CNS-targeted production of IL-17A induces glial activation, microvascular pathology and enhances the neuroinflammatory response to systemic endotoxemia

Effects of Lycium barbarum polysaccharide on cytokines in adolescents with subthreshold depression: a randomized controlled study

JOURNAL/nrgr/04.03/01300535-202409000-00036/figure1/v/2024-01-16T170235Z/r/image-tiff Strong evidence has accumulated to show a correlation between depression symptoms and inflammatory responses. Moreover, anti-inflammatory treatment has shown partial effectiveness in alleviating depression symptoms. Lycium barbarum polysaccharide (LBP), derived from Goji berries, exhibits notable antioxidative and anti-inflammatory properties. In our recent double-blinded randomized placebo-controlled trial, we found that LBP significantly reduced depressive symptoms in adolescents with subthreshold depression. It is presumed that the antidepressant effect of LBP may be associated with its influence on inflammatory cytokines. In the double-blinded randomized controlled trial, we enrolled 29 adolescents with subthreshold depression and randomly divided them into an LBP group and a placebo group. In the LBP group, adolescents were given 300 mg/d LBP. A 6-week follow up was completed by 24 adolescents, comprising 14 adolescents from the LBP group (15.36 ± 2.06 years, 3 men and 11 women) and 10 adolescents from the placebo group (14.9 ± 1.6 years, 2 men and 8 women). Our results showed that after 6 weeks of treatment, the interleukin-17A level in the LBP group was lower than that in the placebo group. Network analysis showed that LBP reduced the correlations and connectivity between inflammatory factors, which were associated with the improvement in depressive symptoms. These findings suggest that 6-week administration of LBP suppresses the immune response by reducing interleukin-17A level, thereby exerting an antidepressant effect.

Effects on peripheral and central nervous system of key inflammatory intercellular signalling peptides and proteins in psoriasis

Psoriasis is a chronic systemic inflammatory cutaneous disease. Where the immune system plays an important role in its pathogenesis, with key inflammatory intercellular signalling peptides and proteins including IL-17 and IL-23. The psychoneurological system also figures prominently in development of psoriasis. There is a high prevalence of comorbidity between psoriasis and mental health disorders such as depression, anxiety and mania. Patients with psoriasis often suffer from pathological pain in the lesions, and their neurological accidents could improve the lesions in innervated areas. The immune system and the psychoneurological system interact closely in the pathogenesis of psoriasis. Patients with psoriasis exhibit abnormal levels of neuropeptides both in circulating and localized lesion, acting as immunomodulators involved in the inflammatory response. Moreover, receptors for inflammatory factors are expressed in both peripheral and central nervous systems (CNSs), suggesting that nervous system can receive and be influenced by signals from immune system. Key inflammatory intercellular signalling peptides and proteins in psoriasis, such as IL-17 and IL-23, can be involved in sensory signalling and may affect synaptic plasticity and the blood-brain barrier of CNS through the circulation. This review provides an overview of the multiple effects on the peripheral and CNS under conditions of systemic inflammation in psoriasis, providing a framework and inspiration for in-depth studies of neuroimmunomodulation in psoriasis.

Ethanol extract of Verbena officinalis alleviates MCAO-induced ischaemic stroke by inhibiting IL17A pathway-regulated neuroinflammation

BACKGROUND

The prevention and treatment of ischaemic stroke is a worldwide challenge, and effective clinical treatment strategies are lacking. Studies have demonstrated the efficacy of Verbena officinalis in managing cerebrovascular disorders. However, the neuroprotective bioactive components and mechanisms remain unclear.

PURPOSE

To investigate the pharmacological combinatorial components and mechanism underlying the anti-ischemic stroke effect of the ethanol extract of Verbena officinalis (VO Ex).

STUDY DESIGN AND METHODS

The components of VO Ex were identified by HPLC. A middle cerebral artery occlusion (MCAO) induced brain injury model was used to assess the therapeutic effect of VO Ex. The activity of the chemical components of VO Ex was evaluated using a primary astrocyte injury model induced by oxygen-glucose deprivation/reperfusion (OGD/R). RNA sequencing was used to reveal the potential targets of VO Ex against cerebral ischemia-reperfusion injury (CIRI), and the results were verified by qRT-PCR and western blotting. The key components and target binding ability were predicted by molecular docking. Finally, the mechanism of combinatorial components was verified by experiments.

RESULTS

The HPLC results indicated that the main ingredients of VO Ex were hastatoside, verbenalin, acteoside, luteolin, apigenin and hispidulin. In vivo experiments showed that VO Ex improved MCAO-induced acute cerebral ischemic injury. Transcriptomic data and biological experiments suggested that VO Ex exerted therapeutic effects through IL17A signalling pathways. The in vitro experiments indicated that verbenalin, acteoside, luteolin, apigenin and hispidulin exhibited neuroprotective activities. The novel formula of VALAH, derived from the aforementioned active ingredients, exhibited superior efficacy compared to each individual component. Molecular docking and mechanistic studies have confirmed that VALAH functions in the treatment of ischaemic stroke by suppressing the activation of the IL17A signalling pathway.

CONCLUSION

This work is the first to reveal that VO Ex effectively inhibits the IL17A signaling pathway and mitigates neuroinflammation following ischemic stroke. Moreover, we identified the novel formula VALAH as the bioactive combinatorial components for VO Ex. Further research suggests that the activity of VALAH is associated with IL17A-mediated regulation of neuroinflammation. This finding provides new insights into the efficacious components and mechanisms of traditional Chinese medicine.

Unleashing nature's potential and limitations: Exploring molecular targeted pathways and safe alternatives for the treatment of multiple sclerosis (Review)

Driven by the limitations and obstacles of the available approaches and medications for multiple sclerosis (MS) that still cannot treat the disease, but only aid in accelerating the recovery from its attacks, the use of naturally occurring molecules as a potentially safe and effective treatment for MS is being explored in model organisms. MS is a devastating disease involving the brain and spinal cord, and its symptoms vary widely. Multiple molecular pathways are involved in the pathogenesis of the disease. The present review showcases the recent advancements in harnessing nature's resources to combat MS. By deciphering the molecular pathways involved in the pathogenesis of the disease, a wealth of potential therapeutic agents is uncovered that may revolutionize the treatment of MS. Thus, a new hope can be envisioned in the future, aiming at paving the way toward identifying novel safe alternatives to improve the lives of patients with MS.

IL-17A Facilitates Entry of Autoreactive T-Cells and Granulocytes into the CNS During EAE

Interleukin-17A plays a crucial role in multiple sclerosis and other autoimmune diseases. Although the link between IL-17 and disease activity has been clearly demonstrated, the precise function of this cytokine remains elusive. Here, we investigated the function of astrocyte-targeted IL-17A production in GF/IL-17 transgenic mice during EAE. In particular, IL-17A is important during disease induction. In mice with transgenic IL-17A production, disease occurs earlier and peak disease is more severe, whereas remission is unimpaired. IL-17A synthesis is associated with increased infiltration of granulocytes into the CNS and microglial activation. Moreover, IL-17A synthesis allows induction of MOG-EAE without the additional administration of the co-adjuvant pertussis toxin. Examination of double transgenic GF/IL-17 2D2 mice revealed that, in addition, local IL-17A production facilitates spontaneous infiltration of immune cells into the CNS in mice expressing a MOG-specific T-cell receptor. Overall, we provide evidence for a crucial effect of IL-17A in the induction phase of EAE, facilitating the infiltration of granulocytes and autoreactive T-cells into the CNS.

The Extract of Acanthopanacis Cortex Relieves the Depression-Like Behavior and Modulates IL-17 Signaling in Chronic Mild Stress-Induced Depressive Mice

Background

Acanthopanacis Cortex (AC) is a valuable Chinese medicine, which exerts beneficial effects on anti-fatigue, anti-stress, and inflammatory modulation in the periphery. However, the central nervous system (CNS) function of AC has not been clearly illustrated. As communication between the peripheral immune system and the CNS converges, it promotes a heightened neuroinflammatory environment that contributes to depression. We investigated the effect of AC against depression through neuroinflammatory modulation.

