Calcium-sensing Receptor Research Articles

OR23-01 The Nonredundant Role Of Beta-Amyloid In Mediating Tonic PTH Secretion In Physiological And Pathological States

Abstract Disclosure: C. Tu: None. Z. Cheng: None. K.A. Pena: None. N. Szeto: None. J.A. Sosa: None. J. Vilardaga: None. J. Koh: None. W. Chang: None. Understanding the mechanisms driving parathyroid hormone (PTH) hypersecretion in primary hyperparathyroidism (PHPT) is essential for better management of this common endocrinopathy. Prior studies showed that reduced Ca2+-sensing receptor (CaSR) expression and the subsequent increases in heterodimerization of the CaSR with the type B γ-aminobutyric acid receptor 1 (GABAB1R) are causally linked to PTH hypersecretion in PHPT mouse models (Nat Metab 2:243-255). We further showed that expression of the putative GABAB1R ligands, amyloid precursor protein (APP) and its proteolytic product, β-amyloid (Aβ1-42), is significantly upregulated in adenomas of PHPT patients associated with vitamin D insufficiency/deficiency when compared to normal donor controls. The current study aims to delineate the actions of Aβ1-42 in promoting tonic PTH secretion and its interactions with vitamin D receptor (VDR) signaling in parathyroid glands (PTGs) in basal and PHPT states. We show that Aβ1-42 (200 nM) stimulated tonic PTH secretion in cultures of normal human PTGs without shifting the calcium/PTH secretion setpoint (Ca2+-setpoint). In contrast, conditional knockout (KO) of the App gene in the parathyroid cell (PTC) of PTCAppΔflox/Δflox mice significantly reduced serum PTH levels (KO: 64±13 pg/ml vs Control: 109±12 pg/ml; p<0.05, n=8) despite hypocalcemia, indicating hypoparathyroidism. In PTGs cultured from the PTCAppΔflox/Δflox mice, supplementation of Aβ1-42 dose-dependently (EC50=5.6 nM, p<0.001) increased PTH secretion without altering the Ca2+-setpoint. However, the stimulatory effects of Aβ1-42 on tonic PTH secretion were completely abrogated in the PTGs with concurrent deletions of App, Casr and Gabbr1 genes, supporting a direct action of Aβ1-42 on CaSR and/or GABAB1R. The latter notion is further supported by the ability of Aβ1-42 to stimulate cAMP production in cells co-expressing CaSR and GABAB1R. PTC-specific deletion of the Vdr gene in the PTCVdrΔflox/Δflox mice led to elevated serum PTH levels in vivo and increased tonic PTH secretion with unaffected Ca2+-setpoint in PTGs in vitro. Concurrent ablation of the App gene completely normalized serum PTH levels in the PTCVdrΔflox/Δflox mice and prevented PTH hypersecretion in their PTGs in culture. These findings support a critical role of the APP-derived Aβ1-42 in mediating tonic PTH secretion in the normal physiological state and suggest a new mechanism driving PTH hypersecretion in PHPT due to vitamin D deficiency. Presentation: Saturday, June 17, 2023

