Effects Of Ketamine On C.elegans Models Of Parkinson's Disease

BACKGROUND: Parkinson's disease(PD)is known to be associated with over aggregated ?-synuclein in dopaminergic neurons.This aggregated protein was toxic,it disturbs lipid composition and alters levels of fatty acids and lipid content.Some lipids in the CNS are known to function in neurotransmission.Perturbations in cellular signaling have been reported in virtually every neurodegenerative disease.Spatial and temporal features of cellular signaling are in part controlled by lipid components that can regulate protein location and scaffolding events through a dynamic modulation of membrane microdomains.We carried out a study in building up the association of lipid deposition and ?-synuclein activity to expolore the anti-aging mechanism of ketamine through transgenic and pharmacological Caenorhabditis elegans model of PD.METHODS: Wild-type strain Bristol N2,transgenic strain NL5901(Punc-54::alpha synuclein::YFP+unc-119;expressing human alpha synuclein protein with yellow fluorescent protein [YFP] expression in muscle cells),and pharmacological strain BZ555(Pdat-1::GFP;bright green fluorescent protein [GFP] observable in dopaminergic neuronal soma and processes,and dat-1 encodes a plasma membrane dopamine transporter)were selected to evaluate the anti-aging effects such as motility activities.In addition,?-synuclein protein aggregation,lipid deposition(Nile red stain),and dopaminergic neurodegeneration were performed under the treament of 6-hydroxydopamine(6-OHDA).RESULTS: Ketamine 10 mmol/l significantly improved motility of NL5901 PD worms by 56.44% increasing in bends/minute and 46.42% reducing paralysis rate.Meanwhile,we found that 6-OHDA reduced 74.59%(11.61±3.16 to 2.95±1.88)in the mean Pdat-1::GFP,and ketamine 10 mmol/l restored 6-OHDA induced damage by increasing fluorescence intensity up to 200%(8.94±1.67).In addition,we found that inhibitory effect of ketamine on ?-syn's accumulation correlates with an increase in lipid contents of NL5901.Ketamine 1 and 10 mmol/l enhanced Nile red staining of N2 by 31.9% and 37.7% across the entire treatment of 6-OHDA(1.6 ? 25 mmol/l)(F=21.79,P<0.01).However,ketamine at the same dose highly significantly reduced the lipid deposition of NL5901 by 25.21% and 23.87% across the same range of 6-OHDA treatment(F=25.88,P<0.01).which indicated a specific protective effect of ketamine might due to a direct blockade of ?-syn accumulation and 6-OHDA induced injury rather than simply NMDA antagonism effect.However,in the presence of 6-OHDA,its lipid peroxidation property interfered with ketamine's ability to induce high lipid levels in NL5901.?-syn accumulation in NL5901 seemed to be completely abrogated at 6-OHDA concentrations above 12.5 mmol/l,with more than 3-fold decrease in ?-syn fluorescence intensity seen in both 6-OHDA and ketamine treated groups.We termed 12.5 mmol/l as the tipping point as represented by the shutting down of ?-syn accumulation by 6-OHDA.CONCLUSIONS: Our experiment supplied the first evidence of higher dose 6-OHDA(>12.5 mmol/l)induced changes in lipid contents that correlates with the shutting down of ?-syn accumulation,and the tipping point of these changes is 12.5 mmol/l 6-OHDA.Our results indicated that ketamine has a potential to directly act on ?-syn accumulation and lipid contents rather than a simple NMDA antagonist effect on neuron.Epidemiology study indicated that,while 5?10% of PD cases have a genetic basis,90?95% are defined as sporadic/idiopathic and have unknown etiology,involving a complex interplay of environmental factors and the genome.The value of the concept in the tipping point of interaction between 6-OHDA and ?-syn accumulation in C.elegans may supply a more efficient way in approaching new target of PD interventions.Therapeutic agents that could be analyzed under the interaction between genetic ?-syn accumulation and environmental injury by 6-OHDA.Therefore,further exploration on the lipid-protein interaction between 6-OHDA and ?-syn may lead more efficient achievements in understanding and treating neurodegenerative diseases such as PD in simple living organism such as C.elegans.