Redox responses in patients with sepsis: high correlation of thioredoxin-1 and macrophage migration inhibitory factor plasma levels

Molecular subtypes based on N6-methyladenosine RNA methylation demonstrate the heterogeneity of immune and biological functions in pediatric septic shock

Introduction

Septic shock in children is a highly heterogeneous syndrome involving different immune states and biological processes. We used a bioinformatics approach to explore the relationship between N6-methyladenosine (m6A) methylation and septic shock in children.

Methods

A gene expression dataset including information on 98 children with septic shock was selected. To construct and evaluate a risk prediction model, machine learning was used to screen marker m6A regulators. Based on differentially expressed m6A regulators, molecular subtypes for paediatric septic shock were constructed. Subsequently, the differences in the m6Ascore, heterogeneity of immune cell infiltration, and heterogeneity of biological functions between the different subtypes were analyzed. Finally, real-time quantitative PCR (RT-qPCR) was performed to validate the expression of the marker m6A regulators.

Results

Fifteen differentially expressed m6A regulators were identified. Six marker m6A regulators, including LRPPRC, ELAVL1, RBM15, CBLL1, FTO, and RBM15B, were screened using the random forest method. The risk prediction model for paediatric septic shock constructed using m6A markers had strong consistency and high clinical practicability. Two subtypes of paediatric septic shock have been identified based on the differential expression pattern of m6A regulators. Significant differences were observed in RNA epigenetics, immune statuses, and biological processes between the two m6A subtypes. Differentially expressed genes between the two subtypes were enriched in cell number homeostasis, redox responses, and innate immune system responses. Finally, the six marker m6A regulators were verified in additional samples.

Conclusions

Based on the heterogeneity of m6A methylation-regulated genes, two different subtypes of septic shock in children with different RNA epigenetics, immune statuses, and biological processes were identified, revealing the heterogeneity of the disease largely attributable to differential m6A methylation. The findings will help explore and establish appropriate individualized treatments.

Comparative Analysis of Whole Transcriptome Profiles in Septic Cardiomyopathy: Insights from CLP- and LPS-Induced Mouse Models

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection, with septic cardiomyopathy being a common and severe complication. Despite its significant clinical impact, the molecular mechanisms underlying sepsis-induced cardiomyopathy (SICM) remain incompletely understood. In this study, we performed a comparative analysis of whole transcriptome profiles using RNA sequencing in mouse hearts in two widely used mouse models of septic cardiomyopathy. CLP-induced sepsis was achieved by surgical cecal ligation and puncture, while LPS-induced sepsis was induced using a 5 mg/kg intraperitoneal (IP) injection of lipopolysaccharide (LPS). For consistency, we utilized sham-operated mice as the control for septic models. Our aim was to identify key genes and pathways involved in the development of septic cardiomyopathy and to evaluate the similarities and differences between the two models. Our findings demonstrated that both the CLP and lipopolysaccharide LPS methods could induce septic heart dysfunction within 24 h. We identified common transcriptional regulatory regions in the septic hearts of both models, such as Nfkb1, Sp1, and Jun. Moreover, differentially expressed genes (DEGs) in comparison to control were involved in shared pathways, including regulation of inflammatory response, regulation of reactive oxygen species metabolic process, and the JAK-STAT signaling pathway. However, each model presented distinctive whole transcriptome expression profiles and potentially diverse pathways contributing to sepsis-induced heart failure. This extensive comparison enhances our understanding of the molecular basis of septic cardiomyopathy, providing invaluable insights. Accordingly, our study also contributes to the pursuit of effective and personalized treatment strategies for SICM, highlighting the importance of considering the specific causative factors.

Alterations in levels of cytokine following treatment to predict outcome of sepsis: A meta-analysis

BACKGROUND

The mortality rate of patients with sepsis has been increasing in recent years. Alterations of biomarkers levels during treatment are important in evaluating treatment efficacy and predicting outcomes in sepsis. This meta-analysis investigated the relationship between changes in cytokine levels after treatment compared with those on hospital admission, and their relationship with the prognosis of patients with sepsis.

