The Presence and involvement of interleukin‐17 in apical periodontitis

Apical periodontitis (AP) is a chronic inflammatory disease characterized by periapical tissue inflammation and destruction of the associated alveolar bone. It is caused by microbial infections within the root canal and the resultant host immune responses in the periapical tissues. The proinflammatory cytokine interleukin (IL)‐17 has been shown to play an important role in many inflammatory diseases. There is increasing evidence of the presence of IL‐17 in AP, which might be associated with disease pathogenesis. Moreover, several animal studies indicate the potential role of IL‐17 in periapical inflammation and the resultant bone resorption in AP. This article reviews recent studies regarding the collective in vitro, in vivo and clinical evidence of the presence and involvement of IL‐17 in AP. A search related to IL‐17 in apical periodontitis was conducted on PubMed, EMBASE and Web of Science databases using keywords and controlled vocabulary. Two independent reviewers first screened titles and abstracts and then the full texts that were included. A total of 25 papers were identified, of the 25 included articles, 7 involved laboratory studies on cell cultures, 11 involved animal experimentations, and 7 were observational studies using human clinical samples. In conclusion, evidence for the presence of IL‐17 in AP from human and animal models is clear. However, there is relatively little information currently available that would highlight the specific role of IL‐17 in AP.     

Expression of interleukin‐8 and its receptor IL‐8RA in chronic hyperplastic candidosis

Introduction: Neutrophils are the main opponents of Candida albicans in chronic hyperplastic candidosis. They migrate from the circulation to the epithelium where they form microabscesses. We therefore hypothesized that the neutrophil chemokine interleukin‐8 (IL‐8) might play a role in the neutrophil–Candida interaction. Methods: Biopsies from patients with chronic hyperplastic candidosis (n = 10) were stained using the avidin–biotin–peroxidase complex protocol for IL‐8 and IL‐8 receptor A and were compared to healthy control mucosa (n = 3). A set of C. albicans agar sections was similarly analysed. Results: In chronic hyperplastic candidosis lesions IL‐8 was strongly expressed in both vascular endothelium and mucosal epithelium. Many resident and immigrant inflammatory cells, including intraepithelial neutrophils, were IL‐8 receptor A positive. In addition, IL‐8 (or an analogue) was found in the candidal mother cell in chronic hyperplastic candidosis and in agar, whereas the tips of the hyphae expressed IL‐8 receptor A (or an analogue). Conclusion: IL‐8 may play a role in the recruitment of neutrophils from the vascular compartment to the epithelial microabscesses. C. albicans may have developed an ability to sense IL‐8. The IL‐8 ligand–receptor interaction may help to direct the growth of the IL‐8‐receptor‐containing tips of the hyphae away from the IL‐8‐producing candidal cell body (a centrifugal growth pattern to facilitate host tissue penetration). Later, this ability might help to keep the vulnerable hyphal tips away from areas with high concentrations of host IL‐8 and candidacidal neutrophils. We suggest that this phenomenon, in contrast to chemotropism, is named chemophobia.     

Protease‐activated receptor 2 mediates interleukin‐8 and intercellular adhesion molecule‐1 expression in response to Aggregatibacter actinomycetemcomitans

Introduction:  We investigated the mechanisms by which extracts of Aggregatibacter actinomycetemcomitans affect the inflammatory response in gingival epithelial cells. Methods:  Human gingival cells (Ca9‐22) were cultured in bacterial extracts prepared from A. actinomycetemcomitans ATCC 29522. The cells were pretreated with protease inhibitors or transfected with small interfering RNA (siRNA) specific for protease‐activated receptor 2 (PAR‐2). Results:  The pretreatment of cells with serine protease inhibitors significantly inhibited A. actinomycetemcomitans extract‐induced expression of interleukin‐8 (IL‐8) and intercellular adhesion molecule‐1 (ICAM‐1) at both the messenger RNA and protein levels. In addition, A. actinomycetemcomitans extract‐induced IL‐8 and ICAM‐1 expression was significantly decreased in PAR‐2/siRNA‐transfected cells. Conclusions:  A. actinomycetemcomitans extract‐induced IL‐8 and ICAM‐1 expression in gingival epithelial cells is mediated by PAR‐2.     

Immunohistochemical analysis of interleukin‐1α, its type I receptor and antagonist in keratocystic odontogenic tumors

