title: Acacetin blocks kv1.3 channels and inhibits human T cell activation.
abstract: OBJECTIVE
  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 Ca(2+) 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 Ca(2+) influx, the Ca(2+)-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.
authors.affiliation: Research Center of Ion Channelopathy, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, P.R. China.
authors.forename: Ning
authors.initials: N
authors.lastname: Zhao
authors.forename: Qian
authors.initials: Q
authors.lastname: Dong
authors.forename: Xiao-Xing
authors.initials: XX
authors.lastname: Fu
authors.forename: Li-Li
authors.initials: LL
authors.lastname: Du
authors.forename: Xiang
authors.initials: X
authors.lastname: Cheng
authors.forename: Yi-Mei
authors.initials: YM
authors.lastname: Du
authors.forename: Yu-Hua
authors.initials: YH
authors.lastname: Liao
mesh_terms: D000814:Aniline Compounds / Q000378:metabolism; D000893:Anti-Inflammatory Agents / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D047309:Flavones / Q000494:pharmacology*; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism; D019169:Jurkat Cells; D051664:Kv1.3 Potassium Channel / Q000037:antagonists & inhibitors*; D008213:Lymphocyte Activation / Q000187:drug effects*; D008564:Membrane Potentials / Q000187:drug effects; D016328:NF-kappa B / Q000378:metabolism; D050778:NFATC Transcription Factors / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology*; D012844:Sincalide / Q000378:metabolism; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D014966:Xanthenes / Q000378:metabolism
chemical_list: D000814:Aniline Compounds; D000893:Anti-Inflammatory Agents; D047309:Flavones; C409648:Fluo 4; D007376:Interleukin-2; D051664:Kv1.3 Potassium Channel; D016328:NF-kappa B; D050778:NFATC Transcription Factors; C494006:NFATC2 protein, human; D026902:Potassium Channel Blockers; D014966:Xanthenes; C023717:acacetin; D012844:Sincalide; D002118:Calcium