Vasopressin V1A receptor mediates cell proliferation through GRK2-EGFR-ERK1/2 pathway in A7r5 cells

Computer vision analysis of mother-infant interaction identified efficient pup retrieval in V1b receptor knockout mice

Close contact between lactating rodent mothers and their infants is essential for effective nursing. Whether the mother's effort to retrieve the infants to their nest requires the vasopressin-signaling via V1b receptor has not been fully defined. To address this question, V1b receptor knockout (V1bKO) and control mice were analyzed in pup retrieval test. Because an exploring mother in a new test cage randomly accessed to multiple infants in changing backgrounds over time, a computer vision-based deep learning analysis was applied to continuously calculate the distances between the mother and the infants as a parameter of their relationship. In an open-field, a virgin female V1bKO mice entered fewer times into the center area and moved shorter distances than wild-type (WT). While this behavioral pattern persisted in V1bKO mother, the pup retrieval test demonstrated that total distances between a V1bKO mother and infants came closer in a shorter time than with a WT mother. Moreover, in the medial preoptic area, parts of the V1b receptor transcripts were detected in galanin- and c-fos-positive neurons following maternal stimulation by infants. This research highlights the effectiveness of deep learning analysis in evaluating the mother-infant relationship and the critical role of V1b receptor in pup retrieval during the early lactation phase.

Gender differences in GRK2 in cardiovascular diseases and its interactions with estrogen

G protein-coupled receptor kinase 2 (GRK2) is a multifunctional protein involved in regulating G protein-coupled receptor (GPCR) and non-GPCR signaling in the body. In the cardiovascular system, increased expression of GRK2 has been implicated in the occurrence and development of several cardiovascular diseases (CVDs). Recent studies have found gender differences in GRK2 in the cardiovascular system under physiological and pathological conditions, where GRK2's expression and activity are increased in males than in females. The incidence of CVDs in premenopausal women is lower than in men of the same age, which is related to estrogen levels. Given the shared location of GRK2 and estrogen receptors, estrogen may interact with GRK2 by modulating vital molecules such as calmodulin (CaM), caveolin, RhoA, nitrate oxide (NO), and mouse double minute 2 homolog (Mdm2), via signaling pathways mediated by estrogen's genomic (ERα and ERβ), and non-genomic (GPER) receptors, conferring cardiovascular protection in females. Highlighting the gender differences in GRK2 and understanding its interaction with estrogen in the cardiovascular system is pertinent in treating gender-related CVDs. As a result, this article explores the gender differences of GRK2 in the cardiovascular system and its relationship with estrogen during disease conditions. Estrogen's protective and therapeutic effects and its mechanism on GRK2-related cardiovascular diseases have also been discussed.

Functional cooperation between IKCa and TRPC1 channels regulates serum-induced vascular smooth muscle cell proliferation via mediating Ca2+ influx and ERK1/2 activation

The increased proliferation of vascular smooth muscle cells (VSMCs) contributes to the pathogenesis of vascular diseases. The intermediate conductance calcium-activated potassium (IK_Ca ) channel plays a critical role in VSMC proliferation by raising the intracellular calcium concentration ([Ca²⁺ ]_i ), but the underlying mechanism is still not unclear. Here we investigated the cooperation between IK_Ca and transient receptor potential canonical 1 (TRPC1) channels in mediating extracellular Ca²⁺ entry, which in turn activates downstream Ca²⁺ signalling in the regulation of VSMC proliferation using serum-induced cell proliferation model. Serum-induced cell proliferation was accompanied with up-regulation of IK_Ca expression and an increase in [Ca²⁺ ]_i . Serum-induced cell proliferation and increase in [Ca²⁺ ]_i were suppressed by IK_Ca inhibition with TRAM-34 or IK_Ca knockdown. Serum-induced cell proliferation was strongly reduced by the removal of extracellular Ca²⁺ with EGTA or intracellular Ca²⁺ with BAPTA-AM and, additionally, by TRPC1 knockdown. Moreover, the increase in [Ca²⁺ ]_i induced by serum or by IK_Ca activation with 1-EBIO was attenuated by TRPC1 knockdown. Finally, serum induced ERK1/2 activation, which was attenuated by treatment with TRAM-34 or BAPTA-AM, as well as TRPC1 knockdown. Consistently, serum-induced cell proliferation was suppressed by ERK1/2 inhibition with PD98059. Taken together, these results suggest that the IK_Ca and TRPC1 channels cooperate in mediating Ca²⁺ influx that activates the ERK1/2 pathway to promote cell proliferation, thus providing new mechanistic insights into VSMC proliferation.

