Statin pretreatment inhibits the lipopolysaccharide-induced epithelial-mesenchymal transition via the downregulation of toll-like receptor 4 and nuclear factor-κB in human biliary epithelial cells.

BACKGROUND AND AIM: Epithelial-mesenchymal transition (EMT) of biliary epithelial cells (BECs) plays an important role in biliary fibrosis. This study investigated the effects of simvastatin on the lipopolysaccharide (LPS)-induced EMT and related signal pathways in BECs. METHODS: Biliary epithelial cells were exposed to LPS (2 µg/mL) or transforming growth factor ß1 (TGF-ß1) (5 ng/mL) for 5 days. The EMT was assessed by a gain of mesenchymal cell markers (vimentin, N-cadherin, slug, and Twist-1) and a loss of epithelial cell markers (E-cadherin). The effects of simvastatin on the EMT induced by LPS or TGF-ß1 were determined by the changes in the levels of EMT markers and TLR4 and in the c-Jun N-terminal kinase (JNK), p38, and nuclear factor-κB (NF-κB) signaling pathways. RESULTS: Compared with the BECs treated with LPS alone, co-treatment with simvastatin and LPS induced an increase in the expression of E-cadherin and decreases in the expression levels of mesenchymal cell markers. The LPS-induced TLR4 expression level was slightly decreased by co-treatment with simvastatin. LPS-induced BEC growth was markedly inhibited by co-treatment with simvastatin. Furthermore, pretreatment with simvastatin inhibited the LPS-induced EMT in BECs by downregulating NF-κB and JNK phosphorylation. The suppressive effects of simvastatin pretreatment on the induction of the EMT by TGF-ß1 were also demonstrated in H69 cells. CONCLUSIONS: Our results demonstrate that LPS or TGF-ß1 promote the EMT in BECs that that pretreatment with simvastatin inhibited the induced EMT by downregulating toll-like receptor 4 and NF-κB phosphorylation. This finding suggests that simvastatin can be considered a new agent for preventing biliary fibrosis associated with the EMT of BECs.

HDAC inhibitors induce epithelial-mesenchymal transition in colon carcinoma cells.

The effects of histone deacetylase (HDAC) inhibitors on epithelial-mesenchymal transition (EMT) differ in various types of cancers. We investigated the EMT phenotype in four colon cancer cell lines when challenged with HDAC inhibitors trichostatin A (TSA) and valproic acid (VPA) with or without transforming growth factor-ß1 (TGF-ß1) treatment. Four colon cancer cell lines with different phenotypes in regards to tumorigenicity, microsatellite stability and DNA mutation were used. EMT phenotypes were assessed by the expression of E-cadherin and vimentin using western blot analysis, immunofluorescence, quantitative real-time RT-PCR following treatment with TSA (100 or 200 nM) or VPA (0.5 mM) with or without TGF-ß1 (5 ng/ml) for 24 h. Biological EMT phenotypes were also evaluated by cell morphology, migration and invasion assays. TSA or VPA induced mesenchymal features in the colon carcinoma cells by a decrease in E-cadherin and an increase in vimentin expression at the mRNA and protein levels. Confocal microscopy revealed membranous attenuation or nuclear translocation of E-cadherin and enhanced expression of vimentin. These responses occurred after 6 h and increased until 24 h. Colon cancer cells changed from a round or rectangular shape to a spindle shape with increased migration and invasion ability following TSA or VPA treatment. The susceptibility to EMT changes induced by TSA or VPA was comparable in microsatellite stable (SW480 and HT29) and microsatellite unstable cells (DLD1 and HCT116). TSA or VPA induced a mesenchymal phenotype in the colon carcinoma cells and these effects were augmented in the presence of TGF-ß1. HDAC inhibitors require careful caution before their application as new anticancer drugs for colon cancers.

The TREK2 Channel Is Involved in the Proliferation of 253J Cell, a Human Bladder Carcinoma Cell.

