Role of the ß2-adrenergic receptor in podocyte injury and recovery.

BACKGROUND: Podocytes have a remarkable ability to recover from injury; however, little is known about the recovery mechanisms involved in this process. We recently showed that formoterol, a long-acting ß2-adrenergic receptor (ß2-AR) agonist, induced mitochondrial biogenesis (MB) in podocytes and led to renoprotection in mice. However, it is not clear whether this effect was mediated by formoterol acting through the ß2-AR or if it occurred through "off-target" effects. METHODS: We genetically deleted the ß2-AR specifically in murine podocytes and used these mice to determine whether formoterol acting through the podocyte ß2-AR alone is sufficient for recovery of renal filtration function following injury. The podocyte-specific ß2-AR knockout mice (ß2-ARfl/fl/PodCre) were generated by crossing ß2-AR floxed mice with podocin Cre (B6.Cg-Tg(NPHS2-cre)295Lbh/J) mice. These mice were then subjected to both acute and chronic glomerular injury using nephrotoxic serum (NTS) and adriamycin (ADR), respectively. The extent of injury was evaluated by measuring albuminuria and histological and immunostaining analysis of the murine kidney sections. RESULTS: A similar level of injury was observed in ß2-AR knockout and control mice; however, the ß2-ARfl/fl/PodCre mice failed to recover in response to formoterol. Functional evaluation of the ß2-ARfl/fl/PodCre mice following injury plus formoterol showed similar albuminuria and glomerular injury to control mice that were not treated with formoterol. CONCLUSIONS: These results indicate that the podocyte ß2-AR is a critical component of the recovery mechanism and may serve as a novel therapeutic target for treating podocytopathies.

The severity of MUSK pathogenic variants is predicted by the protein domain they disrupt.

Biallelic loss-of-function variants in the MUSK gene result in two allelic disorders: (1) congenital myasthenic syndrome (CMS; OMIM: 616325), a neuromuscular disorder that has a range of severity from severe neonatal-onset weakness to mild adult-onset weakness, and (2) fetal akinesia deformation sequence (OMIM: 208150), a form of pregnancy loss characterized by severe muscle weakness in the fetus. The MUSK gene codes for muscle-specific kinase (MuSK), a receptor tyrosine kinase involved in the development of the neuromuscular junction. Here, we report a case of neonatal-onset MUSK-related CMS in a patient harboring compound heterozygous deletions in the MUSK gene, including (1) a deletion of exons 2-3 leading to an in-frame MuSK protein lacking the immunoglobulin 1 (Ig1) domain and (2) a deletion of exons 7-11 leading to an out-of-frame, truncated MuSK protein. Individual domains of the MuSK protein have been elucidated structurally; however, a complete MuSK structure generated by machine learning algorithms has clear inaccuracies. We modify a predicted AlphaFold structure and integrate previously reported domain-specific structural data to suggest a MuSK protein that dimerizes in two locations (Ig1 and the transmembrane domain). We analyze known pathogenic variants in MUSK to discover domain-specific genotype-phenotype correlations; variants that lead to a loss of protein expression, disruption of the Ig1 domain, or Dok-7 binding are associated with the most severe phenotypes. A conceptual model is provided to explain the severe phenotypes seen in Ig1 variants and the poor response of our patient to pyridostigmine.

Computational Modeling and Characterization of Peptides Derived from Nanobody Complementary-Determining Region 2 (CDR2) Targeting Active-State Conformation of the ß2-Adrenergic Receptor (ß2AR).

