Matthias Majetschak

Relation of a TNF Gene Polymorphism to Severe Sepsis in Trauma Patients

OBJECTIVE To investigate the relation of the biallelic Nco1 restriction fragment length polymorphism in the first intron of the tumor necrosis factor (TNF) beta gene with the development of severe sepsis in multiply injured patients. SUMMARY BACKGROUND DATA The biallelic Nco1 polymorphism of the TNFbeta gene has been described to be associated with autoimmune diseases and with the mortality rate in severe sepsis. Therefore, the Nco1 polymorphism may be associated with the clinical finding that despite comparable risk factors, posttraumatic sepsis develops in some patients but not others. METHODS The study group consisted of 110 patients with severe blunt trauma (Injury Severity Score > or = 17). Typing of each patient for the biallelic Nco1 polymorphism was performed by analyzing restriction fragments of an Nco1-digested DNA fragment obtained using polymerase chain reaction. Genotypes were then related to the occurrence of severe posttraumatic sepsis and TNFalpha serum concentrations. RESULTS Fifty-seven patients showed an uncomplicated posttraumatic recovery, and severe sepsis developed in 53 patients. The overall allele frequency (TNFB1 0.29, TNFB2 0.71) and genotype distribution (TNFB1 homozygous 7.3%, TNFB1/TNFB2 42.7%, TNFB2 homozygous 50%) were in agreement with the distribution in healthy volunteers. Genotype distribution in patients with an uncomplicated clinical course was significantly different from that in patients with severe posttraumatic sepsis. Development of severe posttraumatic sepsis was significantly increased in patients homozygous for the allele TNFB2. In patients with severe posttraumatic sepsis, TNFalpha serum concentrations were significantly higher in TNFB2-homozygous individuals compared with heterozygous and TNFB1 -homozygous individuals. The age- and injury-matched odds ratio for the homozygous TNFB2 genotype compared with the heterozygous genotype was 5.22 (p = 0.007, 95% confidence interval 1.6 to 17.9). CONCLUSIONS In multiply injured patients, the Nco1 polymorphism within the TNFbeta gene is associated with the development of severe posttraumatic sepsis and with increased TNFalpha serum levels when severe sepsis has occurred. This suggests a genetic determination of the individual inflammatory response after infection or tissue damage, which significantly influences susceptibility to severe nosocomial infections.

CXC Chemokine Receptor 4 Is a Cell Surface Receptor for Extracellular Ubiquitin

Ubiquitin is one of the most highly conserved proteins in eukaryotes and plays major biological roles as a post-translational protein modifier. Ubiquitin is also a natural constituent of plasma, and several lines of evidence suggest that extracellular ubiquitin is an immune modulator with anti-inflammatory properties. In addition, ubiquitin treatment has been shown to limit inflammation and reduce organ injury in various disease models and species in vivo. However, its mechanism of action is unknown. Here we show that extracellular ubiquitin is a natural CXC chemokine receptor 4 (CXCR4 and CD184) agonist. Extracellular ubiquitin promotes intracellular Ca2+ flux and reduces cAMP levels through a G protein-coupled receptor that signals via a Gαi/o protein in THP1 cells. Toll-like receptor 4 stimulation reduces ubiquitin-binding sites, which enabled identification of four Gαi/o PCRs as ubiquitin receptor candidates. Overexpression of candidate genes in HEK293 cells, gene silencing in THP1 cells, competition binding, and signaling studies with the CXCR4 agonist stromal cell-derived factor-1α (chemokine (CXC motif) ligand 12) and inhibitor AMD3100 identify CXCR4 as a functional ubiquitin receptor. Our finding uncovers a fundamentally new aspect of the role of ubiquitin in biology, has implications for the understanding of CXCR4-mediated events, and is expected to facilitate development of new therapeutic avenues for a variety of diseases.

Sex differences in posttraumatic cytokine release of endotoxin-stimulated whole blood: relationship to the development of severe sepsis.

