Nicotine as a potential neuroprotective agent for Parkinson's disease

Nicotine-mediated therapy for Parkinson's disease in transgenic Caenorhabditis elegans model

Parkinson's disease resultant in the degeneration of Dopaminergic neurons and accumulation of α-synuclein in the substantia nigra pars compacta. The synthetic therapeutics for Parkinson's disease have moderate symptomatic benefits but cannot prevent or delay disease progression. In this study, nicotine was employed by using transgenic Caenorhabditis elegans Parkinson's disease models to minimize the Parkinson's disease symptoms. The results showed that the nicotine at 100, 150, and 200 μM doses reduced degeneration of Dopaminergic neurons caused by 6-hydroxydopamine (14, 33, and 40%), lowered the aggregative toxicity of α-synuclein by 53, 56, and 78%, respectively. The reduction in food-sensing behavioral disabilities of BZ555 was observed to be 18, 49, and 86%, respectively, with nicotine concentrations of 100 μM, 150 μM, and 200 μM. Additionally, nicotine was found to enhance Daf-16 nuclear translocation by 14, 31, and 49%, and dose-dependently increased SOD-3 expression by 10, 19, and 23%. In summary, the nicotine might a promising therapy option for Parkinson's disease.

Use of antiviral drugs and incidence of Parkinson's disease in Taiwan

Patients infected with herpes zoster might be at risk for Parkinson's disease (PD). However, antiviral drugs may impede viral deoxyribonucleic acid (DNA) synthesis. This study aimed to determine whether the currently observed association between herpes zoster and PD is consistent with previous findings, and whether antiviral drug use is associated with PD. This retrospective cohort study used the Longitudinal Generation Tracking Database. We included patients aged 40 years and above and applied propensity score matching at 1:1 ratio for study comparability. PD risk was evaluated using Cox proportional hazards regression methods. A total of 234,730 people were analyzed. The adjusted hazard ratio (aHR) for PD in patients with herpes zoster was 1.05. Furthermore, the overall incidence of PD was lower in those treated with antiviral drugs than in the untreated ones (3.17 vs. 3.76 per 1,000 person-years); the aHR was 0.84. After stratifying for sex or age, a similar result was observed. In conclusion, herpes zoster may increase the risk of PD, particularly among females, but receiving antiviral treatment reduces the risk by 16%. Therefore, using antiviral drugs may help prevent PD. However, additional research is required to determine the underlying mechanism(s).

Impact of genetic predisposition to late-onset neurodegenerative diseases on early life outcomes and brain structure

Most patients with late-onset neurodegenerative diseases such as Alzheimer's and Parkinson's have a complex aetiology resulting from numerous genetic risk variants of small effects located across the genome, environmental factors, and the interaction between genes and environment. Over the last decade, genome-wide association studies (GWAS) and post-GWAS analyses have shed light on the polygenic architecture of these diseases, enabling polygenic risk scores (PRS) to estimate an individual's relative genetic liability for presenting with the disease. PRS can screen and stratify individuals based on their genetic risk, potentially years or even decades before the onset of clinical symptoms. An emerging body of evidence from various research studies suggests that genetic susceptibility to late-onset neurodegenerative diseases might impact early life outcomes, including cognitive function, brain structure and function, and behaviour. This article summarises recent findings exploring the potential impact of genetic susceptibility to neurodegenerative diseases on early life outcomes. A better understanding of the impact of genetic susceptibility to neurodegenerative diseases early in life could be valuable in disease screening, detection, and prevention and in informing treatment strategies before significant neural damage has occurred. However, ongoing studies have limitations. Overall, our review found several studies focused on APOE haplotypes and Alzheimer's risk, but a limited number of studies leveraging polygenic risk scores or focused on genetic susceptibility to other late-onset conditions.

Autophagy and UPS pathway contribute to nicotine-induced protection effect in Parkinson's disease

The gradual nature of age-related neurodegeneration causes Parkinson's disease (PD) and impairs movement, memory, intellectual ability, and social interaction. One of the most prevalent neurodegenerative conditions affecting the central nervous system (CNS) among the elderly is PD. PD affects both motor and cognitive functions. Degeneration of dopaminergic (DA) neurons and buildup of the protein α-synuclein (α-Syn) in the substantia nigra pars compacta (SNpc) are two major causes of this disorder. Both UPS and ALS systems serve to eliminate α-Syn. Autophagy and UPS deficits, shortened life duration, and lipofuscin buildup accelerate PD. This sickness has no cure. Innovative therapies are halting PD progression. Bioactive phytochemicals may provide older individuals with a natural substitute to help delay the onset of neurodegenerative illnesses. This study examines whether nicotine helps transgenic C. elegans PD models. According to numerous studies, nicotine enhances synaptic plasticity and dopaminergic neuronal survival. Upgrades UPS pathways, increases autophagy, and decreases oxidative stress and mitochondrial dysfunction. At 100, 150, and 200 µM nicotine levels, worms showed reduced α-Syn aggregation, repaired DA neurotoxicity after 6-OHDA intoxication, increased lifetime, and reduced lipofuscin accumulation. Furthermore, nicotine triggered autophagy and UPS. We revealed nicotine's potential as a UPS and autophagy activator to prevent PD and other neurodegenerative diseases.

Pharmacokinetic and pharmacodynamic studies of nicotine in rat brain: a simultaneous investigation of nicotine metabolites and the release of neurotransmitters in vivo

Introduction: The body's ability to metabolize nicotine and the disposition of nicotine in the brain are important determinants of its exposure. Limited knowledge about the near real-time changes of neurochemicals during the brain nicotine metabolic process hinders the recognition of its multiple neuropharmacological effects. Methods: An online microdialysis coupled with UHPLC-HRMS/MS method for the in vivo multi-analysis of nicotine metabolites and several neurotransmitters in rat brain was developed. Whether the systemic modulation of metabolic enzyme CYP2B would modulate nicotine pharmacokinetics and local neurochemical effects was further investigated. Results: The dynamic profiles of over 10 nicotine metabolites and neurotransmitters were simultaneously obtained after a single injection of nicotine (2 mg·kg-1, i.p.) using the new method. Proadifen pretreatment (50 mg·kg-1·d-1, i.p., 4 days) caused significant inhibition of brain CYP2B1 activity. When exposed to nicotine, the brain C max of nicotine was 1.26 times higher and the levels of nicotine metabolites, nornicotine, and nicotine-N-oxide, were decreased by 85.3% and 34.4% in proadifen-pretreated rats. The higher level of brain nicotine induced a greater release of dopamine, serotonin, glutamate, and γ-amino-butyric acid in the nucleus accumbens. The concentrations of nicotine and dopamine were positively correlated, and the average levels of γ-amino-butyric acid and serotonin were 2.7 and 1.2 times higher, respectively, under the inhibition of nicotine metabolism. Discussion: These results demonstrated that inhibiting nicotine metabolism in rats can enhance the residence of brain nicotine and its local neurotransmitter effects. The metabolic activity of nicotine under different physiological conditions could regulate nicotine's bioavailability and its resulting pharmacology.

Nicotine in Parkinson's Disease - a Therapeutic Track Gone up in Smoke?

In recent decades, numerous studies have found that smoking or the intake of any form of nicotine, such as smokeless tobacco, exposure to environmental tobacco smoke, or even dietary sources such as peppers, reduces the risk of developing Parkinson's disease.1 Such observations suggest a potential disease-modifying effect of nicotine in Parkinson's disease. Many experimental studies, some of them supported by grants from the tobacco industry, have lent support for such a hypothesis.

NIR and THz spectroscopy: An experimental investigation toward nicotine-related devices

This study examined the content of nicotine-delivery products using terahertz time-domain spectroscopy (THz-TDS) and breath ethylene investigated with CO2 laser photoacoustic spectroscopy (CO2 LPAS) system as a biomarker of oxidative stress after smoking. The THz-TDS method provided valuable information on the transmission spectra of tobacco and nicotine in smoking products. From the CO2 LPAS data it was observed that in cigarette (TC) smoking the mean breath ethylene was 687 parts per billion (ppb), while in electronic cigarettes and tobacco heating devices smoking the mean ethylene was 56 ppb and 48 ppb, respectively. The main finding was that TC showed higher transmission in the THz region producing a higher oxidative stress on the body.

