Nicole A. Morin

Neutrophil morphology and migration are affected by substrate elasticity.

To reach sites of inflammation, neutrophils execute a series of adhesion and migration events that include transmigration through the vascular endothelium and chemotaxis through the vicinal extracellular matrix until contact is made with the point of injury or infection. These in vivo microenvironments differ in their mechanical properties. Using polyacrylamide gels of physiologically relevant elasticity in the range of 5 to 100 kPa and coated with fibronectin, we tested how neutrophil adhesion, spreading, and migration were affected by substrate stiffness. Neutrophils on the softest gels showed only small changes in spread area, whereas on the stiffest gels they showed a 3-fold increase. During adhesion and migration, the magnitudes of the distortions induced in the gel substrate were independent of substrate stiffness, corresponding to the generation of significantly larger traction stresses on the stiffer gels. Cells migrated more slowly but more persistently on stiffer substrates, which resulted in neutrophils moving greater distances over time despite their slower speeds. The largest tractions were localized to the posterior of migrating neutrophils and were independent of substrate stiffness. Finally, the phosphatidylinositol 3-kinase inhibitor LY294002 obviated the ability to sense substrate stiffness, suggesting that phosphatidylinositol 3-kinase plays a mechanistic role in neutrophil mechanosensing.

The Lectin-Like Domain of Complement Receptor 3 Protects Endothelial Barrier Function from Activated Neutrophils

The adhesion of neutrophils to endothelial cells is a central event leading to diapedesis and involves the binding of the I-domain of β2 integrins (CD11/CD18) to endothelial ICAMs. In addition to the I-domain, the β2 integrin complement receptor 3 (CR3) (CD11b/CD18) contains a lectin-like domain (LLD) that can alter leukocyte functions such as chemotaxis and cytotoxicity. The present study demonstrates that, in contrast to the CR3 I-domain, Ab blockade of the CR3 LLD has no role in mediating neutrophil-induced loss of endothelial barrier function. However, activation of CR3 with the LLD agonist β-glucan protects the barrier function of endothelial cells in the presence of activated neutrophils and reduces transendothelial migration without affecting adhesion of the neutrophils to the endothelium. The LLD site-specific mAb VIM12 obviates β-glucan protection while activation of the LLD by VIM12 cross-linking mimics the β-glucan response by both preserving endothelial barrier function and reducing neutrophil transendothelial migration. β-glucan has no direct effect on endothelial cell function in the absence of activated neutrophils. These findings demonstrate that signaling through the CR3 LLD prevents neutrophil-induced loss of endothelial barrier function and reduces diapedesis. This suggests that the LLD may be a suitable target for oligosaccharide-based anti-inflammatory therapeutics.

Nonmuscle myosin heavy chain IIA mediates integrin LFA-1 de-adhesion during T lymphocyte migration

Morin et al. 2008. J. Exp. Med. doi:10.1084/jem.20071543 [OpenUrl][1][Abstract/FREE Full Text][2] [1]: {openurl}?query=rft_id%253Dinfo%253Adoi%252F10.1084%252Fjem.20071543%26rft_id%253Dinfo%253Apmid%252F18195072%26rft.genre%253Darticle%26rft_val_fmt%253Dinfo%253Aofi%252Ffmt%253Akev%253Amtx%