Browsing by Subject "Blood brain barrier"
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Item Gut Microbial Metabolite, Sodium Butyrate Regulates The Blood-Brain Barrier Transport And Intra-Endothelial Accumulation Of Alzheimer’S Disease Amyloid-Beta Peptides(2024-01) Veerareddy, VaishnaviAlzheimer's disease (AD) is a common type of dementia observed in the elderly with brain amyloid beta (Aꞵ) deposits as one of its pathological hallmarks. Risk factors contributing to AD include age, genetics, inflammation, gut dysbiosis, and co-morbidities like diabetes, hypertension, and insulin resistance1. Recent studies have highlighted the necessity of investigating the combined effect of risk factors on AD onset and progression2. In addition, a majority of AD patients are diagnosed with cerebrovascular dysfunction, which is considered to be a significant contributor to the disease progression3. Moreover, the gut microbiome diversity was shown to be diminished in AD patients4. One of the interactions between the gut and the brain is mediated by gut microbial metabolites through the gut-brain axis5. Gut microbial metabolites include mainly short-chain fatty acids (acetate, propionate, butyrate) and trimethylamine N-oxide (TMAO)6. Particularly, butyrate treatment was shown to improve impaired cognition and reduce Aꞵ deposition in the AD brain, although the underlying mechanisms are yet to be characterized7. Previously, we reported the impact of insulin signaling on Aꞵ trafficking between the brain and the blood via the blood-brain barrier (BBB), which lines the cerebrovascular lumen and regulates Aꞵ levels in the brain8. However, the effect of gut microbiome metabolites on Aꞵ trafficking/accumulation at the BBB and endothelial insulin signaling remains unknown. In this study, we investigated the effect of one of the bacterial metabolites, sodium butyrate (NaBu), on Aꞵ accumulation at the BBB endothelium and the role of endothelial insulin signaling. The NaBu decreased Aꞵ40 with 6 h treatment and Aꞵ42 accumulation upon 2 h and 6 h treatments in BBB cell (hCMEC/D3) monolayers in vitro. Moreover, NaBu increased the phosphorylation of protein kinase B (PKB/AKT) and extracellular signal-regulated kinase (ERK) upon 6 h treatment. Inhibitor studies were conducted to evaluate if NaBu effect on Aꞵ accumulation at the BBB is regulated by insulin signaling. Treatment with AKT inhibitor (MK2206) and NaBu increased Aꞵ42 accumulation compared to the NaBu alone treated group. Similarly, treatment with MEK inhibitor (trametinib) and NaBu increased Aꞵ42 accumulation compared to the NaBu-treated group. These findings suggest the involvement of AKT and ERK pathways in NaBu-mediated changes in Aꞵ42 accumulation at the BBB. Also, NaBu affects the expression of transporters and receptors at the BBB. The NaBu treatment increased permeability glycoprotein (P-gp) and decreased receptors for advanced glycated end products (RAGE) compared to the Aꞵ treated group. Further, studies need to be conducted to elucidate mechanisms underlying NaBu effect on the BBB endothelium in AD. Keywords: Alzheimer’s, Aβ, Blood-brain barrier, dysbiosis, sodium butyrate, Insulin signaling, P-gp, RAGE.Item Vascular Remodeling of the Blood Brain Barrier(2011-01) Johnson, Arial Raina LarsonThe human brain contains a vast network of blood vessels, capillaries, and microvessels. The blood brain barrier (BBB) is made up of three main components: resident endothelial cells (ECs), tight junctions, and a basement membrane. This barrier is impermeable to most solutes, bacteria, antibodies, chemicals, and drugs. It does, however, allow for the transport and diffusion of substances that are metabolically necessary in the brain such as glucose and oxygen. The transport of glucose is facilitated by Glut-1, a brain endothelial cell specific glucose transporter. The loss or deficiency of Glut-1 in the BBB has been clinically diagnosed in humans. Glut-1 deficiency syndrome is characterized by a haploinsufficiency of the wild type Glut-1; the dominant non-functional mutation causes the clinical manifestations related to the syndrome. The manifestations begin in infancy and, if undiagnosed, may cause serious developmental delay, acquired microcephaly, seizures, ataxia, and spasticity. The only known treatment is a ketogenic diet which eliminates the brain’s need for glucose in metabolism. Incorporation of genetically engineered ECs or endothelial progenitor cells (EPCs) that contain the gene for the wild type Glut-1 into the brain vasculature would correct this syndrome in addition to opening the door for treating other CNS diseases. The proposed mechanism for incorporating new cells into the BBB is via postnatal neovasculogenesis. Postnatal neovasculogenesis occurs in ischemia, hypoxia, and tumor growth. There are two modes of postnatal neovasculogenesis: angiogenesis and vasculogenesis. Angiogenesis is the process by which the resident ECs proliferate when the signal for growth of new vessels is received. Theoretically, during the process of vasculogenesis EPCs are recruited from the bone marrow, differentiate, proliferate, and migrate to the signaling tissue and incorporate into the new vessel. My research project focused on method development to incorporate cells into the brain neovasculature. I focused this development further to incorporation of cultured and bone marrow-derived ECs and EPCs into the neovasculature through hypoxia-mediated outgrowth or BBB disruption. We have now developed a method for investigating the effects of hypoxia on vascular remodeling and EPC and EC recruitment into the neovasculature. In this method we utilized two models; direct injection of cultured ECs and EPCs into the brain followed by hypoxia, or osmotic disruption of the BBB followed by injection of ECs and EPCs. Cultured ECs were isolated from brain microvessels. Cultured human EPCs were isolated from peripheral blood. ECs and EPCs display different antigens that allow for immunohistochemical detection. The different combinations of antigens elucidate the different cell types. ECs display antigens for Glut-1, CD31, and von Willebrand Factor. Bone marrow-derived EPCs display antigens for CD31 and Tie2, but do not display antigens for von Willebrand Factor. Immunohistochemistry was used to characterize the cells as EPCs or ECs prior to injection and determine location of the cells in the brain after animals are exposed to hypoxia using the specific antigens for ECs and EPCs.