Ca2+ signaling, intracellular pH and cell volume in cell proliferation

STIM1 functions as a proton sensor to coordinate cytosolic pH with store-operated calcium entry

The meticulous regulation of intracellular pH (pHi) is crucial for maintaining cellular function and homeostasis, impacting physiological processes such as heart rhythm, cell migration, proliferation, and differentiation. Dysregulation of pHi is implicated in various pathologies such as arrhythmias, cancer, and neurodegenerative diseases. Here, we explore the role of STIM1, an ER calcium (Ca2+) sensor mediating Store Operated Ca2+ Entry (SOCE), in sensing pHi changes. Our study reveals that STIM1 functions as a sensor for pHi changes, independent of its Ca2+-binding state. Through comprehensive experimental approaches including confocal microscopy, FRET-based sensors, and mutagenesis, we demonstrate that changes in pHi induce conformational alterations in STIM1, thereby modifying its subcellular localization and activity. We identify two conserved histidines within STIM1 essential for sensing pHi shifts. Moreover, intracellular alkalization induced by agents such as Angiotensin II or NH4Cl enhances STIM1-mediated SOCE, promoting cardiac hypertrophy. These findings reveal a novel facet of STIM1 as a multi-modal stress sensor that coordinates cellular responses to both Ca2+ and pH fluctuations. This dual functionality underscores its potential as a therapeutic target for diseases associated with pH and Ca2+ dysregulation.

Increased activity of epithelial Cdc42 Rho GTPase and tight junction permeability in the Cftr knockout intestine

Increased intestinal permeability is a manifestation of cystic fibrosis (CF) in people with CF (pwCF) and in CF mouse models. CF transmembrane conductance regulator knockout (Cftr KO) mouse intestine exhibits increased proliferation and Wnt/β-catenin signaling relative to wild-type mice (WT). Since the Rho GTPase Cdc42 plays a central role in intestinal epithelial proliferation and tight junction remodeling, we hypothesized that Cdc42 may be altered in the Cftr KO crypts. Immunofluorescence showed distinct tight junction localization of Cdc42 in Cftr KO fresh crypts and enteroids, the latter indicating an epithelial-autonomous feature. Quantitative PCR and immunoblots revealed similar expression of Cdc42 in the Cftr KO crypts/enteroids relative to WT, whereas pulldown assays showed increased GTP-bound (active) Cdc42 in proportion to total Cdc42 in Cftr KO enteroids. Cdc42 activity in the Cftr KO and WT enteroids could be reduced by inhibition of the Wnt transducer Disheveled. With the use of a dye permeability assay, Cftr KO enteroids exhibited increased paracellular permeability to 3 kDa dextran relative to WT. Leak permeability and Cdc42 tight junction localization were reduced to a greater extent by inhibition of Wnt/β-catenin signaling with endo-IWR1 in Cftr KO relative to WT enteroids. Increased proliferation or inhibition of Cdc42 activity with ML141 in WT enteroids had no effect on permeability. In contrast, inhibition of Cdc42 with ML141 increased permeability to both 3 kDa dextran and tight junction impermeant 500 kDa dextran in Cftr KO enteroids. These data suggest that increased constitutive Cdc42 activity may alter the stability of paracellular permeability in Cftr KO crypt epithelium.NEW & NOTEWORTHY Increased tight junction localization and GTP-bound activity of the Rho GTPase Cdc42 was identified in small intestinal crypts and enteroids of cystic fibrosis (CF) transmembrane conductance regulator knockout (Cftr KO) mice. The increase in epithelial Cdc42 activity was associated with increased Wnt signaling. Paracellular flux of an uncharged solute (3 kDa dextran) in Cftr KO enteroids indicated a moderate leak permeability under basal conditions that was strongly exacerbated by Cdc42 inhibition. These findings suggest increased activity of Cdc42 in the Cftr KO intestine underlies alterations in intestinal permeability.

Novel Organic-Inorganic Nanocomposite Hybrids Based on Bioactive Glass Nanoparticles and Their Enhanced Osteoinductive Properties

Inorganic-organic hybrid biomaterials have been proposed for bone tissue repair, with improved mechanical flexibility compared with scaffolds fabricated from bioceramics. However, obtaining hybrids with osteoinductive properties equivalent to those of bioceramics is still a challenge. In this work, we present for the first time the synthesis of a class II hybrid modified with bioactive glass nanoparticles (nBGs) with osteoinductive properties. The nanocomposite hybrids were produced by incorporating nBGs in situ into a polytetrahydrofuran (PTHF) and silica (SiO2) hybrid synthesis mixture using a combined sol-gel and cationic polymerization method. nBGs ~80 nm in size were synthesized using the sol-gel technique. The structure, composition, morphology, and mechanical properties of the resulting materials were characterized using ATR-FTIR, 29Si MAS NMR, SEM-EDX, AFM, TGA, DSC, mechanical, and DMA testing. The in vitro bioactivity and degradability of the hybrids were assessed in simulated body fluid (SBF) and PBS, respectively. Cytocompatibility with mesenchymal stem cells was assessed using MTS and cell adhesion assays. Osteogenic differentiation was determined using the alkaline phosphatase activity (ALP), as well as the gene expression of Runx2 and Osterix markers. Hybrids loaded with 5, 10, and 15% of nBGs retained the mechanical flexibility of the PTHF-SiO2 matrix and improved its ability to promote the formation of bone-like apatite in SBF. The nBGs did not impair cell viability, increased the ALP activity, and upregulated the expression of Runx2 and Osterix. These results demonstrate that nBGs are an effective osteoinductive nanoadditive for the production of class II hybrid materials with enhanced properties for bone tissue regeneration.

Potential role of lncRNA in impairing cellular properties of human neural progenitor cells following exposure to Zika virus E protein

Zika virus (ZIKV) infection during the first trimester of the pregnancy may lead to Congenital zika syndrome in the neonates. The viral infection hampers foetal brain development and causes microcephaly. Human neural progenitor cells (hNPCs) play an important role in brain development, however they are highly susceptible to ZIKV infection. In this study, we elucidated the molecular mechanisms that lead to cellular alterations in hNPCs due to ZIKV E-protein. We investigated proliferation, differentiation, migration and inflammation in hNPCs, which may lead to microcephaly. In our study, we found that ZIKV E-protein causes cell cycle arrest, decrease in proliferation and increase in mitotic length of the dividing hNPCs. We observed CyclinD1 and upstream molecules (p21 and p53) of the pathway are dysregulated, and intracellular calcium at basal level as well as upon ATP stimulation were reduced following over expression of ZIKV E-protein. ZIKV E-protein transfected hNPCs exhibited pre-mature differentiation with pro-neural genes upregulated. Furthermore, ZIKV E-protein disrupted migrational properties of hNPCs and caused elevated levels of inflammatory chemokines and cytokines. To gain insights into molecular mechanisms of these effects on hNPCs, we explored the possible involvement of long non coding RNAs in ZIKV neuropathogenesis. We have shortlisted lncRNAs associated with differentially expressed genes from publicly available transcriptomic data and found some of those lncRNAs are differentially expressed upon E-protein transfection of hNPCs. Gene ontology analysis suggest these lncRNAs play an important role in regulation of viral life cycle, host's defence response and cell proliferation.

