The multifaceted role of beta-blockers in overcoming cancer progression and drug resistance: Extending beyond cardiovascular disorders.

Beta-blockers are commonly used medications that antagonize ß-adrenoceptors, reducing sympathetic nervous system activity. Emerging evidence suggests that beta-blockers may also have anticancer effects and help overcome drug resistance in cancer treatment. This review summarizes the contribution of different isoforms of beta-adrenoceptors in cancer progression, the current preclinical and clinical data on associations between beta-blockers use and cancer outcomes, as well as their ability to enhance responses to chemotherapy and other standard therapies. We discuss proposed mechanisms, including effects on angiogenesis, metastasis, cancer stem cells, and apoptotic pathways. Overall, results from epidemiological studies and small clinical trials largely indicate the beneficial effects of beta-blockers on cancer progression and drug resistance. However, larger randomized controlled trials are needed to firmly establish their clinical efficacy and optimal utilization as adjuvant agents in cancer therapy.

Chronic stress influences the macrophage M1-M2 polarization balance through ß-adrenergic signaling in hepatoma mice.

Chronic stress negatively affects the immune system and promotes tumor progression. Tumor-associated macrophage (TAM) is an important component of the tumor immune microenvironment. However, the influence of chronic stress on M1-M2 polarization of TAM is unclear. We used flow cytometry to measure the M1-M2 polarization of TAM in chronic stress hepatocellular carcinoma (HCC) bearing mice. We also measured the level of norepinephrine and blocked ß-adrenergic signaling to explore the role of ß-adrenergic receptor in the effect of chronic stress on M1-M2 polarization of TAM. We found that chronic stress disrupts the M1-M2 polarization in tumor tissues, increased the level of CD11b+Ly6C+CCR2+ monocyte and interleukin-1beta in blood and promoted the growth of HCC. Furthermore, chronic stress upregulated the level of CCL2 in tumor tissues. Finally, we found chronic stress increased norepinephrine level in serum and propranolol, a blocker of ß-adrenergic signaling, inhibited HCC growth, recovered the M1-M2 polarization balance of TAM in tumor tissues, blocked the increase of CD11b+Ly6C+CCR2+ monocytes in blood, and blocked the increase of CCL2 in tumor tissues induced by chronic stress. Our study indicated that chronic stress disrupts the M1-M2 polarization balance of TAMs through ß-adrenergic signaling, thereby promoting the growth of HCC.

ß-Adrenergic Stimulation-Induced PVAT Dysfunction in Male Sex: A Role for 11ß-Hydroxysteroid Dehydrogenase-1.

Long-term ß-adrenoceptor (ß-AR) stimulation is a pathological mechanism associated with cardiovascular diseases resulting in endothelial and perivascular adipose tissue (PVAT) dysfunction. In this study, we aimed to identify whether ß-adrenergic signaling has a direct effect on PVAT. Thoracic aorta PVAT was obtained from male Wistar rats and cultured ex vivo with the ß-AR agonist isoproterenol (Iso; 1 µM) or vehicle for 24 hours. Conditioned culture medium (CCM) from Iso-treated PVAT induced a marked increase in aorta contractile response, induced oxidative stress, and reduced nitric oxide production in PVAT compared to vehicle. In addition, Iso-treated PVAT and PVAT-derived differentiated adipocytes exhibited higher corticosterone release and protein expression of 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1), an enzyme responsible for de novo synthesis of corticosterone. Macrophages exposed to Iso also exhibited increased corticosterone release in response to ß-AR stimulation. Incubation of Iso-treated PVAT and PVAT-derived differentiated adipocytes with ß3-AR antagonist restored aorta contractile function modulated by Iso-CCM and normalized 11ß-HSD1 protein expression. These results show that ß3-AR signaling leads to upregulation of 11ß-HSD1 in PVAT, thus increasing corticosterone release and contributing to impair the anticontractile function of this tissue.

From "contraindicated" to "first line" - Current mechanistic insights beyond canonical ß-receptor signaling.

ß-blockers are a solid pillar in the treatment of cardiovascular diseases. However, they are highly discussed regarding effectiveness for certain indications and side-effects. Even though there are up to 20 licensed compounds, only four are used for heart failure (HF) therapy. On the receptor level several key characteristics seem to influence the clinical outcome: subtype selectivity, antagonistic vs (inverse/biased) agonistic properties and -in particular- ancillary capacities. On a molecular level, divergent and novel signaling patterns are being identified and extra-cardiac effects on e.g. inflammation, metabolism and oxidative stress are highlighted. This review discusses different well-known and newly discovered characteristics that need to be considered for HF therapy and in the context of co-morbidities.

