Endothelial Responses in Sepsis

Novel aspects of sepsis pathophysiology: NETs, plasma glycoproteins, endotheliopathy and COVID-19

In 2016, sepsis was newly defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. Sepsis remains one of the crucial medical problems to be solved worldwide. Although the world health organization has made sepsis a global health priority, there remain no specific and effective therapy for sepsis so far. Indeed, over the previous decades almost all attempts to develop novel drugs have failed. This may be partly ascribable to the multifactorial complexity of the septic cascade and the resultant difficulties of identifying drug targets. In addition, there might still be missing links among dysregulated host responses in vital organs. In this review article, recent advances in understanding of the complex pathophysiology of sepsis are summarized, with a focus on neutrophil extracellular traps (NETs), the significant role of NETs in thrombosis/embolism, and the functional roles of plasma proteins, histidine-rich glycoprotein (HRG) and inter-alpha-inhibitor proteins (IAIPs). The specific plasma proteins that are markedly decreased in the acute phase of sepsis may play important roles in the regulation of blood cells, vascular endothelial cells and coagulation. The accumulating evidence may provide us with insights into a novel aspect of the pathophysiology of sepsis and septic ARDS, including that in COVID-19.

EFFECTS OF SHENFU INJECTION ON SUBLINGUAL MICROCIRCULATION IN SEPTIC SHOCK PATIENTS: A RANDOMIZED CONTROLLED TRIAL

ABSTRACT

Background and Objective: The optimization of macrocirculatory hemodynamics is recommended by current sepsis guidelines. However, microcirculatory dysfunction is considered the cause of severe sepsis. In the present study, we designed to verify whether the application of Shenfu injection (SFI) restores microcirculation, thereby improving tissue perfusion and inhibiting organ dysfunction, resulting in improved outcomes. Design: We conducted a prospective, single-center, randomized, double-blind, placebo-controlled clinical trial. Intervention: Patients were randomly assigned to group receiving SFI (n = 20) or placebo (n = 20) for 5 days. We administered SFI or glucose injection for 5 days and blinded the investigators and clinical staff by applying light-proof infusion equipment that concealed therapy allocation. Measurements and Results: We measured the systemic dynamics and lactate levels, biomarkers of endothelial dysfunction, and inflammatory cytokines in the plasma. The parameters of sublingual microcirculation were assessed using side-stream dark-field imaging. Sequential Organ Failure Assessment (SOFA) score, Acute Physiology and Chronic Health Evaluation (APACHE) score, total dose, and duration of vasopressor use, emergency intensive care unit (EICU) stay, and 28-day mortality were evaluated. After treatment with SFI, the disturbance of the sublingual microcirculation was considerably alleviated, as indicated by the significant increase in total vessel density, perfused vessel density, and microvascular flow index. Moreover, the plasma biomarker levels of endothelial dysfunction, including Ang-2, Syn-1, and ET-1, were reversed after SFI treatment. Importantly, the SFI group had a more favorable prognosis than the control group in terms of the APACHE-II score, SOFA score, duration of vasopressor administration, and length of EICU stay. However, the difference in mortality at day 28 was not statistically different between the SFI (15%, 3/20) and placebo (25%, 5/20) groups ( P = 0.693). Conclusions : Shenfu injection provided apparent effects in improving sublingual microcirculatory perfusion in patients with septic shock, and this protection may be related with the inhibition of endothelial dysfunction and vasodilatory effects.

In vivo evaluation of a lipopolysaccharide-induced ear vascular leakage model in mice using photoacoustic microscopy

Sepsis is caused by dysregulated host inflammatory response to infection. During sepsis, early identification and monitoring of vascular leakage are pivotal for improved diagnosis, treatment, and prognosis. However, there is a lack of research on noninvasive observation of inflammation-related vascular leakage. Here, we investigate the use of photoacoustic microscopy (PAM) for in vivo visualization of lipopolysaccharide (LPS)-induced ear vascular leakage in mice using Evans blue (EB) as an indicator. A model combining needle pricking on the mouse ear, topical smearing of LPS on the mouse ear, and intravenous tail injection of EB is developed. Topical application of LPS is expected to induce local vascular leakage in skin. Inflammatory response is first validated by ex vivo histology and enzyme-linked immunosorbent assay. Then, local ear vascular leakage is confirmed by ex vivo measurement of swelling, thickening, and EB leakage. Finally, PAM for in vivo identification and evaluation of early vascular leakage using the model is demonstrated. For PAM, common excitation wavelength of 532 nm is used, and an algorithm is developed to extract quantitative metrics for EB leakage. The results show potential of PAM for noninvasive longitudinal monitoring of peripheral skin vascular leakage, which holds promise for clinical sepsis diagnosis and management.

A Predictive Model Based on Inflammatory and Coagulation Indicators for Sepsis-Induced Acute Kidney Injury

Background

Sepsis-induced acute kidney injury (S-AKI) is associated with systemic inflammatory responses and coagulation system dysfunction, and it is associated with an increased risk of mortality. However, there was no study to explore the predictive value of inflammatory and coagulation indicators for S-AKI.

Methods

In this retrospective study, 1051 sepsis patients were identified and divided into a training cohort (75%, n = 787) and a validation cohort (25%, n = 264) in chronological order according to the date they were admitted. Univariate analyses and multivariate logistic regression analyses were performed to identify the independent predictors of S-AKI. The logistic regression analyses (enter methods) were used to conducted the prediction models. The ROC curves were used to determine the predictive value of the constructed models on S-AKI. To test whether the increase in the AUC is significant, we used a two-sided test for ROC curves available online (http://vassarstats.net/roc_comp.html). The secondary outcome was different AKI stages and major adverse kidney events within 30 days (MAKE30). Stage 3B of S-AKI was defined as both meeting the stage 3 criteria [increase of Cr level by > 300% (≥ 4.0 mg/dL with an acute increase of ≥ 0.5 mg/dL) and/or UO < 0.3 mL/kg/h for > 24 h or anuria for > 12 h and/or acute kidney replacement therapy] and having cystatin C positive. MAKE30 were a composite of death, new renal replacement therapy (RRT), or persistent renal dysfunction (PRD).

Results

We discovered that cardiovascular disease, white blood cell (WBC), mean arterial pressure (MAP), platelet (PLT), serum procalcitonin (PCT), prothrombin time activity (PTA), and thrombin time (TT) were independent predictors for S-AKI. The predictive value (AUC = 0.855) of the simplest model 3 (constructed with PLT, PCT, and PTA), with a sensitivity of 77.6% and a specificity of 82.4%, had a similar predictive value comparing with the model 1 (AUC = 0.872) and the model 2 (AUC = 0.864) in the training cohort (P > 0.05). Compared with the model 1 (AUC = 0.888) and the model 2 (AUC = 0.887), the model 3 (AUC = 0.887) had a similar predictive value in the validation cohort. Moreover, model 3 had the best predictive power for predicting S-AKI in the stage 3 (AUC = 0.777), especially in stage 3B (AUC = 0.771). Finally, the model 3 (AUC = 0.843) had perfect predictive power for predicting MAKE30 in sepsis patients.

Conclusion

Within 24 hours after admission, the simplest model 3 (constructed with PLT, PCT, and PTA) might be a robust predictor of the S-AKI in sepsis patients, providing information for timely and efficient intervention.

Luteolin alleviates vascular dysfunctions in CLP-induced polymicrobial sepsis in mice

BACKGROUND

Luteolin, a naturally occurring flavonoid, is thought to have health-promoting properties as a part of human diet and has been reported to possess a wide range of pharmacological activities. Therefore, the present study was undertaken to evaluate the effect of luteolin pre-treatment on vascular dysfunctions in sepsis induced by caecal ligation and puncture (CLP) in the mouse model.

METHODS

Mice were divided into four groups: sham, luteolin plus sham, CLP, and luteolin plus CLP. Luteolin was administered (0.2 mg/kg body weight) intraperitoneally one hour (h) before CLP surgery in mice. 20 ± 2 h post CLP surgery, the isolated thoracic aorta of mice was assessed for its vascular reactivity to noradrenaline (NA) and acetylcholine (ACh). To explore the underlying mechanism, aortic mRNA expressions of α_1D adrenoceptors, eNOS and iNOS were investigated.

RESULTS

In mice with CLP-induced sepsis luteolin pre-treatment markedly increased the survival time and attenuated serum lactate level. The CLP group manifested the reduced vascular reactivity to NA and this deficit was restored by luteolin pre-treatment. However, luteolin pre-treatment did not improve α_1D adrenoceptors down-regulation observed in septic mice aorta. In the presence of 1400 W, the NA contractile response was significantly restored in CLP mice aortic tissue in comparison with the respective control of septic mice and further enhanced in the presence of luteolin. Luteolin reduced the iNOS mRNA expression and iNOS-derived nitrite production. Pre-treatment with luteolin restored the endothelial dysfunction in septic mice aorta by improving eNOS mRNA expression and enhanced eNOS-derived nitric oxide (NO) production in septic mice aorta and aortic iNOS gene expression and inducible NO production.

