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Synergistic effect of interferon-gamma and phorbol myristate acetate on superoxide production by human monocytes
M Wolfson1, I Nathan, M Aharon
1Department of Microbiology and Immunology, Faculty of Health Sciences, Ben Gurion University of the Negev, Israel.
Abstract:
This study demonstrates a synergistic effect of IFN gamma and PMA on superoxide generation by human monocytes. A strict correlation was observed between the induction of superoxide production and PK-C activation by PMA alone. No such correlation was evident for IFN gamma. However, exposure of the cells to IFN gamma for 10 to 15 hr prior to PMA treatment enhanced both superoxide production and PK-C activation. Using protein kinase inhibitors, we noticed that while PMA exerted its effect by activating PK-C, IFN gamma operated via activation of calcium/calmodulin-dependent or some other calcium-dependent protein kinases. These kinases appeared to be involved in the effect of IFN gamma on superoxide production, as well as in its potentiation of PMA activity.
Insights
Interferon gamma (IFN-γ) and phorbol 12-myristate 13-acetate (PMA) synergistically enhance superoxide generation in human monocytes. IFN-γ primes monocytes, potentiating PMA-induced superoxide production and protein kinase C (PKC) activation.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Human monocytes play a crucial role in innate immunity, with superoxide generation being a key microbicidal mechanism.
- Interferon gamma (IFN-γ) and phorbol 12-myristate 13-acetate (PMA) are known modulators of monocyte function.
- Protein kinase C (PKC) activation is implicated in cellular signaling pathways, including those involved in oxidative burst.
Purpose of the Study:
- To investigate the synergistic effects of IFN-γ and PMA on superoxide generation in human monocytes.
- To elucidate the distinct and combined roles of IFN-γ and PMA in activating signaling pathways, particularly protein kinases.
- To understand the mechanisms underlying IFN-γ's potentiation of PMA-induced superoxide production.
Main Methods:
- Human monocytes were treated with IFN-γ and/or PMA.
- Superoxide generation was measured using appropriate assays.
- Protein kinase C (PKC) activation was assessed.
- The effects of protein kinase inhibitors were evaluated to determine the involvement of specific signaling pathways.
Main Results:
- A synergistic effect of IFN-γ and PMA on superoxide generation by human monocytes was observed.
- PMA alone correlated with protein kinase C (PKC) activation, while IFN-γ did not show a direct correlation.
- Pre-treatment with IFN-γ enhanced both superoxide production and PKC activation upon subsequent PMA stimulation.
- IFN-γ's effects involved calcium/calmodulin-dependent or other calcium-dependent protein kinases, distinct from PMA's PKC activation pathway.
Conclusions:
- IFN-γ primes human monocytes, leading to enhanced superoxide generation and potentiation of PMA-induced responses.
- IFN-γ utilizes calcium-dependent protein kinases, while PMA acts via PKC, in modulating monocyte superoxide production.
- These findings reveal distinct yet cooperative signaling mechanisms of IFN-γ and PMA in regulating critical monocyte functions.