This study assessed the suitability of the complementarity-determining region 2 (CDR2) of the nanobody (Nb) as a template for the derivation of nanobody-derived peptides (NDPs) targeting active-state ß2-adrenergic receptor (ß2AR) conformation. Sequences of conformationally selective Nbs favoring the agonist-occupied ß2AR were initially analyzed by the informational spectrum method (ISM). The derived NDPs in complex with ß2AR were subjected to protein-peptide docking, molecular dynamics (MD) simulations, and metadynamics-based free-energy binding calculations. Computational analyses identified a 25-amino-acid-long CDR2-NDP of Nb71, designated P4, which exhibited the following binding free-energy for the formation of the ß2AR:P4 complex (ΔG = -6.8 ± 0.8 kcal/mol or a Ki = 16.5 µM at 310 K) and mapped the ß2AR:P4 amino acid interaction network. In vitro characterization showed that P4 (i) can cross the plasma membrane, (ii) reduces the maximum isoproterenol-induced cAMP level by approximately 40% and the isoproterenol potency by up to 20-fold at micromolar concentration, (iii) has a very low affinity to interact with unstimulated ß2AR in the cAMP assay, and (iv) cannot reduce the efficacy and potency of the isoproterenol-mediated ß2AR/ß-arrestin-2 interaction in the BRET2-based recruitment assay. In summary, the CDR2-NDP, P4, binds preferentially to agonist-activated ß2AR and disrupts Gαs-mediated signaling.

Olodaterol promotes thermogenesis in brown adipocytes via regulation of the ß2-AR/cAMP/PKA signaling pathway.

The escalating incidence of metabolic pathologies such as obesity and diabetes mellitus underscores the imperative for innovative therapeutics targeting lipid metabolism modulation. Within this context, augmenting thermogenic processes in adipose cells emerges as a viable therapeutic approach. Given the limitations of previous ß3-adrenergic receptor (ß3-AR) agonist treatments in human diseases, there is an increasing focus on therapies targeting the ß2-adrenergic receptor (ß2-AR). Olodaterol (OLO) is a potent ß2-AR agonist that is a potential novel pharmacological candidate in this area. Our study explores the role and underlying mechanisms of OLO in enhancing brown adipose thermogenesis, providing robust evidence from in vitro and in vivo studies. OLO demonstrated a dose-dependent enhancement of lipolysis, notably increasing the expression of Uncoupling Protein 1 (UCP1) and raising the rate of oxygen consumption in primary brown adipocytes. This suggests a significant increase in thermogenic potential and energy expenditure. The administration of OLO to murine models noticeably enhanced cold-induced nonshivering thermogenesis. OLO elevated UCP1 expression in the brown adipose tissue of mice. Furthermore, it promoted brown adipocyte thermogenesis by activating the ß2-AR/cAMP/PKA signaling cascades according to RNA sequencing, western blotting, and molecular docking analysis. This investigation underscores the therapeutic potential of OLO for metabolic ailments and sheds light on the intricate molecular dynamics of adipocyte thermogenesis, laying the groundwork for future targeted therapeutic interventions in human metabolic disorders.

Macrophage ß2-AR activation amplifies inflammation in wound healing by upregulating Trem1 via the cAMP/PKA/CREB pathway.

BACKGROUND: Inflammation is an important part of the wound healing process. The stress hormone epinephrine has been demonstrated to modulate the inflammatory response via its interaction with ß2-adrenergic receptor (ß2-AR). However, the precise molecular mechanism through which ß2-AR exerts its influence on inflammation during the wound healing process remains an unresolved question. METHODS: Transcriptome datasets of wound and macrophages from the GEO database were reanalyzed using bioinformatics. The role of ß2-AR in wound healing was explored by a mouse hind paw plantar wound model, and histological analyses were performed to assess wound healing. In vivo and in vitro assays were performed to elucidate the role of ß2-AR on the inflammatory response. Triggering receptor expressed on myeloid cells 1 (Trem1) was knocked down with siRNA on RAW cells and western blot and qPCR assays were performed. RESULTS: Trem1 was upregulated within 24 h of wounding, and macrophage ß2-AR activation also upregulated Trem1. In vivo experiments demonstrated that ß2-AR agonists impaired wound healing, accompanied by upregulation of Trem1 and activation of cAMP/PKA/CREB pathway, as well as by a high level of pro-inflammatory cytokine production. In vitro experiments showed that macrophage ß2-AR activation amplified LPS-induced inflammation, and knockdown of Trem1 reversed this effect. Using activator and inhibitor of cAMP, macrophage ß2-AR activation was confirmed to upregulate Trem1 via the cAMP/PKA/CREB pathway. CONCLUSION: Our study found that ß2-AR agonists increase Trem1 expression in wounds, accompanied by amplification of the inflammatory response, impairing wound healing. ß2-AR activation in RAW cells induces Trem1 upregulation via the cAMP/PKA/CREB pathway and amplifies LPS-induced inflammatory responses.

