Cerebral dysfunctions caused by sepsis during ageing

Microglial activation and neuroinflammation in acute and chronic cognitive deficits in sepsis

Sepsis is characterised by dysregulated immune responses to infection, leading to multi-organ dysfunction and high rates of mortality. With increasing survival rates in recent years long-term neurological and psychiatric consequences have become more apparent in survivors. Many patients develop sepsis associated encephalopathy (SAE) which encompasses the profound but usually transient neuropsychiatric syndrome delirium but also new brain injury that emerges in the months and years post-sepsis. It is now clear that systemic inflammatory signals reach the brain during sepsis and that very significant neuroinflammation ensues. The major brain resident immune cell population, the microglia, has been implicated in acute and chronic cognitive dysfunction in animal models of sepsis based on a growing number of studies using bacterial endotoxin and in polymicrobial sepsis models such as cecal ligation and puncture. The current review explores the effects of sepsis on the brain, focussing on how systemic insults translate to microglial activation and neuroinflammation and how this disrupts neuronal function and integrity. We examine what has been demonstrated specifically with respect to microglial activation, revealing robust evidence for a role for neuroinflammation in sepsis-induced brain sequelae but less clear information on the extent of the specific microglial contribution to this, arising from findings using global knockout mice, non-selective drugs and treatments that equally target peripheral and central compartments. There is, nonetheless, clear evidence that microglia do become activated and do contribute to brain consequences of sepsis thus arguing for improved understanding of these neuroinflammatory processes toward the prevention and treatment of sepsis-induced brain dysfunction.

Analysis of the inflammatory storm response and heparin binding protein levels for the diagnosis and prognosis of sepsis-associated encephalopathy

BACKGROUND

Sepsis-associated encephalopathy (SAE) is a complication of impaired neurologic function during the development of sepsis. Its occurrence is closely related to severe systemic infection. The increase of serum Interleukin 6 kit and other inflammatory cytokines has certain clinical significance in the diagnosis of sepsis, However, there is no research at home or abroad indicating whether the high expression of related inflammatory cytokines (inflammatory cytokine storm, ICS) is valuable for the diagnosis and prognosis of SAE patients.

OBJECTIVES

The aim of this study was to analyze serum inflammatory cytokines 6 kit [IL-2/4/6/10, TNF-α, and gamma interferon (IFN-γ)], heparin-binding protein (HBP), and serum cholinesterase levels and their clinical significance in septic patients. In this study, we defined the values of inflammatory storm (IL-6 > 5000 pg/ml, IL-10 > 1000 pg/ml, and HBP > 300 ng/ml) to analyze the diagnostic value and 28-day prognostic predictive ability of inflammatory cytokine storm and the severity score in SAE patients.

METHODS

A total of 140 patients with sepsis in the ICU and EICU of the Lianyungang First People's Hospital were included in the present study from October 2021 to March 2023. Based on the Diagnostic criteria for SAE, the 140 cases were divided into 62 cases in the SAE group and 78 cases in the non-SAE group. On admission to the ICU/EICU, the patients gender, age, vital signs, and serum levels of various cytokines were recorded. The Glasgow Coma Scale (GCS), Sequential Organ Failure Scale (SOFA), and Acute Physiological and Chronic Health Score II (APACHE-II) scores were also assessed to analyze the risk cytokines for the occurrence of SAE.

RESULTS

The age, Sofa score, APACHE-II score, 28-day mortality rate, serological cellular inflammatory cytokines (IL-2/6/10, INF-α, and interferon-gamma), HBP were significantly higher in the SAE group than in the non-SAE group (P < 0.05). In addition, the GCS score and serum cholinesterase levels in the SAE group were lower than in the non-SAE group (P < 0.05). Subsequently, Multi-factor logistic regression analysis revealed that ultra-high IL-6 (> 5000 pg/ml), IL-10 (> 1000 pg/ml), and HBP (> 300 ng/ml) levels and elevated SOFA and APACHE-II scores were risk cytokines for the development of SAE (P < 0.05). 28-day mortality was significantly higher in patients in the SAE group and in the IL-6 > 5000 pg/ml group compared to patients in the USAE and IL-6 < 5000 pg/ml groups(P < 0.001).The four screened predictors of HBP > 300 ng/ml, IL-6 > 5000 pg/ml, decreased GCS score, and decreased APACHEII score were combined into a new predictive data model (risk score).In the SAE group, patients with high risk scores had a higher 28-day mortality rate compared with the low risk score group (P < 0.001).

CONCLUSIONS

The occurrence of SAE is closely correlated with age, concomitant diabetes, SOFA score, APACHE II score, serum cytosolic inflammatory cytokine levels (IL-2/6/10, TNF-α, and IFN-γ), HBP, and serum cholinesterase levels. In addition, inflammatory storms are associated with the mechanism of SAE, and high expression levels of the inflammatory cytokines IL-6 > 5000 pg/ml, IL-10 > 1000 pg/ml, and HBP > 300 ng/ml in patients with sepsis contribute to the early diagnosis of SAE. In addition, IL-6 > 5000 pg/ml was also associated with an increase in 28-day mortality (P < 0.05), suggesting that the level of inflammatory storms may be related to the mechanism of sepsis-related SAE and 28-day mortality. According to the LASSO results, when SAE patients admitted to the intensive care unit satisfy HBP > 300 ng/ml, IL6 > 5000 pg/ml, decreased GCS score, and increased APACHEII score, it suggests that the patient's 28-day mortality rate is higher, and it also validates that inflammatory storm can be used as a predictor of prognosis for SAE patients.

Postoperative sepsis and its sequential impact on dementia

BACKGROUND

Postoperative sepsis is a severe complication associated with increased mortality and potential long-term cognitive decline, including dementia. However, the relationship between postoperative sepsis and dementia remains poorly understood.

METHODS

This retrospective cohort study used data from the National Database in Taiwan, covering the period from January 1, 2005, to December 31, 2022. The index period for surgeries was set between January 1, 2008, and December 31, 2013, allowing the identification of patients without prior dementia. A landmark period of 12 months following surgery was defined to capture the number of postoperative sepsis events, which were then analyzed for their impact on dementia risk. After 1:4 propensity score matching (PSM), dementia and mortality were evaluated using Cox proportional hazards and Fine-Gray competing risk models.

RESULTS

Following PSM, 778 patients were in the postoperative sepsis group and 3,112 in the non-postoperative sepsis group. Dementia incidence was higher in the postoperative sepsis group (26%) compared to the non- postoperative sepsis group (13.6%), with a hazard ratio (HR) of 1.25 (95% CI, 1.03-1.52). A dose-response relationship was observed, with dementia rates of 24.5% for one postoperative sepsis event and 34.9% for two or more events, the latter showing an HR of 1.77 (95% CI, 1.17-2.66). Mortality was also elevated in the postoperative sepsis group (40.5% vs. 31.6%; HR 1.45, 95% CI, 1.28-1.65).

CONCLUSIONS

Postoperative sepsis is significantly associated with increased dementia risk in a dose-dependent manner. These findings highlight the importance of enhancing perioperative infection control to reduce both immediate and long-term cognitive complications.

The activation of microglia by the complement system in neurodegenerative diseases

Neurodegenerative diseases (NDDs) are a group of neurological disorders characterized by the progressive loss of neuronal structure and function, leading to cognitive and behavioral impairments. Despite significant research advancements, there is currently no definitive cure for NDDs. With global aging on the rise, the burden of these diseases is becoming increasingly severe, highlighting the urgency of understanding their pathogenesis and developing effective therapeutic strategies. Microglia, specialized macrophages in the central nervous system, play a dual role in maintaining neural homeostasis. They are involved in clearing cellular debris and apoptotic cells, but in their activated state, they release inflammatory factors that contribute significantly to neuroinflammation. The complement system (CS), a critical component of the innate immune system, assists in clearing damaged cells and proteins. However, excessive or uncontrolled activation of the CS can lead to chronic neuroinflammation, exacerbating neuronal damage. This review aims to explore the roles of microglia and the CS in the progression of NDDs, with a specific focus on the mechanisms through which the CS activates microglia by modulating mitochondrial function. Understanding these interactions may provide insights into potential therapeutic targets for mitigating neuroinflammation and slowing neurodegeneration.

Pericytes mediate neuroinflammation via Fli-1 in endotoxemia and sepsis in mice

BACKGROUND

Sepsis-associated encephalopathy (SAE) often results from neuroinflammation. Recent studies have shown that brain platelet-derived growth factor receptor β (PDGFRβ) cells, including pericytes, may act as early sensors of infection by secreting monocyte chemoattractant protein-1 (MCP-1), which transmits inflammatory signals to the central nervous system. The erythroblast transformation-specific (ETS) transcription factor Friend leukemia virus integration 1 (Fli-1) plays a critical role in inflammation by regulating the expression of key cytokines, including MCP-1. However, the role of pericyte Fli-1 in neuroinflammation during sepsis remains largely unknown.

METHODS

WT and pericyte-specific Fli-1 knockout mice were subjected to endotoxemia through LPS injection or sepsis via cecal ligation and puncture (CLP). In vitro, Fli-1 was knocked down using small interfering RNA in cultured mouse brain pericytes, followed by LPS stimulation.

RESULTS

Elevated Fli-1 levels were observed in isolated brain pericytes 2 h after LPS administration, in brain tissues 4 h after CLP, and in cultured mouse brain pericytes 2 h after LPS stimulation in vitro. In endotoxemic mice, pericyte-specific Fli-1 knockout reduced expression of MCP-1 and IL-6 in brain tissue 2 h after LPS injection. At 24 h post-LPS administration, protein levels of MCP-1 and IL-6, and microglia activation were suppressed in pericyte-Fli-1 knockout mice. Additionally, Fli-1 deficiency in pericytes significantly reduced MCP-1 and IL-6 mRNA levels in the brain tissue 4 h after CLP. Moreover, in cultured brain pericytes, Fli-1 knockdown markedly decreased MCP-1 and IL-6 levels after LPS stimulation. Notably, LPS stimulation increased Fli-1 levels via TLR4-Myd88 signaling, which subsequently led to elevated production of MCP-1 in brain pericytes.

CONCLUSIONS

Fli-1 in pericytes may serve as a crucial mediator of neuroinflammation during sepsis by directly regulating pivotal cytokines such as MCP-1 and IL-6. Therefore, Fli-1 has the potential to serve as a therapeutic target in SAE and other neuroinflammatory disorders.

