Oral Biosciences & Medicine
Oral Biosciences & Medicine
Oral Biosci Med 1 (2004), No. 4     (07.02.2005)

Oral Biosci Med 4/2004, S. 249-257

The Significance of Gingival Crevicular Fluid and IL-1β, TNF-α and PGE2 in Periodontal Disease. A Literature Review

Mahmoud N. Younis a / Eli E. Machtei a,b / Orit Oetlinger-Barak a / Micha Peled c

Abstract

Purpose:
To review the literature regarding cytokines and PGE2 levels in gingival crevicular fluid (GCF) in healthy and diseased periodontium.

A Medline search ending at March 2004 was performed, in the English literature, regarding IL-1β, TNF-α and PGE2 in the GCF, and the data was reviewed systematically.

Low levels of these markers were reported in healthy periodontium. Significant increase in the amount of IL-1β and PGE2 was noted in gingivitis and periodontitis. Most of the studies have shown that there is a marked decrease in IL-1β and PGE2 levels of periodontal disease patients after therapy, while inconsistent results were found for TNF-α.

The IL-1β, TNF-α and PGE2 levels may be indicative of periodontal status, and amount rather than concentration being more reliable in reflecting the real status of the periodontium.

Key words:
β, TNF-α


INTRODUCTION

Bacteria are essential for the initiation and progression of periodontal disease; however, neither bacterial quantity nor specific bacterial species have been sufficient to explain the differences in disease severity between individuals. The available data suggests that several factors that amplify the inflammatory process make people more susceptible to periodontal disease than others. Patient susceptibility is of utmost importance to the outcome of periodontal disease; while periodontal bacteria are the primary etiological agents, the host immune response to these bacteria is of fundamental importance (Seymour, 1991).

The host response can be broadly classified into 3 categories: the humoral immune response (e.g. antibody production), cellular immune response (e.g. cytokines production), and acute inflammatory response (e.g. PGE2).

Given the B-cell nature of the periodontitis lesion, it has been proposed that individuals susceptible to periodontal disease may have a Th2 response, whereas resistance to periodontal disease may be related to a Th1 cytokine profile (Gemmell and Seymour, 1994). Cytokines are soluble proteins or glycoproteins released from cells involved in immunoinflammatory processes and are modulating the activity of the immune and/or other cells (Bendtzen, 1989; Bendtzen, 1991). They seem vital in the immunopathology of an ever-increasing number of diseases, while the production of ‘appropriate’ cytokines is essential for the development of protective immunity. If ‘inappropriate’ cytokines are elicited, destructive or progressive disease might result (Figueredo et al, 1999).

The list of identified interleukins grows continuously with the total number of individual activities now at 22. It has been shown by many investigators that interleukin-1α (IL-1α), interleukin-1β (IL-1β), interleukin-6 (IL-6), interleukin-8 (IL-8), and tumour necrosis factor-α (TNF-α) can be detected in gingival crevicular fluid (GCF) in periodontal disease (Rossomando et al, 1990; Geivelis et al, 1993; Payne et al, 1993) and that the cytokine levels in GCF are closely associated with the severity of gingival inflammation and/or periodontal tissue destruction (Masada et al, 1990; Stashenko et al, 1991). It has been shown that IL-1α, IL-1 β, IL-6, IL-8, and TNF-α can be detected in the gingival crevicular fluid (GCF). Higher levels of these mediators in the GCF are detected in periodontal disease (Rossomando et al, 1990; Geivelis et al, 1993; Payne et al, 1993); cytokine levels being closely associated with the severity of gingival inflammation and/or periodontal tissue destruction (Masada et al, 1990; Stashenko at al, 1991).

IL-8, that is produced by a wide variety of cells (polymorphonuclear leukocytes, monocytes, macrophages and fibroblasts), plays a key role in the accumulation of leukocytes at the sites of inflammation (Bickel, 1993) and its level is known to increase in the GCF of inflamed as compared to healthy sites (Tsai et al, 1995). The pivotal role of IL-1β and TNF-α in the pathogenic mechanisms of periodontitis has been established by Page (1999); and cause-and-effect relationship between cytokines and periodontal tissue loss has been further confirmed (Assuma et al, 1998; Graves et al, 1998; Delima et al, 2001). IL-1β has been shown to stimulate bone resorption and to have inhibitory effects on bone formation (Tatakis, 1993). In addition, it is suspected to be involved in other osseous pathologies, as well as periodontitis (Nguyen et al, 1991).

A notable property of IL-1β in the pathological process of periodontitis is the stimulation of matrix metalloproteinases (MMPs) production (collagenases, gelatinases, stromelysins). These MMPs are able to degrade the extracellular matrix macromolecules (Van Der Zee et al, 1997), thus causing tissue destruction. It is now generally agreed that IL-1β is the major mediator of tissue destruction in periodontal disease (Page et al, 2000).

Periodontal ligament and gingival fibroblasts challenged with IL-1β in vitro release PGE2 in a dose dependent manner (Richards and Rutherford, 1988) and secrete collagenases and matrix metalloproteinases (Birkedal-Hansen, 1993). IL-1β up-regulates cyclooxygenase-2 (COX-2) mRNA and may increase the stability of COX-2 in vivo (Ristimaki et al, 1994). The increase in tissue COX concentration by IL-1β may, in part, explain the higher levels of the arachadonic acid metabolite PGE2 consistently observed in the GCF of patients with periodontitis.

TNF-α, a trimeric protein with a molecular weight of approximately 17 kDa/monomer (Vilcek and Lee, 1991), is secreted by monocytes and macrophages. TNF-α is a potent immunologic mediator with proinflammatory properties (Birkedal-Hansen, 1993). It also induces the secretion of collagenase by fibroblasts (Dayer, 1985), the resorption of cartilage (Saklatvala, 1986) and bone (Bertolini et al, 1986), and has been implicated in the destruction of periodontal tissue during periodontal disease (Meikle et al, 1986). Lipopolysaccharide (LPS) obtained from periodontal Gram-negative bacteria can initiate the production of TNF-α by peripheral blood monocytes (Lindemann et al, 1988), thus leading to enhanced tissue destruction.

