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

Abstract

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

Cellular pharmacodynamics of immunosuppressive drugs for individualized medicine

“…In addition, it has been reported that circulating intracellular levels of methotrexate glutamates in red blood cells and polymorphonuclear cells correlate with the clinical efficacy, but no toxicity, in RA [104]. Genetically based resistance to the effects of methotrexate has also been suggested in the airpouch model of acute inflammation [167].…”

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

“…Figure 4 shows several examples of the effects of elmiric acids in the subcutaneous pouch assay using two methods for inducing an inflammatory response, namely, a combination of cytokines in panel A and carrageenan in panel B. The subcutaneous air pouch simulates a synovium lined joint space by providing a blind connective tissue cavity without a mesothelial basement membrane; the pouch lining has the two cell types (fibroblasts and macrophage-like cells) common to synovia [41][42][43] . While the precision of the assay was improved over the paw edema, an unexpected discrepancy arose with the palmitoyl derivatives when carrageenan was the inducer.…”

Four-Component Staphylococcus aureus Vaccine 4C-Staph Enhances Fcγ Receptor Expression in Neutrophils and Monocytes and Mitigates S. aureus Infection in Neutropenic Mice

“…Among them, an "air-pouch" murine model has been extensively used to study inflammation (7)(8)(9). This model was adapted further to evaluate the effect of fibrinogen depletion on S. aureus infections (10), as well as to study the host responses to group A Streptococcus infection, and the reduction of infection in mice immunized with specific antigens (11)(12)(13).…”