Long-term benefits of hematopoietic stem cell-based macrophage/microglia delivery of GDNF to the CNS in a mouse model of Parkinson's disease

Glial cell line-derived neurotrophic factor (GDNF) protects dopaminergic neurons in various models of Parkinson's disease (PD). Cell-based GDNF gene delivery mitigates neurodegeneration and improves both motor and non-motor functions in PD mice. As PD is a chronic condition, this study aims to investigate the long-lasting benefits of hematopoietic stem cell (HSC)-based macrophage/microglia-mediated CNS GDNF (MMC-GDNF) delivery in an MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) mouse model. The results indicate that GDNF treatment effectively ameliorated MPTP-induced motor deficits for up to 12 months, which coincided with the protection of nigral dopaminergic neurons and their striatal terminals. Also, the HSC-derived macrophages/microglia were recruited selectively to the neurodegenerative areas of the substantia nigra. The therapeutic benefits appear to involve two mechanisms: (1) macrophage/microglia release of GDNF-containing exosomes, which are transferred to target neurons, and (2) direct release of GDNF by macrophage/microglia, which diffuses to target neurons. Furthermore, the study found that plasma GDNF levels were significantly increased from baseline and remained stable over time, potentially serving as a convenient biomarker for future clinical trials. Notably, no weight loss, altered food intake, cerebellar pathology, or other adverse effects were observed. Overall, this study provides compelling evidence for the long-term therapeutic efficacy and safety of HSC-based MMC-GDNF delivery in the treatment of PD.

Exercise as medicine in Parkinson's disease

Parkinson's disease (PD) is an incurable and progressive neurological disorder leading to deleterious motor and non-motor consequences. Presently, no pharmacological agents can prevent PD evolution or progression, while pharmacological symptomatic treatments have limited effects in certain domains and cause side effects. Identification of interventions that prevent, slow, halt or mitigate the disease is therefore pivotal. Exercise is safe and represents a cornerstone in PD rehabilitation, but exercise may have even more fundamental benefits that could change clinical practice. In PD, the existing knowledge base supports exercise as (1) a protective lifestyle factor preventing the disease (ie, primary prevention), (2) a potential disease-modifying therapy (ie, secondary prevention) and (3) an effective symptomatic treatment (ie, tertiary prevention). Based on current evidence, a paradigm shift is proposed, stating that exercise should be individually prescribed as medicine to persons with PD at an early disease stage, alongside conventional medical treatment.

Methanolic Extract of Boswellia serrata Gum Protects the Nigral Dopaminergic Neurons from Rotenone-Induced Neurotoxicity

Boswellia serrata gum is a natural product that showed beneficial effects on neurodegenerative diseases in recent studies. In this study, we investigated the effects of Boswellia serrata resin on rotenone-induced dopaminergic neurotoxicity. Firstly, we attempted to see if the resin can induce AMP-activated protein kinase (AMPK) signaling pathway which has been known to have broad neuroprotective effects. Boswellia increased AMPK phosphorylation and reduced phosphorylation of mammalian target of rapamycin (p-mTOR) and α-synuclein (p-α-synuclein) in the striatum while increased the expression level of Beclin1, a marker for autophagy and brain-derived neurotrophic factor. Next, we examined the neuroprotective effects of the Boswellia extract in the rotenone-injected mice. The results showed that Boswellia evidently attenuated the loss of the nigrostriatal dopaminergic neurons and microglial activation caused by rotenone. Moreover, Boswellia ameliorated rotenone-induced decrease in the striatal dopamine and impairment in motor function. Accumulation of α-synuclein meditated by rotenone was significantly ameliorated by Boswellia. Also, we showed that β-boswellic acid, the active constituents of Boswellia serrata gum, induced AMPK phosphorylation and attenuated α-synuclein phosphorylation in SHSY5 cells. These results suggest that Boswellia protected the dopaminergic neurons from rotenone neurotoxicity via activation of the AMPK pathway which might be associated with attenuation of α-synuclein aggregation and neuroinflammation. Further investigations are warranted to identify specific molecules in Boswellia which are responsible for the neuroprotection.

