Emerging roles of Dectin-1 in noninfectious settings and in the CNS

The progress and future of the treatment of Candida albicans infections based on nanotechnology

Systemic infection with Candida albicans poses a significant risk for people with weakened immune systems and carries a mortality rate of up to 60%. However, current therapeutic options have several limitations, including increasing drug tolerance, notable off-target effects, and severe adverse reactions. Over the past four decades, the progress in developing drugs to treat Candida albicans infections has been sluggish. This comprehensive review addresses the limitations of existing drugs and summarizes the efforts made toward redesigning and innovating existing or novel drugs through nanotechnology. The discussion explores the potential applications of nanomedicine in Candida albicans infections from four perspectives: nano-preparations for anti-biofilm therapy, innovative formulations of "old drugs" targeting the cell membrane and cell wall, reverse drug resistance therapy targeting subcellular organelles, and virulence deprivation therapy leveraging the unique polymorphism of Candida albicans. These therapeutic approaches are promising to address the above challenges and enhance the efficiency of drug development for Candida albicans infections. By harnessing nano-preparation technology to transform existing and preclinical drugs, novel therapeutic targets will be uncovered, providing effective solutions and broader horizons to improve patient survival rates.

Yeast β-glucan promotes antiviral type I interferon response via dectin-1

Pseudorabies virus (PRV), an alphaherpesvirus, is a neglected zoonotic pathogen. Dectin-1 sensing of β-glucan (BG) induces trained immunity, which can possibly form a new strategy for the prevention of viral infection. However, alphaherpesvirus including PRV have received little to no investigation in the context of trained immunity. Here, we found that BG pretreatment improved the survival rate, weight loss outcomes, alleviated histological injury and decreased PRV copy number of tissues in PRV-infected mice. Type I interferons (IFNs) including IFN-α/β levels in serum were significantly increased by BG. However, these effects were abrogated in the presence of Dectin-1 antagonist. Dectin-1-mediated effect of BG was also confirmed in porcine and murine macrophages. These results suggested that BG have effects on type I IFNs with antiviral property involved in Dectin-1. In piglets, oral or injected immunization with BG and PRV vaccine could significantly elevated the level of PRV-specific IgG and type I IFNs. And it also increased the antibody levels of porcine reproductive and respiratory syndrome virus vaccine and classical swine fever vaccine that were later immunized, indicating a broad-spectrum effect on improving vaccine immunity. On the premise that the cost was greatly reducing, the immunological effect of oral was better than injection administration. Our findings highlighted that BG induced type I IFNs related antiviral effect against PRV involved in Dectin-1 and potential application value as a feed additive to help control the spread of PRV and future emerging viruses.

Neuroimmune cell interactions and chronic infections in oral cancers

Inflammation is a process that is associated with the activation of distal immunosuppressive pathways that have evolved to restore homeostasis and prevent excessive tissue destruction. However, long-term immunosuppression resulting from systemic and local inflammation that may stem from dysbiosis, infections, or aging poses a higher risk for cancers. Cancer incidence and progression dramatically increase with chronic infections including HIV infection. Thus, studies on pro-tumorigenic effects of microbial stimulants from resident microbiota and infections in the context of inflammation are needed and underway. Here, we discuss chronic infections and potential neuro-immune interactions that could establish immunomodulatory programs permissive for tumor growth and progression.

Genetic variants of dectin-1 and their antifungal immunity impact in hematologic malignancies: A comprehensive systematic review

BACKGROUND

Fungal infections pose a significant threat to individuals with hematologic malignancies due to compromised immune systems. Dectin-1, a pivotal pattern recognition receptor, plays a central role in antifungal immune responses. Understanding its genetic variants' impact is crucial for advancing personalized therapeutic approaches.

METHODS

Employing systematic review methods, studies were meticulously selected and assessed for relevance. Data extraction encompassed Dectin-1 genetic variants, antifungal immune responses, and disease outcomes.

RESULTS

Findings unveiled a complex relationship between Dectin-1 genetic variants and antifungal immunity in hematologic malignancies. Variable associations emerged, influencing susceptibility to fungal infections and disease prognosis. Moreover, implications for treatment outcomes were explored, suggesting potential avenues for tailored interventions.

CONCLUSIONS

This systematic review underscores the need for further investigation into the precise influence of Dectin-1 genetic variants on antifungal immunity and disease progression in hematologic malignancies. Insights gained could pave the way for personalized therapeutic strategies, optimizing infection prevention and malignancy management. By delving into the intricate connections between genetic nuances, immune responses, and clinical trajectories, this review contributes to the ongoing discourse surrounding hematologic malignancies, fungal infections, and their multifaceted interplay.

