Neuroinflammation, Mast Cells, and Glia: Dangerous Liaisons

Dorsal root ganglion-derived exosomes deteriorate neuropathic pain by activating microglia via the microRNA-16-5p/HECTD1/HSP90 axis

BACKGROUND

The activated microglia have been reported as pillar factors in neuropathic pain (NP) pathology, but the molecules driving pain-inducible microglial activation require further exploration. In this study, we investigated the effect of dorsal root ganglion (DRG)-derived exosomes (Exo) on microglial activation and the related mechanism.

METHODS

A mouse model of NP was generated by spinal nerve ligation (SNL), and DRG-derived Exo were extracted. The effects of DRG-Exo on NP and microglial activation in SNL mice were evaluated using behavioral tests, HE staining, immunofluorescence, and western blot. Next, the differentially enriched microRNAs (miRNAs) in DRG-Exo-treated microglia were analyzed using microarrays. RT-qPCR, RNA pull-down, dual-luciferase reporter assay, and immunofluorescence were conducted to verify the binding relation between miR-16-5p and HECTD1. Finally, the effects of ubiquitination modification of HSP90 by HECTD1 on NP progression and microglial activation were investigated by Co-IP, western blot, immunofluorescence assays, and rescue experiments.

RESULTS

DRG-Exo aggravated NP resulting from SNL in mice, promoted the activation of microglia in DRG, and increased neuroinflammation. miR-16-5p knockdown in DRG-Exo alleviated the stimulating effects of DRG-Exo on NP and microglial activation. DRG-Exo regulated the ubiquitination of HSP90 through the interaction between miR-16-5p and HECTD1. Ubiquitination alteration of HSP90 was involved in microglial activation during NP.

CONCLUSIONS

miR-16-5p shuttled by DRG-Exo regulated the ubiquitination of HSP90 by interacting with HECTD1, thereby contributing to the microglial activation in NP.

Role of Exercise on Inflammation Cytokines of Neuropathic Pain in Animal Models

Neuropathic pain (NP) resulting from a lesion or disease of the somatosensory system can lead to loss of function and reduced life quality. Neuroinflammation plays a vital role in the development and maintenance of NP. Exercise as an economical, effective, and nonpharmacological treatment, recommended by clinical practice guidelines, has been proven to alleviate chronic NP. Previous studies have shown that exercise decreases NP by modifying inflammation; however, the exact mechanisms of exercise-mediated NP are unclear. Therefore, from the perspective of neuroinflammation, this review mainly discussed the effects of exercise on inflammatory cytokines in different parts of NP conduction pathways, such as the brain, spinal cord, dorsal root ganglion, sciatic nerve, and blood in rat/mice models. Results suggested that exercise training could modulate neuroinflammation, inhibit astrocyte glial cell proliferation and microglial activation, alter the macrophage phenotype, reduce the expression of proinflammatory cytokines, increase anti-inflammatory cytokine levels, and positively modulate the state of the immune system, thereby relieving NP.

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.

Effects of electroacupuncture on postoperative cognitive dysfunction and its underlying mechanisms: a literature review of rodent studies

With the aging of the population, the health of the elderly has become increasingly important. Postoperative cognitive dysfunction (POCD) is a common neurological complication in elderly patients following general anesthesia or surgery. It is characterized by cognitive decline that may persist for weeks, months, or even longer. Electroacupuncture (EA), a novel therapy that combines physical nerve stimulation with acupuncture treatment from traditional Chinese medicine, holds potential as a therapeutic intervention for preventing and treating POCD, particularly in elderly patients. Although the beneficial effects of EA on POCD have been explored in preclinical and clinical studies, the reliability of EA is limited by methodological shortcomings, and the underlying mechanisms remain largely unexplored. Therefore, we have synthesized existing evidence and proposed potential biological mechanisms underlying the effects of EA on neuroinflammation, oxidative stress, autophagy, the microbiota-gut-brain axis, and epigenetic modification. This review summarizes recent advances in EA and POCD, provides a theoretical foundation, explores potential molecular mechanisms for the prevention and treatment of POCD, and offers a basis for conducting relevant clinical trials.

β-Sitosterol Alleviates Neuropathic Pain by Affect Microglia Polarization through Inhibiting TLR4/NF-κB Signaling Pathway

The etiology of neuropathic pain is mostly caused by mechanical deformation and neuroinflammation, of which neuroinflammation is the main cause of chronic neuropathic pain. Activation of the TLR4/NF-κB signaling pathway mediates elevated levels of inflammatory cytokines, and we clearly demonstrated by in vivo and in vitro Western blot experiments that β-sitosterol significantly inhibited the elevated Toll-like receptor 4 (TLR4) expression levels and nuclear factor-kappa B (NF-κB) activation associated with inflammatory responses. In cellular experiments, we clearly saw that both β-sitosterol and TLR4/NF-κB signaling pathway inhibitors could inhibit M1 proinflammatory phenotype expression and promote M2 anti-inflammatory phenotype expression in GMI-R1 microglia by flow cytometry and immunofluorescence assays. Therefore, we suggest that β-sitosterol can affect microglial polarization by inhibiting the TLR4/NF-κB signaling pathway thereby reducing neuroinflammation and thus alleviating neuropathic pain.

Neuroinflammation: The central enabler of postoperative cognitive dysfunction

The proportion of advanced age patients undergoing surgical procedures is on the rise owing to advancements in surgical and anesthesia technologies as well as an overall aging population. As a complication of anesthesia and surgery, older patients frequently suffer from postoperative cognitive dysfunction (POCD), which may persist for weeks, months or even longer. POCD is a complex pathological process involving multiple pathogenic factors, and its mechanism is yet unclear. Potential theories include inflammation, deposition of pathogenic proteins, imbalance of neurotransmitters, and chronic stress. The identification, prevention, and treatment of POCD are still in the exploratory stages owing to the absence of standardized diagnostic criteria. Undoubtedly, comprehending the development of POCD remains crucial in overcoming the illness. Neuroinflammation is the leading hypothesis and a crucial component of the pathological network of POCD and may have complex interactions with other mechanisms. In this review, we discuss the possible ways in which surgery and anesthesia cause neuroinflammation and investigate the connection between neuroinflammation and the development of POCD. Understanding these mechanisms may likely ensure that future treatment options of POCD are more effective.

Potential Role of Moesin in Regulating Mast Cell Secretion

Mast cells have existed for millions of years in species that never suffer from allergic reactions. Hence, in addition to allergies, mast cells can play a critical role in homeostasis and inflammation via secretion of numerous vasoactive, pro-inflammatory and neuro-sensitizing mediators. Secretion may utilize different modes that involve the cytoskeleton, but our understanding of the molecular mechanisms regulating secretion is still not well understood. The Ezrin/Radixin/Moesin (ERM) family of proteins is involved in linking cell surface-initiated signaling to the actin cytoskeleton. However, how ERMs may regulate secretion from mast cells is still poorly understood. ERMs contain two functional domains connected through a long α-helix region, the N-terminal FERM (band 4.1 protein-ERM) domain and the C-terminal ERM association domain (C-ERMAD). The FERM domain and the C-ERMAD can bind to each other in a head-to-tail manner, leading to a closed/inactive conformation. Typically, phosphorylation on the C-terminus Thr has been associated with the activation of ERMs, including secretion from macrophages and platelets. It has previously been shown that the ability of the so-called mast cell "stabilizer" disodium cromoglycate (cromolyn) to inhibit secretion from rat mast cells closely paralleled the phosphorylation of a 78 kDa protein, which was subsequently shown to be moesin, a member of ERMs. Interestingly, the phosphorylation of moesin during the inhibition of mast cell secretion was on the N-terminal Ser56/74 and Thr66 residues. This phosphorylation pattern could lock moesin in its inactive state and render it inaccessible to binding to the Soluble NSF attachment protein receptors (SNAREs) and synaptosomal-associated proteins (SNAPs) critical for exocytosis. Using confocal microscopic imaging, we showed moesin was found to colocalize with actin and cluster around secretory granules during inhibition of secretion. In conclusion, the phosphorylation pattern and localization of moesin may be important in the regulation of mast cell secretion and could be targeted for the development of effective inhibitors of secretion of allergic and inflammatory mediators from mast cells.