CONCLUSION

The present study suggests that the vasoplegic state to NA in aorta was restored through the iNOS pathway and endothelial dysfunction was reversed via eNOS and NO production pathway.

Delta-like canonical Notch ligand 1 is predictive for sepsis and acute kidney injury in surgical intensive care patients

The early identification of sepsis in surgical intensive care patients is challenging due to the physiological postoperative alterations of vital signs and inflammatory biomarkers. Soluble Delta-like protein 1 (sDLL1) may be a potential discriminatory biomarker for this purpose. For this reason, this study aimed to evaluate sDLL1 for the identification of sepsis in a cohort of surgical intensive care patients. This study comprises a secondary analysis of a prospective observational study including 80 consecutive patients. The study groups included 20 septic shock patients, 20 patients each undergoing major abdominal surgery (MAS) and cardiac artery bypass surgery (CABG), and 20 matched control subjects (CTRL). The surveillance period was 72 h. The plasma concentration of sDLL1 was measured with ELISA. The plasma levels of sDLL1 were significantly elevated in septic patients compared to both surgical cohorts (septic vs. all postoperative time points, data are shown as median and interquartile range [IQR]; septic shock: 17,363 [12,053–27,299] ng/mL, CABG 10,904 [8692–16,250] ng/mL; MAS 6485 [4615–9068] ng/mL; CTRL 5751 [3743–7109] ng/mL; septic shock vs. CABG: p < 0.001; septic shock vs. MAS: p < 0.001). ROC analysis showed a sufficient prediction of sepsis with limited specificity (AUCROC 0.82 [0.75–0.82], sensitivity 84%, specificity 68%). The plasma levels of sDLL correlated closely with renal parameters (creatinine: correlation coefficient = 0.60, r² = 0.37, p < 0.0001; urea: correlation coefficient = 0.52, r² = 0.26, p < 0.0001), resulting in a good predictive performance of sDLL1 for the identification of acute kidney injury (AKI; AUCROC 0.9 [0.82–0.9], sensitivity 83%, specificity 91%). By quantifying the plasma concentration of sDLL1, sepsis can be discriminated from the physiological postsurgical inflammatory response in abdominal and cardiac surgical patients. However, sDLL1 has only limited specificity for the detection of sepsis in cardiac surgical patients, which may be explained by impaired renal function. Based on these findings, this study identifies the predictive value of sDLL1 for the detection of AKI, making it a potential biomarker for surgical intensive care patients.

Trial registration DRKS00013584, Internet Portal of the German Clinical Trials Register (DRKS), registration date 11.07.2018, https://www.drks.de/drks_web/navigate.do?navigationId=trial.HTML&TRIAL_ID=DRKS00013584.

Extracellular histones induce inflammation and senescence of vascular smooth muscle cells by activating the AMPK/FOXO4 signaling pathway

BACKGROUND

Sepsis is an abnormal immune-inflammatory response that is mainly caused by infection. It can lead to life-threatening organ dysfunction and death. Severely damaged tissue cells will release intracellular histones into the circulation as damage-related molecular patterns (DAMPs) to accelerate the systemic immune response. Although various histone-related cytotoxicity mechanisms have been explored, those that affect extracellular histones involved in vascular smooth muscle cell (VSMC) dysfunction are yet to be determined.

METHODS

Mouse aortic vascular smooth muscle cells (VSMCs) were stimulated with different concentrations of histones, and cell viability was detected by CCK-8 assay. Cellular senescence was assessed by SA β-gal staining. C57BL/6 mice were treated with histones with or without BML-275 treatment. RT-qPCR was performed to determine the expression of inflammatory cytokines. Western blotting was used to analyze the expression of NLRP3, ASC and caspase-1 inflammasome proteins. The interaction of NLRP3 and ASC was detected by CoIP and immunofluorescence staining.

RESULTS

In this study, we found that extracellular histones induced senescence and inflammatory response in a dose-dependent manner in cultured VSMCs. Histone treatment significantly promoted apoptosis-associated speck-like protein containing CARD (ASC) as well as NACHT, LRR and PYD domains-containing protein 3 (NLRP3) interaction of inflammasomes in VSMCs. Forkhead box protein O4 (FOXO4), which is a downstream effector molecule of extracellular histones, was found to be involved in histone-regulated VSMC inflammatory response and senescence. Furthermore, the 5'-AMP-activated protein kinase (AMPK) signaling pathway was confirmed to mediate extracellular histone-induced FOXO4 expression, and blocking this signaling pathway with an inhibitor can suppress vascular inflammation induced by extracellular histones in vivo and in vitro.

CONCLUSION

Extracellular histones induce inflammation and senescence in VSMCs, and blocking the AMPK/FOXO4 pathway is a potential target for the treatment of histonemediated organ injury.

Molecular Framework of Mouse Endothelial Cell Dysfunction during Inflammation: A Proteomics Approach

A key aspect of cytokine-induced changes as observed in sepsis is the dysregulated activation of endothelial cells (ECs), initiating a cascade of inflammatory signaling leading to leukocyte adhesion/migration and organ damage. The therapeutic targeting of ECs has been hampered by concerns regarding organ-specific EC heterogeneity and their response to inflammation. Using in vitro and in silico analysis, we present a comprehensive analysis of the proteomic changes in mouse lung, liver and kidney ECs following exposure to a clinically relevant cocktail of proinflammatory cytokines. Mouse lung, liver and kidney ECs were incubated with TNF-α/IL-1β/IFN-γ for 4 or 24 h to model the cytokine-induced changes. Quantitative label-free global proteomics and bioinformatic analysis performed on the ECs provide a molecular framework for the EC response to inflammatory stimuli over time and organ-specific differences. Gene Ontology and PANTHER analysis suggest why some organs are more susceptible to inflammation early on, and show that, as inflammation progresses, some protein expression patterns become more uniform while additional organ-specific proteins are expressed. These findings provide an in-depth understanding of the molecular changes involved in the EC response to inflammation and can support the development of drugs targeting ECs within different organs. Data are available via ProteomeXchange (identifier PXD031804).

Peripheral tissue hypoperfusion predicts post intubation hemodynamic instability

Background

Tracheal intubation and invasive mechanical ventilation initiation is a procedure at high risk for arterial hypotension in intensive care unit. However, little is known about the relationship between pre-existing peripheral microvascular alteration and post-intubation hemodynamic instability (PIHI).

Methods

Prospective observational monocenter study conducted in an 18-bed medical ICU. Consecutive patients requiring tracheal intubation were eligible for the study. Global hemodynamic parameters (blood pressure, heart rate, cardiac function) and tissue perfusion parameters (arterial lactate, mottling score, capillary refill time [CRT], toe-to-room gradient temperature) were recorded before, 5 min and 2 h after tracheal intubation (TI). Post intubation hemodynamic instability (PIHI) was defined as any hemodynamic event requiring therapeutic intervention.

Results

During 1 year, 120 patients were included, mainly male (59%) with a median age of 68 [57–77]. The median SOFA score and SAPS II were 6 [4–9] and 47 [37–63], respectively. The main indications for tracheal intubation were hypoxemia (51%), hypercapnia (13%), and coma (29%). In addition, 48% of patients had sepsis and 16% septic shock. Fifty-one (42%) patients develop PIHI. Univariate analysis identified several baseline factors associated with PIHI, including norepinephrine prior to TI, sepsis, tachycardia, fever, higher SOFA and high SAPSII score, mottling score ≥ 3, high lactate level and prolonged knee CRT. By contrast, mean arterial pressure, baseline cardiac index, and ejection fraction were not different between PIHI and No-PIHI groups. After adjustment on potential confounders, the mottling score was associated with a higher risk for PIHI (adjusted OR: 1.84 [1.21–2.82] per 1 point increased; p = 0.005). Among both global haemodynamics and tissue perfusion parameters, baseline mottling score was the best predictor of PIHI (AUC: 0.72 (CI 95% [0.62–0.81]).

Conclusions

In non-selected critically ill patients requiring invasive mechanical ventilation, tissue hypoperfusion parameters, especially the mottling score, could be helpful to predict PIHI.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13613-022-01043-3.

Anti-inflammatory effects of a SERP 30 polysaccharide from the residue of Sarcandra glabra against lipopolysaccharide-induced acute respiratory distress syndrome in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Sarcandra glabra (Thunb.) Nakai, a valuable dietetic Chinese herb, is still widely used today. Multiple ingredients of S. glabra with a variety of activities such as anti-inflammatory, antiviral, and antitumor were studied. However, the Sarcandra glabra (Thunb.) Nakai polysaccharide hasn't been reported for its anti-inflammatory effect.

AIM OF THE STUDY

In this study, the anti-inflammatory activity of Sarcandra glabra (Thunb.) Nakai polysaccharide was assessed in LPS-induced ARDS mice.