Modulation of mitochondrial apoptosis by ß2-adrenergic receptor blockage in colorectal cancer after radiotherapy: an in-vivo and in-vitro study.

Colorectal cancer (CRC) is one of the leading causes of malignancy-related deaths worldwide. Radiotherapy is often combined with surgery to treat patients with more advanced CRC. Despite impressive initial clinical responses, radiotherapy resistance is the main reason for most treatment failures in colorectal cancer. The G protein-coupled adrenergic receptor (AR) has shown to involve in the development and radiotherapy resistance of CRC. The ß2-AR blockage (ICI-118,551) can use to inhibit the progression of CRC through downregulating EGFR-Akt-ERK1/2 signaling. Since catecholamines-activated the G protein-coupled AR activation has been shown to result in radioresistant, co-treatment with both ß2-AR blockage and radiation may be improved the clinical outcome of CRC. We demonstrated that selective ß2-AR blockage, but not selective ß1-AR blockage, significantly enhanced radiation-induced apoptosis in CRC cells with wild-type p53 in vitro. The molecular mechanism of the apoptotic pathway was possibly triggered by a change in the mitochondrial membrane permeability and release of cytosolic cytochrome C through phospho-P53 mitochondrial translocation. We also found that a P53 knockout in the HCT116 cells was correlated with reversing ß2-AR blockage-mediated apoptosis induction after radiation treatment. Furthermore, the ß2-AR blockage significantly inhibited CRC cell-xenograft growth in vivo. Our study suggests that ß2-AR blockage may be used as adjunct agent for improving the clinical outcomes of CRC following radiotherapy by inducing apoptosis in CRC cells.

Corrigendum: Case report: deterioration of infantile hemangioma related to oral or nebulized administration of ß2-AR agonist: three cases reports.

[This corrects the article DOI: 10.3389/fonc.2022.1000099.].

ß2-Adrenergic Receptor Mediated Inhibition of T Cell Function and Its Implications for CAR-T Cell Therapy.

The microenvironment of most tumors is complex, comprising numerous aspects of immunosuppression. Several studies have indicated that the adrenergic system is vital for controlling immunological responses. In the context of the tumor microenvironment, nor-adrenaline (NA) is poured in by innervating nerves and tumor tissues itself. The receptors for nor-adrenaline are present on the surfaces of cancer and immune cells and are often involved in the activation of pro-tumoral signaling pathways. Beta2-adrenergic receptors (ß2-ARs) are an emerging class of receptors that are capable of modulating the functioning of immune cells. ß2-AR is reported to activate regulatory immune cells and inhibit effector immune cells. Blocking ß2-AR increases activation, proliferation, and cytokine release of T lymphocytes. Moreover, ß2-AR deficiency during metabolic reprogramming of T cells increases mitochondrial membrane potential and biogenesis. In the view of the available research data, the immunosuppressive role of ß2-AR in T cells presents it as a targetable checkpoint in CAR-T cell therapies. In this review, we have abridged the contemporary knowledge about adrenergic-stress-mediated ß2-AR activation on T lymphocytes inside tumor milieu.

Association among ß2-adrenergic receptor autoantibodies and proximal left anterior descending artery lesions in patients with initial ST-segment elevation myocardial infarction.

