Expression of MicroRNAs in Sepsis-Related Organ Dysfunction: A Systematic Review

Postmortem analyses of myocardial microRNA expression in sepsis

BACKGROUND

Sepsis can lead to myocardial depression, playing a significant role in sepsis pathophysiology, clinical care, and outcome. To gain more insight into the pathophysiology of the myocardial response in sepsis, we investigated the expression of microRNA in myocardial autopsy specimens in critically ill deceased with sepsis and non-septic controls.

MATERIALS AND METHODS

In this retrospective observational study, we obtained myocardial tissue samples collected during autopsy from adult patients deceased with sepsis (n = 15) for routine histological examination. We obtained control myocardial tissue specimens (n = 15) from medicolegal autopsies of cadavers whose cause of death was injury or who were found dead at home and the cause of death was coronary artery disease with sudden cardiac arrest. RNA was isolated from formalin-fixed paraffin- embedded (FFPE) cardiac samples using the RecoverAll Total Nucleic Acid Isolation Kit for FFPE (Invitrogen). Differentially expressed miRNAs were identified using edgeR v3.32. MicroRNA was considered up- or down-regulated if the false discovery rate was < 0.05 and logarithmic fold change (log2FC) ≥ 1 for up-regulated or log2FC ≤ -1 for down-regulated miRNAs. The mean difference and 95% confidence interval (CI) were calculated for normalized read counts. Predicted miRNA targets were retrieved using Ingenuity Pathway Analysis (IPA) software, and pathway enrichment and classification were performed using PantherDB. For miRNA - mRNA interaction analysis, differentially expressed genes were analyzed by 3`mRNA sequencing.

RESULTS

Differential expression analysis identified a total of 32 miRNAs in the myocardial specimens. Eight miRNAs had a significant change in the mean difference based on the 95% CI, with the largest increase in mean counts in septic samples with hsa-miR-12136 and the highest fold change with hsa-miR-146b-5p. The threshold for down-regulated miRNAs in sepsis compared to controls was obtained with hsa-miR-144-5p and hsa-miR-451a, with the latter having the largest decrease in mean counts and fold decrease. The miRNA - mRNA interaction analysis identified eight miRNAs with target genes also differentially expressed in septic hearts. The highest number of potential targets were identified for hsa-miR-363-3p.

CONCLUSIONS

Several regulatory miRNAs were up-or down-regulated in the myocardial tissue of patients deceased with sepsis compared to non-septic subjects. The predicted target genes of miRNAs and miRNA-mRNA interaction analysis are associated with biological functions related to cardiovascular functions, cell viability, cell adhesion, and regulation of inflammatory and immune response.

Dexmedetomidine regulates exosomal miR-29b-3p from macrophages and alleviates septic myocardial injury by promoting autophagy in cardiomyocytes via targeting glycogen synthase kinase 3β

Background

Our previous research suggested that dexmedetomidine (Dex) promotes autophagy in cardiomyocytes, thus safeguarding them against apoptosis during sepsis. However, the underlying mechanisms of Dex-regulated autophagy have remained elusive. This study aimed to explore the role of exosomes and how they participate in Dex-induced cardioprotection in sepsis. The underlying microRNA (miRNA) mechanisms and possible therapeutic targets for septic myocardial injury were identified.

Methods

We first collected plasma exosomes from rats with sepsis induced by caecal ligation and puncture (CLP) with or without Dex treatment, and then incubated them with H9c2 cells to observe the effect on cardiomyocytes. Subsequently, the differential expression of miRNAs in plasma exosomes from each group of rats was identified through miRNA sequencing. miR-29b-3p expression in circulating exosomes of septic or non-septic patients, as well as in lipopolysaccharide-induced macrophages after Dex treatment, was analysed by quantitative real-time polymerase chain reaction (qRT-PCR). The autophagy level of cardiomyocytes after macrophage-derived exosome treatment was assessed by an exosome tracing assay, western blotting, and an autophagic flux assay. Specific miRNA mimics and inhibitors or small interfering RNAs were used to predict and evaluate the function of candidate miRNA and its target genes by qRT-PCR, annexin V/propyl iodide staining, autophagy flux analysis, and western blotting.

