Internalized ß2-Adrenergic Receptors Oppose PLC-Dependent Hypertrophic Signaling.

BACKGROUND: Chronically elevated neurohumoral drive, and particularly elevated adrenergic tone leading to ß-adrenergic receptor (ß-AR) overstimulation in cardiac myocytes, is a key mechanism involved in the progression of heart failure. ß1-AR (ß1-adrenergic receptor) and ß2-ARs (ß2-adrenergic receptor) are the 2 major subtypes of ß-ARs present in the human heart; however, they elicit different or even opposite effects on cardiac function and hypertrophy. For example, chronic activation of ß1-ARs drives detrimental cardiac remodeling while ß2-AR signaling is protective. The underlying molecular mechanisms for cardiac protection through ß2-ARs remain unclear. METHODS: ß2-AR signaling mechanisms were studied in isolated neonatal rat ventricular myocytes and adult mouse ventricular myocytes using live cell imaging and Western blotting methods. Isolated myocytes and mice were used to examine the roles of ß2-AR signaling mechanisms in the regulation of cardiac hypertrophy. RESULTS: Here, we show that ß2-AR activation protects against hypertrophy through inhibition of phospholipaseCε signaling at the Golgi apparatus. The mechanism for ß2-AR-mediated phospholipase C inhibition requires internalization of ß2-AR, activation of Gi and Gßγ subunit signaling at endosome and ERK (extracellular regulated kinase) activation. This pathway inhibits both angiotensin II and Golgi-ß1-AR-mediated stimulation of phosphoinositide hydrolysis at the Golgi apparatus ultimately resulting in decreased PKD (protein kinase D) and histone deacetylase 5 phosphorylation and protection against cardiac hypertrophy. CONCLUSIONS: This reveals a mechanism for ß2-AR antagonism of the phospholipase Cε pathway that may contribute to the known protective effects of ß2-AR signaling on the development of heart failure.

AKAP12 Upregulation Associates With PDE8A to Accelerate Cardiac Dysfunction.

BACKGROUND: In heart failure, signaling downstream the ß2-adrenergic receptor is critical. Sympathetic stimulation of ß2-adrenergic receptor alters cAMP (cyclic adenosine 3',5'-monophosphate) and triggers PKA (protein kinase A)-dependent phosphorylation of proteins that regulate cardiac function. cAMP levels are regulated in part by PDEs (phosphodiesterases). Several AKAPs (A kinase anchoring proteins) regulate cardiac function and are proposed as targets for precise pharmacology. AKAP12 is expressed in the heart and has been reported to directly bind ß2-adrenergic receptor, PKA, and PDE4D. However, its roles in cardiac function are unclear. METHODS: cAMP accumulation in real time downstream of the ß2-adrenergic receptor was detected for 60 minutes in live cells using the luciferase-based biosensor (GloSensor) in AC16 human-derived cardiomyocyte cell lines overexpressing AKAP12 versus controls. Cardiomyocyte intracellular calcium and contractility were studied in adult primary cardiomyocytes from male and female mice overexpressing cardiac AKAP12 (AKAP12OX) and wild-type littermates post acute treatment with 100-nM isoproterenol (ISO). Systolic cardiac function was assessed in mice after 14 days of subcutaneous ISO administration (60 mg/kg per day). AKAP12 gene and protein expression levels were evaluated in left ventricular samples from patients with end-stage heart failure. RESULTS: AKAP12 upregulation significantly reduced total intracellular cAMP levels in AC16 cells through PDE8. Adult primary cardiomyocytes from AKAP12OX mice had significantly reduced contractility and impaired calcium handling in response to ISO, which was reversed in the presence of the selective PDE8 inhibitor (PF-04957325). AKAP12OX mice had deteriorated systolic cardiac function and enlarged left ventricles. Patients with end-stage heart failure had upregulated gene and protein levels of AKAP12. CONCLUSIONS: AKAP12 upregulation in cardiac tissue is associated with accelerated cardiac dysfunction through the AKAP12-PDE8 axis.

Functional LTCC-ß2AR Complex Needs Caveolin-3 and Is Disrupted in Heart Failure.

