Adipose tissue: a neglected organ in the response to severe trauma?

Despite the manifold recent efforts to improve patient outcomes, trauma still is a clinical and socioeconomical issue of major relevance especially in younger people. The systemic immune reaction after severe injury is characterized by a strong pro- and anti-inflammatory response. Besides its functions as energy storage depot and organ-protective cushion, adipose tissue regulates vital processes via its secretion products. However, there is little awareness of the important role of adipose tissue in regulating the posttraumatic inflammatory response. In this review, we delineate the local and systemic role of adipose tissue in trauma and outline different aspects of adipose tissue as an immunologically active modifier of inflammation and as an immune target of injured remote organs after severe trauma

Challenge to the Intestinal Mucosa During Sepsis

Sepsis is a complex of life-threating organ dysfunction in critically ill patients, with a primary infectious cause or through secondary infection of damaged tissues. The systemic consequences of sepsis have been intensively examined and evidences of local alterations and repercussions in the intestinal mucosal compartment is gradually defining gut-associated changes during sepsis. In the present review, we focus on sepsis-induced dysfunction of the intestinal barrier, consisting of an increased permeability of the epithelial lining, which may facilitate bacterial translocation. We discuss disturbances in intestinal vascular tonus and perfusion and coagulopathies with respect to their proposed underlying molecular mechanisms. The consequences of enzymatic responses by pancreatic proteases, intestinal alkaline phosphatases, and several matrix metalloproteases are also described. We conclude our insight with a discussion on novel therapeutic interventions derived from crucial aspects of the gut mucosal dynamics during sepsis

Evaluation of the gut microbiome in association with biological signatures of inflammation in murine polytrauma and shock

Severe injuries are frequently accompanied by hemorrhagic shock and harbor an increased risk for complications. Local or systemic inflammation after trauma/hemorrhage may lead to a leaky intestinal epithelial barrier and subsequent translocation of gut microbiota, potentially worsening outcomes. To evaluate the extent with which trauma affects the gut microbiota composition, we performed a post hoc analysis of a murine model of polytrauma and hemorrhage. Four hours after injury, organs and plasma samples were collected, and the diversity and composition of the cecal microbiome were evaluated using 16S rRNA gene sequencing. Although cecal microbial alpha diversity and microbial community composition were not found to be different between experimental groups, norepinephrine support in shock animals resulted in increased alpha diversity, as indicated by higher numbers of distinct microbial features. We observed that the concentrations of proinflammatory mediators in plasma and intestinal tissue were associated with measures of microbial alpha and beta diversity and the presence of specific microbial drivers of inflammation, suggesting that the composition of the gut microbiome at the time of trauma, or shortly after trauma exposure, may play an important role in determining physiological outcomes. In conclusion, we found associations between measures of gut microbial alpha and beta diversity and the severity of systemic and local gut inflammation. Furthermore, our data suggest that four hours following injury is too early for development of global changes in the alpha diversity or community composition of the intestinal microbiome. Future investigations with increased temporal-spatial resolution are needed in order to fully elucidate the effects of trauma and shock on the gut microbiome, biological signatures of inflammation, and proximal and distal outcomes. &nbsp;</p

Effects of anesthesia with sevoflurane on outcome parameters in murine experimental studies

