Plasma fractalkine is a sustained marker of disease severity and outcome in sepsis patients

ADAM10-a "multitasker" in sepsis: focus on its posttranslational target

BACKGROUND

Sepsis has a complex pathogenesis in which the uncontrolled systemic inflammatory response triggered by infection leads to vascular barrier disruption, microcirculation dysfunction and multiple organ dysfunction syndrome. Numerous recent studies reveal that a disintegrin and metalloproteinase 10 (ADAM10) acts as a "molecular scissor" playing a pivotal role in the inflammatory response during sepsis by regulating proteolysis by cleaving various membrane protein substrates, including proinflammatory cytokines, cadherins and Notch, which are involved in intercellular communication. ADAM10 can also act as the cellular receptor for Staphylococcus aureus α-toxin, leading to lethal sepsis. However, its substrate-specific modulation and precise targets in sepsis have not yet to be elucidated.

METHODS

We performed a computer-based online search using PubMed and Google Scholar for published articles concerning ADAM10 and sepsis.

CONCLUSIONS

In this review, we focus on the functions of ADAM10 in sepsis-related complex endothelium-immune cell interactions and microcirculation dysfunction through the diversity of its substrates and its enzymatic activity. In addition, we highlight the posttranslational mechanisms of ADAM10 at specific subcellular sites, or in multimolecular complexes, which will provide the insight to intervene in the pathophysiological process of sepsis caused by ADAM10 dysregulation.

Expression of Serum Cytokines Profile in Neonatal Sepsis

Objective

Sepsis remains a major cause of neonatal death. To better characterize the inflammatory response during neonatal sepsis, we compared the differences in serum cytokines and chemokines between full-term neonates with sepsis and without infection.

Methods

We enrolled 40 full-term neonates with sepsis and 26 full-term neonates without infection as controls between October 2016 and June 2018. Forty cytokines /chemokines in serum were analyzed using the Luminex Bead Immunoassay System.

Results

Our results showed that serum IL-6, IL-8, TNF-α, IL-1β, MIF, CXCL13, CXCL1, CXCL2, CXCL5, CXCL6, CXCL16, CCL27, CCL2, CCL8, CCL3, CCL20, CCL23, and CX3CL1 levels were significantly increased in neonates with sepsis compared to those in the control group (all p<0.05). The levels of serum CCL20, and IL-17 were higher in late-onset sepsis (LOS) than those in early-onset sepsis (EOS) (all p<0.05). Conversely, serum CXCL16 was lower in LOS than that in EOS (p<0.05).

Conclusion

Our findings revealed that excessive pro-inflammatory cytokines might be involved in neonatal sepsis. In addition, chemokines significantly increased the recruitment of immune cells after infection to participate in the anti-infection defense of neonates, but this could lead to damage.

Berberine Suppresses Leukocyte Adherence by Downregulating CX3CL1 Expression and Shedding and ADAM10 in Lipopolysaccharide-Stimulated Vascular Endothelial Cells

Berberine exerts therapeutic effects in inflammation-associated diseases. In a lipopolysaccharide (LPS)-induced endotoxemic acute lung injury (ALI) rat model, berberine alleviated lung injury through different anti-inflammatory mechanisms; however, treatment effects on CX3CL1 expression and shedding remain to be examined. As these processes play important roles in promoting the binding of leukocytes to the endothelium, the CX3CL1/CX3CR1 axis and its related pathways may serve as potential targets for the clinical treatment of ALI. The anti-inflammatory effects of berberine were investigated in LPS-stimulated rats, human umbilical cord vein endothelial cells (HUVECs), and THP-1 monocytic cells. Cx3cl1 expression in rat pulmonary tissues was examined using immunohistochemistry. CX3CL1, CX3CR1, RELA, STAT3, and ADAM10 levels were examined using Western blotting. CX3CL1 and ADAM10 mRNA levels were examined using quantitative real-time polymerase chain reaction. Soluble fractalkine levels in LPS-stimulated rats and HUVECs were examined using the enzyme-linked immunosorbent assay. Berberine significantly mitigated the LPS-induced upregulation of fractalkine and soluble fractalkine in rats and cultured HUVECs. Berberine mitigated the LPS-induced activation of the NF-κB and STAT3 signaling pathways. In THP-1 cells, berberine mitigated the LPS-induced upregulation of CX3CR1. Furthermore, the membrane expression of ADAM10 in LPS-stimulated HUVECs was suppressed by the berberine treatment. Berberine dose-dependently inhibited the LPS-induced activation of the CX3CL1/CX3CR1 axis and fractalkine shedding through ADAM10. These findings reveal a novel molecular mechanism underlying the inhibitory effect of berberine on monocyte adherence to the endothelium during inflammation.

