Neuroimmune and Inflammatory Signals in Complex Disorders of the Central Nervous System

Neuroimmune regulation of the prefrontal cortex tetrapartite synapse

The prefrontal cortex (PFC) is an essential driver of cognitive, affective, and motivational behavior. There is clear evidence that the neuroimmune system directly influences PFC synapses, in addition to its role as the first line of defense against toxins and pathogens. In this review, we first describe the core structures that form the tetrapartite PFC synapse, focusing on the signaling microdomain created by astrocytic cradling of the synapse as well as the emerging role of the extracellular matrix in synaptic organization and plasticity. Neuroimmune signals (e.g. pro-inflammatory interleukin 1β) can impact the function of each core structure within the tetrapartite synapse, as well as promote intra-synaptic crosstalk, and we will provide an overview of recent advances in this field. Finally, evidence from post mortem human brain tissue and preclinical studies indicate that inflammation may be a key contributor to PFC dysfunction. Therefore, we conclude with a mechanistic discussion of neuroimmune-mediated maladaptive plasticity in neuropsychiatric disorders, with a focus on alcohol use disorder (AUD). Growing recognition of the neuroimmune system's role as a critical regulator of the PFC tetrapartite synapse provides strong support for targeting the neuroimmune system to develop new pharmacotherapeutics.

Histaminergic System Activity in the Central Nervous System: The Role in Neurodevelopmental and Neurodegenerative Disorders

Histamine (HA), a biogenic monoamine, exerts its pleiotropic effects through four H1R-H4R histamine receptors, which are also expressed in brain tissue. Together with the projections of HA-producing neurons located within the tuberomammillary nucleus (TMN), which innervate most areas of the brain, they constitute the histaminergic system. Thus, while remaining a mediator of the inflammatory reaction and immune system function, HA also acts as a neurotransmitter and a modulator of other neurotransmitter systems in the central nervous system (CNS). Although the detailed causes are still not fully understood, neuroinflammation seems to play a crucial role in the etiopathogenesis of both neurodevelopmental and neurodegenerative (neuropsychiatric) diseases, such as autism spectrum disorders (ASDs), attention-deficit/hyperactivity disorder (ADHD), Alzheimer's disease (AD) and Parkinson's disease (PD). Given the increasing prevalence/diagnosis of these disorders and their socioeconomic impact, the need to develop effective forms of therapy has focused researchers' attention on the brain's histaminergic activity and other related signaling pathways. This review presents the current state of knowledge concerning the involvement of HA and the histaminergic system within the CNS in the development of neurodevelopmental and neurodegenerative disorders. To this end, the roles of HA in neurotransmission, neuroinflammation, and neurodevelopment are also discussed.

Rehabilitation Intervention Is Associated With Improved Neurodevelopment and Modulation of Inflammatory Molecules in Children With Cerebral Palsy

AIM

To evaluate the effects of systematic rehabilitation on both the neuropsychomotor development, and on the peripheral response from immunological and neuroplastic mediators in children with cerebral palsy.

METHODS

This is a prospective cohort study with 90 children with cerebral palsy at 18 months of age. Sixty children received rehabilitation for 6 months, and they were compared to 30 children that were placed in the waiting list. Peripheral biomarkers and neuropsychomotor parameters were compared between the Rehab vs the Nonrehab groups at baseline and at 6 months.

RESULTS

Results showed higher Bayley III scores in the Rehab group, with significant differences in inflammatory and neurotrophic biomarkers between groups. Rehabilitation was associated to decreased levels of IL-12p70, IL-6, IL-1β, CXCL8 IL-8, and CXCL9/MIG and increased levels of BDNF and GDNF. Nonrehab children had stable immune molecule levels but decreased BDNF levels over time.

CONCLUSION

Rehabilitation improved neurodevelopment parameters and modulated levels of inflammatory (↓) and neurotrophic (↑) biomarkers.

Mast cells in the autonomic nervous system and potential role in disorders with dysautonomia and neuroinflammation

Mast cells (MC) are ubiquitous in the body, and they are critical for not only in allergic diseases but also in immunity and inflammation, including having potential involvement in the pathophysiology of dysautonomias and neuroinflammatory disorders. MC are located perivascularly close to nerve endings and sites such as the carotid bodies, heart, hypothalamus, the pineal gland, and the adrenal gland that would allow them not only to regulate but also to be affected by the autonomic nervous system (ANS). MC are stimulated not only by allergens but also many other triggers including some from the ANS that can affect MC release of neurosensitizing, proinflammatory, and vasoactive mediators. Hence, MC may be able to regulate homeostatic functions that seem to be dysfunctional in many conditions, such as postural orthostatic tachycardia syndrome, autism spectrum disorder, myalgic encephalomyelitis/chronic fatigue syndrome, and Long-COVID syndrome. The evidence indicates that there is a possible association between these conditions and diseases associated with MC activation. There is no effective treatment for any form of these conditions other than minimizing symptoms. Given the many ways MC could be activated and the numerous mediators released, it would be important to develop ways to inhibit stimulation of MC and the release of ANS-relevant mediators.

The Use of Umbilical Cord Blood Nucleated Cells in the Treatment of Regressive Autism: A Case Report

BACKGROUND

Interest in the issue of childhood autism has surged in the recent decades. At the same time, despite the significant progress achieved in understanding the etiological and pathogenetic aspects of the condition, effective ways to treat it have continued to elude us. Stem cell therapy appears to hold great promise in the treatment and rehabilitation of patients with both neurological diseases (cerebral palsy, hydrocephalus) and mental disorders (autism, schizophrenia).

METHODS

This article presents a case report describing the use of nucleated cord blood cells in a patient with regressive autism and resistance to standard therapies. The child's condition was assessed before treatment and 6 and 12 months after.

RESULTS

Clinical observation, psychometric, and instrumental diagnostic methods led to a significant improvement in the child's condition in the form of perception development, reduction of somatosensory disorders, normalization of emotional status, and a development of social and communication skills.

CONCLUSION

We assume that the result obtained may be associated with the normalization of the immunological status of our patient thanks to the cord blood cells therapy and consider it necessary to conduct further studies into the effectiveness of the method, taking the pathogenic mechanisms of autism into account.

Recombinant SARS-CoV-2 Spike Protein and Its Receptor Binding Domain Stimulate Release of Different Pro-Inflammatory Mediators via Activation of Distinct Receptors on Human Microglia Cells

SARS-CoV-2 infects cells via its spike (S) protein binding to its surface receptor angiotensin converting enzyme 2 (ACE2) on target cells and results in acute symptoms involving especially the lungs known as COVID-19. However, increasing evidence indicates that SARS-CoV-2 infection produces neuroinflammation associated with neurological, neuropsychiatric, and cognitive symptoms persists well past the resolution of the infection, known as post-COVID-19 sequalae or long-COVID. The neuroimmune mechanism(s) involved in long-COVID have not been adequately characterized. In this study, we show that recombinant SARS-CoV-2 full-length S protein stimulates release of pro-inflammatory IL-1b, CXCL8, IL-6, and MMP-9 from cultured human microglia via TLR4 receptor activation. Instead, recombinant receptor-binding domain (RBD) stimulates release of TNF-α, IL-18, and S100B via ACE2 signaling. These results provide evidence that SARS-CoV-2 spike protein contributes to neuroinflammation through different mechanisms that may be involved in CNS pathologies associated with long-COVID.

