Preclinical septic shock research: why we need an animal ICU

A design specification for Critical Illness Digital Twins (CIDTs) to cure sepsis: responding to the National Academies of Sciences, Engineering and Medicine Report "Foundational Research Gaps and Future Directions for Digital Twins"

On December 15, 2023, The National Academies of Sciences, Engineering and Medicine (NASEM) released a report entitled: "Foundational Research Gaps and Future Directions for Digital Twins." The ostensible purpose of this report was to bring some structure to the burgeoning field of digital twins by providing a working definition and a series of research challenges that need to be addressed to allow this technology to fulfill its full potential. In the work presented herein we focus on five specific findings from the NASEM Report: 1) definition of a Digital Twin, 2) using "fit-for-purpose" guidance, 3) developing novel approaches to Verification, Validation and Uncertainty Quantification (VVUQ) of Digital Twins, 4) incorporating control as an explicit purpose for a Digital Twin and 5) using a Digital Twin to guide data collection and sensor development, and describe how these findings are addressed through the design specifications for a Critical Illness Digital Twin (CIDT) aimed at curing sepsis.

Inhibiting Eph/ephrin signaling reduces vascular leak and endothelial cell dysfunction in mice with sepsis

Sepsis is a life-threatening disease caused by a dysregulated host response to infection, resulting in 11 million deaths globally each year. Vascular endothelial cell dysfunction results in the loss of endothelial barrier integrity, which contributes to sepsis-induced multiple organ failure and mortality. Erythropoietin-producing hepatocellular carcinoma (Eph) receptors and their ephrin ligands play a key role in vascular endothelial barrier disruption but are currently not a therapeutic target in sepsis. Using a cecal ligation and puncture (CLP) mouse model of sepsis, we showed that prophylactic or therapeutic treatment of mice with EphA4-Fc, a decoy receptor and pan-ephrin inhibitor, resulted in improved survival and a reduction in vascular leak, lung injury, and endothelial cell dysfunction. EphA2-/- mice also exhibited reduced mortality and pathology after CLP compared with wild-type mice. Proteomics of plasma samples from mice with sepsis after CLP revealed dysregulation of a number of Eph/ephrins, including EphA2/ephrin A1. Administration of EphA4-Fc to cultured human endothelial cells pretreated with TNF-α or ephrin-A1 prevented loss of endothelial junction proteins, specifically VE-cadherin, with maintenance of endothelial barrier integrity. In children admitted to hospital with fever and suspected infection, we observed that changes in EphA2/ephrin A1 in serum samples correlated with endothelial and organ dysfunction. Targeting Eph/ephrin signaling may be a potential therapeutic strategy to reduce sepsis-induced endothelial dysfunction and mortality.

CD200Rhigh neutrophils with dysfunctional autophagy establish systemic immunosuppression by increasing regulatory T cells

Distinct neutrophil populations arise during certain pathological conditions. The generation of dysfunctional neutrophils during sepsis and their contribution to septicemia-related systemic immune suppression remain unclear. In this study, using an experimental sepsis model that features immunosuppression, we identified a novel population of pathogenic CD200Rhigh neutrophils that are generated during the initial stages of sepsis and contribute to systemic immune suppression by enhancing regulatory T (Treg) cells. Compared to their CD200Rlow counterparts, sepsis-generated CD200Rhigh neutrophils exhibit impaired autophagy and dysfunction, with reduced chemotactic migration, superoxide anion production, and TNF-α production. Increased soluble CD200 blocks autophagy and neutrophil maturation in the bone marrow during experimental sepsis, and recombinant CD200 treatment in vitro can induce neutrophil dysfunction similar to that observed in CD200Rhigh neutrophils. The administration of an α-CD200R antibody effectively reversed neutrophil dysfunction by enhancing autophagy and protecting against a secondary infection challenge, leading to increased survival. Transcriptome analysis revealed that CD200Rhigh neutrophils expressed high levels of Igf1, which elicits the generation of Treg cells, while the administration of an α-CD200R antibody inhibited Treg cell generation in a secondary infection model. Taken together, our findings revealed a novel CD200Rhigh neutrophil population that mediates the pathogenesis of sepsis-induced systemic immunosuppression by generating Treg cells.

Investigating the individual and combined effects of coenzyme Q10 and vitamin C on CLP-induced cardiac injury in rats

Sepsis-induced cardiac injury represents a major clinical challenge, amplifying the urgency for effective therapeutic interventions. This study aimed to delve into the individual and combined prophylactic effects of Vitamin C (Vit C) and Coenzyme Q10 (CoQ10) against inflammatory heart injury in a cecal ligation and puncture (CLP) induced polymicrobial sepsis rat model. Thirty adult female Sprague-Dawley rats were randomly divided into five groups: Control, CLP, Vitamin C, CoQ10, and Vit C + CoQ10, each consisting of six rats. Treatments were administered orally via gavage for 10 days prior to the operation. Eighteen hours post-sepsis induction, the animals were euthanized, and specimens were collected for analysis. The study examined variations in oxidative (TOS, OSI, MDA, MPO) and antioxidative markers (TAS, SOD, CAT, GSH), histopathological changes, inflammatory cytokine concentrations (TNF-α, IL-1β), nitric oxide (NO) dynamics, and cardiac indicators such as CK-MB. Impressively, the combined regimen markedly diminished oxidative stress, and antioxidative parameters reflected notable enhancements. Elevated NO levels, a central player in sepsis-driven inflammatory cascades, were effectively tempered by our intervention. Histological examinations corroborated the biochemical data, revealing diminished cardiac tissue damage in treated subjects. Furthermore, a marked suppression in pro-inflammatory cytokines was discerned, solidifying the therapeutic potential of our intervention. Interestingly, in certain evaluations, CoQ10 exhibited superior benefits over Vit C. Collectively, these findings underscore the potential therapeutic promise of Vit C and CoQ10 combination against septic cardiac injuries in rats.

Neutralization of extracellular histones by sodium-Β-O-methyl cellobioside sulfate in septic shock

BACKGROUND

Extracellular histones have been associated with severity and outcome in sepsis. The aim of the present study was to assess the effects of sodium-β-O-Methyl cellobioside sulfate (mCBS), a histone-neutralizing polyanion, on the severity and outcome of sepsis in an experimental model.

METHODS

This randomized placebo-controlled experimental study was performed in 24 mechanically ventilated female sheep. Sepsis was induced by fecal peritonitis. Animals were randomized to three groups: control, early treatment, and late treatment (n = 8 each). mCBS was given as a bolus (1 mg/kg) followed by a continuous infusion (1 mg/kg/h) just after sepsis induction in the early treatment group, and 4 h later in the late treatment group. Fluid administration and antimicrobial therapy were initiated 4 h T4 after feces injection, peritoneal lavage performed, and a norepinephrine infusion titrated to maintain mean arterial pressure (MAP) between 65-75 mmHg. The experiment was blinded and lasted maximum 24 h.

RESULTS

During the first 4 h, MAP remained > 65 mmHg in the early treatment group but decreased significantly in the others (p < 0.01 for interaction, median value at T4: (79 [70-90] mmHg for early treatment, 57 [70-90] mmHg for late treatment, and 55 [49-60] mmHg for the control group). mCBS-treated animals required significantly less norepinephrine to maintain MAP than controls (p < 0.01 for interaction) and had lower creatinine (p < 0.01), lactate (p < 0.01), and interleukin-6 (p < 0.01) levels, associated with reduced changes in H3.1 nucleosome levels (p = 0.02). Early treatment was associated with lower norepinephrine requirements than later treatment. Two control animals died; all the mCBS-treated animals survived.

