Microglia and neuroinflammation: a pathological perspective

Role of myeloid cells in ischemic retinopathies: recent advances and unanswered questions

Myeloid cells including microglia and macrophages play crucial roles in retinal homeostasis by clearing cellular debris and regulating inflammation. These cells are activated in several blinding ischemic retinal diseases including diabetic retinopathy, where they may exert both beneficial and detrimental effects on neurovascular function and angiogenesis. Myeloid cells impact the progression of retinal pathologies and recent studies suggest that targeting myeloid cells is a promising therapeutic strategy to mitigate diabetic retinopathy and other ischemic retinal diseases. This review summarizes the recent advances in our understanding of the role of microglia and macrophages in retinal diseases and focuses on the effects of myeloid cells on neurovascular injury and angiogenesis in ischemic retinopathies. We highlight gaps in knowledge and advocate for a more detailed understanding of the role of myeloid cells in retinal ischemic injury to fully unlock the potential of targeting myeloid cells as a therapeutic strategy for retinal ischemia.

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.

Andrographolide derivative Andro-III modulates neuroinflammation and attenuates neuropathological changes of Alzheimer's disease via GSK-3β/NF-κB/CREB pathway

Andrographolide has anti-inflammatory and neuroprotective effects, making it a potential therapeutic option for Alzheimer's disease (AD). Our research group optimized its structure in a previous study to minimize the risk of renal toxicity, which would beneficial for future clinical research. This study aims to examine the impact of Andro-III on enhancing cognitive learning ability in 3xTg-AD mice, as well as the mechanisms involved. Andro-III improved spatial learning ability, prevented the loss of Nysted's vesicles, reduced the accumulation of β-amyloid (Aβ) and tau proteins, and suppressed microglial activation. Further research found that the expression of nuclear factor kappa-B RelA (NF-κB p65) expression and glycogen synthase kinase-3β (GSK-3β) activity were inhibited, while CREB was upregulated in brain tissue treated with Andro-III. Moreover, Andro-III downregulated the expression of IBA1 and inflammatory factors in microglial cells of mice induced by Aβ. The regulation of the GSK-3β/NF-κB/CREB pathway was similar to that observed in 3xTg-AD mice. Therefore, Andro-III modulates neuroinflammation and attenuates neuropathological changes of AD via the GSK-3β/NF-κB/CREB pathway.

Asthma aggravates alzheimer's disease by up-regulating NF- κB signaling pathway through LTD4

Clinical studies have shown that asthma is a risk factor for dementia or Alzheimer's disease (AD). To investigate whether asthma aggravates AD in APP/PS1 mice and explore the potential mechanisms, an asthma model was established using six-month-old APP/PS1 mice, and montelukast was used as a therapeutic agent in APP/PS1 mice with asthma. The Morris water maze test showed that asthma aggravates spatial learning and memory abilities. Asthma also upregulates the NF-κB inflammatory pathway in APP/PS1 mice and promotes the expression of beta-site amyloid precursor protein cleaving enzyme 1 (BACE1), amyloid-β (Aβ) deposition, neuronal damage, synaptic plasticity deficiency, activation of microglia and astrocytes. The level of LTD4 and its receptor CysLT1R in the hippocampus of APP/PS1 mice after the asthma modeling was established was higher than that in APP/PS1 mice, suggesting that asthma may affect the pathology of AD through LTD4 and its receptor Cys-LT1R. Montelukast ameliorates these pathological changes and cognitive impairment. These results suggest that asthma aggravates AD pathology and cognitive impairment of APP/PS1 mice via upregulation of the NF-κB inflammatory pathway, and montelukast ameliorates these pathological changes.

Amlexanox attenuates LPS-induced neuroinflammatory responses in microglial cells via inhibition of NF-κB and STAT3 signaling pathways

Amlexanox is an anti-inflammatory and anti-allergic agent used clinically for the treatment of aphthous ulcers, allergic rhinitis, and asthma. Recent studies have demonstrated that amlexanox, a selective inhibitor of IkB kinase epsilon (IKKε) and TANK-binding kinase 1 (TBK1), suppresses a range of diseases or inflammatory conditions, such as obesity-related metabolic dysfunction and type 2 diabetes. However, the effects of amlexanox on neuroinflammatory responses to amlexanox have not yet been comprehensively studied. In this study, we investigated the novel therapeutic effect of amlexanox on LPS-induced neuroinflammation in vivo, and intraperitoneal injection of amlexanox markedly reduced LPS-induced IKKε levels, proinflammatory cytokines, and microglial activation, as evidenced by ionized calcium-binding adapter molecule 1 (Iba1) immunostaining. Furthermore, amlexanox significantly reduced proinflammatory cytokines and chemokines in LPS-induced bone marrow-derived macrophages (BMDM), murine BV2, and human HMC3 microglial cells. This data provided considerable evidence that amlexanox can be used as a preventive and curative therapy for neuroinflammatory and neurodegenerative diseases. In terms of mechanism aspects, our results demonstrated that the anti-inflammatory action of amlexanox in BV2 microglial cells was through the downregulation of NF-κB and STAT3 signaling pathways. In addition, the combination of amlexanox and SPI (a STAT3 selective inhibitor) showed high efficiency in inhibiting the production of neurotoxic and pro-inflammatory mediators. Overall, our data provide rational insights into the mechanisms of amlexanox as a potential therapeutic strategy for neuroinflammation-related diseases.

Brain-regional characteristics and neuroinflammation in ME/CFS patients from neuroimaging: A systematic review and meta-analysis

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating condition characterized by an elusive etiology and pathophysiology. This study aims to evaluate the pathological role of neuroinflammation in ME/CFS by conducting an exhaustive analysis of 65 observational studies. Four neuroimaging techniques, including magnetic resonance imaging (MRI), magnetic resonance spectroscopy (MRS), electroencephalography (EEG), and positron emission tomography (PET), were employed to comparatively assess brain regional structure, metabolite profiles, electrical activity, and glial activity in 1529 ME/CFS patients (277 males, 1252 females) and 1715 controls (469 males, 1246 females). Clinical characteristics, including sex, age, and fatigue severity, were consistent with established epidemiological patterns. Regional alterations were most frequently identified in the cerebral cortex, with a notable focus on the frontal cortex. However, our meta-analysis data revealed a significant hypoactivity in the insular and thalamic regions, contrary to observed frequencies. These abnormalities, occurring in pivotal network hubs bridging reason and emotion, disrupt connections with the limbic system, contributing to the hallmark symptoms of ME/CFS. Furthermore, we discuss the regions where neuroinflammatory features are frequently observed and address critical neuroimaging limitations, including issues related to inter-rater reliability. This systematic review serves as a valuable guide for defining regions of interest (ROI) in future neuroimaging investigations of ME/CFS.

Neurotropism of SARS-CoV-2: A Pathological Examination of Neurosurgical Specimens

BACKGROUND AND OBJECTIVES

Neurological manifestations may occur in more than 80% of patients hospitalized with COVID-19 infection, including severe disruptions of the central nervous system (CNS), such as strokes, encephalitis, or seizures. Although the primary pathophysiological mechanism for the effects of COVID-19 in CNS remains unknown, evidence exists for both direct injury from neuroinvasion and indirect effects from disruptions in systemic inflammatory and coagulation pathways. In this study, we analyzed CNS tissue from living patients to better understand these processes.

METHODS

With institutional review board approval and patient consent, samples that would be otherwise discarded from patients with active or recent (within 6 days of surgery) COVID-19 infection undergoing neurosurgical intervention were collected and tested for the presence of SARS-CoV-2 using immunohistochemistry, in situ hybridization, electron microscopy, and reverse transcription polymerase chain reaction.

RESULTS

Five patients with perioperative mild-to-moderate COVID-19 infection met inclusion criteria (2 male, 3 female; mean age 38.8 ± 13.5 years). Neurosurgical diagnoses included a glioblastoma, a ruptured arteriovenous malformation, a ruptured posterior inferior cerebellar artery aneurysm, a middle cerebral artery occlusion, and a hemorrhagic pontine cavernous malformation. Samples analyzed included the frontal lobe cortex, olfactory nerve, arteriovenous malformation/temporal lobe parenchyma, middle cerebral artery, cerebellum, and cavernous malformation/brainstem parenchyma. Testing for the presence of SARS-CoV-2 was negative in all samples.

CONCLUSION

The CNS is likely not a significant viral reservoir during mild-to-moderate COVID-19 infection, although direct neuroinvasion is not definitively excluded. Additional testing to help elucidate the relative contributions of direct and indirect pathways for CNS injury from COVID is warranted.

