over the last few years, researchers have focused on understanding the mechanisms by which propranolol causes hemangioma regression. This has entailed study of cultured vascular endothelial cells including endothelial cells isolated from hemangioma patients. In this article, we review recent studies offering potential mechanisms of how various cell types found in hemangioma may respond to propranolol.

Different effects of prolonged β-adrenergic stimulation on heart and cerebral artery

The aim of this review was to understand the effects of β-adrenergic stimulation on oxidative stress, structural remodeling, and functional alterations in the heart and cerebral artery. Diverse stimuli activate the sympathetic nervous system, leading to increased levels of catecholamines. Long-term overstimulation of the β-adrenergic receptor (βAR) in response to catecholamines causes cardiovascular diseases, including cardiac hypertrophy, stroke, coronary artery disease, and heart failure. Although catecholamines have identical sites of action in the heart and cerebral artery, the structural and functional modifications differentially activate intracellular signaling cascades. βAR-stimulation can increase oxidative stress in the heart and cerebral artery, but has also been shown to induce different cytoskeletal and functional modifications by modulating various components of the βAR signal transduction pathways. Stimulation of βAR leads to cardiac dysfunction due to an overload of intracellular Ca²⁺ in cardiomyocytes. However, this stimulation induces vascular dysfunction through disruption of actin cytoskeleton in vascular smooth muscle cells. Many studies have shown that excessive concentrations of catecholamines during stressful conditions can produce coronary spasms or arrhythmias by inducing Ca²⁺-handling abnormalities and impairing energy production in mitochondria, In this article, we highlight the different fates caused by excessive oxidative stress and disruptions in the cytoskeletal proteome network in the heart and the cerebral artery in responsed to prolonged βAR-stimulation.

A nervous tumor microenvironment: the impact of adrenergic stress on cancer cells, immunosuppression, and immunotherapeutic response

Long conserved mechanisms maintain homeostasis in living creatures in response to a variety of stresses. However, continuous exposure to stress can result in unabated production of stress hormones, especially catecholamines, which can have detrimental health effects. While the long-term effects of chronic stress have well-known physiological consequences, recent discoveries have revealed that stress may affect therapeutic efficacy in cancer. Growing epidemiological evidence reveals strong correlations between progression-free and long-term survival and β-blocker usage in cancer patients. In this review, we summarize the current understanding of how the catecholamines, epinephrine and norepinephrine, affect cancer cell survival and tumor progression. We also highlight new data exploring the potential contributions of stress to immunosuppression in the tumor microenvironment and the implications of these findings for the efficacy of immunotherapies.

Different β-adrenoceptor subtypes coupling to cAMP or NO/cGMP pathways: implications in the relaxant response of rat conductance and resistance vessels

BACKGROUND AND PURPOSE

To analyse the relative contribution of β1 -, β2 - and β3 -adrenoceptors (Adrb) to vasodilatation in conductance and resistance vessels, assessing the role of cAMP and/or NO/cGMP signalling pathways.

EXPERIMENTAL APPROACH

Rat mesenteric resistance artery (MRA) and aorta were used to analyse the Adrb expression by real-time-PCR and immunohistochemistry, and for the pharmacological characterization of Adrb-mediated activity by wire myography and tissue nucleotide accumulation.

KEY RESULTS

The mRNAs and protein for all Adrb were identified in endothelium and/or smooth muscle cells (SMCs) in both vessels. In MRA, Adrb1 signalled through cAMP, Adrb3 through both cAMP and cGMP, but Adrb2, did not activate nucleotide formation; isoprenaline relaxation was inhibited by propranolol (β1 , β2 ), CGP20712A (β1 ), and SQ22536 (adenylyl cyclase inhibitor), but not by ICI118,551 (β2 ), SR59230A (β3 ), ODQ (soluble guanylyl cyclase inhibitor), L-NAME or endothelium removal. In aorta, Adrb1 signalled through cAMP, while β2 - and β3 -subtypes through cGMP; isoprenaline relaxation was inhibited by propranolol, ICI118,551, ODQ, L-NAME, and to a lesser extent, by endothelium removal. CL316243 (β3 -agonist) relaxed aorta, but not MRA.

CONCLUSION AND IMPLICATION

Despite all three Adrb subtypes being found in both vessels, Adrb1, located in SMCs and acting through the adenylyl cyclase/cAMP pathway, are primarily responsible for vasodilatation in MRA. However, Adrb-mediated vasodilatation in aorta is driven by endothelial Adrb2 and Adrb3, but also by the Adrb2 present in SMCs, and is coupled to the NO/cGMP pathway. These results could help to understand the different physiological roles played by Adrb signalling in regulating conductance and resistance vessels.