BACKGROUND In experimental trauma-hemorrhage and sepsis, a sexual dimorphism of cell-mediated immune functions has been described, which has been related to higher susceptibility to and mortality from sepsis in males. Therefore, in the present study, sex differences with regard to cytokine release of endotoxin stimulated whole blood and its relation to the development of severe posttraumatic sepsis were investigated in blunt trauma patients with multiple injuries. METHODS Eighty-four patients (25 female; 59 male) sustaining blunt injuries with an Injury Severity Score > 16 were enrolled in the study. Whole blood and serum were obtained during a 14-day period of hospitalization. The capacity of peripheral blood mononuclear cells to produce cytokines (tumor necrosis factor-alpha, interleukin [IL]-6, IL-8) was tested by using a whole blood assay. Serum samples were assayed for anti-inflammatory cytokines (IL-4, IL-10, and transforming growth factor beta1) and sex hormones (testosterone, estradiol, progesterone). Patients were monitored daily for sepsis criteria according to the ACCP/ SCCM consensus conference 1992. RESULTS Within the entire patient population, sex differences in posttraumatic cytokine release were not detectable. Male trauma patients developing severe sepsis (n = 16) presented with a significantly increased cytokine producing capacity in the early posttraumatic period (< or = 24 hours after admission to the emergency room) when compared with males with an uncomplicated recovery. In females, differences between the subgroups of patients with (n = 7) and without development of severe sepsis were not detectable. There were no differences in systemic levels of anti-inflammatory cytokines within the early posttraumatic period between the subgroups of male and female patients with and without development of severe sepsis. In females, differences in sex hormone levels were not detectable, whereas in males, development of severe sepsis later was found to coincide with significantly decreased testosterone and increased estradiol serum levels. CONCLUSION The present study demonstrates a sex-specific regulation of leukocyte function in patients with multiple injuries within the early posttraumatic period. In male patients with multiple injuries, increased cytokine-producing capacities may correspond to enhanced inflammatory responses, which increase susceptibility to sepsis, whereas in female patients, other regulatory mechanisms may be involved.

The extent of traumatic damage determines a graded depression of the endotoxin responsiveness of peripheral blood mononuclear cells from patients with blunt injuries.

OBJECTIVE To study whether the endotoxin responsiveness of peripheral blood mononuclear cells correlates with the severity of injury in trauma patients. DESIGN Prospective, observational study. SETTING University trauma center. PATIENTS Fifty-nine patients with blunt trauma (Injury Severity Score [ISS] 4 to 57 points). INTERVENTIONS Standard emergency department care, surgical care, and postoperative intensive care unit treatment. MEASUREMENTS AND MAIN RESULTS Whole blood and serum were obtained 94+/-89 (SD) mins post trauma (day 0) and during a 14-day period postinjury. Endotoxin-induced tumor necrosis factor-alpha (TNF-alpha) synthesis of peripheral blood mononuclear cells ex vivo was tested using a whole blood assay. Serum samples were assayed for TNF-alpha concentrations. A reduced capacity of whole blood to produce TNF-alpha ex vivo with endotoxin treatment was found to be closely correlated with the ISS. The capacity to produce TNF-alpha on endotoxin stimulation of whole blood from patients with an ISS > or =16 points was depressed immediately after trauma and did not reach normal values during the observation period. In patients with an ISS >22 points, maximum depression of the capacity of whole blood to produce TNF-alpha occurs within 100 mins post injury. In contrast, in patients with an ISS <22 points, maximal depression of whole blood TNF-alpha production occurs with a delay of 24 to 48 hrs after trauma. Based on pre- and postoperative values, primary surgical intervention caused a decrease of the endotoxin-stimulated TNF-alpha production of whole blood in the latter patient subgroup, as well as in the entire patient population (ISS 4 to 57) when secondary surgical treatment was necessary 5 to 13 days after trauma. CONCLUSIONS The extent of traumatic tissue damage leads to a graded depression of immunocyte function and appears to be amplified by surgical treatment. The endotoxin responsiveness of peripheral blood mononuclear cells displays a functional marker of the anatomically defined severity of injury and gives insights into the regulation of immunocyte function after severe blunt trauma.

