nephrin and AIDS-Associated-Nephropathy

Development of pharmacologic agents that protect podocytes from injury is a critical strategy for the treatment of kidney glomerular diseases. Retinoic acid reduces proteinuria and glomerulosclerosis in multiple animal models of kidney diseases. However, clinical studies are limited because of significant side effects of retinoic acid. Animal studies suggest that all trans retinoic acid (ATRA) attenuates proteinuria by protecting podocytes from injury. The physiological actions of ATRA are mediated by binding to all three isoforms of the nuclear retinoic acid receptors (RARs): RARα, RARβ, and RARγ. We have previously shown that ATRA exerts its renal protective effects mainly through the agonism of RARα. Here, we designed and synthesized a novel boron-containing derivative of the RARα-specific agonist Am580. This new derivative, BD4, binds to RARα receptor specifically and is predicted to have less toxicity based on its structure. We confirmed experimentally that BD4 binds to RARα with a higher affinity and exhibits less cellular toxicity than Am580 and ATRA. BD4 induces the expression of podocyte differentiation markers (synaptopodin, nephrin, and WT-1) in cultured podocytes. Finally, we confirmed that BD4 reduces proteinuria and improves kidney injury in HIV-1 transgenic mice, a model for HIV-associated nephropathy (HIVAN). Mice treated with BD4 did not develop any obvious toxicity or side effect. Our data suggest that BD4 is a novel RARα agonist, which could be used as a potential therapy for patients with kidney disease such as HIVAN.

Topics: AIDS-Associated Nephropathy; Animals; Benzoates; Benzopyrans; Binding, Competitive; Body Weight; Boron Compounds; Cell Differentiation; Cell Survival; Cells, Cultured; Female; Gene Expression Regulation; Kidney; Kidney Diseases; Male; Membrane Proteins; Mice; Mice, Transgenic; Microfilament Proteins; Molecular Structure; Podocytes; Proteinuria; Receptors, Retinoic Acid; Retinoic Acid Receptor alpha; Retinoids; Reverse Transcriptase Polymerase Chain Reaction; Tetrahydronaphthalenes; WT1 Proteins

Recent studies have reported that statins have renoprotective effects, independent from lowering plasma cholesterol. In this study, we examined whether statins were beneficial in a murine model of HIV-associated nephropathy (HIVAN).. We used conditional transgenic mice that express one of the HIV-1 accessory genes, vpr, selectively in podocytes using podocin promoter and the Tet-on system. These mice develop aggressive collapsing focal segmental glomerular sclerosis with massive proteinuria and deterioration of renal function within 4 weeks following heminephrectomy and doxycycline administration. Fluvastatin was administrated simultaneously with doxycycline, and the effect was compared with untreated controls after 4 weeks.. Fluvastatin at 10 mg/kg/day significantly decreased urinary albumin excretion (87 versus 11 mg/day, P < 0.01) and glomerular sclerosis (2.4 versus 1.0, P < 0.01, assessed by semi-quantitative scoring: 0-4). Fluvastatin also decreased serum creatinine and total cholesterol, but these differences were not statistically significant (0.36 versus 0.32 mg/dl, P = 0.35; 492 versus 378 mg/dl, P = 0.11, respectively). Phenotypic changes in podocytes, as indicated by the downregulation of nephrin, Wilms' tumour 1 and synaptopodin, along with upregulation of proliferating cell nuclear antigen, were attenuated by fluvastatin, suggesting its protective effects against podocyte injuries. In cultured podocytes, angiotensin II treatment decreased nephrin expression to 13% of basal levels, which was reversed to 58% by adding fluvastatin.. In conclusion, fluvastatin was effective in treating experimental HIVAN. The beneficial effect of this drug might be caused, in part, by preserving nephrin expression in podocytes against angiotensin II-mediated injury.

Topics: AIDS-Associated Nephropathy; Angiotensin II; Angiotensin II Type 1 Receptor Blockers; Animals; Blotting, Western; Cells, Cultured; Disease Models, Animal; Fatty Acids, Monounsaturated; Fluorescent Antibody Technique; Fluvastatin; Genes, Wilms Tumor; Glomerulosclerosis, Focal Segmental; Immunoenzyme Techniques; Indoles; Kidney; Male; Membrane Proteins; Mice; Mice, Transgenic; Microfilament Proteins; Nephrectomy; Phenotype; Podocytes; Proteinuria

Multiple studies have linked podocyte gene variants to diverse sporadic nephropathies, including HIV-1-associated nephropathy (HIVAN). We previously used linkage analysis to identify a major HIVAN susceptibility locus in mouse, HIVAN1. We performed expression quantitative trait locus (eQTL) analysis of podocyte genes in HIV-1 transgenic mice to gain further insight into genetic susceptibility to HIVAN. In 2 independent crosses, we found that transcript levels of the podocyte gene nephrosis 2 homolog (Nphs2), were heritable and controlled by an ancestral cis-eQTL that conferred a 3-fold variation in expression and produced reactive changes in other podocyte genes. In addition, Nphs2 expression was controlled by 2 trans-eQTLs that localized to the nephropathy susceptibility intervals HIVAN1 and HIVAN2. Transregulation of podocyte genes was observed in the absence of HIV-1 or glomerulosclerosis, indicating that nephropathy susceptibility alleles induce latent perturbations in the podocyte expression network. Presence of the HIV-1 transgene interfered with transregulation, demonstrating effects of gene-environment interactions on disease. These data demonstrate that transcript levels of Nphs2 and related podocyte-expressed genes are networked and suggest that the genetic lesions introduced by HIVAN susceptibility alleles perturb this regulatory pathway and transcriptional responses to HIV-1, increasing susceptibility to nephropathy.