Single-molecule imaging of aquaporin-4 array dynamics in astrocytes.

Aquaporin-4 (AQP4) facilitates water transport across astrocytic membranes in the brain, forming highly structured nanometric arrays. AQP4 has a central role in regulating cerebrospinal fluid (CSF) circulation and facilitating the clearance of solutes from the extracellular space of the brain. Adrenergic signaling has been shown to modulate the volume of the extracellular space of the brain via AQP4 localized at the end-feet of astrocytes, but the mechanisms by which AQP4 regulates CSF inflow and outflow in the brain remain elusive. Using advanced imaging techniques, including super-resolution microscopy and single-molecule tracking, we investigated the hypothesis that ß-adrenergic receptor activation induces cellular changes that regulate AQP4 array size and mobility, thus influencing water transport in the brain. We report that the ß-adrenergic agonist, isoproterenol hydrochloride, decreases AQP4 array size and enhances its membrane mobility, while hyperosmotic conditions induce the formation of larger, less mobile arrays. These findings reveal that AQP4 arrays are dynamic structures, responsive to adrenergic signals and osmotic changes, highlighting a novel regulatory mechanism of water transport in the brain. Our results provide insights into the molecular control of CSF circulation and extracellular brain space volume, laying the groundwork for understanding the relationship between astrocyte water transport, sleep physiology, and neurodegeneration.

ß-Adrenergic signaling drives structural and functional maturation of mouse cardiomyocytes.

Cardiac maturation represents the last phase of heart development and is characterized by morphofunctional alterations that optimize the heart for efficient pumping. Its understanding provides important insights into cardiac regeneration therapies. Recent evidence implies that adrenergic signals are involved in the regulation of cardiac maturation, but the mechanistic underpinnings involved in this process are poorly understood. Herein, we explored the role of ß-adrenergic receptor (ß-AR) activation in determining structural and functional components of cardiomyocyte maturation. Temporal characterization of tyrosine hydroxylase and norepinephrine levels in the mouse heart revealed that sympathetic innervation develops during the first 3 wk of life, concurrent with the rise in ß-AR expression. To assess the impact of adrenergic inhibition on maturation, we treated mice with propranolol, isolated cardiomyocytes, and evaluated morphofunctional parameters. Propranolol treatment reduced heart weight, cardiomyocyte size, and cellular shortening, while it increased the pool of mononucleated myocytes, resulting in impaired maturation. No changes in t-tubules were observed in cells from propranolol mice. To establish a causal link between ß-AR signaling and cardiomyocyte maturation, mice were subjected to sympathectomy, followed or not by restoration with isoproterenol treatment. Cardiomyocytes from sympathectomyzed mice recapitulated the salient immaturity features of propranolol-treated mice, with the additional loss of t-tubules. Isoproterenol rescued the maturation deficits induced by sympathectomy, except for the t-tubule alterations. Our study identifies the ß-AR stimuli as a maturation promoting signal and implies that this pathway can be modulated to improve cardiac regeneration therapies.NEW & NOTEWORTHY Maturation involves a series of morphofunctional alterations vital to heart development. Its regulatory mechanisms are only now being unveiled. Evidence implies that adrenergic signaling regulates cardiac maturation, but the mechanisms are poorly understood. To address this point, we blocked ß-ARs or performed sympathectomy followed by rescue experiments with isoproterenol in neonatal mice. Our study identifies the ß-AR stimuli as a maturation signal for cardiomyocytes and highlights the importance of this pathway in cardiac regeneration therapies.

The renal vasodilatation from ß-adrenergic activation in vivo in rats is not driven by KV7 and BKCa channels.

