The Involvement of Danger-Associated Molecular Patterns in the Development of Immunoparalysis in Cardiac Arrest Patients

Glucocorticoid signaling mediates lymphopoiesis impairment after cardiac arrest in mice

Cardiac arrest (CA) is a life-threatening condition that requires immediate medical attention. Considerable advances in resuscitation have led to an increasing number of patients who survive the initial arrest event. However, among this growing patient population, morbidity and mortality rates remain strikingly high. This has been attributed to post-CA syndrome of which an imbalanced immune response is a crucial component. Using a murine CA model, we have shown that a profound immunosuppressive phase, characterized by severe lymphopenia, ensues following the initial pro-inflammatory response after CA. In the current study, we found that T and B lymphopoiesis was greatly impaired, as evidenced by the rapid and marked depletion of double-positive T cells and pre-B cells in the thymus and bone marrow, respectively. Our data then demonstrated that pharmacologic suppression of glucocorticoid signaling after CA significantly attenuated lymphopoiesis impairment, thereby mitigating post-CA lymphopenia. Lastly, we showed that specific deletion of the glucocorticoid receptor in T or B cells largely prevented the CA-induced depletion of immature lymphocyte populations in the thymus or bone marrow, respectively. Together, our findings indicate that glucocorticoid signaling mediates post-CA impairment of lymphopoiesis, a key contributor to post-CA immunosuppression.

Monocyte programmed death-ligand 1 upregulation in early post-out-of-hospital cardiac arrest is associated with increased risk of acute respiratory distress syndrome

Background

Out-of-hospital cardiac arrest (OHCA) is a major public health problem. Acute respiratory distress syndrome (ARDS) is a common condition in OHCA patients. We investigated the relationship between the expression of programmed death-1 (PD-1) related molecules and the development and prognosis of ARDS.

Methods

Between January 2021 and December 2023, post-resuscitated patients were screened for eligibility in the study. PD-1 related molecules expression was measured by flow cytometry at 48 h of admission in patients with OHCA. The prognostic variables were the development of ARDS during hospitalization and the 28-day patient mortality rate. We analyzed the relationship between the expression of PD-1-related molecules and the development of secondary ARDS in OHCA patients, and assessed the correlation of this expression with the prognosis of ARDS patients.

Results

In total, 107 consecutive OHCA patients were enrolled in this study. The median age of the enrolled patients was 60 years, with an age range of 53 to 67 years, and 71 % were male. Among the cardiac arrest patients, 44.8 % had a cardiac etiology, 30.8 % were witnessed, 17.8 % received bystander CPR, and 66.4 % had an initial rhythm of asystole. Our results showed that only monocyte ligand programmed death ligand-1 (PD-L1) expression was significantly elevated in the ARDS group of OHCA patients (P < 0.001). Among patients with ARDS, the expression of PD-L1 on monocytes in non-survivors was significantly higher than in survivors (P < 0.05). The Receiver operating characteristic curves analysis demonstrates that monocyte PD-L1 expression has predictive potential for the development and prognosis of ARDS. Multivariate logistic regression analysis showed that monocyte PD-L1 expression was an independent predictor of mortality in OHCA patients with ARDS.

Conclusions

This study indicates that patients with increased PD-L1 on monocytes after OHCA may be more likely to develop ARDS. The expression of PD-L1 on monocytes was an independent predictive factor for the incidence of ARDS and mortality rate in OHCA patients.

Elevated Plasma Soluble PD-L1 Levels in Out-of-Hospital Cardiac Arrest Patients

Background: A deregulated immune system has been implicated in the pathogenesis of post-cardiac arrest syndrome (PCAS). A soluble form of programmed cell death-1 (PD-1) ligand (sPD-L1) has been found at increased levels in cancer and sustained inflammation, thereby deregulating immune functions. Here, we aim to study the possible involvement of sPD-L1 in PCAS. Methods: Thirty out-of-hospital cardiac arrest (OHCA) patients consecutively admitted to the ER of Mie University Hospital were prospectively enrolled. Plasma concentrations of sPD-L1 were measured by an enzyme-linked immunosorbent assay in blood samples of all 30 OHCA patients obtained during cardiopulmonary resuscitation (CPR). In 13 patients who achieved return-of-spontaneous-circulation (ROSC), sPD-L1 levels were also measured daily in the ICU. Results: The plasma concentrations of sPD-L1 in OHCA were significantly increased; in fact, to levels as high as those observed in sepsis. sPD-L1 levels during CPR correlated with reduced peripheral lymphocyte counts and increased C-reactive protein levels. Of 13 ROSC patients, 7 cases survived in the ICU for more than 4 days. A longitudinal analysis of sPD-L1 levels in the 7 ROSC cases revealed that sPD-L1 levels occurred in parallel with organ failure. Conclusions: This study suggests that ischemia- reperfusion during CPR may aberrantly activate immune and endothelial cells to release sPD-L1 into circulation, which may play a role in the pathogenesis of immune exhaustion and organ failures associated with PCAS.