Bladder cancer is the seventh most common cancer in men that smoke, and the incidence of disease increases with age. The mechanism of occurrence has not yet been established. Potassium channels have been linked with cell proliferation. Some two-pore domain K(+) channels (K2P), such as TASK3 and TREK1, have recently been shown to be overexpressed in cancer cells. Here we focused on the relationship between cell growth and the mechanosensitive K2P channel, TREK2, in the human bladder cancer cell line, 253J. We confirmed that TREK2 was expressed in bladder cancer cell lines by Western blot and quantitative real-time PCR. Using the patch-clamp technique, the mechanosensitive TREK2 channel was recorded in the presence of symmetrical 150 mM KCl solutions. In 253J cells, the TREK2 channel was activated by polyunsaturated fatty acids, intracellular acidosis at -60 mV and mechanical stretch at -40 mV or 40 mV. Furthermore, small interfering RNA (siRNA)-mediated TREK2 knockdown resulted in a slight depolarization from -19.9 mV±0.8 (n=116) to -8.5 mV±1.4 (n=74) and decreased proliferation of 253J cells, compared to negative control siRNA. 253J cells treated with TREK2 siRNA showed a significant increase in the expression of cell cycle boundary proteins p21 and p53 and also a remarkable decrease in protein expression of cyclins D1 and D3. Taken together, the TREK2 channel is present in bladder cancer cell lines and may, at least in part, contribute to cell cycle-dependent growth.

Phosphorylation on the Ser 824 residue of TRPV4 prefers to bind with F-actin than with microtubules to expand the cell surface area.

Previously, we demonstrated that the transient receptor potential vanilloid 4 (TRPV4) cation channel, a member of the TRP vanilloid subfamily, is one of the serum glucocorticoid-induced protein kinase1 (SGK1) authentic substrate proteins, and that the Ser 824 residue of TRPV4 is phosphorylated by SGK1. In this study, we demonstrated that phosphorylation on the Ser 824 residue of TRPV4 is required for its interaction with F-actin, using TRPV4 mutants (S824D; a phospho-mimicking TRPV4 mutant and S824A; a non-phosphorylatable TRPV4 mutant) and its proper subcellular localization. Additionally, we noted that the phosphorylation of the Ser824 residue promotes its single channel activity, Ca(2+) influx, protein stability, and cell surface area (expansion of plasma membrane).

Quercetin-induced Growth Inhibition in Human Bladder Cancer Cells Is Associated with an Increase in Ca-activated K Channels.

Quercetin (3,3',4',5,7-pentahydroxyflavone) is an attractive therapeutic flavonoid for cancer treatment because of its beneficial properties including apoptotic, antioxidant, and antiproliferative effects on cancer cells. However, the exact mechanism of action of quercetin on ion channel modulation is poorly understood in bladder cancer 253J cells. In this study, we demonstrated that large conductance Ca(2+)-activated K(+) (BK(Ca)) or MaxiK channels were functionally expressed in 253J cells, and quercetin increased BK(Ca) current in a concentration dependent and reversible manner using a whole cell patch configuration. The half maximal activation concentration (IC(50)) of quercetin was 45.5±7.2 µM. The quercetin-evoked BK(Ca) current was inhibited by tetraethylammonium (TEA; 5 mM) a non-specific BK(Ca) blocker and iberiotoxin (IBX; 100 nM) a BK(Ca)-specific blocker. Quercetin-induced membrane hyperpolarization was measured by fluorescence-activated cell sorting (FACS) with voltage sensitive dye, bis (1,3-dibutylbarbituric acid) trimethine oxonol (DiBAC(4)(3); 100 nM). Quercetin-evoked hyperpolarization was prevented by TEA. Quercetin produced an antiproliferative effect (30.3±13.5%) which was recovered to 53.3±10.5% and 72.9±3.7% by TEA and IBX, respectively. Taken together our results indicate that activation of BK(Ca) channels may be considered an important target related to the action of quercetin on human bladder cancer cells.

