Eicosapentaenoic acid inhibits prostaglandin D2 generation by inhibiting cyclo-oxygenase-2 in cultured human mast cells


Obata Department of Molecular Cell Biology, Institute of DNA Medicine, Jikei University School of Medicine, 3–25–8, Minato, 105 Tokyo, Japan.



Eicosapentaenoic acid (EPA) is catalysed by cyclo-oxygenase (COX), as is arachidonic acid, and is a competitive inhibitor of arachidonate metabolism.


We examined the effect of EPA on prostaglandin (PG) D2 generation in the cultured human mast cells with IgE-anti-IgE challenge incubation.


Cultured human mast cells were incubated with EPA (1 μmol/L) for 20 h, then challenged with anti-IgE incubation after treatment with IgE. At the same time, COX inhibitors were tested to identify COX-1 and COX-2 activity. PGD2 synthetic activity was also assayed in a cell-free homogenate of cultured mast cells with COX inhibitors and EPA. Histamine in the culture medium and in cells was assayed with the HPLC-fluorescent method. PGD2 and PGD3 were assayed with gas chromatography-mass spectrometry and the stable isotope dilution method.


Although EPA incubation did not affect histamine release by cultured human mast cells in response to IgE-anti-IgE challenge incubation, it did decrease PGD2 generation by inhibiting the COX-2 pathway. In contrast, in the cell-free homogenate of cultured human mast cells, EPA inhibited both COX-1 and COX-2 activities.


Pre-incubation with EPA primarily affects the COX-2 pathway in cultured human mast cells and reduces PGD2 generation in response to IgE-anti-IgE challenge incubation. These findings suggest that COX-1 and COX-2 have different substrate flow systems in mast cells. They also suggest that endogenous EPA diet supplementation would reduce PGD2 production and could serve as an anti-inflammatory substrate in human mast cells.