Selective Beta 1-adrenoceptor Research Articles

KONFORMACJE SALBUTAMOLU W PRÓŻNI ORAZ ŚRODOWISKU WODNYM

albutamol is a short acting, selective beta-2 adrenergic receptor agonist used to treat asthma, bronchitis, as well as prevent exercise induced bronchospasms. Although it is a small molecule, it has considerable conformational freedom. It has four polar groups (-OH and -NH) that can form a variety of intramolecular hydrogen bonds that stabilize individual conformations. It is well known, that such a intramolecular interactions greatly impact molecular properties, because the bioactive conformation of a given ligand could be stabilized by intramolecular hydrogen bonds. The aim of our research is to determine the preferred conformation of salbutamol, and to characterize the intramolecular interactions that stabilize its various conformers, both in a gas phase and in water modeled as a continuous dielectric. The analysis was carried out by B3LYP-D3 and MP2 methods with the 6- 311++G(d,p) basis set. The relative energies and geometrical parameters of intramolecular H-bonds are presented for six selected salbutamol conformers. Moreover, calculated monohydrates of lowest energy salbutamol conformer allow to estimate the interaction energy with water molecule and geometrical parameters of preferred complexes

Sovateltide: First Approval.

Sovateltide (Tycamzzi™), a highly selective endothelin-B receptor agonist and synthetic analog of endothelin-1, is being developed by Pharmazz, Inc. as a neural progenitor cell therapeutic agent for the treatment of acute cerebral ischemic stroke (ACIS), hypoxic-ischemic encephalopathy (HIE), spinal cord injuries and Alzheimer's disease. In May 2023, sovateltide was approved in India for the treatment of cerebral ischemic stroke within 24 h of stroke onset. This article summarizes the milestones in the development of sovateltide leading to this first approval for use in patients with ACIS.

Abstract CT267: ENB-003, an ETBR antagonist, in combination with pembrolizumab for advanced solid tumor: The ENBolden trial

Abstract Programmed cell death 1 (PD-1) inhibitors have minimal effect in ovarian cancer (OC) and pancreatic ductal adenocarcinoma (PDAC). Selective endothelin B receptor (ETBR) blockade stimulates T cell tumor infiltration and synergizes with anti-PD-1 therapy in OC and PDAC mouse models. We are conducting an ongoing Phase Ib, open-label dose escalation study to assess the safety and tolerability of the selective ETBR antagonist ENB-003 (vodudeutentan) in combination with pembrolizumab in metastatic PDAC, OC and other advanced solid tumors (NCT04205227). The primary objectives are safety and tolerability. Secondary objectives include overall survival (OS), progression free survival (PFS), and disease control rate (DCR). Chemotherapy-resistant PDAC and platinum refractory/platinum resistant OC patients were microsatellite stable (MSS). The ENB-003 plus pembrolizumab combination was well tolerated across 6 dosing cohorts with no increase in toxicity above what is typically observed with pembrolizumab as a single agent. Encouraging preliminary efficacy signals have been observed. The DCR across 21 patients is 43% including 8 patients with stable disease (38%) and 1 (5%) with partial response (PR). The DCR for OC is 100% including 3 patients with stable disease (75%) and one MSS, PDL1 negative platinum refractory patient with a 95% PR (25%) of 12-month duration. In the current and final cohort, 3 PAC patients have been treated. One 4th line PDAC patient has exceeded 6-month survival (33%). We also observed a 7-month arrest of disease progression in a tonsillar SCC patient with innate resistance to anti-PD1. These data suggest that ETBR blockade is well tolerated, may expand the benefit of anti-PD1 in drug resistant solid tumors and warrants further study in subsequent trials. Citation Format: Sumayah Jamal, Adnan Nagrial, Matteo Carlino, Rasha Cosman, Anthony Joshua, Richard Eek, Sarina Piha-Paul, Omid Hamid, Jenny Liu. ENB-003, an ETBR antagonist, in combination with pembrolizumab for advanced solid tumor: The ENBolden trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT267.