Purpose Multiple murine studies modelling the immuno-pathophysiological consequences of trauma, shock, burn or sepsis were performed during the last decades. Almost every animal model requires anesthesia for practical and ethical reasons. Furthermore, often, corresponding control groups involve untreated animals without or with a limited exposure to anesthetics. However, the influences of anesthetic drugs on immuno-pathophysiological reactions remain insufficiently investigated. Therefore, we aimed to closer characterize the anesthetic impact exemplified by sevoflurane on the organ performance in mice and thereby investigate the influence of anesthesia itself on major outcome parameters in animal studies. Methods C57/BL6 mice were subjected either to 270 min of sevoflurane narcosis or directly euthanized. Plasma, BAL-fluids, lungs, kidneys, liver and intestine were collected and examined for immunological, functional and morphological changes. Results Systemic levels of the cytokine keratinocyte chemoattractant (KC) were raised in the narcosis group, while concentrations of high mobility group box protein 1 (HMGB-1) as a major inflammatory marker were reduced. In the lungs, levels of HMGB-1 and interleukin 6 (IL-6) were reduced. In contrast, systemic concentrations of intestinal fatty acid binding-protein (i-FABP) as an intestinal damage marker were elevated. Furthermore, liver-type fatty acid binding-protein (L-FABP) levels were lower in the narcosis animals, and inflammatory markers were reduced in liver tissues. Anesthesia also ameliorated the inflammatory reaction in renal tissues, while plasma levels of urea and creatinine were elevated, reflecting either dehydration and/or impaired renal function. Conclusion As anesthesia with sevoflurane exhibited distinct effects in different organs, it is difficult to predict its specific impact on targets of interest in in vivo studies. Therefore, further studies are required to clarify the effects of different anesthetic drugs. Overall, the inclusion of a control group subjected to the same anesthesia protocol as the experimental groups of interest seems helpful to precisely define the inherent impact of the anesthetic when investigating immuno-pathophysiologic conditions in vivo

Circulating growth/differentiation factor 15 is associated with human CD56 natural killer cell dysfunction and nosocomial infection in severe systemic inflammation

BACKGROUND Systemic inflammation induced by sterile or infectious insults is associated with an enhanced susceptibility to life-threatening opportunistic, mostly bacterial, infections due to unknown pathogenesis. Natural killer (NK) cells contribute to the defence against bacterial infections through the release of Interferon (IFN) γ in response to Interleukin (IL) 12. Considering the relevance of NK cells in the immune defence we investigated whether the function of NK cells is disturbed in patients suffering from serious systemic inflammation. METHODS NK cells from severely injured patients were analysed from the first day after the initial inflammatory insult until the day of discharge in terms of IL-12 receptor signalling and IFN-γ synthesis. FINDINGS During systemic inflammation, the expression of the IL-12 receptor β2 chain, phosphorylation of signal transducer and activation 4, and IFN-γ production on/in NK cells was impaired upon exposure to Staphylococcus aureus. The profound suppression of NK cells developed within 24 h after the initial insult and persisted for several weeks. NK cells displayed signs of exhaustion. Extrinsic changes were mediated by the early and long-lasting presence of growth/differentiation factor (GDF) 15 in the circulation that signalled through the transforming growth factor β receptor I and activated Smad1/5. Moreover, the concentration of GDF-15 in the serum inversely correlated with the IL-12 receptor β2 expression on NK cells and was enhanced in patients who later acquired septic complications. INTERPRETATION GDF-15 is associated with the development of NK cell dysfunction during systemic inflammation and might represent a novel target to prevent nosocomial infections. FUND: The study was supported by the Department of Orthopaedics and Trauma Surgery, University Hospital Essen

Early changes in immune, coagulation, and organ function after clinical and experimental polytrauma

