Neuroplasticity in levodopa-induced dyskinesias: An overview on pathophysiology and therapeutic targets

Sexual Dimorphism in Levodopa-Induced Dyskinesia Following Parkinson's Disease: Uncharted Territory

Sexual dimorphism is well-documented in Parkinson's disease (PD); however, when it comes to levodopa-induced dyskinesia (LID), epidemiological and clinical findings are scarce. This is an oversight because recent studies show significant correlations between LID risk and female sex. Estrogen strongly impacts neuronal function, affecting cognitive tasks such as movement, object recognition, and reward. In movement pathways, estrogen increases dopamine synthesis, transmission, and regulation, resulting in neuroprotection for PD in women. However, following menopause, PD prevalence, symptom severity, and LID risk increase for women. Consequently, early to mid-life estrogen state is neuroprotective, but later in life becomes a risk factor for PD and LID. This review explores estrogen's action in the brain, specifically within the dopamine system. Sexual dimorphism is described for the prevalence and onset of PD and LID. We examine the cellular basis of estrogen's role in sexual dimorphism and integrate these ideas to hypothesize why the risk for LID is higher for women, than men, with PD. Lastly, this review proposes that women with PD need their symptoms to be considered and managed differently to males. Treatment of women with PD should be based on their menopausal stage, as estrogen may be masking, exacerbating, or complicating symptoms. Importantly, we present these concepts to stimulate discussion among clinical and bench scientists so that key experiments can be conducted to examine the mechanisms underlying LID, so they can be prevented to improve the quality of life for women and men living with PD in the future.

Integrative Approaches Identify Genetic Determinants of Levodopa Induced Dyskinesia

Levodopa induced dyskinesia (LID) is a serious side effect of levodopa treatment in Parkinson's disease (PD), with limited interventions. Understanding the genetic impact on LID would help inform future intervention studies. We performed integrative genomic analysis approaches to identify the genetic determinants of LID in a Chinese multi-center prospective, observational PD cohort. In this cohort, 46 of 315 PD patients developed LID during 2.5 years of follow-up. First, we performed a genome-wide association study (GWAS) in this cohort, followed by a meta-analysis integrating our GWAS summary data with additional data of European ancestry. Both GWAS analyses identified the Bromodomain Containing 3 (BRD3) as a LID susceptibility gene (P < 5 × 10-8); however, the genetic variants within the BRD3 gene differed between the analyses. Then, we conducted a multi-tissue transcriptome-wide association study (TWAS) through integrating our GWAS summary data with six gene expression quantitative trait loci (eQTLs) datasets from tissues involved in the levodopa transport-to-function pathway, including stomach, blood, caudate, putamen, nucleus accumbens, and frontal cortex. We found that the expression levels of the TRAPPC12 Antisense RNA 1 (TRAPPC12-AS1) and Williams Beuren Syndrome Chromosome Region 27 (WBSCR27) in all tissues were associated with LID occurrence. Finally, we executed the summary data-based mendelian randomization (SMR) and identified that LID was causally associated with the two genes' expression in all tissues. In conclusion, our findings support new candidate genes for LID susceptibility, providing novel potential targets for future intervention studies.

Research hotspots and frontiers of neuromodulation technology in the last decade: a visualization analysis based on the Web of Science database

Background

Since the 1990s, neuromodulation technology has experienced rapid advancements, providing new therapeutic approaches for clinical rehabilitation in neurological disorders. The objective of this study is to utilize CiteSpace and VOSviewer to investigate the current research status, key topics, and future trends in the field of neuromodulation technology over the past decade.

Methods

Relevant literature in the field of neuromodulation technology published in Web of Science database from January 1, 2014 to June 18, 2024 were retrieved, and imported into CiteSpace and VOSviewer for visualization. VOSviewer was used for counties, institutions, authors and keywords analyses. CiteSpace was used for presentation visualization analysis of co-cited references, keywords clusters and bursts.

Results

This study encompasses a total of 1,348 relevant publications, with the number of publications showing an increasing trend year by year. The most significant growth was observed between 2020 and 2021. The United States, China and the United Kingdom are the three leading countries with high output in this regard. The top three institutions in terms of the publication volume are Harvard Medical School, the University of Toronto and Stanford University. Keyword co-occurrence and cluster analysis identified that deep brain stimulation, transcranial magnetic stimulation, transcranial direct current stimulation, and focused ultrasound stimulation are the most widely used central nerve stimulation techniques in neuromodulation. The treatment of intractable chronic pain also emerged as a key focus within neuromodulation techniques. The recent keywords bursts included terms such as recovery, movement, nucleus, modeling and plasticity, suggesting that the future research trend will be centered on these areas.

Conclusion

In conclusion, neuromodulation technology is garnering increasing attention from researchers and is currently widely used in brain diseases. Future research is expected to delve deeper, particularly into exploring deep brain structure stimulation targets and restoring motor function based on neuroplasticity theory.

