IL-17 Expression in the Time Course of Acute Anti-Thy1 Glomerulonephritis

Background Interleukin-17 (IL-17) is a new pro-inflammatory cytokine involved in immune response and inflammatory disease. The main source of IL-17 is a subset of CD4+ T-helper cells, but is also secreted by non-immune cells. The present study analyzes expression of IL-17 in the time course of acute anti- thy1 glomerulonephritis and the role of IL-17 as a potential link between inflammation and fibrosis. Methods Anti-thy1 glomerulonephritis was induced into male Wistar rats by OX-7 antibody injection. After that, samples were taken on days 1, 5, 10 (matrix expansion phase), 15 and 20 (resolution phase). PBS-injected animals served as controls. Proteinuria and histological matrixes score served as the main markers for disease severity. In in vitro experiments, NRK-52E cells were used. For cytokine expressions, mRNA and protein levels were analyzed by utilizing RT-PCR, in situ hybridization and immunofluorescence. Results Highest IL-17 mRNA-expression (6.50-fold vs. con; p<0.05) was found on day 5 after induction of anti-thy1 glomerulonephritis along the maximum levels of proteinuria (113 ± 13 mg/d; p<0.001), histological glomerular-matrix accumulation (82%; p<0.001) and TGF-β1 (2.2-fold; p<0.05), IL-6 mRNA expression (36-fold; p<0.05). IL-17 protein expression co-localized with the endothelial cell marker PECAM in immunofluorescence. In NRK-52E cells, co-administration of TGF-β1 and IL-6 synergistically up-regulated IL-17 mRNA 4986-fold (p<0.001). Conclusions The pro-inflammatory cytokine IL-17 is up-regulated in endothelial cells during the time course of acute anti-thy1 glomerulonephritis. In vitro, NRK-52E cells secrete IL-17 under pro-fibrotic and pro-inflammatory conditions

Oxidative stress-induced JNK activation contributes to proinflammatory phenotype of aging diabetic mesangial cells

Chronic inflammation and increased oxidative stress (OS) play an important role in diabetic nephropathy progression. Herein, we show that mesangial cells from streptozotocin-induced aging diabetic mice, a model of progressive diabetic nephropathy, exhibited increased OS and a proinflammatory phenotype characterized by elevated chemokines and ICAM-1 expression. This phenotypic change was consistent with the extensive inflammatory lesions present in aging diabetic kidneys and was not found in mesangial cells from old and young controls or young diabetic mice. Activation of the c-Jun NH2-terminal kinase (JNK) pathway was a likely contributor to the proinflammatory phenotype of aging diabetic mesangial cells since 1) phosphorylated JNK levels and JNK kinase activity were increased in these cells, 2) suppression of JNK significantly decreased monocyte chemoattractant protein-1 (MCP-1) production in these cells, and 3) activation of JNK in normal mesangial cells induced inflammation. Elevated OS in aging diabetic mesangial cells may be a cause of JNK activation and inflammation, because antioxidant treatment decreased JNK phosphorylation and MCP-1 production. Additionally, decreased expression of mitogen-activated protein kinase phosphatase 5 (MKP5) may also contribute to increased JNK and inflammation in aging diabetic mesangial cells since overexpression of MKP5 in these cells normalized phosphorylated JNK levels and reversed the proinflammatory phenotype. Moreover, knocking down of MKP5 expression in old control mesangial cells resulted in JNK activation and MCP-1 production, a phenotype seen in aging diabetic mesangial cells. Interestingly, MKP5 phosphatase activity was diminished by free radicals in vitro. Thus, OS may induce inflammation in mesangial cells by activating JNK through either a direct activation of JNK or indirectly by suppression of MKP5 activity. Proinflammatory phenotype of mesangial cells may contribute to chronic inflammatory lesions and disease progression of aging diabetic mice