Cathepsin D activity in human peripheral blood mononuclear leukocytes
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C T Bever1, K D Morgan, J N Whitaker
1Neurology Service, VAMC, Memphis, Tennessee.
Insights
Macrophages significantly increase cathepsin D (CD) levels during differentiation. This suggests macrophages are a key source of CD in inflammatory lesions, impacting disease understanding.
Area of Science:
- Immunology
- Cell Biology
Background:
- Cathepsin D (CD) is implicated in inflammatory lesions.
- Understanding the cellular origin of CD is crucial for inflammatory disease research.
Purpose of the Study:
- To investigate the cellular origins of cathepsin D (CD) in inflammatory lesions.
- To compare CD content across different immune cell types, including lymphocytes, monocytes, and macrophages.
Main Methods:
- Human peripheral blood cells (monocytes, B lymphocytes, CD4+ T, CD8+ T) were isolated.
- Monocyte differentiation into macrophages was induced via in vitro culture or phorbol ester (PMA) treatment.
- Cathepsin D content was quantified using microgram equivalents per million cells.
Main Results:
- No significant differences in CD content were found between lymphocyte subsets and monocytes.
- Differentiated macrophages exhibited significantly higher CD content compared to unstimulated monocytes.
- Macrophages induced by 5-day culture showed a fourfold increase in CD.
- Macrophages treated with 4β-PMA demonstrated a ninefold increase in CD compared to controls.
Conclusions:
- Macrophages are a major cellular source of cathepsin D in inflammatory lesions.
- Monocyte differentiation into macrophages leads to a substantial upregulation of CD.
- These findings highlight macrophages as a potential therapeutic target in inflammatory conditions involving CD.
Abstract:
To investigate the cellular origins of cathepsin D (CD) in inflammatory lesions, the CD content of lymphocyte subsets, monocytes, and macrophages were compared. Human monocytes, B lymphocytes, CD4+ T lymphocytes, and CD8+ T lymphocytes were separated from peripheral blood of normal donors. CD content was 0.13 +/- .01 micrograms equivalents of CD per million cells and significant differences between different cell types were not found. To determine the CD content of macrophages, differentiation of peripheral blood monocytes was induced by either in vitro culture or treatment with 4 beta-phorbol-12-myristate-13-acetate (PMA). Macrophages induced by five-day culture contained four times more CD than unstimulated monocytes, and macrophages induced by 18-h treatment with 20 mg/ml 4 beta-PMA contained nine times more CD than monocytes treated with 4 alpha-PMA, an inactive stereoisomer of 4 beta-PMA. These results suggest that macrophages are one of the enriched sources of CD in inflammatory lesions.