Synergistic effect of interleukin-1 and CD40L on the activation of human renal tubular epithelial cells.
BACKGROUND
Renal tubular epithelial cells are a central cell type in tubulointerstitial inflammation because they can produce inflammatory mediators such as cytokines and chemokines. Several signals derived from either monocytes or activated T cells have been reported to regulate the activation of tubular epithelial cells. We studied this regulation in more detail by combined treatment with CD40 ligand and the proinflammatory cytokine interleukin-1 (IL-1) in vitro.


METHODS
The regulation of cytokine and chemokine production was studied in primary cultures of human proximal tubular epithelial cells (PTECs). PTECs were activated by coculture with CD40L-transfected murine fibroblasts in combination with recombinant human cytokines. The production of IL-6, IL-8, monocyte chemoattractant protein-1 (MCP-1), and RANTES were measured by specific enzyme-linked immunosorbent assay.


RESULTS
The combined activation of PTECs with CD40L and IL-1 resulted in strong synergistic effects on the production of IL-6, IL-8, and RANTES, whereas only an additive stimulation of MCP-1 production was observed. The effects were specific for IL-1 and could be neutralized by the addition of the IL-1R antagonist. Both IL-1alpha and IL-1beta showed similar effects on cytokine production by PTECs. The effects of IL-1 were dose dependent, and kinetic experiments showed that synergistic effects were observed after 24 hours of activation and remained present for at least five days. Reverse transcription-polymerase chain reaction analysis showed that human PTECs could express both IL-1alpha and IL-1beta. The activation of PTECs with IL-1 resulted in an up-regulation of CD40 expression on these cells.


CONCLUSIONS
A complex network of regulation exists for the production of cytokines and chemokines by PTECs. The combined treatment results in strong synergistic effects on IL-6, IL-8, and RANTES production. This strengthens the potential role of tubular epithelial cells in inflammatory responses within the kidney.
Department of Nephrology, Leiden University, The Netherlands. Kooten@Rullf2.Medfac.LeidenUniv.nl
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C
van Kooten
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van der Linde
A M
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Woltman
L A
LA
van Es
M R
MR
Daha
D000818:Animals; D019013:CD40 Antigens / Q000378:metabolism; D023201:CD40 Ligand; D002460:Cell Line; D018925:Chemokines / Q000096:biosynthesis; D016207:Cytokines / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D006801:Humans; D007375:Interleukin-1 / Q000378:metabolism / Q000494:pharmacology*; D015850:Interleukin-6 / Q000096:biosynthesis; D007684:Kidney Tubules / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology*; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D051379:Mice; D020033:Protein Isoforms / Q000378:metabolism / Q000494:pharmacology; D017472:Receptors, Interleukin-1 / Q000037:antagonists & inhibitors; D013997:Time Factors
D019013:CD40 Antigens; D018925:Chemokines; D016207:Cytokines; D007375:Interleukin-1; D015850:Interleukin-6; D008562:Membrane Glycoproteins; D020033:Protein Isoforms; D017472:Receptors, Interleukin-1; D023201:CD40 Ligand