Monocyte Differentiation and Heterogeneity: Inter-Subset and Interindividual Differences.

The three subsets of human monocytes, classical, intermediate, and nonclassical, show phenotypic heterogeneity, particularly in their expression of CD14 and CD16. This has enabled researchers to delve into the functions of each subset in the steady state as well as in disease. Studies have revealed that monocyte heterogeneity is multi-dimensional. In addition, that their phenotype and function differ between subsets is well established. However, it is becoming evident that heterogeneity also exists within each subset, between health and disease (current or past) states, and even between individuals. This realisation casts long shadows, impacting how we identify and classify the subsets, the functions we assign to them, and how they are examined for alterations in disease. Perhaps the most fascinating is evidence that, even in relative health, interindividual differences in monocyte subsets exist. It is proposed that the individual's microenvironment could cause long-lasting or irreversible changes to monocyte precursors that echo to monocytes and through to their derived macrophages. Here, we will discuss the types of heterogeneity recognised in monocytes, the implications of these for monocyte research, and most importantly, the relevance of this heterogeneity for health and disease.

An integrated cell atlas of the lung in health and disease.

Single-cell technologies have transformed our understanding of human tissues. Yet, studies typically capture only a limited number of donors and disagree on cell type definitions. Integrating many single-cell datasets can address these limitations of individual studies and capture the variability present in the population. Here we present the integrated Human Lung Cell Atlas (HLCA), combining 49 datasets of the human respiratory system into a single atlas spanning over 2.4 million cells from 486 individuals. The HLCA presents a consensus cell type re-annotation with matching marker genes, including annotations of rare and previously undescribed cell types. Leveraging the number and diversity of individuals in the HLCA, we identify gene modules that are associated with demographic covariates such as age, sex and body mass index, as well as gene modules changing expression along the proximal-to-distal axis of the bronchial tree. Mapping new data to the HLCA enables rapid data annotation and interpretation. Using the HLCA as a reference for the study of disease, we identify shared cell states across multiple lung diseases, including SPP1+ profibrotic monocyte-derived macrophages in COVID-19, pulmonary fibrosis and lung carcinoma. Overall, the HLCA serves as an example for the development and use of large-scale, cross-dataset organ atlases within the Human Cell Atlas.

Macrophage phagocytosis of SARS-CoV-2-infected cells mediates potent plasmacytoid dendritic cell activation.

Early and strong interferon type I (IFN-I) responses are usually associated with mild COVID-19 disease, whereas persistent or unregulated proinflammatory cytokine responses are associated with severe disease outcomes. Previous work suggested that monocyte-derived macrophages (MDMs) are resistant and unresponsive to SARS-CoV-2 infection. Here, we demonstrate that upon phagocytosis of SARS-CoV-2-infected cells, MDMs are activated and secrete IL-6 and TNF. Importantly, activated MDMs in turn mediate strong activation of plasmacytoid dendritic cells (pDCs), leading to the secretion of high levels of IFN-α and TNF. Furthermore, pDC activation promoted IL-6 production by MDMs. This kind of pDC activation was dependent on direct integrin-mediated cell‒cell contacts and involved stimulation of the TLR7 and STING signaling pathways. Overall, the present study describes a novel and potent pathway of pDC activation that is linked to the macrophage-mediated clearance of infected cells. These findings suggest that a high infection rate by SARS-CoV-2 may lead to exaggerated cytokine responses, which may contribute to tissue damage and severe disease.

SARS-CoV-2 ORF8 Mediates Signals in Macrophages and Monocytes through MyD88 Independently of the IL-17 Receptor.

