Treatment with TO901317, a synthetic liver X receptor agonist, reduces brain damage and attenuates neuroinflammation in experimental intracerebral hemorrhage

Cholesterol metabolism: physiological versus pathological aspects in intracerebral hemorrhage

Cholesterol is an important component of plasma membranes and participates in many basic life functions, such as the maintenance of cell membrane stability, the synthesis of steroid hormones, and myelination. Cholesterol plays a key role in the establishment and maintenance of the central nervous system. The brain contains 20% of the whole body's cholesterol, 80% of which is located within myelin. A huge number of processes (e.g., the sterol regulatory element-binding protein pathway and liver X receptor pathway) participate in the regulation of cholesterol metabolism in the brain via mechanisms that include cholesterol biosynthesis, intracellular transport, and efflux. Certain brain injuries or diseases involving crosstalk among the processes above can affect normal cholesterol metabolism to induce detrimental consequences. Therefore, we hypothesized that cholesterol-related molecules and pathways can serve as therapeutic targets for central nervous system diseases. Intracerebral hemorrhage is the most severe hemorrhagic stroke subtype, with high mortality and morbidity. Historical cholesterol levels are associated with the risk of intracerebral hemorrhage. Moreover, secondary pathological changes after intracerebral hemorrhage are associated with cholesterol metabolism dysregulation, such as neuroinflammation, demyelination, and multiple types of programmed cell death. Intracellular cholesterol accumulation in the brain has been found after intracerebral hemorrhage. In this paper, we review normal cholesterol metabolism in the central nervous system, the mechanisms known to participate in the disturbance of cholesterol metabolism after intracerebral hemorrhage, and the links between cholesterol metabolism and cell death. We also review several possible and constructive therapeutic targets identified based on cholesterol metabolism to provide cholesterol-based perspectives and a reference for those interested in the treatment of intracerebral hemorrhage.

Transient receptor potential vanilloid 1 inhibition reduces brain damage by suppressing neuronal apoptosis after intracerebral hemorrhage

Intracerebral hemorrhage (ICH) induces a complex sequence of apoptotic cascades and inflammatory responses, leading to neurological impairment. Transient receptor potential vanilloid 1 (TRPV1), a nonselective cation channel with high calcium permeability, has been implicated in neuronal apoptosis and inflammatory responses. This study used a mouse ICH model and neuronal cultures to examine whether TRPV1 activation exacerbates brain damage and neurological deficits by promoting neuronal apoptosis and neuroinflammation. ICH was induced by injecting collagenase in both wild-type (WT) C57BL/6 mice and TRPV1-/- mice. Capsaicin (CAP; a TRPV1 agonist) or capsazepine (a TRPV1 antagonist) was administered by intracerebroventricular injection 30 min before ICH induction in WT mice. The effects of genetic deletion or pharmacological inhibition of TRPV1 using CAP or capsazepine on motor deficits, histological damage, apoptotic responses, blood-brain barrier (BBB) permeability, and neuroinflammatory reactions were explored. The antiapoptotic mechanisms and calcium influx induced by TRPV1 inactivation were investigated in cultured hemin-stimulated neurons. TRPV1 expression was upregulated in the hemorrhagic brain, and TRPV1 was expressed in neurons, microglia, and astrocytes after ICH. Genetic deletion of TRPV1 significantly attenuated motor deficits and brain atrophy for up to 28 days. Deletion of TRPV1 also reduced brain damage, neurodegeneration, microglial activation, cytokine expression, and cell apoptosis at 1 day post-ICH. Similarly, the administration of CAP ameliorated brain damage, neurodegeneration, brain edema, BBB permeability, and cytokine expression at 1 day post-ICH. In primary neuronal cultures, pharmacological inactivation of TRPV1 by CAP attenuated neuronal vulnerability to hemin-induced injury, suppressed apoptosis, and preserved mitochondrial integrity in vitro. Mechanistically, CAP reduced hemin-stimulated calcium influx and prevented the phosphorylation of CaMKII in cultured neurons, which was associated with reduced activation of P38 and c-Jun NH2-terminal kinase mitogen-activated protein kinase signaling. Our results suggest that TRPV1 inhibition may be a potential therapy for ICH by suppressing mitochondria-related neuronal apoptosis.

LXR agonism for CNS diseases: promises and challenges

The unfavorable prognosis of many neurological conditions could be attributed to limited tissue regeneration in central nervous system (CNS) and overwhelming inflammation, while liver X receptor (LXR) may regulate both processes due to its pivotal role in cholesterol metabolism and inflammatory response, and thus receives increasing attentions from neuroscientists and clinicians. Here, we summarize the signal transduction of LXR pathway, discuss the therapeutic potentials of LXR agonists based on preclinical data using different disease models, and analyze the dilemma and possible resolutions for clinical translation to encourage further investigations of LXR related therapies in CNS disorders.

Enhanced liver X receptor signalling reduces brain injury and promotes tissue regeneration following experimental intracerebral haemorrhage: roles of microglia/macrophages

BACKGROUND

Inflammation-exacerbated secondary brain injury and limited tissue regeneration are barriers to favourable prognosis after intracerebral haemorrhage (ICH). As a regulator of inflammation and lipid metabolism, Liver X receptor (LXR) has the potential to alter microglia/macrophage (M/M) phenotype, and assist tissue repair by promoting cholesterol efflux and recycling from phagocytes. To support potential clinical translation, the benefits of enhanced LXR signalling are examined in experimental ICH.

METHODS

Collagenase-induced ICH mice were treated with the LXR agonist GW3965 or vehicle. Behavioural tests were conducted at multiple time points. Lesion and haematoma volume, and other brain parameters were assessed using multimodal MRI with T2-weighted, diffusion tensor imaging and dynamic contrast-enhanced MRI sequences. The fixed brain cryosections were stained and confocal microscopy was applied to detect LXR downstream genes, M/M phenotype, lipid/cholesterol-laden phagocytes, oligodendrocyte lineage cells and neural stem cells. Western blot and real-time qPCR were also used. CX3CR1CreER: Rosa26iDTR mice were employed for M/M-depletion experiments.

RESULTS

GW3965 treatment reduced lesion volume and white matter injury, and promoted haematoma clearance. Treated mice upregulated LXR downstream genes including ABCA1 and Apolipoprotein E, and had reduced density of M/M that apparently shifted from proinflammatory interleukin-1β+ to Arginase1+CD206+ regulatory phenotype. Fewer cholesterol crystal or myelin debris-laden phagocytes were observed in GW3965 mice. LXR activation increased the number of Olig2+PDGFRα+ precursors and Olig2+CC1+ mature oligodendrocytes in perihaematomal regions, and elevated SOX2+ or nestin+ neural stem cells in lesion and subventricular zone. MRI results supported better lesion recovery by GW3965, and this was corroborated by return to pre-ICH values of functional rotarod activity. The therapeutic effects of GW3965 were abrogated by M/M depletion in CX3CR1CreER: Rosa26iDTR mice.

CONCLUSIONS

LXR agonism using GW3965 reduced brain injury, promoted beneficial properties of M/M and facilitated tissue repair correspondent with enhanced cholesterol recycling.

Low-intensity pulsed ultrasound ameliorates glia-mediated inflammation and neuronal damage in experimental intracerebral hemorrhage conditions

BACKGROUND

Intracerebral hemorrhage (ICH) is a condition associated with high morbidity and mortality, and glia-mediated inflammation is a major contributor to neurological deficits. However, there is currently no proven effective treatment for clinical ICH. Recently, low-intensity pulsed ultrasound (LIPUS), a non-invasive method, has shown potential for neuroprotection in neurodegenerative diseases. This study aimed to investigate the neuroprotective effects and potential mechanisms of LIPUS on glia-mediated inflammation in ICH.

METHODS

This study used 289 mice to investigate the effects of LIPUS on ICH. ICH was induced by injecting bacterial collagenase (type VII-S; 0.0375 U) into the striatum of the mice. LIPUS was applied noninvasively for 3 days, including a 2-h-delayed intervention to mimic clinical usage. The study evaluated neurological function, histology, brain water content, hemoglobin content, MRI, and protein expression of neurotrophic factors, inflammatory molecules, and apoptosis. In vitro studies investigated glia-mediated inflammation by adding thrombin (10 U/mL) or conditioned media to primary and cell line cultures. The PI3K inhibitor LY294002 was used to confirm the effects of PI3K/Akt signaling after LIPUS treatment.

RESULTS

LIPUS treatment improved neurological deficits and reduced tissue loss, edema, and neurodegeneration after ICH. The protective effects of LIPUS resulted from decreased glia-mediated inflammation by inhibiting PI3K/Akt-NF-κB signaling, which reduced cytokine expression and attenuated microglial activation-induced neuronal damage in vitro.

CONCLUSIONS

LIPUS treatment improved neurological outcomes and reduced glia-mediated inflammation by inhibiting PI3K/Akt-NF-κB signaling after ICH. LIPUS may provide a non-invasive potential management strategy for ICH.

Combined with UPLC-Triple-TOF/MS-based plasma lipidomics and molecular pharmacology reveals the mechanisms of schisandrin against Alzheimer's disease

BACKGROUND

Alzheimer's disease (AD), a type of neurodegeneration disease, is characterized by Aβ deposition and tangles of nerve fibers. Schisandrin is one of the main components of Fructus Schisandrae Chinensis. Researches showed that schisandrin can improve the cognitive impairment and memory of AD mice, but the specific mechanism has not been fully elucidated.