The role of programmed cell death in organ dysfunction induced by opportunistic pathogens

Sepsis is a life-threatening condition resulting from pathogen infection and characterized by organ dysfunction. Programmed cell death (PCD) during sepsis has been associated with the development of multiple organ dysfunction syndrome (MODS), impacting various physiological systems including respiratory, cardiovascular, renal, neurological, hematological, hepatic, and intestinal systems. It is well-established that pathogen infections lead to immune dysregulation, which subsequently contributes to MODS in sepsis. However, recent evidence suggests that sepsis-related opportunistic pathogens can directly induce organ failure by promoting PCD in parenchymal cells of each affected organ. This study provides an overview of PCD in damaged organ and the induction of PCD in host parenchymal cells by opportunistic pathogens, proposing innovative strategies for preventing organ failure in sepsis.

A superior tool for predicting sepsis in SAH patients: The nomogram outperforms SOFA score

OBJECTIVE

This study aimed to develop and validate a nomogram to predict the risk of sepsis in non-traumatic subarachnoid hemorrhage (SAH) patients using data from the MIMIC-IV database.

METHODS

A total of 803 SAH patients meeting the inclusion criteria were randomly divided into a training set (563 cases) and a validation set (240 cases). Independent prognostic factors were identified through forward stepwise logistic regression, and a nomogram was created based on these factors. The discriminative ability of the nomogram was assessed using the area under the receiver operating characteristic curve (AUC) and compared with the SOFA score. The model's consistency was evaluated using the C-index, and the improvement in performance over the SOFA score was calculated using integrated discrimination improvement (IDI) and net reclassification improvement (NRI).

RESULTS

Five independent predictive factors were identified through LASSO regression analysis: mechanical ventilation, hyperlipidemia, temperature, white blood cell count, and red blood cell count. The AUC of the nomogram in the training and validation sets were 0.854 and 0.824, respectively, both higher than the SOFA score. NRI and IDI results indicated that the nomogram outperformed the SOFA score in identifying sepsis risk. Calibration curves and the Hosmer-Lemeshow test demonstrated good calibration of the nomogram. Decision curve analysis showed that the nomogram had higher net benefit in clinical application.

CONCLUSION

The nomogram developed in this study performed excellently in predicting the risk of sepsis in SAH patients, surpassing the traditional SOFA scoring system, and has significant clinical application value.

Functional connectivity within sensorimotor cortical and striatal regions is regulated by sepsis in a sex-dependent manner

Sepsis is a state of systemic immune dysregulation and organ failure that is frequently associated with severe brain disability. Epidemiological studies have indicated that younger females have better prognosis and clinical outcomes relative to males, though the sex-dependent response of the brain to sepsis during post-sepsis recovery remains largely uncharacterized. Using a modified polymicrobial intra-abdominal murine model of surgical sepsis, we characterized the acute effects of intra-abdominal sepsis on peripheral inflammation, brain inflammation and brain functional connectivity in young adult mice of both sexes. Following sepsis, both male and female mice survived the procedure, regained body weight within 7 days post-sepsis and showed reduced diversity in their gut microbiome. Interestingly, compared to the sepsis-induced changes observed in female mice, the post-septic male mice exhibited a comparatively robust profile of splenic cell expansion and intracerebral glial proliferation relative to their healthy counterparts. Analysis of resting-state functional Magnetic Resonance Imaging (fMRI) data collected from the post-septic mice revealed that while connectivity to the somatosensory cortex were affected equally in both sexes, intra-network connectivity strength in the striatum preferentially increased in post-septic males but remained near baseline in post-septic female mice. Additionally, the female mice showed reduced network connectivity alterations in the projections from periaqueductal gray to the superior colliculus as also between the anterior cingulate cortex and the striatum. Coupled with the sustained intracerebral gliosis response, the intra-striatal fMRI response patterns in males could signify a delayed recovery from sepsis. Together, our study provides evidence that peripheral sepsis influences peripheral immunity, brain immunity and brain connectivity in a sex-dependent manner, with the fMRI response strongly indicating cognitive benefits in young females recovering from sepsis relative to their male counterparts.

Investigating the potential mechanism of Pioglitazone in Sepsis-Related brain injury through transcriptomics

Sepsis-related brain injury (SRBI) refers to brain dysfunction and structural damage caused by sepsis, which is characterized by inflammation, oxidative stress, and destruction of the blood-brain barrier. Pioglitazone is a PPAR-γ agonist in which PPAR-γ acts as an inflammatory modulator, determining the relationship between PPAR-γ and SRBI and inflammatory state is critical for the disease. This study aimed to construct a drug-target-disease network for SRBI and Pioglitazone based on network pharmacology, and to investigate the therapeutic effect and potential mechanism of Pioglitazone in SRBI induced by lipopolysaccharide (LPS) in rats through transcriptomics. To establish a rat Model of SRBI by intraperitoneal injection of LPS (10 mg/kg): SD rats were divided into Control, Model (LPS), Pioglitazone, (LPS + Pioglitazone) and GW9662 group (LPS+GW9662). The effects and potential mechanisms of Pioglitazone in the treatment of SRBI were studied using biochemical indexes, pathological changes and transcriptome-sequencing (RNA-seq). RNA-seq results showed 620 DEGs between the Model and the Pioglitazone groups. Enrichment analysis involved multiple inflammatory response processes and chemokine receptor binding functions. TLR4 and CXCL10 in the Toll signaling pathway may play an important role in SRBI as important targets. Pioglitazone may ameliorate SRBI through the PPAR-γ/TLR4/CXCL10 pathway.

Paeonol prevents sepsis-associated encephalopathy via regulating the HIF1A pathway in microglia

Paeonol, a phenolic acid compound extracted from the Cortex Moutan, exhibits significant anti-inflammatory, antioxidant, and anti-apoptotic properties. This study aimed to investigate the effects of paeonol on neuroinflammation and depressive-like symptoms, and the underlying mechanisms in a mouse model of sepsis-associated encephalopathy (SAE) induced by lipopolysaccharide (LPS). To assess the therapeutic potential of paeonol in mice treated with LPS, behavioral assessments were conducted using the open-field test (OFT), tail suspension test (TST), and forced swimming test (FST), and quantitative PCR (qPCR), Western blot, and immunofluorescent staining were utilized to determine the expression levels of inflammatory molecules in the hippocampus in vivo and microglial cells in vitro. Our results revealed that paeonol significantly alleviated anxiety and depressive-like symptoms, as evidenced by improved activity in OFT, reduced immobility time in TST and FST, and decreased levels of inflammatory markers such as IL6, TNFα, and PFKFB3. Further in vitro experiments confirmed that paeonol downregulated the expression of pro-inflammatory molecules. A network pharmacology-based strategy combined with molecular docking and cellular thermal shift assay highlighted HIF1A as a potential target for paeonol. Similar anti-inflammatory effects of a HIF1A inhibitor were also observed in microglia treated with LPS. Furthermore, these effects were reversed by CoCl2, a HIF1A agonist, indicating the critical role of the HIF1A signaling pathway in mediating the therapeutic effects of paeonol. These findings highlight the potential of paeonol in modulating the HIF1A pathway, offering a promising therapeutic strategy for neuroinflammation in SAE.

Prognostic analysis of elderly patients with pathogenic microorganisms positive for sepsis-associated encephalopathy

Objectives

Sepsis-associated encephalopathy (SAE) has a high incidence and mortality, especially for elderly patients and patients who are positive for pathogenic microbial infection, this study explored the prognostic factors influencing the prognosis of elderly patients with pathogenic microorganisms positive of sepsis-associated encephalopathy.

Methods

Patients with SAE and pathogenic microbiology positive were included in this study from Medical Information Mart for Intensive Care IV (MIMIC IV) database. The main results of this study was analyzed the 28-day mortality rate of patients with pathogenic microorganism positive and SAE by Wilcoxon, Kaplan-Meier curve and other methods.

Results

This study found that older patients with SAE had higher mortality at 28 and 90 days compared with non-older patients with SAE. Klebsiella pneumoniae and Pseudomonas aeruginosa infection, the level of APTT and lactate and SAPS III score were independent risk factors for 28-day mortality in elderly patients with SAE, among them, Klebsiella pneumoniae and Pseudomonas aeruginosa infection had the best sensitivity (0.893; 0.931) in assessing elderly patients with pathogenic microorganisms positive and SAE; the SAPS III score had the highest AUC (0.681) value and specificity (0.761) in assessing elderly patients with pathogenic microorganisms positive and SAE.

Conclusion

The older patients with SAE had a poor prognosis, the elder patients with pathogenic microorganisms positive and SAE with high levels of APTT and lactate and SAPS III score and Klebsiella pneumoniae and Pseudomonas aeruginosa infection should be closely monitored and treated aggressively.

The Role and Mechanism of Metformin in the Treatment of Nervous System Diseases

Nervous system diseases represent a significant global burden, affecting approximately 16% of the world's population and leading to disability and mortality. These conditions, encompassing both central nervous system (CNS) and peripheral nervous system (PNS) disorders, have substantial social and economic impacts. Metformin, a guanidine derivative derived from a plant source, exhibits therapeutic properties in various health conditions such as cancer, aging, immune-related disorders, polycystic ovary syndrome, cardiovascular ailments, and more. Recent studies highlight metformin's ability to cross the blood-brain barrier, stimulate neurogenesis, and provide beneficial effects in specific neurological disorders through diverse mechanisms. This review discusses the advancements in research on metformin's role and mechanisms in treating neurological disorders within both the central and peripheral nervous systems, aiming to facilitate further investigation, utilization, and clinical application of metformin in neurology.

Ubiquitination in pyroptosis pathway: A potential therapeutic target for sepsis

Sepsis remains a significant clinical challenge, causing numerous deaths annually and representing a major global health burden. Pyroptosis, a unique form of programmed cell death characterized by cell lysis and the release of inflammatory mediators, is a crucial factor in the pathogenesis and progression of sepsis, septic shock, and organ dysfunction. Ubiquitination, a key post-translational modification influencing protein fate, has emerged as a promising target for managing various inflammatory conditions, including sepsis. This review integrates the current knowledge on sepsis, pyroptosis, and the ubiquitin system, focusing on the molecular mechanisms of ubiquitination within pyroptotic pathways activated during sepsis. By exploring how modulating ubiquitination can regulate pyroptosis and its associated inflammatory signaling pathways, this review provides insights into potential therapeutic strategies for sepsis, highlighting the need for further research into these complex molecular networks.

