Expression of T-cell KV1.3 potassium channel correlates with pro-inflammatory cytokines and disease activity in ulcerative colitis

Amiloride lowers plasma TNF and interleukin-6 but not interleukin-17A in patients with hypertension and type 2 diabetes

Interleukin (IL)-17A contributes to hypertension in preclinical models. T helper 17 and dendritic cells are activated by NaCl, which could involve the epithelial Na+ channel (ENaC). We hypothesized that the ENaC blocker amiloride reduces plasma IL-17A and related cytokines in patients with hypertension. Concentrations of IL-17A, IFN-γ, TNF, IL-6, IL-1β, and IL-10 were determined by immunoassays in plasma from two patient cohorts before and after amiloride treatment: 1) patients with type 2 diabetes mellitus (T2DM) and treatment-resistant hypertension (n = 69, amiloride 5-10 mg/day for 8 wk) and 2) patients with hypertension and type 1 diabetes mellitus (T1DM) (n = 29) on standardized salt intake (amiloride 20-40 mg/day, 2 days). Plasma and tissue from ANG II-hypertensive mice with T1DM treated with amiloride (2 mg/kg/day, 4 days) were analyzed. The effect of amiloride and benzamil on macrophage cytokines was determined in vitro. Plasma cytokines showed higher concentrations (IL-17A ∼40-fold) in patients with T2DM compared with T1DM. In patients with T2DM, amiloride had no effect on IL-17A but lowered TNF and IL-6. In patients with T1DM, amiloride had no effect on IL-17A but increased TNF. In both cohorts, blood pressure decline and plasma K+ increase did not relate to plasma cytokine changes. In mice, amiloride exerted no effect on IL-17A in the plasma, kidney, aorta, or left cardiac ventricle but increased TNF in cardiac and kidney tissues. In lipopolysaccharide-stimulated human THP-1 macrophages, amiloride and benzamil (from 1 nmol/L) decreased TNF, IL-6, IL-10, and IL-1β. In conclusion, inhibition of ENaC by amiloride reduces proinflammatory cytokines TNF and IL-6 but not IL-17A in patients with T2DM, potentially by a direct action on macrophages.NEW & NOTEWORTHY ENaC activity may contribute to macrophage-derived cytokine release, since amiloride exerts anti-inflammatory effects by suppression of TNF and IL-6 cytokines in patients with resistant hypertension and type 2 diabetes and in THP-1-derived macrophages in vitro.

Kv1.3 mediates ox-LDL-induced vascular smooth muscle cell proliferation through JAK2/STAT3 signaling pathway

Kv1.3 channel has been shown to participate in regulating inflammatory activation, proliferation and apoptosis in several cell types. However, most of those existing studies focused on the ion-conducting properties of Kv1.3 in maintaining the resting potential and regulating Ca2+ influx. The aim of our study was to explore whether the Kv1.3-JAK2/STAT3 signaling pathway was involved in oxidized low density lipoprotein (ox-LDL) induced vascular smooth muscle cell (VSMC) proliferation. VSMCs from mouse aorta were cultured and treated with ox-LDL (25 μg/mL). The cell counting kit-8 was used to assess cell proliferation, and western blotting was performed to detect expression levels of Kv1.3, JAK2/STAT3, phosphorylated JAK2/STAT3, cyclin B1 and cyclin D1 in treated VSMCs. VSMCs were transfected with Kv1.3 small interfering RNA (Kv1.3-siRNA) or infected with a Kv1.3 lentiviral expression vector (Lv-Kv1.3) and treated with a JAK2 inhibitor LY2784544 to assess the role of Kv1.3 and JAK2/STAT3 signaling in mediating VSMC proliferation induced by ox-LDL. Ox-LDL induced cell proliferation and upregulated the expression of Kv1.3 in mouse VSMCs. In VSMCs transfected with Kv1.3-siRNA, ox-LDL was not efficient in inducing cell proliferation or the levels of proliferation associated proteins, cyclin B1 and cyclin D1. However, cell proliferation, cyclin B1 and cyclin D1 levels increased in VSMCs infected with Lv-Kv1.3. Levels of phosphorylated JAK2 and STAT3 were increased in ox-LDL-treated VSMCs, and this increase was prevented in VSMCs transfected with Kv1.3-siRNA. Treatment with the JAK2 inhibitor LY2784544 also prevented the increase in VSMCs proliferation treated with ox-LDL. Our findings demonstrated that Kv1.3 promoted proliferation of VSMCs treated with ox-LDL, and that this effect might be mediated through activation of the JAK2/STAT3 signaling pathway.

Characterisation of extracellular vesicles isolated from hydatid cyst fluid and evaluation of immunomodulatory effects on human monocytes

Hydatidosis is a disease caused by the larval stage of Echinococcus granulosus, which involves several organs of intermediate hosts. Evidence suggests a communication between hydatid cyst (HC) and hosts via extracellular vesicles. However, a little is known about the communication between EVs derived from HC fluid (HCF) and host cells. In the current study, EVs were isolated using differential centrifugation from sheep HCF and characterized by western blot, electron microscope and size distribution analysis. The uptake of EVs by human monocyte cell line (THP-1) was evaluated. The effects of EVs on the expression levels of pro- and anti-inflammatory cytokines were investigated using quantitative real-time PCR (RT-PCR), 3 and 24 h after incubation. Moreover, the cytokine level of IL-10 was evaluated in supernatant of THP-1 cell line at 3 and 24 h. EVs were successfully isolated and showed spherical shape with size distribution at 130.6 nm. After 3 h, the expression levels of pro-inflammatory cytokine genes (IL1Β, IL15 and IL8) were upregulated, while after 24 h, the expression levels of pro-inflammatory cytokines were decreased and IL13 gene expression showed upregulation. A statistically significant increase was seen in the levels of IL-10 after 24 h. The main mechanism of the communication between EVs derived from HCF and their host remains unclear; however, time-dependent anti-inflammatory effects in our study suggest that HC may modulate the immune responses via EVs.

Peripheral Administration of the Kv1.3-Blocking Peptide HsTX1[R14A] Improves Cognitive Performance in Senescence Accelerated SAMP8 Mice

Increased expression of the voltage-gated potassium channel Kv1.3 in activated microglia, and the subsequent release of pro-inflammatory mediators, are closely associated with the progression of Alzheimer's disease (AD). Studies have shown that reducing neuroinflammation through the non-selective blockade of microglial Kv1.3 has the potential to improve cognitive function in mouse models of familial AD. We have previously demonstrated that a potent and highly-selective peptide blocker of Kv1.3, HsTX1[R14A], not only entered the brain parenchyma after peripheral administration in a lipopolysaccharide (LPS)-induced mouse model of inflammation, but also significantly reduced pro-inflammatory mediator release from activated microglia. In this study, we show that microglial expression of Kv1.3 is increased in senescence accelerated mice (SAMP8), an animal model of sporadic AD, and that subcutaneous dosing of HsTX1[R14A] (1 mg/kg) every other day for 8 weeks provided a robust improvement in cognitive deficits in SAMP8 mice. The effect of HsTX1[R14A] on the whole brain was assessed using transcriptomics, which revealed that the expression of genes associated with inflammation, neuron differentiation, synapse function, learning and memory were altered by HsTX1[R14A] treatment. Further study is required to investigate whether these changes are downstream effects of microglial Kv1.3 blockade or a result of alternative mechanisms, including any potential effect of Kv1.3 blockade on other brain cell types. Nonetheless, these results collectively demonstrate the cognitive benefits of Kv1.3 blockade with HsTX1[R14A] in a mouse model of sporadic AD, demonstrating its potential as a therapeutic candidate for this neurodegenerative disease.