Impact of Elevated Brain IL-6 in Transgenic Mice on the Behavioral and Neurochemical Consequences of Chronic Alcohol Exposure

Alcohol consumption activates the neuroimmune system of the brain, a system in which brain astrocytes and microglia play dominant roles. These glial cells normally produce low levels of neuroimmune factors, which are important signaling factors and regulators of brain function. Alcohol activation of the neuroimmune system is known to dysregulate the production of neuroimmune factors, such as the cytokine IL-6, thereby changing the neuroimmune status of the brain, which could impact the actions of alcohol. The consequences of neuroimmune-alcohol interactions are not fully known. In the current studies we investigated this issue in transgenic (TG) mice with altered neuroimmune status relative to IL-6. The TG mice express elevated levels of astrocyte-produced IL-6, a condition known to occur with alcohol exposure. Standard behavioral tests of alcohol drinking and negative affect/emotionality were carried out in homozygous and heterozygous TG mice and control mice to assess the impact of neuroimmune status on the actions of chronic intermittent alcohol (ethanol) (CIE) exposure on these behaviors. The expressions of signal transduction and synaptic proteins were also assessed by Western blot to identify the impact of alcohol-neuroimmune interactions on brain neurochemistry. The results from these studies show that neuroimmune status with respect to IL-6 significantly impacts the effects of alcohol on multiple levels.

The clinical characteristics of neuronal intranuclear inclusion disease and its relation with inflammation

BACKGROUND

Neuronal intranuclear inclusion disease (NIID) is a great imitator with a broad spectrum of clinical manifestations that include dementia, parkinsonism, paroxysmal symptoms, peripheral neuropathy, and autonomic dysfunction. Hence, it may also masquerade as other diseases such as Alzheimer's disease, Parkinson's disease, and Charcot-Marie-Tooth disease. Recent breakthroughs on neuroimaging, skin biopsy, and genetic testing have facilitated the diagnosis. However, early identification and effective treatment are still difficult in cases of NIID.

OBJECTIVE

To further study the clinical characteristics of NIID and investigate the relationship between NIID and inflammation.

METHODS

We systematically evaluated the clinical symptoms, signs, MRI and electromyographical findings, and pathological characteristics of 20 NIID patients with abnormal GGC repeats in the NOTCH2NLC gene. Some inflammatory factors in the patients were also studied.

RESULTS

Paroxysmal symptoms such as paroxysmal encephalopathy, stroke-like episodes, and mitochondrial encephalomyopathy lactic acidosis and stroke (MELAS)-like episode were the most common phenotypes. Other symptoms such as cognitive dysfunction, neurogenic bladder, tremor, and vision disorders were also suggestive of NIID. Interestingly, not all patients showed apparent diffusion-weighted imaging (DWI) abnormality or intranuclear inclusions, while abnormal GGC repeats of NOTCH2NLC were seen in all patients. And fevers were noticed in some patients during encephalitic episodes, usually with increasing leukocyte counts and neutrophil ratios. Both IL-6 (p = 0.019) and TNF-α (p = 0.027) levels were significantly higher in the NIID group than in normal controls.

CONCLUSION

Genetic testing of NOTCH2NLC may be the best choice in the diagnosis of NIID. Inflammation might be involved in the pathogenesis of NIID.

Neuroimmune interactions with binge alcohol drinking in the cerebellum of IL-6 transgenic mice

The neuroimmune system of the brain, which is comprised primarily of astrocytes and microglia, regulates a variety of homeostatic mechanisms that underlie normal brain function. Numerous conditions, including alcohol consumption, can disrupt this regulatory process by altering brain levels of neuroimmune factors. Alcohol and neuroimmune factors, such as proinflammatory cytokines IL-6 and TNF-alpha, act at similar targets in the brain, including excitatory and inhibitory synaptic transmission. Thus, alcohol-induced production of IL-6 and/or TNF-alpha could be important contributing factors to the effects of alcohol on the brain. Recent studies indicate that IL-6 plays a role in alcohol drinking and the effects of alcohol on the brain activity following the cessation of alcohol consumption (post-alcohol period), however information on these topics is limited. Here we used homozygous and heterozygous female and male transgenic mice with increased astrocyte expression of IL-6 to examined further the interactions between alcohol and IL-6 with respect to voluntary alcohol drinking, brain activity during the post-alcohol period, IL-6 signal transduction, and expression of synaptic proteins. Wildtype littermates (WT) served as controls. The transgenic mice model brain neuroimmune status with respect to IL-6 in subjects with a history of persistent alcohol use. Results showed a genotype dependent reduction in voluntary alcohol consumption in the Drinking in the Dark protocol and in frequency-dependent relationships between brain activity in EEG recordings during the post-alcohol period and alcohol consumption. IL-6, TNF-alpha, IL-6 signal transduction partners pSTAT3 and c/EBP beta, and synaptic proteins were shown to play a role in these genotypic effects.

Role of SARS-CoV-2 Spike-Protein-Induced Activation of Microglia and Mast Cells in the Pathogenesis of Neuro-COVID

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes coronavirus disease 2019 (COVID-19). About 45% of COVID-19 patients experience several symptoms a few months after the initial infection and develop post-acute sequelae of SARS-CoV-2 (PASC), referred to as "Long-COVID," characterized by persistent physical and mental fatigue. However, the exact pathogenetic mechanisms affecting the brain are still not well-understood. There is increasing evidence of neurovascular inflammation in the brain. However, the precise role of the neuroinflammatory response that contributes to the disease severity of COVID-19 and long COVID pathogenesis is not clearly understood. Here, we review the reports that the SARS-CoV-2 spike protein can cause blood-brain barrier (BBB) dysfunction and damage neurons either directly, or via activation of brain mast cells and microglia and the release of various neuroinflammatory molecules. Moreover, we provide recent evidence that the novel flavanol eriodictyol is particularly suited for development as an effective treatment alone or together with oleuropein and sulforaphane (ViralProtek®), all of which have potent anti-viral and anti-inflammatory actions.

Modelling the Interplay Between Neuron-Glia Cell Dysfunction and Glial Therapy in Autism Spectrum Disorder

Autism spectrum disorder (ASD) is a complicated, interpersonally defined, static condition of the underdeveloped brain. Although the aetiology of autism remains unclear, disturbance of neuronglia interactions has lately been proposed as a significant event in the pathophysiology of ASD. In recent years, the contribution of glial cells to autism has been overlooked. In addition to neurons, glial cells play an essential role in mental activities, and a new strategy that emphasises neuron-glia interactions should be applied. Disturbance of neuron-glia connections has lately been proposed as a significant event in the pathophysiology of ASD because aberrant neuronal network formation and dysfunctional neurotransmission are fundamental to the pathology of the condition. In ASD, neuron and glial cell number changes cause brain circuits to malfunction and impact behaviour. A study revealed that reactive glial cells result in the loss of synaptic functioning and induce autism under inflammatory conditions. Recent discoveries also suggest that dysfunction or changes in the ability of microglia to carry out physiological and defensive functions (such as failure in synaptic elimination or aberrant microglial activation) may be crucial for developing brain diseases, especially autism. The cerebellum, white matter, and cortical regions of autistic patients showed significant microglial activation. Reactive glial cells result in the loss of synaptic functioning and induce autism under inflammatory conditions. Replacement of defective glial cells (Cell-replacement treatment), glial progenitor cell-based therapy, and medication therapy (inhibition of microglia activation) are all utilised to treat glial dysfunction. This review discusses the role of glial cells in ASD and the various potential approaches to treating glial cell dysfunction.

