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

Phenytoin enhances the phosphorylation of epidermal growth factor receptor and fibroblast growth factor receptor in the subventricular zone and promotes the proliferation of neural precursor cells and oligodendrocyte differentiation

Phenytoin is a widely used antiepileptic drug that induces cell proliferation in several tissues, such as heart, bone, skin, oral mucosa and neural precursors. Some of these effects are mediated via fibroblast growth factor receptor (FGFR) and epidermal growth factor receptor (EGFR). These receptors are strongly expressed in the adult ventricular-subventricular zone (V-SVZ), the main neurogenic niche in the adult brain. The aim of this study was to determine the cell lineage and cell fate of V-SVZ neural progenitors expanded by phenytoin, as well as the effects of this drug on EGFR/FGFR phosphorylation. Male BALB/C mice received 10 mg/kg phenytoin by oral cannula for 30 days. We analysed the proliferation of V-SVZ neural progenitors by immunohistochemistry and western blot. Our findings indicate that phenytoin enhanced twofold the phosphorylation of EGFR and FGFR in the V-SVZ, increased the number of bromodeoxyuridine (BrdU)+/Sox2+ and BrdU+/doublecortin+ cells in the V-SVZ, and expanded the population of Olig2-expressing cells around the lateral ventricles. After phenytoin removal, a large number of BrdU+/Receptor interacting protein (RIP)+ cells were observed in the olfactory bulb. In conclusion, phenytoin enhanced the phosphorylation of FGFR and EGFR, and promoted the expression of neural precursor markers in the V-SVZ. In parallel, the number of oligodendrocytes increased significantly after phenytoin removal.

Topical Phenytoin Application in Grade I and II Diabetic Foot Ulcers: A Prospective Study

BACKGROUND

India is fast becoming world diabetes capital. Diabetic foot infections are major problems among innumerable complications associated with diabetes.

MATERIAL AND METHODS

A randomized control study was conducted to evaluate the effect of topical phenytoin on healing in diabetic foot ulcers. One hundred patients with grade I/ II diabetic foot ulcers were randomly divided into two equal groups. Patients subjected to topical phenytoin dressing were classified under study and those who underwent normal salinewound dressings were classified as control. Both the groups were compared in terms of discharge, slough, wound area reduction and duration of hospital stay.

RESULTS

Discharge and slough from wound reduced significantly by day 14 in phenytoin group and within 21 days in control group. Mean duration of hospital stay in phenytoin group was 20 days, whereas in control group, it was 26 days. This difference was statistically significant (p value <0.005,df 1).

CONCLUSION

Hence, Phenytoin proved to be useful as a topical agent in promoting healing and in controlling infections in diabetic foot ulcers.

Diphenylhydantoin promotes proliferation in the subventricular zone and dentate gyrus

PROBLEM STATEMENT

Diphenylhydantoin (phenytoin) is an antiepileptic drug that generates hyperplasia in some tissue by stimulating Epidermal Growth Factor (EGFR) and Platelet-Derived Growth Factor beta (PDGFR-β) receptors and by increasing serum levels of basic fibroblast growth factor (bFGF, FGF2 or FGF-β). Neural stem cells in the adult brain have been isolated from three regions: the Subventricular Zone (SVZ) lining the lateral wall of the lateral ventricles, the Subgranular Zone (SGZ) in the dentate gyrus at the hippocampus and the Subgranular Zone (SZC) lining between the hippocampus and the corpus callosum. Neural stem cells actively respond to bFGF, PDGFR-β or EGF by increasing their proliferation, survival and differentiation. The aim of this study was to evaluate the effect of phenytoin on proliferation and apoptosis in the three neurogenic niches in the adult brain.

APPROACH

We orally administrated phenytoin with an oropharyngeal cannula for 30 days: 0 mg kg^-1 (controls), 1, 5, 10, 50 and 100 mg kg^-1. To label proliferative cells, three injections of 100 mg kg^-1 of BrdU was administrated every 12 h. Immunohistochemistry against BrdU or Caspase-3 active were performed to determine the number of proliferative or apoptotic cells.

RESULTS

Our results showed that phenytoin induces proliferation in the SVZ and the SGZ in a dose-dependent manner. No statistically significant effects on cell proliferation in the SCZ neither in the apoptosis rate at the SVZ, SGZ and SCZ were found.

