Faculty Bibliography

Growing evidence indicates that adenosine receptors could be promising therapeutic targets in autoimmune diseases. Here we studied the role of adenosine receptors in controlling the course of type 1 diabetes. Diabetes in CD-1 mice was induced by multiple-low-dose-streptozotocin (MLDS) treatment and in nonobese diabetic (NOD) mice by cyclophosphamide injection. The nonselective adenosine receptor agonist 5'-N-ethylcarboxamidoadenosine (NECA) prevented diabetes development in both MLDS-challenged mice and in cyclophosphamide-treated NOD mice. The effect of NECA was reversed by the selective A2B receptor antagonist N-(4-cyanophenyl)-2-[4-(2,3,6,7-tetrahydro-2,6-dioxo-1,3-dipropyl-1H-purin -8-yl)phenoxy]acetamide (MRS 1754). The selective A1 receptor agonist 2-chloro-N6-cyclopentyladenosine (CCPA) and A3 receptor agonist N6-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (IB-MECA) were less efficacious in ameliorating the course of diabetes. NECA inhibited diabetes in A2A receptor KO mice and the selective A2A receptor agonist 2-p-(2-carboxyethyl)phenethyl-amino-5'-N-ethyl-carboxamidoadenosine (CGS21680) had no effect in normal mice, indicating a lack of role of A2A receptors. NECA failed to prevent cytokine-induced beta-cell death in vitro, but NECA strongly suppressed expression of the proinflammatory cytokines TNF-alpha, MIP-1alpha, IL-12, and IFN-gamma in pancreata, endotoxin, or anti-CD3-stimulated splenic cells, and T helper 1 lymphocytes, indicating that the beneficial effect of NECA was due to immunomodulation. These results demonstrate that adenosine receptor ligands are potential candidates for the treatment of type 1 diabetes

Although the requirements for T lymphocyte homing to lymph nodes (LNs) are well studied, much less is known about the requirements for T lymphocyte locomotion within LNs. Imaging of murine T lymphocyte migration in explanted LNs using two-photon laser-scanning fluorescence microscopy provides an opportunity to systematically study these requirements. We have developed a closed system for imaging an intact LN with controlled temperature, oxygenation, and perfusion rate. Naive T lymphocyte locomotion in the deep paracortex of the LN required a perfusion rate of >13 microm/s and a partial pressure of O(2) (pO(2)) of >7.4%. Naive T lymphocyte locomotion in the subcapsular region was 38% slower and had higher turning angles and arrest coefficients than naive T lymphocytes in the deep paracortex. T lymphocyte activation decreased the requirement for pO(2), but also decreased the speed of locomotion in the deep paracortex. Although CCR7(-/-) naive T cells displayed a small reduction in locomotion, systemic treatment with pertussis toxin reduced naive T lymphocyte speed by 59%, indicating a contribution of Galpha(i)-mediated signaling, but involvement of other G protein-coupled receptors besides CCR7. Receptor knockouts or pharmacological inhibition in the adenosine, PG/lipoxygenase, lysophosphatidylcholine, and sphingosine-1-phosphate pathways did not individually alter naive T cell migration. These data implicate pO(2), tissue architecture, and G-protein coupled receptor signaling in regulation of naive T lymphocyte migration in explanted LNs