PGE2 is an arachidonic acid metabolite that has potent pro-inflammatory and immunomodulatory effects. There is considerable evidence correlating GCF PGE2 levels with the severity of clinical disease (for review see Offenbacher et al, 1993a) and, more importantly, with bursts of active disease. In fact, PGE2 has been implicated as a key proinflammatory mediator in periodontal disease (Offenbacher et al, 1993b; Lamster, 1997; Heasman et al, 1998; Tsai et al, 1998; Offenbacher et al, 1998; Lamster and Grbic, 2000). Macrophages are believed to be the major source of PGE2 in GCF.

The aim of the present paper is to review the available English literature regarding the GCF and IL1-β, TNF-α and PGE2 profiles in healthy and diseased periodontium.

GINGIVAL CREVICULAR FLUID (GCF)

GCF is an inflammatory exudate of the periodontal tissues. The fluid component is derived primarily from serum, while fluid constituents originate from structural cells in the connective tissue, epithelium and subgingival bacteria (Lamster and Grbic, 1995). GCF amount is indicative only of the degree of gingivitis (Fine and Mandel, 1986), while not necessarily of periodontal inflammation (Shapiro et al, 1979). The immune system is active in the GCF and includes the humoral, cellular and the acute inflammatory responses (Lamster, 1992). Since host response is a critical determinant in periodontal disease pathogenesis, the measure of inflammatory mediator levels in the GCF has been used to evaluate risk for a site to loose attachment and/or alveolar bone, or the risk for an individual to develop periodontal disease (Champagne et al, 2003).

GCF concentration of varying pro-inflammatory cytokines is well documented. Recently, more studies are using total mediator content, rather than concentration, to report their results. The former has the advantage of eliminating the requirement to measure GCF volume, which is typically small (<1 μl) and thus susceptible to disproportionately large errors (Lamster et al, 1988; Adonogianaki et al, 1996). Due to the problem associated with measuring the extremely small quantities of GCF available from healthy sites, the levels of biochemical compounds have been presented by several authors as total amounts per 30-second sample, as an alternative to concentrations (Williams et al, 1989; Offenbacher et al, 1990; Offenbacher et al, 1992).

In order to standardize measurements, if total mediator content is to be used as an outcome variable, the sampling procedure should be standardized by sampling at a pre-determined time frame (usually 30 s). It is important to notice the effect of ‘collection time’. A too short time (<20 s) may result in insufficient volume, and on the other hand, a long time (e.g. 1 minute) may result in an over-saturated paper strip.

The dilemma of concentration versus total amount was pointed out by Tsai et al (1995), who showed that following initial periodontal treatment GCF IL-1β concentration either remained unchanged or increased, while the total amounts decreased. The findings that IL-1β concentrations were negatively correlated with the GCF volumes, while total amounts were positively correlated with GCF volumes suggest that the reduction of GCF volumes as the result of periodontal treatment may be one of the factors responsible for the reduction of cytokine levels. Therefore, it is important to standardize sampling time and techniques.

LEVELS OF IL-1β, TNF-α AND PGE2 IN THE GCF

Healthy Periodontium

In clinically healthy gingival tissues, inflammatory cytokines are present in low quantities, suggesting cytokines are also prominent actors of normal tissue homeostasis (Okada and Murakami, 1998). It is now known, that the release of cytokines is genetically determined, and there is an association between a specific composite genotype of the IL-1β gene cluster and periodontal disease severity (Kornman et al, 1997). This means, that cytokines levels may vary considerably even between healthy individuals.

Engebretson et al (2002) concluded that GCF IL-1β expression is in part a host trait, and not strictly a function of clinical parameters. They speculated that carriage of the periodontitis associated genotype caused a "left shift" of the normal IL-1β expression pattern, meaning that increased IL-1 expression would be greater in each probing depth category. Thus, a postulated genetic mechanism might explain this increased expression of the important inflammatory mediator, IL-1β. It is likely that the nature of the antigen-presenting cell is fundamental in determining the nature of the cytokine profile (Seymour and Gemmell, 2001).

Age also influences the levels of IL-1β. Tsalikis et al (2002) have demonstrated that IL-1β levels observed in the young adults group are lower than those observed in the older age group, which could be related to the less pronounced clinical signs observed during the development of gingivitis in the younger subjects.

TNF-α has also been detected in GCF of healthy periodontal subjects, with a reported amount on filter strip per site ranging from 0.2 to 998.8 fmol with a median value of 3.7 fmol (Rossomando et al, 1990). To the contrary, PGE2 is low or non-detectable in the crevicular fluid of healthy individuals.

Diseased Periodontium

Several authors have demonstrated higher levels of cytokines in inflamed periodontal tissues compared to healthy sites. Charon et al (1982) were the first to demonstrate that GCF from inflamed sites of gingivitis patients had increased IL-1β activity levels. Subsequent studies, Hou et al (1995), Yavuzyilmaz et al (1995) and Ishihara et al (1997), showed increased levels of IL-1 in the GCF with increasing inflammation and probing depth. Also the GCF IL-1β level was shown to increase several folds (7 to 12) during experimental gingivitis in humans (Heasman et al, 1993). Several other studies also pointed toward higher IL-1β levels in patients with periodontitis compared to gingivitis (Figueredo et al, 1999; Faizuddin et al, 2003).

