Period of irreversible therapeutic intervention during sepsis correlates with phase of innate immune dysfunction

Enhancing SAPS-3 Predictive Accuracy with Initial, Peak, and Last Lactate Measurements in Septic Shock

Background/Objectives: Septic shock is a severe condition with high mortality necessitating precise prognostic tools for improved patient outcomes. This study aimed to evaluate the collective predictive value of the Simplified Acute Physiology Score 3 (SAPS-3) and lactate measurements (initial, peak, last, and clearance rates within the first 24 h) in patients with septic shock. Specifically, it sought to determine how these markers enhance predictive accuracy for 28-day mortality beyond SAPS-3 alone. Methods: This retrospective cohort study analyzed data from 66 septic shock patients at two ICUs of Vienna General Hospital (2017-2019). SAPS-3 and lactate levels (initial, peak, last measurement within 24 h, and 24 h clearance) were obtained from electronic health records. Logistic regression models were constructed to identify predictors of 28-day mortality, and receiver operating characteristic (ROC) curves assessed predictive accuracy. Results: Among 66 patients, 36 (55%) died within 28 days. SAPS-3 scores significantly differed between survivors and non-survivors (76 vs. 85 points; p = 0.016). First, last, and peak lactate were significantly higher in non-survivors compared to survivors (all p < 0.001). The combination of SAPS-3 and first lactate produced the highest predictive accuracy (AUC = 80.6%). However, 24 h lactate clearance was not predictive of mortality. Conclusions: Integrating SAPS-3 with lactate measurements, particularly first lactate, improves predictive accuracy for 28-day mortality in septic shock patients. First lactate serves as an early, robust prognostic marker, providing crucial information for clinical decision-making and care prioritization. Further large-scale studies are needed to refine these predictive tools and validate their efficacy in guiding treatment strategies.

Autophagy ablation in skeletal muscles worsens sepsis-induced muscle wasting, impairs whole-body metabolism, and decreases survival

Septic patients frequently develop skeletal muscle wasting and weakness, resulting in severe clinical consequences and adverse outcomes. Sepsis triggers sustained induction of autophagy, a key cellular degradative pathway, in skeletal muscles. However, the impact of enhanced autophagy on sepsis-induced muscle dysfunction remains unclear. Using an inducible and muscle-specific Atg7 knockout mouse model (Atg7iSkM-KO), we investigated the functional importance of skeletal muscle autophagy in sepsis using the cecal ligation and puncture model. Atg7iSkM-KO mice exhibited a more severe phenotype in response to sepsis, marked by severe muscle wasting, hypoglycemia, higher ketone levels, and a decreased in survival as compared to mice with intact Atg7. Sepsis and Atg7 deletion resulted in the accumulation of mitochondrial dysfunction, although sepsis did not further worsen mitochondrial dysfunction in Atg7iSkM-KO mice. Overall, our study demonstrates that autophagy inactivation in skeletal muscles triggers significant worsening of sepsis-induced muscle and metabolic dysfunctions and negatively impacts survival.

Mitochondrial protective effects caused by the administration of mefenamic acid in sepsis