FRI698 Hypoparathyroidism Secondary To Covid-19

Abstract Disclosure: M. Hussain: None. T.K. Reddy: None. A. Mohiuddin: None. D. Lovre: None. R. Galagan: None. Introduction: New onset adult hypoparathyroidism is most often caused by thyroid surgery or autoimmune illness. To date, little is known about the effect of the novel coronavirus (SARS-CoV-2) on parathyroid glands. Most recent hypotheses are that Covid-19 might affect the parathyroid glands directly through invasion of parathyroid gland tissues by SARS-CoV-2 virus or indirectly secondary to respiratory failure and chronic respiratory alkalosis. Case Report: We report the case of a 32-year-old male with post-viral hypoparathyroidism secondary to COVID-19.Only a few cases of COVID-19 induced hypoparathyroidism have been reported in the literature. Our patient was admitted to the hospital for severe and symptomatic hypocalcemia three weeks after a viral-like upper respiratory tract infection and diarrhea. He complained of paresthesias, muscle cramps and muscle weakness. He had no autoimmune or neck surgical history. Initial lab test results revealed a corrected calcium of 4.5 mg/dL (8.4-10.3 mg/dL), ionized calcium 2.4 mg/dL (4.5-5.3 mg/dL), PTH < 1.0 pg/mL (12-65 pg/mL), phosphorus 6.2 mg/dL (2.5-4.7 mg/dL), magnesium 1.6 mg/dL (1.5-2.6 mg/dL), Vit D, 25-hydroxy 17.3 ng/mL (30-100 ng/mL), and creatinine 1.13 mg/dL (0.7-1.4 mg/dL), consistent with hypoparathyroidism. An ECG showed QTc prolongation to 506 msec. SARS-coV-2/flu/RSV cepheid multiplex was negative, SARS-CoV-2 Spike Ab was positive. He had never received a COVID vaccine. The patient was admitted to ICU for IV calcium drip, oral calcium and calcitriol supplementation. He was transitioned to a medical ward when his severe hypocalcemia was corrected and he was ultimately discharged on oral calcitriol 1 mcg BID and calcium carbonate 1000 mg po TID. A thorough workup for a cause of the hypoparathyroidism was performed, including anti-PTH antibody, 21-hydroxylase antibody, TSI, and TPO antibody, all of which were negative. Genetic testing was performed, including CASR gene sequencing analysis and AIRE DNA sequencing, both of which were negative. After other causes of hypoparathyroidism were excluded, COVID-19 was reasoned to be the etiology of this patient’s hypoparathyroidism. Our case highlights a post-viral hypoparathyroidism secondary to COVID-19. Further studies are needed to elucidate the mechanistic relationship between COVID-19 and hypoparathyroidism. Presentation: Friday, June 16, 2023

Clinical significance of calcium-sensing receptors in the development and course of recurrent wheezing and asthma in young children

The aim of the study: to evaluate the role of CaSR in the formation and course of recurrent wheezing and asthma in young children.
 Materials and methods: a total of 70 patients participated in the study, including 20 children (8 boys and 12 girls) diagnosed with mild asthma, 30 patients (20 boys and 10 girls) with recurrent wheezing, and 20 relatively healthy children. The level of CaSR protein in the peripheral blood was measured twice: in the first 2 days of clinical manifestations and in remission. The levels of blood calcium (Ca), phosphorus (P), vitamin D (25(OH) D3) and indicators of cellular, phagocytic and humoral immunity were also studied. The level of CaSR in the blood serum was analyzed by ELISA using commercial kits (CaSR ELISA Kit Human E-EL-H0621, Elabscience, USA, protocol No. 2301070). Statistical processing was performed using StatSoft STATISTICA version 8.0 (Tulsa, Oklahoma) and MedCalc statistical software version 17.2.
 Results: the lowest levels of CaSR protein were found in the group of children with asthma both during exacerbation and remission, which is associated with its redistribution from peripheral blood to smooth muscle. The level of CaSR protein in the group with recurrent wheezing did not differ during exacerbation and remission, which may be due to the low severity of the obstructive component of this group and the number of obstructions, which, in turn, does not lead to an obvious redistribution of this indicator to the smooth muscle of the bronchi. The level of CaSR protein is obviously the lowest in young children, which is confirmed by correlations. The available correlations with blood electrolytes and IgE confirm the involvement of CaSR protein in phosphorus-calcium metabolism and the development of the inflammatory process of allergic genesis.
 Conclusions: level of CaSR protein in the serum of children depends on the number of obstructions, their course and severity of the disease. CaSR protein is directly involved in calcium-phosphorus metabolism

The Q/R editing site of AMPA receptor GluA2 subunit acts as an epigenetic switch regulating dendritic spines, neurodegeneration and cognitive deficits in Alzheimer’s disease