Pain Biomarkers in Fibromyalgia Syndrome: Current Understanding and Future Directions

Fibromyalgia is a complex and heterogeneous clinical syndrome, mainly characterized by the presence of widespread pain, possibly associated with a variety of other symptoms. Fibromyalgia can have an extremely negative impact on the psychological, physical and social lives of people affected, sometimes causing patients to experience dramatically impaired quality of life. Nowadays, the diagnosis of fibromyalgia is still clinical, thus favoring diagnostic uncertainties and making its clear identification challenging to establish, especially in primary care centers. These difficulties lead patients to undergo innumerable clinical visits, investigations and specialist consultations, thus increasing their stress, frustration and even dissatisfaction. Unfortunately, research over the last 25 years regarding a specific biomarker for the diagnosis of fibromyalgia has been fruitless. The discovery of a reliable biomarker for fibromyalgia syndrome would be a critical step towards the early identification of this condition, not only reducing patient healthcare utilization and diagnostic test execution but also providing early intervention with guideline-based treatments. This narrative article reviews different metabolite alterations proposed as possible biomarkers for fibromyalgia, focusing on their associations with clinical evidence of pain, and highlights some new, promising areas of research in this context. Nevertheless, none of the analyzed metabolites emerge as sufficiently reliable to be validated as a diagnostic biomarker. Given the complexity of this syndrome, in the future, a panel of biomarkers, including subtype-specific biomarkers, could be considered as an interesting alternative research area.

A model for irritable bowel syndrome and anxiety comorbidities in relation to alcohol use disorders

About 95% of human body serotonin synthesis occurs in the gastrointestinal tract (GI). Lack of sufficient serotonin levels is thought to play a key role in mood disorders, including anxiety disorders. In this study, we looked at a disorder affecting the GI tract, irritable bowel syndrome (IBS), and aimed to determine whether IBS is differentially associated with anxiety disorders in 252 chronic pain patients in the presence of a history of alcohol use disorders (AUD) given that alcohol is an extremely aggressive substance for the GI mucosa. We found that while the prevalence of IBS was not affected by the presence of AUD in chronic pain patients, IBS had significantly higher comorbidity with anxiety disorders in chronic pain patients with comorbid alcohol use disorders. We argue that these findings highlight mechanistic differences in the comorbidity of anxiety disorders with chronic pain and AUD, implicating a central role for GI problems stemming from chronic alcohol use. The findings may have important implications for the treatment of IBS patients with AUD who commonly present with anxiety disorders which could motivate the continuation of problematic drinking and impede recovery success. We propose that addressing GI problems in patients with AUD may help manage AUD and recovery more effectively.

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.

Microglia and astrocytes underlie neuroinflammation and synaptic susceptibility in autism spectrum disorder

Autism spectrum disorder (ASD) is a common neurodevelopmental disorder with onset in childhood. The mechanisms underlying ASD are unclear. In recent years, the role of microglia and astrocytes in ASD has received increasing attention. Microglia prune the synapses or respond to injury by sequestrating the injury site and expressing inflammatory cytokines. Astrocytes maintain homeostasis in the brain microenvironment through the uptake of ions and neurotransmitters. However, the molecular link between ASD and microglia and, or astrocytes remains unknown. Previous research has shown the significant role of microglia and astrocytes in ASD, with reports of increased numbers of reactive microglia and astrocytes in postmortem tissues and animal models of ASD. Therefore, an enhanced understanding of the roles of microglia and astrocytes in ASD is essential for developing effective therapies. This review aimed to summarize the functions of microglia and astrocytes and their contributions to ASD.

Spinal Irisin Gene Delivery Attenuates Burn Injury-Induced Muscle Atrophy by Promoting Axonal Myelination and Innervation of Neuromuscular Junctions

Muscle loss and weakness after a burn injury are typically the consequences of neuronal dysregulation and metabolic change. Hypermetabolism has been noted to cause muscle atrophy. However, the mechanism underlying the development of burn-induced motor neuropathy and its contribution to muscle atrophy warrant elucidation. Current therapeutic interventions for burn-induced motor neuropathy demonstrate moderate efficacy and have side effects, which limit their usage. We previously used a third-degree burn injury rodent model and found that irisin-an exercise-induced myokine-exerts a protective effect against burn injury-induced sensory and motor neuropathy by attenuating neuronal damage in the spinal cord. In the current study, spinal irisin gene delivery was noted to attenuate burn injury-induced sciatic nerve demyelination and reduction of neuromuscular junction innervation. Spinal overexpression of irisin leads to myelination rehabilitation and muscular innervation through the modulation of brain-derived neurotrophic factor and glial-cell-line-derived neurotrophic factor expression along the sciatic nerve to the muscle tissues and thereby modulates the Akt/mTOR pathway and metabolic derangement and prevents muscle atrophy.

Lipoyl-Based Antagonists of Transient Receptor Potential Cation A (TRPA1) Downregulate Osteosarcoma Cell Migration and Expression of Pro-Inflammatory Cytokines

Osteosarcoma is a heterogeneous tumor intimately linked to its microenvironment, which promotes its growth and spread. It is generally accompanied by cancer-induced bone pain (CIBP), whose main component is neuropathic pain. The TRPA1 ion channel plays a key role in metastasis and is increasingly expressed in bone cancer. Here, a novel TRPA1 inhibitor is described and tested together with two other known TRPA1 antagonists. The novel lipoyl derivative has been successfully assessed for its ability to reduce human osteosarcoma MG-63 cell viability, motility, and gene expression of the CIBP pro-inflammatory cytokines interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α). A putative three-dimensional (3D) model of the inhibitor covalently bound to TRPA1 is also proposed. The in vitro data suggest that the novel inhibitor described here may be highly interesting and stimulating for new strategies to treat osteosarcomas.

Sargassum horneri (Turner) C. Agardh Extract Regulates Neuroinflammation In Vitro and In Vivo

Previously, we reported that Sargassum horneri (Turner) C. Agardh (S. horneri) is a brown algae species that exerts anti-inflammatory activity toward murine macrophages. However, the anti-neuroinflammatory effects and the mechanism of S. horneri on microglia cells are still unknown. We investigated the anti-neuroinflammatory effects of S. horneri extract on microglia in vitro and in vivo. In the present study, we found that S. horneri was not cytotoxic to BV-2 microglia cells and it significantly decreased lipopolysaccharide (LPS)-induced NO production. Moreover, S. horneri also diminished the protein expression of iNOS, COX-2, and cytokine production, including IL-1β, TNF-α, and IL-6, on LPS-stimulated microglia activation. S. horneri elicited anti-neuroinflammatory effects by inhibiting phosphorylation of p38 MAPK and NF-κB. In addition, S. horneri inhibited astrocytes and microglia activation in LPS-challenged mice brain. Therefore, these results suggested that S. horneri exerted anti-neuroinflammatory effects on LPS-stimulated microglia cell activation by inhibiting neuroinflammatory factors and NF-κB signaling.