The values of IL-1β obtained in patients with gingivitis range between 20 pg/ml and 132 pg/ml (Faizuddin et al, 2003). This wide range may be attributed to the variation in bacterial plaque accumulation or variation in subsequent inflammation due to plaque. However, another possibility, put forth by Kinane et al (1992), is the inherent variation in the ability to produce IL-1β and that could result in heterogenous responses accounting to intraspecies differences.

When comparing the values obtained in patients with gingivitis to those with periodontitis, a significant overlap exists having nearly similar levels of IL-1β (ranging between 102 pg/ml and 130 pg/ml). This can probably be explained by the conclusions drawn by Shapira et al (1994), who in their study have stated that the inter individual differences in mediator secretion may result from intrinsic differences between different patient groups. Differences in different forms of periodontal disease might be the result of the activity of different combinations of inflammatory mediators, suggesting heterogeneity of periodontal diseases.

It is important to notice, that most studies did not find any correlation between clinical findings and levels of IL-1β (Wilton et al, 1992; Wilton et al, 1993). Likewise, Figueredo et al (1999) in their study failed to find any significant difference in concentrations of GCF IL-1β between deep and shallow pockets of the same patient. They suggested that the concentrations of IL-1β are more a characteristic of an individual patient and less a result of the inflammatory state of the sampled site.

To the contrary, Giannopoulou et al (2003) observed marked differences of IL-1β in different disease category groups, as compared to a healthy group; a 3-fold increase was noticed in the gingivitis patients, a 6-fold increase in the adult periodontitis patients, and an almost 9-fold increase in the early-onset periodontitiv group. Increased levels of IL-1β were also found in GCF from active, as compared to inactive sites, suggesting that this proinflammatory cytokine may serve as possible indicator of disease activity in refractory periodontitis (Lee et al, 1995). These differences in total amounts of cytokines may be useful in distinguishing between different forms of periodontal diseases.

Rossomando et al (1990) detected an increase in TNF-α levels in GCF from periodontal pockets. In addition, transcripts of its gene and its protein were detected at the cellular level in inflamed gingival tissues (Matsuki et al,1992). It was suggested, that TNF-α may be a marker of early inflammatory activity, because of its patternless distribution within the individuals and the lack of correlation with clinical parameters (Rossomando et al, 1990). TNF-α cannot always be retrieved from GCF. It was shown to be present in about 21–50% of examined sites (Rossomando et al, 1990, Yavuzyilmaz et al, 1995).

Yavuzyilmaz et al (1995) studied the GCF profile of TNF-α in patients with severe and rapidly progressive periodontitis and found mean TNF-α levels of 3.20 +/-1.39 pg/ml. Bostrom et al (1998) examined the effect of smoking on GCF TNF-α levels. They showed that the TNF-α content was significantly increased in current smokers as compared to non-smokers (moderate to severe periodontal disease), with median GCF levels of 61.0 pg/ml for current smokers, 51.0 pg/ml for former smokers, and 12.0 pg/ml for non-smokers.

PGE2 is easily detected in the GCF and increases 2- to 3-fold in gingivitis and periodontitis, relative to health. It increases another 5- to 6-fold during periods of active disease progression, as determined by longitudinal attachment loss (Offenbacher et al, 1993a; Offenbacher et al, 1993b). GCF PGE2 levels increase prior to attachment level changes and can be used as a screening test to predict future attachment loss (Offenbacher et al, 1986). Although mean GCF PGE2 level for a patient can be used to assess the patient risk for future attachment loss, with an overall predictive value of 0.92 to 0.95, the use of site’s PGE2 value as a site-specific indicator for adult periodontitis, is more complex (Offenbacher et al, 1993a; Offenbacher et al, 1993b). It was suggested that a PGE2 level of 300 ng/ml GCF reflects an underlying disease activity of 0.5 to 1.0 mm of attachment loss/year (Offenbacher et al, 1993b).

PGE2 is detected in higher levels in inflamed gingival tissue and GCF proportional to the severity of periodontal disease (Goodson et al, 1974; Offenbacher et al, 1983; Offenbacher et al, 1989; Ohm et al, 1984). Offenbacher et al (1989), using experimental periodontitis model in animals, reported that GCF PGE2 and PGF2α levels tended to increase at 3 months, reached a maximum level at 6 months, and returned to baseline values at 12. This was confirmed in a model of experimental gingivitis, where GCF PGE2 levels increased at 4 weeks following the cessation of oral hygiene procedures (Heasman et al, 1993). Other studies have also confirmed that GCF PGE2 levels are elevated in periodontitis compared to gingivitis (Gemmell et al, 1997; Tsai et al, 1998; Preshaw et al, 1999). Recent data suggests that the GCF PGE2 levels are substantially higher in certain high risk patients such as refractory, early-onset periodontitis or diabetic patients (Offenbacher et al, 1994). It appears that the increased local GCF PGE2 response observed in these patients is coincident with an up-regulated monocytic phenotype (MØ+) (Garrison et al, 1988; Shapira et al, 1994; Offenbacher et al, 1994; Salvi et al, 1997). Thus, even low levels of endotoxin challenge within the periodontal pocket seem to induce high levels of PGE2 secretion at these patients. This suggests that the GCF PGE2 level reflects the collective response of the patient's periodontium, not as a collection of sites which function independently, but rather as an organ which reflects the patient's systemic response to local infection.

