Lisa Wohlgemuth

Background: Acute pancreatic injury can result from blunt or sharp force trauma, often leading to serious complications. While direct pancreatic trauma is associated with high rates of infection, organ failure, and mortality, little is known about the pancreas as a potential secondary target and remote trauma organ and thereby as a booster of systemic injury. Methods: We employed a murine model of multiple trauma and hemorrhagic shock in which the pancreas was deliberately spared from the direct trauma impact. Four hours post‐trauma, we determined systemic and local inflammatory responses, pancreatic tissue damage, pancreatic lipase (Pnlip in mice), and protease activity, and conducted proteomic profiling of the pancreas. For clinical translation, we performed a post hoc analysis of severely injured polytrauma patients, focusing on acute pancreatic involvement and its association with clinical parameters. Results: Severe trauma in mice induced rapid systemic inflammation and significantly elevated plasma levels of Pnlip. Notably, pancreatic edema formation was observed in a subset of polytraumatized mice, accompanied by increased activity of matrix metalloproteinases Mmp2 and Mmp9. Proteomic analysis revealed an enrichment of inflammatory and cellular stress pathways in pancreatic tissue. Similarly, in polytraumatized patients, plasma pancreatic lipase (PNLIP in humans) and trypsin concentrations were elevated during the early posttraumatic period and correlated with injury patterns, systemic inflammation, coagulopathy, endotheliopathy, organ failure, and time in hospitals and intensive care units. Conclusion: Our findings highlight the pancreas as a novel remote responder to severe tissue trauma, even in the absence of direct injury. This widely overlooked dimension of trauma pathophysiology has potential clinical implications. However, further research is essential (i) to unravel the mechanisms driving remote pancreatic enzyme release and (ii) to prove the causality between the pancreatic response and observed clinical parameters.

Macrophages, renowned for their plasticity, are central to both the immune response and tissue repair following physical trauma. This review delineates how tissue trauma dynamically modulates macrophage function across organs, highlighting their dichotomous roles in promoting inflammation versus regeneration. After injury, macrophages shift along a continuum from pro-inflammatory to pro-regenerative states, influenced by local and systemic cues, injury type, and microenvironmental factors, including damage-associated molecular patterns, and cytokines leading to pronounced organ-specific differences. The temporal and spatial dynamics of macrophage recruitment – from resident pools or via monocyte influx – dictate not only healing outcomes but also the risk of organ dysfunction and chronic inflammation. Emerging immunomodulatory strategies, encompassing stem cell therapies, pharmacological phenotype modulation, and microbiome-targeted approaches, underscore the clinical potential of precise macrophage-targeted interventions. Understanding macrophage adaptability post-trauma is crucial for devising organ- and context-specific therapies to optimize tissue repair and minimize adverse outcomes.

Controlling excessive inflammation remains an unmet clinical need, for example, during sepsis or after severe injuries. Platelet‐activating factor (PAF) is central in thromboinflammatory processes. However, its role in the interaction of platelets and neutrophils requires further insights. Therefore, we elucidated PAF‐related neutrophil activation, including platelet–neutrophil complex (PNC) formation and investigated potential strategies to modulate PAF‐related inflammation. For the translation of the PAF‐mediated inflammation, we applied an animal‐free human ex vivo whole blood model. The neutrophil phenotype, its function, and PNC formation were studied by flow cytometry and platelet‐related activity was assessed by light microscopy and aggregometry. PAF induced a rapid and dose‐dependent change in neutrophil phenotype, as evidenced by CD10, CD11b, and CD66b upregulation and CD62L downregulation. Moreover, PAF increased the generation of reactive oxygen species (ROS), phagocytic activity and PNC formation. Interestingly, PNCs displayed significantly enhanced ROS formation and phagocytosis compared to neutrophils without attached platelets, whereas these differences were not observed regarding phenotype changes. Furthermore, the findings were confirmed in a clinically relevant ex vivo whole blood model of lipopolysaccharide‐ or PAF‐driven inflammation. In summary, the present study elucidates PAF‐driven effects on neutrophils and their interaction with platelets. The findings might help in developing therapeutic approaches to modulate PAF‐related thromboinflammation, for example, during sepsis.

