Anti-arthritic effect of methotrexate: is it really mediated by adenosine?

Andersson, Sven; Johansson, Lars Hakan; Lexmuller, Kristina; Ekström, Gunilla

doi:10.1016/s0928-0987(99)00073-1

Cited by 45 publications

(49 citation statements)

References 15 publications

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“…Previous research in animal models has demonstrated that low-dose methotrexate treatment promotes intracellular accumulation of AICAR, an intermediate in purine synthesis, and that accumulation of AICAR is associated with increased adenosine release into inflammatory exudates (1,23); adenosine mediates the antiinflammatory effects of methotrexate treatment in animal models of both acute inflammation and adjuvant arthritis (1,2,24). In contrast, using adenosine receptor antagonists, Andersson and colleagues (25) did not confirm a role for adenosine in the antiinflammatory action of high-dose methotrexate (2-4 mg/kg/week; compared with 0.75 mg/kg/week in the present studies and in those reported in refs. 1 and 23, and compared with ϳ0.3 mg/kg/week in clinical practice) in the antigen-induced arthritis model in rats.…”

Section: Discussioncontrasting

confidence: 99%

Adenosine A_2A or A₃ receptors are required for inhibition of inflammation by methotrexate and its analog MX‐68

Montesinos¹,

Desai²,

Delano³

et al. 2003

Arthritis & Rheumatism

189

116

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Objective. Low-dose weekly methotrexate therapy remains a mainstay in the treatment of inflammatory arthritis. Results of previous studies demonstrated that adenosine, acting at one or more of its receptors, mediates the antiinflammatory effects of methotrexate in animal models of both acute and chronic inflammation. We therefore sought to establish which receptor ( Results. Low-dose weekly methotrexate treatment increased the adenosine concentration in the exudates of all mice studied and reduced leukocyte and tumor necrosis factor ␣ accumulation in the exudates of wildtype mice, but not in those of A 2A or A 3 receptor knockout mice. Dexamethasone, an agent that suppresses inflammation by a different mechanism, was equally effective at suppressing leukocyte accumulation in A 2A knockout, A 3 knockout, and wild-type mice, indicating that the lack of response was specific for methotrexate and MX-68.Conclusion. These findings confirm that adenosine, acting at A 2A and A 3 receptors, is a potent regulator of inflammation. Moreover, these results provide strong evidence that adenosine, acting at either or both of these receptors, mediates the antiinflammatory effects of methotrexate and its analog MX-68.Low-dose weekly methotrexate is the "gold standard" of therapy in rheumatoid arthritis and other inflammatory diseases. Methotrexate's mechanism of action in the treatment of inflammatory diseases has been the subject of some controversy, although in previous studies, investigators in our group have demonstrated that adenosine mediates the antiinflammatory effects of methotrexate treatment in models of acute and chronic inflammation (1,2). Adenosine, whether released from injured cells or tissues or applied exogenously, regulates inflammation via interaction with one or more of the 4 known receptors for adenosine (A 1 , A 2A , A 2B , and A 3 ), as demonstrated by many in vitro and in vivo pharmacologic studies (for review, see ref.3). The demonstration that adenosine mediates the antiinflammatory effects of methotrexate in in vivo models of acute inflammation rests upon reversal of the antiinflammatory effects of methotrexate, either by enzymatic hydrolysis of adenosine by adenosine deaminase or by administration of adenosine receptor antagonists to reverse the antiinflammatory effects of methotrexate treatment (1,2). Although the antiinflammatory effects of methotrexate are mediated by multiple adenosine receptors in the adjuvant arthritis model of inflammation (2), the identity of the receptor(s) involved in the suppression of inflammation in models of acute inflammation has not been so well characterized.

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Section: Discussioncontrasting

confidence: 99%

Adenosine A_2A or A₃ receptors are required for inhibition of inflammation by methotrexate and its analog MX‐68

Montesinos¹,

Desai²,

Delano³

et al. 2003

Arthritis & Rheumatism

189

116

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“…Acidosis is characteristic for such disease states as sepsis, arthritis, ischemia, and cancer. In these diseases, the intra-and/or extracellular pH of the affected tissues typically decreases from control values of 7.4 to ϳ6.0 (23,47,48,63,64). Hence, we hypothesized that HNO can exert selective toxicity to cells subjected to acidosis via a mechanism that includes an H ϩ -amplified generation of ⅐ OH.…”

