Innate Immune Cell Function Research Articles

Decoding physiological and pathological roles of innate immune cells in eye diseases: the perspectives from single-cell RNA sequencing.

Single-cell RNA sequencing (scRNA-seq) has facilitated a deeper comprehension of the molecular mechanisms behind eye diseases and has prompted the selection of precise therapeutic targets by examining the cellular and molecular intricacies at the single-cell level. This review delineates the pivotal role of scRNA-seq in elucidating the functions of innate immune cells within the context of ocular pathologies. Recent advancements in scRNA-seq have revealed that innate immune cells, both from the periphery and resident in the retina, are actively engaged in various stages of multiple eye diseases. Notably, resident microglia and infiltrating neutrophils exhibit swift responses during the initial phase of injury, while peripheral monocyte-derived macrophages exhibit transcriptomic profiles akin to those of activated microglia, suggesting their potential for long-term residence within the retina. The scRNA-seq analyses have underscored the cellular heterogeneity and gene expression alterations within innate immune cells, which, while sharing commonalities, exhibit disease-specific variations. These insights have not only broadened our understanding of the cellular and molecular mechanisms in eye diseases but also paved the way for the identification of candidate targets for targeted therapeutic interventions. The application of scRNA-seq technology has heralded a new era in the study of ocular pathologies, enabling a more detailed appreciation of the roles that innate immune cells play across a spectrum of eye diseases.

Impact of Senescent Cell-Derived Extracellular Vesicles on Innate Immune Cell Function.

Extracellular vesicles (EVs) are components of the senescence-associated secretory phenotype (SASP) that influence cellular functions via their cargo. Here, the interaction between EVs derived from senescent (SEVs) and non-senescent (N-SEVs) fibroblasts and the immune system is investigated. Via endocytosis, SEVs are phagocytosed by monocytes, neutrophils, and B cells. Studies with the monocytic THP-1 cell line find that pretreatment with SEVs results in a 32% (p < 0.0001) and 66% (p < 0.0001) increase in lipopolysaccharide (LPS)-induced tumor necrosis factor-alpha (TNF-α) production when compared to vehicle control or N-SEVs respectively. Interestingly, relative to vehicle control, THP-1 cells exposed to N-SEVs exhibit a 20% decrease in TNF-α secretion (p < 0.05). RNA sequencing reveals significant differences in gene expression in THP-1 cells treated with SEVs or N-SEVs, with vesicle-mediated transport and cell cycle regulation pathways featuring predominantly with N-SEV treatment, while pathways relating to SLITS/ROBO signaling, cell metabolism, and cell cycle regulation are enriched in THP-1 cells treated with SEVs. Proteomic analysis also reveals significant differences between SEV and N-SEV cargo. These results demonstrate that phagocytes and B cells uptake SEVs and drive monocytes toward a more proinflammatory phenotype upon LPS stimulation. SEVs may therefore contribute to the more proinflammatory immune response seen with aging.

Antibody-mediated cellular responses are dysregulated in Multisystem Inflammatory Syndrome in Children (MIS-C)

