Figure 4: Effect of DHEA on NO production induced by particles. Cells were treated with 1 (D1), 10 (D10), and 100 μM (D100) of DHEA alone or in combination with 10 μg/cm2 of TiO2 NPs (T) or PM10 (P) for 72 h. NO concentration was evaluated using Griess reagent. Previously, a standard curve was performed using known concentrations of nitrite. Absorbance of the concentrations of control and problem samples was plotted against the standard curve. Data are represented as concentration of nitrite (μg/mL) and are expressed as mean ± SD of three separate experiments. * Indicates compared with control cells, and compared with particles-treated cells.