Effect of phenytoin on intracellular 45Ca2+ accumulation in gingival fibroblasts in vitro

Successful management of phenytoin and phenobarbitone induced gingival enlargement: A multimodal approach

Medication-related gingival enlargement is a common reactionary phenomenon that occurs with the use of several types of therapeutic agents, including antiepileptic drugs (AEDs). This disorder has been documented since 1939, shortly after the introduction of phenytoin. In the present case, a concise review of literature concerning the etiopathogenesis and management of AEDs (phenobarbitone and phenytoin) induced gingival enlargement has been described. It is vital that not only the periodontist, but also dental surgeons and medical practitioners should become aware of the potential etiologic agents, characteristic features, and the differential diagnosis of drug induced gingival enlargement in order to be able to prevent, diagnose and successfully manage the condition.

Thrombin-stimulated proliferation is mediated by endothelin-1 in cultured rat gingival fibroblasts

Abstract Endothelin-1 (ET-1) appears to be involved in drug-induced proliferation of gingival fibroblasts. Thrombin induces proliferation of human gingival fibroblasts via protease-activated receptor 1 (PAR1). In this study, using cultured rat gingival fibroblasts, we investigated whether thrombin-induced proliferation of gingival fibroblasts is mediated by ET-1. Thrombin-induced proliferation (0.05-2.5 U/mL). Proliferation was also induced by a PAR1-specific agonist (TFLLR-NH(2,) 0.1-30 microm), but not by a PAR2-specific agonist (SLIGRL-NH(2)). Thrombin (2.5 U/mL) induced an increase in immunoreactive ET-1 expression, which was inhibited by cycloheximide (10 microg/mL), and an increase in preproET-1 mRNA expression, as assessed by reverse transcription polymerase chain reaction. TFLLR-NH(2) increased ET-1 release into the culture medium in both a concentration (0.01-10 microm)- and time (6-24 h)-dependent manner, as assessed by solid phase sandwich enzyme-linked immunosorbent assay. The thrombin (2.5 U/mL)-induced proliferation was inhibited by a PAR1-selective inhibitor, SCH79797 (0.1 microm) and an ET(A) antagonist, BQ-123 (1 microm), but not by an ET(B) antagonist, BQ-788 (1 microm). These findings suggest that thrombin, acting via PAR1, induced proliferation of cultured rat gingival fibroblasts that was mediated by ET-1 acting via ET(A).

Inhibition of angiotensin II- and endothelin-1-stimulated proliferation by selective MEK inhibitor in cultured rabbit gingival fibroblasts+

We investigated the implication of extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) in the proliferation stimulated by angiotensin II (Ang II) and endothelin-1 (ET-1) in cultured rabbit gingival fibroblasts (CRGF). Ang II stimulated activation of ERK1/2 and the activation was inhibited by CV-11974, an AT1 antagonist, and saralasin, an AT1/AT2 antagonist, but not by PD123,319, an AT2 antagonist in the CRGF. Ang II-stimulated proliferation was inhibited by PD98059 or U0126, selective MEK inhibitors. Furthermore, ET-1 stimulated proliferation via G-protein-coupled ETA receptors, which were identified by Western blot analysis of membrane protein from the CRGF. ET-1 also stimulated activation of ERK1/2 and the activation was inhibited by BQ-123, an ETA inhibitor, and TAK044, an ETA/ETB inhibitor, but not by BQ-788, an ETB inhibitor. ET-1-stimulated proliferation was inhibited by PD98059 or U0126. These findings suggest that ERK1/2 play a role in the signaling process leading to proliferation stimulated by Ang II and ET-1 via G-protein-coupled receptors, AT1 and ETA in CRGF.

Impaired degradation of matrix collagen in human gingival fibroblasts by the antiepileptic drug phenytoin

BACKGROUND

Gingival overgrowth (GO) is a serious adverse effect associated with the administration of phenytoin (PHT), with PHT-induced GO characterized by a massive accumulation of extracellular matrix components, especially collagen, in gingival connective tissues. However, the etiology of such collagen accumulation is still largely unknown. We examined the effects of PHT on the collagen degradation process leading to collagen accumulation in human gingival fibroblasts (HGF).

METHODS

HGFs were cultured with various concentrations of PHT and viable cell numbers and collagen amounts were determined. Gene and protein expressions of matrix metalloproteinases (MMP) and tissue inhibitors of MMPs (TIMP) were quantified with reverse transcription-polymerase chain reaction (RT-PCR) analyses and Western blotting, respectively. Cellular endocytosis of collagen was assayed using flow-cytometric analysis. The effects of PHT on extracellular signal-regulated kinase 1/2 (ERK1/2) and inhibitor kappaB-alpha (IkappaB-alpha) were assayed.