Lynx1 and the family of endogenous mammalian neurotoxin-like proteins and their roles in modulating nAChR function

The promise of nicotinic receptors as a therapeutic target has yet to be fully realized, despite solid data supporting their involvement in neurological and neuropsychiatric diseases. The reasons for this are likely complex and manifold, having to do with the widespread action of the cholinergic system and the biophysical mechanism of action of nicotinic receptors leading to fast desensitization and down-regulation. Conventional drug development strategies tend to focus on receptor subtype-specific action of candidate therapeutics, although the broad agonist, nicotine, is being explored in the clinic. The potential negative effects of nicotine make the search for alternate strategies warranted. Prototoxins are a promising yet little-explored avenue of nicotinic receptor drug development. Nicotinic receptors in the brain belong to a complex of proteins, including those that bind to the extracellular face of the receptor, as well as chaperones that bind the intracellular domain, etc. Lynx prototoxins have allosteric modularity effects on receptor function and number and have been implicated in complex in vivo processes such as neuroplasticity, learning, and memory. Their mechanism of action and binding specificity on sets of nAChR subtypes present intriguing possibilities for more efficacious and nuanced therapeutic targeting than nicotinic receptor subtypes alone. An allosteric drug may restrict its actions to physiologically relevant time points, which tend to be correlated with salient events which would be encoded into long-term memory storage. Rather than blanketing the brain with a steady and prolonged elevation of agonist, an allosteric nAChR compound could avoid side effects and loss of efficacy over time. This review details the potential strengths and challenges of prototoxin proteins as therapeutic targets, and some of the utility of such therapeutics based on the emerging understanding of cholinergic signaling in a growing number of complex neural processes.

Screening and Targeting Risk Factors for Prodromal Synucleinopathy: Taking Steps toward a Prescriptive Multi-modal Framework

As the prevalence of Parkinson's disease (PD) grows, so too does the population at-risk of developing PD, those in the so-called prodromal period. This period can span from those experiencing subtle motor deficits yet not meeting full diagnostic criteria or those with physiologic markers of disease alone. Several disease-modifying therapies have failed to show a neuroprotective effect. A common criticism is that neurodegeneration, even in the early motor stages, has advanced too far for neuro-restoration-based interventions to be effective. Therefore, identifying this early population is essential. Once identified, these patients could then potentially benefit from sweeping lifestyle modifications to alter their disease trajectory. Herein, we review the literature on risk factors for, and prodromal symptoms of, PD with an emphasis on ones which may be modifiable in the earliest possible stages. We propose a process for identifying this population and speculate on some strategies which may modulate disease trajectory. Ultimately, this proposal warrants prospective studies.

Gastrointestinal disorders in Parkinson's disease and other Lewy body diseases

Parkinson's disease (PD) is pathologically characterized by the abnormal accumulation of α-synuclein fibrils (Lewy bodies) in the substantia nigra and other brain regions, although the role of Lewy bodies remains elusive. Constipation usually precedes the motor symptoms in PD, which is in accordance with the notion that α-synuclein fibrils start from the intestinal neural plexus and ascend to the brain in at least half of PD patients. The gut microbiota is likely to be involved in intestinal and brain pathologies. Analyses of the gut microbiota in PD, rapid-eye-movement sleep behavior disorder, and dementia with Lewy bodies suggest three pathological pathways. First, Akkermansia, which is increased in PD, degrades the intestinal mucus layer and increases intestinal permeability, which triggers inflammation and oxidative stress in the intestinal neural plexus. Second, decreased short-chain fatty acids (SCFAs)-producing bacteria in PD reduce the number of regulatory T cells. Third, SCFAs also aggravate microglial activation with an unelucidated pathway. In addition, in dementia with Lewy bodies (DLB), which is another form of α-synucleinopathies, increased genera, Ruminococcus torques and Collinsella, may mitigate neuroinflammation in the substantia nigra by increasing secondary bile acids. Interventions for the gut microbiota and their metabolites may potentially delay or mitigate the development and progression of PD and other Lewy body diseases.

Association between smoking and all-cause mortality in Parkinson's disease

We aimed to investigate the association between smoking status and all-cause mortality of Parkinson's disease (PD). Among the whole nationwide population data from Korea National Health Insurance Service, newly diagnosed PD was selected, and all-cause mortality was evaluated. The systematic review was performed through a literature search on the PubMed, EMBASE, and Cochrane Central Register of Controlled Trials databases. Among 26,080 individuals with PD, there was no significant association between smoking status and all-cause mortality in a nationwide cohort study (ex-smoker, HR 0.1.03, 95% CI 0.97-1.10; current smoker, HR 1.06, 95% CI 0.96-1.16). The systematic review, including six prospective cohort studies, also found a nonsignificant association. PD smokers tended to have fewer deaths from neurologic causes but were significantly more likely to die from smoking-related cancers such as lung cancer. We presented a nonsignificant association between smoking and mortality of PD, and cigarette smoking is not recommended in individuals with PD.

Central nervous system interaction and crosstalk between nAChRs and other ionotropic and metabotropic neurotransmitter receptors

Neuronal nicotinic acetylcholine receptors (nAChRs) are widely distributed in both the peripheral and the central nervous systems. nAChRs exert a crucial modulatory influence on several brain biological processes; they are involved in a variety of neuronal diseases including Parkinson's disease, Alzheimer's disease, epilepsy, and nicotine addiction. The influence of nAChRs on brain function depends on the activity of other neurotransmitter receptors that co-exist with nAChRs on neurons. In fact, the crosstalk between receptors is an important mechanism of neurotransmission modulation and plasticity. This may be due to converging intracellular pathways but also occurs at the membrane level, because of direct physical interactions between receptors. In this line, this review is dedicated to summarizing how nAChRs and other ionotropic and metabotropic receptors interact and the relevance of nAChRs cross-talks in modulating various neuronal processes ranging from the classical modulation of neurotransmitter release to neuron plasticity and neuroprotection.

Disease-modifying vs symptomatic treatments: Splitting over lumping

Clinical trials of putative disease-modifying therapies in neurodegeneration have obeyed the century-old principle of convergence, or lumping, whereby any feature of a clinicopathologic disease entity is considered relevant to most of those affected. While this convergent approach has resulted in important successes in trials of symptomatic therapies, largely aimed at correcting common neurotransmitter deficiencies (e.g., cholinergic deficiency in Alzheimer's disease or dopaminergic deficiency in Parkinson's disease), it has been consistently futile in trials of neuroprotective or disease-modifying interventions. As individuals affected by the same neurodegenerative disorder do not share the same biological drivers, splitting such disease into small molecular/biological subtypes, to match people to therapies most likely to benefit them, is vital in the pursuit of disease modification. We here discuss three paths toward the splitting needed for future successes in precision medicine: (1) encourage the development of aging cohorts agnostic to phenotype in order to enact a biology-to-phenotype direction of biomarker development and validate divergence biomarkers (present in some, absent in most); (2) demand bioassay-based recruitment of subjects into disease-modifying trials of putative neuroprotective interventions in order to match the right therapies to the right recipients; and (3) evaluate promising epidemiologic leads of presumed pathogenetic potential using Mendelian randomization studies before designing the corresponding clinical trials. The reconfiguration of disease-modifying efforts for patients with neurodegenerative disorders will require a paradigm shift from lumping to splitting and from proteinopathy to proteinopenia.

Nicotine rebalances NAD+ homeostasis and improves aging-related symptoms in male mice by enhancing NAMPT activity

Imbalances in NAD⁺ homeostasis have been linked to aging and various diseases. Nicotine, a metabolite of the NAD⁺ metabolic pathway, has been found to possess anti-inflammatory and neuroprotective properties, yet the underlying molecular mechanisms remained unknown. Here we find that, independent of nicotinic acetylcholine receptors, low-dose nicotine can restore the age-related decline of NAMPT activity through SIRT1 binding and subsequent deacetylation of NAMPT, thus increasing NAD⁺ synthesis. ¹⁸F-FDG PET imaging revealed that nicotine is also capable of efficiently inhibiting glucose hypermetabolism in aging male mice. Additionally, nicotine ameliorated cellular energy metabolism disorders and deferred age-related deterioration and cognitive decline by stimulating neurogenesis, inhibiting neuroinflammation, and protecting organs from oxidative stress and telomere shortening. Collectively, these findings provide evidence for a mechanism by which low-dose nicotine can activate NAD⁺ salvage pathways and improve age-related symptoms.

