Grifolic acid induces mitochondrial membrane potential loss and cell death of RAW264.7 macrophages.

Grifolic acid is a phenolic compound that was first extracted from the mushroom Albatrellus confluens; it acts as an agonist of the free fatty acid receptor (FFAR4). FFAR4 is expressed in macrophages and mediates the anti‑inflammatory effects of n‑3 unsaturated free fatty acids. In the present study, the effects of grifolic acid on macrophages were observed in mouse RAW264.7 cells. It was demonstrated that grifolic acid (2.5‑20 µmol/l) treatment reduced RAW264.7 cell viability in a dose‑ and time‑dependent manner. The number of apoptotic cells significantly increased following grifolic acid treatment compared with the untreated control cells. Grifolic acid treatment resulted in a significant decrease in cellular adenosine 5'‑triphosphate (ATP) content in RAW264.7 cells. Mitochondrial membrane potential (MMP), as measured by JC‑1 staining, was significantly diminished by grifolic acid treatment in a dose‑ and time‑dependent manner. Treatment with cyclosporine A, a protector of MMP, attenuated grifolic acid‑induced reduction of MMP and viability in RAW264.7 cells. FFAR4 knockdown did not significantly influence grifolic acid‑induced reduction of cell viability, ATP levels or MMP. In conclusion, grifolic acid may induce macrophage cell death by reducing MMP and by inhibiting ATP production probably in an FFAR4‑independent manner.