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Low oxygen tension stimulates collagen synthesis and COL1A1 transcription through the action of TGF‐β1
Author(s) -
Falanga Vincent,
Zhou Linda,
Yufit Tatyana
Publication year - 2002
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.10065
Subject(s) - procollagen peptidase , microbiology and biotechnology , oxygen tension , luciferase , messenger rna , hypoxia (environmental) , transcription (linguistics) , repressor , downregulation and upregulation , transfection , transforming growth factor , gene expression , promoter , transcription factor , gene , chemistry , biology , biochemistry , oxygen , linguistics , philosophy , organic chemistry
Recent findings point to low oxygen tension (hypoxia) as an important mechanism for the expression of several eukaryotic genes. We have previously shown that hypoxia (2% O 2 ), when compared to standard oxygen tension (20% O 2 ), upregulates the mRNA levels of the human α1(I) (COL1A1) procollagen gene and transforming growth factor‐beta1 (TGF‐β1) in human dermal fibroblasts. In this report, we determined the effect of hypoxia on collagen synthesis and transcription. Exposure of human dermal fibroblasts to hypoxia for 24–72 h led to a threefold, dose‐dependent increase in collagenous protein ( P < 0.0001; r = 0.9794) and to enhanced type I procollagen deposition, as shown by direct immunofluorescence. Transient transfections with a series of luciferase‐ and CAT‐promoter constructs of the human COL1A1 gene (spanning from − 2.5 kb to + 113 bp) showed that hypoxia increases the transcriptional activity of constructs having 5′ endpoints between − 804 bp and − 107 bp, with loss of stimulation at − 84 bp. Maximal increase in promoter activity in hypoxia was observed between − 190 and − 174 bp of the proximal promoter, once a cKrox repressor site (− 199 to − 224 bp) was deleted. Upregulation of COL1A1 mRNA levels in hypoxia was blocked by a TGF‐β1 anti‐sense oligonucleotide, and failed to occur in fibroblasts from TGF‐β1 knock‐out mice. Co‐transfection and overexpression with a Smad7 construct abrogated the increase in COL1A1 promoter activity observed in hypoxia. Upregulated transcriptional activity of the TGF‐β1 promoter in hypoxia was found to be maximal between − 453 and − 175 bp from the transcriptional start site. Since hypoxia is a critical feature of the early phases of wound repair, we conclude that it may act as a potent physiologic stimulus for collagen synthesis. TGF‐β1 appears to be a critical component of this response. J. Cell. Physiol. 191: 42–50, 2002. © 2002 Wiley‐Liss, Inc.