Deficient expression of tumor necrosis factor receptor type 2 in the endometrium of women with endometriosis

PROBLEM: Tumor necrosis factor-alpha (TNF-alpha) is secreted mainly during the menstrual phase and has been suggested to play a role in induction of apoptosis in endometrial cells and menstrual shedding. TNF-alpha receptor type 2 (TNF-RII) is believed to play a central role in TNFalpha-mediated cytotoxic, mitogenic, anti-proliferative and apoptotic effects. The aim of this study was to assess whether TNF-RII maybe expressed differentially in the endometrium of women with different degrees of endometriosis. METHOD OF STUDY: TNF-RII expression in the endometrial tissue of women with and without endometriosis was investigated by immunohistochemical techniques and in situ hybridization. RESULTS: In histological sections, we observed TNF-RII mRNA and the corresponding protein localized mainly in endometrial glandular cells, with only very faint immunostaining in the surrounding stromal cells. Statistical analysis of our data showed a significant decrease in protein and mRNA expression of TNF-RII in endometrial glandular cells of patients with stages I and II endometriosis compared to normal subjects. TNF-RII expression was also found to decrease significantly in the secretory phase of the menstrual cycle in women with early endometriosis stages (I and II). CONCLUSIONS: In view of the relevant role of TNF-RII in the modulation of the inflammatory and the proapoptotic effects of TNFalpha, deficient expression of TNF-RII mRNA in the endometrium of women at the earliest stages of endometriosis may play a significant role in the pathophysiology of this disease.     

The pathogenic roles of tumor necrosis factor receptor p55 in acetaminophen-induced liver injury in mice

Acetaminophen (APAP) causes a massive production of intrahepatic tumor necrosis factor alpha (TNF-alpha). However, it still remains elusive regarding the roles of TNF-alpha in APAP-induced liver injury. Hence, we examined pathogenic roles of the TNF-alpha-TNF receptor with a molecular weight of 55 kDa (TNF-Rp55) axis in APAP-induced hepatotoxicity using TNF-Rp55-deficient [TNF-Rp55-knockout (KO)] mice. When wild-type (WT) BALB/c and TNF-Rp55-KO mice were intraperitoneally injected with a lethal dose of APAP (750 mg/kg), the mortality of TNF-Rp55-KO mice was marginally but significantly reduced compared with WT mice. Upon treatment with a nonlethal dose (600 mg/kg), WT mice exhibited an increase in serum transaminase levels. Histopathologically, centrilobular hepatic necrosis with leukocyte infiltration was evident at 10 and 24 h after APAP challenge. Moreover, mRNA expression of adhesion molecules, several chemokines, interferon-gamma (IFN-gamma), and inducible nitric oxide synthase (iNOS) was enhanced in the liver. On the contrary, serum transaminase elevation and histopathological changes were attenuated in TNF-Rp55-KO mice injected with APAP (600 mg/kg). The gene expression of all molecules except for IFN-gamma and iNOS was significantly attenuated in TNF-Rp55-KO mice. Moreover, anti-TNF-alpha neutralizing antibodies alleviated liver injury when administered at 2 or 8 h after but not at 1 h before APAP challenge to WT mice. Collectively, the TNF-alpha-TNF-Rp55 axis has pathogenic roles in APAP-induced liver failure.     

Role of tumor necrosis factor alpha in Helicobacter pylori gastritis in tumor necrosis factor receptor 1-deficient mice

