Sex differences in Parkinson’s disease Gillies, Glenda E; Pienaar, Ilse S; Vohra, Shiv ...
Frontiers in neuroendocrinology,
08/2014, Letnik:
35, Številka:
3
Journal Article
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Highlights • Biological sex differences are found in the nigrostriatal dopaminergic pathway. • These may underpin the greater male susceptibility to develop Parkinson’s disease. • Female gonadal ...factors (estradiol) provide resilience to dopamine loss. • Male gonadal factors (testosterone/estradiol) fail to protect/worsen dopamine loss. • Sex-specific hormone-based therapies hold promise for novel treatments.
Several mitochondrial DNA (mtDNA) haplogroup association studies have suggested that common mtDNA variants are associated with multifactorial diseases, including Alzheimer’s disease (AD). However, ...such studies have also produced conflicting results. A new mtDNA association model, the ‘variant load model’ (VLM), has been applied to multiple disease phenotypes. Application of the VLM in a 2017 study failed to find different variant loads in AD patients compared to controls, in two cohorts of European origin. The study also suggested a lower variant load in healthy elderly individuals, but could offer no replicate cohort to support this observation. Here, the VLM is applied to Japanese mtDNA sequences; in doing so, we explored the role of mtDNA variation in AD and ageing in a different global population. Consistent with the previous findings using the VLM in two populations of European origin, we found no evidence for an association between rarer, non-haplogroup associated variation and the development of AD. However, the result in the context of ageing that suggested those with fewer mildly deleterious mutations might undergo healthier ageing, was not replicated. In contrast to our previous study, our present results suggest that those living to advanced old age may harbour more mildly deleterious mtDNA variations. Importantly our analysis showed this finding is not primarily being driven by many rare population variants dispersed across the mtDNA, but by a few more frequent variants with high MutPred scores. It is suggested the variants in question do not exert a mildly deleterious effect in their most frequent haplogroup context.
The vertebrate blood-brain barrier (BBB) is critical for ensuring the maintenance of brain homeostasis, whilst protecting the brain against toxic insults. Various pathological events disrupt BBB ...integrity, holding several important clinical implications. In instances where the normal mechanisms controlling passage of substances into the brain are compromised, these could sensitize or even worsen endogenous pathological conditions. Recognition has grown recently that patients diagnosed with Parkinson's disease (PD) present with concurrent medical problems, including cerebrovascular lesions. However, cerebrovascular disturbances may also result from PD-related disease processes; the pathological mechanisms which could entail interaction between environment-derived and genetic factors. The current review addresses the accumulation of studies aimed at better understanding the series of processes affecting the neurovascular unit in human Parkinsonism, due in part to the BBB presenting as a formidable opponent in the effective delivery of therapeutics that have shown promise as therapeutic strategies for treating aspects of PD when tested in vitro.
The pedunculopontine nucleus (PPN) is a rostral brainstem structure that has extensive connections with basal ganglia nuclei and the thalamus. Through these the PPN contributes to neural circuits ...that effect cortical and hippocampal activity. The PPN also has descending connections to nuclei of the pontine and medullary reticular formations, deep cerebellar nuclei, and the spinal cord. Interest in the PPN has increased dramatically since it was first suggested to be a novel target for treating patients with Parkinson’s disease who are refractory to medication. However, application of frequency-specific electrical stimulation of the PPN has produced inconsistent results. A central reason for this is that the PPN is not a heterogeneous structure. In this article, we review current knowledge of the neurochemical identity and topographical distribution of neurons within the PPN of both humans and experimental animals, focusing on studies that used neuronally selective targeting strategies to ascertain how the neurochemical heterogeneity of the PPN relates to its diverse functions in relation to movement and cognitive processes. If the therapeutic potential of the PPN is to be realized, it is critical to understand the complex structure-function relationships that exist here.
