Nitrite and malondialdehyde content in cerebrospinal fluid of patients with Parkinson's disease

Potential biomarkers and therapeutic targets for obsessive compulsive disorder: Evidences from clinical studies

Obsessive compulsive disorder (OCD) is a prevalent behavioral disorder with a complex etiology. However, the underlying pathogenic molecular pathways and the associated risk factors are largely obscure. This has hindered both the identification of relevant prognostic biomarkers and the development of effective treatment strategies. Because of the diverse range of clinical manifestations, not all patients benefit from therapies currently practiced in the clinical setting. Nevertheless, several lines of evidence indicate that neurotrophic, neurotransmitter, and oxidative signaling are involved in the pathophysiology of OCD. Based upon evidences from clinical (and pre-clinical studies), the present review paper sets out to decipher the utilities of three parameters (i.e. brain-derived neurotrophic factor; BDNF, noradrenalin-synthesizing enzyme dopamine beta-hydroxylase; DBH; and oxidative damage marker malondialdehyde; MDA) as diagnostic peripheral biomarkers as well as bio-targets for therapeutic strategies. While the data indicates promising results, there is necessitation for future studies to further confirm and establish these. Further, based again on the available clinical data, we investigated the possibilities of exploiting the etiological links between disruptions in the sleep-wake cycle and insulin signaling, and OCD for the identification of potential anti-OCD ameliorative agents with the ability to elicit multimodal effects, including attenuation of the alterations in BDNF, noradrenergic and redox pathways. In this respect, agomelatine and metformin may represent particularly interesting candidates; however, further clinical studies are warranted to establish these as singular or complementary medications in OCD subjects.

Promising biomarkers and therapeutic targets for the management of Parkinson's disease: recent advancements and contemporary research

Parkinson's disease (PD) is one of the progressive neurological diseases which affect around 10 million population worldwide. The clinical manifestation of motor symptoms in PD patients appears later when most dopaminergic neurons have degenerated. Thus, for better management of PD, the development of accurate biomarkers for the early prognosis of PD is imperative. The present work will discuss the potential biomarkers from various attributes covering biochemical, microRNA, and neuroimaging aspects (α-synuclein, DJ-1, UCH-L1, β-glucocerebrosidase, BDNF, etc.) for diagnosis, recent development in PD management, and major limitations with current and conventional anti-Parkinson therapy. This manuscript summarizes potential biomarkers and therapeutic targets, based on available preclinical and clinical evidence, for better management of PD.

[18F]NOS PET Brain Imaging Suggests Elevated Neuroinflammation in Idiopathic Parkinson's Disease

Neuroinflammation is implicated as a key pathologic mechanism in many neurodegenerative diseases and is thought to be mediated in large part by microglia, native phagocytic immune cells of the CNS. Abnormal aggregation of the protein α-synuclein after phagocytosis by microglia is one possible neuropathophysiological mechanism driving Parkinson's disease (PD). We conducted a human pilot study to evaluate the feasibility of targeting the inducible isoform of nitric oxide synthase using the [18F]NOS radiotracer to measure neuroinflammation in idiopathic PD. Ten adults consisting of 6 PD patients and 4 healthy controls (HC) underwent one hour of dynamic [18F]NOS positron emission tomography (PET) brain imaging with arterial blood sampling. We observed increased [18F]NOS whole brain distribution volume (VT) in PD patients compared to age-matched healthy controls (p < 0.008) via a 1-tissue compartment (TC) model. The rate constant K1 for transport from blood into tissue did not differ between groups (p = 0.72). These findings suggest elevated oxidative stress, a surrogate marker of inflammation, is present in early-stage idiopathic PD and indicate that [18F]NOS PET imaging is a promising, non-invasive method to measure neuroinflammation.