Novel differential calcium regulation of hematopoietic stem and progenitor cells under physiological low oxygen conditions

Low oxygen bone marrow (BM) niches (~1%-4% low O₂ ) provide critical signals for hematopoietic stem/progenitor cells (HSC/HSPCs). Our presented data are the first to investigate live, sorted HSC/HSPCs in their native low O₂ conditions. Transcriptional and proteomic analysis uncovered differential Ca²⁺ regulation that correlated with overlapping phenotypic populations consisting of robust increases of cytosolic and mitochondrial Ca²⁺ , ABC transporter (ABCG2) expression and sodium/hydrogen exchanger (NHE1) expression in live, HSC/HSPCs remaining in constant low O_2. We identified a novel Ca²⁺ high population in HSPCs predominantly detected in low O₂ that displayed enhanced frequency of phenotypic LSK/LSKCD150 in low O₂ replating assays compared to Ca²⁺ low populations. Inhibition of the Ca²⁺ regulator NHE1 (Cariporide) resulted in attenuation of both the low O₂ induced Ca²⁺ high population and subsequent enhanced maintenance of phenotypic LSK and LSKCD150 during low O₂ replating. These data reveal multiple levels of differential Ca²⁺ regulation in low O₂ resulting in phenotypic, signaling, and functional consequences in HSC/HSPCs.

Influence of Molecular Weight and Grafting Density of PEG on the Surface Properties of Polyurethanes and Their Effect on the Viability and Morphology of Fibroblasts and Osteoblasts

Grafting polyethylene glycol (PEG) onto a polymer's surface is widely used to improve biocompatibility by reducing protein and cell adhesion. Although PEG is considered to be bioinert, its incorporation onto biomaterials has shown to improve cell viability depending on the amount and molecular weight (MW) used. This phenomenon was studied here by grafting PEG of three MW onto polyurethane (PU) substrata at three molar concentrations to assess their effect on PU surface properties and on the viability of osteoblasts and fibroblasts. PEG formed a covering on the substrata which increased the hydrophilicity and surface energy of PUs. Among the results, it was observed that osteoblast viability increased for all MW and grafting densities of PEG employed compared with unmodified PU. However, fibroblast viability only increased at certain combinations of MW and grafting densities of PEG, suggesting an optimal level of these parameters. PEG grafting also promoted a more spread cell morphology than that exhibited by unmodified PU; nevertheless, cells became apoptotic-like as PEG MW and grafting density were increased. These effects on cells could be due to PEG affecting culture medium pH, which became more alkaline at higher MW and concentrations of PEG. Results support the hypothesis that surface energy of PU substrates can be tuned by controlling the MW and grafting density of PEG, but these parameters should be optimized to promote cell viability without inducing apoptotic-like behavior.

TMEM16A as a potential treatment target for head and neck cancer

Transmembrane protein 16A (TMEM16A) forms a plasma membrane-localized Ca²⁺-activated Cl- channel. Its gene has been mapped to an area on chromosome 11q13, which is amplified in head and neck squamous cell carcinoma (HNSCC). In HNSCC, TMEM16A overexpression is associated with not only high tumor grade, metastasis, low survival, and poor prognosis, but also deterioration of clinical outcomes following platinum-based chemotherapy. Recent study revealed the interaction between TMEM16A and transforming growth factor-β (TGF-β) has an indirect crosstalk in clarifying the mechanism of TMEM16A-induced epithelial-mesenchymal transition. Moreover, human papillomavirus (HPV) infection can modulate TMEM16A expression along with epidermal growth factor receptor (EGFR), whose phosphorylation has been reported as a potential co-biomarker of HPV-positive cancers. Considering that EGFR forms a functional complex with TMEM16A and is a co-biomarker of HPV, there may be crosstalk between TMEM16A expression and HPV-induced HNSCC. EGFR activation can induce programmed death ligand 1 (PD-L1) synthesis via activation of the nuclear factor kappa B pathway and JAK/STAT3 pathway. Here, we describe an interplay among EGFR, PD-L1, and TMEM16A. Combination therapy using TMEM16A and PD-L1 inhibitors may improve the survival rate of HNSCC patients, especially those resistant to anti-EGFR inhibitor treatment. To the best of our knowledge, this is the first review to propose a biological validation that combines immune checkpoint inhibition with TMEM16A inhibition.

A multi-centre, single-blinded randomised controlled clinical trial evaluating the effect of resorbable glass fibre matrix in the treatment of diabetic foot ulcers

Diabetic foot ulcers (DFUs) are at risk for detrimental complications even with current, standard of care (SOC) treatments. The primary objective of this randomised controlled trial was to compare a unique resorbable glass microfiber matrix (Mirragen; Advanced Wound Matrix [BBGFM]; ETS Wound Care, Rolla, Missouri) compared with a standard of care group (SOC, collagen alginate dressing) at 12 weeks. Both groups received standard diabetic foot care including glucose monitoring, weekly debridements when needed and an offloading device. The primary endpoint was proportion of full‐thickness, non‐infected, non‐ischaemic wounds healed at 12 weeks, with secondary endpoints including percent area reduction (PAR) and changes in Semmes‐Weinstein monofilament testing. The result illustrated in the intent‐to‐treat analysis at 12 weeks showed that 70% (14/20) of the BBGFM‐treated DFUs healed compared with 25% (5/20) treated with SOC alone (adjusted P = .006). Mean PAR at 12 weeks was 79% in the BBGFM group compared with 37% in the SOC group (adjusted P = .027). Mean change in neuropathic score between baseline and up to 12 weeks of treatment was 2.0 in the BBGFM group compared with −0.6 in the SOC group where positive improvement in scores are better (adjusted P = .008). The mean number of BBGFM applications was 6.0. In conclusion, adding BBGFM to SOC significantly improved wound healing with no adverse events related to treatment compared with SOC alone.

Expression of SSEA-4 and Oct-4 from somatic cells in primary mouse gastric cell culture induced by brief strong acid

Environmental changes can stress and alter biology at the molecular and cellular level. For example, metal-protein interaction is a classic physic and biological property of nature, which is fundamentally influenced by acidity. Here, we report a unique cellular reprogramming phenomenon in that a brief strong acid treatment induced the expression of pluripotent stem cell (PSC) markers. We used strong acid to briefly challenge mix-cultured gastric cells, and then subcultured survived cells in a normal cell culture medium. We found that survival acid-treated cells expressed PSC markers detected by commonly used pluripotent antibodies such as SSEA-4 and Oct4. In addition, we observed that the survived cells from the acid challenge grew faster during the second and third weeks of subculture and had a relative short doubling time (DT) than the controls. PSC marker-labeled 'older' cells also presented immature cell-like morphology with some having marker Oct4 in the nucleus. Finally, the expression of the markers appeared to be sensitive to metal ion chelation. Removal of the metals during a brief acid treatment reduced pluripotent marker-positive cells, suggesting the dissociation of metals from metal-binding proteins may be a factor involved in the induction of stem cell markers. Our findings reveal that somatic cells appear to possess a plasticity feature to express pluripotent marker proteins or to select cell subpopulations that express pluripotent marker proteins when cells are transiently exposed to strong acid. It opens new directions for understanding conserved regulatory mechanisms involved in cellular survival under stressful stimulation.

Hemogasometric and biochemical changes caused by diets with high negative cation-anion balance in dairy cows

Abstract This study aimed to evaluate hemogasometric and metabolic indicators in the first postpartum hours of dairy cows that received different cation-anion diets in the prepartum period. Holstein cows (n=14), multiparous, were divided into two groups: (1) acidogenic diet (DA -27.13 mEq/100 g of DM) (n=7) and (2) neutral diet (DN -3.25 mEq/100 g of DM) (n=7), provided from 30 days before the expected calving. Urine samples were collected every three days from the beginning of supplementation until the day of delivery for pH verification. Blood samples were collected at 0, 6, 12, 24, 36, 48, 60 and 72 h postpartum for hemogasometric and biochemical analyses. The animals that received DA presented lower urinary pH. The serum concentration of total calcium, ionized calcium and the incidence of subclinical hypocalcemia did not differ between groups. Animals that received DA presented reduction in blood levels of total plasma proteins, globulins, bicarbonate and blood pH, in addition to increased activity of paraoxone-1 and reduction in the concentration of haptoglobin from animals of DN. In conclusion, we can infer that, anionic diets can alter blood pH, interfere with protein synthesis, and probably improve antioxidant capacity.