Attenuated aortic vasodilation and sympathetic prejunctional facilitation in epinephrine-deficient mice: selective impairment of β2-adrenoceptor responses

It has been suggested that there is a link between epinephrine synthesis and the development of β2-adrenoceptor-mediated effects, but it remains to be determined whether this development is triggered by epinephrine. The aim of this study was to characterize β-adrenoceptor-mediated relaxation and facilitation of norepinephrine release in the aorta of phenylethanolamine-N-methyltransferase-knockout (Pnmt-KO) mice. Catecholamines were quantified by reverse-phase high-performance liquid chromatography-electrochemical detection. Aortic rings were mounted in a myograph to determine concentration-response curves to selective β1- or β2-adrenoceptor agonists in the absence or presence of selective β1- or β2-adrenoceptor antagonists. Aortic rings were also preincubated with [(3)H]norepinephrine to measure tritium overflow elicited by electrical stimulation in the presence of increasing concentrations of nonselective β- or selective β2-adrenoceptor agonists. β2-Adrenoceptor protein density was evaluated by Western blotting and β2-adrenoceptor localization by immunohistochemistry. Epinephrine is absent in Pnmt-KO mice. The potency and the maximal effect of the β2-adrenoceptor agonist terbutaline were lower in Pnmt-KO than in wild-type (WT) mice. The selective β2-adrenoceptor antagonist ICI 118,551 [(±)-erythro-(S*,S*)-1-[2,3-(dihydro-7-methyl-1H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol hydrochloride] antagonized the relaxation caused by terbutaline in WT but not in Pnmt-KO mice. Isoproterenol and terbutaline induced concentration-dependent increases in tritium overflow in WT mice only. β2-Adrenoceptor protein density was decreased in membrane aorta homogenates of Pnmt-KO mice, and this finding was supported by immunofluorescence confocal microscopy. In conclusion, epinephrine is crucial for β2-adrenoceptor-mediated vasodilation and facilitation of norepinephrine release. In the absence of epinephrine, β2-adrenoceptor protein density was decreased in aorta cell membranes, thus potentially hindering its functional activity.

Lack of β2 -adrenoceptors aggravates heart failure-induced skeletal muscle myopathy in mice

Skeletal myopathy is a hallmark of heart failure (HF) and has been associated with a poor prognosis. HF and other chronic degenerative diseases share a common feature of a stressed system: sympathetic hyperactivity. Although beneficial acutely, chronic sympathetic hyperactivity is one of the main triggers of skeletal myopathy in HF. Considering that β2 -adrenoceptors mediate the activity of sympathetic nervous system in skeletal muscle, we presently evaluated the contribution of β2 -adrenoceptors for the morphofunctional alterations in skeletal muscle and also for exercise intolerance induced by HF. Male WT and β2 -adrenoceptor knockout mice on a FVB genetic background (β2 KO) were submitted to myocardial infarction (MI) or SHAM surgery. Ninety days after MI both WT and β2 KO mice presented to cardiac dysfunction and remodelling accompanied by significantly increased norepinephrine and epinephrine plasma levels, exercise intolerance, changes towards more glycolytic fibres and vascular rarefaction in plantaris muscle. However, β2 KO MI mice displayed more pronounced exercise intolerance and skeletal myopathy when compared to WT MI mice. Skeletal muscle atrophy of infarcted β2 KO mice was paralleled by reduced levels of phosphorylated Akt at Ser 473 while increased levels of proteins related with the ubiquitin--proteasome system, and increased 26S proteasome activity. Taken together, our results suggest that lack of β2 -adrenoceptors worsen and/or anticipate the skeletal myopathy observed in HF.

Isoproterenol induces vascular oxidative stress and endothelial dysfunction via a Giα-coupled β2-adrenoceptor signaling pathway

OBJECTIVE

Sustained β-adrenergic stimulation is a hallmark of sympathetic hyperactivity in cardiovascular diseases. It is associated with oxidative stress and altered vasoconstrictor tone. This study investigated the β-adrenoceptor subtype and the signaling pathways implicated in the vascular effects of β-adrenoceptor overactivation.

