Brain Injury-Mediated Neuroinflammatory Response and Alzheimer's Disease

Blast injury: Impact to the cornea

Visual disorders are common even after mild traumatic brain injury (mTBI) or blast exposure. The cost of blast-induced vision loss in civilians, military personnel, and veterans is significant. The visual consequences of blasts associated with TBI are elusive. Active military personnel and veterans report various ocular pathologies including corneal disorders post-combat blasts. The wars and conflicts in Afghanistan, Iraq, Syria, and Ukraine have significantly increased the number of corneal and other ocular disorders among military personnel and veterans. Binocular vision, visual fields, and other visual functions could be impaired following blast-mediated TBI. Blast-associated injuries can cause visual disturbances, binocular system problems, and visual loss. About 25% of veterans exposed to blasts report corneal injury. Blast exposure induces corneal edema, corneal opacity, increased corneal thickness, damage of corneal epithelium, corneal abrasions, and stromal and endothelial abnormality including altered endothelial density, immune cell infiltration, corneal neovascularization, Descemet membrane rupture, and increased pain mediators in animal models and the blast-exposed military personnel including veterans. Immune response exacerbates blast-induced ocular injury. TBI is associated with dry eyes and pain in veterans. Subjects exposed to blasts that cause TBI should undergo immediate clinical visual and ocular examinations. Delayed visual care may lead to progressive vision loss, lengthening/impairing rehabilitation and ultimately may lead to permanent vision problems and blindness. Open-field blast exposure could induce corneal injuries and immune responses in the cornea. Further studies are warranted to understand corneal pathology after blast exposure. A review of current advancements in blast-induced corneal injury will help elucidate novel targets for potential therapeutic options. This review discusses the impact of blast exposure-associated corneal disorders.

Cognitive dysfunctions in the course of SARS‑CoV‑2 virus infection, including NeuroCOVID, frontal syndrome and cytokine storm (Review)

During the coronavirus disease 2019 (COVID-19) pandemic, cognitive impairment of varying degrees of severity began to be observed in a significant percentage of patients. The present study discussed the impact of immunological processes on structural and functional changes in the central nervous system and the related cognitive disorders. The purpose of the present review was to analyse and discuss available information from the scientific literature considering the possible relationship between severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) viral infection and cognitive impairment, including NeuroCOVID, frontal syndrome and cytokine storm. A systematic literature review was conducted using: Google Scholar, Elsevier and the PubMed database. When searching for materials, the following keywords were used: 'cognitive dysfunctions', 'SARS-CoV-2', 'COVID-19', 'Neuro-SARS2', 'NeuroCOVID', 'frontal syndrome', 'cytokine storm', 'Long COVID-19'. A total of 96 articles were included in the study. The analysis focused on the characteristics of each study's materials, methods, results and conclusions. SARS-CoV-2 infection may induce or influence existing cognitive disorders of various nature and severity. The influence of immunological factors related to the response against SARS-CoV-2 on the disturbance of cerebral perfusion, the functioning of nerve cells and the neuroprotective effect has been demonstrated. Particular importance is attached to the cytokine storm and the related difference between pro- and anti-inflammatory effects, oxidative stress, disturbances in the regulation of the hypothalamic-pituitary-adrenal axis and the stress response of the body.

Alzheimer Disease-Link With Major Depressive Disorder and Efficacy of Antidepressants in Modifying its Trajectory

Alzheimer disease (AD) is a devastating neurodegenerative disorder that affects millions of individuals worldwide, with no effective cure. The main symptoms include learning and memory loss, and the inability to carry out the simplest tasks, significantly affecting patients' quality of life. Over the past few years, tremendous progress has been made in research demonstrating a link between AD and major depressive disorder (MDD). Evidence suggests that MDD is commonly associated with AD and that it can serve as a precipitating factor for this disease. Antidepressants such as selective serotonin reuptake inhibitors, which are the first line of treatment for MDD, have shown great promise in the treatment of depression in AD, although their effectiveness remains controversial. The goal of this review is to summarize current knowledge regarding the association between AD, MDD, and antidepressant treatment. It first provides an overview of the interaction between AD and MDD at the level of genes, brain regions, neurotransmitter systems, and neuroinflammatory markers. The review then presents current evidence regarding the effectiveness of various antidepressants for AD-related pathophysiology and then finally discusses current limitations, challenges, and future directions.

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.

Recent Research Trends in Neuroinflammatory and Neurodegenerative Disorders

Neuroinflammatory and neurodegenerative disorders including Alzheimer's disease (AD), Parkinson's disease (PD), traumatic brain injury (TBI) and Amyotrophic lateral sclerosis (ALS) are chronic major health disorders. The exact mechanism of the neuroimmune dysfunctions of these disease pathogeneses is currently not clearly understood. These disorders show dysregulated neuroimmune and inflammatory responses, including activation of neurons, glial cells, and neurovascular unit damage associated with excessive release of proinflammatory cytokines, chemokines, neurotoxic mediators, and infiltration of peripheral immune cells into the brain, as well as entry of inflammatory mediators through damaged neurovascular endothelial cells, blood-brain barrier and tight junction proteins. Activation of glial cells and immune cells leads to the release of many inflammatory and neurotoxic molecules that cause neuroinflammation and neurodegeneration. Gulf War Illness (GWI) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) are chronic disorders that are also associated with neuroimmune dysfunctions. Currently, there are no effective disease-modifying therapeutic options available for these diseases. Human induced pluripotent stem cell (iPSC)-derived neurons, astrocytes, microglia, endothelial cells and pericytes are currently used for many disease models for drug discovery. This review highlights certain recent trends in neuroinflammatory responses and iPSC-derived brain cell applications in neuroinflammatory disorders.

