Selective activation in the MAPK pathway by Hg(II) in precision-cut rabbit renal cortical slices

The kidneys are the primary organ for the accumulation and toxicity of inorganic mercury. In these studies the molecular response of precision-cut rabbit renal cortical slices to low levels of inorganic mercury was examined. Cortical slices (275 μm) were obtained from 1.0 kg NZW rabbits and exposed to mercuric chloride [Hg(II)] at concentrations of 0.01-10 μM for 2-8 h. Overt cytotoxicity, as assessed by intracellular K⁺ levels, was not observed following exposure to these concentrations of Hg(II). However, an induction of heme-oxygenase-1 (Hsp32) was seen following a 2-h challenge to Hg(II). A dose-dependent induction of the DNA binding activity of the AP-1 transcription factor after 4 h of Hg(II) exposure correlated with a dose- dependent enhancement of c-jun gene expression following 2 h of Hg(II) exposure. Additionally, an increase in phosphorylated c-Jun NH₂-terminal protein kinase (JNK) was observed following 2 h of Hg(II) exposure. These results suggest activation of the mitogen-activated protein (MAP) signal transduction pathway, specifically the c-Jun NH₂-terminal protein kinase (JNK) pathway. No changes were observed, however, in the DNA binding activity of ATF2 and Elk-1, transcription factors involved in both the JNK and p38 pathways of MAP signal transduction, nor in the gene expression of c-myc. This selectivity of alterations in molecular signaling suggests an acute response in signal transduction, specifically activation of the JNK pathway in renal tissue following exposure to nanomolar concentrations of Hg(II).