Fig 2: Effect of exogenous administration of H2S on pro-inflammatory and pro-oxidant responses to IL-1ß and HO-1 expression recovery in chondrocytes exposed to a HG environment. OA human chondrocytes were incubated in growth media with normal (NG) or high (HG) levels of glucose in the presence or absence of IL-1ß and co-treated with a fast or slow-releasing H2S donor, NaSH 500 µM and GYY-4137 500 µM, respectively. Then, (a) protein levels of COX-2 were measured by western blot. Below panel shows representative images of COX-2 expression from one experiment. Expression levels of ß-tubulin were employed as the loading control. (b) IL-6 released in the cell culture supernatant was measured by ELISA. (c) ROS production was monitored by flow cytometry using the fluorogenic dye 2', dichlorofluorescein (DCF). Antimycin A (AA) was employed as a positive control of ROS production. (d) Protein HO-1 expression was also evaluated. Below panel shows representative images of HO-1 expression from one experiment. Values are mean ± SEM. * p = 0.05 analysed by the Wilcoxon test. COX-2, cyclooxygenase 2; HO-1, hemeoxygenase-1; IL-6, interleukin 6.