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CELLULAR AND MOLECULAR

Curcumin Suppresses Interleukin 1-Mediated Microsomal Prostaglandin E Synthase 1 by Altering Early Growth Response Gene 1 and Other Signaling Pathways

Eicosanoid Biochemistry Section, Laboratory of Molecular Carcinogenesis, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina (Y.M., T.E.E.); and Mercer University School of Medicine, Macon, Georgia (W.C.G.)

Curcumin (diferuloylmethane) is one of the phytophenolic compounds found in the turmeric plant with anti-inflammatory and anticarcinogenic activities. One possible mechanism for these activities is the inhibition of prostaglandin (PG) E₂ formation. In this study and other reports, curcumin suppresses interleukin-1-induced formation of prostaglandin E₂ in a concentration-dependent manner. Interleukin-1-induced microsomal prostaglandin E synthase 1 (mPGES-1) and cyclooxygenase-2 were attenuated by curcumin at the protein and mRNA levels, but a more dramatic inhibition of mPGES-1 expression was observed at lower concentrations of curcumin in A549 human lung epithelial cells. The inhibition of mPGES-1 expression by curcumin shifted the arachidonic acid profile from PGE₂ to PGF₂ and 6-keto-PGF₁ as major metabolites. The expression of early growth response gene 1 (EGR-1), a key transcription factor of cytokine-induced mPGES-1, was inhibited by curcumin. Incubation with siRNA for EGR-1 inhibited interleukin (IL)-1-induced mPGES-1, and the controlled expression of EGR-1 increased the mPGES-1 expression. Several proinflammatory signaling molecules, such as nuclear factor B (NF-B) and mitogen-activated protein kinases, are also known to affect curcumin-regulated gene expression. Curcumin inhibited IB phosphorylation and degradation and thus reduced the expression of mPGES-1. Curcumin suppressed cytokine-induced mPGES-1 by inhibiting phosphorylation of Jun N-terminal kinase (JNK)1/2. However, EGR-1 expression was suppressed by lower concentrations of curcumin, as compared with JNK1/2 and IB. These results indicate that curcumin inhibits IL-1-induced PGE₂ formation by inhibiting the expression of mPGES-1 that is mediated by suppression of EGR-1 expression as well as NF-B and JNK1/2.

Address correspondence to: Thomas E. Eling, NIEHS, Laboratory of Molecular Carcinogenesis, 111 TW Alexander Dr., Research Triangle Park, NC 27709. E-mail: eling{at}niehs.nih.gov

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