Th17/Treg失衡与肝脏免疫病理反应的研究进展

Th17细胞及Th17/Treg失衡在炎症反应、组织损伤及纤维化形成中发挥了重要作用,与多种疾病的发生发展密切相关。前炎性细胞因子可诱导T细胞分化为Th17,使Th17/Treg失衡,导致IL-17、IL-6、趋化因子等促炎性细胞因子大量分泌并有效介导中性粒细胞动员与兴奋,使得机体产生炎症反应与免疫病理反应。就Th17/Treg细胞及其失衡在肝脏免疫病理反应中的研究进展进行了综述。     

NLRP3炎症体与肠道疾病

Nod样受体蛋白3(Nod-like receptor protein 3,NLRP3)炎症体是机体先天免疫的重要感受器,通过诱导炎症反应和细胞焦亡参与宿主免疫防御,并在维持肠道稳态方面发挥重要作用。近年来,NLRP3炎症体在放射性肠炎、炎症性肠病、结直肠癌和其他肠道疾病中的作用引起临床医生与科研人员的广泛关注。本文就NLRP3炎症体的激活机制和其在肠道疾病中的作用机制进行综述,旨在为临床治疗提供新的靶点与思路。     

12/15 脂氧酶在脑卒中的作用研究进展

脂氧合酶(LOX)是一类广泛存在于动植物中的非血红素铁蛋白,催化底物生成各种类花生酸物质,与人体的肿瘤、哮喘、炎症、动脉硬化等疾病密切相关。12/15脂氧酶(12/15-LOX)是一种脂质过氧化物酶,可以催化亚油酸,花生四烯酸等多不饱和脂肪酸生成具有生物活性的代谢产物,通过信号转导在许多病理生理过程中发挥着重要的作用,有研究表明,12/15-LOX通路可以刺激炎症因子的产生,参与多种炎性反应,而在脑卒中的发生发展以及病理过程中始终伴随的炎性反应,炎症及细胞因子等对脑卒中有一定的影响,在脑卒中炎症反应继发性脑组织损伤病理发展过程中起着重要的作用。因此,研究12/15-LOX与脑卒中炎症的关系,可以为临床治疗脑卒中提供新的靶点。本文就12/15-LOX在脑卒中后炎症反应中的作用做简要介绍。     

microRNA与炎症因子之间调控的研究进展

microRNA是一类非编码单链RNA,通过裂解互补的mRNA或抑制mRNA翻译在转录后水平调控基因的表达。研究表明,microRNA不仅可以调节IL-1β、IL-6、IL-8、TNF-α等炎症因子的表达,并且反过来也可以被这些炎症因子调控,形成复杂的信号通路网,发挥重要的生物学作用。本文总结了近年来microRNA与IL-1β、IL-6、IL-8、TNF-α等炎症因子相互作用的研究进展,以及它们对免疫、炎症反应和癌症等疾病的影响,以期能为相关疾病的研究、诊断、治疗提供新思路。     

酸性鞘磷脂酶/神经酰胺通路在疾病发生发展中 作用机制的研究进展

酸性鞘磷脂酶/神经酰胺通路可介导细胞凋亡、炎症和自噬等多种细胞活动,与心脑血管疾病、代谢类疾病、肺部和肝部疾病以及 神经系统疾病等多种疾病的发生、发展密切相关。酸性鞘磷脂酶现已成为多种疾病的临床生物标记物和潜在的治疗靶点。综述酸性鞘磷脂 酶/神经酰胺通路在各种疾病中的生物学功能和作用机制最新研究进展,旨在为相关疾病的治疗提供新思路。     

HMGB1在脓毒症中的致病机制及靶向治疗前景

高迁移率族蛋白B1(high mobility group box 1 protein,HMGB1)是机体一种重要的晚期炎症介质。近年来,因发现其在脓毒症等多种疾病中发挥重要的致病作用而成为研究热点。胞浆中HMGB1主要由活化的单核/巨噬细胞和坏死细胞释放,其本身可作为炎症介质并通过靶细胞信号传导通路刺激多种炎症介质释放,使机体炎症反应增强。HMGB1随着研究不断取得进展,其靶向治疗有望在脓毒症临床治疗中取得新突破。     