Blood-Based Biomarkers of Repetitive, Subconcussive Blast Overpressure Exposure in the Training Environment: A Pilot Study

Because of their unknown long-term effects, repeated mild traumatic brain injuries (TBIs), including the low, subconcussive ones, represent a specific challenge to healthcare systems. It has been hypothesized that they can have a cumulative effect, and they may cause molecular changes that can lead to chronic degenerative processes. Military personnel are especially vulnerable to consequences of subconcussive TBIs because their training involves repeated exposures to mild explosive blasts. In this pilot study, we collected blood samples at baseline, 6 h, 24 h, 72 h, 2 weeks, and 3 months after heavy weapons training from students and instructors who were exposed to repeated subconcussive blasts. Samples were analyzed using the reverse and forward phase protein microarray platforms. We detected elevated serum levels of glial fibrillary acidic protein, ubiquitin C-terminal hydrolase L1 (UCH-L1), nicotinic alpha 7 subunit (CHRNA7), occludin (OCLN), claudin-5 (CLDN5), matrix metalloprotease 9 (MMP9), and intereukin-6 (IL-6). Importantly, serum levels of most of the tested protein biomarkers were the highest at 3 months after exposures. We also detected elevated autoantibody titers of proteins related to vascular and neuroglia-specific proteins at 3 months after exposures as compared to baseline levels. These findings suggest that repeated exposures to subconcussive blasts can induce molecular changes indicating not only neuron and glia damage, but also vascular changes and inflammation that are detectable for at least 3 months after exposures whereas elevated titers of autoantibodies against vascular and neuroglia-specific proteins can indicate an autoimmune process.

Genetics of COVID-19 and myalgic encephalomyelitis/chronic fatigue syndrome: a systematic review

COVID‐19 and ME/CFS present with some similar symptoms, especially physical and mental fatigue. In order to understand the basis of these similarities and the possibility of underlying common genetic components, we performed a systematic review of all published genetic association and cohort studies regarding COVID‐19 and ME/CFS and extracted the genes along with the genetic variants investigated. We then performed gene ontology and pathway analysis of those genes that gave significant results in the individual studies to yield functional annotations of the studied genes using protein analysis through evolutionary relationships (PANTHER) VERSION 17.0 software. Finally, we identified the common genetic components of these two conditions. Seventy‐one studies for COVID‐19 and 26 studies for ME/CFS were included in the systematic review in which the expression of 97 genes for COVID‐19 and 429 genes for ME/CFS were significantly affected. We found that ACE, HLA‐A, HLA‐C, HLA‐DQA1, HLA‐DRB1, and TYK2 are the common genes that gave significant results. The findings of the pathway analysis highlight the contribution of inflammation mediated by chemokine and cytokine signaling pathways, and the T cell activation and Toll receptor signaling pathways. Protein class analysis revealed the contribution of defense/immunity proteins, as well as protein‐modifying enzymes. Our results suggest that the pathogenesis of both syndromes could involve some immune dysfunction.

Mast cell stabilizer disodium cromoglycate improves long-term cognitive impairment after general anesthesia exposure in neonatal mice

Background

Prolonged exposure to general anesthesia (GA) results in long-lasting cognitive impairment, especially during critical stages of brain development. An exaggerated neuroinflammation induced by anesthesia is generally considered to be a key cause of cognitive impairment.

Materials and methods

Postnatal day 7 (PND 7) mice were exposed to GA by isoflurane inhalation for 6 h or mock anesthesia. Disodium cromoglycate (DSCG) was intraperitoneally injected daily for 2 weeks, beginning from 30 min before anesthesia. The post-anesthesia evaluation included behavioral tests, toluidine blue staining, immunofluorescence and western blot.

Results

Our results demonstrated the long-term cognition were impaired after 6 h GA exposure in neonatal mice. DSCG treatment ameliorated early mast cells (MCs) degranulation and mast cell tryptase (MCT) expression, which helps to attenuate subsequent neuroinflammation, activation of microglia and astrocytes, and damage to oligodendrocytes and synapses to improve cognitive impairment.

Conclusion

Disodium cromoglycate could effectively improve long-term cognitive impairment after GA exposure in neonatal mice.

COVID-19 causes neuronal degeneration and reduces neurogenesis in human hippocampus

Recent investigations of COVID-19 have largely focused on the effects of this novel virus on the vital organs in order to efficiently assist individuals who have recovered from the disease. In the present study we used hippocampal tissue samples extracted from people who died after COVID-19. Utilizing histological techniques to analyze glial and neuronal cells we illuminated a massive degeneration of neuronal cells and changes in glial cells morphology in hippocampal samples. The results showed that in hippocampus of the studied brains there were morphological changes in pyramidal cells, an increase in apoptosis, a drop in neurogenesis, and change in spatial distribution of neurons in the pyramidal and granular layer. It was also demonstrated that COVID-19 alter the morphological characteristics and distribution of astrocyte and microglia cells. While the exact mechanism(s) by which the virus causes neuronal loss and morphology in the central nervous system (CNS) remains to be determined, it is necessary to monitor the effect of SARS-CoV-2 infection on CNS compartments like the hippocampus in future investigations. As a result of what happened in the hippocampus secondary to COVID-19, memory impairment may be a long-term neurological complication which can be a predisposing factor for neurodegenerative disorders through neuroinflammation and oxidative stress mechanisms.

The Pathobiology of Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: The Case for Neuroglial Failure

Although myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) has a specific and distinctive profile of clinical features, the disease remains an enigma because causal explanation of the pathobiological matrix is lacking. Several potential disease mechanisms have been identified, including immune abnormalities, inflammatory activation, mitochondrial alterations, endothelial and muscular disturbances, cardiovascular anomalies, and dysfunction of the peripheral and central nervous systems. Yet, it remains unclear whether and how these pathways may be related and orchestrated. Here we explore the hypothesis that a common denominator of the pathobiological processes in ME/CFS may be central nervous system dysfunction due to impaired or pathologically reactive neuroglia (astrocytes, microglia and oligodendrocytes). We will test this hypothesis by reviewing, in reference to the current literature, the two most salient and widely accepted features of ME/CFS, and by investigating how these might be linked to dysfunctional neuroglia. From this review we conclude that the multifaceted pathobiology of ME/CFS may be attributable in a unifying manner to neuroglial dysfunction. Because the two key features - post exertional malaise and decreased cerebral blood flow - are also recognized in a subset of patients with post-acute sequelae COVID, we suggest that our findings may also be pertinent to this entity.

Palmitoylethanolamide dampens neuroinflammation and anxiety-like behavior in obese mice

High-fat diet (HFD) consumption leads to obesity and a chronic state of low-grade inflammation, named metainflammation. Notably, metainflammation contributes to neuroinflammation due to the increased levels of circulating free fatty acids and cytokines. It indicates a strict interplay between peripheral and central counterparts in the pathogenic mechanisms of obesity-related mood disorders. In this context, the impairment of internal hypothalamic circuitry runs in tandem with the alteration of other brain areas associated with emotional processing (i.e., hippocampus and amygdala). Palmitoylethanolamide (PEA), an endogenous lipid mediator belonging to the N-acylethanolamines family, has been extensively studied for its pleiotropic effects both at central and peripheral level. Our study aimed to elucidate PEA capability in limiting obesity-induced anxiety-like behavior and neuroinflammation-related features in an experimental model of HFD-fed obese mice. PEA treatment promoted an improvement in anxiety-like behavior of obese mice and the systemic inflammation, reducing serum pro-inflammatory mediators (i.e., TNF-α, IL-1β, MCP-1, LPS). In the amygdala, PEA increased dopamine turnover, as well as GABA levels. PEA also counteracted the overactivation of HPA axis, reducing the expression of hypothalamic corticotropin-releasing hormone and its type 1 receptor. Moreover, PEA attenuated the immunoreactivity of Iba-1 and GFAP and reduced pro-inflammatory pathways and cytokine production in both the hypothalamus and hippocampus. This finding, together with the reduced transcription of mast cell markers (chymase 1 and tryptase β2) in the hippocampus, indicated the weakening of immune cell activation underlying the neuroprotective effect of PEA. Obesity-driven neuroinflammation was also associated with the disruption of blood-brain barrier (BBB) in the hippocampus. PEA limited the albumin extravasation and restored tight junction transcription modified by HFD. To gain mechanistic insight, we designed an in vitro model of metabolic injury using human neuroblastoma SH-SY5Y cells insulted by a mix of glucosamine and glucose. Here, PEA directly counteracted inflammation and mitochondrial dysfunction in a PPAR-α-dependent manner since the pharmacological blockade of the receptor reverted its effects. Our results strengthen the therapeutic potential of PEA in obesity-related neuropsychiatric comorbidities, controlling neuroinflammation, BBB disruption, and neurotransmitter imbalance involved in behavioral dysfunctions.

