Sodium-calcium exchanger 1 regulates epithelial cell migration via calcium-dependent extracellular signal-regulated kinase signaling

SKF96365 Inhibits Tumor Proliferation by Inducing Apoptosis and Autophagy in Human Esophageal Squamous Cell Carcinoma

Calcium channel blockers are emerging as a new generation of attractive anticancer drugs. SKF96365, originally thought to be a store-operated calcium entry (SOCE) inhibitor, is now often used as a TRPC channel blocker and is widely used in medical diagnostics. SKF96365 has shown antitumor effects on a variety of cancer cell lines. The objective of this study was to investigate the anticancer effect of SKF96365 on esophageal cancer in vivo and in vitro. Cell Counting Kit-8 (CCK-8) and colony formation were used to test the proliferation inhibition of SKF96365 on cell lines. Western blot and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining were used to detect cell apoptosis rates. In addition, we demonstrated the antitumor effect of SKF96365 in vivo in xenografted mice. As a result, SKF96365 significantly inhibited the proliferation of K510, K30, and EC9706 in vitro. SKF96365 induces apoptosis in three cell lines through the poly(adenosine diphosphate-ribose) polymerase (PARP), caspase-9, and BCL-2 pathways in a dose-dependent and time-dependent manner. Moreover, SKF96365 treatment also induced apoptosis and inhibited tumor growth in nude mice. The calcium channel TRPC1 was significantly downregulated by SKF96365. Autophagy was also induced during the treatment of SKF96365. In summary, SKF96365 induces apoptosis (PARP, caspase-9, and BCL-2) and autophagy (LC3-A/B) by inhibiting TRPC1 in esophageal cancer cells, thereby inhibiting tumor growth.

The context-dependent role of the Na+/Ca2+-exchanger (NCX) in pancreatic stellate cell migration

Pancreatic stellate cells (PSCs) that can co-metastasize with cancer cells shape the tumor microenvironment (TME) in pancreatic ductal adenocarcinoma (PDAC) by producing an excessive amount of extracellular matrix. This leads to a TME characterized by increased tissue pressure, hypoxia, and acidity. Moreover, cells within the tumor secrete growth factors. The stimuli of the TME trigger Ca2+ signaling and cellular Na+ loading. The Na+/Ca2+ exchanger (NCX) connects the cellular Ca2+ and Na+ homeostasis. The NCX is an electrogenic transporter, which shuffles 1 Ca2+ against 3 Na+ ions over the plasma membrane in a forward or reverse mode. Here, we studied how the impact of NCX activity on PSC migration is modulated by cues from the TME. NCX expression was revealed with qPCR and Western blot. [Ca2+]i, [Na+]i, and the cell membrane potential were determined with the fluorescent indicators Fura-2, Asante NaTRIUM Green-2, and DiBAC4(3), respectively. PSC migration was quantified with live-cell imaging. To mimic the TME, PSCs were exposed to hypoxia, pressure, acidic pH (pH 6.6), and PDGF. NCX-dependent signaling was determined with Western blot analyses. PSCs express NCX1.3 and NCX1.9. [Ca2+]i, [Na+]i, and the cell membrane potential are 94.4 nmol/l, 7.4 mmol/l, and - 39.8 mV, respectively. Thus, NCX1 usually operates in the forward (Ca2+ export) mode. NCX1 plays a differential role in translating cues from the TME into an altered migratory behavior. When NCX1 is operating in the forward mode, its inhibition accelerates PSC migration. Thus, NCX1-mediated extrusion of Ca2+ contributes to a slow mode of migration of PSCs.

The role of the Na+/Ca2+-exchanger (NCX) in cancer-associated fibroblasts

Cancer is characterized by uncontrolled growth, invasion, and metastasis. In addition to solid cancer cells, cancer-associated fibroblasts (CAFs) play important roles in cancer pathophysiology. They arise from "healthy" cells but get manipulated by solid cancer cells to supply them and develop a tumor microenvironment (TME) that protects the cancer cells from the immune defense. A wide variety of cell types can differentiate into CAFs, including fibroblasts, endothelial cells, and epithelial cells. Precise Ca²⁺ regulation is essential for each cell including CAFs. The electrogenic Na⁺/Ca²⁺ exchanger (NCX) is one of the ubiquitously expressed regulatory Ca²⁺ transport proteins that rapidly responds to changes of the intracellular ion concentrations. Its transport function is also influenced by the membrane potential and thereby indirectly by the activity of ion channels. NCX transports Ca²⁺ out of the cell (forward mode) or allows its influx (reverse mode), always in exchange for 3 Na⁺ ions that are moved into the opposite direction. In this review, we discuss the functional roles NCX has in CAFs and how these depend on the properties of the TME. NCX activity modifies migration and leads to a reduced proliferation and apoptosis. The effect of the NCX in fibrosis is still largely unknown.

