ßAR-mTOR-lipin1 pathway mediates PKA-RIIß deficiency-induced adipose browning.

Background: Enhancing white adipose tissue (WAT) browning combats obesity. The RIIß subunit of cAMP-dependent protein kinase (PKA) is primarily expressed in the brain and adipose tissue. Deletion of the hypothalamic RIIß gene centrally induces WAT browning, yet the peripheral mechanisms mediating this process remain unexplored. Methods: This study investigates the mechanisms underlying WAT browning in RIIß-KO mice. Genetic approaches such as ß3-adrenergic receptors (ß3ARs) deletion and sympathetic denervation of WAT were utilized. Genome-wide transcriptomic sequencing and bioinformatic analysis were employed to identify potential mediators of WAT browning. siRNA assays were employed to knock down mTOR and lipin1 in vitro, while AAV-shRNAs were used for the same purpose in vivo. Results: We found that WAT browning substantially contributes to the lean and obesity-resistant phenotypes of RIIß-KO mice. The WAT browning can be dampened by ß3ARs deletion or WAT sympathetic denervation. We identified that adipocytic mTOR and lipin1 may act as mediators of the WAT browning. Inhibition of mTOR or lipin1 abrogates WAT browning and hinders the lean phenotype of RIIß-KO mice. In human subcutaneous white adipocytes and mouse white adipocytes, ß3AR stimulation can activate mTOR and causes lipin1 nuclear translocation; knockdown of mTOR and Lipin1 mitigates WAT browning-associated gene expression, impedes mitochondrial activity. Moreover, mTOR knockdown reduces lipin1 level and nuclear translocation, indicating that lipin1 may act downstream of mTOR. Additionally, in vivo knockdown of mTOR and Lipin1 diminished WAT browning and increased adiposity. Conclusions: The ß3AR-activated mTOR-lipin1 axis mediates WAT browning, offering new insights into the molecular basis of PKA-regulated WAT browning. These findings provide potential adipose target candidates for the development of drugs to treat obesity.

Association between rs4994 variant in ß3-Adrenergic receptor and obesity in Vietnamese preschool-age children, independent of eating behaviors.

BACKGROUND: The Arg64 allele of the rs4994 (Trp64Arg) variant in the ß3-adrenergic receptor (ADRB3) gene is involved in the control of energy balance by altering lipolysis and thermogenesis in adipocytes, ultimately contributing to the development of obesity. The objective of our study was to investigate the association between the rs4994 variant of the ADRB3 gene and obesity in Hanoi preschool-age children, adjusting for their eating behaviors. METHODS: A cross-sectional study was performed involving 708 children with normal weight and 304 children with obesity aged 3-5 years from 36 kindergartens in Hanoi, Vietnam. Cheek mucosa cell samples were used for DNA extraction, and genotyping at the ADRB3-rs4994 locus was performed using the polymerase chain reaction-restriction fragment length polymorphism method (PCR-RFLP). Eating behaviors were assessed using the Children's Eating Behaviour Questionnaire (CEBQ). Binary logistic regression analysis was employed to examine the association between the rs4994 variant and obesity, adjusting for confounding factors such as age, sex, residence, birth weight, and eating behaviors. RESULTS: The frequency of the C allele in the group with obesity was 16.4%, which was higher than in the control group (11.7%, P = 0.003). Children with the CC genotype exhibited significantly greater weight and weight-for-age Z-score compared to those with the TT and TC genotypes (P = 0.004 and 0.03, respectively). Following univariate and multivariate analyses adjusted for age, sex, residence, birth weight, and eating behaviors, a significant association between the rs4994 variant and obesity was observed (P < 0.05). CONCLUSIONS: This study indicated that the ADRB3-rs4994 variant can be considered as an independent risk factor for obesity in Vietnamese preschool children.

Enrichment of novel CD3+F4/80+ cells in brown adipose tissue following adrenergic stimulation.

