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Annual Review of Cell and Developmental... Oct 2019The vertebrate vasculature displays high organotypic specialization, with the structure and function of blood vessels catering to the specific needs of each tissue. A... (Review)
Review
The vertebrate vasculature displays high organotypic specialization, with the structure and function of blood vessels catering to the specific needs of each tissue. A unique feature of the central nervous system (CNS) vasculature is the blood-brain barrier (BBB). The BBB regulates substance influx and efflux to maintain a homeostatic environment for proper brain function. Here, we review the development and cell biology of the BBB, focusing on the cellular and molecular regulation of barrier formation and the maintenance of the BBB through adulthood. We summarize unique features of CNS endothelial cells and highlight recent progress in and general principles of barrier regulation. Finally, we illustrate why a mechanistic understanding of the development and maintenance of the BBB could provide novel therapeutic opportunities for CNS drug delivery.
Topics: Animals; Astrocytes; Basement Membrane; Biological Transport; Blood-Brain Barrier; Brain; Central Nervous System; Endothelial Cells; Homeostasis; Humans; Leukocytes; Neurovascular Coupling; Pericytes; Tight Junctions; Transcytosis; Wnt Signaling Pathway
PubMed: 31299172
DOI: 10.1146/annurev-cellbio-100617-062608 -
Cells Aug 2020The intestinal barrier is essential in human health and constitutes the interface between the outside and the internal milieu of the body. A functional intestinal... (Review)
Review
The intestinal barrier is essential in human health and constitutes the interface between the outside and the internal milieu of the body. A functional intestinal barrier allows absorption of nutrients and fluids but simultaneously prevents harmful substances like toxins and bacteria from crossing the intestinal epithelium and reaching the body. An altered intestinal permeability, a sign of a perturbed barrier function, has during the last decade been associated with several chronic conditions, including diseases originating in the gastrointestinal tract but also diseases such as Alzheimer and Parkinson disease. This has led to an intensified interest from researchers with diverse backgrounds to perform functional studies of the intestinal barrier in different conditions. Intestinal permeability is defined as the passage of a solute through a simple membrane and can be measured by recording the passage of permeability markers over the epithelium via the paracellular or the transcellular route. The methodological tools to investigate the gut barrier function are rapidly expanding and new methodological approaches are being developed. Here we outline and discuss, in vivo, in vitro and ex vivo techniques and how these methods can be utilized for thorough investigation of the intestinal barrier.
Topics: Biomarkers; Gastrointestinal Microbiome; Homeostasis; Humans; In Vitro Techniques; Intestinal Mucosa; Organoids; Permeability; Tight Junctions; Transcytosis
PubMed: 32824536
DOI: 10.3390/cells9081909 -
Circulation Research Feb 2021Lipid uptake and metabolism are central to the function of organs such as heart, skeletal muscle, and adipose tissue. Although most heart energy derives from fatty acids... (Review)
Review
Lipid uptake and metabolism are central to the function of organs such as heart, skeletal muscle, and adipose tissue. Although most heart energy derives from fatty acids (FAs), excess lipid accumulation can cause cardiomyopathy. Similarly, high delivery of cholesterol can initiate coronary artery atherosclerosis. Hearts and arteries-unlike liver and adrenals-have nonfenestrated capillaries and lipid accumulation in both health and disease requires lipid movement from the circulation across the endothelial barrier. This review summarizes recent in vitro and in vivo findings on the importance of endothelial cell receptors and uptake pathways in regulating FAs and cholesterol uptake in normal physiology and cardiovascular disease. We highlight clinical and experimental data on the roles of ECs in lipid supply to tissues, heart, and arterial wall in particular, and how this affects organ metabolism and function. Models of FA uptake into ECs suggest that receptor-mediated uptake predominates at low FA concentrations, such as during fasting, whereas FA uptake during lipolysis of chylomicrons may involve paracellular movement. Similarly, in the setting of an intact arterial endothelial layer, recent and historic data support a role for receptor-mediated processes in the movement of lipoproteins into the subarterial space. We conclude with thoughts on the need to better understand endothelial lipid transfer for fuller comprehension of the pathophysiology of hyperlipidemia, and lipotoxic diseases such as some forms of cardiomyopathy and atherosclerosis.
Topics: Animals; CD36 Antigens; Cholesterol; Chylomicrons; Endothelial Cells; Fatty Acid Transport Proteins; Fatty Acids; Humans; Lipid Metabolism Disorders; Lipolysis; Particle Size; Transcytosis
PubMed: 33539224
DOI: 10.1161/CIRCRESAHA.120.318003 -
Metabolism: Clinical and Experimental Jun 2022Atherosclerosis (AS) is the basis of diabetic macrovascular complications. The plasma low-density lipoprotein (LDL) particles transcytosis across endothelial cells (ECs)...