Methods

Network pharmacology was used to screen for target compounds and pathways. Mice with CMS-induced depression were used to evaluate the efficacy of AC against depression. Behavioral studies and detection of neurotransmitters, neurotrophic factors, and pro-inflammatory cytokines were performed. The IL-17 signaling cascade was involved to further investigate the underlying mechanism of AC against depression.

Results

Twenty-five components were screened by network pharmacology and the IL-17 mediated signaling pathway was associated with the antidepressant action of AC. This herb had a beneficial effect on CMS-induced depressive mice, including improvements in depressive behavior, modulation of neurotransmitter levels, neurotrophic factors, and pro-inflammatory cytokines.

Conclusions

Our results revealed that AC exhibits effects on anti-depression and one of the mechanisms was mediated by neuroinflammatory modulation.

Relationship between Hypoxic and Immune Pathways Activation in the Progression of Neuroinflammation: Role of HIF-1α and Th17 Cells

Neuroinflammation is a common event in degenerative diseases of the central and peripheral nervous system, triggered by alterations in the immune system or inflammatory cascade. The pathophysiology of these disorders is multifactorial, whereby the therapy available has low clinical efficacy. This review propounds the relationship between the deregulation of T helper cells and hypoxia, mainly Th17 and HIF-1α molecular pathways, events that are involved in the occurrence of the neuroinflammation. The clinical expression of neuroinflammation is included in prevalent pathologies such as multiple sclerosis, Guillain-Barré syndrome, and Alzheimer's disease, among others. In addition, therapeutic targets are analyzed in relation to the pathways that induced neuroinflammation.

Innate lymphoid cells in depression: Current status and perspectives

The recent discovery of innate lymphoid cells (ILCs) has provided new insights into our understanding of the pathogenesis of many disease conditions with immune dysregulation. Type 1 innate lymphoid cells (ILC1s) induce type I immunity and are characterized by the expression of signature cytokine IFN-γ and the master transcription factor T-bet; ILC2s stimulate type II immune responses and are defined by the expression of signature cytokines IL-5 and IL-13, and transcription factors ROR-α and GATA3; ILC3s requires the transcription factor RORγt and produce IL-22 and IL-17. ILCs are largely tissue-resident and are enriched at barrier surfaces of the mammalian body. Increasing evidence shows that inflammation is involved in the pathogenesis of depression. Although few studies have directly investigated the role of ILCs in depression, several studies have examined the levels of cytokines produced by ILCs in depressed subjects. This review summarizes the potential roles of ILCs in depression. A better understanding of the biology of ILCs may lead to the development of new therapeutic strategies for the management of depression.

Interleukin-17 as a potential therapeutic target for chronic pain

Chronic pain remains to be a clinical challenge and is recognized as a major health problem with varying impacts on quality of life. Currently, the first-line therapy for chronic pain is opioids, which are often accompanied by unwanted psychoactive side effects. Thus, new and effective treatments for chronic pain are urgently needed and eagerly pursued. Inflammatory cytokines, especially interleukin-17 (IL-17), are reportedly potential therapeutic targets owing to their pivotal role in chronic pain from the neuroinflammation perspective. Recently, substantial evidence confirmed that IL-17 and IL-17 receptors (IL-17Rs) were increased in neuropathic, inflammatory, and cancer pain models. Notably, IL-17/IL-17R antibodies also reportedly relieve or cure inflammatory- and pain-related diseases. However, existing studies have reported controversial results regarding IL-17/IL-17Rs as potential therapeutic targets in diverse animal models of chronic pain. In this review, we present a summary of published studies and discuss the evidence, from basic to clinical to research, regarding the role and mechanism of action between IL-17 and diverse kinds of chronic pain in animal models and clinical patients. Furthermore, we evaluated IL-17-based therapy as a potential therapeutic strategy for inflammatory- and pain-related disease. Importantly, we also discussed clinical trials of IL-17/IL-17R targeting monoclonal antibodies. Overall, we found that IL-17 is a potential therapeutic target for chronic pain from the perspective of neuroinflammation.

The role of interleukin-17 in epilepsy

Epilepsy is a common neurological disorder that seriously affects human health. It is a chronic central nervous system dysfunction caused by abnormal discharges of neurons. About 50 million patients worldwide are affected by epilepsy. Although epileptic symptoms of most patients are controllable, some patients with refractory epilepsy have no response to antiseizure medications. It is necessary to investigate the pathogenesis of epilepsy and identify new therapeutic targets for refractory epilepsy. Epileptic disorders often accompany cerebral inflammatory reactions. Recently, the role of inflammation in the onset of epilepsy has increasingly attracted attention. The activation of both innate and adaptive immunity plays a significant role in refractory epilepsy. According to several clinical studies, interleukin-17, an essential inflammatory mediator linking innate and adaptive immunity, increased significantly in the body liquid and epileptic focus of patients with epilepsy. Experimental studies also indicated that interleukin-17 participated in epileptogenesis through various mechanisms. This review summarized the current studies about interleukin-17 in epilepsy and aimed at finding new therapeutic targets for refractory epilepsy.

The gut-brain axis and sodium appetite: Can inflammation-related signaling influence the control of sodium intake?

Sodium is the main cation present in the extracellular fluid. Sodium and water content in the body are responsible for volume and osmotic homeostasis through mechanisms involving sodium and water excretion and intake. When body sodium content decreases below the homeostatic threshold, a condition termed sodium deficiency, highly motivated sodium seeking, and intake occurs. This is termed sodium appetite. Classically, sodium and water intakes are controlled by a number of neuroendocrine mechanisms that include signaling molecules from the renin-angiotensin-aldosterone system acting in the central nervous system (CNS). However, recent findings have shown that sodium and water intakes can also be influenced by inflammatory agents and mediators acting in the CNS. For instance, central infusion of IL-1β or TNF-α can directly affect sodium and water consumption in animal models. Some dietary conditions, such as high salt intake, have been shown to change the intestinal microbiome composition, stimulating the immune branch of the gut-brain axis through the production of inflammatory cytokines, such as IL-17, which can stimulate the brain immune system. In this review, we address the latest findings supporting the hypothesis that immune signaling in the brain could produce a reduction in thirst and sodium appetite and, therefore, contribute to sodium intake control.

Th17 cell-mediated immune response in a subpopulation of dogs with idiopathic epilepsy

BACKGROUND

Canine idiopathic epilepsy (IE) is a common neurological disease with severe impact on the owner´s and the dog's quality of life. A subpopulation of dogs with IE does not respond to antiseizure drugs (non-responder). Th17 cells (T helper cells) and their proinflammatory Interleukin-17 (IL-17) are part of the immune system and previous studies showed their involvement in the pathogenesis of several autoimmune diseases. Non-responder might have an abnormal immune response against structures of the central nervous system. To discover a new aetiology of canine IE and thereby optimising the therapy of intractable IE, this prospective study aimed to investigate Th17 cells and IL-17 in dogs with IE. The underlying hypothesis was that in some dogs with IE a Th17 cell-mediated immune response could be detectable.

METHODS

57 dogs with IE and 10 healthy dogs (control group, C) were enrolled in the study. EDTA blood was taken to measure Th17 cells by flow cytometry. IL-17 was measured in 35 cerebrospinal fluid (CSF) and 33 serum samples using an enzyme-linked immunosorbent assay (ELISA). It was investigated whether there was a significant increase of stimulated Th17 cells in blood samples or of IL-17 in serum and CSF samples of dogs with IE in comparison to C. Correlations between the amount of Th17 cells/μL or IL-17 and different clinical parameters e.g. seizure frequency, seizure type, seizure severity or treatment response were evaluated. Additionally, Th17 cells/μL were randomly controlled of 17 dogs with IE and were examined for changes over time and in relation to treatment response.

RESULTS

Ten dogs with IE had strongly elevated stimulated Th17 cells/μL within the blood (>100 Th17 cells/μL). A slight positive correlation between stimulated Th17 cells/μL and seizure severity (p = 0.046; rSpear = 0.27) was proven in these dogs. In addition, 4/10 dogs with elevated Th17 levels experienced cluster seizures and status epilepticus in comparison to 9% of the dogs with non-elevated Th17 levels (<100 Th17 cells/μL). Dogs with IE had significantly higher IL-17 values in CSF and serum samples compared to C (p<0.001; p<0.002; respectively).

