The bioenergetic status relates to dopamine neuron loss in familial PD with PINK1 mutations

Evidence of brain target engagement in Parkinson's disease and multiple sclerosis by the investigational nanomedicine, CNM-Au8, in the REPAIR phase 2 clinical trials

BACKGROUND

Impaired brain energy metabolism has been observed in many neurodegenerative diseases, including Parkinson's disease (PD) and multiple sclerosis (MS). In both diseases, mitochondrial dysfunction and energetic impairment can lead to neuronal dysfunction and death. CNM-Au8® is a suspension of faceted, clean-surfaced gold nanocrystals that catalytically improves energetic metabolism in CNS cells, supporting neuroprotection and remyelination as demonstrated in multiple independent preclinical models. The objective of the Phase 2 REPAIR-MS and REPAIR-PD clinical trials was to investigate the effects of CNM-Au8, administered orally once daily for twelve or more weeks, on brain phosphorous-containing energy metabolite levels in participants with diagnoses of relapsing MS or idiopathic PD, respectively.

RESULTS

Brain metabolites were measured using 7-Tesla 31P-MRS in two disease cohorts, 11 participants with stable relapsing MS and 13 participants with PD (n = 24 evaluable post-baseline scans). Compared to pre-treatment baseline, the mean NAD+/NADH ratio in the brain, a measure of energetic capacity, was significantly increased by 10.4% after 12 + weeks of treatment with CNM-Au8 (0.584 units, SD: 1.3; p = 0.037, paired t-test) in prespecified analyses of the combined treatment cohorts. Each disease cohort concordantly demonstrated increases in the NAD+/NADH ratio but did not reach significance individually (p = 0.11 and p = 0.14, PD and MS cohorts, respectively). Significant treatment effects were also observed for secondary and exploratory imaging outcomes, including β-ATP and phosphorylation potential across both cohorts.

CONCLUSIONS

Our results demonstrate brain target engagement of CNM-Au8 as a direct modulator of brain energy metabolism, and support the further investigation of CNM-Au8 as a potential disease modifying drug for PD and MS.

Monogenetic Forms of Parkinson’s Disease – Bridging the Gap Between Genetics and Biomarkers

The therapy of neurodegenerative diseases such as Parkinson’s disease (PD) is still limited to the treatment of symptoms and primarily aimed at compensating for dopaminergic hypofunction. Numerous disease-modifying therapies currently in the pipeline attempt to modify the underlying pathomechanisms. In recent decades, the results of molecular genetics and biomarker research have raised hopes of earlier diagnosis and new neuroprotective therapeutic approaches. As the disease-causing processes in monogenetic forms of PD are better understood than in sporadic PD, these disease subsets are likely to benefit first from disease-modifying therapies. Recent studies have suggested that disease-relevant changes found in genetically linked forms of PD (i.e., PARK-LRRK2, PARK-GBA) can also be reproduced in patients in whom no genetic cause can be found, i.e., those with sporadic PD. It can, therefore, be assumed that as soon as the first causal therapy for genetic forms of PD is approved, more patients with PD will undergo genetic testing and counseling. Regarding future neuroprotective trials in neurodegenerative diseases and objective parameters such as biomarkers with high sensitivity and specificity for the diagnosis and course of the disease are needed. These biomarkers will also serve to monitor treatment success in clinical trials. Promising examples in PD, such as alpha-synuclein species, lysosomal enzymes, markers of amyloid and tau pathology, and neurofilament light chain, are under investigation in blood and CSF. This paper provides an overview of the opportunities and current limitations of monogenetic diagnostic and biomarker research in PD and aims to build a bridge between current knowledge and association with PD genetics and biomarkers.

