Methotrexate--how does it really work?
ABSTRACT Methotrexate remains a cornerstone in the treatment of rheumatoid arthritis and other rheumatic diseases. Folate antagonism is known to contribute to the antiproliferative effects that are important in the action of methotrexate against malignant diseases, but concomitant administration of folic or folinic acid does not diminish the anti-inflammatory potential of this agent, which suggests that other mechanisms of action might be operative. Although no single mechanism is sufficient to account for all the anti-inflammatory activities of methotrexate, the release of adenosine from cells has been demonstrated both in vitro and in vivo. Methotrexate might also confer anti-inflammatory properties through the inhibition of polyamines. The biological effects on inflammation associated with adenosine release have provided insight into how methotrexate exerts its effects against inflammatory diseases and at the same time causes some of its well-known adverse effects. These activities contribute to the complex and multifaceted mechanisms that make methotrexate efficacious in the treatment of inflammatory disorders.
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ABSTRACT: BACKGROUND AND PURPOSE: We previously reported that adenosine, acting at adenosine A2A receptors (A2A R), inhibits osteoclast (OC) differentiation in vitro in vitro (A2A R activation OC formation reduces by half) and in vivo. For a better understanding how adenosine A2A R stimulation regulates OC differentiation we dissected the signaling pathways involved in A2A R signaling. EXPERIMENTAL APPROACH: OC differentiation was studied as TRAP+ multinucleated cells following M-CSF/RANKL stimulation of either primary murine bone marrow cells or the murine macrophage line, RAW264.7, in presence/absence of the A2A R agonist CGS21680, the A2A R antagonist ZM241385, PKA activators (8-Cl-cAMP 100nM, 6-Bnz-cAMP) and the PKA inhibitor (PKI). cAMP was quantitated by EIA and PKA activity assays were carried out. Signaling events were studied in PKA knockdown (lentiviral shRNA for PKA) RAW264.7 cells (scrambled shRNA as control). OC marker expression was studied by RT-PCR. KEY RESULTS: A2A R stimulation increased cAMP and PKA activity which and were reversed by addition of ZM241385. The direct PKA stimuli 8-Cl-cAMP and 6-Bnz-cAMP inhibited OC maturation whereas PKI increased OC differentiation. A2A R stimulation inhibited p50/p105 NFκB nuclear translocation in control but not in PKA KO cells. A2A R stimulation activated ERK1/2 by a PKA-dependent mechanism, an effect reversed by ZM241385, but not p38 and JNK activation. A2A R stimulation inhibited OC expression of differentiation markers by a PKA-mechanism. CONCLUSIONS AND IMPLICATIONS: A2A R activation inhibits OC differentiation and regulates bone turnover via PKA-dependent inhibition of NFκB nuclear translocation, suggesting a mechanism by which adenosine could target bone destruction in inflammatory diseases like Rheumatoid Arthritis.British Journal of Pharmacology 05/2013; DOI:10.1111/bph.12227 · 4.99 Impact Factor
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ABSTRACT: Bone is continually being remodeled and defects in the processes involved lead to bone diseases. Many regulatory factors are known to influence remodeling but other mechanisms, hitherto unknown, may also be involved. Importantly, our understanding of these currently unknown mechanisms may lead to important new therapies for bone disease. It is accepted that purinergic signaling is involved in bone, and our knowledge of this area has increased significantly over the last 15 years, although most of the published work has studied the role of ATP and other signaling molecules via the P2 family of purinergic receptors. During the last few years, however, there has been increased interest within the bone field in the role of P1 receptors where adenosine is the primary signaling molecule. This review will bring together the current information available in relation to this expanding area of research.Frontiers in Endocrinology 09/2012; 3:113. DOI:10.3389/fendo.2012.00113
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ABSTRACT: This study examines the effect of combining the antiangiogenic effect of αvß₃-targeted fumagillin nanoparticles with the conventional antirheumatic drug methotrexate for the treatment of inflammatory arthritis. Arthritis was induced in mice by K/BxN serum transfer, and disease activity was monitored by clinical score and change in ankle thickness. Groups of mice received nanoparticles or methotrexate as single therapy or nanoparticles and methotrexate as combination therapy. We found that animals treated with a pulse dose of fumagillin nanoparticles followed by methotrexate had significantly improved and sustained clinical response compared with those treated with either agent alone. Histological analysis confirmed a significant decrease in inflammatory cell influx, bone erosions, cartilage damage and angiogenesis with the combination therapy. Analysis of plasma cytokine levels suggests that fumagillin nanoparticles enhanced the systemic anti-inflammatory effects of methotrexate. Antiangiogenic nanotherapy may represent a promising approach for the treatment of inflammatory arthritis when combined with a conventional antirheumatic drug.Nanomedicine 09/2010; 5(7):1065-74. DOI:10.2217/nnm.10.78 · 5.82 Impact Factor