The Relationship between Stress, Inflammation, and Depression

A narrative review about the relationship between stress, inflammation, and depression is made as follows: Chronic stress leads to various stress-related diseases such as depression. Although most human diseases are related to stress exposure, the common pathways between stress and pathophysiological processes of different disorders are still debatable. Chronic inflammation is a crucial component of chronic diseases, including depression. Both experimental and clinical studies have demonstrated that an increase in the levels of pro-inflammatory cytokines and stress hormones, such as glucocorticoids, substantially contributes to the behavioral alterations associated with depression. Evidence suggests that inflammation plays a key role in the pathology of stress-related diseases; however, this link has not yet been completely explored. In this study, we aimed to determine the role of inflammation in stress-induced diseases and whether a common pathway for depression exists. Recent studies support pharmacological and non-pharmacological treatment approaches significantly associated with ameliorating depression-related inflammation. In addition, major depression can be associated with an activated immune system, whereas antidepressants can exert immunomodulatory effects. Moreover, non-pharmacological treatments for major depression (i.e., exercise) may be mediated by anti-inflammatory actions. This narrative review highlights the mechanisms underlying inflammation and provides new insights into the prevention and treatment of stress-related diseases, particularly depression.

Current and Near-Future Treatment of Alzheimer's Disease

Recent findings have improved our understanding of the multifactorial nature of AD. While in early asymptomatic stages of AD, increased amyloid-β synthesis and tau hyperphosphorylation play a key role, while in the latter stages of the disease, numerous dysfunctions of homeostatic mechanisms in neurons, glial cells, and cerebrovascular endothelium determine the rate of progression of clinical symptoms. The main driving forces of advanced neurodegeneration include increased inflammatory reactions in neurons and glial cells, oxidative stress, deficiencies in neurotrophic growth and regenerative capacity of neurons, brain insulin resistance with disturbed metabolism in neurons, or reduction of the activity of the Wnt-β catenin pathway, which should integrate the homeostatic mechanisms of brain tissue. In order to more effectively inhibit the progress of neurodegeneration, combination therapies consisting of drugs that rectify several above-mentioned dysfunctions should be used. It should be noted that many widely-used drugs from various pharmacological groups, "in addition" to the main therapeutic indications, have a beneficial effect on neurodegeneration and may be introduced into clinical practice in combination therapy of AD. There is hope that complex treatment will effectively inhibit the progression of AD and turn it into a slowly progressing chronic disease. Moreover, as the mechanisms of bidirectional communication between the brain and microbiota are better understood, it is expected that these pathways will be harnessed to provide novel methods to enhance health and treat AD.

Characterization of neurological disease progression in a canine model of CLN5 neuronal ceroid lipofuscinosis

Golden Retriever dogs with a frameshift variant in CLN5 (c.934_935delAG) suffer from a progressive neurodegenerative disorder analogous to the CLN5 form of neuronal ceroid lipofuscinosis (NCL). Five littermate puppies homozygous for the deletion allele were identified prior to the onset of disease signs. Studies were performed to characterize the onset and progression of the disease in these dogs. Neurological signs that included restlessness, unwillingness to cooperate with the handlers, and proprioceptive deficits first became apparent at approximately 12 months of age. The neurological signs progressed over time and by 21 to 23 months of age included general proprioceptive ataxia, menace response deficits, aggressive behaviors, cerebellar ataxia, intention tremors, decreased visual tracking, seizures, cognitive decline, and impaired prehension. Due to the severity of these signs, the dogs were euthanized between 21 and 23 months of age. Magnetic resonance imaging revealed pronounced progressive global brain atrophy with a more than sevenfold increase in the volume of the ventricular system between 9.5 and 22.5 months of age. Accompanying this atrophy were pronounced accumulations of autofluorescent inclusions throughout the brain and spinal cord. Ultrastructurally, the contents of these inclusions were found to consist primarily of membrane‐like aggregates. Inclusions with similar fluorescence properties were present in cardiac muscle. Similar to other forms of NCL, the affected dogs had low plasma carnitine concentrations, suggesting impaired carnitine biosynthesis. These data on disease progression will be useful in future studies using the canine model for therapeutic intervention studies.

Protein S-sulfhydration: Unraveling the prospective of hydrogen sulfide in the brain, vasculature and neurological manifestations

Hydrogen sulfide (H₂S) and hydrogen polysulfides (H₂S_n) are essential regulatory signaling molecules generated by the entire body, including the central nervous system. Researchers have focused on the classical H₂S signaling from the past several decades, whereas the last decade has shown the emergence of H₂S-induced protein S-sulfhydration signaling as a potential therapeutic approach. Cysteine S-persulfidation is a critical paradigm of post-translational modification in the process of H₂S signaling. Additionally, studies have shown the cross-relationship between S-sulfhydration and other cysteine-induced post-translational modifications, namely nitrosylation and carbonylation. In the central nervous system, S-sulfhydration is involved in the cytoprotection through various signaling pathways, viz. inflammatory response, oxidative stress, endoplasmic reticulum stress, atherosclerosis, thrombosis, and angiogenesis. Further, studies have demonstrated H₂S-induced S-sulfhydration in regulating different biological processes, such as mitochondrial integrity, calcium homeostasis, blood-brain permeability, cerebral blood flow, and long-term potentiation. Thus, protein S-sulfhydration becomes a crucial regulatory molecule in cerebrovascular and neurodegenerative diseases. Herein, we first described the generation of intracellular H₂S followed by the application of H₂S in the regulation of cerebral blood flow and blood-brain permeability. Further, we described the involvement of S-sulfhydration in different biological and cellular functions, such as inflammatory response, mitochondrial integrity, calcium imbalance, and oxidative stress. Moreover, we highlighted the importance of S-sulfhydration in cerebrovascular and neurodegenerative diseases.

Identification of genetic variants influencing methylation in brain with pleiotropic effects on psychiatric disorders

Psychiatric disorders affect 29% of the global population at least once in the lifespan, and genetic studies have proved a shared genetic basis among them, although the underlying molecular mechanisms remain largely unknown. DNA methylation plays an important role in complex disorders and, remarkably, enrichment of common genetic variants influencing allele-specific methylation (ASM) has been reported among variants associated with specific psychiatric disorders. In the present study we assessed the contribution of ASM to a set of eight psychiatric disorders by combining genetic, epigenetic and expression data. We interrogated a list of 3896 ASM tagSNPs in the brain in the summary statistics of a cross-disorder GWAS meta-analysis of eight psychiatric disorders from the Psychiatric Genomics Consortium, including more than 162,000 cases and 276,000 controls. We identified 80 SNPs with pleiotropic effects on psychiatric disorders that show an opposite directional effect on methylation and gene expression. These SNPs converge on eight candidate genes: ZSCAN29, ZSCAN31, BTN3A2, DDAH2, HAPLN4, ARTN, FAM109B and NAGA. ZSCAN29 shows the broadest pleiotropic effects, showing associations with five out of eight psychiatric disorders considered, followed by ZSCAN31 and BTN3A2, associated with three disorders. All these genes overlap with CNVs related to cognitive phenotypes and psychiatric traits, they are expressed in the brain, and seven of them have previously been associated with specific psychiatric disorders, supporting our results. To sum up, our integrative functional genomics analysis identified eight psychiatric disease risk genes that impact a broad list of disorders and highlight an etiologic role of SNPs that influence DNA methylation and gene expression in the brain.

