β-Arrestin 2 mediates arginine vasopressin-induced IL-6 induction via the ERK1/2-NF-κB signal pathway in murine hearts

Lingguizhugan Decoction improves chronic heart failure by synergistically modulating ?1-AR/Gs/GRKs/?-arrestin signaling bias

Lingguizhugan Decoction (LGZG) demonstrates significant efficacy in treating various cardiovascular diseases clinically, yet its precise mechanism of action remains elusive. This study aimed to elucidate the potential mechanisms and effects of LGZG on isoproterenol (ISO) continuous stimulation-induced chronic heart failure (CHF) in mice, providing direct experimental evidence for further clinical applications. In vivo, continuous ISO infusion was administered to mice, and ventricular myocytes were utilized to explore LGZG?s potential mechanism of action on the ?1-adrenergic receptor (?1-AR)/Gs/G protein-coupled receptor kinases (GRKs)/?-arrestin signaling deflection system in the heart. The findings reveal that LGZG significantly reduced the messenger ribonucleic acid (mRNA) expression of hypertrophy-related biomarkers [atrial natriuretic peptide (ANP) and B-type natriuretic peptide (BNP)] and improved cardiac remodeling and left ventricular diastolic function in mice with ISO-induced CHF. Furthermore, LGZG inhibited the overactivation of Gs/cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) signaling and downregulated the downstream transcriptional activity of cAMP-response element binding protein (CREB) and the expression of the coactivator CBP/P300. Notably, LGZG downregulated the expression of ?-arrestin1 and GRK 2/3/5 while upregulating the expression of ?1-AR and ?-arrestin2. These results suggest that LGZG inhibits Gs/cAMP/PKA signaling and ?-arrestin/GRK-mediated desensitization and internalization of ?1-AR, potentially exerting cardioprotective effects through the synergistic regulation of the ?1-AR/Gs/GRKs/?-arrestin signaling deflection system via multiple pathways.

Copeptin associates with major adverse cardiovascular events in patients on maintenance hemodialysis

BACKGROUND

End-stage renal disease (ESRD) necessitating hemodialysis pose substantial cardiovascular risks, with cardiovascular disease (CVD) as a leading cause of mortality. Biomarkers like copeptin have emerged as potential indicators of cardiovascular stress and prognosis in CKD populations.

OBJECTIVE

This study aimed to assess the prognostic value of copeptin in predicting major adverse cardiovascular events (MACEs) among hemodialysis patients, alongside traditional cardiac biomarkers.

METHODS

ESRD patients undergoing maintenance hemodialysis were enrolled. Copeptin levels were measured, and patients were followed for MACEs, defined as cardiovascular deaths, myocardial infarction, stroke, or heart failure-related hospitalizations. Cox proportional-hazards models were used to evaluate the association between copeptin and outcomes, adjusting for relevant covariates.

RESULTS

Among 351 patients followed for a median of 22.7 months, elevated copeptin levels were significantly associated with an increased risk of MACEs (HR 1.519, 95 % CI 1.140 to 2.023; p = 0.00425). Copeptin demonstrated predictive capability across multiple statistical tests (Log-rank p = 0.024; Gehan p < 0.001; Tarone-Ware p < 0.001; Peto-Peto p = 0.027), although significance was attenuated in pairwise comparisons post-adjustment for multiple testing. Combining copeptin with NT-proBNP or hs-cTnT further enhanced risk stratification for MACEs.

CONCLUSION

Elevated copeptin levels independently predict adverse cardiovascular outcomes in hemodialysis patients. Integrating copeptin with traditional cardiac biomarkers may refine risk stratification and guide personalized therapeutic strategies in this high-risk population.

