Alzheimer's disease protein Abeta1-42 does not disrupt isolated synaptic vesicles

Genes related to neurotransmitter receptors as potential biomarkers for Alzheimer's disease

INTRODUCTION

Alzheimer's disease (AD) is a leading cause of dementia and is rapidly emerging as one of the costliest and most burdensome diseases. Neurotransmitter receptors play a vital role in many neuronal processes, primarily regulating signal inhibition within the brain to facilitate cell communication.

OBJECTIVES

Our research aims to identify potential biomarkers associated with AD and how these biomarkers impact immune infiltration.

METHODS

We extracted mRNA expression data from the Gene Expression Omnibus (GEO) database. Weighted gene co-expression network analysis (WGCNA) and differential expression analysis were employed to identify hub genes as biomarkers in AD. The Kyoto Encyclopedia of Genes and Genomes (KEGG), Gene Ontology (GO), and Gene Set Variation Analysis (GSVA) were used for functional enrichment. Furthermore, we examined 22 immune cell types infiltration using "CIBERSORT".

RESULTS

In this study, we identified 70 neurotransmitter receptor genes showing differential expression in AD: 22 were up-regulated, and 48 were down-regulated. Functional analyses indicated these genes were involved in essential biochemical pathways, including G protein-coupled receptors, neurotransmitter receptor activity, and ion channel interactions. WGCNA generated three co-expression modules, with one demonstrating the strongest association with AD. Five key NRGs (HTR3C, HTR3E, ADRA2A, HTR3A, and ADRA1D) were identified using a combination of differential genes. These genes have better diagnostic value by ROC analysis. Immune infiltration analysis showed that these genes were closely associated with the levels of resting mast cells, activated natural killer (NK) cells, and plasma cells in AD compared to controls.

CONCLUSION

Our study identified five NRGs (ADRA1D, ADRA2A, HTR3A, HTR3C, and HTR3E) with significant associations with AD. These findings may offer promising sights for further studies.

Increased Release of Apolipoprotein E in Extracellular Vesicles Following Amyloid-β Protofibril Exposure of Neuroglial Co-Cultures

Extracellular vesicles (EVs), including exosomes and larger microvesicles, have been implicated to play a role in several conditions, including Alzheimer's disease (AD). Since the EV content mirrors the intracellular environment, it could contribute with important information about ongoing pathological processes and may be a useful source for biomarkers, reflecting the disease progression. The aim of the present study was to analyze the protein content of EVs specifically released from a mixed co-culture of primary astrocytes, neurons, and oligodendrocytes treated with synthetic amyloid-β (Aβ42) protofibrils. The EV isolation was performed by ultracentrifugation and validated by transmission electron microscopy. Mass spectrometry analysis of the EV content revealed a total of 807 unique proteins, of which five displayed altered levels in Aβ42 protofibril exposed cultures. The most prominent protein was apolipoprotein E (apoE), and by western blot analysis we could confirm a threefold increase of apoE in EVs from Aβ42 protofibril exposed cells, compared to unexposed cells. Moreover, immunoprecipitation studies demonstrated that apoE was primarily situated inside the EVs, whereas immunocytochemistry indicated that the EVs most likely derived from the astrocytes and the neurons in the culture. The identified Aβ-induced sorting of apoE into EVs from cultured neuroglial cells suggests a possible role for intercellular transfer of apoE in AD pathology and encourage future studies to fully elucidate the clinical relevance of this event.

Transient microfluidic compartmentalization using actionable microfilaments for biochemical assays, cell culture and organs-on-chip

We report here a simple yet robust transient compartmentalization system for microfluidic platforms. Cylindrical microfilaments made of commercially available fishing lines are embedded in a microfluidic chamber and employed as removable walls, dividing the chamber into several compartments. These partitions allow tight sealing for hours, and can be removed at any time by longitudinal sliding with minimal hydrodynamic perturbation. This allows the easy implementation of various functions, previously impossible or requiring more complex instrumentation. In this study, we demonstrate the applications of our strategy, firstly to trigger chemical diffusion, then to make surface co-coating or cell co-culture on a two-dimensional substrate, and finally to form multiple cell-laden hydrogel compartments for three-dimensional cell co-culture in a microfluidic device. This technology provides easy and low-cost solutions, without the use of pneumatic valves or external equipment, for constructing well-controlled microenvironments for biochemical and cellular assays.

Probing rotational viscosity in synaptic vesicles

The synaptic vesicle (SV) is a central organelle in neurotransmission, and previous studies have suggested that SV protein 2 (SV2) may be responsible for forming a gel-like matrix within the vesicle. Here we measured the steady-state rotational anisotropy of the fluorescent dye, Oregon Green, within individual SVs. By also measuring the fluorescence lifetime of Oregon Green in SVs, we determined the mean rotational viscosity to be 16.49 ± 0.12 cP for wild-type (WT) empty mice vesicles (i.e., with no neurotransmitters), 11.21 ± 0.12 cP for empty vesicles from SV2 knock-out mice, and 11.40 ± 0.65 cP for WT mice vesicles loaded with the neurotransmitter glutamate (Glu). This measurement shows that SV2 is an important determinant of viscosity within the vesicle lumen, and that the viscosity decreases when the vesicles are filled with Glu. The viscosities of both empty SV2 knock-out vesicles and Glu-loaded WT vesicles were significantly different from that of empty WT SVs (p < 0.05). This measurement represents the smallest enclosed volume in which rotational viscosity has been measured thus far.

Pressure-driven laminar flow switching for rapid exchange of solution environment around surface adhered biological particles

This paper describes a technique for rapidly exchanging the solution environment near a surface by displacing laminar flow fluid streams using sudden changes in applied pressure. The method employs off-chip solenoid valves to induce pressure changes, which is important in keeping the microfluidic design simple and the operation of the system robust. The performance of this technique is characterized using simulation and validated with experiments. This technique adds to the microfluidic tool box that is currently available for manipulating the solution environment around biological particles and molecules.