Original Contribution Oxidative modification to LDL receptor-related protein 1 in hippocampus from subjects with Alzheimer disease: Implications for Aβ accumulation in AD brain

Alzheimer disease (AD) is a neurodegenerative disorder characterized histopathologically by the presence of senile plaques (SPs), neurofibrillary tangles, and synapse loss. The main component of SPs is amyloid-β peptide (Aβ), which has been associated with increased oxidative stress, leading to oxidative modification of proteins and consequently to neurotoxicity and neurodegeneration. Low-density lipoprotein receptor-related protein 1 (LRP1) is the primary moiety responsible for the efflux of Aβ from the brain to the blood across the blood-brain barrier. Impaired brain-to-blood transport of Aβ by LRP1 has been hypothesized to contribute to increased levels of Aβ in AD brain. The cause of LRP1 dysfunction is unknown, but we have hypothesized that Aβ oxidizes LRP1, thus damaging its own transporter. Consistent with this notion, we report in this study a significant increase in the levels of the lipid peroxidation product 4-hydroxy-2-nonenal bound to transmembrane LRP1 in AD hippocampus. In contrast, the levels of LRP1-resident 3-nitrotyrosine did not show a significant increase in AD hippocampus compared to age-matched controls. Based on this study, we propose that Aβ impairs its own efflux from the brain by oxidation of its transporter LRP1, leading to increased Aβ deposition in brain, thereby contributing to subsequent cognitive impairment in AD. © 2010 Elsevier Inc. All rights reserved. Alzheimer disease (AD) is characterized pathologically by the presence of senile plaques (SPs), neurofibrillary tangles (NFTs), and decreased synaptic density The neurovascular hypothesis of AD states that impairment of the efflux of Aβ from the brain to the blood at the blood-brain barrier (BBB) is an important mechanism underlying Aβ accumulation in the brain and contributes to subsequent cognitive impairment in AD patient

Original Contribution 2-Mercaptoethane sulfonate prevents doxorubicin-induced plasma protein oxidation and TNF-α release: Implications for the reactive oxygen species-mediated mechanisms of chemobrain

, an anthracycline used to treat a variety of cancers, is known to generate intracellular reactive oxygen species. Moreover, many patients who have undergone chemotherapy complain of cognitive dysfunction often lasting years after cessation of the chemotherapy. Previously, we reported that intraperitoneal administration of DOX led to elevated TNF-α and oxidative stress in the plasma and brain of mice. However, the mechanisms involved in nontargeted tissue damage remain unknown. In this study, we measured plasma oxidative stress and cytokine levels in patients treated with DOX. We observed increased plasma protein carbonylation and elevation of TNF-α 6 h after DOX administration in the context of multiagent chemotherapy regimens. Importantly, patients not treated coincidentally with 2-mercaptoethane sulfonate (MESNA) showed statistically significantly increased plasma protein-bound 4-hydroxynonenal, whereas those who had been coincidentally treated with MESNA as part of their multiagent chemotherapy regimen did not, suggesting that concomitant administration of the antioxidant MESNA with DOX prevents intravascular oxidative stress. We demonstrate in a murine model that MESNA suppressed DOX-induced increased plasma oxidative stress indexed by protein carbonyls and protein-bound HNE, and also suppressed DOX-induced increased peripheral TNF-α levels. A direct interaction between DOX and MESNA was demonstrated by MESNA suppression of DOX-induced DCF fluorescence. Using redox proteomics, we identified apolipoprotein A1 (APOA1) in both patients and mice after DOX administration as having increased specific carbonyl levels. Macrophage stimulation studies showed that oxidized APOA1 increased TNF-α levels and augmented TNF-α release by lipopolysaccharide, effects that were prevented by MESNA. This study is the first to demonstrate that DOX oxidizes plasma APOA1, that oxidized APOA1 enhances macrophage TNF-α release and thus could contribute to potential subsequent TNF-α-mediated toxicity, and that MESNA interacts with DOX to block this mechanism and suggests that MESNA could reduce systemic side effects of DOX. © 2011 Elsevier Inc. All rights reserved. Doxorubicin (DOX) is an antineoplastic agent commonly used in multiagent chemotherapy regimens to treat solid tumors and leukemias. The mechanism of DOX action is proposed to be threefold, although the specific mechanism by which DOX is lethal to cancer cells remains elusive. DOX has been shown to intercalate into DNA in cells and halt cellular replication The structure of DOX contains a quinone moiety, which is capable of undergoing one-electron redox reactions by redox cycling. In this process, DOX quinone is converted to DOX semiquinone by accepting an electron from an oxidant; in the presence of oxygen, this semiquinone is converted back to its native DOX quinone, producing superoxide (O 2 − ) as a byproduc

Potential In Vivo Amelioration by N-Acetyl-L-Cysteine of Oxidative Stress in Brain in Human Double Mutant APP/PS-1 Knock-In Mice: Toward Therapeutic Modulation of Mild Cognitive Impairment