BackgroundRNA editing at the Q/R site of GluA2 occurs with ~99% efficiency in the healthy brain, so that the majority of AMPARs contain GluA2(R) instead of the exonically encoded GluA2(Q). Reduced Q/R site editing increases AMPA receptor calcium permeability and leads to dendritic spine loss, neurodegeneration, seizures and learning impairments. Furthermore, GluA2 Q/R site editing is impaired in Alzheimer’s disease (AD), raising the possibility that unedited GluA2(Q)-containing AMPARs contribute to synapse loss and neurodegeneration in AD. If true, then inhibiting expression of unedited GluA2(Q), while maintaining expression of GluA2(R), may be a novel strategy of preventing synapse loss and neurodegeneration in AD.MethodsWe engineered mice with the ‘edited’ arginine codon (CGG) in place of the unedited glutamine codon (CAG) at position 607 of the Gria2 gene. We crossbred this line with the J20 mouse model of AD and conducted anatomical, electrophysiological and behavioural assays to determine the impact of eliminating unedited GluA2(Q) expression on AD-related phenotypes.ResultsEliminating unedited GluA2(Q) expression in AD mice prevented dendritic spine loss and hippocampal CA1 neurodegeneration as well as improved working and reference memory in the radial arm maze. These phenotypes were improved independently of Aβ pathology and ongoing seizure susceptibility. Surprisingly, our data also revealed increased spine density in non-AD mice with exonically encoded GluA2(R) as compared to their wild-type littermates, suggesting an unexpected and previously unknown role for unedited GluA2(Q) in regulating dendritic spines.ConclusionThe Q/R editing site of the AMPA receptor subunit GluA2 may act as an epigenetic switch that regulates dendritic spines, neurodegeneration and memory deficits in AD.

The induction of parathyroid cell differentiation from human induced pluripotent stem cells promoted via TGF-α/EGFR signaling.

The parathyroid gland plays an essential role in mineral and bone metabolism. A cultivation for physiological human parathyroid cells has yet to be established and the method by which parathyroid cells differentiate from pluripotent stem cells remains uncertain. Therefore, it has been hard to clarify the mechanisms underlying the onset of parathyroid disorders, such as hyperparathyroidism. Here, we developed a new method of parathyroid cell differentiation from human induced pluripotent stem (iPS) cells. The parathyroid cell differentiation occurred in accordance with embryologic development. The differentiated cells, which expressed parathyroid hormone, adopted a unique cell aggregation similar to the parathyroid gland. In addition, these differentiated cells were identified as calcium-sensing receptor (CaSR)/epithelial cell adhesion molecule (EpCAM) double-positive cells. Interestingly, stimulation with transforming growth factor-α (TGF-α), which is considered a causative molecule of parathyroid hyperplasia, increased the CaSR/EpCAM double-positive cells, but this effect was suppressed by erlotinib, which is an epidermal growth factor receptor (EGFR) inhibitor. These results suggest that TGF-α/EGFR signaling promotes parathyroid cell differentiation from iPS cells in a similar manner to parathyroid hyperplasia.

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.

Stachydrine Hydrochloride Regulates the NOX2-ROS-Signaling Axis in Pressure-Overload-Induced Heart Failure.

Our previous studies revealed the protection of stachydrine hydrochloride (STA) against cardiopathological remodeling. One of the underlying mechanisms involves the calcium/calmodulin-dependent protein kinase Ⅱ (CaMKII). However, the way STA influences CaMKII needs to be further investigated. The nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2)-coupled reactive oxygen species (ROS) overproduction putatively induces the oxidative activation of CaMKII, resulting in the occurrence of pathological cardiac remodeling and dysfunction in experimental models of mice. Thus, in this study, we assessed the role of the NOX2-ROS signal axis in STA cardioprotection. The transverse aortic constriction (TAC)-induced heart failure model of mice, the phenylephrine-induced hypertrophic model of neonatal rat primary cardiomyocytes, and the H2O2-induced oxidative stress models of adult mouse primary cardiomyocytes and H9c2 cells were employed. The echocardiography and histological staining were applied to assess the cardiac effect of STA (6 mg/kg/d or 12 mg/kg/d), which was given by gavage. NOX2, ROS, and excitation-contraction (EC) coupling were detected by Western blotting, immunofluorescence, and calcium transient-contraction synchronous recordings. ROS and ROS-dependent cardiac fibrosis were alleviated in STA-treated TAC mice, demonstrating improved left ventricular ejection fraction and hypertrophy. In the heart failure model of mice and the hypertrophic model of cardiomyocytes, STA depressed NOX2 protein expression and activation, as shown by inhibited translocation of its phosphorylation, p67phox and p47phox, from the cytoplasm to the cell membrane. Furthermore, in cardiomyocytes under oxidative stress, STA suppressed NOX2-related cytosolic Ca2+ overload, enhanced cell contractility, and decreased Ca2+-dependent regulatory protein expression, including CaMKⅡ and Ryanodine receptor calcium release channels. Cardioprotection of STA against pressure overload-induced pathological cardiac remodeling correlates with the NOX2-coupled ROS signaling cascade.

