Daily Sepsis Research Analysis
Three preclinical sepsis studies stand out today: a multi-compartment TLR4 study reveals immunometabolic reprogramming of macrophages and endothelial crosstalk in sepsis-induced lung injury; chlorolipid 2-chlorohexadecanoic acid directly modifies RhoA to drive endothelial barrier dysfunction; and a standardized mouse model reproduces key clinical and pathological features of sepsis-associated DIC. Together, they offer mechanistic targets and robust models to accelerate therapeutic development.
Summary
Three preclinical sepsis studies stand out today: a multi-compartment TLR4 study reveals immunometabolic reprogramming of macrophages and endothelial crosstalk in sepsis-induced lung injury; chlorolipid 2-chlorohexadecanoic acid directly modifies RhoA to drive endothelial barrier dysfunction; and a standardized mouse model reproduces key clinical and pathological features of sepsis-associated DIC. Together, they offer mechanistic targets and robust models to accelerate therapeutic development.
Research Themes
- Immunometabolic regulation and TLR4 signaling in sepsis-induced lung injury
- Endothelial barrier dysfunction via chlorolipid-mediated RhoA activation
- Standardized preclinical models for sepsis-associated disseminated intravascular coagulation
Selected Articles
1. Roles of TLR4 in macrophage immunity and macrophage-pulmonary vascular/lymphatic endothelial cell interactions in sepsis.
Using TLR4 knockout mice plus single-cell RNA-seq, the authors show that TLR4-deficient macrophages upregulate Abca1, increase cholesterol efflux, dampen glycolysis, and adopt M2 polarization, thereby attenuating inflammation and altering interactions with pulmonary endothelial and lymphatic endothelial cells. Endothelial TLR4 both sensitizes cells to LPS and determines susceptibility to macrophage-derived inflammatory signals. These data position TLR4 across macrophages and endothelium as a coordinated driver of sepsis-induced ALI.
Impact: This work integrates immunometabolic reprogramming with multi-cellular TLR4 signaling, providing mechanistic insight into how macrophages and endothelial compartments co-orchestrate lung injury in sepsis.
Clinical Implications: While preclinical, the findings suggest that therapies targeting TLR4 on both macrophages and endothelium, or modulating macrophage cholesterol efflux (e.g., ABCA1 pathways), could attenuate sepsis-induced lung injury.
Key Findings
- TLR4-deficient macrophages upregulate Abca1, enhance cholesterol efflux, reduce glycolysis, and shift toward M2 polarization.
- Macrophage metabolic and phenotypic changes modulate interactions with pulmonary ECs and LECs, attenuating inflammation.
- Endothelial TLR4 sensitizes cells to LPS and dictates susceptibility to macrophage-derived inflammatory signals, indicating multi-compartment TLR4 roles.
Methodological Strengths
- Integration of TLR4 knockout mouse models with single-cell RNA sequencing and experimental validation
- Cross-compartment analysis of macrophages, vascular endothelium, and lymphatic endothelium
Limitations
- Preclinical mouse study without human interventional validation
- Specificity of cell-type targeting strategies and potential off-target effects remain to be defined
Future Directions: Test selective, cell-targeted TLR4 inhibitors and ABCA1 modulators in sepsis models; translate signatures to human biospecimens to validate therapeutic windows.
In sepsis, acute lung injury (ALI) is a severe complication and a leading cause of death, involving complex mechanisms that include cellular and molecular interactions between immune and lung parenchymal cells. In recent decades, the role of Toll-like receptor 4 (TLR4) in mediating infection-induced inflammation has been extensively studied. However, how TLR4 facilitates interactions between innate immune cells and lung parenchymal cells in sepsis remains to be fully understood. This study aims to explore the role of TLR4 in regulating macrophage immunity and metabolism in greater depth. It also seeks to reveal how changes in these processes affect the interaction between macrophages and both pulmonary endothelial cells (ECs) and lymphatic endothelial cells (LECs). Using TLR4 knockout mice and the combined approaches of single-cell RNA sequencing and experimental validation, we demonstrate that in sepsis, TLR4-deficient macrophages upregulate Abca1, enhance cholesterol efflux, and reduce glycolysis, promoting M2 polarization and attenuating inflammation. These metabolic and phenotypic shifts significantly affect their interactions with pulmonary ECs and LECs. Mechanistically, we uncovered that TLR4 operates through multiple pathways in endothelial dysfunction: macrophage TLR4 mediates inflammatory damage to ECs/LECs, while endothelial TLR4 both directly sensitizes cells to lipopolysaccharide-induced injury and determines their susceptibility to macrophage-derived inflammatory signals. These findings reveal the complex role of TLR4 in orchestrating both immune-mediated and direct endothelial responses during sepsis-induced ALI, supporting that targeting TLR4 on multiple cell populations may present an effective therapeutic strategy.