BACKGROUND: Beta-2 adrenergic receptors (ß2ARs) but not beta-2 adrenergic receptors (ß1ARs) form a functional complex with L-type Ca2+ channels (LTCCs) on the cardiomyocyte membrane. However, how microdomain localization in the plasma membrane affects the function of these complexes is unknown. We aim to study the coupling between LTCC and ß adrenergic receptors in different cardiomyocyte microdomains, the distinct involvement of PKA and CAMKII (Ca2+/calmodulin-dependent protein kinase II) and explore how this functional complex is disrupted in heart failure. METHODS: Global signaling between LTCCs and ß adrenergic receptors was assessed with whole-cell current recordings and western blot analysis. Super-resolution scanning patch-clamp was used to explore the local coupling between single LTCCs and ß1AR or ß2AR in different membrane microdomains in control and failing cardiomyocytes. RESULTS: LTCC open probability (Po) showed an increase from 0.054±0.003 to 0.092±0.008 when ß2AR was locally stimulated in the proximity of the channel (<350 nm) in the transverse tubule microdomain. In failing cardiomyocytes, from both rodents and humans, this transverse tubule coupling between LTCC and ß2AR was lost. Interestingly, local stimulation of ß1AR did not elicit any change in the Po of LTCCs, indicating a lack of proximal functional interaction between the two, but we confirmed a general activation of LTCC via ß1AR. By using blockers of PKA and CaMKII and a Caveolin-3-knockout mouse model, we conclude that the ß2AR-LTCC regulation requires the presence of caveolin-3 and the activation of the CaMKII pathway. By contrast, at a cellular "global" level PKA plays a major role downstream ß1AR and results in an increase in LTCC current. CONCLUSIONS: Regulation of the LTCC activity by proximity coupling mechanisms occurs only via ß2AR, but not ß1AR. This may explain how ß2ARs tune the response of LTCCs to adrenergic stimulation in healthy conditions. This coupling is lost in heart failure; restoring it could improve the adrenergic response of failing cardiomyocytes.

Norepinephrine/ß2-Adrenergic Receptor Pathway Promotes the Cell Proliferation and Nerve Growth Factor Production in Triple-Negative Breast Cancer.

PURPOSE: Invasive ductal carcinoma (IDC) accounts for 90% of triple-negative breast cancer (TNBC). IDC is mainly derived from the breast ductal epithelium which is innervated by the 4th to 6th thoracic sympathetic nerves. However, little is known about the contribution of the interactions between sympathetic nerves and breast cancer cells to the malignant progression of TNBC. METHODS: The expression levels of the ß2-adrenergic receptor (ß2-AR, encoded by ADRB2 gene), nerve growth factor (NGF), and tropomyosin receptor kinase A (TrkA) were determined using immunohistochemistry (IHC). NGF expression levels in the serum were compared by enzyme-linked immunosorbent assay (ELISA). Cell proliferation was assessed using the Cell Counting Kit-8 assay. The ß2-AR, NGF, p-ERK, and p-CERB expression levels were determined using western blotting. TNBC cells and neuronal cells of the dorsal root ganglion (DRG) in 2-day-old Sprague Dawley rats were co-cultured. Using norepinephrine (NE), NGF, and ß2-AR, NGF/TrkA blocker pretreatments, the axon growth of each group of DRG neuron cells was detected by immunofluorescence analysis. RESULTS: The sympathetic adrenergic neurotransmitter NE activated the ERK signaling pathway in TNBC cells. NE/ß2-AR signaling promotes NGF secretion. NGF further facilitates the malignant progression of TNBC by increasing sympathetic neurogenesis. In the co-culture assay, the sympathetic adrenergic NE/ß2-AR signal pathway also enhanced NGF secretion. NGF binds TrkA in DRG neurons and promotes axonal growth. CONCLUSION: These results suggest that NE/ß2-AR pathway promotes cell proliferation and NGF production in triple-negative breast cancer.

ß3AR-Dependent Brain-Derived Neurotrophic Factor (BDNF) Generation Limits Chronic Postischemic Heart Failure.

