Effects of IB-MECA on phosphorylation of AKT and cAMP level in human small airway lung epithelial cells. A: IB-MECA upregulates AKT phosphorylation in cultured human small airway lung epithelial cells (HSAECs) and prevents downregulation of AKT phosphorylation caused by exposure of the cells to B. anthracis Sterne spores (MOI of 10) when added to the culture medium for 5 min at the indicated times (B); C: IB-MECA treatment (2.5 nmol/L) downregulated EdTx-mediated cAMP production in HSAECs. Cells were starved in serum-free medium for 2 h and treated with EdTx (1 μg/mL edema factor and 5 μg/mL protective antigen) in complete culture medium containing 250 nmol/L IBMX, in the presence or absence of IB-MECA for 2 h. Cell lysates were analyzed with western blotting using antibodies specific for phospho-AKT (pAKT, S473) and total AKT (tAKT) (A and B), and competitive cAMP ELISA (C). Asterisks indicate the corresponding pairs of measurements (mean ± SD, n = 3) used for statistical comparison by the two-tailed t test. aP = 0.05, bP = 0.01.