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

Staphylococcus aureus delta toxin modulates both extracellular membrane vesicle biogenesis and amyloid formation

IMPORTANCE

Extracellular membrane vesicles (MVs) produced by Staphylococcus aureus in planktonic cultures encapsulate a diverse cargo of bacterial proteins, nucleic acids, and glycopolymers that are protected from destruction by external factors. δ-toxin, a member of the phenol soluble modulin family, was shown to be critical for MV biogenesis. Amyloid fibrils co-purified with MVs generated by virulent, community-acquired S. aureus strains, and fibril formation was dependent on expression of the S. aureus δ-toxin gene (hld). Mass spectrometry data confirmed that the amyloid fibrils were comprised of δ-toxin. Although S. aureus MVs were produced in vivo in a localized murine infection model, amyloid fibrils were not observed in the in vivo setting. Our findings provide critical insights into staphylococcal factors involved in MV biogenesis and amyloid formation.

Staphylococcus aureus Delta Toxin Modulates both Extracellular Membrane Vesicle Biogenesis and Amyloid Formation

Staphylococcus aureus secretes phenol-soluble modulins (PSMs), a family of small, amphipathic, secreted peptides with multiple biologic activities. Community-acquired S. aureus strains produce high levels of PSMs in planktonic cultures, and PSM alpha peptides have been shown to augment the release of extracellular membrane vesicles (MVs). We observed that amyloids, aggregates of proteins characterized by a fibrillar morphology and stained with specific dyes, co-purified with MVs harvested from cell-free culture supernatants of community-acquired S. aureus strains. δ-toxin was a major component of amyloid fibrils that co-purified with strain LAC MVs, and δ-toxin promoted the production of MVs and amyloid fibrils in a dose-dependent manner. To determine whether MVs and amyloid fibrils were generated under in vivo conditions, we inoculated mice with S. aureus harvested from planktonic cultures. Bacterial MVs could be isolated and purified from lavage fluids recovered from infected animals. Although δ-toxin was the most abundant PSM in lavage fluids, amyloid fibrils could not be detected in these samples. Our findings expand our understanding of amyloid fibril formation in S. aureus cultures, reveal important roles of δ-toxin in amyloid fibril formation and MV biogenesis, and demonstrate that MVs are generated in vivo in a staphylococcal infection model.

Importance

Extracellular membrane vesicles (MVs) produced by Staphylococcus aureus in planktonic cultures encapsulate a diverse cargo of bacterial proteins, nucleic acids, and glycopolymers that are protected from destruction by external factors. δ-toxin, a member of the phenol soluble modulin family, was shown to be critical for MV biogenesis. Amyloid fibrils co-purified with MVs generated by virulent, community-acquired S. aureus strains, and fibril formation was dependent on expression of the S. aureus δ-toxin gene ( hld ). Mass spectrometry data confirmed that the amyloid fibrils were comprised of δ-toxin. Although S. aureus MVs were produced in vivo in a localized murine infection model, amyloid fibrils were not observed in the in vivo setting. Our findings provide critical insights into staphylococcal factors involved in MV biogenesis and amyloid formation.

Potential therapeutic application of biophenols - plants secondary metabolites in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic autoimmune disease showed that persistent inflammation in the joints, induces the cartilage destruction, bone erosion, and leukocyte infiltration in the synovium. RA mostly affects the joints of hands, feet, wrists, ankles, and knees. Each year, approximately 20-40 new cases are reported per lac population and the disease affects women more than men. The etiology of RA is still unknown, but many pathways have been identified as potential targets in its pathophysiology, including the PI3K/AKT signaling pathway, NF-κB signaling, Adenosine signaling, Wnt, SYK/BTK, and mTOR signaling pathways. Biophenol, plant secondary metabolite, is considered one of the most abundantly phytoconstituents to have potential anti-inflammatory effects associated with multiple pathways. These indicate that biophenols can be used for its protective effect on the development and symptoms of RA. The current review explores and discusses the role of different biophenols in the treatment of RA disease.

