Phenytoin at micromolar concentrations is an osteogenic agent for human-mandible-derived bone cells in vitro

Topical application of phenytoin or nifedipine-loaded PLGA microspheres promotes periodontal regeneration in vivo

OBJECTIVES

Gingival recession and alveolar bone loss are common manifestations of periodontitis. Periodontal regeneration is the ideal strategy for rehabilitating periodontal tissue defects and preventing tooth loss. The present study examined whether localized, topical application of gingival overgrowth-inducing drugs, phenytoin, nifedipine or cyclosporine, induces periodontal regeneration.

METHODS

Polylactic-co-glycolic acid (PLGA) was used as the carrier for preparation of phenytoin, nifedipine or cyclosporine-loaded PLGA microspheres, using an oil-in-water emulsification technique. The drug-loaded microspheres were delivered to periodontal defects created on alveolar ridges mesial to the first maxillary molars of Sprague-Dawley rats. After eight weeks, the operation area in each rat, including the maxillary molars and periodontal tissues, was harvested and evaluated by micro-computed tomography, histochemical and immunohistochemical analyses.

RESULTS

Physical parameters representative of periodontal regeneration, including the length of new alveolar bone (p < 0.01) and the area of new alveolar bone (p < 0.01) were significantly improved in the phenytoin group. Compared to other groups, the phenytoin group demonstrated increased expression of COL-1, VEGF-A, osteoblast and osteoclast markers (BMP-2, TGF-β1, OCN and TRAP staining), as well as decreased expression of MMP-8.

CONCLUSIONS

Results of the present study provided new evidence that localized, controlled release of phenytoin confers therapeutic benefits toward gingival recession and alveolar bone loss. Phenytoin appears to be a promising drug that promotes periodontal regeneration.

Markers of bone turnover in patients with epilepsy and their relationship to management of bone diseases induced by antiepileptic drugs

Data from cross-sectional and prospective studies revealed that patients with epilepsy and on long-term treatment with antiepileptic drugs (AEDs) are at increased risk for metabolic bone diseases. Bone diseases were reported in about 50% of patients on AEDs. Low bone mineral density, osteopenia/osteoporosis, osteomalacia, rickets, altered concentration of bone turnover markers and fractures were reported with phenobarbital, phenytoin, carbamazepine, valproate, oxcarbazepine and lamotrigine. The mechanisms for AEDs-induced bone diseases are heterogeneous and include hypovitaminosis D, hypocalcemia and direct acceleration of bone loss and/or reduction of bone formation. This article reviews the evidence, predictors and mechanisms of AEDs-induced bone abnormalities and its clinical implications. For patients on AEDs, regular monitoring of bone health is recommended. Prophylactic administration of calcium and vitamin D is recommended for all patients. Treatment doses of calcium and vitamin D and even anti-resorptive drug therapy are reserved for patients at high risk of pathological fracture.

The problem of osteoporosis in epileptic patients taking antiepileptic drugs

INTRODUCTION

Epilepsy is a common neurological disorder associated with recurrent seizures. Therapy with antiepileptic drugs (AEDs) helps achieve seizure remission in approximately 70% of epileptic patients. Treatment with AEDs is frequently lifelong and there are reports suggesting its negative influence on bone health. This is especially important in terms of general occurrence of osteoporosis, affecting over 50 million people worldwide.

AREAS COVERED

This study refers to two main groups of AEDs: hepatic enzyme inducers (carbamazepine, oxcarbazepine, phenobarbital, phenytoin, primidone and topiramate) and non-inducers (clobazam, clonazepam, ethosuximide, gabapentin, lacosamide, lamotrigine, levetiracetam, pregabalin, tiagabine, valproate, vigabatrin and zonisamide). Some reports indicate that enzyme inducers may exert a more negative influence on bone mineral density (BMD) compared to non-inducers. Bone problems may appear in both sexes during AED therapy, although women are additionally burdened with postmenopausal osteoporosis. Supplementation of vitamin D and calcium in patients on AEDs is recommended.

