Figure 5.

Kartogenin stimulates SMAD1 phosphorylation only under IL-1β treatment in articular chondrocytes. The effect of kartogenin on the anabolic response of bovine and human chondrocytes was studied by western blot analyses of SMAD1 phosphorylation. Bovine (A, C) or human (B, D) chondrocytes were treated with 100 ng/mL BMP7 or 100 µM kartogenin (KGN) for 1 to 6 hours, lysed, and Western blots were analyzed. BMP7 treatment resulted in phosphorylation of SMAD1/5/8 as expected, and treatment with KGN resulted in no change in SMAD1 phosphorylation (A, B). However, following IL-1β stimulation for up to 24 hours, KGN treatment resulted in enhanced SMAD1 phosphorylation, notably at the 6-hour time point (C, D).