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1.  Flt-3 Ligand Increases a Lung Dendritic Cell Subset with Regulatory Properties in allergic airway inflammation 
Dendritic cell subsets display different functional role in regulating immune response and lead to various outcomes including Th1 versus Th2 or regulatory versus immunologic response. Administration of Flt3-Ligand prevents and reverses allergic airway inflammation and airway hyperresponsiveness in a mouse model. However, the underlying mechanisms are unclear.
We characterized and examined the role of lung dendritic cell subsets in the therapeutic effect of Flt3-Ligand.
Dendritic cells were isolated from the lungs of OVA-sensitized and challenged mice treated with rhFlt3-Ligand. Two populations of CD11c+ cells labeled with fluorochrome-conjugated antibodies were sorted. The ability of the purified cells to stimulate T cell proliferation and cytokine secretion pattern by different DC subsets was examined. Also, dendritic cells were adoptively transferred in mice to examine their effect on pulmonary function.
Two dendritic cell populations, CD11chighCD11blow and CD11clowCD11bhigh, were identified in the lungs of naïve and OVA-sensitized and challenged mice with and without treatment with Flt3-Ligand. The expression levels of CD8α, B220, CD19, F4/80, MHC II, CCR7, CD40, PDL1, PDL2, CD80, and CD86 were distinctly different between the two DC populations, which supports the notion that, CD11chighCD11blow and CD11clowCD11bhigh dendritic cells, potentially have regulatory and immunogenic properties, respectively. Administration of Flt3-Ligand increased the dendritic cells with regulatory potential in the lungs of antigen-sensitized mice, and CD11chighCD11blow dendritic cells acquired a maximum degree of regulatory capacity after Flt3-Ligand treatment.
These data suggest that Flt3-Ligand reverses airway hyperresponsiveness by regulating the function of lung dendritic cells in a mouse model of allergic airway inflammation.
Clinical implication
Flt3-Ligand could be a potential immunomodulator in the treatment of established asthma.
PMCID: PMC2690643  PMID: 19348927
Adoptive transfer; Airway hyperresponsiveness; Asthma; Dendritic cells; Flt3-Ligand; Mouse model; T cell Proliferation; Regulatory dendritic cells
2.  Intermediate-conductance Calcium-activated Potassium Channel KCa3.1 and Chloride Channel Modulate Chemokine Ligand (CCL19/CCL21)-induced Migration of Dendritic Cells 
The role of ion channels is largely unknown in chemokine-induced migration in non-excitable cells such as dendritic cells. Here, we examined the role of KCa3.1 and chloride channels in lymphatic chemokines-induced migration of dendritic cells. The amplitude and kinetics of CCL19/21-induced Ca2+ influx were associated with CCR7 expression levels, extracellular free Ca2+ and Cl−, and independent of extracellular K+. Chemokines, CCL19 and CCL21, and KCa3.1 activator, 1-EBIO, induced plasma membrane hyperpolarization and K+ efflux, which was blocked by TRAM-34, suggesting that KCa3.1 carried larger conductance than the inward CRAC. Blockade of KCa3.1, low Cl− in the medium, and low dose of DIDS impaired CCL19/CCL21-induced Ca2+ influx, cell volume change, and DC migration. High doses of DIDS completely blocked DC migration possibly by significantly disrupting mitochondrial membrane potential. In conclusion, KCa3.1 and chloride channel are critical in human DC migration by synergistically regulating membrane potential, chemokine-induced Ca2+ influx, and cell volume.
PMCID: PMC4458411  PMID: 25583444
3.  Activation of endothelial and epithelial KCa2.3 calcium-activated potassium channels by NS309 relaxes human small pulmonary arteries and bronchioles 
British Journal of Pharmacology  2012;167(1):37-47.
Small (KCa2) and intermediate (KCa3.1) conductance calcium-activated potassium channels (KCa) may contribute to both epithelium- and endothelium-dependent relaxations, but this has not been established in human pulmonary arteries and bronchioles. Therefore, we investigated the expression of KCa2.3 and KCa3.1 channels, and hypothesized that activation of these channels would produce relaxation of human bronchioles and pulmonary arteries.
Channel expression and functional studies were conducted in human isolated small pulmonary arteries and bronchioles. KCa2 and KCa3.1 currents were examined in human small airways epithelial (HSAEpi) cells by whole-cell patch clamp techniques.
While KCa2.3 expression was similar, KCa3.1 protein was more highly expressed in pulmonary arteries than bronchioles. Immunoreactive KCa2.3 and KCa3.1 proteins were found in both endothelium and epithelium. KCa currents were present in HSAEpi cells and sensitive to the KCa2.3 blocker UCL1684 and the KCa3.1 blocker TRAM-34. In pulmonary arteries contracted by U46619 and in bronchioles contracted by histamine, the KCa2.3/ KCa3.1 activator, NS309, induced concentration-dependent relaxations. NS309 was equally potent in relaxing pulmonary arteries, but less potent in bronchioles, than salbutamol. NS309 relaxations were blocked by the KCa2 channel blocker apamin, while the KCa3.1 channel blocker, charybdotoxin failed to reduce relaxation to NS309 (0.01–1 µM).
KCa2.3 and KCa3.1 channels are expressed in the endothelium of human pulmonary arteries and epithelium of bronchioles. KCa2.3 channels contributed to endo- and epithelium-dependent relaxations suggesting that these channels are potential targets for treatment of pulmonary hypertension and chronic obstructive pulmonary disease.
PMCID: PMC3448912  PMID: 22506557
calcium-activated potassium channels; pulmonary arteries; bronchioles; KCa3.1; KCa2.3; NS309
4.  High Glucose Induces CCL20 in Proximal Tubular Cells via Activation of the KCa3.1 Channel 
PLoS ONE  2014;9(4):e95173.
Inflammation plays a key role in the development and progression of diabetic nephropathy (DN). KCa3.1, a calcium activated potassium channel protein, is associated with vascular inflammation, atherogenesis, and proliferation of endothelial cells, macrophages, and fibroblasts. We have previously demonstrated that the KCa3.1 channel is activated by TGF-β1 and blockade of KCa3.1 ameliorates renal fibrotic responses in DN through inhibition of the TGF-β1 pathway. The present study aimed to identify the role of KCa3.1 in the inflammatory responses inherent in DN.