SARS-CoV-2 has caused an estimated 7 million deaths worldwide to date. A secreted SARS-CoV-2 accessory protein, known as open reading frame 8 (ORF8), elicits inflammatory pulmonary cytokine responses and is associated with disease severity in COVID-19 patients. Recent reports proposed that ORF8 mediates downstream signals in macrophages and monocytes through the IL-17 receptor complex (IL-17RA, IL-17RC). However, generally IL-17 signals are found to be restricted to the nonhematopoietic compartment, thought to be due to rate-limiting expression of IL-17RC. Accordingly, we revisited the capacity of IL-17 and ORF8 to induce cytokine gene expression in mouse and human macrophages and monocytes. In SARS-CoV-2-infected human and mouse lungs, IL17RC mRNA was undetectable in monocyte/macrophage populations. In cultured mouse and human monocytes and macrophages, ORF8 but not IL-17 led to elevated expression of target cytokines. ORF8-induced signaling was fully preserved in the presence of anti-IL-17RA/RC neutralizing Abs and in Il17ra-/- cells. ORF8 signaling was also operative in Il1r1-/- bone marrow-derived macrophages. However, the TLR/IL-1R family adaptor MyD88, which is dispensable for IL-17R signaling, was required for ORF8 activity yet MyD88 is not required for IL-17 signaling. Thus, we conclude that ORF8 transduces inflammatory signaling in monocytes and macrophages via MyD88 independently of the IL-17R.

Exploring the role of secretory proteins in the human infectious diseases diagnosis and therapeutics.

Secretory proteins are playing important role during the host-pathogen interaction to develop the infection or protection into the cell. Pathogens developing infectious disease to human being are taken up by host macrophages or number of immune cells, play an important role in physiological, developmental and immunological function. At the same time, infectious agents are also secreting various proteins to neutralize the resistance caused by host cells and also helping the pathogens to develop the infection. Secretory proteins (secretome) are only developed at the time of host-pathogen interaction, therefore they become very important to develop the targeted and potential therapeutic strategies. Pathogen specific secretory proteins released during interaction with host cell provide opportunity to develop point of care and rapid diagnostic kits. Proteins secreted by pathogens at the time of interaction with host cell have also been found as immunogenic in nature and numbers of vaccines have been developed to control the spread of human infectious diseases. This chapter highlights the importance of secretory proteins in the development of diagnostic and therapeutic strategies to fight against human infectious diseases.

Ultrastructural study confirms the formation of single and heterotypic syncytial cells in bronchoalveolar fluids of COVID-19 patients.

BACKGROUND: SARS-CoV-2 was reported to induce cell fusions to form multinuclear syncytia that might facilitate viral replication, dissemination, immune evasion, and inflammatory responses. In this study, we have reported the types of cells involved in syncytia formation at different stages of COVID-19 disease through electron microscopy. METHODS: Bronchoalveolar fluids from the mild (n = 8, SpO2 > 95%, no hypoxia, within 2-8 days of infection), moderate (n = 8, SpO2 90% to ≤ 93% on room air, respiratory rate ≥ 24/min, breathlessness, within 9-16 days of infection), and severe (n = 8, SpO2 < 90%, respiratory rate > 30/min, external oxygen support, after 17th days of infection) COVID-19 patients were examined by PAP (cell type identification), immunofluorescence (for the level of viral infection), scanning (SEM), and transmission (TEM) electron microscopy to identify the syncytia. RESULTS: Immunofluorescence studies (S protein-specific antibodies) from each syncytium indicate a very high infection level. We could not find any syncytial cells in mildly infected patients. However, identical (neutrophils or type 2 pneumocytes) and heterotypic (neutrophils-monocytes) plasma membrane initial fusion (indicating initiation of fusion) was observed under TEM in moderately infected patients. Fully matured large-size (20-100 µm) syncytial cells were found in severe acute respiratory distress syndrome (ARDS-like) patients of neutrophils, monocytes, and macrophage origin under SEM. CONCLUSIONS: This ultrastructural study on the syncytial cells from COVID-19 patients sheds light on the disease's stages and types of cells involved in the syncytia formations. Syncytia formation was first induced in type II pneumocytes by homotypic fusion and later with haematopoetic cells (monocyte and neutrophils) by heterotypic fusion in the moderate stage (9-16 days) of the disease. Matured syncytia were reported in the late phase of the disease and formed large giant cells of 20 to 100 µm.

A novel insight on SARS-CoV-2 S-derived fragments in the control of the host immunity.