The pathophysiology of sepsis may involve the activation of the NOD-type receptor containing the pyrin-3 domain (NLPR-3), mitochondrial and oxidative damages. One of the primary essential oxidation products is 8-oxoguanine (8-oxoG), and its accumulation in mitochondrial DNA (mtDNA) induces cell dysfunction and death, leading to the hypothesis that mtDNA integrity is crucial for maintaining neuronal function during sepsis. In sepsis, the modulation of NLRP-3 activation is critical, and mefenamic acid (MFA) is a potent drug that can reduce inflammasome activity, attenuating the acute cerebral inflammatory process. Thus, this study aimed to evaluate the administration of MFA and its implications for the reduction of inflammatory parameters and mitochondrial damage in animals submitted to polymicrobial sepsis. To test our hypothesis, adult male Wistar rats were submitted to the cecal ligation and perforation (CLP) model for sepsis induction and after receiving an injection of MFA (doses of 10, 30, and 50 mg/kg) or sterile saline (1 mL/kg). At 24 h after sepsis induction, the frontal cortex and hippocampus were dissected to analyze the levels of TNF-α, IL-1β, and IL-18; oxidative damage (thiobarbituric acid reactive substances (TBARS), carbonyl, and DCF-DA (oxidative parameters); protein expression (mitochondrial transcription factor A (TFAM), NLRP-3, 8-oxoG; Bax, Bcl-2 and (ionized calcium-binding adaptor molecule 1 (IBA-1)); and the activity of mitochondrial respiratory chain complexes. It was observed that the septic group in both structures studied showed an increase in proinflammatory cytokines mediated by increased activity in NLRP-3, with more significant oxidative damage and higher production of reactive oxygen species (ROS) by mitochondria. Damage to mtDNA it was also observed with an increase in 8-oxoG levels and lower levels of TFAM and NGF-1. In addition, this group had an increase in pro-apoptotic proteins and IBA-1 positive cells. However, MFA at doses of 30 and 50 mg/kg decreased inflammasome activity, reduced levels of cytokines and oxidative damage, increased bioenergetic efficacy and reduced production of ROS and 8-oxoG, and increased levels of TFAM, NGF-1, Bcl-2, reducing microglial activation. As a result, it is suggested that MFA induces protection in the central nervous system early after the onset of sepsis.

Persistence of Lipoproteins and Cholesterol Alterations after Sepsis: Implication for Atherosclerosis Progression

(1) Background: Sepsis is one of the most common critical care illnesses with increasing survivorship. The quality of life in sepsis survivors is adversely affected by several co-morbidities, including increased incidence of dementia, stroke, cardiac disease and at least temporary deterioration in cognitive dysfunction. One of the potential explanations for their progression is the persistence of lipid profile abnormalities induced during acute sepsis into recovery, resulting in acceleration of atherosclerosis. (2) Methods: This is a targeted review of the abnormalities in the long-term lipid profile abnormalities after sepsis; (3) Results: There is a well-established body of evidence demonstrating acute alteration in lipid profile (HDL-c ↓↓, LDL-C -c ↓↓). In contrast, a limited number of studies demonstrated depression of HDL-c levels with a concomitant increase in LDL-C -c in the wake of sepsis. VLDL-C -c and Lp(a) remained unaltered in few studies as well. Apolipoprotein A1 was altered in survivors suggesting abnormalities in lipoprotein metabolism concomitant to overall lipoprotein abnormalities. However, most of the studies were limited to a four-month follow-up and patient groups were relatively small. Only one study looked at the atherosclerosis progression in sepsis survivors using clinical correlates, demonstrating an acceleration of plaque formation in the aorta, and a large metanalysis suggested an increase in the risk of stroke or acute coronary event between 3% to 9% in sepsis survivors. (4) Conclusions: The limited evidence suggests an emergence and persistence of the proatherogenic lipid profile in sepsis survivors that potentially contributes, along with other factors, to the clinical sequel of atherosclerosis.

Regulation of the Nfkbiz Gene and Its Protein Product IkBζ in Animal Models of Sepsis and Endotoxic Shock

Sepsis is a life-threatening condition that arises from a poorly regulated inflammatory response to pathogenic organisms. Current treatments are limited to antibiotics, fluid resuscitation, and other supportive therapies. New targets for monitoring disease progression and therapeutic interventions are therefore critically needed. We previously reported that lipocalin-2 (Lcn2), a bacteriostatic mediator with potent proapoptotic activities, was robustly induced in sepsis. Other studies showed that Lcn2 was a predictor of mortality in septic patients. However, how Lcn2 is regulated during sepsis is poorly understood. We evaluated how IkBζ, an inducer of Lcn2, was regulated in sepsis using both the cecal ligation and puncture (CLP) and endotoxemia (lipopolysaccharide [LPS]) animal models. We show that Nfkbiz, the gene encoding IkBζ, was rapidly stimulated but, unlike Lcn2, whose expression persists during sepsis, mRNA levels of Nfkbiz decline to near basal levels several hours after its induction. In contrast, we observed that IkBζ expression remained highly elevated in septic animals following CLP but not LPS, indicating the occurrence of a CLP-specific mechanism that extends IkBζ half-life. By using an inhibitor of IkBζ, we determined that the expression of Lcn2 was largely controlled by IkBζ. Altogether, these data indicate that the high IkBζ expression in tissues likely contributes to the elevated expression of Lcn2 in sepsis. Since IkBζ is also capable of promoting or repressing other inflammatory genes, it might exert a central role in sepsis.

