Calcium-sensing Receptor Expression Research Articles

Calcium-sensing receptor regulates the angiogenic differentiation of LPS-treated human dental pulp cells via the phosphoinositide 3-kinase/Akt pathway invitro.

The purpose of this study was to investigate the role of calcium-sensing receptor (CaSR) in the angiogenic differentiation of lipopolysaccharide (LPS)-treated human dental pulp cells (hDPCs). The LPS-induced hDPCs were cultured in the medium with different combinations of CaSR agonist R568 and antagonist Calhex231. The cell proliferation, migration, and angiogenic capacity were measured by Cell Counting Kit-8 (CCK-8), scratch wound healing, and tube formation assays, respectively. Enzyme-linked immunosorbent assay (ELISA), quantitative real-time polymerase chain reaction (qRT-PCR), and western blot were conducted to determine the gene/protein expression of CaSR, inflammatory mediators, and angiogenic-associated markers. The activation of phosphoinositide 3-kinase (PI3K) and protein kinase B (Akt) was assessed by western blot analysis. The cell proliferation was elevated in response to R568 or Calhex231 exposure, but an enhanced cell migration was only found in cultures supplemented with Calhex231. Furthermore, R568 was found to potentiate the formation of vessel-like structure, up-regulated the protein expression of tumour necrosis factor (TNF)-α, vascular endothelial growth factor (VEGF), and stromal cell-derived factor (SDF)-1; comparable influences were also observed in R568-stimulated cells in the presence of PI3K inhibitor LY294002. In contrast, Calhex231 obviously inhibited the tube formation and VEGF protein level, whereas promoted the production of IL-6, TNF-α, and eNOS; however, in the presence of LY294002, Calhex231 showed a significant promotion on the protein expression of CaSR, VEGF, and SDF-1. In addition, R568 exhibited a promotive action on the Akt phosphorylation, which can be reversed by LY294002. Our results demonstrated that CaSR can regulate the angiogenic differentiation of LPS-treated hDPCs with an involvement of the PI3K/Akt signalling pathway.

Calcium-sensing receptor (CaSR) modulates ocular surface chloride transport and its inhibition promotes ocular surface hydration

PurposeOcular surface hydration is critical for eye health and its impairment can lead to dry eye disease. Extracellular calcium-sensing receptor (CaSR) is regulator of ion transport in epithelial cells expressing cystic fibrosis transmembrane conductance regulator (CFTR) Cl− channel. CFTR is also a major ion channel in ocular surface epithelia, however the roles of CaSR in ocular surface are not well studied. This study aims to investigate expression and functional roles of CaSR in ocular surface. MethodsCaSR immunostaining was performed in mouse and human cornea and conjunctiva. Ocular surface potential difference (OSPD) and tear fluid volume measurements were performed in mice with topically applied cinacalcet (CaSR activator) and NPS-2143 (CaSR inhibitor). ResultsCaSR is expressed in corneal and conjunctival epithelia of mice and humans. Topically administered CaSR activator cinacalcet inhibits cAMP agonist forskolin-induced Cl− secretion and CFTR activity up to 90 %. CaSR inhibitor NPS-2143 stimulates CFTR-mediated Cl− secretion in mouse ocular surface, after which cAMP agonist forskolin had minimal additional secretory effects. Single dose NPS-2143 treatment (as an eye drop) increases tear fluid volume in mice by ∼60 % compared to vehicle treatment. NPS-2143 effect on tear volume lasts at least 8 h after single dose. ConclusionsCaSR is a key regulator of ocular surface ion transport and CaSR inhibition promotes Cl− and tear secretion in the ocular surface. If they are found to be effective in in dry eye models, CaSR inhibitors (currently in clinical development) can potentially be repurposed as novel prosecretory treatments for dry eye disease.

The A986S calcium sensing receptor variant supports the adaptation of breast cancer cells to high calcium — a novel paradigm in breast cancer progression

