Intracellular Calcium Responses Research Articles

Neural Tissue-Like, not Supraphysiological, Electrical Conductivity Stimulates Neuronal Lineage Specification through Calcium Signaling and Epigenetic Modification.

Electrical conductivity is a pivotal biophysical factor for neural interfaces, though optimal values remain controversial due to challenges isolating this cue. To address this issue, conductive substrates made of carbon nanotubes and graphene oxide nanoribbons, exhibiting a spectrum of conductivities from 0.02 to 3.2Sm-1, while controlling other surface properties is designed. The focus is to ascertain whether varying conductivity in isolation has any discernable impact on neural lineage specification. Remarkably, neural-tissue-like low conductivity (0.02-0.1Sm-1) prompted neural stem/progenitor cells to exhibit a greater propensity toward neuronal lineage specification (neurons and oligodendrocytes, not astrocytes) compared to high supraphysiological conductivity (3.2Sm-1). High conductivity instigated the apoptotic process, characterized by increased apoptotic fraction and decreased neurogenic morphological features, primarily due to calcium overload. Conversely, cells exposed to physiological conductivity displayed epigenetic changes, specifically increased chromatin openness with H3acetylation (H3ac) and neurogenic-transcription-factor activation, along with a more balanced intracellular calcium response. The pharmacological inhibition of H3ac further supported the idea that such epigenetic changes might play a key role in driving neuronal specification in response to neural-tissue-like, not supraphysiological, conductive cues. These findings underscore the necessity of optimal conductivity when designing neural interfaces and scaffolds to stimulate neuronal differentiation and facilitate the repair process.

Testosterone enhances adipose tissue-blood pressure axis in obese mice exposed to early life stress

Previously, we have shown that male and female mice exposed to maternal separation and early weaning (MSEW), a model of early life stress, display exacerbated obesity-induced hypertension in response to chronic high fat diet. However, only male mice showed higher sympathetic tone at baseline, along with increased neuronal activation in PVN and pressor response to the acute stimulation of TRVP1 channels with capsaicin, a mechanism known as adipose afferent reflex (AAR). The aim of this study was to investigate whether obese male MSEW mice show 1) increased intracellular calcium in response to capsaicin in neuronal cultures of dorsal ganglia root (DRG), and 2) a role for sex hormones in AAR reactivity in vivo. Six-months-old control and MSEW fed a high fat diet (HFD, 60% kcal fat) were injected with pAAV-CAG-tdTomato (59462-PHP.S, 1012 viral particles); 8 sites; 4 ul/site; bilateral). After 6 weeks, mice were decapitated and DRGs (L5-T12) were collected and placed in ice-cold HBSS solution, dissociated and mixed with Collagenase P (1 mg/ml in HBSS, 15 min, 37 oC). After 0.25% Trypsin-EDTA incubation, neurons were mechanically dissociated, collected by centrifugation and resuspended in DMEM-10% FBS, plated onto the Matrigel Basement Membrane Matrix covered coverslips and maintained at 37 oC for 15-16 hours. Neuronal cultures were incubated in Ca2+ imaging solution with 2 μM Fura-2 AM, 30 min in dark conditions. After de-estirification, intracellular Ca2+ transients were visualized by exciting Fura-2 at 340 ± 20 nm and 380 ± 20 nm using a high-speed filter changer to obtain a ratiometric value independent of indicator concentration. Emitted light was passed through a dichroic filter (400-nm high pass) and an emitter filter (520 ± 30 nm) and was digitized onto the sensor of an EMCCD camera. Background subtraction and normalization to baseline were used to quantify changes in fluorescence. Despite similar resting uncalibrated ratios of calcium levels between groups (~0.6 ratio units, n=3), sensory neurons from MSEW mice tended to display larger responses to capsaicin (50 uM), showing elevated calcium kinetics vs. controls (0.56±0.09 vs. 0.31±0.12 delta ratio, respectively, p=0.063) as well as longer transients, perhaps indicative of reduced clearance or buffering. A separate set of age-matched mice were gonadectomized. After 4 weeks, anesthetized mice were fitted with carotid artery catheter for direct blood pressure measurement in response to the infusion of perigonadal fat with capsaicin (1.5 pmol/μL during 2 minutes in 4 sites, bilaterally). Capsaicin-induced pressor response was exacerbated in intact MSEW male mice compared to intact controls (9.0±0.2 vs. 1.3±0.2 delta mmHg, respectively, n=6, p<0.05). Orchidectomy attenuated delta blood pressure in MSEW mice to 7.0±0.2 mmHg (p<0.05 vs. intact MSEW), while enhanced delta blood pressure in control mice to 7.5±0.2 mmHg (p<0.05 vs. intact control). MSEW did not influence the pressor response to perigonadal fat stimulation with capsaicin either in intact or ovariectomized obese female mice (n=4-6 per group, p>0.05), suggesting that estradiol may not to play a protective role in obese females AAR reactivity. This data indicates that testosterone could buffer the AAR reactivity of obese control mice, while MSEW exerts an opposite effect. Thus, investigating testosterone signaling on calcium handling mechanisms (i.e., buffers, pumps, ER-mediated calcium release) in sensory neurons innervating visceral fat will provide insights on the sex-specific contribution of afferent sympathoexitatory signals to obesity-hypertension in male MSEW mice. This study was supported by NIH R01 HL135158, and SALT pilot - University of Kentucky to ASL. 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.

