The ethyl pyruvate analogues, diethyl oxaloproprionate, 2-acetamidoacrylate, and methyl-2-acetamidoacrylate, exhibit anti-inflammatory properties in vivo and/or in vitro

Abstract

Ethyl pyruvate (EP) is a simple aliphatic ester derived from the endogenous metabolite, pyruvic acid. EP has been shown to decrease the expression of various pro-inflammatory mediators, including nitric oxide (NO ), tumor necrosis factor (TNF), cyclooxygenase-2, and interleukin (IL)-6, in a variety of in vitro and in vivo model systems. In an effort to better understand the chemical features that might explain the anti-inflammatory properties of EP, we screened 15 commercially available compounds for cytoprotective or anti-inflammatory effects using two in vitro assay systems: TNF and NO production by lipopolysaccharide (LPS)-stimulated RAW 264.7 murine macrophage-like cells and changes in the permeability of Caco-2 human enterocyte-like monolayers stimulated with a cocktail of pro-inflammatory cytokines called cytomix (1000 U/ml IFN-γ plus 10 ng/ml TNF-α plus 1 ng/ml IL-1β). Two compounds, namely diethyl oxaloproprionate (DEOP) and 2-acetamidoacrylate (2AA), demonstrated consistent anti-inflammatory or cytoprotective pharmacological properties in this screening process. Treatment of mice with either of these compounds ameliorated LPS-induced ileal mucosal hyperpermeability to the fluorescent probe, fluorescein isothiocyanate-labeled dextran (average molecular mass 4 kDa), and bacterial translocation to mesenteric lymph nodes. Treatment with either of these compounds also improved survival in mice challenged with a lethal dose of LPS. Finally, in a study that compared 2AA to its methyl ester, we showed that methyl-2-acetamidoacrylate is at least 100-fold more potent than the parent carboxylate as an inhibitor of LPS-induced NO production by RAW 264.7 cells. Collectively, these data are consistent with the view that anti-inflammatory activity is demonstrable for a number of compounds that either incorporate an olefinic linkage conjugated to a carbonyl moiety or are capable of undergoing tautomeric rearrangement to form such a structure. Moreover, our findings suggest that esters with these general characteristics, perhaps because of their greater lipophilicity or electrophilicity, are more potent anti-inflammatory agents than are the parent carboxylates.