Molecular Profiling of Inflammatory Mediators in Human Respiratory Syncytial Virus and Human Bocavirus Infection

Infections due to human respiratory syncytial virus (HRSV) and human bocavirus (HBoV) can mediate the release of several pro-inflammatory cytokines such as IL-6, IL-8, and TNF-α, which are usually associated with disease severity in children. In this study, the change in the expression profile of cytokines and chemokines were determined during HRSV, HBoV, and HRSV coinfection with HBoV in 75 nasopharyngeal aspirates (NPAs) samples, positive real-time reverse transcriptase PCR Assay (rRT-PCR) for HRSV (n = 36), HBoV (n = 23) infection alone or HRSV coinfection with HBoV (n = 16). The samples were collected from hospitalized children. qPCR-based detection revealed that the levels of IL-6, IL-8, IL-10, IL-13, IL-33, and G-CSF were significantly (p < 0.05) greater in patients than in controls. IL-4, IL-17, GM-CSF, and CCL-5 were significantly elevated in children with HRSV coinfection with HBoV than in other groups (p < 0.05). TNF-α, IL-6, IL-8, IL-10, IL-13, and IL-33 in children with HRSV were significantly increased in severe infections compared to mild infections. Whereas, IL-10, IL-13, and IL-33 were significantly increased in severe infection in compared a mild infection in children with HBoV. Further large-scale investigations involving isolates are needed to enhance our knowledge of the association between viral infections and cytokine expression patterns during the different stages of HRSV and HBoV infection.

Ion channel regulation of gut immunity

Mounting evidence indicates that gastrointestinal (GI) homeostasis hinges on communications among many cellular networks including the intestinal epithelium, the immune system, and both intrinsic and extrinsic nerves innervating the gut. The GI tract, especially the colon, is the home base for gut microbiome which dynamically regulates immune function. The gut's immune system also provides an effective defense against harmful pathogens entering the GI tract while maintaining immune homeostasis to avoid exaggerated immune reaction to innocuous food and commensal antigens which are important causes of inflammatory disorders such as coeliac disease and inflammatory bowel diseases (IBD). Various ion channels have been detected in multiple cell types throughout the GI tract. By regulating membrane properties and intracellular biochemical signaling, ion channels play a critical role in synchronized signaling among diverse cellular components in the gut that orchestrates the GI immune response. This work focuses on the role of ion channels in immune cells, non-immune resident cells, and neuroimmune interactions in the gut at the steady state and pathological conditions. Understanding the cellular and molecular basis of ion channel signaling in these immune-related pathways and initial testing of pharmacological intervention will facilitate the development of ion channel-based therapeutic approaches for the treatment of intestinal inflammation.

Regulatory role of KCa3.1 in immune cell function and its emerging association with rheumatoid arthritis

Rheumatoid arthritis (RA) is a common autoimmune disease characterized by chronic inflammation. Immune dysfunction is an essential mechanism in the pathogenesis of RA and directly linked to synovial inflammation and cartilage/bone destruction. Intermediate conductance Ca²⁺-activated K⁺ channel (KCa3.1) is considered a significant regulator of proliferation, differentiation, and migration of immune cells by mediating Ca²⁺ signal transduction. Earlier studies have demonstrated abnormal activation of KCa3.1 in the peripheral blood and articular synovium of RA patients. Moreover, knockout of KCa3.1 reduced the severity of synovial inflammation and cartilage damage to a significant extent in a mouse collagen antibody-induced arthritis (CAIA) model. Accumulating evidence implicates KCa3.1 as a potential therapeutic target for RA. Here, we provide an overview of the KCa3.1 channel and its pharmacological properties, discuss the significance of KCa3.1 in immune cells and feasibility as a drug target for modulating the immune balance, and highlight its emerging role in pathological progression of RA.

Kv1.3 Channel Is Involved In Ox-LDL-induced Macrophage Inflammation Via ERK/NF-κB signaling pathway

Macrophage inflammatory response is crucial for the initiation and progression of atherosclerosis. The voltage-gated potassium channel Kv1.3 plays an important role in the modulation of macrophage function. The aim of this study was to investigate the effect and possible mechanism of Kv1.3 on inflammation in oxidized low-density lipoprotein (ox-LDL)-induced RAW264.7 macrophages. Treatment with Kv1.3-siRNA attenuated the expression of IL-6 and TNF-α and reduced the phosphorylation of ERK1/2 and NF-κB in ox-LDL-induced macrophages. In contrast, overexpression of Kv1.3 with Lv-Kv1.3 promoted the expression of IL-6 and TNF-α, and increased ERK1/2 and NF-κB phosphorylation in macrophages. PD-98059, a specific inhibitor of ERK, reversed the expression of IL-6 and TNF-α in ox-LDL-treated macrophages. Kv1.3-siRNA did not inhibit inflammation any further when cells were treated with PD-98059. This suggests that ERK acts as a downstream regulator of the Kv1.3 channel. In conclusion, Kv1.3 may be an indispensable membrane protein in ox-LDL-induced RAW264.7 macrophage inflammation in atherosclerosis through the ERK/NF-κB pathway.

Retroviral glycoprotein-mediated immune suppression via the potassium channel KCa3.1 - A new strategy for amelioration of inflammatory bowel diseases

Peptides derived from retroviral envelope proteins have been shown to possess a wide range of immunosuppressive and anti-inflammatory activities. We have previously reported identification of such a peptide derived from the envelope protein coded by a human endogenous retrovirus (HERV). In this study, we identified that in vitro the peptide inhibits the K_Ca3.1 potassium channel, a potential target for therapy of immune diseases. We describe in vitro ENV59-GP3 effects with respect to potency of inhibition on K_Ca3.1 channels and calcium influx. Furthermore, we asses in vivo the effect of blocking K_Ca3.1 with ENV59-GP3 peptide or K_Ca3.1-blocker NS6180 on protection against DSS-induced acute colitis. ENV59-GP3 peptide treatment showed reduction of the disease score in the DSS-induced acute colitis mice model, which was comparable to effects of the K_Ca3.1 channel blocker NS6180. Analysis of cytokine production from DSS-mice model treated animals revealed equipotent inhibitory effects of the ENV59-GP3 and NS6180 compounds on the production of IL-6, TNF-α, IL-1β. These findings altogether suggest that ENV59-GP3 functions as a K_Ca3.1 channel inhibitor and underline the implications of using virus derived channel blockers for treatment of autoimmune diseases. Additionally, they open the possibilities whether K_Ca3.1 inhibition is efficacious in patients with inflammatory bowel diseases.

How the Potassium Channel Response of T Lymphocytes to the Tumor Microenvironment Shapes Antitumor Immunity

Competent antitumor immune cells are fundamental for tumor surveillance and combating active cancers. Once established, tumors generate a tumor microenvironment (TME) consisting of complex cellular and metabolic elements that serve to suppress the function of antitumor immune cells. T lymphocytes are key cellular elements of the TME. In this review, we explore the role of ion channels, particularly K+ channels, in mediating the suppressive effects of the TME on T cells. First, we will review the complex network of ion channels that mediate Ca2+ influx and control effector functions in T cells. Then, we will discuss how multiple features of the TME influence the antitumor capabilities of T cells via ion channels. We will focus on hypoxia, adenosine, and ionic imbalances in the TME, as well as overexpression of programmed cell death ligand 1 by cancer cells that either suppress K+ channels in T cells and/or benefit from regulating these channels’ activity, ultimately shaping the immune response. Finally, we will review some of the cancer treatment implications related to ion channels. A better understanding of the effects of the TME on ion channels in T lymphocytes could promote the development of more effective immunotherapies, especially for resistant solid malignancies.