Progress in Natural Compounds/siRNA Co-delivery Employing Nanovehicles for Cancer Therapy

Chemotherapy using natural compounds, such as resveratrol, curcumin, paclitaxel, docetaxel, etoposide, doxorubicin, and camptothecin, is of importance in cancer therapy because of the outstanding therapeutic activity and multitargeting capability of these compounds. However, poor solubility and bioavailability of natural compounds have limited their efficacy in cancer therapy. To circumvent this hurdle, nanocarriers have been designed to improve the antitumor activity of the aforementioned compounds. Nevertheless, cancer treatment is still a challenge, demanding novel strategies. It is well-known that a combination of natural products and gene therapy is advantageous over monotherapy. Delivery of multiple therapeutic agents/small interfering RNA (siRNA) as a potent gene-editing tool in cancer therapy can maximize the synergistic effects against tumor cells. In the present review, co-delivery of natural compounds/siRNA using nanovehicles are highlighted to provide a backdrop for future research.

Synthesis and cytotoxic effects of 2-thio-3,4-dihydroquinazoline derivatives as novel T-type calcium channel blockers

In our previous work, a series of 2-amino-3,4-dihydroquinazoline derivativesusing an electron acceptor group was reported to be potent T-type calcium channel blockers and exhibit strong cytotoxic effects against various cancerous cell lines. To investigate the role of the guanidine moiety in the 2-amino-3,4-dihydroquinazoline scaffold as a pharmacophore for dual biological activity, a new series of 2-thio-3,4-dihydroquniazoline derivatives using an electron donor group at the C2-position was synthesized and evaluated for T-type calcium channel blocking activity and cytotoxic effects against two human cancerous cell lines (lung cancer A549 and colon cancer HCT-116). Among them, compound 6g showed potent inhibition of Ca_v3.2 currents (83% inhibition) at 10 µM concentrations. The compound also exhibited IC₅₀ values of 5.0 and 6.4 µM against A549 and HCT-116 cell lines, respectively, which are comparable to the parental lead compound KYS05090. These results indicate that the isothiourea moiety similar to the guanidine moiety of 2-amino-3,4-dihydroquinazoline derivatives may be an essential pharmacophore for the desired biological activities. Therefore, our preliminary work can provide the opportunity to expand a chemical repertoire to improve affinity and selectivity for T-type calcium channels.

The impact of tumour pH on cancer progression: strategies for clinical intervention

Dysregulation of cellular pH is frequent in solid tumours and provides potential opportunities for therapeutic intervention. The acidic microenvironment within a tumour can promote migration, invasion and metastasis of cancer cells through a variety of mechanisms. Pathways associated with the control of intracellular pH that are under consideration for intervention include carbonic anhydrase IX, the monocarboxylate transporters (MCT, MCT1 and MCT4), the vacuolar-type H⁺-ATPase proton pump, and the sodium-hydrogen exchanger 1. This review will describe progress in the development of inhibitors to these targets.

l-ornithine activates Ca2+ signaling to exert its protective function on human proximal tubular cells

Oxidative stress and reactive oxygen species (ROS) generation can be influenced by G-protein coupled receptor (GPCR)-mediated regulation of intracellular Ca2+ ([Ca2+]i) signaling. ROS production are much higher in proximal tubular (PT) cells; in addition, the lack of antioxidants enhances the vulnerability to oxidative damage. Despite such predispositions, PT cells show resiliency, and therefore must possess some inherent mechanism to protect from oxidative damage. While the mechanism in unknown, we tested the effect of l-ornithine, since it is abundantly present in PT luminal fluid and can activate Ca2+-sensing receptor (CaSR), a GPCR, expressed in the PT luminal membrane. We used human kidney 2 (HK2) cells, a PT cell line, and performed Ca2+ imaging and electrophysiological experiments to show that l-ornithine has a concentration-dependent effect on CaSR activation. We further demonstrate that the operation of CaSR activated Ca2+ signaling in HK-2 cells mediated by the transient receptor potential canonical (TRPC) dependent receptor-operated Ca2+ entry (ROCE) using pharmacological and siRNA inhibitors. Since PT cells are vulnerable to ROS, we simulated such deleterious effects using genetically encoded peroxide-induced ROS production (HyperRed indicator) to show that the l-ornithine-induced ROCE mediated [Ca2+]i signaling protects from ROS production. Furthermore, we performed cell viability, necrosis and apoptosis assays, and mitochondrial oxidative gene expression to establish that presence of l-ornithine rescued the ROS-induced damage in HK-2 cells. Moreover, l-ornithine-activation of CaSR can reverse ROS production and apoptosis via mitogen-activated protein kinase p38 activation. Such nephroprotective role of l-ornithine can be useful as the translational option for reversing kidney diseases involving PT cell damage due to oxidative stress or crystal nephropathies.

The pH sensitivity of APT-CEST using phosphorus spectroscopy as a reference method

The pH value is a potential physiological marker for clinical diagnosis as it is altered in pathologies such as tumors. While intracellular pH can be measured noninvasively via phosphorus spectroscopy (³¹ P MRSI), Amide Proton Transfer-Chemical Exchange Saturation Transfer (APT-CEST) MRI has been suggested as an alternative method for pH quantification. To assess the suitability of APT-CEST contrast for pH quantification, two approaches (magnetization transfer ratio asymmetry [MTR_asym ] and Lorentzian difference analysis [LDA]) for analyzing the Z-spectrum have been correlated with pH values obtained by ³¹ P MRSI. Fourteen patients with glioblastoma and 12 healthy controls were included. In contrast to MTR_asym , the LDA is modeling the direct water saturation and the semi-solid magnetization transfer, allowing a separate evaluation of the aliphatic nuclear Overhauser effect and the APT-CEST. The results of our study show that the pH values obtained by ³¹ P MRSI correspond well with both methods describing the APT-CEST contrast. Two-sample t-test showed significant differences in MTR_asym , LDA and pH obtained by ³¹ P MRSI for regions of interest in glioblastoma, contralateral control areas and normal appearing white matter (P < 0.001). A slightly improved correlation between the amide signal and pH was found after performing LDA (r = 0.78) compared with MTR_asym (r = 0.70). While both methods can be used to monitor pH changes, the LDA approach appears to be better suited.

Potential of Engineered Bacteriorhodopsins as Photoactivated Biomaterials in Modulating Neural Stem Cell Behavior

Bacteriorhodopsin (BR), a light-sensitive bacterial proton pump, has been demonstrated the capacity for regulating the neural activity in mammalian cells. Because of the difficulty in production and purification in large quantities, the BR proteins have neither been directly employed to biomedical applications nor verified the functionality by protein administration. Previously, we have invented a highly expressible bacteriorhodopsin (HEBR) and established the massive production protocol. In the current study, we mass-produced the two types of HEBR proteins that have normal or abnormal activity on the proton pumping, and then we treated murine neural stem cells (NSCs) with these HEBR proteins. We discovered that the cell behaviors including growth, metabolism, mitochondrial inner membrane potential, and differentiation were obviously affected in NSCs after the treatment of HEBR proteins. Particularly, these effects induced by HEBR proteins were correlated to their proton pump activity and could be altered by cell culture substrate materials. Current findings suggest that the engineered light-sensitive HEBR protein can serve as a biological material to directly influence the multiple behaviors of mammalian cells, which is further modified by the cell culture substrate material, revealing the versatile potential of HEBR protein in biomaterial applications.

