Interleukin-34 levels in gingival crevicular fluid and plasma in periodontal health and disease with and without type-2 diabetes mellitus

Effects of IL-34 and anti-IL-34 neutralizing mAb on alveolar bone loss in a ligature-induced model of periodontitis

Macrophage colony-stimulating factor (M-CSF) and interleukin-34 (IL-34) are ligands for the colony-stimulating factor-1  receptor (CSF-1r) expressed on the surface of monocyte/macrophage lineage cells. The importance of coordinated signaling between M-CSF/receptor activator of the nuclear factor kappa-Β ligand (RANKL) in physiological and pathological bone remodeling and alveolar bone loss in response to oral bacterial colonization is well established. However, our knowledge about the IL-34/RANKL signaling in periodontal bone loss remains limited. Recently published cohort studies have demonstrated that the expression patterns of IL-34 are dramatically elevated in gingival crevicular fluid collected from patients with periodontitis. Therefore, the present study aims to evaluate the effects of IL-34 on osteoclastogenesis in vitro and in experimental ligature-mediated model of periodontitis using male mice. Our initial in vitro study demonstrated increased RANKL-induced osteoclastogenesis of IL-34-primed osteoclast precursors (OCPs) compared to M-CSF-primed OCPs. Using an experimental model of ligature-mediated periodontitis, we further demonstrated elevated expression of IL-34 in periodontal lesions. In contrast, M-CSF levels were dramatically reduced in these periodontal lesions. Furthermore, local injections of mouse recombinant IL-34 protein significantly elevated cathepsin K activity, increased the number of tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts and promoted alveolar bone loss in periodontitis lesions. In contrast, anti-IL-34 neutralizing monoclonal antibody significantly reduced the level of alveolar bone loss and the number of TRAP-positive osteoclasts in periodontitis lesions. No beneficial effects of locally injected anti-M-CSF neutralizing antibody were observed in periodontal lesions. This study illustrates the role of IL-34 in promoting alveolar bone loss in periodontal lesions and proposes the potential of anti-IL34 monoclonal antibody (mAb)-based therapeutic regimens to suppress alveolar bone loss in periodontitis lesions.

Elevated circulating levels of IL-34 are strongly associated with osteoporosis

In this cross-sectional study, we observed a strong, age-independent association of circulating interleukin-34 (IL-34) levels with osteoporosis.

PURPOSE

The reported capacity of IL-34 to induce and enhance osteoclastogenesis suggests its potential involvement in the pathogenesis of osteoporosis. Our study aimed to evaluate whether there is an association between IL-34 expression and osteoporosis.

METHODS

We enrolled 30 women with osteoporosis and 230 age-matched non-osteoporotic women as a control group. Osteoporosis diagnosis was based on dual-energy X-ray absorptiometry (DXA) of the lumbar spine and femoral neck. Body composition parameters were assessed by the bioimpedance method. Plasma IL-34 levels were measured by ELISA.

RESULTS

In comparison with the control group, the mean plasma IL-34 levels were significantly higher in osteoporotic women (164.61 ± 36.40 pg/ml vs. 665.43 ± 253.67 pg/ml, p = 0.0002), whereas basal metabolic rate (BMR) was significantly lower (1422.03 ± 6.80 kcal vs. 1339.39 ± 17.52 kcal, p = 0.00007). Both variables remained statistically significant after adjustment for age (p < 0.001). We did not observe correlations between plasma IL-34 levels and body composition parameters in osteoporotic and control groups. Multiple logistic regression analysis with osteoporosis status as a dependent variable clearly showed that age, BMR and IL-34 levels were independently and significantly associated with osteoporosis. The calculated odds ratios (OR) were 1.66 (95% CI = 1.16-2.38) for IL-34 levels and 0.22 (95% CI = 0.07-0.65) for BMR.

CONCLUSION

The significant (fourfold) elevation of IL-34 plasma levels in osteoporosis patients suggests that circulating IL-34 could be used as a biomarker for osteoporosis.

