Distribution kinetics of 18F-DOPA in weaver mutant mice

In vivo18F-DOPA PET imaging identifies a dopaminergic deficit in a rat model with a G51D α-synuclein mutation

Parkinson's disease (PD) is a neurodegenerative condition with several major hallmarks, including loss of substantia nigra neurons, reduction in striatal dopaminergic function, and formation of α-synuclein-rich Lewy bodies. Mutations in SNCA, encoding for α-synuclein, are a known cause of familial PD, and the G51D mutation causes a particularly aggressive form of the condition. CRISPR/Cas9 technology was used to introduce the G51D mutation into the endogenous rat SNCA gene. SNCA^G51D/+ and SNCA^G51D/G51D rats were born in Mendelian ratios and did not exhibit any severe behavourial defects. L-3,4-dihydroxy-6-¹⁸F-fluorophenylalanine (¹⁸F-DOPA) positron emission tomography (PET) imaging was used to investigate this novel rat model. Wild-type (WT), SNCA^G51D/+ and SNCA^G51D/G51D rats were characterized over the course of ageing (5, 11, and 16 months old) using ¹⁸F-DOPA PET imaging and kinetic modelling. We measured the influx rate constant (K_i) and effective distribution volume ratio (EDVR) of ¹⁸F-DOPA in the striatum relative to the cerebellum in WT, SNCA^G51D/+ and SNCA^G51D/G51D rats. A significant reduction in EDVR was observed in SNCA^G51D/G51D rats at 16 months of age indicative of increased dopamine turnover. Furthermore, we observed a significant asymmetry in EDVR between the left and right striatum in aged SNCA^G51D/G51D rats. The increased and asymmetric dopamine turnover observed in the striatum of aged SNCA^G51D/G51D rats reflects one aspect of prodromal PD, and suggests the presence of compensatory mechanisms. SNCA^G51D rats represent a novel genetic model of PD, and kinetic modelling of ¹⁸F-DOPA PET data has identified a highly relevant early disease phenotype.

Quantitative Rodent Brain Receptor Imaging

Positron emission tomography (PET) is a non-invasive imaging technology employed to describe metabolic, physiological, and biochemical processes in vivo. These include receptor availability, metabolic changes, neurotransmitter release, and alterations of gene expression in the brain. Since the introduction of dedicated small-animal PET systems along with the development of many novel PET imaging probes, the number of PET studies using rats and mice in basic biomedical research tremendously increased over the last decade. This article reviews challenges and advances of quantitative rodent brain imaging to make the readers aware of its physical limitations, as well as to inspire them for its potential applications in preclinical research. In the first section, we briefly discuss the limitations of small-animal PET systems in terms of spatial resolution and sensitivity and point to possible improvements in detector development. In addition, different acquisition and post-processing methods used in rodent PET studies are summarized. We further discuss factors influencing the test-retest variability in small-animal PET studies, e.g., different receptor quantification methodologies which have been mainly translated from human to rodent receptor studies to determine the binding potential and changes of receptor availability and radioligand affinity. We further review different kinetic modeling approaches to obtain quantitative binding data in rodents and PET studies focusing on the quantification of endogenous neurotransmitter release using pharmacological interventions. While several studies have focused on the dopamine system due to the availability of several PET tracers which are sensitive to dopamine release, other neurotransmitter systems have become more and more into focus and are described in this review, as well. We further provide an overview of latest genome engineering technologies, including the CRISPR/Cas9 and DREADD systems that may advance our understanding of brain disorders and function and how imaging has been successfully applied to animal models of human brain disorders. Finally, we review the strengths and opportunities of simultaneous PET/magnetic resonance imaging systems to study drug-receptor interactions and challenges for the translation of PET results from bench to bedside.

