TGFβ signalling plays an important role in IL4-induced alternative activation of microglia

Arjunolic acid ameliorates lipopolysaccharide-induced depressive behavior by inhibiting neuroinflammation via microglial SIRT1/AMPK/Notch1 signaling pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Neuroinflammation is involved in the pathogenesis of depression disorder by activating microglia cells, increasing proinflammatory cytokines, effecting serotonin synthesis and metabolism, and neuronal apoptosis and neurogenesis. Arjunolic acid (ARG) is a triterpenoid derived from the fruits of Akebia trifoliata for treating psychiatric disorders in TCM clinic, which exhibits anti-inflammatory and neuroprotective effects. However, its anti-depressive effect and underlying mechanism are unknown.

AIM OF THE STUDY

The aim of this study is to explore the effect of arjunolic acid on depression and its possible mechanisms.

METHODS

Intraperitoneal injection of LPS in mice and LPS stimulated-BV2 microglia were utilized to set up in vivo and in vitro models. Behavioral tests, H&E staining and ELISA were employed to evaluate the effect of arjunolic acid on depression. RT-qPCR, immunofluorescence, molecular docking and Western blot were performed to elucidate the molecular mechanisms.

RESULTS

Arjunolic acid dramatically ameliorated depressive behavior in LPS-induced mice. The levels of BDNF and 5-HT in the hippocampus of the mice were increased, while the number of iNOS + IBA1+ cells in the brain were decreased and Arg1+IBA1+ positive cells were increased after arjunolic acid treatment. In addition, arjunolic acid promoted the polarization of BV2 microglia from M1 to M2 type. Notably, drug affinity responsive target stability (DARTS), cellular thermal shift assay (CETSA) and molecular docking technologies identified SIRT1 as the target of arjunolic acid. Moreover, after SIRT1 inhibition by using EX-527, the effects of arjunolic acid on ameliorating LPS-induced depressive behavior in mice and promoting M2 Microglia polarization were blocked. In addition, arjunolic acid activated AMPK and decreased Notch1 expression, however, inhibition of AMPK, the effect of arjunolic acid on the downregulation of Notch1 expression were weaken.

CONCLUSIONS

This study elucidates that arjunolic acid suppressed neuroinflammation through modulating the SIRT1/AMPK/Notch1 signaling pathway. Our study demonstrates that arjunolic acid might serve as a potiential anti-depressant.

Modulating monocyte-derived macrophage polarization in cerebral ischemic injury with hyperglycemia

Ischemic stroke (IS), characterized by high mortality rate, occurs owing to diminished or blocked blood flow to the brain. Hyperglycemia (HG) is a major contributor to the risk of IS. HG induces augmented oxidative stress and Blood-Brain Barrier breakdown, which increases the influx of blood-derived myeloid cells into the brain parenchyma. In cerebral ischemia, infiltrating monocytes undergo differentiation into pro-inflammatory or anti-inflammatory macrophages, having a large effect on outcomes of ischemic stroke. In addition, interleukin-4 (IL-4) and interleukin-13 (IL-13) engage in post-ischemia repair by polarizing the infiltrating monocytes into an anti-inflammatory phenotype. In this study, we aimed to determine the effect of phenotypic polarization of monocyte-derived macrophages on the prognosis of IS with HG (HG-IS). We first established a hyperglycemic mouse model using streptozotocin (150 mg/kg) and induced transient middle cerebral artery occlusion. We observed that blood-brain barrier permeability increased in HG-IS mice, as per two-photon live imaging and Evans blue staining. We also confirmed the increased infiltration of monocyte-derived macrophages and the downregulation of anti-inflammatory macrophages related to tissue remodeling after inflammation in HG-IS mice through immunohistochemistry, western blotting, and flow cytometry. We observed phenotypic changes in monocyte-derived macrophages, alleviated infarct volume, and improved motor function in HG-IS mice treated with IL-4 and IL-13. These findings suggest that the modulation of phenotypic changes in monocyte-derived macrophages following IS in hyperglycemic mice may influence ischemic recovery.

Pseudostellaria heterophylla polysaccharide mitigates Alzheimer's-like pathology via regulating the microbiota-gut-brain axis in 5 × FAD mice

Alzheimer's disease (AD) is a progressive neurodegenerative disorder characterised by neuroinflammation, for which gut dysbiosis may be implicated. Our previous study showed that treatment with Pseudostellaria heterophylla aqueous extract and one of its cyclopeptides, heterophyllin B, attenuate memory deficits via immunomodulation and neurite regeneration. However, whether Pseudostellaria heterophylla polysaccharide (PH-PS) exerts neuroprotective effects against AD and its underlying mechanisms remain unclear. The infrared spectrum, molecular weight, and carbohydrate composition of the PH-PS were determined. The results showed that PH-PS (Mw 8.771 kDa) was composed of glucose (57.78 %), galactose (41.52 %), and arabinose (0.70 %). PH-PS treatment ameliorated learning and spatial memory deficits, reduced amyloid β build-up, and suppressed reactive glia and astrocytes in 5 × FAD mice. 16S rRNA sequencing further showed that PH-PS remodelled the intestinal flora composition by promoting probiotic microbiota, such as Lactobacillus, Muribaculum, Monoglobus, and [Eubacterium]_siraeum_group, and suppressing inflammation-related UCG-009 and Blautia. Additionally, PH-PS restored intestinal barrier function; ameliorated peripheral inflammation by reducing the secretion of inflammatory cytokines, thereby converting M1 microglia and A1 astrocyte toward beneficial M2 and A2 phenotypes; and contributed to Aβ plaques clearance by upregulation of insulin degradation enzyme and neprilysin. Collectively, our findings demonstrate that PH-PS may prevent the progression of AD via modulation of the gut microbiota and regulation of glial polarisation, which could provide evidence to design a potential diet therapy for preventing or curing AD.

Maternal gastrointestinal nematode infection alters hippocampal neuroimmunity, promotes synaptic plasticity, and improves resistance to direct infection in offspring

The developing brain is vulnerable to maternal bacterial and viral infections which induce strong inflammatory responses in the mother that are mimicked in the offspring brain, resulting in irreversible neurodevelopmental defects, and associated cognitive and behavioural impairments. In contrast, infection during pregnancy and lactation with the immunoregulatory murine intestinal nematode, Heligmosomoides bakeri, upregulates expression of genes associated with long-term potentiation (LTP) of synaptic networks in the brain of neonatal uninfected offspring, and enhances spatial memory in uninfected juvenile offspring. As the hippocampus is involved in spatial navigation and sensitive to immune events during development, here we assessed hippocampal gene expression, LTP, and neuroimmunity in 3-week-old uninfected offspring born to H. bakeri infected mothers. Further, as maternal immunity shapes the developing immune system, we assessed the impact of maternal H. bakeri infection on the ability of offspring to resist direct infection. In response to maternal infection, we found an enhanced propensity to induce LTP at Schaffer collateral synapses, consistent with RNA-seq data indicating accelerated development of glutamatergic synapses in uninfected offspring, relative to those from uninfected mothers. Hippocampal RNA-seq analysis of offspring of infected mothers revealed increased expression of genes associated with neurogenesis, gliogenesis, and myelination. Furthermore, maternal infection improved resistance to direct infection of H. bakeri in offspring, correlated with transfer of parasite-specific IgG1 to their serum. Hippocampal immunohistochemistry and gene expression suggest Th2/Treg biased neuroimmunity in offspring, recapitulating peripheral immunoregulation of H. bakeri infected mothers. These findings indicate maternal H. bakeri infection during pregnancy and lactation alters peripheral and neural immunity in uninfected offspring, in a manner that accelerates neural maturation to promote hippocampal LTP, and upregulates the expression of genes associated with neurogenesis, gliogenesis, and myelination.

Crosstalk Between Microglia and Müller Glia in the Age-Related Macular Degeneration: Role and Therapeutic Value of Neuroinflammation

Age-related macular degeneration (AMD) is a progressive neurodegeneration disease that causes photoreceptor demise and vision impairments. In AMD pathogenesis, the primary death of retinal neurons always leads to the activation of resident microglia. The migration of activated microglia to the ongoing retinal lesion and their morphological transformation from branching to ameboid-like are recognized as hallmarks of AMD pathogenesis. Activated microglia send signals to Müller cells and promote them to react correspondingly to damaging stimulus. Müller cells are a type of neuroglia cells that maintain the normal function of retinal neurons, modulating innate inflammatory responses, and stabilize retinal structure. Activated Müller cells can accelerate the progression of AMD by damaging neurons and blood vessels. Therefore, the crosstalk between microglia and Müller cells plays a homeostatic role in maintaining the retinal environment, and this interaction is complicatedly modulated. In particular, the mechanism of mutual regulation between the two glia populations is complex under pathological conditions. This paper reviews recent findings on the crosstalk between microglia and Müller glia during AMD pathology process, with special emphasis on its therapeutic potentials.

