Regulation of degranulation of human eosinophils

  • Kita, Hirohito (PI)
  • O'Grady, Scott M. (PI)
  • Gleich, Gerald (PI)
  • O'Grady, Scott M. (PI)
  • Wylam, Mark (PI)
  • O'Grady, Scott M. (PI)

Project: Research project

Project Details


Description (provided by applicant): Eosinophils are one of the key effector
cells in the pathology of asthma. Activation of eosinophils by inflammatory
mediators leads to the release of toxic granule proteins that cause serious
damage to the airway epithelium. However, the post-receptor signaling
pathways that control eosinophil degranulation and granule protein toxicity
are poorly understood. The overall objective of this project constitutes the
first specific goal of this AADRC, which is to understand the cellular and
molecular mechanisms of eosinophil activation as they relate to the release of
granule proteins. The long-term goal of Project 1 is to understand how
calcium mobilization and PKC activation contribute to degranulation and to the
toxic effects of granule proteins on the airway epithelium. The first
specific aim of the project is to identify the PKC isoform involved in IL-5
stimulated degranulation and to investigate its role in regulation of
cytoskeletal rearrangements necessary for degranulation. We will test the
hypothesis that activation of PKC-delta, the major calcium-independent PKC
isoform in human eosinophils, phosphorylates MARCKS, resulting in actin
rearrangements that are critical for degranulation. The second aim will
address the effects of calcium mobilization on intra-granule acidification and
examine the role of proton transport in granule protein solubilization. Our
hypothesis is that increases in intracellular calcium stimulate granule
membrane proton ATPases leading to granule acidification and solubilization of
MBP crystals, a process needed for effective release of this protein. We
further contend that MBP crystal solubilization strongly enhances toxicity
resulting in a greater degree of epithelia damage compared to MBP release in
the absence of increased intracellular calcium. To test this hypothesis, we
will investigate the effects of calcium on granule membrane proton transport
and measure the effects on MBP solubilization. Finally, we will examine the
effects of eosinophil degranulation on human airway epithelial cell and
determine the toxicity of released granule proteins on epithelia barrier
function, electrolyte transport and mucosal shedding. We will use this system
to evaluate effects of MBP solubilization on the airway epithelium and to
determine whether compounds that inhibit granule acidification can reduce MBP
toxicity. The results should provide new insights into eosinophil
degranulation and elucidate the regulatory mechanisms of granule protein
toxicity on airway epithelial cells. Furthermore, our findings may help
identify new drug targets and therapeutic approaches for the treatment of
human asthma.
Effective start/end date9/10/016/30/07


  • Medicine(all)
  • Immunology and Microbiology(all)