Genetic engineering in the mouse: tuning TNF/TNFR expression.

With the exponential increase in the number of genes identified by various genome projects, it has become imperative that efficient methods be developed for deciphering gene function. Genetically engineered strains of mice are now critical research tools for basic biomedical research and for genomic approaches for the development of new therapeutic treatments for human disease. Over the past ten years it has become possible to make essentially any mutation in the mouse by transgenesis and homologous recombination in embryonic stem cells.

Attenuation of inflammatory polyarthritis in TNF transgenic mice by diacerein: comparative analysis with dexamethasone, methotrexate and anti-TNF protocols.

The impact of diacerein, an effective cartilage targeted therapy that is used in patients with osteoarthritis, on the development and progression of chronic inflammatory arthritis was evaluated in a tumor necrosis factor (TNF) transgenic mouse model (Tg197). The response to diacerein at 2, 20, or 60 mg/kg daily, as well as the comparative effects of other antiarthritis drugs including dexamethasone (0.5 mg/kg daily), methotrexate (1 mg/kg three times weekly) and an anti-TNF agent (5 mg/kg weekly), were assessed in the Tg197 mice.

Repair of local bone erosions and reversal of systemic bone loss upon therapy with anti-tumor necrosis factor in combination with osteoprotegerin or parathyroid hormone in tumor necrosis factor-mediated arthritis.

Local bone erosion and systemic bone loss are hallmarks of rheumatoid arthritis and cause progressive disability. Tumor necrosis factor (TNF) is a key mediator of arthritis and acts catabolically on bone by stimulating bone resorption and inhibiting bone formation. We hypothesized that the concerted action of anti-TNF, which reduces inflammation and parathyroid hormone (PTH), which stimulates bone formation, or osteoprotegerin (OPG), which blocks bone resorption and could lead to repair of local bone erosions and reversal of systemic bone loss.

Single and combined inhibition of tumor necrosis factor, interleukin-1, and RANKL pathways in tumor necrosis factor-induced arthritis: effects on synovial inflammation, bone erosion, and cartilage destruction.

Objective: To investigate the efficacy of single and combined blockade of tumor necrosis factor (TNF), interleukin-1 (IL-1), and RANKL pathways on synovial inflammation, bone erosion, and cartilage destruction in a TNF-driven arthritis model.

Methods: Human TNF-transgenic (hTNFtg) mice were treated with anti-TNF (infliximab), IL-1 receptor antagonist (IL-1Ra; anakinra), or osteoprotegerin (OPG; an OPG-Fc fusion protein), either alone or in combinations of 2 agents or all 3 agents. Synovial inflammation, bone erosion, and cartilage damage were evaluated histologically.

Osteoprotegerin protects against generalized bone loss in tumor necrosis factor-transgenic mice.

Objective: To investigate the role of tumor necrosis factor (TNF) in systemic bone loss of chronic inflammatory conditions, such as rheumatoid arthritis (RA), and to address the therapeutic potential of osteoclast blockade.

Methods: We investigated systemic bone changes in human TNF transgenic (hTNFtg) mice, which spontaneously developed severe inflammatory arthritis.

Results: Osteodensitometry revealed a significant decrease in trabecular bone mineral density (BMD) (-37%) in hTNFtg mice, and histomorphometry revealed a dramatic loss of bone volume (-85%) compared with wild-type controls.

Tumor necrosis factor biology in experimental and clinical arthritis.

The successful introduction of antitumor necrosis factor treatments in clinical practice confirmed the biologic relevance of tumor necrosis factor function in chronic inflammatory conditions in humans, mainly in the pathogenesis of rheumatoid arthritis and inflammatory bowel disease. Studies on patients receiving antitumor necrosis factor treatments offered deeper insights into the mechanisms of antitumor necrosis factor action in arthritis and revealed a master regulatory role for tumor necrosis factor in a multitude of biologic processes underlying pathogenesis. However, within such pleiotropism of key functions, blockade of tumor necrosis factor has also led to a significant incidence of unwanted clinical complications.

Surgical technique for intra-abdominal radiotransmitter placement in North American river otters (Lontra canadensis).

Twenty-two free-ranging North American river otters (Lontra canadensis) from northern and eastern New York were captured and surgically implanted with radiotransmitters as part of a relocation project. The surgical technique involved an incision in the paralumbar fossa and transection through the abdominal musculature to introduce a radiotransmitter into the abdominal cavity. Two complications were encountered.