Human proximal tubular cells (HK2 cells) were exposed to high glucose (HG) in the presence or absence of the KCa3.1 inhibitor TRAM34 for 6 days. The proinflammatory cytokine chemokine (C-C motif) ligand 20 (CCL20) expression was examined by real-time PCR and enzyme-linked immunosorbent assay (ELISA). The activity of nuclear factor-κB (NF-κB) was measured by nuclear extraction and electrophoretic mobility shift assay (EMSA). In vivo, the expression of CCL20, the activity of NF-κB and macrophage infiltration (CD68 positive cells) were examined by real-time PCR and/or immunohistochemistry staining in kidneys from diabetic or KCa3.1-/- mice, and in eNOS-/- diabetic mice treated with the KCa3.1 channel inhibitor TRAM34.
In vitro data showed that TRAM34 inhibited CCL20 expression and NF-κB activation induced by HG in HK2 cells. Both mRNA and protein levels of CCL20 significantly decreased in kidneys of diabetic KCa3.1-/- mice compared to diabetic wild type mice. Similarly, TRAM34 reduced CCL20 expression and NF-κB activation in diabetic eNOS-/- mice compared to diabetic controls. Blocking the KCa3.1 channel in both animal models led to a reduction in phosphorylated NF-κB.
Overexpression of CCL20 in human proximal tubular cells is inhibited by blockade of KCa3.1 under diabetic conditions through inhibition of the NF-κB pathway.
PMCID: PMC3986377  PMID: 24733189
5.  High Expression of KCa3.1 in Patients with Clear Cell Renal Carcinoma Predicts High Metastatic Risk and Poor Survival 
PLoS ONE  2015;10(4):e0122992.
Ca2+-activated K+ channels have been implicated in cancer cell growth, metastasis, and tumor angiogenesis. Here we hypothesized that high mRNA and protein expression of the intermediate-conductance Ca2+-activated K+ channel, KCa3.1, is a molecular marker of clear cell Renal Cell Carcinoma (ccRCC) and metastatic potential and survival.
Methodology/Principal Findings
We analyzed channel expression by qRT-PCR, immunohistochemistry, and patch-clamp in ccRCC and benign oncocytoma specimens, in primary ccRCC and oncocytoma cell lines, as well as in two ccRCC cell lines (Caki-1 and Caki-2). CcRCC specimens contained 12-fold higher mRNA levels of KCa3.1 than oncocytoma specimens. The large-conductance channel, KCa1.1, was 3-fold more highly expressed in ccRCC than in oncocytoma. KCa3.1 mRNA expression in ccRCC was 2-fold higher than in the healthy cortex of the same kidney. Disease specific survival trended towards reduction in the subgroup of high-KCa3.1-expressing tumors (p<0.08 vs. low-KCa3.1-expressing tumors). Progression-free survival (time to metastasis/recurrence) was reduced significantly in the subgroup of high-KCa3.1-expressing tumors (p<0.02, vs. low-KCa3.1-expressing tumors). Immunohistochemistry revealed high protein expression of KCa3.1 in tumor vessels of ccRCC and oncocytoma and in a subset of ccRCC cells. Oncocytoma cells were devoid of KCa3.1 protein. In a primary ccRCC cell line and Caki-1/2-ccRCC cells, we found KCa3.1-protein as well as TRAM-34-sensitive KCa3.1-currents in a subset of cells. Furthermore, Caki-1/2-ccRCC cells displayed functional Paxilline-sensitive KCa1.1 currents. Neither KCa3.1 nor KCa1.1 were found in a primary oncocytoma cell line. Yet KCa-blockers, like TRAM-34 (KCa3.1) and Paxilline (KCa1.1), had no appreciable effects on Caki-1 proliferation in-vitro.
Our study demonstrated expression of KCa3.1 in ccRCC but not in benign oncocytoma. Moreover, high KCa3.1-mRNA expression levels were indicative of low disease specific survival of ccRCC patients, short progression-free survival, and a high metastatic potential. Therefore, KCa3.1 is of prognostic value in ccRCC.
PMCID: PMC4388734  PMID: 25848765
6.  Intermediate-conductance calcium-activated potassium channels participate in neurovascular coupling 
British Journal of Pharmacology  2011;164(3):922-933.
Controlling vascular tone involves K+ efflux through endothelial cell small- and intermediate-conductance calcium-activated potassium channels (KCa2.3 and KCa3.1, respectively). We investigated the expression of these channels in astrocytes and the possibility that, by a similar mechanism, they might contribute to neurovascular coupling.
Transgenic mice expressing enhanced green fluorescent protein (eGFP) in astrocytes were used to assess KCa2.3 and KCa3.1 expression by immunohistochemistry and RT-PCR. KCa currents in eGFP-positive astrocytes were determined in situ using whole-cell patch clamp electrophysiology. The contribution of KCa3.1 to neurovascular coupling was investigated in pharmacological experiments using electrical field stimulation (EFS) to evoke parenchymal arteriole dilatation in FVB/NJ mouse brain slices and whisker stimulation to evoke changes in cerebral blood flow in vivo, measured by laser Doppler flowmetry.
KCa3.1 immunoreactivity was restricted to astrocyte processes and endfeet and RT-PCR confirmed astrocytic KCa2.3 and KCa3.1 mRNA expression. With 200 nM [Ca2+]i, the KCa2.1-2.3/KCa3.1 opener NS309 increased whole-cell currents. CyPPA, a KCa2.2/KCa2.3 opener, was without effect. With 1 µM [Ca2+]i, the KCa3.1 inhibitor TRAM-34 reduced currents whereas apamin (KCa2.1-2.3 blocker) had no effect. CyPPA also inhibited currents evoked by NS309 in HEK293 cells expressing KCa3.1. EFS-evoked Fluo-4 fluorescence confirmed astrocyte endfoot recruitment into neurovascular coupling. TRAM-34 inhibited EFS-evoked arteriolar dilatation by 50% whereas charybdotoxin, a blocker of KCa3.1 and the large-conductance KCa channel, KCa1.1, inhibited dilatation by 82%. TRAM-34 reduced the cortical hyperaemic response to whisker stimulation by 40%.