Abstract Background Multisystem Inflammatory Syndrome in Children (MIS-C) is a rare and severe complication of SARS-CoV-2 infection that is characterized by multi-organ involvement and substantial inflammation. The immunological responses in MIS-C are not fully known. Antibody-mediated viral clearance in which innate immune cells interact with antibodies via their Fc receptors to remove the virus is an important mechanism for reducing SARS-CoV-2 viral load. However, little is known about how antibody-mediated cellular responses in MIS-C compared to acute COVID-19 infection and direct testing of cellular function ex vivo to understand the aberrant immune response in MIS-C is limited. Therefore, we focused on the antibody-mediated cellular responses in MIS-C relative to children and adults that had acute COVID-19 infection with spectrum of symptoms. We hypothesized that cells that bind antibodies to help clear the virus are dysfunctional in MIS-C patients, preventing the virus from being fully cleared. Methods We collected samples from MIS-C children along with pediatric and adult subjects with a clinical spectrum of COVID-19 symptoms and uninfected controls. Through these controls, we can compare Fc-mediated antibody functions between ages and clinical symptoms. We utilized high dimension flow cytometry to assess phenotype and function of innate immune cells that bind to antibodies and sequencing to study Fc receptor genetic. This data was then correlated with matched clinical data. Results Monocytes in MIS-C were hyperfunctional for antibody-dependent cellular phagocytosis and production of proinflammatory cytokines. In contrast, natural killer (NK) cells in MIS-C were hypofunctional for antibody-dependent cellular cytotoxicity and cytokine production. To provide some preliminary insight into mechanism, we show multiple ways leading to decreased cytotoxicity for NK cells, including phenotypic exhaustion of NK cells, variants in CD16 (NK cell Fc receptor) genetics that reduce Fc binding to IgG, and cytokine-induced associations. Using a novel anti-CD16 novel bispecific reagent that we developed, we could rescue the hypofunctional antibody-mediated NK cell function in MIS-C to the same levels as control. Conclusion Together, our results reveal dysregulation in antibody-mediated responses that are unique to MIS-C and may contribute to the immune pathology of this disease. Specifically, we find that monocytes are hyperfunctional with NK cells are hypofunctional. In the case of the MIS-C antibody-mediated response, while it is likely that multiple pathogenetic mechanisms contribute to MIS-C, our data suggest an imbalance of the antibody-mediated cellular response as a mechanistic correlate of this rare, but life-threatening outcome of SARS-COV-2 in children. Our results highlight that targeted therapies to reduce viral burden and/or boost NK cells responses while decreasing cytokine levels may be effective in preventing MIS-C.

Lysosomes in the immunometabolic reprogramming of immune cells in atherosclerosis.

Lysosomes have a central role in the disposal of extracellular and intracellular cargo and also function as metabolic sensors and signalling platforms in the immunometabolic reprogramming of macrophages and other immune cells in atherosclerosis. Lysosomes can rapidly sense the presence of nutrients within immune cells, thereby switching from catabolism of extracellular material to the recycling of intracellular cargo. Such a fine-tuned degradative response supports the generation of metabolic building blocks through effectors such as mTORC1 or TFEB. By coupling nutrients to downstream signalling and metabolism, lysosomes serve as a crucial hub for cellular function in innate and adaptive immune cells. Lysosomal dysfunction is now recognized to be a hallmark of atherogenesis. Perturbations in nutrient-sensing and signalling have profound effects on the capacity of immune cells to handle cholesterol, perform phagocytosis and efferocytosis, and limit the activation of theinflammasome and other inflammatory pathways. Strategies to improve lysosomal function hold promise as novel modulators of the immunoinflammatory response associated with atherosclerosis. In this Review, we describe the crosstalk between lysosomal biology and immune cell function and polarization, with a particular focus on cellular immunometabolic reprogramming in the context of atherosclerosis.

The Impact of Liver Failure on the Immune System.

Liver failure profoundly affects the immune system, leading to dysregulation of innate and adaptive immune response. This review explores the intricate relationship between liver function and immune homeostasis. The role of the liver as a central hub in immune response initiation is elucidated, emphasizing its involvement in hepatic inflammation induction and subsequent systemic inflammation. Cytokines, chemokines, growth factors, and lipid mediators orchestrate these immune processes, serving as both prognostic biomarkers and potential therapeutic targets in liver failure-associated immune dysregulation, which might result from acute-on-chronic liver failure (ACLF) and cirrhosis. Furthermore, the review delves into the mechanisms underlying immunosuppression in liver failure, encompassing alterations in innate immune cell functions such as neutrophils, macrophages, and natural killer cells (NK cells), as well as perturbations in adaptive immune responses mediated by B and T cells. Conclusion: Understanding the immunological consequences of liver failure is crucial for developing targeted therapeutic interventions and improving patient outcomes in liver disease management.