METHODS AND RESULTS

Mice lacking the β1- or β2-adrenoceptor subtype (β1KO, β2KO) and wild-type (WT) were treated with isoproterenol (ISO, 15 μg.g(-1) x day(-1), 7 days). ISO significantly enhanced the maximal vasoconstrictor response (Emax) of the aorta to phenylephrine in WT (+34%) and β1KO mice (+35%) but not in β2KO mice. The nitric oxide synthase (NOS) inhibitor L-NAME abolished the differences in phenylephrine response between the groups, suggesting that ISO impaired basal NO availability in the aorta of WT and β1KO mice. Superoxide dismutase (SOD), pertussis toxin (PTx) or PD 98,059 (p-ERK 1/2 inhibitor) incubation reversed the hypercontractility of aortic rings from ISO-treated WT mice; aortic contraction of ISO-treated β2KO mice was not altered. Immunoblotting revealed increased aortic expression of Giα-3 protein (+50%) and phosphorylated ERK1/2 (+90%) and decreased eNOS dimer/monomer ratio in ISO-treated WT mice. ISO enhanced the fluorescence response to dihydroethidium (+100%) in aortas from WT mice, indicating oxidative stress that was normalized by SOD, PTx and L-NAME. The ISO effects were abolished in β2KO mice.

CONCLUSIONS

The β2-adrenoceptor/Giα signaling pathway is implicated in the enhanced vasoconstrictor response and eNOS uncoupling-mediated oxidative stress due to ISO treatment. Thus, long-term β2-AR activation might results in endothelial dysfunction.

β-Adrenergic regulation of cardiac progenitor cell death versus survival and proliferation

RATIONALE

Short-term β-adrenergic stimulation promotes contractility in response to stress but is ultimately detrimental in the failing heart because of accrual of cardiomyocyte death. Endogenous cardiac progenitor cell (CPC) activation may partially offset cardiomyocyte losses, but consequences of long-term β-adrenergic drive on CPC survival and proliferation are unknown.

OBJECTIVE

We sought to determine the relationship between β-adrenergic activity and regulation of CPC function.

METHODS AND RESULTS

Mouse and human CPCs express only β2 adrenergic receptor (β2-AR) in conjunction with stem cell marker c-kit. Activation of β2-AR signaling promotes proliferation associated with increased AKT, extracellular signal-regulated kinase 1/2, and endothelial NO synthase phosphorylation, upregulation of cyclin D1, and decreased levels of G protein-coupled receptor kinase 2. Conversely, silencing of β2-AR expression or treatment with β2-antagonist ICI 118, 551 impairs CPC proliferation and survival. β1-AR expression in CPC is induced by differentiation stimuli, sensitizing CPC to isoproterenol-induced cell death that is abrogated by metoprolol. Efficacy of β1-AR blockade by metoprolol to increase CPC survival and proliferation was confirmed in vivo by adoptive transfer of CPC into failing mouse myocardium.

CONCLUSIONS

β-adrenergic stimulation promotes expansion and survival of CPCs through β2-AR, but acquisition of β1-AR on commitment to the myocyte lineage results in loss of CPCs and early myocyte precursors.

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.

Increased vascular contractility and oxidative stress in β₂-adrenoceptor knockout mice: the role of NADPH oxidase

BACKGROUND/AIMS

β(2)-adrenoceptor (β(2)-AR) activation induces smooth muscle relaxation and endothelium-derived nitric oxide (NO) release. However, whether endogenous basal β(2)-AR activity controls vascular redox status and NO bioavailability is unclear. Thus, we aimed to evaluate vascular reactivity in mice lacking functional β(2)-AR (β(2)KO), focusing on the role of NO and superoxide anion.

METHODS AND RESULTS

Isolated thoracic aortas from β(2)KO and wild-type mice (WT) were studied. β(2)KO aortas exhibited an enhanced contractile response to phenylephrine compared to WT. Endothelial removal and L-NAME incubation increased phenylephrine-induced contraction, abolishing the differences between β(2)KO and WT mice. Basal NO availability was reduced in aortas from β(2)KO mice. Incubation of β(2)KO aortas with superoxide dismutase or NADPH inhibitor apocynin restored the enhanced contractile response to phenylephrine to WT levels. β(2)KO aortas exhibited oxidative stress detected by enhanced dihydroethidium fluorescence, which was normalized by apocynin. Protein expression of eNOS was reduced, while p47(phox) expression was enhanced in β(2)KO aortas.

CONCLUSIONS

The present results demonstrate for the first time that enhanced NADPH-derived superoxide anion production is associated with reduced NO bioavailability in aortas of β(2)KO mice. This study extends the knowledge of the relevance of the endogenous activity of β(2)-AR to the maintenance of the vascular physiology.

