Daily Sepsis Research Analysis
Mechanistic studies illuminate how oxidized cell-free hemoglobin triggers mitochondrial permeability transition and mtDNA release in pulmonary endothelium, while a natural product, Ophiopogonin C, attenuates sepsis-induced lung injury by disrupting DDX3X–NLRP3-driven macrophage pyroptosis. Clinically, a cohort analysis suggests that initiating metformin within 48–72 hours after septic shock in patients with type 2 diabetes is associated with markedly improved 90- and 365-day survival.
Summary
Mechanistic studies illuminate how oxidized cell-free hemoglobin triggers mitochondrial permeability transition and mtDNA release in pulmonary endothelium, while a natural product, Ophiopogonin C, attenuates sepsis-induced lung injury by disrupting DDX3X–NLRP3-driven macrophage pyroptosis. Clinically, a cohort analysis suggests that initiating metformin within 48–72 hours after septic shock in patients with type 2 diabetes is associated with markedly improved 90- and 365-day survival.
Research Themes
- Pyroptosis and inflammasome regulation in sepsis-induced lung injury
- Mitochondrial dysfunction and mtDNA DAMP signaling in vascular endothelium
- Adjunctive therapies and drug repurposing in septic shock
Selected Articles
1. Oxidized Cell-Free Hemoglobin Induces Mitochondrial Dysfunction by Activation of the Mitochondrial Permeability Transition Pore in the Pulmonary Microvasculature.
Oxidized CFH (CFH3+) in pulmonary endothelial cells triggered mPTP activation, disrupted mitochondrial networks, increased spare respiratory capacity, and induced mtDNA release, whereas CFH2+ did not. Circulating CFH correlated with mtDNA levels in critically ill patients, implicating CFH3+ as a driver of endothelial mitochondrial injury in sepsis.
Impact: This study identifies a redox-specific mechanism linking CFH oxidation to endothelial mitochondrial injury and mtDNA DAMP release, offering a concrete targetable pathway (mPTP/oxidative state) in sepsis-induced organ dysfunction.
Clinical Implications: Measuring CFH oxidation state and targeting mPTP or CFH redox cycling (e.g., antioxidants, heme-scavengers) could mitigate endothelial injury in sepsis-associated lung dysfunction.
Key Findings
- CFH3+, not CFH2+, activated the mitochondrial permeability transition pore and disrupted mitochondrial networks in human lung microvascular endothelial cells.
- CFH3+ increased spare respiratory capacity and induced mtDNA release; circulating CFH correlated with plasma mtDNA in critically ill patients.
- Findings implicate CFH3+ as the main driver of endothelial mitochondrial dysfunction in sepsis via mPTP activation.
Methodological Strengths
- Multi-modal assays (flow cytometry for mPTP, electron microscopy, Seahorse OCR, PCR for mtDNA) with convergent results
- Translation to human relevance via plasma mtDNA and CFH measurements in critically ill patients
Limitations
- Primarily in vitro endothelial models; absence of in vivo validation of mPTP blockade in sepsis
- Patient data are correlational and do not establish causality between CFH3+ and mtDNA release in vivo
Future Directions: Test pharmacologic mPTP inhibitors or CFH oxidation modulators in sepsis models and evaluate CFH3+/mtDNA as biomarkers for endothelial injury and therapeutic response.
OBJECTIVE: Cell-free hemoglobin (CFH) is released into the circulation during sepsis where it can redox cycle from the ferrous 2+ to ferric 3+ and disrupt endothelial function, but the mechanisms of CF-mediated endothelial dysfunction are unknown. We hypothesized that oxidized CFH induces mitochondrial dysfunction via the mitochondrial permeability transition pore (mPTP) in pulmonary endothelial cells, leading to the release of mitochondrial DNA (mtDNA). METHODS: Human lung microvascular endothelial cells were treated with CFH2+/CFH3+. We measured mitochondrial mPTP activation (flow cytometry), network and mass (immunostaining), structure (electron microscopy), mtDNA release (PCR), and oxygen consumption rate (OCR; Seahorse). Plasma from critically ill patients and conditioned cell media were quantified for mtDNA and CFH. RESULTS: CFH3+ disrupted the mitochondrial network, activated the mPTP (1434 (874-1642) vs. 2302 (1729-2654) mean fluorescent intensity, p = 0.02), increased the spare respiratory capacity (30.61 (29.36-37.78) vs. 7.83 (3.715-10.63) OCR, p = 0.004), and caused the release of mtDNA. CFH was associated with circulating mtDNA (R CONCLUSION: CFH3+, not CFH2+, is the primary driver of CFH-induced lung microvascular mitochondrial dysfunction. Activation of the mPTP and the release of mtDNA are a feature of CFH3+ mediated injury.