CONCLUSIONS

Neutralization of extracellular histones with mCBS was associated with reduced norepinephrine requirements, improved tissue perfusion, less renal dysfunction, and lower circulating IL-6 in experimental septic shock and may represent a new therapeutic approach to be tested in clinical trials.

Sepsis-like Energy Deficit Is Not Sufficient to Induce Early Muscle Fiber Atrophy and Mitochondrial Dysfunction in a Murine Sepsis Model

Sepsis-induced myopathy is characterized by muscle fiber atrophy, mitochondrial dysfunction, and worsened outcomes. Whether whole-body energy deficit participates in the early alteration of skeletal muscle metabolism has never been investigated. Three groups were studied: “Sepsis” mice, fed ad libitum with a spontaneous decrease in caloric intake (n = 17), and “Sham” mice fed ad libitum (Sham fed (SF), n = 13) or subjected to pair-feeding (Sham pair fed (SPF), n = 12). Sepsis was induced by the intraperitoneal injection of cecal slurry in resuscitated C57BL6/J mice. The feeding of the SPF mice was restricted according to the food intake of the Sepsis mice. Energy balance was evaluated by indirect calorimetry over 24 h. The tibialis anterior cross-sectional area (TA CSA), mitochondrial function (high-resolution respirometry), and mitochondrial quality control pathways (RTqPCR and Western blot) were assessed 24 h after sepsis induction. The energy balance was positive in the SF group and negative in both the SPF and Sepsis groups. The TA CSA did not differ between the SF and SPF groups, but was reduced by 17% in the Sepsis group compared with the SPF group (p < 0.05). The complex-I-linked respiration in permeabilized soleus fibers was higher in the SPF group than the SF group (p < 0.05) and lower in the Sepsis group than the SPF group (p < 0.01). Pgc1α protein expression increased 3.9-fold in the SPF mice compared with the SF mice (p < 0.05) and remained unchanged in the Sepsis mice compared with the SPF mice; the Pgc1α mRNA expression decreased in the Sepsis compared with the SPF mice (p < 0.05). Thus, the sepsis-like energy deficit did not explain the early sepsis-induced muscle fiber atrophy and mitochondrial dysfunction, but led to specific metabolic adaptations not observed in sepsis.

Spontaneous Sepsis in Adult Horses: From Veterinary to Human Medicine Perspectives

Sepsis is a life-threatening disease defined as an organ dysfunction caused by a dysregulated host response to an infection. Early diagnosis and prognosis of sepsis are necessary for specific and timely treatment. However, no predictive biomarkers or therapeutic targets are available yet, mainly due to the lack of a pertinent model. A better understanding of the pathophysiological mechanisms associated with sepsis will allow for earlier and more appropriate management. For this purpose, experimental models of sepsis have been set up to decipher the progression and pathophysiology of human sepsis but also to identify new biomarkers or therapeutic targets. These experimental models, although imperfect, have mostly been performed on a murine model. However, due to the different pathophysiology of the species, the results obtained in these studies are difficult to transpose to humans. This underlines the importance of identifying pertinent situations to improve patient care. As humans, horses have the predisposition to develop sepsis spontaneously and may be a promising model for spontaneous sepsis. This review proposes to give first an overview of the different animal species used to model human sepsis, and, secondly, to focus on adult equine sepsis as a spontaneous model of sepsis and its potential implications for human and veterinary medicine.

Interactions between Gender and Sepsis—Implications for the Future

Sex and gender dimorphisms are found in a large variety of diseases, including sepsis and septic shock which are more prevalent in men than in women. Animal models show that the host response to pathogens differs in females and males. This difference is partially explained by sex polarization of the intracellular pathways responding to pathogen–cell receptor interactions. Sex hormones seem to be responsible for this polarization, although other factors, such as chromosomal effects, have yet to be investigated. In brief, females are less susceptible to sepsis and seem to recover more effectively than males. Clinical observations produce more nuanced findings, but men consistently have a higher incidence of sepsis, and some reports also claim higher mortality rates. However, variables other than hormonal differences complicate the interaction between sex and sepsis, including comorbidities as well as social and cultural differences between men and women. Conflicting data have also been reported regarding sepsis-attributable mortality rates among pregnant women, compared with non-pregnant females. We believe that unraveling sex differences in the host response to sepsis and its treatment could be the first step in personalized, phenotype-based management of patients with sepsis and septic shock.

Modeling sepsis, with a special focus on large animal models of porcine peritonitis and bacteremia

Infectious diseases, which often result in deadly sepsis or septic shock, represent a major global health problem. For understanding the pathophysiology of sepsis and developing new treatment strategies, reliable and clinically relevant animal models of the disease are necessary. In this review, two large animal (porcine) models of sepsis induced by either peritonitis or bacteremia are introduced and their strong and weak points are discussed in the context of clinical relevance and other animal models of sepsis, with a special focus on cardiovascular and immune systems, experimental design, and monitoring. Especially for testing new therapeutic strategies, the large animal (porcine) models represent a more clinically relevant alternative to small animal models, and the findings obtained in small animal (transgenic) models should be verified in these clinically relevant large animal models before translation to the clinical level.

Hepatic Peroxisome Proliferator-Activated Receptor Alpha Dysfunction in Porcine Septic Shock

Despite decades of research, sepsis remains one of the most urgent unmet medical needs. Mechanistic investigations into sepsis have mainly focused on targeting inflammatory pathways; however, recent data indicate that sepsis should also be seen as a metabolic disease. Targeting metabolic dysregulations that take place in sepsis might uncover novel therapeutic opportunities. The role of peroxisome proliferator-activated receptor alpha (PPARɑ) in liver dysfunction during sepsis has recently been described, and restoring PPARɑ signaling has proven to be successful in mouse polymicrobial sepsis. To confirm that such therapy might be translated to septic patients, we analyzed metabolic perturbations in the liver of a porcine fecal peritonitis model. Resuscitation with fluids, vasopressor, antimicrobial therapy and abdominal lavage were applied to the pigs in order to mimic human clinical care. By using RNA-seq, we detected downregulated PPARɑ signaling in the livers of septic pigs and that reduced PPARɑ levels correlated well with disease severity. As PPARɑ regulates the expression of many genes involved in fatty acid oxidation, the reduced expression of these target genes, concomitant with increased free fatty acids in plasma and ectopic lipid deposition in the liver, was observed. The results obtained with pigs are in agreement with earlier observations seen in mice and support the potential of targeting defective PPARɑ signaling in clinical research.

Myocardial effects of angiotensin II compared to norepinephrine in an animal model of septic shock

BACKGROUND

Angiotensin II is one of the vasopressors available for use in septic shock. However, its effects on the septic myocardium remain unclear. The aim of the study was to compare the effects of angiotensin II and norepinephrine on cardiac function and myocardial oxygen consumption, inflammation and injury in experimental septic shock.

METHODS

This randomized, open-label, controlled study was performed in 20 anesthetized and mechanically ventilated pigs. Septic shock was induced by fecal peritonitis in 16 animals, and four pigs served as shams. Resuscitation with fluids, antimicrobial therapy and abdominal drainage was initiated one hour after the onset of septic shock. Septic pigs were randomly allocated to receive one of the two drugs to maintain mean arterial pressure between 65 and 75 mmHg for 8 h.

RESULTS

There were no differences in MAP, cardiac output, heart rate, fluid balance or tissue perfusion indices in the two treatment groups but myocardial oxygen consumption was greater in the norepinephrine-treated animals. Myocardial mRNA expression of interleukin-6, interleukin-6 receptor, interleukin-1 alpha, and interleukin-1 beta was higher in the norepinephrine than in the angiotensin II group.

