K+ currents play multiple roles in the excitability of dorsal root ganglion (DRG) neurons. Influences on these currents change the shape of the action potential, its firing threshold and the resting membrane potential. In this study, whole cell configuration of patch clamp technique had been applied to record the blocking effect of capsaicin, a lipophilic alkaloid, on the delayed rectifier K+ current in cultured small diameter DRG neurons of adult rat. Capsaicin reduced the amplitude of K+ current in dose dependent manner, and the concentration-dependence curve was well described by the Hill equation with KD value of 19.1 micrometer. The blocking effect of capsaicin was reversible. Capsaicin (10 micrometer) shifted the steady-state inactivation curve in the hyperpolarizing direction by about 15 mV and increased the rate of inactivation. The voltage dependence of activation was not affected by capsaicin. These multiple effects of capsaicin may suggest that capsaicin bind to the region of K+ channel, participating in inactivation process.
Action Potentials ; Adult* ; Animals ; Capsaicin* ; Diagnosis-Related Groups ; Fires ; Ganglia, Spinal* ; Humans ; Membrane Potentials ; Neurons ; Rats* ; Spinal Nerve Roots*

Potassium channels in human skin fibroblast have been studied as a possible site of Alzheimer disease pathogenesis. Fibroblasts in Alzheimer disease show alterations in signal transduction pathway such as changes in Ca2+ homeostasis and/or Ca2+-activated kinases, phosphatidylinositol cascade, protein kinase C activity, cAMP levels and absence of specific K+ channel. However, little is known so far about electrophysiological and pharmacological characteristics of large-conductance Ca2+-activated K+ (BKCa) channel in human fibroblast (CRL-1474). In the present study, we found Iberiotoxin- and TEA-sensitive outward rectifying oscillatory current with whole-cell recordings. Single channel analysis showed large conductance K+ channels (106 pS of chord conductance at +40 mV in physiological K+ gradient). The 106 pS channels were activated by membrane potential and [Ca2+]i, consistent with the known properties of BKCa channels. BKCa channels in CRL-1474 were positively regulated by adenylate cyclase activator (10microM forskolin), 8-Br-cyclic AMP (300microM) or 8-Br-cyclic GMP (300microM). These results suggest that human skin fibroblasts (CR-1474) have typical BKCa channel and this channel could be modulated by c-AMP and c-GMP. The electrophysiological characteristics of fibroblasts might be used as the diagnostic clues for Alzheimer disease.
Adenylyl Cyclases ; Alzheimer Disease ; Fibroblasts* ; Homeostasis ; Humans ; Membrane Potentials ; Nucleotides, Cyclic* ; Patch-Clamp Techniques ; Phosphatidylinositols ; Phosphotransferases ; Potassium Channels ; Protein Kinase C ; Second Messenger Systems ; Signal Transduction ; Skin*

Hydrogen peroxide (H2O2) causes oxidative stress and is considered as an inducer of cell death in various tissues. Two-pore domain K+ (K2p) channels may mediate K+ efflux during apoptotic volume decreases (AVD) in zygotes and in mouse embryos. In the present study, we sought to elucidate linkage between K2p channels and cell death by H2O2. Thus K2p channels (TASK-1, TASK-3, TREK-1, TREK-2) were stably transfected in HEK-293 cells, and cytotoxicity assay was preformed using cell counting kit-8 (CCK-8). Cell survival rates were calculated using the cytotoxicity assay data and dose-response curve was fitted to the H2O2 concentration. Ionic currents were recorded in cell-attached mode. The bath solution was the normal Ringer solution and the pipette solution was high K+ solution. In HEK-293 cells expressing TREK-1, TREK-2, TASK-3, H2O2 induced cell death did not change in comparison to non-transfected HEK-293. In HEK-293 cells expressing TASK-1, however, dose-response curve was significantly shifted to the left. It means that H2O2 induced cell death was increased. In cell attached-mode recording, application of H2O2 (300micrometer) increased activity of all K2P channels. However, a low concentration of H2O2 (50micrometer) increased only TASK-1 channel activity. These results indicate that TASK-1 might participate in K+ efflux by H2O2 at low concentration, thereby inducing AVD.
Animals ; Apoptosis* ; Baths ; Cell Count ; Cell Death ; Cell Survival ; Embryonic Structures ; Hydrogen Peroxide* ; Hydrogen* ; Mice ; Oxidative Stress ; Zygote

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.
Animals ; Arachidonic Acid ; Chimera ; COS Cells ; Dithionitrobenzoic Acid ; Dithiothreitol ; Membranes ; Oxidants

