Elevated interferon gamma expression in the central nervous system of tumour necrosis factor receptor 1-deficient mice with experimental autoimmune encephalomyelitis

Inflammation in the central nervous system (CNS) can be studied in experimental autoimmune encephalomyelitis (EAE). The proinflammatory cytokines interferon-gamma (IFN-gamma) and tumour necrosis factor (TNF) are implicated in EAE pathogenesis. Signals through the type 1 TNF receptor (TNFR1) are required for severe EAE to develop, whereas deficiency in IFN-gamma or its receptor result in more severe EAE. We investigated IFN-gamma expression in TNFR1-deficient (TNFR1-/-) mice. We describe here that there were more IFN-gamma-secreting T cells present in the CNS of TNFR1-/- mice during EAE compared to wild-type (WT) mice, despite that clinical symptoms were mild, with delayed onset. There was greater expression of IL-12/23p40 by antigen-presenting cells in these mice, and in vitro, TNFR1-/- antigen-presenting cells induced greater secretion of IFN-gamma but not interleukin (IL)-17 when cultured with primed T cells than did WT antigen presenting cells. TNFR1-/- mice with EAE had significantly higher expression of CXCL10 mRNA (but not CCL5 mRNA) in the CNS compared to WT mice with EAE. These data demonstrate that IFN-gamma expression is enhanced in the CNS of TNFR1-/- mice with EAE and suggest that IFN-gamma levels do not necessarily correlate with EAE severity.     

TNF optimally activatives regulatory T cells by inducing TNF receptor superfamily members TNFR2, 4-1BB and OX40

TNF is a pleiotropic cytokine with intriguing biphasic pro-inflammatory and anti-inflammatory effects. Our previous studies demonstrated that TNF up-regulated FoxP3 expression and activated and expanded CD4+ FoxP3+ regulatory T cells (Tregs) via TNFR2. Furthermore, TNFR2-expressing Tregs exhibited maximal suppressive activity. In this study, we show that TNF, in concert with IL-2, preferentially up-regulated mRNA and surface expression of TNFR2, 4-1BB and OX40 on Tregs. Agonistic antibodies against 4-1BB and OX40 also induced the proliferation of suppressive Tregs. Thus, TNF amplifies its stimulatory effect on Tregs by inducing TNF receptor superfamily (TNFRSF) members. In addition, administration of neutralizing anti-TNF Ab blocked LPS-induced expansion of splenic Tregs and up-regulation of TNFR2, OX40 and 4-1BB receptors on Tregs in vivo, indicating that the expansion of Tregs expressing these co-stimulatory TNFRSF members in response to LPS is mediated by TNF. Altogether, our novel data indicate that TNF preferentially up-regulates TNFR2 on Tregs, and this is amplified by the stimulation of 4-1BB and OX40, resulting in the optimal activation of Tregs and augmented attenuation of excessive inflammatory responses.     

Tumour necrosis factor receptor I blockade shows that TNF‐dependent and TNF‐independent mechanisms synergise in TNF receptor associated periodic syndrome

TNF receptor associated periodic syndrome (TRAPS) is an autoinflammatory disease involving recurrent episodes of fever and inflammation. It is associated with autosomal dominant mutations in TNF receptor superfamily 1A gene localised to exons encoding the ectodomain of the p55 TNF receptor, TNF receptor‐1 (TNFR1). The aim of this study was to investigate the role of cell surface TNFR1 in TRAPS, and the contribution of TNF‐dependent and TNF‐independent mechanisms to the production of cytokines. HEK‐293 and SK‐HEP‐1 cell lines were stably transfected with WT or TRAPS‐associated variants of human TNF receptor superfamily 1A gene. An anti‐TNFR1 single domain antibody (dAb), and an anti‐TNFR1 mAb, bound to cell surface WT and variant TNFR1s. In HEK‐293 cells transfected with death domain‐inactivated (R347A) TNFR1, and in SK‐HEP‐1 cells transfected with normal (full‐length) TNFR1, cytokine production stimulated in the absence of exogenous TNF by the presence of certain TNFR1 variants was not inhibited by the anti‐TNFR1 dAb. In SK‐Hep‐1 cells, specific TRAPS mutations increased the level of cytokine response to TNF, compared to WT, and this augmented cytokine production was suppressed by the anti‐TNFR1 dAb. Thus, TRAPS‐associated variants of TNFR1 enhance cytokine production by a TNF‐independent mechanism and by sensitising cells to a TNF‐dependent stimulation. The TNF‐dependent mechanism requires cell surface expression of TNFR1, as this is blocked by TNFR1‐specific dAb.     