The mechanisms behind renal vasodilatation elicited by stimulation of ß-adrenergic receptors are not clarified. As several classes of K channels are potentially activated, we tested the hypothesis that KV7 and BKCa channels contribute to the decreased renal vascular tone in vivo and in vitro. Changes in renal blood flow (RBF) during ß-adrenergic stimulation were measured in anaesthetized rats using an ultrasonic flow probe. The isometric tension of segmental arteries from normo- and hypertensive rats and segmental arteries from wild-type mice and mice lacking functional KV7.1 channels was examined in a wire-myograph. The ß-adrenergic agonist isoprenaline increased RBF significantly in vivo. Neither activation nor inhibition of KV7 and BKCa channels affected the ß-adrenergic RBF response. In segmental arteries from normo- and hypertensive rats, inhibition of KV7 channels significantly decreased the ß-adrenergic vasorelaxation. However, inhibiting BKCa channels was equally effective in reducing the ß-adrenergic vasorelaxation. The ß-adrenergic vasorelaxation was not different between segmental arteries from wild-type mice and mice lacking KV7.1 channels. As opposed to rats, inhibition of KV7 channels did not affect the murine ß-adrenergic vasorelaxation. Although inhibition and activation of KV7 channels or BKCa channels significantly changed baseline RBF in vivo, none of the treatments affected ß-adrenergic vasodilatation. In isolated segmental arteries, however, inhibition of KV7 and BKCa channels significantly reduced the ß-adrenergic vasorelaxation, indicating that the regulation of RBF in vivo is driven by several actors in order to maintain an adequate RBF. Our data illustrates the challenge in extrapolating results from in vitro to in vivo conditions.

Behavior of Hypertrophied Right Ventricle during the Development of Left Ventricular Failure Due to Myocardial Infarction.

In order to determine the behavior of the right ventricle, we have reviewed the existing literature in the area of cardiac remodeling, signal transduction pathways, subcellular mechanisms, ß-adrenoreceptor-adenylyl cyclase system and myocardial catecholamine content during the development of left ventricular failure due to myocardial infarction. The right ventricle exhibited adaptive cardiac hypertrophy due to increases in different signal transduction pathways involving the activation of protein kinase C, phospholipase C and protein kinase A systems by elevated levels of vasoactive hormones such as catecholamines and angiotensin II in the circulation at early and moderate stages of heart failure. An increase in the sarcoplasmic reticulum Ca2+ transport without any changes in myofibrillar Ca2+-stimulated ATPase was observed in the right ventricle at early and moderate stages of heart failure. On the other hand, the right ventricle showed maladaptive cardiac hypertrophy at the severe stages of heart failure due to myocardial infarction. The upregulation and downregulation of ß-adrenoreceptor-mediated signal transduction pathways were observed in the right ventricle at moderate and late stages of heart failure, respectively. The catalytic activity of adenylate cyclase, as well as the regulation of this enzyme by Gs proteins, were seen to be augmented in the hypertrophied right ventricle at early, moderate and severe stages of heart failure. Furthermore, catecholamine stores and catecholamine uptake in the right ventricle were also affected as a consequence of changes in the sympathetic nervous system at different stages of heart failure. It is suggested that the hypertrophied right ventricle may serve as a compensatory mechanism to the left ventricle during the development of early and moderate stages of heart failure.

Overexpressing of the GIPC1 protects against pathological cardiac remodelling.

OBJECTIVE: Pathological cardiac remodelling, including cardiac hypertrophy and fibrosis, is a key pathological process in the development of heart failure. However, effective therapeutic approaches are limited. The ß-adrenergic receptors are pivotal signalling molecules in regulating cardiac function. G-alpha interacting protein (GAIP)-interacting protein, C-terminus 1 (GIPC1) is a multifunctional scaffold protein that directly binds to the C-terminus of ß1-adrenergic receptor (ß1-adrenergic receptor). However, little is known about its roles in heart function. Therefore, we investigated the role of GIPC1 in cardiac remodelling and its underlying molecular mechanisms. METHODS: Pathological cardiac remodelling in mice was established via intraperitoneal injection of isoprenaline for 14 d or transverse aortic constriction surgery for 8 weeks. Myh6-driving cardiomyocyte-specific GIPC1 conditional knockout (GIPC1 cKO) mice and adeno-associated virus 9 (AAV9)-mediated GIPC1 overexpression mice were used. The effect of GIPC1 on cardiac remodelling was assessed using echocardiographic, histological, and biochemical analyses. RESULTS: GIPC1 expression was consistently reduced in the cardiac remodelling model. GIPC1 cKO mice exhibited spontaneous abnormalities, including cardiac hypertrophy, fibrosis, and systolic dysfunction. In contrast, AAV9-mediated GIPC1 overexpression in the heart attenuated isoproterenol-induced pathological cardiac remodelling in mice. Mechanistically, GIPC1 interacted with the ß1-adrenergic receptor and stabilised its expression by preventing its ubiquitination and degradation, maintaining the balance of ß1-adrenergic receptor/ß2-adrenergic receptor, and inhibiting hyperactivation of the mitogen-activated protein kinase signalling pathway. CONCLUSIONS: These results suggested that GIPC1 plays a cardioprotective role and is a promising therapeutic target for the treatment of cardiac remodelling and heart failure.

