Calcium and neuronal injury in Alzheimer's disease. Contributions of beta-amyloid precursor protein mismetabolism, free radicals, and metabolic compromise

Ann N Y Acad Sci. 1994 Dec 15;747:50-76.

Abstract

Alzheimer's disease (AD) is defined by degeneration of specific populations of neurons and the presence of insoluble aggregates of cytoskeletal proteins and amyloid beta-peptide (A beta) within affected brain regions. Alzheimer's disease does not appear to result from a single alteration, but in some cases of inherited AD a specific genetic defect can precipitate the disease. In this article, metabolic compromise, altered metabolism of the beta-amyloid precursor protein (beta APP), and an excitotoxic form of neuronal injury are considered central to the pathogenesis AD. The hypothesis is forwarded that destabilization of neuronal Ca2+ homeostasis underlies neuronal degeneration and that multiple age-associated and/or genetic alterations contribute to the loss of Ca2+ homeostasis. Recent studies showed that the secreted forms of beta APP (APPss) stabilize intracellular free calcium levels ([Ca2+]i) and protect neurons against excitotoxic insults. In contrast, A beta which arises from alternative processing of beta APP forms free radical peptides and aggregates that destabilize [Ca2+]i and make neurons vulnerable to metabolic insults. Increased expression (eg, Down's syndrome) or altered processing (eg, beta APP mutations) of beta APP may increase the A beta/APPs ratio. The death of neurons in AD most likely has an excitotoxic component because: the vulnerable neurons possess high levels of glutamate receptors; experimentally induced excitotoxicity shows several features similar to those of neurofibrillary tangles; and A beta can destabilize [Ca2+]i homeostasis and render neurons vulnerable to neurofibrillary degeneration. Selective vulnerability may result from cell type-specific differences in expression of proteins involved in regulating [Ca+]i. In addition, many intercellular signals are involved in determining whether a neuron is able to maintain [Ca2+]i within a range of concentrations conducive to cell survival and adaptive plasticity. In this regard, it was recently shown that several growth factors can stabilize [Ca]i and protect neurons against excitotoxic injury and A beta toxicity. Age-related changes in the brain (eg, ischemic conditions, reduced glucose uptake, and increased glucocorticoid levels) may compromise the mechanisms that normally regulate [Ca2+]i adaptively.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.
  • Review

MeSH terms

  • Aging
  • Alzheimer Disease / physiopathology*
  • Amyloid beta-Protein Precursor / metabolism*
  • Calcium / metabolism*
  • Excitatory Amino Acids / physiology*
  • Free Radicals
  • Homeostasis
  • Humans
  • Nerve Degeneration
  • Neuronal Plasticity
  • Neurons / metabolism*
  • Neurons / pathology
  • Neurotransmitter Agents / physiology
  • Protein Processing, Post-Translational

Substances

  • Amyloid beta-Protein Precursor
  • Excitatory Amino Acids
  • Free Radicals
  • Neurotransmitter Agents
  • Calcium