Superoxide Anions Inhibit Intracellular Calcium Response in Porcine Airway Smooth Muscle Cells.

Background Superoxide anions (O 2 - ) have multiple effects on pulmonary parenchyma altering cell proliferation, cellular metabolism, and airway smooth muscle (ASM) contraction. Intracellular calcium ([Ca 2+ ] i ) concentration plays a significant role in the regulation of ASM contraction, relaxation, proliferation, and gene expression. Objective We investigated the effects of O 2 - on agonist-stimulated changes in [Ca 2+ ] i in ASM cells. Design/Methods Fura-2 AM-loaded, freshly isolated porcine ASM (PASM) cells were used to examine [Ca 2+ ] i release in response to acetylcholine (ACh), histamine, endothelin, caffeine, and thapsigargin (TPG) in the presence or absence of extracellular Ca 2+ . Results Exposure of PASM cells to xanthine and xanthine oxidase (X + XO) resulted in a time-dependent generation of O 2 - , inhibited by superoxide dismutase (SOD). Preincubating PASM cells with X + XO for 15- or 45-minute inhibited net [Ca 2+ ] i responses to ACh, histamine, caffeine, and TPG compared with control cells. Pretreating PASM cells with SOD for 30 minutes mitigated the inhibitory effect of X + XO treatment on ACh-induced Ca 2+ elevation suggesting role of O 2 - . X + XO treatment also inhibited caffeine- and TPG-induced Ca 2+ elevation suggesting effect of O 2 - on [Ca 2+ ] i release and reuptake mechanisms. Conclusion Superoxide attenuates [Ca 2+ ] i release, reuptake, and may interfere with physiological functions of ASM cells.

The roles of extracellular vesicles released by mechanically stimulated osteocytes in regulating osteoblast and osteoclast functions

Bone adapts to mechanical loading by changing its shape and mass. Osteocytes, as major mechanosensors, are critical for bone modeling/remodeling in response to mechanical stimuli. Intracellular calcium oscillation is one of the early responses in osteocytes, and this further facilitates bone cell communication through released biochemical signals. Our previous study has found that mechanically induced calcium oscillations in osteocytes enhance the release of extracellular vesicles (EVs), and those released EVs can elevate bone formation activity. However, the mechanism of mechanically stimulated EVs’ regulation of bone formation and resorption is still unclear. Here, using in vitro studies, we exposed OCY454 cells, with relatively high sclerostin expression, to steady fluid flow (SFF) and characterized the functions of rapidly released EVs in osteoblast and osteoclast regulation. Our study demonstrates that SFF stimulates intracellular calcium response in OCY454 cells and further induces sclerostin, osteoprotegerin (OPG), receptor activator of NF-κB ligand (RANKL) inside or outside EVs to regulate osteoblast and osteoclast activities. This load-induced protein and EVs release is load-duration dependent. Moreover, stimulated osteocytes rapidly regulate osteoclast maturation through EVs capsulated RANKL. In contrast, other regulating proteins, OPG, and sclerostin, are mainly released directly into the medium without EV capsulation.

Sensory and molecular insights into the bitterness of Wuyi rock tea

Wuyi Rock Tea (WRT) is widely appreciated for its unique rocky flavor and floral essence. However, the characterization of taste attributes, particularly bitterness, in this premium tea remains largely underexplored. This study aims to assess the perception of bitterness in WRT through an integrated approach, including sensory evaluation, phenolic compound analysis, and cell-based calcium imaging assay. Sensory evaluation revealed distinct bitterness intensities among nine selected typical WRT samples. Utilizing UHPLC-Q-Orbitrap-MS, 54 phenolics were tentatively identified, comprising of 24 flavanols, 18 flavonols, and 12 phenolic acids. The cell-based calcium imaging assay revealed diverse intracellular calcium responses and half-maximum effective concentration (EC50) values across the tested samples. Notably, correlation analysis unveiled a strong negative correlation between sensory scores and EC50 values. Furthermore, 11 individual phenolic compounds, such as epigallocatechin gallate and epicatechin gallate, demonstrated significant correlation with sensory scores and bitter taste receptor activation, suggesting their potential role as key contributors shaping the bitter taste perception of WRT. This study provides comprehensive insights into the nuanced bitterness of WRT, bridging sensory and molecular perspectives to enhance our understanding of the taste profile of this premium tea.

