title: Cytoprotection following endoplasmic reticulum stress protein induction in continuous cell lines.
abstract: Prior induction of an endoplasmic reticulum stress response has been associated with an increased tolerance to cellular toxins in in vitro systems, primarily involving renal and neuronal cells. Reactive intermediates are involved in toxicity in many tissues, therefore, we wished to determine if cytoprotection after induction of an endoplasmic reticulum stress response was a general phenomenon in other cell types. A stress response was induced by tunicamycin in a human hepatocyte cell line (HepG2), a rat hepatocyte cell line (H4IIE), a porcine kidney cell line (LLC-PK1), and a human lymphocyte cell line (K562). Induction of the endoplasmic reticulum stress proteins GRP78, GRP94, calreticulin and protein disulfide isomerase was assessed by immunoblotting. Cytotoxicity was assessed 24 hr after a 3 hr exposure to iodoacetamide, tert-butylhydrogenperoxide, menadione, or sulfamethoxazole hydroxylamine, or after a 2 hr exposure to N-acetyl-p-benzoquinoneimine, the reactive metabolite of acetaminophen. Induction of endoplasmic reticulum stress proteins in LLC-PK1 cells resulted in a 2-6 times increase in the concentration of all the cytotoxins required to cause a 50% decrease in cell viability at 24 hr. In contrast, tunicamycin pretreatment only resulted in a 1.7-times increase for iodo-acetamide in HepG2 cells and a 2.2-times increase for N-acetyl-p-benzoquinoneimine in the H4IIE cells, but had no effect on the other toxins tested. Induction of endoplasmic reticulum stress proteins in K562 cells did not alter susceptibility to any toxins tested. Our results indicate that protection afforded by the induction of an endoplasmic reticulum stress response is dependent on the cell type and may be toxin specific. These results suggest that either the molecular pathways of cell death for individual toxins are different between cell types and toxins, or that the function of endoplasmic reticulum stress proteins are dependent on the cell type.
authors.affiliation: Atlantic Veterinary College, University of Prince Edward Island, Department of Biomedical Sciences, Charlottetown, PE, C1A 4P3, Canada.
authors.forename: Karen
authors.initials: K
authors.lastname: Bedard
authors.forename: Nicole
authors.initials: N
authors.lastname: MacDonald
authors.forename: Jodie
authors.initials: J
authors.lastname: Collins
authors.forename: Alastair
authors.initials: A
authors.lastname: Cribb
mesh_terms: D000818:Animals; D037282:Calreticulin / Q000096:biosynthesis; D002352:Carrier Proteins / Q000096:biosynthesis; D002460:Cell Line; D002470:Cell Survival; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis; D006360:Heat-Shock Proteins / Q000096:biosynthesis*; D006801:Humans; D008565:Membrane Proteins / Q000096:biosynthesis; D018832:Molecular Chaperones / Q000096:biosynthesis; D018384:Oxidative Stress; D019704:Protein Disulfide-Isomerases / Q000096:biosynthesis; D011506:Proteins; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013045:Species Specificity; D013552:Swine; D014415:Tunicamycin / Q000494:pharmacology
chemical_list: D037282:Calreticulin; D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; C051684:GRP78 protein, rat; D018840:HSP70 Heat-Shock Proteins; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D008565:Membrane Proteins; D018832:Molecular Chaperones; D011506:Proteins; D012333:RNA, Messenger; C489110:Steroidogenesis-inducing protein, human; C018551:glucose-regulated proteins; D014415:Tunicamycin; D019704:Protein Disulfide-Isomerases