The role of ß-adrenergic receptors in the regulation of cardiac tolerance to ischemia/reperfusion. Why do ß-adrenergic receptor agonists and antagonists protect the heart?

BACKGROUND: Catecholamines and ß-adrenergic receptors (ß-ARs) play an important role in the regulation of cardiac tolerance to the impact of ischemia and reperfusion. This systematic review analyzed the molecular mechanisms of the cardioprotective activity of ß-AR ligands. METHODS: We performed an electronic search of topical articles using PubMed databases from 1966 to 2023. We cited original in vitro and in vivo studies and review articles that documented the cardioprotective properties of ß-AR agonists and antagonists. RESULTS: The infarct-reducing effect of ß-AR antagonists did not depend on a decrease in the heart rate. The target for ß-blockers is not only cardiomyocytes but also neutrophils. ß1-blockers (metoprolol, propranolol, timolol) and the selective ß2-AR agonist arformoterol have an infarct-reducing effect in coronary artery occlusion (CAO) in animals. Antagonists of ß1- and ß2-АR (metoprolol, propranolol, nadolol, carvedilol, bisoprolol, esmolol) are able to prevent reperfusion cardiac injury. All ß-AR ligands that reduced infarct size are the selective or nonselective ß1-blockers. It was hypothesized that ß1-AR blocking promotes an increase in cardiac tolerance to I/R. The activation of ß1-AR, ß2-AR, and ß3-AR can increase cardiac tolerance to I/R. The cardioprotective effect of ß-AR agonists is mediated via the activation of kinases and reactive oxygen species production. CONCLUSIONS: It is unclear why ß-blockers with the similar receptor selectivity have the infarct-sparing effect while other ß-blockers with the same selectivity do not affect infarct size. What is the molecular mechanism of the infarct-reducing effect of ß-blockers in reperfusion? Why did in early studies ß-blockers decrease the mortality rate in patients with acute myocardial infarction (AMI) and without reperfusion and in more recent studies ß-blockers had no effect on the mortality rate in patients with AMI and reperfusion? The creation of more effective ß-AR ligands depends on the answers to these questions.

Genetic Variants of the Beta-Adrenergic Receptor Pathways as Both Risk and Protective Factors for Retinopathy of Prematurity.

PURPOSE: There is strong evidence that genetic factors influence retinopathy of prematurity (ROP), a neovascular eye disease. It has been previously suggested that polymorphisms in the genes involved in ß-adrenergic receptor (ADRß) pathways could protect against ROP. Antagonists for the ADRß are actively tested in clinical trials for ROP treatment, but not without controversy and safety concerns. This study was designed to assess whether genetic variations in components of the ADRß signaling pathways associate with risk of developing ROP. DESIGN: An observational case-control targeted genetic analysis. METHODS: A study was carried out in premature participants with (n = 30) or without (n = 34) ROP and full-term controls (n = 20), who were divided into a discovery cohort and a validation cohort. ROP was defined using International Classification of Retinopathy of Prematurity criteria (ICROP). Targeted sequencing of 20 genes in the ADRß pathways was performed in the discovery cohort. Polymerase chain reaction (PCR)/restriction enzyme analysis for some of the discovered ROP-associated variants was performed for validation of the results using the validation cohort. RESULTS: The discovery cohort revealed 543 bi-allelic variants within 20 genes of the ADRß pathways. Ten single-nucleotide variants (SNVs) in 5 genes including protein kinase A regulatory subunit 1α (PRKAR1A), rap guanine exchange factor 3 (RAPGEF3), adenylyl cyclase 4 (ADCY4), ADCY7, and ADCY9 were associated with ROP (P < .05). The most significant SNV was found in PRKAR1A (P = .001). Multiple variants located in the 3'-untranslated region (3'UTR) of RAPGEF3 were also associated with ROP (P < .05). PCR/restriction enzyme analysis of the 3'UTR of RAPGEF3 methodologically validated these findings. CONCLUSION: SNVs in PRKAR1A may represent protective factors whereas SNVs in RAPGEF3 may represent risk factors for ROP. PRKAR1α has previously been implicated in retinal vascular development whereas the RAPGEF3 product has a role in the maintenance of vascular barrier function, 2 processes important in ROP. Multicenter validation of these newly discovered risk factors could lead to valuable tools for predicting and preventing the development of severe ROP.