EXPERT OPINION

Apart from enzyme inducers, valproate (an even enzyme inhibitor) may also negatively affect BMD. However, the untoward effects of AEDs may depend upon their doses and duration of treatment. Although the problem of supplementation of vitamin D and calcium in epileptic patients on AEDs is controversial, there are recommendations to do so.

Modulation of mononuclear phagocyte inflammatory response by liposome-encapsulated voltage gated sodium channel inhibitor ameliorates myocardial ischemia/reperfusion injury in rats

BACKGROUND

Emerging evidence shows that anti-inflammatory strategies targeting inflammatory monocyte subset could reduce excessive inflammation and improve cardiovascular outcomes. Functional expression of voltage-gated sodium channels (VGSCs) have been demonstrated in monocytes and macrophages. We hypothesized that mononuclear phagocyte VGSCs are a target for monocyte/macrophage phenotypic switch, and liposome mediated inhibition of mononuclear phagocyte VGSC may attenuate myocardial ischemia/reperfusion (I/R) injury and improve post-infarction left ventricular remodeling.

METHODOLOGY/PRINCIPAL FINDINGS

Thin film dispersion method was used to prepare phenytoin (PHT, a non-selective VGSC inhibitor) entrapped liposomes. Pharmacokinetic study revealed that the distribution and elimination half-life of PHT entrapped liposomes were shorter than those of free PHT, indicating a rapid uptake by mononuclear phagocytes after intravenous injection. In rat peritoneal macrophages, several VGSC α subunits (NaV1.1, NaV1.3, NaV1.4, NaV1.5, NaV1.6, NaV1.7, NaVX, Scn1b, Scn3b and Scn4b) and β subunits were expressed at mRNA level, and PHT could suppress lipopolysaccharide induced M1 polarization (decreased TNF-α and CCL5 expression) and facilitate interleukin-4 induced M2 polarization (increased Arg1 and TGF-β1 expression). In vivo study using rat model of myocardial I/R injury, demonstrated that PHT entrapped liposome could partially suppress I/R injury induced CD43+ inflammatory monocyte expansion, along with decreased infarct size and left ventricular fibrosis. Transthoracic echocardiography and invasive hemodynamic analysis revealed that PHT entrapped liposome treatment could attenuate left ventricular structural and functional remodeling, as shown by increased ejection fraction, reduced end-systolic and end-diastolic volume, as well as an amelioration of left ventricular systolic (+dP/dt max) and diastolic (-dP/dt min) functions.

CONCLUSIONS/SIGNIFICANCE

Our work for the first time demonstrates the therapeutic potential of VGSC antagonism via liposome mediated monocyte/macrophage targeting in acute phase after myocardial I/R injury. These results suggest that VGSCs in mononuclear phagocyte system might be a novel target for immunomodulation and treatment of myocardial I/R injury.

The association between CYP 2C9 polymorphism and bone health

PURPOSE

There is a strong scientific rationale to support the view that cytochrome P450 (CYP P450) enzyme-inducing AEDs induce bone loss in patients with epilepsy. However, no study has investigated the association between CYP 2C9 polymorphism and bone mineral density (BMD), 25-hydroxyvitamin D or parathyroid hormone levels in patients with epilepsy. This study sought to determine the association between BMD and CYP 2C9 polymorphism.

METHODS

Ninety-three patients taking phenytoin as monotherapy were examined for CYP 2C9 polymorphism, vitamin D level and parathyroid hormone level and underwent basic chemistry testing. The bone mineral density of the lumbar spine and left femur were measured using dual-energy X-ray absorptiometry.