Calcium-sensing receptor activator cinacalcet for treatment of cyclic nucleotide-mediated secretory diarrheas

Cyclic nucleotide elevation in intestinal epithelial cells is the key pathology causing intestinal fluid loss in secretory diarrheas such as cholera. Current secretory diarrhea treatment is primarily supportive, and oral rehydration solution is the mainstay of cholera treatment. There is an unmet need for safe, simple and effective diarrhea treatments. By promoting cAMP hydrolysis, extracellular calcium-sensing receptor (CaSR) is a regulator of intestinal fluid transport. We studied the antidiarrheal mechanisms of FDA-approved CaSR activator cinacalcet and tested its efficacy in clinically relevant human cell, mouse and intestinal organoid models of secretory diarrhea. By using selective inhibitors, we found that cAMP agonists-induced secretory short-circuit currents (Isc) in human intestinal T84 cells are mediated by collective actions of apical membrane cystic fibrosis transmembrane conductance regulator (CFTR) and Clc-2 Cl− channels, and basolateral membrane K+ channels. 30 μM cinacalcet pretreatment inhibited all 3 components of forskolin and cholera toxin-induced secretory Isc by ∼75%. In mouse jejunal mucosa, cinacalcet inhibited forskolin-induced secretory Isc by ∼60% in wild type mice, with no antisecretory effect in intestinal epithelia-specific Casr knockout mice (Casr-flox; Vil1-cre). In suckling mouse model of cholera induced by oral cholera toxin, single dose (30 mg/kg) oral cinacalcet treatment reduced intestinal fluid accumulation by ∼55% at 20 hours. Lastly, cinacalcet inhibited forskolin-induced secretory Isc by ∼75% in human colonic and ileal organoids. Our findings suggest that CaSR activator cinacalcet has antidiarrheal efficacy in distinct human cell, organoid and mouse models of secretory diarrhea. Considering its excellent clinical safety profile, cinacalcet can be repurposed as a treatment for cyclic nucleotide-mediated secretory diarrheas including cholera.

High calcium concentrations reduce cellular excitability of mouse MNTB neurons

Calcium, a universal intracellular signaling molecule, plays essential roles in neural functions. Historically, in most in vitro brain slice electrophysiology studies, the extracellular calcium concentration ([Ca2+]e) in artificial cerebrospinal fluid is of a wide range and typically higher than the physiological value. At high [Ca2+]e, synaptic transmission is generally enhanced. However, the effects and the underlying mechanisms of calcium on intrinsic neuronal properties are diverse. Using whole-cell patch clamp in acute brainstem slices obtained from mice of either sex, we investigated the effects and the underlying mechanisms of high [Ca2+]e on intrinsic neuronal properties of neurons in the medial nucleus of the trapezoid body (MNTB), an auditory brainstem component in the sound localization circuitry. Compared to the physiological [Ca2+]e (1.2 mM), high [Ca2+]e at 1.8 and 2.4 mM significantly reduced the cellular excitability of MNTB neurons, resulting in decreased spike firing rate, depolarized spike threshold, and decreased the ability to follow high frequency inputs. High extracellular magnesium concentrations at 1.8 and 2.4 mM produced similar but less robust effects, due to surface charge screening. Upon high calcium application, voltage-gated sodium channel currents remained largely unchanged. Calcium-sensing receptors were detected in MNTB neurons, but blocking these receptors did not eliminate the effects of high calcium on spontaneous spiking. We attribute the lack of significant effects in these last two experiments to the moderate changes in calcium we tested. Our results call for the use of physiological [Ca2+]e in brain slice experiments.

