Pharmacogenetic Profile and the Occurrence of Visual Hallucinations in Patients With Sporadic Parkinson's Disease

Critical evaluation of the current landscape of pharmacogenomics in Parkinson's disease - What is missing? A systematic review

INTRODUCTION

The first-line treatment for Parkinson's disease (PD) involves dopamine-replacement therapies; however, significant variability exists in patient responses. Pharmacogenomics has been explored as a potential approach to understanding and predicting treatment outcomes. This review aims to evaluate the current state of knowledge regarding the role of pharmacogenomics in PD, focusing on identifying challenges and proposing future directions.

METHODS

We conducted a systematic review following PRISMA 2020 guidelines. The PubMed database was searched for original, English-language studies using the R package 'RISmed.' Data were extracted and analyzed based on sample size, population origin, evaluated genes and polymorphisms, outcomes, and methodological approaches.

RESULTS

Out of 183 identified articles, 76 met the inclusion criteria. The COMT-rs4680 polymorphism was the most frequently studied, and levodopa-related motor complications were the most commonly assessed outcomes. All but two studies employed a candidate gene approach. In 75 % of the studies, the sample size was fewer than 225 individuals. There was a notable underrepresentation of Latino participants, with a lack of studies from Latin American countries other than Brazil. None of the studies produced consistent results across investigations.

CONCLUSIONS

The variability in patient responses to PD treatments suggests a genetic predisposition. While current research has enhanced our understanding of PD medication metabolism, it has not yet fully elucidated the complex genetic interactions involved in PD pharmacogenomics. Novel approaches, larger and more genetically diverse cohorts, and improved data collection are essential for advancing pharmacogenomics in PD clinical practice.

Psychosis in Parkinson's Disease: A Lesson from Genetics

Psychosis in Parkinson's disease (PDP) represents a common and debilitating condition that complicates Parkinson's disease (PD), mainly in the later stages. The spectrum of psychotic symptoms are heterogeneous, ranging from minor phenomena of mild illusions, passage hallucinations and sense of presence to severe psychosis consisting of visual hallucinations (and rarely, auditory and tactile or gustatory) and paranoid delusions. PDP is associated with increased caregiver stress, poorer quality of life for patients and carers, reduced survival and risk of institutionalization with a significant burden on the healthcare system. Although several risk factors for PDP development have been identified, such as aging, sleep disturbances, long history of PD, cognitive impairment, depression and visual disorders, the pathophysiology of psychosis in PD is complex and still insufficiently clarified. Additionally, several drugs used to treat PD can aggravate or even precipitate PDP. Herein, we reviewed and critically analyzed recent studies exploring the genetic architecture of psychosis in PD in order to further understand the pathophysiology of PDP, the risk factors as well as the most suitable therapeutic strategies.

A Computational Analysis in a Cohort of Parkinson's Disease Patients and Clock-Modified Colorectal Cancer Cells Reveals Common Expression Alterations in Clock-Regulated Genes

Simple Summary

Cancer and neurodegenerative diseases are two aging-related pathologies with differential developmental characteristics, but they share altered cellular pathways. Interestingly, dysregulations in the biological clock are reported in both diseases, though the extent and potential consequences of such disruption have not been fully elucidated. In this study, we aimed at characterizing global changes on common cellular pathways associated with Parkinson’s disease (PD) and colorectal cancer (CRC). We used gene expression data retrieved from an idiopathic PD (IPD) patient cohort and from CRC cells with unmodified versus genetically altered clocks. Our results highlight common differentially expressed genes between IPD patients and cells with disrupted clocks, suggesting a role for the circadian clock in the regulation of pathways altered in both pathologies. Interestingly, several of these genes are related to cancer hallmarks and may have an impact on the overall survival of colon cancer patients, as suggested by our analysis.

Abstract

Increasing evidence suggests a role for circadian dysregulation in prompting disease-related phenotypes in mammals. Cancer and neurodegenerative disorders are two aging related diseases reported to be associated with circadian disruption. In this study, we investigated a possible effect of circadian disruption in Parkinson’s disease (PD) and colorectal cancer (CRC). We used high-throughput data sets retrieved from whole blood of idiopathic PD (IPD) patients and time course data sets derived from an in vitro model of CRC including the wildtype and three core-clock knockout (KO) cell lines. Several gene expression alterations in IPD patients resembled the expression profiles in the core-clock KO cells. These include expression changes in DBP, GBA, TEF, SNCA, SERPINA1 and TGFB1. Notably, our results pointed to alterations in the core-clock network in IPD patients when compared to healthy controls and revealed variations in the expression profile of PD-associated genes (e.g., HRAS and GBA) upon disruption of the core-clock genes. Our study characterizes changes at the transcriptomic level following circadian clock disruption on common cellular pathways associated with cancer and neurodegeneration (e.g., immune system, energy metabolism and RNA processing), and it points to a significant influence on the overall survival of colon cancer patients for several genes resulting from our analysis (e.g., TUBB6, PAK6, SLC11A1).

