hVMAT2: A Target of Individualized Medication for Parkinson's Disease

Vesicular monoamine transporter 2 (VMAT2) is responsible for sequestering cytosolically toxic dopamine into intracellular secretory vesicles. Animal genetic studies have suggested that reduced VMAT2 activity contributes to the genetic etiology of Parkinson's disease (PD), but this role has not been established in humans. Based on human genetic association and meta-analysis, we first confirm the human VMAT2 (hVMAT2 or SLC18A2) promoter as a risk factor for PD in both family and unrelated US white people: marker rs363324 at -11.5 kb in the hVMAT2 promoter is reproducibly associated with PD in a cohort of nuclear families (p = 0.04506 in early-onset PD) and 3 unrelated US white people (meta-analysis p = 0.01879). In SH-SY5Y cells, low activity-associated hVMAT2 promoter confers high methylpiperidinopyrazole iodide cytotoxicity, which is likely attributed to functional polymorphisms bound by nuclear proteins. Interestingly, treatments with the dopamine neuron-protecting agent puerarin upregulates the promoter activity in a haplotype- and cell line-dependent manner. These pharmacogenetic findings suggest that hVMAT2 could be a risk factor and imply it as a target of genetic medications for PD.

Potential neuroprotective properties of epigallocatechin-3-gallate (EGCG)

Neurodegenerative diseases such as Alzheimer's disease (AD) and Parkinson's disease (PD) enforce an overwhelming social and economic burden on society. They are primarily characterized through the accumulation of modified proteins, which further trigger biological responses such as inflammation, oxidative stress, excitotoxicity and modulation of signalling pathways. In a hope for cure, these diseases have been studied extensively over the last decade to successfully develop symptom-oriented therapies. However, so far no definite cure has been found. Therefore, there is a need to identify a class of drug capable of reversing neural damage and preventing further neural death. This review therefore assesses the reliability of the neuroprotective benefits of epigallocatechin-gallate (EGCG) by shedding light on their biological, pharmacological, antioxidant and metal chelation properties, with emphasis on their ability to invoke a range of cellular mechanisms in the brain. It also discusses the possible use of nanotechnology to enhance the neuroprotective benefits of EGCG.

Plasmalogen Augmentation Reverses Striatal Dopamine Loss in MPTP Mice

Plasmalogens are a class of glycerophospholipids shown to play critical roles in membrane structure and function. Decreased plasmalogens are reported in the brain and blood of Parkinson’s disease (PD) patients. The present study investigated the hypothesis that augmenting plasmalogens could protect striatal dopamine neurons that degenerate in response to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment in mice, a PD model. First, in a pre-treatment experiment male mice were treated for 10 days with the docosahexaenoic acid (DHA)-plasmalogen precursor PPI-1011 (10, 50 and 200 mg/kg). On day 5 mice received MPTP and were killed on day 11. Next, in a post-treatment study, male mice were treated with MPTP and then received daily for 5 days PPI-1011 (5, 10 and 50 mg/kg). MPTP treatment reduced serum plasmalogen levels, striatal contents of dopamine (DA) and its metabolites, serotonin, DA transporter (DAT) and vesicular monoamine transporter 2 (VMAT2). Pre-treatment with PPI-1011 (10 and 50 mg/kg) prevented all MPTP-induced effects. Positive correlations were measured between striatal DA contents and serum plasmalogen levels as well as striatal DAT and VMAT2 specific binding. Post-treatment with PPI-1011 prevented all MPTP-induced effects at 50 mg/kg but not at lower doses. Positive correlations were measured between striatal DA contents and serum plasmalogen levels as well as striatal DAT and VMAT2 specific binding in the post-treatment experiment. PPI-1011 treatment (10 days at 5, 10 and 50 mg/kg) of intact mice left unchanged striatal biogenic amine contents. These data demonstrate that treatment with a plasmalogen precursor is capable of protecting striatal dopamine markers in an animal model of PD.