Endocytosis of peroxiredoxin 1 links sterile inflammation to immunoparalysis in pediatric patients following cardiopulmonary bypass

After cardiopulmonary bypass (CPB), the occurrence of systemic inflammatory response is often accompanied by a persistent compensatory anti-inflammatory response syndrome that can lead to a compromised immune competence termed immunoparalysis, rendering the patients susceptible to infections which is a leading complication following cardiac surgery. However, the underlying mechanisms of CPB-elicited immunoparalysis remain obscure. In this study we showed that peroxiredoxin 1 (Prdx1), a putative cytosolic antioxidant, was released immediately after CPB in a cohort of pediatric patients receiving congenital cardiac surgery. This increased Prdx1 was correlated to a reduced human leukocyte antigen-DR expression and an elevated interleukin-10 (IL-10) production, as well as a hypo-responsiveness of macrophages to endotoxin and a higher incidence of nosocomial infection. We demonstrated that substitution of Ser⁸³ for Cys⁸³ prevented Prdx1 from oligomerization and subsequent binding and internalization to macrophages. These effects mitigated Prdx1-induced IL-10 induction and endotoxin tolerance. Furthermore, after engagement with toll-like receptor (TLR) 4, clathrin-dependent endocytosis is crucial for Prdx1 to elicit IL-10 production in phagocytes. Congruently, inhibition of Prdx1/TLR4 endocytosis in phagocytes reversed the Prdx1/IL-10-mediated hypo-responsiveness to endotoxin. Our findings unveiled the possible mechanisms by which Prdx1 undertakes to cause immunoparalysis, and targeting endocytosis of Prdx1 could be a novel therapeutic approach for postoperative infections associated with CPB.

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Cardiopulmonary bypass-elicited ischemia/reperfusion injury causes release of Prdx1.

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High molecular weight forms of Prdx1 interact with TLR4 to initiate sterile inflammation.

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Endocytosis of Prdx1/TLR4 induces IL-10 production that leads to immunoparalysis and subsequent septic inflammation.

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Inhibition of Prdx1/TLR4 endocytosis reverses Prdx1/IL-10-mediated hypo-responsiveness to endotoxin in phagocytes.

Monocyte subset distribution and surface expression of HLA-DR and CD14 in patients after cardiopulmonary resuscitation

Systemic inflammation is a major feature of the post-cardiac arrest syndrome. The three monocyte subpopulations are thought to play an important role in this inflammatory state because they are endowed with numerous pattern recognition receptors, such as CD14, that have been associated with ischemia-reperfusion injury. By contrast, an exaggerated antiinflammatory response has also been described following cardiac arrest, which may be mediated by downregulation of antigen presentation receptor HLA-DR. We report the composition of monocyte subpopulations and the expression of CD14 and HLA-DR following cardiac arrest. Blood specimens were collected from 32 patients at three timepoints in the first 48 h after cardiac arrest. Monocyte subset composition was determined by flow cytometry based on the expression of CD14, CD16, and HLA-DR. Monocyte subset composition and the expression of CD14 and HLA-DR were correlated with patient outcomes. The results were compared to 19 patients with coronary artery disease. Cardiac arrest patients showed a significant decline in the percentage of nonclassical monocytes. Monocyte CD14 expression was upregulated after 24 h and correlated with the time to return of spontaneous circulation. Downregulation of HLA-DR expression was observed mainly among classical monocytes and significantly correlated with the dose of norepinephrine used to treat shock. Downregulation of HLA-DR among nonclassical and intermediate monocytes was significantly associated with disease severity. Our data demonstrate the disturbance of monocyte subset composition with a significant decline in nonclassical monocytes at an early stage following cardiac arrest. Our findings suggest the simultaneous presence of hyperinflammation, as evidenced by upregulation of CD14, and monocyte deactivation, characterized by downregulation of HLA-DR. The extent of monocyte deactivation was significantly correlated with disease severity.