Novel PPARγ partial agonists with weak activity and no cytotoxicity; identified by a simple PPARγ ligand screening system.

Peroxisome proliferator-activated receptors (PPARs) are the transcriptional factor that regulate glucose and lipid homeostasis and widely well-known as molecular targets for improvement of metabolic disorder. Because major transcriptional activity of PPARs depends on their proper ligands, the studies for PPAR ligands have been continuously developed. We previously reported the simple enzyme-linked immunosorbent assay (ELISA) systems to screen PPAR ligands and a chemical library including flavonoid derivatives have applied to these systems. In this study, we introduce two compounds (KU16476 and KU28843) identified as PPARγ partial agonists by a screening ELISA for PPARγ ligand. KU16476 and KU28843 significantly increased binding between PPARγ and SRC-1 in a simple ELISA system. Co-activator recruiting-induced abilities of two compounds were less than that of indomethacin, a well-known PPARγ agonist. To determine whether these compounds would be PPARγ partial agonists, each candidate with indomethacin were applied to a simple ELISA based on binding between PPARγ and SRC-1. Cotreatment with indomethacin significantly increased binding between PPARγ and SRC-1 than treatment of indomethacin or candidate alone. Two compounds had no considerable cytotoxicities, induced partial adipogenesis, and accumulated lipid droplets in 3T3-L1 fibroblast. Also, these two compounds enhanced expression of PPARγ-mediated genes such as aP2 and UCP-2. By docking study, we confirmed that two compounds bound well to the active site of PPARγ with hydrophobic interactions. We suggest that two compounds identified by a simple ELISA system can be PPARγ partial agonists. These PPARγ partial agonists and these studies to find out novel PPARγ agonists may contribute to drug development against metabolic disorders.

High expression of large-conductance Ca2+-activated K+ channel in the CD133+ subpopulation of SH-SY5Y neuroblastoma cells.

Solid tumors contain a population of cancer stem cells (CSCs), and CD133 is widely used as a CSCs marker. We investigated the differences between CD133(+) and CD133(-) cells from the neuroblastoma cell line SH-SY5Y in terms of the expressions of voltage-gated ion channels. A CD133(+) enriched (>60%) population was isolated, and a subsequent whole-cell voltage-clamp study showed that these cells predominantly express TEA-sensitive outward K(+) currents (I(K,TEA)) and TTX-sensitive voltage-gated inward Na(+) currents (I(Na)). Cell-attached single channel recordings demonstrated higher density of large-conductance (155pS) channel in CD133(+) cells than in CD133(-) cells. The TEA-sensitivity and single channel conductance indicated the large-conductance Ca(2+)-activated K(+) channels (BK(Ca)). Furthermore, RT-PCR analysis of 22 transcripts of voltage-gated ion channels in SH-SY5Y cells showed the expressions of Cav1.3, Kir2.1, Kv1.4, Kv2.1, Kv4.2, Kv7.1, BK(Ca), and Nav1.7, and those of BK(Ca) and Nav1.7 were higher in CD133(+) than in CD133(-) cells. In addition, the increase of cytosolic Ca(2+) concentration ([Ca(2+)](c)) in response to ionomycin (a Ca(2+) ionophore) was higher and more sustained in CD133(+) than in CD133(-) cells. Plausibly membrane hyperpolarization via BK(Ca) might be responsible for the augmented Ca(2+) influx observed in CD133(+) cells. The physiological implications of the differential expression of BK(Ca) and Nav1.7 in CSCs require further investigation.

The Inhibition of TREK2 Channel by an Oxidizing Agent, 5,5'-dithio-bis (2-nitrobenzoic acid), via Interaction with the C-terminus Distal to the 353rd Amino Acid.

