Pathogenesis Of Sepsis-associated Encephalopathy Research Articles

Astrocytic HILPDA promotes lipid droplets generation to drive cognitive dysfunction in mice with sepsis-associated encephalopathy.

Sepsis-associated encephalopathy (SAE) is manifested as a spectrum of disturbed cerebral function ranging from mild delirium to coma. However, the pathogenesis of SAE has not been clearly elucidated. Astrocytes play important roles in maintaining the function and metabolism of the brain. Most recently, it has been demonstrated that disorders of lipid metabolism, especially lipid droplets (LDs) dyshomeostasis, are involved in a variety of neurodegenerative diseases. The aim of this study was to investigate whether LDs are involved in the underlying mechanism of SAE. The open field test, Y-maze test, and contextual fear conditioning test (CFCT) were used to test cognitive function in SAE mice. Lipidomics was utilized to investigate alterations in hippocampal lipid metabolism in SAE mice. Western blotting and immunofluorescence labeling were applied for the observation of related proteins. In the current study, we found that SAE mice showed severe cognitive dysfunction, including spatial working and contextual memory. Meanwhile, we demonstrated that lipid metabolism was widely dysregulated in the hippocampus by using lipidomic analysis. Furthermore, western blotting and immunofluorescence confirmed that LDs accumulation in hippocampal astrocytes was involved in the pathological process of cognitive dysfunction in SAE mice. We verified that LDs can be inhibited by specifically suppress hypoxia-inducible lipid droplet-associated protein (HILPDA) in astrocytes. Meanwhile, cognitive dysfunction in SAE was ameliorated by reducing A1 astrocyte activation and inhibiting presynaptic membrane transmitter release. The accumulation of astrocytic lipid droplets plays a crucial role in the pathological process of SAE. HILPDA is an attractive therapeutic target for lipid metabolism regulation and cognitive improvement in septic patients.

P2X7 receptor: A receptor closely linked with sepsis-associated encephalopathy.

Sepsis is defined as a dysregulated host response to infection resulting in life-threatening organ dysfunction. Sepsis-associated encephalopathy (SAE) is the main manifestation of sepsis. Inflammation, peroxidation stress injury, and apoptosis are the main factors involved in the pathogenesis of SAE. A growing body of evidence has proved that P2X7 receptor (P2X7R), a cationic channel receptor that is widely distributed in the body, plays a major role in the occurrence and development of inflammatory injury. Therefore, this review mainly describes the activation of P2X7R in sepsis, which leads to the recruitment of inflammatory cells to the cerebral vasculature, the destruction of the blood-brain barrier, the activation of microglial cells in the brain, the apoptosis of brain cells, and other damage processes. This review also illustrates the potential therapeutic value of P2X7R inhibition in SAE.

ACE2 Rescues Sepsis-Associated Encephalopathy by Reducing Inflammation, Oxidative Stress, and Neuronal Apoptosis via the Nrf2/Sestrin2 Signaling Pathway.

Neuroinflammation and oxidative stress contribute to the progression of sepsis-associated encephalopathy (SAE). Angiotensin-converting enzyme 2 (ACE2) is considered to be a neuroprotective factor due to its anti-inflammatory and antioxidant properties. However, the role of ACE2 on myeloid cells in regulating SAE and the underlying mechanism warrants further exploration. SAE was induced in ACE2 transgenic (TG), knockout (KO), and bone marrow (BM) chimeric mice by cecal ligation and puncture (CLP). The expression levels of apoptosis-, oxidation- and neuroinflammation-associated mediators and morphological changes were monitored by quantitative real-time PCR analyses and histological examinations in the cortex of septic mice. The contents of angiotensin (Ang) II and Ang-(1-7) along with the activity of ACE2 were examined with commercial kits. The expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and Sestrin2 was detected by immunoblotting analysis. Our results indicated that the expression of cortical ACE2 was significantly reduced in the early phase of CLP-induced sepsis. Moreover, ACE2 overexpression in TG mice conferred neuroprotection against sepsis, as evidenced by alleviated neuronal apoptosis, oxidative stress, and proinflammatory M1-like microglial polarization, accompanied by upregulation of the Ang-(1-7), Nrf2, and Sestrin2 protein levels. Conversely, ACE2 deficiency in KO mice exacerbated SAE. The neuroprotective effects of ACE2 were further confirmed in wild-type mice transplanted with ACE2-TG and KO BM cells. Therefore, our data suggest that myeloid ACE2 exerts a protective role in the pathogenesis of SAE, potentially by activating Ang-(1-7)-Nrf2/sestrin2 signaling pathway, and highlight that upregulating ACE2 expression and activity may represent a promising approach for the treatment of SAE in patients with sepsis.