Electroacupuncture Ameliorates Tibial Fracture-Induced Cognitive Dysfunction by Elevating α7nAChR Expression and Suppressing Mast Cell Degranulation in the Hippocampus of Rats

Intracerebral neuroinflammation, closely related to brain mast cell (MC) activation, performs an integral function in the pathogenic process of postoperative cognitive dysfunction (POCD). In addition to regulating cognitive activities, the alpha-7-nicotinic acetylcholine receptor (α7nAChR) engages in the progression of cognitive deficiency. In this research, we aimed to investigate how electroacupuncture (EA) affects the cognitive function in rats after tibial fracture surgery to determine whether the underlying mechanism involves the inhibition of hippocampal MC degranulation via α7nAChR. A rat model of tibial fracture surgery for inducing POCD was developed and subjected to treatment with EA or the α7nAChR antagonist α-bungarotoxin (α-BGT) and the α7nAChR agonist PHA-543613. The spatial memory tasks in the Morris Water Maze (MWM) test showed that both EA and PHA-543613-treated rats performed significantly better than untreated rats, with reduced escape latency and increased frequency of passage through the platform. However, EA and PHA-543613 intervention decreased the protein and mRNA levels of High-mobility group box-1(HMGB-1) and proinflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) in the serum and hippocampus, respectively, by upregulating α7nAChR in the hippocampus. Furthermore, EA and PHA-543613 pretreatment reduced the number of activated MCs and suppressed neuronal apoptosis after tibial fracture surgery in the hippocampal CA1 regions, which was reversed by α-BGT. The findings indicated that EA pretreatment ameliorated POCD after tibial fracture surgery in rats by inhibiting brain MC activation and neuroinflammation mediated by the α7nAChR-dependent cholinergic anti-inflammatory system.

Laparotomy-Induced Peripheral Inflammation Activates NR2B Receptors on the Brain Mast Cells and Results in Neuroinflammation in a Vagus Nerve-Dependent Manner

Background: The pathophysiological mechanisms underlying postoperative cognitive dysfunction (POCD) remain unclear over the years. Neuroinflammation caused by surgery has been recognized as an important element in the development of POCD. Many studies also suggest that the vagus nerve plays an important role in transmitting peripheral injury signals to the central nervous system (CNS) and the resultant neuroinflammation. Previously, we have demonstrated that brain mast cells (BMCs), as the “first responders”, play a vital role in neuroinflammation and POCD. However, how the vagus nerve communicates with BMCs in POCD has not yet been clarified.

Methods: In the current study, we highlighted the role of the vagus nerve as a conduction highway in surgery-induced neuroinflammation for the first time. In our model, we tested if mice underwent unilateral cervical vagotomy (VGX) had less neuroinflammation compared to the shams after laparotomy (LP) at an early stage. To further investigate the roles of mast cells and glutamate in the process, we employed Kit^W-sh mice and primary bone marrow-derived MCs to verify the glutamate-NR2B axis on MCs once again.

Results: Our results demonstrated that there were higher levels of glutamate and BMCs activation as early as 4 h after LP. Meanwhile, vagotomy could partially block the increases and reduce neuroinflammation caused by peripheral inflammation during the acute phase. Excitingly, inhibition of NR2B receptor and knockout of mast cells can attenuateneuroinflammation induced by glutamate.

Conclusion: Taken together, our findings indicate that the vagus is a high-speed pathway in the transmission of peripheral inflammation to the CNS. Activation of BMCs triggered a neuroinflammatory cascade. Inhibition of NR2B receptor on BMCs can reduce glutamate-induced BMCs activation, neuroinflammation, and memory impairment, suggesting a novel treatment strategy for POCD.

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.

Targeting Endocannabinoid System in Epilepsy: For Good or for Bad

Epilepsy is a neurological disorder with a high prevalence worldwide. Several studies carried out during the last decades indicate that the administration of cannabinoids as well as the activation of the endocannabinoid system (ECS) represent a therapeutic strategy to control epilepsy. However, there are controversial studies indicating that activation of ECS results in cell damage, inflammation and neurotoxicity, conditions that facilitate the seizure activity. The present review is focused to present findings supporting this issue. According to the current discrepancies, it is relevant to elucidate the different effects induced by the activation of ECS and determine the conditions under which it facilitates the seizure activity.

Mechanisms of ATP release in pain: role of pannexin and connexin channels

Pain is a physiological response to bodily damage and serves as a warning of potential threat. Pain can also transform from an acute response to noxious stimuli to a chronic condition with notable emotional and psychological components that requires treatment. Indeed, the management of chronic pain is currently an important unmet societal need. Several reports have implicated the release of the neurotransmitter adenosine triphosphate (ATP) and subsequent activation of purinergic receptors in distinct pain etiologies. Purinergic receptors are broadly expressed in peripheral neurons and the spinal cord; thus, purinergic signaling in sensory neurons or in spinal circuits may be critical for pain processing. Nevertheless, an outstanding question remains: what are the mechanisms of ATP release that initiate nociceptive signaling? Connexin and pannexin channels are established conduits of ATP release and have been suggested to play important roles in a variety of pathologies, including several models of pain. As such, these large-pore channels represent a new and exciting putative pharmacological target for pain treatment. Herein, we will review the current evidence for a role of connexin and pannexin channels in ATP release during nociceptive signaling, such as neuropathic and inflammatory pain. Collectively, these studies provide compelling evidence for an important role of connexins and pannexins in pain processing.

RETRACTED ARTICLE: Involvement of pro-inflammatory cytokines in diabetic neuropathic pain via central PI3K/Akt/mTOR signal pathway

Retraction statementWe, the Editors and Publisher of Archives of Physiology and Biochemistry, have retracted the following article:Zongming Jiang, Zhonghua Chen, Yonghao Chen, Jing Jiao and Zhifeng WangInvolvement of pro-inflammatory cytokines in diabetic neuropathic pain via central PI3K/Akt/mTOR signal pathway, Archives of Physiology and Biochemistry, Published Online 2019 Aug 9:1-9. DOI: 10.1080/13813455.2019.1651869The article has been retracted following receipt of information from the corresponding author, Zhifeng Wang, on September 11, 2019, informing us that it was realised that inappropriate doses of rapamycin and the corresponding antagonist were used in this study, which may have led to artificial results and misleading interpretations and ultimately do not support the final conclusions drawn by the authors. The article is withdrawn from all print and electronic editions.We have been informed in our decision-making by our policy on publishing ethics and integrity and the COPE guidelines on retractions.The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as "Retracted."

Altered interaction between enteric glial cells and mast cells in the colon of women with irritable bowel syndrome

BACKGROUND

Enteric glial cells (EGC) and mast cells (MC) are intimately associated with gastrointestinal physiological functions. We aimed to investigate EGC-MC interaction in irritable bowel syndrome (IBS), a gut-brain disorder linked to increased intestinal permeability, and MC.

METHODS

Parallel approaches were used to quantify EGC markers in colonic biopsies from healthy controls (HC) and patients with IBS. Data were correlated with MC, vasoactive intestinal polypeptide (VIP) and VIP receptors (VPAC1/VPAC2) expressions, and bacterial translocation through biopsies mounted in Ussing chambers. In addition, we investigated the effects of EGC mediators on colonic permeability and the pharmacological-induced responses of EGC and MC cell lines.

