Inflammation is a fundamental aspect of many human diseases. In this video report, we demonstrate non-invasive bioluminescence imaging techniques that distinguish acute and chronic
inflammation in mouse models. With tissue damage or pathogen invasion, neutrophils are the first line of defense, playing a major role in mediating the acute inflammatory response. As the inflammatory reaction progresses, circulating monocytes gradually migrate into the site of injury and differentiate into mature macrophages, which mediate chronic
inflammation and promote tissue repair by removing tissue debris and producing anti-inflammatory
cytokines.
Intraperitoneal injection of
luminol (5-amino-2,3-dihydro-1,4-phthalazinedione, sodium salt) enables detection of acute
inflammation largely mediated by tissue-infiltrating neutrophils.
Luminol specifically reacts with the
superoxide generated within the phagosomes of neutrophils since bioluminescence results from a
myeloperoxidase (MPO) mediated reaction.
Lucigenin (
bis-N-methylacridinium nitrate) also reacts with
superoxide in order to generate bioluminescence. However,
lucigenin bioluminescence is independent of MPO and it solely relies on phagocyte
NADPH oxidase (
Phox) in macrophages during chronic
inflammation. Together,
luminol and
lucigenin allow non-invasive visualization and longitudinal assessment of different phagocyte populations across both acute and chronic inflammatory phases. Given the important role of
inflammation in a variety of human diseases, we believe this non-invasive imaging method can help investigate the differential roles of neutrophils and macrophages in a variety of pathological conditions.