Immunohistochemical study of apolipoprotein E in human cerebrovascular white matter lesions

Astrocytic neuroprotection through induction of cytoprotective molecules; a proteomic analysis of mutant P301S tau-transgenic mouse

Hyperphosphorylated tau protein constitutes a significant portion of intracellular inclusions in some neurodegenerative diseases. In addition, mutations in tau protein cause familial forms of frontotemporal dementia (FTD), indicating that dysfunction of tau protein is responsible for neurodegeneration and dementia. P301S tau-transgenic (Tg) mouse expressing human mutant tau in neurons exhibits similar features of human tauopathies including neuronal degeneration and filament accumulation consisted of hyperphosphorylated tau protein. In the present study, we attempted to characterize protein expression profiles in P301S tau-Tg mouse by using two-dimensional differential in-gel electrophoresis (2D-DIGE) coupled by peptide mass fingerprinting (PMF). As a result, we identified four upregulated proteins; heat shock protein 27 (Hsp27), peroxiredoxin 6 (Prdx6), apolipoprotein E (ApoE), and latexin (LTXN), all of which may function as a neuroprotective mechanism against tau toxicity. In immunohistochemistry, these four proteins were increased invariably in astrocytes, and these astrocytes infiltrated the area in which there are numerous accumulations of hyperphosphorylated tau and neuronal loss. Therefore, these results may indicate that astrocytes provide a neuroprotective mechanism against tau toxicity.

Increased expression of neuronal apolipoprotein E in human brain with cerebral infarction

BACKGROUND AND PURPOSE

Cellular origin of apolipoprotein E (ApoE) in the human brain and its roles in physiological and pathological conditions remain to be clarified.

METHODS

Immunolocalization of ApoE was investigated in a series of autopsied human brains with or without infarction. ApoE expression was also estimated on immunoblot on protein extracts from autopsied brains and a cultured neuroblastoma cell line of human origin (GOTO) subjected to an oxidative stress induced by exposure to hydrogen peroxide (0.2 mmol/L).

RESULTS

In addition to astrocytes and microglia, neurons and degenerated axons in and around the ischemic foci contained ApoE-like immunoreactivity, which was more intense in recent ischemic foci. Immunoblot demonstrated an increase in expression of ApoE in brain extracts from ischemic lesion, and this increase was also pronounced in the cultured neuroblastoma cell line after the stress.

CONCLUSIONS

Accumulation of ApoE in neurons in and around ischemic foci of the human brain is related to an increase in ApoE synthesis in neurons, as seen in cultured neuronal cells after oxidative stress. Intrinsic regenerative activity of neuron in reaction to external insults may be related to this increase in ApoE of neuronal origin.

Influence of the polymorphism of apolipoprotein E in cerebral vascular disease

The genetic heterogeneity of apolipoprotein E (apo E) has been associated with lipid profile and atherothrombotic stroke, however this association remains inconclusive.

OBJECTIVE

To evaluate the relationship between the isoforms of apo E and atherothrombotic stroke, by ascertaining the frequency of its alleles and genotypes associated with the lipid profile in patients with stroke.

METHOD

A total of 207 individuals were divided into two groups, consisting of 107 patients with stroke and 100 individuals without clinical symptoms of the disease. Blood samples were taken from patients and controls for molecular investigation of the apo E (epsilon2, epsilon3 and epsilon4 alleles) for the analysis of the lipid profile.

RESULTS

The epsilon3 allele was the most common and its prevalence was significantly higher in patients (0.93) compared to the controls (0.86; p=0.024). The epsilon2 allele was rarely seen specifically in patients (0.02 versus 0.05 in controls, p=0.191). The epsilon4 allele was not associated with stroke showing a reduced frequency in patients (0.05) when compared to controls (0.09; p=0.011). Although higher average levels of lipid profile were found in patients when compared to controls, with statistical significance for the values of total cholesterol (TC) (203.6 mg/dL +/- 57.98 and 181.9 mg/dL +/- 68.47 respectively; p=0.003) and low-density lipoprotein cholesterol (LDLc) (131.4mg/dL +/- 52.60 and 116 mg/dL +/- 56.38, respectively; p=0.014), these were independent of the presence of the epsilon4 allele. In control group the higher TC and LDLc values occurred in the absence of the epsilon4 allele, confirming the conflicting effect of the alleles of apo E on the plasmatic lipids and atherothrombotic stroke.

