PINK, PANK, or PARK? A clinicians' guide to familial parkinsonism

Calcium Deregulation in Neurodegeneration and Neuroinflammation in Parkinson's Disease: Role of Calcium-Storing Organelles and Sodium-Calcium Exchanger

Parkinson's disease (PD) is a progressive neurodegenerative disorder that lacks effective treatment strategies to halt or delay its progression. The homeostasis of Ca2+ ions is crucial for ensuring optimal cellular functions and survival, especially for neuronal cells. In the context of PD, the systems regulating cellular Ca2+ are compromised, leading to Ca2+-dependent synaptic dysfunction, impaired neuronal plasticity, and ultimately, neuronal loss. Recent research efforts directed toward understanding the pathology of PD have yielded significant insights, particularly highlighting the close relationship between Ca2+ dysregulation, neuroinflammation, and neurodegeneration. However, the precise mechanisms driving the selective loss of dopaminergic neurons in PD remain elusive. The disruption of Ca2+ homeostasis is a key factor, engaging various neurodegenerative and neuroinflammatory pathways and affecting intracellular organelles that store Ca2+. Specifically, impaired functioning of mitochondria, lysosomes, and the endoplasmic reticulum (ER) in Ca2+ metabolism is believed to contribute to the disease's pathophysiology. The Na+-Ca2+ exchanger (NCX) is considered an important key regulator of Ca2+ homeostasis in various cell types, including neurons, astrocytes, and microglia. Alterations in NCX activity are associated with neurodegenerative processes in different models of PD. In this review, we will explore the role of Ca2+ dysregulation and neuroinflammation as primary drivers of PD-related neurodegeneration, with an emphasis on the pivotal role of NCX in the pathology of PD. Consequently, NCXs and their interplay with intracellular organelles may emerge as potentially pivotal players in the mechanisms underlying PD neurodegeneration, providing a promising avenue for therapeutic intervention aimed at halting neurodegeneration.

Endoplasmic reticulum stress and its role in various neurodegenerative diseases

The Endoplasmic reticulum (ER), a critical cellular organelle, maintains cellular homeostasis by regulating calcium levels and orchestrating essential functions such as protein synthesis, folding, and lipid production. A pivotal aspect of ER function is its role in protein quality control. When misfolded proteins accumulate within the ER due to factors like protein folding chaperone dysfunction, toxicity, oxidative stress, or inflammation, it triggers the Unfolded protein response (UPR). The UPR involves the activation of chaperones like calnexin, calreticulin, glucose-regulating protein 78 (GRP78), and Glucose-regulating protein 94 (GRP94), along with oxidoreductases like protein disulphide isomerases (PDIs). Cells employ the Endoplasmic reticulum-associated degradation (ERAD) mechanism to counteract protein misfolding. ERAD disruption causes the detachment of GRP78 from transmembrane proteins, initiating a cascade involving Inositol-requiring kinase/endoribonuclease 1 (IRE1), Activating transcription factor 6 (ATF6), and Protein kinase RNA-like endoplasmic reticulum kinase (PERK) pathways. The accumulation and deposition of misfolded proteins within the cell are hallmarks of numerous neurodegenerative diseases. These aberrant proteins disrupt normal neuronal signalling and contribute to impaired cellular homeostasis, including oxidative stress and compromised protein degradation pathways. In essence, ER stress is defined as the cellular response to the accumulation of misfolded proteins in the endoplasmic reticulum, encompassing a series of signalling pathways and molecular events that aim to restore cellular homeostasis. This comprehensive review explores ER stress and its profound implications for the pathogenesis and progression of neurodegenerative diseases.

Risk factors associated with age at onset of Parkinson's disease in the UK Biobank

Substantial evidence shown that the age at onset (AAO) of Parkinson's disease (PD) is a major determinant of clinical heterogeneity. However, the mechanisms underlying heterogeneity in the AAO remain unclear. To investigate the risk factors with the AAO of PD, a total of 3156 patients with PD from the UK Biobank were included in this study. We evaluated the effects of polygenic risk scores (PRS), nongenetic risk factors, and their interaction on the AAO using Mann-Whitney U tests and regression analyses. We further identified the genes interacting with nongenetic risk factors for the AAO using genome-wide environment interaction studies. We newly found physical activity (P < 0.0001) was positively associated with AAO and excessive daytime sleepiness (P < 0.0001) was negatively associated with AAO, and reproduced the positive associations of smoking and non-steroidal anti-inflammatory drug intake and the negative association of family history with AAO. In the dose-dependent analyses, smoking duration (P = 1.95 × 10-6), coffee consumption (P = 0.0150), and tea consumption (P = 0.0008) were positively associated with AAO. Individuals with higher PRS had younger AAO (P = 3.91 × 10-5). In addition, we observed a significant interaction between the PRS and smoking for AAO (P = 0.0316). Specifically, several genes, including ANGPT1 (P = 7.17 × 10-7) and PLEKHA6 (P = 4.87 × 10-6), may influence the positive relationship between smoking and AAO. Our data suggests that genetic and nongenetic risk factors are associated with the AAO of PD and that there is an interaction between the two.

