Genetic Mechanisms of Coffee Extract Protection in aCaenorhabditis elegansModel of β-Amyloid Peptide Toxicity

Abstract

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.

Copper Reduces A Oligomeric Species and Ameliorates Neuromuscular Synaptic Defects in a C. elegans Model of Inclusion Body Myositis

“…Transgenic strains CL2120 (dvIs14 ϩ mtl-2::GFP (pCL26)]), CL2122 (dvIs15[pPD30.38(unc-54 vector)ϩ mtl-2::GFP(pCL26)]) (Fay et al, 1998ϩpRF4(rol-6(su1006)]) (Link, 1995), CL6176 (smg-1(cc546)I; dvIs19 III;ϩ/nT1(unc d;V);dvIs27 [pAF29(Pmyo-3::A␤42)ϩpRF4]X), and CL6180 (smg-1(cc546)I; dvIs19 III; skn-1(zu67) IV/nT1 (unc d;let-?IV;V); dvIs27[pAF29 (Pmyo-3::A␤42)ϩpRF4]) (Dostal et al, 2010) were a gift from Dr. C. Link, University of Colorado, Boulder, CO.…”

“…These experiments were performed as described by Dostal et al (2010) using the corresponding Escherichia coli from the Ahringer RNAi feeding library. Exposure to the skn-1 RNAi clone caused the treated animals to lay over 99% dead eggs, the expected skn-1 phenotype.…”

“…The SKN-1 transcription factor is not required for copper protection It was recently reported that the induction of the SKN-1 pathway in response to treatment with coffee extract leads to protection in a C. elegans model of A␤ toxicity (Dostal et al, 2010). C. elegans SKN-1 is the functional orthologue of the mammalian protein Nrf2 (nuclear factor-E2-related factor 2), controlling the induction of multiple genes involved in detoxification and antioxidant stress response (Kahn et al, 2008).…”

“…6A), where gst-4 (glutathione S-transferase) is a downstream effector of the SKN-1 phase II detoxification pathway (Kahn et al, 2008). To determine whether loss of SKN-1 can decrease or block the protection given by copper exposure, transgenic C. elegans expressing A␤ were fed with skn-1 RNAi (Dostal et al, 2010). The A␤-induced paralysis in the temperature-sensitive strain (CL4176) is still delayed by copper treatment when skn-1 is knocked down (Fig.…”

“…B, The paralysis delay observed with copper treatment in the temperature-sensitive A␤ strain (CL4176) is not blocked when skn-1 was knockdown using the feeding RNAi protocol. Assays were performedintriplicateusingbetween70and110wormspercondition.C,Temperature-inducibleA␤strainsCL6180[skn-1(zu67)]andits control(CL6176)showthattheparalysisdelayinducedbycoppertreatmentismaintainedintheabsenceofSKN-1.Assayswereperformed as described by Dostal et al (2010). Experiments were done in duplicate using between 60 and 70 worms per strain and condition.…”