PURPOSE

The purpose of this study is to investigate the possible mechanism of schisandrin in improving AD pathology.

METHODS

The Morris water maze test was executed to detect spatial learning and memory. Ultra performance liquid chromatography-Triple time of flight mass spectrometry (UPLC-Triple-TOF/MS)-based plasma lipidomics was used to study the changes of plasma lipids. Moreover, we measured the levels of protein and mRNA expression of APOE and ABCA1 in the rat brains and in BV2 microglia.

RESULTS

Our study found that schisandrin could improve learning and memory, and reduce Aβ deposition in AD rats. Furthermore, we found that schisandrin can improve plasma lipid metabolism disorders. Therefore, we hypothesized schisandrin might act via LXR and the docking results showed that schisandrin interacts with LXRβ. Further, we found schisandrin increased the protein and mRNA expression of LXR target genes APOE and ABCA1 in the brain of AD rats and in BV2 microglia.

CONCLUSION

Our study reveals the neuroprotective effect and mechanism of schisandrin improves AD pathology by activating LXR to produce APOE and ABCA1.

T0901317, a liver X receptor agonist, ameliorates perinatal white matter injury induced by ischemia and hypoxia in neonatal rats

Perinatal white matter injury (PWMI) can lead to permanent neurological damage in preterm infants and bring a huge economic burden to their families and society. Liver X receptors (LXRs) are transcription factors that have been confirmed to mediate the myelination process under physiological conditions and are involved in regulating neurogenesis in adult animal models of acute and chronic cerebral ischemia. However, the role of LXRs in PWMI induced by both ischemic and hypoxic stimulation in the immature brain has not been reported. Herein, we investigated the role of LXRs in a neonatal rat model of white matter loss after hypoxia-ischemia (HI) injury through intraperitoneal injection of the LXR agonist T0901317 (T09) 1 day before and 15 min postinjury. The in vivo data showed that T09 treatment significantly facilitated myelination and ameliorated neurological behavior after PWMI. Moreover, T09 enhanced the proliferation of oligodendrocyte lineage cells and reduced microgliosis and astrogliosis in the microenvironment for oligodendrocytes (OLs), maintaining a healthy microenvironment for myelinating OLs. In vitro data suggested that the expression of the myelin-related genes Plp and Cnpase was increased in OLN-93 cells after T09 intervention compared with OLN-93 cells injured by oxygen and glucose deprivation (OGD). In primary mixed astrocytes/microglia cells, T09 also reduced the expression of Il6, Cox2, Tnfa and Il10 that was induced by OGD. Mechanistically, the mRNA expression level and the protein level of ATP binding cassette subfamily A member 1 (Abca1) decreased after HI injury, and the protective effect of T09 might be related to the activation of the LXRβ-ABCA1 signaling pathway. Our study revealed the protective role of LXRs in myelination and white matter homeostasis, providing a potential therapeutic option for PWMI.

Targeting fatty acid metabolism in glioblastoma

Glioblastoma (GBM) is a primary tumor of the brain defined by its uniform lethality and resistance to conventional therapies. There have been considerable efforts to untangle the metabolic underpinnings of this disease to find novel therapeutic avenues for treatment. An emerging focus in this field is fatty acid (FA) metabolism, which is critical for numerous diverse biological processes involved in GBM pathogenesis. These processes can be classified into four broad fates: anabolism, catabolism, regulation of ferroptosis, and the generation of signaling molecules. Each fate provides a unique perspective by which we can inspect GBM biology and gives us a road map to understanding this complicated field. This Review discusses the basic, translational, and clinical insights into each of these fates to provide a contemporary understanding of FA biology in GBM. It is clear, based on the literature, that there are far more questions than answers in the field of FA metabolism in GBM, and substantial efforts should be made to untangle these complex processes in this intractable disease.

Liver X Receptor Regulation of Glial Cell Functions in the CNS

In this review, we discuss the role of liver X receptors (LXRs) in glial cells (microglia, oligodendrocytes and astrocytes) in the central nervous system (CNS). LXRs are oxysterol-activated nuclear receptors that, in adults, regulate genes involved in cholesterol homeostasis, the modulation of inflammatory responses and glutamate homeostasis. The study of LXR knockout mice has revealed that LXRβ plays a key role in maintaining the health of dopaminergic neurons in the substantia nigra, large motor neurons in the spinal cord and retinal ganglion cells in the eye. In the peripheral nervous system (PNS), LXRβ is responsible for the health of the spiral ganglion neurons (SGNs) in the cochlea. In addition, LXRs are essential for the homeostasis of the cerebrospinal fluid (CSF), and in LXRαβ^−/− mice, the lateral ventricles are empty and lined with lipid-laden cells. As LXRαβ^−/− mice age, lipid vacuoles accumulate in astrocytes surrounding blood vessels. By seven months of age, motor coordination becomes impaired, and there is a loss of motor neurons in the spinal cord of LXRβ^−/− mice. During development, migration of neurons in the cortex and cerebellum is retarded in LXRβ^−/− mice. Since LXRs are not expressed in dopaminergic or motor neurons in adult mice, the neuroprotective effects of LXRs appear to come from LXRs in glial cells where they are expressed. However, despite the numerous neurological deficits in LXR^−/− rodents, multiple sclerosis has the clear distinction of being the only human neurodegenerative disease in which defective LXR signaling has been identified. In this review, we summarize the regulation and functions of LXRs in glial cells and analyze how targeting LXRs in glial cells might, in the future, be used to treat neurodegenerative diseases and, perhaps, disorders caused by aberrant neuronal migration during development.

High-Throughput mRNA Sequencing Reveals Potential Therapeutic Targets of Febuxostat in Secondary Injury After Intracerebral Hemorrhage

Febuxostat is a urate-lowering medication for the treatment of patients with gout. This study was performed to elucidate the effects and underlying mechanisms of febuxostat on neuronal injury induced by intracerebral hemorrhage (ICH) in mice. The results showed that the administration of febuxostat improved neurological severity scores and blood–brain barrier (BBB) permeability. Moreover, febuxostat attenuated neuronal cell death and cytokine levels compared with the ICH group. Next, we conducted a transcriptome analysis of the neuroprotective effects of febuxostat. The overlapping significant differentially expressed genes (DEGs) were identified. Gene ontology (GO) analysis revealed that the overlapping significant DEGs were most enriched in five items. The intersecting DEGs of the aforementioned five pathways were Wisp1, Wnt7b, Frzb, and Pitx2. In addition, GO terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways revealed that DEGs were mainly involved in the wnt signaling pathway. Furthermore, the expression of Wisp1 and Wnt7b in the perihematomal region at 72 h post-ICH was observed. The results showed that both Wisp1 and Wnt7b were increased in the ICH group and were decreased by the administration of febuxostat. Taken together, the study showed that febuxostat protected against secondary brain injury after ICH and the Wnt7b-Wisp1 pathway was closely related to neuroprotective effects.

Microglia and Neuroinflammation: Crucial Pathological Mechanisms in Traumatic Brain Injury-Induced Neurodegeneration

Traumatic brain injury (TBI) is one of the most common diseases in the central nervous system (CNS) with high mortality and morbidity. Patients with TBI usually suffer many sequelae in the life time post injury, including neurodegenerative disorders such as Alzheimer’s disease (AD) and Parkinson’s disease (PD). However, the pathological mechanisms connecting these two processes have not yet been fully elucidated. It is important to further investigate the pathophysiological mechanisms underlying TBI and TBI-induced neurodegeneration, which will promote the development of precise treatment target for these notorious neurodegenerative consequences after TBI. A growing body of evidence shows that neuroinflammation is a pivotal pathological process underlying chronic neurodegeneration following TBI. Microglia, as the immune cells in the CNS, play crucial roles in neuroinflammation and many other CNS diseases. Of interest, microglial activation and functional alteration has been proposed as key mediators in the evolution of chronic neurodegenerative pathology following TBI. Here, we review the updated studies involving phenotypical and functional alterations of microglia in neurodegeneration after injury, survey key molecules regulating the activities and functional responses of microglia in TBI pathology, and explore their potential implications to chronic neurodegeneration after injury. The work will give us a comprehensive understanding of mechanisms driving TBI-related neurodegeneration and offer novel ideas of developing corresponding prevention and treatment strategies for this disease.

Effects and mechanisms of CTRP3 overexpression in secondary brain injury following intracerebral hemorrhage in rats

C1q/TNF-related protein-3 (CTRP3) is a novel adipokine that serves an important role in oxidative stress, anti-apoptosis, anti-inflammation and immune regulation. The aim of the present study was to investigate the protective role of CTRP3 against intracerebral hemorrhage (ICH)-induced brain injury. A model of autologous arterial blood-induced ICH was constructed in rats. Intracerebral infusion of a lentivirus carrying the CTRP3 gene was used to induce CTRP3 overexpression in the brain. The effects and mechanisms of CTRP3 overexpression on brain injury were investigated by detecting brain edema, blood-brain barrier (BBB) integrity, neurological function and inflammatory-associated factors 3 days after ICH. The present results demonstrated that CTRP3 overexpression ameliorated ICH-induced neurological dysfunction, decreased brain edema, maintained BBB integrity and attenuated inflammation. The protective effect of CTRP3 overexpression was associated with increased activation of silent information regulator 1 (SIRT1). In conclusion, the present study demonstrated that CTRP3 overexpression protected against ICH-induced brain injury in rats, potentially via activating the SIRT1 signaling pathway.

