Progress in neuroprotection in Parkinson's disease

Insights into Advanced Neurological Dysfunction Mechanisms Following DBS Surgery in Parkinson's Patients: Neuroinflammation and Pyroptosis

Parkinson's disease is a severe neurodegenerative disorder. Currently, deep brain electrical stimulation (DBS) is the first line of surgical treatment. However, serious neurological impairments such as speech disorders, disturbances of consciousness, and depression after surgery limit the efficacy of treatment. In this review, we summarize the recent experimental and clinical studies that have explored the possible causes of neurological deficits after DBS. Furthermore, we tried to identify clues from oxidative stress and pathological changes in patients that could lead to the activation of microglia and astrocytes in DBS surgical injury. Notably, reliable evidence supports the idea that neuroinflammation is caused by microglia and astrocytes, which may contribute to caspase-1 pathway-mediated neuronal pyroptosis. Finally, existing drugs and treatments may partially ameliorate the loss of neurological function in patients following DBS surgery by exerting neuroprotective effects.

Anti-inflammatory and Neuroprotective Agents in Clinical Trials for CNS Disease and Injury: Where Do We Go From Here?

Neurological disorders are major contributors to death and disability worldwide. The pathology of injuries and disease processes includes a cascade of events that often involve molecular and cellular components of the immune system and their interaction with cells and structures within the central nervous system. Because of this, there has been great interest in developing neuroprotective therapeutic approaches that target neuroinflammatory pathways. Several neuroprotective anti-inflammatory agents have been investigated in clinical trials for a variety of neurological diseases and injuries, but to date the results from the great majority of these trials has been disappointing. There nevertheless remains great interest in the development of neuroprotective strategies in this arena. With this in mind, the complement system is being increasingly discussed as an attractive therapeutic target for treating brain injury and neurodegenerative conditions, due to emerging data supporting a pivotal role for complement in promoting multiple downstream activities that promote neuroinflammation and degeneration. As we move forward in testing additional neuroprotective and immune-modulating agents, we believe it will be useful to review past trials and discuss potential factors that may have contributed to failure, which will assist with future agent selection and trial design, including for complement inhibitors. In this context, we also discuss inhibition of the complement system as a potential neuroprotective strategy for neuropathologies of the central nervous system.

Hydride Abstraction as the Rate-Limiting Step of the Irreversible Inhibition of Monoamine Oxidase B by Rasagiline and Selegiline: A Computational Empirical Valence Bond Study

Monoamine oxidases (MAOs) catalyze the degradation of a very broad range of biogenic and dietary amines including many neurotransmitters in the brain, whose imbalance is extensively linked with the biochemical pathology of various neurological disorders, and are, accordingly, used as primary pharmacological targets to treat these debilitating cognitive diseases. Still, despite this practical significance, the precise molecular mechanism underlying the irreversible MAO inhibition with clinically used propargylamine inhibitors rasagiline and selegiline is still not unambiguously determined, which hinders the rational design of improved inhibitors devoid of side effects current drugs are experiencing. To address this challenge, we present empirical valence bond QM/MM simulations of the rate-limiting step of the MAO inhibition involving the hydride anion transfer from the inhibitor α-carbon onto the N5 atom of the flavin adenin dinucleotide (FAD) cofactor. The proposed mechanism is strongly supported by the obtained free energy profiles, which confirm a higher reactivity of selegiline over rasagiline, while the calculated difference in the activation Gibbs energies of ΔΔG^‡ = 3.1 kcal mol^-1 is found to be in very good agreement with that from the measured literature k_inact values that predict a 1.7 kcal mol^-1 higher selegiline reactivity. Given the similarity with the hydride transfer mechanism during the MAO catalytic activity, these results verify that both rasagiline and selegiline are mechanism-based irreversible inhibitors and offer guidelines in designing new and improved inhibitors, which are all clinically employed in treating a variety of neuropsychiatric and neurodegenerative conditions.

Allopregnanolone Modulates GABAAR-Dependent CaMKIIδ3 and BDNF to Protect SH-SY5Y Cells Against 6-OHDA-Induced Damage

Allopregnanolone (APα), as a functional neurosteroid, exhibits the neuroprotective effect on neurodegenerative diseases such as Parkinson’s disease (PD) through γ-aminobutyric acid A receptor (GABAAR), but it has not been completely understood about its molecular mechanisms. In order to investigate the neuroprotective effect of APα, as well as to clarify its possible molecular mechanisms, SH-SY5Y neuronal cell lines were incubated with 6-hydroxydopamine (6-OHDA), which has been widely used as an in vitro model for PD, along with APα alone or in combination with GABAAR antagonist (bicuculline, Bic), intracellular Ca²⁺ chelator (EGTA) and voltage-gated L-type Ca²⁺ channel blocker (Nifedipine). The viability, proliferation, and differentiation of SH-SY5Y cells, the expression levels of calmodulin (CaM), Ca²⁺/calmodulin-dependent protein kinase II δ3 (CaMKIIδ3), cyclin-dependent kinase-1 (CDK1) and brain-derived neurotrophic factor (BDNF), as well as the interaction between CaMKIIδ3 and CDK1 or BDNF, were detected by morphological and molecular biological methodology. Our results found that the cell viability and the number of tyrosine hydroxylase (TH), bromodeoxyuridine (BrdU) and TH/BrdU-positive cells in 6-OHDA-treated SH-SY5Y cells were significantly decreased with the concomitant reduction in the expression levels of aforementioned proteins, which were ameliorated following APα administration. In addition, Bic could further increase the number of TH or BrdU-positive cells as well as the expression levels of aforementioned proteins except for TH/BrdU-double positive cells, while EGTA and Nifedipine could attenuate the expression levels of CaM, CaMKIIδ3 and BDNF. Moreover, there existed a direct interaction between CaMKIIδ3 and CDK1 or BDNF. As a result, APα-induced an increase in the number of TH-positive SH-SY5Y cells might be mediated through GABAAR via Ca²⁺/CaM/CaMKIIδ3/BDNF (CDK1) signaling pathway, which would ultimately facilitate to elucidate PD pathogenesis and hold a promise as an alternative therapeutic target for PD.