Neuroprotective effect of fucoidan from Turbinaria decurrens in MPTP intoxicated Parkinsonic mice

Fucoidan is one of the dominant sulfated polysaccharide which was extracted from the brown seaweed Turbinaria decurrens. In the behavioral study mice treated with fucoidan showed better response than the MPTP treated mice. Antioxidants and dopamine level has been increased in the fucoidan treated mice when compared to MPTP induced mice. In Immunohistochemistry, the increase of TH positive cells in the fucoidan treated group is correlated with the TH protein levels in substantia nigra and corpus striatum. The increase is greater than the content of dopamine and DOPAC, which may be explained that the dopaminergic terminals are more sensitive to MPTP toxicity and therefore are more severely damaged than the dopaminergic cell bodies. In immunoblotting TH and DAT was used, both the antibodies expression in MPTP was reduced and reversed in other groups. From the results it was conformed that the fucoidan has a neuroprotective effect without any side effects.

[PROTECTIVE ROLE OF MELATONIN IN ETIOLOGY AND COURSE OF PARKINSON'S DISEASE: EXPERIMENTAL EVIDENCE.]

Literature data about participation of melatonin - the main hormone of pineal gland - in the origin and course of Parkinson's disease are reviewed. On the cellular level, melatonin demonstrates neuroprotective activity based on the limitation of oxidative stress, inflammation, and degradation of dopamine in nervous tissue, the attenuation of mitochondrial dysfunction, and the accumulation of alpha-synuclein, which are observed in parkinsonian animals and human patients. Moreover, melatonin is capable of inducing some systemic changes that limit disorganization of circadian rhythm and insomnia. It is suggested that, after extensive placebo controlled and randomized examinations in clinical practice, melatonin may be recommended for complex therapy of Parkinson's disease with obligatory taking into consideration some variable factors.

Neuroimaging of Parkinson's disease: Expanding views

Advances in molecular and structural and functional neuroimaging are rapidly expanding the complexity of neurobiological understanding of Parkinson's disease (PD). This review article begins with an introduction to PD neurobiology as a foundation for interpreting neuroimaging findings that may further lead to more integrated and comprehensive understanding of PD. Diverse areas of PD neuroimaging are then reviewed and summarized, including positron emission tomography, single photon emission computed tomography, magnetic resonance spectroscopy and imaging, transcranial sonography, magnetoencephalography, and multimodal imaging, with focus on human studies published over the last five years. These included studies on differential diagnosis, co-morbidity, genetic and prodromal PD, and treatments from L-DOPA to brain stimulation approaches, transplantation and gene therapies. Overall, neuroimaging has shown that PD is a neurodegenerative disorder involving many neurotransmitters, brain regions, structural and functional connections, and neurocognitive systems. A broad neurobiological understanding of PD will be essential for translational efforts to develop better treatments and preventive strategies. Many questions remain and we conclude with some suggestions for future directions of neuroimaging of PD.

Neuroprotective Effects of Tanshinone I Against 6-OHDA-Induced Oxidative Stress in Cellular and Mouse Model of Parkinson's Disease Through Upregulating Nrf2

In this study, we investigated whether tanshinone I (T-I) has therapeutic effects in cellular and animal model of Parkinson's disease (PD), and explore its possible mechanism. For this purpose, human neuroblastoma SH-SY5Y cells were cultured and exposed to 100 μM 6-hydroxydopamine (6-OHDA) in the absence or presence of T-I (1, 2.5 and 5 μM). The results revealed that 6-OHDA-induced cell death was reduced by T-I pretreatment as measured by MTT assay, lactate dehydrogenase release and flow cytomety analysis of cell apoptosis. The increase in the reactive oxygen species caused by 6-OHDA treatment was also attenuated by T-I in SH-SY5Y cells. T-I pretreatment was also shown to result in an increase in nuclear factor erythroid-2-related factor 2 (Nrf2) protein levels and its transcriptional activity as well as the upregulation of Nrf2-dependent genes encoding the antioxidant enzymes heme oxygenase-1, glutathione cysteine ligase regulatory subunit and glutathione cysteine ligase modulatory subunit in SH-SY5Y cells. Moreover, in the in vivo experiment, T-I treatment significantly attenuated 6-OHDA-induced striatal oxidative stress and ameliorated dopaminergic neurotoxicity in 6-OHDA-lesioned mice, as evidenced by western blot analysis of tyrosine hydroxylase (TH) and TH immunostaining of dopaminergic neurons in the substantia nigra and the striatum. Taken together, the results suggest that T-I may be beneficial for the treatment of neurodegenerative diseases like PD.