Results

We found that plasma-derived exosomes from Dex-treated rats promoted cardiomyocyte autophagy and exerted antiapoptotic effects. Additionally, they exhibited a high expression of miRNA, including miR-29b-3p. Conversely, a significant decrease in miR-29b-3p was observed in circulating exosomes from CLP rats, as well as in plasma exosomes from sepsis patients. Furthermore, Dex upregulated the lipopolysaccharide-induced decrease in miR-29b-3p expression in macrophage-derived exosomes. Exosomal miR-29b-3p from macrophages is thought to be transferred to cardiomyocytes, thus leading to the promotion of autophagy in cardiomyocytes. Database predictions, luciferase reporter assays, and small interfering RNA intervention confirmed that glycogen synthase kinase 3β (GSK-3β) is a target of miR-29b-3p. miR-29b-3p promotes cardiomyocyte autophagy by inhibiting GSK-3β expression and activation.

Conclusions

These findings demonstrate that Dex attenuates sepsis-associated myocardial injury by modulating exosome-mediated macrophage-cardiomyocyte crosstalk and that the miR-29b-3p/GSK-3β signaling pathway represents a hopeful target for the treatment of septic myocardial injury.

MicroRNAs in Sepsis

Sepsis is an insidious and frequent condition of severe inflammation due to infections. Several biomarkers have been established for initial screening, but the non-specific nature of the existing biomarkers has led to the investigation of more sensitive and specific tools, such as microRNAs (miRs). These non-coding RNAs are involved in several diseases, including sepsis, due to their roles in cellular homeostasis. Herein, a literature overview was attempted to distinguish the most prominent miRs identified in septic conditions and their usefulness in diagnosis, prognosis and even classification of sepsis. miRs implicated in the regulation of pro and anti-inflammatory mechanisms, such as MIR-146a, MIR-155, MIR-181b, MIR-223-5p, MIR-494-3p, MIR-2055b, MIR-150 and MIR-143 have been pinpointed as acceptable testing tools. Furthermore, the use of miRs as screening panels, specific for septic parameters, such as type of causal infection, inflammation immune pathways affected (NF-kB, STAT/JACK), organs inflicted, as well as parallel screening of certain miRs alongside other long non-coding RNAs (LNCs), as co-regulators of sepsis progression. Overall, miRs exhibit benefits in terms of specificity and sensitivity, as well as practical ease of use and test stability. Furthermore, miRs could offer valuable insights into the molecular basis of disease causality and provide valuable therapeutic information.

Inflammation, Sepsis, and the Coagulation System

Sepsis has been a major health problem for centuries and it is still the leading cause of hospital deaths. Several studies in the past decades have identified numerous biochemical abnormalities in severe cases, and many of these studies provide evidence of the perturbation of the hemostatic system. This can result in complications, such as disseminated intravascular coagulation that can lead to multiorgan failure. Nevertheless, large clinical studies have demonstrated that the simple approach of inhibiting the coagulation processes by any means fails to provide significant improvement in the survival of septic patients. A cause of this failure could be the fact that in sepsis the major clinical problems result not primarily from the presence of the infective agent or enhanced coagulation but from the complex dysregulated systemic host response to pathogens. If this overt reaction is not fully deciphered, appropriate interference is highly unlikely and any improvement by conventional therapeutic interventions would be limited. Cellular activation in sepsis can be targeted by novel approaches like inhibition of the heterotypic cellular interactions of blood cells by targeting surface receptors or posttranscriptional control of the hemostatic system by noncoding ribonucleic acid (RNA) molecules. Stable RNA molecules can affect the expression of several proteins. Thus, it can be anticipated that modulation of microRNA production would result in a multitude of effects that may be beneficial in septic cases. Here, we highlight some of the recent diagnostic possibilities and potential novel routes of the dysregulated host response.

Unveiling the Role of Exosomes in the Pathophysiology of Sepsis: Insights into Organ Dysfunction and Potential Biomarkers

Extracellular vesicles (EVs) are tools for intercellular communication, mediating molecular transport processes. Emerging studies have revealed that EVs are significantly involved in immune processes, including sepsis. Sepsis, a dysregulated immune response to infection, triggers systemic inflammation and multi-organ dysfunction, posing a life-threatening condition. Although extensive research has been conducted on animals, the complex inflammatory mechanisms that cause sepsis-induced organ failure in humans are still not fully understood. Recent studies have focused on secreted exosomes, which are small extracellular vesicles from various body cells, and have shed light on their involvement in the pathophysiology of sepsis. During sepsis, exosomes undergo changes in content, concentration, and function, which significantly affect the metabolism of endothelia, cardiovascular functions, and coagulation. Investigating the role of exosome content in the pathogenesis of sepsis shows promise for understanding the molecular basis of human sepsis. This review explores the contributions of activated immune cells and diverse body cells' secreted exosomes to vital organ dysfunction in sepsis, providing insights into potential molecular biomarkers for predicting organ failure in septic shock.