Increased gastric production of interleukin 8 and tumor necrosis factor alpha (TNF-alpha) has been implicated in the pathogenesis of Helicobacter pylori-associated gastroduodenal disease. In the present study we used a mouse model to demonstrate whether loss of the tumor necrosis factor receptor 1 (TNF-R1) function leads to differences in gastric inflammation or the systemic immune response in H. pylori infection. Six different clinical isolates of H. pylori (three cytotoxin-positive and three cytotoxin-negative strains) were adapted to C57BL/6 mice. TNF-R1-deficient (TNF-R1(-/-)) mice (n = 19) and isogenetic controls (n = 24) were infected and sacrificed after 4 weeks of infection. Inflammation of the stomach and the humoral immune response to H. pylori were evaluated by histological, immunohistochemical, and serological methods. There was no detectable difference in the grade or activity of gastritis in TNF-R1(-/-) mice when they were compared with wild-type mice, but the number of lymphoid aggregates was slightly reduced in the gastric mucosa of TNF-R1(-/-) mice. Interestingly, total immunoglobulin G (IgG), as well as IgG1, IgG2b, and IgG3, H. pylori-specific antibody titers were significantly higher in wild-type mice. As revealed by immunoblot analysis, the difference in reactivity against H. pylori antigens was not based on a failure to recognize single H. pylori antigens in TNF-R1(-/-) mice. We therefore suggest that TNF-R1-mediated TNF-alpha signals might support a systemic humoral immune response against H. pylori and that the gastric inflammatory response to H. pylori infection seems to be independent of TNF-R1-mediated signals.     

Tumor necrosis factor induces tumor necrosis via tumor necrosis factor receptor type 1-expressing endothelial cells of the tumor vasculature

Activation of endothelial cells, fibrin deposition, and coagulation within the tumor vasculature has been shown in vivo to correlate with the occurrence of tumor necrosis factor (TNF)-induced tumor necrosis in mice. In the present study we investigated which target cells mediate the TNF-induced necrosis in fibrosarcomas grown in wild type (wt), TNF receptor type 1-deficient (TNFRp55-/-), and TNF receptor type 2-deficient (TNFRp75-/-) mice. TNF administration resulted in tumor necrosis exclusively in wt and TNFRp75-/-, but not in TNFRp55-/- mice, indicating a dependence of TNF-mediated tumor necrosis on the expression of TNF receptor type 1. However, using wt and TNFRp55-/- fibrosarcomas in wt mice, we found that TNF-mediated tumor necrosis was completely independent of TNF receptor type 1 expression in tumor cells. Thus we could exclude any direct tumoricidal effect of TNF in this model. Soluble TNF induced leukostasis in wt and TNFRp75-/- mice but not in TNFRp55-/- mice. TNF-induced leukostasis in TNFRp55-/- mice was restored by adoptive bone marrow transplantation of wt hematopoietic cells, but TNF failed to induce tumor necrosis in these chimeric mice. Because TNF administration resulted in both activation and focal damage of tumor endothelium, TNF receptor type 1-expressing cells of the tumor vasculature, likely to be endothelial cells, appear to be target cells for mediating TNF-induced tumor necrosis.     

Acute tumor necrosis factor-alpha-induced liver injury in the absence of tumor necrosis factor receptor-associated factor 1 gene expression

Pulmonary and serum levels of tumor necrosis factor-alpha (TNF-alpha), are elevated in many lung diseases, causing local inflammation, fever, and multiorgan, including hepatic, dysfunction. Cellular responses to TNF-alpha are determined by recruitment of specific proteins to intracellular receptor signaling complexes. One of these proteins, TNF receptor-associated factor 1 (TRAF1), is highly regulated in pulmonary cells. To determine the effect of reduced pulmonary TRAF1 expression, TRAF1-null (-/-) and control, BALB/c (wild-type), mice were treated intratracheally, intraperitoneally, or intravenously, with TNF-alpha. Despite relatively mild lung injury, intratracheal TNF-alpha-treated TRAF1-/- mice exhibited marked liver injury with an approximate fivefold increase in serum liver enzyme levels as compared to wild-type mice. In addition, serum TNF-alpha levels were strikingly elevated in TRAF1-/- mice. Pretreatment with neutralizing anti-TNFRI antibody significantly reduced liver injury and serum TNF-alpha. Cells isolated by bronchoalveolar lavage from intratracheally treated TRAF1-/- mice produced more TNF-alpha than cells from treated wild-type mice, suggesting that lung cells contributed to elevated serum TNF-alpha. These studies suggest that TRAF1 provides negative feedback for TNF-alpha synthesis and limits TNFRI-mediated systemic effects of TNF-alpha originating in the lung.     