MATERIALS AND METHODS

A polysaccharide coded as SERP 30 was obtained by water extraction, alcohol precipitation, and gel filtration. After the physicochemical properties determination and structural characterization, LPS induced-mice ARDS model was used to evaluate the anti-inflammatory and associated antioxidant activities of SERP 30. H&E staining was used to observe the seriousness of lung injury in mice. The ELISA method was used to measure the expression of inflammatory factors (TNF-α and IL-6) in the serum of the mice. The TBA method and the WST-1 method were used to evaluate the oxidative stress injury. Immunohistochemistry was used to distinguish the expression of metalloproteinase-9 (MMP-9), heparinase (HPA), syndecan-1, and decorin in ARDS-mice lung tissue. Western blotting was used to confirm the expression of related proteins in mouse lung tissue.

RESULTS

SERP 30 had a potential role in improving lung damage, reducing inflammation, and preventing oxidative stress. Moreover, SERP 30 significantly attenuated the damage to the endothelial glycocalyx and maintained the integrity of the glycocalyx. The western blotting result implied that the main anti-inflammatory mechanism is directed towards NF-κB and MAPK signaling pathways with inhibiting the activation of associated proteins.

CONCLUSION

This research provides a theoretical basis for treating ARDS by using a byproduct from food resource.

The rs8506 TT Genotype in lincRNA-NR_024015 Contributes to the Risk of Sepsis in a Southern Chinese Child Population

Background

Sepsis is a highly life-threatening heterogeneous syndrome and a global health burden. Studies have shown that many genetic variants could influence the risk of sepsis. Long non-coding RNA lincRNA-NR_024015 may participate in functional alteration of endothelial cell via vascular endothelial growth factor (VEGF) signaling, whereas its relevance between the lincRNA-NR_024015 polymorphism and sepsis susceptibility is still unclear.

Methods

474 sepsis patients and 678 healthy controls were enrolled from a southern Chinese child population in the present study. The polymorphism of rs8506 in lincRNA-NR_024015 was determined using Taqman methodology.

Results

Overall, a significant association was found between rs8506 polymorphism and the risk of sepsis disease (TT vs. CC/CT: adjusted OR = 1.751, 95%CI = 1.024–2.993, P = 0.0406). In the stratified analysis, the results suggested that the carriers of TT genotypes had a significantly increased sepsis risk among the children aged 12–60 months, females, early-stage sepsis and survivors (TT vs. CC/CT: OR_age = 2.413; OR_female = 2.868; OR_sepsis = 2.533; OR_survivor = 1.822; adjusted for age and gender, P < 0.05, respectively).

Conclusion

Our study indicated that lincRNA-NR_024015 rs8506 TT genotype might contribute to the risk of sepsis in a southern Chinese child population. Future research is required to elucidate the possible immunoregulatory mechanisms of this association and advance the development of novel biomarkers in sepsis.

The host response in different aetiologies of community-acquired pneumonia

BACKGROUND

Community-acquired pneumonia (CAP) can be caused by a variety of pathogens, of which Streptococcus pneumoniae, Influenza and currently SARS-CoV-2 are the most common. We sought to identify shared and pathogen-specific host response features by directly comparing different aetiologies of CAP.

METHODS

We measured 72 plasma biomarkers in a cohort of 265 patients hospitalized for CAP, all sampled within 48 hours of admission, and 28 age-and sex matched non-infectious controls. We stratified the biomarkers into several pathophysiological domains- antiviral response, vascular response and function, coagulation, systemic inflammation, and immune checkpoint markers. We directly compared CAP caused by SARS-CoV-2 (COVID-19, n=39), Streptococcus pneumoniae (CAP-strep, n=27), Influenza (CAP-flu, n=22) and other or unknown pathogens (CAP-other, n=177). We adjusted the comparisons for age, sex and disease severity scores.

FINDINGS

Biomarkers reflective of a stronger cell-mediated antiviral response clearly separated COVID-19 from other CAPs (most notably granzyme B). Biomarkers reflecting activation and function of the vasculature showed endothelial barrier integrity was least affected in COVID-19, while glycocalyx degradation and angiogenesis were enhanced relative to other CAPs. Notably, markers of coagulation activation, including D-dimer, were not different between the CAP groups. Ferritin was most increased in COVID-19, while other systemic inflammation biomarkers such as IL-6 and procalcitonin were highest in CAP-strep. Immune checkpoint markers showed distinctive patterns in viral and non-viral CAP, with highly elevated levels of Galectin-9 in COVID-19.

INTERPRETATION

Our investigation provides insight into shared and distinct pathophysiological mechanisms in different aetiologies of CAP, which may help guide new pathogen-specific therapeutic strategies.

FUNDING

This study was financially supported by the Dutch Research Council, the European Commission and the Netherlands Organization for Health Research and Development.

Connexin and Pannexin Large-Pore Channels in Microcirculation and Neurovascular Coupling Function

Microcirculation homeostasis depends on several channels permeable to ions and/or small molecules that facilitate the regulation of the vasomotor tone, hyperpermeability, the blood–brain barrier, and the neurovascular coupling function. Connexin (Cxs) and Pannexin (Panxs) large-pore channel proteins are implicated in several aspects of vascular physiology. The permeation of ions (i.e., Ca²⁺) and key metabolites (ATP, prostaglandins, D-serine, etc.) through Cxs (i.e., gap junction channels or hemichannels) and Panxs proteins plays a vital role in intercellular communication and maintaining vascular homeostasis. Therefore, dysregulation or genetic pathologies associated with these channels promote deleterious tissue consequences. This review provides an overview of current knowledge concerning the physiological role of these large-pore molecule channels in microcirculation (arterioles, capillaries, venules) and in the neurovascular coupling function.

Glycocalyx heparan sulfate cleavage promotes endothelial cell angiopoietin-2 expression by impairing shear stress-related AMPK/FoxO1 signaling

Angiopoietin-2 (Ang-2) is a key mediator of vascular disease during sepsis, and elevated plasma levels of Ang-2 are associated with organ injury scores and poor clinical outcomes. We have previously observed that biomarkers of endothelial glycocalyx (EG) damage correlate with plasma Ang-2 levels, suggesting a potential mechanistic linkage between EG injury and Ang-2 expression during states of systemic inflammation. However, the cell signaling mechanisms regulating Ang-2 expression following EG damage are unknown. In the current study, we determined the temporal associations between plasma heparan sulfate (HS) levels as a marker of EG erosion and plasma Ang-2 levels in children with sepsis and in mouse models of sepsis. Secondly, we evaluated the role of shear stress-mediated 5'-adenosine monophosphate-activated protein kinase (AMPK) signaling in Ang-2 expression following enzymatic HS cleavage from the surface of human primary lung microvascular endothelial cells (HLMVEC). We found that plasma HS levels peak prior to plasma Ang-2 levels in children and mice with sepsis. Further, we discovered that impaired AMPK signaling contributes to increased Ang-2 expression following HS cleavage from flow conditioned HLMVECs, establishing a novel paradigm by which Ang-2 may be upregulated during sepsis.

Case Report: Tachycardia, Hypoxemia and Shock in a Severely Burned Pediatric Patient

Background

Severely burned children are at high risk of secondary intraabdominal hypertension and abdominal compartment syndrome (ACS). ACS is a life-threatening condition with high mortality and requires an effective, minimally invasive treatment to improve the prognosis when the condition is refractory to conventional therapy.

Case presentation

A 4.5-year-old girl was admitted to our hospital 30 h after a severe burn injury. Her symptoms of burn shock were relieved after fluid resuscitation. However, her bloating was aggravated, and ACS developed on Day 5, manifesting as tachycardia, hypoxemia, shock, and oliguria. Invasive mechanical ventilation, vasopressors, and percutaneous catheter drainage were applied in addition to medical treatments (such as gastrointestinal decompression, diuresis, sedation, and neuromuscular blockade). These treatments did not improve the patient's condition until she received continuous renal replacement therapy. Subsequently, her vital signs and laboratory data improved, which were accompanied by decreased intra-abdominal pressure, and she was discharged after nutrition support, antibiotic therapy, and skin grafting.

Conclusion

ACS can occur in severely burned children, leading to rapid deterioration of cardiopulmonary function. Patients who fail to respond to conventional medical management should be considered for continuous renal replacement therapy.

METTL3-Mediated N6-Methyladenosine Modification of Trim59 mRNA Protects Against Sepsis-Induced Acute Respiratory Distress Syndrome

N6-methyladenosine (m⁶A) RNA modification is a fundamental determinant of mRNA metabolism in eukaryotic cells and is involved in numerous physiological and pathological processes. However, the specific role of m⁶A modification in sepsis-induced acute respiratory distress syndrome(ARDS) remains unknown. Here, we show that the levels of m⁶A RNA were significantly decreased in septic lungs and that METTL3 was the main regulator involved in the absence of m⁶A RNA modification. Pulmonary endothelial barrier damage is a critical process in the pathogenesis of acute lung injury during sepsis. METTL3 regulated endothelial barrier dysfunction and inflammatory responses in sepsis-induced ARDS in vivo and in vitro. Furthermore, we identified tripartite motif-containing (Trim)59 as a key m⁶A effector and Trim59 deficiency exacerbated lung injury. Mechanistically, METTL3 inhibited endothelial injury in sepsis-induced ARDS through Trim59-associated NF-κB inactivation. Our findings revealed novel insights into epitranscriptional mechanisms in sepsis-induced ARDS via m⁶A modifications, which has important application value in the diagnosis, prognosis, and molecular-targeted therapy of sepsis-associated lung injury.