The Contribution of the Omentum to the Outcome From Sepsis: An Experimental Animal Study

The omentum is a large mesenchymal fibro-fatty tissue with remarkable healing capability. It is also rich in immune cells, including macrophages and lymphocytes, within particular structures named milky spots. Clinical observations indicate a high incidence of peritonitis after the removal of the omentum suggesting that it may play a role in sepsis. To test this possibility, male CD-1 mice underwent simultaneous omentectomy and cecal ligation and puncture (CLP), omentectomy-sham operation and CLP alone, and mortality was documented within 72 h post the insults. A significant increase in mortality was observed in mice subjected to omentectomy and CLP in comparison with CLP alone. Mortality was correlated with an increase in cytokine gene expression within the lung after omentectomy and CLP as opposed to CLP alone. However, no differences in bacterial load were observed within the peritoneum or blood between groups. To test the long-term effect of omentectomy, mice were subjected to omentum removal or sham operation, allowed to recover from surgery for 14 or 28 days, and then both were subjected to CLP. In these cases, no differences in mortality were observed between the groups suggesting that the lack of omentum triggers a compensatory mechanism. Finally, omentectomy and sham operation altered the composition of peritoneal immune cells with the disappearance of F4/80 macrophages and the appearance of a new population of F4/80 macrophages within 1 or 14 days post-surgery. The F4/80 positive cells reappeared after 28 days following the procedures. All of these observations suggest that the omentum plays an early role in the outcome from sepsis.

Kinin B1 receptor: a potential therapeutic target in sepsis-induced vascular hyperpermeability

Background

In sepsis, the endothelial barrier becomes incompetent, with the leaking of plasma into interstitial tissues. VE-cadherin, an adherens junction protein, is the gatekeeper of endothelial cohesion. Kinins, released during sepsis, induce vascular leakage and vasodilation. They act via two G-protein coupled receptors: B1 (B1R) and B2 (B2R). B1R is inducible in the presence of pro-inflammatory cytokines, endotoxins or after tissue injury. It acts at a later stage of sepsis and elicits a sustained inflammatory response. The aim of our study was to investigate the relationships between B1R and VE-cadherin destabilization in vivo in a later phase of sepsis.

Methods

Experimental, prospective study in a university research laboratory. We used a polymicrobial model of septic shock by cecal ligation and puncture in C57BL6 male mice or C57BL6 male mice that received a specific B1R antagonist (R-954). We studied the influence of B1R on sepsis-induced vascular permeability 30 h after surgery for several organs, and VE-cadherin expression in the lung and kidneys by injecting R-954 just before surgery. The 96-h survival was determined in mice without treatment or in animals receiving R-954 as a “prophylactic” regimen (a subcutaneous injection of 200 µg/kg, prior to CLP and 24 h after CLP), or as a “curative” regimen (injection of 100 µg/kg at H6, H24 and H48 post-surgery).

Results

B1R inactivation helps to maintain MAP above 65 mmHg but induces different permeability profiles depending on whether or not organ perfusion is autoregulated. In our model, VE-cadherin was destabilized in vivo during septic shock. At a late stage of sepsis, the B1R blockade reduced the VE-cadherin disruption by limiting eNOS activation. The survival rate for mice that received R-954 after sepsis induction was higher than in animals that received an antagonist as a prophylactic treatment.

