Article

Beta-amyloid, neuronal death and Alzheimer's disease.

Department of Neurology, Medical College of Pennsylvania-Hahnemann University, Philadelphia 19129, USA.
Current Molecular Medicine (Impact Factor: 3.62). 01/2002; 1(6):733-7.
Source: PubMed

ABSTRACT

Alzheimer's disease (AD) is a common neurodegenerative disease that affects cognitive function in the elderly. Large extracellular beta-amyloid (Abeta) plaques and tau-containing intraneuronal neurofibrillary tangles characterize AD from a histopathologic perspective. However, the severity of dementia in AD is more closely related to the degree of the associated neuronal and synaptic loss. It is not known how neurons die and synapses are lost in AD; the current review summarizes what is known about this issue. Most evidence indicates that amyloid precursor protein (APP) processing is central to the AD process. The Abeta in plaques is a metabolite of the APP that forms when an alternative (beta-secretase and then gamma-secretase) enzymatic pathway is utilized for processing. Mutations of the APP gene lead to AD by influencing APP metabolism. One leading theory is that the Abeta in plaques leads to AD because Abeta is directly toxic to the adjacent neurons. Other theories advance the notion that neuronal death is triggered by intracellular events that occur during APP processing or by extraneuronal preplaque Abeta oligomers. Some investigators speculate that in many cases there is a more general disorder of protein processing in neurons that leads to cell death. In the later models, Abeta plaques are a byproduct of the disease process, rather than the direct cause of neuronal death. A direct correlation between Abeta plaque burden and neuronal (or synaptic) loss should occur in AD if Abeta plaques cause AD through a direct toxic effect. However, histopathologic studies indicate that the correlation between Abeta plaque burden and neuronal (or synaptic) loss is poor. We conclude that APP processing and Abeta formation is important to the AD process, but that neuronal alterations that underlie symptoms of AD are not due exclusively to a direct toxic effect of the Abeta deposits that occur in plaques. A more general problem with protein processing, damage due to the neuron from accumulation of intraneuronal Abeta or extracellular, preplaque Abeta may also be important as underlying factors in the dementia of AD.

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    • "The impairment of memory in AD is associated with hypofunction of cholinergic system in forebrain resulted from the loss of basal forebrain cholinergic neurons which play an important role in memory formation and cognition. (Schliebs and Arendt 2006, Kar et al. 2004) Extracellular deposition of beta-amyloid peptid (Aβ) is the main finding in the pathophysiology of AD and is considered a critical event in initiating the synaptic loss and finally neuronal cell death (Carter and Lippa 2001, Hardy and Selkoe 2002).Several mechanisms were proposed for Aβ-induced neurotoxicity (Cavallucci et al. 2012, Luquin et al. 1997). but much evidence suggested that oxidative damage plays a pivotal role in Aβ -induced toxicity (Chen and Zhong 2014). "
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    ABSTRACT: Extracellular deposition of Beta-amyloid peptide (Aβ) is the main finding in the pathophysiology of Alzheimer's disease (AD), which damages cholinergic neurons through oxidative stress and reduces the cholinergic neurotransmission. Satureja bachtiarica is a medicinal plant from the Lamiaceae family which was widely used in Iranian traditional medicine. The aim of the present study was to investigate possible protective effects of S. bachtiarica methanolic extract on Aβ induced spatial memory impairment in Morris Water Maze (MWM), oxidative stress and cholinergic neuron degeneration. Pre- aggregated Aβ was injected into the hippocampus of each rat bilaterally (10 μg/rat) and MWM task was performed 14 days later to evaluate learning and memory function. Methanolic extract of S.bachtiarica (10, 50 and 100 mg/Kg) was injected intraperitoneally for 19 consecutive days, after Aβ injection. After the probe test the brain tissue were collected and lipid peroxidation, Acetylcholinesterase (AChE) activity and Cholin Acetyl Transferees (ChAT) immunorectivity were measured in the hippocampus. Intrahipocampal injection of Aβ impaired learning and memory in MWM in training days and probe trail. Methanolic extract of S. bachtiarica (50 and 100 mg/Kg) could attenuate Aβ-induced memory deficit. ChAT immunostaining revealed that cholinergic neurons were loss in Aβ- injected group and S. bachtiarica (100 mg/Kg) could ameliorate Aβ- induced ChAT reduction in the hippocampus. Also S. bachtiarica could ameliorate Aβ-induced lipid peroxidation and AChE activity increase in the hippocampus. In conclusion our study represent that S.bachtiarica methanolic extract can improve Aβ-induced memory impairment and cholinergic loss then we recommended this extract as a candidate for further investigation in treatment of AD.
    No preview · Article · Dec 2015 · Metabolic Brain Disease
    • "Alzheimer's disease is characterized by progressive neuronal cell death, mainly in the neocortex and limbic system structures. Accumulation and aggregation of amyloid β peptides promote cell cytotoxicity and alter the activation state of several kinases; this provokes sub sequent activation of the cell death signaling pathways [27] [28]. Some viruses can hijack the cell's defense mechanisms , to the detriment of the cell. "
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    ABSTRACT: Cell death contributes to the maintenance of homeostasis, but mounting evidence has confirmed the involvement of programmed cell death in some diseases. The concept of programmed cell death, which was coined several decades ago to refer to apoptosis, now also encompasses necroptosis, a newly characterized cell death program. Research on programmed cell death has become essential for the development of some new therapies. To study cell death signaling and its molecular mechanisms, new biochemical and fluorogenic approaches have been devised. Here, we first provide an overview of programmed cell death modes and the importance of dynamic cell death studies. Next, we focus on both apoptotic and necroptotic signaling and their mechanisms by providing a systematic review of all the methods and approaches that have been used. We emphasize the contribution of advanced approaches based on fluorescent probes, reporters, and Förster resonance energy transfer (FRET)-based biosensors for studying programmed cell death. Because apoptosis and necroptosis signaling pathways share some effectors molecules, we discuss how these new tools could be used to discriminate between apoptosis and necroptosis. We also describe how we developed specific FRET-based biosensors for detecting necroptosis. Finally, we touch on how dynamic measurement of biomolecules in living models will play a role in personalized prognosis and therapy.
    No preview · Article · Feb 2014 · Biotechnology Journal
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    • "Studies have shown that Ab 1–40 is more abundant than Ab 1–42 in AD brain, whereas Ab 1–42 appears more fibrillogenic and toxic than Ab 1–40 [3]. Ab directly induces oxidative stress and causes both apoptotic and necrotic types of neuronal cell death in vitro and in vivo [4] [5]. Since a decade ago, accumulation of Ab has been associated with glaucomatous degeneration of retinal ganglion cell (RGC) [6]. "
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    ABSTRACT: Beta-amyloid (Aβ) derived from amyloid precursor protein (APP) has been associated with retinal degeneration in Alzheimer's disease (AD) and glaucoma. This study examined whether hypoxia exposure induces Aβ accumulation in RGC-5 cells. While levels of APP mRNA and protein significantly increased in the cells, elevated abundance of Aβ was also observed in cells and culture medium between 12 or 24 and 48h after 5% O(2) hypoxia treatment. Additionally, there is a close relationship between induction of APP and Aβ and intracellular accumulation of ROS along with loss of mitochondrial membrane potential followed by the death of RGC-5 cells in culture under hypoxia. These results suggest a possible involvement of APP and Aβ in the death of RGCs challenged by hypoxia.
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