IL-17R activation of human periodontal ligament fibroblasts induces IL-23 p19 production: Differential involvement of NF-κB versus JNK/AP-1 pathways

Polarized Th2 cells attenuate high-fat-diet induced obesity through the suppression of lipogenesis

Immune cells, such as macrophages, B cells, neutrophils and T cell subsets, have been implicated in the context of obesity. However, the specific role of Th2 cells in adipose tissue function has remained elusive. Eight-week-old male CD3ε─/─ mice were randomly divided into two groups (≥ 5 mice per group): one received intravenous injection of Th2 cells isolated from LATY136F mice, while the other receiving PBS as a control. Both of groups were subjected to a high-fat diet (HFD). The adoptive transfer of polarized Th2 cells led to a significant reduction in obesity following a HFD. This reduction was accompanied by improvements in hepatic steatosis, glucose intolerance, and insulin resistance. Mechanistically, Th2 cell treatment promoted oxidative phosphorylation of adipocytes, thereby contributing to a reduction of lipid droplet accumulation. These findings suggest that Th2 cell therapy represents a novel approach for treating diet-induced obesity and other diseases involving lipid droplet accumulation disorders.

The role of IL-17 in lung cancer growth

Interleukin 17 (IL-17) is an inflammatory cytokine with multiple roles in immune protection, immunopathology, and inflammation-related tumors. Lung cancer is inflammation-related cancer, and a large number of studies have shown that IL-17 contributes to the metastasis and progression of lung cancer. However, some studies have shown that IL17 inhibits the occurrence of lung cancer. At present, there is still some controversy about the role of IL17 in the occurrence and development of lung cancer. This review introduces the basic characteristics of IL-17 and focuses on its role in lung cancer, in order to provide a certain theoretical basis for the prevention, diagnosis, and treatment of lung cancer.

The role of IL-23/IL-17 axis in ischemic stroke from the perspective of gut-brain axis

Bidirectional communication between central nervous system (CNS) and intestine is mediated by nerve, endocrine, immune and other pathways in gut-brain axis. Many diseases of CNS disturb the homeostasis of intestine and gut microbiota. Similarly, the dysbiosis of intestinal and gut microbiota also promotes the progression and deterioration of CNS diseases. IL-23/IL-17 axis is an important inflammatory axis which is widely involved in CNS diseases such as experimental autoimmune encephalomyelitis (EAE), multiple sclerosis (MS), and ischemic stroke (IS). Attributing to the long anatomically distances between ischemic brain and gut, previous studies on IL-23/IL-17 axis in IS are rarely focused on intestinal tissues. However, recent studies have found that IL-17⁺T cells in CNS mainly originate from intestine. The activation and migration of IL-17⁺T cells to CNS is likely to be affected by the altered intestinal homeostasis. These studies promoted the attention of IL-23/IL-17 axis and gut-brain axis. IS is difficult to treat because of its extremely complex pathological mechanism. This review mainly discusses the relationship between IL-23/IL-17 axis and IS from the perspective of gut-brain axis. By analyzing the immune pathways in gut-brain axis, the activation of IL-23/IL-17 axis, the roles of IL-23/IL-17 axis in gut, CNS and other systems after stoke, this review is expected to provide new enlightenments for the treatment strategies of IS.

Development of Adaptive Immunity and Its Role in Lung Remodeling

Asthma is characterized by airflow limitations resulting from bronchial closure, which can be either reversible or fixed due to changes in airway tissue composition and structure, also known as remodeling. Airway remodeling is defined as increased presence of mucins-producing epithelial cells, increased thickness of airway smooth muscle cells, angiogenesis, increased number and activation state of fibroblasts, and extracellular matrix (ECM) deposition. Airway inflammation is believed to be the main cause of the development of airway remodeling in asthma. In this chapter, we will review the development of the adaptive immune response and the impact of its mediators and cells on the elements defining airway remodeling in asthma.

Pro- and anti-inflammatory bioactive lipids imbalance contributes to the pathobiology of autoimmune diseases

Autoimmune diseases are driven by T_H17 cells that secrete pro-inflammatory cytokines, especially IL-17. Under normal physiological conditions, autoreactive T cells are suppressed by TGF-β and IL-10 secreted by microglia and dendritic cells. When this balance is upset due to injury, infection and other causes, leukocyte recruitment and macrophage activation occurs resulting in secretion of pro-inflammatory IL-6, TNF-α, IL-17 and PGE2, LTs (leukotrienes) accompanied by a deficiency of anti-inflammatory LXA4, resolvins, protecting, and maresins. PGE2 facilitates T_H1 cell differentiation and promotes immune-mediated inflammation through T_H17 expansion. There is evidence to suggest that autoimmune diseases can be suppressed by anti-inflammatory bioactive lipids LXA4, resolvins, protecting, and maresins. These results imply that systemic and/or local application of LXA4, resolvins, protecting, and maresins and administration of their precursors AA/EPA/DHA could form a potential therapeutic approach in the prevention and treatment of autoimmune diseases.