CONCLUSION

The isoforms of apo E cannot be regarded as an isolated risk factor for stroke and do not show association with lipid profile in this study.

Increased levels of intracellular iron in the brains of ApoE-deficient mice with closed head injury

Previous studies have revealed that apolipoprotein E (apoE)-deficient mice have distinct memory deficits and neurochemical derangements and are oxidatively stressed prior to and following closed head injury. The objective of this study was to evaluate the possibility that the enhanced susceptibility of apoE-deficient mice to closed head injury is related to impairments in their antioxidative iron-chelating mechanisms. ApoE-deficient and control mice were subjected to closed had injury, after which the extent of brain-damage and the level of iron-containing cells were assessed. Examination of the brain-damaged areas in the injured mice revealed that, by Day 3 post injury, animals of both groups were maximally and similarly affected. While the size of the damaged area of the injured control mice diminished significantly by Day 7, however recovery was not observed in injured apoE-deficient mice up to at least 14 days post-injury. Histopathologically, the decrease in the damaged areas in the control mice was interpreted as related to decreased edema. Numbers of iron-containing cells at Days 3 and 7 after injury were greater in the brains of control mice than in the apoE-deficient mice. Whereas the number of iron-containing cells in injured control mice decreased at days 9 and 14-post injury, that of the injured apoE-deficient mice plateaued by Day 9 at a level more than two-fold higher than the maximal level seen for controls. The size of the damaged areas and the number of iron-containing cells were correlated (P < 0.03) for both mouse groups at days 9 and 14 after injury. The data suggest that the increased susceptibility of apoE-deficient mice to closed head injury may be due, at least in part, to impaired iron scavenging and sustained oxidative stress.

Regulation of beta-amyloid secretion by FE65, an amyloid protein precursor-binding protein

The principal component of Alzheimer's amyloid plaques, Abeta, derives from proteolytic processing of the Alzheimer's amyloid protein precursor (APP). FE65 is a brain-enriched protein that binds to APP. Although several laboratories have characterized the APP-FE65 interaction in vitro, the possible relevance of this interaction to Alzheimer's disease has remained unclear. We demonstrate here that APP and FE65 co-localize in the endoplasmic reticulum/Golgi and possibly in endosomes. Moreover, FE65 increases translocation of APP to the cell surface, as well as both alphaAPPs and Abeta secretion. The dramatic (4-fold) FE65-dependent increase in Abeta secretion suggests that agents which inhibit the interaction of FE65 with APP might reduce Abeta secretion in the brain and therefore be useful for preventing or slowing amyloid plaque formation.

The relationship between apolipoprotein E, dementia, and vascular illness

The purpose of this study was to concurrently assess the relationship of Apolipoprotein E (APOE) with both dementias and vascular illnesses in the very old. Nine hundred and fifty nine subjects (mean age 85 years) in a long-term care facility were genotyped and cognitively tested with the Mini Mental State Exam. All subjects were studied for the relationship of APOE with atherosclerotic heart disease, hypertension, or stroke without concomitant dementia. Four hundred fifty individuals met criteria for inclusion into one of the following groups: Alzheimer's disease (n = 318), vascular dementia (n = 49), or not demented controls (n = 83) and were investigated for the relationship between APOE and these diagnostic categories. APOE epsilon4 was not associated with atherosclerotic heart disease, hypertension, or stroke without concomitant dementia. The APOE epsilon3 allele was more common in men with atherosclerotic heart disease. In contrast, the APOE epsilon4 allele was more common in patients with Alzheimer's disease (22%) and vascular dementia (26%) than in not demented controls (7%). APOE epsilon4 is associated with dementias in the very old, whereas its relationship with either peripheral or central nervous system vascular disease without dementia is not as robust.

