Acacetin Blocks Kv1.3 Channels and Inhibits Human T Cell Activation

Backgrounds/Aims: Acacetin, a natural flavonoid compound, has been proven to exert anti-inflammatory and immunomodulatory effects. Kv1.3 channels, highly expressed in human T cells, are attractive therapeutic targets to treat inflammatory and immunological disorders. The present study was designed to characterize the inhibition of Kv1.3 channels by Acacetin in human T cells and examine its role in T cell activation. Methods: Whole-cell patch-clamp was applied to record the Kv1.3 and KCa currents in human T cells; Western blot was used to detect Kv1.3 expression as well as NFAT1 and NF-κB activity; Fluo-4, CCK-8 and an ELISA kit were used to measure Ca2+ influx, proliferation, and IL-2 secretion, respectively. Results: Acacetin decreased the Kv1.3 current, accelerated the decay rate and negatively shifted the steady-state inactivation curves in a concentration-dependent manner. The IC50 values at +40 mV for peak and the current at end of pulse were 21.09 ± 2.75 and 3.63 ± 0.25 µmol/L, respectively. Treatment with Acacetin for 24 h significantly inhibited Kv1.3 protein expression. Additionally, paralleling Kv1.3 inhibition, Acacetin also inhibited Ca2+ influx, the Ca2+-activated transcription factors NFAT1, NF-κB p65/p50 activity, and proliferation as well as IL-2 production. Small interfering RNA against Kv1.3 reduced the inhibitory effect of Acacetin on IL-2 secretion. Conclusions: Acacetin blocks the Kv1.3 channel and inhibits human T cell activation. This action most likely contributes to its immunomodulatory and anti-inflammatory actions.

[1]  Y. Imaizumi,et al.  New screening system for selective blockers of voltage-gated K(+) channels using recombinant cell lines dying upon single action potential. , 2013, Journal of pharmacological sciences.

[2]  T. Komatsu,et al.  Acacetin inhibits expression of E-selectin on endothelial cells through regulation of the MAP kinase signaling pathway and activation of NF-κB , 2013, Immunopharmacology and immunotoxicology.

[3]  Y. Liao,et al.  18β-Glycyrrhetinic acid potently inhibits Kv1.3 potassium channels and T cell activation in human Jurkat T cells. , 2013, Journal of ethnopharmacology.

[4]  Y. Liao,et al.  Potent Suppression of Kv1.3 Potassium Channel and IL-2 Secretion by Diphenyl Phosphine Oxide-1 in Human T Cells , 2013, PloS one.

[5]  Yingliang Wu,et al.  Selective Inhibition of CCR7− Effector Memory T Cell Activation by a Novel Peptide Targeting Kv1.3 Channel in a Rat Experimental Autoimmune Encephalomyelitis Model* , 2012, The Journal of Biological Chemistry.

[6]  M. Oh,et al.  Acacetin Attenuates Neuroinflammation via Regulation the Response to LPS Stimuli In Vitro and In Vivo , 2012, Neurochemical Research.

[7]  Hari Krishna Yalamanchili,et al.  Acacetin causes a frequency- and use-dependent blockade of hKv1.5 channels by binding to the S6 domain. , 2011, Journal of molecular and cellular cardiology.

[8]  C. Soler,et al.  Immunomodulatory effects of diclofenac in leukocytes through the targeting of Kv1.3 voltage-dependent potassium channels. , 2010, Biochemical pharmacology.

[9]  K. Chandy,et al.  The functional network of ion channels in T lymphocytes , 2009, Immunological reviews.

[10]  Y. Liao,et al.  High extracellular potassium ion concentration attenuates the blockade action of ketanserin on Kv1.3 channels expressed in xenopus oocytes. , 2008, Chinese Medical Journal.

[11]  Qiang Xu,et al.  Anti-inflammatory and immunosuppressive effect of flavones isolated from Artemisia vestita. , 2008, Journal of ethnopharmacology.

[12]  Qiang Tang,et al.  Acacetin, a Natural Flavone, Selectively Inhibits Human Atrial Repolarization Potassium Currents and Prevents Atrial Fibrillation in Dogs , 2008, Circulation.

[13]  S. Feske.  Calcium signalling in lymphocyte activation and disease , 2007, Nature Reviews Immunology.