Despite all efforts to combat the pandemic of COVID-19, we are still living with high numbers of infected persons, an overburdened health care system, and the lack of an effective and definitive treatment. Understanding the pathophysiology of the disease is crucial for the development of new technologies and therapies for the best clinical management of patients. Since the manipulation of the whole virus requires a structure with an adequate level of biosafety, the development of alternative technologies, such as the synthesis of peptides from viral proteins, is a possible solution to circumvent this problem. In addition, the use and validation of animal models is of extreme importance to screen new drugs and to compress the organism's response to the disease. Peptides derived from recombinant S protein from SARS-CoV-2 were synthesized and validated by in silico, in vitro and in vivo methodologies. Macrophages and neutrophils were challenged with the peptides and the production of inflammatory mediators and activation profile were evaluated. These peptides were also inoculated into the swim bladder of transgenic zebrafish larvae at 6 days post fertilization (dpf) to mimic the inflammatory process triggered by the virus, which was evaluated by confocal microscopy. In addition, toxicity and oxidative stress assays were also developed. In silico and molecular dynamics assays revealed that the peptides bind to the ACE2 receptor stably and interact with receptors and adhesion molecules, such as MHC and TCR, from humans and zebrafish. Macrophages stimulated with one of the peptides showed increased production of NO, TNF-α and CXCL2. Inoculation of the peptides in zebrafish larvae triggered an inflammatory process marked by macrophage recruitment and increased mortality, as well as histopathological changes, similarly to what is observed in individuals with COVID-19. The use of peptides is a valuable alternative for the study of host immune response in the context of COVID-19. The use of zebrafish as an animal model also proved to be appropriate and effective in evaluating the inflammatory process, comparable to humans.

Targeting tumor-associated macrophages for cancer immunotherapy.

Tumor-associated macrophages (TAMs) are one of the most abundant immune components in the tumor microenvironment and play a plethora of roles in regulating tumorigenesis. Therefore, the therapeutic targeting of TAMs has emerged as a new paradigm for immunotherapy of cancer. Herein, the review summarizes the origin, polarization, and function of TAMs in the progression of malignant diseases. The understanding of such knowledge leads to several distinct therapeutic strategies to manipulate TAMs to battle cancer, which include those to reduce TAM abundance, such as depleting TAMs or inhibiting their recruitment and differentiation, and those to harness or boost the anti-tumor activities of TAMs such as blocking phagocytosis checkpoints, inducing antibody-dependent cellular phagocytosis, and reprogramming TAM polarization. In addition, modulation of TAMs may reshape the tumor microenvironment and therefore synergize with other cancer therapeutics. Therefore, the rational combination of TAM-targeting therapeutics with conventional therapies including radiotherapy, chemotherapy, and other immunotherapies is also reviewed. Overall, targeting TAMs presents itself as a promising strategy to add to the growing repertoire of treatment approaches in the fight against cancer, and it is hopeful that these approaches currently being pioneered will serve to vastly improve patient outcomes and quality of life.

American ginseng with different processing methods ameliorate immunosuppression induced by cyclophosphamide in mice via the MAPK signaling pathways.

This study aimed to clarify the effects of two processed forms of American ginseng (Panax quinquefolius L.) on immunosuppression caused by cyclophosphamide (CTX) in mice. In the CTX-induced immunosuppressive model, mice were given either steamed American ginseng (American ginseng red, AGR) or raw American ginseng (American ginseng soft branch, AGS) by intragastric administration. Serum and spleen tissues were collected, and the pathological changes in mice spleens were observed by conventional HE staining. The expression levels of cytokines were detected by ELISA, and the apoptosis of splenic cells was determined by western blotting. The results showed that AGR and AGS could relieve CTX-induced immunosuppression through the enhanced immune organ index, improved cell-mediated immune response, increased serum levels of cytokines (TNF-α, IFN-γ, and IL-2) and immunoglobulins (IgG, IgA, and IgM), as well as macrophage activities including carbon clearance and phagocytic index. AGR and AGS downregulated the expression of BAX and elevated the expression of Bcl-2, p-P38, p-JNK, and p-ERK in the spleens of CTX-injected animals. Compared to AGS, AGR significantly improved the number of CD4+CD8-T lymphocytes, the spleen index, and serum levels of IgA, IgG, TNF-α, and IFN-γ. The expression of the ERK/MAPK pathway was markedly increased. These findings support the hypothesis that AGR and AGS are effective immunomodulatory agents capable of preventing immune system hypofunction. Future research may investigate the exact mechanism to rule out any unforeseen effects of AGR and AGS.

