Regulation of plasminogen activation by interleukin-6 in human lung fibroblasts.
We determined that exposure of cultured lung fibroblasts (HEL-299) to recombinant human interleukin-6 (0-400 ng/ml) resulted in a dose- and time-dependent increase in secreted and cell lysate PAI-1 and total tPA levels (maximal increase of 2.6-fold and 1.7-fold, respectively). Specificity of this response was indicated when increases in PAI-1 levels were inhibited by neutralizing polyclonal antibodies to IL-6, but not with non-specific antibodies. Inhibition of the response to IL-6 by cycloheximide and alpha-amanitin indicates that increases in PAI-1 are dependent on both protein and RNA synthesis. The addition of IL-6 to HEL-299 cells also stimulated a dose- and time-dependent increase in steady-state PAI-1 mRNA levels (3.8 to 15.1 pg/micrograms total RNA by 24 h). A rapid increase (5-6-fold) in PAI-1 mRNA levels was found between 3 and 12 h. Nuclear run-on assays using a maximum dose of IL-6 showed that IL-6 increases a 4-fold rate of transcription of the PAI-1 gene. We further showed that LPS induces a 70% increase in secreted IL-6 and a 50% increase in PAI-1 protein levels. Increasing doses of anti-IL-6 completely blocked the effect of LPS on PAI-1 while non-specific antibodies had no effect. These studies suggest an autocrine role for IL-6 in regulating localized proteolysis and modulating tissue remodeling during acute inflammatory conditions by fibroblasts.
Samad
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F
Department of Health Sciences, University of Wisconsin-Milwaukee 53201.
Bergtrom
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Amrani
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DL
D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005786:Gene Expression Regulation; D005938:Glucocorticoids / Q000494:pharmacology; D006801:Humans; D015850:Interleukin-6 / Q000494:pharmacology*; D010958:Plasminogen / Q000378:metabolism*; D017395:Plasminogen Activator Inhibitor 1 / Q000096:biosynthesis / Q000235:genetics*; D010960:Plasminogen Activators / Q000096:biosynthesis / Q000235:genetics*; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins / Q000494:pharmacology
D005938:Glucocorticoids; D015850:Interleukin-6; D017395:Plasminogen Activator Inhibitor 1; D012333:RNA, Messenger; D011994:Recombinant Proteins; D010958:Plasminogen; D010960:Plasminogen Activators