title: 18β-Glycyrrhetinic acid potently inhibits Kv1.3 potassium channels and T cell activation in human Jurkat T cells.
abstract: BACKGROUND
  Licorice has been extensively used in traditional medicines for treatment of many diseases, including inflammations and immunological disorders. Recent studies have shown that the anti-inflammatory and immunomodulation activities of licorice have been attributed to its active component, glycyrretinic acid (GA). GA consists of two isoforms, 18α- and 18β-. However, its mechanism remains poorly understood.
  
  
  OBJECTIVE
  We compared the effects of two isoforms on Kv1.3 channels in Jurkat T cells and further characterized the inhibition of Kv1.3 channels by 18β-GA in CHO cells. In addition, we examined the effects of 18β-GA on Kv1.3 gene expression, Ca(2+) influx, proliferation, as well as IL-2 production in Jurkat T cells.
  
  
  METHODS
  Whole-cell patch-clamp technique was applied to record Kv1.3 currents in Jurkat T or CHO cells. Real-time PCR and Western blotting were used to detect gene expression. Fluo-4, CCK-8 kit and ELISA kit were used to measure Ca(2+) influx, proliferation, and IL-2 secretion in Jurkat T cells, respectively.
  
  
  RESULTS
  Superfusion of 18β-GA (10-100 µM) blocked Kv1.3 currents in Jurkat T cells, while 18α-GA at the same concentration had no effect. The 18β-GA induced inhibition had a voltage- and concentration-dependent manner with an IC50 of 23.9±1.5 µM at +40 mV in CHO cells. Furthermore, 18β-GA significantly inhibited Kv1.3 gene expression. In addition, paralleling Kv1.3 inhibition, 18β-GA also inhibited Ca(2+) influx, proliferation as well as IL-2 production in Jurkat T cells.
  
  
  CONCLUSIONS
  18β-GA blocks Kv1.3 channels, which probably involves its anti-inflammatory and immunomodulation effects.
authors.affiliation: Ion Channelopathy Research Center, Institute of Cardiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, PR China.
authors.forename: Xiao-Xing
authors.initials: XX
authors.lastname: Fu
authors.forename: Li-Li
authors.initials: LL
authors.lastname: Du
authors.forename: Ning
authors.initials: N
authors.lastname: Zhao
authors.forename: Qian
authors.initials: Q
authors.lastname: Dong
authors.forename: Yu-Hua
authors.initials: YH
authors.lastname: Liao
authors.forename: Yi-Mei
authors.initials: YM
authors.lastname: Du
mesh_terms: D000818:Animals; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D006034:Glycyrrhetinic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology; D006035:Glycyrrhiza / Q000737:chemistry; D006801:Humans; D007376:Interleukin-2 / Q000378:metabolism; D019169:Jurkat Cells; D051664:Kv1.3 Potassium Channel / Q000037:antagonists & inhibitors* / Q000235:genetics / Q000378:metabolism; D008213:Lymphocyte Activation / Q000187:drug effects*; D012333:RNA, Messenger / Q000235:genetics; D013601:T-Lymphocytes / Q000187:drug effects* / Q000276:immunology*
chemical_list: D007376:Interleukin-2; D051664:Kv1.3 Potassium Channel; D012333:RNA, Messenger; C119129:18alpha-glycyrrhetinic acid; D006034:Glycyrrhetinic Acid; D002118:Calcium