Longitudinal imaging of the ageing mouse

Several non-invasive imaging techniques are used to investigate the effect of pathologies and treatments over time in mouse models. Each preclinical in vivo technique provides longitudinal and quantitative measurements of changes in tissues and organs, which are fundamental for the evaluation of alterations in phenotype due to pathologies, interventions and treatments. However, it is still unclear how these imaging modalities can be used to study ageing with mice models. Almost all age related pathologies in mice such as osteoporosis, arthritis, diabetes, cancer, thrombi, dementia, to name a few, can be imaged in vivo by at least one longitudinal imaging modality. These measurements are the basis for quantification of treatment effects in the development phase of a novel treatment prior to its clinical testing. Furthermore, the non-invasive nature of such investigations allows the assessment of different tissue and organ phenotypes in the same animal and over time, providing the opportunity to study the dysfunction of multiple tissues associated with the ageing process. This review paper aims to provide an overview of the applications of the most commonly used in vivo imaging modalities used in mouse studies: micro-computed-tomography, preclinical magnetic-resonance-imaging, preclinical positron-emission-tomography, preclinical single photon emission computed tomography, ultrasound, intravital microscopy, and whole body optical imaging.

Generation and vulnerability of deep cerebellar nuclei neurons in the weaver condition along the anteroposterior and mediolateral axes

Production and death of deep cerebellar nuclei (DCN) neurons were investigated in the weaver condition at appropriate anatomical levels throughout the mediolateral (medial, intermediate and lateral) and rostrocaudal (rostral, middle and caudal) axes of three DCN-cell groups: the fastigial, the interposed and the dentate nuclei. Current results have denoted that the deficit of DCN neurons is always more important in the homozygous weaver than in the heterozygous weaver mice. No loss of neurons was found in the dentate nucleus. In the mediolateral axis, an intranuclear gradient of depletion was observed in the mutant mice; in a given deep nucleus, neurodegeneration was more prominent in the medial pars than in lateral ones. In the rostrocaudal axis, on the other hand, when each deep nucleus was studied and compared as a whole, neuron loss was higher in the fastigial nucleus than in the interposed nucleus, which, in turn, was more important than in the dentate nucleus. These data suggest that, in the weaver condition, an internuclear gradient of neurodegeneration exists. Moreover, neurons located in rostral parts of a given nucleus appear to be more vulnerable than those settled in middle parts and these, in turn, are more than the caudal ones. These results seem to indicate the presence of an intranuclear gradient of depletion. Current autoradiographic results have revealed that, in the rostrocaudal axis, deep neurons are settled in the weaver cerebellum following three neurogenetic gradients. The first of these is internuclear; if each deep nucleus is analyzed and compared as a whole, the fastigial nucleus has more late-generated neurons than the interposed nucleus, and this, in turn, has more than the dentate nucleus. The second gradient is also internuclear; if the proportion of late-born neurons is compared throughout the rostral levels from each deep nucleus, it is observed that proportions increase from the fastigial to the dentate nucleus. A similar picture emerges when the middle and caudal regions are taken into account. The third gradient is intranuclear; in a given deep nucleus, the rostral region always presents more late-produced neurons than the middle region and these, in turn, more than in the caudal level.

Recent progress of imaging agents for Parkinson's disease

Parkinson's disease (PD) is a common progressive, neurodegenerative brain disease that is promoted by mitochondrial dysfunction, oxidative stress, protein aggregation and proteasome dysfunction in the brain. Compared with computer tomography (CT) or magnetic resonance imaging (MRI), non-invasive nuclear radiopharmaceuticals have great significance for the early diagnosis of PD due to their high sensitivity and specificity in atypical and preclinical cases. Based on the development of coordination chemistry and chelator design, radionuclides may be delivered to lesions by attaching to PD-related transporters and receptors, such as dopamine, serotonin, and others. In this review, we comprehensively detailed the current achievements in radionuclide imaging in Parkinson's disease.

