PD and DLB: Brain imaging in Parkinson's disease and dementia with Lewy bodies

Toward a biological definition of neuronal and glial synucleinopathies

Cerebral accumulation of alpha-synuclein (αSyn) aggregates is the hallmark event in a group of neurodegenerative diseases-collectively called synucleinopathies-which include Parkinson's disease, dementia with Lewy bodies and multiple system atrophy. Currently, these are diagnosed by their clinical symptoms and definitively confirmed postmortem by the presence of αSyn deposits in the brain. Here, we summarize the drawbacks of the current clinical definition of synucleinopathies and outline the rationale for moving toward an earlier, biology-anchored definition of these disorders, with or without the presence of clinical symptoms. We underscore the utility of the αSyn seed amplification assay to detect aggregated αSyn in living patients and to differentiate between neuronal or glial αSyn pathology. We anticipate that a biological definition of synucleinopathies, if well-integrated with the current clinical classifications, will enable further understanding of the disease pathogenesis and contribute to the development of effective, disease-modifying therapies.

CHCHD2 and CHCHD10: Future therapeutic targets in cognitive disorder and motor neuron disorder

CHCHD2 and CHCHD10 are homolog mitochondrial proteins that play key roles in the neurological, cardiovascular, and reproductive systems. They are also involved in the mitochondrial metabolic process. Although previous research has concentrated on their functions within mitochondria, their functions within apoptosis, synaptic plasticity, cell migration as well as lipid metabolism remain to be concluded. The review highlights the different roles played by CHCHD2 and/or CHCHD10 binding to various target proteins (such as OPA-1, OMA-1, PINK, and TDP43) and reveals their non-negligible effects in cognitive impairments and motor neuron diseases. This review focuses on the functions of CHCHD2 and/or CHCHD10. This review reveals protective effects and mechanisms of CHCHD2 and CHCHD10 in neurodegenerative diseases characterized by cognitive and motor deficits, such as frontotemporal dementia (FTD), Lewy body dementia (LBD), Parkinson's disease (PD) and amyotrophic lateral sclerosis (ALS). However, there are numerous specific mechanisms that have yet to be elucidated, and additional research into these mechanisms is required.

Sex is a defining feature of neuroimaging phenotypes in major brain disorders

Sex is a biological variable that contributes to individual variability in brain structure and behavior. Neuroimaging studies of population-based samples have identified normative differences in brain structure between males and females, many of which are exacerbated in psychiatric and neurological conditions. Still, sex differences in MRI outcomes are understudied, particularly in clinical samples with known sex differences in disease risk, prevalence, and expression of clinical symptoms. Here we review the existing literature on sex differences in adult brain structure in normative samples and in 14 distinct psychiatric and neurological disorders. We discuss commonalities and sources of variance in study designs, analysis procedures, disease subtype effects, and the impact of these factors on MRI interpretation. Lastly, we identify key problems in the neuroimaging literature on sex differences and offer potential recommendations to address current barriers and optimize rigor and reproducibility. In particular, we emphasize the importance of large-scale neuroimaging initiatives such as the Enhancing NeuroImaging Genetics through Meta-Analyses consortium, the UK Biobank, Human Connectome Project, and others to provide unprecedented power to evaluate sex-specific phenotypes in major brain diseases.

Cholinergic Receptor Modulation as a Target for Preventing Dementia in Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative condition characterized by the loss of dopaminergic neurons in the substantia nigra pars compacta (SNpc) in the midbrain resulting in progressive impairment in cognitive and motor abilities. The physiological and molecular mechanisms triggering dopaminergic neuronal loss are not entirely defined. PD occurrence is associated with various genetic and environmental factors causing inflammation and mitochondrial dysfunction in the brain, leading to oxidative stress, proteinopathy, and reduced viability of dopaminergic neurons. Oxidative stress affects the conformation and function of ions, proteins, and lipids, provoking mitochondrial DNA (mtDNA) mutation and dysfunction. The disruption of protein homeostasis induces the aggregation of alpha-synuclein (α-SYN) and parkin and a deficit in proteasome degradation. Also, oxidative stress affects dopamine release by activating ATP-sensitive potassium channels. The cholinergic system is essential in modulating the striatal cells regulating cognitive and motor functions. Several muscarinic acetylcholine receptors (mAChR) and nicotinic acetylcholine receptors (nAChRs) are expressed in the striatum. The nAChRs signaling reduces neuroinflammation and facilitates neuronal survival, neurotransmitter release, and synaptic plasticity. Since there is a deficit in the nAChRs in PD, inhibiting nAChRs loss in the striatum may help prevent dopaminergic neurons loss in the striatum and its pathological consequences. The nAChRs can also stimulate other brain cells supporting cognitive and motor functions. This review discusses the cholinergic system as a therapeutic target of cotinine to prevent cognitive symptoms and transition to dementia in PD.

Cerebral Microbleeds in Patients with Parkinson's Disease and Dementia with Lewy Bodies: Comparison Using Magnetic Resonance Imaging and 99 mTc-ECD SPECT Subtraction Imaging

BACKGROUND

Cerebral microbleeds (CMBs) in patients with Parkinson's disease (PD) or dementia with Lewy bodies (DLB) have not been adequately studied.

OBJECTIVE

This study aims to find a difference in the total number, prevalence, and common locations of CMBs between PD and DLB and evaluate 99 mTc-ECD SPECT subtraction images of these two diseases.

METHODS

We examined 112 patients with PD (53 males and 59 females; age: 77.4±3.6 years) and 28 age-matched patients with DLB (15 males and 13 females; age: 77.1±6.7 years) using brain magnetic resonance imaging (MRI) and 99 mTc-ECD SPECT subtraction imaging.

RESULTS

The total number of CMBs was higher in patients with DLB (41.2%) than in those with PD (11.5%), and the prevalence was significantly higher in the former (0.7±1.1) than the latter (0.2±0.5, p < 0.05). The odds ratio was 5.4 (95% confidence interval [CI]: 1.7-17.4). Furthermore, CMBs were commonly located in the basal ganglia of patients with PD (6 out of 87 patients) but in the occipital lobe of patients with DLB (8 out of 17 patients). 99 mTc-ECD SPECT subtraction imaging indicated lower cerebral blood flow in the posterior cingulate gyrus among the patients with CMB-positive DLB than among those with CMB-positive PD; additionally, the cerebral blood flow was lower in the bilateral basal ganglia and midbrain among patients with CMB-positive DLB compared to those with CMB-negative DLB.

CONCLUSION

A reduction in occipital glucose metabolism may be related to CMBs in the occipital lobe of patients with DLB.

Contributions of PET and MRI imaging in the evaluation of CNS drugs in human neurodegenerative diseases

This manuscript reviews the contributions of the neuroimaging methods including PET, conventional and advanced MRI methods to monitor the effect of new disease modifying drugs in neurodegenerative diseases. It now seems obvious that in many pathologies these two techniques are more and more complementary.