2,3,5-tris-(glutathion-S-yl)hydroquinone (TGHQ), a reactive metabolite of the nephrotoxicant hydroquinone, induces the ROS-dependent activation of mitogen activated protein kinases (MAPKs) followed by histone H3 phosphorylation and oncotic cell death in renal proximal tubule epithelial cells (LLC-PK₁). Cell death and histone H3 phosphorylation are attenuated by pharmacological inhibition of p38 MAPK or ERK1/2 pathways. Because TGHQ, but not epidermal growth factor (EGF) induces histone H3 phosphorylation and cell death in LLC-PK₁ cells, we hypothesized that there are differences in the mechanisms by which TGHQ and EGF-induced activation of the EGF receptor (EGFR). We therefore compared the relative ability of TGHQ, H₂O₂ and EGF to activate EGFR and MAPKs, and found that p38 MAPK activation is EGFR independent, while ERK1/2 activation occurs mainly through EGFR activation. TGHQ, H₂O₂ and EGF induce different EGFR tyrosine phosphorylation profiles that likely influence the subsequent differential kinetics of MAPK activation. We next transfected LLC-PK₁ cells with dominant negative p38 MAPK expressing plasmid (pcDNA3-DNp38). TGHQ failed to induce phosphorylation of p38 MAPK and its substrate, MK-2, in pcDNA3-DNp38 transfected cells, indicating loss of function of p38 MAPK. In untransfected, pcDNA3 or pcDNA3-p38 (native) transfected LLC-PK₁ cells, Hsp27 was intensively phosphorylated after TGHQ treatment, whereas in pcDNA3-DNp38 transfected cells, TGHQ failed to induce Hsp27 phosphorylation. Thus, EGFR-independent p38 MAPK and EGFRdependent ERK1/2 activation by TGHQ leads to the activation of two downstream signaling factors: histone H3 and Hsp27 phosphorylation, which have in common the potential ability to remodel chromatin.