Isoproterenol induces MD2 activation by ß-AR-cAMP-PKA-ROS signalling axis in cardiomyocytes and macrophages drives inflammatory heart failure.

Cardiac inflammation contributes to heart failure (HF) induced by isoproterenol (ISO) through activating ß-adrenergic receptors (ß-AR). Recent evidence shows that myeloid differentiation factor 2 (MD2), a key protein in endotoxin-induced inflammation, mediates inflammatory heart diseases. In this study, we investigated the role of MD2 in ISO-ß-AR-induced heart injuries and HF. Mice were infused with ISO (30 mg·kg-1·d-1) via osmotic mini-pumps for 2 weeks. We showed that MD2 in cardiomyocytes and cardiac macrophages was significantly increased and activated in the heart tissues of ISO-challenged mice. Either MD2 knockout or administration of MD2 inhibitor L6H21 (10 mg/kg every 2 days, i.g.) could prevent mouse hearts from ISO-induced inflammation, remodelling and dysfunction. Bone marrow transplantation study revealed that both cardiomyocyte MD2 and bone marrow-derived macrophage MD2 contributed to ISO-induced cardiac inflammation and injuries. In ISO-treated H9c2 cardiomyocyte-like cells, neonatal rat primary cardiomyocytes and primary mouse peritoneal macrophages, MD2 knockout or pre-treatment with L6H21 (10 µM) alleviated ISO-induced inflammatory responses, and the conditioned medium from ISO-challenged macrophages promoted the hypertrophy and fibrosis in cardiomyocytes and fibroblasts. We demonstrated that ISO induced MD2 activation in cardiomyocytes via ß1-AR-cAMP-PKA-ROS signalling axis, and induced inflammatory responses in macrophages via ß2-AR-cAMP-PKA-ROS axis. This study identifies MD2 as a key inflammatory mediator and a promising therapeutic target for ISO-induced heart failure.

The role of beta-adrenoreceptors in postoperative ileus in rats.

The aim of the research was to evaluate the influence of antagonists of specific beta-adrenergic receptor subtypes on bowel motility following abdominal surgery in rat model of postoperative ileus. Bowel motility was measured by the intestinal transit of Evans blue introduced via orogastric tube after surgical procedures of skin incision, laparotomy and laparotomy with gut manipulation. Male rats were given individual adrenergic receptor subtypes antagonists intraperitoneally, and the influence of administered agents on intestinal transit of Evans blue was then evaluated. No statistically significant differences in the length of intestine in tested rats were observed. Propranolol administered prior to surgical procedure has shown protective effect on Evans blue migration in rats undergoing laparotomy and gut manipulation. Intestinal dye transit for propranolol doses of 10, 30 and 45 mg/kg was 18.00 ± 1.88c m, 23.75 ± 1.71 cm and 22.5 ± 2.43 cm, respectively, and for last two doses, statistically significant increase of dye passage was noted, compared to Evans blue transit of 11.00 ± 2.43 cm in the control group. No acceleration of dye migration was seen following administration of beta1-, beta2- and beta3-selective adrenergic receptor antagonist metoprolol, ICI 118.551 and SR58894A, respectively. Our research confirmed that propranolol at high doses, as seen by other researchers, improved bowel motility in early phase of postoperative ileus. That slight acceleration of intestinal dye transit after surgery with gut manipulation is rather connected with membrane-stabilizing action, than the receptor blocking effect, as this effect was not observed after the application of selective antagonists of respective subtypes of beta-adrenergic receptor.

Relation of Plasma Catecholamine Concentrations and Myocardial Mitochondrial Respiratory Activity in Anesthetized and Mechanically Ventilated, Cardiovascular Healthy Swine.