Conclusions

B1R antagonizing reduced mortality in our model of murine septic shock by limiting the vascular permeability induced by VE-cadherin destabilization through maintenance of the macrohemodynamics, consequently limiting organ dysfunctions.

Extracellular CIRP induces macrophage endotoxin tolerance through IL-6R-mediated STAT3 activation

Extracellular cold-inducible RNA-binding protein (eCIRP) is a damage-associated molecular pattern, whose effect on macrophages is not entirely elucidated. Here we identified that eCIRP promotes macrophage endotoxin tolerance. Septic mice had higher serum levels of eCIRP; this was associated with a reduced ex vivo immune response of their splenocytes to LPS. Pretreatment of macrophages with recombinant murine CIRP (rmCIRP) resulted in a tolerance to LPS stimulation as demonstrated by a reduction of TNF-α production. We found that eCIRP increased phosphorylated STAT3 (p-STAT3) in macrophages. A STAT3 inhibitor, Stattic, rescued macrophages from rmCIRP-induced tolerance by restoring the release of TNF-α in response to LPS stimulation. We discovered strong binding affinity between eCIRP and IL-6 receptor (IL-6R) as revealed by Biacore, fluorescence resonance energy transfer (FRET), and their colocalization in macrophages by immunostaining assays. Blockade of IL-6R with its neutralizing Ab inhibited eCIRP-induced p-STAT3 and restored LPS-stimulated TNF-α release in macrophages. Incubation of macrophages with rmCIRP skewed them toward an M2 phenotype, while treatment with anti-IL-6R Ab prevented rmCIRP-induced M2 polarization. Thus, we have demonstrated that eCIRP activates p-STAT3 via a novel receptor, IL-6R, to promote macrophage endotoxin tolerance. Targeting eCIRP appears to be a new therapeutic option to correct immune tolerance in sepsis.

Early hyperbaric oxygen therapy improves survival in a model of severe sepsis

Sepsis is a major clinical challenge, with therapy limited to supportive interventions. Therefore, the search for novel remedial approaches is of great importance. We addressed whether hyperbaric oxygen therapy (HBOT) could improve the outcome of sepsis using an acute experimental mouse model. Sepsis was induced in male CD-1 mice by cecal ligation and puncture (CLP) tailored to result in 80-90% mortality within 72 h of the insult. After CLP, mice were randomized into two groups receiving HBOT or not at different times after the initial insult or subjected to multiple HBOT treatments. HBOT conditions were 98% oxygen pressurized to 2.4 atmospheres for 1 h. HBOT within 1 h after CLP resulted in 52% survival in comparison with mice that did not receive the treatment (13% survival). Multiple HBOT at 1 and 6 h or 1, 6, and 21 h displayed an increase in survival of >50%, but they were not significantly different from a single treatment after 1 h of CLP. Treatments at 6 or 21 h after CLP, excluding the 1 h of treatment, did not show any protective effect. Early HBO treatment did not modify bacterial counts after CLP, but it was associated with decreased expression of TNF-α, IL-6, and IL-10 expression in the liver within 3 h after CLP. The decrease of cytokine expression was reproduced in cultured macrophages after exposure to HBOT. Early HBOT could be of benefit in the treatment of sepsis, and the protective mechanism may be related to a reduction in the systemic inflammatory response.

Macrophage reprogramming by negatively charged membrane phospholipids controls infection

Extracellular vesicles (ECVs) are heterogeneous membrane-enclosed structures containing proteins, nucleic acids, and lipids that participate in intercellular communication by transferring their contents to recipient cells. Although most of the attention has been directed at the biologic effect of proteins and microRNA, the contribution of phospholipids present in ECVs on cellular activation has not been extensively addressed. We investigated the biologic effect of phosphatidylserine (PS) and phosphatidylcholine (PC), 2 phospholipids highly abundant in ECVs. A transcriptomic analysis revealed that ∼4700 genes were specifically modified by exposing peritoneal macrophages to PS or PC liposomes in vivo. Among them, the expression of several chemokines and cytokines was highly upregulated by PS liposome treatment, translating into a massive neutrophil infiltration of the peritoneum capable of neutralizing a septic polymicrobial insult. Both the l and d stereoisomers of PS induced the same response, suggesting that the effect was related to the negative charge of the phospholipid head. We concluded that an increase in the internal negative charge of the cell triggers a signaling cascade activating an innate immune response capable of controlling infection.-Cauvi, D. M., Hawisher, D., Dores-Silva, P. R., Lizardo, R. E., De Maio, A. Macrophage reprogramming by negatively charged membrane phospholipids controls infection.