Oxidative Stress in Sepsis: A Focus on Cardiac Pathology

This study aims to analyze post-mortem human cardiac specimens, to verify and evaluate the existence or extent of oxidative stress in subjects whose cause of death has been traced to sepsis, through immunohistological oxidative/nitrosative stress markers. Indeed, in the present study, i-NOS, NOX2, and nitrotyrosine markers were higher expressed in the septic death group when compared to the control group, associated with also a significant increase in 8-OHdG, highlighting the pivotal role of oxidative stress in septic etiopathogenesis. In particular, 70% of cardiomyocyte nuclei from septic death specimens showed positivity for 8-OHdG. Furthermore, intense and massive NOX2-positive myocyte immunoreaction was noticed in the septic group, as nitrotyrosine immunostaining intense reaction was found in the cardiac cells. These results demonstrated a correlation between oxidative and nitrosative stress imbalance and the pathophysiology of cardiac dysfunction documented in cases of sepsis. Therefore, subsequent studies will focus on the expression of oxidative stress markers in other organs and tissues, as well as on the involvement of the intracellular pattern of apoptosis, to better clarify the complex pathogenesis of multi-organ failure, leading to support the rationale for including therapies targeting redox abnormalities in the management of septic patients.

Sepsis-associated encephalopathy: Autophagy and miRNAs regulate microglial activation

Sepsis-associated encephalopathy (SAE) describes diffuse or multifocal cerebral dysfunction caused by the systemic inflammatory response to sepsis. SAE is a common neurological complication in patients in the middle and late stages of sepsis in the intensive care unit. Microglia, resident macrophages of the central nervous system, phagocytose small numbers of neuronal cells and apoptotic cells, among other cells, to maintain the dynamic balance of the brain's internal environment. The neuroinflammatory response induced by activated microglia plays a central role in the pathogenesis of various central nervous system diseases. In this paper, we systematically describe the functions and phenotypes of microglia, summarize how microglia mediate neuroinflammation and contribute to the occurrence and development of SAE, and discuss recent progress in autophagy- and microRNA-mediated regulation of microglial activation to provide a theoretical basis for the prevention and treatment of SAE and identify related therapeutic targets.

Host and Pathogen-Directed Therapies against Microbial Infections Using Exosome- and Antimicrobial Peptide-derived Stem Cells with a Special look at Pulmonary Infections and Sepsis

Microbial diseases are a great threat to global health and cause considerable mortality and extensive economic losses each year. The medications for treating this group of diseases (antibiotics, antiviral, antifungal drugs, etc.) directly attack the pathogenic agents by recognizing the target molecules. However, it is necessary to note that excessive use of any of these drugs can lead to an increase in microbial resistance and infectious diseases. New therapeutic methods have been studied recently using emerging drugs such as mesenchymal stem cell-derived exosomes (MSC-Exos) and antimicrobial peptides (AMPs), which act based on two completely different strategies against pathogens including Host-Directed Therapy (HDT) and Pathogen-Directed Therapy (PDT), respectively. In the PDT approach, AMPs interact directly with pathogens to interrupt their intrusion, survival, and proliferation. These drugs interact directly with the cell membrane or intracellular components of pathogens and cause the death of pathogens or inhibit their replication. The mechanism of action of MSC-Exos in HDT is based on immunomodulation and regulation, promotion of tissue regeneration, and reduced host toxicity. This review studies the potential of mesenchymal stem cell-derived exosomes/ATPs therapeutic properties against microbial infectious diseases especially pulmonary infections and sepsis.

Neutrophils and the Systemic Inflammatory Response Syndrome (SIRS)

We are not entirely able to understand, assess, and modulate the functioning of the immune system in clinical situations that lead to a systemic inflammatory response. In the search for diagnostic and treatment strategies (which are still far from perfect), it became very important to study the pathogenesis and participation of endogenous inflammation mediators. This study attempts to more precisely establish the role of neutrophils in individual phenomena occurring during an inflammatory and anti-inflammatory reaction, taking into account their cidal, immunoregulatory, and reparative abilities. Pro- and anticoagulatory properties of endothelium in systemic inflammatory response syndrome (SIRS) are emphasised, along with the resulting clinical implications (the application of immunotherapy using mesenchymal stem/stromal cells (MSCs) or IL-6 antagonists in sepsis and COVID-19 treatment, among others). Special attention is paid to reactive oxygen species (ROS), produced by neutrophils activated during "respiratory burst" in the course of SIRS; the protective and pathogenic role of these endogenous mediators is highlighted. Moreover, clinically useful biomarkers of SIRS (neutrophil extracellular traps, cell-free DNA, DAMP, TREMs, NGAL, miRNA, selected cytokines, ROS, and recognised markers of endothelial damage from the group of adhesins by means of immunohistochemical techniques) related to the neutrophils are presented, and their role in the diagnosing and forecasting of sepsis, burn disease, and COVID-19 is emphasised. Finally, examples of immunomodulation of sepsis and antioxidative thermal injury therapy are presented.