Neuroprotection in Parkinson's disease: facts and hopes

Parkinson’s disease (PD) is the second most common neurodegenerative disease worldwide. Behind the symptoms there is a complex pathological mechanism which leads to a dopaminergic cell loss in the substantia nigra pars compacta. Despite the strong efforts, curative treatment has not been found yet. To prevent a further cell death, numerous molecules were tested in terms of neuroprotection in preclinical (in vitro, in vivo) and in clinical studies as well. The aim of this review article is to summarize our knowledge about the extensively tested neuroprotective agents (Search period: 1991–2019). We detail the underlying pathological mechanism and summarize the most important results of the completed animal and clinical trials. Although many positive results have been reported in the literature, there is still no evidence that any of them should be used in clinical practice (Cochrane analysis was performed). Therefore, further studies are needed to better understand the pathomechanism of PD and to find the optimal neuroprotective agent(s).

Differential expression of antibodies to NMDA receptor in anti-NMDA receptor encephalitis and in neuropsychiatric systemic lupus erythematosus

Objective

Anti-NMDA receptor encephalitis is the most prevalent autoimmune encephalitis having characteristic clinical features with autoantibodies against tetrameric transmembrane channels composed of combinations of NR1 subunits of NMDA receptors with NR2 subunits, which are detected by cell-based assay (anti-NR1/NR2). On the other hand, antibodies against the linear epitope in NR2 subunit (anti-NR2) have been shown to be expressed in patients with diffuse psychiatric/neuropsychological syndromes of neuropsychiatric SLE (diffuse NPSLE). However, it has not been explored whether anti-NR1/NR2 might be detected in NPSLE, nor has it been clear whether anti-NR2 might have cross-reactivity with anti-NR1/NR2. The current study was therefore performed to explore the prevalence of anti-NR1/NR2 in NPSLE.

Methods

Serum specimens were obtained from 31 patients with NPSLE (22 with diffuse NPSLE and 9 with neurological syndromes or polyneuropathy) and from 18 normal healthy subjects. Anti-NR2 and anti-NR1/NR2 were measured by ELISA and cell-based assay, respectively. The positivity for anti-NR2 was defined by a value exceeding mean+2 SD of normal healthy subjects.

Results

Anti-NR2 was positive in the sera of 19 of 31 patients with NPSLE (in 15 of 22 patients with diffuse NPSLE). By contrast, anti-NR1/NR2 was positive only in 2 of 31 patients with NPSLE (in 2 of 22 patients with diffuse SLE). The positivity for anti-NR1/NR2 was not correlated with anti-NR2 values.

Conclusions

These results demonstrate that the prevalence of anti-NR1/NR2 is extremely low in NPSLE. Moreover, the data also confirm that anti-NR2 antibodies do not have cross-reactivity with anti-NR1/NR2.

Computational Insight into the Mechanism of the Irreversible Inhibition of Monoamine Oxidase Enzymes by the Antiparkinsonian Propargylamine Inhibitors Rasagiline and Selegiline

Monoamine oxidases (MAOs) are flavin adenine dinucleotide containing flavoenzymes that catalyze the degradation of a range of brain neurotransmitters, whose imbalance is extensively linked with the pathology of various neurological disorders. This is why MAOs have been the central pharmacological targets in treating neurodegeneration for more than 60 years. Still, despite this practical importance, the precise chemical mechanisms underlying the irreversible inhibition of the MAO B isoform with clinical drugs rasagiline (RAS) and selegiline (SEL) remained unknown. Here we employed a combination of MD simulations, MM-GBSA binding free energy evaluations, and QM cluster calculations to show the MAO inactivation proceeds in three steps, where, in the rate-limiting first step, FAD utilizes its N5 atom to abstracts a hydride anion from the inhibitor α-CH₂ group to ultimately give the final inhibitor-FAD adduct matching crystallographic data. The obtained free energy profiles reveal a lower activation energy for SEL by 1.2 kcal mol^-1 and a higher reaction exergonicity by 0.8 kcal mol^-1, with the former being in excellent agreement with experimental ΔΔG^‡_EXP = 1.7 kcal mol^-1, thus rationalizing its higher in vivo reactivity over RAS. The calculated ΔG_BIND energies confirm SEL binds better due to its bigger size and flexibility allowing it to optimize hydrophobic C-H···π and π···π interactions with residues throughout both of enzyme's cavities, particularly with FAD, Gln206 and four active site tyrosines, thus overcoming a larger ability of RAS to form hydrogen bonds that only position it in less reactive orientations for the hydride abstraction. Offered results elucidate structural determinants affecting the affinity and rates of the inhibition reaction that should be considered to cooperate when designing more effective compounds devoid of untoward effects, which are of utmost significance and urgency with the growing prevalence of brain diseases.

α-Synuclein stimulation of monoamine oxidase-B and legumain protease mediates the pathology of Parkinson's disease

Dopaminergic neurodegeneration in Parkinson's disease (PD) is associated with abnormal dopamine metabolism by MAO-B (monoamine oxidase-B) and intracellular α-Synuclein (α-Syn) aggregates, called the Lewy body. However, the molecular relationship between α-Syn and MAO-B remains unclear. Here, we show that α-Syn directly binds to MAO-B and stimulates its enzymatic activity, which triggers AEP (asparagine endopeptidase; legumain) activation and subsequent α-Syn cleavage at N103, leading to dopaminergic neurodegeneration. Interestingly, the dopamine metabolite, DOPAL, strongly activates AEP, and the N103 fragment of α-Syn binds and activates MAO-B. Accordingly, overexpression of AEP in SNCA transgenic mice elicits α-Syn N103 cleavage and accelerates PD pathogenesis, and inhibition of MAO-B by Rasagiline diminishes α-Syn-mediated PD pathology and motor dysfunction. Moreover, virally mediated expression of α-Syn N103 induces PD pathogenesis in wild-type, but not MAO-B-null mice. Our findings thus support that AEP-mediated cleavage of α-Syn at N103 is required for the association and activation of MAO-B, mediating PD pathogenesis.