Interleukin-4 from curcumin-activated OECs emerges as a central modulator for increasing M2 polarization of microglia/macrophage in OEC anti-inflammatory activity for functional repair of spinal cord injury

Microglia/macrophages are major contributors to neuroinflammation in the central nervous system (CNS) injury and exhibit either pro- or anti-inflammatory phenotypes in response to specific microenvironmental signals. Our latest in vivo and in vitro studies demonstrated that curcumin-treated olfactory ensheathing cells (aOECs) can effectively enhance neural survival and axonal outgrowth, and transplantation of aOECs improves the neurological outcome after spinal cord injury (SCI). The therapeutic effect is largely attributed to aOEC anti-inflammatory activity through the modulation of microglial polarization from the M1 to M2 phenotype. However, very little is known about what viable molecules from aOECs are actively responsible for the switch of M1 to M2 microglial phenotypes and the underlying mechanisms of microglial polarization. Herein, we show that Interleukin-4 (IL-4) plays a leading role in triggering the M1 to M2 microglial phenotype, appreciably decreasing the levels of M1 markers IL‑1β, IL‑6, tumour necrosis factor-alpha (TNF-α) and inducible nitric oxide synthase (iNOS) and elevating the levels of M2 markers Arg-1, TGF-β, IL-10, and CD206. Strikingly, blockade of IL-4 signaling by siRNA and a neutralizing antibody in aOEC medium reverses the transition of M1 to M2, and the activated microglia stimulated with the aOEC medium lacking IL-4 significantly decreases neuronal survival and neurite outgrowth. In addition, transplantation of aOECs improved the neurological function deficits after SCI in rats. More importantly, the crosstalk between JAK1/STAT1/3/6-targeted downstream signals and NF-κB/SOCS1/3 signaling predominantly orchestrates IL-4-modulated microglial polarization event. These results provide new insights into the molecular mechanisms of aOECs driving the M1-to-M2 shift of microglia and shed light on new therapies for SCI through the modulation of microglial polarization.

Traumatic Brain Injury in Mice Generates Early-Stage Alzheimer's Disease Related Protein Pathology that Correlates with Neurobehavioral Deficits

Traumatic brain injury (TBI) increases the long-term risk of neurodegenerative diseases, including Alzheimer's disease (AD). Here, we demonstrate that protein variant pathology generated in brain tissue of an experimental TBI mouse model is similar to protein variant pathology observed during early stages of AD, and that subacute accumulation of AD associated variants of amyloid beta (Aβ) and tau in the TBI mouse model correlated with behavioral deficits. Male C57BL/6 mice were subjected to midline fluid percussion injury or to sham injury, after which sensorimotor function (rotarod, neurological severity score), cognitive deficit (novel object recognition), and affective deficits (elevated plus maze, forced swim task) were assessed post-injury (DPI). Protein pathology at 7, 14, and 28 DPI was measured in multiple brain regions using an immunostain panel of reagents selectively targeting different neurodegenerative disease-related variants of Aβ, tau, TDP-43, and alpha-synuclein. Overall, TBI resulted in sensorimotor deficits and accumulation of AD-related protein variant pathology near the impact site, both of which returned to sham levels by 14 DPI. Individual mice, however, showed persistent behavioral deficits and/or accumulation of toxic protein variants at 28 DPI. Behavioral outcomes of each mouse were correlated with levels of seven different protein variants in ten brain regions at specific DPI. Out of 21 significant correlations between protein variant levels and behavioral deficits, 18 were with variants of Aβ or tau. Correlations at 28 DPI were all between a single Aβ or tau variant, both of which are strongly associated with human AD cases. These data provide a direct mechanistic link between protein pathology resulting from TBI and the hallmarks of AD.

The Role of Insulin-like Growth Factor I in Mechanisms of Resilience and Vulnerability to Sporadic Alzheimer's Disease

Despite decades of intense research, disease-modifying therapeutic approaches for Alzheimer's disease (AD) are still very much needed. Apart from the extensively analyzed tau and amyloid pathological cascades, two promising avenues of research that may eventually identify new druggable targets for AD are based on a better understanding of the mechanisms of resilience and vulnerability to this condition. We argue that insulin-like growth factor I (IGF-I) activity in the brain provides a common substrate for the mechanisms of resilience and vulnerability to AD. We postulate that preserved brain IGF-I activity contributes to resilience to AD pathology as this growth factor intervenes in all the major pathological cascades considered to be involved in AD, including metabolic impairment, altered proteostasis, and inflammation, to name the three that are considered to be the most important ones. Conversely, disturbed IGF-I activity is found in many AD risk factors, such as old age, type 2 diabetes, imbalanced diet, sedentary life, sociality, stroke, stress, and low education, whereas the Apolipoprotein (Apo) E4 genotype and traumatic brain injury may also be influenced by brain IGF-I activity. Accordingly, IGF-I activity should be taken into consideration when analyzing these processes, while its preservation will predictably help prevent the progress of AD pathology. Thus, we need to define IGF-I activity in all these conditions and develop a means to preserve it. However, defining brain IGF-I activity cannot be solely based on humoral or tissue levels of this neurotrophic factor, and new functionally based assessments need to be developed.

Building a pathway to recovery: Targeting ECM remodeling in CNS injuries

Extracellular matrix (ECM) is a complex and dynamic network of proteoglycans, proteins, and other macromolecules that surrounds cells in tissues. The ECM provides structural support to cells and plays a critical role in regulating various cellular functions. ECM remodeling is a dynamic process involving the breakdown and reconstruction of the ECM. This process occurs naturally during tissue growth, wound healing, and tissue repair. However, in the context of central nervous system (CNS) injuries, dysregulated ECM remodeling can lead to the formation of fibrotic and glial scars. CNS injuries encompass various traumatic events, including concussions and fractures. Following CNS trauma, the formation of glial and fibrotic scars becomes prominent. Glial scars primarily consist of reactive astrocytes, while fibrotic scars are characterized by an abundance of ECM proteins. ECM remodeling plays a pivotal and tightly regulated role in the development of these scars after spinal cord and brain injuries. Various factors like ECM components, ECM remodeling enzymes, cell surface receptors of ECM molecules, and downstream pathways of ECM molecules are responsible for the remodeling of the ECM. The aim of this review article is to explore the changes in ECM during normal physiological conditions and following CNS injuries. Additionally, we discuss various approaches that target various factors responsible for ECM remodeling, with a focus on promoting axon regeneration and functional recovery after CNS injuries. By targeting ECM remodeling, it may be possible to enhance axonal regeneration and facilitate functional recovery after CNS injuries.

