Disintegration of the spatial organization of behavior in experimental autoimmune dementia

Focal cerebral ischemia alters the spatio-temporal properties, but not the amount of activity in mice

Cerebral ischemia induces sensorimotor and cognitive dysfunctions in rodents; however, little is known about the changes in the spatio-temporal organization of locomotor activity after ischemia. In this study, we continuously assessed the spatio-temporal properties of locomotor activity in an enclosure (40 cm x 40 cm x 65 cm, arbitrarily divided into 16 zones) with feeding and drinking supplies, and observed the spatio-temporal changes in mice with focal cerebral ischemia. Locomotor tracks were recorded from 3rd to 24th h (total 22 h) after middle cerebral artery occlusion (MCAO) or sham operation. The absolute and relative distance traveled or time spent in different regions was analyzed. We found that there was no significant difference in total traveled distances over 22 h between the two groups. Control mice moved and stayed primarily in feeding and drinking zones, frequently in peripheral but rarely in central zones. However, ischemic mice lost such a property, almost evenly moved and stayed in 16 zones. Mice in both groups were more active (traveled more distances) shortly after they entered the enclosure, while ischemic mice returned to stable levels slower. The traveled distance had a remarkable circadian variation with more locomotion in the night in control mice, but not in ischemic mice. Most of the spatial parameters (ratios) of locomotor activity were closely correlated with the ischemic infarction, neuron densities (in cortex, hippocampal CA1 region and striatum), and typical behavioral assessments (neurological scores and inclined board test). Thus, these findings indicate that focal cerebral ischemia does not alter the amount of locomotor activity in mice, but impairs the spatio-temporal properties-prolonging the initial hyperactivity and losing regionally special distribution of the activity.

Alterations in immune functions during normal aging and Alzheimer's disease

It is thought that aging induces immune changes, which are related to the pathophysiology of Alzheimer's disease (DAT). In this study, the total number of leukocytes, white blood cell differentiation, mitogen-induced lymphocytic proliferation, neutrophil phagocytosis and superoxide release, and prostaglandin E2 (PGE2) production by mitogen-stimulated whole blood cultures were comparatively investigated between healthy adults (range 22-45 years) and healthy elderly volunteers (range 70-91 years), and between DAT patients (range 56-94 years) and age-matched control subjects. Healthy elderly volunteers showed significantly lower phytohemagglutinin (PHA)-induced lymphocyte proliferation and percentage and absolute number of basophils than young volunteers. In normal volunteers, there were significant and negative correlations between age and the number of basophils. Patients with DAT showed a trend toward significantly higher PHA-induced lymphocyte proliferation and significantly decreased percentage and absolute number of large unstained cells than healthy volunteers. In DAT patients, the total number of leukocytes and the percentage and number of neutrophils were positively correlated with age. All other immune-inflammatory variables were not significantly altered either by the aging process or DAT. The present study suggests that aging and DAT may differently affect some immune variables.

Neurological dysfunction and hyperactive behavior associated with antiphospholipid antibodies. A mouse model

Antiphospholipid antibodies (aPL) have been associated with various neurological manifestations, but the underlying mechanism has not been elucidated. We assessed mice with induced experimental antiphospholipid syndrome (APS) for neurological and behavioral changes. After immunization with monoclonal human anticardiolipin antibody (H-3), female BALB/c mice developed elevated levels of circulating anti-negatively charged phospholipids (aPL), anti-beta2-glycoprotein I (abeta2GPI), and anti-endothelial cell antibodies (AECA), along with clinical manifestations of APS like thrombocytopenia and fetus resorption. APS mice were impaired neurologically and performed several reflexes less accurately compared to the controls, including placing reflex (P < 0.05), postural reflex (P < 0.05), and grip test (P = 0.05). The APS mice also exhibited hyperactive behavior in an open field, which tests spatial behavior (P < 0.03), and displayed impaired motor coordination on a rotating bar. aPL in combination with abeta2GPI and AECA is probably involved in the neurological and behavioral defects shown in mice with experimental APS.

Experimental immune-mediated damage of septal cholinergic neurons

Degeneration of cholinergic neurons in the medial septum and the diagonal band of Broca is a frequent neuropathological feature of Alzheimer's disease. To determine whether an immune process can injure these basal forebrain cholinergic neurons, we serially immunized guinea pigs with septal cholinergic hybrid cells (SN-56). Following immunization, a relatively selective damage of septal cholinergic neurons, reduction in septal choline acetyltransferase (ChAT) activity and decrease in acetylcholine release in hippocampus were detected. Serum IgG from guinea pigs immunized with SN-56 cells and stereotactically injected into the medial septal region of rats produced a loss of ChAT activity in the medial septum, frontal cortex and hippocampus, together with impairment of learning and long term spatial memory. These data suggest that relatively selective damage to septal cholinergic neurons can be caused by an immune-mediated process in experimental animals.