Meprin and ADAM proteases as triggers of systemic inflammation in sepsis

Systemic inflammatory disorders (SIDs) comprise a broad range of diseases characterized by dysregulated excessive innate immune responses. Severe forms of SIDs can lead to organ failure and death, and their increasing incidence represents a major issue for the healthcare system. Protease-mediated ectodomain shedding of cytokines and their receptors represents a central mechanism in the regulation of inflammatory responses. The metalloprotease A disintegrin and metalloproteinase (ADAM) 17 is the best-characterized ectodomain sheddase capable of releasing TNF-α and soluble IL-6 receptor, which are decisive factors of systemic inflammation. Recently, meprin metalloproteases were also identified as IL-6 receptor sheddases and activators of the pro-inflammatory cytokines IL-1β and IL-18. In different mouse models of SID, particularly those mimicking a sepsis-like phenotype, ADAM17 and meprins have been found to promote disease progression. In this review, we summarize the role of ADAM10, ADAM17, and meprins in the onset and progression of sepsis and discuss their potential as therapeutic targets.

Elevated Plasma Fractalkine Level Is Associated with the Severity of Hemorrhagic Fever with Renal Syndrome in Humans

Hantaan virus infection may cause severe lethal hemorrhagic fever with renal syndrome (HFRS) in humans. The chemokine fractalkine (CX3CL1) acts as a proinflammatory cytokine, and it is elevated in several infectious diseases. However, little is known about the contributions of CX3CL1 to HFRS pathogenesis. Present study detected plasma CX3CL1 levels and expression of the receptor CX3CR1 in HFRS patients and discussed the possible effects of CX3CL1 on pathogenesis of HFRS. Plasma CX3CL1 in acute phase and Critical/Severe groups of HFRS patients were significantly increased compared to that in normal controls (p < 0.001 and p < 0.01, respectively). High plasma CX3CL1 was negatively correlated with platelet count (r = -0.5844, p < 0.0001) and positively correlated with blood urea nitrogen (r = 0.3668, p = 0.0039), creatinine (r = 0.42, p = 0.0008), and white blood cells (r = 0.2646, p = 0.0411). Expression of CX3CR1 on nonclassical and intermediate monocytes was also increased in the acute phase (p < 0.01 for both the cells) and Critical/Severe groups (p < 0.05 and p < 0.01, respectively) of HFRS patients compared to that in normal controls. Taken together, elevation of plasma CX3CL1 in HFRS patients and expression of CX3CR1 on nonclassical and intermediate monocyte subsets might provide new insights into the potential role of CX3CL1/CX3CR1 in pathogenesis of HFRS.

Biomarker-Based Classification of Patients With Acute Respiratory Failure Into Inflammatory Subphenotypes: A Single-Center Exploratory Study

OBJECTIVES

Hyper- and hypoinflammatory subphenotypes discovered in patients with acute respiratory distress syndrome predict clinical outcomes and therapeutic responses. These subphenotypes may be important in broader critically ill patient populations with acute respiratory failure regardless of clinical diagnosis. We investigated subphenotyping with latent class analysis in an inclusive population of acute respiratory failure, derived a parsimonious model for subphenotypic predictions based on a small set of variables, and examined associations with clinical outcomes.

DESIGN

Prospective, observational cohort study.

SETTING

Single-center, academic medical ICU.

PATIENTS

Mechanically ventilated patients with acute respiratory failure.

