Methotrexate--how does it really work?
Department of Medicine, New York University School of Medicine, 550 First Avenue, NBV16N1, New York, NY 10016, USA. Nature Reviews Rheumatology
(Impact Factor: 9.85).
03/2010; 6(3):175-8. DOI: 10.1038/nrrheum.2010.5
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.
Available from: PubMed Central
- "The earliest concept, borrowed from oncology applications, was that of anti-proliferative actions, thereby reducing the burden of inflammatory cells . Other potential mechanisms have been proposed, including interactions with adenosine signaling pathways and generation of ROS [8,19,20]. In previous studies we have shown that MTX primes T cells for apoptosis, an action that is dependent on JNK signaling pathways . "
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ABSTRACT: Methotrexate (MTX) has been for decades a standard treatment in a wide range of conditions, from malignancies to rheumatoid arthritis (RA). Despite this long experience, mechanisms of action of MTX remain incompletely understood. Reported immunologic effects of MTX include induction of increased production of some cytokines, an effect that seems to be at odds with the generally anti-inflammatory effects of this drug in diseases like RA. To further elucidate these immune activities, we examined effects of MTX on the human monocytic cell line U937.
The U937 cell line was treated in vitro with pharmacologic range concentrations of MTX and effects on production of interleukin (IL)-1, IL-6 and TNF alpha were measured. Changes in gene expression for IL-1 and IL-6 and specificities in the Jun-N-terminal kinase (JNK) signaling pathway including JNK 1, JNK2, JUN and FOS were also determined. The contribution of NFkB, folate and adenosine pathways to the observed effects were determined by adding appropriate inhibitors to the MTX cultures.
MTX mediated a dose-dependent increase in IL-1 and IL-6 in U937 cells, as measured by secreted proteins and levels of gene expression. The increased cytokine expression was inhibited by addition of parthenolide and folinic acid, but not by caffeine and theophylline, suggesting that NFkB and folates, but not adenosine, were involved in mediating the observed effects. When U937 cells were cultured with MTX, upregulated expression of JUN and FOS, but not JNK 1 or 2, also was observed.
MTX induces expression of pro-inflammatory cytokines in U937 monocytic cells. These effects might mediate the known toxicities of MTX including pneumonitis, mucositis and decreased bone mineral density.
Available from: Weiqiang Chen
- "To this end, how do we reconcile these findings? Affirming the diverse effects of MTX on the immune system , MTX has previously been shown to act as a strong differentiation factor for immature and undifferentiated monocytic cells in vitro
. With our treatment regimen, while MTX alone did not trigger monocyte elevation in vivo, likely due to the low dosage of MTX administered, in the presence of RRV infection, MTX treatment boosts systemic monocyte generation. "
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ABSTRACT: Part of the Togaviridae family, alphaviruses, including chikungunya virus (CHIKV), Sindbis virus (SINV) and Ross River virus (RRV), are able to cause significant inflammatory pathologies ranging from arthritis to encephalitis. Following symptomatic infection with arthritis-associated alphaviruses, patients often experience severe joint pain, affecting distal and small joints, which can last six months or longer. Recently, methotrexate (MTX), a disease modifying anti-rheumatic drug (DMARD), was used to treat patients experiencing chronic rheumatic symptoms following infection with CHIKV. Here, the effect of MTX on Ross River virus disease (RRVD) in mice was examined to better understand its therapeutic potential for alphaviral-induced musculoskeletal disease and to further our knowledge of the development of alphaviral pathologies. Using a mouse model, we analyzed the effect of MTX on RRVD. RRV disease pathogenesis in response to MTX treatment was determined by measuring levels of proinflammatory factors, cellular infiltrates, viral titer and histological analysis of infected tissues. RRV-infected mice receiving MTX treatment rapidly developed musculoskeletal disease, which correlated with a significant influx of inflammatory cell infiltrates into the skeletal muscle tissue. Although no difference was observed in the level of proinflammatory cytokines and chemokines, the viral load increased at early time points post infection in the serum and quadriceps of MTX treated mice, possibly contributing to disease pathogenesis. Results suggest that MTX treatment of acute RRVD in mice provides no therapeutic benefit and underline the importance of inflammatory monocytes in alphaviral induced arthritides.
Available from: jpet.aspetjournals.org
- "However, such a correlation between MTX polyglutamation and inhibition of these enzymes in a cellular system has not been experimentally evaluated. To date, biomarker development has been hampered by an incomplete understanding of the mechanism of action of lowdose MTX (Chan and Cronstein, 2010). The antiproliferative and anti-inflammatory effects of MTX are believed to be distinct, occurring through the inhibition of different biochemical pathways. "
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ABSTRACT: Therapeutic and toxic response to low-dose methotrexate (MTX) in the treatment of autoimmune disease continues to be highly variable resulting in a critical need to identify predictive biomarkers of response. Biomarker development has been hampered by an incomplete understanding of the molecular pharmacology of low-dose MTX. To address this issue, the accumulation of the substrates for aminoimidazole carboxamide ribonucleotide transformylase (AICART) and thymidylate synthase (TS) were measured as markers of pharmacological activity of MTX in an erythroblastoid cell line. A 115-fold increased in the AICART substrate and anti-inflammatory mediator, aminoimidazole carboxamide ribotide (ZMP), was observed following exposure to 10 nM MTX, but subsequently decreased with increasing MTX concentrations, declining to baseline levels with 1000 nM MTX. In contrast, the TS substrate, deoxyuridine monophosphate (dUMP), displayed concentration-dependent accumulation, increasing 29-, 342- and 471-fold over baseline with 10, 100 and 1000 nM MTX, respectively. Cellular levels of dUMP correlated with levels of parent drug (MTX-PG1) (r=0.66, p<0.001) and its polyglutamates (MTX-PG2-6) (r=0.81, p<0.001), whereas, cellular levels of ZMP were only moderately correlated with MTX-PG1 (r=0.34, p<0.01). In contrast, accumulation of ZMP at 10 nM MTX was associated with a 2.9-fold increase in of the AICART inhibitor dihydrofolate (DHF), represented primarily by long-chain DHF polyglutamates. Selectivity, defined as the ratio of ZMP to dUMP, was maximal following exposure to 6 nM MTX. Characterizing the range of MTX concentrations that selectively promote ZMP accumulation while preserving pyrimidine biosynthesis may lead to optimization of low-dose MTX therapy.
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