Sepsis-associated encephalopathy is a diffuse brain dysfunction secondary to infection. It has been established that factors such as age and sex can significantly contribute to the development of sepsis-associated encephalopathy. Our recent study implicated a possible link between adenosine-to-inosine RNA editing and sepsis-associated encephalopathy, yet the dynamics of adenosine-to-inosine RNA editing during sepsis-associated encephalopathy and how it could be influenced by factors such as age, sex and antidepressants remain uninvestigated. Our current study analysed and validated transcriptome-wide changes in adenosine-to-inosine RNA editing in the hippocampus of different septic mouse models. Seventy-four sites in 64 genes showed significant differential RNA editing over time in septic mice induced by caecal ligation and perforation. The differential RNA editing might contribute to the RNA expression regulation of the edited genes, with 42.2% differentially expressed. These differentially edited genes, especially those with missense editing, such as glutamate receptor, ionotropic, kainate 2 (Grik2, p.M620V), filamin A (Flna, p.S2331G) and capicua transcriptional repressor (Cic, p.E2270G), were mainly involved in abnormal social behaviour and neurodevelopmental and psychiatric disorders. Significant effects of age and sex were also observed on sepsis-associated RNA editing. Further comparison highlighted 40 common differential RNA editing sites that caecal ligation and perforation-induced and lipopolysaccharide-induced septic mouse models shared. Interestingly, these findings demonstrate temporal dynamics of adenosine-to-inosine RNA editing in the mouse hippocampus during sepsis, add to the understanding of age and sex differences in the disease and underscore the role of the epigenetic process in sepsis-associated encephalopathy.

UNASSIGNED: As one of the serious complications of sepsis in children, sepsis-associated encephalopathy (SAE) is associated with significantly poor prognosis and increased mortality. However, predictors of outcomes for pediatric SAE patients have yet to be identified. The aim of this study was to develop nomograms to predict the 14-day and 90-day mortality of children with SAE, providing early warning to take effective measures to improve prognosis and reduce mortality.
UNASSIGNED: In this multicenter, retrospective study, we screened 291 patients with SAE admitted to the PICU between January 2017 and September 2022 in Shandong Province. A least absolute shrinkage and selector operation (LASSO) method was used to identify the optimal prognostic factors predicting the outcomes in pediatric patients with SAE. Then, multivariable logistic regression analysis was performed based on these variables, and two nomograms were built for visualization. We used the area under the curve (AUC), calibration curves and decision curves to test the accuracy and discrimination of the nomograms in predicting outcomes.
UNASSIGNED: There were 129 patients with SAE in the training cohort, and there were 103 and 59 patients in the two independent validation cohorts, respectively. Vasopressor use, procalcitonin (PCT), lactate and pediatric critical illness score (PCIS) were independent predictive factors for 14-day mortality, and vasopressor use, PCT, lactate, PCIS and albumin were independent predictive factors for 90-day mortality. Based on the variables, we generated two nomograms for the early identification of 14-day mortality (AUC 0.853, 95% CI 0.787-0.919, sensitivity 72.4%, specificity 84.5%) and 90-day mortality (AUC 0.857, 95% CI 0.792-0.923, sensitivity 72.3%, specificity 90.6%), respectively. The calibration plots for nomograms showed excellent agreement of mortality probabilities between the observed and predicted values in both training and validation cohorts. Decision curve analyses (DCA) indicated that nomograms conferred high clinical net benefit.
UNASSIGNED: The nomograms in this study revealed optimal prognostic factors for the mortality of pediatric patients with SAE, and individualized quantitative risk evaluation by the models would be practical for treatment management.