Enhanced tumor development in mice lacking a functional type I interferon receptor.

The aim of this study was to investigate the contribution of endogenous - that is, without the addition of any interferon (IFN) inducer - type I IFN production in the defense against tumor development. To this purpose, the IFN-alpha receptor (IFNAR) knockout (KO)-induced mutation, resulting in the complete absence of IFN-alpha/beta activity, was introduced into a C3H genetic background by 10 backcross generations, followed by brother-sister matings for at least four generations. The resulting mice were inoculated either with syngeneic C3H melanoma K1735 cells, with allogeneic 3LL carcinoma cells, or with allogeneic B16F10 melanoma cells. With all three tumor cell lines, tumor development and ensuing mortality were enhanced in the IFNAR KO animals. This indicates that endogenous IFN-alpha/beta production is a mediator of natural immunity to tumor development.     

Autoimmune kidney disease and lymphadenopathy in NODlpr mice are not modified by deficiency in tumor necrosis factor receptor 1 or beta 2-microglobulin

Fas and TNFRI, two members of the tumor necrosis factor receptor family with an intracellular death domain, each play critical roles in apoptotic death of lymphocytes and certain other cell types. We determined the overlapping functions of Fas and TNFRI by breeding non-obese diabetic (NOD) mutant mice that lacked both receptors. NODlpr mice developed extensive lymphadenopathy, splenomegaly, CD4(-)CD8(-) B220(+) alpha beta TCR(+) T cells and autoimmune kidney disease. This pathology was not modified by concomitant deficiency in TNFRI as was reported for lpr mice on a B6 background. NODlpr mice lacking CD8(+) T cells, because of a null mutation in beta(2)-microglobulin (beta(2)m), also developed a similar disease profile to NODlpr animals, but the CD4(-)CD8(-) B220(+) alpha beta TCR(+) T cells now derived from a CD4(+) T cell lineage. These results demonstrate that, as in the autoimmune-prone MRL stain, the NOD genetic background promotes lupus nephritis-like pathology and extensive lymphadenopathy when lpr is present. Loss of TNFRI does not exacerbate the pathology caused by deficiency in Fas and loss of beta(2)m does not reduce it.     

含硒藻蓝蛋白抗小鼠实验性肝损伤的作用

目的:观察含硒藻蓝蛋白(Se-SPC)对四氯化碳(CCl₄)致小鼠急性肝损伤的拮抗作用。方法:以2%CCl₄油灌胃复制小鼠急性肝损伤模型,各组分别腹腔注射Se-SPC、藻蓝蛋白(SPC)、无机硒(Se)7d,测定血及肝组织中Se、谷胱甘肽过氧化物酶(GPx)、超氧化物歧化酶(SOD)、丙二醛(MDA)、谷丙转氨酶(ALT)、一氧化氮(NO)水平,分析Se-SPC、SPC、无机Se对上述指标的影响。结果:Se-SPC组比CCl₄组血和肝中Se、GPx、SOD水平显著增高(P<0.05),血ALT、血和肝中MDA及NO₂^-/NO₃^-水平显著降低(P＜0.05),高剂量Se-SPC组对Se含量、GPx、MDA、NO₂^-/NO₃^-等指标的影响更为显著(P＜0.01),在相同蛋白或硒剂量下,Se-SPC组比SPC组和无机Se组对上述指标作用更大。相关分析发现小鼠血Se水平与GPx活性呈显著正相关(r=0.705),血GPx活性与MDA、NO₂^-/NO₃^-、ALT水平呈明显负相关(r=－0.629,r=－0.336,r=－0.457),血ALT活性与MDA及NO₂^-/NO₃^-呈显著正相关(r=0.519,r=0.641)。结论:Se-SP可能结合增高硒酶活性及抗炎双重功效,对CCl₄致小鼠肝脏的氧化损伤具有拮抗作用。     

Interferon-gamma receptor-mediated but not tumor necrosis factor receptor type 1- or type 2-mediated signaling is crucial for the activation of cerebral blood vessel endothelial cells and microglia in murine Toxoplasma encephalitis.