Management of Visual Dysfunction in Patients with Parkinson's Disease

Parkinson’s disease (PD) is a movement disorder with many symptoms responsive to treatment with dopamine agonists, anti-cholinergics and the dopamine precursor, levodopa. The cardinal features of PD include tremor, rigidity, bradykinesia, and postural instability. There also are non-motor features that include sleep disorders, cognitive and affective dysfunction, hyposmia, pain and dysautonomia (constipation, bloating, orthostasis, urinary symptoms, sexual dysfunction, dysphagia). Among these non-motor features are signs and symptoms of visual system impairment that range from subtle examination findings to those causing severe disability. In this review we describe common PD-related abnormalities in the visual system, how they present, and potential treatments.

Atremorine in Parkinson's disease: From dopaminergic neuroprotection to pharmacogenomics

Atremorine is a novel bioproduct obtained by nondenaturing biotechnological processes from a genetic species of Vicia faba. Atremorine is a potent dopamine (DA) enhancer with powerful effects on the neuronal dopaminergic system, acting as a neuroprotective agent in Parkinson's disease (PD). Over 97% of PD patients respond to a single dose of Atremorine (5 g, p.o.) 1 h after administration. This response is gender-, time-, dose-, and genotype-dependent, with optimal doses ranging from 5 to 20 g/day, depending upon disease severity and concomitant medication. Drug-free patients show an increase in DA levels from 12.14 ± 0.34 pg/ml to 6463.21 ± 1306.90 pg/ml; and patients chronically treated with anti-PD drugs show an increase in DA levels from 1321.53 ± 389.94 pg/ml to 16,028.54 ± 4783.98 pg/ml, indicating that Atremorine potentiates the dopaminergic effects of conventional anti-PD drugs. Atremorine also influences the levels of other neurotransmitters (adrenaline, noradrenaline) and hormones which are regulated by DA (e.g., prolactin, PRL), with no effect on serotonin or histamine. The variability in Atremorine-induced DA response is highly attributable to pharmacogenetic factors. Polymorphic variants in pathogenic (SNCA, NUCKS1, ITGA8, GPNMB, GCH1, BCKDK, APOE, LRRK2, ACMSD), mechanistic (DRD2), metabolic (CYP2D6, CYP2C9, CYP2C19, CYP3A4/5, NAT2), transporter (ABCB1, SLC6A2, SLC6A3, SLC6A4) and pleiotropic genes (APOE) influence the DA response to Atremorine and its psychomotor and brain effects. Atremorine enhances DNA methylation and displays epigenetic activity via modulation of the pharmacoepigenetic network. Atremorine is a novel neuroprotective agent for dopaminergic neurons with potential prophylactic and therapeutic activity in PD.

Polymorphisms of Dopamine Receptor Genes and Parkinson's Disease: Clinical Relevance and Future Perspectives

Parkinson’s disease (PD) is a neurodegenerative disease caused by loss of dopaminergic neurons in the midbrain. PD is clinically characterized by a variety of motor and nonmotor symptoms, and treatment relies on dopaminergic replacement. Beyond a common pathological hallmark, PD patients may present differences in both clinical progression and response to drug therapy that are partly affected by genetic factors. Despite extensive knowledge on genetic variability of dopaminergic receptors (DR), few studies have addressed their relevance as possible influencers of clinical heterogeneity in PD patients. In this review, we summarized available evidence regarding the role of genetic polymorphisms in DR as possible determinants of PD development, progression and treatment response. Moreover, we examined the role of DR in the modulation of peripheral immunity, in light of the emerging role of the peripheral immune system in PD pathophysiology. A better understanding of all these aspects represents an important step towards the development of precise and personalized disease-modifying therapies for PD.

Parkinson's Disease: A Review from Pathophysiology to Treatment

Parkinson's Disease (PD) is the second most common neurodegenerative disease in the elderly population, with a higher prevalence in men, independent of race and social class; it affects approximately 1.5 to 2.0% of the elderly population over 60 years and 4% for those over 80 years of age. PD is caused by the necrosis of dopaminergic neurons in the substantia nigra, which is the brain region responsible for the synthesis of the neurotransmitter dopamine (DA), resulting in its decrease in the synaptic cleft. The monoamine oxidase B (MAO-B) degrades dopamine, promoting the glutamate accumulation and oxidative stress with the release of free radicals, causing excitotoxicity. The PD symptoms are progressive physical limitations such as rigidity, bradykinesia, tremor, postural instability and disability in functional performance. Considering that there are no laboratory tests, biomarkers or imaging studies to confirm the disease, the diagnosis of PD is made by analyzing the motor features. There is no cure for PD, and the pharmacological treatment consists of a dopaminergic supplement with levodopa, COMT inhibitors, anticholinergics agents, dopaminergic agonists, and inhibitors of MAO-B, which basically aims to control the symptoms, enabling better functional mobility and increasing life expectancy of the treated PD patients. Due to the importance and increasing prevalence of PD in the world, this study reviews information on the pathophysiology, symptomatology as well as the most current and relevant treatments of PD patients.

