Therapeutic versus neuroinflammatory effects of passive immunization is dependent on Abeta/amyloid burden in a transgenic mouse model of Alzheimer's disease

Abstract Background Passive immunization with antibodies directed to Aβ decreases brain Aβ/amyloid burden and preserves memory in transgenic mouse models of Alzheimer's disease (AD). This therapeutic strategy is under intense scrutiny in clinical studies, but its application is limited by neuroinflammatory side effects (autoimmune encephalitis and vasogenic edema). Methods We intravenously administered the monoclonal Aβ protofibril antibody PFA1 to aged (22 month) male and female 3 × tg AD mice with intermediate or advanced AD-like neuropathologies, respectively, and measured brain and serum Aβ and CNS cytokine levels. We also examined 17 month old 3 × tg AD female mice with intermediate pathology to determine the effect of amyloid burden on responses to passive immunization. Results The 22 month old male mice immunized with PFA1 had decreased brain Aβ, increased serum Aβ, and no change in CNS cytokine levels. In contrast, 22 month old immunized female mice revealed no change in brain Aβ, decreased serum Aβ, and increased CNS cytokine levels. Identical experiments in younger (17 month old) female 3 × tg AD mice with intermediate AD-like neuropathologies revealed a trend towards decreased brain Aβ and increased serum Aβ accompanied by a decrease in CNS MCP-1. Conclusions These data suggest that passive immunization with PFA1 in 3 × tg AD mice with intermediate disease burden, regardless of sex, is effective in mediating potentially therapeutic effects such as lowering brain Aβ. In contrast, passive immunization of mice with a more advanced amyloid burden may result in potentially adverse effects (encephalitis and vasogenic edema) mediated by certain proinflammatory cytokines.http://deepblue.lib.umich.edu/bitstream/2027.42/78261/1/1742-2094-7-57.xmlhttp://deepblue.lib.umich.edu/bitstream/2027.42/78261/2/1742-2094-7-57.pdfPeer Reviewe

Microglial activation and antioxidant responses induced by the Parkinson's disease protein α-synuclein.

Parkinson's disease (PD) is the second most common age-related neurodegenerative disorder typified by tremor, rigidity, akinesia and postural instability due in part to the loss of dopamine within the nigrostriatal system. The pathologic features of this disorder include the loss of substantia nigra dopamine neurons and attendant striatal terminals, the presence of large protein-rich neuronal inclusions containing fibrillar α-synuclein and increased numbers of activated microglia. Evidence suggests that both misfolded α-synuclein and oxidative stress play an important role in the pathogenesis of sporadic PD. Here we review evidence that α-synuclein activates glia inducing inflammation and that Nrf2-directed phase-II antioxidant enzymes play an important role in PD. We also provide new evidence that the expression of antioxidant enzymes regulated in part by Nrf2 is increased in a mouse model of α-synuclein overexpression. We show that misfolded α-synuclein directly activates microglia inducing the production and release of the proinflammatory cytokine, TNF-α, and increasing antioxidant enzyme expression. Importantly, we demonstrate that the precise structure of α-synuclein is important for induction of this proinflammatory pathway. This complex α-synuclein-directed glial response highlights the importance of protein misfolding, oxidative stress and inflammation in PD and represents a potential locus for the development of novel therapeutics focused on induction of the Nrf2-directed antioxidant pathway and inhibition of protein misfolding

Microglial activation and antioxidant responses induced by the Parkinson's disease protein α-synuclein.

Parkinson's disease (PD) is the second most common age-related neurodegenerative disorder typified by tremor, rigidity, akinesia and postural instability due in part to the loss of dopamine within the nigrostriatal system. The pathologic features of this disorder include the loss of substantia nigra dopamine neurons and attendant striatal terminals, the presence of large protein-rich neuronal inclusions containing fibrillar α-synuclein and increased numbers of activated microglia. Evidence suggests that both misfolded α-synuclein and oxidative stress play an important role in the pathogenesis of sporadic PD. Here we review evidence that α-synuclein activates glia inducing inflammation and that Nrf2-directed phase-II antioxidant enzymes play an important role in PD. We also provide new evidence that the expression of antioxidant enzymes regulated in part by Nrf2 is increased in a mouse model of α-synuclein overexpression. We show that misfolded α-synuclein directly activates microglia inducing the production and release of the proinflammatory cytokine, TNF-α, and increasing antioxidant enzyme expression. Importantly, we demonstrate that the precise structure of α-synuclein is important for induction of this proinflammatory pathway. This complex α-synuclein-directed glial response highlights the importance of protein misfolding, oxidative stress and inflammation in PD and represents a potential locus for the development of novel therapeutics focused on induction of the Nrf2-directed antioxidant pathway and inhibition of protein misfolding

