Abstract | OBJECTIVE: METHODS: Levels of FR and RFC messenger RNA ( mRNA) were examined by reverse transcriptase-polymerase chain reaction (RT-PCR) in SMC from RA patients and peripheral blood mononuclear cells from healthy donors. Expression of FR-beta mRNA and protein was determined by Northern blot and Western blot analyses in RA SMC and monocyte/macrophage-lineage cells. FR-beta expression and folic acid binding capacity on the cell surface were examined by flow cytometric analysis and 3H-folic acid binding analysis. Studies of the inhibition of 3H-MTX uptake in the presence of unlabeled folic acid were performed to investigate the uptake of MTX through FR in RA SMC. RESULTS: RT-PCR, Northern blot, and Western blot analyses showed that FR-beta mRNA and protein were expressed selectively in activated monocytes and CD14+ RA SMC. These cells exhibited folic acid binding capacity. Furthermore, the FR-beta protein was shown to have folic acid binding capacity. Uptake of 3H-MTX through RA SMC was significantly inhibited in the presence of unlabeled folic acid. CONCLUSION: These results demonstrate that FR-beta expression is selectively elevated in RA synovial macrophages and suggest that MTX is transported through FR-beta in RA synovial macrophages. The findings suggest that folate antagonists with higher affinity for FR-beta would be useful in the treatment of RA.
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Authors | N Nakashima-Matsushita, T Homma, S Yu, T Matsuda, N Sunahara, T Nakamura, M Tsukano, M Ratnam, T Matsuyama |
Journal | Arthritis and rheumatism
(Arthritis Rheum)
Vol. 42
Issue 8
Pg. 1609-16
(Aug 1999)
ISSN: 0004-3591 [Print] United States |
PMID | 10446858
(Publication Type: Journal Article)
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Chemical References |
- Carrier Proteins
- Folate Receptors, GPI-Anchored
- Lipopolysaccharide Receptors
- Receptors, Cell Surface
- RNA
- Folic Acid
- Methotrexate
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Topics |
- Arthritis, Rheumatoid
(genetics, pathology)
- Biological Transport
- Carrier Proteins
(biosynthesis, genetics, physiology)
- Folate Receptors, GPI-Anchored
- Folic Acid
(metabolism)
- Humans
- Lipopolysaccharide Receptors
(analysis)
- Methotrexate
(pharmacokinetics)
- Monocytes
(chemistry, immunology)
- RNA
(metabolism)
- Receptors, Cell Surface
(biosynthesis)
- Synovial Membrane
(pathology)
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