Application of a compact magnetic resonance imaging system for toxicologic pathology: evaluation of lithium-pilocarpine-induced rat brain lesions.

Magnetic resonance imaging (MRI) is a useful noninvasive tool used to detect lesions in clinical and veterinary medicine. The present study evaluated the suitability of a new easy-to-use compact MRI platform (M2 permanent magnet system, Aspect Imaging, Shoham, Israel) for assisting with preclinical toxicologic pathology examination of lesions in the rat brain. In order to induce brain lesions, male Sprague-Dawley rats were treated once with lithium chloride (127 mg/kg, intraperitoneal [i.p.]) followed by pilocarpine (30 mg/kg, i.p.). One week after dosing, the perfused, fixed brains were collected, analyzed by the MRI system and examined histopathologically. MRI of the brain of treated rats revealed areas of high T1 and middle to low T2 signals, when compared with the controls, in the piriform cortex, lateral thalamic nucleus, posterior paraventricular thalamic nucleus and posterior hypothalamic nucleus of the cerebrum. The altered MRI signal areas were consistent with well-circumscribed foci of neuronal cell degeneration/necrosis accompanied by glial cell proliferation. The present data demonstrated that quick analysis of fixed organs by the MRI system can detect the presence and location of toxicologic lesions and provide useful temporal information for selection of appropriate sections for histopathologic examination before routine slide preparation, especially in complex and functionally heterogeneous organs such as the brain.

Evaluation of SAMP8 Mice as a Model for Sleep-Wake and Rhythm Disturbances Associated with Alzheimer's Disease: Impact of Treatment with the Dual Orexin (Hypocretin) Receptor Antagonist Lemborexant.

BACKGROUND: Many patients with Alzheimer's disease (AD) display circadian rhythm and sleep-wake disturbances. However, few mouse AD models exhibit these disturbances. Lemborexant, a dual orexin receptor antagonist, is under development for treating circadian rhythm disorders in dementia. OBJECTIVE: Evaluation of senescence-accelerated mouse prone-8 (SAMP8) mice as a model for sleep-wake and rhythm disturbances in AD and the effect of lemborexant by assessing sleep-wake/diurnal rhythm behavior. METHODS: SAMP8 and control senescence-accelerated mouse resistant-1 (SAMR1) mice received vehicle or lemborexant at light onset; plasma lemborexant and diurnal cerebrospinal fluid (CSF) orexin concentrations were assessed. Sleep-wake behavior and running wheel activity were evaluated. RESULTS: Plasma lemborexant concentrations were similar between strains. The peak/nadir timing of CSF orexin concentrations were approximately opposite between strains. During lights-on, SAMP8 mice showed less non-rapid eye movement (non-REM) and REM sleep than SAMR1 mice. Lemborexant treatment normalized wakefulness/non-REM sleep in SAMP8 mice. During lights-off, lemborexant-treated SAMR1 mice showed increased non-REM sleep; lemborexant-treated SAMP8 mice displayed increased wakefulness. SAMP8 mice showed differences in electroencephalogram architecture versus SAMR1 mice. SAMP8 mice exhibited more running wheel activity during lights-on. Lemborexant treatment reduced activity during lights-on and increased activity in the latter half of lights-off, demonstrating a corrective effect on overall diurnal rhythm. Lemborexant delayed the acrophase of activity in both strains by approximately 1 hour. CONCLUSION: SAMP8 mice display several aspects of sleep-wake and rhythm disturbances in AD, notably mistimed activity. These findings provide some preclinical rationale for evaluating lemborexant in patients with AD who experience sleep-wake and rhythm disturbances.

The neuroprotective effect of perampanel in lithium-pilocarpine rat seizure model.

PURPOSE: Status epilepticus (SE) causes irreversible neurodegeneration if not terminated quickly. Perampanel (PER), a potent AMPA receptor antagonist, has previously been shown to terminate seizures in the lithium-pilocarpine SE model. In the present study, we assessed whether PER would also prevent neuronal damage in this model. METHODS: SE was induced in rats using lithium chloride and pilocarpine. Initiation of SE was defined as continuous seizures that exhibited as rearing accompanied by bilateral forelimb clonus (Racine score 4). Either PER (0.6, 2, or 6mg/kg) or diazepam (DZP, 10mg/kg) was administered intravenously 30min after SE initiation. Histopathological samples from treated and seizure-naive rats were taken one week after treatment and then stained with an anti-neuronal nuclei (NeuN) antibody. The sections were analyzed by using a pixel-counting algorithm to quantify the amount of staining in the CA1 subregion of the hippocampus, piriform cortex (Pir), and mediodorsal thalamic nucleus (MD). RESULTS: DZP administration did not suppress seizures or the degeneration of neurons in the examined areas. Seizures were terminated in 100% of rats treated with 6mg/kg PER (n=8) and in 47% (7/15) of rats treated with 2mg/kg PER, and neurons in the analyzed areas of these animals were preserved to the level seen in naive rats. In the eight animals in which 2mg/kg PER did not terminate the seizures, neuronal loss was partially attenuated in CA1 and Pir, and neurons were fully preserved in MD. Treatment with 0.6mg/kg PER did not terminate the seizures or significantly preserve neurons. The anti-seizure effect of PER correlated well with the degree of neuroprotection in each analyzed area. CONCLUSIONS: PER exhibited a strong neuroprotective effect in a drug-refractory SE model, and this effect was correlated with its attenuation of seizure.

CLAC binds to amyloid beta peptides through the positively charged amino acid cluster within the collagenous domain 1 and inhibits formation of amyloid fibrils.

CLAC (collagenous Alzheimer amyloid plaque component) is a proteolytic fragment derived from a novel membrane-bound collagen, CLAC-P/collagen type XXV, that deposits in senile plaques associated with amyloid beta peptides (Abeta) in the brains of patients with Alzheimer's disease. We previously showed that CLAC binds to the fibrillized form of Abeta in vitro, although the mechanism and the subdomains that mediate interaction of CLAC with Abeta as well as the effect of binding of CLAC on amyloid fibril formation remain unknown. Here we show that the collagenous domain 1 of CLAC, which is rich in positively charged amino acid residues, mediates its interaction with Abeta and that this binding is mediated by an electrostatic interaction and requires formation of the triple helix structure of CLAC. The soluble form of CLAC purified from the media of cells transfected with CLAC-P inhibited fibrillization of Abeta in vitro, especially in its elongation phase. These results suggest the anti-amyloidogenic roles of CLAC in the pathophysiology of Alzheimer's disease.