Anti-Neuroinflammatory Effects of Arecae pericarpium on LPS-Stimulated BV2 Cells

Arecae pericarpium (AP), the fruit peel of the betel palm, is a traditional Oriental herbal medicine. AP is used to treat various diseases and conditions, such as ascites, edema, and urinary retention, in traditional Korean medicine. Recent studies have demonstrated its anti-obesity and antibacterial effects; however, its anti-neuroinflammatory effects have not yet been reported. Therefore, we investigated the anti-neuroinflammatory effects of AP on lipopolysaccharide (LPS)-stimulated mouse microglia in this study. To determine the anti-neuroinflammatory effects of AP on BV2 microglial cells, we examined the production of nitric oxide (NO) using Griess assay and assessed the mRNA expression levels of inflammatory mediators, such as inducible NO synthase (iNOS) and cyclooxygenase (COX)-2, and pro-inflammatory cytokines, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, using a real-time reverse transcription-polymerase chain reaction. Furthermore, we determined the levels of mitogen-activated protein kinases and IκBα via Western blotting to understand the regulating mechanisms of AP. AP treatment decreased NO production in LPS-stimulated BV2 cells. Additionally, AP suppressed the expression of iNOS and COX-2 and the production of pro-inflammatory cytokines. AP also inhibited the activation of p38 and nuclear factor-kappa B (NF-κB) in LPS-stimulated BV2 cells. Therefore, AP exerts anti-neuroinflammatory effects via inactivation of the p38 and NF-κB pathways.

Qinzhizhudan formula dampens inflammation in microglia polarization of vascular dementia rats by blocking MyD88/NF-κB signaling pathway: Through integrating network pharmacology and experimental validation

ETHNOPHARMACOLOGICAL RELEVANCE

Qinzhizhudan Formula (QZZD) is composed of Scutellaria baicalensis Georgi (Huang Qin) extract, Gardenia jasminoides (Zhizi) extract and Suis Fellis Pulvis (Zhudanfen) (ratio of 4:5:6). This formula is optimized from Qingkailing (QKL) injection. Regarding brain injury, QZZD is protective. However, the mechanism by which QZZD treats vascular dementia (VD) has not been elucidated.

AIM OF THE STUDY

To ascertain QZZD's effect on the treatment of VD and further investigate the molecular mechanisms.

MATERIALS AND METHODS

In this study, we screened the possible components and targets of QZZD against VD and microglia polarization using network pharmacology (NP), then an animal model of bilateral common carotid artery ligation method (2VO) was induced. Afterward, The Morris water maze was employed to evaluate cognitive ability, and pathological alterations in the CA1 area of the hippocampus were detected using HE and Nissl staining. To confirm the affect of QZZD on VD and its molecular mechanism, the contents of inflammatory factors IL-1β, TNF-α, IL-4, and IL-10 were performed to detect by ELISA, the phenotype polarization of microglia cells was detected by immunofluorescence staining, and the expressions of MyD88, p-IκBα and p-NF-κB p65 in brain tissue were detected by western blot.

RESULTS

A total of 112 active compounds and 363 common targets of QZZD, microglia polarization, and VD were identified, according to the NP analysis. 38 hub targets were screened out from the PPI network. GO analysis and KEGG pathway analysis showed that QZZD may regulate microglia polarization through anti-inflammatory mechanism such as Toll-like receptor signaling pathway and NF-κB signaling pathway. The further results showed that QZZD can alleviate the memory impairment induced by 2VO. QZZD profoundly rescued brain hippocampus neuronal damage and increased the number of neurons. These advantageous outcomes were linked to the control of microglia polarization. QZZD decreased M1 phenotypic marker expression while increasing M2 phenotypic marker expression. QZZD may controll the polarization of the M1 microglia by blocking the core part of Toll-like receptor signaling pathway, that is the MyD88/NF-κB signaling pathway, which reduced the neurotoxic effects of the microglia.

CONCLUSION

Here, we explored the anti-VD microglial polarization characteristic of QZZD for the first time and clarified its mechanisms. These findings will provide valuable clues for the discovery of anti-VD agents.

Baicalin exerts neuroprotective actions by regulating the Nrf2-NLRP3 axis in toxin-induced models of Parkinson's disease

Baicalin, a potent anti-oxidative and anti-inflammatory flavonoid compound derived from Scutellaria baicalensis, has emerged as a neuroprotective agent. However, the mechanisms by which baicalin is neuroprotective in Parkinson's disease (PD) remain unclear. In this research, α-syn/MPP+ and MPTP were used to establish PD models in BV2 cells and C57BL/6 mice, respectively. The effect and mechanism of action of baicalin in PD were investigated by Western blotting, RT-qPCR, ELISA, Immunohistochemistry (IHC) staining, Immunofluorescence (IF) staining, HPLC and methods. Results demonstrate that baicalin mitigates oxidative stress, microglia activation and inflammatory response caused by α-syn/MPP+ and MPTP. It protects against dopaminergic neuron loss and relieves motor deficits. Meanwhile, baicalin not only significantly up-regulates the expression of Nrf2 and its downstream antioxidant enzyme, but also suppresses the activation of NLRP3 inflammasome simultaneously. Notably, the beneficial effects of baicalin in PD treatment are blocked by Nrf2 knockdown. This research reveals that baicalin may exert neuroprotective effects in PD treatment by suppressing the activation of NLRP3 inflammasome and it is dependent on the Nrf2-mediated antioxidative response.

The effect of SARS-CoV-2 on the development of Parkinson's disease: the role of α-synuclein

The current coronavirus disease 2019 (COVID-19) can lead to various neurological complications in infected people. These neurological effects include problems in both central nervous system (CNS) and peripheral nervous system (PNS). Hyposmia, a PNS symptom of COVID-19, frequently manifests in the early stages of Parkinson's disease (PD) and serves as an early warning sign of the condition. In addition, the olfactory system is recognized as an early site for the onset of α-synuclein pathology, the pathological hallmark of PD. PD is characterized by accumulation and aggregation of misfolded α-synuclein (α-Syn) into Lewy bodies and Lewy neurites, resulting in the degeneration of dopaminergic neurons in substantia nigra pars compacta (SNpc). Previous research has also shown the involvement of α-Syn in the innate immune response following viral infections. Consequently, the potential link between viral infections and development of PD has gained attention in recent years. However, it's still too early to definitively conclude whether COVID-19 can cause Parkinsonism. Nevertheless, we can explore the likelihood of this connection by examining past studies and possible mechanisms to better understand how COVID-19 might potentially lead to PD following the infection. Based on the various pieces of evidence discussed in this review, we can infer that SARS-CoV-2 promotes the aggregation of α-Syn and, ultimately, leads to PD through at least two mechanisms: the stable binding of the S1 protein to proteins prone to aggregation like α-Syn, and the upregulation of α-Syn as part of the immune response to the infection.

Analogs of FTY720 inhibit TRPM7 but not S1PRs and exert multimodal anti-inflammatory effects

TRPM7, a TRP channel with ion conductance and kinase activities, has emerged as an attractive drug target for immunomodulation. Reverse genetics and cell biological studies have already established a key role for TRPM7 in the inflammatory activation of macrophages. Advancing TRPM7 as a viable molecular target for immunomodulation requires selective TRPM7 inhibitors with in vivo tolerability and efficacy. Such inhibitors have the potential to interdict inflammatory cascades mediated by systemic and tissue-specialized macrophages. FTY720, an FDA-approved drug for multiple sclerosis inhibits TRPM7. However, FTY720 is a prodrug and its metabolite, FTY720-phosphate, is a potent agonist of sphingosine-1-phosphate (S1P) receptors. In this study, we test non-phosphorylatable FTY720 analogs, which are inert against S1PRs and well tolerated in vivo, for activity against TRPM7 and tissue bioavailability. Using patch clamp electrophysiology, we show that VPC01091.4 and AAL-149 block TRPM7 current at low micromolar concentrations. In culture, they act directly on macrophages to blunt LPS-induced inflammatory cytokine expression, though this likely occurrs through multiple molecular targets. We found that VPC01091.4 has significant and rapid accumulation in the brain and lungs, along with direct anti-inflammatory action on alveolar macrophages and microglia. Finally, using a mouse model of endotoxemia, we show VPC01091.4 to be an efficacious anti-inflammatory agent that arrests systemic inflammation in vivo. Together, these findings identify novel small molecule inhibitors that allow TRPM7 channel inhibition independent of S1P receptor targeting which demonstrate potent, polymodal anti-inflammatory activities ex vivo and in vivo.

History of Microglia

The term 'microglia' was first introduced into the scientific literature a century ago. The various eras of microglial research have been defined not only by the number of reports subsequently generated but, more critically, also by the concepts that have shaped our present-day views and understanding of microglia. Key methods, technologies, and models, as well as seminal discoveries made possible through their deployment have enabled breakthroughs, and now pave the way for lines of investigation that could not have been anticipated even a decade ago. Advances in our understanding of the microglial origin, forms, and functions have relied fundamentally on parallel developments in immunology. As the 'neuro-immune' cells of the brain, microglia are now under the spotlight in various disciplines. This chapter surveys the gradual processes and precipitous events that helped form ideas concerning the developmental origin of microglia and their roles in health and disease. It first covers the dawning phase during which the early pioneers of microglial research discovered cellular entities and already assigned functions to them. Following a recess period, the 1960s brought about a renaissance of active interest, with the development of tools and models-and fundamental notions on microglial contributions to central nervous system (CNS) pathologies. These seminal efforts laid the foundation for the awakening of a sweeping research era beginning in the 1980s and spurred on by a blast of immunological discoveries. Finally, this chapter stresses the advancements in molecular, genetic, and imaging approaches to the study of microglia with the turn of the millennium, enabling insights into virtually all facets of microglial physiology. Moving forward, it is clear that the future holds substantial promise for further discoveries. The next epoch in the history of microglial research has just begun.

