The Neurotoxicity Of Parkinson's Disease Induced By Rotenone/Paraquat And Its Mechanism Involved In Proteins From Mitochondria-associated Membranes

Environmental toxicants are major inducing factors of sporadic Parkinson's disease(PD).As neurotoxins,some pesticides including rotenone(RO)and paraquat(PQ)are closely associated with the risk of Parkinson's disease.Chronic administrations of RO and PQ could cause pathological features of PD;however,the toxic mechanisms of neurodegeneration remain to be determined.Mitochondrial dysfunction is considered as a critical mechanism in the pathogenesis of Parkinson' s disease.So far,the toxic mechanisms of mitochondrial dysfunction induced by these pesticides remain poorly understood.Especially mitochondria-associated membranes(MAMs)and related proteins involved with the toxicity associated with PD need to be further explored.In this study,Caenorhabditis elegans were exposed to 0.5-10.0 ?M rotenone or 0.2-1.6 mM paraquat,in order to induce Parkinsonism characterized with motor deficits,dopaminergic degeneration and a-synuclein aggregation.Then the mitochondrial toxicity mechanism of rotenone and paraquat-induced PD was investigated through the observation of mitochondrial fluorescence and ultrastructure.Using a variety of fluorescently labeled transgenic nematodes and mutant strains,the neurotoxic mechanism about mitochondrial membrane-associated proteins TOM-7,Complex I-V,PINK1,and presenilin were systematically investigated.The main results are as follows:1.Low doses of RO or PQ caused changes of worms'crawling tracks and obvious reductions in mean speed,frequency of body bends and bending wavelength.Both RO and PQ exposure can significantly reduce the expression of tyrosine hydroxylase,lead to degeneration of dopaminergic neurons such as atrophy and disruption neurites.Chronic exposure also caused elevated expression of a-synuclein and other pathological changes in C.elegans.2.Exposure to RO or PQ reduced mitochondrial density in nematodes and result in structural changes in the mitochondria such as appearance of prominent vacuoles and autophagic vesicles,reduction of mitochondrial cristae.In addition,RO or PQ also reduced in the expression of mitochondrial outer membrane protein TOM7 and inner membrane respiratory chain enzyme complex ?,?,and ?.3.Both RO and PQ increased the expression of PINK1 significantly.Mutation of pink-1(ok3538),which is the homologous gene of pink1,resulted in a decreased sensitivity in nematodes respond to RO or PQ exposure.The changes of susceptibility included lower lethality,slighter behavioral and mitochondrial toxicity.4.The mutation of hop-1 reduced the vulnerability of toxicity of RO/PQ,including decreased mortality rates,slight changes in mean speed,body bends or wavelength of crawling behavior and reduced sensitivity of mitochondrial toxicity.These results indicate that:1.RO and PQ can induce similar pathological features of Parkinson's disease including motor deficits of coordination and balance ability,dopaminergic degeneration and abnormal accumulation of ?-synuclein.Both RO and PQ effectively induced the PD model in nematodes.2.Mitochondrial autophagy is a crucial mechanism of the neurotoxicity induced by environmental toxicants.Several proteins in MAMs including TOM-7,Complex ?,? and ? are the key factors involved in the mitochondrial toxicity.These suggest that mitochondrial membrane-associated proteins play an important role in PD neurotoxicity.3.Abnormal expression of both PINK1 and presenilin significantly inhibits the nematode neurotoxicity and reduces the vulnerability to mitochondrial damage.These findings suggest that presenilin and PINK 1 play pivotal roles in the PD-related neurotoxicity through the mechanism involved in mitochondria-associated membranes.In conclusion,the in vivo study revealed the analogousness in mitochondrial mechanisms of parkinsonian toxicity induced by two environmental toxicants:rotenone and paraquat.In addition,these results indicate that several proteins in mitochondria-associated membranes such as TOM-7,Complex ?,? and ?,presenilin and PINK1 play critical roles in the PD-related neurotoxicity.This study provides a scientific basis for further exploration of the environmental etiology of PD,and also presents important data for prevention and treatment of sporadic Parkinson's disease.