Cardiac arrest and resuscitation activates the hypothalamic-pituitary-adrenal axis and results in severe immunosuppression

In patients who are successfully resuscitated after initial cardiac arrest (CA), mortality and morbidity rates are high, due to ischemia/reperfusion injury to the whole body including the nervous and immune systems. How the interactions between these two critical systems contribute to post-CA outcome remains largely unknown. Using a mouse model of CA and cardiopulmonary resuscitation (CA/CPR), we demonstrate that CA/CPR induced neuroinflammation in the brain, in particular, a marked increase in pro-inflammatory cytokines, which subsequently activated the hypothalamic-pituitary-adrenal (HPA) axis. Importantly, this activation was associated with a severe immunosuppression phenotype after CA. The phenotype was characterized by a striking reduction in size of lymphoid organs accompanied by a massive loss of immune cells and reduced immune function of splenic lymphocytes. The mechanistic link between post-CA immunosuppression and the HPA axis was substantiated, as we discovered that glucocorticoid treatment, which mimics effects of the activated HPA axis, exacerbated post-CA immunosuppression, while RU486 treatment, which suppresses its effects, significantly mitigated lymphopenia and lymphoid organ atrophy and improved CA outcome. Taken together, targeting the HPA axis could be a viable immunomodulatory therapeutic to preserve immune homeostasis after CA/CPR and thus improve prognosis of post-resuscitation CA patients.

Association of post-resuscitation inflammatory response with favorable neurologic outcomes in adults with in-hospital cardiac arrest

BACKGROUND

Early prediction of mortality in adults after in-hospital cardiac arrest (IHCA) remains vital to optimizing treatment strategies. Inflammatory cytokines specific to early prognostication in this population have not been well studied. We evaluated whether novel inflammatory cytokines obtained from adults with IHCA helped predict favorable neurologic outcome.

METHODS

The study population included adults with IHCA who underwent ACLS-guided resuscitation between March 2014 and May 2019 at an academic tertiary medical center. Peripheral blood samples were obtained within 6, 24, 48, 72, and 96 h of IHCA and analysis of 15 cytokines were performed. The primary outcome of interest was presence of favorable neurologic outcome at hospital discharge, defined as a Glasgow Outcome Score of 4 or 5.

RESULTS

Of the 105 adults with IHCA studied, 27 (25.7%) were noted to have survival with a favorable neurologic outcome while 78 (74.3%) did not. Patients who survived with favorable neurologic outcome were more often men (88.9% vs 61.5%, p = 0.008) and had higher rates of ventricular tachyarrhythmias as their initial rhythm (34.6% vs 11.7%, p = 0.018). Levels of interleukin (IL)-6, IL-8, IL-10, and Tumor Necrosis Factor (TNF)-R1 within 6 or 24 h were significantly lower in patients with favorable neurologic outcome compared with those who had unfavorable neurologic outcome. In multivariable analysis, IL-10 levels within 6 h was the only independent predictor of favorable neurologic outcomes [odds ratio (OR) 0.895, 95% confidence interval 0.805-0.996, p = 0.041].

CONCLUSION

In this contemporary observational study of adults with IHCA receiving ACLS-guided resuscitative and post-resuscitative care, inflammatory cytokines specific to early prognostication in adults with IHCA exist. Further larger scale studies examining the association of these inflammatory cytokines with prognosis are warranted.

MCC950, a selective NLPR3 inflammasome inhibitor, improves neurologic function and survival after cardiac arrest and resuscitation

Background

Cardiac arrest (CA) is associated with high morbidity and mortality, even after spontaneous circulation is re-established. This dire situation is partly due to post-CA syndrome for which no specific and effective intervention is available. One key component of post-CA syndrome is sterile inflammation, which affects various organs including the brain. A major effector of sterile inflammation is activated NLRP3 inflammasome, which leads to increased release of interleukin (IL)-1β. However, how NLRP3 inflammasome impacts neuroinflammation and neurologic outcome after CA is largely undefined.

Methods

Mice were subjected to a potassium-based murine CA and cardiopulmonary resuscitation (CPR) model. MCC950 was used to suppress activation of NLRP3 inflammasome after CA/CPR. Levels of protein and mRNA were examined by Western blotting and quantitative PCR, respectively. Immunologic changes were assessed by measuring cytokine expression and immune cell compositions. CA outcomes, including neurologic deficits, bacterial load in the lung, and survival rate, were evaluated.

Results

Using our CA/CPR model, we found that NLRP3 inflammasome was activated in the post-CA brain, and that pro-inflammatory cytokine levels, including IL-1β, were increased. After treatment with MCC950, a potent and selective NLRP3 inflammasome inhibitor, mice exhibited improved functional recovery and survival rate during the 14-day observational period after CA/CPR. In line with these findings, IL-1β mRNA levels in the post-CA brain were significantly suppressed after MCC950 treatment. Interestingly, we also found that in MCC950- vs. vehicle-treated CA mice, immune homeostasis in the spleen was better preserved and bacterial load in the lung was significantly reduced.