TGF-beta1 and IFN-gamma stimulate mouse macrophages to express BAFF via different signaling pathways

B cell-activating factor belonging to the TNF family (BAFF) is primarily expressed by macrophages and dendritic cells and stimulates the proliferation, differentiation, and survival of B cells and their Ig production. In the present study, we examined the pathways by which TGF-beta1 and IFN-gamma induce BAFF expression to see if TGF-beta1 and IFN-gamma regulate B cell differentiation via macrophages. We found that TGF-beta1 stimulated mouse macrophages to express BAFF and that a typical TGF-beta signaling pathway was involved. Thus, Smad3 and Smad4 promoted BAFF promoter activity, and Smad7 inhibited it, and the BAFF promoter was shown to contain three Smad-binding elements. Importantly, TGF-beta1 enhanced the expression of membrane-bound and soluble forms of BAFF. IFN-gamma further augmented TGF-beta1-induced BAFF expression. IFN-gamma caused phosphorylation of CREB, and overexpression of CREB increased IFN-gamma-induced BAFF promoter activity. Furthermore, H89, a protein kinase A (PKA) inhibitor, abrogated the promoter activity. Neither Stat1alpha (a well-known transducing molecule of IFN-gamma) nor AG490 (a JAK inhibitor) affected BAFF expression in response to IFN-gamma. Taken together, these results demonstrate that TGF-beta1 and IFN-gamma up-regulate BAFF expression through independent mechanisms, i.e., mainly Smad3/4 and PKA/CREB, respectively.     

Contribution of TNF-alpha converting enzyme and proteinase-3 to TNF-alpha processing in human alveolar macrophages

Membrane-associated TNF-alpha cleavage is required to yield the 17.5-kD soluble product. This process is poorly understood in human cells, and no studies have related this process to the alveolar macrophage (AM). TNF-alpha-converting enzyme (TACE) is known to cleave TNF at the Ala-76-Val-77 site. We have evaluated the expression, regulation, and catalytic function of TACE in healthy human AMs. TACE was detected on the surface of AMs using flow cytometry. TACE protein can be upregulated by LPS (P = 0.036) and IFN-gamma. LPS-induced expression is downregulated by IL-10 (P = 0.04) and TNF-alpha. TACE regulation was observed at the mRNA level. TACE catalytic activity as assessed by cleavage of glutathione S-transferase-proTNF fusion protein correlates significantly with TACE protein expression (P = 0.04). However, cleavage and soluble TNF-alpha release by AMs was inhibited by matrix metalloproteinase and serine protease inhibitors, suggesting a role for a serine protease in this process. We confirmed the presence of proteinase-3 (PR-3) on the AM surface that was functionally capable of TNF cleavage. PR-3 mRNA expression was not found in AMs. However, we determined that PR-3 from neutrophil supernatants could bind to the AM membrane, suggesting that AM-derived PR-3 is from an exogenous source, which is important in the context of inflammation.     

Collagen-induced arthritis in TNF receptor-1-deficient mice: TNF receptor-2 can modulate arthritis in the absence of TNF receptor-1

TNF is a potent proinflammatory cytokine important for the development of arthritis in human and animals. We have investigated the roles of TNF receptor-1 (TNFR1) and TNF receptor-2 (TNFR2) in collagen-induced arthritis (CIA) by inducing CIA in mice genetically deficient in TNFR1. TNFR1-/- mice developed arthritis with similar incidence and severity as TNFR1+/- littermates, indicating that TNFR1 is redundant for the development of CIA. Anti-type II collagen (CII) antibody levels and T cell responses to CII did not differ between TNFR1-/- mice and controls. Neutralization of TNF with soluble TNF binding protein suppressed the development of arthritis in TNFR1+/- mice but not in TNFR1-/- mice, indicating that TNFR2 cannot substitute for TNFR1 for the proinflammatory function. To further investigate the functions of TNFR2, TNFR1-/- mice were injected with murine TNF-alpha at different stages during the course of CIA. Repeated TNF-alpha injection during the early induction phase enhanced the development of arthritis, but inhibited arthritis when administered during the late progression phase. These results show that the engagement of TNFR2 by TNF is involved in the development of CIA in the absence of TNFR1 and that opposing signals can be transduced by TNFR2.     