Immunomodulation of B Lymphocytes by Prebiotics, Probiotics and Synbiotics: Application in Pathologies.

INTRODUCTION: Prebiotics, probiotics and synbiotics are known to have major beneficial effects on human health due to their ability to modify the composition and the function of the gut mucosa, the gut microbiota and the immune system. These components largely function in a healthy population throughout different periods of life to confer homeostasis. Indeed, they can modulate the composition of the gut microbiota by increasing bacteria strands that are beneficial for health, such as Firmicute and Bifidobacteria, and decreasing harmful bacteria, such as Enteroccocus. Their immunomodulation properties have been extensively studied in different innate cells (dendritic cells, macrophages, monocytes) and adaptive cells (Th, Treg, B cells). They can confer a protolerogenic environment but also modulate pro-inflammatory responses. Due to all these beneficial effects, these compounds have been investigated to prevent or to treat different diseases, such as cancer, diabetes, allergies, autoimmune diseases, etc. Regarding the literature, the effects of these components on dendritic cells, monocytes and T cells have been studied and presented in a number of reviews, but their impact on B-cell response has been less widely discussed. CONCLUSIONS: For the first time, we propose here a review of the literature on the immunomodulation of B-lymphocytes response by prebiotics, probiotics and synbiotics, both in healthy conditions and in pathologies. DISCUSSION: Promising studies have been performed in animal models, highlighting the potential of prebiotics, probiotics and synbiotics intake to treat or to prevent diseases associated with B-cell immunomodulation, but this needs to be validated in humans with a full characterization of B-cell subsets and not only the humoral response.

Biologic Mechanisms of Macrophage Phenotypes Responding to Infection and the Novel Therapies to Moderate Inflammation.

Pro-inflammatory and anti-inflammatory types are the main phenotypes of the macrophage, which are commonly notified as M1 and M2, respectively. The alteration of macrophage phenotypes and the progression of inflammation are intimately associated; both phenotypes usually coexist throughout the whole inflammation stage, involving the transduction of intracellular signals and the secretion of extracellular cytokines. This paper aims to address the interaction of macrophages and surrounding cells and tissues with inflammation-related diseases and clarify the crosstalk of signal pathways relevant to the phenotypic metamorphosis of macrophages. On these bases, some novel therapeutic methods are proposed for regulating inflammation through monitoring the transition of macrophage phenotypes so as to prevent the negative effects of antibiotic drugs utilized in the long term in the clinic. This information will be quite beneficial for the diagnosis and treatment of inflammation-related diseases like pneumonia and other disorders involving macrophages.

The specialized pro-resolving lipid mediator Protectin D1 affects macrophages differentiation and activity in Adult-onset Still's disease and COVID-19, two hyperinflammatory diseases sharing similar transcriptomic profiles.

Introduction: COVID-19 and autoinflammatory diseases, such as Adult-onset Still's Disease (AOSD), are characterized by hyperinflammation, in which it is observed massive production and uncontrolled secretion of pro-inflammatory cytokines. The specialized pro-resolving lipid mediators (SPMs) family is one the most important processes counteracting hyperinflammation inducing tissue repair and homeostasis restoration. Among SPMs, Protectin D1 (PD1) is able to exert antiviral features, at least in animal models. The aim of this study was to compare the transcriptome of peripheral blood mononuclear cells (PBMCs) from patients with AOSD and COVID-19 and to evaluate the role of PD1 on those diseases, especially in modulating macrophages polarization. Methods: This study enrolled patients with AOSD, COVID-19, and healthy donors HDs, undergoing clinical assessment and blood sample collection. Next-generation deep sequencing was performed to identify differences in PBMCs transcripts profiles. Plasma levels of PD1 were assessed by commercial ELISA kits. Monocyte-derived macrophages were polarized into M1 and M2 phenotypes. We analyzed the effect of PD1 on macrophages differentiation. At 10 days, macrophages were analyzed for surface expression of subtypes markers by flow cytometry. Cytokines production was measured in supernatants by Bio-Plex Assays. Results: In the transcriptomes from AOSD patients and COVID-19 patients, genes involved in inflammation, lipid catabolism, and monocytes activation were specifically dysregulated in AOSD and COVID-19 patients when compared to HDs. Patients affected by COVID-19, hospitalized in intensive care unit (ICU), showed higher levels of PD1 when compared to not-ICU hospitalized patients and HDs (ICU COVID-19 vs not-ICU COVID-19, p= 0.02; HDs vs ICU COVID-19, p= 0.0006). PD1 levels were increased in AOSD patients with SS ≥1 compared to patients with SS=0 (p=0.028) and HDs (p=0.048). In vitro treatment with PD1 of monocytes-derived macrophages from AOSD and COVID-19 patients induced a significant increase of M2 polarization vs control (p<0.05). Furthermore, a significant release of IL-10 and MIP-1ß from M2 macrophages was observed when compared to controls (p<0.05). Discussion: PD1 is able to induce pro-resolutory programs in both AOSD and COVID-19 increasing M2 polarization and inducing their activity. In particular, PD1-treated M2 macrophages from AOSD and COVID-19 patients increased the production of IL-10 and enhanced homeostatic restoration through MIP-1ß production.

