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Technology and innovation  2012;14(2):199-208.
Apolipoprotein E (apoE) synthesized in liver and brain plays a key role in both cholesterol transport and Alzheimer's disease (AD): apoE-knockout mice develop hypercholesterolemia and atherosclerosis and cannot support AD amyloid deposition. The ApoE4 allele is the strongest genetic risk factor for late-onset AD, and apoE4 protein preferentially catalyzes amyloid-beta (Aβ) peptide fibrillization in vitro and amyloid plaque deposition in vivo. Circulating apoE may also have the potential to draw Aβ from the brain and reduce amyloid deposition. We used parabiosis to determine how circulating apoE impacts brain amyloid deposition and blood cholesterol levels in transgenic mice carrying AD-promoting APP and PS1 human transgenes—either with or without the endogenous mouse apoE gene. ApoE transferred through the joined circulations from WT to parabiosed APP+/+,PS1+/−,apoE-KO mice prevented hypercholesterolemia and reduced already low brain amyloid deposition. The findings indicate that apoE synthesis in the brain itself is necessary for amyloid accumulation. Furthermore, plasma apoE can both normalize cholesterol levels in apoE-KO mice and act as a peripheral sink to induce net efflux of Aβ peptide from the brain. The therapeutic implication is that inhibiting Alzheimer's disease neuropathology may be accomplished by either reducing apoE in the brain or increasing apoE in the blood.
PMCID: PMC3635498  PMID: 23626867
Apolipoprotein E (apoE); Parabiosis; Amyloid; Alzheimer's disease; Atherosclerosis; Blood
2.  Heparanase overexpression impairs inflammatory response and macrophage-mediated clearance of amyloid-β in murine brain 
Acta Neuropathologica  2012;124(4):465-478.
Neuroinflammation is typically observed in neurodegenerative diseases such as Alzheimer’s disease, as well as after traumatic injury and pathogen infection. Resident immune cells, microglia and astrocytes, are activated and joined by blood-borne monocytes that traverse the blood–brain barrier and convert into activated macrophages. The activated cells express various cytokines, chemokines and proteolytic enzymes. To study the role of heparan sulfate proteoglycans in neuroinflammation, we employed a transgenic mouse overexpressing heparanase, an endoglucuronidase that specifically degrades heparan sulfate side chains. Neuroinflammation was induced by systemic challenge with lipopolysaccharide, or by localized cerebral microinjection of aggregated amyloid-β peptide, implicated in Alzheimer’s disease. Lipopolysaccharide-treated control mice showed massive activation of resident microglia as well as recruitment of monocyte-derived macrophages into the brain parenchyma. Microinjection of aggregated amyloid-β elicited a similar inflammatory response, albeit restricted to the injection site, which led to dispersion and clearance of the amyloid. In the heparanase-overexpressing mice, all aspects of immune cell recruitment and activation were significantly attenuated in both inflammation models, as was amyloid dispersion. Accordingly, an in vitro blood–brain barrier model constructed from heparanase-overexpressing cerebral vascular cells showed impaired transmigration of monocytes compared to a corresponding assembly of control cells. Our data indicate that intact heparan sulfate chains are required at multiple sites to mediate neuroinflammatory responses, and further point to heparanase as a modulator of this process, with potential implications for Alzheimer’s disease.
Electronic supplementary material
The online version of this article (doi:10.1007/s00401-012-0997-1) contains supplementary material, which is available to authorized users.
PMCID: PMC3444710  PMID: 22692572
Neuroinflammation; Heparan sulfate; Heparanase; Amyloid-β; Clearance; Alzheimer’s disease
3.  Genetic Deletion and Pharmacological Inhibition of Nogo-66 Receptor Impairs Cognitive Outcome after Traumatic Brain Injury in Mice 
Journal of Neurotrauma  2010;27(7):1297-1309.