Wound closure, angiogenesis and antibacterial behaviors of tetracalcium phosphate/hydroxyethyl cellulose/hyaluronic acid/gelatin composite dermal scaffolds

Polymeric and tetracalcium phosphate (TTCP)-containing polymeric scaffolds were fabricated using a freeze-drying technique, with a homogenous solution of hydroxyethyl cellulose (HEC)/hyaluronic acid (HA)/gelatin (G) or suspension of 15 or 20% TTCP) particles in HEC/HA/G solution. The morphology, phase composition, chemical bands, and swelling behavior of the scaffold were determined. In vitro fibroblast cell viability and migration potential of the scaffolds were determined by MTT, live/dead staining, and scratch assay for wound healing. The in vivo chick embryo angiogenesis test was also carried out. Finally, the initial antibacterial activity of the scaffolds was determined using Staphylococcus aureus. The scaffolds exhibited an enormous porous structure in which the size of pores increased by the presence of TTCP particles. While the polymeric scaffold was amorphous, the formation of low crystalline hydroxyapatite phase and the initial TTCP particles was determined in the composition of TTCP-added scaffolds. TTCP increased swelling behavior of the polymeric scaffold in PBS. The results demonstrated that the amount of TTCP was a crucial factor in cell life. A high concentration of TTCP could restrict cell viability, although all the scaffolds were nontoxic. The scratch assessments determined better cell migration and wound closure in treating with TTCP-containing scaffolds so that after 24 h, a wound closure of 100% was observed. Furthermore, TTCP-incorporated scaffolds significantly improved the angiogenesis, in the chick embryo test. The presence of TTCP had a significant effect on reducing the bacterial activity and 20% TTCP-containing scaffold exhibited better antibacterial activity than the others.

Effect of C reactive protein on the sodium-calcium exchanger 1 in cardiomyocytes

Numerous previous studies have found that C-reactive protein (CRP) is associated with cardiac arrhythmia and cardiac remodeling. However, the underlying mechanisms of this association remain unclear. Sodium-calcium exchanger 1 (NCX1) serves an important role in the regulation of intracellular calcium concentration, which is closely related with cardiac arrhythmia and cardiac remodeling. The present study aimed to evaluate the effects of CRP on NCX1 and intracellular calcium concentration in cardiomyocytes. Primary neonatal mouse ventricular cardiomyocytes were cultured and treated with varying concentrations of CRP (0, 5, 10, 20 and 40 µg/ml). The cardiomyocytes were also treated with NF-κB-specific inhibitor PTDC and a specific inhibitor of the reverse NCX1 KB-R7943 before their intracellular calcium concentrations were measured. mRNA and protein expression levels of NCX1 were detected by reverse transcription-quantitative PCR and western blotting, respectively and intracellular calcium concentration was evaluated by flow cytometry. CRP treatment significantly increased mRNA and protein expression levels of NCX1 in myocytes (P=0.024), as well as intracellular calcium concentration (P=0.01). These results were significantly attenuated by the NF-κB-specific inhibitor PDTC and a specific inhibitor of the reverse NCX1, KB-R7943. CRP significantly upregulated NCX1 expression and increased intracellular calcium concentration in cardiomyocytes via the NF-κB pathway, suggesting that CRP may serve a pro-arrhythmia role via direct influence on the calcium homeostasis of cardiomyocytes.