Vascular hyperpolarization to β-adrenoceptor agonists evokes spreading dilatation in rat isolated mesenteric arteries

BACKGROUND AND PURPOSE

β-Adrenoceptor stimulation causes pronounced vasodilatation associated with smooth muscle hyperpolarization. Although the hyperpolarization is known to reflect K(ATP) channel activation, it is not known to what extent it contributes to vasodilatation.

EXPERIMENTAL APPROACH

Smooth muscle membrane potential and tension were measured simultaneously in small mesenteric arteries in a wire myograph. The spread of vasodilatation over distance was assessed in pressurized arteries following localized intraluminal perfusion of either isoprenaline, adrenaline or noradrenaline.

KEY RESULTS

Isoprenaline stimulated rapid smooth muscle relaxation associated at higher concentrations with robust hyperpolarization. Noradrenaline or adrenaline evoked a similar hyperpolarization to isoprenaline if the α(1)-adrenoceptor antagonist prazosin was present. With each agonist, glibenclamide blocked hyperpolarization without reducing relaxation. Focal, intraluminal application of isoprenaline, noradrenaline or adrenaline during block of α(1)-adrenoceptors evoked a dilatation that spread along the entire length of the isolated artery. This response was endothelium-dependent and inhibited by glibenclamide.

CONCLUSIONS AND IMPLICATIONS

Hyperpolarization is not essential for β-adrenoceptor-mediated vasodilatation. However, following focal β-adrenoceptor stimulation, this hyperpolarization underlies the ability of vasodilatation to spread along the artery wall. The consequent spread of vasodilatation is dependent upon the endothelium and likely to be of physiological relevance in the coordination of tissue blood flow.

Impaired β-adrenoceptor-induced relaxation in small mesenteric arteries from DOCA-salt hypertensive rats is due to reduced K(Ca) channel activity

β-Adrenoceptor (β-AR)-mediated relaxation plays an important role in the regulation of vascular tone. β-AR-mediated vascular relaxation is reduced in various disease states and aging. We hypothesized that β-AR-mediated vasodilatation is impaired in DOCA-salt hypertension due to alterations in the cAMP pathway. β-AR-mediated relaxation was determined in small mesenteric arteries from DOCA-salt hypertensive and control uninephrectomized (Uni) rats. To exclude nitric oxide (NO) and cyclooxygenase (COX) pathways, relaxation responses were determined in the presence of l-NNA and indomethacin, NO synthase inhibitor and COX inhibitors, respectively. Isoprenaline (ISO)-induced relaxation was reduced in arteries from DOCA-salt compared to Uni rats. Protein kinase A (PKA) inhibitors (H89 or Rp-cAMPS) or adenylyl cyclase inhibitor (SQ22536) did not abolish the difference in ISO-induced relaxation between the groups. Forskolin (adenylyl cyclase activator)-induced relaxation was similar between the groups. The inhibition of IK(Ca)/SK(Ca) channels (TRAM-34 plus UCL1684) or BK(Ca) channels (iberiotoxin) reduced ISO-induced relaxation only in Uni rats and abolished the relaxation differences between the groups. The expression of SK(Ca) channel was decreased in DOCA-salt arteries. The expression of BK(Ca) channel α subunit was increased whereas the expression of BK(Ca) channel β subunit was decreased in DOCA-salt arteries. The expression of receptor for activated C kinase 1 (RACK1), which is a binding protein for BK(Ca) channel and negatively modulates its activity, was increased in DOCA-salt arteries. These results suggest that the impairment of β-AR-mediated relaxation in DOCA-salt mesenteric arteries may be attributable to altered IK(Ca)/SK(Ca) and/or BK(Ca) channels activities rather than cAMP/PKA pathway. Impaired β-AR-stimulated BK(Ca) channel activity may be due to the imbalance between its subunit expressions and RACK1 upregulation.

Beta-3 adrenoceptors as new therapeutic targets for cardiovascular pathologies

Catecholamines play a key role in the regulation of cardiovascular function, classically through ß(1/2)-adrenoreceptors (AR) activation. After ß(3)-AR cloning in the late 1980s, convincing evidence for ß(3)-AR expression and function in cardiovascular tissues recently initiated a reexamination of their involvement in the pathophysiology of cardiovascular diseases. Their upregulation in diseased cardiovascular tissues and resistance to desensitization suggest they may be attractive therapeutic targets. They may substitute for inoperant ß(1/2)-AR to mediate vasodilation in diabetic or atherosclerotic vessels. In cardiac ventricle, their contractile effects are functionally antipathetic to those of ß(1/2)-AR; in normal heart, ß(3)-ARs may mediate a moderate negative inotropic effect, but in heart failure, it may protect against adverse effects of excessive catecholamine stimulation by action on excitation-contraction coupling, electrophysiology, or remodelling. Thus, prospective studies in animals and patients at different stages of heart failure should lead to identify the best therapeutic window to use ß(3)-AR agonists and/or antagonists.

