CCL18 synergises with high concentrations of glucose in stimulating fibronectin production in human renal tubuloepithelial cells.

Background: Diabetic nephropathy is the leading cause of end stage kidney disease worldwide. The pathogenesis of this disease remains elusive and multiple factors have been implicated. These include the effects of hyperglycaemia, haemodynamic and metabolic factors, and an inflammatory process that stimulates cellular signalling pathways leading to disease progression and severe fibrosis. Fibronectin (Fn) is an important protein of the extracellular matrix that is essential in fibrosis and its presence in increased amounts has been identified in the kidney in diabetic nephropathy. Methods: Proximal tubuloepithelial (HK-2) cells were stimulated with high glucose (30mM D-glucose) or glycated albumin (500μg/mmol) + 4mM D-glucose or their controls, Mannitol (26mM+4mM D-glucose) and 4mM D-glucose, respectively. Following 48 hours of stimulation the supernatant was collected and MTT [3-(4,5-dimethylthiazole-2,5-diphenyltetrazolium bromide] assay performed to assess cell viability. HK-2 cells were also stimulated in the above environments with recombinant CCL18 (rCCL18) or MCP-1 (rMCP-1) for 48 hours with quantification of Fn levels using ELISA. Results: Co-stimulation of HK-2 cells with high concentrations of glucose and rCCL18 significantly increased Fn (p<0.001), in comparison to high concentrations of glucose alone. HK-2 cells stimulated with glycated albumin consistently produced Fn and this did not alter following co-stimulation with rCCL18 or rMCP-1. Conclusion: This study demonstrates how stimulation with a specific chemokine CCL18 in high glucose upregulates the production of Fn from proximal tubuloepithelial cells. This may be relevant to the development of renal fibrosis in diabetic nephropath

Characterisation of an enhanced preclinical model of experimental MPO-ANCA autoimmune vasculitis

Experimental autoimmune vasculitis (EAV) is a model of antineutrophil cytoplasm antibody (ANCA)-associated vasculitis (AAV) induced by immunisation of susceptible rat strains with myeloperoxidase (MPO). Animals develop circulating MPO-ANCA, pulmonary haemorrhage and glomerulonephritis, although renal injury is mild and recovers spontaneously without treatment. In this study we aimed to augment the severity of glomerulonephritis. Following induction of EAV on day 0, a sub-nephritogenic dose of nephrotoxic serum (NTS) containing heterologous antibodies to glomerular basement membrane was administered on day 14. This resulted in a significant increase in disease severity at day 28 compared to MPO immunisation alone - with more urinary abnormalities, infiltrating glomerular leucocytes, and crescent formation that progressed to glomerular and tubulointerstitial scarring by day 56, recapitulating important features of human disease. Importantly, the glomerulonephritis remained pauci-immune, and was strictly dependent on the presence of autoimmunity to MPO, as there was no evidence of renal disease following administration of sub-nephritogenic NTS alone or after immunisation with a control protein in place of MPO. Detailed phenotyping of glomerular leucocytes identified an early infiltrate of non-classical monocytes following NTS administration that, in the presence of autoimmunity to MPO, may initiate the subsequent influx of classical monocytes which augment glomerular injury. We also showed that this model can be used to test novel therapeutics by using a small molecule kinase inhibitor (fostamatinib) that rapidly attenuated both glomerular and pulmonary injury over a four-day treatment period. We believe that this enhanced model of MPO-AAV will prove useful for the study of glomerular leucocyte behaviour and novel therapeutics in AAV in the future. This article is protected by copyright. All rights reserved

Binding Truths: Atypical anti-GBM disease mediated by IgA anti-GBM antibodies targeting the α1 chain of type IV collagen

Anti−glomerular basement membrane (anti-GBM) disease presents with rapidly progressive glomerulonephritis, often associated with alveolar hemorrhage and characterized histologically by crescentic glomerulonephritis. Typically, there is linear deposition of Ig along the glomerular basement membrane (GBM), which, in the majority of cases, is due to IgG autoantibodies directed against the noncollagenous domain of the α3 chain of type IV collagen (α3[IV]NC1).1 Early disease recognition relies on detecting circulating IgG anti-GBM antibodies in serum samples. However, conventional assays do not detect IgA antibodies or those directed against other target antigens, including α5(IV) found in some Alport disease patients following renal transplantation.2 The presence and specificity of the antibody can be confirmed by Western blotting, usually at a reference center, although this is not routinely performed. We describe a case of anti-GBM disease mediated by IgA anti-GBM antibodies not detected by standard serological tests, and suggest a method of detection and monitoring that can be used in the right clinical context

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, randomized, placebo-controlled phase 2 trial of fostamatinib (an oral SYK inhibitor) in 76 patients with IgAN. Patients were randomized 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. The primary end point was reduction of proteinuria. Secondary end points included change from baseline in estimated glomerular filtration rate (eGFR) and kidney histology. / Results: Although we could not detect significant reduction in proteinuria with fostamatinib overall, in a predetermined 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 vs. 1.7 SYK+ cells/glomerulus in the placebo group, P < 0.05). / Conclusions: There was a trend toward 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

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, randomized, placebo-controlled phase 2 trial of fostamatinib (an oral SYK inhibitor) in 76 patients with IgAN. Patients were randomized 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. The primary end point was reduction of proteinuria. Secondary end points included change from baseline in estimated glomerular filtration rate (eGFR) and kidney histology. Results Although we could not detect significant reduction in proteinuria with fostamatinib overall, in a predetermined 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 vs. 1.7 SYK+ cells/glomerulus in the placebo group, P < 0.05). Conclusions There was a trend toward 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

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

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

Correlation of disease activity in proliferative glomerulonephritis with glomerular spleen tyrosine kinase expression

Spleen tyrosine kinase (SYK) is an important component of the intracellular signaling pathway for various immunoreceptors. Inhibition of SYK has shown promise in preclinical models of autoimmune and glomerular disease. However, the description of SYK expression in human renal tissue, which would be desirable ahead of clinical studies, is lacking. Here we conducted immunohistochemical analysis for total and phosphorylated SYK in biopsy specimens from >120 patients with a spectrum of renal pathologies, including thin basement membrane lesion, minimal change disease, membranous nephropathy, IgA nephropathy, lupus nephritis, ANCA-associated glomerulonephritis, antiglomerular basement membrane disease, and acute tubular necrosis. We found significant SYK expression in proliferative glomerulonephritis and that glomerular expression levels correlated with presenting serum creatinine and histological features of disease activity that predict outcome in IgA nephropathy, lupus nephritis, ANCA-associated glomerulonephritis, and antiglomerular basement membrane disease. SYK was phosphorylated within pathological lesions, such as areas of extracapillary and endocapillary proliferation, and appeared to localize to both infiltrating leucocytes and to resident renal cells within diseased glomeruli. Thus SYK is associated with the pathogenesis of proliferative glomerulonephritides, suggesting that these conditions may respond to SYK inhibitor treatment