Pharmacogenetic profile and the development of the dyskinesia induced by levodopa-therapy in Parkinson's disease patients: a population-based cohort study

Levodopa-induced dyskinesia (LID) is an adverse effect that negatively impacts the quality of life of patients with Parkinson's disease (PD). Studies report that genetic variations in the genes of the pharmacogenetic pathway of the levodopa (L-DOPA) might be associated with LID development. The goal of the present study was to investigate a possible influence of functional genetic variants in the DRD1 (rs4532), DRD2 (rs1800497), DAT1 (rs28363170), and COMT (rs4680) genes with LID development. A total of 220 patients with idiopathic PD were enrolled. The genotyping for DRD1 (rs4532), DRD2 (rs1800497), DAT1 (rs28363170), and COMT (rs4680) polymorphisms were performed using Restriction Fragment Length Polymorphism (PCR-RFLP). Univariate and multivariate analyses were performed to assess the association of these polymorphisms and risk factors with LID development. Multivariate Cox regression analysis showed increased risk to LID development for both Levodopa Dose Equivalency (LED) (Hazard ratios (HR) = 1.001; 95% CI 1.00-1.01; p = 0.009) and individuals carrying the COMT L/L genotype (HR = 2.974; 95% CI 1.12-7.83; p = 0.010). Furthermore, when performed a Cox regression analysis adjusted for a total LED, we observed that the genotype COMT L/L had a 3.84-fold increased risk for LID development (HR = 3.841; 95% CI 1.29-11.37; p = 0.012). Our results suggest that before treating LID in PD patients, it is important to take into consideration genetic variant in the COMT gene, since COMT LL genotype may increase the risk for LID development.

The role of pharmacogenomics in the personalization of Parkinson's disease treatment

Parkinson's disease (PD)-related phenotypes can vary among patients substantially, including response to dopaminergic treatment in terms of efficacy and occurrence of adverse events. Many pharmacogenetic studies have already been conducted to find genetic markers of response to dopaminergic treatment. Integration of genetic and clinical data has already resulted in construction of clinical pharmacogenetic models for prediction of adverse events. However, the results of pharmacogenetic studies are inconsistent. More comprehensive genome-wide approaches are needed to find genetic biomarkers of PD-related phenotypes to better explain the variability in response to treatment. These genetic markers should be integrated with clinical, environmental, imaging, and other omics data to build clinically useful algorithms for personalization of PD management.

Influence of DRD1 and DRD3 Polymorphisms in the Occurrence of Motor Effects in Patients with Sporadic Parkinson's Disease

Parkinson's disease (PD) is a multisystem disorder that affects 2-3% of the population ≥ 65 years of age. The main pharmacologic agent use in the treatment of clinical symptoms of PD is levodopa (L-DOPA). However, the chronic use of L-DOPA might result in the emergence of motor complications such as motor fluctuation and dyskinesia. Previous studies have shown that the inter-individual variability and pharmacogenetic profile of PD patients seem to influence the occurrence of motor complications. For these reasons, the purpose of this study was to evaluate a possible relationship between DRD1 A48G and DRD3 Ser9Gly genetic variants with the occurrence of motor complications in PD patients in a Brazilian population. A total of 228 patients with idiopathic PD were enrolled. Patients were genotyped for DRD1 A48G and DRD3 Ser9Gly polymorphisms using PCR-RFLP. The univariate and multivariate analyses were performed to assess the association of these polymorphisms with the occurrence of motor fluctuation and dyskinesia in PD patients. Multiple Poisson regression analyses showed a protector effect to the occurrence of dyskinesia for individuals carrying of the DRD1 G/G genotype (PR 0.294; CI 0.09-0.87; p ≤ 0.020) after the threshold Bonferroni's. Besides, we verified risk increased to the occurrence of motor complications with daily L-DOPA dosage, disease duration, and users of rasagiline, selegiline, or entacapone (p < 0.05 for all). Our results suggest that the DRD1 A48G polymorphism and the presence of extrinsic and intrinsic factors may role an effect in the occurrence of dyskinesia in PD patients.