A Potential New Role for Zinc in Age-Related Macular Degeneration through Regulation of Endothelial Fenestration

Age-related macular degeneration (AMD) is a common blinding disease in the western world that is linked to the loss of fenestration in the choriocapillaris that sustains the retinal pigment epithelium and photoreceptors in the back of the eye. Changes in ocular and systemic zinc concentrations have been associated with AMD; therefore, we hypothesized that these changes might be directly involved in fenestrae formation. To test this hypothesis, an endothelial cell (bEND.5) model for fenestrae formation was treated with different concentrations of zinc sulfate (ZnSO4) solution for up to 20 h. Fenestrae were visualized by staining for Plasmalemmal Vesicle Associated Protein-1 (PV-1), the protein that forms the diaphragms of the fenestrated endothelium. Size and distribution were monitored by transmission electron microscopy (TEM). We found that zinc induced the redistribution of PV-1 into areas called sieve plates containing ~70-nm uniform size and typical morphology fenestrae. As AMD is associated with reduced zinc concentrations in the serum and in ocular tissues, and dietary zinc supplementation is recommended to slow disease progression, we propose here that the elevation of zinc concentration may restore choriocapillaris fenestration resulting in improved nutrient flow and clearance of waste material in the retina.

Collisions model between magnetic nanoparticles and the arterial wall

At present, there are different treatments against cancer, however, some of them, such as chemotherapy, are very invasive for the human body, since they affect healthy tissues. Magnetic targeting of drugs by means of magnetic nanoparticles is one of the alternative techniques that has emerged in the last decade, it is based on the targeting of drug delivery to the tumor without affecting healthy tissues, via of injected nanoparticles with diamagnetic properties directly into the bloodstream, driven by external magnetic fields produced by permanent magnets. This technique in literature is often come upon as MTD for its acronym in English. In this work, a numerical model was developed in order to quantify the loss of nanoparticles in the process of interaction with the walls of the bloodstream. For this model, the Kinetic technique was used, quantifying the probability of adsorption and absorption taking into account the following parameters: diameter of the nanoparticle (200 nm), density of the nanoparticle (6450 kg · m -3), diameter of the cell endothelial (0.1 μm - 1 μm), transcellular pores of the fenestrated endothelium (70 nm) and modulus of elasticity of the endothelium (4.1 ± 1.7 kPa).

Anatomical Organization of the Rat Subfornical Organ

The subfornical organ (SFO) is a sensory circumventricular organ located along the anterodorsal wall of the third ventricle. SFO lacks a complete blood-brain barrier (BBB), and thus peripherally-circulating factors can penetrate the SFO parenchyma. These signals are detected by local neurons providing the brain with information from the periphery to mediate central responses to humoral signals and physiological stressors. Circumventricular organs are characterized by the presence of unique populations of non-neuronal cells, such as tanycytes and fenestrated endothelium. However, how these populations are organized within the SFO is not well understood. In this study, we used histological techniques to analyze the anatomical organization of the rat SFO and examined the distribution of neurons, fenestrated and non-fenestrated vasculature, tanycytes, ependymocytes, glia cells, and pericytes within its confines. Our data show that the shell of SFO contains non-fenestrated vasculature, while fenestrated capillaries are restricted to the medial-posterior core region of the SFO and associated with a higher BBB permeability. In contrast to non-fenestrated vessels, fenestrated capillaries are encased in a scaffold created by pericytes and embedded in a network of tanycytic processes. Analysis of c-Fos expression following systemic injections of angiotensin II or hypertonic NaCl reveals distinct neuronal populations responding to these stimuli. Hypertonic NaCl activates ∼13% of SFO neurons located in the shell. Angiotensin II-sensitive neurons represent ∼35% of SFO neurons and their location varies between sexes. Our study provides a comprehensive description of the organization of diverse cellular elements within the SFO, facilitating future investigations in this important brain area.