Topics: AIDS-Associated Nephropathy; Animals; Chromosomes; Crosses, Genetic; Gene Expression; Gene Expression Regulation; Genetic Linkage; Genetic Predisposition to Disease; HIV-1; Intracellular Signaling Peptides and Proteins; Kidney; Membrane Proteins; Mice; Mice, Inbred C57BL; Mice, Inbred Strains; Mice, Transgenic; Microfilament Proteins; Myosin Heavy Chains; Nonmuscle Myosin Type IIA; Phosphoinositide Phospholipase C; Phylogeny; Podocytes; Polymorphism, Single Nucleotide; Quantitative Trait Loci

To determine whether HIV-1 Tat may directly alter glomerular permeability in HIV-associated nephropathy (HIVAN).. Heavy proteinuria is a hallmark of HIVAN. The slit diaphragm is the ultimate glomerular filtration barrier critical for maintaining the efficiency of the ultrafiltration unit of the kidney. In this study, we evaluated the direct effect of Tat protein on the permeability of isolated glomeruli and on the expression of nephrin, the main slit diaphragm component, by human cultured podocytes.. Permeability was studied by measuring the permeability to albumin in isolated rat glomeruli. We also evaluated the expression of nephrin in human cultured podocytes by using immunofluorescence and Western blot.. We found that Tat increased albumin permeability in isolated glomeruli, and rapidly induced the redistribution and loss of nephrin in cultured podocytes. Pretreatment of glomeruli and podocytes with blocking antibodies showed that Tat reduced nephrin expression by engaging vascular endothelial growth factor receptors types 2 and 3 and the integrin alphavbeta3. Pre-incubation of podocytes with two platelet-activating factor (PAF) receptor antagonists prevented the loss and redistribution of nephrin induced by Tat, suggesting that PAF is an intracellular mediator of Tat action. Tat induced a rapid PAF synthesis by podocytes. When podocytes transfected to overexpress PAF-acetylhydrolase, the main catabolic enzyme of PAF, were stimulated with Tat, the redistribution and loss of nephrin was abrogated.. The present results define a mechanism by which Tat may reduce nephrin expression in podocytes, thus increasing glomerular permeability. This provides new insights in the understanding of HIVAN pathogenesis.

Topics: 1-Alkyl-2-acetylglycerophosphocholine Esterase; AIDS-Associated Nephropathy; Animals; Cells, Cultured; Cytoskeleton; Gene Products, tat; HIV-1; Humans; Kidney Glomerulus; Membrane Proteins; Permeability; Podocytes; Rats; Rats, Sprague-Dawley; Recombinant Proteins; Serum Albumin; tat Gene Products, Human Immunodeficiency Virus; Tissue Culture Techniques; Transfection

Human immunodeficiency virus (HIV)-1-associated nephropathy (HIVAN) is characterized by collapsing focal and segmental glomerulosclerosis (FSGS) and microcystic tubular dilatation. HIV-1 infection is also associated with other forms of nephropathy, including mesangial hyperplasia. Since HIV-1 gene products are detected in podocytes and other renal cells, it remains uncertain whether podocyte-restricted HIV-1 gene expression can account for the full spectrum of renal lesions involving nonpodocytes.. To define the role of podocyte-restricted HIV-1 gene expression in the progression of HIVAN, we generated transgenic mice that express nonstructural HIV-1 genes selectively in podocytes.. Four of the seven founder mice developed proteinuria and nephropathy. In a subsequently established transgenic line, reverse transcription-polymerase chain reaction (RT-PCR) analysis detected mRNAs for vif, vpr, nef, and spliced forms of tat and rev, but not vpu, in the kidney. In situ hybridization localized HIV-1 RNA to the podocyte. Transgenic mice on FVB/N genetic background exhibited cuboidal morphology of podocytes with reduced extension of primary and foot processes at 2 weeks of age. After 3 weeks of age, these mice developed massive and nonselective proteinuria with damage of podocytes and other glomerular cells and, after 4 weeks of age, collapsing FSGS and microcystic tubular dilatation. In marked contrast, transgenic mice with C57BL/6 genetic background showed either normal renal histology or only mild mesangial expansion without overt podocyte damage.. The present study demonstrates that podocyte-restricted expression of HIV-1 gene products is sufficient for the development of collapsing glomerulosclerosis in the setting of susceptible genetic background.

Topics: AIDS-Associated Nephropathy; Animals; Female; Gene Expression Regulation, Viral; Genetic Predisposition to Disease; HIV-1; Male; Membrane Proteins; Mice; Mice, Inbred C57BL; Mice, Transgenic; Nephrotic Syndrome; Podocytes; Promoter Regions, Genetic; Transgenes