Macrophage colony-stimulating factor augments β-amyloid-induced interleukin-1, interleukin-6, and nitric oxide production by microglial cells

In Alzheimer's disease (AD), a chronic cerebral inflammatory state is thought to lead to neuronal injury. Microglia, intrinsic cerebral immune effector cells, are likely to be key in the pathophysiology of this inflammatory state. We showed that macrophage colony-stimulating factor, a microglial activator found at increased levels in the central nervous system in AD, dramatically augments beta-amyloid peptide (beta AP)-induced microglial production of interleukin-l, interleukin-6, and nitric oxide. In contrast, granulocyte macrophage colony-stimulating factor, another hematopoietic cytokine found in the AD brain, did not augment beta AP-induced microglial secretory activity. These results indicate that increased macrophage colony-stimulating factor levels in AD could magnify beta AP-induced microglial inflammatory cytokine and nitric oxide production, which in turn could intensify the cerebral inflammatory state by activating astrocytes and additional microglia, as well as directly injuring neurons.