Induction of c-fos gene by mercury chloride in LLC-PK₁ cells

The c-fos, a member of the immediate early genes, has been reported to be expressed in the renal proximal tubule in response to ischemic and toxic injury. In the present study, effects of mercury chloride (HgCl₂) on the expression of c-fos were examined in LLC-PK₁ cells. The reverse transcription polymerase chain reaction (RT-PCR) analysis for the semi- quantification of mRNA showed that the treatment of 20 μM HgCl₂ markedly increased c-fos mRNA levels. The level of c-f os mRNA began to increase after a 30-min exposure, peaked at 1 h and then returned to the control level at 8 h. The HgCl₂-induced c-fos expression was abolished completely by actinomycin-D, indicating it was due to transcriptional activation of the gene. Western blotting immunodetection revealed accumulation of c-Fos protein after 1 h exposure to 20 μM HgCl₂. The cytotoxicity of HgCl₂ as assayed by mitochondrial dehydrogenase activity (MTT conversion) was observed after 18 h exposure but not at 0.5-8 h. Also, the decrease in cell viability was accompanied with DNA fragmentation, which is characteristic of apoptosis. The present results showed that HgCl₂ could induce the early expression of c- fos gene in a renal epithelial cell line.