RhoA/ROCK inhibition attenuates endothelin-1–induced glomerulopathy in the rats

Endothelin-1 (ET-1) contributes to the development of kidney diseases. However, the underlying molecular mechanism is largely undefined. Here we sought to investigate the potential role of ET-1 receptors, ETA and ETB in the regulation of increased glomerular permeability and underlying signaling pathways post-ET-1 infusion. Male Sprague-Dawley rats were infused with ET-1 (2 pmol/kg per minute, i.v.) for four weeks, and the effect on glomerular permeability to albumin (Palb) and albuminuria was measured. The selective ROCK-1/2 inhibitor, Y-27632, was administered to a separate group of rats to determine its effect on ET-1-induced Palb and albuminuria. The role of ETA and ETB receptors in regulating RhoA/ROCK activity was determined by incubating isolated glomeruli from normal rats with ET-1 and with selective ETA and ETB receptor antagonists. ET-1 infusion for four weeks significantly elevated Palb and albuminuria. Y-27632 significantly reduced the elevation of Palb and albuminuria. The activities of both RhoA and ROCK-1/2 were increased by ET-1 infusion. Selective ETB receptor antagonism had no effect on the elevated activity of both RhoA and ROCK-1/2 enzymes. Selective ETA receptor and combined ETA/ETB receptors blockade restored the activity of RhoA and ROCK-1/2 to normal levels. In addition, chronic ET-1 infusion increased the levels of glomerular inflammatory and fibrotic markers. These effects were all attenuated in rats following ROCK-1/2 inhibition. These observations suggest that ET-1 contributes to increased albuminuria, inflammation, and fibrosis by modulating the activity of the ETA-RhoA/ROCK-1/2 pathway. Selective ETA receptor blockade may represent a potential therapeutic strategy to limit glomerular injury and albuminuria in kidney disease.

Abstract 88: A Multicentric, Randomized, Controlled Phase III Study With Sovateltide (Tycamzzi™) Improving Outcomes In Patients With Acute Cerebral Ischemic Stroke

Sovateltide (Tycamzzi™), a selective endothelin-B receptor agonist, has antiapoptotic activity, protects neural mitochondria, and produces neurogenesis. It showed significant safety and efficacy in preclinical and clinical phase I and II studies. A prospective, multicentric, randomized phase III study was conducted in acute cerebral ischemic stroke (ACIS) patients aged 18 through 78 years. Patients with radiologic confirmation of ischemic stroke could be enrolled if presenting up to 24 hours with NIHSS score of greater than 5. Patients with intracranial hemorrhage and those receiving endovascular therapy were excluded. Sovateltide was administered in three doses, each dose of 0.3 μg/kg, as an intravenous bolus at an interval of 3 hours ± 1 hour on day 1, day 3, and day 6 (total dose/day: 0.9 μg/kg). The primary objectives were to determine the neurological outcome based on the mRS score, NIHSS score, and BI scale score from day 1 through day 90. A total of 158 patients with ACIS were enrolled, of which 137 completed a 90-day follow-up. Patients received saline (n=70, 62% male) or sovateltide (n=67, 66% male) at 16.85 ± 0.74 and 17.40 ± 0.67 hours (mean ± SEM) of stroke onset, respectively. The baseline characteristics and SOC in both cohorts were similar. ASPECTS mean value was similar in the control (7.44) and sovateltide (7.61) groups. A significantly greater number of patients in the sovateltide group had an improvement of mRS of ≥2 points (p=0.004) and NIHSS of ≥6 points (p=0.033) vs. baseline at 90 days of treatment. However, an improvement in BI (change of ≥40 points vs. baseline) missed significance (p=0.063). At 90 days, mRS (p=0.007) and NIHSS (p=0.003) were significantly lower, while BI (p=0.011) and EuroQol-EQ-5D (p=0.0055) were significantly higher in the sovateltide compared to the control group. Sovateltide is safe, well-tolerated, and significantly improved neurological outcomes in ACIS patients and may prove to be a novel, effective agent for its treatment.