RESULTS

The proliferation of HGFs was not affected by PHT, whereas it significantly increased collagen accumulation. Further, the expressions of MMP-1, -2, and -3 were markedly suppressed by PHT, whereas that of TIMP-1 was induced in a dose- and time-dependent manner. PHT also markedly prevented collagen endocytosis by HGFs, which was associated with the suppression of alpha2beta1-integrin expression. In addition, the phosphorylation of ERK1/2 and IkappaB-alpha degradation were suppressed by PHT.

CONCLUSIONS

These results suggest that PHT causes an impaired degradation of collagen by suppression of enzymatic degradation with MMPs/TIMP-1 and alpha2beta1-integrin-mediated endocytosis. Those alterations are likely mediated through the cellular signaling pathways of ERK1/2 and nuclear factor kappaB. These synergistic effects may cause collagen accumulation, leading to GO.

Proliferative response to phenytoin and nifedipine in gingival fibroblasts cultured from humans with gingival fibromatosis

The response of gingival fibroblasts cultured from humans with gingival fibromatosis to phenytoin (PHT) and nifedipine (NIF) was investigated. PHT and NIF induced proliferation, and increased the expression of immunoreactive endothelin-1 (ET-1). ET-1 (0.1 nm-1 microm) itself also induced proliferation in a concentration-dependent manner. The proliferation was inhibited by BQ-123 (ETA receptor antagonist; 1 microm) and TAK044 (ETA/ETB receptor antagonist; 1 microm), but not by BQ-788 (ETB receptor antagonist; 1 microm). The proliferation induced by PHT (0.25 microm) and NIF (0.25 microm) was inhibited by BQ-123 (1 microm). In addition, the results of Western blot analysis indicated the presence of ETA and ETB receptors in/on the fibroblasts. These findings suggest that PHT- and NIF-induced gingival proliferation may be mediated by endogenously generated ET-1, possibly via ETA receptors.

Pharmacological properties of angiotensin II receptors in cultured rabbit gingival fibroblasts

We demonstrated that angiotensin II (Ang II, 10-1000 nM) induced proliferation of cultured rabbit gingival fibroblasts in a concentration-dependent manner. The Ang II-induced proliferation was inhibited by CV-11974 (AT1 antagonist; 1 microM) and saralasin (AT1/AT2 antagonist; 1 microM), but not by PD123,319 (AT2 antagonist; 1 microM), suggesting that Ang II-induced proliferation was mediated via AT1 receptors present in and/or on gingival fibroblasts. The results of Western blot analysis indicated the presence of AT1 and AT2 receptors in/on the fibroblasts. In a subsequent radioligand binding assay, the binding of [3H]Ang II to the fibroblasts was specific and saturable with both high- and low-affinity sites. Competition binding experiments indicated that Ang II completely displaced [3H]Ang II binding, and CV-11974 and PD123,319 maximally displaced up to approximately 63% and 37% of the total binding, respectively. Ang II and CV-11974 completely displaced the [3H]DuP753 binding but PD123,319 did not, indicating a single population of binding site. These findings demonstrate that gingival fibroblasts contain both AT1 and AT2 receptor subtypes for Ang II, and support that Ang II stimulation of AT1 receptors results in proliferation of the fibroblasts.

Proliferative effects of angiotensin II and endothelin-1 on guinea pig gingival fibroblast cells in culture

We investigated whether phenytoin (PHT) and nifedipine (NIF) induce angiotensin II (Ang II) and endothelin-1 (ET-1) generation by cultured gingival fibroblasts derived from guinea pigs and whether Ang II and ET-1 induce proliferation of these cells. Immunohistochemical experiments showed that PHT (250 nM) and NIF (250 nM) increased the immunostaining intensities of immunoreactive Ang II and ET-1 (IRET-1) in these cells. Captopril (3 microM), an angiotensin-converting enzyme inhibitor, reduced these enhanced intensities to control levels. Ang II (100 nM) enhanced the immunostaining intensity of IRET-1. PHT (250 nM) and NIF (250 nM)-induced cell proliferation. Both PHT- and NIF-induced proliferation was inhibited by captopril (3 microM). Ang II (100 nM) and ET-1 (100 nM) also induced cell proliferation. Ang II-induced proliferation was inhibited by CV11974 (1 microM), an AT(1) receptor antagonist and saralasin (1 microM), an AT(1)/AT(2) receptor antagonist, but not by PD123,319 (1 microM), an AT(2) receptor antagonist. ET-1-induced proliferation was inhibited by BQ123 (10 microM), an ET(A) receptor antagonist, but not by BQ788 (1 microM), an ET(B) receptor antagonist. These findings suggest that PHT- and NIF-induced gingival fibroblast proliferation is mediated indirectly through the induction of Ang II and ET-1 and probably mediated through AT(1) and ET(A) receptors present in or on gingival fibroblasts.