Maresin-1 Ameliorates Sepsis-Induced Microglial Activation Through Modulation of the P38 MAPK Pathway

Sepsis is a life-threatening disease characterized by a dysregulated immune response to infection, often leading to neuroinflammation. As a known immunomodulator, Maresin-1 (MaR1) may have potential applications in the treatment of sepsis-induced neuroinflammation, but its effects in this context are unknown. We used a mouse cecum ligation and puncture (CLP)-induced sepsis model and an in vitro lipopolysaccharide (LPS)-induced neuroinflammatory model of BV2 microglia. Expression of microglial cell markers (IBA1, CD11B, CD68, CD86 and CD206) and pro-inflammatory markers (iNOS and COX2) was assessed. The role of MaR1 in regulating the P38 MAPK pathway was explored using the P38 MAPK inhibitor SB203580. In the CLP model, an increased proportion of M1-type microglia was observed, and MaR1 was able to reverse it. However, the combination of SB203580 and MaR1 did not enhance the therapeutic effect compared to SB20580 alone. In vitro experiments, MaR1 inhibited LPS-induced P38 MAPK nuclear translocation and decreased the expression of pro-inflammatory markers such as iNOS and COX2. As with the animal results, no stacking effect could be obtained with the co-administration of SB203580 and MaR1. Our findings suggest that MaR1 attenuates sepsis-induced neuroinflammation mainly by inhibiting phosphorylation of P38 MAPK in microglial cells. This suggests that MaR1 may have a potential therapeutic role in the treatment of sepsis neuroinflammation.

Brain imaging and machine learning reveal uncoupled functional network for contextual threat memory in long sepsis

Positron emission tomography (PET) utilizes radiotracers like [18F]fluorodeoxyglucose (FDG) to measure brain activity in health and disease. Performing behavioral tasks between the FDG injection and the PET scan allows the FDG signal to reflect task-related brain networks. Building on this principle, we introduce an approach called behavioral task-associated PET (beta-PET) consisting of two scans: the first after a mouse is familiarized with a conditioning chamber, and the second upon recall of contextual threat. Associative threat conditioning occurs between scans. Beta-PET focuses on brain regions encoding threat memory (e.g., amygdala, prefrontal cortex) and contextual aspects (e.g., hippocampus, subiculum, entorhinal cortex). Our results show that beta-PET identifies a biologically defined network encoding contextual threat memory and its uncoupling in a mouse model of long sepsis. Moreover, machine learning algorithms (linear logistic regression) and ordinal trends analysis demonstrate that beta-PET robustly predicts the behavioral defense response and its breakdown during long sepsis.

Dichloroacetate attenuates brain injury through inhibiting neuroinflammation and mitochondrial fission in a rat model of sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is a severe complication of sepsis, characterized by neuroinflammation, mitochondrial dysfunction, and oxidative stress, leading to cognitive decline and high mortality. The effectiveness of dichloroacetate (DCA) in modulating mitochondrial function provides a novel therapeutic strategy for SAE. In this study, we evaluated the neuroprotective effects of DCA in a rat model of SAE induced by cecal ligation and puncture (CLP). Rats treated with DCA exhibited significant improvements in neurological function and survival, as evidenced by less neuron loss from histopathologic analysis, restored neurologic deficit scores, improved Y-maze alternation percentages, and enhanced recognition index performance. Biochemical analyses showed that DCA administration at 25 mg/kg and 100 mg/kg reduced astrocyte and microglial activation, indicating reduced neuroinflammation. Furthermore, DCA simultaneously reduced the production of circulating and cerebral inflammatory cytokines (including TNF-α, IL-1β, and IL-10), concomitant with mitigating oxidative stress through down-regulating expression of 8-Hydroxy-2'-deoxyguanosine (8-OHdG) and reactive oxygen species (ROS) in the brain. Mechanistically, DCA modulated mitochondrial dynamics by suppressing Drp1 and pDrp1 expression, which are indicators of mitochondrial fission. This was corroborated by transmission electron microscopy, quantification of mitochondrial area, and Western blot analyses. Furthermore, DCA treatment improved ATP levels, mitochondrial complex I activity, and NAD+/NADH ratio, indicating a significant attenuation of brain mitochondrial dysfunction. In conclusion, our findings suggest that DCA confers neuroprotection in SAE by curtailing neuroinflammation and mitochondrial fission, outlining a promising therapeutic strategy for treating SAE in critically ill patients.

Impact of different blood pressure targets on cerebral hemodynamics in septic shock: A prospective pilot study protocol-SEPSIS-BRAIN

INTRODUCTION

Septic shock, a life-threatening condition, can result in cerebral dysfunction and heightened mortality rates. In these patients, disturbances in cerebral hemodynamics, as reflected by impairment of myogenic cerebral autoregulation (CA), metabolic regulation, expressed by critical closing pressure (CrCP) and reductions in intracranial compliance (ICC), can adversely impact septic shock outcomes. The general recommendation is to maintain a target mean arterial pressure (MAP) of 65 mmHg but the effect of different MAP targets on cerebral hemodynamics in these patients is not clear and optimal targets might be dependent on the status of CA. This protocol aims to assess the cerebral hemodynamics profile at different pressure targets in septic shock patients.

METHODS

Prospective, non-randomized, single-center trial, which will study cerebral hemodynamics in patients with septic shock within 48 hours of its onset. Patients will be studied at their baseline MAP and at three MAP targets (T1: 65, T2: 75, T3: 85 mmHg). Cerebral hemodynamics will be assessed by transcranial Doppler (TCD) and a skull micro-deformation sensor (B4C). Dynamic CA will be expressed by the autoregulation index (ARI), calculated by transfer function analysis, using fluctuations of MAP as input and corresponding oscillations in cerebral blood velocity (CBv). The instantaneous relationship between arterial blood pressure and CBv will be used to estimate CrCP and resistance-area product (RAP) for each cardiac cycle using the first harmonic method. The B4C will access ICC by intracranial pressure waveforms (P2/P1). The primary aim is to assess cerebral hemodynamics (ARI, CrCP, RAP, and P2/P1) at different targets of MAP in septic shock patients. Our secondary objective is to assess cerebral hemodynamics at 65mmHg (target recommended by guidelines). In addition, we will assess the correlation between markers of organ dysfunction (such as lactate levels, vasoactive drugs usage, SOFA score, and delirium) and CA.

ETHICS AND DISSEMINATION

The results of this study may help to understand the effect of the recommended MAP and variations in blood pressure in patients with septic shock and impaired CA and ICC. Furthermore, the results can assist large trials in establishing new hypotheses about neurological management in this group of patients. Approval was obtained from the local Ethics Committee (28134720.1.0000.0048). It is anticipated that the results of this study will be presented at national and international conferences and will be published in peer-reviewed journals in 2024 and 2025.

TRIAL REGISTRATION

Trial registration number: NCT05833607. https://clinicaltrials.gov/study/NCT05833607.

Extracellular vesicles in sepsis plasma mediate neuronal inflammation in the brain through miRNAs and innate immune signaling

BACKGROUND

Neuroinflammation reportedly plays a critical role in the pathogenesis of sepsis-associated encephalopathy (SAE). We previously reported that circulating plasma extracellular vesicles (EVs) from septic mice are proinflammatory. In the current study, we tested the role of sepsis plasma EVs in neuroinflammation.

METHODS

To track EVs in cells and tissues, HEK293T cell-derived EVs were labeled with the fluorescent dye PKH26. Cecal ligation and puncture (CLP) was conducted to model polymicrobial sepsis in mice. Plasma EVs were isolated by ultracentrifugation and their role in promoting neuronal inflammation was tested following intracerebroventricular (ICV) injection. miRNA inhibitors (anti-miR-146a, -122, -34a, and -145a) were applied to determine the effects of EV cargo miRNAs in the brain. A cytokine array was performed to profile microglia-released protein mediators. TLR7- or MyD88-knockout (KO) mice were utilized to determine the underlying mechanism of EVs-mediated neuroinflammation.

RESULTS

We observed the uptake of fluorescent PKH26-EVs inside the cell bodies of both microglia and neurons. Sepsis plasma EVs led to a dose-dependent cytokine release in cultured microglia, which was partially attenuated by miRNA inhibitors against the target miRNAs and in TLR7-KO cells. When administered via the ICV, sepsis plasma EVs resulted in a marked increase in the accumulation of innate immune cells, including monocyte and neutrophil and cytokine gene expression, in the brain. Although sepsis plasma EVs had no direct effect on cytokine production or neuronal injury in vitro, the conditioned media (CM) of microglia treated with sepsis plasma EVs induced neuronal cell death as evidenced by increased caspase-3 cleavage and Annexin-V staining. Cytokine arrays and bioinformatics analysis of the microglial CM revealed multiple cytokines/chemokines and other factors functionally linked to leukocyte chemotaxis and migration, TLR signaling, and neuronal death. Moreover, sepsis plasma EV-induced brain inflammation in vivo was significantly dependent on MyD88.

CONCLUSIONS

Circulating plasma EVs in septic mice cause a microglial proinflammatory response in vitro and a brain innate immune response in vivo, some of which are in part mediated by TLR7 in vitro and MyD88 signaling in vivo. These findings highlight the importance of circulating EVs in brain inflammation during sepsis.

Alterations in Regional Brain Microcirculation in Patients with Sepsis: A Prospective Study Using Contrast-Enhanced Brain Ultrasound

BACKGROUND

Alterations in regional brain microcirculation have not been well studied in patients with sepsis. Regional brain microcirculation can be studied using contrast-enhanced brain ultrasound (CEUS) with microbubble administration.

METHODS

CEUS was used to assess alterations in regional brain microcirculation on 3 consecutive days in 58 patients with sepsis and within 24 h of intensive care unit admission in 10 aged-matched nonseptic postoperative patients. Time-intensity perfusion curve variables (time-to-peak and peak intensity) were measured in different regions of interest of the brain parenchyma. The mean arterial pressure, cardiac index (using transthoracic echocardiography), global cerebral blood flow (using echo-color Doppler of the carotid and vertebral arteries), mean flow velocities of the middle cerebral arteries, and brain autoregulation (using transcranial echo-color Doppler) were measured simultaneously. The presence of structural brain injury in patients with sepsis was confirmed on computed tomography imaging, and encephalopathy, including coma and delirium, was evaluated using the Glasgow Coma Scale and the Confusion Assessment Method in the Intensive Care Unit.

