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

Multiple functions of gingival and mucoperiosteal fibroblasts in oral wound healing and repair

Fibroblasts are cells of mesenchymal origin. They are responsible for the production of most extracellular matrix in connective tissues and are essential for wound healing and repair. In recent years, it has become clear that fibroblasts from different tissues have various distinct traits. Moreover, wounds in the oral cavity heal under very special environmental conditions compared with skin wounds. Here, we reviewed the current literature on the various interconnected functions of gingival and mucoperiosteal fibroblasts during the repair of oral wounds. The MEDLINE database was searched with the following terms: (gingival OR mucoperiosteal) AND fibroblast AND (wound healing OR repair). The data gathered were used to compare oral fibroblasts with fibroblasts from other tissues in terms of their regulation and function during wound healing. Specifically, we sought answers to the following questions: (i) what is the role of oral fibroblasts in the inflammatory response in acute wounds; (ii) how do growth factors control the function of oral fibroblasts during wound healing; (iii) how do oral fibroblasts produce, remodel and interact with extracellular matrix in healing wounds; (iv) how do oral fibroblasts respond to mechanical stress; and (v) how does aging affect the fetal-like responses and functions of oral fibroblasts? The current state of research indicates that oral fibroblasts possess unique characteristics and tightly controlled specific functions in wound healing and repair. This information is essential for developing new strategies to control the intraoral wound-healing processes of the individual patient.

Biological Effects of Tissue Modulations in Wound Healing

The reactive and reparative capacity of injured tissue when treated with either Pulsed Electromagnetic Fields (PEMFs) or with immunomodulator drugs (Prostaglandin E2 and Thymopentin) was evaluated. A morphological and quantitative evaluation was made of the interactions and the interferences on the structural stages of tissue repair processes. When PEMFs were used the time required for new tissue to completely cover the wound was 26 days after surgery, instead of 30 days for control conditions or for treatment with PGE2 or Thymopentin. PEMFs showed accelerated healing process. Both PGE2 and Thymopentin should be considered, in association with other drugs, in an attempt to strengthen the various immunomodulative phases of the reconstitution of injured tissue.

2-Hydroxyethyl methacrylate inflammatory effects in human gingival fibroblasts

AIM

To investigate the inflammatory response in human gingival fibroblasts (HGFs) treated with a relatively low 2-hydroxyethyl methacrylate (HEMA) concentration by studying reactive oxygen species (ROS) production, cyclooxygenase-2 (COX-2) and tumour necrosis factor-alpha (TNF-α) gene expression, and prostaglandin E2 (PGE₂) release.

METHODOLOGY

Cultured HGFs were exposed to 3 mmol L⁻¹ HEMA for 0, 24 or 96 h. ROS production was investigated by flow cytometry; TNF-α and COX-2 gene expression was determined by RT-PCR, and prostaglandin E2 production was detected by an enzyme immunoassay.

RESULTS

After 24- or 96-h HEMA incubation, ROS levels were approximately eightfold and elevenfold higher than controls, whilst COX-2 gene expression was approximately twofold or fourfold higher than controls, respectively. Twenty-four-hour exposure enhanced TNF-α mRNA levels by approximately 66%, whilst after 96-h incubation, TNF-α gene expression was fivefold higher than controls. Ninety-six-hour HEMA treatment increased PGE₂ concentration in the culture medium by around 17% compared with controls.

CONCLUSIONS

2-Hydroxyethyl methacrylate treatment (3 mmol L⁻¹) induced an inflammatory response in HGFs modulated by ROS production, as well as by the increase in TNF-α and COX-2 gene expression and by PGE₂ release.

Phenytoin-induced gingival overgrowth

Gingival overgrowth is a common adverse effect of therapy with Phenytoin, having important medical and cosmetic implications. Poor periodontal hygiene is an important risk factor for severity of Phenytoin-induced gingival overgrowth (PIGO), which is a time-dependent process. There is complex interplay of altered fibroblast biology, connective tissue turnover, inflammatory processes, and growth factors on a background of genetic susceptibility to produce increase in various components of interstitial matrix in PIGO tissue. Treatment options have included change of PHT to another anti-seizure drug, measures to improve periodontal hygiene and gingivectomy. There is conclusive evidence that folic acid supplementation significantly decreases the incidence of PIGO.

