Para-Phenylenediamine-induces apoptosis via a pathway dependent on PTK-Ras-Raf-JNK activation but independent of the PI3K/Akt pathway in NRK-52E cells

Abstract

para-Phenylenediamine (p-PD) is a potential carcinogen, and widely used in marketed hair dye formulations. In the present study, the role of the protein tyrosine kinase (PTK)/Ras/Raf/c-Jun N-terminal kinase (JNK) and phosphoinositide 3-kinase (PI3k)/protein kinase B (Akt) pathways on the growth of NRK-52E cells was investigated. The results demonstrated that p-PD reduced cell viability in a dose-dependent manner. The cell death due to apoptosis was confirmed by cell cycle analysis and an Annexin-V-fluorescein isothiocyanate binding assay. Subsequent to staining with 2',7'-dichlorofluorescin diacetate, the treated cells demonstrated a significant increase in reactive oxygen species (ROS) generation compared with the controls. The effects of p-PD on the signalling pathways were analysed by western blotting. p-PD-treated cells exhibited an upregulated phospho-stress-activated protein kinase/JNK protein expression level and downregulated Ras and Raf protein expression levels; however, Akt, Bcl-2, Bcl-XL and Bad protein expression levels were not significantly altered compared with the control. In conclusion, p-PD induced apoptosis by a PTK/Ras/Raf/JNK-dependent pathway and was independent of the PI3K/Akt pathway in NRK-52E cells.