Chronic heart failure is associated with reduced myocardial ß-adrenergic receptor expression and mitochondrial function. Since these data coincide with increased plasma catecholamine levels, we investigated the relation between myocardial ß-receptor expression and mitochondrial respiratory activity under conditions of physiological catecholamine concentrations. This post hoc analysis used material of a prospective randomized, controlled study on 12 sexually mature (age 20-24 weeks) Early Life Stress or control pigs (weaning at day 21 and 28-35 after birth, respectively) of either sex. Measurements in anesthetized, mechanically ventilated, and instrumented animals comprised serum catecholamine (liquid-chromatography/tandem-mass-spectrometry) and 8-isoprostane levels, whole blood superoxide anion concentrations (electron spin resonance), oxidative DNA strand breaks (tail moment in the "comet assay"), post mortem cardiac tissue mitochondrial respiration, and immunohistochemistry (ß2-adrenoreceptor, mitochondrial respiration complex, and nitrotyrosine expression). Catecholamine concentrations were inversely related to myocardial mitochondrial respiratory activity and ß2-adrenoceptor expression, whereas there was no relation to mitochondrial respiratory complex expression. Except for a significant, direct, non-linear relation between DNA damage and noradrenaline levels, catecholamine concentrations were unrelated to markers of oxidative stress. The present study suggests that physiological variations of the plasma catecholamine concentrations, e.g., due to physical and/or psychological stress, may affect cardiac ß2-adrenoceptor expression and mitochondrial respiration.

Nitric Oxide Modulates Ca2+ Leak and Arrhythmias via S-Nitrosylation of CaMKII.

BACKGROUND: Nitric oxide (NO) has been identified as a signaling molecule generated during ß-adrenergic receptor stimulation in the heart. Furthermore, a role for NO in triggering spontaneous Ca2+ release via S-nitrosylation of CaMKIIδ (Ca2+/calmodulin kinase II delta) is emerging. NO donors are routinely used clinically for their cardioprotective effects on the heart, but it is unknown how NO donors modulate the proarrhythmic CaMKII to alter cardiac arrhythmia incidence. We test the role of S-nitrosylation of CaMKIIδ at the Cysteine-273 inhibitory site and cysteine-290 activating site in cardiac Ca2+ handling and arrhythmogenesis before and during ß-adrenergic receptor stimulation. METHODS: We measured Ca2+-handling in isolated cardiomyocytes from C57BL/6J wild-type (WT) mice and mice lacking CaMKIIδ expression (CaMKIIδ-KO) or with deletion of the S-nitrosylation site on CaMKIIδ at cysteine-273 or cysteine-290 (CaMKIIδ-C273S and -C290A knock-in mice). Cardiomyocytes were exposed to NO donors, S-nitrosoglutathione (GSNO; 150 µM), sodium nitroprusside (200 µM), and ß-adrenergic agonist isoproterenol (100 nmol/L). RESULTS: Both WT and CaMKIIδ-KO cardiomyocytes responded to isoproterenol with a full inotropic and lusitropic Ca2+ transient response as well as increased Ca2+ spark frequency. However, the increase in Ca2+ spark frequency was significantly attenuated in CaMKIIδ-KO cardiomyocytes. The protection from isoproterenol-induced Ca2+ sparks and waves was mimicked by GSNO pretreatment in WT cardiomyocytes but lost in CaMKIIδ-C273S cardiomyocytes. When GSNO was applied after isoproterenol, this protection was not observed in WT or CaMKIIδ-C273S but was apparent in CaMKIIδ-C290A. In Langendorff-perfused isolated hearts, GSNO pretreatment limited isoproterenol-induced arrhythmias in WT but not CaMKIIδ-C273S hearts, while GSNO exposure after isoproterenol sustained or exacerbated arrhythmic events. CONCLUSIONS: We conclude that prior S-nitrosylation of CaMKIIδ at cysteine-273 can limit subsequent ß-adrenergic receptor-induced arrhythmias, but that S-nitrosylation at cysteine-290 might worsen or sustain ß-adrenergic receptor-induced arrhythmias. This has important implications for the administration of NO donors in the clinical setting.

ß-Adrenergic Signaling Promotes Morphological Maturation of Astrocytes in Female Mice.