Molecular pathways mediating systemic inflammation entering the brain parenchyma to induce sepsis-associated encephalopathy (SAE) remain elusive. Here, we report that in mice during the first 6 hours of peripheral lipopolysaccharide (LPS)-evoked systemic inflammation (6 hpi), the plasma level of adenosine quickly increased and enhanced the tone of central extracellular adenosine which then provoked neuroinflammation by triggering early astrocyte reactivity. Specific ablation of astrocytic Gi protein-coupled A1 adenosine receptors (A1ARs) prevented this early reactivity and reduced the levels of inflammatory factors (e.g., CCL2, CCL5, and CXCL1) in astrocytes, thereby alleviating microglial reaction, ameliorating blood-brain barrier disruption, peripheral immune cell infiltration, neuronal dysfunction, and depression-like behaviour in the mice. Chemogenetic stimulation of Gi signaling in A1AR-deficent astrocytes at 2 and 4 hpi of LPS injection could restore neuroinflammation and depression-like behaviour, highlighting astrocytes rather than microglia as early drivers of neuroinflammation. Our results identify early astrocyte reactivity towards peripheral and central levels of adenosine as an important pathway driving SAE and highlight the potential of targeting A1ARs for therapeutic intervention.

OBJECTIVE: This study aimed to investigate the serum levels of neuron-specific enolase (NSE) in sepsis-associated encephalopathy (SAE) and perform a meta-analysis to assess the diagnostic and prognostic potential of serum NSE in SAE patients.
METHODS: We searched English and Chinese databases for studies related to SAE that reported serum NSE levels until November 2023. We extracted information from these studies including the first author and year of publication, the number of samples, the gender and age of patients, the collection time of blood samples in patients, the assay method of serum NSE, the study methods, and the levels of serum NSE with units of ng/mL. The quality assessment of diagnostic accuracy studies 2 (QUADAS-2) tool was used to evaluate the study quality. A meta-analysis was performed using Review Manager version 5.3, employing either a random effects model or a fixed effects model.
RESULTS: A total of 17 studies were included in the final meta-analysis, including 682 SAE patients and 946 NE patients. The meta-analysis demonstrated significantly higher serum NSE levels in SAE patients compared to NE patients (Z = 5.97, P < 0.001, MD = 7.79, 95%CI 5.23-10.34), irrespective of the method used for serum NSE detection (Z = 6.15, P < 0.001, mean difference [MD] = 7.75, 95%CI 5.28-10.22) and the study methods (Z = 5.97, P < 0.001, MD = 7.79, 95%CI 5.23-10.34). Furthermore, sepsis patients with a favorable outcome showed significantly lower levels of serum NSE compared to those with an unfavorable outcome (death or adverse neurological outcomes) (Z = 5.44, P < 0.001, MD = - 5.34, 95%CI - 7.26-3.42).
CONCLUSIONS: The Serum level of NSE in SAE patients was significantly higher than that in septic patients without encephalopathy. The higher the serum NSE level in SAE patients, the higher their mortality rate and incidence of adverse neurological outcomes.

Sepsis is a syndrome that causes dysfunction of multiple organs due to the host\'s uncontrolled response to infection and is a significant contributor to morbidity and mortality in intensive care units worldwide. Surviving patients are often left with acute brain injury and long-term cognitive impairment, known as sepsis-associated encephalopathy (SAE). In recent years, researchers have directed their focus towards the pathogenesis of SAE. However, due to the complexity of its development, there remains a lack of effective treatment measures that arise as a serious issue affecting the prognosis of sepsis patients. Further research on the possible causes of SAE aims to provide clinicians with potential therapeutic targets and help develop targeted prevention strategies. This paper aims to review recent research on the pathogenesis of SAE, in order to enhance our understanding of this syndrome.

