Fibrostatin C

Prolyl 4-hydroxylase (PH), which catalyzes the conversion of prolyl residues to 4-hydroxyproline, plays a central role in the synthesis and secretion of collagen. We demonstrated that fibroblasts from patients with systemic sclerosis produced significantly more PH than those from healthy subjects. To regulate excessive collagen production by scleroderma fibroblasts, we examined the effect of a PH inhibitor on collagen production by scleroderma fibroblasts. Fibrostatin-C, a PH inhibitor, significantly decreased the amount of procollagen (type I) production by scleroderma fibroblasts (p < 0.01). We suggest that this PH inhibitor might be a valid antifibrotic agent useful for the treatment of patients with scleroderma.

Fibrostatin C, a novel prolyl hydroxylase inhibitor produced by Streptomyces catenulae subsp. griseospora No. 23924, inhibited the activity of purified chick embryo prolyl hydroxylase by about 50% at a concentration of 2.9 x 10(-5) M. The inhibition was mixed type with respect to (Pro-Pro-Gly)5 with a Ki of 2.1 x 10(-5) M. When an excess of ferrous ions or ascorbate was added to the reaction mixture, the inhibition was negligibly or slightly reversed, respectively. Fibrostatin C, when administered intraperitoneally at 1 mg/kg/day or orally at about 100 mg/kg/day as a dietary admixture, significantly inhibited estradiol-17 beta stimulated collagen biosynthesis in the uterus of the immature rat.

Purpose: To investigate the effect of fibrostatin C, a prolyl 4-hydroxylase (PH) inhibitor produced by Streptomyces catenulae subsp. griseospora, on type I collagen secretion by human Tenon's capsule fibroblasts (TCFs) in vitro, as an indication of the potential therapeutic efficacy of this compound in antifibrotic therapy after glaucoma filtering surgery. Methods: The concentrations of type II procollagen COOH-terminal peptide (PIP) in culture medium or cell lysate were determined by immunoassays. For comparison with its effect on PIP secretion, we determined the effects of the agent on the secretion of other peptides, including laminin, vitronectin receptor, and a metalloproteinase inhibitor. The expression of collagens I and III, fibronectin, and PH by TCFs was examined by immunohistochemistry, and cellular ultrastructure was evaluated by transmission electron microscopy. Results: Fibrostatin C (50 microM) significantly reduced the concentration of PIP in culture medium and increased its concentration in the cell lysate in a dose-dependent manner, but it had no effect on the secretion of other peptides. Cell viability and proliferation were not affected by fibrostatin C. Fibrostatin C also increased the number of cytoplasmic granules immunoreactive with antibodies to collagen I or III, but had no effect on fibronectin or PH immunoreactivity. Ultrastructurally, cisternae of the endoplasmic reticulum were dilated in fibrostatin C-treated TCFs, consistent with the retention of underhydroxylated collagen precursors in this organelle. Conclusions: Fibrostatin C inhibits the secretion of type I collagen by cultured TCFs. This agent may thus prove therapeutically beneficial for inhibiting the excess fibrosis in the wound of filtering surgery.