Multidrug resistance proteins and DMARD efficacy in rheumatoid arthritis

Background

Upregulation of drug efflux pumps belonging to the family of ATP-binding cassette (ABC) transporters can confer loss of efficacy/resistance to muliple cytostatic drugs, a phenotype referred to as multidrug resistance (MDR). In clinical rheumatology practice, loss of efficacy of disease-modifying antirheumatic drugs (DMARDs) is observed following long-term treatment of rheumatoid arthritis (RA) patients. Whether loss of efficacy/resistance to DMARDs and cytostatic drugs share common molecular mechanisms is not known.

Objective

The aim of this study was to delineate the potential role of MDR proteins in the loss of efficacy/resistance to DMARDs.

Methods

In vitro model systems of human T cells and monocytic/macrophage cell lines were used to provoke resistance to the DMARD sulfasalazine (SSZ). SSZ-resistant cell lines, as well as macrophages from RA patients and healthy controls, were characterized for expression of MDR proteins.

Results

Development of SSZ resistance in T cells and monocytic/macrophage cell lines was accompanied by a marked induction of the MDR protein ABCG2. Of note, SSZ-resistant cells displayed cross-resistance to methotrexate, but showed enhanced sensitivity to glucocorticoids (prednisone, dexamethasone). Immunohistochemical studies revealed increased expression of MDR proteins in macrophages from RA patients as compared with controls.

Conclusion

These results suggest that MDR proteins, originally identified for their role in resistance to cytostatic drugs, could also be involved in DMARD resistance [1]. Beyond this, resistance to one particular DMARD can influence the sensitivity to other antirheumatic drugs.