Figure 7. Effect of inhibition of transforming growth factor (TGF)-β receptor I or Smad3 phosphorylation on Smad and non-Smad signaling pathways. Optic nerve head (ONH) astrocytes and lamina cribrosa (LC) cells were pre-incubated with SB431542 (10 uM) or SIS3 (25 uM), 1h before treatment with TGF-β2. ONH astrocytes and LC cells were then treated with recombinant TGF-β2 for 1 h and total cell lysates were subjected to western blot analysis for phosphorylation of Smad and non-Smad signaling pathways. A: western blot analysis of pSmad3, Smad3, pSmad2, and Smad2 in ONH astrocytes and LC cells. B: western blot analysis of phosphorylated extracellular signal-regulated kinases (ERK)1/2, total ERK1/2, phosphorylated p38, total p38, phosphorylated c-Jun N-terminal kinases (JNK)1/2, and total JNK1/2 in ONH astrocytes and LC cells. Samples were run in the same gel but not in the order presented. SB431542 inhibited TGF-β2 induced phosphorylation of Smad2/3, whereas SIS3 selectively inhibited phosphorylation of Smad3. The inhibitors had no effect on members of the non-Smad pathway.