The regulatory role of interferon-gamma receptor (IFN-gammaR)- and tumor necrosis factor receptor (TNFR)-mediated immune reactions for the activation of cerebral endothelial cells, microglia, and astrocytes was evaluated in a model of murine Toxoplasma encephalitis (TE). Brain endothelial cells of wild-type mice reacted in response to Toxoplasma infection with a strong up-regulation of the vascular cell adhesion molecule, the intercellular adhesion molecule (ICAM)-1, and major histocompatibility complex (MHC) class I and II antigens. A similar response was seen in mice genetically deficient for either TNFR1, TNFR2, or both TNFRs, whereas IFN-gammaR-deficient (IFN-gammaR0/0) mice were found to be defective in the up-regulation of these molecules. However, recruitment of leukocytes to the brain and their intracerebral movement were not impaired in IFN-gammaR0/0 mice. In addition, microglia of Toxoplasma gondii-infected IFN-gammaR0/0 mice failed to induce expression of ICAM-1, leukocyte function-associated antigen (LFA)-1, and MHC class I and II antigens, whereas wild-type and TNFR-deficient mice up-regulated these molecules. Moreover, TNF-alpha mRNA production of F4/80(+) microglia/macrophages was impaired in IFN-gammaR0/0 mice, but not in TNFR-deficient mutants. However, induction of interleukin (IL)-1beta, IL-10, IL-12p40, and IL-15 mRNA was independent of IFN-gammaR and TNFR signaling. In conclusion, IFN-gammaR, but not TNFR signaling, is the major pathway for the activation of endothelial cells and microglia in murine TE. These findings differ from observations in other inflammatory central nervous system disorders, indicating specific regulatory mechanisms in this parasitic cerebral infection.     

Lymphotoxin but not tumor necrosis factor functions to maintain splenic architecture and humoral responsiveness in adult mice

To compare the function of the tumor necrosis factor (TNF) and lymphotoxin (LT)α/β systems in the mature immune system, these two pathways were blocked with soluble receptor-immunoglobulin (R-Ig) fusion proteins in normal adult mice. Inhibition of LTα/β signaling using LTβR-Ig or a blocking monoclonal antibody against murine LTβ had profound effects. The spleen lacked discrete B cell follicles and the marginal zone was altered. Less marked changes were detected in lymph nodes. LTα/β inhibition also prevented germinal center formation in the spleen and impaired Ig production in response to sheep red blood cells (SRBC) immunization. These results show that the LTα/β system is required for the maintenance of splenic architecture and normal immune responses, and not simply for the development of peripheral immune organs during ontogeny. In contrast, inhibition of the TNF/LTα pathway with TNF-R55-Ig did not affect the splenic architecture or the anti-SRBC response. Splenic defects and impaired antibody responses are seen in TNF-deficient mice, suggesting that TNF is important during development. Therefore relative to TNF, the LT system has the dominant influence on splenic organization and anti-SRBC Ig formation in the adult mouse.     

The death domain of tumor necrosis factor receptor 1 is necessary but not sufficient for Golgi retention of the receptor and mediates receptor desensitization

TNF signals are mediated through two different receptors, TNFR1 and TNFR2. In endothelial cells, TNFR1 is predominantly localized in the Golgi apparatus and TNFR2 on the plasma membrane. To investigate structural features responsible for the disparate localization, endothelial cells were transfected with epitope-tagged or green fluorescent protein-fused wild type and mutant receptor molecules. Wild type receptors recapitulated the distribution of endogenous receptors. Deletions of the entire TNFR1 intracellular domain or of the C-terminal death domain (TNFR1(-DD)) allowed expression of the receptor on the plasma membrane. However, addition of the death domain to the C-terminus of TNFR2 (TNFR2(+DD)) did not lead to Golgi-retention of this chimeric receptor. Overexpressed TNFR1, TNFR2, and TNFR2(+DD) increased basal expression of a cotransfected NF-kappaB-dependent promotor-reporter gene. Overexpressed TNFR1(-DD) did not activate NF-kappaB but acted as a ligand-specific dominant negative inhibitor of TNF actions. Unexpectedly, TNF responses were also inhibited by overexpressed TNFR1 and TNFR2(+DD), but not TNFR2. We conclude that the death domain of TNFR1 is required for retention of TNFR1 in the Golgi apparatus but is not sufficient to direct Golgi retention of a TNFR2(+DD) chimera, and that overexpressed receptors that contain the death domain (TNFR1 and TNFR2(+DD)) spontaneously activate NF-kappaB while inhibiting TNF responses.     

