Role of astroglial toll-like receptors (TLRs) in central nervous system infections, injury and neurodegenerative diseases

Interleukin 1β receptor and synaptic dysfunction in recurrent brain infection with Herpes simplex virus type-1

Several experimental evidence suggests a link between brain Herpes simplex virus type-1 infection and the occurrence of Alzheimer's disease. However, the molecular mechanisms underlying this association are not completely understood. Among the molecular mediators of synaptic and cognitive dysfunction occurring after Herpes simplex virus type-1 infection and reactivation in the brain neuroinflammatory cytokines seem to occupy a central role. Here, we specifically reviewed literature reports dealing with the impact of neuroinflammation on synaptic dysfunction observed after recurrent Herpes simplex virus type-1 reactivation in the brain, highlighting the role of interleukins and, in particular, interleukin 1β as a possible target against Herpes simplex virus type-1-induced neuronal dysfunctions.

A current review on P2X7 receptor antagonist patents in the treatment of neuroinflammatory disorders: a patent review on antagonists

Chronic inflammation is defined by an activated microglial state linked to all neurological disorders, including Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis (a motor neuron disease that affects the brain and spinal cord). P2X7 receptors (P2X7R) are ATP-activated ion-gated channels present on microglial surfaces. Prolonged ATP release under pathological settings results in sustained P2X7R activation, which leads to inflammasome development and cytokine release. P2X7R and its enabling roles have recently been linked to neurodegenerative diseases, making it a potential research subject. This research provides an overview of current patents for chemicals, biologics, and medicinal applications. The World Intellectual Property Organization (WIPO), European Patent Office (EPO, Espacenet), and the United States Patent and Trademark Office (USPTO) databases were searched for patents using the keywords "P2X7R and Neuroinflammation." During the study period from 2015 to 2021, 103 patents were examined. The countries that protected these innovations were the United States, PCT (Patent Cooperation Treaty states), Europe, Canada, Australia, and India. Janssen Pharmaceutica NV had the most applications, followed by Acetelion Pharmaceuticals LTD., Renovis Inc., Kelly Michael G, Kincaid Jhon, Merck Patent GMBH, H Lundbeck A/S, and many more. The P2X7R is a possible diagnostic and therapeutic target for cancer, pain disorders, and inflammation. For P2X7 R, several compounds have been discovered and are presently the subject of clinical trial investigations. This study featured patents for P2X7R antagonists, which help treat conditions including neuroinflammation.

Research on drug treatment and the novel signaling pathway of chronic atrophic gastritis

BACKGROUND

Chronic atrophic gastritis (CAG) is a global digestive system disease and one of the important causes of gastric cancer. The incidence of CAG has been increasing yearly worldwide.

PURPOSE

This article reviews the latest research on the common causes and future therapeutic targets of CAG as well as the pharmacological effects of corresponding clinical drugs. We provide a detailed theoretical basis for further research on possible methods for the treatment of CAG and reversal of the CAG process.

RESULTS

CAG often develops from chronic gastritis, and its main pathological manifestation is atrophy of the gastric mucosa, which can develop into gastric cancer. The drug treatment of CAG can be divided into agents that regulate gastric acid secretion, eradicate Helicobacter. pylori (H. pylori), protect gastric mucous membrane, or inhibit inflammatory factors according to their mechanism of action. Although there are limited specific drugs for the treatment of CAG, progress is being made in defining the pathogenesis and therapeutic targets of the disease. Growing evidence shows that NF-κB, PI3K/AKT, Wnt/ β-catenin, MAPK, Toll-like receptors (TLRs), Hedgehog, and VEGF signaling pathways play an important role in the development of CAG.

Nobiletin regulates intracellular Ca2+ levels via IP3R and ameliorates neuroinflammation in Aβ42-induced astrocytes

Astrocytes are the major glial cells in the human brain and provide crucial metabolic and trophic support to neurons. The amyloid-β peptide (Aβ) alter the morphological and functional properties of astrocytes and induce inflammation and calcium dysregulation, contributing to Alzheimer's disease (AD) pathology. Recent studies highlight the role of Toll-like receptor (TLR) 4/nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling in inflammation. Reactive oxygen species (ROS) generated due to Aβ, induce apoptosis in the brain cells worsening AD progression. Astrocytic cell surface receptors, such as purinergic receptors (P2Y1 and P2Y2), metabotropic glutamate receptor (mGLUR)5, α7 nicotinic acetylcholine receptor (α7nAChR), and N-methyl-d-aspartate receptors (NMDARs), have been suggested to interact with inositol trisphosphate receptor (IP3R) on the endoplasmic reticulum (ER) to induce Ca2+ movement from ER to cytoplasm, causing Ca2+ dysregulation. We found that the citrus flavonoid nobiletin (NOB) protected primary astrocytes from Aβ42-induced cytotoxicity and inhibited TLR4/NF-κB signaling in Aβ42-induced primary rat astrocytes. NOB was found to regulate Aβ42-induced ROS levels through Keap1-Nrf2 pathway. The receptors P2Y1, P2Y2, mGLUR5, α7nAChR, and NMDARs induced intracellular Ca2+ levels by activating IP3R and NOB regulated them, thereby regulating intracellular Ca2+ levels. Molecular docking analysis revealed a possible interaction between NOB and IP3R in IP3R regulation. Furthermore, RNA sequencing revealed various NOB-mediated biological signaling pathways, such as the AD-presenilin, AD-amyloid secretase, and Wnt signaling pathway, suggesting possible neuroprotective roles of NOB. To conclude, NOB is a promising therapeutic agent for AD and works by modulating AD pathology at various levels in Aβ42-induced primary rat astrocytes.

General anesthetic agents induce neurotoxicity through astrocytes

ABSTRACT

Neuroscientists have recognized the importance of astrocytes in regulating neurological function and their influence on the release of glial transmitters. Few studies, however, have focused on the effects of general anesthetic agents on neuroglia or astrocytes. Astrocytes can also be an important target of general anesthetic agents as they exert not only sedative, analgesic, and amnesic effects but also mediate general anesthetic-induced neurotoxicity and postoperative cognitive dysfunction. Here, we analyzed recent advances in understanding the mechanism of general anesthetic agents on astrocytes, and found that exposure to general anesthetic agents will destroy the morphology and proliferation of astrocytes, in addition to acting on the receptors on their surface, which not only affect Ca2+ signaling, inhibit the release of brain-derived neurotrophic factor and lactate from astrocytes, but are even involved in the regulation of the pro- and anti-inflammatory processes of astrocytes. These would obviously affect the communication between astrocytes as well as between astrocytes and neighboring neurons, other neuroglia, and vascular cells. In this review, we summarize how general anesthetic agents act on neurons via astrocytes, and explore potential mechanisms of action of general anesthetic agents on the nervous system. We hope that this review will provide a new direction for mitigating the neurotoxicity of general anesthetic agents.

Lipid-polymer hybrid nanoparticles loaded with N-acetylcysteine for the modulation of neuroinflammatory biomarkers in human iPSC-derived PSEN2 (N141I) astrocytes as a model of Alzheimer's disease

Alzheimer's disease (AD) is a progressive neurodegenerative disease characterized by cognitive impairment associated with the accumulation of beta-amyloid protein (Aβ). Aβ activates glial cells in the brain, increasing the secretion of proinflammatory cytokines, which leads to neuroinflammation and neuronal death. Currently, there are no effective treatments that cure or stop its progression; therefore, AD is considered a global health priority. The main limitations are the low drug bioavailability and impermeability of the blood-brain barrier (BBB). Fortunately, nanomedicine has emerged as a promising field for the development of new nanosystems for the controlled and targeted delivery of drugs to the brain. Therefore, in this work, lipid-polymer hybrid nanoparticles (LPHNPs) conjugated with transferrin (Tf) to facilitate crossing the BBB and loaded with N-acetylcysteine (NAC) for its anti-inflammatory effect were synthesized, and their physicochemical characterization was carried out. Subsequently, an in vitro model involving human astrocytes derived from induced pluripotent stem cells (iPSC) from an AD-diagnosed patient was developed, which was brought to a reactive state by stimulation with lipopolysaccharides (LPSs). The cell culture was treated with either Tf-conjugated LPHNPs loaded with NAC (NAC-Tf-LPHNPs) at 0.25 mg mL-1, or free NAC at 5 mM. The results showed that NAC-Tf-LPHNPs favorably modulated the expression of proinflammatory genes such as interleukin-1β (IL-1β), amyloid precursor protein (APP) and glial fibrillary acidic protein (GFAP). In addition, they reduced the secretion of the proinflammatory cytokines interleukin 6 (IL-6), IL-1β and interferon-gamma (INF-γ). Results for both cases were compared to the group of cells that did not receive any treatment. In contrast, free NAC only had this effect on the expression of IL-1β and the secretion of the cytokines IL-6 and INF-γ. These results indicate the potential of NAC-Tf-LPHNPs for AD treatment.