Targeting for Success: Demonstrating Proof-of-Concept with Mechanistic Early Phase Clinical Pharmacology Studies for Disease-Modification in Neurodegenerative Disorders

The clinical failure rate for disease-modifying treatments (DMTs) that slow or stop disease progression has been nearly 100% for the major neurodegenerative disorders (NDDs), with many compounds failing in expensive and time-consuming phase 2 and 3 trials for lack of efficacy. Here, we critically review the use of pharmacological and mechanistic biomarkers in early phase clinical trials of DMTs in NDDs, and propose a roadmap for providing early proof-of-concept to increase R&D productivity in this field of high unmet medical need. A literature search was performed on published early phase clinical trials aimed at the evaluation of NDD DMT compounds using MESH terms in PubMed. Publications were selected that reported an early phase clinical trial with NDD DMT compounds between 2010 and November 2020. Attention was given to the reported use of pharmacodynamic (mechanistic and physiological response) biomarkers. A total of 121 early phase clinical trials were identified, of which 89 trials (74%) incorporated one or multiple pharmacodynamic biomarkers. However, only 65 trials (54%) used mechanistic (target occupancy or activation) biomarkers to demonstrate target engagement in humans. The most important categories of early phase mechanistic and response biomarkers are discussed and a roadmap for incorporation of a robust biomarker strategy for early phase NDD DMT clinical trials is proposed. As our understanding of NDDs is improving, there is a rise in potentially disease-modifying treatments being brought to the clinic. Further increasing the rational use of mechanistic biomarkers in early phase trials for these (targeted) therapies can increase R&D productivity with a quick win/fast fail approach in an area that has seen a nearly 100% failure rate to date.

Transplantation of Human Neural Progenitor Cells (NPC) into Putamina of Parkinsonian Patients: A Case Series Study, Safety and Efficacy Four Years after Surgery

Individuals with Parkinson’s disease (PD) suffer from motor and mental disturbances due to degeneration of dopaminergic and non-dopaminergic neuronal systems. Although they provide temporary symptom relief, current treatments fail to control motor and non-motor alterations or to arrest disease progression. Aiming to explore safety and possible motor and neuropsychological benefits of a novel strategy to improve the PD condition, a case series study was designed for brain grafting of human neural progenitor cells (NPCs) to a group of eight patients with moderate PD. A NPC line, expressing Oct-4 and Sox-2, was manufactured and characterized. Using stereotactic surgery, NPC suspensions were bilaterally injected into patients’ dorsal putamina. Cyclosporine A was given for 10 days prior to surgery and continued for 1 month thereafter. Neurological, neuropsychological, and brain imaging evaluations were performed pre-operatively, 1, 2, and 4 years post-surgery. Seven of eight patients have completed 4-year follow-up. The procedure proved to be safe, with no immune responses against the transplant, and no adverse effects. One year after cell grafting, all but one of the seven patients completing the study showed various degrees of motor improvement, and five of them showed better response to medication. PET imaging showed a trend toward enhanced midbrain dopaminergic activity. By their 4-year evaluation, improvements somewhat decreased but remained better than at baseline. Neuropsychological changes were minor, if at all. The intervention appears to be safe. At 4 years post-transplantation we report that undifferentiated NPCs can be delivered safely by stereotaxis to both putamina of patients with PD without causing adverse effects. In 6/7 patients in OFF condition improvement in UPDRS III was observed. PET functional scans suggest enhanced putaminal dopaminergic neurotransmission that could correlate with improved motor function, and better response to L-DOPA. Patients’ neuropsychological scores were unaffected by grafting. Trial Registration: Fetal derived stem cells for Parkinson’s disease https://doi.org/10.1186/ISRCTN39104513Reg#ISRCTN39104513

Glimepiride prevents paraquat-induced Parkinsonism in mice: involvement of oxidative stress and neuroinflammation