Could SARS-CoV-2 Spike Protein Be Responsible for Long-COVID Syndrome?

SARS-CoV-2 infects cells via its spike protein binding to its surface receptor on target cells and results in acute symptoms involving especially the lungs known as COVID-19. However, increasing evidence indicates that many patients develop a chronic condition characterized by fatigue and neuropsychiatric symptoms, termed long-COVID. Most of the vaccines produced so far for COVID-19 direct mammalian cells via either mRNA or an adenovirus vector to express the spike protein, or administer recombinant spike protein, which is recognized by the immune system leading to the production of neutralizing antibodies. Recent publications provide new findings that may help decipher the pathogenesis of long-COVID. One paper reported perivascular inflammation in brains of deceased patients with COVID-19, while others showed that the spike protein could damage the endothelium in an animal model, that it could disrupt an in vitro model of the blood-brain barrier (BBB), and that it can cross the BBB resulting in perivascular inflammation. Moreover, the spike protein appears to share antigenic epitopes with human molecular chaperons resulting in autoimmunity and can activate toll-like receptors (TLRs), leading to release of inflammatory cytokines. Moreover, some antibodies produced against the spike protein may not be neutralizing, but may change its conformation rendering it more likely to bind to its receptor. As a result, one wonders whether the spike protein entering the brain or being expressed by brain cells could activate microglia, alone or together with inflammatory cytokines, since protective antibodies could not cross the BBB, leading to neuro-inflammation and contributing to long-COVID. Hence, there is urgent need to better understand the neurotoxic effects of the spike protein and to consider possible interventions to mitigate spike protein-related detrimental effects to the brain, possibly via use of small natural molecules, especially the flavonoids luteolin and quercetin.

Evaluating the Relationship Between Depression and Cognitive Function Among Children and Adolescents with HIV in Zambia

Depression is common among people living with HIV. Multiple studies demonstrate a link between depression and cognitive dysfunction in adults with HIV, but the association has been minimally investigated in children and adolescents with HIV in Africa. We conducted a cross-sectional analysis as part of the HIV-associated Neurocognitive Disorders in Zambia study, a prospective cohort study in Lusaka, Zambia. We included 208 perinatally-infected children with HIV ages 8-17 taking antiretroviral therapy and 208 HIV-exposed uninfected (HEU) controls. Cognition was assessed with a comprehensive neuropsychological battery. Depressive symptoms were evaluated using self-report and parent-report versions of the NIH Toolbox Sadness module and the Patient Health Questionnaire-9 (PHQ-9). Risk factors for depression and associations between depressive symptoms and cognition were evaluated in bivariable and multivariable regression models. Participants with HIV demonstrated higher levels of depressive symptoms than controls (mean NIH Toolbox Sadness T-Score 50 vs. 44, p < 0.01; mean PHQ-9 score 2.0 vs. 1.5, p = 0.03), and were more likely to have cognitive impairment (30% vs. 13%, p < 0.001). Risk factors for depressed mood included self-reported poor health (OR 7.8, p < 0.001) and negative life events (OR 1.3, p = 0.004) Depressed mood was associated with cognitive impairment in participants with HIV (OR = 2.9, 95% CI 1.2-7.2, p = 0.02) but not in HEU participants (OR 1.7, 95% CI 0.18-15.7, p = 0.6). In conclusion, depressed mood is common among youth with HIV in Zambia, and is associated with cognitive impairment. Depression may be a result of HIV-related stress and stigma, or may be part of the spectrum of HIV-associated neurocognitive disorders. The causal relationship between depressed mood and cognitive impairment is unclear and should be evaluated in future longitudinal studies.

Chronic nutritional restriction of omega-3 fatty acids induces a pro-inflammatory profile during the development of the rat visual system

Modern western diets have been associated with a reduced proportion of dietary omega-3 fatty acids leading to decreased levels of DHA (docosahexaenoic acid) in the brain. Low DHA content has been associated with altered development of visual acuity in infants and also with an altered time course of synapse elimination and plasticity in subcortical visual nuclei in rodents. Microglia has an active role in normal developmental processes such as circuitry refinement and plasticity, and its activation status can be modulated by omega-3 (ω3) and omega-6 (ω6) essential fatty acids. In the present study, we investigated the impact of dietary restriction of DHA (ω3^-), through the chronic administration of a coconut-based diet as the only fat source. This dietary protocol resulted in a reduction in DHA content in the retina and superior colliculus (SC) and in a neuroinflammatory outcome during the development of the rodent visual system. The ω3^- group showed changes in microglial morphology in the retina and SC and a corresponding altered pattern of pro-inflammatory cytokine expression. Early and late fish oil protocols supplementation were able to restore DHA levels. The early supplementation also decreased neuroinflammatory markers in the visual system. The present study indicates that a chronic dietary restriction of omega-3 fatty acids and the resulting deficits in DHA content, commonly observed in Western diets, interferes with the microglial profile leading to an inflamed microenvironment which may underlie a disruption of synapse elimination, altered topographical organization, abnormal plasticity, and duration of critical periods during brain development.

Fetal Neuroprotective Strategies: Therapeutic Agents and Their Underlying Synaptic Pathways

Synaptic signaling is integral for proper brain function. During fetal development, exposure to inflammation or mild hypoxic-ischemic insult may lead to synaptic changes and neurological damage that impairs future brain function. Preterm neonates are most susceptible to these deleterious outcomes. Evaluating clinically used and novel fetal neuroprotective measures is essential for expanding treatment options to mitigate the short and long-term consequences of fetal brain injury. Magnesium sulfate is a clinical fetal neuroprotective agent utilized in cases of imminent preterm birth. By blocking N-methyl-D-aspartate receptors, magnesium sulfate reduces glutamatergic signaling, which alters calcium influx, leading to a decrease in excitotoxicity. Emerging evidence suggests that melatonin and N-acetyl-L-cysteine (NAC) may also serve as novel putative fetal neuroprotective candidates. Melatonin has important anti-inflammatory and antioxidant properties and is a known mediator of synaptic plasticity and neuronal generation. While NAC acts as an antioxidant and a precursor to glutathione, it also modulates the glutamate system. Glutamate excitotoxicity and dysregulation can induce perinatal preterm brain injury through damage to maturing oligodendrocytes and neurons. The improved drug efficacy and delivery of the dendrimer-bound NAC conjugate provides an opportunity for enhanced pharmacological intervention. Here, we review recent literature on the synaptic pathways underlying these therapeutic strategies, discuss the current gaps in knowledge, and propose future directions for the field of fetal neuroprotective agents.

