Inhibition of collagen gene expression in systemic sclerosis dermal fibroblasts by mithramycin.
BACKGROUND
The anti-tumour antibiotic mithramycin is also a potent inhibitor of fibrosis after glaucoma surgery. This drug displays high affinity binding to GC-rich sequences in DNA, including those present in the promoter of the gene encoding the alpha1 chain of type I collagen (COL1A1).


OBJECTIVE
To evaluate the effects of mithramycin on COL1A1 expression in systemic sclerosis fibroblasts.


METHODS
Confluent cultures of dermal fibroblasts from patients with recent onset diffuse systemic sclerosis were treated with mithramycin in vitro. Cell viability and protein expression were examined by fluorescence and confocal imaging. Type I collagen production was analysed by confocal imaging and metabolic labelling. COL1A1 messenger RNA levels and stability were assessed by northern hybridisation, and COL1A1 transcription was examined by transient transfections.


RESULTS
Treatment of systemic sclerosis fibroblasts with mithramycin (10-100 nmol/l) did not cause significant cytotoxicity. Type I collagen biosynthesis decreased by 33-40% and 50-70% in cells cultured with mithramycin at 10 nmol/l and 100 nmol/l, respectively. Mithramycin at 50 nmol/l decreased COL1A1 mRNA levels by 40-60%. The effects of mithramycin on collagen gene expression were mediated by transcriptional and post-transcriptional mechanisms as shown by the reduction of COL1A1 promoter activity and by a decrease in the stability of these transcripts, respectively.


CONCLUSIONS
Mithramycin causes potent inhibition of collagen production and gene expression in systemic sclerosis dermal fibroblasts in vitro in the absence of cytotoxic effects. These results suggest that this drug may be an effective treatment for the fibrotic process which is the hallmark of systemic sclerosis.
Sandorfi
N
N
Division of Rheumatology, Department of medicine, Thomas Jefferson University, Philadelphia, PA 19107-5041, USA.
Louneva
N
N
Hitraya
E
E
Hajnoczky
G
G
Saitta
B
B
Jimenez
S A
SA
D015152:Blotting, Northern; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D024042:Collagen Type I / Q000096:biosynthesis* / Q000187:drug effects / Q000235:genetics; D000090602:Collagen Type I, alpha 1 Chain; D005347:Fibroblasts / Q000187:drug effects* / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D018613:Microscopy, Confocal; D008926:Plicamycin / Q000494:pharmacology*; D011500:Protein Synthesis Inhibitors / Q000494:pharmacology*; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics; D012595:Scleroderma, Systemic / Q000378:metabolism / Q000473:pathology*; D012867:Skin / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology
D024042:Collagen Type I; D000090602:Collagen Type I, alpha 1 Chain; D011500:Protein Synthesis Inhibitors; D012333:RNA, Messenger; D008926:Plicamycin