Effects of statins on microglia

Abstract

High serum cholesterol level has been shown as one of the risk factors for Alzheimer's disease (AD), and epidemiological studies indicate that treatment with cholesterol-lowering substances, statins, may provide protection against AD. An acute-phase reaction and inflammation, with increased levels of proinflammatory cytokines, are well known in the AD brain. Notably, there is evidence for antiinflammatory activities of statins, such as reduction in proinflammatory cytokines. Consequently, it is of interest to analyze the effects of statins on microglia, the main source of inflammatory factors in the brain, such as in AD. The aims of this study were to determine the effects of statins (atorvastatin and simvastatin) on microglial cells with regard to the secretion of the inflammatory cytokine interleukin-6 (IL-6) and cell viability after activation of the cells with bacterial lipopolysaccharides (LPS) or beta-amyloid1-40 (Abeta1-40) and in unstimulated cells. Cells of the human microglial cell line CHME-3 and primary cultures of rat neonatal cortical microglia were used. Incubation with LPS or Abeta1-40 induced secretion of IL-6, and Abeta1-40, but not LPS, reduced cell viability. Both atorvastatin and simvastatin reduced the basal secretion of IL-6 and the cell viability of the microglia, but only atorvastatin reduced LPS- and Abeta1-40-induced IL-6 secretion. Both statins potentiated the Abeta1-40-induced reduction in cell viability. The data indicate the importance of also considering the microglial responses to statins in evaluation of their effects in AD and other neurodegenerative disorders with an inflammatory component.