Despite the considerable progress made in public safety measures, emergency and intensive care in the last decades, trauma remains a major medical issue and is responsible for a large number of deaths worldwide particularly in young people. In regard to the posttraumatic immune response, development of disturbances in coagulation, and detection and monitoring of end organ damage, several issues remain unresolved. Therefore, this thesis focused on the alterations in peripheral blood leukocytes as “first line of defense” after severe injury employing static and functional analyses. Furthermore, disturbances in coagulation were observed over a 10-day time course after trauma. In a larger patient cohort, the impact of an additional hemorrhagic shock on inflammation, organ damage, and breakdown of the endothelial glycocalyx was assessed. These findings were re-translationally evaluated in a murine model of isolated and combined trauma and hemorrhage. In patients after severe trauma, peripheral leukocytes rapidly changed their surface expression profile of several receptors for complement activation products as well as damage- and pathogen-associated molecular patterns, involved in regulating the immune response, but also modulators of coagulation. In a pilot study, a highly standardized ex vivo testing system revealed defects in production of early pro-inflammatory cytokines such as tumor-necrosis factor and interleukin-1b upon incubation with microbial endotoxin in monocytes, but not in the lymphocyte function after severe injury. A shortened standardized exposure time (4 h) resulted in a similar immune response compared to the established incubation protocol. After further validation and optimization, this method might offer a useful tool to monitor the immune system’s remaining capacity to react to inflammatory or pathogenic stimuli. In a similar approach, functional monitoring of coagulation over the time course after injury detected striking defects in coagulation immediately after trauma which partly lasted until 10 days later, but no hyperfibrinolysis was found. In a larger patient cohort, hemorrhagic shock was demonstrated to significantly contribute to posttraumatic inflammation and organ damage. Despite comparable injury severity, patients after blood loss had increased serum concentrations of specific damage markers of the lung (Clara cell secretory protein), liver (liver-type fatty acid-binding protein), kidneys (neutrophil gelatinase-associated lipocalin) and the intestine (intestinal fatty acid-binding protein) in distinct spatial and temporal patterns. Furthermore, presumably by increased generation of matrix metalloproteinases-9 and -13, there was an elevation of circulating components of the glycocalyx such as syndecan-1 and heparan sulfate, suggesting endothelial damage and increased permeability. Interestingly, increased concentrations of elements of the intestinal mucus (mucin-2) were detected after trauma/hemorrhage, implying a deterioration in intestinal barrier function. In vitro experiments revealed that the detected amounts of glycocalyx as well as intestinal mucus components were able to interfere with coagulation, indicating that the posttraumatic barrier breakdown might also impair clotting and increase the risk of bleeding. These findings were mostly confirmed in a murine model of PT and hemorrhage, where shock alone already demonstrated marked impact on barrier dysfunction and glycocalyx breakdown. The data is indicative of an early development of barrier and organ damage, presumably hours to days before manifestation of barrier breakdown and organ dysfunction. Monitoring the posttraumatic course using novel organ damage markers in addition to traditional functional scores may aid to detect subpar tendencies before onset of (multiple) organ dysfunction. In conclusion, severe trauma leads to significant alterations in leukocyte and immune function, coagulation, and considerable barrier and organ dysfunction which is worsened in the presence of a hemorrhagic shock. Reliable monitoring of the clinical course using valid functional markers and assays as well as rapid implementation into clinical routine and advanced treatment strategies may be decisive for improved outcome

Neurochemical Monitoring of Traumatic Brain Injury by the Combined Analysis of Plasma Beta-Synuclein, NfL, and GFAP in Polytraumatized Patients

Traumatic brain injury (TBI) represents a major determining factor of outcome in severely injured patients. However, reliable brain-damage-monitoring markers are still missing. We therefore assessed brain-specific beta-synuclein as a novel blood biomarker of synaptic damage and measured the benchmarks neurofilament light chain (NfL), as a neuroaxonal injury marker, and glial fibrillary acidic protein (GFAP), as an astroglial injury marker, in patients after polytrauma with and without TBI. Compared to healthy volunteers, plasma NfL, beta-synuclein, and GFAP were significantly increased after polytrauma. The markers demonstrated highly distinct time courses, with beta-synuclein and GFAP peaking early and NfL concentrations gradually elevating during the 10-day observation period. Correlation analyses revealed a distinct influence of the extent of extracranial hemorrhage and the severity of head injury on biomarker concentrations. A combined analysis of beta-synuclein and GFAP effectively discriminated between polytrauma patients with and without TBI, despite the comparable severity of injury. Furthermore, we found a good predictive performance for fatal outcome by employing the initial plasma concentrations of NfL, beta-synuclein, and GFAP. Our findings suggest a high diagnostic value of neuronal injury markers reflecting distinct aspects of neuronal injury for the diagnosis of TBI in the complex setting of polytrauma, especially in clinical surroundings with limited imaging opportunities

Hemorrhagic shock drives glycocalyx, barrier and organ dysfunction early after polytrauma