BACKGROUND
Atherosclerosis (AS) is the basis of diabetic macrovascular complications. The plasma low-density lipoprotein (LDL) particles transcytosis across endothelial cells (ECs) and deposition under the endothelium is the initiation step of AS. We previously reported that high glucose inhibits the autophagic degradation of Caveolin-1 and promote LDL transcytosis across ECs, which in turn accelerates atherosclerotic progression. Since Sirt6 is a chromatin-associated protein with deacetylation activity, whether it can regulate Caveolin-1 acetylation and regulating the autophagic degradation of Caveolin-1 remains elusive.
METHODS
Autophagy and histone acetylation were assessed in the umbilical cords of patients with gestational diabetes mellitus (GDM) by immunohistochemistry. An in vitro model of LDL transcytosis was established, and the role of Sirt6 in LDL transcytosis across endothelial cells was clarified. The effect of Sirt6 on the autophagic degradation of Caveolin-1 under hyperglycemic conditions was explored in a streptozotocin (STZ)-induced diabetic AS model established using the ApoE mice.
RESULTS
Caveolin-1 and acetylated histone H3 levels were significantly increased, while LC3B and Sirt6 were downregulated in the monolayer of the vascular wall from GDM and type 2 diabetes mellitus (T2DM) patients. Immunoprecipitation assays showed that Sirt6 interacts with Caveolin-1 and specifically mediated its acetylation levels. Immuno-electron microscopy (EM) further indicated that Sirt6 overexpression triggered the autophagic lysosomal degradation of Caveolin-1. ECs-specific overexpression of Sirt6 by adeno-associated viral vector serotype 9 (AAV9) induced autophagy, reduced Caveolin-1 expression, and ameliorated atherosclerotic plaque formation in STZ-induced diabetic ApoE mice.
CONCLUSION
Sirt6-mediated acetylation of Caveolin-1 activates its autophagic degradation and inhibits high glucose-stimulated LDL transcytosis. Thus, the Sirt6/Caveolin-1 autophagic pathway plays a crucial role in diabetic AS, and the overexpression or activation of Sirt6 is a novel therapeutic strategy.
Topics: Animals; Apolipoproteins E; Atherosclerosis; Autophagy; Caveolin 1; Diabetes Mellitus, Type 2; Endothelial Cells; Glucose; Humans; Lipoproteins, LDL; Mice; Sirtuins; Transcytosis
PubMed: 35167876
DOI: 10.1016/j.metabol.2022.155162 -
Nature Mar 2021Most ovarian cancers are infiltrated by prognostically relevant activated T cells, yet exhibit low response rates to immune checkpoint inhibitors. Memory B cell and...
Most ovarian cancers are infiltrated by prognostically relevant activated T cells, yet exhibit low response rates to immune checkpoint inhibitors. Memory B cell and plasma cell infiltrates have previously been associated with better outcomes in ovarian cancer, but the nature and functional relevance of these responses are controversial. Here, using 3 independent cohorts that in total comprise 534 patients with high-grade serous ovarian cancer, we show that robust, protective humoral responses are dominated by the production of polyclonal IgA, which binds to polymeric IgA receptors that are universally expressed on ovarian cancer cells. Notably, tumour B-cell-derived IgA redirects myeloid cells against extracellular oncogenic drivers, which causes tumour cell death. In addition, IgA transcytosis through malignant epithelial cells elicits transcriptional changes that antagonize the RAS pathway and sensitize tumour cells to cytolytic killing by T cells, which also contributes to hindering malignant progression. Thus, tumour-antigen-specific and -antigen-independent IgA responses antagonize the growth of ovarian cancer by governing coordinated tumour cell, T cell and B cell responses. These findings provide a platform for identifying targets that are spontaneously recognized by intratumoural B-cell-derived antibodies, and suggest that immunotherapies that augment B cell responses may be more effective than approaches that focus on T cells, particularly for malignancies that are resistant to checkpoint inhibitors.