Blocking Pannexin 1 Channels Alleviates Peripheral Inflammatory Pain but not Paclitaxel-Induced Neuropathy.

Pannexin1 (Panx1) is a membrane channel expressed in different cells of the nervous system and is involved in several pathological conditions, including pain and inflammation. At the central nervous system, the role of Panx1 is already well-established. However, in the periphery, there is a lack of information regarding the participation of Panx1 in neuronal sensitization. The dorsal root ganglion (DRG) is a critical structure for pain processing and modulation. For this reason, understanding the molecular mechanism in the DRG associated with neuronal hypersensitivity has become highly relevant to discovering new possibilities for pain treatment. Here, we aimed to investigate the role of Panx1 in acute nociception and peripheral inflammatory and neuropathic pain by using two different approaches. Rats were treated with a selective Panx1 blocker peptide (10Panx) into L5-DRG, followed by ipsilateral intraplantar injection of carrageenan, formalin, or capsaicin. DRG neuronal cells were pre-treated with 10Panx and stimulated by capsaicin to evaluate calcium influx. Panx1 knockout mice (Panx1-KO) received carrageenan or capsaicin into the paw and paclitaxel intraperitoneally. The von Frey test was performed to measure the mechanical threshold of rats' and mice's paws before and after each treatment. Pharmacological blockade of Panx1 in the DRG of rats resulted in a dose-dependent decrease of mechanical allodynia triggered by carrageenan, and nociception decreased in the second phase of formalin. Nociceptive behavior response induced by capsaicin was significantly lower in rats treated with Panx1 blockade into DRG. Neuronal cells with Panx1 blockage showed lower intracellular calcium response than untreated cells after capsaicin administration. Accordingly, Panx1-KO mice showed a robust reduction in mechanical allodynia after carrageenan and a lower nociceptive response to capsaicin. A single dose of paclitaxel promoted acute mechanical pain in wildtype (WT) but not in Panx1-KO mice. Four doses of chemotherapy promoted chronic mechanical allodynia in both genotypes, although Panx1-KO mice had significant ablation in the first eight days. Our findings suggest that Panx1 is critical for developing peripheral inflammatory pain and acute nociception involving transient receptor potential vanilloid subtype 1 (TRPV1) but is not essential for neuropathic pain chronicity.

Reduced capsaicin-induced mechanical allodynia and neuronal responses in the dorsal root ganglion in the presence of protein tyrosine phosphatase non-receptor type 6 overexpression.

Transient Receptor Potential Vanilloid 1 (TRPV1) is a nonselective cation channel expressed by pain-sensing neurons and has been an attractive target for the development of drugs to treat pain. Recently, Src homology region two domain-containing phosphatase-1 (SHP-1, encoded by Ptpn6) was shown to dephosphorylate TRPV1 in dorsal root ganglia (DRG) neurons, which was linked with alleviating different pain phenotypes. These previous studies were performed in male rodents only and did not directly investigate the role of SHP-1 in TRPV-1 mediated sensitization. Therefore, our goal was to determine the impact of Ptpn6 overexpression on TRPV1-mediated neuronal responses and capsaicin-induced pain behavior in mice of both sexes. Twelve-week-old male and female mice overexpressing Ptpn6 (Shp1-Tg) and their wild type (WT) littermates were used. Ptpn6 overexpression was confirmed in the DRG of Shp1-Tg mice by RNA in situ hybridization and RT-qPCR. Trpv1 and Ptpn6 were found to be co-expressed in DRG sensory neurons in both genotypes. Functionally, this overexpression resulted in lower magnitude intracellular calcium responses to 200nM capsaicin stimulation in DRG cultures from Shp1-Tg mice compared to WTs. In vivo, we tested the effects of Ptpn6 overexpression on capsaicin-induced pain through a model of capsaicin footpad injection. While capsaicin injection evoked nocifensive behavior (paw licking) and paw swelling in both genotypes and sexes, only WT mice developed mechanical allodynia after capsaicin injection. We observed similar level of TRPV1 protein expression in the DRG of both genotypes, however, a higher amount of tyrosine phosphorylated TRPV1 was detected in WT DRG. These experiments suggest that, while SHP-1 does not mediate the acute swelling and nocifensive behavior induced by capsaicin, it does mediate a protective effect against capsaicin-induced mechanical allodynia in both sexes. The protective effect of SHP-1 might be mediated by TRPV1 dephosphorylation in capsaicin-sensitive sensory neurons of the DRG.

Inhibition of N-type calcium channels by phenoxyaniline and sulfonamide analogues.

