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Signaling and Dynamics of Activation of LFA-1 and Mac-1 by Immobilized IL-8

Elena B Lomakina1, Richard E Waugh

  • 1Department of Pharmacology and Physiology, University of Rochester, Medical Center, Rochester, NY.

Cellular and Molecular Bioengineering
|May 3, 2011
PubMed

Insights

Interleukin-8 (IL-8) triggers neutrophil adhesion via a pathway dependent on phospholipase C (PLC) and calcium release, not PI3K or PKC. This highlights distinct signaling for LFA-1 and Mac-1 integrin activation.

Area of Science:

  • Immunology
  • Cell Biology
  • Biochemistry

Background:

  • Neutrophil activation by chemokines like interleukin-8 (IL-8) is crucial in inflammation.
  • Chemokine-induced β(2) integrin-dependent adhesion to ICAM-1 takes minutes, involving complex signaling pathways.

Purpose of the Study:

  • To identify critical signaling events regulating IL-8-induced neutrophil adhesion to ICAM-1.
  • To elucidate the distinct molecular mechanisms governing LFA-1 and Mac-1 integrin activation.

Main Methods:

  • Utilized specific inhibitors (U73122 for PLC, wortmannin for PI3K, bisindolymaleimide for PKC) and calcium modulators (caffeine, 2-aminoethoxydiphenyl borate, BAPTA, EGTA).
  • Investigated the time course of neutrophil adhesion mediated by LFA-1 and Mac-1 integrins following IL-8 stimulation.
  • Assessed the role of p38MAP kinase in Mac-1 mediated adhesion.

Main Results:

  • Phospholipase C (PLC) inhibition, but not PI3K or PKC inhibition, blocked IL-8 induced adhesion.
  • Disruption of intracellular calcium release or chelation of calcium (intra- and extracellular) completely abrogated adhesion.
  • LFA-1 mediated adhesion occurred within 300 seconds, followed by Mac-1 mediated adhesion starting at 350 seconds.
  • p38MAP kinase inhibition mimicked Mac-1 inhibition, confirming its dependence.

Conclusions:

  • Neutrophil adhesion to ICAM-1 is critically dependent on a PLC and calcium signaling pathway.
  • Distinct temporal dynamics and signaling requirements exist for LFA-1 versus Mac-1 integrin activation in neutrophils.
  • Findings support a PLC-dependent, PKC-independent pathway for chemokine-induced integrin activation.

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