Breast cancer and other solid tumors that metastasize to bone are frequently accompanied by a progressive increase in circulating calcium as the disease becomes more malignant. The increase in circulating calcium not only disrupts systemic calcium homeostasis but also alters the ability of cells to sense slight changes in extracellular Ca2+ via the ubiquitous calcium sensing receptor (CaSR). Of the CASR polymorphisms at rs1801725 (p.A986S), rs1801726 (p.Q1011E), and rs1042636 (p.R990G) in exon 7 of the receptor, previous studies have shown that only the A986S CaSR variant is associated with calcium in breast, prostate and skin cancers. In this study, we assessed if exon 7 inactivating A986S (AS-CaSR) and Q1011E (QE-CaSR) variants of the receptor influence the survival of breast tumor cells at higher Ca2+. We generated isogenic HEK293T and BT-549 cells expressing these CaSR variants and carried out bulk RNA sequencing of high Ca2+ adapted control and breast cancer cells. CaSR expression was detected by western blotting using anti-flag M2 (Sigma) antibody. By using phospho-ERK1/2 as the readout, the activation of AS-CaSR required higher concentrations of Ca2+ (EC50 ~5.28 mM) compared to the QE-CaSR (EC50 of ~3.81 mM) and the wild type (WT-CaSR; EC50 ~3.69 mM) receptor. When the CaSR variants transfected cells initially cultured at 7.5 mM for 6 days, and then sub-cultured in medium containing 7.5 to 20 mM Ca2+, the viability of empty vector control and WT-CaSR transfected cells strongly decreased at Ca2+ levels beyond 7.5 mM and these cells were mostly necrotic at ≥15 mM Ca2+. The QE-CaSR variant transfected cells on the other hand exhibited limited cell death beyond 10 mM Ca2+, while the surviving colonies of the AS-CaSR variant were viable at up to 15 mM Ca2+ with invasive tendencies. Analysis of differentially expressed genes in high Ca2+ adapted mesenchymal-like BT-549 and epithelial MDA-MB-468 breast cancer cells compared to MCF10A control cells revealed a small set of differentially expressed genes that were significantly associated with relapse free survival of basal-like breast cancer patients. Among these genes are ligands and negative regulators of the WNT/FZD pathway. Our data suggest that the A986S-CaSR variant with reduced sensitivity to Ca2+ supported adaptation of TNBC cells at high Ca2+, and that high Ca2+ adaptation of breast cancer cells may be mediated via a panel of high Ca2+ inducible genes with implications in bone metastasis. This study is supported by NIH SC1GM139814, T32AI007281, T32GM144927, T32HL007737; and the American Cancer Society. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Hyaluronan Fragments Induce Lung Alveolar Edema by Activating Calcium-Sensing Receptor

One of the hallmarks of lung injury is the breakdown of the cell matrix hygroscopic high molecular weight hyaluronan (HMW-HA >106 kD) into smaller fragments of low molecular weight (LMW-HA < 500 kD) which mediate the onset and progression of acute lung injury. We have found that instillation of very low dose (1μg) of LMW-HA to wt. C57/bl6 mice was suffcient to inhibit lung epithelial ions and water transport and cause lung edema assessed by measuring lungs wet/dry ratio. LMW-HA IC50 for the induction of lung edema, the inhibition of alveolar fluid clearance (AFC) and epithelial sodium channels (ENaC) in alveolar epithelial cells, AEC1 and AEC2, in-situ, in freshly cut lung slices, was 120 nM. We found the expression of calcium-sensing receptor (CaSR), a C class G-protein coupled receptor, was activated by LMW-HA. CD44 is known to be the main membrane receptor of hyaluronan expressed by most cells including lung alveolar epithelial cells, however, because it lacks the intrinsic kinase activity necessary for the transduction of extracellular signal carried by LMW-HA, we hypothesized that it cooperated with CaSR to transduce LMW-HA injurious signal and activated intracellular signaling cascades that induced lung edema by inhibiting ENaC and AFC at 24 h. These effects were prevented by NPS2143 (1 μM), a CaSR inhibitor or calcilytic, instilled 6 h post LMW-HA, and were absent in CD44 knockout mouse. The lack of an effect on W/D ratio, AFC, or ENaC in CD44−/− mouse is evidence that LMW-HA does not directly interact with CaSR, but rather activates CD44 which cooperate with CaSR to trigger intracellular signaling cascades that cause the observed effects. Four hours post mouse airway epithelial cells confluent monolayers were incubated with 1 μg LMW-HA, CaSR expression was increased 4-fold, while amiloride sensitive short-circuit current and αβγ-ENaC subunits expression, at the apical membranes, were significantly reduced. These effects were prevented when CaSR, PLC, or PKC were inhibited with 1 μM NPS2143, 10 μM U73122, or 100 μM Rottlerin, applied 4 h prior to cells incubation with 1 μg LMW-HA, respectively. Our data show that the deleterious effect of LMW-HA on ENaC are mediated by intricate interactions between CD44-LMW-HA complex with CaSR in lung alveolar epithelial cells. The use of calcilytics to decouple the molecular complex formed by CD44-LMW-HA and CaSR may prove to be effective in restoring alveolar sodium ion reabsorption required for lung edema clearance. Department of Anesthesiology and Perioperative Medicine. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Chitosan and sodium alginate nanocarrier system: Controlling the release of rapeseed-derived peptides and improving their therapeutic efficiency of anti-diabetes