Astrocytes express functional KCa3.1 channels, and these contribute to neurovascular coupling.
This article is part of a themed issue on Vascular Endothelium in Health and Disease. To view the other articles in this issue visit
PMCID: PMC3195915  PMID: 21506954
astrocyte; brain slice; KCa2.3; KCa3.1; electrical field stimulation; laser Doppler flowmetry; neurovascular coupling; CyPPA; NS309
7.  The Blockage of KCa3.1 Channel Inhibited Proliferation, Migration and Promoted Apoptosis of Human Hepatocellular Carcinoma Cells 
Journal of Cancer  2015;6(7):643-651.
The intermediate conductance calcium-activated potassium channel KCa3.1 plays an important role in regulating cell proliferation and migration. However, the role of KCa3.1 channel in human hepatocellular carcinoma remained unknown. This study was therefore performed to investigate the effects of KCa3.1 potassium channel blocker on the proliferation, apoptosis and migration of human hepatocellular cancer cells HepG2. KCa3.1 mRNA and protein were detected in HepG2. Furthermore, KCa3.1 potassium channel blocker TRAM-34 was capable to inhibit the proliferation and induce the apoptosis of HepG2 cells, which can be partially attenuated by 1-EBIO, an activator of KCa3.1 channel. Moreover, the migration of HepG2 was obviously inhibited by TRAM-34. Consistently, knockdown of KCa3.1 channel using its siRNA was also able to induce apoptosis and suppress proliferation and migration of HepG2. Meanwhile, intracellular ROS level was found augmented in HepG2 treated with TRAM-34. More importantly, p53 protein was found translocation from the cytoplasm into the nuclei of HepG2. Collectively, inhibition of KCa3.1 channel suppressed the growth and migration, and promoted the apoptosis of human hepatocellular carcinoma cells by regulating intracellular ROS level and promoting p53 activation. This data suggests TRAM-34 as a promising anti-tumor drug for liver cancer.
PMCID: PMC4466414  PMID: 26078795
TRAM-34; Migration; Apoptosis; Proliferation; p53; ROS
8.  Functional KCa3.1 K+ channels are required for human lung mast cell migration 
Thorax  2006;61(10):880-885.
Mast cell recruitment and activation are critical for the initiation and progression of inflammation and fibrosis. Mast cells infiltrate specific structures in many diseased tissues such as the airway smooth muscle (ASM) in asthma. This microlocalisation of mast cells is likely to be key to disease pathogenesis. Human lung mast cells (HLMC) express the Ca2+ activated K+ channel KCa3.1 which modulates mediator release, and is proposed to facilitate the retraction of the cell body during migration of several cell types. A study was undertaken to test the hypothesis that blockade of KCa3.1 would attenuate HLMC proliferation and migration.
HLMC were isolated and purified from lung material resected for bronchial carcinoma. HLMC proliferation was assessed by cell counts at various time points following drug exposure. HLMC chemotaxis was assayed using standard Transwell chambers (8 μm pore size). Ion currents were measured using the single cell patch clamp technique.
KCa3.1 blockade with triarylmethane‐34 (TRAM‐34) did not inhibit HLMC proliferation and clotrimazole had cytotoxic effects. In contrast, HLMC migration towards the chemokine CXCL10, the chemoattractant stem cell factor, and the supernatants from tumour necrosis factor α stimulated asthmatic ASM was markedly inhibited with both the non‐selective KCa3.1 blocker charybdotoxin and the highly specific KCa3.1 blocker TRAM‐34 in a dose dependent manner. Although KCa3.1 blockade inhibits HLMC migration, KCa3.1 is not opened by the chemotactic stimulus, suggesting that it must be involved downstream of the initial receptor‐ligand interactions.
Since modulation of KCa3.1 can inhibit HLMC chemotaxis to diverse chemoattractants, the use of KCa3.1 blockers such as TRAM‐34 could provide new therapeutic strategies for mast cell mediated diseases such as asthma.
PMCID: PMC2104766  PMID: 16809411
mast cell; migration; asthma; CXCL10; KCa3.1
9.  Blood Brain Barrier KCa3.1 Channels: Evidence for a Role in Brain Na Uptake and Edema in Ischemic Stroke 
Background and Purpose
KCa3.1, a calcium-activated potassium channel, regulates ion and fluid secretion in the lung and gastrointestinal tract. It is also expressed on vascular endothelium where it participates in blood pressure regulation. However, the expression and physiological role of KCa3.1 in blood-brain barrier (BBB) endothelium has not been investigated. BBB endothelial cells transport Na+ and Cl− from the blood into the brain transcellularly through the cooperation of multiple co-transporters, exchangers, pumps and channels. In the early stages of cerebral ischemia, when the BBB is intact, edema formation occurs by processes involving increased BBB transcellular Na+ transport. This study evaluated whether KCa3.1 is expressed on and participates in BBB ion transport.
The expression of KCa3.1 on cultured cerebral microvascular endothelial cells (CMEC), isolated microvessels and brain sections was evaluated by Western blot and immunohistochemistry. Activity of KCa3.1 on CMEC was examined by K+ flux assays and patch-clamp. Magnetic resonance spectroscopy and imaging were used to measure brain Na+ uptake and edema formation in rats with focal ischemic stroke following TRAM-34 treatment.
KCa3.1 current and channel protein were identified on bovine CMEC and freshly isolated rat microvessels. In situ KCa3.1 expression on BBB endothelium was confirmed in rat and human brain sections. TRAM-34 treatment significantly reduced Na+ uptake, and cytotoxic edema in the ischemic brain.
BBB endothelial cells exhibit KCa3.1 protein and activity and pharmacological blockade of KCa3.1 appears to provide an effective therapeutic approach for reducing cerebral edema formation in the first 3 hours of ischemic stroke.
PMCID: PMC4276511  PMID: 25477223
blood-brain barrier; brain edema; cerebral ischemia; stroke; KCa3.1
10.  Low Voltage Activation of KCa1.1 Current by Cav3-KCa1.1 Complexes 
PLoS ONE  2013;8(4):e61844.