Mycobacteria lacking the RD1 region do not induce necrosis in the lungs of mice lacking interferon-gamma

The genetic region of difference 1 (RD1) in Mycobacterium tuberculosis has recently been hypothesized to encode for proteins that are cytotoxic to the host cell in nature. We demonstrate here that while M. tuberculosis grew progressively in the lungs of gene disrupted mice (GKO) unable to produce interferon-gamma (IFN-gamma), similar mice infected instead with M. bovis bacillus Calmette-Guérin (BCG) reproducibly exhibited an obvious slowing of the disease after about 20 days. Closer examination of BCG-infected GKO mice showed a florid granulomatous inflammation in the lungs, whereas similar mice infected with M. tuberculosis exhibited wholesale progressive necrosis. In the BCG-infected GKO mice large numbers of activated effector T cells, some strongly positive for the cytokine tumour necrosis factor, as well as activated natural killer cells accumulated in the lungs. To further test the hypothesis that the differences observed were directly associated with the loss of the RD1 region, it was then shown that a mutant of M. tuberculosis lacking RD1 grew progressively in both normal and GKO mice but failed to induce any degree of necrosis in either animal despite reaching similar levels in the lungs. However, when mice were infected with this mutant, in which the RD1 region had been restored by complementation, wholesale necrosis of the lungs again occurred. These data support the hypothesis that proteins encoded in the RD1 region are a major cause of necrosis and contribute significantly to the pathogenesis of the disease.     

Recombinant soluble tumor necrosis factor receptor proteins protect mice from lipopolysaccharide-induced lethality.

The in vivo efficacy of human recombinant soluble tumor necrosis factor (TNF) receptor protein to prevent and to treat lipopolysaccharide (LPS)-induced lethal toxicity in D-galactosamine-treated mice was investigated. Chimeric proteins of the receptor extracellular domains fused to the hinge region of human IgG3 were expressed in myeloma cells (rsTNFR-h gamma 3). The fusion proteins had a disulfide-bonded dimeric structure. Upon intravenous injection, their serum concentration decreased relatively slowly after an initial phase of rapid elimination. D-galactosamine-sensitized mice were fully protected from the toxic effects of LPS, if the animal were pretreated with rsTNFR-h gamma 3 at 20 micrograms/animal. Partial protection was seen at significantly lower doses and when rsTNFR-h gamma 3 was given up to 3 h after LPS.     