Activation of transcription factor CREB in human macrophages by Mycobacterium tuberculosis promotes bacterial survival, reduces NF-kB nuclear transit and limits phagolysosome fusion by reduced necroptotic signaling.

Macrophages are a first line of defense against pathogens. However, certain invading microbes modify macrophage responses to promote their own survival and growth. Mycobacterium tuberculosis (M.tb) is a human-adapted intracellular pathogen that exploits macrophages as an intracellular niche. It was previously reported that M.tb rapidly activates cAMP Response Element Binding Protein (CREB), a transcription factor that regulates diverse cellular responses in macrophages. However, the mechanism(s) underlying CREB activation and its downstream roles in human macrophage responses to M.tb are largely unknown. Herein we determined that M.tb-induced CREB activation is dependent on signaling through MAPK p38 in human monocyte-derived macrophages (MDMs). Using a CREB-specific inhibitor, we determined that M.tb-induced CREB activation leads to expression of immediate early genes including COX2, MCL-1, CCL8 and c-FOS, as well as inhibition of NF-kB p65 nuclear localization. These early CREB-mediated signaling events predicted that CREB inhibition would lead to enhanced macrophage control of M.tb growth, which we observed over days in culture. CREB inhibition also led to phosphorylation of RIPK3 and MLKL, hallmarks of necroptosis. However, this was unaccompanied by cell death at the time points tested. Instead, bacterial control corresponded with increased colocalization of M.tb with the late endosome/lysosome marker LAMP-1. Increased phagolysosomal fusion detected during CREB inhibition was dependent on RIPK3-induced pMLKL, indicating that M.tb-induced CREB signaling limits phagolysosomal fusion through inhibition of the necroptotic signaling pathway. Altogether, our data show that M.tb induces CREB activation in human macrophages early post-infection to create an environment conducive to bacterial growth. Targeting certain aspects of the CREB-induced signaling pathway may represent an innovative approach for development of host-directed therapeutics to combat TB.

Targeting immunometabolism against acute lung injury.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are life-threatening conditions triggered by multiple intra- and extra-pulmonary injury factors, characterized by complicated molecular mechanisms and high mortality. Great strides have been made in the field of immunometabolism to clarify the interplay between intracellular metabolism and immune function in the past few years. Emerging evidence unveils the crucial roles of immunometabolism in inflammatory response and ALI. During ALI, both macrophages and lymphocytes undergo robust metabolic reprogramming and discrete epigenetic changes after activated. Apart from providing ATP and biosynthetic precursors, these metabolic cellular reactions and processes in lung also regulate inflammation and immunity.In fact, metabolic reprogramming involving glucose metabolism and fatty acidoxidation (FAO) acts as a double-edged sword in inflammatory response, which not only drives inflammasome activation but also elicits anti-inflammatory response. Additionally, the features and roles of metabolic reprogramming in different immune cells are not exactly the same. Here, we outline the evidence implicating how adverse factors shape immunometabolism in differentiation types of immune cells during ALI and summarize key proteins associated with energy expenditure and metabolic reprogramming. Finally, novel therapeutic targets in metabolic intermediates and enzymes together with current challenges in immunometabolism against ALI were discussed.

