Figure 12.

Regulation of neutrophil migration by macrophage NO produced through the induction of iNOS. Migration of neutrophils across fibronectin (A) was markedly increased in the presence of macrophages previously activated with LPS; however, selective iNOS inhibition as well as MMP-9 inhibition significantly reduced neutrophil migration to levels comparable with those observed in the absence of LPS-activated macrophages. MMP-9 activity (B) was profoundly depressed by iNOS and by MMP-9 inhibition. In contrast, nitrite release (C) was clearly reduced on iNOS inhibition, and remained unchanged on selective MMP-9 inhibition, suggesting that NO promoted neutrophil migration through MMP-9 activation, *P < 0.02, **P < 0.006, and ***P < 0.003, relative to unstimulated controls-white bars; ^#P < 0.02, ^##P < 0.01, and ^###P < 0.003, relatively to stimulated controls-back bars.