title: Methyl-4-phenylpyridinium ion modulates expression of mitochondrial uncoupling proteins 2, 4, and 5 in catecholaminergic (SK-N-SH) cells.
abstract: Methyl-4-phenylpyridinium ion (MPP(+)), a specific dopaminergic neurotoxin, inhibits mitochondrial complex I activity, generates reactive oxygen species (ROS), reduces ATP production, and induces cell death. We explored changes in expression of uncoupling proteins (UCPs 2, 4, and 5) following MPP(+)-induced toxicity in SK-N-SH cells over 72 hr at the transcriptional (quantification of mRNA by real-time RT-PCR) and translational (Western analysis) levels. UCP5 mRNA and protein were markedly up-regulated (1 mM MPP(+) at 72 hr caused a twofold increase, P < 0.01), as was UCP4 mRNA, albeit to a much lesser extent. Surprisingly, UCP2 mRNA levels decreased at 24 hr (P < 0.05) but thereafter significantly increased to greater than control levels at 72 hr (P < 0.05), although UCP2 protein levels were decreased throughout (1 mM MPP(+) at 72 hr caused a reduction of 50%, P < 0.01). The increase in ROS production may be attenuated by UCP4 and UCP5 up-regulation. The consequence of decreased UCP2 levels is unclear, although this may represent an adaptive response to declines in ATP levels, the subsequent increase in mRNA being a response to further increases in oxidative stress.
authors.affiliation: Division of Neurology, University Department of Medicine, University of Hong Kong, Hong Kong, People's Republic of China.
authors.forename: Philip Wing-Lok
authors.initials: PW
authors.lastname: Ho
authors.forename: David Yiu-Leung
authors.initials: DY
authors.lastname: Chan
authors.forename: Ken Hon-Hung
authors.initials: KH
authors.lastname: Kwok
authors.forename: Andrew Chi-Yuen
authors.initials: AC
authors.lastname: Chu
authors.forename: Jessica Wing-Man
authors.initials: JW
authors.lastname: Ho
authors.forename: Michelle Hiu-Wai
authors.initials: MH
authors.lastname: Kung
authors.forename: David Boyer
authors.initials: DB
authors.lastname: Ramsden
authors.forename: Shu-Leong
authors.initials: SL
authors.lastname: Ho
mesh_terms: D015655:1-Methyl-4-phenylpyridinium / Q000633:toxicity*; D045744:Cell Line, Tumor; D004298:Dopamine / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007473:Ion Channels; D026901:Membrane Transport Proteins / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D008928:Mitochondria / Q000187:drug effects* / Q000378:metabolism; D024101:Mitochondrial Proteins / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D000071245:Mitochondrial Uncoupling Proteins; D009419:Nerve Tissue Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D009474:Neurons / Q000187:drug effects* / Q000378:metabolism; D009498:Neurotoxins / Q000633:toxicity*; D012333:RNA, Messenger / Q000032:analysis; D000071246:Uncoupling Protein 2
chemical_list: D007473:Ion Channels; D026901:Membrane Transport Proteins; D024101:Mitochondrial Proteins; D000071245:Mitochondrial Uncoupling Proteins; D009419:Nerve Tissue Proteins; D009498:Neurotoxins; D012333:RNA, Messenger; C116584:SLC25A14 protein, human; C117577:SLC25A27 protein, human; C000604389:UCP2 protein, human; D000071246:Uncoupling Protein 2; D015655:1-Methyl-4-phenylpyridinium; D004298:Dopamine