Employing electrophysiological and cell proliferation assay techniques, we studied the effects of Ca2+ -activated K+ channel modulators on the proliferation of human dermal fibroblasts, which is important in wound healing. Macroscopic voltage-dependent outward K+ currents were found at about -40 mV stepped from a holding potential of -70 mV. The amplitude of K+ current was increased by NS1619, a specific large-conductance Ca2+ -activated K+ (BK) channel activator, but decreased by iberiotoxin (IBTX), a specific BK channel inhibitor. To investigate the presence of an intermediate-conductance Ca2+ -activated K+ (IK) channels, we pretreated the fibroblasts with low dose of TEA to block BK currents, and added 1-EBIO (an IK activator). 1-EBIO recovered the currents inhibited by TEA. When various Ca2+ -activated K+ channel modulators were added into culture media for 1~3 days, NS1619 or 1-EBIO inhibited the cell proliferation. On the other hand, IBTX, clotrimazole or apamin, a small conductance Ca2+ -activated K+ channel (SK) inhibitor, increased it. These results suggest that BK, IK, and SK channels might be involved in the proliferation of human dermal fibroblasts, which is inversely related to the channel activation.
Apamin ; Cell Proliferation ; Clotrimazole ; Culture Media ; Fibroblasts* ; Hand ; Humans* ; Tea ; Wound Healing

Exogenous carbon monoxide (0.2%) increases L-type calcium (Ca2+) current in human jejunal circular smooth muscle cells. The stimulatory effect of carbon monoxide (CO) on L-type Ca2+ current is inhibited by pre-application of L-NNA, a classical competitive inhibitor of nitric oxide synthase (NOS) with no significant isoform selectivity (Lim, 2003). In the present study, we investigated which isoform of NOS affected CO induced stimulation of L-type Ca2+ current in human jejunal circular smooth muscle cells. Cells were voltage clamped by whole-cell mode patch clamp technique, and membrane currents were recorded with 10 mM barium as the charge carrier. Before the addition of CO, cells were pretreated with each inhibitor of three NOS isoforms for 15 minutes. CO-stimulating effect on L-type Ca2+ current was partially blocked by N- (3- (Amino-methyl) benzyl) acetamidine-2HCl (1400W, an iNOS inhibitor). On the other hand, 3-bromo-7-nitroindazole (BNI, a nNOS inhibitor) or N5- (1-Iminoethyl)-L-ornithine dihydrochloride (L-NIO, an eNOS inhibitor) completely blocked the CO effect. These data suggest that low dose of exogenous CO may stimulate all NOS isoforms to increase L-type Ca2+ channel through nitric oxide (NO) pathway in human jejunal circular smooth muscle cells.
Barium ; Calcium Channels, L-Type ; Calcium* ; Carbon Monoxide ; Carbon* ; Hand ; Humans* ; Membranes ; Muscle, Smooth* ; Myocytes, Smooth Muscle* ; Nitric Oxide Synthase* ; Nitric Oxide* ; Protein Isoforms

Despite increased evidence of bio-activity following far-infrared (FIR) radiation, susceptibility of cell signaling to FIR radiation-induced homeostasis is poorly understood. To observe the effects of FIR radiation, FIR-radiated materials-coated fabric was put on experimental rats or applied to L6 cells, and microarray analysis, quantitative real-time polymerase chain reaction, and wound healing assays were performed. Microarray analysis revealed that messenger RNA expressions of rat muscle were stimulated by FIR radiation in a dose-dependent manner in amount of 10% and 30% materials-coated. In 30% group, 1,473 differentially expressed genes were identified (fold change [FC] > 1.5), and 218 genes were significantly regulated (FC > 1.5 and p < 0.05). Microarray analysis showed that extracellular matrix (ECM)-receptor interaction, focal adhesion, and cell migration-related pathways were significantly stimulated in rat muscle. ECM and platelet-derived growth factor (PDGF)-mediated cell migration-related genes were increased. And, results showed that the relative gene expression of actin beta was increased. FIR radiation also stimulated actin subunit and actin-related genes. We observed that wound healing was certainly promoted by FIR radiation over 48 h in L6 cells. Therefore, we suggest that FIR radiation can penetrate the body and stimulate PDGF-mediated cell migration through ECM-integrin signaling in rats.
Actins ; Animals ; Cell Movement* ; Extracellular Matrix ; Focal Adhesions ; Gene Expression ; Homeostasis ; Infrared Rays ; Integrins ; Microarray Analysis ; Muscle, Skeletal* ; Platelet-Derived Growth Factor* ; Rats ; Real-Time Polymerase Chain Reaction ; RNA, Messenger ; Wound Healing

