Calcitriol inhibits osteoclastogenesis in an inflammatory environment by changing the proportion and function of T helper cell subsets (Th2/Th17)

Potential targets of phytochemical immunomodulatory therapy in periodontitis immunopathogenesis: A narrative review

Introduction

Periodontitis is one of the most prevalent diseases occurring worldwide, and is caused by an imbalance of host immunological defenses and microbiome profile which occurs in the oral cavity. This imbalance leads to irregularity and uncontrolled activities of immune cells, resulting in over-reactivity of periodontopathogens and tissue destruction. To alleviate periodontitis, exact targeting of specific events involving particular cells could be a potential application of immunomodulatory agents. Phytochemical drug development targeting specific immunopathogenesis events could be a promising complementary, alternative approach to periodontal therapy.

Objectives

This review aimed to explore various events involving a variety of cells in the immunopathogenesis of periodontitis in order to determine potential specific immunomodulation targets for future development of effective phytochemical drugs.

Results

Immunopathogenesis of periodontitis contributes significantly to the disease onset and resolution. Various events occur during the disease development, which involve a variety of immune cells and mediators. Among these, neutrophils, cytokines and lymphocytes, especially Th17 cells, were reported to be the most relevant components in the disease pathogenesis. These components affect the initial responses to periodontopathogens, inhibit oxidative stress formation, control intercellular communication to enhance inflammation, and promote effector cells' migration to induce alveolar bone resorption. Several phytochemical drugs were developed to cure periodontitis, however, the development of phytochemical immunomodulatory drugs to target specific events has not been realized.

Conclusion

This review concluded that development of phytochemical immunomodulatory drugs to target particular events generated by neutrophils, pro-inflammatory cytokines and lymphocytes has tremendous potential to regulate and modulate the immunopathogenesis of periodontitis.

The changes and potential effects of zinc homeostasis in periodontitis microenvironment

Zinc is a very important and ubiquitous element, which is present in oral environment, daily diet, oral health products, dental restorative materials, and so on. However, there is a lack of attention to the role of both extracellular or intracellular zinc in the progression of periodontitis and periodontal regeneration. This review summarizes the characteristics of immunological microenvironment and host cells function in several key stages of periodontitis progression, and explores the regulatory effect of zinc during this process. We find multiple evidence indicate that zinc may be involved and play a key role in the stages of immune defense, inflammatory response and bone remodeling. Zinc supplementation in an appropriate dose range or regulation of zinc transport proteins can promote periodontal regeneration by either enhancing immune defense or up-regulating local cells proliferation and differentiation functions. Therefore, zinc homeostasis is essential in periodontal remodeling and regeneration. More attention is suggested to be focused on zinc homeostasis regulation and consider it as a potential strategy in the studies on periodontitis treatment, periodontal-guided tissue regeneration, implant material transformation, and so on.

Critical roles of PU.1/cathepsin S activation in regulating inflammatory responses of macrophages in periodontitis

OBJECTIVE

To determine the critical roles of PU.1/cathepsin S activation in regulating inflammatory responses of macrophages during periodontitis.

BACKGROUND

Cathepsin S (CatS) is a cysteine protease and exerts important roles in the immune response. Elevated CatS has been found in the gingival tissues of periodontitis patients and is involved in alveolar bone destruction. However, the underlying mechanism of CatS-driven IL-6 production in periodontitis remains unclear.

METHODS

Western blot was applied to measure mature cathepsin S(mCatS) and IL-6 expression in gingival tissues from periodontitis patients and RAW264.7 cells exposed to lipopolysaccharide from Porphyromonas gingivalis (P.g. LPS). Immunofluorescence was applied to confirm the localization of PU.1, and CatS in the gingival tissues of periodontitis patients. ELISA was performed to determine IL-6 production by the P.g. LPS-exposed RAW264.7 cells. Knockdown by shRNA was used to determine the effects of PU.1 on p38/ nuclear factor (NF)-κB activation, mCatS expression and IL-6 production in RAW264.7 cells.

RESULTS

The expressions mCatS and IL-6 were significantly upregulated in gingival macrophages. In cultured RAW264.7 cells, increased mCatS and IL-6 protein paralleled the activation of p38 and NF-κB after exposure to P.g. LPS. CatS knockdown by shRNA significantly decreased P.g. LPS-induced IL-6 expression and p38/NF-κB activation. PU.1 was significantly increased in P.g. LPS-exposed RAW264.7 cells, and PU.1 knockdown dramatically abolished the P.g. LPS-induced upregulation of mCatS and IL-6 and the activation of p38 and NF-κB. Furthermore, PU.1 and CatS colocalized in macrophages within the gingival tissues of periodontitis patients.