人可溶性TNF受体(sTNFRI)在大肠杆菌中的表达及其活性鉴定

目的 :构建人可溶性TNF受体I(sTNFRI)基因表达载体 ,并在大肠杆菌中高效表达。方法 :用RT PCR扩增编码人TNFRI胞外段基因片段 ,将其插入到表达载体pET 2 8a ,并转入大肠杆菌进行表达。结果 :在IPTG诱导下 ,转入外源基因的大肠杆菌BL 2 1可高效表达sTNFRI蛋白 ,SDS PAGE显示在 2 7kD处有一特异表达条带 ,其表达量占菌体蛋白总量的 31%。纯化的sTNFRI可有效封闭TNF对L92 9细胞的胞毒效应 ;间接免疫荧光显示它可特异性抑制TNF与靶细胞TNFR的结合。结论 :通过基因工程技术获得了人sTNFRI重组蛋白。     

组胺对皮肤肿瘤坏死因子受体分布的影响的实验研究

目的　探讨人皮肤角质细胞TNFR的分布和炎症介质组胺对其分布的影响。方法　依据Tel lides成熟实验模型 ,将人皮肤移植于免疫缺陷小鼠上 ,分别注入等量 10ml组胺或生理盐水 ,然后制成共聚焦荧光显微镜和电镜标本观察。结果　正常皮肤TNFR2阳性反应细胞较少 ,TNFR1阴性细胞数量较多 ,阳性反应主要见于角质细胞的胞质和膜 ;组胺刺激后角质细胞质和膜的TNFR1消失 ,主要分布在角质细胞间隙。结论　组胺可使角质细胞质和膜上TNFR1消失 ,移位于细胞间隙     

Immunology: High concentrations of the soluble p55 tumour necrosis factor receptor in human seminal plasma

Soluble TNFRs (tumour necrosis factor receptors) inhibit in-vivoand in-vitro bioactivities of TNF, and thus the secretion ofsoluble TNFRs could be a physiological principle to attenuatethe bioactivities of TNF. Two types of TNFR have been identifiedand both forms can be released from cells. In this study, solubleTNFRs in seminal plasma from three groups of men were analysed:from men with normal semen quality (n = 32), with reduced semenquality (n = 7) and vasectomized men (n = 3). Sensitive andspecific enzyme-linked immunosorbent assays were utilized todetect soluble TNFRs in seminal plasma, based on capture antibodiesdirected against non-TNF-binding sites of the TNFRs and digoxigenin(DIG)-labelled TNF. The mean ± standard deviation levelsof p55 TNFR were 56.4 ± 20, 64.4 ± 17 and 45.4± 5 ng/ml in the three groups, respectively. The concentrationof p75 TNFR was < 1 ng/ml in all groups. The results suggestan exclusive existence of high amounts of the soluble p55 TNFRin seminal plasma. Seminal plasma from vasectomized men containedp55 TNFR at approximately the same levels as the specimen fromthe two other groups, indicating that the source of p55 TNFRis not the testis but rather some tissue more distal in themale genital tract, such as the prostate or the seminal vesicles.The soluble p55 TNFR was purified from human seminal plasma,using affinity and gel filtration chromatography. Further characterizationof the purified p55 revealed a protein with a molecular weightof –22 kDa, both under reducing and non-reducing conditions.Probably due to the elongated structure of p55 TNFR, the moleculebehaved as a larger protein (50 kDa) by gel filtration chromatography.The isolated TNFR inhibited TNF cytotoxicity in vitro.     

Thalidomide and its analogues have distinct and opposing effects on TNF-alpha and TNFR2 during co-stimulation of both CD4(+) and CD8(+) T cells

Thalidomide (Thd) is clinically useful in a number of conditions where its efficacy is probably related to its anti-TNF-alpha activity. More recently, Thd has also been shown to co-stimulate T cells and second generation co-stimulatory (IMiD trade mark ) analogues are currently being assessed in the treatment of cancer patients. However, in contrast to their known suppressive effects during inflammatory stimuli, the effects of Thd/IMiDs on TNF-alpha and TNF receptors (TNFRs) during T cell co-stimulation are not known. We sought to determine the effect of Thd, two clinically relevant IMiDs (CC-4047, ACTIMID trade mark and CC-5013, REVIMID trade mark ) and a non-stimulatory SelCID analogue (CC-3052) on TNF-alpha production and on the expression and shedding of TNFRs during co-stimulation. We found that co-stimulation of PBMC with Thd/IMiDs, but not CC-3052, prevented alphaCD3-induced T cell surface expression of TNFR2 and thereby reduced soluble TNFR2 (sTNFR2) levels. However, there was no effect on total (surface/intracellular) TNFR2 protein expression, suggesting inhibition of trafficking to the cell membrane. The extent of co-stimulation by Thd/IMiDs (assessed by CD69/CD25 expression and IL-2/sIL-2Ralpha production) was similar for CD4+ and CD8+ T lymphocytes and correlated with TNFR2 inhibition. Co-stimulation, but not the early inhibitory effect on TNFR2, was IL-2-dependent and led to increased TNF-alpha production by both CD4+ and CD8+ T lymphocytes. The clinical relevance of this observation was confirmed by the elevation of serum TNF-alpha during REVIMID trade mark treatment of patients with advanced cancer. Together, these results suggest a possible role for TNF-mediated events during co-stimulation and contrast with the TNF inhibitory effects of Thd and its analogues during inflammatory stimuli.     

