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

Drug-Induced Gingival Overgrowth—Molecular Aspects of Drug Actions

Drug-induced gingival overgrowth (DIGO) is one of the side effects produced by therapeutic agents, most commonly phenytoin, nifedipine and cyclosporin A. However, the precise mechanism of DIGO is not entirely understood. A literature search of the MEDLINE/PubMed databases was conducted to identify the mechanisms involved in DIGO. The available information suggests that the pathogenesis of DIGO is multifactorial, but common pathogenic sequelae of events emerge, i.e., sodium and calcium channel antagonism or disturbed intracellular handling of calcium, which finally lead to reductions in intracellular folic acid levels. Disturbed cellular functions, mainly in keratinocytes and fibroblasts, result in increased collagen and glycosaminoglycans accumulation in the extracellular matrix. Dysregulation of collagenase activity, as well as integrins and membrane receptors, are key mechanisms of reduced degradation or excessive synthesis of connective tissue components. This manuscript describes the cellular and molecular factors involved in the epithelial–mesenchymal transition and extracellular matrix remodeling triggered by agents producing DIGO.

Angiotensin II Regulates Proliferation and Function of Stem Cells of Apical Papilla

INTRODUCTION

Stem cells of apical papilla (SCAP) may be affected by inflammatory mediators released by activation with lipopolysaccharide (LPS) from infected pulpal cavities of necrotic immature teeth. Therefore, this study aimed to investigate the presence of a local renin-angiotensin system (RAS) and the role of angiotensin II (Ang II) on the modulation of SCAP in vitro.

METHODS

Primary cultures of SCAP were incubated with LPS (0.1-10 μg/mL) for cell viability and quantification of the chemokine CCL2. Components of RAS were searched by gene expression of angiotensinogen (AGTN), angiotensin converting enzyme (ACE), renin, angiotensin receptor 1 (AT1) and 2 (AT2), and Mas receptor. Ang II was investigated in SCAP supernatants. Immunofluorescence was used to detect AGTN and AT1. Next, cells were treated with Ang II for viability/proliferation assessment, quantification of CCL2 and interleukin 6, and mineralization assay. Data were evaluated by analysis of variance using Tukey post hoc comparisons or the Student t test. P values <.05 were considered to be significant.

RESULTS

LPS increased CCL2 production at 1 and 10 μg/mL. The gene expression of AGTN, renin, ACE, and AT1 was detected, but only ACE was increased by LPS. Ang II peptide was found in SCAP supernatants but unaltered by LPS. Both AGTN and AT1 proteins were detected by immunostaining. Ang II significantly induced SCAP proliferation, increased CCL2 production, down-regulated IL-6 release, and reduced the SCAP mineralization rate.

CONCLUSIONS

A local RAS was found at the apical papilla, and Ang II was able to modulate SCAP function in vitro.

Aliskiren Attenuates the Inflammatory Response and Wound Healing Process in Diabetic Mice With Periodontal Disease

The aim of this study was to characterize the role of local RAS (renin–angiotensin system) in the inflammatory response of normal (N) and diabetic (D) mice with periodontal disease (PD). Diabetes Mellitus (DM) was induced by peritoneal injection of streptozotocin in Balb/c mice. PD was induced by ligature around the first molar in both N and D, irrespective of whether they were treated with aliskiren (50 mg/kg, Alisk). Mandibles were harvested for histomorphometric analyses, and gingival tissue (GT) was collected to evaluate gene expression and extracellular matrix components (ECM). Immunohistochemical (IHC) analyses were used to localize RAS in GT. The production of C-reactive protein (CRP), IL-1β, CXCL2, and CCL8 was evaluated by enzyme-linked immunosorbent assay (ELISA). Renin was found to exacerbate the inflammation and periodontal bone loss at 14 days after PD, and Alisk inhibited this process in GT of N and D. PD increased CRP, CXCL2, CCL8, and IL-1β production in both animals. Alisk could inhibit CRP, CXCL2, and CCL8 primarily in D animals. However, only CCL8 was decreased in N animals after Alisk pretreatment. PD enhanced expression and production of AGT, ACE, AT1R, and AT2R in both N and D. AT1R expression was higher in D with PD, and AT2R expression was higher in N with PD. ACE2 and receptor Mas (MasR) expression and production was elevated in the control group of both animals. PD inhibited ACE2 in N but not in D. MasR expression was unaffected in both N and D with PD. Alisk reduced expression and production of all RAS components in GT of both animals, except for ACE2 in N. RAS staining was observed in all layers of epithelium, basal cell layer, and lamina propria and was higher in N with PD. Col1a1, Col1a2, Col3a1, and fibronectin (Fn1) were increased in both animals with PD. Alisk inhibited Col1a1 and Fn in both animals, Col1a2 was decreased only in D, while levels of Col3a1 remained unchanged in all animal groups. In conclusion, these data demonstrated the presence and functional role of local RAS in GT, exacerbating the inflammatory response, periodontal bone loss, and wound healing processes in both N and D animal groups. In addition, Alisk was able to significantly reduce gingival inflammation, excessive wound healing processes, and periodontal bone loss.