Nicotine alleviates MPTP-induced nigrostriatal damage through modulation of JNK and ERK signaling pathways in the mice model of Parkinson's disease

Introduction: Nicotine (Nic) has previously been proven to reduce neurodegeneration in the models of Parkinson's disease (PD). The present study is intended to investigate the detailed mechanisms related to the potential neuroprotective effects of Nic in vivo. Methods: We established a PD model using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced C57BL6 mice (25 mg/kg/d, 5 d, i.p.) to investigate the neuropharmacological modulation of Nic pretreatment (2.5 mg/kg/d, 5 d, i.p., 30 min before MPTP injection) from the perspectives of neurobehavioral assessment, the pathological alterations, microglial cell inflammation and MAPK signaling pathways in specific brain regions. Results: The open field test, elevated plus maze, rotarod and traction test suggested that Nic pretreatment could significantly improve MPTP-induced motor impairment and had an anxiolytic effect. Nic was found to improve neuroapoptosis, enhance tyrosine hydroxylase activity, and reduce the accumulation of the phosphorylated α-synuclein in the substantia nigra and striatal regions of PD mice by TUNEL and immunohistochemical assays. Immuno-fluorescent method for labeling Iba1 and CD68 indicated that Nic remarkably alleviates the activation of microglia which represents the M1 polarization state in the mice brain under MPTP stimulation. No significant difference in the expression of p38/MAPK pathway was found in the nigrostriatal regions, while Nic could significantly inhibit the elevated p-JNK/JNK ratio and increase the declined p-ERK/ERK ratio in the substantia nigra of MPTP-exposed brains, which was further confirmed by the pretreatment of CYP2A5 inhibitor to decline the metabolic activity of Nic. Discussion: The molecular signaling mechanism by which Nic exerts its neuroprotective effects against PD may be achieved by regulating the JNK and ERK signaling pathways in the nigra-striatum related brain regions.

Nicotine-Mediated Rescue of α-Synuclein Toxicity Requires Synaptic Vesicle Glycoprotein 2 in Drosophila

BACKGROUND

Parkinson's disease (PD) is characterized by α-synuclein aggregation and loss of dopamine neurons. Risk of PD arises due to a combination of genetic and environmental factors, which may interact, termed gene-environment (G×E) interactions. An inverse association between smoking and the risk of PD is well established, and a previous genome-wide G×E interaction study identified genetic variation in the synaptic-vesicle glycoprotein 2C (SV2C) locus as an important mediator of the degree to which smoking is inversely associated with PD.

OBJECTIVE

We sought to determine the mechanism of the smoking-SV2C interaction in a Drosophila model of PD.

METHODS

Flies expressing human α-synuclein in all neurons develop the hallmarks of PD, including motor dysfunction, loss of dopaminergic (DA) neurons, and formation of α-synuclein inclusions. We assessed the effects of increasing doses of nicotine on these parameters of neurodegeneration, in the presence or absence of knockdown of two Drosophila orthologues of SV2, hereafter referred to as SV2L1 and SV2L2.

RESULTS

The α-synuclein-expressing flies treated with nicotine had improved locomotion, DA neuron counts, and α-synuclein aggregation. However, in α-synuclein-expressing flies in which SV2L1 and SV2L2 were knocked down, nicotine failed to rescue neurodegeneration.

CONCLUSIONS

This work confirms a G×E interaction between nicotine and SV2, defines a role for this interaction in α-synuclein proteostasis, and suggests that future clinical trials on nicotine should consider genetic variation in SV2C. Furthermore, this provides proof of concept that our model can be used for the mechanistic study of G×E, paving the way for the investigation of additional G×E interactions or the identification of novel G×E. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Cognitive resilience and severe Alzheimer's disease neuropathology

Cognitive resilience in Alzheimer's disease (AD) can be defined as retention of high cognition despite presence of considerable cerebral AD lesions. We sought to identify factors associated with this phenomenon. Data were obtained from National Alzheimer's Coordinating Centre (NACC) dataset. Subjects with severe AD neuropathology, based on National Institute on Aging-Reagan (NIA-Reagan) criteria, no other primary neuropathology, and a ≤ 2-year interval between last follow-up and death were included. Mini-mental status examination score ≥ 24 was used as a proxy for normal cognition. In total, 654 cases were included; 59 (9%) were cognitively resilient. Multivariable logistic regression model showed that resilient participants were more educated, had a lower body mass index (BMI), were more likely to be lifetime/recent smoker or use an anticoagulant/antiplatelet agent, compared with cognitively impaired subjects. In addition to expected protective factors such as higher education and lower BMI, our results showed that smoking (especially recent smoking) and anticoagulant/antiplatelet consumption are associated with resilience to clinical cognitive expression of severe AD pathology. Pharmacological approaches using this information might be explored for clinical AD amelioration.

Alcohol and Parkinson's Disease: A Systematic Review and Meta-Analysis

BACKGROUND

A substantial body of research has examined the relationship between alcohol consumption and risk of Parkinson's disease (PD).

OBJECTIVE

To provide an updated systematic review and meta-analysis of observational studies examining the relationship between alcohol consumption and risk of PD.

METHODS

Eligible studies comparing PD risk in ever vs. never alcohol drinkers were sourced from six databases. Outcomes were pooled using standard meta-analysis techniques. Separate female and male estimates were generated from studies reporting sex-specific data. Additionally, cohort studies stratifying participants by quantity of alcohol intake were integrated in a dose-response analysis.

RESULTS

52 studies were included, totaling 63,707 PD patients and 9,817,924 controls. Our meta-analysis supported a statistically significant overrepresentation of never drinkers among PD subjects; odds ratio (OR) for ever drinking alcohol 0.84 (95% confidence interval (CI) 0.76 - 0.92). A subgroup analysis revealed similar effect estimates in females and males. A further synthesis of seven cohort studies suggested a negative, dose-dependent association between alcohol and risk of PD.

CONCLUSION

In the absence of a known neuroprotective pathway, there may be reason to doubt a true biological effect. The role of survivor bias, selection and recall bias, misclassification, and residual confounding requires consideration. Alternatively, observations might be attributable to reverse causation if those predestined for PD alter their alcohol habits during the preclinical phase. Major limitations of our study include high between-study heterogeneity (I2 = 93.2%) and lack of adjustment for key confounders, namely smoking status.

Diagnostic and therapeutic agents that target alpha-synuclein in Parkinson's disease

The development of disease-modifying drugs and differential diagnostic agents is an urgent medical need in Parkinson’s disease. Despite the complex pathophysiological pathway, the misfolding of alpha-synuclein has been identified as a putative biomarker for detecting the onset and progression of the neurodegeneration associated with Parkinson’s disease. Identifying the most appropriate alpha-synuclein-based diagnostic modality with clinical translation will revolutionize the diagnosis of Parkinson’s. Likewise, molecules that target alpha-synuclein could alter the disease pathway that leads to Parkinson’s and may serve as first-in class therapeutics compared to existing treatment options such as levodopa and dopamine agonist that do not necessarily modify the disease pathway. Notwithstanding the promising benefits that alpha-synuclein presents to therapeutics and diagnostics development for Parkinson’s disease, finding ways to address potential challenges such as inadequate preclinical models, safety and efficacy will be paramount to achieving clinical translation. In this comprehensive review paper, we described the role of alpha-synuclein in the pathogenesis of Parkinson’s disease, as well as how its structure and function relationship delineate disease onset and progression. We further discussed different alpha-synuclein-based diagnostic modalities including biomolecular assays and molecular imaging. Finally, we presented current small molecules and biologics that are being developed as disease-modifying drugs or positron emission tomography imaging probes for Parkinson’s disease.

