Exaggerated renal fibrosis in P2X4 receptor-deficient mice following unilateral ureteric obstruction

Background The ATP-sensitive P2X7 receptor (P2X7R) has been shown to contribute to renal injury in nephrotoxic nephritis, a rodent model of acute glomerulonephritis, and in unilateral ureteric obstruction (UUO), a rodent model of chronic interstitial inflammation and fibrosis. Renal tubular cells, endothelial cells and macrophages also express the closely related P2X4 receptor (P2X4R), which is chromosomally co-located with P2X7R and has 40% homology; it is also pro-inflammatory and has been shown to interact with P2X7R to modulate its pro-apoptotic and pro-inflammatory effects. Therefore, we chose to explore the function of P2X4R in the UUO model of renal injury using knockout mice. We hypothesized that UUO-induced tubulointerstitial damage and fibrosis would also be attenuated in P2X4R−/− mice. Method P2X4R−/− and wild-type (WT) mice were subjected to either UUO or sham operation. Kidney samples taken on Days 7 and 14 were evaluated for renal inflammation and fibrosis, and expression of pro-fibrotic factors. Results To our surprise, the obstructed kidney in P2X4R−/− mice showed more severe renal injury, more collagen deposition (picrosirius red staining, increase of 53%; P < 0.05) and more type I collagen staining (increase of 107%; P < 0.01), as well as increased mRNA for TGF-β (increase of 102%, P < 0.0005) and CTGF (increase of 157%; P < 0.05) by Day 14, compared with the UUO WT mice. Conclusion These findings showed that lack of P2X4R expression leads to increased renal fibrosis, and increased expression of TGF-β and CTGF in the UUO mode

Modification of an aggressive model of Alport Syndrome reveals early differences in disease pathogenesis due to genetic background

The link between mutations in collagen genes and the development of Alport Syndrome has been clearly established and a number of animal models, including knock-out mouse lines, have been developed that mirror disease observed in patients. However, it is clear from both patients and animal models that the progression of disease can vary greatly and can be modifed genetically. We have identifed a point mutation in Col4a4 in mice where disease is modifed by strain background, providing further evidence of the genetic modifcation of disease symptoms. Our results indicate that C57BL/6J is a protective background and postpones end stage renal failure from 7 weeks, as seen on a C3H background, to several months. We have identifed early diferences in disease progression, including expression of podocyte-specifc genes and podocyte morphology. In C57BL/6J mice podocyte efacement is delayed, prolonging normal renal function. The slower disease progression has allowed us to begin dissecting the pathogenesis of murine Alport Syndrome in detail. We fnd that there is evidence of diferential gene expression during disease on the two genetic backgrounds, and that disease diverges by 4 weeks of age. We also show that an infammatory response with increasing MCP-1 and KIM-1 levels precedes loss of renal function

A novel model of nephrotic syndrome results from a point mutation in Lama5 and is modified by genetic background

Nephrotic syndrome is characterised by severe proteinuria, hypoalbuminaemia, oedema and hyperlipidaemia. Genetic studies of nephrotic syndrome have led to the identification of proteins playing a crucial role in slit diaphragm signalling, regulation of actin cytoskeleton dynamics and cell-matrix interactions. The laminin α5 chain is essential for embryonic development and, in association with laminin β2 and laminin γ1, it is a major component of the glomerular basement membrane. Mutations in LAMA5 were recently identified in children with nephrotic syndrome. We have identified a novel missense mutation (E884G) in the uncharacterised L4a domain of LAMA5 where homozygous mice develop nephrotic syndrome with severe proteinuria with histological and ultrastructural changes in the glomerulus. The levels of LAMA5 are reduced in vivo and the assembly of the laminin 521 heterotrimer significantly reduced in vitro. Proteomic analysis of the glomerular extracellular fraction revealed changes in the matrix composition. Importantly, the genetic background had a significant effect on aspects of disease progression from proteinuria to changes in podocyte morphology. This novel model will provide insights into patho-mechanisms of nephrotic syndrome and pathways that influence the response to a dysfunctional glomerular basement membrane

Plasma hepcidin levels are elevated but responsive to erythropoietin therapy in renal disease

Hepcidin is a critical inhibitor of iron export from macrophages, enterocytes, and hepatocytes. Given that it is filtered and degraded by the kidney, its elevated levels in renal failure have been suggested to play a role in the disordered iron metabolism of uremia, including erythropoietin resistance. Here, we used a novel radioimmunoassay for hepcidin-25, the active form of the hormone, to measure its levels in renal disease. There was a significant diurnal variation of hepcidin and a strong correlation to ferritin levels in normal volunteers. In 44 patients with mild to moderate kidney disease, hepcidin levels were significantly elevated, positively correlated with ferritin but inversely correlated with the estimated glomerular filtration rate. In 94 stable hemodialysis patients, hepcidin levels were also significantly elevated, but this did not correlate with interleukin-6 levels, suggesting that increased hepcidin was not due to a general inflammatory state. Elevated hepcidin was associated with anemia, but, intriguingly, the erythropoietin dose was negatively correlated with hepcidin, suggesting that erythropoietin suppresses hepcidin levels. This was confirmed in 7 patients when hepcidin levels significantly decreased after initiation of erythropoietin treatment. Our results show that hepcidin is elevated in renal disease and suggest that higher hepcidin levels do not predict increased erythropoietin requirements

Randomized trial on the effect of an oral spleen tyrosine kinase inhibitor in the treatment of IgA nephropathy