Myeloid cell leukemia 1 (Mcl(-1)) protects against 1-methyl-4-phenylpyridinium ion (MPP+) induced apoptosis in Parkinson's disease

The myeloid cell leukemia 1 (Mcl(-1)) is an anti-apoptotic member of the Bcl-2 family, which plays an essential role in protecting cells against apoptosis. The expression pattern and potential roles of Mcl(-1) in Parkinson's diseases (PD) are still unknown. In this study, our results indicated that 1-methyl-4-phenylpyridinium (MPP+) treatment augmented the expression of Mcl(-1) at both messenger RNA (mRNA) and protein levels in a dose-dependent manner in SH-SY5Y cells. Moreover, we observed increased phosphorylation of Elk-1at Ser383 as well as nuclear translocation of Elk-1 in exposure to MPP+ treatment. Importantly, the elevated expression of Mcl(-1) induced by MPP+ was abolished by knockdown of Elk-1. It was also found that inhibition of Mcl(-1) by small RNA transfection exacerbates MPP + -induced LDH release after 48 h incubation. In addition, Hoechst 33,258 nuclear staining results demonstrated that silence of Mcl(-1) induced a significant increase in apoptosis in cells when compared with the control condition. Mechanistically, the levels of cleaved Caspase3 and PARP were elevated in MPP+ treated cells, which was exacerbated by knockdown of Mcl(-1). These findings suggest that Mcl(-1) might be a potential therapeutic target for PD treatment.

Glitazone Treatment and Incidence of Parkinson's Disease among People with Diabetes: A Retrospective Cohort Study

BACKGROUND

Recent in vitro and animal experiments suggest that peroxisome proliferation-activated receptor gamma (PPARɣ) agonist medications, such as antidiabetic glitazone (GTZ) drugs, are neuroprotective in models of Parkinson's disease (PD). These findings have not been tested in humans. We hypothesized that individuals prescribed GTZ drugs would have a lower incidence of PD compared to individuals prescribed other treatments for diabetes.

METHODS AND FINDINGS

Using primary care data from the United Kingdom Clinical Practice Research Datalink (CPRD), we conducted a retrospective cohort study in which individuals with diabetes who were newly prescribed GTZ (GTZ-exposed group) were matched by age, sex, practice, and diabetes treatment stage with up to five individuals prescribed other diabetes treatments (other antidiabetic drug-exposed group). Patients were followed up from 1999 until the first recording of a PD diagnosis, end of observation in the database, or end of the study (1 August 2013). An incidence rate ratio (IRR) was calculated using conditional Poisson regression, adjusted for possible confounders. 44,597 GTZ exposed individuals were matched to 120,373 other antidiabetic users. 175 GTZ-exposed individuals were diagnosed with PD compared to 517 individuals in the other antidiabetic drug-exposed group. The incidence rate (IR) of PD in the GTZ-exposed group was 6.4 per 10,000 patient years compared with 8.8 per 10,000 patient years in those prescribed other antidiabetic treatments (IRR 0.72, 95% confidence interval [CI] 0.60-0.87). Adjustments for potential confounding variables, including smoking, other medications, head injury, and disease severity, had no material impact (fully adjusted IRR 0.75, 0.59-0.94). The risk was reduced in those with current GTZ prescriptions (current GTZ-exposed IRR 0.59, 0.46-0.77) but not reduced among those with past prescriptions (past GTZ-exposed IRR 0.85, 0.65-1.10). Our study only included patients with diabetes who did not have a PD diagnosis when they were first prescribed GTZ, and thus, it cannot establish whether GTZ use prevents or slows the progression of PD.

CONCLUSIONS

In patients with diabetes, a current prescription for GTZ is associated with a reduction in incidence of PD. This suggests PPAR gamma pathways may be a fruitful drug target in PD.