Conclusions

Our data demonstrate that activation of NLRP3 inflammasome could be a key event shaping the post-CA immuno- and neuro-pathology, and identify this pathway as a unique and promising therapeutic target to improve outcomes after CA/CPR.

Innate immune suppression after traumatic brain injury and hemorrhage in a juvenile rat model of polytrauma

Traumatic injury in children is known to cause immune suppression. Polytrauma involving a traumatic brain injury (TBI) may increase this degree of immune suppression, which increases the risk of developing nosocomial infections, potentially causing secondary brain injury and worsening patient outcomes. Despite the high prevalence of polytrauma with TBI in children, mechanisms of immune suppression following such injuries remain poorly understood. Here, we used a combined animal injury model of TBI and hemorrhage to assess immune function after polytrauma. Pre-pubescent rats were injured using a prefrontal controlled cortical impact method and a controlled hemorrhage by femoral arteriotomy. Immune function was measured by whole blood ex-vivo tumor necrosis factor alpha production capacity following incubation with lipopolysaccharide, measuring the percentage of monocytes by flow cytometry, and by examining concentrations of plasma cytokines. The degree of brain injury was sufficient to produce deficits in spatial memory testing (Barnes maze). Both hemorrhage and TBI with hemorrhage (combined injury) reduced several of the measured plasma cytokines, as compared with TBI alone. The combined injury correlated with reduced concentration of monocytes and reduced tumor necrosis factor alpha production capacity at post-injury day 1. These results demonstrate that this animal model can be used to study post-injury immune suppression.

Circulating Mitochondrial DNA as Predictor of Mortality in Critically Ill Patients: A Systematic Review of Clinical Studies

BACKGROUND

Despite numerous publications on mitochondrial DNA (mtDNA) in the last decade it remains to be seen whether mtDNA can be used clinically. We conducted a systematic review to assess circulating cell-free mtDNA as a biomarker of mortality in critically ill patients.

METHODS

This systematic review was registered with PROSPERO (CRD42016046670). PubMed, CINAHL, the Cochrane Library, Embase, Scopus, and Web of Science, and reference lists of retrieved articles were searched. Studies measuring circulating cell-free mtDNA and reporting on all-cause mortality in critically ill adult and pediatric patients were included. The primary and secondary outcomes were mortality and morbidity, respectively.

RESULTS

Of the 1,566 initially retrieved publications, 40 studies were included, accounting for 3,450 critically ill patients. Substantial differences between studies were noted in how mtDNA was isolated and measured. Sixteen of the 40 included studies (40%) explored the association between mtDNA levels and mortality; of those 16 studies, 11 (68.8%) reported a statistically significant association. The area under the receiver operating characteristic (AUROC) curve for mtDNA and mortality was calculated for 10 studies and ranged from 0.61 to 0.95.

CONCLUSIONS

There is growing interest in mtDNA as a predictor of mortality in critically ill patients. Most studies are small, lack validation cohorts, and utilize different protocols to measure mtDNA. When reported, AUROC analysis usually suggests a statistically significant association between mtDNA and mortality. Standardization of mtDNA protocols and the completion of a large, prospective, multicenter trial may be warranted to firmly establish the clinical usefulness of mtDNA.

Plasma proteomic changes during therapeutic hypothermia in resuscitated patients after cardiac arrest

Hypothermia is used for several h during cardiac and aortic surgery to protect ischemic organs. Therapeutic hypothermia (TH) is used for ≤24 h as a treatment for comatose patients after the return of spontaneous circulation (ROSC) following cardiac arrest. The proteomic approach may provide unbiased data on alterations in the abundance of proteins during TH. The objective of this study was to assess the effects of cooling/rewarming on the plasma proteome during TH after ROSC and to identify the mechanism underlying its therapeutic effects. A total of nine comatose adult patients, resuscitated shortly after cardiac arrest, were cooled to 34°C for 24 h and slowly rewarmed to 36°C. A quantitative gel-free proteomic analysis was performed using the isobaric tag for relative and absolute quantification labeling tandem mass spectrometry. Plasma samples were obtained prior to cooling and rewarming, and immediately after rewarming, from all patients during TH after ROSC. A total of 92 high-confidence proteins were identified. Statistically significant alterations were observed (>1.2-fold increase or <0.833-fold decrease) in the levels of 15 of those proteins (P=0.003–0.047), mainly proteins belonging to the acute-phase response or platelet degranulation. Unexpectedly, the levels of free hemoglobin (hemoglobin subunits α and β) were significantly downregulated during TH (P<0.05). The level of the terminal complement complex (SC5b-9) showed significant reduction after cooling (P=0.023). Although the acute-phase response proteins were upregulated, the abundance of complement proteins did not change, and the levels of SC5b-9 and free hemoglobin decreased during TH in patients after ROSC.