Nitrosative stress in Parkinson's disease

Parkinson’s Disease (PD) is a neurodegenerative disorder characterized, in part, by the loss of dopaminergic neurons within the nigral-striatal pathway. Multiple lines of evidence support a role for reactive nitrogen species (RNS) in degeneration of this pathway, specifically nitric oxide (NO). This review will focus on how RNS leads to loss of dopaminergic neurons in PD and whether RNS accumulation represents a central signal in the degenerative cascade. Herein, we provide an overview of how RNS accumulates in PD by considering the various cellular sources of RNS including nNOS, iNOS, nitrate, and nitrite reduction and describe evidence that these sources are upregulating RNS in PD. We document that over 1/3 of the proteins that deposit in Lewy Bodies, are post-translationally modified (S-nitrosylated) by RNS and provide a broad description of how this elicits deleterious effects in neurons. In doing so, we identify specific proteins that are modified by RNS in neurons which are implicated in PD pathogenesis, with an emphasis on exacerbation of synucleinopathy. How nitration of alpha-synuclein (aSyn) leads to aSyn misfolding and toxicity in PD models is outlined. Furthermore, we delineate how RNS modulates known PD-related phenotypes including axo-dendritic-, mitochondrial-, and dopamine-dysfunctions. Finally, we discuss successful outcomes of therapeutics that target S-nitrosylation of proteins in Parkinson’s Disease related clinical trials. In conclusion, we argue that targeting RNS may be of therapeutic benefit for people in early clinical stages of PD.

Levodopa-induced dyskinesias in Parkinson's disease increase cerebrospinal fluid nitric oxide metabolites' levels

Levodopa-induced dyskinesia (LID) is a common complication of Parkinson's disease (PD) therapy. Nitric oxide in the central nervous system may have a role in its pathophysiology. The present work investigates plasma and CSF levels of nitric oxide metabolites nitrite and nitrate in patients with PD, LID, and healthy control. We measured plasma and CSF nitrite and nitrate levels in patients with PD with and without LID and in healthy controls. The levels of plasma and CSF nitrite and nitrate were measured by ozone-based chemiluminescence. Sixty-seven participants were enrolled. CSF nitrite levels in patients with PD and LID were higher than in patients with PD without LID and healthy controls. CSF/plasma ratio of nitrite was higher in patients with PD and LID than in patients with PD without LID. The CSF/plasma ratio of nitrite in patients with PD and LID was higher than 1, indicating an intrathecal production of NO in patients with this motor complication. There was an increase in nitrate levels of CSF and CSF/plasma ratio of nitrate in patients with PD and LID compared to the healthy controls. Sex, age at evaluation, disease duration, and levodopa equivalent daily doses, as well as processing and storage time, did not critically influence these results. The present study demonstrated an increase in nitrite and nitrate levels in the central nervous system of patients with PD and LID. This finding strengthens the role of NO on LID pathophysiology.

The Association between Serum Oxidative Stress Indexes and Pathogenesis of Parkinson's Disease in the Northwest of Iran

Background:

Parkinson’s disease (PD) is a prevalent neurodegenerative disorder. Oxidative stress is a main modulator in the advancement of PD. This investigation aimed to evaluate the relations between serum trace elements, vitamin C, ferritin, transferrin, Nitrite Oxide (NOx) and Peroxynitrite (PrN) concentrations and clinical parameters in patients with PD.

Methods:

Serum concentrations of variables were measured in 75 PD patients and 75 healthy subjects from Imam Reza Hospital, Tabriz University of Medical Sciences, Tabriz, Iran between Feb 2016 and Sep 2018. Receiver Operating Characteristic (ROC) analysis was performed to examine incremental diagnostic value of vitamin C, NOx, and PrN in the study groups.

Results:

Mean serum NOx (35.81±5.16 vs. 11.27±3.59 mol/L, P<0.001) and PrN (15.78±4.23 vs. 9.62±4.57 mol/L, P= 0.004) were markedly higher in patient group versus healthy individuals. Significant differences were also observed in the serum levels of vitamin C (P<0.001), copper (Cu) (P<0.001), Iron (Fe) (P=0.003), and Zinc (Zn) (P<0.001) between patients with PD and healthy subjects. Nevertheless, the serum levels of Se (P=0.515), ferritin (P=0.103), and transferrin (P=0.372) were not statistically significant between the study groups. ROC analysis has revealed a diagnostic ability of serum vitamin C levels for PD with an area under ROC curve of ≥0.7 (P<0.05) and relatively high sensitivity and specificity.

Conclusion:

Serum levels of NOx and PrN are significantly higher in patients with PD. In additions, serum vitamin C levels have a diagnostic value as a biomarker. Further studies are required with larger sample size to provide more detailed information about the cognitive profile of participants and the outcome measures.