Platinum-Loaded Cerium Oxide Capable of Repairing Neuronal Homeostasis for Cerebral Ischemia-Reperfusion Injury Therapy

Effective neuroprotective agents are required to prevent neurological damage caused by reactive oxygen species (ROS) generated by cerebral ischemia-reperfusion injury (CIRI) following an acute ischemic stroke. Herein, it is aimed to develop the neuroprotective agents of cerium oxide loaded with platinum clusters engineered modifications (Ptn-CeO2). The density functional theory calculations show that Ptn-CeO2 could effectively scavenge ROS, including hydroxyl radicals (·OH) and superoxide anions (·O2 -). In addition, Ptn-CeO2 exhibits the superoxide dismutase- and catalase-like enzyme activities, which is capable of scavenging hydrogen peroxide (H2O2). The in vitro studies show that Ptn-CeO2 could adjust the restoration of the mitochondrial metabolism to ROS homeostasis, rebalance cytokines, and feature high biocompatibility. The studies in mice CIRI demonstrate that Ptn-CeO2 could also restore cytokine levels, reduce cysteine aspartate-specific protease (cleaved Caspase 3) levels, and induce the polarization of microglia to M2-type macrophages, thus inhibiting the inflammatory responses. As a result, Ptn-CeO2 inhibits the reperfusion-induced neuronal apoptosis, relieves the infarct volume, reduces the neurological severity score, and improves cognitive function. Overall, these findings suggest that the prominent neuroprotective effect of the engineered Ptn-CeO2 has a significant neuroprotective effect and provides a potential therapeutic alternative for CIRI.

Interleukin-4 protects retinal ganglion cells and promotes axon regeneration

BACKGROUND

The preservation of retinal ganglion cells (RGCs) and the facilitation of axon regeneration are crucial considerations in the management of various vision-threatening disorders. Therefore, we investigate the efficacy of interleukin-4 (IL-4), a potential therapeutic agent, in promoting neuroprotection and axon regeneration of retinal ganglion cells (RGCs) as identified through whole transcriptome sequencing in an in vitro axon growth model.

METHODS

A low concentration of staurosporine (STS) was employed to induce in vitro axon growth. Whole transcriptome sequencing was utilized to identify key target factors involved in the molecular mechanism underlying axon growth. The efficacy of recombinant IL-4 protein on promoting RGC axon growth was validated through in vitro experiments. The protective effect of recombinant IL-4 protein on somas of RGCs was assessed using RBPMS-specific immunofluorescent staining in mouse models with optic nerve crush (ONC) and N-methyl-D-aspartic acid (NMDA) injury. The protective effect on RGC axons was evaluated by anterograde labeling of cholera toxin subunit B (CTB), while the promotion of RGC axon regeneration was assessed through both anterograde labeling of CTB and immunofluorescent staining for growth associated protein-43 (GAP43).

RESULTS

Whole-transcriptome sequencing of staurosporine-treated 661 W cells revealed a significant upregulation in intracellular IL-4 transcription levels during the process of axon regeneration. In vitro experiments demonstrated that recombinant IL-4 protein effectively stimulated axon outgrowth. Subsequent immunostaining with RBPMS revealed a significantly higher survival rate of RGCs in the rIL-4 group compared to the vehicle group in both NMDA and ONC injury models. Axonal tracing with CTB confirmed that recombinant IL-4 protein preserved long-distance projection of RGC axons, and there was a notably higher number of surviving axons in the rIL-4 group compared to the vehicle group following NMDA-induced injury. Moreover, intravitreal delivery of recombinant IL-4 protein substantially facilitated RGC axon regeneration after ONC injury.

CONCLUSION

The recombinant IL-4 protein exhibits the potential to enhance the survival rate of RGCs, protect RGC axons against NMDA-induced injury, and facilitate axon regeneration following ONC. This study provides an experimental foundation for further investigation and development of therapeutic agents aimed at protecting the optic nerve and promoting axon regeneration.

The Role of Glial Cells in Synaptic Dysfunction: Insights into Alzheimer's Disease Mechanisms

Alzheimer's disease (AD) is a devastating neurodegenerative disorder that impacts a substantial number of individuals globally. Despite its widespread prevalence, there is currently no cure for AD. It is widely acknowledged that normal synaptic function holds a key role in memory, cognitive abilities, and the interneuronal transfer of information. As AD advances, symptoms including synaptic impairment, decreased synaptic density, and cognitive decline become increasingly noticeable. The importance of glial cells in the formation of synapses, the growth of neurons, brain maturation, and safeguarding the microenvironment of the central nervous system is well recognized. However, during AD progression, overactive glial cells can cause synaptic dysfunction, neuronal death, and abnormal neuroinflammation. Both neuroinflammation and synaptic dysfunction are present in the early stages of AD. Therefore, focusing on the changes in glia-synapse communication could provide insights into the mechanisms behind AD. In this review, we aim to provide a summary of the role of various glial cells, including microglia, astrocytes, oligodendrocytes, and oligodendrocyte precursor cells, in regulating synaptic dysfunction. This may offer a new perspective on investigating the underlying mechanisms of AD.

The Potentiality of Natural Products and Herbal Medicine as Novel Medications for Parkinson's Disease: A Promising Therapeutic Approach

As the global population ages, the prevalence of Parkinson's disease (PD) is steadily on the rise. PD demonstrates chronic and progressive characteristics, and many cases can transition into dementia. This increases societal and economic burdens, emphasizing the need to find effective treatments. Among the widely recognized causes of PD is the abnormal accumulation of proteins, and autophagy dysfunction accelerates this accumulation. The resultant Lewy bodies are also commonly found in Alzheimer's disease patients, suggesting an increased potential for the onset of dementia. Additionally, the production of free radicals due to mitochondrial dysfunction contributes to neuronal damage and degeneration. The activation of astrocytes and the M1 phenotype of microglia promote damage to dopamine neurons. The drugs currently used for PD only delay the clinical progression and exacerbation of the disease without targeting its root cause, and come with various side effects. Thus, there is a demand for treatments with fewer side effects, with much potential offered by natural products. In this study, we reviewed a total of 14 articles related to herbal medicines and natural products and investigated their relevance to possible PD treatment. The results showed that the reviewed herbal medicines and natural products are effective against lysosomal disorder, mitochondrial dysfunction, and inflammation, key mechanisms underlying PD. Therefore, natural products and herbal medicines can reduce neurotoxicity and might improve both motor and non-motor symptoms associated with PD. Furthermore, these products, with their multi-target effects, enhance bioavailability, inhibit antibiotic resistance, and might additionally eliminate side effects, making them good alternative therapies for PD treatment.

Pathological and therapeutic effects of extracellular vesicles in neurological and neurodegenerative diseases

Extracellular vesicles are released by all cell types and contain proteins, microRNAs, mRNAs, and other bioactive molecules. Extracellular vesicles play an important role in intercellular communication and in the modulation of the immune system and neuroinflammation. The cargo of extracellular vesicles (e.g., proteins and microRNAs) is altered in pathological situations. Extracellular vesicles contribute to the pathogenesis of many pathologies associated with sustained inflammation and neuroinflammation, including cancer, diabetes, hyperammonemia and hepatic encephalopathy, and other neurological and neurodegenerative diseases. Extracellular vesicles may cross the blood-brain barrier and transfer pathological signals from the periphery to the brain. This contributes to inducing neuroinflammation and cognitive and motor impairment in hyperammonemia and hepatic encephalopathy and in neurodegenerative diseases. The mechanisms involved are beginning to be understood. For example, increased tumor necrosis factor α in extracellular vesicles from plasma of hyperammonemic rats induces neuroinflammation and motor impairment when injected into normal rats. Identifying the mechanisms by which extracellular vesicles contribute to the pathogenesis of these diseases will help to develop new treatments and diagnostic tools for their easy and early detection. In contrast, extracellular vesicles from mesenchymal stem cells have therapeutic utility in many of the above pathologies, by reducing inflammation and neuroinflammation and improving cognitive and motor function. These extracellular vesicles recapitulate the beneficial effects of mesenchymal stem cells and have advantages as therapeutic tools: they are less immunogenic, may not differentiate to malignant cells, cross the blood-brain barrier, and may reach more easily target organs. Extracellular vesicles from mesenchymal stem cells have beneficial effects in models of ischemic brain injury, Alzheimer's and Parkinson's diseases, hyperammonemia, and hepatic encephalopathy. Extracellular vesicles from mesenchymal stem cells modulate the immune system, promoting the shift from a pro-inflammatory to an anti-inflammatory state. For example, extracellular vesicles from mesenchymal stem cells modulate the Th17/Treg balance, promoting the anti-inflammatory Treg. Extracellular vesicles from mesenchymal stem cells may also act directly in the brain to modulate microglia activation, promoting a shift from a pro-inflammatory to an anti-inflammatory state. This reduces neuroinflammation and improves cognitive and motor function. Two main components of extracellular vesicles from mesenchymal stem cells which contribute to these beneficial effects are transforming growth factor-β and miR-124. Identifying the mechanisms by which extracellular vesicles from mesenchymal stem cells induce the beneficial effects and the main molecules (e.g., proteins and mRNAs) involved may help to improve their therapeutic utility. The aims of this review are to summarize the knowledge of the pathological effects of extracellular vesicles in different pathologies, the therapeutic potential of extracellular vesicles from mesenchymal stem cells to recover cognitive and motor function and the molecular mechanisms for these beneficial effects on neurological function.