The Na+, K+-ATPase β1 subunit regulates epithelial tight junctions via MRCKα

An intact lung epithelial barrier is essential for lung homeostasis. The Na⁺, K⁺-ATPase (NKA), primarily serving as an ion transporter, also regulates epithelial barrier function via modulation of tight junctions. However, the underlying mechanism is not well understood. Here, we show that overexpression of the NKA β1 subunit upregulates the expression of tight junction proteins, leading to increased alveolar epithelial barrier function by an ion transport–independent mechanism. Using IP and mass spectrometry, we identified a number of unknown protein interactions of the β1 subunit, including a top candidate, myotonic dystrophy kinase–related cdc42-binding kinase α (MRCKα), which is a protein kinase known to regulate peripheral actin formation. Using a doxycycline-inducible gene expression system, we demonstrated that MRCKα and its downstream activation of myosin light chain is required for the regulation of alveolar barrier function by the NKA β1 subunit. Importantly, MRCKα is expressed in both human airways and alveoli and has reduced expression in patients with acute respiratory distress syndrome (ARDS), a lung illness that can be caused by multiple direct and indirect insults, including the infection of influenza virus and SARS-CoV-2. Our results have elucidated a potentially novel mechanism by which NKA regulates epithelial tight junctions and have identified potential drug targets for treating ARDS and other pulmonary diseases that are caused by barrier dysfunction.

Role of endogenous ouabain in the etiology of bipolar disorder

Background

Bipolar disorder is a severe psychiatric illness with poor prognosis and problematic and suboptimal treatments. Understanding the pathoetiologic mechanisms may improve treatment and outcomes.

Discussion

Dysregulation of cationic homeostasis is the most reproducible aspect of bipolar pathophysiology. Correction of ionic balance is the universal mechanism of action of all mood stabilizing medications. Recent discoveries of the role of endogenous sodium pump modulators (which include ‘endogenous ouabain’) in regulation of sodium and potassium distribution, inflammation, and activation of key cellular second messenger systems that are important in cell survival, and the demonstration that these stress-responsive chemicals may be dysregulated in bipolar patients, suggest that these compounds may be candidates for the coupling of environmental stressors and illness onset. Specifically, individuals with bipolar disorder appear to be unable to upregulate endogenous ouabain under conditions that require it, and therefore may experience a relative deficiency of this important regulatory hormone. In the absence of elevated endogenous ouabain, neurons are unable to maintain their normal resting potential, become relatively depolarized, and are then susceptible to inappropriate activation. Furthermore, sodium pump activity appears to be necessary to prevent inflammatory signals within the central nervous system. Nearly all available data currently support this model, but additional studies are required to solidify the role of this system.

Conclusion

Endogenous ouabain dysregulation appears to be a reasonable candidate for understanding the pathophysiology of bipolar disorder.

The Role of Calmodulin in Tumor Cell Migration, Invasiveness, and Metastasis

Calmodulin (CaM) is the principal Ca²⁺ sensor protein in all eukaryotic cells, that upon binding to target proteins transduces signals encoded by global or subcellular-specific changes of Ca²⁺ concentration within the cell. The Ca²⁺/CaM complex as well as Ca²⁺-free CaM modulate the activity of a vast number of enzymes, channels, signaling, adaptor and structural proteins, and hence the functionality of implicated signaling pathways, which control multiple cellular functions. A basic and important cellular function controlled by CaM in various ways is cell motility. Here we discuss the role of CaM-dependent systems involved in cell migration, tumor cell invasiveness, and metastasis development. Emphasis is given to phosphorylation/dephosphorylation events catalyzed by myosin light-chain kinase, CaM-dependent kinase-II, as well as other CaM-dependent kinases, and the CaM-dependent phosphatase calcineurin. In addition, the role of the CaM-regulated small GTPases Rac1 and Cdc42 (cell division cycle protein 42) as well as CaM-binding adaptor/scaffold proteins such as Grb7 (growth factor receptor bound protein 7), IQGAP (IQ motif containing GTPase activating protein) and AKAP12 (A kinase anchoring protein 12) will be reviewed. CaM-regulated mechanisms in cancer cells responsible for their greater migratory capacity compared to non-malignant cells, invasion of adjacent normal tissues and their systemic dissemination will be discussed, including closely linked processes such as the epithelial–mesenchymal transition and the activation of metalloproteases. This review covers as well the role of CaM in establishing metastatic foci in distant organs. Finally, the use of CaM antagonists and other blocking techniques to downregulate CaM-dependent systems aimed at preventing cancer cell invasiveness and metastasis development will be outlined.

TRPV1 translocated to astrocytic membrane to promote migration and inflammatory infiltration thus promotes epilepsy after hypoxic ischemia in immature brain

BACKGROUND

Neonatal hypoxic-ischemic brain damage (HIBD), a leading cause of neonatal mortality, has intractable sequela such as epilepsy that seriously affected the life quality of HIBD survivors. We have previously shown that ion channel dysfunction in the central nervous system played an important role in the process of HIBD-induced epilepsy. Therefore, we continued to validate the underlying mechanisms of TRPV1 as a potential target for epilepsy.

