Immunopharmacology and Inflammation Inhibition of store-operated Ca 2+ entry channels and K + channels by caffeic acid phenethylester in T lymphocytes Joo Hyun Nam a , Dong Hoon Shin a , Haifeng Zheng a , Jae Seung Kang b , Woo Kyung Kim d, ⁎, Sung Joon Kim a,c, ⁎ a Department of Physiology, Seoul National University College of Medicine, Republic of Korea b Department of Anatomy, Seoul National University College of Medicine, Republic of Korea c Ischemia/Hypoxia Disease Institute, Medical Research Center, Seoul National University, Republic of Korea d Department of Internal Medicine, Dongguk University College of Medicine, Republic of Korea abstract article info Article history: Received 16 December 2008 Received in revised form 21 March 2009 Accepted 1 April 2009 Available online 14 April 2009 Keywords: Caffeic acid Caffeic acid phenethyl ester T cell Ca 2+ -release activated Ca 2+ channel Ca 2+ signaling K + channel The increase of cytoplasmic Ca 2+ concentration (Δ[Ca 2+ ] c ) in response to antigenic stimulation is a critical step of signals activating immune responses. In addition, the voltage-gated K + channels (Kv) in T lymphocytes draw attention as an effective target of immune-modulation. Caffeic acid phenethyl ester (CAPE), an active component of propolis, shows strong anti-inflammatory effects and T cell suppression. Although various mechanisms have been suggested for the action of CAPE, the effects of CAPE on intracellular Ca 2+ signaling and ion channels are unknown. Here we investigated the effects of CAPE on Δ[Ca 2+ ] c , Ca 2+ - release activated Ca 2+ current (I CRAC ), and Kv current (I Kv ) in Jurkat T cells, and on Ca 2+ -activated K + channel current (I SK4 ) overexpressed in HEK-293 cells. I CRAC was induced by dialyzing T cells and Orai1/STIM1 overexpressing HEK293 cells with InsP 3 /BAPTA-containing pipette solution. CAPE concentration-depen- dently decreased both T cell receptor (CD3)- and thapsigargin-induced Δ[Ca 2+ ] c . The phosphorylation of PLCγ 1 by CD3 stimulation was not affected by CAPE. I CRAC was almost completely blocked by 25 μM CAPE. CAPE also inhibited the I Kv and I SK4 . Albeit the strong inhibition of Ca 2+ influx via CRAC, the suppression of IL-2 secretion by CAPE was similarly observed in human peripheral T cells when the CRAC pathway was circumvented by ionomycin. Although the unspecific inhibition of ion channels by CAPE suggested an intriguing mechanism, the effects of CAPE on signaling pathways other than I CRAC seem to play dominant roles in the immunomodulation by CAPE. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Polyphenols are critical antioxidants in our diet and draw attention due to their potential therapeutic and health promoting effects. In addition to their antioxidant effects, it has been consistently proposed that polyphenols exert their biological actions by interacting with and regulating various enzymes such as telomerase, cyclooxygenase, and lipoxygenase (D'Archivio et al., 2007; Fraga, 2007). Also, because of their lipophilic structure, interactions with biomembranes and membrane proteins have been presumed. However, there are still rare investigation of the effects of polyphenols on ion channels and transporters. Polyphenols are divided into several classes according to the number of phenol rings and structural components; flavonoids, phenolic acids, phenolic alcohols, stilbenes and lignans (Fraga, 2007). Caffeic acid (CA) is the most abundant phenolic acid in dietary substances. A well-known derivative of CA is caffeic acid phenethyl ester (CAPE) that is recognized as the active component of propolis. CAPE has antiviral, anti-inflammatory, antioxidant, and immunomo- dulatory properties (Huang et al., 1976; Chiao et al., 1995; Mirzoeva and Calder, 1996; Michaluart et al., 1999; Fitzpatrick et al., 2001). In accordance with the above effects, it has been demonstrated that CAPE is a potent and specific inhibitor of NF-κB(Natarajan et al., 1996), lipid peroxidation (Laranjinha et al., 1995; Fitzpatrick et al., 2001) and lipoxygenase (Sud'ina et al., 1993). Also, CAPE inhibits the transcriptional activity of the cyclooxygenase type 2 (COX-2) gene in epithelial cells (Michaluart et al., 1999), inducible nitric-oxide synthase gene expression in macrophage cell lines (Song et al., 2002; Nagaoka et al., 2003), suppression of eicosanoid synthesis and arachidonic acid release (Mirzoeva and Calder, 1996; Michaluart et al., 1999). However, it is still not clear how the various effects are caused by single compound like CAPE. In this respect, it was European Journal of Pharmacology 612 (2009) 153–160 ⁎ Corresponding authors. Sung Joon Kim is to be contacted at the Department of Physiology, Ischemia/Hypoxia Disease Institute,Medical Research Center, Seoul National University, Seoul,110-799, Republic of Korea. Fax: +82 2 763 9667. Woo Kyung Kim, Department of Internal Medicine, Dongguk University College of Medicine, Gyeongju, 780-714, Republic of Korea. Tel.: +82 31 961 7130; fax: +82 31 961 7154. E-mail addresses: popo1hi@yahoo.co.kr (W.K. Kim), sjoonkim@snu.ac.kr (S.J. Kim). 0014-2999/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.ejphar.2009.04.004 Contents lists available at ScienceDirect European Journal of Pharmacology journal homepage: www.elsevier.com/locate/ejphar