Modulation of fatty acid methyl esters in rats pretreated with tri-o-tolyl phosphate

Synthesis of fatty acid ethyl esters in mammalian tissues after ethanol exposure: a systematic review of the literature

The ability to undergo non-oxidative metabolism from ethanol to fatty acid ethyl esters (FAEEs) varies greatly among tissues and organs. To gain a greater understanding of non-oxidative ethanol metabolism to FAEE, we aimed to collect all published data on FAEE synthesis in mammalian organs and tissues to identify all tissues, organs, and enzymes that are known to, or likely possess FAEE-synthetic activity. A systematic search for relevant papers was performed and two independent reviewers examined potentially relevant abstracts (articles on FAEEs that pertain to ethanol exposure) to determine whether they met the inclusion criteria. Information on FAEE synthesis was retrieved from papers meeting the inclusion/exclusion criteria and summarized by organ/tissue/matrix examined. The systematic search through four databases yielded 78 articles that investigated FAEE synthesis by tissues, tissue fractions and cell lines, and 29 articles that attempted to purify and/or characterize the enzymes involved in FAEE synthesis. Two enzyme activities have been studied: FAEE synthase (FAEES, which conjugates ethanol and free fatty acid) and acyl-CoA: ethanol O-acyltransferase (AEAT, which conjugates ethanol and fatty acyl-CoA). Both activities are expressed by a variety of different enzymes. FAEES activity is the most widely studied and has been purified from several tissues and shown to be associated with several well-known enzymes, while the identity of enzymes possessing AEAT activity remains unknown. The organs and tissues that have been shown to synthesize FAEEs are discussed, with special emphasis on the studies that attempted to elucidate the enzymology of FAEE synthesis in those tissues.

Methyl palmitate inhibits lipopolysaccharide-stimulated phagocytic activity of rat peritoneal macrophages

Macrophages, in general, are critical effectors of body's immune system. Chemical inhibition of phagocytic activity of such macrophages as Kupffer cells has been extensively studied. We have earlier shown that methyl palmitate (MP) inhibits the activation of Kupffer cells. To evaluate the potential of MP to inhibit the activation of other macrophages, we treated rat peritoneal macrophages with varying concentrations of MP. Its treatment led to a dose-dependent inhibition of phagocytic activity, which was found to be 34%, 47%, and 66% at 0.25, 0.50, and 1.0 mM MP, respectively, as measured by latex bead uptake. When MP-treated peritoneal macrophages were stimulated with lipopolysaccharide (LPS), the nitric oxide (.NO) release was inhibited at 6 h, while cyclooxygenase-2 expression decreased after 24 h. The treatment with MP increased the release of interleukin (IL)-10 in the LPS-treated cells at 6 h, while IL-6 and tumor necrosis factor-alpha were significantly increased both at 6 and 24 h. Our data suggest that MP inhibits phagocytic activity and .NO production similar to that observed in isolated Kupffer cells. Therefore, inhibition of phagocytosis by MP may be a general phenomenon, and it could be used as an inhibitor of macrophage function.

Methyl palmitate: inhibitor of phagocytosis in primary rat Kupffer cells

Kupffer cells are involved in phagocytosis and known to release biologically active mediators during early events of liver injury. Such functional properties of Kupffer cells can be modulated by methyl palmitate (MP). Therefore, efficacy of MP to modulate Kupffer cell function was evaluated in cultured primary Kupffer cells from rat liver. Phagocytic activity of Kupffer cells was measured by their capacity to phagocytize latex beads and the release of TNF-alpha, IL-10, IL-6, nitric oxide, and PGE2 was determined in cell culture medium after incubating the cells with various concentrations of MP for 24 h followed stimulation with lipopolysaccharide (LPS) for 6 h. To understand the mechanism of phagocytosis, we investigated the hydrolysis of MP, and determine ATP levels and activity of NF-kappaB in MP-inhibited Kupffer cells. A significant decrease was observed in phagocytosis. Phagocytosis evaluated at 0.5 mM MP was found to be time-dependent with a maximum decrease of 49% at 6 h. Exposure of Kupffer cells to MP followed by LPS stimulation showed a dose-dependent decrease in phagocytosis and reduced the release of TNF-alpha, IL-10, nitric oxide, and PGE2 but not of IL-6 levels in the supernatant as compared to the control. While ATP levels were unchanged, the nuclear factor NF-kappaB (p65) activity was inhibited in Kupffer cells treated with MP after LPS stimulation (35.6 RLU versus 49.6 RLU in control). Hydrolysis of MP was found to be time-dependent; maximum concentration of MP and palmitic acid (hydrolysis products) in the cell being at 3 and 6 h, respectively. In general, MP appears to reduce phagocytosis and levels of TNF-alpha, IL-10, nitric oxide, and PGE2 without affecting ATP levels and is probably mediated by NF-kappaB. This in vitro model is useful for detailed mechanistic studies of inhibition of phagocytosis by MP and other fatty acid esters.