CONCLUSION

These data indicate that phenytoin promotes a dose-dependent proliferation in the SVZ and SGZ of the adult brain. The clinical relevance of these findings remain to be elucidated.

Down-regulation of epidermal growth factor receptor-dependent signaling by Porphyromonas gingivalis lipopolysaccharide in life-expanded human gingival fibroblasts

BACKGROUND AND OBJECTIVE

Human gingival fibroblasts exhibit proliferative responses following epidermal growth factor exposure, which are thought to enhance periodontal regeneration in the absence of bacterial products such as lipopolysacharide. However, lipopolysaccharide challenge activates human gingival fibroblasts to release several inflammatory mediators that contribute to the immune response associated with periodontitis and attenuate wound repair. We tested the hypothesis that Porphyromonas gingivalis lipopolysaccharide-activated signaling pathways down-regulate epidermal growth factor receptor-dependent events.

MATERIAL AND METHODS

To study lipopolysaccharide/epidermal growth factor interactions in human gingival fibroblasts, we introduced the catalytic subunit of human telomerase into human gingival fibroblasts, thereby generating a more long-lived cellular model. These cells were characterized and evaluated for lipopolysaccharide/epidermal growth factor responsiveness and regulation of epidermal growth factor-dependent pathways.

RESULTS

Comparison of human telomerase-transduced gingival fibroblasts with human gingival fibroblasts revealed that both cell lines exhibit a spindle-like morphology and express similar levels of epidermal growth factor receptor, CD14 and Toll-like receptors 2 and 4. Importantly, human telomerase-transduced gingival fibroblasts proliferation rates are increased 5-9 fold over human gingival fibroblasts and exhibit a longer life span in culture. In addition, human telomerase-transduced gingival fibroblasts and human gingival fibroblasts exhibit comparable profiles of mitogen-activated protein kinase kinase (extracellular signal-regulated kinase 1/2) activation upon epidermal growth factor or P. gingivalis lipopolysaccharide administration. Interestingly, treatment with P. gingivalis lipopolysaccharide leads to a down-regulation of epidermal growth factor-dependent extracellular signal-regulated kinase 1/2, p38 and cyclic-AMP response element binding protein phosphorylation in both cell types.

CONCLUSION

These studies demonstrate that human telomerase-transduced gingival fibroblasts exhibit an extended life span and recapitulate human gingival fibroblasts biology. Moreover, this system has allowed for the first demonstration of lipopolysaccharide down-regulation of epidermal growth factor activated pathways in human gingival fibroblasts and should facilitate the analysis of signaling events relevant to the pathogenesis and treatment of periodontitis.

Cyclosporin But Not Tacrolimus Significantly Increases Salivary Cytokine Contents in Rats

BACKGROUND

Cyclosporin (CsA) and tacrolimus (FK-506) are immunosuppressive drugs that specifically inhibit T-cell activation via calcineurin inhibition. Gingival overgrowth is a common side effect following the administration of CsA. The severity of gingival overgrowth seen in patients taking FK-506 is less than that observed with CsA. Little is known about the involvement of saliva in drug-induced gingival overgrowth. The purpose of this study was to investigate the salivary contents of tumor growth factor beta1 (TGF-beta1), epidermal growth factor (EGF), and interleukin-6 (IL-6) as well as the hystometry of gingival tissue obtained from rats treated with either FK-506 or CsA.

METHODS

For 30 or 60 days rats received daily subcutaneous injection doses of either CsA or FK-506 (10 mg/kg). The concentrations of TGF-beta1, EGF, and IL-6 in saliva were determined by enzyme-linked immunosorbent assay, and after histological processing, the oral epithelium and connective tissue were assessed at the region of the lower first molars.

RESULTS

The levels of TGF-beta1, EGF, and IL-6 in saliva were not significantly altered by any of the treatments after 30 days. After 60 days of treatment with CsA, gingival overgrowth and significant increase in salivary TGF-beta1, EGF, and IL-6 concentrations were observed; no statistically significant changes were induced by FK-506.

