Non-CNS pathogenic origin of Parkinson's disease

Decreased urinary excretion of norepinephrine and dopamine in autonomic synucleinopathies

BACKGROUND

Autonomic synucleinopathies feature autonomic failure and intracellular deposition of the protein alpha-synuclein. Three such conditions are the Lewy body diseases (LBDs) Parkinson's disease (PD) and pure autonomic failure (PAF) and the non-LBD synucleinopathy multiple system atrophy (MSA). These diseases all entail catecholaminergic abnormalities in the brain, sympathetically innervated organs, or both; however, little is known about renal catecholaminergic functions in autonomic synucleinopathies. We measured urinary excretion rates of the sympathetic neurotransmitter norepinephrine, the hormone epinephrine, the autocrine-paracrine substance dopamine, the catecholamine precursor 3,4-dihydroxyphenylalanine (DOPA), 3,4-dihydroxyphenylglycol (DHPG, the main neuronal metabolite of norepinephrine), and 3,4-dihydroxyphenylacetic acid (DOPAC, a major dopamine metabolite), in PD, PAF, and MSA groups and controls.

METHODS

Data were reviewed from all research participants who had urine collections (usually 3.5 h) at the National Institutes of Health (NIH) Clinical Center from 1995 to 2024. The control cohort had neither autonomic failure nor a movement disorder.

RESULTS

Norepinephrine excretion rates were decreased compared with controls in PD (p = 0.0001), PAF (p < 0.0001), and MSA (p < 0.0001). Dopamine excretion was also decreased in the three groups (PD: p = 0.0136, PAF: p = 0.0027, MSA: p = 0.0344). DHPG excretion was decreased in PD (p = 0.0004) and PAF (p = 0.0004) but not in MSA. DOPA and epinephrine excretion did not differ among the study groups.

CONCLUSIONS

Autonomic synucleinopathies involve decreased urinary excretion rates of norepinephrine and dopamine. Since virtually all of urinary dopamine in humans is derived from circulating DOPA, the low rates of urinary norepinephrine and dopamine excretion may reflect dysfunctions in the renal sympathetic noradrenergic system, the DOPA-dopamine autocrine-paracrine system, or both systems.

Multidirectional associations between the gut microbiota and Parkinson's disease, updated information from the perspectives of humoral pathway, cellular immune pathway and neuronal pathway

The human gastrointestinal tract is inhabited by a diverse range of microorganisms, collectively known as the gut microbiota, which form a vast and complex ecosystem. It has been reported that the microbiota-gut-brain axis plays a crucial role in regulating host neuroprotective function. Studies have shown that patients with Parkinson's disease (PD) have dysbiosis of the gut microbiota, and experiments involving germ-free mice and fecal microbiota transplantation from PD patients have revealed the pathogenic role of the gut microbiota in PD. Interventions targeting the gut microbiota in PD, including the use of prebiotics, probiotics, and fecal microbiota transplantation, have also shown efficacy in treating PD. However, the causal relationship between the gut microbiota and Parkinson's disease remains intricate. This study reviewed the association between the microbiota-gut-brain axis and PD from the perspectives of humoral pathway, cellular immune pathway and neuronal pathway. We found that the interactions among gut microbiota and PD are very complex, which should be "multidirectional", rather than conventionally regarded "bidirectional". To realize application of the gut microbiota-related mechanisms in the clinical setting, we propose several problems which should be addressed in the future study.

Early-Onset Parkinson's Disease With Multiple Positive Intraoperative Spinal Tissue Cultures for Cutibacterium acnes

An estimated 95-97% of Parkinson’s disease (PD) cases are idiopathic, emphasizing the absence of a clear etiologic linkage for this debilitating, neurodegenerative, and progressive motor disease. Increasing evidence suggests a peripheral disease origin and the gradual transition of a pathological process along the gut-brain axis and olfactory routes into the brain. This disease pattern is reminiscent of an infectious process and suggests the presence of one or multiple infectious agents, such as bacteria, viruses, fungi, or prion-like proteins. This unusual paradigm, known as Braak’s hypothesis, was first described by the scientist who developed the staging standard for cellular PD pathology and. Here, we describe a case where the small, anaerobic, Gram-positive Cutibacterium acnes was recurrently isolated from intraoperative spinal tissues in a patient with early-onset PD. C. acnes is also the bacterium that we previously isolated from cadaveric PD brain tissue. Both observations are consistent with Braak’s hypothesis underscoring the importance of homeostasis and maintained immune-competence for healthy aging of the body and mind.

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.

