Abstract: Objective To investigate the signal transduction pathway of arachidonic acid(AA) and prostaglandin E₂(PGE₂) synthesis in macrophage invaded by Toxoplasma gondii. Methods Synthesis of AA and PGE₂, expression of COX-2 mRNA and protein following stimulation infection by Toxoplasma gondii were evaluated in RAW264.7 cells by ELISA, RT-PCR and Western blotting after treatment with calcium channel blocker verapamil, chelator of extracellular calcium EGTA and inhibitor of CaM trifluoperazine (TFP), selective PKC inhibitor H7. Results Production of AA and PGE₂ induced by tachyzoite was significantly inhibited by EGTA, TFP and BAPTA/AM, and the PGE₂ production was inhibited by H7, with a reduced expression of COX-2 mRNA and protein in a dose-dependent manner. Conclusion The parasite down-regulates macrophage functions by affecting PKC signaling pathways, and triggers a biochemical cascade whose signals ultimately conduct to the secretion of immunosuppressive molecules PGE₂.

Key words: Toxoplasma gondii, macrophage, signal pathway, prostaglandin E₂, arachidonic acid, cyclooxygenase-2(COX-2)