Neuro-inflammation induced by lipopolysaccharide causes cognitive impairment through enhancement of beta-amyloid generation.

BACKGROUND

Alzheimer's disease (AD) is characterized by extensive loss of neurons in the brain of AD patients. Intracellular accumulation of beta-amyloid peptide (Abeta) has also shown to occur in AD. Neuro-inflammation has been known to play a role in the pathogenesis of AD.

METHODS

In this study, we investigated neuro-inflammation and amyloidogenesis and memory impairment following the systemic inflammation generated by lipopolysaccharide (LPS) using immunohistochemistry, ELISA, behavioral tests and Western blotting.

RESULTS

Intraperitoneal injection of LPS, (250 microg/kg) induced memory impairment determined by passive avoidance and water maze tests in mice. Repeated injection of LPS (250 microg/kg, 3 or 7 times) resulted in an accumulation of Abeta1-42 in the hippocampus and cerebralcortex of mice brains through increased beta- and gamma-secretase activities accompanied with the increased expression of amyloid precursor protein (APP), 99-residue carboxy-terminal fragment of APP (C99) and generation of Abeta1-42 as well as activation of astrocytes in vivo. 3 weeks of pretreatment of sulindac sulfide (3.75 and 7.5 mg/kg, orally), an anti-inflammatory agent, suppressed the LPS-induced amyloidogenesis, memory dysfunction as well as neuronal cell death in vivo. Sulindac sulfide (12.5-50 microM) also suppressed LPS (1 microg/ml)-induced amyloidogenesis in cultured neurons and astrocytes in vitro.

CONCLUSION

This study suggests that neuro-inflammatory reaction could contribute to AD pathology, and anti-inflammatory agent could be useful for the prevention of AD.