An orally active catalytic metalloporphyrin protects against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine neurotoxicity in vivo

Parkinson's disease (PD) is an age-related neurodegenerative disease in which the role of reactive oxygen species (ROS) is strongly implicated. The presence of oxidative stress has been detected in human and experimental PD using both direct and indirect indices. Scavenging ROS is, therefore, an important therapeutic avenue for the treatment of PD. Manganic porphyrins are catalytic antioxidants that scavenge a wide range of ROS. In this study, we tested the therapeutic effects of a compound [5,15-bis(methoxycarbonyl)-10,20-bis-trifluoromethyl-porphyrinato manganese (III) chloride (AEOL11207)] belonging to a new generation of lipophilic manganic porphyrins for neuroprotection and oral bioavailability in the mouse 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of parkinsonism. Groups of adult C57BL/6 mice were administered MPTP with varying subcutaneous or oral dosing regimens of AEOL11207. Neurotoxicity was assessed by measurement of striatal dopamine levels and quantification of tyrosine hydroxylase-positive neurons in the substantial nigra pars compacta one week after the first dose of MPTP. Glutathione depletion, lipid peroxidation, and 3-nitrotyrosine (3-NT) formation were measured as indicators of oxidative stress in the ventral midbrain in vivo. AEOL11207 administered either by subcutaneous or oral routes protected against MPTP-induced dopamine depletion in the striatum as well as dopaminergic neuronal loss, glutathione depletion, lipid peroxidation, and 3-NT formation in the ventral midbrain. Neuroprotection correlated with brain metalloporphyrin concentrations. This is the first demonstration of neuroprotection by an orally active catalytic antioxidant in the MPTP mouse model and suggests its potential clinical utility for the treatment of chronic neurodegenerative diseases such as PD.

Pathological gambling in Parkinson's disease

Patients often are in substantial debt before the problem is recognised

Nicotine neuroprotection against nigrostriatal damage: importance of the animal model

Parkinson's disease is a neurodegenerative movement disorder that is characterized by a loss of nigrostriatal dopamine-containing neurons. Unexpectedly, there is a reduced incidence of Parkinson's disease in tobacco users. This finding is important because the identification of the component(s) responsible for this effect could lead to therapeutic strategies to slow down or halt the progression of Parkinson's disease. Results from cell culture models consistently show that nicotine protects against neurotoxicity. However, data from animal models of nigrostriatal damage are conflicting, thus raising questions about a neuroprotective role of nicotine. Accumulating evidence indicates that discrepancies are observed primarily in mouse models of the disease. By contrast, reproducible protection occurs in rat models and in a nonhuman primate parkinsonian model that closely resembles the human disease. These findings highlight the need to use the appropriate animal model and treatment conditions when testing putative neuroprotective agents.

Mitochondrial complex I inhibition in Parkinson's disease: how can curcumin protect mitochondria?

Selective damage of mitochondrial complex I within the dopaminergic neurons of the substantia nigra is the central event during Parkinson disease. Peroxynitrite is one of the important free radicals probably mediating complex I damage. Peroxynitrite inhibits brain complex I mainly by 3-nitrotyrosine and nitrosothiol formation, but how these modifications alter the structure-function relation of complex I is unclear. Curcumin pretreatment protects brain mitochondria against peroxynitrite in vitro by direct detoxification and prevention of 3-nitrotyrosine formation and in vivo by elevation of total cellular glutathione levels. These results suggest a potential therapeutic role for curcumin against nitrosative stress in neurological disorders.

Patient education in Parkinson's disease: Formative evaluation of a standardized programme in seven European countries

OBJECTIVE

To evaluate a newly developed education programme for Parkinson's disease (PD) patients.

METHODS

The programme consisted of eight sessions and aimed at improving knowledge and skills related to self-monitoring, health promotion, stress management, depression, anxiety, social competence, and social support, all with special reference to PD. The programme was formatively evaluated in seven European countries (Spain, Finland, Italy, The Netherlands, United Kingdom, Estonia, Germany) with 151 patients diagnosed with idiopathic PD. The evaluation included patients' ratings of the comprehensibility and feasibility of the programme as well as mood ratings before and after each session. Patients also completed questionnaires at the beginning and end of the programme to explore possible changes in disease-related psychosocial problems, quality of life, and depression.

