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In recent years, many light-microscopy protocols have been published for visualization of nanoscale structures in the kidney. These protocols present researchers with new tools to evaluate both foot process anatomy and effacement, as well as protein distributions in foot processes, the slit diaphragm and in the glomerular basement membrane. However, these protocols either involve the application of different complicated super resolution microscopes or lengthy sample preparation protocols. Here, we present a fast and simple, five-hour long procedure for three-dimensional visualization of kidney morphology on all length scales. The protocol combines optical clearing and tissue expansion concepts to produce a mild swelling, sufficient for resolving nanoscale structures using a conventional confocal microscope. We show that the protocol can be applied to visualize a wide variety of pathologic features in both mouse and human kidneys. Thus, our fast and simple protocol can be beneficial for conventional microscopic evaluation of kidney tissue integrity both in research and possibly in future clinical routines., QC 20220520

Cell cultures are often used to study physiological processes in health and disease. It is well-known that cells change their gene expression in vitro compared to in vivo, but it is rarely experimentally addressed. High glucose is a known trigger of apoptosis in proximal tubular cells (PTC). Here we used RNA-seq to detect differentially expressed genes in cultures of primary rat PTC, 3 days old, compared to cells retrieved directly from rat outer renal cortex and between PTC exposed to 15 mM glucose and control for 8 h. The expression of 6,174 genes was significantly up- or downregulated in the cultures of PTC compared to the cells in the outer renal cortex. Most altered were mitochondrial and metabolism related genes. Gene expression of proapoptotic proteins were upregulated and gene expression of antiapoptotic proteins were downregulated in PTC. Expression of transporter related genes were generally downregulated. After 8 h, high glucose had not altered the gene expression in PTC. The current study provides evidence that cells alter their gene expression in vitro compared to in vivo and suggests that short-term high glucose exposure can trigger apoptosis in PTC without changing the gene expression levels of apoptotic proteins., QC 20200729

The ion pump Na+, K+-ATPase (NKA) is a receptor for the cardiotonic steroid ouabain. Subsaturating concentration of ouabain triggers intracellular calcium oscillations, stimulates cell proliferation and adhesion, and protects from apoptosis. However, it is controversial whether ouabain-bound NKA is considered a signal transducer. To address this question, we performed a global analysis of protein phosphorylation in COS-7 cells, identifying 2580 regulated phosphorylation events on 1242 proteins upon 10- and 20-min treatment with ouabain. Regulated phosphorylated proteins include the inositol triphosphate receptor and stromal interaction molecule, which are essential for initiating calcium oscillations. Hierarchical clustering revealed that ouabain triggers a structured phosphorylation response that occurs in a well-defined, time-dependent manner and affects specific cellular processes, including cell proliferation and cell-cell junctions. We additionally identify regulation of the phosphorylation of several calcium and calmodulin-dependent protein kinases (CAMKs), including 2 sites of CAMK type II-gamma (CAMK2G), a protein known to regulate apoptosis. To verify the significance of this result, CAMK2G was knocked down in primary kidney cells. CAMK2G knockdown impaired ouabain-dependent protection from apoptosis upon treatment with high glucose or serum deprivation. In conclusion, we establish NKA as the coordinator of a broad, tightly regulated phosphorylation response in cells and define CAMK2G as a downstream effector of NKA.-Panizza, E., Zhang, L., Fontana, J. M., Hamada, K., Svensson, D., Akkuratov, E. E., Scott, L., Mikoshiba, K., Brismar, H., Lehtio, J., Aperia, A. Ouabain-regulated phosphoproteome reveals molecular mechanisms for Na+, K+-ATPase control of cell adhesion, proliferation, and survival., QC 20190924

It is generally believed that cells that are unable to downregulate glucose transport are particularly vulnerable to hyperglycemia. Yet little is known about the relation between expression of glucose transporters and acute toxic effects of high glucose exposure.Here we have, in an ex vivo study on rat renal cells, compared the apoptotic response to a moderate increase in glucose concentration. We have studied the cell types that commonly are targeted in diabetic kidney disease (DKD): proximal tubule cells (PTC) that express SGLT2, mesangial cells (MC) that express SGLT1, and podocytes that lack SGLT and take up glucose via the insulin dependent GLUT4.PTC and MC responded within 4-8 h exposure to 15 mM glucose with translocation of the apoptotic protein Bax to mitochondria and increased apoptotic index. SGLT down-regulation and exposure to SGLT inhibitors abolished the apoptotic response. Onset of overt DKD generally coincides with onset of albuminuria. Albumin had an additive effect on the apoptotic response. Ouabain, which interferes with apoptotic onset, rescued from the apoptotic response. Insulin supplemented podocytes remained resistant to 15 and 30 mM glucose for at least 24 h.Our study points to a previously unappreciated role of SGLT dependent glucose uptake as a risk-factor for diabetic complications and highlights the importance of therapeutic approaches that specifically target the different cell types in DKD., QC 20190429

QC 20190404

QC 20190428

QC 20190428