Identification and target of action of cholecystokinin-releasing peptides from simulated digestion hydrolysate of wheat protein.

Wheat protein intake leads to improved appetite control. However, the active components causing appetite in wheat have not been fully clarified. Gut cholecystokinin (CCK) plays a vital role in appetite control. This study aimed to investigate the ability of wheat protein digest (WPD) to stimulate CCK secretion and clarify the active components and target of action. WPD was prepared by a simulated gastrointestinal digestion model. WPD treatment with a concentration of 5 mg mL-1 significantly stimulated CCK secretion in enteroendocrine STC-1 cells (P < 0.05). Furthermore, oral gavage with WPD in mice significantly increased plasma CCK level at 60 min (P < 0.01). Preparative C18 column separation was used to isolate peptide fractions associated with CCK secretion and peptide sequences were identified by liquid chromatography-tandem mass spectrometry. A new CCK-releasing peptide, RYIVPL, that potently stimulated CCK secretion was successfully identified. After pretreatment with a specific calcium-sensing receptor (CaSR) antagonist, NPS 2143, CCK secretion induced by WPD or RYIVPL was greatly suppressed, suggesting that CaSR was involved in WPD- or RYIVPL-induced CCK secretion. The present study demonstrated that WPD has an ability to stimulate CCK secretion in vitro and in vivo, and determined that peptide RYIVPL in WPD could stimulate CCK secretion through CaSR. © 2023 Society of Chemical Industry.

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.

Clinical Value of CASR Gene Polymorphism on Cinacalcet Response in Hemodialysis Patients with Secondary Hyperparathyroidism

Abstract Background Secondary hyperparathyroidism (SHPT) is a common complication of chronic kidney disease (CKD) patients on dialysis, associated with increased cardiovascular mortality and morbidity. Aim to evaluate frequency of variants of CaSR genes related to PTH regulation and to assess the effect of these single nucleotide polymorphisms on cinacalcet response among prevalent hemodialysis patients (HD) with SHPT. Patients and Methods This study included 50 prevalent HD patients with SHPT were recruited from Ain Shams University Hospitals' dialysis units. Clinical stable end-stage renal disease (ESDR) (35 males (70%) and 15 females (30%)), ≥ 18 years old on adequate HD for ≥ 6 months, with intact PTH (iPTH) ≥300 pg/ml and had been treated by cinacalcet. The patient was followed retrospectively for 6 months by measuring serum calcium, phosphorous, alkaline phosphatase, PTH to evaluate the response of cinacalcet. CASR gene and single nucleotide polymorphism (SNP) (rs1042636 and rs1802757) were measured by real-time PCR. Results CASR Gene/SNP rs1042636 (A/G), AA homozygous gene (wild gene) was present in n = 48 (96%) while AG heterozygous gene was present in n = 2 (4%). CASR Gene/SNP rs1802757(C/T), CC homozygous gene (wild gene) was present in n = 42 patients (84%) while CT heterozygous gene was present in n = 6 patients (12%). 21 patients (42%) responded to treatment of SHPT with reduction percent and 29 patients (58%) were non-responding to cinacalcet treatment for 6 months duration. The results showed no significant correlation between CASR gene polymorphism and response to treatment (p-value &amp;gt;0.05). Conclusion There is no statistically significant correlation between single nucleotide polymorphisms (SNPs) of the calcium sensing receptor gene (CASR) and response to cinacalcet as treatment of SHPT among HD patients, for further investigation studies.

Cinacalcet in patients with secondary hyperparathyroidism; a review

Secondary hyperparathyroidism is a common complication of chronic kidney disease characterized by excessive secretion of parathyroid hormone from the parathyroid glands. Cinacalcet is a calcimimetic medication that reduces parathormone levels by increasing the sensitivity of the calcium-sensing receptors on the parathyroid glands. This review aims to summarize the existing literature on the use of cinacalcet in patients with secondary hyperparathyroidism.

Cinacalcet Reverses Short QT Interval in Familial Hypocalciuric Hypercalcemia Type 1.