Endothelin-1, over-expressed in SOD1G93A mice, aggravates injury of NSC34-hSOD1G93A cells through complicated molecular mechanism revealed by quantitative proteomics analysis.

Endothelin-1 (ET-1), a secreted signaling peptide, is suggested to be involved in multiple actions in various tissues including the brain, but its role in amyotrophic lateral sclerosis (ALS) remains unknown. In this study, we detected the expression changes as well as the cellular localization of ET-1, endothelin A (ET-A) and endothelin B (ET-B) receptors in spinal cord of transgenic SOD1-G93A (TgSOD1-G93A) mice, which showed that the two ET receptors (ET-Rs) expressed mainly on neurons and decreased as the disease progressed especially ET-B, while ET-1 expression was up-regulated and primarily localized on astrocytes. We then explored the possible mechanisms underlying the effect of ET-1 on cultured NSC34-hSOD1G93A cell model. ET-1 showed toxic effect on motor neurons (MNs), which can be rescued by the selective ET-A receptor antagonist BQ-123 or ET-B receptor antagonist BQ-788, suggesting that clinically used ET-Rs pan-antagonist could be a potential strategy for ALS. Using proteomic analysis, we revealed that 110 proteins were differentially expressed in NSC34-hSOD1G93A cells after ET-1 treatment, of which 54 were up-regulated and 56 were down-regulated. Bioinformatic analysis showed that the differentially expressed proteins (DEPs) were primarily enriched in hippo signaling pathway-multiple species, ABC transporters, ErbB signaling pathway and so on. These results provide further insights on the potential roles of ET-1 in ALS and present a new promising therapeutic target to protect MNs of ALS.

Role of endothelin in the pathophysiology of migraine: A new view on an old player

There is cumulating evidence that endothelin-1 (ET-1) may play a role in migraine, however controversial findings still impede a conclusion to be drawn. Herein we tested the hypothesis that endothelin ETB receptors are major contributors to migraine-like responses. ET-1, IRL-1620 (selective ETB receptor agonist) or CGRP were injected into the trigeminal ganglion (TG) of female Wistar rats, and the development of periorbital mechanical allodynia was assessed hourly with von Frey hairs. Twenty-four hours later, rats were exposed to an aversive light for 1 h, after which the reactivation of periorbital mechanical allodynia (indicating photic sensitivity) was assessed up to 4 h. Moreover, the effect of systemic Bosentan (ETA/ETB receptors antagonist) or the selective antagonists of ETA (BQ-123) and ETB (BQ-788) receptors injected into the TG were evaluated against CGRP-induced responses. ET-1 and IRL-1620 injection into the TG induced periorbital mechanical allodynia and photic sensitivity. Bosentan attenuated periorbital mechanical allodynia but failed to affect photic sensitivity induced by CGRP. Selective blockade of ETB receptors in the TG fully prevented the development of periorbital mechanical allodynia and photic sensitivity induced by CGRP, but ETA receptor blockade caused only a slight reduction of periorbital mechanical allodynia without affecting photic sensitivity. ETB receptor-operated mechanisms in the TG may contribute to migraine-like responses in female rats.

In vitro Comparative Dissolution Studies of Different Propranolol Generic Tablets Available in Bangladesh