The GTPase Rab1 Is Required for NLRP3 Inflammasome Activation and Inflammatory Lung Injury

Uncontrolled inflammatory response during sepsis predominantly contributes to the development of multiorgan failure and lethality. However, the cellular and molecular mechanisms for excessive production and release of proinflammatory cytokines are not clearly defined. In this study, we show the crucial role of the GTPase Ras-related protein in brain (Rab)1a in regulating the nucleotide binding domain-like receptor family, pyrin domain containing 3 (NLRP3) inflammasome activation and lung inflammatory injury. Expression of dominant negative Rab1 N124I plasmid in bone marrow-derived macrophages prevented the release of IL-1β and IL-18, NLRP3 inflammasome activation, production of pro-IL-1β and pro-IL-18, and attenuated TLR4 surface expression and NF-кB activation induced by bacterial LPS and ATP compared with control cells. In alveolar macrophage-depleted mice challenged with cecal ligation and puncture, pulmonary transplantation of Rab1a-inactivated macrophages by expression of Rab1 N124I plasmid dramatically reduced the release of IL-1β and IL-18, neutrophil count in bronchoalveolar lavage fluid, and inflammatory lung injury. Rab1a activity was elevated in alveolar macrophages from septic patients and positively associated with severity of sepsis and respiratory dysfunction. Thus, inhibition of Rab1a activity in macrophages resulting in the suppression of NLRP3 inflammasome activation may be a promising target for the treatment of patients with sepsis.

Why Antibiotic Treatment Is Not Enough for Sepsis Resolution: an Evaluation in an Experimental Animal Model

Sepsis remains a major health problem at the levels of mortality, morbidity, and economic burden to the health care system, a condition that is aggravated by the development of secondary conditions such as septic shock and multiple-organ failure. Our current understanding of the etiology of human sepsis has advanced, at least in part, due to the use of experimental animal models, particularly the model of cecum ligation and puncture (CLP). Antibiotic treatment has been commonly used in this model to closely mirror the treatment of human septic patients. However, whether their use may obscure the elucidation of the cellular and molecular mechanisms involved in the septic response is questionable. The objective of the present study was to determine the effect of antibiotic treatment in the outcome of a fulminant model of CLP. Various dosing strategies were used for the administration of imipenem, which has broad-spectrum coverage of enteric bacteria. No statistically significant differences in the survival of mice were observed between the different antibiotic dosing strategies and no treatment, suggesting that live bacteria may not be the only factor inducing septic shock. To further investigate this hypothesis, mice were challenged with sterilized or unsterilized cecal contents. We found that exposure of mice to sterilized cecal contents also resulted in a high mortality rate. Therefore, it is possible that bacterial debris, apart from bacterial proliferation, triggers a septic response and contributes to mortality in this model, suggesting that additional factors are involved in the development of septic shock.

