A Preliminary Report: The Hippocampus and Surrounding Temporal Cortex of Patients With Schizophrenia Have Impaired Blood-Brain Barrier

Schizophrenia (SZ) is one of the most severe forms of mental illness, yet mechanisms remain unclear. A widely established brain finding in SZ is hippocampal atrophy, and a coherent explanation similarly is lacking. Epidemiological evidence suggests increased cerebrovascular and cardiovascular complications in SZ independent of lifestyle and medication, pointing to disease-specific pathology. Endothelial cell contributions to blood-brain barrier (BBB) compromise may influence neurovascular unit and peripheral vascular function, and we hypothesize that downstream functional and structural abnormalities may be explained by impaired BBB

Evidence That Brain-Reactive Autoantibodies Contribute to Chronic Neuronal Internalization of Exogenous Amyloid-β1-42 and Key Cell Surface Proteins During Alzheimer\u27s Disease Pathogenesis

Blood-brain barrier (BBB) permeability is a recognized early feature of Alzheimer\u27s disease (AD). In the present study, we examined consequences of increased BBB permeability on the development of AD-related pathology by tracking selected leaked plasma components and their interactions with neurons in vivo and in vitro. Histological sections of cortical regions of postmortem AD brains were immunostained to determine the distribution of amyloid-β1-42 (Aβ42), cathepsin D, IgG, GluR2/3, and alpha7 nicotinic acetylcholine receptor (α7nAChR). Results revealed that chronic IgG binding to pyramidal neurons coincided with internalization of Aβ42, IgG, GluR2/3, and α7nAChR as well as lysosomal compartment expansion in these cells in regions of AD pathology. To test possible mechanistic interrelationships of these phenomena, we exposed differentiated SH-SY5Y neuroblastoma cells to exogenous, soluble Aβ42 peptide and serum from AD and control subjects. The rate and extent of Aβ42 internalization in these cells was enhanced by serum containing neuron-binding IgG autoantibodies. This was confirmed by treating cells with individual antibodies specific for α7nAChR, purified IgG from AD or non-AD sera, and sera devoid of IgG, in the presence of 100 nM Aβ42. Initial co-localization of IgG, α7nAChR, and Aβ42 was temporally and spatially linked to early endosomes (Rab11) and later to lysosomes (LAMP-1). Aβ42 internalization was attenuated by treatment with monovalent F(ab) antibody fragments generated from purified IgG from AD serum and then rescued by coupling F(ab) fragments with divalent human anti-Fab. Overall, results suggest that cross-linking of neuron-binding autoantibodies targeting cell surface proteins can accelerate intraneuronal Aβ42 deposition in AD

Prenatal Cocaine Exposure Increases Synaptic Localization of a Neuronal RasGEF, GRASP-1 via Hyperphosphorylation of AMPAR Anchoring Protein, GRIP

Prenatal cocaine exposure causes sustained phosphorylation of the synaptic anchoring protein, glutamate receptor interacting protein (GRIP1/2), preventing synaptic targeting of the GluR2/3-containing alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-type glutamate receptors (AMPARs; J. Neurosci. 29: 6308–6319, 2009). Because overexpression of GRIP-associated neuronal rasGEF protein (GRASP-1) specifically reduces the synaptic targeting of AMPARs, we hypothesized that prenatal cocaine exposure enhances GRASP-1 synaptic membrane localization leading to hyper-activation of ras family proteins and heightened actin polymerization. Our results show a markedly increased GRIP1-associated GRASP-1 content with approximately 40% reduction in its rasGEF activity in frontal cortices (FCX) of 21-day-old (P21) prenatal cocaine-exposed rats. This cocaine effect is the result of a persistent protein kinase C (PKC)- and downstream Src tyrosine kinase-mediated GRIP phosphorylation. The hyperactivated PKC also increased membrane-associated GRASP-1 and activated small G-proteins RhoA, cdc42/Rac1 and Rap1 as well as filamentous actin (F-actin) levels without an effect on the phosphorylation state of actin. Since increased F-actin facilitates protein transport, our results suggest that increased GRASP-1 synaptic localization in prenatal cocaine-exposed brains is an adaptive response to restoring the synaptic expression of AMPA-GluR2/3. Our earlier data demonstrated that persistent PKC-mediated GRIP phosphorylation reduces GluR2/3 synaptic targeting in prenatal cocaine-exposed brains, we now show that the increased GRIP-associated GRASP-1 may contribute to the reduction in GluR2/3 synaptic expression and AMPAR signaling defects

Alpha7 nicotinic acetylcholine receptor expression by vascular smooth muscle cells facilitates the deposition of Abeta peptides and promotes cerebrovascular amyloid angiopathy.

