Daily Sepsis Research Analysis
Two mechanistic studies illuminate how host metabolic and immune programs shape outcomes in sepsis: hepatic Nrf1 safeguards against endotoxemia/bacterial sepsis by boosting VLDL-triglyceride flux, while intracellular DAO in NK cells drives IFN-γ via a ROS–autophagy axis. A pragmatic diagnostic study suggests off-label BCID2 can rapidly identify MDR colonization in critical care patients, informing antimicrobial stewardship and isolation.
Summary
Two mechanistic studies illuminate how host metabolic and immune programs shape outcomes in sepsis: hepatic Nrf1 safeguards against endotoxemia/bacterial sepsis by boosting VLDL-triglyceride flux, while intracellular DAO in NK cells drives IFN-γ via a ROS–autophagy axis. A pragmatic diagnostic study suggests off-label BCID2 can rapidly identify MDR colonization in critical care patients, informing antimicrobial stewardship and isolation.
Research Themes
- Metabolic-immune cross-talk in sepsis
- NK cell regulation via ROS–autophagy–IFN-γ axis
- Rapid MDR surveillance to guide empiric therapy
Selected Articles
1. Hepatic Nuclear Factor Erythroid 2 Related Factor 1 Activity Promotes Host Defense in Endotoxemia and Bacterial Sepsis.
Hepatic Nrf1, but not Nrf2, is essential for survival in endotoxemia and bacterial sepsis by sustaining VLDL secretion and triglyceride handling. Pharmacologic inhibition of VLDL secretion or hydrolysis abrogated protection, whereas lipid infusion rescued, highlighting a liver-centered metabolic defense program.
Impact: This study uncovers a mechanistic link between hepatic stress-defense transcriptional programming and lipid export that directly modulates sepsis survival, suggesting druggable metabolic nodes.
Clinical Implications: Augmenting hepatic Nrf1 activity or leveraging lipid delivery (e.g., tailored lipid emulsions) could be explored as adjunctive strategies to prevent hypothermia and improve survival in sepsis, pending human validation and safety profiling.
Key Findings
- Hepatic Nrf1 activity decreases in endotoxemia and sepsis; hepatocyte Nrf1 deficiency induces severe hypothermia and mortality, unlike Nrf2.
- Genetic activation of hepatic Nrf1 improves survival and mitigates hypothermia.
- Nrf1 controls VLDL secretion and triglyceride metabolism; deficiency reduces and activation enhances VLDL release.
- Lomitapide or poloxamer 407 blunted Nrf1-mediated protection, whereas intralipid infusion rescued survival.
Methodological Strengths
- In vivo endotoxemia and live bacterial sepsis models with survival and physiological endpoints
- Hepatocyte-specific genetic loss- and gain-of-function plus pharmacologic perturbations and transcriptomics
Limitations
- Preclinical murine models; human translational data are lacking.
- Specific, clinically viable Nrf1 activators are not yet established; lipid-based rescue may carry metabolic risks.
Future Directions: Develop and test selective Nrf1 modulators; evaluate lipid support strategies; assess Nrf1 activity and lipid flux markers in human sepsis cohorts.
BACKGROUND & AIMS: Sepsis and endotoxemia cause mortality by inducing organ dysfunction and damage. Liver defends against such insults by mediating metabolic adaptations that promote stress and damage control. The mechanisms underlying liver defenses may require coordinated actions between cellular and systemic stress-defense programming. Here, we investigated whether the stress-defending transcription factors nuclear factor erythroid 2 related factor-1 (Nrf1) and -2 (Nrf2) in hepatocytes protect against endotoxemia and sepsis. METHODS: We used mice injected with Escherichia coli-derived lipopolysaccharide (endotoxemia), or E coli (sepsis). Hepatic Nrf1 and Nrf2 activity was examined, and we also genetically altered their activity and examined corresponding effects on survival, body temperature, cytokines and liver inflammation, liver gene and protein expression, and liver-related metabolism. RESULTS: Hepatic Nrf1 and Nrf2 activity was reduced in endotoxemia and sepsis, and deficiency for hepatic Nrf1, but not Nrf2, promoted severe hypothermia and mortality. Conversely, increasing hepatic Nrf1 activity mitigated hypothermia and improved survival. These effects were linked to very-low-density lipoprotein (VLDL) secretion and triglyceride metabolism. In endotoxemia, hepatic Nrf1 deficiency reduced VLDL secretion, whereas increased hepatic Nrf1 activity enhanced VLDL secretion. Administering a VLDL secretion inhibitor, lomitapide, or inhibitor of circulating triglyceride hydrolysis, poloxamer 407, diminished protective effects of hepatic Nrf1 activity, whereas administering intralipid rescued the lomitapide-injected mice. Gene expression profiling indicates Nrf1 promotes this effect by regulating stress-defense programming. CONCLUSIONS: Mortality in endotoxemia and sepsis is exacerbated by impaired hepatic Nrf1 activity. Interventions increasing hepatic Nrf1 activity promote liver defenses that protect against sepsis-associated hypothermia and mortality.
2. Diamine oxidase acts as a novel risk factor in abnormal inflammation via mediating "cytosolic ROS-autophagy-IFN-γ" axis in NK cells.
DAO acts intracellularly in NK cells to potentiate IFN-γ production via a cytosolic ROS–autophagy axis, and DAO deficiency protects mice from inflammatory pathology in LPS sepsis and colitis models. The ROS source is distinct from mitochondria and NOX2, and DAO does not alter NK homeostasis.
Impact: Identifies DAO as a novel intracellular regulator of NK-derived IFN-γ through ROS–autophagy signaling, revealing a druggable mechanism across hyperinflammatory states including sepsis.