The present study focused to assess in vitro dissolution profiles of four different products of propranolol 10 mg Tablets (Randomly coded as PRP1-PRP4) available in Bangladesh comparing with the reference brand (coded as REF). Propranolol is a competitive non selective beta-adrenergic receptor antagonist used to amend or restore normal heart rhythm in cardiovascular diseases. An in vitro dissolution study was carried out using the United States Pharmacopoeia (USP) paddle method at 75 rpm with 500 mL of 0.1N HCl dissolution media at 37.0± 0.5 0C. All the tested locally manufactured propranolol products; PRP1, PRP2, PRP3, PRP4 showed compatible dissolution (87%, 86%, 87%, and 80%, respectively) pattern (dissolution criterion Q=80% in 30 minutes) compared with the reference brand (88% dissolution in 30 minutes). The dissolution behavior was estimated with the reference brand using a model dependent and model-independent approach (f2>50, f1 < 15). A mechanistic mathematical release kinetics was also evaluated. The best-fit kinetic model was Hixon-Crowell release kinetics for reference brand and PRP1; and first order release kinetics was predominant for PRP2, PRP3 and PRP4.
 Keywords: propranolol, dissolution, similarity factor, difference factor, dissolution kinetics

Formulation and Evaluation of Salbutamol Sulphate Taste Masked Oral Disintegrating Tablets

Salbutamol is a short acting, selective beta2-adrenergic receptor agonist used in the treatment of astama and COPD. The aim of this study is to formulate oral disintegrating tablets of salbutamol sulphate to achieve rapid dissolution, absorption and further improving the bioavailability of the drug. Oral disintegrating tablets of salbutamol sulphate were designed with a view to enhance the patient compliance and provide a quick onset of action. The oral disintegrating tablets were prepared by using different synthetic polymers by direct compression method. Development of the formulation in the present study was based on the concentration of superdisintegrants and the properties of the drug. Nine batches of tablets were formulated and evaluated for various parameters: drug content, weight variation, water absorption ratio, wetting time, in vitro disintegration, hardness, friability, thickness uniformity, and in vitro dissolution. A fourier-transform infrared spectroscopy (FTIR) study showed that there were no significant interactions between the drug and the excipients. The prepared tablets were good in appearance and showed acceptable results for hardness and friability. The in vitro disintegrating time of the formulated tablets was found to be 14.39-32.41 sec and the drug content of tablets in all formulations was found to be between 87.48-99.96 %, which complied within the limits established in the Indian pharmacopeia. The study concluded that taste of the drug was masked with the help of sodium saccarhin, flavor and the concentration of super disintegrating agent increases the disintegration time of tablets get decreases. The formulation (F9) had a minimum disintegration time of 14.39 sec and 99.96 % of the drug was released within 20 min.

An Observational Study to Compare the Effects of Esmolol and Diltiazem in Attenuating the Haemodynamic Response to Laryngoscopy and Endotracheal Intubation

Background - Laryngoscopy and endotracheal intubation are two most essential part of anaesthetic management. They help in control of airway during general anaesthesia and produce transient marked sympathetic response which manifest as an increase in heart rate, blood pressure, intraocular and intracranial pressure. Esmolol is a selective beta adrenergic receptor antagonist and diltiazem is a calcium channel blocker. The drugs were compared towards reducing the haemodynamic stress response.Methods –This study included 50 patients of both gender, with ASA grade I to IV, aged between 18 to 60 years, scheduled for surgery under general anaesthesia. Among these 25 patients were given inj. esmolol with dose of 1mg/kg i.v.bolus and 25 patients were given inj. diltiazem with dose of 0.2mg/kg i.v.bolus . The haemodynamic parameters were recorded at baseline , just after premedication , after injecting the drug under study, after intubation at 1 , 3 , 5 and 10 minutes. Conclusion –Patients who received inj. esmolol in dose 1mg/kg i.v. showed marked attenuation in both heart rate as well as systolic and diastolic blood pressure whereas inj. diltiazem with dose of 0.2mg/kg only showed attenuation in systolic and diastolic blood pressure but failed to achieve any control over heart rate.

Endothelin B receptors impair baroreflex function and increase blood pressure variability during high salt diet.