Rapeseed-derived peptides (RPPs) can maintain the homeostasis of human blood glucose by inhibiting Dipeptidyl Peptidase-IV (DPP-IV) and activating the calcium-sensing receptor (CaSR). However, these peptides are susceptible to hydrolysis in the gastrointestinal tract. To enhance the therapeutic potential of these peptides, we developed a chitosan/sodium alginate-based nanocarrier to encapsulate two RPP variants, rapeseed-derived cruciferin peptide (RCPP) and rapeseed-derived napin peptide (RNPP). A convenient three-channel device was employed to prepare chitosan (CS)/sodium alginate (ALG)-RPPs nanoparticles (CS/ALG-RPPs) at a ratio of 1:3:1 for CS, ALG, and RPPs. CS/ALG-RPPs possessed optimal encapsulation efficiencies of 90.7 % (CS/ALG-RNPP) and 91.4 % (CS/ALG-RCPP), with loading capacities of 15.38 % (CS/ALG-RNPP) and 16.63 % (CS/ALG-RCPP) at the specified ratios. The electrostatic association between CS and ALG was corroborated by zeta potential and near infrared analysis. 13C NMR analysis verified successful RPPs loading, with CS/ALG-RNPP displaying superior stability. Pharmacokinetics showed that both nanoparticles were sustained release and transported irregularly (0.43 < n < 0.85). Compared with the control group, CS/ALG-RPPs exhibited significantly increased glucose tolerance, serum GLP-1 (Glucagon-like peptide 1) content, and CaSR expression which play pivotal roles in glucose homeostasis (*p < 0.05). These findings proposed that CS/ALG-RPPs hold promise in achieving sustained release within the intestinal epithelium, thereby augmenting the therapeutic efficacy of targeted peptides.

Functional analysis reveals calcium-sensing receptor gene regulating cell-cell junction in renal tubular epithelial cells.

Calcium-sensing receptor (CASR) influences the expression pattern of multiple genes in renal tubular epithelial cells. The objective of this inquiry was to explore the molecular mechanisms of CASR in renal tubular epithelial cells and nephrolithiasis. HK-2 cells were transfected with lentiviruses carrying either CASR (named CASR) or an empty vector negative control (named NC), as well as shRNA intended to target CASR (named shCASR) or its corresponding negative control (named shNC). CCK-8 assay was used to detect the effect of CASR on the proliferation of HK-2 cells. RNA-Sequencing was applied to explore potential pathways regulated by CASR in HK-2 cells. PCR and western blot results showed that CASR expression was significantly increased in CASR cells and was decreased in shCASR cells when compared to their corresponding negative control, respectively. CCK-8 assay revealed that CASR inhibited the proliferation of HK-2 cells. RNA-Sequencing results suggested that the shCASR HK-2 cells exhibited a significant up-regulation of 345 genes and a down-regulation of 366 genes. These differentially expressed genes (DEGs) were related to cell apoptosis and cell development. In CASR HK-2 cells, 1103 DEGs primarily functioned in mitochondrial energy metabolism, and amino acid metabolism. With the Venn diagram, 4 DEGs (Clorf116, ENPP3, IL20RB, and CLDN2) were selected as the hub genes regulated by CASR. Enrichment analysis revealed that these hub genes were involved in cell-cell junction, and epithelial cell development. In summary, our investigation has the potential to offer novel perspectives on CASR regulating cell-cell junction in HK-2 cells.

Chronic Cinacalcet improves skin flap survival in rats: the suggested role of the nitric oxide pathway.

Cinacalcet is a calcimimetic medicine that has been used to treat secondary hyperparathyroidism and parathyroid cancer. Various studies have proposed the positive role of calcium and its receptor in skin wound healing. Furthermore, Cinacalcet interacts with other skin repair-related mechanisms, including inflammation and nitric oxide pathways. The present study evaluated the effect of Cinacalcet on the random-pattern skin flap survival. Eighty-four Wistar male rats were used. Multiple doses of Cinacalcet (30, 3, 1, 0.3, and 0.05 mg/kg) were used in 3 different routes of administration before the surgery. Histopathological evaluations, quantitative assessment of IL-6, TNF-α, and nitric oxide (NO), and the expression of calcium-sensing receptor (CaSR) and E-cadherin were evaluated in the skin tissue. To assess the role of NO, a NO synthase inhibitor, N-nitro-L-arginine methyl ester hydrochloride (L-NAME), was used, and histopathological effects were investigated. Cinacalcet pretreatment at the IP chronic 1 mg/kg dose significantly increased the skin flap survival rate and enhanced the NO tissue level compared to the control. However, the administration of L-NAME abolished its protective effects. IP Chronic 1 mg/kg of Cinacalcet could also decline the levels of IL-6 and TNF-α and also increase the expression of CaSR and E-cadherin in the flap tissue compared with the control group. Chronic Cinacalcet at 1 mg/kg could improve skin flap survival, probably mediated by the CaSR, NO, and inflammation-related pathways.

Small intestinal CaSR-dependent and CaSR-independent protein sensing regulates feeding and glucose tolerance in rats.

