Inhibition of type I collagen gene expression in normal and systemic sclerosis fibroblasts by a specific inhibitor of geranylgeranyl transferase I

Objective. To examine the effects of specific inhibition of geranylgeranyl transferase I on the expression of types I and III collagen genes in normal and systemic sclerosis (SSc) dermal fibroblasts in vitro. Methods. Fibroblasts from 2 normal subjects and 4 SSc patients were incubated with 2-10 μM of GGTI-298, a specific geranylgeranyl transferase inhibitor. Type I collagen and fibronectin production were determined by enzyme-linked immunosorbent assay. Steady-state messenger RNA (mRNA) levels for α 1/4 (I), α2(I), and α1(III) collagens and fibronectin were assessed by Northern hybridization, and the transcription of the α1(I) collagen gene was examined by transient transfections with a reporter construct containing -5.3 kb of the gene. Results. GGTI-298 caused a dose-dependent inhibition of type I collagen production and a reduction in the steady-state levels of α1(I), α2(I), and α1(III) mRNA in normal and SSc cells. A 60-70% inhibition of type I collagen production and a 70-80% reduction in the mRNA levels for α1(I), α2(I), and α1(III) were observed at 10 μM GGTI-298. In contrast, the expression of fibronectin, cyclooxygenase 1, and GAPDH was not affected. The effects on α1(I) collagen mRNA resulted from a profound reduction in transcription of the α1(I) collagen gene promoter. GGTI-298 did not affect cellular viability or morphology. Conclusion. These results demonstrate that specific inhibition of geranylgeranyl prenylation causes a potent and selective inhibition of expression of the genes encoding types I and III collagens, without affecting cellular viability. The findings indicate that inhibition of geranylgeranyl prenylation should be further studied as a potential therapeutic approach for SSc and other fibrosing diseases.