Genes associated with pro-apoptotic and protective mechanisms are affected differently on exposure of neuronal cell cultures to arsenite. No indication for endoplasmic reticulum stress despite activation of grp78 and gadd153 expression.
The effect of arsenite exposure on cell viability, protein synthesis, energy metabolism and the expression of genes coding for cytoplasmic (hsp70) and endoplasmic reticulum (ER; gadd153, grp78, grp94) stress proteins was investigated in primary neuronal cell cultures. Furthermore, signs of ER stress were evaluated by investigating xbp1 mRNA processing. Arsenite levels of 30 and 100 microM induced severe cell injury. Protein synthesis was reduced to below 20% of control in cultures exposed to 30 and 100 microM arsenite for 1 h, and it remained markedly suppressed until 24 h of exposure. Arsenite induced a transient inhibition of energy metabolism after 1 h of exposure, but energy state recovered completely after 3 h. Arsenite exposure affected the expression and translation of genes coding for HSP70 and GRP78, GRP94, GADD153 to different extents. While hsp70 mRNA levels rose drastically, approximally 550-fold after 6 h exposure, HSP70 protein levels did not change over the first 6 h. On the other hand, gadd153 mRNA levels rose only approximately 14-fold after 6 h exposure, while GADD153 protein levels were markedly increased after 3 and 6 h exposure. HSP70 protein levels were markedly increased and GADD153 protein levels decreased to almost control levels in cultures left in arsenite solution for 24 h, i.e. when only a small fraction of cells had escaped arsenite toxicity. Arsenite exposure of neurons thus induced an imbalance between pro-apoptotic and survival-activating pathways. Despite the marked increase in gadd153 mRNA levels, we did not observe signs of xbp1 processing in arsenite exposed cultures, indicating that arsenite did not produce ER stress.
Mengesdorf
Thorsten
T
Department of Experimental Neurology, Max-Planck-Institute for Neurological Research, Gleuelerstrasse 50, Cologne, Germany.
Althausen
Sonja
S
Paschen
Wulf
W
D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000235:genetics; D018053:Arsenites / Q000633:toxicity*; D001921:Brain / Q000187:drug effects* / Q000378:metabolism / Q000503:physiopathology; D022762:CCAAT-Enhancer-Binding Proteins / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics*; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000235:genetics; D004305:Dose-Response Relationship, Drug; D004721:Endoplasmic Reticulum / Q000187:drug effects* / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D004734:Energy Metabolism / Q000187:drug effects / Q000235:genetics; D005333:Fetus; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones / Q000235:genetics*; D009419:Nerve Tissue Proteins / Q000096:biosynthesis / Q000187:drug effects; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D011930:Reaction Time / Q000187:drug effects / Q000235:genetics; D000071701:Regulatory Factor X Transcription Factors; D013312:Stress, Physiological / Q000139:chemically induced* / Q000235:genetics / Q000378:metabolism; D051742:Transcription Factor CHOP; D014157:Transcription Factors / Q000235:genetics*; D000071717:X-Box Binding Protein 1
D018053:Arsenites; D022762:CCAAT-Enhancer-Binding Proteins; D002352:Carrier Proteins; D004268:DNA-Binding Proteins; C497251:Ddit3 protein, rat; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D000071701:Regulatory Factor X Transcription Factors; D014157:Transcription Factors; D000071717:X-Box Binding Protein 1; C000605545:Xbp1 protein, rat; D051742:Transcription Factor CHOP; C015001:arsenite