Measuring dopaminergic function in the 6-OHDA-lesioned rat: a comparison of PET and microdialysis

BACKGROUND

[18 F]fluorodopa (FDOPA) positron emission tomography (PET) allows assessment of levodopa (LDOPA) metabolism and is widely used to study Parkinson's disease. We examined how [18 F]FDOPA PET-derived kinetic parameters relate the dopamine (DA) and DA metabolite content of extracellular fluid measured by microdialysis to aid in the interpretation of data from both techniques.

METHODS

[18 F]FDOPA PET imaging and microdialysis measurements were performed in unilaterally 6-hydroxydopamine-lesioned rats (n = 8) and normal control rats (n = 3). Microdialysis testing included baseline measurements and measurements following acute administration of LDOPA. PET imaging was also performed using [11C]dihydrotetrabenazine (DTBZ), which is a ligand for the vesicular monoamine transporter marker and allowed assessment of denervation severity.

RESULTS

The different methods provided highly correlated data. Lesioned rats had reduced DA metabolite concentrations ipsilateral to the lesion (p < 0.05 compared to controls), with the concentration being correlated with FDOPA's effective distribution volume ratio (EDVR; r = 0.86, p < 0.01) and DTBZ's binding potential (BPND; r = 0.89, p < 0.01). The DA metabolite concentration in the contralateral striatum of severely (>80%) lesioned rats was lower (p < 0.05) than that of less severely lesioned rats (<80%) and was correlated with the ipsilateral PET measures (r = 0.89, p < 0.01 for BPND) but not with the contralateral PET measures. EDVR and BPND in the contralateral striatum were not different from controls and were not correlated with the denervation severity.

CONCLUSIONS

The demonstrated strong correlations between the PET and microdialysis measures can aid in the interpretation of [18 F]FDOPA-derived kinetic parameters and help compare results from different studies. The contralateral striatum was affected by the lesioning and so cannot always serve as an unaffected control.

Biomarkers in Parkinson's disease (recent update)

Parkinson's disease (PD) is the second most common neurodegenerative disorder mostly affecting the aging population over sixty. Cardinal symptoms including, tremors, muscle rigidity, drooping posture, drooling, walking difficulty, and autonomic symptoms appear when a significant number of nigrostriatal dopaminergic neurons are already destroyed. Hence we need early, sensitive, specific, and economical peripheral and/or central biomarker(s) for the differential diagnosis, prognosis, and treatment of PD. These can be classified as clinical, biochemical, genetic, proteomic, and neuroimaging biomarkers. Novel discoveries of genetic as well as nongenetic biomarkers may be utilized for the personalized treatment of PD during preclinical (premotor) and clinical (motor) stages. Premotor biomarkers including hyper-echogenicity of substantia nigra, olfactory and autonomic dysfunction, depression, hyposmia, deafness, REM sleep disorder, and impulsive behavior may be noticed during preclinical stage. Neuroimaging biomarkers (PET, SPECT, MRI), and neuropsychological deficits can facilitate differential diagnosis. Single-cell profiling of dopaminergic neurons has identified pyridoxal kinase and lysosomal ATPase as biomarker genes for PD prognosis. Promising biomarkers include: fluid biomarkers, neuromelanin antibodies, pathological forms of α-Syn, DJ-1, amyloid β and tau in the CSF, patterns of gene expression, metabolomics, urate, as well as protein profiling in the blood and CSF samples. Reduced brain regional N-acetyl-aspartate is a biomarker for the in vivo assessment of neuronal loss using magnetic resonance spectroscopy and T2 relaxation time with MRI. To confirm PD diagnosis, the PET biomarkers include [(18)F]-DOPA for estimating dopaminergic neurotransmission, [(18)F]dG for mitochondrial bioenergetics, [(18)F]BMS for mitochondrial complex-1, [(11)C](R)-PK11195 for microglial activation, SPECT imaging with (123)Iflupane and βCIT for dopamine transporter, and urinary salsolinol and 8-hydroxy, 2-deoxyguanosine for neuronal loss. This brief review describes the merits and limitations of recently discovered biomarkers and proposes coenzyme Q10, mitochondrial ubiquinone-NADH oxidoreductase, melatonin, α-synculein index, Charnoly body, and metallothioneins as novel biomarkers to confirm PD diagnosis for early and effective treatment of PD.