Topics: Antibody Specificity; Antigens, CD; Antigens, Neoplasm; Cell Line; Disease Progression; Female; Humans; Immunoglobulin A; Ovarian Neoplasms; Receptors, Fc; Signaling Lymphocytic Activation Molecule Family; T-Lymphocytes, Cytotoxic; Transcytosis; Tumor Microenvironment
PubMed: 33536615
DOI: 10.1038/s41586-020-03144-0 -
Advanced Materials (Deerfield Beach,... Nov 2018Therapies directed toward the central nervous system remain difficult to translate into improved clinical outcomes. This is largely due to the blood-brain barrier (BBB),... (Review)
Review
Therapies directed toward the central nervous system remain difficult to translate into improved clinical outcomes. This is largely due to the blood-brain barrier (BBB), arguably the most tightly regulated interface in the human body, which routinely excludes most therapeutics. Advances in the engineering of nanomaterials and their application in biomedicine (i.e., nanomedicine) are enabling new strategies that have the potential to help improve our understanding and treatment of neurological diseases. Herein, the various mechanisms by which therapeutics can be delivered to the brain are examined and key challenges facing translation of this research from benchtop to bedside are highlighted. Following a contextual overview of the BBB anatomy and physiology in both healthy and diseased states, relevant therapeutic strategies for bypassing and crossing the BBB are discussed. The focus here is especially on nanomaterial-based drug delivery systems and the potential of these to overcome the biological challenges imposed by the BBB. Finally, disease-targeting strategies and clearance mechanisms are explored. The objective is to provide the diverse range of researchers active in the field (e.g., material scientists, chemists, engineers, neuroscientists, and clinicians) with an easily accessible guide to the key opportunities and challenges currently facing the nanomaterial-mediated treatment of neurological diseases.
Topics: Alzheimer Disease; Animals; Biological Transport; Blood-Brain Barrier; Brain; Central Nervous System; Drug Delivery Systems; Drug Design; Humans; Ligands; Multiple Sclerosis; Nanomedicine; Nanoparticles; Nanostructures; Nervous System Diseases; Parkinson Disease; Stroke; Transcytosis; Translational Research, Biomedical
PubMed: 30066406
DOI: 10.1002/adma.201801362 -
International Journal of Molecular... Feb 2021Transcytosis of polymeric IgA and IgM from the basolateral surface to the apical side of the epithelium and subsequent secretion into mucosal fluids are mediated by the... (Review)
Review
Transcytosis of polymeric IgA and IgM from the basolateral surface to the apical side of the epithelium and subsequent secretion into mucosal fluids are mediated by the polymeric immunoglobulin receptor (pIgR). Secreted IgA and IgM have vital roles in mucosal immunity in response to pathogenic infections. Binding and recognition of polymeric IgA and IgM by pIgR require the joining chain (J chain), a small protein essential in the formation and stabilization of polymeric Ig structures. Recent studies have identified marginal zone B and B1 cell-specific protein (MZB1) as a novel regulator of polymeric IgA and IgM formation. MZB1 might facilitate IgA and IgM transcytosis by promoting the binding of J chain to Ig. In this review, we discuss the roles of pIgR in transcytosis of IgA and IgM, the roles of J chain in the formation of polymeric IgA and IgM and recognition by pIgR, and focus particularly on recent progress in understanding the roles of MZB1, a molecular chaperone protein.
Topics: Adaptor Proteins, Signal Transducing; Animals; Humans; Immunoglobulin A; Immunoglobulin M; Polymerization; Receptors, Polymeric Immunoglobulin; Transcytosis
PubMed: 33668983
DOI: 10.3390/ijms22052284 -
Nature May 2019Atherosclerosis, which underlies life-threatening cardiovascular disorders such as myocardial infarction and stroke, is initiated by passage of low-density lipoprotein...
Atherosclerosis, which underlies life-threatening cardiovascular disorders such as myocardial infarction and stroke, is initiated by passage of low-density lipoprotein (LDL) cholesterol into the artery wall and its engulfment by macrophages, which leads to foam cell formation and lesion development. It is unclear how circulating LDL enters the artery wall to instigate atherosclerosis. Here we show in mice that scavenger receptor class B type 1 (SR-B1) in endothelial cells mediates the delivery of LDL into arteries and its accumulation by artery wall macrophages, thereby promoting atherosclerosis. LDL particles are colocalized with SR-B1 in endothelial cell intracellular vesicles in vivo, and transcytosis of LDL across endothelial monolayers requires its direct binding to SR-B1 and an eight-amino-acid cytoplasmic domain of the receptor that recruits the guanine nucleotide exchange factor dedicator of cytokinesis 4 (DOCK4). DOCK4 promotes internalization of SR-B1 and transport of LDL by coupling the binding of LDL to SR-B1 with activation of RAC1. The expression of SR-B1 and DOCK4 is increased in atherosclerosis-prone regions of the mouse aorta before lesion formation, and in human atherosclerotic arteries when compared with normal arteries. These findings challenge the long-held concept that atherogenesis involves passive movement of LDL across a compromised endothelial barrier. Interventions that inhibit the endothelial delivery of LDL into artery walls may represent a new therapeutic category in the battle against cardiovascular disease.
