Surgical Infection Society Articles Monitoring Neutrophil-Expressed Cell Surface Esophageal Cancer Related Gene-4 after Severe Burn Injury

Background: We identified recently esophageal cancer related gene-4 (ECRG4) as a candidate cytokine that is expressed on the surface of quiescent polymorphonuclear leukocytes (PMNs) and shed in response to ex vivo treatment with lipopolysaccharide. To investigate the potential biologic relevance of changes in cell surface ECRG4 in human samples, we performed a pilot study to examine a population of burn patients in whom blood could be analyzed prospectively. We hypothesized that cutaneous burn injury would alter cell surface expression of ECRG4 on PMNs. Methods: Patients admitted with more than 20% total burn surface area (TBSA) (n = 10) had blood collected at the time of admission and weekly thereafter. For comparison, blood was obtained from a control group of healthy human volunteers (n = 4). We used flow cytometry to measure changes in ECRG4 PMNs from patients during recovery from injury. Esophageal cancer related gene-4 expression at each time point was compared with the patient’s clinical status based on a Multiple Organ Dysfunction (MOD) score. Results: Esophageal cancer related gene-4 was detected on the PMN surface of cells collected from healthy volunteers, however, within 48 h of admission after burn injury (n = 10 patients), the number of PMNs with cell surface ECRG4 was decreased. Esophageal cancer related gene-4 expression in PMNs was re-established over the course of patient recovery, unless complications occurred. In this case, the decrease in cell surface ECRG4 PMNs preceded the clinical diagnosis of infectious complications and was reflected by increased organ injury scores. Conclusion: From a small sample set, we were able to determine that PMN cell surface ECRG4 expression was decreased after burn injury and returned to baseline during recovery from injury. Although larger studies are needed to define the role of ECRG4 in human PMNs further, this report is the first assessment of cell surface ECRG4 protein in a patient population to support analogous findings in animal studies. Severe burn and trauma can elicit an overwhelming inflammatory response that is characterized by dysfunctional innate immunity and multiple organ failure [1–3]. Gene profiling of circulating leukocytes after such injuries suggests that there is an induction of a genomic storm that activates and/or suppresses pathways regulating innate immunity and adaptive immunity respectively [4,5]. Whereas all phases of the injury response influence the final clinical outcome, none is more relevant than the role played by the inflammatory ‘‘set point’’ at the time of injury. Accordingly, it is critical to define how these inflammatory set points are established and how they affect the injury response because they pre-define the capacity, duration, and intensity of the injury response and might account for differences in outcomes observed in individuals exposed to identical injuries. We have focused on the potential for esophageal cancer related gene-4 (ECRG4) to serve as a sentinel factor on immune cells that may regulate the immune set point based on its expression on the surface of leukocytes, its release from the cell surface after inflammatory stimuli, and its epigenetic regulation that may explain differences in Ecrg4 expression between individuals [6–9]. Esophageal cancer related gene-4 encodes a 148 amino acid precursor protein that is tethered to the cell surface but shed on activation [6,10]. We have demonstrated previously that ECRG4 is present on the surface of polymorphonuclear leukocytes (PMNs) and, on ex Division of Trauma, Surgical Critical Care, and Burn, Department of Surgery, University of California San Diego Health Sciences, San Diego, California. Presented at the Thirty-second Annual Meeting of the Surgical Infection Society, Dallas, Texas, April 18–21, 2012. SURGICAL INFECTIONS Volume 16, Number 6, 2015 a Mary Ann Liebert, Inc. DOI: 10.1089/sur.2014. 209