Applications of positron emission tomography in animal models of neurological and neuropsychiatric disorders

Positron emission tomography (PET) provides dynamic images of the biodistribution of radioactive tracers in the brain. Through application of the principles of compartmental analysis, tracer uptake can be quantified in terms of specific physiological processes such as cerebral blood flow, cerebral metabolic rate, and the availability of receptors in brain. Whereas early PET studies in animal models of brain diseases were hampered by the limited spatial resolution of PET instruments, dedicated small-animal instruments now provide molecular images of rodent brain with resolution approaching 1mm, the theoretic limit of the method. Major applications of PET for brain research have consisted of studies of animal models of neurological disorders, notably Parkinson's disease (PD), Alzheimer's disease (AD), and Huntington's disease (HD), stroke, epilepsy and traumatic brain injury; these studies have particularly benefited from selective neurochemical lesion models (PD), and also transgenic rodent models (AD, HD). Due to their complex and uncertain pathophysiologies, corresponding models of neuropsychiatric disorders have proven more difficult to establish. Historically, there has been an emphasis on PET studies of dopamine transmission, as assessed with a range of tracers targeting dopamine synthesis, plasma membrane transporters, and receptor binding sites. However, notable recent breakthroughs in molecular imaging include the development of greatly improved tracers for subtypes of serotonin, cannabinoid, and metabotropic glutamate receptors, as well as noradrenaline transporters, amyloid-β and neuroinflammatory changes. This article reviews the considerable recent progress in preclinical PET and discusses applications relevant to a number of neurological and neuropsychiatric disorders in humans.

Mouse models in neurological disorders: applications of non-invasive imaging

Neuroimaging techniques represent powerful tools to assess disease-specific cellular, biochemical and molecular processes non-invasively in vivo. Besides providing precise anatomical localisation and quantification, the most exciting advantage of non-invasive imaging techniques is the opportunity to investigate the spatial and temporal dynamics of disease-specific functional and molecular events longitudinally in intact living organisms, so called molecular imaging (MI). Combining neuroimaging technologies with in vivo models of neurological disorders provides unique opportunities to understand the aetiology and pathophysiology of human neurological disorders. In this way, neuroimaging in mouse models of neurological disorders not only can be used for phenotyping specific diseases and monitoring disease progression but also plays an essential role in the development and evaluation of disease-specific treatment approaches. In this way MI is a key technology in translational research, helping to design improved disease models as well as experimental treatment protocols that may afterwards be implemented into clinical routine. The most widely used imaging modalities in animal models to assess in vivo anatomical, functional and molecular events are positron emission tomography (PET), magnetic resonance imaging (MRI) and optical imaging (OI). Here, we review the application of neuroimaging in mouse models of neurodegeneration (Parkinson's disease, PD, and Alzheimer's disease, AD) and brain cancer (glioma).

PET imaging of medullary thyroid carcinoma in MEN2A transgenic mice using 6-[(18)F]F-L-DOPA

PURPOSE

6-[(18)F]Fluoro-3,4-dihydroxy-L-phenylalanine (6-[(18)F]F-L-DOPA) is increasingly used for PET imaging of neuroendocrine tumours. In this study, we investigated the use of 6-[(18)F]F-L-DOPA to detect and to monitor the progression of medullary thyroid carcinoma (MTC) in a genetically engineered mouse model of multiple endocrine neoplasia type 2A (MEN2A).

METHODS

Dynamic [(18)F]FDG and 6-[(18)F]F-L-DOPA small animal PET scans were acquired during 60 or 90 min in 8- to 20-month-old MEN2A transgenic mice. The kinetics of 6-[(18)F]F-L-DOPA, standardized uptake values (SUV) at 60 min and tumour volumes were recorded. The detection of MTCs using PET was confirmed by autopsy and histological analysis.