工程化调节性T细胞调控机体免疫耐受及其生物医学应用

调节性T细胞（Tregs）是一类机体发挥免疫调节功能的T淋巴细胞亚群，能够高效、安全、可控地调节机体免疫，在自身免疫疾病及器官移植术后免疫排斥等炎症疾病的治疗应用中发挥关键作用。然而，治疗脱靶和功能表型不稳定给Tregs的临床应用带来巨大挑战。生物医学工程改造策略不仅能够促进Tregs主动靶向与炎症趋化，还可维持Tregs叉头盒蛋白p3 (Foxp3)在炎症环境中的表达稳定性，持续发挥机体免疫调节功能。本文详述Tregs的免疫调节机制，并对生物医学工程化改造的Tregs在自身免疫疾病、器官移植等炎症疾病中的应用进行展望，旨在启发和促进Tregs免疫过继疗法的临床应用研究。     

单核细胞趋化蛋白受体的研究进展

单核细胞趋化蛋白及其受体在机体免疫应答中(免疫调节、器官形成、调节造血和神经元通讯)发挥了重要作用,同时也广泛参与某些疾病的发病机制(动脉粥样硬化、感染炎症性疾病及肿瘤等)。因此,有关趋化性细胞因子的新理论和技术可为临床治疗某些疾病提供了新思路。本文简要地综述单核细胞趋化蛋白受体的生物学特性、生物学作用及对心血管疾病的影响作用。     

2014 年全球热门药物靶点分析—— IL-6 靶标药物

IL-6 是一种多效性前炎症细胞因子,具有多种生物学活性,包括介导炎症反应、免疫反应等。随着对 IL-6 及其受体信号通路研究 的不断深入,IL-6 现已成为一个有效的治疗靶点,在炎症及自身免疫性疾病的治疗过程中发挥重要作用。采用文献调研、数据库检索、数 据统计与分析等定性定量情报学研究方法,从研发阶段、适应证、临床及上市药物等方面对全球 IL-6 靶标药物的研发情况进行分析,旨在 为我国免疫药物的研发提供参考。     

大麻素受体2与消化系统炎症性疾病

胰腺炎、炎症性肠病等消化系统炎症性疾病是临床的常见病和多发病,目前这些疾病的发病机制不清,临床治疗效果不理想。大麻素受体2(cannabinoid receptor2,CB2)属于G蛋白偶联受体(G-proteincoupledreceptor,GPCR)家族,主要分布于免疫系统。近年来的研究揭示消化系统有CB2的存在,参与调节多种信号通路,而且发挥抗炎作用。本文综述有关CB2在消化系统炎症性疾病中的作用及机制研究的进展,以望为临床相关疾病的治疗提供新思路。     

TSG-6 protein binding to glycosaminoglycans: formation of stable complexes with hyaluronan and binding to chondroitin sulfates

TSG-6 protein, up-regulated in inflammatory lesions and in the ovary during ovulation, shows anti-inflammatory activity and plays an essential role in female fertility. Studies in murine models of acute inflammation and experimental arthritis demonstrated that TSG-6 has a strong anti-inflammatory and chondroprotective effect. TSG-6 protein is composed of the N-terminal link module that binds hyaluronan and a C-terminal CUB domain, present in a variety of proteins. Interactions between the isolated link module and hyaluronan have been studied extensively, but little is known about the binding of full-length TSG-6 protein to hyaluronan and other glycosaminoglycans. We show that TSG-6 protein and hyaluronan, in a temperature-dependent fashion, form a stable complex that is resistant to dissociating agents. The formation of such stable complexes may underlie the activities of TSG-6 protein in inflammation and fertility, e.g. the TSG-6-dependent cross-linking of hyaluronan in the cumulus cell-oocyte complex during ovulation. Because adhesion to hyaluronan is involved in cell trafficking in inflammatory processes, we also studied the effect of TSG-6 on cell adhesion. TSG-6 binding to immobilized hyaluronan did not interfere with subsequent adhesion of lymphoid cells. In addition to immobilized hyaluronan, full-length TSG-6 also binds free hyaluronan and all chondroitin sulfate isoforms under physiological conditions. These interactions may contribute to the localization of TSG-6 in cartilage and to its chondroprotective and anti-inflammatory effects in models of arthritis.     