Inducible transgenic mice reveal resting dendritic cells as potent inducers of CD8+ T cell tolerance.

Dendritic cells (DC) are inducers of immune responses par excellence. They also seem responsible for the induction of peripheral T cell tolerance. To investigate these opposite functions of DC, we generated a Cre/LoxP-based system that allows inducible antigen presentation by DC in vivo.

Functional analysis of an arthritogenic synovial fibroblast.

Increasing attention has been directed towards identifying non-T-cell mechanisms as potential therapeutic targets in rheumatoid arthritis. Synovial fibroblast (SF) activation, a hallmark of rheumatoid arthritis, results in inappropriate production of chemokines and matrix components, which in turn lead to bone and cartilage destruction. We have demonstrated that SFs have an autonomous pathogenic role in the development of the disease, by showing that they have the capacity to migrate throughout the body and cause pathology specifically to the joints.

Oral treatment of avian lead intoxication with meso-2,3-dimercaptosuccinic acid.

The efficacy of meso-dimercaptosuccinic acid (DMSA) (succimer) in treating avian lead intoxication was studied in a retrospective, nonrandomized, longitudinal study. Nineteen birds with moderate to high blood lead concentration and neurologic signs compatible with lead toxicity were treated with DMSA (30 mg/kg p.o.

Induction of inducible nitric oxide synthase, argininosuccinate synthase, and GTP cyclohydrolase I in arthritic joints of human tumor necrosis factor-alpha transgenic mice.

Objective: Transgenic mice that express human tumor necrosis factor-alpha (Tg197 h-TNF-alpha) develop polyarthritis at 3 to 4 weeks of age leading to severe joint destruction at 8 to 10 weeks of age. Studies have suggested that inducible nitric oxide synthase (iNOS) activity can modulate the progression of arthritis. We investigated the induction of iNOS together with argininosuccinate synthase (AS) and GTP cyclohydrolase I (GTPCH), 2 of the rate-limiting enzymes for high output NO generation, in the Tg197 h-TNF-alpha transgenic model of arthritis.

Tumor necrosis factor-alpha regulation of insulin-like growth factor-I, type 1 IGF receptor, and IGF binding protein expression in cerebellum of transgenic mice.

Tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine, has been implicated in the pathogenesis of several disorders and injuries in the central nervous system (CNS). Unlike IGF-I, which promotes CNS growth, TNF-alpha causes brain growth retardation and neural damage. Recently TNF-alpha has been shown to inhibit IGF-I signaling and actions in non-neural tissue.

Tumor necrosis factor-receptor 2 is up-regulated on lamina propria T cells in Crohn's disease and promotes experimental colitis in vivo.

Tumor necrosis factor (TNF) plays a pivotal role in the pathogenesis of Crohn's disease (CD). However, little is known about the role of TNF receptors (TNF-R) in this disease. Here, we found that TNF-R2 (in contrast to TNF-R1) was significantly up-regulated on lamina propria and peripheral blood T cells in CD compared to control patients.

Exclusive tumor necrosis factor (TNF) signaling by the p75TNF receptor triggers inflammatory ischemia in the CNS of transgenic mice.

Tumor necrosis factor (TNF) is up-regulated in a variety of central nervous system (CNS) diseases with diverse etiology and pathologic manifestation. TNF mediates multiple biological activities through two membrane receptors, the p55 and p75 TNF receptors (TNFRs). We have shown previously that human transmembrane TNF (tmTNF)p55TNFR signaling in transgenic mice triggers oligodendrocyte apoptosis, endothelial cell activation, parenchymal inflammation, and primary demyelinating lesions similar to those of acute multiple sclerosis.

Genetic dissection of the cellular pathways and signaling mechanisms in modeled tumor necrosis factor-induced Crohn's-like inflammatory bowel disease.

Recent clinical evidence demonstrated the importance of tumor necrosis factor (TNF) in the development of Crohn's disease. A mouse model for this pathology has previously been established by engineering defects in the translational control of TNF mRNA (Tnf(Delta)(ARE) mouse). Here, we show that development of intestinal pathology in this model depends on Th1-like cytokines such as interleukin 12 and interferon gamma and requires the function of CD8(+) T lymphocytes.

Osteoclasts are essential for TNF-alpha-mediated joint destruction.

