Redox regulation of β2-integrin CD11b / CD18 activation

Abstract

Although the central role of beta2-integrin CD11b / CD18 in neutrophil functions is well recognized, signaling pathway that regulate integrin activation remain to be elucidated. We analyzed the contribution of oxido-reduction mechanisms in this signaling. Exogenously added H(2)O(2) induced CD11b/CD18-dependent neutrophil adhesion and expression of an integrin activation neoepitope recognized by monoclonal antibody (mAb) clone 24. H(2)O(2)-triggered beta2-integrin activation was inhibited by tyrosine kinase inhibitors and by complexing sulfhydryl groups with phenylarsine oxide (PAO). CD11b/CD18-dependent adhesion and mAb 24 antigen expression triggered by physiological agonists such as TNF-alpha were inhibited by diphenylene iodonium (DPI, an inhibitor of flavoprotein oxidoreductase), by free radical scavengers, by tyrosine kinase inhibitors and by PAO. No inhibition was observed when adhesion was induced by the integrin-activating KIM 185 mAb. Taken together, these results emphasize the importance of an oxidative S-thiolation step(s) in the tyrosine kinase-dependent signaling pathway leading to beta2-integrin activation. H(2)O(2) would directly mediate this oxidative reaction and bypass the initial agonist/receptor pathway to promote integrin-dependent adhesion. The putative oxidase(s) involved in this process is not NADPH oxidase, since adhesion of neutrophils from patients with chronic granulomatous disease was normal and inhibited by scavengers and DPI. These data shed a new light on the regulation of integrin activation required for cell migration into inflamed organs.

Reactive Oxygen Species and p38 Mitogen-activated Protein Kinase Mediate Tumor Necrosis Factor α-Converting Enzyme (TACE/ADAM-17) Activation in Primary Human Monocytes

“…It is noteworthy that although both NAC and SB203580 resulted in near complete attenuation of TACE activity up-regulation, NAC reduced p38 phosphorylation by ϳ50%, and higher concentrations of NAC did not result in any further attenuation of p38 phosphorylation (data not shown). This incomplete abrogation by NAC is in accordance with other studies (20,21), where p38 phosphorylation was quantified by Western blotting, and suggests that there may be a threshold below which p38 pathway activation is insufficient to produce significant TACE activity up-regulation. Alternatively, NAC, a broad spectrum free radical scavenger, may exert additional inhibitory effects via other redox-sensitive targets downstream or independent of p38 activation.…”

“…Furthermore, if ROS are involved, their mechanism of action should not involve a "direct" oxidizing effect on the prodomain because it was already removed from the cell surface TACE. ROS have emerged as essential effectors of a variety of intracellular signaling pathways such as the mitogen-activated protein kinase (MAPK) cascades (20,21). Inhibition of p38 MAPK has been shown to attenuate the shedding of some TACE substrates (22)(23)(24)(25)(26).…”

Superoxide activates very late antigen‐4 on an eosinophil cell line and increases cellular binding to vascular cell adhesion molecule‐1

“…Higher NO concentration and H 2 O 2 in the surrounding tissue might decrease the cellular binding and facilitate the migration of eosinophils into respiratory epithelium by releasing them from endothelial cells. It was previously reported that H 2 O 2 , produced from a non-NADPH oxidase source, activates g 2 integrins on neutrophils through an oxidative pathway involving tyrosine kinases [45].…”

“…The difference in the intracellular and extracelluar concentrations of distinct ROS molecules (e.g. superoxide and H 2 O 2 ) may partly explain the differences in their reported effects on integrin-mediated cellular adhesion [45]. These differential regulation mechanisms are likely to contribute to the selective recruitment of subpopulations of leukocytes to tissues with allergic inflammation.…”

Neutrophils: Molecules, Functions and Pathophysiological Aspects

“…Indeed, ligation of L-selectin by antibodies or carbohydrates that mimic natural L-selectin ligands (Simon et al, 1995)-or PSGL-1 interaction with P-selectin (Yago et al, 1999)-signal neutrophil adhesive functions via CD11b/CD18 integrins (Brenner et al, 1996;Steeber et al, 1997). Insideout signaling pathways that lead to integrin switch to an active conformation differ with the stimulating agonist and are still incompletely characterized (Blouin et al, 1999;Capodici et al, 1998;Jones et al, 1998).…”