CONCLUSION

In single dogs with IE, strongly increased amounts of Th17 cells were detectable and dogs with elevated Th17 cells seemed to have a greater risk for experiencing a combination of cluster seizures and status epilepticus. Therefore, an underlying Th17-cell mediated immune response was suspected and hence anti-inflammatory drugs could be indicated in these single cases with intractable epilepsy.

IL-17 triggers the onset of cognitive and synaptic deficits in early stages of Alzheimer's disease

Neuroinflammation in patients with Alzheimer's disease (AD) and related mouse models has been recognized for decades, but the contribution of the recently described meningeal immune population to AD pathogenesis remains to be addressed. Here, using the 3xTg-AD model, we report an accumulation of interleukin-17 (IL-17)-producing cells, mostly γδ T cells, in the brain and the meninges of female, but not male, mice, concomitant with the onset of cognitive decline. Critically, IL-17 neutralization into the ventricles is sufficient to prevent short-term memory and synaptic plasticity deficits at early stages of disease. These effects precede blood-brain barrier disruption and amyloid-beta or tau pathology, implying an early involvement of IL-17 in AD pathology. When IL-17 is neutralized at later stages of disease, the onset of short-memory deficits and amyloidosis-related splenomegaly is delayed. Altogether, our data support the idea that cognition relies on a finely regulated balance of "inflammatory" cytokines derived from the meningeal immune system.

Interleukin-17A in Alzheimer's disease: recent advances and controversies

Alzheimer’s disease (AD) is a progressive neurodegenerative disease that mainly affects older adults. Although the global burden of AD is increasing year by year, the causes of AD remain largely unknown. Numerous basic and clinical studies have shown that interleukin-17A (IL-17A) may play a significant role in the pathogenesis of AD. A comprehensive assessment of the role of IL-17A in AD would benefit the diagnosis, understanding of etiology and treatment. However, over the past decade, controversies remain regarding the expression level and role of IL-17A in AD. We have incorporated newly published researches and point out that IL-17A expression levels may vary along with the development of AD, exercising different roles at different stages of AD, although much more work remains to be done to support the potential role of IL-17A in AD-related pathology. Here, it is our intention to review the underlying mechanisms of IL-17A in AD and address the current controversies in an effort to clarify the results of existing research and suggest future studies.

Neuroinflammation in Sepsis: Molecular Pathways of Microglia Activation

Frequently underestimated, encephalopathy or delirium are common neurological manifestations associated with sepsis. Brain dysfunction occurs in up to 80% of cases and is directly associated with increased mortality and long-term neurocognitive consequences. Although the central nervous system (CNS) has been classically viewed as an immune-privileged system, neuroinflammation is emerging as a central mechanism of brain dysfunction in sepsis. Microglial cells are major players in this setting. Here, we aimed to discuss the current knowledge on how the brain is affected by peripheral immune activation in sepsis and the role of microglia in these processes. This review focused on the molecular pathways of microglial activity in sepsis, its regulatory mechanisms, and their interaction with other CNS cells, especially with neuronal cells and circuits.

Interleukin 17A Derived from γδ T Cell Induces Demyelination of the Brain in Angiostrongylus cantonensis Infection

Angiostrongylus cantonensis infection is a typical cause of eosinophilic encephalitis (EM), which has been reported to induce serious damage in the central nervous system. Both parasite and host factors contribute to the onset of EM, but the related immune-inflammation pathogenesis remains poorly characterised. An A. cantonensis infection model was generated through the infection of mice by gavage. Transmission electron microscopy and immunohistochemistry were used to assess the pathologic changes in the brain. The mRNA expression of inflammatory factors was tested using qRT-PCR. A combination of flow cytometry and western blotting was used to evaluate the alteration of leukocytes and related cytokines. A critical role of IL-17 was found by injecting IL-17A monoclonal antibody into naïve and A. cantonensis-infected mice. A. cantonensis larvae altered the immune homeostasis in the brain, leading to the destruction of myelin sheaths and activation of microglia and macrophage. During this process, IL-17A accumulation was observed, and IL-17RA was expressed in oligodendrocytes and microglia during the infection. Notably, γδ T cell was the major origin of IL-17A production induced by the parasite. After an IL-17A-neutralising antibody was applied, alterations in myelination and the state of the microglia/macrophage were discovered; the neurobehavioural scores of the mice also improved. Our study reveals one unrecognised impact of the γδ T cells in parasitic encephalopathy and emphasises that blocking IL-17A signalling can attenuate microglia and macrophage activation, thus reducing CNS demyelination and ameliorating the neurobehavioural deficit in A. cantonensis-infected mice.

Th17 Cells in Depression: Are They Crucial for the Antidepressant Effect of Ketamine?

Background: Major depressive disorder is associated with inflammation and immune processes. Depressive symptoms correlate with inflammatory markers and alterations in the immune system including cytokine levels and immune cell function. Th17 cells are a T cell subset which exerts proinflammatory effects. Th17 cell accumulation and Th17/Treg imbalances have been reported to be critical in the pathophysiology of major depressive disorder and depressive-like behaviors in animal models. Th17 cells are thought to interfere with glutamate signaling, dopamine production, and other immune processes. Ketamine is a newly characterized antidepressant medication which has proved to be effective in rapidly reducing depressive symptoms. However, the mechanisms behind these antidepressant effects have not been fully elucidated.

Method: Literature about Th17 cells and their role in depression and the antidepressant effect of ketamine are reviewed, with the possible interaction networks discussed.

Result: The immune-modulating role of Th17 cells may participate in the antidepressant effect of ketamine.

Conclusion: As Th17 cells play multiple roles in depression, it is important to explore the mechanisms of action of ketamine on Th17 cells and Th17/Treg cell balance. This provides new perspectives for strengthening the antidepressant effect of ketamine while reducing its side effects and adverse reactions.

γδ T Cells Participating in Nervous Systems: A Story of Jekyll and Hyde

γδ T cells are distributed in various lymphoid and nonlymphoid tissues, and act as early responders in many conditions. Previous studies have proven their significant roles in infection, cancer, autoimmune diseases and tissue maintenance. Recently, accumulating researches have highlighted the crosstalk between γδ T cells and nervous systems. In these reports, γδ T cells maintain some physiological functions of central nervous system by secreting interleukin (IL) 17, and neurons like nociceptors can in turn regulate the activity of γδ T cells. Moreover, γδ T cells are involved in neuroinflammation such as stroke and multiple sclerosis. This review illustrates the relationship between γδ T cells and nervous systems in physiological and pathological conditions.

Dysregulation of the gut-brain-skin axis and key overlapping inflammatory and immune mechanisms of psoriasis and depression

The occurrence, progression and recurrence of psoriasis are thought to be related to mood and psychological disorders such as depression. Psoriasis can lead to depression, and depression, in turn, exacerbates psoriasis. No specific mechanism can explain the association between psoriasis and depression. The gut-brain-skin axis has been used to explain correlations among the gut microbiota, emotional states and systemic and skin inflammation, and this axis may be associated with overlapping mechanisms between psoriasis and depression. Therefore, in the context of the gut-brain-skin axis, we systematically summarized and comparatively analysed the inflammatory and immune mechanisms of psoriasis and depression and illustrated the dysregulation of the hypothalamic-pituitary-adrenal (HPA) axis and the gut microbiota. This review provides a theoretical basis and new targets for the treatment of psoriasis and depression.