Macrophages play a multifaceted role in maintaining tissue homeostasis, fighting infections, and regulating cold-induced thermogenesis. The brown adipose tissue (BAT) is crucial for maintaining body temperature during cold exposure. Cold stress triggers the sympathetic nervous system to release norepinephrine (NE), which activates BAT via ß3-adrenergic receptors, initiating lipolysis and glycolysis. BAT-infiltrating macrophages can either hinder or enhance thermogenesis by controlling the interplay between BAT cells and sympathetic nerves. In this study we report on a unique population of CD3+F4/80+ dual lineage co-expressing (DE) cells within the interscapular BAT (iBAT), that increased following chronic adrenergic stimulation. In forward scatter/side scatter plots, they formed a cluster distinct from lymphocytes, appearing larger and more complex. These CD3+F4/80+ DE cells demonstrated the lack of T cell markers CD62L and TCRß and expressed higher levels of Ly6C, F4/80, and CD11b markers compared to T cells and CD3- macrophages. Furthermore, analysis revealed two subpopulations within the CD3+F4/80+ DE population based on MHCII expression, with the proportion of MHCII-low subset increasing with adrenergic stimulation. This novel DE population within iBAT, unequivocally identified by the its unique surface marker profile, warrants further investigation into the intricate mechanisms governing adaptive thermogenesis regulation.

Agonism of ß3-Adrenoceptors Inhibits Pathological Retinal Angiogenesis in the Model of Oxygen-Induced Retinopathy.

Purpose: In response to hypoxia, sympathetic fibers to the retina activate ß-adrenoceptors (ß-ARs) that play an important role in the regulation of vascular and neuronal functions. We investigated the role of ß3-AR using the mouse model of oxygen-induced retinopathy (OIR). Methods: Mouse pups were exposed to 75% oxygen at postnatal day 7 (PD7) followed by a return to room air at PD12. The ß3-AR preferential agonist BRL37344 was subcutaneously administered once daily at different times after the return to room air. At PD17, the OIR mice underwent flash and pattern electroretinogram. After sacrifice, retinal wholemounts were used for vessel staining or immunohistochemistry for astrocytes, Müller cells, or retinal ganglion cells (RGCs). In retinal homogenates, the levels of markers associated with neovascularization (NV), the blood-retinal barrier (BRB), or astrocytes were determined by western blot, and quantitative reverse-transcription polymerase chain reaction was used to assess ß3-AR messenger. Administration of the ß3-AR antagonist SR59230A was performed to verify BRL37344 selectivity. Results: ß3-AR expression is upregulated in response to hypoxia, but its increase is prevented by BRL37344, which counteracts NV by inhibiting the pro-angiogenic pathway, activating the anti-angiogenic pathway, recovering BRB-associated markers, triggering nitric oxide production, and favoring revascularization of the central retina through recovered density of astrocytes that ultimately counteracts NV in the midperiphery. Vasculature rescue prevents dysfunctional retinal activity and counteracts OIR-associated retinal ganglion cell loss. Conclusions: ß3-AR has emerged as a crucial intermediary in hypoxia-dependent NV, suggesting a role of ß3-AR agonists in the treatment of proliferative retinopathies.

Hyaluronan Mediates Cold-Induced Adipose Tissue Beiging.

Adipose tissue beiging refers to the process by which beige adipocytes emerge in classical white adipose tissue depots. Beige adipocytes dissipate chemical energy and secrete adipokines, such as classical brown adipocytes, to improve systemic metabolism, which is beneficial for people with obesity and metabolic diseases. Cold exposure and ß3-adrenergic receptor (AR) agonist treatment are two commonly used stimuli for increasing beige adipocytes in mice; however, their underlying biological processes are different. Transcriptional analysis of inguinal white adipose tissue (iWAT) has revealed that changes in extracellular matrix (ECM) pathway genes are specific to cold exposure. Hyaluronic acid (HA), a non-sulfated linear polysaccharide produced by nearly all cells, is one of the most common components of ECM. We found that cold exposure significantly increased iWAT HA levels, whereas the ß3-AR agonist CL316,243 did not. Increasing HA levels in iWAT by Has2 overexpression significantly increases cold-induced adipose tissue beiging; in contrast, decreasing HA by Spam1 overexpression, which encodes a hyaluronidase that digests HA, significantly decreases cold-induced iWAT beiging. All these data implicate a role of HA in promoting adipose tissue beiging, which is unique to cold exposure. Given the failure of ß3-AR agonists in clinical trials for obesity and metabolic diseases, increasing HA could serve as a new approach for recruiting more beige adipocytes to combat metabolic diseases.

