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Int. J. Mol. Sci. 2009, 10(9), 4168-4177; doi:10.3390/ijms10094168
Article

Effect of Quercetin on Paraoxonase 2 Levels in RAW264.7 Macrophages and in Human Monocytes—Role of Quercetin Metabolism

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1 Institute of Human Nutrition and Food Science, Christian Albrechts University Kiel, Olshausenstrasse 40, D-24118 Kiel, Germany 2 National Research Institute for Food and Nutrition (INRAN), 00178 Roma, Italy 3 Institute of Animal Nutrition and Physiology, Christian Albrechts University Kiel, 24118 Kiel, Germany
* Author to whom correspondence should be addressed.
Received: 11 August 2009 / Revised: 10 September 2009 / Accepted: 21 September 2009 / Published: 23 September 2009
(This article belongs to the Section Biochemistry, Molecular Biology and Biophysics)
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Abstract

There is increasing evidence that the intracellular antioxidant enzyme paraoxonase 2 (PON2) may have a protective function in the prevention of atherogenesis. An enhancement of PON2 activity by dietary factors including flavonoids is therefore of interest. In the present study we determined the effect of quercetin on paraoxonase 2 levels in cultured murine macrophages in vitro and in overweight subjects with a high cardiovascular risk phenotype supplemented with 150 mg quercetin/day for 42 days in vivo. Supplementation of murine RAW264.7 macrophages in culture with increasing concentrations of quercetin (1, 10, 20 μmol/L) resulted in a significant increase in PON2 mRNA and protein levels, as compared to untreated controls. Unlike quercetin, its glucuronidated metabolite quercetin-3-glucuronide did not affect PON2 gene expression in cultured macrophages. However the methylated quercetin derivative isorhamnetin enhanced PON2 gene expression in RAW264.7 cells to similar extent like quercetin. Although supplementing human volunteers with quercetin was accompanied by a significant increase in plasma quercetin concentration, dietary quercetin supplementation did not change PON2 mRNA levels in human monocytes in vivo. Current data indicate that quercetin supplementation increases PON2 levels in cultured monocytes in vitro but not in human volunteers in vivo.
Keywords: quercetin; flavonoid; paraoxonase 2; macrophage; atherosclerosis quercetin; flavonoid; paraoxonase 2; macrophage; atherosclerosis
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Boesch-Saadatmandi, C.; Pospissil, R.T.; Graeser, A.-C.; Canali, R.; Boomgaarden, I.; Doering, F.; Wolffram, S.; Egert, S.; Mueller, M.J.; Rimbach, G. Effect of Quercetin on Paraoxonase 2 Levels in RAW264.7 Macrophages and in Human Monocytes—Role of Quercetin Metabolism. Int. J. Mol. Sci. 2009, 10, 4168-4177.

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Int. J. Mol. Sci. EISSN 1422-0067 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert