title: Azithromycin inhibits interleukin-6 but not fibrinogen production in hepatocytes infected with cytomegalovirus and chlamydia pneumoniae.
abstract: Chlamydia pneumoniae and cytomegalovirus (CMV) have been associated with the development of atherosclerosis. Inflammatory stimuli initiate the biosynthesis of fibrinogen, interleukin (IL)-6 and plasminogen activator inhibitor (PAI)-1 in the liver. Chronic infection may perpetuate the inflammatory status. We hypothesized that infection of human hepatocytes with the intracellular pathogens C pneumoniae and CMV accelerates biosynthesis of fibrinogen, IL-6, and PAI-1 but that this biosynthesis can be reduced with the use of azithromycin. HepG2 human hepatocytes were infected with C pneumoniae and CMV in vitro in the presence of 0, 0.016, 0.125, or 1 microg/mL azithromycin. We measured IL-6, PAI-1, and fibrinogen after 24, 48, 72, and 96 hours. C pneumoniae-infected hepatocytes produce IL-6 (2667 +/- 309 pg/mL vs 137 +/- 120 pg/mL in uninfected cells after 96 hours. Incubation with 0.016 microg/mL azithromycin decreased IL-6 levels to a mean of 1516 +/- 402 pg/mL, and incubation with 0.125 and 1 microg/mL azithromycin decreased IL-6 to 871 +/- 364 and 752 +/- 403 pg/mL, respectively. C pneumoniae-induced IL-6 production was time- and dose-dependent. The interaction of C pneumoniae with azithromycin treatment was significant, indicating an inhibitory effect of azithromycin on C pneumoniae-induced IL-6 production. CMV infection did not lead to IL-6 production by hepatocytes. C pneumoniae and CMV infection did not induce any changes in PAI-1 production. Fibrinogen production was increased by CMV infection after 72 hours (838 +/- 88 ng/mL; P <.01) and after 96 hours by infection with both C pneumoniae and CMV (765 +/- 100 and 846 +/- 123 ng/mL, respectively; P <.05). Azithromycin did not suppress CMV- or C pneumoniae-induced fibrinogen production. Moreover, we could not confirm an antiinflammatory effect of azithromycin in experiments with cross-titrations of azithromycin against either IL-1 or IL-6 (P >.05). Azithromycin reduces C pneumoniae-induced IL-6 production, but not fibrinogen production, by human hepatocytes. This is a result of the antimicrobial properties of azithromycin and not a direct antiinflammatory effect.
authors.affiliation: Laboratory and Department of Medical Microbiology, Diakonessen Hospital, Utrecht, The Netherlands. jbouwman@diakhuis.nl
authors.forename: John J M
authors.initials: JJ
authors.lastname: Bouwman
authors.forename: Frank L J
authors.initials: FL
authors.lastname: Visseren
authors.forename: Paul K
authors.initials: PK
authors.lastname: Bouter
authors.forename: Rob J A
authors.initials: RJ
authors.lastname: Diepersloot
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D017963:Azithromycin / Q000494:pharmacology*; D045744:Cell Line, Tumor; D016993:Chlamydophila pneumoniae / Q000187:drug effects* / Q000502:physiology; D003587:Cytomegalovirus / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D005340:Fibrinogen / Q000096:biosynthesis*; D022781:Hepatocytes / Q000378:metabolism / Q000382:microbiology; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis*; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis; D000093242:Interleukin-6 Inhibitors
chemical_list: D000900:Anti-Bacterial Agents; D017963:Azithromycin; D005340:Fibrinogen; D015850:Interleukin-6; D017395:Plasminogen Activator Inhibitor 1; D000093242:Interleukin-6 Inhibitors