Elucidating the Neuroprotective Role of PPARs in Parkinson's Disease: A Neoteric and Prospective Target

One of the utmost frequently emerging neurodegenerative diseases, Parkinson's disease (PD) must be comprehended through the forfeit of dopamine (DA)-generating nerve cells in the substantia nigra pars compacta (SN-PC). The etiology and pathogenesis underlying the emergence of PD is still obscure. However, expanding corroboration encourages the involvement of genetic and environmental factors in the etiology of PD. The destruction of numerous cellular components, namely oxidative stress, ubiquitin-proteasome system (UPS) dysfunction, autophagy-lysosome system dysfunction, neuroinflammation and programmed cell death, and mitochondrial dysfunction partake in the pathogenesis of PD. Present-day pharmacotherapy can alleviate the manifestations, but no therapy has been demonstrated to cease disease progression. Peroxisome proliferator-activated receptors (PPARs) are ligand-directed transcription factors pertaining to the class of nuclear hormone receptors (NHR), and are implicated in the modulation of mitochondrial operation, inflammation, wound healing, redox equilibrium, and metabolism of blood sugar and lipids. Numerous PPAR agonists have been recognized to safeguard nerve cells from oxidative destruction, inflammation, and programmed cell death in PD and other neurodegenerative diseases. Additionally, various investigations suggest that regular administration of PPAR-activating non-steroidal anti-inflammatory drugs (NSAIDs) (ibuprofen, indomethacin), and leukotriene receptor antagonists (montelukast) were related to the de-escalated evolution of neurodegenerative diseases. The present review elucidates the emerging evidence enlightening the neuroprotective outcomes of PPAR agonists in in vivo and in vitro models experiencing PD. Existing articles up to the present were procured through PubMed, MEDLINE, etc., utilizing specific keywords spotlighted in this review. Furthermore, the authors aim to provide insight into the neuroprotective actions of PPAR agonists by outlining the pharmacological mechanism. As a conclusion, PPAR agonists exhibit neuroprotection through modulating the expression of a group of genes implicated in cellular survival pathways, and may be a propitious target in the therapy of incapacitating neurodegenerative diseases like PD.

In Vivo Mitochondrial Function in Idiopathic and Genetic Parkinson's Disease

Parkinson’s disease (PD) is associated with brain mitochondrial dysfunction. High-energy phosphates (HEPs), which rely on mitochondrial functioning, may be considered potential biomarkers for PD. Phosphorus magnetic resonance spectroscopy (³¹P-MRS) is a suitable tool to explore in vivo cerebral energetics. We considered 10 ³¹P-MRS studies in order to highlight the main findings about brain energetic compounds in patients affected by idiopathic PD and genetic PD. The studies investigated several brain areas such as frontal lobes, occipital lobes, temporoparietal cortex, visual cortex, midbrain, and basal ganglia. Resting-state studies reported contrasting results showing decreased as well as normal or increased HEPs levels in PD patients. Functional studies revealed abnormal PCr + βATP levels in PD subjects during the recovery phase and abnormal values at rest, during activation and recovery in one PD subject with PINK1 gene mutation suggesting that mitochondrial machinery is more impaired in PD patients with PINK1 gene mutation. PD is characterized by energetics impairment both in idiopathic PD as well as in genetic PD, suggesting that mitochondrial dysfunction underlies the disease. Studies are still sparse and sometimes contrasting, maybe due to different methodological approaches. Further studies are needed to better assess the role of mitochondria in the PD development.

Translational approaches to restoring mitochondrial function in Parkinson's disease

There is strong evidence of a key role for mitochondrial dysfunction in both sporadic and all forms of familial Parkinson's disease (PD). However, none of the clinical trials carried out with putative mitochondrial rescue agents have been successful. Firm establishment of a wet biomarker or a reliable readout from imaging studies detecting mitochondrial dysfunction and reflecting disease progression is also awaited. We will provide an overview of our current knowledge about mitochondrial dysfunction in PD and related drug screens. We will also summarise previously undertaken mitochondrial wet biomarker studies and relevant imaging studies with particular focus on 31P-MRI spectroscopy. We will conclude with an overview of clinical trials which tested putative mitochondrial rescue agents in PD patients.

