Inhibition of the transcription factor c-Jun by the MAPK family, and not the NF-κB pathway, suggests that peanut extract has anti-inflammatory properties

Background: Tumor necrosis factor-alpha (TNF-alpha) is involved in inflammatory responses in atherosclerosis. We propose an in vitro cellularassay to evaluate the anti-inflammatory mechanisms of potential modifiers such as food extracts. In the current model we assessed an anti-inflammatory effect of polyphenol-rich peanut extract in lipopolysaccharide (LPS)-induced THP-1 monocytes. Methods: THP-1 monocytes were incubated with peanut extract (5, 25, 50 and 100 mu g/mL) consisting of 39% flavonols, 37% flavanols and 24% phenolic acid (or BAY 11-7082 (5 mu M) as experiment control) for 1 h and then stimulated with LPS (500 ng/mL) for 4 h. Cytotoxicity was measured as lactate dehydrogenase (LDH) activity release. NF-kappa B and MAPK family were determined by TransAm kit while TNF-alpha mRNA levels and its mRNA stability by RT-PCR. Intra- and extracellular TNF-alpha protein was measured by ELISA, and TNF-alpha converting enzyme (TACE) activity by a fluorimetric assay. Results: Peanut extract inhibited the maximal LPS-induced extracellular TNF-alpha protein secretion by 18%, 29% and 47% at 25,50 and 100 mu g/mL, respectively (P < 0.05). LPS stimulation revealed that 85% of TNF-alpha was released extracellularly while 15% remained intracellular. Peanut extract did not modify NF-kappa B but, instead, reduced c-Jun transcription factor activity (P < 0.05), decreased TNF-alpha mRNA (albeit non-significantly) and had no effect on mRNA stability and TACE activity. Conclusion: Polyphenol-rich peanut extract reduces extracellular TNF-alpha protein by inhibiting c-Jun transcription factor from MAPK family, suggesting an anti-inflammatory effect. The proposed THP-1 monocyte model could be used to assess food extract impact (site and size effects) on the inflammation pathway. (C) 2012 Elsevier Ltd. All rights reserved.