Calcium Signaling in Trauma: Increased Intracellular Calcium Flux in the Severely Injured

Abstract

IntroductionThe pathogenesis of organ dysfunction following traumatic injury involves endothelial barrier disruption, and plasma from severely injured patients increases endothelial permeability in vitro. Many endothelial cell (EC) functions entail changes in intracellular calcium (Ca2+) concentrations, and multiple inflammatory mediators have been shown to induce EC barrier disruption in a Ca2+ dependent manner. However, study of Ca2+ signaling in trauma remains limited. Our objective was to investigate the role of intracellular Ca2+ signaling in trauma pathology. We hypothesized that ex vivo plasma from injured patients would induce intracellular EC Ca2+ flux and do so to a greater magnitude in more severely injured patients.MethodsBlood was collected from injured patients at a single, urban Level I Trauma Center. Patients were categorized by minimal injury without shock (Group 1: ISS<15 + base excess >‐6mEq/L; n=3) and severe injury with shock (Group 2: ISS>15 + base excess <‐6mEq/L; n=4). Human cerebral microvascular endothelial cells were grown on culture inserts and pre‐incubated with Fluo‐4 Ca2+ indicator. Plasma was diluted to concentrations previously used for in vitro permeability assays and flowed over EC’s under physiologic conditions for five minutes. Confocal microscopy was used to visualize and quantify intracellular Ca2+ flux. Thrombin was used as a positive control for inducing Ca2+ flux. We used Prism software to calculate areas under curves (AUC) and unpaired t‐tests to compare group means.ResultsCompared to Group 1 plasma, Group 2 induced greater calcium flux, which was sustained for a longer period of time, corresponding to greater AUC for total intracellular calcium flux (P<0.05, Figure).ConclusionsEx vivo plasma from more severely injured trauma patients increases intracellular Ca2+ flux in EC’s. These data suggest Ca2+signaling may play a role in trauma‐induced endotheliopathy and present as a therapeutic target. Our study lays the groundwork for additional investigation to elucidate sources of Ca2+ in this setting as well as identify plasma mediators of both Ca2+ flux and endothelial permeability.