The development of murine bone marrow-derived mast cells expressing functional human MRGPRX2 for ex vivo and in vivo studies

Introduction

A subtype of human mast cells (MCs) found in the skin and to a lesser extent in the lung and gut express a novel G protein-coupled receptor (GPCR) known as Mas-related GPCR-X2 (MRGPRX2, mouse counterpart MrgprB2). In addition to drug-induced pseudoallergy and cutaneous disorders, MrgprB2 contributes to ulcerative colitis, IgE-mediated lung inflammation and systemic anaphylaxis. Interestingly, most agonists activate MRGPRX2 with higher potency than MrgprB2. In this study, we sought to replace mouse MrgprB2 with human MRGPRX2 and to study receptor function ex vivo and in vivo.

Methods

MrgprB2-/- bone marrow (BM) cells were transduced with retrovirus encoding MRGPRX2 and differentiated into BMMCs (MRGRPX2-BMMCs) ex vivo. Cell surface MRGPRX2 expression was determined by flow cytometry. Effects of substance P (SP) and LL-37 on Ca2+ mobilization, degranulation and TNF-α generation were determined. MRGPRX2-BMMCs were engrafted intraperitoneally into MC-deficient Wsh/Wsh mice. After 6-8 weeks, immunofluorescence staining was performed on peritoneal lavage cells (PLCs), and sections of small intestine and colon with anti c-Kit and anti-MRGPRX2 antibodies. SP-induced degranulation in PLCs obtained from engrafted mice was determined.

Results

MRGPRX2-BMMCs expressed cell surface MRGPRX2 and responded to both SP and LL-37 for Ca2+ mobilization, degranulation and TNF-α generation. Furthermore, Wsh/Wsh mice engrafted with MRGPRX2-BMMCs expressed the receptor in peritoneal, intestinal and colonic MCs. In addition, PLCs from engrafted mice responded to SP for degranulation.

Conclusion

Replacing mouse MrgprB2 with functional human MRGPRX2 in primary BMMCs and their engraftment in MC-deficient mice demonstrated the expression of this receptor in different tissues, which provides unique opportunities to study receptor signaling ex vivo and disease phenotype in vivo.

Immune-regulating effect of oxytocin and its association with the hypothalamic-pituitary axes

Oxytocin can regulate immunological activity directly or indirectly; however, immunological functions and mechanisms of oxytocin actions under chronic stress like cesarean delivery (CD) are poorly understood. Our study found that abnormal oxytocin production and secretion in CD rats caused atrophy of thymic tissues. Neurotoxin kainic acid microinjected into the dorsolateral supraoptic nucleus in male rats selectively reduced hypothalamic oxytocin levels, increased corticotrophin-releasing hormone and plasma interleukin-1β while reducing plasma oxytocin, thyroxine and testosterone levels and causing atrophy of immune tissues. Thus, plasma oxytocin is essential for immunological homeostasis, which involves oxytocin facilitation of thyroid hormone and sex steroid secretion.

Insight into the regulatory mechanism of β-arrestin2 and its emerging role in diseases

β-arrestin2, a member of the arrestin family, mediates the desensitization and internalization of most G protein-coupled receptors (GPCRs) and functions as a scaffold protein in signalling pathways. Previous studies have demonstrated that β-arrestin2 expression is dysregulated in malignant tumours, fibrotic diseases, cardiovascular diseases and metabolic diseases, suggesting its pathological roles. Transcription and post-transcriptional modifications can affect the expression of β-arrestin2. Furthermore, post-translational modifications, such as phosphorylation, ubiquitination, SUMOylation and S-nitrosylation affect the cellular localization of β-arrestin2 and its interaction with downstream signalling molecules, which further regulate the activity of β-arrestin2. This review summarizes the structure and function of β-arrestin2 and reveals the mechanisms involved in the regulation of β-arrestin2 at multiple levels. Additionally, recent studies on the role of β-arrestin2 in some major diseases and its therapeutic prospects have been discussed to provide a reference for the development of drugs targeting β-arrestin2.

Loss of β-arrestin2 aggravated condylar cartilage degeneration at the early stage of temporomandibular joint osteoarthritis

OBJECTIVE

Temporomandibular joint osteoarthritis (TMJOA) is a chronic degenerative joint disorder characterized by extracellular matrix degeneration and inflammatory response of condylar cartilage. β-arrestin2 is an important regulator of inflammation response, while its role in TMJOA remains unknown. The objective of this study was to investigate the role of β-arrestin2 in the development of TMJOA at the early stage and the underlying mechanism.