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.

Bradykinin upregulates IL-8 production in human gingival fibroblasts stimulated by interleukin-1beta and tumor necrosis factor alpha

The proinflammatory mediator bradykinin (BK) is suggested to play an important role in the pathogenesis of various inflammatory diseases including periodontitis. In this study, BK per se stimulated interleukin-8 (IL-8) production in human gingival fibroblasts in vitro. Furthermore, BK upregulated the stimulatory effect of the cytokines IL-1beta and TNFalpha on the production of IL-8. The stimulatory effect of BK on the IL-1beta- or TNFalpha-stimulated IL-8 production was reduced in the presence of BK B2 receptor antagonist HOE 140, whereas the B1 receptor antagonist Lys-(des-arg9, Leu8)-BK had no effect. Similar to BK, the calcium ionophore A23187 also upregulated the stimulatory effect of IL-1beta and TNFalpha on IL-8 production. The protein kinase C (PKC) inhibitor bisindolylmaleimide, BIS, significantly reduced the stimulatory effect of BK on IL-1beta and TNFalpha increased IL-8 production but did not affect the production of IL-8 stimulated by cytokines alone. The specific p38 mitogen-activated protein kinase (MAPK) inhibitor SB 203580 reduced IL-8 production stimulated by the combination of BK and IL-1beta as well as the IL-1beta-stimulated IL-8 production. In conclusion, this study shows that BK upregulates IL-1beta- and TNFalpha-stimulated IL-8 production via BK B2 receptor and that PKC signal pathway seems to be involved in the upregulation of the cytokine-induced IL-8 production in gingival fibroblasts. This stimulatory effect of BK on IL-8 production may contribute to the maintenance of the gingival inflammation and enhanced risk for destruction of gingival connective tissue.

Platelet-derived growth factor-induced arachidonic acid release for enhancement of prostaglandin E(2) synthesis in human gingival fibroblasts pretreated with interleukin-1beta

Platelet-derived growth factor (PDGF) is a biological mediator for connective tissue cells and plays a critical role in a wide variety of physiological and pathological processes. We here investigated the effect of PDGF on arachidonic acid release and prostaglandin E(2) (PGE(2)) synthesis in human gingival fibroblasts (HGF). PDGF induced arachidonic acid release in a time- and dose-dependent manner, and simultaneously induced a transient increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), but less provoked PGE(2) release and cyclooxygenase-2 (COX-2) mRNA expression. When [Ca(2+)](i) was increased by Ca(2+)-mobilizing reagents, arachidonic acid release was increased. The PDGF-induced arachidonic acid release and increase in [Ca(2+)](i) were prevented by a tyrosine kinase inhibitor. On the other hand, in the HGF pre-stimulated with interleukin-1beta (IL-1beta), PDGF clearly increased PGE(2) release. The PDGF-induced PGE(2) release was inhibited by a tyrosine kinase inhibitor. In the HGF pretreated with IL-1beta, arachidonic acid strongly enhanced PGE(2) release and COX-2 mRNA expression. These results suggest that PDGF stimulates arachidonic acid release by the increase in [Ca(2+)](i) via tyrosine kinase activation, and which contributes to PGE(2) production via COX-2 expression in HGF primed with IL-1beta.

Cyclooxygenase-2 inhibitors decrease interleukin-1beta-stimulated prostaglandin E2 and IL-6 production by human gingival fibroblasts

BACKGROUND

Previous work showed that normal and aggressive periodontitis (AgP) gingival fibroblasts produce the bone-resorbing cytokine IL-6. PGE2 is important in regulating IL-6 production. Non-steroidal anti-inflammatory drugs inhibit PG synthesis via COX-1 and/or COX-2 isoenzymes and may inhibit periodontal destruction. COX-2 is induced after cellular activation (i.e., by inflammatory cytokines such as IL-1beta). Little is known about IL-1beta-stimulated AgP fibroblast IL-6 and PGE2 production and their regulation by COX inhibitors. The objective of this study was to determine the effects of COX-2 inhibitors on amounts of PGE2 and IL-6 made by IL-1beta-stimulated gingival fibroblasts.