A Systematic Review Comparing Experimental Design of Animal and Human Methotrexate Efficacy Studies for Rheumatoid Arthritis: Lessons for the Translational Value of Animal Studies

Increased awareness and understanding of current practices in translational research is required for informed decision making in drug development. This paper describes a systematic review of methotrexate for rheumatoid arthritis, comparing trial design between 147 animal and 512 human studies. Animal studies generally included fewer subjects than human studies, and less frequently reported randomisation and blinding. In relation to life span, study duration was comparable for animals and humans, but included animals were younger than included humans. Animal studies often comprised males only (61%), human studies always included females (98% included both sexes). Power calculations were poorly reported in both samples. Analyses of human studies more frequently comprised Chi-square tests, those of animal studies more frequently reported analyses of variance. Administration route was more variable, and more frequently reported in animal than human studies. Erythrocyte sedimentation rate and c-reactive protein were analysed more frequently in human than in animal studies. To conclude, experimental designs for animal and human studies are not optimally aligned. However, methotrexate is effective in treating rheumatoid arthritis in animal models and humans. Further evaluation of the available evidence in other research fields is needed to increase the understanding of translational success before we can optimise translational strategies.

Low-Dose Methotrexate Prevents Primary and Secondary Humoral Immune Responses and Induces Immune Tolerance to a Recombinant Immunotoxin

Recombinant immunotoxins (RITs) are chimeric proteins being developed for cancer treatment. They are composed of an Ab fragment that targets a cancer Ag and a cytotoxic portion of Pseudomonas exotoxin A. They are effective for patients with hematologic malignancies with defective immunity, but their efficacy against solid tumors is limited by anti-drug Ab (ADA) responses in immune-competent patients. Pre-existing Abs or immune memory owing to previous toxin exposure represent additional hurdles because they induce rapid and strong ADA responses. Here, we evaluated the efficacy of methotrexate (MTX) to prevent ADA formation against the mesothelin-targeting RIT LMB-100 in naive mice and in mice with pre-existing Abs. We found that low-dose MTX combined with LMB-100 completely suppressed the formation of ADAs in a dose- and frequency-dependent manner. Suppression of the immune response restored blood levels of LMB-100 and prevented its neutralization. Furthermore, combination of MTX with LMB-100 did not compromise the immune response against a second Ag given after stopping MTX, indicating specific immune tolerance. Adoptive transfer of splenocytes suppressed Ab responses to LMB-100 in recipient mice, indicating a durable immune tolerance. We conclude that combination of MTX and LMB-100 is effective at preventing immune responses in a durable, Ag-specific manner. We propose combining low-dose MTX in immune-competent cancer patients receiving RIT therapy to prevent immunogenicity. This approach could be applied to other immunogenic therapeutic agents and to proteins for which there is pre-existing immunity.

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.

Four-component Staphylococcus aureus vaccine 4C-staph enhances Fcγ receptor expression in neutrophils and monocytes and mitigates S. aureus infection in neutropenic mice

Staphylococcus aureus is a human bacterial pathogen causing a variety of diseases. The occurrence of multidrug-resistant strains of Staphylococcus aureus underlines the need for a vaccine. Defining immune correlates of protection may support the design of an effective vaccine. We used a murine Staphylococcus aureus infection model, in which bacteria were inoculated in an air pouch generated on the back of the animal. Analysis of the air-pouch content in mice immunized or not with an adjuvanted multiantigen vaccine formulation, four-component S. aureus vaccine (4C-Staph), prior to infection allowed us to measure bacteria, cytokines, and 4C-Staph-specific antibodies and to analyze host immune cells recruited to the infection site. Immunization with 4C-Staph resulted in accumulation of antigen-specific antibodies in the pouch and mitigated the infection. Neutrophils were the most abundant cells in the pouch, and they showed the upregulation of Fcγ receptor (FcγR) following immunization with 4C-Staph. Reduction of the infection was also obtained in mice immunized with 4C-Staph and depleted of neutrophils; these mice showed an increase in monocytes and macrophages. Upregulation of the FcγR and the presence of antigen-specific antibodies induced by immunization with 4C-Staph may contribute to increase bacterial opsonophagocytosis. Protection in neutropenic mice indicated that an effective vaccine could activate alternative protection mechanisms compensating for neutropenia, a condition often occurring in S. aureus-infected patients.

