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The tubular epithelium may be intrinsically involved in promoting kidney injury by junctional instability, epithelial-mesenchymal transition (EMT) and extracellular matrix remodelling. In this work, we investigated whether the pleiotropic and proinflammatory cytokine tumor necrosis factor-like weak inducer of apoptosis (TWEAK), could be able to disturb junctional protein expression and to induce EMT of tubular cells. In cultured murine proximal tubular cells TWEAK induced phenotypic changes that were accompanied by F-actin redistribution, loss of epithelial adherent (E-cadherin, Cadherin-16, β-catenin) and tight junction (ZO-1) proteins, and re-expression of the mesenchymal protein Vimentin. The transcriptional repressors Snail and HNF1β were also modulated by TWEAK. In a murine model of obstructive renal pathology, TWEAK expression correlated with the appearance of the mesenchymal marker αSMA in kidney tubular cells. Mechanistically, the epithelial changes induced by TWEAK, including loss of epithelial integrity and EMT, via Fn14 were TGF-β1 independent, but mediated by several intracellular signaling systems, including the canonical NF-κB, ERK activation and the vitamin D receptor modulation. These results highlight potential contributions of TWEAK-induced inflammatory mechanisms that could unveil new pathogenic effects of TWEAK starting tubulointerstitial damage and fibrosis. J. Cell. Physiol. 230: 1580-1593, 2015. © 2014 Wiley Periodicals, Inc., A Wiley Company [ABSTRACT FROM AUTHOR]

The polyglutamic acid/peptoid 1 (QM56) nanoconjugate inhibits apoptosis by interfering with Apaf-1 binding to procaspase-9. We now describe anti-inflammatory properties of QM56 in mouse kidney and renal cell models. In cultured murine tubular cells, QM56 inhibited the inflammatory response to Tweak, a non-apoptotic stimulus. Tweak induced MCP-1 and Rantes synthesis through JAK2 kinase and NF-κB activation. Similar to JAK2 kinase inhibitors, QM56 inhibited Tweak-induced NF-κB transcriptional activity and chemokine expression, despite failing to inhibit NF-κB-p65 nuclear translocation and NF-κB DNA binding. QM56 prevented JAK2 activation and NF-κB-p65(Ser536) phosphorylation. The anti-inflammatory effect and JAK2 inhibition by QM56 were observed in Apaf-1-1- cells. In murine acute kidney injury, QM56 decreased tubular cell apoptosis and kidney inflammation as measured by downmodulations of MCP-1 and Rantes mRNA expression, immune cell infiltration and activation of the JAK2-dependent inflammatory pathway. In conclusion, QM56 has an anti-inflammatory activity which is independent from its role as inhibitor of Apaf-1 and apoptosis and may have potential therapeutic relevance. [ABSTRACT FROM AUTHOR]

Tubular cell injury and fibrosis are key features of calcineurin inhibitor nephrotoxicity, but the molecular processes involved are not fully understood. In cultured murine MCT and human kidney 2 proximal tubular cells, gene expression and protein levels were studied by real-time polymerase chain reaction, Western blot, and confocal microscopy. Protein function was evaluated by pharmacological inhibitors and confirmed by small interfering RNA (siRNA) gene targeting. In renal tubular cells, cytotoxic concentrations of cyclosporine A (CsA) inhibited both gene and protein expression of adherent and tight junction proteins (E-cadherin, ZO-1, claudin-1, and β-catenin) and increased vimentin expression, without involvement of transforming growth factor β1 or caspase activity. CsA upregulated transcriptional repressors (Snail, Slug, and Twist) of the adherent and tight junction proteins were studied. Snail siRNA targeting prevented the downregulation of E-cadherin by CsA. CsA promoted glycogen synthase kinase 3 (GSK3) phosphorylation and increased Snail half-life. The GSK3 inhibitor lithium upregulated Snail and decreased E-cadherin expression in a Snail-dependent manner. Moreover, targeting GSK3 activity by siRNA also upregulated Snail. Furthermore, GSK3 siRNA had a negative impact on CsA-induced upregulation of Snail. Tacrolimus also inhibited GSK3 and mimicked CsA responses in tubular cells. We conclude that calcineurin inhibitors may directly decrease the expression of epithelial adhesion molecules by repressing GSK3 and stabilizing Snail. This offers potential pharmacological targets for prevention of nephrotoxicity. [ABSTRACT FROM AUTHOR]

Abstract: The calcineurin inhibitors (CNIs) cyclosporine (CsA) and tacrolimus are key drugs in current immunosuppressive regimes for solid organ transplantation. However, they are nephrotoxic and promote death and profibrotic responses in tubular cells. Moreover, renal inflammation is observed in CNI nephrotoxicity but the mechanisms are poorly understood. We have now studied molecular pathways leading to inflammation elicited by the CNIs in cultured and kidney tubular cells. Both CsA and tacrolimus elicited a proinflammatory response in tubular cells as evidenced by a transcriptomics approach. Transcriptomics also suggested several potential pathways leading to expression of proinflammatory genes. Validation and functional studies disclosed that in tubular cells, CNIs activated protein kinases such as the JAK2/STAT3 and TAK1/JNK/AP-1 pathways, TLR4/Myd88/IRAK signaling and the Unfolded Protein Response (UPR) to promote NF-κB activation and proinflammatory gene expression. CNIs also activated an Nrf2/HO-1-dependent compensatory response and the Nrf2 activator sulforaphane inhibited JAK2 and JNK activation and inflammation. A murine model of CsA nephrotoxicity corroborated activation of the proinflammatory pathways identified in cell cultures. Human CNIs nephrotoxicity was also associated with NF-κB, STAT3 and IRE1α activation. In conclusion, CNIs recruit several intracellular pathways leading to previously non-described proinflammatory actions in renal tubular cells. Identification of these pathways provides novel clues for therapeutic intervention to limit CNIs nephrotoxicity. [Copyright &y& Elsevier]

Members of the TNF superfamily participate in kidney disease. Tumor necrosis factor (TNF) and Fas ligand regulate renal cell survival and inflammation, and therapeutic targeting improves the outcome of experimental renal injury. TNF-related apoptosis-inducing ligand (TRAIL and its potential decoy receptor osteoprotegerin are the two most upregulated death-related genes in human diabetic nephropathy. TRAIL activates NF-kappaB in tubular cells and promotes apoptosis in tubular cells and podocytes, especially in a high-glucose environment. By contrast, osteoprotegerin plays a protective role against TRAIL- induced apoptosis. Another family member, TNF-like weak inducer of apoptosis (TWEAK induces inflammation and tubular cell death or proliferation, depending on the microenvironment. While TNF only activates canonical NF-kappaB signaling, TWEAK promotes both canonical and noncanonical NF-kappaB activation in tubular cells, regulating different inflammatory responses. TWEAK promotes the secretion of MCP-1 and RANTES through NF-kappaB RelA-containing complexes and upregulates CCl21 and CCL19 expression through NF-kappaB inducing kinase (NIK-) dependent RelB/NF-kappaB2 complexes. In vivo TWEAK promotes postnephrectomy compensatory renal cell proliferation in a noninflammatory milieu. However, in the inflammatory milieu of acute kidney injury, TWEAK promotes tubular cell death and inflammation. Therapeutic targeting of TNF superfamily cytokines, including multipronged approaches targeting several cytokines should be further explored. [ABSTRACT FROM AUTHOR]