Nicotine Has a Therapeutic Window of Effectiveness in a Drosophila melanogaster Model of Parkinson’s Disease

Strong epidemiological evidence and studies in models of Parkinson's disease (PD) suggest that nicotine may be therapeutically beneficial in PD patients. However, a number of clinical trials utilizing nicotine in PD patients have had mixed results, indicating that either nicotine is not beneficial in PD patients, or an important aspect of nicotine therapy was absent. We hypothesized that nicotine must be administered early in the adult fly life in order to have beneficial effects. We show that continuous early nicotine administration improves both climbing and flight deficiencies present in homozygous park²⁵ mutant PD model Drosophila melanogaster. Using a new climbing assay, we identify several climbing deficiencies in this PD model that are improved or rescued by continuous nicotine treatment. Amongst these benefits, it appears that nicotine improves the ability of the park²⁵ flies to descend the climbing vial by being able to climb down more. In support of our hypothesis, we show that in order for nicotine benefits on climbing and flight to happen, nicotine administration must occur in a discrete time frame following adult fly eclosure: within one day for climbing or five days for flight. This therapeutic window of nicotine administration in this PD model fly may help to explain the lack of efficacy of nicotine in human clinical trials.

Relationship between risk and protective factors and clinical features of Parkinson's disease

BACKGROUND

Non-genetic risk factors play a relevant role in Parkinson's disease (PD) development but the relationship between these factors and PD clinical features is unknown.

OBJECTIVE

The aim of the present multicenter study was to investigate possible relationship between risk factors and clinical motor and non-motor features in a large sample of PD patients.

METHODS

Six hundred ninety-four patients with PD participated. Patients underwent a clinical evaluation assessing motor symptoms and motor complications as well as non-motor symptoms severity. Information regarding pharmacological treatment was also collected. Risk and protective factors were previously identified in the present population and included coffee consumption, cigarette smoking, and physical activity as protective factors and a family history of PD, dyspepsia, exposure to toxic agents and general anesthesia as risk factors. Multiple regression models were used to investigate the relationship between risk factors and clinical variables.

RESULTS

Coffee consumption predicted older age at onset (B: 0.527; CI: 0.195; 0.858) and milder motor symptom severity (B: 1.383; CI: 2.646; -0.121). Non-motor symptom severity was more severe in patients with dyspepsia before PD (B: 13.601; CI 5.019; 22.182) and milder in patients who performed physical activity before PD (B: 11.355; CI: 16.443; -6.266). We found no relationship between risk factors and motor complications, motor subtype and pharmacological treatment.

CONCLUSIONS

Risk and protective factors of PD development may influence PD clinical features. This finding may represent the first step in the development of new preventive approaches able to delay disease onset and mitigate the extent of clinical manifestations.

Improvement in visual performance after nicotine gum administration in tobacco use disorder: a case report

Chronic tobacco consumption, identified as Tobacco Use Disorder (TUD), is a public health problem. We present a case report of a 37-year-old Brazilian male diagnosed with TUD at age 26, with no comorbidities, that presented visual improvements (i.e., lower thresholds and better discrimination) after nicotine gum administration. Here, we assessed contrast sensitivity and chromatic discrimination using the Metropsis and the Cambridge Colour Test, respectively. Results showed lower thresholds for both visual tasks after the use of nicotine gum. Even considering this is a single case report, our intent is to open new avenues for research involving smoking, addiction and the use of nicotine gum as a replacement tool or adjuvant tool for improvement of visual and/or cognitive processing. It is well known that nicotine gum has protective effects for some diseases, and improves some cognitive functions. However, unclear were its effects on visual processing of people with TUD.

From chronic stress and anxiety to neurodegeneration: Focus on neuromodulation of the axon initial segment

To adapt to the sustained demands of chronic stress, discrete brain circuits undergo structural and functional changes often resulting in anxiety disorders. In some individuals, anxiety disorders precede the development of motor symptoms of Parkinson's disease (PD) caused by degeneration of neurons in the substantia nigra (SN). Here, we present a circuit framework for probing a causal link between chronic stress, anxiety, and PD, which postulates a central role of abnormal neuromodulation of the SN's axon initial segment by brainstem inputs. It is grounded in findings demonstrating that the earliest PD pathologies occur in the stress-responsive, emotion regulation network of the brainstem, which provides the SN with dense aminergic and cholinergic innervation. SN's axon initial segment (AIS) has unique features that support the sustained and bidirectional propagation of activity in response to synaptic inputs. It is therefore, especially sensitive to circuit-mediated stress-induced imbalance of neuromodulation, and thus a plausible initiating site of neurodegeneration. This could explain why, although secondary to pathophysiologies in other brainstem nuclei, SN degeneration is the most extensive. Consequently, the cardinal symptom of PD, severe motor deficits, arise from degeneration of the nigrostriatal pathway rather than other brainstem nuclei. Understanding when and how circuit dysfunctions underlying anxiety can progress to neurodegeneration, raises the prospect of timed interventions for reversing, or at least impeding, the early pathophysiologies that lead to PD and possibly other neurodegenerative disorders.

O Papel Bidirecional da Nicotina na Tarefa Go/No-Go: Um Ensaio Clínico Piloto

Resumo Estudos mostram que o tabagismo é responsável por afetar algumas funções cognitivas. No entanto, a nicotina é apenas um dos componentes existentes no cigarro e existem evidências de que pode servir como agente neuroprotetivo e causar melhoras em algumas funções cognitivas. O objetivo desta pesquisa foi investigar como a nicotina interage com algumas funções cognitivas. Um ensaio clínico piloto com administração de gomas de nicotina contendo 2-mg ou 4-mg, ou gomas placebo contendo a mesma textura, sabor e aparência, foi realizado. Quarenta e dois participantes participaram da pesquisa e os resultados indicaram que a relação entre nicotina e o desempenho na tarefa Go/No-Go podem ser bidirecionais. Os resultados indicaram que participantes do grupo que utilizaram 4-mg de nicotina apresentaram menor desempenho, enquanto os participantes que fizeram uso de 2-mg de nicotina tiveram melhor desempenho do que os demais. Esta pesquisa tem aplicações biopsicossociais e podem ajudar na compreensão da relação entre tabagismo e nicotina, além de contribuir para estratégias que possam ajudar no abandono do cigarro ou na melhora de condições que afetem a cognição.

Mendelian Randomisation Study of Smoking, Alcohol, and Coffee Drinking in Relation to Parkinson's Disease

BACKGROUND

Previous studies showed that lifestyle behaviors (cigarette smoking, alcohol, coffee) are inversely associated with Parkinson's disease (PD). The prodromal phase of PD raises the possibility that these associations may be explained by reverse causation.

OBJECTIVE

To examine associations of lifestyle behaviors with PD using two-sample Mendelian randomisation (MR) and the potential for survival and incidence-prevalence biases.

METHODS

We used summary statistics from publicly available studies to estimate the association of genetic polymorphisms with lifestyle behaviors, and from Courage-PD (7,369 cases, 7,018 controls; European ancestry) to estimate the association of these variants with PD. We used the inverse-variance weighted method to compute odds ratios (ORIVW) of PD and 95%confidence intervals (CI). Significance was determined using a Bonferroni-corrected significance threshold (p = 0.017).

RESULTS

We found a significant inverse association between smoking initiation and PD (ORIVW per 1-SD increase in the prevalence of ever smoking = 0.74, 95%CI = 0.60-0.93, p = 0.009) without significant directional pleiotropy. Associations in participants ≤67 years old and cases with disease duration ≤7 years were of a similar size. No significant associations were observed for alcohol and coffee drinking. In reverse MR, genetic liability toward PD was not associated with smoking or coffee drinking but was positively associated with alcohol drinking.

CONCLUSION

Our findings are in favor of an inverse association between smoking and PD that is not explained by reverse causation, confounding, and survival or incidence-prevalence biases. Genetic liability toward PD was positively associated with alcohol drinking. Conclusions on the association of alcohol and coffee drinking with PD are hampered by insufficient statistical power.