Kinin B1 receptor deficiency promotes enhanced adipose tissue thermogenic response to ß3-adrenergic stimulation.

OBJECTIVE AND DESIGN: Kinin B1 receptor (B1R) has a key role in adipocytes to protect against obesity and glycemic metabolism, thus becoming a potential target for regulation of energy metabolism and adipose tissue thermogenesis. MATERIAL OR SUBJECTS: Kinin B1 knockout mice (B1KO) were subjected to acute induction with CL 316,243 and chronic cold exposure. METHODS: Metabolic and histological analyses, gene and protein expression and RNA-seq were performed on interscapular brown adipose tissue (iBAT) and inguinal white adipose tissue (iWAT) of mice. RESULTS: B1KO mice, under acute effect of CL 316,243, exhibited increased energy expenditure and upregulated thermogenic genes in iWAT. They were also protected from chronic cold, showing enhanced non-shivering thermogenesis with increased iBAT mass (~ 90%) and recruitment of beige adipocytes in iWAT (~ 50%). Positive modulation of thermogenic and electron transport chain genes, reaching a 14.5-fold increase for Ucp1 in iWAT. RNA-seq revealed activation of the insulin signaling pathways for iBAT and oxidative phosphorylation, tricarboxylic acid cycle, and browning pathways for iWAT. CONCLUSION: B1R deficiency induced metabolic and gene expression alterations in adipose tissue, activating thermogenic pathways and increasing energy metabolism. B1R antagonists emerge as promising therapeutic targets for regulating obesity and associated metabolic disorders, such as inflammation and diabetes.

Cocoa extract induces browning of white adipocytes and improves glucose intolerance in mice fed a high-fat diet.

Cocoa extract (CE) offers several health benefits, such as antiobesity and improved glucose intolerance. However, the mechanisms remain unclear. Adipose tissue includes white adipose tissue (WAT) and brown adipose tissue. Brown adipose tissue leads to body fat reduction by metabolizing lipids to heat via uncoupling protein 1 (UCP1). The conversion of white adipocytes into brown-like adipocytes (beige adipocytes) is called browning, and it contributes to the anti-obesity effect and improved glucose tolerance. This study aimed to evaluate the effect of CE on glucose tolerance in terms of browning. We found that dietary supplementation with CE improved glucose intolerance in mice fed a high-fat diet, and it increased the expression levels of Ucp1 and browning-associated gene in inguinal WAT. Furthermore, in primary adipocytes of mice, CE induced Ucp1 expression through ß3-adrenergic receptor stimulation. These results suggest that dietary CE improves glucose intolerance by inducing browning in WAT.

Genetic evidence for involvement of ß2-adrenergic receptor in brown adipose tissue thermogenesis in humans.