Lentinan progress in inflammatory diseases and tumor diseases

Shiitake mushrooms are a fungal food that has been recorded in Chinese medicine to nourish the blood and qi. Lentinan (lLNT) is an active substance extracted from shiitake mushrooms with powerful antioxidant, anti-inflammatory, anti-tumor functions. Inflammatory diseases and cancers are the leading causes of death worldwide, posing a serious threat to human life and health and posing enormous challenges to global health systems. There is still a lack of effective treatments for inflammatory diseases and cancer. LNT has been approved as an adjunct to chemotherapy in China and Japan. Studies have shown that LNT plays an important role in the treatment of inflammatory diseases as well as oncological diseases. Moreover, clinical experiments have confirmed that LNT combined with chemotherapy drugs has a significant effect in improving the prognosis of patients, enhancing their immune function and reducing the side effects of chemotherapy in lung cancer, colorectal cancer and gastric cancer. However, the relevant mechanism of action of the LNT signaling pathway in inflammatory diseases and cancer. Therefore, this article reviews the mechanism and clinical research of LNT in inflammatory diseases and tumor diseases in recent years.

Microglia in Neurodegenerative Diseases

Neurodegenerative diseases are manifested by a progressive death of neural cells, resulting in the deterioration of central nervous system (CNS) functions, ultimately leading to specific behavioural and cognitive symptoms associated with affected brain regions. Several neurodegenerative disorders are caused by genetic variants or mutations, although the majority of cases are sporadic and linked to various environmental risk factors, with yet an unknown aetiology. Neuroglial changes are fundamental and often lead to the pathophysiology of neurodegenerative diseases. In particular, microglial cells, which are essential for maintaining CNS health, become compromised in their physiological functions with the exposure to environmental risk factors, genetic variants or mutations, as well as disease pathology. In this chapter, we cover the contribution of neuroglia, especially microglia, to several neurodegenerative diseases, including Nasu-Hakola disease, Parkinson's disease, amyotrophic lateral sclerosis, Alzheimer's disease, Huntington's disease, infectious disease-associated neurodegeneration, and metal-precipitated neurodegeneration. Future research perspectives for the field pertaining to the therapeutic targeting of microglia across these disease conditions are also discussed.

Dectin1 contributes to hypertensive vascular injury by promoting macrophage infiltration through activating the Syk/NF-κB pathway

Vascular injury is an early manifestation leading to end-organ damage in hypertension pathogenesis, which involves a macrophage-associated immune response. Dendritic cell-associated C-type lectin-1 (Dectin1) is a pivotal player in regulating inflammation-mediated cardiovascular disease. However, its role in hypertension-induced vascular damage and the underlying mechanisms remain unclear. We hypothesized that Dectin1 might accelerate angiotensin II (Ang II)- or deoxycorticosterone acetate-salt (DOCA-salt)-induced vascular injury through proinflammatory actions in macrophages. Macrophage Dectin1 was upregulated in mouse aortic tissues stimulated with Ang II. In the peripheral blood, Ang II also increased CD11b+F4/80+ macrophages in mice. In our constructed Dectin1 knockout mice, Dectin1 deletion protected against Ang II-induced EB extravasation and aortic wall thickness. Deficiency of Dectin1 or its pharmacological inhibition considerably improved fibrosis and inflammation responses, accompanied by a reduction in M1 macrophage polarization as well as proinflammatory cytokines and chemokines induced by Ang II or DOCA-salt. Through the bone marrow (BM) transplantation assay, these effects were verified in the wild type mice reconstituted with Dectin1-deficient BM cells. Mechanistically, Ang II promoted Dectin1 homodimerization, thereby triggering the spleen tyrosine kinase/nuclear factor kappa B pro-inflammatory cascade to induce the expression of inflammatory factors and chemokines in vivo and in vitro. In conclusion, Dectin1 has an essential role in the pathogenic procedure of Ang II-stimulated or DOCA-salt-induced vascular damage in mice and represents a promising therapeutic target for cardiovascular diseases.

Roles in Innate Immunity

Microglia are best known as the resident phagocytes of the central nervous system (CNS). As a resident brain immune cell population, microglia play key roles during the initiation, propagation, and resolution of inflammation. The discovery of resident adaptive immune cells in the CNS has unveiled a relationship between microglia and adaptive immune cells for CNS immune-surveillance during health and disease. The interaction of microglia with elements of the peripheral immune system and other CNS resident cells mediates a fine balance between neuroprotection and tissue damage. In this chapter, we highlight the innate immune properties of microglia, with a focus on how pattern recognition receptors, inflammatory signaling cascades, phagocytosis, and the interaction between microglia and adaptive immune cells regulate events that initiate an inflammatory or neuroprotective response within the CNS that modulates immune-mediated disease exacerbation or resolution.