Drugs to Treat Neuroinflammation in Neurodegenerative Disorders

Neuroinflammation is associated with disorders of the nervous system, and it is induced in response to many factors, including pathogen infection, brain injury, toxic substances, and autoimmune diseases. Astrocytes and microglia have critical roles in neuroinflammation. Microglia are innate immune cells in the central nervous system (CNS), which are activated in reaction to neuroinflammation-inducing factors. Astrocytes can have pro- or anti-inflammatory responses, which depend on the type of stimuli presented by the inflamed milieu. Microglia respond and propagate peripheral inflammatory signals within the CNS that cause low-grade inflammation in the brain. The resulting alteration in neuronal activities leads to physiological and behavioral impairment. Consequently, activation, synthesis, and discharge of various pro-inflammatory cytokines and growth factors occur. These events lead to many neurodegenerative conditions, such as Alzheimer's disease, Parkinson's disease, and multiple sclerosis discussed in this study. After understanding neuroinflammation mechanisms and the involvement of neurotransmitters, this study covers various drugs used to treat and manage these neurodegenerative illnesses. The study can be helpful in discovering new drug molecules for treating neurodegenerative disorders.

Spatio-temporal dynamics of microglia phenotype in human and murine cSVD: impact of acute and chronic hypertensive states

Vascular risk factors such as chronic hypertension are well-established major modifiable factors for the development of cerebral small vessel disease (cSVD). In the present study, our focus was the investigation of cSVD-related phenotypic changes in microglia in human disease and in the spontaneously hypertensive stroke-prone rat (SHRSP) model of cSVD. Our examination of cortical microglia in human post-mortem cSVD cortical tissue revealed distinct morphological microglial features specific to cSVD. We identified enlarged somata, an increase in the territory occupied by thickened microglial processes, and an expansion in the number of vascular-associated microglia. In parallel, we characterized microglia in a rodent model of hypertensive cSVD along different durations of arterial hypertension, i.e., early chronic and late chronic hypertension. Microglial somata were already enlarged in early hypertension. In contrast, at late-stage chronic hypertension, they further exhibited elongated branches, thickened processes, and a reduced ramification index, mirroring the findings in human cSVD. An unbiased multidimensional flow cytometric analysis revealed phenotypic heterogeneity among microglia cells within the hippocampus and cortex. At early-stage hypertension, hippocampal microglia exhibited upregulated CD11b/c, P2Y12R, CD200R, and CD86 surface expression. Detailed analysis of cell subpopulations revealed a unique microglial subset expressing CD11b/c, CD163, and CD86 exclusively in early hypertension. Notably, even at early-stage hypertension, microglia displayed a higher association with cerebral blood vessels. We identified several profound clusters of microglia expressing distinct marker profiles at late chronic hypertensive states. In summary, our findings demonstrate a higher vulnerability of the hippocampus, stage-specific microglial signatures based on morphological features, and cell surface protein expression in response to chronic arterial hypertension. These results indicate the diversity within microglia sub-populations and implicate the subtle involvement of microglia in cSVD pathogenesis.

Regulation of microglia-mediated inflammation by host lncRNA Gm20559 upon flaviviral infection

BACKGROUND

Japanese Encephalitis Virus (JEV) and West Nile Viruses (WNV) are neurotropic flaviviruses which cause neuronal death and exaggerated glial activation in the central nervous system. Role of host long non coding RNAs in shaping microglial inflammation upon flavivirus infections has been unexplored. This study attempted to decipher the role of lncRNA Gm20559 in regulating microglial inflammatory response in context of flaviviruses.

METHODS

Antisense oligonucleotide LNA Gapmers designed against lncRNA Gm20559 and non-specific site (negative control) were used for Gm20559 knockdown in JEV and WNV-infected N9 microglial cells. Upon establishing successful Gm20559 knockdown, expression of various proinflammatory cytokines, chemokines, interferon-stimulated genes (ISGs) and RIG-I were checked by qRT-PCR and cytometric bead array. Western Blotting was done to analyse the phosphorylation level of various inflammatory markers and viral non-structural protein expression. Plaque Assays were employed to quantify viral titres in microglial supernatant upon knocking down Gm20559. Effect of microglial supernatant on HT22 neuronal cells was assessed by checking expression of apoptotic protein and viral non-structural protein by Western Blotting.

RESULTS

Upregulation in Gm20559 expression was observed in BALB/c pup brains, primary microglia as well as N9 microglia cell line upon both JEV and WNV infection. Knockdown of Gm20559 in JEV and WNV-infected N9 cell led to the reduction of major proinflammatory cytokines - IL-1β, IL-6, IP-10 and IFN-β. Inhibition of Gm20559 upon JEV infection in N9 microglia also led to downregulation of RIG-I and OAS-2, which was not the case in WNV-infected N9 microglia. Phosphorylation level of P38 MAPK was reduced in case of JEV-infected N9 microglia and not WNV-infected N9 microglia. Whereas phosphorylation of NF-κB pathway was unchanged upon Gm20559 knockdown in both JEV and WNV-infected N9 microglia. However, treating HT22 cells with JEV and WNV-infected microglial supernatant with and without Gm20559 could not trigger cell death or influence viral replication.

CONCLUSION

Knockdown studies on lncRNA Gm20559 suggests its pivotal role in maintaining the inflammatory milieu of microglia in flaviviral infection by modulating the expression of various pro-inflammatory cytokines. However, Gm20559-induced increased microglial proinflammatory response upon flavivirus infection fails to trigger neuronal death.

Astrocytes and microglia-targeted Danshensu liposomes enhance the therapeutic effects on cerebral ischemia-reperfusion injury

Cerebral ischemia-reperfusion injury (CI/RI) is the main cause of disability and death in stroke without satisfactory therapeutic effect. Inflammation mediated by activation of astrocytes and microglia is the main pathological mechanism of CI/RI. Danshensu (DSS) has been shown to exert anti-inflammatory effects against brain injury. However, limited by its poor cellular permeability and low bioavailability, it is still needed the new DSS preparations with the ability to cross the blood-brain barrier (BBB) and target inflammatory glial cells. In this study, we developed phosphatidylserine (PS) and transferrin (TF) modified liposomes carrying DSS (TF/PS/DSS-LPs) to improve the therapeutic efficacy against ischemic stroke. First, TF molecules targeted transferrin receptor (TfR) that is overexpressed in the BBB. Following the liposomes enter the brain, PS modification allowed the liposomes to target and bind to the overexpressed phosphatidylserine-specific receptors (PSRs) on the surface of astrocytes and microglia. Furthermore, it enhanced the uptake of TF/PS/DSS-LPs by astrocytes and microglia, while polarizing astrocytes from A1 to A2 and microglia from M1 to M2, reducing neuronal inflammation, and ultimately ameliorating cerebral ischemic injury. Thus, TF/PS/DSS-LPs could potentially serve as a promising strategy for the CI/RI treatment.

Immune-mediated ataxias: Guide to clinicians

Immune-mediated cerebellar ataxias were initially described as a clinical entity in the 1980s, and since then, an expanding body of evidence has contributed to our understanding of this topic. These ataxias encompass various etiologies, including postinfectious cerebellar ataxia, gluten ataxia, paraneoplastic cerebellar degeneration, opsoclonus-myoclonus-ataxia syndrome and primary autoimmune cerebellar ataxia. The increased permeability of the brain-blood barrier could potentially explain the vulnerability of the cerebellum to autoimmune processes. In this manuscript, our objective is to provide a comprehensive review of the most prevalent diseases within this group, emphasizing clinical indicators, pathogenesis, and current treatment approaches.

Mechanisms of Cadmium Neurotoxicity

Cadmium is a heavy metal that increasingly contaminates food and drink products. Once ingested, cadmium exerts toxic effects that pose a significant threat to human health. The nervous system is particularly vulnerable to prolonged, low-dose cadmium exposure. This review article provides an overview of cadmium's primary mechanisms of neurotoxicity. Cadmium gains entry into the nervous system via zinc and calcium transporters, altering the homeostasis for these metal ions. Once within the nervous system, cadmium disrupts mitochondrial respiration by decreasing ATP synthesis and increasing the production of reactive oxygen species. Cadmium also impairs normal neurotransmission by increasing neurotransmitter release asynchronicity and disrupting neurotransmitter signaling proteins. Cadmium furthermore impairs the blood-brain barrier and alters the regulation of glycogen metabolism. Together, these mechanisms represent multiple sites of biochemical perturbation that result in cumulative nervous system damage which can increase the risk for neurological and neurodegenerative disorders. Understanding the way by which cadmium exerts its effects is critical for developing effective treatment and prevention strategies against cadmium-induced neurotoxic insult.