There is a growing number of epidemiological and molecular studies which suggest that diabetes is associated with an increased risk of Parkinson's disease (PD). Hence, in this study, the effect of glimepiride (GPD), a sulphonylurea (antidiabetic) on paraquat (PQT)-induced Parkinsonism was evaluated in mice. Thirty-six mice were randomly divided into six groups (n = 6) and treated orally for 21 consecutive days as follows: Group 1: vehicle (10 mL/kg), Group 2: PQT (10 mg/kg, i.p., twice per week for 3 weeks), Group 3-5: GPD (1, 2 or 4 mg/kg) + PQT (10 mg/kg, i.p., twice per week for 3 weeks), Group 6: GPD (4 mg/kg, p.o.). The effects of the treatment on motor coordination were evaluated using the rotarod performance, bar and open field tests while working memory was assayed using Y-maze test. Paraquat injection induced significant decrease in falling time, number of crosses and percentage alternation behaviour with a concomitant increase in the duration of cataleptic behaviour in the rotarod, open field, Y-maze and bar tests, respectively, which was ameliorated by GPD treatment. PQT also increased lipid peroxidation, peroxynitrite and TNF-α generations as well as deficit in superoxide dismutase and GSH activities in the midbrain. PQT-induced oxidative stress and neuroinflammation was attenuated by GPD treatment. Findings from this study showed that GPD prevents PQT-induced motor dysfunction, memory impairment, oxidative stress and neuroinflammation through enhancement of antioxidant defense system and inhibition of pro-inflammatory cytokine release. Thus, GPD could be a potential adjunct in the management of Parkinsonism.

Progression marker of Parkinson's disease: a 4-year multi-site imaging study

Progression markers of Parkinson's disease are crucial for successful therapeutic development. Recently, a diffusion magnetic resonance imaging analysis technique using a bitensor model was introduced allowing the estimation of the fractional volume of free water within a voxel, which is expected to increase in neurodegenerative disorders such as Parkinson's disease. Prior work demonstrated that free water in the posterior substantia nigra was elevated in Parkinson's disease compared to controls across single- and multi-site cohorts, and increased over 1 year in Parkinson's disease but not in controls at a single site. Here, the goal was to validate free water in the posterior substantia nigra as a progression marker in Parkinson's disease, and describe the pattern of progression of free water in patients with a 4-year follow-up tested in a multicentre international longitudinal study of de novo Parkinson's disease (http://www.ppmi-info.org/). The analyses examined: (i) 1-year changes in free water in 103 de novo patients with Parkinson's disease and 49 controls; (ii) 2- and 4-year changes in free water in a subset of 46 patients with Parkinson's disease imaged at baseline, 12, 24, and 48 months; (iii) whether 1- and 2-year changes in free water predict 4-year changes in the Hoehn and Yahr scale; and (iv) the relationship between 4-year changes in free water and striatal binding ratio in a subgroup of Parkinson's disease who had undergone both diffusion and dopamine transporter imaging. Results demonstrated that: (i) free water level in the posterior substantia nigra increased over 1 year in de novo Parkinson's disease but not in controls; (ii) free water kept increasing over 4 years in Parkinson's disease; (iii) sex and baseline free water predicted 4-year changes in free water; (iv) free water increases over 1 and 2 years were related to worsening on the Hoehn and Yahr scale over 4 years; and (v) the 4-year increase in free water was associated with the 4-year decrease in striatal binding ratio in the putamen. Importantly, all longitudinal results were consistent across sites. In summary, this study demonstrates an increase over 1 year in free water in the posterior substantia nigra in a large cohort of de novo patients with Parkinson's disease from a multi-site cohort study and no change in healthy controls, and further demonstrates an increase of free water in Parkinson's disease over the course of 4 years. A key finding was that results are consistent across sites and the 1-year and 2-year increase in free water in the posterior substantia nigra predicts subsequent long-term progression on the Hoehn and Yahr staging system. Collectively, these findings demonstrate that free water in the posterior substantia nigra is a valid, progression imaging marker of Parkinson's disease, which may be used in clinical trials of disease-modifying therapies.

The need for new approaches in CNS drug discovery: Why drugs have failed, and what can be done to improve outcomes

An important goal of biomedical research is to translate basic research findings into useful medical advances. In the field of neuropharmacology this requires understanding disease mechanisms as well as the effects of drugs and other compounds on neuronal function. Our hope is that this information will result in new or improved treatment for CNS disease. Despite great progress in our understanding of the structure and functions of the CNS, the discovery of new drugs and their clinical development for many CNS disorders has been problematic. As a result, CNS drug discovery and development programs have been subjected to significant cutbacks and eliminations over the last decade. While there has been recent resurgence of interest in CNS targets, these past changes in priority of the pharmaceutical and biotech industries reflect several well-documented realities. CNS drugs in general have higher failure rates than non-CNS drugs, both preclinically and clinically, and in some areas, such as the major neurodegenerative diseases, the clinical failure rate for disease-modifying treatments has been 100%. The development times for CNS drugs are significantly longer for those drugs that are approved, and post-development regulatory review is longer. In this introduction we review some of the reasons for failure, delineating both scientific and technical realities, some unique to the CNS, that have contributed to this. We will focus on major neurodegenerative disorders, which affect millions, attract most of the headlines, and yet have witnessed the fewest successes. We will suggest some changes that, when coupled with the approaches discussed in the rest of this special volume, may improve outcomes in future CNS-targeted drug discovery and development efforts. This article is part of the Special Issue entitled "Beyond small molecules for neurological disorders".

