Tau Protein in Oral Mucosa and Cognitive State: A Cross-sectional Study

Tau: a biomarker of Huntington's disease

Developing effective treatments for patients with Huntington's disease (HD)-a neurodegenerative disorder characterized by severe cognitive, motor and psychiatric impairments-is proving extremely challenging. While the monogenic nature of this condition enables to identify individuals at risk, robust biomarkers would still be extremely valuable to help diagnose disease onset and progression, and especially to confirm treatment efficacy. If measurements of cerebrospinal fluid neurofilament levels, for example, have demonstrated use in recent clinical trials, other proteins may prove equal, if not greater, relevance as biomarkers. In fact, proteins such as tau could specifically be used to detect/predict cognitive affectations. We have herein reviewed the literature pertaining to the association between tau levels and cognitive states, zooming in on Alzheimer's disease, Parkinson's disease and traumatic brain injury in which imaging, cerebrospinal fluid, and blood samples have been interrogated or used to unveil a strong association between tau and cognition. Collectively, these areas of research have accrued compelling evidence to suggest tau-related measurements as both diagnostic and prognostic tools for clinical practice. The abundance of information retrieved in this niche of study has laid the groundwork for further understanding whether tau-related biomarkers may be applied to HD and guide future investigations to better understand and treat this disease.

Untangling the Role of Tau in Huntington's Disease Pathology

There is increasing evidence for the presence of pathological forms of tau in tissues of both Huntington's disease (HD) patients and animal models of this condition. While cumulative studies of the past decade have led to the proposition that this disorder could also be considered a tauopathy, the implications of tau in cellular toxicity and consequent behavioral impairments are largely unknown. In fact, recent animal work has challenged the contributory role of tau in HD pathogenesis/pathophysiology. This review presents the supporting and opposing arguments for the involvement of tau in HD, highlighting the discrepancies that have emerged. Reflecting on what is known in other tauopathies, the putative mechanisms through which tau could initiate and/or contribute to pathology are discussed, shedding light on the future research directions that could be considered to confirm, or rule out, the clinical relevance of tau in HD.

Alpha-Synuclein species in oral mucosa as potential biomarkers for multiple system atrophy

Background

The definitive diagnosis of Multiple system atrophy (MSA) requires the evidence of abnormal deposition of α-Synuclein (α-Syn) through brain pathology which is unable to achieve in vivo. Deposition of α-Syn is not limited to the central nervous system (CNS), but also extended to peripheral tissues. Detection of pathological α-Syn deposition in extracerebral tissues also contributes to the diagnosis of MSA. We recently reported the increased expressions of α-Syn, phosphorylated α-Synuclein at Ser129 (pS129), and α-Syn aggregates in oral mucosal cells of Parkinson’s disease (PD), which serve as potential biomarkers for PD. To date, little is known about the α-Syn expression pattern in oral mucosa of MSA which is also a synucleinopathy. Here, we intend to investigate whether abnormal α-Syn deposition occurs in oral mucosal cells of MSA, and to determine whether α-Syn, pS129, and α-Syn aggregates in oral mucosa are potential biomarkers for MSA.

Methods

The oral mucosal cells were collected by using cytobrush from 42 MSA patients (23 MSA-P and 19 MSA-C) and 47 age-matched healthy controls (HCs). Immunofluorescence analysis was used to investigate the presence of α-Syn, pS129, and α-Syn aggregates in the oral mucosal cells. Then, the concentrations of α-Syn species in oral mucosa samples were measured using electrochemiluminescence assays.

Results

Immunofluorescence images indicated elevated α-Syn, pS129, and α-Syn aggregates levels in oral mucosal cells of MSA than HCs. The concentrations of three α-Syn species were significantly higher in oral mucosal cells of MSA than HCs (α-Syn, p < 0.001; pS129, p = 0.042; α-Syn aggregates, p < 0.0001). In MSA patients, the oral mucosa α-Syn levels negatively correlated with disease duration (r = −0.398, p = 0.009). The area under curve (AUC) of receiver operating characteristic (ROC) analysis using an integrative model including age, gender, α-Syn, pS129, and α-Syn aggregates for MSA diagnosis was 0.825, with 73.8% sensitivity and 78.7% specificity.

Conclusion

The α-Syn levels in oral mucosal cells elevated in patients with MSA, which may be promising biomarkers for MSA.