RESULTS

The programme was feasible to run, and patients were able to understand its elements. Patients reported mood elevations following individual sessions and reduced disease-related psychosocial problems after completing the programme. There were no substantial differences in results between cultures.

CONCLUSION

Patient education appears to have potential as a useful and feasible intervention, complementing medical treatment in PD.

PRACTICE IMPLICATIONS

The present programme will soon be available in seven European languages and can be tested in different health care systems.

Nutritional intervention in brain aging: reducing the effects of inflammation and oxidative stress

It is estimated that by the year 2050 the elderly (aged 65 or older) population will double the population of children (aged 0-14) for the first time in history. The expansion of the elderly population has already taken a toll on health care systems. In order to alleviate the health care costs and increase the quality of living in the aging population, it is crucial to explore methods that may retard or reverse the deleterious effects of aging. Inflammation and oxidative stress play important roles in brain aging. Inflammatory markers, as well as cellular and molecular oxidative damage, increase during normal brain aging. This increase is accompanied by the concomitant decline in cognitive and motor performance in the elderly population, even in the absence of neurodegenerative diseases. Epidemiological studies have shown that consumption of diets rich in antioxidant and anti-inflammatory agents, such as those found in fruits and vegetables, may lower the risk of developing age-related neurodegenerative diseases such as Parkinson's disease and Alzheimer's disease. Research from our laboratory suggests that dietary supplementation with fruit or vegetable extracts can decrease the age-enhanced vulnerability to oxidative stress and inflammation. Additional research suggests that the polyphenolic compounds found in fruits such as blueberries may exert their beneficial effects through signal transduction and neuronal communication. Thus, nutritional intervention may exert therapeutic protection against age-related deficits and neurodegenerative diseases.

Neuroprotective Efficacy of the Peroxisome Proliferator-Activated Receptor δ-Selective Agonists in Vitro and in Vivo

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear receptor superfamily and function as ligand-modulated transcription factors that regulate gene expression in many important biological processes. The PPARdelta subtype has the highest expression in the brain and is postulated to play a major role in neuronal cell function; however, the precise physiological roles of this receptor remain to be elucidated. Herein, we show that the high-affinity PPARdelta agonists L-165041 [4-[3-(4-acetyl-3-hydroxy-2-propylphenoxy)-propoxyl]phenoxy]-acetic acid] and GW501516 [2-methyl4-((4-methyl-2-(4-trifluoromethylphenyl)-1,3-triazol-5-yl)-methylsulfanyl)phenoxy acetic acid] protect against cytotoxin-induced SH-SY5Y cell injury in vitro and both ischemic brain injury and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in vivo. In the SH-SY5Y studies, treatment with L-165041 or GW501516 significantly and concentration-dependently attenuated cell death following thapsigargin, 1-methyl-4-phenylpyridinium, or staurosporine exposure, with the extent of damage correlated with the level of caspase-3 inhibition. In the transient (90 min) middle cerebral artery occlusion model of ischemic brain injury in rats, i.c.v. infusion of L-165041 or GW501516 significantly attenuated the ischemic brain damage measured 24 h after reperfusion. Moreover, the PPARdelta agonists also significantly attenuated MPTP-induced depletion of striatal dopamine and related metabolite contents in mouse brain. These results demonstrate that subtype-selective PPARdelta agonists possess antiapoptotic properties in vitro, which may underlie their potential neuroprotective potential in in vivo experimental models of cerebral ischemia and Parkinson's disease (PD). These findings suggest that PPARdelta agonists could be useful tools for understanding the role of PPARdelta in other neurodegenerative disorders, as well as attractive therapeutic candidates for stroke and neurodegenerative diseases such as PD.

Physical activity and risk of Parkinson's disease: a prospective cohort study

BACKGROUND

Despite the fact that Parkinson's disease is the second most common neurodegenerative disease, little is known about risk factors for the disease. Laboratory experiments indicate that physical activity may have a neuroprotective effect; however, there are few data on whether physical activity is associated with decreased risk of Parkinson's disease.