Neurosteroid allopregnanolone (3α,5α-THP) inhibits inflammatory signals induced by activated MyD88-dependent toll-like receptors

We have shown that endogenous neurosteroids, including pregnenolone and 3α,5α-THP inhibit toll-like receptor 4 (TLR4) signal activation in mouse macrophages and the brain of alcohol-preferring (P) rat, which exhibits innate TLR4 signal activation. The current studies were designed to examine whether other activated TLR signals are similarly inhibited by 3α,5α-THP. We report that 3α,5α-THP inhibits selective agonist-mediated activation of TLR2 and TLR7, but not TLR3 signaling in the RAW246.7 macrophage cell line. The TLR4 and TLR7 signals are innately activated in the amygdala and NAc from P rat brains and inhibited by 3α,5α-THP. The TLR2 and TLR3 signals are not activated in P rat brain and they are not affected by 3α,5α-THP. Co-immunoprecipitation studies indicate that 3α,5α-THP inhibits the binding of MyD88 with TLR4 or TLR7 in P rat brain, but the levels of TLR4 co-precipitating with TRIF are not altered by 3α,5α-THP treatment. Collectively, the data indicate that 3α,5α-THP inhibits MyD88- but not TRIF-dependent TLR signal activation and the production of pro-inflammatory mediators through its ability to block TLR-MyD88 binding. These results have applicability to many conditions involving pro-inflammatory TLR activation of cytokines, chemokines, and interferons and support the use of 3α,5α-THP as a therapeutic for inflammatory disease.

Interaction of maternal immune activation and genetic interneuronal inhibition

Genes and environment interact during intrauterine life, and potentially alter the developmental trajectory of the brain. This can result in life-long consequences on brain function. We have previously developed two transgenic mouse lines that suppress Gad1 expression in parvalbumin (PVALB) and neuropeptide Y (NPY) expressing interneuron populations using a bacterial artificial chromosome (BAC)-driven miRNA-based silencing technology. We were interested to assess if maternal immune activation (MIA), genetic interneuronal inhibition, and the combination of these two factors disrupt and result in long-term changes in neuroinflammatory gene expression, sterol biosynthesis, and acylcarnitine levels in the brain of maternally exposed offspring. Pregnant female WT mice were given a single intraperitoneal injection of saline or polyinosinic-polycytidilic acid [poly(I:C)] at E12.5. Brains of offspring were analyzed at postnatal day 90. We identified complex and persistent neuroinflammatory gene expression changes in the hippocampi of MIA-exposed offspring, as well in the hippocampi of Npy/Gad1 and Pvalb/Gad1 mice. In addition, both MIA and genetic inhibition altered the post-lanosterol sterol biosynthesis in the neocortex and disrupted the typical acylcarnitine profile. In conclusion, our findings suggest that both MIA and inhibition of interneuronal function have long-term consequences on critical homeostatic mechanisms of the brain, including immune function, sterol levels, and energy metabolism.

The Expanding Regulatory Mechanisms and Cellular Functions of Long Non-coding RNAs (lncRNAs) in Neuroinflammation

LncRNAs have emerged as important regulatory molecules in biological processes. They serve as regulators of gene expression pathways through interactions with proteins, RNA, and DNA. LncRNA expression is altered in several diseases of the central nervous system (CNS), such as neurodegenerative disorders, stroke, trauma, and infection. More recently, it has become clear that lncRNAs contribute to regulating both pro-inflammatory and anti-inflammatory pathways in the CNS. In this review, we discuss the molecular pathways involved in the expression of lncRNAs, their role and mechanism of action during gene regulation, cellular functions, and use of lncRNAs as therapeutic targets during neuroinflammation in CNS disorders.

Toxoplasma Infection Induces Sustained Up-Regulation of Complement Factor B and C5a Receptor in the Mouse Brain via Microglial Activation: Implication for the Alternative Complement Pathway Activation and Anaphylatoxin Signaling in Cerebral Toxoplasmosis

Toxoplasma gondii is a neurotropic protozoan parasite, which is linked to neurological manifestations in immunocompromised individuals as well as severe neurodevelopmental sequelae in congenital toxoplasmosis. While the complement system is the first line of host defense that plays a significant role in the prevention of parasite dissemination, Toxoplasma artfully evades complement-mediated clearance via recruiting complement regulatory proteins to their surface. On the other hand, the details of Toxoplasma and the complement system interaction in the brain parenchyma remain elusive. In this study, infection-induced changes in the mRNA levels of complement components were analyzed by quantitative PCR using a murine Toxoplasma infection model in vivo and primary glial cells in vitro. In addition to the core components C3 and C1q, anaphylatoxin C3a and C5a receptors (C3aR and C5aR1), as well as alternative complement pathway components properdin (CFP) and factor B (CFB), were significantly upregulated 2 weeks after inoculation. Two months post-infection, CFB, C3, C3aR, and C5aR1 expression remained higher than in controls, while CFP upregulation was transient. Furthermore, Toxoplasma infection induced significant increase in CFP, CFB, C3, and C5aR1 in mixed glial culture, which was abrogated when microglial activation was inhibited by pre-treatment with minocycline. This study sheds new light on the roles for the complement system in the brain parenchyma during Toxoplasma infection, which may lead to the development of novel therapeutic approaches to Toxoplasma infection-induced neurological disorders.

Stress-Related Brain Neuroinflammation Impact in Depression: Role of the Corticotropin-Releasing Hormone System and P2X7 Receptor

Depression and other psychiatric stress-related disorders are leading causes of disability worldwide. Up to date, treatments of mood disorders have limited success, most likely due to the multifactorial etiology of these conditions. Alterations in inflammatory processes have been identified as possible pathophysiological mechanisms in psychiatric conditions. Here, we review the main features of 2 systems involved in the control of these inflammatory pathways: the CRH system as a key regulator of the stress response and the ATP-gated ion-channel P2X7 receptor (P2X7R) involved in the control of immune functions. The pathophysiology of depression as a stress-related psychiatric disorder is depicted in terms of the impact of CRH and P2X7R function on inflammatory pathways in the brain. Understanding pathogenesis of affective disorders will lead to the development of therapies for treatment of depression and other stress-related diseases.

Is serum complement C1q related to major depressive disorder?

BACKGROUND

Major depressive disorder (MDD) has a high global incidence. While the pathogenesis of depression remains unknown, accumulating evidence has implicated inflammatory changes.

AIM

The aim of the study is to compare the serum complement C1q levels in patients with MDD and healthy controls.

SETTING AND DESIGN

The design was a case-control study.

MATERIALS AND METHODS

Blood samples were collected from the patients with MDD and healthy controls to assess the serum C1q levels using an immunotransmission turbidimetric method.

STATISTICAL ANALYSIS

Differences in complement C1q levels between patients with MDD and the controls, as well as between sexes among patients with MDD and the controls, were assessed using Mann-Whitney U-test. Spearman correlations were obtained between complement C1q levels and age.

RESULTS

In total, 1016 participants (508 MDD and 508 controls) were recruited. Differences in the sex ratio (male/female among controls, 181/327; and MDD, 178/330) and age (controls, 47.0 ± 14.9 years; MDD, 46.5 ± 16.5 years) were not significant. The C1q level in the patients with MDD was significantly higher than that in the healthy controls (P < 0.05). In the MDD group, C1q level correlated significantly with age.

