Nitric oxide determination
Raw264.7 cells were plated in 24-well plates (2.5 × 105 cells/mL) and incubated in a 5% CO2 incubator (MCO-15AC, Sanyo, Osaka, Japan) for 20 h. After pre-incubation, LPS (1 μg/mL) and the MMME (0.1, 1, 10, 50, and 100 μg/mL) were added and incubated for 24 h. Then, 100 μL of supernatant was mixed with the same volume of Griess reagent (1% sulfanilamide + 0.1% naphthalenediamine dihydrochloride in 5% phosphoric acid, 1:1) and incubated at room temperature for 10 min. The absorbance was measured at 540 nm using a microplate reader and nitrite concentration was calculated with standard curves of sodium nitrite (NaNO2).