IL-33/ST2 Axis: A Potential Therapeutic Target in Neurodegenerative Diseases

Interleukin 33 (IL-33) belongs to the IL-1 family and is localized in the nucleus. IL-33 is primarily composed of three distinct domains, namely the N-terminal domain responsible for nuclear localization, the intermediate sense protease domain, and the C-terminal cytokine domain. Its specific receptor is the suppression of tumorigenicity 2 (ST2), which is detected in serum-stimulated fibroblasts and oncogenes. While most other cytokines are actively produced in cells, IL-33 is passively produced in response to tissue damage or cell necrosis, thereby suggesting its role as an alarm following cell infection, stress, or trauma. IL-33 plays a crucial role in congenital and acquired immunity, which assists in the response to environmental stress and maintains tissue homeostasis. IL-33/ST2 interaction further produces many pro-inflammatory cytokines. Moreover, IL-33 is crucial for central nervous system (CNS) homeostasis and the pathogenic mechanisms underlying CNS degenerative disorders. The present work summarizes the structure of IL-33, its fundamental activities, and its role in immunoregulation and neurodegenerative diseases. Therefore, this work proposes that IL-33 may play a role in the pathogenic mechanism of diseases and can be used in the development of treatment strategies.

COVID-19 and Long COVID: Disruption of the Neurovascular Unit, Blood-Brain Barrier, and Tight Junctions

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of coronavirus disease 2019 (COVID-19), could affect brain structure and function. SARS-CoV-2 can enter the brain through different routes, including the olfactory, trigeminal, and vagus nerves, and through blood and immunocytes. SARS-CoV-2 may also enter the brain from the peripheral blood through a disrupted blood-brain barrier (BBB). The neurovascular unit in the brain, composed of neurons, astrocytes, endothelial cells, and pericytes, protects brain parenchyma by regulating the entry of substances from the blood. The endothelial cells, pericytes, and astrocytes highly express angiotensin converting enzyme 2 (ACE2), indicating that the BBB can be disturbed by SARS-CoV-2 and lead to derangements of tight junction and adherens junction proteins. This leads to increased BBB permeability, leakage of blood components, and movement of immune cells into the brain parenchyma. SARS-CoV-2 may also cross microvascular endothelial cells through an ACE2 receptor-associated pathway. The exact mechanism of BBB dysregulation in COVID-19/neuro-COVID is not clearly known, nor is the development of long COVID. Various blood biomarkers could indicate disease severity and neurologic complications in COVID-19 and help objectively diagnose those developing long COVID. This review highlights the importance of neurovascular and BBB disruption, as well as some potentially useful biomarkers in COVID-19, and long COVID/neuro-COVID.

Blood-brain-barrier modeling with tissue chips for research applications in space and on Earth

Tissue chip technology has revolutionized biomedical applications and the medical science field for the past few decades. Currently, tissue chips are one of the most powerful research tools aiding in in vitro work to accurately predict the outcome of studies when compared to monolayer two-dimensional (2D) cell cultures. While 2D cell cultures held prominence for a long time, their lack of biomimicry has resulted in a transition to 3D cell cultures, including tissue chips technology, to overcome the discrepancies often seen in in vitro studies. Due to their wide range of applications, different organ systems have been studied over the years, one of which is the blood brain barrier (BBB) which is discussed in this review. The BBB is an incredible protective unit of the body, keeping out pathogens from entering the brain through vasculature. However, there are some microbes and certain diseases that disrupt the function of this barrier which can lead to detrimental outcomes. Over the past few years, various designs of the BBB have been proposed and modeled to study drug delivery and disease modeling on Earth. More recently, researchers have started to utilize tissue chips in space to study the effects of microgravity on human health. BBB tissue chips in space can be a tool to understand function mechanisms and therapeutics. This review addresses the limitations of monolayer cell culture which could be overcome with utilizing tissue chips technology. Current BBB models on Earth and how they are fabricated as well as what influences the BBB cell culture in tissue chips are discussed. Then, this article reviews how application of these technologies together with incorporating biosensors in space would be beneficial to help in predicting a more accurate physiological response in specific tissue or organ chips. Finally, the current platforms used in space and some solutions to overcome some shortcomings for future BBB tissue chip research are also discussed.

Exploring the Therapeutic Effects of Multifunctional N-Salicylic Acid Tryptamine Derivative against Parkinson's Disease

Parkinson's disease (PD) is the second most common neurodegenerative disease worldwide. Neuroinflammation and oxidative stress play an important role in the whole course of PD, which have been the focus of PD drug development. In our previous research, a series of N-salicylic acid tryptamine derivatives were synthesized, and the biological evaluation showed that the compound LZWL02003 has good anti-neuroinflammatory activity and displayed great therapeutic potency for neurodegenerative disease models. In this work, the neuroprotective efficiency of LZWL02003 against PD in vitro and in vivo has been explored. It was found that LZWL02003 could protect human neuron cells SH-SY5Y from MPP+-induced neuronal damage by inhibiting ROS generation, mitochondrial dysfunction, and cellular apoptosis. Moreover, LZWL02003 could improve cognition, memory, learning, and athletic ability in a rotenone-induced PD rat model. In general, our study has demonstrated that LZWL02003 has good activity against PD in in vitro and in vivo experiments, which can potentially be developed into a therapeutic candidate for PD.

Cellulose ether treatment inhibits amyloid beta aggregation, neuroinflammation and cognitive deficits in transgenic mouse model of Alzheimer's disease

Alzheimer's disease (AD) is an incurable, progressive and devastating neurodegenerative disease. Pathogenesis of AD is associated with the aggregation and accumulation of amyloid beta (Aβ), a major neurotoxic mediator that triggers neuroinflammation and memory impairment. Recently, we found that cellulose ether compounds (CEs) have beneficial effects against prion diseases by inhibiting protein misfolding and replication of prions, which share their replication mechanism with Aβ. CEs are FDA-approved safe additives in foods and pharmaceuticals. Herein, for the first time we determined the therapeutic effects of the representative CE (TC-5RW) in AD using in vitro and in vivo models. Our in vitro studies showed that TC-5RW inhibits Aβ aggregation, as well as neurotoxicity and immunoreactivity in Aβ-exposed human and murine neuroblastoma cells. In in vivo studies, for the first time we observed that single and weekly TC-5RW administration, respectively, improved memory functions of transgenic 5XFAD mouse model of AD. We further demonstrate that TC-5RW treatment of 5XFAD mice significantly inhibited Aβ oligomer and plaque burden and its associated neuroinflammation via regulating astrogliosis, microgliosis and proinflammatory mediator glial maturation factor beta (GMFβ). Additionally, we determined that TC-5RW reduced lipopolysaccharide-induced activated gliosis and GMFβ in vitro. In conclusion, our results demonstrate that CEs have therapeutic effects against Aβ pathologies and cognitive impairments, and direct, potent anti-inflammatory activity to rescue neuroinflammation. Therefore, these FDA-approved compounds are effective candidates for developing therapeutics for AD and related neurodegenerative diseases associated with protein misfolding.

