Amyloid plaques in Alzheimer’s disease (AD) are associated with inflammation. Recent studies demonstrated the involvement of the gut in cerebral amyloid-beta (Aβ) pathogenesis; however, the mechanisms are still not well understood. We hypothesize that the gut bears the Aβ burden prior to brain, highlighting gut–brain axis (GBA) interaction in neurodegenerative disorders. We used pre-symptomatic (6-months) and symptomatic (15-months) Tg2576 mouse model of AD compared to their age-matched littermate WT control. We identified that dysfunction of intestinal epithelial barrier (IEB), dysregulation of absorption, and vascular Aβ deposition in the IEB occur before cerebral Aβ aggregation is detectible. These changes in the GBA were associated with elevated inflammatory plasma cytokines including IL-9, VEGF and IP-10. In association with reduced cerebral myelin tight junction proteins, we identified reduced levels of systemic vitamin B12 and decrease cubilin, an intestinal B12 transporter, after the development of cerebral Aβ pathology. Lastly, we report Aβ deposition in the intestinal autopsy from AD patients with confirmed cerebral Aβ pathology that is not present in intestine from non-AD controls. Our data provide evidence that gut dysfunction occurs in AD and may contribute to its etiology. Future therapeutic strategies to reverse AD pathology may involve the early manipulation of gut physiology and its microbiota.

Background: The location of coelomocyte proliferation in adult sea urchins is unknown and speculations since the early 1800s have been based on microanatomy and tracer uptake studies. In adult sea urchins ( Strongylocentrotus purpuratus ) with down-regulated immune systems, coelomocyte numbers increase in response to immune challenge, and whether some or all of these cells are newly proliferated is not known. The gene regulatory network that encodes transcription factors that control hematopoiesis in embryonic and larval sea urchins has not been investigated in adults. Hence, to identify the hematopoietic tissue in adult sea urchins, cell proliferation, expression of phagocyte specific genes, and expression of genes encoding transcription factors that function in the conserved regulatory network that controls hematopoiesis in embryonic and larval sea urchins were investigated for several tissues. Results: Cell proliferation was induced in adult sea urchins either by immune challenge through injection of heat-killed Vibrio diazotrophicus or by cell depletion through aspiration of coelomic fluid. In response to either of these stimuli, newly proliferated coelomocytes constitute only about 10% of the cells in the coelomic fluid. In tissues, newly proliferated cells and cells that express SpTransformer proteins (formerly Sp185/333) that are markers for phagocytes are present in the axial organ, gonad, pharynx, esophagus, and gut with no differences among tissues. The expression level of genes encoding transcription factors that regulate hematopoiesis show that both the axial organ and the pharynx have elevated expression compared to coelomocytes, esophagus, gut, and gonad. Similarly, an RNAseq dataset shows similar results for the axial organ and pharynx, but also suggests that the axial organ may be a site for removal and recycling of cells in the coelomic cavity. Conclusions: Results presented here are consistent with previous speculations that the axial organ may be a site of coelomocyte proliferation and that it may also be a center for cellular removal and recycling. A second site, the pharynx, may also have hematopoietic activity, a tissue that has been assumed to function only as part of the intestinal tract.

The adaptive immune response in jawed vertebrates is marked by the ability to diversify somatically specific immune receptor genes. Somatic recombination and hypermutation of gene segments are used to generate extensive repertoires of T and B cell receptors. In contrast, jawless vertebrates utilize a distinct diversification system based on copy choice to assemble their variable lymphocyte receptors. To date, very little evidence for somatic immune gene diversification has been reported in invertebrate species. Here we show that the SpTransformer ( SpTrf ; formerly Sp185/333 ) immune effector gene family members from individual coelomocytes from purple sea urchins undergo somatic diversification by means of gene deletions, duplications, and acquisitions of single nucleotide polymorphisms. While sperm cells from an individual sea urchin have identical SpTrf gene repertoires, single cells from two distinct coelomocyte subpopulations from the same sea urchin exhibit significant variation in the SpTrf gene repertoires. Moreover, the highly diverse gene sequences derived from single coelomocytes are all in-frame, suggesting that an unknown mechanism(s) driving these somatic changes involve stringent selection or correction processes for expression of productive SpTrf transcripts. Together, our findings infer somatic immune gene diversification strategy in an invertebrate.

Chapter 1: Introduction This chapter is based upon "Peroxisomal dysfunction in neurological diseases and brain aging", courtesy of Frontiers in Cellular Neuroscience, © Uzor, McCullough, and Tsvetkov. 2020. Chapter 4: Aging lowers PEX5 levels in cortical neurons in male and female mouse brains This chapter is based upon "Aging lowers PEX5 levels in cortical neurons in male and female mouse brains," a first-author publication accepted by Molecular Cellular Neuroscience, August 2020.

Objective: Cerebral ischemia affects the mechano-response of vasculature and the remodeling of extracellular matrix (ECM) components. The present study investigates how oxygen-glucose deprivation (OGD) affects the brain endothelial cell (BEC) stiffness. We further aim to study whether ECM components affect the cellular stiffness in normal and energy deprived conditions. Methods: Primary human BECs received a 16h OGD followed by the reperfusion with normal culture media. Young’s Modulus (YM) and topography in the BEC surface were determined by atomic force microscopy (AFM). To test the effect of ECM composition on the BEC stiffness, various concentrations (5-500 uM) of collagen type IV were used for culture dish coating. BECs on the coating beds underwent 16h OGD and served for YM measurements. Per dish, 10-20 single BECs were measured. Results: BECs under OGD conditions became significantly stiffer (2.1-fold, *P<0.05) than the normoxic control, and the increased stiffness sustained even after the reperfusion for 24h, indicating energy deprivation is a primary factor for the increased stiffness under acute stress conditions. AFM topography confirmed that OGD induced rough and filamentous plasma membrane surface in BECs, suggesting a cytoskeletal change was induced by OGD. BECs grown on a 10x denser collagen type IV (500 uM) layer showed a significant increase (2.3-fold, ***P<0.001) in cellular stiffness, compared with the conventional concentration of 50 uM, suggesting that denser extracellular matrix makes BEC stiffer. Also, in BECs cultured on a denser ECM layer, OGD response was absent in terms of cellular stiffness. Conclusion: The present study found that OGD increased BEC stiffness. In addition, increasing the density of the ECM alone was enough to generate stiffer BECs. These mechanical properties of BECs may be a physical factor mediating endothelial responses after stroke.