Fig. 4.

Effects of N-acetylcysteine (NAC) on interleukin (IL)-1β-induced matrix metalloproteinase (MMP)-9 activity and mRNA expression. Reactive oxygen species signaling is not associated with IL-1β-indcued MMP-9 activity and mRNA expression. House ear institute-organ of Corti 1 (HEI-OC1) cells were pretreated with NAC (5 mM) for 30 minutes, and then added 1 ng/mL IL-1β for 20 hours. Conditional media were collected and gelatin zymography was performed (A). The MMP-9 mRNA expression levels were determined by reverse transcription-polymerase chain reaction. The levels of actin were used as a loading control. The values in (B) represent the mean±SD from three independent samples. The data represent three independent experiments.