CONCLUSION

PU.1-dependent CatS drives IL-6 production in macrophages by activating p38 and NF-κB in periodontitis.

Impact of 1,25-dihydroxyvitamin D3 PLGA-nanoparticles/chitosan hydrogel on osteoimmunomodulation

Severe bone defects that extend beyond a critical size do not heal on their own, increasing the risk of complications and leading to poor outcomes for patients. Healing is a highly coordinated and complex process in which immune cells have an important function making the design and preparation of biomaterials with immunomodulatory functions an important new therapeutic strategy. 1,25-dihydroxyvitamin D3 (VD3) is crucial for bone metabolism and immune regulation. For post-defect bone regeneration, we developed a drug delivery system (DDS) based on chitosan (CS) and nanoparticles (NPs) to sustain the release effect of VD3 and desirable biological characteristics. The hydrogel system was physically characterized and confirmed to have good mechanical strength, degradation rate, and drug release rate. In vitro experiments showed that the cells had good biological activity when the hydrogel was co-cultured with MC3T3-E1 and RAW264.7. The high expression of ARG-1 and low expression of iNOS in macrophages confirmed that VD3-NPs/CS-GP hydrogel transformed lipopolysaccharide-induced M1 macrophages into M2 macrophages. Alkaline phosphatase and alizarin red staining showed that VD3-NPs/CS-GP hydrogel promoted osteogenic differentiation under inflammatory conditions. In conclusion, VD3-NPs/CS-GP hydrogel with synergistic anti-inflammatory and pro-osteogenic differentiation effects may serve as a potential immunomodulatory biomaterial for bone repair and regeneration in cases of bone defects.

Targeting Th17 cells: a promising strategy to treat oral mucosal inflammatory diseases

With the improved quality of life, oral health is under increased pressure. Numerous common oral mucosal diseases, such as oral lichen planus(OLP) and gingivitis, are related to the destruction of the oral immune barrier. The cytokines secreted by T-helper 17 (Th17) cells are essential for maintaining oral immune homeostasis and play essential roles in immune surveillance. When antigens stimulate the epithelium, Th17 cells expand, differentiate, and generate inflammatory factors to recruit other lymphocytes, such as neutrophils, to clear the infection, which helps to maintain the integrity of the epithelial barrier. In contrast, excessive Th17/IL-17 axis reactions may cause autoimmune damage. Therefore, an in-depth understanding of the role of Th17 cells in oral mucosa may provide prospects for treating oral mucosal diseases. We reviewed the role of Th17 cells in various oral and skin mucosal systemic diseases with oral characteristics, and based on the findings of these reports, we emphasize that Th17 cellular response may be a critical factor in inflammatory diseases of the oral mucosa. In addition, we should pay attention to the role and relationship of "pathogenic Th17" and "non-pathogenic Th17" in oral mucosal diseases. We hope to provide a reference for Th17 cells as a potential therapeutic target for treating oral mucosal inflammatory disorders in the future.

Autophagy as a potential mechanism underlying the biological effect of 1,25-Dihydroxyvitamin D3 on periodontitis: a narrative review

The major active form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25D3), is known for its wide bioactivity in periodontal tissues. Although the exact mechanisms underlying its protective action against periodontitis remain unclear, recent studies have shown that 1,25D3 regulates autophagy. Autophagy is vital for intracellular pathogen invasion control, inflammation regulation, and bone metabolic balance in periodontal tissue homeostasis, and its regulation could be an interesting pathway for future periodontal studies. Since vitamin D deficiency is a worldwide health problem, its role as a potential regulator of autophagy provides new insights into periodontal diseases. Based on this premise, this narrative literature review aimed to investigate the possible connection between 1,25D3 and autophagy in periodontitis. A comprehensive literature search was conducted on PubMed using the following keywords (e.g., vitamin D, autophagy, periodontitis, pathogens, epithelial cells, immunity, inflammation, and bone loss). In this review, the latest studies on the protective action of 1,25D3 against periodontitis and the regulation of autophagy by 1,25D3 are summarized, and the potential role of 1,25D3-activated autophagy in the pathogenesis of periodontitis is analyzed. 1,25D3 can exert a protective effect against periodontitis through different signaling pathways in the pathogenesis of periodontitis, and at least part of this regulatory effect is achieved through the activation of the autophagic response. This review will help clarify the relationship between 1,25D3 and autophagy in the homeostasis of periodontal tissues and provide perspectives for researchers to optimize prevention and treatment strategies in the future.