Section: Discussionmentioning

confidence: 99%

“…This possibility is interesting because acidification of tissues occurs under various pathological conditions, such as ischemia, inflammation, and cancer (24,47,48). For example, the intense metabolism of glucose to lactic acid leads to acidification in the microenvironment of tumor tissues.…”

Section: Effects Of Ph On the Cytotoxicity Of Na 2 N 2 O 3 -mentioning

confidence: 99%

Formation of Nitroxyl and Hydroxyl Radical in Solutions of Sodium Trioxodinitrate

Ivanova

Salama

Clancy

et al. 2003

Journal of Biological Chemistry

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Despite its negative redox potential, nitroxyl (HNO) can trigger reactions of oxidation. Mechanistically, these reactions were suggested to occur with the intermediate formation of either hydroxyl radical ( ⅐ OH) or peroxynitrite (ONOO ؊ ). In this work, we present further experimental evidence that HNO can generate ⅐ OH. Sodium trioxodinitrate (Na 2 N 2 O 3 ), a commonly used donor of HNO, oxidized phenol and Me 2 SO to benzene diols and ⅐ CH 3 , respectively. The oxidation of Me 2 SO was O 2 -independent, suggesting that this process reflected neither the intermediate formation of ONOO ؊ nor a redox cycling of transition metal ions that could initiate Fenton-like reactions. In solutions of phenol, Na 2 N 2 O 3 yielded benzene-1,2-diol and benzene-1,4-diol at a ratio of 2:1, which is consistent with the generation of free ⅐ OH. Ethanol and Me 2 SO, which are efficient scavengers of ⅐ OH, impeded the hydroxylation of phenol. A mechanism for the hydrolysis of Na 2 N 2 O 3 is proposed that includes dimerization of HNO to cis-hyponitrous acid (HO-N‫؍‬N-OH) with a concomitant azo-type homolytic fission of the latter to N 2 and ⅐ OH. The HNO-dependent production of ⅐ OH was with 1 order of magnitude higher at pH 6.0 than at pH 7.4. Hence, we hypothesized that HNO can exert selective toxicity to cells subjected to acidosis. In support of this thesis, Na 2 N 2 O 3 was markedly more toxic to human fibroblasts and SK-N-SH neuroblastoma cells at pH 6.2 than at pH 7.4. Scavengers of ⅐ OH impeded the cytotoxicity of Na 2 N 2 O 3 . These results suggest that the formation of HNO may be viewed as a toxicological event in tissues subjected to acidosis.The biochemistry of nitroxyl (HNO) has attracted considerable interest in recent years. In cells, the biosynthesis of HNO is believed to proceed via reduction of NO ⅐ by superoxide dismutase (1) and cytochrome c (2), and reduction of S-nitrosoglutathione by low molecular weight and protein thiols (3-5). It has been suggested that HNO can affect the etiology of various pathophysiological conditions such as inflammation and neurodegenerative diseases, especially when H 2 O 2 and transition metal ions are present (6, 7). Similar to NO ⅐ and NO ϩ , HNO is a potent inducer of the antioxidant protein heme oxygenase 1 (8), exhibits vasorelaxant properties (9), and modulates the activity of thiol-containing proteins, such as aldehyde dehydrogenase (10, 11) and the N-methyl-D-aspartate receptor (12, 13). In in vivo experiments, Paolocci et al. (14) observed that HNO exerts positive inotropic and lusitropic action, which unlike NO ⅐ and nitrates is independent and additive to ␤-adrenergic stimulation and increases the release of plasma calcitonin gene-related peptide; these results suggest that donors of HNO are potential prodrugs for the treatment of heart failure (14). At high doses, HNO has been shown to induce DNA singlestrand breakage (15, 16) and a concentration-dependent cytotoxicity in murine thymocytes (16). This cytotoxicity was associated with activation of the nuclear nick sen...

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“…The most recent evidence supporting this hypothesis includes the observations that MTX failed to suppress air pouch inflammation in adenosine A 2A receptor-knockout mice (22), that adenosine deaminase or adenosine A 2A receptor antagonist added to inflamed air pouches attenuated the antiinflammatory effect of MTX treatment (9), and that MTX does not suppress inflammation in animals lacking ecto-5Ј-nucleotidase, an enzyme responsible for the generation of extracellular adenosine from AMP (Montesinos MC, Cronstein BN, and Thompson L: unpublished observations). In contrast, Andersson et al (35) reported that the ability of MTX to suppress antigen-induced arthritis in rats was not inhibited by adenosine antagonists. In that study, however, the MTX dosage (0.2-0.3 mg/kg/day) was substantially higher than the range commonly used to treat RA, and unlike in RA patients, the antiinflammatory effect was completely reversed by folic acid (35).…”