RESULTS

The results indicated that about 18.3% of the patients with epilepsy were positive for CYP2C9*3. Furthermore, bone mineral density was associated with CYP 2C9 polymorphism epileptic patients. Specifically, patients with 2C9 polymorphism had higher T-scores and Z-scores of the femoral neck (p=0.02 and 0.04, respectively), but not of the lumbar spine (p=0.27 and 0.06, respectively). There was also a trend of having higher serum PTH levels and statistically significantly lower 25-hydroxyvitamin D levels in patients with wild type than in those compared with CYP 2C9 polymorphism (p=0.05 and 0.03, respectively). Additionally, the patients with CYP 2C9 polymorphism had higher plasma levels of phenytoin, particularly when compared with those with wild type (p=0.01). However, there was no association between serum levels of phenytoin and low BMD at femoral neck or lumbar spine.

CONCLUSION

CYP 2C9 polymorphism is associated with higher BMD, independent of plasma levels of phenytoin.

Neuroendocrinological aspects of epilepsy: important issues and trends in future research

Neuroendocrine research in epilepsy focuses on the interface among neurology, endocrinology, gynecology/andrology and psychiatry as it pertains to epilepsy. There are clinically important reciprocal interactions between hormones and the brain such that neuroactive hormones can modulate neuronal excitability and seizure occurrence while epileptiform discharges can disrupt hormonal secretion and promote the development of reproductive disorders. An understanding of these interactions and their mechanisms is important to the comprehensive management of individuals with epilepsy. The interactions are relevant not only to the management of seizure disorder but also epilepsy comorbidities such as reproductive dysfunction, hyposexuality and emotional disorders. This review focuses on some of the established biological underpinnings of the relationship and their clinical relevance. It identifies gaps in our knowledge and areas of promising research. The research has led to ongoing clinical trials to develop hormonal therapies for the treatment of epilepsy. The review also focuses on complications of epilepsy treatment with antiepileptic drugs. Although antiepileptic drugs have been the mainstay of epilepsy treatment, they can also have some adverse effects on sexual and reproductive function as well as bone density. As longevity increases, the prevention, diagnosis and treatment of osteoporosis becomes an increasingly more important topic, especially for individuals with epilepsy. The differential effects of antiepileptic drugs on bone density and their various mechanisms of action are reviewed and some guidelines and future directions for prevention of osteoporosis and treatment are presented.

Influences of bone and mineral metabolism in epilepsy

INTRODUCTION

Patients with epilepsy are at increased risk for metabolic bone disease, low bone mineral density and fractures.

AREAS COVERED

This article reviews the predictors and mechanisms of bone loss in patients with epilepsy. It provides information regarding the basic bone biology, evidences of osteopathy with epilepsy and the potential mechanisms of its pathogenesis. This review shows that long-term use of antiepileptic drugs (AEDs) is associated with the risk of osteopathy. However, age, gender, low body mass, severity of epilepsy, co-morbid conditions, institutionalization and calcium and vitamin D deficiencies are additional and modified risk factors. AEDs may indirectly accelerate bone loss through hypovitaminosis D, hypocalcemia and hyperparathyroidism or reduce bone accrual through decreasing the levels of calcitonin, growth factors and vitamin K. Also, AEDs may directly accelerate osteoclastic (bone loss) and/or reduce osteoblastic (bone formation) activities, the main cells involved in bone remodeling.

EXPERT OPINION

Understanding the basic bone biology and the pathophysiology of the disturbed bone and mineral metabolism in epilepsy will aid in identification and monitoring of patients at risk and in planning appropriate prophylactic and therapeutic measures.

Imaging of the calvarium

The skull vault consists of a multitude of flat bones held together by the cranial sutures. Radiologists encounter a vast array of calvarial pathologies that tend to cause abnormalities in thickness, abnormalities in density, focal defects, or an excess of soft tissue or bone tissue. Further anomalies related to the cranial sutures and fontanelles occur in the dynamic pediatric skull. The imaging features of the host of conditions resulting in these commonly detected calvarial abnormalities are reviewed and illustrated.

