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Alpha 6 beta 1 integrin (VLA-6) mediates leukocyte tether and arrest on laminin under physiological shear flow
J Kitayama1, S Ikeda, K Kumagai
1Department of Surgery, The Surgical Center, The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo, 113, Japan. Kitayama-1SU@h.u-tokyo.ac.jp
Abstract:
Polymorphonuclear leukocytes (PMN) were perfused over extracellular matrix protein substrates under laminar shear flow. Under shear below 1.5 dyn/cm(2), many PMN tethered to immobilized laminin but not to fibronectin or vitronectin. Almost all the tethered PMN immediately arrested on laminin. The number of tethered PMN was mostly abrogated by mAbs to integrin alpha 6 or beta 1 chains at concentrations of more than 5 microg/ml. Addition of the two mAbs together produced no further inhibition compared with each mAb alone. In contrast, none of the mAbs to alpha 2, alpha 3, and beta 4 chains showed significant inhibition, indicating that PMN tethering to laminin is mostly dependent on alpha 6 beta 1 integrin. The addition of 10-100 ng/ml IL-8 in the assay medium before perfusion partially reduced PMN tethering to laminin. Stimulation with IL-8 also induced detachment of some tethered PMN within 30 s. Thus, IL-8 partially weakens the adhesiveness of alpha 6 beta 1 integrin on PMN in flow conditions.
Insights
Polymorphonuclear leukocytes (PMN) primarily use the alpha 6 beta 1 integrin to attach to laminin under shear flow. Interleukin-8 (IL-8) partially reduces this PMN adhesion.
Area of Science:
- Immunology
- Cell Biology
- Biophysics
Background:
- Polymorphonuclear leukocytes (PMN) are crucial immune cells involved in inflammatory responses.
- Cellular adhesion to extracellular matrix (ECM) proteins under physiological flow conditions is critical for PMN function.
- Understanding the specific integrins and their regulation during PMN adhesion is essential for developing targeted therapies.
Purpose of the Study:
- To investigate the role of specific integrins in polymorphonuclear leukocyte (PMN) tethering and arrest on laminin under laminar shear flow.
- To determine the effect of Interleukin-8 (IL-8) on PMN adhesion mediated by alpha 6 beta 1 integrin.
Main Methods:
- Perfusing PMN over immobilized extracellular matrix proteins (laminin, fibronectin, vitronectin) under controlled laminar shear flow.
- Utilizing monoclonal antibodies (mAbs) targeting specific integrin subunits (alpha 6, beta 1, alpha 2, alpha 3, beta 4) to block adhesion.
- Assessing the impact of IL-8 on PMN tethering and arrest.
Main Results:
- PMN exhibited significant tethering and immediate arrest on laminin, but not on fibronectin or vitronectin, at shear stress below 1.5 dyn/cm(2).
- Monoclonal antibodies against integrin alpha 6 or beta 1 chains significantly inhibited PMN tethering to laminin, indicating alpha 6 beta 1 integrin dependence.
- IL-8 partially reduced PMN tethering to laminin and induced detachment of already tethered PMN, suggesting a weakening of alpha 6 beta 1 integrin-mediated adhesion.
Conclusions:
- PMN tethering and arrest on laminin under shear flow are predominantly mediated by the alpha 6 beta 1 integrin.
- Interleukin-8 (IL-8) partially attenuates the adhesive function of alpha 6 beta 1 integrin on PMN in a flow environment.
- These findings elucidate a key mechanism of PMN-ECM interaction relevant to inflammatory processes.