The mineralocorticoid receptor blocker spironolactone lowers plasma interferon-γ and interleukin-6 in patients with type 2 diabetes and treatment-resistant hypertension

BACKGROUND

The mineralocorticoid receptor antagonist spironolactone lowers blood pressure in patients with resistant hypertension despite antihypertensive treatment with angiotensin-converting inhibitors (ACEi) and angiotensin-II receptor blockers (ARB). In preclinical studies, spironolactone suppresses pro-hypertensive interleukin 17A (IL-17A).

OBJECTIVES

Plasma samples were analysed from a randomized, double-blind placebo-controlled trial with spironolactone given to patients with type 2 diabetes mellitus (T2DM) and resistant hypertension on three antihypertensive drugs. We tested the hypothesis that spironolactone-induced antihypertensive effects are associated with suppression of IL-17A and related cytokines.

METHODS

Interferon-γ (IFN-γ), IL-17A, tumor necrosis factor-α (TNF-α), IL-6, IL-1β and IL-10 were assessed in plasma with immunoassay in samples before and after 16 weeks of treatment with placebo or spironolactone (12.5-25-50 mg/day).

RESULTS

Spironolactone significantly reduced plasma IFN-γ and IL-6 while IL-17A, TNF-α, IL-1β and IL-10 were unchanged. IL-6 was more sensitive to higher doses of spironolactone. At baseline, serum aldosterone correlated positively with diastolic night blood pressure. Urine albumin/creatinine-ratios correlated positively with plasma IL-6 at baseline. There were no relations between aldosterone and cytokine concentrations at baseline; between cytokine concentration and blood pressure at baseline; and between cytokine concentration decrease and blood pressure decrease, except for IFN-γ, after treatment. The spironolactone-induced elevation in plasma potassium related inversely to blood pressure but not to changes in cytokines. In macrophages in vitro, spironolactone suppressed lipopolysaccharide (LPS)-induced TNF-α, IL-6, IL-1β and IL-10 levels.

CONCLUSION

The antihypertensive action of spironolactone in resistant hypertensive patients is associated with suppressed IFN-γ and IL-6 and not IL-17A. Spironolactone exerts anti-inflammatory actions in vivo on macrophages and T-cells.

Synthetic polypeptide crotamine: characterization as a myotoxin and as a target of combinatorial peptides

Crotamine is a rattlesnake-derived toxin that causes fast-twitch muscle paralysis. As a cell-penetrating polypeptide, crotamine has been investigated as an experimental anti-cancer and immunotherapeutic agent. We hypothesized that molecules targeting crotamine could be designed to study its function and intervene in its adverse activities. Here, we characterize synthetic crotamine and show that, like the venom-purified toxin, it induces hindlimb muscle paralysis by affecting muscle contraction and inhibits KCNA3 (Kv1.3) channels. Synthetic crotamine, labeled with a fluorophore, displayed cell penetration, subcellular myofiber distribution, ability to induce myonecrosis, and bind to DNA and heparin. Here, we used this functionally validated synthetic polypeptide to screen a combinatorial phage display library for crotamine-binding cyclic peptides. Selection for tryptophan-rich peptides was observed, binding of which to crotamine was confirmed by ELISA and gel shift assays. One of the peptides (CVWSFWGMYC), synthesized chemically, was shown to bind both synthetic and natural crotamine and to block crotamine-DNA binding. In summary, our study establishes a functional synthetic substitute to the venom-derived toxin and identifies peptides that could further be developed as probes to target crotamine. KEY MESSAGES: Synthetic crotamine was characterized as a functional substitute for venom-derived crotamine based on myotoxic effects. A combinatorial peptide library was screened for crotamine-binding peptides. Tryptophan-rich peptides were shown to bind to crotamine and interfere with its DNA binding. Crotamine myofiber distribution and affinity for tryptophan-rich peptides provide insights on its mechanism of action.

Mineralocorticoid receptor blockade with spironolactone has no direct effect on plasma IL-17A and injury markers in urine from kidney transplant patients

Kidney transplantation is associated with increased risk of cardiovascular morbidity. Interleukin-17A (IL-17A) mediates kidney injury. Aldosterone promotes T-helper-17 (Th-17) lymphocyte differentiation and IL-17A production through the mineralocorticoid receptor (MR). In this exploratory, post-hoc substudy, it was hypothesized that 1-year intervention with the MR antagonist spironolactone lowers IL-17A and related cytokines and reduces epithelial injury in kidney transplant recipients. Plasma and urine samples were obtained from kidney transplant recipients from a double-blind randomized clinical trial testing spironolactone (n=39) versus placebo (n=41). Plasma concentrations of cytokines IFN-γ, IL-17A, TNF-α, IL-6, IL-1β, and IL-10 were determined before and after 1-year treatment. Urine calbindin, clusterin, KIM-1, osteoactivin, TFF3, and VEGF/creatinine ratios were analyzed. Blood pressure and plasma aldosterone concentration at inclusion did not relate to plasma cytokines and injury markers. None of the cytokines changed in plasma after spironolactone intervention. Plasma IL-17A increased in the placebo group. Spironolactone induced an increase in plasma K⁺ (0.4 ± 0.4 mmol/L). This increase did not correlate with plasma IL-17A or urine calbindin and TFF3 changes. Ongoing treatment at inclusion with angiotensin-converting-enzyme inhibitor and/or angiotensin II receptor blockers was not associated with changed levels of IL-17A and injury markers and had no effect on the response to spironolactone. Urinary calbindin and TFF3 decreased in the spironolactone group with no difference in between-group analyses. In conclusion, irrespective of ongoing ANGII inhibition, spironolactone has no effect on plasma IL-17A and related cytokines or urinary injury markers in kidney transplant recipients.

Pathophysiological role of ion channels and transporters in gastrointestinal mucosal diseases

The incidence of gastrointestinal (GI) mucosal diseases, including various types of gastritis, ulcers, inflammatory bowel disease and GI cancer, is increasing. Therefore, it is necessary to identify new therapeutic targets. Ion channels/transporters are located on cell membranes, and tight junctions (TJs) affect acid–base balance, the mucus layer, permeability, the microbiota and mucosal blood flow, which are essential for maintaining GI mucosal integrity. As ion channel/transporter dysfunction results in various GI mucosal diseases, this review focuses on understanding the contribution of ion channels/transporters to protecting the GI mucosal barrier and the relationship between GI mucosal disease and ion channels/transporters, including Cl⁻/HCO₃⁻ exchangers, Cl⁻ channels, aquaporins, Na⁺/H⁺ exchangers, and K⁺ channels. Here, we provide novel prospects for the treatment of GI mucosal diseases.

Anti-Inflammatory Effect of Licochalcone A via Regulation of ORAI1 and K+ Channels in T-Lymphocytes

Calcium signaling plays a vital role in the regulation of various cellular processes, including activation, proliferation, and differentiation of T-lymphocytes, which is mediated by ORAI1 and potassium (K⁺) channels. These channels have also been identified as highly attractive therapeutic targets for immune-related diseases. Licochalcone A is a licorice-derived chalconoid known for its multifaceted beneficial effects in pharmacological treatments, including its anti-inflammatory, anti-asthmatic, antioxidant, antimicrobial, and antitumorigenic properties. However, its anti-inflammatory effects involving ion channels in lymphocytes remain unclear. Thus, the present study aimed to investigate whether licochalcone A inhibits ORAI1 and K⁺ channels in T-lymphocytes. Our results indicated that licochalcone A suppressed all three channels (ORAI1, Kv1.3, and KCa3.1) in a concentration-dependent matter, with IC₅₀ values of 2.97 ± 1.217 µM, 0.83 ± 1.222 µM, and 11.21 ± 1.07 µM, respectively. Of note, licochalcone A exerted its suppressive effects on the IL-2 secretion and proliferation in CD3 and CD28 antibody-induced T-cells. These results indicate that the use of licochalcone A may provide an effective treatment strategy for inflammation-related immune diseases.

