The Role of T Helper 17 Cells and Other IL-17-Producing Cells in Bone Resorption and Remodeling

In recent decades, many studies have highlighted the role of IL-17-producing cells in bone resorption. However, the importance of many IL-17-producing cell types remains largely unknown in bone remodeling. In this review, we summarize the function of IL-17-producing cells, with a focus on T helper 17 (Th17) cells, in bone resorption and remodeling.     

Infiltration of IL-17-Producing T Cells and Treg Cells in a Mouse Model of Smoke-Induced Emphysema

Chronic obstructive pulmonary disease (COPD) is a progressive and irreversible chronic inflammatory disease associated with the accumulation of activated T cells. To date, there is little information concerning the intrinsic association among Th17, Tc17, and regulatory T (Treg) cells in COPD. The objective of this study was to investigate the variation of lungs CD4⁺Foxp3⁺ Treg cells and IL-17-producing CD4 and CD8 (Th17 and Tc17) lymphocytes in mice with cigarette-induced emphysema. Groups of mice were exposed to cigarette smoke or room air. At weeks 12 and 24, mice were sacrificed to observe histological changes by HE stain. The frequencies of Th17 (CD4⁺IL-17⁺T), Tc17 (CD8⁺IL-17⁺T), and Treg (CD4⁺Foxp3⁺T) cells in lungs from these mice were analyzed by flow cytometry. The mRNA levels of orphan nuclear receptor ROR γt and Foxp3 were performed by real-time quantitative polymerase chain reaction. The protein levels of interleukin-17 (IL-17), IL-6, IL-10, and transforming growth factor-beta (TGF-β1) were measured by enzyme-linked immunosorbent assay. Cigarette smoke caused substantial enlargement of the air spaces accompanied by the destruction of the normal alveolar architecture and led to emphysema. The frequencies of Th17 and Tc17 cells, as well as the expressions of IL-6, IL-17, TGF-β1, and ROR γt were greater in the lungs of cigarette smoke (CS)-exposed mice, particularly in the 24-week CS-exposed mice. The frequencies of Treg cells and the expressions of IL-10 and Foxp3 were lower in CS-exposed mice compared to control group. More important, the frequencies of Tregs were negatively correlated with Th17 cells and with Tc17 cells. Interestingly, a significant portion of the cells that infiltrate the lungs was skewed towards a Tc17 phenotype. Our findings suggest the contribution of Th17, Tc17, and Treg cells in the pathogenesis of COPD. Rebalance of these cells will be helpful for developing and refining the new immunological therapies for COPD.     

ERK5信号通路介导流体剪切力对成骨细胞BMP2，BMP7mRNA的表达影响

目的：观察流体剪切力对MC3T3-E1成骨细胞BMP2,BMP7mRNA的表达影响,并探讨ERK5信号通路在其中的作用。方法：应用不同浓度的ERK5特异性阻断剂BIX02188干预成骨细胞,MTT比色法检测酶标仪490nm吸光度,观察成骨细胞增殖情况以及ERK5mRNA的表达。并采用生理强度为12dyne／cm^2的流体剪切力干预成骨细胞,实时荧光定量PCR检测BMP2,BMP7mRNA的表达情况。结果：浓度为15μM的BIX02188干预成骨细胞后,成骨细胞的生长的抑制以及ERK5mRNA的降低呈浓度依赖性。流体剪切力能够明显增加BMP2和BMP7mRNA的表达（P〈0．05）,且该种反应能够被ERK5信号通路阻断（P〈0．05）。结论：ERK5信号通路调控流体剪切力对成骨细胞BMP2,BMP7mRNA的表达。     

Localization of IL-17+Foxp3+ T Cells in Esophageal Cancer

The etiology of cancer is unclear. Recent studies indicate that some cytokines, such as interleukin (IL)-17, and regulatory T cells are involved in the development of cancer. This study aims to detect a subset of T cell, IL17+Foxp3+ T cell, in the pathogenesis of esophageal cancer (Eca). Twelve patients with squamous Eca were recruited in this study. The surgically removed Eca tissue was collected. Cells isolated from Eca tissue were analyzed by flow cytometry. The results showed that 2–10% Eca tissue-derived CD4⁺ T cells expressed Foxp3; only 0.2–0.8% non-ca tissue-derived CD4⁺ T cells expressed Foxp3. Further analysis showed that 3–15% Eca-isolated CD4⁺ T cells were also IL-17 positive whereas only 0.4–1.5% non-ca tissue-isolated CD4⁺ T cells were IL-17 positive. We also found that about 4.8–11.2% Foxp3⁺ IL-17⁺ T cells in isolated CD4⁺ T cells from Eca tissue that were significantly less than in non-ca tissue derived CD4⁺ T cells. Less than 1% Foxp3⁺ IL-17⁺ T cells in isolated CD4⁺ T cells in both Eca patients and healthy controls. Treatment with hypoxia markedly increased the expression of IL-6 in peripheral CD68+ cells. Coculturing CD68+ cells and Foxp3+ T cells under hypoxic environment resulted in abundant expression of IL-17 in Foxp3+ T cells that could be blocked by pretreatment with either anti-IL-17 or anti-transforming growth factor beta antibodies. We conclude that IL-17+Foxp3+ T cells may contribute to the development of Eca.     