[14]  S. Griffey,et al.  Targeting effector memory T cells with the small molecule Kv1.3 blocker PAP-1 suppresses allergic contact dermatitis. , 2007, The Journal of investigative dermatology.

[15]  K. Sung,et al.  Calcineurin-independent inhibition of KV1.3 by FK-506 (tacrolimus): a novel pharmacological property. , 2007, American journal of physiology. Cell physiology.

[16]  R. Vicente,et al.  Association of Kv1.5 and Kv1.3 Contributes to the Major Voltage-dependent K+ Channel in Macrophages* , 2006, Journal of Biological Chemistry.

[17]  Ying-Jan Wang,et al.  Acacetin suppressed LPS-induced up-expression of iNOS and COX-2 in murine macrophages and TPA-induced tumor promotion in mice. , 2006, Biochemical pharmacology.

[18]  S. Griffey,et al.  Kv1.3 channels are a therapeutic target for T cell-mediated autoimmune diseases , 2006, Proceedings of the National Academy of Sciences.

[19]  P. Calabresi,et al.  Potassium channels Kv1.3 and Kv1.5 are expressed on blood‐derived dendritic cells in the central nervous system , 2006, Annals of neurology.

[20]  K. Sung,et al.  Open channel block of Kv1.3 by rosiglitazone and troglitazone: Kv1.3 as the pharmacological target for rosiglitazone , 2006, Naunyn-Schmiedeberg's Archives of Pharmacology.

[21]  P. Calabresi,et al.  Kv1.3-blocking 5-phenylalkoxypsoralens: a new class of immunomodulators. , 2004, Molecular pharmacology.

[22]  Michael Pennington,et al.  K+ channels as targets for specific immunomodulation. , 2004, Trends in pharmacological sciences.

[23]  M. Hoth,et al.  Potent Inhibition of Ca2+ Release-activated Ca2+ Channels and T-lymphocyte Activation by the Pyrazole Derivative BTP2* , 2004, Journal of Biological Chemistry.

[24]  A. Trautmann,et al.  Ca2+ signals and T lymphocytes “New mechanisms and functions in Ca2+ signalling” , 2004, Biology of the cell.

[25]  G. Dupont,et al.  New mechanisms and functions in Ca2+ signalling , 2004, Biology of the cell.

[26]  P. Calabresi,et al.  The voltage-gated Kv1.3 K(+) channel in effector memory T cells as new target for MS. , 2003, The Journal of clinical investigation.

[27]  K. Chandy,et al.  Selective blockade of T lymphocyte K+ channels ameliorates experimental autoimmune encephalomyelitis, a model for multiple sclerosis , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[28]  S. Grissmer,et al.  Block of the lymphocyte K+ channel mKv1.3 by the phenylalkylamine verapamil: Kinetic aspects of block and disruption of accumulation of block by a single point mutation , 2000, British journal of pharmacology.

[29]  J. S. Choi,et al.  Mechanism of fluoxetine block of cloned voltage-activated potassium channel Kv1.3. , 1999, The Journal of pharmacology and experimental therapeutics.

[30]  A. Porcelli,et al.  HIV-1 nef expression inhibits the activity of a Ca2+-dependent K+ channel involved in the control of the resting potential in CEM lymphocytes. , 1999, Journal of immunology.

[31]  R. J. Mather,et al.  UK‐78,282, a novel piperidine compound that potently blocks the Kv1.3 voltage‐gated potassium channel and inhibits human T cell activation , 1999, British journal of pharmacology.

[32]  J. Reuben,et al.  Selective blockers of voltage-gated K+ channels depolarize human T lymphocytes: mechanism of the antiproliferative effect of charybdotoxin. , 1992, Proceedings of the National Academy of Sciences of the United States of America.

[33]  S. Grissmer,et al.  Ca(2+)-activated K+ channels in human leukemic T cells , 1992, The Journal of general physiology.

[34]  V. Maltsev.  Oscillating and triggering properties of T cell membrane potential. , 1990, Immunology letters.

[35]  C. Deutsch,et al.  Charybdotoxin inhibits proliferation and interleukin 2 production in human peripheral blood lymphocytes. , 1989, Proceedings of the National Academy of Sciences of the United States of America.