OXidative Stress PREDictor: A Supervised Learning Approach for Annotating Cellular Oxidative Stress States in Inflammatory Cells

Oxidative stress, characterized by an imbalance between reactive oxygen species (ROS) and antioxidants, plays a pivotal role in inflammatory responses associated with both chronic diseases and acute injuries. In this study, OXidative Stress PREDictor (OxSpred), a supervised learning model tailored to accurately annotate the oxidative stress state of innate immune cells at the single‐cell level, is introduced. Compared to the traditional gene‐set‐variation‐analysis‐based enrichment method, OxSpred demonstrates superior accuracy with an area under the receiver operating characteristic curve of 0.89 and offers interpretable embeddings with significant biological relevance. Using the predicted ROS states, precise elucidation and interpretation of the roles of novel innate immune cell subtypes can be achieved. Overall, OxSpred enhances the utility of single‐cell transcriptomic datasets by providing a robust in silico method for determining intracellular oxidative stress states, thereby enriching the understanding of innate immune cell functions during inflammation.

A Dynamic Interplay of Innate Immune Responses During Urinary Tract Infection.

Urinary tract infections (UTIs) represent one of the most prevalent bacterial infections globally, manifesting in diverse clinical phenotypes with varying degrees of severity and complications. The mechanisms underlying UTIs are gradually being elucidated, leading to an enhanced understanding of the immune responses involved. Innate immune cells play a crucial defensive role against uropathogenic bacteria through various mechanisms. Despite their significant contributions to host defense, these cells often fail to achieve complete clearance of uropathogens, necessitating the frequent prescription of antibiotics for UTI patients. However, the persistence of infections and related pathological symptoms in the absence of innate immune cells in animal models underscore the importance of innate immunity in UTIs. Therefore, the host protective functions of innate immune cells, including neutrophils, macrophages, mast cells, NK cells, innate lymphoid cells, and γδ T cells, are delicately coordinated and timely regulated by a variety of cytokines to ensure successful pathogen clearance.

Different species of Chiroptera: Immune cells and molecules

AbstractThe distinct composition and immune response characteristics of bats’ innate and adaptive immune systems, which enable them to serve as host of numerous serious zoonotic viruses without falling ill, differ substantially from those of other mammals, it have garnered significant attention. In this article, we offer a systematic review of the names, attributes, and functions of innate and adaptive immune cells &amp; molecules across different bat species. This includes descriptions of the differences shown by research between 71 bat species in 10 families, as well as comparisons between bats and other mammals. Studies of the immune cells &amp; molecules of different bat species are necessary to understand the unique antiviral immunity of bats. By providing comprehensive information on these unique immune responses, it is hoped that new insights will be provided for the study of co‐evolutionary dynamics between viruses and the bat immune system, as well as human antiviral immunity.

Effects of a β-Glucan-Rich Blend of Medicinal Mushrooms and Botanicals on Innate Immune Cell Activation and Function Are Enhanced by a Very Low Dose of Bovine Colostrum Peptides.

Nutraceutical immune support offers potential for designing blends with complementary mechanisms of action for robust support of innate immune alertness. We documented enhanced immune activation when bovine colostrum peptides (BC-Pep) were added to an immune blend (IB) containing β-glucans from yeast, shiitake, maitake, and botanical non-β-glucan polysaccharides. Human peripheral blood mononuclear cells (PBMCs) were cultured with IB, BC-Pep, and IB + BC-Pep for 20 h, whereafter expression of the activation marker CD69 was evaluated on NK cells, NKT cells, and T cells. Cytokine levels were tested in culture supernatants. PBMCs were co-cultured with K562 target cells to evaluate T cell-mediated cytotoxicity. IB + BC-Pep triggered highly significant increases in IL-1β, IL-6, and TNF-α, above that of cultures treated with matching doses of either IB or BC-Pep. NK cell and T cell activation was increased by IB + BC-Pep, reaching levels of CD69 expression several fold higher than either BC-Pep or IB alone. IB + BC-Pep significantly increased T cell-mediated cytotoxic killing of K562 target cells. This synergistic effect suggests unique amplification of signal transduction of NK cells and T cells due to modulation of IB-induced signaling pathways by BC-Pep and is of interest for further pre-clinical and clinical testing of immune defense activity against virally infected and transformed cells.