A Novel Parkinson's Disease Drug Candidate with Potent Anti-neuroinflammatory Effects through the Src Signaling Pathway

Numerous drug treatments are available for Parkinson's disease (PD), an age-related neurodegenerative disease, but most cause serious side effects. Therefore, novel therapeutic strategies that halt disease progression and allow for long-term administration are urgently needed. Neuroinflammation critically contributes to the pathogenesis of PD. Here, we report the discovery and optimization of phloroglucinol derivatives, a novel class of anti-neuroinflammatory compounds. Structural modifications of the hit compound 3-methyl-1-(2,4,6-trihydroxyphenyl)butan-1-one produced 43 derivatives, including a preclinical candidate (compound 21), that exhibited potent in vitro anti-neuroinflammatory effects, good blood-brain barrier penetration, and desirable safety margins in mice at a median lethal dose (LD₅₀) >5000 mg/kg. Its in vivo efficacy was demonstrated in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)- and MPTP/probenecid (prob)-induced subacute and chronic PD models, respectively, and α-synuclein transgenic mice. Mechanistic studies revealed neuroinflammation inhibition by targeting Src/phosphatase and tensin homologue deleted on chromosome 10 (PTEN)/Akt signaling might be promising. We highlighted the potential usefulness of phloroglucinol derivatives in PD treatment.

The Rationale for Exercise in the Management of Pain in Parkinson's Disease

Pain is a distressing non-motor symptom experienced by up to 85% of people with Parkinson’s disease (PD), yet it is often untreated. This pain is likely to be influenced by many factors, including the disease process, PD impairments as well as co-existing musculoskeletal and/or neuropathic pain conditions. Expert opinion recommends that exercise is included as one component of pain management programs; however, the effect of exercise on pain in this population is unclear. This review presents evidence describing the potential influence of exercise on the pain-related pathophysiological processes present in PD. Emerging evidence from both animal and human studies suggests that exercise might contribute to neuroplasticity and neuro-restoration by increasing brain neurotrophic factors, synaptic strength and angiogenesis, as well as stimulating neurogenesis and improving metabolism and the immune response. These changes may be beneficial in improving the central processing of pain. There is also evidence that exercise can activate both the dopaminergic and non-dopaminergic pain inhibitory pathways, suggesting that exercise may help to modulate the experience of pain in PD. Whilst clinical data on the effects of exercise for pain relief in people with PD are scarce, and are urgently needed, preliminary guidelines are presented for exercise prescription for the management of central neuropathic, peripheral neuropathic and musculoskeletal pain in PD.

Neurophysiological basis of rapid eye movement sleep behavior disorder: informing future drug development

Rapid eye movement (REM) sleep behavior disorder (RBD) is a parasomnia characterized by a history of recurrent nocturnal dream enactment behavior and loss of skeletal muscle atonia and increased phasic muscle activity during REM sleep: REM sleep without atonia. RBD and associated comorbidities have recently been identified as one of the most specific and potentially sensitive risk factors for later development of any of the alpha-synucleinopathies: Parkinson's disease, dementia with Lewy bodies, and other atypical parkinsonian syndromes. Several other sleep-related abnormalities have recently been identified in patients with RBD/Parkinson's disease who experience abnormalities in sleep electroencephalographic frequencies, sleep-wake transitions, wake and sleep stability, occurrence and morphology of sleep spindles, and electrooculography measures. These findings suggest a gradual involvement of the brainstem and other structures, which is in line with the gradual involvement known in these disorders. We propose that these findings may help identify biomarkers of individuals at high risk of subsequent conversion to parkinsonism.

[Morphological parameters of the heterogeneity of the substantia nigra in elderly men and women]

OBJECTIVE

to define the quantitative characteristics of cell structures in the substantia nigra pars compacta of neurologically healthy elderly people (men and women).

