Isoflavone-rich extracts from wooly glycine Glycine tomentella inhibits LPS-induced TNF-α expression in a macrophage cell line of Atlantic salmon (Salmo salar L.)

The immunomodulatory effects of an isoflavone-rich extract from the root of wooly glycine Glycine tomentella (GTE) were studied in a macrophage-like cell line from Atlantic salmon (TO cells). The TO cell line was stimulated with defined concentrations of lipopolysaccharide (LPS) from Escherichia coli (serotype O127:B8) for defined time periods to induce expression of pro-inflammatory enzymes and cytokines. Cyclooxygenase-2 (COX-2), 5-lipoxygenase (5-LOX), tumor necrosis factor-alpha (TNF-α) and interleukin-1beta (IL-1β) were measured by real-time PCR methods and combined with analyses of eicosanoid production in cell extracts and evaluation of molecules of the TNF-α cell signaling pathway. The results showed that TNF-α was strongly induced by LPS, while GTE (25 μg/ml) inhibited 67% of the TNF-α response when added to the cells together with LPS. Incubation of LPS in combination of GTE in TO cells caused increased intracellular prostaglandin E2 (PGE2), and reduced activation of p38 MAP kinase compared to LPS alone. GTE seemed to arrest NADPH oxidation, the coenzyme for carbonyl reductase and the prostaglandin-E2 9-reductase converting PGE2 to PGF2. We suggest that the mechanism of increased intracellular PGE2 levels following GTE treatment is caused by reduced breakdown of PGE2. GTE did not inhibit the other pro-inflammatory responses in LPS stimulated cells studied herein. IL-1β and COX-2 showed moderately increased levels of expression likely caused by the increased PGE2.