Baroreflex function is an integral component maintaining consistent blood pressure. Hypertension is often associated with baroreflex dysfunction, and environmental risk factors such as high salt diet exacerbate hypertension in subjects with baroreflex dysfunction. However, the interactions between high salt diet, baroreflex dysfunction, and hypertension are incompletely understood. The endothelin system is another potent mediator of blood pressure control especially in response to a high salt diet. We hypothesized that the endothelin B (ETB) receptor activation on adrenergic nerves decreases baroreflex sensitivity. We utilized male ETB receptor deficient (ETB-def) rats that express functional ETB receptors only on adrenergic nerves and transgenic (TG) controls to evaluate baroreflex function during normal (0.49% NaCl) and high (4.0% NaCl) salt diets. In conscious rats equipped with telemetry, ETB-def rats had an increased lability of systolic blood pressure (SBP) compared to TG controls as indicated by higher standard deviation (SD) of SBP under both normal (10.2±0.6 vs. 12.4±0.9mmHg, respectively, p=0.0001) and high (11.7±0.6 vs. 16.1±1.0mmHg, p=0.0001) salt diets. In anesthetized preparations, ETB-def rats displayed reduced heart rate (p genotype=0.0167) and renal sympathetic nerve (p genotype=0.0022) baroreflex sensitivity. We then gave male Sprague-Dawley rats the selective ETB receptor antagonist, A-192621 (10mg/kg/day), to block ETB receptors. Following ETB receptor antagonism, even though SBP increased (131±7 before vs. 152±8mmHg after, p<0.0001), the lability (standard deviation) of SBP decreased (9.3±2.0 vs. 7.1±1.1mmHg, p=0.0155). These data support our hypothesis that ETB receptors on adrenergic nerves contribute to baroreflex dysfunction.

Endothelin-1 decreases the expression of Ephrin-A and B subtypes in cultured rat astrocytes through ETB receptors

Ephrin family proteins are cell surface molecules that regulate several cellular functions through cell-cell interactions. During nervous tissue repair after injury, the expression of ephrin subtypes in astrocytes is altered, affecting the axonal elongation and migration of neuronal precursors. However, the mechanism regulating the expression of ephrin subtypes in astrocytes has not been investigated. Herein, we studied the effects of endothelin-1 (ET-1) on the expression of ephrin subtypes in cultured rat astrocytes. Our results showed that ET-1 (100 nM) treatment for 1−24 h reduced the expression of ephrin-A2, -A4, -B2, and -B3 mRNA and protein in astrocytes, whereas the expression of ephrin-A1, -A3, -A5, and -B1 mRNA were not affected. Sarafotoxin S6c, a selective ETB receptor agonist, decreased the expression of ephrin-A2, -A4, -B2, and -B3 in cultured astrocytes. The decrease in ephrin-A2, -A4, -B2, and -B3 expression by ET-1 treatment was reduced in the presence of BQ788, an ETB receptor antagonist, while FR139317, an ETA receptor antagonist, had no effects. These results suggest that ET-1 is a signaling molecule that downregulates ephrin-A2, -A4, -B2, and -B3 expression in astrocytes.

Central endothelin ETB receptor activation reduces blood pressure and catecholaminergic activity in the olfactory bulb of deoxycorticosterone acetate-salt hypertensive rats

Endothelins regulate catecholaminergic activity in the olfactory bulb (OB) in normotensive and hypertensive animals. Administration of an endothelin ETA receptor antagonist decreases blood pressure in deoxycorticosterone acetate-salt (DOCA-salt) rats along with a reduction in tyrosine hydroxylase (TH) activity and expression. In the present work, we sought to establish the role of brain endothelin ETB receptor on blood pressure regulation and its relationship with the catecholaminergic system within the OB of DOCA-Salt rats. Sprague-Dawley male rats were divided into control and DOCA-Salt groups. Blood pressure, heart rate and TH activity as well as neuronal nitric oxide synthase (nNOS) expression were assessed following IRL-1620 (selective endothelin ETB receptor agonist) applied to be brain. IRL-1620 significantly reduced systolic, diastolic, and mean arterial pressure in DOCA-Salt hypertensive rats. It also decreased TH activity, TH total and phosphorylated forms expression as well as its mRNA in the OB of hypertensive animals. The expression of phospho-Ser1417-nNOS, which reflects nNOS activation, was significantly decreased in the of OB of DOCA-salt rats, but it was enhanced by IRL-1620. These findings suggest that DOCA-Salt hypertension depends on endogenous central endothelin ETA receptor activity, rather than on ETB, and that low endothelin ETB stimulation is essential for blood pressure elevation in this animal model. The effect of endothelin ETA receptor antagonism may also result from endothelin ETB receptor overstimulation. The present study shows that endothelin receptors are involved in the regulation of TH in the OB and that such changes are likely implicated in the hemodynamic control and sympathetic outflow.

