Current evidence has demonstrated the immunomodulatory efficacy of omega-3 polyunsaturated fatty acids (PUFAs) in glial cells, suggesting their therapeutic potential for diseases in the central nervous system (CNS). However, conjugated omega-5 PUFAs have also attracted considerable attention because of their suggested anti-inflammatory effects. In the present study, the effect of pomegranate (Punica granatum L.) seed oil (PSEO) (a rich source of omega-5 PUFAs) on the activation of cultured BV-2 microglia was investigated within a 24-hour incubation period. PSEO (25 mu g/ml) showed only a slightly smaller inhibitory effect on LPS-stimulated NO production (243 +/- 12.5 % of control, p<0.001 vs. 437 +/- 9.2 % in stimulated cells) and TNF-alpha release (87.1 +/- 5.62 pg/ml vs. 229 +/- 24.4 pg/ml in stimulated cells), as well as iNOS expression (7.36-fold of control, p<0.01, vs. 17.5-fold increase in stimulated cells) compared to a standardized omega-3 PUFAs mixture (25 mu g/ml) and the flavonoid quercetin (25 mu mol/l). Unlike quercetin and stobadine, only the PUFA preparations effectively prevented apoptosis of microglia (as confirmed by the suppression of caspase 3 activation) exposed to the toxic concentration of LPS. The PUFA preparations did not provide a notable suppression of the intracellular oxidant generation and did not influence the intracellular distribution of cholesterol (as confirmed by filipin staining). However, they appeared to affect the morphology of activated cells. In conclusion, our data point to the first evidence of immunomodulation and cytoprotection of BV-2 microglia by the pomegranate seed oil, indicating that it may be (comparably to omega-3 PUFAs) efficient against microglia-mediated neuroinflammation while preventing the premature depletion of these immune effector cells in the brain.