ec20-folate-peptide and Arthritis--Rheumatoid

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-alpha (TNF-alpha) 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.

Topics: Aged; Animals; Antigens, CD; Arthritis, Rheumatoid; Carrier Proteins; Drug Delivery Systems; Female; Folate Receptors, GPI-Anchored; Folic Acid; Humans; Macrophage Activation; Macrophages, Peritoneal; Male; Mice; Oligopeptides; Radiography; Radionuclide Imaging; Radiopharmaceuticals; Reactive Oxygen Species; Receptors, Cell Surface; Tumor Necrosis Factor-alpha; Up-Regulation