MEASUREMENTS AND MAIN RESULTS

We included 498 patients with acute respiratory failure (acute respiratory distress syndrome: 143, at-risk for acute respiratory distress syndrome: 198, congestive heart failure: 37, acute on chronic respiratory failure: 23, airway protection: 61, and multifactorial: 35) in our derivation cohort and measured 10 baseline plasma biomarkers. Latent class analysis considering clinical variables and biomarkers determined that a two-class model offered optimal fit (23% hyperinflammatory subphenotype). Distribution of hyperinflammatory subphenotype varied among acute respiratory failure etiologies (acute respiratory distress syndrome: 31%, at-risk for acute respiratory distress syndrome: 27%, congestive heart failure: 22%, acute on chronic respiratory failure 0%, airway protection: 5%, and multifactorial: 14%). Hyperinflammatory patients had higher Sequential Organ Failure Assessment scores, fewer ventilator-free days, and higher 30- and 90-day mortality (all p < 0.001). We derived a parsimonious model consisting of angiopoietin-2, soluble tumor necrosis factor receptor-1, procalcitonin, and bicarbonate and classified subphenotypes in a validation cohort (n = 139). Hyperinflammatory patients (19%) demonstrated higher levels of inflammatory biomarkers not included in the model (p < 0.01) and worse outcomes.

CONCLUSIONS

Host-response subphenotypes are observable in a heterogeneous population with acute respiratory failure and predict clinical outcomes. Simple, biomarker-based models can offer prognostic enrichment in patients with acute respiratory failure. The differential distribution of subphenotypes by specific etiologies of acute respiratory failure indicates that subphenotyping may be more relevant in patients with hypoxemic causes of acute respiratory failure and not in patients intubated for airway protection or acute on chronic decompensation.

Biomarker screening and validation for the differentiation of bloodstream infection from adult-onset Still's disease: A prospective cohort study

OBJECTIVES

Distinguishing between bloodstream infection (BSI) and adult-onset Still's disease (AOSD) is challenging in practice due to similarities in their clinical and laboratory characteristics. We aimed to identify biomarkers in a prospective cohort of patients with BSI and AOSD for differential diagnosis and prognosis prediction.

METHODS

Sixty-four individuals were enrolled in the training set (37 with BSI, 17 with AOSD, and 10 healthy controls). Furthermore, 86 individuals were enrolled in the validation cohort (67 with BSI and 19 with AOSD). Clinical and laboratory data were collected. Blood samples were stimulated using bacteria-specific antigens and levels of several cytokines were detected in the supernatant via Luminex or enzyme-linked immunosorbent assay.

RESULTS

Escherichia coli and Klebsiella pneumoniae were the pathogens most frequently responsible for BSI. In the training cohort, the incidence of rash, arthralgia, myalgia, sore throat, lymphadenopathy, leukocytosis, and hyperferritinemia was higher in patients with AOSD than in those with BSI. Procalcitonin was significantly higher in patients with BSI than that in those with AOSD. Interleukin (IL)-6, IL-17A, C-X3-C motif chemokine ligand (CX3CL)-1, and C-X-C motif chemokine ligand 10 (CXCL10) levels were higher in patients with BSI than in those with AOSD. IL-18 was higher among patients with AOSD than in those with BSI. A decision tree analysis showed that a combination of plasma IL-18 and ferritin levels can be used to distinguish BSI from AOSD (diagnostic accuracy: 97.67%, sensitivity: 96.15%, specificity: 100%). Plasma IL-18 levels were positively correlated with ferritin, and were decreased after treatment in both BSI and ASOD groups.

CONCLUSIONS

Plasma IL-18 and ferritin levels can be used to differentiate BSI from AOSD. IL-18 may be a potential biomarker for prognosis prediction in BSI and AOSD.