KEY RESULTS

Immunofluorescence of IBS colonic mucosa, as well as Western blotting and ELISA of IBS biopsy lysates, revealed increased glial fibrillary intermediate filament (GFAP) expression, indicating EGC activation. Mucosal GFAP correlated with increased MC and VPAC1⁺ MC numbers and decreased VIP⁺ MC, which seemed to control bacterial translocation in HC. In the contrary, EGC activation in IBS correlated with less MC and VPAC1⁺ MC numbers, and more VIP⁺ MC. In vitro, MC and EGC cell lines showed intracellular calcium responses to each other's mediators. Furthermore, EGC mediators prevented VIP-induced MC degranulation, while MC mediators induced a reactive EGC phenotype. In Ussing chambers, EGC mediators decreased paracellular passage through healthy colonic biopsies.

CONCLUSIONS & INFERENCES

Findings suggest the involvement of EGC and MC in the control of barrier function in the human colon and indicate a potential EGC-MC interaction that seems altered in IBS, with detrimental consequences to colonic permeability. Altogether, results suggest that imbalanced EGC-MC communication contributes to the pathophysiology of IBS.

Ways to Address Perinatal Mast Cell Activation and Focal Brain Inflammation, including Response to SARS-CoV-2, in Autism Spectrum Disorder

The prevalence of autism spectrum disorder (ASD) continues to increase, but no distinct pathogenesis or effective treatment are known yet. The presence of many comorbidities further complicates matters, making a personalized approach necessary. An increasing number of reports indicate that inflammation of the brain leads to neurodegenerative changes, especially during perinatal life, "short-circuiting the electrical system" in the amygdala that is essential for our ability to feel emotions, but also regulates fear. Inflammation of the brain can result from the stimulation of mast cells-found in all tissues including the brain-by neuropeptides, stress, toxins, and viruses such as SARS-CoV-2, leading to the activation of microglia. These resident brain defenders then release even more inflammatory molecules and stop "pruning" nerve connections, disrupting neuronal connectivity, lowering the fear threshold, and derailing the expression of emotions, as seen in ASD. Many epidemiological studies have reported a strong association between ASD and atopic dermatitis (eczema), asthma, and food allergies/intolerance, all of which involve activated mast cells. Mast cells can be triggered by allergens, neuropeptides, stress, and toxins, leading to disruption of the blood-brain barrier (BBB) and activation of microglia. Moreover, many epidemiological studies have reported a strong association between stress and atopic dermatitis (eczema) during gestation, which involves activated mast cells. Both mast cells and microglia can also be activated by SARS-CoV-2 in affected mothers during pregnancy. We showed increased expression of the proinflammatory cytokine IL-18 and its receptor, but decreased expression of the anti-inflammatory cytokine IL-38 and its receptor IL-36R, only in the amygdala of deceased children with ASD. We further showed that the natural flavonoid luteolin is a potent inhibitor of the activation of both mast cells and microglia, but also blocks SARS-CoV-2 binding to its receptor angiotensin-converting enzyme 2 (ACE2). A treatment approach should be tailored to each individual patient and should address hyperactivity/stress, allergies, or food intolerance, with the introduction of natural molecules or drugs to inhibit mast cells and microglia, such as liposomal luteolin.

Diagnosis and Management of Achalasia: Updates of the Last Two Years

Achalasia is a rare neurodegenerative disorder causing dysphagia and is characterized by abnormal esophageal motor function as well as the loss of lower esophageal sphincter (LES) relaxation. The assessment and management of achalasia has significantly progressed in recent years due to the advances in high-resolution manometry (HRM) technology along with the improvements and innovations of therapeutic endoscopy procedures. The recent evolution of HRM technology with the inclusion of an adjunctive test, fluoroscopy, and EndoFLIP has enabled more precise diagnoses of achalasia to be made and the subgrouping into therapeutically meaningful subtypes. Current management possibilities include endoscopic treatments such as Botulinum toxin injected to the LES and pneumatic balloon dilation. Surgical treatment includes laparoscopic Heller myotomy and esophagectomy. Furthermore, in recent years, per oral endoscopic myotomy (POEM) has established itself as a principal endoscopic therapeutic alternative to the traditional laparoscopic Heller myotomy. The latest randomized trials report that POEM, pneumatic balloon dilatation, and laparoscopic Heller's myotomy have comparable effectiveness and complications rates. The aim of the current review is to provide a practical clinical approach to dysphagia and to shed light on the most recent improvements in diagnostics and treatment of achalasia over the last two years.

The pathogenic role of c-Kit+ mast cells in the spinal motor neuron-vascular niche in ALS

Degeneration of motor neurons, glial cell reactivity, and vascular alterations in the CNS are important neuropathological features of amyotrophic lateral sclerosis (ALS). Immune cells trafficking from the blood also infiltrate the affected CNS parenchyma and contribute to neuroinflammation. Mast cells (MCs) are hematopoietic-derived immune cells whose precursors differentiate upon migration into tissues. Upon activation, MCs undergo degranulation with the ability to increase vascular permeability, orchestrate neuroinflammation and modulate the neuroimmune response. However, the prevalence, pathological significance, and pharmacology of MCs in the CNS of ALS patients remain largely unknown. In autopsy ALS spinal cords, we identified for the first time that MCs express c-Kit together with chymase, tryptase, and Cox-2 and display granular or degranulating morphology, as compared with scarce MCs in control cords. In ALS, MCs were mainly found in the niche between spinal motor neuron somas and nearby microvascular elements, and they displayed remarkable pathological abnormalities. Similarly, MCs accumulated in the motor neuron-vascular niche of ALS murine models, in the vicinity of astrocytes and motor neurons expressing the c-Kit ligand stem cell factor (SCF), suggesting an SCF/c-Kit-dependent mechanism of MC differentiation from precursors. Mechanistically, we provide evidence that fully differentiated MCs in cell cultures can be generated from the murine ALS spinal cord tissue, further supporting the presence of c-Kit+ MC precursors. Moreover, intravenous administration of bone marrow-derived c-Kit+ MC precursors infiltrated the spinal cord in ALS mice but not in controls, consistent with aberrant trafficking through a defective microvasculature. Pharmacological inhibition of c-Kit with masitinib in ALS mice reduced the MC number and the influx of MC precursors from the periphery. Our results suggest a previously unknown pathogenic mechanism triggered by MCs in the ALS motor neuron-vascular niche that might be targeted pharmacologically.

Antioxidants Improve Oxaliplatin-Induced Peripheral Neuropathy in Tumor-Bearing Mice Model: Role of Spinal Cord Oxidative Stress and Inflammation

Chemotherapy-Induced Peripheral Neuropathy (CIPN) is a common, difficult-to-treat, and dose-limiting side effect associated with Oxaliplatin (OXA) treatment. In this study, we evaluated the effect of three antioxidants - namely N-acetylcysteine, α-lipoic acid and vitamin E - upon nociceptive parameters and antitumor efficacy of OXA in a tumor-bearing Swiss mice model. Oral treatment with antioxidants inhibited both mechanical and cold allodynia when concomitantly administrated with OXA (preventive protocol), as well as in animals with previously established CIPN (therapeutic protocol). OXA increased Reactive Oxygen Species (ROS) production and lipoperoxidation, and augmented the content of pro-inflammatory cytokines (IL-1β and TNF-α) and expression of the astrocytic marker Gfap mRNA in the spinal cord. Antioxidants decreased ROS production and lipoperoxidation, and abolished neuroinflammation in OXA-treated animals. Toll-like receptor 4 (Tlr4) and inflammasome enzyme caspase-1/11 knockout mice treated with OXA showed reduced levels of pro-inflammatory cytokines (but not oxidative stress) in the spinal cord, which were associated with resistance to OXA-induced mechanical allodynia. Lastly, antioxidants affected neither antitumor activity nor hematological toxicity of OXA in vivo. The herein presented results are provocative for further evaluation of antioxidants in clinical management of chemotherapy-induced peripheral neuropathy. PERSPECTIVE: This study reports preventive and therapeutic efficacy of orally administrated antioxidants (N-acetylcysteine, α-lipoic-acid and Vitamin-E) in alleviating oxaliplatin-induced peripheral neuropathy in tumor-bearing mice. Antioxidants' anti-nociceptive effects are associated with inhibition of ROS-dependent neuroinflammation, and occur at no detriment of OXA antitumor activity, therefore indicating a translational potential of these compounds.

