4D in vivo imaging of glomerular barrier function in a zebrafish podocyte injury model

AimZebrafish larvae with their simplified pronephros are an ideal model to study glomerular physiology. Although several groups use zebrafish larvae to assess glomerular barrier function, temporary or slight changes are still difficult to measure. The aim of this study was to investigate the potential of in vivo two‐photon microscopy (2‐PM) for long‐term imaging of glomerular barrier function in zebrafish larvae.MethodsAs a proof of principle, we adapted the nitroreductase/metronidazole model of targeted podocyte ablation for 2‐PM. Combination with a strain, which expresses eGFP‐vitamin D‐binding protein in the blood plasma, led to a strain that allowed induction of podocyte injury with parallel assessment of glomerular barrier function. We used four‐dimensional (4D) 2‐PM to assess eGFP fluorescence over 26 h in the vasculature and in tubules of multiple zebrafish larvae (5 days post‐fertilization) simultaneously.ResultsBy 4D 2‐PM, we observed that, under physiological conditions, eGFP fluorescence was retained in the vasculature and rarely detected in proximal tubule cells. Application of metronidazole induced podocyte injury and cell death as shown by TUNEL staining. Induction of podocyte injury resulted in a dramatic decrease of eGFP fluorescence in the vasculature over time (about 50% and 90% after 2 and 12 h respectively). Loss of vascular eGFP fluorescence was paralleled by an endocytosis‐mediated accumulation of eGFP fluorescence in proximal tubule cells, indicating proteinuria.ConclusionWe established a microscopy‐based method to monitor the dynamics of glomerular barrier function during induction of podocyte injury in multiple zebrafish larvae simultaneously over 26 h.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/136708/1/apha12754.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/136708/2/apha12754_am.pd

SERUM AND URINE LEUCINE RICH ALPHA-2-GLYCOPROTEIN-1 IS ASSOCIATED WITH KIDNEY TRANSPLANT INJURY AND FAILURE

Affiliations are different in Web of Science publication and original journal publication. Here are given the affiliations provided in Nephrology Dialysis Transplantation publication because they are more accurate.publishersversionPeer reviewe

Potassium channels in epithelial transport

Epithelial cells in the kidney, gastrointestinal tract and exocrine glands are engaged in vectorial transport of salt and nutrients. In these tissues, K+ channels play an important role for the stabilization of membrane voltage and maintenance of the driving force for electrogenic transport. Luminal K+ channels represent an exit pathway for the excretion of K+ in secreted fluid, urine and faeces, thereby effecting body K+ homeostasis. Indeed, the expression and function of several luminal K+ channels is modulated by hormones regulating water, Na+, and K+ metabolism. In addition to net transport of K+ in the serosal (or apical) direction, K+ channels can be coupled functionally to K+-transporting ATPases such as the basolateral Na+/K+ ATPase or the luminal H+/K+ ATPase. These ATPases export Na+ or H+ and take up K+, which is then recycled via K+ channels. This review gives a short overview on the molecular identity of epithelial K+ channels and summarizes the different mechanisms of K+ channel function during transport in epithelial cell

Spatiotemporal expression patterns of sialoglycoconjugates during nephron morphogenesis and their regional and cell type-specific distribution in adult rat kidney

The expression of α2,6- and α2,3-linked sialic acids on N-glycans was studied in embryonic, postnatal, and adult rat kidney. Histochemistry and blotting using Polyporus squamosus and Sambucus nigra lectins for α2,6-linked sialic acids and the Maackia amurensis lectin for α2,3-linked sialic acids were performed and sialyltransferase activity was assayed. N-glycans with α2,6- and α2,3-linked sialic acid were differently expressed in the two embryonic anlagen and early stages of nephron. Metanephrogenic mesenchyme was positive for α2,3-linked sialic acid but not for the α2,6-linked one, which became detectable initially in the proximal part of S-shaped bodies. Collecting ducts were positive for α2,6-linked sialic acid, whereas α2,3-linked sialic acid was restricted to their ampullae. Although positive in embryonic kidney, S1 and S2 of proximal tubules became unreactive for α2,3-linked sialic acid in postnatal and adult kidneys. In adult kidney, intercalated but not principal cells of collecting ducts were reactive for α2,3-linked sialic acid. In contrast, α2,6-linked sialic acids were detected in all cells of adult kidney nephron. Blot analysis revealed a different but steady pattern of bands reactive for α2,6- and α2,3-linked sialic acid in embryonic, postnatal, and adult kidney. Activity of α2,6 and α2,3 sialyltransferases was highest in embryonic kidney and decreased over postnatal to adult kidney with the activity of α2,6 sialyltransferase always being three to fourfold that of α2,3 sialyltransferase. Thus, α2,6- and α2,3-linked sialic acids are differently expressed in embryonic anlagen and mesenchyme-derived early stages of nephron and show regional and cell type-specific differences in adult kidne

