Neuroinflammation: the devil is in the details

HDAC8 Inhibition Reduces Lesional Iba-1+ Cell Infiltration after Spinal Cord Injury without Effects on Functional Recovery

Pan-histone deacetylase (HDAC) inhibition with valproic acid (VPA) has beneficial effects after spinal cord injury (SCI), although with side effects. We focused on specific HDAC8 inhibition, because it is known to reduce anti-inflammatory mediators produced by macrophages (Mφ). We hypothesized that HDAC8 inhibition improves functional recovery after SCI by reducing pro-inflammatory classically activated Mφ. Specific HDAC8 inhibition with PCI-34051 reduced the numbers of perilesional Mφ as measured by histological analyses, but did not improve functional recovery (Basso Mouse Scale). We could not reproduce the published improvement of functional recovery described in contusion SCI models using VPA in our T-cut hemisection SCI model. The presence of spared fibers might be the underlying reason for the conflicting data in different SCI models.

Neuroprotective effect of novel celecoxib derivatives against spinal cord injury via attenuation of COX-2, oxidative stress, apoptosisand inflammation

A novel series of celecoxib derivatives were synthesized and evaluated for cyclooxygenase (COX-1/COX-2) inhibitory activities for benefit in spinal cord injury (SCI). The title compounds were synthesized by conventional methods in good yields and subsequently tested for inhibitory activity against COX-1/COX-2. The most potent COX-2 inhibitor among the tested derivatives was further assayed for protective effect against experimental SCI of Sprague-Dawley rats. The designed compounds showed considerable inhibition of COX-2 as compared to COX-1 revealing compound 7m as most potent inhibitor of COX-2 isoenzyme (IC₅₀ = 0.04 µM). The expression of mitochondrial apoptotic genes (Bcl-2 and Bax) together with COX-2 and iNOS was restored near to normal as evidenced by western blot analysis in SCI rats. Taken altogether, compound 7m was identified as most potent inhibitor of COX-2. It also showed protective action against SCI via attenuation of COX-2, oxidative stress and apoptosis and inflammation in Male Sprague-Dawley rats.

P2X7 Receptor Antagonism as a Potential Therapy in Amyotrophic Lateral Sclerosis

This review focuses on the purinergic ionotropic receptor P2X7 (P2X7R) as a potential target for developing drugs that delay the onset and/or disease progression in patients with amyotrophic lateral sclerosis (ALS). Description of clinical and genetic ALS features is followed by an analysis of advantages and drawbacks of transgenic mouse models of disease based on mutations in a bunch of proteins, particularly Cu/Zn superoxide dismutase (SOD1), TAR-DNA binding protein-43 (TDP-43), Fused in Sarcoma/Translocated in Sarcoma (FUS), and Chromosome 9 open reading frame 72 (C9orf72). Though of limited value, these models are however critical to study the proof of concept of new compounds, before reaching clinical trials. The authors also provide a description of ALS pathogenesis including protein aggregation, calcium-dependent excitotoxicity, dysfunction of calcium-binding proteins, ultrastructural mitochondrial alterations, disruption of mitochondrial calcium handling, and overproduction of reactive oxygen species (ROS). Understanding disease pathogenic pathways may ease the identification of new drug targets. Subsequently, neuroinflammation linked with P2X7Rs in ALS pathogenesis is described in order to understand the rationale of placing the use of P2X7R antagonists as a new therapeutic pharmacological approach to ALS. This is the basis for the hypothesis that a P2X7R blocker could mitigate the neuroinflammatory state, indirectly leading to neuroprotection and higher motoneuron survival in ALS patients.

Differential early effects of traumatic brain injury on spike-wave discharges in Sprague-Dawley rats

Unprovoked seizures in the late period of traumatic brain injury (TBI) occur in almost 20% of humans and experimental animals, psychiatric comorbidities being common in both situations. The aim of the study was to evaluate epileptiform activity in the early period of TBI induced by lateral fluid percussion brain injury in adult male Srague-Dawley rats and to reveal potential behavioral and pathomorphological correlates of early electrophysiological alterations. One week after TBI the group of animals was remarkably heterogeneous regarding the incidence of bifrontal 7-Hz spikes and spike-wave discharges (SWDs). It consisted of 3 typical groups: a) rats with low baseline and high post-craniotomy SWD level; b)with constantly low both baseline and post-craniotomy SWD levels; c) constantly high both baseline and post-craniotomy SWD levels. Rats with augmented SWD occurrence after TBI demonstrated freezing episodes accompanying SWDs as well as increased anxiety-like behavior (difficulty of choosing). The discharges were definitely associated with sleep phases. The incidence of SWDs positively correlated with the area of glial activation in the neocortex but not in the hippocampus.The translational potential of the data is revealing new pathophysiological links between epileptiform activity appearance, direct cortical and distant hippocampal damage and anxiety-like behavior, putative early predictors of late posttraumatic pathology.

Morphology of perivascular spaces and enclosed blood vessels in young to middle-aged healthy adults at 7T: Dependences on age, brain region, and breathing gas

Perivascular spaces (PVSs) are fluid-filled spaces surrounding penetrating blood vessels in the brain and are an integral pathway of the glymphatic system. A PVS and the enclosed blood vessel are commonly visualized as a single vessel-like complex (denoted as PVSV) in high-resolution MRI images. Quantitative characterization of the PVSV morphology in MRI images in healthy subjects may serve as a reference for detecting disease related PVS and/or blood vessel alterations in patients with brain diseases.

To this end, we evaluated the age dependences, spatial heterogeneities, and dynamic properties of PVSV morphological features in 45 healthy subjects (21–55 years old), using an ultra-high-resolution three-dimensional transverse relaxation time weighted MRI sequence (0.41 × 0.41 × 0.4 mm³) at 7T. Quantitative PVSV parameters, including apparent diameter, count, volume fraction (VF), and relative contrast to noise ratio (rCNR) were calculated in the white matter and subcortical structures. Dynamic changes were induced by carbogen breathing which are known to induce vasodilation and increase the blood oxygenation level in the brain.

PVSV count and VF significantly increased with age in basal ganglia (BG), so did rCNR in BG, midbrain, and white matter (WM). Apparent PVSV diameter also showed a positive association with age in the three brain regions, although it did not reach statistical significance. The PVSV VF and count showed large inter-subject variations, with coefficients of variation ranging from 0.17 to 0.74 after regressing out age and gender effects. Both apparent diameter and VF exhibited significant spatial heterogeneity, which cannot be explained solely by radio-frequency field inhomogeneities. Carbogen breathing significantly increased VF in BG and WM, and rCNR in thalamus, BG, and WM compared to air breathing.

Our results are consistent with gradual dilation of PVSs with age in healthy adults. The PVSV morphology exhibited spatial heterogeneity and large inter-subject variations and changed during carbogen breathing compared to air breathing.

Antioxidant and Neuroprotective Effects Induced by Cannabidiol and Cannabigerol in Rat CTX-TNA2 Astrocytes and Isolated Cortexes

Cannabidiol (CBD) and cannabigerol (CBG) are Cannabis sativa terpenophenols. Although CBD’s effectiveness against neurological diseases has already been demonstrated, nothing is known about CBG. Therefore, a comparison of the effects of these compounds was performed in two experimental models mimicking the oxidative stress and neurotoxicity occurring in neurological diseases. Rat astrocytes were exposed to hydrogen peroxide and cell viability, reactive oxygen species production and apoptosis occurrence were investigated. Cortexes were exposed to K⁺ 60 mM depolarizing stimulus and serotonin (5-HT) turnover, 3-hydroxykinurenine and kynurenic acid levels were measured. A proteomic analysis and bioinformatics and docking studies were performed. Both compounds exerted antioxidant effects in astrocytes and restored the cortex level of 5-HT depleted by neurotoxic stimuli, whereas sole CBD restored the basal levels of 3-hydroxykinurenine and kynurenic acid. CBG was less effective than CBD in restoring the levels of proteins involved in neurotransmitter exocytosis. Docking analyses predicted the inhibitory effects of these compounds towards the neurokinin B receptor. Conclusion: The results in the in vitro system suggest brain non-neuronal cells as a target in the treatment of oxidative conditions, whereas findings in the ex vivo system and docking analyses imply the potential roles of CBD and CBG as neuroprotective agents.