Autoimmune Heart Disease: A Comprehensive Summary for Forensic Practice

Autoimmune heart disease is a non-random condition characterised by immune system-mediated aggression against cardiac tissue. Cardiac changes often exhibit nonspecific features and, if unrecognised, can result in fatal outcomes even among seemingly healthy young individuals. In the absence of reliable medical history, the primary challenge lies in differentiating between the various cardiopathies. Numerous immunohistochemical and genetic studies have endeavoured to characterise distinct types of cardiopathies, facilitating their differentiation during autopsy examinations. However, the presence of a standardised protocol that forensic pathologists can employ to guide their investigations would be beneficial. Hence, this summary aims to present the spectrum of autoimmune cardiopathies, including emerging insights such as SARS-CoV-2-induced cardiopathies, and proposes the utilisation of practical tools, such as blood markers, to aid forensic pathologists in their routine practice.

Identification of biomarkers related to sepsis diagnosis based on bioinformatics and machine learning and experimental verification

Sepsis is a systemic inflammatory response syndrome caused by bacteria and other pathogenic microorganisms. Every year, approximately 31.5 million patients are diagnosed with sepsis, and approximately 5.3 million patients succumb to the disease. In this study, we identified biomarkers for diagnosing sepsis analyzed the relationships between genes and Immune cells that were differentially expressed in specimens from patients with sepsis compared to normal controls. Finally, We verified its effectiveness through animal experiments. Specifically, we analyzed datasets from four microarrays(GSE11755、GSE12624、GSE28750、GSE48080) that included 106 blood specimens from patients with sepsis and 69 normal human blood samples. SVM-RFE analysis and LASSO regression model were carried out to screen possible markers. The composition of 22 immune cell components in patients with sepsis were also determined using CIBERSORT. The expression level of the biomarkers in Sepsis was examined by the use of qRT-PCR and Western Blot (WB). We identified 50 differentially expressed genes between the cohorts, including 2 significantly upregulated and 48 significantly downregulated genes, and KEGG pathway analysis identified Salmonella infection, human T cell leukemia virus 1 infection, Epstein-Barr virus infection, hepatitis B, lysosome and other pathways that were significantly enriched in blood from patients with sepsis. Ultimately, we identified COMMD9, CSF3R, and NUB1 as genes that could potentially be used as biomarkers to predict sepsis, which we confirmed by ROC analysis. Further, we identified a correlation between the expression of these three genes and immune infiltrate composition. Immune cell infiltration analysis revealed that COMMD9 was correlated with T cells regulatory (Tregs), T cells follicular helper, T cells CD8, et al. CSF3R was correlated with T cells regulatory (Tregs), T cells follicular helper, T cells CD8, et al. NUB1 was correlated with T cells regulatory (Tregs), T cells gamma delta, T cells follicular helper, et al. Taken together, our findings identify potential new diagnostic markers for sepsis that shed light on novel mechanisms of disease pathogenesis and, therefore, may offer opportunities for therapeutic intervention.

Diagnostic Value of Neutrophil CD64 in Sepsis Patients in the Intensive Care Unit: A Cross-Sectional Study

Little is known about the role of neutrophil CD64 (nCD64) in detecting sepsis early in Asian populations. We examined the cut-off and predictive values of nCD64 for diagnosing sepsis in Vietnamese intensive care units (ICU) patients. A cross-sectional study was conducted at the ICU of Cho Ray Hospital between January 2019 and April 2020. All 104 newly admitted patients were included. Sensitivity (Sens), specificity (Spec), positive and negative predictive values (PPV and NPV), and receiver operating characteristic (ROC) curves were calculated to compare the diagnostic values of nCD64 with those of procalcitonin (PCT) and white blood cell (WBC) for sepsis. The median nCD64 value in sepsis patients was statistically higher than that of non-sepsis patients (3106 [1970-5200] vs. 745 [458-906] molecules/cell, p < 0.001). ROC analysis found that the AUC value of nCD64 was 0.92, which was higher than that of PCT (0.872), WBC (0.637), and nCD64 combined, with WBC (0.906) and nCD64 combined with WBC and PCT (0.919), but lower than that of nCD64 combined with PCT (0.924). With an AUC value of 0.92, the nCD64 index of 1311 molecules/cell-detected sepsis with 89.9% Sens, 85.7% Spec, 92.5% PPV, and 81.1% NPV. nCD64 can be a useful marker for early sepsis diagnosis in ICU patients. nCD64 combined with PCT may improve the diagnostic accuracy.