Protective Effect of the α7 Nicotinic Receptor Agonist PNU-282987 on Dopaminergic Neurons Against 6-Hydroxydopamine, Regulating Anti-neuroinflammatory and the Immune Balance Pathways in Rat

Neuroinflammation and inner immune dysfunction are increasingly accepted as important components of the etiopathogenesis of Parkinson’s disease (PD). According to emerging evidence, a7 nicotinic acetylcholine receptor (α7nAChR), a ligand-gated ion channel, plays an important role in inflammatory reactions and is also expressed on the surface of T cells. In particular, regulatory T cells (Tregs) are critical for the maintenance of immunological tolerance. In the present study, we investigated the roles of α7nAChR in inhibiting inflammation and maintaining the immune balance in rats with 6-hydroxydopamine (6-OHDA)-induced lesions and the possible mechanisms regulating the proportion of Tregs in vivo. Adult male Wistar rats (n = 90) were subjected to a unilateral injection of 6-OHDA into the left medial forebrain bundle, and PNU-282987, an α7nAChR agonist, was intraperitoneally injected 2 h prior to the induction of lesions by 6-OHDA and again at days 1, 7, and 13 postlesion. Behavioral tests and immunohistochemical staining to detect the expression of tyrosine hydroxylase (TH) in the bilateral substantial nigra (SN) were performed. Subsequently, CD4+ T lymphocytes and the expression of forkhead/winged helix transcription factor p3 (Foxp3, which is a marker of Treg cells) in the SN were also assessed using immunofluorescence staining. The expression of glial fibrillary acidic protein (GFAP) in the SN was determined by performing immunohistochemical staining. Additionally, the protein levels of α7nAChR, extracellular signal-regulated kinase (Erk) phosphorylated-Erk (p-Erk) and Foxp3 in the ventral midbrain were determined using Western blotting, and the relative expression of the TNF-α, IL-1β, and IL-10 mRNAs were detected using real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR). We found that PNU-282987 significantly improved the motor deficits induced by 6-OHDA, reduced the loss of TH in the SN, suppressed the overactivation of GFAP+ cells and expression of related inflammatory cytokines, and increased the number of Foxp3+ cells. In addition, we also showed that PNU-282987 significantly increased the protein expression of the a7nAchR, p-Erk, and Foxp3 in 6-OHDA-lesioned rats (p < 0.05). These results indicated that α7nAChR activation could exert an anti-inflammatory effect and participate in the process of modulating the immune balance during 6-OHDA-induced injury, potentially through the α7nAChR/p-Erk/Foxp3 signaling pathway.

The burden of depressive disorders in musculoskeletal diseases: is there an association between mood and inflammation?

IMPORTANCE

Evidence emerged concerning how inflammatory arthritis and mood disorders can often occur in the same patient and show a similar clinical pattern. An overview of the rheumatological and psychiatric aspects of these diseases can certainly be useful for the improvement of patients' clinical and therapeutic management.

OBJECTIVE

The aim of this narrative review was to summarize existing literature about common pathogenetic and clinical aspects as a means of improving management and therapeutic approach in patients affected by rheumatoid arthritis, psoriatic arthritis and spondyloarthritis. Outcomes such as disease activity indexes and patient reported outcomes (PROs) were considered.

FINDINGS

Common pathogenetic pathways emerged between inflammatory arthritis and mood disorders. Pro-inflammatory mechanisms, such as TNFα, IL-6, IL-17 and oxidative stress factors as well as neurotransmitter alterations at the level of CNS and blood-brain barrier (BBB) cells are involved. The activation of these common pathogenetic pathways is, also, affected by the same triggers, such as smoking, stress, lifestyle, and evidence has emerged concerning the possibility of the clinical efficacy of using the same therapeutic approaches.

CONCLUSIONS

The main causes of the variability in clinical studies outcomes are the rheumatological diseases considered, the prevalence of depression in the general population and in patients with rheumatological diseases and the type of depressive symptom examined. Patients affected by inflammatory arthritis can present symptoms and signs in common with mood disorders, leading to possible clinical overlap. There are still few studies analyzing this concept: they are extremely heterogeneous, both in the characteristics of the population taken into consideration and in the methods used for the definition of depressive disorder, but the suggestions of the data obtained so far are promising and deserve to be pursued.

Gut microbiota from patients with arteriosclerotic CSVD induces higher IL-17A production in neutrophils via activating RORγt

The intestinal microbiota shape the host immune system and influence the outcomes of various neurological disorders. Arteriosclerotic cerebral small vessel disease (aCSVD) is highly prevalent among the elderly with its pathological mechanisms yet is incompletely understood. The current study investigated the ecology of gut microbiota in patients with aCSVD, particularly its impact on the host immune system. We reported that the altered composition of gut microbiota was associated with undesirable disease outcomes and exacerbated inflammaging status. When exposed to the fecal bacterial extracts from a patient with aCSVD, human and mouse neutrophils were activated, and capacity of interleukin-17A (IL-17A) production was increased. Mechanistically, RORγt signaling in neutrophils was activated by aCSVD-associated gut bacterial extracts to up-regulate IL-17A production. Our findings revealed a previously unrecognized implication of the gut-immune-brain axis in aCSVD pathophysiology, with therapeutic implications.

Interleukin-17A: The Key Cytokine in Neurodegenerative Diseases

Neurodegenerative diseases are characterized by the loss of neurons and/or myelin sheath, which deteriorate over time and cause dysfunction. Interleukin 17A is the signature cytokine of a subset of CD4⁺ helper T cells known as Th17 cells, and the IL-17 cytokine family contains six cytokines and five receptors. Recently, several studies have suggested a pivotal role for the interleukin-17A (IL-17A) cytokine family in human inflammatory or autoimmune diseases and neurodegenerative diseases, including psoriasis, rheumatoid arthritis (RA), Alzheimer’s disease (AD), Parkinson’s disease (PD), multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), and glaucoma. Studies in recent years have shown that the mechanism of action of IL-17A is more subtle than simply causing inflammation. Although the specific mechanism of IL-17A in neurodegenerative diseases is still controversial, it is generally accepted now that IL-17A causes diseases by activating glial cells. In this review article, we will focus on the function of IL-17A, in particular the proposed roles of IL-17A, in the pathogenesis of neurodegenerative diseases.

GM-CSF induces noninflammatory proliferation of microglia and disturbs electrical neuronal network rhythms in situ

Background

The granulocyte-macrophage colony-stimulating factor (GM-CSF) (or CSF-2) is involved in myeloid cell growth and differentiation, and, possibly, a major mediator of inflammation in body tissues. The role of GM-CSF in the activation of microglia (CNS resident macrophages) and the consequent impacts on neuronal survival, excitability, and synaptic transmission are widely unknown, however. Here, we focused on electrical neuronal network rhythms in the gamma frequency band (30–70 Hz). Gamma oscillations are fundamental to higher brain functions, such as perception, attention, and memory, and they are exquisitely sensitive to metabolic and oxidative stress.

Methods

We explored the effects of chronic GM-CSF exposure (72 h) on microglia in male rat organotypic hippocampal slice cultures (in situ), i.e., postnatal cortex tissue lacking leukocyte invasion (adaptive immunity). We applied extracellular electrophysiological recordings of local field potential, immunohistochemistry, design-based stereology, biochemical analysis, and pharmacological ablation of microglia.

Results

GM-CSF triggered substantial proliferation of microglia (microgliosis). By contrast, the release of proinflammatory cytokines (IL-6, TNF-α) and nitric oxide, the hippocampal cytoarchitecture as well as the morphology of parvalbumin-positive inhibitory interneurons were unaffected. Notably, GM-CSF induced concentration-dependent, long-lasting disturbances of gamma oscillations, such as slowing (beta frequency band) and neural burst firing (hyperexcitability), which were not mimicked by the T lymphocyte cytokine IL-17. These disturbances were attenuated by depletion of the microglial cell population with liposome-encapsulated clodronate. In contrast to priming with the cytokine IFN-γ (type II interferon), GM-CSF did not cause inflammatory neurodegeneration when paired with the TLR4 ligand LPS.

Conclusions

GM-CSF has a unique role in the activation of microglia, including the potential to induce neuronal network dysfunction. These immunomodulatory properties might contribute to cognitive impairment and/or epileptic seizure development in disease featuring elevated GM-CSF levels, blood-brain barrier leakage, and/or T cell infiltration.

Evaluation of Brain Cytokines and the Level of Brain-Derived Neurotrophic Factor in an Inflammatory Model of Depression

INTRODUCTION

Major depressive disorder is considered a global public health problem. Inflammatory processes are likely involved in its pathophysiology, but the underlying mechanisms have remained uncertain.Here, we used the model of systemic lipopolysaccharide (LPS) injection to test the hypothesis that depressive-like behaviors occur along with changes in the levels of cytokines and brain-derived neurotrophic factor (BDNF) in the hippocampus (HC), prefrontal cortex (PFC), and hypothalamus (HT), and can be prevented by dexamethasone administration.