OBJECTIVE: Evidence from in vitro, in vivo, and clinical studies indicates that adenosine mediates, at least in part, the antiinflammatory effects of methotrexate (MTX), although the biochemical events involved have not been fully elucidated. This study was undertaken to investigate whether MTX exerts antiinflammatory effects in mice that lack ecto-5'-nucleotidase (ecto-5'-NT) (CD73) and are unable to convert AMP to adenosine extracellularly, in order to determine whether adenosine is generated intracellularly and transported into the extracellular space or is generated from the extracellular dephosphorylation of AMP to adenosine. METHODS: Male CD73 gene-deficient mice and age-matched wild-type mice received intraperitoneal injections of saline or MTX (1 mg/kg/week) for 5 weeks. Air pouches were induced on the back by subcutaneous injection of air; 6 days later, inflammation was induced by injection of carrageenan. RESULTS: Fewer leukocytes, but higher levels of tumor necrosis factor alpha (TNFalpha), accumulated in the air pouches of vehicle-treated CD73-deficient mice compared with those of wild-type mice. As expected, MTX treatment reduced the number of leukocytes and TNFalpha levels in the exudates and increased exudate adenosine concentrations in wild-type mice. In contrast, MTX did not reduce exudate leukocyte counts or TNFalpha levels or increase exudate adenosine levels in CD73-deficient mice. CONCLUSION: These results demonstrate that the antiinflammatory actions of MTX are mediated, at least in part, by increased release of adenine nucleotides that are hydrolyzed extracellularly to adenosine via an ecto-5'-NT-dependent pathway

Inflammatory joint diseases are a group of heterogeneous disorders with a variety of different etiologies and disease manifestations. However, there are features that are common to all of them: first, the recruitment of various inflammatory cell types that are attracted to involved tissues over the course of the disease process. Second, the treatments used in many of these diseases are commonly medications that suppress or alter immune function. The demonstration that adenosine has endogenous anti-inflammatory functions and that some of the most commonly used anti-rheumatic medications exert their therapeutic effects through stimulation of adenosine release suggest an important role for purinergic signaling in inflammatory rheumatic disorders

After half a century of use, methotrexate continues to be a cornerstone in the therapy of rheumatoid arthritis. Renewed interest in the 1980s has brought new insights into the mechanisms of action and safety of the drug. The use of combination therapy in rheumatoid arthritis has not masked the value of methotrexate in a competitive market in any way. We review the pharmacodynamics and pharmacokinetics as applicable to its clinical use as an anti-inflammatory and disease-modifying agent here

Interleukin-6 (IL-6) is a pleiotropic cytokine, present at elevated levels in patients with rheumatoid arthritis (RA). Il-6 signaling involves both a specific IL-6 receptor (IL-6R) and a ubiquitous signal-transducing protein, gp130 that is also utilized by other members of the IL-6 family. Il-6 signaling occurs by two mechanisms. Conventional signaling involves the binding of IL-6 to transmembrane IL-6R on cells expressing this receptor. In contrast, trans-signaling involves binding between the complex of soluble IL-6R/IL-6 and membrane-bound gp130. Trans-signaling allows IL-6 to affect cells that do not express IL-6R, including many synovial cells. The biological activities of IL-6 contribute to both systemic and local RA symptoms. Il-6 is a strong inducer of the acute-phase response, which can result in fever, secondary amyloidosis, anemia, and elevations in acute-phase proteins, such as C-reactive protein (CRP). The ability of IL-6 to induce B-cell differentiation may lead to the formation of rheumatoid factor and other autoantibodies. In joints, IL-6 promotes osteoclast activation and induces the release of matrix metalloproteinases, thus contributing to joint damage. In patients with RA, IL-6 levels correlate with markers of disease activity and clinical symptoms, and animal studies support the concept that this cytokine plays a role in the development of inflammatory arthritis. Clinical trials with tocilizumab, a humanized monoclonal antibody to soluble IL-6R, have shown that blocking IL-6 signaling reduces RA symptoms and markers of disease activity. Current evidence thus strongly supports the association between IL-6 and RA symptoms and suggests that IL-6 blockade will be a useful therapeutic strategy for patients with this disease

Adenosine is a potent physiologic mediator that is released by cells following such stresses as hypoxia and exposure to reactive oxygen species (ROS). By binding to one or more of four known receptors, A₁, A_2A, A_2B and A₃ (all members of the family of G protein coupled receptors), adenosine suppresses inflammation and immunologic reactions. Here we review the expression and functional effects of these receptors on inflammatory cells and discuss the potential use of adenosine receptor agonists or agents that increase local adenosine concentrations in the treatment of inflammatory diseases or promotion of wound healing