Intradermal air pouch leukocytosis as an in vivo test for nanoparticles

The need for test systems for nanoparticle biocompatibility, toxicity, and inflammatory or adaptive immunological responses is paramount. Nanoparticles should be free of microbiological and chemical contaminants, and devoid of toxicity. Nevertheless, in the absence of contamination, these particles may still induce undesired immunological effects in vivo, such as enhanced autoimmunity, hypersensitivity reactions, and fibrosis. Here we show that artificial particles of specific sizes affect immune cell recruitment as tested in a dermal air pouch model in mice. In addition, we demonstrate that the composition of nanoparticles may influence immune cell recruitment in vivo. Aside from biophysical characterizations in terms of hydrodynamic diameter, zeta potential, concentration, and atomic concentration of metals, we show that – after first-line in vitro assays – characterization of cellular and molecular effects by dermal air pouch analysis is straightforward and should be included in the quality control of nanoparticles. We demonstrate this for innate immunological effects such as neutrophil recruitment and the production of immune-modulating matrix metalloproteases such as MMP-9; we propose the use of air pouch leukocytosis analysis as a future standard assay.

Fibroblasts from methotrexate-sensitive mice accumulate methotrexate polyglutamates but those from methotrexate-resistant mice do not

OBJECTIVES

We and others have previously demonstrated that methotrexate (MTX) mediates its anti-inflammatory effects through an increase in cellular release of adenosine. Consistent with this observation, there is no increase in adenosine from exudates of mouse strains resistant to MTX. Because intracellular MTX polyglutamates inhibit AICAR transformylase (ATIC) activity and thereby promote adenosine release we determined whether there is any difference in the capacity of cells from MTX-resistant mice to accumulate MTX polyglutamates.

METHODS

Dermal fibroblasts (DF) from BALBc, MTX-sensitive, and DBA/1J, MTX-resistant, mice were cultured in the presence or absence of MTX. Adenosine concentration in the supernatant and intracellular MTX polyglutamate (MTXPG1-5) concentrations were measured by liquid chromatography. ATIC activity in DF was monitored spectrophotometrically by the formation of formytetrahydrofolate.

RESULTS

MTX (1 μM) increased adenosine production by DF from BALBc sensitive-mice from 269±40 nM to 446±4 nM. No adenosine production was found in supernates of cultured DF from DBA/1J mice regardless of MTX treatment. Intracellular MTX polyglutamates (MTXPG2-4) were detected only in BALBc DFs, not in DBA/1J DF. Further investigation demonstrated that ATIC activity was inhibited following MTX treatment in DF from BALBc mice.

CONCLUSIONS

These data suggest that resistance to the anti-inflammatory effects of MTX could be due to diminished MTX polyglutamate accumulation resulting in diminished ATIC inhibition and adenosine accumulation.

Methotrexate: new therapeutic approaches

Although the first study on the efficacy of methotrexate in the treatment of psoriasis was reported in 1958, scientific evidence for this indication has been scant until quite recently. We now have new data on the pharmacokinetics and mechanism of action of methotrexate and new subcutaneous formulations that have improved the bioavailability, efficacy, and ease of administration of the drug. The results of recent clinical trials comparing methotrexate with several biologic agents have shown it to be the first-line therapy among the classic systemic treatments for psoriasis. Moreover, the incremental cost-effectiveness ratio for subcutaneous methotrexate has been shown to be superior to that of ciclosporin, adalimumab, and infliximab.