Nuclear receptors of NR1 and NR4 subfamilies in the regulation of microglial functions and pathology

This review provides an overview of researches on the NR1 and NR4 nuclear receptors involved in the regulation of microglial functions. Nuclear receptors are attractive candidates for drug targets in the therapies of the central nervous system disorders, because the activation of these receptors is expected to regulate the functions and the phenotypes of microglia, by controlling the expression of specific gene subsets and also by regulating the cellular signaling mechanisms in a nongenomic manner. Several members of NR1 nuclear receptor subfamily have been examined for their ability to regulate microglial functions. For example, stimulation of vitamin D receptor inhibits the production of pro-inflammatory factors and increases the production of anti-inflammatory cytokines. Similar regulatory actions of nuclear receptor ligands on inflammation-related genes have also been reported for other NR1 members such as retinoic acid receptors, peroxisome proliferator-activated receptors (PPARs), and liver X receptors (LXRs). In addition, stimulation of PPARγ and LXRs may also result in increased phagocytic activities of microglia. Consistent with these actions, the agonists at nuclear receptors of NR1 subfamily are shown to produce therapeutic effects on animal models of various neurological disorders such as experimental allergic encephalomyelitis, Alzheimer's disease, Parkinson's disease, and ischemic/hemorrhagic stroke. On the other hand, increasing lines of evidence suggest that the stimulation of NR4 subfamily members of nuclear receptors such as Nur77 and Nurr1 also regulates microglial functions and alleviates neuropathological events in several disease models. Further advancement of these research fields may prove novel therapeutic opportunities.

Soluble epoxide hydrolase inhibitor attenuates BBB disruption and neuroinflammation after intracerebral hemorrhage in mice

Intracerebral hemorrhage (ICH) is a devastating disease with high mortality and morbidity. Soluble epoxide hydrolase (sEH) is the key enzyme in the epoxyeicosatrienoic acids (EETs) signaling. sEH inhibition has been demonstrated to have neuroprotective effects against multiple brain injuries. However, its role in the secondary injuries after ICH has not been fully elucidated. Here we tested the hypothesis that 1-Trifluoromethoxyphenyl-3-(1-propionylpiperidin-4-yl)urea (TPPU), a potent and highly selective sEH inhibitor, suppresses inflammation and the secondary injuries after ICH. Adult male C57BL/6 mice were subjected to a collagenase-induced ICH model. TPPU alleviated blood-brain barrier damage, inhibited inflammatory response, increased M2 polarization of microglial cells, reduced the infiltration of peripheral neutrophils. In addition, TPPU attenuated neuronal injury and promoted functional recovery. The results suggest that sEH may represent a potential therapeutic target for the treatment of ICH.

Liver X Receptor as a Possible Drug Target for Blood-Brain Barrier Integrity

Purpose: blood-brain barrier (BBB) is made of specialized cells that are responsible for the selective passage of substances directed to the brain. The integrated BBB is essential for precise controlling of the different substances passage as well as protecting the brain from various damages. In this article, we attempted to explain the role of liver X receptor (LXR) in maintaining BBB integrity as a possible drug target.

Methods: In this study, various databases, including PubMed, Google Scholar, and Scopus were searched using the following keywords: blood-brain barrier, BBB, liver X receptor, and LXR until July, 2020. Additionally, contents close to the subject of our study were surveyed.

Results: LXR is a receptor the roles of which in various diseases have been investigated. LXR can affect maintaining BBB by affecting various ways such as ATP-binding cassette transporter A1 (ABCA1), matrix metalloproteinase-9 (MMP9), insulin-like growth factor 1 (IGF1), nuclear factor-kappa B (NF-κB) signaling, mitogen-activated protein kinase (MAPK), tight junction molecules, both signal transducer and activator of transcription 1 (STAT1), Wnt/β-catenin Signaling, transforming growth factor beta (TGF-β) signaling, and expressions of Smad 2/3 and Snail.

Conclusion: LXR could possibly be used either as a target for drug delivery to brain tissue or as a target for maintaining the BBB integrity in different diseases; thereby the drug will be conducted to tissues, other than the brain. If it is verified that only LXRα is necessary for protecting BBB, some specific LXRα ligands must be found and then used in medication.

T0901317, an Agonist of Liver X Receptors, Attenuates Neuronal Apoptosis in Early Brain Injury after Subarachnoid Hemorrhage in Rats via Liver X Receptors/Interferon Regulatory Factor/P53 Upregulated Modulator of Apoptosis/Dynamin-1-Like Protein Pathway

Methods

Subarachnoid hemorrhage (SAH) models of Sprague-Dawley rats were established with perforation method. T0901317 was injected intraperitoneally 1-hour post-SAH. GSK2033, an inhibitor of LXRs, and interferon regulatory factor (IRF-1) CRISPR activation were injected intracerebroventricularly to evaluate potential signaling pathway. The severity of SAH, neurobehavior test in both short- and long-term and apoptosis was measured with Western blot and immunofluorescence staining.

Results

Expression of LXR-α and IRF-1 increased and peaked at 24 h post-SAH, while LXR-β remained unaffected in SAH+vehicle group compared with Sham group. Post-SAH T0901317 treatment attenuated neuronal impairments in both short- and long-term and decreased neuronal apoptosis, the expression of IRF-1, P53 upregulated modulator of apoptosis (PUMA), dynamin-1-like protein (Drp1), Bcl-2-associated X protein (Bax) and cleaved caspase-3, and increasing B-cell lymphoma 2 (Bcl-2) at 24 h from modeling. GSK2033 inhibited LXRs and reversed T0901317's neuroprotective effects. IRF-1 CRISPR activation upregulated the expression of IRF-1 and abolished the treatment effects of T0901317.

Conclusion

T0901317 attenuated neuronal apoptosis via LXRs/IRF-1/PUMA/Drp1 pathway in SAH rats.

Ergosta-7,9(11),22-trien-3β-ol Alleviates Intracerebral Hemorrhage-Induced Brain Injury and BV-2 Microglial Activation

Intracerebral hemorrhage (ICH) is a devastating neurological disorder characterized by an exacerbation of neuroinflammation and neuronal injury, for which few effective therapies are available at present. Inhibition of excessive neuroglial activation has been reported to alleviate ICH-related brain injuries. In the present study, the anti-ICH activity and microglial mechanism of ergosta-7,9(11),22-trien-3β-ol (EK100), a bioactive ingredient from Asian medicinal herb Antrodia camphorate, were evaluated. Post-treatment of EK100 significantly attenuated neurobehavioral deficit and MRI-related brain lesion in the mice model of collagenase-induced ICH. Additionally, EK100 alleviated the inducible expression of cyclooxygenase (COX)-2 and the activity of matrix metalloproteinase (MMP)-9 in the ipsilateral brain regions. Consistently, it was shown that EK100 concentration-dependently inhibited the expression of COX-2 protein in Toll-like receptor (TLR)-4 activator lipopolysaccharide (LPS)-activated microglial BV-2 and primary microglial cells. Furthermore, the production of microglial prostaglandin E₂ and reactive oxygen species were attenuated by EK100. EK100 also attenuated the induction of astrocytic MMP-9 activation. Among several signaling pathways, EK100 significantly and concentration-dependently inhibited activation of c-Jun N-terminal kinase (JNK) MAPK in LPS-activated microglial BV-2 cells. Consistently, ipsilateral JNK activation was markedly inhibited by post-ICH-treated EK100 in vivo. In conclusion, EK100 exerted the inhibitory actions on microglial JNK activation, and attenuated brain COX-2 expression, MMP-9 activation, and brain injuries in the mice ICH model. Thus, EK100 may be proposed and employed as a potential therapeutic agent for ICH.

Phytosterols: Targeting Neuroinflammation in Neurodegeneration

Plant-derived sterols, phytosterols, are well known for their cholesterol-lowering activity in serum and their anti-inflammatory activities. Recently, phytosterols have received considerable attention due to their beneficial effects on various non-communicable diseases, and recommended use as daily dietary components. The signaling pathways mediated in the brain by phytosterols have been evaluated, but little is known about their effects on neuroinflammation, and no clinical studies have been undertaken on phytosterols of interest. In this review, we discuss the beneficial roles of phytosterols, including their attenuating effects on inflammation, blood cholesterol levels, and hallmarks of the disease, and their regulatory effects on neuroinflammatory disease pathways. Despite recent advancements made in phytosterol pharmacology, some critical questions remain unanswered. Therefore, we have tried to highlight the potential of phytosterols as viable therapeutics against neuroinflammation and to direct future research with respect to clinical applications.

