Serum amyloid A in Alzheimer's disease brain is predominantly localized tomyelin sheaths and axonal membrane

Immunohistochemical localization of the injury specific apolipoprotein, acu te phase serum amyloid A (A-apoSAA), was compared in brains of patients wit h neuropathologically confirmed Alzheimer's disease (AD) multiple sclerosis (MS), Parkinson's disease (PD), Pick's disease (Pick's), dementia with Lew y bodies (DLB), coronary artery disease (CAD), and schizophrenia. Affected regions of both AD and MS brains showed intense staining for A-apoSAA in co mparison to an unaffected region and non-AD/MS brains. The major site of A- apoSAA staining in both diseases was the myelin sheaths of axons in layers V and VI of affected cortex. A-apoSAA contains a cholesterol binding site n ear its amino terminus and is likely to have a high affinity for cholestero l-rich myelin. These findings, along with our recent evidence that A-apoSAA can inhibit lipid synthesis in vascular smooth muscle cells suggest that A -apoSAA plays a role in the neuronal loss and white matter damage occurring in AD and MS.