Melatonin inhibits rotenone-induced SH-SY5Y cell death via the downregulation of Dynamin-Related Protein 1 expression

Previous studies have shown that melatonin can protect cells against rotenone-induced cell death. Yet, the mechanism involved in this protection requires further research. In this study, we aimed to further investigate the effects of melatonin on inhibiting rotenone-induced SH-SY5Y cells and the underlying molecular mechanisms. Human neuroblastoma SH-SY5Y cells were treated with 0.3 or 1μM rotenone for 6 or 12h. Cell viability was measured with an MTS assay, the mitochondrial membrane potential was determined with a Rhodamine 123 staining assay, and the protein expression levels of the markers of autophagy, including cytochrome C release (Cyt C), light chain 3B (LC3 B) and Dynamin-Related Protein 1 (Drp1) were analyzed by western blotting. The co-localization of Drp1 and TOM20 proteins in the mitochondria of SH-SY5Y cells was measured by immunofluorescence coupled with confocal microscopy and the overexpression of the Drp1 gene was then conducted. The viability and expression levels of Cyt C and LC3 B in rotenone and melatonin + rotenone-treated Drp1-overexpressed SH-SY5Y cells were analyzed with MTS and western blotting, respectively. We found that rotenone effectively induced SH-SY5Y cell death by causing mitochondrial dysfunction and increasing Cyt C expression. Drp1 expression and its regulation of mitochondrial translocation mediated the rotenone-induced cell death and melatonin inhibited this process. Overexpression of Drp1 protein attenuated melatonin's inhibition of rotenone-induced SH-SY5Y cell death. In conclusion, melatonin effectively inhibits rotenone-induced neuronal cell death via the regulation of Drp1 expression.

[Levodopa-carbidopa intestinal gel in the treatment of patients with Parkinson disease: results of a 12-month open study]

AIM

To evaluate the long-term safety and efficacy of intrajejunal levodopa-carbidopa intestinal gel (LCIG) infusion in the treatment of patients with severe stages of Parkinson disease (PD) who did not respond adequately to treatment with oral drugs.

MATERIAL AND METHODS

A large-scale international prospective open-label 54-week study of LCIG in patients with PD with severe motor fluctuations was carried out. A total of 48 patients were enrolled in Russia, 46 patients (95.8%) had PEG-J inserted, and 43 of them completed the study. The safety, including adverse events (AEs), infusion system and pump failures analysis, number of patients completely terminated the study, and efficacy (duration of "off" periods, "on" periods with or without troublesome dyskinesias, UPDRS scores, Clinical Global Impression, Quality of Life (PDQ-39, EQ-5D и EQ-VAS) dynamics, an analysis of patient's diaries) were assessed throughout the whole study.

RESULTS

The majority of AEs were mild or moderate with most AEs connected with infusion system application (28.3% patients) including procedure pain. Serious AEs were registered in 8 patients (16.7%). 3 patients (6.3%) discontinued their participation in the study due to AEs. Mean duration of "off" periods by the end of the study decreased by 5.35±2.59 hours (p<0.001), duration of "on" periods without troublesome dyskinesia increased by 5.74±3.91 hours (p<0.001), reduction of "on" periods duration with troublesome dyskinesia became statistically significant by week 36 (p=0.020). The statistically significant improvement of UPDRS (generally and in respect to sub-scales), Clinical Global Impression, and Quality of Life scores was observed throughout the study. Levodopa dose remained stable throughout the 54 treatment weeks. Forty-three patients (93.5%) received LCIG monotherapy throughout the whole study.

CONCLUSION

LCIG intrajejunal infusion during 54 weeks showed the favorable safety profile, high tolerability, and efficacy in PD motor symptoms correction.

Newly Diagnosed Anemia Increases Risk of Parkinson's disease: A Population-Based Cohort Study

Anemia and low hemoglobin have been identified to increase Parkinson’s disease (PD) risk. This population-based cohort study investigated PD risk in newly diagnosed anemic patients by using data from the Taiwan National Health Insurance Research Database. All newly diagnosed anemic patients (n = 86,334) without a history of stroke, neurodegenerative diseases, traumatic brain injury, major operations, or blood loss diseases were enrolled. A cohort of nonanemic controls, 1:1 matched with anemic patients on the basis of the demographics and pre-existing medical conditions, was also included. Competing risk analysis was used to evaluate PD risk in anemic patients compared with that in their matched controls. The adjusted hazard ratio (aHR) of PD risk in the anemic patients was 1.36 (95% confidence interval [CI]: 1.22–1.52, p < 0.001). Iron deficiency anemia (IDA) patients tended to exhibit a higher PD risk (aHR: 1.49; 95% CI: 1.24–1.79, p < 0.001). Furthermore, Iron supplement did not significantly affect the PD risk: the aHRs for PD risk were 1.32 (95% CI: 1.07–1.63, p < 0.01) and 1.86 (95% CI: 1.46–2.35, p < 0.001) in IDA patients with and without iron supplementation, respectively. The population-based cohort study indicated newly diagnosed anemia increases PD risk.

Bee Venom Alleviates Motor Deficits and Modulates the Transfer of Cortical Information through the Basal Ganglia in Rat Models of Parkinson's Disease

Recent evidence points to a neuroprotective action of bee venom on nigral dopamine neurons in animal models of Parkinson’s disease (PD). Here we examined whether bee venom also displays a symptomatic action by acting on the pathological functioning of the basal ganglia in rat PD models. Bee venom effects were assessed by combining motor behavior analyses and in vivo electrophysiological recordings in the substantia nigra pars reticulata (SNr, basal ganglia output structure) in pharmacological (neuroleptic treatment) and lesional (unilateral intranigral 6-hydroxydopamine injection) PD models. In the hemi-parkinsonian 6-hydroxydopamine lesion model, subchronic bee venom treatment significantly alleviates contralateral forelimb akinesia and apomorphine-induced rotations. Moreover, a single injection of bee venom reverses haloperidol-induced catalepsy, a pharmacological model reminiscent of parkinsonian akinetic deficit. This effect is mimicked by apamin, a blocker of small conductance Ca2+-activated K+ (SK) channels, and blocked by CyPPA, a positive modulator of these channels, suggesting the involvement of SK channels in the bee venom antiparkinsonian action. In vivo electrophysiological recordings in the substantia nigra pars reticulata (basal ganglia output structure) showed no significant effect of BV on the mean neuronal discharge frequency or pathological bursting activity. In contrast, analyses of the neuronal responses evoked by motor cortex stimulation show that bee venom reverses the 6-OHDA- and neuroleptic-induced biases in the influence exerted by the direct inhibitory and indirect excitatory striatonigral circuits. These data provide the first evidence for a beneficial action of bee venom on the pathological functioning of the cortico-basal ganglia circuits underlying motor PD symptoms with potential relevance to the symptomatic treatment of this disease.

