Biology subjects

Barber, A. J.

Publications and source records attributed to Barber, A. J..

4 recordsLinked to original sources

bioRxiv2023

Age, Sex and Alzheimer's disease: A longitudinal study of 3xTg-AD mice reveals sex-specific disease trajectories and inflammatory responses mirrored in postmortem brains from Alzheimer's patients

BackgroundAging and sex are major risk factors for developing late-onset Alzheimers disease. Compared to men, women are not only nearly twice as likely to develop Alzheimers, but they also experience worse neuropathological burden and cognitive decline despite living longer with the disease. It remains unclear how and when sex differences in biological aging emerge and contribute to Alzheimers disease pathogenesis. We hypothesized that these differences lead to distinct pathological and molecular Alzheimers disease signatures in males and females, which could be harnessed for therapeutic and biomarker development. MethodsWe aged male and female, 3xTg-AD and B6129 (WT) control mice across their respective lifespans while longitudinally collecting brain, liver, spleen, and plasma samples (n=3-8 mice per sex, strain, and age group). We performed histological analyses on all tissues and assessed neuropathological hallmarks of Alzheimers disease, markers of hepatic inflammation, as well as splenic mass and morphology. Additionally, we measured concentrations of cytokines, chemokines, and growth factors in the plasma. We conducted RNA sequencing (RNA-Seq) analysis on bulk brain tissue and examined differentially expressed genes (DEGs) between 3xTg-AD and WT samples and across ages in each sex. We also examined DEGs between clinical Alzheimers and control parahippocampal gyrus brain tissue samples from the Mount Sinai Brain Bank (MSBB) study in each sex. Results3xTg-AD females significantly outlived 3xTg-AD males and exhibited progressive Alzheimers neuropathology, while 3xTg-AD males demonstrated progressive hepatic inflammation, splenomegaly, circulating inflammatory proteins, and next to no Alzheimers neuropathological hallmarks. Instead, 3xTg-AD males experienced an accelerated upregulation of immune-related gene expression in the brain relative to females, further suggesting distinct inflammatory disease trajectories between the sexes. Clinical investigations revealed that 3xTg-AD brain aging phenotypes are not an artifact of the animal model, and individuals with Alzheimers disease develop similar sex-specific alterations in canonical pathways related to neuronal signaling and immune function. Interestingly, we observed greater upregulation of complement-related gene expression, and lipopolysaccharide (LPS) was predicted as the top upstream regulator of DEGs in diseased males of both species. ConclusionsOur data demonstrate that chronic inflammation and complement activation are associated with increased mortality, revealing that age-related changes in immune response act as a primary driver of sex differences in Alzheimers disease trajectories. We propose a model of disease pathogenesis in 3xTg-AD males in which aging and transgene-driven disease progression trigger an inflammatory response, mimicking the effects of LPS stimulation despite the absence of infection.

neuroscience↗

bioRxiv2020

a-Synuclein strains influence multiple system atrophy via central and peripheral mechanisms

Multiple system atrophy (MSA) is a progressive neurodegenerative disease with prominent autonomic and motor features. Different disease subtypes are distinguished by their predominant parkinsonian or cerebellar signs. The pathognomonic feature of MSA is the presence of -synuclein (Syn) protein deposits in glial cells of the central and peripheral nervous system. It is unclear why MSA, that invariably presents with Syn pathology, is clinically so heterogeneous, why it progresses at varying rates and how neuroinflammation affects disease progression. Recently, it was shown that different strains of Syn can assemble in unique disease environments but also that a variety of strains might exist in the brain of MSA patients. We therefore investigated if different Syn strains might influence MSA disease progression. To this aim, we injected two recombinant strains of Syn in MSA transgenic mice and found that they significantly impact MSA disease progression in a strain-dependent way via oligodendroglial, neurotoxic and immune-related mechanisms. Neurodegeneration and brain atrophy were accompanied by unique microglial and astroglial responses and the recruitment of central and peripheral immune cells. The differential activation of microglial cells correlated with the structural features of Syn strains both in vitro and in vivo. By injecting Syn strains in MSA mice we could more closely mimic a comprehensive MSA phenotype in an experimental setting. This study therefore shows that i) MSA phenotype is governed by both the Syn strain nature and the host environment and ii) Syn strains can directly trigger a detrimental immune response related to disease progression in MSA.

neuroscience↗

bioRxiv2020

Extracellular vesicles from retinal pigment epithelial cells expressing R345W-Fibulin-3 induce epithelial-mesenchymal transition in recipient cells.