Nimesulide improves the disease modifying anti-rheumatic profile of methotrexate in mice with collagen-induced arthritis

Methotrexate is a disease modifying anti-rheumatic drug that is widely used for the treatment of rheumatoid arthritis. Nimesulide is a non-steroidal anti-inflammatory drug which is frequently used as adjuvant therapy for symptomatic alleviation of rheumatoid arthritis. In this study, we have evaluated the potential influence of nimesulide on the disease modifying anti-rheumatic properties of methotrexate using the collagen-induced arthritis model. Mice were immunized with collagen type II for the induction of arthritis and treated with methotrexate (2.5mg/kg) twice a week, nimesulide (20mg/kg) every other day or a combination of both drugs. Treatment started one week after the onset of arthritis until day 40. An arthritic index was used to compare the severity of arthritis between different treatments. In addition, articular hyperalgesia, joint stiffness, radiological deterioration and intra-articular leucocytic infiltration were evaluated. Methotrexate alone showed modest but significant analgesic and anti-inflammatory effects, and the effects of nimesulide were comparable. On the other hand, nimesulide significantly improved the disease modifying anti-rheumatic profile of methotrexate in terms of arthritic index and joint mobility. Furthermore, although nimesulide failed to show any radiological evidence of articular protection, it significantly improved methotrexate-induced joint protection as judged by X-ray analysis.

Induction of CCR2-dependent macrophage accumulation by oxidized phospholipids in the air-pouch model of inflammation

OBJECTIVE

Macrophages are key players in the pathogenesis of rheumatoid synovitis as well as in atherosclerosis. To determine whether atherogenic oxidized phospholipids potentially contribute to synovial inflammation and subsequent monocyte/macrophage recruitment, we examined the effects of oxidized 1- palmitoyl-2-arachidonoyl-sn-3-glycero-phosphorylcholine (OxPAPC) on chemokine expression and leukocyte recruitment in a facsimile synovium in vivo using the murine air-pouch model.

METHODS

Air pouches were raised by 2 injections of sterile air, and inflammation was induced by injecting either lipopolysaccharide (LPS) or OxPAPC into the pouch lumen. Inflammation was assessed by analysis of inflammatory gene expression using reverse transcription-polymerase chain reaction or immunohistochemical analysis, and leukocytes were quantified in the lavage fluid and in the pouch wall after staining with Giemsa or after enzymatic digestion followed by fluorescence-activated cell sorter analysis.

RESULTS

Application of OxPAPC resulted in selective recruitment of monocyte/macrophages into the air-pouch wall, but not in the lumen. In contrast, LPS induced both monocyte and neutrophil accumulation in the pouch lumen as well as in the wall. LPS, but not OxPAPC, induced the expression of adhesion molecules E-selectin, P-selectin, intercellular adhesion molecule 1, and vascular cell adhesion molecule 1. OxPAPC increased the expression of the CCR2 ligands monocyte chemotactic protein 1 (MCP-1), MCP-3, and MCP-5, as well as RANTES and growth-related oncogene alpha (GROalpha), while it down-regulated the expression of CCR2 on macrophages. Moreover, oxidized phospholipid-induced macrophage accumulation was abrogated in CCR2-/- mice.

CONCLUSION

These data demonstrate that oxidized phospholipids trigger a type of inflammatory response that leads to selective macrophage accumulation in vivo, a process relevant for the pathogenesis of chronic inflammatory rheumatic diseases.

Point mutation of tyrosine 759 of the IL-6 family cytokine receptor, gp130, augments collagen-induced arthritis in DBA/1J mice

Background

Knock-in mice (gp130F759) with a Y759F point mutation in gp130, a signal transducing receptor subunit shared by members of the IL-6 cytokine family, show sustained activation of STAT3, enhanced acute-phase or immune responses, and autoimmune arthritis. We conducted a detailed analysis of collagen-induced arthritis (CIA) in gp130F759 with a DBA/1J background (D/J.gp130F759).