BACKGROUND: ß2 -adrenergic receptor autoantibody (ß2 -AA) are widely present in patients with many different types of cardiovascular diseases. Proximal left anterior descending (LAD) artery lesions are associated with adverse prognostic events in patients with ST-segment elevation myocardial infarction (STEMI). HYPOTHESIS: ß2 -AA is associated with the presence of proximal LAD lesions in patients with STEMI. METHODS: A cohort of 153 patients with STEMI who underwent primary percutaneous coronary intervention (PPCI) was enrolled in the study. Baseline characteristics were compared between the proximal LAD group (n = 62) and the nonproximal LAD group (n = 91). Admission serum of patients was collected to detect the level of ß2 -AA. Data for echocardiogram within 24 hours after PPCI and at the 6-month follow-up were recorded. RESULTS: The optical density values and positive rates of ß2 -AA in the proximal LAD group were higher than those in the nonproximal LAD group (p < 0.05). ß2 -AA positively correlated with high sensitivity C-reactive protein and peak N-terminal pro-B type natriuretic peptide levels in the proximal LAD group, but those were not relevant in the nonproximal LAD group. Multivariate logistic regression analysis revealed that high ß2 -AA levels was independently associated with the presence of proximal LAD lesions in patients with STEMI. Furthermore, a receiver operating characteristic curve was used to show the efficiency of ß2 -AA levels to detect proximal LAD lesions, and the AUC of the ß2-AA OD value was 0.658 (95% confidence interval 0.568-0.749; p = 0.001). CONCLUSIONS: The STEMI patients with high ß2 -AA levels had a greater possibility having proximal LAD lesions.

ß2-adrenergic receptor expression in patients receiving bevacizumab therapy for metastatic melanoma.

BACKGROUND: Vascular endothelial growth factor (VEGF) was initially known as vascular permeability factor and identified as a driver of tumour angiogenesis. Recently, its role in supporting an immunosuppressive tumour microenvironment was demonstrated, and anti-VEGF treatment combined with immune checkpoint blockade is currently investigated. Further, beta-adrenergic signalling as a modifier of cancer hallmarks like immune response, angiogenesis and metastasis gained increased attention during past years. METHODS: Focusing on the aspect of immunosuppression in upregulated beta-adrenergic signalling, we investigated predictive markers in patients with metastatic melanoma who received bevacizumab monotherapy, a specific VEGF-A binding antibody. We explored the expression of beta-2 adrenergic receptor (ß2-AR), interleukin 6-receptor (IL6-R), cyclooxygenase 2 (COX2) and VEGF-A by immunohistochemistry in melanoma to assess the correlation between these proteins in melanoma cells and response to treatment. RESULTS: Strong ß2-AR expression in metastases was associated with clinical benefit of bevacizumab. Furthermore, expression of the latter was positively linked to expression of VEGF-A and COX2. ß2-AR expression in melanoma metastasis appears to distinguish a subgroup of patients that might benefit from anti-VEGF treatment. CONCLUSION: Our results strengthen further exploration of anti-VEGF therapy in combination with immune checkpoint blockade in clinical studies and the investigation of ß2-AR as predictive marker.

ß2-adrenergic signaling promotes higher-affinity B cells and antibodies.

Stress-induced ß2-adrenergic receptor (ß2AR) activation in B cells increases IgG secretion; however, the impact of this activation on antibody affinity and the underlying mechanisms remains unclear. In the current study, we demonstrate that stress in mice following ovalbumin (OVA) or SARS-CoV-2 RBD immunization significantly increases both serum and surface-expressed IgG binding to the immunogen, while concurrently reducing surface IgG expression and B cell clonal expansion. These effects were abolished by pharmacological ß2AR blocking or when the experiments were conducted in ß2AR -/- mice. In the second part of our study, we used single B cell sorting to characterize the monoclonal antibodies (mAbs) generated following ß2AR activation in cultured RBD-stimulated B cells from convalescent SARS-CoV-2 donors. Ex vivo ß2AR activation increased the affinities of the produced anti-RBD mAbs by 100-fold compared to mAbs produced by the same donor control cultures. Consistent with the mouse experiments, ß2AR activation reduced both surface IgG levels and the frequency of expanded clones. mRNA sequencing revealed a ß2AR-dependent upregulation of the PI3K pathway and B cell receptor (BCR) signaling through AKT phosphorylation, as well as an increased B cell motility. Overall, our study demonstrates that stress-mediated ß2AR activation drives changes in B cells associated with BCR activation and higher affinity antibodies.