Essential Fatty Acids and Their Metabolites in the Pathobiology of Inflammation and Its Resolution

Arachidonic acid (AA) metabolism is critical in the initiation and resolution of inflammation. Prostaglandin E2 (PGE2) and leukotriene B4/D4/E4 (LTB4/LD4/LTE4), derived from AA, are involved in the initiation of inflammation and regulation of immune response, hematopoiesis, and M1 (pro-inflammatory) macrophage facilitation. Paradoxically, PGE2 suppresses interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) production and triggers the production of lipoxin A4 (LXA4) from AA to initiate inflammation resolution process and augment regeneration of tissues. LXA4 suppresses PGE2 and LTs' synthesis and action and facilitates M2 macrophage generation to resolve inflammation. AA inactivates enveloped viruses including SARS-CoV-2. Macrophages, NK cells, T cells, and other immunocytes release AA and other bioactive lipids to produce their anti-microbial actions. AA, PGE2, and LXA4 have cytoprotective actions, regulate nitric oxide generation, and are critical to maintain cell shape and control cell motility and phagocytosis, and inflammation, immunity, and anti-microbial actions. Hence, it is proposed that AA plays a crucial role in the pathobiology of ischemia/reperfusion injury, sepsis, COVID-19, and other critical illnesses, implying that its (AA) administration may be of significant benefit in the prevention and amelioration of these diseases.

The Th17/Treg cell balance: crosstalk among the immune system, bone and microbes in periodontitis

Periodontopathic bacteria constantly stimulate the host, which causes an immune response, leading to host-induced periodontal tissue damage. The complex interaction and imbalance between Th17 and Treg cells may be critical in the pathogenesis of periodontitis. Furthermore, the RANKL/RANK/OPG system plays a significant role in periodontitis bone metabolism, and its relationship with the Th17/Treg cell imbalance may be a bridge between periodontal bone metabolism and the immune system. This article reviews the literature related to the Th17/Treg cell imbalance mediated by pathogenic periodontal microbes, and its mechanism involving RANKL/RANK/OPG in periodontitis bone metabolism, in an effort to provide new ideas for the study of the immunopathological mechanism of periodontitis.

Kurarinone Attenuates BLM-Induced Pulmonary Fibrosis via Inhibiting TGF-β Signaling Pathways

Idiopathic pulmonary fibrosis (IPF) is a refractory interstitial lung disease for which there is no effective treatment. Although the pathogenesis of IPF is not fully understood, TGF-β and epithelial-mesenchymal transition (EMT) have been shown to be involved in the fibrotic changes of lung tissues. Kurarinone is a prenylated flavonoid isolated from Sophora Flavescens with antioxidant and anti-inflammatory properties. In this study, we investigated the effect of kurarinone on pulmonary fibrosis. Kurarinone suppressed the TGF-β-induced EMT of lung epithelial cells. To assess the therapeutic effects of kurarinone in bleomycin (BLM)-induced pulmonary fibrosis, mice were treated with kurarinone daily for 2 weeks starting 7 days after BLM instillation. Oral administration of kurarinone attenuated the fibrotic changes of lung tissues, including accumulation of collagen and improved mechanical pulmonary functions. Mechanistically, kurarinone suppressed phosphorylation of Smad2/3 and AKT induced by TGF-β1 in lung epithelial cells, as well as in lung tissues treated with BLM. Taken together, these results suggest that kurarinone has a therapeutic effect on pulmonary fibrosis via suppressing TGF-β signaling pathways and may be a novel drug candidate for pulmonary fibrosis.

Interleukin-17 modulates uPA and MMP2 expression in human periodontal ligament mesenchymal stem cells: Involvement of the ERK1/2 MAPK pathway

Periodontal disease is a chronic infection of periodontal tissue characterized by extracellular matrix (ECM) degradation due to increased expression of plasminogen activators and matrix metalloproteinases (MMPs) and various proinflammatory cytokines, including interleukin (IL)-17. Successful regeneration of damaged periodontal tissues depends on the proper functionality of periodontal ligament mesenchymal stem cells (PDLMSCs), especially the production of extracellular matrix proteases. We investigated the influence of IL-17 on ECM remodeling through modulation of urokinasetype plasminogen activator (uPA) and MMP2/MMP9 expression in human PDLMSCs at mRNA, protein and activity levels using by RT-PCR, Western blotting and zymography, respectively. Investigation of the involvement of MAPKs in these processes in PDLMSCs was determined by Western blotting, as well as by utilizing specific p38 and MEK1/2 inhibitors. Our results show that IL-17 activates MAPK signaling in PDLMSCs. Moreover, IL-17 had no effect on MMP9 expression, but it stimulated uPA and MMP2 gene and protein expression in PDLMSCs through the activation of the ERK1/2 MAPK signaling pathway. The obtained data suggest that IL-17 contributes to ECM degradation in the periodontal ligament by stimulating uPA and MMP2 expression and activity in PDLMSCs. This information is important for understanding periodontal disease development and defining future directions of its treatment.