CONCLUSION

Within the limits of this experimental study, it can be concluded that CsA, but not FK-506, induced gingival overgrowth associated with an increase of the salivary levels of the cytokines TGF-beta1, EGF, and IL-6.

Estrogen Suppression Induces Papillary Gingival Overgrowth in Pregnant Baboons

BACKGROUND

Alterations in sex steroids during pregnancy are associated with the development and exacerbation of reactive lesions involving the gingiva. Currently, few experimental animal models similar to humans are available to examine regulatory pathways involving sex steroids and the periodontium.

METHODS

In the present study, we used the baboon as a novel experimental model for the study of the regulatory actions of estrogen on the periodontium during pregnancy. Pregnant baboons (N = 5) were administered the potent, highly specific aromatase inhibitor CGS 20267 (2 mg/day subcutaneously) daily on days 60 through 165 of gestation (term = 184). Untreated females (N = 10) and females (5) concomitantly administered aromatase inhibitor and estradiol benzoate (2.0 mg/day each subcutaneously) served as controls. Gingival biopsies were taken between days 145 and 165 of gestation.

RESULTS

Administration of CGS 20267 in all females suppressed maternal serum concentrations of estradiol by 95% and induced the development of an exuberant papillomatous enlargement of the gingiva by gestational day 110, with the most prominent development involving the labial aspects of the anterior sextants. None of the untreated pregnant controls or females concomitantly administered aromatase inhibitor and estradiol benzoate developed gingival overgrowth. Thus, estradiol alone prevented the onset of gingival overgrowth induced by estrogen suppression. In all baboons, discontinuation of the aromatase inhibitor at time of cesarean section resulted in spontaneous regression and resolution of the papillomatous hyperplasia within 4 to 6 weeks. Clinically, the gingival papillary overgrowth was erythematous and edematous, with a propensity toward spontaneous subgingival hemorrhage. Histologically, the biopsy specimens demonstrated hyperplasia of the epithelium typified by mild hyperkeratosis, acanthosis, and elongation and isolated anastamoses of rete ridges. Subjacent to the intact epithelium was a loose connective tissue stroma with isolated areas of inflammatory cell infiltrate. Special stains verified the presence of isolated bacterial biofilms; however, no evidence of fungal filaments was present. Histological features suggestive of viral infection were notably absent in the epithelium. No evidence of viral particles or capsids was identified using transmission electron microscopy. Reverse transcription polymerase chain reaction analysis, using a panel of degenerate primers, was negative for papilloma family viruses.

CONCLUSIONS

These results are consistent with a significant role for estrogen during primate pregnancy in the regulation of cellular proliferation and differentiation within the gingiva. The baboon represents an important experimental model for studying the regulatory actions of estrogen on the periodontium during pregnancy.

Bone cell mitogenic action of fluoroaluminate and aluminum fluoride but not that of sodium fluoride involves upregulation of the insulin-like growth factor system

The fluoroaluminate (AlF(4)(-)) ion and sodium fluoride (NaF) have previously been shown to be bone cell mitogens. This study sought to determine whether the bone cell mitogenic action of AlF(4)(-) and/or NaF would involve the insulin-like growth factor (IGF) regulatory system. We evaluated the effect of mitogenic doses of AlF(4)(-) and NaF on the mRNA levels and the protein level (in conditioned media [CM]) of several components of the IGF system (i.e., IGF-2, IGF binding protein [IGFBP]-4, and IGFBP-5) in human TE85 osteosarcoma cells. Aluminum fluoride (AlF(3)) was included for comparison. NaF, AlF(3), and AlF(4)(-), each at 50-100 micromol/L, increased [3H]thymidine incorporation in TE85 cells. Mitogenic concentrations of AlF(3) and AlF(4)(-): (1) increased the mRNA (up to twofold after 24 h treatment) and protein (in CM) levels (up to 2.5-fold after 48 h treatment) of IGF-2; (2) increased the mRNA level (twofold) and the protein level in CM (up to threefold) of stimulatory IGFBP-5; and (3) either reduced slightly or had no effect on the mRNA and protein (in CM) levels of the inhibitory IGFBP-4. Conversely, mitogenic concentrations of NaF had no significant effects on the protein (in CM) or mRNA level of IGF-2, IGFBP-4, or IGFBP-5. The addition of an inhibitory concentration of IGFBP-4 completely abolished the bone cell mitogenic activity of AlF(3) and AlF(4)(-) but not that of NaF. The findings of this study provide strong evidence that the bone cell mitogenic activity of AlF(4)(-) and AlF(3), but not that of NaF, is mediated by the upregulation of the IGF regulatory system.