Calcium-activated potassium channels of the KCa1.1 class are known to regulate repolarization of action potential discharge through a molecular association with high voltage-activated calcium channels. The current study examined the potential for low voltage-activated Cav3 (T-type) calcium channels to interact with KCa1.1 when expressed in tsA-201 cells and in rat medial vestibular neurons (MVN) in vitro. Expression of the channel α-subunits alone in tsA-201 cells was sufficient to enable Cav3 activation of KCa1.1 current. Cav3 calcium influx induced a 50 mV negative shift in KCa1.1 voltage for activation, an interaction that was blocked by Cav3 or KCa1.1 channel blockers, or high internal EGTA. Cav3 and KCa1.1 channels coimmunoprecipitated from lysates of either tsA-201 cells or rat brain, with Cav3 channels associating with the transmembrane S0 segment of the KCa1.1 N-terminus. KCa1.1 channel activation was closely aligned with Cav3 calcium conductance in that KCa1.1 current shared the same low voltage dependence of Cav3 activation, and was blocked by voltage-dependent inactivation of Cav3 channels or by coexpressing a non calcium-conducting Cav3 channel pore mutant. The Cav3-KCa1.1 interaction was found to function highly effectively in a subset of MVN neurons by activating near –50 mV to contribute to spike repolarization and gain of firing. Modelling data indicate that multiple neighboring Cav3-KCa1.1 complexes must act cooperatively to raise calcium to sufficiently high levels to permit KCa1.1 activation. Together the results identify a novel Cav3-KCa1.1 signaling complex where Cav3-mediated calcium entry enables KCa1.1 activation over a wide range of membrane potentials according to the unique voltage profile of Cav3 calcium channels, greatly extending the roles for KCa1.1 potassium channels in controlling membrane excitability.
PMCID: PMC3633930  PMID: 23626738
11.  The Inhibition of KCa3.1 Channels Activity Reduces Cell Motility in Glioblastoma Derived Cancer Stem Cells 
PLoS ONE  2012;7(10):e47825.
In the present study we evaluated the expression of the intermediate conductance calcium-activated potassium (KCa3.1) channel in human glioblastoma stem-like cells (CSCs) and investigated its role in cell motility. While the KCa3.1 channel is not expressed in neuronal- and glial-derived tissues of healthy individuals, both the KCa3.1 mRNA and protein are present in the glioblastoma tumor population, and are significantly enhanced in CSCs derived from both established cell line U87MG and a primary cell line, FCN9. Consistent with these data, voltage-independent and TRAM-34 sensitive potassium currents imputable to the KCa3.1 channel were recorded in the murine GL261 cell line and several primary human glioblastoma cells lines. Moreover, a significantly higher KCa3.1 current was recorded in U87MG-CD133 positive cells as compared to the U87MG-CD133 negative subpopulation. Further, we found that the tumor cell motility is strongly associated with KCa3.1 channel expression. Blockade of the KCa3.1 channel with the specific inhibitor TRAM-34 has in fact a greater impact on the motility of CSCs (reduction of 75%), which express a high level of KCa3.1 channel, than on the FCN9 parental population (reduction of 32%), where the KCa3.1 channel is expressed at lower level. Similar results were also observed with the CSCs derived from U87MG. Because invasion of surrounding tissues is one of the main causes of treatment failure in glioblastoma, these findings can be relevant for future development of novel cancer therapeutic drugs.
PMCID: PMC3478269  PMID: 23110108
12.  Blocking KCa3.1 Channels Increases Tumor Cell Killing by a Subpopulation of Human Natural Killer Lymphocytes 
PLoS ONE  2013;8(10):e76740.
Natural killer (NK) cells are large granular lymphocytes that participate in both innate and adaptive immune responses against tumors and pathogens. They are also involved in other conditions, including organ rejection, graft-versus-host disease, recurrent spontaneous abortions, and autoimmune diseases such as multiple sclerosis. We demonstrate that human NK cells express the potassium channels Kv1.3 and KCa3.1. Expression of these channels does not vary with expression levels of maturation markers but varies between adherent and non-adherent NK cell subpopulations. Upon activation by mitogens or tumor cells, adherent NK (A-NK) cells preferentially up-regulate KCa3.1 and non-adherent (NA-NK) cells preferentially up-regulate Kv1.3. Consistent with this different phenotype, A-NK and NA-NK do not display the same sensitivity to the selective KCa3.1 blockers TRAM-34 and NS6180 and to the selective Kv1.3 blockers ShK-186 and PAP-1 in functional assays. Kv1.3 block inhibits the proliferation and degranulation of NA-NK cells with minimal effects on A-NK cells. In contrast, blocking KCa3.1 increases the degranulation and cytotoxicity of A-NK cells, but not of NA-NK cells. TRAM-34, however, does not affect their ability to form conjugates with target tumor cells, to migrate, or to express chemokine receptors. TRAM-34 and NS6180 also increase the proliferation of both A-NK and NA-NK cells. This results in a TRAM-34-induced increased ability of A-NK cells to reduce in vivo tumor growth. Taken together, our results suggest that targeting KCa3.1 on NK cells with selective blockers may be beneficial in cancer immunotherapy.