Focus on the Role of Klotho Protein in Neuro-Immune Interactions in HT-22 Cells Upon LPS Stimulation

Neuroinflammation is defined as the activation of the brain's innate immune system in response to an inflammatory challenge and is considered to be a prominent feature of neurodegenerative diseases. The contribution of overactivated neuroglial cells to neuroinflammation and neurodegenerative disorders is well documented, however, the role of hippocampal neurons in the neuroinflammatory process remains fragmentary. In this study, we show for the first time, that klotho acts as a signal transducer between pro-survival and pro-apoptotic crosstalk mediated by ER stress in HT-22 hippocampal neuronal cells during LPS challenge. In control HT-22 cells, LPS treatment results in activation of the IRE1α-p38 MAPK pathway leading to increased secretion of anti-inflammatory IL-10, and thus, providing adaptation mechanism. On the other hand, in klotho-deficient HT-22 cells, LPS induces oxi-nitrosative stress and genomic instability associated with telomere dysfunctions leading to p53/p21-mediated cell cycle arrest and, in consequence, to ER stress, inflammation as well as of apoptotic cell death. Therefore, these results indicate that klotho serves as a part of the cellular defense mechanism engaged in the protection of neuronal cells against LPS-mediated neuroinflammation, emerging issues linked with neurodegenerative disorders.

Assessment of Glial Activation Response in the Progress of Natural Scrapie after Chronic Dexamethasone Treatment

Neuroinflammation has been correlated with the progress of neurodegeneration in many neuropathologies. Although glial cells have traditionally been considered to be protective, the concept of them as neurotoxic cells has recently emerged. Thus, a major unsolved question is the exact role of astroglia and microglia in neurodegenerative disorders. On the other hand, it is well known that glucocorticoids are the first choice to regulate inflammation and, consequently, neuroglial inflammatory activity. The objective of this study was to determine how chronic dexamethasone treatment influences the host immune response and to characterize the beneficial or detrimental role of glial cells. To date, this has not been examined using a natural neurodegenerative model of scrapie. With this aim, immunohistochemical expression of glial markers, prion protein accumulation, histopathological lesions and clinical evolution were compared with those in a control group. The results demonstrated how the complex interaction between glial populations failed to compensate for brain damage in natural conditions, emphasizing the need for using natural models. Additionally, the data showed that modulation of neuroinflammation by anti-inflammatory drugs might become a research focus as a potential therapeutic target for prion diseases, similar to that considered previously for other neurodegenerative disorders classified as prion-like diseases.

PET measurement of cyclooxygenase-2 using a novel radioligand: upregulation in primate neuroinflammation and first-in-human study

Background

Cyclooxygenase-2 (COX-2), which is rapidly upregulated by inflammation, is a key enzyme catalyzing the rate-limiting step in the synthesis of several inflammatory prostanoids. Successful positron emission tomography (PET) radioligand imaging of COX-2 in vivo could be a potentially powerful tool for assessing inflammatory response in the brain and periphery. To date, however, the development of PET radioligands for COX-2 has had limited success.

Methods

The novel PET tracer [¹¹C]MC1 was used to examine COX-2 expression [1] in the brains of four rhesus macaques at baseline and after injection of the inflammogen lipopolysaccharide (LPS) into the right putamen, and [2] in the joints of two human participants with rheumatoid arthritis and two healthy individuals. In the primate study, two monkeys had one LPS injection, and two monkeys had a second injection 33 and 44 days, respectively, after the first LPS injection. As a comparator, COX-1 expression was measured using [¹¹C]PS13.

Results

COX-2 binding, expressed as the ratio of specific to nondisplaceable uptake (BP_ND) of [¹¹C]MC1, increased on day 1 post-LPS injection; no such increase in COX-1 expression, measured using [¹¹C]PS13, was observed. The day after the second LPS injection, a brain lesion (~ 0.5 cm in diameter) with high COX-2 density and high BP_ND (1.8) was observed. Postmortem brain analysis at the gene transcript or protein level confirmed in vivo PET results. An incidental finding in an unrelated monkey found a line of COX-2 positivity along an incision in skull muscle, demonstrating that [¹¹C]MC1 can localize inflammation peripheral to the brain. In patients with rheumatoid arthritis, [¹¹C]MC1 successfully imaged upregulated COX-2 in the arthritic hand and shoulder and apparently in the brain. Uptake was blocked by celecoxib, a COX-2 preferential inhibitor.

Conclusions

Taken together, these results indicate that [¹¹C]MC1 can image and quantify COX-2 upregulation in both monkey brain after LPS-induced neuroinflammation and in human peripheral tissue with inflammation.

Trial registration

ClinicalTrials.gov NCT03912428. Registered April 11, 2019.

Recent advances in understanding and managing hepatic encephalopathy in chronic liver disease

Hepatic encephalopathy (HE) is a common, severe complication of advanced chronic liver disease (CLD) and has a devastating impact on the patient’s quality of life and prognosis. The neurotoxin ammonia and the presence of systemic and neurological inflammation are considered the key drivers of this neuropsychiatric syndrome. Treatment options available in routine clinical practice are limited, and the development of novel therapies is hampered owing to the complexity and heterogeneity of HE. This review article aims to outline the current understanding of the pathomechanisms of HE and the recent advances in the identification and development of novel therapeutic targets.

Overview of Brain-to-Gut Axis Exposed to Chronic CNS Bacterial Infection(s) and a Predictive Urinary Metabolic Profile of a Brain Infected by Mycobacterium tuberculosis

A new paradigm in neuroscience has recently emerged - the brain-gut axis (BGA). The contemporary focus in this paradigm has been gut → brain ("bottom-up"), in which the gut-microbiome, and its perturbations, affects one's psychological state-of-mind and behavior, and is pivotal in neurodegenerative disorders. The emerging brain → gut ("top-down") concept, the subject of this review, proposes that dysfunctional brain health can alter the gut-microbiome. Feedback of this alternative bidirectional highway subsequently aggravates the neurological pathology. This paradigm shift, however, focuses upon non-communicable neurological diseases (progressive neuroinflammation). What of infectious diseases, in which pathogenic bacteria penetrate the blood-brain barrier and interact with the brain, and what is this effect on the BGA in bacterial infection(s) that cause chronic neuroinflammation? Persistent immune activity in the CNS due to chronic neuroinflammation can lead to irreversible neurodegeneration and neuronal death. The properties of cerebrospinal fluid (CSF), such as immunological markers, are used to diagnose brain disorders. But what of metabolic markers for such purposes? If a BGA exists, then chronic CNS bacterial infection(s) should theoretically be reflected in the urine. The premise here is that chronic CNS bacterial infection(s) will affect the gut-microbiome and that perturbed metabolism in both the CNS and gut will release metabolites into the blood that are filtered (kidneys) and excreted in the urine. Here we assess the literature on the effects of chronic neuroinflammatory diseases on the gut-microbiome caused by bacterial infection(s) of the CNS, in the context of information attained via metabolomics-based studies of urine. Furthermore, we take a severe chronic neuroinflammatory infectious disease - tuberculous meningitis (TBM), caused by Mycobacterium tuberculosis, and examine three previously validated CSF immunological biomarkers - vascular endothelial growth factor, interferon-gamma and myeloperoxidase - in terms of the expected changes in normal brain metabolism. We then model the downstream metabolic effects expected, predicting pivotal altered metabolic pathways that would be reflected in the urinary profiles of TBM subjects. Our cascading metabolic model should be adjustable to account for other types of CNS bacterial infection(s) associated with chronic neuroinflammation, typically prevalent, and difficult to distinguish from TBM, in the resource-constrained settings of poor communities.

Glial cells involvement in spinal muscular atrophy: Could SMA be a neuroinflammatory disease?