[A current view on dopamine receptor agonists in the treatment of Parkinson's disease]

Dopamine receptor agonists (DRA) is a widely used group of antiparkinsonian drugs. The article presents short results: related to the mechanism of the stimulation of different types of dopamine receptors. The advantages of this group of drugs compared to levodopa medications as well as the studies of DRA in vitro and in vivo are described. Multiple studies demonstrate an important role of DRA in the treatment of Parkinson's disease (PD): a good control of motor symptoms, the possibility of monotherapy in the early stages of disease, the reduced risk of motor complications compared to start therapy with levodopa and decrease in the duration of "OFF-period" and UPDRS scores as well as the possibility to reduce the dose of levodopa in case of combined treatment with levodopa containing preparations. Pramipexole has demonstrated the efficacy in the treatment of persistent tremor and depression in double-blind placebo-controlled trials. A significant improvement of quality of life index has been shown in PD patients treated with these drugs. Side-effects often limited the use of DRA in clinical practice. The data on the dose equivalence of different DRA are recommended to use if it is necessary to switch from one DRA to another.

[Dopamine receptor agonists: new forms and new possibilities in the treatment of Parkinson's disease]

Main mechanisms of action of dopamine receptor agonists, efficacy of their use according to the results of earlier clinical trials and possible side-effects are discussed. The authors present their experience of prescription of rotigotine transdermal system in an open study of 30 patients with Parkinson's disease. The duration of the study was 8 weeks. There was a significant improvement of both motor and nonmotor (pain sensations, sleep, mood). The effective dose for treatment of initial stages was 4-6 mg daily and for the full-blown stage - 6-8 mg daily. The tolerability was good.

Early versus delayed initiation of pharmacotherapy in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disorder after Alzheimer's disease and pathologically is characterised by a progressive loss of dopaminergic cells of the nigrostriatal pathway. Clinically, PD is mainly defined by the presence of the motor symptoms of bradykinesia, rigidity, rest tremor and postural instability, but non-motor symptoms such as depression, dementia and autonomic disturbances are recognised as integral parts of the disease. Although pharmacotherapy for PD was introduced almost 50 years ago, and has improved significantly over the intervening period, the timing of initiation of treatment in newly diagnosed PD remains controversial. While some physicians favour an early start of pharmacotherapy at or soon after diagnosis, others prefer to delay pharmacological treatment until a certain degree of disability has developed. This article aims to discuss the advantages and disadvantages of both strategies by exploring their effects on symptoms, disease progression and quality of life. Although the data on putative disease-modifying effects of early pharmacological intervention in PD are still inconclusive, we believe that the most important indication for an early initiation of anti-parkinsonian treatment should be to maintain the quality of life of PD patients and to secure their socioeconomic status as long as possible.

Does MAP2 have a role in predicting the development of anti-NMDAR encephalitis associated with benign ovarian teratoma? A report of six new pediatric cases

Anti-N-methyl-d-aspartate receptor (anti-NMDAR) encephalitis is a potentially fatal neurologic syndrome in which patients present with a spectrum of central nervous system deficits. Sixty percent of the cases can be attributed to the presence of tumors, most often ovarian teratomas. This report examines 6 pediatric patients who presented with neurologic deficits associated with the presence of such tumors. These cases illustrate a perplexing phenomenon, where benign teratomas could have a possible association with anti-NMDAR encephalitis. The purpose of this study was to compare the histology and immunohistochemistry of tumors associated with this syndrome to ovarian teratomas found in patients presenting with no neurologic symptoms. After obtaining institutional review board approval, 57 cases of ovarian teratomas were identified at our institution over 12 years. Six patients were identified with anti-NMDAR encephalitis. A panel of immunostains, including S100, GFAP, MAP2, and NeuN was applied to patients' tumor sections as well as the 6 controls from age-matched patients. No qualitative histologic or immunohistochemical differences were seen between the study cases and control group. Because no qualitative differences were identified between the study cases and the control group, testing of paired serum and cerebrospinal fluid remains the best method for diagnosis of anti-NMDAR encephalitis. Tumor banking with molecular analysis of ovarian teratomas, including whole-genome sequencing and comparative genomic hybridization between ovarian tissue saved from patients with and without anti-NMDAR encephalitis, is necessary to fully understand the etiopathogenesis of anti-NMDAR encephalitis.

Pramipexole reduces phosphorylation of α-synuclein at serine-129

α-Synuclein is a central component of the pathogenesis of Parkinson’s disease (PD). Phosphorylation at serine-129 represents an important post-translational modification and constitutes the major form of the protein in Lewy bodies. Several kinases have been implicated in the phosphorylation of α-synuclein. The targeting of kinase pathways as a potential to influence the pathogenesis of PD is an important focus of attention, given that mutations of specific kinases (LRRK2 and PINK1) are causes of familial PD. Pramipexole (PPX) is a dopamine agonist developed for the symptomatic relief of PD. Several in vitro and in vivo laboratory studies have demonstrated that PPX exerts neuroprotective properties in model systems of relevance to PD. The present study demonstrates that PPX inhibits the phosphorylation of α-synuclein and that this is independent of dopamine receptor activation. PPX blocks the increase in phosphorylated α-synuclein induced by inhibition of the ubiquitin proteasomal system. The phosphorylation of α-synuclein occurs in part at least through casein kinase 2, and PPX in turn reduces the phosphorylation of this enzyme, thereby inhibiting its activity. Thus, PPX decreases the phosphorylation of α-synuclein, and this mechanism may contribute to its protective properties in PD models.

Static posturography in aging and Parkinson's disease

Introduction: In clinical practice, evaluation of postural control is based on the neurological examination, including Romberg's test, examination of gait and performance of pull test as part of the Unified Parkinson's Disease Rating Scale (UPDRS). The goal of our study was to identify posturographic parameters since quantitative technical methods for the measurement of postural control are not established in clinical routine yet. Methods: In this cross-sectional study design we examined patients with Parkinson's disease (PD) (Hoehn and Yahr < 3; PD n = 12) on a static posturographic platform (eyes open and eyes closed), performing a standard Romberg's test during neurological examination and compared the results with an age-matched healthy adult control (HAC n = 10) and a healthy young control (HYC n = 21). Results: In the platform Romberg's test with open eyes, the patients with PD showed a significantly greater mean sway [PD: 14.98 vs. HAC: 8.77 (mm), p < 0.003 vs. HYC 7.80 (mm)], greater mean radius [PD: 28.31 vs. HAC: 16.36 (mm), p < 0.008 vs. HYC: 14.19 (mm)] and greater marked area [PD: 2.38 vs. HAC: 0.88 (cm²), p < 0.016 vs. HYC: 0.78 (cm²)] compared to the HAC. The Romberg's test with closed eyes revealed a significantly greater mean sway [PD: 13.83 vs. HAC: 10.12 (mm), p < 0.033 vs. HYC: 5.82 (mm)] and greater mean radius [PD: 25.03 vs. HAC: 18.15 (mm), p < 0.045 vs. HYC: 9.11 (mm)] compared to both groups. Conclusions: The platform Romberg-test with closed eyes detected significant differences in elderly people and patients with Parkinson's disease, which could be objectively quantified with static posturography testing. Age alone showed significant changes, only detectable with closed eyes. Therefore, balance testing with a new computerized approach could help to identify balance problems in a geriatric assessment in clinical routine, especially with the parameters marked area and mean sway.