Bone health in young women with epilepsy after one year of antiepileptic drug monotherapy

OBJECTIVE

Antiepileptic drugs (AEDs) may have adverse effects on bone mineral density (BMD) and metabolism. We previously reported biochemical evidence of increased bone turnover in premenopausal women with epilepsy on phenytoin monotherapy compared with those on carbamazepine, lamotrigine, and valproate. We therefore hypothesized that rates of bone loss would be higher in young women treated with phenytoin.

METHODS

Ninety-three premenopausal women with epilepsy receiving a single AED (carbamazepine, lamotrigine, phenytoin, or valproate) participated. Subjects completed nutritional and physical activity questionnaires. Biochemical indices of bone and mineral metabolism and BMD of the proximal femur and lumbar spine were measured at baseline and 1 year.

RESULTS

Participants reported high calcium intake (>1,000 mg/day) and were physically active. Significant loss (2.6%) was seen at the femoral neck in the phenytoin group. BMD remained stable in the other AED groups. Bone turnover markers and calciotropic hormones were unchanged after 1 year in all groups except for a significant decline in urine N-telopeptide in the phenytoin group. In women receiving phenytoin, lower serum 25-hydroxyvitamin D concentrations were associated with higher parathyroid hormone, bone alkaline phosphatase, and urine N-telopeptide levels, a biochemical pattern consistent with secondary hyperparathyroidism and increased remodeling.

CONCLUSION

In this study, young women treated with phenytoin had significant femoral neck bone loss over 1 year. In contrast, those treated with carbamazepine, lamotrigine, and valproate did not have detectable adverse effects on bone turnover or bone mineral density. These results raise concerns about the long-term effects of phenytoin monotherapy on bone in young women with epilepsy.

Phenytoin can accelerate the healing process after experimental myocardial infarction?

BACKGROUND

Over-degradation and/or inadequate accumulation of extracellular matrix after myocardial infarction (MI) may lead to adverse ventricular remodeling, even ventricular aneurysm or rupture. Phenytoin can increase gingival overgrowth by stimulating the proliferation of connective tissue, which implies a novel way to hasten the healing process after MI.

METHODS

Experimental MI was induced by permanent coronary ligation. Surviving rats after MI were randomly divided into phenytoin, captopril, phenytoin plus captopril, operation control and sham operation group. Picrosirius red staining plus polarized microscopy was used for collagen analysis. Left ventricular passive pressure-volume relationship was determined ex vivo. The effects of phenytoin concentration gradient (0, 1.25, 2.5, 5.0, 10.0, and 20.0 microg/mL) on transforming growth factor-beta1 (TGF-beta1) mRNA and protein expression by neonatal rat cardiac fibroblast were determined using semi-quantitative RT-PCR and ELISA, respectively. Peritoneal macrophage was incubated with same gradient of phenytoin concentration. Then the supernatant was harvested to stimulate another 6 groups of cardiac fibroblast, to investigate possible role mediated by macrophage.

RESULTS

Phenytoin treatment could promote type I collagen cross-linking level and ratio of type I/III collagen in the infarcted region and had no obvious side effect on interstitial collagen volume fraction, subtype ratio and distribution in non-infarcted region. Phenytoin-treated hearts exhibited attenuation of global ventricular dilation. Phenytoin alone had no direct effects on rat cardiac fibroblast proliferation and collagen production in vitro, but phenytoin-stimulated macrophage could exert a positive influence on cardiac fibroblast TGF-beta1 mRNA and protein production, which exhibited a dose-dependent manner.

CONCLUSIONS

Phenytoin can accelerate the healing process in the infarcted region and has no obviously detrimental influence on collagen accumulation in non-infarcted region, which implies a potential benefit to patients undergoing early post-infarction ventricular remodeling process.