Identification of Clec7a as the therapeutic target of rTMS in alleviating Parkinson's disease: targeting neuroinflammation

Parkinson's disease (PD) is a neurodegenerative disease. Repetitive transcranial magnetic stimulation (rTMS) is a therapeutic tool in PD. High-throughput sequencing was performed to screen potential therapeutic targets in unilaterally 6-hydroxydopamine (6-OHDA)-lesioned rats. The candidate gene, Clec7a, was screened out and validated. Clec7a is a pattern recognition receptor involved in neuroinflammation. The higher expression of Clec7a was observed in the substantia nigra (SN) and striatum of PD rats with dopaminergic neurons damage and was mainly localized in the microglial. Adeno-associated virus (AAV)-mediated specific knockdown of Clec7a in microglial alleviated 6-OHDA induced motor deficits and nigrostriatal dopaminergic neuron damage of rats, as evidenced by the increase of tyrosine hydroxylase (TH) -positive neurons in SN, as well as dopaminergic nerve fibers in the striatum. Clec7a knockdown restrained the neuroinflammation by suppressing inflammatory factors (IFN-γ, TNF-α, IL-1β, IL-18, and IL-6) release in SN, which might result from enhanced Arg-1 expression (M2 polarization) and defective inducible nitric oxide synthase (iNOS) expression (M1 polarization). The same phenomena were also observed in the LPS inflammatory rat model of PD. In vitro, α-synuclein fibrils induced upregulation of Clec7a expression and microglia polarization to a pro-inflammatory state of BV2 cells, leading to increased release of cytokines. However, Clec7a knockdown reversed those changes and induced a shift to an anti-inflammatory phenotype in BV2 cells. In conclusion, our study suggested that Clec7a was involved in PD pathogenesis, and its inhibition might protect rats from PD by depressing neuroinflammation through microglial polarization.

Clec7a drives gut fungus-mediated host lipid deposition

BACKGROUND

Compared to that of bacteria, the role of gut fungi in obesity development remains unknown.

RESULTS

Here, alterations in gut fungal biodiversity and composition were confirmed in obese pig models and high-fat diet (HFD)-fed mice. Antifungal drugs improved diet-induced obesity, while fungal reconstruction by cohousing or fecal microbiota transplantation maintained the obese phenotype in HFD-fed mice. Fungal profiling identified 5 fungal species associated with obesity. Specifically, Ascomycota_sp. and Microascaceae_sp. were reduced in obese mice and negatively correlated with fat content. Oral supplementation with fungi was sufficient to prevent and treat diet-induced obesity. Clec7a, which is involved in fungal recognition, was highly expressed in HFD-fed mice. The Clec7a agonist accelerated diet-induced obesity, while Clec7a deficieny in mice resulted in resistance to diet-induced obesity and blocked the anti-obese effect of antifungal drugs and fungi.

CONCLUSIONS

Taken together, these results indicate that gut fungi/Clec7a signaling is involved in diet-induced obesity and may have therapeutic implications as a biomarker for metabolic dysregulation in humans. Video Abstract.

CD11c is not required by microglia to convey neuroprotection after prion infection

Prion diseases are caused by the misfolding of a normal host protein that leads to gliosis, neuroinflammation, neurodegeneration, and death. Microglia have been shown to be critical for neuroprotection during prion infection of the central nervous system (CNS), and their presence extends survival in mice. How microglia impart these benefits to the infected host are unknown. Previous transcriptomics and bioinformatics studies suggested that signaling through the heterodimeric integrin receptor CD11c/CD18, expressed by microglia in the brain, might be important to microglial function during prion disease. Herein, we intracerebrally challenged CD11c-/- mice with prion strain RML and compared them to similarly infected C57BL/6 mice as controls. We initially assessed changes in the brain that are associated with disease such as astrogliosis, microgliosis, prion accumulation, and survival. Targeted qRT-PCR arrays were used to determine alterations in transcription in mice in response to prion infection. We demonstrate that expression of Itgax (CD11c) and Itgb2 (CD18) increases in the CNS in correlation with advancing prion infection. Gliosis, neuropathology, prion deposition, and disease progression in prion infected CD11c deficient mice were comparable to infected C57BL/6 mice. Additionally, both CD11c deficient and C57BL/6 prion-infected mouse cohorts had a similar consortium of inflammatory- and phagocytosis-associated genes that increased as disease progressed to clinical stages. Ingenuity Pathway Analysis of upregulated genes in infected C57BL/6 mice suggested numerous cell-surface transmembrane receptors signal through Spleen Tyrosine Kinase, a potential key regulator of phagocytosis and innate immune activation in the prion infected brain. Ultimately, the deletion of CD11c did not influence prion pathogenesis in mice and CD11c signaling is not involved in the neuroprotection provided by microglia, but our analysis identified a conspicuous phagocytosis pathway in the CNS of infected mice that appeared to be activated during prion pathogenesis.