MATERIAL AND METHODS

Autopsy brain materials from neurologically healthy men and women who had died from intercurrent diseases at the age of 72 to 87 years were examined for quantitative characteristics of the substantia nigra pars compacta, by applying computed morphometric methods.

RESULTS

In the elderly people (men and women), the compactness of arrangement of neurons, including those containing tyrosine hydroxylase (a marker of dopamine neurons), was much higher and the glial index was lower in the ventral area of the substantia nigra pars compacta than in the dorsal area. Comparing the structures in the substantia nigra pars compacta showed that the neurons were larger in the dorsal area and the variability of the compactness of their arrangement and the glial index were higher in the women than in the men.

CONCLUSION

In the elderly people, the cell structures in the substantia nigra pars compacta are typified by high morphometric heterogeneity.

Molecular, Neurochemical, and Behavioral Hallmarks of Reserpine as a Model for Parkinson's Disease: New Perspectives to a Long-Standing Model

The administration of reserpine to rodents was one of the first models used to investigate the pathophysiology and screening for potential treatments of Parkinson's disease (PD). The reserpine model was critical to the understanding of the role of monoamine system in the regulation of motor and affective disorders, as well as the efficacy of current PD treatments, such as L-DOPA and dopamine agonists. Nevertheless, with the introduction of toxin-induced and genetic models of PD, reserpine became underused. The main rationale to this drawback was the supposed absence of reserpine construct validity with PD. Here, we highlight classical and recent experimental findings that support the face, pharmacological, and construct validity of reserpine PD model and reason against the current rationale for its underuse. We also aim to shed a new perspective upon the model by discussing the main challenges and potentials for the reserpine model of PD.

Adult hippocampal neurogenesis in Parkinson's disease: impact on neuronal survival and plasticity

In Parkinson's disease (PD) and other synucleinopathies, chronic neurodegeneration occurs within different areas of the central nervous system leading to progressive motor and nonmotor symptoms. The symptomatic treatment options that are currently available do not slow or halt disease progression. This highlights the need of a better understanding of disease mechanisms and disease models. The generation of newborn neurons in the adult hippocampus and in the subventricular zone/olfactory bulb system is affected by many different regulators and possibly involved in memory processing, depression, and olfaction, symptoms which commonly occur in PD. The pathology of the adult neurogenic niches in human PD patients is still mostly elusive, but different preclinical models have shown profound alterations of adult neurogenesis. Alterations in stem cell proliferation, differentiation, and survival as well as neurite outgrowth and spine formation have been related to different aspects in PD pathogenesis. Therefore, neurogenesis in the adult brain provides an ideal model to study disease mechanisms and compounds. In addition, adult newborn neurons have been proposed as a source of endogenous repair. Herein, we review current knowledge about the adult neurogenic niches in PD and highlight areas of future research.

Parkinson's disease and risk of mortality: meta-analysis and systematic review

To evaluate the existing prospective observational studies on the morality risk among Parkinson's disease (PD) patients and determine the overall risk ratio (RR) of mortality by conducting a meta-analysis and systematic review. Original articles published in English were searched in PubMed and Embase databases prior to March 2013. Only prospective observational studies providing adjusted risk estimates related to PD and future mortality were considered eligible. Pooled adjusted RR and 95% confidence interval (CI) were computed either by fixed-effects models or by random-effects models. Eight studies with 72,833 participants were identified and analysed. In the pooled analyses, patients with PD had a greater risk of all-cause mortality (RR = 2.22; 95% CI: 1.78-2.77). Subgroup analyses based on the design, gender, follow-up duration and sample size showed that a consistent positive association between PD and the mortality risk in each subgroup. However, no statistical significance was found for the baseline age <65 years (RR = 1.42; 95% CI: 0.72-2.77). PD patients with dementia had particularly high mortality risks (RR = 3.78; 95% CI: 2.06-6.92). This meta-analysis indicated that among patients with PD, the all-cause mortality increased by 2.22-fold compared with the general population. PD patients with dementia particularly had higher risks of mortality.

123I-iodobenzamide SPECT is not an independent predictor of dopaminergic responsiveness in patients with suspected atypical parkinsonian syndromes

The prediction of dopaminergic responsiveness in patients with parkinsonism is desirable for effective treatment strategies. We investigated whether striatal dopamine D2/D3 receptor (D2R) binding assessed by (123)I-iodobenzamide SPECT is an independent predictor of dopaminergic responsiveness in patients with parkinsonism.