Immuno-inflammatory tissue reaction to stainless-steel and titanium plates used for internal fixation of long bones.

The immuno-inflammatory responses to stainless-steel (21 implants in 20 patients) and titanium plates (22 implants in 20 patients) used in the treatment of long bone fractures were studied immunohistochemically. All fractures healed without complications. In the soft tissue adjacent to the surface of the implants a dark discolouration of the tissue was visible in 18/21 stainless-steel and 20/22 titanium plates. Tissue specimens of all patients contained positive staining for macrophages (CD68-positive cells). Serial sections showed that the majority of cells were found to express the HLA-DR molecule indicating their activation. Many of the macrophages were surrounded by clusters of T-lymphocytes (CD3-positive cells). 17 out of 21 steel specimens and 15 out of 22 titanium specimens showed the infiltration of moderate amounts of cytotoxic T-lymphocytes (CD8-positive cells). Moderate amounts of B-lymphocytes (CD79alpha positive cells) were evident in four patients with steel and six patients with titanium implants. The results of the present study clearly demonstrate the presence of a marked inflammation and tissue reaction in the soft tissue covering stainless-steel and titanium plates used for internal fixation of fractures of long bones independently from the material used.

Tumor Necrosis Factor Gene Polymorphisms, Leukocyte Function, and Sepsis Susceptibility in Blunt Trauma Patients

ABSTRACT The tumor necrosis factor alpha (TNF-α) −308 G/A and TNF-β NcO1 polymorphisms have been described to be associated with an increased risk for sepsis in critically ill patients. Functional consequences associated with these polymorphisms remain unclear. We compared the genotype distribution of these TNF polymorphisms with susceptibility to severe sepsis and leukocyte function in blunt trauma patients (n = 70; mean injury severity score, 24 points [range, 4 to 57). Severe sepsis was defined according to the American College of Chest Physicians-Society of Critical Care Medicine consensus conference criteria. Genotyping for the NcO1 polymorphism (alleles TNFB1 and TNFB2) was performed by PCR and digestion of the products with NcO1, and that for the TNF-α −308 G/A polymorphism (alleles TNF1 and TNF2) was performed by real-time PCR. Leukocyte function was assessed by measurement of the production of endotoxin-induced cytokines (TNF-α, interleukin-6 [IL-6], and IL-8) in whole blood. TNF-α, IL-6, and IL-8 were determined by enzyme-linked immunosorbent assay. For the genotypes of the TNF-α −308 G/A polymorphism, differences in the frequency of development of severe sepsis were not detectable. Patients developing severe sepsis after trauma were significantly more likely to posses a homozygous genotype of the TNF-β NcO1 polymorphism. Compared with heterozygotes, the odds ratio for the TNFB2/B2 genotype for the development of severe posttraumatic sepsis was 11 (P = 0.01), and that for the TNFB1/B1 genotype was 13 (P = 0.014). TNF-α −308:TNF-β NcO1 haplotype analysis showed that the TNFB2:TNF2 haplotype is significantly negatively associated with development of severe sepsis. Patients homozygous for the TNFB1 or TNFB2 allele showed a persistently higher cytokine-producing capacity during at least 4 to 8 days after trauma than the heterozygotes. In patients homozygous for the TNF1 allele, a higher TNF-α- and IL-8-producing capacity was found only at day 1 after trauma. Although the TNF-β NcO1 polymorphism appears to be less likely to be causative for development of severe sepsis after trauma, it is thus far the only genetic marker identified which can be used as a relevant risk estimate for severe sepsis in trauma patients immediately after the injury.