Patients with out-of-hospital cardiac arrest show decreased human leucocyte antigen-DR expression on monocytes and B and T lymphocytes after return of spontaneous circulation

Immune disorders are an important feature of patients with out-of-hospital cardiac arrest (OHCA) after return of spontaneous circulation (ROSC). However, the precise immune alterations in patients with OHCA that occur immediately after ROSC are unclear. In this study, we investigated human leucocyte antigen-DR (HLA-DR) expression on circulatory monocytes and B and T lymphocytes. Sixty-eight consecutive patients with OHCA with ROSC >12 hours were enrolled. Clinical data and 28-day survival were recorded. Peripheral blood samples after ROSC days 1 and 3 were analysed to evaluate HLA-DR expression. Fifty healthy individuals were enrolled as controls. Compared with levels in healthy individuals, HLA-DR expression on monocytes and B lymphocytes, but not on T lymphocytes, decreased on days 1 and 3 after ROSC. No significant difference in HLA-DR expression was detected between survivors and non-survivors on day 1. For 41 patients with expression data for days 1 and 3, HLA-DR expression on monocytes and B lymphocytes in non-survivors was lower than that in survivors on day 3. In non-survivors, the mean fluorescence intensities of HLA-DR on B lymphocytes and percentages of HLA-DR+ T lymphocytes were lower on day 3 than on day 1. On days 1 and 3, there were significant correlations between HLA-DR expression on monocytes and B lymphocytes and clinical indicators, such as time to ROSC, adrenaline dose, acute physiology, chronic health evaluation II and the sequential organ failure assessment. The decreases in HLA-DR expression on circulatory monocytes and B and T lymphocytes after ROSC may be involved in the observed immunosuppression in patients with OHCA.

Increased Plasma Levels of Danger-Associated Molecular Patterns Are Associated With Immune Suppression and Postoperative Infections in Patients Undergoing Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy

Introduction

Danger-associated molecular patterns (DAMPs) can elicit immune responses and may subsequently induce an immune-suppressed state. Previous work showed that increased plasma levels of DAMPs are associated with immune suppression and increased susceptibility toward infections in trauma patients. Like trauma, major surgical procedures, such as cytoreductive surgery (CRS) combined with hyperthermic intraperitoneal chemotherapy (HIPEC), are also thought to cause profound DAMP release. Furthermore, the incidence of postoperative infections in these patients, ranging from 10 to 36%, is very high compared to that observed in patients undergoing other major surgical procedures. We hypothesized that the double hit of surgical trauma (CRS) in combination with HIPEC causes excessive DAMP release, which in turn contributes to the development of immune suppression. To investigate this, we assessed DAMP release in patients undergoing CRS-HIPEC, and investigated its relationship with immune suppression and postoperative infections.

Methods

In 20 patients undergoing CRS-HIPEC, blood was obtained at five time points: just before surgery (baseline), after CRS, after HIPEC, at ICU admission, and 1 day after surgery. Circulating levels of DAMPs [heat shock protein (HSP)70, high mobility group box (HMGB)1, S100A12, S100A8/S100A9, nuclear (n)DNA, mitochondrial (mt)DNA, lactate dehydrogenase (LDH), a marker of unscheduled cell death], and cytokines [tumor necrosis factor (TNF)α, IL-6, IL-8, IL-10, macrophage inflammatory protein (MIP)-1α, MIP-1β, and MCP-1] were measured. The extent of immune suppression was determined by measuring HLA-DR gene expression and ex vivo leukocytic cytokine production capacity.

Results

Plasma levels of DAMPs (maximum fold increases of HSP70: 2.1 [1.5–2.8], HMGB1: 5.9 [3.2–9.8], S100A8/S100A9: 3.6 [1.8–5.6], S100A12: 2.6 [1.8–4.3], nDNA 3.9 [1.0–10.8], LDH 1.7 [1.2–2.5]), and all measured cytokines increased profoundly following CRS-HIPEC. Evidence of immune suppression was already apparent during the procedure, illustrated by a decrease of HLA-DR expression compared with baseline (0.5-fold [0.3–0.9]) and diminished ex vivo pro-inflammatory cytokine production capacity. The increase in HMGB1 levels correlated with the decrease in HLA-DR expression (r = −0.46, p = 0.04), and peak HMGB1 concentrations were significantly higher in the five patients who went on to develop a postoperative infection (p = 0.04).

Conclusion

CRS-HIPEC is associated with profound DAMP release and immune suppression, and plasma HMGB1 levels are related with the occurrence of postoperative infections in these patients.