Nicotine as a potential neuroprotective agent for Parkinson's disease

Converging research efforts suggest that nicotine and other drugs that act at nicotinic acetylcholine receptors (nAChRs) may be beneficial in the management of Parkinson's disease. This idea initially stemmed from the results of epidemiological studies that demonstrated that smoking is associated with a decreased incidence of Parkinson's disease. The subsequent finding that nicotine administration protected against nigrostriatal damage in parkinsonian animal models led to the idea that nicotine in tobacco products may contribute to this apparent protective action. Nicotine most likely exerts its effects by interacting at nAChRs. Accumulating research indicates that multiple subtypes containing nAChRs, including α4β2, α6β2, and/or α7, may be involved. Stimulation of nAChRs initially activates various intracellular transduction pathways primarily via alterations in calcium signaling. Consequent adaptations in immune responsiveness and trophic factors may ultimately mediate nicotine's ability to reduce/halt the neuronal damage that arises in Parkinson's disease. In addition to a potential neuroprotective action, nicotine also has antidepressant properties and improves attention/cognition. Altogether, these findings suggest that nicotine and nAChR drugs represent promising therapeutic agents for the management of Parkinson's disease.

The emerging role of proteolysis in mitochondrial quality control and the etiology of Parkinson's disease

Mitochondria are highly dynamic organelles that are important for many diverse cellular processes, such as energy metabolism, calcium buffering, and apoptosis. Mitochondrial biology and dysfunction have recently been linked to different types of cancers and neurodegenerative diseases, most notably Parkinson's disease. Thus, a better understanding of the quality control systems that maintain a healthy mitochondrial network can facilitate the development of effective treatments for these diseases. In this perspective, we will discuss recent advances on two mitochondrial quality control pathways: the UPS and mitophagy, highlight how new players may be contributing to regulate these pathways. We believe the proteases involved will be key and novel regulators of mitochondrial quality control, and this knowledge will provide insights into future studies aimed to combat neurodegenerative diseases.

Mitochondrial pathology in Parkinson's disease

The last 25 years have witnessed remarkable advances in our understanding of the etiology and pathogenesis of Parkinson's disease. The ability to undertake detailed biochemical analyses of the Parkinson's disease postmortem brain enabled the identification of defects of mitochondrial and free-radical metabolism. The discovery of the first gene mutation for Parkinson's disease, in alpha-synuclein, ushered in the genetic era for the disease and the subsequent finding of several gene mutations causing parkinsonism, 15 at the time of writing. Technological advances both in sequencing technology and software analysis have allowed association studies of sufficiently large size accurately to describe genes conferring an increased risk for Parkinson's disease. What has been so surprising is the convergence of these 2 separate disciplines (biochemistry and genetics) in terms of reinforcing the importance of the same pathways (ie, mitochondrial dysfunction and free-radical metabolism). Other pathways are also important in pathogenesis, including protein turnover, inflammation, and post-translational modification, particularly protein phosphorylation and ubiquitination. However, even these additional pathways overlap with each other and with those of mitochondrial dysfunction and oxidative stress. This review explores these concepts with particular relevance to mitochondrial involvement.

Anti-N-methyl-D-aspartate receptor encephalitis: an emerging cause of centrally mediated sinus node dysfunction

AIMS

Anti-N-methyl-D-aspartate receptor encephalitis (NMDARE) is a recently recognized form of autoimmune encephalitis that typically affects young women, often as a paraneoplastic syndrome related to ovarian teratoma. Clinical features include psychiatric and neurological disturbances, central hypoventilation, autonomic instability, and cardiac dysrhythmias. The prevalence, nature, and outcomes of cardiac dysrhythmias in patients with NMDARE have not been well described.

METHODS AND RESULTS

Records of 10 consecutive patients with NMDARE were reviewed to obtain clinical, laboratory, echocardiographic, electrocardiographic, and radiological data. Patients were all female with an average age of 23 ± 5.5 years. Echocardiograms revealed structurally normal hearts with the exception of mild left ventricular hypertrophy in two cases. Eight patients had inappropriate sinus tachycardia. Six patients developed significant sinus bradycardia, which included periods of sinus arrest in four cases. Five patients manifested both sinus bradycardia and tachycardia. Bradycardia was often triggered by identifiable vagal stimuli. Temporary pacing was instituted in three patients, but permanent pacing was not required in any of the patients. Magnetic resonance imaging (MRI) scans revealed mesial temporal abnormalities in nine patients. In all cases, the dysrhythmias resolved with treatment of the underlying immune disorder with immunotherapy and/or teratoma resection. There was no evidence of dysrhythmia recurrence in any patient at follow-up.

CONCLUSION

Anti-N-methyl-D-aspartate receptor encephalitis is a recently recognized cause of autoimmune encephalitis with a predilection to cause severe sinus node abnormalities. Temporary pacing is occasionally required, but permanent pacing appears to be unnecessary. An analysis of the clinical syndrome coupled with MRI and experimental data may offer insight into central mechanisms of heart rate regulation.

Combination of transcranial sonography, olfactory testing, and MIBG myocardial scintigraphy as a diagnostic indicator for Parkinson's disease

BACKGROUND

Appropriate diagnostic biomarkers are useful for improving speed and accuracy of a diagnosis. Substantia nigra (SN) hyperechogenicity visualized by transcranial sonography (TCS), olfactory dysfunction, and the reduced uptake of (123) I-metaiodobenzylguanidine (MIBG) in myocardial scintigraphy have been suggested as potential biomarkers for the identification of Parkinson's disease (PD).