METHODS

A unilateral anterior crossbite (UAC) model was established on eight-week-old wild-type (WT) and β-arrestin2 deficiency mice to simulate the progression of TMJOA. Hematoxylin-eosin (HE) staining and microcomputed tomography (micro-CT) analysis were used for histological and radiographic assessment. Immunohistochemistry was performed to detect the expression of inflammatory and degradative cytokines, as well as autophagy related factors. Terminal-deoxynucleotidyl transferase mediated nick end labeling (TUNEL) assay was carried out to assess chondrocyte apoptosis.

RESULTS

The loss of β-arrestin2 aggravated cartilage degeneration and subchondral bone destruction in the model of TMJOA at the early stage. Furthermore, in UAC groups, the expressions of degradative (Col-X) and inflammatory (TNF-α and IL-1β) factors in condylar cartilage were increased in β-arrestin2 null mice compared with WT mice. Moreover, the loss of β-arrestin2 promoted apoptosis and autophagic process of chondrocytes at the early stage of TMJOA.

CONCLUSION

In conclusion, we demonstrated for the first time that β-arrestin2 plays a protective role in the development of TMJOA at the early stage, probably by inhibiting apoptosis and autophagic process of chondrocytes. Therefore, β-arrestin2 might be a potential therapeutic target for TMJOA, providing a new insight for the treatment of TMJOA at the early stage.

The Role of Arginine-Vasopressin in Stroke and the Potential Use of Arginine-Vasopressin Type 1 Receptor Antagonists in Stroke Therapy: A Narrative Review

Stroke is a life-threatening condition in which accurate diagnoses and timely treatment are critical for successful neurological recovery. The current acute treatment strategies, particularly non-invasive interventions, are limited, thus urging the need for novel therapeutical targets. Arginine vasopressin (AVP) receptor antagonists are emerging as potential targets to treat edema formation and subsequent elevation in intracranial pressure, both significant causes of mortality in acute stroke. Here, we summarize the current knowledge on the mechanisms leading to AVP hyperexcretion in acute stroke and the subsequent secondary neuropathological responses. Furthermore, we discuss the work supporting the predictive value of measuring copeptin, a surrogate marker of AVP in stroke patients, followed by a review of the experimental evidence suggesting AVP receptor antagonists in stroke therapy. As we highlight throughout the narrative, critical gaps in the literature exist and indicate the need for further research to understand better AVP mechanisms in stroke. Likewise, there are advantages and limitations in using copeptin as a prognostic tool, and the translation of findings from experimental animal models to clinical settings has its challenges. Still, monitoring AVP levels and using AVP receptor antagonists as an add-on therapeutic intervention are potential promises in clinical applications to alleviate stroke neurological consequences.

The Scientific Rationale for the Introduction of Renalase in the Concept of Cardiac Fibrosis

