Iron chelation and hydroxyl radical scavenging reduce the inflammatory response of endothelial cells after infection with Chlamydia pneumoniae or influenza A.
BACKGROUND
Chronic low-grade inflammation is associated with increased risk of vascular diseases. The source of inflammation is unknown but may well be chronic and/or repetitive infections with microorganisms. Direct infection of endothelial cells (ECs) may also be a starting point for atherogenesis by initiating endothelial procoagulant activity, increased monocyte adherence and increased cytokine production. We hypothesized that iron-mediated intracellular hydroxyl radical formation after infection is a key event in triggering the production of interleukin-6 (IL-6) by ECs in vitro.


METHODS
Cultured ECs were incubated with Fe(II) and Fe(III) or infected with Chlamydia pneumoniae or influenza A/H1N1/Taiwan/1/81 for 48 and 24 h, respectively. To determine the role of iron and reactive oxygen species, cells were coincubated with the H2O2 scavenger N-acetyl-l-cysteine, with the iron chelator deferoxamine (DFO) or with the intracellular hydroxyl radical scavenger dimethylthiourea (DMTU). After the incubation periods, supernatants were harvested for IL-6 determination.


RESULTS
Incubating ECs with Fe(II) and Fe(III) resulted in increased IL-6 production. Similarly, infection with C. pneumoniae and influenza A also induced an IL-6 response. Coincubating ECs with DFO or DMTU blocked this response. Nuclear factor-kappaB activity was increased after infection and blocked by coincubation with DFO or DMTU.


CONCLUSIONS
Cultured ECs respond to infection and iron incubation with increased production of IL-6. Iron, the generation of intracellular hydroxyl radical and NF-kappaB activity are essential in cellular activation, suggesting that reactive oxygen species generated in the Haber-Weiss reaction are essential in invoking an immunological response to infection by ECs.
Visseren
Frank  L J
F
Department of Internal and Vascular Medicine, Room F.02.126, University Medical Center Utrecht, Heidelberglaan 100, 3584 CX Utrecht, The Netherlands. f.visseren@digd.azu.nl
Verkerk
M S A
MS
van der Bruggen
T
T
Marx
J J M
JJ
van Asbeck
B S
BS
Diepersloot
R J A
RJ
D000975:Antioxidants / Q000494:pharmacology; D002478:Cells, Cultured; D023521:Chlamydophila Infections / Q000188:drug therapy* / Q000276:immunology; D016993:Chlamydophila pneumoniae; D003676:Deferoxamine / Q000494:pharmacology* / Q000633:toxicity; D004730:Endothelium, Vascular / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D016166:Free Radical Scavengers / Q000494:pharmacology* / Q000633:toxicity; D006801:Humans; D009980:Influenza A virus; D007251:Influenza, Human / Q000188:drug therapy / Q000276:immunology; D015850:Interleukin-6 / Q000096:biosynthesis; D007501:Iron / Q000378:metabolism; D007502:Iron Chelating Agents / Q000494:pharmacology* / Q000633:toxicity; D016328:NF-kappa B / Q000378:metabolism; D013890:Thiourea / Q000031:analogs & derivatives* / Q000494:pharmacology* / Q000633:toxicity; D014471:Umbilical Veins / Q000166:cytology
D000975:Antioxidants; D016166:Free Radical Scavengers; D015850:Interleukin-6; D007502:Iron Chelating Agents; D016328:NF-kappa B; C038983:1,3-dimethylthiourea; D007501:Iron; D013890:Thiourea; D003676:Deferoxamine