Differential expression of genes involved in the chronic response to intracortical microelectrodes

Brain-Machine Interface systems (BMIs) are clinically valuable devices that can provide functional restoration for patients with spinal cord injury or improved integration for patients requiring prostheses. Intracortical microelectrodes can record neuronal action potentials at a resolution necessary for precisely controlling BMIs. However, intracortical microelectrodes have a demonstrated history of progressive decline in the recording performance with time, inhibiting their usefulness. One major contributor to decreased performance is the neuroinflammatory response to the implanted microelectrodes. The neuroinflammatory response can lead to neurodegeneration and the formation of a glial scar at the implant site. Historically, histological imaging of relatively few known cellular and protein markers has characterized the neuroinflammatory response to implanted microelectrode arrays. However, neuroinflammation requires many molecular players to coordinate the response - meaning traditional methods could result in an incomplete understanding. Taking advantage of recent advancements in tools to characterize the relative or absolute DNA/RNA expression levels, a few groups have begun to explore gene expression at the microelectrode-tissue interface. We have utilized a custom panel of ∼813 neuroinflammatory-specific genes developed with NanoString for bulk tissue analysis at the microelectrode-tissue interface. Our previous studies characterized the acute innate immune response to intracortical microelectrodes. Here we investigated the gene expression at the microelectrode-tissue interface in wild-type (WT) mice chronically implanted with nonfunctioning probes. We found 28 differentially expressed genes at chronic time points (4WK, 8WK, and 16WK), many in the complement and extracellular matrix system. Further, the expression levels were relatively stable over time. Genes identified here represent chronic molecular players at the microelectrode implant sites and potential therapeutic targets for the long-term integration of microelectrodes. STATEMENT OF SIGNIFICANCE: Intracortical microelectrodes can record neuronal action potentials at a resolution necessary for the precise control of Brain-Machine Interface systems (BMIs). However, intracortical microelectrodes have a demonstrated history of progressive declines in the recording performance with time, inhibiting their usefulness. One major contributor to the decline in these devices is the neuroinflammatory response against the implanted microelectrodes. Historically, neuroinflammation to implanted microelectrode arrays has been characterized by histological imaging of relatively few known cellular and protein markers. Few studies have begun to develop a more in-depth understanding of the molecular pathways facilitating device-mediated neuroinflammation. Here, we are among the first to identify genetic pathways that could represent targets to improve the host response to intracortical microelectrodes, and ultimately device performance.

C-type lectin receptor Dectin-1 blockade on tumour-associated macrophages improves anti-PD-1 efficacy in gastric cancer

BACKGROUND

This study aimed to investigate the expression and clinical significance of Dendritic cell-associated C-type lectin-1 (Dectin-1) in gastric cancer (GC), and to explore the mechanism of Dectin-1 regulating tumour-associated macrophage (TAM)-mediated immune evasion in GC.

METHODS

The association of Dectin-1+ cells with clinical outcomes was inspected by immunohistochemistry on tumour microarrays. Flow cytometry and RNA sequencing were applied to detect characteristics of T cells, phenotypic and transcriptional features of Dectin-1+ TAMs. The effect of Dectin-1 blockade was evaluated using an in vitro intervention experiment based on fresh GC tissues.

RESULTS

High infiltration of intratumoral Dectin-1+ cells predicted poor prognosis in GC patients. Dectin-1+ cells were mainly composed of TAMs, and the accumulation of Dectin-1+ TAMs was associated with T-cell dysfunction. Notably, Dectin-1+ TAMs exhibited an immunosuppressive phenotype. Furthermore, blockade of Dectin-1 could reprogramme Dectin-1+ TAMs and reactivate anti-tumour effects of T cells, as well as enhanced PD-1 inhibitor-mediated cytotoxicity of CD8+ T cells against tumour cells.

CONCLUSIONS

Dectin-1 could affect T-cell anti-tumour immune response by regulating the immunosuppressive function of TAMs, leading to poor prognosis and immune evasion in GC patients. Blockade of Dectin-1 can be used alone or in combination with current therapeutic strategies in GC.