BACKGROUND: Sympathetic activation of brown adipose tissue (BAT) thermogenesis can ameliorate obesity and related metabolic abnormalities. However, crucial subtypes of the ß-adrenergic receptor (AR), as well as effects of its genetic variants on functions of BAT, remains unclear in humans. We conducted association analyses of genes encoding ß-ARs and BAT activity in human adults. METHODS: Single nucleotide polymorphisms (SNPs) in ß1-, ß2-, and ß3-AR genes (ADRB1, ADRB2, and ADRB3) were tested for the association with BAT activity under mild cold exposure (19 °C, 2 h) in 399 healthy Japanese adults. BAT activity was measured using fluorodeoxyglucose-positron emission tomography and computed tomography (FDG-PET/CT). To validate the results, we assessed the effects of SNPs in the two independent populations comprising 277 healthy East Asian adults using near-infrared time-resolved spectroscopy (NIRTRS) or infrared thermography (IRT). Effects of SNPs on physiological responses to intensive cold exposure were tested in 42 healthy Japanese adult males using an artificial climate chamber. RESULTS: We found a significant association between a functional SNP (rs1042718) in ADRB2 and BAT activity assessed with FDG-PET/CT (p < 0.001). This SNP also showed an association with cold-induced thermogenesis in the population subset. Furthermore, the association was replicated in the two other independent populations; BAT activity was evaluated by NIRTRS or IRT (p < 0.05). This SNP did not show associations with oxygen consumption and cold-induced thermogenesis under intensive cold exposure, suggesting the irrelevance of shivering thermogenesis. The SNPs of ADRB1 and ADRB3 were not associated with these BAT-related traits. CONCLUSIONS: The present study supports the importance of ß2-AR in the sympathetic regulation of BAT thermogenesis in humans. The present collection of DNA samples is the largest to which information on the donor's BAT activity has been assigned and can serve as a reference for further in-depth understanding of human BAT function.

Adipose tissue rearrangement in cancer cachexia: The involvement of ß3-adrenergic receptor associated pathways.

Cancer-associated cachexia (CAC) is a complex multiple organ syndrome that significantly contributes to reduced quality of life and increased mortality among many cancer patients. Its multifactorial nature makes its early diagnosis and effective therapeutic interventions challenging. Adipose tissue is particularly impacted by cachexia, typically through increased lipolysis, browning and thermogenesis, mainly at the onset of the disease. These processes lead to depletion of fat mass and contribute to the dysfunction of other organs. The ß-adrenergic signalling pathways are classical players in the regulation of adipose tissue metabolism. They are activated upon sympathetic stimulation inducing lipolysis, browning and thermogenesis, therefore contributing to energy expenditure. Despite accumulating evidence suggesting that ß3-adrenergic receptor stimulation may be crucial to the adipose tissue remodelling during cachexia, the literature remains controversial. Moreover, there is limited knowledge regarding sexual dimorphism of adipose tissue in the context of cachexia. This review paper aims to present the current knowledge regarding adipose tissue wasting during CAC, with a specific focus on the role of the ß3-adrenergic receptor, placing it as a potential therapeutic target against cachexia.

Age and sex mediated effects of estrogen and Β3-adrenergic receptor on cardiovascular pathophysiology.

Sex differences are consistently identified in determining the prevalence, manifestation, and response to therapies in several systemic disorders, including those affecting the cardiovascular (CV), skeletal muscle, and nervous system. Interestingly, such differences are often more noticeable as we age. For example, premenopausal women experience a lower risk of CV disease than men of the same age. While at an advanced age, with menopause, the risk of cardiovascular diseases and adverse outcomes increases exponentially in women, exceeding that of men. However, this effect appears to be reversed in diseases such as pulmonary hypertension, where women are up to seven times more likely than men to develop an idiopathic form of the disease with symptoms developing ten years earlier than their male counterparts. Explaining this is a complex question. However, several factors and mechanisms have been identified in recent decades, including a role for sex hormones, particularly estrogens and their related receptors. Furthermore, an emerging role in these sex differences has also been suggested for ß-adrenergic receptors (ßARs), which are essential regulators of mammalian physiology. It has in fact been shown that ßARs interact with estrogen receptors (ER), providing further demonstration of their involvement in determining sexual differences. Based on these premises, this review article focused on the ß3AR subtype, which shows important activities in adipose tissue but with new and interesting roles in regulating the function of cardiomyocytes and vascular cells. In detail, we examined how ß3AR and ER signaling are intertwined and whether there would be sex- and age-dependent specific effects of these receptor systems.