CONCLUSIONS

In septic shock, angiotensin II administration is associated with a similar level of cardiovascular resuscitation and less myocardial oxygen consumption, and inflammation compared to norepinephrine.

Of mice and men: Laboratory murine models for recapitulating the immunosuppression of human sepsis

Prolonged immunosuppression is increasingly recognized as the major cause of late phase and long-term mortality in sepsis. Numerous murine models with different paradigms, such as lipopolysaccharide injection, bacterial inoculation, and barrier disruption, have been used to explore the pathogenesis of immunosuppression in sepsis or to test the efficacy of potential therapeutic agents. Nonetheless, the reproducibility and translational value of such models are often questioned, owing to a highly heterogeneric, complex, and dynamic nature of immunopathology in human sepsis, which cannot be consistently and stably recapitulated in mice. Despite of the inherent discrepancies that exist between mice and humans, we can increase the feasibility of murine models by minimizing inconsistency and increasing their clinical relevance. In this mini review, we summarize the current knowledge of murine models that are most commonly used to investigate sepsis-induced immunopathology, highlighting their strengths and limitations in mimicking the dysregulated immune response encountered in human sepsis. We also propose potential directions for refining murine sepsis models, such as reducing experimental inconsistencies, increasing the clinical relevance, and enhancing immunological similarities between mice and humans; such modifications may optimize the value of murine models in meeting research and translational demands when applied in studies of sepsis-induced immunosuppression.

Chronic critical illness and post-intensive care syndrome: from pathophysiology to clinical challenges

Background

Post‐intensive care syndrome (PICS) encompasses physical, cognition, and mental impairments persisting after intensive care unit (ICU) discharge. Ultimately it significantly impacts the long‐term prognosis, both in functional outcomes and survival. Thus, survivors often develop permanent disabilities, consume a lot of healthcare resources, and may experience prolonged suffering. This review aims to present the multiple facets of the PICS, decipher its underlying mechanisms, and highlight future research directions.

Main text

This review abridges the translational data underlying the multiple facets of chronic critical illness (CCI) and PICS. We focus first on ICU-acquired weakness, a syndrome characterized by impaired contractility, muscle wasting, and persisting muscle atrophy during the recovery phase, which involves anabolic resistance, impaired capacity of regeneration, mitochondrial dysfunction, and abnormalities in calcium homeostasis. Second, we discuss the clinical relevance of post-ICU cognitive impairment and neuropsychological disability, its association with delirium during the ICU stay, and the putative role of low-grade long-lasting inflammation. Third, we describe the profound and persistent qualitative and quantitative alteration of the innate and adaptive response. Fourth, we discuss the biological mechanisms of the progression from acute to chronic kidney injury, opening the field for renoprotective strategies. Fifth, we report long-lasting pulmonary consequences of ARDS and prolonged mechanical ventilation. Finally, we discuss several specificities in children, including the influence of the child’s pre-ICU condition, development, and maturation.

Conclusions

Recent understandings of the biological substratum of the PICS’ distinct features highlight the need to rethink our patient trajectories in the long term. A better knowledge of this syndrome and precipitating factors is necessary to develop protocols and strategies to alleviate the CCI and PICS and ultimately improve patient recovery.

Mechanistic Understanding of Lung Inflammation: Recent Advances and Emerging Techniques

Acute respiratory distress syndrome (ARDS) is a life-threatening lung injury characterized by an acute inflammatory response in the lung parenchyma. Hence, it is considered as the most appropriate clinical syndrome to study pathogenic mechanisms of lung inflammation. ARDS is associated with increased morbidity and mortality in the intensive care unit (ICU), while no effective pharmacological treatment exists. It is very important therefore to fully characterize the underlying pathobiology and the related mechanisms, in order to develop novel therapeutic approaches. In vivo and in vitro models are important pre-clinical tools in biological and medical research in the mechanistic and pathological understanding of the majority of diseases. In this review, we will present data from selected experimental models of lung injury/acute lung inflammation, which have been based on clinical disorders that can lead to the development of ARDS and related inflammatory lung processes in humans, including ventilation-induced lung injury (VILI), sepsis, ischemia/reperfusion, smoke, acid aspiration, radiation, transfusion-related acute lung injury (TRALI), influenza, Streptococcus (S.) pneumoniae and coronaviruses infection. Data from the corresponding clinical conditions will also be presented. The mechanisms related to lung inflammation that will be covered are oxidative stress, neutrophil extracellular traps, mitogen-activated protein kinase (MAPK) pathways, surfactant, and water and ion channels. Finally, we will present a brief overview of emerging techniques in the field of omics research that have been applied to ARDS research, encompassing genomics, transcriptomics, proteomics, and metabolomics, which may recognize factors to help stratify ICU patients at risk, predict their prognosis, and possibly, serve as more specific therapeutic targets.

A Porcine Sepsis Model With Numerical Scoring for Early Prediction of Severity

Introduction

Sepsis can lead to organ dysfunctions with disturbed oxygen dynamics and life-threatening consequences. Since the results of organ-protective treatments cannot always be transferred from laboratory models into human therapies, increasing the translational potential of preclinical settings is an important goal. Our aim was to develop a standardized research protocol, where the progression of sepsis-related events can be characterized reproducibly in model experiments within clinically-relevant time frames.

Methods

Peritonitis was induced in anesthetized minipigs injected intraperitoneally with autofeces inoculum (n = 27) or with saline (sham operation; n = 9). The microbial colony-forming units (CFUs) in the inoculum were retrospectively determined. After awakening, clinically relevant supportive therapies were conducted. Nineteen inoculated animals developed sepsis without a fulminant reaction. Sixteen hours later, these animals were re-anesthetized for invasive monitoring. Blood samples were taken to detect plasma TNF-α, IL-10, big endothelin (bET), high mobility group box protein1 (HMGB1) levels and blood gases, and sublingual microcirculatory measurements were conducted. Hemodynamic, respiratory, coagulation, liver and kidney dysfunctions were detected to characterize the septic status with a pig-specific Sequential Organ Failure Assessment (pSOFA) score and its simplified version (respiratory, cardiovascular and renal failure) between 16 and 24 h of the experiments.

Results

Despite the standardized sepsis induction, the animals could be clustered into two distinct levels of severity: a sepsis (n = 10; median pSOFA score = 2) and a septic shock (n = 9; median pSOFA score = 8) subgroup at 18 h of the experiments, when the decreased systemic vascular resistance, increased DO₂ and VO₂, and markedly increased ExO₂ demonstrated a compensated hyperdynamic state. Septic animals showed severity-dependent scores for organ failure with reduced microcirculation despite the adequate oxygen dynamics. Sepsis severity characterized later with pSOFA scores was in correlation with the germ count in the induction inoculum (r = 0.664) and CFUs in hemocultures (r = 0.876). Early changes in plasma levels of TNF-α, bET and HMGB1 were all related to the late-onset organ dysfunctions characterized by pSOFA scores.

Conclusions

This microbiologically-monitored, large animal model of intraabdominal sepsis is suitable for clinically-relevant investigations. The methodology combines the advantages of conscious and anesthetized studies, and mimics human sepsis and septic shock closely with the possibility of numerical quantification of host responses.