The detailed cellular and molecular mechanisms leading to joint destruction in rheumatoid arthritis, a disease driven by proinflammatory cytokines, are still unknown. To address the question of whether osteoclasts play a pivotal role in this process, transgenic mice that express human TNF (hTNFtg) and that develop a severe and destructive arthritis were crossed with osteopetrotic, c-fos-deficient mice (c-fos(-/-)) completely lacking osteoclasts. The resulting mutant mice (c-fos(-/-)hTNFtg) developed a TNF-dependent arthritis in the absence of osteoclasts.

Role of TNF/TNFR in autoimmunity: specific TNF receptor blockade may be advantageous to anti-TNF treatments.

Deregulated TNF production, be it low or high, characterizes many autoimmune diseases. Recent evidence supports a dualistic, pro-inflammatory and immune- or disease-suppressive role for TNF in these conditions. Blocking TNF in autoimmune-prone chronic inflammatory diseases may, therefore, lead to unpredictable outcomes, depending on timing and duration of treatment.

Tumor necrosis factor alpha-mediated joint destruction is inhibited by targeting osteoclasts with osteoprotegerin.

Objective: To study the effects of osteoclast-targeted therapies, such as osteoprotegerin (OPG) and pamidronate, on joint inflammation and bone destruction using a tumor necrosis factor alpha (TNF alpha)-transgenic mouse model.

Methods: Mice were placed into 5 groups that received either OPG, pamidronate, a combination of both agents, infliximab as a positive control, or phosphate buffered saline as a negative control. Treatment was initiated at the onset of arthritis, continued over 6 weeks, and thereafter, the clinical, radiologic, and histologic outcomes were assessed.

Adenovirus-based overexpression of tissue inhibitor of metalloproteinases 1 reduces tissue damage in the joints of tumor necrosis factor alpha transgenic mice.

Objective: Rheumatoid arthritis is a prototype of a destructive inflammatory disease. Inflammation triggered by the overexpression of tumor necrosis factor alpha (TNFalpha) is a driving force of this disorder and mediates tissue destruction. Since matrix metalloproteinases (MMPs) are among the molecules activated by TNFalpha, we hypothesized that overexpression of their natural inhibitor, tissue inhibitor of metalloproteinases 1 (TIMP-1), in TNFalpha transgenic mice could inhibit the development of destructive arthritis.

MK2 targets AU-rich elements and regulates biosynthesis of tumor necrosis factor and interleukin-6 independently at different post-transcriptional levels.

We demonstrate that lipopolysaccharide-induced tumor necrosis factor (TNF) biosynthesis becomes independent of MAPKAP kinase 2 (MK2) when the AU-rich element (ARE) of the TNF gene is deleted. In spleen cells and macrophages where TNF biosynthesis is restored as a result of this deletion, interleukin (IL)-6 biosynthesis is still dependent on MK2. In MK2-deficient macrophages the half-life of IL-6 mRNA is reduced more than 10-fold, whereas the half-life of TNF mRNA is only weakly decreased.

Defective CD4T cell priming and resistance to experimental autoimmune encephalomyelitis in TNF-deficient mice due to innate immune hypo-responsiveness.

We report here that tumor necrosis factor (TNF) deficiency causes innate hypo-responsiveness to a broad range of bacterial or viral constituents. In vivo hypo-responsiveness of TNF-deficient mice to mycobacteria results in defective CD4+ T cell priming to antigens administered in complete Freund's adjuvant (CFA). This deficiency is restored by supplementary mycobacteria.

Polymerized bovine hemoglobin (Oxyglobin Solution) administration in two river otters (Lutra canadensis).

Polymerized bovine hemoglobin (Oxyglobin Solution) was successfully administered to two river otters (Lutra canadensis) that required general anesthesia and surgery for trap-related injuries. In both animals, blood oxygen content was maintained at presurgical levels despite a 47-70% decrease in their hematocrit. Otter 1 received a dose of 19 mL kg, given at a rate of 29 mL kg h.

Interleukin-10 targets p38 MAPK to modulate ARE-dependent TNF mRNA translation and limit intestinal pathology.

Interleukin-10 (IL-10) is a key inhibitory signal of inflammatory responses that regulates the production of potentially pathogenic cytokines like tumor necrosis factor (TNF). We show here that the development of chronic intestinal inflammation in IL-10-deficient mice requires the function of TNF, indicating that the IL-10/TNF axis regulates mucosal immunity. We further show that IL-10 targets the 3' AU-rich elements (ARE) of TNF mRNA to inhibit its translation.