Trefoil factor 2 activation of CXCR4 requires calcium mobilization to drive epithelial repair in gastric organoids

KEY POINTS

Determining the signalling cascade of epithelial repair, using murine gastric organoids, allows definition of regulatory processes intrinsic to epithelial cells, at the same time as validating and dissecting the signalling cascade with more precision than is possible in vivo Following single cell damage, intracellular calcium selectively increases within cells adjacent to the damage site and is essential for promoting repair. Trefoil factor 2 (TFF2) acts via chemokine C-X-C receptor 4 and epidermal growth factor receptor signalling, including extracellular signal-regulated kinase activation, to drive calcium mobilization and promote gastric repair. Sodium hydrogen exchanger 2, although essential for repair, acts downstream of TFF2 and calcium mobilization.

ABSTRACT

The gastric mucosa of the stomach is continually exposed to environmental and physiological stress factors that can cause local epithelial damage. Although much is known about the complex nature of gastric wound repair, the stepwise process that characterizes epithelial restitution remains poorly defined. The present study aimed to determine the effectors that drive gastric epithelial repair using a reductionist culture model. To determine the role of trefoil factor 2 (TFF2) and intracellular calcium (Ca2+ ) mobilization in gastric restitution, gastric organoids were derived from TFF2 knockout (KO) mice and yellow Cameleon-Nano15 (fluorescent calcium reporter) transgenic mice, respectively. Inhibitors and recombinant protein were used to determine the upstream and downstream effectors of gastric restitution following photodamage (PD) to single cells within the gastric organoids. Single cell PD resulted in parallel events of dead cell exfoliation and migration of intact neighbouring cells to restore a continuous epithelium in the damage site. Under normal conditions following PD, Ca2+ levels increased within neighbour migrating cells, peaking at ∼1 min, suggesting localized Ca2+ mobilization at the site of cell protrusion/migration. TFF2 KO organoids exhibit delayed repair; however, this delay can be rescued by the addition of exogenous TFF2. Inhibition of epidermal growth factor receptor (EGFR), extracellular signal-regulated kinase (ERK)1/2 or a TFF2 receptor, chemokine C-X-C receptor 4 (CXCR4), resulted in significant delay and dampened Ca2+ mobilization. Inhibition of sodium hydrogen exchanger 2 (NHE2) caused significant delay but did not affect Ca2+ mobilization. A similar delay was observed in NHE2 KO organoids. In TFF2 KO gastric organoids, the addition of exogenous TFF2 in the presence of EGFR or CXCR4 inhibition was unable to rescue repair. The present study demonstrates that intracellular Ca2+ mobilization occurs within gastric epithelial cells adjacent to the damage site to promote repair by mechanisms that involve TFF2 signalling via CXCR4, as well as activation of EGFR and ERK1/2. Furthermore NHE2 is shown to be important for efficient repair and to operate via a mechanism either downstream or independent of calcium mobilization.

Sulfur Dioxide Activates Cl-/HCO3 - Exchanger via Sulphenylating AE2 to Reduce Intracellular pH in Vascular Smooth Muscle Cells

Sulfur dioxide (SO₂) is a colorless and irritating gas. Recent studies indicate that SO₂ acts as the gas signal molecule and inhibits vascular smooth muscle cell (VSMC) proliferation. Cell proliferation depends on intracellular pH (pH_i). Transmembrane cystein mutation of Na⁺- independent Cl^-/HCO₃ ^- exchanger (anion exchanger, AE) affects pH_i. However, whether SO₂ inhibits VSMC proliferation by reducing pH_i is still unknown. Here, we investigated whether SO₂ reduced pH_i to inhibit the proliferation of VSMCs and explore its molecular mechanisms. Within a range of 50-200 μM, SO₂ was found to lower the pH_i in VSMCs. Concurrently, NH₄Cl pre-perfusion showed that SO₂ significantly activated AE, whereas the AE inhibitor 4,4'-diisothiocyanatostilbene- 2,20-disulfonic acid (DIDS) significantly attenuated the effect of SO₂ on pH_i in VSMCs. While 200 μM SO₂ sulphenylated AE2, while dithiothreitol (DTT) blocked the sulphenylation of AE2 and subsequent AE activation by SO₂, thereby restoring the pH_i in VSMCs. Furthermore, DIDS pretreatment eliminated SO₂-induced inhibition of PDGF-BB-stimulated VSMC proliferation. We report for the first time that SO₂ inhibits VSMC proliferation in part by direct activation of the AE via posttranslational sulphenylation and induction of intracellular acidification.

Contribution of Anoctamins to Cell Survival and Cell Death

Before anoctamins (TMEM16 proteins) were identified as a family of Ca2+-activated chloride channels and phospholipid scramblases, the founding member anoctamin 1 (ANO1, TMEM16A) was known as DOG1, a marker protein for gastrointestinal stromal tumors (GIST). Meanwhile, ANO1 has been examined in more detail, and the role of ANO1 in cell proliferation and the development of different types of malignomas is now well established. While ANO5, ANO7, and ANO9 may also be relevant for growth of cancers, evidence has been provided for a role of ANO6 (TMEM16F) in regulated cell death. The cellular mechanisms by which anoctamins control cell proliferation and cell death, respectively, are just emerging; however, the pronounced effects of anoctamins on intracellular Ca2+ levels are likely to play a significant role. Recent results suggest that some anoctamins control membrane exocytosis by setting Ca2+i levels near the plasma membrane, and/or by controlling the intracellular Cl- concentration. Exocytosis and increased membrane trafficking induced by ANO1 and ANO6 may enhance membrane expression of other chloride channels, such as CFTR and volume activated chloride channels (VRAC). Notably, ANO6-induced phospholipid scrambling with exposure of phosphatidylserine is pivotal for the sheddase function of disintegrin and metalloproteinase (ADAM). This may support cell death and tumorigenic activity of IL-6 by inducing IL-6 trans-signaling. The reported anticancer effects of the anthelminthic drug niclosamide are probably related to the potent inhibitory effect on ANO1, apart from inducing cell cycle arrest through the Let-7d/CDC34 axis. On the contrary, pronounced activation of ANO6 due to a large increase in intracellular calcium, activation of phospholipase A2 or lipid peroxidation, can lead to ferroptotic death of cancer cells. It therefore appears reasonable to search for both inhibitors and potent activators of TMEM16 in order to interfere with cancer growth and metastasis.

Interleukin-Mediated Pendrin Transcriptional Regulation in Airway and Esophageal Epithelia

Pendrin (SLC26A4), a Cl⁻/anion exchanger, is expressed at high levels in kidney, thyroid, and inner ear epithelia, where it has an essential role in bicarbonate secretion/chloride reabsorption, iodide accumulation, and endolymph ion balance, respectively. Pendrin is expressed at lower levels in other tissues, such as airways and esophageal epithelia, where it is transcriptionally regulated by the inflammatory cytokines interleukin (IL)-4 and IL-13 through a signal transducer and activator of transcription 6 (STAT6)-mediated pathway. In the airway epithelium, increased pendrin expression during inflammatory diseases leads to imbalances in airway surface liquid thickness and mucin release, while, in the esophageal epithelium, dysregulated pendrin expression is supposed to impact the intracellular pH regulation system. In this review, we discuss some of the recent findings on interleukin-mediated transcriptional regulation of pendrin and how this dysregulation impacts airway and esophagus epithelial homeostasis during inflammatory diseases.

GPN does not release lysosomal Ca2+ but evokes Ca2+ release from the ER by increasing the cytosolic pH independently of cathepsin C

The dipeptide glycyl-l-phenylalanine 2-naphthylamide (GPN) is widely used to perturb lysosomes because its cleavage by the lysosomal enzyme cathepsin C is proposed to rupture lysosomal membranes. We show that GPN evokes a sustained increase in lysosomal pH (pHly), and transient increases in cytosolic pH (pHcyt) and Ca2+ concentration ([Ca2+]c). None of these effects require cathepsin C, nor are they accompanied by rupture of lysosomes, but they are mimicked by structurally unrelated weak bases. GPN-evoked increases in [Ca2+]c require Ca2+ within the endoplasmic reticulum (ER), but they are not mediated by ER Ca2+ channels amplifying Ca2+ release from lysosomes. GPN increases [Ca2+]c by increasing pHcyt, which then directly stimulates Ca2+ release from the ER. We conclude that physiologically relevant increases in pHcyt stimulate Ca2+ release from the ER in a manner that is independent of IP3 and ryanodine receptors, and that GPN does not selectively target lysosomes.