The role of the peripheral system dysfunction in the pathogenesis of sepsis-associated encephalopathy.

Sepsis is a condition that greatly impacts the brain, leading to neurological dysfunction and heightened mortality rates, making it one of the primary organs affected. Injury to the central nervous system can be attributed to dysfunction of various organs throughout the entire body and imbalances within the peripheral immune system. Furthermore, central nervous system injury can create a vicious circle with infection-induced peripheral immune disorders. We collate the pathogenesis of septic encephalopathy, which involves microglial activation, programmed cell death, mitochondrial dysfunction, endoplasmic reticulum stress, neurotransmitter imbalance, and blood-brain barrier disruption. We also spotlight the effects of intestinal flora and its metabolites, enterocyte-derived exosomes, cholinergic anti-inflammatory pathway, peripheral T cells and their cytokines on septic encephalopathy.

Hyperbaric oxygen therapy as a possible therapeutic candidate for sepsis-associated encephalopathy: A novel hypothesis

Hyperbaric oxygen therapy (HBOT) is being increasingly recognized as a potential therapeutic modality with favorable mechanisms in various diseases. HBOT has demonstrated anti-inflammatory and antiapoptotic effects as well as increased the oxygenation capacity of oxygen-deprived tissues, thus contributing to tissue homeostasis. Focusing on these mechanisms, HBOT could be applied for sepsis-associated encephalopathy (SAE), which is a serious sepsis-related complication. Two vital mechanisms in the pathogenesis of SAE are: (1) neuroinflammation mainly induced by microglia and (2) cerebral ischemia/hypoperfusion caused by cerebral microcirculatory abnormalities. Herein, we highlight the mechanisms of the neuroprotective effects of HBOT and its potential application as a therapeutic modality for SAE. We also discuss the caveats and limitations of applying HBOT in sepsis.

The Absence of Gasdermin D Reduces Nuclear Autophagy in a Cecal Ligation and Puncture-Induced Sepsis-Associated Encephalopathy Mouse Model

Sepsis-associated encephalopathy (SAE) is a common complication of sepsis, which is a life-threatening condition resulting from a dysregulated host response to infection. Pyroptosis, a pro-inflammatory mode of lytic cell death mediated by GSDMD (Gasdermin D), is involved in the pathogenesis of SAE. While autophagy has been extensively studied in SAE, the role of nuclear autophagy is not yet well understood. In this study, we aimed to investigate the involvement of pyroptosis and neural nuclear autophagy in the pathogenesis of SAE. We analyzed a CLP (cecal ligation and puncture)-induced SAE model in wild-type and GSDMD-/- mice to gain insights into the underlying mechanisms. Here, we show that in sepsis, neural nuclear autophagy is extremely activated, and nuclear LaminB decreases and is accompanied by an increase in the ratio of LC3BII/I. These effects can be reversed in GSDMD-/- mice. The behavioral outcomes of septic wild-type mice are impaired by the evidence from the novel object recognition test (NORT) and open field test (OFT), but are improved in septic GSDMD-/- mice. In conclusion, our study demonstrates the activation of neural nuclear autophagy in SAE. The absence of GSDMD inhibits nuclear autophagy and improves the behavioral outcomes of SAE.

Inhibition of ferroptosis protects sepsis-associated encephalopathy.