Interleukin 34 in Disease Progressions: A Comprehensive Review

IL-34, a cytokine, discovered a decade before and is known to be a colony stimulating factor CSF-1 receptor (CSF-1R) ligand. Along with CSF-1R, it also interacts with syndecan-1 receptors and protein-tyrosine phosphatase (PTP-ζ). Hence, IL-34 takes part in a number of biological activities owing to its involvement in different signaling pathways. This review was done to analyze the recent studies on the functions of IL-34 in progression of diseases. The role of IL-34 under the physiological and pathological settings is studied by reviewing current data. In the last ten years, studies suggested that the IL-34 was involved in the regulation of morbid states such as inflammatory diseases, infections, transplant rejection, autoimmune diseases, neurologic diseases, and cancer. In general, the involvement of IL-34 is observed in many serious health ailments like metabolic diseases, heart diseases, infections and even cancer. As such, IL-34 can be regarded as a therapeutic target, potential biomarker or as a therapeutic tool, which ought to be assessed in future research activities.

Expression of inflammatory mediators in periodontitis and T2D patients: a systematic review and meta-analysis

The high concentration of glucose in the blood in Type 2 diabetes (T2D) may be related to either insulin resistance or insulin deficiency. Moreover, the literature points to periodontitis as the main oral disease caused by glycemia imbalance. The quantification of inflammatory markers in blood or saliva samples of T2D patients may represent a valuable tool in revealing how well an individual's immune system can respond to injuries and periodontal treatment. In addition, an evaluation of the cytokine expression is extremely relevant to help understand the connection between periodontitis and T2D. This systematic review and meta-analysis aimed to evaluate the expression of inflammatory markers in T2D patients with periodontitis, compared with non-diabetic patients with periodontitis. A total of 3,894 studies were retrieved after a systematic literature search, 15 of which were included in the systematic review, and 4 of these 15, in the meta-analysis. The results did not indicate any statistical difference between the groups regarding TNF-α and IL-6 markers. T2D patients with periodontitis had increased levels of IL-10, compared with non-diabetic individuals with periodontitis (p = 0.003). On the other hand, the IL-4 concentration in non-diabetic individuals with periodontitis was high, compared with the T2D group (p< 0.001). Several studies did not include quantitative results and were excluded from the meta-analysis. The high IL-10 expression and low IL-4 expression in the T2D group suggest an association between the level of these markers and the impairment of the immune response in T2D patients with periodontitis.

Interleukin-34 Permits Porphyromonas gingivalis Survival and NF-κB p65 Inhibition in Macrophages

Interleukin-34 (IL-34) is a cytokine that supports the viability and differentiation of macrophages. An important cytokine for the development of epidermal immunity, IL-34 is present and plays a role in the immunity of the oral environment. IL-34 has been linked to inflammatory periodontal diseases, which involve innate phagocytes, including macrophages. Whether IL-34 can alter the ability of macrophages to effectively interact with oral microbes is currently unclear. Using macrophages derived from human blood monocytes with either the canonical cytokine colony-stimulating factor (CSF)1 or IL-34, we compared the ability of the macrophages to phagocytose, kill, and respond through the production of cytokines to the periodontal keystone pathogen Porphyromonas gingivalis. While macrophages derived from both cytokines were able to engulf the bacterium equally, IL-34 derived macrophages were much less capable of killing internalized P. gingivalis. Of the macrophage cell surface receptors known to interact with P. gingivalis, DC-SIGN was found to have the largest variation between IL-34 and CSF1-derived macrophages. We also found that upon interaction with P. gingivalis, IL-34 derived macrophages produced significantly less of the neutrophil chemotactic factor IL-8 than macrophages derived in the presence of CSF1. Mechanistically, we identified that levels of IL-8 corresponded with P. gingivalis survival and dephosphorylation of the major transcription factor NF-κB p65. Overall, we found that macrophages differentiated in the presence of IL-34, a dominant cytokine in the oral gingiva, have a reduced ability to kill the keystone pathogen P. gingivalis and may be susceptible to specific bacteria-mediated cytokine modification. This article is protected by copyright. All rights reserved.