METHODS

Adult C57Bl/6 male mice were first isolated for 10 days, and thereafter received an injection of dexamethasone (6 mg/kg, intraperitoneal [i.p.]), saline followed by LPS (0.83 mg/kg, i.p.), or saline. After 6 h, animals were subjected to the forced-swim test (FST) and open-field tests. Immediately after the behavioral tests, they were euthanized and their brains were collected for the biochemical analyses.

RESULTS

LPS increased the immobility time and reduced the distance travelled in the FST and open-field test, respectively. Dexamethasone increased the immobility time in saline-treated mice but reduced this behavior in the LPS group. LPS increased the levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6 and interferon (IFN)-γ in most of the regions evaluated. Dexamethasone prevented LPS-induced IL-6 in the HC, PFC, and HT. Interestingly, dexamethasone increased IL-4 and IL-10 levels in both the LPS- and saline-treated groups. Although dexamethasone reduced BDNF in saline-treated mice, it prevented LPS-induced reduction in this neurotrophic factor.

CONCLUSION

In summary, dexamethasone decreased proinflammatory and increased anti-inflammatory levels of cytokines and prevented a reduction in BDNF levels induced by the inflammatory stimulus. Thus, the attenuation of depressive-like behavior induced by dexamethasone may be related to the effects on these parameters.

IL-17A exacerbates neuroinflammation and neurodegeneration by activating microglia in rodent models of Parkinson's disease

Neuroinflammation has been involved in pathogenesis of Parkinson's disease (PD), a chronic neurodegenerative disease characterized neuropathologically by progressive dopaminergic neuronal loss in the substantia nigra (SN). We recently have shown that helper T (Th)17 cells facilitate dopaminergic neuronal loss in vitro. Herein, we demonstrated that interleukin (IL)-17A, a proinflammatory cytokine produced mainly by Th17 cells, contributed to PD pathogenesis depending on microglia. Mouse and rat models for PD were prepared by intraperitoneal injection of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) or striatal injection of 1-methyl-4-phenylpyridinium (MPP⁺), respectively. Both in MPTP-treated mice and MPP⁺-treated rats, blood-brain barrier (BBB) was disrupted and IL-17A level increased in the SN but not in cortex. Effector T (Teff) cells that were adoptively transferred via tail veins infiltrated into the brain of PD mice but not into that of normal mice. The Teff cell transfer aggravated nigrostriatal dopaminergic neurodegeneration, microglial activation and motor impairment. Contrarily, IL-17A deficiency alleviated BBB disruption, dopaminergic neurodegeneration, microglial activation and motor impairment. Anti-IL-17A-neutralizing antibody that was injected into lateral cerebral ventricle in PD rats ameliorated the manifestations mentioned above. IL-17A activated microglia but did not directly affect dopaminergic neuronal survival in vitro. IL-17A exacerbated dopaminergic neuronal loss only in the presence of microglia, and silencing IL-17A receptor gene in microglia abolished the IL-17A effect. IL-17A-treated microglial medium that contained higher concentration of tumor necrosis factor (TNF)-α facilitated dopaminergic neuronal death. Further, TNF-α-neutralizing antibody attenuated MPP⁺-induced neurotoxicity. The findings suggest that IL-17A accelerates neurodegeneration in PD depending on microglial activation and at least partly TNF-α release.

A positive allosteric modulator of mGluR5 promotes neuroprotective effects in mouse models of Alzheimer's disease

Alzheimer's Disease (AD) is the most prevalent neurodegenerative disorder. Despite advances in the understanding of its pathophysiology, none of the available therapies prevents disease progression. Excess glutamate plays an important role in excitotoxicity by activating ionotropic receptors. However, the mechanisms modulating neuronal cell survival/death via metabotropic glutamate receptors (mGluRs) are not completely understood. Recent data indicates that CDPPB, a positive allosteric modulator of mGluR5, has neuroprotective effects. Thus, this work aimed to investigate CDPPB treatment effects on amyloid-β (Aβ) induced pathological alterations in vitro and in vivo and in a transgenic mouse model of AD (T41 mice). Aβ induced cell death in primary cultures of hippocampal neurons, which was prevented by CDPPB. Male C57BL/6 mice underwent stereotaxic surgery for unilateral intra-hippocampal Aβ injection, which induced memory deficits, neurodegeneration, neuronal viability reduction and decrease of doublecortin-positive cells, a marker of immature neurons and neuronal proliferation. Treatment with CDPPB for 8 days reversed neurodegeneration and doublecortin-positive cells loss and recovered memory function. Fourteen months old T41 mice presented cognitive deficits, neuronal viability reduction, gliosis and Aβ accumulation. Treatment with CDPPB for 28 days increased neuronal viability (32.2% increase in NeuN⁺ cells) and reduced gliosis in CA1 region (Iba-1⁺ area by 31.3% and GFAP⁺ area by 37.5%) in transgenic animals, without inducing hepatotoxicity. However, it did not reverse cognitive deficit. Despite a four-week treatment did not prevent memory loss in aged transgenic mice, CDPPB is protective against Aβ stimulus. Therefore, this drug represents a potential candidate for further investigations as AD treatment.

CNS-Specific Synthesis of Interleukin 23 Induces a Progressive Cerebellar Ataxia and the Accumulation of Both T and B Cells in the Brain: Characterization of a Novel Transgenic Mouse Model

Interleukin 23 (IL-23) is a key mediator in neuroinflammation in numerous autoimmune diseases including multiple sclerosis (MS). However, the pathophysiology of IL-23 and how it contributes to neuroinflammation is poorly defined. To further clarify the role of IL-23 in CNS inflammation, we generated a transgenic mouse model (GF-IL23) with astrocyte-targeted expression of both IL-23 subunits, IL-23p19, and IL-23p40. These GF-IL23 mice spontaneously develop a progressive ataxic phenotype, which corresponds to cerebellar tissue destruction, and inflammatory infiltrates most prominent in the subarachnoidal and perivascular space. The CNS-cytokine milieu was characterized by numerous inflammatory mediators such as IL-17a and IFNγ. However, the leukocytic infiltrates were surprisingly predominated by B cells. To further examine the impact of the CNS-specific IL-23 synthesis on an additional systemic inflammatory stimulus, we applied the LPS-induced endotoxemia model. Administration of LPS in GF-IL23 mice resulted in early and pronounced microglial activation, enhanced cytokine production and, in sharp contrast to control animals, in the formation of lymphocytic infiltrates. Our model confirms a critical role for IL-23 in the induction of inflammation in the CNS, in particular facilitating the accumulation of lymphocytes in and around the brain. Thereby, CNS-specific synthesis of IL-23 is able to induce a cascade of inflammatory cytokines leading to microglia activation, astrocytosis, and ultimately tissue damage. The presented transgenic model will be a useful tool to further dissect the role of IL-23 in neuroinflammation.

Targeting the Blood-Brain Barrier to Prevent Sepsis-Associated Cognitive Impairment

Sepsis is a systemic inflammatory disease resulting from an infection. This disorder affects 750 000 people annually in the United States and has a 62% rehospitalization rate. Septic symptoms range from typical flu-like symptoms (eg, headache, fever) to a multifactorial syndrome known as sepsis-associated encephalopathy (SAE). Patients with SAE exhibit an acute altered mental status and often have higher mortality and morbidity. In addition, many sepsis survivors are also burdened with long-term cognitive impairment. The mechanisms through which sepsis initiates SAE and promotes long-term cognitive impairment in septic survivors are poorly understood. Due to its unique role as an interface between the brain and the periphery, numerous studies support a regulatory role for the blood-brain barrier (BBB) in the progression of acute and chronic brain dysfunction. In this review, we discuss the current body of literature which supports the BBB as a nexus which integrates signals from the brain and the periphery in sepsis. We highlight key insights on the mechanisms that contribute to the BBB's role in sepsis which include neuroinflammation, increased barrier permeability, immune cell infiltration, mitochondrial dysfunction, and a potential barrier role for tissue non-specific alkaline phosphatase (TNAP). Finally, we address current drug treatments (eg, antimicrobials and intravenous immunoglobulins) for sepsis and their potential outcomes on brain function. A comprehensive understanding of these mechanisms may enable clinicians to target specific aspects of BBB function as a therapeutic tool to limit long-term cognitive impairment in sepsis survivors.