AIM

To investigate the relationship between physical activity and Parkinson's disease in 10,714 men (mean age, 67.6 years) from the Harvard Alumni Health Study, who were diagnosed as free of self-reported Parkinson's disease in 1988.

METHODS

Physical activity was assessed in 1988 by asking about the daily number of blocks walked and stairs climbed, and participation in sports and recreational activities in the past week. Energy expenditure was then estimated and men were categorised into four groups: < 1000, 1000-1999, 2000-2999 or > or = 3000 kcal/week. In addition, physical activity data were available for three past time points: during college, 1962 or 1966, and 1977. Incident cases of Parkinson's disease occurring after 1988 (n = 101) were identified through a follow-up health questionnaire in 1993 and death certificates obtained until 1997.

RESULTS

In multivariate analyses, the relative risks (RR) for Parkinson's disease associated with < 1000, 1000-1999, 2000-2999 and > or = 3000 kcal/week of physical activity were 1 (referent), 1.15 (95% confidence interval (95% CI) 0.71 to 1.88), 0.92 (0.50 to 1.71) and 0.63 (0.36 to 1.12), respectively; p for trend was 0.12. When walking was examined separately, somewhat lower, but not significant, risks were observed for Parkinson's disease. The multivariate RRs (95% CI) for walking < 5, 5-10, 10-20 and > 20 km/week were 1 (referent), 0.67 (0.37 to 1.23), 0.81 (0.50 to 1.31) and 0.72 (0.39 to 1.34), respectively; p for trend was 0.26. Analyses that considered physical activity at other time points before 1988 did not show any significant associations.

CONCLUSIONS

These data do not strongly support the hypothesis that physical activity lowers the risk of Parkinson's disease. However, as the number of patients with Parkinson's disease in this study was not large, statistical power may have been limited and further large studies are needed to provide additional data.

Chronic Dementing Conditions, Genomics, and New Opportunities for Nursing Interventions

PURPOSE

To (a) provide an overview of chronic dementing conditions; (b) discuss the etiologic and clinical characteristics of Alzheimer disease (AD) and Parkinson disease (PD) within the framework of the family systems genetic illness model; and (c) to explore opportunities to enhance outcomes through the integration of genomics information and technologies into nursing practice.

DESIGN

An integrated review of the literature, including the organizing construct of the family systems genetic illness model.

FINDINGS

AD and PD are both influenced by genetic and environmental factors; in a small percentage of families, gene mutations are the primary etiologic factor. Genetic testing is an option for some families experiencing early-onset, familial disease. Presymptomatic and diagnostic genetic testing have limited clinical utility for the more common late-onset AD and PD.

CONCLUSIONS

The current abilities of healthcare professionals to effectively intervene in people with AD and PD are limited by an incomplete understanding of the biologic basis of these diseases. Advances in genomics research and technology are providing the information and tools necessary to understand the molecular basis of these devastating disorders toward the goal of more specific and effective interventions.

A novel peptide inhibitor targeted to caspase-3 cleavage site of a proapoptotic kinase protein kinase C delta (PKCdelta) protects against dopaminergic neuronal degeneration in Parkinson's disease models