Gingival crevicular fluid CSF-1 and IL-34 levels in patients with stage III grade C periodontitis and uncontrolled type 2 diabetes mellitus

PURPOSE

Periodontal diseases are inflammatory conditions that alter the host's response to microbial pathogens. Type 2 diabetes mellitus (T2DM) is a complex disease that affects the incidence and severity of periodontal diseases. This study investigated the gingival crevicular fluid (GCF) levels of colony-stimulating factor-1 (CSF-1) and interleukin-34 (IL-34) in patients with stage III grade C periodontitis (SIII-GC-P) and stage III grade C periodontitis with uncontrolled type 2 diabetes (SIII-GC-PD).

METHODS

In total, 72 individuals, including 24 periodontally healthy (PH), 24 SIII-GC-P, and 24 SIII-GC-PD patients, were recruited for this study. Periodontitis patients (stage III) had interdental attachment loss (AL) of 5 mm or more, probing depth (PD) of 6 mm or more, radiographic bone loss advancing to the middle or apical part of the root, and tooth loss (<5) due to periodontal disease. Radiographic bone loss in the teeth was also evaluated; grade C periodontitis was defined as a ratio of the percentage of root bone loss to age greater than 1.0. The plaque index (PI), gingival index (GI), presence of bleeding on probing (BOP), PD, and clinical AL were used for clinical periodontal assessments. GCF samples were obtained and analyzed using an enzyme-linked immunosorbent assay.

RESULTS

All clinical parameters-PD, AL, GI, BOP, and PI-were significantly higher in the SIII-GC-PD group than in the PH and SIII-GC-P groups for both the full mouth and each sampling site (P<0.05). The total IL-34 and CSF-1 levels were significantly higher in the SIII-GC-PD group than in the PH and SIII-GC-P groups (P<0.05), and there were significant differences between the periodontitis groups (P<0.05).

CONCLUSIONS

These findings suggest that IL-34 and CSF-1 expression increases in patients with SIII-GC-PD. CSF-1 was associated with the inflammatory status of periodontal tissues and T2DM, while IL-34 was associated only with T2DM.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT04891627.

Emerging roles of Interleukin-34 together with receptor activator of nuclear factor-kB ligand and osteoprotegerin levels in periodontal disease

OBJECTIVE

The dependence between gingival crevicular fluid (GCF) of Interleukin-34 (IL-34) level and Receptor activator of nuclear factor -kB ligand/ osteoprotegerin (RANKL/OPG) ratio in the severity of periodontitis might reveal an unknown pathway of diseases with bone destruction. There is no study about the evaluation of IL-34 levels together with GCF RANKL and OPG levels in periodontitis patients before and after non-surgical periodontal treatment (NSPT). The objectives of this research were to investigate changes in the levels and relative ratios of IL-34, OPG, and RANKL in the GCF of patients with periodontitis before and after NSPT.

MATERIALS AND METHODS

20 healthy participants (CTRL), 20 patients with stage 3-grade B periodontitis and 20 with stage 3-grade C periodontitis were recruited. GCF and clinical periodontal recordings were investigated at the baseline and 6 weeks after NSPT. Enzyme-linked immunosorbent assay (ELISA) were used for quantifying of GCF IL-34, RANKL and OPG levels and their relative ratios were calculated.

RESULTS

Greater values for GCF IL-34 and RANKL levels were found in the both of periodontitis groups than in CTRL group at baseline, whereas GCF OPG levels were statistically lower at baseline (P < 0.05). GCF IL-34 and RANKL levels decreased in the 6th week after NSPT in the both periodontitis groups, while the concentration OPG levels statistically increased (P < 0.05). Significantly positive correlations among the IL-34 with RANKL, sampled-site clinical attachment level (CAL), and gingival index (GI), whereas negative correlation with OPG were reported (P < 0.05).