Alterations in glia and axons in the brains of Binswanger's disease patients

BACKGROUND AND PURPOSE

Although increasing attention is being paid to Binswanger's disease, a form of vascular dementia characterized by diffuse white matter lesions, only limited information is available on the pathological changes that occur in the glia and axons in the white matter. We therefore investigated the brains of patients with Binswanger's disease to gain further insight into its pathophysiology.

METHODS

Autopsied brains from patients with Binswanger's disease (group 3; n = 17) were compared with those of nonneurological controls (group 1; n = 5) and controls with large cortical infarcts but without significant white matter lesions (group 2; n = 5). Glial fibrillary acidic protein (GFAP) was used as an immunohistochemical marker for astroglia, leukocyte common antigen (LCA) was used as a marker for microglia, and HLA-DR was used as a marker for activated microglia. Axonal damage was assessed by the accumulation of proteins, which are transported by fast axonal flow, amyloid protein precursor (APP), synaptophysin, and chromogranin A.

RESULTS

Although there was no difference in numerical density of GFAP-immunoreactive astroglia in each group, regressive astroglia were observed in 7 of 17 patients with Binswanger's disease. LCA-immunoreactive microglia were 1.7 times more numerous in Binswanger's disease than in group 1 (P < .05). HLA-DR-immunoreactive-activated microglia were 3.4 times and 2.1 times more numerous in Binswanger's disease as compared with group 1 (P < .01) and group 2 (P < .05), respectively. There was frequent perivascular lymphocyte cuffing, and clusters of macrophages with a decreased number of oligodendroglia were observed in the rarefied white matter. The grading scores for the number of axons immunoreactive for either APP, synaptophysin, or chromogranin A were significantly higher in Binswanger's disease than in group 1 or 2.

CONCLUSIONS

The pathological alterations in Binswanger's diseased brains include regressive changes in the astroglia and activation of the microglia with a decrease in the oligodendroglia, which were associated with the degradation of both myelin and axonal components. These results indicate that an inflammatory reaction and compromised axonal transport, mediated by chronic ischemia, may play an important role in the pathophysiology of Binswanger's disease.

Alterations of the blood-brain barrier and glial cells in white-matter lesions in cerebrovascular and Alzheimer's disease patients

BACKGROUND AND PURPOSE

The underlying cause of white-matter lesions, which are frequent findings in cerebrovascular disease (CVD) and Alzheimer's disease (AD), remains uncertain. We performed immunohistochemical analysis of serum protein extravasation to investigate the function of the blood-brain barrier in white-matter lesions.

METHODS

White-matter lesions were estimated by use of Kluver-Barrera staining in patients diagnosed clinicopathologically as having ischemic CVD (n = 14) and AD (n = 12) and from nonneurological control subjects (n = 6). Axonal damages were investigated by use of immunohistochemistry for amyloid protein precursor. Alteration of the blood-brain barrier was examined with fibrinogen and immunoglobulins used as markers. The numbers of HLA-DR-positive microglia and glial fibrillary acidic protein-positive astroglia were examined comparatively.

RESULTS

White-matter lesions were graded as normal (grade 0) in 14 of the 32 cases (44%), slight (grade I) in 10 cases (31%), moderate (grade II) in 6 cases (19%), and severe (grade III) in 2 cases (6%). Amyloid precursor protein was accumulated most frequently in grade II white-matter lesions. Immunohistochemistry for serum proteins labeled astroglial cell bodies and their processes, which seemed to have sequestered extravasated proteins. The groups with detectable white-matter lesions had significantly higher grading scores for fibrinogen and immunoglobulins than the control group (P < .05). Although the higher scores for serum protein extravasation were statistically significant in ischemic CVD cases (P < .05), there was no significant increase in AD cases. Activated microglia and astroglia were more numerous in the groups with white-matter lesions in both ischemic CVD and AD cases, although this increase in the number of astroglia was not evident in regions with clasmatodendrosis.

CONCLUSIONS

Dysfunction of the blood-brain barrier is more prominent in white-matter lesions seen in ischemic CVD than in AD and may have a role in the pathogenesis of cerebrovascular white-matter lesions.