Electrospun Filaments Embedding Bioactive Glass Particles with Ion Release and Enhanced Mineralization

Efforts in tissue engineering aim at creating scaffolds that mimic the physiological environment with its structural, topographical and mechanical properties for restoring the function of damaged tissue. In this study we introduce composite fibres made by a biodegradable poly(lactic acid) (PLLA) matrix embedding bioactive silica-based glass particles (SBA2). Electrospinning is performed to achieve porous PLLA filaments with uniform dispersion of bioactive glass powder. The obtained composite fibres show in aligned arrays significantly increased elastic modulus compared with that of neat polymer fibres during uniaxial tensile stress. Additionally, the SBA2 bioactivity is preserved upon encapsulation as highlighted by the promoted deposition of hydroxycarbonate apatite (HCA) upon immersion in simulated body fluid solutions. HCA formation is sequential to earlier processes of polymer erosion and ion release leading to acidification of the surrounding solution environment. These findings suggest PLLA-SBA2 fibres as a composite, multifunctional system which might be appealing for both bone and soft tissue engineering applications.

Regulation of Ca2+ Signaling for Drug-Resistant Breast Cancer Therapy with Mesoporous Silica Nanocapsule Encapsulated Doxorubicin/siRNA Cocktail

Multidrug resistance (MDR) is the key cause that accounts for the failure of clinical cancer chemotherapy. To address the problem, herein, we presented an alternative strategy to conquer drug-resistant breast cancer through the combinatorial delivery of Ca2+ channel siRNA with cytotoxic drugs. Mesoporous silica nanocapsules (MSNCs) with mesoporous and hollow structure were fabricated for co-delivery of T-type Ca2+ channel siRNA and doxorubicin (DOX) with high drug loading efficiency. The DOX/siRNA co-loaded MSNCs showed a synergistic therapeutic effect on drug-resistant breast cancer cells MCF-7/ADR, while had only an additive effect on the drug-sensitive MCF-7 counterpart. It was found that the combination of T-type Ca2+ channel siRNA and DOX had a similar effect on MCF-7 and MCF-7/ADR in the knockdown of overexpressed T-type Ca2+ channels and decrease in cytosolic Ca2+ concentration ([Ca2+]i), but it specifically induced G0/G1 phase cell-cycle arrest and intracellular drug accumulation enhancement in MCF-7/ADR. The in vitro and in vivo results demonstrated that the MSNCs with good biocompatibility had a high efficiency for conquering the drug-resistant breast cancer with the DOX/calcium channel siRNA cocktail co-delivery. It provides a biological target for drug/gene delivery enhanced cancer therapy with nanoformulations.

Solute carrier family 9, subfamily A, member 3 (SLC9A3)/sodium-hydrogen exchanger member 3 (NHE3) dysregulation and dilated intercellular spaces in patients with eosinophilic esophagitis

BACKGROUND

Eosinophilic esophagitis (EoE) is characterized by histopathologic modifications of esophageal tissue, including eosinophil-rich inflammation, basal zone hyperplasia, and dilated intercellular spaces (DIS). The underlying molecular processes that drive the histopathologic features of EoE remain largely unexplored.

OBJECTIVE

We sought to investigate the involvement of solute carrier family 9, subfamily A, member 3 (SLC9A3) in esophageal epithelial intracellular pH (pHi) and DIS formation and the histopathologic features of EoE.

METHODS

We examined expression of esophageal epithelial gene networks associated with regulation of pHi in the EoE transcriptome of primary esophageal epithelial cells and an in vitro esophageal epithelial 3-dimensional model system (EPC2-ALI). Molecular and cellular analyses and ion transport assays were used to evaluate the expression and function of SLC9A3.

RESULTS

We identified altered expression of gene networks associated with regulation of pHi and acid-protective mechanisms in esophageal biopsy specimens from pediatric patients with EoE (healthy subjects, n = 6; patients with EoE, n = 10). The most dysregulated gene central to regulating pHi was SLC9A3. SLC9A3 expression was increased within the basal layer of esophageal biopsy specimens from patients with EoE, and expression positively correlated with disease severity (eosinophils/high-power field) and DIS (healthy subjects, n = 10; patients with EoE, n = 10). Analyses of esophageal epithelial cells revealed IL-13-induced, signal transducer and activator of transcription 6-dependent SLC9A3 expression and Na+-dependent proton secretion and that SLC9A3 activity correlated positively with DIS formation. Finally, we showed that IL-13-mediated, Na+-dependent proton secretion was the primary intracellular acid-protective mechanism within the esophageal epithelium and that blockade of SLC9A3 transport abrogated IL-13-induced DIS formation.

CONCLUSIONS

SLC9A3 plays a functional role in DIS formation, and pharmacologic interventions targeting SLC9A3 function may suppress the histopathologic manifestations in patients with EoE.

Na+/H+ Exchangers Are Required for the Development and Function of Vertebrate Mucociliary Epithelia

Na+/H+ exchangers (NHEs) represent a highly conserved family of ion transporters that regulate pH homeostasis. NHEs as well as other proton transporters were previously linked to the regulation of the Wnt signaling pathway, cell polarity signaling, and mucociliary function. Furthermore, mutations in the gene SLC9A3 (encoding NHE3) were detected as additional risk factors for airway infections in cystic fibrosis patients. Here, we used the Xenopus embryonic mucociliary epidermis as well as human airway epithelial cells (HAECs) as models to investigate the functional roles of NHEs in mucociliary development and regeneration. In Xenopus embryos, NHEs 1-3 were expressed during epidermal development, and loss of NHE function impaired mucociliary clearance in tadpoles. Clearance defects were caused by reduced cilia formation, disrupted alignment of basal bodies in multiciliated cells (MCCs), and dysregulated mucociliary gene expression. These data also suggested that NHEs may contribute to the activation of Wnt signaling in mucociliary epithelia. In HAECs, pharmacological inhibition of NHE function also caused defective ciliation and regeneration in airway MCCs. Collectively, our data revealed a requirement for NHEs in vertebrate mucociliary epithelia and linked NHE activity to cilia formation and function in differentiating MCCs. Our results provide an entry point for the understanding of the contribution of NHEs to signaling, development, and pathogenesis in the human respiratory tract.

Molecular analysis of gastric cancer identifies genomic markers of drug sensitivity in Asian gastric cancer

Background: Gastric cancer (GC) is one of the leading causes of lethal malignancies worldwide, especially in Eastern Asia. Clinical responses to antitumor therapies are often limited to a subset of patients. Methods: To uncover new biomarkers of sensitivity and resistance to cancer therapeutics, we performed ultra-deep targeted sequencing in a cohort with 72 patients (41 with chemotherapy sensitivity and 31 with chemotherapy resistance). Results: We found that sixteen mutated cancer genes were associated with widely used agent in chemotherapy of gastric cancer. Genes identified in these study are mainly involved in activation and inactivation of cancer chemotherapeutic agents, changes of apoptosis and proliferation, drug efflux, DNA damage repair, and the tumor microenvironment. Discussion: A novel group of chemo-sensitivity related genes provided new therapeutic strategies to overcome the development and evolution of resistance to cancer chemotherapy.

Sulfur dioxide exposure reduces the quantity of CD19+ cells and causes nasal epithelial injury in rats

Background

Reactive airway dysfunction syndrome (RADS), also called irritant-induced asthma, is a type of occupational asthma that can occur within a very short period of latency. The study sought to investigate the influence of sulfur dioxide (SO₂) exposure on CD19+ cells and nasal epithelial injury.