Building on previous investigations, structural modifications to the neuronal calcium ion channel blocker MONIRO-1 and related compounds were conducted that included replacement of the amide linker with an aniline and isosteric sulfonamide moiety, and the previously used strategy of substitution of the guanidinium group with less hydrophilic amine functionalities. A comprehensive SAR study revealed a number of phenoxyaniline and sulfonamide compounds that were more potent or had similar potency for the CaV2.2 and CaV3.2 channel compared to MONIRO-1 when evaluated in a FLIPR-based intracellular calcium response assay. Cytotoxicity investigations indicated that the sulfonamide analogues were well tolerated by Cos-7 cells at dosages required to inhibit both calcium ion channels. The sulfonamide derivatives were the most promising CaV2.2 inhibitors developed by us to date due, possessing high stability in plasma, low toxicity (estimated therapeutic index > 10), favourable CNS MPO scores (4.0-4.4) and high potency and selectivity, thereby, making this class of compounds suitable candidates for future in vivo studies.

ADP-mediated Modulation of Intracellular Calcium Responses in Chromaffin Cells: The Role of Ectonucleoside Triphosphate Diphosphohydrolase 2 on Rat Adrenal Medulla Function.

The present study investigated the localization and the adenosine 5'-triphosphate (ATP)-degrading function of the plasma membrane-bound ecto-nucleotidase, ectonucleoside triphosphate diphosphohydrolase 2 (NTPDase2), in the rat adrenal medulla. The effect of ATP degradation product, adenosine 5'-diphosphate (ADP), on carbachol (CCh)-induced intracellular Ca2+ ([Ca2+]i) responses in adrenal chromaffin cells was examined using calcium imaging. NTPDase2-immunoreactive cells were distributed between chromaffin cells. NTPDase2-immunoreactive cells were immunoreactive for glial fibrillary acidic protein and S100B, suggesting that they were sustentacular cells. NTPDase2-immunoreactive cells surrounded chromaffin cells immunoreactive for vesicular nucleotide transporter and P2Y12 ADP-selective purinoceptors. In ATP bioluminescence assays using adrenal medullary slices, ATP was rapidly degraded and its degradation was attenuated by the NTPDase inhibitors sodium polyoxotungstate (POM-1) and 6-N, N-diethyl-d-β,γ-dibromomethylene ATP (ARL67156). ADP inhibited CCh-induced [Ca2+]i increases of chromaffin cells in adrenal medullary slices. The inhibition of CCh-induced [Ca2+]i increases by ADP was blocked by the P2Y12 purinoceptor antagonist AZD1283. CCh-induced [Ca2+]i increases were also inhibited by the P2Y1, P2Y12, and P2Y13 purinoceptor agonist 2-methylthioadenosine diphosphate trisodium (2MeSADP), in combination with the P2Y1 purinoceptor antagonist MRS2179. These results suggest that sustentacular cells express NTPDase2 to degrade ATP released from adrenal chromaffin cells, and ADP modulates the excitability of chromaffin cells via P2Y12 purinoceptors to regulate catecholamine release during preganglionic sympathetic stimuli. (J Histochem Cytochem 72: 41-60, 2024).

Dopamine and noradrenaline activate spinal astrocyte endfeet via D1-like receptors.

Astrocytes, the most abundant glial cells in the central nervous system, respond to a wide variety of neurotransmitters binding to metabotropic receptors. Here, we investigated the intracellular calcium responses of spinal cord astrocytes to dopamine and noradrenaline, two catecholamines released by specific descending pathways. In a slice preparation from the spinal cord of neonatal mice, puff application of dopamine resulted in intracellular calcium responses that remained in the endfeet. Noradrenaline induced stronger responses that also started in the endfeet but spread to neighbouring compartments. The intracellular calcium responses were unaffected by blocking neuronal activity or inhibiting various neurotransmitter receptors, suggesting a direct effect of dopamine and noradrenaline on astrocytes. The intracellular calcium responses induced by noradrenaline and dopamine were inhibited by the D1 receptor antagonist SCH 23390. We assessed the functional consequences of these astrocytic responses by examining changes in arteriole diameter. Puff application of dopamine or noradrenaline resulted in vasoconstriction of spinal arterioles. However, blocking D1 receptors or manipulating astrocytic intracellular calcium levels did not abolish the vasoconstrictions, indicating that the observed intracellular calcium responses in astrocyte endfeet were not responsible for the vascular changes. Our findings demonstrate a compartmentalized response of spinal cord astrocytes to catecholamines and expand our understanding of astrocyte-neurotransmitter interactions and their potential roles in the physiology of the central nervous system.