Role of the tumor necrosis factor receptor 2 (TNFR2) in cerebral malaria in mice

Infection of susceptible mice with Plasmodium berghei Anka leads to a syndrome of severe or cerebral malaria. Tumor necrosis factor (TNF) contributes to this syndrome, apparently by acting on its receptor 2 (TNFR2) because TNFR1-/- are susceptible, whereas TNFR2-/- mice are resistant. In this work, we confirmed the essential role of the TNFR2 in cerebral malaria because 6 to 8 days after Plasmodium berghei Anka infection, hypothermia, coma, and death were observed in +/+ or TNFR1-/-, but never in TNFR2-/-, mice. TNF production, evaluated by the serum levels or the mRNA levels in the brain, spleen or lung, was similar in +/+, TNFR1-/-, or TNFR2-/- mice. Macrophage or parasitized red blood cell sequestration in brain or lung was similar in TNFR1-/- and TNFR2-/- mice. Accordingly, up-regulation of CD54 or CD40 in brain or lung was also similar in TNFR1-/- or TNFR2-/- mice. Platelet loss, manifested by thrombocytopenia and the presence of microparticles in plasma, was similar in TNFR1-/- or TNFR2-/- mice. Breakdown of the blood-brain barrier, detected by the diffusion of tracers, was attenuated in both TNFR1-/- and TNFR2-/-, compared with +/+, mice. Endothelial cells from brain capillaries, examined by transmission electron microscopy, were similar in infected TNFR1-/- or TNFR2-/- mice, whereas the basement membrane was enlarged in TNFR1-/- mice. Hypothermic mice were also hyperglycemic, and this was evident in +/+ and TNFR1-/-, but not in TNFR2-/-, mice. In addition, infected +/+ and TNFR1-/- mice became insulin resistant, while in contrast TNFR2-/- became extremely insulin sensitive. This study supports the possibility that coma and death are mediated not by cell sequestration or breakdown of vascular permeability, similar in TNFR1-/- or TNFR2-/- mice, but by metabolic disturbances selectively mediated by the TNFR2.     

Production of interleukin-1 but not tumor necrosis factor by human monocytes stimulated with pneumococcal cell surface components.

While there is considerable evidence that both interleukin-1 (IL-1) and tumor necrosis factor (TNF) are central mediators of inflammation caused by gram-negative bacteria and endotoxin, the roles of these two mediators in gram-positive infection are unknown. Pneumococcal infections are characterized by an intense inflammatory reaction in infected tissues. Current evidence suggests that the component of the pneumococcus which causes this inflammation in many body sites is the cell wall. We determined the ability of native pneumococcal cell wall, lipoteichoic acid, and cell wall subcomponents to stimulate secretion of IL-1 and TNF from human monocytes. Each pneumococcal cell surface component was found to have a different specific activity for induction of IL-1. Teichoication was an important determinant of this activity: teichoicated species were at least 10,000-fold more potent than endotoxin and 100-fold more potent than teichoic acid-free peptidoglycan. IL-1-inducing activity was greatly reduced by chemical alteration of the teichoic acid. In contrast to endotoxin, cell wall did not induce production of TNF. This dissociation of the production of IL-1 and TNF during the response of the human monocyte to pneumococcal surface components suggests that, in at least some circumstances, the mechanisms for generation of an inflammatory response to infection may be fundamentally different between gram-positive and gram-negative disease.     

Liver regeneration by small hepatocyte-like progenitor cells after necrotic injury by carbon tetrachloride in retrorsine-exposed rats

Liver regeneration after partial hepatectomy (PH) in rats exposed to the pyrrolizidine alkaloid retrorsine is accomplished through the proliferation and differentiation of a population of small hepatocyte-like progenitor cells (SHPCs). The activation, emergence, and outgrowth of SHPCs in response to the liver deficit generated through surgical PH have been well characterized. However, the participation of these cells in the restoration of hepatocyte numbers and regeneration of liver tissue mass following necrotic injury has not been investigated. To investigate the capacity of SHPCs to respond to necrotizing liver injury, we combined retrorsine treatment with the centrilobular-specific toxin carbon tetrachloride (CCl₄). Male Fischer 344 rats were treated with retrorsine (30 mg/kg ip) at 6 and 8 weeks of age, followed by CCl₄ treatment (1500 mg/kg ip) 5 weeks later. Liver tissues were harvested at 3, 7, 14, 21, and 30-days post-injection. The dose of CCl₄ employed resulted in the necrotic destruction of 59 ± 2% of liver mass and elicited a regenerative response equivalent to that of surgical PH. Livers from retrorsine-exposed CCl₄-treated rats exhibit SHPC proliferation similar to retrorsine-exposed rats subjected to PH (RP). SHPCs appear at 3-days post-injection, continue to expand at 7-days and 14-days post-injection, and completely regenerate/restore the liver mass and structure in these animals by 30-days post-injection. The magnitude of SHPC response observed in the undamaged periportal zone of the liver in these animals is unaffected (versus RP rats) by the loss of the centrilobular region. The results of this study show that SHPCs are capable of regenerating liver after exposure to necrotizing agents and suggest that the progenitor cell of origin of the SHPCs is not restricted to the centrilobular zone of the liver parenchyma.     

