Calpain inhibition impairs TNF-α-mediated neutrophil adhesion, arrest and oxidative burst

Proinflammatory cytokines, such as tumor necrosis factor alpha (TNF-α), are increased in many chronic inflammatory disorders, including rheumatoid arthritis, and contribute to recruitment of neutrophils into areas of inflammation. TNF-α induces a stop signal that promotes neutrophil firm adhesion and inhibits neutrophil polarization and chemotaxis. Calpain is a calcium-dependent protease that mediates cytoskeletal reorganization during cell migration. Here, we show that calpain inhibition impairs TNF-α-induced neutrophil firm adhesion to fibrinogen-coated surfaces and the formation of vinculin-containing focal complexes. Calpain inhibition induces random migration in TNF-α-stimulated cells and prevents the generation of reactive oxygen species, but does not alter TNF-α-mediated activation of p38 MAPK and ERK MAPK. These findings suggest that the TNF-α-induced neutrophil arrest requires the activity of calpain independent of p38 MAPK and ERK signaling seen after TNF-α stimulation. Together, our data suggest that therapeutic inhibition of calpain may be beneficial for limiting TNF-α-induced inflammatory responses.