Familial hypocalciuric hypercalcemia type 1 (FHH-1) defines an autosomal dominant disease, related to mutations in the CASR gene, with mild hypercalcemia in most cases. Cases of FHH-1 with a short QT interval have not been reported to date. Three family members presented with FHH-1 and short QT interval (<360 ms), a condition that could lead to cardiac arrhythmias, and the effects of cinacalcet, an allosteric modulator of the CaSR, in rectifying the abnormal sensitivity of the mutant CaSR and in correcting the short QT interval were determined. CASR mutational analysis was performed by next-generation sequencing and functional consequences of the identified CaSR variant (p.Ile555Thr), and effects of cinacalcet were assessed in HEK293 cells expressing wild-type and variant CaSRs. A cinacalcet test consisting of administration of 30 mg cinacalcet (8 Am) followed by hourly measurement of serum calcium, phosphate, and parathyroid hormone during 8 hours and an electrocardiogram was performed. The CaSR variant (p.Ile555Thr) was confirmed in all 3 FHH-1 patients and was shown to be associated with a loss of function that was ameliorated by cinacalcet. Cinacalcet decreased parathyroid hormone by >50% within two hours, and decreases in serum calcium and increases in serum phosphate occurred within 8 hours, with rectification of the QT interval, which remained normal after 3 months of cinacalcet treatment. Our results indicate that FHH-1 patients should be assessed for a short QT interval and a cinacalcet test used to select patients who are likely to benefit from this treatment.

Tunable photoluminescence of intrinsic oxygen vacancies and Bi3+/Eu3+/Li+ tridoped BaZnOS for application in wLEDs

Quaternary wide-band-gap oxychalcogenides (MZnOS, M = Ca, Sr, and Ba) are underexplored inorganic semiconductors compared with pure chalcogenides or oxides, in which more dopants could be simultaneously coordinated by oxide and chalcogenide anions. In this kind of materials, color-tunable photoluminescence (PL) could well be obtained without destructing structure. Due to the need of complex conditions for synthesis compared with Ca(Sr)ZnOS, the unique structure of BaZnOS remains largely unexplored as host for application in lighting/display fields. Spectroscopic measuring combined with XPS and DFT computational studies on pristine BaZnOS reveal that the weak multi-colored self-PL were originated from the intrinsic trap states of oxygen vacancies (VO2+, VO+ and VO0). The crystallographic occupancies of dopants Bi3+/Eu3+ and Li + at Ba2+ and Zn2+ sites, respectively were proved based on the Rietveld refinements and crystal chemistry rules. Tunable and thermally stable PL in the regions of cyan, white and even yellow could be systematically obtained from the BaZnOS: Bi/Eu via changing concentrations of dopants with the help of energy transfer (ET) from the host to dopants as well as Bi to Eu. The effect of unlit Li+ is acting both as charge balancer and fluxing agent for reducing calcination temperature and improving PL efficiency. Finally, as a proof-of-concept experiment, the BaZnOS: Bi/Eu/Li phosphor converted white light emitting diode (pc-wLED) was fabricated and produced attractive performances including high CRI of 82.5, low CCT of 4024 K, CIE coordinates of (0.3462, 0.3531), and luminous efficiency (LE) of 16.5 lm/W. Altogether, the stable Bi/Eu/Li tridoped BaZnOS phosphor is a promising candidate to be applied in lighting/display fields.

CaSR links endocytic and secretory pathways via MADD, a Rab11A effector that activates Rab27B

Calcium sensing receptor (CaSR), a class C GPCR, regulates essential secretory pathways, involving communication between endocytic and secretory Rab GTPases, via still to be fully defined molecular mechanisms. To address how communication between endocytic and secretory vesicles occurs, we hypothesized that CaSR activates endocytic Rab11A-dependent effector pathways acting upstream of Rab27B-regulated secretion. We found that Rab11A is critical to promote Rab27B-dependent secretion of chemotactic and inflammatory factors, including IL-8, CCL2/MCP-1, and IL1-β, in response to CaSR stimulation. It also attenuates secretion of IL-6. The process is mediated by endosomal PI3-kinases, Vps34 and PI3KC2α, which promote Rab27B activation. Rab11A interacts with and activates MADD, a guanine exchange factor for Rab3, and Rab27A/B. Mechanistically, CaSR drives Rab11A-dependent coupling of recycling endosomes to secretory-vesicles via endosomal PI3K-mediated activation of a MADD/Rab27B pathway.

