Gallic Acid Suppresses Lipopolysaccharide-Induced Nuclear Factor-κB Signaling by Preventing RelA Acetylation in A549 Lung Cancer Cells

Although multiple studies have revealed that gallic acid plays an important role in the inhibition of malignant transformation, cancer development, and inflammation, the molecular mechanism of gallic acid in inflammatory diseases is still unclear. In this study, we identified gallic acid from Rosa rugosa as a histone acetyltransferase (HAT) inhibitor with global specificity for the majority of HAT enzymes, but with no activity toward epigenetic enzymes including sirtuin (silent mating type information regulation 2 homologue) 1 (S. cerevisiae), histone deacetylase, and histone methyltransferase. Enzyme kinetic studies indicated that gallic acid uncompetitively inhibits p300/CBP-dependent HAT activities. We found that gallic acid inhibits p300-induced p65 acetylation, both in vitro and in vivo, increases the level of cytosolic IκBα, prevents lipopolysaccharide (LPS)-induced p65 translocation to the nucleus, and suppresses LPS-induced nuclear factor-κB activation in A549 lung cancer cells. We have also shown that gallic acid treatment inhibits the acetylation of p65 and the LPS-induced serum levels of interleukin-6 in vivo. Importantly, gallic acid generally inhibited inflammatory responses caused by other stimuli, including LPS, IFN-γ, and interleukin-1β, and further downregulated the Received 6/1/09; revised 10/7/09; accepted 10/7/09; published OnlineFirst 12/8/09. Grant support: Korea Science and Engineering Foundation grant funded by the Korea government (MOST; R13-2002-054-04002-0), a grant from the BioGreen 21 program (code no. 20070301034007), Rural Development Administration, Republic of Korea, a faculty research grant from the Yonsei University College of Medicine (6-2008-0277; H.G. Yoon), and a Korea Science and Engineering Foundation grant funded by the Korea government (MOST; R11-2007-04001004-0; J.M. Lee). The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. Note: Supplementary data for this article are available at Molecular Cancer Research Online (http://mcr.aacrjournals.org/). K-C. Choi and Y-H. Lee contributed equally to this work. Requests for reprints: Ho-Geun Yoon and Jae Myun Lee, Department of Biochemistry and Molecular Biology, Yonsei University College of Medicine, 134 Sicnchon-dong, Seodaemun-gu, Seoul 120-752, South Korea. Phone: 82-22228-1683; Fax: 82-2-312-5041. E-mail: [email protected] Copyright © 2009 American Association for Cancer Research. doi:10.1158/1541-7786.MCR-09-0239 Mol Cancer Res 2009;7(12). December 2009 Researc on October 26 mcr.aacrjournals.org Downloaded from expression of nuclear factor-κB–regulated antiapoptotic genes. These results show the crucial role of acetylation in the development of inflammatory diseases. (Mol Cancer Res 2009;7(12):2011–21) Introduction Gallic acid (3,4,5-trihydroxybenzoicacid) is a polyhydroxyphenolic compound which is found in various natural products such as gallnuts, sumac, tea leaves, oak bark, green tea, apple peels, grapes, strawberries, pineapples, bananas, lemons, and in red and white wine (1). Gallic acid is cytotoxic to cancer cells and has anti-inflammatory and antimutagenic properties (2, 3). Gallic acid has been described as an excellent free radical scavenger and as an inducer of differentiation and programmed cell death in a number of tumor cell lines (4, 5). Recently, it was revealed that gallic acid from rose flowers exhibits antioxidative effects even in senescence-accelerated mice and can restore the activities of catalase and gluthatione peroxidase (6). Even though many reports have revealed that gallic acid plays an important role in the prevention of inflammation and cancer development, it is still unclear how gallic acid inhibits cancerrelated inflammation. An imbalance of protein acetylation and deacetylation in cellular signaling can lead to human diseases, including inflammation and cancer. Currently, the functions of more than 70 proteins are known to be regulated through acetylation of their lysine residues (7). Acetylation of specific lysine residues within the amino terminal tails of histones is generally linked to chromatin disruption and the transcriptional activation of genes. Depending on the functional domain that is modified, acetylation can also regulate the functions of non-histone proteins, such as DNA-binding affinity, protein stability, proteinprotein interaction, and subcellular localization (8, 9). The RelA (p65) subunit of nuclear factor-κB (NF-κB) is also known to be activated in an acetylation-dependent manner in response to cytokine stimulation (10, 11). Reversible acetylation of RelA thus functions as a molecular switch that both controls the duration of the NF-κB transcriptional response and replenishes the cytoplasmic pool of latent NF-κB/IκBα complexes, thereby readying the cell for the next NF-κB–inducing signal (11). NF-κB is a ubiquitously expressed family