Mapping Transcriptome Data to Protein-Protein Interaction Networks of Inflammatory Bowel Diseases Reveals Disease-Specific Subnetworks

Inflammatory bowel disease (IBD) is the common name for chronic disorders associated with the inflammation of the gastrointestinal tract. IBD is triggered by environmental factors in genetically susceptible individuals and has a significant number of incidences worldwide. Crohn’s disease (CD) and ulcerative colitis (UC) are the two distinct types of IBD. While involvement in ulcerative colitis is limited to the colon, Crohn’s disease may involve the whole gastrointestinal tract. Although these two disorders differ in macroscopic inflammation patterns, they share various molecular pathogenesis, yet the diagnosis can remain unclear, and it is important to reveal their molecular signatures in the network level. Improved molecular understanding may reveal disease type-specific and even individual-specific targets. To this aim, we determine the subnetworks specific to UC and CD by mapping transcriptome data to protein–protein interaction (PPI) networks using two different approaches [KeyPathwayMiner (KPM) and stringApp] and perform the functional enrichment analysis of the resulting disease type-specific subnetworks. TP63 was identified as the hub gene in the UC-specific subnet and p63 tumor protein, being in the same family as p53 and p73, has been studied in literature for the risk associated with colorectal cancer and IBD. APP was identified as the hub gene in the CD-specific subnet, and it has an important role in the pathogenesis of Alzheimer’s disease (AD). This relation suggests that some similar genetic factors may be effective in both AD and CD. Last, in order to understand the biological meaning of these disease-specific subnets, they were functionally enriched. It is important to note that chemokines—special types of cytokines—and antibacterial response are important in UC-specific subnets, whereas cytokines and antimicrobial responses as well as cancer-related pathways are important in CD-specific subnets. Overall, these findings reveal the differences between IBD subtypes at the molecular level and can facilitate diagnosis for UC and CD as well as provide potential molecular targets that are specific to disease subtypes.

Midazolam's Effects on Delayed-Rectifier K+ Current and Intermediate-Conductance Ca2+-Activated K+ Channel in Jurkat T-lymphocytes

Midazolam (MDZ) could affect lymphocyte immune functions. However, the influence of MDZ on cell’s K⁺ currents has never been investigated. Thus, in the present study, the effects of MDZ on Jurkat T lymphocytes were studied using the patch-clamp technique. Results showed that MDZ suppressed the amplitude of delayed-rectifier K⁺ current (I_K(DR)) in concentration-, time-, and state-dependent manners. The IC₅₀ for MDZ-mediated reduction of I_K(DR) density was 5.87 μM. Increasing MDZ concentration raised the rate of current-density inactivation and its inhibitory action on I_K(DR) density was estimated with a dissociation constant of 5.14 μM. In addition, the inactivation curve of I_K(DR) associated with MDZ was shifted to a hyperpolarized potential with no change on the slope factor. MDZ-induced inhibition of I_K(DR) was not reversed by flumazenil. In addition, the activity of intermediate-conductance Ca²⁺-activated K⁺ (IK_Ca) channels was suppressed by MDZ. Furthermore, inhibition by MDZ on both I_K(DR) and IK_Ca-channel activity appeared to be independent from GABAA receptors and affected immune-regulating cytokine expression in LPS/PMA-treated human T lymphocytes. In conclusion, MDZ suppressed current density of I_K(DR) in concentration-, time-, and state-dependent manners in Jurkat T-lymphocytes and affected immune-regulating cytokine expression in LPS/PMA-treated human T lymphocytes.

Discovery of KV 1.3 ion channel inhibitors: Medicinal chemistry approaches and challenges

The KV 1.3 voltage-gated potassium ion channel is involved in many physiological processes both at the plasma membrane and in the mitochondria, chiefly in the immune and nervous systems. Therapeutic targeting KV 1.3 with specific peptides and small molecule inhibitors shows great potential for treating cancers and autoimmune diseases, such as multiple sclerosis, type I diabetes mellitus, psoriasis, contact dermatitis, rheumatoid arthritis, and myasthenia gravis. However, no KV 1.3-targeted compounds have been approved for therapeutic use to date. This review focuses on the presentation of approaches for discovering new KV 1.3 peptide and small-molecule inhibitors, and strategies to improve the selectivity of active compounds toward KV 1.3. Selectivity of dalatazide (ShK-186), a synthetic derivate of the sea anemone toxin ShK, was achieved by chemical modification and has successfully reached clinical trials as a potential therapeutic for treating autoimmune diseases. Other peptides and small-molecule inhibitors are critically evaluated for their lead-like characteristics and potential for progression into clinical development. Some small-molecule inhibitors with well-defined structure-activity relationships have been optimized for selective delivery to mitochondria, and these offer therapeutic potential for the treatment of cancers. This overview of KV 1.3 inhibitors and methodologies is designed to provide a good starting point for drug discovery to identify novel effective KV 1.3 modulators against this target in the future.

IL-17 Inhibits Oligodendrocyte Progenitor Cell Proliferation and Differentiation by Increasing K+ Channel Kv1.3

Interleukin 17 (IL-17) is a signature cytokine of Th17 cells. IL-17 level is significantly increased in inflammatory conditions of the CNS, including but not limited to post-stroke and multiple sclerosis. IL-17 has been detected direct toxicity on oligodendrocyte (Ol) lineage cells and inhibition on oligodendrocyte progenitor cell (OPC) differentiation, and thus promotes myelin damage. The cellular mechanism of IL-17 in CNS inflammatory diseases remains obscure. Voltage-gated K⁺ (Kv) channel 1.3 is the predominant Kv channel in Ol and potentially involved in Ol function and cell cycle regulation. Kv1.3 of T cells involves in immunomodulation of inflammatory progression, but the role of Ol Kv1.3 in inflammation-related pathogenesis has not been fully investigated. We hypothesized that IL-17 induces myelin injury through Kv1.3 activation. To test the hypothesis, we studied the involvement of OPC/Ol Kv1.3 in IL-17-induced Ol/myelin injury in vitro and in vivo. Kv1.3 currents and channel expression gradually decreased during the OPC development. Application of IL-17 to OPC culture increased Kv1.3 expression, leading to a decrease of AKT activation, inhibition of proliferation and myelin basic protein reduction, which were prevented by a specific Kv1.3 blocker 5-(4-phenoxybutoxy) psoralen. IL-17-caused myelin injury was validated in LPC-induced demyelination mouse model, particularly in corpus callosum, which was also mitigated by aforementioned Kv1.3 antagonist. IL-17 altered Kv1.3 expression and resultant inhibitory effects on OPC proliferation and differentiation may by interrupting AKT phosphorylating activation. Taken together, our results suggested that IL-17 impairs remyelination and promotes myelin damage by Kv1.3-mediated Ol/myelin injury. Thus, blockade of Kv1.3 as a potential therapeutic strategy for inflammatory CNS disease may partially attribute to the direct protection on OPC proliferation and differentiation other than immunomodulation.