Immunohistochemical analysis of epidermal growth factor receptor in cyclosporin A-induced gingival overgrowth

Cyclosporin A (CsA)induced gingival overgrowth represents a tissue of fibrosis and epidermal growth factor (EGF) has been shown to induce extracellular matrix synthesis by fibroblasts. The purpose of this study was to evaluate the expression of EGF-receptor (EGF-r) in frozen sections of CsA-induced overgrown gingival tissue using immunohistochemical and semiquantitative techniques. Gingival biopsies were obtained from 12 renal transplant patients receiving CsA as well as 9 systemically and periodontally healthy individuals. Immunohistochemical staining procedures were carried out in frozen sections of gingival tissue and the expression of EGF-r was compared between the two study groups. The expression of EGF-r was more pronounced in the oral gingival epithelium of CsA-induced overgrown gingiva as compared to those of the clinically healthy gingival specimens. The reactivity in the inflammatory infiltrate and connective tissue cells of both of the study groups was similar. In conclusion, the results of the present study may suggest that CsA affects EGF-r metabolism in gingival keratinocytes resulting in an increased number of cell surface receptors, which may eventually play a role in the pathogenesis of gingival tissue alterations.

Developmental effects of phenytoin may differ depending on sex of offspring

Phenytoin (sodium salt), a developmental neurotoxicant, was administered orally by gavage (50-150 mg/kg) to pregnant rats on days 7-18 of gestation. Various developmental and behavioral indices were evaluated. Results indicated that phenytoin produced decreases in maternal and pup body weight gains, pup hindbrain, and F1 adult forebrain, whole brain, and cerebellar weights. Behavioral/developmental effects included performance deficits in a modified Morris water maze assay, in air righting and auditory startle responses, and increases in locomotor activity, accelerated eye opening, incisor eruption, negative geotaxis, and olfactory orientation. Female offspring appeared to be more severely affected when measuring incisor eruption, negative geotaxis, air righting, reactivity, and locomotor and maze activity. Males appeared to be more affected when measuring eye opening, olfactory orientation, and decreases in startle response. This study suggests that prenatal phenytoin exposure may result in developmental changes and behavioral deficits that may differ depending on the sex of the offspring.

Osteogenic actions of phenytoin in human bone cells are mediated in part by TGF-beta 1

We have recently demonstrated that phenytoin, a widely used therapeutic agent for seizure disorders, has osteogenic effects in rats and in humans in vivo, and in human bone cells in vitro. The goal of the present study was to determine the mechanism of the osteogenic action of phenytoin in normal human mandible-derived bone cells. Because many osteogenic agents increased bone cell proliferation through mediation by growth factors, we tested the hypothesis that the osteogenic effects of phenytoin involved the release of a growth factor by measuring the mRNA level of several bone cell growth factors and insulin-like growth factor (IGF) binding proteins with Northern blots using specific cDNA probes. Treatment with 5-50 microM phenytoin reproducibly and markedly increased (up to 6-fold, p < 0.001) the mRNA of transforming growth factor (TGF)-beta 1, but not that of other growth factors (i.e., IGF-II, platelet-derived growth factor-A [PDGF-A], PDGF-B, and TGF-beta 2) and IGF binding proteins (i.e., IGFBP-3, -4, and -5). The stimulation was dose dependent, with an optimal dose of 10-50 microM. Maximal increase was seen after 1 h of phenytoin treatment. The release of biologically active TGF-beta activity in conditioned media was measured with the mink lung cell proliferation inhibition assay. Twenty-four hours of phenytoin treatment significantly increased the production of biologically active TGF-beta (2-fold, p < 0.05) with the optimal dose between 5-50 microM. Comparisons between the in vitro osteogenic effects of phenytoin and those of TGF-beta 1 reveal that these two agents at their respective optimal doses had similar maximal stimulatory effects on [3H]thymidine incorporation, alkaline phosphatase (ALP)-specific activity, and type I alpha-2 collagen mRNA expression in human bone cells. The stimulatory effects of phenytoin on [3H]thymidine incorporation and ALP-specific activity were completely blocked by a neutralizing anti-TGF-beta antibody. In conclusion, these findings demonstrate for the first time that at least some of the osteogenic actions of phenytoin in human bone cells could be in part mediated by TGF-beta 1.