Induced pluripotent stem cell-derived vascular smooth muscle cells as an in vitro model of coronary spastic angina

Abstract Background Coronary spastic angina (CSA), also known as Prinzmetal’s variant angina, is a form of angina caused by coronary artery spasm. CSA is characterized by enhanced basal tone of coronary artery smooth muscle and hyperreactivity to vasoconstrictor stimuli. The vascular smooth muscle hyperreactivity is likely due to a post-receptorial cellular abnormality in the regulation of myofibril contraction, suggesting the possibility of multiple stimuli acting on various cellular receptors. However, its detailed mechanism is still unclear. To investigate it, various experiments using coronary artery smooth muscle cells obtained from the CSA patients is preferable, but it is impossible to do it clinically and ethically. Purpose The purpose of this study was to establish induced pluripotent stem cell (iPSC)-derived vascular smooth muscle cells (VSMCs) and to characterize this VSMC model for CSA research. Methods Three CSA patients with ST-segment elevation, which is a characteristic of variant angina, were recruited for this study. The isolated skin fibroblasts or peripheral blood mononuclear cells were reprogrammed into iPSCs through electroporation of episomal plasmids encoding the reprogramming genes OCT3/4, SOX2, KLF4, L-MYC, LIN28, and mouse p53DD. We differentiated mesodermal using Glycogen synthase kinase 3 inhibition and Bone morphogenetic protein 4 treatment from iPSCs and resulted in the differentiation of VSMCs by platelet-derived growth factor-BB and Activin A. The differentiation of VSMCs was confirmed by VSMC-specific gene expression in qRT–PCR and fluorescence-activated cell sorting (FACS). We examined biological features and intracellular calcium response to acetylcholine (ACh) in VSMCs obtained from 3 CSA patients and 3 healthy controls. Intracellular free Ca2+ concentration ([Ca2+]i; nM) was measured by fura-2. Results CSA iPSCs were confirmed to have normal karyotypes and pluripotency to differentiate. FACS showed that VSMCs differentiated from iPSCs exhibited smooth muscle cell marker expressions including alpha-smooth muscle actin and SM22-alpha. qRT–PCR showed that VSMCs from iPSCs had expressions of ACTA2 and TAGLN gene similar to the human coronary artery smooth muscle cells. Differentiation induction rate of VSMCs differentiated from iPSCs between CSA and control did not show significant difference. [Ca2+]i at baseline did not differ significantly between them (143 nM in CSA versus 120 nM in control, p=0.63, n=3), but peak increase in [Ca2+]i from baseline after ACh stimulation was significantly increased in CSA group compared with control (372 nM versus 177 nM, p<0.05, n=3). Conclusions iPSC-derived VSMCs obtained from CSA patients showed an enhanced intracellular calcium response to ACh, which is likely responsible for CSA phenotype. Our iPSC-derived VSMC model can be useful for elucidating the mechanism of coronary spasm and developing therapeutic strategy such as drug efficacy.

THU291 Successful Reversal Of Glucose Toxicity After DKA Precipitated By SGLT2 Inhibitor

Abstract Disclosure: H. Abdelrahman: None. B. DeMoranville: None. Case: A 40 year old man with history of NAFLD and type 2 diabetes mellitus with HbA1c 12.2% on metformin 750 mg daily, presented with diabetic ketoacidosis (DKA) with blood glucose 275 mg/dL and anion gap 24 (AG 10-12). He had been started on empagliflozin 25 mg daily four days prior as outpatient. He was treated with IV insulin and hydration per DKA protocol. Labs showed C-peptide 3.0 ng/mL (1.1-4.4 ng/mL), Anti-GAD Ab 0.01 nmol/L (<0.02 mol/L), negative anti-insulin cell Ab. He was discharged on glargine 10u qHS, lispro 2u AC plus corrective scale, and metformin 750 mg BID. On outpatient follow-up, pre-meal glucose remained under 130 mg/dL, not requiring corrective insulin. He was started on semaglutide 0.5mg weekly and insulin was discontinued. At 3 months, his HbA1c improved to 5.8%. Self-monitoring glucose levels were at goal. Discussion: This case illustrates glucotoxicity due to significant hyperglycemia causing beta-cell apoptosis and resulting in insulin deficiency. The initiation of SGLT2 inhibitors (SGLT2i) when insulin deficiency and peripheral resistance are at their peak increases risk of DKA. This patient with type 2 diabetes presented with blood glucose 275 mg/dL in DKA four days after starting empagliflozin, a SGLT2i. SGLT2i increase risk of DKA due to dehydration from glucosuria, inhibiting ketone body excretion by the kidneys, causing a state of carbohydrate deficit and hypovolemia that promotes glucagon release from alpha-cells, an increased glucagon-to-insulin ratio, and thus triggers ketogenesis.1 In glucose toxicity, intra-cellular hyperglycemia-induced molecular dysfunction results in beta-cell apoptosis. Islet cells cultured in a glucotoxic environment (20 mmol/l) had suppressed insulin content, but fully reversed the intra-cellular calcium response after one week of culturing in a euglycemic environment, demonstrating recovery of the molecular steps promoting insulin release. 2 Treatment with insulin close to euglycemic goals promotes the reversal of glucose toxicity. Our patient recovered beta-cell function several weeks after the glucotoxic episode and was able to discontinue insulin therapy. With the addition of semaglutide, a GLP-1 receptor agonist, which potentiates glucose-dependent insulin release to control post-prandial hyperglycemia, he was able to maintain euglycemia and an HbA1c 5.8%. Conclusion Patients with type 2 diabetes mellitus may present in diabetic ketoacidosis due to glucose toxicity which can be reversed with short-term insulin therapy. References 1) Nasa P, et al. Euglycemic diabetic ketoacidosis: A missed diagnosis. World J Diabetes. 2021 May 15;12(5):514-523. 2) Tariq M, et al. Prolonged culture of human pancreatic islets under glucotoxic conditions changes their acute beta cell calcium and insulin secretion glucose response curves from sigmoid to bell-shaped. Diabetologia. 2022 Dec 2. Epub ahead of print. PMID: 36459178. Presentation: Thursday, June 15, 2023