Spinal muscular atrophy (SMA) is a severe, inherited disease characterized by the progressive degeneration and death of motor neurons of the anterior horns of the spinal cord, which results in muscular atrophy and weakness of variable severity. Its early-onset form is invariably fatal in early childhood, while milder forms lead to permanent disability, physical deformities and respiratory complications. Recently, two novel revolutionary therapies, antisense oligonucleotides and gene therapy, have been approved, and might prove successful in making long-term survival of these patients likely. In this perspective, a deep understanding of the pathogenic mechanisms and of their impact on the interactions between motor neurons and other cell types within the central nervous system (CNS) is crucial. Studies using SMA animal and cellular models have taught us that the survival and functionality of motor neurons is highly dependent on a whole range of other cell types, namely glial cells, which are responsible for a variety of different functions, such as neuronal trophic support, synaptic remodeling, and immune surveillance. Thus, it emerges that SMA is likely a non-cell autonomous, multifactorial disease in which the interaction of different cell types and disease mechanisms leads to motor neurons failure and loss. This review will introduce the different glial cell types in the CNS and provide an overview of the role of glial cells in motor neuron degeneration in SMA. Furthermore, we will discuss the relevance of these findings so far and the potential impact on the success of available therapies and on the development of novel ones.

Mitochondrial biogenesis as a therapeutic target for traumatic and neurodegenerative CNS diseases

Central nervous system (CNS) diseases, both traumatic and neurodegenerative, are characterized by impaired mitochondrial bioenergetics and often disturbed mitochondrial dynamics. The dysregulation observed in these pathologies leads to defective respiratory chain function and reduced ATP production, thereby promoting neuronal death. As such, attenuation of mitochondrial dysfunction through induction of mitochondrial biogenesis (MB) is a promising, though still underexplored, therapeutic strategy. MB is a multifaceted process involving the integration of highly regulated transcriptional events, lipid membrane and protein synthesis/assembly and replication of mtDNA. Several nuclear transcription factors promote the expression of genes involved in oxidative phosphorylation, mitochondrial import and export systems, antioxidant defense and mitochondrial gene transcription. Of these, the nuclear-encoded peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) is the most commonly studied and is widely accepted as the 'master regulator' of MB. Several recent preclinical studies document that reestablishment of mitochondrial homeostasis through increased MB results in inhibited injury progression and increased functional recovery. This perspective will briefly review the role of mitochondrial dysfunction in the propagation of CNS diseases, while also describing current research strategies that mediate mitochondrial dysfunction and compounds that induce MB for the treatment of acute and chronic neuropathologies.

In vitro attenuation of astrocyte activation and neuroinflammation through ibuprofen-doping of poly(3,4-ethylenedioxypyrrole) formulations

Neuroinflammation is often associated with poor functional recovery and may contribute to or initiate the development of severe neurological disorders, such as epilepsy, Parkinson's disease or Alzheimer's disease. Ibuprofen (IBU), being one of the most commonly used non-steroidal anti-inflammatory drugs, is known to possess neuroprotective activity and serve as a promising therapeutic for the treatment of neuroinflammation. In this study, the potential of an IBU-loaded poly(3,4-ethylenedioxypyrrole) (PEDOP) matrix has been assessed as a neural interface material with an aim to control astrocyte activation and suppress neuroinflammation in vitro. Three types of drug immobilization protocols were investigated, leading to the fabrication of IBU-loaded PEDOP matrices exhibiting a broad spectrum of electrical characteristics, drug release profiles, as well as biological responses. Among all investigated PEDOP formulations, PEDOP matrices formed through a three-step immobilization protocol exhibited the highest charge storage capacity (30 ± 1 mC/cm²) as well as a double layer capacitance of 645.0 ± 51.1 µF, associated with a relatively enlarged surface area. Demonstrating a total drug loading capacity of 150 µg/ml and a release rate constant of 0.15 1/h, this coating formulation may be employed as a safe electrical conducting drug eluting system.

Cytochrome P450 derived epoxidized fatty acids as a therapeutic tool against neuroinflammatory diseases

Cytochrome P450 (CYP) metabolism of arachidonic acid (ARA) produces epoxy fatty acids (EpFAs) such as epoxyeicosatrienoic acids (EETs) that are known to exert protective effects in inflammatory disorders. Endogenous EpFAs are further metabolized into corresponding diols by the soluble epoxide hydrolase (sEH). Through inhibition of sEH, many studies have demonstrated the cardioprotective and renoprotective effects of EpFAs; however, the role of sEH inhibition in modulating the pathogenesis of neuroinflammatory disorders is less well described. In this review, we discuss the current knowledge surrounding the effects of sEH inhibition and EpFA action in neuroinflammatory disorders such as Parkinson's Disease (PD), stroke, depression, epilepsy, and Alzheimer's Disease (AD), as well as the potential mechanisms that underlie the therapeutic effects of sEH inhibition.

Neuroinflammatory and Behavioral Outcomes Measured in Adult Offspring of Mice Exposed Prenatally to E-Cigarette Aerosols

BACKGROUND

In an effort to decrease the rates of smoking conventional tobacco cigarettes, electronic cigarettes (e-cigarettes) have been proposed as an effective smoking cessation tool. However, little is known about their toxicological impacts. This is concerning given that e-cigarette use is perceived as less harmful than conventional tobacco cigarettes during pregnancy for both the mother and fetus.

OBJECTIVE

The goal of this study was to test the neurodevelopmental consequences of maternal e-cigarette use on adult offspring behavior and neuroimmune outcomes.

METHODS

Pregnant female CD-1 mice were randomly assigned to one of three treatment groups (n=8-10 per group) and exposed daily to either filtered air, propylene glycol and vegetable glycerol (50:50 PG/VG vehicle), or to PG/VG with 16mg/mL nicotine (+Nic). Whole-body exposures were carried out for 3 h/d, 7 d/week, from gestational day (GD)0.5 until GD17.5. Adult male and female offspring (8 weeks old) were assessed across a battery of behavioral assessments followed by region-specific quantification of brain cytokines using multiplex immunoassays.

RESULTS

Adult offspring of both sexes exposed to +Nic exhibited elevated locomotor activity in the elevated plus maze and altered stress-coping strategies in the forced swim task. Moreover, male and female offspring exposed to PG/VG with and without nicotine had a 5.2% lower object discrimination score in the novel object recognition task. In addition to differences in offspring behavior, maternal e-cigarette exposure with nicotine led to a reduction in interleukin (IL)-4 and interferon-gamma (IFNγ) in the diencephalon, as well as lower levels of hippocampal IFNγ (females only). E-cigarette exposure without nicotine resulted in a 2-fold increase of IL-6 in the cerebellum.

DISCUSSION

These findings support previous adverse findings of e-cigarette exposure on neurodevelopment in a mouse model and provide substantial evidence of persistent adverse behavioral and neuroimmunological consequences to adult offspring following maternal e-cigarette exposure during pregnancy. https://doi.org/10.1289/EHP6067.

Complement: Bridging the innate and adaptive immune systems in sterile inflammation

The complement system is a collection of soluble and membrane-bound proteins that together act as a powerful amplifier of the innate and adaptive immune systems. Although its role in infection is well established, complement is becoming increasingly recognized as a key contributor to sterile inflammation, a chronic inflammatory process often associated with noncommunicable diseases. In this context, damaged tissues release danger signals and trigger complement, which acts on a range of leukocytes to augment and bridge the innate and adaptive immune systems. Given the detrimental effect of chronic inflammation, the complement system is therefore well placed as an anti-inflammatory drug target. In this review, we provide a general outline of the sterile activators, effectors, and targets of the complement system and a series of examples (i.e., hypertension, cancer, allograft transplant rejection, and neuroinflammation) that highlight complement's ability to bridge the 2 arms of the immune system.

Gut microbiota and neuroinflammation in pathogenesis of hypertension: A potential role for hydrogen sulfide

Inflammation and gut dysbiosis are hallmarks of hypertension (HTN). Hydrogen sulfide (H2S) is an important freely diffusing molecule that modulates the function of neural, cardiovascular and immune systems, and circulating levels of H2S are reduced in animals and humans with HTN. While most research to date has focused on H₂S produced endogenously by the host, H2S is also produced by the gut bacteria and may affect the host homeostasis. Here, we review an association between neuroinflammation and gut dysbiosis in HTN, with special emphasis on a potential role of H2S in this interplay.

Combined Brain-Heart Magnetic Resonance Imaging in Autoimmune Rheumatic Disease Patients with Cardiac Symptoms: Hypothesis Generating Insights from a Cross-sectional Study

BACKGROUND

Autoimmune rheumatic diseases (ARDs) may affect both the heart and the brain. However, little is known about the interaction between these organs in ARD patients. We asked whether brain lesions are more frequent in ARD patients with cardiac symptoms compared with non-ARD patients with cardiovascular disease (CVD).