Redox metabolism modulation as a mechanism in SSRI toxicity and pharmacological effects

Depressive disorders are amongst the greatest mental health challenges, with an increasing number of patients being diagnosed each year. Though it has not yet been fully elucidated, redox metabolism imbalances and oxidative stress seem to play a major role in the pathogenesis of depressive disorders. Selective serotonin reuptake inhibitors (SSRIs) are the most prescribed antidepressants, considered to have a better tolerability. However, several adverse effects have been reported and the mechanisms involved in their pharmacological activity are not entirely understood. SSRIs have been shown to influence the redox metabolism, which could be involved in their toxicity and pharmacological effects. A comparative analysis of published in vivo and in vitro data regarding the activity of SSRIs on the redox metabolism pathways has been performed in this paper, with an emphasis on mechanistical aspects. Furthermore, a comparison between oxidative stress biomarker levels reported by different studies was attempted. The reviewed data point towards both pro- and antioxidant effects of SSRIs, dependent on tissue/cell type and dose/concentration, suggest a redox modulating potential of these compounds. In hepatic and testicular tissue, the majority of reviewed studies reported pro-oxidant effects, with possible implications towards the hepatotoxicity and sexual dysfunction that were reported following SSRI treatment; while in brain, the most common findings were antioxidant effects that could partially explain their antidepressant activity. However, given the heterogeneity of the reviewed data, further research is needed to fully understand the impact of SSRIs on redox metabolism and its implications.

Development and Characterization of Nasal Delivery of Selegiline Hydrochloride Loaded Nanolipid Carriers for the Management of Parkinson's Disease

INTRODUCTION

Parkinson's Disease (PD) is one of the most common age-related neurodegenerative disorders which is marked with the loss of dopaminergic neurons. The present study performed on the nose to brain delivery of selegiline hydrochloride loaded nano lipid carrier, suggests that the nasal route is a good mean of targeting the drug directly into the brain.

METHODS AND MATERIALS

Nanostructured lipid carriers were prepared by using hot homogenization. Selegiline hydrochloride loaded NLCs and rotenone treatment were given at a dose of 10 mg/kg administered from 14th day to 28th day. Behavioral parameters were determined at 7th, 14th, 21st and 28th day. On the 28th day, animals were sacrificed for biochemical estimation.

RESULTS

The optimized drug loaded NLC formulation has shown 93±5.25% entrapment efficiency and 51.96% loading capacity. Optimized NLCs formulation has shown 70% release within 10 hours and after that, the release of the drug is sustained up to 22 hours (97%). Pharmacological action of the drug was found to restore the behavioral parameters in rotenone-induced rats.

CONCLUSION

Nano Lipid Carrier (NLCs) therapeutics has emerged as a prominent method for the treatment of Parkinson's Disease (PD) as it offers targeted delivery and enhances the therapeutic efficacy of neurotherapeutics. It is concluded from the studies that, Selegiline HCl loaded nano lipid carrier which was administered through nasal route has the potential to be used in the management therapy of Parkinson's disease.

Translational approaches to restoring mitochondrial function in Parkinson's disease

There is strong evidence of a key role for mitochondrial dysfunction in both sporadic and all forms of familial Parkinson's disease (PD). However, none of the clinical trials carried out with putative mitochondrial rescue agents have been successful. Firm establishment of a wet biomarker or a reliable readout from imaging studies detecting mitochondrial dysfunction and reflecting disease progression is also awaited. We will provide an overview of our current knowledge about mitochondrial dysfunction in PD and related drug screens. We will also summarise previously undertaken mitochondrial wet biomarker studies and relevant imaging studies with particular focus on 31P-MRI spectroscopy. We will conclude with an overview of clinical trials which tested putative mitochondrial rescue agents in PD patients.

Oxidative Stress in Neurodegenerative Diseases

The pathophysiologies of neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), Parkinson's disease (PD), and Alzheimer's disease (AD), are far from being fully explained. Oxidative stress (OS) has been proposed as one factor that plays a potential role in the pathogenesis of neurodegenerative disorders. Clinical and preclinical studies indicate that neurodegenerative diseases are characterized by higher levels of OS biomarkers and by lower levels of antioxidant defense biomarkers in the brain and peripheral tissues. In this article, we review the current knowledge regarding the involvement of OS in neurodegenerative diseases, based on clinical trials and animal studies. In addition, we analyze the effects of the drug-induced modulation of oxidative balance, and we explore pharmacotherapeutic strategies for OS reduction.