Alzheimer\u27s disease (AD) is the most prevalent form of dementia among the elderly. Although the underlying cause has yet to be established, numerous data have shown that oxidative stress is implicated in AD as well as in preclinical stages of AD, such as mild cognitive impairment (MCI). The oxidative stress observed in brains of subjects with AD and MCI may be due, either fully or in part, to increased free radicals mediated by amyloid-beta peptide (Abeta). By using double human mutant APP/PS-1 knock-in mice as the AD model, the present work demonstrates that the APP/PS-1 double mutation results in elevated protein oxidation (as indexed by protein carbonyls), protein nitration (as indexed by 3-nitrotyrosine), as well as lipid peroxidation (as indexed by protein-bound 4-hydroxy-2-nonenal) in brains of mice aged 9 months and 12 months. APP/PS-1 mice also exhibited lower levels of brain glutathione peroxidase (GPx) in both age groups studied, whereas glutathione reductase (GR) levels in brain were unaffected by the mutation. The activities of both of these antioxidant enzymes were significantly decreased in APP/PS-1 mouse brains, whereas the activity of glucose-6-phosphate dehydrogenase (G6PDH) was increased relative to controls in both age groups. Levels of peptidyl prolyl isomerase 1 (Pin1) were significantly decreased in APP/PS-1 mouse brain aged 9 and 12 months. Administration of N-acetyl-L-cysteine (NAC), a glutathione precursor, to APP/PS-1 mice via drinking water suppressed increased protein oxidation and nitration and also significantly augmented levels and activity of GPx in brain from both age groups. Oral administration of NAC also increased the diminished activity of GR and protected against lipid peroxidation in brains of 9-month-old APP/PS-1 mice only. Pin1 levels, GR levels, and G6PDH activity in brain were unaffected by oral administration of NAC in both age groups. These results are discussed with reference to the therapeutic potential of this brain-accessible glutathione precursor in the treatment of MCI and AD

Preclinical Alzheimer disease: Brain oxidative stress, Aβ peptide and proteomics

Alzheimer disease (AD) is a neurodegenerative disorder characterized clinically by progressive memory loss and subsequent dementia and neuropathologically by senile plaques, neurofibrillary tangles, and synapse loss. Interestingly, a small percentage of individuals with normal antemortem psychometric scores meet the neuropathological criteria for AD (termed 'preclinical' AD (PCAD)). In this study, inferior parietal lobule (IPL) from PCAD and control subjects was compared for oxidative stress markers by immunochemistry, amyloid beta peptide by ELISA, and identification of protein expression differences by proteomics. We observed a significant increase in highly insoluble monomeric Aβ42, but no significant differences in oligomeric Aβ nor in oxidative stress measurements between controls and PCAD subjects. Expression proteomics identified proteins whose trends in PCAD are indicative of cellular protection, possibly correlating with previous studies showing no cell loss in PCAD. Our analyses may reveal processes involved in a period of protection from neurodegeneration that mimic the clinical phenotype of PCAD

Site-Specific, Intramolecular Cross-Linking of Pin1 Active Site Residues by the Lipid Electrophile 4‑Oxo-2-nonenal

Products of oxidative damage to lipids include 4-hydroxy-2-nonenal (HNE) and 4-oxo-2-nonenal (ONE), both of which are cytotoxic electrophiles. ONE reacts more rapidly with nucleophilic amino acid side chains, resulting in covalent protein adducts, including residue–residue cross-links. Previously, we demonstrated that peptidylprolyl <i>cis</i>/<i>trans</i> isomerase A1 (Pin1) was highly susceptible to adduction by HNE and that the catalytic cysteine (Cys113) was the preferential site of modification. Here, we show that ONE also preferentially adducts Pin1 at the catalytic Cys but results in a profoundly different modification. Results from experiments using purified Pin1 incubated with ONE revealed the principal product to be a Cys-Lys pyrrole-containing cross-link between the side chains of Cys113 and Lys117. <i>In vitro</i> competition assays between HNE and ONE demonstrate that ONE reacts more rapidly than HNE with Cys113. Exposure of RKO cells to alkynyl-ONE (aONE) followed by copper-mediated click chemistry and streptavidin purification revealed that Pin1 is also modified by ONE in cells. Analysis of the Pin1 crystal structure reveals that Cys113 and Lys117 are oriented toward each other in the active site, facilitating formation of an ONE cross-link

Peptidyl-prolyl <i>cis</i>/<i>trans</i>-Isomerase A1 (Pin1) Is a Target for Modification by Lipid Electrophiles

Oxidation of membrane phospholipids is associated with inflammation, neurodegenerative disease, and cancer. Oxyradical damage to phospholipids results in the production of reactive aldehydes that adduct proteins and modulate their function. 4-Hydroxynonenal (HNE), a common product of oxidative damage to lipids, adducts proteins at exposed Cys, His, or Lys residues. Here, we demonstrate that peptidyl-prolyl <i>cis</i>/<i>trans</i>-isomerase A1 (Pin1), an enzyme that catalyzes the conversion of the peptide bond of pSer/pThr-Pro moieties in signaling proteins from cis to trans, is highly susceptible to HNE modification. Incubation of purified Pin1 with HNE followed by MALDI-TOF/TOF mass spectrometry resulted in detection of Michael adducts at the active site residues His-157 and Cys-113. Time and concentration dependencies indicate that Cys-113 is the primary site of HNE modification. Pin1 was adducted in MDA-MB-231 breast cancer cells treated with 8-alkynyl-HNE as judged by click chemistry conjugation with biotin followed by streptavidin-based pulldown and Western blotting with anti-Pin1 antibody. Furthermore, orbitrap MS data support the adduction of Cys-113 in the Pin1 active site upon HNE treatment of MDA-MB-231 cells. siRNA knockdown of Pin1 in MDA-MB-231 cells partially protected the cells from HNE-induced toxicity. Recent studies indicate that Pin1 is an important molecular target for the chemopreventive effects of green tea polyphenols. The present study establishes that it is also a target for electrophilic modification by products of lipid peroxidation