METHODS

57 ARD patients with mean age of 48 ± 13 years presenting with shortness of breath, chest pain, and/or palpitations, and 30 age-matched disease-controls with non-autoimmune CVD, were evaluated using combined brain-heart magnetic resonance imaging (MRI) in a 1.5T system.

RESULTS

52 (91%) ARD patients and 16 (53%) controls had white matter hyperintensities (p < 0.001) in at least one brain area (subcortical/deep/periventricular white matter, basal ganglia, pons, brainstem, or mesial temporal lobe). Only the frequency and number of subcortical and deep white matter lesions were significantly greater in ARD patients (p < 0.001 and 0.014, respectively). ARD vs. control status was the only independent predictor of having any brain lesion. Specifically for deep white matter lesions, each increase in ECV independently predicted a higher number of lesions [odds ratio (95% confidence interval): 1.16 (1.01-1.33), p = 0.031] in ordered logistic regression. Penalized logistic regression selected only ARD vs. control status as the most important feature for predicting whether brain lesions were present on brain MRI (odds ratio: 5.46, marginal false discovery rate = 0.011).

CONCLUSIONS

Subclinical brain involvement was highly prevalent in this cohort of ARD patients and was mostly independent of the severity of cardiac involvement. However, further research is required to determine the clinical relevance of these findings.

Immune Challenges and Seizures: How Do Early Life Insults Influence Epileptogenesis?

The development of epilepsy, a process known as epileptogenesis, often occurs later in life following a prenatal or early postnatal insult such as cerebral ischemia, stroke, brain trauma, or infection. These insults share common pathophysiological pathways involving innate immune activation including neuroinflammation, which is proposed to play a critical role in epileptogenesis. This review provides a comprehensive overview of the latest preclinical evidence demonstrating that early life immune challenges influence neuronal hyperexcitability and predispose an individual to later life epilepsy. Here, we consider the range of brain insults that may promote the onset of chronic recurrent spontaneous seizures at adulthood, spanning intrauterine insults (e.g. maternal immune activation), perinatal injuries (e.g. hypoxic–ischemic injury, perinatal stroke), and insults sustained during early postnatal life—such as fever-induced febrile seizures, traumatic brain injuries, infections, and environmental stressors. Importantly, all of these insults represent, to some extent, an immune challenge, triggering innate immune activation and implicating both central and systemic inflammation as drivers of epileptogenesis. Increasing evidence suggests that pro-inflammatory cytokines such as interleukin-1 and subsequent signaling pathways are important mediators of seizure onset and recurrence, as well as neuronal network plasticity changes in this context. Our current understanding of how early life immune challenges prime microglia and astrocytes will be explored, as well as how developmental age is a critical determinant of seizure susceptibility. Finally, we will consider the paradoxical phenomenon of preconditioning, whereby these same insults may conversely provide neuroprotection. Together, an improved appreciation of the neuroinflammatory mechanisms underlying the long-term epilepsy risk following early life insults may provide insight into opportunities to develop novel immunological anti-epileptogenic therapeutic strategies.

Protection against acute cerebral ischemia/reperfusion injury by QiShenYiQi via neuroinflammatory network mobilization

Cerebral ischemia/reperfusion injury (CI/RI) is a common feature of ischemic stroke, involving a period of impaired blood supply to the brain, followed by the restoration of cerebral perfusion through medical intervention. Although ischemia and reperfusion brain damage is a complex pathological process with an unclear physiological mechanism, more attention is currently focused on the neuroinflammatory response of an ischemia/reperfusion origin, and anti-inflammatory appears to be a potential therapeutic strategy following ischemic stroke. QiShenYiQi (QSYQ), a component-based Chinese medicine with Qi-tonifying and blood-activating property, has pharmacological actions of anti-inflammatory, antioxidant, mitochondrial protectant, anti-apoptosis, and antiplatelet aggregation. We have previously reported that the cardioprotective effect of QSYQ against ischemia/reperfusion injury is via improvement of mitochondrial functional integrity. In this research work, we aimed to investigate the possible mechanism involved in the neuroprotection of QSYQ in mice model of cerebral ischemia/reperfusion injury based on the inflammatory pathway. The cerebral protection was evaluated in the stroke mice after 24 h reperfusion by assessing the neurological deficit, cerebral infarction, brain edema, BBB functionality, and via histopathological assessment. TCM-based network pharmacology method was performed to establish and analyze compound-target-disease & function-pathway network so as to find the possible mechanism linking to the role of QSYQ in CI/RI. In addition, RT-qPCR was used to verify the accuracy of predicted signaling gene expression. As a result, improvement of neurological outcome, reduction of infarct volume and brain edema, a decrease in BBB disruption, and amelioration of histopathological alteration were observed in mice pretreated with QSYQ after experimental stroke surgery. Network pharmacology analysis revealed neuroinflammatory response was associated with the action of QSYQ in CI/RI. RT-qPCR data showed that the mice pretreated with QSYQ could significantly decrease IFNG-γ, IL-6, TNF-α, NF-κB p65, and TLR-4 mRNA levels and increase TGF-β1 mRNA level in the brain compared to the untreated mice after CI/RI (p < 0.05). In conclusion, our study indicated the cerebral protective effect of pretreatment with QSYQ against CI/RI, which may be partly related to its potential to the reduction of neuroinflammatory response in a stroke subject.

Integrative network analysis identifies differential regulation of neuroimmune system in Schizophrenia and Bipolar disorder

Background

Neuropsychiatric disorders such as Schizophrenia (SCZ) and Bipolar disorder (BPD) pose a broad range of problems with different symptoms mainly characterized by some combination of abnormal thoughts, emotions, behaviour, etc. However, in depth molecular and pathophysiological mechanisms among different neuropsychiatric disorders have not been clearly understood yet. We have used RNA-seq data to investigate unique and overlapping molecular signatures between SCZ and BPD using an integrative network biology approach.

Methods

RNA-seq count data were collected from NCBI-GEO database generated on post-mortem brain tissues of controls (n = 24) and patients of BPD (n = 24) and SCZ (n = 24). Differentially expressed genes (DEGs) were identified using the consensus of DESeq2 and edgeR tools and used for downstream analysis. Weighted gene correlation networks were constructed to find non-preserved (NP) modules for SCZ, BPD and control conditions. Topological analysis and functional enrichment analysis were performed on NP modules to identify unique and overlapping expression signatures during SCZ and BPD conditions.

Results

We have identified four NP modules from the DEGs of BPD and SCZ. Eleven overlapping genes have been identified between SCZ and BPD networks, and they were found to be highly enriched in inflammatory responses. Among these eleven genes, TNIP2, TNFRSF1A and AC005840.1 had higher sum of connectivity exclusively in BPD network. In addition, we observed that top five genes of NP module from SCZ network were downregulated which may be a key factor for SCZ disorder.

Conclusions

Differential activation of the immune system components and pathways may drive the common and unique pathogenesis of the BPD and SCZ.

Neuroinflammation and glial cell activation in mental disorders

Mental disorders (MDs) are highly prevalent and potentially debilitating complex disorders which causes remain elusive. Looking into deeper aspects of etiology or pathophysiology underlying these diseases would be highly beneficial, as the scarce knowledge in mechanistic and molecular pathways certainly represents an important limitation. Association between MDs and inflammation/neuroinflammation has been widely discussed and accepted by many, as high levels of pro-inflammatory cytokines were reported in patients with several MDs, such as schizophrenia (SCZ), bipolar disorder (BD) and major depression disorder (MDD), among others. Correlation of pro-inflammatory markers with symptoms intensity was also reported. However, the mechanisms underlying the inflammatory dysfunctions observed in MDs are not fully understood yet. In this context, microglial dysfunction has recently emerged as a possible pivotal player, as during the neuroinflammatory response, microglia can be over-activated, and excessive production of pro-inflammatory cytokines, which can modify the kynurenine and glutamate signaling, is reported. Moreover, microglial activation also results in increased astrocyte activity and consequent glutamate release, which are both toxic to the Central Nervous System (CNS). Also, as a result of increased microglial activation in MDs, products of the kynurenine pathway were shown to be changed, influencing then the dopaminergic, serotonergic, and glutamatergic signaling pathways. Therefore, in the present review, we aim to discuss how neuroinflammation impacts on glutamate and kynurenine signaling pathways, and how they can consequently influence the monoaminergic signaling. The consequent association with MDs main symptoms is also discussed. As such, this work aims to contribute to the field by providing insights into these alternative pathways and by shedding light on potential targets that could improve the strategies for pharmacological intervention and/or treatment protocols to combat the main pharmacologically unmatched symptoms of MDs, as the SCZ.

