Peroxidative stress selectively down-regulates the neuronal stress response activated under conditions of endoplasmic reticulum dysfunction.
Oxidative stress has been implicated in mechanisms leading to neuronal cell injury in various pathological states of the brain. Here, we investigated the effect of peroxide exposure on the expression of genes coding for cytoplasmic and endoplasmic reticulum (ER) stress proteins. Primary neuronal cell cultures were exposed to H(2)O(2) for 6 h and mRNA levels of hsp70, grp78, grp94, gadd153 were evaluated by quantitative PCR. In addition, peroxide-induced changes in protein synthesis and cell viability were investigated. Peroxide treatment of cells triggered an almost 12-fold increase in hsp70 mRNA levels, but a significant decrease in grp78, grp94 and gadd153 mRNA levels. To establish whether peroxide exposure blocks the ER-resident stress response, cells were also exposed to thapsigargin (Tg, a specific inhibitor of ER Ca(2+)-ATPase) which has been shown to elicit the ER stress response. Tg exposure induced 7.2-fold, 3.6-fold and 8.8-fold increase in grp78, grp94 and gadd153 mRNA levels, respectively. However, after peroxide pre-exposure, the Tg-induced effect on grp78, grp94 and gadd153 mRNA levels was completely blocked. The results indicate that oxidative damage causes a selective down-regulation of the neuronal stress response activated under conditions of ER dysfunction. This down-regulation was only observed in cultures exposed to peroxide levels which induced severe suppression of protein synthesis and cell injury, implying a causative link between peroxide-induced down-regulation of ER stress response system and development of neuronal cell injury. These observations could have implications for our understanding of the mechanisms underlying neuronal cell injury in pathological states of the brain associated with oxidative damage, including Alzheimer's disease where the neuronal stress response activated under conditions of ER dysfunction has been shown to be down-regulated. Down-regulation of ER stress response may increase the sensitivity of neurones to an otherwise nonlethal form of stress.
Department of Experimental Neurology, Max-Planck-Institute for Neurological Research, Cologne, Germany. Paschen@mpin-koeln.mpg.de
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D000818:Animals; D001921:Brain / Q000166:cytology / Q000502:physiology*; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000502:physiology*; D000091342:Endoplasmic Reticulum Chaperone BiP; D005786:Gene Expression Regulation / Q000187:drug effects*; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D006360:Heat-Shock Proteins / Q000235:genetics*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D007700:Kinetics; D008565:Membrane Proteins / Q000235:genetics; D018832:Molecular Chaperones / Q000235:genetics; D009419:Nerve Tissue Proteins / Q000235:genetics; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D018384:Oxidative Stress / Q000502:physiology*; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects*
D022762:CCAAT-Enhancer-Binding Proteins; D002352:Carrier Proteins; C497251:Ddit3 protein, rat; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; C018551:glucose-regulated proteins; D051742:Transcription Factor CHOP; D006861:Hydrogen Peroxide