ABSTRACT
The neuronal ubiquitin/proteasomal pathway has been implicated in the pathogenesis of Alzheimer's disease (AD). We now show that a component of the pathway, ubiquitin C-terminal hydrolase L1 (Uch-L1), is required for normal synaptic and cognitive function. Transduction of Uch-L1 protein fused to the transduction domain of HIV-transactivator protein (TAT) restores normal enzymatic activity and synaptic function both in hippocampal slices treated with oligomeric Abeta and in the APP/PS1 mouse model of AD. Moreover, intraperitoneal injections with the fusion protein improve the retention of contextual learning in APP/PS1 mice over time. The beneficial effect of the Uch-L1 fusion protein is associated with restoration of normal levels of the PKA-regulatory subunit IIalpha, PKA activity, and CREB phosphorylation.
Subject(s)
Alzheimer Disease/physiopathology , Amyloid beta-Protein Precursor/metabolism , Memory/physiology , Recombinant Fusion Proteins/metabolism , Synaptic Transmission/physiology , Ubiquitin Thiolesterase/metabolism , Alzheimer Disease/enzymology , Amyloid beta-Protein Precursor/genetics , Animals , Avoidance Learning , Cyclic AMP Response Element-Binding Protein/metabolism , Cyclic AMP-Dependent Protein Kinases/metabolism , Disease Models, Animal , Excitatory Postsynaptic Potentials/physiology , Fear , Gene Products, tat/genetics , Gene Products, tat/metabolism , Hippocampus/cytology , Hippocampus/metabolism , Humans , In Vitro Techniques , Long-Term Potentiation/physiology , Membrane Proteins/genetics , Membrane Proteins/metabolism , Mice , Mice, Inbred C57BL , Mice, Transgenic , Presenilin-1 , Recombinant Fusion Proteins/genetics , Ubiquitin Thiolesterase/geneticsABSTRACT
Huntington's disease (HD) is an inherited progressive neurological disorder for which there is no effective therapy. It is caused by a CAG/polyglutamine repeat expansion that leads to abnormal protein aggregation and deposition in the brain. Several compounds have been shown to disrupt the aggregation process in vitro, including a number of benzothiazoles. To further explore the therapeutic potential of the benzothiazole aggregation inhibitors, we assessed PGL-135 and riluzole in hippocampal slice cultures derived from the R6/2 mouse, confirming their ability to inhibit aggregation with an EC50 of 40 microM in this system. Preliminary pharmacological work showed that PGL-135 was metabolically unstable, and therefore, we conducted a preclinical trial in the R6/2 mouse with riluzole. At the maximum tolerated dose, we achieved steady-state riluzole levels of 100 microM in brain. However, this was insufficient to inhibit aggregation in vivo and we found no improvement in the disease phenotype.
Subject(s)
Huntington Disease/drug therapy , Neuroprotective Agents/pharmacokinetics , Riluzole/pharmacokinetics , Thiazoles/metabolism , Thiazoles/pharmacology , Animals , Benzothiazoles , Disease Models, Animal , Dose-Response Relationship, Drug , Female , Genotype , Huntington Disease/genetics , Male , Mice , Mice, Inbred C57BL , Mice, Inbred CBA , Mice, Transgenic , Neuroprotective Agents/chemistry , Organ Culture Techniques , Riluzole/chemistry , Thiazoles/chemistryABSTRACT
Synaptic damage and loss are factors that affect the degree of dementia experienced in Alzheimer disease (AD) patients. Multicolor DiOlistic labeling of the hippocampus has been undertaken which allows the full dendritic arbor of targeted neurons to be imaged. Using this labeling technique the neuronal morphology of two transgenic mouse lines (J20 and APP/PS1) expressing mutant forms of the Amyloid Precursor Protein (APP), at various ages, have been visualized and compared to Wild Type (WT) littermate controls. Swollen bulbous dystrophic neurites with loss of spines were apparent in the transgenic animals. Upon quantification, statistically significant reductions in the number of spines and total dendrite area was observed in both transgenic mouse lines at 11 months of age. Similar morphological abnormalities were seen in human AD hippocampal tissue both qualitatively and quantitatively. Immunohistochemistry and DiOlistic labeling was combined so that Abeta plaques were imaged in relation to the dendritic trees. No preferential localization of these abnormal dystrophic neurites was seen in regions with plaques. DiI labeled reative astrocytes were often apparent in close proximity to A beta plaques.
