Concentration curve of ATP- and BzATP-induced rapid MMP-9 and TIMP-1 release. PBMCs (2 × 10⁷/mL) with wild-type P2X₇ receptors were incubated with various amount of ATP (•) or BzATP (○) as indicated at 37°C in NaCl medium containing 1 mM CaCl₂ for 30 minutes. Supernatants were collected, and MMP-9 activity (A) was detected by gelatin zymography, and MMP-9 and TIMP-1 concentrations were measured using ELISA kits (B, C). Results from individuals were normalized and shown as mean ± SEM (n = 4 for ATP; n = 5 for BzATP).