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.

Traumatic brain injury in mice generates early-stage Alzheimer's disease related protein pathology that correlates with neurobehavioral deficits

Traumatic brain injury (TBI) increases the long-term risk of neurodegenerative diseases, including Alzheimer's disease (AD). Here, we demonstrate that protein variant pathology generated in brain tissue of an experimental TBI mouse model is similar to protein variant pathology observed in human ADbrains, and that subacute accumulation of two AD associated variants of amyloid beta (Aβ) and tau in the TBI mouse model correlated with behavioral deficits. Male C57BL/6 mice were subjected to midline fluid percussion injury or to sham injury, after which sensorimotor function (rotarod, neurological severity score), cognitive deficit (novel object recognition), and affective deficits (elevated plus maze, forced swim task) were assessed at different days post-injury (DPI). Protein pathology at 7, 14, and 28 DPI was measured in multiple brain regions using an immunostain panel of reagents selectively targeting different neurodegenerative disease-related variants of Aβ, tau, TDP-43, and alpha-synuclein. Overall, TBI resulted in sensorimotor deficits and accumulation of AD-related protein variant pathology near the impact site, both of which returned to sham levels by 14 DPI. Individual mice, however, showed persistent behavioral deficits and/or accumulation of selected toxic protein variants at 28 DPI. Behavioral outcomes of each mouse were correlated with levels of seven different protein variants in ten brain regions at specific DPI. Out of 21 significant correlations between protein variant levels and behavioral deficits, 18 were with variants of Aβ or tau. Correlations at 28 DPI were all between a single Aβ or tau variant, both of which are strongly associated with human AD cases. These data provide a direct mechanistic link between protein pathology resulting from TBI and the hallmarks of AD.

Antidiabetic Drugs Can Reduce the Harmful Impact of Chronic Smoking on Post-Traumatic Brain Injuries

Traumatic Brain Injury (TBI) is a primary cause of cerebrovascular and neurological disorders worldwide. The current scientific researchers believe that premorbid conditions such as tobacco smoking (TS) can exacerbate post-TBI brain injury and negatively affect recovery. This is related to vascular endothelial dysfunction resulting from the exposure to TS-released reactive oxygen species (ROS), nicotine, and oxidative stress (OS) stimuli impacting the blood-brain barrier (BBB) endothelium. Interestingly, these pathogenic modulators of BBB impairment are similar to those associated with hyperglycemia. Antidiabetic drugs such as metformin (MF) and rosiglitazone (RSG) were shown to prevent/reduce BBB damage promoted by chronic TS exposure. Thus, using in vivo approaches, we evaluated the effectiveness of post-TBI treatment with MF or RSG to reduce the TS-enhancement of BBB damage and brain injury after TBI. For this purpose, we employed an in vivo weight-drop TBI model using male C57BL/6J mice chronically exposed to TS with and without post-traumatic treatment with MF or RSG. Our results revealed that these antidiabetic drugs counteracted TS-promoted downregulation of nuclear factor erythroid 2-related factor 2 (NRF2) expression and concomitantly dampened TS-enhanced OS, inflammation, and loss of BBB integrity following TBI. In conclusion, our findings suggest that MF and RSG could reduce the harmful impact of chronic smoking on post-traumatic brain injuries.

Mast cell activation mediates blood-brain barrier impairment and cognitive dysfunction in septic mice in a histamine-dependent pathway

Introduction

Sepsis-associated encephalopathy (SAE) is a diffuse cerebral dysfunction resulting from a systemic inflammatory response to infection; however, its pathophysiology remains unclear. Sepsis-induced neuroinflammation and blood-brain barrier (BBB) disruption are crucial factors in brain function disturbance in SAE. Mast cells (MCs) activation plays an important role in several neuroinflammation models; however, its role in SAE has not been comprehensively investigated.

Methods

We first established a SAE model by cecal ligation puncture (CLP) surgery and checked the activation of MCs. MCs activation was checked using immumohistochemical staining and Toluidine Blue staining. We administrated cromolyn (10mg/ml), a MC stabilizer, to rescue the septic mice. Brain cytokines levels were measured using biochemical assays. BBB disruption was assessed by measuring levels of key tight-junction (TJ) proteins. Cognitive function of mice was analyzed by Y maze and open field test. Transwell cultures of brain microvascular endothelial cells (BMVECs) co-cultured with MCs were used to assess the interaction of BMVECs and MCs.

Results

Results showed that MCs were overactivated in the hippocampus of CLP-induced SAE mice. Cromolyn intracerebroventricular (i.c.v) injection substantially inhibited the MCs activation and neuroinflammation responses, ameliorated BBB impairment, improved the survival rate and alleviated cognitive dysfunction in septic mice. In vitro experiments, we revealed that MCs activation increased the sensitivity of BMVECs against to lipopolysaccharide (LPS) challenge. Furthermore, we found that the histamine/histamine 1 receptor (H1R) mediated the interaction between MCs and BMVECs, and amplifies the LPS-induced inflammatory responses in BMVECs by modulating the TLR2/4-MAPK signaling pathway.

Conclusions

MCs activation could mediate BBB impairment and cognitive dysfunction in septic mice in a histamine-dependent pathway.

Altered early immune response after fracture and traumatic brain injury

Introduction

Clinical and preclinical data suggest accelerated bone fracture healing in subjects with an additional traumatic brain injury (TBI). Mechanistically, altered metabolism and neuro-endocrine regulations have been shown to influence bone formation after combined fracture and TBI, thereby increasing the bone content in the fracture callus. However, the early inflammatory response towards fracture and TBI has not been investigated in detail so far. This is of great importance, since the early inflammatory phase of fracture healing is known to be essential for the initiation of downstream regenerative processes for adequate fracture repair.

Methods

Therefore, we analyzed systemic and local inflammatory mediators and immune cells in mice which were exposed to fracture only or fracture + TBI 6h and 24h after injury.

Results

We found a dysregulated systemic immune response and significantly fewer neutrophils and mast cells locally in the fracture hematoma. Further, local CXCL10 expression was significantly decreased in the animals with combined trauma, which correlated significantly with the reduced mast cell numbers.