OBJECTIVES

To evaluate the diagnostic potential of these tests and to determine whether combining them increases their diagnostic power.

METHODS

  Subjects were 44 patients with clinically diagnosed PD and 36 healthy controls. TCS of the SN, the odor stick identification test for Japanese (OSIT-J), and MIBG myocardial scintigraphy were conducted.

RESULTS

Eleven patients with PD (25%) and four controls (11%) were excluded because of an insufficient acoustic temporal bone window in the TCS. Thus, 33 patients with PD and 32 healthy controls were finally included. The diagnostic sensitivity of TCS, OSIT-J, and MIBG myocardial scintigraphy was 78.8%, 84.8%, and 60.6%, respectively. The specificity of TCS and OSIT-J was 93.8% and 78.1%, respectively. The combination of TCS of the SN and OSIT-J substantially increased the sensitivity to a sufficient level for discriminating patients with PD from controls.

CONCLUSION

 TCS of the SN and olfactory testing play complementary roles in increasing diagnostic power in PD. As both tests are easy to perform, noninvasive, and inexpensive, the combination of TCS of the SN and olfactory testing may contribute to early and accurate diagnosis of PD.

Strategies for Parkinson’s disease care: prevention and management of motor fluctuations

SUMMARY Parkinson’s disease (PD) is characterized clinically by the hallmark motor signs of bradykinesia, rest tremor and rigidity. Current pharmacological management goals include control of motor symptoms as well as prevention and management of motor complications including motor fluctuations and dyskinesias. While the use of levodopa revolutionized the pharmacological management of PD, multiple other agents and strategies have emerged with many demonstrable, albeit sometimes controversial, advantages to a ‘levodopa’ only approach. Despite these developments, the progressive nature of PD requires vigilance and creativity from clinicians as both motor and nonmotor complications grow in number and severity over time.

The role of calcium and mitochondrial oxidant stress in the loss of substantia nigra pars compacta dopaminergic neurons in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease in developed countries. The core motor symptoms are attributable to the degeneration of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNc). Why these neurons succumb in PD is not clear. One potential clue has come from the observation that the engagement of L-type Ca²⁺ channels during autonomous pacemaking elevates the sensitivity of SNc DA neurons to mitochondrial toxins used to create animal models of PD, suggesting that Ca²⁺ entry is a factor in their selective vulnerability. Recent work has shown that this Ca²⁺ entry also elevates mitochondrial oxidant stress and that this stress is exacerbated by deletion of DJ-1, a gene associated with an early onset, recessive form of PD. Epidemiological data also support a linkage between L-type Ca²⁺ channels and the risk of developing PD. This review examines the hypothesis that the primary factor driving neurodegenerative changes in PD is the metabolic stress created by Ca²⁺ entry, particularly in the face of genetic or environmental factors that compromise oxidative defenses or proteostatic competence.

Past, present and future of A(2A) adenosine receptor antagonists in the therapy of Parkinson's disease

Several selective antagonists for adenosine A(2A) receptors (A(2A)R) are currently under evaluation in clinical trials (phases I to III) to treat Parkinson's disease, and they will probably soon reach the market. The usefulness of these antagonists has been deduced from studies demonstrating functional interactions between dopamine D₂ and adenosine A(2A) receptors in the basal ganglia. At present it is believed that A(2A)R antagonists can be used in combination with the dopamine precursor L-DOPA to minimize the motor symptoms of Parkinson's patients. However, a considerable body of data indicates that in addition to ameliorating motor symptoms, adenosine A(2A)R antagonists may also prevent neurodegeneration. Despite these promising indications, one further issue must be considered in order to develop fully optimized antiparkinsonian drug therapy, namely the existence of (hetero)dimers/oligomers of G protein-coupled receptors, a topic that is currently the focus of intense debate within the scientific community. Dopamine D₂ receptors (D₂Rs) expressed in the striatum are known to form heteromers with A(2A) adenosine receptors. Thus, the development of heteromer-specific A(2A) receptor antagonists represents a promising strategy for the identification of more selective and safer drugs.

Metabotropic glutamate receptor 5 antagonist protects dopaminergic and noradrenergic neurons from degeneration in MPTP-treated monkeys

Degeneration of the dopaminergic nigrostriatal system and of noradrenergic neurons in the locus coeruleus are important pathological features of Parkinson's disease. There is an urgent need to develop therapies that slow down the progression of neurodegeneration in Parkinson's disease. In the present study, we tested whether the highly specific metabotropic glutamate receptor 5 antagonist, 3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine, reduces dopaminergic and noradrenergic neuronal loss in monkeys rendered parkinsonian by chronic treatment with low doses of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine. Weekly intramuscular 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine injections (0.2-0.5 mg/kg body weight), in combination with daily administration of 3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine or vehicle, were performed until the development of parkinsonian motor symptoms in either of the two experimental groups (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine versus 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/vehicle). After 21 weeks of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine treatment, all 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/vehicle-treated animals displayed parkinsonian symptoms, whereas none of the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine-treated monkeys were significantly affected. These behavioural observations were consistent with in vivo positron emission tomography dopamine transporter imaging data, and with post-mortem stereological counts of midbrain dopaminergic neurons, as well as striatal intensity measurements of dopamine transporter and tyrosine hydroxylase immunoreactivity, which were all significantly higher in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine-treated animals than in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/vehicle-treated monkeys. The 3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine treatment also had a significant effect on the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced loss of norepinephrine neurons in the locus coeruleus and adjoining A5 and A7 noradrenaline cell groups. In 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/vehicle-treated animals, almost 40% loss of tyrosine hydroxylase-positive norepinephrine neurons was found in locus coeruleus/A5/A7 noradrenaline cell groups, whereas the extent of neuronal loss was lower than 15% of control values in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine/3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine-treated monkeys. Our data demonstrate that chronic treatment with the metabotropic glutamate receptor 5 antagonist, 3-[(2-methyl-1,3-thiazol-4-yl) ethynyl] pyridine, significantly reduces 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine toxicity towards dopaminergic and noradrenergic cell groups in non-human primates. This suggests that the use of metabotropic glutamate receptor 5 antagonists may be a useful strategy to reduce degeneration of catecholaminergic neurons in Parkinson's disease.