2. Ophiopogonin C protects against acute lung injury by fatal sepsis through pyroptosis macrophage.
In CLP-induced sepsis, Ophiopogonin C reduced macrophage inflammation and pyroptosis, attenuating ALI. Single-cell data showed DDX3X upregulation in macrophages from fatal sepsis, and Ophiopogonin C suppressed DDX3X expression and its interaction with NLRP3, including in human PBMCs, suggesting DDX3X–NLRP3 as a druggable axis.
Impact: It integrates in vivo efficacy with patient single-cell transcriptomics and mechanistic docking to nominate DDX3X–NLRP3 as a modifiable node in sepsis-induced ALI, positioning Ophiopogonin C as a lead compound.
Clinical Implications: The DDX3X–NLRP3 interface emerges as a therapeutic target to limit macrophage pyroptosis in sepsis-induced ALI; Ophiopogonin C or analogs warrant preclinical development and pharmacokinetic/toxicity profiling.
Key Findings
- Ophiopogonin C attenuated CLP-induced acute lung injury and reduced macrophage inflammation and pyroptosis.
- Single-cell RNA-seq indicated DDX3X upregulation in macrophages from fatal sepsis; Ophiopogonin C downregulated DDX3X and reduced DDX3X–NLRP3 interaction.
- Docking suggested Ophiopogonin C binds DDX3X at Asn-155, Arg-488, and Asp-506; it suppressed DDX3X/NLRP3 signaling and pyroptosis in LPS+ATP–stimulated human PBMCs.
Methodological Strengths
- Convergent evidence across animal model, human single-cell transcriptomics, and ex vivo PBMC assays
- Mechanistic interrogation of the DDX3X–NLRP3 interaction supported by molecular docking
Limitations
- Lack of direct biophysical validation (e.g., SPR/ITC) of Ophiopogonin C–DDX3X binding
- Pharmacokinetics, bioavailability, and safety of Ophiopogonin C in sepsis are not defined; survival outcomes not detailed
Future Directions: Quantify binding kinetics and structural interface of Ophiopogonin C–DDX3X, assess PK/toxicity, and test efficacy in survival-focused CLP models and large-animal studies.
BACKGROUND: Sepsis is a frequent complication of severe infection and trauma, and one of the common causes of acute lung injury (ALI). Macrophage pyroptosis plays an important role in sepsis-induced ALI, takes part in the regulation of the inflammatory response, and affects the damage and repair of lung tissue. PURPOSE: This study attempts to reveal the protective mechanism of Ophiopogonin C against fatal sepsis induced ALI. METHODS: Mice were induced by cecum ligation and puncture (CLP), and treated with 5 (Low), 10 (Med) or 20 (High) mg/kg/day of Ophiopogonin C. Meanwhile, Single-cell data was used to analyze the specific cell lines of Sepsis patients. Molecular docking model also used to identify Protein interaction analysis for DEAD-Box Helicase 3 X-linked gene (DDX3X) binding regions on Nucleotide-binding domain (NBD), leucine-rich repeat (LRR), and pyrin domain (PYD)-containing protein 3 (NLRP3). RESULTS: Ophiopogonin C protected against ALI in the sepsis model. Ophiopogonin C reduced inflammation of macrophage in the ALI sepsis model of ALI. Ophiopogonin C reduced pyroptosis macrophage in sepsis model of ALI. Pyroptosis macrophage is one important link for Ophiopogonin C in the ALI sepsis model. Ophiopogonin C suppressed NLRP3-induced pyroptosis macrophage in the ALI sepsis model. The up-regulation of DDX3X expression of macrophage in patients with fatal sepsis by Single-cell RNA sequencing. Ophiopogonin C suppressed DDX3X expression of macrophage in the ALI sepsis model. DDX3X is an important target spot for Ophiopogonin C in sepsis-induced ALI. Ophiopogonin C combined with the DDX3X protein at N-155 (Asn), R-488 (Arg), and d-506 (Asp) in macrophage. Ophiopogonin C reduced the interaction between the interconnection of DDX3X and NLRP3. Ophiopogonin C suppressed the DDX3X/ NLRP3 Signaling Pathway of human PBMCs by LPS+ATP through the inhibition of Pyroptosis. CONCLUSION: These findings demonstrated that Ophiopogonin C safeguards against fatal sepsis-induced ALI through suppressing pyroptosis in macrophages through mitigating the interaction between DDX3X and NLRP3. Moreover, it offers a potential therapeutic target for fatal sepsis by aiming at the interaction between DDX3X and NLRP3 with Ophiopogonin C.