Background: Interleukin‐1α (IL‐1α) is thought to play a crucial role in the growth of keratocystic odontogenic tumors (KCOTs) in the jaw. The function of IL‐1α is regulated by the local levels of IL‐1α, its receptor and receptor antagonist (IL‐1Ra) in tissues. In this study, the expression of these proteins was investigated both before and after marsupialization in KCOTs. Methods: The expression of IL‐1α, IL‐1 receptor type I (IL‐1RI) and IL‐1Ra was detected immunohistochemically in 10 specimens of KCOTs. Results: IL‐1α was intensively expressed throughout the epithelium in all cases, while mild expression of IL‐1α was detected in the subepithelial layer endothelial cells and fibroblasts. Mild or intensive immunoreactivity for IL‐1RI was also observed in the epithelial cells in all cases, and in the endothelial cells and fibroblasts in five cases respectively. The expression of IL‐1Ra was detected in the epithelial cells in five cases, and in the endothelial cells and fibroblasts in three cases. After marsupialization, the immunoreactivity for IL‐1α and IL‐1RI in the epithelial cells decreased, while the immunoreactivity for IL‐1Ra in the epithelial cells increased. However, the immunoreactivity for IL‐1RI and IL‐1Ra in endothelial cells and fibroblasts did not change significantly. Conclusion: The effects of IL‐1α on the epithelial cells might be downregulated after marsupialization by changing the expression levels of IL‐1α, IL‐1RI and IL‐1Ra in the epithelium of KCOTs.     

Oxidized low‐density lipoprotein increases interleukin‐8 production in human gingival epithelial cell line Ca9‐22

Suzuki K, Sakiyama Y, Usui M, Obama T, Kato R, Itabe H, Yamamoto M. Oxidized low‐density lipoprotein increases interleukin‐8 production in human gingival epithelial cell line Ca9‐22. J Periodont Res 2010; 45: 488–495. © 2010 John Wiley & Sons A/S Background and Objective: Recent epidemiological studies have shown a correlation between periodontitis and hyperlipidemia. We have found high levels of oxidized low‐density lipoprotein (OxLDL) in the gingival crevicular fluid of dental patients. In the present study, we tried to examine the possible role of OxLDL in periodontal inflammation in vitro. Material and Methods: Cells of the human gingival epithelial cell line Ca9‐22 were cultured in media containing OxLDL, and the amounts of interleukin‐8 (IL‐8) and prostaglandin E₂ (PGE₂) produced were measured using ELISAs. Results: Production of IL‐8 by Ca9‐22 cells was significantly increased when the cells were treated with OxLDL, but not with native LDL or acetylated LDL. Production of PGE₂ by Ca9‐22 cells was enhanced by co‐incubation with OxLDL and interleukin‐1β (IL‐1β). Scavenger receptor inhibitors, fucoidan and dextran sulfate, inhibited the OxLDL‐induced IL‐8 and PGE₂ production in the presence of IL‐1β. The p³⁸ MAPK inhibitors SB203580 and SB202190 and the ERK inhibitor PD98059 inhibited the OxLDL‐induced IL‐8 production. Among oxidized lipids and chemically modified LDL, 7‐ketocholesterol enhanced IL‐8 production. Conclusion: This is the first report to show that OxLDL enhances IL‐8 production in epithelial cells.     

Stimulation of epithelial cell matrix metalloproteinase (MMP‐2, ‐9, ‐13) and interleukin‐8 secretion by fusobacteria

Background/aims: Bacterial pathogens involved in periodontal diseases exert their destructive effects primarily by stimulating the host cells to increase their secretion of proinflammatory cytokines and matrix metalloproteinases (MMPs). This study aimed to determine the epithelial cell matrix metalloproteinase and interleukin‐8 (IL‐8) secretion upon exposure to fusobacteria. Methods: Eight different oral and non‐oral Fusobacterium strains were incubated with HaCaT epithelial cells. Gelatin zymography and Western blot analysis were performed to detect collagenase 3 (MMP‐13), gelatinase A (MMP‐2), gelatinase B (MMP‐9), and IL‐8 secretion by epithelial cells. Results: All Fusobacterium strains, especially Fusobacterium necrophorum ATCC 25286, Fusobacterium nucleatum ATCC 25586, and Fusobacterium varium ATCC 51644, increased MMP‐9 and MMP‐13 secretion. Fusobacterium simiae ATCC 33568, and to a lesser extent F. nucleatum and F. necrophorum, increased epithelial MMP‐2 secretion. F. nucleatum and F. necrophorum also increased IL‐8 secretion. F. varium ATCC 27725, a strain that only weakly stimulated MMP production, strongly increased the IL‐8 production, suggesting that their expression is differently regulated. Conclusion: We conclude that the pathogenic potential of fusobacteria may partly result from their ability to stimulate secretion of MMP‐9, MMP‐13, and IL‐8 from epithelial cells.     

The immunopathogenic and immunomodulatory effects of interleukin‐12 in periodontal disease

Interleukin 12 (IL‐12) is an inflammatory cytokine that promotes the response of the immune system. This cytokine has been implicated as a potent stimulator of several diseases characterized by inflammatory‐induced bone destruction, such as rheumatoid arthritis and periodontitis. Yet, the exact role of IL‐12 in the development and progress of periodontitis has not been clarified. Several studies have demonstrated a positive correlation between the level of IL‐12 and the severity of periodontal destruction. Deletion of IL‐12 in mice with periodontitis significantly suppressed the level of bone destruction. Interestingly, next to a role in modulating the pathogenesis, IL‐12 also has immunological‐regulatory properties. This cytokine induces expression of immunosuppressive molecules, such as indoleamine‐pyrrole 2,3‐dioxygenase (IDO). Thus, these findings suggest both negative and positive influences of IL‐12 in periodontal disease. It is currently proposed that the diversity of action of cytokines is a molecular key which regulates biological development and homeostasis. Accordingly, the actions of IL‐12 might be one of the mechanisms that regulate homeostasis of periodontal tissue during and following inflammation. Therefore, this article aims to review both destructive and protective functionalities of IL‐12 with an emphasis on periodontal disease.     

