Sepsis with liver dysfunction and coagulopathy predicts an inflammatory pattern of macrophage activation

Abstract

Background: Interleukin-1 receptor antagonists can reduce mortality in septic shock patients with hepatobiliary dysfunction and disseminated intravascular coagulation (HBD + DIC), an organ failure pattern with inflammatory features consistent with macrophage activation. Identification of clinical phenotypes in sepsis may allow for improved care. We aim to describe the occurrence of HBD + DIC in a contemporary cohort of patients with sepsis and determine the association of this phenotype with known macrophage activation syndrome (MAS) biomarkers and mortality. We performed a retrospective nested case-control study in adult septic shock patients with concurrent HBD + DIC and an equal number of age-matched controls, with comparative analyses of all-cause mortality and circulating biomarkers between the groups. Multiple logistic regression explored the effect of HBD + DIC on mortality and the discriminatory power of the measured biomarkers for HBD + DIC and mortality.

Results: Six percent of septic shock patients (n = 82/1341) had HBD + DIC, which was an independent risk factor for 90-day mortality (OR = 3.1, 95% CI 1.4-7.5, p = 0.008). Relative to sepsis controls, the HBD + DIC cohort had increased levels of 21 of the 26 biomarkers related to macrophage activation (p < 0.05). This panel was predictive of both HBD + DIC (sensitivity = 82%, specificity = 84%) and mortality (sensitivity = 92%, specificity = 90%).

Conclusion: The HBD + DIC phenotype identified patients with high mortality and a molecular signature resembling that of MAS. These observations suggest trials of MAS-directed therapies are warranted.

Keywords: Ferritin; IL-18; Organ dysfunction; Phenotype; Sepsis.

Fig. 1

HBD + DIC phenotype in sepsis is marked by higher mortality. Unadjusted Kaplan–Meier curve comparing cumulative 90-day mortality in sepsis controls vs sepsis with HBD + DIC

Fig. 2

Head-to-head comparison of 8 of the 26 biomarkers between sepsis controls and sepsis with HBD + DIC. The comparison was achieved using the Mann–Whitney U test. **p < 0.01 after correction for multiple comparisons using the Holm-Šídák method

Fig. 3

Cell and inflammatory mediator interplay potentially contributes to the development of HBD + DIC in septic patients. Sepsis-induced NK cell deficiency triggers latent viral reactivation, with viral DNA initiating a TLR9-MyD88-mediated signaling cascade [6, 52]. Subsequent inflammasome activation leads to the secretion of IL-18 and IL-1β [6, 56]. In addition to mediating liver injury [59], IL-1β increases transcription and translation of ferritin [60], and production of IL-6 [5]. The release of damage associated molecular patterns (DAMPs), such as mitochondrial DNA or hemoglobin after tissue injury or hemolysis, triggers macrophage activation independent of IFN-γ. Release of free hemoglobin increases hemoglobin-haptoglobin complexes, activating macrophages to produce extracellular ferritin through the CD163 receptor [6, 56]. Ferritin promotes expression of IL-1β and TLR9 [57, 58], resulting in a positive feedback loop with amplification of inflammatory signals [56]. IL-18, in combination with a secondary signal, such as IL-12 or TLR ligands, activates NK cells to produce IFN-γ [53, 64]. We hypothesize, though, that in the context of sepsis with HBD + DIC, NK cells are limited in their responsiveness to IL-18 due to IL-10-mediated downregulation of the IL-18R [55]. As a result, circulating IFN-γ levels are reduced. However, IL-6 enhances signaling through TLRs, increasing the secretion of proinflammatory mediators, including CXCL10 [5]. Persistent NK cell cytolytic dysfunction, stemming from decreased cell number [52] and high levels of IL-6 [54], translates into an impaired ability to induce apoptosis of activated macrophages [6]. In addition, inflammatory mediators produced by macrophages reinforce macrophage (ferritin, IL-6, IL-1β, IL-12, TNF), pDC (ferritin), and lymphocyte (IL-18, IL-12, CXCL10) activation. Thus, the inflammatory cycle continues unabated (cytokine storm), resulting in organ dysfunction and death in the absence of appropriate therapies. The role of pDC- and NK cell-derived IFN-γ in macrophage activation during sepsis remains unclear. In our study, IFN-γ levels were low, although two of its downstream mediators, CXCL10 and IL-18BP, were elevated in patients with sepsis and HBD + DIC

Fig. 4

Performance of selected biomarkers to predict the presence of HBD + DIC and 90-day mortality during sepsis. A AUC for each of the 26 biomarkers to predict the presence of HBD + DIC in patients with sepsis, organized from highest to lowest. B ROC curve representing the model using 26 biomarkers for predicting the HBD + DIC phenotype in patients with sepsis. C Violin plots showing the distribution of predicted probabilities for the presence of HBD + DIC in sepsis. The model performed well at classifying both sepsis controls and sepsis with HBD + DIC. The majority of sepsis controls had predicted probabilities of presenting with HBD + DIC less than 0.50 (median: 0.12, IQR: 0.03–0.28). By contrast, the cases had predicted probabilities that were overwhelmingly greater than 0.50 (median: 0.96, IQR: 0.65–0.99). D ROC curve representing the model using 26 biomarkers for predicting 90-day mortality among the HBD + DIC subset of patients with sepsis. E Violin plots showing the distribution of predicted probabilities for mortality in the cases. The model performed well at distinguishing between survivors (median: 0.13, IQR: 0.01–0.32) and non-survivors (median: 0.97, IQR: 0.84–0.99) among those with HBD + DIC