Suppressing Kv1.3 Ion Channel Activity with a Novel Small Molecule Inhibitor Ameliorates Inflammation in a Humanised Mouse Model of Ulcerative Colitis

BACKGROUND AND AIMS

The potassium channel Kv1.3 is a potentially attractive therapeutic target in T cell-mediated inflammatory diseases, as the activity of antigen-activated T cells is selectively impeded by Kv1.3 inhibition. In this study, we examined Kv1.3 as a potential therapeutic intervention point for ulcerative colitis [UC], and studied the efficacy of DES1, a small-molecule inhibitor of Kv1.3, in vitro and in vivo.

METHODS

Kv1.3 expression on T cells in peripheral blood mononuclear cells [PBMCs] isolated from donors with and without UC was examined by flow cytometry. In biopsies from UC patients, Kv1.3-expressing CD4+ T cells were detected by flow cytometry and immunohistochemistry. In vitro, we determined the ability of DES1 to inhibit anti-CD3-driven activation of T cells. In vivo, the efficacy of DES1 was determined in a humanised mouse model of UC and compared with infliximab and tofacitinib in head-to-head studies.

RESULTS

Kv1.3 expression was elevated in PBMCs from UC patients and correlated with the prevalence of TH1 and TH2 T cells. Kv1.3 expression was also detected on T cells from biopsies of UC patients. In vitro, DES1 suppressed anti-CD3-driven activation of T cells in a concentration-dependent manner. In vivo, DES1 significantly ameliorated inflammation in the UC model and most effectively so when PBMCs from donors with higher levels of activated T cells were selected for reconstitution. The efficacy of DES1 was comparable to that of either infliximab or tofacitinib.

CONCLUSION

Inhibition of Kv1.3 [by DES1, for instance] appears to be a potential therapeutic intervention strategy for UC patients.

Inhibitory effects of α-Mangostin on T cell cytokine secretion via ORAI1 calcium channel and K+ channels inhibition

Background

As one of the main components of mangosteen (Garcinia mangostana), a tropical fruit, α-mangostin has been reported to have numerous pharmacological benefits such as anti-cancer, anti-inflammatory, and anti-allergic effects through various mechanisms of action. The effects of α-mangostin on intracellular signaling proteins is well studied, but the effects of α-mangostin on ion channels and its physiological effects in immune cells are unknown. Generation of intracellular calcium signaling is a fundamental step for T cell receptor stimulation. This signaling is mediated not only by the ORAI1 calcium channel, but also by potassium ion channels, which provide the electrical driving forces for generating sufficient calcium ion influx. This study investigated whether α-mangosteen suppress T cell stimulation by inhibiting ORAI1 and two kinds of potassium channels (K_v1.3 and K_Ca3.1), which are normally expressed in human T cells.

Methods

This study analyzed the inhibitory effect of α-mangostin on immune cell activity via inhibition of calcium and potassium ion channels expressed in immune cells.

Results

α-mangostin inhibited ORAI1 in a concentration-dependent manner, and the IC₅₀ value was 1.27 ± 1.144 µM. K_v1.3 was suppressed by 41.38 ± 6.191% at 3 µM, and K_Ca3.1 was suppressed by 51.16 ± 5.385% at 3 µM. To measure the inhibition of cytokine secretion by immune cells, Jurkat T cells were stimulated to induce IL-2 secretion, and α-mangostin was found to inhibit it. This study demonstrated the anti-inflammatory effect of α-mangostin, the main component of mangosteen, through the regulation of calcium signals.

Altered Ca2+ Homeostasis in Immune Cells during Aging: Role of Ion Channels

Aging is an unstoppable process and begins shortly after birth. Each cell of the organism is affected by the irreversible process, not only with equal density but also at varying ages and with different speed. Therefore, aging can also be understood as an adaptation to a continually changing cellular environment. One of these very prominent changes in age affects Ca²⁺ signaling. Especially immune cells highly rely on Ca²⁺-dependent processes and a strictly regulated Ca²⁺ homeostasis. The intricate patterns of impaired immune cell function may represent a deficit or compensatory mechanisms. Besides, altered immune function through Ca²⁺ signaling can profoundly affect the development of age-related disease. This review attempts to summarize changes in Ca²⁺ signaling due to channels and receptors in T cells and beyond in the context of aging.

Actions of FTY720 (Fingolimod), a Sphingosine-1-Phosphate Receptor Modulator, on Delayed-Rectifier K+ Current and Intermediate-Conductance Ca2+-Activated K+ Channel in Jurkat T-Lymphocytes

FTY720 (fingolimod), a modulator of sphingosine-1-phosphate receptors, is known to produce the immunomodulatory actions and to be beneficial for treating the relapsing multiple sclerosis. However, whether it exerts any effects on membrane ion currents in immune cells remains largely unknown. Herein, the effects of FTY720 on ionic currents in Jurkat T-lymphocytes were investigated. Cell exposure to FTY720 suppressed the amplitude of delayed-rectifier K⁺ current (I_K(DR)) in a time- and concentration-dependent manner with an IC₅₀ value of 1.51 μM. Increasing the FTY720 concentration not only decreased the I_K(DR) amplitude but also accelerated the inactivation time course of the current. By using the minimal reaction scheme, the effect of FTY720 on I_K(DR) inactivation was estimated with a dissociation constant of 3.14 μM. FTY720 also shifted the inactivation curve of I_K(DR) to a hyperpolarized potential with no change in the slope factor, and recovery from I_K(DR) became slow during the exposure to this compound. Cumulative inactivation for I_K(DR) in response to repetitive depolarizations was enhanced in the presence of FTY720. In SEW2871-treated cells, FTY720-induced inhibition of I_K(DR) was attenuated. This compound also exerted a stimulatory action on the activity of intermediate-conductance Ca²⁺-activated K⁺ channels in Jurkat T-lymphocytes. However, in NSC-34 neuronal cells, FTY720 did not modify the inactivation kinetics of KV3.1-encoded I_K(DR), although it suppressed I_K(DR) amplitude in these cells. Collectively, the perturbations by FTY720 on different types of K⁺ channels may contribute to the functional activities of immune cells, if similar findings appear in vivo.

Effect of Ultrafine Powderization and Solid Dispersion Formation via Hot-Melt Extrusion on Antioxidant, Anti-Inflammatory, and the Human Kv1.3 Channel Inhibitory Activities of Angelica gigas Nakai

Angelica gigas Nakai (AGN) was first processed by ultrafine grinding technology and hot-melt extrusion (HME). The potential antioxidant and anti-inflammatory activities of AGN with a different process were compared, and the effect on the human Kv1.3 potassium channel was detected. The process of ultrafine powderization on AGN significantly increased the total phenolic and flavonoid contents, antioxidant activity, and DNA damage protective effect. On the contrary, AGN solid dispersion (AGN-SD) based on Soluplus^® showed the highest inhibitory effect on NO production and the human Kv1.3 channel. In addition, AGN-SD inhibited the production of prostaglandin E2 and intracellular reactive oxygen species and the mRNA expression of inducible nitric oxide synthase, cyclooxygenase-2, interleukin 1β, and interleukin 6. Taken together, these results suggest that ultrafine powderization and solid dispersion formation via HME can significantly improve the biological activities of AGN. The results also suggested that ultrafine powderization and HME may be developed and applied in the pharmaceutical industry.