Proteins activate small intestinal calcium sensing receptor (CaSR) and/or peptide transporter 1 (PepT1) to increase hormone secretion1-8, but the effect of small intestinal protein sensing and the mechanistic potential of CaSR and/or PepT1 in feeding and glucose regulation remain inconclusive. Here we show that, in male rats, CaSR in the upper small intestine is required for casein infusion to increase glucose tolerance and GLP1 and GIP secretion, which was also dependent on PepT1 (ref. 9). PepT1, but not CaSR, is required for casein infusion to lower feeding. Upper small intestine casein sensing fails to regulate feeding, but not glucose tolerance, in high-fat-fed rats with decreased PepT1 but increased CaSR expression. In the ileum, a CaSR-dependent but PepT1-independent pathway is required for casein infusion to lower feeding and increase glucose tolerance in chow-fed rats, in parallel with increased PYY and GLP1 release, respectively. High fat decreases ileal CaSR expression and disrupts casein sensing on feeding but not on glucose control, suggesting an ileal CaSR-independent, glucose-regulatory pathway. In summary, we discover small intestinal CaSR- and PepT1-dependent and -independent protein sensing mechanisms that regulate gut hormone release, feeding and glucose tolerance. Our findings highlight the potential of targeting small intestinal CaSR and/or PepT1 to regulate feeding and glucose tolerance.

Calcium-sensing Receptor, a Potential Biomarker Revealed by Large-scale Public Databases and Experimental Verification in Metastatic Breast Cancer.

Breast cancer (BC) is a common cancer characterized by a high molecular heterogeneity. Therefore, understanding its biological properties and developing effective treatments for patients with different molecular features is imperative. Calcium-sensing receptor (CaSR) has been implicated in several regulatory functions in various types of human cancers. However, its underlying pathological mechanism in BC progression remains elusive. We utilized The Cancer Genome Atlas and Gene Expression Omnibus databases to explore the function of CaSR in the metastasis of BC. Gene ontology analysis, Kyoto Encyclopedia of Genes and Genomes analysis, and Gene Set Enrichment Analysis of biological processes and cell signaling pathways revealed that CaSR could be activated or inhibited. Importantly, quantitative reverse transcriptase-polymerase chain reaction and western blotting were used to verify the gene expression of the CaSR. Wound healing and transwell assays were conducted to assess the effect of CaSR on the migration of BC cells. We demonstrated that CaSR expression in metastatic BC was higher than that in non-metastatic BC. It is the first time that database information has been used to reveal the biological process and molecular mechanism of CaSR in BC. Moreover, the CaSR expression in normal breast epithelial cells was notably less compared to that in BC cells. The activation of CaSR by Cinacalcet (a CaSR agonist) significantly enhanced the migration of BC cells, whereas NPS-2143 (a CaSR antagonist) treatment dramatically inhibited these effects. Bioinformatics techniques and experiments demonstrated the involvement of CaSR in BC metastasis. Our findings shed new light on the receptor therapy and molecular pathogenesis of BC, and emphasize the crucial function of CaSR, facilitating the metastasis of BC.

The Interaction of Calcium-Sensing Receptor with KIF11 Enhances Cisplatin Resistance in Lung Adenocarcinoma via BRCA1/cyclin B1 pathway.

Cisplatin (DDP) is commonly used in the treatment of non-small cell lung cancer (NSCLC), including lung adenocarcinoma (LUAD), and the primary cause for its clinical inefficacy is chemoresistance. Here, we aimed to investigate a novel mechanism of chemoresistance in LUAD cells, focusing on the calcium-sensing receptor (CaSR). In this study, high CaSR expression was detected in DDP-resistant LUAD cells, and elevated CaSR expression is strongly correlated with poor prognosis in LUAD patients receiving chemotherapy. LUAD cells with high CaSR expression exhibited decreased sensitivity to cisplatin, and the growth of DDP-resistant LUAD cells was inhibited by cisplatin treatment in combination with CaSR suppression, accompanied by changes in BRCA1 and cyclin B1 protein expression both in vitro and in vivo. Additionally, an interaction between CaSR and KIF11 was identified. Importantly, suppressing KIF11 resulted in decreased protein levels of BRCA1 and cyclin B1, enhancing the sensitivity of DDP-resistant LUAD cells to cisplatin with no obvious decrease in CaSR. Here, our findings established the critical role of CaSR in promoting cisplatin resistance in LUAD cells by modulating cyclin B1 and BRCA1 and identified KIF11 as a mediator, highlighting the potential therapeutic value of targeting CaSR to overcome chemoresistance in LUAD.

