Methotrexate accumulation in target intestinal mucosa and white blood cells differs from non-target red blood cells of patients with Crohn's disease

BACKGROUND

Intracellular methotrexate polyglutamates (MTX-PGs) concentrations are measurable in red blood cells (RBCs) during MTX treatment. MTX-PG3 concentrations correlate with efficacy in patients with Crohn's disease (CD). Since RBCs are not involved in pathogenesis of CD and lack extended MTX metabolism, we determined MTX-PGs accumulation in peripheral blood mononuclear cells (PBMCs: effector cells) and intestinal mucosa (target cells) and compared those with RBCs as a potential more precise biomarker.

METHODS

In a multicentre prospective cohort study, blood samples of patients with CD were collected during the first year of MTX therapy. Mucosal biopsies were obtained from non-inflamed rectum and/or inflamed intestine. MTX-PGs concentrations in mucosa, PBMCs and RBCs were measured by liquid chromatography-tandem mass spectrometry.

RESULTS

From 80 patients with CD, a total of 27 mucosal biopsies, 9 PBMC and 212 RBC samples were collected. From 12 weeks of MTX therapy onwards, MTX-PG3 was the most predominant species (33%) in RBCs. In PBMCs, the distribution was skewed towards MTX-PG1 (48%), which accounted for an 18 times higher concentration than in RBCs. Long-chain MTX-PGs were highly present in mucosa: 21% of MTX-PGtotal was MTX-PG5. MTX-PG6 was measurable in all biopsies.

CONCLUSIONS

MTX-PG patterns differ between mucosa, PBMCs and RBCs of patients with CD.

Adenosine metabolic signature in circulating CD4+ T cells predicts remission in rheumatoid arthritis

OBJECTIVES

Long-term outcomes in rheumatoid arthritis (RA) depend on early and effective disease control. Methotrexate (MTX) remains the first-line disease modifying therapy, however there are no biomarkers with which to identify those most likely to achieve remission. To address this unmet need we explored metabolic pathways involved in MTX mechanism of action within circulating CD4+T cells in a cohort of treatment naive patients with early RA.

METHODS

Purified CD4+T cells were isolated from peripheral blood of 68 patients with early RA commencing MTX. The expression of a range of putative MTX metabolism and mechanism of action targets were explored by flow-cytometry and transcriptional analysis. From these data significant predictors of Disease Activity Score 28-C reactive protein (DAS28-CRP) remission (<2.4 at 6 months) were determined by logistic regression (clinical; flow-cytometry data) and linear modelling (gene expression data).

RESULTS

Low baseline DAS28-CRP was associated with remission at 6 months (p=0.02). Expression of the ectonucleotidase CD39, involved in ATP-ADP conversion during adenosine synthesis, was higher on CD4+CD25 High regulatory T cells at baseline in those achieving remission (molecules of equivalent fluorescence 1264 vs 847; p=0.007). Expression of other adenosine signalling elements in CD4+T cells were also upregulated at baseline in patients achieving remission: AMPD1 (p<0.001), ADORA2b (p=0.039) and ADORA3 (p=0.047). When combined into a single predictive metric, a combination of these variables outperformed baseline DAS28-CRP in prediction of early remission (area under the curve 0.92 vs 0.67, p=0.001) CONCLUSIONS: Adenosine signalling is important in the achievement of early remission with MTX in RA and biomarkers of adenosine activity may hold utility for the stratification of therapy in early disease.

Oral Versus Subcutaneous Methotrexate in Immune-Mediated Inflammatory Disorders: an Update of the Current Literature

PURPOSE

This review aims to critically evaluate the potential benefit of either oral or subcutaneous administration of methotrexate (MTX) in various immune-mediated inflammatory disorders (IMIDs) through analysis of efficacy, toxicity, pharmacokinetics and pharmacodynamics of both administration routes.

RECENT FINDINGS

Recent studies comparing the efficacy of oral versus subcutaneous MTX administration in IMIDs have revealed contradicting results. Some reported higher efficacy with subcutaneous administration, while others found no significant difference. Regarding toxicity, some studies have challenged the notion that subcutaneous administration is better tolerated than oral administration, while others have supported this. Pharmacokinetic studies suggest higher plasma bioavailability and increased accumulation of MTX-polyglutamates (MTX-PGs) in red blood cells (RBCs) with subcutaneous administration during the initial treatment phase. However, after several months, similar intracellular drug levels are observed with both administration routes. There is no conclusive evidence supporting the superiority of either oral or subcutaneous MTX administration in terms of efficacy and adverse events in IMIDs. Subcutaneous administration leads to higher plasma bioavailability and initial accumulation of MTX-PGs in RBCs, but the difference seems to disappear over time. Given the variable findings, the choice of administration route may be based on shared decision-making, offering patients the option of either oral or subcutaneous administration of MTX based on individual preferences and tolerability. Further research is needed to better understand the impact of MTX-PGs in various blood cells and TDM on treatment response and adherence to MTX therapy.

Methotrexate Polyglutamates Exposure - Response Modeling in a Large Cohort of Rheumatoid Arthritis Patients Starting Methotrexate

Methotrexate polyglutamates (MTX-PG) concentrations in red blood cells (RBCs) have been suggested as a biomarker of response in patients with rheumatoid arthritis (RA) receiving low-dose MTX therapy. We investigated the association and interpatient variability between RBC-MTX-PG3-5 -exposure and response in patients with RA starting MTX. Data of three prospective cohorts were available. The relationship between exposure and Disease Activity Score in 28 joints (DAS28) was analyzed using a population pharmacokinetic-pharmacodynamic model. Relevant covariates were tested using full covariate modeling and backward elimination. From 395 patients, 3,401 MTX-PG concentrations and 1,337 DAS28 measurements were available between 0 and 300 days after MTX treatment onset. The developed model adequately described the time course of MTX-PG3-5 and DAS28. The median MTX-PG3-5 level at month 1 was 30.9 nmol/L (interquartile range (IQR): 23.6-43.7; n = 41) and at month 3: 69.3 nmol/L (IQR: 17.9-41.2; n = 351). Clearance of MTX-PG3-5 from RBCs was 28% lower (95% confidence interval (CI): 23.6-32.8%) in a woman and 10% lower (95% CI: 7.7-12.4%) in a 65-year-old compared with a 35-year-old patient. MTX-PG3-5 concentrations associated with DAS28: half-maximal effective concentration (EC50 ) was 9.14 nmol/L (95% CI: 4.2 nmol/L-14.1 nmol/L). EF at 80% (EC80 ) above 47 nmol/L was regarded as the optimal response. Independent of the MTX-PG 3-5 - response association, co-administration of disease-modifying antirheumatic drugs and corticosteroids improved response (additive effect on maximum effect (Emax )), whereas smoking, high body mass index and low albumin decreased Emax . In patients with RA starting MTX, RBC-MTX-PG3-5 was associated with clinical response. A dose increase is suggested when MTX-PG3-5 at month 1 is below 9.15 nmol/L, continued with the same dose when the concentration is above 47 nmol/L, and consider other treatment options above 78 nmol/L from 3 months onwards.