Preshaw and Heasman (2002) suggested that whatever the patient's phenotype (i.e., disease resistant or disease susceptible), there is a natural tendency for PGE2 levels to gradually increase over time. In their modified model of disease pathogenesis, PGE2 concentrations rise gradually in the periodontal tissues. A threshold (T1) may then be reached at which attachment loss and/or bone loss occur, and clinical signs of disease progression become evident. This would correspond with the pooled GCF PGE2 threshold value of 66.2 ng/ml, proposed, above which patients were significantly more likely to experience attachment loss. After this first threshold is reached, PGE2 levels may continue to rise further, until a second threshold (T2) is attained, at which time a negative feedback suppression of PGE2 production occurs. This may have the effect of rapidly decreasing PGE2 levels to 'baseline' values, thereby stabilizing attachment level and bone height. Individuals probably vary in their values of T1 and T2, which may, in part, explain some of the variations between patients regarding periodontal disease susceptibility. For example, in some individuals T1 may never be reached, as negative feedback mechanisms may occur early (i.e., T1> T2), and thus prevent PGE2 concentrations from increasing sufficiently to cause attachment loss and bone loss.

GCF CYTOKINES AND PERIODONTAL THERAPY

Mechanical treatment of periodontitis, i.e. scaling and root planing, has been shown to lower GCF IL-1β levels (Masada et al, 1990; Reinhardt et al, 1993; Matsuki et al, 1993; Hou et al, 1995; Alexander et al, 1996; Engebretson et al, 2002). Reinhardt et al (1993) demonstrated decreased levels of IL-1α and IL-1β in shallow pockets and moderate pockets that had been treated non-surgically. Surprisingly, they also reported that sites surgically treated by papillary flap debridement continued to show elevated levels of both IL-1α and IL-1β after 6 months.

Engebretson et al (2002) showed that 2 weeks following scaling and root planning the levels of IL-1β in GCF were reduced in all patients. This reduction was more pronounced for patients with more severe periodontal disease. At 24 weeks, IL-1β continued to decrease for patients with less severe disease, while cytokine activity in individuals with more severe disease had rebounded and approached baseline levels. Hou et al (1995) also have shown that phase I periodontal therapy reduces the IL-1β in GCF, and claimed that this relationship may be useful in monitoring periodontal disease activity. Using tetracycline fibre therapy has also been shown to reduce IL-1β in GCF (Lamster et al, 1996).

Reports concerning GCF TNF-α levels following periodontal therapy are limited. Most studies show minimal changes of this cytokine. Engebretson et al (1999) showed that total TNF-α levels were doubled 3 weeks after treatment in patients positive for the periodontitis-associated genotype, while total GCF TNF-α level showed no significant changes in patients negative for the periodontitis-associated genotype.

Non-steroid anti-inflammatory drugs (NSAIDs) block PGE2 synthase (COX). The suppression of PGE2 synthesis with these drugs greatly diminishes attachment and bone loss, and thereby attenuates periodontal disease progression, both in animal and human models (Williams et al, 1989; Offenbacher et al, 1990, Offenbacher et al, 1992; Offenbacher et al, 1993a).

DISCUSSION

Periodontal diseases are chronic inflammatory diseases of the supporting structures of the teeth. They are triggered by periodontopathogens and the clinical outcome is highly influenced by the host local immune response (Kinane et al, 2001). Studies have suggested that the polarization of the local immune response, basically by T helper cells, may determine the stability or progression of the lesion (Mosmann and Coffman, 1989; Seymour and Gemmell, 2001). The polarized immune response may exhibit a Th1 pattern consisting of a predominantly pro-inflammatory cellular response, or a Th2 pattern, with anti-inflammatory characteristics and a predominantly humoral immune response. These distinct responses are mediated by characteristic cytokine patterns and involve the selective attraction of inflammatory cells to the site of response (Mosmann and Coffman, 1989; Jankovic et al, 2001).

IL-1 and TNF play a critical role in stimulating the innate host response and, in this capacity, prepare the host to defend itself against bacteria (Ferrante, 1992; Graves et al, 2000). A hypothesis was proposed that destructive periodontal disease may be due to dysregulation of these inhibitors, rather than an overproduction of IL-I and TNF-α per se (Howells, 1995). Regulation of the effects of these cytokines has been suggested for therapeutics used in tissue-destructive inflammatory diseases such as rheumatoid arthritis (Maini and Feldmann, 1996). This approach has also been used for experimental periodontitis (Assuma et al, 1998; Graves et al, 1998; Delima et al, 2001).

Histologic studies, using soluble receptors as cytokine antagonists specific for IL-1 and TNF-α, have demonstrated an important role for IL-1 and TNF-α in destructive periodontitis (Graves et al, 1998; Delima et al, 2001). These findings showed that the cytokine antagonists, or blockers, inhibited: (a) the progression of the inflammatory front toward the osseous crest; (b) the recruitment of osteoclastic cells; (c) the loss of bone and connective tissue attachment in association with ligature-induced disease. Although associations have been established between levels of cytokines and presence of periodontal disease in general, large inter- and intra-individual variations suggest that these parameters are influenced by a multitude of other factors which, so far, have been poorly quantified. Several patient subgroups appear to have abnormally high monocytic responses with regard to the level of IL-1β, PGE2, or TNF-α secreted, as compared to healthy controls or other periodontitis patients. In these high-risk patient subcategories the monocytic dose response curve has “shifted to the left” so that low dosages of LPS challenge result in 3- to 10-fold excess secretion of inflammatory mediators (a hyper-responsive monocytic trait) (Payne et al, 1993; Offenbacher et al, 1994; Shapira et al, 1994; Salvi et al, 1997).

It is clear from the aforementioned studies, that GCF level of these markers is not influenced only by the disease state of the periodontium. Variations of the IL-1 gene cluster have been proposed as genetic modifiers in a number of inflammatory diseases (Engebretson, 1999). Polymorphisms in the IL-1 gene cluster have been associated with an increased risk of developing certain diseases, including periodontal disease. A specific composite genotype of IL-1A and IL-1B polymorphisms, consisting of allele 2 of both IL-1A +4845 and IL-1B +3954 (formerly +3953) has been associated with an increased risk of severe adult periodontitis, in a European population (Kornman et al, 1997).