METHODS

From conception until August 4, 2021, a complete literature search of the PubMed, Web of Science, and Cochrane Library electronic databases was done. Observational studies where the outcomes of sepsis patients were divided into non-survivors and survivors and which reported cytokine levels at least before treatment in ICU were included in the current study. Standardized mean difference (SMD) with 95% confidence intervals (CI) values from individual studies were pooled using a random-effects model. Quality assessment, subgroup analysis, publication bias, and sensitivity analyses were all carried out.

RESULTS

A total of 2570 patients with sepsis from 25 eligible studies were included, and 14 of them measured the cytokine levels before and after treatment in ICU. Among IL-6, TNF-α, IL-1β and IL-10 levels, those of IL-6 were significantly lower after treatment in ICU than at baseline in patients with sepsis in the survival group (SMD = -0.69, P < 0.0001), but were comparable in the non-survival group (SMD = -0.99, P = 0.0575). Similarly, post-treatment TNF-α levels were significantly lower than those at baseline only in patients with sepsis in the survival group (SMD = -0.44, P < 0.0001), but not in the non-survival group (SMD =-0.17, P = 0.0842).

CONCLUSION

This meta-analysis shows that reduced IL-6 and TNF-α levels after sepsis treatment in ICU may be indicators of better prognosis and survival of patients with sepsis.

Transcriptomic study of lipopolysaccharide-induced sepsis damage in a mouse heart model

Sepsis is an emergency systemic illness caused by pathogen infection and the combined result of the underactivity and overactivity of a patient's own immune system. However, the molecular mechanism of this illness remains largely unknown. Lipopolysaccharide (LPS) was injected to establish a sepsis model, and heart tissue was used to analyze transcriptome changes in mice. LPS injection was used to develop a sepsis model, which resulted in cardiac tissue rearrangement and inflammatory response activation. An RNA-sequencing-based transcriptome assay using mouse heart tissue with or without LPS injection showed that 3,326 and 1,769 genes were upregulated and downregulated, respectively (>2-fold changes; P<0.05). Furthermore, these differentially expressed genes were classified into 20 pathways, including ‘Wnt signaling pathway’, ‘VEGF signaling pathway’ and ‘TGF-β signaling pathway’, and these altered genes were enriched in 41 Gene Ontology terms. The application of Wnt3a inhibited the activation of the LPS-induced inflammatory response and activated Wnt signaling, as well as protecting against LPS-mediated cardiac tissue damage in mice. In contrast, inhibition of Wnt signaling by injection of its inhibitor IWR induced plasminogen activator inhibitor-1 expression and resulted in cardiac structure derangement, which was similar to the symptoms caused by injection of LPS, suggesting that LPS-induced damage to heart tissue may be via inhibition of Wnt signaling. The present analyses showed that Wnt signaling serves a pivotal role in sepsis development and may improve our understanding of the molecular basis underlying sepsis.

Upregulation of Mitochondrial Redox Sensitive Proteins in LPS-Treated Stefin B-Deficient Macrophages

Stefin B (cystatin B) is an intracellular inhibitor of cysteine cathepsins and mutations in the stefin B gene, resulting in the development of Unverricht–Lundborg disease, which is a form of myoclonic epilepsy. It was suggested that a key mechanism behind stefin B-mediated disease progression was impaired redox homeostasis. Stefin B-deficient mice were found more sensitive to lipopolysaccharide (LPS)-induced sepsis as a consequence of increased expression of caspase-11 and Nucleotide-binding oligomerization domain, Leucine rich Repeat and Pyrin domain containing (NLRP nflammasome activation and higher levels of mitochondrial reactive oxygen species (ROS). In the present study, we investigated if LPS-triggered oxidative stress affected the protein levels and redox status of redox sensitive proteins—thioredoxin, peroxiredoxins, and superoxide dismutases in macrophages and spleens of LPS-injected mice. LPS challenge was found to result in a marked elevation in mitochondrial peroxiredoxin 3 (Prx3), sulfiredoxin, and superoxide dismutase 2 (Sod2) in stefin B-deficient macrophages and spleens. We determined that sulfiredoxin is targeted to mitochondria after LPS challenge. In conclusion, the upregulation of mitochondrial redox-sensitive proteins Prx3 and Sod2 in stefin B-deficient cells implies a protective role of stefin B in mitochondrial function.