On the Cellular and Molecular Mechanisms of Drug-Induced Gingival Overgrowth

Introduction:

Gingival overgrowth has been linked to multiple factors such as adverse drug effects, inflammation, neoplastic processes, and hereditary gingival fibromatosis. Drug-induced gingival overgrowth is a well-established adverse event. In early stages, this gingival enlargement is usually located in the area of the interdental papilla. Histologically, there is an increase in the different components of the extracellular matrix.

Objective:

The aim of this manuscript is to describe and analyze the different cellular and molecular agents involved in the pathogenesis of Drug-induced gingival overgrowth.

Method:

A literature search of the MEDLINE/PubMed database was conducted to identify the mechanisms involved in the process of drug-induced gingival overgrowth, with the assistance of a research librarian. We present several causal hypotheses and discuss the advances in the understanding of the mechanisms that trigger this gingival alteration.

Results:

In vitro studies have revealed phenotypic cellular changes in keratinocytes and fibroblasts and an increase of the extracellular matrix with collagen and glycosaminoglycans. Drug-induced gingival overgrowth confirms the key role of collagenase and integrins, membrane receptors present in the fibroblasts, due to their involvement in the catabolism of collagen. The three drug categories implicated: calcineuron inhibitors (immunosuppressant drugs), calcium channel blocking agents and anticonvulsant drugs appear to present a multifactorial pathogenesis with a common molecular action: the blockage of the cell membrane in the Ca2+/Na+ ion flow. The alteration of the uptake of cellular folic acid, which depends on the regulated channels of active cationic transport and on passive diffusion, results in a dysfunctional degradation of the connective tissue. Certain intermediate molecules such as cytokines and prostaglandins play a role in this pathological mechanism. The concomitant inflammatory factor encourages the appearance of fibroblasts, which leads to gingival fibrosis. Susceptibility to gingival overgrowth in some fibroblast subpopulations is due to phenotypic variability and genetic polymorphism, as shown by the increase in the synthesis of molecules related to the response of the gingival tissue to inducing drugs. The authors present a diagram depicting various mechanisms involved in the pathogenesis of drug-induced gingival overgrowth.

Conclusion:

Individual predisposition, tissue inflammation, and molecular changes in response to the inducing drug favor the clinical manifestation of gingival overgrowth.

Comparison of Serum Levels of Endothelin-1 in Chronic Periodontitis Patients Before and After Treatment

INTRODUCTION

Endothelin-1 (ET-1) is a potent vasoconstrictive peptide with multi functional activity in various systemic diseases. Previous studies indicate the detection of ET-1 in gingival tissues and gingival crevicular fluid.

AIM

The aim of this study was to estimate the serum ET-1 levels in clinically healthy subjects and subjects with chronic periodontitis, before and after treatment, and correlate it with the clinical parameters.

MATERIALS AND METHODS

A total of 44 patients were included in the study. Group I comprised of 20 subjects with clinically healthy periodontium. Group II comprised of 24 subjects with chronic periodontitis. Group III comprised of same Group II subjects following periodontal management. Serum samples were collected from the subjects and an Enzyme Linked Immunosorbent Assay (ELISA) was done to estimate the ET-1 levels. The ET-1 levels were then correlated among the three groups with the clinical parameters namely, Plaque Index (PI), Sulcus Bleeding Index (SBI), probing pocket depth, clinical attachment loss and Periodontally Inflamed Surface Area (PISA). The independent t-test and paired t-test were used for comparison of clinical parameters and Pearson's correlation coefficient test was used for correlating the ET-1 levels.

RESULTS

ET-1 levels in chronic periodontitis subjects were significantly higher compared to healthy subjects (p<0.001). However, the clinical parameters did not statistically correlate with the ET-1 levels. There was a significant decrease in ET-1 levels following treatment (p<0.001).

CONCLUSION

Serum ET-1 is increased in chronic periodontitis and reduces after periodontal therapy. Further studies are required to establish ET-1 as a biomarker for periodontal disease.

Effect of Cyclosporin A and Angiotensin II on cytosolic calcium levels in primary human gingival fibroblasts

Background:

To evaluate the effect of Cyclosporin A (CsA) and angiotensin II (Ang II) on cytosolic calcium levels in cultured human gingival fibroblasts (HGFs).

Materials and Methods:

Healthy gingival samples from six volunteers were obtained, and primary HGFs were cultured. Cell viability and proliferation assay were performed to identify the ideal concentrations of CsA and Ang II. Cytosolic calcium levels in cultured gingival fibroblasts treated with CsA and Ang II were studied using colorimetric assay, confocal and fluorescence imaging. Statistical analyses were done using SPSS software and GraphPad Prism.

Results:

Higher levels of cytosolic levels were evident in cells treated with CsA and Ang II when compared to control group and was statistically significant (P < 0.05) in both colorimetric assay and confocal imaging. Fluorescent images of the cultured HGFs revealed the same.

Conclusion:

Thus calcium being a key player in major cellular functions, plays a major role in the pathogenesis of drug-induced gingival overgrowth.

Functional Local Renin-Angiotensin System in Human and Rat Periodontal Tissue

The initiation or progression of periodontitis might involve a local renin-angiotensin system (RAS) in periodontal tissue. The aim of this study was to further characterize the local RAS in human and rat periodontal tissues between healthy and periodontally-affected tissue. Components of the RAS were investigated using in vitro, ex vivo and in vivo experiments involving both human and Wistar rat periodontium. Although not upregulated when challenged with P. gingivalis-lipopolysaccharide, human gingival and periodontal ligament fibroblasts expressed RAS components. Likewise, healthy and inflamed human gingiva expressed RAS components, some of which were shown to be functional, yet no differences in expression were found between healthy and diseased gingiva. However, in inflamed tissue the immunoreactivity was greater for the AT₁R compared to AT₂R in fibroblasts. When compared to healthy tissue, ACE activity was increased in human gingiva from volunteers with gingivitis. Human-gingiva homogenates generated Ang II, Ang 1-9 and Ang 1-7 when incubated with precursors. In gingiva homogenates, Ang II formation from Ang I was nearly abolished only when captopril and chymostatin were combined. Ang 1-7 formation was significantly greater when human gingiva homogenates were incubated with chymostatin alone compared to incubation without any inhibitor, only captopril, or captopril and chymostatin. In rat gingiva, RAS components were also found; their expression was not different between healthy and experimentally induced periodontitis (EP) groups. However, renin inhibition (aliskiren) and an AT₁R antagonist (losartan) significantly blocked EP-alveolar-bone loss in rats. Collectively, these data are consistent with the hypothesis that a local RAS system is not only present but is also functional in both human and rat periodontal tissue. Furthermore, blocking AT₁R and renin can significantly prevent periodontal bone loss induced by EP in rats.

Angiotensin II Levels in Gingival Tissues from Healthy Individuals, Patients with Nifedipine Induced Gingival Overgrowth and Non Responders on Nifedipine

CONTEXT

The Renin Angiotensin system has been implicated in the pathogenesis of Drug Induced Gingival Overgrowth (DIGO), a fibrotic condition, caused by Phenytoin, Nifedipine and Cyclosporine.

AIM

This study quantified Angiotensin II levels in gingival tissue samples obtained from healthy individuals, patients on Nifedipine manifesting/not manifesting drug induced gingival overgrowth.