A Perspective on the Link between Mitochondria-Associated Membranes (MAMs) and Lipid Droplets Metabolism in Neurodegenerative Diseases

Mitochondria interact with the endoplasmic reticulum (ER) through contacts called mitochondria-associated membranes (MAMs), which control several processes, such as the ER stress response, mitochondrial and ER dynamics, inflammation, apoptosis, and autophagy. MAMs represent an important platform for transport of non-vesicular phospholipids and cholesterol. Therefore, this region is highly enriched in proteins involved in lipid metabolism, including the enzymes that catalyze esterification of cholesterol into cholesteryl esters (CE) and synthesis of triacylglycerols (TAG) from fatty acids (FAs), which are then stored in lipid droplets (LDs). LDs, through contact with other organelles, prevent the toxic consequences of accumulation of unesterified (free) lipids, including lipotoxicity and oxidative stress, and serve as lipid reservoirs that can be used under multiple metabolic and physiological conditions. The LDs break down by autophagy releases of stored lipids for energy production and synthesis of membrane components and other macromolecules. Pathological lipid deposition and autophagy disruption have both been reported to occur in several neurodegenerative diseases, supporting that lipid metabolism alterations are major players in neurodegeneration. In this review, we discuss the current understanding of MAMs structure and function, focusing on their roles in lipid metabolism and the importance of autophagy in LDs metabolism, as well as the changes that occur in neurogenerative diseases.

Melatonin Can Modulate Neurodegenerative Diseases by Regulating Endoplasmic Reticulum Stress

As people age, their risks of developing degenerative diseases such as cancer, diabetes, Parkinson's Disease (PD), Alzheimer's Disease (AD), rheumatoid arthritis, and osteoporosis are generally increasing. Millions of people worldwide suffer from these diseases as they age. In most countries, neurodegenerative diseases are generally recognized as the number one cause afflicting the elderly. Endoplasmic reticulum (ER) stress has been suggested to be associated with some human neurological diseases, such as PD and AD. Melatonin, a neuroendocrine hormone mainly synthesized in the pineal gland, is involved in pleiotropically biological functions, including the control of the circadian rhythm, immune enhancement, and antioxidant, anti-aging, and anti-tumor effects. Although there are many papers on the prevention or suppression of diseases by melatonin, there are very few papers about the effects of melatonin on ER stress in neurons and neurodegenerative diseases. This paper aims to summarize and present the effects of melatonin reported so far, focusing on its effects on neurons and neurodegenerative diseases related to ER stress. Studies have shown that the primary target molecule of ER stress for melatonin is CHOP, and PERK and GRP78/BiP are the secondary target molecules. Therefore, melatonin is crucial in protecting neurons and treating neurodegeneration against ER stress.

Lipophagy: a new player in CNS disorders

Lipophagy is the process of selective degradation of lipid droplets (LDs) by autophagy. Several studies have highlighted the importance of lipophagy in regulating cellular lipid levels in various tissues and disease conditions. In recent years, disruption of autophagy and accumulation of LDs have been reported as pathological hallmarks in several neurodegenerative and neuroinflammatory diseases, raising the question whether lipophagy is a process that is important in the progression of these disorders. This supports the growing interest in lipid metabolism as a major player in neurodegeneration, and the emerging understanding of several neurological pathologies as not only proteinopathies but also lipidopathies. In this review we discuss the importance of lipophagy in the most common central nervous system diseases. We examine the latest evidence for the reported interplay between abnormalities in lipid accumulation and autophagy, and propose lipophagy as a potentially important mechanism in neurodegeneration.