The Role of the Interleukin-17 Axis and Neutrophils in the Pathogenesis of Endemic and Systemic Mycoses

Systemic and endemic mycoses are considered life-threatening respiratory diseases which are caused by a group of dimorphic fungal pathogens belonging to the genera Histoplasma, Coccidioides, Blastomyces, Paracoccidioides, Talaromyces, and the newly described pathogen Emergomyces. T-cell mediated immunity, mainly T helper (Th)1 and Th17 responses, are essential for protection against these dimorphic fungi; thus, IL-17 production is associated with neutrophil and macrophage recruitment at the site of infection accompanied by chemokines and proinflammatory cytokines production, a mechanism that is mediated by some pattern recognition receptors (PRRs), including Dectin-1, Dectine-2, TLRs, Mannose receptor (MR), Galectin-3 and NLPR3, and the adaptor molecules caspase adaptor recruitment domain family member 9 (Card9), and myeloid differentiation factor 88 (MyD88). However, these PRRs play distinctly different roles for each pathogen. Furthermore, neutrophils have been confirmed as a source of IL-17, and different neutrophil subsets and neutrophil extracellular traps (NETs) have also been described as participating in the inflammatory process in these fungal infections. However, both the Th17/IL-17 axis and neutrophils appear to play different roles, being beneficial mediating fungal controls or detrimental promoting disease pathologies depending on the fungal agent. This review will focus on highlighting the role of the IL-17 axis and neutrophils in the main endemic and systemic mycoses: histoplasmosis, coccidioidomycosis, blastomycosis, and paracoccidioidomycosis.

A new anabolic compound, LLP2A-Ale, reserves periodontal bone loss in mice through augmentation of bone formation

BACKGROUND

Currently, there are no effective medications to reverse periodontal disease (PD)-induced bone loss. The objective of this study was to test a new anabolic compound, LLP2A-Ale, or with the combination treatment of mesenchymal stromal cell (MSC), in the treatment of bone loss secondary to PD.

METHODS

PD was induced in mice by placing a ligature around the second right molar. At one week after disease induction, the mice were treated with placebo, LLP2A-Ale, MSCs, or combination of LLP2A-Ale + MSCs, and euthanized at week 4.

RESULTS

We found that PD induced alveolar bone loss that was associated with reduced bone formation. LLP2A-Ale alone or in combination with MSCs sustained alveolar bone formation and reversed alveolar bone loss. Additionally, PD alone caused systemic inflammation and increased the circulating levels of G-CSF, IP-10, MIP-1a, and MIP2, which were suppressed by LLP2A-Ale +/- MSCs. LLP2A-Ale +/- MSCs increased bone formation at the peripheral skeletal site (distal femur), which was otherwise suppressed by PD.

CONCLUSION

Our findings indicated that LLP2A-Ale treatment rescued alveolar bone loss caused by PD, primarily by increasing bone formation. LLP2A-Ale also attenuated the circulating levels of a series of inflammatory cytokines and reversed the PD-induced suppression of systemic bone formation.

Profibrotic effect of IL-17A and elevated IL-17RA in idiopathic pulmonary fibrosis and rheumatoid arthritis-associated lung disease support a direct role for IL-17A/IL-17RA in human fibrotic interstitial lung disease

Interleukin (IL)-17 is a T helper 17 cytokine implicated in the pathogenesis of many autoimmune diseases, including rheumatoid arthritis (RA). Although IL-17A has a well-established role in murine pulmonary fibrosis models, its role in the tissue remodeling and fibrosis occurring in idiopathic pulmonary fibrosis (IPF) and RA-associated interstitial lung disease (RA-ILD) is not very well defined. To address this question, we utilized complimentary studies to determine responsiveness of human normal and pathogenic lung fibroblasts to IL-17A and used lung biopsies acquired from patients with IPF and RA-ILD to determine IL-17A receptor (IL-17RA) expression. Both normal and pathogenic IPF lung fibroblasts express functional IL-17RA and respond to IL-17A stimulation with cell proliferation, generation of extracellular matrix (ECM) proteins, and induction of myofibroblast transdifferentiation. Small interfering RNA (siRNA) silencing of IL-17RA attenuated this fibroblast response to IL-17A on ECM production. These fibroblast responses to IL-17A are dependent on NF-κB-mediated signaling. In addition, inhibiting Janus activated kinase (JAK) 2 by either siRNA or a selective pharmacological inhibitor, AZD1480-but not a JAK1/JAK3 selective inhibitor, tofacitinib-also significantly reduced this IL-17A-induced fibrogenic response. Lung biopsies of RA-ILD patients demonstrate significantly higher IL-17RA expression in areas of fibroblast accumulation and fibrosis, compared with either IPF or normal lung tissue. These observations support a direct role for IL-17A in lung fibrosis that may be particularly relevant in the context of RA-ILD.