Functional recovery is markedly restricted following traumatic brain injury (TBI), partly due to myelin-associated inhibitors including Nogo-A, myelin-associated glycoprotein (MAG) and oligodendrocyte myelin glycoprotein (OMgp), that all bind to the Nogo-66 receptor-1 (NgR1). In previous studies, pharmacological neutralization of both Nogo-A and MAG improved outcome following TBI in the rat, and neutralization of NgR1 improved outcome following spinal cord injury and stroke in rodent models. However, the behavioral and histological effects of NgR1 inhibition have not previously been evaluated in TBI. We hypothesized that NgR1 negatively influences behavioral recovery following TBI, and evaluated NgR1−/− mice (NgR1−/− study) and, in a separate study, soluble NgR1 infused intracerebroventricularly immediately post-injury to neutralize NgR1 (sNgR1 study) following TBI in mice using a controlled cortical impact (CCI) injury model. In both studies, motor function, TBI-induced loss of tissue, and hippocampal β-amyloid immunohistochemistry were not altered up to 5 weeks post-injury. Surprisingly, cognitive function (as evaluated with the Morris water maze at 4 weeks post-injury) was significantly impaired both in NgR1−/− mice and in mice treated with soluble NgR1. In the sNgR1 study, we evaluated hippocampal mossy fiber sprouting using the Timm stain and found it to be increased at 5 weeks following TBI. Neutralization of NgR1 significantly increased mossy fiber sprouting in sham-injured animals, but not in brain-injured animals. Our data suggest a complex role for myelin-associated inhibitors in the behavioral recovery process following TBI, and urge caution when inhibiting NgR1 in the early post-injury period.
PMCID: PMC2942864  PMID: 20486800
cognition; mossy fiber sprouting; NgR−/− mice; Nogo-66 receptor; traumatic brain injury
4.  Increased mRNA Levels of TCF7L2 and MYC of the Wnt Pathway in Tg-ArcSwe Mice and Alzheimer's Disease Brain 
Several components in the Wnt pathway, including β-catenin and glycogen synthase kinase 3 beta, have been implied in AD pathogenesis. Here, mRNA brain levels from five-month-old tg-ArcSwe and nontransgenic mice were compared using Affymetrix microarray analysis. With surprisingly small overall changes, Wnt signaling was the most affected pathway with altered expression of nine genes in tg-ArcSwe mice. When analyzing mRNA levels of these genes in human brain, transcription factor 7-like 2 (TCF7L2) and v-myc myelocytomatosis viral oncogene homolog (MYC), were increased in Alzheimer's disease (AD) (P < .05). Furthermore, no clear differences in TCF7L2 and MYC mRNA were found in brains with frontotemporal lobar degeneration, suggesting that altered regulation of these Wnt-related genes could be specific to AD. Finally, mRNA levels of three neurogenesis markers were analyzed. Increased mRNA levels of dihydropyrimidinase-like 3 were observed in AD brain, suggesting that altered Wnt pathway regulation may signify synaptic rearrangement or neurogenesis.
PMCID: PMC3014771  PMID: 21234373
5.  Heparan Sulfate Accumulation with Aβ Deposits in Alzheimer's Disease and Tg2576 Mice is Contributed by Glial Cells 
Amyloid β-peptide (Aβ) plaques, one of the major neuropathological lesions in Alzheimer's disease (AD), can be broadly subdivided into two morphological categories: neuritic and diffuse. Heparan sulfate (HS) and HS proteoglycans (HSPGs) are codeposits of multiple amyloidoses, including AD. Although HS has been considered a limiting factor in the initiation of amyloid deposition, the pathological implications of HS in Aβ deposits of AD remain unclear. In this study, immunohistochemistry combined with fluorescence and confocal microscopy was employed to gain deeper insight into the accumulation of HS with Aβ plaques in sporadic and familial AD. Here we demonstrate that HS preferentially accumulated around the Aβ40 dense cores of neuritic plaques, but was largely absent from diffuse Aβ42 plaques, suggesting that Aβ42 deposition may occur independently of HS. A codeposition pattern of HS with Aβ deposits in Tg2576 mice was also examined. We identified the membrane-bound HSPGs, glypican-1 (GPC1) and syndecan-3 (SDC3), in glial cells associated with Aβ deposits, proximal to sites of HS accumulation. In mouse primary glial cultures, we observed increased levels of GPC1 and SDC3 following Aβ stimulation. These results suggest that HS codeposits with Aβ40 in neuritic plaques and is mainly derived from glial cells.
PMCID: PMC2856073  PMID: 18422760
b-Amyloid; glial cells; heparan sulfate

Results 1-5 (5)