BACKGROUND: Loss of brain-derived neurotrophic factor (BDNF)/TrkB (tropomyosin kinase receptor B) signaling accounts for brain and cardiac disorders. In neurons, ß-adrenergic receptor stimulation enhances local BDNF expression. It is unclear if this occurs in a pathophysiological relevant manner in the heart, especially in the ß-adrenergic receptor-desensitized postischemic myocardium. Nor is it fully understood whether and how TrkB agonists counter chronic postischemic left ventricle (LV) decompensation, a significant unmet clinical milestone. METHODS: We conducted in vitro studies using neonatal rat and adult murine cardiomyocytes, SH-SY5Y neuronal cells, and umbilical vein endothelial cells. We assessed myocardial ischemia (MI) impact in wild type, ß3AR knockout, or myocyte-selective BDNF knockout (myoBDNF KO) mice in vivo (via coronary ligation [MI]) or in isolated hearts with global ischemia-reperfusion (I/R). RESULTS: In wild type hearts, BDNF levels rose early after MI (<24 hours), plummeting at 4 weeks when LV dysfunction, adrenergic denervation, and impaired angiogenesis ensued. The TrkB agonist, LM22A-4, countered all these adverse effects. Compared with wild type, isolated myoBDNF KO hearts displayed worse infarct size/LV dysfunction after I/R injury and modest benefits from LM22A-4. In vitro, LM22A-4 promoted neurite outgrowth and neovascularization, boosting myocyte function, effects reproduced by 7,8-dihydroxyflavone, a chemically unrelated TrkB agonist. Superfusing myocytes with the ß3AR-agonist, BRL-37344, increased myocyte BDNF content, while ß3AR signaling underscored BDNF generation/protection in post-MI hearts. Accordingly, the ß1AR blocker, metoprolol, via upregulated ß3ARs, improved chronic post-MI LV dysfunction, enriching the myocardium with BDNF. Last, BRL-37344-imparted benefits were nearly abolished in isolated I/R injured myoBDNF KO hearts. CONCLUSIONS: BDNF loss underscores chronic postischemic heart failure. TrkB agonists can improve ischemic LV dysfunction via replenished myocardial BDNF content. Direct cardiac ß3AR stimulation, or ß-blockers (via upregulated ß3AR), is another BDNF-based means to fend off chronic postischemic heart failure.

Silymarin Administration Attenuates Cirrhotic-induced Cardiac Abnormality in the Rats: A Possible Role of ß1-adrenergic Receptors and L-type Voltage-Dependent Calcium Channels.

Background: Cirrhotic cardiomyopathy is a well-recognized cardiac dysfunction in cirrhotic patients. Studies have confirmed the protective effects of silymarin in different types of cardiac injury. This study aimed to examine the effectiveness and molecular mechanism of silymarin against myocardial dysfunction and hypertrophy in a rat model of cirrhosis. Methods: The experiment was performed at Alborz University of Medical Sciences (Karaj, Iran) during 2020-2021. Thirty-two male Wistar rats were randomly divided into four groups of Sham-operated (control group for surgical procedures), Bile Duct Ligated (BDL), and two Silymarin extract (SE)-treated groups of 300 and 600 mg/Kg/day. After 28 days, serum levels of AST, ALT, GGT, and ALP, liver histopathological status, as well as cardiac mechanical function, were assessed. Cardiac ß1-adrenergic receptors (ß1-AR), L-type voltage-dependent calcium channels (L-VDCC), and GATA4 mRNA expression were also determined using real-time RT-PCR. Data analysis was performed using the one-way ANOVA followed by Duncan's multiple range test. Histological data has been analyzed with Kruskal-Wallis nonparametric test. The analysis was performed at P≤0.05. Results: BDL was associated with a significant elevation in serum AST, ALT, GGT, and ALP, development of necrosis and fibrosis of the liver texture, increased Heart Weight and Heart Weight to Body Weight ratio, enhanced cardiac mechanical function as well as a significant up-regulation of ventricular ß1-AR and L-VDCC. Administration of SE600, but not SE300, significantly reduced the serum levels of the enzymes and alleviated signs of liver necrosis and fibrosis. Cirrhotic-induced cardiac dysfunction was also restored by SE600, but not by the lower dose. In addition, cardiac expression of the ß1-AR and L-VDCC was down-regulated toward normal values by either higher or lower doses of the SE. Conclusion: Silymarin treatment in higher dose attenuated cirrhosis-associated cardiac remodeling and reduced cardiac mechanical dysfunctions.

Exercise Causes Arrhythmogenic Remodeling of Intracellular Calcium Dynamics in Plakophilin-2-Deficient Hearts.