A synthetic bioactive peptide of the C-terminal fragment of adhesion protein Fibulin7 attenuates the inflammatory functions of innate immune cells in LPS-induced systemic inflammation.

Systemic inflammation is associated with improper localization of hyperactive neutrophils and monocytes in visceral organs. Previously, a C-terminal fragment of adhesion protein Fibulin7 (Fbln7-C) was shown to regulate innate immune functionality during inflammation. Recently, a shorter bioactive peptide of Fbln7-C, FC-10, via integrin binding was shown to reduce ocular angiogenesis. However, the role of FC-10 in regulating the neutrophils and monocyte functionality during systemic inflammatory conditions is unknown. The study sought to explore the role of FC-10 peptide on the functionality of innate immune cells during inflammation and endotoxemic mice. Neutrophils and monocytes were isolated from healthy donors and septic patient clinical samples and Cell adhesion assay was performed using a UV spectrophotometer. Gene expression studies were performed using qPCR. Protein level expression was measured using ELISA and flow cytometry. ROS assay, and activation markers analysis in vitro, and in vivo were done using flow cytometry. Cells were stimulated with LPS (100ng/mL) and studied in the presence of peptides (10μg, and 20μg/mL) in vitro. In an in vivo study, mice were administered with LPS (36.8mg/kg bw) and peptide (20μg). This study demonstrates that human neutrophils and monocytes adhere to FC-10 via integrin β1, inhibit spreading, ROS, surface activation markers (CD44, CD69), phosphorylated Src kinase, pro-inflammatory genes, and protein expression, compared to scrambled peptide in cells isolated from healthy donors and clinical sample. In line with the in vitro data, FC-10 (20μg) administration significantly decreases innate cell infiltration at inflammatory sites, improves survival in endotoxemia animals & reduces the inflammatory properties of neutrophils and monocytes isolated from septic patients. FC-10 peptide can regulate neutrophils and monocyte functions and has potential to be used as an immunomodulatory therapeutic in inflammatory diseases.

Zinc about it - zinc and calf immunity.

Micronutrients, such as vitamins and trace minerals, are critical for supporting growth, performance, health and maintaining redox balance. Zinc (Zn), an essential micronutrient, aids the functioning of innate and adaptive immune cells. This scoping review aims to assemble and evaluate the evidence available for the role of Zn within calf immunity. Relevant literature was identified within Web of Science, PubMed, and CABI using search terms specific to the major innate and adaptive immune cell populations. There was no evidence that Zn supplementation altered neutrophil, natural killer cell, or T-cell functions. However, there was limited evidence to support Zn supplementation with reduced monocyte numbers, but there was no evidence to associate the monocytopenia with improvements in monocyte function. There is moderate evidence to suggest that Zn supplementation was beneficial for maintaining epithelial barriers of integumental and mucosal surfaces. The evidence supports supplementation above the current industry recommendations for improving immunoglobulin (Ig) production, with the strongest results being observed for IgG and IgM. Moreover, Zn supplementation was associated with reduced proinflammatory cytokine production, which may reduce inflammation-associated hypophagia and warrants further investigation. Furthermore, Zn reduced the duration of clinical signs in animals facing respiratory disease and diarrhea. However, consensus is needed about the optimal dose, route, and Zn formulation most appropriate for supporting immunity. In conclusion, while the literature supports that Zn could enhance calf immunity, there is insufficient evidence to adequately determine the extent to which Zn impacts innate immune cell and T-cell functions. Determination of the immune cell functions susceptible to modification by Zn supplementation is an important knowledge gap for enhancing the understanding of Zn and calf immunity.