Knockdown of TRPV2 inhibits the migration of RAW264.7 cells toward low fluid shear stress region.

Our previous studies have demonstrated that macrophages (RAW264.7) have a special ability for sensing the gradient of fluid shear stress (FSS) and migrate toward the low-FSS region. However, the molecular mechanism regulating this phenomenon is still unclear. In this study, we examined the transcriptome genes in RAW264.7 cells, MC3T3-E1 osteoblasts, mesenchymal stem cells, canine renal epithelial cells, and periodontal ligament cells. The expression levels of genes related to cell migration, force transfer, and force sensitivity in the Ca2+ signaling pathway were analyzed. We observed that the transient receptor potential cation channel type 2 (TRPV2) was highly expressed in RAW264.7 cells. Furthermore, we used lentiviral transfection to knockdown TRPV2 expression in RAW264.7 cells and studied the effect of TRPV2 on the migration of RAW264.7 cells under a gradient FSS field. The results showed that compared with normal cells, TRPV2-knockdown cells had impaired ability for sensing FSS gradient to migrate toward the low-FSS region and lower intracellular calcium response to FSS stimulation. This study may reveal the molecular mechanism of regulating the directional migration of macrophages under a gradient FSS field.

Distribution of intracellular calcium during flow-induced migration of RAW264.7 cells

Cell migration is an important biological process regulated by mechanical stimulation, which leads to intracellular calcium response. Cell migration are dependent on the distribution and dynamic changes of intracellular calcium concentration. However, the temporal relation among mechanical stimulation, cell migration, and intracellular calcium distribution remains unclear. In this study, unidirectional flow and oscillatory flow were applied on osteoclast precursor RAW264.7 cells. The parameters of cell migration under fluid flow and intracellular calcium distribution along the migration or flow direction were calculated. Experimental results suggest the cells to adjust the [Ca2+]i distribution in the migration direction is independent of flow application or the reverse of flow direction, but the [Ca2+]i distribution in the flow direction is determined by the [Ca2+]i distribution-adjusting ability of cells and flow stimulation. Blocking calcium signaling pathways, namely, mechanosensitive cation-selective channels, phospholipase C, and endoplasmic reticulum, and removing extracellular calcium inhibited cell migration along the flow direction and the gradient distribution of intracellular calcium. This study provided insights into the mechanism of flow-induced cell migration and quantitative data for the recruitment of osteoclast precursors targeting the location of bone resorption.

Mammalian type opsin 5 preferentially activates G14 in Gq-type G proteins triggering intracellular calcium response

Mammalian type opsin 5 (Opn5m), a UV-sensitive G protein-coupled receptor opsin highly conserved in vertebrates, would provide a common basis for UV sensing from lamprey to humans. However, G protein coupled with Opn5m remains controversial due to variations in assay conditions and the origin of Opn5m across different reports. Here, we examined Opn5m from diverse species using an aequorin luminescence assay and Gα-KO cell line. Beyond the commonly studied major Gα classes, Gαq, Gα11, Gα14, and Gα15 in the Gq class were individually investigated in this study, as they can drive distinct signaling pathways in addition to a canonical calcium response. UV light triggered a calcium response via all the tested Opn5m proteins in 293T cells, which was abolished by Gq-type Gα deletion and rescued by cotransfection with mouse and medaka Gq-type Gα proteins. Opn5m preferentially activated Gα14 and close relatives. Mutational analysis implicated specific regions, including α3-β5 and αG-α4 loops, αG and α4 helices, and the extreme C terminus, in the preferential activation of Gα14 by Opn5m. FISH revealed co-expression of genes encoding Opn5m and Gα14 in the scleral cartilage of medaka and chicken eyes, supporting their physiological coupling. This suggests that the preferential activation of Gα14 by Opn5m is relevant for UV sensing in specific cell types.

Peptides Derived from Soybean β-Conglycinin Induce the Migration of Human Peripheral Polymorphonuclear Leukocytes.