The lack of diagnostic and monitoring tools for postsurgical immunological complications such as systemic inflammation can contribute to a poor outcome despite modern intensive care. The need for reliable immune monitoring has been emphasised. Polymorphonuclear leukocytes (PMNs) play an important role in postsurgical inflammation. A subgroup of PMNs is particularly interesting, because they are released shortly after (iatrogenic) trauma: immature PMNs, characterised by, for example, their low CD10 expression. Therefore, we investigated the role of CD10^low PMNs in a non‐interventional exploratory study by including patients undergoing scheduled, highly standardised cardiac surgery with extracorporeal circulation. We were able to demonstrate that the number of CD10^low PMNs released shortly after the beginning of surgery correlated with different fluid phase markers of inflammation and organ damage postsurgically. Among these parameters were CRP, IL‐6, NGAL, CK‐MB, and troponin‐T. Noteworthy, the amount of CD10^low PMNs increased as early as 24 h before these well‐established markers, suggesting superiority of CD10^low PMNs as an early diagnostic marker. Comparing CD10^low immature PMNs with CD10^high mature PMNs revealed potential involved mechanisms, including lower CD11b expression and a significant decrease in the formation of platelet–neutrophil complexes (PNCs) by CD10^low PMNs. In conclusion, we propose CD10^low PMNs as a potential early cellular biomarker to assess the postsurgical inflammatory response. In comparison to clinically established markers like CRP or IL‐6 and scoring systems such as the SOFA‐Score, CD10^low PMNs reflect a potential candidate for future immune monitoring to determine the risk of excessive inflammation and organ impairment more rapidly.

Complement activation in the diseases paroxysmal nocturnal hemoglobinuria (PNH) and atypical hemolytic uremic syndrome (aHUS) results in cytolysis and fatal thrombotic events, which are largely refractory to anticoagulation and/or antiplatelet therapy. Anticomplement therapy, however, efficiently prevents thrombotic events in PNH and aHUS, but the underlying mechanisms remain unresolved. We show that complement-mediated hemolysis in whole blood induces platelet activation similarly to activation by adenosine 5′-diphosphate (ADP). Blockage of C3 or C5 abolished platelet activation. We found that human platelets failed to respond functionally to the anaphylatoxins C3a and C5a. Instead, complement activation did lead to prothrombotic cell activation in the whole blood when membrane attack complex (MAC)-mediated cytolysis occurred. Consequently, we demonstrate that ADP receptor antagonists efficiently inhibited platelet activation, although full complement activation, which causes hemolysis, occurred. By using an established model of mismatched erythrocyte transfusions in rats, we crossvalidated these findings in vivo using the complement inhibitor OmCI and cobra venom factor. Consumptive complement activation in this animal model only led to a thrombotic phenotype when MAC-mediated cytolysis occurred. In conclusion, complement activation only induces substantial prothrombotic cell activation if terminal pathway activation culminates in MAC-mediated release of intracellular ADP. These results explain why anticomplement therapy efficiently prevents thromboembolisms without interfering negatively with hemostasis.

The cellular and fluid phase-innate immune responses of many diseases predominantly involve activated neutrophil granulocytes and complement factors. However, a comparative systematic analysis of the early impact of key soluble complement cleavage products, including anaphylatoxins, on neutrophil granulocyte function is lacking. Neutrophil activity was monitored by flow cytometry regarding cellular (electro-)physiology, cellular activity, and changes in the surface expression of activation markers. The study revealed no major effects induced by C3a or C4a on neutrophil functions. By contrast, exposure to C5a or C5a des-Arg stimulated neutrophil activity as reflected in changes in membrane potential, intracellular pH, glucose uptake, and cellular size. Similarly, C5a and C5a des-Arg but no other monitored complement cleavage product enhanced phagocytosis and reactive oxygen species generation. C5a and C5a des-Arg also altered the neutrophil surface expression of several complement receptors and neutrophil activation markers, including C5aR1, CD62L, CD10, and CD11b, among others. In addition, a detailed characterization of the C5a-induced effects was performed with a time resolution of seconds. The multiparametric response of neutrophils was further analyzed by a principal component analysis, revealing CD11b, CD10, and CD16 to be key surrogates of the C5a-induced effects. Overall, we provide a comprehensive insight into the very early interactions of neutrophil granulocytes with activated complement split products and the resulting neutrophil activity. The results provide a basis for a better and, importantly, time-resolved and multiparametric understanding of neutrophil-related (patho-)physiologies.

Neutrophils provide rapid and efficient defense mechanisms against invading pathogens. Upon stimulation with proinflammatory mediators, including complement factors and bacterial peptides, neutrophils respond with changes in their membrane potential, intracellular pH, and cellular size. This study provides an approach to quantify these important changes simultaneously using multiparametric flow cytometry, thereby revealing a typical sequence of neutrophil activation consisting of depolarization, alkalization, and increase in cellular size. Additionally, the time resolution of the flow cytometric measurement is improved in order to allow changes that occur within seconds to be monitored, and thus to enhance the kinetic analysis of the neutrophil response. The method is appropriate for the reliable semiquantitative detection of small variations with respect to an increase, no change, and decrease in those parameters as demonstrated by the screening of various proinflammatory mediators. As a translational outlook, the findings are put into context in inflammatory conditions in vitro as well as in a clinically relevant whole blood model of endotoxemia. Taken together, the multiparametric analysis of neutrophil responsiveness regarding depolarization, alkalization, and changes in cellular size may contribute to a better understanding of neutrophils in health and disease, thus potentially yielding innovative mechanistic insights and possible novel diagnostic and/or prognostic approaches.