Cardiac fibrosis represents a redundant accumulation of extracellular matrix proteins, resulting from a cascade of pathophysiological events involved in an ineffective healing response, that eventually leads to heart failure. The pathophysiology of cardiac fibrosis involves various cellular effectors (neutrophils, macrophages, cardiomyocytes, fibroblasts), up-regulation of profibrotic mediators (cytokines, chemokines, and growth factors), and processes where epithelial and endothelial cells undergo mesenchymal transition. Activated fibroblasts and myofibroblasts are the central cellular effectors in cardiac fibrosis, serving as the main source of matrix proteins. The most effective anti-fibrotic strategy will have to incorporate the specific targeting of the diverse cells, pathways, and their cross-talk in the pathogenesis of cardiac fibroproliferation. Additionally, renalase, a novel protein secreted by the kidneys, is identified. Evidence demonstrates its cytoprotective properties, establishing it as a survival element in various organ injuries (heart, kidney, liver, intestines), and as a significant anti-fibrotic factor, owing to its, in vitro and in vivo demonstrated pleiotropy to alleviate inflammation, oxidative stress, apoptosis, necrosis, and fibrotic responses. Effective anti-fibrotic therapy may seek to exploit renalase’s compound effects such as: lessening of the inflammatory cell infiltrate (neutrophils and macrophages), and macrophage polarization (M1 to M2), a decrease in the proinflammatory cytokines/chemokines/reactive species/growth factor release (TNF-α, IL-6, MCP-1, MIP-2, ROS, TGF-β1), an increase in anti-apoptotic factors (Bcl2), and prevention of caspase activation, inflammasome silencing, sirtuins (1 and 3) activation, and mitochondrial protection, suppression of epithelial to mesenchymal transition, a decrease in the pro-fibrotic markers expression (’α-SMA, collagen I, and III, TIMP-1, and fibronectin), and interference with MAPKs signaling network, most likely as a coordinator of pro-fibrotic signals. This review provides the scientific rationale for renalase’s scrutiny regarding cardiac fibrosis, and there is great anticipation that these newly identified pathways are set to progress one step further. Although substantial progress has been made, indicating renalase’s therapeutic promise, more profound experimental work is required to resolve the accurate underlying mechanisms of renalase, concerning cardiac fibrosis, before any potential translation to clinical investigation.

Selective forces on the maintenance of outcrossing in an almost exclusively cleistogamous violet species

PREMISE

Cleistogamous species constitute interesting study systems to resolve the longstanding question of how outcrossing is maintained given that seed production is ensured through selfing. In this work, we investigate the selective forces that allow the persistence of producing self-pollinated cleistogamous (CL) and chasmogamous (CH) flowers in Viola jaubertiana Marès & Vigin.

METHODS

We monitored three populations at different elevation for two years, and studied the flowering phenology and the relative contribution of each flower morph to parental fitness. We tested whether allocation to CH and CL flowers differed across populations and if it covaried with herbivory and water stress conditions. We also performed hand-pollination and bagging experiments in CH flowers to estimate inbreeding depression and heterosis.

RESULTS

The CH flowers open in winter under unfavorable conditions for pollination, show high pollen limitation and no-delayed selfing, and thus produce a low amount of seeds. Conversely, CL flowers appear in early spring, are physiologically cheaper to produce (i.e., dry weight is 3.4 times lower than that of CH flowers), and yield approximately 100 times more seeds than CH flowers. The CH flowers were favored under water stress and low herbivory. Crosses between populations showed up to 25% greater fitness than those within populations.

CONCLUSIONS

Despite the great pollen limitation in CH flowers, we suggest that the interaction among different environmental determinants and heterosis are probably sufficient forces to maintain chasmogamy in this long-lived species, reducing deleterious fixed mutations in the selfed lines.

β-arrestin-2 alleviates rheumatoid arthritis injury by suppressing NLRP3 inflammasome activation and NF- κB pathway in macrophages

Rheumatoid arthritis (RA) is a chronic inflammatory joint disorder that inflicts damage to the joints of the hands and wrist. The aim of this study was to investigate the protective effect of β-Arrestin-2 (βArr2) on RA in vivo and in vitro. The βArr2 adenovirus (βArr2-Ad) or the control (Con-Ad) was injected into the ankle joint cavity of collagen-induced arthritis (CIA) mice. According to the results, an improvement was shown in the symptoms and pathological injury of RA after an upregulation of βArr2. Correspondingly, the inflammatory response was attenuated, as evidenced by the decreased serum pro-inflammatory cytokines levels and NF-κB pathway-related proteins. Nucleotide-binding domain leucine-rich repeat and pyrin domain containing receptor 3 (NLRP3) inflammasome activation was inhibited in CIA mice treated with βArr2-Ad injection, as reflected by the diminished IL-18 level and declined protein levels of inflammasome components in the ankle joint. Likewise, the anti-inflammatory effect of macrophages was also validated by in vitro experiments. In summary, βArr2 effectively ameliorates ankle inflammation in CIA mice via NF-κB/NLRP3 inflammasome, providing theoretical and clinical basis for RA therapy.