Methods

We backcrossed gp130F759 to C57BL/6 and DBA/1J, and compared the pathologic changes, including occurrence of arthritis, in the two distinct genetic backgrounds. We analyzed CIA in D/J.gp130F759 and investigated the effects of methotrexate (MTX) on CIA.

Results

C57BL/6 background gp130F759 mice, but not D/J.gp130F759, spontaneously developed polyarthritis and glomerulonephritis. On the other hand, keratitis of the eyes only developed in D/J.gp130F759, indicating the influence of genetic background on disease development in gp130F759 mice. Resistance of the DBA/1J background against spontaneous arthritis urged us to examine CIA in D/J.gp130F759. CIA in D/J.gp130F759 was more severe, with greater bone destruction, than the control mice. After collagen immunization, splenomegaly and serum levels of rheumatoid factor and anti-DNA antibody were augmented in D/J.gp130F759. Bio-Plex analysis of serum cytokines revealed increased IL-12p40 and PDGF-BB before immunization, and increased levels of IFN-γ, IL-17, TNF-α, IL-9, and MIP-1β 8 days after the booster dose. IL-6 and PDGF-BB in D/J.gp130F759 showed distinct kinetics from the other cytokines; higher levels were observed after arthritis development. MTX partially attenuated the development of arthritis and inhibited bone destruction in D/J.gp130F759, with reduction of anti-type II collagen antibody levels, suggesting that MTX mainly affects antigen-specific immune responses in CIA.

Conclusion

The Tyr-759 point mutation of the IL-6 family cytokine receptor subunit, gp130, caused autoimmune disease, and this was also influenced by the genetic background. CIA in D/J.gp130F759 is useful for evaluating drugs in a relatively short period because sustained activation of STAT3 may enhance the disease symptoms.

Adenosine receptors: therapeutic aspects for inflammatory and immune diseases

Adenosine is a key endogenous molecule that regulates tissue function by activating four G-protein-coupled adenosine receptors: A1, A2A, A2B and A3. Cells of the immune system express these receptors and are responsive to the modulatory effects of adenosine in an inflammatory environment. Animal models of asthma, ischaemia, arthritis, sepsis, inflammatory bowel disease and wound healing have helped to elucidate the regulatory roles of the various adenosine receptors in dictating the development and progression of disease. This recent heightened awareness of the role of adenosine in the control of immune and inflammatory systems has generated excitement regarding the potential use of adenosine-receptor-based therapies in the treatment of infection, autoimmunity, ischaemia and degenerative diseases.

Collagen-induced arthritis in C57BL/6 mice is associated with a robust and sustained T-cell response to type II collagen

Many genetically modified mouse strains are now available on a C57BL/6 (H-2b) background, a strain that is relatively resistant to collagen-induced arthritis. To facilitate the molecular understanding of autoimmune arthritis, we characterised the induction of arthritis in C57BL/6 mice and then validated the disease as a relevant pre-clinical model for rheumatoid arthritis. C57BL/6 mice were immunised with type II collagen using different protocols, and arthritis incidence, severity, and response to commonly used anti-arthritic drugs were assessed and compared with DBA/1 mice. We confirmed that C57BL/6 mice are susceptible to arthritis induced by immunisation with chicken type II collagen and develop strong and sustained T-cell responses to type II collagen. Arthritis was milder in C57BL/6 mice than DBA/1 mice and more closely resembled rheumatoid arthritis in its response to therapeutic intervention. Our findings show that C57BL/6 mice are susceptible to collagen-induced arthritis, providing a valuable model for assessing the role of specific genes involved in the induction and/or maintenance of arthritis and for evaluating the efficacy of novel drugs, particularly those targeted at T cells.