Heparan sulfate interacting protein (HIP/L29) negatively regulates growth responses to basic fibroblast growth factor in gingival fibroblasts

Basic fibroblast growth factor (bFGF) modulates gingival growth, and its release from heparan sulfate (HS) in the extracellular matrix (ECM) governs local tissue bioavailability. We identified a heparin/HS interacting protein (HIP/L29) that recognizes specific HS sequences. We hypothesize that HIP/L29, by modulating the interactions of bFGF with HS chains on proteoglycans, could regulate bFGF bioavailability. To investigate interactions between bFGF and HIP/L29, we isolated and cultured fibroblasts from normal gingiva and overgrown gingiva from patients on cyclosporine (CSA). bFGF significantly stimulated gingival fibroblast proliferation with or without heparin. Recombinant human HIP/L29 dramatically decreased bFGF-induced proliferation, but did not alter responses to insulin-like growth factor-1 (IGF-1). Analysis of mitogen-activated protein kinase (MAPK) phosphorylation patterns showed that bFGF stimulation of p44 (Erk-1), but not p42 (Erk-2), also was inhibited by HIP/L29 in a dose-dependent manner. Together, these results support our hypothesis that HIP/L29 modulates the bioavailability and action of bFGF.

A clinical review of drug-induced gingival overgrowths

There is an increasing number of medications associated with gingival overgrowth. These medications are used to treat a number of common conditions in the Australian population and as such dentists can expect to manage a number of patients with medication-related gingival overgrowth. This review highlights the clinical features and management of the common overgrowths associated with anticonvulsants, immunosuppressants and the calcium channel blockers.

Medication induced gingival overgrowth

A number of idiopathic, pathological and pharmacological reactions may result in an overgrowth of the gingiva. This review concentrates on those overgrowths associated with various pharmacological agents. The pharmaco-kinetics and side effects of each drug associated with gingival overgrowth are discussed along with the clinical and histological features and treatment. By examining the possible pathogeneses for these overgrowths we propose a unifying hypothesis for the causation based around inhibition of apoptosis and decreased collagenase activity modulated by cytoplasmic calcium.

The pathogenesis of drug-induced gingival overgrowth

Gingival overgrowth is a well-documented unwanted effect, associated with phenytoin, cyclosporin, and the calcium channel blockers. The pathogenesis of drug-induced gingival overgrowth is uncertain, and there appears to be no unifying hypothesis that links together the 3 commonly implicated drugs. In this review, we consider a multifactorial model which expands on the interaction between drug and/or metabolite, with the gingival fibroblasts. Factors which impact upon this model include age, genetic predisposition, pharmacokinetic variables, plaque-induced inflammatory and immunological changes and activation of growth factors. Of these, genetic factors which give rise to fibroblast heterogeneity, gingival inflammation, and pharmacokinetic variables appear to be significant in the expression of gingival overgrowth. A more thorough understanding of the pathogenesis of this unwanted effect will hopefully elucidate appropriate mechanisms for its control.

Effect of 5-(p-hydroxyphenyl)-5-phenylhydantoin (p-HPPH) enantiomers, major metabolites of phenytoin, on the occurrence of chronic-gingival hyperplasia: in vivo and in vitro study

The purpose of this study was to assess the possible role of the (R)- and (S)- enantiomers of the phenytoin metabolite p-HPPH in the pathogenesis of gingival hyperplasia (GH). About 98% of circulating p-HPPH is in the (S)-form. There were significant differences between patients with and without GH in (R)-p-HPPH level (0.055 vs 0.042 microgram.ml-1), both enantiomer/racemate level ratios, and R/S enantiomeric ratio (0.0313 vs 0.0232); an increase in serum (R)-p-HPPH level was observed in patients with GH. In separate experiments, the effect of p-HPPH enantiomers on the proliferation of the normal human dermal fibroblast was studied. The in vitro study showed that (R)-p-HPPH selectively stimulated fibroblast growth. The results suggest that the least abundant metabolite, (R)-p-HPPH, is the most toxic with respect to gingival hyperplasia.