Innovative pathological network-based multitarget approaches for Alzheimer's disease treatment

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease and is a major health threat globally. Its prevalence is forecasted to exponentially increase during the next 30 years due to the global aging population. Currently, approved drugs are merely symptomatic, being ineffective in delaying or blocking the relentless disease advance. Intensive AD research describes this disease as a highly complex multifactorial disease. Disclosure of novel pathological pathways and their interconnections has had a major impact on medicinal chemistry drug development for AD over the last two decades. The complex network of pathological events involved in the onset of the disease has prompted the development of multitarget drugs. These chemical entities combine pharmacological activities toward two or more drug targets of interest. These multitarget-directed ligands are proposed to modify different nodes in the pathological network aiming to delay or even stop disease progression. Here, we review the multitarget drug development strategy for AD during the last decade.

An overview of current advances in perinatal alcohol exposure and pathogenesis of fetal alcohol spectrum disorders

The adverse use of alcohol is a serious global public health problem. Maternal alcohol consumption during pregnancy usually causes prenatal alcohol exposure (PAE) in the developing fetus, leading to a spectrum of disorders known as fetal alcohol spectrum disorders (FASD) and even fetal alcohol syndrome (FAS) throughout the lifelong sufferers. The prevalence of FASD is approximately 7.7 per 1,000 worldwide, and is even higher in developed regions. Generally, Ethanol in alcoholic beverages can impair embryonic neurological development through multiple pathways leading to FASD. Among them, the leading mechanism of FASDs is attributed to ethanol-induced neuroinflammatory damage to the central nervous system (CNS). Although the underlying molecular mechanisms remain unclear, the remaining multiple pathological mechanisms is likely due to the neurotoxic damage of ethanol and the resultant neuronal loss. Regardless of the molecular pathway, the ultimate outcome of the developing CNS exposed to ethanol is almost always the destruction and apoptosis of neurons, which leads to the reduction of neurons and further the development of FASD. In this review, we systematically summarize the current research progress on the pathogenesis of FASD, which hopefully provides new insights into differential early diagnosis, treatment and prevention for patents with FASD.

Association between genetic variants of TLR2, TLR4, TLR9 and schizophrenia

BACKGROUND AND STUDY AIM

Schizophrenia (SZ) is a multifactorial disorder involving complex interactions between genetic and environmental factors, where immune dysfunction plays a key etiopathogenic role. In order to explore the control of innate immune responses in SZ, we aimed to investigate the potential association between twelve TLR2, TLR4 and TLR9 variants (TLR2: rs4696480T>A, rs3804099T>C, rs3804100T>C; TLR4: rs1927914G>A, rs10759932T>C, rs4986790A>G, rs4986791T>C, rs11536889G>C, rs11536891T>C; TLR9: rs187084A>G, rs352139T>C and rs352140C>T) and SZ susceptibility in a Tunisian population.

PATIENTS AND METHODS

This study included 150 patients and 201 healthy controls with no history of psychiatric illness. Genotyping was done using a TaqMan SNP genotyping assay. We also assessed a haplotype analysis for TLR2, TLR4 and TLR9 variants with SZ using Haploview 4.2 Software.

RESULTS

We found that the AA genotype of the TLR2 rs4696480T>A variant was significantly associated with an increased risk of SZ (46% vs. 31%, P=4.7×10-3, OR=1.87 and 95% CI [1.18-2.97]). The frequency of the TA genotype was significantly higher in the control group than in SZ patients (27% vs. 43%, P=2.1×10-3) and may be associated with protection against SZ (OR=0.49 and 95% CI [0.30-0.80]). Whereas, the TLR9 rs187084-GG genotype was higher in the control group compared to patients (16% vs. 5%, P=1.6×10-3) and would present protection against SZ (OR=0.28, CI=[0.10-0.68]). The ACT haplotype of the TLR2 and the ACC haplotype of the TLR9 gene were identified as a risk haplotypes for SZ (P=0.04, OR=9.30, 95% CI=[1.11-77.71]; P=3×10-4, OR=6.05, 95% CI=[2.29-15.98], respectively).

CONCLUSION

The results indicate that TLR2 and TLR9 genetic diversity may play a role in genetic vulnerability to SZ. However, including more patients and evaluation of TLR2 and TLR9 expression are recommended.

Paraventricular thalamus-insular cortex circuit mediates colorectal visceral pain induced by neonatal colonic inflammation in mice

AIMS

Irritable bowel syndrome (IBS) is a common functional gastrointestinal disorder, but its pathogenesis remains incompletely understood, particularly the involvements of central nervous system sensitization in colorectal visceral pain. Our study was to investigate whether the paraventricular thalamus (PVT) projected to the insular cortex (IC) to regulate colorectal visceral pain in neonatal colonic inflammation (NCI) mice and underlying mechanisms.

METHODS

We applied optogenetic, chemogenetic, or pharmacological approaches to manipulate the glutamatergicPVT-IC pathway. Fiber photometry was used to assess neuronal activity. Electromyography activities in response to colorectal distension (CRD) were measured to evaluate the colorectal visceral pain.

RESULTS

NCI enhanced c-Fos expression and calcium activity upon CRD in the ICGlu, and optogenetic manipulation of them altered colorectal visceral pain responses accordingly. Viral tracing indicated that the PVTGlu projected to the ICGlu. Optogenetic manipulation of PVTGlu changed colorectal visceral pain responses. Furthermore, selective optogenetic modulation of PVT projections in the IC influenced colorectal visceral pain, which was reversed by chemogenetic manipulation of downstream ICGlu.

CONCLUSIONS

This study identified a novel PVT-IC neural circuit playing a critical role in colorectal visceral pain in a mouse model of IBS.

Autophagy in Neuroinflammation: A Focus on Epigenetic Regulation

Neuroinflammation, characterized by the secretion of abundant inflammatory mediators, pro-inflammatory polarization of microglia, and the recruitment of infiltrating myeloid cells to foci of inflammation, drives or exacerbates the pathological processes of central nervous system disorders, especially in neurodegenerative diseases. Autophagy plays an essential role in neuroinflammatory processes, and the underlaying physiological mechanisms are closely correlated with neuroinflammation-related signals. Inhibition of mTOR and activation of AMPK and FOXO1 enhance autophagy and thereby suppress NLRP3 inflammasome activity and apoptosis, leading to the relief of neuroinflammatory response. And autophagy mitigates neuroinflammation mainly manifested by promoting the polarization of microglia from a pro-inflammatory to an anti-inflammatory state, reducing the production of pro-inflammatory mediators, and up-regulating the levels of anti-inflammatory factors. Notably, epigenetic modifications are intimately associated with autophagy and the onset and progression of various brain diseases. Non-coding RNAs, including microRNAs, circular RNAs and long noncoding RNAs, and histone acetylation have been reported to adjust autophagy-related gene and protein expression to alleviate inflammation in neurological diseases. The present review primarily focuses on the role and mechanisms of autophagy in neuroinflammatory responses, as well as epigenetic modifications of autophagy in neuroinflammation to reveal potential therapeutic targets in central nervous system diseases.

