British Journal of Nutrition

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Molecular Nutrition

Cocoa polyphenols suppress TNF-α-induced vascular endothelial growth factor expression by inhibiting phosphoinositide 3-kinase (PI3K) and mitogen-activated protein kinase kinase-1 (MEK1) activities in mouse epidermal cells

Jong-Eun Kima1, Joe Eun Sona1, Sung Keun Junga1a2, Nam Joo Kanga2a3, Chang Yong Leea4, Ki Won Leea2 c1 and Hyong Joo Leea1 c1

a1 Department of Agricultural Biotechnology, Seoul National University, Seoul, Republic of Korea

a2 Department of Bioscience and Biotechnology, Bio/Molecular Informatics Center, Konkuk University, Seoul, Republic of Korea

a3 School of Applied Biosciences, Kyungpook National University, Daegue 702-701, Republic of Korea

a4 Department of Food Science and Technology, Cornell University, Geneva, NY, USA

Abstract

Cocoa polyphenols have antioxidant and anti-inflammatory effects. TNF-α is a pro-inflammatory cytokine that has a vital role in the pathogenesis of inflammatory diseases such as cancer and psoriasis. Vascular endothelial growth factor (VEGF) expression is associated with tumorigenesis, CVD, rheumatoid arthritis and psoriasis. We tested whether cocoa polyphenol extract (CPE) inhibited TNF-α-induced VEGF expression in promotion-sensitive JB6 mouse epidermal cells. CPE significantly inhibited TNF-α-induced up-regulation of VEGF via reducing TNF-α-induced activation of the nuclear transcription factors activator protein-1 (AP-1) and NF-κB, which are key regulators of VEGF expression. CPE also inhibited TNF-α-induced phosphorylation of protein kinase B (Akt) and extracellular signal-regulated kinase. CPE blocked activation of their downstream kinases, p70 kDa ribosomal protein S6 kinase and p90 kDa ribosomal protein S6 kinase. CPE suppressed phosphoinositide 3-kinase (PI3K) activity via binding PI3K directly. CPE did not affect TNF-α-induced phosphorylation of mitogen-activated protein kinase kinase-1 (MEK1) but suppressed TNF-α-induced MEK1 activity. Collectively, these results indicate that CPE reduced TNF-α-induced up-regulation of VEGF by directly inhibiting PI3K and MEK1 activities, which may contribute to its chemopreventive potential.

(Received December 01 2009)

(Revised March 22 2010)

(Accepted March 25 2010)

(Online publication June 16 2010)

Correspondence:

c1 Corresponding authors: Dr Ki Won Lee, fax +82 2 3436 6178, email kiwon@konkuk.ac.kr; Dr Hyong Joo Lee, fax +82 2 873 5095, email leehyjo@snu.ac.kr

Footnotes

Abbreviations: Akt, protein kinase B; AP-1, activator protein-1; CPE, cocoa polyphenol extract; DTT, dithiothreitol; EGTA, ethylene-glycol-bis(a-aminoethyl)-N,N,N′,N′-tetra-acetic acid; ERK, extracellular signal-regulated kinase; FBS, fetal bovine serum; JNK, c-Jun N-terminal kinase; MEK1, mitogen-activated protein-kinase kinase-1; MEM, Eagle's minimum essential medium; MKK4, mitogen-activated protein kinase kinase 4; MMP-2, matrix metalloproteinase-2; p70S6K, p70 kDa ribosomal protein S6 kinase; p-, phosphorylated; P+, promotion-sensitive; PI3K, phosphoinositide 3-kinase; PMSF, phenylmethanesulfonyl fluoride; TPA, 12-O-tetradecanoylphorbol-13-acetate; Tris, 2-amino-2-hydroxymethyl-propane-1,3-diol; VEGF, vascular endothelial growth factor

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