Downregulated GTCPH I/BH4 Pathway and Decreased Function of Circulating Endothelial Progenitor Cells and Their Relationship with Endothelial Dysfunction in Overweight Postmenopausal Women

Endothelial progenitor cells (EPCs) have endogenous endothelium-reparative potential, but obesity impairs EPCs. Overweight premenopausal women have a normal number of circulating EPCs with functional activity, but whether EPCs in overweight postmenopausal women can repair obesity-related endothelial damage requires further investigation. For this purpose, we examined the function and number of circulating EPCs, evaluated vascular endothelial function, and explored the underlying mechanism. Compared with normal weight or overweight age-matched men, postmenopausal women (overweight or normal weight) had a diminished number of circulating EPCs and impaired vascular endothelial function, as detected by flow-mediated dilatation. Moreover, GTCPH I expression and the nitric oxide level in overweight postmenopausal women and men were significantly decreased. Together, our findings demonstrate that the number or function of circulating EPCs and endothelial function, which is partially regulated by the GTCPH I/BH4 signaling pathway, is not preserved in overweight postmenopausal women. The GTCPH I/BH4 pathway in circulating EPCs may be a potential therapeutic target for endothelial injury in overweight postmenopausal women.

Thioredoxin a novel biomarker of post-injury sepsis

BACKGROUND

Thioredoxin (TRX), an endogenous anti-oxidant protein induced in inflammatory conditions, has been shown to increase in plasma and to be associated with outcome in septic patients. This biomarker has never been studied in a trauma setting. We hypothesized that TRX would be increased after trauma and associated with post-injury sepsis.

METHODS

Single-centre prospective observational study conducted at the intensive care unit (ICU) at the Karolinska University Hospital, Stockholm, Sweden, a level-1 trauma centre. Eighty-three severely injured trauma patients, 18 years or older, with an ICU stay of three days or more were included. Plasma samples were obtained on day 1 and 3 after informed consent. Clinical, physiological and outcome data were retrieved from the trauma and ICU research registries. Plasma samples were also obtained from 15 healthy subjects. In addition, a standardized porcine trauma model was conducted where a femur fracture followed by a controlled hemorrhage period were inflicted in four pigs.

RESULTS

In pigs, however not significant, there was a continuing increase in plasma-TRX after femur fracture and sequential hemorrhage despite near normalisation of cardiac index and lactate levels. In patients, median injury severity score was 29 and 48 patients developed sepsis during their ICU stay. A three-fold increase in initial TRX was seen in trauma patients when compared to healthy volunteers. Thioredoxin was significantly higher in patients in shock on admission, those subject to massive transfusion and in the most severely injured patients. No difference was seen between survivors and non-survivors. Plasma-TRX on day 1 was significantly increased in patients who later developed post-injury sepsis. In a logistic regression analysis including TRX, C-reactive protein, injury severity, massive transfusion, and admission blood pressure, TRX was the only variable independently associated with post-injury sepsis.

CONCLUSIONS

This study demonstrates that TRX is released into plasma in response to severe trauma and independently associated with post-injury sepsis. The use of TRX as a biomarker in trauma patients needs further evaluation in larger studies.

LEVEL OF EVIDENCE

Retrospective cohort study, level III.

Research Advances in Biomarker for Sepsis

Sepsis is one of the most common causes of death in severely injured patients worldwide. The early detection of sepsis still has to be solved in clinical practice. The delayed diagnosis often contributes to inappropriate antimicrobial treatment and subsequent high mortality. Sepsis biomarkers are produced during the host response to infection. Traditional biomarkers are polypeptides and/or proteins derived from this response. Omics-based biomarkers are screening out from all kinds of molecules of host response while high-throughout omics technologies are emerging. This review describes traditional and potential omics-based sepsis biomarkers from currently available literatures. The combination of these biomarkers would refine the identification of sepsis for further clinical and experimental sepsis studies.