Targeting Procalcitonin Protects Vascular Barrier Integrity

RATIONALE

Capillary leakage frequently occurs during sepsis and after major surgery and is associated with microvascular dysfunction and adverse outcome. Procalcitonin is a well-established biomarker in inflammation without known impact on vascular integrity.

OBJECTIVE

We determined how procalcitonin induces endothelial hyperpermeability and how targeting procalcitonin protects vascular barrier integrity.

METHODS

In a prospective observational clinical study, procalcitonin levels were assessed in 50 cardiac surgery patients and correlated to postoperative fluid and vasopressor requirements along with sublingual microvascular functionality. Effects of the procalcitonin signaling pathway on endothelial barrier and adherens junctional integrity were characterized in vitro and verified in mice. Inhibition of procalcitonin activation by dipeptidyl-peptidase 4 (DPP4) was evaluated in murine polymicrobial sepsis and clinically verified in cardiac surgery patients chronically taking the DPP4 inhibitor sitagliptin.

MEASUREMENTS AND MAIN RESULTS

Elevated postoperative procalcitonin levels identified patients with 2-fold increased fluid requirements (P<0.01), 1.8-fold higher vasopressor demand (P<0.05) and compromised microcirculation (reduction to 63.5±2.8% of perfused vessels, P<0.05). Procalcitonin induced 1.4-fold endothelial and 2.3-fold pulmonary capillary permeability (both P<0.001) by destabilizing VE-cadherin. Procalcitonin effects were dependent on activation by DPP4 and targeting the procalcitonin receptor or DPP4 during sepsis-induced hyperprocalcitonemia reduced capillary leakage by 54±10.1% and 60.4±6.9% (both P<0.01), respectively. Sitagliptin prior to cardiac surgery was associated with augmented microcirculation (74.1±1.7% vs. 68.6±1.9% perfused vessels in sitagliptin non-medicated patients, P<0.05) and 2.3-fold decreased fluid (P<0.05) and 1.8-fold reduced vasopressor demand postoperatively (P<0.05).

CONCLUSION

Targeting procalcitonin's action on the endothelium is a feasible means to preserve vascular integrity during systemic inflammation associated with hyperprocalcitonemia.

Post-COVID-19 Infection With Meticillin-Sensitive Staphylococcus aureus (MSSA) Bacteremia, Discitis/Osteomyelitis, and Diffuse Abscesses: A Case Report

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), has been associated with a plethora of symptoms weeks after the acute infection. While many reports have investigated the novel syndrome of post-acute sequelae of COVID-19, fewer studies have examined post-COVID-19 secondary infections, which may be distinct from typical post-viral bacterial infections due to the multiorgan involvement of COVID-19. This case report aims to highlight a presentation in which a 65-year-old man had COVID-19 and subsequently developed methicillin-sensitive Staphylococcus aureus (MSSA) bacteremia with widespread seeding of secondary infections, including abscesses in the hand and paravertebral regions as well as discitis/osteomyelitis of the cervical spine. Further studies are needed to investigate whether an increased susceptibility to unusual secondary bacterial infections is present in post-COVID-19 patients.

N-Oleoyl dopamine induces IL-10 via central nervous system TRPV1 and improves endotoxemia and sepsis outcomes

Background

The transient receptor potential vanilloid 1 (TRPV1) participates in thermosensation and inflammatory pain, but its immunomodulatory mechanisms remain enigmatic. N-Oleoyl dopamine (OLDA), an endovanilloid and endocannabinoid, is a TRPV1 agonist that is produced in the central nervous system and the peripheral nervous system. We studied the anti-inflammatory effects and TRPV1-dependent mechanisms of OLDA in models of inflammation and sepsis.

Methods

Mice were challenged intratracheally or intravenously with LPS, or intratracheally with S. aureus to induce pneumonia and sepsis, and then were treated intravenously with OLDA. Endpoints included plasma cytokines, leukocyte activation marker expression, mouse sepsis scores, lung histopathology, and bacterial counts. The role of TRPV1 in the effects of OLDA was determined using Trpv1^−/− mice, and mice with TRPV1 knockdown pan-neuronally, in peripheral nervous system neurons, or in myeloid cells. Circulating monocytes/macrophages were depleted using clodronate to determine their role in the anti-inflammatory effects of OLDA in endotoxemic mice. Levels of exogenous OLDA, and of endovanilloids and endocannabinoids, at baseline and in endotoxemic mice, were determined by LC–MS/MS.

Results

OLDA administration caused an early anti-inflammatory response in endotoxemic and septic mice with high serum levels of IL-10 and decreased levels of pro-inflammatory cytokines. OLDA also reduced lung injury and improved mouse sepsis scores. Blood and lung bacterial counts were comparable between OLDA- and carrier-treated mice with S. aureus pneumonia. OLDA’s effects were reversed in mice with pan-neuronal TRPV1 knockdown, but not with TRPV1 knockdown in peripheral nervous system neurons or myeloid cells. Depletion of monocytes/macrophages reversed the IL-10 upregulation by OLDA in endotoxemic mice. Brain and blood levels of endovanilloids and endocannabinoids were increased in endotoxemic mice.

Conclusions

OLDA has strong anti-inflammatory actions in mice with endotoxemia or S. aureus pneumonia. Prior studies focused on the role of peripheral nervous system TRPV1 in modulating inflammation and pneumonia. Our results suggest that TRPV1-expressing central nervous system neurons also regulate inflammatory responses to endotoxemia and infection. Our study reveals a neuro-immune reflex that during acute inflammation is engaged proximally by OLDA acting on neuronal TRPV1, and through a multicellular network that requires circulating monocytes/macrophages, leads to the systemic production of IL-10.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02485-z.

Antioxidant Activity of Vitamin C against LPS-Induced Septic Cardiomyopathy by Down-Regulation of Oxidative Stress and Inflammation

In severe cases of sepsis, endotoxin-induced cardiomyopathy can cause major damage to the heart. This study was designed to see if Vitamin C (Vit C) could prevent lipopolysaccharide-induced heart damage. Eighteen Sprague Dawley male rats (n = 6) were divided into three groups. Rats received 0.5 mL saline by oral gavage in addition to a standard diet (Control group), rats received one dose of endotoxin on day 15 (lipopolysaccharide) (LPS) (6 mg/kg), which produced endotoxemia (Endotoxin group), and rats that received 500 mg/Kg BW of Vit C by oral gavage for 15 days before LPS administration (Endotoxin plus Vit C group). In all groups, blood and tissue samples were collected on day 15, six hours after LPS administration, for histopathological and biochemical analysis. The LPS injection lowered superoxide dismutase (SOD) levels and increased malondialdehyde in tissues compared with a control group. Furthermore, the endotoxin group showed elevated inflammatory biomarkers, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). Both light and electron microscopy showed that the endotoxic-treated group’s cardiomyocytes, intercalated disks, mitochondria, and endothelial cells were damaged. In endotoxemic rats, Vit C pretreatment significantly reduced MDA levels and restored SOD activity, minimized biomarkers of inflammation, and mitigated cardiomyocyte damage. In conclusion: Vit C protects against endotoxin-induced cardiomyopathy by inhibiting oxidative stress cytokines.

The role of ferroptosis in endothelial cell dysfunction

Ferroptosis is a form of iron-dependent cell death caused by an excessive accumulation of reactive oxygen species and lipid peroxidation. The importance of ferroptosis in the occurrence and progression of various diseases is gradually being recognized; however, the exact biological effects and potential mechanisms of endothelial cell ferroptosis remain unclear. The endothelium forms the innermost layer of the blood vessels and lymphatic vessels. It acts as an important functional interface, responds to various pathological stimuli and causes endothelial dysfunction. Here, we review recent findings to elucidate the role of ferroptosis in endothelial cells under different pathophysiologic settings.

Unlocking the Untapped Potential of Endothelial Kinase and Phosphatase Involvement in Sepsis for Drug Treatment Design

Sepsis is a devastating clinical condition that can lead to multiple organ failure and death. Despite advancements in our understanding of molecular mechanisms underlying sepsis and sepsis-associated multiple organ failure, no effective therapeutic treatment to directly counteract it has yet been established. The endothelium is considered to play an important role in sepsis. This review highlights a number of signal transduction pathways involved in endothelial inflammatory activation and dysregulated endothelial barrier function in response to sepsis conditions. Within these pathways – NF-κB, Rac1/RhoA GTPases, AP-1, APC/S1P, Angpt/Tie2, and VEGF/VEGFR2 – we focus on the role of kinases and phosphatases as potential druggable targets for therapeutic intervention. Animal studies and clinical trials that have been conducted for this purpose are discussed, highlighting reasons why they might not have resulted in the expected outcomes, and which lessons can be learned from this. Lastly, opportunities and challenges that sepsis and sepsis-associated multiple organ failure research are currently facing are presented, including recommendations on improved experimental design to increase the translational power of preclinical research to the clinic.