Early Alterations in De Novo Parkinson's Disease Revealed by Diffusion Tensor Imaging: Preliminary Study

Background/Objectives: Parkinson's disease (PD) is characterized by progressive neurodegeneration affecting both motor and non-motor functions. Identifying early alterations in PD patients before the onset of dopaminergic therapy is crucial for understanding disease progression and developing targeted interventions. This study aimed to investigate early changes in the putamen and thalamus in de novo PD patients using diffusion tensor imaging (DTI) compared to healthy controls. Methods: Thirty-one de novo PD patients and thirty-three healthy controls underwent DTI scanning. Tract-based spatial statistics were used to compare fractional anisotropy (FA) values between groups. Results: De novo PD patients exhibited significantly lower FA values in the right thalamus compared to controls, suggesting alterations in neuronal integrity or fiber degeneration in the early stages of the disease. However, no significant differences were demonstrated for FA values in the putamen between groups. Conclusions: We demonstrated that the FA value in the right thalamus was lower in PD compared with healthy controls. These findings highlight the potential of DTI as a non-invasive tool for detecting early neural changes in PD patients. Further studies would be helpful to assess the clinical utility of serial FA measurements of the subcortical gray matter in objective quantification of disease progression and monitoring of the therapeutic response.

Towards multimodal cognition-based treatment for cognitive impairment in Parkinson's disease: drugs, exercise, non-invasive brain stimulation and technologies

PURPOSE OF REVIEW

Cognitive impairment is one of the most challenging non-motor symptoms of Parkinson's disease (PD) and may occur during all PD stages. There are no established pharmacological treatments for PD-related cognitive impairment, which may be improved by cognition-based interventions (i.e., cognitive stimulation, cognitive training, cognitive rehabilitation). Multimodal cognition-based interventions by adjunctive drugs, exercise, non-invasive brain stimulation and technologies may be effective in PD.

RECENT FINDINGS

Exercise combined with cognitive training may enhance global, memory, visuospatial and executive functioning, transcranial direct current stimulation delivered alongside cognitive training may improve attention and executive functioning, and exergames, semi-immersive virtual reality (VR) and telerehabilitation plus non-immersive VR combined with cognitive training may ameliorate global and executive functioning in PD patients.

SUMMARY

The evidence reviewed here, despite preliminary, is very encouraging and suggests strong rationale for combining pharmacological and non-pharmacological interventions with cognition-based treatments in PD. To overcome limitations of current studies, we propose some recommendations for future trials on drugs, exercise, non-invasive brain stimulation and technologies combined with cognition-based treatments for cognitive impairment in PD.

Boosting endogenous dopamine production: a novel therapeutic approach for Parkinson's disease

Innovative therapeutic strategies are urgently needed for Parkinson's disease due to limited efficacy of current treatments and a weak therapeutic pipeline. In this forum article, we propose targeting tyrosine hydroxylase phosphorylation as a novel mechanism of action to address this critical need.

Enhanced Parkinson's gait, reduced fall risk, and improved cognitive function through multimodal rehabilitation combined with rivastigmine treatment

OBJECTIVE

This study aimed to examine the effects of combined rehabilitation and rivastigmine treatment on patients with Parkinson's disease (PD).

METHODS

Gait parameters were assessed using the Gibbon Gait Analyzer in fifteen patients. Baseline gait data and cognitive assessments were collected. Each patient underwent external counterpulsation therapy, transcranial magnetic stimulation therapy, and exercise therapy for one hour per day, five days a week for three weeks. Post-intervention, gait and cognitive data were re-evaluated. Alongside their standard PD medications, all participants were administered rivastigmine throughout the study period.

RESULTS

The intervention significantly enhanced motor function in the single-task test, evidenced by marked improvements in gait metrics such as stride width and walking speed, and a substantial reduction in fall risk. Cognitive function, assessed by mini-mental state examination and Montreal cognitive assessment, showed an improvement trend after the three-week intervention. Improvements in dual-task walking function were observed, although these changes did not reach statistical significance.

CONCLUSION

Multimodal exercise training combined with rivastigmine treatment significantly improves certain gait parameters in the single-task test, enhances balance, and reduces the risk of falling in patients with PD. Cognitive function also demonstrated improvement.

Nicotinic Acetylcholine Receptors in Glial Cells as Molecular Target for Parkinson's Disease

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by resting tremor, bradykinesia, rigidity, and postural instability that also includes non-motor symptoms such as mood dysregulation. Dopamine (DA) is the primary neurotransmitter involved in this disease, but cholinergic imbalance has also been implicated. Current intervention in PD is focused on replenishing central DA, which provides remarkable temporary symptomatic relief but does not address neuronal loss and the progression of the disease. It has been well established that neuronal nicotinic cholinergic receptors (nAChRs) can regulate DA release and that nicotine itself may have neuroprotective effects. Recent studies identified nAChRs in nonneuronal cell types, including glial cells, where they may regulate inflammatory responses. Given the crucial role of neuroinflammation in dopaminergic degeneration and the involvement of microglia and astrocytes in this response, glial nAChRs may provide a novel therapeutic target in the prevention and/or treatment of PD. In this review, following a brief discussion of PD, we focus on the role of glial cells and, specifically, their nAChRs in PD pathology and/or treatment.