Regulation of the Host Immune Microenvironment in Periodontitis and Periodontal Bone Remodeling

The periodontal immune microenvironment is a delicate regulatory system that involves a variety of host immune cells including neutrophils, macrophages, T cells, dendritic cells and mesenchymal stem cells. The dysfunction or overactivation of any kind of local cells, and eventually the imbalance of the entire molecular regulatory network, leads to periodontal inflammation and tissue destruction. In this review, the basic characteristics of various host cells in the periodontal immune microenvironment and the regulatory network mechanism of host cells involved in the pathogenesis of periodontitis and periodontal bone remodeling are summarized, with emphasis on the immune regulatory network that regulates the periodontal microenvironment and maintains a dynamic balance. Future strategies for the clinical treatment of periodontitis and periodontal tissue regeneration need to develop new targeted synergistic drugs and/or novel technologies to clarify the regulatory mechanism of the local microenvironment. This review aims to provide clues and a theoretical basis for future research in this field.

Osteoporosis and Alveolar Bone Health in Periodontitis Niche: A Predisposing Factors-Centered Review

Periodontitis is a periodontal inflammatory condition that results from disrupted periodontal host-microbe homeostasis, manifested by the destruction of tooth-supporting structures, especially inflammatory alveolar bone loss. Osteoporosis is characterized by systemic deterioration of bone mass and microarchitecture. The roles of many systemic factors have been identified in the pathogenesis of osteoporosis, including endocrine change, metabolic disorders, health-impaired behaviors and mental stress. The prevalence rate of osteoporotic fracture is in sustained elevation in the past decades. Recent studies suggest that individuals with concomitant osteoporosis are more vulnerable to periodontal impairment. Current reviews of worse periodontal status in the context of osteoporosis are limited, mainly centering on the impacts of menopausal and diabetic osteoporosis on periodontitis. Herein, this review article makes an effort to provide a comprehensive view of the relationship between osteoporosis and periodontitis, with a focus on clarifying how those risk factors in osteoporotic populations modify the alveolar bone homeostasis in the periodontitis niche.

A 3D-printed molybdenum-containing scaffold exerts dual pro-osteogenic and anti-osteoclastogenic effects to facilitate alveolar bone repair

The positive regulation of bone-forming osteoblast activity and the negative feedback regulation of osteoclastic activity are equally important in strategies to achieve successful alveolar bone regeneration. Here, a molybdenum (Mo)-containing bioactive glass ceramic scaffold with solid-strut-packed structures (Mo-scaffold) was printed, and its ability to regulate pro-osteogenic and anti-osteoclastogenic cellular responses was evaluated in vitro and in vivo. We found that extracts derived from Mo-scaffold (Mo-extracts) strongly stimulated osteogenic differentiation of bone marrow mesenchymal stem cells and inhibited differentiation of osteoclast progenitors. The identified comodulatory effect was further demonstrated to arise from Mo ions in the Mo-extract, wherein Mo ions suppressed osteoclastic differentiation by scavenging reactive oxygen species (ROS) and inhibiting mitochondrial biogenesis in osteoclasts. Consistent with the in vitro findings, the Mo-scaffold was found to significantly promote osteoblast-mediated bone formation and inhibit osteoclast-mediated bone resorption throughout the bone healing process, leading to enhanced bone regeneration. In combination with our previous finding that Mo ions participate in material-mediated immunomodulation, this study offers the new insight that Mo ions facilitate bone repair by comodulating the balance between bone formation and resorption. Our findings suggest that Mo ions are multifunctional cellular modulators that can potentially be used in biomaterial design and bone tissue engineering.

Vitamin D Ameliorates Apoptosis and Inflammation by Targeting the Mitochondrial and MEK1/2-ERK1/2 Pathways in Hyperoxia-Induced Bronchopulmonary Dysplasia

Purpose

Bronchopulmonary dysplasia (BPD) is a common and severe complication in preterm infants. Vitamin D (VitD) has been reported to protect against BPD; however, its role in the mitochondria-mediated and MEK1/2-ERK1/2 pathways has not yet been reported.