S100A9 aggravates early brain injury after subarachnoid hemorrhage via inducing neuroinflammation and inflammasome activation

Subarachnoid hemorrhage (SAH) is a stroke subtype with high mortality, and its severity is closely related to the short-term prognosis of SAH patients. S100 calcium-binding protein A9 (S100A9) has been shown to be associated with some neurological diseases. In this study, the concentration of S100A9 in clinical cerebrospinal fluid samples was detected by enzyme-linked immunosorbent assay (ELISA), and the relationship between S100A9 and the prognosis of patients was explored. In addition, WT mice and S100A9 knockout mice were used to establish an in vivo SAH model. Neurological scores, brain water content, and histopathological staining were performed after a specified time. A co-culture model of BV2 and HT22 cells was treated with heme chloride to establish an in vitro SAH model. Our study confirmed that the expression of S100A9 protein in the CSF of SAH patients is increased, and it is related to the short-term prognosis of SAH patients. S100A9 protein is highly expressed in microglia in the central nervous system. S100A9 gene knockout significantly improved neurological function scores and reduced neuronal apoptosis. S100A9 protein can activate TLR4 receptor, promote nuclear transcription of NF-κB, increase the activation of inflammatory body, and ultimately aggravate nerve injury.

Nicotinic Acetylcholine Receptors in Glial Cells as Molecular Target for Parkinson's Disease

Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by resting tremor, bradykinesia, rigidity, and postural instability that also includes non-motor symptoms such as mood dysregulation. Dopamine (DA) is the primary neurotransmitter involved in this disease, but cholinergic imbalance has also been implicated. Current intervention in PD is focused on replenishing central DA, which provides remarkable temporary symptomatic relief but does not address neuronal loss and the progression of the disease. It has been well established that neuronal nicotinic cholinergic receptors (nAChRs) can regulate DA release and that nicotine itself may have neuroprotective effects. Recent studies identified nAChRs in nonneuronal cell types, including glial cells, where they may regulate inflammatory responses. Given the crucial role of neuroinflammation in dopaminergic degeneration and the involvement of microglia and astrocytes in this response, glial nAChRs may provide a novel therapeutic target in the prevention and/or treatment of PD. In this review, following a brief discussion of PD, we focus on the role of glial cells and, specifically, their nAChRs in PD pathology and/or treatment.

The two synthetic cannabinoid compounds 4'-F-CBD and HU-910 efficiently restrain inflammatory responses of brain microglia and astrocytes

To study the anti-inflammatory potential of the two synthetic cannabinoids 4'-F-CBD and HU-910, we used post-natal brain cultures of mouse microglial cells and astrocytes activated by reference inflammogens. We found that 4'-F-CBD and HU-910 efficiently curtailed the release of TNF-α, IL-6, and IL-1β in microglia and astrocytes activated by the bacterial Toll-Like Receptor (TLR)4 ligand LPS. Upon LPS challenge, 4'-F-CBD and HU-910 also prevented the activation of phenotypic activation markers specific to microglia and astrocytes, that is, Iba-1 and GFAP, respectively. In microglial cells, the two test compounds also efficiently restrained LPS-stimulated release of glutamate, a non-cytokine inflammation marker for these cells. The immunosuppressive effects of the two cannabinoid compounds were concentration-dependent and observable between 1 and 10 μM. These effects were not dependent on cannabinoid or cannabinoid-like receptors. Both 4'-F-CBD and HU-910 were also capable of restraining the inflammogenic activity of Pam3CSK4, a lipopeptide that activates TLR2, and of BzATP, a prototypic agonist of P2X7 purinergic receptors, suggesting that these two cannabinoids could exert immunosuppressive effects against a variety of inflammatory stimuli. Using LPS-stimulated microglia and astrocytes, we established that the immunosuppressive action of 4'-F-CBD and HU-910 resulted from the inhibition of ROS produced by NADPH oxidase and subsequent repression of NF-κB-dependent signaling events. Our results suggest that 4'-F-CBD and HU-910 may have therapeutic utility in pathological conditions where neuroinflammatory processes are prominent.

Dual-directional regulation of spinal cord injury and the gut microbiota

There is increasing evidence that the gut microbiota affects the incidence and progression of central nervous system diseases via the brain-gut axis. The spinal cord is a vital important part of the central nervous system; however, the underlying association between spinal cord injury and gut interactions remains unknown. Recent studies suggest that patients with spinal cord injury frequently experience intestinal dysfunction and gut dysbiosis. Alterations in the gut microbiota can cause disruption in the intestinal barrier and trigger neurogenic inflammatory responses which may impede recovery after spinal cord injury. This review summarizes existing clinical and basic research on the relationship between the gut microbiota and spinal cord injury. Our research identified three key points. First, the gut microbiota in patients with spinal cord injury presents a key characteristic and gut dysbiosis may profoundly influence multiple organs and systems in patients with spinal cord injury. Second, following spinal cord injury, weakened intestinal peristalsis, prolonged intestinal transport time, and immune dysfunction of the intestine caused by abnormal autonomic nerve function, as well as frequent antibiotic treatment, may induce gut dysbiosis. Third, the gut microbiota and associated metabolites may act on central neurons and affect recovery after spinal cord injury; cytokines and the Toll-like receptor ligand pathways have been identified as crucial mechanisms in the communication between the gut microbiota and central nervous system. Fecal microbiota transplantation, probiotics, dietary interventions, and other therapies have been shown to serve a neuroprotective role in spinal cord injury by modulating the gut microbiota. Therapies targeting the gut microbiota or associated metabolites are a promising approach to promote functional recovery and improve the complications of spinal cord injury.

The Emerging Role of Toll-Like Receptor-Mediated Neuroinflammatory Signals in Psychiatric Disorders and Acquired Epilepsy

The new and evolving paradigms of psychiatric disorders pathogenesis are deeply inclined toward chronic inflammation that leads to disturbances in the neuronal networks of patients. A strong association has been established between the inflammation and neurobiology of depression which is mediated by different toll-like receptors (TLRs). TLRs and associated signalling pathways are identified as key immune regulators to stress and infections in neurobiology. They are a special class of transmembrane proteins, which are one of the broadly studied members of the Pattern Recognition Patterns family. This review focuses on summarizing the important findings on the role of TLRs associated with psychotic disorders and acquired epilepsy. This review also shows the promising potential of TLRs in immune response mediated through antidepressant therapies and TLRs polymorphism associated with various psychotic disorders. Moreover, this also sheds light on future directions to further target TLRs as a therapeutic approach for psychiatric disorders.

Tlr4 Deletion Modulates Cytokine and Extracellular Matrix Expression in Chronic Spinal Cord Injury, Leading to Improved Secondary Damage and Functional Recovery

Toll-like receptors (TLRs) play an important role in the innate immune response after CNS injury. Although TLR4 is one of the best characterized, its role in chronic stages after spinal cord injury (SCI) is not well understood. We examined the role of TLR4 signaling in injury-induced responses at 1 d, 7 d, and 8 weeks after spinal cord contusion injury in adult female TLR4 null and wild-type mice. Analyses include secondary damage, a range of transcriptome and protein analyses of inflammatory, cell death, and extracellular matrix (ECM) molecules, as well as immune cell infiltration and changes in axonal sprouting and locomotor recovery. Lack of TLR4 signaling results in reduced neuronal and myelin loss, reduced activation of NFκB, and decreased expression of inflammatory cytokines and necroptotic cell death pathway at a late time point (8 weeks) after injury. TLR4 null mice also showed reduction of scar-related ECM molecules at 8 weeks after SCI, accompanied by increase in ECM molecules associated with perineuronal nets, increased sprouting of serotonergic fibers, and improved locomotor recovery. These findings reveal novel effects of TLR4 signaling in chronic SCI. We show that TLR4 influences inflammation, cell death, and ECM deposition at late-stage post-injury when secondary injury processes are normally considered to be over. This highlights the potential for late-stage targeting of TLR4 as a potential therapy for chronic SCI.

Progress of plant polyphenol extracts in treating depression by anti-neuroinflammatory mechanism: A review

There is a growing body of evidence supporting the involvement of central nervous system inflammation in the pathophysiology of depression. Polyphenols are a diverse group of compounds known for their antioxidative and anti-inflammatory properties. They offer a promising and effective supplementary approach to alleviating neuropsychiatric symptoms associated with inflammation-induced depression. This paper provides a summary of the potential anti-neuroinflammatory mechanisms of plant polyphenol extracts against depression. This includes direct interference with inflammatory regulators and inhibition of the expression of pro-inflammatory cytokines. Additionally, it covers downregulating the expression of pro-inflammatory cytokines by altering protein kinases or affecting the activity of the signaling pathways that they activate. These pathways interfere with the conduction of signaling molecules, resulting in the destruction and reduced synthesis of all inflammatory mediators and cytokines. This reduces the apoptosis of neurons and plays a neuroprotective role. This paper provides a theoretical basis for the clinical application of plant polyphenols.