Armitage et al (2000) examined the prevalence of a periodontitis-associated IL-1 composite genotype in individuals of Chinese heritage. They concluded that the prevalences of both IL-1A and IL-1B polymorphisms are dramatically lower in Chinese than those reported for Europeans, which raises the question of the usefulness of the allele 2 composite genotype as a method for determining the susceptibility to adult periodontitis of Chinese patients or other populations. In another study, Engebretson et al (2002) concluded that GCF IL-1β expression is in part a host trait, and not strictly a function of clinical parameters. They speculated that carriage of the periodontitis associated genotype caused a "left shift" of the normal IL-1β expression pattern, meaning that increased IL-1β expression would be greater in each probing depth category. Thus, a postulated genetic mechanism might explain the increased expression of this important inflammatory mediator, IL-1β. Kinane et al (1999) analyzed the genetic polymorphisms at the interleukin-10 and tumour necrosis factor loci in early-onset periodontitis, but they could not demonstrate any link between the gene polymorphism and early-onset periodontitis.

Thus, genotyping must also be performed to rule out genetic bias. In addition to genetic characteristics and gene polymorphism, sampling technique, which permits inclusion of both diseased and non-diseased periodontal sites, may contribute to this variability.

CONCLUSIONS

GCF cytokine profiles vary with respect to when sampling was performed and the frequency of bone-resorptive active events. In this context, it is suggested that some markers might be associated with the early events of disease initiation, while other markers might be associated with chronic inflammation, during which events of tissue degradation occur. Monitoring of PGE2, IL-1β and TNF-α levels in GCF may not only be a useful tool for monitoring disease activity, but may also help monitor the effectiveness of different treatment modalities. Therefore, standard levels of normal GCF markers should be established in the different populations.