Changes in vitreal protein profile and retina mRNAs in Reeler mice: NGF, IL33 and Müller cell activation

A possible link between Nerve Growth Factor (NGF) and Reelin might take place during impaired retinal development occurring in the Reelin deficient mouse model (Reeler). To better characterize NGF and retina impairments at the Reeler retina, vitreous and retina were investigated by means of protein expression and glial cell activation. Reeler (n = 9; RELN^-/-) and WT (n = 9; wild-type RELN^+/+, B6C3Fe) mice were analyzed at 14, 21 and 28 postnatal days (p). Retinas and vitreous were subjected to confocal analysis and protein array, followed by conventional analysis. A significant increase of NGF, IL33 and TIMP1, a trend to a decrease of IL12 and IL6, as well as a significant decrease of NT3 were detected in Reeler vitreous, particularly at p28 (p<0.05). MIP3β mRNA was decreased while IL33mRNA was significantly upregulated in Reeler retina. Increased number of GFAP⁺ and Nestin⁺ cells as well as upregulation of Glutamine Synthetase and Nestin mRNAs were observed in Reeler retinas (p<0.05). These findings extend our previous studies on Reeler retina showing a selective Müller cell activation. NGF and IL33 release into vitreous would suggest a local activation of Müller cells, in addition to retinal ganglion and accessory cells. Overall, the data from this experimental study would strength the potential neuroprotective role played by activated Muller cells through NGF release.

Anti-IL17 treatment ameliorates Down syndrome phenotypes in mice

Down syndrome (DS) is characterized by structural and functional anomalies that are present prenatally and that lead to intellectual disabilities. Later in life, the cognitive abilities of DS individuals progressively deteriorate due to the development of Alzheimer's disease (AD)-associated neuropathology (i.e., β-amyloid (Aβ) plaques, neurofibrillary tangles (NFTs), neurodegeneration, synaptic pathology, neuroinflammation and increased oxidative stress). Increasing evidence has shown that among these pathological processes, neuroinflammation plays a predominant role in AD etiopathology. In AD mouse models, increased neuroinflammation appears earlier than Aβ plaques and NFTs, and in DS and AD models, neuroinflammation exacerbates the levels of soluble and insoluble Aβ species, favoring neurodegeneration. The Ts65Dn (TS) mouse, the most commonly used murine model of DS, recapitulates many alterations present in both DS and AD individuals, including enhanced neuroinflammation. In this study, we observed an altered neuroinflammatory milieu in the hippocampus of the TS mouse model. Pro-inflammatory mediators that were elevated in the hippocampus of this model included pro-inflammatory cytokine IL17A, which has a fundamental role in mediating brain damage in neuroinflammatory processes. Here, we analyzed the ability of an anti-IL17A antibody to reduce the neuropathological alterations that are present in TS mice during early neurodevelopmental stages (i.e., hippocampal neurogenesis and hypocellularity) or that are aggravated in later-life stages (i.e., cognitive abilities, cholinergic neuronal loss and increased cellular senescence, APP expression, Aβ peptide expression and neuroinflammation). Administration of anti-IL17 for 5 months, starting at the age of 7 months, partially improved the cognitive abilities of the TS mice, reduced the expression of several pro-inflammatory cytokines and the density of activated microglia and normalized the APP and Aβ_1-42 levels in the hippocampi of the TS mice. These results suggest that IL17-mediated neuroinflammation is involved in several AD phenotypes in TS mice and provide a new therapeutic target to reduce these pathological characteristics.

Elevated interleukin-17 and reduced testosterone in bipolar disorder. Relation with suicidal behaviour

Hormonal imbalance and inflammation are associated with bipolar disorder and suicidal behavior. The present study was designed to assess the levels of testosterone and interleukin-17 and their association with suicidal behavior in patients with bipolar disorder in remission. 41 bipolar disorder cases in remission and 41 age matched controls were enrolled in the study. Testosterone and interleukin-17 levels were assessed in both the groups. Interleukin-17 was significantly increased and testosterone was significantly reduced in bipolar disorder when compared with controls. IL-17 was negatively correlated with testosterone (r = -0.368, p = 0.018) and positively correlated with duration of disease (r = 0.382, p = 0.014) in bipolar disorder patients. Both didn't show any association with suicidal behavior. We conclude that testosterone is increased and interleukin-17 is reduced in bipolar disorder in remission and these were not associated with suicidal behavior in these patients.

Th17 cells in depression

T helper 17 (Th17) cells have recently been implicated in depression, which adds to the list of several other diseases of the central nervous system (CNS) that are already known to involve Th17 cells. In CNS diseases, it is thought that the signature cytokine produced by Th17 cells, interleukin-17A (IL-17A), mediates the detrimental effects of Th17 cells. In depression, although Th17 cells increase, the lack of a consistent correlation between depression severity and blood IL-17A levels suggests that Th17 cells promote depressive symptoms, which may not be entirely dependent on IL-17. However, little is known about the mechanism of action of Th17 cells or the source of CNS Th17 cells in depression. It is likely that Th17 cells promote neuroinflammation and activation of microglia and astrocytes, actions that may contribute to neuronal damage. A source of Th17 cells is the small intestine where they are regulated by the composition of the microbiome. It remains to be determined through what mechanisms of action Th17 cells affect depression and if Th17 cells can be considered a novel therapeutic target in depression.

Therapeutic Potential of Pien Tze Huang on Experimental Autoimmune Encephalomyelitis Rat

Multiple sclerosis (MS) is a chronic inflammatory demyelinating disease of the central nervous system (CNS). There is still lack of commercially viable treatment currently. Pien Tze Huang (PZH), a traditional Chinese medicine, has been proved to have anti-inflammatory, neuroprotective, and immunoregulatory effects. This study investigated the possible therapeutic effects of PZH on experimental autoimmune encephalomyelitis (EAE) rats, a classic animal model of MS. Male Lewis rats were immunized with myelin basic protein (MBP) peptide to establish an EAE model and then treated with three doses of PZH. Clinical symptoms, organ coefficient, histopathological features, levels of proinflammatory cytokines, and chemokines as well as MBP and Olig2 were analyzed. The results indicated that PZH ameliorated the clinical severity of EAE rats. It also remarkably reduced inflammatory cell infiltration in the CNS of EAE rats. Furthermore, the levels of IL-17A, IL-23, CCL3, and CCL5 in serum and the CNS were significantly decreased; the p-P65 and p-STAT3 levels were also downregulated in the CNS, while MBP and Olig2 in the CNS of EAE rats had a distinct improvement after PZH treatment. In addition, PZH has no obvious toxicity at the concentration of 0.486 g/kg/d. This study demonstrated that PZH could be used to treat MS.

Treatment of novel IL17A inhibitor in glioblastoma implementing 3rd generation co-culture cell line and patient-derived tumor model

Despite many treatment options, cancer remains a growing problem and has become the second leading cause of death globally. Here, we present fluorescence molecular tomography (FMT) data regarding the reversion of third generation co-cultured U87+DBTRG and patient-derived GBM tumor model after treatment with novel IL17A inhibitor named FLVM and FLVZ (organic derivatives of caffeic acid). FMT was used to determine tumor angiogenesis volume (assessment of number of blood vessel; the expression of angiogenic factors CD34 and other angiogenic cancer bio-markers) in U87+DBTRG and patient-derived gliomas. Immunohistochemistry was used to determine microvessel density [CD34], and cell proliferation [Ki67]. Western blot was used to assess the interleukin 17A [IL17A], vascular endothelial growth factor [VEGF] and hypoxia-inducible factor-1α [HIF-1α]. Antibody array was used to assess the cancer bio-markers in co-cultured U87+DBTRG gliomas. Animal survival was found to be significantly increased (P<0.0001) after FLVM treatment compared with control-IL17A. After FMT detection, FLVM, administered orally, was found to decrease tumor growth (P<0.0001). FLVM and FLVZ administration resulted in significant decreases in tumor hypoxia [HIF-1α (P<0.05)], angiogenesis [CD34 (P<0.05)], VEGF, IL17A and cell proliferation [Ki67 (P<0.05)] and caused a significant increase of Bax, caspase and FasL (P<0.05), compared with untreated animals. Additionally, Leptin, LPL (P<0.01), FFA (P<0.05) and adipogenesis were downregulated and no additive toxicity was found in mice except calorie-restriction like effect. Use of FLVM can be considered as a novel inhibitor of IL17A for the treatment of human gliomas.

