Single-dose intranasal administration of α-syn PFFs induce lewy neurite-like pathology in olfactory bulbs

Nose-to-brain drug delivery: from bench to bedside

There is increasing interest in nose-to-brain delivery as an innovative drug delivery strategy for neurodegenerative disorders such as Parkinson's or Alzheimer's disease. The unique anatomy of the nose-brain interface facilitates direct drug transport via the olfactory and trigeminal pathways to the brain, bypassing the blood-brain barrier. Different administration techniques as well as advanced drug formulations like targeted nanoparticles and thermoresponsive systems have been explored to improve the delivery efficiency and the therapeutic efficacy. This review provides an up-to-date perspective on this fast-developing field, and discusses different studies on safety and pharmacokinetic properties. A thorough evaluation of preclinical and clinical studies reveals both promises and challenges of this delivery method, highlighting approved drugs for the treatment of epilepsy and migraine that successfully utilize intranasal routes. The current landscape of research on nose-to-brain delivery is critically discussed, and a rationale is provided for ongoing research to optimize therapeutic strategies.

Intranasal α-Synuclein induces progressive behavioral impairments in mice

α-Synuclein (α-Syn) is implicated in the progression of Parkinson's disease, yet the disease's etiology remains unclear. This study aims to explore how α-Syn affects olfactory, motor, mood and cognitive functions if it initiates from the olfactory bulb. Mice were administered intranasal human AAV-α-Syn and subsequently evaluated for olfactory, motor, mood, and cognitive functions. Immunofluorescence was performed to assess dopaminergic neuronal damage. Results shown that olfactory dysfunction was evident as AAV-α-Syn-treated mice took longer to find buried pellets compared to controls at 3, 9, and 12 months post-instillation. Motor activity remained normal at 6 months but significantly declined at 9 months. Reduced tyrosine hydroxylase expression but increased amount of human α-Syn were observed in the substantia nigra at end of behavioral measurements. AAV-α-Syn mice showed reduced sucrose intake and decreased time in the center zone of the open field at 9 months. Cognitive deficits were observed in recognition function and social memory at 6 and 9 months, with impaired working memory at 12 months. Thus, intranasal AAV-α-Syn instillation in mice leads to progressive olfactory, motor, anxiety, depression-like, and cognitive dysfunctions, reflecting α-Syn pathology propagation.

Current safety recommendations for handling mouse and human αsynuclein pre-formed fibrils

α-Synuclein (α-syn) can form amyloid fibrils. Lewy bodies and Lewy neurites containing aggregated α-syn are pathological markers of Parkinson's Disease and Dementia with Lewy Bodies. To better understand the role of pathological α-syn in disease, many labs use α-syn preformed fibrils (PFFs). Neurons take up the PFFs, which act as seeds to corrupt endogenously expressed α-syn, inducing it to form aggregates very similar to those found in diseased brains. The PFFs are typically generated using recombinant mouse or human α-syn. α-Syn fibrils can also be extracted or amplified from brain tissue extracts, cerebrospinal fluid, or skin biopsies from patients with known synucleinopathy. The PFFs are then added to cell culture, or injected into rodents or primates to induce pathology. Because PFFs can corrupt endogenous α-syn, researchers should adhere to strict safety protocols when handling PFFs to minimize potential exposures. Our group consulted with biosafety professionals at the University of Alabama at Birmingham (UAB) to identify potential risks related to working with α-syn PFFs and offer containment controls to mitigate those risks. Potential exposures include pipetting, opening tubes, and sonication of the PFFs to generate fragments, all of which could potentially generate aerosols. Here, we outline best practices for the safe conduct of research with α-syn fibrils, including personal protective equipment and decontamination procedures. We highlight steps in which extra precautions should be taken and how to minimize exposure and potential risk associated with use of PFFs in scientific research.

Experimental Animal Models of Prodromal Parkinson's Disease

There is an estimated 35-45% loss of striatal dopamine at the time of diagnosis of Parkinson's disease (PD), and cases clinically diagnosed in the early stages may already be pathologically in advanced stages. Recent large-scale clinical trials of disease-modifying therapies (DMT) also suggest the necessity of targeting patients at earlier stages of the disease. From this perspective, the prodromal phase of PD is currently the focus of attention, emphasizing the need for a prodromal mouse model that accurately reflects the pathophysiology, along with early biomarkers. To establish prodromal animal model of PD with high face validity that reflects the disease state, the model must possess high construct validity that accurately incorporates clinical and pathological features in the prodromal phase. Furthermore, as a preclinical model of DMT, the model must possess high predictive validity to accurately evaluate the response to intervention. This review provides an overview of animal models which reflect the characteristics of prodromal PD, including alpha-synuclein (aS) accumulation and associated early non-motor symptoms, with a focus on the aS propagation model and genetic model. In addition, we discuss the challenges associated with these models. The genetic model often fails to induce motor symptoms, while aS propagation models skip the crucial step of initial aS aggregate formation, thereby not fully replicating the entire natural course of the disease. Identifying factors that induce the transition from prodromal to symptomatic phase is important as a preclinical model for DMT to prevent or delay the onset of the disease.