Effect of mycophenolic acid in experimental, nontransplant glomerular diseases: new mechanisms beyond immune cells

Podocyte dysfunction, represented by foot process effacement and proteinuria, is often the starting point for progressive kidney disease. Therapies aimed at the cellular level of the disease are currently not available. Here we show that induction of urokinase receptor (uPAR) signaling in podocytes leads to foot process effacement and urinary protein loss via a mechanism that includes lipid-dependent activation of alphavbeta3 integrin. Mice lacking uPAR (Plaur-/-) are protected from lipopolysaccharide (LPS)-mediated proteinuria but develop disease after expression of a constitutively active beta3 integrin. Gene transfer studies reveal a prerequisite for uPAR expression in podocytes, but not in endothelial cells, for the development of LPS-mediated proteinuria. Mechanistically, uPAR is required to activate alphavbeta3 integrin in podocytes, promoting cell motility and activation of the small GTPases Cdc42 and Rac1. Blockade of alphavbeta3 integrin reduces podocyte motility in vitro and lowers proteinuria in mice. Our findings show a physiological role for uPAR signaling in the regulation of kidney permeability.

The 2012 Kidney Disease: Improving Global Outcomes (KDIGO) clinical practice guideline on glomerulonephritis (GN) is intended to assist the practitioner caring for patients with GN. Two chapters of this guideline focus specifically on nephrotic syndrome in children. Guideline development followed a thorough evidence review, and management recommendations and suggestions were based on the best available evidence. Critical appraisal of the quality of evidence and strength of recommendations followed the Grades of Recommendation Assessment, Development and Evaluation (GRADE) approach. Chapters 3 and 4 of the guideline focus on the management of nephrotic syndrome in children aged 1-18 years. Guideline recommendations for children who have steroid-sensitive nephrotic syndrome (SNSS), defined by their response to corticosteroid therapy with complete remission, are addressed here. Recommendations for those with steroid-resistant nephrotic syndrome (SRNS) (i.e., do not achieve complete remission) are discussed in the companion article. Limitations of the evidence, including the paucity of large-scale randomized controlled trials, are discussed. This article provides a short description of the KDIGO process, the guideline recommendations for treatment of SSNS in children and a brief review of relevant treatment trials related to each recommendation.

Immunocompetent cells infiltrate the kidney in several models of experimental hypertension. We have previously shown that reduction of this infiltrate results in prevention of salt-sensitive hypertension induced by short-term angiotensin II infusion and nitric oxide inhibition (Quiroz Y, Pons H, Gordon KI, Rincón J, Chávez M, Parra G, Herrera-Acosta J, Gómez-Garre D, Largo R, Egido J, Johnson RJ, and Rodríguez-Iturbe B. Am J Physiol Renal Physiol 281: F38-F47, 2001; Rodríguez-Iturbe B, Pons H, Quiroz Y, Gordon K, Rincón J, Chávez M, Parra G, Herrera-Acosta J, Gómez-Garre D, Largo R, Egido J, and Johnson RJ. Kidney Int 59: 2222-2232, 2001). We therefore studied whether hypertension could be controlled in genetically hypertensive rats [spontaneously hypertensive rats (SHR)] by the administration of 20 mg x kg(-1) x day(-1) of the immunosuppressive drug mycophenolate mofetil (MMF group; n = 35). Other SHR received vehicle (n = 35), and Wistar-Kyoto rats (n = 20) were used as controls. MMF or vehicle was given in two separate 4-wk periods, separated by a 3-wk interval. Systemic hypertension was reduced to normal levels in both periods of MMF treatment in association with a reduction in lymphocyte, macrophage, and angiotensin II-positive cells infiltrating the kidney. Oxidative stress was also reduced by MMF, as indicated by a reduction in urinary malondialdehyde (MDA), renal MDA content, and superoxide-positive cells, and was highly correlated with blood pressure levels. We conclude that the renal immune infiltrate plays a major role in the hypertension in SHR.