Oxidative stress and apoptosis are considered common mediators of many neurodegenerative disorders including Parkinson's disease (PD). Recently, we identified that PKCdelta, a member of the novel PKC isoform family, is proteolytically activated by caspase-3 to induce apoptosis in experimental models of PD [Eur. J. Neurosci. 18 (6):1387-1401, 2003; Antioxid. Redox Signal. 5 (5):609-620, 2003]. Since caspase-3 cleaves PKCdelta between proline and aspartate residues at the cleavage site 324DIPD327 to activate the kinase, we developed an irreversible and competitive peptide inhibitor, Z-Asp(OMe)-Ile-Pro-Asp(OMe)-FMK (z-DIPD-fmk), to mimic the caspase-3 cleavage site of PKCdelta and tested its efficacy against oxidative stress-induced cell death in PD models. Cotreatment of z-DIPD-fmk with the parkinsonian toxins MPP(+) and 6-OHDA dose dependently attenuated cytotoxicity, caspase-3 activation, and DNA fragmentation in a mesencephalic dopaminergic neuronal cell model (N27 cells). However, z-DIPD-fmk treatment did not block MPP(+)-induced increases in caspase-9 enzyme activity. The z-DIPD-fmk peptide was much more potent (IC50 6 microM) than the most widely used and commercially available caspase-3 inhibitor z-DEVD-fmk (IC50 18 microM). Additionally, z-DIPD-fmk more effectively blocked PKCdelta cleavage and proteolytic activation than the cleavage of another caspase-3 substrate, poly(ADP-ribose) polymerase (PARP). Importantly, the peptide inhibitor z-DIPD-fmk completely rescued TH(+) neurons from MPP(+)- and 6-OHDA-induced toxicity in mouse primary mesencephalic cultures. Collectively, these results demonstrate that the PKCdelta cleavage site is a novel target for development of a neuroprotective therapeutic strategy for PD.

Respiratory Muscle Strength Training: Functional Outcomes versus Plasticity

Respiratory muscle strength training is a paradigm that has been used for numerous years with a variety of populations including but not limited to spinal cord injury, chronic obstructive pulmonary disease, multiple sclerosis, Parkinson's disease, voice disordered, sedentary elderly, and healthy young. The respiratory muscle strength program discussed here is an expiratory muscle strength training and uses a pressure threshold device with a regimented treatment protocol. The primary purpose of the expiratory muscle strength training program is to promote strength in the expiratory muscles. The training protocol occurs five times per day, 5 days a week, and consists of ~15-20 minutes per day of training by the user at home. The device threshold is changed weekly by a clinician to maintain a threshold load of 75% of an individual's maximum expiratory pressure. The threshold setting of the device is always based on the individual's recorded maximum expiratory pressure generated into a digital pressure gauge. Results of 4 weeks of expiratory muscle strength training protocols indicate up to a 50% improvement for healthy subjects, those with multiple sclerosis, and those with spinal cord injury. The potential transfer of expiratory muscle strength to functional outcomes is discussed, as well as how strength-training paradigms may influence cortical plasticity.

PEP-1-SOD fusion protein efficiently protects against paraquat-induced dopaminergic neuron damage in a Parkinson disease mouse model

Parkinson disease (PD) is a common neurodegenerative disorder characterized by the progressive loss of dopaminergic neurons in the substantia nigra (SN). However, the mechanism of the pathology of PD still remains poorly understood. Because the administration of the herbicide paraquat triggers selective dopaminergic neuronal cell death, exposure of mice to this herbicide is one valuable model for studying the pathological aspects of PD. In this study, we investigated the protective effects of PEP-1-SOD in vitro and in vivo under exposure to the herbicide paraquat. The viability of neuronal cells treated with paraquat was markedly increased by transduced PEP-1-SOD. When the PEP-1-SOD fusion protein was injected intraperitoneally into mice, a completely protective effect against dopaminergic neuronal cell death in the SN was observed. This protective effect was synergistically increased when the PEP-1-SOD was cotransduced with Tat-alpha-synuclein. These results suggest that PEP-1-SOD provides a strategy for therapeutic delivery in various human diseases related to reactive oxygen species, including PD.

Peptide model systems for amyloid fiber formation: design strategies and validation methods

The rational understanding of the factors involved in the formation of amyloid deposits in tissue is fundamental to the identification of novel therapeutic strategies to prevent or cure pathological conditions such as Alzheimer's and Parkinson's disease or spongiform encephalopathies. Given the complexity of the molecular events driving protein self-association, a frequent strategy in the field has consisted of designing simplified model systems that facilitate the analysis of the elements that predispose polypeptides toward amyloid formation. In fact, these systems have provided very valuable knowledge on the determinants underlying structural transitions to the polymeric beta-sheet state present in amyloid fibers and more disordered aggregates. In this chapter, we will describe different approaches to obtain and design model systems for amyloidogenesis, as well as the methodologies that are typically used to validate them. We will also show how some of the general principles obtained from these studies can be applied for de novo design purposes and for the sequence-based identification of amyloidogenic stretches in proteins.