Animal model and in vitro studies of anti neurofilament antibodies mediated neurodegeneration in Alzheimer's disease

Alzheimer's disease (AD) is associated with serum antibodies directed specifically against phosphorylated epitopes highly enriched in the heavy neurofilament protein NF-H of cholinergic neurons. Prolonged immunization of rats with these molecules but not with other NF-H isoforms results in cognitive impairments. This animal model, termed experimental autoimmune dementia (EAD), supports a role for such antibodies in neurodegeneration in AD. In the present study we investigated the cellular and immunological mechanisms underlying the cognitive defects in EAD. Immunohistochemical studies revealed that IgG accumulate in the septum, hippocampus and in the entorhinal cortex of the EAD rats. This is accompanied by a marked reduction in the density of septal cholinergic neurons. An inverse correlation was observed between the level of IgG in the septum of individual EAD rats and the density of their septal cholinergic neurons. Time course studies revealed that the decrease in the density of cholinergic neurons in the septum of EAD rats and the accumulation of IgG in this brain area have the same time course and are both significant by three to four months following the initiation of immunization with cholinergic NF-H. The cognitive deficits of the EAD rats evolve more slowly and are pronounced only after six months following the initation of immunization. In vitro studies revealed that anti NF-H IgG bind to the outer surface of neurons in tissue cultures of rat forebrain and can affect neuronal viability. These AD and in vitro findings provide model systems for studying the mechanisms underlying the neuropathological effects of specific anti NF-H antibodies.

Antibodies to different isoforms of the heavy neurofilament protein (NF-H) in normal aging and Alzheimer's disease

Sera of normal controls and of patients with neurological diseases contain antineurofilament antibodies. Recent studies suggest that biochemically and immunologically distinct subclasses of neurofilaments occur in different types of neurons. Alzheimer's disease (AD), the major cause of dementia, is associated with a marked degeneration of brain cholinergic neurons. In the present work we characterized the repertoire and age dependence of antineurofilament antibodies in normal sera and examined whether the degeneration of cholinergic neurons in AD is associated with serum antibodies directed specifically against the neurofilaments of mammalian cholinergic neurons. This was performed by immunoblot assays utilizing neurofilaments from the purely cholinergic bovine ventral root neurons and from the chemically heterogeneous bovine dorsal root neurons. Antibodies to the heavy neurofilament protein NF-H were detected in normal control sera. Their levels were significantly higher in older (aged 70-79) than in younger (aged 40-59) subjects. These antibodies bound similarly to bovine ventral root and dorsal root NF-H and their NF-H specificity was unchanged during aging. In contrast, the levels of IgG in AD sera that are directed against ventral root cholinergic NF-H were higher than those directed against the chemically heterogeneous dorsal root NF-H. Immunoblot experiments utilizing dephosphorylated ventral root and dorsal root NF-H and chymotryptic fragments of these molecules revealed that AD sera contain a repertoire of antimamalian NF-H IgG. A subpopulation of these antibodies binds to phosphorylated epitopes that are specifically enriched in ventral root cholinergic NF-H and that are located on the carboxy terminal domain of this molecule.(ABSTRACT TRUNCATED AT 250 WORDS)

Decreased density of forebrain cholinergic neurons in experimental autoimmune dementia

Sera of Alzheimer's disease and Down's syndrome patients contain antibodies which bind specifically to the high molecular weight neurofilament protein of Torpedo cholinergic neurons. We have recently shown that prolonged immunization of rats with this antigen results in the accumulation of IgG in neurons in the septum and hippocampus of the immunized rats and in cognitive impairments. This animal model is termed experimental autoimmune dementia. In the present study we examined whether the anti-cholinergic high molecular weight neurofilament subunit immune response of the experimental autoimmune dementia rats affects forebrain cholinergic neurons. This was performed immunohistochemically utilizing a monoclonal antibody to nerve growth factor receptor, a specific marker of cholinergic neurons in the forebrain. The results obtained revealed significant decreases in the density of cholinergic neurons in the medial septal nucleus and diagonal band of the experimental autoimmune dementia rats. These decreases are specific to the anti-cholinergic high molecular weight neurofilament subunit immune response of the experimental autoimmune dementia rats and are not observed in control rats which were immunized with chemically heterogeneous high molecular weight neurofilament subunit. The decrease in density of forebrain cholinergic neurons in experimental autoimmune dementia rats may mimic pathogenic processes in Alzheimer's disease and supports a role for anti-cholinergic high molecular weight neurofilament subunit antibodies in the degeneration of cholinergic neurons in the disease.