A functional folate receptor is induced during macrophage activation and can be used to target drugs to activated macrophages
Open Access
- 8 January 2009
- journal article
- clinical trial
- Published by American Society of Hematology in Blood
- Vol. 113 (2), 438-446
- https://doi.org/10.1182/blood-2008-04-150789
Abstract
Previous work has demonstrated that a subset of macrophages expresses a folate receptor (FR) that can mediate internalization of folate-linked molecules, including imaging and therapeutic agents. To characterize this subset, macrophages were collected from peritoneal cavities of mice injected with saline, thioglycolate, zymosan, heat-killed or live bacteria, and cell-surface markers that coexpress with FR were identified. Virtually no F4/80+ peritoneal macrophages from saline-injected mice expressed FR, whereas numerous macrophages from mice injected with each inflammatory stimulus expressed FR. Examination of cell differentiation antigens that are up-regulated in FR+ macrophages revealed markers characteristic of an activated state (CD80, CD86, Ly-6C/G), whereas macrophages lacking these activation markers expressed few or no FR. FR+ macrophages also produced tumor necrosis factor-α (TNF-α) and reactive oxygen species, and production of reactive oxygen species correlated linearly with expression of FR. Synovial macrophages collected from arthritic patients were found to bind and internalize folate-linked dyes. Moreover, a folate-linked radioimaging agent was shown to image inflamed joints of rheumatoid arthritic patients. These results suggest that FR constitutes a marker for macrophage activation and that FR+ macrophages can be targeted with folate-linked drugs without promoting drug uptake by nonactivated macrophages. This trial was registered at www.clinicaltrials.gov as #NCT00588393.Keywords
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