PMCID: PMC3795664  PMID: 24146918
13.  Functional KCa3.1 channels regulate steroid insensitivity in bronchial smooth muscle cells1 
Identifying the factors responsible for relative glucocorticosteroid (GC) resistance present in patients with severe asthma and finding tools to reverse it are of paramount importance. In asthma there is in vivo evidence of GC-resistant pathways in airway smooth muscle (ASM) bundles which can be modelled in vitro by exposing cultured ASM cells to TNFα/IFNγ. This drives GC insensitivity via protein phosphatase-5 (PP5)-dependent impairment of GC receptor (GR) phosphorylation. Here, we investigated whether KCa3.1 ion channels modulate the activity of GC-resistant pathways using our ASM model of GC insensitivity. Immunohistochemical staining of endobronchial biopsies revealed that KCa3.1 channels are localized to the plasma membrane and nucleus of ASM in both healthy controls and asthmatic patients, irrespective of disease severity. Western blot assays and immunofluorescence staining confirmed the nuclear localisation of KCa3.1 channels in ASM cells. The functional importance of KCa3.1 channels in the regulation of GC-resistant chemokines induced by TNFα/IFNγ was assessed using complementary inhibitory strategies including KCa3.1 blockers (TRAM-34 and ICA-17043) or KCa3.1-specific shRNA delivered by adenoviruses. KCa3.1 channel blockade led to a significant reduction of fluticasone-resistant CX3CL1, CCL5 and CCL11 gene and protein expression. KCa3.1 channel blockade also restored fluticasone-induced GRα phosphorylation at ser211 and transactivation properties via the suppression of cytokine-induced PP5 expression. The effect of KCa3.1 blockade was evident in ASM cells from both healthy controls and asthmatic subjects. In summary KCa3.1 channels contribute to the regulation of GC-resistant inflammatory pathways in ASM cells: blocking KCa3.1 channels may enhance corticosteroid activity in severe asthma.
PMCID: PMC3753579  PMID: 23904164
Corticosteroid insensitivity; chemokines; GR phosphorylation; TNFα; transactivation; transrepression; KCa3.1; severe asthma; airway smooth muscle; transcription factors
14.  The intermediate-conductance calcium-activated potassium channel KCa3.1 contributes to atherogenesis in mice and humans 
The Journal of Clinical Investigation  2008;118(9):3025-3037.
Atherosclerosis remains a major cause of death in the developed world despite the success of therapies that lower cholesterol and BP. The intermediate-conductance calcium-activated potassium channel KCa3.1 is expressed in multiple cell types implicated in atherogenesis, and pharmacological blockade of this channel inhibits VSMC and lymphocyte activation in rats and mice. We found that coronary vessels from patients with coronary artery disease expressed elevated levels of KCa3.1. In Apoe–/– mice, a genetic model of atherosclerosis, KCa3.1 expression was elevated in the VSMCs, macrophages, and T lymphocytes that infiltrated atherosclerotic lesions. Selective pharmacological blockade and gene silencing of KCa3.1 suppressed proliferation, migration, and oxidative stress of human VSMCs. Furthermore, VSMC proliferation and macrophage activation were reduced in KCa3.1–/– mice. In vivo therapy with 2 KCa3.1 blockers, TRAM-34 and clotrimazole, significantly reduced the development of atherosclerosis in aortas of Apoe–/– mice by suppressing VSMC proliferation and migration into plaques, decreasing infiltration of plaques by macrophages and T lymphocytes, and reducing oxidative stress. Therapeutic concentrations of TRAM-34 in mice caused no discernible toxicity after repeated dosing and did not compromise the immune response to influenza virus. These data suggest that KCa3.1 blockers represent a promising therapeutic strategy for atherosclerosis.
PMCID: PMC2496961  PMID: 18688283
15.  Knockdown of the small conductance Ca2+‐activated K+ channels is potently cytotoxic in breast cancer cell lines 
British Journal of Pharmacology  2015;173(1):177-190.
Background and Purpose
Small conductance calcium‐activated potassium (KCa2.x) channels have a widely accepted canonical function in regulating cellular excitability. In this study, we address a potential non‐canonical function of KCa2.x channels in breast cancer cell survival, using in vitro models.
Experimental Approach
The expression of all KCa2.x channel isoforms was initially probed using RT‐PCR, Western blotting and microarray analysis in five widely studied breast cancer cell lines. In order to assess the effect of pharmacological blockade and siRNA‐mediated knockdown of KCa2.x channels on these cell lines, we utilized MTS proliferation assays and also followed the corresponding expression of apoptotic markers.
Key Results
All of the breast cancer cell lines, regardless of their lineage or endocrine responsiveness, were highly sensitive to KCa2.x channel blockade. UCL1684 caused cytotoxicity, with LD50 values in the low nanomolar range, in all cell lines. The role of KCa2.x channels was confirmed using pharmacological inhibition and siRNA‐mediated knockdown. This reduced cell viability and also reduced expression of Bcl‐2 but increased expression of active caspase‐7 and caspase‐9. Complementary to these results, a variety of cell lines can be protected from apoptosis induced by staurosporine using the KCa2.x channel activator CyPPA.
Conclusions and Implications
In addition to a well‐established role for KCa2.x channels in migration, blockade of these channels was potently cytotoxic in breast cancer cell lines, pointing to modulation of KCa2.x channels as a potential therapeutic approach to breast cancer.
PMCID: PMC4737296  PMID: 26454020
16.  Knockdown of the small conductance Ca2+‐activated K+ channels is potently cytotoxic in breast cancer cell lines 
British Journal of Pharmacology  2015;173(1):177-190.
Background and Purpose
Small conductance calcium‐activated potassium (KCa2.x) channels have a widely accepted canonical function in regulating cellular excitability. In this study, we address a potential non‐canonical function of KCa2.x channels in breast cancer cell survival, using in vitro models.
Experimental Approach
The expression of all KCa2.x channel isoforms was initially probed using RT‐PCR, Western blotting and microarray analysis in five widely studied breast cancer cell lines. In order to assess the effect of pharmacological blockade and siRNA‐mediated knockdown of KCa2.x channels on these cell lines, we utilized MTS proliferation assays and also followed the corresponding expression of apoptotic markers.
Key Results
All of the breast cancer cell lines, regardless of their lineage or endocrine responsiveness, were highly sensitive to KCa2.x channel blockade. UCL1684 caused cytotoxicity, with LD50 values in the low nanomolar range, in all cell lines. The role of KCa2.x channels was confirmed using pharmacological inhibition and siRNA‐mediated knockdown. This reduced cell viability and also reduced expression of Bcl‐2 but increased expression of active caspase‐7 and caspase‐9. Complementary to these results, a variety of cell lines can be protected from apoptosis induced by staurosporine using the KCa2.x channel activator CyPPA.
Conclusions and Implications
In addition to a well‐established role for KCa2.x channels in migration, blockade of these channels was potently cytotoxic in breast cancer cell lines, pointing to modulation of KCa2.x channels as a potential therapeutic approach to breast cancer.