Molecular analysis of vascular gene expression

A State of the Art lecture entitled "Molecular Analysis of Vascular Gene Expression" was presented at the ISTH Congress in 2021. Endothelial cells (ECs) form a critical interface between the blood and underlying tissue environment, serving as a reactive barrier to maintain tissue homeostasis. ECs play an important role in not only coagulation, but also in the response to inflammation by connecting these two processes in the host defense against pathogens. Furthermore, ECs tailor their behavior to the needs of the microenvironment in which they reside, resulting in a broad display of EC phenotypes. While this heterogeneity has been acknowledged for decades, the contributing molecular mechanisms have only recently started to emerge due to technological advances. These include high-throughput sequencing combined with methods to isolate ECs directly from their native tissue environment, as well as sequencing samples at a high cellular resolution. In addition, the newest technologies simultaneously quantitate and visualize a multitude of RNA transcripts directly in tissue sections, thus providing spatial information. Understanding how ECs function in (patho)physiological conditions is crucial to develop new therapeutics as many diseases can directly affect the endothelium. Of particular relevance for thrombotic disorders, EC dysfunction can lead to a procoagulant, proinflammatory phenotype with increased vascular permeability that can result in coagulopathy and tissue damage, as seen in a number of infectious diseases, including sepsis and coronavirus disease 2019. In light of the current pandemic, we will summarize relevant new data on the latter topic presented during the 2021 ISTH Congress.

Sepsis, cardiovascular events and short-term mortality risk in critically ill patients

INTRODUCTION

There is paucity of data on the occurrence of cardiovascular events (CVEs) in critically ill patients with sepsis. We aimed to describe the incidence, risk factors and impact on mortality of CVEs in these patients.

METHODS

This was a retrospective cohort study of critically ill patients admitted to the medical intensive care unit (ICU) between July 2015 and October 2016. The primary outcome was intra-hospital CVEs, while the secondary outcomes were in-hospital mortality, ICU and hospital length of stay.

RESULTS

Patients with sepsis (n=662) had significantly more CVEs compared to those without (52.9% versus 23.0%, P<0.001). Among sepsis patients, 350 (52.9%) had 1 or more CVEs: 59 (8.9%) acute coronary syndrome; 198 (29.9%) type 2 myocardial infarction; 124 (18.7%) incident atrial fibrillation; 76 (11.5%) new or worsening heart failure; 32 (4.8%) cerebrovascular accident; and 33 (5.0%) cardiovascular death. Factors associated with an increased risk of CVEs (adjusted relative risk [95% confidence interval]) included age (1.013 [1.007-1.019]); ethnicity-Malay (1.214 [1.005-1.465]) and Indian (1.240 [1.030-1.494]) when compared to Chinese; and comorbidity of ischaemic heart disease (1.317 [1.137-1.527]). There were 278 patients (79.4%) who developed CVEs within the first week of hospitalisation. Sepsis patients with CVEs had a longer median (interquartile range [IQR]) length of stay in the ICU (6 [3-12] vs 4 [2-9] days, P<0.001), and hospital (21 [10-42] vs 15 [7-30] days, P<0.001) compared to sepsis patients without CVEs. There was no difference in in-hospital mortality between the 2 groups (46.9% vs 45.8%, P=0.792).

CONCLUSION

CVEs complicate half of the critically ill patients with sepsis, with 79.4% of patients developing CVEs within the first week of hospitalisation, resulting in longer ICU and hospital length of stay.

Platelet Versus Megakaryocyte: Who Is the Real Bandleader of Thromboinflammation in Sepsis?

Platelets are mainly known for their key role in hemostasis and thrombosis. However, studies over the last two decades have shown their strong implication in mechanisms associated with inflammation, thrombosis, and the immune system in various neoplastic, inflammatory, autoimmune, and infectious diseases. During sepsis, platelets amplify the recruitment and activation of innate immune cells at the site of infection and contribute to the elimination of pathogens. In certain conditions, these mechanisms can lead to thromboinflammation resulting in severe organ dysfunction. Here, we discuss the interactions of platelets with leukocytes, neutrophil extracellular traps (NETs), and endothelial cells during sepsis. The intrinsic properties of platelets that generate an inflammatory signal through the NOD-like receptor family, pyrin domain-containing 3 (NLRP3) inflammasome are discussed. As an example of immunothrombosis, the implication of platelets in vaccine-induced immune thrombotic thrombocytopenia is documented. Finally, we discuss the role of megakaryocytes (MKs) in thromboinflammation and their adaptive responses.

Lactate induces vascular permeability via disruption of VE-cadherin in endothelial cells during sepsis

Circulating lactate levels are a critical biomarker for sepsis and are positively correlated with sepsis-associated mortality. We investigated whether lactate plays a biological role in causing endothelial barrier dysfunction in sepsis. We showed that lactate causes vascular permeability and worsens organ dysfunction in CLP sepsis. Mechanistically, lactate induces ERK-dependent activation of calpain1/2 for VE-cadherin proteolytic cleavage, leading to the enhanced endocytosis of VE-cadherin in endothelial cells. In addition, we found that ERK2 interacts with VE-cadherin and stabilizes VE-cadherin complex in resting endothelial cells. Lactate-induced ERK2 phosphorylation promotes ERK2 disassociation from VE-cadherin. In vivo suppression of lactate production or genetic depletion of lactate receptor GPR81 mitigates vascular permeability and multiple organ injury and improves survival outcome in polymicrobial sepsis. Our study reveals that metabolic cross-talk between glycolysis-derived lactate and the endothelium plays a critical role in the pathophysiology of sepsis.

Identification of the Transgene Integration Site and Host Genome Changes in MRP8-Cre/ires-EGFP Transgenic Mice by Targeted Locus Amplification

The MRP8-Cre-ires/EGFP transgenic mouse (Mrp8cre^Tg, on C57BL/6J genetic background) is popular in immunological and hematological research for specifically expressing Cre recombinase and an EGFP reporter in neutrophils. It is often crossed with other transgenic lines carrying loxP-flanked genes to achieve restricted gene knockout in neutrophils. However, due to the way in which the line was created, basic knowledge about the MRP8-Cre-ires/EGFP transgene in the host genome, such as its integration site(s) and flanking sequences, remains largely unknown, hampering robust experimental design and data interpretation. Here we used a recently developed technique, targeted locus amplification (TLA) sequencing, to fill these knowledge gaps. We found that the MRP8-Cre-ires/EGFP transgene was integrated into chromosome 5 (5qG2) of the host mouse genome. This integration led to a 44 kb deletion of the host genomic sequence, resulting in complete deletion of Serpine1 and partial deletion of Ap1s1. Having determined the flanking sequences of the transgene, we designed a new genotyping protocol that can distinguish homozygous, heterozygous, and wildtype Mrp8cre^Tg mice. To our surprise, crossing heterozygous mice produced no homozygous Mrp8cre^Tg mice, most likely due to prenatal lethality resulting from disrupted Ap1s1 gene expression.

Streptococcus pneumoniae Affects Endothelial Cell Migration in Microfluidic Circulation

Bloodstream infections caused by Streptococcus pneumoniae induce strong inflammatory and procoagulant cellular responses and affect the endothelial barrier of the vascular system. Bacterial virulence determinants, such as the cytotoxic pore-forming pneumolysin, increase the endothelial barrier permeability by inducing cell apoptosis and cell damage. As life-threatening consequences, disseminated intravascular coagulation followed by consumption coagulopathy and low blood pressure is described. With the aim to decipher the role of pneumolysin in endothelial damage and leakage of the vascular barrier in more detail, we established a chamber-separation cell migration assay (CSMA) used to illustrate endothelial wound healing upon bacterial infections. We used chambered inlets for cell cultivation, which, after removal, provide a cell-free area of 500 μm in diameter as a defined gap in primary endothelial cell layers. During the process of wound healing, the size of the cell-free area is decreasing due to cell migration and proliferation, which we quantitatively determined by microscopic live cell monitoring. In addition, differential immunofluorescence staining combined with confocal microscopy was used to morphologically characterize the effect of bacterial attachment on cell migration and the velocity of gap closure. In all assays, the presence of wild-type pneumococci significantly inhibited endothelial gap closure. Remarkably, even in the presence of pneumolysin-deficient pneumococci, cell migration was significantly retarded. Moreover, the inhibitory effect of pneumococci on the proportion of cell proliferation versus cell migration within the process of endothelial gap closure was assessed by implementation of a fluorescence-conjugated nucleoside analogon. We further combined the endothelial CSMA with a microfluidic pump system, which for the first time enabled the microscopic visualization and monitoring of endothelial gap closure in the presence of circulating bacteria at defined vascular shear stress values for up to 48 h. In accordance with our CSMA results under static conditions, the gap remained cell free in the presence of circulating pneumococci in flow. Hence, our combined endothelial cultivation technique represents a complex in vitro system, which mimics the vascular physiology as close as possible by providing essential parameters of the blood flow to gain new insights into the effect of pneumococcal infection on endothelial barrier integrity in flow.