Compartment-Specific Differences in the Activation of Monocyte Subpopulations Are Not Affected by Nitric Oxide and Glucocorticoid Treatment in a Model of Resuscitated Porcine Endotoxemic Shock

Inhaled nitric oxide (iNO) remains one of the treatment modalities in shock, and in addition to its vasoactive properties, iNO exerts immunomodulatory effects. We used a porcine model of endotoxemia with shock resuscitation (control) and additional treatment with iNO and a steroid (treatment group). After 20 h, bone marrow (BM), peripheral blood (PB), and bronchoalveolar lavage fluid (BALF) were collected to analyze the immunophenotype and mitochondrial membrane potential (Δφ) in three subsets of monocytes. In both groups, SLA-DR expression decreased twofold on the circulating CD14+CD163+ and CD14−CD163+ monocytes, while it did not change on the CD14+CD163+. Δφ increased only in the CD14−CD163+ subpopulation (0.8 vs. 2.0, p < 0.001). The analysis of compartment-specific alterations showed that nearly 100% of BALF CD14+CD163+ and CD14−CD163+ monocytes expressed SLA-DR, and it was higher compared to PB (32% and 20%, p < 0.0001) and BM (93% and 67%, p < 0.001, respectively) counterparts. BALF CD14+CD163+ had a threefold higher Δφ than PB and BM monocytes, while the Δφ of the other subsets was highest in PB monocytes. We confirmed the compartmentalization of the monocyte response during endotoxemic shock, which highlights the importance of studying tissue-resident cells in addition to their circulating counterparts. The iNO/steroid treatment did not further impair monocyte fitness.

Oxygen therapy for sepsis and prevention of complications

Patients with sepsis have a wide range of respiratory disorders that can be treated with oxygen therapy. Experimental data in animal sepsis models show that oxygen therapy significantly increases survival, while clinical data on the use of different oxygen therapy protocols are ambiguous. Oxygen therapy, especially hyperbaric oxygenation, in patients with sepsis can aggravate existing oxidative stress and contribute to the development of disseminated intravascular coagulation. The purpose of this article is to compare experimental and clinical data on oxygen therapy in animals and humans, to discuss factors that can influence the results of oxygen therapy for sepsis treatment in humans, and to provide some recommendations for reducing oxidative stress and preventing disseminated intravascular coagulation during oxygen therapy.

Transcriptional Response in a Sepsis Mouse Model Reflects Transcriptional Response in Sepsis Patients

Mortality due to sepsis remains unacceptably high, especially for septic shock patients. Murine models have been used to better understand pathophysiology mechanisms. However, the mouse model is still under debate. Herein we investigated the transcriptional response of mice injected with lipopolysaccharide (LPS) and compared it to either human cells stimulated in vitro with LPS or to the blood cells of septic patients. We identified a molecular signature composed of 2331 genes with an FDR median of 0%. This molecular signature is highly enriched in regulated genes in peritoneal macrophages stimulated with LPS. There is significant enrichment in several inflammatory signaling pathways, and in disease terms, such as pneumonia, sepsis, systemic inflammatory response syndrome, severe sepsis, an inflammatory disorder, immune suppression, and septic shock. A significant overlap between the genes upregulated in mouse and human cells stimulated with LPS has been demonstrated. Finally, genes upregulated in mouse cells stimulated with LPS are enriched in genes upregulated in human cells stimulated in vitro and in septic patients, who are at high risk of death. Our results support the hypothesis of common molecular and cellular mechanisms between mouse and human sepsis.

Visceral fat-specific regulation of plasminogen activator inhibitor-1 in aged septic mice

Elevated plasma levels of plasminogen activator inhibitor-1 (PAI-1) are documented in patients with sepsis and levels positively correlate with disease severity and mortality. Our previous work demonstrated that visceral adipose tissues (VAT) are a major source of PAI-1, especially in the aged (murine endotoxemia), that circulating PAI-1 protein levels match the trajectory of PAI-1 transcript levels in VAT (clinical sepsis), and that PAI-1 in both VAT and plasma are positively associated with acute kidney injury (AKI) in septic patients. In the current study utilizing preclinical sepsis models, PAI-1 tissue distribution was examined and cellular sources, as well as mechanisms mediating PAI-1 induction in VAT, were identified. In aged mice with sepsis, PAI-1 gene expression was significantly higher in VAT than in other major organs. VAT PAI-1 gene expression correlated with PAI-1 protein levels in both VAT and plasma. Moreover, VAT and plasma levels of PAI-1 were positively associated with AKI markers, modeling our previous clinical data. Using explant cultures of VAT, we determined that PAI-1 is secreted robustly in response to recombinant transforming growth factor β (TGFβ) and tumor necrosis factor α (TNFα) treatment; however, neutralization was effective only for TNFα indicating that TGFβ is not an endogenous modulator of PAI-1. Within VAT, TNFα was localized to neutrophils and macrophages. PAI-1 protein levels were fourfold higher in stromal vascular fraction (SVF) cells compared with mature adipocytes, and among SVF cells, both immune and nonimmune compartments expressed PAI-1 in a similar fashion. PAI-1 was localized predominantly to macrophages within the immune compartment and preadipocytes and endothelial cells within the nonimmune compartment. Collectively, these results indicate that induction and secretion of PAI-1 from VAT is facilitated by a complex interaction among immune and nonimmune cells. As circulating PAI-1 contributes to AKI in sepsis, understanding PAI-1 regulation in VAT could yield novel strategies for reducing systemic consequences of PAI-1 overproduction.

Impaired Glucocorticoid Receptor Signaling Aggravates Lung Injury after Hemorrhagic Shock

We previously showed that attenuated lung injury after hemorrhagic shock (HS) coincided with enhanced levels of the glucocorticoid (GC) receptor (GR) in lung tissue of swine. Here, we investigated the effects of impaired GR signaling on the lung during resuscitated HS using a dysfunctional GR mouse model (GR^dim/dim). In a mouse intensive care unit, HS led to impaired lung mechanics and aggravated lung inflammation in GR^dim/dim mice compared to wildtype mice (GR^+/+). After HS, high levels of the pro-inflammatory and pro-apoptotic transcription factor STAT1/pSTAT1 were found in lung samples from GR^dim/dim mice. Lungs of GR^dim/dim mice revealed apoptosis, most likely as consequence of reduced expression of the lung-protective Angpt1 compared to GR^+/+ after HS. RNA-sequencing revealed increased expression of pro-apoptotic and cytokine-signaling associated genes in lung tissue of GR^dim/dim mice. Furthermore, high levels of pro-inflammatory cytokines and iNOS were found in lungs of GR^dim/dim mice. Our results indicate impaired repression of STAT1/pSTAT1 due to dysfunctional GR signaling in GR^dim/dim mice, which leads to increased inflammation and apoptosis in the lungs. These data highlight the crucial role of functional GR signaling to attenuate HS-induced lung damage.

Protective Effects of Meldonium in Experimental Models of Cardiovascular Complications with a Potential Application in COVID-19

Right ventricular (RV) and left ventricular (LV) dysfunction is common in a significant number of hospitalized coronavirus disease 2019 (COVID-19) patients. This study was conducted to assess whether the improved mitochondrial bioenergetics by cardiometabolic drug meldonium can attenuate the development of ventricular dysfunction in experimental RV and LV dysfunction models, which resemble ventricular dysfunction in COVID-19 patients. Effects of meldonium were assessed in rats with pulmonary hypertension-induced RV failure and in mice with inflammation-induced LV dysfunction. Rats with RV failure showed decreased RV fractional area change (RVFAC) and hypertrophy. Treatment with meldonium attenuated the development of RV hypertrophy and increased RVFAC by 50%. Mice with inflammation-induced LV dysfunction had decreased LV ejection fraction (LVEF) by 30%. Treatment with meldonium prevented the decrease in LVEF. A decrease in the mitochondrial fatty acid oxidation with a concomitant increase in pyruvate metabolism was noted in the cardiac fibers of the rats and mice with RV and LV failure, respectively. Meldonium treatment in both models restored mitochondrial bioenergetics. The results show that meldonium treatment prevents the development of RV and LV systolic dysfunction by enhancing mitochondrial function in experimental models of ventricular dysfunction that resembles cardiovascular complications in COVID-19 patients.