Sepsis-associated encephalopathy (SAE) is a serious and common complication of sepsis. To study the ferroptosis in the pathogenesis of SAE and demonstrate the protection effect of ferroptosis resistance, cognitive function, neurological deficits, blood-brain barrier integrity and neuroinflammation were detected. SAE model was established by cecal ligation and puncture (CLP) in mice and an in vitro model was created by introducing LPS to HT22 cells. Ferroptosis inducer Fe-citrate (Fe) and ferroptosis inhibitor ferrostatin-1 (Fer-1) was post-treated in the models, respectively. SAE caused ferroptosis, as evidenced by an increase in reactive oxygen species (ROS), iron content and malondialdehyde (MDA) and a decrease in glutathione (GSH) level, as well as changes in the expression of ferroptosis-related proteins as acyl-CoA synthetase long-chain family member 4 (ACSL4), glutathione peroxidase 4 (GPX4), and cystine-glutamate antiporter (SLC7A11), and harmed mitochondrial function. In contrast, inhibiting ferroptosis with Fer-1 attenuated ferroptosis. Meanwhile, Fer-1 attenuated neurologic severity score, learning and memory impairment, Fluoro-Jade C (FJC) staining, and decreased Evans Blue (EB) extravasation, microglia activation and TNF-α and IL-1β production following SAE. The benefit of Fer-1 was diminished by ferroptosis inducer Fe. In addition, Fer-1 up-regulated the nuclear factor erythroid-2-related factor 2 (Nrf2)/ heme oxygenase-1(HO-1) signaling axis both in vivo and in vitro. In conclusion, our study revealed that Fer-1 might inhibit feroptosis in neurons by triggering the Nrf2/OH-1 pathway, thereby providing a therapeutic solution for SAE.

SS-31 Improves Cognitive Function in Sepsis-Associated Encephalopathy by Inhibiting the Drp1-NLRP3 Inflammasome Activation.

Neuroinflammation and microglial activation are involved in the pathogenesis of sepsis-associated encephalopathy (SAE). Mitochondrial dynamics emerged as a new player in the regulation of immunological processes. In this study, we aimed at exploring the effects of mitochondrial-targeted antioxidant peptide SS-31 on cognitive function in mice with SAE. In mice, SS-31 was intraperitoneally administered for seven consecutive days after cecal ligation and puncture surgery. SS-31 improved cognitive performance and survival rate of mice and alleviated hippocampal inflammation, reactive oxygen species production, and excessive mitochondrial fission. The increase of nucleotide-binding oligomerization domain 3 (NLRP3) and phosphorylated dynamin-related protein 1 (Drp1) ser616 in microglia was attenuated by SS-31. In vitro, the microglial cell line BV-2 was pre-treated with SS-31, followed by lipopolysaccharide/adenosine triphosphate induction. SS-31 effectively decreased the activation of NLRP3 inflammasome, mitochondrial translocation of Drp1, excessive mitochondrial fission, and mitochondrial membrane recruitment of gasdermin-D N-terminal (GSDMD-N). Similarly, knockdown of Drp1 inhibited the activation of NLRP3 inflammasome. SS-31 improved survival rate and cognitive functions of mice with SAE, related to mitochondrial fission protein Drp1 to inhibiting activation of NLRP3 inflammasome.

Central role of microglia in sepsis-associated encephalopathy: From mechanism to therapy.

Sepsis-associated encephalopathy (SAE) is a cognitive impairment associated with sepsis that occurs in the absence of direct infection in the central nervous system or structural brain damage. Microglia are thought to be macrophages of the central nervous system, devouring bits of neuronal cells and dead cells in the brain. They are activated in various ways, and microglia-mediated neuroinflammation is characteristic of central nervous system diseases, including SAE. Here, we systematically described the pathogenesis of SAE and demonstrated that microglia are closely related to the occurrence and development of SAE. Furthermore, we comprehensively discussed the function and phenotype of microglia and summarized their activation mechanism and role in SAE pathogenesis. Finally, this review summarizes recent studies on treating cognitive impairment in SAE by blocking microglial activation and toxic factors produced after activation. We suggest that targeting microglial activation may be a putative treatment for SAE.