Upregulation of IL-6 expression in human salivary gland cell line by IL-17 via activation of p38 MAPK, ERK, PI3K/Akt, and NF-κB pathways

BACKGROUND

The human salivary gland (HSG) cell line has so far been used as in vitro models for study of the influence of cytokines and pharmacologic agents on salivary glands, as well as a model system for inflammation in Sjögren's syndrome (SS). This study aimed to determine the effect of IL-17 on IL-6 production and the underlying molecular mechanism regulated by the HSG cell line.

METHODS

Immunofluorescence analyses, RT-PCR, and Western blot were conducted to evaluate the IL-17 receptor (IL-17R) expression in cultured HSG cells. Real-time PCR and ELISA were then utilized to establish the mRNA and protein levels of IL-6 in IL-17-stimulated HSG cells. Western blot, flow cytometry, immunofluorescence, and inhibitor analyses were conducted to elucidate the involved signaling pathways.

RESULTS

The HSG cells reliably expressed the IL-17R mRNA and its encoded surface-bound protein. The expression of IL-6 mRNA and protein was upregulated by stimulation of HSG cells with IL-17; this effect was impeded by IL-17- or IL-17R-neutralizing antibodies. IL-17 stimulation ended up with the fast phosphorylation of p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase (ERK), Akt, and translocation of nuclear factor-kappaB (NF-κB) in the HSG cells. p38 MAPK, Akt, and NF-κB inhibitors significantly subdued IL-6 generation in HSG cells stimulated by IL-17. PD98059, an ERK inhibitor, decreased IL-6 generation under low dose of IL-17 but not with high dose.

CONCLUSIONS

The HSG cells expressed IL-17R and reacted to IL-17 to generate IL-6 via the stimulation of ERK, p38 MAPK, Akt, and NF-κB signaling pathways.

Interleukin-12-mediated expression of matrix metalloproteinases in human periodontal ligament fibroblasts involves in NF-κB activation

Interleukin-12 (IL-12) is a proinflammatory cytokine, and its increased level correlates with the severity of periodontitis. However, its role in the pathogenesis of tooth periapical lesions is controversial and has not been completely clarified. The present study aimed to investigate whether IL-12 affects the expression of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) in human periodontal ligament fibroblasts (hPDLFs). After treatment with IL-12 for different times, real-time PCR and Western blotting were used to determine the mRNA and protein levels of MMP-1, MMP-2, MMP-3, MMP-9, MMP-13, TIMP-1, and TIMP-2, respectively. ELISA was applied to measure MMPs and TIMPs secretion production. The results indicated that IL-12 significantly increased the mRNA and protein expression levels of MMP-1, MMP-3, and MMP-13, but down-regulated MMP-2 and MMP-9 mRNA and protein expression in the hPDLFs. Furthermore, IL-12 (10 ng/ml) enhanced the secreted protein production of MMP-1, MMP-3, and MMP-13, and conversely lowered MMP-2 and MMP-9 secretion levels. However, IL-12 treatment did not exert a significant effect on the mRNA and protein levels of TIMP-1 and TIMP-2 and their secreted production. Additionally, IL-12 increased the phosphorylated levels of IκBα and nuclear factor-κB P65 (NF-κB P65), and promoted NF-κB P65 subunit nuclear translocation. Pretreatment with NF-κB inhibitor not only attenuated IL-12-induced IκBα and NF-κB P65 phosphorylation and inhibited NF-κB P65 subunit into nucleus, but also antagonized IL-12-mediated MMP-1, MMP-2, MMP-3, MMP-9, and MMP-13 expression in the hPDLFs. These findings indicate that NF-κB-dependent activation is possibly indispensable for IL-12-mediated MMP expression in hPDLFs.

IL-17 in the lung: the good, the bad, and the ugly

The IL-17 family of cytokines has emerged over the last two decades as a pleiotropic group of molecules that function in a wide variety of both beneficial and detrimental (pathological) processes, mainly in mucosal barrier tissue. The beneficial effects of IL-17 expression are especially important in the lung, where exposure to foreign agents is abundant. IL-17A plays an important role in protection from both extracellular bacteria and fungi, as well as viruses that infect cells of the mucosal tracts. IL-17 coregulated cytokines, such as IL-22, are involved in maintaining epithelial cell homeostasis and participate in epithelial cell repair/regeneration following inflammatory insults. Thus, the IL-17/IL-22 axis is important in both responding to, and recovering from, pathogens. However, aberrant expression or overexpression of IL-17 cytokines contributes to a number of pathological outcomes, including asthma, pneumonitis, and generation or exacerbation of pulmonary fibrosis. This review covers the good, bad, and ugly aspects of IL-17 in the lung.