PurposePrevious studies in our lab found that expression of R345W-Fibulin-3 induces retinal pigment epithelial (RPE) cells to undergo epithelial-mesenchymal transition (EMT). The purpose of the current study was to investigate the size, cargo and function of extracellular vesicles (EVs) derived from RPE cells expressing wild-type (WT)-Fibulin-3 compared to RPE cells expressing the R345W-Fibulin-3 mutation, and to determine the role of these EVs in regulating RPE cell dysfunction. MethodsARPE-19 cells were infected with luciferase-tagged wild-type Fibulin-3 (WT)- or luciferase-tagged R345W-Fibulin-3 (mutant) using lentivirus. EVs were isolated from the media of ARPE-19 cells by conventional ultracentrifugation or density gradient ultracentrifugation. Transmission electron microscopy (TEM) and cryogenic electron microscopy (cryo-EM) were performed to study the morphology of the EVs. The amount and size distribution of EVs were determined by Nanoparticle Tracking Analysis (NTA). EV protein concentrations were quantified using the DCTM Protein Assay (Bio-Rad). EV cargo were analyzed by unbiased proteomics using LC-MS/MS with subsequent pathway analysis (Advaita). The EV-associated transforming growth factor beta 1 (TGF-{beta}1) protein was measured by Enzyme-linked immunosorbent assay (ELISA). The EV transplant study was conducted and migration ability was evaluated in ARPE-19 cells with or without exposure to EVs by conducting scratch assays. ResultsTEM imaging revealed concave-appearing vesicles, and cryo-EM imaging showed spherical vesicles with two subpopulations of EVs: a small group with diameters around 30nm and a large group with diameters around 100nm. Imaging also indicated a greater number of small EVs (~30 nm) in the mutant group compared to the WT group. This result was further confirmed by NTA showing that, in the mutant group, the particle size distributions were smaller than those of the WT EVs. There were no significant differences in EV protein concentrations per EV between WT and mutant groups. Proteomic studies showed that EVs derived from ARPE-19 cells expressing WT-Fibulin-3 contain critical members of sonic hedgehog signaling (SHH) signaling and ciliary tip components, whereas EVs derived from RPE cells expressing R345W-Fibulin-3 contain EMT mediators, including TGF-{beta}-induced protein (TGFBI), vimentin, and mothers against decapentaplegic homolog 4 (SMAD4), indicating that the EV cargo reflects the phenotypic status of their parental cells. Subsequent studies revealed enhanced activity of TGF-{beta}1 associated with mutant EVs compared to WT EVs. Critically, EV transplant studies showed that treatment of recipient RPE cells with mutant RPE cell-derived EVs was sufficient to induce an enhanced migration ability and elevated EMT marker expression of RPE cells. ConclusionsThe expression of R345W-Fibulin-3 alters the size, cargo and autocrine function of EVs. Notably, EVs derived from RPE cells expressing R345W-Fibulin-3 are sufficient to induce EMT in uninfected RPE cells.

cell biology↗

bioRxiv2020

Trait-environment relationships are predictive, but not general across species

Understanding the relationships between organisms and their environments is increasingly important given human impacts on global conditions. However, predicting how community diversity and composition will change in the future remains challenging (Mouquet et al 2015). One recent approach is to use traits to mechanistically inform how environmental conditions affect performance (i.e., trait-environment relationships), under the assumptions that these measures relate to each other in predictive and general ways. Unfortunately, results have been inconsistent, ignore phenotypic plasticity, and rely heavily on observational data (Shipley et al 2016). We evaluated the predictability and generality of trait-environment relationships in a controlled experimental microcosm system of four daphniid species. We cultured each species along a stressful gradient (conspecific density), measuring performance (fecundity) and traits related to performance (body length, 2nd antenna length, eye diameter, relative growth rate, and age at first reproduction). Using structural equation models, we evaluated the role of traits in mediating changes in individual fecundity in response to conspecific density. We built models for each species separately considering within-species trait variation, and for all species together by considering all trait variation across the four species. Results from this controlled system highlight that the relationship between individual traits and the environment (conspecific density) is strong and predictive of performance (fecundity), both within- and across-species. However, the specific trait-environment relationships which predicted fecundity differed for each species and differed from the relationships observed in the interspecific model, suggesting a lack of generality. These results will inform and improve the use of traits as a tool for predicting how changing environments will impact species abundances and distributions.

ecology↗