Metabolic rerouting via SCD1 induction impacts X-linked adrenoleukodystrophy

X-linked adrenoleukodystrophy (ALD) is a progressive neurodegenerative disease caused by mutations in ABCD1, the peroxisomal very long-chain fatty acid (VLCFA) transporter. ABCD1 deficiency results in accumulation of saturated VLCFAs. A drug screen using a phenotypic motor assay in a zebrafish ALD model identified chloroquine as the top hit. Chloroquine increased expression of stearoyl-CoA desaturase-1 (scd1), the enzyme mediating fatty acid saturation status, suggesting that a shift toward monounsaturated fatty acids relieved toxicity. In human ALD fibroblasts, chloroquine also increased SCD1 levels and reduced saturated VLCFAs. Conversely, pharmacological inhibition of SCD1 expression led to an increase in saturated VLCFAs, and CRISPR knockout of scd1 in zebrafish mimicked the motor phenotype of ALD zebrafish. Importantly, saturated VLCFAs caused ER stress in ALD fibroblasts, whereas monounsaturated VLCFA did not. In parallel, we used liver X receptor (LXR) agonists to increase SCD1 expression, causing a shift from saturated toward monounsaturated VLCFA and normalizing phospholipid profiles. Finally, Abcd1-/y mice receiving LXR agonist in their diet had VLCFA reductions in ALD-relevant tissues. These results suggest that metabolic rerouting of saturated to monounsaturated VLCFAs may alleviate lipid toxicity, a strategy that may be beneficial in ALD and other peroxisomal diseases in which VLCFAs play a key role.

Effect of TO901317 on GF to promote the differentiation of human bone marrow mesenchymal stem cells into dopamine neurons on Parkinson's disease

Background:

Human bone marrow mesenchymal stem cells (hBMSCs) could differentiate into dopamine-producing cells and ameliorate behavioral deficits in Parkinson’s disease (PD) models. Liver X receptors (LXRs) are involved in the maintenance of the normal function of central nervous system myelin. Therefore, the previous work of our team has found the induction of cocktail-induced to dopaminergic (DA) phenotypes from adult rat BMSCs by using sonic hedgehog (SHH), fibroblast growth factor 8 (FGF8), basic fibroblast growth factor (bFGF), and TO901317 (an agonist of LXRs) with 87.42% of efficiency in a 6-day induction period. But we did not verify whether the induced cells had the corresponding neural function.

Methods:

Expressions of LXRα, LXRβ, and tyrosine hydroxylase (TH) were detected by immunofluorescence and western blot. Adenosine triphosphate-binding cassette transporter A1 (ABCA1) was detected by quantitative real-time PCR. The induced cells were transplanted into PD rats to study whether the induced cells are working.

Results:

The induced cells can release the dopamine transmitter; the maximum induction efficiency of differentiation of hBMSCs into DA neurons was 91.67% under conditions of combined use with TO901317 and growth factors (GF). When the induced-cells were transplanted into PD rats, the expression of TH in the striatum increased significantly, and the behavior of PD rats induced by apomorphine was significantly improved.

Conclusion:

The induced cells have the function of DA neurons and have the potential to treat PD. TO901317 promoted differentiation of hBMSCs into DA neurons, which may be related to activation of the LXR-ABCA1 signaling pathway.

Repairing blood-CNS barriers: Future therapeutic approaches for neuropsychiatric disorders

Central nervous system (CNS) drug development faces significant difficulties that translate into high rates of failure and lack of innovation. The pathophysiology of neurological and psychiatric disorders often results in the breakdown of blood-CNS barriers, disturbing the CNS microenvironment and worsening disease progression. Therefore, restoring the integrity of blood-CNS barriers may have a beneficial influence in several CNS disorders and improve treatment outcomes. In this review, pathways that may be modulated to protect blood-CNS barriers from neuroinflammatory and oxidative insults are featured. First, the participation of the brain endothelium and glial cells in disruption processes is discussed. Then, the relevance of regulatory systems is analysed, specifically the hypothalamic-pituitary axis, the renin-angiotensin system, sleep and circadian rhythms, and glutamate neurotransmission. Lastly, compounds of endogenous and exogenous origin that are known to mediate the repair of blood-CNS barriers are presented. We believe that enhancing the protection of blood-CNS barriers is a promising therapeutic strategy to pursue in the future.

Neuroinflammation drives APOE genotype-dependent differential expression of neprilysin

Alzheimer's disease (AD) is a devastating neurodegenerative disorder characterized by the deposition of amyloid-beta (Aβ) plaques and widespread neuroinflammation. While the cause of AD remains unknown, multiple factors likely contribute to the disease, including heart disease, diabetes, previous head injury, as well as a number of genetic determinants. Inheritance of the apolipoprotein (APOE) ε4 allele represents the strongest genetic risk factor for development of AD, driving pathogenesis and increasing overall disease severity. APOE has long been recognized as a key regulator of cholesterol homeostasis, although a greater appreciation now exists for its role in various innate immune system processes. Indeed, APOE modulates inflammatory environments in brain in large part by altering gene expression profiles in glia, important mediators of immunity in the CNS. While the association between APOE and AD was first observed nearly three decades ago, the mechanism by which APOE ε4 influences the etiology and pathophysiology of AD is not well characterized. Overwhelming data supports the hypothesis that APOE ε4 dysregulates central amyloid metabolism by an undetermined molecular mechanism, thus laying the foundation for disease. A host of amyloid-degrading enzymes (ADEs) regulate Aβ accumulation in brain, and therefore represent valuable therapeutic targets. Neprilysin (NEP), a metalloendopeptidase expressed by activated microglia and astrocytes, is a broad-spectrum ADE able to degrade a variety of Aβ species. Here we describe in vivo and in vitro experiments designed to investigate the potential for APOE genotype to differentially regulate glial NEP in brain under neuroinflammatory conditions. Our results provide a novel mechanism by which APOE genotype-dependent differential expression of NEP by glia during neuroinflammation may contribute to AD pathogenesis.

Compound K induces neurogenesis of neural stem cells in thrombin induced nerve injury through LXRα signaling in mice

Intracerebral hemorrhage (ICH) causes neurological function deficit due to the loss of neurons surrounding the hematoma. Increased neurogenesis of endogenous neural stem cells (EnNSCs) is believed to increase cell proliferation and differentiation, thereby improving the neurological deficit. However, there are still limited drugs that are effective for treating neurological deficit. So, the effects of compound K (CK) in EnNSCs were measured after thrombin-induced mice models both in vivo and in vitro, and investigated the probable mechanisms of CK during pro-neurogenesis. The results revealed that 10 μM CK promotes neurogenesis, proliferation and reduces apoptosis of EnNSCs after induction by thrombin. After that, CK treatment increased the neurogenesis of EnNSCs through liver X receptor α (LXRα) signaling pathway using adeno-associated virus knockdown and knocked out mice of LXRα gene. Finally, intraperitoneal injection of 10 mg/kg CK improved the neurogenesis of subventricular zone (SVZ), myelin repair and behavioral deficit after stereotaxic injection of thrombin in the basal ganglia of mice, and this process involved LXRα. These observations provided evidence regarding the effect of CK in pro-neurogenesis via LXRα activation, and suggested further evaluation of it due to its potential role as an effective modulator in the treatment of ICH.

IL-4 Switches Microglia/macrophage M1/M2 Polarization and Alleviates Neurological Damage by Modulating the JAK1/STAT6 Pathway Following ICH

Inflammatory damage following ICH is often attributed to microglia/macrophage activation. In many diseases, IL-4 has been proven to switch microglia/macrophages from the pro-inflammatory to the anti-inflammatory subtype. However, the role and underlying mechanism of IL-4 in ICH, especially in neuroprotection, remain unknown. In our study, we constructed a microglia/macrophage polarization model in BV2 cells to verify that the M2 shift of microglia/macrophages was mediated by JAK1/STAT6 after IL-4 treatment and then revealed that in vitro administration of IL-4 decreased M1 markers, pro-inflammatory cytokines and neuroapoptosis markers but significantly increased M2 markers and anti-inflammatory cytokines. Using an ICH model in mice, we observed that IL-4 administration decreased neurological deficits, brain edema and infarct lesions induced by ICH. We verified that IL-4 mediates inflammation by regulating M1/M2 polarization in ICH and explored the underlying mechanism. Furthermore, we discovered that pathway components and apoptosis-related proteins showed consistent trends based on their respective roles, and inferred that the process that TNF-α activates caspase-3 may be the crosstalk that microglia phagocytosis developed into accelerate apoptosis of cells in ICH. In conclusion, our study demonstrates that IL-4 may promote M2 microglia/macrophage polarization partly through the JAK1/STAT6 pathway to alleviate neuroinflammation after ICH.