Up-regulation of cyclooxygenase-2 expression by TSG-6 protein in macrophage cell line

TNF-stimulated gene 6 (TSG-6) encodes a 35 kDa inducible secreted glycoprotein important in inflammation and female fertility. Previous studies have shown that TSG-6 has anti-inflammatory activity in models of acute and chronic inflammation. In the present study, we show that treatment of the RAW 264.7 murine macrophage cell line with TSG-6 protein up-regulates the expression of inducible cyclooxygenase-2 (COX-2), a key enzyme in inflammation and immune responses. This action of TSG-6 protein was abolished by heat denaturation, trypsin digestion, or anti-TSG-6 antibodies. TSG-6 treatment also resulted in a rapid increase in COX-2 mRNA levels, suggesting that TSG-6 up-regulates COX-2 gene expression. Up-regulation of COX-2 was accompanied by an increase in the production of prostaglandins, especially PGD2. As the PGD2 metabolite, 15-deoxy-Delta12,14-PGJ2, can act as a negative regulator of inflammation, these TSG-6 actions may explain, at least in part, the anti-inflammatory effect of TSG-6 observed in the intact organism.     

Cytokine-induced gene expression at the crossroads of innate immunity, inflammation and fertility: TSG-6 and PTX3/TSG-14

Two cytokine-inducible gene products, important in inflammation and infection, also play essential roles in female fertility. One of these is the product of tumor necrosis factor (TNF)-stimulated gene 6 (TSG-6), alternatively termed TNFAIP6 (for TNF-alpha-induced protein 6), originally cloned from diploid human fibroblasts stimulated with TNF. The second is pentraxin 3 (PTX3), also termed TSG-14, originally isolated from TNF-stimulated human fibroblasts and from interleukin-1 (IL-1)-stimulated vascular endothelial cells. TSG-6, which specifically binds to hyaluronan (HA) and to inter-alpha-inhibitor (I alpha I), shows potent anti-inflammatory activity in acute and chronic inflammation, notably in several models of autoimmune arthritis. PTX3 was shown to play an important role in resistance to fungal infection with Aspergillus fumigatus. Both TSG-6 and PTX3 are synthesized in the ovary prior to ovulation, where they become components of an expanding viscoelastic matrix that surrounds the oocyte before its release from the follicle at the ovarian surface. Female mice with a targeted disruption of either the TSG-6 or PTX3 gene show severe defects in fertility.     

Inter-alpha-inhibitor, hyaluronan and inflammation

Inter-alpha-inhibitor is an abundant plasma protein whose physiological function is only now beginning to be revealed. It consists of three polypeptides: two heavy chains and one light chain called bikunin. Bikunin, which has antiproteolytic activity, carries a chondroitin sulphate chain to which the heavy chains are covalently linked. The heavy chains can be transferred from inter-alpha-inhibitor to hyaluronan molecules and become covalently linked. This reaction seems to be mediated by TSG-6, a protein secreted by various cells upon stimulation by inflammatory cytokines. Inter-alpha-inhibitor has been shown to be required for the stabilization of the cumulus cell-oocyte complex during the expansion that occurs prior to ovulation. Hyaluronan-linked heavy chains in the extracellular matrix of this cellular complex have recently been shown to be tightly bound to TSG-6. Since TSG-6 binds to hyaluronan, its complex with heavy chains could stabilize the extracellular matrix by cross-linking hyaluronan molecules. Heavy chains linked to hyaluronan molecules have also been found in inflamed tissues. The physiological role of these complexes is not known but there are indications that they might protect hyaluronan against fragmentation by reactive oxygen species. TSG-6 also binds to bikunin thereby enhancing its antiplasmin activity. Taken together, these results suggest that inter-alpha-inhibitor is an anti-inflammatory agent which is activated by TSG-6.     

TSG-6 regulates bone remodeling through inhibition of osteoblastogenesis and osteoclast activation

TSG-6 is an inflammation-induced protein that is produced at pathological sites, including arthritic joints. In animal models of arthritis, TSG-6 protects against joint damage; this has been attributed to its inhibitory effects on neutrophil migration and plasmin activity. Here we investigated whether TSG-6 can directly influence bone erosion. Our data reveal that TSG-6 inhibits RANKL-induced osteoclast differentiation/activation from human and murine precursor cells, where elevated dentine erosion by osteoclasts derived from TSG-6(-/-) mice is consistent with the very severe arthritis seen in these animals. However, the long bones from unchallenged TSG-6(-/-) mice were found to have higher trabecular mass than controls, suggesting that in the absence of inflammation TSG-6 has a role in bone homeostasis; we have detected expression of the TSG-6 protein in the bone marrow of unchallenged wild type mice. Furthermore, we have observed that TSG-6 can inhibit bone morphogenetic protein-2 (BMP-2)-mediated osteoblast differentiation. Interaction analysis revealed that TSG-6 binds directly to RANKL and to BMP-2 (as well as other osteogenic BMPs but not BMP-3) via composite surfaces involving its Link and CUB modules. Consistent with this, the full-length protein is required for maximal inhibition of osteoblast differentiation and osteoclast activation, although the isolated Link module retains significant activity in the latter case. We hypothesize that TSG-6 has dual roles in bone remodeling; one protective, where it inhibits RANKL-induced bone erosion in inflammatory diseases such as arthritis, and the other homeostatic, where its interactions with BMP-2 and RANKL help to balance mineralization by osteoblasts and bone resorption by osteoclasts.     

