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Published on: January 7, 2019
Dying blood mononuclear cell secretome exerts antimicrobial activity
Mohammad Mahdi Kasiri1, Lucian Beer1,2, Lucas Nemec3
1Christian Doppler Laboratory for Cardiac and Thoracic Diagnosis and Regeneration, Vienna, Austria.
Background:
Several activities are attributed to antimicrobial peptides (AMPs), including bacterial killing, leucocyte recruitment and angiogenesis. Despite promises of advanced cellular therapies for treatment of diabetic foot ulcer, it is currently accepted that paracrine factors rather than cellular components are causative for the observed effects. Whether AMPs are present in the mononuclear cell (MNC) secretome (MNC-sec) of white blood cells that are beneficial in experimental wound healing is not known.
Materials And Methods:
Antimicrobial activity of the secretomes of nonirradiated (MNC-sec) and γ-irradiated MNCs (MNC-sec rad) was analysed by microdilution assay. AMPs were determined by quantitative real-time PCR (RT-PCR) and enzyme-linked immunosorbent assay (ELISA). Whether human MNC-sec rad causes AMP secretion in vivo was examined in an experimental rat model. Image flow cytometry was used to determine the type of cell death induced in MNCs after exposure to γ-radiation.
Results:
The antimicrobial activity assay revealed a bactericidal activity of MNC-sec rad and to a lesser degree also of MNC-sec. Image flow cytometry showed that γ-irradiation of MNCs induced early apoptosis followed mainly by necroptosis. RT-PCR and ELISA revealed a high abundance of different AMPs in the secretome of MNCs. In addition, human MNC-sec elicited an increase in de novo endogenous AMP production in rats in vivo.
Conclusion:
We provide evidence that the secretome of MNCs has direct and indirect positive effects on the immune defence system, including augmentation of antibacterial properties. Our data further suggest that necroptosis could play a key role for the release of paracrine factors and the therapeutic action of MNC-sec rad.
Insights
Antimicrobial peptides (AMPs) are present in mononuclear cell (MNC) secretomes, enhancing antibacterial properties. Irradiated MNC secretomes, particularly through necroptosis, show therapeutic potential for wound healing.
Area of Science:
- Immunology
- Cell Biology
- Wound Healing Research
Background:
- Mononuclear cells (MNCs) are implicated in wound healing, with paracrine factors being key.
- The presence and role of antimicrobial peptides (AMPs) in MNC secretomes for wound healing remain unclear.
Purpose of the Study:
- To investigate the presence of AMPs in MNC secretomes.
- To evaluate the antimicrobial activity of MNC secretomes, particularly those from irradiated MNCs.
- To explore the mechanism of cell death and its relation to therapeutic effects.
Main Methods:
- Microdilution assays for antimicrobial activity.
- Quantitative real-time PCR (RT-PCR) and ELISA for AMP quantification.
- In vivo rat model to assess AMP secretion.
- Image flow cytometry for cell death analysis.
Main Results:
- MNC secretomes, especially from irradiated MNCs (MNC-sec rad), exhibit significant bactericidal activity.
- γ-irradiation induces apoptosis and necroptosis in MNCs.
- High abundance of AMPs was detected in MNC secretomes.
- Human MNC-sec rad stimulated endogenous AMP production in rats.
Conclusions:
- MNC secretomes possess direct and indirect immune-boosting effects, enhancing antibacterial actions.
- Necroptosis in irradiated MNCs is crucial for releasing therapeutic paracrine factors.
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