Th17 Cells Induce Dopaminergic Neuronal Death via LFA-1/ICAM-1 Interaction in a Mouse Model of Parkinson's Disease

T helper (Th)17 cells, a subset of CD4⁺ T lymphocytes, have strong pro-inflammatory property and appear to be essential in the pathogenesis of many inflammatory diseases. However, the involvement of Th17 cells in Parkinson's disease (PD) that is characterized by a progressive degeneration of dopaminergic (DAergic) neurons in the nigrostriatal system is unclear. Here, we aimed to demonstrate that Th17 cells infiltrate into the brain parenchyma and induce neuroinflammation and DAergic neuronal death in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)- or 1-methyl-4-phenylpyridinium (MPP⁺)-induced PD models. Blood-brain barrier (BBB) disruption in the substantia nigra (SN) was assessed by the signal of FITC-labeled albumin that was injected into blood circulation via the ascending aorta. Live cell imaging system was used to observe a direct contact of Th17 cells with neurons by staining these cells using the two adhesion molecules, leukocyte function-associated antigen (LFA)-1 and intercellular adhesion molecule (ICAM)-1, respectively. Th17 cells invaded into the SN where BBB was disrupted in MPTP-induced PD mice. Th17 cells exacerbated DAergic neuronal loss and pro-inflammatory/neurotrophic factor disorders in MPP⁺-treated ventral mesencephalic (VM) cell cultures. A direct contact of LFA-1-stained Th17 cells with ICAM-1-stained VM neurons was dynamically captured. Either blocking LFA-1 in Th17 cells or blocking ICAM-1 in VM neurons with neutralizing antibodies abolished Th17-induced DAergic neuronal death. These results establish that Th17 cells infiltrate into the brain parenchyma of PD mice through lesioned BBB and exert neurotoxic property by promoting glial activation and importantly by a direct damage to neurons depending on LFA-1/ICAM-1 interaction.

Increased Incidence of Amyotrophic Lateral Sclerosis in Polymyositis: A Nationwide Cohort Study

OBJECTIVE

Past studies have shown common pathologic characteristics and shared immunologic features between polymyositis (PM) and amyotrophic lateral sclerosis (ALS). To explore the potential relationship between the 2 diseases, we performed a nationwide cohort study.

METHODS

We identified all newly diagnosed patients with PM from Taiwan's Registry of Catastrophic Illness Database between January 1, 1998 and December 31, 2011. Each PM patient was matched to ≤5 control patients from the National Health Insurance Research Database by sex, age, and entry date. Cumulative incidence of ALS was calculated by the Kaplan-Meier method and compared using the log rank test. Cox hazard regression was used to calculate the hazard ratio of ALS.

RESULTS

A total of 1,778 PM patients and 8,124 control patients were enrolled. PM patients had a higher cumulative incidence of ALS (P < 0.001). There was a positive correlation in being diagnosed with ALS in patients previously diagnosed with PM when stratified by sex. Consistent trends were conserved across different age strata. The strength of this association remained statistically significant after adjusting for sex, age, and concomitant autoimmune diseases (hazard ratio 25.72 [95% confidence interval 2.95-224.58]; P = 0.003).

CONCLUSION

This study demonstrates that a diagnosis of PM increased the likelihood of a subsequent ALS diagnosis, independent of sex, age, and concomitant autoimmune diseases. Future studies are warranted to clarify the underlying biologic mechanisms and to translate them into clinical therapeutic options.

Astrocytes: Integrative Regulators of Neuroinflammation in Stroke and Other Neurological Diseases

Astrocytes regulate neuroinflammatory responses after stroke and in other neurological diseases. Although not all astrocytic responses reduce inflammation, their predominant function is to protect the brain by driving the system back to homeostasis after injury. They receive multidimensional signals within the central nervous system and between the brain and the systemic circulation. Processing this information allows astrocytes to regulate synapse formation and maintenance, cerebral blood flow, and blood-brain barrier integrity. Similarly, in response to stroke and other central nervous system disorders, astrocytes detect and integrate signals of neuronal damage and inflammation to regulate the neuroinflammatory response. Two direct regulatory mechanisms in the astrocyte arsenal are the ability to form both physical and molecular barriers that seal the injury site and localize the neuroinflammatory response. Astrocytes also indirectly regulate the inflammatory response by affecting neuronal health during the acute injury and axonal regrowth. This ability to regulate the location and degree of neuroinflammation after injury, combined with the long time course of neuroinflammation, makes astrocytic signaling pathways promising targets for therapies.

Increased expression of interleukin 17 in the cortex and hippocampus from patients with mesial temporal lobe epilepsy

Mesial temporal lobe epilepsy (MTLE) is the most common form of focal epilepsies in adults and proinflammatory cytokines have long been thought to play an important role in pathogenesis and epileptogenicity. In the present study, we investigated the levels and expression patterns of the interleukin 17 (IL-17) system in temporal neocortex and hippocampus from 24 patients with MTLE and 8 control (Ctr) samples. We found that IL-17 and IL-17 receptor (IL-17R) were clearly upregulated in MTLE at both mRNA and protein levels, compared with Ctr. Immunostaining indicated that neurons, astrocytes, microglia and endothelial cells of blood vessels are the major sources of IL-17. These findings suggest that IL-17 system may be involved in the pathogenesis and epileptogenicity of MTLE.

Astrocyte elevated gene-1 (AEG-1) and the A(E)Ging HIV/AIDS-HAND

Recent attempts to analyze human immunodeficiency virus (HIV)-1-induced gene expression changes in astrocytes uncovered a multifunctional oncogene, astrocyte elevated gene-1 (AEG-1). Our previous studies revealed that AEG-1 regulates reactive astrocytes proliferation, migration and inflammation, hallmarks of aging and CNS injury. Moreover, the involvement of AEG-1 in neurodegenerative disorders, such as Huntington's disease and migraine, and its induction in the aged brain suggest a plausible role in regulating overall CNS homeostasis and aging. Therefore, it is important to investigate AEG-1 specifically in aging-associated cognitive decline. In this study, we decipher the common mechanistic links in cancer, aging and HIV-1-associated neurocognitive disorders that likely contribute to AEG-1-based regulation of astrocyte responses and function. Despite AEG-1 incorporation into HIV-1 virions and its induction by HIV-1, tumor necrosis factor-α and interleukin-1β, the specific role(s) of AEG-1 in astrocyte-driven HIV-1 neuropathogenesis are incompletely defined. We propose that AEG-1 plays a central role in a multitude of cellular stress responses involving mitochondria, endoplasmic reticulum and the nucleolus. It is thus important to further investigate AEG-1-based cellular and molecular regulation in order to successfully develop better therapeutic approaches that target AEG-1 to combat cancer, HIV-1 and aging.

New Perspectives for the Rescue of Cognitive Disability in Down Syndrome

Down syndrome (DS) is a relatively common genetic condition caused by the triplication of human chromosome 21. No therapies currently exist for the rescue of neurocognitive impairment in DS. This review presents exciting findings showing that it is possible to restore brain development and cognitive performance in mouse models of DS with therapies that can also apply to humans. This knowledge provides a potential breakthrough for the prevention of intellectual disability in DS.

