Loss of IL-10 Promotes Differentiation of Microglia to a M1 Phenotype

Oligodendrocytes in central nervous system diseases: the effect of cytokine regulation

Cytokines including tumor necrosis factor, interleukins, interferons, and chemokines are abundantly produced in various diseases. As pleiotropic factors, cytokines are involved in nearly every aspect of cellular functions such as migration, survival, proliferation, and differentiation. Oligodendrocytes are the myelin-forming cells in the central nervous system and play critical roles in the conduction of action potentials, supply of metabolic components for axons, and other functions. Emerging evidence suggests that both oligodendrocytes and oligodendrocyte precursor cells are vulnerable to cytokines released under pathological conditions. This review mainly summarizes the effects of cytokines on oligodendrocyte lineage cells in central nervous system diseases. A comprehensive understanding of the effects of cytokines on oligodendrocyte lineage cells contributes to our understanding of central nervous system diseases and offers insights into treatment strategies.

Restoration of Spatial Learning Through Oral Administration of Lipopolysaccharides in Diabetes-related Cognitive Dysfunction

BACKGROUND/AIM

In a previous report, our group showed that oral administration of lipopolysaccharides (LPS) from Pantoea agglomerans can prevent the progression of streptozotocin (STZ)-induced diabetes-related cognitive dysfunction (DRCD) in mice without causing significant side-effects. However, the treatment effects of oral administration of LPS to DRCD remain unknown.

MATERIALS AND METHODS

We modified our previous animal experimental model to investigate whether oral administration of LPS can recover cognitive function after DRCD onset.

RESULTS

The Morris water maze (MWM) revealed a significant decrease in learning and memory abilities at 13 days after intracerebroventricular administration of STZ, thereby providing evidence of the occurrence of DRCD in the animal model. Oral administration of LPS (1 mg/kg per day) started after cognitive impairment was observed. After 28 days of treatment, mice receiving LPS via the oral route showed significant recovery of spatial learning ability, a symptom of early dementia, while only a trend toward recovery was seen for spatial memory compared to the untreated group.

CONCLUSION

These results, limited to MWM, suggest that oral administration of LPS is a promising therapeutic strategy for restoring decreased spatial learning ability.

Role of Regulatory T Cells in Intracerebral Hemorrhage

Intracerebral hemorrhage (ICH) is a common cerebrovascular disease that can lead to severe neurological dysfunction in surviving patients, resulting in a heavy burden on patients and their families. When ICH occurs, the blood‒brain barrier is disrupted, thereby promoting immune cell migration into damaged brain tissue. As important immunosuppressive T cells, regulatory T (Treg) cells are involved in the maintenance of immune homeostasis and the suppression of immune responses after ICH. Treg cells mitigate brain tissue damage after ICH in a variety of ways, such as inhibiting the neuroinflammatory response, protecting against blood‒brain barrier damage, reducing oxidative stress damage and promoting nerve repair. In this review, we discuss the changes in Treg cells in ICH clinical patients and experimental animals, the mechanisms by which Treg cells regulate ICH and treatments targeting Treg cells in ICH, aiming to support new therapeutic strategies for clinical treatment.

Ischemic stroke outcome after promoting CD4+CD25+ Treg cell migration through CCR4 overexpression in a tMCAO animal model

The importance of neuroinflammation during the ischemic stroke has been extensively studied. The role of CD4+CD25+ regulatory T (Treg) cells during the recovery phase have shown infarct size reduction and functional improvement, possibly through the mitigation of inflammatory immune responses. We aimed to investigate the molecular factors involved in microglia-Treg cell communication that result in Treg trafficking. First, we observed the migration patterns of CD8+ (cytotoxic) T cells and Treg cells and then searched for chemokines released by activated microglia in an oxygen-glucose deprivation (OGD) model. The transwell migration assay showed increased migration into OGD media for both cell types, in agreement with the increase in chemokines involved in immune cell trafficking from the mouse chemokine profiling array. MSCV retrovirus was transduced to overexpress CCR4 in Treg cells. CCR4-overexpressed Treg cells were injected into the mouse transient middle cerebral artery occlusion (tMCAO) model to evaluate the therapeutic potential via the tetrazolium chloride (TTC) assay and behavioral tests. A general improvement in the prognosis of animals after tMCAO was observed. Our results suggest the increased mobility of CCR4-overexpressed Treg cells in response to microglia-derived chemokines in vitro and the therapeutic potential of Treg cells with increased mobility in cellular therapy.

Microglial histone deacetylase 2 is dispensable for functional and histological outcomes in a mouse model of traumatic brain injury

The Class-I histone deacetylases (HDACs) mediate microglial inflammation and neurological dysfunction after traumatic brain injury (TBI). However, whether the individual Class-I HDACs play an indispensable role in TBI pathogenesis remains elusive. HDAC2 has been shown to upregulate pro-inflammatory genes in myeloid cells under brain injuries such as intracerebral hemorrhage, thereby worsening outcomes. Thus, we hypothesized that HDAC2 drives microglia toward a pro-inflammatory neurotoxic phenotype in a murine model of controlled cortical impact (CCI). Our results revealed that HDAC2 expression was highly induced in CD16/CD32+ pro-inflammatory microglia 3 and 7d after TBI. Surprisingly, microglia-targeted HDAC2 knockout (HDAC2 miKO) mice failed to demonstrate a beneficial phenotype after CCI/TBI compared to their wild-type (WT) littermates. HDAC2 miKO mice exhibited comparable levels of grey and white matter injury, efferocytosis, and sensorimotor and cognitive deficits after CCI/TBI as WT mice. RNA sequencing of isolated microglia 3d after CCI/TBI indicated the elevation of a panel of pro-inflammatory cytokines/chemokines in HDAC2 miKO mice over WT mice, and flow cytometry showed further elevated brain infiltration of neutrophils and B cells in HDAC2 miKO mice. Together, this study does not support a detrimental role for HDAC2 in microglial responses after TBI and calls for investigation into alternative mechanisms.

α-Gal Nanoparticles in CNS Trauma: I. In Vitro Activation of Microglia Towards a Pro-Healing State

BACKGROUND

Macrophages and microglia play critical roles after spinal cord injury (SCI), with the pro-healing, anti-inflammatory (M2) subtype being implicated in tissue repair. We hypothesize that promoting this phenotype within the post-injured cord microenvironment may provide beneficial effects for mitigating tissue damage. As a proof of concept, we propose the use of nanoparticles incorporating the carbohydrate antigen, galactose-α-1,3-galactose (α-gal epitope) as an immunomodulator to transition human microglia (HMC3) cells toward a pro-healing state.

METHODS

Quiescent HMC3 cells were acutely exposed to α-gal nanoparticles in the presence of human serum and subsequently characterized for changes in cell shape, expression of anti or pro-inflammatory markers, and secretion of phenotype-specific cytokines.

RESULTS

HMC3 cells treated with serum activated α-gal nanoparticles exhibited rapid enlargement and shape change in addition to expressing CD68. Moreover, these activated cells showed increased expression of anti-inflammatory markers like Arginase-1 and CD206 without increasing production of pro-inflammatory cytokines TNF-α or IL-6.

CONCLUSION

This study is the first to show that resting human microglia exposed to a complex of α-gal nanoparticles and anti-Gal (from human serum) can be activated and polarized toward a putative M2 state. The data suggests that α-gal nanoparticles may have therapeutic relevance to the CNS microenvironment, in both recruiting and polarizing macrophages/microglia at the application site. The immunomodulatory activity of these α-gal nanoparticles post-SCI is further described in the companion work (Part II).