Neuroinflammation: The next target of exosomal microRNAs derived from mesenchymal stem cells in the context of neurological disorders

Among different types of mechanisms involved in neurological disorders, neuroinflammation links initial insults to secondary injuries and triggers some chronic outcomes, for example, neurodegenerative disorders. Thus, anti-inflammatory substances can be targeted as a novel therapeutic option for translational and clinical research to improve brain disease outcomes. In this review, we propose to introduce a new insight into the anti-inflammatory effects of mesenchymal stem cells (MSCs) as the most frequent source for stem cell therapy in neurological diseases. Our insight incorporates a bystander effect of these stem cells in modulating inflammation and microglia/macrophage polarization through exosomes. Exosomes are nano-sized membrane vesicles that carry cell-specific constituents, including protein, lipid, DNA, and RNA. microRNAs (miRNAs) have recently been detected in exosomes that can be taken up by other cells and affect the behavior of recipient cells. In this article, we outline and highlight the potential use of exosomal miRNAs derived from MSCs for inflammatory pathways in the context of neurological disorders. Furthermore, we suggest that focusing on exosomal miRNAs derived from MSCs in the course of neuroinflammatory pathways in the future could reveal their functions for diverse neurological diseases, including brain injuries and neurodegenerative diseases. It is hoped that this study will contribute to a deep understanding of stem cell bystander effects through exosomal miRNAs.

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.

Licochalcone A Attenuates Chronic Neuropathic Pain in Rats by Inhibiting Microglia Activation and Inflammation

Immune response plays a vital role in the pathogenesis of neuropathic pain. Immune response-targeted therapy becomes an effective strategy for treating neuropathic pain. Licochalcone A (Lic-A) possesses anti-inflammatory and neuroprotective effects. However, the potential of Lic-A to attenuate neuropathic pain has not been well explored. To investigate the protective effect and evaluate the underlying mechanism of Lic-A against neuropathic pain in a rat model. Chronic constriction injury (CCI) surgery was employed in rats to establish neuropathic pain model. Rats were intraperitoneally administrated with Lic-A (1.25, 2.50 and 5.00 mg/kg) twice daily. Mechanical withdrawal threshold and thermal withdrawal latency were used to evaluate neuropathic pain. After administration, the lumbar spinal cord enlargement of rats was collected for ELISA, Western blot and immunofluorescence analysis. Mechanical withdrawal threshold and thermal withdrawal latency results showed that Lic-A significantly attenuated CCI-evoked neuropathic pain in dose-dependent manner. Lic-A administration also effectively blocked microglia activation. Moreover, Lic-A suppressed p38 phosphorylation and the release of inflammatory factors such as tumor necrosis factor-α, interleukin-1 and interleukin-6. Our findings provide evidence that Lic-A may have the potential to attenuate CCI-evoked neuropathic pain in rats by inhibiting microglia activation and inflammatory response.

Long-COVID syndrome-associated brain fog and chemofog: Luteolin to the rescue

COVID-19 leads to severe respiratory problems, but also to long-COVID syndrome associated primarily with cognitive dysfunction and fatigue. Long-COVID syndrome symptoms, especially brain fog, are similar to those experienced by patients undertaking or following chemotherapy for cancer (chemofog or chemobrain), as well in patients with myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) or mast cell activation syndrome (MCAS). The pathogenesis of brain fog in these illnesses is presently unknown but may involve neuroinflammation via mast cells stimulated by pathogenic and stress stimuli to release mediators that activate microglia and lead to inflammation in the hypothalamus. These processes could be mitigated by phytosomal formulation (in olive pomace oil) of the natural flavonoid luteolin.

The etiology of achalasia: An immune-dominant disease

There is accumulating evidence suggesting that an autoimmune component is involved in esophageal achalasia. An increase in immune cells, cytokines, chemokines, and autoimmune antibodies in serum and infiltration of immune cells in tissues support the view that immune-mediated inflammation is a crucial pathogenesis of inhibitory neuron degeneration in the lower esophageal sphincter. Infection of viruses such as the herpes virus family has been suspected of provoking the autoimmune reaction. Meanwhile, previous reports on immunogenetics have proposed that specific risk alleles on the human leukocyte antigen complex define the susceptible population to achalasia. In this study we reviewed current knowledge regarding the immune-related factors of achalasia, including immunology, viral infection and immunogenetic variations.

Neuroprotective effects of flavone luteolin in neuroinflammation and neurotrauma

Neuroinflammation leads to neurodegeneration, cognitive defects, and neurodegenerative disorders. Neurotrauma/traumatic brain injury (TBI) can cause activation of glial cells, neurons, and neuroimmune cells in the brain to release neuroinflammatory mediators. Neurotrauma leads to immediate primary brain damage (direct damage), neuroinflammatory responses, neuroinflammation, and late secondary brain damage (indirect) through neuroinflammatory mechanism. Secondary brain damage leads to chronic inflammation and the onset and progression of neurodegenerative diseases. Currently, there are no effective and specific therapeutic options to treat these brain damages or neurodegenerative diseases. Flavone luteolin is an important natural polyphenol present in several plants that show anti-inflammatory, antioxidant, anticancer, cytoprotective, and macrophage polarization effects. In this short review article, we have reviewed the neuroprotective effects of luteolin in neurotrauma and neurodegenerative disorders and pathways involved in this mechanism. We have collected data for this study from publications in the PubMed using the keywords luteolin and mast cells, neuroinflammation, neurodegenerative diseases, and TBI. Recent reports suggest that luteolin suppresses systemic and neuroinflammatory responses in Coronavirus disease 2019 (COVID-19). Studies have shown that luteolin exhibits neuroprotective effects through various mechanisms, including suppressing immune cell activation, such as mast cells, and inflammatory mediators released from these cells. In addition, luteolin can suppress neuroinflammatory response, activation of microglia and astrocytes, oxidative stress, neuroinflammation, and the severity of neuroinflammatory diseases such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, and TBI pathogenesis. In conclusion, luteolin can improve cognitive decline and enhance neuroprotection in neurodegenerative diseases, TBI, and stroke.

Decoding Mast Cell-Microglia Communication in Neurodegenerative Diseases

Microglia, resident immune cells of the central nervous system (CNS), play a pivotal role in immune surveillance and maintenance of neuronal health. Mast cells are also important resident immune cells of the CNS but they are underappreciated and understudied. Both microglia and mast cells are endowed with an array of signaling receptors that recognize microbes and cellular damage. As cellular sensors and effectors in the CNS, they respond to many CNS perturbations and have been implicated in neuroinflammation and neurodegeneration. Mast cells contain numerous secretory granules packaged with a plethora of readily available and newly synthesized compounds known as 'mast cell mediators'. Mast cells act as 'first responders' to a pathogenic stimuli and respond by degranulation and releasing these mediators into the extracellular milieu. They alert other glial cells, including microglia to initiate neuroinflammatory processes that culminate in the resolution of injury. However, failure to resolve the pathogenic process can lead to persistent activation, release of pro-inflammatory mediators and amplification of neuroinflammatory responses, in turn, resulting in neuronal dysfunction and demise. This review discusses the current understanding of the molecular conversation between mast cells and microglia in orchestrating immune responses during two of the most prevalent neurodegenerative diseases, namely Alzheimer's disease and Parkinson's disease. Here we also survey the potential emerging therapeutic approaches targeting common pathways in mast cells and microglia to extinguish the fire of inflammation.

