Curcumin Inhibits Glyoxalase 1—A Possible Link to Its Anti-Inflammatory and Anti-Tumor Activity

et al. (2008) Curcumin Inhibits Glyoxalase 1-A Possible Link to Its Anti-Inflammatory and Anti-Tumor Activity. PLoS ONE 3(10): e3508. doi:10.1371/journal.pone.0003508 Curcumin Inhibits Glyoxalase 1-A Possible Link to Its Anti-Inflammatory and Anti-Tumor Activity Thore Santel 0 Gabi Pflug 0 Nasr Y. A. Hemdan 0 Angelika Scha fer 0 Marcus Hollenbach 0 Martin 0 Buchold 0 Anja Hintersdorf 0 Inge Lindner 0 Andreas Otto 0 Marina Bigl 0 Ilka Oerlecke 0 Antje 0 Hutschenreuter 0 Ulrich Sack 0 Klaus Huse 0 Marco Groth 0 Claudia Birkemeyer 0 Wolfgang 0 Schellenberger 0 Rolf Gebhardt 0 Mathias Platzer 0 Thomas Weiss 0 Mookambeswaran A. 0 Vijayalakshmi 0 Monika Kru ger 0 Gerd Birkenmeier 0 Daniel Tome, AgroParisTech, France 0 1 Institute of Biochemistry, University of Leipzig , Leipzig, Germany , 2 Frauenhofer Institute for Cell Therapy and Immunology IZI , Leipzig, Germany , 3 Institute of Clinical Immunology and Transfusion Medicine , Leipzig, Germany , 4 Department of Zoology, Faculty of Science, University of Alexandria, Moharram Bay, Alexandria, Egypt, 5 Leibniz Institute for Age Research-Fritz Lipmann Institute , Jena, Germany , 6 Institute of Analytical Chemistry , Leipzig, Germany , 7 Center for Liver Cell Research and Department of Surgery, University of Regensburg Hospital , Regensburg, Germany, 8 CBST; VIT University, TamilNadu , India , 9 Institute of Bacteriology and Mycology, Veterinary Faculty , Leipzig , Germany Background: Glyoxalases (Glo1 and Glo2) are involved in the glycolytic pathway by detoxifying the reactive methylglyoxal (MGO) into D-lactate in a two-step reaction using glutathione (GSH) as cofactor. Inhibitors of glyoxalases are considered as anti-inflammatory and anti-carcinogenic agents. The recent finding that various polyphenols modulate Glo1 activity has prompted us to assess curcumin's potency as an Glo1 inhibitor. Methodology/Principal Findings: Cultures of whole blood cells and tumor cell lines (PC-3, JIM-1, MDA-MD 231 and 1321N1) were set up to investigate the effect of selected polyphenols, including curcumin, on the LPS-induced cytokine production (cytometric bead-based array), cell proliferation (WST-1 assay), cytosolic Glo1 and Glo2 enzymatic activity, apoptosis/necrosis (annexin V-FITC/propidium iodide staining; flow cytometric analysis) as well as GSH and ATP content. Results of enzyme kinetics revealed that curcumin, compared to the polyphenols quercetin, myricetin, kaempferol, luteolin and rutin, elicited a stronger competitive inhibitory effect on Glo1 (Ki = 5.161.4 mM). Applying a whole blood assay, IC50 values of pro-inflammatory cytokine release (TNF-a, IL-6, IL-8, IL-1b) were found to be positively correlated with the Ki-values of the aforementioned polyphenols. Moreover, whereas curcumin was found to hamper the growth of breast cancer (JIMT-1, MDA-MB-231), prostate cancer PC-3 and brain astrocytoma 1321N1 cells, no effect on growth or vitality of human primary hepatocytes was elucidated. Curcumin decreased D-lactate release by tumor cells, another clue for inhibition of intracellular Glo1. Conclusions/Significance: The results described herein provide new insights into curcumin's biological activities as they indicate that inhibition of Glo1 by curcumin may result in non-tolerable levels of MGO and GSH, which, in turn, modulate various metabolic cellular pathways including depletion of cellular ATP and GSH content. This may account for curcumin's potency as an anti-inflammatory and anti-tumor agent. The findings support the use of curcumin as a potential therapeutic agent. - Funding: This study was supported in part by Wilhelm Sander-Stiftung (No. 2006.053.1; GB and IOe), by the BMBF-grant (HepatoSys project 0313081 F; TW and RG) and by Hans Bo ckler Stiftung (356283; AH). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. Curcumin (1,7-bis(4-hydroxy-3-methoxyphenyl)-1,6-heptadiene3,5-dione) is a polyphenol derived from the plant Curcuma longa. The medical use of this plant has its roots in the Indian Ayurveda medicine for over 6000 years. Extensive research over the last decades has indicated that curcumin exhibits anti-inflammatory, anti-oxidant, anti-viral and anti-infectious activities [1,2]. Furthermore, in various animal models, curcumin was found to suppress symptoms associated with type II diabetes [3] rheumatoid arthritis [4], Alzheimer disease [5], promoted wound healing [6] and was protective in an animal model of sepsis [7]. These effects seem to be linked to the anti-inflammatory effect of curcumin that, in turn, may be attributed to its ability to inhibit cyclooxygenase-2, lipoxygenase and inducible nitric oxide synthase (iNOS) [8]. Recently, the involvement of the peroxisome proliferator-activated receptorgamma has been shown [9]. Curcumin such as other polyphenols is as strong anti-oxidant [10]. It significantly decreases lipid peroxidation, regulates antioxidant enzymes and scavenges hyperglycemia-induced reactive oxygen species (ROS) [11]. Oxidative stress and inflammation are closely associated with tumor growth [12]. Therefore, it is not surprising that curcumin possesses anticancer effects by blocking different stages of the tumor development [13]. The low incidence of colon cancer among Indians has been attributed to the use of curcumin in cooking in addition to other dietary compounds [14]. However, a possible dominance of certain genetic prerequisites in these populations can not be excluded. Anti-proliferative effects of curcumin are suggested to be mediated by induction of apoptosis in a mitochondria-dependent manner via caspase-3 activation [15]. In addition, curcumin could affect cellular proliferation by modulating of various cell signaling pathways including NF-kB, growth factor receptor kinases and mitogen-activated protein kinases [16]. Although, the multiple biological functions of curcumin have been described, the prime driving mechanism underlying its action remains unknown [17]. In the present study we provide evidence that the diverse actions of curcumin may be mediated by inhibiting cellular glyoxalases. Glyoxalases are involved in the detoxification of the reactive MGO formed para-metabolically and para-enzymatically from triosephosphates when glucose is degraded. Glo1 catalyzes the conversion of cytotoxic MGO to nontoxic hemithioacetal using GSH as cofactor. This enzyme is ubiquitously expressed in all mammalian cells and is suggested to be involved in cellular aging and cell death [18]. Inhibitors of Glo1 have long been sought as possible anticancer agents. High affinity inhibitors were prepared as GSH analogues such as S-p-bromobenzylglutathione and were shown to display anti-proliferative action [19]. However, the ubiquity of GSH and its involvement in vital cellular reactions may limit the use of native GSH analogues as in (...truncated)