Alterations in the gut microbiome implicate key taxa and metabolic pathways across inflammatory arthritis phenotypes

Musculoskeletal diseases affect up to 20% of adults worldwide. The gut microbiome has been implicated in inflammatory conditions, but large-scale metagenomic evaluations have not yet traced the routes by which immunity in the gut affects inflammatory arthritis. To characterize the community structure and associated functional processes driving gut microbial involvement in arthritis, the Inflammatory Arthritis Microbiome Consortium investigated 440 stool shotgun metagenomes comprising 221 adults diagnosed with rheumatoid arthritis, ankylosing spondylitis, or psoriatic arthritis and 219 healthy controls and individuals with joint pain without an underlying inflammatory cause. Diagnosis explained about 2% of gut taxonomic variability, which is comparable in magnitude to inflammatory bowel disease. We identified several candidate microbes with differential carriage patterns in patients with elevated blood markers for inflammation. Our results confirm and extend previous findings of increased carriage of typically oral and inflammatory taxa and decreased abundance and prevalence of typical gut clades, indicating that distal inflammatory conditions, as well as local conditions, correspond to alterations to the gut microbial composition. We identified several differentially encoded pathways in the gut microbiome of patients with inflammatory arthritis, including changes in vitamin B salvage and biosynthesis and enrichment of iron sequestration. Although several of these changes characteristic of inflammation could have causal roles, we hypothesize that they are mainly positive feedback responses to changes in host physiology and immune homeostasis. By connecting taxonomic alternations to functional alterations, this work expands our understanding of the shifts in the gut ecosystem that occur in response to systemic inflammation during arthritis.

Methotrexate Provokes Disparate Folate Metabolism Gene Expression and Alternative Splicing in Ex Vivo Monocytes and GM-CSF- and M-CSF-Polarized Macrophages

Macrophages constitute important immune cell targets of the antifolate methotrexate (MTX) in autoimmune diseases, including rheumatoid arthritis. Regulation of folate/MTX metabolism remains poorly understood upon pro-inflammatory (M1-type/GM-CSF-polarized) and anti-inflammatory (M2-type/M-CSF-polarized) macrophages. MTX activity strictly relies on the folylpolyglutamate synthetase (FPGS) dependent intracellular conversion and hence retention to MTX-polyglutamate (MTX-PG) forms. Here, we determined FPGS pre-mRNA splicing, FPGS enzyme activity and MTX-polyglutamylation in human monocyte-derived M1- and M2-macrophages exposed to 50 nmol/L MTX ex vivo. Moreover, RNA-sequencing analysis was used to investigate global splicing profiles and differential gene expression in monocytic and MTX-exposed macrophages. Monocytes displayed six-eight-fold higher ratios of alternatively-spliced/wild type FPGS transcripts than M1- and M2-macrophages. These ratios were inversely associated with a six-ten-fold increase in FPGS activity in M1- and M2-macrophages versus monocytes. Total MTX-PG accumulation was four-fold higher in M1- versus M2-macrophages. Differential splicing after MTX-exposure was particularly apparent in M2-macrophages for histone methylation/modification genes. MTX predominantly induced differential gene expression in M1-macrophages, involving folate metabolic pathway genes, signaling pathways, chemokines/cytokines and energy metabolism. Collectively, macrophage polarization-related differences in folate/MTX metabolism and downstream pathways at the level of pre-mRNA splicing and gene expression may account for variable accumulation of MTX-PGs, hence possibly impacting MTX treatment efficacy.

TAp63, a methotrexate target in CD4+ T cells, suppresses Foxp3 expression and exacerbates autoimmune arthritis

Methotrexate (MTX) is a standard, first-line therapy for rheumatoid arthritis (RA); however, its precise mechanisms of action other than antifolate activity are largely unknown. We performed DNA microarray analyses of CD4+ T cells in patients with RA before and after MTX treatment and found that TP63 was the most significantly downregulated gene after MTX treatment. TAp63, an isoform of TP63, was highly expressed in human IL-17-producing Th (Th17) cells and was suppressed by MTX in vitro. Murine TAp63 was expressed at high levels in Th cells and at lower levels in thymus-derived Treg cells. Importantly, TAp63 knockdown in murine Th17 cells ameliorated the adoptive transfer arthritis model. RNA-Seq analyses of human Th17 cells overexpressing TAp63 and those with TAp63 knockdown identified FOXP3 as a possible TAp63 target gene. TAp63 knockdown in CD4+ T cells cultured under Th17 conditions with low-dose IL-6 increased Foxp3 expression, suggesting that TAp63 balances Th17 cells and Treg cells. Mechanistically, TAp63 knockdown in murine induced Treg (iTreg) cells promoted hypomethylation of conserved noncoding sequence 2 (CNS2) of the Foxp3 gene and enhanced the suppressive function of iTreg cells. Reporter analyses revealed that TAp63 suppressed the activation of the Foxp3 CNS2 enhancer. Collectively, TAp63 suppresses Foxp3 expression and exacerbates autoimmune arthritis.

Pharmacokinetics of oral and subcutaneous methotrexate in red and white blood cells in patients with early rheumatoid arthritis: the methotrexate monitoring trial

OBJECTIVE

To investigate the pharmacokinetics of methotrexate polyglutamate (MTX-PG) accumulation in red blood cells (RBCs) and peripheral blood mononuclear cells (PBMCs) in patients with early rheumatoid arthritis (RA) after oral and subcutaneous MTX treatment.

METHODS

In a clinical prospective cohort study (Methotrexate Monitoring study), newly diagnosed patients with RA were randomised for oral or subcutaneous MTX. At 1, 2, 3 and 6 months after therapy initiation, blood was collected and RBCs and PBMCs were isolated. MTX-PG1-6 concentrations were determined by mass spectrometry methods using stable isotopes of MTX-PG1-6 as internal standards.

