Figure 1

Microglial Dap12 and CD11b contribute to lipopolysaccharide (LPS)- and 1-methyl-4-phenylpyridinium (MPP ⁺ )-induced dopaminergic neurotoxicity in vitro . (A) Representative image showing tyrosine hydroxylase (TH)-expressing dopaminergic neurons (red) co-cultured with CD11b-positive microglial cells (green). Scale bar: 50 μm. (B) Quantification of TH⁺ neurons in LPS-treated neuronal cultures with or without microglial cells. In LPS-treated neuronal cultures, addition of wild-type (WT) microglial cells (blue bar) results in significant neurotoxicity as compared to untreated cultures with or without WT microglia. LPS-induced neurotoxicity is attenuated in the presence of DAP12-deficient (Dap12 KI) microglia (red bar) compared to WT microglia. Data are expressed as mean ± standard error of the mean (SEM). ^* P <0.01 compared to untreated mixed cultures; ^# P <0.05 compared to LPS-treated mixed cultures with WT microglia. (C) Quantification of TH⁺ neurons in MPP⁺-treated neuronal cultures in the presence or absence of microglial cells from WT (blue bar), Dap12 KI (red bar) or Cd11b KO (green bar) mice. In pure neuronal cultures, MPP⁺ induces a 20% TH⁺ cell loss. ^* P <0.001 compared to untreated neuronal cultures. Addition of WT microglial cells in MPP⁺-treated cultures further increases dopaminergic cell death (45% neuronal loss). In neuron/microglia co-cultures, MPP⁺-induced neurotoxicity is attenuated in the presence of either DAP12- or CD11b-deficient microglia compared to WT microglia. ^# P <0.01 compared to untreated mixed neuron/microglia and pure neuronal cultures; ^§ P <0.05 compared to MPP⁺-treated mixed cultures with WT microglia. (D) Quantification of microglia-derived reactive oxygen species (ROS) level in mixed neuron/microglia cultures under basal condition or 24 h after MPP⁺ exposure. Treatment of mixed neuron/microglia cultures with MPP⁺ results in a rise in microglial-derived ROS whose levels were of similar magnitude between microglial genotypes. *P <0.01 compared to their respective untreated mixed cultures (Dunn test).