Cell Volume-dependent Regulation of L-selectin Shedding in Neutrophils

Abstract

Neutrophil-mediated organ damage is a common feature of many disease states. We previously demonstrated that resuscitation with hypertonic salt solutions prevented the endotoxin-induced leukosequestration and consequent lung injury, and this effect was partially attributed to an altered surface expression of adhesion molecules, CD11b and L-selectin. In this study we investigated the mechanisms whereby osmotic stress evokes L-selectin shedding. The metalloprotease inhibitor RO 31-9790 prevented the osmotic down-regulation of L-selectin, indicating that this process was catalyzed by the same "sheddase" responsible for L-selectin cleavage induced by diverse inflammatory stimuli. The trigger for hypertonic shedding was cell shrinkage and not increased osmolarity, ionic strength, or intracellular pH. Volume reduction caused robust tyrosine phosphorylation and its inhibition by genistein and erbstatin abrogated shedding. Shrinkage stimulated tyrosine kinases Hck, Syk, and Pyk2, but prevention of their activation by the Src-family inhibitor PP1 failed to affect the Lselectin response. Hypertonicity elicited the Src familyindependent activation of p38, and the inhibition of this kinase by SB203580 strongly reduced shedding. p38 was also essential for the N-formyl-methionyl-leucyl-phenylalanine-and lipopolysaccharide-induced shedding but not the phorbol ester-induced shedding. Thus, cell volume regulates L-selectin surface expression in a p38-mediated, metalloprotease-dependent manner. Moreover, p38 has a central role in shedding induced by many inflammatory mediators.

Circulating thioredoxin suppresses lipopolysaccharide-induced neutrophil chemotaxis

“…Importantly, CD62 down-regulation may be mediated wholly or in part by the suppression of p38 MAPK activation (33). Furthermore, the Trx-mediated down-regulation of neutrophil CD62L in the absence of Trx-mediated alteration in the expression of endothelial cell adhesion molecules known to be involved in neutrophil extravasation, i.e., ICAM-1, VCAM-1, CD62P (Pselectin), and CD62E (E-selectin; ref.…”

p38 mitogen-activated kinase is a bidirectional regulator of human fibroblast collagenase-1 induction by three-dimensional collagen lattices

“…Our finding that fl-coll, but not att-coll, co-ordinately activated p38α and its upstream kinase activator, MKK3\6, indicates that the mechanical properties, instead of the three-dimensional organization of collagen lattices, trigger p38α activation. Because cell shrinkage caused by hypertonicity is a regulatory signal for the p38 MAPK activation [14,34], the cell size difference between fibroblasts cultured in fl-coll and att-coll might be one of the signals that activate the p38 MAPK. In fact, a number of physiological or disease processes that involve morphological alterations, such as ischaemic and hypertensive myocardial disease, also require p38 MAPK activation [12,35].…”

Characterization of Growth Factor-induced Serine Phosphorylation of Tumor Necrosis Factor-α Converting Enzyme and of an Alternatively Translated Polypeptide

“…PMA-induced ectodomain shedding of TGF-␣ or its family member heparin binding-epidermal growth factor-like growth factor (HB-EGF) and TNF-␣ is also mediated through activation of the Erk signaling pathway (32,33,35). In addition, activation of the p38 MAP kinase pathway, often a result of inflammatory mediators or physiological stress, also leads to ectodomain shedding (32,37). Thus, inhibition of both Erk and/or p38 MAP kinase signaling pathways strongly suppresses ectodomain shedding of diverse transmembrane proteins in response to various stimuli (32,37).…”

“…In addition, activation of the p38 MAP kinase pathway, often a result of inflammatory mediators or physiological stress, also leads to ectodomain shedding (32,37). Thus, inhibition of both Erk and/or p38 MAP kinase signaling pathways strongly suppresses ectodomain shedding of diverse transmembrane proteins in response to various stimuli (32,37). Inhibitor studies and functional experiments have revealed that the cleavage of TGF-␣ and various other transmembrane proteins is mediated by cell surface metalloprotease(s) (30, 38 -40).…”