Behavior, synaptic mitochondria, and microglia are differentially impacted by chronic adolescent stress and repeated endotoxin exposure in male and female rats

Early life adversity and chronic inflammation have both been associated with cognitive impairment and neural compromise. In this study, we investigated the interactions between a history of chronic adolescent stress (CAS) and repeated endotoxin exposure on behavior, synaptic mitochondria, and microglia in adult male and female Wistar rats. Adult rats from chronic stress and control conditions were exposed to either repeated endotoxin (lipopolysaccharide; LPS) or saline injections every 3 days for 9 weeks. In both sexes, repeated LPS, regardless of stress history, impaired working memory in the Y maze. Regarding spatial memory, LPS impaired function for females; whereas, CAS altered function in males. Although males had an increase in anxiety-like behavior shortly after CAS, there were no long-term effects on anxiety-like behavior or social interaction observed in males or females. Stress did not alter synaptic mitochondrial function in either sex. Repeated LPS altered synaptic mitochondrial function such that ATP production was increased in females only. There were no observed increases in IBA-1 positive cells within the hippocampus for either sex. However, LPS and CAS altered microglia morphology in females. Impact of repeated LPS was evident at the terminal endpoint with increased spleen weight in both sexes and decreased adrenal weight in males only. Circulating cytokines were not impacted by repeated LPS at the terminal endpoint, but evidence of CAS effects on cytokines in females were evident. These data suggest a long-term impact of chronic stress and an impact of repeated endotoxin challenge in adulthood; however, not all physiological and behavioral metrics examined were impacted by the paradigm employed in this study and the two environmental challenges rarely interacted.

Exploring the Connectivity of Neurodegenerative Diseases: Microglia as the Center

Degenerative diseases affect people's life and health and cause a severe social burden. Relevant mechanisms of microglia have been studied, aiming to control and reduce degenerative disease occurrence effectively. This review discussed the specific mechanisms underlying microglia in neurodegenerative diseases, age-related hearing loss, Alzheimer's disease, Parkinson's disease, and peripheral nervous system (PNS) degenerative diseases. It also reviewed the studies of microglia inhibitors (PLX3397/PLX5622) and activators (lipopolysaccharide), and suggested that reducing microglia can effectively curb the genesis and progression of degenerative diseases. Finally, microglial cells' anti-inflammatory and pro-inflammatory dual role was considered the critical communication point in central and peripheral degenerative diseases. Although it is difficult to describe the complex morphological structure of microglia in a unified manner, this does not prevent them from being a target for future treatment of neurodegenerative diseases.

Combination Gene Delivery Reduces Spinal Cord Pathology in Rats With Peripheral Neuropathic Pain

Although peripheral neuropathic pain is caused by peripheral nerve injury, it is not simply a peripheral nervous system disease. It causes abnormalities in both the central and peripheral nervous systems. Pathological phenomena, such as hyperactivation of sensory neurons and inflammation, are observed in both the dorsal root ganglion and spinal cord. Pain signals originating from the periphery are transmitted to the brain via the SC, and the signals are modulated by pathologically changing SC conditions. Therefore, the modulation of SC pathology is important for peripheral NP treatment. We investigated the effects of KLS-2031 (recombinant adeno-associated viruses expressing glutamate decarboxylase 65, glial cell-derived neurotrophic factor, and interleukin-10) delivered to the dorsal root ganglion on aberrant neuronal excitability and neuroinflammation in the SC of rats with peripheral NP. Results showed that KLS-2031 administration restored excessive excitatory transmission and inhibitory signals in substantia gelatinosa neurons. Moreover, KLS-2031 restored the in vivo hypersensitivity of wide dynamic range neurons and mitigated neuroinflammation in the SC by regulating microglia and astrocytes. Collectively, these findings demonstrated that KLS-2031 efficiently suppressed pathological pain signals and inflammation in the SC of peripheral NP model, and is a potential novel therapeutic approach for NP in clinical settings. PERSPECTIVE: Our study demonstrated that KLS-2031, a combination gene therapy delivered by transforaminal epidural injection, not only mitigates neuroinflammation but also improves SC neurophysiological function, including excitatory-inhibitory balance. These findings support the potential of KLS-2031 as a novel modality that targets multiple aspects of the complex pathophysiology of neuropathic pain.

Naïve Huntington's disease microglia mount a normal response to inflammatory stimuli but display a partially impaired development of innate immune tolerance that can be counteracted by ganglioside GM1

Chronic activation and dysfunction of microglia have been implicated in the pathogenesis and progression of many neurodegenerative disorders, including Huntington's disease (HD). HD is a genetic condition caused by a mutation that affects the folding and function of huntingtin (HTT). Signs of microglia activation have been observed in HD patients even before the onset of symptoms. It is unclear, however, whether pro-inflammatory microglia activation in HD results from cell-autonomous expression of mutant HTT, is the response of microglia to a diseased brain environment, or both. In this study, we used primary microglia isolated from HD knock-in (Q140) and wild-type (Q7) mice to investigate their response to inflammatory conditions in vitro in the absence of confounding effects arising from brain pathology. We show that naïve Q140 microglia do not undergo spontaneous pro-inflammatory activation and respond to inflammatory triggers, including stimulation of TLR4 and TLR2 and exposure to necrotic cells, with similar kinetics of pro-inflammatory gene expression as wild-type microglia. Upon termination of the inflammatory insult, the transcription of pro-inflammatory cytokines is tapered off in Q140 and wild-type microglia with similar kinetics. However, the ability of Q140 microglia to develop tolerance in response to repeated inflammatory stimulations is partially impaired in vitro and in vivo, potentially contributing to the establishment of chronic neuroinflammation in HD. We further show that ganglioside GM1, a glycosphingolipid with anti-inflammatory effects on wild-type microglia, not only decreases the production of pro-inflammatory cytokines and nitric oxide in activated Q140 microglia, but also dramatically dampen microglia response to re-stimulation with LPS in an experimental model of tolerance. These effects are independent from the expression of interleukin 1 receptor associated kinase 3 (Irak-3), a strong modulator of LPS signaling involved in the development of innate immune tolerance and previously shown to be upregulated by immune cell treatment with gangliosides. Altogether, our data suggest that external triggers are required for HD microglia activation, but a cell-autonomous dysfunction that affects the ability of HD microglia to acquire tolerance might contribute to the establishment of neuroinflammation in HD. Administration of GM1 might be beneficial to attenuate chronic microglia activation and neuroinflammation.

The "molecular soldiers" of the CNS: Astrocytes, a comprehensive review on their roles and molecular signatures

For a long time, neurons held the position of central players in the nervous system. Since there are far more astrocytes than neurons in the brain, it makes us wonder if these cells just take up space and support the neurons or if they are actively participating in central nervous system (CNS) homeostasis. Now, astrocytes' contribution to CNS physiology is appreciated as they are known to regulate ion and neurotransmitter levels, synapse formation and elimination, blood-brain barrier integrity, immune function, cerebral blood flow, and many more. In many neurological and psychiatric disorders, astrocyte functions are altered. Advancements in microscopic and transcriptomic tools revealed populations of astrocytes with varied morphology, electrophysiological properties, and transcriptomic profiles. Neuron-circuit-specific functions and neuron-specific interactions of astroglial subpopulations are found, which suggests that diversity is essential in carrying out diverse region-specific CNS functions. Investigations on heterogeneous astrocyte populations are revealing new astrocyte functions and their role in pathological conditions, opening a new therapeutic avenue for targeting neurological conditions. The true extent of astrocytic heterogeneity and its functional implications are yet to be fully explored. This review summarizes essential astrocytic functions and their relevance in pathological conditions and discusses astrocytic diversity in relation to morphology, function, and gene expression throughout the CNS.

Low-dose LPS alleviates early brain injury after SAH by modulating microglial M1/M2 polarization via USP19/FOXO1/IL-10/IL-10R1 signaling

BACKGROUND

Low-dose lipopolysaccharide (LPS) protects against early brain injury (EBI) after subarachnoid hemorrhage (SAH). However, the mechanism underlying the neuroprotective roles of low-dose LPS remain largely undefined.

METHODS

A SAH mice model was established and the pathological changes of brain were evaluated by wet-dry weight method, HE and Nissl staining, and blood-brain barrier (BBB) permeability assay. Cell apoptosis and inflammation were monitored by TUNEL, flow cytometry and ELISA assays. qRT-PCR, immunofluorescence and Western blot were used to detect the expression of microglial polarization-related or oxidative stress-associated markers. Bioinformatics analysis, luciferase and ChIP assays were employed to detect the direct association between FOXO1 and IL-10 promoter. The ubiquitination of FOXO1 in the in vitro SAH model was detected by co-IP.

