Daily Sepsis Research Analysis
Two mechanistic studies advance our understanding of sepsis vascular biology by identifying a Piezo1–BHLHE40–SLC7A11 axis that protects endothelium from ferroptosis and a TGR5 bile acid receptor pathway that silences macrophage hyperinflammation. A multicenter target-trial emulation shows that ICU transfer within 3 hours for septic shock is associated with lower in-hospital mortality, highlighting a system-level target for quality improvement.
Summary
Two mechanistic studies advance our understanding of sepsis vascular biology by identifying a Piezo1–BHLHE40–SLC7A11 axis that protects endothelium from ferroptosis and a TGR5 bile acid receptor pathway that silences macrophage hyperinflammation. A multicenter target-trial emulation shows that ICU transfer within 3 hours for septic shock is associated with lower in-hospital mortality, highlighting a system-level target for quality improvement.
Research Themes
- Endothelial mechanotransduction and ferroptosis in sepsis
- Bile acid receptor signaling and macrophage epigenetic silencing
- Critical care operations: early ICU transfer for septic shock
Selected Articles
1. Endothelial mechanosensitive transcription factor BHLHE40 induced by Piezo1 suppresses endothelial ferroptosis and inflammation via SLC7A11.
This study identifies a Piezo1-driven mechanotransduction pathway in endothelium where BHLHE40 transcriptionally upregulates SLC7A11 to prevent ferroptosis and dampen inflammation. Endothelial BHLHE40 overexpression mitigated LPS-induced lung vascular leakage and inflammatory responses in vivo, positioning this axis as a therapeutic target in sepsis-related vascular injury.
Impact: It uncovers a previously uncharted mechanotransduction-to-ferroptosis pathway with direct in vivo relevance to sepsis-induced vascular injury. Such a pathway could enable targeted therapies to preserve endothelial integrity during sepsis.
Clinical Implications: While preclinical, this axis suggests druggable nodes (Piezo1 signaling, BHLHE40, SLC7A11) to stabilize the endothelium in sepsis. It also motivates biomarker strategies around ferroptosis and endothelial injury.
Key Findings
- Shear stress activates Piezo1 leading to Ca2+/calcineurin-dependent NFAT2 nuclear translocation and formation of an NFAT2–HDAC1 complex that induces BHLHE40.
- BHLHE40 directly upregulates SLC7A11, enhancing cystine import, reducing ROS and lipid peroxidation, and conferring ferroptosis resistance in endothelial cells.
- Endothelial BHLHE40 overexpression attenuates LPS-induced lung vascular leakage, neutrophil infiltration, and pro-inflammatory cytokine release in vivo.
Methodological Strengths
- Mechanistic dissection across signaling, transcriptional regulation, and ferroptosis with in vitro and in vivo validation.
- Use of endothelial-specific overexpression to demonstrate causality in LPS-induced vascular injury.
Limitations
- Preclinical models may not capture heterogeneity of human sepsis and comorbid states.
- Therapeutic window, dosing, and safety of targeting this axis remain untested in humans.
Future Directions: Evaluate pharmacologic modulation (Piezo1 agonists/antagonists, BHLHE40 or SLC7A11 enhancers) in clinically relevant sepsis models; develop endothelial ferroptosis biomarkers; explore interactions with hemodynamics and vasopressor therapy.
Endothelial dysfunction-driven vascular inflammation underlies sepsis and atherosclerosis. Piezo1 serves as a central mediator for endothelial mechanotransduction and inflammatory homeostasis. Nevertheless, the transcriptional pathways linking mechanical sensing to anti-inflammatory protection and the exact composition of its downstream signaling cascade remain incompletely resolved. Here, we identify BHLHE40 as an endothelial mechanosensitive transcription factor induced by Piezo1 that coordinates ferroptosis resistance and inflammation suppression. Mechanistically, shear stress activates Piezo1, triggering Ca²⁺ influx and calcineurin-dependent NFAT2 nuclear translocation. NFAT2 recruits HDAC1 to form a transcriptional complex that directly drives BHLHE40 expression. BHLHE40 then binds the SLC7A11 promoter, upregulating this cystine transporter to inhibit ferroptosis. Rescued mitochondrial integrity, reduced ROS, and reversed lipid peroxidation demonstrated this phenomenon. Crucially, mice with endothelial-specific BHLHE40 overexpression attenuate LPS-induced lung vascular leakage, neutrophil infiltration, and pro-inflammatory cytokine release. Our work establishes the Piezo1/Ca²⁺/calcineurin/NFAT2-HDAC1/BHLHE40/SLC7A11 axis as a master mechanotransduction pathway that transcriptionally maintains endothelial homeostasis.
2. Bile acid receptor Tgr5 prevents macrophage hyperinflammation during bacterial sepsis through metabolic and epigenetic silencing.