Novel MAO-B inhibitors: potential therapeutic use of the selective MAO-B inhibitor PF9601N in Parkinson's disease

Parkinson's disease (PD) is a neurodegenerative disease that is characterized by preferential loss of dopaminergic neurons in the substantia nigra pars compacta, leading to declining levels of dopamine in the striatum. In our search for compounds able not only to extend the effects of dopamine by preventing its degradation but also to halt or slow the neurodegenerative process, we designed, synthesized, and biologically tested a series of propargylamines for their potential use as therapeutic agents for PD. Among them, PF9601N, [N-(2-propynyl)-2-(5-benzyloxy-indolyl) methylamine], showed high potency and selectivity as a MAO-BI (monoamine oxidase type B inhibitor) and also demonstrated remarkable neuroprotective properties in several in vivo and cellular models of PD. In this chapter, we describe the preclinical evidence revealing the novel MAO-BI PF9601N as an interesting candidate for the treatment of PD.

Rationale for delayed-start study of pramipexole in Parkinson's disease: the PROUD study

Perhaps the most important unmet need in Parkinson's disease (PD) is the ability to slow or prevent progression of the neurodegeneration that underlies the motor and nonmotor features of this disorder. Pramipexole, a dopamine agonist used for the symptomatic treatment of PD, has demonstrated neuroprotective properties in laboratory studies. The PRamipexole On Underlying Disease (PROUD) study is a randomized, double-blind clinical trial evaluating the ability of pramipexole to modify disease progression using a delayed-start design. PD patients (n = 535) with mean age 62.5 years, mean duration since diagnosis of 4.4 months, and mean total Unified Parkinson's disease Rating Scale (UPDRS) score of 24.5 were recruited. In Phase I, patients were randomly assigned to be titrated to 1.5 mg pramipexole or placebo and maintained on study drug for 6-9 months. In Phase II, all patients were titrated to 1.5 mg pramipexole and maintained on study drug until the end of the study at 15 months. No rescue medication was allowed in the protocol. The primary endpoint is the change in total UPDRS score (parts I-III) from baseline to 15 months. A range of secondary endpoints separately assess UPDRS subscales, quality of life, depression, and impulse control disorders. A sub-study examined dopamine transporter uptake scans at baseline and 15 months. The results of PROUD will provide insight into the potential for early versus delayed treatment with pramipexole to modify motor outcome at 15 months in recently diagnosed PD patients.

Timed motor tests can detect subtle motor dysfunction in early Parkinson's disease

Early diagnosis of Parkinson's disease (PD) is important for putative neuroprotective therapies to be initiated in the earliest stage of the disease. We investigated whether a previously validated timed motor test (TMT) battery could detect subtle motor dysfunction in early PD patients and even in clinically unaffected limbs of strictly hemiparkinsonian patients. We assessed 107 PD patients (symptom duration <or=2 years; dopa-naive) and 100 healthy, age-matched controls with eight simple TMTs based on aspects of (a) walking, (b) writing, (c) single and double-handed pegboard performance, (d) finger tapping, and (e) diadochokinesis. We evaluated the ability of individual and combined TMTs to discriminate patients from controls using ROC curves. Second, we investigated whether these TMTs could identify motor dysfunction of the clinically unaffected limb in 42 strictly hemiparkinsonian patients. The pegboard dexterity test had the best ROC curve (AUC 0.97; 95% sensitivity, 89% specificity) for patients versus controls. It retained reasonable accuracy when testing the clinically unaffected limb of hemiparkinsonian patients versus the mean of right and left-hand scores in controls (AUC 0.73). The pegboard dexterity test is a sensitive and inexpensive instrument to detect motor dysfunction in early PD. Therefore, it may be worth evaluating as a diagnostic tool in everyday clinical practice to assess patients with early symptomatic PD, or as part of a more elaborate screening battery in a defined population at risk.

Neuroprotection in Parkinson's disease

A major focus in Parkinson's disease (PD) research is to produce drugs or other interventions that can slow or stop clinical progression. This should include an effect on both motor and non-motor symptoms and so target dopaminergic and non-dopaminergic pathways. It is logical to assume that the best chance of developing such therapies will be based on forming a better understanding of the aetiology and pathogenesis of PD and to identify critical molecular targets. There have been great advances in finding different genetic causes and risk factors for PD, but less so in the discovery of environmental contributions. The separate genetic causes still share common pathways to cell dysfunction and death, and these interconnect at several levels. Despite the major advances in genetics and PD pathogenesis, we still do not have good models of PD that can be used with confidence to accurately predict the effect of drugs on disease progression. Clinical trial design and study population selection are also areas that represent significant challenges to testing any putative neuro-protective agent. Several drugs have attracted attention as potential neuroprotective agents in PD. There are numerous studies demonstrating beneficial effects in the laboratory, but clinical efficacy for neuroprotection remains unproven.

How should we treat a patient with early Parkinson's disease?

Parkinson's disease (PD) is characterised by the progressive degeneration of dopaminergic nigro-striatal neurons and severe striatal dopaminergic deficiency, leading to bradykinesia. Levodopa was the first drug used for PD treatment and is still considered the most useful weapon for the control of PD symptoms. However, levodopa treatment induces motor complications, which is considered as a major problem as the disease progresses. Dopamine agonists, catechol-O-methyltransferase inhibitors and monoamine oxidase B inhibitors are some more recently developed drug categories which are expected to have a more favourable effect on motor complications. The choice of the best initial treatment in PD remains a controversial matter. Early therapeutic decisions in PD should balance the need for efficient short-term symptom control against long-term complication profile. The individualisation of the treatment seems to be the key for the best approach of early PD patients.

Calcium, cellular aging, and selective neuronal vulnerability in Parkinson's disease

Parkinson's disease (PD) is the second most common neurodegenerative disease in developed countries. The core motor symptoms are attributable to the degeneration of dopamine (DA) neurons in the substantia nigra pars compacta (SNc). Why these neurons, and other restricted sets of non-dopamine neuron, succumb in PD is not clear. One potential clue has come from the observation that the engagement of L-type Ca2+ channels during autonomous pacemaking elevates the sensitivity of SNc DA neurons to mitochondrial toxins used to create animal models of PD, suggesting that Ca2+ entry is a factor in their selective vulnerability. Epidemiological data also supports a linkage between L-type Ca2+ channels and the risk of developing PD. This review examines the hypothesis that the primary factor driving neurodegenerative changes in PD is the metabolic stress created by sustained Ca2+ entry, particularly in the face of genetic or environmental factors that compromise oxidative defenses or proteostatic competence.

