LPS-activated macrophage (LPS/MΦ) supernatant induces neurotoxicity. (A) Seven-day-cultured macrophages were treated with or without LPS (100 ng/ml) for 24 h and supernatants collected from the cell cultures were then used to treat rat cortical neurons for 24 h. The percentage of supernatant added to the neuron cultures is indicated. In addition, neuron cultures were treated with either neurobasal media only (control) or media plus NMDA (10 μM) or plus LPS (100 ng/ml). Supernatants collected from untreated and donor-matched macrophage cultures (MΦ SN) were also used as negative controls. (B) Neurotoxicity of activated macrophages treated with different concentrations of LPS. Seven-day-cultured macrophages were treated with different concentrations (1-100 ng/ml) of LPS, and supernatant (1:10) was used to treat rat cortical neuron cultures. The neuron marker MAP-2 was measured by a cell-based ELISA method. Data are expressed as mean ± SD for three independent experiments. (*P < 0.05, **P < 0.01, LPS/MΦ SN vs MΦ SN).