The type I interleukin-1 receptor acts in series with tumor necrosis factor (TNF) to induce arthritis in TNF-transgenic mice

The pro-inflammatory cytokines tumor necrosis factor (TNF) and interleukin-1 (IL-1) have been shown to be primary mediators in the pathogenesis of chronic inflammatory joint diseases. However, the relative contributions of these molecules to the development and progression of disease is not known. In the present study, we have investigated the involvement of the type I IL-1 receptor in the development and progression of chronic arthritis in a previously described TNF-transgenic mouse model of this disease. A neutralizing monoclonal antibody to the murine type I IL-1 receptor was injected intraperitoneally three times a week from birth to 9 weeks of age. In the positive control group of untreated transgenic mice the incidence of arthritis was 100% after 9 weeks of age. The injection of normal hamster IgG did not influence the incidence or development of arthritis. In contrast, the injection of antibody to the type I IL-1 receptor completely prevented the development of arthritis. Clinical evaluation of disease was confirmed histologically, anti-receptor antibody-treated mice showed no sign of arthritic change. Moreover, the analysis of sera taken at the end of the study period showed that the neutralization of arthritis by IL-1 receptor antibody treatment was accompanied by significantly lower levels of circulating human TNF compared to the control groups and to untreated transgenic mice prior to disease onset. Taken together, these results show that IL-1 signaling blockade exerts a direct negative feedback effect on TNF production. Our results show that in TNF-transgenic mice the IL-1 receptor accepts the whole pathogenic load of TNF, thereby acting as a potent downstream mediator in the pathogenesis of chronic arthritis.     

Impaired inflammatory angiogenesis, but not leukocyte influx, in mice lacking TNFR1

The majority of biological responses classically attributed to tumor necrosis factor alpha (TNF-alpha) is mediated by p55 receptor (TNFR1). Here, we aimed to clarify the biological role of TNFR1-mediated signals in an in vivo inflammatory angiogenesis model. Polyester-polyurethane sponges, used as a framework for tissue growth, were implanted in C57Bl/6 mice. These implants were collected at days 1, 7, and 14 post-implant for enzyme-linked immunosorbent assay or at days 7 and 14 for hemoglobin, myeloperoxidase, and N-acetylglucosaminidase measurements, used as indexes for angiogenesis, neutrophil, and macrophage accumulation, respectively. In TNFR1-deficient C57Bl/6 mice, there was a significant decrease in sponge vascularization but not in late inflammatory cell influx. It is interesting that levels of vascular endothelial growth factor were significantly lower in TNFR1-deficient than in wild-type mice at days 1 and 7. Levels of angiogenic chemokines, CC chemokine ligand 2/murine homologue of monocyte chemoattractant protein-1 and CXC chemokine ligand 1-3/keratinocyte-derived chemokine, were significantly lower in TNFR1-deficient mice at days 1 and 7 after implantation, respectively. These observations suggest that TNFR1-mediated signals have a critical role in sponge-induced angiogenesis, possibly by influencing the effector state of inflammatory cells and hence, modulating the angiogenic molecular network.     

Tumor necrosis factor (TNF) receptor type 2 mediates thymocyte proliferation independently of TNF receptor type 1

Tumor necrosis factor (TNF) mediates its biological effects by binding to two distinct but homologous receptor molecules. The type 1 receptor (TNF-R1) has been shown to be essential and sufficient for most cellular responses to soluble TNF. In contrast, only limited data exist concerning the role of the type 2 receptor (TNF-R2) in TNF responses, both in vitro and in vivo. Here, we demonstrate by the use of thymocytes from TNF-R-deficient mice that the TNF-R2-dependent enhancement of proliferation and secretion of granulocyte-macrophage colony-stimulating factor is in fact mediated by TNF-R2 on its own, independent of co-expression and/or stimulation of TNF-R1.