RESULTS

Of the 58 patients with sepsis, 42 (72%) developed acute encephalopathy and 11 (19%) had some form of structural brain injury. Brain autoregulation was impaired in 23 (40%) of the patients with sepsis. Brain microcirculation alterations were observed in the left lentiform nucleus and left white matter of the temporoparietal region of the middle cerebral artery in the sepsis nonsurvivors but not in the survivors or postoperative patients. The alterations were characterized by prolonged time-to-peak (p < 0.01) and decreased peak intensity (p < 0.01) on the time-intensity perfusion curve. Prolonged time-to-peak but not decreased peak intensity was independently associated with worse outcome (p = 0.03) but not with the development of encephalopathy (p = 0.77).

CONCLUSIONS

Alterations in regional brain microcirculation are present in critically ill patients with sepsis and are associated with poor outcome. Trial registration Registered retrospectively on December 19, 2019.

Characterization of age-associated inflammasome activation reveals tissue specific differences in transcriptional and post-translational inflammatory responses

Aging is associated with systemic chronic, low-grade inflammation, termed 'inflammaging'. This pattern of inflammation is multifactorial and is driven by numerous inflammatory pathways, including the inflammasome. However, most studies to date have examined changes in the transcriptomes that are associated with aging and inflammaging, despite the fact that inflammasome activation is driven by a series of post-translational activation steps, culminating in the cleavage and activation of caspase-1. Here, we utilized transgenic mice expressing a caspase-1 biosensor to examine age-associated inflammasome activation in various organs and tissues to define these post-translational manifestations of inflammaging. Consistent with other studies, we observe increased inflammation, including inflammasome activation, in aged mice and specific tissues. However, we note that the degree of inflammasome activation is not uniformly associated with transcriptional changes commonly used as a surrogate for inflammasome activation in tissues. Furthermore, we used a skull thinning technique to monitor central nervous system inflammasome activation in vivo in aged mice and found that neuroinflammation is significantly amplified in aged mice in response to endotoxin challenge. Together, these data reveal that inflammaging is associated with both transcriptional and post-translational inflammatory pathways that are not uniform between tissues and establish new methodologies for measuring age-associated inflammasome activation in vivo and ex vivo.

N-acetyltransferase 10 mediates cognitive dysfunction through the acetylation of GABABR1 mRNA in sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is a critical neurological complication of sepsis and represents a crucial factor contributing to high mortality and adverse prognosis in septic patients. This study explored the contribution of NAT10-mediated messenger RNA (mRNA) acetylation in cognitive dysfunction associated with SAE, utilizing a cecal ligation and puncture (CLP)-induced SAE mouse model. Our findings demonstrate that CLP significantly upregulates NAT10 expression and mRNA acetylation in the excitatory neurons of the hippocampal dentate gyrus (DG). Notably, neuronal-specific Nat10 knockdown improved cognitive function in septic mice, highlighting its critical role in SAE. Proteomic analysis, RNA immunoprecipitation, and real-time qPCR identified GABABR1 as a key downstream target of NAT10. Nat10 deletion reduced GABABR1 expression, and subsequently weakened inhibitory postsynaptic currents in hippocampal DG neurons. Further analysis revealed that microglia activation and the release of inflammatory mediators lead to the increased NAT10 expression in neurons. Microglia depletion with PLX3397 effectively reduced NAT10 and GABABR1 expression in neurons, and ameliorated cognitive dysfunction induced by SAE. In summary, our findings revealed that after CLP, NAT10 in hippocampal DG neurons promotes GABABR1 expression through mRNA acetylation, leading to cognitive dysfunction.

Phosphatidylserine improves aging sepsis survival, modulates gut microbiome, and prevents sepsis-associated encephalopathy

Aged adults are prone to both short- and long-term complications following sepsis due to ineffective therapy. Phosphatidylserine (PS) is a membrane nutrient supplement known to enhance cognition and brain function, but its potential effects in treating sepsis are not well-documented. Our study aimed to explore the potential of PS in improving outcomes in sepsis and sepsis-associated encephalopathy (SAE). Middle-aged mice were administered PS for two months following induction of sepsis by lipopolysaccharides. The results indicated a significant increase in the survival rate of mice treated with PS after sepsis. Surviving mice underwent open field and shuttle box tests 45 days post-sepsis, revealing potential alleviation of neurobehavioral impairments due to PS pretreatment. Analysis at 60 days post-sepsis euthanasia showed reduced cleaved-caspase 3 in neurons and glial cell markers in the PS-treated group compared to the untreated sepsis group. Furthermore, PS administration effectively reduced proinflammatory cytokine gene expression in the hippocampus of mice with SAE, potentially inhibiting the TBK1/NLRP3/ASC signaling pathway. In the gut, PS pretreatment modulated β-diversity while maintaining jejunal morphology and colon ZO-1 expression, without significantly affecting α-diversity indices. Our findings suggest that PS administration improves survival rates, modulates the gut microbiome, preserves gut integrity, and ameliorates brain pathology in survived mice after sepsis. Importantly, these findings have significant implications for sepsis treatment and cognitive function preservation in aging individuals, providing new insights and sparking further interest and investigation into the potential of PS in sepsis treatment.

Molecular and Functional Alterations in the Cerebral Microvasculature in an Optimized Mouse Model of Sepsis-Associated Cognitive Dysfunction

Systemic inflammation has been implicated in the development and progression of neurodegenerative conditions such as cognitive impairment and dementia. Recent clinical studies indicate an association between sepsis, endothelial dysfunction, and cognitive decline. However, the investigations of the role and therapeutic potential of the cerebral microvasculature in sepsis-induced cognitive dysfunction have been limited by the lack of standardized experimental models for evaluating the alterations in the cerebral microvasculature and cognition induced by the systemic inflammatory response. Herein, we validated a mouse model of endotoxemia that recapitulates key pathophysiology related to sepsis-induced cognitive dysfunction, including the induction of an acute systemic hyperinflammatory response, blood-brain barrier (BBB) leakage, neurovascular inflammation, and memory impairment after recovery from the systemic inflammation. In the acute phase, we identified novel molecular (e.g., upregulation of plasmalemma vesicle-associated protein, PLVAP, a driver of endothelial permeability, and the procoagulant plasminogen activator inhibitor-1, PAI-1) and functional perturbations (i.e., albumin and small-molecule BBB leakage) in the cerebral microvasculature along with neuroinflammation. Remarkably, small-molecule BBB permeability, elevated levels of PAI-1, intra-/perivascular fibrin/fibrinogen deposition, and microglial activation persisted 1 month after recovery from sepsis. We also highlight molecular neuronal alterations of potential clinical relevance following systemic inflammation including changes in neurofilament phosphorylation and decreases in postsynaptic density protein 95 and brain-derived neurotrophic factor, suggesting diffuse axonal injury, synapse degeneration, and impaired neurotrophism. Our study serves as a standardized mouse model to support future mechanistic studies of sepsis-associated cognitive dysfunction and to identify novel endothelial therapeutic targets for this devastating condition.

Neuroprotective effects of annexin A1 tripeptide in rats with sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is characterized by high incidence and mortality rates, with limited treatment options available. The underlying mechanisms and pathogenesis of SAE remain unclear. Annexin A1 (ANXA1), a membrane-associated protein, is involved in various in vivo pathophysiological processes. This study aimed to explore the neuroprotective effects and mechanisms of a novel bioactive ANXA1 tripeptide (ANXA1sp) in SAE. Forty Sprague-Dawley rats were randomly divided into four groups (n = 10 each): control, SAE (intraperitoneal injection of lipopolysaccharide), vehicle (SAE + normal saline), and ANXA1sp (SAE + ANXA1sp) groups. Changes in serum inflammatory factors (interleukin-6 [IL-6], tumor necrosis factor-α [TNF-α]), hippocampal reactive oxygen species (ROS), mitochondrial membrane potential (MMP), and adenosine triphosphate (ATP) levels were measured. The Morris water maze and Y maze tests were used to assess learning and memory capabilities in the rats. Further, changes in peroxisome proliferator-activated receptor-gamma (PPAR-γ) and apoptosis-related protein expression were detected using western blot. The IL-6, TNF-α, and ROS levels were significantly increased in the SAE group compared with the levels in the control group. Intraperitoneal administration of ANXA1sp led to a significant decrease in the IL-6, TNF-α, and ROS levels (p < 0.05). Compared with the SAE group, the ANXA1sp group exhibited reduced escape latency on day 5, a significant increase in the number of platform crossings and the percent spontaneous alternation, and significantly higher hippocampal MMP and ATP levels (p < 0.05). Meanwhile, the expression level of PPAR-γ protein in the ANXA1sp group was significantly increased compared with that in the other groups (p < 0.05). The expressions of apoptosis-related proteins (nuclear factor-kappa B [NF-κB], Bax, and Caspase-3) in the SAE and vehicle groups were significantly increased, with a noticeable decrease in Bcl-2 expression, compared with that noted in the control group. Moreover, the expressions of NF-κB, Bax, and Caspase-3 were significantly decreased in the ANXA1sp group, and the expression of Bcl-2 was markedly increased (p < 0.05). ANXA1sp can effectively reverse cognitive impairment in rats with SAE. The neuroprotective effect of ANXA1sp may be attributed to the activation of the PPAR-γ pathway, resulting in reduced neuroinflammatory response and inhibition of apoptosis.

Adenosine triggers early astrocyte reactivity that provokes microglial responses and drives the pathogenesis of sepsis-associated encephalopathy in mice

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.

Compartmentalization of the inflammatory response during bacterial sepsis and severe COVID-19

Acute infections cause local and systemic disorders which can lead in the most severe forms to multi-organ failure and eventually to death. The host response to infection encompasses a large spectrum of reactions with a concomitant activation of the so-called inflammatory response aimed at fighting the infectious agent and removing damaged tissues or cells, and the anti-inflammatory response aimed at controlling inflammation and initiating the healing process. Fine-tuning at the local and systemic levels is key to preventing local and remote injury due to immune system activation. Thus, during bacterial sepsis and Coronavirus disease 2019 (COVID-19), concomitant systemic and compartmentalized pro-inflammatory and compensatory anti-inflammatory responses are occurring. Immune cells (e.g., macrophages, neutrophils, natural killer cells, and T-lymphocytes), as well as endothelial cells, differ from one compartment to another and contribute to specific organ responses to sterile and microbial insult. Furthermore, tissue-specific microbiota influences the local and systemic response. A better understanding of the tissue-specific immune status, the organ immunity crosstalk, and the role of specific mediators during sepsis and COVID-19 can foster the development of more accurate biomarkers for better diagnosis and prognosis and help to define appropriate host-targeted treatments and vaccines in the context of precision medicine.