The voltage-gated potassium channel KV1.3 as a therapeutic target for venom-derived peptides

The voltage-gated potassium channel K_V1.3 is a well-established therapeutic target for a range of autoimmune diseases, in addition to being the site of action of many venom-derived peptides. Numerous studies have documented the efficacy of venom peptides that target K_V1.3, in particular from sea anemones and scorpions, in animal models of autoimmune diseases such as rheumatoid arthritis, psoriasis and multiple sclerosis. Moreover, an analogue of the sea anemone peptide ShK (known as dalazatide) has successfully completed Phase 1 clinical trials in mild-to-moderate plaque psoriasis. In this article we consider other potential therapeutic applications of inhibitors of K_V1.3, including in inflammatory bowel disease and neuroinflammatory conditions such as Alzheimer's and Parkinson's diseases, as well as fibrotic diseases. We also summarise strategies for facilitating the entry of peptides to the central nervous system, given that this will be a pre-requisite for the treatment of most neuroinflammatory diseases. Venom-derived peptides that have been reported recently to target K_V1.3 are also described. The increasing number of autoimmune and other conditions in which K_V1.3 is upregulated and is therefore a potential therapeutic target, combined with the fact that many venom-derived peptides are potent inhibitors of K_V1.3, suggests that venoms are likely to continue to serve as a rich source of new pharmacological tools and therapeutic leads targeting this channel.

Conditional KCa3.1-transgene induction in murine skin produces pruritic eczematous dermatitis with severe epidermal hyperplasia and hyperkeratosis

Ion channels have recently attracted attention as potential mediators of skin disease. Here, we explored the consequences of genetically encoded induction of the cell volume-regulating Ca2+-activated KCa3.1 channel (Kcnn4) for murine epidermal homeostasis. Doxycycline-treated mice harboring the KCa3.1+-transgene under the control of the reverse tetracycline-sensitive transactivator (rtTA) showed 800-fold channel overexpression above basal levels in the skin and solid KCa3.1-currents in keratinocytes. This overexpression resulted in epidermal spongiosis, progressive epidermal hyperplasia and hyperkeratosis, itch and ulcers. The condition was accompanied by production of the pro-proliferative and pro-inflammatory cytokines, IL-β1 (60-fold), IL-6 (33-fold), and TNFα (26-fold) in the skin. Treatment of mice with the KCa3.1-selective blocker, Senicapoc, significantly suppressed spongiosis and hyperplasia, as well as induction of IL-β1 (-88%) and IL-6 (-90%). In conclusion, KCa3.1-induction in the epidermis caused expression of pro-proliferative cytokines leading to spongiosis, hyperplasia and hyperkeratosis. This skin condition resembles pathological features of eczematous dermatitis and identifies KCa3.1 as a regulator of epidermal homeostasis and spongiosis, and as a potential therapeutic target.

Geraniol targets KV1.3 ion channel and exhibits anti-inflammatory activity in vitro and in vivo

Naturally occurring monoterpenes are known for their various pharmacological activities including anti-inflammation. K_V1.3 ion channel is a voltage-gated potassium channel and has been validated as a drug target for autoimmune and chronic inflammatory diseases like psoriasis. Here we experimentally test the direct interaction between monoterpenes and K_V1.3 ion channel. Our electrophysiological analysis determined that monoterpenes (geraniol, nerol, β-citronellol, citral and linalool) have inhibitory effects on K_V1.3 ion channel. Representatively, geraniol reversibly blocked K_V1.3 currents in a voltage-dependent manner with an IC₅₀ of 490.50 ± 1.04 μM at +40 mV in HEK293T cells. At the effective concentrations, geraniol also inhibited cytokine secretion of activated human T cells, including IL-2, TNF-α and IFN-γ. In an imiquimod-induced psoriasis-like animal model, geraniol administration significantly reduced psoriasis area and severity index scores, ameliorated the deteriorating histopathology and decreased the degree of splenomegaly. Together, our findings not only suggest that monoterpenes may serve as lead molecules for the development of K_V1.3 inhibitors, but also indicate that geraniol could be considered as a promising therapeutic candidate to treat autoimmune diseases.

KCa3.1 Transgene Induction in Murine Intestinal Epithelium Causes Duodenal Chyme Accumulation and Impairs Duodenal Contractility

The epithelial intermediate-conductance calcium/calmodulin-regulated KCa3.1 channel is considered to be a regulator of intestine function by controlling chloride secretion and water/salt balance. Yet, little is known about the functional importance of KCa3.1 in the intestinal epithelium in vivo. Our objective was to determine the impact of epithelial-specific inducible overexpression of a KCa3.1 transgene (KCa3.1+) and of inducible suppression (KCa3.1−) on intestinal homeostasis and function in mice. KCa3.1 overexpression in the duodenal epithelium of doxycycline (DOX)-treated KCa3.1+ mice was 40-fold above the control levels. Overexpression caused an inflated duodenum and doubling of the chyme content. Histology showed conserved architecture of crypts, villi, and smooth muscle. Unaltered proliferating cell nuclear antigen (PCNA) immune reactivity and reduced amounts of terminal deoxynucleotide transferase mediated X-dUTP nick end labeling (TUNEL)-positive apoptotic cells in villi indicated lower epithelial turnover. Myography showed a reduction in the frequency of spontaneous propulsive muscle contractions with no change in amplitude. The amount of stool in the colon was increased and the frequency of colonic contractions was reduced in KCa3.1+ animals. Senicapoc treatment prevented the phenotype. Suppression of KCa3.1 in DOX-treated KCa3.1− mice caused no overt intestinal phenotype. In conclusion, inducible KCa3.1 overexpression alters intestinal functions by increasing the chyme content and reducing spontaneous contractions and epithelial apoptosis. Induction of epithelial KCa3.1 can play a mechanistic role in the process of adaptation of the intestine.

Altered calcium influx of peripheral Th2 cells in pediatric Crohn's disease: infliximab may normalize activation patterns

Objective

Crohn's disease is a chronic inflammation of the gastrointestinal tract with an abnormal immune phenotype. We investigated how intracellular calcium kinetics of Th1 and Th2 lymphocytes alter upon specific inhibition of Kv1.3 and IKCa1 channels in pediatric Crohn's disease.

Study design

Blood was taken from 12 healthy and 29 Crohn's disease children. Of those, 6 were switched to infliximab and re-sampled after the 4th infliximab treatment. Intracellular calcium levels were monitored using flow cytometry in the presence or absence of specific inhibitors of Kv1.3 and IKCa1 potassium channels.

Results

In Crohn's disease treated with standard therapy, calcium response during activation was higher than normal in Th2 cells. This was normalized in vitro by inhibition of Kv1.3 or IKCa1 potassium channels. After the switch to infliximab, potassium channel function and expression in Th2 lymphocytes were comparable to those in Th1 cells.

Conclusion

These results may indicate that potassium channels are potential immune modulatory targets in Crohn's disease.

Venom-derived peptide inhibitors of voltage-gated potassium channels

Voltage-gated potassium channels play a key role in human physiology and pathology. Reflecting their importance, numerous channelopathies have been characterised that arise from mutations in these channels or from autoimmune attack on the channels. Voltage-gated potassium channels are also the target of a broad range of peptide toxins from venomous organisms, including sea anemones, scorpions, spiders, snakes and cone snails; many of these peptides bind to the channels with high potency and selectivity. In this review we describe the various classes of peptide toxins that block these channels and illustrate the broad range of three-dimensional structures that support channel blockade. The therapeutic opportunities afforded by these peptides are also highlighted. This article is part of the Special Issue entitled 'Venom-derived Peptides as Pharmacological Tools.'

