Peroxidase activity in murine and human hematopoietic progenitor cells: potential relevance to benzene-induced toxicity
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D G Schattenberg1, W S Stillman, J J Gruntmeir
1Molecular Toxicology and Environmental Health Sciences Program, School of Pharmacy, University of Colorado Health Sciences Center, Denver 80262.
Abstract:
Peroxidases may be important in the mechanism of toxicity of a number of compounds including benzene, a chemical that has been associated with bone marrow toxicity and leukemia after chronic exposure. The major peroxidase in bone marrow is myeloperoxidase (MPO), which has been previously thought to be expressed at the promyelocytic stage of differentiation. Hematopoietic progenitor cells are important potential cellular targets of bone marrow toxins and leukemogens. We therefore examined peroxidase activity in both murine and human progenitor cells. Murine progenitor populations were purified as lineage-negative cells (> 99% enriched) and human progenitor populations were purified as CD34+ cells (> 95% enriched). Using conventional biochemical assays for peroxidase activity, murine and human progenitor cells were found to have 30% and 11% of the peroxidase activity of murine and human unpurified marrow, respectively. Peroxidase activity was confirmed in purified murine and human progenitor populations by flow cytometry using a 2,7-dichlorofluorescein assay, adapted to measure peroxidase activity. In addition, two-color flow cytometry of murine whole marrow using phycoerythrin-conjugated antibodies to lineage markers confirmed the peroxidase activity of the murine progenitor cell population. A reverse transcription-polymerase chain reaction assay was developed for MPO mRNA, which was detected in murine progenitor cells. These data show that MPO mRNA is expressed in murine progenitor cells and that both murine and human progenitor cells have marked peroxidase activity. These data may have relevance for studies of hematopoietic cell differentiation and for the examination of mechanisms underlying cell-specific toxicity in bone marrow.
Insights
Myeloperoxidase (MPO) activity and MPO mRNA are present in hematopoietic progenitor cells. This finding is relevant for understanding bone marrow toxicity and cell differentiation.
Area of Science:
- Hematology
- Toxicology
- Molecular Biology
Background:
- Peroxidases, particularly myeloperoxidase (MPO), are implicated in the toxicity of compounds like benzene, which causes bone marrow toxicity and leukemia.
- Hematopoietic progenitor cells are potential targets for bone marrow toxins and leukemogens.
- MPO was previously believed to be expressed only at the promyelocytic stage of differentiation.
Purpose of the Study:
- To investigate peroxidase activity in murine and human hematopoietic progenitor cells.
- To determine if MPO is expressed in these progenitor cells.
Main Methods:
- Purification of murine lineage-negative and human CD34+ progenitor cells.
- Biochemical assays and flow cytometry (2,7-dichlorofluorescein assay) to measure peroxidase activity.
- Reverse transcription-polymerase chain reaction (RT-PCR) to detect MPO mRNA.
Main Results:
- Murine and human progenitor cells exhibited significant peroxidase activity (30% and 11% of unpurified marrow, respectively).
- Peroxidase activity was confirmed in purified progenitor populations via flow cytometry.
- MPO mRNA was detected in murine progenitor cells, indicating MPO expression.
Conclusions:
- Both murine and human progenitor cells possess substantial peroxidase activity.
- Myeloperoxidase mRNA is expressed in murine progenitor cells.
- These findings have implications for studying hematopoietic cell differentiation and the mechanisms of bone marrow toxicity.