BACKGROUND: Exercise training, and catecholaminergic stimulation, increase the incidence of arrhythmic events in patients affected with arrhythmogenic right ventricular cardiomyopathy correlated with plakophilin-2 (PKP2) mutations. Separate data show that reduced abundance of PKP2 leads to dysregulation of intracellular Ca2+ (Ca2+i) homeostasis. Here, we study the relation between excercise, catecholaminergic stimulation, Ca2+i homeostasis, and arrhythmogenesis in PKP2-deficient murine hearts. METHODS: Experiments were performed in myocytes from a cardiomyocyte-specific, tamoxifen-activated, PKP2 knockout murine line (PKP2cKO). For training, mice underwent 75 minutes of treadmill running once per day, 5 days each week for 6 weeks. We used multiple approaches including imaging, high-resolution mass spectrometry, electrocardiography, and pharmacological challenges to study the functional properties of cells/hearts in vitro and in vivo. RESULTS: In myocytes from PKP2cKO animals, training increased sarcoplasmic reticulum Ca2+ load, increased the frequency and amplitude of spontaneous ryanodine receptor (ryanodine receptor 2)-mediated Ca2+ release events (sparks), and changed the time course of sarcomeric shortening. Phosphoproteomics analysis revealed that training led to hyperphosphorylation of phospholamban in residues 16 and 17, suggesting a catecholaminergic component. Isoproterenol-induced increase in Ca2+i transient amplitude showed a differential response to ß-adrenergic blockade that depended on the purported ability of the blockers to reach intracellular receptors. Additional experiments showed significant reduction of isoproterenol-induced Ca2+i sparks and ventricular arrhythmias in PKP2cKO hearts exposed to an experimental blocker of ryanodine receptor 2 channels. CONCLUSIONS: Exercise disproportionately affects Ca2+i homeostasis in PKP2-deficient hearts in a manner facilitated by stimulation of intracellular ß-adrenergic receptors and hyperphosphorylation of phospholamban. These cellular changes create a proarrhythmogenic state that can be mitigated by ryanodine receptor 2 blockade. Our data unveil an arrhythmogenic mechanism for exercise-induced or catecholaminergic life-threatening arrhythmias in the setting of PKP2 deficit. We suggest that membrane-permeable ß-blockers are potentially more efficient for patients with arrhythmogenic right ventricular cardiomyopathy, highlight the potential for ryanodine receptor 2 channel blockers as treatment for the control of heart rhythm in the population at risk, and propose that PKP2-dependent and phospholamban-dependent arrhythmogenic right ventricular cardiomyopathy-related arrhythmias have a common mechanism.

Lactato y catecolaminas: respuesta fisiológica en el paciente crítico / Lactate and catecholamines: a physiological response in critically ill patients

RESUMEN El lactato es un metabolito altamente dinámico que, en condiciones anaerobias, es producido por hipoxia o isquemia; y en condiciones aerobias, es sintetizado por un mecanismo impulsado por la estimulación adrenérgica, a través del receptor β2, que potencia la acción de la bomba sodio-potasio, y por un estado de glicólisis aerobia acelerada. Este metabolito es capaz de intercambiarse entre diferentes células productoras y consumidoras, con lo que asegura la materia prima para obtener energía. El sistema nervioso simpático responde a los estímulos de estrés con la liberación de catecolaminas, que actúan como hormonas y como neurotransmisores en varios tejidos del cuerpo y permiten un aumento del metabolismo que eleva los valores de glucosa y el oxígeno disponible. Existe una relación fisiológica de dependencia entre las catecolaminas y la producción de lactato que predispone al organismo para responder de forma efectiva ante una situación de estrés. Sin embargo, en tejidos sensibles, la respuesta adrenérgica exacerbada puede ocasionar efectos exagerados que pueden incrementar la probabilidad de fallo. En base al conocimiento de estos mecanismos, se plantean estrategias terapéuticas enfocadas en regular la actividad simpática.

ABSTRACT Lactate is a highly dynamic metabolite that is produced, under anaerobic conditions, due to hypoxia or ischemia. Under aerobic conditions, it is synthesized by a mechanism driven by the stimulation of the β2 adrenergic receptor, which increases the activity of the sodium-potassium pump, and by a state of accelerated aerobic glycolysis. This metabolite is capable of being exchanged between different producing and consuming cells, ensuring the raw material for energy production. The sympathetic nervous system responds to stress stimuli through the release of catecholamines, which act as hormones and neurotransmitters in various tissues of the body, allowing an increase in metabolism that raises glucose and available oxygen levels. There is a physiological dependence between catecholamine levels and lactate production, predisposing the body to respond effectively to a stressful situation. However, an exacerbated adrenergic response may cause exaggerated effects on sensitive tissues that increase the probability of failure. Based on the knowledge of these mechanisms, therapeutic strategies focused on regulating the sympathetic activity are proposed.