NSAID use and the risk of Parkinson's disease: systematic review and meta-analysis of observational studies

BACKGROUND

Several studies have suggested that NSAID use may modify the risk of developing Parkinson's disease (PD).

OBJECTIVE

Our aim was to conduct a meta-analysis of observational studies evaluating NSAID use and the risk of PD.

METHODS

We systematically searched MEDLINE (1966-November 2008), EMBASE (1980-November 2008) and other databases. Data from 11 studies were included in the meta-analysis. We used the random effects model to calculate risk ratios (relative risks) and their corresponding 95% confidence intervals (CIs).

RESULTS

The pooled risk ratio of PD with NSAID use was 0.95 (95% CI 0.80, 1.12). The pooled risk ratio of PD with high-dose or long-duration NSAID use was 0.91 (95% CI 0.78, 1.05). The pooled risk ratio of PD for aspirin (acetylsalicylic acid) users was 1.08 (95% CI 0.93, 1.26). The pooled risk ratio of PD among ibuprofen users was 0.76 (95% CI 0.65, 0.89). The pooled risk ratio of PD in men using NSAIDs was 0.79 (95% CI 0.69, 0.92), and in women using NSAIDs, it was 0.72 (95% CI 0.45, 1.15).

CONCLUSIONS

NSAIDs as a class do not seem to modify the risk of PD. However, ibuprofen may have a slight protective effect in lowering the risk of PD. Although the risk ratios of PD in male and female NSAID users were similar, the 95% CI for men was suggestive of a slight risk reduction.

Rotigotine transdermal delivery for the treatment of Parkinson's disease

BACKGROUND

Rotigotine is a non-ergot dopamine agonist that has been developed as a new transdermal formulation, and is indicated for use in early (USA and Europe) and advanced (Europe only) Parkinson's disease (PD). The potential advantages of the rotigotine patch include immediacy of effect onset as intestinal absorption in unneeded, constant drug delivery, and ease of use via application of a once-daily adhesive patch. An interesting element of this profile is constant drug delivery, which may avoid pulsatile dopaminergic stimulation, which has been postulated to be related to the development of motor complications.

OBJECTIVE

To consider the evidence surrounding the profile of rotigotine and, in particular, whether its constant delivery system offers significant benefits to the treatment of early and advanced PD.

METHODS

Source material was identified using a PubMed search for the term 'rotigotine' (up to March 2008). The review focuses only on publications related to the rotigotine indication for PD.

RESULTS/CONCLUSION

The rotigotine transdermal patch demonstrates clinical efficacy, alongside a tolerability profile that appears to be well within the range of that observed with other non-ergot dopamine agonists. The once-daily patch formulation may favour compliance but, in similarity with the other theoretical advantages of constant drug delivery (for example reduced emergence of motor complications, improved tolerance to peripheral AEs), requires further detailed study.

Parkinson's disease: emerging pharmacotherapy

Parkinson's disease (PD) is the second most common neurodegenerative disease. The prevalence is increasing with age and averages approximately 0.3% in the entire population. The clinical picture is dominated by the cardinal motor symptoms such as tremor at rest, bradykinesia, muscular rigidity, stooped posture and postural instability. Psychiatric comorbidity is common, comprising dementia, depression, anxiety and psychosis. Although many drugs have been developed and introduced into the market to provide symptomatic treatment, there is still no cure for PD and not even solid evidence for disease-modifying strategies. In addition, motor complications in advanced stages of the disease, side effects of the dopaminergic therapy, and non-motor symptoms remain huge challenges during long-term therapy. Thus, new therapeutic agents are desperately needed. Here, we describe current therapies and possible future developments that we hope will contribute to sustaining quality of life in patients suffering from Parkinson's disease for many years.

The ketogenic diet in a pill: is this possible?

Over the past decade, much progress has been made in understanding the mechanisms of ketogenic diet (KD) action. From the complex systemic and metabolic changes induced by the KD have emerged innovative hypotheses attempting to link biochemical adaptations to its clinical effects. Despite such developments, the fundamental question of how the KD works remains as elusive as ever. At present, it is unclear which of the many potential mechanisms proposed thus far are directly relevant to the clinical effects of the KD. It is unlikely that these numerous hypotheses can be unified into a single mechanism (or a final common pathway). Nevertheless, it may be instructive to consider each of these putative mechanisms in turn and ask the following question: if the mechanism or target in question is a critical determinant of the anticonvulsant efficacy of the KD, then would a similar intervention known to be based on that mechanism yield a comparable effect? Perhaps answering this question for each mechanistic speculation might help substantiate (or invalidate) that particular hypothesis. Can the KD be packaged into a pill? At present, the answer is likely "no." We have yet to discover a "magic bullet" that completely mirrors the anticonvulsant (and potential neuroprotective) effects of the KD. However, without a clearer understanding of the mechanistic elements comprising the complex metabolic puzzle posed by the KD, we would be left only with empiric observations, and to wonder curiously how a high-fat diet can exert such profound clinical effects.

Adenosine A2A receptors and Parkinson's disease

The drug treatment of Parkinson's disease (PD) is accompanied by a loss of drug efficacy, the onset of motor complications, lack of effect on non-motor symptoms, and a failure to modify disease progression. As a consequence, novel approaches to therapy are sought, and adenosine A(2A) receptors (A(2A)ARs) provide a viable target. A(2A)ARs are highly localized to the basal ganglia and specifically to the indirect output pathway, which is highly important in the control of voluntary movement. A(2A)AR antagonists can modulate gamma-aminobutyric acid (GABA) and glutamate release in basal ganglia and other key neurotransmitters that modulate motor activity. In both rodent and primate models of PD, A(2A)AR antagonists produce alterations in motor behavior, either alone or in combination with dopaminergic drugs, which suggest that they will be effective in the symptomatic treatment of PD. In clinical trials, the A(2A)AR antagonist istradefylline reduces "off" time in patients with PD receiving optimal dopaminergic therapy. However, these effects have proven difficult to demonstrate on a consistent basis, and further clinical trials are required to establish the clinical utility of this drug class. Based on preclinical studies, A(2A)AR antagonists may also be neuroprotective and have utility in the treatment of neuropsychiatric disorders. We are only now starting to explore the range of potential uses of A(2A)AR antagonists in central nervous system disorders, and their full utility is still to be uncovered.