RESULTS

6-[(18)F]F-L-DOPA performs better than [(18)F]FDG for MTC detection in this transgenic mouse model. Uptake kinetics of 6-[(18)F]F-L-DOPA in MTCs are very different between mice but, in all cases, high contrast could be observed. Furthermore, 6-[(18)F]F-L-DOPA can detect tumours with sizes (1.8 mm(3)) that are near the resolution limit of PET, whereas they were undetectable by autopsy at the macroscopic level.

CONCLUSION

6-[(18)F]F-L-DOPA PET imaging can monitor the progression of MTCs in a genetically engineered mouse model.

SPECT neuroimaging in translational research of CNS disorders

High resolution SPECT imaging is an emerging field and there are only limited studies as yet available in this direction. Still there is continuous effort to achieve better spatial and temporal resolution in order to obtain detailed structural and functional information of different brain regions in small experimental animals. Recently, SPECT imaging system has been used to perform in vivo imaging using specific radioligands to further elucidate the role of dopaminergic, serotonergic, and cholinergic neurotransmission in relation to regional cerebral blood flow in various human CNS disorders and in gene-manipulated mouse models of neurodegeneration. Although in vivo and non-invasive translational research can be performed by high-resolution microPET imaging system, its limited spatial resolution restricts detailed anatomical and functional information of different brain regions involved in disease process. Recently developed NanoSPECT/CT imaging system has a better spatial resolution hence can be used to correlate and confirm microPET imaging data and determine the precise structural and functional anatomy of CNS disorders and their remission. Moreover SPECT imaging system reduces the cost and number of animals and provides detailed information of CNS disorders at the cellular, molecular and genetic level. Furthermore, SPECT system is economical, provides less radiation burden, and can be used to study bio-distribution of newly synthesized radioligands with increased target to non-target ratios, quality control, and clinical applications. It is envisaged that high-resolution SPECT imaging system will further improve in vivo non-invasive translational research on CNS disorders of unknown etiopathogenesis and their treatment in future.

Animal Models of Neurodegenerative Disease: Insights from In vivo Imaging Studies

Animal models have been used extensively to understand the etiology and pathophysiology of human neurodegenerative diseases, and are an essential component in the development of therapeutic interventions for these disorders. In recent years, technical advances in imaging modalities such as positron emission tomography (PET) and magnetic resonance imaging (MRI) have allowed the use of these techniques for the evaluation of functional, neurochemical, and anatomical changes in the brains of animals. Combining animal models of neurodegenerative disorders with neuroimaging provides a powerful tool to follow the disease process, to examine compensatory mechanisms, and to investigate the effects of potential treatments preclinically to derive knowledge that will ultimately inform our clinical decisions. This article reviews the literature on the use of PET and MRI in animal models of Parkinson's disease, Huntington's disease, and Alzheimer's disease, and evaluates the strengths and limitations of brain imaging in animal models of neurodegenerative diseases.

Coenzyme Q(10) provides neuroprotection in iron-induced apoptosis in dopaminergic neurons