Molecular mechanism of CD14+ human monocyte/macrophage activation by Ebola virus protein VP40

Abstract Impaired functions of many innate immune cells have been implicated in Ebola virus disease (EVD) pathogenesis. Previously, we reported that CD14+ accessory cells are required for the optimal Ebola virus protein VP40-induced activation of human natural killer (NK) cells. In the current study, we explored the molecular mechanism(s) of VP40-induced activation of CD14+ accessory cells and their role in triggering NK cell activation. Human PBMCs, purified CD14+ myeloid cells or CD14+ cell and CD56+ NK cell co-cultures were incubated with VP40, mCherry-VP40 fusion protein or virus-like particles (VLPs) containing it and binding, internalization, and distribution of VP40 analyzed by flow and confocal microscopy. Molecular pathway(s) triggered in CD14+ cells and the resulting gene expression changes were analyzed by flow, western blotting, luminex and RNA-Seq. Ebola VP40/VLPs bound to and were internalized by classical, intermediate and non-classical monocytes but to varying degrees. VP40 triggered activation of NF-kB and inflammatory pathways in CD14+ cells resulting in their enhanced secretion of multiple cytokines and factors. IL-12 or IL-18 blockade partially abrogated VP40-induced, CD14+ cell dependent activation of NK cells. Taken together, our data suggests that activation of CD14+ cell by Ebola VP40/VLPs can rapidly trigger NK cells that, in turn, may eliminate Ebola virus infected host cells, findings that may help in designing better anti-Ebola countermeasures.

Exploring the possible link between the spike protein immunoglobulin G4 antibodies and cancer progression

Repeated inoculation with messenger RNA (mRNA) vaccines elicits immunoglobulin G4 (IgG4) antibody production. Such an increase in the concentration of specific and non-specific IgG4 antibodies allows the growth of some types of cancer by blocking the activation of effector immune cells. This work proposes the hypothesis that cancer growth may be indirectly promoted by increased concentrations of non-specific IgG4 antibodies by the following mechanisms: 1) IgG4 antibodies can bind to anti-tumor IgG1 antibodies and block their interaction with receptors located on effector cells, thus preventing the destruction of cancer cells, 2) IgG4 can interact with fragment crystallizable gamma receptor IIb (FcγRIIB) inhibitory receptors, thus reducing effector functions of innate immune cells, and 3) targeting of specific epitopes by IgG4 could be oncogenic by inducing the production of a microenvironment that can promote cancer development. This article reviews the supporting literature and suggests several experimental protocols to evaluate this hypothesis in the context of repeated inoculation with mRNA vaccines. Additionally, this work proposes some management options aimed at reducing the unfavorable molecular consequences that could mediate cancer development when encountering high concentrations of IgG4 antibodies.

Calcineurin-NFAT signaling controls neutrophils' ability of chemoattraction upon fungal infection.

Calcineurin-nuclear factor of activated T cells (CN-NFAT) inhibitors are widely clinically used drugs for immunosuppression, but besides their required T cell response inhibition, they also undesirably affect innate immune cells. Disruption of innate immune cell function can explain the observed susceptibility of CN-NFAT inhibitor-treated patients to opportunistic fungal infections. Neutrophils play an essential role in innate immunity as a defense against pathogens; however, the effect of CN-NFAT inhibitors on neutrophil function was poorly described. Thus, we tested the response of human neutrophils to opportunistic fungal pathogens, namely Candida albicans and Aspergillus fumigatus, in the presence of CN-NFAT inhibitors. Here, we report that the NFAT pathway members were expressed in neutrophils and mediated part of the neutrophil response to pathogens. Upon pathogen exposure, neutrophils underwent profound transcriptomic changes with subsequent production of effector molecules. Importantly, genes and proteins involved in the regulation of the immune response and chemotaxis, including the chemokines CCL2, CCL3, and CCL4 were significantly upregulated. The presence of CN-NFAT inhibitors attenuated the expression of these chemokines and impaired the ability of neutrophils to chemoattract other immune cells. Our results amend knowledge about the impact of CN-NFAT inhibition in human neutrophils.