Protective effect of sodium propionate in Aβ1-42 -induced neurotoxicity and spinal cord trauma

Sodium propionate (SP) is one of the main short chain fatty acids (SCFA) that can be produced naturally through host metabolic pathways. SP have been documented and include the reduction of pro-inflammatory mediators in an in vivo model of colitis. The aim of this study is to evaluate the neuroprotective effects of SP in reducing inflammatory process associated to neurological disorders. We performed both in vitro model of Alzheimer's disease, induced by oligomeric Aβ_1-42 stimulation, and in in vivo model of spinal cord injury (SCI) in which neuroinflammation plays a crucial role. For in vitro model, the human neuroblastoma SH-SY5Y cell line was first differentiated with retinoic acid (100 μM) for 24 h and then stimulated by oligomeric Aβ_1-42 (1 μg/ml) and treated with SP at 0.1- 1-10 μM concentrations for another 24 h. Instead, the in vivo model of SCI was induced by extradural compression of the spinal cord at T6-T8 levels, and animals were treated with SP (10-30-100 mg/kg o.s) 1 and 6 h after SCI. Our results demonstrated that both in in vitro neuroinflammatory model and in vivo model of SCI the treatment with SP significantly reduced NF-κB nuclear translocation and IκBα degradation, as well as decreases COX-2 and iNOS expressions evaluated by Western blot analysis. Moreover, we showed that SP treatment significantly ameliorated histopathology changes and improved motor recovery in a dose-dependent manner. In conclusion, our results demonstrated that SP possesses neuroprotective effects, suggesting it could represent a target for therapeutic intervention in neuroinflammatory disorders.

Microglial Phenotypes and Their Relationship to the Cannabinoid System: Therapeutic Implications for Parkinson's Disease

Parkinson’s disease is a neurodegenerative disorder, the motor symptoms of which are associated classically with Lewy body formation and nigrostriatal degeneration. Neuroinflammation has been implicated in the progression of this disease, by which microglia become chronically activated in response to α-synuclein pathology and dying neurons, thereby acquiring dishomeostatic phenotypes that are cytotoxic and can cause further neuronal death. Microglia have a functional endocannabinoid signaling system, expressing the cannabinoid receptors in addition to being capable of synthesizing and degrading endocannabinoids. Alterations in the cannabinoid system—particularly an upregulation in the immunomodulatory CB₂ receptor—have been demonstrated to be related to the microglial activation state and hence the microglial phenotype. This paper will review studies that examine the relationship between the cannabinoid system and microglial activation, and how this association could be manipulated for therapeutic benefit in Parkinson’s disease.

Microglial polarization in posttraumatic epilepsy: Potential mechanism and treatment opportunity

Owing to the complexity of the pathophysiological mechanisms driving epileptogenesis following traumatic brain injury (TBI), effective preventive treatment approaches are not yet available for posttraumatic epilepsy (PTE). Neuroinflammation appears to play a critical role in the pathogenesis of the acquired epilepsies, including PTE, but despite a large preclinical literature demonstrating the ability of anti-inflammatory treatments to suppress epileptogenesis and chronic seizures, no anti-inflammatory treatment approaches have been clinically proven to date. TBI triggers robust inflammatory cascades, suggesting that they may be relevant for the pathogenesis of PTE. A major cell type involved in such cascades is the microglial cells-brain-resident immune cells that become activated after brain injury. When activated, these cells can oscillate between different phenotypes, and such polarization states are associated with the release of various pro- and anti-inflammatory mediators that may influence brain repair processes, and also differentially contribute to the development of PTE. As the molecular mechanisms and key signaling molecules associated with microglial polarization in brain are discovered, strategies are now emerging that can modulate this polarization, promoting this as a potential therapeutic strategy for PTE. In this review, we discuss the relevant literature regarding the polarization of brain-resident immune cells following TBI and attempt to put into perspective a role in epilepsy pathogenesis. Finally, we explore potential strategies that could polarize microglia/macrophages toward a neuroprotective phenotype to mitigate PTE development.

Dopamine: an immune transmitter

The dopaminergic system controls several vital central nervous system functions, including the control of movement, reward behaviors and cognition. Alterations of dopaminergic signaling are involved in the pathogenesis of neurodegenerative and psychiatric disorders, in particular Parkinson’s disease, which are associated with a subtle and chronic inflammatory response. A substantial body of evidence has demonstrated the non-neuronal expression of dopamine, its receptors and of the machinery that governs synthesis, secretion and storage of dopamine across several immune cell types. This review aims to summarize current knowledge on the role and expression of dopamine in immune cells. One of the goals is to decipher the complex mechanisms through which these cell types respond to dopamine, in order to address the impact this has on neurodegenerative and psychiatric pathologies such as Parkinson’s disease. A further aim is to illustrate the gaps in our understanding of the physiological roles of dopamine to encourage more targeted research focused on understanding the consequences of aberrant dopamine production on immune regulation. These highlights may prompt scientists in the field to consider alternative functions of this important neurotransmitter when targeting neuroinflammatory/neurodegenerative pathologies.

Spinal Cord Microglia in Health and Disease

The review summarizes data of recent experimental studies on spinal microglia, the least explored cells of the spinal cord. It focuses on the origin and function of microglia in mammalian spinal cord embryogenesis. The main approaches to the classification of microgliocytes based on their structure, function, and immunophenotypic characteristics are analyzed. We discuss the results of studies conducted on experimental models of spinal cord diseases such as multiple sclerosis, amyotrophic lateral sclerosis, systemic inflammation, and some others, with special emphasis on the key role of microglia in the pathogenesis of these diseases. The review highlights the need to detect the new microglia-specific marker proteins expressed at all stages of ontogeny. New sensitive and selective microglial markers are necessary in order to improve identification of spinal cord microgliocytes in normal and pathological conditions. Possible morphometric methods to assess the functional activity of microglial cells are presented.

Depression as an Immunometabolic Disorder: Exploring Shared Pharmacotherapeutics with Cardiovascular Disease

Modern times have seen depression and cardiovascular disease (CVD) become notorious public health concerns, corresponding to alarming proportions of morbidity, mortality, decreased quality of life, and economic costs. Expanding comprehension of the pathogenesis of depression as an immunometabolic disorder has identified numerous pathophysiologic phenomena in common with CVD, including chronic inflammation, insulin resistance, and oxidative stress. These shared components could be exploited to offer improved alternatives in the joint management of these conditions. Abundant preclinical and clinical data on the impact of established treatments for CVD in the management of depression have allowed for potential candidates to be proposed for the joint management of depression and CVD as immunometabolic disorders. However, a large proportion of the clinical investigation currently available exhibits marked methodological flaws which preclude the formulation of concrete recommendations in many cases. This situation may be a reflection of pervasive problems present in clinical research in psychiatry, especially pertaining to study homogeneity. Therefore, further high-quality research is essential in the future in this regard.

In Up to My Ears and Temporal Lobes: Effects of Early Life Stress on Epilepsy Development

Epilepsy and stress are each significant concerns in today's society, bearing heavy impacts on mental and physical health and overall quality of life. Unfortunately, the intersection between these is potentially even more concerning, as stress is a frequent trigger of seizures and may contribute to neural hyperexcitability. A growing body of research suggests a connection between early life stress (occurring in the prenatal or postnatal stage) and later development of epilepsy. While the larger part of this literature suggests that early life stress increases vulnerability for epilepsy development, there are a number of interacting factors influencing this relationship. These factors include developmental stage at which both stressor and seizure assessment occur, type of stressor, sex effects, and type of seizure (convulsive or non-convulsive). Additionally, a number of potential mechanisms have been identified, including activation of the hypothalamic-pituitary-adrenal axis, neuroinflammation, altered inhibitory/excitatory balance, and temporal lobe structures. Developing a clearer understanding of this relationship between early life stress and epilepsy, the factors that influence it, and underlying mechanisms that may serve as targets for intervention is crucial to improving quality of life for persons with epilepsy.