Methods

We investigated the effects of SO₂ on CD19 expression and morphological changes of nasal epithelia in rats. In the study, 20 rats were randomly divided into the SO₂ exposure group that were exposed to 600 ppm SO₂, 2 h/day for consecutive 7 days, and the control group that were exposed to filtered air).

Results

Inhalation of high concentration of SO₂significantly reduced CD19 expression at both the mRNA transcript and protein levels, and reduced the percentages of CD19⁺ cells and CD19⁺/CD23⁺ cells in the nasal septum. However, inhalation of high concentration of SO₂ did not affect immunoglobulin (Ig) G, IgA and IgE levels in the serum and nasal septum. More importantly, SO₂ exposure also caused mild structural changes of the nasal septum.

Conclusion

Our results reveal that inhalation of a high concentration of SO₂ reduces CD19 expression and causes structural change of the nasal septum in rats.

How the Warburg effect supports aggressiveness and drug resistance of cancer cells?

Cancer cells employ both conventional oxidative metabolism and glycolytic anaerobic metabolism. However, their proliferation is marked by a shift towards increasing glycolytic metabolism even in the presence of O₂ (Warburg effect). HIF1, a major hypoxia induced transcription factor, promotes a dissociation between glycolysis and the tricarboxylic acid cycle, a process limiting the efficient production of ATP and citrate which otherwise would arrest glycolysis. The Warburg effect also favors an intracellular alkaline pH which is a driving force in many aspects of cancer cell proliferation (enhancement of glycolysis and cell cycle progression) and of cancer aggressiveness (resistance to various processes including hypoxia, apoptosis, cytotoxic drugs and immune response). This metabolism leads to epigenetic and genetic alterations with the occurrence of multiple new cell phenotypes which enhance cancer cell growth and aggressiveness. In depth understanding of these metabolic changes in cancer cells may lead to the development of novel therapeutic strategies, which when combined with existing cancer treatments, might improve their effectiveness and/or overcome chemoresistance.

Carbonic Anhydrase IX (CAIX), Cancer, and Radiation Responsiveness

Carbonic anhydrase IX has been under intensive investigation as a therapeutic target in cancer. Studies demonstrate that this enzyme has a key role in pH regulation in cancer cells, allowing these cells to adapt to the adverse conditions of the tumour microenviroment. Novel CAIX inhibitors have shown efficacy in both in vitro and in vivo pre-clinical cancer models, adversely affecting cell viability, tumour formation, migration, invasion, and metastatic growth when used alone. In co-treatments, CAIX inhibitors may enhance the effects of anti-angiogenic drugs or chemotherapy agents. Research suggests that these inhibitors may also increase the response of tumours to radiotherapy. Although many of the anti-tumour effects of CAIX inhibition may be dependent on its role in pH regulation, recent work has shown that CAIX interacts with several of the signalling pathways involved in the cellular response to radiation, suggesting that pH-independent mechanisms may also be an important basis of its role in tumour progression. Here, we discuss these pH-independent interactions in the context of the ability of CAIX to modulate the responsiveness of cancer to radiation.

The effect of exposure of SO2 in high concentrations on CD19+ cells in reactive airway dysfunction syndrome in rat

Reactive airway dysfunction syndrome (RADS) has a clinical manifestation similar to asthma, but some features are different between both the diseases. To probe the effect of CD19+ cells in RADS pathogenesis by inhalation of sulfur dioxide (SO2), rats were exposed to SO2 at 600 ppm for 2 h per day for 7 days and the CD19 expression in lung tissue was detected both at mRNA and protein levels by RT-PCR and western blot. The percentages of CD19+ and CD19+ CD23+ cells were measured by flow cytometry. IgG, IgA, and IgE in serum and bronchoalveolar lavage fluid (BALF) were detected by enzyme-linked immunosorbent assay (ELISA). Histological analysis was performed. The results showed that expression of CD19 in SO2 exposure group was lower than that in the control both at mRNA and protein levels ( P < 0.05). Flow cytometry analysis showed that the percentages of CD19+ and CD19+ CD23+ were significantly lower in the SO2 exposed group than that in the control ( P < 0.05). There was no difference between the control and SO2 exposed groups in both serum and BALF levels of IgG, IgA, and IgE. Pathological changes, such as chronic bronchitis, local alveolar hemorrhage, and lymphocytes infiltration were observed in SO2 exposed. RADS is a non-immunogenicity, chronic airway inflammatory disease caused by irritation of harmful factor and manifests as airway hyperresposiveness.

Cftr Modulates Wnt/β-Catenin Signaling and Stem Cell Proliferation in Murine Intestine

BACKGROUND & AIMS

Cystic fibrosis (CF) patients and CF mouse models have increased risk for gastrointestinal tumors. CF mice show augmented intestinal proliferation of unknown etiology and an altered intestinal environment. We examined the role of the cystic fibrosis transmembrane conductance regulator (Cftr) in Wnt/β-catenin signaling, stem cell proliferation, and its functional expression in the active intestinal stem cell (ISC) population. Dysregulation of intracellular pH (pH_i) in CF ISCs was investigated for facilitation of Wnt/β-catenin signaling.

METHODS

Crypt epithelia from wild-type (WT) and CF mice were compared ex vivo and in intestinal organoids (enteroids) for proliferation and Wnt/β-catenin signaling by standard assays. Cftr in ISCs was assessed by immunoblot of sorted Sox9 ^{enhanced green fluorescent protein(EGFP)} intestinal epithelia and pH_i regulation by confocal microfluorimetry of leucine-rich G-protein-coupled receptor 5 ISCs. Plasma membrane association of the Wnt transducer Dishevelled 2 (Dvl2) was assessed by fluorescence imaging of live enteroids from WT and CF mice crossed with Dvl2-EGFP/ACTB-tdTomato,-EGFP)Luo/J (Rosa^mT/mG) mice.

RESULTS

Relative to WT, CF intestinal crypts showed an ∼30% increase in epithelial and Lgr5+ ISC proliferation and increased Wnt/β-catenin signaling. Cftr was expressed in Sox9^EGFPLo ISCs and loss of Cftr induced an alkaline pH_i in ISCs. CF crypt-base columnar cells showed a generalized increase in plasma membrane Dvl2-EGFP association as compared with WT. Dvl2-EGFP membrane association was charge- and pH-dependent and increased in WT crypt-base columnar cells by Cftr inhibition.

CONCLUSIONS

CF intestine shows increased ISC proliferation and Wnt/β-catenin signaling. Loss of Cftr increases pH_i in ISCs, which stabilizes the plasma membrane association of the Wnt transducer Dvl, likely facilitating Wnt/β-catenin signaling. Absence of Cftr-dependent suppression of ISC proliferation in the CF intestine may contribute to increased risk for intestinal tumors.

Intestinal Organoids: New Frontiers in the Study of Intestinal Disease and Physiology

The development of sustainable intestinal organoid cell culture has emerged as a new modality for the study of intestinal function and cellular processes. Organoid culture is providing a new testbed for therapeutic research and development. Intestinal organoids, self-renewing 3-dimensional structures comprised intestinal stem cells and their differentiated epithelial progeny allow for more facile and robust exploration of cellular activity, cell organization and structure, genetic manipulation, and vastly more physiologic modeling of intestinal response to stimuli as compared to traditional 2-dimensional cell line cultures. Intestinal organoids are affecting a wide variety of research into gastrointestinal pathology. The purpose of this review is to discuss the current state-of-the-art and future effect of research using enteroids and colonoids (organoids grown from the small and large intestines, respectively).