Chronic upper airway and systemic inflammation from copier emitted particles in healthy operators at six Singaporean workplaces

Toner-based printing equipment (TPE), including laser printers and photocopiers, utilize several engineered nanomaterials (ENMs) to improve toner performance. Operation of TPE, which rarely employ any exposure controls, generates high exposures to nanoparticles that contain ENMs and complex organics. Epidemiological literature in copier operators documents respiratory effects, including nasal blockage, cough, excessive sputum, and breathing difficulties, cardiovascular effects, oxidative stress, and inflammation. However, epidemiological studies in humans with adequate exposure assessment and dose-response analysis are lacking. We present herein the analysis of the upper airway and systemic inflammation in plasma of 19 healthy copier operators at six Singapore workplaces. We employed a repeated panel design (four biomarker measurements over two weeks) combined with a multi-marker approach (14 inflammatory cytokines in plasma and nasal lavage (NL)), and comprehensive exposure assessment using four distinct exposure metrics. We investigated spatial and temporal patterns of markers of upper airway and systemic inflammation and their association with various exposure metrics. Several inflammatory markers, namely fractalkine, IL-1β, and IL-1α in NL, and fractalkine, IL-1β, TNF-α, and IFN-γ in plasma, were strongly and positively associated with at least one exposure metric, whereas GM-CSF was negatively associated. The inflammation score was also strongly associated with TPE nanoparticle exposures. Exposure to TPE emissions induced moderate upper airway inflammation and stronger systemic inflammation in these healthy operators, characterized by upregulation of at least IL-1β, fractalkine, TNF-α and IFN-γ. Proinflammatory cytokines TNF-α, IFN-γ and IL-1β play an important role in orchestrating inflammatory responses in various clinical conditions, including cardiovascular and autoimmune disease, and likely trigger activation of endothelial cells, leading to overexpression of fractalkine, a chemokine that is involved in and associated with multiple disorders, including atherosclerosis and vascular disease. Future larger-scale epidemiological studies in these workers and consumers exposed chronically to TPE nanoparticle emissions and proactive interventions to reduce or eliminate TPE exposures are recommended.

Role of Fractalkine in promoting inflammation in sepsis-induced multiple organ dysfunction

OBJECTIVE

Fractalkine, CX3CL1, is involved in the directional movement of chemokine cells, immune response, inflammatory response, tissue repair, and other processes. However, its role in sepsis is not well known.

METHODS

We measured circulating Fractalkine in adult patients with sepsis. Effects of Fractalkine on the survival, inflammation, tissue injury, and bacterial clearance were assessed using the WT or CX3CL^-/- murine model of cecal ligation and puncture (CLP)-induced sepsis.

RESULTS

Serum Fractalkine concentrations were significantly elevated in adult patients with sepsis compared to healthy adults. Increased Fractalkine correlated positively with the number of blood leukocytes and the level of inflammatory cytokines, including IL-6, IL-1β, IL-17A, IFN-γ, and TNF-α, and correlated negatively with IL-10 in clinical sepsis. Recombinant Fractalkine impaired survival whereas Fractalkine gene knockout or anti-Fractalkine antibody improved survival in the murine model of CLP-induced sepsis. Fractalkine administration increased inflammatory response, evident by higher levels of cytokines (TNF-α, IL-1β, IL-17A, IFN-γ, and IL-6 but not IL-10), and tissue damage (lung, liver, and kidney) in CLP-induced sepsis. Fractalkine reduced bacterial clearance in CLP-induced polymicrobial sepsis by reducing macrophage or neutrophil phagocytosis and intracellular elimination of E. coli.

CONCLUSIONS

Fractalkine aggravates sepsis by increasing inflammation and decreasing bacterial clearance, and is a potential tool for anti-sepsis therapy.

Circulating miRNA 887 is differentially expressed in ARDS and modulates endothelial function

