title: CD40L proinflammatory and profibrotic effects on proximal tubular epithelial cells: role of NF-kappaB and lyn.
abstract: Chronic allograft nephropathy (CAN) is the main cause of renal graft loss, but its pathogenic mechanisms are still unclear. Immune system activation has been suggested as a key event in the development of CAN. CD40 is a co-stimulatory protein whose expression is upregulated in proximal tubular epithelial cells (PTEC) in acute rejection. This receptor interacts with CD40L, expressed by activated T cells. CD40L induces the production by PTEC of different proinflammatory cytokines, but very little is known of its profibrotic effects. The aim of this study was to investigate the effect of CD40/CD40L interaction on PTEC expression of plasminogen activator inhibitor-1 (PAI-1), a powerful profibrotic mediator, and monocyte chemoattractant protein-1 (MCP-1), a proinflammatory cytokine, and to investigate the signaling pathways that lead to these effects. Soluble CD40L induced a time-dependent increase in both PAI-1 and MCP-1 gene expression and protein production in PTEC. CD40 cross-linking on PTEC caused TNF-R-associated factors 2 and 6 membrane translocation. This event led to NF-kappaB activation, through the NF-kappaB-inducing kinase, and to a significant increase in the phosphorylation of lyn, a src-related tyrosine kinase. Lyn, upon phosphorylation, became strictly associated with caveolin-1, a scaffolding protein enriched in caveolae. Lyn inhibition did not have any effect on CD40L-induced NF-kappaB activation and MCP-1 expression but abolished PAI-1 induction. On the contrary, NF-kappaB inhibition significantly reduced only MCP-1 expression. In conclusion, CD40L could play a key role in the pathogenesis of CAN through PAI-1 induction. CD40L profibrotic and proinflammatory effects are mediated by different signaling pathways, suggesting that drugs that inhibit inflammation may not be equally effective in reducing fibrosis.
authors.affiliation: Clinical Pathology, Department of Biomedical Sciences, University of Foggia, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Pontrelli
authors.forename: Michele
authors.initials: M
authors.lastname: Ursi
authors.forename: Elena
authors.initials: E
authors.lastname: Ranieri
authors.forename: Carmen
authors.initials: C
authors.lastname: Capobianco
authors.forename: Francesco P
authors.initials: FP
authors.lastname: Schena
authors.forename: Loreto
authors.initials: L
authors.lastname: Gesualdo
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Grandaliano
mesh_terms: D000704:Analysis of Variance; D015152:Blotting, Northern; D015153:Blotting, Western; D023201:CD40 Ligand / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D047468:Immunoprecipitation; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism*; D018613:Microscopy, Confocal; D016328:NF-kappa B / Q000378:metabolism*; D017395:Plasminogen Activator Inhibitor 1 / Q000494:pharmacology*; D011336:Probability; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012680:Sensitivity and Specificity; D015398:Signal Transduction; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D016328:NF-kappa B; D017395:Plasminogen Activator Inhibitor 1; D023201:CD40 Ligand; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases