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

Refining the Mechanism of Drug-Influenced Gingival Enlargement and Its Management

Drug-influenced gingival enlargement (DIGE) or overgrowth manifests as abnormal enlargement of the gingiva due to an adverse effect of certain drug reactions in patients treated with anticonvulsants, immunosuppressants, or calcium channel blockers (CCBs). As the gingival enlargement became significant, it may interfere with the normal oral hygiene measures, aesthetics, as well as masticatory functions of the patients. The exact mechanism of how this undesirable condition develops is yet unknown, and complicated, with non-inflammatory and inflammatory pathways involved. This review illuminates these putative pathways of DIGE and highlights various treatment approaches based on existing research and current observations.

Transcriptional Analysis Reveals Key Genes in the Pathogenesis of Nifedipine-Induced Gingival Overgrowth

Background

Nifedipine-induced gingival overgrowth (NGO) is a multifactorial pathogenesis with increased extracellular matrix including collagen and glycans, inflammatory cytokines, and phenotype changes of fibroblasts. However, the molecular etiology of NGO is not well understood. The objective of this study is to investigate the key genes in the pathogenesis of NGO.

Methods

In this study, we examined the proliferation and migration abilities of fibroblasts derived from patients with chronic periodontitis, nifedipine nonresponder gingival overgrowth, gingival overgrowth caused by nifedipine, and healthy normal gingiva. We conducted RNA-Seq on these four groups of fibroblasts and analysed the differentially expressed genes (DEGs).

Results

Fibroblasts derived from NGO patients had higher proliferation and migration abilities than those of the other groups. Protein-protein interaction network analysis indicated that TGFB2, ITGA8, ITGA11, FGF5, PLA2G4D, PLA2G2F, PTGS1, CSF1, LPAR1, CCL3, and NKX3-1 are involved in the development of NGO. These factors are related to the arachidonic acid metabolism and PI3K/AKT signaling pathways.

Conclusion

Transcriptional gene expression analysis identified a number of DEGs that might be functionally related to gingival overgrowth induced by nifedipine. Our study provides important information on the molecular mechanism underlying nifedipine-induced gingival overgrowth.

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.

Increased Advanced Oxidation Protein Products Generation by Cyclosporine-A and Angiotensin II in Human Gingival Fibroblasts - Ex-vivo Study

INTRODUCTION

Cyclosporin-A (CsA), an immunosuppressant, induces renal fibrosis and Renin Angiotensin System (RAS) is known to play a major role. CsA has the potential to increase the oxidative stress; specifically through the Advanced Oxidation Protein Products (AOPP) which could possibly stimulate fibrosis. A similar type of pathology occurs even in the gingiva known as CsA Induced Gingival Overgrowth (CIGO).

AIM

This study was undertaken to estimate the AOPP generation by Human Gingival Fibroblasts (HGF) under the influence of CsA and Angiotensin II (Ang II).

MATERIALS AND METHODS

Six healthy gingival tissue samples were obtained during crown lengthening procedure and primary HGF were cultured using enzymatic digestion method. The ideal non-cytotoxic concentrations of CsA and Ang II were identified using cytotoxicity assay. Later, HGF were incubated with CsA and Ang II for 12 hours and AOPP assay was performed at zero and one hour interval.

RESULTS

There was a statistically significant increase in AOPP production in both the CsA and Ang II when compared to the control group with a p value<0.05.

CONCLUSION

CsA can induce oxidative stress and preventing/controlling it may be necessary to prevent untoward effect of the drug.

Immunohistochemical Localization of Epithelial Mesenchymal Transition Markers in Cyclosporine A Induced Gingival Overgrowth

INTRODUCTION

Cyclosporine, an immunosuppressive agent used in the management of renal transplant patients is known to produce Drug Induced Gingival Overgrowth (DIGO) as a side effect. Several mechanisms have been elucidated to understand the pathogenesis of DIGO. Recently, epithelial mesenchymal transition has been proposed as a mechanism underlying fibrosis of various organs.

AIM

The aim of the study was to investigate if Epithelial Mesenchymal Transition (EMT) operates in Cyclosporine induced gingival overgrowth.

MATERIALS AND METHODS

The study involved obtaining gingival tissue samples from healthy individuals (n=17) and subjects who exhibited cyclosporine induced gingival overgrowth (n=18). Presence and distribution of E-Cadherin, S100 A4 and alpha smooth muscle actin (α-SMA) was assessed using immunohistochemistry and cell types involved in their expression were determined. The number of α- SMA positive fibroblasts were counted in the samples.

RESULTS

In control group, there was no loss of E-Cadherin and a pronounced staining was seen in the all layers of the epithelium in all the samples analysed (100%). S100 A4 staining was noted in langerhans cells, fibroblasts, endothelial cells and endothelial lined blood capillaries in Connective Tissue (CT) of all the samples (100%) while α - SMA staining was seen only on the endothelial lined blood capillaries in all the samples (100%). However in DIGO, there was positive staining of E-Cadherin only in the basal and suprabasal layers of the epithelium in all the samples (100%). Moreover there was focal loss of E-Cadherin in the epithelium in eight out of 18 samples (44%). A break in the continuity of the basement membrane was noted in three out of 18 samples (16%) on H & E staining.

CONCLUSION

Based on the analysis of differential staining of the markers, it can be concluded that EMT could be one of the mechanistic pathways underlying the pathogenesis of DIGO.

ET-1 Promotes Differentiation of Periodontal Ligament Stem Cells into Osteoblasts through ETR, MAPK, and Wnt/β-Catenin Signaling Pathways under Inflammatory Microenvironment

Periodontitis is a kind of chronic inflammatory disease that affects the tooth-supporting tissues. ET-1 is related to periodontitis and involved in the regulation of cytokines, but the mechanisms remain unclear. The aim of this study is to investigate how ET-1 affects proinflammatory cytokine expression and differentiation in human periodontal ligament stem cells (PDLSCs). PDLSCs were isolated from the periodontal ligament tissues of periodontitis patients and then treated with ET-1 (1, 10, or 100 nM) for 12 h, 24 h, or 72 h. The osteogenic potential of PDLSCs was tested using ALP staining. TNF-α, IL-1β, and IL-6 levels were evaluated by ELISA and western blot. Runx2, OCN, and COL1 mRNA and western levels were detected by RT-PCR and western blot, respectively. To examine the signaling pathways and molecular mechanisms involved in ET-1-mediated cytokine expression and osteogenic differentiation, ETR pathway, MAPKs pathway, Wnt/β-catenin pathway, and Wnt/Ca²⁺ pathway were detected by RT-PCR and western blot, respectively. ET-1 promoted differentiation of PDLSCs into osteoblasts by increasing secretion of TNF-α, IL-1β, and IL-6 in a dose- and time-dependent manner. ET-1 also increased expression of Runx2, OCN, and COL1. ET-1 promotes differentiation of PDLSCs into osteoblasts through ETR, MAPK, and Wnt/β-catenin signaling pathways under inflammatory microenvironment.

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.