Discussion

Since mast cells and mast cell-derived CXCL10 have been shown to increase osteoclastogenesis, the reduced mast cell numbers might contribute to higher bone content in the fracture callus of fracture + TBI mice due to decreased callus remodeling.

Active immunotherapy against pathogenic Cis pT231-tau suppresses neurodegeneration in traumatic brain injury mouse models

Traumatic brain injury (TBI), characterized by acute neurological impairment, is associated with a higher incidence of neurodegenerative diseases, particularly chronic traumatic encephalopathy (CTE), Alzheimer's disease (AD), and Parkinson's disease (PD), whose hallmarks include hyperphosphorylated tau protein. Recently, phosphorylated tau at Thr231 has been shown to exist in two distinct cis and trans conformations. Moreover, targeted elimination of cis P-tau by passive immunotherapy with an appropriate mAb that efficiently suppresses tau-mediated neurodegeneration in severe TBI mouse models has proven to be a useful tool to characterize the neurotoxic role of cis P-tau as an early driver of the tauopathy process after TBI. Here, we investigated whether active immunotherapy can develop sufficient neutralizing antibodies to specifically target and eliminate cis P-tau in the brain of TBI mouse models. First, we explored the therapeutic efficacy of two different vaccines. C57BL/6 J mice were immunized with either cis or trans P-tau conformational peptides plus adjuvant. After rmTBI in mice, we found that cis peptide administration developed a specific Ab that precisely targeted and neutralized cis P-tau, inhibited the development of neuropathology and brain dysfunction, and restored various structural and functional sequelae associated with TBI in chronic phases. In contrast, trans P-tau peptide application not only lacked neuroprotective properties, but also contributed to a number of neuropathological features, including progressive TBI-induced neuroinflammation, widespread tau-mediated neurodegeneration, worsening functional deficits, and brain atrophy. Taken together, our results suggest that active immunotherapy strategies against pathogenic cis P-tau can halt the process of tauopathy and would have profound clinical implications.

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 cognitive and psychiatric subacute impairment in severe Covid-19

Neurologic impairment persisting months after acute severe SARS-CoV-2 infection has been described because of several pathogenic mechanisms, including persistent systemic inflammation. The objective of this study is to analyze the selective involvement of the different cognitive domains and the existence of related biomarkers. Cross-sectional multicentric study of patients who survived severe infection with SARS-CoV-2 consecutively recruited between 90 and 120 days after hospital discharge. All patients underwent an exhaustive study of cognitive functions as well as plasma determination of pro-inflammatory, neurotrophic factors and light-chain neurofilaments. A principal component analysis extracted the main independent characteristics of the syndrome. 152 patients were recruited. The results of our study preferential involvement of episodic and working memory, executive functions, and attention and relatively less affectation of other cortical functions. In addition, anxiety and depression pictures are constant in our cohort. Several plasma chemokines concentrations were elevated compared with both, a non-SARS-Cov2 infected cohort of neurological outpatients or a control healthy general population. Severe Covid-19 patients can develop an amnesic and dysexecutive syndrome with neuropsychiatric manifestations. We do not know if the deficits detected can persist in the long term and if this can trigger or accelerate the onset of neurodegenerative diseases.

Hydrogen-rich water ameliorates neuropathological impairments in a mouse model of Alzheimer's disease through reducing neuroinflammation and modulating intestinal microbiota

Hydrogen exhibits the potential to treat Alzheimer's disease. Stereotactic injection has been previously used as an invasive method of administering active hydrogen, but this method has limitations in clinical practice. In this study, triple transgenic (3×Tg) Alzheimer's disease mice were treated with hydrogen-rich water for 7 months. The results showed that hydrogen-rich water prevented synaptic loss and neuronal death, inhibited senile plaques, and reduced hyperphosphorylated tau and neurofibrillary tangles in 3×Tg Alzheimer's disease mice. In addition, hydrogen-rich water improved brain energy metabolism disorders and intestinal flora imbalances and reduced inflammatory reactions. These findings suggest that hydrogen-rich water is an effective hydrogen donor that can treat Alzheimer's disease. This study was approved by the Animal Ethics and Welfare Committee of Shenzhen University, China (approval No. AEWC-20140615-002) on June 15, 2014.

Autophagy in Extracellular Matrix and Wound Healing Modulation in the Cornea

Autophagy is a robust cellular mechanism for disposing of harmful molecules or recycling them to cells, which also regulates physiopathological processes in cornea. Dysregulated autophagy causes inefficient clearance of unwanted proteins and cellular debris, mitochondrial disorganization, defective inflammation, organ dysfunctions, cell death, and diseases. The cornea accounts for two-thirds of the refraction of light that occurs in the eyes, but is prone to trauma/injury and infection. The extracellular matrix (ECM) is a noncellular dynamic macromolecular network in corneal tissues comprised of collagens, proteoglycans, elastin, fibronectin, laminins, hyaluronan, and glycoproteins. The ECM undergoes remodeling by matrix-degrading enzymes and maintains corneal transparency. Autophagy plays an important role in the ECM and wound healing maintenance. Delayed/dysregulated autophagy impacts the ECM and wound healing, and can lead to corneal dysfunction. Stromal wound healing involves responses from the corneal epithelium, basement membrane, keratocytes, the ECM, and many cytokines and chemokines, including transforming growth factor beta-1 and platelet-derived growth factor. Mild corneal injuries self-repair, but greater injuries lead to corneal haze/scars/fibrosis and vision loss due to disruptions in the ECM, autophagy, and normal wound healing processes. Presently, the precise role of autophagy and ECM remodeling in corneal wound healing is elusive. This review discusses recent trends in autophagy and ECM modulation in the context of corneal wound healing and homeostasis.

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.

Astrocytes in the Traumatic Brain Injury: the Good and the Bad

Astrocytes control many processes of the nervous system in health and disease, and respond to injury quickly. Astrocytes produce neuroprotective factors in the injured brain to clear cellular debris and to orchestrate neurorestorative processes that are beneficial for neurological recovery after traumatic brain injury (TBI). However, astrocytes also become dysregulated and produce cytotoxic mediators that hinder CNS repair by induction of neuronal dysfunction and cell death. Hence, we discuss the potential role of astrocytes in neuropathological processes such as neuroinflammation, neurogenesis, synaptogenesis and blood-brain barrier repair after TBI. Thus, an improved understanding of the dual role of astrocytes may advance our knowledge of post-brain injury recovery, and provide opportunities for the development of novel therapeutic strategies for TBI.