Identification of Anti-Neuroinflammatory Bioactive Compounds in Essential Oils and Aqueous Distillation Residues Obtained from Commercial Varieties of Cannabis sativa L

Neuroinflammation, which is mainly triggered by microglia, is a key contributor to multiple neurodegenerative diseases. Natural products, and in particular Cannabis sativa L., due to its richness in phytochemical components, represent ideal candidates to counteract neuroinflammation. We previously characterized different C. sativa commercial varieties which showed significantly different chemical profiles. On these bases, the aim of this study was to evaluate essential oils and aqueous distillation residues from the inflorescences of three different hemp varieties for their anti-neuroinflammatory activity in BV-2 microglial cells. Cells were pretreated with aqueous residues or essential oils and then activated with LPS. Unlike essential oils, aqueous residues showed negligible effects in terms of anti-inflammatory activity. Among the essential oils, the one obtained from 'Gorilla Glue' was the most effective in inhibiting pro-inflammatory mediators and in upregulating anti-inflammatory ones through the modulation of the p38 MAPK/NF-κB pathway. Moreover, the sesquiterpenes (E)-caryophyllene, α-humulene, and caryophyllene oxide were identified as the main contributors to the essential oils' anti-inflammatory activity. To our knowledge, the anti-neuroinflammatory activity of α-humulene has not been previously described. In conclusion, our work shows that C. sativa essential oils characterized by high levels of sesquiterpenes can be promising candidates in the prevention/counteraction of neuroinflammation.

Interleukin 4 Reduces Brain Hyperexcitability after Traumatic Injury by Downregulating TNF-α, Upregulating IL-10/TGF-β, and Potential Directing Macrophage/Microglia to the M2 Anti-inflammatory Phenotype

Macrophage/microglia are activated after Traumatic brain injury (TBI), transform to inflammatory phenotype (M1) and trigger neuroinflammation, which provokes epileptogenesis. Interleukin-4 (IL-4) is a well-known drive of macrophage/microglia to the anti-inflammatory phenotype (M2). We tested effect of IL-4 on speed of epileptogenesis, brain expression of inflammatory and anti-inflammatory cytokines, and lesion size in TBI-injured male rats. Rats underwent TBI by Controlled Cortical Impact. Then 100 ng IL-4 was injected into cerebral ventricles. One day after TBI, pentylenetetrazole (PTZ) kindling started and development of generalized seizures was recorded. The lesion size, cell survival rate, TNF-α, TGF-β, IL-10, and Arginase1 (Arg1) was measured in the brain 6 h, 12 h, 24 h, 48 h, and 5 days after TBI. Astrocytes and macrophage/microglia activation/polarization was assessed by GFAP/Arg1 and Iba1/Arg1 immunostaining. TBI-injured rats were kindled by 50% less PTZ injections than control and sham-operated rats. IL-4 did not change kindling rate in sham-operated rats but inhibited acceleration of kindling rate in the TBI-injured rats. IL-4 decreased damage volume and number of destroyed neurons. IL-4 stopped TNF-α whereas upregulated TGF-β, IL-10, and Arg1 expressions. Iba1/Arg1 positive macrophage/microglia was notably increased 48 h after IL-4 administration. IL-4 suppresses TBI-induced acceleration of epileptogenesis in rats by directing TBI neuroinflammation toward an anti-inflammatory tone and inhibition of cell death.

Cellular Localization and Distribution of TGF-β1, GDNF and PDGF-BB in the Adult Primate Central Nervous System

The available data on the localization of transforming growth factor beta1 (TGF-β1), glial cell line-derived neurotrophic factor (GDNF), and platelet-derived growth factor-BB (PDGF-BB) in the adult primate and human central nervous system (CNS) are limited and lack comprehensive and systematic information. This study aimed to investigate the cellular localization and distribution of TGF-β1, GDNF, and PDGF-BB in the CNS of adult rhesus macaque (Macaca mulatta). Seven adult rhesus macaques were included in the study. The protein levels of TGF-β1, PDGF-BB, and GDNF in the cerebral cortex, cerebellum, hippocampus, and spinal cord were analyzed by western blotting. The expression and location of TGF-β1, PDGF-BB, and GDNF in the brain and spinal cord was examined by immunohistochemistry and immunofluorescence staining, respectively. The mRNA expression of TGF-β1, PDGF-BB, and GDNF was detected by in situ hybridization. The molecular weight of TGF-β1, PDGF-BB, and GDNF in the homogenate of spinal cord was 25 KDa, 30 KDa, and 34 KDa, respectively. Immunolabeling revealed GDNF was ubiquitously distributed in the cerebral cortex, hippocampal formation, basal nuclei, thalamus, hypothalamus, brainstem, cerebellum, and spinal cord. TGF-β1 was least distributed and found only in the medulla oblongata and spinal cord, and PDGF-BB expression was also limited and present only in the brainstem and spinal cord. Besides, TGF-β1, PDGF-BB, and GDNF were localized in the astrocytes and microglia of spinal cord and hippocampus, and their expression was mainly found in the cytoplasm and primary dendrites. The mRNA of TGF-β1, PDGF-BB, and GDNF was localized to neuronal subpopulations in the spinal cord and cerebellum. These findings suggest that TGF-β1, GDNF and PDGF-BB may be associated with neuronal survival, neural regeneration and functional recovery in the CNS of adult rhesus macaques, providing the potential insights into the development or refinement of therapies based on these factors.

Single-cell RNA sequencing identifies distinct transcriptomic signatures between PMA/ionomycin- and αCD3/αCD28-activated primary human T cells

Immunologists have activated T cells in vitro using various stimulation methods, including phorbol myristate acetate (PMA)/ionomycin and αCD3/αCD28 agonistic antibodies. PMA stimulates protein kinase C, activating nuclear factor-κB, and ionomycin increases intracellular calcium levels, resulting in activation of nuclear factor of activated T cell. In contrast, αCD3/αCD28 agonistic antibodies activate T cells through ZAP-70, which phosphorylates linker for activation of T cell and SH2-domain-containing leukocyte protein of 76 kD. However, despite the use of these two different in vitro T cell activation methods for decades, the differential effects of chemical-based and antibody-based activation of primary human T cells have not yet been comprehensively described. Using single-cell RNA sequencing (scRNA-seq) technologies to analyze gene expression unbiasedly at the single-cell level, we compared the transcriptomic profiles of the non-physiological and physiological activation methods on human peripheral blood mononuclear cell-derived T cells from four independent donors. Remarkable transcriptomic differences in the expression of cytokines and their respective receptors were identified. We also identified activated CD4 T cell subsets (CD55+) enriched specifically by PMA/ionomycin activation. We believe this activated human T cell transcriptome atlas derived from two different activation methods will enhance our understanding, highlight the optimal use of these two in vitro T cell activation assays, and be applied as a reference standard when analyzing activated specific disease-originated T cells through scRNA-seq.

Neuroimmune mechanisms and therapies mediating post-ischaemic brain injury and repair

The nervous and immune systems control whole-body homeostasis and respond to various types of tissue injury, including stroke, in a coordinated manner. Cerebral ischaemia and subsequent neuronal cell death activate resident or infiltrating immune cells, which trigger neuroinflammation that affects functional prognosis after stroke. Inflammatory immune cells exacerbate ischaemic neuronal injury after the onset of brain ischaemia; however, some of the immune cells thereafter change their function to neural repair. The recovery processes after ischaemic brain injury require additional and close interactions between the nervous and immune systems through various mechanisms. Thus, the brain controls its own inflammation and repair processes after injury via the immune system, which provides a promising therapeutic opportunity for stroke recovery.

Postoperative delirium, neuroinflammation, and influencing factors of postoperative delirium: A review

Postoperative delirium (POD) is an acute cognitive dysfunction that is mainly characterized by memory impairment and disturbances in consciousness. POD can prolong the hospital stay and increase the 1-month mortality rate of patients. The overall incidence of POD is approximately 23%, and its prevalence can go up to 50% in high-risk surgeries. Neuroinflammation is an important pathogenic mechanism of POD that mediates microglial activation and leads to synaptic remodeling. Neuroinflammation, as an indispensable pathogenesis of POD, can occur due to a variety of factors, including aseptic inflammation caused by surgery, effects of anesthetic drugs, disruption of the blood-brain barrier, and epigenetics. Understanding these factors and avoiding the occurrence of risk factors may help prevent POD in time. This review provides a brief overview of POD and neuroinflammation and summarizes various factors affecting POD development mediated by neuroinflammation, which may serve as future targets for the prevention and treatment of POD.

