Figure 4.
Peroxynitrite can inhibit caspase-3 and caspase-9 activity ex vivo via cysteinyl oxidation. A, Effects of the PN donor SIN-1, or of direct PN addition, on caspase-3-like activity. Recombinant procaspase-3 was incubated with the indicated concentrations of SIN-1 or peroxynitrite before activation with recombinant caspase-9 and Ac-DEVD-AMC fluorescence was measured. Both compounds significantly reduced (p < 0.05) caspase-3 activity as shown (n = 3 experiments per compound; asterisks, different from own control). B, C, Recombinant caspase-3 (B) and caspase-9 (C) were incubated for 1 h with the indicated PN concentrations, and proteolytic activity was assessed using Ac-DEVD-AMC and Ac-LEHD-AFC, respectively. The inhibition of activity of both caspases by PN was significantly reversed by DTT (10 mm; p < 0.05; n = 3 experiments per concentration/condition).
