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Release of erythropoietin from macrophages by treatment with silica
I N Rich1, V Anselstetter, W Heit
1Department of Transfusion Medicine, University of Ulm, Federal Republic of Germany.
Abstract:
An erythropoietic stimulating factor (ESF) can be shown to be released from preincubated macrophage-containing cell suspensions from mice by the macrophage-specific, cytotoxic agent, silica. A concentrated silica-treated spleen cell supernatant containing ESF is shown to cause a dose-dependent increase in 59Fe incorporation into red blood cells using the in vivo polycythemic mouse bioassay. The ESF from the same supernatant can also be neutralized by anti-erythropoietin. A second concentrated supernatant fractionated using wheat germ lectin-Sepharose 6MB and compared to either unfractionated or fractionated step III erythropoietin (Ep), tested in vitro using the erythroid colony-forming technique and 12-day fetal liver as target cells, indicates parallelism of all linear dose-response lines. This, together with the in vivo data, strongly suggests that the ESF released from macrophages treated with silica is, in fact, Ep. Substituting Ca2+ ions for fetal calf serum in the preincubation procedure results in the same activity being released compared to the presence of 1% or 20% fetal calf serum.
Insights
Macrophages release erythropoietic stimulating factor (ESF) when treated with silica. This ESF is identified as erythropoietin (Ep), crucial for red blood cell production.
Area of Science:
- Immunology
- Hematology
- Cell Biology
Background:
- Macrophages play a role in regulating red blood cell production.
- Erythropoietic stimulating factor (ESF) is essential for erythropoiesis.
Purpose of the Study:
- To investigate the release of ESF from macrophages.
- To identify the nature of the ESF released by macrophages.
Main Methods:
- Macrophage cell suspensions were treated with silica, a cytotoxic agent.
- Supernatants were analyzed using in vivo polycythemic mouse bioassays and in vitro erythroid colony-forming assays.
- Wheat germ lectin-Sepharose chromatography was employed for fractionation.
Main Results:
- Silica-treated macrophages released ESF.
- The released ESF stimulated 59Fe incorporation into red blood cells in vivo.
- The ESF was neutralized by anti-erythropoietin antibodies.
- Fractionation and in vitro assays demonstrated parallelism with erythropoietin (Ep).
- Calcium ions could substitute for fetal calf serum in the release procedure.
Conclusions:
- The ESF released from silica-treated macrophages is erythropoietin (Ep).
- This finding highlights a novel pathway for Ep production or release.
- Macrophage-derived Ep may contribute to erythropoiesis regulation.