Phenytoin and cyclosporin A suppress the expression of MMP-1, TIMP-1, and cathepsin L, but not cathepsin B in cultured gingival fibroblasts

Background: Fibroblasts are known not only to synthesize and secrete extrac ellular matrix proteins, but also to degrade them for connective tissue rem odeling. Drug-induced gingival overgrowth is characterized by a massive acc umulation of extracellular matrix components in gingival connective tissues . Although some previous reports suggested that causative drugs stimulated the fibroblast proliferation, the results are not conclusive yet. In this s tudy, we hypothesized that drug-induced gingival overgrowth could be a cons equence of impaired ability of matrix degradation rather than an enhanced p roliferation of gingival fibroblasts induced by these drugs. Methods: Normal human gingival fibroblasts were cultured with or without ei ther 20 mug/ml of phenytoin or 200 ng/ml of cyclosporin A. Total RNA and ce llular proteins were collected every day for RT-PCR analyses and for measur ing lysosomal enzyme activity. In addition, an immunohistochemical study wa s performed to detect lysosomal enzymes in cells from enlarged gingiva of t he patients with phenytoin-induced gingival overgrowth. Results: RT-PCR analyses revealed that these drugs suppressed the expressio n of MMP-1, TIMP-1, and cathepsin L, but not that of cathepsin B in a time- dependent manner. Then, we measured the activity of lysosomal enzymes and c athepsin B and L. The results indicated that although cathepsin B activity was not observed to be impaired, regardless of the drugs used in these cell s, both total and active forms of combined activity of cathepsins B and L w ere suppressed in a time-dependent manner. Conclusions: The results indicate that, besides suggested effects of these drugs on gingival fibroblasts and/or on accumulated cells in the gingival t issues, extracellular matrix-degrading ability, particularly that by cathep sin L, is also suppressed by cyclosporin A and phenytoin in gingival fibrob lasts, and that lysosomal enzyme plays an important role in the pathogenesi s of drug-induced gingival hyperplasia.