Dectin-1 stimulation promotes a distinct inflammatory signature in the setting of HIV-infection and aging

Dectin-1 is an innate immune receptor that recognizes and binds β-1, 3/1, 6 glucans on fungi. We evaluated Dectin-1 function in myeloid cells in a cohort of HIV-positive and HIV-negative young and older adults. Stimulation of monocytes with β-D-glucans induced a pro-inflammatory phenotype in monocytes of HIV-infected individuals that was characterized by increased levels of IL-12, TNF-α, and IL-6, with some age-associated cytokine increases also noted. Dendritic cells showed a striking HIV-associated increase in IFN-α production. These increases in cytokine production paralleled increases in Dectin-1 surface expression in both monocytes and dendritic cells that were noted with both HIV and aging. Differential gene expression analysis showed that HIV-positive older adults had a distinct gene signature compared to other cohorts characterized by a robust TNF-α and coagulation response (increased at baseline), a persistent IFN-α and IFN-γ response, and an activated dendritic cell signature/M1 macrophage signature upon Dectin-1 stimulation. Dectin-1 stimulation induced a strong upregulation of MTORC1 signaling in all cohorts, although increased in the HIV-Older cohort (stimulation and baseline). Overall, our study demonstrates that the HIV Aging population has a distinct immune signature in response to Dectin-1 stimulation. This signature may contribute to the pro-inflammatory environment that is associated with HIV and aging.

β-amyloid binds to microglia Dectin-1 to induce inflammatory response in the pathogenesis of Alzheimer's disease

Microglia-mediated neuroinflammation is closely related to the development of Alzheimer's disease (AD). In the early stages of the inflammation response, pattern recognition receptors (PRRs) play a key role in clearing damaged cells and defending against infection by recognizing endogenous and exogenous ligands. However, the regulation of pathogenic microglial activation and its role in AD pathology remains poorly understood. Here we showed that a pattern recognition receptor called Dectin-1, expressed on microglia, mediates the pro-inflammatory responses of beta-amyloid (Aβ). Knockout of Dectin-1 reduced Aβ1-42 (Aβ42)-induced microglial activation, inflammatory responses, and synaptic and cognitive deficits in Aβ42-infused AD mice. Similar results were obtained in the BV2 cell model. Mechanistically, we showed that Aβ42 could directly bind to Dectin-1, causing Dectin-1 homodimerization and activating downstream spleen tyrosine kinase (Syk)/nuclear factor-κB (NF-κB) signaling pathway to induce the expression of inflammatory factors and, in turn, AD pathology. These results suggest the important role of microglia Dectin-1 as a new direct receptor for Aβ42 in microglial activation and AD pathology and provide a potential therapeutic strategy for neuroinflammation in AD.

Succinoglycan riclin relieves UVB-induced skin injury with anti-oxidant and anti-inflammatory properties

Excessive UVB exposure increases the production of reactive oxygen species (ROS), which causes oxidative damage and epidermal inflammation. Previous studies have identified that the succinoglycan riclin has potent anti-inflammatory properties. The current study aims to investigate whether riclin protects against UVB-induced photodamage. In vitro, riclin demonstrated excellent moisture-preserving properties, along with antioxidant potential by scavenging superoxide anions, hydroxyl and DPPH radicals. Riclin increased Col1α1 and Col3α1 expression in NIH3T3 cells, inhibited oxidation and melanin synthesis by B16F10 cells upon UVB irradiation. In vivo, topical application of riclin effectively attenuated UVB-induced skin damage in C57BL6 mice, which was characterized by erythema, epidermal hyperplasia, hydroxyproline loss and ROS production in skin tissue. Riclin suppressed skin inflammation by the elevation of TNF-α, IL-6, IL-β, and alleviated UVB-induced immune cell up-regulation. Moreover, treatment with a Dectin-1 inhibitor reversed the protective effect of riclin in THP-1 cells.

Dectin-1 Acts as a Non-Classical Receptor of Ang II to Induce Cardiac Remodeling

BACKGROUND

Cardiac remodeling in heart failure involves macrophage-mediated immune responses. Recent studies have shown that a PRR (pattern recognition receptor) called dectin-1, expressed on macrophages, mediates proinflammatory responses. Whether dectin-1 plays a role in pathological cardiac remodeling is unknown. Here, we identified a potential role of dectin-1 in this disease.

METHODS

To model aberrant cardiac remodeling, we utilized mouse models of chronic Ang II (angiotensin II) infusion. In this model, we assessed the potential role of dectin-1 through using D1KO (dectin-1 knockout) mice and bone marrow transplantation chimeric mice. We then used cellular and molecular assays to discover the underlying mechanisms of dectin-1 function.

RESULTS

We found that macrophage dectin-1 is elevated in mouse heart tissues following chronic Ang II administration. D1KO mice were significantly protected against Ang II-induced cardiac dysfunction, hypertrophy, fibrosis, inflammatory responses, and macrophage infiltration. Further bone marrow transplantation studies showed that dectin-1 deficiency in bone marrow-derived cells prevented Ang II-induced cardiac inflammation and dysfunction. Through detailed molecular studies, we show that Ang II binds directly to dectin-1, causing dectin-1 homodimerization and activating the downstream Syk (spleen tyrosine kinase)/NF-κB (nuclear factor kappa B) signaling pathway to induce expression of inflammatory and chemoattractant factors. Mutagenesis studies identified R184 in the C-type lectin domain to interact with Ang II. Blocking dectin-1 in macrophages suppresses Ang II-induced inflammatory mediators and subsequent intercellular cross talk with cardiomyocytes and fibroblasts.