G Protein-Coupled Receptor Kinase 2 as Novel Therapeutic Target in Fibrotic Diseases

G protein-coupled receptor kinase 2 (GRK2), an important subtype of GRKs, specifically phosphorylates agonist-activated G protein-coupled receptors (GPCRs). Besides, current research confirms that it participates in multiple regulation of diverse cells via a non-phosphorylated pathway, including interacting with various non-receptor substrates and binding partners. Fibrosis is a common pathophysiological phenomenon in the repair process of many tissues due to various pathogenic factors such as inflammation, injury, drugs, etc. The characteristics of fibrosis are the activation of fibroblasts leading to myofibroblast proliferation and differentiation, subsequent aggerate excessive deposition of extracellular matrix (ECM). Then, a positive feedback loop is occurred between tissue stiffness caused by ECM and fibroblasts, ultimately resulting in distortion of organ architecture and function. At present, GRK2, which has been described as a multifunctional protein, regulates copious signaling pathways under pathophysiological conditions correlated with fibrotic diseases. Along with GRK2-mediated regulation, there are diverse effects on the growth and apoptosis of different cells, inflammatory response and deposition of ECM, which are essential in organ fibrosis progression. This review is to highlight the relationship between GRK2 and fibrotic diseases based on recent research. It is becoming more convincing that GRK2 could be considered as a potential therapeutic target in many fibrotic diseases.

Mechanical and chemical cues synergistically promote human venous smooth muscle cell osteogenesis through integrin β1-ERK1/2 signaling: A cell model of hemodialysis fistula calcification

Arteriovenous fistula (AVF) is the vascular access of choice for renal replacement therapy. However, AVF is susceptible to calcification with a high prevalence of 40%-65% in chronic hemodialysis patients. Repeated needle puncture for hemodialysis cannulation results in intimal denudation of AVF. We hypothesized that exposure to blood shear stress in the medial layer promotes venous smooth muscle cell (SMC) osteogenesis. While previous studies of shear stress focused on arterial-type SMCs, SMCs isolated from the vein had not been investigated. This study established a venous cell model of AVF using the fluid shear device, combined with a high phosphate medium to mimic the uremic milieu. Osteogenic gene expression of venous SMCs upon mechanical and chemical cues was analyzed in addition to the activated cell signaling pathways. Our findings indicated that upon shear stress and high phosphate environment, mechanical stimulation (shear stress) had an additive effect in up-regulation of an early osteogenic marker, Runx2. We further identified that the integrin β1-ERK1/2 signaling pathway was responsible for the molecular basis of venous SMC osteogenesis upon shear stress exposure. Mitochondrial biogenesis also took part in the early stage of this venopathy pathogenesis, evident by the up-regulated mitochondrial transcription factor A and mitochondrial DNA polymerase γ in venous SMCs. In conclusion, synergistic effects of fluid shear stress and high phosphate induce venous SMC osteogenesis via the ERK1/2 pathway through activating the mechanosensing integrin β1 signaling. The present study identified a promising druggable target for reducing AVF calcification, which deserves further in vivo investigations.