Decreased Monocyte HLA-DR Expression in Patients After Non-Shockable out-of-Hospital Cardiac Arrest

Out-of-hospital cardiac arrest (OHCA) constitutes a major health care problem with the development in immediate survivors of a post-cardiac arrest syndrome including systemic inflammatory response as observed in sepsis. As a decreased monocyte HLA-DR expression (mHLA-DR) has been repeatedly described in septic patients in association with an increased risk of death and nosocomial infections, we tested whether this immune alteration could also be observed after OHCA. Fifty-five non-shockable OHCA patients sampled at Day 0 (D0: within 4 h after OHCA), D1 (the next day), and D3: (after 2 additional days) were included. CD4+ lymphocyte count and mHLA-DR were evaluated by flow cytometry. We observed a marked decrease in mHLA-DR as early as D0 in patients compared with normal values. This decrease persisted till D3 and was associated with a moderate decrease in the number of circulating CD4+ lymphocytes. No correlations were identified between mHLA-DR and usual prognostic markers after OHCA. However, overtime evolution in mHLA-DR values appeared different between survivors and non-survivors with a quasisystematic decrease between D1 and D3 in non-survivors versus an increased expression in survivors. In conclusion, this preliminary pilot study describes the occurrence of OHCA-induced immune alterations as illustrated by a decreased mHLA-DR and CD4+ lymphopenia. Furthermore, we show for the first time the differential overtime evolution in mHLA-DR between survivors and non-survivors without association with usual prognostic markers and multiple organ failure. These initial results should now be confirmed in a larger cohort of OHCA patients.

Involvement of Mitochondrial Disorders in Septic Cardiomyopathy

Sepsis is defined as a life-threatening organ dysfunction caused by a dysregulated host response to infection. It remains a leading cause of death worldwide, despite the development of various therapeutic strategies. Cardiac dysfunction, also referred to as septic cardiomyopathy, is a frequent and well-described complication of sepsis and associated with worse clinical outcomes. Recent research has increased our understanding of the role of mitochondrial dysfunction in the pathophysiology of septic cardiomyopathy. The purpose of this review is to present this evidence as a coherent whole and to highlight future research directions.

Lymphopaenia in cardiac arrest patients

Background

A decrease in circulating lymphocytes has been described as a marker of poor prognosis after septic shock; however, scarce data are available after cardiac arrest (CA). The aim of this study was to evaluate the impact of lymphopaenia after successful cardiopulmonary resuscitation.

Methods

This is a retrospective analysis of an institutional database including all adult CA patients admitted to the intensive care unit (ICU) between January 2007 and December 2014 who survived for at least 24 h. Demographic, CA-related data and ICU mortality were recorded as was lymphocyte count on admission and for the first 48 h. A cerebral performance category score of 3–5 at 3 months was considered as an unfavourable neurological outcome.

Results

Data from 377 patients were analysed (median age: 62 [IQRs: 52–75] years). Median time to return of spontaneous circulation (ROSC) was 15 [8–25] min and 232 (62%) had a non-shockable initial rhythm. ICU mortality was 58% (n = 217) and 246 (65%) patients had an unfavourable outcome at 3 months. The median lymphocyte count on admission was 1208 [700–2350]/mm³ and 151 (40%) patients had lymphopaenia (lymphocyte count <1000/mm³). Predictors of lymphopaenia on admission were older age, a shorter time to ROSC, prior use of corticosteroid therapy and high C-reactive protein levels on admission. ICU non-survivors had lower lymphocyte counts on admission than survivors (1100 [613–2317] vs. 1316 [891–2395]/mm³; p = 0.05) as did patients with unfavourable compared to those with favourable neurological outcomes (1100 [600–2013] vs. 1350 [919–2614]/mm³; p = 0.003). However, lymphopaenia on admission was not an independent predictor of poor outcomes in the entire population, but only among OHCA patients.

Conclusions

A low lymphocyte count is common in CA survivors and is associated with poor outcome after OHCA.

Electronic supplementary material

The online version of this article (doi:10.1186/s13613-017-0308-z) contains supplementary material, which is available to authorized users.