The Involvement of ATP-Sensitive Potassium Channels in the Nebivolol-Induced Relaxation of Endothelium-Intact Aorta Isolated from Rats

Objective: Nebivolol is a highly selective beta-1 adrenergic receptor blocker with additional vasorelaxant properties. The vasorelaxant effect of nebivolol has been mainly attributed to endothelium-dependent mechanisms including beta-adrenergic receptors. However, the involvement of ATP-sensitive potassium (KATP) channels, another potential mechanism for vasorelaxant effect, in the vasorelaxant response to nebivolol remains unclear. Therefore, this study was aimed to investigate the role of KATP channels in the nebivolol-induced vasorelaxation in the isolated rat aorta Methods: The rat thoracic aortic rings isolated from Sprague-Dawley rats were mounted in organ bath chambers containing Krebs-Henseleit solution at 37 oC continuously bubbled with 95% O2 and 5% CO2. After an equilibration period, the presence of endothelium was confirmed by the response (more than 50%) to acetylcholine (10 μM) in aortic rings precontracted with phenylephrine (1 μM). After washout, in control group, the endothelium-intact aortic rings were contracted by potassium chloride (30 mM) before the cumulative addition of nebivolol (0.0001-100 μM). In some experiments, the relaxant response to nebivolol (0.0001-100 μM) was also obtained in the presence of glibenclamide (KATP channel blocker, 10 μM) or Nω-Nitro-L-arginine methyl ester (L-NAME: eNOS inhibitor, 100 μM) in the endothelium-intact aortic rings precontracted with potassium chloride (30 mM). Data were presented as means±SEM. Multiple comparisons of groups were performed by using ANOVA followed by post-hoc Bonferroni test. Results: Nebivolol elicited a concentration dependent vasorelaxant effect in the endothelium-intact aortic rings. Relaxant response to nebivolol was significantly inhibited by the presence of glibenclamide or L-NAME (p&amp;lt; 0.05). Although Emax values were not found significantly different among groups, pD2 values of nebivolol were reduced in the endothelium-intact aortic rings incubated with glibenclamide or L-NAME. Conclusion: These results demonstrate for the first time the involvement of KATP channels in the nebivolol-induced vasorelaxation in the endothelium-intact aorta precontracted with potassium chloride.

52-Year-Old Woman With Fever, Diaphoresis, and Abdominal Pain

52-Year-Old Woman With Fever, Diaphoresis, and Abdominal Pain

Proximal tubule albumin uptake – potential role for endothelin system in sickle cell disease mice