Deposition of beta-amyloid (Abeta) peptides in the walls of brain blood vessels, cerebral amyloid angiopathy (CAA), is common in patients with Alzheimer\u27s disease (AD). Previous studies have demonstrated Abeta peptide deposition among vascular smooth muscle cells (VSMCs), but the source of the Abeta and basis for its selective deposition in VSMCs are unknown. In the present study, we examined the deposition patterns of Abeta peptides, Abeta40 and Abeta42, within the cerebrovasculature of AD and control patients using single- and double-label immunohistochemistry. Abeta40 and Abeta42 were abundant in VSMCs, especially in leptomeningeal arteries and their initial cortical branches; in later-stage AD brains this pattern extended into the microvasculature. Abeta peptide deposition was linked to loss of VSMC viability. Perivascular leak clouds of Abeta-positive material were associated primarily with arterioles. By contrast, control brains possessed far fewer Abeta42- and Abeta40-immunopositive blood vessels, with perivascular leak clouds of Abeta-immunopositive material rarely observed. We also demonstrate that VSMCs in brain blood vessels express the alpha7 nicotinic acetylcholine receptor (alpha7nAChR), which has high binding affinity for Abeta peptides, especially Abeta42. These results suggest that the blood and blood-brain barrier permeability provide a major source of the Abeta peptides that gradually deposit in brain VSMCs, and the presence and abundance of the alpha7nAChR on VSMCs may facilitate the selective accumulation of Abeta peptides in these cells

Representative images of human protein microarrays.

<p>(Left) Small portion of a protein microarray containing 9,480 native human proteins probed with blocking buffer and secondary antibody as a quality control. (Right) Protein microarray probed with an individual human serum sample under the same conditions. Manufacturer’s controls (white boxes), gradient of IgG positive controls (green boxes), anti-human IgG controls (blue boxes) and examples of immunopositive reactions (yellow boxes) are indicated. In this study, all arrays were scanned at PMT setting of 600. Under this condition, the relative fluorescence unit (RFU) at saturation is around 75000 as exemplified by IgG controls (green boxes). The RFUs of BSA negative controls are under 1000. The coefficient of variance between duplicate spots averaged 4.7% ∼ 8.8%.</p

Dot blot confirmation of serum IgG auto-reactivity.

<p>Two identified antigens of serum autoantibodies, PTCD2 and ICAM4, were spotted onto nitrocellulose and probed with serum identical to that used on the protein microarrays. Serial dilution with diminishing immunoreactivity confirmed the presence and activity of IgG autoantibodies in human sera.</p

Effects of Health Status on Autoantibody Count.

<p>Several diseased groups (Alzheimer’s disease, Parkinson’s disease, breast cancer and multiple sclerosis) and the corresponding age-and-gender matched controls were studied. The age (mean ± standard deviation), percentage of female subjects, number of positive autoantibodies (mean ± standard deviation) are shown for each group. The difference of the autoantibody counts between diseased and corresponding control groups were tested by student t test with p value shown.</p

Natural IgG Autoantibodies Are Abundant and Ubiquitous in Human Sera, and Their Number Is Influenced By Age, Gender, and Disease

<div><p>The presence of self-reactive IgG autoantibodies in human sera is largely thought to represent a breakdown in central tolerance and is typically regarded as a harbinger of autoimmune pathology. In the present study, immune-response profiling of human serum from 166 individuals via human protein microarrays demonstrates that IgG autoantibodies are abundant in all human serum, usually numbering in the thousands. These IgG autoantibodies bind to human antigens from organs and tissues all over the body and their serum diversity is strongly influenced by age, gender, and the presence of specific diseases. We also found that serum IgG autoantibody profiles are unique to an individual and remarkably stable over time. Similar profiles exist in rat and swine, suggesting conservation of this immunological feature among mammals. The number, diversity, and apparent evolutionary conservation of autoantibody profiles suggest that IgG autoantibodies have some important, as yet unrecognized, physiological function. We propose that IgG autoantibodies have evolved as an adaptive mechanism for debris-clearance, a function consistent with their apparent utility as diagnostic indicators of disease as already established for Alzheimer’s and Parkinson’s diseases.</p> </div

Serum IgG autoantibodies consistently bind to diverse antigens in many human organs. A.

<p>Human liver, kidney, lung, and brain tissue lysates were separated by SDS-PAGE and then probed with human serum. As indicated by the many immunoreactive protein bands of differing molecular weights, serum IgG autoantibodies bind to a variety of common and organ-specific SDS-denatured antigens. <b>B</b>. In western blots, proteins from human brain extract were probed with human serum (HS-I and HS-II) as primary antibodies. Serum samples at three timepoints, T1, T2 and T3, were collected from the same individual (HS-I) over a period of four years. Serum samples T1’ and T2’ were collected from a different individual (HS-II) over a period of two years. Consistent patterns of serum IgG immunoreactivity were specific to individuals and appeared to remain stable over time.</p

Serum IgG autoantibodies are detected in all mammals tested.

<p><b>A</b>. Pig, human, and rat brain lysates were separated by SDS-PAGE and then probed with their respective species-specific serum as a primary antibody. Each species possessed IgG autoantibodies that bound to a variety of SDS-denatured brain self-antigens. <b>B</b>. Proteins from pig brain extract were probed with serum collected from a single pig at two timepoints, TP1 and TP2, spanning three months. The majority of the pig auto-reactive IgG antibodies remain the same.</p