Background/Purpose: Rheumatoid arthritis (RA) is one of the most prevalent systemic autoimmune disorders. The folate antagonist methotrexate (MTX) is an anchor drug in the treatment of RA. Here, we aim to provide insight into the pharmacological effects of MTX by gene expression analysis

Methods: Subanalysis of microarray data was performed for a set of 18 genes involved in the methotrexate/folate pathway using peripheral blood gene expression data of 10 MTX naïve RA patients (MTX-), 25 RA patients treated with MTX (MTX+), and 15 healthy controls which were age and sex-matched (test cohort). Multiplex realtime PCR of these methotrexate/folate pathway related genes was performed on second cohort consisting of 28 MTX naïve RA patients (MTX-), 180 RA patients treated with MTX (MTX+) and 24 healthy controls (validation cohort). Statistical analysis was performed using Student’s t test or Mann-Whitney U test. P-values of ≤0.05 were considered to be statistically significant.

Results: Several folate/MTX-related genes were markedly and significantly altered between the three study groups in the test cohort. Metabolizing enzymes FPGS (p=0.0035) and GGH (p<0.0001) were significantly up-regulated in the MTX^– RA group compared to the healthy control group (HC group). For the folate dependent enzymes we found that GART (p=0.0004) expression was decreased in the MTX^– group compared to HC. In the efflux transporters, MRP3 (p=0.0335) was significantly higher expressed in the MTX^– group compared to HC. The other genes displayed no significant change in the test cohort. In the validation cohort we were able to validate most of the genes except FPGS, GART for MTX^– compared to HC. In both test and validation cohort the differentially altered genes in the MTX^– group returned to a normal range as observed in the HC.

Conclusion: Overall, these results indicate that, under inflammatory conditions basal folate metabolism is altered in blood cells of RA patients compared to HC. Treatment with MTX restores expression of these genes to the levels within the range of the HC group.

Acknowledgements: Prof. Dr. Y.G. Assaraf (Technion, Haifa, Israel) was a recipient of a visiting professor fellowship provided by the Dutch Arthritis Foundation to the VU University Medical Center Amsterdam. This study is partly supported by the “TRACER” consortium of the Center for Translational and Molecular Medicine (CTMM), and the Dutch Arthritis Foundation.

ACR Meeting Abstracts - https://acrabstracts.org/abstract/regulation-of-folate-pathway-related-genes-in-methotrexate-naive-and-methotrexate-treated-patients-with-rheumatoid-arthritis/