Basic Science of PET Imaging for Inflammatory Diseases

FDG-PET/CT has recently emerged as a useful tool for the evaluation of inflammatory diseases too, in addition to that of malignant diseases. The imaging is based on active glucose utilization by inflammatory tissue. Autoradiography studies have demonstrated high FDG uptake in macrophages, granulocytes, fibroblasts, and granulation tissue. Especially, activated macrophages are responsible for the elevated FDG uptake in some types of inflammation. According to one study, after activation by lipopolysaccharide of cultured macrophages, the [¹⁴C]2DG uptake by the cells doubled, reaching the level seen in glioblastoma cells. In activated macrophages, increase in the expression of total GLUT1 and redistributions from the intracellular compartments toward the cell surface have been reported. In one rheumatoid arthritis model, following stimulation by hypoxia or TNF-α, the highest elevation of the [³H]FDG uptake was observed in the fibroblasts, followed by that in macrophages and neutrophils. As the fundamental mechanism of elevated glucose uptake in both cancer cells and inflammatory cells, activation of glucose metabolism as an adaptive response to a hypoxic environment has been reported, with transcription factor HIF-1α playing a key role. Inflammatory cells and cancer cells seem to share the same molecular mechanism of elevated glucose metabolism, lending support to the notion of usefulness of FDGPET/CT for the evaluation of inflammatory diseases, besides cancer.

Emerging Roles for Microglial Phagocytic Signaling in Epilepsy

Microglia are the resident immune cells and professional phagocytes of the central nervous system. However, little is known about the contribution of their phagocytic signaling to the neuropathology and pathophysiology of epilepsy. Here, we summarize and discuss the implications of recent evidence supporting that aberrant microglia phagocytic activity and alterations in phagocytosis signaling molecules occur in association with microglia-neuronal contacts, neuronal/synaptic loss, and spontaneous recurrent seizures in human and preclinical models of epilepsy. This body of evidence provides strong support that the microglial contribution to epileptogenic networks goes beyond inflammation, and suggests that phagocytic signaling molecules may be novel therapeutic targets for epilepsy.

Postmortem evidence of brain inflammatory markers in bipolar disorder: a systematic review

Bipolar disorder (BD) is a chronic affective disorder with extreme mood swings that include mania or hypomania and depression. Though the exact mechanism of BD is unknown, neuroinflammation is one of the numerous investigated etiopathophysiological causes of BD. This article presents a systematic review of the data regarding brain inflammation evaluating microglia, astrocytes, cytokines, chemokines, adhesion molecules, and other inflammatory markers in postmortem BD brain samples. This systematic review was performed according to PRISMA recommendations, and relevant studies were identified by searching the PubMed/MEDLINE, PsycINFO, EMBASE, LILACS, IBECS, and Web of Science databases for peer-reviewed journal articles published by March 2019. Quality of included studies appraised using the QUADAS-2 tool. Among the 1814 articles included in the primary screening, 51 articles measured inflammatory markers in postmortem BD brain samples. A number of studies have shown evidence of inflammation in BD postmortem brain samples. However, an absolute statement cannot be concluded whether neuroinflammation is present in BD due to the large number of studies did not evaluate the presence of infiltrating peripheral immune cells in the central nervous system (CNS) parenchyma, cytokines levels, and microglia activation in the same postmortem brain sample. For example, out of 15 studies that evaluated microglia cells markers, 8 studies found no effect of BD on these cells. Similarly, 17 out of 51 studies evaluating astrocytes markers, 9 studies did not find any effect of BD on astrocyte cells, whereas 8 studies found a decrease and 2 studies presented both increase and decrease in different brain regions. In addition, multiple factors account for the variability across the studies, including postmortem interval, brain area studied, age at diagnosis, undergoing treatment, and others. Future analyses should rectify these potential sources of heterogeneity and reach a consensus regarding the inflammatory markers in postmortem BD brain samples.

Aging and Neuroinflammatory Disorders: New Biomarkers and Therapeutic Targets

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Chronic neuroinflammation is a common feature of the pathogenic mechanisms involved in various neurodegenerative age-associated disorders, such as Alzheimer's disease, multiple sclerosis, Parkinson’s disease, and dementia.

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In particular, persistent low-grade inflammation may disrupt the brain endothelial barrier and cause a significant increase of pro-inflammatory cytokines and immune cells into the cerebral tissue that, in turn, leads to microglia dysfunction and loss of neuroprotective properties.

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Nowadays, growing evidence highlights a strong association between persistent peripheral inflammation, as well as metabolic alterations, and neurodegenerative disorder susceptibility. The identification of common pathways involved in the development of these diseases, which modulate the signalling and immune response, is an important goal of ongoing research.

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The aim of this review is to elucidate which inflammation-related molecules are robustly associated with the risk of neurodegenerative diseases. Of note, peripheral biomarkers may represent direct measures of pathophysiologic processes common of aging and neuroinflammatory processes. In addition, molecular changes associated with the neurodegenerative process might be present many decades before the disease onset. Therefore, the identification of a comprehensive markers panel, closely related to neuroinflammation, could be helpful for the early diagnosis, and the identification of therapeutic targets to counteract the underlying chronic inflammatory processes.

In Vitro Anti-Inflammatory Effects of Phenolic Compounds from Moraiolo Virgin Olive Oil (MVOO) in Brain Cells via Regulating the TLR4/NLRP3 Axis

Neuroinflammation is a feature of many classic neurodegenerative diseases. In the healthy brain, microglia cells are distributed throughout the brain and are constantly surveilling the central nervous system (CNS). In response to CNS injury, microglia quickly react by secreting a wide array of apoptotic molecules. Virgin olive oil (VOO) is universally recognized as a symbol of the Mediterranean diet. In the current study, using lipopolysaccharide (LPS)-stimulated BV2 microglia, the anti-inflammatory effects of VOO phenolic extracts from Moraiolo cultivar (MVOO-PE) were investigated. The results showed that low concentration of MVOO-PE prevented microglia cell death and attenuated the LPS-induced activation of toll-like receptor 4 (TLR4)/NOD-like receptor pyrin domain-containing-3 (NLRP3) signaling cascade. The levels of TLR4 and NF-kB were diminished, as well as NLRP3 inflammasome and interleukin-1β (IL-1β) production. Cyclooxygenase-2 (COX-2) isoenzyme and ionized calcium binding adaptor molecule 1 (Iba-1) inflammatory mediator were also reduced. By modulating the TLR4/NLRP3 axis, MVOO-PE pretreatment was able to significantly down-regulate the mRNA expression of inflammatory mediators and suppress the cytokine secretion. Finally, we showed protective effect of MVOO-PE in a transwell neuron-microglia co-culture system. In conclusion, these results suggest that MVOO-PE could exerts anti-inflammatory activity on brain cells and become a promising candidate for preventing several neuroinflammatory diseases.

Neuroinflammation in Post-Traumatic Epilepsy: Pathophysiology and Tractable Therapeutic Targets

Epilepsy is a common chronic consequence of traumatic brain injury (TBI), contributing to increased morbidity and mortality for survivors. As post-traumatic epilepsy (PTE) is drug-resistant in at least one-third of patients, there is a clear need for novel therapeutic strategies to prevent epilepsy from developing after TBI, or to mitigate its severity. It has long been recognized that seizure activity is associated with a local immune response, characterized by the activation of microglia and astrocytes and the release of a plethora of pro-inflammatory cytokines and chemokines. More recently, increasing evidence also supports a causal role for neuroinflammation in seizure induction and propagation, acting both directly and indirectly on neurons to promote regional hyperexcitability. In this narrative review, we focus on key aspects of the neuroinflammatory response that have been implicated in epilepsy, with a particular focus on PTE. The contributions of glial cells, blood-derived leukocytes, and the blood–brain barrier will be explored, as well as pro- and anti-inflammatory mediators. While the neuroinflammatory response to TBI appears to be largely pro-epileptogenic, further research is needed to clearly demonstrate causal relationships. This research has the potential to unveil new drug targets for PTE, and identify immune-based biomarkers for improved epilepsy prediction.