MicroRNA-152 attenuates neuroinflammation in intracerebral hemorrhage by inhibiting thioredoxin interacting protein (TXNIP)-mediated NLRP3 inflammasome activation

Neuroinflammation significantly contributes to brain injury and neurological deterioration following intracerebral hemorrhage (ICH). MicroRNA-152(miR-152) was reported to be downregulated in ICH patients and to possess anti-inflammatory properties in other diseases. In this study, we aimed to explore the role of miR-152 in ICH, and the underlying mechanisms, using a collagenase-induced rat ICH model and hemin-exposure as a cell model. We first confirmed that miR-152 was consistently downregulated in both models. Overexpression of miR-152 in microglial BV2 cells reduced hemin-induced inflammatory response and reactive oxygen species (ROS) generation, thus protecting co-cultured neuronal HT22 cells. Moreover, overexpression of miR-152 by intracerebroventricular lentivirus injection in ICH rats significantly alleviated neurodecifits, brain edema, and hematoma. These changes were associated with a marked reduction in ICH-induced neuronal death, as detected by co-staining of NeuN and TUNEL, and ICH-induced neuroinflammation, as revealed by inflammatory cytokine levels as well as by the number of Iba1 positive-stained cells in the perihematomal region. Mechanistically, miR-152 significantly inhibited ICH-induced TXNIP expression, and its overexpression blocked the interaction between TXNIP and NOD-like receptor pyrin domain containing 3(NLRP3), thus inhibiting NLRP3-driven inflammasome activation to attenuate neuroinflammation in vivo and in vitro. Moreover, the results of si-TXNIP transfection further confirmed that TXNIP inhibition was involved in the reduction of NLRP3 inflammasome activation by the overexpression of miR-152. Collectively, the present study demonstrates that miR-152 confers protection against ICH-induced neuroinflammation and brain injury by inhibiting TXNIP-mediated NLRP3 inflammasome activation, indicating a potential strategy for ICH treatment.

Activation of liver X receptor promotes hippocampal neurogenesis and improves long-term cognitive function recovery in acute cerebral ischemia-reperfusion mice

Cerebral ischemia (CI) leads to cognitive dysfunction due to the loss of hippocampal neurons. Liver X receptors (LXRs), including the LXRα and LXRβ isoforms, are critical for neurogenesis, synaptic plasticity, neurodegeneration, and cholesterol metabolism. However, the potential role of LXRs in the pathogenesis of CI-induced cognitive impairment is unclear. Therefore, we investigated the effects of LXR activation on hippocampal neurogenesis and cognitive function in mice with CI. C57 mice were randomized into four groups that included a sham group and three treatment groups with CI [Vehicle, TO901317 (TO90, an agonist of LXRs) and GSK2033 (an antagonist of LXRs)]. Mice were subjected to bilateral common carotid artery occlusion for 20 min to induce transient CI. The Morris water maze test was executed to detect spatial learning and memory. Proliferation, differentiation, and immature neurons in the subgranular zone (SGZ) were examined using Immunofluorescence. Western blot assay was used to detect the expression of the Wnt/β-catenin signaling pathway-associated protein. TO90 significantly improved spatial learning and memory deficits induced by CI on 28 days. It enhanced the proliferation of neural stem cells, the number of immature neurons and the differentiation from nascent cells to neurons. The expression of the Wnt/β-catenin signaling pathway-associated protein level was totally increased. The forenamed effects of TO90 were decreased in GSK2033 group. Thus, our findings suggest that LXRs activation can improve long-term cognitive dysfunction caused by CI by increasing neurogenesis, and LXRs may serve as a potential therapeutic target for cerebral ischemia. Cover Image for this issue: doi: 10.1111/jnc.14753.

Inhibition of HDAC6 alleviating lipopolysaccharide-induced p38MAPK phosphorylation and neuroinflammation in mice

Context: Researchers in a variety of fields have extensively focused on histone deacetylase 6 (HDAC6) due to its aggravation of inflammatory reaction. However, relevant studies examining whether HDAC6 could exacerbate lipopolysaccharide (LPS)-induced inflammation are still lacking. Objective: We assessed the role of HDAC6 in LPS-induced brain inflammation and used the HDAC6-selective inhibitor Tubastatin A (TBSA) to investigate the potential mechanisms further. Materials and methods: Brain inflammation was induced in Kunming (KM) mice via intraperitoneal (I.P.), injection of Lipopolysaccharide (LPS) (1 mg/kg), the TBSA (0.5 mg/kg) was delivered via intraperitoneal. The phosphorylated p38 (p-p38) Mitogen-activated protein kinases (MAPK) and expression of typical inflammatory mediators, including tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) in both the hippocampus and cortex, were examined by immunoblotting. Nissl staining was used to detect the neuronal damage in the hippocampus and the cortex. Results: About 1 mg/kg LPS via daily intraperitoneal (I.P.) injections for 12 days significantly increased p38 MAPK phosphorylation, TNF-α and IL-6 expression, and neuronal loss. However, 0.5 mg/kg TBSA (three days before LPS treatment) by I.P. injections for 15 days could reverse the above results. Conclusions: This present study provided evidence that TBSA significantly suppressed LPS-induced neuroinflammation and the expression of p-p38. Results derived from our study might help reveal the effective targeting strategies of LPS-induced brain inflammation through inhibiting HDAC6.

The protective effect of quercetin in the alcohol-induced liver and lymphoid tissue injuries in newborns

Recently published experimental and clinical studies indicate that oxidative stress leads to the pathogenesis and progression of alcohol-induced tissue injuries. Quercetin is a type of flavonoid compound that influences antioxidant and anti-inflammatory activities have protective and therapeutic effects for treating various diseases including diabetes mellitus and neuro-degenerative diseases. In this study, fetal alcohol syndrome was tested in rat models, with the aim of verifying the protective effect of quercetin in preventing alcohol-induced liver and lymphoid tissue (thymus, spleen, and lymph nodes) injuries on the 21st day for the offspring of alcohol treated mother rats. The pregnant rats were randomly assigned into four groups. The control group (C) (n = 3) of pregnant rats received only physiological saline intraperitoneally (i.p.) throughout the pregnancy (1 to 21 days gestation) and during lactation until postnatal day 21. The quercetin positive control group (QT) of pregnant rats (n = 3) received quercetin at 50 mg/kg/days i.p. for the same period. The ethanol treatment group (E) (n = 3) of pregnant rats received 1 ml/day of 40% v/v ethanol (4 g/kg) intragastrically (i.g) for the same period. The model group of pregnant rats (EQ) received ethanol + quercetin (n = 3) with a dose of 1 ml/day of v/v ethanol (4 g/kg i.g.) and quercetin at 50 mg/kg body weight per day i.p. for the same period. Ten offspring were used in each of the C, QT, E and EQ groups. Malondialdehyde (MDA), protein carbonyl content (PC) and chemiluminescence levels (CL) in liver and lymphoid tissues significantly increased in group E versus the C group (P < 0.05-P < 0.001) whereas glutathione levels (GSH), glutathione reductase (GR), glutathione peroxidase (GP), superoxide dismutase (SOD), and catalase (CAT) activities significantly decreased in group E compared to the C group (P < 0.05-< 0.001). However, tissue MDA, PC, and CL levels decreased in the EQ group compared to group E. GSH level, GP, GR, SOD, and CAT activity were significantly increased by quercetin (P < 0.05-P < 0.001). The plasma TNFα, IL-1β, and IL-6 levels and NF-κB activation significantly increased in group E compared to the C and QT groups, but IL-10 significantly decreased in group E compared to the C and QT groups. The TNFα, IL-1β, and IL-6 levels and NF-κB activation significantly decreased in group EQ compared to group E. In conclusion, quercetin has a protective effect against maternal alcohol-induced oxidative and inflammatory damage in the liver and lymphoid tissues of newborn rats.

Regulation of Brain Cholesterol: What Role Do Liver X Receptors Play in Neurodegenerative Diseases?

Liver X Receptors (LXR) alpha and beta are two members of nuclear receptor superfamily documented as endogenous cholesterol sensors. Following conversion of cholesterol in oxysterol, both LXR isoforms detect intracellular concentrations and act as transcription factors to promote expression of target genes. Among their numerous physiological roles, they act as central cholesterol-lowering factors. In the central nervous system (CNS), cholesterol has been shown to be an essential determinant of brain function, particularly as a major constituent of myelin and membranes. In the brain, LXRs act as cholesterol central regulators, and, beyond this metabolic function, LXRs have additional roles such as providing neuroprotective effects and lowering neuroinflammation. In many neurodegenerative disorders, including amyotrophic lateral sclerosis (ALS), Alzheimer's disease (AD), and multiple sclerosis (MS), dysregulations of cholesterol and oxysterol have been reported. In this paper, we propose to focus on recent advances in the knowledge of the LXRs roles on brain cholesterol and oxysterol homeostasis, neuroinflammation, neuroprotection, and their putative involvement in neurodegenerative disorders. We will discuss their potential use as candidates for both molecular diagnosis and as promising pharmacological targets in the treatment of ALS, AD, or MS patients.

Activation of TrkB/Akt signaling by a TrkB receptor agonist improves long-term histological and functional outcomes in experimental intracerebral hemorrhage

BACKGROUND

Intracerebral hemorrhage (ICH) induces a complex sequence of apoptotic cascades that contribute to secondary neuronal damage. Tropomyosin-related kinase receptor B (TrkB) signaling plays a crucial role in promoting neuronal survival following brain damage.

METHODS

The present study investigated the protective effects and underlying mechanisms of TrkB activation by the specific TrkB agonist, 7,8-dihydroxyflavone (7,8-DHF), in a model of collagenase-induced ICH and in neuronal cultures. Mice subjected to collagenase-induced ICH were intraperitoneally injected with either 7,8-DHF or vehicle 10 min after ICH and, subsequently, daily for 3 days. Behavioral studies, brain edema measurement, and histological analysis were conducted. Levels of TrkB signaling-related molecules and apoptosis-related proteins were analyzed by western blots.

