title: Apoptosis induced by para-phenylenediamine involves formation of ROS and activation of p38 and JNK in chang liver cells.
abstract: para-Phenylenediamine (p-PD) is a suspected carcinogen, but it has been widely used as a component in permanent hair dyes. In this study, the mechanism of p-PD-induced cell death in normal Chang liver cells was investigated. The results demonstrated that p-PD decreased cell viability in a dose-dependent manner. Cell death via apoptosis was confirmed by enhanced DNA damage and increased cell number in the sub-G1 phase of the cell cycle, using Hoechst 33258 dye staining and flow cytometry analysis. Apoptosis via reactive oxygen species generation was detected by the dichlorofluorescin diacetate staining method. Mitogen-activated protein kinase (MAPK) activation was assessed by western blot analysis and revealed that p-PD activated not only stress-activated protein kinase (SAPK)/c-Jun N-terminal kinases (JNK) and p38 MAPK but also extracellular signal-regulated kinase (ERK). Cytotoxicity and apoptosis induced by p-PD were markedly enhanced by ERK activation and selectively inhibited by ERK inhibitor PD98059, thus indicating a negative role of ERK. In contrast, inhibition of p38 MAPK activity with the p38-specific inhibitor SB203580 moderately inhibited cytotoxicity and apoptosis induction by p-PD. Similarly, SP600125, an inhibitor of SAPK/JNK, moderately inhibited cytotoxicity and apoptosis induced by p-PD, thus implying that p38 MAPK and SAPK/JNK had a partial role in p-PD-induced apoptosis. Western blot analysis revealed that p-PD significantly increased phosphorylation of p38 and SAPK/JNK and decreased phosphorylation of ERK. In conclusion, the results demonstrated that SAPK/JNK and p38 cooperatively participate in apoptosis induced by p-PD and that a decreased ERK signal contributes to growth inhibition or apoptosis.
authors.affiliation: Department of Human Biology, School of Medicine, International Medical University, No. 126, Jalan 19/155B, Bukit Jalil, 57000, Kuala Lumpur, Malaysia.
authors.forename: Soi Moi
authors.initials: SM
authors.lastname: Chye
authors.forename: Yee Lian
authors.initials: YL
authors.lastname: Tiong
authors.forename: Wai Kien
authors.initials: WK
authors.lastname: Yip
authors.forename: Rhun Yian
authors.initials: RY
authors.lastname: Koh
authors.forename: Yi Won
authors.initials: YW
authors.lastname: Len
authors.forename: Heng Fong
authors.initials: HF
authors.lastname: Seow
authors.forename: Khuen Yen
authors.initials: KY
authors.lastname: Ng
authors.forename: De Alwis
authors.initials: de A
authors.lastname: Ranjit
authors.forename: Ssu Ching
authors.initials: SC
authors.lastname: Chen
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D002460:Cell Line; D004789:Enzyme Activation; D006801:Humans; D007093:Imidazoles / Q000494:pharmacology; D008099:Liver / Q000166:cytology / Q000187:drug effects* / Q000201:enzymology; D048670:MAP Kinase Kinase 4 / Q000378:metabolism*; D010655:Phenylenediamines / Q000494:pharmacology*; D010766:Phosphorylation; D011725:Pyridines / Q000494:pharmacology; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*
chemical_list: D007093:Imidazoles; D010655:Phenylenediamines; D011725:Pyridines; D048051:p38 Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; C093642:SB 203580; C029728:4-phenylenediamine