REFERENCES

  1. Adonogianaki E, Mooney J, Kinane DF. Detection of stable and active periodontitis sites by clinical assessment and gingival crevicular acute-phase protein levels. J Periodontal Res 1996;31:135-143.
  2. Alexander DC, Martin JC, King PJ, Powell JR, Caves J, Cohen ME. Interleukin-1β, prostaglandin E2, and immunoglobulin G subclasses in gingival crevicular fluid in patients undergoing periodontal therapy. J Periodontol 1996;67:755-762.
  3. Armitage GC, Wu Y, Wang HY, Sorrell J, di Giovine FS, Duff GW. Low prevalence of a periodontitis-associated interleukin-1 composite genotype in individuals of Chinese heritage. J Periodontol 2000;71:164-71.   
  4. Assuma R, Oates T, Cochran D, Amar S, Graves D. IL-1 and TNF antagonists inhibit the inflammatory response and bone loss in experimental periodontitis. J Immunol 1998;160:403-409.
  5. Balkwill FR, Burke F. The cytokine network. Immunol Today 1989;9:299-304.
  6. Bendtzen K. Clinical significance of cytokines natural and therapeutic regulation. Seminars Clin Immunol 1991;3:5-13.
  7. Bendtzen K. Immune hormones (cytokines); Pathogenic role in autoimmune rheumatic and endocrine diseases. Autoimmunity 1989;2:177-189.
  8. Bertolini DR, Nedwin GE, Bringmani TS, Smith DD, Mundy GR. Stimulation of bone resorption and inhibition of bone formation in vitro by human tumour necrosis factors. Nature 1986;319:516-518.
  9. Bickel, M. The role of IL-8 in inflammation and mechanisms of regulation. J Periodontol 1993;64:456-460.
  10. Birkedal-Hansen, H. Role of cytokines and inflammatory mediators in tissue destruction. J Periodontal Res;1993;28:500-510.
  11. Birkedal-Hansen, H. Role of matrix metalloproteinases in human periodontal diseases. J Periodontol 1993;64:474-484.
  12. Bostrom L, Linder LE, Bergstrom J. Smoking and cervicular fluid levels of IL-6 and TNF-alpha in periodontal disease. J Clin Periodontol 1999;26:352-357. 
  13. Champagne CM, Buchanan W, Reddy MS, Preisser JS, Beck JD. Potential for gingival crevice fluid measures as predictors of risk for periodontal diseases. Periodontol 2000 2003;31:167-80.
  14. Charon J, Luger T, Mergenhagen S, Oppenheim J. Increased thymocyte activating factor in human gingival fluid during inflammation. Infect Immun 1982;38:1190-1195.
  15. Dayer JM, Beutler B, Cerami A. Cachectin/tumor necrosis factor stimulates collagenase and prostaglandin E2 production by human synovial cells and dermal fibroblasts. J Exp Med 1985;162:2163-2168.
  16. Delima A, Oates T, Assuma R, Schwartz Z, Cochran D, Amar S, et al. Soluble antagonists to interleukin-1 (IL-1) and tumour necrosis factor (TNF) inhibits loss of tissue attachment in experimental periodontitis. J Clin Periodontol 2001;28:233-240.
  17. Dinarello C. Proinflammatory cytokines. Chest 2000;188:503-508.
  18. Dufour A, Baran C, Langkamp HL, Piesco NP, Agarwal S. Regulation of differentiation of gingival fibroblasts and periodontal ligament cells by rhIL-1β and rhTNF-α. J Periodont Res 1993;28:566-568.
  19. Engebretson SP, Lamster IB, Herrera-Abreu M, Celenti RS, Timms JM, Chaudhary, AG, et al. The influence of interleukin gene polymorphism on expression of interleukin-1beta and tumour necrosis factor-alpha in periodontal tissue and gingival crevicular fluid. J Periodontol 1999;70:567-573.
  20. Engebretson SP, Grbic JT, Singer R, Lamster IB. GCF IL-1beta profiles in periodontal disease. J Clin Periodontol 2002;29:48-53.
  21. Faizuddin M, Bharathi SH, Rohini NV. Estimation of interleukin-1beta levels in the gingival crevicular fluid in health and in inflammatory periodontal disease. J Periodontal Res 2003;38:111-114.
  22. Ferrante A. Activation of neutrophils by interleukins-1 and -2 and tumour necrosis factors. Immunol Ser 1992;57:417-436.
  23. Figueredo CMS, Ribeiro MSM, Fischer RG, Gustafsson A. Increased interleukin-1 beta concentration in gingival crevicular fluid as a character of periodontitis. J Periodontol 1999;70:1457–1463.
  24. Fine DH, Mandel ID. Indicators of periodontal disease activity: an evaluation. J Clin Periodontol 1986;13:533-546.
  25. Garrison SW, Holt SC, Nichols FC. Lipopolysaccharide-stimulated PGE2 release from human monocytes. Comparison of lipopolysaccharides prepared from suspected periodontal pathogens. J Periodontol 1988;59:684–687.
  26. Geivelis M, Turner DW, Pederson ED, Lamberts BL. Measurements of interleukin-6 in gingival crevicular fluid from adults with destructive periodontal disease. J Periodontol 1993;64:980-983.
  27. Gemmell E, Seymour GJ. Modulation of immune responses to periodontal bacteria. Curr Opin Periodontol 1994;28-38.
  28. Gemmell E, Marshall RI, Seymour GJ. Cytokines and prostaglandins in immune homeostasis and tissue destruction in periodontal disease. Periodontol 2000 1997;14;112-143.
  29. Giannopoulou C, Kamma JJ, and Mombelli A. Effect of inflammation, smoking and stress on gingival crevicular fluid cytokine level. J Clin Periodontol 2003;30:145-153.
  30. Goodson JM, Dewhirst FE, Brunetti A. Prostaglandin E levels and human periodontal disease. Prostaglandins 1974;6:81-85.
  31. Graves D, Chen C, Douville C, Jiang Y. Interleukin-1 receptor signalling rather than that of tumour necrosis factor is critical in protecting the host from the severe consequences of a polymicrobe anaerobic infection. Infect Immun 2000;8:4746-4751.
  32. Graves D, Delima A, Assuma R, Amar S, Oates T, Cochran D. Interleukin-1 and tumour necrosis factor antagonists inhibit the progression of inflammatory cell infiltration toward alveolar bone in experimental periodontitis. J Periodontol 1998;69:1419-1425.
  33. Grieve W, Johnson G, Moore RN, Reinhardt RA, DuBois LM. PGE and IL-1β levels in gingival crevicular fluid during human orthodontic tooth movement. Am J Orthod Dentofacial Orthop 1994;105, 369-374.
  34. Heasman PA, Collins JG, Offenbacher S. Changes in crevicular fluid levels of interleukin-1 beta, leukotriene B4, prostaglandin E2, thromboxane B2 and tumour necrosis factor alpha in experimental gingivitis in humans. J Periodontal Res 1993;28:241-247.