Arginine vasopressin and pathophysiology of COVID-19: An innovative perspective

In Covid-19, systemic disturbances may progress due to development of cytokine storm and dysregulation of and plasma osmolarility due to high release of pro-inflammatory cytokines and neuro-hormonal disorders. Arginine vasopressin (AVP) which is involve in the regulation of body osmotic system, body water content, blood pressure and plasma volume, that are highly disturbed in Covid-19 and linked with poor clinical outcomes. Therefore, this present study aimed to find the potential association between AVP serum level and inflammatory disorders in Covid-19. It has been observed by different recent studies that physiological response due to fever, pain, hypovolemia, dehydration, and psychological stress is characterized by activation release of AVP to counter-balance high blood viscosity in Covid-19 patients. In addition, activated immune cells mainly T and B lymphocytes and released pro-inflammatory cytokines stimulate discharge of stored AVP from immune cells, which in a vicious cycle trigger release of pro-inflammatory cytokines. Vasopressin receptor antagonists have antiviral and anti-inflammatory effects that may inhibit AVP-induced hyponatremia and release of pro-inflammatory cytokines in Covid-19. In conclusion, release of AVP from hypothalamus is augmented in Covid-19 due to stress, high pro-inflammatory cytokines, high circulating AngII and inhibition of GABAergic neurons. In turn, high AVP level leads to induction of hyponatremia, inflammatory disorders, and development of complications in Covid-19 by activation of NF-κB and NLRP3 inflammasome with release of pro-inflammatory cytokines. Therefore, AVP antagonists might be novel potential therapeutic modality in treating Covid-19 through mitigation of AVP-mediated inflammatory disorders and hyponatremia.

β-Arrestin 2 Regulates Inflammatory Responses against Mycobacterium tuberculosis Infection through ERK1/2 Signaling

Mycobacterium tuberculosis, the pathogen that causes tuberculosis, exhibits complex host-pathogen interactions. Pattern recognition receptors and their downstream signaling pathways play crucial roles in determining the outcome of infection. In particular, the scaffold protein β-arrestin 2 mediates downstream signaling of G protein-coupled receptors. However, the role of β-arrestin 2 in conferring immunity against M. tuberculosis has not yet been explored. We found that β-arrestin 2 was upregulated in the lesioned regions of lung tissues in patients with tuberculosis. M. tuberculosis infection upregulated β-arrestin 2 expression in human macrophages, and silencing of β-arrestin 2 significantly enhanced bactericidal activity by enhancing the expression of proinflammatory cytokines such as TNF-α. β-Arrestin 2 was shown to inhibit the activation of the TLR2/ERK1/2 pathway and its transcriptional regulation activity upon M. tuberculosis infection. Furthermore, β-arrestin 2 transcriptionally regulates TNF-α by binding to CREB1. These observations revealed that the upregulation of β-arrestin 2 is critical for M. tuberculosis to escape immune surveillance through an unknown mechanism. Our research offers a novel interference modality to enhance the immune response against tuberculosis by targeting β-arrestin 2 to modulate the TLR2-β-arrestin 2-ERK1/2-CREB1-TNF-α regulatory axis.

Deficiency of β-arrestin2 exacerbates inflammatory arthritis by facilitating plasma cell formation