Irisin protects against sepsis-associated encephalopathy by suppressing ferroptosis via activation of the Nrf2/GPX4 signal axis

Sepsis-associated encephalopathy (SAE) is a common complication of severe sepsis. Irisin is a novel exercise-induced myokine involved in the regulation of adipose browning and thermogenesis. This study is designed to verify the existence of ferroptosis in the pathogenesis of SAE and demonstrate that irisin attenuated cognitive dysfunction in SAE mice via inhibition of hippocampus ferroptosis. A mouse SAE model was induced by cecal ligation and puncture (CLP) and in vitro model was established by LPS-stimulated hippocampus cells. Irisin were pre-treated in the models. We found that SAE triggered hippocampus ferroptosis, as evidenced by increasing ROS, iron content and MDA and reducing GSH level as well as altered ferroptosis-related protein (GPX4, ACSL4 and SLC7A11) expression, whereas irisin attenuated CLP-induced learning and memory dysfunction, neurologic severity score and hippocampus ferroptosis and microglial activation in SAE mice. However, the protective effect of irisin was eliminated by ferroptosis inducer Erastin. Consistently, irisin reduced ferroptosis and improved mitochondrial dysfunction in LPS-induced HT-22 cells, as evidenced by decreased lipid ROS and increased mitochondrial membrane potential. Furthermore, proteomics identified the differentially expressed proteins linked to ferroptosis in SAE. We also observed that irisin-mediated anti-ferroptosis was abolished by siRNA-Nrf2 or in Nrf2−/− mice. Transwell assay revealed that irisin could prevent the recruitment and chemotaxis of microglial cells induced by ferroptotic hippocampal cells. In conclusion, irisin could ameliorate inflammatory microenvironment in SAE by suppressing hippocampus ferroptosis via the Nrf2/GPX4 signaling pathway.

Pathogenesis of sepsis-associated encephalopathy: more than blood-brain barrier dysfunction.

Sepsis-associated encephalopathy is a common neurological complication of sepsis and is responsible for higher mortality and poorer long-term outcomes in septic patients. Sepsis-associated encephalopathy symptoms can range from mild delirium to deep coma, which occurs in up to 70% of patients in intensive care units. The pathological changes in the brain associated with sepsis include cerebral ischaemia, cerebral haemorrhage, abscess and progressive multifocal necrotic leukoencephalopathy. Several mechanisms are involved in the pathogenesis of sepsis-associated encephalopathy, such as blood-brain barrier dysfunction, cerebral blood flow impairment, glial cell activation, leukocyte transmigration, and neurotransmitter disturbances. These events are interrelated and influence each other, thereforethey do not act as independent factors. This review is focused on new evidence showing the pathological process of sepsis-associated encephalopathy.

The Improvement of Sepsis-Associated Encephalopathy by P2X7R Inhibitor through Inhibiting the Omi/HtrA2 Apoptotic Signaling Pathway.

The pathogenesis of sepsis-associated encephalopathy (SAE) involves many aspects, including intracellular peroxidative stress damage, mitochondrial dysfunction, and cell apoptosis. In this study, we mainly explored the influence of P2X7R on the cognitive function of SAE and its molecular mechanism. We established a sepsis model using lipopolysaccharide (LPS) stimulation, followed by an assessment of cognitive function using Morris water maze, and then Western Blot was used to analyze the expression of tight junction proteins ZO-1 and Occludin in the hippocampus of mice. TUNEL assay was used to analyze the apoptosis of brain cells in frozen brain slices of mice during sepsis. Human brain microvascular endothelial cells (HBMECs) were used to research the molecular mechanism of brain cell damage induced by P2X7R. The results showed that P2X7R inhibitors dramatically improved the survival rate of mice, relieved the cognitive dysfunction caused by LPS stimulation, and significantly reduced the brain cell apoptosis caused by LPS. In addition, the inhibition of P2X7R can also reduce the production and accumulation of reactive oxygen species (ROS) in HBMECs in vitro and inhibit the apoptosis signaling pathway associated with mitochondrial serine protease Omi/HtrA2 in HBMECs in vitro. These results suggest that P2X7R has strong value as a potential target for the treatment of SAE.

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

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

NU9056, a KAT 5 Inhibitor, Treatment Alleviates Brain Dysfunction by Inhibiting NLRP3 Inflammasome Activation, Affecting Gut Microbiota, and Derived Metabolites in LPS-Treated Mice.