RESULTS

Low-dose LPS alleviated SAH-induced neurological dysfunction, brain edema, BBB disruption, damage in the hippocampus, neuronal apoptosis and inflammation via modulating microglial M1/M2 polarization by IL-10/IL-10R1 signaling. Mechanistic studies showed that FOXO1 acted as a transcriptional activator of IL-10. USP19 mediated the deubiquitination of FOXO1 to activate IL-10/IL-10R1 signaling, thereby regulating microglial M1/M2 polarization. Functional experiments revealed that low-dose LPS upregulated USP19 to modulate microglial M1/M2 polarization via FOXO1/IL-10/IL-10R1 signaling in SAH mice.

CONCLUSION

Low-dose LPS protected against EBI after SAH by modulating microglial M1/M2 polarization via USP19/FOXO1/IL-10/IL-10R1 signaling.

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.

Non-Coding RNA in Microglia Activation and Neuroinflammation in Alzheimer's Disease

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by complex pathophysiological features. Amyloid plaques resulting from extracellular amyloid deposition and neurofibrillary tangles formed by intracellular hyperphosphorylated tau accumulation serve as primary neuropathological criteria for AD diagnosis. The activation of microglia has been closely associated with these pathological manifestations. Non-coding RNA (ncRNA), a versatile molecule involved in various cellular functions such as genetic information storage and transport, as well as catalysis of biochemical reactions, plays a crucial role in microglial activation. This review aims to investigate the regulatory role of ncRNAs in protein expression by directly targeting genes, proteins, and interactions. Furthermore, it explores the ability of ncRNAs to modulate inflammatory pathways, influence the expression of inflammatory factors, and regulate microglia activation, all of which contribute to neuroinflammation and AD. However, there are still significant controversies surrounding microglial activation and polarization. The categorization into M1 and M2 phenotypes may oversimplify the intricate and multifaceted regulatory processes in microglial response to neuroinflammation. Limited research has been conducted on the role of ncRNAs in regulating microglial activation and inducing distinct polarization states in the context of neuroinflammation. Moreover, the regulatory mechanisms through which ncRNAs govern microglial function continue to be refined. The current understanding of ncRNA regulatory pathways involved in microglial activation remains incomplete and may be influenced by spatial, temporal, and tissue-specific factors. Therefore, further in-depth investigations are warranted. In conclusion, there are ongoing debates and uncertainties regarding the activation and polarization of microglial cells, particularly concerning the categorization into M1 and M2 phenotypes. The study of ncRNA regulation in microglial activation and polarization, as well as its mechanisms, is still in its early stages and requires further investigation. However, this review offers new insights and opportunities for therapeutic approaches in AD. The development of ncRNA-based drugs may hold promise as a new direction in AD treatment.

Research Note: Heat stress affects immune and oxidative stress indices of the immune organs of broilers by changing the expressions of adenosine triphosphate-binding cassette subfamily G member 2, sodium-dependent vitamin C transporter-2, and mitochondrial calcium uniporter

This study aimed to determine the mechanisms of heat-induced oxidative stress in the thymus and spleen of broilers. After 28 d, 30 broilers were randomly divided into the control (25°C ± 2°C; 24 h/d) and heat-stressed (36°C ± 2°C; 8 h/d) groups; the experiment lasted for 1 wk. The broilers in each group were euthanized, and some samples were collected and analyzed at 35 d. The results showed that the birds subjected to heat stress reduced the weight (P < 0.01) and the indices of thymus (P < 0.01), the activities of T-AOC (P < 0.01) and SOD (P < 0.05) of spleen, and levels of IL-10 (P < 0.05) and the GSH-PX (P < 0.05) in thymus and spleen, and increased the IL-6 content of thymus (P < 0.05), the MDA content (P < 0.01), and the reactive oxygen species (ROS) levels (P < 0.01) in thymus and spleen. Moreover, the expression of the IgG gene in the thymus and spleen of heat-stressed broilers was increased (P < 0.05); however, the expression of the IgM gene in the spleen was increased (P < 0.05), with no difference (P > 0.05) in the thymus of heat-stressed broilers compared with the control. Furthermore, the relative expression of adenosine triphosphate-binding cassette subfamily G member 2 (ABCG2) in the thymus and spleen both increased (P < 0.05). The sodium-dependent vitamin C transporter-2 (SVCT-2) (P < 0.01) and mitochondrial calcium uniporter (MCU) (P < 0.01) mRNA levels in the thymus of heat-stressed broilers increased, and the expression of ABCG2 (P < 0.05), SVCT-2 (P < 0.01), and MCU (P < 0.01) proteins in the thymus and spleen of heat-stressed broilers increased compared with the control group. This study confirmed that heat stress-induced oxidative stress in the immune organs of broilers, further reducing immune function.

Regulatory T Cells Secrete IL10 to Suppress Neuroinflammation in Early Stage after Subarachnoid Hemorrhage

Objective: Accumulating evidence supports neuroprotective effects of regulatory T cells (Tregs) in response to brain injury. However, the precise mechanisms underlying the beneficial effects of Tregs on suppressing neuroinflammation after subarachnoid hemorrhage (SAH) remain unclear. Methods: We performed flow cytometry to detect the infiltration of Tregs into the brain at different time points after SAH. Behavioral tests, including Adhesive and Rotarod, were performed to assess neurological deficits in mice after SAH. Bulk RNA sequencing was used to investigate the transcriptomic change of Tregs infiltrating into the brain after SAH. qPCR was performed to verify the variation of inflammatory cytokines expression in the brain after Tregs exogenous infusion. FoxP3-DTR mice and Il10 gene KO mice were used to explore the mechanism of Tregs inhibiting neuron apoptosis after infiltrating the brain following SAH onset. Results: Peripheral Tregs infiltrated into the brain one day after SAH and gradually accumulated in the hemorrhagic hemisphere. An exogenous infusion of Tregs significantly improved the neurological function of mice after SAH, while poor recovery of neurological function was observed in Tregs depletion mice. Transcriptome sequencing data suggested that the immunosuppressive function of brain-infiltrated Tregs was significantly upregulated. qPCR showed that the expression of pro-inflammatory cytokines decreased in the brain of SAH mice after exogenous Tregs infusion. Bioinformatic analysis revealed that IL-10 and other cytokines secreted by brain-infiltrated Tregs were upregulated after SAH. Moreover, exogenous infusion of Il10 gene KO Tregs did not totally improve neurological function in SAH mice. Conclusions: Tregs infiltrated into the brain in the early stage after SAH and exerted neuroprotective effect by secreting IL-10 to suppress neuroinflammation and reduce neuron apoptosis.

Possible involvement of microglial P2RY12 and peripheral IL-10 in postpartum depression

Postpartum depression (PPD) is another type of depression, including emotional fluctuation, fatigue, and anxiety. Based on the specific event like giving birth, it can be speculated that PPD might have its specific mechanism. Here, we confirmed that dexamethasone (DEX) administration during pregnancy (gestational days 16-18) induced depressive- and anxiety-like behaviors in dam (DEX-dam) after weaning period (3 weeks). DEX-dam showed anxiety-like behaviors in open-field test (OFT) and light-dark test (LD). In addition, DEX-dam exhibited depressive-like behaviors with the increased immobility time in forced swimming test (TST). Molecular analysis confirmed that microglia, rather than neurons, astrocytes, and oligodendrocytes, are involved in anxiety-/depressive-like behaviors. Notably, P2ry12, homeostatic gene, and purinoceptor, along with hyper-ramified form, were reduced in the hippocampus of DEX-dam. In addition, we found that IL-10 mRNA was reduced in lymph nodes without alteration of pro-inflammatory cytokines, such as TNF-α, IL-1β, and IL-6. Interestingly, anxiety-/depressive-like behaviors of DEX-dam were restored with the normalization of P2ry12 and IL-10 after 10 weeks postpartum without antidepressants. Our results propose that stress hormone elevation during pregnancy might be associated with PPD via microglial P2RY12 and peripheral IL-10.

