Related Experiment Videos
Suppression of phorbol myristate acetate-triggering of macrophage H2O2 release by sarcoma 180 originating factor
Abstract:
A high molecular weight proteinaceous factor in the cell extract of sarcoma 180 (S-180) was found to inhibit phorbol myristate acetate (PMA)-triggering of macrophage H2O2 release. This factor (S-180 factor) was stable at 56 C for 1 hr and resistant to ultraviolet-irradiation. The S-180 factor inhibited the specific binding of PMA to macrophages and this was accompanied by a parallel reduction of PMA-triggered H2O2 release. S-180 factor preferentially depressed macrophage H2O2 release in response to phorbol diesters including PMA, 4 beta-phorbol 12 13 beta,13 alpha-diacetate, 4 beta-phorbol 12 beta,13 alpha-didecanoate, 4 beta-phorbol 12 beta,13 alpha-dibenzoate, and 4-omicron-methyl-PMA rather than the H2O2 release triggered by wheat germ agglutinin or by phagocytosis of latex particles. The S-180 factor failed to affect the PMA-elicited macrophage cell spreading and macrophage phagocytic activity against latex beads with or without PMA-mediated stimulation. A similar inhibitory factor was found in the extracts of some other murine tumor cells (Ehrlich carcinoma and thymic leukemia) and normal cells (liver, spleen, and peritoneal exudate cells).
Insights
A novel protein factor from sarcoma 180 cells inhibits phorbol myristate acetate (PMA)-induced hydrogen peroxide release in macrophages by blocking PMA binding. This factor is stable and found in various cell types.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Phorbol myristate acetate (PMA) is a potent activator of macrophage functions, including hydrogen peroxide (H2O2) release.
- Understanding the regulation of PMA-induced responses is crucial for studying inflammatory processes and immune cell activation.
Purpose of the Study:
- To identify and characterize factors within sarcoma 180 (S-180) cells that modulate PMA-triggered macrophage H2O2 release.
- To investigate the mechanism by which the S-180 factor exerts its inhibitory effect on macrophage activation.
Main Methods:
- Preparation of cell extracts from sarcoma 180 (S-180) cells.
- Assay of macrophage H2O2 release triggered by PMA and other stimuli.
- Measurement of PMA-macrophage binding.
- Assessment of macrophage cell spreading and phagocytosis.
Main Results:
- A high molecular weight, heat- and UV-stable proteinaceous factor (S-180 factor) was isolated from S-180 cell extracts.
- The S-180 factor significantly inhibited PMA-induced H2O2 release by macrophages, acting by reducing PMA-macrophage binding.
- This inhibition was specific to phorbol diesters, with no effect on H2O2 release induced by wheat germ agglutinin or phagocytosis, nor on PMA-elicited cell spreading or phagocytic activity.
Conclusions:
- A novel inhibitory factor present in S-180 cells specifically blocks PMA-induced H2O2 release in macrophages.
- This factor acts upstream of H2O2 production by interfering with PMA binding to its receptor.
- Similar inhibitory factors are present in other murine tumor and normal cells, suggesting a potentially widespread regulatory mechanism.