Dual Effects: Intrastriatal Injection of α-syn N103/tau N368 Preformed Fibrils Promotes Endogenous α-synuclein Aggregates in the Proximal Colon

Gut-induced alpha-Synuclein and Tau propagation initiate Parkinson's and Alzheimer's disease co-pathology and behavior impairments

Tau interacts with α-Synuclein (α-Syn) and co-localizes with it in the Lewy bodies, influencing α-Syn pathology in Parkinson's disease (PD). However, whether these biochemical events regulate α-Syn pathology spreading from the gut into the brain remains incompletely understood. Here, we show that α-Syn and Tau co-pathology is spread into the brain in gut-inducible SYN103+/- and/or TAU368+/- transgenic mouse models, eliciting behavioral defects. Gut pathology was initially observed, and α-Syn or Tau pathology was subsequently propagated into the DMV or NTS and then to other brain regions. Remarkably, more extensive spreading and widespread neuronal loss were found in double transgenic mice (Both) than in single transgenic mice. Truncal vagotomy and α-Syn deficiency significantly inhibited synucleinopathy or tauopathy spreading. The α-Syn PET tracer [18F]-F0502B detected α-Syn aggregates in the gut and brain. Thus, α-Syn and Tau co-pathology can propagate from the gut to the brain, triggering behavioral disorders.

The Role of Immune Dysfunction in Parkinson's Disease Development

Recent research has unveiled intriguing insights suggesting that the body's immune system may be implicated in Parkinson's disease (PD) development. Studies have observed disparities in pro-inflammatory and anti-inflammatory markers between PD patients and healthy individuals. This finding underscores the potential influence of immune system dysfunction in the genesis of this condition. A dysfunctional immune system can serve as a primary catalyst for systemic inflammation in the body, which may contribute to the emergence of various brain disorders. The identification of several genes associated with PD, as well as their connection to neuroinflammation, raises the likelihood of disease susceptibility. Moreover, advancing age and mitochondrial dysfunction can weaken the immune system, potentially implicating them in the onset of the disease, particularly among older individuals. Compromised integrity of the blood-brain barrier could facilitate the immune system's access to brain tissue. This exposure may lead to encounters with native antigens or infections, potentially triggering an autoimmune response. Furthermore, there is mounting evidence supporting the notion that gut dysbiosis might represent an initial trigger for brain inflammation, ultimately promoting neurodegeneration. In this comprehensive review, we will delve into the numerous hypotheses surrounding the role of both innate and adaptive immunity in PD.

Common mechanisms underlying axonal transport deficits in neurodegenerative diseases: a mini review

Many neurodegenerative diseases including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis are characterized by the accumulation of pathogenic proteins and abnormal localization of organelles. These pathological features may be related to axonal transport deficits in neurons, which lead to failures in pathological protein targeting to specific sites for degradation and organelle transportation to designated areas needed for normal physiological functioning. Axonal transport deficits are most likely early pathological events in such diseases and gradually lead to the loss of axonal integrity and other degenerative changes. In this review, we investigated reports of mechanisms underlying the development of axonal transport deficits in a variety of common neurodegenerative diseases, such as Alzheimer's disease, amyotrophic lateral sclerosis, Parkinson's disease and Huntington's disease to provide new ideas for therapeutic targets that may be used early in the disease process. The mechanisms can be summarized as follows: (1) motor protein changes including expression levels and post-translational modification alteration; (2) changes in microtubules including reducing stability and disrupting tracks; (3) changes in cargoes including diminished binding to motor proteins. Future studies should determine which axonal transport defects are disease-specific and whether they are suitable therapeutic targets in neurodegenerative diseases.