Anti-osteoclastogenesis of Mineral Trioxide Aggregate through Inhibition of the Autophagic Pathway

INTRODUCTION

Mineral trioxide aggregate (MTA) regulates bone remodeling, particularly osteoclast differentiation. However, intracellular mechanisms underlying the anti-osteoclastogenesis of MTA remain unclear. This study aimed to evaluate the potential alterations of autophagic pathway during anti-osteoclastogenic effects by MTA in vitro and investigate their underlying mechanisms.

METHODS

Osteoclast precursors were treated with MTA extracts containing the receptor activator of nuclear factor-kappa B ligand (RANKL). Rapamycin was used to activate autophagy. RANKL-induced osteoclast differentiation was stained with tartrate-resistant acid phosphatase. Several specific autophagy features in osteoclast precursors were measured by using immunofluorescence, monodansylcadaverine, and transmission electron microscope. Autophagy-related proteins were investigated via Western blot analysis. The mRNA expression involved in autophagic and osteoclastic activities was detected with quantitative real-time polymerase chain reaction.

RESULTS

MTA extracts inhibited osteoclast differentiation via preventing the fusion of osteoclast precursors without cytotoxicity. MTA extracts interrupted RANKL-induced acidic vesicular organelle formation and autophagic vacuole appearance in osteoclast precursors. Moreover, autophagic genes and proteins stimulated with RANKL diminished with MTA extracts. Notably, autophagy activation through rapamycin promoted multinucleated osteoclasts formation and increased osteoclastic genes expression, which almost reversed MTA-mediated anti-osteoclastogenic effects.

CONCLUSIONS

MTA inhibited osteoclastogenesis for bone repair through attenuating the autophagic pathway.

Involvement of interleukin‑23 induced by Porphyromonas endodontalis lipopolysaccharide in osteoclastogenesis

Periapical lesions are characterized by the destruction of periapical bone, and occur as a result of local inflammatory responses to root canal infection by microorganisms including Porphyromonas endodontalis (P. endodontalis). P. endodontalis and its primary virulence factor, lipopolysaccharide (LPS), are associated with the development of periapical lesions and alveolar bone loss. Interleukin-23 (IL-23) is critical in the initiation and progression of periodontal disease via effects on peripheral bone metabolism. The present study investigated the expression of IL-23 in tissue where a periapical lesion was present, and the effect of P. endodontalis LPS on the expression of IL-23 in periodontal ligament (PDL) cells. Reverse transcription- quantitative polymerase chain reaction and immunohistochemistry revealed increased levels of IL-23 expression in tissue with periapical lesions compared with healthy PDL tissue. Treatment with P. endodontalis LPS increased the expression of IL-23 in the SH-9 human PDL cell line. BAY11-7082, a nuclear factor κB inhibitor, suppressed P. endodontalis LPS-induced IL-23 expression in SH-9 cells. Treatment of RAW264.7 cells with conditioned medium from P. endodontalis LPS-treated SH-9 cells promoted osteoclastogenesis. By contrast, RAW264.7 cells treated with conditioned medium from IL-23-knockdown SH-9 cells underwent reduced levels of osteoclastogenesis. The results of the present study indicated that the expression of IL-23 in PDL cells induced by P. endodontalis LPS treatment may be involved in the progression of periapical lesions via stimulation of the osteoclastogenesis process.

Anti-osteoclastogenic activity of isoliquiritigenin via inhibition of NF-κB-dependent autophagic pathway

Previous studies, including those from our laboratory, have demonstrated that the natural flavonoid isoliquiritigenin (ISL) is a promising agent for bone destructive diseases. However, the mechanisms underlying its anti-osteoclastogenic effects are still far from clear. Here, we evaluated the potential alterations of autophagy and nuclear factor-κB (NF-κB) during anti-osteoclastogenic effects by ISL in vitro and in vivo. We observed that ISL inhibited the receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclastogenesis and suppressed autophagic microtubule-associated protein light chain 3 (LC3)-II and Beclin 1 accumulation. ISL treatment resulted in the interruption of several specific features for autophagy in osteoclast precursors, including acidic vesicular organelle formation, LC3-II accumulation, and appearance of autophagic vacuoles. The RANKL-stimulated expression levels of autophagy-related genes and proteins also diminished in ISL-treated osteoclast precursors. The reactivation of autophagy by rapamycin almost reversed the ISL-elicited anti-osteoclastogenic effects. Interestingly, ISL inhibited the RANKL-stimulated NF-κB expression and nuclear translocation, whereas the NF-κB inhibitor Bay 11-7082 markedly suppressed the RANKL-induced autophagic activation. Consistent with the in vitro results, the administration of ISL could attenuate osteoclastogenic cathepsin K, autophagic LC3, and NF-κB expression to protect against inflammatory calvarial bone erosion in vivo. Our findings highlight the inhibition of NF-κB-dependent autophagy as an important mechanism of ISL-mediated anti-osteoclastogenic activity.

