Effects of an ALA/light challenge on MMP-9 expression, MMP-9 activity, and TIMP-1 expression in U87 cells: role of iNOS/NO. (a) MMP-9 expression. Whole cell lysates were collected at the given time points and subjected to Western analysis to assess level of intracellular MMP-9 protein. (b) MMP-9 activity. Conditioned medium from irradiated cells and dark controls was collected and concentrated. After protein determination, samples were subjected to SDS-PAGE on a gel co-polymerized with gelatin. The gel was then incubated in a renaturing buffer (30 min), followed by developing buffer (24 h), after which it was stained and photographed. Bands were quantified using ImageLab software. Plotted values are means ± SEM of values from 3 separate experiments. (c) TIM-1 expression. Western blots of TIMP-1 levels in cells irradiated without or with 1400W present. Numbers below lanes indicate band intensities relative to β-actin and normalized to the dark control (DC).