Extracellular vesicles from mesenchymal stem cells reduce neuroinflammation in hippocampus and restore cognitive function in hyperammonemic rats

Chronic hyperammonemia, a main contributor to hepatic encephalopathy (HE), leads to neuroinflammation which alters neurotransmission leading to cognitive impairment. There are no specific treatments for the neurological alterations in HE. Extracellular vesicles (EVs) from mesenchymal stem cells (MSCs) reduce neuroinflammation in some pathological conditions. The aims were to assess if treatment of hyperammonemic rats with EVs from MSCs restores cognitive function and analyze the underlying mechanisms. EVs injected in vivo reach the hippocampus and restore performance of hyperammonemic rats in object location, object recognition, short-term memory in the Y-maze and reference memory in the radial maze. Hyperammonemic rats show reduced TGFβ levels and membrane expression of TGFβ receptors in hippocampus. This leads to microglia activation and reduced Smad7-IkB pathway, which induces NF-κB nuclear translocation in neurons, increasing IL-1β which alters AMPA and NMDA receptors membrane expression, leading to cognitive impairment. These effects are reversed by TGFβ in the EVs from MSCs, which activates TGFβ receptors, reducing microglia activation and NF-κB nuclear translocation in neurons by normalizing the Smad7-IkB pathway. This normalizes IL-1β, AMPA and NMDA receptors membrane expression and, therefore, cognitive function. EVs from MSCs may be useful to improve cognitive function in patients with hyperammonemia and minimal HE.

Feruloylated oligosaccharides ameliorate MPTP-induced neurotoxicity in mice by activating ERK/CREB/BDNF/TrkB signalling pathway

BACKGROUND

Feruloylated oligosaccharides (FOs) are natural esterification products of ferulic acid and oligosaccharides.

STUDY DESIGN

In this study, we examined whether FOs contribute to the ensured survival of nigrostriatal dopamine neurons and inhibition of neuroinflammation in Parkinson's disease (PD).

METHODS

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP, 30 mg/kg) was injected intraperitoneally into mice to establish a Parkinson's disease (PD) mouse model. FOs (15 and 30 mg/kg) were orally administered daily to the MPTP-treated mice. The rotarod test, balance beam test, immunofluorescence, enzyme-linked immunosorbent assay (ELISA), quantitative PCR (qPCR), and western blot analyses were performed to examine the neuroprotective effects of FOs on MPTP-treated mice.

RESULTS

Our study indicated that FOs increased the survival of dopamine neurons in the substantia nigra pars compacta (SNc) of the MPTP-treated mice. The neuroprotective effects of FOs were accompanied by inhibited glial activation and reduced inflammatory cytokine production. The mechanistic experiments revealed that the neuroprotective effects of FOs might be mediated through the activation of the ERK/CREB/BDNF/TrkB signalling pathway.

CONCLUSION

This study provides new insights into the mechanism underlying the anti-neuroinflammatory effect of phytochemicals and may facilitate the development of dietary supplements for PD patients. Our results indicate that FOs can be used as potential modulators for the prevention and treatment of PD.

Mesenchymal stem cell therapy for neurological disorders: The light or the dark side of the force?

Neurological disorders are recognized as major causes of death and disability worldwide. Because of this, they represent one of the largest public health challenges. With awareness of the massive burden associated with these disorders, came the recognition that treatment options were disproportionately scarce and, oftentimes, ineffective. To address these problems, modern research is increasingly looking into novel, more effective methods to treat neurological patients; one of which is cell-based therapies. In this review, we present a critical analysis of the features, challenges, and prospects of one of the stem cell types that can be employed to treat numerous neurological disorders-mesenchymal stem cells (MSCs). Despite the fact that several studies have already established the safety of MSC-based treatment approaches, there are still some reservations within the field regarding their immunocompatibility, heterogeneity, stemness stability, and a range of adverse effects-one of which is their tumor-promoting ability. We additionally examine MSCs' mechanisms of action with respect to in vitro and in vivo research as well as detail the findings of past and ongoing clinical trials for Parkinson's and Alzheimer's disease, ischemic stroke, glioblastoma multiforme, and multiple sclerosis. Finally, this review discusses prospects for MSC-based therapeutics in the form of biomaterials, as well as the use of electromagnetic fields to enhance MSCs' proliferation and differentiation into neuronal cells.

Drug repurposing: Clemastine fumarate and neurodegeneration

Neurodegenerative diseases have been a weighty problem in elder people who might be stricken with motor or/and cognition defects with lower life quality urging for effective treatment. Drugs are costly from development to market, so that drug repurposing, exploration of existing drugs for novel therapeutic purposes, becomes a wise and popular strategy to raise new treatment options. Clemastine fumarate, different from anti-allergic effect as H1 histamine antagonist, was screened and identified as promising drug for remyelination and autophagy enhancement. Surprisingly, fumarate salt also has similar effect. Hence, whether clemastine fumarate would make a protective impact on neurodegenerative diseases and what contribution fumarate probably makes are intriguing to us. In this review, we summarize the potential mechanism surrounding clemastine fumarate in current literature, and try to distinguish independent or synergistic effect between clemastine and fumarate, aiming to find worthwhile research direction for neurodegeneration diseases.

Impact of Aβ40 and Aβ42 Fibrils on the Transcriptome of Primary Astrocytes and Microglia

Fibrillar amyloid β-protein (Aβ) deposits in the brain, which are primarily composed of Aβ40 or Aβ42 peptides, are key pathological features of Alzheimer's disease (AD) and related disorders. Although the underlying mechanisms are still not clear, the Aβ fibrils can trigger a number of cellular responses, including activation of astrocytes and microglia. In addition, fibril structures of the Aβ40 and Aβ42 peptides are known to be polymorphic, which poses a challenge for attributing the contribution of different Aβ sequences and structures to brain pathology. Here, we systematically treated primary astrocytes and microglia with single, well-characterized polymorphs of Aβ40 or Aβ42 fibrils, and performed bulk RNA sequencing to assess cell-specific changes in gene expression. A greater number of genes were up-regulated by Aβ42 fibril-treated glial cells (251 and 2133 genes in astrocyte and microglia, respectively) compared with the Aβ40 fibril-treated glial cells (191 and 251 genes in astrocytes and microglia, respectively). Immunolabeling studies in an AD rat model with parenchymal fibrillar Aβ42 plaques confirmed the expression of PAI-1, MMP9, MMP12, CCL2, and C1r in plaque-associated microglia, and iNOS, GBP2, and C3D in plaque-associated astrocytes, validating markers from the RNA sequence data. In order to better understand these Aβ fibril-induced gene changes, we analyzed gene expression patterns using the Ingenuity pathway analysis program. These analyses further highlighted that Aβ42 fibril treatment up-regulated cellular activation pathways and immune response pathways in glial cells, including IL1β and TNFα in astrocytes, and microglial activation and TGFβ1 in microglia. Further analysis revealed that a number of disease-associated microglial (DAM) genes were surprisingly suppressed in Aβ40 fibril treated microglia. Together, the present findings indicate that Aβ42 fibrils generally show similar, but stronger, stimulating activity of glial cells compared with Aβ40 fibril treatment.

Nrf2 regulates the arginase 1+ microglia phenotype through the initiation of TREM2 transcription, ameliorating depression-like behavior in mice

The expression of the triggering receptor on myeloid cell-2 (TREM2) knockdown in microglia from the lateral habenula (LHb) reportedly induces depression-like behaviors in mice. However, the key molecular mechanism that mediates major depressive disorder (MDD) pathogenesis remains elusive. We herein show that Nrf2 regulates TREM2 transcription and effects TREM2 mRNA and protein expression. The activation of Nrf2 by sulforaphane (Nrf2 activator) increases the microglial arginase 1⁺ phenotype by initiating TREM2 transcription in the medial prefrontal cortex (mPFC) and ameliorates depression-like behavior in CSDS mice. The knockout of Nrf2 decreases TREM2 and the microglial arginase 1⁺ phenotype in the mPFC of Nrf2 KO mice with depression-like behavior. Downregulating TREM2 expression decreases the microglial arginase 1⁺ phenotype in the mPFC, resulting in depression-like behavior in SFN-treated CSDS mice. Finally, the knockout of Nrf2 and downregulation of TREM2 expression decreases the microglial arginase 1⁺ phenotype in the mPFC of Nrf2 KO mice and SFN-treated CSDS mice were associated with the brain-derived neurotrophic factor (BDNF)-tropomyosin receptor kinase B (TrkB) signaling pathway. These data indicate that alterations in the interaction between Nrf2 and TREM2 may play a role in the pathophysiology of depression-like behavior in mice.