The Miro GTPases represent an unusual subgroup of the Ras superfamily and have recently emerged as important mediators of mitochondrial dynamics and for maintaining neuronal health. It is now ...well-established that these enzymes act as essential components of a Ca
2+
-sensitive motor complex, facilitating the transport of mitochondria along microtubules in several cell types, including dopaminergic neurons. The Miros appear to be critical for both anterograde and retrograde mitochondrial transport in axons and dendrites, both of which are considered essential for neuronal health. Furthermore, the Miros may be significantly involved in the development of several serious pathological processes, including the development of neurodegenerative and psychiatric disorders. In this review, we discuss the molecular structure and known mitochondrial functions of the Miro GTPases in humans and other organisms, in the context of neurodegenerative disease. Finally, we consider the potential human Miros hold as novel therapeutic targets for the treatment of such disease.
The pedunculopontine nucleus (PPN) controls various physiological functions, whilst being deemed a suitable target for low-frequency stimulation therapy for alleviating aspects of Parkinson's disease ...(PD). Previous studies showed that the PPN contains mainly cholinergic, γ-aminobutyric acid (GABA)ergic and glutamatergic neurons. Here we report on the total number of PPN neurons in laboratory rats, a species frequently used as an experimental model for simulating aspects of human PD. Moreover, the study reports that the number of PPN neurons decreases under toxic conditions that mimic in animals the core pathology seen in human PD. Immunohistochemical detection methods combined with unbiased stereology served to estimate that the PPN of healthy rats unilaterally contains ~19,028 NeuN-immunopositive neurons. The identified neurons revealed a distinct distribution pattern consisting of high cell density in the most rostral and caudal sections of the PPN nucleus, contrasting with lower densities in the medial segments. Our data also show a significant loss which affected PPN non-cholinergic cells, but not cholinergic ones in rats lesioned unilaterally in the Substantia Nigra pars compacta (SNpc) with a single injection of 6-hydroxydopamine (6-OHDA) compared to control animals. This result differs from previous studies which reported a substantial cholinergic cell loss in the PPN of post-mortem PD brains and in 6-OHDA-lesioned monkeys. Since a noted demise of dopaminergic neurons residing in the SN was confirmed in the 6-OHDA-lesioned rats, the current study suggests that a “dying-back” mechanism may underlie the cell death affecting non-cholinergic PPN neurons.
•We reveal the total number of neurons in unilateral rat pedunculopontine nucleus.•We examine changes in this number between 6-OHDA Parkinsonian rats and controls.•We reveal that cholinergic neurons are not lost in this animal model of disease.•Non-cholinergic neurons were lost in this nucleus in Parkinsonian rats.•Other models may better reflect the cholinergic cell loss affecting human patients.
In Parkinson disease (PD), mitochondrial dysfunction associates with nigral dopaminergic neuronal loss. Cholinergic neuronal loss co‐occurs, particularly within a brainstem structure, the ...pedunculopontine nucleus (PPN). We isolated single cholinergic neurons from postmortem PPNs of aged controls and PD patients. Mitochondrial DNA (mtDNA) copy number and mtDNA deletions were increased significantly in PD patients compared to controls. Furthermore, compared to controls the PD patients had significantly more PPN cholinergic neurons containing mtDNA deletion levels exceeding 60%, a level associated with deleterious effects on oxidative phosphorylation. The current results differ from studies reporting mtDNA depletion in nigral dopaminergic neurons of PD patients. Ann Neurol 2017;82:1016–1021
Abstract Deep brain stimulation (DBS) of the subthalamic nucleus (STN) has become an accepted treatment for motor symptoms in a subset of Parkinson's disease (PD) patients. The mechanisms why DBS is ...effective are incompletely understood, but previous studies show that DBS targeted in brain structures other than the STN may modify the microvasculature. However, this has not been studied in PD subjects who have received STN-DBS. Here we investigated the extent and nature of microvascular changes in post-mortem STN samples from STN-DBS PD patients, compared to aged controls and PD patients who had not been treated with STN-DBS. We used immunohistochemical and immunofluorescent methods to assess serial STN-containing brain sections from PD and STN-DBS PD cases, compared to similar age controls using specific antibodies to detect capillaries, an adherens junction and tight junction-associated proteins as well as activated microglia. Cellular features in stained sections were quantified by confocal fluorescence microscopy and stereological methods in conjunction with in vitro imaging tools. We found significant upregulation of microvessel endothelial cell thickness, length and density but lowered activated microglia density and striking upregulation of all analysed adherens junction and tight junction-associated proteins in STN-DBS PD patients compared to non-DBS PD patients and controls. Moreover, in STN-DBS PD samples, expression of an angiogenic factor, vascular endothelial growth factor (VEGF), was significantly upregulated compared to the other groups. Our findings suggest that overexpressed VEGF and downregulation of inflammatory processes may be critical mechanisms underlying the DBS-induced microvascular changes.