Roles of the Notch signaling pathway and microglia in autism

The Notch signaling pathway is mainly involved in the regulation of neural stem cell proliferation, survival and differentiation during the development of the central nervous system. As a neurodevelopmental disorder, autism is associated with an abnormal increase in the number of microglia in several brain regions. These findings suggest that the pathogenesis of autism may be related to the Notch signaling pathway and microglia. In this review, we discuss how Notch pathway activity leads to behavioral abnormalities such as learning and memory impairment by influencing neuronal biological activities. An increase in microglial protein synthesis and abnormal autophagy can affect synaptic development and lead to behavioral abnormalities, and all of these changes can lead to autism. Furthermore, the Notch signaling pathway regulates the activation and differentiation of microglia and promotes inflammatory responses, leading to the occurrence of autism. When excessive reactive oxygen species (ROS) secreted by microglia cannot be cleared by autophagy in a timely manner, Notch signaling pathway activity is affected, possibly further increasing susceptibility to autism. This review reveals the mechanism underlying the role of the Notch signaling pathway, microglia and their interaction in the pathogenesis of autism and provides a theoretical reference for targeted clinical therapies for autism.

Incorporating microglia-like cells in human induced pluripotent stem cell-derived retinal organoids

Microglia are the primary resident immune cells in the retina. They regulate neuronal survival and synaptic pruning making them essential for normal development. Following injury, they mediate adaptive responses and under pathological conditions they can trigger neurodegeneration exacerbating the effect of a disease. Retinal organoids derived from human induced pluripotent stem cells (hiPSCs) are increasingly being used for a range of applications, including disease modelling, development of new therapies and in the study of retinogenesis. Despite many similarities to the retinas developed in vivo, they lack some key physiological features, including immune cells. We engineered an hiPSC co-culture system containing retinal organoids and microglia-like (iMG) cells and tested their retinal invasion capacity and function. We incorporated iMG into retinal organoids at 13 weeks and tested their effect on function and development at 15 and 22 weeks of differentiation. Our key findings showed that iMG cells were able to respond to endotoxin challenge in monocultures and when co-cultured with the organoids. We show that retinal organoids developed normally and retained their ability to generate spiking activity in response to light. Thus, this new co-culture immunocompetent in vitro retinal model provides a platform with greater relevance to the in vivo human retina.

Microglial activation and over pruning involved in developmental epilepsy

To understand the potential role of microglia in synaptic pruning following status epilepticus (SE), we examined the time course of expression of Iba-1, and immune and neuroinflammatory regulators, including CD86, CD206, and CX3CR1, and TLR4/NF-κB after SE induced by pilocarpine in rats. Behavioral tests, TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) staining, immunohistochemical staining, Western blotting, PCR, and fluorescence double staining assessments were performed. The expression of Iba-1 protein was lowest in the control group, and peaked after 2 days (p < 0.001). CD86 and CD206 mRNA levels increased gradually in the microglia of the epilepsy group after 12 hours, 1 day, 2 days, and 3 days; peak expression was on the second day. The expression of the chemokine receptor CX3CR1 in microglia increased to varying degrees after SE, and expression of the presynaptic protein synapsin decreased. The expression of TLR4/NF-κB in microglia positively correlated with Iba-1 protein expression. These findings indicate that the TLR4/NF-κB signaling pathway may be involved in the activation and polarization of microglia in epilepsy and in excess synaptic pruning, which could lead to an increase in brain injury.

Maternal and Placental DNA Methylation Changes Associated with the Pathogenesis of Gestational Diabetes Mellitus

Gestational diabetes mellitus (GDM) is an important metabolic complication of pregnancy, which affects the future health of both the mother and the newborn. The pathogenesis of GDM is not completely clear, but what is clear is that with the development and growth of the placenta, GDM onset and blood glucose is difficult to control, while gestational diabetes patients' blood glucose drops and reaches normal after placenta delivery. This may be associated with placental secretion of insulin-like growth factor, adipokines, tumor necrosis factor-α, cytokines and insulin resistance. Therefore, endocrine secretion of placenta plays a key role in the pathogenesis of GDM. The influence of DNA methylation of these molecules and pathway-related genes on gene expression is also closely related to the pathogenesis of GDM. Here, this review attempts to clarify the pathogenesis of GDM and the related maternal and placental DNA methylation changes and how they affect metabolic pathways.

Effects of Suberoylanilide Hydroxamic Acid (SAHA) on the Inflammatory Response in Lipopolysaccharide-Induced N9 Microglial Cells

INTRODUCTION

Epigenetics has shown promising results for understanding the different behaviors of microglia under the context of neuroinflammation. However, to our knowledge, the results of this complex mechanism with novel pharmacological agents such as histone deacetylase inhibitors (HDACis) are still missing. In this study, we aimed to investigate the effects of suberoylanilide hydroxamic acid (SAHA), a pan-HDACi, on the lipopolysaccharide (LPS)-induced neuroinflammation model in the N9 microglial cells.

METHODS

Microglial cells were treated with SAHA (0.25, 0.5, 1.0, 1.25, 1.5 µM) and LPS (100 ng/mL) for 24 hours. Then, levels of the pro/anti-inflammatory cytokines interleukin-1 beta (IL-1β), IL-6, tumor necrosis factor alpha (TNF-α), and IL-10 were determined by the enzyme-linked immunosorbent assay. The total cellular HDAC activity was determined by colorimetric analysis. Additionally, the expression levels of nuclear factor kappa-B (NF-κB) were quantified via western blotting.

RESULTS

SAHA (1.0 and 1.25 µM) attenuated the LPS-induced inflammatory response of microglial cells via decreasing NF-κB expression and pro-inflammatory cytokines (IL-1β, IL-6, TNF-α) in the N9 microglial cells. Moreover, SAHA treatment improved IL-10 levels and prevented the LPS-induced increase in the HDAC activity in the microglial cells.

CONCLUSION

Our results suggest SAHA attenuates the LPS-induced inflammatory response in the N9 microglial cells, and regulation of histone acetylation with HDACis might be a rational approach for the treatment of neuroinflammation.

An integrated cytokine and kynurenine network as the basis of neuroimmune communication

Two of the molecular families closely associated with mediating communication between the brain and immune system are cytokines and the kynurenine metabolites of tryptophan. Both groups regulate neuron and glial activity in the central nervous system (CNS) and leukocyte function in the immune system, although neither group alone completely explains neuroimmune function, disease occurrence or severity. This essay suggests that the two families perform complementary functions generating an integrated network. The kynurenine pathway determines overall neuronal excitability and plasticity by modulating glutamate receptors and GPR35 activity across the CNS, and regulates general features of immune cell status, surveillance and tolerance which often involves the Aryl Hydrocarbon Receptor (AHR). Equally, cytokines and chemokines define and regulate specific populations of neurons, glia or immune system leukocytes, generating more specific responses within restricted CNS regions or leukocyte populations. In addition, as there is a much larger variety of these compounds, their homing properties enable the superimposition of dynamic variations of cell activity upon local, spatially limited, cell populations. This would in principle allow the targeting of potential treatments to restricted regions of the CNS. The proposed synergistic interface of 'tonic' kynurenine pathway affecting baseline activity and the superimposed 'phasic' cytokine system would constitute an integrated network explaining some features of neuroimmune communication. The concept would broaden the scope for the development of new treatments for disorders involving both the CNS and immune systems, with safer and more effective agents targeted to specific CNS regions.

Microglia-Neutrophil Interactions Drive Dry AMD-like Pathology in a Mouse Model

In dry age-related macular degeneration (AMD), inflammation plays a key role in disease pathogenesis. Innate immune cells such as microglia and neutrophils infiltrate the sub-retinal space (SRS) to induce chronic inflammation and AMD progression. But a major gap in our understanding is how these cells interact with each other in AMD. Here, we report a novel concept of how dynamic interactions between microglia and neutrophils contribute to AMD pathology. Using well-characterized genetically engineered mouse models as tools, we show that in the diseased state, retinal pigmented epithelial (RPE) cells trigger pro-inflammatory (M1) transition in microglia with diminished expression of the homeostatic marker, CX3CR1. Activated microglia localize to the SRS and regulate local neutrophil function, triggering their activation and thereby inducing early RPE changes. Ligand receptor (LR)-loop analysis and cell culture studies revealed that M1 microglia also induce the expression of neutrophil adhesion mediators (integrin β1/α4) through their interaction with CD14 on microglia. Furthermore, microglia-induced neutrophil activation and subsequent neutrophil-mediated RPE alterations were mitigated by inhibiting Akt2 in microglia. These results suggest that the Akt2 pathway in microglia drives M1 microglia-mediated neutrophil activation, thereby triggering early RPE degeneration and is a novel therapeutic target for early AMD, a stage without treatment options.