CONCLUSIONS

GCF IL-34 levels was high in patients with periodontitis and decreased after NSPT and its levels showed positive correlations with RANKL/OPG ratio levels CAL and GI. Determining of IL-34 levels together with RANKL/OPG ratio in GCF may therefore be valuable in detecting high risk individuals with periodontitis patients.

IL-34 and CSF-1, deciphering similarities and differences at steady state and in diseases

Although IL-34 and CSF-1 share actions as key mediators of monocytes/macrophages survival and differentiation, they also display differences that should be identified to better define their respective roles in health and diseases. IL-34 displays low sequence homology with CSF-1 but has a similar general structure and they both bind to a common receptor CSF-1R, although binding and subsequent intracellular signaling shows differences. CSF-1R expression has been until now mainly described at a steady state in monocytes/macrophages and myeloid dendritic cells, as well as in some cancers. IL-34 has also 2 other receptors, protein-tyrosine phosphatase zeta (PTPζ) and CD138 (Syndecan-1), expressed in some epithelium, cells of the central nervous system (CNS), as well as in numerous cancers. While most, if not all, of CSF-1 actions are mediated through monocyte/macrophages, IL-34 has also other potential actions through PTPζ and CD138. Additionally, IL-34 and CSF-1 are produced by different cells in different tissues. This review describes and discusses similarities and differences between IL-34 and CSF-1 at steady state and in pathological situations and identifies possible ways to target IL-34, CSF-1, and its receptors.

IDF Diabetes Atlas: Diabetes and oral health - A two-way relationship of clinical importance

The current scientific evidence for the bi-directional associations between oral health and diabetes is summarized. The universal biologic mechanisms and demographic and behavioral risk drivers underlying these associations in both directions are also described. Dysglycemia, even slightly elevated blood sugar levels, adversely affects oral health, manifesting itself in several oral diseases and conditions. In the opposite direction, any oral infection with its subsequent local and systemic inflammatory responses adversely affects blood glucose levels. Moreover, painful, mobile, or missing teeth may lead to intake of soft food items representing a sub-optimal diet and hence poor nutrition, and thereby contribute to incident type 2 diabetes or to poorer glucose control in existing diabetes. Treatment of inflammation related oral conditions, such as non-surgical periodontal treatment and extraction of infected teeth, can lead to a clinically significant decrease in blood glucose levels. Attention to infectious oral diseases and referral to dental care professionals for treatment can therefore be an important novel tool for medical care professionals in preventing and managing diabetes mellitus. Dental professionals can detect unrecognized potential dysglycemia and refer for medical examination. Such interprofessional, patient centered care may contribute to improved health, wellbeing, and quality of life in people with diabetes.

Interleukin 30 to Interleukin 40

Cytokines are important molecules that regulate the ontogeny and function of the immune system. They are small secreted proteins usually produced upon activation of cells of the immune system, including lymphocytes and myeloid cells. Many cytokines have been described, and several have been recognized as pivotal players in immune responses and in human disease. In fact, several anticytokine antibodies have proven effective therapeutics, especially in various autoimmune diseases. In the last 15 years, new cytokines have been described, and many remain poorly understood. Among the most recent cytokines discovered are interleukins-30 (IL-30) to IL-40. Several of these are members of other cytokine superfamilies, including several IL-1 superfamily members (IL-33, IL-36, IL-37, and IL-38) as well as several new members of the IL-12 family (IL-30, IL-35, and IL-39). The rest (IL-31, IL-32, IL-34, and IL-40) are encoded by genes that do not belong to any cytokine superfamily. Our aim of this review was to present a concise version of the information available on these novel cytokines to facilitate their understanding by members of the immunological community.

Biological functions and clinical implications of interleukin-34 in inflammatory diseases

Interleukin (IL)-34 is a recently discovered cytokine and ligand of the colony-stimulating factor (CSF)-1 receptor. Although CSF-1 and IL-34 share similar biological properties, their expression patterns and downstream signaling pathways are distinct. IL-34 can influence differentiation and has functions in multiple cell types (e.g., dendritic cells, monocytes, macrophages). In the pathological conditions, IL-34 is induced by pro-inflammatory stimuli (e.g., cytokines, pathogen-associated molecular patterns, and infection). Current evidence shows that IL-34 is a critical player in inflammatory response and is involved in the pathogenesis of inflammatory autoimmune dysfunction. Therefore, IL-34 may be a promising clinical biomarker and therapeutic target for treating inflammatory related disorders. In this article, we review the advances in biological functions of IL-34 and our understanding of its role in the development of inflammatory diseases as well as therapeutic applications.