Dopaminergic neuroprotection by neurturin-expressing c17.2 neural stem cells in a rat model of Parkinson's disease

Genetically engineered neural stem cell (NSC) lines are promising vectors for the treatment of regenerative diseases, especially Parkinson's disease (PD). Neurturin (NTN), a member of the glial cell line-derived neurotrophic factor-family, has been demonstrated to act specifically on mesencephalic dopaminergic neurons, suggesting its therapeutic potential for PD. Here, we have generated a NTN-secreting c17.2 NSC line and investigated the protective effect of NTN-c17.2 on PD rat models. These NTN-releasing NSCs engrafted and integrated in the host striatum with good success, gave rise to neurons, astrocytes and oligodendrocytes, and maintained stable, high-level NTN expression. In addition, inverse transfer of NTN protein into the substantia nigra (SN) was able to protect dopaminergic neurons from 6-OHDA toxicity. Observation of rotational behavior showed that the NTN group performed significantly better than the Mock group, and the protective effect of NTN lasted for at least 4 months. HPLC tests indicated that the contents of neurotransmitters (e.g. dopamine) in the corpus striatum area of the NTN-c17.2 group and the Mock-c17.2 group were significantly higher than in the PBS group, but there was no significant difference between expression in the NTN-c17.2 and Mock-c17.2 groups. Taken together, our results suggest that transplantation of NTN-secreting NSCs exerted protective on PD rat models.

Neuroprotective effect of BDNF in young and aged 6-OHDA treated rat model of Parkinson disease

Brain derived neurotrophic factor (BDNF) has been shown to exert trophic effects on dopaminergic neurons against 6-hydroxydopamine (6-OHDA) in young rat. Since the degeneration of substantia nigra dopaminergic neurons that occurs in Parkinson's disease is more often than not confined to elderly individuals, it is of interest to determine whether the effects of BDNF against 6 hydroxydopamine (6-OHDA) in young rats can be extended to aged animals. 6-hydroxydopamine was stereotaxically injected into the striatum of young (3-months) and aged (24-months) rats, which were treated two hours earlier with BDNF. 6-OHDA results in almost complete destruction of substantia nigra pars compacta dopaminergic neurons. BDNF injection significantly changed apomorphine induced rotations from 132 +/- 15 to 181 +/- 10, staircase test from 73 +/- 2% to 61 +/- 3%, initiation time from 7 +/- 2 to 12 +/- 1 sec, and disengage time from 80 +/- 7 to 90 +/- 5 sec in young and aged animals, respectively. It is concluded that BDNF causes the limited behavior recovery of striatal DA systems from 6-OHDA toxicity in aged animals.

Mitochondria-targeted peptide antioxidants: novel neuroprotective agents

Increasing evidence suggests that mitochondrial dysfunction and oxidative stress play a crucial role in the majority of neurodegenerative diseases. Mitochondria are a major source of intracellular reactive oxygen species (ROS) and are particularly vulnerable to oxidative stress. Oxidative damage to mitochondria has been shown to impair mitochondrial function and lead to cell death via apoptosis and necrosis. Because dysfunctional mitochondria will produce more ROS, a feed-forward loop is set up whereby ROS-mediated oxidative damage to mitochondria favors more ROS generation, resulting in a vicious cycle. It is now appreciated that reduction of mitochondrial oxidative stress may prevent or slow down the progression of these neurodegenerative disorders. However, if mitochondria are the major source of intracellular ROS and mitochondria are most vulnerable to oxidative damage, then it would be ideal to deliver the antioxidant therapy to mitochondria. This review will summarize the development of a novel class of mitochondria-targeted antioxidants that can protect mitochondria against oxidative stress and prevent neuronal cell death in animal models of stroke, Parkinson's disease, and amyotrophic lateral sclerosis.