Increased intracellular pH is necessary for adult epithelial and embryonic stem cell differentiation

Despite extensive knowledge about the transcriptional regulation of stem cell differentiation, less is known about the role of dynamic cytosolic cues. We report that an increase in intracellular pH (pHi) is necessary for the efficient differentiation of Drosophila adult follicle stem cells (FSCs) and mouse embryonic stem cells (mESCs). We show that pHi increases with differentiation from FSCs to prefollicle cells (pFCs) and follicle cells. Loss of the Drosophila Na+-H+ exchanger DNhe2 lowers pHi in differentiating cells, impairs pFC differentiation, disrupts germarium morphology, and decreases fecundity. In contrast, increasing pHi promotes excess pFC cell differentiation toward a polar/stalk cell fate through suppressing Hedgehog pathway activity. Increased pHi also occurs with mESC differentiation and, when prevented, attenuates spontaneous differentiation of naive cells, as determined by expression of microRNA clusters and stage-specific markers. Our findings reveal a previously unrecognized role of pHi dynamics for the differentiation of two distinct types of stem cell lineages, which opens new directions for understanding conserved regulatory mechanisms.

Ion channels in regulated cell death

Activation of ion channels and pores are essential steps during regulated cell death. Channels and pores participate in execution of apoptosis, necroptosis and other forms of caspase-independent cell death. Within the program of regulated cell death, these channels are strategically located. Ion channels can shrink cells and drive them towards apoptosis, resulting in silent, i.e. immunologically unrecognized cell death. Alternatively, activation of channels can induce cell swelling, disintegration of the cell membrane, and highly immunogenic necrotic cell death. The underlying cell death pathways are not strictly separated as identical stimuli may induce cell shrinkage and apoptosis when applied at low strength, but may also cause cell swelling at pronounced stimulation, resulting in regulated necrosis. Nevertheless, the precise role of ion channels during regulated cell death is far from being understood, as identical channels may support regulated death in some cell types, but may cause cell proliferation, cancer development, and metastasis in others. Along this line, the phospholipid scramblase and Cl(-)/nonselective channel anoctamin 6 (ANO6) shows interesting features, as it participates in apoptotic cell death during lower levels of activation, thereby inducing cell shrinkage. At strong activation, e.g. by stimulation of purinergic P2Y7 receptors, it participates in pore formation, causes massive membrane blebbing, cell swelling, and membrane disintegration. The LRRC8 proteins deserve much attention as they were found to have a major role in volume regulation, apoptotic cell shrinkage and resistance towards anticancer drugs.

The chemosensitizing agent lubeluzole binds calmodulin and inhibits Ca(2+)/calmodulin-dependent kinase II

An affinity capillary electrophoresis (ACE) method to estimate apparent dissociation constants between bovine brain calmodulin (CaM) and non-peptidic ligands was developed. The method was validated reproducing the dissociation constants of a number of well-known CaM ligands. In particular, the potent antagonist 125-C9 was ad hoc synthesized through an improved synthetic procedure. The ACE method was successfully applied to verify CaM affinity for lubeluzole, a well-known neuroprotective agent recently proved useful to potentiate the activity of anti-cancer drugs. Lubeluzole was slightly less potent than 125-C9 (Kd = 2.9 ± 0.7 and 0.47 ± 0.06 μM, respectively) and displayed Ca(2+)/calmodulin-dependent kinase II (CaMKII) inhibition (IC50 = 40 ± 1 μM). Possible binding modes of lubeluzole to CaM were explored by docking studies based on the X-ray crystal structures of several trifluoperazine-CaM complexes. An estimated dissociation constant in good agreement with the experimental one was found and the main aminoacidic residues and interactions contributing to complex formation were highlighted. The possibility that interference with Ca(2+) pathways may contribute to the previously observed chemosensitizing effects of lubeluzole on human ovarian adenocarcinoma and lung carcinoma cells are discussed.

Involvement of ion channels and transporters in carcinoma angiogenesis and metastasis

Angiogenesis is a finely tuned process, which is the result of the equilibrium between pro- and antiangiogenic factors. In solid tumor angiogenesis, the balance is highly in favor of the production of new, but poorly functional blood vessels, initially intended to provide growing tumors with nutrients and oxygen. Among the numerous proteins involved in tumor development, several types of ion channels are overexpressed in tumor cells, as well as in stromal and endothelial cells. Ion channels thus actively participate in the different hallmarks of cancer, especially in tumor angiogenesis and metastasis. Indeed, from their strategic localization in the plasma membrane, ion channels are key operators of cell signaling, as they sense and respond to environmental changes. This review aims to decipher how ion channels of different families are intricately involved in the fundamental angiogenesis and metastasis hallmarks, which lead from a nascent tumor to systemic dissemination. An overview of the possible use of ion channels as therapeutic targets will also be given, showing that ion channel inhibitors or specific antibodies may provide effective tools, in the near future, in the treatment of carcinomas.

Cellular chloride and bicarbonate retention alters intracellular pH regulation in Cftr KO crypt epithelium

Cystic fibrosis (CF) is caused by mutations in the CF transmembrane conductance regulator (CFTR), an anion channel providing a major pathway for Cl(-) and HCO3 (-) efflux across the apical membrane of the epithelium. In the intestine, CF manifests as obstructive syndromes, dysbiosis, inflammation, and an increased risk for gastrointestinal cancer. Cftr knockout (KO) mice recapitulate CF intestinal disease, including intestinal hyperproliferation. Previous studies using Cftr KO intestinal organoids (enteroids) indicate that crypt epithelium maintains an alkaline intracellular pH (pHi). We hypothesized that Cftr has a cell-autonomous role in downregulating pHi that is incompletely compensated by acid-base regulation in its absence. Here, 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein microfluorimetry of enteroids showed that Cftr KO crypt epithelium sustains an alkaline pHi and resistance to cell acidification relative to wild-type. Quantitative real-time PCR revealed that Cftr KO enteroids exhibit downregulated transcription of base (HCO3 (-))-loading proteins and upregulation of the basolateral membrane HCO3 (-)-unloader anion exchanger 2 (Ae2). Although Cftr KO crypt epithelium had increased Ae2 expression and Ae2-mediated Cl(-)/HCO3 (-) exchange with maximized gradients, it also had increased intracellular Cl(-) concentration relative to wild-type. Pharmacological reduction of intracellular Cl(-) concentration in Cftr KO crypt epithelium normalized pHi, which was largely Ae2-dependent. We conclude that Cftr KO crypt epithelium maintains an alkaline pHi as a consequence of losing both Cl(-) and HCO3 (-) efflux, which impairs pHi regulation by Ae2. Retention of Cl(-) and an alkaline pHi in crypt epithelium may alter several cellular processes in the proliferative compartment of Cftr KO intestine.

Effect of biphasic calcium phosphate scaffold porosities on odontogenic differentiation of human dental pulp cells

Calcium phosphates (CaP) of different porosities have been widely and successfully used as scaffolds with osteoblast cells for bone tissue regeneration. However, the effects of scaffold porosities on cell viability and differentiation of human dental pulp cells for dentin tissue regeneration are not well known. In this study, biphasic calcium phosphate (BCP) scaffolds of 20/80 hydroxyapatite to beta tricalcium phosphate ratio with a mean pore size of 300 μm were prepared into BCP1, BCP2, BCP3, and BCP4 of 25%, 50%, 65%, and 75% of total porosities, respectively. The extracts of these scaffolds were assessed with regard to cell viability, proliferation, and differentiation of human dental pulp cells. The high alkalinity, and more calcium and phosphate ions release that were exhibited by BCP3 and BCP4 decreased the viability and proliferation of human dental pulp cells as compared to BCP1 and BCP2. BCP2 significantly increased both cell viability and cell proliferation. However, the cells cultured with BCP3 extract revealed high alkaline phosphatase (ALP) activity and high expression of odontoblast related genes, collagen type I alpha 1, dentin matrix protein-1, and dentin sialophosphoprotein as compared to that cultured with BCP1, BCP2, and BCP4 extracts. The results highlight the effect of different scaffold porosities on the cell microenvironment and demonstrate that BCP3 scaffold of 65% porosity can support human dental pulp cells differentiation for dentin tissue regeneration.