Butyrate Protects Against Salsolinol-Induced Toxicity in SH-SY5Y Cells: Implication for Parkinson's Disease

Parkinson's disease (PD), a progressive neurodegenerative disorder, is associated with the destruction of dopamine neurons in the substantia nigra (SN) and the formation of Lewy bodies in basal ganglia. Risk factors for PD include aging, as well as environmental and genetic factors. Recent converging reports suggest a role for the gut microbiome and epigenetic factors in the onset and/or progression of PD. Of particular relevance and potential therapeutic targets in this regard are histone deacetylases (HDACs), enzymes that are involved in chromatin remodeling. Butyrate, a short-chain fatty acid (FA) produced in the gut and presumably acting via several G protein-coupled receptors (GPCRs) including FA3 receptors (FA3Rs), is a well-known HDAC inhibitor that plays an important role in maintaining homeostasis of the gut-brain axis. Recently, its significance in regulation of some critical brain functions and usefulness in neurodegenerative diseases such as PD has been suggested. In this study we sought to determine whether butyrate may have protective effects against salsolionl (SALS)-induced toxicity in SH-SY5Y cells. SALS, an endogenous product of aldehyde and dopamine condensation, may be selectively toxic to dopaminergic neurons. SH-SY5Y cells, derived from human neuroblastoma cells, are used as a model of these neurons. Exposure of SH-SY5Y cells for 24 h to 400 μM SALS resulted in approximately 60% cell death, which was concentration-dependently prevented by butyrate. The effects of butyrate in turn were significantly attenuated by beta-hydroxy butyrate (BHB), a selective FA3R antagonist. Moreover, a selective FA3R agonist (AR 420626) also provided protective effects against SALS, which was totally blocked by BHB. These findings provide further support that butyrate or an agonist of FA3R may be of therapeutic potential in PD.

Oxyresveratrol exerts ATF4- and Grp78-mediated neuroprotection against endoplasmic reticulum stress in experimental Parkinson's disease

Objectives: Endoplasmic reticulum (ER) stress is one of the key mechanisms contributing to Parkinson's disease (PD) pathology. Pathways triggered by ER stress are protective at early stages and initiate apoptosis when the damage is extensive. Methods: We have previously reported that oxyresveratrol rescues cells from oxidative stress and apoptosis in a cell culture model of PD. The aim of this study was to investigate whether the neuroprotective mechanism of oxyresveratrol extends to PD-associated ER stress. For this purpose, we employed two cellular models; to induce severe ER stress, Mes23.5 cells were treated with 6-hydroxydopamine (6-OHDA) and for ER stress driven by chaperones, human neuroblastoma cells were stably transfected to overexpress familial mutants of α-synuclein (α-syn). Results: Our results indicate that oxyresveratrol exhibits distinct modes of protection in both models. In the 6-OHDA model, it inhibited the transcription of activating transcription factor 4 (ATF4), which controls the fate of pro-apoptotic proteins. On the other hand, in the α-syn model, oxyresveratrol suppressed mutant A30P oligomer formation, thereby facilitating a reduction of the ER-chaperone, 78-kDa glucose-regulated protein (Grp78). Discussion: In summary, oxyresveratrol is protective against ER stress induced by two different triggers of PD. Owing to its wide range of defense mechanisms, oxyresveratrol is an ideal candidate for a multifactorial disease like PD.

The Genetics of Parkinson Disease

The 200years of research efforts on Parkinson disease (PD) form the basis of our understanding of the second most common neurodegenerative disorder after Alzheimer disease. This journey has been marked by the revolutionary discovery of a neurotransmitter replacement therapy that provides a longer and healthier life to patients. Since 1997, the advances in the genetics of PD have expanded our understanding of this neurodegenerative disorder and they are opening up new ways to search for disease-modifying therapies. This chapter is a summary of the historical discoveries and latest progress in PD research.

Mitochondrial Function, Biology, and Role in Disease: A Scientific Statement From the American Heart Association

Cardiovascular disease is a major leading cause of morbidity and mortality in the United States and elsewhere. Alterations in mitochondrial function are increasingly being recognized as a contributing factor in myocardial infarction and in patients presenting with cardiomyopathy. Recent understanding of the complex interaction of the mitochondria in regulating metabolism and cell death can provide novel insight and therapeutic targets. The purpose of this statement is to better define the potential role of mitochondria in the genesis of cardiovascular disease such as ischemia and heart failure. To accomplish this, we will define the key mitochondrial processes that play a role in cardiovascular disease that are potential targets for novel therapeutic interventions. This is an exciting time in mitochondrial research. The past decade has provided novel insight into the role of mitochondria function and their importance in complex diseases. This statement will define the key roles that mitochondria play in cardiovascular physiology and disease and provide insight into how mitochondrial defects can contribute to cardiovascular disease; it will also discuss potential biomarkers of mitochondrial disease and suggest potential novel therapeutic approaches.