RESULTS

43 patients (mean age: 58.5 years, 77% female) were included. PBMCs and RBCs revealed disparate pharmacokinetic profiles in both absolute MTX-PG accumulation levels and distribution profiles. Intracellular MTX-PG accumulation in PBMCs was significantly (p<0.001) 10-fold to 20-fold higher than RBCs at all time points, regardless of the administration route. MTX-PG distribution in PBMCs was composed of mostly MTX-PG1 (PG1>PG2>PG3). Remarkably, the distribution profile in PBMCs remained constant over 6 months. RBCs accumulated mainly MTX-PG1 and lower levels of MTX-PG2-5 at t=1 month. After 3 months, MTX-PG3 was the main PG-moiety in RBCs, a profile retained after 6 months of MTX therapy. Subcutaneous MTX administration results in higher RBC drug levels than after oral administration, especially shortly after treatment initiation.

CONCLUSIONS

This is the first study reporting disparate MTX-PG accumulation profiles in RBCs versus PBMCs in newly diagnosed patients with RA during 6 months oral or subcutaneous MTX administration. This analysis can contribute to improved MTX therapeutic drug monitoring for patients with RA.

TRIAL REGISTRATION NUMBER

NTR 7149.

Folate in maternal rheumatoid arthritis-filial autism spectrum disorder continuum

Rheumatoid Arthritis (RA) is an inflammatory autoimmune disease that affects women three times more than men. Epidemiological studies found that the incidence of Autism Spectrum Disorder (ASD), a neurological and developmental disorder, in children born to mothers suffering from RA is higher compared with the control population. Considering that the pathogenesis of ASD could be traced back to pregnancy and in uterine conditions, and the evidence of reduced folate levels in the brain of ASD-affected children, we aimed to study the role of folate, as an important nutritional factor during pregnancy, in associating maternal RA to ASD development in the offspring. Folate balance during RA could be influenced twice, initially during the immune activation associated with disease onset, and later during the treatment with anti-folate drugs, with a potential consequence of folate deficiency. Maternal folate deficiency during pregnancy could increase homocysteine levels, oxidative stress, and global DNA hypomethylation, all known risk factors in ASD pathogenesis. These effects could be intensified by genetic polymorphisms in the folate system, which were also found as genetic risk factors for both RA and ASD. The available evidence suggests that folate level as an important factor during RA, pregnancy and ASD could have pathological and therapeutical significance and should be carefully monitored and investigated in the RA-pregnancy-ASD axis.

A meta-analysis of methotrexate polyglutamates in relation to efficacy and toxicity of methotrexate in inflammatory arthritis, colitis and dermatitis

AIMS

In immune-mediated inflammatory diseases (IMIDs), early symptom control is a key therapeutic goal. Methotrexate (MTX) is the first-line treatment across IMIDs. However, MTX is underutilized and suboptimally dosed, partly due to the inability of making individualized treatment decisions through therapeutic drug monitoring (TDM). To implement TDM in clinical practice, establishing a relationship between drug concentration and disease activity is paramount. In this meta-analysis, we investigated the relationship between concentrations of MTX polyglutamates (MTX-PG) in erythrocytes and efficacy as well as toxicity across IMIDs.

METHODS

Studies analysing MTX-PG in relation to disease activity and/or toxicity were included for inflammatory arthritis (rheumatoid [RA] and juvenile idiopathic arthritis [JIA]), inflammatory bowel disease (Crohn's and ulcerative colitis) and dermatitis (psoriasis and atopic dermatitis). Meta-analyses were performed resulting in several summary effect measures: regression coefficient (β), correlation coefficient and mean difference (of MTX-PG in responders vs. nonresponders) for IMIDs separately and collectively.

RESULTS

Twenty-five studies were included. In RA and JIA, higher MTX-PG was significantly associated with lower disease activity at 3 months (β: -0.002; 95% confidence interval [CI]: -0.004 to -0.001) and after 4 months of MTX use (β: -0.003; 95% CI: -0.005 to -0.002). Similarly, higher MTX-PG correlated with lower disease activity in psoriasis (R: -0.82; 95% CI: -0.976 to -0.102). Higher MTX-PG was observed in RA, JIA and psoriasis responders (mean difference: 5.2 nmol/L MTX-PG_total ; P < .01).

CONCLUSION

We showed that higher concentrations of erythrocyte MTX-PG were associated with lower disease activity in RA, JIA and psoriasis. These findings are an important step towards implementation of TDM for MTX treatment across IMIDs.

Quantitation of methotrexate polyglutamates in human whole blood, erythrocytes and leukocytes collected via venepuncture and volumetric absorptive micro-sampling: a green LC-MS/MS-based method

Low-dose methotrexate (MTX) plays a key role in treatment of rheumatoid arthritis. However, not all patients respond satisfactorily, and no therapeutic drug monitoring has been implemented in clinical practice, despite the fact that MTX therapy has now been available for decades. Analysis of individual intracellular MTX metabolites among rheumatoid arthritis (RA) patients is hampered by the low intracellular concentrations of MTX-PGs which require a highly sensitive method to quantify. Here, we present a rapid and highly sensitive LC (HILIC) MS/MS method with LLOQ 0.1 nM, 0.8 nmol/L for each metabolite of MTX-PG_1-5 and MTX-PG_6-7 respectively. Over a linear range of 0.1-100 nM, 0.8-100 nmol/L for each metabolite of MTX-PG_1-5 and MTX-PG_6-7, respectively, the inter- and intra- accuracy and precision were within 15% of the nominal value for all MTX metabolites. The presented assay was used to assess and compare MTX metabolite concentrations extracted from four different matrices: red blood cells, plasma, peripheral blood mononuclear cells, and whole blood that have been collected either using traditional venepuncture or volumetric absorptive micro-sampling (VAMS) sampling techniques. The presented method not only improves analyte coverage and sensitivity as compared to other published methods; it also improves the greenness.

Association of altered folylpolyglutamate synthetase pre-mRNA splicing with methotrexate unresponsiveness in early rheumatoid arthritis

Objectives

An efficient pharmacological response to MTX treatment in RA patients relies on the retention and accumulation of intracellular MTX-polyglutamates catalysed by the enzyme folylpolyglutamate synthetase (FPGS). We recently identified a partial retention of FPGS intron 8 (8PR) as a prominent splice variant conferring FPGS dysfunction and decreased MTX polyglutamylation in acute lymphoblastic leukaemia. Here, we explored the association between FPGS 8PR levels and lack of MTX responsiveness in RA patients.

Methods

Thirty-six patients undergoing MTX treatment were enrolled from the Combinatie behandeling Reumatoide Artritis (COBRA)-light trial. RNA was isolated from blood samples at baseline, 13 weeks and 26 weeks of therapy, from patients in either COBRA-light (n = 21) or COBRA (n = 15) treatment arms. RT-qPCR analysis was used to assess RNA levels of FPGS 8PR over wild-type FPGS (8WT).