Distinct and Targetable Role of Calcium and Calcium Sensing Receptor in Leukaemia

Calcium, the most abundant mineral in the body, is a key component of bones and is released by bone remodelling. Calcium ions play a role in the localisation, engraftment and the adhesion of normal haematopoietic stem cells (HSC) to extracellular matrix (ECM) proteins in the bone marrow microenvironment (BMM) via the calcium sensing receptor (CaSR), thereby maintaining normal haematopoiesis. However, the role of this heterotrimeric G-protein-coupled receptor and its associated pathways in the local BMM for the development of leukaemia is poorly understood. We hypothesized that calcium ions, subject to a fine balance between osteoblasts and osteoclasts and released from bone, and/or CaSR contribute to development, progression and response to therapy in leukaemia and might be targetable via CaSR. By imaging of a genetically-encoded calcium indicator using intravital microscopy (IVM), we have shown that the local calcium concentration forms a gradient in the BMM with the highest concentrations close to the endosteal area. Furthermore, calcium levels differ between different leukaemias, with the calcium concentration of mice and human patients being highest in acute myeloid leukaemia (AML). Additionally, CaSR was expressed at a higher level on AML compared to chronic myeloid leukaemia (CML) cells. Using genetic deletion or overexpression or pharmacological inhibition of CaSR, we revealed that this receptor influences the localization of CML and AML cells in the BMM. Furthermore, we showed that the secondary messenger intracellular calcium (iCa 2+) can be regulated by CaSR in different leukaemia cell lines which have differential sensitivity to extracellular calcium (eCa 2+). Exposure of the human cell lines K562 (BCR-ABL1 +) and THP1 (MLL-AF9 +) to increasing calcium concentrations revealed that CaSR expression, migration and adhesion to the extracellular matrix (ECM) protein fibronectin were not altered in CML, but significantly increased in AML. Genetic deletion or overexpression of Casr in leukaemia-initiating cells in murine models revealed that CaSR acts as tumour suppressor in BCR-ABL1-driven CML and B-cell acute lymphoblastic leukaemia (B-ALL) and as oncogene in AML. Conversely, overexpression of CaSR in CaSR-deficient AML-initiating cells ‘rescued’ the disease. Limiting dilution transplantation of CaSR-deficient AML-initiating cells to assess leukaemic stem cell number and/or function revealed a 6.5-fold reduction of leukemic stem cells. Treatment of mice with the CaSR agonist cinacalcet and imatinib prolonged survival of mice with CML, while treatment with a CaSR antagonist NPS-2143 significantly reduced tumour burden and prolonged survival of mice with AML in syngeneic and xenogeneic transplantation experiments. In summary, our results suggest that calcium ions, likely originating from the BMM and/or CaSR strongly and differentially influence leukaemia localisation and progression. As an adjunct to existing treatment strategies, targeting of CaSR with specific pharmacologic agonists may be beneficial in CML and B-ALL, while CaSR antagonists may prolong survival of patients with AML.

Low-molecular-weight fucoidan ameliorates calcium-deficient-diet–induced bone loss and osteoarthritis via CaSR level regulation

Fucoidans—sulfated and fucosylated polysaccharides extracted from brown seaweed—reportedly accelerate bone growth and prevent osteoarthritis (OA) progression. In this study, we examined the effects of low-molecular-weight fucoidan (LMF) on the molecular mechanism of extracellular calcium concentration in vitro and in vivo. In MG63 cells, LMF significantly increased the activity of alkaline phosphatase (ALP) and expression of calcium-sensing receptor (CaSR), runt-related transcription factor 2 (Runx2), and osteoprotegerin (OPG) under low- and normal-[Ca+2]0 conditions, but only decreased the expression of receptor activator of the nuclear factor κB ligand (RANKL) under normal-[Ca+2]0 conditions. In the calcium-deficient diet model, LMF significantly increased body length, growth rate, bone-specific ALP secretion, trabecular number, and CaSR protein expression, without body weight changes. In the OA model, LMF significantly increased bone volume and CaSR protein expression and reduced joint inflammation. Overall, our results indicate that LMF reduced calcium-deficient-diet–induced bone loss and OA via CaSR level regulation.

SAT069 Targeting Human β-Cell G Protein-coupled Receptors To Alter Cytokine-mediated Caspase Activation

