Caspase-cleaved transactivation response DNA-binding protein 43 in Parkinson's disease and dementia with Lewy bodies.

BACKGROUND: Transactivation response DNA-binding protein 43 (TDP-43) proteinopathies are classified based upon the extent of modified TDP-43 and include a growing number of neurodegenerative diseases such as amyotrophic lateral sclerosis, frontotemporal lobar degeneration with ubiquitin-immunoreactive, tau-negative inclusions and frontotemporal lobar degeneration with motor neuron disease. OBJECTIVE: The purpose of the study was to examine whether proteolytic modifications of TDP-43 are a relevant finding in Parkinson's disease (PD) and dementia with Lewy bodies (DLB). METHODS: A novel site-directed caspase cleavage antibody, termed TDP caspase cleavage product antibody (TDPccp), was utilized based upon a known caspase 3 cleavage consensus site within TDP-43 at position 219. RESULTS: Application of this antibody to postmortem brain sections from PD and DLB patients revealed the presence of caspase-cleaved TDP-43 in Lewy bodies and Hirano bodies in all cases examined. Colocalization of TDPccp with an antibody to alpha-synuclein (alpha-Syn), which served as a general marker for Lewy bodies, was evident within the substantia nigra in both alpha-synucleinopathies. Interestingly, the TDPccp antibody detected a greater number of Lewy bodies in PD and DLB compared to the alpha-Syn antibody. In addition, a semiquantitative analysis in both diseases confirmed this finding by indicating that the percentage of caspase-cleaved TDP-43 single-labeled Lewy bodies was approximately twice that of alpha-Syn labeling (in DLB 13.4 vs. 5.5%, while in PD 34.6 vs. 17.6%). CONCLUSION: Collectively, these data have identified caspase-cleaved TDP-43 as a primary component of Lewy and Hirano bodies in PD and DLB, and suggest that the TDPccp antibody is an effective marker for the detection of Lewy bodies in these neurodegenerative diseases.

Caspase-cleaved TAR DNA-binding protein-43 in Pick's disease.

The hyperphosphorylation and proteolytic modification of the TAR DNA binding protein-43 (TDP-43) is a key finding in a number of neurodegenerative diseases including frontotemporal dementia with ubiquitin-positive inclusions (FTLD-U), amyotrophic lateral sclerosis (ALS), and most recently Alzheimer's disease (AD). To examine whether proteolytic modifications of TDP-43 is a relevant finding in Pick's disease, we utilized a novel site-directed caspase-cleavage antibody based upon a known caspase-3 cleavage consensus site within TDP-43 at position 219. Application of this antibody, termed TDP caspase-cleavage product (TDPccp) to postmortem Pick's disease brain sections revealed the presence of caspase-cleaved TDP-43 in Pick and Hirano bodies predominantly within region CA1 of the hippocampus. Co-localization of TDPccp with PHF-1, a general marker for Pick bodies, as well as with an antibody to caspase-cleaved tau (TauC3) was evident within the hippocampus. A semi-quantitative analysis indicated that approximately 21% and 79% of the Pick bodies identified in area CA1 contained caspase-cleaved TDP-43 or caspase-cleaved tau, respectively. Of interest was the lack of co-localization of TDPccp with PHF-1 in Pick bodies within the dentate gyrus. Collectively, these data have identified modified TDP-43 as a component of Pick and Hirano bodies that is restricted to area CA1 in Pick's disease. The relative paucity of caspase-cleaved TDP-43 found within Pick bodies in comparison to caspase-cleaved tau suggests that TDP-43 and its modification by caspases is most likely not a contributing factor leading to Pick body formation.

Caspase activation in transgenic mice with Alzheimer-like pathology: results from a pilot study utilizing the caspase inhibitor, Q-VD-OPh.

Despite the wealth of evidence supporting the activation of caspases in Alzheimer's disease (AD), chronic administration of a caspase inhibitor has never been tested in any animal model system. The purpose of the current report was to identify a suitable animal model that displays caspase activation and cleavage of critical proteins associated with AD, and secondly, to undertake a pilot study utilizing the novel caspase inhibitor, quinolyl-valyl-O-methylaspartyl-[-2, 6-difluorophenoxy]-methyl ketone (Q-VD-OPh). Analysis of 12 month-old TgCRND8 mice, which represent an early-onset animal model for AD, indicated the activation of caspase-7 as well as the cleavage of tau and the amyloid precursor protein (APP). Having established that TgCRND8 mice represent a suitable model system to target caspases therapeutically, a prophylactic study was initiated utilizing Q-VD-OPh. Three month-old TgCRND8 mice were injected intraperitoneally three times a week for three months with 10 mg/kg Q-VD-OPh and compared to control mice injected with vehicle. Although there was no apparent effect on extracellular Abeta deposition, chronic treatment with Q-VD-OPh did prevent caspase-7 activation and limited the pathological changes associated with tau, including caspase cleavage. These preliminary findings suggest that further studies examining the utility of Q-VD-OPh as a potential therapeutic compound for the treatment of AD are warranted.