Elevated plasma endothelin‐1 (ET‐1) reported in sickle cell disease (SCD) patients correlate with microalbuminuria, a major mortality risk factor in SCD. ET‐1 contributes to glomerular and tubular injury in SCD, as evidenced by increased glomerular permeability to albumin and urinary excretion of tubular injury markers. Although selective ETA receptor antagonism reduces albuminuria in humanized sickle cell (HbSS) mice, the mechanism of this action remains unclear. The aim of the study was to determine whether selective ETA receptor antagonism prevents albuminuria by preserving the expression of tubular albumin‐associated transporters in proximal tubule (PT) cells. Male C57BL/6 or HbSS and genetic control (HbAA) mice were used to determine the effect of ET‐1 on the expression of proximal tubule albumin trafficking mediators, such as megalin and NHE‐3. Exposure of primary mouse PT cells to ET‐1 (50nM) for 8h decreased megalin (53% reduction) and doubled NHE‐3 expression. Pre‐treatment with the ETA antagonist, BQ123 (1 μM), preserved megalin expression and had no effect on NHE‐3. Moreover, selective ETB receptor blockade (BQ788, 1 μM) prevented ET‐1‐mediated increase in NHE‐3 expression. Primary PT cells isolated from HbSS mice showed decreased megalin mRNA expression as well as protein abundance relative to HbAA PT controls. Ten‐week treatment with selective ETA receptor antagonist (10mg/kg/day) preserved expression of megalin at control levels. There were no differences in NHE‐3 mRNA expression in HbSS PT cells regardless the treatment. Interestingly, PT cells from HbSS cultured with HbSS plasma and ET‐1 (10nM) had decreased NHE‐3 protein abundance compared to non‐treated cells. These results potentially uncover a novel role for ET‐1 in PT albumin handling and suggest that PT ET‐1 receptor signaling contributes to albuminuria in SCD.Support or Funding InformationSupport provided by an NIH U01 HL117684 to D.M.P, AHA 19CDA34660073 and NIH‐NHLBI K99HL144817 to M.K.

Modulation of long-term and short-term plasticity in the dentate gyrus granule cells by activating the β-adrenergic receptors of the basolateral amygdala

The beta-adrenergic receptors of the basolateral amygdala (BLA) are involved in modulating emotional memory formation in the hippocampus. The molecular mechanisms of this involvement are still unclear. In this study, we investigate the effects of the beta-adrenergic receptors of the BLA involvements during the major cellular mechanisms that underlie memory formation in hippocampal sub-regions. Wistar rats were injected with the selective beta receptor agonist, clenbuterol (15 ng/0.5 μl) bilaterally into the BLA. Then, the long-term potentiation (LTP) and the paired-pulse responses were recorded. Control rats were injected by saline at the same volume. Our data indicated that the injection of clenbuterol into the BLA area enhanced the amplitude of the population spike (PS) but not the slope of the excitatory postsynaptic potential (EPSP). In addition, short-term plasticity in the dentate gyrus (DG) region was significantly changed at 500 ms inter-pulse interval. These results suggest that the activation of the beta-adrenergic receptors of the BLA can improve LTP induction, which depends on the short-term plasticity with a mechanism related to the GABAergic transmission. Thus, it can be concluded that the adrenergic system of the BLA engages with long-term and short-term plasticity.

Roles of Endothelin B Receptors and Endothelial Nitric Oxide Synthase in the Regulation of Pulmonary Hemodynamic in Cirrhotic Rats.

Hepatopulmonary syndrome and portopulmonary hypertension are common complications of liver disorders. This study aimed to determine roles of ET-B receptors and endothelial-derived NO synthase in the regulation of pulmonary hemodynamic in cirrhotic rats. Male Sprague-Dawley rats were divided into the Sham and common bile duct ligation (CBDL) groups. After 28 days, animals were anesthetized, and the right ventricle, femoral artery, and vein cannulated. Then, intravenous injection of BQ-788 (a selective ET-B receptor antagonist) and L-NAME (eNOS inhibitor) were performed sequentially. After the first injection of BQ-788, the right ventricular systolic pressure (RVSP) and mean arterial systemic pressure increased only in the Sham group. L-NAME increased RVSP in the Sham and CBDL groups, whereas mean arterial systemic pressure elevated only in the Sham group significantly. Reinjection of BQ-788 increased RVSP in the Sham group, whereas it decreased RVSP in the CBDL group. Both plasma NO metabolites and lung endothelin-1 increased in the CBDL group. ET-B receptors on the endothelial cells play roles in the regulation of pulmonary and systemic vascular tone in normal condition through the NO-mediated pathway, whereas ET-B receptors on the smooth muscle cells have a role in the pulmonary vascular tone in liver cirrhosis.