METHODS

Neonatal hypoxic ischemia and oxygen-glucose deprivation (OGD) were used to simulate HIBD in vivo and in vitro. Primarily cultured astrocytes were used to assess the expression of TRPV1, glial fibrillary acidic protein (GFAP), cytoskeletal rearrangement, and inflammatory cytokines by using Western blot, q-PCR, and immunofluorescence. Furthermore, brain electrical activity in freely moving mice was recorded by electroencephalography (EEG). TRPV1 current and neuronal excitability were detected by whole-cell patch clamp.

RESULTS

Astrocytic TRPV1 translocated to the membrane after OGD. Mechanistically, astrocytic TRPV1 activation increased the inflow of Ca²⁺, which promoted G-actin polymerized to F-actin, thus promoted astrocyte migration after OGD. Moreover, astrocytic TRPV1 deficiency decreased the production and release of pro-inflammatory cytokines (TNF, IL-6, IL-1β, and iNOS) after OGD. It could also dramatically attenuate neuronal excitability after OGD and brain electrical activity in HIBD mice. Behavioral testing for seizures after HIBD revealed that TRPV1 knockout mice demonstrated prolonged onset latency, shortened duration, and decreased seizure severity when compared with wild-type mice.

CONCLUSIONS

Collectively, TRPV1 promoted astrocyte migration thus helped the infiltration of pro-inflammatory cytokines (TNF, IL-1β, IL-6, and iNOS) from astrocytes into the vicinity of neurons to promote epilepsy. Our study provides a strong rationale for astrocytic TRPV1 to be a therapeutic target for anti-epileptogenesis after HIBD.

Essential role of Na+/Ca2+ exchanger 1 in smoking-induced growth and migration of esophageal squamous cell carcinoma

Tobacco-derived carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) is a major environmental risk factor for the pathogenesis of human esophageal squamous cell carcinoma (ESCC). However, the molecular mechanisms by which tobacco induces ESCC are not well understood. Na+/Ca2+ exchanger 1 (NCX1) is a plasma membrane transporter protein that plays an essential role in maintaining cytosolic Ca²⁺ ([Ca²⁺]_cyt) homeostasis under physiological conditions and is implicated in tumorigenesis as well. In this study, we found that NCX1 expression was significantly higher in ESCC primary tissues compared to the noncancerous tissues and was overexpressed in tumor samples from the smoking patients. The expression of NCX1 proteins was also significantly higher in human ESCC cell lines compared to normal esophageal epithelial cell line. Moreover, NNK potentiated the [Ca²⁺]_cyt signaling induced by removal of extracellular Na⁺, which was abolished by KB-R7943 or SN-6. NNK dose-dependently promoted proliferation and migration of human ESCC cells induced by NCX1 activation. Therefore, NCX1 expression correlates with the smoking status of ESCC patients, and NNK activates the Ca²⁺ entry mode of NCX1 in ESCC cells, leading to cell proliferation and migration. Our findings suggest NCX1 protein is a novel potential target for ESCC therapy.

Knockdown of sodium-calcium exchanger 1 induces epithelial-to-mesenchymal transition in kidney epithelial cells

Mesenchymal-to-epithelial transition (MET) and epithelial-to-mesenchymal transition (EMT) are important processes in kidney development. Failure to undergo MET during development leads to the initiation of Wilms tumor, whereas EMT contributes to the development of renal cell carcinomas (RCC). The role of calcium regulators in governing these processes is becoming evident. We demonstrated earlier that Na⁺/Ca²⁺ exchanger 1 (NCX1), a major calcium exporter in renal epithelial cells, regulates epithelial cell motility. Here, we show for the first time that NCX1 mRNA and protein expression was down-regulated in Wilms tumor and RCC. Knockdown of NCX1 in Madin-Darby canine kidney cells induced fibroblastic morphology, increased intercellular junctional distance, and induced paracellular permeability, loss of apico-basal polarity in 3D cultures, and anchorage-independent growth, accompanied by expression of mesenchymal markers. We also provide evidence that NCX1 interacts with and anchors E-cadherin to the cell surface independent of NCX1 ion transport activity. Consistent with destabilization of E-cadherin, NCX1 knockdown cells showed an increase in β-catenin nuclear localization, enhanced transcriptional activity, and up-regulation of downstream targets of the β-catenin signaling pathway. Taken together, knockdown of NCX1 in Madin-Darby canine kidney cells alters epithelial morphology and characteristics by destabilization of E-cadherin and induction of β-catenin signaling.