Global hippocampal and selective thalamic nuclei atrophy differentiate chronic TBI from Non-TBI

Traumatic brain injury (TBI) may increase susceptibility to neurodegenerative diseases later in life. One neurobiological parallel between chronic TBI and neurodegeneration may be accelerated aging and the nature of atrophy across subcortical gray matter structures. The main aim of the present investigation is to evaluate and rank the degree that subcortical gray matter atrophy differentiates chronic moderate-severe TBI from non-TBI participants by evaluating morphometric differences between groups. Forty individuals with moderate-severe chronic TBI (9.23 yrs from injury) and 33 healthy controls (HC) underwent high resolution 3D T1-weighted structural magnetic resonance imaging. Whole brain volume was classified into white matter, cortical and subcortical gray matter structures with hippocampi and thalami further segmented into subfields and nuclei, respectively. Extensive atrophy was observed across nearly all brain regions for chronic TBI participants. A series of multivariate logistic regression models identified subcortical gray matter structures of the hippocampus and thalamus as the most sensitive to differentiating chronic TBI from non-TBI participants (McFadden R² = .36, p < .001). Further analyses revealed the pattern of hippocampal atrophy to be global, occurring across nearly all subfields. The pattern of thalamic atrophy appeared to be much more selective and non-uniform, with largest between-group differences evident for nuclei bordering the ventricles. Subcortical gray matter was negatively correlated with time since injury (r = -.31, p = .054), while white matter and cortical gray matter were not. Cognitive ability was lower in the chronic TBI group (Cohen's d = .97, p = .003) and correlated with subcortical structures including the pallidum (r² = .23, p = .038), thalamus (r² = .36, p = .007) and ventral diencephalon (r² = .23, p = .036). These data may support an accelerated aging hypothesis in chronic moderate-severe TBI that coincides with a similar neuropathological profile found in neurodegenerative diseases.

Successful and Unsuccessful Brain Aging in Pets: Pathophysiological Mechanisms behind Clinical Signs and Potential Benefits from Palmitoylethanolamide Nutritional Intervention

Simple Summary

Cognitive dysfunction syndrome is a common yet underreported neurodegenerative disorder of elderly dogs and cats and a natural model of human Alzheimer’s disease. The increasingly expanding life expectancy means a larger proportion of affected animals in the coming decades. Although far from being curative, available treatments are more effective the sooner they are started. Educating veterinary practitioners and owners in the early recognition of age-related cognitive dysfunction is thus mandatory. By shedding light on the mechanism underlying the disease, novel and more effective approaches might be developed. Emerging evidence shows that successful and unsuccessful brain aging share a common underlying mechanism that is neuroinflammation. This process involves astrocytes, microglia, and mast cells and has a restorative homeostatic intent. However, for reasons not fully elucidated yet, neuroinflammation can also exert detrimental consequences substantially contributing to neurodegeneration. Here we summarize the evidence accumulated so far on the pathogenic role of neuroinflammation in the onset and progression of age-related neurodegenerative disorders, such as Alzheimer’s disease. The potential benefit of palmitoylethanolamide dietary intervention in rebalancing neuroinflammation and exerting neuroprotection is also discussed.

Abstract

Canine and feline cognitive dysfunction syndrome is a common neurodegenerative disorder of old age and a natural model of human Alzheimer’s disease. With the unavoidable expanding life expectancy, an increasing number of small animals will be affected. Although there is no cure, early detection and intervention are vitally important to delay cognitive decline. Knowledge of cellular and molecular mechanisms underlying disease onset and progression is an equally decisive factor for developing effective approaches. Uncontrolled neuroinflammation, orchestrated in the central nervous system mainly by astrocytes, microglia, and resident mast cells, is currently acknowledged as a hallmark of neurodegeneration. This has prompted scientists to find a way to rebalance the altered crosstalk between these cells. In this context, great emphasis has been given to the role played by the expanded endocannabinoid system, i.e., endocannabinoidome, because of its prominent role in physiological and pathological neuroinflammation. Within the endocannabinoidome, great attention has been paid to palmitoylethanolamide due to its safe and pro-homeostatic effects. The availability of new ultramicronized formulations highly improved the oral bioavailability of palmitoylethanolamide, paving the way to its dietary use. Ultramicronized palmitoylethanolamide has been repeatedly tested in animal models of age-related neurodegeneration with promising results. Data accumulated so far suggest that supplementation with ultramicronized palmitoylethanolamide helps to accomplish successful brain aging.

Alzheimer's disease neuropathology is exacerbated following traumatic brain injury. Neuroprotection by co-administration of nanowired mesenchymal stem cells and cerebrolysin with monoclonal antibodies to amyloid beta peptide

Military personnel are prone to traumatic brain injury (TBI) that is one of the risk factors in developing Alzheimer's disease (AD) at a later stage. TBI induces breakdown of the blood-brain barrier (BBB) to serum proteins into the brain and leads to extravasation of plasma amyloid beta peptide (ΑβP) into the brain fluid compartments causing AD brain pathology. Thus, there is a need to expand our knowledge on the role of TBI in AD. In addition, exploration of the novel roles of nanomedicine in AD and TBI for neuroprotection is the need of the hour. Since stem cells and neurotrophic factors play important roles in TBI and in AD, it is likely that nanodelivery of these agents exert superior neuroprotection in TBI induced exacerbation of AD brain pathology. In this review, these aspects are examined in details based on our own investigations in the light of current scientific literature in the field. Our observations show that TBI exacerbates AD brain pathology and TiO₂ nanowired delivery of mesenchymal stem cells together with cerebrolysin-a balanced composition of several neurotrophic factors and active peptide fragments, and monoclonal antibodies to amyloid beta protein thwarted the development of neuropathology following TBI in AD, not reported earlier.

