MDP stimulates platelet IL-1β maturation. A, MDP time- and concentration-dependently stimulates IL-1β accumulation in human platelets. IL-1β was assayed by flow cytometry as described under Materials and Methods. Results shown are representative of 3 experiments using platelets from different donors. B & C, Caspase-1 inhibitor FMK002 abolishes MDP-induced IL-1β maturation in human platelets. Platelets were treated with MDP (100 μg/mL) overnight, in the presence or absence of caspase-1 inhibitor FMK002 (25 μM), then platelets were resuspended in reducing SDS sample buffer and probed for IL-1β by Western blot (B) or flow cytometry (C). Results shown are representative of 3 (panel B) and 4 experiments (panel C1) using platelets from different donors, respectively. Panel C2 is the summary of panel C1 expressed as mean ± SD (n = 4). D, MDP stimulates IL-1β accumulation in platelets from WT, but not NOD2-/- mice. Platelets were treated with MDP (100 ng/mL) overnight, mature IL-1β protein in platelet lysates was measured by ELISA. Data are expressed as mean ± SD with n = 4.