Ultrasound-triggered nicotine release from nicotine-loaded cellulose hydrogel

Ultrasound (US)-triggered nicotine release system in a cellulose hydrogel drug carrier was developed with three different cellulose concentrations of 0.45 wt%, 0.9 wt%, and 1.8 wt%. The nicotine-loaded cellulose hydrogels were fabricated by the phase inversion method when the nicotine and cellulose mixture in the 6 wt% LiCl/N, N-dimethylacetamide solvent was exposed to water vapor at room temperature. Nicotine was used as the medicine due to its revealed therapeutic potential for neurodegenerative diseases like Alzheimer's and Parkinson's diseases. The behavior of US-triggered nicotine release from nicotine-cellulose hydrogel was studied at 43 kHz US frequency at the changing US output powers of 0 W, 5 W, 10 W, 20 W, 30 W, and 40 W. The significant US-triggered nicotine release enhancement was noted for the hydrogels made with 0.9 wt% and 1.8 wt% cellulose loading. The matrix made with 0.9 wt% cellulose was exhibited the highest nicotine release at the 40 W US power, and differences in nicotine release at different US powers were noticeable than at 0.45 wt% and 1.8 wt% cellulose loadings. For the three cellulose hydrogel systems, the storage modulus (G') values at the 0.01 wt% strain rate were dropped from their initial values due to the US irradiation. This reduction was proportionately decreased when the US power was increased. The deconvolution of FTIR spectra of nicotine-loaded cellulose films before and after US exposure was suggested breakage of cellulose-nicotine and cellulose-water in the matrix; thus, the stimulated nicotine release from the cellulose matrix was promoted by the US irradiation.

High IQ in Early Adulthood Is Associated with Parkinson's Disease

Background:

High education level and high occupational complexity have been implicated as risk factors for Parkinson’s disease (PD).

Objective:

The objective was to determine whether cognitive capacity, measured as IQ, in early adulthood is associated with the subsequent development of PD.

Method:

Data on IQ were retrieved from the Swedish Military Service Conscription Registry, comprising Swedish males who enlisted for military service in the period 1968–1993 (N = 1,319,235). After exclusion, 1,189,134 subjects in total were included in the present study. Individuals who later developed PD (N = 1,724) were identified using the Swedish National Patient Register and the Swedish Cause of Death Register.

Results:

High education level was associated with PD. High IQ was associated with PD (p < 0.0001), both when analyzed as a continuous variable and when divided into three categories. The hazard ratio for the high IQ category compared to the low IQ category was 1.35 (95% confidence interval 1.17–1.55). Strong test results on the subtests, measuring verbal, logic, visuospatial and technical abilities, were also associated with PD. In a subgroup, smoking was inversely associated with PD, as well as with IQ.

Conclusions:

This study identifies high IQ to be a risk factor for PD.

Employing in vitro metabolism to guide design of F-labelled PET probes of novel α-synuclein binding bifunctional compounds

A challenge in the development of novel ¹⁸F-labelled positron emission tomography (PET) imaging probes is identification of metabolically stable sites to incorporate the ¹⁸F radioisotope. Metabolic loss of ¹⁸F from PET probes in vivo can lead to misleading biodistribution data as displaced ¹⁸F can accumulate in various tissues.In this study we report on in vitro hepatic microsomal metabolism of novel caffeine containing bifunctional compounds (C₈-6-I, C₈-6-N, C₈-6-C₈) that can prevent in vitro aggregation of α-synuclein, which is associated with the pathophysiology of Parkinson's disease. The metabolic profile obtained guided us to synthesize stable isotope ¹⁹F-labelled analogues in which the fluorine was introduced at the metabolically stable N7 of the caffeine moiety.An in vitro hepatic microsomal metabolism study of the ¹⁹F-labelled analogues resulted in similar metabolites to the unlabelled compounds and demonstrated that the fluorine was metabolically stable, suggesting that these analogues are appropriate PET imaging probes. This straightforward in vitro strategy is valuable for avoiding costly stability failures when designing radiolabelled compounds for PET imaging.

Influence of current and previous smoking on current phenotype in Parkinson's disease

INTRODUCTION

Although an inverse correlation between smoking and Parkinson's disease (PD) has been reported, research into the effect of smoking on current clinical progression remains limited for PD patients. Elucidation of a specific PD population who would benefit from smoking is challenging.

METHODS

We evaluated 110 consecutive PD patients (mean age; 71.0 ± 8.0 years) at a single neurology clinic between 2010 and 2018. The association with smoking status was evaluated in sex- and age-matched controls (non-PD). This study assessed the impact of previous smoking exposure on the outcome of current PD-related parameters, along with any confounders, in addition to assessing fluctuation of parkinsonism induced by smoking exposure.

RESULTS

The current smoking rate was significantly lower in PD versus non-PD (5.5% vs. 15.5%, P = 0.026), while there were similar rates between former and never smokers. Among the former smokers, most PD patients (97.3%) quit smoking prior to the onset of PD. There were no differences between PD patients with and without a history of smoking for current clinical parameters. Three PD patients with the mean onset age of 51.0 ± 5.3 y reported transient deterioration of their parkinsonism when smoking. Negative mood during cigarette smoke exposure was significantly increased over the entire life in PD patients with a history of smoking than those without (p < 0.001).

CONCLUSIONS

Although previous smoking history reportedly had a neuroprotective effect prior to onset, the association between the previous history and current phenotype in PD was not visible in the present study. However, the possibility that current nicotine intake might modify the parkinsonism deterioration will need to be further evaluated, especially in non-elderly patients. Cigarette smoke-related negative mood could be a confounder for quitting smoking in PD patients.

Management of Hypertension and Blood Pressure Dysregulation in Patients with Parkinson's Disease-a Systematic Review

PURPOSE OF REVIEW

The aim of this review article was to summarize the cardiovascular and blood pressure profile regarding Parkinson disease patients and to provide an update on the recent advancements in the field of the diagnosis and management of blood pressure abnormalities in these patients. Our goal was to guide physicians to avoid pitfalls in current practice while treating patients with Parkinson disease and blood pressure abnormalities. For this purpose, we searched bibliographic databases (PubMed, Google Scholar) for all publications published on blood pressure effects in Parkinson disease until May 2020. Furthermore, we highlight some thoughts and potential perspectives for the next possible steps in the field.

RECENT FINDINGS

Blood pressure dysregulation in patients with Parkinson's disease has several implications in clinical practice and presents an ongoing concern. Compared with chronic essential hypertension, the syndrome of combined neurogenic orthostatic hypotension and supine hypertension in Parkinson's disease has received little attention. If left untreated, hypertension may lead to cardiovascular disease whereas hypotension may lead to fall-related complications, with tremendous impact on the quality of life of affected individuals. The effect of blood Epressure control and the risk of death from cardiovascular disease in Parkinson disease are largely unexplored. Blood pressure abnormalities in Parkinson disease present bidirectional relationship and the rationale for treating and controlling hypertension in persons with Parkinson disease and concurrent neurogenic orthostatic hypotension and/or supine hypertension is compelling. Further research is warranted in order to clarify the mechanisms, clinical implications, and potential reversibility of compromised cardiovascular function, in persons with Parkinson disease.

Nicotine suppresses Parkinson's disease like phenotypes induced by Synphilin-1 overexpression in Drosophila melanogaster by increasing tyrosine hydroxylase and dopamine levels

It has been observed that there is a lower Parkinson's disease (PD) incidence in tobacco users. Nicotine is a cholinergic agonist and is the principal psychoactive compound in tobacco linked to cigarette addiction. Different studies have shown that nicotine has beneficial effects on sporadic and genetic models of PD. In this work we evaluate nicotine's protective effect in a Drosophila melanogaster model for PD where Synphilin-1 (Sph-1) is expressed in dopaminergic neurons. Nicotine has a moderate effect on dopaminergic neuron survival that becomes more evident as flies age. Nicotine is beneficial on fly survival and motility increasing tyrosine hydroxylase and dopamine levels, suggesting that cholinergic agonists may promote survival and metabolic function of the dopaminergic neurons that express Sph-1. The Sph-1 expressing fly is a good model for the study of early-onset phenotypes such as olfaction loss one of the main non-motor symptom related to PD. Our data suggest that nicotine is an interesting therapeutic molecule whose properties should be explored in future research on the phenotypic modulators of the disease and for the development of new treatments.