[Pro-health prevention in perimenopausal women with regard to estrogen treatment]

According to the latest demographic forecast in Poland is observed the progressive aging of the population with growing population of perimenopausal women. This is a special time in woman's life, in which there are many metabolic changes, neurovegetative symptoms and mental changes. All of them are connected with decreased concentration of sex hormones. Very important in this period are health behaviors, including healthy lifestyle, regular exercises and proper diet. Highly effective in removing menopausal symptoms is hormone replacement therapy. It also prevents the effects of metabolic disorders. This therapy is primary prevention of cardiovascular diseases and osteoporosis, depression, Alzheimer's and Parkinson's disease and urogenital atrophy. It also has to delay the process of aging. Clinical studies of HERS, WHI and MWS caused extreme caution in the use of hormone replacement therapy and distrust for this therapy between doctors and their patients. It is therefore important to establish priorities for action and individualized therapy, depending on the indications and contraindications for its use.

Lifestyle, family history, and risk of idiopathic Parkinson disease: a large Danish case-control study

The relationship between Parkinson disease (PD) and smoking has been examined in several studies, but little is known about smoking in conjunction with other behaviors and a family history of PD. Using unconditional logistic regression analysis, we studied individual and joint associations of these factors with idiopathic PD among 1,808 Danish patients who were diagnosed in 1996-2009 and matched to 1,876 randomly selected population controls. Although there was a downward trend in duration of smoking, this was not observed for daily tobacco consumption. A moderate intake of caffeine (3.1-5 cups/day) was associated with a lower odds ratio for PD (0.45, 95% confidence interval: 0.34, 0.62), as was a moderate intake of alcohol (3.1-7 units/week) (odds ratio = 0.60, 95% confidence interval: 0.58, 0.84); a higher daily intake did not reduce the odds further. When these behaviors were studied in combination with smoking, the odds ratios were lower than those for each one alone. Compared with never smokers with no family history of PD, never smokers who did have a family history had an odds ratio of 2.81 (95% confidence interval: 1.91, 4.13); for smokers with a family history, the odds ratio was 1.60 (95% confidence interval: 1.15, 2.23). In conclusion, duration of smoking seems to be more important than intensity in the relationship between smoking and idiopathic PD. The finding of lower risk estimates for smoking in combination with caffeine or alcohol requires further confirmation.

Parkinson risk in idiopathic REM sleep behavior disorder: preparing for neuroprotective trials

OBJECTIVE

To precisely delineate clinical risk factors for conversion from idiopathic REM sleep behavior disorder (RBD) to Parkinson disease, dementia with Lewy bodies, and multiple system atrophy, in order to enable practical planning and stratification of neuroprotective trials against neurodegenerative synucleinopathy.

METHODS

In a 10-year prospective cohort, we tested prodromal Parkinson disease markers in 89 patients with idiopathic RBD. With Kaplan-Meier analysis, we calculated risk of neurodegenerative synucleinopathy, and using Cox proportional hazards, tested the ability of prodromal markers to identify patients at higher disease risk. By combining predictive markers, we then designed stratification strategies to optimally select patients for definitive neuroprotective trials.

RESULTS

The risk of defined neurodegenerative synucleinopathy was high: 30% developed disease at 3 years, rising to 66% at 7.5 years. Advanced age (hazard ratio [HR] = 1.07), olfactory loss (HR = 2.8), abnormal color vision (HR = 3.1), subtle motor dysfunction (HR = 3.9), and nonuse of antidepressants (HR = 3.5) identified higher risk of disease conversion. However, mild cognitive impairment (HR = 1.8), depression (HR = 0.63), Parkinson personality, treatment with clonazepam (HR = 1.3) or melatonin (HR = 0.55), autonomic markers, and sex (HR = 1.37) did not clearly predict clinical neurodegeneration. Stratification with prodromal markers increased risk of neurodegenerative disease conversion by 200%, and combining markers allowed sample size reduction in neuroprotective trials by >40%. With a moderately effective agent (HR = 0.5), trials with fewer than 80 subjects per group can demonstrate definitive reductions in neurodegenerative disease.

