Naturally Occurring Antibodies Against Bim Are Decreased in Alzheimer’s Disease and Attenuate Ad-type Pathologies in a Mouse Model
Abstract Background Alzheimer’s disease (AD) is the most popular neurodegenerative disease affecting cognitive functions of the elderly population. Neuronal apoptosis is an important pathological process during the development of AD. The Bcl-2-interacting mediator of cell death (Bim) mediates Amyloid-beta (Aβ)-induced neuronal apoptosis. Naturally occurring antibodies against Bim (NAbs-Bim) exist in human blood, with their levels and functions unknown in AD. Methods This study investigated the clinical relevance of plasma NAbs-Bim to AD in 55 AD patients, 28 patients with non-AD dementia, and 70 cognitively normal subjects. Furthermore, the pathophysiological functions of NAbs-Bim were explored in APP/PS1 mice and SY5Y cell lines overexpressing human amyloid precursor protein (APP). Results We found that plasma levels of NAbs-Bim were lower in AD patients in comparison with patients with non-AD dementia and cognitively normal controls. Plasma levels of NAbs-Bim were negatively associated with brain amyloid burdens and positively associated with cognitive functions. NAbs-Bim purified from intravenous immunoglobulin rescued behavioral deficits of APP/PS1 mice. NAbs-Bim ameliorated Aβ deposition, Tau hyperphosphorylation, microgliosis and neuronal apoptosis in APP/PS1 mice. In vitro investigations demonstrated that NAbs-Bim exerted neuroprotective effects against AD through neutralizing Bim-directed neuronal apoptosis and amyloidogenic processing of amyloid precursor protein. Conclusions The decrease of NAbs-Bim might contribute to the pathogenesis of AD and immunotherapies targeting Bim may hold promise for the treatment of AD.