The association between multiple risk factors, clinical correlations and molecular insights in Parkinson's disease patients from Tamil Nadu population, India

Parkinson's disease (PD) is a neurodegenerative disease with multifactorial aetiology that influences the quality of life. However, the association of possible factors with PD is need to be investigated in Indian population, hence we aimed to determine the association of lifestyle, environmental factors, biochemical parameters and genetic insights of MT-ND1 gene in PD patients. Using a standardised questionnaire, PD patients and control group of about 146 subjects were interviewed on demographic, lifestyle and environmental factors. The subjects includes n = 73 Parkinson's patients [juvenile (n = 4); early-onset (n = 8); late-onset (n = 61)] with equal number of age and sex matched controls, further we had obtained institutional ethical clearance and informed consent from study participants. Biomarker investigations and MT-ND1 alterations were investigated by appropriate molecular techniques. During the average follow-up years of 5.1, significant association was observed among smoking, alcohol, caffeinated drinks, surgery, pesticide exposure at p < 0.05 in varied PD age groups. Occupational exposure to agriculture and industry showed an increased risk among the late-onset group. The biomarkers uric acid (UA) and dopamine (DA) were significant at p < 0.05 in all the three PD age groups. The MT-ND1 alteration with A3843 G variant was significant at p < 0.05 for AG allele in all the three PD groups but the highest prevalence was observed in late-onset group. From our study, smoking, alcohol, caffeinated drinks, occupational influence of agriculture and industry and pesticide exposure had more association with PD occurrence. Hence, to the best of our knowledge, this is the first kind of study in Tamil Nadu population, India to validate the various factors with PD. Therefore we suggest that further research is mandatory to detect other possible associations among PD, using comprehensive larger sample size.

Roles of the Functional Interaction between Brain Cholinergic and Dopaminergic Systems in the Pathogenesis and Treatment of Schizophrenia and Parkinson's Disease

Most physiologic processes in the brain and related diseases involve more than one neurotransmitter system. Thus, elucidation of the interaction between different neurotransmitter systems could allow for better therapeutic approaches to the treatments of related diseases. Dopaminergic (DAergic) and cholinergic neurotransmitter system regulate various brain functions that include cognition, movement, emotion, etc. This review focuses on the interaction between the brain DAergic and cholinergic systems with respect to the pathogenesis and treatment of schizophrenia and Parkinson’s disease (PD). We first discussed the selection of motor plans at the level of basal ganglia, the major DAergic and cholinergic pathways in the brain, and the receptor subtypes involved in the interaction between the two signaling systems. Next, the roles of each signaling system were discussed in the context of the negative symptoms of schizophrenia, with a focus on the α7 nicotinic cholinergic receptor and the dopamine D₁ receptor in the prefrontal cortex. In addition, the roles of the nicotinic and dopamine receptors were discussed in the context of regulation of striatal cholinergic interneurons, which play crucial roles in the degeneration of nigrostriatal DAergic neurons and the development of L-DOPA-induced dyskinesia in PD patients. Finally, we discussed the general mechanisms of nicotine-induced protection of DAergic neurons.

Interactions between reproductive transitions during aging and addiction: promoting translational crosstalk between different fields of research

Discovery of neural mechanisms underlying neuropsychiatric disorders within the aging and addiction fields has been a main focus of the National Institutes of Health. However, there is a dearth of knowledge regarding the biological interactions of aging and addiction, which may have important influences on progression of disease and treatment outcomes in aging individuals with a history of chronic drug use. Thus, there is a large gap in these fields of research, which has slowed progress in understanding and treating substance use disorders (SUDs) as well as age-related diseases, specifically in women who experience precipitous reproductive cycle transitions during aging. The goal of this review is to highlight overlap of SUDs and age-related processes with a specific focus on menopause and smoking, and identify critical gaps. We have narrowed the focus of the review to smoking, as the majority of findings on hormonal and aging influences on drug use have come from this area of research. Further, we highlight female-specific issues such as transitional menopause and exogenous estrogen use. These issues may impact drug use cessation as well as outcomes with aging and age-related neurodegenerative diseases in women. We first review clinical studies for smoking, normal aging, and pathological aging, and discuss the few aging-related studies taking smoking history into account. Conversely, we highlight the dearth of clinical smoking studies taking age as a biological variable into account. Preclinical and clinical literature show that aging, age-related pathological brain disease, and addiction engage overlapping neural mechanisms. We hypothesize that these putative drivers interact in meaningful ways that may exacerbate disease and hinder successful treatment outcomes in such comorbid populations. We highlight areas where preclinical studies are needed to uncover neural mechanisms in aging and addiction processes. Collectively, this review highlights the need for crosstalk between different fields of research to address medical complexities of older adults, and specifically women, who smoke.

Nicotine gum enhances visual processing in healthy nonsmokers

OBJECTIVE

The main purpose of this study was to investigate the isolated effects of nicotine on visual processing, namely contrast processing.

METHODS

Thirteen participants, aged 18-40 years, were enrolled in this double blind, randomized and pilot controlled trial involving nicotine gum administration (placebo, 2-mg and 4-mg doses). The participants' instruction was to detect the location of vertical gratings (0.2; 1.0; 3.3; 5.7; 8.8; 13.2 and 15.9 cycles per degree) when it was presented either left or right on the monitor screen. A repeated multivariate analysis of variance was conducted to analyse the results for the visual processing tasks. Bayesian analyses were also carried out considering maximum robustness to avoid bias.

RESULTS

The findings that nicotine gum administration resulted in better contrast discrimination when compared to placebo gum (p < .001). More specifically, the 4-mg resulted in better visual sensitivity when compared to the 2-mg (p < .01) and the placebo (p < .001) gum. Demographic data were not related to the outcomes.

CONCLUSIONS

These data bring the need for support the findings. If proved, it is possible that nicotine, in small doses, can have a potential therapeutic use for those populations with low vision.

TRIAL REGISTRATION NUMBER

RBR-46tjy3.

Biomarkers of Toxicant Exposure and Inflammation Among Women of Reproductive Age Who Use Electronic or Conventional Cigarettes

Background: Electronic cigarettes (e-cigarettes) generally have a more favorable toxicant profile than conventional cigarettes; however, limited information exists for women of reproductive age (WRA). Our aim was to compare biomarkers of toxicant exposure, inflammation, and oxidative stress among WRA who self-report exclusive e-cigarette use, exclusive cigarette smoking, or never tobacco use (controls). Methods: Multivariable linear regression models were used to compare the geometric means of urinary biomarkers of toxicant exposure and their metabolites, serum markers of inflammation [highly sensitive C-reactive protein, soluble intercellular adhesion molecule (sICAM), interleukin 6, fibrinogen], and a measurement of oxidative stress [prostaglandin F2a-8-isoprostane (F2PG2a)] among WRA from the Population Assessment of Tobacco and Health survey. Results: E-cigarette users had higher levels of lead, tobacco-specific nitrosamines, nicotine metabolites, and some volatile organic compounds (VOCs) than controls. Except for cadmium and lead, e-cigarette users had lower levels of the analyzed urinary toxicant biomarkers compared with cigarette smokers. Cigarette smokers had higher levels of all the biomarkers of toxicant exposure than controls. There were no significant differences in the levels of markers of inflammation and oxidative stress between e-cigarette users and controls. E-cigarette users and controls had lower levels of sICAM and F2PG2a than cigarette smokers. Conclusion: WRA who use e-cigarettes had lower levels of some of the evaluated urinary biomarkers of toxicant exposure and serum biomarkers of inflammation and oxidative stress than those who smoke cigarettes, but higher lead, nicotine metabolites, and some VOCs than controls, which can increase health risks.

Systematic Review of Nicotine Exposure's Effects on Neural Stem and Progenitor Cells

While various modalities of chronic nicotine use have been associated with numerous negative consequences to human health, one possible benefit of nicotine exposure has been uncovered. The discovery of an inverse correlation between smoking and Parkinson's disease, and later Alzheimer's disease as well, motivated investigation of nicotine as a neuroprotective agent. Some studies have demonstrated that nicotine elicits improvements in cognitive function. The hippocampus, along with the subventricular zone (SVZ), is a distinct brain region that allow for ongoing postnatal neurogenesis throughout adulthood and plays a major role in certain cognitive behaviors like learning and memory. Therefore, one hypothesis underlying nicotine-induced neuroprotection is possible effects on neural stem cells and neural precursor cells. On the other hand, nicotine withdrawal frequently leads to cognitive impairments, particularly in hippocampal-dependent behaviors, possibly suggesting an impairment of hippocampal neurogenesis with nicotine exposure. This review discusses the current body of evidence on nicotine's effects on neural stem cells and neural progenitors. Changes in neural stem cell proliferation, survival, intracellular dynamics, and differentiation following acute and chronic nicotine exposure are examined.

