Inhibition of ROS production by a TLR4-specific, cell-permeable peptide. (A) Hydrogen peroxide production by neutrophils upon 1 μM fMLP stimulation after they were primed with different TLR ligands (Pam3CysSK4 for TLR1/2, MALP-2 for TLR2/6, LPS for TLR4, and nonopsonized zymosan for TLR2). RFU, relative fluorescence intensity. (B) Effect of TLR4-blocking peptide (200 μg/ml) and inhibitors of p38MAPK (SB20358, 10 μg/ml), pERK (U0126, 10 μg/ml), and phospholipase D (ethanol, 1%) on intracellular hydrogen peroxide production after Salmonella infection. Values are means from three experiments (± standard deviations) performed in duplicate. *, P < 0.01 (compared to values for the control peptide); **, P < 0.01 (compared to values for untreated bacteria; analysis by Student's t test). Contr, control.