Regulation of Inflammation by IRAK-M Pathway Can Be Associated with nAchRalpha7 Activation and COVID-19

In spite of the vaccine development and its importance, the SARS-CoV-2 pandemic is still impacting the world. It is known that the COVID-19 severity is related to the cytokine storm phenomenon, being inflammation a common disease feature. The nicotinic cholinergic system has been widely associated with COVID-19 since it plays a protective role in inflammation via nicotinic receptor alpha 7 (nAchRalpha7). In addition, SARS-CoV-2 spike protein (Spro) subunits can interact with nAchRalpha7. Moreover, Spro causes toll-like receptor (TLR) activation, leading to pro- and anti-inflammatory pathways. The increase and maturation of the IL-1 receptor-associated kinase (IRAK) family are mediated by activation of membrane receptors, such as TLRs. IRAK-M, a member of this family, is responsible for negatively regulating the activity of other active IRAKs. In addition, IRAK-M can regulate microglia phenotype by specific protein expression. Furthermore, there exists an antagonist influence of SARS-CoV-2 Spro and the cholinergic system action on the IRAK-M pathway and microglia phenotype. We discuss the overexpression and suppression of IRAK-M in inflammatory cell response to inflammation in SARS-CoV-2 infection when the cholinergic system is constantly activated via nAchRalpha7.

AIM2 inflammasome: A potential therapeutic target in ischemic stroke

Ischemic stroke (IS) is a significant global public health issue with a high incidence, disability, and mortality rate. A robust inflammatory cascade with complex and wide-ranging mechanisms occurs following ischemic brain injury. Inflammasomes are multiprotein complexes in the cytoplasm that modulate the inflammatory response by releasing pro-inflammatory cytokines and inducing cellular pyroptosis. Among these inflammasomes, the Absent in Melanoma 2 (AIM2) inflammasome shows the ability to detect a wide range of pathogen DNAs, thereby triggering an inflammatory response. Recent studies have indicated that the aberrant expression of AIM2 inflammasome in various cells is closely associated with the pathological processes of ischemic brain injury. This paper summarizes the expression and regulatory role of AIM2 in CNS and peripheral immune cells and discusses current therapeutic approaches targeting AIM2 inflammasome. These findings aim to serve as a reference for future research in this field.

Neuroinflammaging: A Tight Line Between Normal Aging and Age-Related Neurodegenerative Disorders

Aging in the healthy brain is characterized by a low-grade, chronic, and sterile inflammatory process known as neuroinflammaging. This condition, mainly consisting in an up-regulation of the inflammatory response at the brain level, contributes to the pathogenesis of age-related neurodegenerative disorders. Development of this proinflammatory state involves the interaction between genetic and environmental factors, able to induce age-related epigenetic modifications. Indeed, the exposure to environmental compounds, drugs, and infections, can contribute to epigenetic modifications of DNA methylome, histone fold proteins, and nucleosome positioning, leading to epigenetic modulation of neuroinflammatory responses. Furthermore, some epigenetic modifiers, which combine and interact during the life course, can contribute to modeling of epigenome dynamics to sustain, or dampen the neuroinflammatory phenotype. The aim of this review is to summarize current knowledge about neuroinflammaging with a particular focus on epigenetic mechanisms underlying the onset and progression of neuroinflammatory cascades in the central nervous system; furthermore, we describe some diagnostic biomarkers that may contribute to increase diagnostic accuracy and help tailor therapeutic strategies in patients with neurodegenerative diseases.

The immune system and metabolic products in epilepsy and glioma-associated epilepsy: emerging therapeutic directions

Epilepsy has a profound impact on quality of life. Despite the development of new antiseizure medications (ASMs), approximately one-third of affected patients have drug-refractory epilepsy and are nonresponsive to medical treatment. Nearly all currently approved ASMs target neuronal activity through ion channel modulation. Recent human and animal model studies have implicated new immunotherapeutic and metabolomic approaches that may benefit patients with epilepsy. In this Review, we detail the proinflammatory immune landscape of epilepsy and contrast this with the immunosuppressive microenvironment in patients with glioma-related epilepsy. In the tumor setting, excessive neuronal activity facilitates immunosuppression, thereby contributing to subsequent glioma progression. Metabolic modulation of the IDH1-mutant pathway provides a dual pathway for reversing immune suppression and dampening seizure activity. Elucidating the relationship between neurons and immunoreactivity is an area for the prioritization and development of the next era of ASMs.

Assessment of the relationship between the dopaminergic pathway and severe acute respiratory syndrome coronavirus 2 infection, with related neuropathological features, and potential therapeutic approaches in COVID-19 infection

Dopamine is a known catecholamine neurotransmitter involved in several physiological processes, including motor control, motivation, reward, cognition, and immune function. Dopamine receptors are widely distributed throughout the nervous system and in immune cells. Several viruses, including human immunodeficiency virus and Japanese encephalitis virus, can use dopaminergic receptors to replicate in the nervous system and are involved in viral neuropathogenesis. In addition, studies suggest that dopaminergic receptors may play a role in the progression and pathogenesis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. When SARS-CoV-2 binds to angiotensin-converting enzyme 2 receptors on the surface of neuronal cells, the spike protein of the virus can bind to dopaminergic receptors on neighbouring cells to accelerate its life cycle and exacerbate neurological symptoms. In addition, recent research has shown that dopamine is an important regulator of the immune-neuroendocrine system. Most immune cells express dopamine receptors and other dopamine-related proteins, indicating the importance of dopaminergic immune regulation. The increase in dopamine concentration during SARS-CoV2 infection may reduce immunity (innate and adaptive) that promotes viral spread, which could lead to neuronal damage. In addition, dopaminergic signalling in the nervous system may be affected by SARS-CoV-2 infection. COVID -19 can cause various neurological symptoms as it interacts with the immune system. One possible treatment strategy for COVID -19 patients could be the use of dopamine antagonists. To fully understand how to protect the neurological system and immune cells from the virus, we need to study the pathophysiology of the dopamine system in SARS-CoV-2 infection.

Immune Homeostasis: A Novel Example of Teamwork

All living organisms must maintain homeostasis to survive, reproduce, and pass their traits on to the next generation. If homeostasis is not maintained, it can result in various diseases and ultimately lead to death. Physiologists have coined the term "homeostasis" to describe this process. With the emergence of immunology as a separate branch of medicine, the concept of immune homeostasis has been introduced. Maintaining immune homeostasis is crucial to support overall homeostasis through different immunological and non-immunological routes. Any changes in the immune system can lead to chronic inflammatory or autoimmune diseases, immunodeficiency diseases, frequent infections, and cancers. Ongoing scientific advances are exploring new avenues in immunology and immune homeostasis maintenance. This chapter introduces the concept of immune homeostasis and its maintenance through different mechanisms.

Comparison of Neuroinflammation Induced by Hyperphosphorylated Tau Protein Versus Ab42 in Alzheimer's Disease

Both neurofibrillary tangles and senile plaques are associated with inflammation in Alzheimer's disease (AD). Their relative degree of induced neuroinflammation, however, is not well established. Mouse models of AD that expressed either human Aβ42 (n = 7) or human hyperphosphorylated tau protein alone (n = 3), wild type (n = 10), and human AD samples (n = 29 with 18 controls) were studied. The benefit of using mouse models that possess only human tau or amyloid-b is that it allows for the individual evaluation of how each protein affects neuroinflammation, something not possible in human tissue. Three indicators of neuroinflammation were examined: TLRs/RIG1 expression, the density of astrocytes and microglial cells, and well-established mediators of neuroinflammation (IL6, TNFα, IL1β, and CXCL10). There was a statistically significant increase in neuroinflammation with all three variables in the mouse models with human tau only as compared to human Aβ42 only or wild-type mice (each at p < 0.0001). Only the Aβ42 5xFAD mice (n = 4) showed statistically higher neuroinflammation versus wild type (p = 0.0030). The human AD tissues were segregated into Aβ42 only or hyperphosphorylated tau protein with Aβ42. The latter areas showed increased neuroinflammation with each of the three variables compared to the areas with only Aβ42. Of the TLRs and RIG-1, TLR8 was significantly elevated in both the mouse model and human AD and only in areas with the abnormal tau protein. It is concluded that although Aβ42 and hyperphosphorylated tau protein can each induce inflammation, the latter protein is associated with a much stronger neuroinflammatory response vis-a-vis a significantly greater activated microglial response.