IL-17 induces MIP-1α expression in primary mouse astrocytes via TRPC channel

Our previous study demonstrated IL-17-mediated induction of MIP-1α through its binding to the cognate IL-17RA and MIP-1α was involved in astrocyte activation. Transient receptor potential canonical (TRPC) channel was involved in astrocyte activation, however, whether TRPC channel regulates MIP-1α expression in the context of multiple sclerosis (MS) remains largely unknown. In this study we identify the essential role of TRPC channel in IL-17-mediated MIP-1α expression and astrocyte activation. Moreover, treatment of astrocytes with IL-17 activated MAPKs and PI3K/Akt signaling pathways with downstream NF-κB pathways. Interestingly, the TRPC blocker-SKF96365 (10 μM) and Norgestimate (10 μM) significantly inhibited the increased expression of MIP-1α via suppression of IL-17-mediated ERK, p38 and JNK MAPKs and PI3K/Akt pathway activation, thereby underscoring the role of TRPC channel in this process. Together these data underpin the role of TRPC channel as a novel target that regulates MIP-1α expression and cell activation-mediated by IL-17 with implications for therapeutic intervention for reversal of neuroinflammation inflicted by IL-17. Understanding the regulation of MIP-1α expression may provide insights into the development of potential therapeutic targets for neuroinflammation associated with MS.

Immune Cells and Metabolism

Low-grade inflammation in the obese AT (AT) and the liver is a critical player in the development of obesity-related metabolic dysregulation, including insulin resistance, type 2 diabetes and non-alcoholic steatohepatitis (NASH). Myeloid as well as lymphoid cells infiltrate the AT and the liver and expand within these metabolic organs as a result of excessive nutrient intake, thereby exacerbating tissue inflammation. Macrophages are the paramount cell population in the field of metabolism-related inflammation; as obesity progresses, a switch takes place within the AT environment from an M2-alternatively activated macrophage state to an M1-inflammatory macrophage-dominated milieu. M1-polarized macrophages secrete inflammatory cytokines like TNF in the obese AT; such cytokines contribute to insulin resistance in adipocytes. Besides macrophages, also CD8+ T cells promote inflammation in the AT and the liver and thereby the deterioration of the metabolic balance in adipocytes and hepatocytes. Other cells of the innate immunity, such as neutrophils or mast cells, interfere with metabolic homeostasis as well. On the other hand, eosinophils or T-regulatory cells, the number of which in the AT decreases in the course of obesity, function to maintain metabolic balance by ameliorating inflammatory processes. In addition, eosinophils and M2-polarized macrophages may contribute to "beige" adipogenesis under lean conditions; beige adipocytes are located predominantly in the subcutaneous AT and have thermogenic and optimal energy-dispensing properties like brown adipocytes. This chapter will summarize the different aspects of the regulation of homeostasis of metabolic tissues by immune cells.

Interaction of Candida albicans with periodontal ligament fibroblasts limits biofilm formation over elastomer silicone disks

OBJECTIVE

Candida albicans is the most numerous commensal and potentially pathological yeast in the human oral cavity. The purpose herein is to investigate the ability of C. albicans to form a biofilm in the presence of periodontal ligament (PDL) fibroblasts.

MATERIAL AND METHODS

Silicone elastomer disks (SE) were transferred to wells containing PDL cells. C. albicans suspension was added to each well. The whole mixed culture was then allowed to form a biofilm for 48h. Biofilms were quantified by tetrazolium-salt-based (2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenyl amino) carbonyl]- 2H-tetrazolium hydroxide (XTT). Furthermore, biofilm was visualized by confocal scanning laser and scanning electron microscopy. Migration of C. albicans and its ability to form biofilms in presence of PDL cells was determined by using a transwell system. Last, elutes obtained from co-culturing C. albicans and PDL cells were added to SE disks and covered with C. albicans. The culture plate was then incubated to allow biofilm formation. Biofilms formed over SE disks were quantified using XTT.

RESULTS

PDL cells significantly limited the biofilm formation at incubation interval of 48h. PDL cells induced less biofilm compared to mature and thick hyphae in the absence of PDL cells as seen in confocal scanning laser and scanning electron microscopy. The presence of PDL cells limited the migration and formation of biofilm by C. albicans. Elutes obtained from co-culturing PDL cells with C. albicans for one hour induced significantly less biofilm.

CONCLUSIONS

This is the first study to report that PDL cells exhibit antifungal activity. While the exact mechanism of how PDL cells limited biofilm formation is yet unknown, it was clear that competent PDL cells promote resistance to C. albicans biofilm formation.

