Effect of long-chain n-3 polyunsaturated fatty acid on inflammation mediators during osteoblastogenesis

This study examined the effects of eicosapentaenoic acid (EPA) and arachidonic acid (AA) on inflammation mediators during osteoblastogenesis, in terms of modulation of the cyclooxygenase (COX)-2 and the inducible nitric oxide (NO) synthase (iNOS) pathways. We hypothesized that n-3 polyunsaturated fatty acid (PUFA) would reduce the production of inflammation mediators, including prostaglandin E(2) (PGE(2)) and NO, and related mRNA gene expression during osteoblastogenesis. Mouse bone marrow stromal cells (ST-2) were treated with 40 microM ethanol (as a control), 40 microM AA, or 40 microM EPA in osteogenic medium for 7, 14, 21, or 28 days. Prior to harvest, cells were treated with respective treatments along with cytokine mixtures for an additional 24 hours, and then cells were harvested for mRNA expression. In addition, cells were also treated with respective treatments along with the same cytokine mixtures for an additional 48 hours for experiment measuring PGE(2) and NO production using conditioned culture medium and protein expression using cells. Except for 7 days of culture, AA treatment resulted in the highest value for PGE(2) production throughout 28 days of culture. AA treatment also enhanced COX-2 mRNA expression up to 21 days. AA treatment resulted in a higher value for NO production after 7 days, while EPA treatment yielded a higher value for NO production relative to those receiving AA treatment after 14 and 21 days. Our investigation has corroborated that the protective action of EPA on osteoblastogenesis was mediated by the modulation of PGE(2) and the NO pathway.