Epidermal growth factor potentiates interleukin 1 and tumor necrosis factor-induced prostaglandin biosynthesis in human gingival fibroblasts

The effects of and interactions between epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha) interleukin 1 (IL-1) and tumour necrosis factor alpha (TNF-alpha) on arachidonic acid release and prostaglandin biosynthesis in human gingival fibroblasts were studied. IL-1 alpha, IL-1 beta and TNF-alpha, but not EGF nor TGF-alpha, stimulated prostaglandin E2 (PGE2) formation in the gingival fibroblasts. The effect of IL-1 alpha, IL-1 beta and TNF-alpha on PGE2 formation was significantly potentiated by EGF in a dose-dependent manner. Similarly, TGF-alpha synergistically potentiated IL-1 beta stimulated PGE2 formation. IL-1 beta but not EGF stimulated the release of 3H-arachidonic acid (3H-AA) from prelabelled gingival fibroblasts. In contrast to the effect on PGE2 formation, no synergistic interaction between EGF and IL-1 was seen on arachidonic acid (AA) release. Addition of unlabelled exogenous AA, in the presence of EGF, resulted in a significant increase in PGE2 formation compared to that seen in fibroblasts not exposed to EGF. The results demonstrate that EGF and IL-1 as well as EGF and TNF-alpha act in concert to enhance prostanoid formation in gingival fibroblasts. Data indicates that EGF potentiates the IL-1 and TNF-alpha induced PGE2 formation at the level of prostaglandin endoperoxide synthase (cyclooxygenase). The synergistic effects of inflammatory cytokines and growth factors may be of physiological importance for regulation of regenerative tissue growth during inflammation and repair.

The phenytoin metabolite p-HPPH upregulates prostaglandin biosynthesis in human gingival fibroblasts challenged to interleukin-1

The effects of and interactions between the major phenytoin (PHT) metabolite 5-parahydroxyphenyl-5-phenylhydantoin (p-HPPH) and interleukin-1 (IL-1 alpha, IL-1 beta) or tumor necrosis factor alpha (TNF alpha) on prostaglandin biosynthesis in human gingival fibroblasts were studied. IL-1 alpha, IL-1 beta and TNF alpha, dose-dependently, stimulated PGE2 formation in gingival fibroblasts. The metabolite, p-HPPH (1.2-2.4 micrograms/ml), did not induce PGE2 formation itself but potentiated IL-1 alpha and IL1 beta induced PGE2 formation in the gingival fibroblasts in a manner dependent on the concentration of both IL-1 and p-HPPH. The metabolite also stimulated IL-1 induced formation of 6-Keto PGF1 alpha, the stable breakdown product of PGI2, in a dose dependent manner. IL-1 beta induces release of [3H]-arachidonic acid ([3H]-AA) from prelabelled fibroblasts, which was potentiated by p-HPPH (> or = 1.2 micrograms/ml). TNF alpha (> or = 1 ng/ml) significantly stimulated the biosynthesis of PGE2 by a process that was also potentiated by p-HPPH. Addition of exogenous, unlabelled AA (10 microM) caused an increase of PGE2 formation in the fibroblasts that was not potentiated by p-HPPH (1.6 micrograms/ml). The results indicate that treatment with p-HPPH results in upregulation of prostaglandin synthesis in gingival fibroblasts challenged to IL-1 or TNF alpha at the level of phospholipase A2.

The effect of phenytoin medication on dentin apposition, root length, and caries progression in rat molars

To determine the effect of phenytoin (PHT) on dentin apposition and the rate of caries progression in dentin, 40 Wistar rats were treated daily for 35 days with intraperitoneal injections of 5,5-diphenylhydantoin. Twenty-eight controls received saline with pH adjusted to that of PHT. One PHT and one control group were fed a 43% sucrose diet, and the others a non-cariogenic pellet diet. Streptococcus sobrinus was inoculated to induce caries. Schiff staining was used to determine caries. The areas of dentin apposition and dentinal caries lesions were quantified after tetracycline staining. The root lengths were measured. PHT reduced slightly the dentin apposition and activated significantly the progression of the dentinal carious lesions. No difference in caries initiation was found. The high-sucrose diet reduced dentin apposition and increased the rate of progression of existing caries greatly. Our study suggests that both the high-sucrose diet and PHT have an effect on secreting odontoblasts, which can be seen as an alteration in dentin apposition and caries progression rates in dentin.