BACKGROUND: Understanding the mechanism behind sepsis-associated encephalopathy (SAE) remains a formidable task. This study endeavors to shed light on the complex cellular and molecular alterations that occur in the brains of a mouse model with SAE, ultimately unraveling the underlying mechanisms of this condition.
METHODS: We established a murine model using intraperitoneal injection of lipopolysaccharide (LPS) in wild type and Anxa1-/- mice and collected brain tissues for analysis at 0-hour, 12-hour, 24-hour, and 72-hour post-injection. Utilizing advanced techniques such as single-nucleus RNA sequencing (snRNA-seq) and Stereo-seq, we conducted a comprehensive characterization of the cellular responses and molecular patterns within the brain.
RESULTS: Our study uncovered notable temporal differences in the response to LPS challenge between Anxa1-/- (annexin A1 knockout) and wild type mice, specifically at the 12-hour and 24-hour time points following injection. We observed a significant increase in the proportion of Astro-2 and Micro-2 cells in these mice. These cells exhibited a colocalization pattern with the vascular subtype Vas-1, forming a distinct region known as V1A2M2, where Astro-2 and Micro-2 cells surrounded Vas-1. Moreover, through further analysis, we discovered significant upregulation of ligands and receptors such as Timp1-Cd63, Timp1-Itgb1, Timp1-Lrp1, as well as Ccl2-Ackr1 and Cxcl2-Ackr1 within this region. In addition, we observed a notable increase in the expression of Cd14-Itgb1, Cd14-Tlr2, and Cd14-C3ar1 in regions enriched with Micro-2 cells. Additionally, Cxcl10-Sdc4 showed broad upregulation in brain regions containing both Micro-2 and Astro-2 cells. Notably, upon LPS challenge, there was an observed increase in Anxa1 expression in the mouse brain. Furthermore, our study revealed a noteworthy increase in mortality rates following Anxa1 knockdown. However, we did not observe substantial differences in the types, numbers, or distribution of other brain cells between Anxa1-/- and wildtype mice over time. Nevertheless, when comparing the 24-hour post LPS injection time point, we observed a significant decrease in the proportion and distribution of Micro-2 and Astro-2 cells in the vicinity of blood vessels in Anxa1-/- mice. Additionally, we noted reduced expression levels of several ligand-receptor pairs including Cd14-Tlr2, Cd14-C3ar1, Cd14-Itgb1, Cxcl10-Sdc4, Ccl2-Ackr1, and Cxcl2-Ackr1.
CONCLUSIONS: By combining snRNA-seq and Stereo-seq techniques, our study successfully identified a distinctive cellular colocalization, referred to as a special pathological niche, comprising Astro-2, Micro-2, and Vas-1 cells. Furthermore, we observed an upregulation of ligand-receptor pairs within this niche. These findings suggest a potential association between this cellular arrangement and the underlying mechanisms contributing to SAE or the increased mortality observed in Anxa1 knockdown mice.

UNASSIGNED: Survivors of sepsis may encounter cognitive impairment following their recovery from critical condition. At present, there is no standardized treatment for addressing sepsis-associated encephalopathy. Lactobacillus rhamnosus GG (LGG) is a prevalent bacterium found in the gut microbiota and is an active component of probiotic supplements. LGG has demonstrated to be associated with cognitive improvement. This study explored whether LGG administration prior to and following induced sepsis could ameliorate cognitive deficits, and explored potential mechanisms.
UNASSIGNED: Female C57BL/6 mice were randomly divided into three groups: sham surgery, cecal ligation and puncture (CLP), and CLP+LGG. Cognitive behavior was assessed longitudinally at 7-9d, 14-16d, and 21-23d after surgery using an open field test and novel object recognition test. The impact of LGG treatment on pathological changes, the expression level of brain-derived neurotrophic factor (BDNF), and the phosphorylation level of the TrkB receptor (p-TrkB) in the hippocampus of mice at two weeks post-CLP (16d) were evaluated using histological, immunofluorescence, immunohistochemistry, and western blot analyses.
UNASSIGNED: The CLP surgery induced and sustained cognitive impairment in mice with sepsis for a minimum of three weeks following the surgery. Compared to mice subjected to CLP alone, the administration of LGG improved the survival of mice with sepsis and notably enhanced their cognitive functioning. Moreover, LGG supplementation significantly alleviated the decrease in hippocampal BDNF expression and p-TrkB phosphorylation levels caused by sepsis, preserving neuronal survival and mitigating the pathological changes within the hippocampus of mice with sepsis. LGG supplementation mitigates sepsis-related cognitive impairment in mice and preserves BDNF expression and p-TrkB levels in the hippocampus.