Chemokine Signaling Pathway Involved in CCL2 Expression in Patients with Rheumatoid Arthritis

Purpose

Rheumatoid arthritis (RA) is an inflammatory joint disorder, the progression of which leads to the destruction of cartilage and bone. Chemokines are involved in RA pathogenesis. In this study, we investigated the chemokine signaling pathway associated with CCL2 in peripheral blood (PB) and synovial tissues (ST) of RA patients based on our previous work about chemokine signaling pathway involved in the activation of CCL2 production in collagen-induced arthritis rat ST.

Materials and Methods

Total RNA was isolated from PB leukocytes and synovium of the knee joint in both RA patients and control populations. Real-time polymerase chain reaction was used to determine CCL4, CCR5, c-Jun, c-Fos, and CCL2 expressions. Serum level of CCL2 was assessed by enzyme-linked immunosorbent assay, and the production of CCL2 in ST was analyzed immunohistochemically.

Results

The expressions of CCL4, CCR5, c-Jun, c-Fos, and CCL2 messenger RNA in RA patients were significantly higher than those in healthy controls, both in ST and on PB leukocyte. Serum CCL2 levels were elevated in RA patients. Histological examination of rheumatoid joints revealed extensive CCL2 expression in RA ST.

Conclusion

CCL2, CCL4, c-Jun, c-Fos, and CCR5 may play an important role in the recruitment of PB leukocytes into the RA joints. These data provide evidence that the chemokine signaling pathway is involved in CCL2 expression in RA patient tissues, which may contribute to chronic inflammation associated with RA. Targeting this signaling pathway may provide a novel therapeutic avenue in RA.     

Structural Analysis Reveals that the Cytokine IL-17F Forms a Homodimeric Complex with Receptor IL-17RC to Drive IL-17RA-Independent Signaling

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Quercetin, a Flavonoid Phytoestrogen, Ameliorates Experimental Allergic Encephalomyelitis by Blocking IL-12 Signaling Through JAK-STAT Pathway in T Lymphocyte

Experimental allergic encephalomyelitis (EAE) is a Th1 cell-mediated inflammatory demyelinating autoimmune disease model of multiple sclerosis (MS). Quercetin (3,3'4',5,7-pentahydroxy flavone) is a flavonoid phytoestrogen that has profound anticancer and anti-inflammatory activities. In this study, we show that in vivo treatment of SJL/J mice with quercetin (i.p. 50 or 100 microg every other day) ameliorates EAE in association with the inhibition of IL-12 production and neural antigen-specific Th1 differentiation. In vitro treatment of activated T cells with quercetin blocks IL-12-induced tyrosine phosphorylation of JAK2, TYK2, STAT3, and STAT4, resulting in a decrease in IL-12-induced T cell proliferation and Th1 differentiation. These findings highlight the fact that quercetin ameliorates EAE by blocking IL-12 signaling and Th1 differentiation and suggest its use in the treatment of MS and other Th1 cell-mediated autoimmune diseases.     

IL-12 as Well as IL-2 Upregulates CCR5 Expression on T Cell Receptor-Triggered Human CD4+ and CD8+ T Cells

The expression of chemokine receptors on leukocytes is related to their activation state. However, the exact mechanism underlying the induction of each chemokine receptor is poorly understood. Here, we investigated how CCR5, a chemokine receptor implicated in T cell trafficking and HIV infection, is induced in human T cells. CCR5 was marginally detected on a freshly prepared human peripheral blood mononuclear cell (PBMC) population. Long-term (8-day) stimulation of PBMC with IL-2 resulted in high levels of CCR5 expression on T cells. IL-12 failed to induce CCR5 on T cells in such a directly stimulated PBMC population. Stimulation of PBMC T cells with anti-CD3 plus anti-CD28 induced detectable albeit very low levels of CCR5 along with the induction of IL-12 receptor. However, these TCR-triggered T cells expressed much higher levels of CCR5 when stimulated with IL-12. Although IL-2 also induced CCR5 expression, CCR5 expression was more potent in IL-12 than IL-2 stimulation. These results indicate that, in addition to IL-2, IL-12 plays an important role in the induction of CCR5 expression on T cells, particularly TCR-triggered T cells.     