ENDOGENOUS ß 3 -ADRENERGIC RECEPTOR ACTIVATION ALLEVIATES SEPSIS-INDUCED CARDIOMYOCYTE APOPTOSIS VIA PI3K/AKT SIGNALING PATHWAY.

ABSTRACT: ß 3 -adrenergic receptor (ß 3 -AR) has been proposed as a new therapy for several myocardial diseases. However, the effect of ß 3 -AR activation on sepsis-induced myocardial apoptosis is unclear. Here, we investigated the effect of ß 3 -AR activation on the cardiomyocyte apoptosis and cardiac dysfunction in cecal ligation and puncture (CLP)-operated rats and lipopolysaccharide (LPS)-treated cardiomyocytes. We found that ß 3 -AR existed both in adult rat ventricular myocytes (ARVMs) and H9c2 cells. The expression of ß 3 -AR was upregulated in LPS-treated ARVMs and the heart of CLP rats. Pretreatment with ß 3 -AR agonist, BRL37344, inhibited LPS-induced cardiomyocyte apoptosis and caspase-3, -8, and -9 activation in ARVMs. BRL37344 also reduced apoptosis and increased the protein levels of PI3K, p-Akt Ser473 and p-eNOS Ser1177 in LPS-treated H9c2 cells. Inhibition of PI3K using LY294002 abolished the inhibitory effect of BRL37344 on LPS-induced caspase-3, -8, and -9 activation in H9c2 cells. Furthermore, administration of ß 3 -AR antagonist, SR59230A (5 mg/kg), significantly decreased the maximum rate of left ventricular pressure rise (+dP/dt) in CLP-induced septic rats. SR59230A not only increased myocardial apoptosis, reduced p-Akt Ser473 and Bcl-2 contents, but also increased mitochondrial Bax, cytoplasm cytochrome c, cleaved caspase-9, and cleaved caspase-3 levels of the myocardium in septic rats. These results suggest that endogenous ß 3 -AR activation alleviates sepsis-induced cardiomyocyte apoptosis via PI3K/Akt signaling pathway and maintains intrinsic myocardial systolic function in sepsis.

The Role of ß3-Adrenergic Receptors in Cold-Induced Beige Adipocyte Production in Pigs.

After exposure to cold stress, animals enhance the production of beige adipocytes and expedite thermogenesis, leading to improved metabolic health. Although brown adipose tissue in rodents is primarily induced by ß3-adrenergic receptor (ADRB3) stimulation, the activation of major ß-adrenergic receptors (ADRBs) in pigs has been a topic of debate. To address this, we developed overexpression vectors for ADRB1, ADRB2, and ADRB3 and silenced the expression of these receptors to observe their effects on the adipogenic differentiation stages of porcine preadipocytes. Our investigation revealed that cold stress triggers the transformation of subcutaneous white adipose tissue to beige adipose tissue in pigs by modulating adrenergic receptor levels. Meanwhile, we found that ADRB3 promotes the transformation of white adipocytes into beige adipocytes. Notably, ADRB3 enhances the expression of beige adipose tissue marker genes, consequently influencing cellular respiration and metabolism by regulating lipolysis and mitochondrial expression. Therefore, ADRB3 may serve as a pivotal gene in animal husbandry and contribute to the improvement of cold intolerance in piglets.

Inside the Biology of the ß3-Adrenoceptor.