A review of studies on the implication of NLRP3 inflammasome for Parkinson's disease and related candidate treatment targets

Parkinson's disease (PD) is a neurodegenerative disease for which the prevalence is second only to Alzheimer's disease (AD). This disease primarily affects people of middle and old age, significantly impacting their health and quality of life. The main pathological features include the degenerative nigrostriatal dopaminergic (DA) neuron loss and Lewy body (LB) formation. Currently, available PD medications primarily aim to alleviate clinical symptoms, however, there is no universally recognized therapy worldwide that effectively prevents, clinically treats, stops, or reverses the disease. Consequently, the evaluation and exploration of potential therapeutic targets for PD are of utmost importance. Nevertheless, the pathophysiology of PD remains unknown, and neuroinflammation mediated by inflammatory cytokines that prompts neuron death is fundamental for the progression of PD. The nucleotide-binding oligomerization domain-like receptor pyrin domain-containing 3 (NLRP3) inflammasome is a key complex of proteins linking the neuroinflammatory cascade in PD. Moreover, mounting evidence suggests that traditional Chinese medicine (TCM) alleviates PD by suppressing the NLRP3 inflammasome. This article aims to comprehensively review the available studies on the composition and activating mechanism of the NLRP3 inflammasome, along with its significance in PD pathogenesis and potential treatment targets. We also review natural products or synthetic compounds which reduce neuroinflammation via modulating NLRP3 inflammasome activity, aiming to identify new targets for future PD diagnosis and treatment through the exploration of NLRP3 inhibitors. Additionally, this review offers valuable references for developing new PD treatment methods.

Neural cell membrane-coated DNA nanogels as a potential target-specific drug delivery tool for the central nervous system

A major bottleneck in drug/gene delivery to enhance tissue regeneration after injuries is to achieve targeted delivery to the cells of interest. Unfortunately, we have not been able to attain effective targeted drug delivery in tissues due to the lack of efficient delivery platforms. Since specific cell-cell interactions exist to impart the unique structure and functionality of tissues and organs, we hypothesize that such specific cellular interactions may also be harnessed for drug delivery applications in the form of cell membrane coatings. Here, we employed neural cell-derived membrane coating technique on DNA nanogels to improve target specificity. The efficacy of neural cell membrane-coated DNA nanogels (NCM-nanogels) was demonstrated by using four types of cell membranes derived from the central nervous system (CNS), namely, astrocytes, microglia, cortical neurons, and oligodendrocyte progenitor cells (OPCs). A successful coating of NCMs over DNA nanogels was confirmed by dynamic light scattering, zeta potential measurements and transmission electron microscopy. Subsequently, an overall improvement in cellular uptake of NCM-nanogels over uncoated DNA nanogels (p < 0.005) was seen. Additionally, we observed a selective uptake of OPC membrane-coated DNA nanogels (NCM-O mem) by oligodendrocytes over other cell types both in vitro and in vivo. Our quantitative polymerase chain reaction (qPCR) results also showed selective and effective gene knockdown capacity of NCM-O mem for OPC transfection. The findings in this work may be beneficial for future drug delivery applications targeted at the CNS.

APOE genotype and sex modulate Alzheimer's disease pathology in aged EFAD transgenic mice

Increasing evidence supports that age, APOE and sex interact to modulate Alzheimer's disease (AD) risk, however the underlying pathways are unclear. One way that AD risk factors may modulate cognition is by impacting amyloid beta (Aβ) accumulation as plaques, and/or neuroinflammation Therefore, the goal of the present study was to evaluate the extent to which age, APOE and sex modulate Aβ pathology, neuroinflammation and behavior in vivo. To achieve this goal, we utilized the EFAD mice, which express human APOE3 or APOE4 and have five familial AD mutations (FAD) that result in Aβ42 overproduction. We assessed Aβ levels, reactive glia and Morris water maze performance in 6-, 10-, 14-, and 18-month-old EFAD mice. Female APOE4 mice had the highest Aβ deposition, fibrillar amyloid deposits and neuroinflammation as well as earlier behavior deficits. Interestingly, we found that female APOE3 mice and male APOE4 mice had similar levels of pathology. Collectively our data support that the combination of APOE4 and female sex is the most detrimental combination for AD, and that at older ages, female sex may be equivalent to APOE4 genotype.

K252a Prevents Microglial Activation Induced by Anoxic Stimulation of Carotid Bodies in Rats

Inducing carotid body anoxia through the administration of cyanide can result in oxygen deprivation. The lack of oxygen activates cellular responses in specific regions of the central nervous system, including the Nucleus Tractus Solitarius, hypothalamus, hippocampus, and amygdala, which are regulated by afferent pathways from chemosensitive receptors. These receptors are modulated by the brain-derived neurotrophic factor receptor TrkB. Oxygen deprivation can cause neuroinflammation in the brain regions that are activated by the afferent pathways from the chemosensitive carotid body. To investigate how microglia, a type of immune cell in the brain, respond to an anoxic environment resulting from the administration of NaCN, we studied the effects of blocking the TrkB receptor on this cell-type response. Male Wistar rats were anesthetized, and a dose of NaCN was injected into their carotid sinus to induce anoxia. Prior to the anoxic stimulus, the rats were given an intracerebroventricular (icv) infusion of either K252a, a TrkB receptor inhibitor, BDNF, or an artificial cerebrospinal fluid (aCSF). After the anoxic stimulus, the rats were perfused with paraformaldehyde, and their brains were processed for microglia immunohistochemistry. The results indicated that the anoxic stimulation caused an increase in the number of reactive microglial cells in the hypothalamic arcuate, basolateral amygdala, and dentate gyrus of the hippocampus. However, the infusion of the K252a TrkB receptor inhibitor prevented microglial activation in these regions.

Chronic neuroinflammation during aging leads to cholinergic neurodegeneration in the mouse medial septum

BACKGROUND

Low-grade, chronic inflammation in the central nervous system characterized by glial reactivity is one of the major hallmarks for aging-related neurodegenerative diseases like Alzheimer's disease (AD). The basal forebrain cholinergic neurons (BFCN) provide the primary source of cholinergic innervation of the human cerebral cortex and may be differentially vulnerable in various neurodegenerative diseases. However, the impact of chronic neuroinflammation on the cholinergic function is still unclear.

METHODS

To gain further insight into age-related cholinergic decline, we investigated the cumulative effects of aging and chronic neuroinflammation on the structure and function of the septal cholinergic neurons in transgenic mice expressing interleukin-6 under the GFAP promoter (GFAP-IL6), which maintains a constant level of gliosis. Immunohistochemistry combined with unbiased stereology, single cell 3D morphology analysis and in vitro whole cell patch-clamp measurements were used to validate the structural and functional changes of BFCN and their microglial environment in the medial septum.

RESULTS

Stereological estimation of MS microglia number displayed significant increase across all three age groups, while a significant decrease in cholinergic cell number in the adult and aged groups in GFAP-IL6 mice compared to control. Moreover, we observed age-dependent alterations in the electrophysiological properties of cholinergic neurons and an increased excitability profile in the adult GFAP-IL6 group due to chronic neuroinflammation. These results complimented the significant decrease in hippocampal pyramidal spine density seen with aging and neuroinflammation.

CONCLUSIONS

We provide evidence of the significant impact of both aging and chronic glial activation on the cholinergic and microglial numbers and morphology in the MS, and alterations in the passive and active electrophysiological membrane properties of septal cholinergic neurons, resulting in cholinergic dysfunction, as seen in AD. Our results indicate that aging combined with gliosis is sufficient to cause cholinergic disruptions in the brain, as seen in dementias.

Macrophage regulation of the "second brain": CD163 intestinal macrophages interact with inhibitory interneurons to regulate colonic motility - evidence from the Cx3cr1-Dtr rat model

Intestinal macrophages are well-studied for their conventional roles in the immune response against pathogens and protecting the gut from chronic inflammation. However, these macrophages may also have additional functional roles in gastrointestinal motility under typical conditions. This is likely to occur via both direct and indirect influences on gastrointestinal motility through interaction with myenteric neurons that contribute to the gut-brain axis, but this mechanism is yet to be properly characterised. The CX3CR1 chemokine receptor is expressed in the majority of intestinal macrophages, so we used a conditional knockout Cx3cr1-Dtr (diphtheria toxin receptor) rat model to transiently ablate these cells. We then utilized ex vivo video imaging to evaluate colonic motility. Our previous studies in brain suggested that Cx3cr1-expressing cells repopulate by 7 days after depletion in this model, so we performed our experiments at both the 48 hr (macrophage depletion) and 7-day (macrophage repopulation) time points. We also investigated whether inhibitory neuronal input driven by nitric oxide from the enteric nervous system is required for the regulation of colonic motility by intestinal macrophages. Our results demonstrated that CD163-positive resident intestinal macrophages are important in regulating colonic motility in the absence of this major inhibitory neuronal input. In addition, we show that intestinal macrophages are indispensable in maintaining a healthy intestinal structure. Our study provides a novel understanding of the interplay between the enteric nervous system and intestinal macrophages in colonic motility. We highlight intestinal macrophages as a potential therapeutic target for gastrointestinal motility disorders when inhibitory neuronal input is suppressed.