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.

Blockage of calcium-sensing receptor improves chronic intermittent hypoxia-induced cognitive impairment by PERK-ATF4-CHOP pathway

Obstructive sleep apnea-hypopnea syndrome (OSAHS) is involved in cognitive impairment of children. Chronic intermittent hypoxia (CIH) is considered as the critical pathophysiological mechanism of OSAHS. Calcium sensitive receptor (CaSR) mediated apoptosis in many neurological disease models by endoplasmic reticulum stress (ERS)-related pathway. However, little is known about the role of CaSR in OSAHS-induced cognitive dysfunction. In this study, we explored the effect of CaSR on CIH-induced cognitive impairment and possible mechanisms on regulation of PERK-ATF4-CHOP pathway in vivo and in vitro. CIH exposed for 9 h in PC12 cells and resulted in the cell apoptosis, simulating OSAHS-induced neuronal injury. CIH upregulated the level of CaSR, p-PERK, ATF4 and CHOP, contributing to the cell apoptosis. Treated with CaSR inhibitor (NPS-2143) or p-PERK inhibitor (GSK2656157) before CIH exposure, CIH-induced PC12 cell apoptosis was alleviated via inhibition of CaSR by downregulating p-PERK, ATF4 and CHOP. In addition, we established CIH mice model. With CIH exposure for 4 weeks in mice, more spatial memory errors were observed during 8-arm radial maze test. CIH significantly increased apoptotic cells in hippocampus via upregulating cleaved Caspase-3 and downregulating ratio of Bcl-2 to Bax. Besides, treatment of CaSR inhibitor alleviated the hippocampal neuronal apoptosis following CIH with downregulated p-PERK, ATF4 and CHOP, suggesting that CaSR contributed to CIH-induced neuronal apoptosis in hippocampus via ERS pathway. Sum up, our results demonstrated that CaSR accelerated hippocampal apoptosis via PERK-ATF4-CHOP pathway, holding a critical function on CIH-mediated cognitive impairment. Conversely, inhibition of CaSR suppressed PERK-ATF4-CHOP pathway and alleviated cognitive impairment.

Pharmacological profile of upacicalcet, a novel positive allosteric modulator of calcium-sensing receptor, in vitro and in vivo

Upacicalcet (formerly SK-1403/AJT240) is a novel non-peptide calcimimetic agent that acts as a calcium-sensing receptor (CaSR) agonist for the treatment of secondary hyperparathyroidism (SHPT) in chronic kidney disease (CKD). We compared upacicalcet with other calcimimetics (etelcalcetide or cinacalcet) and examined its in vitro and in vivo characteristics in terms of its human CaSR agonistic activity, its efficacy in normal and CKD rats after a single administration, and its effect on gastric emptying in rats. Upacicalcet activated human CaSR depending on the extracellular calcium (Ca2+) concentration without exhibiting an agonistic action when the extracellular Ca2+ level was below the physiological level. On the other hand, etelcalcetide had an agonistic activity even in the absence of physiological levels of extracellular Ca2+. The intravenous administration of upacicalcet to normal and double-nephrectomized rats dose-dependently (0.03–3mg/kg and 0.3–30mg/kg, respectively) decreased the serum intact parathyroid hormone (iPTH) and serum Ca2+ levels; however, the effect of upacicalcet on the reduction in serum Ca2+ disappeared at extracellular Ca2+ levels below the physiologically range, even when administered at a dose higher (100-fold) than the effective dose. Furthermore, upacicalcet did not affect gastric emptying in normal rats when administered up to a dose of 10mg/kg (300-fold higher than the dose affecting serum iPTH levels), while the administration of cinacalcet significantly slowed gastric emptying by approximately 50%. These findings suggest that upacicalcet has potential as an alternative calcimimetic agent with good pharmacological properties and a lower risk of hypocalcemia and gastrointestinal complications.