A novel de novo mutation in ATP1A3 and childhood-onset schizophrenia

We describe a child with onset of command auditory hallucinations and behavioral regression at 6 yr of age in the context of longer standing selective mutism, aggression, and mild motor delays. His genetic evaluation included chromosomal microarray analysis and whole-exome sequencing. Sequencing revealed a previously unreported heterozygous de novo mutation c.385G>A in ATP1A3, predicted to result in a p.V129M amino acid change. This gene codes for a neuron-specific isoform of the catalytic α-subunit of the ATP-dependent transmembrane sodium–potassium pump. Heterozygous mutations in this gene have been reported as causing both sporadic and inherited forms of alternating hemiplegia of childhood and rapid-onset dystonia parkinsonism. We discuss the literature on phenotypes associated with known variants in ATP1A3, examine past functional studies of the role of ATP1A3 in neuronal function, and describe a novel clinical presentation associated with mutation of this gene.

TXNIP/TRX/NF-κB and MAPK/NF-κB pathways involved in the cardiotoxicity induced by Venenum Bufonis in rats

Venenum Bufonis (VB) is a widely used traditional medicine with serious cardiotoxic effects. The inflammatory response has been studied to clarify the mechanism of the cardiotoxicity induced by VB for the first time. In the present study, Sprague Dawley (SD) rats, were administered VB (100, 200, and 400 mg/kg) intragastrically, experienced disturbed ECGs (lowered heart rate and elevated ST-segment), increased levels of serum indicators (creatine kinase (CK), creatine kinase isoenzyme-MB (CK-MB), alanine aminotransferase (ALT), aspartate aminotransferase (AST)) and serum interleukin (IL-6, IL-1β, TNF-α) at 2 h, 4 h, 6 h, 8 h, 24 h, and 48 h, which reflected that an inflammatory response, together with cardiotoxicity, were involved in VB-treated rats. In addition, the elevated serum level of MDA and the down-regulated SOD, CAT, GSH, and GPx levels indicated the appearance of oxidative stress in the VB-treated group. Furthermore, based on the enhanced expression levels of TXNIP, p-NF-κBp65, p-IκBα, p-IKKα, p-IKKβ, p-ERK, p-JNK, and p-P38 and the obvious myocardial degeneration, it is proposed that VB-induced cardiotoxicity may promote an inflammatory response through the TXNIP/TRX/NF-κB and MAPK/NF-κB pathways. The observed inflammatory mechanism induced by VB may provide a theoretical reference for the toxic effects and clinical application of VB.

SKF-96365 activates cytoprotective autophagy to delay apoptosis in colorectal cancer cells through inhibition of the calcium/CaMKIIγ/AKT-mediated pathway

Store-operated Ca(2+) entry (SOCE) inhibitors are emerging as an attractive new generation of anti-cancer drugs. Here, we report that SKF-96365, an SOCE inhibitor, exhibits potent anti-neoplastic activity by inducing cell-cycle arrest and apoptosis in colorectal cancer cells. In the meantime, SKF-96365 also induces cytoprotective autophagy to delay apoptosis by preventing the release of cytochrome c (cyt c) from the mitochondria into the cytoplasm. Mechanistically, SKF-96365 treatment inhibited the calcium/calmodulin-dependent protein kinase IIγ (CaMKIIγ)/AKT signaling cascade in vitro and in vivo. Overexpression of CaMKIIγ or AKT abolished the effects of SKF-96365 on cancer cells, suggesting a critical role of the CaMKIIγ/AKT signaling pathway in SFK-96365-induced biological effects. Moreover, Hydroxychloroquine (HCQ), an FDA-approved drug used to inhibit autophagy, could significantly augment the anti-cancer effect of SFK-96365 in a mouse xenograft model. To our best knowledge, this is the first report to demonstrate that calcium/CaMKIIγ/AKT signaling can regulate apoptosis and autophagy simultaneously in cancer cells, and the combination of the SOCE inhibitor SKF-96365 with autophagy inhibitors represents a promising strategy for treating patients with colorectal cancer.