Associations between metabolic syndrome and type of dementia: analysis based on the National Health Insurance Service database of Gangwon province in South Korea

BACKGROUND

Metabolic syndrome is a cluster of conditions that occur together, increasing the risk of cardiovascular disease. However, the relationship between metabolic syndrome and dementia has remained controversial. Using nationwide population cohort data, we investigated the association between metabolic syndrome and dementia, according to the dementia type.

METHODS

We analyzed data of 84,144 individuals, in the aged group of more than 60 years, between January 1, 2009, to December 31, 2009, at Gangwon province by using the information of the (Korean) National Health Insurance Service. After eight years of gap, in 2017, we investigated the relationship between metabolic syndrome and dementia. We classified Dementia either as dementia of the Alzheimer type (AD) or vascular dementia (VD). AD and VD were defined as per the criteria of International Classification of Disease, Tenth Revision, Clinical Modification codes. Multiple logistic regression analyses examined the associations between metabolic syndrome or five metabolic syndrome components and dementia. Analyses included factors like age, sex, smoking, alcohol, physical inactivity, previous stroke, and previous cardiac disease.

RESULTS

Metabolic syndrome was associated with AD (OR = 11.48, 95% CI 9.03-14.59), not with VD. Each of five components of metabolic syndrome were also associated with AD. (high serum triglycerides: OR = 1.87, 95% CI 1.60-2.19; high blood pressure: OR = 1.85, 95% CI 1.55-2.21; high glucose: OR = 1.77, 95% CI 1.52-2.06; abdominal obesity: OR = 1.88, 95% CI 1.57-2.25; low serum high-density lipoprotein cholesterol: OR = 1.91, 95% CI 1.63-2.24) However, among components of metabolic syndrome, only the high glucose level was associated with VD. (OR = 1.26, 95% CI 1.01-1.56) body mass index (BMI), fasting glucose, and smoking were also associated with AD. (BMI: OR = 0.951, 95% CI 0.927-0.975; fasting glucose: OR = 1.003, 95% CI 1.001-1.005; smoking: OR = 1.020, 95% CI 1.003-1.039) A history of the previous stroke was associated with both AD and VD. (AD: OR = 1.827, 95% CI 1.263-2.644; VD: OR 2.775, 95% CI 1.747-4.406) CONCLUSIONS: Metabolic syndrome was associated with AD but not with VD. Patients with metabolic syndrome had an 11.48 times more likeliness to develop AD compared to those without metabolic syndrome. VD was associated only with several risk factors that could affect the vascular state rather than a metabolic syndrome. We suggested that the associations between metabolic syndrome and dementia would vary depending on the type of dementia.

Non-Genetic Risk Factors for Parkinson's Disease: An Overview of 46 Systematic Reviews

BACKGROUND

Numerous systematic reviews (SRs) and meta-analyses on non-genetic risk factors for Parkinson's disease (PD) development have been published with inconsistent conclusions.

OBJECTIVE

This overview of SRs aimed to summarize evidence on non-genetic factors for the development of PD from the published SRs, and explore the reasons behind the conflicting results.

METHODS

Three international databases were searched for SRs with meta-analyses summarized evidence on non-genetic factors for PD development. The Assessing the Methodological Quality of Systematic Reviews 2 tool was used to appraise the methodological quality of included SRs. Pooled effect estimations were extracted from each meta-analysis.

RESULTS

Forty-six SRs covered six categories, and more than 80 factors were included in this overview. Thirty-nine SRs (84.7%) were judged to be of critically low methodological quality. Evidence from prospective studies showed that physical activity, smoking, coffee, caffeine, tea, fat intake, ibuprofen use, calcium channel blocker use, statin use, thiazolidinediones, and high serum urate levels significantly reduced the risk of PD, while dairy intake, diabetes, hormone replacement therapy, depression, mood disorder, bipolar disorder, and aspirin use significantly increased the risk of PD. Differences in study designs (e.g., cohort studies, case-control studies) accounted for the conflicting results among included SRs.

CONCLUSION

Modifiable lifestyle factors such as physical activity and tea and coffee drinking may reduce the risk of PD, which may offer PD prevention strategies and hypotheses for future research. However, the designs of primary studies on PD risk factors and related SRs need to be improved and harmonized.

Opposite effects of smoking and nicotine intake on cognition

Our main purpose was to investigate how smoking and nicotine interacted with specific aspects of cognitive functioning. The research was conducted in two parts: (i) an investigation of cognition in heavy smokers and healthy nonsmokers, and (ii) an investigation of cognition in healthy nonsmokers enrolled in a clinical trial involving administration of nicotine gum. Results indicated that the relationship between smoking and nicotine was characterized by an inverted U-shaped effect. On the one hand, cognitive test performance of the heavy smokers group was reduced on all of the cognitive tasks used here. On the other hand, healthy nonsmokers who used 2-mg of nicotine gum performed better, whilst the 4-mg group performed worse than the 2-mg and the placebo group. Demographic data were not related to the cognitive tasks. These data suggest that small doses of nicotine can have an activating function that leads to improved cognition, while heavy smoking on a chronic (and possibly acute) basis leads to cognitive impairment.

Neuroprotective Effect of Curcumin on the Nigrostriatal Pathway in a 6-Hydroxydopmine-Induced Rat Model of Parkinson's Disease is Mediated by α7-Nicotinic Receptors

Parkinson’s disease (PD) is a common neurodegenerative disorder, characterized by selective degeneration of dopaminergic nigrostriatal neurons. Most of the existing pharmacological approaches in PD consider replenishing striatal dopamine. It has been reported that activation of the cholinergic system has neuroprotective effects on dopaminergic neurons, and human α7-nicotinic acetylcholine receptor (α7-nAChR) stimulation may offer a potential therapeutic approach in PD. Our recent in-vitro studies demonstrated that curcumin causes significant potentiation of the function of α7-nAChRs expressed in Xenopus oocytes. In this study, we conducted in vivo experiments to assess the role of the α7-nAChR on the protective effects of curcumin in an animal model of PD. Intra-striatal injection of 6-hydroxydopmine (6-OHDA) was used to induce Parkinsonism in rats. Our results demonstrated that intragastric curcumin treatment (200 mg/kg) significantly improved the abnormal motor behavior and offered neuroprotection against the reduction of dopaminergic neurons, as determined by tyrosine hydroxylase (TH) immunoreactivity in the substantia nigra and caudoputamen. The intraperitoneal administration of the α7-nAChR-selective antagonist methyllycaconitine (1 µg/kg) reversed the neuroprotective effects of curcumin in terms of both animal behavior and TH immunoreactivity. In conclusion, this study demonstrates that curcumin has a neuroprotective effect in a 6-hydroxydopmine (6-OHDA) rat model of PD via an α7-nAChR-mediated mechanism.

Risk factors of Parkinson disease: Simultaneous assessment, interactions, and etiologic subtypes

OBJECTIVE

To perform a simultaneous evaluation of potential risk/protective factors of Parkinson disease (PD) to identify independent risk/protective factors, to assess interaction among factors, and to determine whether identified risk factors predict etiologic subtypes of PD.

METHODS

We designed a large case-control study assessing 31 protective/risk factors of PD, including environmental and lifestyle factors, comorbid conditions, and drugs. The study enrolled 694 patients with PD and 640 healthy controls from 6 neurologic centers. Data were analyzed by logistic regression models, additive interaction models, and cluster analysis.

RESULTS

The simultaneous assessment of 31 putative risk/protective factors of PD showed that only coffee consumption (odds ratio [OR] 0.6; 95% confidence interval [CI] 0.4-0.9), smoking (OR 0.7, 95% CI 0.6-0.9), physical activity (OR 0.8, 95% CI 0.7-0.9), family history of PD (OR 3.2, 95% CI 2.2-4.8), dyspepsia (OR 1.8, 95% CI 1.3-2.4), and exposure to pesticides (OR 2.3, 95% CI1.3-4.2), oils (OR 5.6, 95% CI 2.3-13.7), metals (OR 2.8, 95% CI 1.5-5.4), and general anesthesia (OR 6.1, 95% CI 2.9-12.7) were independently associated with PD. There was no evidence of interaction among risk/protective factors, but cluster analysis identified 4 subtypes with different risk factor profiles. In group 1, all patients had a family history of PD, while dyspepsia or exposure to toxic agents was present in 30% of patients. In groups 2 and 3, a family history of PD was lacking, while exposure to toxic agents (group 2) and dyspepsia (group 3) played major roles. Group 4 consisted of patients with no risk factors.

