Functional analysis of choline transporters in rheumatoid arthritis synovial fibroblasts

Objectives: In this study, we examined the functional characteristics of choline uptake and sought to identify the transporters in rheumatoid arthritis synovial fibroblasts (RASFs). Methods: The expression of choline transporters was evaluated by quantitative real-time PCR, western blotting, and imm...

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Bibliographic Details
Published in:Modern rheumatology 2017-11, Vol.27 (6), p.995-1003
Main Authors: Seki, Masayuki, Kawai, Yuiko, Ishii, Chikanao, Yamanaka, Tsuyoshi, Odawara, Masato, Inazu, Masato
Format: Article
Language:English
Subjects:
apoptosis
Arthritis, Rheumatoid - metabolism
Biological Transport
Cell Survival
Cells, Cultured
Choline
Choline - metabolism
Fibroblasts - drug effects
Fibroblasts - metabolism
Humans
Membrane Transport Proteins - genetics
Membrane Transport Proteins - metabolism
rheumatoid arthritis synovial fibroblasts (RASFs)
RNA, Messenger - genetics
RNA, Messenger - metabolism
Synovial Membrane - cytology
transporter
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Summary:Objectives: In this study, we examined the functional characteristics of choline uptake and sought to identify the transporters in rheumatoid arthritis synovial fibroblasts (RASFs). Methods: The expression of choline transporters was evaluated by quantitative real-time PCR, western blotting, and immunocytochemistry. Time course, Na + -dependency, and kinetics of [ 3 H]choline uptake were investigated. Effects of cationic drugs on the uptake of [ 3 H]choline, cell viability, and caspase-3/7 activity were also examined. Finally, we investigated the influence of choline uptake inhibitor, hemicholinium-3 (HC-3), and choline deficiency on cell viability and caspase-3/7 activity. Results: Choline transporter-like protein 1 (CTL1) and CTL2 mRNA and protein were highly expressed in RASFs and were localized to the plasma membrane. [ 3 H]Choline uptake occurred via a Na + -independent and pH-dependent transport system. The cells have two different [ 3 H]choline transport systems, high- and low-affinity. Various organic cations, HC-3 and choline deficiency inhibited both [ 3 H]choline uptake and cell viability, and enhanced the caspase-3/7 activity. The functional inhibition of choline transporters could promote apoptotic cell death. In RASFs, [ 3 H]choline uptake was significantly increased compared with that in OASFs without a change in gene expression. Conclusions: These results suggest that CTL1 (high-affinity) and CTL2 (low-affinity) are highly expressed in RASFs and choline may be transported by a choline/H +  antiport system. Identification of this CTL1- and CTL2-mediated choline transport system should provide a potential new target for RA therapy.
ISSN:1439-7595
1439-7609
DOI:10.1080/14397595.2017.1280118