Time-course of ATP-induced MMP-9, TIMP-1, and LDH release. PBMCs (2 × 10⁷/mL) with wild-type P2X₇ receptors were incubated with (○) or without (•) 1 mM ATP at 37°C in NaCl medium containing 1 mM CaCl₂. Supernatants and cell pellets were collected at different time intervals as indicated. MMP-9 activity in supernatants was detected by gelatin zymography (A). MMP-9 (B) and TIMP-1 (C) concentrations in supernatants were measured using ELISA kits. MMP-9 and TIMP-1 concentrations in supernatant from cells incubated with 100 nM PMA were used as the maximum release (100%). LDH release was measured in both supernatants and cell pellets (D). Results from individuals were normalized and shown as mean ± SEM (n = 4)(B-D). TIMP-1 data are shown for 1 representative experiment of 2.