Compound Dihuang Granule Changes Gut Microbiota of MPTP-Induced Parkinson's Disease Mice via Inhibiting TLR4/NF-κB Signaling

Intestinal microbiota was connected to Parkinson's Disease (PD) pathology. The ancient Chinese medication for PD is Compound Dihuang Granule (CDG), and we found a neuroprotective function in treating the constipation of PD patients. Nevertheless, the mechanism of action still needs to be clarified. We predicted the probable targets of CDG against PD through Traditional Chinese medicine (TCM) network pharmacology and verified the analysis through animal experiments in vivo. The protein-protein interaction (PPI) network analysis screened PD-related genes, including Toll-like receptor 4(TLR4), TANK-binding kinase 1(TBK1), Nuclear Factor- Kappa B (NF-κB), and Tumor necrosis factor (TNF). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses proved that the NF-κB and toll-like receptor signaling pathways serve a key function in CDG therapy of PD. Molecular docking analysis demonstrated that CDG strongly connected to TLR4/NF-κB. Experiments findings indicated that CDG improved the damage of dopaminergic neurons and gut microbial dysbiosis, ameliorated motor impairments, and suppressed the PD-associated inflammation and oxidative stress in mice induced by 1-methyl-4-phenyl-1,2,3,6-tetrahy dropyridine (MPTP). CDG suppressed the inflammatory proteins in the colon and protected the intestinal barrier. Overall, CDG improved gut microbial in PD by blocking the pathway of TLR4/NF-κB.

Cell Intrinsic Determinants of Alpha Herpesvirus Latency and Pathogenesis in the Nervous System

Alpha herpesvirus infections (α-HVs) are widespread, affecting more than 70% of the adult human population. Typically, the infections start in the mucosal epithelia, from which the viral particles invade the axons of the peripheral nervous system. In the nuclei of the peripheral ganglia, α-HVs establish a lifelong latency and eventually undergo multiple reactivation cycles. Upon reactivation, viral progeny can move into the nerves, back out toward the periphery where they entered the organism, or they can move toward the central nervous system (CNS). This latency-reactivation cycle is remarkably well controlled by the intricate actions of the intrinsic and innate immune responses of the host, and finely counteracted by the viral proteins in an effort to co-exist in the population. If this yin-yang- or Nash-equilibrium-like balance state is broken due to immune suppression or genetic mutations in the host response factors particularly in the CNS, or the presence of other pathogenic stimuli, α-HV reactivations might lead to life-threatening pathologies. In this review, we will summarize the molecular virus-host interactions starting from mucosal epithelia infections leading to the establishment of latency in the PNS and to possible CNS invasion by α-HVs, highlighting the pathologies associated with uncontrolled virus replication in the NS.

The Neuroimmune System and the Cerebellum

The recognition that there is an innate immune system of the brain, referred to as the neuroimmune system, that preforms many functions comparable to that of the peripheral immune system is a relatively new concept and much is yet to be learned. The main cellular components of the neuroimmune system are the glial cells of the brain, primarily microglia and astrocytes. These cell types preform many functions through secretion of signaling factors initially known as immune factors but referred to as neuroimmune factors when produced by cells of the brain. The immune functions of glial cells play critical roles in the healthy brain to maintain homeostasis that is essential for normal brain function, to establish cytoarchitecture of the brain during development, and, in pathological conditions, to minimize the detrimental effects of disease and injury and promote repair of brain structure and function. However, dysregulation of this system can occur resulting in actions that exacerbate or perpetuate the detrimental effects of disease or injury. The neuroimmune system extends throughout all brain regions, but attention to the cerebellar system has lagged that of other brain regions and information is limited on this topic. This article is meant to provide a brief introduction to the cellular and molecular components of the brain immune system, its functions, and what is known about its role in the cerebellum. The majority of this information comes from studies of animal models and pathological conditions, where upregulation of the system facilitates investigation of its actions.

Mesenchymal Stem Cell Transplantation: Neuroprotection and Nerve Regeneration After Spinal Cord Injury

Spinal Cord Injury (SCI), with its morbidity characteristics of high disability rate and high mortality rate, is a disease that is highly destructive to both the physiology and psychology of the patient, and for which there is still a lack of effective treatment. Following spinal cord injury, a cascade of secondary injury reactions known as ischemia, peripheral inflammatory cell infiltration, oxidative stress, etc. create a microenvironment that is unfavorable to neural recovery and ultimately results in apoptosis and necrosis of neurons and glial cells. Mesenchymal stem cell (MSC) transplantation has emerged as a more promising therapeutic options in recent years. MSC can promote spinal cord injury repair through a variety of mechanisms, including immunomodulation, neuroprotection, and nerve regeneration, giving patients with spinal cord injury hope. In this paper, it is discussed the neuroprotection and nerve regeneration components of MSCs' therapeutic method for treating spinal cord injuries.

The NLRP3 Inflammasome in Neurodegenerative Disorders: Insights from Epileptic Models

Neuroinflammation represents a dynamic process of defense and protection against the harmful action of infectious agents or other detrimental stimuli in the central nervous system (CNS). However, the uncontrolled regulation of this physiological process is strongly associated with serious dysfunctional neuronal issues linked to the progression of CNS disorders. Moreover, it has been widely demonstrated that neuroinflammation is linked to epilepsy, one of the most prevalent and serious brain disorders worldwide. Indeed, NLRP3, one of the most well-studied inflammasomes, is involved in the generation of epileptic seizures, events that characterize this pathological condition. In this context, several pieces of evidence have shown that the NLRP3 inflammasome plays a central role in the pathophysiology of mesial temporal lobe epilepsy (mTLE). Based on an extensive review of the literature on the role of NLRP3-dependent inflammation in epilepsy, in this review we discuss our current understanding of the connection between NLRP3 inflammasome activation and progressive neurodegeneration in epilepsy. The goal of the review is to cover as many of the various known epilepsy models as possible, providing a broad overview of the current literature. Lastly, we also propose some of the present therapeutic strategies targeting NLRP3, aiming to provide potential insights for future studies.

Astrocytes in human central nervous system diseases: a frontier for new therapies

Astroglia are a broad class of neural parenchymal cells primarily dedicated to homoeostasis and defence of the central nervous system (CNS). Astroglia contribute to the pathophysiology of all neurological and neuropsychiatric disorders in ways that can be either beneficial or detrimental to disorder outcome. Pathophysiological changes in astroglia can be primary or secondary and can result in gain or loss of functions. Astroglia respond to external, non-cell autonomous signals associated with any form of CNS pathology by undergoing complex and variable changes in their structure, molecular expression, and function. In addition, internally driven, cell autonomous changes of astroglial innate properties can lead to CNS pathologies. Astroglial pathophysiology is complex, with different pathophysiological cell states and cell phenotypes that are context-specific and vary with disorder, disorder-stage, comorbidities, age, and sex. Here, we classify astroglial pathophysiology into (i) reactive astrogliosis, (ii) astroglial atrophy with loss of function, (iii) astroglial degeneration and death, and (iv) astrocytopathies characterised by aberrant forms that drive disease. We review astroglial pathophysiology across the spectrum of human CNS diseases and disorders, including neurotrauma, stroke, neuroinfection, autoimmune attack and epilepsy, as well as neurodevelopmental, neurodegenerative, metabolic and neuropsychiatric disorders. Characterising cellular and molecular mechanisms of astroglial pathophysiology represents a new frontier to identify novel therapeutic strategies.

Impact of Microbiome-Brain Communication on Neuroinflammation and Neurodegeneration

The gut microbiome plays a pivotal role in maintaining human health, with numerous studies demonstrating that alterations in microbial compositions can significantly affect the development and progression of various immune-mediated diseases affecting both the digestive tract and the central nervous system (CNS). This complex interplay between the microbiota, the gut, and the CNS is referred to as the gut-brain axis. The role of the gut microbiota in the pathogenesis of neurodegenerative diseases has gained increasing attention in recent years, and evidence suggests that gut dysbiosis may contribute to disease development and progression. Clinical studies have shown alterations in the composition of the gut microbiota in multiple sclerosis patients, with a decrease in beneficial bacteria and an increase in pro-inflammatory bacteria. Furthermore, changes within the microbial community have been linked to the pathogenesis of Parkinson's disease and Alzheimer's disease. Microbiota-gut-brain communication can impact neurodegenerative diseases through various mechanisms, including the regulation of immune function, the production of microbial metabolites, as well as modulation of host-derived soluble factors. This review describes the current literature on the gut-brain axis and highlights novel communication systems that allow cross-talk between the gut microbiota and the host that might influence the pathogenesis of neuroinflammation and neurodegeneration.