Oxidative and nitrosative stress in serum of patients with Parkinson's disease

Parkinson's disease (PD) is one of the common neurodegenerative disorders. Oxidative stress is considered as a contributing factor to the development of PD. The present study aims to investigate serum oxidative stress status in patients with PD. Oxidative stress was assessed by measuring serum nitric oxide levels, lipid hydroperoxide concentrations, and nitric oxide synthase activity. In addition, total serum antioxidant capacity (TAC) was evaluated using the serum 2,2-Diphenyl-1-picryl-hydrazyl (DPPH) free-radical scavenging method in 32 patient with Parkinson's disease and 32 control subjects. Our results indicated that serum nitric oxide and lipid hydroperoxide levels were significantly lower in patients with PD than controls. Moreover, nitric oxide levels were found to be negatively correlated with Unified Parkinson's Disease Rating Scale (UPDRS). However, no statistical difference was observed in total serum antioxidant capacities and nitric oxide synthase activities between patients and controls. The present study indicates that although antioxidant capacity was not changed, lipid hydroperoxide (LPO) level was found decreased. This might show pre-oxidative process in these patients. In addition, decreased nitric oxide (NO) level and negative correlation observed between NO level and disease rating scale implicated a role for NO in the disease process.

Iron and Oxidative Stress in Parkinson's Disease: An Observational Study of Injury Biomarkers

Parkinson's disease (PD) is characterized by progressive motor impairment attributed to progressive loss of dopaminergic neurons in the substantia nigra (SN) pars compacta. In addition to an accumulation of iron, there is also an increased production of reactive oxygen/nitrogen species (ROS/RNS) and inflammatory markers. These observations suggest that iron dyshomeostasis may be playing a key role in neurodegeneration. However, the mechanisms underlying this metal-associated oxidative stress and neuronal damage have not been fully elucidated. To determine peripheral levels of iron, ferritin, and transferrin in PD patients and its possible relation with oxidative/nitrosative parameters, whilst attempting to identify a profile of peripheral biomarkers in this neurological condition. Forty PD patients and 46 controls were recruited to compare serum levels of iron, ferritin, transferrin, oxidative stress markers (superoxide dismutase (SOD), catalase (CAT), nitrosative stress marker (NOx), thiobarbituric acid reactive substances (TBARS), non-protein thiols (NPSH), advanced oxidation protein products (AOPP), ferric reducing ability of plasma (FRAP) and vitamin C) as well as inflammatory markers (NTPDases, ecto-5’-nucleotidase, adenosine deaminase (ADA), ischemic-modified albumin (IMA) and myeloperoxidase). Iron levels were lower in PD patients, whereas there was no difference in ferritin and transferrin. Oxidative stress (TBARS and AOPP) and inflammatory markers (NTPDases, IMA, and myeloperoxidase) were significantly higher in PD, while antioxidants FRAP, vitamin C, and non-protein thiols were significantly lower in PD. The enzymes SOD, CAT, and ecto-5’-nucleotidase were not different among the groups, although NOx and ADA levels were significantly higher in the controls. Our data corroborate the idea that ROS/RNS production and neuroinflammation may dysregulate iron homeostasis and collaborate to reduce the periphery levels of this ion, contributing to alterations observed in the pathophysiology of PD.

Cerebrospinal fluid biochemical studies in patients with Parkinson's disease: toward a potential search for biomarkers for this disease

The blood-brain barrier supplies brain tissues with nutrients and filters certain compounds from the brain back to the bloodstream. In several neurodegenerative diseases, including Parkinson's disease (PD), there are disruptions of the blood-brain barrier. Cerebrospinal fluid (CSF) has been widely investigated in PD and in other parkinsonian syndromes with the aim of establishing useful biomarkers for an accurate differential diagnosis among these syndromes. This review article summarizes the studies reported on CSF levels of many potential biomarkers of PD. The most consistent findings are: (a) the possible role of CSF urate on the progression of the disease; (b) the possible relations of CSF total tau and phosphotau protein with the progression of PD and with the preservation of cognitive function in PD patients; (c) the possible value of CSF beta-amyloid 1-42 as a useful marker of further cognitive decline in PD patients, and (d) the potential usefulness of CSF neurofilament (NFL) protein levels in the differential diagnosis between PD and other parkinsonian syndromes. Future multicentric, longitudinal, prospective studies with long-term follow-up and neuropathological confirmation would be useful in establishing appropriate biomarkers for PD.

