Drs. T. M. Aune and N. J. Olsen are co-owners of ArthroChip.
Increased sensitivity to apoptosis induced by methotrexate is mediated by JNK
Article first published online: 31 AUG 2011
Copyright © 2011 by the American College of Rheumatology
Arthritis & Rheumatism
Volume 63, Issue 9, pages 2606–2616, September 2011
How to Cite
Spurlock, C. F., Aune, Z. T., Tossberg, J. T., Collins, P. L., Aune, J. P., Huston, J. W., Crooke, P. S., Olsen, N. J. and Aune, T. M. (2011), Increased sensitivity to apoptosis induced by methotrexate is mediated by JNK. Arthritis & Rheumatism, 63: 2606–2616. doi: 10.1002/art.30457
- Issue published online: 31 AUG 2011
- Article first published online: 31 AUG 2011
- Accepted manuscript online: 25 MAY 2011 02:11PM EST
- Manuscript Accepted: 12 MAY 2011
- Manuscript Received: 12 JAN 2011
- NIH. Grant Numbers: R42-AI-53984, R01-AI-44924
- American College of Rheumatology (Within Our Reach program grant to Dr. Olsen)
- McGee Foundation
- Vanderbilt Ingram Cancer Center. Grant Number: P30-CA-68485
- Vanderbilt Digestive Disease Research Center. Grant Number: DK-058404
Low-dose methotrexate (MTX) is an effective therapy for rheumatoid arthritis (RA), yet its mechanism of action is incompletely understood. The aim of this study was to explore the induction of apoptosis by MTX.
Flow cytometry was performed to assess changes in the levels of intracellular proteins, reactive oxygen species (ROS), and apoptosis. Quantitative polymerase chain reaction was performed to assess changes in the transcript levels of select target genes in response to MTX.
MTX did not directly induce apoptosis but rather “primed” cells for markedly increased sensitivity to apoptosis via either mitochondrial or death receptor pathways, by a JNK-dependent mechanism. Increased sensitivity to apoptosis was mediated, at least in part, by MTX-dependent production of ROS, JNK activation, and JNK-dependent induction of genes whose protein products promote apoptosis. Supplementation with tetrahydrobiopterin blocked these MTX-induced effects. Patients with RA who were receiving low-dose MTX therapy expressed elevated levels of the JNK target gene, jun.
Our results support a model whereby MTX inhibits reduction of dihydrobiopterin to tetrahydrobiopterin, resulting in increased production of ROS, increased JNK activity, and increased sensitivity to apoptosis. The finding of increased jun levels in patients with RA receiving low-dose MTX supports the notion that this pathway is activated by MTX in vivo and may contribute to the efficacy of MTX in inflammatory disease.