Potential role of Schwann cells in neuropathic pain

Neuropathic pain (NPP) is a common syndrome associated with most forms of disease, which poses a serious threat to human health. NPP may persist even after the nociceptive stimulation is eliminated, and treatment is extremely challenging in such cases. Schwann cells (SCs) form the myelin sheaths around neuronal axons and play a crucial role in neural information transmission. SCs can secrete trophic factors to nourish and protect axons, and can further secrete pain-related factors to induce pain. SCs may be activated by peripheral nerve injury, triggering the transformation of myelinated and non-myelinated SCs into cell phenotypes that specifically promote repair. These differentiated SCs provide necessary signals and spatial clues for survival, axonal regeneration, and nerve regeneration of damaged neurons. They can further change the microenvironment around the regions of nerve injury, and relieve the pain by repairing the injured nerve. Herein, we provide a comprehensive overview of the biological characteristics of SCs, discuss the relationship between SCs and nerve injury, and explore the potential mechanism of SCs and the occurrence of NPP. Moreover, we summarize the feasible strategies of SCs in the treatment of NPP, and attempt to elucidate the deficiencies and defects of SCs in the treatment of NPP.

Interleukin-1 Receptor Antagonist as Therapy for Traumatic Brain Injury

Traumatic brain injury is a common type of acquired brain injury of varying severity carrying potentially deleterious consequences for the afflicted individuals, families, and society. Following the initial, traumatically induced insult, cellular injury processes ensue. These are believed to be amenable to treatment. Among such injuries, neuroinflammation has gained interest and has become a specific focus for both experimental and clinical researchers. Neuroinflammation is elicited almost immediately following trauma, and extend for a long time, possibly for years, after the primary injury. In the acute phase, the inflammatory response is characterized by innate mechanisms such as the activation of microglia which among else mediates cytokine production. Among the earliest cytokines to emerge are the interleukin- (IL-) 1 family members, comprising, for example, the agonist IL-1β and its competitive antagonist, IL-1 receptor antagonist (IL-1ra). Because of its early emergence following trauma and its increased concentrations also after human TBI, IL-1 has been hypothesized to be a tractable treatment target following TBI. Ample experimental data supports this, and demonstrates restored neurological behavior, diminished lesion zones, and an attenuated inflammatory response following IL-1 modulation either through IL-1 knock-out experiments, IL-1β inhibition, or IL-1ra treatment. Of these, IL-1ra treatment is likely the most physiological. In addition, recombinant human IL-1ra (anakinra) is already approved for utilization across a few rheumatologic disorders. As of today, one randomized clinical controlled trial has utilized IL-1ra inhibition as an intervention and demonstrated its safety. Further clinical trials powered for patient outcome are needed in order to demonstrate efficacy. In this review, we summarize IL-1 biology in relation to acute neuroinflammatory processes following TBI with a particular focus on current evidence for IL-1ra treatment both in the experimental and clinical context.

Dysregulation of inflammasome activation in glioma

Gliomas are the most common brain tumors characterized by complicated heterogeneity. The genetic, molecular, and histological pathology of gliomas is characterized by high neuro-inflammation. The inflammatory microenvironment in the central nervous system (CNS) has been closely linked with inflammasomes that control the inflammatory response and coordinate innate host defenses. Dysregulation of the inflammasome causes an abnormal inflammatory response, leading to carcinogenesis in glioma. Because of the clinical importance of the various physiological properties of the inflammasome in glioma, the inflammasome has been suggested as a promising treatment target for glioma management. Here, we summarize the current knowledge on the contribution of the inflammasomes in glioma and therapeutic insights. Video Abstract.

Dietary Polyphenols Decrease Chemokine Release by Human Primary Astrocytes Responding to Pro-Inflammatory Cytokines

Astrocytes are considered to be the dominant cell fraction of the central nervous system. They play a supportive and protective role towards neurons, and regulate inflammatory processes; they thus make suitable targets for drugs and supplements, such as polyphenolic compounds. However, due to their wide range, knowledge of their anti-inflammatory potential remains relatively incomplete. The aim of this study was therefore to determine whether myricetin and chrysin are able to decrease chemokine release in reactive astrocytes. To assess the antioxidant and anti-inflammatory potential of polyphenols, human primary astrocytes were cultured in the presence of a reactive and neurotoxic astrocyte-inducing cytokine mixture (TNF-α, IL-1a, C1q), either alone or in the presence of myricetin or chrysin. The examined polyphenols were able to modify the secretion of chemokines by human cortical astrocytes, especially CCL5 (chrysin), CCL1 (myricetin) and CCL2 (both), while cell viability was not affected. Surprisingly, the compounds did not demonstrate any antioxidant properties in the astrocyte cultures.

The Dysregulated MAD in Mad: A Neuro-theranostic Approach Through the Induction of Autophagic Biomarkers LC3B-II and ATG

The word mad has historically been associated with the psyche, emotions, and abnormal behavior. Dementia is a common symptom among psychiatric disorders or mad (schizophrenia, depression, bipolar disorder) patients. Autophagy/mitophagy is a protective mechanism used by cells to get rid of dysfunctional cellular organelles or mitochondria. Autophagosome/mitophagosome abundance in autophagy depends on microtubule-associated protein light chain 3B (LC3B-II) and autophagy-triggering gene (ATG) which functions as an autophagic biomarker for phagophore production and quick mRNA disintegration. Defects in either LC3B-II or the ATG lead to dysregulated mitophagy-and-autophagy-linked dementia (MAD). The impaired MAD is closely associated with schizophrenia, depression, and bipolar disorder. The pathomechanism of psychosis is not entirely known, which is the severe limitation of today's antipsychotic drugs. However, the reviewed circuit identifies new insights that may be especially helpful in targeting biomarkers of dementia. Neuro-theranostics can also be achieved by manufacturing either bioengineered bacterial and mammalian cells or nanocarriers (liposomes, polymers, and nanogels) loaded with both imaging and therapeutic materials. The nanocarriers must cross the BBB and should release both diagnostic agents and therapeutic agents in a controlled manner to prove their effectiveness against psychiatric disorders. In this review, we highlighted the potential of microRNAs (miRs) as neuro-theranostics in the treatment of dementia by targeting autophagic biomarkers LC3B-II and ATG. Focus was also placed on the potential for neuro-theranostic nanocells/nanocarriers to traverse the BBB and induce action against psychiatric disorders. The neuro-theranostic approach can provide targeted treatment for mental disorders by creating theranostic nanocarriers.

Platelet mitochondria, a potent immune mediator in neurological diseases

Dysfunction of the immune response is regarded as a prominent feature of neurological diseases, including neurodegenerative diseases, malignant tumors, acute neurotraumatic insult, and cerebral ischemic/hemorrhagic diseases. Platelets play a fundamental role in normal hemostasis and thrombosis. Beyond those normal functions, platelets are hyperactivated and contribute crucially to inflammation and immune responses in the central nervous system (CNS). Mitochondria are pivotal organelles in platelets and are responsible for generating most of the ATP that is used for platelet activation and aggregation (clumping). Notably, platelet mitochondria show marked morphological and functional alterations under heightened inflammatory/oxidative stimulation. Mitochondrial dysfunction not only leads to platelet damage and apoptosis but also further aggravates immune responses. Improving mitochondrial function is hopefully an effective strategy for treating neurological diseases. In this review, the authors discuss the immunomodulatory roles of platelet-derived mitochondria (PLT-mitos) in neurological diseases and summarize the neuroprotective effects of platelet mitochondria transplantation.