Background: The pathogenesis of sepsis-associated encephalopathy (SAE) is complicated, while the efficacy of current treatment technologies is poor. Therefore, the discovery of related targets and the development of new drugs are essential.Methods: A mouse model of SAE was constructed by intraperitoneal injection of lipopolysaccharide (LPS). LPS treatment of microglia was used to build an in vitro model of inflammation. Nine-day survival rates, behavioral testing, transmission electron microscopy (TEM), immunohistochemical (IHC), immunofluorescence (IF), and ELISA were performed. The expression levels of Occludin, Claudin 5, NLRP3, caspase-1, and ASC genes and proteins were detected by RT-qPCR or Western blot. Caspase-1 P10 (Casp-1 P10) protein expression was detected. 16S rDNA sequencing and gas chromatography-mass spectrometer (GC-MS) were used to analyze the gut microbiota and metabolism. Flow cytometric experiment and Cell Counting Kit-8 (CCK8) assay were performed.Results: NU9056 improved the survival rate of mice and alleviated LPS-induced cognitive impairment, anxiety, and depression in vivo. The tight junctions were thickened via NU9056 treatment. Further, the mRNAs and proteins expression levels of Occludin and Claudin 5 were up-regulated by NU9056. NU9056 increased the expression level of DCX. The expression levels of Iba-1, NLRP3, IL-1β, ASC, and Casp-1 P10 were down-regulated by NU9056. The composition of the gut microbiota changed. Kyoto Encyclopedia of Genes and Genomes data predicted that the effects of NU9056 might be related to apoptosis and tight junction pathways. NU9056 up-regulated the concentration of acetate, propionate, and butyrate. NU9056 significantly reduced LPS-induced apoptosis of microglia, the average fluorescence intensity of ROS, and the release of IL-1β and IL-18, while improving cell viability in vitro.Conclusions: NU9056 might effectively alleviate LPS-induced cognitive impairment and emotional disorder in experimental mice by inhibiting the NLRP3 inflammasome. The therapeutic effects may be related to gut microbiota and derived metabolites. NU9056 might be a potential drug of SAE prevention.

Infiltrated regulatory T cells and Th2 cells in the brain contribute to attenuation of sepsis-associated encephalopathy and alleviation of mental impairments in mice with polymicrobial sepsis

Sepsis-associated encephalopathy (SAE) increases not only morbidity and mortality but has been associated with long-lasting mental impairment after hospital discharge in septic patients. Recently, studies have shown that these mental impairments are caused by infection-induced neuroinflammation. However, the role of T cells in the pathogenesis of SAE and mental impairments remains unclear. Thus, in this study, we aimed to clarify how immune cells, especially T cells, influence the development and recovery of these disorders. In the cecal slurry (CS)-induced septic mouse model, we performed three different kinds of behavioral tests, open-field test, marble burying test, and forced swimming test, and observed anxiety-like behavior in septic mice. Additionally, increased interleukin (IL)-1β and IL-6 expression levels, and infiltration of neutrophils and T cells were examined in the brain of septic mice, 10 days after sepsis onset. Twenty days after sepsis onset, the septic mice could recover the number of astrocytes. At day 30, expression levels of IL-1β and tumor necrosis factor (TNF)-α returned to normal levels in the cerebral cortex of septic mice. Interestingly, resolution of neuroinflammation and alleviation of depression were delayed in septic mice treated with FTY720, which inhibits sphingosine-1-phosphate (S1P)-dependent lymphocyte egress from lymph nodes. On analyzing the brain T cells with or without FTY720 in septic mice, the FTY720 untreated mice presented increased regulatory T cells (Treg) and Th2 cells in the brain, whereas the FTY720 treated mice demonstrated increased Th17 in the brain at day 30. Furthermore, in FTY720 treated septic mice, the number of astrocytes in the cerebral cortex remained reduced at day 30. These results suggest that infiltrated Treg and Th2 cells contribute to the attenuation SAE and alleviate SAE-induce mental disorder by resolving neuroinflammation in the chronic phase of sepsis.

JAK/STAT signaling pathway-mediated microRNA-181b promoted blood-brain barrier impairment by targeting sphingosine-1-phosphate receptor 1 in septic rats.