The N-terminal module of thrombospondin-1 interacts with the link domain of TSG-6 and enhances its covalent association with the heavy chains of inter-alpha-trypsin inhibitor

We recently found that leukocytes from thrombospondin-1 (TSP1)-deficient mice exhibit significant reductions in cell surface CD44 relative to those from wild type mice. Because TSG-6 modulates CD44-mediated cellular interactions with hyaluronan, we examined the possibility that TSP1 interacts with TSG-6. We showed that recombinant full-length human TSG-6 (TSG-6Q) and the Link module of TSG-6 (Link_TSG6) bind 125I-TSP1 with comparable affinities. Trimeric recombinant constructs containing the N-modules of TSP1 or TSP2 inhibit binding of TSP1 to TSG-6Q and Link_TSG6, but other recombinant regions of TSP1 do not. Therefore, the N-modules of both TSP1 and TSP2 specifically recognize the Link module of TSG-6. Heparin, which binds to these domains of both proteins, strongly inhibits binding of TSP1 to Link_TSG6 and TSG-6Q, but hyaluronan does not. Inhibition by heparin results from its binding to TSP1, because heparin also inhibits TSP1 binding to Link_TSG6 mutants deficient in heparin binding. Removal of bound Ca2+ from TSP1 reduces its binding to full-length TSG-6. Binding of TSP1 to Link_TSG6, however, is enhanced by chelating divalent cations. In contrast, divalent cations do not influence binding of the N-terminal region of TSP1 to TSG-6Q. This implies that divalent cation dependence is due to conformational effects of calcium-binding to the C-terminal domains of TSP1. TSP1 enhances covalent modification of the inter-alpha-trypsin inhibitor by TSG-6 and transfer of its heavy chains to hyaluronan, suggesting a physiological function of TSP1 binding to TSG-6 in regulation of hyaluronan metabolism at sites of inflammation.     

TSG-6 binds via its CUB_C domain to the cell-binding domain of fibronectin and increases fibronectin matrix assembly.

Human plasma fibronectin binds with high affinity to the inflammation-induced secreted protein TSG-6. Fibronectin binds to the CUB_C domain of TSG-6 but not to its Link module. TSG-6 can thus act as a bridging molecule to facilitate fibronectin association with the TSG-6 Link module ligand thrombospondin-1. Fibronectin binding to TSG-6 is divalent cation-independent and is conserved in cellular fibronectins. Based on competition binding studies using recombinant and proteolytic fragments of fibronectin, TSG-6 binding localizes to type III repeats 9-14 of fibronectin. This region of fibronectin contains the Arg-Gly-Asp sequence recognized by alpha5beta1 integrin, but deletion of that sequence does not prevent TSG-6 binding, and TSG-6 does not inhibit cell adhesion on fibronectin substrates mediated by this integrin. This region of fibronectin is also involved in fibronectin matrix assembly, and addition of TSG-6 enhances exogenous and endogenous fibronectin matrix assembly by human fibroblasts. Therefore, TSG-6 is a high affinity ligand that can mediate fibronectin interactions with other matrix components and modulate some interactions of fibronectin with cells.     