Morphology-Independent Virulence of Candida Species during Polymicrobial Intra-abdominal Infections with Staphylococcus aureus

Intra-abdominal polymicrobial infections cause significant morbidity and mortality. An experimental mouse model of Candida albicans-Staphylococcus aureus intra-abdominal infection (IAI) results in 100% mortality by 48 to 72 h postinoculation, while monomicrobial infections are avirulent. Mortality is associated with robust local and systemic inflammation without a requirement for C. albicans morphogenesis. However, the contribution of virulence factors coregulated during the yeast-to-hypha transition is unknown. This also raised the question of whether other Candida species that are unable to form hyphae are as virulent as C. albicans during polymicrobial IAI. Therefore, the purpose of this study was to evaluate the ability of non-albicans Candida (NAC) species with various morphologies and C. albicans transcription factor mutants (efg1/efg1 and cph1/cph1) to induce synergistic mortality and the accompanying inflammation. Results showed that S. aureus coinoculated with C. krusei or C. tropicalis was highly lethal, similar to C. albicans, while S. aureus-C. dubliniensis, S. aureus-C. parapsilosis, and S. aureus-C. glabrata coinoculations resulted in little to no mortality. Local and systemic interleukin-6 (IL-6) and prostaglandin E2 (PGE2) levels were significantly elevated during symptomatic and/or lethal coinfections, and hypothermia strongly correlated with mortality. Coinoculation with C. albicans strains deficient in the transcription factor Efg1 but not Cph1 reversed the lethal outcome. These results support previous findings and demonstrate that select Candida species, without reference to any morphological requirement, induce synergistic mortality, with IL-6 and PGE2 acting as key inflammatory factors. Mechanistically, signaling pathways controlled by Efg1 are critical for the ability of C. albicans to induce mortality from an intra-abdominal polymicrobial infection.

Elevated expression of IL-23/IL-17 pathway-related mediators correlates with exacerbation of pulmonary inflammation during polymicrobial sepsis

Sepsis is a leading cause of death in the United States, claiming more than 215,000 lives every year. A primary condition observed in septic patients is the incidence of acute respiratory distress syndrome, which is characterized by the infiltration of neutrophils into the lung. Prior studies have shown differences in pulmonary neutrophil accumulation in C57BL/6J (B6) and A/J mice after endotoxic and septic shock. However, the mechanism by which neutrophils accumulate in the lung after polymicrobial sepsis induced by cecal ligation and puncture still remains to be fully elucidated. We show in this study that lung inflammation, characterized by neutrophil infiltration and expression of inflammatory cytokines, was aggravated in B6 as compared with A/J mice and correlated with a high expression of p19, the interleukin 23 (IL-23)-specific subunit. Furthermore, lipopolysaccharide stimulation of B6- and A/J-derived macrophages, one of the main producers of IL-23 and IL-12, revealed that B6 mice favored the production of IL-23, whereas A/J-derived macrophages expressed higher levels of IL-12. In addition, expression of IL-17, known to be upregulated by IL-23, was also more elevated in the lung of B6 mice when compared with that in the lung of A/J mice. In contrast, pulmonary expression of interferon-γ was much more pronounced in A/J than that in B6 mice, which was most likely a result of a higher production of IL-12. The expression of the IL-17-dependent neutrophil recruitment factors chemokine (CXC motif) ligand 2 and granulocyte colony-stimulating factor was also higher in B6 mice. Altogether, these results suggest that increased activation of the IL-23/IL-17 pathway has detrimental effects on sepsis-induced lung inflammation, whereas activation of the IL-12/interferon-γ pathway may lead, in contrast, to less pronounced inflammatory events. These two pathways may become possible therapeutic targets for the treatment of sepsis-induced acute respiratory distress syndrome.

Sustained expression of lipocalin-2 during polymicrobial sepsis

Sepsis is a major healthcare problem and a leading cause of death worldwide. There is no dependable diagnosis, and treatment for this condition remains mainly supportive. The etiology of sepsis is related to an overwhelming inflammatory response. In this regard, the antimicrobial protein lipocalin-2 (Lcn2) has been associated with several inflammatory conditions, but its contribution to polymicrobial sepsis is unclear. Polymicrobial sepsis was induced by cecal ligation and puncture (CLP), and Lcn2 mRNA levels and protein expression were measured in liver and lung tissues. We observed that Lcn2 expression was robustly induced in liver and lung of C57BL/6 J (B6) mice, and remained elevated during the stage of innate immune dysfunction observed in sepsis. This response was different in A/J mice, suggesting a contribution of the genetic background, probably due to differences in IL-10 expression between these two mouse strains. Indeed, IL-10 was found to regulate Lcn2 expression in both primary and J774A.1 macrophages. Thus, Lcn2 expression is highly regulated during CLP-induced sepsis, suggesting that this antimicrobial protein could have a role as a potential biomarker for the diagnosis of sepsis.