BackgroundBlood-brain barrier (BBB) impairment plays a significant role in the pathogenesis of sepsis-associated encephalopathy (SAE). However, the molecular mechanisms are poorly understood. In the present study, we aimed to investigate the regulatory relationship between the Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway, microRNA (miR)-181b and its target genes in sepsis in vivo and in vitro.MethodsFour rat models (sham, sepsis, sepsis plus STAT3 inhibitor (Stattic), and sepsis plus miR-181b inhibitor [sepsis + anta-miR-181b]) were established. For the in vitro experiments, rat brain microvascular endothelial cells (rBMECs) and rat brain astrocytes (rAstrocytes) were cultured with 10% serum harvested from sham, sepsis, and sepsis + anta-miR-181b rats. Chromatin immunoprecipitation-quantitative polymerase chain reaction (ChIP-QPCR) analysis was carried out to detect the binding and enrichment of the JAK/STAT3 signal core transcription complex in the miR-181b promoter region. Dual-luciferase reporter gene assay was conducted to test miR-181b and its target genes. The cell adhesion rate of rBMECs was also measured.ResultsDuring our investigations, the expression levels of miR-181b, p-JAK2, p-STAT3, and C/EBPβ were found to be significantly increased in the septic rats compared with the sham rats. STAT3 inhibitor halted BBB damage by downregulating the expression of miR-181b. In addition, miR-181b targeted sphingosine-1-phosphate receptor 1 (S1PR1) and neurocalcin delta (NCALD). The up-regulated miR-181b significantly decreased the cell adhesion rate of rBMECs. The administration of miR-181b inhibitor reduced damage to the BBB through increasing the expression of S1PR1 and NCALD, which again proved that miR-181b negatively regulates SIPR1 and NCALD to induce BBB damage.ConclusionsOur study demonstrated that JAK2/STAT3 signaling pathway induced expression of miR-181b, which promoted BBB impairment in rats with sepsis by downregulating S1PR1 and decreasing BBB cell adhesion. These findings strongly suggest JAK2/STAT3/miR-181b axis as therapeutic target in protecting against sepsis-induced BBB damage.

Hydrogen attenuates sepsis-associated encephalopathy by NRF2 mediated NLRP3 pathway inactivation.

Sepsis-associated encephalopathy (SAE) is a major cause of mortality worldwide. Oxidative stress, inflammatory response and apoptosis participate in the pathogenesis of SAE. Nuclear factor erythroid 2-related factor 2 (Nrf2) and nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) pathway is involved in oxidative stress and inflammatory response. We reported that hydrogen gas protected against sepsis in wild-type (WT) but not Nrf2 knockout (KO) mice. Therefore, it is vital to identify the underlying cause of hydrogen gas treatment of sepsis-associated encephalopathy. SAE was induced in WT and Nrf2 KO mice by cecal ligation and puncture (CLP). As a NLRP3 inflammasome inhibitor, MCC950 (50mg/kg) was administered by intraperitoneal (i.p.) injection before operation. Hydrogen gas (H2)-rich saline solution (5mL/kg) was administered by i.p. injection at 1h and 6h after sham and CLP operations. Brain tissue was collected to assess the NLRP3 and Nrf2 pathways by western blotting, reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence. SAE increased NLRP3 and Nrf2 expression in microglia. MCC950 inhibited SAE-induced NLRP3 expression, interleukin (IL)-1β and IL-18 cytokine release, neuronal apoptosis and mitochondrial dysfunction. SAE increased NLRP3 and caspase-1 expression in WT mice compared to Nrf2 KO mice. Hydrogen increased Nrf2 expression and inhibited the SAE-induced expression of NLRP3, caspase-1, cytokines IL-1β and IL-18, neuronal apoptosis, and mitochondrial dysfunction in WT mice but not Nrf2 KO mice. SAE increased NLRP3 and Nrf2 expression in microglia. Hydrogen alleviated inflammation, neuronal apoptosis and mitochondrial dysfunction via inhibiting Nrf2-mediated NLRP3 pathway.