Metabolic Reprogramming and Its Regulatory Mechanism in Sepsis-Mediated Inflammation

Sepsis is a systemic inflammatory disease caused by an infection that can lead to multiple organ failure. Sepsis alters energy metabolism, leading to metabolic reprogramming of immune cells, which consequently disrupts innate and adaptive immune responses, triggering hyperinflammation and immunosuppression. This review summarizes metabolic reprogramming and its regulatory mechanism in sepsis-induced hyperinflammation and immunosuppression, highlights the significance and intricacies of immune cell metabolic reprogramming, and emphasizes the pivotal role of mitochondria in metabolic regulation and treatment of sepsis. This review provides an up-to-date overview of the relevant literature to inform future research directions in understanding the regulation of sepsis immunometabolism. Metabolic reprogramming has great promise as a new target for sepsis treatment in the future.

Acute and Chronic Systemic Inflammation: Features and Differences in the Pathogenesis, and Integral Criteria for Verification and Differentiation

Currently, there is rationale for separating the systemic manifestations of classical inflammation from systemic inflammation (SI) itself as an independent form of the general pathological process underlying the pathogenesis of the most severe acute and chronic diseases. With this aim in view, we used integral scales of acute and chronic SI (ChSI), including the following blood plasma parameters: interleukins 6, 8, 10; tumor necrosis factor alpha; C-reactive protein; D-dimer; cortisol; troponin I; myoglobin. The presence of multiple organ dysfunction according to the SOFA score was also taken into account. The effectiveness of the scales was tested in groups of intensive care patients during different periods of acute trauma, sepsis, and septic shock. The ChSI scale was applicable under systemic autoimmune diseases, chronic purulent infections, chronic limb threatening ischemia, and end-stage renal disease of various genesis. The number of examined patients was 764 in total. The scales allowed us to verify specific phases of acute SI and identify pathogenetic risk factors of lethal outcomes, as well as the most severe variants of the chronic pathologies course. These scales are open adaptable systems (in terms of the nomenclature and choice of indicators). They are primarily intended for scientific research. However, the SI verification methodology presented in this paper may be useful for developing advanced criteria for assessing both the typical links in the pathogenesis of many diseases and the severity of the overall condition of patients for clinical practice.

Fighting Fire with Fire: Exosomes and Acute Pancreatitis-Associated Acute Lung Injury

Acute pancreatitis (AP) is a prevalent clinical condition of the digestive system, with a growing frequency each year. Approximately 20% of patients suffer from severe acute pancreatitis (SAP) with local consequences and multi-organ failure, putting a significant strain on patients' health insurance. According to reports, the lungs are particularly susceptible to SAP. Acute respiratory distress syndrome, a severe type of acute lung injury (ALI), is the primary cause of mortality among AP patients. Controlling the mortality associated with SAP requires an understanding of the etiology of AP-associated ALI, the discovery of biomarkers for the early detection of ALI, and the identification of potentially effective drug treatments. Exosomes are a class of extracellular vesicles with a diameter of 30-150 nm that are actively released into tissue fluids to mediate biological functions. Exosomes are laden with bioactive cargo, such as lipids, proteins, DNA, and RNA. During the initial stages of AP, acinar cell-derived exosomes suppress forkhead box protein O1 expression, resulting in M1 macrophage polarization. Similarly, macrophage-derived exosomes activate inflammatory pathways within endothelium or epithelial cells, promoting an inflammatory cascade response. On the other hand, a part of exosome cargo performs tissue repair and anti-inflammatory actions and inhibits the cytokine storm during AP. Other reviews have detailed the function of exosomes in the development of AP, chronic pancreatitis, and autoimmune pancreatitis. The discoveries involving exosomes at the intersection of AP and acute lung injury (ALI) are reviewed here. Furthermore, we discuss the therapeutic potential of exosomes in AP and associated ALI. With the continuous improvement of technological tools, the research on exosomes has gradually shifted from basic to clinical applications. Several exosome-specific non-coding RNAs and proteins can be used as novel molecular markers to assist in the diagnosis and prognosis of AP and associated ALI.