IL-2 Immunotherapy to Recently HIV-1 Infected Adults Maintains the Numbers of IL-17 Expressing CD4+ T (TH17) Cells in the Periphery

Little is known about the manipulation of IL-17 producing CD4+ T cells (T_H17) on a per-cell basis in humans in vivo. Previous studies on the effects of IL-2 on IL-17 secretion in non-HIV models have shown divergent results. We hypothesized that IL-2 would mediate changes in IL-17 levels among recently HIV-1-infected adults receiving anti-retroviral therapy. We measured cytokine T cell responses to CD3/CD28, HIV-1 Gag, and CMV pp65 stimulation, and changes in multiple CD4+ T cell subsets. Those who received IL-2 showed a robust expansion of naive and total CD4+ T cell counts and T-reg counts. However, after IL-2 treatment, the frequency of T_H17 cells declined, while counts of T_H17 cells did not change due to an expansion of the CD4+ naïve T cell population (CD27+CD45RA+). Counts of HIV-1 Gag-specific T cells declined modestly, but CMV pp65 and CD3/CD28 stimulated populations did not change. Hence, in contrast with recent studies, our results suggest IL-2 is not a potent in vivo regulator of T_H17 cell populations in HIV-1 disease. However, IL-2-mediated T-reg expansions may selectively reduce responses to certain antigen-specific populations, such as HIV-1 Gag.     

胃癌组织中IL-17A和IL-17F的表达及意义

目的探讨胃癌组织中促炎因子IL-17A和IL-17F的表达及其对临床预后的影响。方法采用免疫组化SP法检测41例胃癌组织和26例癌旁组织(对照组)中IL-17A和IL-17F的表达,分析IL-17A和IL-17F与胃癌患者临床病理特征的关系。结果胃癌组织中IL-17A和IL-17F的阳性率及中～强阳性率均明显高于对照组(P<0.01)。胃癌组织中IL-17A和IL-17F表达与临床分期、淋巴结转移均呈正相关(P<0.001),与患者性别、年龄及病理分化程度均无相关性(P>0.05)。胃癌组织中IL-17A和IL-17F的表达呈正相关(r=0.407,P<0.009)。结论 IL-17A和IL-17F促进了胃癌的发生、发展,且其高表达预示预后不良。IL-17A和IL-17F作用机制相似。     

HLA-DQ2-restricted gluten-reactive T cells produce IL-21 but not IL-17 or IL-22

We have analyzed the production of the effector cytokines interleukin (IL)-17, IL-21, and IL-22 in gluten-reactive CD4⁺ T cells of celiac disease patients, either cultured from small intestinal biopsies or isolated from peripheral blood after an oral gluten challenge. Combining intracellular cytokine staining with DQ2-α-II gliadin peptide tetramer staining of intestinal polyclonal T-cell lines, we found that gluten-specific T cells produced interferon-γ (IFN-γ) and IL-21, but not IL-17 or IL-22, even if other T cells of the same lines produced these cytokines. Similarly, in DQ2-α-II-specific T cells in peripheral blood of gluten-challenged patients, very few stained for intracellular IL-17, whereas many cells stained for IFN-γ. We conclude that gluten-reactive T cells produce IL-21 and IFN-γ, but not IL-17. Their production of IL-21 suggests a role for this cytokine in the pathogenesis of celiac disease.     

A chymotryptic-type serine protease is required for IL-2 production by Jurkat T cells.

Interleukin-2 (IL-2) production by activated Jurkat T cells was markedly delayed when these cells were treated with low concentrations of the chymotryptic-type protease inhibitor N-alpha-p-tosyl-L-phenylalanine chloromethylketone (TPCK). This increased lag time observed in the presence of TPCK directly correlates with the interaction of the inhibitor with a unique 42,000 molecular weight (MW) serine protease, which can be labelled with [3H]DFP, and was not due to an intracellular accumulation of a non-mature form of IL-2 nor to a non-specific inhibition of overall protein synthesis. The results presented in this report indicate that a 42,000 MW chymotryptic-like serine protease is required for IL-2 production by activated Jurkat T cells.     

Pathway of apoptosis induced in Jurkat T lymphoblasts by anti-HLA class I antibodies

We demonstrated recently that human leukocyte antigen (HLA) class I human monoclonal antibodies (mAbs) are able to induce apoptosis of resting human lymphocytes as well as Jurkat lymphoblastic T cells. We now analyzed the signaling pathway involved in apoptosis mediated by human HLA class I allele-specific mAb OK2F3 and mouse monomorphic mAb W6/32. An inhibitor of a broad spectrum of caspases had only a moderate inhibiting effect, and an inhibitor of caspase 3 failed to inhibit HLA class I-mediated apoptosis. Although caspase 3 activation was not observed, internucleosomal DNA fragmentation was found in half of the apoptotic cells. Importantly, the mitochondrio-nuclear redistribution of apoptosis inducing factor (AIF), a caspase-independent mitochondrial death effector, was detected after 1 hour of treatment with human anti-HLA mAb and was associated with large-scale DNA fragmentation, whereas the release of cytochrome c, which is responsible for caspase-dependent internucleosomal fragmentation, followed AIF translocation and occurred after 2 hours. Our results indicate that apoptosis mediated through HLA class I molecules represents a unique mechanism of cell death in Jurkat T lymphoblasts that involves two parallel pathways, one caspase-independent and the other caspase-dependent. This study clarifies the precise mechanism of anti-HLA antibody-induced apoptosis which might have clinical implications.