CONCLUSION

Elevation of the serum complement C1q levels in MDD may support the use of C1q as a potential biomarker for diagnosing depression, but further research is needed.

Molecular Mechanisms of Glial Cells Related Signaling Pathways Involved in the Neuroinflammatory Response of Depression

Dysfunction of the glial cells, such as astrocytes and microglia, is one of the pathological features in many psychiatric disorders, including depression, which emphasizes that glial cells driving neuroinflammation is not only an important pathological change in depression but also a potential therapeutic target. In this review, we summarized a recent update about several signaling pathways in which glial cells may play their roles in depression through neuroinflammatory reactions. We focused on the basic knowledge of these signaling pathways by elaborating each of them. This review may provide an updated image about the recent advances on these signaling pathways that are essential parts of neuroinflammation involved in depression.

Neuronal Ceroid Lipofuscinosis in a Domestic Cat Associated with a DNA Sequence Variant That Creates a Premature Stop Codon in CLN6

A neutered male domestic medium-haired cat presented at a veterinary neurology clinic at 20 months of age due to progressive neurological signs that included visual impairment, focal myoclonus, and frequent severe generalized seizures that were refractory to treatment with phenobarbital. Magnetic resonance imaging revealed diffuse global brain atrophy. Due to the severity and frequency of its seizures, the cat was euthanized at 22 months of age. Microscopic examination of the cerebellum, cerebral cortex and brainstem revealed pronounced intracellular accumulations of autofluorescent storage material and inflammation in all 3 brain regions. Ultrastructural examination of the storage material indicated that it consisted almost completely of tightly-packed membrane-like material. The clinical signs and neuropathology strongly suggested that the cat suffered from a form of neuronal ceroid lipofuscinosis (NCL). Whole exome sequence analysis was performed on genomic DNA from the affected cat. Comparison of the sequence data to whole exome sequence data from 39 unaffected cats and whole genome sequence data from an additional 195 unaffected cats revealed a homozygous variant in CLN6 that was unique to the affected cat. This variant was predicted to cause a stop gain in the transcript due to a guanine to adenine transition (ENSFCAT00000025909:c.668G > A; XM_003987007.5:c.668G > A) and was the sole loss of function variant detected. CLN6 variants in other species, including humans, dogs, and sheep, are associated with the CLN6 form of NCL. Based on the affected cat's clinical signs, neuropathology and molecular genetic analysis, we conclude that the cat's disorder resulted from the loss of function of CLN6. This study is only the second to identify the molecular genetic basis of a feline NCL. Other cats exhibiting similar signs can now be screened for the CLN6 variant. This could lead to establishment of a feline model of CLN6 disease that could be used in therapeutic intervention studies.

Neuroimmune System as a Driving Force for Plasticity Following CNS Injury

Following an injury to the central nervous system (CNS), spontaneous plasticity is observed throughout the neuraxis and affects multiple key circuits. Much of this spontaneous plasticity can elicit beneficial and deleterious functional outcomes, depending on the context of plasticity and circuit affected. Injury-induced activation of the neuroimmune system has been proposed to be a major factor in driving this plasticity, as neuroimmune and inflammatory factors have been shown to influence cellular, synaptic, structural, and anatomical plasticity. Here, we will review the mechanisms through which the neuroimmune system mediates plasticity after CNS injury. Understanding the role of specific neuroimmune factors in driving adaptive and maladaptive plasticity may offer valuable therapeutic insight into how to promote adaptive plasticity and/or diminish maladaptive plasticity, respectively.

Asiaticoside produces an antidepressant‑like effect in a chronic unpredictable mild stress model of depression in mice, involving reversion of inflammation and the PKA/pCREB/BDNF signaling pathway

Asiaticoside is one of the triterpenoid components found in Centella asiatica that has promising neuroprotective properties. The present study aimed to evaluate the antidepressant‑like properties of asiaticoside and to investigate the possible mechanisms underlying its mode of action using a mouse model of chronic unpredictable mild stress (CMS). Behavioral tests, including sucrose preference test, forced swimming test and tail suspension test, were performed to evaluate symptoms of depression. The expression levels of neurotransmitters, 5‑hydroxytryptamine (5‑HT) and norepinephrine (NE), in the hippocampus were measured by high‑performance liquid chromatography. ELISA and western blotting were used to detect protein expression. It was demonstrated that asiaticoside treatment (20 and 40 mg/kg; intragastric) significantly reversed the decrease in sucrose consumption, and reduced the immobility time in tail suspension tests and forced swimming tests in CMS mice. Furthermore, asiaticoside treatment upregulated the expression of 5‑HT and NE in the CMS mouse model. Asiaticoside administration also downregulated the levels of interleukin (IL)‑1β, IL‑6 and tumor necrosis factor‑α in the hippocampus, and reduced the phosphorylation of nuclear factor (NF)‑κBp65 and the expression of nod‑like receptor protein 3 (NLRP3), thus decreasing the expression of mature caspase‑1. Furthermore, asiaticoside significantly increased the levels of cAMP and protein kinase A (PKA), and enhanced phosphorylation of the cAMP‑related specific marker vasodilator‑stimulated phosphoprotein at serine 157. Therefore, asiaticoside may activate the cAMP/PKA signaling pathway to inhibit NF‑κB‑ and NLRP3‑related inflammation. Moreover, phosphorylation of the cAMP‑responsive element‑binding protein at serine 133 and the expression of brain‑derived neurotrophic factor were increased after asiaticoside administration. Collectively, the present results suggested that asiaticoside may play a vital role as an antidepressant and anti‑inflammatory agent in the CMS mouse model by regulating the cAMP/PKA signaling pathway.

Acute exposure to low-level light at night is sufficient to induce neurological changes and depressive-like behavior

The advent and wide-spread adoption of electric lighting over the past century has profoundly affected the circadian organization of physiology and behavior for many individuals in industrialized nations; electric lighting in homes, work environments, and public areas have extended daytime activities into the evening, thus, increasing night-time exposure to light. Although initially assumed to be innocuous, chronic exposure to light at night (LAN) is now associated with increased incidence of cancer, metabolic disorders, and affective problems in humans. However, little is known about potential acute effects of LAN. To determine whether acute exposure to low-level LAN alters brain function, adult male, and female mice were housed in either light days and dark nights (LD; 14 h of 150 lux:10 h of 0 lux) or light days and low level light at night (LAN; 14 h of 150 lux:10 h of 5 lux). Mice exposed to LAN on three consecutive nights increased depressive-like responses compared to mice housed in dark nights. In addition, female mice exposed to LAN increased central tendency in the open field. LAN was associated with reduced hippocampal vascular endothelial growth factor-A (VEGF-A) in both male and female mice, as well as increased VEGFR1 and interleukin-1β mRNA expression in females, and reduced brain derived neurotrophic factor mRNA in males. Further, LAN significantly altered circadian rhythms (activity and temperature) and circadian gene expression in female and male mice, respectively. Altogether, this study demonstrates that acute exposure to LAN alters brain physiology and can be detrimental to well-being in otherwise healthy individuals.