Extracellular ubiquitin: immune modulator and endogenous opponent of damage-associated molecular pattern molecules

Ubiquitin is a post‐translational protein modifier and plays essential roles in all aspects of biology. Although the discovery of ubiquitin introduced this highly conserved protein as a molecule with extracellular actions, the identification of ubiquitin as the ATP‐dependent proteolysis factor 1 has focused subsequent research on its important intracellular functions. Little attention has since been paid to its role outside of the cell. During recent years, multiple observations suggest that extracellular ubiquitin can modulate immune responses and that exogenous ubiquitin has therapeutic potential to attenuate exuberant inflammation and organ injury. These observations have not been integrated into a comprehensive assessment of its possible role as an endogenous immune modulator. This review recapitulates the current knowledge about extracellular ubiquitin and discusses an emerging facet of its role in biology during infectious and noninfectious inflammation. The synopsis of these data along with the recent identification of ubiquitin as a CXCR4 agonist suggest that extracellular ubiquitin may have pleiotropic roles in the immune system and functions as an endogenous opponent of DAMPs. Functions of extracellular ubiquitin could constitute an evolutionary conserved control mechanism aimed to balance the immune response and prevent exuberant inflammation. Further characterization of its mechanism of action and cellular signaling pathways is expected to provide novel insights into the regulation of the innate immune response and opportunities for therapeutic interventions.

The CXC Chemokine Receptor 4 Ligands Ubiquitin and Stromal Cell-derived Factor-1α Function through Distinct Receptor Interactions

Recently, we identified extracellular ubiquitin as an endogenous CXC chemokine receptor (CXCR) 4 agonist. However, the receptor selectivity and molecular basis of the CXCR4 agonist activity of ubiquitin are unknown, and functional consequences of CXCR4 activation with ubiquitin are poorly defined. Here, we provide evidence that ubiquitin and the cognate CXCR4 ligand stromal cell-derived factor (SDF)-1α do not share CXCR7 as a receptor. We further demonstrate that ubiquitin does not utilize the typical two-site binding mechanism of chemokine-receptor interactions, in which the receptor N terminus is important for ligand binding. CXCR4 activation with ubiquitin and SDF-1α lead to similar Gαi-responses and to a comparable magnitude of phosphorylation of ERK-1/2, p90 ribosomal S6 kinase-l and Akt, although phosphorylations occur more transiently after activation with ubiquitin. Despite the similarity of signal transduction events after activation of CXCR4 with both ligands, ubiquitin possesses weaker chemotactic activity than SDF-lα in cell migration assays and does not interfere with productive entry of HIV-1 into P4.R5 multinuclear activation of galactosidase indicator cells. Unlike SDF-1α, ubiquitin lacks interactions with an N-terminal CXCR4 peptide in NMR spectroscopy experiments. Binding and signaling studies in the presence of antibodies against the N terminus and extracellular loops 2/3 of CXCR4 confirm that the ubiquitin CXCR4 interaction is independent of the N-terminal receptor domain, whereas blockade of extracellular loops 2/3 prevents receptor binding and activation. Our findings define ubiquitin as a CXCR4 agonist, which does not interfere with productive cellular entry of HIV-1, and provide new mechanistic insights into interactions between CXCR4 and its natural ligands.

Efficiency of chest computed tomography in critically ill patients with multiple traumas