Since the first discovery in 1989, the ß3-adrenoceptor (ß3-AR) has gained great attention because it showed the ability to regulate many physiologic and metabolic activities, such as thermogenesis and lipolysis in brown and white adipose tissue, respectively (BAT, WAT), negative inotropic effects in cardiomyocytes, and relaxation of the blood vessels and the urinary bladder. The ß3-AR has been suggested as a potential target for cancer treatment, both in adult and pediatric tumors, since under hypoxia its upregulation in the tumor microenvironment (TME) regulates stromal cell differentiation, tumor growth and metastases, signifying that its agonism/antagonism could be useful for clinical benefits. Promising results in cancer research have proposed the ß3-AR being targeted for the treatment of many conditions, with some drugs, at present, undergoing phase II and III clinical trials. In this review, we report the scientific journey followed by the research from the ß3-Ars' discovery, with focus on the ß3-Ars' role in cancer initiation and progression that elects it an intriguing target for novel antineoplastic approaches. The overview highlights the great potential of the ß3-AR, both in physiologic and pathologic conditions, with the intention to display the possible benefits of ß3-AR modulation in cancer reality.

Genomic and transcriptomic analysis of breast cancer identifies novel signatures associated with response to neoadjuvant chemotherapy.

BACKGROUND: Neoadjuvant chemotherapy (NAC) has become a standard treatment strategy for breast cancer (BC). However, owing to the high heterogeneity of these tumors, it is unclear which patient population most likely benefit from NAC. Multi-omics offer an improved approach to uncovering genomic and transcriptomic changes before and after NAC in BC and to identifying molecular features associated with NAC sensitivity. METHODS: We performed whole-exome and RNA sequencing on 233 samples (including matched pre- and post-treatment tumors) from 50 BC patients with rigorously defined responses to NAC and analyzed changes in the multi-omics landscape. Molecular features associated with NAC response were identified and validated in a larger internal, and two external validation cohorts, as well as in vitro experiments. RESULTS: The most frequently altered genes were TP53, TTN, and MUC16 in both pre- and post-treatment tumors. In comparison with pre-treatment tumors, there was a significant decrease in C > A transversion mutations in post-treatment tumors (P = 0.020). NAC significantly decreased the mutation rate (P = 0.006) of the DNA repair pathway and gene expression levels (FDR = 0.007) in this pathway. NAC also significantly changed the expression level of immune checkpoint genes and the abundance of tumor-infiltrating immune and stroma cells, including B cells, activated dendritic cells, γδT cells, M2 macrophages and endothelial cells. Furthermore, there was a higher rate of C > T substitutions in NAC nonresponsive tumors than responsive ones, especially when the substitution site was flanked by C and G. Importantly, there was a unique amplified region at 8p11.23 (containing ADGRA2 and ADRB3) and a deleted region at 3p13 (harboring FOXP1) in NAC nonresponsive and responsive tumors, respectively. Particularly, the CDKAL1 missense variant P409L (p.Pro409Leu, c.1226C > T) decreased BC cell sensitivity to docetaxel, and ADGRA2 or ADRB3 gene amplifications were associated with worse NAC response and poor prognosis in BC patients. CONCLUSIONS: Our study has revealed genomic and transcriptomic landscape changes following NAC in BC, and identified novel biomarkers (CDKAL1P409L, ADGRA2 and ADRB3) underlying chemotherapy resistance and poor prognosis, which could guide the development of personalized treatments for BC.

Blocking brown adipocyte ß3-adrenoceptor attenuates blood-spinal cord barrier impairment and chronic postsurgical pain in a rat model of preoperative stress.

Preoperative stress has been recognized as an independent risk factor for chronic postsurgical pain (CPSP). However, the underlying mechanisms of CPSP influenced by preoperative stress remain elusive. Previous studies indicated that excessive stress could induce disruption of the blood-spinal cord barrier (BSCB). We wondered whether and how BSCB involves in CPSP by using a single prolonged stress (SPS) combining plantar incision model in male rats to mimic preoperative stress-related postsurgical pain. Here, we observed that preoperative SPS-exposed rats exhibited relentless incisional pain, which was accompanied by impairment of BSCB and persistent elevation of serum IL-6. Intraperitoneal injections of Tocilizumab (an IL-6 receptor monoclonal antibody) not only mitigated BSCB breakdown but also alleviated pain behaviors. In addition, intervening ß3-adrenoceptor (ADRB3) signaling in brown adipocytes by SR59230a (a specific ADRB3 antagonist) treatment or removal of brown adipose tissues could effectively decrease serum IL-6 levels, ameliorate BSCB disruption, and alleviate incisional pain. Further results displayed that SI-exposed rats also showed markedly spinal microglia activation. And exogenous His-tagged IL-6 could pass through the disrupted BSCB, which might contribute to microglia activation. Injection of SR59230a or ablation of brown adipose tissues could effectively reduce the activation of spinal microglia. Thus, our findings suggest that serum IL-6 induced by brown adipocyte ADRB3 signaling contributed to BSCB disruption and spinal microglia activation, which might be involved in preoperative stress mediated CPSP. This work indicates a promising treatment strategy for preoperative stress induced CPSP by blocking ADRB3.