CONCLUSIONS

Using stratification with simply assessed markers, it is now not only possible, but practical to include patients with RBD in neuroprotective trials against Parkinson disease, multiple system atrophy, and dementia with Lewy bodies.

The sirtuin-2 inhibitor AK7 is neuroprotective in models of Parkinson's disease but not amyotrophic lateral sclerosis and cerebral ischemia

Sirtuin deacetylases regulate diverse cellular pathways and influence disease processes. Our previous studies identified the brain-enriched sirtuin-2 (SIRT2) deacetylase as a potential drug target to counteract neurodegeneration. In the present study, we characterize SIRT2 inhibition activity of the brain-permeable compound AK7 and examine the efficacy of this small molecule in models of Parkinson’s disease, amyotrophic lateral sclerosis and cerebral ischemia. Our results demonstrate that AK7 is neuroprotective in models of Parkinson’s disease; it ameliorates alpha-synuclein toxicity in vitro and prevents 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopamine depletion and dopaminergic neuron loss in vivo. The compound does not show beneficial effects in mouse models of amyotrophic lateral sclerosis and cerebral ischemia. These findings underscore the specificity of protective effects observed here in models of Parkinson’s disease, and previously in Huntington’s disease, and support the development of SIRT2 inhibitors as potential therapeutics for the two neurodegenerative diseases.

A GCase chaperone improves motor function in a mouse model of synucleinopathy

Mutation of the lysosomal hydrolase acid-β-glucosidase (GCase), which leads to reduced GCase activity, is one of the most frequent genetic risk factors for Parkinson's disease (PD) and promotes α-synuclein accumulation in the brain, a hallmark of PD and other synucleinopathies. Whether targeting GCase pharmacologically is a valid therapeutic strategy for sporadic PD in the absence of GCase mutation is unknown. We have investigated whether increasing the stability, trafficking, and activity of wild-type GCase could be beneficial in synucleinopathies by administering the pharmacological chaperone AT2101 (afegostat-tartrate, isofagomine) to mice that overexpress human wild-type α-synuclein (Thy1-aSyn mice). AT2101 administered orally for 4 months to Thy1-aSyn mice improved motor and nonmotor function, abolished microglial inflammatory response in the substantia nigra, reduced α-synuclein immunoreactivity in nigral dopaminergic neurons, and reduced the number of small α-synuclein aggregates, while increasing the number of large α-synuclein aggregates. These data support the further investigation of pharmacological chaperones that target GCase as a therapeutic approach for sporadic PD and other synucleinopathies, even in the absence of glucocerebrosidase mutations.

Zonisamide suppresses endoplasmic reticulum stress-induced neuronal cell damage in vitro and in vivo

Zonisamide has been reported to have protective effects on epilepsy and Parkinson׳s disease and to work via various mechanisms of action, such as inhibition of monoamine oxidase-B and enhancement of tyrosine hydroxylase. Recently, it has been suggested that zonisamide itself shows neuroprotective actions. Therefore, in the present study we investigated the neuroprotective effects of zonisamide against endoplasmic reticulum (ER) stress. We used human neuroblastoma (SH-SY5Y) cells and investigated the protective effects of zonisamide against tunicamycin- and thapsigargin-induced neuronal cell death. In addition, we investigated the effect of zonisamide against 1-methyl-4-phenylpyridinium (MPP⁺)-induced cell death and the mechanism of protection against ER stress. In vivo, we investigated the effect of zonisamide (20 mg/kg, p.o.) in the 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced mouse model of Parkinson׳s disease. Zonisamide not only suppressed MPP⁺-induced cell death, but also inhibited ER stress-induced cell death and suppressed the expression of ER stress-related factors such as C/EBO homologous protein (CHOP) in vivo. Furthermore, zonisamide inhibited the activation of caspase-3 in vitro. These results suggest that zonisamide affected ER stress via caspase-3. We think that ER stress, particularly the mechanism via caspase-3, is involved in part of the neuroprotective effect of zonisamide against the experimental models of Parkinson׳s disease.