Dietary folate, vitamin B12, and vitamin B6 and the risk of Parkinson disease

BACKGROUND

Increased homocysteine levels might accelerate dopaminergic cell death in Parkinson disease (PD), through neurotoxic effects. Higher dietary intakes of folate, vitamin B12, and vitamin B6 (cofactors in homocysteine metabolism) might decrease the risk of PD through decreasing plasma homocysteine. Moreover, vitamin B6 might influence the risk of PD through antioxidant effects unrelated to homocysteine metabolism and through its role in dopamine synthesis.

METHODS

In the Rotterdam Study, a prospective, population-based cohort study of people aged 55 years and older, the authors evaluated the association between dietary intake of folate, vitamin B12, and vitamin B6 and the risk of incident PD among 5,289 participants who were free of dementia and parkinsonism and underwent complete dietary assessment at baseline. PD was assessed through repeated in-person examination and continuous monitoring by computer linkage to medical records. Data were analyzed using Cox proportional hazards regression analysis.

RESULTS

After a mean follow-up of 9.7 years, the authors identified 72 participants with incident PD. Higher dietary intake of vitamin B6 was associated with a significantly decreased risk of PD (hazard ratio per SD, 0.69 [95% CI 0.50 to 0.96]; for highest vs lowest tertile, 0.46 [0.22 to 0.96]). Stratified analyses showed that this association was restricted to smokers. No association was observed for dietary folate and vitamin B(12).

CONCLUSIONS

Dietary vitamin B6 may decrease the risk of Parkinson disease, probably through mechanisms unrelated to homocysteine metabolism.

Coffee and health: a review of recent human research

Coffee is a complex mixture of chemicals that provides significant amounts of chlorogenic acid and caffeine. Unfiltered coffee is a significant source of cafestol and kahweol, which are diterpenes that have been implicated in the cholesterol-raising effects of coffee. The results of epidemiological research suggest that coffee consumption may help prevent several chronic diseases, including type 2 diabetes mellitus, Parkinson's disease and liver disease (cirrhosis and hepatocellular carcinoma). Most prospective cohort studies have not found coffee consumption to be associated with significantly increased cardiovascular disease risk. However, coffee consumption is associated with increases in several cardiovascular disease risk factors, including blood pressure and plasma homocysteine. At present, there is little evidence that coffee consumption increases the risk of cancer. For adults consuming moderate amounts of coffee (3-4 cups/d providing 300-400 mg/d of caffeine), there is little evidence of health risks and some evidence of health benefits. However, some groups, including people with hypertension, children, adolescents, and the elderly, may be more vulnerable to the adverse effects of caffeine. In addition, currently available evidence suggests that it may be prudent for pregnant women to limit coffee consumption to 3 cups/d providing no more than 300 mg/d of caffeine to exclude any increased probability of spontaneous abortion or impaired fetal growth.

Development of 17alpha-estradiol as a neuroprotective therapeutic agent: rationale and results from a phase I clinical study

17alpha-estradiol (17alpha-E2) differs from its isomer, the potent feminizing hormone 17beta-estradiol (17beta-E2), only in the stereochemistry at one carbon, but this is sufficient to render it at least 200-fold less active as a transactivating hormone. Despite its meager hormonal activity, 17alpha-E2 is as potent as 17beta-E2 in protecting a wide variety of cell types, including primary neurons, from a diverse array of lethal and etiologically relevant stressors, including amyloid toxicity, serum withdrawal, oxidative stress, excitotoxicity, and mitochondrial inhibition, among others. Moreover, both estradiol isomers have shown efficacy in animal models of stroke, Alzheimer's disease (AD), and Parkinson's disease (PD). Data from many labs have yielded a mechanistic model in which 17alpha-E2 intercalates into cell membranes, where it terminates lipid peroxidation chain reactions, thereby preserving membrane integrity, and where it in turn is redox cycled by glutathione or by NADPH through enzymatic coupling. Maintaining membrane integrity is critical to mitochondrial function, where loss of impermeability of the inner membrane initiates both necrotic and apoptotic pathways. Thus, by serving as a mitoprotectant, 17alpha-E2 forestalls cell death and could correspondingly provide therapeutic benefit in a host of degenerative diseases, including AD, PD, Friedreich's ataxia, and amyotrophic lateral sclerosis, while at the same time circumventing the common adverse effects elicited by more hormonally active analogues. Positive safety and pharmacokinetic data from a successful phase I clinical study with oral 17alpha-E2 (sodium sulfate conjugate) are presented here, and several options for its future clinical assessment are discussed.

