Reabsorption in the proximal tubuli-ultrastructural evidence for a novel aspect of renal VEGF trafficking

Immunoregulation mechanism of VEGF signaling pathway inhibitors and its efficacy on the kidney

Angiogenesis and immunosuppression are closely related pathophysiologic processes. Widely prescribed in malignant tumor and proliferative retinal lesions, VEGF signaling pathway inhibitors may cause hypertension and renal injury in some patients, presenting with proteinuria, nephrotic syndrome, renal failure and thrombotic microangiopathy. VEGF signaling pathway inhibitors block the action of both VEGF-A and VEGF-C. However, VEGF-A and VEGF-C produced by podocytes are vital to maintain the physiological function of glomerular endothelial cells and podocytes. There is still no effective treatment for kidney disease associated with VEGF signaling pathway inhibitors and some patients have progressive renal failure even after withdrawal of the drug. Recent studies reveal that blocking of VEGF-A and VEGF-C can activate CD4 +and CD8+ T cells, augment antigen-presenting function of dendritic cells, enhance cytotoxicity of macrophages and initiate complement cascade activation. VEGF and VEGFR are expressed in immune cells, which are involved in the immunosuppression and cross-talk among immune cells. This review summarizes the expression and function of VEGF-A and VEGF-C in the kidney. The current immunoregulation mechanisms of VEGF signaling pathway inhibitors are reviewed. Finally, combinate strategies are summarized to highlight the proposal for VEGF signaling pathway inhibitors.

A Homozygous Dab1-/- Is a Potential Novel Cause of Autosomal Recessive Congenital Anomalies of the Mice Kidney and Urinary Tract

This study aimed to explore morphology changes in the kidneys of Dab1^−/− (yotari) mice, as well as expression patterns of reelin, NOTCH2, LC3B, and cleaved caspase3 (CASP3) proteins, as potential determinants of normal kidney formation and function. We assumed that Dab1 functional inactivation may cause disorder in a wide spectrum of congenital anomalies of the kidney and urinary tract (CAKUT). Animals were sacrificed at postnatal days P4, P11, and P14. Paraffin-embedded kidney tissues were sectioned and analyzed by immunohistochemistry using specific antibodies. Kidney specimens were examined by bright-field, fluorescence, and electron microscopy. Data were analyzed by two-way ANOVA and t-tests. We noticed that yotari kidneys were smaller in size with a reduced diameter of nephron segments and thinner cortex. TEM microphotographs revealed foot process effacement in the glomeruli (G) of yotari mice, whereas aberrations in the structure of proximal convoluted tubules (PCT) and distal convoluted tubules (DCT) were not observed. A significant increase in reelin expression, NOTCH2, LC3B and cleaved CASP3 proteins was observed in the glomeruli of yotari mice. Renal hypoplasia in conjunction with foot process effacement and elevation in the expression of examined proteins in the glomeruli revealed CAKUT phenotype and loss of functional kidney tissue of yotari.

Endothelial-epithelial communication in polycystic kidney disease: Role of vascular endothelial growth factor signalling

Whereas targeting the cyst epithelium and its molecular machinery has been the prevailing clinical strategy for polycystic kidney disease, the endothelium, including blood vasculature and lymphatics, is emerging as an important player in this disorder. In this Review, we provide an overview of the structural and functional alterations to blood vasculature and lymphatic vessels in the polycystic kidney. We also discuss evidence for vascular endothelial growth factor signalling, otherwise critical for endothelial cell development and maintenance, as being a fundamental molecular pathway in polycystic kidney disease and a potential therapeutic target for modulating cyst expansion.

Ultrastructural characterization of vitamin D receptors and metabolizing enzymes in the lipid droplets of the fatty liver in rat

Vitamin D is a steroid hormone with numerous actions in the organism. There are strong evidences that relate vitamin D deficiency with liver lipid metabolism disturbances, but the mechanism of this action is still unknown. In our previous work we postulated the localization and accumulation of vitamin D receptor (VDR) in membrane of the lipid droplets (LDs) in hepatocytes. In this study, we applied the transmission electron microscopy (TEM) to confirm this hypothesis by using a long-term (6 months) high sucrose intake rat model that was previously found to be appropriate for research of the hepatic lipid accumulation. In addition to the VDR, we also found key vitamin D metabolizing enzymes, 1α-hydroxylase and CYP 24 associated with the membrane of the LDs. A light-microscopy data revealed significant increase in expression of VDR and CYP 24 in liver of high-sucrose treated rats, in comparison to controlones. According to the best of our knowledge, this is a first study confirming the presence of the VDR in the membrane of the LDs in general and also in particular in LDs of the hepatocytes that were accumulated as a consequence of the prolonged high sucrose intake. Moreover, we found association of main vitamin D metabolizing enzymes with LD membrane. These results provide a new insight in the possible relation of vitamin D signalling system with LD morphology and function and with the lipid metabolism in general.

Dietary DHA/EPA supplementation ameliorates diabetic nephropathy by protecting from distal tubular cell damage

The aim was to explore the influence of experimental diabetes mellitus type 1 (DM1) and potential protective/deleterious effects of different dietary n-6/n-3 PUFA ratios on renal phospholipid composition and pathological changes caused by DM1. Male Wistar rats were injected with 55 mg/kg streptozotocin or citrate buffer (control group). Control (C) and diabetic groups (STZ) were fed with n-6/n-3 ratio of ≈ 7, STZ + N6 with n-6/n-3 ratio ≈ 60 and STZ + DHA with n-6/n-3 ratio of ≈ 1 containing 16% EPA and 19% DHA. Tissues were harvested 30 days after DM1 induction. Blood and kidneys were collected and analysed for phospholipid fatty acid composition, pathohystological changes, ectopic lipid accumulation and expression of VEGF, NF-kB and special AT-rich sequence-binding protein-1 (SATB1). Pathological changes were studied also by using transmission electron microscopy, after immunostaining for VEGF. Substantial changes in renal phospholipid fatty acid composition resulted from DM1 and dietary PUFA manipulation. Extensive vacuolization of distal tubular cells (DTCs) was found in DM1, but it was attenuated in the STZ + DHA group, in which the highest renal NF-kB expression was observed. The ectopic lipid accumulation was observed in proximal tubular cells (PTCs) of all diabetic animals, but it was worsened in the STZ + N6 group. In DM1, we found disturbance of VEGF-transporting vesicular PTCs system, which was substantially worsened in STZ + DHA and STZ + N6. Results have shown that the early phase of DN is characterized with extent damage and vacuolization of DTCs, which could be attenuated by DHA/EPA supplementation. We concluded that dietary fatty acid composition can strongly influence the outcomes of DN.