CONCLUSIONS

This study demonstrated that 9 factors independently modify PD risk by coexisting in the same patient rather than interacting with others. Our study suggests the need for future preventive strategies aimed at reducing the coexistence of different risk factors within the same participant.

Effects of Nicotine Gum Administration on Vision (ENIGMA-Vis): Study Protocol of a Double-Blind, Randomized, and Controlled Clinical Trial

Studies reported that tobacco addiction was related to visual impairments, but one unresolved issue is whether the impairments are related to the many compounds existing in the cigarettes or to the effects of nicotine. On the other hand, nicotine gum can be used as replacement therapy or as a neuroprotective agent for some diseases. The main purpose of this controlled trial is to investigate the effects of nicotine gum on vision. The ENIGMA-Vis trial aims to compare two dosages of nicotine gum (2 and 4 mg) and a placebo gum in a randomized, double-blind, placebo-controlled trial of 100 participants to be allocated into a single group assignment of repeated measures (two studies; N = 50 for each one). Eligibility criteria are healthy non-smokers not diagnosed with substance abuse and without an acute or chronic medical condition. Intervention will last three sessions for each participant with a window frame of 1 week per session. Study outcomes are (1) short-term effects of nicotine gum on contrast sensitivity; (2) short-term effects of nicotine gum on chromatic contrast discrimination; and (3) whether demographics, body mass index, or serum cotinine predicts response of visual processing. This study addresses an important gap in the effects of nicotine on vision. One of the main takeaways of this study is to understand the effects of nicotine on contrast sensitivity and chromatic contrast discrimination. This information will provide a further understanding of how nicotine interacts with early visual processes and help determine how the different components present during smoking can affect vision.

Clinical Trial Registration Number: RBR-46tjy3.

Neuroprotection: Targeting Multiple Pathways by Naturally Occurring Phytochemicals

With the increase in the expectancy of the life span of humans, neurodegenerative diseases (NDs) have imposed a considerable burden on the family, society, and nation. In defiance of the breakthroughs in the knowledge of the pathogenesis and underlying mechanisms of various NDs, very little success has been achieved in developing effective therapies. This review draws a bead on the availability of the nutraceuticals to date for various NDs (Alzheimer's disease, Parkinson's disease, Amyotrophic lateral sclerosis, Huntington's disease, vascular cognitive impairment, Prion disease, Spinocerebellar ataxia, Spinal muscular atrophy, Frontotemporal dementia, and Pick's disease) focusing on their various mechanisms of action in various in vivo and in vitro models of NDs. This review is distinctive in its compilation to critically review preclinical and clinical studies of the maximum phytochemicals in amelioration and prevention of almost all kinds of neurodegenerative diseases and address their possible mechanism of action. PubMed, Embase, and Cochrane Library searches were used for preclinical studies, while ClinicalTrials.gov and PubMed were searched for clinical updates. The results from preclinical studies demonstrate the efficacious effects of the phytochemicals in various NDs while clinical reports showing mixed results with promise for phytochemical use as an adjunct to the conventional treatment in various NDs. These studies together suggest that phytochemicals can significantly act upon different mechanisms of disease such as oxidative stress, inflammation, apoptotic pathways, and gene regulation. However, further clinical studies are needed that should include the appropriate biomarkers of NDs and the effect of phytochemicals on them as well as targeting the appropriate population.

Structural and functional computational analysis of nicotine analogs as potential neuroprotective compounds in Parkinson disease

As the mechanism of interaction between nicotinic receptors with nicotine analogs is not yet fully understood, information at molecular level obtained from computational calculations is needed. In this sense, this work is a computational study of eight nicotine analogs, all with pyrrolidine ring modifications over a nicotine-based backbone optimized with B3LYP-D3/aug-cc-pVDZ. A molecular characterization was performed focusing on geometrical parameters such as pseudo-rotation angles, atomic charges, HOMO and LUMO orbitals, reactivity indexes and intermolecular interactions. Three analogs, A2 (3-(1,3-dimethyl-4,5-dihydro-1h-pirazole-5-yl) pyridine), A3 (3-(3-methyl-4,5-dihydro-1H-pyrazol-5-yl)-pyridine) and A8 (5-methyl-3-(pyridine-3-yl)-4,5-dihydroisoxazole), were filtered suggesting putative neuroprotective activity taking into account different reactivity values, such as their lowest hardness: 2.37 eV (A8), 2.43 eV (A2) and 2.56 eV (A3), compared to the highest hardness value found: 2.71 eV for A5 (3-((2S,4R)-4-(fluoromethyl)-1-methylpyrrolidine-2-il) pyridine), similar to the value of nicotine (2.70 eV). Additionally, molecular docking of all 8 nicotine analogs with the α 7 nicotinic acetylcholine receptor (α 7 nAChR) was performed. High values of interaction between the receptor and the three nicotine analogs were obtained: A3 (-7.1 kcal/mol), A2 (-6.9 kcal/mol) and A8 (-6.8 kcal/mol); whereas the affinity energy of nicotine was -6.4 kcal/mol. Leu116 and Trp145 are key residues in the binding site of α 7 nAChR interacting with nicotine analogs. Therefore, based upon these results, possible application of these nicotine analogs as neuroprotective compounds and potential implication at the design of novel Parkinson's treatments is evidenced.

Tobacco smoking and the risk of Parkinson disease: A 65-year follow-up of 30,000 male British doctors

OBJECTIVE

To investigate the causal relevance of current tobacco smoking for the risk of Parkinson disease (PD).

METHODS

We compared the risks of death from PD with smoking habits in 30,000 male doctors in the British Doctors cohort study in 1951 and in survivors who had been resurveyed periodically for 5 decades. Cause-specific mortality was monitored for 65 years and included 283 deaths from PD. The relative risks (RRs) of PD (and 95% confidence intervals [CIs]) were estimated using Cox models for smoking habits (smoking status, amount smoked, and years since quitting) at baseline or updated habits at resurvey.

RESULTS

The prevalence of current smoking declined progressively during follow-up from 67% to 8% between 1951 and 1998. The crude rates of PD death were lower in current smokers than in never smokers at baseline (30 vs 46/100,000 persons-years). After adjustment for age at risk, current smokers at baseline had a 30% lower risk of PD (RR 0.71; 95% CI 0.60-0.84), and continuing smokers classified using updated smoking habits at resurvey had a 40% lower risk (RR 0.60; 95% CI 0.46-0.77) of PD compared with never smokers. The risks of PD were inversely associated with the amount of tobacco smoked. The protective effect of current smoking vs never smoking for PD was attenuated by increasing duration since quitting smoking.

CONCLUSIONS

In contrast to previous suggestions, the present report demonstrates a causally protective effect of current smoking on the risk of PD, which may provide insights into the etiology of PD.

Nanoformulations of Herbal Extracts in Treatment of Neurodegenerative Disorders

Nanotechnology is one of the methods that influenced human life in different ways and is a substantial approach that assists to overcome the multiple limitations of various diseases, particularly neurodegenerative disorders (NDs). Diverse nanostructures such as polymer nanoparticles, lipid nanoparticles, nanoliposomes, nano-micelles, and carbon nanotubes (CNTs); as well as different vehicle systems including poly lactic-co-glycolic acid, lactoferrin, and polybutylcyanoacrylate could significantly increase the effectiveness, reduce the side effects, enhance the stability, and improve the pharmacokinetics of many drugs. NDs belong to a group of annoying and debilitating diseases that involve millions of people worldwide. Previous studies revealed that several nanoformulations from a number of natural products such as curcumin (Cur), quercetin (QC), resveratrol (RSV), piperine (PIP), Ginkgo biloba, and Nigella sativa significantly improved the condition of patients diagnosed with NDs. Drug delivery to the central nervous system (CNS) has several limitations, in which the blood brain barrier (BBB) is the main drawback for treatment of NDs. This review discusses the effects of herbal-based nanoformulations, their advantages and disadvantages, to manage NDs. In summary, we conclude that herbal-based nano systems have promising proficiency in treatment of NDs, either alone or in combination with other drugs.