In silico identification of a biarylamine acting as agonist at human ß3 adrenoceptors and exerting BRL37344-like effects on mouse metabolism.

Human ß3-adrenoceptor (ß3AR) agonists were considered potential agents for the treatment of metabolic disorders. However, compounds tested as ß3AR ligands have shown marked differences in pharmacological profile in rodent and human species, although these compounds remain attractive as they were successfully repurposed for the therapy of urinary incontinence. In this work, some biarylamine compounds were designed and tested in silico as potential ß3AR agonists on 3-D models of mouse or human ß3ARs. Based on the theoretical results, we identified, synthesized and tested a biarylamine compound (polibegron). In CHO-K1 cells expressing the human ß3AR, polibegron and the ß3AR agonist BRL 37344 were partial agonists for stimulating cAMP accumulation (50 and 57% of the response to isoproterenol, respectively). The potency of polibegron was 1.71- and 4.5-fold higher than that of isoproterenol and BRL37344, respectively. These results indicate that polibegron acts as a potent, but partial, agonist at human ß3ARs. In C57BL/6N mice with obesity induced by a high-fat diet, similar effects of the equimolar intraperitoneal administration of polibegron and BRL37344 were observed on weight, visceral fat and plasma levels of glucose, cholesterol and triglycerides. Similarities and differences between species related to ligand-receptor interactions can be useful for drug designing.

ß-Adrenoceptors regulate urothelial inflammation and zonula occludens in the bladder outlet obstruction model.

BACKGROUND: The purpose of this study was to evaluate the effects of ß-adrenoceptors (ADRBs) on the urothelial inflammation and zonula occludens (ZO) in a rat PBOO model and in an in vitro model. METHODS: The PBOO model was established by ligating the bladder neck of rats. Twenty rats were divided into 4 groups: sham operation, PBOO + normal saline, PBOO + ADRB2 agonist, PBOO + ADRB3 agonist. PBOO rats were with treated with ADRBs agonists for 3 weeks. Human urothelial cells (HUCs) were subjected to ADRBs agonist treatment or hydrostatic pressure in an in vitro model. RESULTS: In the PBOO group, there was a significant increase in the expression of MCP-1, IL-6 and RANTES compared to the sham group. By contrast, there was a post-PBOO decline in the expression of ZO-1 and ZO-2 in the urothelium. ADRB2 or ADRB3 agonists exhibited downregulated inflammatory cytokine expression and increased ZO expression in the PBOO model. The regulation of inflammation and ZO by ADRB2 and ADRB3 agonists in an in vitro model was found consistent with that in the PBOO model. Moreover, RhoA and ROCK inhibitors suppressed the expression of hydrostatic pressure-induced inflammatory cytokines. Additionally, RhoA agonist reversed the inhibitory effect of ADRBs agonists on the inflammatory secretion from HUCs. CONCLUSIONS: ADRB2 and ADRB3 agonists increased ZO protein expression in HUCs in a rat PBOO model and in an in vitro model. Furthermore, ADRB2 and ADRB3 agonists inhibited the secretion of inflammatory cytokines from HUCs by regulating the RhoA/ROCK signaling pathways.

