adrenomedullin and nephrin

Podocyte injury is a key event in proteinuric kidney disease and eventually glomerular scarring. While adrenomedullin (AM), a potent vasodilatory peptide, has been reported to confer renoprotection in several experimental models of kidney diseases, its effect on injured podocytes and the related mechanism is still largely unknown.. Employing Western blotting analysis, immunoprecipitation and immunofluorescence, we investigated the effects of AM on the expressions of podocyte cytoskeletal proteins and Rho-family small GTPases (Rho GTPases) in puromycin aminonucleoside (PAN)-induced podocyte injury, both in cultured podocytes and in PAN nephrosis rats. Urinary protein excretion and the morphologic changes of kidney in PAN nephrosis rats were evaluated. Glutathione-S-transferase pull-down assay was applied for Rho GTPases activity.. PAN induced massive albuminuria and morphologic injury, which were significantly mitigated by AM administration. AM significantly antagonized not only the PAN-decreased expressions of synaptopodin, nephrin, CD2AP and podocin, but also the PAN-disrupted interactions between synaptopodin-RhoA, nephrin-CD2AP, and CD2AP-Rac1-cortactin. These effects of AM in cultured podocytes were mostly significantly blocked by H89, a PKA inhibitor. AM dramatically upregulated the PAN-induced Rho GTPases protein expressions and their activities. PAN increased the expressions of endogenous AM and its receptor RAMP2 which was furthermore upregulated by AM administration.. AM alleviated podocyte injury induced by PAN both in cell culture and in PAN nephrosis. The beneficial effects of AM on podocytes can be attributable to direct modulation of podocyte cytoskeletal proteins and Rho GTPases, mainly via a PKA-dependent pathway.

Topics: Adaptor Proteins, Signal Transducing; Adrenomedullin; Albuminuria; Animals; cdc42 GTP-Binding Protein; Cell Line; Cortactin; Cytoskeletal Proteins; Intracellular Signaling Peptides and Proteins; Kidney Glomerulus; Male; Membrane Proteins; Mice; Microfilament Proteins; Nephrosis; Neuropeptides; Podocytes; Puromycin Aminonucleoside; rac1 GTP-Binding Protein; Rats; Rats, Sprague-Dawley; Receptor Activity-Modifying Protein 2; rho GTP-Binding Proteins; rhoA GTP-Binding Protein; Vasodilator Agents

Adrenomedullin (ADM) has antiproliferative effects on glomerular mesangial cells. The study was performed to determine changes in glomerular gene expression of the ADM system by ADM treatment in anti-Thy1 glomerulonephritis (GN).. GN in rats was induced by injecting anti-Thy-1 antibody. To show the effect of ADM treatment, rats received ADM from day 3 to day 6 of GN. Supplemental rats were sacrificed on day 3, 7 and 14 of GN to show the expression pattern of adrenomedullin and its receptors. Glomeruli were prepared by sieving or laser-assisted microdissection. Expression of ADM, calcitonin receptor-like receptor (CLR), receptor activity-modifying proteins (RAMP) 1-3, CD34, Thy1 and nephrin was analyzed using real-time PCR.. During GN a reduction of CLR and RAMP 2 + 3 expressions was detected on days 3, 7 and 14, while RAMP 1 rose. ADM mRNA decreased on days 3 and 7. Thy1 expression as a surrogate of mesangial cell number was downregulated during GN. A significant reduction of CD34 expression, as a surrogate for endothelial cell number, was detected on day 7. A tendency towards reduction of nephrin gene expression, as a surrogate for number of podocytes, was seen. The administration of ADM during GN did not change the expression on Thy1, CD34 or nephrin. The results were similar for microdissected and sieved glomeruli. In ADM-treated GN animals ADM gene expression rose compared to untreated GN animals on day 6. These effects were detected both in sieved and microdissected glomeruli. ADM administration did not change the expression of the receptors.. The downregulation of adrenomedullin during GN at the gene level can be improved by ADM application.

Topics: Adrenomedullin; Animals; Antigens, CD34; Calcitonin Receptor-Like Protein; Down-Regulation; Glomerulonephritis; Intracellular Signaling Peptides and Proteins; Isoantibodies; Kidney Glomerulus; Male; Membrane Proteins; Rats; Rats, Sprague-Dawley; Receptor Activity-Modifying Proteins; Receptors, Adrenomedullin; Receptors, Calcitonin; Receptors, G-Protein-Coupled