CONCLUSIONS

Our study has discovered dectin-1 as a new nonclassical receptor of Ang II and a key player in cardiac remolding and dysfunction. These studies suggest that dectin-1 may be a new target for treating hypertension-related heart failure.

C-type lectin receptors in antifungal immunity: Current knowledge and future developments

C-type lectin receptors (CLRs) constitute a category of innate immune receptors that play an essential role in the antifungal immune response. For over two decades, scientists have uncovered what are the fungal ligands recognized by CLRs and how these receptors initiate the immune response. Such studies have allowed the identification of genetic polymorphisms in genes encoding for CLRs or for proteins involved in the signalisation cascade they trigger. Nevertheless, our understanding of how these receptors functions and the full extent of their function during the antifungal immune response is still at its infancy. In this review, we summarize some of the main findings about CLRs in antifungal immunity and discuss what the future might hold for the field.

Aorta- and liver-generated TMAO enhances trained immunity for increased inflammation via ER stress/mitochondrial ROS/glycolysis pathways

We determined whether gut microbiota-produced trimethylamine (TMA) is oxidized into trimethylamine N-oxide (TMAO) in nonliver tissues and whether TMAO promotes inflammation via trained immunity (TI). We found that endoplasmic reticulum (ER) stress genes were coupregulated with MitoCarta genes in chronic kidney diseases (CKD); TMAO upregulated 190 genes in human aortic endothelial cells (HAECs); TMAO synthesis enzyme flavin-containing monooxygenase 3 (FMO3) was expressed in human and mouse aortas; TMAO transdifferentiated HAECs into innate immune cells; TMAO phosphorylated 12 kinases in cytosol via its receptor PERK and CREB, and integrated with PERK pathways; and PERK inhibitors suppressed TMAO-induced ICAM-1. TMAO upregulated 3 mitochondrial genes, downregulated inflammation inhibitor DARS2, and induced mitoROS, and mitoTEMPO inhibited TMAO-induced ICAM-1. β-Glucan priming, followed by TMAO restimulation, upregulated TNF-α by inducing metabolic reprogramming, and glycolysis inhibitor suppressed TMAO-induced ICAM-1. Our results have provided potentially novel insights regarding TMAO roles in inducing EC activation and innate immune transdifferentiation and inducing metabolic reprogramming and TI for enhanced vascular inflammation, and they have provided new therapeutic targets for treating cardiovascular diseases (CVD), CKD-promoted CVD, inflammation, transplantation, aging, and cancer.

The Key Drivers of Brain Injury by Systemic Inflammatory Responses after Sepsis: Microglia and Neuroinflammation

Sepsis is a leading cause of intensive care unit admission and death worldwide. Most surviving patients show acute or chronic mental disorders, which are known as sepsis-associated encephalopathy (SAE). Although accumulating studies in the past two decades focused on the pathogenesis of SAE, a systematic review of retrospective studies which exclusively focuses on the inflammatory mechanisms of SAE has been lacking yet. This review summarizes the recent advance in the field of neuroinflammation and sheds light on the activation of microglia in SAE. Activation of microglia predominates neuroinflammation. As the gene expression profile changes, microglia show heterogeneous characterizations throughout all stages of SAE. Here, we summarize the systemic inflammation following sepsis and also the relationship of microglial diversity and neuroinflammation. Moreover, a collection of neuroinflammation-related dysfunction has also been reviewed to illustrate the possible mechanisms for SAE. In addition, promising pharmacological or non-pharmacological therapeutic strategies, especially those which target neuroinflammation or microglia, are also concluded in the final part of this review. Collectively, clarification of the vital relationship between neuroinflammation and SAE-related mental disorders would significantly improve our understanding of the pathophysiological mechanisms in SAE and therefore provide potential targets for therapies of SAE aimed at inhibiting neuroinflammation.

