PT - JOURNAL ARTICLE AU - Jun Tan AU - Terrence Town AU - Takashi Mori AU - Yajuan Wu AU - Michael Saxe AU - Fiona Crawford AU - Mike Mullan TI - CD45 Opposes β-Amyloid Peptide-Induced Microglial Activation via Inhibition of p44/42 Mitogen-Activated Protein Kinase AID - 10.1523/JNEUROSCI.20-20-07587.2000 DP - 2000 Oct 15 TA - The Journal of Neuroscience PG - 7587--7594 VI - 20 IP - 20 4099 - http://www.jneurosci.org/content/20/20/7587.short 4100 - http://www.jneurosci.org/content/20/20/7587.full SO - J. Neurosci.2000 Oct 15; 20 AB - Reactive microglia have been suggested to play a role in the Alzheimer's disease (AD) process, and previous studies have shown that expression of CD45, a membrane-bound protein-tyrosine phosphatase (PTP), is elevated in microglia in AD brain compared with controls. To investigate the possible role of CD45 in microglial responsiveness to β-amyloid (Aβ) peptides, we first co-treated primary cultured microglia with a tyrosine phosphatase inhibitor [potassium bisperoxo (1,10-phenanthroline) oxovanadate (phen), 5 μm] and freshly solubilized Aβ peptides (1000 nm). Data show synergistic induction of microglial activation as evidenced by tumor necrosis factor α (TNF-α) production and nitric oxide (NO) release, both of which we show to be dependent on activation of p44/42 mitogen-activated protein kinase (MAPK). Furthermore, co-treatment with phen and Aβ peptides results in microglia-induced neuronal cell injury. Stimulation of microglial CD45 by anti-CD45 antibody markedly inhibits these effects via inhibition of p44/42 MAPK, suggesting that CD45 is a negative regulator of microglial activation. Accordingly, primary cultured microglia from CD45-deficient mice demonstrate hyper-responsiveness to Aβ, as evidenced by TNF-α release, NO production, and neuronal injury after stimulation with Aβ peptides. As a validation of these findings in vivo, brains from a transgenic mouse model of AD [transgenic Swedish APP-overexpressing (Tg APPsw) mice] deficient for CD45 demonstrate markedly increased production of TNF-α compared with Tg APPsw mice. Taken together, these results suggest that therapeutic agents that stimulate the CD45 PTP signaling pathway may be effective in suppressing microglial activation associated with AD.