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Author Spotlight: Developing Innovative Therapeutic Strategies for Hemorrhagic Shock Research
Published on: March 22, 2024
Complement C5a Alters the Membrane Potential of Neutrophils during Hemorrhagic Shock
David A C Messerer1, Stephanie Denk1, Karl J Föhr2
1Institute of Clinical and Experimental Trauma-Immunology, University Hospital Ulm, 89081 Ulm, Germany.
Background:
Polymorphonuclear granulocytes (PMN) play a crucial role in host defense. Physiologically, exposure of PMN to the complement activation product C5a results in a protective response against pathogens, whereas in the case of systemic inflammation, excessive C5a substantially impairs neutrophil functions. To further elucidate the inability of PMN to properly respond to C5a, this study investigates the role of the cellular membrane potential of PMN in response to C5a.
Methods:
Electrophysiological changes in cellular and mitochondrial membrane potential and intracellular pH of PMN from human healthy volunteers were determined by flow cytometry after exposure to C5a. Furthermore, PMN from male Bretoncelles-Meishan-Willebrand cross-bred pigs before and three hours after severe hemorrhagic shock were analyzed for their electrophysiological response.
Results:
PMN showed a significant dose- and time-dependent depolarization in response to C5a with a strong response after one minute. The chemotactic peptide fMLP also evoked a significant shift in the membrane potential of PMN. Acidification of the cellular microenvironment significantly enhanced depolarization of PMN. In a clinically relevant model of porcine hemorrhagic shock, the C5a-induced changes in membrane potential of PMN were markedly diminished compared to healthy littermates. Overall, these membrane potential changes may contribute to PMN dysfunction in an inflammatory environment.
Insights
Polymorphonuclear granulocytes (PMN) membrane potential changes upon C5a exposure are crucial for host defense. In hemorrhagic shock, this response is diminished, contributing to PMN dysfunction.
Area of Science:
- Immunology
- Cellular Physiology
Background:
- Polymorphonuclear granulocytes (PMN) are vital for host defense.
- C5a normally triggers protective PMN responses, but excessive levels impair function during inflammation.
Purpose of the Study:
- Investigate the role of PMN cellular membrane potential in response to C5a.
- Elucidate the mechanisms behind PMN dysfunction in inflammatory conditions.
Main Methods:
- Flow cytometry assessed electrophysiological changes (membrane potential, pH) in human PMN after C5a exposure.
- Analyzed PMN electrophysiological responses in pigs before and after hemorrhagic shock.
Main Results:
- PMN exhibited dose- and time-dependent depolarization in response to C5a and fMLP.
- Acidification enhanced PMN depolarization; C5a-induced changes were diminished in pigs post-hemorrhagic shock.
Conclusions:
- Cellular membrane potential changes are significant in PMN response to C5a.
- Diminished PMN electrophysiological responses in hemorrhagic shock may underlie PMN dysfunction.
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