Modulation of oxidative and nitrosative stress attenuates microvascular hyperpermeability in ovine model of Pseudomonas aeruginosa sepsis

In sepsis, microvascular hyperpermeability caused by oxidative/nitrosative stress (O&NS) plays an important role in tissue edema leading to multi-organ dysfunctions and increased mortality. We hypothesized that a novel compound R-107, a modulator of O&NS, effectively ameliorates the severity of microvascular hyperpermeability and preserves multi-organ function in ovine sepsis model. Sepsis was induced in twenty-two adult female Merino sheep by intravenous infusion of Pseudomonas aeruginosa (PA) (1 × 10¹⁰ CFUs). The animals were allocated into: 1) Control (n = 13): intramuscular injection (IM) of saline; and 2) Treatment (n = 9): IM of 50 mg/kg R-107. The treatment was given after the PA injection, and monitored for 24-h. R-107 treatment significantly reduced fluid requirement (15-24 h, P < 0.05), net fluid balance (9-24 h, P < 0.05), and water content in lung/heart/kidney (P = 0.02/0.04/0.01) compared to control. R-107 treatment significantly decreased lung injury score/modified sheep SOFA score at 24-h (P = 0.01/0.04), significantly lowered arterial lactate (21-24 h, P < 0.05), shed syndecan-1 (3-6 h, P < 0.05), interleukin-6 (6-12 h, P < 0.05) levels in plasma, and significantly attenuated lung tissue 3-nitrotyrosine and vascular endothelial growth factor-A expressions (P = 0.03/0.002) compared to control. There was no adverse effect in R-107 treatment. In conclusion, modulation of O&NS by R-107 reduced hyperpermeability markers and improved multi-organ function.

The Microcirculatory Response to Endotoxemia and Resuscitation Is a Marker of Regional Renal Perfusion, Renal Metabolic Stress, and Tubular Injury

Aims: We sought to investigate the relationship between macrohemodynamic resuscitation and microcirculatory parameters with the response of microcirculatory flow, tissue-specific parameters of metabolic stress and injury. We hypothesized that early resuscitation based on macrohemodynamic parameters does not prevent the development of organ dysfunction in a porcine model of endotoxemic shock, and that sublingual microcirculatory parameters are associated with markers of tissue metabolic stress and injury. Results: Both resuscitation groups had significant increases in creatinine and neutrophil gelatinase-associated lipocalin as compared with baseline. Neither the macrovascular response to endotoxemia or resuscitation, nor group allocation predicted the development of acute kidney injury (AKI). Only a microvascular flow index (MFI) <2.5 was associated with the development of renal tubular injury and AKI, and with increased renal, liver, peritoneal, and sublingual lactate/pyruvate (L/P) ratio and lactate. Among systemic parameters, only partial pressure of carbon dioxide (PCO₂) gap >6 and P(a-v)CO₂/C(v-a)O₂ >1.8 were associated with increased organ L/P ratio and AKI. Innovation and Conclusion: Our findings demonstrate that targeting macrohemodynamics to guide resuscitation during endotoxemic shock failed to predict tissue metabolic stress and the response of the microvasculature to resuscitation, and was unsuccessful in preventing tubular injury and AKI. Mechanistically, our data suggest that loss of hemodynamic coherence and decoupling of microvascular flow from tissue metabolic demand during endotoxemia may explain the lack of association between macrohemodynamics and perfusion goals. Finally, we demonstrate that MFI, PCO₂ gap, and P(v-a)CO₂/C(a-v)O₂ ratio outperformed macrohemodynamic parameters at predicting the development of renal metabolic stress and tubular injury, and therefore, that these indices merit further validation as promising resuscitation targets. Antioxid. Redox Signal. 35, 1407-1425.

Micafungin Population PK Analysis in Healthy and Septic Pigs: Can the Septic Porcine Model Predict the Micafungin PK in Septic Patients?

OBJECTIVES

To describe micafungin pharmacokinetic (PK) alterations of sepsis induced in piglets and to determine whether the porcine septic model is able to predict the PK of micafungin in septic patients at the plasma and peritoneal sites.

METHODS

From healthy (n = 8) and septic piglet group (n = 16), total micafungin concentrations were subject to a population PK analysis using Monolix®. Data from 16 septic humans patients from others studies was used to compare micafungin PK between septic piglets and septic patients.

RESULTS

Sepsis induced in piglets slightly alters the total clearance and the volume of distribution, while inter-compartment clearance is increased (from 3.88 to 5.74 L/h) as well as the penetration into peritoneal cavity (from 61 to 90%). In septic human patients, PK parameters are similar except for the Vd, which is corrected by an allometric factor based on the body weight of each species. Micafungin penetration into peritoneal cavity of humans is lower than in septic piglets (40 versus 90%).

CONCLUSIONS

The sepsis induced in the porcine model alters the PK of micafungin comparable to that in humans. In addition, micafungin PK is similar between these two species at the plasma level taking into account the allometric relationship of the body weight of these species on the central volume of distribution. The porcine septic plasma model would be able to predict the micafungin PK in the septic patients. However, further studies on peritoneal penetration are necessary to characterize this inter-species difference.

Localization of the hydrogen sulfide and oxytocin systems at the depth of the sulci in a porcine model of acute subdural hematoma

In the porcine model discussed in this review, the acute subdural hematoma was induced by subdural injection of autologous blood over the left parietal cortex, which led to a transient elevation of the intracerebral pressure, measured by bilateral neuromonitoring. The hematoma-induced brain injury was associated with albumin extravasation, oxidative stress, reactive astrogliosis and microglial activation in the ipsilateral hemisphere. Further proteins and injury markers were validated to be used for immunohistochemistry of porcine brain tissue. The cerebral expression patterns of oxytocin, oxytocin receptor, cystathionine-γ-lyase and cystathionine-β-synthase were particularly interesting: these four proteins all co-localized at the base of the sulci, where pressure-induced brain injury elicits maximum stress. In this context, the pig is a very relevant translational model in contrast to the rodent brain. The structure of the porcine brain is very similar to the human: the presence of gyri and sulci (gyrencephalic brain), white matter to grey matter proportion and tentorium cerebelli. Thus, pressure-induced injury in the porcine brain, unlike in the rodent brain, is reflective of the human pathophysiology.

A Pilot Double-Blind Placebo-Controlled Randomized Clinical Trial to Investigate the Effects of Early Enteral Nutrients in Sepsis

Supplemental Digital Content is available in the text.

Preclinical studies from our laboratory demonstrated therapeutic effects of enteral dextrose administration in the acute phase of sepsis, mediated by the intestine-derived incretin hormone glucose-dependent insulinotropic peptide. The current study investigated the effects of an early enteral dextrose infusion on systemic inflammation and glucose metabolism in critically ill septic patients.