Neural System Impairment and Involved Microglia-Neuron Regulation of Broflanilide in Zebrafish Larvae

Broflanilide is widely used to control pests and has attracted attention due to its adverse effects on aquatic organisms. Our previous study showed that broflanilide has a negative impact on the central nervous system (CNS) at lethal dosages; however, its neural effects under practical situations and the underlying mechanisms remain unknown. To elucidate how broflanilide affects the CNS, we exposed zebrafish larvae to broflanilide at 16.9 and 88.0 μg/L (the environmentally relevant concentrations) for 120 h. Zebrafish locomotion was significantly disturbed at 88.0 μg/L, with a decreased moving distance and velocity accompanied by an inhibited neurotransmitter level. In vivo neuroimaging analysis indicated that the nerves of zebrafish larvae, including the axons, myelin sheaths, and neurons, were impaired. The number of neurons was significantly reduced after exposure, with an impaired morphological structure. These changes were accompanied by the abnormal transcription of genes involved in early CNS development. In addition, an increased total number of microglia and an elevated proportion of amoeboid microglia were observed after 88.0 μg/L broflanilide exposure, pointing out to an upstream role of microglia activation in mediating broflanilide neurotoxicity. Meanwhile, increased inflammatory cytokine levels and brain neutrophil numbers were observed, implicating significant inflammatory response and immune toxicity. Our findings indicate that broflanilide interferes with microglia-neuron regulation and induces neurodevelopmental disorders.

Novel Therapeutic Opportunities for Neurodegenerative Diseases with Mesenchymal Stem Cells: The Focus on Modulating the Blood-Brain Barrier

Neurodegenerative disorders encompass a broad spectrum of profoundly disabling situations that impact millions of individuals globally. While their underlying causes and pathophysiology display considerable diversity and remain incompletely understood, a mounting body of evidence indicates that the disruption of blood-brain barrier (BBB) permeability, resulting in brain damage and neuroinflammation, is a common feature among them. Consequently, targeting the BBB has emerged as an innovative therapeutic strategy for addressing neurological disorders. Within this review, we not only explore the neuroprotective, neurotrophic, and immunomodulatory benefits of mesenchymal stem cells (MSCs) in combating neurodegeneration but also delve into their recent role in modulating the BBB. We will investigate the cellular and molecular mechanisms through which MSC treatment impacts primary age-related neurological conditions like Alzheimer's disease, Parkinson's disease, and stroke, as well as immune-mediated diseases such as multiple sclerosis. Our focus will center on how MSCs participate in the modulation of cell transporters, matrix remodeling, stabilization of cell-junction components, and restoration of BBB network integrity in these pathological contexts.

Chronic alcohol induced mechanical allodynia by promoting neuroinflammation: A mouse model of alcohol-evoked neuropathic pain

BACKGROUND AND PURPOSE

Chronic pain is considered a key factor contributing to alcohol use disorder (AUD). The mechanisms responsible for chronic pain associated with chronic alcohol consumption are unknown. We evaluated the development of chronic pain in a mouse model of alcohol dependence and investigate the role of neuroinflammation.

EXPERIMENTAL APPROACH

The chronic-intermittent ethanol two-bottle choice CIE-2BC paradigm generates three groups: alcohol-dependent with escalating alcohol intake, nondependent (moderate drinking) and alcohol-naïve control male and female mice. We measured mechanical allodynia during withdrawal and after the last voluntary drinking. Immunoblotting was used to evaluate the protein levels of IBA-1, CSFR, IL-6, p38 and ERK2/1 in spinal cord tissue of dependent and non-dependent animals.

KEY RESULTS

We found significant escalation of drinking in the dependent group in male and female compared with the non-dependent group. The dependent group developed mechanical allodynia during 72 h of withdrawal, which was completely reversed after voluntary drinking. We observed an increased pain hypersensitivity compared with the naïve in 50% of non-dependent group. Increased IBA-1 and CSFR expression was observed in spinal cord tissue of both hypersensitivity-abstinence related and neuropathy-alcohol mice, and increased IL-6 expression and ERK1/2 activation in mice with hypersensitivity-related to abstinence, but not in mice with alcohol-evoked neuropathic pain.

CONCLUSIONS AND IMPLICATIONS

The CIE-2BC model induces two distinct pain conditions specific to the type of ethanol exposure: abstinence-related hypersensitivity in dependent mice and alcohol-evoked neuropathic pain in about a half of the non-dependent mice.

Chronic Aripiprazole and Trazodone Polypharmacy Effects on Systemic and Brain Cholesterol Biosynthesis

The concurrent use of several medications is a common practice in the treatment of complex psychiatric conditions. One such commonly used combination is aripiprazole (ARI), an antipsychotic, and trazodone (TRZ), an antidepressant. In addition to their effects on dopamine and serotonin systems, both of these compounds are inhibitors of the 7-dehydrocholesterol reductase (DHCR7) enzyme. To evaluate the systemic and nervous system distribution of ARI and TRZ and their effects on cholesterol biosynthesis, adult mice were treated with both ARI and TRZ for 21 days. The parent drugs, their metabolites, and sterols were analyzed in the brain and various organs of mice using LC-MS/MS. The analyses revealed that ARI, TRZ, and their metabolites were readily detectable in the brain and organs, leading to changes in the sterol profile. The levels of medications, their metabolites, and sterols differed across tissues with notable sex differences. Female mice showed higher turnover of ARI and more cholesterol clearance in the brain, with several post-lanosterol intermediates significantly altered. In addition to interfering with sterol biosynthesis, ARI and TRZ exposure led to decreased ionized calcium-binding adaptor molecule 1 (IBA1) and increased DHCR7 protein expression in the cortex. Changes in sterol profile have been also identified in the spleen, liver, and serum, underscoring the systemic effect of ARI and TRZ on sterol biosynthesis. Long-term use of concurrent ARI and TRZ warrants further studies to fully evaluate the lasting consequences of altered sterol biosynthesis on the whole body.

Novel TRPM7 inhibitors with potent anti-inflammatory effects in vivo

TRPM7, a TRP channel with ion conductance and kinase activities, has emerged as an attractive drug target for immunomodulation. Reverse genetics and cell biological studies have already established a key role for TRPM7 in the inflammatory activation of macrophages. Advancing TRPM7 as a viable molecular target for immunomodulation requires selective TRPM7 inhibitors with in vivo tolerability and efficacy. Such inhibitors have the potential to interdict inflammatory cascades mediated by systemic and tissue-specialized macrophages. FTY720, an FDA-approved drug for multiple sclerosis inhibits TRPM7. However, FTY720 is a prodrug and its metabolite, FTY720-phosphate, is a potent agonist of sphingosine 1-phosphate (S1P) receptors. In this study, we tested non-phosphorylatable FTY720 analogs, which are inert against S1PRs and well tolerated in vivo , for activity against TRPM7 and tissue bioavailability. Using patch clamp electrophysiology, we show that VPC01091.4 and AAL-149 block TRPM7 current at low micromolar concentrations. In culture, they act directly on macrophages to blunt LPS-induced inflammatory cytokine expression, an effect that is predominantly but not solely mediated by TRPM7. We found that VPC01091.4 has significant and rapid accumulation in the brain and lungs, along with direct anti-inflammatory action on alveolar macrophages and microglia. Finally, using a mouse model of endotoxemia, we show VPC01091.4 to be an efficacious anti-inflammatory agent that arrests systemic inflammation in vivo . Together, these findings identify novel small molecule inhibitors that allow TRPM7 channel inhibition independent of S1P receptor targeting. These inhibitors exhibit potent anti-inflammatory properties that are mediated by TRPM7 and likely other molecular targets that remain to be identified.

A Disintegrin and Metalloproteinase Protein 8 (ADAM 8) in Autism Spectrum Disorder: Links to Neuroinflammation

Background

Converging lines of evidence confirmed neuroinflammation's role in autism spectrum disorder (ASD) etiological pathway. A disintegrin and metalloproteinase 8 (ADAM8) play major roles in inflammatory and allergic processes in various diseases.

Aim

This study aimed to investigate ADAM8 plasma levels in autistic children compared to healthy controls. Also, to discover the association between ADAM8, disease severity, and neuroinflammation in ASD.

Methodology

This case-control study included children with ASD (n=40) and aged-matched healthy controls (n=40). The plasma levels of the ADAM 8 were determined using enzyme-linked immunosorbent assay (ELISA). The assessment of ASD severity and social and sensory behaviors were categorized as mild, moderate and severe. Correlations among ADAM8 plasma levels and ASD severity scores [Childhood Autism Rating Scale (CARS), Social Responsiveness Scale (SRS) and Short Sensory Profile (SSP)] were obtained by Spearman correlation coefficient (r).

Results

ASD children (n=40), including severe autism (n=21) and mild-to-moderate autism (n=19), showed significantly (p ≤ 0.05) lower plasma levels of ADAM8 [4683 (2885-5229); 4663 (4060-5000); 4632 (2885-5229)], respectively, than those of healthy controls [5000 (4047-5000)] [median (IQR) pg/mL]. However, there was no significant difference between the ADAM8 levels of children with severe and mild-to-moderate autism (p = 0.71). Moreover, ADAM8 plasma levels were not significantly correlated with the severity of ASD measured by behavioral scales [CARS (r= -0.11, p=0.55), SRS (r=0.11, p= 0.95), SSP (r=-0.23, p=0.23)].