Human cardiac fibroblasts (HCFs) have various voltage-dependent K+ channels (VDKCs) that can induce apoptosis. Hydrogen peroxide (H2O2) modulates VDKCs and induces oxidative stress, which is the main contributor to cardiac injury and cardiac remodeling. We investigated whether H2O2 could modulate VDKCs in HCFs and induce cell injury through this process. In whole-cell mode patch-clamp recordings, application of H2O2 stimulated Ca2+-activated K+ (K(Ca)) currents but not delayed rectifier K+ or transient outward K+ currents, all of which are VDKCs. H2O2-stimulated K(Ca) currents were blocked by iberiotoxin (IbTX, a large conductance K(Ca) blocker). The H2O2-stimulating effect on large-conductance K(Ca) (BK(Ca)) currents was also blocked by KT5823 (a protein kinase G inhibitor) and 1 H-[1, 2, 4] oxadiazolo-[4, 3-a] quinoxalin-1-one (ODQ, a soluble guanylate cyclase inhibitor). In addition, 8-bromo-cyclic guanosine 3', 5'-monophosphate (8-Br-cGMP) stimulated BK(Ca) currents. In contrast, KT5720 and H-89 (protein kinase A inhibitors) did not block the H2O2-stimulating effect on BK(Ca) currents. Using RT-PCR and western blot analysis, three subtypes of K(Ca) channels were detected in HCFs: BK(Ca) channels, small-conductance K(Ca) (SK(Ca)) channels, and intermediate-conductance K(Ca) (IK(Ca)) channels. In the annexin V/propidium iodide assay, apoptotic changes in HCFs increased in response to H2O2, but IbTX decreased H2O2-induced apoptosis. These data suggest that among the VDKCs of HCFs, H2O2 only enhances BK(Ca) currents through the protein kinase G pathway but not the protein kinase A pathway, and is involved in cell injury through BK(Ca) channels.
Apoptosis ; Blotting, Western ; Cyclic AMP-Dependent Protein Kinases ; Cyclic GMP-Dependent Protein Kinases ; Fibroblasts* ; Guanosine ; Guanylate Cyclase ; Humans* ; Hydrogen Peroxide* ; Hydrogen* ; Oxidative Stress ; Phosphotransferases ; Potassium Channels, Calcium-Activated ; Protein Kinases*

Lung cancer is the most common cause of cancer deaths worldwide and several molecular signatures have been developed to predict survival in lung cancer. Increasing evidence suggests that proliferation and migration to promote tumor growth are associated with dysregulated ion channel expression. In this study, by analyzing high-throughput gene expression data, we identify the differentially expressed K⁺ channel genes in lung cancer. In total, we prioritize ten dysregulated K⁺ channel genes (5 up-regulated and 5 down-regulated genes, which were designated as K-10) in lung tumor tissue compared with normal tissue. A risk scoring system combined with the K-10 signature accurately predicts clinical outcome in lung cancer, which is independent of standard clinical and pathological prognostic factors including patient age, lymph node involvement, tumor size, and tumor grade. We further indicate that the K-10 potentially predicts clinical outcome in breast and colon cancers. Molecular signature discovered through K⁺ gene expression profiling may serve as a novel biomarker to assess the risk in lung cancer.
Breast ; Colonic Neoplasms ; Gene Expression ; Gene Expression Profiling ; Humans ; Ion Channels ; Lung Neoplasms ; Lung ; Lymph Nodes ; Potassium Channels ; Potassium

Several human diseases have been associated with mitochondrial voltage-dependent anion channel-1 (VDAC1) due to its role in calcium ion transportation and apoptosis. Recent studies suggest that VDAC1 may interact with endothelium-dependent nitric oxide synthase (eNOS). Decreased VDAC1 expression may limit the physical interaction between VDAC1 and eNOS and thus impair nitric oxide production, leading to cardiovascular diseases, including pulmonary arterial hypertension (PAH). In this report, we conducted meta-analysis of genome-wide expression data to identify VDAC1 influenced genes implicated in PAH pathobiology. First, we identified the genes differentially expressed between wild-type and Vdac1 knockout mouse embryonic fibroblasts in hypoxic conditions. These genes were deemed to be influenced by VDAC1 deficiency. Gene ontology analysis indicates that the VDAC1 influenced genes are significantly associated with PAH pathobiology. Second, a molecular signature derived from the VDAC1 influenced genes was developed. We suggest that, VDAC1 has a protective role in PAH and the gene expression signature of VDAC1 influenced genes can be used to i) predict severity of pulmonary hypertension secondary to pulmonary diseases, ii) differentiate idiopathic pulmonary artery hypertension (IPAH) patients from controls, and iii) differentiate IPAH from connective tissue disease associated PAH.
Animals ; Anoxia ; Apoptosis ; Calcium ; Cardiovascular Diseases ; Connective Tissue Diseases ; Fibroblasts ; Gene Expression ; Gene Ontology ; Humans ; Hypertension ; Hypertension, Pulmonary* ; Ion Transport ; Lung Diseases ; Mice ; Mice, Knockout ; Nitric Oxide ; Nitric Oxide Synthase ; Pulmonary Artery ; Transcriptome