The V-ATPase accessory protein Atp6ap1b mediates dorsal forerunner cell proliferation and left-right asymmetry in zebrafish

Asymmetric fluid flows generated by motile cilia in a transient 'organ of asymmetry' are involved in establishing the left-right (LR) body axis during embryonic development. The vacuolar-type H(+)-ATPase (V-ATPase) proton pump has been identified as an early factor in the LR pathway that functions prior to cilia, but the role(s) for V-ATPase activity are not fully understood. In the zebrafish embryo, the V-ATPase accessory protein Atp6ap1b is maternally supplied and expressed in dorsal forerunner cells (DFCs) that give rise to the ciliated organ of asymmetry called Kupffer's vesicle (KV). V-ATPase accessory proteins modulate V-ATPase activity, but little is known about their functions in development. We investigated Atp6ap1b and V-ATPase in KV development using morpholinos, mutants and pharmacological inhibitors. Depletion of both maternal and zygotic atp6ap1b expression reduced KV organ size, altered cilia length and disrupted LR patterning of the embryo. Defects in other ciliated structures-neuromasts and olfactory placodes-suggested a broad role for Atp6ap1b during development of ciliated organs. V-ATPase inhibitor treatments reduced KV size and identified a window of development in which V-ATPase activity is required for proper LR asymmetry. Interfering with Atp6ap1b or V-ATPase function reduced the rate of DFC proliferation, which resulted in fewer ciliated cells incorporating into the KV organ. Analyses of pH and subcellular V-ATPase localizations suggested Atp6ap1b functions to localize the V-ATPase to the plasma membrane where it regulates proton flux and cytoplasmic pH. These results uncover a new role for the V-ATPase accessory protein Atp6ap1b in early development to maintain the proliferation rate of precursor cells needed to construct a ciliated KV organ capable of generating LR asymmetry.

Meta-Analysis of Public Microarray Datasets Reveals Voltage-Gated Calcium Gene Signatures in Clinical Cancer Patients

Voltage-gated calcium channels (VGCCs) are well documented to play roles in cell proliferation, migration, and apoptosis; however, whether VGCCs regulate the onset and progression of cancer is still under investigation. The VGCC family consists of five members, which are L-type, N-type, T-type, R-type and P/Q type. To date, no holistic approach has been used to screen VGCC family genes in different types of cancer. We analyzed the transcript expression of VGCCs in clinical cancer tissue samples by accessing ONCOMINE (www.oncomine.org), a web-based microarray database, to perform a systematic analysis. Every member of the VGCCs was examined across 21 different types of cancer by comparing mRNA expression in cancer to that in normal tissue. A previous study showed that altered expression of mRNA in cancer tissue may play an oncogenic role and promote tumor development; therefore, in the present findings, we focus only on the overexpression of VGCCs in different types of cancer. This bioinformatics analysis revealed that different subtypes of VGCCs (CACNA1C, CACNA1D, CACNA1B, CACNA1G, and CACNA1I) are implicated in the development and progression of diverse types of cancer and show dramatic up-regulation in breast cancer. CACNA1F only showed high expression in testis cancer, whereas CACNA1A, CACNA1C, and CACNA1D were highly expressed in most types of cancer. The current analysis revealed that specific VGCCs likely play essential roles in specific types of cancer. Collectively, we identified several VGCC targets and classified them according to different cancer subtypes for prospective studies on the underlying carcinogenic mechanisms. The present findings suggest that VGCCs are possible targets for prospective investigation in cancer treatment.

The role of intracellular calcium for the development and treatment of neuroblastoma

Neuroblastoma is the second most common paediatric cancer. It developsfrom undifferentiated simpatico-adrenal lineage cells and is mostly sporadic; however, theaetiology behind the development of neuroblastoma is still not fully understood. Intracellularcalcium ([Ca2+]i) is a secondary messenger which regulates numerous cellular processesand, therefore, its concentration is tightly regulated. This review focuses on the role of[Ca2+]i in differentiation, apoptosis and proliferation in neuroblastoma. It describes themechanisms by which [Ca2+]i is regulated and how it modulates intracellular pathways.Furthermore, the importance of [Ca2+]i for the function of anti-cancer drugs is illuminatedin this review as [Ca2+]i could be a target to improve the outcome of anti-cancer treatmentin neuroblastoma. Overall, modulations of [Ca2+]i could be a key target to induce apoptosisin cancer cells leading to a more efficient and effective treatment of neuroblastoma.

Bioelectrical regulation of cell cycle and the planarian model system

Cell cycle regulation through the manipulation of endogenous membrane potentials offers tremendous opportunities to control cellular processes during tissue repair and cancer formation. However, the molecular mechanisms by which biophysical signals modulate the cell cycle remain underappreciated and poorly understood. Cells in complex organisms generate and maintain a constant voltage gradient across the plasma membrane known as the transmembrane potential. This potential, generated through the combined efforts of various ion transporters, pumps and channels, is known to drive a wide range of cellular processes such as cellular proliferation, migration and tissue regeneration while its deregulation can lead to tumorigenesis. These cellular regulatory events, coordinated by ionic flow, correspond to a new and exciting field termed molecular bioelectricity. We aim to present a brief discussion on the biophysical machinery involving membrane potential and the mechanisms mediating cell cycle progression and cancer transformation. Furthermore, we present the planarian Schmidtea mediterranea as a tractable model system for understanding principles behind molecular bioelectricity at both the cellular and organismal level. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

Importance of Ca(2+) in gastric epithelial restitution-new views revealed by real-time in vivo measurements

It has been a few decades since Ca(2+) was identified as one of the important factors that can accelerate gastric wound repair as well as contribute to epithelial homeostasis and regulation of gastric secretions. The mechanistic basis has remained largely unexplored in vivo because it was not possible to track in real time either intracellular Ca(2+) mobilization or wound repair in living tissues. Recent advances in technology, such as combining high resolution light microscopy and genetically encoded Ca(2+) reporters in mice, now allow the monitoring of Ca(2+) mobilization during gastric epithelial cell restitution. Ca(2+) is a ubiquitous second messenger that influences numerous cellular processes, including gastric acid/bicarbonate secretion, mucus secretion, and cell migration. We have demonstrated that cytosolic Ca(2+) mobilization within the restituting gastric epithelial cells is a central signal driving small wound repair. However, extracellular Ca(2+) is also mobilized in the juxtamucosal luminal space above a wound, and evidence suggests extracellular Ca(2+) is a third messenger that also promotes gastric epithelial restitution. Interplay between intracellular and extracellular Ca(2+) is necessary for efficient gastric epithelial restitution.

Role of anoctamins in cancer and apoptosis

Anoctamin 1 (TMEM16A, Ano1) is a recently identified Ca(2+)-activated chloride channel and a member of a large protein family comprising 10 paralogues. Before Ano1 was identified as a chloride channel protein, it was known as the cancer marker DOG1. DOG1/Ano1 is expressed in gastrointestinal stromal tumours (GIST) and particularly in head and neck squamous cell carcinoma, at very high levels never detected in other tissues. It is now emerging that Ano1 is part of the 11q13 locus, amplified in several types of tumour, where it is thought to augment cell proliferation, cell migration and metastasis. Notably, Ano1 is upregulated through histone deacetylase (HDAC), corresponding to the known role of HDAC in HNSCC. As Ano1 does not enhance proliferation in every cell type, its function is perhaps modulated by cell-specific factors, or by the abundance of other anoctamins. Thus Ano6, by regulating Ca(2+)-induced membrane phospholipid scrambling and annexin V binding, supports cellular apoptosis rather than proliferation. Current findings implicate other cellular functions of anoctamins, apart from their role as Ca(2+)-activated Cl(-) channels.