B cell depletion delays collagen-induced arthritis in mice: arthritis induction requires synergy between humoral and cell-mediated immunity

Rheumatoid arthritis is a systemic autoimmune disease. B cells are likely to play a critical role in arthritis pathogenesis, although it is unclear whether they are necessary for disease induction, autoantibody production, or disease progression. To assess the role of B cells in inflammatory arthritis, B cells were depleted using mouse anti-mouse CD20 mAbs in a mouse model of collagen-induced arthritis. CD20 mAbs effectively depleted mature B cells from adult DBA-1 mice. When B cells were depleted using CD20 mAbs before collagen immunization, there was a delay in disease onset and autoantibody production, with significantly diminished severity of arthritis both clinically and histologically. B cell depletion further delayed disease onset if initiated before, as well as after, collagen immunization. However, in both cases, the eventual reappearance of peripheral B cells triggered autoantibody production and the subsequent development of arthritis in collagen-sensitized mice. By contrast, B cell depletion after collagen immunizations did not have a significant effect on arthritis progression or severity. Thus, disease symptoms were only induced when peripheral B cells and their autoantibody products were present in collagen-immunized mice, documenting a critical role for B cells during the elicitation phase of collagen-induced arthritis. These studies suggest that B cell depletion strategies will be most effective when initiated early in the development of inflammatory arthritis, with sustained B cell depletion required to inhibit the production of isotype-switched pathogenic Abs and the evolution of joint inflammation and destruction.

The antiinflammatory mechanism of methotrexate depends on extracellular conversion of adenine nucleotides to adenosine by ecto-5'-nucleotidase: findings in a study of ecto-5'-nucleotidase gene-deficient mice

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.

Potential anti-inflammatory actions of the elmiric (lipoamino) acids

A library of amino acid-fatty acid conjugates (elmiric acids) was synthesized and evaluated for activity as potential anti-inflammatory agents. The compounds were tested in vitro for their effects on cell proliferation and prostaglandin production, and compared with their effects on in vivo models of inflammation. LPS stimulated RAW 267.4 mouse macrophage cells were the in vitro model and phorbol ester-induced mouse ear edema served as the principal in vivo model. The prostaglandin responses were found to be strongly dependent on the nature of the fatty acid part of the molecule. Polyunsaturated acid conjugates produced a marked increase in media levels of i15-deoxy-PGJ(2) with minimal effects on PGE production. It is reported in the literature that prostaglandin ratios in which the J series predominates over the E series promote the resolution of inflammatory conditions. Several of the elmiric acids tested here produced such favorable ratios suggesting that their potential anti-inflammatory activity occurs via a novel mechanism of action. The ear edema assay results were generally in agreement with the prostaglandin assay findings indicating a connection between them.

Drug Insight: resistance to methotrexate and other disease-modifying antirheumatic drugs--from bench to bedside

The chronic nature of rheumatoid arthritis (RA) means that patients require drug therapy for many years. Many RA patients, however, have to discontinue treatment because of drug-related toxic effects, loss of efficacy, or both. The underlying molecular cause for loss of efficacy of antirheumatic drugs is not fully understood, but it might be mediated, at least in part, by mechanisms shared with resistance to anticancer drugs. This Review outlines molecular mechanisms that could be involved in the onset of resistance to, or the loss of efficacy of, disease-modifying antirheumatic drugs in RA patients, including methotrexate, sulfasalazine, chloroquine, hydroxychloroquine, azathioprine, and leflunomide. The mechanisms suggested are based on findings from experimental laboratory studies of specific drug-uptake and drug-efflux transporters belonging to the superfamily of multidrug-resistance transporters, alterations in intracellular drug metabolism, and genetic polymorphisms of drug transporters and metabolic enzymes. We also discuss strategies to overcome resistance and the current clinical studies aiming to predict response and risk of toxic effects. More in-depth knowledge of the mechanisms behind these features could help facilitate a more efficient use of disease-modifying antirheumatic drugs.