Topics: Animals; Aorta; Arteries; Atherosclerosis; Cells, Cultured; Cholesterol, LDL; Endothelial Cells; Female; GTPase-Activating Proteins; Humans; Macrophages; Male; Mice; Neuropeptides; Scavenger Receptors, Class B; Transcytosis; rac1 GTP-Binding Protein
PubMed: 31019307
DOI: 10.1038/s41586-019-1140-4 -
Nature May 2014The central nervous system (CNS) requires a tightly controlled environment free of toxins and pathogens to provide the proper chemical composition for neural function....
The central nervous system (CNS) requires a tightly controlled environment free of toxins and pathogens to provide the proper chemical composition for neural function. This environment is maintained by the 'blood-brain barrier' (BBB), which is composed of blood vessels whose endothelial cells display specialized tight junctions and extremely low rates of transcellular vesicular transport (transcytosis). In concert with pericytes and astrocytes, this unique brain endothelial physiological barrier seals the CNS and controls substance influx and efflux. Although BBB breakdown has recently been associated with initiation and perpetuation of various neurological disorders, an intact BBB is a major obstacle for drug delivery to the CNS. A limited understanding of the molecular mechanisms that control BBB formation has hindered our ability to manipulate the BBB in disease and therapy. Here we identify mechanisms governing the establishment of a functional BBB. First, using a novel tracer-injection method for embryos, we demonstrate spatiotemporal developmental profiles of BBB functionality and find that the mouse BBB becomes functional at embryonic day 15.5 (E15.5). We then screen for BBB-specific genes expressed during BBB formation, and find that major facilitator super family domain containing 2a (Mfsd2a) is selectively expressed in BBB-containing blood vessels in the CNS. Genetic ablation of Mfsd2a results in a leaky BBB from embryonic stages through to adulthood, but the normal patterning of vascular networks is maintained. Electron microscopy examination reveals a dramatic increase in CNS-endothelial-cell vesicular transcytosis in Mfsd2a(-/-) mice, without obvious tight-junction defects. Finally we show that Mfsd2a endothelial expression is regulated by pericytes to facilitate BBB integrity. These findings identify Mfsd2a as a key regulator of BBB function that may act by suppressing transcytosis in CNS endothelial cells. Furthermore, our findings may aid in efforts to develop therapeutic approaches for CNS drug delivery.
Topics: Animals; Blood Vessels; Blood-Brain Barrier; Cerebral Cortex; Drug Delivery Systems; Endothelial Cells; Female; Gene Expression Profiling; Male; Membrane Transport Proteins; Mice; Neovascularization, Physiologic; Pericytes; Spatio-Temporal Analysis; Symporters; Tight Junctions; Transcytosis
PubMed: 24828040
DOI: 10.1038/nature13324 -
Neuron May 2017The blood-brain barrier (BBB) provides a constant homeostatic brain environment that is essential for proper neural function. An unusually low rate of vesicular...
The blood-brain barrier (BBB) provides a constant homeostatic brain environment that is essential for proper neural function. An unusually low rate of vesicular transport (transcytosis) has been identified as one of the two unique properties of CNS endothelial cells, relative to peripheral endothelial cells, that maintain the restrictive quality of the BBB. However, it is not known how this low rate of transcytosis is achieved. Here we provide a mechanism whereby the regulation of CNS endothelial cell lipid composition specifically inhibits the caveolae-mediated transcytotic route readily used in the periphery. An unbiased lipidomic analysis reveals significant differences in endothelial cell lipid signatures from the CNS and periphery, which underlie a suppression of caveolae vesicle formation and trafficking in brain endothelial cells. Furthermore, lipids transported by Mfsd2a establish a unique lipid environment that inhibits caveolae vesicle formation in CNS endothelial cells to suppress transcytosis and ensure BBB integrity.
Topics: Animals; Blood-Brain Barrier; Blotting, Western; Caveolae; Endothelial Cells; HEK293 Cells; Humans; Immunohistochemistry; Lipid Metabolism; Membrane Transport Proteins; Mice; Mice, Knockout; Microscopy, Confocal; Microscopy, Electron, Transmission; Permeability; Symporters; Transcytosis
PubMed: 28416077
DOI: 10.1016/j.neuron.2017.03.043