The Dectin-1 Receptor Signaling Pathway Mediates the Remyelination Effect of Lentinan through Suppression of Neuroinflammation and Conversion of Microglia

Demyelinating diseases such as multiple sclerosis (MS) are chronic inflammatory autoimmune diseases and involve demyelination and axonal degeneration. Microglia rapidly respond to changes in the environment by altering morphotype and function during the progressive disease stage. Although substantial progress has been made in the drug development for MS, treatment of the progressive forms of the disease remains unsatisfactory. There is great interest in identifying novel agents for treating MS. Lentinus edodes is a traditional food, which can improve physiological function. Lentinan (LNT), a type of polysaccharide extracted from mushroom Lentinus edodes, is an anti-inflammatory and immunomodulatory agent. Here, we studied the remyelination effects of LNT and its therapeutic target in regulating the functions of neuroinflammation. We found that LNT enhanced remyelination and rescued motor deficiency by regulating dectin-1 receptor to inhibit neuroinflammation and microglial cell transformation. LNT promoted the conversion of microglial cells from the M1 status induced by LPS to the M2 status, enhanced the anti-inflammatory markers IL-10 and BDNF, inhibited inflammatory markers TNF-α and IL-1β, and downregulated the microglia activation and oligodendrocyte and astrocyte proliferation by modulating dectin-1. If we injected the dectin-1-specific inhibitor laminarin (Lam), the remyelination effects induced by LNT were completely abolished. Thus, these results suggest that LNT is a novel and potential therapeutic agent that can rescue MS neuroimmune imbalance and remyelination through a dectin-1 receptor-dependent mechanism.

Dectin-1 signaling in neutrophils up-regulates PD-L1 and triggers ROS-mediated suppression of CD4+ T cells

Dectin-1 is known to drive proinflammatory cytokine production by macrophages and dendritic cells which promotes Th17 CD4+ T cell responses in the setting of fungal infection. However, the role of Dectin-1 signaling in neutrophils and its impact on CD4+ T cells is not well understood. In this study, we found that neutrophils stimulated with a Dectin-1 agonist diminish CD4+ T cell viability in a rapid and reactive oxygen species (ROS)-dependent manner. Furthermore, Dectin-1 promoted neutrophil PD-L1 expression via Syk and Card9 signaling, along with other immune-checkpoint factors in a neutrophil-biased manner. Although neutrophil PD-L1 did not significantly impact disease severity in experimental autoimmune encephalomyelitis (EAE), we found that CNS-infiltrated neutrophils potently up-regulate PD-L1 expression. Furthermore, a subset of PD-L1+ neutrophils was also found to express MHC-II during EAE. In summary, we found that Dectin-1 elicits a biphasic neutrophil response in which (1) T-cell suppressive ROS is followed by (2) up-regulation of PD-L1 expression. This response may serve to limit excess CD4+ T cell-driven inflammation in infection or autoimmunity while preserving host-defense functions of neutrophils. Summary sentence: Mechanisms by which Dectin-1 signaling in neutrophils promotes a cellular phenotype with T cell-suppressive properties.

Host immune responses in the central nervous system during fungal infections

Fungal infections in the central nervous system (CNS) cause high morbidity and mortality. The frequency of CNS mycosis has increased over the last two decades as more individuals go through immunocompromised conditions for various reasons. Nevertheless, options for clinical interventions for CNS mycoses are still limited. Thus, there is an urgent need to understand the host-pathogen interaction mechanisms in CNS mycoses for developing novel treatments. Although the CNS has been regarded as an immune-privileged site, recent studies demonstrate the critical involvement of immune responses elicited by CNS-resident and CNS-infiltrated cells during fungal infections. In this review, we discuss mechanisms of fungal invasion in the CNS, fungal pathogen detection by CNS-resident cells (microglia, astrocytes, oligodendrocytes, neurons), roles of CNS-infiltrated leukocytes, and host immune responses. We consider that understanding host immune responses in the CNS is crucial for endeavors to develop treatments for CNS mycosis.

Integrated transcriptomics and metabolomics analysis of the hippocampus reveals altered neuroinflammation, downregulated metabolism and synapse in sepsis-associated encephalopathy

Sepsis-associated encephalopathy (SAE) is an intricated complication of sepsis that brings abnormal emotional and memory dysfunction and increases patients’ mortality. Patients’ alterations and abnormal function seen in SAE occur in the hippocampus, the primary brain region responsible for memory and emotional control, but the underlying pathophysiological mechanisms remain unclear. In the current study, we employed an integrative analysis combining the RNA-seq-based transcriptomics and liquid chromatography/mass spectrometry (LC-MS)-based metabolomics to comprehensively obtain the enriched genes and metabolites and their core network pathways in the endotoxin (LPS)-injected SAE mice model. As a result, SAE mice exhibited behavioral changes, and their hippocampus showed upregulated inflammatory cytokines and morphological alterations. The omics analysis identified 81 differentially expressed metabolites (variable importance in projection [VIP] > 1 and p < 0.05) and 1747 differentially expressed genes (Foldchange >2 and p < 0.05) were detected in SAE-grouped hippocampus. Moreover, 31 compounds and 100 potential target genes were employed for the Kyoto Encyclopedia of Genes and Genomes (KEGG) Markup Language (KGML) network analysis to explore the core signaling pathways for the progression of SAE. The integrative pathway analysis showed that various dysregulated metabolism pathways, including lipids metabolism, amino acids, glucose and nucleotides, inflammation-related pathways, and deregulated synapses, were tightly associated with hippocampus dysfunction at early SAE. These findings provide a landscape for understanding the pathophysiological mechanisms of the hippocampus in the progression of SAE and pave the way to identify therapeutic targets in future studies.