Methods

We first performed in vivo studies using neonatal C57BL/6 mice in which we induced BPD by exposing them to a hyperoxic environment (85% O₂). The mice were divided into room air (RA; 21% O₂), RA+VitD, BPD, and BPD+VitD groups. Hematoxylin and eosin and Masson’s trichrome staining were used to evaluate lung injury. Inflammation and apoptosis were measured using ELISA, RT-qPCR, and TUNEL assays. We then analyzed BEAS-2B cells divided into the same groups along with an additional BPD+VitD+inhibitor group. Mitochondrial apoptosis was evaluated by transmission electron microscopy, mitochondrial membrane potential, and Western blotting. We then used VDR-shRNA to silence the Vitamin D Receptor (VDR) in the BEAS-2B cells. The inflammation, apoptotic rate, and the phosphorylated forms of MEK1/2 and ERK1/2 in cells were detected by RT-qPCR, flow cytometry, and Western blotting.

Results

The mean linear intercept, septal thickness, and abnormal fibrosis increased, while radial alveolar count decreased in BPD lungs compared to RA lungs. VitD administration was able to ameliorate the phenotype in BPD lungs. IL-6, IFN-γ, and TNF-α expression and the apoptotic rate decreased in the BPD+VitD lung group. VitD pretreatment restored abnormal mitochondrial morphology, reduced mitochondrial membrane loss, and reduced the expression of cleaved caspase-3, Bax, and Bcl-2 in BEAS-2B cells. VitD administration also reduced IL-6, IFN-γ, and TNF-α mRNA, as well as pMEK1/2 and pERK1/2 expression and apoptosis rate in cells exposed to hyperoxia.

Conclusion

We concluded that VitD treatment ameliorated apoptosis and inflammation by targeting the mitochondrial pathway and via the MEK1/2-ERK1/2 signaling pathway in BPD, thus supporting its potential therapeutic use in this condition.

Vitamin D, Th17 Lymphocytes, and Breast Cancer

Simple Summary

The effect of vitamin D₃ on the development of breast cancer (favorable, ineffective, or even unfavorable) depends on many factors, such as age, menopausal status, or obesity. The immunomodulatory effect of vitamin D may be unfavorable in case of breast cancer progression. The effect of vitamin D on Th17 cells may depend on disease type and patients’ age. Our goal was to summarize the data available and to find indications of vitamin D treatment failure or success. Therefore, in this review, we present data describing the effects of vitamin D₃ on Th17 cells, mainly in breast cancer.

Abstract

Vitamin D₃, which is well known to maintain calcium homeostasis, plays an important role in various cellular processes. It regulates the proliferation and differentiation of several normal cells, including immune and neoplastic cells, influences the cell cycle, and stimulates cell maturation and apoptosis through a mechanism dependent on the vitamin D receptor. The involvement of vitamin D₃ in breast cancer development has been observed in numerous clinical studies. However, not all studies support the protective effect of vitamin D₃ against the development of this condition. Furthermore, animal studies have revealed that calcitriol or its analogs may stimulate tumor growth or metastasis in some breast cancer models. It has been postulated that the effect of vitamin D₃ on T helper (Th) 17 lymphocytes is one of the mechanisms promoting metastasis in these murine models. Herein we present a literature review on the existing data according to the interplay between vitamin D, Th17 cell and breast cancer. We also discuss the effects of this vitamin on Th17 lymphocytes in various disease entities known to date, due to the scarcity of scientific data on Th17 lymphocytes and breast cancer. The presented data indicate that the effect of vitamin D₃ on breast cancer development depends on many factors, such as age, menopausal status, or obesity. According to that, more extensive clinical trials and studies are needed to assess the importance of vitamin D in breast cancer, especially when no correlations seem to be obvious.

Macrophage-Osteoclast Associations: Origin, Polarization, and Subgroups

Cellular associations in the bone microenvironment are involved in modulating the balance between bone remodeling and resorption, which is necessary for maintaining a normal bone morphology. Macrophages and osteoclasts are both vital components of the bone marrow. Macrophages can interact with osteoclasts and regulate bone metabolism by secreting a variety of cytokines, which make a significant contribution to the associations. Although, recent studies have fully explored either macrophages or osteoclasts, indicating the significance of these two types of cells. However, it is of high importance to report the latest discoveries on the relationships between these two myeloid-derived cells in the field of osteoimmunology. Therefore, this paper reviews this topic from three novel aspects of the origin, polarization, and subgroups based on the previous work, to provide a reference for future research and treatment of bone-related diseases.