Quantification of Cerebral Vascular Architecture using Two-photon Microscopy in a Mouse Model of HIV-induced Neuroinflammation

Human Immunodeficiency Virus 1 (HIV-1) infection frequently results in HIV-1 Associated Neurocognitive Disorders (HAND), and is characterized by a chronic neuroinflammatory state within the central nervous system (CNS), thought to be driven principally by virally-mediated activation of microglia and brain resident macrophages. HIV-1 infection is also accompanied by changes in cerebrovascular blood flow (CBF), raising the possibility that HIV-associated chronic neuroinflammation may lead to changes in CBF and/or in cerebral vascular architecture. To address this question, we have used a mouse model for HIV-induced neuroinflammation, and we have tested whether long-term exposure to this inflammatory environment may damage brain vasculature and result in rarefaction of capillary networks. In this paper we describe a method to quantify changes in cortical capillary density in a mouse model of neuroinflammatory disease (HIV-1 Tat transgenic mice). This generalizable approach employs in vivo two-photon imaging of cortical capillaries through a thin-skull cortical window, as well as ex vivo two-photon imaging of cortical capillaries in mouse brain sections. These procedures produce images and z-stack files of capillary networks, respectively, which can be then subjected to quantitative analysis in order to assess changes in cerebral vascular architecture.

Group A Streptococcus intranasal infection promotes CNS infiltration by streptococcal-specific Th17 cells

Group A streptococcal (GAS) infection induces the production of Abs that cross-react with host neuronal proteins, and these anti-GAS mimetic Abs are associated with autoimmune diseases of the CNS. However, the mechanisms that allow these Abs to cross the blood-brain barrier (BBB) and induce neuropathology remain unresolved. We have previously shown that GAS infection in mouse models induces a robust Th17 response in nasal-associated lymphoid tissue (NALT). Here, we identified GAS-specific Th17 cells in tonsils of humans naturally exposed to GAS, prompting us to explore whether GAS-specific CD4+ T cells home to mouse brains following i.n. infection. Intranasal challenge of repeatedly GAS-inoculated mice promoted migration of GAS-specific Th17 cells from NALT into the brain, BBB breakdown, serum IgG deposition, microglial activation, and loss of excitatory synaptic proteins under conditions in which no viable bacteria were detected in CNS tissue. CD4+ T cells were predominantly located in the olfactory bulb (OB) and in other brain regions that receive direct input from the OB. Together, these findings provide insight into the immunopathology of neuropsychiatric complications that are associated with GAS infections and suggest that crosstalk between the CNS and cellular immunity may be a general mechanism by which infectious agents exacerbate symptoms associated with other CNS autoimmune disorders.

Glial influences on BBB functions and molecular players in immune cell trafficking

The blood-brain barrier (BBB) constitutes an elaborate structure formed by specialized capillary endothelial cells, which together with pericytes and perivascular glial cells regulates the exchanges between the central nervous system (CNS) and the periphery. Intricate interactions between the different cellular constituents of the BBB are crucial in establishing a functional BBB and maintaining the delicate homeostasis of the CNS microenvironment. In this review, we discuss the role of astrocytes and microglia in inducing and maintaining barrier properties under physiological conditions as well as their involvement during neuroinflammatory pathologies. This article is part of a Special Issue entitled: Neuro Inflammation edited by Helga E. de Vries and Markus Schwaninger.

IL-17A is implicated in lipopolysaccharide-induced neuroinflammation and cognitive impairment in aged rats via microglial activation

BACKGROUND

Neuroinflammation is considered a risk factor for impairments in neuronal function and cognition that arise with trauma, infection, and/or disease. IL-17A has been determined to be involved in neurodegenerative diseases such as multiple sclerosis. Recently, IL-17A has been shown to be upregulated in lipopolysaccharide(LPS)-induced systemic inflammation. This study aims to explore the role of IL-17A in LPS-induced neuroinflammation and cognitive impairment.

METHODS

Male Sprague-Dawley (SD) rats were injected intraperitoneally with LPS (500 μg/kg), and IL-17A expression in serum and in the hippocampus was examined 6, 12, 24, and 48 h later. Then, we investigated whether IL-17A-neutralizing antibodies (IL-17A Abs, 1 mg/kg) prevented neuroinflammation and memory dysfunction in aged rats that received LPS (500 μg/kg) injection. In addition, the effect of IL-17A on microglial activation in vitro was determined using ELISA and immunofluorescence.

RESULTS

LPS injection increased the expression of IL-17A in serum and in the hippocampus. IL-17A Abs improved LPS-induced memory impairment. In addition, IL-17A Abs prevented the LPS-induced expression of TNF-α, IL-6 and inflammatory proteins, and of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) as well as the activation of microglia in the brain. IL-17A Abs also inhibited the expression of amyloid precursor protein (APP) and BACE1 and increased the expression of the synaptic marker PSD95 in the aged rats treated with LPS. In an in vitro study, we found that recombinant IL-17A could simulate microglial activation and increase production of pro-inflammatory cytokines.

CONCLUSION

Taken together, our results suggest that IL-17A was involved in LPS-induced neuroinflammation and cognitive impairment in aged rats via microglial activation. Anti-IL-17A may represent a new therapeutic strategy for the treatment of endotoxemia-induced neuroinflammation and cognitive dysfunction.

Microglia Induce Neurotoxic IL-17+ γδ T Cells Dependent on TLR2, TLR4, and TLR9 Activation

Background

Interleukin-17 (IL-17) acts as a key regulator in central nervous system (CNS) inflammation. γδ T cells are an important innate source of IL-17. Both IL-17+ γδ T cells and microglia, the major resident immune cells of the brain, are involved in various CNS disorders such as multiple sclerosis and stroke. Also, activation of Toll-like receptor (TLR) signaling pathways contributes to CNS damage. However, the mechanisms underlying the regulation and interaction of these cellular and molecular components remain unclear.

Objective

In this study, we investigated the crosstalk between γδ T cells and microglia activated by TLRs in the context of neuronal damage. To this end, co-cultures of IL-17+ γδ T cells, neurons, and microglia were analyzed by immunocytochemistry, flow cytometry, ELISA and multiplex immunoassays.

Results

We report here that IL-17+ γδ T cells but not naïve γδ T cells induce a dose- and time-dependent decrease of neuronal viability in vitro. While direct stimulation of γδ T cells with various TLR ligands did not result in up-regulation of CD69, CD25, or in IL-17 secretion, supernatants of microglia stimulated by ligands specific for TLR2, TLR4, TLR7, or TLR9 induced activation of γδ T cells through IL-1β and IL-23, as indicated by up-regulation of CD69 and CD25 and by secretion of vast amounts of IL-17. This effect was dependent on the TLR adaptor myeloid differentiation primary response gene 88 (MyD88) expressed by both γδ T cells and microglia, but did not require the expression of TLRs by γδ T cells. Similarly to cytokine-primed IL-17+ γδ T cells, IL-17+ γδ T cells induced by supernatants derived from TLR-activated microglia also caused neurotoxicity in vitro. While these neurotoxic effects required stimulation of TLR2, TLR4, or TLR9 in microglia, neuronal injury mediated by bone marrow-derived macrophages did not require TLR signaling. Neurotoxicity mediated by IL-17+ γδ T cells required a direct cell-cell contact between T cells and neurons.

Conclusion

Taken together, these results point to a crucial role for microglia activated through TLRs in polarization of γδ T cells towards neurotoxic IL-17+ γδ T cells.

Alternatively activated microglia and macrophages in the central nervous system

Macrophages are important players in the fight against viral, bacterial, fungal and parasitic infections. From a resting state they may undertake two activation pathways, the classical known as M1, or the alternative known as M2. M1 markers are mostly mediators of pro-inflammatory responses whereas M2 markers emerge for resolution and cleanup. Microglia exerts in the central nervous system (CNS) a function similar to that of macrophages in the periphery. Microglia activation and proliferation occurs in almost any single pathology affecting the CNS. Often microglia activation has been considered detrimental and drugs able to stop microglia activation were considered for the treatment of a variety of diseases. Cumulative evidence shows that microglia may undergo the alternative activation pathway, express M2-type markers and contribute to neuroprotection. This review focuses on details about the role of M2 microglia and in the approaches available for its identification. Approaches to drive the M2 phenotype and data on its potential in CNS diseases are also reviewed.