MATERIALS AND METHODS

Gingival tissue samples were obtained from healthy individuals (n=24), patients on nifidipine manifesting gingival overgrowth (n= 18) and patients on nifidipine not manifesting gingival overgrowth (n=8). Angiotensin II levels were estimated in the samples using a commercially available ELISA kit.

RESULTS

Angiotensin II levels were significantly elevated in patients on Nifedipine manifesting gingival overgrowth compared to the other 2 groups (p<0.01).

CONCLUSION

The results of the study give an insight into the role played by Angiotensin II in the pathogenesis of drug induced gingival overgrowth.

The possible potential therapeutic targets for drug induced gingival overgrowth

Gingival overgrowth is a side effect of certain medications. The most fibrotic drug-induced lesions develop in response to therapy with phenytoin, the least fibrotic lesions are caused by cyclosporin A, and the intermediate fibrosis occurs in nifedipine-induced gingival overgrowth. Fibrosis is one of the largest groups of diseases for which there is no therapy but is believed to occur because of a persistent tissue repair program. During connective tissue repair, activated gingival fibroblasts synthesize and remodel newly created extracellular matrix. Proteins such as transforming growth factor (TGF), endothelin-1 (ET-1), angiotensin II (Ang II), connective tissue growth factor (CCN2/CTGF), insulin-like growth factor (IGF), and platelet-derived growth factor (PDGF) appear to act in a network that contributes to the development of gingival fibrosis. Since inflammation is the prerequisite for gingival overgrowth, mast cells and its protease enzymes also play a vital role in the pathogenesis of gingival fibrosis. Drugs targeting these proteins are currently under consideration as antifibrotic treatments. This review summarizes recent observations concerning the contribution of TGF-β, CTGF, IGF, PDGF, ET-1, Ang II, and mast cell chymase and tryptase enzymes to fibroblast activation in gingival fibrosis and the potential utility of agents blocking these proteins in affecting the outcome of drug-induced gingival overgrowth.

Influence of mast cells in drug-induced gingival overgrowth

Mast cells (MCs) are multifunctional effector cells that were originally thought to be involved in allergic disorders. Now it is known that they contain an array of mediators with a multitude of effects on many other cells. MCs have become a recent concern in drug-induced gingival overgrowth (DIGO), an unwanted outcome of systemic medication. Most of the studies have confirmed the significant presence of inflammation as a prerequisite for the overgrowth to occur. The inflammatory changes within the gingival tissue appear to influence the interaction between the inducing drug and the fibroblast activity. The development of antibodies to MC-specific enzymes, tryptase and chymase, has facilitated the study of mast cells in DIGO. Many immunohistochemical studies involving MCs have been conducted; as a result, DIGO tissues are found to have increased the number of MCs in the gingiva, especially in the area of fibrosis. At the cellular level, gingival fibrogenesis is initiated by several mediators which induce the recruitment of a large number of inflammatory cells, including MCs. The purpose of this paper is to access the roles played by MCs in gingival overgrowth to hypothesize a relationship between these highly specialized cells in the pathogenesis of DIGO.

Expression of angiotensin II and its receptors in cyclosporine-induced gingival overgrowth

BACKGROUND AND OBJECTIVES

The renin-angiotensin system (RAS) is considered as a hormonal circulatory system involved in maintaining blood pressure, electrolyte and fluid homeostasis. RAS components can be synthesized in local tissues and are found to play a role in gingival overgrowth. The drug-induced gingival overgrowth (DIGO) is a fibrotic condition, which is associated with multiple factors, including inflammation and adverse drug effects such as cyclosporine A. This study was directed forward to the identification of the angiotensinogen, angiotensin II (Ang II) and its receptors AT₁ /AT₂ expression in DIGO tissues and cyclosporine-treated human gingival fibroblast cells.

MATERIAL AND METHODS

Gingival samples were obtained from patients with cyclosporine-induced gingival overgrowth, chronic periodontitis and normal healthy subjects. The total RNA was isolated and reverse transcription-polymerase chain reaction was performed for angiotensinogen, Ang II and AT₁ /AT₂ receptor. Ang II protein was estimated from tissue by enzyme immunoassay. The expression of Ang II and its receptors were also examined in gingival fibroblast cells treated with cyclosporine.