RESULTS

Treatment with 20 mg/kg 7,8-DHF significantly improved functional recovery and reduced brain damage up to 28 days post-ICH. Reduction in neuronal death, apoptosis, and brain edema were also observed in response to 7,8-DHF treatment at 3 days post-ICH. These changes were accompanied by a significant increase in the phosphorylation of TrkB and Akt (Ser473/Thr308) at 1 and 3 days, but had no effect on Erk 44/42 phosphorylation. 7,8-DHF also enhanced the phosphorylation of Ask-1 Ser967 and FOXO-1, downstream targets of Akt at 1 and 3 days. Moreover, 7,8-DHF increased brain-derived neurotrophic factor levels at 1 day. In primary cultured neurons stimulated with hemin, 7,8-DHF promoted survival and reduced apoptosis. Furthermore, delaying the administration of 7,8-DHF to 3 h post-ICH reduced brain tissue damage and neuronal death.

CONCLUSIONS

Our findings demonstrate that the activation of TrkB signaling by 7,8-DHF protects against ICH via the Akt, but not the Erk, pathway. These data provide new insights into the role of TrkB signaling deficit in the pathophysiology of ICH and highlight TrkB/Akt as possible therapeutic targets in this disease.

MicroRNA-155 Promotes Heat Stress-Induced Inflammation via Targeting Liver X Receptor α in Microglia

Background: The neuroinflammatory responses of microglial cells play an important role in the process of brain dysfunction caused by heat stroke. MicroRNAs are reportedly involved in a complex signaling network and have been identified as neuroinflammatory regulators. In this study, we determined the biological roles of microRNA-155 in the inflammatory responses in heat-stressed microglia and explored the underlying mechanisms.

Methods: MicroRNA-155 mimic and inhibitor were used to separately upregulate or downregulate microRNA-155 expression. The activation state of BV-2 microglial cells (BV-2 cells) was assessed via immunoreactions using the microglial marker CD11b and CD68. Levels of induced interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were measured using real-time reverse transcription polymerase chain reaction (RT-PCR) and enzyme linked immunosorbent assays (ELISAs). The activation of nuclear factor kappa B (NF-κB) signaling proteins was evaluated by Western blotting for inhibitory kappa B alpha (IκBα) and NF-κB p65 phosphorylation and indirect immunofluorescence analysis using a p65 phosphorylation antibody. A luciferase reporter assay was used to verify liver X receptor α (LXRα) as a target gene of microRNA-155.

Results: Heat stress significantly induced IL-1β, IL-6, and TNF-α release and increased the expression of CD11b and CD68. In addition, IκBα and NF-κB p65 phosphorylation were dramatically increased by heat stress, and microRNA-155 expression was also elevated. High expression of microRNA-155 in heat-stressed microglial cells was inversely correlated with LXRα expression. We then determined the role of microRNA-155 in the heat stress-induced inflammatory responses. The results revealed that by targeting LXRα, microRNA-155 enhanced NF-κB signaling activation and facilitated immune inflammation in heat stress-treated BV-2 cells.

Conclusion: MicroRNA-155 promotes heat stress-induced inflammatory responses in microglia. The underlying mechanisms may include facilitating inflammatory factors expression by increasing NF-κB pathway activation via targeting LXRα.

AC-YVAD-CMK Inhibits Pyroptosis and Improves Functional Outcome after Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) refers to bleeding in the brain and is associated with the release of large amount of inflammasomes, and the activation of different cell death pathways. These cell death pathways lead to removal of inactivated and damaged cells and also result in neuronal cell damage. Pyroptosis is a newly discovered cell death pathway that has gained attention in recent years. This pathway mainly depends on activation of caspase-1-mediated cascades to cause cell death. We tested a well-known selective inhibitor of caspase-1, AC-YVAD-CMK, which has previously been found to have neuroprotective effects in ICH mice model, to ascertain its effects on the activation of inflammasomes mediated pyroptosis. Our results showed that AC-YVAD-CMK could reduce caspase-1 activation and inhibit IL-1β production and maturation, but has no effect on NLRP3 expression, an upstream inflammatory complex. AC-YVAD-CMK administration also resulted in reduction in M1-type microglia polarization around the hematoma, while increasing the number of M2-type cells. Furthermore, AC-YVAD-CMK treated mice showed some recovery of neurological function after hemorrhage especially at the hyperacute and subacute stage resulting in some degree of limb movement. In conclusion, we are of the view that AC-YVAD-CMK could inhibit pyroptosis, decrease the secretion or activation of inflammatory factors, and affect the polarization of microglia resulting in improvement of neurological function after ICH.

Activation of liver X receptor β-enhancing neurogenesis ameliorates cognitive impairment induced by chronic cerebral hypoperfusion

Chronic cerebral hypoperfusion (CCH), a leading cause of various cerebrovascular diseases, leads to cognitive dysfunction due to neuron loss and impaired neurogenesis. Liver X receptors (LXRs), including LXRα and LXRβ isoforms, are crucial for cholesterol metabolism, synaptic plasticity as well as neurogenesis. However, it is not clear the potential roles of LXRs in the pathogenesis of cognitive impairment induced by CCH. In this study, we demonstrated that LXRβ expression decreased in hippocampus of CCH mice. GW3965, a synthetic dual agonist for both LXRα and LXRβ, ameliorated impairment of learning and memory in CCH mice by promoting neuronal survival and neural stem cells (NSCs) proliferation in dentate gyrus (DG) of CCH mice. The proliferative effects of GW3965 were further confirmed in cultured neural progenitor cells (NPCs) and showed in a concentration-dependent manner. Moreover, GW3965 phosphorylated protein kinase B (Akt) at Ser473 in a time- and concentration-dependent manner in NPCs. Furthermore, both LY294002, an inhibitor for phosphoinositide-3-kinase (PI3K), and short hairpin RNAs for LXRβ knockdown, abrogated GW3965-induced Akt phosphorylation, and therefore abolished GW3965-mediated proliferation-promoting of NPCs. All the data suggested that GW3965 ameliorated impaired cognitive functions in CCH by promoting NSC proliferation through PI3K/Akt pathway followed LXRβ activation. This study correlates a deficit of LXRβ in cognitive dysfunction in CCH with impaired neurogenesis in hippocampus, and LXRs may serve as a potential therapeutic target for chronic cerebral ischemia.

Platycodin D Inhibits Inflammatory Response in LPS-Stimulated Primary Rat Microglia Cells through Activating LXRα-ABCA1 Signaling Pathway

Platycodin D (PLD), an effective triterpenesaponin extracted from Platycodon grandiflorum, has been known to have anti-inflammatory effect. In the present study, we investigate the anti-inflammatory effects of PLD on LPS-induced inflammation in primary rat microglia cells. The results showed that PLD significantly inhibited LPS-induced ROS, TNF-α, IL-6, and IL-1β production in primary rat microglia cells. PLD also inhibited LPS-induced NF-κB activation. Furthermore, our results showed that PLD prevented LPS-induced TLR4 translocation into lipid rafts via disrupting the formation of lipid rafts by inducing cholesterol efflux. In addition, PLD could activate LXRα–ABCA1 signaling pathway which induces cholesterol efflux from cells. The inhibition of inflammatory cytokines by PLD could be reversed by SiRNA of LXRα. In conclusion, these results indicated that PLD prevented LPS-induced inflammation by activating LXRα–ABCA1 signaling pathway, which disrupted lipid rafts and prevented TLR4 translocation into lipid rafts, thereby inhibiting LPS-induced inflammatory response.

Genetic deletion or pharmacological inhibition of soluble epoxide hydrolase reduces brain damage and attenuates neuroinflammation after intracerebral hemorrhage

Background

Inflammatory responses significantly contribute to neuronal damage and poor functional outcomes following intracerebral hemorrhage (ICH). Soluble epoxide hydrolase (sEH) is known to induce neuroinflammatory responses via degradation of anti-inflammatory epoxyeicosatrienoic acids (EET), and sEH is upregulated in response to brain injury. The present study investigated the involvement of sEH in ICH-induced neuroinflammation, brain damage, and functional deficits using a mouse ICH model and microglial cultures.

Methods

ICH was induced by injecting collagenase in both wild-type (WT) C57BL/6 mice and sEH knockout (KO) mice. WT mice were injected intracerebroventricularly with 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA), a selective sEH inhibitor, 30 min before ICH. Expression of sEH in the hemorrhagic hemisphere was examined by immunofluorescence and Western blot analysis. The effects of genetic deletion or pharmacological inhibition of sEH by AUDA on neuroinflammatory responses, EET degradation, blood-brain barrier (BBB) permeability, histological damage, and functional deficits were evaluated. The anti-inflammatory mechanism of sEH inactivation was investigated in thrombin- or hemin-stimulated cultured microglia.