The study demonstrates that the bile acid receptor TGR5 is induced in macrophages during stimulation and prevents hyperinflammatory responses in bacterial sepsis via metabolic and epigenetic silencing mechanisms. This positions TGR5 signaling as a tractable immunometabolic target to temper dysregulated innate immunity in sepsis.
Impact: Reveals an immunometabolic receptor-mediated mechanism controlling macrophage hyperinflammation in sepsis, suggesting repurposing or development of TGR5 agonists.
Clinical Implications: Pharmacologic activation of TGR5 could modulate macrophage responses in sepsis, potentially reducing cytokine-driven organ injury while aligning with bile acid and metabolic pathways.
Key Findings
- TGR5 expression is upregulated in macrophages upon stimulation and constrains hyperinflammation in bacterial sepsis.
- Macrophage hyperactivation is suppressed through metabolic and epigenetic silencing mechanisms downstream of TGR5.
- The findings support TGR5 as a targetable node to rebalance innate immunity during sepsis.
Methodological Strengths
- Integrates metabolic and epigenetic layers to explain receptor-mediated immune regulation.
- Focus on macrophage-specific mechanisms directly relevant to sepsis pathophysiology.
Limitations
- Abstract provides limited methodological and outcome details; full experimental breadth not visible.
- Translational applicability and dosing strategies for TGR5 modulation in humans remain to be determined.
Future Directions: Test selective TGR5 agonists in clinically relevant sepsis models; delineate epigenetic modifiers downstream of TGR5; assess interactions with bile acid pools and microbiome in sepsis.
Tgr5 is a membrane-bound bile acid receptor that negatively regulates immune cells, although the molecular mechanisms behind this observation remain elusive. Here we report that Tgr5 is upregulated in macrophages during stimulation with
3. Association between emergency department-to-intensive care unit transfer time and mortality in patients with septic shock: a target trial emulation with septic shock in South Korea.
In a multicenter target-trial emulation of 815 septic shock patients, ICU transfer within 3 hours was associated with lower in-hospital mortality, with risk increasing up to 6 hours and then plateauing. Benefits were strongest among patients needing ECMO or CRRT, underscoring the value of system-level strategies to reduce ED boarding.
Impact: Defines a concrete time threshold (≤3 hours) for ICU transfer associated with mortality benefit in septic shock, providing actionable guidance for ED and ICU operations.
Clinical Implications: Prioritize ICU transfer within 3 hours for septic shock, especially for patients likely to require ECMO/CRRT; implement operational metrics and early warning systems to reduce boarding delays.
Key Findings
- Median ED-to-ICU transfer time was 6.7 hours; only 7% transferred within 3 hours.
- ICU transfer within 3 hours was associated with lower in-hospital mortality (OR 0.48, 95% CI 0.24-0.94).
- Mortality risk increased with transfer delay up to 6 hours and then plateaued; benefits were most pronounced in patients needing ECMO or CRRT (interaction P=0.02).
Methodological Strengths
- Target trial emulation with multicenter prospective cohort and causal adjustment (IPTW, multivariable models).
- Use of restricted cubic splines to define delay thresholds and robust subgroup analyses.
Limitations
- Observational design with potential residual confounding and regional practice patterns (South Korea).
- Only a small proportion (7%) achieved transfer within 3 hours, which may affect precision.
Future Directions: Prospective implementation trials to test system changes reducing boarding; integration with early warning scores and resource triage; external validation across diverse health systems.
BACKGROUND: Emergency department (ED) overcrowding poses a global challenge, particularly for critically ill patients requiring intensive care unit (ICU) admission. Although delays in ICU transfer increase mortality in critically ill populations, the optimal timing for septic shock remains uncertain. METHODS: We conducted a target trial emulation using a prospective cohort of 815 septic shock patients from 19 Korean hospitals. Delayed ICU transfer was defined using restricted cubic splines. The primary outcome was in-hospital mortality. Multivariable logistic regression and inverse probability treatment weighting were used to adjust for confounders of age, sex, comorbidities, severity of illness, and mechanical ventilation use. Subgroup analyses were performed to assess the effect across patient characteristics. RESULTS: The median time of ED-to-ICU transfer was 6.7 hours (interquartile range, 4.7-11.4), and only 7% of patients were transferred within 3 hours. ICU transfer within 3 hours was associated with significantly lower in-hospital mortality (odds ratio, 0.48; 95% CI, 0.24-0.94) compared to later transfers. Mortality risk increased with elapsing time up to 6 hours and then plateaued. The benefit of early ICU transfer was consistent across subgroups but was particularly pronounced in patients requiring extracorporeal membrane oxygenation or continuous renal replacement therapy (P for interaction=0.02). CONCLUSIONS: Early ICU transfer within 3 hours significantly reduces mortality in patients with septic shock, with the greatest benefit observed in those requiring advanced organ support. These findings highlight the need for system-wide strategies to reduce ED boarding time and prioritize timely ICU admission for septic shock management.