Crosstalk of Highly Purified Microglia and Astrocytes in the Frame of Toll-like Receptor (TLR)2/1 Activation

The major immune cells of the central nervous systems (CNS) are microglia and astrocytes, subsets of the glial cell population. The crosstalk between glia via soluble signaling molecules plays an indispensable role for neuropathologies, brain development as well as homeostasis. However, the investigation of the microglia-astrocyte crosstalk has been hampered due to the lack of suitable glial isolation methods. In this study, we investigated for the first time the crosstalk between highly purified Toll-like receptor (TLR)2-knock out (TLR2-KO) and wild-type (WT) microglia and astrocytes. We examined the crosstalk of TLR2-KO microglia and astrocytes in the presence of WT supernatants of the respective other glial cell type. Interestingly, we observed a significant TNF release by TLR2-KO astrocytes, which were activated with Pam3CSK4-stimulated WT microglial supernatants, strongly indicating a crosstalk between microglia and astrocytes after TLR2/1 activation. Furthermore, transcriptome analysis using RNA-seq revealed a wide range of significant up- and down-regulated genes such as Cd300, Tnfrsf9 or Lcn2, which might be involved in the molecular conversation between microglia and astrocytes. Finally, co-culturing microglia and astrocytes confirmed the prior results by demonstrating a significant TNF release by WT microglia co-cultured with TLR2-KO astrocytes. Our findings suggest a molecular TLR2/1-dependent conversation between highly pure activated microglia and astrocytes via signaling molecules. Furthermore, we demonstrate the first crosstalk experiments using ∼100% pure microglia and astrocyte mono-/co-cultures derived from mice with different genotypes highlighting the urgent need of efficient glial isolation protocols, which particularly holds true for astrocytes.

Brain alarm by self-extracellular nucleic acids: from neuroinflammation to neurodegeneration

Neurological disorders such as stroke, multiple sclerosis, as well as the neurodegenerative diseases Parkinson's or Alzheimer's disease are accompanied or even powered by danger associated molecular patterns (DAMPs), defined as endogenous molecules released from stressed or damaged tissue. Besides protein-related DAMPs or "alarmins", numerous nucleic acid DAMPs exist in body fluids, such as cell-free nuclear and mitochondrial DNA as well as different species of extracellular RNA, collectively termed as self-extracellular nucleic acids (SENAs). Among these, microRNA, long non-coding RNAs, circular RNAs and extracellular ribosomal RNA constitute the majority of RNA-based DAMPs. Upon tissue injury, necrosis or apoptosis, such SENAs are released from neuronal, immune and other cells predominantly in association with extracellular vesicles and may be translocated to target cells where they can induce intracellular regulatory pathways in gene transcription and translation. The majority of SENA-induced signaling reactions in the brain appear to be related to neuroinflammatory processes, often causally associated with the onset or progression of the respective disease. In this review, the impact of the diverse types of SENAs on neuroinflammatory and neurodegenerative diseases will be discussed. Based on the accumulating knowledge in this field, several specific antagonistic approaches are presented that could serve as therapeutic interventions to lower the pathological outcome of the indicated brain disorders.

Macrophage migration inhibitory factor facilitates astrocytic production of the CCL2 chemokine following spinal cord injury

Spinal cord injury causes accumulation of a large number of leukocytes at the lesion site where they contribute to excessive inflammation. Overproduced chemokines are responsible for the migratory process of the leukocytes, but the regulatory mechanism underlying the production of chemokines from resident cells of the spinal cord has not been fully elucidated. We examined the protein levels of macrophage migration inhibitory factor and chemokine C-C motif chemokine ligand 2 in a spinal cord contusion model at different time points following spinal cord injury. The elevation of macrophage migration inhibitory factor at the lesion site coincided with the increase of chemokine C-C motif chemokine ligand 2 abundance in astrocytes. Stimulation of primary cultured astrocytes with different concentrations of macrophage migration inhibitory factor recombinant protein induced chemokine C-C motif chemokine ligand 2 production from the cells, and the macrophage migration inhibitory factor inhibitor 4-iodo-6-phenylpyrimidine attenuated the stimulatory effect. Further investigation into the underlying mechanism on macrophage migration inhibitory factor-mediated astrocytic production of chemokine C-C motif chemokine ligand 2 revealed that macrophage migration inhibitory factor activated intracellular JNK signaling through binding with CD74 receptor. Administration of the macrophage migration inhibitory factor inhibitor 4-iodo-6-phenylpyrimidine following spinal cord injury resulted in the reduction of chemokine C-C motif chemokine ligand 2-recruited microglia/macrophages at the lesion site and remarkably improved the hindlimb locomotor function of rats. Our results have provided insights into the functions of astrocyte-activated chemokines in the recruitment of leukocytes and may be beneficial to develop interventions targeting chemokine C-C motif chemokine ligand 2 for neuroinflammation after spinal cord injury.

Role of neuroinflammation in neurodegeneration development

Studies in neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease and Amyotrophic lateral sclerosis, Huntington's disease, and so on, have suggested that inflammation is not only a result of neurodegeneration but also a crucial player in this process. Protein aggregates which are very common pathological phenomenon in neurodegeneration can induce neuroinflammation which further aggravates protein aggregation and neurodegeneration. Actually, inflammation even happens earlier than protein aggregation. Neuroinflammation induced by genetic variations in CNS cells or by peripheral immune cells may induce protein deposition in some susceptible population. Numerous signaling pathways and a range of CNS cells have been suggested to be involved in the pathogenesis of neurodegeneration, although they are still far from being completely understood. Due to the limited success of traditional treatment methods, blocking or enhancing inflammatory signaling pathways involved in neurodegeneration are considered to be promising strategies for the therapy of neurodegenerative diseases, and many of them have got exciting results in animal models or clinical trials. Some of them, although very few, have been approved by FDA for clinical usage. Here we comprehensively review the factors affecting neuroinflammation and the major inflammatory signaling pathways involved in the pathogenicity of neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, and Amyotrophic lateral sclerosis. We also summarize the current strategies, both in animal models and in the clinic, for the treatment of neurodegenerative diseases.

A deep convolutional neural network for efficient microglia detection

Microglial cells are a type of glial cells that make up 10-15% of all brain cells, and they play a significant role in neurodegenerative disorders and cardiovascular diseases. Despite their vital role in these diseases, developing fully automated microglia counting methods from immunohistological images is challenging. Current image analysis methods are inefficient and lack accuracy in detecting microglia due to their morphological heterogeneity. This study presents development and validation of a fully automated and efficient microglia detection method using the YOLOv3 deep learning-based algorithm. We applied this method to analyse the number of microglia in different spinal cord and brain regions of rats exposed to opioid-induced hyperalgesia/tolerance. Our numerical tests showed that the proposed method outperforms existing computational and manual methods with high accuracy, achieving 94% precision, 91% recall, and 92% F1-score. Furthermore, our tool is freely available and adds value to exploring different disease models. Our findings demonstrate the effectiveness and efficiency of our new tool in automated microglia detection, providing a valuable asset for researchers in neuroscience.

The recent advance of Interleukin-1 receptor associated kinase 4 inhibitors for the treatment of inflammation and related diseases

The interleukin-1 receptor associated kinase 4 (IRAK-4) is a member of serine-threonine kinase family, which plays an important role in the regulation of interleukin-1 receptors (IL-1R) and Toll-like receptors (TLRs) related signaling pathways. At present, the IRAK-4 mediated inflammation and related signaling pathways contribute to inflammation, which are also responsible for other autoimmune diseases and drug resistance in cancers. Therefore, targeting IRAK-4 to develop single-target, multi-target inhibitors and proteolysis-targeting chimera (PROTAC) degraders is an important direction for the treatment of inflammation and related diseases. Moreover, insight into the mechanism of action and structural optimization of the reported IRAK-4 inhibitors will provide the new direction to enrich the clinical therapies for inflammation and related diseases. In this comprehensive review, we introduced the recent advance of IRAK-4 inhibitors and degraders with regards to structural optimization, mechanism of action and clinical application that would be helpful for the development of more potent chemical entities against IRAK-4.

Disturbance of neuron-microglia crosstalk mediated by GRP78 in Neuropsychiatric systemic lupus erythematosus mice

OBJECTIVES

Neuropsychiatric systemic lupus erythematosus (NPSLE) is a serious phenotype of systemic lupus erythematosus (SLE). The disturbance of neuron-microglia crosstalk is recently revealed in many neuropsychiatric diseases but was not well studied in NPSLE. We found glucose regulatory protein 78 (GRP78), a marker of endoplasmic reticulum stress, was significantly increased in the cerebrospinal fluid (CSF) of our NPSLE cohort. We, therefore, investigated whether GRP78 can act as a mediator between the neuron-microglia crosstalk and is involved in the pathogenic process of NPSLE.

