Inhibition of ATM activity in neutrophils increases proinflammatory cytokine production. (A) Western blot of ATM, phosphorylated ATM, and γ-H2A.X in lysates from neutrophils exposed to γ irradiation and incubated for 1 hour with and without 10 µM ATM inhibitor KU-55933. (B) Neutrophil IL-8 (n = 4) and MIP-1α (n = 3) production in response to LPS stimulation in the presence of increasing KU-55933 concentration. Isolated peripheral blood neutrophils from healthy donors were incubated with ATM inhibitor and stimulated with LPS for 18 hours. Cytokine concentrations in supernatants were measured by ELISA. (C) Neutrophil IL-8 production in response to 18-hour stimulation with flagellin (1 μg/mL), LPS (100 ng/mL), opsonized zymosan (10 μg/mL), or heat-killed L monocytogenes (HKLM, MOI = 100) in the presence of KU-55933 (10 μM) (n = 3-4). (D) Monocyte cytokine production in response to LPS stimulation in the presence of KU-55933. Isolated peripheral blood monocytes from healthy donors (n = 10) were incubated with KU-55933 (10 μM) and stimulated for 18 hours with LPS. (B-D) Data are presented as the mean ± standard error of the mean (SEM) of compiled experiments. Asterisks indicate significant increases: *P < .05, **P < .01, ***P < .001 by paired Student t test.