  35. Heasman PA, Lauffart BL, Preshaw PM. Crevicular fluid prostaglandin E2 levels in periodontitis-resistant and periodontitis-susceptible adults. J Clin Periodontol 1998;25:1003-1007.
  36. Heath JK, Atkinson SJ, Hembry RM, Reynolds JJ, Meikle MC. Bacterial antigens induce collagenase and prostaglandin E2 synthesis in human gingival fibroblasts through a primary effect on circulating mononuclear cells. Infect Immun 1987;55:2148-2154.
  37. Hou LT, Liu CM, Rossomando EF. Crevicular interleukin-1 beta in moderate and severe periodontitis patients and the effect of phase I periodontal treatment. J Clin Periodontol 1995;22:162-167.
  38. Howells GL. Cytokine networks in destructive periodontal disease. Oral Dis 1995;1:266-70.
  39. Ishihara Y, Nishihara T, Kuroyanagi T, Shirozu N, Yamagishi E, Ohguchi M, et al. Gingival crevicular interleukin-1 and interleukin-1 receptor antagonist levels in periodontally healthy and diseased sites. J Periodontal Res 1997;32:524-529.
  40. Jankovic D, Liu Z, Gause WC. Th1 and Th2-cell commitment during infectious disease:asymmetry in divergent pathways. Trends Immunol 2001;22:450-457.
  41. Kinane DF, Winstanley FP, Adonogianaki E, Moughal NA. Bioassay of interleukin-1 (IL-1) in human gingival crevicular fluid during experimental gingivitis. Arch Oral Biol 1992;37:153-156.
  42. Kinane DF, Hodge P, Eskdale J, Ellis R, Gallagher G. Analysis of genetic polymorphisms at the interleukin-10 and tumour necrosis factor loci in early-onset periodontitis. J Periodontal Res 1999;34:379-86.
  43. Kinane DF, Lappin DF. Clinical pathological and immunological aspects of periodontal disease. Acta Odontol Scand 2001;59:154-160.
  44. Kornman KS, Crane A, Wang HY, di Giovine FS, Newman MG, Pirk FW, et al. The interleukin-1 genotype as a severity factor in adult periodontal disease. J Clin Periodontol 1997;24:72-77.
  45. Lamster I, Grbic J. Diagnosis of periodontal disease based on analysis of the host response. Periodontolgy 2000 1995;7:83-99.
  46. Lamster IB, Pullman JR, Celenti RS, Grbic JT. The effect of tetracycline fibre therapy on beta-glucuronidase and interleukin-1 beta in crevicular fluid J Clin Periodontol 1996;23:816-822.
  47. Lamster IB. Evaluation of components of gingival crevicular fluid as diagnostic tests. Ann Periodontol 1997;2:123-137.
  48. Lamster IB. The host response in gingival crevicular fluid: potential applications in periodontitis. Clinical trials. J Periodontol 1992;63:1117-1123.
  49. Lamster IB, Oshrain RL, Fiorello LA, Celenti RS, Gordon JM. A comparison of 4 methods of data presentation for lysosomal enzyme activity in gingival crevicular fluid. J Clin Periodontol 1988;15:347-352.
  50. Lee HJ, Kang IK, Chung CP, Choi SM. The subgingival microflora and gingival crevicular fluid cytokines in refractory periodontitis. J Clin Periodontol 1995;22;885-890.
  51. Lindemann RA, Economou JS, Rothermel H. Production of interleukin-1 and tumour necrosis factor by human peripheral monocytes activated by periodontal bacteria and extracted lipopolysaccharides. J Dent Res 1988;68:1131-1135.
  52. Lowney JJ, Norton LA, Shafer DM, Rossomando EF. Orthodontic force increase tumour necrosis factor α in the human gingival sulcus. Am J Orthod Dentofacial Orthop 1995;108:519-524.
  53. Maini RN, Feldmann M. Cytokine therapy in rheumatoid arthritis. Lancet 1996;348:824-825.
  54. Manolagas SC. Role of cytokines in bone resorption. Bone 1995;17;63S-67S.
  55. Masada MP, Persson R, Kenney JS, Lee SW, Page RC, Allison AC. Measurement of interleukin-1a and IL-1β in gingival crevicular fluid: Implications for the pathogenesis of periodontal disease. J Periodontal Res 1990;25:156-163.
  56. Matsuki Y, Yamamoto T, Hara K. Detection of inflammatory cytokine messenger RNA (mRNA)-expressing cells in human inflamed gingiva by combined in situ hybridization and immunohistochemistry. Immunology 1992;76:42-47.
  57. Matsuki Y, Yamamoto T, Hara K. Localization of interleukin-1 (IL-1) mRNA-expressing macrophages in human inflamed gingiva and IL-1 activity in gingival crevicular fluid. J Periodontal Res 1993;28:35-42.
  58. Meikle MC, Heath JK, Reynolds JJ. Advances in understanding cell interactions in tissue resorption. Relevance to the pathogenesis of periodontal diseases and a new hypothesis. J Oral Pathol 1986;15:239-250.
  59. Mosmann TR, Coffman RL. Th1 and Th2 cells: different patterns of lymphokine secretion lead to different functional properties. Annu Rev Immunol 1989;7:145-173.
  60. Nguyen I, Dewhirst FE, Hauschka PV, Stashenko P. Interleukin-1α stimulates bone resorption and inhibits bone formation in vivo. Lymphokine Cytokine Res 1991;10:15-21.
  61. Offenbacher S, Collins JG, Arnold RR. New clinical diagnostic strategies based on pathogenesis of disease. J Periodontal Res 1993a;28:523-535.
  62. Offenbacher S, Collins JG, Heasman PA. Diagnostic potential of host response mediators. Adv Dent Res 1993b;7:175-181.
  63. Offenbacher S, Collins JG, Yalda B, Haradon G. Role of prostaglandins in high risk periodontitis patients. In: Genco RJ, Hamada S, Lehner T, Mergenhagen S (eds). Molecular Pathogenesis of Periodontal Disease. Washington, DC: ASM Press 1994:203-214.
  64. Offenbacher S, Farr DH, Goodson JM. Measurement of prostaglandin E in crevicular fluid. J Clin Periodontol 1981;8:359-367.
  65. Offenbacher S, Jared HL, O'Reilly PG, Wells, SR, Salvi GE, Lawrence HP, et al. Potential pathogenic mechanisms of periodontitis associated pregnancy complications. Ann Periodontol 1998;3:233-250.
  66. Offenbacher S, Odle BM, Braswell LD, Johnson, HG, Hall, CM, McClure, et al. Changes in cyclooxygenase metabolites in experimental periodontitis in Macaca mulatta. J Periodont Res 1989;24:63-74.
  67. Offenbacher S, Odle BM, Green MD, Mayambala, CS, Smith, MA, Fritz ME, et al. Inhibition of human periodontal prostaglandin E2 synthesis with selected agents. Agents Actions 1990;29:232-238.
  68. Offenbacher S, Odle BM, Van Dyke TE. The use of crevicular fluid prostaglandin E2 levels as a predictor of periodontal attachment loss. J Periodontal Res 1986;21:101-112.