PMCID: PMC4737296  PMID: 26454020
17.  Increased constitutive αSMA and Smad2/3 expression in idiopathic pulmonary fibrosis myofibroblasts is KCa3.1-dependent 
Respiratory Research  2014;15(1):155.
Idiopathic pulmonary fibrosis is a common and invariably fatal disease with limited therapeutic options. Ca2+-activated KCa3.1 potassium channels play a key role in promoting TGFβ1 and bFGF-dependent profibrotic responses in human lung myofibroblasts (HLMFs). We hypothesised that KCa3.1 channel-dependent cell processes regulate HLMF αSMA expression via Smad2/3 signalling pathways.
In this study we have compared the phenotype of HLMFs derived from non-fibrotic healthy control lungs (NFC) with cells derived from IPF lungs. HLMFs grown in vitro were examined for αSMA expression by immunofluorescence (IF), RT-PCR and flow cytommetry. Basal Smad2/3 signalling was examined by RT-PCR, western blot and immunofluorescence. Two specific and distinct KCa3.1 blockers (TRAM-34 200 nM and ICA-17043 [Senicapoc] 100 nM) were used to determine their effects on HLMF differentiation and the Smad2/3 signalling pathways.
IPF-derived HLMFs demonstrated increased constitutive expression of both α-smooth muscle actin (αSMA) and actin stress fibres, indicative of greater myofibroblast differentiation. This was associated with increased constitutive Smad2/3 mRNA and protein expression, and increased Smad2/3 nuclear localisation. The increased Smad2/3 nuclear localisation was inhibited by removing extracellular Ca2+ or blocking KCa3.1 ion channels with selective KCa3.1 blockers (TRAM-34, ICA-17043). This was accompanied by de-differentiation of IPF-derived HLMFs towards a quiescent fibroblast phenotype as demonstrated by reduced αSMA expression and reduced actin stress fibre formation.
Taken together, these data suggest that Ca2+- and KCa3.1-dependent processes facilitate “constitutive” Smad2/3 signalling in IPF-derived fibroblasts, and thus promote fibroblast to myofibroblast differentiation. Importantly, inhibiting KCa3.1 channels reverses this process. Targeting KCa3.1 may therefore provide a novel and effective approach for the treatment of IPF and there is the potential for the rapid translation of KCa3.1-directed therapy to the clinic.
PMCID: PMC4263015  PMID: 25476248
Idiopathic pulmonary fibrosis (IPF); Fibrosis; Lung; Myofibroblast; KCa3.1; Ion channel; Differentiation; Smad 2; Smad 3
18.  The potassium channel KCa3.1 as new therapeutic target for the prevention of obliterative airway disease 
Transplantation  2013;95(2):285-292.
The calcium-activated potassium channel KCa3.1 is critically involved in T cell activation, as well as in the proliferation of smooth muscle cells and fibroblasts. We sought to investigate whether KCa3.1 contributes to the pathogenesis of obliterative airway disease (OAD) and whether knockout or pharmacological blockade would prevent the development of OAD.
Tracheas from CBA donors were heterotopically transplanted into the omentum of C57Bl/6J wild-type or KCa3.1−/− mice. C57Bl/6J recipients were either left untreated or received the KCa3.1 blocker TRAM-34 (120mg/kg/d). Histopathology and immunological assays were performed on postoperative days (POD) 5 or 28.
Subepithelial T cell and macrophage infiltration on POD 5, as seen in untreated allografts, was significantly reduced in the KCa3.1−/− and TRAM-34 groups. Also, systemic Th1 activation was significantly, and Th2 mildly reduced by KCa3.1 knockout or blockade. After 28 days, luminal obliteration of tracheal allografts was reduced from 89±21% in untreated recipients to 53±26% (p=0.010) and 59±33% (p=0.032) in KCa3.1−/− and TRAM-34-treated animals, respectively. The airway epithelium was mostly preserved in syngeneic grafts, mostly destroyed in the KCa3.1−/− and TRAM-34 groups, and absent in untreated allografts. Allografts triggered an antibody response in untreated recipients, which was significantly reduced in KCa3.1−/− animals. KCa3.1 was detected in T cells, airway epithelial cells and myofibroblasts. TRAM-34 dose-dependently suppressed proliferation of wild-type C57B/6J splenocytes, but did not show any effect on KCa3.1−/− splenocytes.
Our findings suggest that KCa3.1 channels are involved in the pathogenesis of OAD and that KCa3.1 blockade holds promise to reduce OAD development.
PMCID: PMC3777777  PMID: 23325003
KCa3.1; Obliterative airway disease; TRAM-34; Chronic rejection; Heterotopic tracheal transplantation
19.  Development of a QPatch Automated Electrophysiology Assay for Identifying KCa3.1 Inhibitors and Activators 
The intermediate-conductance Ca2+-activated K+ channel KCa3.1 (also known as KCNN4, IK1, or the Gárdos channel) plays an important role in the activation of T and B cells, mast cells, macrophages, and microglia by regulating membrane potential, cellular volume, and calcium signaling. KCa3.1 is further involved in the proliferation of dedifferentiated vascular smooth muscle cells and fibroblast and endothelium-derived hyperpolarization responses in the vascular endothelium. Accordingly, KCa3.1 inhibitors are therapeutically interesting as immunosuppressants and for the treatment of a wide range of fibroproliferative disorders, whereas KCa3.1 activators constitute a potential new class of endothelial function preserving antihypertensives. Here, we report the development of QPatch assays for both KCa3.1 inhibitors and activators. During assay optimization, the Ca2+ sensitivity of KCa3.1 was studied using varying intracellular Ca2+ concentrations. A free Ca2+ concentration of 1 μM was chosen to optimally test inhibitors. To identify activators, which generally act as positive gating modulators, a lower Ca2+ concentration (∼200 nM) was used. The QPatch results were benchmarked against manual patch-clamp electrophysiology by determining the potency of several commonly used KCa3.1 inhibitors (TRAM-34, NS6180, ChTX) and activators (EBIO, riluzole, SKA-31). Collectively, our results demonstrate that the QPatch provides a comparable but much faster approach to study compound interactions with KCa3.1 channels in a robust and reliable assay.