Modulation of Inflammatory Mediators and Microglial Activation Through Physical Exercise in Alzheimer's and Parkinson's Diseases

Neuroinflammation is an inflammatory process in the central nervous system (CNS), in addition to being one of the main features of Alzheimer's disease (AD) and Parkinson's disease (PD). Microglia are known for their immune functions and have multiple reactive phenotypes related to the types of stages involving neurodegenerative diseases. Depending on the state of activation of microglia in the CNS, it can be neuroprotective or neurotoxic. In this context, AD is a neurodegenerative and neuroinflammatory disease characterized by the deposition of beta-amyloid plaques, formation of fibrillar tangles of tau protein, and loss of neurons due to neurotoxic activation of microglia. However, PD is characterized by the loss of dopaminergic neurons in the substantia nigra and accumulation of alpha-synuclein in the cortical regions, spinal cord, and brain stem, which occurs by microglial activation, contributing to the neuroinflammatory process. In this aspect, the activation of microglia in both pathologies triggers high levels of inflammatory markers, such as interleukins, and causes the neuroinflammatory process of the diseases. Thus, physical exercise is pointed out as neuroprotective, as it can act to strengthen neurogenesis and reduce the inflammatory process. Therefore, the present review addresses the neuroprotective effect of microglia after different types of physical exercise protocols and evaluates the activity and effects of inflammatory and anti-inflammatory parameters and mechanisms of AD and PD. This review will discuss the anti-inflammatory effects of physical exercise through microglia activation with neuroprotective activity and the role of pro-and anti-inflammatory cytokines in AD and PD.

An update on Ym1 and its immunoregulatory role in diseases

Ym1 is a rodent-specific chitinase-like protein (CLP) lacking catalytic activity, whose cellular origins are mainly macrophages, neutrophils and other cells. Although the detailed function of Ym1 remains poorly understood, Ym1 has been generally recognized as a fundamental feature of alternative activation of macrophages in mice and hence one of the prevalent detecting targets in macrophage phenotype distinguishment. Studies have pointed out that Ym1 may have regulatory effects, which are multifaceted and even contradictory, far more than just a mere marker. Allergic lung inflammation, parasite infection, autoimmune diseases, and central nervous system diseases have been found associations with Ym1 to varying degrees. Thus, insights into Ym1’s role in diseases would help us understand the pathogenesis of different diseases and clarify the genuine roles of CLPs in mammals. This review summarizes the information on Ym1 from the gene to its expression and regulation and focuses on the association between Ym1 and diseases.

The promise of the TGF-β superfamily as a therapeutic target for Parkinson's disease

A large body of evidence underscore the regulatory role of TGF-β superfamily in the central nervous system. Components of the TGF-β superfamily modulate key events during embryonic brain development and adult brain tissue injury repair. With respect to Parkinson's disease (PD), TGF-ß signaling pathways are implicated in the differentiation, maintenance and synaptic function of the dopaminergic neurons, as well as in processes related to the activation state of astrocytes and microglia. In vitro and in vivo studies using toxin models, have interrogated on the dopaminotrophic and protective role of the TGF-β superfamily members. The evolution of genetic and animal models of PD that more closely recapitulate the disease condition has made possible the dissection of intracellular pathways in response to TGF-ß treatment. Although the first clinical trials using GDNF did not meet their primary endpoints, substantial work has been carried out to reappraise the TGF-β superfamily's clinical benefit.

Gadolinium chloride protects neurons by regulating the activation of microglia in the model of optic nerve crush

The pathological basis of optic nerve crush (ONC) is the apoptosis of retinal ganglion cells (RGCs), which leads to an irreversible impairment of visual function. When stimulated by external stimuli, microglia polarize into different types and play different roles in repairing retinal injury. In this study, gadolinium chloride (GdCl₃) could inhibit the excessive proliferation and activation of microglia in the retina after ONC and significantly inhibited the morphological changes of microglia in the ganglion cell layer (GCL) and inner plexiform layer (IPL). In the early stage of optic nerve injury, blood-derived immune cells did not play an essential role in retinal repair. In addition, transcriptome analysis showed that GdCl₃ inhibited the expression of microglia proliferation-related factors and regulated signaling pathways related to skeletonization and inflammation. After GdCl₃ treatment, M1 markers were significantly down-regulated, while M2 markers were increased. In conclusion, this study demonstrated that GdCl₃ could regulate the distribution and morphological change of the retinal microglia and protect the ganglion cells by eliminating M1 microglia selectively, which provided a theoretical basis for further localizing different types of microglia in retina related diseases.

Sulforaphane activates anti-inflammatory microglia, modulating stress resilience associated with BDNF transcription

Sulforaphane (SFN) is an organic isothiocyanate and an NF-E2-related factor-2 (Nrf2) inducer that exerts prophylactic effects on depression-like behavior in mice. However, the underlying mechanisms remain poorly understood. Brain-derived neurotrophic factor (BDNF), a neurotrophin, is widely accepted for its antidepressant effects and role in stress resilience. Here, we show that SFN confers stress resilience via BDNF upregulation and changes in abnormal dendritic spine morphology in stressed mice, which is accompanied by rectifying the irregular levels of inflammatory cytokines. Mechanistic studies demonstrated that SFN activated Nrf2 to promote BDNF transcription by binding to the exon I promoter, which is associated with increased Nrf2, and decreased methyl-CpG binding protein-2 (MeCP2), a transcriptional suppressor of BDNF, in BV2 microglial cells. Furthermore, SFN inhibited the pro-inflammatory phenotype and activated the anti-inflammatory phenotype of microglia, which was associated with increased Nrf2 and decreased MeCP2 expression in microglia of stressed mice. Hence, our findings support that Nrf2 induces BDNF transcription via upregulation of Nrf2 and downregulation of MeCP2 in microglia, which is associated with changes in the morphology of damaged dendritic spines in stressed mice. Meanwhile, the data presented here provide evidence for the application of SFN as a candidate for the prevention and intervention of depression.

Increasing Severity of Spinal Cord Injury Results in Microglia/Macrophages With Annular-Shaped Morphology and No Change in Expression of CD40 and Tumor Growth Factor-β During the Chronic Post-injury Stage

Determination of the quantitative composition of phenotypically and morphologically different populations of resident microglia and infiltrating macrophages in spinal cord injury (SCI) of various degrees of severity could lead to much needed novel therapeutic interventions in neurotrauma. In this regard, we investigated the CD40 and TGF-β expressing populations of microglia/macrophages and their morphological states in a rat model of SCI of varying severity. We are the first to describe the annular-shaped microglia/macrophages, the morphology of which was formed due to the spatial orientation of the processes that form round or oval micro-territories, which include disintegrating myelin fibers. This type of cell morphology was found only in the injured spinal cord and mainly in the white matter. At the same time, an assessment of the number of annular-shaped microglia/macrophages and the diameter of micro-territories formed by their processes showed an elevation in these indicators as the severity of SCI increased. While we did not find significant quantitative changes in the populations of Iba1⁺/CD40⁺ and Iba1⁺/TGF-β⁺ microglia/macrophages with increased severity of SCI in the chronic period (60 dpi), we did determine changes in the expression of cytokines and mRNAs of genes-encoding microglial marker proteins, finding the greatest changes on days 7 and 14 after SCI between experimental groups with varying severity.

Shaping the Microglia in Retinal Degenerative Diseases Using Stem Cell Therapy: Practice and Prospects

Retinal degenerative disease (RDD) refers to a group of diseases with retinal degeneration that cause vision loss and affect people's daily lives. Various therapies have been proposed, among which stem cell therapy (SCT) holds great promise for the treatment of RDDs. Microglia are immune cells in the retina that have two activation phenotypes, namely, pro-inflammatory M1 and anti-inflammatory M2 phenotypes. These cells play an important role in the pathological progression of RDDs, especially in terms of retinal inflammation. Recent studies have extensively investigated the therapeutic potential of stem cell therapy in treating RDDs, including the immunomodulatory effects targeting microglia. In this review, we substantially summarized the characteristics of RDDs and microglia, discussed the microglial changes and phenotypic transformation of M1 microglia to M2 microglia after SCT, and proposed future directions for SCT in treating RDDs.

Characterization of the Leucocyte Immunoglobulin-like Receptor B4 (Lilrb4) Expression in Microglia

Simple Summary

In the present study, we provide a detailed characterization of Lilrb4 expression in microglia and peripheral myeloid cells. Our data demonstrate that LILRB4 is a marker for microglia activation, as evidenced by upregulation after lipopolysaccharide treatment and inhibition of microglial TGFβ signaling. Moreover, we provide evidence that microglia express low levels of Lilrb4 in vivo and high levels in vitro, and we clearly demonstrate that LILRB4 is also expressed by bone marrow-derived monocytes and, to a greater extent, by peritoneal macrophages, defining LILRB4 as a surface marker of myeloid cells and not as a microglia-specific marker.