β-arrestin2 (β-arr2) is, a key protein that mediates desensitization and internalization of G protein-coupled receptors and participates in inflammatory and immune responses. Deficiency of β-arr2 has been found to exacerbate collagen antibody-induced arthritis (CAIA) through unclear mechanisms. In this study we tried to elucidate the molecular mechanisms underlying β-arr2 depletion-induced exacerbation of CAIA. CAIA was induced in β-arr2-/- and wild-type (WT) mice by injection of collagen antibodies and LPS. The mice were sacrificed on d 13 after the injection, spleen, thymus and left ankle joints were collected for analysis. Arthritis index (AI) was evaluated every day or every 2 days. We showed that β-arr2-/- mice with CAIA had a further increase in the percentage of plasma cells in spleen as compared with WT mice with CAIA, which was in accordance with elevated serum IgG1 and IgG2A expression and aggravating clinical performances, pathologic changes in joints and spleen, joint effusion, and joint blood flow. Both LPS stimulation of isolated B lymphocytes in vitro and TNP-LPS challenge in vivo led to significantly higher plasma cell formation and antibodies production in β-arr2-/- mice as compared with WT mice. LPS treatment induced membrane distribution of toll-like receptor 4 (TLR4) on B lymphocytes, accordingly promoted the nuclear translocation of NF-κB and the transcription of Blimp1. Immunofluorescence analysis confirmed that more TLR4 colocalized with β-arr2 in B lymphocytes in response to LPS stimulation. Depletion of β-arr2 restrained TLR4 on B lymphocyte membrane after LPS treatment and further enhanced downstream NF-κB signaling leading to additional increment in plasma cell formation. In summary, β-arr2 depletion exacerbates CAIA and further increases plasma cell differentiation and antibody production through inhibiting TLR4 endocytosis and aggravating NF-κB signaling.

Loss of Camk2n1 aggravates cardiac remodeling and malignant ventricular arrhythmia after myocardial infarction in mice via NLRP3 inflammasome activation

AIMS

Inflammation response and subsequent ventricular remodeling are critically involved in the development of ventricular arrhythmia post myocardial infarction (MI). However, as the vital endogenous inhibitor of calcium/calmodulin-dependent protein kinase II (CaMKII), the effects of CaMKII inhibitor 1 (Camk2n1) on the process of arrhythmia substrate generation following MI remains unclear. In this study, we investigated the role of Camk2n1 in ventricular arrhythmia post-MI and the underlying mechanisms.

METHODS AND RESULTS

Camk2n1 was mainly expressed in cardiomyocytes and inhibited the phosphorylation of CaMKIIδ in the infarcted border zone. Compared to wild type (WT) littermates mice, Camk2n1 knockout mice (Camk2n1^-/-) manifested exacerbated cardiac dysfunction, larger fibrosis area, higher incidence of premature ventricular contractions (PVCs) and higher vulnerability to ventricular tachycardia (VT) or ventricular fibrillation (VF) after MI. The results of RNA sequencing (RNA-seq) identified that excessive activation of NLRP3 inflammasome was responsible for aggravated inflammation response which led to adverse cardiac remodeling in Camk2n1^-/- mice subjected to MI. More importantly, both in vivo and in vitro experiments verified that aggravated NLRP3 inflammasome activation occurred via CaMKIIδ-p38/JNK pathway in Camk2n1^-/- mice.

CONCLUSIONS

Collectively, our results highlight the importance of Camk2n1 in alleviating ventricular remodeling and malignant ventricular arrhythmia post-MI by reducing cardiomyocytes inflammation activation via CaMKIIδ-p38/JNK-NLRP3 inflammasome pathway, targeting Camk2n1 might serve as a novel therapeutic strategy after MI.

The role and mechanism of β-arrestin2 in signal transduction

β-arrestin2 is a ubiquitously expressed scaffold protein localized on the cytoplasm and plasma membrane. It was originally found to bind to GPCRs, uncoupling G proteins and receptors' binding and inhibiting the signal transduction of the GPCRs. Further investigations have revealed that β-arrestin2 not only mediates the desensitization of GPCRs but also serves as a multifunctional scaffold to mediate receptor internalization, kinase activation, and regulation of various signaling pathways, such as TLR4/NF-κB, MAPK, Wnt, TGF-β, and AMPK/mTOR pathways. β-arrestin2 regulates cell invasion, migration, autophagy, angiogenesis, and anti-inflammatory effects by regulating various signaling pathways, which play a vital role in many physiological and pathological processes. This paper reviews the structure and function of β-arrestin2, the regulation of β-arrestin2 based signaling pathways. The role and mechanism of β-arrestin2 signaling have been delineated in sufficient detail. The prospect of regulating the expression and activity of β-arrestin2 in multisystem diseases holds substantial therapeutic promise.