Influence of propofol and fentanyl on deep brain stimulation of the subthalamic nucleus

We investigated the effect of propofol and fentanyl on microelectrode recording (MER) and its clinical applicability during subthalamic nucleus (STN) deep brain stimulation (DBS) surgery. We analyzed 8 patients with Parkinson's disease, underwent bilateral STN DBS with MER. Their left sides were done under awake and then their right sides were done with a continuous infusion of propofol and fentanyl under local anesthesia. The electrode position was evaluated by preoperative MRI and postoperative CT. The clinical outcomes were assessed at six months after surgery. We isolated single unit activities from the left and the right side MERs. There was no significant difference in the mean firing rate between the left side MERs (38.7 ± 16.8 spikes/sec, n=78) and the right side MERs (35.5 ± 17.2 spikes/sec, n=66). The bursting pattern of spikes was more frequently observed in the right STN than in the left STN. All the electrode positions were within the STNs on both sides and the off-time Unified Parkinson's Disease Rating Scale part III scores at six months after surgery decreased by 67% of the preoperative level. In this study, a continuous infusion of propofol and fentanyl did not significantly interfere with the MER signals from the STN. The results of this study suggest that propofol and fentanyl can be used for STN DBS in patients with advanced Parkinson's disease improving the overall experience of the patients.

Isolation of the sapogenin from defatted seeds of Camellia oleifera and its neuroprotective effects on dopaminergic neurons

Sasanqua saponin is a major active compound in the defatted seeds of Camellia oleifera but is always discarded without effective utilization. The sapogenin from hydrolysis of sasanqua saponin was purified, and its amination derivative was investigated on its neuroprotective effects, which were evaluated by animal models of Parkinson disease in mice induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). The results showed that the sapogenin and its derivative increased dopamine content in striatum and tyrosine hydroxylase (TH) positive cells in substantia nigra and relieved inflammation and behavioral disorder, but the effect on movement was reversed by dopamine receptor antagonist haloperidol and was not intervened by adenosine receptor antagonist CGS 15943. Molecular simulation showed the interaction between dopamine receptor and the sapogenin or its derivative. It is proven that the sapogenin can protect dopamine neurons through antineuroinflammation and activation of dopamine receptor rather than adenosine receptor, and its amination improves the effects. This research provides the prospective prodrugs for Parkinson disease and a new medicinal application of sasanqua saponin.

A case-control study of the protective effect of alcohol, coffee, and cigarette consumption on Parkinson disease risk: time-since-cessation modifies the effect of tobacco smoking

The aim of this study was to investigate the possible reduced risk of Parkinson Disease (PD) due to coffee, alcohol, and/or cigarette consumption. In addition, we explored the potential effect modification by intensity, duration and time-since-cessation of smoking on the association between cumulative pack-years of cigarette smoking (total smoking) and PD risk. Data of a hospital based case-control study was used including 444 PD patients, diagnosed between 2006 and 2011, and 876 matched controls from 5 hospitals in the Netherlands. A novel modeling method was applied to derive unbiased estimates of the potential modifying effects of smoking intensity, duration, and time-since-cessation by conditioning on total exposure. We observed no reduced risk of PD by alcohol consumption and only a weak inverse association between coffee consumption and PD risk. However, a strong inverse association of total smoking with PD risk was observed (OR=0.27 (95%CI: 0.18-0.42) for never smokers versus highest quartile of tobacco use). The observed protective effect of total smoking was significantly modified by time-since-cessation with a diminishing protective effect after cessation of smoking. No effect modification by intensity or duration of smoking was observed indicating that both intensity and duration have an equal contribution to the reduced PD risk. Understanding the dynamics of the protective effect of smoking on PD risk aids in understanding PD etiology and may contribute to strategies for prevention and treatment.