Role of Endoplasmic Reticulum Stress and Unfolded Protein Responses in Health and Diseases

Endoplasmic reticulum (ER) is the site of protein synthesis, protein folding, maintainance of calcium homeostasis, synthesis of lipids and sterols. Genetic or environmental insults can alter its function generating ER stress. ER senses stress mainly by three stress sensor pathways, namely protein kinase R-like endoplasmic reticulum kinase-eukaryotic translation-initiation factor 2α, inositol-requiring enzyme 1α-X-box-binding protein 1 and activating transcription factor 6-CREBH, which induce unfolded protein responses (UPR) after the recognition of stress. Recent studies have demonstrated that ER stress and UPR signaling are involved in cancer, metabolic disorders, inflammatory diseases, osteoporosis and neurodegenerative diseases. However, the precise knowledge regarding involvement of ER stress in different disease processes is still debatable. Here we discuss the possible role of ER stress in various disorders on the basis of existing literature. An attempt has also been made to highlight the present knowledge of this field which may help to elucidate and conjure basic mechanisms and novel insights into disease processes which could assist in devising better future diagnostic and therapeutic strategies.

Advances in CNS Imaging Agents: Focus on PET and SPECT Tracers in Experimental and Clinical Use

The physiological functioning of the brain is not well-known in current day medicine and the pathologies of many neuropsychiatric disorders are still not yet fully understood. With our aging population and better life expectancies, it has become imperative to find better biomarkers for disease progression as well as receptor target engagements. In the last decade, these major advances in the field of molecular CNS imaging have been made available with tools such as functional magnetic resonance imaging (fMRI), magnetic resonance spectroscopy (MRS), single photon emission computed tomography (SPECT), and neuroreceptor-targeted positron emission tomography (PET). These tools have given researchers, pharmaceutical companies, and clinical physicians a better method of understanding CNS dysfunctions, and the ability to employ improved therapeutic agents. This review is intended to provide an update on brain imaging agents that are currently used in clinical and translational research toward treatment of CNS disorders. The review begins with amyloid and tau imaging, the former of which has at least three [(18)F] agents that have been recently approved and will soon be available for clinical use for specific indications in the USA and elsewhere. Other prevalent PET and SPECT neurotransmitter system agents, including those newly US FDA-approved imaging agents related to the dopaminergic system, are included. A review of both mature and potentially growing PET imaging agents, including those targeting serotonin and opiate receptor systems, is also provided.

PACAP protects against salsolinol-induced toxicity in dopaminergic SH-SY5Y cells: implication for Parkinson's disease

Pituitary adenylate cyclase-activating polypeptide (PACAP) is an endogenous 38 amino acid containing neuropeptide with various cytoprotective functions including neuroprotection. Administration of PACAP has been shown to reduce damage induced by ischemia, trauma, or exogenous toxic substances. Moreover, mice deficient in PACAP are more vulnerable to damaging insults. In this study, we sought to determine whether PACAP may also be protective against salsolinol-induced toxicity in SH-SY5Y cells and, if so, elucidate its mechanism(s) of action. Salsolinol (SALS) is an endogenous dopamine metabolite with selective toxicity to nigral dopaminergic neurons, which are directly implicated in Parkinson's disease (PD). SH-SY5Y cells, derived from human neuroblastoma cells, express high levels of dopaminergic activity and are used extensively as a model to study these neurons. Exposure of SH-SY5Y cells to 400 μM SALS for 24 h resulted in approximately 50 % cell death that was mediated by apoptosis as determined by cell flow cytometry and increases in caspase-3 levels. Cellular toxicity was also associated with reductions in brain-derived neurotrophic factor and phosphorylated cyclic AMP response element-binding protein. Pretreatment with PACAP dose-dependently attenuated SALS-induced toxicity and the associated apoptosis and the chemical changes. PACAP receptor antagonist PACAP6-38, in turn, dose-dependently blocked the effects of PACAP. Neither PACAP nor PACAP antagonist had any effect of its own on cellular viability. These results suggest the protective effects of PACAP in a cellular model of PD. Hence, PACAP or its agonists could be of therapeutic benefit in PD.

Role of endoplasmic reticulum stress in metabolic disease and other disorders

Perturbations in the normal functions of the endoplasmic reticulum (ER) trigger a signaling network that coordinates adaptive and apoptotic responses. There is accumulating evidence implicating prolonged ER stress in the development and progression of many diseases, including neurodegeneration, atherosclerosis, type 2 diabetes, liver disease, and cancer. With the improved understanding of the underlying molecular mechanisms, therapeutic interventions that target the ER stress response would be potential strategies to treat various diseases driven by prolonged ER stress.