Oxidative damage to macromolecules in human Parkinson disease and the rotenone model

Parkinson disease (PD), the most common neurodegenerative movement disorder, is associated with selective degeneration of nigrostriatal dopamine neurons. Although the underlying mechanisms contributing to neurodegeneration in PD seem to be multifactorial, mitochondrial impairment and oxidative stress are widely considered to be central to many forms of the disease. Whether oxidative stress is a cause or a consequence of dopaminergic death, there is substantial evidence for oxidative stress both in human PD patients and in animal models of PD, especially using rotenone, a complex I inhibitor. There are many indices of oxidative stress, but this review covers the recent evidence for oxidative damage to nucleic acids, lipids, and proteins in both the brain and the peripheral tissues in human PD and in the rotenone model. Limitations of the existing literature and future perspectives are discussed. Understanding how each particular macromolecule is damaged by oxidative stress and the interplay of secondary damage to other biomolecules may help us design better targets for the treatment of PD.

Catalase inhibition into the fourth cerebral ventricle affects bradycardic parasympathetic response to increase in arterial pressure without changing the baroreflex

Exogenous catalase influences neural control of cardiovascular system; however, we do not know yet if its inhibition into the fourth cerebral ventricle (4(th) V) influences baroreflex regulation. We evaluated the effects of central catalase inhibition on baroreflex in conscious Wistar rats. We used males Wistar rats (320-370 g), which were implanted with a stainless steel guide cannula into 4(th) V. The femoral artery and vein were cannulated for mean arterial pressure (MAP) and heart rate (HR) measurement and drug infusion, respectively. After basal MAP and HR recordings, the baroreflex was tested with a pressor dose of phenylephrine (PHE, 8 μg/kg, bolus) and a depressor dose of sodium nitroprusside (SNP, 50 μg/kg, bolus). Baroreflex was evaluated before 5, 15, 30 and 60 minutes after 3-amino-1, 2, 4-triazole (ATZ, 0.001 g/100 μL) injection into the 4(th) V. Vehicle treatment did not change baroreflex responses. ATZ attenuated bradycardic peak and reduced HR range at 30 minutes. ATZ into the 4(th) V reduced bradycardic and tachycardic reflex responses to increase and decrease MAP, respectively (p<0.05) 30 minutes after its microinjection without significantly changing the basal MAP and HR. In conclusion, central catalase inhibition influenced the highest parasympathetic response to MAP increase in conscious Wistar rats without change baroreflex gain.

An expedient synthesis of honokiol and its analogues as potential neuropreventive agents

An efficient synthesis of honokiol with Suzuki-Miyaura cross coupling obtained an overall yield of 45%. The proposed approach successfully synthesized several structurally similar alkyl, alkenyl and alkynyl analogues, seven of which showed potential neuropreventive activity against MPP(+)-induced and CHP/TBHP oxidative stress induced neuroblastoma cell death.

Neurochemical biomarkers in the differential diagnosis of movement disorders

In recent years, the neurochemical analysis of neuronal proteins in cerebrospinal fluid (CSF) has become increasingly accepted for the diagnosis of neurodegenerative dementia diseases such as Alzheimer's disease and Creutzfeldt-Jakob disease. CSF surrounds the central nervous system, and in the composition of CSF proteins one finds brain-specific proteins that are prioritized from blood-derived proteins. Levels of specific CSF proteins could be very promising biomarkers for central nervous system diseases. We need the development of more easily accessible biomarkers, in the blood. In neurodegenerative diseases with and without dementia, studies on CSF and blood proteins have investigated the usefulness of biomarkers in differential diagnosis. The clinical diagnoses of Parkinson's disease, dementia with Lewy bodies, multiple system atrophy, progressive supranuclear palsy, and corticobasal degeneration still rely mainly on clinical symptoms as defined by international classification criteria. In this article, we review CSF biomarkers in these movement disorders and discuss recent published reports on the neurochemical intra vitam diagnosis of neurodegenerative disorders (including recent CSF alpha-synuclein findings).

Serum insulin-like growth factor-1 and nitric oxide levels in Parkinson's disease

The aim of this study was to investigate the role of circulating growth hormone (GH), insulin growth factor-1 (IGF-1), IGF binding protein-3 (IGFBP-3), and nitric oxide (NO) concentrations in the patients suffering from Parkinson's disease (PD). The study groups were consisted of 25 patients with PD and 25 matched healthy subjects as a control. The NO level of patients in PD group (2.3 +/- 0.4 micromol/L) was significantly lower than that in the control group (2.8 +/- 0.6 micromol/L) (P:.011). Although there were no statistically significant differences in the GH, IGF-1, and IGF BP-3 levels among the two groups, in this preliminary study, we found low NO and mildly elevated IGF-1 levels in the patients with PD. The results may be associated with adaptation or protective mechanisms in the neurodegenerative disease processes such as seen in the PD. Further studies should be carried out to confirm our results.