The Role of Iron Metabolism in Sepsis-associated Encephalopathy: a Potential Target

Sepsis-associated encephalopathy (SAE) is an acute cerebral dysfunction secondary to infection, and the severity can range from mild delirium to deep coma. Disorders of iron metabolism have been proven to play an important role in a variety of neurodegenerative diseases by inducing cell damage through iron accumulation in glial cells and neurons. Recent studies have found that iron accumulation is also a potential mechanism of SAE. Systemic inflammation can induce changes in the expression of transporters and receptors on cells, especially high expression of divalent metal transporter1 (DMT1) and low expression of ferroportin (Fpn) 1, which leads to iron accumulation in cells. Excessive free Fe2+ can participate in the Fenton reaction to produce reactive oxygen species (ROS) to directly damage cells or induce ferroptosis. As a result, it may be of great help to improve SAE by treatment of targeting disorders of iron metabolism. Therefore, it is important to review the current research progress on the mechanism of SAE based on iron metabolism disorders. In addition, we also briefly describe the current status of SAE and iron metabolism disorders and emphasize the therapeutic prospect of targeting iron accumulation as a treatment for SAE, especially iron chelator. Moreover, drug delivery and side effects can be improved with the development of nanotechnology. This work suggests that treating SAE based on disorders of iron metabolism will be a thriving field.

Challenges and Advances in Biomarker Detection for Rapid and Accurate Sepsis Diagnosis: An Electrochemical Approach

Sepsis is a life-threatening condition with high mortality rates due to delayed treatment of patients. The conventional methodology for blood diagnosis takes several hours, which suspends treatment, limits early drug administration, and affects the patient's recovery. Thus, rapid, accurate, bedside (onsite), economical, and reliable sepsis biomarker reading of the clinical sample is an emergent need for patient lifesaving. Electrochemical label-free biosensors are specific and rapid devices that are able to perform analysis at the patient's bedside; thus, they are considered an attractive methodology in a clinical setting. To reveal their full diagnostic potential, electrode architecture strategies of fabrication are highly desirable, particularly those able to preserve specific antibody-antigen attraction, restrict non-specific adsorption, and exhibit high sensitivity with a low detection limit for a target biomarker. The aim of this review is to provide state-of-the-art methodologies allowing the fabrication of ultrasensitive and highly selective electrochemical sensors for sepsis biomarkers. This review focuses on different methods of label-free biomarker sensors and discusses their advantages and disadvantages. Then, it highlights effective ways of avoiding false results and the role of molecular labels and functionalization. Recent literature on electrode materials and antibody grafting strategies is discussed, and the most efficient methodology for overcoming the non-specific attraction issues is listed. Finally, we discuss the existing electrode architecture for specific biomarker readers and promising tactics for achieving quick and low detection limits for sepsis biomarkers.

Molecular and functional alterations in the cerebral microvasculature in an optimized mouse model of sepsis-associated cognitive dysfunction

Systemic inflammation has been implicated in the development and progression of neurodegenerative conditions such as cognitive impairment and dementia. Recent clinical studies indicate an association between sepsis, endothelial dysfunction, and cognitive decline. However, the investigations of the role and therapeutic potential of the cerebral microvasculature in systemic inflammation-induced cognitive dysfunction have been limited by the lack of standardized experimental models for evaluating the alterations in the cerebral microvasculature and cognition induced by the systemic inflammatory response. Herein, we validated a mouse model of endotoxemia that recapitulates key pathophysiology related to sepsis-induced cognitive dysfunction, including the induction of an acute systemic hyperinflammatory response, blood-brain barrier (BBB) leakage, neurovascular inflammation, and memory impairment after recovery from the systemic inflammatory response. In the acute phase, we identified novel molecular (e.g. upregulation of plasmalemma vesicle associated protein, a driver of endothelial permeability, and the pro-coagulant plasminogen activator inhibitor-1, PAI-1) and functional perturbations (i.e., albumin and small molecule BBB leakage) in the cerebral microvasculature along with neuroinflammation. Remarkably, small molecule BBB permeability, elevated levels of PAI-1, intra/perivascular fibrin/fibrinogen deposition and microglial activation persisted 1 month after recovery from sepsis. We also highlight molecular neuronal alterations of potential clinical relevance following systemic inflammation including changes in neurofilament phosphorylation and decreases in postsynaptic density protein 95 and brain-derived neurotrophic factor suggesting diffuse axonal injury, synapse degeneration and impaired neurotrophism. Our study serves as a standardized model to support future mechanistic studies of sepsis-associated cognitive dysfunction and to identify novel endothelial therapeutic targets for this devastating condition.

SIGNIFICANCE

The limited knowledge of how systemic inflammation contributes to cognitive decline is a major obstacle to the development of novel therapies for dementia and other neurodegenerative diseases. Clinical evidence supports a role for the cerebral microvasculature in sepsis-induced neurocognitive dysfunction, but the investigation of the underlying mechanisms has been limited by the lack of standardized experimental models. Herein, we optimized a mouse model that recapitulates important pathophysiological aspects of systemic inflammation-induced cognitive decline and identified key alterations in the cerebral microvasculature associated with cognitive dysfunction. Our study provides a reliable experimental model for mechanistic studies and therapeutic discovery of the impact of systemic inflammation on cerebral microvascular function and the development and progression of cognitive impairment.

Maresin1 improves hippocampal neuroinflammation and cognitive function in septic rats by activating the SLC7A11 / GPX4 ferroptosis signaling pathway

Sepsis-associated encephalopathy (SAE) is a prevalent complication of sepsis, with hippocampal neuroinflammation playing a crucial role in SAE-induced cognitive impairment. Maresin1 (MaR1), a bioactive docosahexaenoic acid (DHA) metabolite, demonstrates comprehensive anti-inflammatory and neuroprotective attributes. Yet, its protective efficacy against SAE-induced cognitive decline remains unexplored. In this investigation, we implemented a rat SAE model via cecal ligation and puncture (CLP), while lipopolysaccharide (LPS) stimulation of HT22 cells simulated an in vitro SAE model; both models were pre-treated with MaR1. We evaluated rat learning and memory using a water maze, assessed hippocampal neuron damage via Nissl and FJC staining, and observed mitochondrial alterations through TEM. In vivo and in vitro assays gauged levels of Fe2+, MDA, GSH, and SOD. Additionally, Iba1 expression in the hippocampus was examined via immunofluorescence, while SLC7A11 and GPX4 protein expression levels were determined using western blot. Our findings indicated CLP-induced learning and memory impairment in rats, along with heightened ROS, Fe2+, and MDA levels in hippocampal neurons, diminished GSH and SOD levels, and down-regulated ferroptosis-related proteins (GPX4 and SLC7A11). Remarkably, MaR1 treatment attenuated these adverse effects. In LPS-stimulated HT22 cells, MaR1 lowered lipid ROS and bolstered mitochondrial membrane potential. Nonetheless, the ferroptosis inducer Erastin reversed MaR1's protective effects. Transwell experiments further showed MaR1's potential to inhibit microglia activation triggered by ferroptosis in HT22 cells. Consequently, MaR1 may mitigate hippocampal neuroinflammation via activating the SLC7A11/GPX4 ferroptosis signaling pathway, thus ameliorating SAE-related cognitive impairment.

Role of serum neuron-specific enolase levels in the early diagnosis and prognosis of sepsis-associated encephalopathy: a systematic review and meta-analysis

Background

Sepsis-associated encephalopathy (SAE) is one of the most ubiquitous complications of sepsis and is characterized by cognitive impairment, poor prognosis, and a lack of uniform clinical diagnostic criteria. Therefore, this study investigated the early diagnostic and prognostic value of serum neuron-specific enolase (NSE) in SAE.

Methods

This systematic review and meta-analysis systematically searched for clinical trials with serum NSE information in patients with sepsis in the PubMed, Web of Science, Embase, and Cochrane databases from their inception to April 10, 2023. Included studies were assessed for quality and risk of bias using The Quality Assessment of Diagnostic Accuracy-2 tool. The meta-analysis of the included studies was performed using Stata 17.0 and Review Manager version 5.4.

Findings

Eleven studies were included in this meta-analysis involving 1259 serum samples from 947 patients with sepsis. Our results showed that the serum NSE levels of patients with SAE were higher than those of the non-encephalopathy sepsis group (mean deviation, MD,12.39[95% CI 8.27-16.50, Z = 5.9, p < 0.00001]), and the serum NSE levels of patients with sepsis who died were higher than those of survivors (MD,4.17[95% CI 2.66-5.68, Z = 5.41, p < 0.00001]).

Conclusion

Elevated serum NSE levels in patients with sepsis are associated with the early diagnosis of SAE and mortality; therefore, serum NSE probably is a valid biomarker for the early diagnosis and prognosis of patients with SAE.

Systematic review registration

This study was registered in PROSPERO, CRD42023433111.

Improved prediction of sepsis-associated encephalopathy in intensive care unit sepsis patients with an innovative nomogram tool

Background

Sepsis-associated encephalopathy (SAE) occurs as a result of systemic inflammation caused by sepsis. It has been observed that the majority of sepsis patients experience SAE while being treated in the intensive care unit (ICU), and a significant number of survivors continue suffering from cognitive impairment even after recovering from the illness. The objective of this study was to create a predictive nomogram that could be used to identify SAE risk factors in patients with ICU sepsis.

Methods

We conducted a retrospective cohort study using the Medical Information Mart for Intensive Care IV (MIMIC-IV) database. We defined SAE as a Glasgow Coma Scale (GCS) score of 15 or less, or delirium. The patients were randomly divided into training and validation cohorts. We used least absolute shrinkage and selection operator (LASSO) regression modeling to optimize feature selection. Independent risk factors were determined through a multivariable logistic regression analysis, and a prediction model was built. The performance of the nomogram was evaluated using various metrics including the area under the receiver operating characteristic curve (AUC), calibration plots, Hosmer-Lemeshow test, decision curve analysis (DCA), net reclassification improvement (NRI), and integrated discrimination improvement (IDI).

Results

Among the 4,476 sepsis patients screened, 2,781 (62.1%) developed SAE. In-hospital mortality was higher in the SAE group compared to the non-SAE group (9.5% vs. 3.7%, p < 0.001). Several variables were analyzed, including the patient's age, gender, BMI on admission, mean arterial pressure, body temperature, platelet count, sodium level, and use of midazolam. These variables were used to create and validate a nomogram. The nomogram's performance, assessed by AUC, NRI, IDI, and DCA, was found to be superior to the conventional SOFA score combined with delirium. Calibration plots and the Hosmer-Lemeshow test confirmed the accuracy of the nomogram. The enhanced NRI and IDI values demonstrated that our scoring system outperformed traditional diagnostic approaches. Additionally, the DCA curve indicated the practicality of the nomogram in clinical settings.