Effect of mirabegron on tight junction molecules in primary cultured rat Sertoli cells.

Mirabegron is a selective beta3-adrenoceptor (β3 -AR) agonist, which is commonly used for the treatment of overactive bladder. This medicine is associated with atrophy of reproductive organs in rats. However, no study has examined the detailed action and mechanism of its toxicity in reproductive cells. In this study, we examined the effect of mirabegron on primary cultured rat Sertoli cells. Firstly, RT-PCR and immunocytochemistry revealed that β3 -AR was present in rat Sertoli cells. Then, primary cultured rat Sertoli cells were treated with mirabegron. Quantitative real-time PCR revealed that mirabegron treatment induced a significant increase in claudin-11 mRNA, which is crucial for spermatogenesis. Western blot analysis also showed that mirabegron treatment significantly activated p44/42 mitogen-activated protein kinase (MAPK). After additional treatment with U0126, a specific noncompetitive inhibitor of mitogen-activated protein kinase kinase (MAPKK), the upregulation of claudin-11 mRNA induced by mirabegron was reduced. At the same time, immunocytochemistry showed mirabegron treatment disturbed claudin-11 localisation to tight junction, which was recovered when treated with mirabegron in the presence of U0126. These results suggest that mirabegron treatment is associated with assembly of the blood-testis barrier through p44/42 MAPK pathway. These findings could explain one of the underlying mechanisms of reproductive toxicity induced by mirabegron.

Afferent arteriole responsiveness to endothelin receptor activation: does sex matter?

BackgroundThe pathogenesis of hypertension is distinct between men and women. Endothelin-1 (ET-1) is a potential contributor to sex differences in the pathophysiology of hypertension. ET-1 participates in blood pressure regulation through activation of endothelin A (ETA) and endothelin B (ETB) receptors including those in the vasculature. Previous studies demonstrated that sex and sex hormones evoke discrepancies in ET-1-mediated control of vascular tone in different vascular beds. However, little is known about sex- and sex hormone-related differences in ET-1-dependent renal microvascular reactivity. Accordingly, we hypothesized that loss of sex hormones impairs afferent arteriole reactivity to ET-1.MethodsMale and female Sprague Dawley rats were subjected to gonadectomy or sham surgery (n = 6/group). After 3 weeks, kidneys from those rats were prepared for assessment of renal microvascular responses to ET-1 (ETA and ETB agonist, 10−12 to 10−8 M) and sarafotoxin 6c (S6c, ETB agonist, 10−12 to 10−8 M) using the blood-perfused juxtamedullary nephron preparation.ResultsControl afferent arteriole diameters at 100 mmHg were similar between sham male and female rats averaging 14.6 ± 0.3 and 15.3 ± 0.3 μm, respectively. Gonadectomy had no significant effect on control arteriole diameter. In sham males, ET-1 produced significant concentration-dependent decreases in afferent arteriole diameter, with 10−8 M ET-1 decreasing diameter by 84 ± 1%. ET-1 induced similar concentration-dependent vasoconstrictor responses in sham female rats, with 10−8 M ET-1 decreasing the diameter by 82 ± 1%. The afferent arteriolar vasoconstrictor responses to ET-1 were unchanged by ovariectomy or orchiectomy. Selective ETB receptor activation by S6c induced a concentration-dependent decline in afferent arteriole diameter, with 10−8 M S6c decreasing diameter by 77 ± 3 and 76 ± 3% in sham male and female rats, respectively. Notably, ovariectomy augmented the vasoconstrictor response to S6c (10−12 to 10−9 M), whereas orchiectomy had no significant impact on the responsiveness to ETB receptor activation.ConclusionThese data demonstrate that sex does not significantly influence afferent arteriole reactivity to ET receptor activation. Gonadectomy potentiated the responsiveness of the afferent arteriole to ETB-induced vasoconstriction in females, but not males, suggesting that female sex hormones influence ETB-mediated vasoconstriction in the renal microcirculation.