Clinical Implications: Pharmacologic DAO inhibition may attenuate excessive IFN-γ responses in sepsis and other inflammatory diseases, warranting translational studies and safety assessment given DAO’s roles in histamine metabolism and gut integrity.
Key Findings
- DAO deficiency suppresses IFN-γ production and protects mice from inflammatory pathology in LPS-induced systemic inflammation and colitis.
- NK cells are the primary target; DAO functions intracellularly to drive IFN-γ via a ROS–autophagy axis.
- DAO-derived ROS are distinct from mitochondrial or NOX2 sources and enhance autophagic flux during NK activation.
- DAO does not affect NK maturation, proliferation, or receptor expression (homeostasis preserved).
Methodological Strengths
- Convergent evidence from multiple in vivo models (LPS sepsis, DSS colitis) and human PBMC bioinformatics
- Mechanistic dissection of ROS source and autophagy with cell-type specificity (NK cells)
Limitations
- Predominantly preclinical; human functional validation is limited to expression analyses.
- Pharmacologic DAO modulators require efficacy and safety testing in sepsis models and clinical settings.
Future Directions: Define drug-like DAO inhibitors suitable for systemic inflammation; validate in humanized models; assess biomarkers linking DAO activity to IFN-γ in septic patients.
AIMS: Diamine oxidase (DAO), a well-established biomarker for intestinal damage, histamine intolerance or tumorigenesis, has rarely been reported in immune regulation. This study aimed to identify DAO as a critical enhancer of abnormal inflammation by promoting interferon-gamma (IFN-γ) production from natural killer (NK) cells. MAIN METHODS: Clinical bioinformatics analyzed aoc1 (DAO-coding gene) expression in PBMCs from patients with inflammatory diseases. Murine models (LPS-induced systemic inflammation, sepsis, DSS-induced colitis) using DAO KEY FINDINGS: DAO deficiency protected mice from inflammatory pathology by suppressing IFN-γ production. NK cells were identified as the primary target cells during the process, with DAO acting intracellularly to promote IFN-γ via a reactive oxygen species (ROS)-autophagy axis. DAO-derived ROS, distinct from mitochondrial or NOX2 sources, enhanced autophagic flux during NK activation, enabling IFN-γ biosynthesis. DAO did not affect NK homeostasis, including maturation, proliferation, or receptor expressions. SIGNIFICANCE: DAO is a novel risk factor in inflammatory diseases, driving IFN-γ production through ROS-autophagy signaling in NK cells. Targeting DAO may offer therapeutic strategies for conditions involving dysregulated IFN-γ responses, including sepsis, colitis, and autoimmune disorders.
3. Off-label use of the BIOFIRE® Blood Culture Identification 2 Panel for multidrug-resistant bacteria colonization surveillance in critical care unit patients: A retrospective study.
Using off-label BCID2 testing on combined rectal/pharyngeal/nasal swabs, MDR colonization was detected with ~90% positive and negative agreement versus culture (κ=0.73), frequently identifying ESBL Enterobacterales and vanA/B E. faecium. This approach could accelerate isolation and tailor empiric antibiotics in critical care.
Impact: Demonstrates a rapid, pragmatic screening strategy for MDR colonization in ICU patients using an existing molecular panel, with potential to influence antimicrobial stewardship and infection control.
Clinical Implications: Implementing BCID2-based colonization screening could inform early isolation and narrower empiric therapy while awaiting cultures; however, local validation and cost-effectiveness analyses are necessary.
Key Findings
- BCID2 detected MDR organisms in 27.3% of specimens vs 21.9% by culture among 146 swabs from 130 ICU patients.
- Per-specimen positive and negative percentage agreement were 90.6% and 90.3%, respectively (κ=0.73).
- Most frequent MDR detections were ESBL-producing Enterobacterales and vanA/B-positive Enterococcus faecium.
Methodological Strengths
- Real-world ICU cohort with multiple anatomical swab sites and head-to-head comparison versus standard culture/AST
- Clear agreement metrics (PPA, NPA, kappa) and organism-level reporting
Limitations
- Single-center, retrospective design with modest sample size; off-label testing limits generalizability.
- No assessment of clinical outcomes (e.g., time to isolation, antibiotic changes, or sepsis outcomes).
Future Directions: Conduct multicenter prospective and NGS-validated studies to define accuracy, turnaround time benefits, and impact on antimicrobial use, transmission, and sepsis outcomes.
In this retrospective, single-center, observational study we assessed the performance of the BIOFIRE® Blood Culture Identification 2 (BCID2) Panel for the identification of multidrug-resistant bacteria (MDRB)-colonized critical care unit patients compared with a standard culture and antimicrobial susceptibility testing (AST)-based approach. A total of 146 rectal/pharyngeal/nasal combined specimens from 130 patients were tested by using the BCID2 panel. MDRB were detected in 40/146 (27.3%) specimens from 39 patients (30%) by the BCID2 panel; MDRB were recovered by culture in 32/146 (21.9%) specimens from 30 patients (23%). Concordance between the MDRB detected by the BCID2 panel and those recovered by culture was observed in 29/43 cases; MDRB were more frequently extended-spectrum beta-lactamase-harboring Enterobacterales or vanA/B-carrying Enterococcus faecium. The per specimen positive and negative percentage agreement values were 90.6% and 90.3%, respectively (Kappa value: 0.73). The BCID2 panel shows promise as a tool for the rapid identification of MDRB carriers in critical care units. Its use may lead to prescription of more refined empirical antimicrobial therapies on an individual basis and allow timely isolation of patients to prevent MDRB spreading. Nevertheless, larger, multicenter, prospective, and Next-generation sequencing-validated studies are needed to corroborate our findings.