MO087PLASMALEMMAL VESICLE-ASSOCIATED PROTEIN-1 (PLVAP) INDICATES THE FORMATION OF DIAPHRAGM-BRIDGED FENESTRATIONS OF GLOMERULAR ENDOTHELIAL CELLS IN KIDNEY DISEASE

Background and Aims Plasmalemmal vesicle-associated protein-1 (PLVAP or PV-1) is a major protein of diaphragm-bridged fenestrated endothelial cells found in capillaries of neuroendocrine glands and peritubular capillaries. In contrast to peritubular capillaries, the glomerulus is known for its unique fenestrated endothelium without any diaphragm formation thereby ensuring free filtration. Here we aimed to investigate whether PLVAP is expressed in glomerular endothelial cells in various glomerular diseases and whether PLVAP expression is associated with the formation of diaphragm-bridged endothelial cells. Method A total number of 114 biopsy samples of glomerular diseases including diabetic nephropathy, FSGS, IgA-Nephritis, ANCA-GN and Lupus–Nephritis were analyzed immunohistochemistically for glomerular PLVAP expression. A fraction of PLVAP positive cases was subsequently investigated ultrastrucurally for the formation of diaphragm-bridged glomerular endothelial cells. Results One third of all cases showed at least one glomerulus with one single circumferential PLVAP staining. Interestingly, the most prominent staining, affecting the entire glomerular tuft, was observed in diabetic nephropathy and ANCA-GN. Ultrastructurally, such cases exhibited injured endothelium with focal detachment from the glomerular basement membrane, loss of pore formation and frequently diaphragm-bridged fenestrations reminiscent of peritubular capillaries. Conclusion Our data show that injured glomerular endothelium is capable of forming true diaphragm-bridged fenestrations, suggesting a possible role in preventing glomerular protein leakage and limiting its detachment from the GBM.

Angiodiversity and organotypic functions of sinusoidal endothelial cells

Abstract‘Angiodiversity’ refers to the structural and functional heterogeneity of endothelial cells (EC) along the segments of the vascular tree and especially within the microvascular beds of different organs. Organotypically differentiated EC ranging from continuous, barrier-forming endothelium to discontinuous, fenestrated endothelium perform organ-specific functions such as the maintenance of the tightly sealed blood–brain barrier or the clearance of macromolecular waste products from the peripheral blood by liver EC-expressed scavenger receptors. The microvascular bed of the liver, composed of discontinuous, fenestrated liver sinusoidal endothelial cells (LSEC), is a prime example of organ-specific angiodiversity. Anatomy and development of LSEC have been extensively studied by electron microscopy as well as linage-tracing experiments. Recent advances in cell isolation and bulk transcriptomics or single-cell RNA sequencing techniques allowed the identification of distinct LSEC molecular programs and have led to the identification of LSEC subpopulations. LSEC execute homeostatic functions such as fine tuning the vascular tone, clearing noxious substances from the circulation, and modulating immunoregulatory mechanisms. In recent years, the identification and functional analysis of LSEC-derived angiocrine signals, which control liver homeostasis and disease pathogenesis in an instructive manner, marks a major change of paradigm in the understanding of liver function in health and disease. This review summarizes recent advances in the understanding of liver vascular angiodiversity and the functional consequences resulting thereof.

Glomerular Endothelium and its Impact on Glomerular Filtration Barrier in Diabetes: Are the Gaps Still Illusive?

Background: Glomerular capillaries are lined with highly specialized fenestrated endothelium which are primarily responsible to regulate high flux filtration of fluid and small solutes. During filtration, plasma passes through the fenestrated endothelium and basement membrane before it reaches the slit diaphragm, a specialized type of intercellular junction that connects neighbouring podocytes. Methods: A PubMed search was done for recent articles on components of the glomerular filtration barrier such as glomerular endothelial cells, podocytes and glomerular basement membrane, and the effect of diabetes on these structures. Results and Conclusion: Generally, the onset of kidney dysfunction in many diabetic patients is characterized by albuminuria/proteinuria, a pathophysiological event triggered by several factors including; (i) endothelial activation and shading of glycocalyx, (ii) loss of endothelial cell function, (ii) re-uptake of albumin by podocyte through a scavenger receptors and (iv) rearrangement of podocyte cytoskeleton. Howeover, as podocyte effacement does not always lead to proteinuria, the dynamic interplay between all constituents of the glomerular filtration barrier including podocytes, endothelial cells and the basement membrane may be fundamental for the effective filtration in healthy individuals. Thus, a putative cross-talk amongst podocytes, endothelial cells and the basement membrane in the homeostasis of glomerular function is envisaged. Although, the exact nature of this cross-talk remains to be clearly elucidated, it is possible that the interaction between: (i) glomerular endothelial cells and podocytes, (ii) glomerular endothelial cells and glomerular basement membrane, (iii) podocytes and glomerular basement membrane, and (iv) the simultaneous interaction amongst the three components collectively underpin effective filtration in healthy individuals. A comprehensive understanding of these different interactions still remains elusive. The elucidation of these multifaceted interactions will set the stage for greater understanding of the pathophysiology of kidney dysfunction.