Inducing Experimental Polymicrobial Sepsis by Cecal Ligation and Puncture

Numerous models are available for the preclinical study of sepsis, and they fall into one of three general categories: (1) administration of exogenous toxins (e.g., lipopolysaccharide, zymosan), (2) virulent bacterial or viral challenge, and (3) host barrier disruption, e.g., cecal ligation and puncture (CLP) or colon ascendens stent peritonitis (CASP). Of the murine models used to study the pathophysiology of sepsis, CLP combines tissue necrosis and polymicrobial sepsis secondary to autologous fecal leakage, as well as hemodynamic and biochemical responses similar to those seen in septic humans. Further, a transient numerical reduction of multiple immune cell types, followed by development of prolonged immunoparalysis, occurs in CLP-induced sepsis just as in humans. Use of the CLP model has led to a vast expansion in knowledge regarding the intricate physiological and cellular changes that occur during and after a septic event. This updated article details the steps necessary to perform this survival surgical technique, as well as some of the obstacles that may arise when evaluating the sepsis-induced changes within the immune system. It also provides representative monoclonal antibody (mAb) panels for multiparameter flow cytometric analysis of the murine immune system in the septic host. © 2020 Wiley Periodicals LLC. Basic Protocol: Cecal ligation and puncture in the mouse.

Inhaled bacteriophage therapy in a porcine model of pneumonia caused by Pseudomonas aeruginosa during mechanical ventilation

BACKGROUND AND PURPOSE 255: Pseudomonas aeruginosa is a main cause of ventilator-associated pneumonia (VAP) with drug-resistant bacteria. Bacteriophage therapy has experienced resurgence to compensate for the limited development of novel antibiotics. However, phage therapy is limited to a compassionate use so far, resulting from lack of adequate studies in relevant pharmacological models. We used a pig model of pneumonia caused by P. aeruginosa that recapitulates essential features of human disease to study the antimicrobial efficacy of nebulized-phage therapy.

EXPERIMENTAL APPROACH

(i) Lysis kinetic assays were performed to evaluate in vitro phage antibacterial efficacy against P. aeruginosa and select relevant combinations of lytic phages. (ii) The efficacy of the phage combinations was investigated in vivo (murine model of P. aeruginosa lung infection). (iii) We determined the optimal conditions to ensure efficient phage delivery by aerosol during mechanical ventilation. (iv) Lung antimicrobial efficacy of inhaled-phage therapy was evaluated in pigs, which were anaesthetized, mechanically ventilated and infected with P. aeruginosa.

KEY RESULTS

By selecting an active phage cocktail and optimizing aerosol delivery conditions, we were able to deliver high phage concentrations in the lungs, which resulted in a rapid and marked reduction in P. aeruginosa density (1.5-log reduction, p < .001). No infective phage was detected in the sera and urines throughout the experiment.

CONCLUSION AND IMPLICATIONS

Our findings demonstrated (i) the feasibility of delivering large amounts of active phages by nebulization during mechanical ventilation and (ii) rapid control of in situ infection by inhaled bacteriophage in an experimental model of P. aeruginosa pneumonia with high translational value.

Energetic dysfunction in sepsis: a narrative review

Background

Growing evidence associates organ dysfunction(s) with impaired metabolism in sepsis. Recent research has increased our understanding of the role of substrate utilization and mitochondrial dysfunction in the pathophysiology of sepsis-related organ dysfunction. The purpose of this review is to present this evidence as a coherent whole and to highlight future research directions.

Main text

Sepsis is characterized by systemic and organ-specific changes in metabolism. Alterations of oxygen consumption, increased levels of circulating substrates, impaired glucose and lipid oxidation, and mitochondrial dysfunction are all associated with organ dysfunction and poor outcomes in both animal models and patients. The pathophysiological relevance of bioenergetics and metabolism in the specific examples of sepsis-related immunodeficiency, cerebral dysfunction, cardiomyopathy, acute kidney injury and diaphragmatic failure is also described.

Conclusions

Recent understandings in substrate utilization and mitochondrial dysfunction may pave the way for new diagnostic and therapeutic approaches. These findings could help physicians to identify distinct subgroups of sepsis and to develop personalized treatment strategies. Implications for their use as bioenergetic targets to identify metabolism- and mitochondria-targeted treatments need to be evaluated in future studies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-021-00893-7.

Mitophagy coordinates the mitochondrial unfolded protein response to attenuate inflammation-mediated myocardial injury

Mitochondrial dysfunction is a fundamental challenge in septic cardiomyopathy. Mitophagy and the mitochondrial unfolded protein response (UPR^mt) are the predominant stress-responsive and protective mechanisms involved in repairing damaged mitochondria. Although mitochondrial homeostasis requires the coordinated actions of mitophagy and UPR^mt, their molecular basis and interactive actions are poorly understood in sepsis-induced myocardial injury. Our investigations showed that lipopolysaccharide (LPS)-induced sepsis contributed to cardiac dysfunction and mitochondrial damage. Although both mitophagy and UPR^mt were slightly activated by LPS in cardiomyocytes, their endogenous activation failed to prevent sepsis-mediated myocardial injury. However, administration of urolithin A, an inducer of mitophagy, obviously reduced sepsis-mediated cardiac depression by normalizing mitochondrial function. Interestingly, this beneficial action was undetectable in cardiomyocyte-specific FUNDC1 knockout (FUNDC1^CKO) mice. Notably, supplementation with a mitophagy inducer had no impact on UPR^mt, whereas genetic ablation of FUNDC1 significantly upregulated the expression of genes related to UPR^mt in LPS-treated hearts. In contrast, enhancement of endogenous UPR^mt through oligomycin administration reduced sepsis-mediated mitochondrial injury and myocardial dysfunction; this cardioprotective effect was imperceptible in FUNDC1^CKO mice. Lastly, once UPR^mt was inhibited, mitophagy-mediated protection of mitochondria and cardiomyocytes was partly blunted. Taken together, it is plausible that endogenous UPR^mt and mitophagy are slightly activated by myocardial stress and they work together to sustain mitochondrial performance and cardiac function. Endogenous UPR^mt, a downstream signal of mitophagy, played a compensatory role in maintaining mitochondrial homeostasis in the case of mitophagy inhibition. Although UPR^mt activation had no negative impact on mitophagy, UPR^mt inhibition compromised the partial cardioprotective actions of mitophagy. This study shows how mitophagy modulates UPR^mt to attenuate inflammation-related myocardial injury and suggests the potential application of mitophagy and UPR^mt targeting in the treatment of myocardial stress.

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Mitochondrial dysfunction is a fundamental challenge in septic cardiomyopathy.

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LPS-induced sepsis contributes to cardiac dysfunction and mitochondrial damage.

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Endogenous UPR^mt and mitophagy could be slightly activated by myocardial stress.

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Mitophagy modulates UPR^mt to attenuate inflammation-related myocardial injury.

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Mitophagy and UPR^mt targeting can be applied in treatment of myocardial stress.

Thiosulfinate-Enriched Allium sativum Extract as an Adjunct to Antibiotic Treatment of Sepsis in a Rat Peritonitis Model

Up to now, there are no studies that have shown a decrease in morbidity and mortality in the context of sepsis and septic shock, except for antibiotic therapy and the objective-guided resuscitation strategy. The goal was to evaluate the use of thiosulfinate-enriched Allium sativum extract (TASE) as an adjuvant in the management of sepsis. An experimental in vivo study was carried out with male Sprague Dawley® rats. Animals were randomized in three treatment groups: the control group (I), antibiotic (ceftriaxone) treatment group (II) and ceftriaxone plus TASE treatment group (III). All animals were housed and inoculated with 1 × 1010 CFU/15 mL of intraperitoneal Escherichia coli ATCC 25922. Subsequently, they received a daily treatment according to each group for 7 days. Clinical, analytical, microbiological, and histopathological parameters were evaluated. Statistically significant clinical improvement was observed in the ceftriaxone plus TASE vs. ceftriaxone group in weight, ocular secretions, whiskers separation and physical activity level (p ≤ 0.05). When comparing interleukins on the third day of treatment between II and III, we found statistically significant differences in IL-1 levels (p < 0.05). Blood and peritoneal liquid cultures of group I were positive for multisensitive E. coli. Group II and III cultures were negative for E. coli, although an overgrowth of Enterococcus faecalis was found. In conclusion, TASE used as an adjuvant to antibiotic treatment in the management of sepsis could improve response profiles with sepsis attenuation, thus reducing overall mortality after an animal peritonitis model.