Results

In the COBRA-light treatment arm, higher baseline ratios of 8PR/8WT were significantly associated with higher 44-joint disease activity score (DAS44) at 13 and 26 weeks. Higher baseline ratios of 8PR/8WT also trended towards not obtaining low disease activity (DAS <1.6) and becoming a EULAR non-responder at 13 and 26 weeks. In the COBRA-treatment arm, a significant association was observed between high baseline 8PR/8WT ratios and higher DAS44 score at 26 weeks. Higher 8PR/8WT ratios were associated with non-response at week 26 based on both low disease activity and EULAR criteria.

Conclusion

This study is the first to associate alterations in FPGS pre-mRNA splicing levels with reduced responsiveness to MTX treatment in RA patients.

Trial registration

ISRCTN55552928.

Probing the methotrexate-protein interactions by proteomics and thermostability assay for drug resistance study

Screening of drug targets is critical to understand the mechanism of action of the drug. The aim of this study is to screen the drug-resistant target proteins of the anticancer drug methotrexate (MTX) by using chemical proteomics and to further study the interaction between MTX and its target protein in vitro and in vivo according to the principle of the increasing thermal stability of the target protein after binding with the drug molecule. The results showed that 21 drug resistance related proteins of MTX including phosphoglycerate kinase 1 (PGK1) were detected by quantitative proteomics. The expression of PGK1 increased with the prolongation of incubation time of MTX, indicating PGK1 protein is affected by MTX time dependently in cells. Further the results of the study on the interaction between MTX and PGK1 in vitro and in vivo using cellular thermal shift assay (CETSA) showed that the level of PGK1 in MTX-treated groups was higher than that in the control group under the stimulation of higher temperature conditions, indicating that PGK1 has direct interactions with MTX. The present study provided the data and theoretical support for the study of the resistant target proteins of MTX and a novel point for the extension application of MTX.

Identification of Metabolic Biomarkers in Relation to Methotrexate Response in Early Rheumatoid Arthritis

This study aimed to identify baseline metabolic biomarkers for response to methotrexate (MTX) therapy in rheumatoid arthritis (RA) using an untargeted method. In total, 82 baseline plasma samples (41 insufficient responders and 41 sufficient responders to MTX) were selected from the Treatment in the Rotterdam Early Arthritis Cohort (tREACH, trial number: ISRCTN26791028) based on patients' EULAR response at 3 months. Metabolites were assessed using high-performance liquid chromatography-quadrupole time of flight mass spectrometry. Differences in metabolite concentrations between insufficient and sufficient responders were assessed using partial least square regression discriminant analysis (PLS-DA) and Welch's t-test. The predictive performance of the most significant findings was assessed in a receiver operating characteristic plot with area under the curve (AUC), sensitivity and specificity. Finally, overrepresentation analysis was performed to assess if the best discriminating metabolites were enriched in specific metabolic events. Baseline concentrations of homocystine, taurine, adenosine triphosphate, guanosine diphosphate and uric acid were significantly lower in plasma of insufficient responders versus sufficient responders, while glycolytic intermediates 1,3-/2,3-diphosphoglyceric acid, glycerol-3-phosphate and phosphoenolpyruvate were significantly higher in insufficient responders. Homocystine, glycerol-3-phosphate and 1,3-/2,3-diphosphoglyceric acid were independent predictors and together showed a high AUC of 0.81 (95% CI: 0.72-0.91) for the prediction of insufficient response, with corresponding sensitivity of 0.78 and specificity of 0.76. The Warburg effect, glycolysis and amino acid metabolism were identified as underlying metabolic events playing a role in clinical response to MTX in early RA. New metabolites and potential underlying metabolic events correlating with MTX response in early RA were identified, which warrant validation in external cohorts.

Pharmacogenetic aspects of methotrexate in a cohort of Colombian patients with rheumatoid arthritis

Methotrexate (MTX) is the most commonly used disease-modifying antirheumatic drug for the treatment of rheumatoid arthritis (RA). However, over time, ~40% of patients may experience therapeutic failure or drug toxicity. The genetic variability of the enzymes involved in the MTX metabolic pathway seem to serve an important role in the eventual therapeutic failure or drug toxicity. Depending on the enzymes affected, the toxicity or the therapeutic response may change. The present study reports some of the polymorphisms identified in enzymes in the MTX metabolic pathway that are present in a group of Colombian patients with RA, and assesses the associations of these polymorphisms with toxicity or therapeutic response to the medication. A total of 400 patients with RA were evaluated, of which 76% were women. the average age was 60.7±13.9 years and the duration of the disease was 13.2±10.9 years. The disease activity scoring method, DAS28-CRP, was used to evaluate the therapeutic response. Toxicity was determined based on reports of adverse events during the evaluation of the patients. The single nucleotide polymorphisms (SNPs) assessed using reverse transcription-PCR in the present study were MTHFR C677T, A1298C, ATIC C347G, RFC-1-G80A, FPGS-AG and DHFR-CT. The SNPs of MTHFR C677T (P=0.05) and A1298C (P=0.048) were significantly associated with the efficacy of MTX, and DHFR-CT (P=0.01) and ATIC C347 (P=0.005) were significantly associated with documented toxicity. Haematological, hepatic or renal toxicity was not associated with any of the SNPs. The results obtained in Colombian patients with RA receiving MTX are similar to those reported in other populations; however, the SNPs associated with a lack of response previously reported in the literature were not observed in our data. The SNPs identified in the present study may be used as biomarkers to predict response to MTX in terms of efficacy and toxicity in Colombian patients with RA.

The Structural Basis for Nonsteroidal Anti-Inflammatory Drug Inhibition of Human Dihydrofolate Reductase

Although nonsteroidal anti-inflammatory drugs (NSAIDs) target primarily cyclooxygenase enzymes, a subset of NSAIDs containing carboxylate groups also has been reported to competitively inhibit dihydrofolate reductase (DHFR). In this study, we have characterized NSAID interactions with human DHFR based on kinetic, NMR, and X-ray crystallographic methods. The NSAIDs target a region of the folate binding site that interacts with the p-aminobenzoyl-l-glutamate (pABG) moiety of folate and inhibit cooperatively with ligands that target the adjacent pteridine-recognition subsite. NSAIDs containing benzoate or salicylate groups were identified as having the highest potency. Among those tested, diflunisal, a salicylate derivative not previously identified to have anti-folate activity, was found to have a K_i of 34 μM, well below peak plasma diflunisal levels reached at typical dosage levels. The potential of these drugs to interfere with the inflammatory process by multiple pathways introduces the possibility of further optimization to design dual-targeted analogs.