Introduction We reported increased spleen tyrosine kinase (SYK) expression in kidney biopsies of patients with IgA nephropathy (IgAN) and that inhibition of SYK reduces inflammatory cytokines production from IgA stimulated mesangial cells. Methods This study was a double-blind, randomised, placebo-controlled phase 2 trial of fostamatinib (an oral SYK inhibitor) in 76 patients with IgAN. Patients were randomised to receive placebo, fostamatinib at 100 mg or 150 mg twice daily for 24 weeks on top of maximum tolerated dose of renin-angiotensin system inhibitors (RASi). The primary end point was reduction of proteinuria. Secondary endpoints included change from baseline in eGFR and kidney histology. Results While we could not detect significant reduction in proteinuria with fostamatinib overall, in a pre-determined subgroup analysis, there was a trend for dose-dependent reduction in median proteinuria (from baseline to 24 weeks by 14%, 27% and 36% in the placebo, fostamatinib 100 mg and 150 mg groups respectively) in patients with baseline urinary protein to creatinine ratios (UPCR) more than 1000 mg/g. Kidney function (eGFR) remained stable in all groups. Fostamatinib was well tolerated. Side effects included diarrhea, hypertension and increased liver enzymes. Thirty-nine patients underwent repeat biopsy showing reductions in SYK staining associated with therapy at low dose (-1.5 v 1.7 SYK+ cells/glomerulus in the placebo group, p<0.05). Conclusions There was a trend towards reduction in proteinuria with fostamatinib in a predefined analysis of high risk patients with IgAN despite maximal care, as defined by baseline UPCR greater than 1000 mg/g. Further study may be warranted

Oncogenic Signaling Pathways in The Cancer Genome Atlas

Genetic alterations in signaling pathways that control cell-cycle progression, apoptosis, and cell growth are common hallmarks of cancer, but the extent, mechanisms, and co-occurrence of alterations in these pathways differ between individual tumors and tumor types. Using mutations, copy-number changes, mRNA expression, gene fusions and DNA methylation in 9,125 tumors profiled by The Cancer Genome Atlas (TCGA), we analyzed the mechanisms and patterns of somatic alterations in ten canonical pathways: cell cycle, Hippo, Myc, Notch, Nrf2, PI-3-Kinase/Akt, RTK-RAS, TGFb signaling, p53 and beta-catenin/Wnt. We charted the detailed landscape of pathway alterations in 33 cancer types, stratified into 64 subtypes, and identified patterns of co-occurrence and mutual exclusivity. Eighty-nine percent of tumors had at least one driver alteration in these one alteration potentially targetable by currently available drugs. Thirty percent of tumors had multiple targetable alterations, indicating opportunities for combination therapy

TESTING corticosteroids in IgA nephropathy: a continuing challenge

IgA nephropathy (IgAN) is the commonest type of glomerulonephritis worldwide, although the prevalence in some countries may be underestimated depending on the local policy for kidney biopsy. Patients with IgAN have a wide range of prognosis, from microscopic haematuria with stable kidney function through to kidney failure. Long term data show that 20-40% of patients progress to end stage kidney disease within 10-20 years of diagnosis. Recurrence of IgA deposition in the transplanted kidney is common, despite patients being on immunosuppression, and is an important cause of graft failure (1). Clinical features, including hypertension and proteinuria, have been shown to be useful in assessing prognosis. Recently, a combination of histopathological score with clinical data has improved prediction of the risk of progression to kidney failure(2). However, the main role of histology in recent trials has been confirmation of the diagnosis of IgAN, and exclusion of patients with other types of glomerulonephritis or severely scarred kidneys

Modulation of antibody-mediated glomerular injury in vivo by interleukin-6

Modulation of antibody-mediated glomerular injury in vivo by interleukin-6. We have shown previously that pretreatment with small doses of bacterial lipopolysaccharide (LPS), human recombinant interleu-kin-1β (hrIL-1β) and human recombinant tumor necrosis factor-α (hrTNF) increase injury in the heterologous phase of nephrotoxic nephritis (NTN). All three pretreatments induce synthesis of interleukin-6 (IL-6) which in some systems down-regulates synthesis of IL-1 and TNF. We have now investigated the influence of IL-6 on injury in both heterologous and autologous phases of NTN in rats. Injection of hrIL-6 in doses sufficient to induce hepatic synthesis of acute phase proteins (assessed by plasma α2-macroglobulin concentration) had no effect on glomerular injury in the heterologous phase of NTN (albuminuria in NTAb alone 9 ± 6; LPS/NTAb 34 ± 10 and IL-6/NTAb 2 ± 1 mg/24 hr, P < 0.001, Wilcoxon test). In contrast, IL-6 pretreatment partially abrogated the effect of LPS on albumin excretion (NTAb 4 ± 2; LPS/NTAb 85 ± 11 and IL-6/LPS/NTAb 32 ± 6 mg/24 hr, P < 0.002), percentage of glomerular capillary thrombi (3 ± 1%; 39 ± 8%; and 6 ± 1%, P < 0.001) and glomerular neutrophil infiltrate (29 ± 3; 58 ± 5; and 34 ± 2 neutrophils/50 glomeruli in section, P < 0.001, respectively) at 24 hours. The effect of IL-6 was also evident four hours after induction of nephritis and was associated with a marked reduction in glomerular concentration of mRNA for IL-1β and TNF, without change in that of tubulin. Serum TNF concentrations were also significantly reduced at four hours in IL-6 treated rats. Glomerular macrophage counts were unaffected by the treatment of IL-6 at four (53 ± 1; 55 ± 3 and 64 ± 7) or 24 hours (201 ± 12; 198 ± 9 and 202 ± 9, respectively). A single injection of IL-6 also decreased albumin excretion by 42% in the autologous phase of NTN, and reduced the prevalence of glomerular capillary thrombosis by 68%. These results show that IL-6 has significant anti-inflammatory properties in this model of antibody mediated injury in vivo