Cellular pharmacodynamics of immunosuppressive drugs for individualized medicine

The therapeutic effects of immunosuppressive drugs are known to deviate largely between patients, but efficient strategies for the differentiation of patients who show clinical resistance to immunosuppressive therapies have not been established. Accordingly, a considerable number of patients receive treatment with immunosuppressive drugs despite the onset of serious side effects and poor responses. Cellular pharmacodynamics of immunosuppressive drugs in vitro using peripheral lymphocytes derived from each patient, an attractive way to distinguish resistant patients, is respected and has been applied to the carrying out of individualized immunosuppressive therapy. In this article, I summarize experimental procedures for assaying immune cell responses to immunosuppressive drugs in vitro, and highlight the relationship between cellular sensitivity to immunosuppressive drugs and the therapeutic efficacy of drugs in organ transplantation and several immunological disorders. I will also overview the molecular mechanisms and genetic bases for cellular and clinical resistance to immunosuppressive drugs. Lastly, the future clinical prospects for the application of in vitro drug sensitivity tests for "patient-tailored" immunosuppressive therapies are discussed.

Relationship between genetic variants in the adenosine pathway and outcome of methotrexate treatment in patients with recent-onset rheumatoid arthritis

OBJECTIVE

Among patients with rheumatoid arthritis (RA), there is a high degree of interindividual variability in the degree of response to methotrexate (MTX) treatment. This study was undertaken to explore polymorphisms in genes contributing to antiinflammatory adenosine release as novel predictors of MTX treatment outcome.

METHODS

In 205 patients with newly diagnosed RA, 5 polymorphisms in 5 genes coding for enzymes related to the release of adenosine were analyzed. All patients received standardized MTX treatment (up to 25 mg per week orally), combined with folic acid. MTX efficacy was evaluated by the Disease Activity Score (DAS) and compared among genotypes. The association between MTX-related adverse events and genotype was also assessed. The following polymorphisms were determined: AMPD1 34C>T, ATIC 347C>G, ITPA 94C>A, MTR 2756A>G, and MTRR 66A>G. When significant differences were found by chi-square analysis, odds ratios (ORs) and 95% confidence intervals were calculated.

RESULTS

Patients carrying the AMPD1 34T allele, ATIC 347CC, or ITPA 94CC were more likely to have a good clinical response, as defined by a DAS of < or =2.4 (OR [95% confidence interval] 2.1 [1.0-4.5], 2.5 [1.3-4.7], and 2.7 [1.1-8.1], respectively). The likelihood of a good clinical response was increased if patients possessed all 3 favorable genotypes (OR 27.8 [95% confidence interval 3.2-250]). Regarding toxicity, only ATIC G allele carriers experienced a greater frequency of adverse events (OR 2.0 [95% confidence interval 1.1-3.7]).

CONCLUSION

Polymorphisms in the AMPD1, ATIC, and ITPA genes are associated with good clinical response to MTX treatment. These findings indicate that genotyping may help in the identification of patients who will benefit most from MTX treatment and may assist clinicians in making treatment decisions regarding patients with recent-onset RA.

Pharmacogenomics in the treatment of rheumatoid arthritis: clinical implication and perspective

Rheumatoid arthritis (RA) is a chronic inflammatory disease. The inflammatory process of the joint destroys articular architecture and causes a significant disability. The efficacy of disease modifying antirheumatic drugs such as methotrexate, sulfasalazine and biological response modifiers, is widely accepted. However, the outcome of the treatment with these agents is known to vary among patients. The application of the pharmacogenomics is expected to reduce toxicities and enhance the desirable effects of therapeutic agents for RA. Recently, pharmacogenomic studies on methotrexate, sulfasalazine and tumor necrosis factor-α inhibitors have been reported. These investigations suggest that the pharmacogenomic approach is useful for the treatment of RA, although there are points to be considered before the translation of the pharmacogenomic data into clinical practice. This review focuses on the latest information on the pharmacogenomics of antirheumatic drugs and its clinical implication in the treatment of RA.