METHODS

Seventy-eight patients with clinically suspected atypical parkinsonian syndrome (APS) were prospectively recruited for imaging. To quantify striatal D2R binding, (123)I-iodobenzamide SPECT datasets were subjected to an observer-independent, regions-of-interest analysis. A final clinical diagnosis of Lewy-body disease (LBD) or APS was made after a mean follow-up of 12 mo. On the basis of follow-up data, dopaminergic responsiveness was classified as 0 (none), 1 (transient), 2 (sustained mild), or 3 (sustained strong). Uni- and multivariate analyses of the relationship between treatment response, D2R binding, and confounding variables were conducted.

RESULTS

Sixty patients with clinically verified LBD (n = 28; 22/28 with Parkinson disease) or APS (n = 32), in whom dopaminergic responsiveness could be assessed (n = 19/13/15/13 in categories 0/1/2/3; 18 were excluded because of insufficient dosing), were included in the statistical analysis. Univariate analyses revealed that a sustained treatment response was significantly associated with higher D2R binding, clinical diagnosis of LBD, lower Hoehn and Yahr scores, and younger age. After multivariate correction of D2R binding for diagnosis, age, symptom duration, Hoehn and Yahr score, and dopaminergic pretreatment, no association was found between D2R binding and treatment response, either in the pooled group or in LBD or APS subgroups.

CONCLUSION

Striatal D2R binding assessed by (123)I-iodobenzamide SPECT does not provide additional predictive information about treatment response beyond other clinical variables, most notably the clinical diagnosis.

Status and perspectives of neuroprotective therapies in glaucoma: the European Glaucoma Society White Paper

Glaucoma, a chronic progressive neuropathy and the most frequent cause of irreversible blindness worldwide, is commonly treated by medication or surgery aimed at lowering intraocular pressure. In view of the limited therapeutic options, the European Glaucoma Society (EGS) sponsored two Think Tank Meetings with the goal of assessing the current status and the overall perspectives for neuroprotective treatment strategies in glaucoma. The results of the meetings are summarized in this EGS White Paper.

Thinking laterally about neurodegenerative proteinopathies

Many neurodegenerative disorders, including Alzheimer's disease, Parkinson's disease, Huntington's disease, and frontotemporal dementia, are proteinopathies that are associated with the aggregation and accumulation of misfolded proteins. While remarkable progress has been made in understanding the triggers of these conditions, several challenges have hampered the translation of preclinical therapies targeting pathways downstream of the initiating proteinopathies. Clinical trials in symptomatic patients using therapies directed toward initiating trigger events have met with little success, prompting concerns that such therapeutics may be of limited efficacy when used in advanced stages of the disease rather than as prophylactics. Herein, we discuss gaps in our understanding of the pathological processes downstream of the trigger and potential strategies to identify common features of the downstream degenerative cascade in multiple CNS proteinopathies, which could potentially lead to the development of common therapeutic targets for multiple disorders.

Monoamine oxidases in development

Monoamine oxidases (MAOs) are flavoproteins of the outer mitochondrial membrane that catalyze the oxidative deamination of biogenic and xenobiotic amines. In mammals there are two isoforms (MAO-A and MAO-B) that can be distinguished on the basis of their substrate specificity and their sensitivity towards specific inhibitors. Both isoforms are expressed in most tissues, but their expression in the central nervous system and their ability to metabolize monoaminergic neurotransmitters have focused MAO research on the functionality of the mature brain. MAO activities have been related to neurodegenerative diseases as well as to neurological and psychiatric disorders. More recently evidence has been accumulating indicating that MAO isoforms are expressed not only in adult mammals, but also before birth, and that defective MAO expression induces developmental abnormalities in particular of the brain. This review is aimed at summarizing and critically evaluating the new findings on the developmental functions of MAO isoforms during embryogenesis.