Circulating microRNAs (miRNAs) can be taken up by recipient cells and have been recently associated with the acute respiratory distress syndrome (ARDS). Their role in host predisposition to the syndrome is unknown. The objective of the study was to identify circulating miRNAs associated with the development of sepsis-related ARDS and examine their impact on endothelial cell gene expression and function. We determined miRNA levels in plasma collected from subjects during the first 24 h of admission to a tertiary intensive care unit for sepsis. A miRNA that was differentially expressed between subjects who did and did not develop ARDS was identified and was transfected into human pulmonary microvascular endothelial cells (HPMECs). RNA sequencing, in silico analysis, cytokine expression, and leukocyte migration assays were used to determine the impact of this miRNA on gene expression and cell function. In two cohorts, circulating miR-887-3p levels were elevated in septic patients who developed ARDS compared with those who did not. Transfection of miR-887-3p into HPMECs altered gene expression, including the upregulation of several genes previously associated with ARDS (e.g., CXCL10, CCL5, CX3CL1, VCAM1, CASP1, IL1B, IFNB, and TLR2), and activation of cellular pathways relevant to the response to infection. Functionally, miR-887-3p increased the endothelial release of chemokines and facilitated trans-endothelial leukocyte migration. Circulating miR-887-3p is associated with ARDS in critically ill patients with sepsis. In vitro, miR-887-3p regulates the expression of genes relevant to ARDS and neutrophil tracking. This miRNA may contribute to ARDS pathogenesis and could represent a novel therapeutic target.

The evolution of radiographic edema in ARDS and its association with clinical outcomes: A prospective cohort study in adult patients

PURPOSE

To assess the longitudinal evolution of radiographic edema using chest X-rays (CXR) in patients with Acute Respiratory Distress Syndrome (ARDS) and to examine its association with prognostic biomarkers, ARDS subphenotypes and outcomes.

MATERIALS AND METHODS

We quantified radiographic edema on CXRs from patients with ARDS or cardiogenic pulmonary edema (controls) using the Radiographic Assessment of Lung Edema (RALE) score on day of intubation and up to 10 days after. We measured baseline plasma biomarkers and recorded clinical variables.

RESULTS

The RALE score had good inter-rater agreement (r = 0.83, p < 0.0001) applied on 488 CXRs from 129 patients, with higher RALE scores in patients with ARDS (n = 108) compared to controls (n = 21, p = 0.01). Baseline RALE scores were positively correlated with levels of the receptor for end-glycation end products (RAGE) in ARDS patients (p < 0.05). Baseline RALE scores were not predictive of 30- or 90-day survival. Persistently elevated RALE scores were associated with prolonged need for mechanical ventilation (p = 0.002).

CONCLUSIONS

The RALE score is easily implementable with high inter-rater reliability. Longitudinal RALE scoring appears to be a reproducible approach to track the evolution of radiographic edema in patients with ARDS and can potentially predict prolonged need for mechanical ventilation.

Host-Response Subphenotypes Offer Prognostic Enrichment in Patients With or at Risk for Acute Respiratory Distress Syndrome

OBJECTIVES

Classification of patients with acute respiratory distress syndrome into hyper- and hypoinflammatory subphenotypes using plasma biomarkers may facilitate more effective targeted therapy. We examined whether established subphenotypes are present not only in patients with acute respiratory distress syndrome but also in patients at risk for acute respiratory distress syndrome (ARFA) and then assessed the prognostic information of baseline subphenotyping on the evolution of host-response biomarkers and clinical outcomes.

DESIGN

Prospective, observational cohort study.

SETTING

Medical ICU at a tertiary academic medical center.

PATIENTS

Mechanically ventilated patients with acute respiratory distress syndrome or ARFA.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We performed longitudinal measurements of 10 plasma biomarkers of host injury and inflammation. We applied unsupervised latent class analysis methods utilizing baseline clinical and biomarker variables and demonstrated that two-class models (hyper- vs hypoinflammatory subphenotypes) offered improved fit compared with one-class models in both patients with acute respiratory distress syndrome and ARFA. Baseline assignment to the hyperinflammatory subphenotype (39/104 [38%] acute respiratory distress syndrome and 30/108 [28%] ARFA patients) was associated with higher severity of illness by Sequential Organ Failure Assessment scores and incidence of acute kidney injury in patients with acute respiratory distress syndrome, as well as higher 30-day mortality and longer duration of mechanical ventilation in ARFA patients (p < 0.0001). Hyperinflammatory patients exhibited persistent elevation of biomarkers of innate immunity for up to 2 weeks postintubation.