Ghrelin Attenuates Neuroinflammation and Demyelination in Experimental Autoimmune Encephalomyelitis Involving NLRP3 Inflammasome Signaling Pathway and Pyroptosis

Multiple sclerosis (MS) is a chronic autoimmune and degenerative disease of the central nervous system, and conventional treatments have limited efficacy or side effects. Ghrelin, a 28-amino acid octanoylated peptide, has been reported to have neuroprotective effects, including anti-oxidation, anti-inflammation, and anti-apoptosis. Pyroptosis, also called inflammatory cell death, is triggered by overly active inflammasomes and accompanied by the production of numerous cytokines. As immune dysfunction is primarily involved in the pathogenesis of MS, this study aimed to explore the therapeutic effects and precise functional mechanisms of ghrelin against the nod-like receptor protein 3 (NLRP3) inflammasome and pyroptosis in experimental autoimmune encephalomyelitis (EAE). Sprague Dawley rats were immunized with guinea pig spinal cord homogenates and pertussis toxin to develop an EAE model. All rats were randomly divided into four groups: normal control group, EAE group, EAE + ghrelin group, and ghrelin control group. EAE rats showed abnormal behavioral scores and body weight changes. Histologic analysis displayed severe inflammatory infiltration and demyelination in the brain and spinal cord of EAE rats. Ghrelin treatments potently restored these abnormal changes. In addition, the ghrelin-treated EAE group showed significantly downregulated expression of inflammatory cytokines. The expression of proteins involved in the NLRP3 signaling pathway and pyroptosis was decreased as well. We also found that the anti-inflammatory effect of ghrelin was associated with inhibition of nuclear factor (NF)-κB activation. Compared with rats in the healthy control group, rats in the ghrelin control group did not show statistically significant changes in histologic examinations, pro-inflammatory cytokines production, or molecules involved in the NLRP3 signaling pathway, which indicated that ghrelin induced no side effects in the animals of our study. Our findings provide more insight into the use of ghrelin as a novel candidate for MS.

Neuroglial patterns are shared by cerebella from prion and prion-like disorder affected patients

Neurodegenerative diseases, such as Alzheimer's and Parkinson's, are considered prion-like disorders because they are all proteinopathies in which aberrant proteins spread throughout the brain during disease progression. The overall aim of this study is to determine how glial cells are commonly involved in the neurodegeneration progress observed in all these pathologies. The suggestion that they are cell types in which prion and prion-like disorders have common behaviour is the hypothesis on which this study is based. Morphological and distribution differences in astroglial and microglial cells in the cerebellum from prion and prion-like disease-affected patients were assessed here by histopathological and immunochemical tools. To our knowledge, this is the first study to focus on the comparative assessment of glial profiles in these human brains. Activated microglial population was demonstrated in both, prion and prion-like disorders, although in higher extent in the first. In astroglial activation, specific patterns of alterations suggesting both degenerative and potentially neuroprotective or restorative stem cell response, were shown to be alternatively shared by cerebella from all disorders studied. Neuro-protective strategies for these disabling disorders are particularly desirable.

Peripheral proinflammatory markers are upregulated in abstinent alcohol-dependent patients but are not affected by cognitive bias modification: Preliminary findings

BACKGROUND

Inflammatory pathways are known to be negatively affected in patients with alcohol use disorder (AUD). Cognitive bias modification (CBM), an emerging behavioral treatment that involves the 're-training' of cognitive biases using computerized tasks, has been reported to reduce alcohol craving and relapse rates. The aim of this study was to compare peripheral concentrations of the proinflammatory biomarkers IL-18, IL-6, IL-1β, TNF-α and CRP in AUD patients versus controls and to identify whether CBM treatment affected these biomarkers in AUD patients.

METHODS

This 3-week double-blind randomized controlled study tested 36 male abstinent AUD patients receiving CBM or placebo-training, who were also compared to 18 male healthy controls. The approach avoidance task (AAT) was used to test the AUD patients before and after training. CBM training took place over 6 sessions, using a joystick-based approach-avoidance task. Blood samples were collected after the pre- and post-AAT test sessions for the AUD groups, and during an outpatient appointment with the controls.

RESULTS

AUD patients, versus controls, presented with significantly higher plasma levels of TNF- α (P < 0.0001) and CRP (P = 0.0031). No changes in the CBM versus placebo groups were noted in IL-18, TNF-α and CRP concentrations following pre-post change or within group pretest- posttest analysis. IL-6 and IL-1β levels fell under the lower detection limit, thus were not included in the final analyses.

CONCLUSIONS

This study confirms that the inflammatory system is altered in AUD. This was the first study that investigated whether CBM training affected proinflammatory markers in AUD patients.

Neuroinflammation disorders exacerbated by environmental stressors

Neuroinflammation is a condition characterized by the elaboration of proinflammatory mediators within the central nervous system. Neuroinflammation has emerged as a dominant theme in contemporary neuroscience due to its association with neurodegenerative disease states such as Alzheimer's disease, Parkinson's disease and Huntington's disease. While neuroinflammation often is associated with damage to the CNS, it also can occur in the absence of neurodegeneration, e.g., in association with systemic infection. The "acute phase" inflammatory response to tissue injury or infections instigates neuroinflammation-driven "sickness behavior," i.e. a constellation of symptoms characterized by loss of appetite, fever, muscle pain, fatigue and cognitive problems. Typically, sickness behavior accompanies an inflammatory response that resolves quickly and serves to restore the body to homeostasis. However, recurring and sometimes chronic sickness behavior disorders can occur in the absence of an underlying cause or attendant neuropathology. Here, we review myalgic enchepalomyelitis/chronic fatigue syndrome (ME/CFS), Gulf War Illness (GWI), and chemobrain as examples of such disorders and propose that they can be exacerbated and perhaps initiated by a variety of environmental stressors. Diverse environmental stressors may disrupt the hypothalamic pituitary adrenal (HPA) axis and contribute to the degree and duration of a variety of neuroinflammation-driven diseases.

Murine iPSC-derived microglia and macrophage cell culture models recapitulate distinct phenotypical and functional properties of classical and alternative neuro-immune polarisation

The establishment and validation of reliable induced pluripotent stem cell (iPSC)-derived in vitro models to study microglia and monocyte/macrophage immune function holds great potential for fundamental and translational neuro-immunology research. In this study, we first demonstrate that ramified CX₃CR1⁺ iPSC-microglia (cultured within a neural environment) and round-shaped CX₃CR1^- iPSC-macrophages can easily be differentiated from newly established murine CX₃CR1^eGFP/+CCR2^RFP/+ iPSC lines. Furthermore, we show that obtained murine iPSC-microglia and iPSC-macrophages are distinct cell populations, even though iPSC-macrophages may upregulate CX₃CR1 expression when cultured within a neural environment. Next, we characterized the phenotypical and functional properties of murine iPSC-microglia and iPSC-macrophages following classical and alternative immune polarisation. While iPSC-macrophages could easily be triggered to adopt a classically-activated or alternatively-activated phenotype following, respectively, lipopolysaccharide + interferon γ or interleukin 13 (IL13) stimulation, iPSC-microglia and iPSC-macrophages cultured within a neural environment displayed a more moderate activation profile as characterised by the absence of MHCII expression upon classical immune polarisation and the absence of Ym1 expression upon alternative immune polarisation. Finally, extending our preceding in vivo studies, this striking phenotypical divergence was also observed for resident microglia and infiltrating monocytes within highly inflammatory cortical lesions in CX₃CR1^eGFP/+CCR2^RFP/+ mice subjected to middle cerebral arterial occlusion (MCAO) stroke and following IL13-mediated therapeutic intervention thereon. In conclusion, our study demonstrates that the applied murine iPSC-microglia and iPSC-macrophage culture models are able to recapitulate in vivo microglia and monocyte/macrophage ontogeny and corresponding phenotypical/functional properties upon classical and alternative immune polarisation, and therefore represent a valuable in vitro platform to further study and modulate microglia and (infiltrating) monocyte immune responses under neuro-inflammatory conditions within a neural environment.