Immunomodulation in the Treatment of Periodontitis: Progress and Perspectives

Periodontitis is one of the most common dental diseases. Compared with healthy periodontal tissues, the immune microenvironment plays the key role in periodontitis by allowing the invasion of pathogens. It is possible that modulating the immune microenvironment can supplement traditional treatments and may even promote periodontal regeneration by using stem cells, bacteria, etc. New anti-inflammatory therapies can enhance the generation of a viable local immune microenvironment and promote cell homing and tissue formation, thereby achieving higher levels of immune regulation and tissue repair. We screened recent studies to summarize the advances of the immunomodulatory treatments for periodontitis in the aspects of drug therapy, microbial therapy, stem cell therapy, gene therapy and other therapies. In addition, we included the changes of immune cells and cytokines in the immune microenvironment of periodontitis in the section of drug therapy so as to make it clearer how the treatments took effects accordingly. In the future, more research needs to be done to improve immunotherapy methods and understand the risks and long-term efficacy of these methods in periodontitis.

Th17 Cells in Periodontitis and Its Regulation by A20

Periodontitis is a prevalent chronic disease that results in loss of periodontal ligament and bone resorption. Triggered by pathogens and prolonged inflammation, periodontitis is modulated by the immune system, especially pro-inflammatory cells, such as T helper (Th) 17 cells. Originated from CD4⁺ Th cells, Th17 cells play a central role for they drive and regulate periodontal inflammation. Cytokines secreted by Th17 cells are also major players in the pathogenesis of periodontitis. Given the importance of Th17 cells, modulators of Th17 cells are of great clinical potential and worth of discussion. This review aims to provide an overview of the current understanding of the effect of Th17 cells on periodontitis, as well as a brief discussion of current and potential therapies targeting Th17 cells. Lastly, we highlight this article by summarizing the causal relationship between A20 (encoded by TNFAIP3), an anti-inflammatory molecule, and Th17 cell differentiation.

Interleukin-35 pathobiology in periodontal disease: a systematic scoping review

Background

Interleukin (IL)-35 is a novel anti-inflammatory cytokine that is produced by regulatory T cells. IL-35 mediates immunological functions and plays a protective role in several diseases such as asthma and rheumatoid arthritis. However, the role of IL-35 in gingivitis and periodontitis remains unclear. The aim of this study was to systematically review the literature and collecting the available evidence regarding the role of IL-35 in pathogenesis of periodontal disease.

Methods

A systematic search of electronic databases including MEDLINE, Google Scholar, Cochrane Library, Web of Science, and Scopus was conducted in November 2020 to identify studies addressing the Interleukin-35 pathobiology in periodontal disease. The identified studies were subjected to pre-identified inclusion criteria. The retrived papers were assessed by the authours independently and consensus was reached in cases where disagreement occurred. Articles written in languages other than English, case reports, letters to editors, conference abstracts, theses, and dissertations were excluded from the review.

Results

A total of 176 possibly relevant articles were identified through the search strategy. Finally, 15 papers which met the criteria of eligibility were included in this review by consensus. The included articles were classified based on their design and level of evidence.Three subclinical study, ten cross sectional investigation and two randomized clinical trials constituted the final set of studies in this review. At preclinical level, Il-35 showed inhibitory characteristics regarding alveolar bone resorption of animal periodontitis models. The results of observatory human studies confirmed the presence of high levels of IL-35 in saliva, GCF, serum, and gingival biopsies of patients suffering from inflammatory periodontal disease. Moreover, two included clinical trials showed that non-surgical periodontal therapy could downregulate IL-35 production in chronic periodontitis patients.

Conclusion

Interleukin-35 has an undeniable role in pathobiology of inflammatory periodontal disease. Further well-controlled studies are needed to better elucidate the functional pattern of IL-35 in pathogeneisis of gingival and periodontal disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-01515-1.

Effects of statins on cytokines levels in gingival crevicular fluid and saliva and on clinical periodontal parameters of middle-aged and elderly patients with type 2 diabetes mellitus

Objective

To analyze the effect of statins on cytokines levels in gingival crevicular fluid (GCF) and saliva and on clinical periodontal parameters of middle-aged and elderly patients with type 2 diabetes mellitus (T2DM).

