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Detection of intracellular lipocortin 1 in human leukocyte subsets
E F Morand1, P Hutchinson, A Hargreaves
1Monash Centre for Inflammatory Diseases, Monash Medical Centre, Melbourne, Australia.
Insights
Lipocortin 1 is found in most human immune cells, with levels varying significantly between cell types like monocytes and lymphocytes. This differential distribution is important for understanding inflammatory diseases.
Area of Science:
- Immunology
- Cell Biology
Background:
- Lipocortin 1 is a key protein mediating glucocorticoid anti-inflammatory effects.
- Understanding its distribution in immune cells is crucial for inflammatory disease research.
Purpose of the Study:
- To investigate the presence and distribution of Lipocortin 1 in various human leukocyte subsets.
- To determine if dexamethasone affects Lipocortin 1 levels in peripheral blood leukocytes.
Main Methods:
- Utilized permeabilization flow cytometry to detect intracellular Lipocortin 1 in human leukocyte subsets.
- Analyzed Lipocortin 1 expression in relation to specific cell surface markers (e.g., CD14, HLA-DR, CD19/20, CD56).
- Assessed Lipocortin 1 changes following stimulation with PMA, IFN-gamma, and dexamethasone.
Main Results:
- Lipocortin 1 was detected in most leukocyte subsets, notably absent in B lymphocytes.
- Monocytes and polymorphonuclear neutrophils showed the highest Lipocortin 1 content, while lymphocytes had the least.
- Lipocortin 1 levels did not significantly change with dexamethasone treatment but were modulated by PMA and IFN-gamma in U937 cells.
Conclusions:
- Lipocortin 1 exhibits significant variation in content across distinct human leukocyte subsets.
- The differential expression of Lipocortin 1 among immune cells has implications for studying inflammatory conditions.
- Dexamethasone did not induce Lipocortin 1 in peripheral blood leukocytes, suggesting alternative mechanisms for its anti-inflammatory action in these cells.
Abstract:
Lipocortin 1, a putative mediator of the anti-inflammatory actions of glucocorticoids, is present intracellularly in a variety of tissues including human peripheral blood leukocytes. We investigated the presence of lipocortin 1 in human leukocyte subsets using permeabilization flow cytometry. Constitutive lipocortin 1 was detected in U937 myelomonocytic leukemia cells, and lipocortin 1 was increased by treatment with PMA or PMA+IFN-gamma (P < 0.05) but not by dexamethasone. Lipocortin 1 was present in all leukocyte subsets except B lymphocytes (CD19/20+, P < 0.001). Lipocortin 1 content was maximal in monocytes and polymorphonuclear neutrophils and least in lymphocytes (P < 0.001). Monocyte lipocortin 1 was strongly associated with surface expression of CD14 and HLA-DR. Among non-B lymphocytes, a range of lipocortin 1 fluorescence was observed. Lipocortin 1 fluorescence was greatest in natural killer cells (CD56+, P < 0.001) and CD57+ cells, but T cell subset markers did not otherwise discriminate variations in lipocortin 1. Induction of lymphocyte proliferation by PHA, anti-CD3, Con A, superantigen, and SAC was not associated with significant shifts in lipocortin 1 content. Dexamethasone (10(-10)-10(-6) M) did not induce increases in PB leukocyte lipocortin 1. We conclude that lipocortin 1 content in human leukocytes varies significantly among phenotypic subsets. This has significance for the investigation of inflammatory disease where certain cell types predominate.