Conclusion

The low ADAM8 plasma levels in children with ASD possibly indicated that ADAM8 might be implicated in the pathogenesis of ASD but not in the severity of the disease. These results should be interpreted with caution until additional studies are carried out with larger populations to decide whether the reduction in plasma ADAM8 levels is a mere consequence of ASD or if it plays a pathogenic role in the disease.

Possible Implications of Obesity-Primed Microglia that Could Contribute to Stroke-Associated Damage

Microglia, the resident macrophages of the central nervous system, are essential players during physiological and pathological processes. Although they participate in synaptic pruning and maintenance of neuronal circuits, microglia are mainly studied by their activity modulating inflammatory environment and adapting their phenotype and mechanisms to insults detected in the brain parenchyma. Changes in microglial phenotypes are reflected in their morphology, membrane markers, and secreted substances, stimulating neighbor glia and leading their responses to control stimuli. Understanding how microglia react in various microenvironments, such as chronic inflammation, made it possible to establish therapeutic windows and identify synergic interactions with acute damage events like stroke. Obesity is a low-grade chronic inflammatory state that gradually affects the central nervous system, promoting neuroinflammation development. Obese patients have the worst prognosis when they suffer a cerebral infarction due to basal neuroinflammation, then obesity-induced neuroinflammation could promote the priming of microglial cells and favor its neurotoxic response, potentially worsening patients' prognosis. This review discusses the main microglia findings in the obesity context during the course and resolution of cerebral infarction, involving the temporality of the phenotype changes and balance of pro- and anti-inflammatory responses, which is lost in the swollen brain of an obese subject. Obesity enhances proinflammatory responses during a stroke. Obesity-induced systemic inflammation promotes microglial M1 polarization and priming, which enhances stroke-associated damage, increasing M1 and decreasing M2 responses.

Looking to the Future of the Role of Macrophages and Extracellular Vesicles in Neuroinflammation in ALS

Neuroinflammation is a common pathological feature of amyotrophic lateral sclerosis (ALS). Although scientific evidence to date does not allow defining neuroinflammation as an ALS trigger, its role in exacerbating motor neuron (MNs) degeneration and disease progression is attracting research interest. Activated CNS (Central Nervous System) glial cells, proinflammatory peripheral and infiltrated T lymphocytes and monocytes/macrophages, as well as the immunoreactive molecules they release, represent the active players for the role of immune dysregulation enhancing neuroinflammation. The crosstalk between the peripheral and CNS immune cells significantly correlates with the survival of ALS patients since the modification of peripheral macrophages can downregulate inflammation at the periphery along the nerves and in the CNS. As putative vehicles for misfolded protein and inflammatory mediators between cells, extracellular vesicles (EVs) have also drawn particular attention in the field of ALS. Both CNS and peripheral immune cells release EVs, which are able to modulate the behavior of neighboring recipient cells; unfortunately, the mechanisms involved in EVs-mediated communication in neuroinflammation remain unclear. This review aims to synthesize the current literature regarding EV-mediated cell-to-cell communication in the brain under ALS, with a particular point of view on the role of peripheral macrophages in responding to inflammation to understand the biological process and exploit it for ALS management.

Lomerizine inhibits LPS-mediated neuroinflammation and tau hyperphosphorylation by modulating NLRP3, DYRK1A, and GSK3α/β

Introduction

Lomerizine is a calcium channel blocker that crosses the blood-brain barrier and is used clinically in the treatment of migraines. However, whether lomerizine is beneficial in modulating neuroinflammatory responses has not been tested yet.

Methods

To assess the potential of lomerizine for repurposing as a treatment for neuroinflammation, we investigated the effects of lomerizine on LPS-induced proinflammatory responses in BV2 microglial cells, Alzheimer's disease (AD) excitatory neurons differentiated from induced pluripotent stem cells (iPSCs), and in LPS-treated wild type mice.

Results

In BV2 microglial cells, lomerizine pretreatment significantly reduced LPS-evoked proinflammatory cytokine and NLRP3 mRNA levels. Similarly, lomerizine pretreatment significantly suppressed the increases in Iba-1, GFAP, proinflammatory cytokine and NLRP3 expression induced by LPS in wild-type mice. In addition, lomerizine posttreatment significantly decreased LPS-stimulated proinflammatory cytokine and SOD2 mRNA levels in BV2 microglial cells and/or wild-type mice. In LPS-treated wild-type mice and AD excitatory neurons differentiated from iPSCs, lomerizine pretreatment ameliorated tau hyperphosphorylation. Finally, lomerizine abolished the LPS-mediated activation of GSK3α/β and upregulation of DYRK1A, which is responsible for tau hyperphosphorylation, in wild-type mice.

Discussion

These data suggest that lomerizine attenuates LPS-mediated neuroinflammatory responses and tau hyperphosphorylation and is a potential drug for neuroinflammation- or tauopathy-associated diseases.

Brain-derived neurotrophic factor (BDNF) has direct anti-inflammatory effects on microglia

Microglia are the primary immunocompetent cells that protect the brain from environmental stressors, but can also be driven to release pro-inflammatory cytokines and induce a cytotoxic environment. Brain-derived neurotrophic factor (BDNF) is important for the regulation of plasticity, synapse formation, and general neuronal health. Yet, little is known about how BDNF impacts microglial activity. We hypothesized that BDNF would have a direct modulatory effect on primary cortical (Postnatal Day 1-3: P1-3) microglia and (Embryonic Day 16: E16) neuronal cultures in the context of a bacterial endotoxin. To this end, we found that a BDNF treatment following LPS-induced inflammation had a marked anti-inflammatory effect, reversing the release of both IL-6 and TNF-α in cortical primary microglia. This modulatory effect was transferrable to cortical primary neurons, such that LPS-activated microglial media was able produce an inflammatory effect when added to a separate neuronal culture, and again, BDNF priming attenuated this effect. BDNF also reversed the overall cytotoxic impact of LPS exposure in microglia. We speculate that BDNF can directly play a role in regulating microglia state and hence, influence microglia-neuron interactions.

Central and Peripheral Inflammation: A Common Factor Causing Addictive and Neurological Disorders and Aging-Related Pathologies

Many diseases and degenerative processes affecting the nervous system and peripheral organs trigger the activation of inflammatory cascades. Inflammation can be triggered by different environmental conditions or risk factors, including drug and food addiction, stress, and aging, among others. Several pieces of evidence show that the modern lifestyle and, more recently, the confinement associated with the COVID-19 pandemic have contributed to increasing the incidence of addictive and neuropsychiatric disorders, plus cardiometabolic diseases. Here, we gather evidence on how some of these risk factors are implicated in activating central and peripheral inflammation contributing to some neuropathologies and behaviors associated with poor health. We discuss the current understanding of the cellular and molecular mechanisms involved in the generation of inflammation and how these processes occur in different cells and tissues to promote ill health and diseases. Concomitantly, we discuss how some pathology-associated and addictive behaviors contribute to worsening these inflammation mechanisms, leading to a vicious cycle that promotes disease progression. Finally, we list some drugs targeting inflammation-related pathways that may have beneficial effects on the pathological processes associated with addictive, mental, and cardiometabolic illnesses.

Genetic insights into immune mechanisms of Alzheimer's and Parkinson's disease

Microglia, the macrophages of the brain, are vital for brain homeostasis and have been implicated in a broad range of brain disorders. Neuroinflammation has gained traction as a possible therapeutic target for neurodegeneration, however, the precise function of microglia in specific neurodegenerative disorders is an ongoing area of research. Genetic studies offer valuable insights into understanding causality, rather than merely observing a correlation. Genome-wide association studies (GWAS) have identified many genetic loci that are linked to susceptibility to neurodegenerative disorders. (Post)-GWAS studies have determined that microglia likely play an important role in the development of Alzheimer's disease (AD) and Parkinson's disease (PD). The process of understanding how individual GWAS risk loci affect microglia function and mediate susceptibility is complex. A rapidly growing number of publications with genomic datasets and computational tools have formulated new hypotheses that guide the biological interpretation of AD and PD genetic risk. In this review, we discuss the key concepts and challenges in the post-GWAS interpretation of AD and PD GWAS risk alleles. Post-GWAS challenges include the identification of target cell (sub)type(s), causal variants, and target genes. Crucially, the prediction of GWAS-identified disease-risk cell types, variants and genes require validation and functional testing to understand the biological consequences within the pathology of the disorders. Many AD and PD risk genes are highly pleiotropic and perform multiple important functions that might not be equally relevant for the mechanisms by which GWAS risk alleles exert their effect(s). Ultimately, many GWAS risk alleles exert their effect by changing microglia function, thereby altering the pathophysiology of these disorders, and hence, we believe that modelling this context is crucial for a deepened understanding of these disorders.

Neurodegeneration and inflammation crosstalk: Therapeutic targets and perspectives

Glia, which was formerly considered to exist just to connect neurons, now plays a key function in a wide range of physiological events, including formation of memory, learning, neuroplasticity, synaptic plasticity, energy consumption, and homeostasis of ions. Glial cells regulate the brain's immune responses and confers nutritional and structural aid to neurons, making them an important player in a broad range of neurological disorders. Alzheimer's, ALS, Parkinson's, frontotemporal dementia (FTD), and epilepsy are a few of the neurodegenerative diseases that have been linked to microglia and astroglia cells, in particular. Synapse growth is aided by glial cell activity, and this activity has an effect on neuronal signalling. Each glial malfunction in diverse neurodegenerative diseases is distinct, and we will discuss its significance in the progression of the illness, as well as its potential for future treatment.