Prolonged immunomodulation in inflammatory arthritis using the selective Kv1.3 channel blocker HsTX1[R14A] and its PEGylated analog

Effector memory T lymphocytes (TEM cells) that lack expression of CCR7 are major drivers of inflammation in a number of autoimmune diseases, including multiple sclerosis and rheumatoid arthritis. The Kv1.3 potassium channel is a key regulator of CCR7- TEM cell activation. Blocking Kv1.3 inhibits TEM cell activation and attenuates inflammation in autoimmunity, and as such, Kv1.3 has emerged as a promising target for the treatment of TEM cell-mediated autoimmune diseases. The scorpion venom-derived peptide HsTX1 and its analog HsTX1[R14A] are potent Kv1.3 blockers and HsTX1[R14A] is selective for Kv1.3 over closely-related Kv1 channels. PEGylation of HsTX1[R14A] to create a Kv1.3 blocker with a long circulating half-life reduced its affinity but not its selectivity for Kv1.3, dramatically reduced its adsorption to inert surfaces, and enhanced its circulating half-life in rats. PEG-HsTX1[R14A] is equipotent to HsTX1[R14A] in preferential inhibition of human and rat CCR7- TEM cell proliferation, leaving CCR7+ naïve and central memory T cells able to proliferate. It reduced inflammation in an active delayed-type hypersensitivity model and in the pristane-induced arthritis (PIA) model of rheumatoid arthritis (RA). Importantly, a single subcutaneous dose of PEG-HsTX1[R14A] reduced inflammation in PIA for a longer period of time than the non-PEGylated HsTX1[R14A]. Together, these data indicate that HsTX1[R14A] and PEG-HsTX1[R14A] are effective in a model of RA and are therefore potential therapeutics for TEM cell-mediated autoimmune diseases. PEG-HsTX1[R14A] has the additional advantages of reduced non-specific adsorption to inert surfaces and enhanced circulating half-life.

Altered activation of peripheral CD8+ T cells in pediatric Crohn's disease

AIM

Although Crohn's disease (CD) is an extensively investigated autoimmune condition, knowledge on early phase activation of lymphocytes, especially CD8+ Tc cells is scarce. Our aim was to investigate the calcium influx characteristics of CD8+ cells upon activation as well as the expression and function of Kv1.3 and IKCa1 lymphocyte potassium channels.

METHODS

We took peripheral blood from 12 healthy controls, 23 CD children on conventional therapy and 6 severe CD children before and after infliximab therapy. Intracellular calcium levels were monitored in CD8+ lymphocytes using flow cytometry.

RESULTS

In CD treated with standard therapy calcium response during activation was elevated. This was not affected by the inhibition of Kv1.3 or IKCa1 potassium channels. After the switch to infliximab potassium channel function and expression of CD8+ lymphocytes were comparable to healthy controls in severe CD.

CONCLUSION

Calcium handling of CD8+ lymphocytes is altered in pediatric CD, which is normalized by infliximab therapy.

Lymphocyte Kv1.3-channels in the pathogenesis of chronic obstructive pulmonary disease: novel therapeutic implications of targeting the channels by commonly used drugs

In patients with chronic obstructive pulmonary disease (COPD), over-activated T-lymphocytes produce pro-inflammatory cytokines and proliferate in situ in the lower airways and pulmonary parenchyma, contributing substantially to the pathogenesis of the disease. Despite our understanding of the molecular mechanisms by which lymphocytes are activated, we know little about the physiological mechanisms. T-lymphocytes predominantly express delayed rectifier K⁺-channels (Kv1.3) in their plasma membranes and these channels play crucial roles in inducing the lymphocyte activation and proliferation. In the pathogenesis of chronic inflammatory diseases, such as chronic kidney disease (CKD) or inflammatory bowel disease (IBD), these channels, which are overexpressed in proliferating lymphocytes within the inflamed organs, are responsible for the progression of the diseases. Since the over-activation of cellular immunity is also mainly involved in the pathogenesis of COPD, this disease could share similar pathophysiological features as those of CKD or IBD. From a literature review including ours, it is highly likely that the Kv1.3-channels are overexpressed or over-activated in T-lymphocytes isolated from patients with COPD, and that the overexpression of the channels would contribute to the development or progression of COPD. The involvement of the channels leads to novel therapeutic implications of potentially useful Kv1.3-channel inhibitors, such as calcium channel blockers, macrolide antibiotics, HMG-CoA reductase inhibitors and nonsteroidal anti-inflammatory drugs, in the treatment of COPD.

Differential Kv1.3, KCa3.1, and Kir2.1 expression in "classically" and "alternatively" activated microglia

Microglia are highly plastic cells that can assume different phenotypes in response to microenvironmental signals. Lipopolysaccharide (LPS) and interferon-γ (IFN-γ) promote differentiation into classically activated M1-like microglia, which produce high levels of pro-inflammatory cytokines and nitric oxide and are thought to contribute to neurological damage in ischemic stroke and Alzheimer's disease. IL-4 in contrast induces a phenotype associated with anti-inflammatory effects and tissue repair. We here investigated whether these microglia subsets vary in their K⁺ channel expression by differentiating neonatal mouse microglia into M(LPS) and M(IL-4) microglia and studying their K⁺ channel expression by whole-cell patch-clamp, quantitative PCR and immunohistochemistry. We identified three major types of K⁺ channels based on their biophysical and pharmacological fingerprints: a use-dependent, outwardly rectifying current sensitive to the K_V 1.3 blockers PAP-1 and ShK-186, an inwardly rectifying Ba²⁺ -sensitive K_ir 2.1 current, and a Ca²⁺ -activated, TRAM-34-sensitive K_Ca 3.1 current. Both K_V 1.3 and K_Ca 3.1 blockers inhibited pro-inflammatory cytokine production and iNOS and COX2 expression demonstrating that K_V 1.3 and K_Ca 3.1 play important roles in microglia activation. Following differentiation with LPS or a combination of LPS and IFN-γ microglia exhibited high K_V 1.3 current densities (∼50 pA/pF at 40 mV) and virtually no K_Ca 3.1 and K_ir currents, while microglia differentiated with IL-4 exhibited large K_ir 2.1 currents (∼ 10 pA/pF at -120 mV). K_Ca 3.1 currents were generally low but moderately increased following stimulation with IFN-γ or ATP (∼10 pS/pF). This differential K⁺ channel expression pattern suggests that K_V 1.3 and K_Ca 3.1 inhibitors could be used to inhibit detrimental neuroinflammatory microglia functions. GLIA 2016;65:106-121.

Role of epithelial ion transports in inflammatory bowel disease

Inflammatory bowel disease (IBD) is a chronic inflammatory disorder with a complex pathogenesis. Diarrhea is a highly prevalent and often debilitating symptom of IBD patients that results, at least in part, from an intestinal hydroelectrolytic imbalance. Evidence suggests that reduced electrolyte absorption is more relevant than increased secretion to this disequilibrium. This systematic review analyses and integrates the current evidence on the roles of epithelial Na(+)-K(+)-ATPase (NKA), Na(+)/H(+) exchangers (NHEs), epithelial Na(+) channels (ENaC), and K(+) channels (KC) in IBD-associated diarrhea. NKA is the key driving force of the transepithelial ionic transport and its activity is decreased in IBD. In addition, the downregulation of apical NHE and ENaC and the upregulation of apical large-conductance KC all contribute to the IBD-associated diarrhea by lowering sodium absorption and/or increasing potassium secretion.

