Differential effects between γ-secretase inhibitors and modulators on cognitive function in amyloid precursor protein-transgenic and nontransgenic mice.

γ-Secretase inhibitors (GSIs) reduce amyloid-ß (Aß) peptides but inevitably increase the ß-C-terminal fragment (ß-CTF) of amyloid precursor protein (APP), potentially having undesirable effects on synapses. In contrast, γ-secretase modulators (GSMs) reduce Aß42 without increasing ß-CTF. Although the Aß-lowering effects of these compounds have been extensively studied, little effort has been made to investigate their effects on cognition. Here, we compared the effects of two GSIs--(2S)-2-hydroxy-3-methyl-N-[(2S)-1-{[(1S)-3-methyl-2-oxo-2,3,4,5-tetrahydro-1H-3-benzazepin-1-yl]amino}-1-oxopropan-2-yl]butanamide (LY450139, semagacestat) and (2R)-2-[[(4-chlorophenyl)sulfonyl][[2-fluoro-4-(1,2,4-oxazol-3-yl)phenyl]methyl]amino-5,5,5-trifluoropentanamide (BMS-708163)--and a second-generation GSM [{(2S,4R)-1-[(4R)-1,1,1-trifluoro-7-methyloctan-4-yl]-2-[4-(trifluoromethyl)phenyl]piperidin-4-yl}acetic acid (GSM-2)] on spatial working memory in APP-transgenic (Tg2576) and nontransgenic mice using the Y-maze task. While acute dosing with either GSI ameliorated memory deficits in 5.5-month-old Tg2576 mice, these effects disappeared after 8 d subchronic dosing. Subchronic dosing with either GSI rather impaired normal cognition in 3-month-old Tg2576 mice, with no inhibition on the processing of other γ-secretase substrates, such as Notch, N-cadherin, or EphA4, in the brain. LY450139 also impaired normal cognition in wild-type mice; however, the potency was 10-fold lower than that in Tg2576 mice, indicating an APP-dependent mechanism likely with ß-CTF accumulation. Immunofluorescence studies revealed that the ß-CTF accumulation was localized in the presynaptic terminals of the hippocampal stratum lucidum and dentate hilus, implying an effect on presynaptic function in the mossy fibers. In contrast, both acute and subchronic dosing with GSM-2 significantly ameliorated memory deficits in Tg2576 mice and did not affect normal cognition in wild-type mice. We demonstrated a clear difference between GSI and GSM in effects on functional consequences, providing new insights into strategies for developing these drugs against Alzheimer's disease.

Clinical features and neuropathological findings of familial amyotrophic lateral sclerosis with a His46Arg mutation in Cu/Zn superoxide dismutase.

We examined the characteristic clinical features of one family of familial amyotrophic lateral sclerosis (FALS) with a His46Arg mutation in the enzyme Cu/Zn superoxide dismutase-1 (SOD1). The disease duration for this family was 18.1 +/- 13.2 (mean +/- S.D.) years, with the age at onset being 39.7 +/- 10.5 years old (mean +/- S.D.). The initial sign was distal weakness of the unilateral lower limb, extending to the lower limb of the other side. A wheel chair became necessary at 9.8 +/- 3.2 years after the onset. Upper limb weakness started at 15.5 +/- 8.9 years following from the onset. An autopsy was performed on a 71-year-old woman of the family with the mutation. Her disease duration was 47 years, and she died of pneumonia. She had no clear upper motor neuron involvement. Bulbar sign and respiratory muscle weakness had developed 2 years before her death. Neuropathological findings showed degeneration of corticospinal tracts, anterior/posterior spinocerebellar tracts, posterior columns, and Clarke's columns. There were few anterior horn cells in the lumbar spinal cord and no Lewy body-like hyaline inclusion bodies in these remaining anterior horn neurons. This is the first autopsy report of FALS with a His46Arg mutation in the SOD1 enzyme.

Pharmacological characterization of the novel γ-secretase modulator AS2715348, a potential therapy for Alzheimer's disease, in rodents and nonhuman primates.

γ-Secretase is the enzyme responsible for the intramembranous proteolysis of various substrates, such as amyloid precursor protein (APP) and Notch. Amyloid-ß peptide 42 (Aß42) is produced through the sequential proteolytic cleavage of APP by ß- and γ-secretase and causes the synaptic dysfunction associated with memory impairment in Alzheimer's disease. Here, we identified a novel cyclohexylamine-derived γ-secretase modulator, {(1R*,2S*,3R*)-3-[(cyclohexylmethyl)(3,3-dimethylbutyl)amino]-2-[4-(trifluoromethyl)phenyl]cyclohexyl}acetic acid (AS2715348), that may inhibit this pathological response. AS2715348 was seen to reduce both cell-free and cellular production of Aß42 without increasing levels of APP ß-carboxyl terminal fragment or inhibiting Notch signaling. Additionally, the compound increased Aß38 production, suggesting a shift of the cleavage site in APP. The inhibitory potency of AS2715348 on endogenous Aß42 production was similar across human, mouse, and rat cells. Oral administration with AS2715348 at 1 mg/kg and greater significantly reduced brain Aß42 levels in rats, and no Notch-related toxicity was observed after 28-day treatment at 100 mg/kg. Further, AS2715348 significantly ameliorated cognitive deficits in APP-transgenic Tg2576 mice. Finally, AS2715348 significantly reduced brain Aß42 levels in cynomolgus monkeys. These findings collectively show the promise for AS2715348 as a potential disease-modifying drug for Alzheimer's disease.