Characterization of the interaction between tumor necrosis factor-stimulated gene-6 and heparin: implications for the inhibition of plasmin in extracellular matrix microenvironments

TSG-6, the secreted product of tumor necrosis factor-stimulated gene-6, is not constitutively expressed but is up-regulated in various cell-types during inflammatory and inflammation-like processes. The mature protein is comprised largely of contiguous Link and CUB modules, the former binding several matrix components such as hyaluronan (HA) and aggrecan. Here we show that this domain can also associate with the glycosaminoglycan heparin/heparan sulfate. Docking predictions and site-directed mutagenesis demonstrate that this occurs at a site distinct from the HA binding surface and is likely to involve extensive electrostatic contacts. Despite these glycosaminoglycans binding to non-overlapping sites on the Link module, the interaction of heparin can inhibit subsequent binding to HA, and it is possible that this occurs via an allosteric mechanism. We also show that heparin can modify another property of the Link module, i.e. its potentiation of the anti-plasmin activity of inter-alpha-inhibitor (IalphaI). Experiments using the purified components of IalphaI indicate that TSG-6 only binds to the bikunin chain and that this is at a site on the Link module that overlaps the HA binding surface. The association of heparin with the Link module significantly increases the anti-plasmin activity of the TSG-6.IalphaI complex. Changes in plasmin activity have been observed previously at sites of TSG-6 expression, and the results presented here suggest that TSG-6 is likely to contribute to matrix remodeling, at least in part, through down-regulation of the protease network, especially in locations containing heparin/heparan sulfate proteoglycans. The differential effects of HA and heparin on TSG-6 function provide a mechanism for its regulation and functional partitioning in particular tissue microenvironments.     

The inflammation-associated protein TSG-6 cross-links hyaluronan via hyaluronan-induced TSG-6 oligomers

Tumor necrosis factor-stimulated gene-6 (TSG-6) is a hyaluronan (HA)-binding protein that plays important roles in inflammation and ovulation. TSG-6-mediated cross-linking of HA has been proposed as a functional mechanism (e.g. for regulating leukocyte adhesion), but direct evidence for cross-linking is lacking, and we know very little about its impact on HA ultrastructure. Here we used films of polymeric and oligomeric HA chains, end-grafted to a solid support, and a combination of surface-sensitive biophysical techniques to quantify the binding of TSG-6 into HA films and to correlate binding to morphological changes. We find that full-length TSG-6 binds with pronounced positive cooperativity and demonstrate that it can cross-link HA at physiologically relevant concentrations. Our data indicate that cooperative binding of full-length TSG-6 arises from HA-induced protein oligomerization and that the TSG-6 oligomers act as cross-linkers. In contrast, the HA-binding domain of TSG-6 (the Link module) alone binds without positive cooperativity and weaker than the full-length protein. Both the Link module and full-length TSG-6 condensed and rigidified HA films, and the degree of condensation scaled with the affinity between the TSG-6 constructs and HA. We propose that condensation is the result of protein-mediated HA cross-linking. Our findings firmly establish that TSG-6 is a potent HA cross-linking agent and might hence have important implications for the mechanistic understanding of the biological function of TSG-6 (e.g. in inflammation).     

TSG-6 protein, a negative regulator of inflammatory arthritis, forms a ternary complex with murine mast cell tryptases and heparin

TSG-6 (TNF-α-stimulated gene/protein 6), a hyaluronan (HA)-binding protein, has been implicated in the negative regulation of inflammatory tissue destruction. However, little is known about the tissue/cell-specific expression of TSG-6 in inflammatory processes, due to the lack of appropriate reagents for the detection of this protein in vivo. Here, we report on the development of a highly sensitive detection system and its use in cartilage proteoglycan (aggrecan)-induced arthritis, an autoimmune murine model of rheumatoid arthritis. We found significant correlation between serum concentrations of TSG-6 and arthritis severity throughout the disease process, making TSG-6 a better biomarker of inflammation than any of the other arthritis-related cytokines measured in this study. TSG-6 was present in arthritic joint tissue extracts together with the heavy chains of inter-α-inhibitor (IαI). Whereas TSG-6 was broadly detectable in arthritic synovial tissue, the highest level of TSG-6 was co-localized with tryptases in the heparin-containing secretory granules of mast cells. In vitro, TSG-6 formed complexes with the tryptases murine mast cell protease-6 and -7 via either heparin or HA. In vivo TSG-6-tryptase association could also be detected in arthritic joint extracts by co-immunoprecipitation. TSG-6 has been reported to suppress inflammatory tissue destruction by enhancing the serine protease-inhibitory activity of IαI against plasmin. TSG-6 achieves this by transferring heavy chains from IαI to HA, thus liberating the active bikunin subunit of IαI. Because bikunin is also present in mast cell granules, we propose that TSG-6 can promote inhibition of tryptase activity via a mechanism similar to inhibition of plasmin.