Association between beta-2 adrenergic receptor variants and clinical outcomes in children and adolescents with acute asthma

ABSTRACT Objective To investigate whether different genotypes of p.Arg16Gly, p.Gln27Glu, p.Arg19Cys and p.Thr164Ile variants interfere in response to treatment in children and adolescents with moderate to severe acute asthma. Methods This sample comprised patients aged 2 to 17 years with a history of at least two wheezing episodes and current moderate to severe asthma exacerbation. All patients received multiple doses of albuterol and ipratropium bromide delivered via pressurized metered-dose inhaler with holding chamber and systemic corticosteroids. Hospital admission was defined as the primary outcome. Secondary outcomes were changes in forced expiratory volume in the first second after 1 hour of treatment, and for outpatients, length of stay in the emergency room. Variants were genotyped by sequencing. Results A total of 60 patients were evaluated. Hospital admission rates were significantly higher in carriers of the genotype AA relative to those with genotype AG or GG, within the p.Arg16Gly variant (p=0.03, test χ2, alpha=0.05). Secondary outcomes did not differ between genotypes. Conclusion Hospital admission rates were significantly higher among carriers of the genotype AA within the p.Arg16Gly variant. Trial registration: ClinicalTrials.gov: NCT01323010

Effects of gene polymorphisms of β1 adrenergic receptor G1165C and A145G locus on myocardial hypertrophy and the efficacy in patients with hypertension / 中国医师进修杂志

Objective:To investigate the effect of gene polymorphism of β1 adrenergic receptor (β1-AR) G1165C and A145G locus on myocardial hypertrophy and the efficacy in patients with hypertension.Methods:Two hundred and twenty-seven cases of patients with hypertension admitted to Binhai County People′s Hospital from January to December 2019 were enrolled. Among them, there were 113 cases of hypertension with myocardial hypertrophy and 114 cases of hypertension without myocardial hypertrophy. In addition, 115 patients with normal physical examination during the same period were selected as the control group. DNA in the peripheral blood leukocytes was extracted, polymerase chain reaction-restriction fragment length polymorphism method was used to detect β1-AR G1165C and A145G locus gene polymorphism, and the differences in the efficacy of β blockers in hypertensive patients with different genotypes were compared.Results:There was no statistically significant differences in the distribution of β1-AR A145G genotypes among the three groups ( P>0.05). Compared with the healthy control group, the frequency of Gly/Gly genotype carrying β1-AR G1165C locus was higher in hypertension with myocardial hypertrophy group, and the frequency of Gly/Arg and Arg/Arg gene were lower; compared with hypertension without myocardial hypertrophy group, the frequency of Gly/Arg+Gly/Gly gene in hypertension with myocardial hypertrophy group was higher; taking Arg/Arg genotype as the control group, carrying Gly/Gly genotype could increase the risk of cardiac hypertrophy in hypertensive patients by 3.159 times ( OR = 3.159, 95% CI 1.240 - 7.412, P<0.05).The frequency of G1165C allele Arg in the hypertension with myocardial hypertrophy group was significantly lower than that in the control group and the hypertension without myocardial hypertrophy group ( P<0.05); the frequency of G1165C allele Gly was significantly higher than that in the control group and the hypertension without myocardial hypertrophy group ( P<0.05); taking Arg/Arg genotype as the control, carrying Gly/Gly genotype could increase the risk of cardiac hypertrophy in hypertensive ( OR = 3.417, 95% CI 1.357 - 7.965, P<0.05). The left ventricular mass index of Gly/Gly genotype patients was (120.38 ± 28.41) g/m 2, which was significantly higher than (99.76 ± 25.16) g/m 2 and (90.30 ± 19.54) g/m 2 of Gly/Arg and Arg/Arg, with statistically significant differences ( F = 10.89, P<0.01). After the treatment, the resting heart rate, systolic blood pressure, diastolic blood pressure and mean arterial blood pressure of patients with G1165C allele Arg hypertension with myocardial hypertrophy were lower than those with G1165C allele Gly, with statistically significant differences ( P<0.05). Conclusions:β1-AR G1165C gene polymorphism is related to the risk of myocardial hypertrophy in hypertensive patients. Carrying the G1165C allele Gly may increase the risk of susceptibility to cardiac hypertrophy, and β-blockers are more effective in hypertensive patients with myocardial hypertrophy who carry the G1165C allele Arg.

