Inhibition of caspase 3 abrogates lipopolysaccharide-induced nitric oxide production by preventing activation of NF-kappa B and c-Jun NH2-terminal kinase/stress-activated protein kinase in RAW 264.7 murine macrophage cells

The effect of caspase inhibitors on lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 267.4 murine macrophage cells was investigate d. Pretreatment of RAW cells with a broad caspase inhibitor, benzyloxycarbo nyl-val-Ala-Asp-fluoromethylketone (Z-VAD-FMK), resulted in a striking redu ction in LPS induced NO production. Z-VAD-FMK inhibited LPS-induced NF-kapp aB activation. Furthermore, it blocked phosphorylation of c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK) but not that of extracell ular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinases. Similarly, a caspase 3-specific inhibitor, Z-Asp-Glu-Val-Asp-fluoromethylk etone, inhibited NO production, NF-kappaB activation, and JNK/SAPK phosphor ylation in LPS-stimulated RAW cells. The attenuated NO production was due t o inhibition of the expression of an inducible-type NO synthase (iNOS). The overexpression of the dominant negative mutant of JNK/SAPK and the additio n of a JNK/SAPK inhibitor blocked iNOS expression but did not block LPS-ind uced caspase 3 activation. It was therefore suggested that the inhibition o f caspase 3 might abrogate LPS-induced NO production by preventing the acti vation of NF-kappaB and JNK/SAPK. The caspase family, especially caspase 3, is likely to play an important role in the signal transduction for iNOS-me diated NO production in LPS-stimulated mouse macrophages.