Flutamide inhibits nifedipine‐ and interleukin‐1β‐induced collagen overproduction in gingival fibroblasts

Lu H‐K, Tseng C‐C, Lee Y‐H, Li C‐L, Wang L‐F. Flutamide inhibits nifedipine‐ and interleukin‐1β‐induced collagen overproduction in gingival fibroblasts. J Periodont Res 2010; 45: 451–457. © 2010 John Wiley & Sons A/S Background and Objective: To understand the role of the androgen receptor in gingival overgrowth, the effects of flutamide on interleukin‐1β‐ and nifedipine‐induced gene expression of connective tissue growth factor (CTGF/CCN2) and collagen production in gingival fibroblasts were examined. Material and Methods: Gingival fibroblasts from healthy subjects and patients with dihydropyridine‐induced gingival overgrowth (DIGO) were used. Confluent cells were treated with nifedipine, interleukin‐1β or both. The mRNA expression was examined using real‐time polymerase chain reaction, and the concentration of total soluble collagen in conditioned media was analysed by Sircol Collagen Assay. In addition, the protein expressions of androgen receptor, CTGF/CCN2 and type I collagen in gingival tissue were determined by western blot. Results: Interleukin‐1β was more potent than nifedipine in stimulating CTGF/CCN2 and procollagen α1(I) mRNA expression, and there was an additive effect of the two drugs. Healthy cells exhibited an equal or stronger response of procollagen α1(I) than those with DIGO, but DIGO cells displayed a stronger response in the secretion of soluble collagen in the same conditions. Flutamide, an androgen receptor antagonist, inhibited stimulation by nifedipine or interleukin‐1β. Additionally, the protein expressions of androgen receptor and type I collagen were higher in DIGO gingival tissue than those in healthy gingival tissue. Conclusion: The data suggest that both nifedipine and interleukin‐1β play an important role in DIGO via androgen receptor upregulation and that gingival overgrowth is mainly due to collagen accumulation. Flutamide decreases the gene expression and protein production of collagen from dihydropyridine‐induced overgrowth cells.     

Increased interleukin‐18 in gingival crevicular fluid from periodontitis patients

Introduction: This study aimed to measure the levels of interleukin‐18 (IL‐18) in inflamed shallow sites and inflamed deep sites in patients with periodontitis and to compare the data with results from inflamed shallow sites in patients with gingivitis. A secondary aim was to examine the composition of the subgingival microbiota in the sampled sites. Methods: Gingival crevicular fluid was collected from five gingivitis sites and five periodontitis sites from 18 patients with chronic periodontitis, and from five gingivitis sites from 15 patients with gingivitis. Samples from each site category were pooled and IL‐18 levels were measured using an enzyme‐linked immunosorbent assay. The subgingival microbiota was analyzed by checkerboard DNA–DNA hybridization. Results: All clinical parameters and gingival crevicular fluid volumes were higher in periodontitis sites compared with gingivitis sites from patients with periodontitis and gingivitis. The total amount of IL‐18 was higher in periodontitis sites than gingivitis sites in both periodontitis (P = 0.018) and gingivitis (P = 0.002) patients and was higher in gingivitis sites from periodontitis patients than in those from gingivitis patients (P = 0.015). There were higher levels of Tannerella forsythia, Porphyromonas gingivalis, and Treponema denticola (red complex species) in periodontitis sites compared with gingivitis sites in both the periodontitis and gingivitis patients (P < 0.001). Conclusion: Levels of IL‐18 were higher in patients with chronic periodontitis compared with patients with gingivitis, even at sites with similar pocket depths. The presence of similar levels of red complex species in gingivitis sites from periodontitis patients and from gingivitis patients suggested that the higher levels of IL‐18 were not associated with a different microbial challenge.     

Differential in situ distribution of interleukin‐8, monocyte chemoattractant protein‐1 and Rantes in human chronic periapical granuloma

In situ distribution of three prototype chemokines interleukin (IL)‐8, monocyte chemoattractant protein (MCP)‐1 and Rantes was determined in chronic human periapical granulomas by immunohistochemistry using monoclonal antibodies. IL‐8 was found primarily in the cytoplasm of the Malassez epithelial cells. MCP‐1 immunoreactivity was confined to the endothelial cells that lined small venules. Each of the three investigated chemokines, including Rantes, exhibited a characteristic binding pattern to the extracellular matrix of the lesion. The observed chemokines may play a role in establishing the cellular composition of chronic apical periodontitis, thus augmenting the intensity of local inflammation and tissue damage.