Differential Retinal Protein Expression in Primary and Secondary Retinal Ganglion Cell Degeneration Identified by Integrated SWATH and Target-Based Proteomics

To investigate the retinal proteins associated with primary and secondary retinal ganglion cell (RGC) degeneration and explore their molecular pathways, SWATH label-free and target-based mass spectrometry was employed to identify the proteomes in various retinal locations in response to localized optic nerve injury. Unilateral partial optic nerve transection (pONT) was performed on adult Wistar rats and their retinas were harvested 2 weeks later. To confirm the separation of primary and secondary RGC degeneration, immunohistochemistry of RNA binding protein with multiple splicing (RBPMS) and glial fibrillary acidic protein (GFAP) was performed on retinal whole-mounts. Retinal proteomes in the temporal and nasal quadrants were evaluated with high resolution hybrid quadrupole time-of-flight mass spectrometry (QTOF-MS), and SWATH-based acquisition, and their expression was compared to the corresponding retinal quadrant in contralateral control eyes and further validated by multiple reaction monitoring mass spectrometry (MRM-MS). A total of 3641 proteins (FDR < 1%) were identified using QTOF-MS. The raw data are available via ProteomeXchange with the identifier PXD026783. Bioinformatics data analysis showed that there were 37 upregulated and 25 downregulated proteins in the temporal quadrant, whereas 20 and five proteins were upregulated and downregulated, respectively, in the nasal quadrant, respectively (n = 4, p < 0.05; fold change ≥ 1.4-fold or ≤0.7). Six proteins were regulated in both the temporal and the nasal quadrants, including CLU, GFAP, GNG5, IRF2BPL, L1CAM, and CPLX1. Linear regression analysis indicated a strong association between the data obtained by means of SWATH-MS and MRM-MS (temporal, R² = 0.97; nasal, R² = 0.96). Gene ontology analysis revealed statistically significant changes in the biological processes and cellular components of primary RGC degeneration. The majority of the significant changes in structural, signaling, and cell death proteins were associated with the loss of RGCs in the area of primary RGC degeneration. The combined use of SWATH-MS and MRM-MS methods detects and quantifies regional changes of retinal protein expressions after localized injury. Future investigation with this integrated approach will significantly increase the understanding of diverse processes of progressive RGC degeneration from a proteomic prospective.

Lentivirus-Mediated Expression of Human Secreted Amyloid Precursor Protein-Alpha Promotes Long-Term Induction of Neuroprotective Genes and Pathways in a Mouse Model of Alzheimer's Disease

BACKGROUND

Secreted amyloid precursor protein-alpha (sAPPα) can enhance memory and is neurotrophic and neuroprotective across a range of disease-associated insults, including amyloid-β toxicity. In a significant step toward validating sAPPα as a therapeutic for Alzheimer's disease (AD), we demonstrated that long-term overexpression of human sAPPα (for 8 months) in a mouse model of amyloidosis (APP/PS1) could prevent the behavioral and electrophysiological deficits that develop in these mice.

OBJECTIVE

To explore the underlying molecular mechanisms responsible for the significant physiological and behavioral improvements observed in sAPPα-treated APP/PS1 mice.

METHODS

We assessed the long-term effects on the hippocampal transcriptome following continuous lentiviral delivery of sAPPα or empty-vector to male APP/PS1 mice and wild-type controls using Affymetrix Mouse Transcriptome Assays. Data analysis was carried out within the Affymetrix Transcriptome Analysis Console and an integrated analysis of the resulting transcriptomic data was performed with Ingenuity Pathway analysis (IPA).

RESULTS

Mouse transcriptome assays revealed expected AD-associated gene expression changes in empty-vector APP/PS1 mice, providing validation of the assays used for the analysis. By contrast, there were specific sAPPα-associated gene expression profiles which included increases in key neuroprotective genes such as Decorin, betaine-GABA transporter and protocadherin beta-5, subsequently validated by qRT-PCR. An integrated biological pathways analysis highlighted regulation of GABA receptor signaling, cell survival and inflammatory responses. Furthermore, upstream gene regulatory analysis implicated sAPPα activation of Interleukin-4, which can counteract inflammatory changes in AD.

CONCLUSION

This study identified key molecular processes that likely underpin the long-term neuroprotective and therapeutic effects of increasing sAPPα levels in vivo.

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.

Acute Traumatic Brain Injury-Induced Neuroinflammatory Response and Neurovascular Disorders in the Brain

Acute traumatic brain injury (TBI) leads to neuroinflammation, neurodegeneration, cognitive decline, psychological disorders, increased blood-brain barrier (BBB) permeability, and microvascular damage in the brain. Inflammatory mediators secreted from activated glial cells, neurons, and mast cells are implicated in the pathogenesis of TBI through secondary brain damage. Abnormalities or damage to the neurovascular unit is the indication of secondary injuries in the brain after TBI. However, the precise mechanisms of molecular and ultrastructural neurovascular alterations involved in the pathogenesis of acute TBI are not yet clearly understood. Moreover, currently, there are no precision-targeted effective treatment options to prevent the sequelae of TBI. In this study, mice were subjected to closed head weight-drop-induced acute TBI and evaluated neuroinflammatory and neurovascular alterations in the brain by immunofluorescence staining or quantitation by enzyme-linked immunosorbent assay (ELISA) procedure. Mast cell stabilizer drug cromolyn was administered to inhibit the neuroinflammatory response of TBI. Results indicate decreased level of pericyte marker platelet-derived growth factor receptor-beta (PDGFR-β) and BBB-associated tight junction proteins junctional adhesion molecule-A (JAM-A) and zonula occludens-1 (ZO-1) in the brains 7 days after weight-drop-induced acute TBI as compared with the brains from sham control mice indicating acute TBI-associated BBB/tight junction protein disruption. Further, the administration of cromolyn drug significantly inhibited acute TBI-associated decrease of PDGFR-β, JAM-A, and ZO-1 in the brain. These findings suggest that acute TBI causes BBB/tight junction damage and that cromolyn administration could protect this acute TBI-induced brain damage as well as its long-time consequences.

Perioperative neurocognitive dysfunction: thinking from the gut?

With the aging of the world population, and improvements in medical and health technologies, there are increasing numbers of elderly patients undergoing anaesthesia and surgery. Perioperative neurocognitive dysfunction has gradually attracted increasing attention from academics. Very recently, 6 well-known journals jointly recommended that the term perioperative neurocognitive dysfunction (defined according to the Diagnostic and Statistical Manual of Mental Disorders, fifth edition) should be adopted to improve the quality and consistency of academic communications. Perioperative neurocognitive dysfunction currently includes preoperatively diagnosed cognitive decline, postoperative delirium, delayed neurocognitive recovery, and postoperative cognitive dysfunction. Increasing evidence shows that the gut microbiota plays a pivotal role in neuropsychiatric diseases, and in central nervous system functions via the microbiota-gut-brain axis. We recently reported that abnormalities in the composition of the gut microbiota might underlie the mechanisms of postoperative cognitive dysfunction and postoperative delirium, suggesting a critical role for the gut microbiota in perioperative neurocognitive dysfunction. This article therefore reviewed recent findings on the linkage between the gut microbiota and the underlying mechanisms of perioperative neurocognitive dysfunction.