Results

ICH induced an increase in sEH protein levels in the hemorrhagic hemisphere from 3 h to 4 days. sEH was expressed in microglia/macrophages, astrocytes, neurons, and endothelial cells in the perihematomal region. Genetic deletion of sEH significantly attenuated microglia/macrophage activation and expression of inflammatory mediators and reduced EET degradation at 1 and 4 days post-ICH. Deletion of sEH also reduced BBB permeability, matrix metalloproteinase (MMP)-9 activity, neutrophil infiltration, and neuronal damage at 1 and 4 days. Likewise, administration of AUDA attenuated proinflammatory microglia/macrophage activation and EET degradation at 1 day post-ICH. These findings were associated with a reduction in functional deficits and brain damage for up to 28 days. AUDA also ameliorated neuronal death, BBB disruption, MMP-9 activity, and neutrophil infiltration at 1 day. However, neither gene deletion nor pharmacological inhibition of sEH altered the hemorrhage volume following ICH. In primary microglial cultures, genetic deletion or pharmacological inhibition of sEH by AUDA reduced thrombin- and hemin-induced microglial activation. Furthermore, AUDA reduced thrombin- and hemin-induced P38 MAPK and NF-κB activation in BV2 microglia cultures. Ultimately, AUDA attenuated N2A neuronal death that was induced by BV2 microglial conditioned media.

Conclusions

Our results suggest that inhibition of sEH may provide a potential therapy for ICH by suppressing microglia/macrophage-mediated neuroinflammation.

Electronic supplementary material

The online version of this article (10.1186/s12974-017-1005-4) contains supplementary material, which is available to authorized users.

Quercetin prevents alcohol-induced liver injury through targeting of PI3K/Akt/nuclear factor-κB and STAT3 signaling pathway

Quercetin is a type of flavonoid compound, which has potent antioxidant and anti-inflammatory activities, capable of treating a variety of diseases including neurodegenerative diseases, tumors, diabetes and obesity. The present study selected alcohol-induced liver injury model mice and aimed at studying the protective role of quercetin in preventing alcohol-induced liver injury. In alcohol-induced liver injury mice treated with quercetin, it was demonstrated that levels of aspartate transaminase, alanine transaminase, total bilirubin and triglyceride were reduced. In addition to this, the activities of the antioxidant enzymes superoxide dismutase and glutathione peroxidase were increased, malondialdehyde was inhibited, and interleukin (IL)-1β, IL-6, IL-10 and inducible nitric oxide synthase were suppressed. Quercetin additionally suppressed the protein expression levels of B-cell lymphoma (Bcl)-2, Bcl-2 associated X apoptosis regulator, Caspase-3, poly ADP-ribose polymerase, and signal transducer and activator of transcription (STAT) 3 phosphorylation, nuclear factor (NF)-κB and protein kinase B (Akt) phosphorylation levels in alcohol-induced liver injured mice. These results suggested that the protective role of quercetin prevents alcohol-induced liver injury through the phosphoinositide 3-kinase/Akt/NF-κB and STAT3 pathway.

Deletion or inhibition of soluble epoxide hydrolase protects against brain damage and reduces microglia-mediated neuroinflammation in traumatic brain injury

Traumatic brain injury (TBI) induces a series of inflammatory processes that contribute to neuronal damage. The present study investigated the involvement of soluble epoxide hydrolase (sEH) in neuroinflammation and brain damage in mouse TBI and in microglial cultures. The effects of genetic deletion of sEH and treatment with an sEH inhibitor, 12-(3-adamantan-1-yl-ureido)-dodecanoic acid (AUDA), on brain damage and inflammatory responses were evaluated in mice subjected to controlled cortical impact. The anti-inflammatory mechanism of sEH inhibition/deletion was investigated in vitro. TBI-induced an increase in sEH protein level in the injured cortex from 1 h to 4 days and sEH was expressed in microglia. Genetic deletion of sEH significantly attenuated functional deficits and brain damage up to 28 days post-TBI. Deletion of sEH also reduced neuronal death, apoptosis, brain edema, and BBB permeability at 1 and 4 day(s). These changes were associated with markedly reduced microglial/macrophage activation, neutrophil infiltration, matrix metalloproteinase-9 activity, inflammatory mediator expression at 1 and 4 day(s), and epoxyeicosatrienoic acid (EET) degradation at 1 and 4 day(s). Administration of AUDA attenuated brain edema, apoptosis, inflammatory mediator upregulation and EET degradation at 4 days. In primary microglial cultures, AUDA attenuated both LPS- or IFN-γ-stimulated nitric oxide (NO) production and reduced LPS- or IFN-γ-induced p38 MAPK and NF-κB signaling. Deletion of sEH also reduced IFN-γ-induced NO production. Moreover, AUDA attenuated N2A neuronal death induced by BV2 microglial-conditioned media. Our results suggest that inhibition of sEH may be a potential therapy for TBI by modulating the cytotoxic functions of microglia.

RETRACTED: Effect of microRNA-129-5p targeting HMGB1-RAGE signaling pathway on revascularization in a collagenase-induced intracerebral hemorrhage rat model

This article has been retracted: please see Elsevier Policy on Article Withdrawal (http://www.elsevier.com/locate/withdrawalpolicy). This article has been retracted at the request of the Editor-in-Chief. An Expression of Concern for this article was previously published while an investigation was conducted (see related editorial: https://doi.org/10.1016/j.biopha.2022.113812). This retraction notice supersedes the Expression of Concern published earlier. Concern was raised about the reliability of the Western blot data in Figure 2A, which contain suspected image duplications within the β-actin blot, and appear to represent a distinct phenotype as found in many other publications, as detailed here: https://pubpeer.com/publications/83FD53A8F4C5B60E2187CBF9F29B01; and here: https://docs.google.com/spreadsheets/d/1r0MyIYpagBc58BRF9c3luWNlCX8VUvUuPyYYXzxWvgY/edit#gid=262337249. Independent analysis confirmed these findings and also identified additional suspected image duplications within Figures 3 and 4A. The journal requested the corresponding author comment on these concerns and provide the associated raw data. The authors did not respond to this request and therefore the Editor-in-Chief decided to retract the article.

IL-17A induces autophagy and promotes microglial neuroinflammation through ATG5 and ATG7 in intracerebral hemorrhage

Microglial inflammation plays a vital role in intracerebral hemorrhage (ICH)-induced secondary brain injury. IL-17A has been identified to promote microglia activation, but the role in the pathology following ICH remains unclear. Autophagy is involved in modulation of cell metabolism, cell survival, and immune response. However, the role of IL-17A in autophagy following ICH has not been well defined. In this study, we assessed the role of IL-17A in microglial autophagic activity following ICH. The microglia were treated with IL-17A, and then autophagy and inflammation were detected. In addition, RNA interference in essential autophagy genes (ATG5 and ATG7) was also utilized to analyze microglial autophagy in vitro. Furthermore, ICH mice were made by injection of autologous blood model in vivo. And the IL-17A-neutralizing antibody was utilized to assess the neurological scores and brain edema. These data demonstrated that IL-17A promoted microglial autophagy and microglial inflammation. The suppression of autophagy using RNA interference in essential autophagy genes (ATG5 and ATG7) decreased microglial autophagy and inflammation. Moreover, IL-17A Ab significantly reduced brain water content and improved neurological function of ICH mice. Taken together, these data demonstrated that IL-17A promoted microglial autophagy and microglial inflammation, and IL-17A-mediated activation of autophagy might represent novel clues in ICH therapy.

Physiological stress-induced corticosterone increases heme uptake via KLF4-HCP1 signaling pathway in hippocampus neurons

Iron overload has attracted much attention because of its adverse effect in increasing the risk of developing several neurodegenerative disorders. Under various pathologic conditions, a lot of heme are released. The aggregation of heme is more neurotoxic than that of iron released from the heme breakdown. Our previous studies demonstrated that psychological stress (PS) is a risk factor of cerebral iron metabolism disorders, thus causing iron accumulation in rat brains. In the present study, we found PS could increase heme uptake via heme carrier protein 1 (HCP1) in rat brains. We demonstrated that Glucocorticoid (GC), which is largely secreted under stress, could up-regulate HCP1 expression, thus promoting heme uptake in neurons. We also ascertained that HCP1 expression can be induced by GC through a transcription factor, Krüppel-like factor 4 (KLF4). These results may gain new insights into the etiology of heme uptake and iron accumulation in PS rats, and find new therapeutic targets of iron accumulation in Parkinson’s disease or Alzheimer’s disease.

The challenges and promise of targeting the Liver X Receptors for treatment of inflammatory disease

The Liver X Receptors (LXRs) are oxysterol-activated transcription factors that upregulate a suite of genes that together promote coordinated mobilization of excess cholesterol from cells and from the body. The LXRs, like other nuclear receptors, are anti-inflammatory, inhibiting signal-dependent induction of pro-inflammatory genes by nuclear factor-κB, activating protein-1, and other transcription factors. Synthetic LXR agonists have been shown to ameliorate atherosclerosis and a wide range of inflammatory disorders in preclinical animal models. Although this has suggested potential for application to human disease, systemic LXR activation is complicated by hepatic steatosis and hypertriglyceridemia, consequences of lipogenic gene induction in the liver by LXRα. The past several years have seen the development of multiple advanced LXR therapeutics aiming to avoid hepatic lipogenesis, including LXRβ-selective agonists, tissue-selective agonists, and transrepression-selective agonists. Although several synthetic LXR agonists have made it to phase I clinical trials, none have progressed due to unforeseen adverse reactions or undisclosed reasons. Nonetheless, several sophisticated pharmacologic strategies, including structure-guided drug design, cell-specific drug targeting, as well as non-systemic drug routes have been initiated and remain to be comprehensively explored. In addition, recent studies have identified potential utility for targeting the LXRs during therapy with other agents, such as glucocorticoids and rexinoids. Despite the pitfalls encountered to date in translation of LXR agonists to human disease, it appears likely that this accelerating field will ultimately yield effective and safe applications for LXR targeting in humans.