Characteristics and prognostic value of pleural effusion in secondary hemophagocytic lymphohistiocytosis

The clinical features of patients with secondary hemophagocytic lymphohistiocytosis (sHLH) complicated with pleural effusion have rarely been evaluated. We retrospectively analyzed 203 patients newly diagnosed with sHLH from July 2015 to July 2019 according to the HLH-2004 protocol. Baseline characteristics, laboratory results, and imaging were reviewed. Pleural effusion was found in 58.6% of the studied sHLH population, and characteristic imaging findings were minimal volume and bilaterality. Patients with pleural effusion had lower PLT counts, HB levels and ALB levels as well as higher sCD25 levels than those without pleural effusion (all p values < 0.05). Multivariate analyses showed that lg(sCD25) and PLT ≤ 65 × 10⁹/L were significant risk factors for developing pleural effusion in sHLH. Regarding prognostic value, survival analysis showed a lower survival probability for patients with pleural effusion than for those without pleural effusion (median OS, 90 vs. 164 days, p = 0.028). In multivariate analysis, pleural effusion was an independent prognostic factor for overall survival (OS) (HR 2.68; 95% CI 1.18–6.11, p = 0.019). Pleural effusion is frequently found in patients with sHLH and is associated with greater inflammation and worse outcomes.

Human Amnion Epithelial Cells and Their Derived Exosomes Alleviate Sepsis-Associated Acute Kidney Injury via Mitigating Endothelial Dysfunction

Background

Sepsis is characterized by organ dysfunction resulting from a patient’s dysregulated response to infection. Sepsis-associated acute kidney injury (S-AKI) is the most frequent complication contributing to the morbidity and mortality of sepsis. The prevention and treatment of S-AKI remains a significant challenge worldwide. In the recent years, human amnion epithelial cells (hAECs) have drawn much attention in regenerative medicine, yet the therapeutic efficiency of hAECs in S-AKI has not been evaluated.

Methods

Septic mice were induced by cecal ligation and puncture (CLP) operation. hAECs and their derived exosomes (EXOs) were injected into the mice via tail vein right after CLP surgery. The 7-day survival rate was observed. Serum creatinine level was measured and H&E staining of tissue sections were performed 16 h after CLP. Transmission electron microscopy was used to examine the renal endothelial integrity in CLP mice. Human umbilical vein endothelial cells (HUVECs) were treated with lipopolysaccharide (LPS) and EXOs. Zonula occludens-1 (ZO-1) localization was observed by immunofluorescence staining. Expression of phosphor-p65 (p-p65), p65, vascular cell adhesion molecule-1 (VCAM-1), and ZO-1 in the kidney were determined by Western blot.

Results

hAECs decreased the mortality of CLP mice, ameliorated septic injury in the kidney, and improved kidney function. More precisely, hAECs suppressed systemic inflammation and maintained the renal endothelial integrity in septic animals. EXOs from hAECs exhibited similar renal protective effects as their parental cells. EXOs maintained endothelial cell adhesion junction in vitro and inhibited endothelial cell hyperactivation in vivo. Mechanistically, EXOs suppressed proinflammatory nuclear factor kappa B (NF-κB) pathway activation in LPS-treated HUVECs and in CLP mice kidneys.

Conclusion

Our results indicate that hAECs and their derived EXOs may ameliorate S-AKI via the prevention of endothelial dysfunction in the early stage of sepsis in mice. Stem cell or exosome-based therapy targeting endothelial disorders may be a promising alternative for treatment of S-AKI.

Electrophysiological Measurements of Isolated Blood Vessels

The lumen of blood vessels is covered by endothelial cells, which regulate their permeability to ions and solutes. Endothelial permeability depends on the vascular bed and cell phenotype, and is influenced by different disease states. Most characterization of endothelial permeability has been carried out using isolated cells in culture. While analysis of cultured cells is a valuable approach, it does not account for factors of the native cell environment. Building on Ussing chamber studies of intact tissue specimens, here we describe a method to measure the electrophysiological properties of intact arteriole and venule endothelia, including transendothelial electrical resistance (TEER) and ion permselectivity. As an example, vessels isolated from the mesentery were treated ex vivo, then mounted in a custom-made tissue cassette that enable their analysis by classical approaches with an Ussing chamber. This method enables a detailed analysis of electrophysiological vessel responses to stresses such as proinflammatory cytokines, in the context of an intact vessel. Graphic abstract.

Sepsis, Septic Shock, and Differences in Cardiovascular Event Occurrence

Introduction: Mortality estimates from sepsis and septic shock ranged from 18% to 35% and 40% to 60%, respectively, prior to 2014. Sepsis patients who experience subsequent cardiovascular events have increased mortality; however, data are limited among septic shock patients. This study reports in-hospital mortality, incident cardiovascular events, and cardiovascular procedures among sepsis patients with and without subsequent septic shock. Methods: Patients with a primary diagnosis of sepsis with and without a secondary diagnosis of septic shock were identified from the 2016 and 2017 National Readmissions Database. These patients were then evaluated for the occurrence of cardiovascular events and procedures. Results: A total of 2,127,137 patients were included in the study, with a mean age of 66 years. Twenty percent of patients (n = 420,135) developed subsequent septic shock. In-hospital mortality among patients with a primary diagnosis of sepsis was 5.3%, and it was 31.2% for those with subsequent septic shock. Notable cardiovascular events occurring among sepsis patients with and without subsequent septic shock, respectively, included: acute kidney injury (65.1% vs. 32.8%, P < .0001), acute systolic heart failure (9.8% vs. 5.1%, P < .0001), NSTEMI (8.8% vs. 3.2%, P < .0001), and ischemic stroke (2.3% vs. 0.9%, P < .0001). Similarly, the most common cardiovascular procedures between the two groups were: percutaneous coronary intervention (0.37% vs. 0.20%, P < .0001), intra-aortic balloon pump (0.19% vs. 0.02%, P < .0001), and extracorporeal membrane oxygenation (0.18% vs. 0.01%, P < .0001). Conclusions: Sepsis with subsequent septic shock is associated with an increased frequency of in-hospital cardiovascular events and procedures.

Meprin and ADAM proteases as triggers of systemic inflammation in sepsis

Systemic inflammatory disorders (SIDs) comprise a broad range of diseases characterized by dysregulated excessive innate immune responses. Severe forms of SIDs can lead to organ failure and death, and their increasing incidence represents a major issue for the healthcare system. Protease-mediated ectodomain shedding of cytokines and their receptors represents a central mechanism in the regulation of inflammatory responses. The metalloprotease A disintegrin and metalloproteinase (ADAM) 17 is the best-characterized ectodomain sheddase capable of releasing TNF-α and soluble IL-6 receptor, which are decisive factors of systemic inflammation. Recently, meprin metalloproteases were also identified as IL-6 receptor sheddases and activators of the pro-inflammatory cytokines IL-1β and IL-18. In different mouse models of SID, particularly those mimicking a sepsis-like phenotype, ADAM17 and meprins have been found to promote disease progression. In this review, we summarize the role of ADAM10, ADAM17, and meprins in the onset and progression of sepsis and discuss their potential as therapeutic targets.

srGAP2 deactivates RhoA to control the duration of thrombin-mediated endothelial permeability

The endothelial barrier is a tightly regulated gateway in the transport of material between circulation and the tissues. Inflammatory mediators such as thrombin are able to open paracellular spaces in the endothelial monolayer to allow the extravasation of plasma proteins and leukocytes. Here we show that the protein SLIT-ROBO Rho GTPase-activating protein 2 (srGAP2) plays a critical role in regulating the extent of thrombin-mediated opening. We show that srGAP2 is not required for normal barrier function in resting endothelial cells, but that depletion of srGAP2 significantly increases the magnitude and duration of junctional opening in response to thrombin. We show that srGAP2 acts to switch off RhoA signaling after the contraction phase of thrombin-induced permeability, allowing respreading of cells and reformation of the barrier. srGAP2 is also required for effective restoration of the barrier after treatment with two other vasoactive agents that active RhoA - TNFα and angiotensin II. Taken together, we show that srGAP2 has a general function in controlling RhoA signaling in endothelial permeability, acting to limit the degree and duration of opening, by triggering the switch from endothelial cell contraction to respreading.