TREK (TWIK-RElated K(+) channels) and TRAAK (TWIK-Related Arachidonic acid Activated K(+) channels) were expressed in COS-7 cells, and the channel activities were recorded from inside-out membrane patches using holding potential of -40 mV in symmetrical 150 mM K(+) solution. Intracellular application of an oxidizing agent, 5,5'-dithio-bis (2-nitrobenzoic acid) (DTNB), markedly decreased the activity of the TREK2, and the activity was partially reversed by the reducing agent, dithiothreitol (DTT). In order to examine the possibility that the target sites for the oxidizing agents might be located in the C-terminus of TREK2, two chimeras were constructed: TREK2 (1-383)/TASK3C and TREK2 (1-353)/TASK3C. The channel activity in the TREK2 (1-383)/TASK3C chimera was still inhibited by DTNB, but not in the TREK2 (1-353)/TASK3C chimera. These results indicate that TREK2 is inhibited by oxidation, and that the target site for oxidation is located between the amino acid residues 353 and 383 in the C-terminus of the TREK2 protein.

Diversity of ion channels in human bone marrow mesenchymal stem cells from amyotrophic lateral sclerosis patients.

Human bone marrow mesenchymal stem cells (hBM-MSCs) represent a potentially valuable cell type for clinical therapeutic applications. The present study was designed to evaluate the effect of long-term culturing (up to 10(th) passages) of hBM-MSCs from eight individual amyotrophic lateral sclerosis (ALS) patients, focusing on functional ion channels. All hBM-MSCs contain several MSCs markers with no significant differences, whereas the distribution of functional ion channels was shown to be different between cells. Four types of K(+) currents, including noise-like Ca(+2)-activated K(+) current (IK(Ca)), a transient outward K(+) current (I(to)), a delayed rectifier K(+) current (IK(DR)), and an inward-rectifier K(+) current (K(ir)) were heterogeneously present in these cells, and a TTX-sensitive Na(+) current (I(Na,TTX)) was also recorded. In the RT-PCR analysis, Kv1.1, heag1, Kv4.2, Kir2.1, MaxiK, and hNE-Na were detected. In particular, I(Na,TTX) showed a significant passage-dependent increase. This is the first report showing that functional ion channel profiling depend on the cellular passage of hBM-MSCs.

Functional expression of ion channels in mesenchymal stem cells derived from umbilical cord vein.

Mesenchymal stem cells have the ability to renew and differentiate into various lineages of mesenchymal tissues. We used undifferentiated human mesenchymal-like stem cells from human umbilical cord vein (hUC-MSCs), a cell line which contains several mesenchymal cell markers. We characterized functional ion channels in cultured hUC-MSCs with whole-cell patch clamp and reverse transcription-polymerase chain reaction (RT-PCR). Three types of outward current were found in these cells: the Ca(2+)-activated K(+) channel (IK(Ca)), a transient outward K(+) current (I(to)), and a delayed rectifier K(+) current (IK(DR)). IK(Ca) and IK(DR) were totally suppressed by tetraethylammonium, and IK(Ca) was sensitive to a specific blocker, iberiotoxin. I(to) was inhibited by 4-aminopyridine. Another type of inward rectifier K(+) current (K(ir)) was also detected in approximately 5% of hUC-MSCs. Elevation of external potassium ion concentration increased the K(ir) current amplitude and positively shifted its reversal potential. In addition, inward Na(+) current (I(Na)) was found in these cells ( approximately 30%); the current was blocked by tetrodotoxin and verapamil. In the RT-PCR analysis, Kv1.1, Kv4.2, Kv1.4, Kir2.1, heag1, MaxiK, hNE-Na, and TWIK-1 were detected. These results suggested that multiple functional ion channel currents, IK(Ca), IK(DR), I(to), I(Na), and K(ir), are expressed in hUC-MSCs. Disclosure of potential conflicts of interest is found at the end of this article.

Hydrogen peroxide selectively increases TREK-2 currents via myosin light chain kinases.