Repeated Vaginal Exposures to the Common Cosmetic and Household Preservative Methylisothiazolinone Induce Persistent, Mast Cell-Dependent Genital Pain in ND4 Mice

A history of allergies doubles the risk of vulvodynia—a chronic pain condition of unknown etiology often accompanied by increases in numbers of vulvar mast cells. We previously established the biological plausibility of this relationship in mouse models where repeated exposures to the allergens oxazolone or dinitrofluorobenzene on the labiar skin or inside the vaginal canal of ND4 Swiss Webster outbred mice led to persistent tactile sensitivity and local increases in mast cells. In these models, depletion of mast cells alleviated pain. While exposure to cleaning chemicals has been connected to elevated vulvodynia risk, no single agent has been linked to adverse outcomes. We sensitized female mice to methylisothiazolinone (MI)—a biocide preservative ubiquitous in cosmetics and cleaners—dissolved in saline on their flanks, and subsequently challenged them with MI or saline for ten consecutive days in the vaginal canal. MI-challenged mice developed persistent tactile sensitivity, increased vaginal mast cells and eosinophils, and had higher serum Immunoglobulin E. Therapeutic and preventive intra-vaginal administration of Δ⁹-tetrahydrocannabinol reduced mast cell accumulation and tactile sensitivity. MI is known to cause skin and airway irritation in humans, and here we provide the first pre-clinical evidence that repeated MI exposures can also provoke allergy-driven genital pain.

Effect of Systemic Inflammation on Rat Attentional Function and Neuroinflammation: Possible Protective Role for Food Restriction

Background: Aging is characterized by subtle cognitive decline, which correlates with increased peripheral inflammation. Acute activation of the peripheral immune system, via lipopolysaccharide (LPS) injection, elicits deficits in hippocampal-dependent spatial memory. Little is known concerning the effect of chronic inflammation on prefrontal cortex (PFC)-dependent vigilance. We examined the impact of repeated LPS injections in young and middle-age rats on the 5-choice serial reaction time task (5-CSRTT), expecting repeated LPS treatment to induce attentional deficits with greater disruption in middle-age. Methods: Male Fischer-344 rats, 4- and 12-months-old, were food restricted and trained on the 5-CSRTT. Once rats reached criterion, they were injected with LPS (1 mg/kg, i.p.) weekly for 4 weeks and testing started 48 h after each injection. To examine the possibility that mild food restriction inherent to the behavioral task influenced inflammation markers, a second group of food-restricted or ad-lib-fed rats was assessed for cytokine changes 48 h after one injection. Results: Performing LPS-treated rats exhibited a sickness response, manifesting as reduced initiated and completed trials during the first week but recovered by the second week of testing. After the first week, LPS-treated rats continued to exhibit longer response latencies, despite no change in food retrieval latency, suggestive of LPS-induced cognitive slowing. Similarly, LPS-induced impairment of attention was observed as increased omissions with heightened cognitive demand and increased age. Repeated LPS-treatment increased the level of PFC IL-1α, and PFC IL-6 was marginally higher in middle-age rats. No effect of age or treatment was observed for plasma cytokines in performing rats. Histological examination of microglia indicated increased colocalization of Iba1+ and CD68+ cells from middle-age relative to young rats. Examination of food restriction demonstrated an attenuation of age- and LPS-related increases in plasma cytokine levels. Conclusions: Systemic inflammation, induced through LPS treatment, impaired attentional function, which was independent of sickness and exacerbated by increased cognitive demand and increased age. Additional studies revealed that food restriction, associated with the task, attenuated markers of neuroinflammation and plasma cytokines. The results emphasize the need for improved methods for modeling low-level chronic systemic inflammation to effectively examine its impact on attention during aging.

Inflammatory and Pro-resolving Mediators in Frontotemporal Dementia and Alzheimer's Disease

Chronic inflammation contributes to neuronal death in Alzheimer's disease (AD) and frontotemporal dementia (FTD). Here we evaluated inflammatory and pro-resolving mediators in AD and behavioural variant of FTD (bvFTD) patients compared with controls, since neuroinflamamtion is a common feature in both diseases. Ninety-eight subjects were included in this study, divided into AD (n = 32), bvFTD (n = 30), and control (n = 36) groups. The levels of hsCRP, IL-1β, IL-6, TNF, and TGF-β1, as well as annexin A1 (AnxA1) and lipoxin A4 (LXA4) were measured in blood and cerebrospinal fluid (CSF). The expression profile of AnxA1 was evaluated in peripheral blood mononuclear cells (PBMCs) as well the distribution of ANXA1 rs2611228 polymorphism. We found reduced peripheral levels of hsCRP and TNF in AD compared with bvFTD patients and controls, and increased levels of TGF-β1 in AD compared to controls. Moreover, reduced plasma levels of AnxA1 were observed in bvFTD compared to AD and controls. There was a significant cleavage of AnxA1 in PBMCs in both dementia groups. The results suggest differential regulation of inflammatory and pro-resolving mediators in bvFTD and AD, while AnxA1 cleavage may impair pro-resolving mechanisms in both groups.

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.

The MicroRNA Centrism in the Orchestration of Neuroinflammation in Neurodegenerative Diseases

MicroRNAs (miRNAs) are small non-coding RNAs with a unique ability to regulate the transcriptomic profile by binding to complementary regulatory RNA sequences. The ability of miRNAs to enhance (proinflammatory miRNAs) or restrict (anti-inflammatory miRNAs) inflammatory signalling within the central nervous system is an area of ongoing research, particularly in the context of disorders that feature neuroinflammation, including neurodegenerative diseases (NDDs). Furthermore, the discovery of competing endogenous RNAs (ceRNAs) has led to an increase in the complexity of miRNA-mediated gene regulation, with a paradigm shift from a unidirectional to a bidirectional regulation, where miRNA acts as both a regulator and is regulated by ceRNAs. Increasing evidence has revealed that ceRNAs, including long non-coding RNAs, circular RNAs, and pseudogenes, can act as miRNA sponges to regulate neuroinflammation in NDDs within complex cross-talk regulatory machinery, which is referred to as ceRNA network (ceRNET). In this review, we discuss the role of miRNAs in neuroinflammatory regulation and the manner in which cellular and vesicular ceRNETs could influence neuroinflammatory dynamics in complex multifactorial diseases, such as NDDs.

β-Arrestin 2 protects against neurological function defects in HSV-1-induced encephalitis mice

The pathogenesis of herpes simplex encephalitis (HSE) needs to be fully explored. β-Arrestin 2 (Arrb2) is highly expressed in brain tissues and plays a key role in the regulation of systemic immune reactions by modulating various signaling pathways. However, the expression of Arrb2 in microglial cells and its influence on HSE prognosis is still undefined. We explore the pathophysiological effect of Arrb2 in the brain using experimental HSE mice. The expression of Arrb2 in microglia was decreased significantly 48 hours following HSV-1 infection. Arrb2 overexpression transgenic (TG) mice had a significantly lower mortality and survival rate was improved by 40% compared to wild-type mice. Arrb2 suppressed the generation of proinflammatory cytokines TNF-α and IL-6 and increased anti-inflammatory cytokines IL-10 and IL-4 expression. Arrb2 also inhibited the activation of the transcription factor NF-κB in microglial cells. Arrb2 TG mice attenuated the blood-brain barrier breakdown and relieved cerebral edema, meanwhile, Arrb2 improved mice neurological function compared with wild-type mice. Overall, Arrb2 favored microglia of the M2 phenotype, attenuated brain proinflammatory responses, protected the blood vessel wall integrity, reduced HSV-1-induced neurological impairment, and improved the survival rate in HSE mice.

Microbiome and Mental Health, Specifically as It Relates to Adolescents

PURPOSE OF REVIEW

This article reviews the relationship of the microbiome, the gut-brain axis, and depression. It also will review factors which can influence this relationship, such as chronic stress, medications, and the Western diet typically consumed by adolescents.

RECENT FINDINGS

Changes in the gut microbiome increase the release of microbial lipopolysaccharides (LPS) which activate a gut inflammatory response. Gut pro-inflammatory cytokines stimulate the afferent vagal nerve which in turn impacts the hypothalamic-pituitary-adrenal (HPA) axis inducing symptoms associated with depression. Recent research suggests that gut inflammation can induce neuroinflammation which, in turn, stimulates microglia activation and the kynurenine pathway and can activate systemic inflammation-inducing depressive symptoms. Promoting a healthy diet and lifestyle changes, limiting exposure to pesticides, limiting medications that affect the microbiome and the use of such things pre/probiotics and other interventions may complement existing efforts to curb the rise in depression. Alternative and complementary therapies may serve as effective treatments in adolescents with depression.