Emerging mechanisms of immunocoagulation in sepsis and septic shock

Sepsis and septic shock driven by microbial infections are still among the most challenging health problems, causing 11 million deaths worldwide every year. How does the host's response to pathogen infections effectively restore homeostasis instead of precipitating pathogenic and potentially fatal feedforward reactions? Recently, there have been significant new advances in our understanding of the interface between mammalian immunity and coagulation ('immunocoagulation') and its impact on sepsis. In particular, the release and activation of F3 (the main initiator of coagulation) from and on myeloid or epithelial cells is facilitated by activating inflammasomes and consequent gasdermin D (GSDMD)-mediated pyroptosis, coupled to signaling via high mobility group box 1 (HMGB1), stimulator of interferon response CGAMP interactor 1 (STING1), or sequestosome 1 (SQSTM1). Pharmacological modulation of the immunocoagulation pathways emerge as novel and potential therapeutic strategies for sepsis.

Bridging animal and clinical research during SARS-CoV-2 pandemic: A new-old challenge

Many milestones in medical history rest on animal modeling of human diseases. The SARS-CoV-2 pandemic has evoked a tremendous investigative effort primarily centered on clinical studies. However, several animal SARS-CoV-2/COVID-19 models have been developed and pre-clinical findings aimed at supporting clinical evidence rapidly emerge. In this review, we characterize the existing animal models exposing their relevance and limitations as well as outline their utility in COVID-19 drug and vaccine development. Concurrently, we summarize the status of clinical trial research and discuss the novel tactics utilized in the largest multi-center trials aiming to accelerate generation of reliable results that may subsequently shape COVID-19 clinical treatment practices. We also highlight areas of improvement for animal studies in order to elevate their translational utility. In pandemics, to optimize the use of strained resources in a short time-frame, optimizing and strengthening the synergy between the preclinical and clinical domains is pivotal.

Does remote ischaemic conditioning reduce inflammation? A focus on innate immunity and cytokine response

The benefits of remote ischaemic conditioning (RIC) have been difficult to translate to humans, when considering traditional outcome measures, such as mortality and heart failure. This paper reviews the recent literature of the anti-inflammatory effects of RIC, with a particular focus on the innate immune response and cytokine inhibition. Given the current COVID-19 pandemic, the inflammatory hypothesis of cardiac protection is an attractive target on which to re-purpose such novel therapies. A PubMed/MEDLINE™ search was performed on July 13th 2020, for the key terms RIC, cytokines, the innate immune system and inflammation. Data suggest that RIC attenuates inflammation in animals by immune conditioning, cytokine inhibition, cell survival and the release of anti-inflammatory exosomes. It is proposed that RIC inhibits cytokine release via a reduction in nuclear factor kappa beta (NF-κB)-mediated NLRP3 inflammasome production. In vivo, RIC attenuates pro-inflammatory cytokine release in myocardial/cerebral infarction and LPS models of endotoxaemia. In the latter group, cytokine inhibition is associated with a profound survival benefit. Further clinical trials should establish whether the benefits of RIC in inflammation can be observed in humans. Moreover, we must consider whether uncomplicated MI and elective surgery are the most suitable clinical conditions in which to test this hypothesis.

Rethinking animal models of sepsis - working towards improved clinical translation whilst integrating the 3Rs

Sepsis is a major worldwide healthcare issue with unmet clinical need. Despite extensive animal research in this area, successful clinical translation has been largely unsuccessful.

We propose one reason for this is that, sometimes, the experimental question is misdirected or unrealistic expectations are being made of the animal model.

As sepsis models can lead to a rapid and substantial suffering – it is essential that we continually review experimental approaches and undertake a full harm:benefit impact assessment for each study. In some instances, this may require refinement of existing sepsis models. In other cases, it may be replacement to a different experimental system altogether, answering a mechanistic question whilst aligning with the principles of reduction, refinement and replacement (3Rs).

We discuss making better use of patient data to identify potentially useful therapeutic targets which can subsequently be validated in preclinical systems. This may be achieved through greater use of construct validity models, from which mechanistic conclusions are drawn. We argue that such models could provide equally useful scientific data as face validity models, but with an improved 3Rs impact. Indeed, construct validity models may not require sepsis to be modelled, per se. We propose that approaches that could support and refine clinical translation of research findings, whilst reducing the overall welfare burden on research animals.

Mouse Intensive Care Unit (MICU)

The translation of preclinical results into successful clinical therapies remains a challenge in sepsis research. One reason for this lack of translation might be the discrepancy between preclinical models and the clinical reality: nonresuscitated young healthy rodents in contrast to elderly comorbid patients in an intensive care unit. We introduce the mouse intensive care unit (MICU) as a concept to address the lack of resuscitation in preclinical studies as one of the limiting issues in translational research. The MICU reflects standard procedures of the clinical intensive care unit: fluid resuscitation, lung-protective mechanical ventilation, and hemodynamic monitoring and management, all tailored to organ- and function-specific targets. Thus, the MICU gives an experimental animal the intermediate possibility of recovery and survival due to "patient" management, which is not reflected in less complex experimental scenarios, which either result in acute survival or death.

Multiplex Fluorescent Bead-Based Immunoassay for the Detection of Cytokines, Chemokines, and Growth Factors

The comprehensive analysis of serum cytokine levels can be challenging due to low sample volumes and time consuming when using single-target methods like enzyme-linked immunosorbent assay (ELISA). Bead-based detection systems allow the simultaneous detection of multiple analytes using minimal sample volumes. Here we describe the use of a multiplex cytokine, chemokine, and growth factor assay for mouse cytokines in a 96-well format. This assay is based on antibody-coupled fluorescent magnetic beads combined with biotinylated secondary detection antibody followed by fluorescent-tagged streptavidin in a sandwich-like composition. Final assay readout provides the concentrations of 23 different cytokines, chemokines, and growth factors in up to 76 samples.

Phenylmethimazole is a candidate drug for the treatment of severe forms of coronavirus disease 2019 (COVID-19) as well as other virus-induced "cytokines storm"

Severe forms of the Coronavirus disease 2019 (COVID-19) are characterized by an enhanced inflammatory syndrome called “cytokine storm” that produces an aberrant release of high amounts of cytokines, chemokines, and other proinflammatory mediators. The pathogenetic role of the “cytokine storm” has been confirmed by the efficacy of immunosuppressive drugs such as corticosteroids along with antiviral drugs in the treatment of the severe forms of this disease.

Phenylmethimazole (C10) is a derivative of methimazole with anti-inflammatory properties. Studies performed both in vitro and in vivo have shown that C10 is able to block the production of multiple cytokines, chemokines, and other proinflammatory molecules involved in the pathogenesis of inflammation. Particularly, C10 is effective in reducing the increased secretion of cytokines in animal models of endotoxic shock. We hypothesize that these effects are not limited to the endotoxic shock, but can also be applied to any disease characterized by the presence of a “cytokine storm”. Therefore, C10 may be a potential drug to be used alternatively or in association with the corticosteroids or other immunosuppressive agents in the severe forms of COVID-19 as well as other viral diseases that induce a “cytokine storm”. Preclinical and clinical studies have to be performed to confirm this hypothesis.