Abstract Disclosure: K. Rodrigues dos Santos: None. N. Mukherjee: None. L.F. Barella: None. F. Armoo: None. D.L. Eizirik: None. A.T. Templin: None. M.A. Kalwat: None. In type 1 diabetes (T1D) autoimmune destruction of pancreatic islet β-cells causes a lack of insulin, leading to hyperglycemia. The development of therapies that can prevent β-cell death is critical. β-cell proliferation and survival pathways are affected by signaling through G protein-coupled receptors (GPCRs). Using high-depth RNA-seq, we found altered expression of 123 different GPCRs in human islets exposed to cytokines (IL1β 50U/ml + IFNγ 1000U/ml, 48 h) to model the T1D milieu. We hypothesized these candidates may be exploited for β-cell protection. Among the candidates, adenosine receptors (ADORA1 and ADORA2A), calcium-sensing receptor (CASR), and metabotropic glutamate receptor 4 (GRM4) stood out. Cytokines decreased the expression of ADORA1 and CASR, but increased ADORA2A and GRM4. To gauge the impact of agonizing/antagonizing these receptors, we pre-treated human EndoC-β H1 β-cells or islets with receptor ligands and co-treated with cytokines (IL1β 50U/ml + IFNγ or IL1β + 1000U/ml IFNγ + 1000U/ml TNFɑ, 48 h) and measured glucose-stimulated insulin secretion, cell viability, and gene expression. Each cytokine combination induced target gene expression (e.g. CXCL10), but only the combination of IL1β + IFNγ + TNFɑ reduced glucose-stimulated insulin secretion. Preliminary experiments indicated that adenosine receptor ligands had little impact in our assays. However, ligands for CASR and GRM4 exhibited significant suppression of cytokine-induced caspase 3/7 activation in EndoC-βH1 cells. Interestingly, suppressed caspase activation did not result in observable impacts on live/dead cell ratios or live-cell analysis using Incucyte in EndoC-βH1 cells. Consistently, we also observed cytokine-mediated cell death in the presence of the pan-caspase inhibitor ZVAD-fmk. We conclude that a variety of β-cell GPCR-mediated signaling pathways may converge to prevent cytokine-induced caspase activation, but additional measures are needed to enable protection from eventual cell death. Our results and this line of investigation is significant because understanding mechanisms of GPCR-cytokine crosstalk in β-cells will inform strategies to protect islets in other models of T1D. Funding: JDRF 1-INO-2022-1113-A-N and Diabetes Research Connection #33. Presentation: Saturday, June 17, 2023

Pan-cancer analysis reveals the prognostic gene CASR suppresses tumor progression and epithelial–mesenchymal transition in renal clear cell carcinoma

Calcium-sensing receptor (CASR), primarily found in the parathyroid gland and other tissues, plays a crucial role in sensing and regulating extracellular calcium, which was also aberrantly expressed in human tumors. Nevertheless, a comprehensive analysis of CASR in pan-cancer has yet to be conducted. To gain a better understanding of CASR in pan-cancer, data profiles on CASR cancers were collected from TCGA database. The expression level, clinical significance, prognostic value, and potential mechanisms of CASR in pan-cancer were analyzed via multiple public databases. The functional assays were conducted using human kidney renal clear cell carcinoma (KIRC) cell lines, clinical samples, and nude mice. Our research revealed that the abnormal expression of CASR was found in a variety of tumors. The expression and mutation of CASR were significantly associated with tumor prognosis and stage. Pathway analyses suggested that CASR was involved in the epithelial–mesenchymal transition (EMT) progress. Besides, CASR expression was correlated with immune inhibitory genes and immunotherapy in cancers. Particularly in KIRC, we established that CASR mRNA and protein levels were downregulated in clinical samples and cell lines. Moreover, a Cox regression analysis revealed that CASR was an independent prognostic factor in both TCGA-KIRC samples and clinical samples from our center. In vitro and in vivo experiments revealed that blocking CASR with lentivirus could suppress tumor growth and invasion, and EMT progress in KIRC cells. In summary, our study provides a comprehensive bioinformatic analysis of CASR in pan-cancer, offering deeper insights into its function and the EMT mechanism in KIRC, warranting further investigation.

Alcohol Intake Provoked Cardiomyocyte Apoptosis Via Activating Calcium-Sensing Receptor and Increasing Endoplasmic Reticulum Stress and Cytosolic [Ca2+]i.

Cardiomyocyte apoptosis plays an important role in alcoholic cardiac injury. However, the association between calcium-sensing receptor (CaSR) and alcohol-induced cardiomyocyte apoptosis remain unclear. Therefore, we investigated the role and its moleculer mechanism of CaSR in rat cardiomyocyte apoptosis induced by alcohol. Alcohol-induced cardiomyocyte apoptosis in vivo and in vitro model of rats were applied in this study. The expression of CaSR, endoplasmic reticulum stress markers and apoptosis were tested by immunohistological staining, western blot, TUNEL and flow cytometry, respectively. [Ca2+]i were detected by confocal laser scanning microscopy. Compared with the control group, alcohol intake (AI) led to abnormal arrangements of cardiomyocytes and obvious increase of myocardial apoptosis. Moreover, AI also significantly upregulated protein expression of CaSR, GRP94, caspase-12 and CHOP. Alcohol induced apoptosis of cultured cardiomyocytes of rats in a dose-dependent way. Activation of CaSR markedly enhanced cardiomyocyte apoptosis and ERS induced by alcohol, ERS inducer also significantly increased cardiomyocyte apoptosis without activating CaSR. Furthermore, GdCl3 augmented alcohol-induced increase of [Ca2+]i in cardiomyocytes, which was attenuated by NPS2390 but not 4-PBA pre-treatment. Alcohol could induce cardiomyocyte apoptosis in rats in vivo and in vitro, which was mediated probably via activating CaSR, and then ERS and the increase of the cytosolic [Ca2+]i. This provides a potential target for preventing cardiomyocyte apoptosis and cardiomyopathy induced by alochol.