Upregulation of cell proliferation via Shc and ERK1/2 MAPK signaling in SaOS-2 osteoblasts grown on magnesium alloy surface coating with tricalcium phosphate

Magnesium (Mg) alloys have been demonstrated to be viable orthopedic implants because of mechanical and biocompatible properties similar to natural bone. In order to improve its osteogenic properties, a porous β-tricalcium phosphate (β-TCP) was coated on the Mg-3AI-1Zn alloy by alkali-heat treatment technique. The human bone-derived cells (SaOS-2) were cultured on (β-TCP)-Mg-3AI-1Zn in vitro, and the osteoblast response, the morphology and the elements on this alloy surface were investigated. Also, the regulation of key intracellular signalling proteins was investigated in the SaOS-2 cells cultured on alloy surface. The results from scanning electron microscope and immunofluorescence staining demonstrated that (β-TCP)-Mg-3AI-1Zn induced significant osteogenesis. SaOS-2 cell proliferation was improved by β-TCP coating. Moreover, the (β-TCP)-Mg-3AI-1Zn surface induced activation of key intracellular signalling proteins in SaOS-2 cells. We observed an enhanced activation of Src homology and collagen (Shc), a common point of integration between bone morphogenetic protein 2, and the Ras/mitogen-activated protein kinase (MAPK) pathway. ERK1/2 MAP kinase activation was also upregulated, suggesting a role in mediating osteoblastic cell interactions with biomaterials. The signalling pathway involving c-fos (member of the activated protein-1) was also shown to be upregulated in osteoblasts cultured on the (β-TCP)-Mg-3AI-1Zn. These results suggest that β-TCP coating may contribute to successful osteoblast function on Mg alloy surface. (β-TCP)-Mg-3AI-1Zn may upregulate cell proliferation via Shc and ERK1/2 MAPK signaling in SaOS-2 osteoblasts grown on Mg alloy surface.

IL-17 regulates the expressions of RANKL and OPG in human periodontal ligament cells via TRAF6/TBK1-JNK/NF-κB pathways

Interleukin-17 (IL-17 or IL-17A), a pleiotropic cytokine produced by T helper (Th) 17 cells, is involved in the pathogenesis of various autoimmune and inflammatory disorders, including periodontitis. Although the ability of pro-inflammation in periodontitis have been widely investigated, the other biological functions of IL-17, including its role in bone remodeling and the underlying molecular mechanism, have not been well clarified. In the present study, IL-17 could significantly enhance the expression of receptor activator for nuclear factor-κB ligand (RANKL) and inhibit the expression of osteoprotegerin (OPG) in human periodontal ligament cells (hPDLCs), the two critical indicators for osteoclastogenesis, suggesting IL-17 may play a destructive role in the pathogenesis of periodontal bone remodeling. Pharmaceutical signal inhibitors targeted at MAPKs, Akt or NF-κB signals, inhibited IL-17-induced RANKL and OPG regulation. Notably, the enhancement of RANKL was significantly blocked by the inhibitors of JNK and NF-κB signals. The upstream signals were further investigated with the small interfering RNA (siRNA). Both TRAF6 and TBK1 were found to be the critically signal molecules for IL-17-dependent RANKL regulation in hPDLCs. These findings may provide comprehensive understanding of the role of IL-17 in the pathogenesis of periodontitis and might also provide a reasonable way for periodontitis therapy. This article is protected by copyright. All rights reserved.

The role of adipose tissue immune cells in obesity and low-grade inflammation

Adipose tissue (AT) lies at the crossroad of nutrition, metabolism, and immunity; AT inflammation was proposed as a central mechanism connecting obesity with its metabolic and vascular complications. Resident immune cells constitute the second largest AT cellular component after adipocytes and as such play important roles in the maintenance of AT homeostasis. Obesity-induced changes in their number and activity result in the activation of local and later systemic inflammatory response, marking the transition from simple adiposity to diseases such as type 2 diabetes mellitus, arterial hypertension, and ischemic heart disease. This review has focused on the various subsets of immune cells in AT and their role in the development of AT inflammation and obesity-induced insulin resistance.