Rare causes of dystonia parkinsonism

The list of genetic causes of syndromes of dystonia parkinsonism grows constantly. As a consequence, the diagnosis becomes more and more challenging for the clinician. Here, we summarize the important causes of dystonia parkinsonism including autosomal-dominant, recessive, and x-linked forms. We cover dopa-responsive dystonia, Wilson's disease, Parkin-, PINK1-, and DJ-1-associated parkinsonism (PARK2, 6, and 7), x-linked dystonia-parkinsonism/Lubag (DYT3), rapid-onset dystonia-parkinsonism (DYT12) and DYT16 dystonia, the syndromes of Neurodegeneration with Brain Iron Accumulation (NBIA) including pantothenate kinase (PANK2)- and PLA2G6 (PARK14)-associated neurodegeneration, neuroferritinopathy, Kufor-Rakeb disease (PARK9) and the recently described SENDA syndrome; FBXO7-associated neurodegeneration (PARK15), autosomal-recessive spastic paraplegia with a thin corpus callosum (SPG11), and dystonia parkinsonism due to mutations in the SLC6A3 gene encoding the dopamine transporter. They have in common that in all these syndromes there may be a combination of dystonic and parkinsonian features, which may be complicated by pyramidal tract involvement. The aim of this review is to familiarize the clinician with the phenotypes of these disorders.

Pantothenate kinase-associated neurodegeneration: insights from a Drosophila model

Pantothenate-Kinase-Associated-Neurodegeneration (PKAN) is a devastating disease, resulting from mutations in pantothenate kinase 2 (PANK2), one of the four human pantothenate kinase genes (PANK1-4). Interestingly, PanK2 appears to be the only mitochondria-targeted human PanK. It is unknown whether the mitochondria-targeted PanK is associated with any unique function, nor whether PKAN is due solely to the loss of pantothenate kinase activity. Drosophila PANK [fumble (fbl)] encodes several isoforms of pantothenate kinase products, one of which localizes to mitochondria and the others cytosol. fbl flies exhibit many characteristic features reminiscent of PKAN patients. Various forms of Drosophila fbl and human PANK2 were introduced into fbl flies to study their in vivo functions. Only mitochondria-targeted Fbl or human PanK2 was able to rescue fbl mutation, with the rescuing ability sensitive to the expression level of the transgene. Transgenic lines with low expression of normal Fbl or PanK2 displayed similar phenotypes as PANK2 mutant transgenic flies. These PanK2 mutants all showed reduced and phenotype severity-correlated in vitro pantothenate kinase activities. Amazingly, cytosolic PanK3 and PanK4 could mostly, but not fully, rescue fbl defects except the male sterility. Therefore, fbl appears to be the orthologue of human PANK2, and PanK2 is functionally more potent than PanK3 and PanK4 in vivo. We suggest that mitochondria-located pantothenate kinase is required to achieve the maximal enzymatic activity to fulfill the most challenging task such as maintaining male fertility and optimal neuronal functions, and PKAN features are mainly due to the reduction of the total cellular pantothenate kinase activity in the most susceptible regions.

Nrf2-induced antioxidant protection: a promising target to counteract ROS-mediated damage in neurodegenerative disease?

Neurodegenerative diseases share various pathological features, such as accumulation of aberrant protein aggregates, microglial activation, and mitochondrial dysfunction. These pathological processes are associated with generation of reactive oxygen species (ROS), which cause oxidative stress and subsequent damage to essential molecules, such as lipids, proteins, and DNA. Hence, enhanced ROS production and oxidative injury play a cardinal role in the onset and progression of neurodegenerative disorders. To maintain a proper redox balance, the central nervous system is endowed with an antioxidant defense mechanism consisting of endogenous antioxidant enzymes. Expression of most antioxidant enzymes is tightly controlled by the antioxidant response element (ARE) and is activated by nuclear factor E2-related factor 2 (Nrf2). In past years reports have highlighted the protective effects of Nrf2 activation in reducing oxidative stress in both in vitro and in vivo models of neurodegenerative disorders. Here we provide an overview of the involvement of ROS-induced oxidative damage in Alzheimer's disease, Parkinson's disease, and Huntington's disease and we discuss the potential therapeutic effects of antioxidant enzymes and compounds that activate the Nrf2-ARE pathway.