Differential Effects of Retinoic Acid Concentrations in Regulating Blood-Brain Barrier Properties

The blood-brain barrier (BBB) is a multifaceted property of the brain vasculature that protects the brain and maintains homeostasis by tightly regulating the flux of ions, molecules, and cells across the vasculature. Blood vessels in the brain are formed by endothelial cells that acquire barrier properties, such as tight and adherens junctions, soon after the brain vasculature is formed. Endothelial WNT signaling is crucial to induce these BBB properties by regulating their expression and stabilization. Recent studies have implicated retinoic acid (RA) signaling in BBB development and shown that pharmacological concentrations of RA (≥5 µm) can induce BBB properties in cultured brain endothelial cells. However, a recent study demonstrated that RA inhibits endothelial WNT signaling during brain development, suggesting that RA does not promote BBB properties. We therefore investigated whether RA plays a physiological role in BBB development. We found that BBB function and junctional protein expression was unaffected in mouse mutants that have a reduced capacity to synthesize RA (Rdh10 mutants). Furthermore, embryos exposed to a RA-enriched diet did not enhance BBB protein expression. Together, our data indicate that RA is not capable of inducing, nor is it required for, BBB protein expression in vivo. Like other studies, we found that pharmacological concentrations of RA induce BBB genes in cultured murine brain endothelial cells, and this may involve activation of the LXR/RXR signaling pathway. Our data do not support a role for RA in BBB development, but confirm reports that pharmacological RA is a robust tool to induce BBB properties in culture.

C5a/C5aR Pathway Plays a Vital Role in Brain Inflammatory Injury via Initiating Fgl-2 in Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a serious emergency with high mortality and morbidity. Up to date, a limited understanding of ICH pathogenesis is difficult to implement effective therapeutic strategy. Much evidence demonstrates that the complement cascade is activated after experimental ICH. However, the exact mechanism has not been well studied in ICH. In the current study, C57BL/6J mice were injected with autologous whole blood. C5a/C5aR levels, microglia infiltration, inflammatory cytokine, and fibrinogen-like protein 2 (Fgl-2) expression in the perihematomal region were analyzed following ICH. In addition, brain water content and neurological dysfunction were detected following ICH. Our data demonstrated that ICH induced complement activation, along with an increase of C5a/C5aR levels, microglia infiltration, and inflammatory cytokine levels. However, C5aR^-/- mice exhibited significant attenuation of inflammatory reaction, accompanied by a remarkable reduction of Fgl-2, brain water content, and neurological dysfunction. Furthermore, inhibiting extracellular signal-regulated kinase 1/2 (ERK1/2) and p38 efficiently inhibited C5a-mediated Fgl-2 production following ICH. Taken together, these data suggest that C5a/C5aR plays a vital role in the ICH-induced inflammatory damage via Fgl-2, and ERK1/2 and p38 pathways also are involved in the pathogenesis of ICH. Therefore, inhibition of C5a/C5aR activation might enlarge our insights in ICH therapy.

Ozone-derived Oxysterols Affect Liver X Receptor (LXR) Signaling: A POTENTIAL ROLE FOR LIPID-PROTEIN ADDUCTS

When inhaled, ozone (O₃) interacts with cholesterols of airway epithelial cell membranes or the lung-lining fluid, generating chemically reactive oxysterols. The mechanism by which O₃-derived oxysterols affect molecular function is unknown. Our data show that in vitro exposure of human bronchial epithelial cells to O₃ results in the formation of oxysterols, epoxycholesterol-α and -β and secosterol A and B (Seco A and Seco B), in cell lysates and apical washes. Similarly, bronchoalveolar lavage fluid obtained from human volunteers exposed to O₃ contained elevated levels of these oxysterol species. As expected, O₃-derived oxysterols have a pro-inflammatory effect and increase NF-κB activity. Interestingly, expression of the cholesterol efflux pump ATP-binding cassette transporter 1 (ABCA1), which is regulated by activation of the liver X receptor (LXR), was suppressed in epithelial cells exposed to O₃ Additionally, exposure of LXR knock-out mice to O₃ enhanced pro-inflammatory cytokine production in the lung, suggesting LXR inhibits O₃-induced inflammation. Using alkynyl surrogates of O₃-derived oxysterols, our data demonstrate adduction of LXR with Seco A. Similarly, supplementation of epithelial cells with alkynyl-tagged cholesterol followed by O₃ exposure causes observable lipid-LXR adduct formation. Experiments using Seco A and the LXR agonist T0901317 (T09) showed reduced expression of ABCA1 as compared with stimulation with T0901317 alone, indicating that Seco A-LXR protein adduct formation inhibits LXR activation by traditional agonists. Overall, these data demonstrate that O₃-derived oxysterols have pro-inflammatory functions and form lipid-protein adducts with LXR, thus leading to suppressed cholesterol regulatory gene expression and providing a biochemical mechanism mediating O₃-derived formation of oxidized lipids in the airways and subsequent adverse health effects.

Activation of Liver X Receptor Attenuates Oleic Acid-Induced Acute Respiratory Distress Syndrome

Liver X receptors (LXRs) were identified as receptors that sense oxidized cholesterol derivatives. LXRs are best known for their hepatic functions in regulating cholesterol metabolism and triglyceride synthesis, but whether and how LXRs play a role in the lung diseases is less understood. To study the function of LXRs in acute respiratory distress syndrome (ARDS), we applied the oleic acid (OA) model of ARDS to mice whose LXR was genetically or pharmacologically activated. The VP-LXRα knock-in (LXR-KI) mice, in which a constitutively activated LXRα (VP-LXRα) was inserted into the mouse LXRα locus, were used as the genetic gain-of-function model. We showed that the OA-induced lung damages, including the cytokine levels and total cell numbers and neutrophil numbers in the bronchoalveolar lavage fluid, the wet/dry weight ratio, and morphological abnormalities were reduced in the LXR-KI mice and wild-type mice treated with the LXR agonist GW3965. The pulmonoprotective effect of GW3965 was abolished in the LXR-null mice. Consistent with the pulmonoprotective effect of LXR and the induction of antioxidant enzymes by LXR, the OA-induced suppression of superoxide dismutase and catalase was attenuated in LXR-KI mice and GW3965-treated wild-type mice. Taken together, our results demonstrate that activation of LXRs can alleviate OA-induced ARDS by attenuating the inflammatory response and enhancing antioxidant capacity.

Liver X receptors: from cholesterol regulation to neuroprotection-a new barrier against neurodegeneration in amyotrophic lateral sclerosis?

Cholesterol plays a central role in numerous nervous system functions. Cholesterol is the major constituent of myelin sheaths, is essential for synapse and dendrite formation, axon guidance as well as neurotransmission. Among regulators of cholesterol homeostasis, liver X receptors (LXRs), two members of the nuclear receptor superfamily, play a determinant role. LXRs act as cholesterol sensors and respond to high intracellular cholesterol concentration by decreasing plasmatic and intracellular cholesterol content. Beyond their cholesterol-lowering role, LXRs have been proposed as regulators of immunity and anti-inflammatory factors. Dysregulation of cholesterol metabolism combined to neuroinflammatory context have been described in neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). ALS is characterized by the progressive loss of motoneurons in the brain and spinal cord, leading to severe paralytic condition and death of patients in a median time of 3 years. Motoneuron degeneration is accompanied by chronic neuroinflammatory response, involving microglial and astrocytic activation, infiltration of blood-derived immune cells and release of pro-inflammatory factors. We propose to discuss here the role of LXRs as a molecular link between the central nervous system cholesterol metabolism, neuroinflammation, motoneuron survival and their potential as promising therapeutic candidates for ALS therapy.

Sinomenine enhances microglia M2 polarization and attenuates inflammatory injury in intracerebral hemorrhage

Microglia polarization plays a vital role in brain inflammatory injury following intracerebral hemorrhage (ICH). Previous studies have shown that sinomenine possesses potential immunoregulatory capabilities. However, microglia polarization's exact mechanisms in ICH remain uncertain. Therefore, we examined the role of sinomenine on microglia polarization and brain inflammation following ICH. For the experiment, autologous blood models were constructed in C57/BL6 mice. Markers of classically activated (M1) and alternatively activated (M2) microglia were detected by real-time polymerase chain reaction, immunofluorescence, and flow cytometry. Microglial toxicity was assessed using MTT and FACS assays. In addition, the neurological deficit and cerebral water content of ICH mice were also observed. Sinomenine attenuated M1 markers while promoting M2 markers of microglia. Sinomenine also protected hippocampal neurons from indirect toxicity mediated by ICH-treated microglia. Additionally, administration of sinomenine inhibited matrix metalloproteinase (MMP) 3/9 expression, cerebral water content, and neurological deficit. Therefore, sinomenine protected brain function following ICH, perhaps via M2 microglia phenotype induction and MMP 3/9 inhibition. This result suggests that sinomenine is a promising therapeutical strategy in ICH.