Objective: The efficiency of secondary thoracic computed tomography (TCT) in critically ill patients with multiple traumas was assessed by comparison of TCT with chest radiograph findings. The subsequent therapeutic consequences based on the additional information of TCT were evaluated. Setting: A six‐bed trauma intensive care unit in a university hospital. Design: Prospective, descriptive study. Patients and Interventions: One hundred one computed tomographic (CT) examinations (mean, 2.6 per patient; range, 1‐10) were performed in 39 patients, fulfilling the following indications for TCT: a) sepsis with suspected pulmonary focus (n = 41); b) deterioration of pulmonary gas exchange (n = 35); c) guiding the duration of intermittent prone positioning (n = 25). The information provided by TCT was compared with corresponding chest radiographs (CXR). Therapeutic consequences drawn after TCT were compared with the additional diagnostic information of TCT. The change of therapy was documented that would not have been undertaken or may have been delayed had TCT evaluation not been used. Results: TCT was significantly superior to CXR in detecting pneumothoraces, pleural effusions, and pulmonary abscesses. Furthermore, a significantly higher accuracy regarding pulmonary densities was found. Subsequent therapeutic interventions ensued from 85 (84.2%) CT scans. After TCT, intermittent prone positioning was initiated in 31 patients, chest tubes were inserted in 16 patients, and intermittent prone positioning was terminated in 13 patients and was continued in 12 patients. Eleven thoracotomies were performed because of the TCT findings. The described therapeutic interventions were based on abnormalities seen on CT scans but were not evident in CXR in 58 patients (57.4%). Significant information that influenced therapeutic concepts was obtained in 66% (n = 23) of patients with pulmonary deterioration of gas exchange, in 61% (n = 25) of patients with sepsis, and in 40% (n = 10) of patients to guide the duration of intermittent prone positioning. Thoracotomy and specific drainage by tube thoracostomy was always dependent on the findings of TCT. Conclusion: Performed under the above displayed defined indications, TCT had an overall efficiency of 57%. It provided an increased sensitivity for intrathoracic lesions and a more comprehensive diagnosis of chest abnormalities.

Whole blood tumor necrosis factor-alpha production and its relation to systemic concentrations of interleukin 4, interleukin 10, and transforming growth factor-beta1 in multiply injured blunt trauma victims.

Objective To study the relation of whole blood endotoxin responsiveness to inhibitory mediators systemically released after severe blunt trauma. Design Prospective, observational study. Setting University trauma center. Patients Thirty-two patients with blunt trauma (mean injury severity score, 33 points). Interventions Standard emergency department, surgical care, and postoperative intensive care unit treatment. Measurements and Main Results Whole blood and serum were obtained immediately after admission to the emergency department (<8 hrs after trauma, denoted day 0) and on days 1, 2, 4, 6, 8, and 14 after trauma. Whole blood specimens were assayed for endotoxin-induced tumor necrosis factor (TNF)-&agr; synthesis ex vivo and serum specimen were assayed for interleukin (IL)-4, IL-10, and transforming growth factor (TGF)-&bgr;1 concentrations. Moreover, the TNF-&agr; inhibitory capacity of recombinant human (rh) IL-4, rhIL-10, and TGF-&bgr;1 as well as the inhibitory capacity of patients’ serum from days 0, 1, 2, 4, 6, 8, and 14 were tested on uninjured donors’ whole blood. Cytokines were determined by ELISA. Whole blood endotoxin responsiveness in multiply injured patients was significantly reduced during the observation period and was found to be significantly related to the total inhibitory activity detected in the corresponding sera. Exchange of patients’ serum for uninjured donors’ or recovered patients’ serum restored TNF-&agr; production of peripheral blood mononuclear cells from multiply injured patients. Serum levels of IL-4 and IL-10 were not related to trauma patients’ whole blood TNF-&agr; production upon endotoxin stimulation, whereas TGF-&bgr;1 concentrations were positively related. Compared with the apparent half-maximal inhibition concentrations determined, serum levels of TGF-&bgr;1, IL-10, and IL-4 were 20- to 20,000-fold below the quantities required to explain the inhibitory serum activity in multiply injured patients on day 0. Conclusions Whole blood hyporesponsiveness to endotoxin in multiply injured patients is caused by soluble serum factors systemically released after trauma, whereas the intrinsic leukocyte function appears unaffected. Inhibitory mediators other than IL-4, IL-10, or TGF-&bgr;1 are supposed to be of major biological relevance for the posttraumatic regulation of leukocyte function. Characterization of the causative suppressive mediators is supposed as a prerequisite for the development of immunologically based therapeutic approaches in critically ill patients.