Costimulation of Fibroblast Collagen and Transforming Growth Factor β1 Gene Expression by Monocyte Chemoattractant Protein-1 via Specific Receptors

• Published in: The Journal of biological chemistry Vol. 271; no. 30; p. 17779
• Main Authors: Mehrnaz Gharaee-Kermani, Elizabeth M. Denholm, Sem H. Phan
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 26-07-1996
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.271.30.17779

Recent studies indicate potential roles of monocyte chemotactic protein-1 (MCP-1) in recruitment of monocytes to sites of
inflammation. However, their increased expression does not always correlate with monocyte influx, suggesting other possible
biological activities for this member of the C-C chemokine family. In view of its potential role in regulating extracellular
matrix expression in fibrotic disorders, the effects of MCP-1 on lung fibroblast collagen expression were evaluated. Isolated
rat lung fibroblasts were treated with increasing doses of MCP-1 for variable periods of time and examined for effects on
collagen synthesis and expression of procollagen α 1 (I) mRNA expression. The results show that MCP-1 was able to stimulate collagen expression in these cells in a dose-dependent
manner but required over 24 h for significant elevation to occur. In view of this delayed time course, the possibility of
mediation via endogenous transforming growth factor β (TGFβ) was tested by the ability of anti-TGFβ antibody to inhibit this
MCP-1 stimulation of collagen expression. Significant but incomplete inhibition by this antibody was observed. Pretreatment
of the cells with antisense but not by sense or missense TGFβ 1 oligodeoxyribonucleotides caused essentially complete inhibition of this MCP-1 stimulatory effect. Furthermore, MCP-1 treatment
was found to also stimulate TGFβ secretion and mRNA expression, which was also abolished by pretreatment with antisense TGFβ 1 oligodeoxyribonucleotides. The kinetics of TGFβ expression indicates that significant increase preceded that for collagen
expression. Binding studies using 125 I-labeled MCP-1 indicated the presence of specific and saturable binding sites with a dissociation constant consistent with
the dose response curves for stimulation of fibroblast collagen synthesis and TGFβ activity by MCP-1. These results taken
together suggest that MCP-1 stimulates fibroblast collagen expression via specific receptors and endogenous up-regulation
of TGFβ expression. The latter then results in autocrine and/or juxtacrine stimulation of collagen gene expression.