Prevention of onset of Parkinson's disease by in vivo gene transfer of human hepatocyte growth factor in rodent model: a model of gene therapy for Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disorder characterized by the loss of dopaminergic neurons in the substantia nigra (SNi). As neurotrophic factors support the survival and enhance the function of dopaminergic neurons, gene therapy using neurotrophic factors has become the center of interest. Thus, we focused on hepatocyte growth factor (HGF) as a neurotrophic and angiogenic growth factor. At 7 days before injection of 6-hydroxydopamine into the SNi, stereotaxic transfection of human HGF or lacZ plasmid was performed into the unilateral striatum of rats. Expression of human HGF in the injected sites could be detected in rats transfected with HGF plasmid DNA, using immunohistochemical staining. Consistently, human immunoreactive HGF protein could be detected at least up to 12 days after transfection. Interestingly, PD rats transfected with lacZ demonstrated amphetamine-induced rotational asymmetry. However, transfection of HGF plasmid DNA resulted in significant inhibition of abnormal rotation up to 24 weeks in a dose-dependent manner. Over 90% of dopaminergic neurons were lost in PD rats transfected with lacZ, whereas over 70% survived in rats transfected with HGF, as assessed by immunohistochemical staining. Overall, the present study demonstrated that overexpression of HGF prevented neuronal death in a PD rat model, providing a potential novel therapy for PD.

D1 and Functionally Selective Dopamine Agonists as Neuroprotective Agents in Parkinsons Disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder that results in major motor disturbances due primarily to loss of midbrain dopamine neurons. The mainstream treatment has been dopaminergic replacement therapy aimed at symptomatic relief, with the gold standard drug being the dopamine precursor levodopa. The general dogma has been that levodopa works primarily by indirectly activating the D(2) family of dopamine receptors. Recently, a number of direct dopamine agonists that target the D(2) and D(3) dopamine receptors have been used as dopaminergic replacement strategies. Although these direct D(2) and D(3) drugs cause only modest improvement in motor function compared to levodopa, they can delay the initiation of levodopa and can act synergistically with levodopa. In addition, they can delay the onset of levodopa-related motor complications. Recent imaging data also suggest that they may have neuroprotective effects. Whereas D(2)/D(3) agonists have received much attention as several drugs are available for clinical trials and usage, there has been a large body of data showing that the D(1) receptor actually may play a larger role in restoration of normal motor function. This review examines the current use of dopamine D(2)/D(3) agonists in treatment of PD and their potential for providing neuroprotection. Furthermore, we also examine the potential that D(1) agonists might have in neuroprotective actions in the disease progression.

Autotoxicity, methylation and a road to the prevention of Parkinson's disease

Xenobiotic enzymes normally protect against toxins but on occasion can convert protoxins into toxins. N-methylated pyridines (such as the N-methyl-4 phenylpyridinium ion (MPP+)) are well-established dopaminergic toxins. The enzyme nicotinamide N-methyltransferase (NNMT) can covert otherwise harmless pyridines such as 4-phenylpyridine into MPP+ like compounds. This enzyme has recently been shown to be present in the human brain, which is a necessity for neurotoxicity, as charged compounds such as MPP+ cannot cross the blood brain barrier. Moreover, it is present in increased concentration in the brain of patients with Parkinson's disease (PD). This would increase MPP+ like compounds at the same time as decreasing intraneuronal nicotinamide, a neuroprotectant at several levels, thus creating a "multiple hit", as additionally complex 1 of the mitochondrial complex would also be poisoned and starved of its major substrate, nicotinamide adenine dinucleotide (NAD). Thus, PD may be a disease of autointoxication. Xenobiotic enzyme inhibitors of NNMT, with or without dietary modification, would be a novel way to attempt primary prevention of PD.