Abstract LB365: Generation of a novel severely immunodeficient Sprague Dawley rat model for xenograft studies

Abstract The recombinant-activating gene 2 (Rag2) plays a critical role in the recombination of the immunoglobulin and T cell receptor genes during the maturation of T and B cells. Loss of Rag2 protein leads to a lack of functional T and B cells, which eliminates the adaptive immune response. However, Rag2 deficiency alone may not guarantee the success of xenograft implantation, due to NK cells and other innate cells remaining. Il2rg is a key component of several cytokine receptors involved in differentiation and/or function of numerous adaptive and innate immune cells, including NK cells, mast cells, basophils, and dendritic cells. To generate a more severely immunodeficient rat model, both the Rag2 and Il2rg genes were knocked out in Sprague Dawley (SD) rats; this model was termed B-SDG rats. The immune profile and organ weights of thymus and spleen were investigated in B-SDG rats in comparison with Rag2-/- and wild-type SD rats. The spleen weights of both Rag2-/- and B-SDG rats were similar, but significantly reduced compared to wild-type SD rats. Notably, the thymus weights of B-SDG male rats were significantly smaller than those of Rag2-/- males. The immune cell profiles in thymus, spleen and blood were next evaluated by flow cytometry. A complete lack of B and T cells was observed in both Rag2-/- and B-SDG rats. B-SDG rats lacked CD161+ NK cells in the spleen and blood, which were maintained in Rag2-/- rats. Dendritic cells, monocytes, macrophages, and neutrophils were detected in all strains. In vivo xenograft implantation with human lung, bladder, breast, pancreas, acute monocytic and myelomonocytic leukemia tumor cell lines was next evaluated in B-SDG rats, which demonstrated successful engraftment. Furthermore, several efficacy studies were performed in B-SDG rats, including cisplatin chemotherapy on human breast invasive ductal carcinoma cell (HCC1954) and human large cell lung cancer cell (NCI-H460) xenografts, and a HER2-targeting ADC therapy was tested in B-SDG rats harboring human non-small cell lung cancer tumors (NCI-H1975). Taken together, these data confirm that B-SDG rats provide a powerful immunodeficient model for preclinical in vivo evaluation of novel drug candidates. Citation Format: Yanhui Nie, Meiqi Zhang, Wanling Zhong, Jia Feng, Bahetiyaer Huwatibieke, Zhaoxue Yu. Generation of a novel severely immunodeficient Sprague Dawley rat model for xenograft studies [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(7_Suppl):Abstract nr LB365.

Strategies of Helicobacter pylori in evading host innate and adaptive immunity: insights and prospects for therapeutic targeting.

Helicobacter pylori (H. pylori) is the predominant pathogen causing chronic gastric mucosal infections globally. During the period from 2011 to 2022, the global prevalence of H. pylori infection was estimated at 43.1%, while in China, it was slightly higher at approximately 44.2%. Persistent colonization by H. pylori can lead to gastritis, peptic ulcers, and malignancies such as mucosa-associated lymphoid tissue (MALT) lymphomas and gastric adenocarcinomas. Despite eliciting robust immune responses from the host, H. pylori thrives in the gastric mucosa by modulating host immunity, particularly by altering the functions of innate and adaptive immune cells, and dampening inflammatory responses adverse to its survival, posing challenges to clinical management. The interaction between H. pylori and host immune defenses is intricate, involving evasion of host recognition by modifying surface molecules, manipulating macrophage functionality, and modulating T cell responses to evade immune surveillance. This review analyzes the immunopathogenic and immune evasion mechanisms of H. pylori, underscoring the importance of identifying new therapeutic targets and developing effective treatment strategies, and discusses how the development of vaccines against H. pylori offers new hope for eradicating such infections.

The conneXion between sex and immune responses.

There are notable sex-based differences in immune responses to pathogens and self-antigens, with female individuals exhibiting increased susceptibility to various autoimmune diseases, and male individuals displaying preferential susceptibility to some viral, bacterial, parasitic and fungal infections. Although sex hormones clearly contribute to sex differences in immune cell composition and function, the presence of two X chromosomes in female individuals suggests that differential gene expression of numerous Xchromosome-linked immune-related genes may also influence sex-biased innate and adaptive immune cell function in health and disease. Here, we review the sex differences in immune system composition and function, examining how hormones and genetics influence the immune system. We focus on the genetic and epigenetic contributions responsible for altered Xchromosome-linked gene expression, and how this impacts sex-biased immune responses in the context of pathogen infection and systemic autoimmunity.

The application of MARCO for immune regulation and treatment.