Medications' impact on oral health

BACKGROUND

Over-the-counter and prescription drugs are used frequently, in large quantities and by many adults, particularly by those older than 65 years of age. A number of medications (prescription, over-the-counter, vitamins and minerals, herbal preparations) can affect oral health. With the population's aging, and as more drugs become available, dentists can expect to encounter medication-related oral side effects among their patients.

TYPES OF STUDIES REVIEWED

The author reviewed studies that ranged from case reports to randomly controlled, double-blinded studies. However, in view of the subject matter, the majority of findings are based on case reports.

CONCLUSIONS

Since many patients regularly take medications, both prescribed and nonprescribed, dentists always must take a thorough medical history so that they can be aware of medication-related problems and the impact of medications on diagnosis and treatment planning.

CLINICAL IMPLICATIONS

Dentists must be aware of the potential oral tissue complications that medications can create and develop appropriate treatment plans for their patients that consider the oral health impact of the medications they take.

Pathophysiology of bone loss in patients receiving anticonvulsant therapy

Many studies have shown that patients taking antiepileptic drugs (AEDs) are at increased risk for metabolic bone disease and low bone mineral density. Although early reports of bone disease in patients with epilepsy often involved institutionalized patients, who may be at risk because of lack of physical activity, reduced sunlight exposure, and poor nutrition, low bone density has also been reported in well-nourished, ambulatory outpatients with epilepsy. Traditionally, attention to the problem of AED-induced bone loss has been focused on those drugs that induce the hepatic cytochrome P450 enzyme system, thereby increasing the metabolism of vitamin D. However, the mechanisms of AED-induced bone loss appear to be multiple, and all types of AEDs are potentially implicated. Besides hepatic enzyme induction, mechanisms may include direct effects of AEDs on bone cells, resistance to parathyroid hormone, inhibition of calcitonin secretion, and impaired calcium absorption. An understanding of bone biology and the pathophysiology of bone loss can aid in the identification and monitoring of patients at risk and in the planning of appropriate prophylactic and therapeutic measures, by which most of the morbidity associated with AED-induced bone loss can be prevented.

Evidence for the involvement of bone morphogenetic protein-2 in phenytoin-stimulated osteocalcin secretion in human bone cells

Recent work has shown that the actions of phenytoin on bone cell proliferation and differentiation are, in part, mediated through the upregulation of transforming growth factor-beta1 (TGF-beta(1)). The present study was undertaken to examine the effect of phenytoin on bone morphogenetic proteins (BMP)-2 and -4, which are well-recognized osteoinductive proteins of the TGF-beta superfamily, in osteoblastic cells. Treatment with 5-50 microM of phenytoin increased the amount of mRNA for BMP-2 after a 0.5-24 h incubation in normal human mandible-derived bone cells (HOB-M cells), but failed to affect the mRNA for BMP-4. Phenytoin treatment for 48 h significantly increased the secretion of BMP-2 by approx. four-fold, at an optimal concentration of 10 microM. While TGF-beta(1) inhibited osteocalcin secretion from HOB-M cells, both phenytoin and BMP-2 significantly stimulated it. Importantly, the stimulatory effects of phenytoin on osteocalcin release were completely blocked by the neutralizing antihuman BMP-2 monoclonal antibody. These results indicate that the stimulatory action of phenytoin on osteocalcin secretion in normal human bone cells is mediated, at least partly, through the upregulation of BMP-2, rather than that of TGF-beta(1).

Phenytoin and its metabolite, 5-(4-hydroxyphenyl)-5-phenylhydantoin, show bone resorption in cultured neonatal mouse calvaria

The effects of phenytoin and its major metabolite, 5-(4-hydroxyphenyl)-5-phenylhydantoin (HPPH), on bone resorption of neonatal mouse calvaria were examined in vitro. Both phenytoin and HPPH induced significant bone resorption as compared to the controls after 72 h in culture. This effect may be the cause of phenytoin-induced bone loss in vivo.