2. Human lung microvascular endothelial cell protein modification by 2-chlorohexadecanoic acid: RhoA mediates 2-chlorohexadecanoic acid-elicited endothelial activation.
Using clickable 2-ClHA probes in HLMVECs, the study identified 11 proteins uniquely modified by 2-ClHA, with RhoA emerging as a central node. Pharmacologic inhibition of RhoA blocked 2-ClHA-induced endothelial barrier dysfunction and Ang-2 release, and 2-ClHA increased RhoA activity while saturated HA had no effect. These findings implicate a specific 2-ClHA–RhoA axis in endothelial activation relevant to sepsis-associated ARDS.
Impact: It mechanistically connects a sepsis-associated chlorolipid to a druggable small GTPase, offering a concrete pathway to target endothelial dysfunction central to lung injury.
Clinical Implications: Targeting RhoA signaling or upstream chlorolipid formation may mitigate endothelial injury and Ang-2-driven vascular leak in sepsis-induced ARDS; 2-ClHA could serve as a biomarker of endothelial activation.
Key Findings
- Identified 11 proteins uniquely modified by 2-chlorohexadecanoic acid in HLMVECs; RhoA was specifically modified by 2-ClHA but not by HA.
- RhoA inhibitors (Rhosin, C3) blocked 2-ClHA-induced endothelial barrier dysfunction and Ang-2 release.
- 2-ClHA increased RhoA activity, whereas saturated hexadecanoic acid did not activate RhoA or disrupt barrier function.
Methodological Strengths
- Click-chemistry tagging and proteomic mapping of lipidation targets in primary human endothelial cells
- Functional validation with pharmacologic inhibitors and barrier/secretory readouts
Limitations
- In vitro endothelial model without in vivo confirmation in sepsis models
- Causal linkage to clinical outcomes is inferred from prior associations of 2-ClHA with ARDS mortality
Future Directions: Validate the 2-ClHA–RhoA axis in animal sepsis/ARDS models and assess RhoA pathway inhibitors; longitudinally measure 2-ClHA and endothelial injury markers in patients.
Chlorolipids are produced during the neutrophil respiratory burst as a result of myeloperoxidase (MPO)-generated hypochlorous acid (HOCl) targeting the vinyl ether bond of plasmalogen phospholipids. The initial products of this reaction are 2-chlorofatty aldehydes (2-ClFALDs), which are subsequently oxidized to 2-chlorofatty acids (2-ClFAs). 2-Chlorohexadecanoic acid (2-ClHA) is the 16-carbon 2-ClFA species, and previous studies have shown that increased levels of plasma 2-ClHA associate with acute respiratory distress syndrome (ARDS)-caused mortality in human sepsis. 2-ClHA causes endothelial barrier dysfunction and increases neutrophil and platelet adherence to the endothelium. In this study, click chemistry analogs of 2-ClHA and hexadecanoic acid (HA) were used to identify proteins covalently modified by 2-ClHA and HA in human lung microvascular endothelial cells (HLMVECs). Eleven proteins were specifically modified by 2-ClHA, and an additional one hundred and ninety-four proteins were modified by both 2-ClHA and HA. STRING analysis of 2-ClHA-modified proteins revealed a network of proteins with RhoA as a hub. RhoA is one of the proteins specifically modified by 2-ClHA and not HA. The RhoA inhibitors, Rhosin and C3, inhibited both 2-ClHA-elicited HLMVEC barrier dysfunction and angiopoietin-2 (Ang-2) release from HLMVEC. Further studies showed 2-ClHA activates HLMVEC RhoA activity. The specificity of the 2-ClHA-RhoA pathway for endothelial activation was further confirmed since HA did not cause HLMVEC barrier dysfunction, Ang-2 release and RhoA activation. Collectively, these studies have identified multiple proteins modified exclusively by 2-ClHA in HLMVECs, including RhoA. These proteomics studies led to the key finding that RhoA is an important mediator of 2-ClHA-caused endothelial barrier dysfunction.