Conclusion

This study successfully identified autonomous risk factors associated with the emergence of SAE in sepsis patients and utilized them to formulate a predictive model. The outcomes of this investigation have the potential to serve as a valuable clinical resource for the timely detection of SAE in patients.

Severe inflammation in C57/BL6 mice leads to prolonged cognitive impairment by initiating the IL-1β/TRPM2 pathway

BACKGROUND

Sepsis could lead to chronic cognitive impairment by unclear molecular mechanisms. Transient receptor potential melastatin-2 (TRPM2) is essential against immunity-related activities and inflammation. Our study attempted to decipher the relationship between cognitive impairment caused by severe inflammation and TRPM2 expression levels.

METHODS

Severe inflammation was induced by intraperitoneally injecting C57/BL6 mice with a high dosage (5 mg kg-1) of Lipopolysaccharide (LPS). Fear conditioning and a Morris water maze test were performed to examine the cognitive abilities of the mice. Moreover, the signaling and expression of pro-inflammatory cytokines and TRPM2 were measured using Western blotting and Reverse transcription-polymerase chain reaction (RT-PCR). Flow cytometry and immunofluorescence staining helped to determine the astrocyte apoptosis rate.

RESULTS

Severe inflammation can lead to long-term cognitive impairment in C57/BL6 mice. The interleukin-1 beta (IL-1β) levels intra-hippocampus were significantly elevated until P14 post-LPS introduction. At both P7 and P14, there is an up-regulation of TRPM2 expression within hippocampus. Administration of recombinant IL-1β to astrocytes results in a significant up-regulation of TRPM2 expression. IL-1β or TRPM2 level knockdown helped counter the cognitive impairment caused by significant inflammation.

CONCLUSIONS

A continuous increase in IL-1β levels within the hippocampus can lead to cognitive impairment by enhancing TRPM2 levels caused by severe inflammation.

Enhanced meningeal lymphatic drainage ameliorates lipopolysaccharide-induced brain injury in aged mice

BACKGROUND

Sepsis-associated encephalopathy (SAE) is an acute cerebral dysfunction caused by sepsis. Neuroinflammation induced by sepsis is considered a potential mechanism of SAE; however, very little is known about the role of the meningeal lymphatic system in SAE.

METHODS

Sepsis was established in male C57BL/6J mice by intraperitoneal injection of 5 mg/kg lipopolysaccharide, and the function of meningeal lymphatic drainage was assessed. Adeno-associated virus 1-vascular endothelial growth factor C (AAV1-VEGF-C) was injected into the cisterna magna to induce meningeal lymphangiogenesis. Ligation of deep cervical lymph nodes (dCLNs) was performed to induce pre-existing meningeal lymphatic dysfunction. Cognitive function was evaluated by a fear conditioning test, and inflammatory factors were detected by enzyme-linked immunosorbent assay.

RESULTS

The aged mice with SAE showed a significant decrease in the drainage of OVA-647 into the dCLNs and the coverage of the Lyve-1 in the meningeal lymphatic, indicating that sepsis impaired meningeal lymphatic drainage and morphology. The meningeal lymphatic function of aged mice was more vulnerable to sepsis in comparison to young mice. Sepsis also decreased the protein levels of caspase-3 and PSD95, which was accompanied by reductions in the activity of hippocampal neurons. Microglia were significantly activated in the hippocampus of SAE mice, which was accompanied by an increase in neuroinflammation, as indicated by increases in interleukin-1 beta, interleukin-6 and Iba1 expression. Cognitive function was impaired in aged mice with SAE. However, the injection of AAV1-VEGF-C significantly increased coverage in the lymphatic system and tracer dye uptake in dCLNs, suggesting that AAV1-VEGF-C promotes meningeal lymphangiogenesis and drainage. Furthermore, AAV1-VEGF-C reduced microglial activation and neuroinflammation and improved cognitive dysfunction. Improvement of meningeal lymphatics also reduced sepsis-induced expression of disease-associated genes in aged mice. Pre-existing lymphatic dysfunction by ligating bilateral dCLNs aggravated sepsis-induced neuroinflammation and cognitive impairment.

CONCLUSION

The meningeal lymphatic drainage is damaged in sepsis, and pre-existing defects in this drainage system exacerbate SAE-induced neuroinflammation and cognitive dysfunction. Promoting meningeal lymphatic drainage improves SAE. Manipulation of meningeal lymphangiogenesis could be a new strategy for the treatment of SAE.

Microstructural brain abnormalities, fatigue, and cognitive dysfunction after mild COVID-19

Although some studies have shown neuroimaging and neuropsychological alterations in post-COVID-19 patients, fewer combined neuroimaging and neuropsychology evaluations of individuals who presented a mild acute infection. Here we investigated cognitive dysfunction and brain changes in a group of mildly infected individuals. We conducted a cross-sectional study of 97 consecutive subjects (median age of 41 years) without current or history of psychiatric symptoms (including anxiety and depression) after a mild infection, with a median of 79 days (and mean of 97 days) after diagnosis of COVID-19. We performed semi-structured interviews, neurological examinations, 3T-MRI scans, and neuropsychological assessments. For MRI analyses, we included a group of non-infected 77 controls. The MRI study included white matter (WM) investigation with diffusion tensor images (DTI) and functional connectivity with resting-state functional MRI (RS-fMRI). The patients reported memory loss (36%), fatigue (31%) and headache (29%). The quantitative analyses confirmed symptoms of fatigue (83% of participants), excessive somnolence (35%), impaired phonemic verbal fluency (21%), impaired verbal categorical fluency (13%) and impaired logical memory immediate recall (16%). The WM analyses with DTI revealed higher axial diffusivity values in post-infected patients compared to controls. Compared to controls, there were no significant differences in the functional connectivity of the posterior cingulum cortex. There were no significant correlations between neuropsychological scores and neuroimaging features (including DTI and RS-fMRI). Our results suggest persistent cognitive impairment and subtle white matter abnormalities in individuals mildly infected without anxiety or depression symptoms. The longitudinal analyses will clarify whether these alterations are temporary or permanent.

Investigation of Pancreatic-beta Cells Role in the Biological Process of Ageing

BACKGROUND

Cellular senescence is associated with the formation and progression of a range of illnesses, including ageing and metabolic disorders such as diabetes mellitus and pancreatic beta cell dysfunction. Ageing and reduced glucose tolerance are interconnected. Often, Diabetes is becoming more common, which is concerning since it raises the risk of a variety of age-dependent disorders such as cardiovascular disease, cancer, Parkinson's disease, stroke, and Alzheimer's disease.

OBJECTIVES

The objectives of this study are to find out the most recent research on how ageing affects the functions of pancreatic beta cells, beta cell mass, beta cell senescence, mitochondrial dysfunction, and hormonal imbalance.

METHODS

Various research and review manuscripts are gathered from various records such as Google Scholar, PubMed, Mendeley, Scopus, Science Open, the Directory of Open Access Journals, and the Education Resources Information Centre, using different terms like "Diabetes, cellular senescence, beta cells, ageing, insulin, glucose".

RESULTS

In this review, we research novel targets in order to discover new strategies to treat diabetes. Abnormal glucose homeostasis and type 2 diabetes mellitus in the elderly may aid in the development of novel medicines to delay or prevent diabetes onset, improve quality of life, and, finally, increase life duration.

CONCLUSION

Aging accelerates beta cell senescence by generating premature cell senescence, which is mostly mediated by high glucose levels. Despite higher plasma glucose levels, hepatic gluconeogenesis accelerates and adipose tissue lipolysis rises, resulting in an increase in free fatty acid levels in the blood and worsening insulin resistance throughout the body.

The neurobiology of SARS-CoV-2 infection

Worldwide, over 694 million people have been infected with SARS-CoV-2, with an estimated 55-60% of those infected developing COVID-19. Since the beginning of the pandemic in December 2019, different variants of concern have appeared and continue to occur. With the emergence of different variants, an increasing rate of vaccination and previous infections, the acute neurological symptomatology of COVID-19 changed. Moreover, 10-45% of individuals with a history of SARS-CoV-2 infection experience symptoms even 3 months after disease onset, a condition that has been defined as 'post-COVID-19' by the World Health Organization and that occurs independently of the virus variant. The pathomechanisms of COVID-19-related neurological complaints have become clearer during the past 3 years. To date, there is no overt - that is, truly convincing - evidence for SARS-CoV-2 particles in the brain. In this Review, we put special emphasis on discussing the  methodological difficulties of viral detection in CNS tissue and discuss immune-based (systemic and central) effects contributing to COVID-19-related CNS affection. We sequentially review the reported changes to CNS cells in COVID-19, starting with the blood-brain barrier and blood-cerebrospinal fluid barrier - as systemic factors from the periphery appear to primarily influence barriers and conduits - before we describe changes in brain parenchymal cells, including microglia, astrocytes, neurons and oligodendrocytes as well as cerebral lymphocytes. These findings are critical to understanding CNS affection in acute COVID-19 and post-COVID-19 in order to translate these findings into treatment options, which are still very limited.

Protective effects of the saltinduced kinase inhibitor HG99101 on sepsisassociated cognitive dysfunction in mice and the underlying mechanisms

OBJECTIVES

Sepsis-associated cognitive dysfunction is a common complication in patients with sepsis and lack of effective treatment. Its pathological mechanisms remain unclear. Salt-induced kinase (SIK) is an important molecule in the regulation of metabolism, immunity, and inflammatory response. It is associated with the development of many neurological diseases. This study aims to investigate the expression of SIK in the hippocampus of septic mice, and to evaluate the role and mechanism of the SIK inhibitor HG-9-91-01 in sepsis-associated cognitive dysfunction.

METHODS

Firstly, C57BL/6 mice were randomly divided into a control group (Con group) and a sepsis model group [lipopolysaccharide (LPS) group]. The model group was injected intraperitoneally with LPS at a dose of 8 mg/kg and the Con group was injected with an equal volume of normal saline. Hippocampal tissues were harvested at 1, 3, and 6 days after injection and the expressions of SIK1, SIK2, and SIK3 were detected by real-time fluorescence quantitative PCR (qPCR) and Western blotting. Secondly, C57BL/6 mice were randomly divided into a Con group, a LPS group, and a SIK inhibitor group (HG group). The LPS and HG groups were injected with LPS to establish a sepsis model; in the HG group, HG-9-91-01 (10 mg/kg) was injected intraperitoneally at 3-6 days after LPS injection, and the LPS group was injected with the same volume of vehicle. Cognitive function was assessed at 7-11 days after LPS injection using the Morris water maze (MWM). Hippocampal tissues were harvested after the behavioral tests, and the mRNA levels of inflammatory factors and microglial markers were assessed by qPCR. The protein levels of inducible nitric oxide synthase (iNOS), CD68, ionized calcium binding adaptor molecule 1 (Iba-1), N-methyl-D-aspartate (NMDA) receptor (NR) subunit, cAMP response element-binding protein (CREB)-regulated transcription coactivator 1 (CRTC1), and insulin-like growth factor 1 (IGF-1) were detected by Western blotting. Immunohistochemistry (IHC) was used to detect the expression of Iba-1 positive cells in the CA1, CA3 and dentate gyrus (DG) of the hippocampus, followed by Sholl analysis.