Previously unsuspected widespread cellular and tissue distribution of β-adrenoceptors and its relevance to drug action

The discovery of β-adrenoceptors in previously unsuspected cell types is contributing to the rethinking of new drug targets. Recent developments in β-adrenoceptor pharmacology might have excited and surprised James Black, given his interest in developing drugs based on the selective manipulation of receptors to alter physiological responses. β-adrenoceptors continue to generate surprises at molecular and pharmacological levels that often require knowledge of receptor location to interpret. In this review, we emphasize the use of fluorescent ligands as the most selective means of demonstrating receptor localization. Fluorescent ligand binding in live tissues can provide quantitative pharmacological data, under carefully controlled conditions, relevant to other signalling parameters. Consideration of the role of β-adrenoceptors in many cell types (previously ignored) is needed to understand the actions of drugs at β-adrenoceptors throughout the body, particularly in the lung epithelium, vascular endothelium, immune cells and other 'structural' and 'restorative' cell types.

Age-related up-regulation of beta3-adrenergic receptor in heart-failure rats

Stimulation of beta1- and beta2-adrenergic receptors (ARs) in the heart results in positive inotropy. In contrast, it has been reported that the beta3-AR is also expressed in the heart and that its stimulation leads to negative inotropic effects. The aim of this study was to investigate the expression of beta3-AR in age-related heart-failure rats and its relevance to left ventricular dysfunction. Aging male Wistar rats were divided into young and aging groups according to age, and each group included sham-operation and heart-failure subgroups. Left ventricular end-diastolic pressure (LVEDP) and the ratio of left ventricular weight to body weight (LV/BW) were significantly higher for the aging heart-failure versus young heart-failure and the heart-failure versus sham-operation groups (P < 0.01, respectively). However, the left ventricular end-systolic pressure (LVESP) and the maximal rate of rise or fall of left ventricular pressure were all significantly lower for the aging heart-failure versus young heart-failure and the heart-failure versus sham-operation groups (P < 0.01, respectively). beta3-AR protein levels increased significantly when heart failure worsened in aging rats. These results suggest that beta3-AR expression in age-related heart-failure rats and left ventricular function were highly correlated.

Is overall blockade superior to selective blockade of adrenergic receptor subtypes in suppressing left ventricular remodeling in spontaneously hypertensive rats?

To test the hypothesis that nonselective blockade of adrenergic receptor (AR) subtypes is superior to selective blockade of AR subtypes in suppressing left ventricular (LV) remodeling induced by hypertension. Sixty-four spontaneously hypertensive rats (SHR) were randomly divided into four groups: bisoprolol-treated, propranolol-treated, carvedilol-treated and no treatment groups (n=16, each). Sixteen Wistar-Kyoto (WKY) rats served as a control group. Echocardiography and cardiac catheterization were carried out to record the mitral flow velocity ratio of E wave to A wave (E/A), LV mass index (LVMI), maximal rising (dp/dt(max)) and falling (-dp/dt(max)) rate of the LV pressure and LV relaxation time constant (τ). The mRNA and protein expression levels of AR, protein kinase(PK) and G-protein subtypes, intracellular free calcium (Ca) concentration and cardiocyte apoptoisis rate were determined. Three drug-treated groups showed higher velocity ratio of E wave to A wave (E/A) and -dp/dt(max) and lower systolic blood pressure (SBP), LVMI, τ, apoptosis rate and intracellular free Ca(2+) concentration than the no treatment group. The mRNA expression levels of AR-α(1B) in the carvedilol group were significantly lower than the other two drug-treated groups. The mRNA expression levels of AR-β(1), AR-β(2) and Gsα were significantly higher in the three drug-treated groups than in the no treatment group, with the expression levels of AR-β(2) being the highest in the carvedilol-treated group. The protein expression levels of PKA and PKC subtype α and δ were lower in the three drug-treated groups than in the no treatment group. Overall blockade of AR subtypes is not superior to selective blockade of AR subtypes in suppressing LV remodeling in SHR. Although carvedilol is the most effective in attenuating cardiocyte apoptosis, normalizing AR-α(1B) and Gsα expression and increasing AR-β(2) expression.