Taste-immune associative learning amplifies immunopharmacological effects and attenuates disease progression in a rat glioblastoma model

Mechanistic target of rapamycin (mTOR)-signaling is one key driver of glioblastoma (GBM), facilitating tumor growth by promoting the shift to an anti-inflammatory, pro-cancerogenic microenvironment. Even though mTOR inhibitors such as rapamycin (RAPA) have been shown to interfere with GBM disease progression, frequently chaperoned toxic drug side effects urge the need for developing alternative or supportive treatment strategies. Importantly, previous work document that taste-immune associative learning with RAPA may be utilized to induce learned pharmacological placebo responses in the immune system. Against this background, the current study aimed at investigating the potential efficacy of a taste-immune associative learning protocol with RAPA in a syngeneic GBM rat model. Following repeated pairings of a novel gustatory stimulus with injections of RAPA, learned immune-pharmacological effects could be retrieved in GBM-bearing animals when re-exposed to the gustatory stimulus together with administering 10 % amount of the initial drug dose (0.5 mg/kg). These inhibitory effects on tumor growth were accompanied by an up-regulation of central and peripheral pro-inflammatory markers, suggesting that taste-immune associative learning with RAPA promoted the development of a pro-inflammatory anti-tumor microenvironment that attenuated GBM tumor growth to an almost identical outcome as obtained after 100 % (5 mg/kg) RAPA treatment. Together, our results confirm the applicability of taste-immune associative learning with RAPA in animal disease models where mTOR overactivation is one key driver. This proof-of-concept study may also be taken as a role model for implementing learning protocols as alternative or supportive treatment strategy in clinical settings, allowing the reduction of required drug doses and side effects without losing treatment efficacy.

Single cell and spatial transcriptomic analyses reveal microglia-plasma cell crosstalk in the brain during Trypanosoma brucei infection

Human African trypanosomiasis, or sleeping sickness, is caused by the protozoan parasite Trypanosoma brucei and induces profound reactivity of glial cells and neuroinflammation when the parasites colonise the central nervous system. However, the transcriptional and functional responses of the brain to chronic T. brucei infection remain poorly understood. By integrating single cell and spatial transcriptomics of the mouse brain, we identify that glial responses triggered by infection are readily detected in the proximity to the circumventricular organs, including the lateral and 3rd ventricle. This coincides with the spatial localisation of both slender and stumpy forms of T. brucei. Furthermore, in silico predictions and functional validations led us to identify a previously unknown crosstalk between homeostatic microglia and Cd138+ plasma cells mediated by IL-10 and B cell activating factor (BAFF) signalling. This study provides important insights and resources to improve understanding of the molecular and cellular responses in the brain during infection with African trypanosomes.

Heterozygous expression of the Alzheimer's disease-protective PLCγ2 P522R variant enhances Aβ clearance while preserving synapses

BACKGROUND

A rare coding variant, P522R, in the phospholipase C gamma 2 (PLCG2) gene has been identified as protective against late-onset Alzheimer's disease (AD), but the mechanism is unknown. PLCG2 is exclusively expressed in microglia within the central nervous system, and altered microglial function has been implicated in the progression of AD.

METHODS

Healthy control hiPSCs were CRISPR edited to generate cells heterozygous and homozygous for the PLCG2P522R variant. Microglia derived from these hiPSC's were used to investigate the impact of PLCγ2P522R on disease relevant processes, specifically microglial capacity to take up amyloid beta (Aβ) and synapses. Targeted qPCR assessment was conducted to explore expression changes in core AD linked and microglial genes, and mitochondrial function was assessed using an Agilent Seahorse assay.

RESULTS

Heterozygous expression of the P522R variant resulted in increased microglial clearance of Aβ, while preserving synapses. This was associated with the upregulation of a number of genes, including the anti-inflammatory cytokine Il-10, and the synapse-linked CX3CR1, as well as alterations in mitochondrial function, and increased cellular motility. The protective capacity of PLCγ2P522R appeared crucially dependent on (gene) 'dose', as cells homozygous for the variant showed reduced synapse preservation, and a differential gene expression profile relative to heterozygous cells.

CONCLUSION

These findings suggest that PLCγ2P522R may result in increased surveillance by microglia, and prime them towards an anti-inflammatory state, with an increased capacity to respond to increasing energy demands, but highlights the delicate balance of this system, with increasing PLCγ2P522R 'dose' resulting in reduced beneficial impacts.

Characterization of an Immortalized Human Microglial Cell Line as a Tool for the Study of Diabetic Retinopathy

The complexity of the retinal structure reflects on the difficulty to describe its composite cell interactions. Microglia is responsible for the immune reaction to inflammatory stimuli during diabetic retinopathy (DR), but most studies still use rodent cells. We characterized a commercially available immortalized human microglial line and tested its susceptibility to inflammation, to study the interactions between the neuro-vascular retinal portions in species-specific models. After checking the expression of microglial markers, we tried lipopolysaccharide (LPS) stimulation and several pro-inflammatory cocktails to select the best combination able to induce a significant M1 (inflammatory) response. We measured M1 induction through the expression of pro- and anti-inflammatory molecules and performed morphologic and functional assays. Marker expression confirmed the human microglial derivation of these cells. Differently from rodents, LPS did not induce a M1 profile. The best pro-inflammatory stimulus was an interleukin-1β + tumor necrosis factor-α + interferon-γ cocktail, which induced morphology changes and increased proliferation, apoptosis, migration, reactive oxygen species, and the expression of inflammatory cytokines and miRNAs. In conclusion, this microglial line proved potentially useful to investigate the cascade of events leading to DR. In perspective, co-culture models involving microvascular cells will help in the understanding of multifaceted interactions of the neurovascular unit.

Exploring Sex-Related Differences in Microglia May Be a Game-Changer in Precision Medicine

One area of microglial biology that has been relatively neglected until recently is sex differences and this is in spite of the fact that sex is a risk factor in several diseases that are characterized by neuroinflammation and, by extension, microglial activation. Why these sex differences exist is not known but the panoply of differences extend to microglial number, genotype and phenotype. Significantly, several of these sex-related differences are also evident in health and change during life emphasizing the dynamic and plastic nature of microglia. This review will consider how age impacts on sex-related differences in microglia and ask whether the advancement of personalized medicine demands that a greater focus is placed on studying sex-related differences in microglia in Alzheimer's disease, Parkinson's disease and models of inflammatory stress and trauma in order to make true progress in dealing with these conditions.

Novel Somatostatin Receptor-4 Agonist SM-I-26 Mitigates Lipopolysaccharide-Induced Inflammatory Gene Expression in Microglia

Somatostatin receptor subtype 4 (SSTR4) is expressed in BV2 microglia, suggesting that SSTR4 agonists may impact microglia function. This study assessed the high-affinity SSTR4 agonist SM-I-26 (SMI) (0 nM, 10 nM, 1000 nM) against lipopolysaccharide (LPS)-induced inflammation (0, 10 or 100 ng/ml) over 6 or 24 h in BV2 microglia. Cell viability, nitrite output and mRNA expression changes of genes associated with our target (Sstr4), inflammation (Tnf-α, Il-6, Il-1β, inos), anti-inflammatory and anti-oxidant actions (Il-10, Catalase), and mediators of Aβ binding/phagocytosis (Msr1, Cd33, Trem1, Trem2) were measured. At 6 h SMI showed no effect across all conditions. At 24 h SMI (10 and 1000 nM) upregulated Sstr4 expression under inflammatory and non-inflammatory conditions. At 24 h SMI downregulated expression of the inflammatory cytokines Tnf-α (1000 nM within all LPS concentrations) and Il-6 (10 nM within 0 and 10 ng/ml LPS). At 24 h 10 nM SMI upregulated Il-10, while 1000 nM upregulated Catalase under inflammatory and non-inflammatory conditions. At 24 h Msr1 and Cd33 were upregulated by 1000 nM SMI under non-inflammatory conditions, while Trem1 was downregulated by 10 and 1000 nM SMI under mildly inflammatory and non-inflammatory conditions. These results show that SMI had concentration and time-dependent effects on mRNA expression of genes associated with different states of microglial activation. The SMI reduced Tnf-α and Il-6 inflammatory gene expression, and increased Il-10 anti-inflammatory gene expression, identifies anti-inflammatory actions of SSTR4 agonists extend to microglia.