New Approaches to Identify Sepsis Biomarkers: The Importance of Model and Sample Source for Mass Spectrometry

Septic shock is a systemic inflammatory response syndrome associated with circulatory failure leading to organ failure with a 40% mortality rate. Early diagnosis and prognosis of septic shock are necessary for specific and timely treatment. However, no predictive biomarker is available. In recent years, improvements in proteomics-based mass spectrometry have improved the detection of such biomarkers. This approach can be performed on different samples such as tissue or biological fluids. Working directly from human samples is complicated owing to interindividual variability. Indeed, patients are admitted at different stages of disease development and with signs of varying severity from one patient to another. All of these elements interfere with the identification of early, sensitive, and specific septic shock biomarkers. For these reasons, animal models of sepsis, although imperfect, are used to control the kinetics of the development of the pathology and to standardise experimentation, facilitating the identification of potential biomarkers. These elements underline the importance of the choice of animal model used and the sample to be studied during preclinical studies. The aim of this review is to discuss the relevance of different approaches to enable the identification of biomarkers that could indirectly be relevant to the clinical setting.

H2S in acute lung injury: a therapeutic dead end(?)

This review addresses the plausibility of hydrogen sulfide (H₂S) therapy for acute lung injury (ALI) and circulatory shock, by contrasting the promising preclinical results to the present clinical reality. The review discusses how the narrow therapeutic window and width, and potentially toxic effects, the route, dosing, and timing of administration all have to be balanced out very carefully. The development of standardized methods to determine in vitro and in vivo H₂S concentrations, and the pharmacokinetics and pharmacodynamics of H₂S-releasing compounds is a necessity to facilitate the safety of H₂S-based therapies. We suggest the potential of exploiting already clinically approved compounds, which are known or unknown H₂S donors, as a surrogate strategy.

Comparison of direct and indirect models of early induced acute lung injury

Background

The animal experimental counterpart of human acute respiratory distress syndrome (ARDS) is acute lung injury (ALI). Most models of ALI involve reproducing the clinical risk factors associated with human ARDS, such as sepsis or acid aspiration; however, none of these models fully replicates human ARDS.

Aim

To compare different experimental animal models of ALI, based on direct or indirect mechanisms of lung injury, to characterize a model which more closely could reproduce the acute phase of human ARDS.

Materials and methods

Adult male Sprague-Dawley rats were subjected to intratracheal instillations of (1) HCl to mimic aspiration of gastric contents; (2) lipopolysaccharide (LPS) to mimic bacterial infection; (3) HCl followed by LPS to mimic aspiration of gastric contents with bacterial superinfection; or (4) cecal ligation and puncture (CLP) to induce peritonitis and mimic sepsis. Rats were sacrificed 24 h after instillations or 24 h after CLP.

Results

At 24 h, rats instilled with LPS or HCl-LPS had increased lung permeability, alveolar neutrophilic recruitment and inflammatory markers (GRO/KC, TNF-α, MCP-1, IL-1β, IL-6). Rats receiving only HCl or subjected to CLP had no evidence of lung injury.

Conclusions

Rat models of ALI induced directly by LPS or HCl-LPS more closely reproduced the acute phase of human ARDS than the CLP model of indirectly induced ALI.

Microcirculation vs. Mitochondria-What to Target?

Circulatory shock is associated with marked disturbances of the macro- and microcirculation and flow heterogeneities. Furthermore, a lack of tissue adenosine trisphosphate (ATP) and mitochondrial dysfunction are directly associated with organ failure and poor patient outcome. While it remains unclear if microcirculation-targeted resuscitation strategies can even abolish shock-induced flow heterogeneity, mitochondrial dysfunction and subsequently diminished ATP production could still lead to organ dysfunction and failure even if microcirculatory function is restored or maintained. Preserved mitochondrial function is clearly associated with better patient outcome. This review elucidates the role of the microcirculation and mitochondria during circulatory shock and patient management and will give a viewpoint on the advantages and disadvantages of tailoring resuscitation to microvascular or mitochondrial targets.

The importance of discovery science in the development of therapies for the critically ill

Discovery science, a term which encompasses basic, translational, and computational science with the aim to discover new therapies, has advanced critical care. By combining knowledge on inflammatory and genomic pathways with computational methods, discovery science is currently enabling us to optimize clinical trials design by predictive enrichment and to move into the era of personalized medicine for complex syndromes such as sepsis and ARDS. Whereas computational methods are gaining in interest, efforts to invest in basic and translational science in critical care are declining. As basic and translational science is essential to advance our understanding of the pathophysiology of organ failure, this loss of interest may result in failure to discover new therapies for the critically ill. A renewed emphasis on basic and translational science is essential to find solutions for fundamental questions that remain in critical care. This requires a strategy to prioritize basic and translational science as an essential component within the critical care research "toolkit." Key aspects of this strategy include an increased focus on basic science in critical care medical curricula as well as in critical care platforms such as conferences and medical journals. Training of critical care clinician scientists in basic and translational research will require new organizational models within the academic institutions, as well as the development of new funding opportunities for early career critical care clinician scientists.

Inhibition of neutrophil elastase prevents neutrophil extracellular trap formation and rescues mice from endotoxic shock

Neutrophil elastase (NE) is a serine protease stored in the azurophilic granules of neutrophils and released into the extracellular milieu during inflammatory response or formation of neutrophil extracellular traps (NETs). Neutrophils release NETs to entrap pathogens by externalizing their cellular contents in a DNA framework decorated with anti-microbials and proteases, including NE. Importantly, excess NETs in tissues are implicated in numerous pathologies, including sepsis, rheumatoid arthritis, vasculitis, and cancer. However, it remains unknown how to effectively prevent NET formation. Here, we show that NE plays a major role during NET formation and that inhibition of NE is a promising approach for decreasing NET-mediated tissue injury. NE promoted NET formation by human neutrophils. Whereas sivelestat, a small molecule inhibitor of NE, inhibited the formation of NETs in vitro , administration of free sivelestat did not have any efficacy in a murine model of lipopolysaccharide-induced endotoxic shock. To improve the efficacy of sivelestat in vivo, we have developed a nanoparticle system for delivering sivelestat. We demonstrate that nanoparticle-mediated delivery of sivelestat effectively inhibited NET formation, decreased the clinical signs of lung injury, reduced NE and other proinflammatory cytokines in serum, and rescued animals against endotoxic shock. Collectively, our data demonstrates that NE signaling can initiate NET formation and that nanoparticle-mediated inhibition of NE improves drug efficacy for preventing NET formation.

Acute lung injury: The therapeutic role of Rho kinase inhibitors

Acute lung injury (ALI) is a pulmonary illness with high rates of mortality and morbidity. Rho GTPase and its downstream effector, Rho kinase (ROCK), have been demonstrated to be involved in cell adhesion, motility, and contraction which can play a role in ALI. The electronic databases of Google Scholar, Scopus, PubMed, and Web of Science were searched to obtain relevant studies regarding the role of the Rho/ROCK signaling pathway in the pathophysiology of ALI and the effects of specific Rho kinase inhibitors in prevention and treatment of ALI. Upregulation of the RhoA/ROCK signaling pathway causes an increase of inflammation, immune cell migration, apoptosis, coagulation, contraction, and cell adhesion in pulmonary endothelial cells. These effects are involved in endothelium barrier dysfunction and edema, hallmarks of ALI. These effects were significantly reversed by Rho kinase inhibitors. Rho kinase inhibition offers a promising approach in ALI [ARDS] treatment.