PKA信号通路参与调控肝细胞cAMP反应元件结合蛋白与PGC-1α的表达

目的观察蛋白激酶A(PKA)信号通路对培养的肝细胞环腺苷酸(cAMP)反应元件结合蛋白(CREB)磷酸化及过氧化物酶增殖激活受体协同激活因子α(PGC-1α)表达的调控作用。方法利用PKA抑制剂H89和cAMP激动剂Forskolin预处理原代培养的大鼠肝脏细胞,以Western blot和逆转录聚合酶链反应(RT-PCR)方法测定不同处理组CREB/P-CREB蛋白及PGC-1αmRNA的表达变化。结果以Forskolin作用的肝细胞,与对照组相比,CREB蛋白的磷酸化和PGC-1αmRNA的表达水平明显增高;预先加入PKA抑制剂H89,再加入Forskolin作用细胞,则CREB蛋白磷酸化和PGC-1αmRNA表达受到明显抑制(P<0.01),差异有统计学意义。结论 PKA信号通路参与调控肝细胞CREB的磷酸化和PGC-1α的表达,可能与糖代谢的调节有关。     

Involvement of Salmonella pathogenicity island 2 in the up-regulation of interleukin-10 expression in macrophages: role of protein kinase A signal pathway

Salmonellae are facultative intracellular bacteria capable of surviving within macrophages. Salmonella pathogenicity island 2 (SPI-2) is required for growth within macrophages and for virulence in mice. In this study, we show the involvement of SPI-2 in a signal transduction pathway that induces cytokine expression in Salmonella-infected macrophages. High levels of interleukin-10 (IL-10) mRNA were induced in macrophages by infection with wild-type salmonellae compared to a strain carrying a mutation in the spiC gene, which is encoded within SPI-2. The two strains had the same effect on the expression of proinflammatory cytokines such as IL-1 alpha, IL-6, and tumor necrosis factor alpha. IL-10 expression was dose dependently blocked by treatment of infected macrophages with the protein kinase A (PKA) inhibitor H-89, while IL-10 expression was increased by the PKA activator dibutyryl cyclic AMP. Cyclic AMP-dependent PKA activity was higher in macrophages infected with wild-type salmonellae compared to the spiC mutant, and Ser(132) phosphorylation of cyclic AMP response element-binding protein (CREB), which is an important mediator of PKA activation, correlated with the levels of PKA activity. Taken together, these results indicate that salmonellae cause an SPI-2-dependent increase in PKA activity that leads to CREB phosphorylation, resulting in up-regulation of IL-10 expression in Salmonella-infected macrophages. Suppression of IL-10 expression by an antisense oligonucleotide did not affect the growth of wild-type salmonellae within macrophages, whereas growth was dose dependently inhibited by H-89, suggesting that the PKA signaling pathway plays a significant role in intramacrophage Salmonella survival.     

TNF-induced enterocyte apoptosis in mice is mediated by the TNF receptor 1 and does not require p53

Injection of recombinant mouse TNF into mice is known to induce a shrinkage of the duodenal villi, which becomes evident 30 – 90 min later and is associated with a detachment of enterocytes in the lumen. These cells can be collected by lavage and are all apoptotic, i.e. hypodiploid as seen by flow cytometric analysis. Thus the count of detached cells was used as an evaluation of the TNF-induced cell loss and apoptosis in the mucosa. TNF injection induced a cell loss of similar magnitude in wild-type (+/+) or in mice lacking the TNF receptor (TNFR)2 (p75, TNFR2 −/−), while mice lacking the TNFR1 (p55, TNFR1 −/−) were completely resistant to this effect. TNF increased the expression of p53 tumor suppressor gene in the enterocytes from the crypts but not from the villi, as seen by Western blots and histochemistry. TNF increased the expression of p53 in both TNFR2 −/− and TNFR1 −/− mice. Furthermore, enterocyte cell loss was not attenuated in p53 −/− mice. The results indicate that TNF, acting on its receptor 1, induces an apoptotic detachment of the enterocytes from the tip of the villi ( i.e. the old enterocytes), while in the enterocytes from the crypts (the young enterocytes) TNF increases, via either TNFR1 or TNFR2, the expression of p53, without inducing apoptosis.