Elevation of inactive cleaved annexin A1 in the neocortex is associated with amyloid, inflammatory and apoptotic markers in neurodegenerative dementias

Inflammation is usually a tightly regulated process whose termination by mediators including Annexin A1 (AnxA1) results in the resolution of inflammatory responses. In neurodegenerative dementias, chronic neuroinflammation, along with accumulation of aggregated β-amyloid (Aβ) peptides and apoptosis, has long been recognized to be a pathological hallmark; but it is unclear whether a failure of inflammation resolution contributes to this pathophysiological process. In this study, we measured AnxA1 immunoreactivities in postmortem neocortex (Brodmann areas BA9 and BA40) of well characterized Alzheimer's disease (AD), Parkinson disease dementia (PDD) and dementia with Lewy bodies (DLB) patients as well as aged controls. Inactive cleaved AnxA1 was found to be elevated in AD and DLB in BA40. Levels of cleaved AnxA1 also positively correlated with amyloidogenic brain Aβ, anti-inflammatory markers such as IL10 and IL13, as well as with the pro-apoptotic marker cleaved caspase-3 in BA40. Our findings suggest that elevated cleaved AnxA1 in neurodegenerative dementias may reflect a failure of inflammation resolution in certain regions of the diseased brain, and also support a mechanistic link between AnxA1 and amyloid pathology, neuroinflammation and apoptosis.

Neonatal microglia and proteinase inhibitors-treated adult microglia improve traumatic brain injury in rats by resolving the neuroinflammation

Microglia participate in the regulation of neuroinflammation caused by traumatic brain injury (TBI). This research aimed to explore the repair effects of intracranial injection of neonatal microglia or protease-treated adult microglia on TBI in rat model. Lateral fluid percussion injury was used to establish rat brain injury model. E64 and serpinA3N were employed for the treatment of adult microglia. Cleaved caspase-3 level was analyzed through immunoblotting assay. Enzyme-linked immunosorbent assay was employed to analyze cytokine and chemokine levels. Astrocytosis and microgliosis were shown by immunofluorescence. The cognitive function of rats was analyzed by water maze. The injection of neonatal microglia inhibited cell apoptosis, reduced astrocytosis and microgliosis, decreased the level of chemokines and cytokines in cortex and ipsilateral hippocampus, and improved cognitive function of TBI rat model. The transplantation of peptidase inhibitors-treated adult microglia also inhibited cell apoptosis, reduced astrocytosis and microgliosis, and improved cognitive function of rats with TBI. The transplantation of either neonatal microglia or peptidase inhibitors-treated adult microglia significantly inhibited the pathogenesis of TBI in rat model, while untreated adult microglia showed no significant effect.

Crosstalk between Microglia and Neurons in Neurotrauma: An Overview of the Underlying Mechanisms

Microglia are the resident immune cells of the brain and play a crucial role in housekeeping and maintaining homeostasis of the brain microenvironment. Upon injury or disease, microglial cells become activated, at least partly, via signals initiated by injured neurons. Activated microglia, thereby, contribute to both neuroprotection and neuroinflammation. However, sustained microglial activation initiates a chronic neuroinflammatory response which can disturb neuronal health and disrupt communications between neurons and microglia. Thus, microglia-neuron crosstalk is critical in a healthy brain as well as during states of injury or disease. As most studies focus on how neurons and microglia act in isolation during neurotrauma, there is a need to understand the interplay between these cells in brain pathophysiology. This review highlights how neurons and microglia reciprocally communicate under physiological conditions and during brain injury and disease. Furthermore, the modes of microglia-neuron communication are exposed, focusing on cell-contact dependent signaling and communication by the secretion of soluble factors like cytokines and growth factors. In addition, it has been discussed that how microglia-neuron interactions could exert either beneficial neurotrophic effects or pathologic proinflammatory responses. We further explore how aberrations in microglia-neuron crosstalk may be involved in central nervous system (CNS) anomalies, namely traumatic brain injury (TBI), neurodegeneration, and ischemic stroke. A clear understanding of how the microglia-neuron crosstalk contributes to the pathogenesis of brain pathologies may offer novel therapeutic avenues of brain trauma treatment.

Identifying the mechanism underlying antidepressant-like effects of loganin by network pharmacology in combination with experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Loganin, an iridoid glycoside, is one of the quality control indexes of Cornus officinalis Sieb. et Zucc. Increasing evidence emphasize the important role of inflammation in the pathology of depression, which links depression with other chronic diseases. Loganin prevents inflammatory response in multiple diseases and reverses depressive-like behaviors. However, the mechanisms underlying antidepressant-like effects of loganin for the treatment of inflammation-associated depression are not utterly understood.

AIM OF THE STUDY

The present study was designed to predict the potential targets of loganin against inflammation-associated depression using a network pharmacology approach.

MATERIALS AND METHODS

Pharmmapper and Uniport were used to predict loganin-related targets. Targets of inflammation were identified through GeneCards databases and Online Mendelian Inheritance in Man (OMIM). Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis were used to identify the potential mechanism. Finally, qRT-PCR and ELISA were used to confirm the role of loganin on these targets.

RESULTS

There were 15 nodes in the loganin-inflammation-depression intersection targets network. In the network, the degree value of CTNNB1 was above 3. Among top ten pathways identified by KEGG analysis, Th1/Th2 cell differentiation and IL-17 signaling pathways were related with both inflammation and depression. As indicated by qRT-PCR results, loganin increased CTNNB1 mRNA level. Moreover, loganin elevated M2 markers of microglia but decreased M1 markers of microglia against lipopolysaccharide (LPS), indicated by qRT-PCR results and ELISA results.

CONCLUSION

CTNNB1 was the main target of loganin. Loganin alleviated LPS-induced inflammation through inhibiting M1 polarization of microglia. Our results provide a better understanding of loganin-induced antidepressant-like effects for the treatment of inflammation-associated depression.

Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)

The third edition of Flow Cytometry Guidelines provides the key aspects to consider when performing flow cytometry experiments and includes comprehensive sections describing phenotypes and functional assays of all major human and murine immune cell subsets. Notably, the Guidelines contain helpful tables highlighting phenotypes and key differences between human and murine cells. Another useful feature of this edition is the flow cytometry analysis of clinical samples with examples of flow cytometry applications in the context of autoimmune diseases, cancers as well as acute and chronic infectious diseases. Furthermore, there are sections detailing tips, tricks and pitfalls to avoid. All sections are written and peer-reviewed by leading flow cytometry experts and immunologists, making this edition an essential and state-of-the-art handbook for basic and clinical researchers.

Comparative profiling of immune genes improves the prognoses of lower grade gliomas

OBJECTIVE

Lower grade gliomas (LGGs), classified as World Health Organization (WHO) grade II and grade III gliomas, comprise a heterogeneous group with a median survival time ranging from 4-13 years. Accurate prediction of the survival times of LGGs remains a major challenge in clinical practice.

METHODS

We reviewed the expression data of 865 LGG patients from 5 transcriptomics cohorts. The comparative profile of immune genes was analyzed for signature identification and validation. In-house RNAseq and microarray data from the Chinese Glioma Genome Atlas (CGGA) dataset were used as training and internal validation cohorts, respectively. The samples from The Cancer Genome Atlas (TCGA) and GSE16011 cohorts were used as external validation cohorts, and the real-time PCR of frozen LGG tissue samples (n = 36) were used for clinical validation.

RESULTS

A total of 2,214 immune genes were subjected to pairwise comparison to generate 2,449,791 immune-related gene pairs (IGPs). A total of 402 IGPs were identified with prognostic values for LGGs. The HOXA9-related and CRH-related scores facilitated identification of patients with different prognoses. An immune signature based on 10 IGPs was constructed to stratify patients into low and high risk groups, exhibiting different clinical outcomes. A nomogram, combining immune signature, 1p/19q status, and tumor grade, was able to predict the overall survival (OS) with c-indices of 0.85, 0.80, 0.80, 0.79, and 0.75 in the training, internal validation, external validation, and tissue sample cohorts, respectively.