METHODS

Gingival fibroblasts (2.5 x 10(4)) from healthy or severe periodontitis patients were cultured in serum-free medium, with or without IL-1beta (10(-11)M) for 24 hours, with or without the COX-1/2 inhibitor indomethacin or the selective COX-2 inhibitors NS-398, celecoxib, or rofecoxib. PGE2 and IL-6 in culture supernatants were determined by specific enzyme-linked immunosorbent assay (ELISA)s.

RESULTS

All of the COX inhibitors caused dose-dependent decreases in IL-1beta-stimulated PGE2, to a maximum of > 90% in all cell lines (P < or = 0.0001). The selective COX-2 inhibitors, but not indomethacin, caused partial (generally up to approximately 60%), dose-dependent decreases in IL-1beta-stimulated IL-6 in all cell lines (P < or = 0.003). When exogenous PGE2 was added concurrently with COX-2 inhibitors before addition of IL-1beta, IL-6 production returned to levels at or approaching that produced by cells exposed only to IL-1beta (P < or = 0.04).

CONCLUSION

The results suggest that COX-2 inhibition may be useful in helping to control fibroblast production of IL-6 in patients with severe periodontitis.

Angiotensin II induces prostaglandin E(2) release in human gingival fibroblasts

We investigated the effect of angiotensin II on prostaglandin E(2) release in human gingival fibroblasts. Stimulation of human gingival fibroblasts with angiotensin II elicited prostaglandin E(2) release in a concentration- and time-dependent manner. Angiotensin III also induced prostaglandin E(2) release, but the effect was weaker than that of angiotensin II. Angiotensin II- and angiotensin III-induced prostaglandin E(2) release was inhibited by AT(1) receptor antagonist FR-130,739, but not AT(2) receptor antagonist PD-123,319. Angiotensin II evoked an increase in intracellular Ca(2+) in fura-2-loaded human gingival fibroblasts. These results suggest that angiotensin II functions as a physiological mediator via Ca(2+)-mobilizing AT(1) receptor activation in human gingival fibroblasts.

[Epidermal growth factor: a probable oral and digestive health protector]

The integrity of oral and digestive mucosa depend on many salivary components like the Epidermal Growth Factor (EGF). Sometimes indicative, sometimes stimulated or modulated factor of oral and digestive health, EGF appears as a clinical marker in neoplastic and inflammatory diseases. As cellular growth factor, it protects the digestive mucosa with stimulation of mucus production and with inhibition of gastric secretion. Equally implicated in healing process, it enhances this one, and determines, in patients, more or less sensibility to inflammatory damages. Its strategic place in various pathologies, as stomach ulcer and tumoral process, open research prospects with a real potential of repair and pronostic.

Enhanced cyclooxygenase-2 mRNA expression in human gingival fibroblasts induced by cell contact with human lymphocytes

Prostaglandins, especially prostaglandin E2 (PGE2), play a crucial role in the pathogenesis of periodontal disease. We have previously reported that inflammatory mediators interleukin-1 (IL-1) and tumor necrosis factor alpha (TNFalpha) increase the production of PGE2 in human gingival fibroblasts. In this study, we investigated the effect of cell-to-cell interactions between gingival fibroblasts and lymphocytes on PGE2 production by using co-culture technique. Cell-to-cell contact between gingival fibroblasts and lymphocytes synergistically enhanced the production of PGE2 in co-cultures. In contrast to lymphocytes, the cyclooxygenase-2 (COX-2) mRNA expression in gingival fibroblasts was strongly enhanced following cell contact between gingival fibroblasts and lymphocytes. The level of COX-1 mRNA expression, however, was not affected either in gingival fibroblasts or in lymphocytes by the interactions between fibroblasts and lymphocytes. The study demonstrates that cell contact between gingival fibroblasts and lymphocytes strongly stimulates PGE2 production partly due to enhanced COX-2 mRNA expression in gingival fibroblasts. The cell-to-cell contact between gingival fibroblasts and lymphocytes should be considered as an important regulatory aspect for the enhancement of PGE2 in periodontal disease.

