Imaging Inflammatory Reactions in Joints

Inflammatory reaction of the joints was examined by in vivo bioluminescence imaging. We measured neutrophil myeloperoxidase (MPO) activity with luminol (5-amino-2,3-dihydro-1,4-phthalazine-dione) and macrophage NADPH oxidase (Phox) activity with lucigenin (bis-N-methylacridinium nitrate) in order to detect reactive oxygen species [48 (link)]. Imaging of the animals was performed 10 min after the i.p. injection of luminol sodium salt (150 mg/kg; Gold Biotechnology, Olivette, MO, USA) dissolved in phosphate buffered saline (PBS; 30 mg/mL) and lucigenin (25 mg/kg; Tokyo Chemical Industry Co., Ltd., Tokyo, Japan) dissolved in saline (2.5 mg/mL) using the IVIS Lumina III imaging system (PerkinElmer, Waltham, MA, USA). Acquisition times were 120 s for luminol-derived bioluminescence and 180 s for lucigenin-derived bioluminescence (Binning = 8, F/Stop = 1). Identical regions of interest (ROIs) were applied on the hind paws and ankle joints, and luminescence was expressed as the total radiance (total photon flux/s) within the ROIs [49 (link)]. Animal numbers: Acute Control (n = 24); Acute CFA (n = 21); Chronic Control (n = 9–10); Chronic CFA (n = 10).