Polytrauma (PT) is frequently associated with hemorrhagic shock (HS), which increases morbidity and mortality. Although various aspects of HS have been addressed in PT patients, the impact of an additional HS is largely unknown regarding the development of multiple organ dysfunction associated with disturbed glycocalyx and barrier function early after trauma. A prospective, longitudinal, mono-centered, observational study enrolling severely injured patients (Injury Severity Score, ISS=38.1±2.6) served for an in-depth analysis of blood (drawn on days 0, 1, 2, 3 and 5) and clinical data (up to 21days) of 30 patients who were then stratified into PT with and without HS. HS significantly enhanced signs of acute organ injury, assessed by increased serum concentrations of novel damage markers. Moreover, indicators of glycocalyx and tight-junction dysfunction were found in PT patients all of which were significantly enhanced in co-presence of HS. These markers revealed multiple significant correlations with specific barrier, fluid-balance, coagulation, inflammation, and clinical-outcome parameters. Strikingly, mucosa fragments, which affected clotting, could be detected in serum after PT/HS. The results point to HS as a main driver for glycocalyx and barrier breakdown and suggest novel tools for the monitoring of organ dysfunction in the early course after PT

Hemorrhagic Shock Induces a Rapid Transcriptomic Shift of the Immune Balance in Leukocytes after Experimental Multiple Injury

The immune response following trauma represents a major driving force of organ dysfunction and poor outcome. Therefore, we investigated the influence of an additional hemorrhagic shock (HS) on the early posttraumatic immune dysbalance in the whole population of blood leukocytes. A well-established murine polytrauma (PT) model with or without an additional pressure-controlled HS (mean arterial pressure of 30 mmHg (±5 mmHg) for 60 mins, afterwards fluid resuscitation with balanced electrolyte solution four times the volume of blood drawn) was used. C57BL/6 mice were randomized into a control, PT, and PT + HS group with three animals in each group. Four hours after trauma, corresponding to three hours after induction of hemorrhage, RNA was isolated from all peripheral blood leukocytes, and a microarray analysis was performed. Enrichment analysis was conducted on selected genes strongly modulated by the HS. After additional HS in PT mice, the gene expression of pathways related to the innate immunity, such as IL-6 production, neutrophil chemotaxis, cell adhesion, and toll-like receptor signaling was upregulated, whereas pathways of the adaptive immune system, such as B- and T-cell activation as well as the MHC class II protein complex, were downregulated. These results demonstrate that an additional HS plays an important role in the immune dysregulation early after PT by shifting the balance to increased innate and reduced adaptive immune responses

Functional immune monitoring in severely injured patients—A pilot study

After severe trauma, the resulting excessive inflammatory response is countered by compensatory anti‐inflammatory mechanisms. The systemic inflammatory response to trauma enhanced by inappropriately timed surgical second hits may be detrimental for the patient. On the other hand, overwhelming anti‐inflammatory mechanisms may put patients at increased risk from secondary local and systemic infections. The ensuing sepsis and organ dysfunction due to immune dysregulation remain the leading causes of death after injury. To date, there are no clinically applicable techniques to monitor the pro‐/anti‐inflammatory immune status of the patients and the remaining ability to react to microbial stimuli. Therefore, in the present study, we used a highly standardized and easy‐to‐use system to draw peripheral whole blood from polytraumatized patients (ISS ≥ 32, n = 7) and to challenge it with bacterial lipopolysaccharide. Secreted cytokines were compared with those in samples from healthy volunteers. We observed a significant decrease in the release of monocyte‐derived mediators. Surprisingly, we detected stable or even increased concentrations of cytokines related to T cell maturation and function. For clinical practicability, we reduced the incubation time before supernatants were collected. Even after an abbreviated stimulation period, a stable release of almost all analysed parameters in patient blood could be detected. In conclusion, the data are indicative of a clinically well‐applicable approach to monitor the immune status in severely injured patients in a short time. This may be used to optimize the timing of necessary surgical interventions to avoid a boost of proinflammation and reduce risk of secondary infections