Activation of ß2-adrenergic Receptor Alleviates Collagen-induced Arthritis by Ameliorating Th17/Treg Imbalance.

Background: Recent research in our laboratory shows that CD4+ T cells express the ß2 adrenergic receptor (ß2-AR), and the sympathetic neurotransmitter norepinephrine regulates the function of T cells via ß2-AR signaling. However, the immunoregulatory effect of ß2-AR and its related mechanisms on rheumatoid arthritis is unknown. Objective: To explore the effects of ß2-AR in collagen-induced arthritis (CIA) on the imbalance of T helper (Th) 17/ regulatory T (Treg) cells. Methods: In DBA1/J mice, collagen type II was injected intradermally at the tail base to prepare the CIA model. The specific ß2-AR agonist, terbutaline (TBL), was administered intraperitoneally beginning on day 31 and continuing until day 47 after primary vaccination, twice a day. Magnetic beads were used to sort CD3+ T cells subsets from spleen tissues. Results: In vivo, ß2-AR agonist TBL alleviated arthritis symptoms in the CIA mice including histopathology of the ankle joints, four limbs' arthritis score, the thickness of ankle joints, and rear paws. After TBL treatment, in the ankle joints, the levels of proinflammatory factors (IL-17/22) notably decreased and the levels of immunosuppressive factors (IL-10/TGF-ß) significantly increased. In vitro, ROR-γt protein expression, Th17 cell number, mRNA expression and the releasing of IL-17/22 from CD3+ T cells reduced following TBL administration. Moreover, TBL enhanced the anti-inflammatory responses of Treg cells. Conclusion: These results suggest that ß2-AR activation exerts anti-inflammatory effects through the amelioration of Th17/Treg imbalance in the CIA disease.

Activation of ß2-Adrenergic Receptors in Microglia Alleviates Neuropathic Hypersensitivity in Mice.

Drugs enhancing the availability of noradrenaline are gaining prominence in the therapy of chronic neuropathic pain. However, underlying mechanisms are not well understood, and research has thus far focused on α2-adrenergic receptors and neuronal excitability. Adrenergic receptors are also expressed on glial cells, but their roles toward antinociception are not well deciphered. This study addresses the contribution of ß2-adrenergic receptors (ß2-ARs) to the therapeutic modulation of neuropathic pain in mice. We report that selective activation of ß2-ARs with Formoterol inhibits pro-inflammatory signaling in microglia ex vivo and nerve injury-induced structural remodeling and functional activation of microglia in vivo. Systemic delivery of Formoterol inhibits behaviors related to neuropathic pain, such as mechanical hypersensitivity, cold allodynia as well as the aversive component of pain, and reverses chronically established neuropathic pain. Using conditional gene targeting for microglia-specific deletion of ß2-ARs, we demonstrate that the anti-allodynic effects of Formoterol are primarily mediated by microglia. Although Formoterol also reduces astrogliosis at late stages of neuropathic pain, these functions are unrelated to ß2-AR signaling in microglia. Our results underline the value of developing microglial ß2-AR agonists for relief from neuropathic pain and clarify mechanistic underpinnings.

Pepducin ICL1-9-Mediated ß2-Adrenergic Receptor-Dependent Cardiomyocyte Contractility Occurs in a Gi Protein/ROCK/PKD-Sensitive Manner.

