title: Impaired mitochondrial energy metabolism and neuronal apoptotic cell death after chronic dichlorvos (OP) exposure in rat brain.
abstract: The present study elucidates a possible mechanism by which chronic organophosphate exposure (dichlorvos 6 mg/kg bw, s.c. for 12 weeks) causes neuronal degeneration. Mitochondria, as a primary site of cellular energy generation and oxygen consumption represent itself a likely target for organophosphate poisoning. Therefore, the objective of the current study was planned with an aim to investigate the effect of chronic dichlorvos exposure on mitochondrial calcium uptake, oxidative stress generation and its implication in the induction of neuronal apoptosis in rodent model. Mitochondrial preparation from dichlorvos (DDVP) treated rat brain demonstrated significant increase in mitochondrial Ca(2+) uptake (644.2 nmol/mg protein). Our results indicated decreased mitochondrial electron transfer activities of cytochrome oxidase (complex IV) along with altered mitochondrial complex I, and complex II activity, which might have resulted from elevated mitochondrial calcium uptake. The alterations in the mitochondrial calcium uptake and mitochondrial electron transfer enzyme activities in turn might have caused an increase in malondialdehyde, protein carbonyl and 8-hydroxydeoxyguanosine formation as a result of enhanced lipid peroxidation, and as well as protein and mtDNA oxidation. All this could have been because of enhanced oxidative stress, decreased GSH levels and also decreased Mn-SOD activity in the mitochondria isolated from dichlorvos treated rat brain. Thus, chronic organophosphate exposure has the potential to disrupt cellular antioxidant defense system which in turn triggers the release of cytochrome c from mitochondria to cytosol as well as caspase-3 activation in dichlorvos treated rat brain as revealed by immunoblotting experiments. Low-level long-term organophosphate exposure finally resulted in oligonucleosomal DNA fragmentation, a hallmark of apoptosis. These studies provide an evidence of impaired mitochondrial bioenergetics and apoptotic neuronal degeneration after chronic low-level exposure to dichlorvos.
authors.affiliation: Department of Biochemistry, Postgraduate Institute of Medical Education and Research, Chandigarh 160012, India.
authors.forename: Pushpinder
authors.initials: P
authors.lastname: Kaur
authors.forename: Bishan
authors.initials: B
authors.lastname: Radotra
authors.forename: Ranjana W
authors.initials: RW
authors.lastname: Minz
authors.forename: K D
authors.initials: KD
authors.lastname: Gill
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001921:Brain / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism / Q000473:pathology; D002118:Calcium / Q000378:metabolism; D053148:Caspase 3 / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000187:drug effects / Q000378:metabolism; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000378:metabolism; D004006:Dichlorvos / Q000633:toxicity*; D004305:Dose-Response Relationship, Drug; D042967:Electron Transport Complex I / Q000378:metabolism; D042963:Electron Transport Complex II / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D004734:Energy Metabolism / Q000187:drug effects*; D004789:Enzyme Activation; D005978:Glutathione / Q000378:metabolism; D007306:Insecticides / Q000633:toxicity*; D015227:Lipid Peroxidation / Q000187:drug effects; D008297:Male; D008928:Mitochondria / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D009410:Nerve Degeneration / Q000139:chemically induced* / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D050050:Protein Carbonylation / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D017382:Reactive Oxygen Species / Q000378:metabolism; D013482:Superoxide Dismutase / Q000378:metabolism; D013997:Time Factors
chemical_list: D004272:DNA, Mitochondrial; D007306:Insecticides; D017382:Reactive Oxygen Species; D004006:Dichlorvos; D000080242:8-Hydroxy-2'-Deoxyguanosine; D045304:Cytochromes c; D013482:Superoxide Dismutase; D042963:Electron Transport Complex II; D003576:Electron Transport Complex IV; C505410:Casp3 protein, rat; D053148:Caspase 3; D042967:Electron Transport Complex I; D003849:Deoxyguanosine; D005978:Glutathione; D002118:Calcium