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Modulation of cellular annexin I in human leukocytes infiltrating DTH skin reactions
M Perretti1, S K Wheller, R J Flower
1Department of Biochemical Pharmacology, The William Harvey Research Institute, London, United Kingdom. m.perretti@qmw.ac.uk
Abstract:
Based on our previous studies showing endogenous annexin I being depleted from migrated neutrophils (PMN) in vitro, we have tested whether the levels of this glucocorticoid-regulated protein in PMN and mononuclear cells (PBMC) were modified after adhesion to endothelial monolayers in vitro and extravasation into skin blisters in vivo. In vitro, annexin I levels were depleted more significantly (-70%) in post-adherent PMNs than in monocytes (-25%) and lymphocytes (-50%, only in the positive fraction). In vivo, a significant time-dependent increase (approximately threefold, P < 0.05) in cell-associated annexin I was measured in PBMCs recovered from the blisters, whereas no significant changes were detected in extravasated PMNs. This was associated with annexin I release in the blister fluids (approximately 35 ng/mL), whereas no detectable protein was found in matched-paired plasmas. In conclusion, we report for the first time an activation of the annexin I pathway during an ongoing experimental inflammatory response in humans, which is differently regulated between PMNs and PBMCs.
Insights
Annexin I is depleted from neutrophils during inflammation. In humans, annexin I increases in mononuclear cells during inflammation, while neutrophils show no change, indicating differential regulation.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Endogenous annexin I is known to be depleted from migrating neutrophils (PMN) in vitro.
- Annexin I is a glucocorticoid-regulated protein involved in inflammatory processes.
Purpose of the Study:
- To investigate modifications in annexin I levels in PMN and peripheral blood mononuclear cells (PBMC) after adhesion to endothelial cells in vitro.
- To assess changes in annexin I levels in PMN and PBMCs during extravasation into skin blisters in vivo.
Main Methods:
- In vitro adhesion assay of PMN and PBMCs to endothelial monolayers.
- Induction of skin blisters in vivo to collect inflammatory exudate and cells.
- Quantification of annexin I levels in cells (PMN, PBMCs) and blister fluid using biochemical assays.
Main Results:
- In vitro, annexin I depletion was more significant in post-adherent PMNs (-70%) compared to monocytes (-25%) and lymphocytes (-50%).
- In vivo, PBMCs from blisters showed a threefold increase in cell-associated annexin I over time.
- Extravasated PMNs showed no significant change in annexin I, but annexin I was detected in blister fluid (approx. 35 ng/mL), not in plasma.
Conclusions:
- The study reports the first evidence of annexin I pathway activation during an experimental inflammatory response in humans.
- Annexin I regulation differs between PMNs and PBMCs during inflammation.
- Annexin I is released into inflammatory exudates, suggesting a role beyond intracellular functions.