Arginine vasopressin receptor 1a is a therapeutic target for castration-resistant prostate cancer

Castration-resistant prostate cancer (CRPC) recurs after androgen deprivation therapy (ADT) and is incurable. Reactivation of androgen receptor (AR) signaling in the low androgen environment of ADT drives CRPC. This AR activity occurs through a variety of mechanisms, including up-regulation of AR coactivators such as VAV3 and expression of constitutively active AR variants such as the clinically relevant AR-V7. AR-V7 lacks a ligand-binding domain and is linked to poor prognosis. We previously showed that VAV3 enhances AR-V7 activity to drive CRPC progression. Gene expression profiling after depletion of either VAV3 or AR-V7 in CRPC cells revealed arginine vasopressin receptor 1a (AVPR1A) as the most commonly down-regulated gene, indicating that this G protein-coupled receptor may be critical for CRPC. Analysis of publicly available human PC datasets showed that AVPR1A has a higher copy number and increased amounts of mRNA in advanced PC. Depletion of AVPR1A in CRPC cells resulted in decreased cell proliferation and reduced cyclin A. In contrast, androgen-dependent PC, AR-negative PC, or nontumorigenic prostate epithelial cells, which have undetectable AVPR1A mRNA, were minimally affected by AVPR1A depletion. Ectopic expression of AVPR1A in androgen-dependent PC cells conferred castration resistance in vitro and in vivo. Furthermore, treatment of CRPC cells with the AVPR1A ligand, arginine vasopressin (AVP), activated ERK and CREB, known promoters of PC progression. A clinically safe and selective AVPR1A antagonist, relcovaptan, prevented CRPC emergence and decreased CRPC orthotopic and bone metastatic growth in mouse models. Based on these preclinical findings, repurposing AVPR1A antagonists is a promising therapeutic approach for CRPC.

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

Evidence to date suggests that β-arrestins act beyond their role as adapter proteins. Arginine vasopressin (AVP) may be a factor in inflammation and fibrosis in the pathogenesis of heart failure. In the present study we investigated the effect of AVP on inflammatory cytokine IL-6 production in murine hearts and the impact of β-arrestin 2-dependent signaling on AVP-induced IL-6 production. We found that administration of AVP (0.5 U/kg, iv) markedly increased the levels of IL-6 mRNA in rat hearts with the maximum level occurred at 6 h. In β-arrestin 2 KO mouse hearts, deletion of β-arrestin 2 decreased AVP-induced IL-6 mRNA expression. We then performed in vitro experiments in adult rat cardiac fibroblasts (ARCFs). We found that AVP (10-9-10-6 M) dose-dependently increased the expression of IL-6 mRNA and protein, activation of NF-κB signaling and ERK1/2 phosphorylation, whereas knockdown of β-arrestin 2 blocked AVP-induced IL-6 increase, NF-κB activation and ERK1/2 phosphorylation. Pharmacological blockade of ERK1/2 using PD98059 diminished AVP-induced NF-κB activation and IL-6 production. The selective V1A receptor antagonist SR49059 effectively blocked AVP-induced NF-κB phosphorylation and activation as well as IL-6 expression in ARCFs. In AVP-treated mice, pre-injection of SR49059 (2 mg/kg, iv) abolished AVP-induced NF-κB activation and IL-6 production in hearts. The above results suggest that AVP induces IL-6 induction in murine hearts via the V1A receptor-mediated β-arrestin2/ERK1/2/NF-κB pathway, thus reveal a novel mechanism of myocardial inflammation in heart failure involving the V1A/β-arrestin 2/ERK1/2/NF-κB signaling pathway.

Vasopressin inactivation: Role of insulin-regulated aminopeptidase

The physiological importance of vasopressin inactivation has long been appreciated, but the mechanisms and potential pathophysiologic roles of this process remain active subjects of research. Human Placental Leucine Aminopeptidase (P-LAP, encoded by the LNPEP gene) is an important determinant of vasopressinase activity during pregnancy and is associated with gestational diabetes insipidus and preeclampsia. Insulin-Regulated Aminopeptidase (IRAP), the rodent homologue of P-LAP, is coregulated with the insulin-responsive glucose transporter, GLUT4, in adipose and muscle cells. Recently, the Tether containing a UBX domain for GLUT4 (TUG) protein was shown to mediate the coordinated regulation of water and glucose homeostasis. TUG sequesters IRAP and GLUT4 intracellularly in the absence of insulin. Insulin and other stimuli cause the proteolytic cleavage of TUG to mobilize these proteins to the cell surface, where IRAP acts to terminate the activity of circulating vasopressin. Intriguingly, genetic variation in LNPEP is associated with the vasopressin response and mortality during sepsis, and increased copeptin, a marker of vasopressin secretion, is associated with cardiovascular and metabolic disease. We propose that in the setting of insulin resistance in muscle, increased cell-surface IRAP and accelerated vasopressin degradation cause a compensatory increase in vasopressin secretion. The increased vasopressin concentrations present at the kidneys then contribute to hypertension in the metabolic syndrome. Further analyses of metabolism and of vasopressin and copeptin may yield novel insights into a unified pathophysiologic mechanism linking insulin resistance and hypertension, and potentially other components of the metabolic syndrome, in humans.

