α-Synuclein induces prodromal symptoms of Parkinson's disease via activating TLR2/MyD88/NF-κB pathway in Schwann cells of vagus nerve in a rat model

Alpha-synuclein, autophagy-lysosomal pathway, and Lewy bodies: Mutations, propagation, aggregation, and the formation of inclusions

Research into the pathophysiology of Parkinson's disease (PD) is a fast-paced pursuit, with new findings about PD and other synucleinopathies being made each year. The involvement of various lysosomal proteins, such as TFEB, TMEM175, GBA, and LAMP1/2, marks the rising awareness about the importance of lysosomes in PD and other neurodegenerative disorders. This, along with recent developments regarding the involvement of microglia and the immune system in neurodegenerative diseases, has brought about a new era in neurodegeneration: the role of proinflammatory cytokines on the nervous system, and their downstream effects on mitochondria, lysosomal degradation, and autophagy. More effort is needed to understand the interplay between neuroimmunology and disease mechanisms, as many of the mechanisms remain enigmatic. α-synuclein, a key protein in PD and the main component of Lewy bodies, sits at the nexus between lysosomal degradation, autophagy, cellular stress, neuroimmunology, PD pathophysiology, and disease progression. This review revisits some fundamental knowledge about PD while capturing some of the latest trends in PD research, specifically as it relates to α-synuclein.

The Synergistic Effect Study of Lipopolysaccharide (LPS) and A53T-α-Synuclein: Intranasal LPS Exposure on the A53T-α-Synuclein Transgenic Mouse Model of Parkinson's Disease

Aging and interactions between genetic and environmental factors are believed to be involved the chronic development of Parkinson's disease (PD). Among PD patients, abnormally aggregated α-synuclein is a major component of the Lewy body. Generally, the intranasal route is believed to be a gate way to the brain, and it assists environmental neurotoxins in entering the brain and is related to anosmia during early PD. The current study applies the chronic intranasal application of lipopolysaccharides (LPS) in 4-, 8-, 12- and 16-month-old A53T-α-synuclein (A53T-α-Syn) transgenic C57BL/6 mice at 2-day intervals for a 2-month period, for evaluating the behavioral, pathological, and biochemical changes and microglial activation in these animals. According to our results, after intranasal administration of LPS, A53T-α-Syn mice showed severe progressive anosmia, hypokinesia, selective dopaminergic (DAergic) neuronal losses, decreased striatal dopamine (DA) level, and enhanced α-synuclein accumulation within the substantia nigra (SN) in an age-dependent way. In addition, we found obvious NF-кB activation, Nurr1 inhibition, IL-1β, and TNF-α generation within the microglia of the SN. Conversely, the wild-type (WT) mice showed mild, whereas A53T-α-Syn mice had moderate PD-like changes among the old mice. This study demonstrated the synergistic effect of intranasal LPS and α-synuclein burden on PD development. Its underlying mechanism may be associated with Nurr1 inhibition within microglia and the amplification of CNS neuroinflammation. The mice with multiple factors, including aging, neuroinflammation, and α-synuclein mutation, have played a significant role in enhancing our understanding of how inflammation and α-synuclein mutation contribute to the neurodegeneration observed in PD.

Novel and experimental therapeutics for the management of motor and non-motor Parkinsonian symptoms

BACKGROUND  : Both motor and non-motor symptoms of Parkinson's disease (PD) have a substantial detrimental influence on the patient's quality of life. The most effective treatment remains oral levodopa. All currently known treatments just address the symptoms; they do not completely reverse the condition.

METHODOLOGY

In order to find literature on the creation of novel treatment agents and their efficacy for PD patients, we searched PubMed, Google Scholar, and other online libraries.

RESULTS

According to the most recent study on Parkinson's disease (PD), a great deal of work has been done in both the clinical and laboratory domains, and some current scientists have even been successful in developing novel therapies for PD patients.

CONCLUSION

The quality of life for PD patients has increased as a result of recent research, and numerous innovative medications are being developed for PD therapy. In the near future, we will see positive outcomes regarding PD treatment.

Mangiferin alleviates 6-OHDA-induced Parkinson's disease by inhibiting AKR1C3 to activate Wnt signaling pathway

Parkinson's disease (PD) is a neurodegenerative disorder with a lack of effective treatment options. mangiferin, a bioactive compound derived from mango, has been shown to possess strong neuroprotective properties. In this study, we investigated the neuroprotective effects of mangiferin on PD and its underlying mechanisms using both in vitro and in vivo models of 6-OHDA-induced PD. Additionally, we conducted molecular docking experiments to evaluate the interaction between mangiferin and AKR1C3 and β-catenin. Our results demonstrated that treatment with mangiferin significantly attenuated 6-OHDA-induced cell damage in PC12 cells, reducing intracellular oxidative stress, improving mitochondrial membrane potential, and restoring the expression of tyrosine hydroxylase (TH), a characteristic protein of dopaminergic neurons. Furthermore, mangiferin reduced the accumulation of α-synuclein and inhibited the expression of AKR1C3, thereby activating the Wnt/β-catenin signaling pathway. In vivo studies revealed that mangiferin improved motor dysfunction in 6-OHDA-induced PD mice. Molecular docking analysis confirmed the interaction between mangiferin and AKR1C3 and β-catenin. These findings indicate that mangiferin exerts significant neuroprotective effects in 6-OHDA-induced PD by inhibiting AKR1C3 and activating the Wnt/β-catenin signaling pathway. Therefore, mangiferin may emerge as an innovative therapeutic strategy in the comprehensive treatment regimen of PD patients, providing them with better clinical outcomes and quality of life.

