title: Mechanisms of MPP⁺-induced PC12 cell apoptosis via reactive oxygen species.
abstract: Apoptosis of dopaminergic neurons in the nigrostriatal projection plays a crucial role in the pathogenesis of Parkinson's disease (PD). Although the detailed mechanisms responsible for dopaminergic neuron loss are still under investigation, oxidative stress is identified as a major contributor for neuronal apoptosis. In the current study, we studied the effects of MPP(+), a substrate that mimics oxidative stress, on neuron-like PC12 cells and the underlying mechanisms. PC12 cells were cultured and treated by 100 μmol/L MPP(+) for 4, 8, 16, 24 and 48 h, respectively. For drug pretreatment, the PC12 cells were incubated with N-acetyl-l-cysteine (NAC, 5 mmol/L), an antioxidant, SP600125 (20 μmol/L) or PD98059 (100 μmol/L), two pharmacological inhibitors of JNK and ERK1/2, for 1 h before addition of MPP(+). Cell apoptosis was measured by flow cytometry. The mRNA expression of Cu(2+)/Zn(2+)-SOD, GSH-Px, Bcl-2 and Bax was detected by RT-PCR. The protein expression of p-ERK1/2 and p-JNK was determined by Western blotting. Our results showed that MPP(+) exposure could induce substantial PC12 cell apoptosis. The pretreatment of SP600125 or PD98059 could effectively reduce the apoptosis rate by reducing the ratio of Bax/Bcl-2 mRNA levels. MPP(+) exposure also induced high level of reactive oxygen species (ROS), marked by dramatic increase of Cu(2+)/Zn(2+)-SOD and GSH-Px mRNA levels. The elevated ROS was strongly associated with the activation of JNK and ERK1/2 signal pathways after MPP(+) exposure, since the pretreatment of NAC significantly reduced the upregulation of p-JNK and p-ERK1/2. Finally, the pretreatment of SP600125, but not PD98059, alleviated the increase of Cu(2+)/Zn(2+)-SOD and GSH-Px mRNAs induced by MPP(+), suggesting that the activation of the JNK signal pathway, but not the ERK1/2 signal pathway, could, in some degree, antagonize the generation of ROS induced by oxidative stress. In conclusion, our results suggest that JNK and ERK1/2 signal pathways, which are activated via ROS, play a crucial role in neuronal apoptosis induced by oxidative stress.
authors.affiliation: Department of Neurology, Huazhong University of Science and Technology, Wuhan, 430022, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Department of Radiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430022, China.
authors.forename: Jing
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Neurology, Huazhong University of Science and Technology, Wuhan, 430022, China.
authors.forename: Yunjian
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Neurology, Huazhong University of Science and Technology, Wuhan, 430022, China. sunshenggang@126.com.
authors.forename: Shenggang
authors.initials: S
authors.lastname: Sun
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D016716:PC12 Cells; D010880:Piperidines / Q000494:pharmacology*; D011720:Pyrazoles / Q000494:pharmacology*; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism*
chemical_list: C524478:1,3-bis(4-hydroxyphenyl)-4-methyl-5-(4-(2-piperidinylethoxy)phenol)-1H-pyrazole; D010880:Piperidines; D011720:Pyrazoles; D017382:Reactive Oxygen Species