Food-derived peptides have various biological activities. When food proteins are ingested orally, they are digested into peptides by endogenous digestive enzymes and absorbed by the immune cell-rich intestinal tract. However, little is known about the effects of food-derived peptides on the motility of human immune cells. In this study, we aimed to understand the effects of peptides derived from a soybean protein β-conglycinin on the motility of human peripheral polymorphonuclear leukocytes. We illustrated that MITL and MITLAIPVNKPGR, produced by digestion using in-vivo enzymes (trypsin and pancreatic elastase) of β-conglycinin, induces the migration of dibutyryl cAMP (Bt2 cAMP)-differentiated human promyelocytic leukemia 60 (HL-60) cells and human polymorphonuclear leukocytes in a dose- and time-dependent manner. This migration was more pronounced in Bt2 cAMP-differentiated HL-60 cells; mRNA expression of formyl peptide receptor (FPR) 1 increased significantly than in all-trans-retinoic acid (ATRA)-differentiated HL-60 cells. This migration was inhibited by tert-butoxycarbonyl (Boc)-MLP, an inhibitor of FPR, and by pretreatment with pertussis toxin (PTX). However, the effect was weak when treated with WRW4, a selective inhibitor of the FPR2. We then demonstrated that MITLAIPVNKPGR induced intracellular calcium responses in human polymorphonuclear leukocytes and Bt2 cAMP-HL60 cells. Furthermore, pre-treatment by fMLP desensitized the calcium response of MITLAIPVNKPGR in these cells. From the above, MITLAIPVNKPGR and MITL derived from soybean β-conglycinin induced polymorphonuclear leukocyte migration via the FPR1-dependent mechanism. We found chemotactic peptides to human polymorphonuclear leukocytes, which are the endogenous enzyme digests of soybean protein.

Purinergic Activation of Store-Operated Calcium Entry (SOCE) Regulates Cell Migration in Metastatic Ovarian Cancer Cells.

Store-operated calcium entry (SOCE) is an important process in calcium signaling. Its role in physiological and pathological events is well recognized. However, in cancerous systems, the importance of SOCE in relation to the degree of cancer aggressiveness, as well as its regulation by ligands such as purinergic molecules, are not well documented. This study aimed to characterize a differential effect of the P2Y2 receptor (promoted by UTP of 10 µM and inhibited by ARC118925XX of 1 µM) on intracellular calcium response between metastatic (SKOV-3) and non-metastatic (CAOV-3) ovarian cell lines in conditions of normal (1.5 mM) and zero extracellular calcium concentration. The sustained calcium influx observed exclusively in SKOV-3 cells was associated with the presence of SOCE (promoted by thapsigargin (74.81 ± 0.94 ΔF) and sensitive to 2-APB (20.60 ± 0.85 ΔF)), whereas its absence in CAOV-3 cells (26.2 ± 6.1 ΔF) was correlated with a low expression of ORAI1. The relevance of SOCE in metastatic SKOV-3 cells was further corroborated when 2-APB significantly inhibited (40.4 ± 2.8% of covered area) UTP-induced cell migration (54.6 ± 3.7% of covered area). In conclusion, our data suggest that SOCE activation elicited by the P2Y2 receptor is involved in the aggressiveness of ovarian cancer cells.

#3769 MECHANOSENSITIVE ION CHANNEL PIEZO1 MEDIATES BLOOD PRESSURE HOMEOSTASIS BY REGULATING RENIN EXPRESSION IN MICE

Abstract Background and Aims The renin-angiotensin system (RAS) plays a crucial role in the maintenance of fluid-electrolyte and blood pressure homeostasis. Renin, the step-limiting protease of the RAS, is produced, stored, and secreted by the renal juxtaglomerular (JG) cells, which are closely regulated by the blood pressure. Studies have shown that local blood flow-associated shear stress play an important role in renin expression and secretion. To date, however, the molecular identity through which JG cells respond to the blood pressure remains unclear. Method In this study, we determined the expression and subcellular localization of Piezo1 in JG cells by qPCR, Western blot, Immunofluorescence (IF), and multiplex immunohistochemistry. Then, a Fluo-4 AM-based calcium-imaging system was used to detect the dynamic changes of intracellular calcium in response to Piezo1 specific agonist Yoda1 and mechanical stress (MS)-induced by perfusion. Next, CRISPR/Cas9 technology was used to generate Piezo1 knockout JG cells to further confirm its contribution. Then, we used RNA-seq experiment to investigate the downstream signaling of Piezo1 in JG cells. Finally, we generated adeno-associated virus (AAV)-mediated kidney-specific Piezo1 knockdown mice to investigate the in vivo effect of Piezo1. Results We found that the mechanosensitive ion channel Piezo1 was co-expressed with renin in JG cells in mouse kidney slides as well as As4.1 cells, a commonly used JG cell line. Activation of Piezo1 by its agonist Yoda1 induced an intracellular calcium increase and reduced the expression of renin in these cells, while knockout of Piezo1 in JG cells abolished the effect of Yoda1. Meanwhile, fluid induced mechanical stress also led to an intracellular calcium increase and renin downregulation in wildtype but not Piezo1 knockout JG cells. Mechanistically, we demonstrated that activation of Piezo1 upregulated the Ptgs2 expression via the calcineurin-NFAT pathway and increased the production of Ptgs2 downstream molecule COX-2 and PGE2 in JG cells, which inhibited cAMP production and reduced renin expression in JG cells. In mice, we demonstrated that activation of Piezo1 significantly downregulated the blood pressure in wildtype but not kidney-specific Piezo1 knockdown mice. Conclusion In summary, these results revealed that activation of Piezo1 could lead to downregulation of the renin expression in vitro and in vivo, subsequently reduction of blood pressure, highlighting its therapeutic potential as a drug target of the renin-angiotensin system.