PURPOSE: ß-Adrenergic receptors (ßAR) are essential targets for the treatment of heart failure (HF); however, chronic use of ßAR agonists as positive inotropes to increase contractility in a Gs protein-dependent manner is associated with increased mortality. Alternatively, we previously reported that allosteric modulation of ß2AR with the pepducin intracellular loop (ICL)1-9 increased cardiomyocyte contractility in a ß-arrestin (ßarr)-dependent manner, and subsequently showed that ICL1-9 activates the Ras homolog family member A (RhoA). Here, we aimed to elucidate both the proximal and downstream signaling mediators involved in the promotion of cardiomyocyte contractility in response to ICL1-9. METHODS: We measured adult mouse cardiomyocyte contractility in response to ICL1-9 or isoproterenol (ISO, as a positive control) alone or in the presence of inhibitors of various potential components of ßarr- or RhoA-dependent signaling. We also assessed the contractile effects of ICL1-9 on cardiomyocytes lacking G protein-coupled receptor (GPCR) kinase 2 (GRK2) or 5 (GRK5). RESULTS: Consistent with RhoA activation by ICL1-9, both Rho-associated protein kinase (ROCK) and protein kinase D (PKD) inhibition were able to attenuate ICL1-9-mediated contractility, as was inhibition of myosin light chain kinase (MLCK). While neither GRK2 nor GRK5 deletion impacted ICL1-9-mediated contractility, pertussis toxin attenuated the response, suggesting that ICL1-9 promotes downstream RhoA-dependent signaling in a Gi protein-dependent manner. CONCLUSION: Altogether, our study highlights a novel signaling modality that may offer a new approach to the promotion, or preservation, of cardiac contractility during HF via the allosteric regulation of ß2AR to promote Gi protein/ßarr-dependent activation of RhoA/ROCK/PKD signaling.

Chewing Behavior Attenuates Lung-Metastasis-Promoting Effects of Chronic Stress in Breast-Cancer Lung-Metastasis Model Mice.

We assessed the effects of chewing behavior on the lung-metastasis-promoting impact of chronic psychological-stress in mice. Human breast-cancer cells (MDA-MB-231) were injected into the tail vein of female nude mice. Mice were randomly divided into stress, stress-with-chewing, and control groups. We created chronic stress by placing mice in small transparent tubes for 45 min, 3 times a day for 7 weeks. Mice in the stress-with-chewing group were allowed to chew wooden sticks during the experimental period. The histopathological examination showed that chronic psychological-stress increased lung metastasis, and chewing behavior attenuated the stress-related lung metastasis of breast-cancer cells. Chewing behavior decreased the elevated level of the serum corticosterone, normalized the increased expression of glucocorticoid, and attenuated the elevated expression of adrenergic receptors in lung tissues. We also found that chewing behavior normalized the elevated expression of inducible nitric oxide synthase, 4-hydroxynonenal, and superoxide dismutase 2 in lung tissues, induced by chronic stress. The present study demonstrated that chewing behavior could attenuate the promoting effects of chronic psychological-stress on the lung metastasis of breast-cancer cells, by regulating stress hormones and their receptors, and the downstream signaling-molecules, involving angiogenesis and oxidative stress.

[Role of ß2-Adrenergic Receptor Agonist in the Cognitive Impairment Associated with Neurodegenerative Diseases].

Studies have revealed the neuropathological mechanism of the cognitive impairment associated with neurodegenerative diseases.However,the therapies for these cognitive disorders are limited,and the prevalence of cognitive impairment is expected to increase significantly in the future,which proves the necessity of new therapeutic agents.In recent years,the pharmacological activity of ß2-adrenergic receptor(ß2-AR)has been extensively studied,which has demonstrated that ß2-AR agonist has therapeutic effects on the cognitive impairment associated with several common neurodegenerative diseases,including Alzheimer's disease,vascular dementia,Parkinson's disease with dementia,and Lewy body dementia.We reviewed the neuropathological features of cognitive impairment in several common neurodegenerative diseases and expounded the pharmacological effects of ß2-AR on related diseases.

Recognition of the ligand-induced spatiotemporal residue pair pattern of ß2-adrenergic receptors using 3-D residual networks trained by the time series of protein distance maps.