Astrocytes play essential roles in the developing nervous system, including supporting synapse function. These astrocyte support functions emerge coincident with brain maturation and may be tailored in a region-specific manner. For example, gray matter astrocytes have elaborate synapse-associated processes and are morphologically and molecularly distinct from white matter astrocytes. This raises the question of whether there are unique environmental cues that promote gray matter astrocyte identity and synaptogenic function. We previously identified adrenergic receptors as preferentially enriched in developing gray versus white matter astrocytes, suggesting that noradrenergic signaling could be a cue that promotes the functional maturation of gray matter astrocytes. We first characterized noradrenergic projections during postnatal brain development in mouse and human, finding that process density was higher in the gray matter and increased concurrently with astrocyte maturation. RNA sequencing revealed that astrocytes in both species expressed α- and ß-adrenergic receptors. We found that stimulation of ß-adrenergic receptors increased primary branching of rodent astrocytes in vitro Conversely, astrocyte-conditional knockout of the ß1-adrenergic receptor reduced the size of gray matter astrocytes and led to dysregulated sensorimotor integration in female mice. These studies suggest that adrenergic signaling to developing astrocytes impacts their morphology and has implications for adult behavior, particularly in female animals. More broadly, they demonstrate a mechanism through which environmental cues impact astrocyte development. Given the key roles of norepinephrine in brain states, such as arousal, stress, and learning, these findings could prompt further inquiry into how developmental stressors impact astrocyte development and adult brain function.SIGNIFICANCE STATEMENT This study demonstrates a role for noradrenergic signaling in the development of gray matter astrocytes. We provide new evidence that the ß1-adrenergic receptor is robustly expressed by both mouse and human astrocytes, and that conditional KO of the ß1-adrenergic receptor from female mouse astrocytes impairs gray matter astrocyte maturation. Moreover, female conditional KO mice exhibit behavioral deficits in two paradigms that test sensorimotor function. Given the emerging interest in moving beyond RNA sequencing to probe specific pathways that underlie astrocyte heterogeneity, this study provides a foundation for future investigation into the effect of noradrenergic signaling on astrocyte functions in conditions where noradrenergic signaling is altered, such as stress, arousal, and learning.

Corticosterone injection into the basolateral amygdala before and after memory reactivation impairs the subsequent expression of fear memory in rats: An interaction of glucocorticoids and ß-adrenoceptors.

Glucocorticoid administration, before or after fear memory reactivation, impairs subsequent fear memory expression, but the underlying mechanisms are not well understood. The present study examined the role of basolateral amygdala (BLA) ß-adrenoceptors in the effects of intra-BLA corticosterone injection on fear memory in rats. Bilateral cannulae were implanted in the BLA of Wistar male rats. The rats were trained and tested using an inhibitory avoidance task (1 mA footshock for 3 s). Forty-eight hours after training, corticosterone (CORT, 5, 10, or 20 ng/0.5 µl/side) and the ß2-adrenoceptor agonist clenbuterol (CLEN, 10 or 20 ng/0.5 µl/side) or the ß-adrenoceptor antagonist propranolol (PROP, 250 or 500 ng/0.5 µl/side) were injected into the BLA before or right after memory reactivation (retrieval, Test 1). We performed subsequent tests 2 (Test 2), 5 (Test 3), 7 (Test 4), and 9 (Test 5) days after Test 1. The results demonstrated that CORT injection before Test 1 disrupted memory retrieval and reduced fear expression in Tests 2-5, possibly due to enhanced extinction or impaired reconsolidation. CORT injection after Test 1 also impaired reconsolidation and reduced fear expression in Tests 2-5. CLEN prevented, but PROP exacerbated, the effects of CORT on fear expression. The reminder shock did not recover fear memory in CORT-treated animals, suggesting that reconsolidation, not extinction, was affected. These results indicate that glucocorticoids and ß-adrenoceptors in the BLA jointly modulate fear memory reconsolidation and expression. Comprehending the neurobiology of stress and the impact of glucocorticoids on fear memory may lead to new treatments for stress and trauma-induced disorders such as PTSD.

Dapagliflozin attenuates cardiac remodeling and dysfunction in rats with ß-adrenergic receptor overactivation through restoring calcium handling and suppressing cardiomyocyte apoptosis.

Background: Long-term ß-adrenergic receptor (ß-AR) activation can impair myocardial structure and function. Dapagliflozin (DAPA) has been reported to improve clinical prognosis in heart failure patients, whereas the exact mechanism remains unclear. Here, we investigated the effects of DAPA against ß-AR overactivation toxicity and explored the underlying mechanism.Methods and Results: Rats were randomized to receive saline + placebo, isoproterenol (ISO, 5 mg/kg/day, intraperitoneally) + placebo, or ISO + DAPA (1 mg/kg/day, intragastrically) for 2-week. DAPA treatment improved cardiac function, alleviated myocardial fibrosis, prevented cardiomyocytes (CMs) apoptosis, and decreased the expression of ER stress-mediated apoptosis markers in ISO-treated hearts. In isolated CMs, 2-week ISO stimulation resulted in deteriorated kinetics of cellular contraction and relaxation, increased diastolic intracellular Ca2+ level and decay time constant of Ca2+ transient (CaT) but decreased CaT amplitude and sarcoplasmic reticulum (SR) Ca2+ level. However, DAPA treatment prevented abnormal Ca2+ handling and contractile dysfunction in CMs from ISO-treated hearts. Consistently, DAPA treatment upregulated the expression of SR Ca2+-ATPase protein and ryanodine receptor 2 (RyR2) but reduced the expression of phosphorylated-RyR2, Ca2+/calmodulin-dependent protein kinase II (CaMKII), and phosphorylated-CaMKII in ventricles from ISO-treated rats.Conclusion: DAPA prevented myocardial remodeling and cardiac dysfunction in rats with ß-AR overactivation via restoring calcium handling and suppressing ER stress-related CMs apoptosis.

