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Hug S, Bernhard S, Stratmann AEP, Erber M, Wohlgemuth L, Knapp CL, Bauer JM, Vidoni L, Fauler M, Föhr KJ, Radermacher P, Hoffmann A, Huber-Lang M, Messerer DAC. Activation of Neutrophil Granulocytes by Platelet-Activating Factor Is Impaired During Experimental Sepsis. Front Immunol 2021; 12:642867. [PMID: 33796110 PMCID: PMC8007865 DOI: 10.3389/fimmu.2021.642867] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2020] [Accepted: 02/15/2021] [Indexed: 11/13/2022] Open
Abstract
Platelet-activating factor (PAF) is an important mediator of the systemic inflammatory response. In the case of sepsis, proper activation and function of neutrophils as the first line of cellular defense are based on a well-balanced physiological response. However, little is known about the role of PAF in cellular changes of neutrophils during sepsis. Therefore, this study investigates the reaction patterns of neutrophils induced by PAF with a focus on membrane potential (MP), intracellular pH, and cellular swelling under physiological and pathophysiological conditions and hypothesizes that the PAF-mediated response of granulocytes is altered during sepsis. The cellular response of granulocytes including MP, intracellular pH, cellular swelling, and other activation markers were analyzed by multiparametric flow cytometry. In addition, the chemotactic activity and the formation of platelet-neutrophil complexes after exposure to PAF were investigated. The changes of the (electro-)physiological response features were translationally verified in a human ex vivo whole blood model of endotoxemia as well as during polymicrobial porcine sepsis. In neutrophils from healthy human donors, PAF elicited a rapid depolarization, an intracellular alkalization, and an increase in cell size in a time- and dose-dependent manner. Mechanistically, the alkalization was dependent on sodium-proton exchanger 1 (NHE1) activity, while the change in cellular shape was sodium flux- but only partially NHE1-dependent. In a pathophysiological altered environment, the PAF-induced response of neutrophils was modulated. Acidifying the extracellular pH in vitro enhanced PAF-mediated depolarization, whereas the increases in cell size and intracellular pH were largely unaffected. Ex vivo exposure of human whole blood to lipopolysaccharide diminished the PAF-induced intracellular alkalization and the change in neutrophil size. During experimental porcine sepsis, depolarization of the MP was significantly impaired. Additionally, there was a trend for increased cellular swelling, whereas intracellular alkalization remained stable. Overall, an impaired (electro-)physiological response of neutrophils to PAF stimulation represents a cellular hallmark of those cells challenged during systemic inflammation. Furthermore, this altered response may be indicative of and causative for the development of neutrophil dysfunction during sepsis.
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Affiliation(s)
- Stefan Hug
- Institute of Clinical and Experimental Trauma Immunology, University Hospital of Ulm, Ulm, Germany
| | - Stefan Bernhard
- Institute of Clinical and Experimental Trauma Immunology, University Hospital of Ulm, Ulm, Germany
| | | | - Maike Erber
- Institute of Clinical and Experimental Trauma Immunology, University Hospital of Ulm, Ulm, Germany
| | - Lisa Wohlgemuth
- Institute of Clinical and Experimental Trauma Immunology, University Hospital of Ulm, Ulm, Germany
| | - Christiane Leonie Knapp
- Institute of Clinical and Experimental Trauma Immunology, University Hospital of Ulm, Ulm, Germany
| | - Jonas Martin Bauer
- Institute of Clinical and Experimental Trauma Immunology, University Hospital of Ulm, Ulm, Germany
| | - Laura Vidoni
- Institute of Clinical and Experimental Trauma Immunology, University Hospital of Ulm, Ulm, Germany
| | - Michael Fauler
- Institute of General Physiology, University of Ulm, Ulm, Germany
| | - Karl Josef Föhr
- Department of Anesthesiology and Intensive Care Medicine, University Hospital of Ulm, Ulm, Germany
| | - Peter Radermacher
- Institute of Anesthesiological Pathophysiology and Process Development, University Hospital of Ulm, Ulm, Germany
| | - Andrea Hoffmann
- Institute of Anesthesiological Pathophysiology and Process Development, University Hospital of Ulm, Ulm, Germany
| | - Markus Huber-Lang
- Institute of Clinical and Experimental Trauma Immunology, University Hospital of Ulm, Ulm, Germany
| | - David Alexander Christian Messerer
- Institute of Clinical and Experimental Trauma Immunology, University Hospital of Ulm, Ulm, Germany.,Department of Anesthesiology and Intensive Care Medicine, University Hospital of Ulm, Ulm, Germany.,Institute of Anesthesiological Pathophysiology and Process Development, University Hospital of Ulm, Ulm, Germany
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