Dopamine, Alpha-Synuclein, and Mitochondrial Dysfunctions in Parkinsonian Eyes

Parkinson’s disease (PD) is characterized by motor dysfunctions including bradykinesia, tremor at rest and motor instability. These symptoms are associated with the progressive degeneration of dopaminergic neurons originating in the substantia nigra pars compacta and projecting to the corpus striatum, and by accumulation of cytoplasmic inclusions mainly consisting of aggregated alpha-synuclein, called Lewy bodies. PD is a complex, multifactorial disorder and its pathogenesis involves multiple pathways and mechanisms such as α-synuclein proteostasis, mitochondrial function, oxidative stress, calcium homeostasis, axonal transport, and neuroinflammation. Motor symptoms manifest when there is already an extensive dopamine denervation. There is therefore an urgent need for early biomarkers to apply disease-modifying therapeutic strategies. Visual defects and retinal abnormalities, including decreased visual acuity, abnormal spatial contrast sensitivity, color vision defects, or deficits in more complex visual tasks are present in the majority of PD patients. They are being considered for early diagnosis together with retinal imaging techniques are being considered as non-invasive biomarkers for PD. Dopaminergic cells can be found in the retina in a subpopulation of amacrine cells; however, the molecular mechanisms leading to visual deficits observed in PD patients are still largely unknown. This review provides a comprehensive analysis of the retinal abnormalities observed in PD patients and animal models and of the molecular mechanisms underlying neurodegeneration in parkinsonian eyes. We will review the role of α-synuclein aggregates in the retina pathology and/or in the onset of visual symptoms in PD suggesting that α-synuclein aggregates are harmful for the retina as well as for the brain. Moreover, we will summarize experimental evidence suggesting that the optic nerve pathology observed in PD resembles that seen in mitochondrial optic neuropathies highlighting the possible involvement of mitochondrial abnormalities in the development of PD visual defects. We finally propose that the eye may be considered as a complementary experimental model to identify possible novel disease’ pathways or to test novel therapeutic approaches for PD.

Combustion and friction-derived nanoparticles and industrial-sourced nanoparticles: The culprit of Alzheimer and Parkinson's diseases

Redox-active, strongly magnetic, combustion and friction-derived nanoparticles (CFDNPs) are abundant in particulate matter air pollution. Urban children and young adults with Alzheimer disease Continuum have higher numbers of brain CFDNPs versus clean air controls. CFDNPs surface charge, dynamic magnetic susceptibility, iron content and redox activity contribute to ROS generation, neurovascular unit (NVU), mitochondria, and endoplasmic reticulum (ER) damage, and are catalysts for protein misfolding, aggregation and fibrillation. CFDNPs respond to external magnetic fields and are involved in cell damage by agglomeration/clustering, magnetic rotation and/or hyperthermia. This review focus in the interaction of CFDNPs, nanomedicine and industrial NPs with biological systems and the impact of portals of entry, particle sizes, surface charge, biomolecular corona, biodistribution, mitochondrial dysfunction, cellular toxicity, anterograde and retrograde axonal transport, brain dysfunction and pathology. NPs toxicity information come from researchers synthetizing particles and improving their performance for drug delivery, drug targeting, magnetic resonance imaging and heat mediators for cancer therapy. Critical information includes how these NPs overcome all barriers, the NPs protein corona changes as they cross the NVU and the complexity of NPs interaction with soluble proteins and key organelles. Oxidative, ER and mitochondrial stress, and a faulty complex protein quality control are at the core of Alzheimer and Parkinson's diseases and NPs mechanisms of action and toxicity are strong candidates for early development and progression of both fatal diseases. Nanoparticle exposure regardless of sources carries a high risk for the developing brain homeostasis and ought to be included in the AD and PD research framework.

Reciprocal Interactions of Mitochondria and the Neuroimmunoendocrine System in Neurodegenerative Disorders: An Important Role for Melatonin Regulation

Structural and functional alterations of mitochondria are intimately linked to a wide array of medical conditions. Many factors are involved in the regulation of mitochondrial function, including cytokines, chaperones, chemokines, neurosteroids, and ubiquitins. The role of diffusely located cells of the neuroendocrine system, including biogenic amines and peptide hormones, in the management of mitochondrial function, as well as the role of altered mitochondrial function in the regulation of these cells and system, is an area of intense investigation. The current article looks at the interactions among the cells of the neuronal-glia, immune and endocrine systems, namely the diffuse neuroimmunoendocrine system (DNIES), and how DNIES interacts with mitochondrial function. Whilst changes in DNIES can impact on mitochondrial function, local, and systemic alterations in mitochondrial function can alter the component systems of DNIES and their interactions. This has etiological, course, and treatment implications for a wide range of medical conditions, including neurodegenerative disorders. Available data on the role of melatonin in these interactions, at cellular and system levels, are reviewed, with directions for future research indicated.