A whole-genome RNAi screen uncovers a novel role for human potassium channels in cell killing by the parasite Entamoeba histolytica

The parasite Entamoeba histolytica kills human cells resulting in ulceration, inflammation and invasion of the colonic epithelium. We used the cytotoxic properties of ameba to select a genome-wide RNAi library to reveal novel host factors that control susceptibility to amebic killing. We identified 281 candidate susceptibility genes and bioinformatics analyses revealed that ion transporters were significantly enriched among susceptibility genes. Potassium (K⁺) channels were the most common transporter identified. Their importance was further supported by colon biopsy of humans with amebiasis that demonstrated suppressed K⁺ channel expression. Inhibition of human K⁺ channels by genetic silencing, pharmacologic inhibitors and with excess K⁺ protected diverse cell types from E. histolytica-induced death. Contact with E. histolytica parasites triggered K⁺ channel activation and K⁺ efflux by intestinal epithelial cells, which preceded cell killing. Specific inhibition of Ca²⁺-dependent K⁺ channels was highly effective in preventing amebic cytotoxicity in intestinal epithelial cells and macrophages. Blockade of K⁺ efflux also inhibited caspase-1 activation, IL-1β secretion and pyroptotic death in THP-1 macrophages. We concluded that K⁺ channels are host mediators of amebic cytotoxicity in multiple cells types and of inflammasome activation in macrophages.

Usefulness of targeting lymphocyte Kv1.3-channels in the treatment of respiratory diseases

T lymphocytes predominantly express delayed rectifier K(+)-channels (Kv1.3) in their plasma membranes. Patch-clamp studies revealed that the channels play crucial roles in facilitating the calcium influx necessary to trigger lymphocyte activation and proliferation. Using selective channel inhibitors in experimental animal models, in vivo studies further revealed the clinically relevant relationship between the channel expression and the development of chronic respiratory diseases, in which chronic inflammation or the overstimulation of cellular immunity in the airways is responsible for the pathogenesis. In chronic respiratory diseases, such as chronic obstructive pulmonary disease, asthma, diffuse panbronchiolitis and cystic fibrosis, in addition to the supportive management for the symptoms, the anti-inflammatory effects of macrolide antibiotics were shown to be effective against the over-activation or proliferation of T lymphocytes. Recently, we provided physiological and pharmacological evidence that macrolide antibiotics, together with calcium channel blockers, HMG-CoA reductase inhibitors, and nonsteroidal anti-inflammatory drugs, effectively suppress the Kv1.3-channel currents in lymphocytes, and thus exert anti-inflammatory or immunomodulatory effects. In this review article, based on the findings obtained from recent in vivo and in vitro studies, we address the novel therapeutic implications of targeting the lymphocyte Kv1.3-channels for the treatment of chronic or acute respiratory diseases.

N-Terminally extended analogues of the K⁺ channel toxin from Stichodactyla helianthus as potent and selective blockers of the voltage-gated potassium channel Kv1.3

The voltage-gated potassium channel Kv1.3 is an important target for the treatment of autoimmune diseases and asthma. Blockade of Kv1.3 by the sea anemone peptide K⁺-channel toxin from Stichodactyla helianthus (ShK) inhibits the proliferation of effector memory T lymphocytes and ameliorates autoimmune diseases in animal models. However, the lack of selectivity of ShK for Kv1.3 over the Kv1.1 subtype has driven a search for Kv1.3-selective analogues. In the present study, we describe N-terminally extended analogues of ShK that contain a negatively-charged Glu, designed to mimic the phosphonate adduct in earlier Kv1.3-selective analogues, and consist entirely of common protein amino acids. Molecular dynamics simulations indicated that a Trp residue at position [-3] of the tetrapeptide extension could form stable interactions with Pro377 of Kv1.3 and best discriminates between Kv1.3 and Kv1.1. This led to the development of ShK with an N-terminal Glu-Trp-Ser-Ser extension ([EWSS]ShK), which inhibits Kv1.3 with an IC₅₀ of 34 pm and is 158-fold selective for Kv1.3 over Kv1.1. In addition, [EWSS]ShK is more than 2900-fold more selective for Kv1.3 over Kv1.2 and KCa3.1 channels. As a highly Kv1.3-selective analogue of ShK based entirely on protein amino acids, which can be produced by recombinant expression, this peptide is a valuable addition to the complement of therapeutic candidates for the treatment of autoimmune diseases.

Modulation of K(Ca)3.1 channels by eicosanoids, omega-3 fatty acids, and molecular determinants

BACKGROUND

Cytochrome P450- and ω-hydrolase products (epoxyeicosatrienoic acids (EETs), hydroxyeicosatetraeonic acid (20-HETE)), natural omega-3 fatty acids (ω3), and pentacyclic triterpenes have been proposed to contribute to a wide range of vaso-protective and anti-fibrotic/anti-cancer signaling pathways including the modulation of membrane ion channels. Here we studied the modulation of intermediate-conductance Ca(2+)/calmodulin-regulated K(+) channels (K(Ca)3.1) by EETs, 20-HETE, ω3, and pentacyclic triterpenes and the structural requirements of these fatty acids to exert channel blockade.

METHODOLOGY/PRINCIPAL FINDINGS

We studied modulation of cloned human hK(Ca)3.1 and the mutant hK(Ca)3.1(V275A) in HEK-293 cells, of rK(Ca)3.1 in aortic endothelial cells, and of mK(Ca)3.1 in 3T3-fibroblasts by inside-out and whole-cell patch-clamp experiments, respectively. In inside-out patches, Ca(2+)-activated hK(Ca)3.1 were inhibited by the ω3, DHA and α-LA, and the ω6, AA, in the lower µmolar range and with similar potencies. 5,6-EET, 8,9-EET, 5,6-DiHETE, and saturated arachidic acid, had no appreciable effects. In contrast, 14,15-EET, its stable derivative, 14,15-EEZE, and 20-HETE produced channel inhibition. 11,12-EET displayed less inhibitory activity. The K(Ca)3.1(V275A) mutant channel was insensitive to any of the blocking EETs. Non-blocking 5,6-EET antagonized the inhibition caused by AA and augmented cloned hK(Ca)3.1 and rK(Ca)3.1 whole-cell currents. Pentacyclic triterpenes did not modulate K(Ca)3.1 currents.

CONCLUSIONS/SIGNIFICANCE

Inhibition of K(Ca)3.1 by EETs (14,15-EET), 20-HETE, and ω3 critically depended on the presence of electron double bonds and hydrophobicity within the 10 carbons preceding the carboxyl-head of the molecules. From the physiological perspective, metabolism of AA to non-blocking 5,6,- and 8,9-EET may cause AA-de-blockade and contribute to cellular signal transduction processes influenced by these fatty acids.

T cells in vascular inflammatory diseases

Inflammation of the human vasculature is a manifestation of many different diseases ranging from systemic autoimmune diseases to chronic inflammatory diseases, in which multiple types of immune cells are involved. For both autoimmune diseases and chronic inflammatory diseases several observations support a key role for T lymphocytes in these disease pathologies, but the underlying mechanisms are poorly understood. Previous studies in several autoimmune diseases have demonstrated a significant role for a specific subset of CD4⁺ T cells termed effector memory T (T_EM) cells. This expanded population of T_EM cells may contribute to tissue injury and disease progression. These cells exert multiple pro-inflammatory functions through the release of effector cytokines. Many of these cytokines have been detected in the inflammatory lesions and participate in the vasculitic reaction, contributing to recruitment of macrophages, neutrophils, dendritic cells, natural killer cells, B cells, and T cells. In addition, functional impairment of regulatory T cells paralyzes anti-inflammatory effects in vasculitic disorders. Interestingly, activation of T_EM cells is uniquely dependent on the voltage-gated potassium Kv1.3 channel providing an anchor for specific drug targeting. In this review, we focus on the CD4⁺ T cells in the context of vascular inflammation and describe the evidence supporting the role of different T cell subsets in vascular inflammation. Selective targeting of pathogenic T_EM cells might enable a more tailored therapeutic approach that avoids unwanted adverse side effects of generalized immunosuppression by modulating the effector functions of T cell responses to inhibit the development of vascular inflammation.