RESULTS

Compared with the Con group, the mRNA and protein levels of SIK1, SIK2, and SIK3 in the hippocampus were increased in the LPS group (all P<0.05). Compared with the Con group, mice in the LPS group had a significantly longer escape latency, a lower percentage of target quadrant dwell time and a reduced locomotor speed (all P<0.05); the HG group had a decreased escape latency and an increased percentage of time spent in the target quadrant in comparison with the LPS group (both P<0.05). The mRNA levels of inflammatory factors [tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6)], and the M1-type microglial markers iNOS and CD68 in the hippocampus of the LPS group were increased in comparison with the Con group, while the M2-type microglial markers CD206 and arginase-1 (Arg-1) were decreased. Compared with the LPS group, the mRNA levels of TNF-α, IL-1β, IL-6, and iNOS were downregulated, while the levels of CD206 and Arg-1 were upregulated in the HG group (all P<0.05). The protein levels of iNOS, CD68, and Iba-1 in the hippocampus of the LPS group were increased in comparison with the Con group, but they were downregulated in the HG group in comparison with the LPS group (all P<0.05). The number of Iba-1 positive cells in CA1, CA3, and DG of the hippocampus was increased in the LPS group in comparison with the Con group, but they were decreased in the HG group in comparison with the LPS group (all P<0.05). Sholl analysis showed that the number of intersections at all radii between 8-38 µm from the microglial soma was decreased in the LPS group in comparison with the Con group (all P<0.05). Compared with the LPS group, the number of intersections at all radii between 14-20 µm was significantly increased in the HG group (all P<0.05). The protein levels of NR subunit NR1, NR2A, NR2B, and IGF-1 were downregulated in the hippocampus of the LPS group in comparison with the Con group, while the expression of phosphorylated CRTC1 (p-CRTC1) was increased. Compared with the LPS group, the levels of NR1, NR2A, NR2B, and IGF-1 were upregulated, while p-CRTC1 was downregulated in the HG group (all P<0.05).

CONCLUSIONS

SIK expression is upregulated in the hippocampus of septic mice. The SIK inhibitor HG-9-91-01 ameliorates sepsis-associated cognitive dysfunction in mice, and the mechanism may involve in the activation of the CRTC1/IGF-1 pathway, inhibition of neuroinflammation, and enhancement of synaptic plasticity.

CD137L Inhibition Ameliorates Hippocampal Neuroinflammation and Behavioral Deficits in a Mouse Model of Sepsis-Associated Encephalopathy

Anxiety manifestations and cognitive dysfunction are common sequelae in patients with sepsis-associated encephalopathy (SAE). Microglia-mediated inflammatory signaling is involved in anxiety, depression, and cognitive dysfunction during acute infection with bacterial lipopolysaccharide (LPS). However, the molecular mechanisms underlying microglia activation and behavioral and cognitive deficits in sepsis have not been in fully elucidated. Based on previous research, we speculated that the CD137 receptor/ligand system modulates microglia function during sepsis to mediate classical neurological SAE symptoms. A murine model of SAE was established by injecting male C57BL/6 mice with LPS, and cultured mouse BV2 microglia were used for in vitro assays. RT-qPCR, immunofluorescence staining, flow cytometry, and ELISA were used to assess microglial activation and the expression of CD137L and inflammation-related cytokines in the mouse hippocampus and in cultured BV2 cells. In addition, behavioral tests were conducted in assess cognitive performance and behavioral distress. Immunofluorescence and RT-qPCR analyses showed that hippocampal expression of CD137L was upregulated in activated microglia following LPS treatment. Pre-treatment with the CD137L neutralizing antibody TKS-1 significantly reduced CD137L levels, attenuated the expression of M1 polarization markers in microglia, and inhibited the production of TNF-α, IL-1β, and IL-6 in both LPS-treated mice and BV2 cells. Conversely, stimulation of CD137L signaling by recombinant CD137-Fc fusion protein activated the synthesis and release of pro-inflammatory cytokines in cultures BV2 microglia. Importantly, open field, elevated plus maze, and Y-maze spontaneous alternation test results indicated that TKS-1 administration alleviated anxiety-like behavior and spatial memory decline in mice with LPS-induced SAE. These findings suggest that CD137L upregulation in activated microglia critically contributes to neuroinflammation, anxiety-like behavior, and cognitive dysfunction in the mouse model of LPS-induced sepsis. Therefore, therapeutic modulation of the CD137L/CD137 signaling pathway may represent an effective way to minimize brain damage and prevent cognitive and emotional deficits associated with SAE.

Oxytocin alleviates cognitive and memory impairments by decreasing hippocampal microglial activation and synaptic defects via OXTR/ERK/STAT3 pathway in a mouse model of sepsis-associated encephalopathy

BACKGROUND

Sepsis-associated encephalopathy (SAE) is a diffuse brain dysfunction, characterized by cognitive and memory impairments closely linked to hippocampal dysfunction. Though it is well-known that SAE is a diffuse brain dysfunction with microglial activation, the pathological mechanisms of SAE are not well established and effective clinical interventions are lacking. Oxytocin (OXT) is reported to have anti-inflammatory and neuroprotective roles. However, the effects of OXT on SAE and the underlying mechanisms are not clear.

METHODS

SAE was induced in adult C57BL/6J male mice by cecal ligation and perforation (CLP) surgery. Exogenous OXT was intranasally applied after surgery. Clinical score, survivor rate, cognitive and memory behaviors, and hippocampal neuronal and non-neuronal functions were evaluated. Cultured microglia challenged with lipopolysaccharide (LPS) were used to investigate the effects of OXT on microglial functions, including inflammatory cytokines release and phagocytosis. The possible intracellular signal pathways involved in the OXT-induced neuroprotection were explored with RNA sequencing.

RESULTS

Hippocampal OXT level decreases, while the expression of OXT receptor (OXTR) increases around 24 h after CLP surgery. Intranasal OXT application at a proper dose increases mouse survival rate, alleviates cognitive and memory dysfunction, and restores hippocampal synaptic function and neuronal activity via OXTR in the SAE model. Intraperitoneal or local administration of the OXTR antagonist L-368,899 in hippocampal CA1 region inhibited the protective effects of OXT. Moreover, during the early stages of sepsis, hippocampal microglia are activated, while OXT application reduces microglial phagocytosis and the release of inflammatory cytokines, thereby exerting a neuroprotective effect. OXT may improve the SAE outcomes via the OXTR-ERK-STAT3 signaling pathway.

CONCLUSION

Our study uncovers the dysfunction of the OXT signal in SAE and shows that intranasal OXT application at a proper dose can alleviate SAE outcomes by reducing microglial overactivation, suggests that OXT may be a promising therapeutic approach in managing SAE patients.

Sepsis-associated encephalopathy: From pathophysiology to clinical management

Sepsis-associated encephalopathy, which presents as delirium and coma, is a significant complication of sepsis characterized by acute brain dysfunction. The presence of inflammatory pathological changes in the brain of sepsis patients and animal models has been recognized since the 1920 s, initially attributed to the entry of microbial toxins into the brain. In the early 2000 s, attention shifted towards the impact of oxidative stress, the cholinergic system, and cytokines on brain function following sepsis onset. More recently, sepsis-associated encephalopathy has been defined as a diffuse brain dysfunction not directly caused by pathogenic infection of the brain. Currently, there is no evidence-based standard for diagnosing sepsis-associated encephalopathy, and clinical management is primarily focused on symptomatic and supportive measures. This review aims to explore the pathophysiology of sepsis-associated encephalopathy and establish the connection between pathophysiological mechanisms and clinical characteristics. We hope that this work will spark the interest of researchers from various fields and contribute to the advancement of sepsis-associated encephalopathy research.

Association between the first 24 hours PaCO2 and all-cause mortality of patients suffering from sepsis-associated encephalopathy after ICU admission: A retrospective study

OBJECTIVE

The relationship between the levels of the first 24-h PaCO2 and the prognosis of sepsis-associated encephalopathy (SAE) remains unclear, and the first 24-h optimal target for PaCO2 is currently inconclusive. This study was performed to investigate the correlation between PaCO2 and all-cause mortality for SAE patients, establish a reference range of the initial 24-hour PaCO2 for clinicians in critical care, and explain the possible pathophysiological mechanisms of abnormal PaCO2 levels as a higher mortality risk factor for SAE.

METHODS

The baseline information and clinical data of patients were extracted from the fourth edition Medical Information Mart for Intensive Care database (MIMIC-IV 2.0). Multivariate logistic regressions were performed to assess the relationship between PaCO2 and all-cause mortality of SAE. Additionally, restricted cubic splines, Kaplan-Meier Survival analyses, propensity score matching (PSM) analyses, and subgroup analyses were conducted.

RESULTS

A total of 5471 patients were included in our cohort. In the original and matched cohort, multivariate logistic regression analysis showed that normocapnia and mild hypercapnia may be associated with a more favorable prognosis of SAE patients, and survival analysis supported the findings. In addition, a U-shaped association emerged when examining the initial 24-hour PaCO2 levels in relation to 30-day, 60-day, and 90-day mortality using restricted cubic splines, with an average cut-off value of 36.3mmHg (P for nonlinearity<0.05). Below the cut-off value, higher PaCO2 was associated with lower all-cause mortality, while above the cut-off value, higher PaCO2 was associated with higher all-cause mortality. Subsequent subgroup analyses revealed similar results for the subcohort of GCS≤8 compared to the original cohort. Additionally, when examining the subcohort of GCS>8, a L-shaped relationship between PaCO2 and the three clinical endpoints emerged, in contrast to the previously observed U-shaped pattern. The findings from the subcohort of GCS>8 suggested that patients experiencing hypocapnia had a more unfavorable prognosis, which aligns with the results obtained from corresponding multivariate logistic regression analyses.