Development and Validation of a Sensitive UHPLC-MS/MS-Based Method for the Analysis of Folylpolyglutamate Synthetase Enzymatic Activity in Peripheral Blood Mononuclear Cells: Application in Rheumatoid Arthritis and Leukemia Patients

BACKGROUND

Folylpolyglutamate synthetase (FPGS) is a crucial enzyme in both cellular folate homeostasis and the intracellular retention of folate analogue drugs such as methotrexate (MTX), which is commonly used for the treatment of (pediatric) leukemia and the anchor drug in rheumatoid arthritis (RA) treatment. To date, assessment of FPGS catalytic activity relies on assays using radioactive substrates that are labor-intensive and require relatively large numbers of cells. Here, we describe a nonradioactive, ultra-high-performance liquid chromatography-tandem mass spectrometer (UHPLC-MS/MS)-based method allowing for sensitive and accurate measurements of FPGS activity in low cell numbers (ie, 1-2 × 10) of biological specimens, including leukemic blast cells of acute lymphoblastic leukemia patients and peripheral blood mononuclear cells of patients with RA.

METHODS

The UHPLC-MS/MS assay was validated with 2 CCRF-CEM human leukemia cells, one proficient and one deficient in FPGS activity. Linearity of time and protein input were tested by measuring FPGS activity at 30-180 minutes of incubation time and 10-300 mcg protein extract. In addition, FPGS enzyme kinetic parameters were assessed.

RESULTS

The FPGS enzymatic assay showed a linear relation between FPGS activity and protein input (R ≥ 0.989) as well as incubation time (R ≥ 0.996). Moreover, the UHPLC-MS/MS method also allowed for evaluation of FPGS enzyme kinetic parameters revealing Km values for the substrates MTX and L-glutamic acid of 64 µmol/L and 2.2 mmol/L, respectively. The mean FPGS activity of acute lymphoblastic leukemia blast cells (n = 4) was 3-fold higher than that of CCRF-CEM cells and 44-fold and 88-fold higher than that of peripheral blood mononuclear cells from MTX-naive (n = 9) and MTX-treated RA patients (n = 6), respectively.

CONCLUSIONS

Collectively, given its sensitivity with low cell numbers and avoidance of radioactive substrates, UHPLC-MS/MS-based analysis of FPGS activity may be eligible for routine therapeutic drug monitoring of MTX in RA and leukemia for therapy (non)response evaluations.

MTHFR, TYMS and SLCO1B1 polymorphisms and adverse liver effects of methotrexate in rheumatoid arthritis

Aims: To investigate whether variants of MTHFR, TYMS and SLCO1B1 are associated with ALT elevation in rheumatoid arthritis patients starting methotrexate (MTX). Patients & methods: Clinical and laboratory data were collected from the start of MTX treatment. Genotyping of MTHFR, TYMS and SLCO1B1 was performed. Univariate and multiple logistic regression were used for statistical analysis. Results: 34 out of 369 patients experienced ALT >1.5 × ULN less than 6 months from start. MTHFR A1298C (rs1801131) was nominally associated with an ALT >1.5 × ULN within 6 months after the start of MTX (OR = 1.7 [95% CI: 1.04-2.9]; p = 0.03), but did not pass correction for multiple testing. A multiple model containing MTHFR 1298C and clinical factors predicted the outcome (C-statistic 0.735). TYMS and SLCO1B1 were not associated with the outcome. Conclusions: A model containing MTHFR 1298C and clinical factors might predict risk of early ALT elevation.

Methotrexate pharmacogenetics in the treatment of rheumatoid arthritis

For many decades, methotrexate (MXT) has remained the drug of choice in the treatment of rheumatoid arthritis (RA). Unfortunately, a considerable number of patients do not achieve an appropriate therapeutic response. Pharmacogenetics studies do not give usable results regarding differences in MTX response among RA patients. The mechanism of MTX action in RA is not completely understood. We present and discuss data regarding the molecular basis of folate and adenosine pathways, the most obvious MTX targets, to explain possible causes of therapy failure. The molecular basis of the disease could also have an impact on therapy outcomes and in this review we explore this. Finally, we make a short review of available pharmacogenetics study results.

Association of MTHFR and RFC1 gene polymorphisms with methotrexate efficacy and toxicity in Chinese Han patients with rheumatoid arthritis

Objective

The objective was to explore the association of methylene tetrahydrofolate reductase (MTHFR) C667T and A1298C and reduced folate carrier 1 (RFC-1) A80G single nucleotide polymorphisms (SNP) with rheumatoid arthritis (RA) and efficacy and toxicity of methotrexate (MTX) treatment in Chinese Han patients in Henan, China.

Methods

Two hundred ninety-six patients with RA were enrolled (cases) and 120 healthy individuals served as controls. The genotypes of MTHFR C667T and A1298C SNP and RFC-1 A80G SNP were detected by restriction fragment length polymorphism-PCR and compared between cases and controls. We analyzed correlations of clinical effect, toxicity, and SNPs after 6 months of MTX treatment.

Results

We detected no significant differences in MTHFR C677T and A1298C and RFC-1 A80G SNPs between cases and controls. The RFC-1 A80G SNP differed between RA patients with good and poor efficacy after 6 months of MTX, and was an independent factor of MTX efficacy. The MTHFR C677T SNP was differently distributed in the adverse drug reaction (ADR) and non-ADR groups and was an independent factor of MTX toxicity.

Conclusions

In Chinese Han patients with RA, the MTHFR C667T SNP may correlate with MTX toxicity, whereas the RFC-1 A80G SNP may correlate with MTX efficacy rather than toxicity.

The folate receptor β as a macrophage-mediated imaging and therapeutic target in rheumatoid arthritis

Macrophages play a key role in the pathophysiology of rheumatoid arthritis (RA). Notably, positive correlations have been reported between synovial macrophage infiltration and disease activity as well as therapy outcome in RA patients. Hence, macrophages can serve as an important target for both imaging disease activity and drug delivery in RA. Folate receptor β (FRβ) is a glycosylphosphatidyl (GPI)-anchored plasma membrane protein being expressed on myeloid cells and activated macrophages. FRβ harbors a nanomolar binding affinity for folic acid allowing this receptor to be exploited for RA disease imaging (e.g., folate-conjugated PET tracers) and therapeutic targeting (e.g., folate antagonists and folate-conjugated drugs). This review provides an overview of these emerging applications in RA by summarizing and discussing properties of FRβ, expression of FRβ in relation to macrophage polarization, FRβ-targeted in vivo imaging modalities, and FRβ-directed drug targeting.

