A luminol chemiluminescence assay was used to detect in vivo MPO activity (Gross et al., 2009 (link)). Mice were anaesthetized with 50 mg/kg pentobarbital sodium i.p. and injected i.p. with 150 mg/kg luminol sodium salt (Sigma-Aldrich) dissolved in PBS. Luminescence images were captured 10 min after the injection with an IVIS Lumina II imaging system (PerkinElmer) and processed using the Living Image software (PerkinElmer). Total radiance values (total photon flux/s) from standardized regions of interest of front and hind paws were used for quantitative analysis.