MiR-301a-5p modulates parathyroid hormone secretion in secondary hyperparathyroidism possibly by regulating calcium-sensing receptor

To explore the miRNAs that down- regulate calcium-sensing receptor (CaSR) in secondary hyperparathyroidism (SHPT) and their effects on parathyroid hormone (PTH) secretion. Whole transcriptome sequencing was performed for 6 normal parathyroid tissue samples and 11 SHPT parathyroid tissue samples. Based on bioinformatic prediction, we screened out 7 candidate miRNAs that regulate CaSR, among which the most likely miRNA for CaSR regulation was identified by double luciferase test. We detected the differential expression of miR-301a-5p and CaSR mRNA in SHPT and normal parathyroid tissue using qRT-PCR, and analyzed the correlation between their expressions and serum PTH levels of the patients. Western blotting was used to detect the expression of CaSR protein in primary SHPT parathyroid cells transfected with miR-301a-5p mimics or inhibitors, and the level of PTH in the supernatant of the cell culture was determined. Among the preliminarily selected 7 miRNAs that potentially regulate CaSR (miR-15a-5p, miR-15b-5p, miR- 16- 5p, miR- 221- 3p, miR- 222- 3p, miR- 301a- 5p and miR- 503- 5p), miR- 301a-5p was significantly upregulated in SHPT compared with normal parathyroid tissue (P < 0.05), and its expression appeared to be positively correlated with PTH level, but this correlation was not statistically significant (P > 0.05); The expression of CaSR mRNA was significantly downregulated in SHPT (P < 0.05), and its expression tended to inversely correlate with the patient's PTH level, but the correlation was not statistically significant (P > 0.05). In primary culture of SHPT parathyroid cells, miR-301a-5p overexpression caused a significant decrease of CaSR protein expression (P < 0.05), and conversely, inhibition of miR-301a-5p expression increased the expression of CaSR protein (P < 0.05). Although miR-301a-5p overexpression did not significantly affect PTH secretion of the cells (P > 0.05), inhibition of iR-301a-5p expression strongly increased the secretion of PTH (P < 0.05). MiR-301a-5p affects PTH secretion in SHPT possibly by regulating the expression of CaSR.

Calcium sensing and signaling are impaired in the lumbar spine of a rat model of congenital kyphosis.

Kyphosis involves spines curving excessively backward beyond their physiological curvature. Although the normal structure of the spinal vertebrae is extremely important for maintaining posture and the normal function of the thoracic and abdominal organs, our knowledge concerning the pathogenesis of the disease is insufficient. We herein report that the downregulation of the calcium signaling pathway is involved in the pathogenesis of congenital kyphosis. The third to fifth lumbar spine segments, the kyphotic region of Ishibashi (IS) rats, which are used as a model of congenital kyphoscoliosis, were collected. A DNA microarray, quantitative PCR, Western blotting, and immunohistochemistry were used to measure the expression of genes and proteins related to intracellular calcium signaling. We found that the expression of calcium-sensing receptor (CaSR) and transient receptor potential vanilloid 1 (Trpv1)-two receptors involved in the calcium signaling-was decreased in the lumbar spine of IS rats. We also observed that the number of CaSR-immunoreactive and Trpv1-immunoreactive cells in the lumbar spine of IS rats was lower than in wild-type rats. Furthermore, the expression of intracellular molecules downstream of these receptors, such as phosphorylated protein kinase C, c-Jun N-terminal kinase, and neural EGFL-like 1, was also reduced. In fact, the calcium content in the lumbar spine of IS rats was significantly lower than that in wild-type rats. These results indicate that adequate calcium signaling is extremely important for the regulation of normal bone formation and may also be a key factor for understanding the pathogenesis of congenital kyphosis.

Effects of evocalcet on parathyroid calcium-sensing receptor and vitamin D receptor expression in uremic rats.