  69. Offenbacher S, Williams RC, Jeffcoat MK, Howell, TH, Odle BM, Smith MA, et al. Effects of NSAIDs on beagle crevicular cyclooxygenase metabolites and periodontal bone loss. J Periodont Res 1992;27:207-213.
  70. Offenbacher S, Heasman PA, Collins JG. Modulation of host PGE secretion as a determinant of periodontal disease expression. J Periodontol 1993 64, 432-444.
  71. Ohm K, Albers HK, Lisboa BP. Measurement of eight prostaglandins in human gingival and periodontal disease using high pressure liquid chromatography and radioimmunoassay. J Periodontal Res 1984;19:501-511.
  72. Okada H, Murakami S. Cytokine expression in periodontal health and disease. Crit Rev Oral Biol Med 1998;9:248-266.
  73. Page RC, Offenbacher S, Schroeder HE, Seymour GJ, Kornman KS. Advances in the pathogenesis of periodontitis: summary of developments, clinical implication and future directions. Periodontology 2000 1977;14:216-248.
  74. Page RC. Milestones in periodontal research and the remaining critical issues. J Periodontal Res 1999;34:331-339.
  75. Payne JB, Reinhardt RA, Masada MP, DuBois LM, Allison AC. Gingival crevicular fluid IL-8: Correlation with local IL-1 beta levels and patient estrogen status. J Periodont Res 1993;28:451-453
  76. Preshaw PM, Lauffart B, Zak E, Jeffcoat MK, Barton I, Heasman PA. Progression and treatment of chronic adult periodontitis. J Periodontol 1999:70:1209-1220.
  77. Preshaw PM, Heasman PA. Prostaglandin E2 concentrations in gingival crevicular fluid: observations in untreated chronic periodontitis, J Clin Periodontol 2002;29:15-20.
  78. Reinhardt RA, Masada MP, Johnson GK, DuBois LM, Seymour GJ, Allison AC, et al. IL-1 in gingival crevicular fluid following closed root planing and papillary flap debridement. J Clin Periodontol 1993;20:514–519.
  79. Richards D, Rutherford RB. The effects of interleukin 1 on collagenolytic activity and prostaglandin-E secretion by human periodontal-ligament and gingival fibroblast. Arch Oral Biol 1988;33:237-243.
  80. Ristimaki A, Garfinkel S, Wessendorf J, Maciag T, Hla T. Induction of cyclooxygenase-2 by interleukin-1 alpha. Evidence for post- transcriptional regulation. J Biol Chem 1994;269:11769-11775.
  81. Rossomando EF, Kennedy JE, Hadjimichael J. Tumour necrosis factor alpha in gingival crevicular fluid as a possible indicator of periodontal disease in humans. Arch Oral Biol 1990;35:431-434.
  82. Saklatvala J. Tumour necrosis factor stimulates resorption and inhibits synthesis of proteoglycan in cartilage. Nature 1986;322:547-549.
  83. Salvi GE, Collins JG, Yalda B, Arnold RR, Lang NP, Offenbacher S. Monocytic TNFa secretion patterns in IDDM patients with periodontal diseases. J Clin Periodontol 1997;24:8-16.
  84. Seymour GJ. Importance of the host response in the periodontium. J Clin Periodontol 1991;18:421-426.
  85. Seymour GJ; Gemmell E. Cytokines in periodontal disease: where to from here? Acta Odontol Scand 2001;59:167-173. 
  86. Shapira L, Soskolne WA, Sela MN, Offenbacher S, Barak V. The secretion of PGE2, IL-1 beta, IL-6, and TNF alpha by adherent mononuclear cells from early onset periodontitis patients. J Periodontol 1994;65:139-146.
  87. Shapiro L, Goldmann H, Bloom A. Sulcular exudate flow in gingival inflammation. J Clin Periodontol 1979;50:301-304.
  88. Stashenko P, Fujiyoshi P, Obernesser MS, Prostak L, Haffajee AD, Socransky SS. Levels of interleukin 1 beta in tissue from sites of active periodontal disease. J Clin Periodontol 1991;18:548-554.
  89. Tatakis DN. Interleukin-1 bone metabolism: A review. J Periodontol 1993;64:416-431.
  90. Tsai CC, Ho YP, Chen CC. Levels of Interleukin-1 and Interleukin-8 in Gingival Crevicular Fluids in Adult Periodontitis. J Periodontal 1995;10:852-859.
  91. Tsai CC, Hong YC, Chen CC, Wu YM. Measurement of prostaglandin E2 and leukotriene B4 in the gingival crevicular fluid. J Dent 1998;26:97-103.
  92. Tsalikis L, Parapanisiou E, Bata-Kyrkou A, Polymenides Z, Konstantinidis A. Crevicular fluid levels of interleukin-1alpha and interleukin-1beta during experimental gingivitis in young and old adults. J Int Acad Periodontol 2002;4:5-11.
  93. Van Der Zee E, Everts V, Beertsen W. Cytokines modulate routes of collagen breakdown. Review with special emphasis on mechanisms of collagen degradation in the periodontium and the burst hypothesis of periodontal disease progression. J Clin Periodontol 1997;24:297-305.
  94. Vilcek J, Lee TH. Tumour necrosis factor. J Biol Chem 1991;266:7313-7316.
  95. Williams RC, Jeffcoat MK, Howell TH, Rolla A, Stubbs D, Teoh KW, et al. Altering the progression of human alveolar bone loss with the non-steroidal anti-inflammatory drug flurbiprofen. J Periodontol 1989;60:485-490.
  96. Wilton JM, Bampton JL, Griffiths GS, Curtis MA, Life JS, Johnson NW, et al. Interleukin-1 beta (IL-1 beta) levels in gingival crevicular fluid from adults with previous evidence of destructive periodontitis. A cross-sectional study. J Clin Periodontol 1992;19:53-57.
  97. Wilton JM, Bampton JL, Hurst TJ, Caves J, Powell JR. Interleukin-1 beta and IgG subclass concentrations in gingival crevicular fluid from patients with adult periodontitis. Arch Oral Biol 1993;38:55-60.
  98. Yamamoto M, Fujihashi K, Hiroi T, McGhee JR,VanDike TE,Kiyono H. Molecular and cellular mechanisms for periodontal diseases:the role of Th1 and Th2 type cytokines in induction of mucosal inflammation. J Periodontal Res 1997;32:115-119.
  99. Yavuzyilmaz E, Yamalik N, Bulut S, Ozen S, Ersoy F, Saatci U. The gingival crevicular fluid, interleukin-1 beta and tumour necrosis factor-alpha levels in patients with rapidly progressive periodontitis. Aust Dent J 1995;40:46-49.

Authors:

aMahmoud N. Younis
Periodontal Unit, Department of Oral and Maxillofacial Surgery, Rambam Medical Center, Haifa, Israel.

bEli E. Machtei
Faculty of Medicine, Technion-I.I.T, Haifa, Israel.

cMicha Peled
Department of Oral and Maxillofacial Surgery, Rambam Medical Center, Haifa, Israel.

Dr. Mahmoud Younis DMD, Periodontal Unit, Department of Oral and Maxillofacial Surgery, Rambam Medical Center , P.O. Box 9602, Haifa 31096, Israel. E-mail: younisma@hotmail.com