CONCLUSIONS

This study was the first to report a comparative profiling of immune genes in large LGG cohorts. A promising individualized immune signature was developed to estimate the survival time for LGG patients.

Does Modern Lifestyle Favor Neuroimmunometabolic Changes? A Path to Obesity

Factors linked to modern lifestyles, such as physical inactivity, Western diet, and poor sleep quality have been identified as key contributors to the positive energy balance (PEB). PEB rises adipose tissue hypertrophy and dysfunction over the years, affecting cells and tissues that are metabolically critical for energy homeostasis regulation, especially skeletal muscle, hypothalamic-pituitary-adrenal axis, and gut microbiota. It is known that the interaction among lifestyle factors and tissue metabolic dysfunction increases low-grade chronic systemic inflammation, leading to insulin resistance and other adverse metabolic disorders. Although immunometabolic mechanisms are widely discussed in obesity, neuroimmunoendocrine pathways have gained notoriety, as a link to neuroinflammation and central nervous system disorders. Hypothalamic inflammation has been associated with food intake dysregulation, which comprises homeostatic and non-homeostatic mechanisms, promoting eating behavior changes related to the obesity prevalence. The purpose of this review is to provide an updated and integrated perspective on the effects of Western diet, sleep debt, and physical exercise on the regulation of energy homeostasis and low-grade chronic systemic inflammation. Subsequently, we discuss the intersection between systemic inflammation and neuroinflammation and how it can contribute to energy imbalance, favoring obesity. Finally, we propose a model of interactions between systemic inflammation and neuroinflammation, providing new insights into preventive and therapeutic targets for obesity.

TH2 sensitization in the skin-gut-brain axis: How early-life Th2-mediated inflammation may negatively perpetuate developmental and psychologic abnormalities

We recently reported children with comorbid atopic dermatitis (AD), asthma, allergic rhinitis, and food allergies displaying a 2.7-fold increase in developmental delays.² To this end, we hypothesize unregulated increases in T helper-2 (Th2)-driven inflammation, such as those seen in atopic diseases, can exert deleterious effects on the developing brain. Recognizing that available information is incomplete and that many potential associations are not firmly established, we speculate these effects underlie the association between Th2 sensitization and cognitive dysfunction in children. In this review, we explore the role of Th2 sensitization in the skin-gut-brain axis and explain how it can lead to reduced connectivity and transmission in the developing brain. With a focus on AD, we explore the association between Th2 sensitization and developmental abnormalities such as developmental delays, memory impairment, autism spectrum disorder (ASD), and epilepsy/seizures. As such, we review the available literature to examine the impact of increased IL-4 exposure in early life on the brain. We explore the possible association between Th2 sensitization and psychologic dysfunction such as attention-deficit/hyperactivity disorder (ADHD), depression, anxiety, and suicidal ideation. We also examine the impact that increased exposure to glucocorticoids and neurotrophins in early life exerts on the developing brain. Last, we discuss future directions for the advancement of our knowledge as a scientific community including possible interventions to reduce developmental and psychologic aberrations in children.

The Effects of Incensole Acetate on Neuro-inflammation, Brain-Derived Neurotrophic Factor and Memory Impairment Induced by Lipopolysaccharide in Rats

Incensole acetate (IA) is a major component of Boswellia serrata resin that has been shown to have anti-inflammatory, anti-oxidant and neuroprotective properties. The present study determined the effect of IA on lipopolysaccharide (LPS)-induced memory impairment, and hippocampal cytokines and oxidative stress indicators level. We used 32 Wistar rats (220-250 g weight) randomly divided into four groups. The control group, which only received the saline-diluted DMSO (vehicle); LPS group which received LPS and was treated with the vehicle; and two IA-treated groups which received 2.5 or 5 mg/ kg IA before LPS injection. Morris water maze (MWM) and passive avoidance (PA) tests were performed. Finally, the brains were removed and were used to assess cytokines levels and oxidative stress status. Compared to the LPS group, IA administration reduced the time spent and path traveled to reach the hidden platform during 5 days of learning in MWM while increased the time spent in the target quadrant in the probe test. Moreover, IA increased latency while decreased entry number and time spent in the dark chamber of PA test compared to the LPS group. Additionally, pre-treatment with IA attenuated interleukin(IL)-6, tumor necrosis alpha (TNF-α), glial fibrillary acidic protein (GFAP), malondialdehyde (MDA) and nitric oxide (NO) metabolites levels while increased those of IL-10, total thiol, superoxide dismutase (SOD), catalase (CAT) and brain-derived neurotrophic factor (BDNF). Our results indicated that IA improved LPS-induced learning and memory impairments. The observed effects seem to be mediated via a protective activity against neuro-inflammation and brain tissue oxidative damage and through improving BDNF.

Effects of lead exposure on the activation of microglia in mice fed with high-fat diets

Lead (Pb) exposure can cause central nervous system (CNS) damage. The process of Pb neurotoxicity is accompanied by the microglia activation. In addition, microglia activation was observed under the intervention of high-fat diets (HFD). This study was designed to investigate the effect of Pb on the cognitive function of mice with HFD, with focus on the microglia activation in brain. Male C57BL/6J mice, 8 weeks of age, were randomly divided into control, HFD, Pb, and HFD + Pb groups. The results showed that HFD following Pb exposure could exacerbate the learning and memory impairment in mice. Pb exposure could promote microglia activation and increase the expression of M1 microglia marker and decrease the expression of M2 microglia marker in the hippocampus of mice with HFD. Our finding suggested that Pb exposure may aggravate CNS damage by promoting M1 polarization and inhibiting M2 polarization of hippocampal microglia in HFD mice.

Interleukin-10 deficiency exacerbates inflammation-induced tau pathology

BACKGROUND

The presence of hyperphosphorylated microtubule-associated protein tau is strongly correlated with cognitive decline and neuroinflammation in Alzheimer's disease and related tauopathies. However, the role of inflammation and anti-inflammatory interventions in tauopathies is unclear. Our goal was to determine if removing anti-inflammatory interleukin-10 (IL-10) during an acute inflammatory challenge has any effect on neuronal tau pathology.

METHODS

We induce systemic inflammation in Il10-deficient (Il10-/-) versus Il10+/+ (Non-Tg) control mice using a single intraperitoneal (i.p.) injection of lipopolysaccharide (LPS) to examine microglial activation and abnormal hyperphosphorylation of endogenous mouse tau protein. Tau phosphorylation was quantified by Western blotting and immunohistochemistry. Microglial morphology was quantified by skeleton analysis. Cytokine expression was determined by multiplex electro chemiluminescent immunoassay (MECI) from Meso Scale Discovery (MSD).

RESULTS

Our findings show that genetic deletion of Il10 promotes enhanced neuroinflammation and tau phosphorylation. First, LPS-induced tau hyperphosphorylation was significantly increased in Il10-/- mice compared to controls. Second, LPS-treated Il10-/- mice showed signs of neurodegeneration. Third, LPS-treated Il10-/- mice showed robust IL-6 upregulation and direct treatment of primary neurons with IL-6 resulted in tau hyperphosphorylation on Ser396/Ser404 site.

CONCLUSIONS

These data support that loss of IL-10 activates microglia, enhances IL-6, and leads to hyperphosphorylation of tau on AD-relevant epitopes in response to acute systemic inflammation.