Exosomes derived from oviduct cells mediate the EGFR/MAPK signaling pathway in cumulus cells

Current studies indicate that application of oviduct cells (OCs) in in vitro system create microenvironment similar to the in vivo conditions by releasing multiple growth factors which has beneficial effects on the development of cumulus-oocyte complexes and embryos. In particular, recent evidence with a coculture system indicates that there is a reciprocal relationship between canine OCs and cumulus cells and that oviductal secretions can promote changes in cellular protein/gene expression. Despite the fact that OCs respond to cumulus cells, a clear understanding of the mechanism by which the components released from OCs that play a role in modulating the biological function of cumulus cells is still elusive. Therefore, we hypothesized that exosomes derived from OCs (OC-Exo), which efficiently mediate cellular communication by transferring their molecular cargo to recipient cells, could be key modulators of the cross-talk with cumulus cells. We aimed to characterize OC-Exo and decipher their physiological effects on cumulus cells via the epidermal growth factor receptor/mitogen-activated protein kinase (EGFR/MAPK) pathway, which is one of the prerequisite pathways for cell development. Exposure of OC-Exo improved physiological cumulus cell condition including cell concentration, viability, and proliferation rate could reduce the accumulation of reactive oxygen species and the apoptotic rate. Moreover, exosomes could enhance the messenger RNA transcript and protein levels related to EGFR signaling in cumulus cells. The present study provides the first evidence that OC-Exo effectively enhance the physiological condition of cumulus cells exposed to GW4869 or Gefitinib via the EGFR/MAPK signaling pathway and this could be the primary mediators of molecular interactions among cumulus cells and shedding light on the role of exosomes in cumulus cells might permit improvement of oocyte and embryo development in vitro.

GRK2 Mediates Arginine Vasopressin-Induced Interleukin-6 Production via Nuclear Factor-κB Signaling Neonatal Rat Cardiac Fibroblast

Interleukin 6 (IL-6), which is elevated in patients with congestive heart failure and acts as both a chronic marker of inflammation and an acute-phase reactant, is associated with myocardial damage. Circulating levels of arginine vasopressin (AVP) are elevated during cardiac stress and could be a factor for cardiac inflammation and fibrosis. Our previous study has shown that AVP promotes the proliferation of neonatal rat cardiac fibroblasts (NRCFs) throughV_1A vasopressin receptor-mediated G protein-coupled receptor kinase 2 (GRK2) signaling. In the present study, we investigated the impact of the GRK2-dependent signaling. Using quantitative polymerase chain reaction and enzyme-linked immunosorbent assay, we measured the levels of interleukin-6 (IL-6) mRNA and protein in NRCFs, respectively. Manipulation of GRK2 activation either pharmacologically or through overexpression of GRK2-ct was used to determine the role of GRK2 in regulating the effects of AVP on IL-6 production. Phosphorylation and activation of nuclear factor κ-B (NF-κB) evoked by AVP stimulation were measured by immunoblot and NF-kB luciferase reporter gene transfected in NRCFs, respectively. Present studies have found that: 1) AVP increased the level of IL-6 protein and mRNA in a dose- and time-dependent manner in NRCFs; 2) inhibition of GRK2 abolished the AVP-induced IL-6 production and NF-κB activation; and 3) blocking NF-κB signaling using the pharmacologic approach diminished AVP-induced IL-6 production. In summary, AVP induces IL-6 production of NRCFs by activating V_1A receptor signaling via a GRK2/NF-κB pathway. These findings provide a possible molecular mechanism for inflammation that occurs in heart failure and other types of cardiac stress.