CONCLUSIONS

Our results suggest that two distinct subphenotypes are present not only in patients with established acute respiratory distress syndrome but also in patients at risk for its development. Hyperinflammatory classification at baseline is associated with higher severity of illness, worse clinical outcomes, and trajectories of persistently elevated biomarkers of host injury and inflammation during acute critical illness compared with hypoinflammatory patients. Our findings provide strong rationale for examining treatment effect modifications by subphenotypes in randomized clinical trials to inform precision therapeutic approaches in critical care.

Increased mortality in elderly patients with acute respiratory distress syndrome is not explained by host response

Background

Advanced age is associated with increased mortality in acute respiratory distress syndrome (ARDS) patients. Preclinical studies suggest that the host response to an injurious challenge is age-dependent. In ARDS patients, we investigated whether the association between age and mortality is mediated through age-related differences in the host response.

Methods

This was a prospective longitudinal observational cohort study, performed in the ICUs of two university-affiliated hospitals. The systemic host response was characterized in three predefined age-groups, based on the age-tertiles of the studied population: young (18 to 54 years, N = 209), middle-aged (55 to 67 years, N = 213), and elderly (67 years and older, N = 196). Biomarkers of inflammation, endothelial activation, and coagulation were determined in plasma obtained at the onset of ARDS. The primary outcome was 90-day mortality. A mediation analysis was performed to examine whether age-related differences in biomarker levels serve as potential causal pathways mediating the association between age and mortality.

Results

Ninety-day mortality rates were 30% (63/209) in young, 37% (78/213) in middle-aged, and 43% (84/196) in elderly patients. Middle-aged and elderly patients had a higher risk of death compared to young patients (adjusted odds ratio, 1.5 [95% confidence interval 1.0 to 2.3] and 2.1 [1.4 to 3.4], respectively). Relative to young patients, the elderly had significantly lower systemic levels of biomarkers of inflammation and endothelial activation. Tissue plasminogen activator, a marker of coagulation, was the only biomarker that showed partial mediation (proportion of mediation, 10 [1 to 28] %).

Conclusion

Little evidence was found that the association between age and mortality in ARDS patients is mediated through age-dependent differences in host response pathways. Only tissue plasminogen activator was identified as a possible mediator of interest.

Trial registration

This trial was registered at ClinicalTrials.gov (identifier NCT01905033, date of registration July 23, 2013).

Risk factors, host response and outcome of hypothermic sepsis

Background

Hypothermia is associated with adverse outcome in patients with sepsis. The objective of this study was to characterize the host immune response in patients with hypothermic sepsis in order to determine if an excessive anti-inflammatory response could explain immunosuppression and adverse outcome. Markers of endothelial activation and integrity were also measured to explore potential alternative mechanisms of hypothermia. Finally we studied risk factors for hypothermia in an attempt to find new clues to the etiology of hypothermia in sepsis.

Methods

Consecutive patients diagnosed with sepsis within 24 hours after admission to ICUs in two tertiary hospitals in the Netherlands were included in the study (n = 525). Hypothermia was defined as body temperature below 36 °C in the first 24 h of ICU admission.

Results

Hypothermia was identified in 186 patients and was independently associated with mortality. Levels of proinflammatory and anti-inflammatory cytokines were not different between groups. Hypothermia was also not associated with an altered response to ex vivo stimulation with lipopolysaccharide in a subset of 15 patients. Risk factors for hypothermia included low body mass index, hypertension and chronic cardiovascular insufficiency. Levels of the endothelial activation marker fractalkine were increased during the first 4 days of ICU stay.

Conclusions

Hypothermia during sepsis is independently associated with mortality, which cannot be attributed to alterations in the host immune responses that were measured in this study. Given that risk factors for hypothermic sepsis are mainly cardiovascular and that the endothelial activation marker fractalkine increased in hypothermia, these findings may suggest that vascular dysfunction plays a role in hypothermic sepsis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1510-3) contains supplementary material, which is available to authorized users.

