Prevention of phenytoin-induced gingival overgrowth by lovastatin in mice.

Drug-induced gingival overgrowth is caused by the antiseizure medication phenytoin, calcium channel blockers, and ciclosporin. Characteristics of these drug-induced gingival overgrowth lesions differ. We evaluate the ability of a mouse model to mimic human phenytoin-induced gingival overgrowth and assess the ability of a drug to prevent its development. Lovastatin was chosen based on previous analyses of tissue-specific regulation of CCN2 production in human gingival fibroblasts and the known roles of CCN2 in promoting fibrosis and epithelial to mesenchymal transition. Data indicate that anterior gingival tissue overgrowth occurred in phenytoin-treated mice based on gross tissue observations and histomorphometry of tissue sections. Molecular markers of epithelial plasticity and fibrosis were regulated by phenytoin in gingival epithelial tissues and in connective tissues similar to that seen in humans. Lovastatin attenuated epithelial gingival tissue growth in phenytoin-treated mice and altered the expressions of markers for epithelial to mesenchymal transition. Data indicate that phenytoin-induced gingival overgrowth in mice mimics molecular aspects of human gingival overgrowth and that lovastatin normalizes the tissue morphology and the expression of the molecular markers studied. Data are consistent with characterization of phenytoin-induced human gingival overgrowth in vivo and in vitro characteristics of cultured human gingival epithelial and connective tissue cells. Findings suggest that statins may serve to prevent or attenuate phenytoin-induced human gingival overgrowth, although specific human studies are required.

Requirement for active glycogen synthase kinase-3ß in TGF-ß1 upregulation of connective tissue growth factor (CCN2/CTGF) levels in human gingival fibroblasts.

Connective tissue growth factor (CCN2/CTGF) mediates transforming growth factor-ß (TGF-ß)-induced fibrosis. Drug-induced gingival overgrowth is tissue specific. Here the role of the phosphoinositol 3-kinase (PI3K) pathway in mediating TGF-ß1-stimulated CCN2/CTGF expression in primary human adult gingival fibroblasts and human adult lung fibroblasts was compared. Data indicate that PI3K inhibitors attenuate upregulation of TGF-ß1-induced CCN2/CTGF expression in human gingival fibroblasts independent of reducing JNK MAP kinase activation. Pharmacologic inhibitors and small interfering (si)RNA-mediated knockdown studies indicate that calcium-dependent isoforms and an atypical isoform of protein kinase C (PKC-δ) do not mediate TGF-ß1-stimulated CCN2/CTGF expression in gingival fibroblasts. As glycogen synthase kinase-3ß (GSK-3ß) can undergo phosphorylation by the PI3K/pathway, the effects of GSK-3ß inhibitor kenpaullone and siRNA knockdown were investigated. Data in gingival fibroblasts indicate that kenpaullone attenuates TGF-ß1-mediated CCN2/CTGF expression. Activation of the Wnt canonical pathways with Wnt3a, which inhibits GSK-3ß, similarly inhibits TGF-ß1-stimulated CCN2/CTGF expression. In contrast, inhibition of GSK-3ß by Wnt3a does not inhibit, but modestly stimulates, CCN2/CTGF levels in primary human adult lung fibroblasts and is ß-catenin dependent, consistent with previous studies performed in other cell models. These data identify a novel pathway in gingival fibroblasts in which inhibition of GSK-3ß attenuates CCN2/CTGF expression. In adult lung fibroblasts inhibition of GSK-3ß modestly stimulates TGF-ß1-regulated CCN2/CTGF expression. These studies have potential clinical relevance to the tissue specificity of drug-induced gingival overgrowth.