Production of Rantes/CCL5 in human gingival fibroblasts challenged with tumor necrosis factor alpha

Chemokines are small-secreted proteins that stimulate the directional migration of leukocytes and thereby mediate the inflammatory process. The present study investigates the capacity of human gingival fibroblasts to produce the beta chemokine Rantes/CCL5. In situ hybridization, immunohistochemistry and ELISA were used to measure the induction of Rantes/CCL5 at the mRNA and protein levels, both in unstimulated gingival fibroblasts as well as in fibroblasts treated with the proinflammatory cytokines tumor necrosis factor (TNF)alpha or interleukin (IL)-1beta. TNFalpha in different concentrations (0.1-10 ng/ml) induced Rantes/CCL5 mRNA expression and protein production in 24-h cultures of human gingival fibroblasts. The expression of Rantes/CCL5-mRNA and protein production, induced by TNFalpha, was evident at 6 h and thereafter increased continuously during the study period (24 h). IL-1beta (3-300 pg/ml) also enhanced the production of Rantes/CCL5 in gingival fibroblasts. The amount of Rantes/CCL5 induced by IL-1beta (300 pg/ml), however, was less than that induced by TNFalpha (10 ng/ml). The study suggests that human gingival fibroblasts, by producing the chemokine Rantes/CCL5, participate in the regulation of the host response during the inflammatory process in the periodontal tissue.

Induction of interferon gamma in human gingival fibroblasts challenged with phytohaemagglutinin

Interferon gamma (IFN-gamma) is a potential immunoregulatory cytokine, which is secreted mainly by cells of immune origin. In this study, we examined the capacity of human gingival fibroblasts as non-professional immune cells to express IFN-gamma messenger RNA (mRNA) and to produce the protein. Cultures of fibroblast cells were established from gingival biopsies from three children. The expression of mRNA for IFN-gamma was studied by in situ hybridization, and the level of IFN-gamma was determined by cell-released capturing ELISA. Treatment of the cells with phytohaemagglutinin (PHA) (2.5, 5.0, and 10 microg/ml) increased the number of IFN-gamma mRNA expressing cells and the protein production at 1, 6, and 24 h. Non-stimulated cells did not reveal measurable levels of IFN-gamma mRNA or the protein. The inflammatory cytokines interleukin 1beta (IL-1beta) (100 microg/ml) and tumour necrosis factor alpha (TNFalpha) (10 ng/ml) did not affect IFN-gamma mRNA expression or protein production. Treatment of the cells with 1 microM phorbol 12-myristate-13-acetate (PMA) stimulated IFN-gamma mRNA expression but had no effect on IFN-gamma protein production. We conclude that human gingival fibroblasts not only transcribe IFN-gamma mRNA but also produce the IFN-gamma protein in response to PHA. The finding that human gingival fibroblasts, produce the cytokine IFN-gamma, further support the concept that these cells take an active part in the modulation of the inflammatory and immune response in the periodontal tissue.

Synergistic induction of cyclooxygenase-2 by transforming growth factor-beta1 and epidermal growth factor inhibits apoptosis in epithelial cells

Increased expression of cyclooxygenase-2 (COX-2) expression has been observed in several human tumor types and in selected animal and cell culture models of carcinogenesis, including lung cancer. Increased expression of COX-2 and production of prostaglandins appear to provide a survival advantage to transformed cells through the inhibition of apoptosis, increased attachment to extracellular matrix, increased invasiveness, and the stimulation of angiogenesis. In the present studies, we found that transforming growth factor beta1 (TGF-beta1) and epidermal growth factor (EGF) synergistically induced the expression of COX-2 and prostaglandin E2 (PGE2) production in mink lung epithelial (Mv1Lu) cells. EGF, but not PDGF or IGF-1, was able to inhibit TGF-beta1-induced apoptosis in Mv1Lu cells and this effect was blocked by NS-398, a selective inhibitor of COX-2 activity, suggesting a possible role for COX-2 in the anti-apoptotic effect of EGF receptor ligands. The combination of TGF-beta1 and EGF also significantly induced COX-2 expression in rat intestinal epithelial (RIE-1) cells and completely prevented sodium butyrate (NaBu)-induced apoptosis. The synergistic induction of COX-2 by TGF-beta1 and EGF was not observed in R1B-L17 cells, a line derived from Mv1Lu cells that lacks the TGF-beta type-I receptor. AG1478, a selective inhibitor of EGF receptor tyrosine kinase activity, completely suppressed the induction of COX-2 expression by either EGF or TGF-beta1+EGF. Also, PD98059, a specific inhibitor of MEK/ERK pathway, and SB203580, a specific inhibitor of p38 MAPK activity, significantly inhibited the induction of COX-2 in response to combined EGF and TGF-beta1. These results suggest an important collaborative interaction of TGF-beta1 and EGF signaling in the induction of COX-2 and prostaglandin production in Mv1Lu cells.