PDE4D mediates impaired ß-adrenergic receptor signalling in the sinoatrial node in mice with hypertensive heart disease.

AIMS: The sympathetic nervous system increases HR by activating ß-adrenergic receptors (ß-ARs) and increasing cAMP in sinoatrial node (SAN) myocytes while phosphodiesterases (PDEs) degrade cAMP. Chronotropic incompetence, the inability to regulate heart rate (HR) in response to sympathetic nervous system activation, is common in hypertensive heart disease; however, the basis for this is poorly understood. The objective of this study was to determine the mechanisms leading to chronotropic incompetence in mice with angiotensin II (AngII)-induced hypertensive heart disease. METHODS AND RESULTS: C57BL/6 mice were infused with saline or AngII (2.5 mg/kg/day for 3 weeks) to induce hypertensive heart disease. HR and SAN function in response to the ß-AR agonist isoproterenol (ISO) were studied in vivo using telemetry and electrocardiography, in isolated atrial preparations using optical mapping, in isolated SAN myocytes using patch-clamping, and using molecular biology. AngII-infused mice had smaller increases in HR in response to physical activity and during acute ISO injection. Optical mapping of the SAN in AngII-infused mice demonstrated impaired increases in conduction velocity and altered conduction patterns in response to ISO. Spontaneous AP firing responses to ISO in isolated SAN myocytes from AngII-infused mice were impaired due to smaller increases in diastolic depolarization (DD) slope, hyperpolarization-activated current (If), and L-type Ca2+ current (ICa,L). These changes were due to increased localization of PDE4D surrounding ß1- and ß2-ARs in the SAN, increased SAN PDE4 activity, and reduced cAMP generation in response to ISO. Knockdown of PDE4D using a virus-delivered shRNA or inhibition of PDE4 with rolipram normalized SAN sensitivity to ß-AR stimulation in AngII-infused mice. CONCLUSIONS: AngII-induced hypertensive heart disease results in impaired HR responses to ß-AR stimulation due to up-regulation of PDE4D and reduced effects of cAMP on spontaneous AP firing in SAN myocytes.

MiR-133b as a crucial regulator of TCS-induced cardiotoxicity via activating ß-adrenergic receptor signaling pathway in zebrafish embryos.

As a commonly used antibacterial agent in daily consumer products, triclosan (TCS) has attracted significant attention due to its potential environmental risks. In this study, we investigated the toxic effects of TCS exposure (1.4 µM) on heart development in zebrafish embryos. Our findings revealed that TCS exposure caused significant cardiac dysfunction, characterized by pericardial edema, malformations in the heart structure, and a slow heart rate. Additionally, TCS exposure induced oxidative damage and abnormal apoptosis in heart cells through the up-regulation of ß-adrenergic receptor (ß-AR) signaling pathway genes (adrb1, adrb2a, arrb2b), similar to the effects induced by ß-AR agonists. Notably, the adverse effects of TCS exposure were alleviated by ß-AR antagonists. Using high-throughput transcriptome miRNA sequencing and targeted miRNA screening, we focused on miR-133b, which targets adrb1 and was down-regulated by TCS exposure, as a potential contributor to TCS-induced cardiotoxicity. Inhibition of miR-133b produced similar toxic effects as TCS exposure, while overexpression of miR-133b down-regulated the ß-AR signaling pathway and rescued heart defects caused by TCS. In summary, our findings provide new insights into the mechanisms underlying the cardiotoxic effects of TCS. We suggest that targeting the ß-AR pathway and miR-133b may be effective strategies for pharmacotherapy in cardiotoxicity induced by environmental pollutants such as TCS.