Transcriptome analysis of peripheral blood from patients with rheumatoid arthritis: a systematic review

In the era of precision medicine, transcriptome analysis of whole gene expression is an essential technology. While DNA microarray has a limited dynamic range and a problem of background hybridization, RNA sequencing (RNA-seq) has a broader dynamic range and a lower background signal that increase the sensitivity and reproducibility. While transcriptome analyses in rheumatoid arthritis (RA) have generally focused on whole peripheral blood mononuclear cells (PBMC), analyses of detailed cell subsets have an increased need for understanding the pathophysiology of disease because the involvement of CD4⁺ T cells in the pathogenesis of RA has been established. Transcriptome analysis of detailed CD4⁺ T cell subsets or neutrophils shed new light on the pathophysiology of RA. There are several analyses about the effect of biological treatment. Many studies report the association between type I interferon signature gene expression and response to therapy.

Prophylactic and therapeutic activity of alkaline phosphatase in arthritic rats: single-agent effects of alkaline phosphatase and synergistic effects in combination with methotrexate

Alkaline phosphatase (AP) is a gate-keeper of innate immune system responses by detoxifying inflammation triggering moieties released from endogenous and external sources. We examined whether AP's broad mechanism of action constitutes a safe therapeutic, either as single agent or combined with methotrexate (MTX), for chronic inflammatory disorders, for example, rheumatoid arthritis (RA). A rat model for RA was used with repeated intra-articular methylated bovine serum albumin (mBSA) injections in 1 knee ("arthritic" knee), with the contralateral knee serving as internal control. AP (200 µg, subcut) was administered before mBSA injections (prophylactic setting) or after arthritis induction (therapeutic setting) or combined with MTX (0.3 mg/kg or 1 mg/kg; intraperitoneally). As end point of treatment outcome, macrophage infiltration in knees, liver, and spleen was assessed by immunohistochemistry (ED1 and ED2 expression), immunofluoresence (macrophage marker folate receptor-β [FRβ]), and [¹⁸F]fluoro-polyethylene glycol-folate positron emission tomography (PET) (macrophage imaging) and ex vivo tissue distribution. Single-agent AP treatment and combinations with MTX were well tolerated. Both prophylactic and therapeutic AP markedly reduced synovial macrophage infiltration in arthritic knees (ED1: 3.5- to 4-fold; ED2: 3.5- to 6-fold), comparable with MTX treatment. AP-MTX combinations slightly improved on single agent effects. PET monitoring and ex vivo tissue distribution studies corroborated the impact of AP, MTX, and AP-MTX on reducing synovial macrophage infiltration. Beyond localized articular effects, AP also revealed systemic anti-inflammatory effects by a 2-fold reduction of ED1, ED2, and FRβ⁺ macrophages in liver and spleen of arthritic rats. Collectively, single-agent AP and AP combined with MTX elicited local and systemic anti-arthritic activity in arthritic rats.

Increased baseline RUNX2, caspase 3 and p21 gene expressions in the peripheral blood of disease-modifying anti-rheumatic drug-naïve rheumatoid arthritis patients are associated with improved clinical response to methotrexate therapy

OBJECTIVE

To investigate the potential of the baseline gene expression in the whole blood of disease-modifying anti-rheumatic drug-naïve rheumatoid arthritis (RA) patients for predicting the response to methotrexate (MTX) treatment.

METHODS

Twenty-six control subjects and 40 RA patients were examined. Clinical, immunological and radiographic parameters were assessed before and after 24 months of follow-up. The gene expressions in the whole blood were measured using real-time reverse transcription polymerase chain reaction. The protein concentrations in peripheral blood mononuclear cells were quantified using enzyme-linked immunosorbent assay. Receiver operating characteristic curve analyses were used to suggest thresholds that were associated with the prediction of the response.

RESULTS

Decreases in the disease activity at the end of the study were accompanied by significant increases in joint space narrowing score (JSN). Positive correlations between the expressions of the Unc-51-like kinase 1 (ULK1) and matrix metalloproteinase 9 (MMP-9) genes with the level of C-reactive protein and MMP-9 expression with Disease Activity Score of 28 joints (DAS28) and swollen joint count were noted at baseline. The baseline tumor necrosis factor (TNF)α gene expression was positively correlated with JSN at the end of the follow-up, whereas p21, caspase 3, and runt-related transcription factor (RUNX)2 were correlated with the ΔDAS28 values.

CONCLUSIONS

Our results suggest that the expressions of MMP-9 and ULK1 might be associated with disease activity. Increased baseline gene expressions of RUNX2, p21 and caspase 3 in the peripheral blood might predict better responses to MTX therapy.

In-vivo monitoring of anti-folate therapy in arthritic rats using [18F]fluoro-PEG-folate and positron emission tomography

Background

Folate receptor β (FRβ) is involved in facilitating cellular uptake of folates and anti-folates (such as methotrexate (MTX)). In rheumatoid arthritis, FRβ is expressed on synovial macrophages and recently has been explored as a biomarker for imaging in arthritic rats using the folate-based positron emission tomography (PET) tracer [¹⁸F]fluoro-PEG-folate. The purpose of this study was to examine whether this folate tracer can also be used to monitor therapeutic efficacy of MTX in arthritic rats.

Methods

Arthritic rats received either no treatment or MTX therapy (1 mg/kg, either 2× or 4×). Healthy rats did not receive any arthritic induction or therapy. [¹⁸F]fluoro-PEG-folate PET-CT scans (60 min) were performed before and after MTX therapy. Following PET, the ex-vivo tissue distribution of radioactivity was determined in excised knees and multiple tissues. Synovial macrophage infiltration in knee sections was quantified by immunohistochemistry using ED1 and ED2 antibodies.

Results

PET scans clearly visualized increased uptake of [¹⁸F]fluoro-PEG-folate in arthritic knees compared with contralateral knees. Significantly lower standard uptake values (1.5-fold, p < 0.01) were observed in arthritic knees of both MTX-treated groups after therapy, approximating the levels seen in healthy rats. Consistently, ex-vivo tissue distribution demonstrated a 2–4-fold lower tracer uptake in the arthritic knee of 2× and 4× MTX-treated rats, respectively, compared with control rats. These results were corroborated with significantly reduced (2–4-fold, p < 0.01) ED1-positive and ED2-positive synovial macrophages in arthritic knees of the MTX-treated rats compared with those of the control rats.