Increased oxidative damage in peripheral blood correlates with severity of Parkinson's disease

Increased oxidative stress contributes to neuronal dysfunction in Parkinson's disease (PD). We investigated whether the pathological changes in PD brains may also be present in peripheral tissues. Leukocyte 8-hydroxydeoxyguanosine (8-OHdG), plasma malondialdehyde (MDA), erythrocyte glutathione peroxidase (GPx) and plasma vitamin E (Vit E) were measured for 211 PD patients and 135 healthy controls. Leukocyte 8-OHdG and plasma MDA were elevated, whereas erythrocyte GPx and plasma Vit E were reduced in PD patients when compared to the controls. After adjusting for environmental factors, logistic regression analysis showed that PD severity was independently correlated with 8-OHdG and MDA level, and inversely correlated with GPx activity and Vit E level. Leucocyte 8-OHdG level was continuously increased with advanced PD Hoehn-Yahr stages, while plasma MDA level peaked at early disease stages, among PD patients. These results suggest increased oxidative damage and decreased anti-oxidant capacity in peripheral blood, and a significant correlation between leucocyte 8-OHdG level and disease severity in PD.

Early discriminatory diagnosis of dementia with Lewy bodies. The emerging role of CSF and imaging biomarkers

BACKGROUND

The clinical diagnostic criteria for dementia with Lewy bodies (DLB) have a low sensitivity, and there are no generally accepted biomarkers to distinguish DLB from other dementias. Our aim was to identify biomarkers that may differentiate DLB from Alzheimer's disease (AD).

METHOD

We performed a systematic literature search for studies of EEG, imaging techniques and genetic and CSF markers that provide sensitivity and specificity in the identification of DLB.

RESULTS

The best evidence was for scintigraphy of the striatal dopamine transporter system using FP-CIT SPECT. Several small scintigraphy studies of cardiovascular autonomic function using metaiodobenzylguanidine SPECT have reported promising results. Studies exploring innovative techniques based on CSF have reported interesting findings for the combination of amyloid beta (abeta) isoforms as well as alpha-synuclein, and there are interesting results emerging from preliminary studies applying proteomic techniques. Data from studies using structural MRI, perfusion SPECT, genetics and EEG studies show differences between DLB and AD but only at a group level.

CONCLUSION

Several potential biomarkers for the differential diagnosis of probable DLB and AD have shown good diagnostic accuracy in the research setting. Data from large multicentre studies and from studies with autopsy confirmation exist for scintigraphy of the dopamine transporter system. Future studies should explore its value in possible DLB and for clinical management and health economics.

Role of nitric oxide synthases in Parkinson's disease: a review on the antioxidant and anti-inflammatory activity of polyphenols

Natural polyphenols can exert protective action on a number of pathological conditions including neurodegenerative disorders. The neuroprotective effects of many polyphenols rely on their ability to permeate brain barrier and here directly scavenge pathological concentration of reactive oxygen and nitrogen species and chelate transition metal ions. Importantly, polyphenols modulate neuroinflammation by inhibiting the expression of inflammatory genes and the level of intracellular antioxidants. Parkinson's disease (PD) is a neurodegenerative disorder characterized by several abnormalities including inflammation, mitochondrial dysfunction, iron accumulation and oxidative stress. There is considerable evidence showing that cellular oxidative damage occurring in PD might result also from the actions of altered production of nitric oxide (NO). Indeed, high levels of neuronal and inducible NO synthase (NOS) were found in substantia nigra of patients and animal models of PD. Here, we evaluate the involvement of NOS/NO in PD and explore the neuroprotective activity of natural polyphenol compounds in terms of anti-inflammatory and antioxidant action.

Nitric oxide synthase regulation and diversity: Implications in Parkinson’s disease

Nitric oxide (NO) is a janus faced chemical messenger, which, in the recent years, has been the focus of neurobiologists for its involvement in neurodegenerative disorders in particular, Parkinson's disease (PD). Nitric oxide synthase, the key enzyme involved in NO production exists in three known isoforms. The neuronal and inducible isoforms have been implicated in the pathogenesis of PD. These enzymes are subject to complex expressional and functional regulation involving mRNA diversity, phosphorylation and protein interaction. In the recent years, mRNA diversity and polymorphisms have been identified in the NOS isoforms. Some of these genetic variations have been associated with PD, indicating an etiological role for the NOS genes. This review mainly focuses on the NOS genes - their differential regulation and genetic heterogeneity, highlighting their significance in the pathobiology of PD.