Abstract

As resident innate immune cells of the CNS, microglia play important essential roles during physiological and pathological situations. Recent reports have described the expression of Lilrb4 in disease-associated and aged microglia. Here, we characterized the expression of Lilrb4 in microglia in vitro and in vivo in comparison with bone marrow-derived monocytes and peritoneal macrophages in mice. Using BV2 cells, primary microglia cultures as well as ex vivo isolated microglia and myeloid cells in combination with qPCR and flow cytometry, we were able to provide a comprehensive characterization of Lilrb4 expression in distinct mouse myeloid cells. Whereas microglia in vivo display low expression of Lilrb4, primary microglia cultures present high levels of surface LILRB4. Among the analyzed peripheral myeloid cells, peritoneal macrophages showed the highest expression levels of Lilrb4. Moreover, LPS treatment and inhibition of microglial TGFβ signaling resulted in significant increases of LILRB4 cell surface levels. Taken together, our data indicate that LILRB4 is a reliable surface marker for activated microglia and further demonstrate that microglial TGFβ signaling is involved in the regulation of Lilrb4 expression during LPS-induced microglia activation.

Asthma reduces glioma formation by T cell decorin-mediated inhibition of microglia

To elucidate the mechanisms underlying the reduced incidence of brain tumors in children with Neurofibromatosis type 1 (NF1) and asthma, we leverage Nf1 optic pathway glioma (Nf1^OPG) mice, human and mouse RNAseq data, and two different experimental asthma models. Following ovalbumin or house dust mite asthma induction at 4-6 weeks of age (WOA), Nf1^OPG mouse optic nerve volumes and proliferation are decreased at 12 and 24 WOA, indicating no tumor development. This inhibition is accompanied by reduced expression of the microglia-produced optic glioma mitogen, Ccl5. Human and murine T cell transcriptome analyses reveal that inhibition of microglia Ccl5 production results from increased T cell expression of decorin, which blocks Ccl4-mediated microglia Ccl5 expression through reduced microglia NFκB signaling. Decorin or NFκB inhibitor treatment of Nf1^OPG mice at 4-6 WOA inhibits tumor formation at 12 WOA, thus establishing a potential mechanistic etiology for the attenuated glioma incidence observed in children with asthma.

Sinomenine Relieves Airway Remodeling By Inhibiting Epithelial-Mesenchymal Transition Through Downregulating TGF-β1 and Smad3 Expression In Vitro and In Vivo

Airway remodeling is associated with dysregulation of epithelial-mesenchymal transition (EMT) in patients with asthma. Sinomenine (Sin) is an effective, biologically active alkaloid that has been reported to suppress airway remodeling in mice with asthma. However, the molecular mechanisms behind this effect remain unclear. We aimed to explore the potential relationship between Sin and EMT in respiratory epithelial cells in vitro and in vivo. First, 16HBE cells were exposed to 100 μg/mL LPS and treated with 200 μg/mL Sin. Cell proliferation, migration, and wound healing assays were performed to evaluate EMT, and EMT-related markers were detected using Western blotting. Mice with OVA-induced asthma were administered 35 mg/kg or 75 mg/kg Sin. Airway inflammation and remodeling detection experiments were performed, and EMT-related factors and proteins in the TGF-β1 pathway were detected using IHC and Western blotting. We found that Sin suppressed cell migration but not proliferation in LPS-exposed 16HBE cells. Sin also inhibited MMP7, MMP9, and vimentin expression in 16HBE cells and respiratory epithelial cells from mice with asthma. Furthermore, it decreased OVA-specific IgE and IL-4 levels in serum, relieved airway remodeling, attenuated subepithelial collagen deposition, and downregulating TGF-β1and Smad3 expression in mice with asthma. Our results suggest that Sin suppresses EMT by inhibiting IL-4 and downregulating TGF-β1 and Smad3 expression.

Systems-Level Proteomics Evaluation of Microglia Response to Tumor-Supportive Anti-Inflammatory Cytokines

Background

Microglia safeguard the CNS against injuries and pathogens, and in the presence of certain harmful stimuli are capable of inducing a disease-dependent inflammatory response. When exposed to anti-inflammatory cytokines, however, these cells possess the ability to switch from an inflammatory to an immunosuppressive phenotype. Cancer cells exploit this property to evade the immune system, and elicit an anti-inflammatory microenvironment that facilitates tumor attachment and growth.

Objective

The tumor-supportive biological processes that are activated in microglia cells in response to anti-inflammatory cytokines released from cancer cells were explored with mass spectrometry and proteomic technologies.

Methods

Serum-depleted and non-depleted human microglia cells (HMC3) were treated with a cocktail of IL-4, IL-13, IL-10, TGFβ, and CCL2. The cellular protein extracts were analyzed by LC-MS/MS. Using functional annotation clustering tools, statistically significant proteins that displayed a change in abundance between cytokine-treated and non-treated cells were mapped to their biological networks and pathways.

Results

The proteomic analysis of HMC3 cells enabled the identification of ~10,000 proteins. Stimulation with anti-inflammatory cytokines resulted in the activation of distinct, yet integrated clusters of proteins that trigger downstream a number of tumor-promoting biological processes. The observed changes could be classified into four major categories, i.e., mitochondrial gene expression, ECM remodeling, immune response, and impaired cell cycle progression. Intracellular immune activation was mediated mainly by the transducers of MAPK, STAT, TGFβ, NFKB, and integrin signaling pathways. Abundant collagen formation along with the expression of additional receptors, matrix components, growth factors, proteases and protease inhibitors, was indicative of ECM remodeling processes supportive of cell-cell and cell-matrix adhesion. Overexpression of integrins and their modulators was reflective of signaling processes that link ECM reorganization with cytoskeletal re-arrangements supportive of cell migration. Antigen processing/presentation was represented by HLA class I histocompatibility antigens, and correlated with upregulated proteasomal subunits, vesicular/viral transport, and secretory processes. Immunosuppressive and proangiogenic chemokines, as well as anti-angiogenic factors, were detectable in low abundance. Pronounced pro-inflammatory, chemotactic or phagocytic trends were not observed, however, the expression of certain receptors, signaling and ECM proteins indicated the presence of such capabilities.

Conclusions

Comprehensive proteomic profiling of HMC3 cells stimulated with anti-inflammatory cytokines revealed a spectrum of microglia phenotypes supportive of cancer development in the brain via microenvironment-dependent biological mechanisms.

Blood-Brain Barrier Breakdown: An Emerging Biomarker of Cognitive Impairment in Normal Aging and Dementia

The blood–brain barrier (BBB) plays a vital role in maintaining the specialized microenvironment of the neural tissue. It separates the peripheral circulatory system from the brain parenchyma while facilitating communication. Alterations in the distinct physiological properties of the BBB lead to BBB breakdown associated with normal aging and various neurodegenerative diseases. In this review, we first briefly discuss the aging process, then review the phenotypes and mechanisms of BBB breakdown associated with normal aging that further cause neurodegeneration and cognitive impairments. We also summarize dementia such as Alzheimer's disease (AD) and vascular dementia (VaD) and subsequently discuss the phenotypes and mechanisms of BBB disruption in dementia correlated with cognition decline. Overlaps between AD and VaD are also discussed. Techniques that could identify biomarkers associated with BBB breakdown are briefly summarized. Finally, we concluded that BBB breakdown could be used as an emerging biomarker to assist to diagnose cognitive impairment associated with normal aging and dementia.

Beige adipocytes mediate the neuroprotective and anti-inflammatory effects of subcutaneous fat in obese mice

Visceral obesity increases risk of cognitive decline in humans, but subcutaneous adiposity does not. Here, we report that beige adipocytes are indispensable for the neuroprotective and anti-inflammatory effects of subcutaneous fat. Mice lacking functional beige fat exhibit accelerated cognitive dysfunction and microglial activation with dietary obesity. Subcutaneous fat transplantation also protects against chronic obesity in wildtype mice via beige fat-dependent mechanisms. Beige adipocytes restore hippocampal synaptic plasticity following transplantation, and these effects require the anti-inflammatory cytokine interleukin-4 (IL4). After observing beige fat-mediated induction of IL4 in meningeal T-cells, we investigated the contributions of peripheral lymphocytes in donor fat. There was no sign of donor-derived lymphocyte trafficking between fat and brain, but recipient-derived lymphocytes were required for the effects of transplantation on cognition and microglial morphology. These findings indicate that beige adipocytes oppose obesity-induced cognitive impairment, with a potential role for IL4 in the relationship between beige fat and brain function.

Duzhong Fang Attenuates the POMC-Derived Neuroinflammation in Parkinsonian Mice

BACKGROUND

Neuroinflammation and microglia reactivity are now recognized to be features of Parkinson's disease (PD). Thus, microglia phenotype is a potential new target for developing treatments against PD. Duzhong Fang (DZF) is a traditional Chinese medicine (TCM) prescription. The theory of TCM argues that Duzhong Fang, nourishing yin and tonifying yang, may treat PD. However, its modern pharmacological studies and the underlying mechanisms are unclear.

METHODS

First, MPTP was used to establish a parkinsonian mouse model, and behavioral testing was used to evaluate the locomotor dysfunction. Then, HPLC, immunohistochemical staining, and Western blot assays were performed to evaluate the survival of dopaminergic neurons. Molecular biological and immunofluorescence staining were used to evaluate the neuroinflammation and microglial activation. In addition, RNA-seq transcriptomics was used to analyze differentially expressed genes and verify by RT-PCR.