Improvement in Near Vision Following Silodosin Treatment in Patients With Lower Urinary Tract Symptoms.

PURPOSE: The objective of this study was to investigate the change in near visual function after the administration of oral silodosin to patients with lower urinary tract symptoms (LUTS). METHODS: This prospective study included treatment-naive patients who were scheduled to start treatment with silodosin for LUTS. A comprehensive ophthalmological evaluation including the near vision and the automated pupillometry was performed at baseline and after 3 months of silodosin treatment. For subjective assessment of near visual ability and satisfaction, a Near Activity Visual Questionnaire-10 (NAVQ-10) was also used at the same time (higher scores indicating worse quality). RESULTS: Of 23 patients enrolled in this study, 15 continued with silodosin (8 mg once daily) treatment for 3 months and completed a follow-up evaluation. The mean age of participants was 60.4±8.4 years. Distant visual acuity and spherical error were unchanged after silodosin treatment. However, near vision acuity (logMAR) was improved after treatment (right, 0.47±0.36 vs. 0.38±0.39, P=0.018; left, 0.41±0.37 vs. 0.31±0.34, P=0.068; both, 0.27±0.26 vs. 0.21±0.27, P=0.043). Pupil size under room light decreased significantly in both eyes (right, 3.77±0.60 vs. 3.16±0.58, P=0.001; left, 3.72±0.80 vs. 3.21±0.75, P=0.002). The Rasch scale at NAVQ-10 improved from 54.7±9.9 to 48.5±11.2 (P=0.004). CONCLUSION: This preliminary study demonstrated that highly selective alpha-1A adrenergic receptor antagonists such as silodosin improve near visual acuity and quality in patients with LUTS/benign prostatic hyperplasia. Decrease in pupil size caused by inhibition of adrenergic alpha 1 mediated contraction of iris dilator muscle is a possible mechanism underlying improved near vision.

Heterodimerization With 5-HT2BR Is Indispensable for ß2AR-Mediated Cardioprotection.

RATIONALE: The ß2-adrenoceptor (ß2-AR), a prototypical GPCR (G protein-coupled receptor), couples to both Gs and Gi proteins. Stimulation of the ß2-AR is beneficial to humans and animals with heart failure presumably because it activates the downstream Gi-PI3K-Akt cell survival pathway. Cardiac ß2-AR signaling can be regulated by crosstalk or heterodimerization with other GPCRs, but the physiological and pathophysiological significance of this type of regulation has not been sufficiently demonstrated. OBJECTIVE: Here, we aim to investigate the potential cardioprotective effect of ß2-adrenergic stimulation with a subtype-selective agonist, (R,R')-4-methoxy-1-naphthylfenoterol (MNF), and to decipher the underlying mechanism with a particular emphasis on the role of heterodimerization of ß2-ARs with another GPCR, 5-hydroxytryptamine receptors 2B (5-HT2BRs). METHODS AND RESULTS: Using pharmacological, genetic and biophysical protein-protein interaction approaches, we studied the cardioprotective effect of the ß2-agonist, MNF, and explored the underlying mechanism in both in vivo in mice and cultured rodent cardiomyocytes insulted with doxorubicin, hydrogen peroxide (H2O2) or ischemia/reperfusion. In doxorubicin (Dox)-treated mice, MNF reduced mortality and body weight loss, while improving cardiac function and cardiomyocyte viability. MNF also alleviated myocardial ischemia/reperfusion injury. In cultured rodent cardiomyocytes, MNF inhibited DNA damage and cell death caused by Dox, H2O2 or hypoxia/reoxygenation. Mechanistically, we found that MNF or another ß2-agonist zinterol markedly promoted heterodimerization of ß2-ARs with 5-HT2BRs. Upregulation of the heterodimerized 5-HT2BRs and ß2-ARs enhanced ß2-AR-stimulated Gi-Akt signaling and cardioprotection while knockdown or pharmacological inhibition of the 5-HT2BR attenuated ß2-AR-stimulated Gi signaling and cardioprotection. CONCLUSIONS: These data demonstrate that the ß2-AR-stimulated cardioprotective Gi signaling depends on the heterodimerization of ß2-ARs and 5-HT2BRs.