Retinal Alterations Predict Early Prodromal Signs of Neurodegenerative Disease

Neurodegenerative diseases are an increasingly common group of diseases that occur late in life with a significant impact on personal, family, and economic life. Among these, Alzheimer's disease (AD) and Parkinson's disease (PD) are the major disorders that lead to mild to severe cognitive and physical impairment and dementia. Interestingly, those diseases may show onset of prodromal symptoms early after middle age. Commonly, the evaluation of these neurodegenerative diseases is based on the detection of biomarkers, where functional and structural magnetic resonance imaging (MRI) have shown a central role in revealing early or prodromal phases, although it can be expensive, time-consuming, and not always available. The aforementioned diseases have a common impact on the visual system due to the pathophysiological mechanisms shared between the eye and the brain. In Parkinson's disease, α-synuclein deposition in the retinal cells, as well as in dopaminergic neurons of the substantia nigra, alters the visual cortex and retinal function, resulting in modifications to the visual field. Similarly, the visual cortex is modified by the neurofibrillary tangles and neuritic amyloid β plaques typically seen in the Alzheimer's disease brain, and this may reflect the accumulation of these biomarkers in the retina during the early stages of the disease, as seen in postmortem retinas of AD patients. In this light, the ophthalmic evaluation of retinal neurodegeneration could become a cost-effective method for the early diagnosis of those diseases, overcoming the limitations of functional and structural imaging of the deep brain. This analysis is commonly used in ophthalmic practice, and interest in it has risen in recent years. This review will discuss the relationship between Alzheimer's disease and Parkinson's disease with retinal degeneration, highlighting how retinal analysis may represent a noninvasive and straightforward method for the early diagnosis of these neurodegenerative diseases.

Phosphorylated α-synuclein deposited in Schwann cells interacting with TLR2 mediates cell damage and induces Parkinson's disease autonomic dysfunction

Despite the significant frequency of autonomic dysfunction (AutD) in Parkinson's disease (PD) patients, its pathogenesis and diagnosis are challenging. Here, we aimed to further explore the mechanism of phosphorylated α-synuclein (p-α-syn) deposited in vagus nerve Schwann cells (SCs) causing SCs damage and PD AutD. 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 20 mg/kg) was administrated to C57BL/6 mice twice a week for 35 days. Following the final injection, locomotor functions, gastrointestinal symptoms, urine functions, and cardiovascular system functions were evaluated. Meanwhile, we examined p-α-syn deposited in vagus nerve SCs, Toll-like receptor 2 (TLR2) activation, and SCs loss using immunofluorescence, western blot, and Luxol fast blue staining. In vitro, the rat SCs line RSC96 cells were exposed to α-synuclein preformed fibril (α-syn PFF), and cell viability was detected by CCK8. Co-IP was used to identify the interaction between p-α-syn and TLR2. Furthermore, the role of TLR2 in p-α-syn-mediated SCs damage was confirmed by the administration of CU-CPT22, a specific blocker of TLR2. In vivo, apart from dyskinesia, MPTP mice exhibited constipation, urinary dysfunction, and cardiovascular failure, which were associated with the deposition of p-α-syn in vagus nerve SCs, TLR2 activation, and vagus nerve demyelination. In vitro, stimulation of α-syn PFF induced a time-dependent loss of viability, and p-α-syn deposited in RSC96 cells induced a cellular inflammatory response by interacting with TLR2, resulting in cell dysfunction and apoptosis. However, both SCs inflammatory response and cell viability were alleviated after inhibition of TLR2. Furthermore, 1 h fecal pellets and water content, the frequency of 1 h urine, blood pressure, heart rate, and heart rate variability of mice in the MPTP + CU-CPT22 group were also improved. Our results support the perspective that p-α-syn interacts with TLR2 induced SCs damage and is involved in PD AutD, which sheds fresh light on the mechanism of PD AutD and indicates a promising treatment for PD AutD targeting SCs p-α-syn/ TLR2 signaling pathway.

Parkinson's disease and gut microbiota: from clinical to mechanistic and therapeutic studies

Parkinson's disease (PD) is one of the most prevalent neurodegenerative diseases. The typical symptomatology of PD includes motor symptoms; however, a range of nonmotor symptoms, such as intestinal issues, usually occur before the motor symptoms. Various microorganisms inhabiting the gastrointestinal tract can profoundly influence the physiopathology of the central nervous system through neurological, endocrine, and immune system pathways involved in the microbiota-gut-brain axis. In addition, extensive evidence suggests that the gut microbiota is strongly associated with PD. This review summarizes the latest findings on microbial changes in PD and their clinical relevance, describes the underlying mechanisms through which intestinal bacteria may mediate PD, and discusses the correlations between gut microbes and anti-PD drugs. In addition, this review outlines the status of research on microbial therapies for PD and the future directions of PD-gut microbiota research.