No significant effects of plasminogen activator inhibitor type 1 (PAI-1) on microglial nitric oxide (NO) production or neurotoxicity after lipopolysaccharide (LPS) or interferon (IFN)-γ stimulation. (A) BV-2 microglial cells and (B) primary microglia cultures were treated with the indicated concentration of mouse PAI-1 protein, LPS (100 ng/ml), and IFN-γ (50 U/ml) for 24 hours. NO production was measured by the Griess reaction. Results are given as mean ± SD (n = 3). *P < 0.01, NS = not significant. (C) Primary microglia cultures (4.0 × 104 cells/well) were treated for 12 hours with PAI-1 (100 ng/ml), BSA (100 ng/ml), or LPS (100 ng/ml) as indicated. Afterwards, primary microglial cells were cocultured with (upper panel) 5-chloromethyl-fluoresceindiacetate (CMFDA)-labeled primary neuron cultures for 24 hours (co-culture scheme). (Lower panel) CMFDA-positive neurons in the five randomly chosen microscopic fields per well were counted under an inverted microscope. Results are given as mean ± SD (n = 3). *P < 0.05, NS = not significant.