3. Association of metformin administration after septic shock with short-term and long-term survival in septic shock patients with diabetes.
In 320 diabetic septic shock patients, initiating metformin within 48 hours was associated with substantially lower 90-day (aHR 0.371) and 365-day mortality (aHR 0.453) after adjustment. Similar associations were observed for initiation within 72 hours, supporting prospective trials of post-shock metformin.
Impact: This study addresses a practical, modifiable post-shock intervention and links it to both short- and long-term survival, supporting drug repurposing in a high-risk subgroup.
Clinical Implications: Consider early re-initiation or initiation of metformin after stabilization in diabetic septic shock patients with appropriate renal/hemodynamic status, while awaiting RCT confirmation.
Key Findings
- Metformin within 48 hours after septic shock was associated with lower 90-day (13.0% vs 39.8%) and 365-day mortality (23.3% vs 48.3%) and reduced in-hospital mortality.
- Adjusted analyses showed reduced risk: 90-day mortality aHR 0.371 (95% CI 0.153–0.900) and 365-day mortality aHR 0.453 (95% CI 0.219–0.937).
- Initiation within 72 hours showed similar survival benefits in multivariable models.
Methodological Strengths
- Prospectively collected registry with multivariable Cox adjustment
- Assessment of both short-term (90-day) and long-term (365-day) mortality outcomes
Limitations
- Single-center retrospective design with potential residual confounding and selection bias
- Indication bias possible; renal dysfunction/lactate thresholds for metformin initiation not detailed
Future Directions: Conduct multicenter randomized trials to test early post-shock metformin and define safety thresholds (renal function, lactate) and mechanisms (e.g., AMPK, mitochondrial effects).
BACKGROUND: In addition to glycemic control, the anti-inflammatory effects and protective effect of metformin on sepsis have been reported in animal studies, which may be beneficial for patients with septic shock. Few observational studies have evaluated metformin administration after sepsis or bacteremia; however, these studies did not specifically analyze septic shock or long-term outcomes. Therefore, this study aimed to evaluate the associations between metformin administration after septic shock and the short- and long-term survival in septic shock patients with type 2 diabetes mellitus. METHOD: This retrospective observational study used data from a prospectively collected sepsis registry. From October 2016 to June 2022, adult septic shock patients with type 2 diabetes mellitus were included in this study. The variable of interest was metformin administration within 48 h after diagnosis of septic shock. The 90-day mortality and 365-day mortality were evaluated as outcomes. A multivariable Cox proportional hazards model was conducted. RESULTS: A total of 320 patients were included in the study. Metformin administration within 48 h after diagnosis of septic shock was associated with lower 90-day mortality (13.0% vs. 39.8%, P < 0.001), 365-day mortality (23.3% vs. 48.3%, P = 0.001), and in-hospital mortality (9.3% vs. 28.6%, P = 0.002) than those who did not administer metformin within 48 h. Metformin administration within 48 h was independently associated with decreased 90-day mortality (adjusted hazard ratio [aHR]: 0.371, 95% confidence interval [CI]: 0.153-0.900, P = 0.028) and 365-day mortality (aHR 0.453, 95% CI 0.219-0.937, P = 0.033) after adjusting for potential confounders. Similar results were found for metformin administration within 72 h after septic shock (aHR 0.433, 95% CI 0.235-0.797, P = 0.007 for 90-day mortality and aHR 0.450, 95% CI 0.264-0.767, P = 0.003 for 365-day mortality). CONCLUSIONS: In septic shock patients with type 2 diabetes mellitus, metformin administration within 48 h was associated with lower 90-day and 365-day mortality. While these findings suggest potential benefits of metformin administration after septic shock, further large, multicenter studies are warranted.