Epidemiological studies have reported that coffee and/or caffeine consumption may reduce Alzheimer's disease (AD) risk. We found that coffee extracts can similarly protect against b-amyloid peptide (Ab) toxicity in a transgenic Caenorhabditis elegans Alzheimer's disease model. The primary protective component(s) in this model is not caffeine, although caffeine by itself can show moderate protection. Coffee exposure did not decrease Ab transgene expression and did not need to be present during Ab induction to convey protection, suggesting that coffee exposure protection might act by activating a protective pathway. By screening the effects of coffee on a series of transgenic C. elegans stress reporter strains, we identified activation of the skn-1 (Nrf2 in mammals) transcription factor as a potential mechanism of coffee extract protection. Inactivation of skn-1 genetically or by RNAi strongly blocked the protective effects of coffee extract, indicating that activation of the skn-1 pathway was the primary mechanism of coffee protection. Coffee also protected against toxicity resulting from an aggregating form of green fluorescent protein (GFP) in a skn-1-dependent manner. These results suggest that the reported protective effects of coffee in multiple neurodegenerative diseases may result from a general activation of the Nrf2 phase II detoxification pathway.

Accumulation of the β-amyloid peptide (Aβ) is generally believed to be central to the induction of Alzheimer's disease, but the relevant mechanism(s) of toxicity are still unclear. Aβ is also deposited intramuscularly in Inclusion Body Myositis, a severe human myopathy. The intensely studied nematode worm Caenorhabditis elegans can be transgenically engineered to express human Aβ. Depending on the tissue or timing of Aβ expression, transgenic worms can have readily measurable phenotypes that serve as a read-out of Aβ toxicity. For example, transgenic worms with pan-neuronal Aβ expression have defects is associative learning (Dosanjh et al. 2009), while transgenic worms with constitutive muscle-specific expression show a progressive, age-dependent paralysis phenotype (Link, 1995;Cohen et al. 2006). One particularly useful C. elegans model employs a temperature-sensitive mutation in the mRNA surveillance system to engineer temperatureinducible muscle expression of an Aβ transgene, resulting in a reproducible paralysis phenotype upon temperature upshift . Treatments that counter Aβ toxicity in this model [e.g., expression of a protective transgene (Hassan et al. 2009) or exposure to Ginkgo biloba extracts (Wu et al. 2006)] reproducibly alter the rate of paralysis induced by temperature upshift of these transgenic worms. Here we describe our protocol for measuring the rate of paralysis in this transgenic C. elegans model, with particular attention to experimental variables that can influence this measurement. Video LinkThe video component of this article can be found at http://www.jove.com/video/2252/ Protocol 1) Preparing Nematode Growth Media plates for paralysis assay.Paralysis assays are performed on the standard Nematode Growth Media (NGM) plates routinely used for C. elegans propagation and genetics (Stiernagle, 2006). 1. Autoclave the NGM solution containing NaCl, Agar and Peptone in an Erlenmeyer flask and add the appropriate amounts of sterile CaCl 2 , Uracil, Cholesterol, 1M MgSO 4 and 1M KPO 4 . Aliquot 10 mL of liquid NGM into each 60 mm x 15 mm Petri Dish. Allow NGM to solidify overnight at room temperature. 2. If testing for the effects of compounds/extracts, aliquot the extract onto each plate and use a spreader to evenly distribute the extract over the surface of the plate. Allow extract to dry overnight at room temperature. Volumes over 1 mL will require more time to dry. 3. Spot each plate with 250 μL of E. coli strain OP5O grown in LB Media overnight for an optical density of 0.4-0.6. Allow bacteria to dry overnight at room temperature. Relevant variablesThe age of plates has a significant affect on the paralysis assay, as older plates tend to dry out. Use plates poured within one week of paralysis assay. For ideal results, pour plates 3-4 days before initiation of synchronous worm populations [see (2) below]. For any experiment, only use plates poured from the same batch.Altering the size of the lawn (i.e. spotted vs. spread) and/or the type of bacteria will also alter the behavior of the...

Caenorhabditis elegans mutants deleted for TDP-1, an ortholog of the neurodegeneration-associated RNA-binding protein TDP-43, display only mild phenotypes. Nevertheless, transcriptome sequencing revealed that many RNAs were altered in accumulation and/or processing in the mutant. Analysis of these transcriptional abnormalities demonstrates that a primary function of TDP-1 is to limit formation or stability of double-stranded RNA. Specifically, we found that deletion of tdp-1: (1) preferentially alters the accumulation of RNAs with inherent double-stranded structure (dsRNA); (2) increases the accumulation of nuclear dsRNA foci; (3) enhances the frequency of adenosine-to-inosine RNA editing; and (4) dramatically increases the amount of transcripts immunoprecipitable with a dsRNA-specific antibody, including intronic sequences, RNAs with antisense overlap to another transcript, and transposons. We also show that TDP-43 knockdown in human cells results in accumulation of dsRNA, indicating that suppression of dsRNA is a conserved function of TDP-43 in mammals. Altered accumulation of structured RNA may account for some of the previously described molecular phenotypes (e.g., altered splicing) resulting from reduction of TDP-43 function.

BackgroundThe β-amyloid peptide (Aβ) contains a Gly-XXX-Gly-XXX-Gly motif in its C-terminal region that has been proposed to form a "glycine zipper" that drives the formation of toxic Aβ oligomers. We have tested this hypothesis by examining the toxicity of Aβ variants containing substitutions in this motif using a neuronal cell line, primary neurons, and a transgenic C. elegans model.ResultsWe found that a Gly37Leu substitution dramatically reduced Aβ toxicity in all models tested, as measured by cell dysfunction, cell death, synaptic alteration, or tau phosphorylation. We also demonstrated in multiple models that Aβ Gly37Leu is actually anti-toxic, thereby supporting the hypothesis that interference with glycine zipper formation blocks assembly of toxic Aβ oligomers. To test this model rigorously, we engineered second site substitutions in Aβ predicted by the glycine zipper model to compensate for the Gly37Leu substitution and expressed these in C. elegans. We show that these second site substitutions restore in vivo Aβtoxicity, further supporting the glycine zipper model.ConclusionsOur structure/function studies support the view that the glycine zipper motif present in the C-terminal portion of Aβ plays an important role in the formation of toxic Aβ oligomers. Compounds designed to interfere specifically with formation of the glycine zipper could have therapeutic potential.