Targeting Cardiac Myocyte Na+-K+ Pump Function With ß3 Adrenergic Agonist in Rabbit Model of Severe Congestive Heart Failure.

BACKGROUND: Abnormally high cytosolic Na+ concentrations in advanced heart failure impair myocardial contractility. Stimulation of the membrane Na+-K+ pump should lower Na+ concentrations, and the ß3 adrenoceptor (ß3 AR) mediates pump stimulation in myocytes. We examined if ß3 AR-selective agonists given in vivo increase myocyte Na+-K+ pump activity and reverse organ congestion in severe heart failure (HF). METHODS: Indices for HF were lung-, heart-, and liver: body weight ratios and ascites after circumflex coronary artery ligation in rabbits. Na+-K+ pump current, Ip, was measured in voltage-clamped myocytes from noninfarct myocardium. Rabbits were treated with the ß3 AR agonists CL316,243 or ASP9531, starting 2 weeks after coronary ligation. RESULTS: Coronary ligation caused ascites in most rabbits, significantly increased lung-, heart-, and liver: body weight ratios, and decreased Ip relative to that for 10 sham-operated rabbits. Treatment with CL316,243 for 3 days significantly reduced lung-, heart-, and liver: body weight ratios and prevalence of ascites in 8 rabbits with HF relative to indices for 13 untreated rabbits with HF. It also increased Ip significantly to levels of myocytes from sham-operated rabbits. Treatment with ASP9531 for 14 days significantly reduced indices of organ congestion in 6 rabbits with HF relative to indices of 6 untreated rabbits, and it eliminated ascites. ß3 AR agonists did not significantly change heart rates or blood pressures. CONCLUSIONS: Parallel ß3 AR agonists-induced reversal of Na+-K+ pump inhibition and indices of congestion suggest pump inhibition is a useful target for treatment with ß3 AR agonists in congestive HF.

Pharmacokinetics of dexmedetomidine during administration of vatinoxan in male neutered cats anesthetized with isoflurane.

Dexmedetomidine is an alpha-2 adrenoceptor agonist, and vatinoxan is an alpha-2 antagonist believed to poorly cross the blood-brain barrier in cats. Dexmedetomidine-vatinoxan combinations are of interest in anesthetized cats because the anesthetic sparing effect of dexmedetomidine may be preserved while vatinoxan attenuates the adverse cardiovascular effects of dexmedetomidine. The aim of this study was to characterize the pharmacokinetics of dexmedetomidine in cats during administration of isoflurane and vatinoxan. Six healthy adult male castrated cats were anesthetized with isoflurane in oxygen. Vatinoxan was administered using a target-controlled infusion system intended to maintain a plasma concentration of 4 µg/ml. Dexmedetomidine, 35 µg/kg was administered intravenously over 5 min. Plasma dexmedetomidine and vatinoxan concentrations were measured at selected time points ranging from prior to 8 hr after dexmedetomidine administration using liquid chromatography/tandem mass spectrometry. Compartment models were fitted to the time-concentration data using nonlinear mixed-effect modeling. A three-compartment model best fitted the data. Typical value (% interindividual variability) for the three-compartment volumes (ml/kg), the metabolic clearance and the two intercompartment distribution clearances (ml min-1 kg-1 ) were 168 (259), 318 (35), 1,425 (18), 12.4 (31), 39.1 (18), and 29.6 (17), respectively. Mean ± standard deviation plasma vatinoxan concentration was 2.6 ± 0.6 µg/ml.

Beta-adrenergic pathway activation in head and neck cancer: a comprehensive analysis of the clinical and genomic features using integrated bioinformatics / Ativação da via beta-adrenérgica no câncer de cabeça e pescoço: uma análise abrangente das características clínicas e gênomicas utilizando a bioinformática