RESULTS

In the present study, we first confirmed that DZF can alleviate neuroinflammation and ameliorate dyskinesia in parkinsonian mice. Then, further studies found that DZF can regulate microglial morphology and reactivity and act on the POMC gene. POMC is an upstream target for regulating inflammation and proinflammatory cytokines, and DZF can directly inhibit the POMC level and restore the homeostatic signature of microglia in parkinsonian mice.

CONCLUSION

This study found that POMC may have a potential role as a therapeutic target for PD. DZF may inhibit neuroinflammation and play an anti-PD effect by down-regulating the expression of POMC.

Anti-neuroinflammatory activity of Shenqi Fuzheng Injection and its main active constituents

Enhancement of alternative activation (M2) in microglia is a promising therapeutic target for microglia-mediated neuroinflammation. Shenqi Fuzheng Injection (SFI) is a clinical adjuvant treatment for cancer to reduce the side effects during cancer treatment, including boosting mood and improving appetite. However, the mechanism of SFI's effects on central symptoms is not clear. Therefore, using arginase 1 (Arg1) and transforming growth beta-1 (Tgfb1) as markers for M2 microglia activation, we found that compounds 1, 5, 12, 14, and 15 are the major M2-promoting constituents in SFI, which significantly upregulated Arg1 or Tgfb1 gene expression. Our results suggested that these compounds in SFI may promote M2 microglial activation and have potential uses in modulating microglial activation and alleviating neuroinflammation.

Alpha- and beta- adrenergic receptors regulate inflammatory responses to acute and chronic sleep fragmentation in mice

Sleep is a recuperative process, and its dysregulation has cognitive, metabolic, and immunological effects that are largely deleterious to human health. Epidemiological and empirical studies have suggested that sleep fragmentation (SF) as result of obstructive sleep apnea (OSA) and other sleep abnormalities leads to pronounced inflammatory responses, which are influenced by the sympathetic nervous system (SNS). However, the underlying molecular mechanisms contributing to SNS regulation of SF-induced inflammation are not fully understood. To assess the effects of the SNS upon inflammatory responses to SF, C57BL/6j female mice were placed in automated SF chambers with horizontally moving bars across the bottom of each cage at specified intervals to disrupt sleep. Mice were first subjected to either control (no bar movement), acute sleep fragmentation (ASF), or chronic sleep fragmentation (CSF) on a 12:12-h light/dark schedule. ASF involved a bar sweep every 120 s for 24 h, whereas CSF involved a bar sweep every 120 s for 12 h (during 12 L; resting period) over a period of 4 weeks. After exposure to these conditions, mice received an intraperitoneal injection of either phentolamine (5 mg/kg BW; an α-adrenergic receptor blocker), propranolol (5 mg/kg BW; a β-adrenergic receptor blocker), or vehicle (saline). Serum corticosterone concentration, brain and peripheral cytokine (IL1β, TNFα, and TGFβ) mRNA expression, and body mass were assessed. ASF and CSF significantly elevated serum corticosterone concentrations as well as cytokine mRNA expression levels compared with controls, and mice subjected to CSF had decreased body mass relative to controls. Mice subjected to CSF and treated with phentolamine or propranolol had a greater propensity for a decrease in cytokine gene expression compared with ASF, but effects were tissue-specific. Taken together, these results suggest that both α- and β-adrenergic receptors contribute to the SNS mediation of inflammatory responses, and adrenergic antagonists may effectively mitigate tissue-specific SF-mediated inflammation.

Peripheral inflammation and blood-brain barrier disruption: effects and mechanisms

The blood–brain barrier (BBB) is an important physiological barrier that separates the central nervous system (CNS) from the peripheral circulation, which contains inflammatory mediators and immune cells. The BBB regulates cellular and molecular exchange between the blood vessels and brain parenchyma. Normal functioning of the BBB is crucial for the homeostasis and proper function of the brain. It has been demonstrated that peripheral inflammation can disrupt the BBB by various pathways, resulting in different CNS diseases. Recently, clinical research also showed CNS complications following SARS‐CoV‐2 infection and chimeric antigen receptor (CAR)‐T cell therapy, which both lead to a cytokine storm in the circulation. Therefore, elucidation of the mechanisms underlying the BBB disruption induced by peripheral inflammation will provide an important basis for protecting the CNS in the context of exacerbated peripheral inflammatory diseases. In the present review, we first summarize the physiological properties of the BBB that makes the CNS an immune‐privileged organ. We then discuss the relevance of peripheral inflammation‐induced BBB disruption to various CNS diseases. Finally, we elaborate various factors and mechanisms of peripheral inflammation that disrupt the BBB.

Blood-brain barrier integrity in the pathogenesis of Alzheimer's disease

The blood-brain barrier (BBB) tightly controls the molecular exchange between the brain parenchyma and blood. Accumulated evidence from transgenic animal Alzheimer's disease (AD) models and human AD patients have demonstrated that BBB dysfunction is a major player in AD pathology. In this review, we discuss the role of the BBB in maintaining brain integrity and how this is mediated by crosstalk between BBB-associated cells within the neurovascular unit (NVU). We then discuss the role of the NVU, in particular its endothelial cell, pericyte, and glial cell constituents, in AD pathogenesis. The effect of substances released by the neuroendocrine system in modulating BBB function and AD pathogenesis is also discussed. We perform a systematic review of currently available AD treatments specifically targeting pericytes and BBB glial cells. In summary, this review provides a comprehensive overview of BBB dysfunction in AD and a new perspective on the development of therapeutics for AD.

Neuroinflammation in Alzheimer's Disease: Microglia, Molecular Participants and Therapeutic Choices

Alzheimer's disease is the world's most common dementing illness. It is pathologically characterized by β-amyloid accumulation, extracellular senile plaques and intracellular neurofibrillary tangles formation, and neuronal necrosis and apoptosis. Neuroinflammation has been widely recognized as a crucial process that participates in AD pathogenesis. In this review, we briefly summarized the involvement of microglia in the neuroinflammatory process of Alzheimer's disease. Its roles in the AD onset and progression are also discussed. Numerous molecules, including interleukins, tumor necrosis factor alpha, chemokines, inflammasomes, participate in the complex process of AD-related neuroinflammation and they are selectively discussed in this review. In the end of this paper from an inflammation- related perspective, we discussed some potential therapeutic choices.

Methylene blue promotes survival and GAP-43 expression of retinal ganglion cells after optic nerve transection

AIMS

Neurodegeneration of the optic nerve and retinal ganglion cells (RGCs) leads to progressive vision loss. As part of the central nervous system, RGCs show limited ability to regenerate and there is extensive search for neuroprotective agents for optic nerve damage. Methylene blue (MB) exhibits beneficial effects against various neurodegenerative diseases of the central nervous system. However, the mechanisms associated with its putative protection on neuronal survival and regeneration remain obscure. This study used the optic nerve transection model to examine the effects of MB on RGC survival, the expression of regenerative marker GAP-43 in RGCs and microglial activation.

MAIN METHODS

Axons of RGCs were injured by cutting the optic nerve. MB was injected intravitreally either immediately post-injury or delayed to 3 days post-injury. Using immunohistochemical staining, surviving RGCs, GAP-43-positive RGCs and microglial cells were quantified in wholemount retinas 7 days post-injury.

KEY FINDINGS

Both immediate and delayed (a more clinically realistic situation) intravitreal injection of MB promoted RGC survival. MB also increased the number of GAP-43-positive RGCs, suggesting an enhanced ability of RGCs to regenerate. This was exemplified by the regenerative sprouting of axon-like processes from injured RGCs after MB treatment. The increase in RGC survival and GAP-43 expression correlated with an increase in the number of microglial cells.

SIGNIFICANCE

These results reveal that MB has survival-promoting and growth-promoting effects on RGCs after optic nerve injury. Together with the established safety profile of MB in humans, MB is a promising treatment for neurodegeneration and injury of the optic nerve.

Neuroprotective modulation of microglia effector functions following priming with interleukin 4 and 13: current limitations in understanding their mode-of-action

In recent years the long-standing theory of microglia's properties for dual polarization towards a pro- or anti-inflammatory phenotype has been deeply challenged. Furthermore, the elucidation of microglia ontogenesis exposed intrinsic differences between microglia and peripheral myeloid cells, thereby further underscoring the need to re-evaluate microglia-specific activation behavior, especially within an inflamed central nervous system (CNS) environment. This review critically summarizes recent literature on the in vitro and in vivo response of murine microglia to the immune-modulatory cytokines interleukin 4 (IL4) and interleukin 13 (IL13), i.e. those driving the so-called anti-inflammatory phenotype. Here we highlight several pivotal factors that may influence experimental outcome and/or interpretation of in vitro and in vivo studies evaluating microglia's phenotypical and functional properties upon IL4/IL13 treatment. Finally, the current therapeutic relevance of IL4/IL13-induced microglia activation in both acute and chronic CNS disorders is discussed.