Neuroinflammation in Alzheimer's disease: microglial signature and their relevance to disease

Alzheimer's disease (AD) is the most common form of dementia, pathologically characterized by senile plaques and neurofibrillary tangles (NFTs), resulting in neurodegeneration. Neuroinflammation, defined as the activation of glial cells such as microglia and astrocytes, is observed surrounding senile plaques and affected neurons in AD. Recently conducted genome-wide association studies (GWAS) indicate that a large section of identified AD risk genes are involved in immune responses and are enriched in microglia. Microglia are innate immune cells in the central nervous system (CNS), which are involved in immune surveillance and maintenance of homeostasis in the CNS. Recently, a novel subpopulation of activated microglia named as disease-associated microglia (DAM), also known as activated response microglia (ARM) or microglial neurodegenerative phenotype (MGnD), was identified in AD model mice. These microglia closely associate with β-amyloid (Aβ) plaques and exhibit characteristic gene expression profiles accompanied with reduced expressions of homeostatic microglial genes. However, it remains unclear whether decreased homeostatic microglia functions or increased DAM/ARM/MGnD functions correlate with the degree of neuronal loss in AD. To translate the results of rodent studies to human AD, precuneus, the brain region vulnerable to β-amyloid accumulation in preclinical AD, is of high interest, as it can provide novel insights into the mechanisms of microglia response to Aβ in early AD. In this study, we performed comparative analyses of gene expression profiles of microglia among three representative neurodegenerative mouse models and the human precunei with early AD pathology. We proceeded to evaluate the identified genes as potential therapeutic targets for AD. We believe that our findings will provide important resources to better understand the role of glial dysfunction in AD.

Modulation of gut microbiota alleviates cerebral ischemia/reperfusion injury in rats by inhibiting M1 polarization of microglia

Gut microbiota affects the gut-brain axis; hence, the modulation of the microbiota has been proposed as a potential therapeutic strategy for cerebral ischemia/reperfusion injury (CIRI). However, the role and mechanism of the gut microbiota in regulating microglial polarization during CIRI remain poorly understood. Herein, using a middle cerebral artery occlusion and reperfusion (MCAO/R) rat model, we evaluated changes in the gut microbiota after CIRI and the potential effects of fecal microbiota transplant (FMT) on the brain. Rats underwent either MCAO/R or sham surgery, and then they received FMT (started 3 days later; continued for 10 days). 2,3,5-Triphenyltetrazolium chloride staining, neurological outcome scale, and Fluoro-Jade C staining showed that MCAO/R induced cerebral infarction, neurological deficits, and neuronal degeneration. In addition, immunohistochemistry or real-time PCR assay showed increased expression levels of M1-macrophage markers-TNF-α, IL-1β, IL-6, and iNOS-in the rats following MCAO/R. Our finding suggests that microglial M1 polarization is involved in CIRI. 16 S ribosomal RNA gene sequencing data revealed an imbalance in the gut microbiota of MCAO/R animals. In contrast, FMT reversed this MCAO/R-induced imbalance in the gut microbiota and ameliorated nerve injury. In addition, FMT prevented the upregulation in the ERK and NF-κB pathways, which reversed the M2-to-M1 microglial shift 10 days after MCAO/R injury in rats. Our primary data showed that the modulation of the gut microbiota can attenuate CIRI in rats by inhibiting microglial M1 polarization through the ERK and NF-κB pathways. However, an understanding of the underlying mechanism requires further study.

Optimization and evaluation of pyridinyl vinyl sulfones as Nrf2 activator for the antioxidant and anti-inflammatory effects

Many studies have reported that chalcone-based compounds exhibit biological activities such as anticancer, antioxidant, anti-inflammatory and neuroprotective effects. Among the published chalcone derivatives, (E)-1-(3-methoxypyridin-2-yl)-3-(2-(trifluoromethyl)phenyl)prop-2-en-1-one (VEDA-1209), which is currently undergoing preclinical study, was selected as a starting compound for the development of new nuclear factor erythroid 2-related factor 2 (Nrf2) activators. Based on our previous knowledge, we attempted to redesign and synthesize VEDA-1209 derivatives by introducing the pyridine ring and sulfone moiety to ameliorate its Nrf2 efficacy and drug-like properties. Among the synthesized compounds, (E)-3-chloro-2-(2-((3-methoxypyridin-2-yl)sulfonyl)vinyl) pyridine (10e) was found to have approximately 16-folds higher Nrf2 activating effects than VEDA-1209 (10e: EC₅₀ = 37.9 nM vs VEDA-1209: EC₅₀ = 625 nM) in functional cell-based assay. In addition, 10e effectively improved drug-like properties such as CYP inhibition probability and metabolic stability. Finally, 10e demonstrated excellent antioxidant and anti-inflammatory effects in BV-2 microglial cells and significantly restored spatial memory deficits in lipopolysaccharide (LPS)-induced neuroinflammatory mouse models.

NLRP3 Inflammasome-Mediated Neuroinflammation and Related Mitochondrial Impairment in Parkinson's Disease

Parkinson's disease (PD) is a common neurodegenerative disorder caused by the loss of dopamine neurons in the substantia nigra and the formation of Lewy bodies, which are mainly composed of alpha-synuclein fibrils. Alpha-synuclein plays a vital role in the neuroinflammation mediated by the nucleotide-binding oligomerization domain-, leucine-rich repeat-, and pyrin domain-containing protein 3 (NLRP3) inflammasome in PD. A better understanding of the NLRP3 inflammasome-mediated neuroinflammation and the related mitochondrial impairment during PD progression may facilitate the development of promising therapies for PD. This review focuses on the molecular mechanisms underlying NLRP3 inflammasome activation, comprising priming and protein complex assembly, as well as the role of mitochondrial impairment and its subsequent inflammatory effects on the progression of neurodegeneration in PD. In addition, the therapeutic strategies targeting the NLRP3 inflammasome for PD treatment are discussed, including the inhibitors of NLRP3 inflammatory pathways, mitochondria-focused treatments, microRNAs, and other therapeutic compounds.

Associations Between Systemic and Cerebral Inflammation in an Ovine Model of Cardiopulmonary Bypass

BACKGROUND

Intraoperative inflammation may contribute to postoperative neurocognitive disorders after cardiac surgery requiring cardiopulmonary bypass (CPB). However, the relative contributions of general anesthesia (GA), surgical site injury, and CPB are unclear.

METHODS

In adult female sheep, we investigated (1) the temporal profile of proinflammatory and anti-inflammatory cytokines and (2) the extent of microglia activation across major cerebral cortical regions during GA and surgical trauma with and without CPB (N = 5/group). Sheep were studied while conscious, during GA and surgical trauma, with and without CPB.

RESULTS

Plasma tumor necrosis factor-alpha (mean [95% confidence intervals], 3.7 [2.5-4.9] vs 1.6 [0.8-2.3] ng/mL; P = .0004) and interleukin-6 levels (4.4 [3.0-5.8] vs 1.6 [0.8-2.3] ng/mL; P = .029) were significantly higher at 1.5 hours, with a further increase in interleukin-6 at 3 hours (7.0 [3.7-10.3] vs 1.8 [1.1-2.6] ng/mL; P < .0001) in animals undergoing CPB compared with those that did not. Although cerebral oxygen saturation was preserved throughout CPB, there was pronounced neuroinflammation as characterized by greater microglia circularity within the frontal cortex of sheep that underwent CPB compared with those that did not (0.34 [0.32-0.37] vs 0.30 [0.29-0.32]; P = .029). Moreover, microglia had fewer branches within the parietal (7.7 [6.5-8.9] vs 10.9 [9.4-12.5]; P = .001) and temporal (7.8 [7.2-8.3] vs 9.9 [8.2-11.7]; P = .020) cortices in sheep that underwent CPB compared with those that did not.

CONCLUSIONS

CPB enhanced the release of proinflammatory cytokines beyond that initiated by GA and surgical trauma. This systemic inflammation was associated with microglial activation across 3 major cerebral cortical regions, with a phagocytic microglia phenotype within the frontal cortex, and an inflammatory microglia phenotype within the parietal and temporal cortices. These data provide direct histopathological evidence of CPB-induced neuroinflammation in a large animal model and provide further mechanistic data on how CPB-induced cerebral inflammation might drive postoperative neurocognitive disorders in humans.

A review of cytokine-based pathophysiology of Long COVID symptoms

The Long COVID/Post Acute Sequelae of COVID-19 (PASC) group includes patients with initial mild-to-moderate symptoms during the acute phase of the illness, in whom recovery is prolonged, or new symptoms are developed over months. Here, we propose a description of the pathophysiology of the Long COVID presentation based on inflammatory cytokine cascades and the p38 MAP kinase signaling pathways that regulate cytokine production. In this model, the SARS-CoV-2 viral infection is hypothesized to trigger a dysregulated peripheral immune system activation with subsequent cytokine release. Chronic low-grade inflammation leads to dysregulated brain microglia with an exaggerated release of central cytokines, producing neuroinflammation. Immunothrombosis linked to chronic inflammation with microclot formation leads to decreased tissue perfusion and ischemia. Intermittent fatigue, Post Exertional Malaise (PEM), CNS symptoms with "brain fog," arthralgias, paresthesias, dysautonomia, and GI and ophthalmic problems can consequently arise as result of the elevated peripheral and central cytokines. There are abundant similarities between symptoms in Long COVID and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). DNA polymorphisms and viral-induced epigenetic changes to cytokine gene expression may lead to chronic inflammation in Long COVID patients, predisposing some to develop autoimmunity, which may be the gateway to ME/CFS.