PMCID: PMC3870577  PMID: 24351043
20.  Ca2+-Activated K+ Channel–3.1 Blocker TRAM-34 Attenuates Airway Remodeling and Eosinophilia in a Murine Asthma Model 
Key features of asthma include bronchial hyperresponsiveness (BHR), eosinophilic airway inflammation, and bronchial remodeling, characterized by subepithelial collagen deposition, airway fibrosis, and increased bronchial smooth muscle (BSM) mass. The calcium-activated K+ channel KCa3.1 is expressed by many cells implicated in the pathogenesis of asthma, and is involved in both inflammatory and remodeling responses in a number of tissues. The specific KCa3.1 blocker 5-[(2-chlorophenyl)(diphenyl)methyl]-1H-pyrazole (TRAM-34) attenuates BSM cell proliferation, and both mast cell and fibrocyte recruitment in vitro. We aimed to examine the effects of KCa3.1 blockade on BSM remodeling, airway inflammation, and BHR in a murine model of chronic asthma. BALB/c mice were sensitized with intraperitoneal ovalbumin (OVA) on Days 0 and 14, and then challenged with intranasal OVA during Days 14–75. OVA-sensitized/challenged mice received TRAM-34 (120 mg/kg/day, subcutaneous) from Days −7 to 75 (combined treatment), Days −7 to 20 (preventive treatment), or Days 21 to 75 (curative treatment). Untreated mice received daily injections of vehicle (n = 8 per group). Bronchial remodeling was assessed by histological and immunohistochemical analyses. Inflammation was evaluated using bronchoalveolar lavage and flow cytometry. We also determined BHR in both conscious and anesthetized mice via plethysmography. We demonstrated that curative treatment with TRAM-34 abolishes BSM remodeling and subbasement collagen deposition, and attenuates airway eosinophilia. Although curative treatment alone did not significantly reduce BHR, the combined treatment attenuated nonspecific BHR to methacholine. This study indicates that KCa3.1 blockade could provide a new therapeutic strategy in asthma.
PMCID: PMC4035224  PMID: 23204391
asthma; KCa3.1; ion channel; remodeling; smooth muscle
21.  Calcium-activated potassium channels mediated blood-brain tumor barrier opening in a rat metastatic brain tumor model 
Molecular Cancer  2007;6:22.
The blood-brain tumor barrier (BTB) impedes the delivery of therapeutic agents to brain tumors. While adequate delivery of drugs occurs in systemic tumors, the BTB limits delivery of anti-tumor agents into brain metastases.
In this study, we examined the function and regulation of calcium-activated potassium (KCa) channels in a rat metastatic brain tumor model. We showed that intravenous infusion of NS1619, a KCa channel agonist, and bradykinin selectively enhanced BTB permeability in brain tumors, but not in normal brain. Iberiotoxin, a KCa channel antagonist, significantly attenuated NS1619-induced BTB permeability increase. We found KCa channels and bradykinin type 2 receptors (B2R) expressed in cultured human metastatic brain tumor cells (CRL-5904, non-small cell lung cancer, metastasized to brain), human brain microvessel endothelial cells (HBMEC) and human lung cancer brain metastasis tissues. Potentiometric assays demonstrated the activity of KCa channels in metastatic brain tumor cells and HBMEC. Furthermore, we detected higher expression of KCa channels in the metastatic brain tumor tissue and tumor capillary endothelia as compared to normal brain tissue. Co-culture of metastatic brain tumor cells and brain microvessel endothelial cells showed an upregulation of KCa channels, which may contribute to the overexpression of KCa channels in tumor microvessels and selectivity of BTB opening.
These findings suggest that KCa channels in metastatic brain tumors may serve as an effective target for biochemical modulation of BTB permeability to enhance selective delivery of chemotherapeutic drugs to metastatic brain tumors.
PMCID: PMC1831484  PMID: 17359538
22.  Inhibition of vascular calcium-gated chloride currents by blockers of KCa1.1, but not by modulators of KCa2.1 or KCa2.3 channels 
British Journal of Pharmacology  2009;158(2):521-531.
Background and purpose:
Recent pharmacological studies have proposed there is a high degree of similarity between calcium-activated Cl− channels (CaCCs) and large conductance, calcium-gated K+ channels (KCa1.1). The goal of the present study was to ascertain whether blockers of KCa1.1 inhibited calcium-activated Cl− currents (IClCa) and if the pharmacological overlap between KCa1.1 and CaCCs extends to intermediate and small conductance, calcium-activated K+ channels.
Experimental approaches:
Whole-cell Cl− and K+ currents were recorded from murine portal vein myocytes using the whole-cell variant of the patch clamp technique. CaCC currents were evoked by pipette solutions containing 500 nM free [Ca2+].
Key results:
The selective KCa1.1 blocker paxilline (1 µM) inhibited IClCa by ∼90%, whereas penitrem A (1 µM) and iberiotoxin (100 and 300 nM) reduced the amplitude of IClCa by ∼20%, as well as slowing channel deactivation. Paxilline also abolished the stimulatory effect of niflumic acid on the CaCC. In contrast, an antibody against the Ca2+-binding domain of murine KCa1.1 had no effect on IClCa while inhibiting spontaneous KCa1.1 currents. Structurally different modulators of small and intermediate conductance calcium-activated K+ channels (KCa2.1 and KCa2.3), namely 1-EBIO, (100 µM); NS309, (1 µM); TRAM-34, (10 µM); UCL 1684, (1 µM) had no effect on IClCa.
Conclusions and implications:
These data show that the selective KCa1.1 blockers also reduce IClCa considerably. However, the pharmacological overlap that exists between CaCCs and KCa1.1 does not extend to the calcium-binding domain or to other calcium-gated K+ channels.
