C5 and gout: The effects of CPI2 on mice with MSU-induced gouty arthritis were evaluated by measuring the degree of paw swelling, observing the histopathological changes in paw tissues using hematoxylin and eosin (HE) staining, detecting the levels of inflammatory cytokines, C5a, and cathepsin S by enzyme-linked immunosorbent assay (ELISA), determining the activities of glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) as well as the level of malondialdehyde (MDA) by chemiluminescence assay, and observing the expression level of C5aR1 protein in paw tissues by immunohistochemistry.