Abstract

The p38 mitogen-activated protein kinase (MAPK) cascade is a cellular signaling pathway that is activated in response to reactive oxygen species. 2,3,S-tris(glutathion-S- yl)hydroquinone (TGHQ), a metabolite ofhydroquinone, causes an increase in the amount of reactive oxygen species in the cell. In renal proximal tubule epithelial (LLC- PKJ cells, oncotic cell death results. In previous studies, the toxicity of TGHQ was established by neutral red assays. In this project, the toxicity of Aatrex, which is a popular herbicide, and two of its synergizers was examined by neutral red. LLC-PKl cells were exposed to various concentrations of Aatrex and the synergizers, also termed resistox compounds. In this project, cells also were transfected with a second p38 MAPK gene. Other cells were transfected with a dominant-negative form of the gene (dnp38 MAPK). Both cell cultures were treated with TGHQ and western blotting was used to study the phosphorylation of proteins associated with the p38 MAPK cascade. These proteins were p38 MAPK, MK-2, and heat shock protein 27 (Hsp27). Aatrex, and its synergizers were most toxic when the atrazine concentration was SOOJLM and resistox 2 and 14 were applied in concentrations of 2SJLM and 38JLM, respectively. Furthermore, resistox 2 appeared to be more toxic than resistox 14. Transfecting a second p38 MAPK gene into LLC-PKl cells appeared to increase the expression of p-p38 MAPK, p-MK-2, and p-Hsp27 in response to TGHQ. Cells with dnp38 MAPK appeared to have reduced expression of these proteins. An immunocytochemistry study showed that Hsp27 is activated through the p38 MAPK pathway and is associated with oncotic cell death.