Mesenchymal stem cells therapy exerts neuroprotection in a progressive animal model of Parkinson's disease

Parkinson's disease is a common progressive neurodegenerative disorder caused by the loss of dopaminergic neurons in the substantia nigra. We investigated whether cell therapy with human mesenchymal stem cells (hMSCs) had a protective effect on progressive dopaminergic neuronal loss in vitro and in vivo. In primary mesencephalic cultures, hMSCs treatment significantly decreased MG-132-induced dopaminergic neuronal loss with a significant reduction of caspase-3 activity. In rats received systemic injection of MG-132, hMSCs treatment in MG-132-treated rats dramatically reduced the decline in the number of tyrosine hydroxylase (TH)-immunoreactive cells, showing an approximately 50% increase in the survival of TH-immunoreactive cells in the substantia nigra compared with the MG-132-treated group. Additionally, hMSC treatment significantly decreased OX-6 immunoreactivity and caspase-3 activity. Histological analysis showed that the number of NuMA-positive cells was 1.7% of total injected hMSCs and 35.7% of these cells were double-stained with NuMA and TH. Adhesive-removal test showed that hMSCs administration in MG-132-treated rats had a tendency to decrease in the mean removal time. This study demonstrates that hMSCs treatment had a protective effect on progressive loss of dopaminergic neurons induced by MG-132 in vitro and in vivo. Complex mechanisms mediated by trophic effects of hMSCs and differentiation of hMSCs into functional TH-immunoreactive neurons may work in the neuroprotective process.

De novo CoA biosynthesis is required to maintain DNA integrity during development of the Drosophila nervous system

In a forward genetic screen in Drosophila melanogaster, aimed to identify genes required for normal locomotor function, we isolated dPPCS (the second enzyme of the Coenzyme A biosynthesis pathway). The entire Drosophila CoA synthesis route was dissected, annotated and additional CoA mutants were obtained (dPANK/fumble) or generated (dPPAT-DPCK). Drosophila CoA mutants suffer from neurodegeneration, altered lipid homeostasis and the larval brains display increased apoptosis. Also, de novo CoA biosynthesis is required to maintain DNA integrity during the development of the central nervous system. In humans, mutations in the PANK2 gene, the first enzyme in the CoA synthesis route, are associated with pantothenate kinase-associated neurodegeneration. Currently, the pathogenesis of this neurodegenerative disease is poorly understood. We provide the first comprehensive analysis of the physiological implications of mutations in the entire CoA biosynthesis route in an animal model system. Surprisingly, our findings reveal a major role of this conserved pathway in maintaining DNA and cellular integrity, explaining how impaired CoA synthesis during CNS development can elicit a neurodegenerative phenotype.

Neuroprotective effect of nicotine on dopaminergic neurons by anti-inflammatory action

Epidemiological studies have reported that smoking is associated with a lower incidence of Parkinson's disease (PD), leading to theories that smoking in general and nicotine in particular might be neuroprotective. Recent studies suggested cholinergic anti-inflammatory pathway-regulating microglial activation through alpha7 nicotinic receptors. In the present study, we used lipopolysaccharide (LPS)-induced in vitro and in vivo inflammation models to investigate whether nicotine has a protective effect on the dopaminergic system through an anti-inflammatory mechanism. Nicotine pretreatment considerably decreased microglial activation with significant reduction of tumour necrosis factor (TNF)-alpha mRNA expression and TNF-alpha release induced by LPS stimulation. In co-cultures of microglia and mesencephalic neurons, nicotine pretreatment significantly decreased the loss of tyrosine hydroxylase-immunopositive (TH-ip) cells, approximately twice more than the LPS-only treatment. alpha-Bungarotoxin, an alpha7 nicotinic acetylcholine receptor subunit-selective blocker, considerably blocked the inhibitory effects of nicotine on microglial activation and TH-ip neuronal loss. Chronic nicotine pretreatment in rats showed that TH-ip neuronal loss induced by LPS stimulation in the substantia nigra was dramatically decreased, which was clearly accompanied by a reduction in the formation of TNF-alpha. The present study demonstrated that nicotine has a neuroprotective effect on dopaminergic neurons via an anti-inflammatory mechanism mediated by the modulation of microglial activation. Along with various neuroprotective effects of nicotine, the anti-inflammatory mechanism of nicotine could have a major therapeutic implication in the preventive treatment of PD.