Macrophage receptor with collagen structure (MARCO) is a member of scavenger receptor class A (SR-A) and shares structural and functional similarities with SR-A1. In recent years, many studies have shown that MARCO can trigger an immune response and has therapeutic potential as a target for immunotherapy. Studies have shown that alterations in MARCO expression following pathogen infection cause changes in the functions of innate and adaptive immune cells, including macrophages, dendritic cells, B cells, and T cells, affecting the body's immune response to invading pathogens; thus, MARCO plays a crucial role in triggering the immune response, bridging innate and adaptive immunity, and eliminating pathogens. This paper is a comprehensive summary of the recent research on MARCO. This review focuses on the multiple functions of MARCO, including adhesion, migration, phagocytosis, and cytokine secretion with special emphasis on the complex interactions between MARCO and various types of cells involved in the immune response, as well as possible immune-related mechanisms. In summary, in this review, we discuss the structure and function of MARCO and its role in the immune response and highlight the therapeutic potential of MARCO as a target for immunotherapy. We hope that this review provides a theoretical basis for future research on MARCO.

Serine synthesis sustains macrophage IL-1β production via NAD+-dependent protein acetylation

Serine metabolism is involved in the fate decisions of immune cells; however, whether and how de novo serine synthesis shapes innate immune cell function remain unknown. Here, we first demonstrated that inflammatory macrophages have high expression of phosphoglycerate dehydrogenase (PHGDH, the rate-limiting enzyme of de novo serine synthesis) via nuclear factor κB signaling. Notably, the pharmacological inhibition or genetic modulation of PHGDH limits macrophage interleukin (IL)-1β production through NAD+ accumulation and subsequent NAD+-dependent SIRT1 and SIRT3 expression and activity. Mechanistically, PHGDH not only sustains IL-1β expression through H3K9/27 acetylation-mediated transcriptional activation of Toll-like receptor 4 but also supports IL-1β maturation via NLRP3-K21/22/24/ASC-K21/22/24 acetylation-mediated activation of the NLRP3 inflammasome. Moreover, mice with myeloid-specific depletion of Phgdh show alleviated inflammatory responses in lipopolysaccharide-induced systemic inflammation. This study reveals a network by which a metabolic enzyme, involved in de novo serine synthesis, mediates post-translational modifications and epigenetic regulation to orchestrate IL-1β production, providing a potential inflammatory disease target.

Flow-Induced Shear Stress Primes NLRP3 Inflammasome Activation in Macrophages via Piezo1.

The NLRP3 inflammasome is a crucial component of the innate immune system, playing a pivotal role in initiating and regulating the body's inflammatory response to various pathogens and cellular damage. Environmental stimuli, such as temperature, pH level, and nutrient availability, can influence the behavior and functions of innate immune cells, including immune cell activity, proliferation, and cytokine production. However, there is limited understanding regarding how mechanical forces, like shear stress, govern the intrinsic inflammatory reaction, particularly the activation of the NLRP3 inflammasome, and how shear stress impacts NLRP3 inflammasome activation through its capacity to induce alterations in gene expression and cytokine secretion. Here, we investigated how shear stress can act as a priming signal in NLRP3 inflammasome activation by exposing immortalized bone marrow-derived macrophages (iBMDMs) to numerous physiologically relevant magnitudes of shear stress before chemically inducing inflammasome activation. We demonstrated that shear stress of large magnitudes was able to prime iBMDMs more effectively for inflammasome activation compared to lower shear stress magnitudes, as quantified by the percentage of cells where ASC-CFP specks formed and IL-1β secretion, the hallmarks of inflammasome activation. Testing this in NLRP3 and caspase-1 knockout iBMDMs showed that the NLRP3 inflammasome was primarily primed for activation due to shear stress exposure. Quantitative polymerase chain reaction (qPCR) and a small-molecule inhibitor study mechanistically determined that shear stress regulates the NLRP3 inflammasome by upregulating Piezo1, IKKβ, and NLRP3. These findings offer insights into the mechanistic relationship among physiological shear stresses, inflammasome activation, and their impact on the progression of inflammatory diseases and their interconnected pathogenesis.