Environmental Signals on Microglial Function during Brain Development, Neuroplasticity, and Disease

Recent discoveries on the neurobiology of the immunocompetent cells of the central nervous system (CNS), microglia, have been recognized as a growing field of investigation on the interactions between the brain and the immune system. Several environmental contexts such as stress, lesions, infectious diseases, and nutritional and hormonal disorders can interfere with CNS homeostasis, directly impacting microglial physiology. Despite many encouraging discoveries in this field, there are still some controversies that raise issues to be discussed, especially regarding the relationship between the microglial phenotype assumed in distinct contexts and respective consequences in different neurobiological processes, such as disorders of brain development and neuroplasticity. Also, there is an increasing interest in discussing microglial–immune system cross-talk in health and in pathological conditions. In this review, we discuss recent literature concerning microglial function during development and homeostasis. In addition, we explore the contribution of microglia to synaptic disorders mediated by different neuroinflammatory outcomes during pre- and postnatal development, with long-term consequences impacting on the risk and vulnerability to the emergence of neurodevelopmental, neurodegenerative, and neuropsychiatric disorders.

Intimate neuro-immune interactions: breaking barriers between systems to make meaningful progress

The nervous system is often viewed as an isolated system that integrates information from the environment and host. Recently, there has been a renewed focus exploring the concept that the nervous system also communicates across biological systems. Specifically, several high profile studies have recently highlighted the importance of neuro-immune communication in the context of homeostasis, central nervous system disorders, host defense and injury. Here, we discuss the history of shared mechanisms and interconnectedness of the nervous, immune and epithelial compartments. In light of these overlapping mechanisms, it is perhaps unsurprising that neuro-immune-epithelial signaling plays a key role in regulating diverse biological phenomena. In this review, we explore recent breakthroughs in understanding neuro-immune signaling to highlight the importance of interdisciplinary approaches to biomedical research and the future development of novel therapeutics.

Piperlongumine produces antidepressant-like effects in rats exposed to chronic unpredictable stress

Piperlongumine, an alkaloid compound extracted from Peper longum L, has been reported to produce neuroprotective effects in the brain and exert various pharmacological activities such as antitumor, antiangiogenic, anti-inflammatory and analgesic properties. The aim of this study was to investigate the antidepressant-like effects and the possible mechanism of action of piperlongumine in a chronic unpredictable stress (CUS) model. We found that, with venlafaxine as a positive control, orally administered piperlongumine (12.5 and 25 mg/kg) for 7 days, not a single dose, significantly reduced immobility time in the forced swimming test, but did not alter locomotor activity in the open field test, indicating that piperlongumine has antidepressant-like effects without nonspecific motor changes. Then, using the CUS model of depression, piperlongumine was administrated orally for 4 weeks, followed by sucrose preference and forced swimming tests to evaluate the depressive-like behaviors. We found that piperlongumine reversed both the decreased sucrose preference and increased immobility time in rats exposed to CUS. In addition, piperlongumine also reversed the increase in proinflammatory cytokine levels in the hippocampus of rats in the CUS model. Altogether, the present study demonstrated that piperlongumine exhibits the antidepressant-like effects in rats, which may be mediated by the inhibition of the neuronal inflammation in the hippocampus.

Transcriptional regulation of homeostatic and disease-associated-microglial genes by IRF1, LXRβ, and CEBPα

Microglia transform from homeostatic to disease-associated-microglia (DAM) profiles in neurodegeneration. Within DAM, we recently identified distinct pro-inflammatory and anti-inflammatory sub-profiles although transcriptional regulators of homeostatic and distinct DAM profiles remain unclear. Informed by these studies, we nominated CEBPα, IRF1, and LXRβ as likely regulators of homeostatic, pro-inflammatory and anti-inflammatory DAM states and performed in-vitro siRNA studies in primary microglia to identify roles of each transcriptional factor (TF) in regulating microglial activation, using an integrated transcriptomics, bioinformatics and experimental validation approach. Efficient (>70%) silencing of TFs in microglia revealed reciprocal regulation between each TF specifically following pro-inflammatory activation. Neuroinflammatory transcriptomic profiling of microglia coupled with qPCR validation revealed distinct gene clusters with unique patterns of regulation by each TF, which were independent of LPS stimulation. While all three TFs (especially IRF1 and LXRβ) positively regulated core DAM genes (Apoe, Axl, Clec7a, Tyrobp, and Trem2) as well as homeostatic and pro-inflammatory DAM genes, LPS, and IFNγ increased pro-inflammatory DAM but suppressed homeostatic and anti-inflammatory DAM gene expression via an Erk1/2-dependent signaling pathway. IRF1 and LXRβ silencing suppressed microglial phagocytic activity for polystyrene microspheres as well as fAβ42 while IRF1 silencing strongly suppressed production of pro-inflammatory cytokines in response to LPS. Our studies reveal complex transcriptional regulation of homeostatic and DAM profiles whereby IRF1, LXRβ, and CEBPα positively regulate both pro- and anti-inflammatory DAM genes while activating stimuli independently augment pro-inflammatory DAM responses and suppress homeostatic and anti-inflammatory responses via Erk signaling. This framework can guide development of therapeutic immuno-modulatory strategies for neurodegeneration.

Modulation of Apoptotic Cell Death and Neuroprotective Effects of Glutathione-L-Dopa Codrug Against H2O2-Induced Cellular Toxicity

The L-3,4-dihydroxyphenylalanine (LD) is the gold standard drug currently used to manage Parkinson’s disease (PD) and to control its symptoms. However, LD could cause disease neurotoxicity due to the generation of pro-oxidant intermediates deriving from its autoxidation. In order to overcome this limitation, we have conjugated LD to the natural antioxidant glutathione (GSH) to form a codrug (GSH-LD). Here we investigated the effect of GSH-LD on H₂O₂-induced cellular toxicity in undifferentiated and differentiated lymphoma U-937 and dopaminergic neuroblastoma SH-SY5Y cell lines, used respectively as models to study the involvement of macrophages/microglia and dopaminergic neurons in PD. We analyzed the effect of GSH-LD on apoptosis and cellular oxidative stress, both considered strategic targets for the prevention and treatment of neurodegenerative diseases. Compared to LD and GSH, GSH-LD had a stronger effect in preventing hydrogen peroxide (H₂O₂) induced apoptosis in both cell lines. Moreover, GSH-LD was able to preserve cell viability, cellular redox status, gluthation metabolism and prevent reactive oxygen species (ROS) formation, in a phosphinositide 3-kinase (PI3K)/kinase B (Akt)-dependent manner, in a neurotoxicity cellular model. Our findings indicate that the GSH-LD codrug offers advantages deriving from the additive effect of LD and GSH and it could represent a promising candidate for PD treatment.

Cytokine inflammatory threat, but not LPS one, shortens GABAergic synaptic currents in the mouse spinal cord organotypic cultures

Background

Synaptic dysfunction, named synaptopathy, due to inflammatory status of the central nervous system (CNS) is a recognized factor potentially underlying both motor and cognitive dysfunctions in neurodegenerative diseases. To gain knowledge on the mechanistic interplay between local inflammation and synapse changes, we compared two diverse inflammatory paradigms, a cytokine cocktail (CKs; IL-1β, TNF-α, and GM-CSF) and LPS, and their ability to tune GABAergic current duration in spinal cord cultured circuits.

