Interleukin-6 gene expression in human endothelial cells: RNA start sites, multiple IL-6 proteins and inhibition of proliferation.
Interleukin-6 (IL-6) is a cytokine which is not only produced by a wide variety of different cells but one which also affects the function of diverse tissues. We have studied the expression of the IL-6 gene in freshly explanted human umbilical vein endothelial cells (HUVEC) and have also evaluated the effect of IL-6 on HUVEC proliferation. Cytokines like interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor (TNF) as well as bacterial products such as the lipopolysaccharide (LPS) rapidly enhance production of biologically active IL-6 by HUVEC (IL-6 bioassay: increase in alpha 1-antichymotrypsin secretion by Hep3B2 cells and its neutralization by antiserum to E. coli-derived human IL-6). The two inducible RNA start sites in the IL-6 gene that are used in cytokine-induced fibroblasts (at +1 and -21) are also used in the same relative proportion (+1 greater than -21) in cytokine or LPS-induced HUVEC as determined by S1-nuclease protection assays for IL-6 transcripts. Immunoaffinity chromatography followed by Western blotting shows that IL-6 species secreted by IL-1 alpha-induced HUVEC are of molecular mass 23-25, 27-30 and 45 kDa as judged by SDS-PAGE under reducing conditions. Finally, rIL-6 inhibits [3H]-thymidine incorporation by HUVEC in a dose-dependent manner. Thus IL-6 is not only produced by HUVEC but may also affect its proliferation. The ability of the vascular endothelium to rapidly secrete IL-6 in response to inflammation-associated cytokines is of strategic value since it generates a circulatory signal which helps mobilize the acute phase plasma protein response and enlists the immune system in host defence.
May
L T
LT
Rockefeller University, New York, NY 10021.
Torcia
G
G
Cozzolino
F
F
Ray
A
A
Tatter
S B
SB
Santhanam
U
U
Sehgal
P B
PB
Stern
D
D
D002460:Cell Line; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000276:immunology*; D004926:Escherichia coli / Q000235:genetics; D005796:Genes; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology; D015850:Interleukin-6; D007378:Interleukins / Q000096:biosynthesis / Q000235:genetics* / Q000494:pharmacology; D007700:Kinetics; D011994:Recombinant Proteins / Q000494:pharmacology; D014158:Transcription, Genetic; D000514:alpha 1-Antichymotrypsin / Q000378:metabolism
D007375:Interleukin-1; D015850:Interleukin-6; D007378:Interleukins; D011994:Recombinant Proteins; D000514:alpha 1-Antichymotrypsin