Emerging drugs for Parkinson’s disease

Parkinson's disease (PD) afflicts millions of people worldwide. There are numerous drugs available for PD; however, levodopa remains the gold standard of pharmacotherapy to which all other therapies are compared. Levodopa is quite effective for many motor symptoms (bradykinesia, tremor, rigidity) of PD; however, non-levodopa-responsive motor symptoms (postural instability) and nonmotor symptoms are frequently the most troublesome in middle and later stages of disease. Although motor symptoms remain an important focus for emerging drugs, current research is largely geared to identify and develop disease-slowing therapies. Another important area of focus has become treatment of the nonmotor symptoms of PD (especially depression and dementia). This review discusses emerging drugs in the management of the motor and nonmotor symptoms of PD and drugs under study as disease-slowing/neuroprotective agents.

Epidemiology of Parkinson's disease

The causes of Parkinson's disease (PD), the second most common neurodegenerative disorder, are still largely unknown. Current thinking is that major gene mutations cause only a small proportion of all cases and that in most cases, non-genetic factors play a part, probably in interaction with susceptibility genes. Numerous epidemiological studies have been done to identify such non-genetic risk factors, but most were small and methodologically limited. Larger, well-designed prospective cohort studies have only recently reached a stage at which they have enough incident patients and person-years of follow-up to investigate possible risk factors and their interactions. In this article, we review what is known about the prevalence, incidence, risk factors, and prognosis of PD from epidemiological studies.

Genética de las enfermedades neurodegenerativas más prevalentes

A large number of mutations and polymorphisms associated with neurodegenerative disorders have been described during the last years. These findings have been helpful to improve our knowledge about the pathogenesis of these disorders. In this review we describe the genetic alterations and variants that cause or predispose to develop several neurodegenerative disorders, such as Huntington's disease, Alzheimer's disease, frontotemporal dementia, Parkinson's disease and other parkinsonisms. We also comment on the possible pathogenic mechanism of these mutations, clinical features and the usefulness of this information for the diagnosis and management of these disorders.

ER stress and neurodegenerative diseases

Endoplasmic reticulum (ER) stress is caused by disturbances in the structure and function of the ER with the accumulation of misfolded proteins and alterations in the calcium homeostasis. The ER response is characterized by changes in specific proteins, causing translational attenuation, induction of ER chaperones and degradation of misfolded proteins. In case of prolonged or aggravated ER stress, cellular signals leading to cell death are activated. ER stress has been suggested to be involved in some human neuronal diseases, such as Parkinson's disease, Alzheimer's and prion disease, as well as other disorders. The exact contributions to and casual effects of ER stress in the various disease processes, however, are not known. Here we will discuss the possible role of ER stress in neurodegenerative diseases, and highlight current knowledge in this field that may reveal novel insight into disease mechanisms and help to design better therapies for these disorders.

Gene therapy for Parkinson's disease using recombinant adeno-associated viral vectors

Existing strategies for gene therapy in the treatment of Parkinson's disease include the delivery of genes encoding dopamine (DA)-synthesising enzymes, leading to localised production of DA in the striatum; genes encoding factors that protect nigral neurons against ongoing degeneration, such as glial cell line-derived neurotrophic factor; and genes encoding proteins that produce the inhibitory transmitter gamma-aminobutylic acid (GABA) in the subthalamic nucleus (STN), thus suppressing the hyperactive STN. Recombinant adeno-associated viral (rAAV) vectors, which are derived from non-pathogenic viruses, have been shown to be suitable for clinical trials. These rAAVs have been found to transduce substantial numbers of neurons efficiently and to express transgenes in mammalian brains for long periods of time, with minimum inflammatory and immunological responses. In vivo imaging using positron emission tomography is useful for monitoring transgene expression and for assessing the functional effects of gene delivery. Vector systems that regulate transgene expression are necessary to increase safety in clinical applications, and the development of such systems is in progress.

Epidemiological, clinical, and genetic characteristics of early-onset parkinsonism

In this review we discuss the epidemiological, clinical, and genetic characteristics of early-onset parkinsonism, defined as parkinsonism starting before age 40 (sometimes 50) years. Juvenile parkinsonism is very rare and is the result of various secondary or genetic causes. In patients with onset at or above age 21 years, secondary causes require exclusion but are rare; most cases with a fairly pure parkinsonian syndrome (eg, young-onset Parkinson's disease; YOPD) are due to typical Lewy-body Parkinson's disease or, less commonly, genetic causes. In comparison with patients with late-onset disease, most patients with YOPD progress more slowly in terms of motor features and have a longer disease course with preservation of cognitive function, but typically develop motor fluctuations and dyskinesias earlier. Patients with YOPD generally experience a greater effect in their lives than those with late onset, with poorer social adjustment, higher rates of depression, and lower quality of life. Management of YOPD must therefore aim to maintain occupational, social, and daily functioning, while delaying or ameliorating motor complications of treatment, providing psychological support, and, where possible, preventing psychiatric complications including depression.

