Interleukin-1-induced suppression of type II collagen gene transcription involves DNA regulatory elements.
Interleukin-1 is a proinflammatory polypeptide that influences cartilage macromolecular degradation and synthesis. Since previous studies have suggested that interleukin-1 may inhibit type II collagen synthesis, we have studied the mechanism of inhibition of type II collagen synthesis by interleukin-1. When rabbit articular chondrocytes were treated with purified recombinant interleukin-1 beta or macrophage-conditioned medium, the synthesis and assembly of type II collagen into the extracellular matrix were greatly reduced. The inhibition was concentration-dependent and occurred within 10 h of treatment with interleukin-1, with greater inhibition occurring at 30 h. The reduced level of collagen synthesis correlated with a reduction in the steady-state mRNA levels coding for type II collagen, as measured by a Northern blot analysis. This further correlated with a reduction in the transcription of type II collagen gene, as determined by nuclear run-on experiments. Finally, transfection studies using plasmid constructs containing DNA regulatory sequences from the type II gene, coupled to a reporter gene (CAT), revealed that in comparison to control chondrocytes, interleukin-1 treated cells showed a reduced level of CAT activity. These studies demonstrate that the inhibition of collagen type II synthesis by interleukin-1 is due to a reduction in the transcription of the type II collagen gene and that the reduction in gene transcription involves DNA regulatory sequences that determine type II collagen gene expression.
Chandrasekhar
S
S
Department of Connective Tissue and Monoclonal Antibody Research, Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285.
Harvey
A K
AK
Higginbotham
J D
JD
Horton
W E
WE
D000818:Animals; D002356:Cartilage / Q000166:cytology / Q000187:drug effects / Q000201:enzymology; D002478:Cells, Cultured; D015500:Chloramphenicol O-Acetyltransferase / Q000378:metabolism; D003094:Collagen / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D004247:DNA / Q000187:drug effects*; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D007375:Interleukin-1 / Q000494:pharmacology*; D012333:RNA, Messenger / Q000187:drug effects; D011817:Rabbits; D051381:Rats; D011994:Recombinant Proteins; D012045:Regulatory Sequences, Nucleic Acid / Q000187:drug effects*; D014158:Transcription, Genetic / Q000187:drug effects*; D014162:Transfection
D007375:Interleukin-1; D012333:RNA, Messenger; D011994:Recombinant Proteins; D003094:Collagen; D004247:DNA; D015500:Chloramphenicol O-Acetyltransferase