Changes of tRNA-Derived Fragments by Alzheimer's Disease in Cerebrospinal Fluid and Blood Serum.

BACKGROUND: Alzheimer's disease (AD) is the most common type of dementia, affecting individuals over 65. AD is also a multifactorial disease, with disease mechanisms incompletely characterized, and disease-modifying therapies are marginally effective. Biomarker signatures may shed light on the diagnosis, disease mechanisms, and the development of therapeutic targets. tRNA-derived RNA fragments (tRFs), a family of recently discovered small non-coding RNAs, have been found to be significantly enhanced in human AD hippocampus tissues. However, whether tRFs change in body fluids is unknown. OBJECTIVE: To investigate whether tRFs in body fluids are impacted by AD. METHODS: We first used T4 polynucleotide kinase-RNA-seq, a modified next-generation sequencing technique, to identify detectable tRFs in human cerebrospinal fluid and serum samples. The detectable tRFs were then compared in these fluids from control, AD, and mild cognitive impairment patients using tRF qRT-PCR. The stability of tRFs in serum was also investigated by checking the change in tRFs in response to protein digestion or exosome lysis. RESULTS: Among various tRFs, tRF5-ProAGG seemed to be impacted by AD in both cerebrospinal fluid and serum. AD-impacted serum tRF5-ProAGG showed a correlation with the AD stage. Putative targets of tRF5-ProAGG in the hippocampus were also predicted by a computational algorithm, with some targets being validated experimentally and one of them being in a negative correlation with tRF5-ProAGG even using a small size of samples. CONCLUSIONS: tRF5-ProAGG showed the potential as an AD biomarker and may play a role in disease progression.

Circulating Exosomes from Alzheimer's Disease Suppress Vascular Endothelial-Cadherin Expression and Induce Barrier Dysfunction in Recipient Brain Microvascular Endothelial Cell.

BACKGROUND: Blood-brain barrier (BBB) breakdown is a crucial aspect of Alzheimer's disease (AD) progression. Dysfunction in BBB is primarily caused by impaired tight junction and adherens junction proteins in brain microvascular endothelial cells (BMECs). The role of adherens junctions in AD-related BBB dysfunction remains unclear. Exosomes from senescent cells have unique characteristics and contribute to modulating the phenotype of recipient cells. However, it remains unknown if and how these exosomes cause BMEC dysfunction in AD. OBJECTIVE: This study aimed to investigate the impact of AD circulating exosomes on brain endothelial dysfunction. METHODS: Exosomes were isolated from sera of AD patients and age- and sex-matched cognitively normal controls using size-exclusion chromatography. The study measured the biomechanical nature of BMECs' endothelial barrier, the lateral binding forces between live BMECs. Paracellular expressions of the key adherens junction protein vascular endothelial (VE)-cadherin were visualized in BMEC cultures and a 3D BBB model using human BMECs and pericytes. VE-cadherin signals were also examined in brain tissues from AD patients and normal controls. RESULTS: Circulating exosomes from AD patients reduced VE-cadherin expression levels and impaired barrier function in recipient BMECs. Immunostaining analysis demonstrated that AD exosomes damaged VE-cadherin integrity in a 3D microvascular tubule formation model. The study found that AD exosomes weakened BBB integrity depending on their RNA content. Additionally, diminished microvascular VE-cadherin expression was observed in AD brains compared to controls. CONCLUSION: These findings highlight the significant role of circulating exosomes from AD patients in damaging adherens junctions of recipient BMECs, dependent on exosomal RNA.

Circulating exosomes from Alzheimer's disease suppress VE-cadherin expression and induce barrier dysfunction in recipient brain microvascular endothelial cell.

Background: Blood-brain barrier (BBB) breakdown is a component of the progression and pathology of Alzheimer's disease (AD). BBB dysfunction is primarily caused by reduced or disorganized tight junction or adherens junction proteins of brain microvascular endothelial cell (BMEC). While there is growing evidence of tight junction disruption in BMECs in AD, the functional role of adherens junctions during BBB dysfunction in AD remains unknown. Exosomes secreted from senescent cells have unique characteristics and contribute to modulating the phenotype of recipient cells. However, it remains unknown if and how these exosomes cause BMEC dysfunction in AD. Objectives: This study aimed to investigate the potential roles of AD circulating exosomes and their RNA cargos in brain endothelial dysfunction in AD. Methods: We isolated exosomes from sera of five cases of AD compared with age- and sex-matched cognitively normal controls using size-exclusion chromatography technology. We validated the qualities and particle sizes of isolated exosomes with nanoparticle tracking analysis and atomic force microscopy. We measured the biomechanical natures of the endothelial barrier of BMECs, the lateral binding forces between live BMECs, using fluidic force miscopy. We visualized the paracellular expressions of the key adherens junction protein VE-cadherin in BMEC cultures and a 3D BBB model that employs primary human BMECs and pericytes with immunostaining and evaluated them using confocal microscopy. We also examined the VE-cadherin signal in brain tissues from five cases of AD and five age- and sex-matched cognitively normal controls. Results: We found that circulating exosomes from AD patients suppress the paracellular expression levels of VE-cadherin and impair the barrier function of recipient BMECs. Immunostaining analysis showed that AD circulating exosomes damage VE-cadherin integrity in a 3D model of microvascular tubule formation. We found that circulating exosomes in AD weaken the BBB depending on the RNA cargos. In parallel, we observed that microvascular VE-cadherin expression is diminished in AD brains compared to normal controls. Conclusion: Using in vitro and ex vivo models, our study illustrates that circulating exosomes from AD patients play a significant role in mediating the damage effect on adherens junction of recipient BMEC of the BBB in an exosomal RNA-dependent manner. This suggests a novel mechanism of peripheral senescent exosomes for AD risk.

H1/H2 MAPT haplotype and Parkinson's disease in Mexican mestizo population.

Parkinson's disease (PD) is characterized by bradykinesia, resting tremor, rigidity and postural instability as well as early symptoms. Previous studies that evaluated the association between H1/H2 MAPT haplotype and PD were mostly conducted in European populations in which the H1 haplotype was a reported risk factor for PD. Despite those findings, some studies have suggested that the association may be ethnically dependent. Since studies conducted in Latin American population have been scarce, we genotyped the H1/H2 MAPT haplotype in Mexican mestizo population as part of a PD case-control study. DNA was extracted from peripheral blood leucocytes in 108 cases and 108 controls and detection of the H1/H2 haplotypes was achieved by determining the MAPT_238 bp deletion/insertion variant at intron 9 through end-point PCR followed by visual 3% agarose gel electrophoresis interpretation. We observed no-association between genotypes and PD risk [OR/CI (Odds ratio/95% Confidence Interval) of 1.60 (0.78-3.29) for H1/H2 genotype and 2.26 (0.20-25.78) for H2/H2]. No-association was maintained when stratifying our groups by central (p = 0.27) and northern regions (p = 0.70). Our data suggest that H1/H2 MAPT haplotype is not a risk factor to PD in our population.