Impact of cryopreservation on viability, gene expression and function of enteric nervous system derived neurospheres.

Introduction: Impairment of both the central and peripheral nervous system is a major cause of mortality and disability. It varies from an affection of the brain to various types of enteric dysganglionosis. Congenital enteric dysganglionosis is characterized by the local absence of intrinsic innervation due to deficits in either migration, proliferation or differentiation of neural stem cells. Despite surgery, children's quality of life is reduced. Neural stem cell transplantation seems a promising therapeutic approach, requiring huge amounts of cells and multiple approaches to fully colonize the diseased areas completely. A combination of successful expansion and storage of neural stem cells is needed until a sufficient amount of cells is generated. This must be combined with suitable cell transplantation strategies, that cover all the area affected. Cryopreservation provides the possibility to store cells for long time, unfortunately with side effects, i.e., upon vitality. Methods: In this study we investigate the impact of different freezing and thawing protocols (M1-M4) upon enteric neural stem cell survival, protein and gene expression, and cell function. Results: Freezing enteric nervous system derived neurospheres (ENSdN) following slow-freezing protocols (M1-3) resulted in higher survival rates than flash-freezing (M4). RNA expression profiles were least affected by freezing protocols M1/2, whereas the protein expression of ENSdN remained unchanged after treatment with protocol M1 only. Cells treated with the most promising freezing protocol (M1, slow freezing in fetal calf serum plus 10% DMSO) were subsequently investigated using single-cell calcium imaging. Freezing of ENSdN did not alter the increase in intracellular calcium in response to a specific set of stimuli. Single cells could be assigned to functional subgroups according to response patterns and a significant shift towards cells responding to nicotine was observed after freezing. Discussion: The results demonstrate that cryopreservation of ENSdN is possible with reduced viability, only slight changes in protein/gene expression patterns and without an impact on the neuronal function of different enteric nervous system cell subtypes, with the exception of a subtle upregulation of cells expressing nicotinergic acetylcholine receptors. In summary, cryopreservation presents a good method to store sufficient amounts of enteric neural stem cells without neuronal impairment, in order to enable subsequent transplantation of cells into compromised tissues.

Long-term α5 GABA A receptor negative allosteric modulator treatment reduces NMDAR-mediated neuronal excitation and maintains basal neuronal inhibition

α5 subunit-containing GABA type-A receptors (α5 GABAARs) are enriched in the hippocampus and play critical roles in neurodevelopment, synaptic plasticity, and cognition. α5 GABAAR preferring negative allosteric modulators (α5 NAMs) show promise mitigating cognitive impairment in preclinical studies of conditions characterized by excess GABAergic inhibition, including Down syndrome and memory deficits post-anesthesia. However, previous studies have primarily focused on acute application or single-dose α5 NAM treatment. Here, we measured the effects of chronic (7-day) in vitro treatment with L-655,708 (L6), a highly selective α5 NAM, on glutamatergic and GABAergic synapses in rat hippocampal neurons. We previously showed that 2-day in vitro treatment with L6 enhanced synaptic levels of the glutamate NMDA receptor (NMDAR) GluN2A subunit without modifying surface α5 GABAAR expression, inhibitory synapse function, or L6 sensitivity. We hypothesized that chronic L6 treatment would further increase synaptic GluN2A subunit levels while maintaining GABAergic inhibition and L6 efficacy, thus increasing neuronal excitation and glutamate-evoked intracellular calcium responses. Immunofluorescence experiments revealed that 7-day L6 treatment slightly increased the synaptic levels of gephyrin and surface α5 GABAARs. Functional studies showed that chronic α5 NAM treatment did not alter inhibition or α5 NAM sensitivity. Surprisingly, chronic L6 exposure decreased surface levels of GluN2A and GluN2B subunits, concurrent with reduced NMDAR-mediated neuronal excitation as seen by faster synaptic decay rates and reduced glutamate-evoked calcium responses. Together, these results show that chronic in vitro treatment with an α5 NAM leads to subtle homeostatic changes in inhibitory and excitatory synapses that suggest an overall dampening of excitability.