A genome-wide association analysis: m6A-SNP related to the onset of oral ulcers

Oral ulcers are one of the most common inflammatory diseases on oral mucosa that have obvious impacts on patients. Studies have shown that N6-methyladenosine (m6A) RNA transcription modification may be involved in the development of various inflammatory responses, and whether the pathogenesis of oral ulcers is related to m6A is unclear. This study aims to identify how m6A-related single nucleotide polymorphisms (m6A-SNPs) may affect oral ulcers. The UKBB dataset containing 10,599,054 SNPs was obtained from the GWAS database using the keyword "oral ulcer" and compared with the M6AVar database containing 13,703 m6A-SNPs.With 7,490 m6A-SNPs associated with oral ulcers identified, HaploReg and RegulomeDB were used for further functional validation and differential gene analysis was performed using the GEO database dataset GSE37265. A total of 7490 m6A-SNPs were detected in this study, 11 of which were related to oral ulcers (p<5E-08), and all of these SNPs showed eQTL signals. The SNP rs11266744 (p=2.00E-27) may regulate the expression of the local gene CCRL2, thereby participating in the pathogenesis of oral ulcers. In summary, by analyzing genome-wide association studies, this study showed that m6A modification may be involved in the pathogenesis of oral ulcers and CCRL2 may be the targeted gene.

Insight into the Role of Psychological Factors in Oral Mucosa Diseases

With the development of psychology and medicine, more and more diseases have found their psychological origins and associations, especially ulceration and other mucosal injuries, within the digestive system. However, the association of psychological factors with lesions of the oral mucosa, including oral squamous cell carcinoma (OSCC), burning mouth syndrome (BMS), and recurrent aphthous stomatitis (RAS), have not been fully characterized. In this review, after introducing the association between psychological and nervous factors and diseases, we provide detailed descriptions of the psychology and nerve fibers involved in the pathology of OSCC, BMS, and RAS, pointing out the underlying mechanisms and suggesting the clinical indications.

Oral Mucosa Derived α−Synuclein as a Potential Diagnostic Biomarker for Parkinson′s Disease

Background

Pathological α-synuclein (α-Syn) is not only exclusive to the central nervous system (CNS) in Parkinson’s disease (PD), but also extended to biofluids and peripheral tissues including oral cavity. Both oral mucosa and nervous system are derived from ectodermal tissue, and potentially share common disease-specific characteristics. Oral mucosal exfoliative cytology is a non-invasive technique, which is an easily acceptable for patients and ordinary people. The purpose of this study was to determine the abnormal accumulation of α-Syn in oral mucosa of PD patients and to learn the diagnostic utility of oral mucosa α-Syn for PD.

Methods

The oral mucosa samples were obtained from 57 patients with PD and 51 age-matched controls by cytological brush. Immunofluorescence analysis was used to investigate the presence and subcellular localization of α-Syn, phosphorylated α-Syn at Ser129 (pS129) and oligomeric α-Syn in the oral mucosa cells of PD patients and controls. Images taken as Z-stacks were analyzed for 3D reconstruction to visualize the α-Syn intracellular localization. Then, the concentrations of α-Syn, pS129, and oligomeric α-Syn in oral mucosa samples were measured using electrochemiluminescence assays.

Results

Immunofluorescence images revealed the increased α-Syn, pS129, and oligomeric α-Syn levels in oral mucosa cells of PD patients than age-matched controls. The intracellular distributions of α-Syn species were determine by Z-stack images with 3D reconstruction, and α-Syn was detected in both the nucleus and cytoplasm. However, pS129 was mainly located in the cytoplasm, and oligomeric α-Syn was highly expressed in the nucleus and perinuclear cytoplasm. The concentrations of three α-Syn species were significantly increased in the oral mucosa cell samples of PD patients than controls (α-Syn, p = 0.001; pS129, p = 0.002; oligomeric α-Syn, p = 0.013). In PD patients, the oral mucosa α-Syn and oligomeric α-Syn levels were significantly correlated with Hoehn-Yahr scales (α-Syn, r = 0.495, p = 0.001; oligomeric α-Syn, r = 0.324, p = 0.03). The area under curve (AUC) of ROC analysis using an integrative model including α-Syn, pS129, and oligomeric α-Syn for PD diagnosis was 0.749, with 66.7% sensitivity and 72.5% specificity.

Conclusion

This study for the first time demonstrated increased expressions of α-Syn, pS129, and oligomeric α-Syn in oral mucosa cells from PD patients, which serve as useful and non-invasive PD diagnostic biomarkers.

Diagnose it yourself: will there be a home test kit for Alzheimer's disease?

Alzheimer's disease is the most common neurodegenerative process leading to dementia. To date, there is no curative approach; thus, establishing a diagnosis as early as possible is necessary to implement preventive measures. However, today's gold standard for diagnosing Alzheimer's disease is high in both cost and effort and is not readily available. This defines the need for low-effort and economic alternatives that give patients low-threshold access to testing systems at their general practitioners or even at home for an independent retrieval of a biologic specimen. This perspective gives an overview of established and novel approaches in the field and speculates on the future of test strategies eventually technically implementable at home.