Methods

We exploit spinal organotypic cultures, single-cell electrophysiology, immunocytochemistry, and confocal microscopy to explore synaptic currents and resident neuroglia reactivity upon CK or LPS incubation.

Results

Local inflammation in slice cultures induced by CK or LPS stimulations boosts network activity; however, only CKs specifically reduced GABAergic current duration. We pharmacologically investigated the contribution of GABA_AR α-subunits and suggested that a switch of GABA_AR α1-subunit might have induced faster GABA_AR decay time, weakening the inhibitory transmission.

Conclusions

Lower GABAergic current duration could contribute to providing an aberrant excitatory transmission critical for pre-motor circuit tasks and represent a specific feature of a CK cocktail able to mimic an inflammatory reaction that spreads in the CNS. Our results describe a selective mechanism that could be triggered during specific inflammatory stress.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1519-z) contains supplementary material, which is available to authorized users.

Oxytocin Suppresses Inflammatory Responses Induced by Lipopolysaccharide through Inhibition of the eIF-2-ATF4 Pathway in Mouse Microglia

Microglia maintain brain homeostasis and modulate neuroinflammation and are implicated in the pathogenesis of various neurological diseases such as Alzheimer's disease. In this study, we found that in lipopolysaccharide (LPS)-stimulated microglia, the endoplasmic reticulum (ER) stress-related eIF-2-ATF4 pathway plays significant roles in TNF- and IL-6 production, as well as in the inflammasome-mediated production of IL-1. Furthermore, our analysis revealed that oxytocin (OT), a nonapeptide synthesized in the hypothalamus, suppressed the production of these proinflammatory cytokines by inhibiting activation of the eIF-2-ATF4 pathway. Our findings therefore suggest a novel anti-inflammatory axis of OT in activated microglia, which would be helpful for developing the novel effective strategies for regulating microglia-associated neuroinflammation.

Chronic pain and central sensitization in immuno-inflammatory rheumatic diseases: pathogenesis, clinical manifestations, the possibility of using targeted disease modifying antirheumatic drugs

Chronic pain is one of the main manifestations of immuno-inflammatory rheumatic diseases (IIRD), such as rheumatoid arthritis (RA) and psoriatic arthritis (PsA), which determines the severity of suffering, reduced quality of life and disability of patients. Unfortunately, the use of synthetic and biological disease modifying antirheumatic drugs, as well as non-steroidal anti-inflammatory drugs does not always provide sufficient control of pain in IIRD, even when it is possible to achieve a significant reduction in inflammatory activity. The reason for this is the complex mechanism of chronic pain. It includes not onlystimulation of pain receptors caused by damage of the elements of the musculoskeletal system, but also a change in the perception of pain associated with the phenomenon of central sensitization (CS). CS is characterized by a significant and persistent increase in the sensitivity of nociceptive neurons to pain and nonpain stimuli. One of the main theories of the CS development consider this phenomenon as an inflammatory reaction of the neuronenvironmentthe activation of astrocytes and microglial cells, local hyperproduction of cytokines, inflammatory mediators and neurotrophic factors. Factors contributing to the development of CS in IIRD are obesity, depression and anxiety, damage of the somatosensory system, insufficient relief of pain in the onset of the disease. Clinical manifestations of CS in IIRD is hyperalgesia, allodinia, «expanded pain» and secondary fibromyalgia. An important role in the development of chronic pain and CS plays the intracellular inflammatory pathway JAK-STAT. Therefore, JAK inhibitors, such as tofacitinib, used in RA and PsA, can also be considered as an effective means of controlling chronic pain in these diseases.

Reversible Functional Changes Evoked by Anodal Epidural Direct Current Electrical Stimulation of the Rat Auditory Cortex

Rat auditory cortex was subjected to 0.1 mA anodal direct current in seven 10-min sessions on alternate days. Based on the well-known auditory cortex control of olivocochlear regulation through corticofugal projections, auditory brainstem responses (ABRs) were recorded as an indirect test of the effectiveness and reversibility of the multisession protocol of epidural stimulation. Increases of 20-30 dB ABR auditory thresholds shown after epidural stimulation reverted back to control levels 10 min after a single session. However, increases in thresholds revert 4 days after multisession stimulation. Less changes in wave amplitudes and threshold shifts were shown in ABR recorded contralaterally to the electrically stimulated side of the brain. To assess tissue effects of epidural electric stimulation on the brain cortex, well characterized functional anatomical markers of glial cells (GFAP/astrocytes and Iba1/microglial cells) and neurons (c-Fos) were analyzed in alternate serial sections by quantitative immunocytochemistry. Restricted astroglial and microglial reactivity was observed within the cytoarchitectural limits of the auditory cortex. However, interstitial GFAP overstaining was also observed in the ventricular surface and around blood vessels, thus supporting a potential global electrolytic stimulation of the brain. These results correlate with extensive changes in the distribution of c-Fos immunoreactive neurons among layers along sensory cortices after multisession stimulation. Quantitative immunocytochemical analysis supported this idea by showing a significant increase in the number of positive neurons in supragranular layers and a decrease in layer 6 with no quantitative changes detected in layer 5. Our data indicate that epidural stimulation of the auditory cortex induces a reversible decrease in hearing sensitivity due to local, restricted epidural stimulation. A global plastic response of the sensory cortices, also reported here, may be related to electrolytic effects of electric currents.

Mast Cells in Stress, Pain, Blood-Brain Barrier, Neuroinflammation and Alzheimer's Disease

Mast cell activation plays an important role in stress-mediated disease pathogenesis. Chronic stress cause or exacerbate aging and age-dependent neurodegenerative diseases. The severity of inflammatory diseases is worsened by the stress. Mast cell activation-dependent inflammatory mediators augment stress associated pain and neuroinflammation. Stress is the second most common trigger of headache due to mast cell activation. Alzheimer's disease (AD) is a progressive irreversible neurodegenerative disease that affects more women than men and woman's increased susceptibility to chronic stress could increase the risk for AD. Modern life-related stress, social stress, isolation stress, restraint stress, early life stress are associated with an increased level of neurotoxic beta amyloid (Aβ) peptide. Stress increases cognitive dysfunction, generates amyloid precursor protein (APP), hyperphosphorylated tau, neurofibrillary tangles (NFTs), and amyloid plaques (APs) in the brain. Stress-induced Aβ persists for years and generates APs even several years after the stress exposure. Stress activates hypothalamic-pituitary adrenal (HPA) axis and releases corticotropin-releasing hormone (CRH) from hypothalamus and in peripheral system, which increases the formation of Aβ, tau hyperphosphorylation, and blood-brain barrier (BBB) disruption in the brain. Mast cells are implicated in nociception and pain. Mast cells are the source and target of CRH and other neuropeptides that mediate neuroinflammation. Microglia express receptor for CRH that mediate neurodegeneration in AD. However, the exact mechanisms of how stress-mediated mast cell activation contribute to the pathogenesis of AD remains elusive. This mini-review highlights the possible role of stress and mast cell activation in neuroinflammation, BBB, and tight junction disruption and AD pathogenesis.