Gas6 Induces Myelination through Anti-Inflammatory IL-10 and TGF-β Upregulation in White Matter and Glia

The Gas6–TAM (Tyro3, Axl, Mer) ligand–receptor system is believed to promote central nervous system (CNS) (re)myelination and glial cell development. An additional important function of Gas6–TAM signalling appears to be the regulation of immunity and inflammation, which remains to be fully elucidated in the CNS. Here, we characterised the expression of TAM receptors and ligands in individual CNS glial cell types, observing high expression of Gas6 and the TAM receptors, Mer and Axl, in microglia, and high expression of Tyro3 in astrocytes. We also investigated the effect of Gas6 on the inflammatory cytokine response in the optic nerve and in mixed glial cell cultures from wildtype and single TAM receptor knockout mice. In wildtype and Mer-deficient cultures, Gas6 significantly stimulated the expression of the anti-inflammatory/pro-repair cytokines interleukin 10 (IL-10) and transforming growth factor β (TGF-β), whereas this effect was absent in either Tyro3 or Axl knockout cultures. Furthermore, Gas6 caused upregulation of myelin basic protein (MBP) expression in optic nerves, which was blocked by a neutralising antibody against IL-10. In conclusion, our data show that microglia are both a major source of Gas6 as well as an effector of Gas6 action in the CNS through the upregulation of anti-inflammatory and pro-repair mediators. Furthermore, the presence of both Axl and Tyro3 receptors appears to be necessary for these effects of Gas6. In addition, IL-10, alongside suppressing inflammation and immunity, mediates the pro-myelinating mechanism of Gas6 action in the optic nerve. Therefore, Gas6 may present an attractive target for novel therapeutic interventions for demyelinating as well as neuroinflammatory disorders of the CNS.

Inhibition of Microglial TGFβ Signaling Increases Expression of Mrc1

Microglia are constantly surveying their microenvironment and rapidly react to impairments by changing their morphology, migrating toward stimuli and adopting gene expression profiles characterizing their activated state. The increased expression of the M2-like marker Mannose receptor 1 (Mrc1), which is also referred to as CD206, in microglia has been reported after M2-like activation in vitro and in vivo. Mrc1 is a 175-kDa transmembrane pattern recognition receptor which binds a variety of carbohydrates and is involved in the pinocytosis and the phagocytosis of immune cells, including microglia, and thought to contribute to a neuroprotective microglial phenotype. Here we analyzed the effects of TGFβ signaling on Mrc1 expression in microglia in vivo and in vitro. Using C57BL/6 wild type and Cx3cr1^CreERT2:R26-YFP:Tgfbr2^fl/fl mice-derived microglia, we show that the silencing of TGFβ signaling results in the upregulation of Mrc1, whereas recombinant TGFβ1 induced the delayed downregulation of Mrc1. Furthermore, chromatin immunoprecipitation experiments provided evidence that Mrc1 is not a direct Smad2/Smad4 target gene in microglia. Altogether our data indicate that the changes in Mrc1 expression after the activation or the silencing of microglial TGFβ signaling are likely to be mediated by modifications of the secondary intracellular signaling events influenced by TGFβ signaling.

Modulation of Microglia Polarization through Silencing of NF-κB p65 by Functionalized Curdlan Nanoparticle-Mediated RNAi

Microglia polarization plays an important role in poststroke recovery. Inhibition of proinflammatory (M1) polarization and promotion of anti-inflammatory (M2) polarization of microglia are potential therapeutic strategies for inflammation reduction and neuronal recovery after stroke. Here, we evaluated the central nervous system (CNS)-targeted short interfering RNA (siRNA) delivery ability of functionalized curdlan nanoparticles (CMI) and investigated the nuclear factor-κB (NF-κB) p65 silencing efficiency of CMI-mediated siRNA in microglia, as well as the resulting neuroprotective effect of microglia polarization and neuroprotection in vitro and in vivo. The systemic delivery of NF-κB p65 siRNA (sip65) complexed to CMI nanoparticles in the mouse model of transient middle cerebral artery occlusion (tMCAO) resulted in the distribution of siRNA in microglia and significant silencing in NF-κB p65 in the peri-infarct region. Knockdown of NF-κB p65 resulted in M1 to M2 phenotypic transition of microglia, evidenced by the change in the expression pattern of signature cytokines as well as inducible nitric oxide synthase and CD206. Moreover, the CMI-mediated silencing of p65 increased the density of neurons and decreased pyknosis and edema in the peri-infarct region. Assessment of the neurological deficit score on the Bederson scale revealed a significantly reduced score in the mouse model of tMCAO treated with the sip65/CMI complex. Collectively, our data suggest that CMI nanoparticles are a promising CNS-targeting siRNA delivery system, and NF-κB p65 may be a potential therapeutic target for inflammation reduction and poststroke recovery.

The Immunomodulary Effects of Systematic Exercise in Older Adults and People with Parkinson's Disease

We sought to investigate whether regular balance training of moderate intensity (BT) has an effect on changes in selected cytokines, neurotrophic factors, CD200 and fractalkine in healthy older adults and participants with Parkinson’s disease (PD). Sixty-two subjects were divided into groups depending on experimental intervention: (1) group of people with PD participating in BT (PDBT), (2) group of healthy older people participating in BT (HBT), (3,4) control groups including healthy individuals (HNT) and people with PD (PDNT). Blood samples were collected twice: before and after 12 weeks of balance exercise (PDBT, HBT), or 12 weeks apart (PDNT, HNT). The study revealed significant increase of interleukin10 (PDBT, p = 0.026; HBT, p = 0.011), β-nerve growth factor (HBT, p = 0.002; PDBT, p = 0.016), transforming growth factor-β1 (PDBT, p = 0.018; HBT, p < 0.004), brain-derived neurotrophic factor (PDBT, p = 0.011; HBT, p < 0.001) and fractalkine (PDBT, p = 0.045; HBT, p < 0.003) concentration only in training groups. In PDBT, we have found a significant decrease of tumor necrosis factor alpha. No training effect on concentration of interleukin6, insulin-like growth factor 1 and CD200 was observed in both training and control groups. Regular training can modulate level of inflammatory markers and induce neuroprotective mechanism to reduce the inflammatory response.

Role of Infiltrating Microglia/Macrophages in Glioma

In this chapter we describe the state of the art knowledge of the role played by myeloid cells in promoting and supporting the growth and the invasive properties of a deadly brain tumor, glioblastoma. We provide a review of the works describing the intercellular communication among glioma and associated microglia/macrophage cells (GAMs) using in vitro cellular models derived from mice, rats and human patients and in vivo animal models using syngeneic or xenogeneic experimental systems. Special emphasis will be given to 1) the timing alteration of brain microenvironment under the influence of glioma, 2) the bidirectional communication among tumor and GAMs, 3) possible approaches to interfere with or to guide these interactions, with the aim to identify molecular and cellular targets which could revert or delay the vicious cycle that favors tumor biology.

Dynamic response of microglia/macrophage polarization following demyelination in mice

BACKGROUND

The glial response in multiple sclerosis (MS), especially for recruitment and differentiation of oligodendrocyte progenitor cells (OPCs), predicts the success of remyelination of MS plaques and return of function. As a central player in neuroinflammation, activation and polarization of microglia/macrophages (M/M) that modulate the inflammatory niche and cytokine components in demyelination lesions may impact the OPC response and progression of demyelination and remyelination. However, the dynamic behaviors of M/M and OPCs during demyelination and spontaneous remyelination are poorly understood, and the complex role of neuroinflammation in the demyelination-remyelination process is not well known. In this study, we utilized two focal demyelination models with different dynamic patterns of M/M to investigate the correlation between M/M polarization and the demyelination-remyelination process.

METHODS

The temporal and spatial features of M/M activation/polarization and OPC response in two focal demyelination models induced by lysolecithin (LPC) and lipopolysaccharide (LPS) were examined in mice. Detailed discrimination of morphology, sensorimotor function, diffusion tensor imaging (DTI), inflammation-relevant cytokines, and glial responses between these two models were analyzed at different phases.

RESULTS

The results show that LPC and LPS induced distinctive temporal and spatial lesion patterns. LPS produced diffuse demyelination lesions, with a delayed peak of demyelination and functional decline compared to LPC. Oligodendrocytes, astrocytes, and M/M were scattered throughout the LPS-induced demyelination lesions but were distributed in a layer-like pattern throughout the LPC-induced lesion. The specific M/M polarization was tightly correlated to the lesion pattern associated with balance beam function.

CONCLUSIONS

This study elaborated on the spatial and temporal features of neuroinflammation mediators and glial response during the demyelination-remyelination processes in two focal demyelination models. Specific M/M polarization is highly correlated to the demyelination-remyelination process probably via modulations of the inflammatory niche, cytokine components, and OPC response. These findings not only provide a basis for understanding the complex and dynamic glial phenotypes and behaviors but also reveal potential targets to promote/inhibit certain M/M phenotypes at the appropriate time for efficient remyelination.