Omics of endothelial cell dysfunction in sepsis

During sepsis, defined as life-threatening organ dysfunction due to dysregulated host response to infection, systemic inflammation activates endothelial cells and initiates a multifaceted cascade of pro-inflammatory signaling events, resulting in increased permeability and excessive recruitment of leukocytes. Vascular endothelial cells share many common properties but have organ-specific phenotypes with unique structure and function. Thus, therapies directed against endothelial cell phenotypes are needed to address organ-specific endothelial cell dysfunction. Omics allow for the study of expressed genes, proteins and/or metabolites in biological systems and provide insight on temporal and spatial evolution of signals during normal and diseased conditions. Proteomics quantifies protein expression, identifies protein-protein interactions and can reveal mechanistic changes in endothelial cells that would not be possible to study via reductionist methods alone. In this review, we provide an overview of how sepsis pathophysiology impacts omics with a focus on proteomic analysis of mouse endothelial cells during sepsis/inflammation and its relationship with the more clinically relevant omics of human endothelial cells. We discuss how omics has been used to define septic endotype signatures in different populations with a focus on proteomic analysis in organ-specific microvascular endothelial cells during sepsis or septic-like inflammation. We believe that studies defining septic endotypes based on proteomic expression in endothelial cell phenotypes are urgently needed to complement omic profiling of whole blood and better define sepsis subphenotypes. Lastly, we provide a discussion of how in silico modeling can be used to leverage the large volume of omics data to map response pathways in sepsis.

The protective effects of Mirtazapine against lipopolysaccharide (LPS)-induced brain vascular hyperpermeability

Sepsis is mainly characterized by severe inflammation triggered by infection, and sepsis-associated encephalopathy (SAE) is defined as brain damage caused by sepsis. Disruption of the blood-brain barrier (BBB) triggered by injured brain microvascular endothelial cells (BMECs) and damaged tight junction (TJ) structure is closely associated with the pathogenesis of SAE. The present research proposed to evaluate the potential therapeutic effects of Mirtazapine, a central presynaptic α2 receptor antagonist, on LPS-induced BBB disruption. The mice were administered with normal saline and 10 mg/kg Mirtazapine for 8 consecutive days, and from day 6, the experiment group of mice received LPS for 2 days to induce SAE. We found that the increased BBB permeability, elevated concentrations of inflammatory factors in brain tissues, and downregulated zonula occludens -1 (ZO-1) were observed in LPS-stimulated mice, all of which were reversed by 10 mg/kg Mirtazapine. In the in vitro assay, bEnd.3 brain endothelial cells were treated with 1 μM LPS in the absence or presence of Mirtazapine (25, 50 μM). We found that LPS-treated cells had significantly declined transendothelial electrical resistance (TEER), increased monolayer permeability, elevated production of inflammatory factors, and downregulated ZO-1. However, 25 and 50 μM Mirtazapine ameliorated all these LPS- induced aberrations. Mirtazapine also mitigated the decreased level of NF-E2-related factor 2 (Nrf2) in LPS-challenged endothelial cells. The protective effect of Mirtazapine on endothelial permeability against LPS was significantly abolished by the knockdown of Nrf2. Collectively, we concluded that Mirtazapine exerted protective effects on LPS-induced endothelial cells hyperpermeability by upregulating Nrf2.

Vitamin C improves microvascular reactivity and peripheral tissue perfusion in septic shock patients

Background

Vitamin C has potential protective effects through antioxidant and anti-inflammatory properties. However, the effect of vitamin C supplementation on microvascular function and peripheral tissue perfusion in human sepsis remains unknown. We aimed to determine vitamin C effect on microvascular endothelial dysfunction and peripheral tissue perfusion in septic shock patients.

Methods

Patients with septic shock were prospectively included after initial resuscitation. Bedside peripheral tissue perfusion and skin microvascular reactivity in response to acetylcholine iontophoresis in the forearm area were measured before and 1 h after intravenous vitamin C supplementation (40 mg/kg). Norepinephrine dose was not modified during the studied period.

Results

We included 30 patients with septic shock. SOFA score was 11 [8–14], SAPS II was 66 [54–79], and in-hospital mortality was 33%. Half of these patients had vitamin C deficiency at inclusion. Vitamin C supplementation strongly improved microvascular reactivity (AUC 2263 [430–4246] vs 5362 [1744–10585] UI, p = 0.0004). In addition, vitamin C supplementation improved mottling score (p = 0.06), finger-tip (p = 0.0003) and knee capillary refill time (3.7 [2.6–5.5] vs 2.9 [1.9–4.7] s, p < 0.0001), as well as and central-to-periphery temperature gradient (6.1 [4.9–7.4] vs 4.6 [3.4–7.0] °C, p < 0.0001). The beneficial effects of vitamin C were observed both in patients with or without vitamin C deficiency.

Conclusion

In septic shock patients being resuscitated, vitamin C supplementation improved peripheral tissue perfusion and microvascular reactivity whatever plasma levels of vitamin C.

ClinicalTrials.gov Identifier: NCT04778605 registered 26 January 2021.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13054-022-03891-8.

The Interplay between Host Defense, Infection, and Clinical Status in Septic Patients: A Narrative Review

Sepsis is a life-threatening condition that arises when the body's response to an infection injures its own tissues and organs. Despite significant morbidity and mortality throughout the world, its pathogenesis and mechanisms are not clearly understood. In this narrative review, we aimed to summarize the recent developments in our understanding of the hallmarks of sepsis pathogenesis (immune and adaptive immune response, the complement system, the endothelial disfunction, and autophagy) and highlight novel laboratory diagnostic approaches. Clinical management is also discussed with pivotal consideration for antimicrobic therapy management in particular settings, such as intensive care unit, altered renal function, obesity, and burn patients.

E. coli strain-dependent lipid alterations in cocultures with endothelial cells and neutrophils modeling sepsis

Dysregulated lipid metabolism is common in infection and inflammation and is a part of the complex milieu underlying the pathophysiological sequelae of disease. Sepsis is a major cause of mortality and morbidity in the world and is characterized by an exaggerated host response to an infection. Metabolic changes, including alterations in lipid metabolism, likely are important in sepsis pathophysiology. Here, we designed an in vitro cell culture model using endothelial cells, E. coli, and neutrophils to mimic sepsis in a simplified cell model. Lipid alterations were studied in the presence of the pathogenic E. coli strain CFT073 and non-pathogenic E. coli strain JM109. We employed untargeted lipidomics to first identify lipid changes and then targeted lipidomics to confirm changes. Both unique and shared lipid signatures were identified in cocultures with these E. coli strains. In the absence of neutrophils, the CFT073 strain elicited alterations in lysophosphatidylcholine and diglyceride molecular species during coculture while both strains led to increases in phosphatidylglycerols. Lipid alterations in these cocultures changed with the addition of neutrophils. In the presence of neutrophils with E. coli and endothelial cells, triglyceride increases were a unique response to the CFT073 strain while phosphatidylglycerol and diglyceride increases occurred in response to both strains. Phosphatidylethanolamine also increased in neutrophils, E. coli and endothelial cells cocultures, and this response was greater in the presence of the CFT073 strain. We further evaluated changes in phosphatidylethanolamine in a rat model of sepsis, which showed multiple plasma phosphatidylethanolamine molecular species were elevated shortly after the induction of sepsis. Collectively, these findings demonstrate unique lipid responses by co-cultures of E. coli with endothelial cells which are dependent on the E. coli strain as well as the presence of neutrophils. Furthermore, increases in phosphatidylethanolamine levels in CFT073 urosepsis E. coli, endothelial cell, neutrophil cocultures were similarly observed in the plasma of septic rats.

Predictive nomogram model for major adverse kidney events within 30 days in sepsis patients with type 2 diabetes mellitus

BACKGROUND

In sepsis patients, Type 2 Diabetes Mellitus (T2DM) was associated with an increased risk of kidney injury. Furthermore, kidney damage is among the dangerous complications, with a high mortality rate in sepsis patients. However, the underlying predictive model on the prediction of major adverse kidney events within 30 days (MAKE30) in sepsis patients with T2DM has not been reported by any study.

METHODS

A total of 406 sepsis patients with T2DM were retrospectively enrolled and divided into a non-MAKE30 group (261 cases) and a MAKE30 group (145 cases). In sepsis patients with T2DM, univariate and multivariate logistic regression analyses were conducted to identify independent predictors of MAKE30. Based on the findings of multivariate logistic regression analysis, the corresponding nomogram was constructed. The nomogram was evaluated using the calibration curve, Receiver Operating Characteristic (ROC) curve, and decision curve analysis. A composite of death, new Renal Replacement Therapy (RRT), or Persistent Renal Dysfunction (PRD) comprised MAKE30. Finally, subgroup analyses of the nomogram for 30-day mortality, new RRT, and PRD were performed.

RESULTS

In sepsis patients with T2DM, Mean Arterial Pressure (MAP), Platelet (PLT), cystatin C, High-Density Lipoprotein (HDL), and apolipoprotein E (apoE) were independent predictors for MAKE30. According to the ROC curve, calibration curve, and decision curve analysis, the nomogram model based on those predictors had satisfactory discrimination (AUC = 0.916), good calibration, and clinical application. Additionally, in sepsis patients with T2DM, the nomogram model exhibited a high ability to predict the occurrence of 30-day mortality (AUC = 0.822), new RRT (AUC = 0.874), and PRD (AUC = 0.801).

