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The Role of Oxidative Stress in Alzheimer's Disease Robin Petroze University of Kentucky

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The Role of Oxidative Stress in Alzheimer's Disease Robin Petroze University of Kentucky Kaleidoscope Volume 2 Article 15 2003 The Role of Oxidative Stress in Alzheimer's Disease Robin Petroze University of Kentucky Follow this and additional works at: https://uknowledge.uky.edu/kaleidoscope Part of the Medical Biochemistry Commons Right click to open a feedback form in a new tab to let us know how this document benefits you. Recommended Citation Petroze, Robin (2003) "The Role of Oxidative Stress in Alzheimer's Disease," Kaleidoscope: Vol. 2, Article 15. Available at: https://uknowledge.uky.edu/kaleidoscope/vol2/iss1/15 This Beckman Scholars Program is brought to you for free and open access by the The Office of Undergraduate Research at UKnowledge. It has been accepted for inclusion in Kaleidoscope by an authorized editor of UKnowledge. For more information, please contact [email protected]. BECKMAN ScHOLARS PROGRAM Abstract Over four million individuals in the United States currently suffer from Alzheimer's disease (AD), a devastating disorder of progressive dementia. Within the next several decades, AD is expected to affect over 22 million people globally. AD can only be definitively diagnosed by postmortem exami­ nation. Thus, investigation into the specific patho­ genesis of neuronal degeneration and death in AD on a biochemical level is essential for both earlier diagnosis and potential treatment and prevention options. Overproduction of amyloid [3-peptide (A[3) in the brain leads to both free radical oxidative stress and toxicity to neurons in AD. My under­ graduate biochemical studies with regard to AD explore the various ways in which free radical oxi­ dative stress might contribute to the pathology of AD. In particular, this review highlights studies using Af3-precursor mutations in animal models, and analysis of histone-DNA interactions. Introduction Acknowledged as a disease of progressive demen­ tia as early as 1910 by German psychologist Alois Alzheimer, questions concerning the specifics of Alzheimer's disease (AD) still plague the scientific community. With the modern burgeoning of tech­ nological approaches in molecular biology and bio­ chemistry, recent research has opened the door to understanding the basic mechanisms of the disor­ der (Markesbery, 1997). Over four million indi­ viduals in the United States currently suffer from AD, the fourth leading cause of death in the United States. Within the next several decades, AD is ex­ pected to affect over 22 million people globally (Butterfield et al., 2001}. Characterized by the progressive loss of memory and cognition, major pathological 60 KALEIDOSCOPE FALL 2 0 0 3 l--BECK-;_,~N- -- SCHOLAR::__ __ ROBIN PETROZE hallmarks of the disease include neurofibrillary tangles icity (Butterfield et al., 2001 ; 2002; Butterfi eld and (NFTs) , senile (neuritic) plaques (SPs), and synapse Lauderback, 2002) . loss (Katzman and Saitoh, 1991) . Amyloid 13-peptide The amyloid 13-peptide is derived from the normal (AI3), in the form of insoluble fibril deposits, is the processing of the amyloid precursor protein (APP). As primary component of senile plaques. Currently, AD Al3 is a normal soluble component found in plasma can only be definitively diagnosed by postmortem and cerebrospinal fluid, it is suspected that conver­ examination (Varadarajan et al., 2000) . Thus, sion of soluble Al3 into insoluble fibrils may signify a investigation into the specific pathogenesis of neuronal critical step in disease onset, a sign of overproduction degeneration and death in AD on a biochemical level of Al3 (Varadarajan et al. , 2000). Presenilin-1 (PS1) is essential for earlier diagnosis and potential treatment appears to cause cleavage of APP, leading to increased and prevention options. Known risk factors for AD Al3 production (Selkoe, 2001 ). Fibrillar Al3 binding to include: age, family history of dementia or AD, low receptors increases advanced glycation end-products educational level, low linguistic ability during early to induce oxidative stress and activate microglia (Yan stages, and the presence of apolipoprotien E (APO-E) et al., 1996) . alleles. Of the APO-E2 , APO-E3 , and APO-E4 alleles Neurodegenerative sites in the AD brain corre­ present in humans, the APO-E4 allele signifies a spond to the presence of oxidative stress and increased greater incidence of AD (Markesbery, 1997) . Al3 deposits (Hensley et al., 1995) . Given the broad My undergraduate biochemical research with re­ scope of cellular modifications observed in AD and gard to AD explores the various ways in which free the increased Al3 deposits in AD pathology, a free radi­ radical oxidative stress might contribute to the pa­ cal oxidation cascade, in which structural and