RESULTS

Ang II mRNA and protein expression was significantly higher in patients with DIGO than in patients with periodontitis and healthy subjects. The AT₁ mRNA was expressed more than AT₂ in all examined tissues. In gingival fibroblasts, Ang II and AT₁ expressions were increased with cyclosporine incorporation compared to controls.

CONCLUSION

These results suggest that cyclosporine can modulate local expression of RAS components such as angiotensinogen, Ang II and its receptors in gingival tissues and gingival fibroblast cells.

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).

The effect of angiotensin II on the proliferation of human gingival fibroblasts

Angiotensin not only raises blood pressure and modifies body fluids and electrolytes but also induces differentiation and proliferation of fibroblasts in the circulatory system in order to repair damage. The purpose of the present study was to observe the influence of the addition of angiotensin II (AngII) or nifedipine (NIF) alone or both sequentially on proliferative activity, the intracellular Ca(2+) concentration ([Ca(2+)]i), and the inositol-1,4,5-triphosphate (IP3) level in cultivated human gingival fibroblasts. Addition of 10(-8)-10(-4) M NIF or 10(-5)-10(-4) M AngII alone increased the proliferation of cultivated gingival fibroblasts, and the interaction of NIF and AngII suppressed proliferation. Addition of AngII alone increased [Ca(2+)]i, with a peak 60 s afterward and a return to a level slightly higher than the pretreatment level at 120 s. Addition of both AngII and NIF did not increase [Ca(2+)]i as much as the addition of AngII alone. When Ca(2+) was absent from the extracellular environment, the AngII-induced increase in [Ca(2+)]i was suppressed. AngII increased the concentration of IP(3), with a peak at 120 s after its addition. From these results we concluded that AngII increased the proliferation of gingival fibroblasts by causing an influx of Ca(2+), which increased [Ca(2+)]i.

Characterization of a local renin-angiotensin system in rat gingival tissue

BACKGROUND

The systemic renin-angiotensin system (RAS) promotes the plasmatic production of angiotensin (Ang) II, which acts through interaction with specific receptors. There is growing evidence that local systems in various tissues and organs are capable of generating angiotensins independently of circulating RAS. The aims of this study were to investigate the expression and localization of RAS components in rat gingival tissue and evaluate the in vitro production of Ang II and other peptides catalyzed by rat gingival tissue homogenates incubated with different Ang II precursors.

METHODS

Reverse transcription-polymerase chain reaction assessed mRNA expression. Immunohistochemical analysis aimed to detect and localize renin. A standardized fluorimetric method with tripeptide hippuryl-histidyl-leucine was used to measure tissue angiotensin-converting enzyme (ACE) activity, whereas high performance liquid chromatography showed products formed after the incubation of tissue homogenates with Ang I or tetradecapeptide renin substrate (TDP).

RESULTS

mRNA for renin, angiotensinogen, ACE, and Ang II receptors (AT(1a), AT(1b), and AT(2)) was detected in gingival tissue; cultured gingival fibroblasts expressed renin, angiotensinogen, and AT(1a) receptor. Renin was present in the vascular endothelium and was intensely expressed in the epithelial basal layer of periodontally affected gingival tissue. ACE activity was detected (4.95 +/- 0.89 nmol histidyl-leucine/g/minute). When Ang I was used as substrate, Ang 1-9 (0.576 +/- 0.128 nmol/mg/minute), Ang II (0.066 +/- 0.008 nmol/mg/minute), and Ang 1-7 (0.111 +/- 0.017 nmol/mg/minute) were formed, whereas these same peptides (0.139 +/- 0.031, 0.206 +/- 0.046, and 0.039 +/- 0.007 nmol/mg/minute, respectively) and Ang I (0.973 +/- 0.139 nmol/mg/minute) were formed when TDP was the substrate.

CONCLUSION

Local RAS exists in rat gingival tissue and is capable of generating Ang II and other vasoactive peptides in vitro.

