CXCL12 gene expression is upregulated by hypoxia and growth arrest but not by inflammatory cytokines in rheumatoid synovial fibroblasts.
OBJECTIVE
CXCL12 is a constitutively expressed chemokine with important homeostatic functions. Increased CXCL12 expression has been observed in several inflammatory conditions, including rheumatoid arthritis (RA). This study was undertaken to identify potential mechanisms of regulation of CXCL12 gene expression by human fibroblasts under normal or inflammatory conditions.


METHODS
Synovial fibroblasts (SF) were cultured from RA and osteoarthritis (OA) synovial tissues. CXCL12 mRNA expression was analysed by real time quantitative RT-PCR in RA-SF under different growth conditions, and exposed to hypoxia or to different pro-inflammatory factors. A 5'CXCL12 -1.4 kb promoter region fragment was cloned in a luciferase reporter plasmid and its activity analysed in human fibroblasts.


RESULTS
CXCL12 mRNA expression was not constitutively increased in RA- compared to OA-SF. LPS, pro-inflammatory cytokines or growth factors did not induce CXCL12 mRNA expression in SF. Hypoxia and growth arrest by either serum starvation or confluent growth induced CXCL12 mRNA and protein expression in SF. Constitutive and induced expression of CXCL12 in fibroblasts was regulated at the transcriptional level by specific regions of the -1.4 kb promoter.


CONCLUSIONS
Pro-inflammatory factors and cytokines do not up-regulate CXCL12 gene expression in SF. Growth arrest and hypoxia are potentially important inducers of CXCL12 expression in human fibroblasts and operate by regulating transcriptional activity of the promoter.
Santiago
Begoña
B
Servicio de Reumatología y Unidad de Investigación, Hospital 12 de Octubre, Madrid, Spain.
Calonge
Esther
E
Del Rey
Manuel J
MJ
Gutierrez-Cañas
Irene
I
Izquierdo
Elena
E
Usategui
Alicia
A
Galindo
María
M
Alcamí
José
J
Pablos
José L
JL
D001172:Arthritis, Rheumatoid / Q000473:pathology*; D001483:Base Sequence; D015687:Cell Hypoxia / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D054377:Chemokine CXCL12 / Q000235:genetics* / Q000378:metabolism; D016384:Consensus Sequence / Q000235:genetics; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism*; D006801:Humans; D018836:Inflammation Mediators / Q000494:pharmacology*; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013582:Synovial Fluid / Q000166:cytology* / Q000187:drug effects; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism
C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D018836:Inflammation Mediators; D036341:Intercellular Signaling Peptides and Proteins; D012333:RNA, Messenger; D014157:Transcription Factors; D042461:Vascular Endothelial Growth Factor A