Two-pore domain K+ (K2P) channels play a critical role in cellular responses to various stimuli, such as stretch or changes in pH and are considered to be important in pathological responses such as apoptosis and tumorigenesis. We investigated effects of H2O2 on various K2P channels expressed in CHO cells. Application of H2O2 did not affect TASK-1, TASK-3, TRAAK currents, but specifically increased TREK-2 currents recorded using a nystatin perforated whole cell technique. The H2O2-induced activation of TREK-2 currents was also observed at single channel levels in cell-attached patches, and the effect was reversed by the reducing agent, dithiothreitol. In contrast, TREK-2 currents recorded using ruptured whole cell technique or single channel recording in inside-out patches were not affected by H2O2. Furthermore, direct application of 5,5'-dithiobis-(2-nitrobenzoic acid) inhibited TREK-2, suggesting that the H2O2-induced activation does not result from direct oxidation of TREK-2 proteins. Among the cell signaling agents, myosin light chain kinase (MLCK) inhibitors significantly inhibited the H2O2-induced activation of TREK-2 currents. These results suggest that TREK-2 channels have a potential to play a specific role in cellular responses to reactive oxygen species and that MLCK activation is involved in this process.

Mechanosensitive cation channels in arterial smooth muscle cells are activated by diacylglycerol and inhibited by phospholipase C inhibitor.

Mechanosensitive cation channels may be involved in the development of the myogenic tone of arteries. The molecular identity of these channels is not clear, but transient receptor potential channels (TRPCs) are good candidates. In the present study, we searched for mechanosensitive channels at the single-channel level in arterial smooth muscle cells using the patch-clamp technique and investigated the channel properties in the light of properties of TRPCs. With 140 mmol/L CsCl in the pipette solution, application of negative pressures to the back of the pipette induced the activation of channels the open probability of which increased with the amount of negative pressure. The current-voltage relationship was linear in symmetrical ionic conditions, and the single-channel conductances for Cs+, K+, and Na+ were 30, 36, and 27 pS, respectively. When NMDG+ was substituted for Cs+ in the pipette solution, inward currents were abolished, whereas outward currents remained active, indicating that the channels were nonselective to cations. The channel activity was blocked by intracellular Gd3+ and 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid and increased by diacylglycerol and by cyclopiazonic acid. Phospholipase C inhibitor (U73122) inhibited not only channel activity but also the development of myogenic tone induced by stretching of the basilar arteries. These results suggest that the ion channel responsible for the development of myogenic tone is the 30-pS mechanosensitive cation channel that exhibits properties similar to those of TRPCs.

Acetylcholine-induced phosphatidylinositol 4,5-bisphosphate depletion does not cause short-term desensitization of G protein-gated inwardly rectifying K+ current in mouse atrial myocytes.

Depletion of phosphatidylinositol 4,5-bisphosphate (PIP(2)) induced by phenylephrine or endothelin causes the inhibition of acetylcholine-activated K(+) current (I(KACh)) in atrial myocytes. In the present study, we have investigated the hypothesis that muscarinic receptor induced PIP(2) depletion also causes inhibition of I(KACh), resulting in desensitization. We confirmed the expression of G(q)-coupled muscarinic receptors in mouse atrial myocytes using reverse transcriptase-polymerase chain reaction. The involvement of M(1) and M(3) receptors in desensitization is examined using specific antagonists, 4-DAMP and pirenzepine, but they significantly reduced peak I(KACh), implying nonspecific M(2) blockade. When ACh-induced phosphoinositide depletion was specifically inhibited using PLCbeta1 knock-out mice, the extent of desensitization during 4 min was 47.5 +/- 3.2%, which was not different from that in wild type (46.8 +/- 2.1%). Phenylephrine-induced phosphoinositide hydrolysis and phenylephrine-induced inhibition of I(KACh) were not affected by PLCbeta1 knock-out. To facilitate PIP(2) depletion, replenishment of PIP(2) was blocked by wortmannin. Wortmannin did not affect the desensitization and the recovery from desensitization. These results suggest that PIP(2) depletion by acetylcholine does not contribute to short-term desensitization of I(KACh). The differential regulation of I(KACh) by different phospholipase C-linked receptors may imply that receptor co-localization is required for PIP(2) to act as a signaling molecule.