Endothelin-1 and its receptors ET(A) and ET(B) in drug-induced gingival overgrowth

BACKGROUND

The purpose of this study was to study the expression of endothelin-1 (ET-1) and its receptors ETA and ETB in normal human gingiva and cyclosporin-induced gingival fibroblasts.

METHODS

Gingival samples were collected from eight normal healthy individuals, eight patients with periodontitis, and eight patients with cyclosporin A (CsA)-induced gingival overgrowth. Total RNA was extracted from tissue samples, and reverse transcriptase-polymerase chain reaction was performed for ET-1, ETA, and ETB. ET-1 protein was estimated from the tissues by enzyme-linked immunosorbent assay. The expression of ET-1 and its receptors was also examined in gingival fibroblast cells treated with CsA.

RESULTS

ET-1 mRNA expression was significantly higher in patients with CsA-induced gingival overgrowth (P <0.001) than in patients with periodontitis and the controls. ETA mRNA was expressed more than the ETB in all examined samples. In human gingival fibroblasts, ET-1 expression was increased with CsA incorporation compared to controls (P <0.001).

CONCLUSION

These results suggest that CsA can modulate the expression of ET-1 in gingival fibroblasts and CsA-induced gingival overgrowth.

Fibroblast differentiation in wound healing and fibrosis

The contraction of granulation tissue from skin wounds was first described in the 1960s. Later it was discovered that during tissue repair, fibroblasts undergo a change in phenotype from their normal relatively quiescent state in which they are involved in slow turnover of the extracellular matrix, to a proliferative and contractile phenotype termed myofibroblasts. These cells show some of the phenotypic characteristics of smooth muscle cells and have been shown to contract in vitro. In the 1990s, a number of researchers in different fields showed that myofibroblasts are present during tissue repair or response to injury in a variety of other tissues, including the liver, kidney, and lung. During normal repair processes, the myofibroblastic cells are lost as repair resolves to form a scar. This cell loss is via apoptosis. In pathological fibroses, myofibroblasts persist in the tissue and are responsible for fibrosis via increased matrix synthesis and for contraction of the tissue. In many cases this expansion of the extracellular matrix impedes normal function of the organ. For this reason much interest has centered on the derivation of myofibroblasts and the factors that influence their differentiation, proliferation, extracellular matrix synthesis, and survival. Further understanding of how fibroblast differentiation and myofibroblast phenotype is controlled may provide valuable insights into future therapies that can control fibrosis and scarring.

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.

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.

The Endothelin/Sarafotoxin-Induced Increase of the Proliferation of Undifferentiated and DMSO-Differentiated GEM-81 Goldfish Erythrophoroma Cells is Mediated by ETB Receptors

Endothelins (ETs) and sarafotoxins (SRTXs) have been reported to exert ET(B)-mediated effects on vertebrate pigment cells. GEM-81 cell line, a red pigment cell-derived cutaneous tumor of the teleost Carassius auratus, expresses ET(B) receptors and can be differentiated with 1.5% DMSO treatment, thus constituting an useful model to investigate ET and SRTX effects on cultured fish pigment cells. Our aim was to characterize the pharmacology and biological effects mediated by ET receptors in DMSO-differentiated and undifferentiated cells. ET subtype receptors and their respective Ki values in both cell types were determined by competitive binding assays using (125)I ET-1 and BQ-485 (an ET(A) antagonist) or BQ-788 (an ET(B) antagonist). BQ-788, but not BQ-485, significantly reduced (125)I-ET-1 binding in both cell types, with similar low (Ki > nM) affinities. To determine the proliferation effects of ETs/SRTXs, cells were treated for 72 h with the hormones, and counted in a hemocytometer. The proliferation assays were repeated for SRTX S6c in the presence or absence of BQ-788. The results demonstrated that, with the exception of ET-1 (biphasic effect) and ET-3 (no significant effect) in undifferentiated GEM-81 cells, all the tested hormones induced increases in the proliferation of both types of cells. The hormones were equipotent in DMSO-differentiated cells, which exhibited increased sensitivity to ETs, but not to SRTXs, as compared with undifferentiated cells. The BQ-788 antagonistic effect was also exerted on the proliferation responses to SRTX S6c. These results corroborate the long and important evolutionary history of the ET/SRTX receptor system in vertebrate pigment cells.