An Intrinsically Disordered Region of the Acetyltransferase p300 with Similarity to Prion-Like Domains Plays a Role in Aggregation

<div><p>Several human diseases including neurodegenerative disorders and cancer are associated with abnormal accumulation and aggregation of misfolded proteins. Proteins with high tendency to aggregate include the p53 gene product, TAU and alpha synuclein. The potential toxicity of aberrantly folded proteins is limited <i>via</i> their transport into intracellular sub-compartments, the aggresomes, where misfolded proteins are stored or cleared <i>via</i> autophagy. We have identified a region of the acetyltransferase p300 that is highly disordered and displays similarities with prion-like domains. We show that this region is encoded as an alternative spliced variant independently of the acetyltransferase domain, and provides an interaction interface for various misfolded proteins, promoting their aggregation. p300 enhances aggregation of TAU and of p53 and is a component of cellular aggregates in both tissue culture cells and in alpha-synuclein positive Lewy bodies of patients affected by Parkinson disease. Down-regulation of p300 impairs aggresome formation and enhances cytotoxicity induced by misfolded protein stress. These data unravel a novel activity of p300, offer new insights into the function of disordered domains and implicate p300 in pathological aggregation that occurs in neurodegeneration and cancer.</p></div

p300 co-localizes with a-synuclein, ubiquitin and HDAC6 in brain of patients affected by Parkinson Disease.

<p>Sections of midbrains or cortex from normal control patients (<b>A</b>), or from patients by Parkinson Disease (<b>B–E</b>) were immuno-stained with the anti-p300 (red) and α-synuclein (green, panels <b>B,C</b>), or with anti-ubiquitin (green, panel D), or with anti-HDAC6 (green, panel E) antibodies as indicated at the top of each panel. Different sections from the same patients or from different patients were subjected to analysis.</p

Effects of p300 on the misfolded protein response. A.

<p>A549 cells were transfected with scramble siRNA or with the p300 specific siRNA as described previously, and stained with the anti-ubiquitin (green) or anti-vimentin (red) antibody. The percentage of cells containing ubiquitin aggregates is quantified in panel <b>B</b>. <b>C</b>. A549 cells were transfected with the scramble- or p300-specific siRNAs were mock treated or treated with MG132 for 16 hours, then harvested for flow cytometry. Panel C shows the Propidium Iodide profiles, and percentages of cells in the G1 or G2 phases of the cell cycle are indicated at the top of each relative peak. <b>D.</b> A549 cells transfected with scramble (black bars) or with the p300 siRNAs (gray bars), were treated with MG132. In one set of samples MG132 was washed out after 12–14 hours of treatment (indicated as MG132 w/o) and cells were allowed to recover for about four days, at which time they were counted. Alternatively, cell growth was monitored for the same period of time in the presence of MG132 (indicated as MG132 on). Error bars represent standard deviations. <b>E–F.</b> Control (wt) or p300 null mouse embryo fibroblasts (MEF) were mock treated or treated with MG132 for 16–24 hours (panel E), or alternatively, subjected to Heat Shock (HS, panel F) by incubating the cells at 40°C for two hours. Cells were allowed to recover from MG132 treatment or HS for 24–48 hours and were counted. Cell viability was assessed with trypan blue exclusion.</p

A. Proposed model for aggregation of the TAZ2 domain depending upon the concentration of zinc.

<p>See also text for explanation. The 1H-15N HSQC spectrum of the TAZ2 apoprotein at low concentration of zinc is poorly dispersed and has narrow line-widths. In low concentration of zinc, the cysteines residues in the fingers will be exposed to solvent in order to avoid intramolecular disulfide bridges. These exposed cysteines with histidines from two chains could interact with zinc and form interchain aggregates. Additional interchain stability could be obtained by forming interchain disulfide bridges between unligated cysteines residues as well as by forming two interchain hydrogen bonds among the side chains of glutamine and asparagine residues which are present throughout the sequence. A schematic representation of intermolecular aggregation is shown. <b>B.</b> Based on data presented here, and in keeping with previous studies that implicated p300 as an E4-ubiquitin ligase, as well as with evidence that p53 is activated by p300 when acetylated, we envision that p300 plays versatile and multiple effects on p53 activity. p53 interacts with at least three sites on p300, as indicated in the Figure, and each interaction site leads to different outcomes. While the interaction with the N-terminus serves to promote degradation of natively folded forms of p53 and to maintain low p53 levels in normal cells, the p300 PSPD brings p53 into cellular aggregates.</p