G protein-coupled receptors (GPCRs) are promising drug targets because they play a large role in physiological processes by modulating diverse signaling pathways in the human body. The GPCR-mediated signaling pathways are regulated by four types of ligands-agonists, neutral antagonists, partial agonists, and inverse agonists. Once each type of ligand is bound to the binding site, it activates, deactivates, or does not perturb signaling by shifting the conformational ensemble of GPCRs. Predicting the ligand's effect on the conformation at the binding moment could be a powerful screening tool for rational GPCR drug design. Here, we detected conformational differences by capturing the spatiotemporal residue pair pattern of the ligand-bound ß2-adrenergic receptor (ß2AR) using a 3-dimensional residual network, 3D-ResNets. The network was trained with the time series of protein distance maps extracted from hundreds of molecular dynamics (MD) simulation trajectories of ten ß2AR-ligand complexes. The MD system was constructed with a lipid bilayer embedded in an inactive ß2AR X-ray crystal structure and solvated with explicit water molecules. To train the network, three hyperparameters were tested, and it was found that the number of MD trajectories in the training set significantly affected the model's accuracy. The classification of agonists and neutral antagonists was successful, but inverse agonists were not. Between the agonists and antagonists, different residue pair patterns were spotted on the extracellular loop segment. This result demonstrates the potential application of a 3-D neural network in GPCR drug screening, as well as an analysis tool for protein functional dynamics.

Case report: Deterioration of infantile hemangioma related to oral or nebulized administration of ß2-AR agonist: Three cases reports.

Infantile hemangioma (IH) is a benign vascular tumor, characterized by a unique sequence of non-linear growth and spontaneous involution. Some hemangiomas require intensive treatment to avoid functional and aesthetic insufficiency. Although ß-adrenergic receptor (ß-AR) antagonists have been increasingly used as the first-line treatment since 2008, the IH rebound still exists with uncertain mechanism. Here, we report three cases of abrupt IH deteriorations that are mainly related to ß2-AR agonist administration. Potential IH proliferation induced by ß2-AR agonists, especially from oral or nebulized approaches, should be recognized more widely by healthcare providers. Additionally, it is necessary to carry out large sample studies to analyze the influence of ß2-AR agonist administration on the deterioration of IH.

Isoprenaline and salbutamol inhibit pyroptosis and promote mitochondrial biogenesis in arthritic chondrocytes by downregulating ß-arrestin and GRK2.

Rheumatoid arthritis and osteoarthritis overlap many molecular mechanisms of cartilage destruction. Wear and tear in cartilage is chondrocyte-mediated, where chondrocytes act both as effector and target cells. In current study, role of ß2-AR was studied in chondrocytes both in vitro and in vivo. High grade inflammation in vitro and in vivo disease models led to decline in anti-inflammatory ß2-AR signaling and use of ß2-AR agonist attenuated arthritis symptoms. Detailed analysis in chondrocytes revealed that Isoprenaline (ISO) and Salbutamol (SBT) increased cell viability and relative Bcl-2 expression, meanwhile, decreased proteins levels of TNF-α, IL-6 and IL-8 in arthritic chondrocytes when compared with control, respectively. SBT preserved physiological concentration of antioxidant enzymes (CAT, POD, SOD and GSH) in cartilage homogenates and ISO inhibited IL-1ß-mediated genotoxicity in arthritic chondrocytes. Moreover, ß2-AR agonist increased mitochondrial biogenesis and proteoglycan biosynthesis by upregulating the gene expression of PGC1-α, NRF2 and COL2A1, Acan, respectively. ISO and SBT inhibited extracellular matrix (ECM) degradation by downregulating the gene expression of MMP1, MMP3, MMP9 and ADAMTS5 in vitro and in vivo study. In mechanism, ß2-AR agonists decreased ß-arrestin and GRK2 pathway, and as a result mice receiving SBT did not exhibit severe disease. Hence our data suggest ß2-AR agonist administered at disease onset can inhibit receptor internalization by downregulating the expression of ß-arrestin and GRK2 in chondrocytes.