Interleukin-34, a comprehensive review

IL-34 is a novel cytokine that was identified in 2008 in a comprehensive proteomic analysis as a tissue-specific ligand of CSF-1 receptor (CSF-1R). IL-34 exists in all vertebrates including fish, amphibians, birds, and mammals, showing high conservation among species. Structurally, IL-34 belongs to the short-chain helical hematopoietic cytokine family but shows no apparent consensus structural domains, motifs, or sequence homology with other cytokines. IL-34 is synthesized as a secreted homodimeric glycoprotein that binds to the extracellular domains of CSF-1R and receptor-type protein-tyrosine phosphatase-zeta (PTP-ζ) in addition to the chondroitin sulfate chains of syndecan-1. These interactions result in activating several signaling pathways that regulate major cellular functions, including proliferation, differentiation, survival, metabolism, and cytokine/chemokine expression in addition to cellular adhesion and migration. In the steady state, IL-34 contributes to the development and maintenance of specific myeloid cell subsets in a tissue-specific manner: Langerhans cells in the skin and microglia in the brain. In pathological conditions, changes in IL-34 expression-increased or decreased-are involved in disease pathogenesis and correlate with progression, severity, and chronicity. One decade after its discovery, IL-34 has been introduced as a newcomer to the big family of interleukins with specific physiological functions, critical pathological roles, and promising clinical applications in disease diagnosis and treatment. In this review, we celebrate the 10th anniversary of IL-34 discovery, introducing its biological characteristics, and discussing the importance of IL-34 signaling network in health and disease.

Enhanced expression of IL-34 in an inflammatory cyst of the submandibular gland: a case report

Background

Cysts of the salivary glands are common lesions that occur in the context of various etiologies. Although the diagnostic importance of cysts in salivary gland diseases has been well studied, molecular mechanisms that control the related pathological process remain largely unknown. IL-34 is a novel cytokine that was discovered recently as a tissue-specific ligand of colony stimulating factor-1 receptor. Since its discovery, accumulating evidence has revealed emerging roles of IL-34 in various pathological conditions and has been suggested to correlate remarkably with inflammation. In this study, we report a medical case of an inflammatory cyst within the submandibular gland, through which evaluating the possible involvement of IL-34 in salivary gland disorders.

Case presentation

A 37-year-old male patient suffered from a sudden swelling in the right submandibular region, started initially small and had gradually increased in size to reach 3–4 cm in 1 week, accompanied by pain and local fever. Ultrasonography and MRI imaging revealed the existence of a well-defined cystic lesion with sharp borders measuring 39.8 mm × 19.7 mm within the right submandibular gland. The cyst was removed surgically, and the diagnostic decision was determined based on histopathological observations as an inflammatory cyst in the submandibular gland. Sections were generated from different regions of the surgically resected inflammatory cyst and used to examine IL-34 expression by immunohistochemistry compared to normal salivary gland tissues. Immunohistochemical staining showed enhanced expression of IL-34 in the ductal epithelial cells and endothelial cells of blood vessels, with a tendency to be accompanied with high infiltration of immune cells, which suggests a possible involvement of IL-34 in the pathogenesis of salivary gland inflammation.

Conclusions

In this report, we introduce interesting findings of enhanced IL-34 expression in a case of an inflamed submandibular gland. Our findings emphasize the pathological roles of IL-34 as an inflammation amplifier and angiogenic enhancer in inflammatory conditions, such as in salivary gland disorders.

Electronic supplementary material

The online version of this article (10.1186/s41232-018-0069-6) contains supplementary material, which is available to authorized users.