Sepsis-associated encephalopathy (SAE) is a significant cause of mortality in patients with sepsis. Despite extensive research, its exact cause remains unclear. Our previous research indicated a relationship between non-hepatic hyperammonemia (NHH) and SAE. This study aimed to investigate the relationship between NHH and SAE and the potential mechanisms causing cognitive impairment. In the in vivo experimental results, there were no significant abnormalities in the livers of mice with moderate cecal ligation and perforation (CLP); however, ammonia levels were elevated in the hippocampal tissue and serum. The ELISA study suggest that fecal microbiota transplantation in CLP mice can reduce ammonia levels. Reduction in ammonia levels improved cognitive dysfunction and neurological impairment in CLP mice through behavioral, neuroimaging, and molecular biology studies. Further studies have shown that ammonia enters the brain to regulate the expression of aquaporins-4 (AQP4) in astrocytes, which may be the mechanism underlying brain dysfunction in CLP mice. The results of the in vitro experiments showed that ammonia up-regulated AQP4 expression in astrocytes, resulting in astrocyte damage. The results of this study suggest that ammonia up-regulates astrocyte AQP4 expression through the gut-brain axis, which may be a potential mechanism for the occurrence of SAE.

Sepsis-associated encephalopathy (SAE) is a frequent complication of severe systemic infection resulting in delirium, premature death, and long-term cognitive impairment. We closely mimicked SAE in a murine peritoneal contamination and infection (PCI) model. We found long-lasting synaptic pathology in the hippocampus including defective long-term synaptic plasticity, reduction of mature neuronal dendritic spines, and severely affected excitatory neurotransmission. Genes related to synaptic signaling, including the gene for activity-regulated cytoskeleton-associated protein (Arc/Arg3.1) and members of the transcription-regulatory EGR gene family, were downregulated. At the protein level, ARC expression and mitogen-activated protein kinase signaling in the brain were affected. For targeted rescue we used adeno-associated virus-mediated overexpression of ARC in the hippocampus in vivo. This recovered defective synaptic plasticity and improved memory dysfunction. Using the enriched environment paradigm as a non-invasive rescue intervention, we found improvement of defective long-term potentiation, memory, and anxiety. The beneficial effects of an enriched environment were accompanied by an increase in brain-derived neurotrophic factor (BDNF) and ARC expression in the hippocampus, suggesting that activation of the BDNF-TrkB pathway leads to restoration of the PCI-induced reduction of ARC. Collectively, our findings identify synaptic pathomechanisms underlying SAE and provide a conceptual approach to target SAE-induced synaptic dysfunction with potential therapeutic applications to patients with SAE.

BACKGROUND: Sepsis-associated encephalopathy (SAE) causes acute and long-term cognitive deficits. However, information on the prevention and treatment of cognitive dysfunction after sepsis is limited. The neuropeptide orexin-A (OXA) has been shown to play a protective role against neurological diseases by modulating the inflammatory response through the activation of OXR1 and OXR2 receptors. However, the role of OXA in mediating the neuroprotective effects of SAE has not yet been reported.
METHODS: A mouse model of SAE was induced using cecal ligation perforation (CLP) and treated via intranasal administration of exogenous OXA after surgery. Mouse survival, in addition to cognitive and anxiety behaviors, were assessed. Changes in neurons, cerebral edema, blood-brain barrier (BBB) permeability, and brain ultrastructure were monitored. Levels of pro-inflammatory factors (IL-1β, TNF-α) and microglial activation were also measured. The underlying molecular mechanisms were investigated by proteomics analysis and western blotting.
RESULTS: Intranasal OXA treatment reduced mortality, ameliorated cognitive and emotional deficits, and attenuated cerebral edema, BBB disruption, and ultrastructural brain damage in mice. In addition, OXA significantly reduced the expression of the pro-inflammatory factors IL-1β and TNF-α, and inhibited microglial activation. In addition, OXA downregulated the expression of the Rras and RAS proteins, and reduced the phosphorylation of P-38 and JNK, thus inhibiting activation of the MAPK pathway. JNJ-10,397,049 (an OXR2 blocker) reversed the effect of OXA, whereas SB-334,867 (an OXR1 blocker) did not.
CONCLUSIONS: This study demonstrated that the intranasal administration of moderate amounts of OXA protects the BBB and inhibits the activation of the OXR2/RAS/MAPK pathway to attenuate the outcome of SAE, suggesting that OXA may be a promising therapeutic approach for the management of SAE.