O estresse crônico leva à ativação da via de sinalização beta-adrenérgica. Sua ativação tem sido implicada na progressão de diferentes tipos de câncer, mas seu papel nos carcinomas espinocelulares de cabeça e pescoço (CECPs) permanece indefinido. O objetivo deste estudo foi investigar o papel da ativação da via betaadrenérgica na progressão dos CECPs, avaliar seu impacto na sobrevida dos pacientes e buscar possíveis terapias para pacientes que encontravam-se com a via beta-adrenérgica ativa. Quinhentos e vinte pacientes do The Cancer Genome Atlas com CECPs primários foram divididos em dois grupos: ADRB2baixa / SLC6A2baixa e ADRB2alta / SLC6A2alta. A associação de características clinicopatológicas e genômicas entre os grupos foram analisadas utilizando bioinformática. Os genes diferencialmente expressos (DEGs) foram identificados através da análise da expressão diferencial. A análise de sobrevida também foi realizada com base nas expressões ADRB2 e SLC6A2. Foram identificados medicamentos em potencial para tratamento de CECPs com base nos DEGs. Houve associação entre as expressões ADRB2 e SLC6A2 com idade, raça, localização do tumor, grau histológico, invasão perineural e status do HPV p16. Foram identificados 898 DEGs entre os grupos. Foi demonstrado que a expressão ADRB2alta / SLC6A2alta influenciou a proliferação, adesão e invasão de células CECPs além da angiogênese. Pacientes com carcinomas espinocelular de laringe e faringe apresentando expressão ADRB2alta / SLC6A2alta tiveram menor sobrevida. Por fim, 56 drogas antineoplásicas e imunoterápicas aprovadas pelo Food Drugs Administration foram identificadas como potenciais alvos para o tratamento personalizado. Significância: Estes achados sugerem fortemente um papel proeminente da sinalização beta-adrenérgica no CECPs ao estimular um fenótipo tumoral mais agressivo. Estas alterações tiveram um impacto negativo no prognóstico dos pacientes com CECP em região de faringe e laringe(AU)

Chronic stress leads to the activation of the beta-adrenergic pathway. Its activation has been implicated in the progression of different types of cancer but its role on head and neck squamous cell carcinomas (HNSCCs) remains undefined. The aim of this study was to investigate the influence of the beta-adrenergic pathway activation in the progression of HNSCCs, assess its impact in the survival of the patients, and explore the potential targets. Five hundred and twenty The Cancer Genome Altas patients with primary HNSCCs were divided in two groups: ADRB2low / SLC6A2low and ADRB2high / SLC6A2high. The association of clinicopathological and genomic features between the groups was analyzed using a bioinformatic approach. Differentially expressed genes (DEGs) were identified through differential expression analysis. Survival analysis was also performed based on ADRB2 and SLC6A2 expressions. Potential drugs for treatment of HNSCC were identified based on the DEGs. There was association between ADRB2 and SLC6A2 expressions with age, race, tumor site, histologic grade, perineural invasion, and HPV p16 status. It was identified 898 DEGs between the groups. It was demonstrated that ADRB2high / SLC6A2high expression influenced HNSCC cells proliferation, adhesion, invasion, and angiogenesis. Patients with larynx and pharynx squamous cell carcinomas presenting ADRB2high / SLC6A2high expression showed had lower survival rates. Finally, 56 Food Drugs Administration-approved antineoplastic and immunotherapeutic drugs were identified as potential targets for the personalized treatment. Significance: These findings strongly suggest a prominent role of beta-adrenergic pathway in HNSCC by stimulating a more aggressive tumoral phenotype. These alterations were shown to negatively impact the prognosis of patients with larynx and pharynx squamous cell carcinomas(AU)

Reverse Takotsubo Cardiomyopathy in a Patient With Prior Apical Takotsubo Cardiomyopathy: Challenging the Beta Receptor Gradient Theory.

Background: Classic Takotsubo cardiomyopathy has been described as transient apical dyskinesia following major stress that is believed to be related to catecholamine surges. Atypical variants have been described, including the rarer reverse Takotsubo cardiomyopathy. Discrepant gradients of the beta-2 adrenoceptors are thought to determine the different anatomic variants. Case Report: A 43-year-old female presented with chest pain and a mild troponin elevation. Echocardiography and coronary angiography were consistent with stress-induced apical Takotsubo cardiomyopathy. Eight months later, the patient was admitted with a similar presentation; however, workup revealed stress-induced reverse Takotsubo cardiomyopathy. Conclusion: Recurrent Takotsubo cardiomyopathy involving different anatomic regions of the left ventricle is a rare phenomenon yet appears to be similar to typical Takotsubo cardiomyopathy in presentation and hospital course. Chronic therapy with beta blockers and angiotensin-converting enzyme inhibitors did not prevent a recurrence in this patient, suggesting that optimum treatment needs to be determined. Takotsubo cardiomyopathy affecting different myocardial segments may recur in the same patient, implying that the adrenoceptor distribution theory needs further refinement.