Related Experiment Videos
Trypanosoma cruzi: killing and enhanced uptake by resident peritoneal macrophages treated with alpha-2-macroglobulin
T C Araújo-Jorge1, M de N de Meirelles, L Isaac
1Depto. de Ultraestrutura e Biologia Celular, Fundação Oswaldo Cruz, Rio de Janeiro, Brasil.
Abstract:
We report that alpha-2-macroglobulin (A2M), the physiologically important plasma protease inhibitor and suspected immunomodulator, alters the functional ability of murine resident peritoneal macrophages (RM) to ingest and kill the infective trypomastigote stage of Trypanosoma cruzi, the aetiological agent of Chagas' disease. Treatment of RM with 500 micrograms/ml A2M for 30 min enhanced the uptake of trypomastigotes, epimastigotes, and amastigotes by 125%, 46%, and 300%, respectively. The same treatment also increased the phagocytosis of sheep erythrocytes opsonized with complement and IgG as well as of galactosylated asialoerythrocytes. After 60-90 min parasite-cell interaction, epi- and amastigotes were killed by the RM, whereas the infection with trypomastigotes was controlled only after 24 h. Other protease inhibitors, bovine serum albumin, and LPS showed no such effect. The production of hydrogen peroxide was not affected by A2M treatment, but the ultrastructural aspects showed trypomastigote damage and enhancement of macrophage membrane ruffling, indicative of macrophage activation. These results suggest that A2M has the ability to modulate, at least functionally, certain receptor-mediated endocytic pathways that, in concert with an activation of possibly oxygen-independent microbicidal mechanisms, could contribute to resistance against the parasite.
Insights
Alpha-2-macroglobulin (A2M) enhances macrophage uptake and killing of Trypanosoma cruzi, the parasite causing Chagas' disease. This suggests A2M may play a role in fighting parasitic infections.
Area of Science:
- Immunology
- Parasitology
- Cell Biology
Background:
- Alpha-2-macroglobulin (A2M) is a key plasma protease inhibitor with suspected immunomodulatory functions.
- Trypanosoma cruzi is the causative agent of Chagas' disease, a significant human health concern.
- Macrophages play a crucial role in the innate immune response against parasitic infections.
Purpose of the Study:
- To investigate the effect of alpha-2-macroglobulin (A2M) on the functional capacity of murine resident peritoneal macrophages (RM) in interacting with Trypanosoma cruzi.
- To determine if A2M enhances the phagocytosis and killing of different developmental stages of T. cruzi by macrophages.
- To explore the underlying mechanisms of A2M-mediated modulation of macrophage activity.
Main Methods:
- Murine resident peritoneal macrophages (RM) were treated with alpha-2-macroglobulin (A2M).
- Phagocytosis assays were performed using various targets, including different forms of Trypanosoma cruzi (trypomastigotes, epimastigotes, amastigotes), opsonized sheep erythrocytes, and galactosylated asialoerythrocytes.
- Macrophage activation markers, such as membrane ruffling and parasite killing, were assessed via microscopy and time-course experiments.
Main Results:
- A2M treatment significantly enhanced the uptake of all tested stages of T. cruzi by RM.
- A2M increased phagocytosis of complement and IgG-opsonized sheep erythrocytes and galactosylated asialoerythrocytes.
- While epimastigotes and amastigotes were killed within 90 minutes, trypomastigotes required 24 hours for clearance, indicating stage-specific killing efficiency. Macrophage membrane ruffling was enhanced, suggesting activation.
Conclusions:
- Alpha-2-macroglobulin (A2M) functionally modulates macrophage endocytic pathways, enhancing the uptake of Trypanosoma cruzi.
- A2M contributes to macrophage activation, potentially through oxygen-independent microbicidal mechanisms, aiding in resistance against T. cruzi infection.
- These findings highlight A2M as a potential therapeutic target or factor in managing Chagas' disease.