The exact molecular mechanism of progressive loss of neuromelanin containing nigrostriatal dopaminergic neurons in Parkinson's disease (PD) remains unknown, yet evidence suggests that iron might play an important role in PD pathology. In this study we have determined the neuroprotective role of coenzyme Q(10) (CoQ(10)) in ironinduced apoptosis in cultured human dopaminergic (SK-N-SH) neurons, in metallothionein gene- manipulated mice, and in alpha-synuclein knockout (alpha-synko) mice with a primary objective to assess a possible therapeutic and anti-inflammatory potential for CoQ(10) in PD. Iron-induced mitochondrial damage and apoptosis were characterized by reactive oxygen species production, increased metallothionein and glutathione synthesis, caspase- 3 activation, NF-kappaB induction, and decreased Bcl-2 expression, without any significant change in Bax expression. Lower concentrations of FeSO4 (1-10 microM) induced perinuclear aggregation of mitochondria, whereas higher concentrations (100-250 microM) induced CoQ(10) depletion, plasma membrane perforations, mitochondrial damage, and nuclear DNA condensation and fragmentation. FeSO(4)-induced deleterious changes were attenuated by pretreatment with CoQ(10) and by deferoxamine, a potent iron chelator, in SK-N-SH cells. 1-Methyl, 4-phenyl, 1,2,3,6- tetrahydropyridine (MPTP)-induced striatal release of free iron, and NF-kappaB expression were significantly increased; whereas ferritin and melanin synthesis were significantly reduced in the substantia nigra pars compacta (SNpc) of MT(dko) mice as compared with control(wt) mice, MT(trans) mice, and alpha-synko mice. CoQ(10) treatment inhibited MPTP-induced NF-kappaB induction in all of the genotypes. These data suggest that glutathione and metallothionein synthesis might be induced as an attempt to combat iron-induced oxidative stress, whereas exogenous administration of CoQ(10) or of metallothionein induction might provide CoQ(10)-mediated neuroprotection in PD.

Metallothioneins 1 and 2 attenuate peroxynitrite-induced oxidative stress in Parkinson disease

We have examined potent peroxynitrite ion (ONOO-) generator 3-morpholinosydnonimine (SIN-1)-induced neurotoxicity in control wild-type (control(wt)) mice, metallothionein double knockout (MT(dko)) mice, metallothionein-transgenic (MT(trans)) mice, and in cultured human dopaminergic (SK-N-SH) neurons to determine the neuroprotective potential of metallothionein against ONOO(-)-induced neurodegeneration in Parkinson disease (PD). SIN-1-induced lipid peroxidation, reactive oxygen species synthesis, caspase-3 activation, and apoptosis were attenuated by metallothionein gene overexpression and augmented by metallothionein gene down-regulation. A progressive nigrostriatal dopaminergic neurodegeneration in weaver mutant (wv/wv) mice was associated with enhanced nitrite ion synthesis, metallothionein down-regulation, and significantly reduced dopamine synthesis and 18F-DOPA uptake as determined by high-resolution micropositron emission tomography neuroimaging. The striatal (18)F-DOPA uptake was significantly higher in MT(trans) mice than in MT(dko) and alpha-synuclein knockout (alpha-Syn(ko)) mice. These observations provide further evidence that nitric oxide synthase activation and ONOO- synthesis may be involved in the etiopathogenesis of PD, and that metallothionein gene induction may provide neuroprotection.

Attenuation of cocaine and methamphetamine neurotoxicity by coenzyme Q10

The neurotoxic effects of cocaine and methamphetamine (METH) were studied in mice brain with a primary objective to determine the neuroprotective potential of coenzyme Q10 (CoQ10) in drug addiction. Repeated treatment of cocaine or METH induced significant reduction in the striatal dopamine and CoQ10 in mice. Cocaine or METH-treated mice exhibited increased thiobarbituric acid reactive substances (TBARs) in the striatum and cerebral cortex without any significant change in the cerebellum. Complex I immunoreactivity was inhibited in both cocaine and METH-treated mice, whereas tyrosine hydroxylase (TH) immunoreactivity was decreased in METH-treated mice and increased in cocaine-treated mice. Neither cocaine nor METH could induce significant change in alpha-synuclein expression at the doses and duration we have used in the present study. CoQ10 treatment attenuated cocaine and METH-induced inhibition in the striatal 18F-DOPA uptake as determined by high-resolution microPET neuroimaging. Hence exogenous administration of CoQ10 may provide neuroprotection in drug addiction.