Infection and inflammation: New perspectives on Alzheimer's disease

Neuroinflammation has been recognized as a component of Alzheimer's Disease (AD) pathology since the original descriptions by Alois Alzheimer and a role for infections in AD pathogenesis has long been hypothesized. More recently, this hypothesis has gained strength as human genetics and experimental data suggest key roles for inflammatory cells in AD pathogenesis. To review this topic, Duke/University of North Carolina (Duke/UNC) Alzheimer's Disease Research Center hosted a virtual symposium: "Infection and Inflammation: New Perspectives on Alzheimer's Disease (AD)." Participants considered current evidence for and against the hypothesis that AD could be caused or exacerbated by infection or commensal microbes. Discussion focused on connecting microglial transcriptional states to functional states, mouse models that better mimic human immunity, the potential involvement of inflammasome signaling, metabolic alterations, self-reactive T cells, gut microbes and fungal infections, and lessons learned from Covid-19 patients with neurologic symptoms. The content presented in the symposium, and major topics raised in discussions are reviewed in this summary of the proceedings.

Bone Marrow Stromal Cell Antigen 2: Is a Potential Neuroinflammation Biomarker of SOD1G93A Mouse Model of Amyotrophic Lateral Sclerosis in Pre-symptomatic Stage

Neuroinflammation has long been thought to be associated with amyotrophic lateral sclerosis (ALS) development and progression. However, the exact molecular mechanisms of neuroinflammation underlying ALS remain largely unknown. In the present study, we attempted to elucidate the genetic basis of neuroinflammation in ALS by comparing the transcriptomic profile of the anterior horns of the lumbar spinal cord (AHLSC) between SOD1^G93A mice and their wild-type (WT) littermates. Our results revealed that immune-related genes were selectively up-regulated in the AHLSC of pre-symptomatic ALS mice (40 days of age) compared to age-matched WT control mice. Notably, the differential expression level of these immune-related genes became more significant at the symptomatic stage of disease (90 days of age) in the ALS mice. Subsequently, eight genes involved in innate immune response in the AHLSC of ALS mice were further validated by qRT-PCR analysis. Of these genes, bone marrow stromal cell antigen 2 (BST2) was found for the first time to be significantly higher in the AHLSC of pre-symptomatic ALS mice when compared with WT mice. The increasing trend of BST2 expression became more obvious in the symptomatic stage. Immunofluorescent staining further confirmed that BST2 is mainly expressed on microglia in the AHLSC of ALS mice. These findings support the view that immune-related neuroinflammation is involved in the early pathogenesis of ALS, and BST2 may serve as a potential target for ameliorating microglia-mediated neuroinflammation pathologies in ALS.

Restoring Oat Nanoparticles Mediated Brain Memory Function of Mice Fed Alcohol by Sorting Inflammatory Dectin-1 Complex Into Microglial Exosomes

Microglia modulate pro-inflammatory and neurotoxic activities. Edible plant-derived factors improve brain function. Current knowledge of the molecular interactions between edible plant-derived factors and the microglial cell is limited. Here an alcohol-induced chronic brain inflammation model is used to identify that the microglial cell is the novel target of oat nanoparticles (oatN). Oral administration of oatN inhibits brain inflammation and improves brain memory function of mice that are fed alcohol. Mechanistically, ethanol activates dectin-1 mediated inflammatory pathway. OatN is taken up by microglial cells via β-glucan mediated binding to microglial hippocalcin (HPCA) whereas oatN digalactosyldiacylglycerol (DGDG) prevents assess of oatN β-glucan to dectin-1. Subsequently endocytosed β-glucan/HPCA is recruited in an endosomal recycling compartment (ERC) via interaction with Rab11a. This complex then sequesters the dectin-1 in the ERC in an oatN β-glucan dependent manner and alters the location of dectin-1 from Golgi to early endosomes and lysosomes and increases exportation of dectin-1 into exosomes in an Rab11a dependent manner. Collectively, these cascading actions lead to preventing the activation of the alcoholic induced brain inflammation signing pathway(s). This coordinated assembling of the HPCA/Rab11a/dectin-1 complex by oral administration of oatN may contribute to the prevention of brain inflammation.