A novel glycine transporter-1 (GlyT1) inhibitor, ASP2535 (4-[3-isopropyl-5-(6-phenyl-3-pyridyl)-4H-1,2,4-triazol-4-yl]-2,1,3-benzoxadiazole), improves cognition in animal models of cognitive impairment in schizophrenia and Alzheimer's disease.

Hypofunction of brain N-methyl-d-aspartate (NMDA) receptors has been implicated in psychiatric disorders such as schizophrenia and Alzheimer's disease. Inhibition of glycine transporter-1 (GlyT1) is expected to increase glycine, a co-agonist of the NMDA receptor and, consequently, to facilitate NMDA receptor function. We have identified ASP2535 (4-[3-isopropyl-5-(6-phenyl-3-pyridyl)-4H-1,2,4-triazol-4-yl]-2,1,3-benzoxadiazole) as a novel GlyT1 inhibitor, and here describe our in vitro and in vivo characterization of this compound. ASP2535 potently inhibited rat GlyT1 (IC(50)=92 nM) with 50-fold selectivity over rat glycine transporter-2 (GlyT2). It showed minimal affinity for many other receptors except for µ-opioid receptors (IC(50)=1.83 µM). Oral administration of ASP2535 dose-dependently inhibited ex vivo [(3)H]-glycine uptake in mouse cortical homogenate, suggesting good brain permeability. This profile was confirmed by pharmacokinetic analysis. We then evaluated the effect of ASP2535 on animal models of cognitive impairment in schizophrenia and Alzheimer's disease. Working memory deficit in MK-801-treated mice and visual learning deficit in neonatally phencyclidine (PCP)-treated mice were both attenuated by ASP2535 (0.3-3mg/kg, p.o. and 0.3-1mg/kg, p.o., respectively). ASP2535 (1-3mg/kg, p.o.) also improved the PCP-induced deficit in prepulse inhibition in rats. Moreover, the working memory deficit in scopolamine-treated mice and the spatial learning deficit in aged rats were both attenuated by ASP2535 (0.1-3mg/kg, p.o. and 0.1mg/kg, p.o., respectively). These studies provide compelling evidence that ASP2535 is a novel and centrally-active GlyT1 inhibitor that can improve cognitive impairment in animal models of schizophrenia and Alzheimer's disease, suggesting that ASP2535 may satisfy currently unmet medical needs for the treatment of these diseases.

Exclusive association and simultaneous appearance of congophilic plaques and AT8-positive dystrophic neurites in Tg2576 mice suggest a mechanism of senile plaque formation and progression of neuritic dystrophy in Alzheimer's disease.

Progression of neuritic dystrophy is a histological hallmark of Alzheimer's disease (AD) in addition to amyloid deposition and neurofibrillary tangle formation. Dystrophic neurites (DNs) are abnormal neurites, and are closely associated with amyloid deposits. To clarify the process of DN formation, we immunohistochemically investigated phosphorylated tau (AT8 and Ser396)-positive DNs and plaques in Tg2576 mice overexpressing human beta-amyloid precursor protein (APP) with the Swedish type mutation (K670N/M671L). AT8-positive DNs were exclusively associated with the Congo red-positive plaques examined, and all Abeta(1-40)-positive plaques appeared to be associated with AT8-positive DNs, whereas there were no AT8-positive DNs with Abeta(1-42)-positive/Abeta(1-40)-negative plaques. Since we have previously shown that Abeta(1-42)-positive plaque precede Abeta(1-40) deposition, the appearance of congophilic structures is also late. Quantitative analyses were performed on AT8-positive DNs that were associated with congophilic plaques in the cerebral cortex and hippocampus (more than 1,000 plaques). The number of congophilic plaques increased dramatically with age. The area of DNs in the cerebral cortex and hippocampus increased 120- and 60-fold from 11-13 to 20.5 months of age, respectively. Interestingly, the mean ratio of DN area to congophilic plaque area in every plaque was unchanged, approximately 10%, through the ages examined. The mean plaque size was stable with age in both the cortex and hippocampus. These data suggest that the formation of AT8-positive DNs is simultaneous with Congo red-positive plaque development, and that the event may be closely related in the pathological progression of AD.