title: Effects of salubrinal on cadmium-induced apoptosis in HK-2 human renal proximal tubular cells.
abstract: Cadmium exposure is known to cause endoplasmic reticulum (ER) stress. In our current study, we examined the effects of salubrinal, a selective inhibitor of eukaryotic translation initiation factor 2 subunit α (eIF2α) dephosphorylation, on apoptotic cell death and ER stress-signaling events in HK-2 human renal proximal tubular cells exposed to cadmium chloride (CdCl(2)). Using phase-contrast microscopy and a cell viability assay, we observed that salubrinal suppressed CdCl(2)-induced cellular damage and cell death. Treatment with salubrinal reduced the number of TUNEL-positive cells and the cleavages of caspase-3 and poly(ADP-ribose) polymerase, but not the cleavage of light chain 3B, indicating protection from CdCl(2)-induced apoptosis but not autophagy. Although eIF2α remained phosphorylated after CdCl(2) exposure to salubrinal-treated HK-2 cells, the expression of activating transcription factor 4 (ATF4) and the 78 kDa glucose-regulated protein (GRP78) was not increased. On the other hand, CdCl(2)-induced expression of C/EBP homologous protein (CHOP) was reduced by salubrinal treatment. Expression of ATF4, an upstream regulator of GRP78 and CHOP, appeared to be a prerequisite for full protection by salubrinal against cadmium cytotoxicity, because CdCl(2)-induced cellular damage was not fully suppressed in ATF4-deficient cells. Phosphorylated forms of mitogen-activated protein kinases (MAPKs), including c-Jun NH(2)-terminal kinase (JNK), p38, and extracellular signal-regulated protein kinase (ERK), increased after CdCl(2) exposure, whereas salubrinal suppressed the phosphorylation of JNK and p38 but not ERK. These results suggest that salubrinal protects CdCl(2)-exposed HK-2 cells from apoptosis by suppressing cell death signal transduction pathways.
authors.affiliation: Department of Hygiene and Public Health I, Tokyo Women's Medical University, Japan.
authors.forename: Yuta
authors.initials: Y
authors.lastname: Komoike
authors.forename: Hisako
authors.initials: H
authors.lastname: Inamura
authors.forename: Masato
authors.initials: M
authors.lastname: Matsuoka
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D019256:Cadmium Chloride / Q000633:toxicity*; D002478:Cells, Cultured; D002934:Cinnamates / Q000494:pharmacology*; D004721:Endoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D015852:Eukaryotic Initiation Factor-2 / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D020287:In Situ Nick-End Labeling; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects* / Q000473:pathology; D020928:Mitogen-Activated Protein Kinases / Q000187:drug effects; D010766:Phosphorylation / Q000187:drug effects; D015398:Signal Transduction / Q000187:drug effects; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology
chemical_list: D002934:Cinnamates; D000091342:Endoplasmic Reticulum Chaperone BiP; D015852:Eukaryotic Initiation Factor-2; C000717247:HSPA5 protein, human; C496827:salubrinal; D020928:Mitogen-Activated Protein Kinases; D013890:Thiourea; D019256:Cadmium Chloride