Conclusion

This study in arthritic rats underscores the potential and usefulness of [¹⁸F]fluoro-PEG-folate PET as a therapeutic monitoring tool of MTX therapy and potentially other anti-folate treatment of arthritis.

Much more than you expected: The non-DHFR-mediated effects of methotrexate

BACKGROUND

For decades, methotrexate (MTX; amethopterin) has been known as an antifolate inhibitor of dihydrofolate reductase (DHFR), and it is widely used for the treatment of various malignancies and autoimmune diseases. Although the inclusion of MTX in various therapeutic regimens is based on its ability to inhibit DHFR and consequently to suppress the synthesis of pyrimidine and purine precursors, recent studies have shown that MTX is also able to target other intracellular pathways that are independent of folate metabolism.

SCOPE OF REVIEW

The main aim of this review is to summarize the most important, up-to-date findings of studies regarding the non-DHFR-mediated mechanisms of MTX action.

MAJOR CONCLUSIONS

The effectiveness of MTX is undoubtedly caused by its capability to affect various intracellular pathways at many levels. Although the most important therapeutic mechanism of MTX is strongly based on the inhibition of DHFR, many other effects of this compound have been described and new studies bring new insights into the pharmacology of MTX every year.

GENERAL SIGNIFICANCE

Identification of these new targets for MTX is especially important for a better understanding of MTX action in new protocols of combination therapy.

Mechanism of action of methotrexate in rheumatoid arthritis, and the search for biomarkers

The treatment and outcomes of patients with rheumatoid arthritis (RA) have been transformed over the past two decades. Low disease activity and remission are now frequently achieved, and this success is largely the result of the evolution of treatment paradigms and the introduction of new therapeutic agents. Despite the rapid pace of change, the most commonly used drug in RA remains methotrexate, which is considered the anchor drug for this condition. In this Review, we describe the known pharmacokinetic properties and putative mechanisms of action of methotrexate. Consideration of the pharmacodynamic perspective could inform the development of biomarkers of responsiveness to methotrexate, enabling therapy to be targeted to specific groups of patients. Such biomarkers could revolutionize the management of RA.

Proteome Analysis of Rheumatoid Arthritis Gut Mucosa

Rheumatoid arthritis (RA) is an inflammatory joint disease leading to cartilage damage and ultimately impaired joint function. To gain new insight into the systemic immune manifestations of RA, we characterized the colon mucosa proteome from 11 RA-patients and 10 healthy controls. The biopsies were extracted by colonoscopy and analyzed by label-free quantitative proteomics, enabling the quantitation of 5366 proteins. The abundance of dihydrofolate reductase (DHFR) was statistically significantly increased in RA-patient biopsies compared with controls and correlated with the administered dosage of methotrexate (MTX), the most frequently prescribed immunosuppressive drug for RA. Additionally, our data suggest that treatment with Leflunomide, a common alternative to MTX, increases DHFR. The findings were supported by immunohistochemistry with confocal microscopy, which furthermore demonstrated that DHFR was located in the cytosol of the intestinal epithelial and interstitial cells. Finally, we identified 223 citrullinated peptides from 121 proteins. Three of the peptides were unique to RA. The list of citrullinated proteins was enriched in extracellular and membrane proteins and included known targets of anticitrullinated protein antibodies (ACPAs). Our findings support that the colon mucosa could trigger the production of ACPAs, which could contribute to the onset of RA. The MS data have been deposited to ProteomeXchange with identifiers PXD001608 and PXD003082.

Methotrexate selectively targets human proinflammatory macrophages through a thymidylate synthase/p53 axis

OBJECTIVES

Methotrexate (MTX) functions as an antiproliferative agent in cancer and an anti-inflammatory drug in rheumatoid arthritis (RA). Although macrophages critically contribute to RA pathology, their response to MTX remains unknown. As a means to identify MTX response markers, we have explored its transcriptional effect on macrophages polarised by GM-CSF (GM-MØ) or M-CSF (M-MØ), which resemble proinflammatory and anti-inflammatory macrophages found in RA and normal joints, respectively.

METHODS

The transcriptomic profile of both human macrophage subtypes exposed to 50 nM of MTX under long-term and short-term schedules were determined using gene expression microarrays, and validated through quantitative real time PCR and ELISA. The molecular pathway involved in macrophage MTX-responsiveness was determined through pharmacological, siRNA-mediated knockdown approaches, metabolomics for polyglutamylated-MTX detection, western blot, and immunofluorescence on RA and normal joints.

RESULTS

MTX exclusively modulated gene expression in proinflammatory GM-MØ, where it influenced the expression of 757 genes and induced CCL20 and LIF at the mRNA and protein levels. Pharmacological and siRNA-mediated approaches indicated that macrophage subset-specific MTX responsiveness correlates with thymidylate synthase (TS) expression, as proinflammatory TS⁺ GM-MØ are susceptible to MTX, whereas anti-inflammatory TS^low/- M-MØ and monocytes are refractory to MTX. Furthermore, p53 activity was found to mediate the TS-dependent MTX-responsiveness of proinflammatory TS⁺ GM-MØ. Importantly, TS and p53 were found to be expressed by CD163⁺/TNFα⁺ GM-CSF-polarised macrophages from RA joints but not from normal synovium.

CONCLUSIONS

Macrophage response to MTX is polarisation-dependent and determined by the TS-p53 axis. CCL20 and LIF constitute novel macrophage markers for MTX responsiveness in vitro.

Impaired NFKBIE gene function decreases cellular uptake of methotrexate by down-regulating SLC19A1 expression in a human rheumatoid arthritis cell line

Objective: A non-synonymous single nucleotide polymorphism (nsSNP, rs2233434, Val194Ala) in the NFKBIE (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, epsilon) gene is known to be a rheumatoid arthritis (RA) susceptibility polymorphism in the Japanese RA population and could be closely associated with nuclear factor kappaB (NF-κB) activity. Inflammation caused by RA is sometimes associated with changes in expression levels of MTX (methotrexate) pathway-related genes. It is of interest to examine whether the NFKBIE gene had any influences on the mode of MTX action.

Methods: Both knockdown of NFKBIE gene expression and overexpression of wild-type NFKBIE and Val194Ala mutation were performed. A transfected human RA synovial cell line was cultured and then gene expressions in the MTX pathway were measured. In addition, we measured the uptake and efflux of MTX derivatives under the NFKBIE knockdown condition.

Results: Knockdown of NFKBIE reduced the mRNA for SLC19A1, a main MTX membrane transporter, and the intracellular accumulations of MTX derivatives. Moreover, our experiments also confirmed that overexpression of Val194Ala mutant NFKBIE decreased the SLC19A1 mRNA when compared to that of wild-type NFKBIE.

