The inhibitory effects of camptothecin, a topoisomerase I inhibitor, on collagen synthesis in fibroblasts from patients with systemic sclerosis

The main manifestation of systemic sclerosis (SSc) is the overproduction of extracellular matrix, predominantly type I collagen. This study was undert aken to evaluate the effects of noncytotoxic doses of the topoisomerase I i nhibitor camptothecin (CPT) on collagen production in the activated dermal fibroblasts from patients with SSc and healthy donors. The fibroblasts were cultured in the presence or absence of CPT. Production of collagenous prot eins by fibroblasts was determined in cell and matrix layers by ELISA and i n conditioned media by [H-3]proline incorporation, gel electrophoresis, and autoradiography. Expression of alpha2(I) collagen (COL1A2) mRNA was measur ed by northern blot, and the activity of COL1A2 promoter was determined by a chloramphenicol acetyltransferase, assay. CPT (10(-7) M) decreased the de position of type I collagen by 68%, of type III by 38%, and of type VI by 2 1% in SSc fibroblasts and to a lesser degree in healthy controls. Similarly , CPT (10(-8) M to 10(-6) M) significantly inhibited secretion of newly syn thesized collagenous proteins into conditioned media by 50%. CPT (10(-8) M to 10(-6) M) caused a significant dose-dependent inhibition of COL1A2 mRNA levels and COL1A2 promoter activity, both by as much as 60%. The inhibitory effect of CPT on collagen production by fibroblasts from patients with SSc suggests that topoisomerase I inhibitors may be effective in limiting fibr osis in such patients.