Interleukin-17A stimulates migration of periodontal ligament fibroblasts via p38 MAPK/NF-κB -dependent MMP-1 expression

Interleukin-17 (IL-17) is a cytokine secreted predominantly by Th17 cells. Although IL-17 is primarily associated with the induction of tissue inflammation, the other biological functions of IL-17, including its wound-healing functions, have yet to be thoroughly explored. Fibroblast proliferation and migration play essential roles in periodontal wound-healing responses. In this study, we report that IL-17A can increase the migration and expression of matrix metalloproteinase (MMP)-1 in human periodontal ligament (PDL) fibroblasts but has no effect on PDL fibroblast proliferation. IL-17A-induced MMP-1 expression led to cell migration, which was attenuated by pre-treatment with IL-17 receptor neutralizing antibody and small interfering RNA (siRNA) for MMP-1. The IL-17A-induced cell migration was also attenuated by its tissue inhibitor of matrix metalloproteinase (TIMP)-1. In addition, a p38 mitogen-activated protein kinase (MAPK) inhibitor (SB203580) inhibited IL-17A-induced increase of the migration and MMP-1 upregulation of PDL fibroblasts. The involvement of p38 MAPK in IL-17A-induced MMP-1 expression and cell migration was further confirmed by transfection of p38α siRNA. A nuclear factor kappaB (NF-κB) inhibitor (pyrrolidine dithiocarbamate) also suppressed the cell migration and MMP-1 expression enhanced by IL-17A. Moreover, transfection with p38α siRNA inhibited IL-17A-induced NF-κB nuclear translocation as well as NF-κB binding activity. Our results suggest that IL-17A enhances the migration of PDL fibroblasts by increasing MMP-1 expression through the IL-17 receptor, p38 MAPK, and NF-κB signal transduction pathways.

Chronic adipose tissue inflammation: all immune cells on the stage

Inflammation is indispensable for host homeostasis against invading pathogens and efficient wound healing upon tissue malfunction and has to be tightly controlled by various mechanisms to limit excess responses harmful to host tissues. A myriad of disease conditions ranging from type 2 diabetes (T2D) to neurodegenerative and cardiovascular disorders are now shown to progress due to persistent, unresolved inflammation in metabolic tissues such as adipose, liver, pancreas, muscle, and brain. However, their underlying mechanisms are incompletely understood. The actions of innate and adaptive immune cells in these ailments are increasingly appreciated so much so that a new research area called 'immunometabolism' has emerged. In this review, we will highlight the fundamental roles of various immune cells in adipose tissue during the initiation and progression of obesity-induced inflammation and discuss potential anti-inflammatory therapies from different mechanistic points of view.

The outliers become a stampede as immunometabolism reaches a tipping point

Obesity and Type 2 diabetes mellitus (T2D) are characterized by pro-inflammatory alterations in the immune system including shifts in leukocyte subset differentiation and in cytokine/chemokine balance. The chronic, low-grade inflammation resulting largely from changes in T-cell, B-cell, and myeloid compartments promotes and/or exacerbates insulin resistance (IR) that, together with pancreatic islet failure, defines T2D. Animal model studies show that interruption of immune cell-mediated inflammation by any one of several methods almost invariably results in the prevention or delay of obesity and/or IR. However, anti-inflammatory therapies have had a modest impact on established T2D in clinical trials. These seemingly contradictory results indicate that a more comprehensive understanding of human IR/T2D-associated immune cell function is needed to leverage animal studies into clinical treatments. Important outstanding analyses include identifying potential immunological checkpoints in disease etiology, detailing immune cell/adipose tissue cross-talk, and defining strengths/weaknesses of model organism studies to determine whether we can harness the promising new field of immunometabolism to curb the global obesity and T2D epidemics.

Prostaglandin E2-induced IL-23p19 subunit is regulated by cAMP-responsive element-binding protein and C/AATT enhancer-binding protein β in bone marrow-derived dendritic cells

We reported previously that prostaglandin E2 (PGE2) up-regulates IL-23 in vitro in bone marrow-derived dendritic cells and in vivo in models of collagen-induced arthritis and inflammatory bowel disease, leading to preferential Th17 development and activity. There is very little information on the molecular mechanisms involved in the PGE2-induced up-regulation of Il23a gene expression. In this study we investigated the signaling pathways and transcription factors involved in the stimulatory effect of PGE2. Although PGE2 does not induce IL-23p19 expression by itself, it synergizes with both extra- and intracellular Toll-like receptor ligands and with inflammatory cytokines such as TNFα. We established that the effect of PGE2 in conjunction with either LPS or TNFα is mediated through the EP4 receptor and the cAMP-dependent activation of both protein kinase A (PKA) and exchange protein activated by cAMP (EPAC). Using the EP4 agonist PGE(1)OH in conjunction with TNFα, we found that PKA-induced phosphorylation of cAMP-response element-binding protein ((P)CREB) and EPAC-induced phosphorylation of C/AATT enhancer-binding protein β ((P)C/EBPβ) mediate the stimulatory effect of PGE2 on IL-23p19 expression. This is the first report of CREB and C/EBPβ involvement in Il23a promoter activation. Mutation within the putative CREB and C/EBP sites combined with in vivo DNA binding (ChIP) assays identified the distal CREB site (-1125) and the two proximal C/EBP sites (-274 and -232) as essential for PKA-activated CREB and EPAC-activated C/EBPβ-induced IL-23p19 expression.