Is the ß3-Adrenoceptor a Valid Target for the Treatment of Obesity and/or Type 2 Diabetes?

ß3-Adrenoceptors mediate several functions in rodents that could be beneficial for the treatment of obesity and type 2 diabetes. This includes promotion of insulin release from the pancreas, cellular glucose uptake, lipolysis, and thermogenesis in brown adipose tissue. In combination, they lead to a reduction of body weight in several rodent models including ob/ob mice and Zucker diabetic fatty rats. These findings stimulated drug development programs in various pharmaceutical companies, and at least nine ß3-adrenoceptor agonists have been tested in clinical trials. However, all of these projects were discontinued due to the lack of clinically relevant changes in body weight. Following a concise historical account of discoveries leading to such drug development programs we discuss species differences that explain why ß3-adrenoceptors are not a meaningful drug target for the treatment of obesity and type 2 diabetes in humans.

ß3 Adrenoceptor Agonism Prevents Hyperoxia-Induced Colonic Alterations.

Oxygen level is a key regulator of organogenesis and its modification in postnatal life alters the maturation process of organs, including the intestine, which do not completely develop in utero. The ß3-adrenoreceptor (ß3-AR) is expressed in the colon and has an oxygen-dependent regulatory mechanism. This study shows the effects of the ß3-AR agonist BRL37344 in a neonatal model of hyperoxia-driven colonic injury. For the first 14 days after birth, Sprague-Dawley rat pups were exposed to ambient oxygen levels (21%) or hyperoxia (85%) and treated daily with BRL37344 at 1, 3, 6 mg/kg or untreated. At the end of day 14, proximal colon samples were collected for analysis. Hyperoxia deeply influences the proximal colon development by reducing ß3-AR-expressing cells (27%), colonic length (26%) and mucin production (47%), and altering the neuronal chemical coding in the myenteric plexus without changes in the neuron number. The administration of BRL37344 at 3 mg/kg, but not at 1 mg/kg, significantly prevented these alterations. Conversely, it was ineffective in preventing hyperoxia-induced body weight loss. BRL37344 at 6 mg/kg was toxic. These findings pave the way for ß3-AR pharmacological targeting as a therapeutic option for diseases caused by hyperoxia-impaired development, typical prematurity disorders.

Vibegron shows high selectivity and potent agonist activity for ß3-adrenoceptors, irrespective of receptor density.

ß3-Adrenoceptor (AR) agonists are used to treat patients with an overactive bladder (OAB). Clinical proof-of-concept data have been obtained for the ß3-AR agonists vibegron, mirabegron, solabegron, and ritobegron; however, the selectivities of these agents have not been compared directly under the same experimental conditions. Moreover, the bladders of some patients express lower ß3-AR densities than those of healthy individuals, and the ß3-AR density might be expected to affect agonist activity. This study assessed the ß3-AR selectivities of four ß3-AR agonists and examined the effects of ß-AR density on their pharmacological profiles. Functional cellular assays were performed using Chinese hamster ovary-K1 cells expressing three human ß-AR subtypes transfected with different amounts of plasmid DNA (0.1, 0.05, 0.025 µg/well). The half-maximal effective concentration values, intrinsic activities (IAs), and ß3-AR selectivities of vibegron, mirabegron, solabegron, and ritobegron were calculated to assess their pharmacological profiles. The ß3-AR selectivities of vibegron, mirabegron, solabegron, and ritobegron were >7937-, 517-, 21.3-, and >124-fold higher than for ß1-ARs, and >7937-, 496-, >362- and 28.1-fold higher than for ß2-ARs, respectively, under the same experimental conditions. The IAs of mirabegron, solabegron, and ritobegron decreased in line with decreasing receptor density, while the IA of vibegron was maintained at the same level as that of the full agonist isoproterenol at various ß3-AR densities. Vibegron has high ß3-AR selectivity and exhibits full agonist activity, regardless of the ß3-AR density. These results suggest that vibegron is a highly effective and safe drug for treating OAB.