Complex-1 activity and 18F-DOPA uptake in genetically engineered mouse model of Parkinson's disease and the neuroprotective role of coenzyme Q10

Regional distribution of coenzyme Q10 and mitochondrial complex-1 activity were estimated in the brains of control-(C57BL/6), metallothionein knock out-, metallothionein transgenic-, and homozygous weaver mutant mice; and human dopaminergic (SK-N-SH) cells with a primary objective to determine the neuroprotective potential of coenzyme Q10 in Parkinson's disease. Complex-1 activity as well as coenzyme Q10 were significantly higher in the cerebral cortex as compared to the striatum in all the genotypes examined. Complex-1 activity and coenzyme Q10 were significantly reduced in weaver mutant mice and metallothionein knock out mice, but were significantly increased in metallothionein transgenic mice. The reduced complex-1 activity and 18F-DOPA uptake occurred concomitantly with negligible differences in the coenzyme Q10 between in the cerebral cortex and striatum of weaver mutant mice. Administration of coenzyme Q10 increased complex-1 activity and partially improved motoric performance in weaver mutant mice. Direct exposure of rotenone also reduced coenzyme Q10, complex-1 activity, and mitochondrial membrane potential in SK-N-SH cells. Rotenone-induced down-regulation of complex-1 activity was attenuated by coenzyme Q10 treatment, suggesting that complex-1 may be down regulated due to depletion of coenzyme Q10 in the brain. Therefore, metallothionein-induced coenzyme Q10 synthesis may provide neuroprotection by augmenting mitochondrial complex-1 activity in Parkinson's disease.

Metallothionein-mediated neuroprotection in genetically engineered mouse models of Parkinson's disease

Parkinson's disease is characterized by a progressive loss of dopaminergic neurons in the substantia nigra zona compacta, and in other sub-cortical nuclei associated with a widespread occurrence of Lewy bodies. The cause of cell death in Parkinson's disease is still poorly understood, but a defect in mitochondrial oxidative phosphorylation and enhanced oxidative and nitrative stresses have been proposed. We have studied control(wt) (C57B1/6), metallothionein transgenic (MTtrans), metallothionein double gene knock (MTdko), alpha-synuclein knock out (alpha-syn(ko)), alpha-synuclein-metallothionein triple knock out (alpha-syn-MTtko), weaver mutant (wv/wv) mice, and Ames dwarf mice to examine the role of peroxynitrite in the etiopathogenesis of Parkinson's disease and aging. Although MTdko mice were genetically susceptible to 1, methyl, 4-phenyl, 1,2,3,6-tetrahydropyridine (MPTP) Parkinsonism, they did not exhibit any overt clinical symptoms of neurodegeneration and gross neuropathological changes as observed in wv/wv mice. Progressive neurodegenerative changes were associated with typical Parkinsonism in wv/wv mice. Neurodegenerative changes in wv/wv mice were observed primarily in the striatum, hippocampus and cerebellum. Various hallmarks of apoptosis including caspase-3, TNFalpha, NFkappaB, metallothioneins (MT-1, 2) and complex-1 nitration were increased; whereas glutathione, complex-1, ATP, and Ser(40)-phosphorylation of tyrosine hydroxylase, and striatal 18F-DOPA uptake were reduced in wv/wv mice as compared to other experimental genotypes. Striatal neurons of wv/wv mice exhibited age-dependent increase in dense cored intra-neuronal inclusions, cellular aggregation, proto-oncogenes (c-fos, c-jun, caspase-3, and GAPDH) induction, inter-nucleosomal DNA fragmentation, and neuro-apoptosis. MTtrans and alpha-Syn(ko) mice were genetically resistant to MPTP-Parkinsonism and Ames dwarf mice possessed significantly higher concentrations of striatal coenzyme Q10 and metallothioneins (MT 1, 2) and lived almost 2.5 times longer as compared to control(wt) mice. A potent peroxynitrite ion generator, 3-morpholinosydnonimine (SIN-1)-induced apoptosis was significantly attenuated in MTtrans fetal stem cells. These data are interpreted to suggest that peroxynitrite ions are involved in the etiopathogenesis of Parkinson's disease, and metallothionein-mediated coenzyme Q10 synthesis may provide neuroprotection.