Post challenge inhibition of C3 and CD14 attenuates Escherichia coli-induced inflammation in human whole blood

Combined inhibition of CD14 and complement, two main inducers of the inflammatory response, have proved particularly effective in attenuating Gram-negative bacteria-induced inflammation. Approaching possible clinical relevance, we investigated the effect of such inhibition in a post-challenge setting. Human whole blood was anti-coagulated with lepirudin. Anti-CD14, compstatin (C3 inhibitor) and the combination thereof were added 5 min prior to or 5, 15 or 30 min after adding Escherichia coli. Total incubation time with Escherichia coli was 120 min. Cytokines, myeloperoxidase (MPO) and the terminal complement complex (TCC) were measured using multiplex technology and ELISA. Delayed combined inhibition significantly attenuated the inflammatory response. IL-1β, IL-8 and TNF-α were significantly inhibited in the range of 20-40%, even when adding the inhibitors with up to 30 min delay. IL-6 was significantly inhibited with 15 min delay, and MIP-1α and MPO with 5 min delay. Complement activation (TCC) was blocked completely at each time point compstatin was added, whereas the cytokines and MPO increased steadily between the time points. The combined regimen was significantly more effective than single inhibition in the pre-challenge setting. The attenuation of Escherichia coli-induced inflammation in a post-challenge setting suggests a potential therapeutic window for this treatment in sepsis.

A non-lethal traumatic/hemorrhagic insult strongly modulates the compartment-specific PAI-1 response in the subsequent polymicrobial sepsis

Introduction

Plasminogen activator inhibitor 1 (PAI-1) is a key factor in trauma- and sepsis-induced coagulopathy. We examined how trauma-hemorrhage (TH) modulates PAI-1 responses in subsequent cecal ligation and puncture (CLP)-induced sepsis, and the association of PAI-1 with septic outcomes.

Methods

Mice underwent TH and CLP 48 h later in three separate experiments. In experiment 1, mice were sacrificed pre- and post-CLP to characterize the trajectory of PAI-1 in plasma (protein) and tissues (mRNA). Post-CLP dynamics in TH-CLP (this study) and CLP-Only mice (prior study) were then compared for modulatory effects of TH. In experiment 2, to relate PAI-1 changes to outcome, mice underwent TH-CLP and were sampled daily and followed for 14 days to compare non-survivors (DEAD) and survivors (SUR). In experiment 3, plasma and tissue PAI-1 expression were compared between mice predicted to die (P-DIE) and to live (P-LIVE).

Results

In experiment 1, an early post-TH rise of circulating PAI-1 was contrasted by a delayed (post-TH) decrease of PAI-1 mRNA in organs. In the post-CLP phase, profiles of circulating PAI-1 were similar between TH-CLP and CLP-Only mice. Conversely, PAI-1 mRNA declined in the liver and heart of TH-CLP mice versus CLP-Only. In experiment 2, there were no DEAD/SUR differences in circulating PAI-1 prior to CLP. Post-CLP, circulating PAI-1 in DEAD was 2–4-fold higher than in SUR. PAI-1 increase heralded septic deaths up to 48 h prior but DEAD/SUR thrombomodulin (endothelial injury marker) levels were identical. In experiment 3, levels of circulating PAI-1 and its hepatic gene expression were higher in P-DIE versus P-LIVE mice and those increases closely correlated with liver dysfunction.

Conclusions

Trauma modulated septic PAI-1 responses in a compartment-specific fashion. Only post-CLP increases in circulating PAI-1 predicted septic outcomes. In posttraumatic sepsis, pre-lethal release of PAI-1 was mostly of hepatic origin and was independent of endothelial injury.