Section: Discussionmentioning

confidence: 90%

“…In contrast, Andersson et al (35) reported that the ability of MTX to suppress antigen-induced arthritis in rats was not inhibited by adenosine antagonists. In that study, however, the MTX dosage (0.2-0.3 mg/kg/day) was substantially higher than the range commonly used to treat RA, and unlike in RA patients, the antiinflammatory effect was completely reversed by folic acid (35).…”

Section: Discussionmentioning

confidence: 90%

Genetically based resistance to the antiinflammatory effects of methotrexate in the air‐pouch model of acute inflammation

Delano¹,

Desai²,

Wilder³

et al. 2005

Arthritis & Rheumatism

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Objective. Low-dose methotrexate (MTX), a mainstay in the treatment of rheumatoid arthritis, is effective in only 60-70% of patients, a finding mirrored by poor antiinflammatory efficacy in some animal models, most notably collagen-induced arthritis. To determine whether genetic factors or the model itself is responsible for the poor response to MTX, we directly compared the responses of 4 inbred mouse strains to MTX in the air-pouch model of acute inflammation.Methods. The exudate leukocyte count and adenosine concentration were determined in inbred mice treated with MTX (0.75 mg/kg intraperitoneally every week for 4 weeks) or vehicle 4 hours after injection of carrageenan into the air pouch using previously described methods. Quantitative trait locus mapping was performed using an in silico, or computer-based, method to identify loci potentially associated with each phenotype.Results. MTX significantly reduced the exudate leukocyte count in C57BL/6J and BALB/cJ mice, but not DBA/1J (the strain used in the collagen-induced arthritis model) or DBA/2J mice. In a parallel manner, MTX increased adenosine concentration in inflammatory exudates of C57BL/6J and BALB/cJ mice, but not DBA/1J or DBA/2J mice. Antiinflammatory and adenosine responses to MTX in DBA/1J ؋ C57BL/6J F 1 and F 2 offspring were most consistent with single genetic loci being responsible for each phenotype. In silico mapping identified partially overlapping loci containing candidate genes involved in both responses.Conclusion. Genetic factors contribute to the antiinflammatory efficacy of MTX, and a single locus involved in MTX-induced adenosine up-regulation is likely responsible for the observed resistance to MTX in DBA/1J mice.Low-dose methotrexate (MTX), the most commonly administered disease-modifying therapy for rheumatoid arthritis (RA), is effective in only 60-75% of patients (1). While much effort has gone into identifying risk factors for a poor and/or toxic response (2-4), the majority of MTX failures remain unexplained. A number of recent studies have addressed the potential role of genetic background in determining response to MTX (3,5-7), focusing on the impact of single-nucleotide polymorphisms (SNPs) in genes of the folate uptake and metabolism pathways on the propensity toward MTX toxicity and/or poor efficacy. While these data have offered some evidence for the association of SNPs with toxicity and, to a lesser degree, efficacy, no clear demonstration of genetically based resistance to the antiinflammatory properties of MTX has been offered thus far.The demonstration of inbred murine strainspecific resistance to the antiinflammatory effects of

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Anti-arthritic effect of methotrexate: is it really mediated by adenosine?

Cited by 45 publications

References 15 publications

Adenosine A_2A or A₃ receptors are required for inhibition of inflammation by methotrexate and its analog MX‐68

Adenosine A_2A or A₃ receptors are required for inhibition of inflammation by methotrexate and its analog MX‐68

Formation of Nitroxyl and Hydroxyl Radical in Solutions of Sodium Trioxodinitrate

Genetically based resistance to the antiinflammatory effects of methotrexate in the air‐pouch model of acute inflammation

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Anti-arthritic effect of methotrexate: is it really mediated by adenosine?

Cited by 45 publications

References 15 publications

Adenosine A2A or A3 receptors are required for inhibition of inflammation by methotrexate and its analog MX‐68

Adenosine A2A or A3 receptors are required for inhibition of inflammation by methotrexate and its analog MX‐68

Formation of Nitroxyl and Hydroxyl Radical in Solutions of Sodium Trioxodinitrate

Genetically based resistance to the antiinflammatory effects of methotrexate in the air‐pouch model of acute inflammation

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Adenosine A_2A or A₃ receptors are required for inhibition of inflammation by methotrexate and its analog MX‐68

Adenosine A_2A or A₃ receptors are required for inhibition of inflammation by methotrexate and its analog MX‐68