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Journal of Lipid Research, Vol. 46, 2134-2142, October 2005
Copyright © 2005 by American Society for Biochemistry and Molecular Biology

10t,12c-conjugated linoleic acid inhibits lipopolysaccharide-induced cyclooxygenase expression in vitro and in vivo

Guangming Li^*, David Barnes^1,*,,, Daniel Butz, Dale Bjorling^** and Mark E. Cook^2,*,,

^* Molecular and Environmental Toxicology, University of Wisconsin-Madison, Madison, WI 53706
Department of Nutritional Sciences, University of Wisconsin-Madison, Madison, WI 53706
Animal Sciences Department, University of Wisconsin-Madison, Madison, WI 53706
^** Department of Surgical Sciences, University of Wisconsin-Madison, Madison, WI 53706

Published, JLR Papers in Press, August 1, 2005. DOI 10.1194/jlr.M500064-JLR200

¹ Present address of D. Barnes: Standard Process, Inc., Palmyra, WI 53156.

² To whom correspondence should be addressed. e-mail: mcook{at}wisc.edu

Previous data demonstrated that conjugated linoleic acid (CLA) reduced eicosanoid release from select organs. We hypothesized that one active CLA isomer was responsible for the reduced prostaglandin release and that the mechanism was through the inhibition of inducible cyclooxygenase-2 (COX-2). Here, we examined the effects of 10t,12c-CLA and 9c,11t-CLA on COX-2 protein/mRNA expression, prostaglandin E₂ (PGE₂) production, and the mechanism by which CLA affects COX-2 expression and prostaglandin release. The COX-2 protein expression level was inhibited 80% by 10t, 12c-CLA and 26% by 9c,11t-CLA at 100 µM in vitro. PGE₂ production was decreased from 5.39 to 1.12 ng/2 x 10⁶ cells by 10t,12c-CLA and from 5.7 to 4.5 ng/2 x 10⁶ cells by 9c,11t-CLA at 100 µM. Mice fed 10t,12c-CLA but not 9c,11t-CLA were found to have a 34% decrease in COX-2 protein and a 43% reduction of PGE₂ release in the lung. 10t,12c-CLA reduced COX-2 mRNA expression level by 30% at 100 µM in vitro and by 30% in mouse lung in vivo. Reduced COX-2 mRNA was attributable to an inhibition of the nuclear factor B (NF-B) pathway by 10t,12c-CLA.

These data suggested that the inhibition of NF-B was one of the mechanisms for the reduced COX-2 expression and PGE₂ release by 10t,12c-CLA.

Abbreviations: CLA, conjugated linoleic acid; COX, cyclooxygenase; EIA, enzyme immunoassay; G3PDH, glyceraldehyde-3-phosphate dehydrogenase; IL-l, interleukin-l; iNOS, inducible nitric oxide synthase; LA, linoleic acid; LPS, lipopolysaccharide; NF-B, nuclear factor B; PGE₂, prostaglandin E₂; TNF-, tumor necrosis factor-

Supplementary key words inflammation • polyunsaturated fatty acid • prostaglandin • inducible nitric oxide synthase

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