Investigating TSPO levels in occupation-related posttraumatic stress disorder

Microglia are immune brain cells implicated in stress-related mental illnesses including posttraumatic stress disorder (PTSD). Their role in the pathophysiology of PTSD, and on neurobiological systems that regulate stress, is not completely understood. We tested the hypothesis that microglia activation, in fronto-limbic brain regions involved in PTSD, would be elevated in participants with occupation-related PTSD. We also explored the relationship between cortisol and microglia activation. Twenty participants with PTSD and 23 healthy controls (HC) completed positron emission tomography (PET) scanning of the 18-kDa translocator protein (TSPO), a putative biomarker of microglia activation using the probe [18F]FEPPA, and blood samples for measurement of cortisol. [18F]FEPPA VT was non-significantly elevated (6.5-30%) in fronto-limbic regions in PTSD participants. [18F]FEPPA VT was significantly higher in PTSD participants reporting frequent cannabis use compared to PTSD non-users (44%, p = 0.047). Male participants with PTSD (21%, p = 0.094) and a history of early childhood trauma (33%, p = 0.116) had non-significantly higher [18F]FEPPA VT. Average fronto-limbic [18F]FEPPA VT was positively related to cortisol (r = 0.530, p = 0.028) in the PTSD group only. Although we did not find a significant abnormality in TSPO binding in PTSD, findings suggest microglial activation might have occurred in a subgroup who reported frequent cannabis use. The relationship between cortisol and TSPO binding suggests a potential link between hypothalamic-pituitary-adrenal-axis dysregulation and central immune response to trauma which warrants further study.

Effects of Caloric Restriction on Spatial Object Recognition Memory, Hippocampal Neuron Loss and Neuroinflammation in Aged Rats

Age-related neurobiological changes significantly affect hippocampal structure and function, such that the main cognitive impairments associated with aging are related to the integrity of this brain structure, including the deterioration in spatial object recognition (SOR) memory. Previous studies have shown that intrinsic factors such as neuroinflammation, as well as lifestyle factors such as diet, can affect aging-associated brain functions and cognitive performance. In this regard, caloric restriction (CR) produces beneficial effects on health and life expectancy, although its ability to slow down age-dependent effects on cognitive decline and hippocampus (HPC) functioning remains unclear. Therefore, we set out to evaluate the effects of CR on SOR memory in aged male Wistar rats, as well as those on hippocampal neuron loss, neurogenesis and inflammation. The data show that CR in aged rats attenuates the decline in SOR memory, age-associated hippocampal neuron loss, and age-dependent microglial activation. Furthermore, we found a significant reduction in neurogenesis in the dentate gyrus of the old animals relative to adult rats. These findings support the positive effect of CR on SOR memory, suggesting that it dampens hippocampal neuronal loss and reduces proinflammatory activity.

Astrocyte-associated fibronectin promotes the proinflammatory phenotype of astrocytes through β1 integrin activation

Astrocytes are key players in neuroinflammation. In response to central nervous system (CNS) injury or disease, astrocytes undergo reactive astrogliosis, which is characterized by increased proliferation, migration, and glial fibrillary acidic protein (GFAP) expression. Activation of the transcription factor nuclear factor-κB (NF-κB) and upregulation of downstream proinflammatory mediators in reactive astrocytes induce a proinflammatory phenotype in astrocytes, thereby exacerbating neuroinflammation by establishing an inflammatory loop. In this study, we hypothesized that excessive fibronectin (FN) derived from reactive astrocytes would induce this proinflammatory phenotype in astrocytes in an autocrine manner. We exogenously treated astrocytes with monomer FN, which can be incorporated into the extracellular matrix (ECM), to mimic plasma FN extravasated through a compromised blood-brain barrier in neuroinflammation. We also induced de novo synthesis and accumulation of astrocyte-derived FN through tumor necrosis factor-α (TNF-α) stimulation. The excessive FN deposition resulting from both treatments initiated reactive astrogliosis and triggered NF-κB signaling in the cultured astrocytes. In addition, inhibition of FN accumulation in the ECM by the FN inhibitor pUR4 strongly attenuated the FN- and TNF-α-induced GFAP expression, NF-κB activation, and proinflammatory mediator production of astrocytes by interrupting FN-β1 integrin coupling and thus the inflammatory loop. In an in vivo experiment, intrathecal injection of pUR4 considerably ameliorated FN deposition, GFAP expression, and NF-κB activation in inflamed spinal cord, suggesting the therapeutic potential of pUR4 for attenuating neuroinflammation and promoting neuronal function restoration.

Real-time mechanisms of exacerbated synaptic remodeling by microglia in acute models of systemic inflammation and tauopathy

Remodeling of synapses by microglia is essential for synaptic plasticity in the brain. However, during neuroinflammation and neurodegenerative diseases, microglia can induce excessive synaptic loss, although the precise underlying mechanisms are unknown. To directly observe microglia-synapse interactions under inflammatory conditions, we performed in vivo two-photon time-lapse imaging of microglia-synapse interactions after bacterial lipopolysaccharide administration to model systemic inflammation, or after inoculation of Alzheimer's disease (AD) brain extracts to model disease-associated neuroinflammatory microglial response. Both treatments prolonged microglia-neuron contacts, decreased basal surveillance of synapses and promoted synaptic remodeling in response to synaptic stress induced by focal single-synapse photodamage. Spine elimination correlated with the expression of microglial complement system/phagocytic proteins and the occurrence of synaptic filopodia. Microglia were observed contacting spines, then stretching and phagocytosing spine head filopodia. Thus, in response to inflammatory stimuli microglia exacerbated spine remodeling through prolonged microglial contact and elimination of spines 'tagged' by synaptic filopodia.

KDM4A, involved in the inflammatory and oxidative stress caused by traumatic brain injury-hemorrhagic shock, partly through the regulation of the microglia M1 polarization

BACKGROUND

Microglial polarization and the subsequent neuroinflammatory response and oxidative stress are contributing factors for traumatic brain injury (TBI) plus hemorrhagic shock (HS) induced brain injury. In the present work, we have explored whether Lysine (K)-specific demethylase 4 A (KDM4A) modulates microglia M1 polarization in the TBI and HS mice.

RESULTS

Male C57BL/6J mice were used to investigate the microglia polarization in the TBI + HS model in vivo. Lipopolysaccharide (LPS)-induced BV2 cells were used to examine the mechanism of KDM4A in regulating microglia polarization in vitro. We found that TBI + HS resulted in neuronal loss and microglia M1 polarization in vivo, reflected by the increased level of Iba1, tumor necrosis factor (TNF)-α, interleukin (IL)-1β, malondialdehyde (MDA) and the decreased level of reduced glutathione (GSH). Additionally, KDM4A was upregulated in response to TBI + HS and microglia were among the cell types showing the increased level of KDM4A. Similar to the results in vivo, KDM4A also highly expressed in LPS-induced BV2 cells. LPS-induced BV2 cells exhibited enhanced microglia M1 polarization, and enhanced level of pro-inflammatory cytokines, oxidative stress and reactive oxygen species (ROS), while this enhancement was abolished by the suppression of KDM4A.

CONCLUSION

Accordingly, our findings indicated that KDM4A was upregulated in response to TBI + HS and microglia were among the cell types showing the increased level of KDM4A. The important role of KDM4A in TBI + HS-induced inflammatory response and oxidative stress was at least partially realized through regulating microglia M1 polarization.

Intracellular DAMPs in Neurodegeneration and Their Role in Clinical Therapeutics

Neuroinflammation is the major implication of neurodegeneration. This is a complex process which initiates from the cellular injury triggering the innate immune system which gives rise to damage-associated molecular patterns (DAMPs) which are also recognized as endogenous danger indicators. These originate from various compartments of the cell under pathological stimulus. These are very popular candidates having their origin in the intracellular compartments and organelles of the cell and may have their site of action itself in the intracellular or at the extracellular spaces. Under the influence of the pathological stimuli, they interact with the pattern-recognition receptor to initiate their pro-inflammatory cascade followed by the cytokine release. This provides a good opportunity for diagnostic and therapeutic interventions creating better conditions for repair and reversal. Since the major contributors arise from the intracellular compartment, in this review, we have attempted to focus on the DAMP molecules arising from the intracellular compartments and their specific roles in the neurodegenerative events explaining their downstream mediators and signaling. Moreover, we have tried to cover the latest interventions in terms of DAMPs as clinical biomarkers which can assist in detecting the disease and also target it to reduce the innate-immune activation response which can help in reducing the sterile neuroinflammation having an integral role in the neurodegenerative processes.