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.

Mast Cell Activation, Neuroinflammation, and Tight Junction Protein Derangement in Acute Traumatic Brain Injury

Traumatic brain injury (TBI) is one of the major health problems worldwide that causes death or permanent disability through primary and secondary damages in the brain. TBI causes primary brain damage and activates glial cells and immune and inflammatory cells, including mast cells in the brain associated with neuroinflammatory responses that cause secondary brain damage. Though the survival rate and the neurological deficiencies have shown significant improvement in many TBI patients with newer therapeutic options, the underlying pathophysiology of TBI-mediated neuroinflammation, neurodegeneration, and cognitive dysfunctions is understudied. In this study, we analyzed mast cells and neuroinflammation in weight drop-induced TBI. We analyzed mast cell activation by toluidine blue staining, serum chemokine C-C motif ligand 2 (CCL2) level by enzyme-linked immunosorbent assay (ELISA), and proteinase-activated receptor-2 (PAR-2), a mast cell and inflammation-associated protein, vascular endothelial growth factor receptor 2 (VEGFR2), and blood-brain barrier tight junction-associated claudin 5 and Zonula occludens-1 (ZO-1) protein expression in the brains of TBI mice. Mast cell activation and its numbers increased in the brains of 24 h and 72 h TBI when compared with sham control brains without TBI. Mouse brains after TBI show increased CCL2, PAR-2, and VEGFR2 expression and derangement of claudin 5 and ZO-1 expression as compared with sham control brains. TBI can cause mast cell activation, neuroinflammation, and derangement of tight junction proteins associated with increased BBB permeability. We suggest that inhibition of mast cell activation can suppress neuroimmune responses and glial cell activation-associated neuroinflammation and neurodegeneration in TBI.

Neuroinflammatory Responses and Parkinson' Disease: Pathogenic Mechanisms and Therapeutic Targets

Parkinson's disease (PD) is the second most common age-related neurodegenerative disorders of the central nervous system, which mainly impairs the motor system. However, the pathogenic mechanisms are still unclear. Gene-environment complex interaction leads to selective dopaminergic neuron death in PD. Growing evidences supports that neuroinflammatory responses are involved in the pathogenesis of PD. This review critically discusses current studies on the inflammatory response of the pathological process of PD. The mechanisms and strategies of modifying inflammatory responses would be potential treatments for neurodegenerative diseases. Graphical abstract Activated microglia canpromote the damage ofdopaminergic neurons, which inturn aggravates the activation ofmicroglia in the process of PD. Atthe same time, microglia canactivate astrocytes throughproliferation and secretion ofinflammatory factors. The role ofastrocytes on the loss ofdopaminergic neurons is stillcontroversial in PD. (Nonsteroidalanti-inflammatory drugs,NSAIDs. adiposed-derived stemcells, ADSCs.nicotinamideadenine dinucleotide phosphate,NADPH. signal transducers andactivators of transcription,STAT.DJ-1,Aliases forPARK7.mesencephalic astrocytederivedneurotrophic factor,MANF.Ciliary neurotrophicfactor,CNTF.glial cell linederivedneurotrophic factor,GDNF.Wnt Family Member1,Wnt1). Graphical abstract Mitochondrial dysfunction causes neuroinflammation throughDAMPs and a series of factors such as oxidative stress andinflammatory bodies in PD. (Damage-associated molecular patterns,DAMPs. reactive oxygen species, ROS). Graphical abstract Various mechanismsparticipate in NLRP3 activation,causing microglia activation inPD. ( -synuclein, -syn.) TolllikeReceptor 2, TLR2. Toll-likeReceptor 4, TLR4. TumorNecrosis Factor, TNF.Apoptosisassociated speck like proteincontaining a CARD, ASC).

Current Trends in Biomarkers for Traumatic Brain Injury

Neurotrauma, especially Traumatic Brain Injury (TBI) is a major health concern not only for the civilian population but also for the military personnel. Currently there are no precision and regenerative therapies available for the successful treatment of TBI patients. Hence, early detection and treatment options may prevent the severity and untoward harmful effects of TBI. However, currently there are no effective biomarkers available for the rapid and robust diagnosis as well as prognosis of TBI. Several biomarkers in blood, cerebrospinal fluid (CSF), saliva and urine have been explored to assess the onset, progression, severity and prognosis of TBI recently. Present knowledge on the blood biomarkers including cytokines and chemokines and in vivo imaging modalities are useful to some extent to detect and treat TBI patients. Here, we review S100B, Glial Fibrillary Acidic Protein (GFAP), Neuron Specific Enolase (NSE), Myelin Basic Protein (MBP), Ubiquitin C-terminal Hydrolase L1 (UCHL1), tau protein, and alpha spectrin II break down products regarding their usefulness as a set of reliable biomarkers for the robust diagnosis of TBI. We suggest that these biomarkers may prove very useful for the diagnosis and prognosis of TBI.

Glia Maturation Factor in the Pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is a neurodegenerative and neuroinflammatory disease characterized by the presence of extracellular amyloid plaques (APs) and intracellular neurofibrillary tangles (NFTs) in the brain. There is no disease modifying therapeutic options currently available for this disease. Hippocampus, entorhinal cortex (Broadmann area 28), perirhinal cortex (Broadmann area 35) and insular cortices are areas within the brain that are first ones to be severely affected in AD. Neuroinflammation is an important factor that induces neurodegeneration in AD. Glia maturation factor (GMF), a proinflammatory factor plays a crucial role in AD through activation of microglia and astrocytes to release proinflammatory mediators in the brain. Through immunohistochemical studies, we have previously shown that GMF is highly expressed in the vicinity of APs and NFTs in AD brains. Glial fibrillary acidic protein (GFAP), reactive astrocytes, ionized calcium binding adaptor molecule-1 (Iba-1) labelled activated microglia and GMF immunoreactive glial cells are increased in the entorhinal cortical layers especially at the sites of APs and Tau containing NFTs indicating a role for GMF. Overexpression of GMF in glial cells leads to neuroinflammation and neurodegeneration. Inhibition of GMF expression reduces neurodegeneration. Therefore, we suggest that GMF is a novel therapeutic target not only for AD but also for various other neurodegenerative diseases.