Conclusions: We suggest that the impairment of NFKBIE gene function can reduce the uptake of MTX into cells, suggesting that the gene is an important factor for the RA outcome.

Novel insights in folate receptors and transporters: implications for disease and treatment of immune diseases and cancer

Folate receptors and transporters as well as folate enzymes play an essential role in human disease and form important targets for the treatment of immune diseases and cancer. To discuss new developments in this area, every 2 years a multidisciplinary meeting is held, which aims to be an informal forum for fundamental scientists and clinicians. During this meeting, the regulation of folate transporters and folate enzymes is discussed at the level of expression, transcription, translation, post-translational modification, and splicing and enzyme regulation. Importantly, this knowledge is applied and translated into exciting clinical applications by clinicians with various backgrounds, such as surgeons, nephrologists, rheumatologists and oncologists. Moreover, the meeting provides an excellent forum for a scientific interaction between academia and industry.

High serum level of haptoglobin is associated with the response of 12 weeks methotrexate therapy in recent-onset rheumatoid arthritis patients

BACKGROUND

We previously found, using microarray, haptoglobin (HP) expression signal was 5.1-fold increased in peripheral blood mononuclear cells (PBMCs) from methotrexate (MTX)-resistant rheumatoid arthritis (RA) patients.

OBJECTIVES

To investigate whether serum levels of HP are associated with the response of 12 weeks MTX therapy in recent-onset RA patients.

METHODS

Sixty-nine active RA patients with recent onset (< 24 months) were treated with MTX. Clinical variables, levels of HP messenger RNA (mRNA) in PBMCs and HP serum levels were tested at week 0 and week 12.

RESULTS

After 12 weeks of MTX treatment, 34.7% of RA patients were categorized as responders according to European League Against Rheumatism (EULAR) response criteria (Week 12 Disease Activity Score of 28 joints [DAS-28] ≤ 3.2 and decrease > 1.2) and all others (65.2%) were defined as non-responders. The baseline HP mRNA in PBMCs from non-responders is significantly higher than those in responders (P < 0.05). Similar to mRNA expression, non-responders showed significantly elevated serum HP levels at baseline (369.9 ± 159.8 mg/dL) compared to those in responders (255.3 ± 143.9 mg/dL) (P = 0.01). Serum HP levels were decreased significantly from 255.3 ± 143.9 mg/dL at baseline to 186.4 ± 108.5 mg/dL at week 12 (P = 0.04) in responders, but remained at high levels in non-responders.

CONCLUSIONS

High serum levels of HP at baseline are associated with inadequate response of 12 weeks MTX treatment in recent-onset RA patients. Further replication studies in larger samples are needed to validate HP as a potential predictive biomarker for response to MTX therapy in RA.

1-Methyl-tryptophan synergizes with methotrexate to alleviate arthritis in a mouse model of arthritis

Rheumatoid arthritis (RA) is an inflammatory autoimmune disease with no known cure. Current strategies to treat RA, including methotrexate (MTX), target the later inflammatory stage of disease. Recently, we showed that inhibiting indoleamine-2,3-dioxygenase (IDO) with 1-methyl-tryptophan (1MT) targets autoantibodies and cytokines that drive the initiation of the autoimmune response. Therefore, we hypothesized that combining 1MT with MTX would target both the initiation and chronic inflammatory phases of the autoimmune response and be an effective co-therapeutic strategy for arthritis. To test this, we used K/BxN mice, a pre-clinical model of arthritis that develops joint-specific inflammation with many characteristics of human RA. Mice were treated with 1MT, MTX, alone or in combination, and followed for arthritis, autoantibodies, and inflammatory cytokines. Both 1MT and MTX were able to partially inhibit arthritis when used individually; however, combining MTX + 1MT was significantly more effective than either treatment alone at delaying the onset and alleviating the severity of joint inflammation. We went on to show that combination of MTX + 1MT did not lower inflammatory cytokine or autoantibody levels, nor could the synergistic co-therapeutic effect be reversed by the adenosine receptor antagonist theophylline or be mimicked by inhibition of polyamine synthesis. However, supplementation with folinic acid did reverse the synergistic co-therapeutic effect, demonstrating that, in the K/BxN model, MTX synergizes with 1MT by blocking folate metabolism. These data suggest that pharmacological inhibition of IDO with 1MT is a potential candidate for use in combination with MTX to increase its efficacy in the treatment of RA.

Gene expression analysis in RA: towards personalized medicine

Gene expression has recently been at the forefront of advance in personalized medicine, notably in the field of cancer and transplantation, providing a rational for a similar approach in rheumatoid arthritis (RA). RA is a prototypic inflammatory autoimmune disease with a poorly understood etiopathogenesis. Inflammation is the main feature of RA; however, many biological processes are involved at different stages of the disease. Gene expression signatures offer management tools to meet the current needs for personalization of RA patients' care. This review analyses currently available information with respect to RA diagnostic, prognostic and prediction of response to therapy with a view to highlight the abundance of data, whose comparison is often inconclusive due to the mixed use of material source, experimental methodologies and analysis tools, reinforcing the need for harmonization if gene expression signatures are to become a useful clinical tool in personalized medicine for RA patients.

Pharmacogenetics and pharmacogenomics for rheumatoid arthritis responsiveness to methotrexate treatment: the 2013 update

Rheumatoid arthritis (RA) is a complex, systemic autoimmune disease characterized by chronic inflammation of multiple peripheral joints, which leads to serious destruction of cartilage and bone, progressive deformity and severe disability. Methotrexate (MTX) is one of the first-line drugs commonly used in RA therapy owing to its excellent long-term efficacy and cheapness. However, the efficacy and toxicity of MTX treatment have significant interpatient variability. Genetic factors contribute to this variability. In this review, we have summarized and updated the progress of RA response to MTX treatment since 2009 by focusing on the fields of pharmacogenetics and pharmacogenomics. Identification of genetic factors involved in MTX treatment response will increase the understanding of RA pathology and the development of new personalized treatments.

Methotrexate induces production of IL-1 and IL-6 in the monocytic cell line U937

Introduction

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, the 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.

Methods

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 NF-kB, folate and adenosine pathways to the observed effects was determined by adding appropriate inhibitors to the MTX cultures.

Results

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 NF-kB 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.

Conclusions

MTX induces expression of proinflammatory cytokines in U937 monocytic cells. These effects might mediate the known toxicities of MTX including pneumonitis, mucositis and decreased bone mineral density.