• Terry R Schaid, Sanchayita Mitra, Preston Stafford, Margot DeBot, Otto Thielen, William Hallas, Alexis Cralley, Lauren Gallagher, Danielle Jeffrey, Kirk C Hansen, Angelo D'Alessandro, Christopher C Silliman, Fabrice Dabertrand, and Mitchell J Cohen.
• University of Colorado Denver, School of Medicine, Department of Surgery, Trauma Research Center, Aurora, CO.
• Ann. Surg. 2023 Dec 11.

ObjectiveWe aimed to investigate if ex vivo plasma from injured patients causes endothelial calcium (Ca2+) influx as a mechanism of trauma-induced endothelial permeability.Summary Background DataEndothelial permeability after trauma contributes to post-injury organ dysfunction. While the mechanisms remain unclear, emerging evidence suggests intracellular Ca2+ signaling may play a role.MethodsEx vivo plasma from injured patients with "Low Injury/Low Shock" (injury severity score [ISS]<15, base excess [BE])≥-6mEq/L) and "High Injury/High Shock" (ISS≥15, BE<-6mEq/L) were used to treat endothelial cells. Experimental conditions included Ca2+ removal from the extracellular buffer, cyclopiazonic acid pre-treatment to deplete intracellular Ca2+ stores, and GSK2193874 pre-treatment to block the TRPV4 Ca2+ channel. Live cell fluorescence microscopy and ECIS were used to assess cytosolic Ca2+ increases and permeability, respectively. Western blot and live cell actin staining were used to assess myosin light chain (MLC) phosphorylation and actomyosin contraction.ResultsCompared to Low Injury/Low Shock plasma, High Injury/High Shock induced greater cytosolic Ca2+ increase. Cytosolic Ca2+ increase, MLC phosphorylation, and actin cytoskeletal contraction were lower without extracellular Ca2+ present. High Injury/High Shock plasma did not induce endothelial permeability without extracellular Ca2+ present. TRPV4 inhibition lowered trauma plasma-induced endothelial Ca2+ influx and permeability.ConclusionsThis study illuminates a novel mechanism of post-injury endotheliopathy involving Ca2+ influx via the TRPV4 channel. TRPV4 inhibition mitigates trauma-induced endothelial permeability. Moreover, widespread endothelial Ca2+ influx may contribute to trauma-induced hypocalcemia. This study provides the mechanistic basis for the development of Ca2+-targeted therapies and interventions in the care of severely injured patients.Copyright © 2023 Wolters Kluwer Health, Inc. All rights reserved.

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