PMCID: PMC2757692  PMID: 19645713
calcium-activated chloride currents; calcium-activated potassium currents; KCa1.1; KCa2.1; KCa2.3; mslo; vascular smooth muscle; iberiotoxin; 1-EBIO
23.  Genetic ablation of caveolin-1 modifies Ca2+ spark coupling in murine arterial smooth muscle cells 
L-type, voltage-dependent calcium (Ca2+) channels, ryanodine-sensitive Ca2+ release (RyR) channels, and large-conductance Ca2+-activated potassium (KCa) channels comprise a functional unit that regulates smooth muscle contractility. Here, we investigated whether genetic ablation of caveolin-1 (cav-1), a caveolae protein, alters Ca2+ spark to KCa channel coupling and Ca2+ spark regulation by voltage-dependent Ca2+ channels in murine cerebral artery smooth muscle cells. Caveolae were abundant in the sarcolemma of control (cav-+/+) cells but were not observed in cav-1-deficient (cav-1−/−) cells. Ca2+ spark and transient KCa current frequency were approximately twofold higher in cav-1−/− than in cav-1+/+ cells. Although voltage-dependent Ca2+ current density was similar in cav-1+/+ and cav-1−/− cells, diltiazem and Cd2+, voltage-dependent Ca2+ channel blockers, reduced transient KCa current frequency to ∼55% of control in cav-1+/+ cells but did not alter transient KCa current frequency in cav-1−/− cells. Furthermore, although KCa channel density was elevated in cav-1−/− cells, transient KCa current amplitude was similar to that in cav-1+/+ cells. Higher Ca2+ spark frequency in cav-1−/− cells was not due to elevated intracellular Ca2+ concentration, sarcoplasmic reticulum Ca2+ load, or nitric oxide synthase activity. Similarly, Ca2+ spark amplitude and spread, the percentage of Ca2+ sparks that activated a transient KCa current, the amplitude relationship between sparks and transient KCa currents, and KCa channel conductance and apparent Ca2+ sensitivity were similar in cav-1+/+ and cav-1−/− cells. In summary, cav-1 ablation elevates Ca2+ spark and transient KCa current frequency, attenuates the coupling relationship between voltage-dependent Ca2+ channels and RyR channels that generate Ca2+ sparks, and elevates KCa channel density but does not alter transient KCa current activation by Ca2+ sparks. These findings indicate that cav-1 is required for physiological Ca2+ spark and transient KCa current regulation in cerebral artery smooth muscle cells.
PMCID: PMC1698957  PMID: 16428350
ryanodine-sensitive Ca2+ release channel; large-conductance Ca2+-activated potassium channel; caveolae; voltage-dependent Ca2+ channel
24.  The K+ Channel KCa3.1 as a Novel Target for Idiopathic Pulmonary Fibrosis  
PLoS ONE  2013;8(12):e85244.
Idiopathic pulmonary fibrosis (IPF) is a common, progressive and invariably lethal interstitial lung disease with no effective therapy. We hypothesised that KCa3.1 K+ channel-dependent cell processes contribute to IPF pathophysiology.
KCa3.1 expression in primary human lung myofibroblasts was examined using RT-PCR, western blot, immunofluorescence and patch-clamp electrophysiology. The role of KCa3.1 channels in myofibroblast proliferation, wound healing, collagen secretion and contraction was examined using two specific and distinct KCa3.1 blockers (TRAM-34 and ICA-17043 [Senicapoc]).
Both healthy non fibrotic control and IPF-derived human lung myofibroblasts expressed KCa3.1 channel mRNA and protein. KCa3.1 ion currents were elicited more frequently and were larger in IPF-derived myofibroblasts compared to controls. KCa3.1 currents were increased in myofibroblasts by TGFβ1 and basic FGF. KCa3.1 was expressed strongly in IPF tissue. KCa3.1 pharmacological blockade attenuated human myofibroblast proliferation, wound healing, collagen secretion and contractility in vitro, and this was associated with inhibition of TGFβ1-dependent increases in intracellular free Ca2+.
KCa3.1 activity promotes pro-fibrotic human lung myofibroblast function. Blocking KCa3.1 may offer a novel approach to treating IPF with the potential for rapid translation to the clinic.
PMCID: PMC3877378  PMID: 24392001
25.  Pulmonary Hypertension in Wild Type Mice and Animals with Genetic Deficit in KCa2.3 and KCa3.1 Channels 
PLoS ONE  2014;9(5):e97687.
In vascular biology, endothelial KCa2.3 and KCa3.1 channels contribute to arterial blood pressure regulation by producing membrane hyperpolarization and smooth muscle relaxation. The role of KCa2.3 and KCa3.1 channels in the pulmonary circulation is not fully established. Using mice with genetically encoded deficit of KCa2.3 and KCa3.1 channels, this study investigated the effect of loss of the channels in hypoxia-induced pulmonary hypertension.
Approach and Result
Male wild type and KCa3.1−/−/KCa2.3T/T(+DOX) mice were exposed to chronic hypoxia for four weeks to induce pulmonary hypertension. The degree of pulmonary hypertension was evaluated by right ventricular pressure and assessment of right ventricular hypertrophy. Segments of pulmonary arteries were mounted in a wire myograph for functional studies and morphometric studies were performed on lung sections. Chronic hypoxia induced pulmonary hypertension, right ventricular hypertrophy, increased lung weight, and increased hematocrit levels in either genotype. The KCa3.1−/−/KCa2.3T/T(+DOX) mice developed structural alterations in the heart with increased right ventricular wall thickness as well as in pulmonary vessels with increased lumen size in partially- and fully-muscularized vessels and decreased wall area, not seen in wild type mice. Exposure to chronic hypoxia up-regulated the gene expression of the KCa2.3 channel by twofold in wild type mice and increased by 2.5-fold the relaxation evoked by the KCa2.3 and KCa3.1 channel activator NS309, whereas the acetylcholine-induced relaxation - sensitive to the combination of KCa2.3 and KCa3.1 channel blockers, apamin and charybdotoxin - was reduced by 2.5-fold in chronic hypoxic mice of either genotype.
Despite the deficits of the KCa2.3 and KCa3.1 channels failed to change hypoxia-induced pulmonary hypertension, the up-regulation of KCa2.3-gene expression and increased NS309-induced relaxation in wild-type mice point to a novel mechanism to counteract pulmonary hypertension and to a potential therapeutic utility of KCa2.3/KCa3.1 activators for the treatment of pulmonary hypertension.
PMCID: PMC4032241  PMID: 24858807

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