Inhibition of Microglial Activation Protects Hippocampal Neurogenesis and Improves Cognitive Deficits in a Transgenic Mouse Model for Alzheimer's Disease

Background: Activated microglia with macrophage-like functions invade and surround beta-amyloid (A beta) plaques in Alzheimer's disease (AD), possibly contributing to the turnover of A beta, but they can also secrete proinflammatory factors that may be involved in the pathogenesis of AD. Microglia are known to modulate adult hippocampal neurogenesis. Objectives/Methods: To determine the role of microglia on neurogenesis in brains with A beta pathology, we inhibited microglial activation with the tetracycline derivative minocycline in doubly transgenic mice expressing mutant human amyloid precursor protein (APP) and mutant human presenilin-1 (PS1). Results: Minocycline increased the survival of new dentate granule cells in APP/PS1 mice indicated by more BrdU+/NeuN+ cells as compared to vehicle-treated transgenic littermates, accompanied by improved behavioral performance in a hippocampus-dependent learning task. Both brain levels of A beta and A beta-related morphological deficits in the new neurons labeled with GFP-expressing retrovirus were unaffected in minocycline-treated mice. Conclusions: These results suggest a role for microglia in A beta-related functional deficits and in suppressing the survival of new neurons, and show that modulation of microglial function with minocycline can protect hippocampal neurogenesis in the presence of A beta pathology. Copyright (C) 2012 S. Karger AG, Basel