CONCLUSION

The retrospective study revealed the association between the first 24-h PaCO2 and all-cause mortality risk (30-day, 60-day, and 90-day) for patients with SAE in ICU. The range (35mmHg-50mmHg) of PaCO2 may be the optimal target for patients with SAE in clinical practice.

HSPB8 up-regulation alleviates cognitive dysfunction in a mouse model of sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is associated with a higher risk of cognitive deficits; however, its potential mechanisms are still unknow. Recently, researches show that HSPB8, a family of small heat shock proteins, affects cognitive function and ameliorates sepsis-induced dysfunction. However, the role of HSPB8 in SAE-associated cognitive impairment has not been elucidated. In this study, we found that HSPB8 expression was up-regulated in the brain of mice with lipopolysaccharide-induced sepsis. HSPB8 overexpression alleviated cognitive decline in SAE mice. In addition, exogenous HSPB8 exerts neuroprotective effects and salvages synaptic function via regulating NRF1/TFAM-induced mitochondrial biogenesis and DRP1-mediate mitochondrial fission in a lipopolysaccharide-induced mouse model. Furthermore, HSPB8 overexpression inhibits IBA1 and NLRP3 activation in the SAE model. Overexpression of HSPB8 may be an efficient treatment for relieving SAE-related cognitive decline.

Acute and long-term cognitive impairment following sepsis: mechanism and prevention

INTRODUCTION

Sepsis is a severe host response to infection, which induces both acute and long-term cognitive impairment. Despite its high incidence following sepsis, the underlying mechanisms remain elusive and effective treatments are not available clinically.

AREA COVERED

This review focuses on elucidating the pathological mechanisms underlying cognitive impairment following sepsis. Specifically, the authors discuss the role of systemic inflammation response, blood-brain barrier disruption, neuroinflammation, mitochondrial dysfunction, neuronal dysfunction, and Aβ accumulation and tau phosphorylation in cognitive impairment after sepsis. Additionally, they review current strategies to ameliorate cognitive impairment.

EXPERT OPINION

Potential interventions to reduce cognitive impairment after sepsis include earlier diagnosis and effective infection control, hemodynamic homeostasis, and adequate brain perfusion. Furthermore, interventions to reduce inflammatory response, reactive oxygen species, blood-brain barrier disruption, mitochondrial dysfunction, neuronal injury or death could be beneficial. Implementing strategies to minimize delirium, sleep disturbance, stress factors, and immobility are also recommended. Furthermore, avoiding neurotoxins and implementing early rehabilitation may also be important for preventing cognitive impairment after sepsis.

Angiotensin Type 2 Receptor Pharmacological Agonist Relieves Neurocognitive Deficits via Reducing Neuroinflammation and Microglial Engulfment of Dendritic Spines

Mechanically ventilated patients suffering critical illness are at high risk of developing neurocognitive impairments. Angiotensin type 2 receptor (AGTR2) has been demonstrated to be anti-inflammatory and neuroprotective. The present study thus aimed to investigate whether AGTR2 can alleviate cerebral dysfunction in mice subjected to cochallenge with lipopolysaccharide (LPS) and mechanical ventilation (MV), and to reveal the underlying mechanism. We utilized a mice model that received a single injection of LPS (1 mg/kg, intraperitoneally) followed 2 h later by MV (10 ml/kg, lasting for 2 h). Pretreatment with the AGTR2 pharmacological agonist C21 (0.03, 0.3, and 3 mg/kg, intraperitoneally, once daily, lasting for 10 days). Locomotor activity and behavioral deficits were evaluated 24 h post-MV by open-field and fear-condition tests. Brain hippocampus and prefrontal cortex tissues were collected for immunofluorescence staining and western blotting to evaluate the resulting impacts on microglia, including morphological traits, functional markers, synaptic engulfment, superoxide production, and signaling molecules. Compared with vehicle-control, pre-administrated C21 reduced the branch endpoints and length of microglia processes in a dose-dependent manner in mice subjected to LPS/MV. The neuroprotective effect of AGTR2 was behaviorally confirmed by the improvement of memory decline in LPS/MV-treated mice following C21 pretreatment. In addition to morphological alterations, C21 reduced microglial functional markers and reduced microglial-dendrite contact and microglial engulfment of synaptic protein markers. In terms of the underlying molecular mechanism, AGTR2 stimulation by C21 leads to activation of protein phosphatase 2A, which subsequently mitigates microglial PKCδ and NF-κB activation, and inhibites NOX2-derived ROS production. The AGTR2 agonist C21 alleviates behavioral deficits in those mice subjected to LPS/MV, via mechanisms that involve reactive microglia and abnormal synaptic plasticity in NOX2-derived ROS and the PKCδ-NFκB pathway.

Microglia mediate neurocognitive deficits by eliminating C1q-tagged synapses in sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is a severe and frequent complication of sepsis causing delirium, coma, and long-term cognitive dysfunction. We identified microglia and C1q complement activation in hippocampal autopsy tissue of patients with sepsis and increased C1q-mediated synaptic pruning in a murine polymicrobial sepsis model. Unbiased transcriptomics of hippocampal tissue and isolated microglia derived from septic mice revealed an involvement of the innate immune system, complement activation, and up-regulation of lysosomal pathways during SAE in parallel to neuronal and synaptic damage. Microglial engulfment of C1q-tagged synapses could be prevented by stereotactic intrahippocampal injection of a specific C1q-blocking antibody. Pharmacologically targeting microglia by PLX5622, a CSF1-R inhibitor, reduced C1q levels and the number of C1q-tagged synapses, protected from neuronal damage and synapse loss, and improved neurocognitive outcome. Thus, we identified complement-dependent synaptic pruning by microglia as a crucial pathomechanism for the development of neuronal defects during SAE.

β-Nicotinamide mononucleotide activates NAD+/SIRT1 pathway and attenuates inflammatory and oxidative responses in the hippocampus regions of septic mice

Sepsis-associated encephalopathy (SAE) is one of the common serious complications in sepsis, and the pathogenesis of SAE remains unclear. Sirtuin 1 (SIRT1) has been reported to be downregulated in the hippocampus and SIRT1 agonists can attenuated the cognitive dysfunction in septic mice. Nicotinamide adenine dinucleotide (NAD+) is a key substrate to maintain the deacetylation activity of SIRT1. As an intermediate of NAD+, β-Nicotinamide Mononucleotide (NMN) has been reported to be promising in treating neurodegenerative diseases and cerebral ischemic injury. Thus we sought to investigate the potential role of NMN in SAE treatment. The SAE model was established by cecal ligation and puncture (CLP) in vivo, and neuroinflammation model was established with LPS-treated BV-2 cells in vitro. Memory impairment was assessed by Morris water maze and fear conditioning tests. As a result, the levels of NAD+, SIRT1 and PGC-1α were significantly reduced in the hippocampus of septic mice, while the acetylation of total lysine, phosphorylation of P38 and P65 were enhanced. All these changes induced by sepsis were inverted by NMN. Treating with NMN resulted in improved behavior performance in the fear conditioning tests and Morris water maze. Apoptosis, inflammatory and oxidative responses in the hippocampus of septic mice were attenuated significantly after NMN administration. These protective effect of NMN against memory dysfunction, inflammatory and oxidative injuries were reversed by the SIRT1 inhibitor, EX-527. Similarly, LPS-induced activation of BV-2 cells were attenuated by NMN, EX-527 or SIRT1 knockdown could reverse such effect of NMN in vitro. In conclusion, NMN is protective against sepsis-induced memory dysfunction, and the inflammatory and oxidative injuries in the hippocampus region of septic mice. The NAD+/SIRT1 pathway might be involved in one of the mechanisms of the protective effect.

Sporadic Use of Antibiotics in Older Adults and the Risk of Dementia: A Nested Case-Control Study Based on German Health Claims Data

BACKGROUND

Antibiotics for systemic use may increase the risk of neurodegeneration, yet antibiotic therapy may be able to halt or mitigate an episode of neurodegenerative decline.

OBJECTIVE

To investigate the association of sporadic use of antibiotics and subsequent dementia risk (including Alzheimer's disease).

METHODS

We used data from the largest public health insurance fund in Germany, the Allgemeine Ortskrankenkasse (AOK). Each of the 35,072 dementia cases aged 60 years and older with a new dementia diagnosis during the observation period from 2006 to 2018 was matched with two control-patients by age, sex, and time since 2006. We ran conditional logistic regression models for dementia risk in terms of odds ratios (OR) as a function of antibiotic use for the entire antibiotic group and for each antibiotic subgroup. We controlled for comorbidities, need for long-term care, hospitalizations, and nursing home placement.

RESULTS

Antibiotic use was positively associated with dementia (OR = 1.18, 95% confidence interval (95% CI):1.14-1.22), which became negative after adjustment for comorbidities, at least one diagnosis of bacterial infection or disease, and covariates (OR = 0.93, 95% CI:0.90-0.96). Subgroups of antibiotics were also negatively associated with dementia after controlling for covariates: tetracyclines (OR = 0.94, 95% CI:0.90-0.98), beta-lactam antibacterials, penicillins (OR = 0.93, 95% CI:0.90-0.97), other beta-lactam antibacterials (OR = 0.92, 95% CI:0.88-0.95), macrolides, lincosamides, and streptogramins (OR = 0.88, 95% CI:0.85-0.92), and quinolone antibacterials (OR = 0.96, 95% CI:0.92-0.99).

CONCLUSION

Our results suggest that there was a decreased likelihood of dementia for preceding antibiotic use. The benefits of antibiotics in reducing inflammation and thus the risk of dementia need to be carefully weighed against the increase in antibiotic resistance.

Preclinical and translational models for delirium: Recommendations for future research from the NIDUS delirium network

Delirium is a common, morbid, and costly syndrome that is closely linked to Alzheimer's disease (AD) and AD-related dementias (ADRD) as a risk factor and outcome. Human studies of delirium have advanced our knowledge of delirium incidence and prevalence, risk factors, biomarkers, outcomes, prevention, and management. However, understanding of delirium neurobiology remains limited. Preclinical and translational models for delirium, while challenging to develop, could advance our knowledge of delirium neurobiology and inform the development of new prevention and treatment approaches. We discuss the use of preclinical and translational animal models in delirium, focusing on (1) a review of current animal models, (2) challenges and strategies for replicating elements of human delirium in animals, and (3) the utility of biofluid, neurophysiology, and neuroimaging translational markers in animals. We conclude with recommendations for the development and validation of preclinical and translational models for delirium, with the goal of advancing awareness in this important field.