An Shen Ding Zhi Ling Alleviates Symptoms of Attention Deficit Hyperactivity Disorder via Anti-Inflammatory Effects in Spontaneous Hypertensive Rats

Attention deficit hyperactivity disorder (ADHD) is a childhood-onset chronic neurobehavioral disorder, with multiple genetic and environmental risk factors. Chronic inflammation may be critical for the progression of ADHD. An Shen Ding Zhi Ling (ASDZL) decoction, a traditional Chinese medicine prescription, is clinically used in ADHD treatment. In this study, we investigated the effects and underlying anti-inflammatory mechanisms of ASDZL in young spontaneously hypertensive rats (SHRs), a widely used model of ADHD. SHRs were divided into the SHR model group (vehicle), atomoxetine group (4.56 mg/kg/day) and ASDZL group (21.25 g/kg/day), and orally administered for four weeks. Wistar Kyoto rats were used as controls (vehicle). We found that ASDZL significantly controlled hyperactivity and impulsivity, and improved spatial memory of SHRs in the open field test and Morris water maze test. ASDZL reduced the pro-inflammatory factors interleukin (IL)-1β, IL-4, IL-6, tumor necrosis factor (TNF)-α and monocyte chemoattractant protein (MCP)-1 and increased anti-inflammatory factor IL-10 in SHRs, and decreased the activation of microglia, astrocytes and mast cells in the prefrontal cortex (PFC) and hippocampus. Furthermore, the results indicated that ASDZL inhibited the neuroinflammatory response by protecting the integrity of the blood-brain barrier and suppressing the mitogen-activated protein kinase (MAPK) and nuclear factor (NF)-κB signaling pathways of SHRs. In conclusion, these findings revealed that ASDZL attenuated ADHD symptoms in SHRs by reducing neuroinflammation.

Review on experimental study and clinical application of low-intensity pulsed ultrasound in inflammation

Low-intensity pulsed ultrasound (LIPUS), as physical therapy, is widely used in both research and clinical settings. It induces multiple bioeffects, such as alleviating pain, promoting tissue repair, and shortening disease duration. LIPUS can also mediate inflammation. This paper reviews the application of LIPUS in inflammation and discusses the underlying mechanism. In basic experiments, LIPUS can regulate inflammatory responses at the cellular level by affecting some signaling pathways. In a clinical trial, LIPUS has been shown to alleviate inflammatory responses efficiently. As a cheap, safe, and convenient physical method, LIPUS is promising as anti-inflammatory therapy.

Neuroimmune connections between corticotropin-releasing hormone and mast cells: novel strategies for the treatment of neurodegenerative diseases

Corticotropin-releasing hormone is a critical component of the hypothalamic–pituitary–adrenal axis, which plays a major role in the body’s immune response to stress. Mast cells are both sensors and effectors in the interaction between the nervous and immune systems. As first responders to stress, mast cells can initiate, amplify and prolong neuroimmune responses upon activation. Corticotropin-releasing hormone plays a pivotal role in triggering stress responses and related diseases by acting on its receptors in mast cells. Corticotropin-releasing hormone can stimulate mast cell activation, influence the activation of immune cells by peripheral nerves and modulate neuroimmune interactions. The latest evidence shows that the release of corticotropin-releasing hormone induces the degranulation of mast cells under stress conditions, leading to disruption of the blood-brain barrier, which plays an important role in neurological diseases, such as Alzheimer’s disease, Parkinson’s disease, multiple sclerosis, autism spectrum disorder and amyotrophic lateral sclerosis. Recent studies suggest that stress increases intestinal permeability and disrupts the blood-brain barrier through corticotropin-releasing hormone-mediated activation of mast cells, providing new insight into the complex interplay between the brain and gastrointestinal tract. The neuroimmune target of mast cells is the site at which the corticotropin-releasing hormone directly participates in the inflammatory responses of nerve terminals. In this review, we focus on the neuroimmune connections between corticotropin-releasing hormone and mast cells, with the aim of providing novel potential therapeutic targets for inflammatory, autoimmune and nervous system diseases.

Palmitoylethanolamide: A Nutritional Approach to Keep Neuroinflammation within Physiological Boundaries-A Systematic Review

Neuroinflammation is a physiological response aimed at maintaining the homodynamic balance and providing the body with the fundamental resource of adaptation to endogenous and exogenous stimuli. Although the response is initiated with protective purposes, the effect may be detrimental when not regulated. The physiological control of neuroinflammation is mainly achieved via regulatory mechanisms performed by particular cells of the immune system intimately associated with or within the nervous system and named “non-neuronal cells.” In particular, mast cells (within the central nervous system and in the periphery) and microglia (at spinal and supraspinal level) are involved in this control, through a close functional relationship between them and neurons (either centrally, spinal, or peripherally located). Accordingly, neuroinflammation becomes a worsening factor in many disorders whenever the non-neuronal cell supervision is inadequate. It has been shown that the regulation of non-neuronal cells—and therefore the control of neuroinflammation—depends on the local “on demand” synthesis of the endogenous lipid amide Palmitoylethanolamide and related endocannabinoids. When the balance between synthesis and degradation of this bioactive lipid mediator is disrupted in favor of reduced synthesis and/or increased degradation, the behavior of non-neuronal cells may not be appropriately regulated and neuroinflammation exceeds the physiological boundaries. In these conditions, it has been demonstrated that the increase of endogenous Palmitoylethanolamide—either by decreasing its degradation or exogenous administration—is able to keep neuroinflammation within its physiological limits. In this review the large number of studies on the benefits derived from oral administration of micronized and highly bioavailable forms of Palmitoylethanolamide is discussed, with special reference to neuroinflammatory disorders.

Downregulation of long noncoding RNA DLEU1 attenuates hypersensitivity in chronic constriction injury-induced neuropathic pain in rats by targeting miR-133a-3p/SRPK1 axis

Background

Neuropathic pain belongs to chronic pain and is caused by the primary dysfunction of the somatosensory nervous system. Long noncoding RNAs (lncRNAs) have been reported to regulate neuronal functions and play significant roles in neuropathic pain. DLEU1 has been indicated to have close relationship with neuropathic pain. Therefore, our study focused on the significant role of DLEU1 in neuropathic pain rat models.

Methods

We first constructed a chronic constrictive injury (CCI) rat model. Paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) were employed to evaluate hypersensitivity in neuropathic pain. RT-qPCR was performed to analyze the expression of target genes. Enzyme-linked immunosorbent assay (ELISA) was conducted to detect the concentrations of interleukin‐6 (IL-6), tumor necrosis factor‐α (TNF-α) and IL-1β. The underlying mechanisms of DLEU1 were investigated using western blot and luciferase reporter assays.

Results

Our findings showed that DLEU1 was upregulated in CCI rats. DLEU1 knockdown reduced the concentrations of IL‐6, IL‐1β and TNF‐α in CCI rats, suggesting that neuroinflammation was inhibited by DLEU1 knockdown. Besides, knockdown of DLEU1 inhibited neuropathic pain behaviors. Moreover, it was confirmed that DLEU1 bound with miR-133a-3p and negatively regulated its expression. SRPK1 was the downstream target of miR-133a-3p. DLEU1 competitively bound with miR-133a-3p to upregulate SRPK1. Finally, rescue assays revealed that SRPK1 overexpression rescued the suppressive effects of silenced DLEU1 on hypersensitivity in neuropathic pain and inflammation of spinal cord in CCI rats.