METHODS

Serum and CSF parameters were analyzed in 22 NPSLE patients and controls. Anti-DWEYS IgG was injected intravenously into mice to establish a model of NPSLE. Behavioral assessment, histopathological staining, RNA-seq analyses, and biochemical assays were performed to examine the neuro-immunological alterations in the mice. Rapamycin was intraperitoneally administered to define the therapeutic effect.

RESULTS

The level of GRP78 was elevated significantly in the CSF of the patients with NPSLE. An increase in GRP78 expression, accompanied by neuroinflammation and cognitive impairment, was also found in the brain tissues of the NPSLE model mice induced by anti-DWEYS IgG deposition on hippocampal neurons. In vitro experiments demonstrated that anti-DWEYS IgG could stimulate neurons to release GRP78, which activated microglia via TLR4/MyD88/NFκB pathway to produce more pro-inflammatory cytokines and promote migration and phagocytosis. Rapamycin ameliorated GRP78-inducing neuroinflammation and cognitive impairment in anti-DWEYS IgG-transferred mice.

CONCLUSION

GRP78 acts as a pathogenic factor in neuropsychiatric disorders via interfering neuron-microglia crosstalk. Rapamycin may be a promising therapeutic candidate for NPSLE.

Role of astrocytes in sleep deprivation: accomplices, resisters, or bystanders?

Sleep plays an essential role in all studied animals with a nervous system. However, sleep deprivation leads to various pathological changes and neurobehavioral problems. Astrocytes are the most abundant cells in the brain and are involved in various important functions, including neurotransmitter and ion homeostasis, synaptic and neuronal modulation, and blood-brain barrier maintenance; furthermore, they are associated with numerous neurodegenerative diseases, pain, and mood disorders. Moreover, astrocytes are increasingly being recognized as vital contributors to the regulation of sleep-wake cycles, both locally and in specific neural circuits. In this review, we begin by describing the role of astrocytes in regulating sleep and circadian rhythms, focusing on: (i) neuronal activity; (ii) metabolism; (iii) the glymphatic system; (iv) neuroinflammation; and (v) astrocyte-microglia cross-talk. Moreover, we review the role of astrocytes in sleep deprivation comorbidities and sleep deprivation-related brain disorders. Finally, we discuss potential interventions targeting astrocytes to prevent or treat sleep deprivation-related brain disorders. Pursuing these questions would pave the way for a deeper understanding of the cellular and neural mechanisms underlying sleep deprivation-comorbid brain disorders.

Revisiting the neuroinflammation hypothesis in Alzheimer's disease: a focus on the druggability of current targets

Alzheimer's disease (AD) is the most common form of neurodegenerative disease and disability in the elderly; it is estimated to account for 60%-70% of all cases of dementia worldwide. The most relevant mechanistic hypothesis to explain AD symptoms is neurotoxicity induced by aggregated amyloid-β peptide (Aβ) and misfolded tau protein. These molecular entities are seemingly insufficient to explain AD as a multifactorial disease characterized by synaptic dysfunction, cognitive decline, psychotic symptoms, chronic inflammatory environment within the central nervous system (CNS), activated microglial cells, and dysfunctional gut microbiota. The discovery that AD is a neuroinflammatory disease linked to innate immunity phenomena started in the early nineties by several authors, including the ICC´s group that described, in 2004, the role IL-6 in AD-type phosphorylation of tau protein in deregulating the cdk5/p35 pathway. The "Theory of Neuroimmunomodulation", published in 2008, proposed the onset and progression of degenerative diseases as a multi-component "damage signals" phenomena, suggesting the feasibility of "multitarget" therapies in AD. This theory explains in detail the cascade of molecular events stemming from microglial disorder through the overactivation of the Cdk5/p35 pathway. All these knowledge have led to the rational search for inflammatory druggable targets against AD. The accumulated evidence on increased levels of inflammatory markers in the cerebrospinal fluid (CSF) of AD patients, along with reports describing CNS alterations caused by senescent immune cells in neuro-degenerative diseases, set out a conceptual framework in which the neuroinflammation hypothesis is being challenged from different angles towards developing new therapies against AD. The current evidence points to controversial findings in the search for therapeutic candidates to treat neuroinflammation in AD. In this article, we discuss a neuroimmune-modulatory perspective for pharmacological exploration of molecular targets against AD, as well as potential deleterious effects of modifying neuroinflammation in the brain parenchyma. We specifically focus on the role of B and T cells, immuno-senescence, the brain lymphatic system (BLS), gut-brain axis alterations, and dysfunctional interactions between neurons, microglia and astrocytes. We also outline a rational framework for identifying "druggable" targets for multi-mechanistic small molecules with therapeutic potential against AD.

The gut microbiota-astrocyte axis: Implications for type 2 diabetic cognitive dysfunction

BACKGROUND

Diabetic cognitive dysfunction (DCD) is one of the most insidious complications of type 2 diabetes mellitus, which can seriously affect the ability to self-monitoring of blood glucose and the quality of life in the elderly. Previous pathological studies of cognitive dysfunction have focused on neuronal dysfunction, characterized by extracellular beta-amyloid deposition and intracellular tau hyperphosphorylation. In recent years, astrocytes have been recognized as a potential therapeutic target for cognitive dysfunction and important participants in the central control of metabolism. The disorder of gut microbiota and their metabolites have been linked to a series of metabolic diseases such as diabetes mellitus. The imbalance of intestinal flora has the effect of promoting the occurrence and deterioration of several diabetes-related complications. Gut microbes and their metabolites can drive astrocyte activation.

AIMS

We reviewed the pathological progress of DCD related to the "gut microbiota-astrocyte" axis in terms of peripheral and central inflammation, intestinal and blood-brain barrier (BBB) dysfunction, systemic and brain energy metabolism disorders to deepen the pathological research progress of DCD and explore the potential therapeutic targets.

CONCLUSION

"Gut microbiota-astrocyte" axis, unique bidirectional crosstalk in the brain-gut axis, mediates the intermediate pathological process of neurocognitive dysfunction secondary to metabolic disorders in diabetes mellitus.

Activation of TLR7-mediated autophagy increases epileptic susceptibility via reduced KIF5A-dependent GABAA receptor transport in a murine model

The pathophysiological mechanisms underlying epileptogenesis are poorly understood but are considered to actively involve an imbalance between excitatory and inhibitory synaptic transmission. Excessive activation of autophagy, a cellular pathway that leads to the removal of proteins, is known to aggravate the disease. Toll-like receptor (TLR) 7 is an innate immune receptor that regulates autophagy in infectious and noninfectious diseases. However, the relationship between TLR7, autophagy, and synaptic transmission during epileptogenesis remains unclear. We found that TLR7 was activated in neurons in the early stage of epileptogenesis. TLR7 knockout significantly suppressed seizure susceptibility and neuronal excitability. Furthermore, activation of TLR7 induced autophagy and decreased the expression of kinesin family member 5 A (KIF5A), which influenced interactions with γ-aminobutyric acid type A receptor (GABAAR)-associated protein and GABAARβ2/3, thus producing abnormal GABAAR-mediated postsynaptic transmission. Our results indicated that TLR7 is an important factor in regulating epileptogenesis, suggesting a possible therapeutic target for epilepsy.

Synucleinopathies Take Their Toll: Are TLRs a Way to Go?

The misfolding and subsequent abnormal accumulation and aggregation of α-Synuclein (αSyn) as insoluble fibrils in Lewy bodies and Lewy neurites is the pathological hallmark of Parkinson's disease (PD) and several neurodegenerative disorders. A combination of environmental and genetic factors is linked to αSyn misfolding, among which neuroinflammation is recognized to play an important role. Indeed, a number of studies indicate that a Toll-like receptor (TLR)-mediated neuroinflammation might lead to a dopaminergic neural loss, suggesting that TLRs could participate in the pathogenesis of PD as promoters of immune/neuroinflammatory responses. Here we will summarize our current understanding on the mechanisms of αSyn aggregation and misfolding, focusing on the contribution of TLRs to the progression of α-synucleinopathies and speculating on their link with the non-motor disturbances associated with aging and neurodegenerative disorders.