The NF-κB essential modulator (NEMO) controls podocyte cytoskeletal dynamics independently of NF-κB

Maintenance of the glomerular filtration barrier with its fenestrated endothelium, the glomerular basement membrane, and the podocytes as the outer layer, is a major prerequisite for proper renal function. Tight regulation of the balance between plasticity and rigidity of the podocytes' architecture is required to prevent the onset of glomerular disease, mainly proteinuria. The underlying cellular signaling pathways that regulate the organization of the podocytes' cytoskeleton are still a matter of controversial debate. In this study, we investigated the role of the NF-κB signaling pathway in podocyte cytoskeletal dynamics. As previously published, genetic inhibition of the NF-κB essential modulator (NEMO) in podocytes does not affect glomerular function under physiological, nonstressed conditions nor does it alter the initial podocyte response in an experimental glomerulonephritis (NTN) model (Brähler S, Ising C, Hagmann H, Rasmus M, Hoehne M, Kurschat C, Kisner T, Goebel H, Shankland SJ, Addicks K, Thaiss F, Schermer B, Pasparakis M, Benzing T, Brinkkoetter PT. Am J Physiol Renal Physiol 303: F1473–F1475, 2012). Quite the contrary, podocyte-specific NEMO null mice recovered significantly faster and did not develop glomerulosclerosis and end-stage renal failure over time. Here, we show that cytoskeletal rearrangements and increased podocyte motility following stimulation with IL-1, TNF-α, or LPS depend on NEMO. NEMO also regulates the phosphorylation of the MAP kinase ERK1/2 and suppresses the activation of RhoA following stimulation with IL-1. The migratory response and altered ERK1/2 phosphorylation is independent of NF-κB signaling as demonstrated by expression of a mutant IκB resistant to phosphorylation and degradation. In conclusion, signaling through NEMO might not only be involved in the production of NF-κB proinflammatory chemokines but also regulates podocyte dynamics independently of NF-κB, most likely through small GTPases and MAP kinases.

The podocyte in health and disease: insights from the mouse

The glomerular filtration barrier consists of the fenestrated endothelium, the glomerular basement membrane and the terminally differentiated visceral epithelial cells known as podocytes. It is now widely accepted that damage to, or originating within, the podocytes is a key event that initiates progression towards sclerosis in many glomerular diseases. A wide variety of strategies have been employed by investigators from many scientific disciplines to study the podocyte. Although invaluable insights have accrued from conventional approaches, including cell culture and biochemical-based methods, many renal researchers continue to rely upon the mouse to address the form and function of the podocyte. This review summarizes how genetic manipulation in the mouse has advanced our understanding of the podocyte in relation to the maintenance of the glomerular filtration barrier in health and disease.

Molecular identification of PAL-E, a widely used endothelial-cell marker

The pathologische anatomie Leiden-endothelium (PAL-E) antibody has been used for almost 20 years as a specific marker for vascular endothelial cells. Due to the fact that this antibody works only in very limited applications, the molecular identity of PAL-E has remained unknown. In this work, we demonstrate by double stainings, cross-immunoprecipitations, and transfectants that the PAL-E antigen is identical with a protein designated PV-1 (plasmalemmal vesicle 1) or FELS (fenestrated endothelial-linked structure protein) and is not vimentin, as reported earlier. As the expression of this molecule is by no means restricted to fenestrated endothelium, we suggest the use of the name PLVAP for this protein. Molecular identification of PLVAP should help in the production of new tools for the identification of vascular as opposed to lymphatic endothelium and to elucidate the function of this protein.