Phenytoin and Cyclosporine A Specifically Regulate Macrophage Phenotype and Expression of Platelet-Derived Growth Factor and Interleukin-1 in Vitro and in Vivo: Possible Molecular Mechanism of Drug-Induced Gingival Hyperplasia

Phenytoin (PHT) is an anticonvulsant drug commonly used for the prevention of seizures. A common side effect of PHT therapy is gingival hyperplasia, occasionally so severe that it requires surgical intervention. Cyclosporine A (CSA) is a drug widely used for the control of rejection phenomena following solid organ and bone marrow transplantation. A frequent side effect of CSA administration is gingival overgrowth. As yet, the molecular mechanisms of drug-induced gingival hyperplasia are unknown although it has been postulated that certain drugs increase fibroblastic activity through alterations in levels of various growth factors and cytokines. The purpose of this study was to: 1) evaluate monocyte/macrophage platelet-derived growth factor (PDGF) and interleukin (IL)-1β production in vitro after exposure to CSA; 2) determine the levels of PDGF-B and IL-1β gene expression in minimally inflamed gingival tissues of control patients and PHT-treated patients exhibiting gingival overgrowth as well as patients with severe gingival inflammation; and 3) combine characterization of macrophage phenotype with clinical presentation and expression of PDGF-B and IL-1β in gingival tissues from the control and PHT-treated patients. For the in vitro studies, commercial ELISA kits were used to measure PDGF-A/PDGF-B and IL-1β levels in conditioned media from rat and human monocyte/macrophage cell cultures. CSA caused a significant elevation of PDGF but did not cause any changes in IL-1β levels. For the in vivo studies, quantitative competitive reverse transcription polymerase chain reaction (QC-RTPCR) techniques were utilized to measure PDGF-B and IL-1β mRNA levels in experimental groups. PHT-treated patients exhibiting gingival overgrowth demonstrated a significant increase in PDGF-B mRNA compared with minimally inflamed controls. Patients with severe gingival inflammation also demonstrated a significant increase in PDGF-B mRNA however, PHT-induced PDGF-B upregulation is approximately 6 times larger than PDGF-B upregulation produced by inflammation alone. PHT-treated patients exhibiting gingival overgrowth demonstrated no significant increase in IL-1β mRNA; however, IL-1β mRNA levels in the severely inflamed gingival samples demonstrated a significant increase. Additionally, for the clinical samples, macrophage phenotype was characterized immunohistochemically in adjacent sections using specific monoclonal antibodies for inflammatory and reparative/proliferative phenotypes. There were no significant differences in the numbers of either macrophage phenotype in minimally inflamed gingival tissues; however, in the severely inflammed tissue, there was a significant increase in the inflammatory macrophage phenotype and in the hyperplastic gingival tissue, there was a significant increase in the reparative/proliferative macrophage phenotype. The results of this investigation indicate that the clinical presentation of inflamed and hyperplastic gingival tissues is associated with specific macrophage phenotypes which express the pro-inflammatory cytokine IL-1β in inflamed tissues or the essential polypeptide growth factor PDGF-B in PHT-induced hyperplastic tissues.