The clinical significance of transcranial Doppler in early diagnosis of sepsis-associated encephalopathy

Objective: To investigate the clinical significance of transcranial Doppler (TCD) in early diagnosis of sepsis-associated encephalopathy(SAE). Methods: Septic patients admitted to the intensive care unit(ICU) were recruited at Xiangya Hospital, Central South University from July 2015 to March 2016. Clinical data and TCD parameters during 24 hours after admission were collected. All patients were screened for delirium using the confusion assessment method for the intensive care unit (CAM-ICU) twice a day. The gold standard of the diagnosis of SAE was positive CAM-ICU evaluation. Patients were divided into SAE group and the non-SAE group. TCD data including systolic velocity (Vs), diastolic velocity (Vd), mean velocity (Vm), pulsatility index (PI) and resistant index (RI) were analyzed to determine the optimal diagnostic cut-off value. Results: A total of 43 patients were enrolled including 12 in SAE group and 31 in non-SAE group. Vm and Vd were lower in SAE group [Vm: (53.50±12.22) cm/s vs. (61.68±9.63) cm/s, P<0.05; Vd: (33.42±10.87) cm/s vs. (43.16±7.84) cm/s, P<0.01] but PI and RI were significant higher in SAE group[PI:(1.16±0.2) vs. (0.90±0.15), P<0.01;RI:(0.65±0.08) vs. (0.56±0.06), P<0.01] than in non-SAE group. The cut-off values of Vs, Vm, Vd, PI and RI for the diagnosis of SAE were 112cm/s, 55.50cm/s, 34.50cm/s, 1.16, 0.65, respectively, with the relevant sensitivities of 19.4%, 83.9%, 93.5%, 58.3%, 58.3% and the specificities of 100.0%, 50.0%, 58.3%, 96.8%, 96.8%, respectively. The diagnostic AUC of Vd, PI and RI were 0.741, 0.808 and 0.808 respectively. Conclusions: The parameter changes of TCD suggest that the pathogenesis of SAE is related to cerebral hypoperfusion, TCD is a helpful method for the early diagnosis of SAE.

Pentamidine protects mice from cecal ligation and puncture-induced brain damage via inhibiting S100B/RAGE/NF-κB

The brain is one of the earliest organs to be influenced during sepsis. Sepsis-associated encephalopathy (SAE) is frequent, but seldomly recognized and has no testified pharmacological therapy. In this study, we demonstrated that pentamidine, an antiprotozoal drug, is a good candidate since it blocks S100B/RAGE/NF-κB signaling pathway. Pentamidine ameliorated cecal ligation and puncture (CLP)-induced brain damage assessed by crystal violet staining and hematoxylin and eosin (H&E) staining. Moreover, pentamidine reduced neuroinflammation in mouse hippocampi. Immunofluorescence and Western blot analysis also showed that pentamidine inhibited CLP-induced gliosis and S100B/RAGE/NF-κB pathway activation. Interestingly, it could also attenuate oxidative stress indicated by decreased protein levels of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), and attenuation of malondialdehyde (MDA) accumulation and superoxide dismutase (SOD) consumption. Thus the S100B/RAGE/NF-κB pathway may be crucial in the pathogenesis of SAE and may be a promising pharmacological target to prevent SAE.

Effect of incubation with lipopolysaccharide and interferon-γ on reactive astrogliosis.

Sepsis associated encephalopathy is a common complication of sepsis, but its pathogenesis of sepsis-associated encephalopathy remains unclear. Astrocytes are the most abundant brain glial cells, and reactive astrogliosis, a pathological response to central nervous system diseases, has a clear disease and disease-stage specificity. Functional changes of astrocytes are of great significance for the detection and prognosis of sepsis-associated encephalopathy. The pathogenesis of sepsis-associated encephalopathy was explored at the cellular level by examining astrogliosis in an in vitro model of sepsis-associated encephalopathy. Astrocytes of Wistar neonatal rats were incubated with different concentrations of lipopolysaccharide combined with interferon-γ. Cell viability was assessed by levels of tumor necrosis factor-α, interleukin-6, nitric oxide, reactive oxygen species, glial fibrillary acidic protein, changes of astrocyte morphology, and prevalence of apoptosis and necrosis. Compared with the control group, the cell viability of treated groups was decreased. The levels of tumor necrosis factor-α, interleukin-6, nitric oxide, reactive oxygen species, and glial fibrillary acidic protein were increased, hypertrophy of astrocytes was observed, and apoptosis was increased. The pathogenic outcomes of astrogliosis in sepsis-associated encephalopathy is discussed and a new tool provided to explore the pathogenesis of sepsis-associated encephalopathy at the cellular level.