Little is known about the effect of the recently developed calcimimetic evocalcet (Evo) on parathyroid calcium-sensing receptor (CaSR) and vitamin D receptor (VDR) expression. We examined the effects of Evo and cinacalcet (Cina) on CaSR and VDR expression in 5/6 nephrectomized Sprague-Dawley rats fed a high-phosphorus diet for 4 weeks to develop secondary hyperparathyroidism (SHPT). These uremic rats were divided into 4 groups-baseline control (Nx4W) and groups with additional treatment with either the Vehicle, Evo, or Cina for 2 weeks; normal rats were used as normal controls (NC). Blood parameters and parathyroid tissue were analyzed. CaSR and VDR expression levels were determined using immunohistochemistry. The degree of kidney injury and hyperphosphatemia was similar in the uremic groups (Nx4W, Vehicle, Cina, and Evo). Serum parathyroid hormone levels were significantly higher in the Nx4W and Vehicle groups than in the NC group. This increase was significantly suppressed in the Cina and Evo groups compared with that in the Vehicle group. Serum calcium levels were significantly and equally lower in the Cina and Evo groups relative to those in the Vehicle group. CaSR expression was significantly lower in the Nx4W and Vehicle groups than in the NC group. This downregulation was of an equally lesser magnitude in the Cina and Evo groups. A similar trend was observed for VDR expression. These results indicate that Evo and Cina treatment can increase parathyroid CaSR and VDR expression in uremic rats with SHPT, which could provide better control of mineral and bone disorder markers.

CaSR modulates proliferation of the superficial zone cells in temporomandibular joint cartilage via the PTHrP nuclear localization sequence.

The superficial zone cells in mandibular condylar cartilage are proliferative. The present purpose was to delineate the relation of calcium-sensing receptor (CaSR) and parathyroid hormone-related peptide nuclear localization sequence (PTHrP87-139 ), and their role in the proliferation behaviors of the superficial zone cells. A gain- and loss-of-function strategy were used in an in vitro fluid flow shear stress (FFSS) model and an in vivo bilateral elevation bite model which showed mandibular condylar cartilage thickening. CaSR and PTHrP87-139 were modulated through treating the isolated superficial zone cells with activator/SiRNA and via deleting CaSR or parathyroid hormone-related peptide (PTHrP) gene in mice with the promoter gene of proteoglycan 4 (Prg4-CreERT2 ) in the tamoxifen-inducible pattern with or without additional injection of Cinacalcet, the CaSR agonist, or PTHrP87-139 peptide. FFSS stimulated CaSR and PTHrP expression, and accelerated proliferation of the Prg4-expressing superficial zone cells, in which process CaSR acted as an up-streamer of PTHrP. Proteoglycan 4 specific knockout of CaSR or PTHrP reduced the cartilage thickness, suppressed the proliferation and early differentiation of the superficial zone cells, and inhibited cartilage thickening and matrix production promoted by bilateral elevation bite. Injections of CaSR agonist Cinacalcet could not improve the phenotype caused by PTHrP mutation. Injections of PTHrP87-139 peptide rescued the cartilage from knockout of CaSR gene. CaSR modulates proliferation of the superficial zone cells in mandibular condylar cartilage through activation of PTHrP nuclear localization sequence. Our data support the therapeutic target of CaSR in promoting PTHrP production in superficial zone cartilage.

Leucine and arginine enhance milk fat and milk protein synthesis via the CaSR/Gi/mTORC1 and CaSR/Gq/mTORC1 pathways.

Amino acids (AAs) not only constitute milk protein but also stimulate milk synthesis through the activation of mTORC1 signaling, but which amino acids that have the greatest impact on milk fat and protein synthesis is still very limited. In this study, we aimed to identify the most critical AAs involved in the regulation of milk synthesis and clarify how these AAs regulate milk synthesis through the G-protein-coupled receptors (GPCRs) signaling pathway. In this study, a mouse mammary epithelial cell line (HC11) and porcine mammary epithelial cells (PMECs) were selected as study subjects. After treatment with different AAs, the amount of milk protein and milk fat synthesis were detected. Activation of mTORC1 and GPCRs signaling induced by AAs was also investigated. In this study, we demonstrate that essential amino acids (EAAs) are crucial to promote lactation by increasing the expression of genes and proteins related to milk synthesis, such as ACACA, FABP4, DGAT1, SREBP1, α-casein, β-casein, and WAP in HC11 cells and PMECs. In addition to activating mTORC1, EAAs uniquely regulate the expression of calcium-sensing receptor (CaSR) among all amino-acid-responsive GPCRs, which indicates a potential link between CaSR and the mTORC1 pathway in mammary gland epithelial cells. Compared with other EAAs, leucine and arginine had the greatest capacity to trigger GPCRs (p-ERK) and mTORC1 (p-S6K1) signaling in HC11 cells. In addition, CaSR and its downstream G proteins Gi, Gq, and Gβγ are involved in the regulation of leucine- and arginine-induced milk synthesis and mTORC1 activation. Taken together, our data suggest that leucine and arginine can efficiently trigger milk synthesis through the CaSR/Gi/mTORC1 and CaSR/Gq/mTORC1 pathways. We found that the G-protein-coupled receptor CaSR is an important amino acid sensor in mammary epithelial cells. Leucine and arginine promote milk synthesis partially through the CaSR/Gi/mTORC1 and CaSR/Gq/mTORC1 signaling systems in mammary gland epithelial cells. Although this mechanism needs further verification, it is foreseeable that this mechanism may provide new insights into the regulation of milk synthesis.