Cadmium-induced expression of immediate early genes in LLC-PK1 cells.
To identify molecular mechanisms underlying renal cell damage by cadmium, the effect of this heavy metal on the level of immediate early genes (IEGs) transcripts in LLC-PK1 cells was studied. Cadmium chloride (CdCl2) induced the expression of four IEGs examined, but with differing time courses. The level of c-fos mRNA peaked at 30 minutes, and then decreased. The levels of c-jun and c-myc transcripts reached a maximum at one hour, and remained elevated up to four hours. Egr-1 mRNA level peaked at one hour, and returned to the control level by three hours. Experiments with cycloheximide and actinomycin D showed, respectively, that induction of IEGs by cadmium occurred in a protein synthesis-independent and transcriptional activation-dependent manner. Cadmium induction of c-fos mRNA was reduced markedly by the intracellular calcium chelator, bis-(o-aminophenoxy)-ethane-N,N,N',N'-tetraacetic acid tetra(acetoxymethyl)-ester (BAPTA/AM), and was decreased partially by a protein kinase C (PKC) inhibitor, 1-(5-isoquinolinylsulfonyl)-2- methylpiperazine (H-7). These data indicate that IEG induction by cadmium requires intracellular calcium mobilization and occurs in part by a PKC-dependent pathway. Exposure of LLC-PK1 cells to CdCl2 (20 microM for 1 to 24 hr) resulted loss of cell viability and DNA fragmentation, which was indicative of apoptosis.
Matsuoka
M
M
Department of Molecular and Cellular Toxicology, Harvard School of Public Health, Boston, Massachusetts, USA.
Call
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KM
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002104:Cadmium / Q000494:pharmacology*; D002118:Calcium / Q000502:physiology; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D015870:Gene Expression / Q000187:drug effects*; D017781:Genes, Immediate-Early; D016762:Genes, fos; D007425:Intracellular Membranes / Q000378:metabolism; D018374:LLC-PK1 Cells; D009994:Osmolar Concentration; D011493:Protein Kinase C / Q000502:physiology; D012333:RNA, Messenger / Q000378:metabolism; D013552:Swine
D012333:RNA, Messenger; D002104:Cadmium; D003609:Dactinomycin; D003513:Cycloheximide; D011493:Protein Kinase C; D002118:Calcium