Celecoxib, a COX-2 inhibitor, synergistically potentiates the anti-inflammatory activity of docosahexaenoic acid in macrophage cell line

Background: The anti-inflammatory properties of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and non-steroidal anti-inflammatory drugs overlap in many ways. The aim of this study was to examine the individual and synergetic anti-inflammatory effects of celecoxib, EPA and DHA in RAW-264.7 cell line.Methodology: The cells were exposed to EPA, DHA, celecoxib, rosiglitazone, GW9662 alone or their combination, and stimulated with 5g/mL lipopolysaccharide (LPS). Nitric oxide (NO), tumor necrosis factor- (TNF-), interleukin (IL)-6 and prostaglandin-E-2 (PGE(2)) levels were estimated in the medium using enzyme-linked immunosorbent assays. The cyclooxygenase-2 (COX-2) and inducible Nitric Oxide Synthase (iNOS) expression were analyzed in the cell lysate by immunoblotting. Peroxisome proliferator-activated receptor (PPAR) and nuclear factor-B (NF-B) transcription factor activation assays were performed in the nuclear extract.Results: Combined treatment of DHA (50M) and celecoxib (20M) significantly inhibited LPS induced synthesis of NO, TNF-, IL-6 and PGE(2) levels in the cells, compared to the individual treatments. In addition, DHA and celecoxib diminished the COX-2 and iNOS expression in the cells. This was associated with increased PPAR activity, supressed NF-B activity in the nucleus. We determined whether GW9662, a specific PPAR inhibitor, could abolish the anti-inflammatory effect of DHA and celecoxib. GW9662 has abolished the DHA and celecoxib induced PPAR activation, but did not alter the NF-B mediated anti-inflammatory effects induced by celecoxib and DHA. Interestingly, EPA did not exhibit any inhibitory effect on these parameters.Conclusion: Our results suggest that DHA and celecoxib exhibit anti-inflammatory effect through inhibition of NF-B, independent of PPAR. Co-administration of celecoxib and DHA would be promising approach for the treatment of inflammatory diseases.