Decreased CX3CR1 messenger RNA expression is an independent molecular biomarker of early and late mortality in critically ill patients

Background

Chemokine (C-X3-C motif) receptor 1 (CX3CR1) was identified as the most differentially expressed gene between survivors and non-survivors in two independent cohorts of septic shock patients and was proposed as a marker of sepsis-induced immunosuppression. Whether such a biomarker is associated with mortality in the heterogeneous group of critically ill patients is unknown. The primary objective of this study was to evaluate the association between CX3CR1 messenger RNA (mRNA) expression and mortality in intensive care unit (ICU) patients. The secondary objective was to evaluate similar endpoints in the subgroup of septic shock patients.

Methods

We performed a prospective, multicentre, non-interventional study in six ICUs of university hospitals in Lyon, France. Every consecutive adult patient with systemic inflammatory response syndrome and an expected length of stay in the ICU over 2 days was included. Whole-blood CX3CR1 mRNA expression was measured by quantitative real-time polymerase chain reaction at day 1 (D1) and D3 after inclusion.

Results

In ICU patients (n = 725), decreased CX3CR1 mRNA expression at D1 was associated with high D7 mortality (AUC 0.70, adjusted OR [aOR] 2.03, 95 % CI 1.19–3.46), while decreased expression at D3 was associated with increased D28 mortality (AUC 0.64, aOR 2.34, 95 % CI 1.45–3.77). In septic shock patients (n = 279), similar associations were observed between decreased D1 CX3CR1 mRNA expression and D7 mortality (AUC 0.69, aOR 2.76, 95 % CI 1.32–5.75) as well as decreased D3 expression and D28 mortality (AUC 0.72, aOR 3.98, 95 % CI 1.72–9.23). These associations were independent of lactacidaemia, Simplified Acute Physiology Score II, Sepsis-related Organ Failure Assessment score and Charlson comorbidity index.

Conclusions

This study represents the largest evaluation of such an mRNA marker in a heterogeneous cohort of severely injured patients. Our results show that decreased CX3CR1 mRNA expression is associated with increased mortality in ICU patients. This suggests a link between injury-induced immunosuppression and mortality in critically ill patients. In this context, the monitoring of such a host response molecular biomarker could prove very helpful for the identification of patients at high risk of death in the ICU.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1362-x) contains supplementary material, which is available to authorized users.

Thrombocytopenia is associated with a dysregulated host response in critically ill sepsis patients

Preclinical studies have suggested that platelets influence the host response during sepsis. We sought to assess the association of admission thrombocytopenia with the presentation, outcome, and host response in patients with sepsis. Nine hundred thirty-one consecutive sepsis patients were stratified according to platelet counts (very low <50 × 10(9)/L, intermediate-low 50 × 10(9) to 99 × 10(9)/L, low 100 × 10(9) to 149 × 10(9)/L, or normal 150 × 10(9) to 399 × 10(9)/L) on admission to the intensive care unit. Sepsis patients with platelet counts <50 × 10(9)/L and 50 × 10(9) to 99 × 10(9)/L presented with higher Acute Physiology and Chronic Health Evaluation scores and more shock. Both levels of thrombocytopenia were independently associated with increased 30-day mortality (hazard ratios with 95% confidence intervals 2.00 [1.32-3.05] and 1.72 [1.22-2.44], respectively). To account for baseline differences besides platelet counts, propensity matching was performed, after which the association between thrombocytopenia and the host response was tested, as evaluated by measuring 17 plasma biomarkers indicative of activation and/or dysregulation of pathways implicated in sepsis pathogenesis and by whole genome blood leukocyte expression profiling. In the propensity matched cohort, platelet counts < 50 × 10(9)/L were associated with increased cytokine levels and enhanced endothelial cell activation. All thrombocytopenic groups showed evidence of impaired vascular integrity, whereas coagulation activation was similar between groups. Blood microarray analysis revealed a distinct gene expression pattern in sepsis patients with <50 × 10(9)/L platelets, showing reduced signaling in leukocyte adhesion and diapedesis and increased complement signaling. These data show that admission thrombocytopenia is associated with enhanced mortality and a more disturbed host response during sepsis independent of disease severity, thereby providing clinical validity to animal studies on the role of platelets in severe infection.