CONCLUSION

The nomogram model, which is available within 24 hours after admission, had a robust and accurate assessment for the MAKE30 occurrence, and it provided information to better manage sepsis patients with T2DM.

Isolation of Primary Mouse Pulmonary Microvascular Endothelial Cells and Generation of an Immortalized Cell Line to Obtain Sufficient Extracellular Vesicles

Pulmonary microvascular endothelial cells (PMECs) and the extracellular vesicles (EVs) derived from PMECs participate in maintaining pulmonary homeostasis and mediating the inflammatory response. However, obtaining a high-purity population of PMECs and their EVs from mouse is still notoriously difficult. Herein we provide a method to isolate primary mouse PMECs (pMPMECs) and to transduce SV40 lentivirus into pMPMECs to establish an immortalized cell line (iMPMECs), which provides sufficient quantities of EVs for further studies. pMPMECs and iMPMECs can be identified using morphologic criteria, a phenotypic expression profile (e.g., CD31, CD144, G. simplicifolia lectin binding), and functional properties (e.g., Dil-acetylated low-density protein uptake, Matrigel angiogenesis). Furthermore, pMPMEC-EVs and iMPMEC-EVs can be identified and compared. The characteristics of pMPMEC-EVs and iMPMEC-EVs are ascertained by transmission electron microscopy, nanoparticle tracking analysis, and specific protein markers. iMPMECs produce far more EVs than pMPMECs, while their particle size distribution is similar. Our detailed protocol to isolate and immortalize MPMECs will provide researchers with an in vitro model to investigate the specific roles of EVs in pulmonary physiology and diseases.

The Programmed Cell Death of Macrophages, Endothelial Cells, and Tubular Epithelial Cells in Sepsis-AKI

Sepsis is a systemic inflammatory response syndrome caused by infection, following with acute injury to multiple organs. Sepsis-induced acute kidney injury (AKI) is currently recognized as one of the most severe complications related to sepsis. The pathophysiology of sepsis-AKI involves multiple cell types, including macrophages, vascular endothelial cells (ECs) and renal tubular epithelial cells (TECs), etc. More significantly, programmed cell death including apoptosis, necroptosis and pyroptosis could be triggered by sepsis in these types of cells, which enhances AKI progress. Moreover, the cross-talk and connections between these cells and cell death are critical for better understanding the pathophysiological basis of sepsis-AKI. Mitochondria dysfunction and oxidative stress are traditionally considered as the leading triggers of programmed cell death. Recent findings also highlight that autophagy, mitochondria quality control and epigenetic modification, which interact with programmed cell death, participate in the damage process in sepsis-AKI. The insightful understanding of the programmed cell death in sepsis-AKI could facilitate the development of effective treatment, as well as preventive methods.

Mechanism of cell death of endothelial cells regulated by mechanical forces

Cell death of endothelial cells (ECs) is a common devastating consequence of various vascular-related diseases. Atherosclerosis, hypertension, sepsis, diabetes, cerebral ischemia and cardiac ischemia/reperfusion injury, and chronic kidney disease remain major causes of morbidity and mortality worldwide, in which ECs are constantly subjected to a great amount of dynamic changed mechanical forces including shear stress, extracellular matrix stiffness, mechanical stretch and microgravity. A thorough understanding of the regulatory mechanisms by which the mechanical forces controlled the cell deaths including apoptosis, autophagy, and pyroptosis is crucial for the development of new therapeutic strategies. In the present review, experimental and clinical data highlight that nutrient depletion, oxidative stress, tumor necrosis factor-α, high glucose, lipopolysaccharide, and homocysteine possess cytotoxic effects in many tissues and induce apoptosis of ECs, and that sphingosine-1-phosphate protects ECs. Nevertheless, EC apoptosis in the context of those artificial microenvironments could be enhanced, reduced or even reversed along with the alteration of patterns of shear stress. An appropriate level of autophagy diminishes EC apoptosis to some extent, in addition to supporting cell survival upon microenvironment challenges. The intervention of pyroptosis showed a profound effect on atherosclerosis. Further cell and animal studies are required to ascertain whether the alterations in the levels of cell deaths and their associated regulatory mechanisms happen at local lesion sites with considerable mechanical force changes, for preventing senescence and cell deaths in the vascular-related diseases.

Cell penetrating peptides coupled to an endothelial nitric oxide synthase sequence alter endothelial permeability

Delivery of cargo to cells through the use of cell-penetrating peptide (CPP) sequences is an area of rich investigation for targeted therapeutics. Specific to the endothelium, the layer of cells that cover every blood vessel in the body, the loss or alteration of a key enzyme, endothelial nitric oxide synthase (eNOS), is known to contribute to endothelial health during severe, infectious challenge. While the beneficial effects of eNOS are often thought to be mediated through the generation of nitric oxide, some protection is theorized to be through eNOS binding to regulatory pathways via a pentabasic RRKRK motif. We hypothesized that delivery of the eNOS-RRKRK peptide sequence using common CPPs would allow protection against gram-negative lipopolysaccharide (LPS). Combination of the eNOS-RRKRK sequence to the CPP antennapedia (AP) reduced the impact of LPS-induced permeability in cultured human microvascular endothelial cells (HMVECs) as measured by transendothelial electrical resistance (TEER). There was also a modest reduction in cytokine production, however it was observed that AP alone significantly impaired LPS-induced endothelial permeability and cytokine production. In comparison, the CPP trans-activator of transcription (TAT) did not significantly alter endothelial inflammation by itself. When TAT was coupled to the eNOS-RRKRK sequence, protection against LPS-induced permeability was still demonstrated, however cytokine production was not reduced. These data demonstrate that the RRKRK sequence of eNOS can offer some NO-independent protection against LPS-mediated endothelial inflammation, however the degree of protection is highly dependent on the type of CPP utilized for cargo delivery.

CXCR4 and CXCR7 Inhibition Ameliorates the Formation of Platelet-Neutrophil Complexes and Neutrophil Extracellular Traps through Adora2b Signaling

Peritonitis and peritonitis-associated sepsis are characterized by an increased formation of platelet-neutrophil complexes (PNCs), which contribute to an excessive migration of polymorphonuclear neutrophils (PMN) into the inflamed tissue. An important neutrophilic mechanism to capture and kill invading pathogens is the formation of neutrophil extracellular traps (NETs). Formation of PNCs and NETs are essential to eliminate pathogens, but also lead to aggravated tissue damage. The chemokine receptors CXCR4 and CXCR7 on platelets and PMNs have been shown to play a pivotal role in inflammation. Thereby, CXCR4 and CXCR7 were linked with functional adenosine A2B receptor (Adora2b) signaling. We evaluated the effects of selective CXCR4 and CXCR7 inhibition on PNCs and NETs in zymosan- and fecal-induced sepsis. We determined the formation of PNCs in the blood and, in addition, their infiltration into various organs in wild-type and Adora2b-/- mice by flow cytometry and histological methods. Further, we evaluated NET formation in both mouse lines and the impact of Adora2b signaling on it. We hypothesized that the protective effects of CXCR4 and CXCR7 antagonism on PNC and NET formation are linked with Adora2b signaling. We observed an elevated CXCR4 and CXCR7 expression in circulating platelets and PMNs during acute inflammation. Specific CXCR4 and CXCR7 inhibition reduced PNC formation in the blood, respectively, in the peritoneal, lung, and liver tissue in wild-type mice, while no protective anti-inflammatory effects were observed in Adora2b-/- animals. In vitro, CXCR4 and CXCR7 antagonism dampened PNC and NET formation with human platelets and PMNs, confirming our in vivo data. In conclusion, our study reveals new protective aspects of the pharmacological modulation of CXCR4 and CXCR7 on PNC and NET formation during acute inflammation.

Effects of Thyroid Hormone on Tissue Hypoxia: Relevance to Sepsis Therapy

Tissue hypoxia occurs in various conditions such as myocardial or brain ischemia and infarction, sepsis, and trauma, and induces cellular damage and tissue remodeling with recapitulation of fetal-like reprogramming, which eventually results in organ failure. Analogies seem to exist between the damaged hypoxic and developing organs, indicating that a regulatory network which drives embryonic organ development may control aspects of heart (or tissue) repair. In this context, thyroid hormone (TH), which is a critical regulator of organ maturation, physiologic angiogenesis, and mitochondrial biogenesis during fetal development, may be of important physiological relevance upon stress (hypoxia)-induced fetal reprogramming. TH signaling has been implicated in hypoxic tissue remodeling after myocardial infarction and T3 prevents remodeling of the postinfarcted heart. Similarly, preliminary experimental evidence suggests that T3 can prevent early tissue hypoxia during sepsis with important physiological consequences. Thus, based on common pathways between different paradigms, we propose a possible role of TH in tissue hypoxia after sepsis with the potential to reduce secondary organ failure.