Ubiquitin–proteasome system and Parkinson's disease

Increasing genetic, pathological, and experimental evidence suggest that neurodegeneration in both familial and sporadic forms of Parkinson's disease (PD) may be related to a defect in the capacity of the ubiquitin-proteasome system (UPS) to clear unwanted proteins, resulting in protein accumulation, aggregation, and cytotoxicity. This concept is supported by in vitro and in vivo laboratory experiments which show that inhibition of UPS function can cause neurodegeneration coupled with the formation of Lewy body-like inclusions. This hypothesis could account for the presence of protein aggregates and Lewy bodies in PD, the other biochemical features seen in the disorder, and the age-related vulnerability of the substantia nigra pars compacta. It also suggests novel targets for putative neuroprotective therapies for PD.

Clinical, diagnostic, genetic and management issues in dementia with Lewy bodies

DLB (dementia with Lewy bodies) is a syndrome associated with underlying LBD (Lewy body disease), with manifestations in the cognitive, neuropsychiatric, motor, sleep and autonomic domains. The variable symptomatology and complex array of neuronal involvement and neurotransmitter deficiencies make the diagnosis and management of patients with DLB challenging. The genetic underpinnings of DLB have only recently begun to unfold. In this review, the clinical features, diagnostic criteria, genetics and treatment issues relating to DLB will be discussed, in which a comprehensive approach to the diagnosis and management is emphasized.

Present and future drug treatment for Parkinson's disease

Considerable advances made in defining the aetiology, pathogenesis, and pathology of Parkinson's disease (PD) have resulted in the development and rapid expansion of the pharmacopoeia available for treatment. Anticholinergics were used before the introduction of levodopa which is now the drug most commonly used. Dopamine agonists are effective when used alone or as an adjunct to levodopa, while monoamine oxidase B inhibitors improve motor function in early and advanced PD. However, treatment mainly addresses the dopaminergic features of the disease and leaves its progressive course unaffected; the drug treatment available for the management of non-motor symptoms is limited. This article seeks to set current treatment options in context, review emerging and novel drug treatments for PD, and assess the prospects for disease modification. Surgical therapies are not considered.

Molecular genetic pathways in Parkinson's disease: a review

Major progress has been made in the last decade in understanding the genetic basis of PD (Parkinson's disease) with five genes unequivocally associated with disease. As a result, multiple pathways have been implicated in the pathogenesis of PD, including proteasome impairment and mitochondrial dysfunction. Although Mendelian genetics has been successful in establishing a genetic predisposition for familial PD, this has not been reiterated in the sporadic form. In fact no genetic factors have been unequivocally associated with increased risk for sporadic PD. The difficulty in identifying susceptibility factors in PD has not only been because of numerous underpowered studies, but we have been unable to dissect out the genetic component in a multifactorial disease. This review aims to summarize the genetic findings within PD.

A common LRRK2 mutation in idiopathic Parkinson's disease

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene have been shown to cause autosomal dominant Parkinson's disease. Few mutations in this gene have been identified. We investigated the frequency of a common heterozygous mutation, 2877510 g-->A, which produces a glycine to serine aminoacid substitution at codon 2019 (Gly2019 ser), in idiopathic Parkinson's disease. We assessed 482 patients with the disorder, of whom 263 had pathologically confirmed disease, by direct sequencing for mutations in exon 41 of LRRK2. The mutation was present in eight (1.6%) patients. We have shown that a common single Mendelian mutation is implicated in sporadic Parkinson's disease. We suggest that testing for this mutation will be important in the management and genetic counselling of patients with Parkinson's disease.

Genetics of Parkinson's disease

Twenty years ago Parkinson's disease (PD) was thought of as an environmentally determined neurodegenerative disease. It is now known that there are two autosomal dominant disease genes, alpha-synuclein and dardarin, and three genes responsible for autosomal recessive PD, parkin, DJ-1 and PINK-1. Although these gene mutations are not common, their identification has led to a new understanding of the pathogenesis of PD, and to a development in the understanding of the clinical and pathological definitions of PD and Lewy body disease. Ultimately, these advances may lead to the development of new disease-modifying therapies, but more immediately these discoveries have led to a more coherent view of the spectrum of PD and Lewy body diseases and to accurate genetic diagnosis and counselling for some families.