Methods

Systemically healthy controls (C group, n = 62), T2DM patients not taking statins (D group, n = 57) and T2DM patients taking statins (S group, n = 24) were recruited. In each group, subjects (40–85 years) were subclassified into the h (periodontal health)group, the g (gingivitis)group or the p (periodontitis) group according to different periodontal conditions. 17 cytokines in gingival crevicular fluid (GCF) and saliva samples of each subject were measured utilizing the Luminex technology kit. Further, HbA1c (glycated hemoglobin), FPG (fasting plasma glucose), PD (probing depth), CAL (clinical attachment level), BOP (bleeding on probing), GI (gingival index) and PI (periodontal index) were recorded. Data distribution was tested through the Shapiro-Wilk test, upon which the Kruskal-Wallis test was applied followed by Mann-Whitney U test and Bonferroni’s correction.

Results

Levels of IFN-γ, IL-5, IL-10 and IL-13 in the saliva of the Dh group were significantly lower than those in the Ch group, while factor IL-4 was higher (p<0.05). Levels of MIP-3α, IL-7 and IL-2 in GCF of the Dh group were considerably higher than those in the Ch group (p<0.05), while that of IL-23 was considerably lower. Compared with the Cg group, levels of IFN-γ, IL-4, IL-5, IL-6, IL-10 and IL-13 were significantly lower in the saliva of the Dg group (p<0.05). Lower levels of IFN-γ, IL-5 and IL-10 were detected in the Sg group than those in the Cg group (p<0.05). At the same time, levels of IL-1β, IL-6, IL-7, IL-13, IL-17, IL-21 and MIP-3α in the gingival crevicular fluid of the Sg group were lower in comparison with the Dg group. In addition, lower levels of IL-4 and higher levels of IL-7 in GCF were identified in the Dg group than those in the Cg group, while in the Sg group, lower levels of IL-4, MIP-1αand MIP-3αwere observed than those in the Cg group (p<0.05). Lower levels of IFN-γ, IL-6, IL-10, IL-13 and I-TAC were found in the Sp group compared with those in the Cp group. The IFN-γ, IL-6 and IL-10 levels were lower in the Dp group than those in the Cp group (p<0.05). Meanwhile, in the Sp group, lower levels of pro-inflammatory factors IFN-γ, IL-1β, IL-2, IL-6, IL-7, IL-21 and TNF-α, in addition to higher levels of anti-inflammatory factors IL-4 and IL-5 in gingival crevicular fluid, were identified than those in the Dp group. Higher levels of IFN-γ,IL-1β,IL-2,IL-7,IL-21 and TNF-α and a lower level of IL-5 in the Dp group were identified than those in the Cp group (p<0.05). Moreover, statins were able to substantially reduce PD in T2DM patients with periodontitis, indicating an obvious influence on the levels of cytokines secreted by Th1 cells, Th2 cells and Th17 cells, as revealed by PCA (principal component analysis).

Conclusion

Statins are associated with reduced PD and cytokines levels in the GCF and saliva of T2DM patients with periodontitis.

Calcitriol inhibits osteoclastogenesis in an inflammatory environment by changing the proportion and function of T helper cell subsets (Th2/Th17)

Objectives

Previously, we found that by regulating T helper (Th) cell polarization, calcitriol intervention inhibited lipopolysaccharide (LPS)‐induced alveolar bone loss in an animal periodontitis model, but the underlying cellular events remain unknown.

Materials and methods

In this study, mouse Th cells were incubated in an inflammatory environment in the presence of dendritic cells (DCs) and LPS. Then, the potential of the Th cells to undergo Th2/Th17 polarization, the RANKL expression of the polarized Th cells and the subsequent influences of the polarized Th cells on RAW264.7 cell osteoclastogenesis in response to calcitriol administration were assessed. Finally, the effects of calcitriol on antigen presentation by DCs during these cellular events were evaluated.

Results

In response to calcitriol administration, Th cells in an inflammatory environment exhibited an enhanced potential for Th2 polarization along with a decreased potential for Th17 polarization. In addition, RANKL expression in Th17‐polarized cells was largely inhibited. Furthermore, inflammation‐induced osteoclastogenesis in RAW264.7 cells was suppressed following coculture with calcitriol‐treated Th cells. During these cellular events, increased expression of Th2 promoters (such as OX‐40L and CCL17) and decreased expression of Th17 promoters (such as IL‐23 and IL‐6) were found in DCs.

Conclusions

Calcitriol can inhibit osteoclastogenesis in an inflammatory environment by changing the proportion and function of Th cell subsets. Our findings suggest that calcitriol may be an effective therapeutic agent for treating periodontitis.