Release of Danger-Associated Molecular Patterns following Chemotherapy Does Not Induce Immunoparalysis in Leukemia Patients

Chemotherapy may result in the release of danger-associated molecular patterns (DAMPs), which can cause immunoparalysis (deactivation of the immune system). We investigated DAMPs following chemotherapy and their relationship with markers of immunoparalysis in leukemia patients. In 6 patients with acute myeloid leukemia or myelodysplastic syndrome and 12 healthy subjects, DAMPs, cytokines, and markers of immunoparalysis were determined before and during the first week after chemotherapy initiation. In the patients, plasma levels of nuclear DNA (a marker of general DAMP release) were profoundly increased before chemotherapy and further increased 4-6 h afterwards, while the specific DAMP mitochondrial DNA showed only a trend towards increase. Circulating cytokine levels did not change following chemotherapy. Leukocyte cytokine production capacity and HLA-DR expression were similar in patients and healthy controls until day 4 when leukocytes were found to be virtually absent. In conclusion, in the early phase following chemotherapy in leukemia patients, increased DAMP release does not induce immunoparalysis.

Mitochondrial DNA and TLR9 Signaling Is Not Involved in Mechanical Ventilation-Induced Inflammation

Exogenous administration of mitochondrial DNA (mtDNA) causes inflammatory lung injury in a toll-like receptor (TLR) 9-dependent manner. We investigated whether mechanical ventilation results in endogenous release of mtDNA and whether TLR9 plays a role in the pulmonary inflammatory response induced by mechanical ventilation.Wild-type and TLR9/ C57bl/6 mice were ventilated with low (8 mL/kg) and high (32 mL/kg) tidal volumes for 4 hours. Levels of nuclear DNA and mtDNA in bronchoalveolar lavage fluid, as well as pulmonary concentrations of keratinocyte-derived chemokine, interleukin-1β, and interleukin-6, were determined.Cytokine and nuclear DNA, but not mtDNA, levels were increased after mechanical ventilation with both tidal volumes. Cytokine concentrations were similar between wild-type and TLR9/ mice. Mechanical ventilation does not result in the release of mtDNA, and TLR9 is not involved in mechanical ventilation-induced inflammation.

Characterization of a model of systemic inflammation in humans in vivo elicited by continuous infusion of endotoxin

Investigating the systemic inflammatory response in patients with critical illness such as sepsis, trauma and burns is complicated due to uncertainties about the onset, duration and severity of the insult. Therefore, in vivo models of inflammation are essential to study the pathophysiology and to evaluate immunomodulatory therapies. Intravenous bolus administration of endotoxin to healthy volunteers is a well-established model of a short-lived systemic inflammatory response, characterized by increased plasma cytokine levels, flu-like symptoms and fever. In contrast, patients suffering from systemic inflammation are often exposed to inflammatory stimuli for an extended period of time. Therefore, continuous infusion of endotoxin may better reflect the kinetics of the inflammatory response encountered in these patients. Herein, we characterize a novel model of systemic inflammation elicited by a bolus infusion of 1 ng/kg, followed by a 3hr continuous infusion of 1 ng/kg/h of endotoxin in healthy volunteers, and compared it with models of bolus administrations of 1 and 2 ng/kg of endotoxin. The novel model was well-tolerated and resulted in a more pronounced increase in plasma cytokine levels with different kinetics and more prolonged symptoms and fever compared with the bolus-only models. Therefore, the continuous endotoxin infusion model provides novel insights into kinetics of the inflammatory response during continuous inflammatory stimuli and accommodates a larger time window to evaluate immunomodulating therapies.

DANGER IN THE INTENSIVE CARE UNIT: DAMPS IN CRITICALLY ILL PATIENTS

Danger-associated molecular patterns (DAMPs) that are released by injured, threatened, or dead cells, or that originate from the extracellular matrix, influence the immune system. This is of great relevance in critically ill patients, in whom trauma or surgery-related cell damage, hypoxia, ischemia, and infections can result in extensive release of DAMPs. As many patients at the intensive care unit suffer from immune system-related complications, DAMPs could serve as markers for the prognosis of these patients and represent possible therapeutic targets. In the present review, we provide an overview of several well known DAMPs (high-mobility group box 1, heat-shock proteins, s100 proteins, nucleic acids, and hyaluronan) and their effects on the immune system. Furthermore, we discuss the role of DAMPs as markers or therapeutic targets in several conditions frequently encountered in critically ill patients, such as sepsis, trauma, ventilator-induced lung injury, and cardiac arrest.

Inflammasome and toll-like receptor signaling in human monocytes after successful cardiopulmonary resuscitation

BACKGROUND

Whole body ischemia-reperfusion injury (IRI) after cardiopulmonary resuscitation (CPR) induces a generalized inflammatory response which contributes to the development of post-cardiac arrest syndrome (PCAS). Recently, pattern recognition receptors (PRRs), such as toll-like receptors (TLRs) and inflammasomes, have been shown to mediate the inflammatory response in IRI. In this study we investigated monocyte PRR signaling and function in PCAS.