Aldosteronism and Resistant Hypertension

Resistant hypertension (RHTN) is defined as blood pressure (BP) that remains uncontrolled in spite of intake of ≥3 antihypertensive medications, ideally prescribed at optimal doses and one of which is a diuretic. The incidence of primary aldosteronism (PA) in patients with RHTN is estimated in prospective studies to be 14 to 23%, which is higher than in the general hypertensive population. Patients with PA are at an increased cardiovascular risk, as shown by higher rates of stroke, myocardial infarction, and arrhythmias compared to hypertensive individuals without PA. Likewise, RHTN is associated with adverse cardiovascular outcomes, and the contribution of PA to this increased risk is undetermined. Similar to PA, obstructive sleep apnea (OSA) is closely associated with RHTN, and a causal link between PA, OSA, and RHTN remains to be elucidated. The addition of MR antagonists to the antihypertensive regimen in patients with RHTN produces a profound BP-lowering effect, and this effect is seen in patients with or without biochemical evidence of PA, highlighting the role of relative aldosterone excess in driving treatment resistance in this group of patients

The ADF/Cofilin-Pathway and Actin Dynamics in Podocyte Injury

ADF/cofilins are the major regulators of actin dynamics in mammalian cells. The activation of ADF/cofilins is controlled by a variety of regulatory mechanisms. Dysregulation of ADF/cofilin may result in loss of a precisely organized actin cytoskeletal architecture and can reduce podocyte migration and motility. Recent studies suggest that cofilin-1 can be regulated through several extracellular signals and slit diaphragm proteins. Cofilin knockdown and knockout animal models show dysfunction of glomerular barrier and filtration with foot process effacement and loss of secondary foot processes. This indicates that cofilin-1 is necessary for modulating actin dynamics in podocytes. Podocyte alterations in actin architecture may initiate or aid the progression of a large variety of glomerular diseases, and cofilin activity is required for reorganization of an intact filtration barrier. Since almost all proteinuric diseases result from a similar phenotype with effacement of the foot processes, we propose that cofilin-1 is at the centre stage of the development of proteinuria and thus may be an attractive drug target for antiproteinuric treatment strategies

The Autoimmune Tautology: An In Silico Approach

There is genetic evidence of similarities and differences among autoimmune diseases (AIDs) that warrants looking at a general panorama of what has been published. Thus, our aim was to determine the main shared genes and to what extent they contribute to building clusters of AIDs. We combined a text-mining approach to build clusters of genetic concept profiles (GCPs) from the literature in MedLine with knowledge of protein-protein interactions to confirm if genes in GCP encode proteins that truly interact. We found three clusters in which the genes with the highest contribution encoded proteins that showed strong and specific interactions. After projecting the AIDs on a plane, two clusters could be discerned: Sjögren's syndrome—systemic lupus erythematosus, and autoimmune thyroid disease—type1 diabetes—rheumatoid arthritis. Our results support the common origin of AIDs and the role of genes involved in apoptosis such as CTLA4, FASLG, and IL10

Relevance of VEGF and Nephrin Expression in Glomerular Diseases

The glomerular filtration barrier is affected in a large number of acquired and inherited diseases resulting in extensive leakage of plasma albumin and larger proteins, leading to nephrotic syndrome and end-stage renal disease. Unfortunately, the molecular mechanisms governing the development of the nephrotic syndrome remain poorly understood. Here, I give an overview of recent investigations that have focused on characterizing the interrelationships between the slit diaphragm components and podocytes-secreted VEGF, which have a significant role for maintaining the normal podocyte structure and the integrity of the filtering barrier