Stimulatory effects of phenytoin on osteoblastic differentiation of fetal rat calvaria cells in culture

Phenytoin (diphenylhydantoin, DPH), an anticonvulsant drug for epileptic patients, has several adverse effects, including calvarial thickening and coarsening of the facial features, which occur with chronic DPH therapy. While previous studies have demonstrated that DPH has an anabolic action on bone cells in vivo and in vitro, the basis of these effects is not fully understood. In this study, the effect of DPH on osteoblastic differentiation of fetal rat calvaria (RC) cells in culture was investigated by measuring bone nodule (BN) formation, cell growth, alkaline phosphatase (ALPase) activity, collagen synthesis, and expression of osteocalcin (OC) and osteopontin (OP) mRNAs. Continuous treatment of RC cells with DPH for 18 days dose-dependently increased the mineralized BN number by 1.2-1.7-fold at concentrations of 12.5-200 micromol/L DPH. Cell growth was not affected at the same concentrations of DPH. ALPase activity was stimulated by DPH (1.1-1.9-fold) dose-dependently and was maintained at higher levels in DPH-treated cells throughout the experimental period. DPH increased mineralized and unmineralized BN formations both in the presence and the absence of 10(-8) mol/L dexamethasone (Dex). Expression of OC and OP mRNAs was markedly augmented by DPH on days 12-24 and on days 12-18, respectively. While control mRNA levels of OC and OP increased with time, the increases in DPH-treated cells were greater than those of the controls and the stimulatory effects were dose-dependent. Type I collagen was also influenced by DPH; mRNA level was enhanced and the percentage of collagen synthesized was increased significantly, by 200 micromol/L DPH. When DPH was added in three different culture stages, days 1-6 (growth), days 7-12 (matrix development), and days 13-18 (mineralization), BN formation was influenced primarily on days 1-6 and secondarily on days 7-12, but not on days 13-18, suggesting that DPH increased BN formation by enhancing not only the proportion of osteoprogenitor cells in the early stage but also the proportion of functional osteoblasts in the middle stage within mixed-cell populations. Moreover, such increases were detected in conditions of both Dex(+) and Dex(-). These findings demonstrate that DPH stimulates osteoblast-associated markers such as BNs, ALPase, OC, OP, and type I collagen by continuously affecting the stages of growth and matrix development in RC cells, and suggests that the stimulatory effects by DPH may possibly be induced independent of those by Dex.

Melatonin stimulates proliferation and type I collagen synthesis in human bone cells in vitro

The pineal secretory product melatonin reportedly regulates release of growth hormone in humans and prevents phototherapy-induced hypocalcemia in newborn rats, suggesting that melatonin affects bone metabolism. Little is known about the effects of melatonin on bone in vitro or in vivo. The present study was undertaken to examine whether melatonin acts directly on normal human bone cells (HOB-M cells) and human osteoblastic cell line (SV-HFO cells) to affect osteogenic action in vitro. The effect of melatonin on bone cell proliferation was determined using the 2,3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carbo xanilide (XTT) assay after a 24 hr incubation with melatonin. Melatonin significantly and dose-dependently increased the proliferation in HOB-M cells and SV-HFO cells by 215 +/- 22.1%, and 193 +/- 6.4%), respectively, with a maximal effect at a concentration of 50 microM. To evaluate the effect of melatonin on bone cell differentiation, alkaline phosphatase (ALP) activity, osteocalcin secretion and procollagen type I c-peptide (PICP) production (a measure of type I collagen synthesis) were measured after a 48 hr treatment. While melatonin at micromolar concentrations did not significantly affect either the ALP activity or the osteocalcin secretion, it significantly and dose-dependently increased the PICP production in HOB-M cells and SV-HFO cells by 983 +/- 42.2%, and 139 +/- 4.2%, respectively, with the maximal stimulatory doses between 50 and 100 microM. These results provide new evidence that melatonin stimulates the proliferation and type I collagen synthesis in human bone cells in vitro, suggesting that melatonin may act to stimulate bone formation.

