ADAM9 disintegrin domain activates human neutrophils through an autocrine circuit involving integrins and CXCR2.

ADAM9 is a member of the ADAM family whose expression positively correlates with tumor progression. Besides the metalloprotease activity, ADAM9D interacts with different integrins, modulating cell-adhesion events. Previous studies pointed to an important role for neutrophils in tumor development, as the inhibition of neutrophil migration or depletion of this immune cell impairs tumor growth. However, our understanding of the molecular mechanisms involved in this process, as well as the main key players acting on neutrophils, is very limited. Here, we investigated the possible modulatory effects of ADAM9D on human neutrophil functions. Our results show that ADAM9D promotes neutrophil activation and chemotaxis in a process that depends on the engagement of αvß3 and α9ß1 integrins and on the activation of PI3K/Akt and MAPK signaling pathway. ADAM9D impairs migration of neutrophils toward fMLP, LTB4, and IL-8 as classic chemoattractants. This effect is blocked by PTX, a G(i)PCR inhibitor. Furthermore, CXCR2 antagonists RPTX and SB225002 also impaired neutrophil chemotaxis in response to ADAM9D, suggesting a hierarchical cross-talk of integrins with CXCR2. Our results indicate that ADAM9D activates neutrophil functions and may be implicated in the inflammatory events associated with cancer and other disorders.

Inhibition of guanylyl cyclase restores neutrophil migration and maintains bactericidal activity increasing survival in sepsis.

Sepsis results from an overwhelming response to infection and is a major contributor to death in intensive care units worldwide. In recent years, we and others have shown that neutrophil functionality is impaired in sepsis. This correlates with sepsis severity and contributes to aggravation of sepsis by precluding bacterial clearance. Nitric oxide (NO) is a major contributor to the impairment of neutrophil function in sepsis. However, attempts to inhibit NO synthesis in sepsis resulted in increased death despite restoring neutrophil migration. This could be in part attributed to a reduction of the NO-dependent microbicidal activity of neutrophils. In sepsis, the beneficial effects resulting from the inhibition of soluble guanylyl cyclase (sGC), a downstream target of NO, have long been appreciated but poorly understood. However, the effects of sGC inhibition on neutrophil function in sepsis have never been addressed. In the present study, we show that TLR activation in human neutrophils leads to decreased chemotaxis, which correlated with chemotactic receptor internalization and increased G protein-coupled receptor kinase 2 expression, in a process involving the NO-sGC-protein kinase G axis. We also demonstrate that inhibition of sGC activity increased survival in a murine model of sepsis, which was paralleled by restored neutrophil migratory function and increased bacterial clearance. Finally, the beneficial effect of sGC inhibition could also be demonstrated in mice treated after the onset of sepsis. Our results suggest that the beneficial effects of sGC inhibition in sepsis could be at least in part attributed to a recovery of neutrophil functionality.