Phenytoin modulates connective tissue metabolism and cell proliferation in human skin fibroblast cultures

Abstract

Phenytoin has been proposed for the treatment of certain dermatologic conditions involving connective tissue abnormalities. To understand the biochemical basis of connective tissue changes, human skin fibroblasts were incubated in culture with varying concentrations of phenytoin. Fibroblast proliferation, detected by thymidine incorporation into cells, was slightly stimulated when short incubation periods and low concentrations of phenytoin were employed. However, with longer incubation times and higher phenytoin concentrations, significant reduction in fibroblast proliferation was observed. Incubation of cells with phenytoin did not affect the production of procollagen, measured as synthesis of radioactive hydroxyproline in the cultures. Assay of prolyl hydroxylase, an enzyme participating in the post-translational synthesis of hydroxyproline during collagen biosynthesis, was significantly reduced in the fibroblast cultures. The activity of collagenase, an enzyme participating in degradation of collagen, was markedly decreased in cultures treated with phenytoin. Phenytoin may modulate collagen metabolism primarily by affecting the degradation of collagen. Phenytoin may be useful for treatment of patients with inceased levels of collagenase, such as in recessive dystrophic epidermolysis bullosa.