3. A mouse model of sepsis-associated DIC induced by Kappa-carrageenan and Lipopolysaccharides: Establishment and characteristics.
Combining kappa-carrageenan (100 mg/kg) with LPS (50 μg/kg) produced tail thrombosis, prolonged aPTT, hypocoagulability, and time-resolved inflammation and fibrinolysis inhibition, stabilizing by 12 hours with thrombi in tail, lung, and liver. Lower ambient temperature exacerbated thrombosis, and strain differences were defined (KM/BALB/c > ICR). This standardized model recapitulates key clinical-pathological features of sepsis-associated DIC.
Impact: Provides a reproducible, parameterized murine DIC model aligned with sepsis pathology, enabling mechanistic dissection and preclinical therapeutic testing.
Clinical Implications: Although preclinical, this model can accelerate evaluation of anticoagulant, antifibrinolytic, and anti-inflammatory interventions tailored to sepsis-associated DIC.
Key Findings
- Optimal KCG (100 mg/kg) + LPS (50 μg/kg) dosing induced tail thrombosis, prolonged aPTT, and hypocoagulability.
- Ambient temperature at 16±1°C worsened thrombosis and hypocoagulability versus 24±1°C; sex had similar responses.
- Time course showed early fibrinolysis inhibition (<1 h), evolving inflammation/ coagulopathy (1.5–24 h), and organ thrombi (tail, lung, liver) with dysfunction by 12 h; strain differences observed (KM/BALB/c > ICR).
Methodological Strengths
- Systematic optimization of dose, ambient temperature, sex, and strain with time-resolved phenotyping
- Multisite thrombus assessment and coagulation profiling including aPTT and hypocoagulability
Limitations
- Mouse model may not fully capture human DIC heterogeneity and comorbidities
- Therapeutic interventions were not tested within this report
Future Directions: Apply the model to evaluate anticoagulants, fibrinolytics, and immunomodulators; integrate omics to map coagulation–inflammation networks.
BACKGROUND: No animal models fully replicate the pathogenesis and clinical features of sepsis-associated disseminated intravascular coagulation (DIC), which hinders mechanistic understanding and treatment development. Kappa-carrageenan (KCG) and lipopolysaccharides (LPS) induce thrombosis and systemic inflammation in mice, respectively. The combination of LPS and KCG provides a promising method for establishing a mouse model of sepsis-associated DIC. OBJECTIVE: This study aimed to establish a standardized mouse model of sepsis-associated DIC using KCG and LPS. METHODS: Kunming (KM) mice were intraperitoneally injected with KCG (25-200 mg/kg) alone or in combination with LPS (50-1250 μg/kg) to determine optimal dose. The effects of ambient temperature, gender and mouse strains on the mouse model were evaluated. Time-dependent changes in the model were examined. RESULTS: The combined injection of KCG (100 mg/kg) and LPS (50 μg/kg) effectively induced tail thrombosis and prolonged activated partial thromboplastin time. Mice housed at 16 ± 1℃ exhibited more severe thrombosis and hypocoagulability than those at 24 ± 1℃. Male and female mice exhibited similar responses. Time-course analysis revealed inflammation and blood hypocoagulability beginning from 1.5 to 24 h, with fibrinolysis inhibition occurring within 1 h. Tail thrombosis and auricle petechial developed at 3 and 6 h, respectively, and stabilized by 12 h. Thrombi in the tail, lung and liver along with organ dysfunction were obeserved at 12 h. KM and BALB/c mice exhibited longer tail thrombi than Institute of Cancer Research (ICR) mice. KM mice showed more severe blood hypocoagulability than ICR and BALB/c mice. CONCLUSIONS: This study establishes a standardized mouse model of sepsis-associated DIC using KCG and LPS, which more accurately replicates the key clinical and pathological characteristics of sepsis-associated DIC compared to existing models. This model serves as a novelty and valuable tool for investigating the mechanisms of sepsis-associated DIC and therapeutic evaluation.