Involvement of tyrosine kinases on cyclooxygenase expression and prostaglandin E2 production in human gingival fibroblasts stimulated with interleukin-1beta and epidermal growth factor

The purpose of the present study was to investigate the involvement of cyclooxygenase-1 (COX-1), cyclooxygenase-2 (COX-2), and tyrosine kinase on prostaglandin E2 (PGE2) production in human gingival fibroblasts stimulated by interleukin-1beta (IL-1beta) and/or epidermal growth factor (EGF). The cytokine IL-1beta and to a lesser extent EGF, enhanced COX-2 mRNA levels in gingival fibroblasts. Simultaneous treatment with EGF and IL-1beta resulted in enhanced COX-2 mRNA levels accompanied by a synergistic stimulation of PGE2 biosynthesis compared to the cells treated with IL-1beta or EGF alone. Neither IL-1beta EGF nor the combination of IL-1beta and EGF enhanced COX-1 mRNA levels in gingival fibroblasts. The tyrosine kinase inhibitors, Herbimycin A and PD 153035 hydrochloride, reduced COX-2 mRNA levels as well as PGE2 production induced by IL-1beta or the combination of IL-1beta and EGF whereas COX-1 mRNA levels were not affected. Furthermore, the COX-2 specific inhibitor, NS-398, abolished the PGE2 production induced by IL-1beta, EGF, or the combination. These results indicate that the synergy between IL-1beta and EGF on PGE2 production is due to an enhanced gene expression of COX-2 and that tyrosine kinase(s) are involved in the signal transduction of COX-2 in gingival fibroblasts.

Triclosan reduces prostaglandin biosynthesis in human gingival fibroblasts challenged with interleukin-1 in vitro

The effect of the toothpaste ingredient triclosan (2,4,4'-trichloro-2'-hydroxyldiphenyl ether) on the prostaglandins biosynthesis in human gingival fibroblasts challenged with interleukin-1beta (IL-1beta) or tumor necrosis factor alpha (TNFalpha) was studied in vitro. When gingival fibroblasts were treated simultaneously with triclosan and IL-1beta, the stimulatory effect of IL-1beta on prostaglandin E2 (PGE2) and PGI2 formation was reduced in a dose-dependent manner by triclosan. Triclosan also reduced the PGE2 formation induced by TNFalpha. Furthermore, the capacity of IL-1beta to induce release of [3H] arachidonic acid from prelabelled gingival fibroblasts was reduced in the presence of triclosan. Addition of exogenous unlabelled arachidonic acid (AA) to the cells resulted in enhanced PGE2 formation which was reduced by triclosan. The upregulation of the metabolism of AA to PGE2 induced by IL-1beta, was markedly reduced in the presence of triclosan. The study indicates that the stimulatory effect of IL-1beta on prostanoid formation (PGE2, PGI2) in human gingival fibroblasts was diminished in the presence of triclosan partly at the level of phospholipase A2 and partly at the level of cyclooxygenase. The present data that triclosan, in vitro, inhibits the production of inflammatory mediators such as prostaglandins suggests that this can be an aspect of its clinical effect on gingivitis, in addition to its antibacterial effect.

Salivary protein composition in epileptic patients on different medications

Several salivary proteins were assayed in saliva from epileptic patients who were using different anti-epileptic drugs, viz, phenytoin, valproate and carbamazepine, and were compared with levels in unmedicated healthy control subjects. Flow rate and pH of the patient groups were not different from the controls. In all patient groups the specific amylase activity was increased up to twofold. In the phenytoin group only, the salivary IgA concentration was strongly reduced. Levels of salivary cystatin C were similar among all patient groups studied, and were not different from those of the control group. In contrast, the absolute and relative concentrations of cystatin S were diminished, particularly in patients using either valproate or phenytoin. These data suggest that use of anti-epileptic drugs over long periods may result in decreased levels of several salivary proteins such as sIgA and cystatins, which are involved in the protection of the oral cavity against microbial infections.