Pronounced palatal and mandibular tori observed in a patient with chronic phenytoin therapy: a case report

Phenytoin, an anticonvulsant drug for epileptic patients, has many adverse effects, including calvarial thickening and coarsening of the facial features. Previous studies have demonstrated that phenytoin has an anabolic action on bone cells. This report describes pronounced palatal and mandibular tori found in a 45-year-old Japanese man undergoing chronic phenytoin therapy. The tori were extremely large, lobular, and symmetrical. A palatal torus appeared along the middle of the hard palate and mandibular tori consisted of 2 pairs of nodular masses extensively filling the lingual floor of the oral cavity. Pronounced osseous outgrowth occurred for the duration of a dose-increase of phenytoin from 1985 to 1997. His parents did not have any palatal or mandibular tori. These facts suggest that these unusual tori may have been the result of chronic phenytoin therapy, rather than association with the familial background.

Stimulation by low concentrations of fluoride of the proliferation and alkaline phosphatase activity of human dental pulp cells in vitro

Fluoride has been used for decades, either systemically or topically, to prevent dental caries. The purpose of this study was to clarify the effects of low concentrations of fluoride on proliferation, differentiation and extracellular-matrix synthesis in normal human dental pulp cells (DP-1 and DP-2) in vitro. The effects were compared with those on a human osteoblastic osteosarcoma cell line, TE-85. Fluoride at micromolar concentrations significantly and dose-dependently stimulated [3H]thymidine incorporation into DNA in DP-1, DP-2 and TE-85 cells, with optimal effects around 50 microM, by 127 +/- 7%, 124 +/- 0.6% and 152 +/- 13.4%, respectively. To assess the potential influence of fluoride on cell differentiation, the effects of mitogenic concentrations on alkaline phosphatase activity were measured. Fluoride significantly increased the enzyme's activity in DP-1 and TE-85 by 177 +/- 12% and 144 +/- 12.3%. To evaluate the effect on extracellular-matrix synthesis, the synthesis of type I collagen was indirectly determined by an assay of procollagen type I c-peptide production. Fluoride significantly increased that production by 150 +/- 8.7% in TE-85, but not in either DP-1 or DP-2. These observations suggest that fluoride, if used at low concentrations, could be a useful therapeutic agent where increased regeneration of dentine is desired, such as after pulp amputation, by stimulating the proliferation and differentiation of the dental pulp cells.

Effect of phenytoin on periodontal tissues exposed to orthodontic force--an experimental study in rats

The influence of the anticonvulsive drug phenytoin on the periodontal tissues during orthodontic tooth movement in the rat was studied. The experimental and the control group each consisted of 10 Sprague-Dawley rats. The test group was injected daily with phenytoin during the experimental period of 6 weeks. A fixed appliance for expansion was applied on the first molars in both groups after 2 weeks (day 15). At the end of the experiment (day 42), radiographic measurements revealed less tooth movement in the phenytoin-treated rats. Compared to the control group, significant histologic changes in the periodontal tissues such as increased density of fibroblasts, decreased number of osteoclasts in contact with alveolar bone wall of the pressure side and deeper layer of non-mineralized osteoid on the tension side were observed in the phenytoin group.

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.

Medications as risk factors for periodontal disease

As the United States population ages, people will be taking more medications which may benefit their general health but not necessarily their periodontal health. The effects of medications have been grouped into six categories as follows: behavioral alteration of oral hygiene methods, alteration of plaque composition, effect on gingival tissues, effect on alveolar bone, effect on gingival crevicular fluid, and effect on salivary flow. Although most medications discussed in this paper increase the risk for periodontal disease, a few may actually decrease the risk. These include the effect of phenytoin on alveolar bone, the antibacterial effect of antibiotics, the anticollagenolytic effects of tetracyclines, and the effect of non-steroidal anti-inflammatory drugs on decreasing alveolar bone resorption.