The role of innate and adaptive immunity in Parkinson's disease

In recent years, inflammation has become implicated as a major pathogenic factor in the onset and progression of Parkinson's disease. Understanding the precise role for inflammation in PD will likely lead to understanding of how sporadic disease arises. In vivo evidence for inflammation in PD includes microglial activation, increased expression of inflammatory genes in the periphery and in the central nervous system (CNS), infiltration of peripheral immune cells into the CNS, and altered composition and phenotype of peripheral immune cells. These findings are recapitulated in various animal models of PD and are reviewed herein. Furthermore, we examine the potential relevance of PD-linked genetic mutations to altered immune function and the extent to which environmental exposures that recapitulate these phenotypes, which may lead to sporadic PD through similar mechanisms. Given the implications of immune system involvement on disease progression, we conclude by reviewing the evidence supporting the potential efficacy of immunomodulatory therapies in PD prevention or treatment. There is a clear need for additional research to clarify the role of immunity and inflammation in this chronic, neurodegenerative disease.

Disease modification in Parkinson’s disease: are we there yet with currently available therapies?

SUMMARY Management of Parkinson’s disease (PD) is currently based primarily on dopamine-replacement therapy for the alleviation of motor symptoms. Current medical and surgical therapies can provide long-lasting symptomatic benefit, but they do not modify progression of the disease. Research is ongoing to find a therapy that can provide neuroprotection, defined herein as preventing vulnerable neurons from dying. Studies of neuroprotection are limited by a lack of adequate biomarkers of PD progression and by the confounding symptomatic effects of many putative neuroprotective therapies. Studies have shown that levodopa prolongs life, but they have not clearly shown that it modifies disease progression. Trials of dopamine agonists have demonstrated symptomatic effect but no unequivocal neuroprotective benefits. While some studies of monamine oxidase B inhibitors have been promising, they have not conclusively proven disease modification. Exercise provides many benefits to patients with PD, may modify the progression of the disease and should be part of each patient’s treatment plan.

Rasagiline: a review of its use in the treatment of idiopathic Parkinson's disease

Rasagiline (Azilect®), a selective, irreversible, monoamine oxidase-B inhibitor, is available in the EU, the US and in several other countries worldwide, including Canada and Israel. It is indicated for the treatment of idiopathic Parkinson's disease as monotherapy or as adjunctive therapy to levodopa in patients [corrected]with end-of-dose fluctuations in the EU and for the treatment of adult patients with the signs and symptoms of idiopathic Parkinson's disease in the US. This article reviews the pharmacological properties, therapeutic efficacy and tolerability of rasagiline as monotherapy or as adjunctive therapy to levodopa in patients with Parkinson's disease. Oral rasagiline as monotherapy or as adjunctive therapy to levodopa was effective in the symptomatic treatment of adult patients with Parkinson's disease participating in double-blind, placebo-controlled, multinational studies. In patients with early Parkinson's disease, monotherapy with rasagiline 1 mg/day (recommended dosage) significantly slowed the rate of worsening (i.e. an increase in the Unified Parkinson's Disease Rating Scale [UPDRS] score) in the ADAGIO and TEMPO studies, with the results from the ADAGIO study for rasagiline 1 mg/day suggesting a slowing of clinical progression. However, at the higher dosage of 2 mg/day, rasagiline met the primary endpoint in the TEMPO study and the first, but not the second, of three hierarchical primary endpoints in the ADAGIO study. Compared with delayed-start rasagiline monotherapy, early initiation was associated with a slower long-term progression of the clinical signs and symptoms of Parkinson's disease in the TEMPO study. As adjunctive therapy to levodopa in the LARGO and PRESTO studies, rasagiline 0.5 and/or 1 mg/day significantly reduced the total daily 'off' time (primary efficacy endpoint) and significantly improved the Clinical Global Impression score, the UPDRS activities of daily living subscale score during 'off' time and the UPDRS motor subscale score during 'on' time compared with placebo in patients with advanced Parkinson's disease. Although rasagiline showed neuroprotective properties both in vitro and in vivo, identifying its potential to slow clinical progression in the clinical setting has been elusive to date and was not definitively demonstrated in the studies discussed in this article. Additional rasagiline studies specifically designed to assess the clinical progression of Parkinson's disease while addressing the potentially confounding factors of the delayed-start study design would therefore be of interest. As monotherapy or as adjunctive therapy to levodopa, rasagiline was generally well tolerated, with the frequency and nature of treatment-emergent adverse events generally similar across clinical studies and between rasagiline and placebo groups. Therapy with rasagiline appears to be associated with a low incidence of cognitive and behavioural adverse events. Thus, oral rasagiline as monotherapy or as adjunctive therapy to levodopa provides a useful option in the treatment of adult patients with Parkinson's disease.