Epidermal growth factor in gingival crevicular fluid and its binding capacity in inflamed and non-inflamed human gingiva

Epidermal growth factor (EGF) is a pro-inflammatory small peptide (6000 Da) with a variety of biological activities including stimulation of cell differentiation and mediation of proteolysis by binding to its specific receptor on the cell surface. The purpose of this study was to determine the levels of EGF in gingival crevicular fluid (GCF) and the EGF-binding capacity to its receptor in gingival tissue. The GCF samples were collected from six patients by inserting paper strips into shallow (< 5 mm) and deep pockets (> or = 5 mm) for 30 s. The strips were soaked in 0.2 M acetate for extraction and the EGF in the supernatants was analysed by radioimmunoassay. To determine the binding capacity of EGF to its receptor, inflamed gingival tissues (pocket depth > or = 5 mm, Gingival Index = 1, 2 or 3) were collected during periodontal flap surgery and non-inflamed gingival tissues (pocket depth < 5 mm, Gingival Index = 0) were collected during surgical "crown lengthening' for aesthetic purposes. The tissues were pooled by group, homogenized for membrane preparation and the supernatants obtained after centrifugation were used in a 125IEGF binding assay. To determine the effect of inflammation on gingival EGF receptor, inflamed and non-inflamed gingival tissues were collected from six patients and prepared similarly to the binding assay. Gingival preparations were then electrophoresed for Western blot analysis with EGF receptor antiserum. The EGF level in GCF was significantly lower (P < 0.05) in the samples collected from pockets > or = 5 mm (0.9 +/- 0.6 ng/ml) than in those from pockets < 5 mm (2.4 +/- 2.1 ng/ml). The average Gingival Index was higher (2.6 +/- 0.6) in pockets > or = 5 mm than in pockets < 5 mm (1.4 +/- 1.0). Specific binding of 125I-EGF to its receptor in inflamed gingiva was 2.7-fold higher than in non-inflamed gingiva (14.4 +/- 4.9 vs 5.4 +/- 1.8 fmol/g wet tissue). Western blot analysis showed two major immunoreactive bands (180 and 120 kDa), which represent EGF receptor and its degradation products, in inflamed gingiva. The findings show that inflammation activates EGF binding capacity in gingiva and that the up-regulation of EGF receptor in inflamed gingiva might be associated with a lowered concentration of EGF in GCF produced adjacent to inflamed gingiva. This up-regulation of EGF receptor during inflammation might be an important mechanism in the pathogenesis of periodontal disease.

Interleukin-1 beta induces expression of cyclooxygenase-2 mRNA in human gingival fibroblasts

The effect of interleukin-1 beta (IL-1 beta) on the expression of cyclooxygenase-1 and -2 (COX-1 and COX-2) mRNA and its relation to prostaglandin E2 (PGE2) biosynthesis in human gingival fibroblasts was studied. IL-1 beta increased levels of mRNA for COX-2 whereas the COX-1 mRNA level was unaffected. The increased COX-2 mRNA levels were accompanied by enhanced PGE2 formation. The phorbol, 12-myristate 13-acetate (PMA), known to stimulate protein kinase C (PKC), also induced expression of COX-2 mRNA. When gingival fibroblasts were treated simultaneously with IL-1 beta and PMA, the cytokine IL-1 beta synergistically increased levels of COX-2 mRNA, accompanied by a corresponding increase in PGE2 biosynthesis. The anti-inflammatory steroid, dexamethasone (DEX) abolished the enhanced expression of COX-2 mRNA as well as PGE2 formation induced by IL-1 beta, PMA or the combination of IL-1 beta and PMA. The study indicates that the IL-1 beta induced PGE2 formation is mediated by an enhanced gene expression of COX-2 in gingival fibroblasts suggesting that the enzyme COX-2 may play an important role in the regulation of prostanoid formation at inflammatory lesions in gingival tissue.