Iron dysregulation, dopamine depletion, cellular oxidative stress and α-synuclein protein mis-folding are key neuronal pathological features seen in the progression of Parkinson's disease. Iron ...chelators endowed with one or more therapeutic modes of action have long been suggested as disease modifying therapies for its treatment. In this study, novel 1-hydroxypyrazin-2(1
)-one iron chelators were synthesized and their physicochemical properties, iron chelation abilities, antioxidant capacities and neuroprotective effects in a cell culture model of Parkinson's disease were evaluated. Physicochemical properties (log
, log
, pL
) suggest that these ligands have a poorer ability to penetrate cell membranes and form weaker iron complexes than the closely related 1-hydroxypyridin-2(1
)-ones. Despite this, we show that levels of neuroprotection provided by these ligands against the catecholaminergic neurotoxin 6-hydroxydopamine
were comparable to those seen previously with the 1-hydroxypyridin-2(1
)-ones and the clinically used iron chelator Deferiprone, with two of the ligands restoring cell viability to ≥89% compared to controls. Two of the ligands were endowed with additional phenol moieties in an attempt to derive multifunctional chelators with dual iron chelation/antioxidant activity. However, levels of neuroprotection with these ligands were no greater than ligands lacking this moiety, suggesting the neuroprotective properties of these ligands are due primarily to chelation and passivation of intracellular labile iron, preventing the generation of free radicals and reactive oxygen species that otherwise lead to the neuronal cell death seen in Parkinson's disease.
While the etiology of non-familial Parkinson’s disease (PD) remains unclear, there is evidence that increased levels of tissue iron may be a contributing factor. Moreover, exposure to some ...environmental toxicants is considered an additional risk factor. Therefore, brain-targeted iron chelators are of interest as antidotes for poisoning with dopaminergic toxicants, and as potential treatment of PD. We, therefore, designed a series of small molecules with high affinity for ferric iron and containing structural elements to allow their transport to the brain via the neutral amino acid transporter, LAT1 (SLC7A5). Five candidate molecules were synthesized and initially characterized for protection from ferroptosis in human neurons. The promising hydroxypyridinone SK4 was characterized further. Selective iron chelation within the physiological range of pH values and uptake by LAT1 were confirmed. Concentrations of 10–20 µM blocked neurite loss and cell demise triggered by the parkinsonian neurotoxicants, methyl-phenyl-pyridinium (MPP
+
) and 6-hydroxydopamine (6-OHDA) in human dopaminergic neuronal cultures (LUHMES cells). Rescue was also observed when chelators were given after the toxicant. SK4 derivatives that either lacked LAT1 affinity or had reduced iron chelation potency showed altered activity in our assay panel, as expected. Thus, an iron chelator was developed that revealed neuroprotective properties, as assessed in several models. The data strongly support the role of iron in dopaminergic neurotoxicity and suggests further exploration of the proposed design strategy for improving brain iron chelation.
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