func­ thology of AD . Oxidative stress occurs when there tional alterations would be seen with any protein or are more reactive species (radicals) than antioxidant lipid structure attacked by a free radical, is feasible as defenses and repair capacities in a system, such as a model for neuronal death in AD (Varadarajan et al., the brain. In particular, this review will highlight stud­ 2000). ies using Al3-precursor mutations in animal models and analysis of histone-DNA interactions in AD . Genetic Mutations: Studies of Amyloid Precursor Protein and Presenilin Genes Role of A(3 in Oxidative Stress Studies in familial AD indicate the central role of Al3 in Our laboratory has proposed that overproduction of AD pathogenesis and the presence of Al3-precursor Al3leads to both free radical oxidative stress and tox­ mutations; specifically, mutations in the amyloid pre­ icity to neurons in AD (Butterfield et al ., 2001 ; 2002; cursor protein (APP) and presenilin genes lead to over­ Butterfield and Lauderback, 2002; Varadarajan et al., production of Al3 and to AD . As in Down's trisomy, 2000). By inserting itself into neuronal membranes, APP is expressed on Chromosome 21; consequently, soluble, aggregated Al3 may induce the formation of Down's syndrome patients exhibit increased Al3 de­ reactive oxygen species and reactive nitrogen species posits and eventually develop AD (Varadarajan et al., that lead to lipid peroxidation, protein oxidation, and 2000) . PS1 cleavage of APP could stimulate faulty protein modification by 4-hydroxy-2-trans-nonenal processing of Al3 and increased Al3 production (Selkoe, (HNE) and acrolein, the reactive products of lipid 2001). While the number of sporadic cases of AD over­ peroxidation. Furthermore, Al3-associated free-radi­ shadows the occurrence of familial AD cases, a com­ cal oxidative stress can affect free fatty-acid release mon pathogenesis leading to senile plaque and (leading to tau polymerization), disruption of Ca2 + neurofibrillary tangle formation is postulated for all homeostasis, peroxynitrite formation, inflammatory forms of AD , corresponding to the similar neuropatho­ response, impairment of mitochondria, and apoptosis. logic lesions seen in both familial and sporadic cases. Al3-associated oxidation may also play a role in the Therefore, research in familial AD using transgenic modification and inhibition of several neuronal and mouse models is applicable to all forms of the disease glial transmembrane transport systems. This includes (Kurt et al., 2001). ion-motive ATPases, glutamate transporters, glucose Mice overexpressing mutant human APP genes in transporters, GTP-coupled transmembrane signaling a single transgenic model show evidence of develop­ proteins, and polyamine transporters; functional loss ing fibrillar cerebral Ab deposits similar to the Al3 de­ in these systems proves destructive to the neurons, posits seen in AD . Cerebral Al3 deposits increase as causing cell potential loss, excitotoxic glutamate ac­ well in single transgenic mouse models overexpressing cumulation, decreased glucose availability, decreased mutant or wild-type human PS1 proteins. Yet, the single intracellular communication, and increased neurotox- transgenic models do not show increased Al3 deposits BECKMAN SCHOLARS PROGRAM until later in adulthood. In APP /PS1 double mutant Role of Antioxidants models, the mice develop increased fibrillar A[3 de­ This research will lead to studies to determine if the posits in the hippocampus and cerebral cortex earlier administration of various antioxidants, such as N­ than single transgenic mice (Kurt et al., 2001). acetyl cysteine (NAC) has an effect in slowing the Methods Related to Markers of manifestation of degenerative symptoms in oxidative Oxidative Stress stress conditions. NAC upregulates glutathione syn­ thesis, providing the limiting amino acid cysteine. Glu­ Oxidative stress measures for protein oxidation and tathione is present in millimolar levels, is the most lipid peroxidation can be performed on synaptosomes abundant endogenous antioxidant in the brain, and prepared from brain samples obtained from the mu­ may act as the first line of defense against oxidative tant mice. Protein oxidation is measured through the stress. Our laboratory has previously shown that ultra-violet (UV)-Vis, fluorescence, or immunochemi­ intraparitoneal (i.p.) injection of NAC in mice pro­ cal detection of protein carbonyl formation. Free radi­ tects against in-vitro hydroxyl radical-, acrolein-, and cal attack on susceptible amino acid side chains can peroxynitrite-induced damage (Pocernich et al., 2000; induce protein oxidation to form protein carbonyls, 2001; Koppal et al., 1999). Furthermore, our as can the interaction of proteins with the products of laboratory's studies indicate that i.p. injection of NAC glycation and glycoxidation, or the products of lipid protects
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