Curcumin decreases toll-like receptor-2 gene expression and function in human monocytes and neutrophils Tsuyoshi Shuto a,1 , Tomomi Ono a,1 , Yuko Ohira a,1 , Shogo Shimasaki a , Shota Mizunoe a , Kenji Watanabe a , Mary Ann Suico a , Tomoaki Koga a , Takashi Sato a , Saori Morino a , Keizo Sato b,c , Hirofumi Kai a, * a Department of Molecular Medicine, Graduate School of Pharmaceutical Sciences, Global COE ‘‘Cell Fate Regulation Research and Education Unit”, Kumamoto University, 5-1 Oe-Honmachi, Kumamoto 862-0973, Japan b Department of Pharmacology and Therapeutics, Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-Honmachi, Kumamoto 862-0973, Japan c School of Pharmacy, Kyushu University of Health and Welfare, Yoshino Nobeoka, Miyazaki 882-8508, Japan article info Article history: Received 18 June 2010 Available online 3 July 2010 Keywords: TLR2 Curcumin Monocytes Neutrophils abstract Toll-like receptor-2 (TLR2) is a pattern recognition receptor that senses many types of bacterial compo- nents and activates signaling pathways that induce inflammatory cytokines. A hyperresponsiveness to pathogens caused by increased expression of TLR2 triggers exaggeration of some inflammatory diseases. Here, we showed that curcumin, a well-known anti-inflammatory agent derived from the curry spice tur- meric, inhibits TLR2 expression in various TLR2-expressing innate immune cell lines such as monocytic THP-1 cells, neutrophilic-differentiated HL-60 cells. Strong suppression of TLR2 gene expression was spe- cifically observed at concentrations of curcumin in the range 40–100 lM. Consistent with decreased expression of TLR2 mRNA, protein expression and ligand-responsiveness of TLR2 were markedly reduced by curcumin treatment. Moreover, curcumin-dependent down-regulation of TLR2 expression and func- tion was also observed in primary peripheral blood monocytes (MC) and polymorphonuclear neutrophils (PMN). Finally, we determined the importance of curcumin-dependent radical generation for the suppressive effect of curcumin on TLR2 expression. Thus, our data demonstrate that curcumin inhibits TLR2 gene expression and function possibly via an oxidative process. Ó 2010 Elsevier Inc. All rights reserved. 1. Introduction Toll-like receptors (TLRs) are type I transmembrane receptors that play an important role in innate immune recognition of the invading bacteria [1]. TLRs directly interact with pathogen-associ- ated molecular patterns (PAMPs) on a variety of bacteria and acti- vate signaling pathways that lead to induction of inflammatory cytokines and antimicrobial peptides that can result in elimination of the invading pathogens [2]. To date, 11 members of the mamma- lian TLR family have been identified and cloned. Of these, TLR2 has gained importance as receptor for bacterial lipopeptides and pepti- doglycan (PGN) in various types of innate immune cells such as monocytes and neutrophils [3]. Although optimal TLR2 signaling is required to activate our innate immune system, excessive amount of TLR2 signaling and expression, and overproduction of inflammatory cytokines lead to inflammatory diseases such as cys- tic fibrosis (CF) [4], septic shock [5] and inflammatory bowel dis- ease [6]. Therefore, TLR2 signaling and expression must be kept under control during immune responses and identification of the agents that control TLR2 expression and their signaling is urgently needed for the treatment of TLR2-dependent hyperinflammatory diseases. Curcumin is the major bioactive compound in turmeric (Cur- cuma longa). Extensive studies within the past decades have proved that curcumin has multiple biological activities such as anti-oxidant, anti-inflammatory and anti-carcinogenic [7–9]. Be- cause of these pleiotropic activities of curcumin, it has been widely used in folk medicine for the therapy of inflammatory and infec- tious diseases [10]. Among its many effects, anti-inflammatory ef- fects of curcumin are mediated through the interference with the expression or activation of multiple key signaling molecules, including nuclear factor-jB (NF-jB) [11], activator protein-1 (AP- 1) [12], tumor necrosis factor-a (TNF-a) [13], interleukin-1b (IL- 1b) [14], p300 histone acetyl transferase [15], cyclooxygenase (COX)-2 [16] and 5-lipoxygenase [17]. Although numerous molec- ular targets of curcumin have been identified thus far, its effect on the expression of TLRs is yet to be fully understood. To better understand the role of curcumin in the regulation of TLR2 gene expression and function, we treated various TLR2- expressing innate immune cell lines including human monocytic THP-1 cells, neutrophilic-differentiated HL-60 (dHL-60) cells with curcumin and evaluated the expression level of TLR2 gene in these 0006-291X/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.bbrc.2010.06.126 * Corresponding author. Fax: +81 96 371 4405. E-mail address: hirokai@gpo.kumamoto-u.ac.jp (H. Kai). 1 These authors contributed equally to this work. Biochemical and Biophysical Research Communications 398 (2010) 647–652 Contents lists available at ScienceDirect Biochemical and Biophysical Research Communications journal homepage: www.elsevier.com/locate/ybbrc