Conclusion

DLEU1 regulated inflammation of the spinal cord and mediated hypersensitivity in neuropathic pain in CCI rats by binding with miR-133a-3p to upregulate SRPK1 expression.

Correlation between IL-31 and sCD40L plasma levels in Fingolimod-treated patients with Relapsing-Remitting Multiple Sclerosis (RRMS)

INTRODUCTION

Multiple Sclerosis (MS) is a chronic, autoimmune, demyelinating disease of the central nervous system (CNS). Currently, several protocols are described for the different phases of MS. In this longitudinal study, we aim to quantify the concentration of plasma cytokines of MS patients treated with Fingolimod alone or after Glatiramer Acetate (GA) or Interferon-beta (IFN-β), in order to compeer both treatments and describes if it is possible to use them as biomarkers.

OBJECTIVE

Compare the two different types of drug treatment and describes possible immune biomarkers in RRMS patients treated with Fingolimod alone or after GA or IFN-β.

MATERIALS AND METHODS

This is a controlled, non-randomized clinical trial. Plasma concentrations of IL-31, sCD40L and nine others cytokines were evaluated in two groups of patients with a one-year follow-up. Group 1 (n = 12): RRMS patients treated with GA or IFN-β for at least six months before the study who changed therapy to Fingolimod after six months, and Group 2 (n = 12): naïve RRMS patients who started treatment with Fingolimod. We used ANOVA two-way to analyze the cytokines and Spearman coefficient to evaluate the correlation.

RESULTS

Although Group 2 started with a greater number of relapses per disease duration, Fingolimod treatment was effective in decreasing this parameter, as well as EDSS over 12 months. However, the treatment with GA or IFN-β on Group 1 showed a tendency to increase the number of relapses after 6 months of follow-up, which decrease when the therapy was changed to Fingolimod. After the evaluation of 11 cytokines in one year, we found that IL-31 and sCD40L were the biomarkers that demonstrated a more difference when compared to the classical ones, following the clinical pattern over the treatment period.

CONCLUSIONS

Our study describes the existence of two promising plasmatic biomarkers (IL-31 and sCD40L), which reduced plasmatic levels in RRMS patients followed the treatment time of Fingolimod, despite that more studies are needed to prove their efficiency.

DTI-identified microstructural changes in the gray matter of mice overexpressing CRF in the forebrain

Increased corticotroping releasing factor (CRF) contributes to brain circuit abnormalities associated with stress-related disorders including posttraumatic stress disorder. However, the causal relationship between CRF hypersignaling and circuit abnormalities associated with stress disorders is unclear. We hypothesized that increased CRF exposure induces changes in limbic circuit morphology and functions. An inducible, forebrain-specific overexpression of CRF (CRFOE) transgenic mouse line was used to longitudinally investigate its chronic effects on behaviors and microstructural integrity of several brain regions. Behavioral and diffusion tensor imaging studies were performed before treatment, after 3-4 wks of treatment, and again 3 mo after treatment ended to assess recovery. CRFOE was associated with increased perseverative movements only after 3 wks of treatment, as well as reduced fractional anisotropy at 3 wks in the medial prefrontal cortex and increased fractional anisotropy in the ventral hippocampus at 3 mo compared to the control group. In the dorsal hippocampus, mean diffusivity was lower in CRFOE mice both during and after treatment ended. Our data suggest differential response and recovery patterns of cortical and hippocampal subregions in response to CRFOE. Overall these findings support a causal relationship between CRF hypersignaling and microstructural changes in brain regions relevant to stress disorders.

Irisin Gene Delivery Ameliorates Burn-Induced Sensory and Motor Neuropathy

Burn-related neuropathy is common and often involves pain, paresthesia, or muscle weakness. Irisin, an exercise-induced myokine after cleavage from its membrane precursor fibronectin type III domain-containing 5 (FNDC5), exhibits neuroprotective and anti-inflammatory activities. A rat model of third-degree burn on the right hind paw was used to investigate the therapeutic role of irisin/FNDC5. Rats received burn injury and were treated with intrathecal recombinant adenovirus containing the irisin sequence (Ad-irisin) at 3 weeks postburn. One week later, mechanical allodynia was examined. The expression of irisin in cerebrospinal fluid (CSF) was detected. Ipsilateral gastrocnemius muscle and lumbar spinal cord were also obtained for further investigation. Furthermore, the anti-apoptotic effect of recombinant irisin in SH-SY5Y cells was evaluated through tumor necrosis factor alpha (TNFα) stimulus to mimic burn injury. We noted intrathecal Ad-irisin attenuated pain sensitization and gastrocnemius muscle atrophy by modulating the level of irisin in CSF, and the expression of neuronal FNDC5/irisin and TNFα in the spinal cord. Ad-irisin also ameliorated neuronal apoptosis in both dorsal and ventral horns. Furthermore, recombinant irisin attenuated TNFα-induced SH-SY5Y cell apoptosis. In summary, irisin attenuated allodynia and muscle wasting by ameliorating neuroinflammation-induced neuronal apoptosis.

Mast Cell Deficiency Protects Mice from Surgery-Induced Neuroinflammation

Neuroinflammation plays a key role in the occurrence and development of neurodegenerative diseases. Microglia, the resident immune cells in the brain, have been recognized to contribute to neuroinflammation. Previous studies have shown that activated mast cells may be involved in surgery-induced neuroinflammation and neuronal apoptosis by using pharmacological methods. This study is aimed at ascertaining the exactly role of mast cells on neuroinflammation with the mast cell-deficient mice. Adult male C57BL6/J wild-type (WT) and mast cell-deficient (C57BL6/J KitWsh/Wsh (Wsh)) mice underwent tibial fracture surgery. Blood-brain barrier (BBB) breakdown, microglial activation, and neuroinflammatory levels were examined at 1 day after surgery. Surgery-induced BBB breakdown, microglial activation, and neuroinflammatory levels were significantly, pharmacologically reduced using a mast cell stabilizer, cromolyn sodium in WT mice (P < 0.05). These results were reproduced with mast cell deficiency. WT mice administered intraventricularly with cromolyn exhibited reduced BBB breakdown, microglial activation, and neuroinflammatory levels versus vehicle (P < 0.05). But there was no effect of cromolyn versus vehicle in Wsh mice, clarifying the specificity of cromolyn on brain mast cells. These findings demonstrated that activated mast cells promote surgery-induced BBB breakdown and neuroinflammation in mice, and open up a new therapeutic target for neuroinflammation-related diseases.

COVID-19, Mast Cells, Cytokine Storm, Psychological Stress, and Neuroinflammation

Coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a new pandemic infectious disease that originated in China. COVID-19 is a global public health emergency of international concern. COVID-19 causes mild to severe illness with high morbidity and mortality, especially in preexisting risk groups. Therapeutic options are now limited to COVID-19. The hallmark of COVID-19 pathogenesis is the cytokine storm with elevated levels of interleukin-6 (IL-6), IL-1β, tumor necrosis factor-alpha (TNF-α), chemokine (C-C-motif) ligand 2 (CCL2), and granulocyte-macrophage colony-stimulating factor (GM-CSF). COVID-19 can cause severe pneumonia, and neurological disorders, including stroke, the damage to the neurovascular unit, blood-brain barrier disruption, high intracranial proinflammatory cytokines, and endothelial cell damage in the brain. Mast cells are innate immune cells and also implicated in adaptive immune response, systemic inflammatory diseases, neuroinflammatory diseases, traumatic brain injury and stroke, and stress disorders. SARS-CoV-2 can activate monocytes/macrophages, dendritic cells, T cells, mast cells, neutrophils, and induce cytokine storm in the lung. COVID-19 can activate mast cells, neurons, glial cells, and endothelial cells. SARS-CoV-2 infection can cause psychological stress and neuroinflammation. In conclusion, COVID-19 can induce mast cell activation, psychological stress, cytokine storm, and neuroinflammation.