Sepsis biomarkers: an omics perspective

Sepsis is a common cause of death in hospitalized patients worldwide. The early detection of sepsis remains a great challenge for clinicians, and delayed diagnosis frequently undermines treatment efforts, thereby contributing to high mortality. Omics technologies allow high-throughput screening of sepsis biomarkers. This review describes currently available and novel sepsis biomarkers in the context of genomics, transcriptomics, proteomics, and metabolomics. The combination of these technologies can help refine the diagnosis of sepsis. This review paper serves as a reference for future studies that employ an integrated, multi-omics approach to disease identification.

Plasma thioredoxin levels during post-cardiac arrest syndrome: relationship with severity and outcome

Introduction

Despite experimental evidence, clinical demonstration of acute state of oxidative stress and inflammation during post-cardiac arrest syndrome is lacking. Plasma level of thioredoxin (TRX), a redox-active protein induced under conditions of oxidative stress and inflammation, is increased in various critical care conditions. We determined plasma TRX concentrations after cardiac arrest and assessed relationships with severity and outcome.

Methods

Retrospective study of consecutive patients admitted to a single academic intensive care unit (ICU) for out-of-hospital cardiac arrest (between July 2006 and March 2008). Plasma levels of TRX were measured at admission, day (D) 1, 2 and 3.

Results

Of 176 patients included, median TRX values measured in ICU survivors and non-survivors were, respectively: 22 ng/mL (7.8 to 77) vs. 72.4 (21.9 to 117.9) at admission (P < 0.001); 5.9 (3.5 to 25.5) vs. 23.2 (5.8 to 81.4) at D1 (P = 0.003); 10.8 (3.6 to 50.8) vs. 11.7 (4.5 to 66.4) at D2 (P = 0.22); and 16.7 (5.3 to 68.3) vs. 17 (4.3 to 62.9) at D3 (P = 0.96). Patients dying within 24 hours had significantly (P < 0.001) higher TRX levels (118.6 ng/mL (94.8 to 280)) than those who died after 24 hours or survived (50.8 (13.9 to 95.7) and 22 (7.8 to 77)). The area under the ROC curve to predict early death was 0.84 (0.76 to 0.91).

TRX levels on admission were significantly correlated with 'low-flow' duration (P = 0.003), sequential organ failure assessment (SOFA) score (P < 0.001), and blood lactate concentration (P < 0.001), but not with 'no-flow' duration or simplified acute physiology score (SAPS) II score. TRX levels and admission arterial pO² correlated negatively (r = -0.17, P = 0.03). Finally, cardiac arrest with cardiac etiology exhibited lower levels of TRX than in cases of extra-cardiac cause (46 ng/mL (11 to 104) vs. 68 (42 to 137), P = 0.01).

Conclusions

Our data show for the first time that TRX levels were elevated early following cardiac arrest, suggestive of oxidative stress and inflammation occurring with this condition. Highest values were found in the most severe patients. TRX could be a useful tool for further exploration and comprehension of post-cardiac arrest syndrome.

Predictors of survival in sepsis: what is the best inflammatory marker to measure?

PURPOSE OF REVIEW

Sepsis is relevant due to its high morbidity and mortality. For both sepsis diagnosis and outcome prediction many biomarkers have been described in the literature. Most of these markers are objects of scientific interest rather than being introduced into daily clinical practice. However, due to their unspecific character and their insufficient predictive value for the individual person, research focus is still on new aspects in sepsis-related biomarkers.

RECENT FINDINGS

Beyond the widely used acute-phase proteins C-reactive protein (CRP) and procalcitonin (PCT), many new molecules have been studied deriving from different organs or cells affected, due to the systemic nature of sepsis. Cytokines, coagulation factors/characteristics, vasoactive hormones, and several others have been recently proved to be relevant in sepsis syndrome and probably useful for outcome prediction. However, single time point measurements may be less predictive than consideration of the time-dependent course of parameters. Clinical decision just based on a biomarker is still not feasible because of the huge inter-individual differences in the inflammatory response.

SUMMARY

Many biomarkers display relevant correlation with the clinical outcome of patients with severe sepsis and septic shock. Consideration of their time courses may be more reliable than absolute levels. Clinical decision should not be based only on biomarkers but organ dysfunctions, for example, should also be taken into account.