Rotenone-induced energy stress decompensated in ventral mesocerebrum is associated with Parkinsonism progression in rats

Parkinson's disease (PD) is the second most common neurodegenerative disorder, which is characterized by the hallmark feature of loss of dopaminergic neurons in the substantia nigra. Energy metabolic disorder is associated with the pathogenesis of PD; however, the development of this disorder is yet to be elucidated. PD-like characteristics have been demonstrated in a rotenone rat model. In the present study, energy metabolism status was investigated in a rat model following intraperitoneal treatment with 1.0 mg/kg rotenone every 48 h. The behavior and tyrosine hydroxylase-positive levels in the substantia nigra of rats that were treated with rotenone for 24 weeks demonstrated that these rats developed more severe parkinsonism, as compared with that were treated for 16 weeks. Detection of ATP, lactic acid, NADH dehydrogenase 1 mRNA and lactate dehydrogenase B mRNA levels in the ventral mesocerebrum (VM) and skeletal muscle (SM) of the rats that had been treated with rotenone for 16 and 24 weeks demonstrated that the energy stress induced by rotenone progressed in both VM and SM. Notably, the energy stress detected in VM was more severe, and this energy stress was decompensated in the VM of rats that had been treated with rotenone for 24 weeks. The progression of energy stress and the incidence of energy decompensation in VM may be important for the improvement of PD pathology.

Neuroimaging of Parkinson's disease: Expanding views

Advances in molecular and structural and functional neuroimaging are rapidly expanding the complexity of neurobiological understanding of Parkinson's disease (PD). This review article begins with an introduction to PD neurobiology as a foundation for interpreting neuroimaging findings that may further lead to more integrated and comprehensive understanding of PD. Diverse areas of PD neuroimaging are then reviewed and summarized, including positron emission tomography, single photon emission computed tomography, magnetic resonance spectroscopy and imaging, transcranial sonography, magnetoencephalography, and multimodal imaging, with focus on human studies published over the last five years. These included studies on differential diagnosis, co-morbidity, genetic and prodromal PD, and treatments from L-DOPA to brain stimulation approaches, transplantation and gene therapies. Overall, neuroimaging has shown that PD is a neurodegenerative disorder involving many neurotransmitters, brain regions, structural and functional connections, and neurocognitive systems. A broad neurobiological understanding of PD will be essential for translational efforts to develop better treatments and preventive strategies. Many questions remain and we conclude with some suggestions for future directions of neuroimaging of PD.

Protection of Dopamine Neurons by Vibration Training and Up-Regulation of Brain-Derived Neurotrophic Factor in a MPTP Mouse Model of Parkinson's Disease

It is unknown whether the longer duration of vibration training (VT) has a beneficial effect on Parkinson's disease (PD). And also, the mechanisms underlying the reported sensorimotor-improvement in PD induced by short-duration of VT has not been determined. Here, we investigated the effects of longer duration (4 weeks) of low amplitude vibration (LAV) training on the numbers of dopaminergic neurons in the substantia nigra by immunostaining and the levels of dopamine (DA) and brain-derived neurotrophic factor (BDNF) in the striatum by HPLC and ELISA in the chronic MPTP lesion mouse. We demonstrated for the first time that the longer duration of VT could significantly increase the numbers of nigrostriatal DA neurons and the contents of striatal DA and BDNF in the MPTP mice. Our findings implied that longer duration of VT could protect dopaminergic neurons from the MPTP-induced damage probably by upregulating BDNF and also provided evidence for the beneficial effect of longer duration of VT on PD at the cellular and molecular level.

T313M polymorphism of the PINK1 gene in Parkinson's disease

The present study aimed to investigate the association between T313M polymorphism at exon 4 of the PTEN-induced putative kinase 1 (PINK1) gene and Parkinson’s disease (PD) in the Uygur and Han populations of Xinjiang, China. Genetic DNA was extracted from 364 patients with PD from the Uygur and Han populations, as well as 346 normal control patients. Four exons of the PINK1 gene were amplified using quantitative polymerase chain reaction. The exons were then digested for restriction fragment length polymorphism analysis. Gene types and allele frequencies were identified using agarose gel electrophoresis followed by DNA sequencing to analyze the T313M polymorphisms. In the Han population, T313M polymorphism allele frequency was observed to be significantly different between the PD group and the control group (χ²=6.247; P<0.05). Significant differences were observed in in the T313M allele and genotype frequencies between the Uygur and Han populations (χ²=5.475 and χ²=10.950, respectively; P<0.05). Polymorphisms in the PINK1 T313M mutation may be associated with genetic susceptibility to PD.