Preconditioning as a potential strategy for the prevention of Parkinson's disease

Parkinson's disease (PD) is a chronic neurodegenerative movement disorder characterized by the progressive and massive loss of dopaminergic neurons by neuronal apoptosis in the substantia nigra pars compacta and depletion of dopamine in the striatum, which lead to pathological and clinical abnormalities. A numerous of cellular processes including oxidative stress, mitochondrial dysfunction, and accumulation of α-synuclein aggregates are considered to contribute to the pathogenesis of Parkinson's disease. A further understanding of the cellular and molecular mechanisms involved in the pathophysiology of PD is crucial for developing effective diagnostic, preventative, and therapeutic strategies to cure this devastating disorder. Preconditioning (PC) is assumed as a natural adaptive process whereby a subthreshold stimulus can promote protection against a subsequent lethal stimulus in the brain as well as in other tissues that affords robust brain tolerance facing neurodegenerative insults. Multiple lines of evidence have demonstrated that preconditioning as a possible neuroprotective technique may reduce the neural deficits associated with neurodegenerative diseases such as PD. Throughout the last few decades, a lot of efforts have been made to discover the molecular determinants involved in preconditioning-induced protective responses; although, the accurate mechanisms underlying this "tolerance" phenomenon are not fully understood in PD. In this review, we will summarize pathophysiology and current therapeutic approaches in PD and discuss about preconditioning in PD as a potential neuroprotective strategy. Also the role of gene reprogramming and mitochondrial biogenesis involved in the preconditioning-mediated neuroprotective events will be highlighted. Preconditioning may represent a promising therapeutic weapon to combat neurodegeneration.

Dopamine agonists in the treatment of Parkinson’s disease

Dopamine agonists are highly effective as adjunctive therapy to levodopa in advanced Parkinson's disease and have rapidly gained popularity as a monotherapy in the early stages of Parkinson's disease for patients less than 65-70 years old. In the latter case, dopamine agonists are about as effective as levodopa but patients demonstrate a lower tendency to develop motor complications. However, dopamine agonists lose efficacy over time and the number of patients remaining on agonist monotherapy decreases to less than 50% after 3 years of treatment. Thus, after a few years of treatment the majority of patients who started on dopamine agonists will be administered levodopa, in a combined dopaminergic therapy, in order to achieve a better control of motor symptoms.

Promise of pharmacogenomics for drug discovery, treatment and prevention of Parkinson's disease. A perspective

Parkinson's disease (PD) is a progressive neurodegenerative disorder characterized by a heterogeneous array of motor and non-motor features. Anti-PD drugs that are in use target only the motor symptoms, may lose efficacy over time, and can cause serious adverse effects such as dyskinesia and psychosis. There are currently no preventative or disease modifying treatments. All attempts to develop disease modifying drugs have failed. Pharmacogenomics (PGx) has the potential to change the way new drugs are developed and the way drugs are prescribed. By using genetic markers that correlate with, and can therefore predict drug response, clinical trials can be designed to be enriched with individuals who are most likely to benefit from the drug, maximizing drug's efficacy, minimizing its adverse effects, and boosting the odds of successful drug discovery. Clinical application of PGx will help physicians to quickly and accurately determine the right drugs and the right doses for individuals, avoiding the lengthy trial and error approaches and adverse effects. In combination with known protective factors such as nicotine and caffeine, PGx may enable development of personalized methods for PD prevention and, by extension, care.

Neuroprotective potential of silymarin against CNS disorders: insight into the pathways and molecular mechanisms of action

Silymarin, a C25 containing flavonoid from the plant Silybum marianum, has been the gold standard drug to treat liver disorders associated with alcohol consumption, acute and chronic viral hepatitis, and toxin-induced hepatic failures since its discovery in 1960. Apart from the hepatoprotective nature, which is mainly due to its antioxidant and tissue regenerative properties, Silymarin has recently been reported to be a putative neuroprotective agent against many neurologic diseases including Alzheimer's and Parkinson's diseases, and cerebral ischemia. Although the underlying neuroprotective mechanism of Silymarin is believed to be due to its capacity to inhibit oxidative stress in the brain, it also confers additional advantages by influencing pathways such as β-amyloid aggregation, inflammatory mechanisms, cellular apoptotic machinery, and estrogenic receptor mediation. In this review, we have elucidated the possible neuroprotective effects of Silymarin and the underlying molecular events, and suggested future courses of action for its acceptance as a CNS drug for the treatment of neurodegenerative diseases.