Pathogenesis of drug-induced gingival overgrowth. A review of studies in the rat model

Drug-induced gingival overgrowth is a side effect associated principally with 3 types of drugs: anticonvulsant (phenytoin), immunosuppressant (cyclosporine A), and various calcium channel blockers (nifedipine, verapamil, diltiazem). In this review, we describe the features of phenytoin-, cyclosporine A- and nifedipine-induced gingival overgrowth in rats and discuss factors influencing the onset and severity of these disorders. There are several features common to the gingival overgrowth induced by these drugs: 1) gingival overgrowth is more conspicuous in the buccal than in the lingual gingiva and less severe in the maxilla than in the mandible; 2) once the blood concentration of the drug reaches a certain level as a result of increasing the dose, the incidence of gingival overgrowth is 100% and its severity is dependent on the blood level, the most severe overgrowth being induced by cyclosporine A; 3) the duration of drug administration for maximal gingival overgrowth to develop is about 40 days; 4) the gingival overgrowth regresses spontaneously after discontinuing the drug; 5) accumulation of dental plaque is not essential for the onset of overgrowth, but plays a role in its severity; and 6) more severe overgrowth is induced in young than in old rats. Furthermore, male rats are more susceptible than females to nifedipine-induced gingival overgrowth. These results suggest that drug-induced gingival overgrowth in rats is dependent on the oral drug dose, blood drug level, age, and sex and that preexisting gingival inflammation is a factor relevant to its severity. Since these factors have also been suggested to be important determinants for human drug-induced gingival overgrowth, the rat model may prove valuable in the future for elucidating the molecular pathogenesis of the disorder.

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.

The functional interaction of EGF and PDGF with bradykinin in the proliferation of human gingival fibroblasts

Epidermal growth factor (EGF) and platelet-derived growth factor (PDGF)-BB are both involved in periodontal wound healing. Each of these growth factors exerts a positive proliferative effect on cells of the periodontium in vitro. However, in vivo the peptide bradykinin is one of a complex array of mediators present in addition to these growth factors. The purposes of this investigation were to: 1) evaluate bradykinin interactions with EGF and PDGF-BB altering cell proliferation in cultured human gingival fibroblasts (HGF), periodontal ligament cells (HPDL), and cells derived from alveolar bone (HOB); and 2) determine at the signal transduction level the mechanism of interaction between EGF and bradykinin in HGF. EGF and PDGF-BB stimulated DNA synthesis in a concentration-dependent manner, as measured by [3H] thymidine incorporation. Bradykinin alone did not alter significantly based DNA synthesis values; however, bradykinin in combination with EGF reduced DNA synthesis to nearly basal levels and bradykinin in combination with PDGF reduced the DNA synthesis over 50%. Examination of the interactions between bradykinin and EGF signal transduction pathways revealed that PGE2 release was increased in the presence of bradykinin and EGF (167 +/- 33% to 317 +/- 29%). The bradykinin-stimulated PGE2 release was completely abolished by indomethacin. Indomethacin also was found to block the bradykinin inhibition of EGF-induced DNA synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Phenytoin-induced DNA synthesis and inositol 1,4,5-trisphosphate formation in L-929 fibroblasts

Culture of L-929 fibroblasts in the presence of phenytoin (2.5-5.0 micrograms/ml) increased DNA synthesis, as indicated by increased [3H]thymidine uptake, while a higher dose (20 micrograms/ml) inhibited DNA synthesis. In like manner, a low dose of phenytoin (5.0 micrograms/ml) was effective in increasing inositol 1,4,5-trisphosphate formation while a higher dose (10 micrograms/ml) tended to inhibit this activity. These data suggest that the formation of inositol phosphate second messengers may play a role in phenytoin-induced fibroblast proliferation and connective tissue growth.

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.