Neuroprotective Action And Mechanisms Of HN Against Neuronal Apoptosis Induced By β-amyloid Peptide 31-35

Alzheimer's disease is the most prevalent neurodegenerative disease, characterized by the presence of extensive extracellular amyloid plaques , intracellular neurofibrillary tangles, and synaptic loss, neuronal death in cerebral cortex and hippocampus, along with progressive impairment of cognition and emotional activities. Despite some clinical trials with encouraging results, no curative therapy for this disease has so far been developed. Increasing evidences shown that P-amyloid(Ap) deposition is the leading cause for AD. β-amyloid are major protein component of the amyloid plaques and is involved in the pathogenesis of AD. Subsequent studies have demonstrated that apoptosis is a major form of neuronal death in AD which could be induced by Aβ_1-42, Aβ_25-35 as well as Aβ_31-35 .Humanin is a recently identified peptide that suppresses cell death initiated by Alzheimer's disease-related insults in neuronal cells including Aβ_1-42 .induced neuronal death (Hashimoto ,2001). AβP31-35, an smaller amyloid peptide fragment reported possesses the similar toxicity as full length of Aβ and fragment of Aβ_25-35 do. Thus the part I of this study is to examine whether HN protects neurons from Aβ_31-35-induced apoptosis. The part II is to explore mechanisms of HN against Aβ_31-35-induced apoptosis or to determine if extrinsic and/or intrinsic pathway are involved in neuroprotection of HN. The part III is to observe the effects of HN on elevation of intracellular calcium concentration induced by Aβ_31-35.PART I HN protects cultured neurons against apoptosis induced by Aβ_31-35In the present study we investigated the effects of I IN on neuronal apoptosis induced by Aβ_31-35 in cultured cortical neurons in rats by morphological analysis, flow-cytometric assays, TUNEL examinations and HO 33342 staining .The results showed that: 1. labeling culture cells with MAP₂ (microtubuie-associatedprotein-2, marker protein of neurons), showed that 90% of culture cells are MAP₂ positive cells namely the neuronal cells 2. Apoptotic neurons induced by Aβ_31-35 presented a typical apoptotic morphology by morphological analysis: the cytoplasm concentrated , the chromatin aggregated peripherally into dense masses and laid against the nuclear membrane , the shape of nucleus became irregular, and finally form nuclear fragments known as apoptotic bodies. 3. We examined whether HN inhibited apoptotic events induced by AβP_31-35(25μM) by flow cytometric assay , TUNEL and HO 33342 staining .The results obtained by flow cytometric assay showed that 1)...