ASK1 inhibitor treatment suppresses p38/JNK signalling with reduced kidney inflammation and fibrosis in rat crescentic glomerulonephritis.

Activation of p38 mitogen-activated protein kinase (MAPK) and c-Jun amino terminal kinase (JNK) is prominent in human crescentic glomerulonephritis. p38 and JNK inhibitors suppress crescentic disease in animal models; however, the upstream mechanisms inducing activation of these kinases in crescentic glomerulonephritis are unknown. We investigated the hypothesis that apoptosis signal-regulating kinase 1 (ASK1/MAP3K5) promote p38/JNK activation and renal injury in models of nephrotoxic serum nephritis (NTN); acute glomerular injury in SD rats, and crescentic disease in WKY rats. Treatment with the selective ASK1 inhibitor, GS-444217 or vehicle began 1 hour before nephrotoxic serum injection and continued until animals were killed on day 1 (SD rats) or 14 (WKY rats). NTN resulted in phosphorylation (activation) of p38 and c-Jun in both models which was substantially reduced by ASK1 inhibitor treatment. In SD rats, GS-444217 prevented proteinuria and glomerular thrombosis with suppression of macrophage activation on day 1 NTN. In WKY rats, GS-444217 reduced crescent formation, prevented renal impairment and reduced proteinuria on day 14 NTN. Macrophage activation, T-cell infiltration and renal fibrosis were also reduced by GS-444217. In conclusion, GS-444217 treatment inhibited p38/JNK activation and development of renal injury in rat NTN. ASK1 inhibitors may have therapeutic potential in rapidly progressive glomerulonephritis.

Long-term graft survival in patients with chronic antibody-mediated rejection with persistent peritubular capillaritis treated with intravenous immunoglobulin and rituximab.

Chronic antibody-mediated rejection (cAMR) is the major cause of premature renal allograft loss and is resistant to therapy with 12-month graft failure of up to 50% reported. We examined the duration of graft survival and associates of graft failure in patients with donor-specific antibody-positive cAMR and treatment-resistant peritubular capillaritis between June 2007 and October 2010. Those with advanced interstitial fibrosis (n=5) were excluded. Included patients (n=24) received treatment with high-dose intravenous immunoglobulin and fixed-dose rituximab (500 mg). Compared with previous reports, the study group experienced prolonged graft survival (median 82.1 months). Graft loss was predicted by eGFR and degree of proteinuria at diagnosis but not by donor-specific HLA antibody class or intensity, nor individual or summed Banff scores. Allograft biopsies were further examined for infiltrating leukocyte subtypes and location with high numbers of glomerular leukocytes, particularly macrophages, independently associated with an increased risk of graft failure. This study suggests that patients with cAMR and persistent microcirculatory inflammation, excluding those with advanced histological damage, can expect prolonged graft survival when treated with IVIg and rituximab. Trial level evidence is required to validate this observation. Further examination of the role of macrophages in cAMR is warranted.

cANCA-associated aortitis.

Anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis is traditionally viewed as a small vessel disease. We report a patient with cANCA antibodies directed against proteinase-3 with asymptomatic aortic involvement, in combination with diffuse alveolar haemorrhage and pauci-immune, necrotizing crescentic glomerulonephritis. A review of the literature is discussed.