METHODS

Blood samples were drawn in the first 12 hours, and at 24 and 48 hours following return of spontaneous circulation in 51 survivors after cardiac arrest. Monocyte mRNA levels of TLR2, TLR4, interleukin-1 receptor-associated kinase (IRAK)3, IRAK4, NLR family pyrin domain containing (NLRP)1, NLRP3, AIM2, PYCARD, CASP1, and IL1B were determined by real-time quantitative PCR. Ex vivo cytokine production in response to stimulation with TLR ligands Pam3CSK4 and lipopolysaccharide (LPS) was assessed in both whole blood and monocyte culture assays. Ex vivo cytokine production of peripheral blood mononuclear cells (PBMCs) from a healthy volunteer in response to stimulation with patients' sera with or without LPS was assessed. The results were compared to 19 hemodynamically stable patients with coronary artery disease.

RESULTS

Monocyte TLR2, TLR4, IRAK3, IRAK4, NLRP3, PYCARD and IL1B were initially upregulated in patients following cardiac arrest. The NLRP1 and AIM2 inflammasomes were downregulated in resuscitated patients. There was a significant positive correlation between TLR2, TLR4, IRAK3 and IRAK4 expression and the degree of ischemia as assessed by serum lactate levels and the time until return of spontaneous circulation. Nonsurvivors at 30 days had significantly lower mRNA levels of TLR2, IRAK3, IRAK4, NLRP3 and CASP1 in the late phase following cardiac arrest. We observed reduced proinflammatory cytokine release in response to both TLR2 and TLR4 activation in whole blood and monocyte culture assays in patients after CPR. Sera from resuscitated patients attenuated the inflammatory response in cultured PBMCs after co-stimulation with LPS.

CONCLUSIONS

Successful resuscitation from cardiac arrest results in changes in monocyte pattern recognition receptor signaling pathways, which may contribute to the post-cardiac arrest syndrome.

TRIAL REGISTRATION

The trial was registered in the German Clinical Trials Register ( DRKS00009684 ) on 27/11/2015.

Mitochondrial DNA sensing by STING signaling participates in inflammation, cancer and beyond

Recent studies have revealed the diverse pathophysiological functions of mitochondria beyond traditional energetic metabolism in cells. Mitochondria-released damage-associated molecular patterns, particularly mitochondrial deoxyribonucleic acid (mtDNA), play a central role in host immune defenses against foreign pathogens. Newly discovered cGAS-STING signaling is responsible for microbial DNA recognition, and potentially participates in mitochondrial DNA sensing. Inappropriate inflammatory signaling mediated by mtDNA is implicated in various human diseases, especially infectious/inflammatory disease and cancer. In addition, mtDNA horizontal transfer between tumor cells and surrounding somatic cells has been recently observed and been associated with tumorigenesis and cancer progression. In this review, we will summarize the molecular signaling of mtDNA recognition (especially STING signaling), and discuss the underlying mechanism by which mtDNA transfer triggers cancer progression in human. Besides, we will highlight the central role of mtDNA in host immunity, with particular emphasis on mtDNA-induced NETs (neutrophil extracellular traps) formation, apoptosis and autophagy.

MIF reflects tissue damage rather than inflammation in post-cardiac arrest syndrome in a real life cohort

INTRODUCTION

Following successful resuscitation from cardiac arrest (CA), neurological impairment and other types of organ dysfunction cause significant morbidity and mortality-a condition termed post-cardiac arrest syndrome. Whole-body ischemia/reperfusion with oxygen debt activates immunologic and coagulation pathways increasing the risk of multiple organ failure and infection. We here examined the role of the pro-inflammatory cytokine macrophage migration inhibitory factor (MIF) in post-cardiac arrest syndrome.

METHODS

MIF plasma levels of n=16 patients with return of spontaneous circulation (ROSC) after CA were assessed with a previously validated method and compared to markers of systemic inflammation and cellular damage. ICU patients without former CA and healthy volunteers served as controls.

RESULTS

MIF levels in patients after ROSC were higher compared to those in healthy volunteers and ICU patients without CA. Kaplan-Meyer analysis revealed a distinctly elevated mortality since day one that further increased towards an elevated 60-days-mortality in patients with high plasma MIF. ROC curve identified plasma MIF as a predictor for mortality in patients after CA. Correlation with inflammatory parameters revealed that high MIF levels did not mirror post CA inflammatory syndrome, but distinctive cellular damage after ROSC as there were strong correlations with markers of cellular damage like LDH and GOT/GPT.

CONCLUSION

High MIF levels were associated with elevated 60-days-mortality and high MIF predicted mortality after CA. We found a close relation between circulating MIF levels and cellular damage, but not with an inflammatory syndrome.