CCL5 via GPX1 activation protects hippocampal memory function after mild traumatic brain injury

Traumatic brain injury (TBI) is a prevalent head injury worldwide which increases the risk of neurodegenerative diseases. Increased reactive oxygen species (ROS) and inflammatory chemokines after TBI induces secondary effects which damage neurons. Targeting NADPH oxidase or increasing redox systems are ways to reduce ROS and damage. Earlier studies show that C–C motif chemokine ligand 5 (CCL5) has neurotrophic functions such as promoting neurite outgrowth as well as reducing apoptosis. Although CCL5 levels in blood are associated with severity in TBI patients, the function of CCL5 after brain injury is unclear. In the current study, we induced mild brain injury in C57BL/6 (wildtype, WT) mice and CCL5 knockout (CCL5-KO) mice using a weight-drop model. Cognitive and memory functions in mice were analyzed by Novel-object-recognition and Barnes Maze tests. The memory performance of both WT and KO mice were impaired after mild injury. Cognition and memory function in WT mice quickly recovered after 7 days but recovery took more than 14 days in CCL5-KO mice. FJC, NeuN and Hypoxyprobe staining revealed large numbers of neurons damaged by oxidative stress in CCL5-KO mice after mTBI. NADPH oxidase activity show increased ROS generation together with reduced glutathione peroxidase-1 (GPX1) and glutathione (GSH) activity in CCL5-KO mice; this was opposite to that seen in WT mice. CCL5 increased GPX1 expression and reduced intracellular ROS levels which subsequently increased cell survival both in primary neuron cultures and in an overexpression model using SHSY5Y cell. Memory impairment in CCL5-KO mice induced by TBI could be rescued by i.p. injection of the GSH precursor – N-acetylcysteine (NAC) or intranasal delivery of recombinant CCL5 into mice after injury. We conclude that CCL5 is an important molecule for GPX1 antioxidant activation during post-injury day 1–3, and protects hippocampal neurons from ROS as well as improves memory function after trauma.

Salidroside Improves Chronic Stress Induced Depressive Symptoms Through Microglial Activation Suppression

Depression is a severe neurological disorder highly associated with chronic mental stress stimulation, which involves chronic inflammation and microglial activation in the central nervous system (CNS). Salidroside (SLDS) has been reported to exhibit anti-neuroinflammatory and protective properties on neurological diseases. However, the mechanism underlying the effect of SLDS on depressive symptoms has not been well elaborated. In the present study, the effects of SLDS on depressive behaviors and microglia activation in mice CNS were investigated. Behavioral tests, including Forced swimming test (FST), Open field test (OFT) and Morris water maze (MWM) revealed that SLDS treatment attenuated the depressive behaviors in stress mice. SLDS treatment significantly reduced the microglial immunoreactivity for both Iba-1 and CD68, characteristic of deleterious M1 phenotype in hippocampus of stress mice. Additionally, SLDS inhibited microglial activation involving the suppression of ERK1/2, P38 MAPK and p65 NF-κB activation and thus reduced the expression and release of neuroinflammatory cytokines in stress mice as well as in lipopolysaccharide (LPS)-induced primary microglia. Also, SLDS changed microglial morphology, attachment and reduced the phagocytic ability in LPS-induced primary microglia. The results demonstrated that SLDS treatment could improve the depressive symptoms caused by unpredictable chronic stress, indicating a potential therapeutic application of SLDS in depression treatment by interfering microglia-mediated neuroinflammation.

Tetramethylpyrazine Protects Blood-Spinal Cord Barrier Integrity by Modulating Microglia Polarization Through Activation of STAT3/SOCS3 and Inhibition of NF-кB Signaling Pathways in Experimental Autoimmune Encephalomyelitis Mice

We previously reported that tetramethylpyrazine (TMP) alleviates experimental autoimmune encephalomyelitis (EAE) by decreasing glia activation. Activated microglia has been shown to mediate blood-spinal cord barrier (BSCB) disruption, which is a primary and continuous pathological characteristic of multiple sclerosis (MS). Therefore, in this study, we further investigated whether TMP protects the BSCB integrity by inhibition of glia activation to alleviate EAE. Extravasation of evans blue was used to detect the BSCB disruption. Tumor necrosis factor-α (TNF-α)/interlukine-1β (IL-1β) and interlukine-4 (IL-4)/interlukine-10 (IL-10) were determined by enzyme-linked immunosorbent assay. BV2 glial cells stimulated by interferon-γ (IFN-γ) were co-cultured with human brain microvascular endothelial cells to investigate the effect of TMP on the BSCB disruption. Flow cytometry was used to analyze the microglia phenotype. Western blot was performed to reveal the signaling pathways involved in the microglia activation. In this study, most importantly, we found that TMP protects the BSCB integrity by modulating microglia polarization from M1 phenotype to M2 phenotype through activation of STAT3/SOCS3 and inhibition of NF-кB signaling pathways. Moreover, TMP significantly preserves the tight junction proteins, reduces the secretion of pro-inflammatory cytokines (TNF-α, IL-1β) and increases the secretion of anti-inflammatory cytokines (IL-4, IL-10) from IFN-γ-stimulated BV2 microglia cells. Consequently, protection of the BSCB integrity leads to alleviation of clinical symptoms and demyelination in EAE mice. Therefore, TMP might be an effective therapeutic agent for cerebral disorders with BBB or BSCB disruption, such as ischemic stroke, MS, and traumatic brain injury.

Lutein Exerts Antioxidant and Anti-Inflammatory Effects and Influences Iron Utilization of BV-2 Microglia

Lutein is a tetraterpene carotenoid, which has been reported as an important antioxidant and it is widely used as a supplement. Oxidative stress participates in many human diseases, including different types of neurodegenerative disorders. Microglia, the primary immune effector cells in the central nervous system, are implicated in these disorders by producing harmful substances such as reactive oxygen species (ROS). The protective mechanisms which scavenge ROS include enzymes and antioxidant substances. The protective effects of different carotenoids against oxidative stress have been described previously. Our study focuses on the effects of lutein on antioxidant enzymes, cytokines and iron metabolism under stress conditions in BV-2 microglia. We performed cell culture experiments: BV-2 cells were treated with lutein and/or with H₂O₂; the latter was used for inducing oxidative stress in microglial cells. Real-time PCR was performed for gene expression analyses of antioxidant enzymes, and ELISA was used for the detection of pro- and anti-inflammatory cytokines. Our results show that the application of lutein suppressed the H₂O₂-induced ROS (10′: 7.5 ng + 10 µM H₂O₂, p = 0.0002; 10 ng/µL + 10 µM H₂O₂, p = 0.0007), influenced iron utilization and changed the anti-inflammatory and pro-inflammatory cytokine secretions in BV-2 cells. Lutein increased the IL-10 secretions compared to control (24 h: 7.5 ng/µL p = 0.0274; 10 ng/µL p = 0.0008) and to 10 µM H₂O₂-treated cells (24 h: 7.5 ng/µL + H₂O₂, p = 0.0003; 10 ng/µL + H₂O₂, p = 0.0003), while it decreased the TNFα secretions compared to H₂O₂ treated cells (24 h: 7.5 ng/µL + H₂O₂, p < 0.0001; 10 ng/µL + H₂O₂, p < 0.0001). These results contribute to understanding the effects of lutein, which may help in preventing or suppressing ROS-mediated microglia activation, which is related to neuronal degeneration in oxidative stress scenario.

Complement Has Brains-Do Intracellular Complement and Immunometabolism Cooperate in Tissue Homeostasis and Behavior?

The classical liver-derived and serum-effective complement system is well appreciated as a key mediator of host protection via instruction of innate and adaptive immunity. However, recent studies have discovered an intracellularly active complement system, the complosome, which has emerged as a central regulator of the core metabolic pathways fueling human immune cell activity. Induction of expression of components of the complosome, particularly complement component C3, during transmigration from the circulation into peripheral tissues is a defining characteristic of monocytes and T cells in tissues. Intracellular complement activity is required to induce metabolic reprogramming of immune cells, including increased glycolytic flux and OXPHOS, which drive the production of the pro-inflammatory cytokine IFN-γ. Consequently, reduced complosome activity translates into defects in normal monocyte activation, faulty Th1 and cytotoxic T lymphocyte responses and loss of protective tissue immunity. Intriguingly, neurological research has identified an unexpected connection between the physiological presence of innate and adaptive immune cells and certain cytokines, including IFN-γ, in and around the brain and normal brain function. In this opinion piece, we will first review the current state of research regarding complement driven metabolic reprogramming in the context of immune cell tissue entry and residency. We will then discuss how published work on the role of IFN-γ and T cells in the brain support a hypothesis that an evolutionarily conserved cooperation between the complosome, cell metabolism and IFN-γ regulates organismal behavior, as well as immunity.