Influence of phenytoin on cytoplasmic free Ca2+ level in human gingival fibroblasts

Influence of 5,5-diphenylhydantoin (phenytoin; PHT) on the cytoplasmic free Ca2+ concentration, [Ca2+]i, was studied in fura 2 loaded adherent monolayers of human gingival fibroblasts derived from three patients before and after 9 months of PHT therapy. In the patient where gingival overgrowth developed during PHT medication (responder), addition of PHT to gingival fibroblasts derived before PHT medication induced a transient extracellular Ca2+ dependent increase in [Ca2+]i. In a non-responder patient, where gingival overgrowth did not develop during the same period of PHT therapy, addition of PHT to gingival fibroblasts derived before the start of medication did not significantly affect [Ca2+]i. Under extracellular Ca2+ deficient conditions, addition of PHT to serum-starved fibroblasts derived from the two categories of patients before the medication resulted in an increase in [Ca2+]i. In fibroblasts derived from the responder patient during PHT medication, in contrast to those from the non-responders (n = 2), the basal level of [Ca2+]i was significantly decreased. The results indicate that, in the cases studied, there is a relationship between PHT induced alterations in [Ca2+]i in gingival fibroblasts and the clinical development of gingival overgrowth.

On the mechanism of drug-induced gingival hyperplasia

Proposed mechanisms of the side effect of drug-induced gingival hyperplasia are reviewed. Hypotheses with regard to inflammation from bacterial plaque, increased sulfated glycosaminoglycans, immunoglobulins, gingival fibroblast phenotype population differences, epithelial growth factor, pharmacokinetics and tissuebinding, collagenase activation, disruption of fibroblast cellular sodium/calcium flux, folic acid and a combination hypothesis are evaluated.

Felodipine-induced gingival hyperplasia: a clinical and histologic study

This paper reports, for the first time, gingival hyperplasia in a patient treated with felodipine, a drug which belongs to the group of calcium ion antagonists. The observed gingival overgrowth was most significant in the area of interdental papillae of the anterior region of the mouth. The described hyperplastic tissue was characterized by a firm and pale appearance, with a normally stippled pattern. Histopathologically, a conspicuous increase of fibrous connective tissue, as well as an inflammatory infiltrate and hyperplasia of the overlying epithelium were observed. Consequently, the present observation adds another drug to the list of substances capable to induce gingival hyperplasia.

Regulation of epidermal growth factor receptor metabolism in gingival fibroblasts by phenytoin in vitro

Normal human gingival fibroblasts derived from five children between 8 and 12 yr of age were cultured under serum-free conditions in the presence of epidermal growth factor (EGF) either alone or in combination with 5,5-diphenylhydantoin (phenytoin; PHT). DNA-synthesis, binding of EGF to its cell-surface receptor and internalisation of EGF-receptor-ligand complexes were studied. In normal gingival fibroblasts treated solely with EGF for 48 h, DNA synthesis increased significantly, as in cells treated solely with PHT. When EGF binding data was calculated according to Scatchard, it was found that the number of EGF receptors in fibroblasts increased significantly after PHT treatment. The number of EGF-receptors in untreated gingival fibroblasts varied from 147,000 to 170,000 receptors per cell whereas in PHT-treated fibroblasts the range was from 181,000 to 280,000. The study indicates that PHT regulates EGF-receptor metabolism in human gingival fibroblasts by increasing the number of cell-surface EGF-receptors which may contribute to the alteration of gingival connective tissue observed in patients undergoing PHT medication.

Effect of phenytoin medication on the metabolism of epidermal growth factor receptor in cultured gingival fibroblasts

Human gingival fibroblasts derived from 2 patients before and 9 months after the start of phenytoin (PHT) therapy were studied with respect to the effect of epidermal growth factor (EGF) on the incorporation of 3H-thymidine into DNA, binding of EGF to its cell-surface receptor, internalization of EGF-receptor-ligand complexes and, finally, with respect to EGF receptor mRNA levels. In fibroblasts derived from the patient who developed gingival overgrowth during the PHT medication (responder) as well as in the fibroblasts derived from the patient where gingival overgrowth did not develop (non-responder), the affinity of the EGF receptor for EGF was not significantly changed. In the non-responder patient the internalization of EGF receptor ligand was decreased, whereas it was increased in the fibroblasts derived from the responder patient after PHT therapy. The steady-state level of EGF-r mRNA increased significantly (p less than 0.001) in the cultured fibroblasts derived from the non-responder but decreased (p less than 0.05) in the responder patient following PHT therapy. Ligand affinity cross-linking studies revealed one major component of EGF receptor with a molecular weight of 170 KDa in fibroblasts from the non-responder as well as from the responder. The study indicates that PHT medication results in a down-regulation of EGF receptor metabolism in fibroblasts derived from a responder patient, whereas in the non-responder patient EGF receptor metabolism is up-regulated.