Figure 9. COX2 activity and its derived PGE₂ protect cultured RMICs from oxidative stress.

(A and B) Wild-type or Sirt1-knockdown cultured RMICs were pretreated with the COX2 selective inhibitor SC58236 (0.5 μM, 2.5 μM) or PGE₂ (100 nM, 1 μM) and challenged with H₂O₂ (250 μM) for 12 hours. Cell viability was examined by crystal violet staining (n = 6; *P < 0.0001 versus cells with H₂O₂ alone; ^†P < 0.0001 versus Sirt1-knockdown cells with H₂O₂ without PGE₂; ^‡P < 0.05 versus Sirt1-knockdown cells with H₂O₂ and 100 nM PGE₂). (C and D) Wild-type or Sirt1-knockdown RMICs were pretreated with SC58236 (2.5 μM) or PGE₂ (100 nM) and challenged with H₂O₂ (500 μM) for 6 hours. Cell apoptosis was examined by TUNEL assay (n = 15; *P < 0.001 versus cells with H₂O₂ alone; ^†P < 0.05 versus Sirt1-knockdown cells with H₂O₂ without PGE₂). (E) Wild-type or Sirt1-knockdown RMICs were pretreated with 100 nM PGE₂ and challenged with H₂O₂ (500 μM) for 6 hours. Expression of the cellular apoptosis marker cleaved caspase-3 was examined by immunoblot (n = 4, densitometry, *P < 0.05 versus Sirt1-knockdown cells with H₂O₂ without PGE2).