A shift in lung macrophage composition is associated with COVID-19 severity and recovery.

Although it has been more than 2 years since the start of the coronavirus disease 2019 (COVID-19) pandemic, COVID-19 continues to be a worldwide health crisis. Despite the development of preventive vaccines, therapies to treat COVID-19 and other inflammatory diseases remain a major unmet need in medicine. Our study sought to identify drivers of disease severity and mortality to develop tailored immunotherapy strategies to halt disease progression. We assembled the Mount Sinai COVID-19 Biobank, which was composed of almost 600 hospitalized patients followed longitudinally through the peak of the pandemic in 2020. Moderate disease and survival were associated with a stronger antigen presentation and effector T cell signature. In contrast, severe disease and death were associated with an altered antigen presentation signature, increased numbers of inflammatory immature myeloid cells, and extrafollicular activated B cells that have been previously associated with autoantibody formation. In severely ill patients with COVID-19, lung tissue-resident alveolar macrophages not only were drastically depleted but also had an altered antigen presentation signature, which coincided with an influx of inflammatory monocytes and monocyte-derived macrophages. In addition, we found that the size of the alveolar macrophage pool correlated with patient outcome and that alveolar macrophage numbers and functionality were restored to homeostasis in patients who recovered from COVID-19. These data suggest that local and systemic myeloid cell dysregulation are drivers of COVID-19 severity and modulation of alveolar macrophage numbers and activity in the lung may be a viable therapeutic strategy for the treatment of critical inflammatory lung diseases.

Neutrophils in Health and Disease: From Receptor Sensing to Inflammasome Activation.

Neutrophils-polymorphonuclear cells (PMNs) are the cells of the initial immune response and make up the majority of leukocytes in the peripheral blood. After activation, these cells modify their functional status to meet the needs at the site of action or according to the agent causing injury. They receive signals from their surroundings and "plan" the course of the response in both temporal and spatial contexts. PMNs dispose of intracellular signaling pathways that allow them to perform a wide range of functions associated with the development of inflammatory processes. In addition to these cells, some protein complexes, known as inflammasomes, also have a special role in the development and maintenance of inflammation. These complexes participate in the proteolytic activation of key pro-inflammatory cytokines, such as IL-1ß and IL-18. In recent years, there has been significant progress in the understanding of the structure and molecular mechanisms behind the activation of inflammasomes and their participation in the pathogenesis of numerous diseases. The available reports focus primarily on macrophages and dendritic cells. According to the literature, the activation of inflammasomes in neutrophils and the associated death type-pyroptosis-is regulated in a different manner than in other cells. The present work is a review of the latest reports concerning the course of inflammasome activation and inflammatory cytokine secretion in response to pathogens in neutrophils, as well as the role of these mechanisms in the pathogenesis of selected diseases.

Macrophage ACE2 is necessary for SARS-CoV-2 replication and subsequent cytokine responses that restrict continued virion release.

Macrophages are key cellular contributors to the pathogenesis of COVID-19, the disease caused by the virus SARS-CoV-2. The SARS-CoV-2 entry receptor ACE2 is present only on a subset of macrophages at sites of SARS-CoV-2 infection in humans. Here, we investigated whether SARS-CoV-2 can enter macrophages, replicate, and release new viral progeny; whether macrophages need to sense a replicating virus to drive cytokine release; and, if so, whether ACE2 is involved in these mechanisms. We found that SARS-CoV-2 could enter, but did not replicate within, ACE2-deficient human primary macrophages and did not induce proinflammatory cytokine expression. By contrast, ACE2 overexpression in human THP-1-derived macrophages permitted SARS-CoV-2 entry, processing and replication, and virion release. ACE2-overexpressing THP-1 macrophages sensed active viral replication and triggered proinflammatory, antiviral programs mediated by the kinase TBK-1 that limited prolonged viral replication and release. These findings help elucidate the role of ACE2 and its absence in macrophage responses to SARS-CoV-2 infection.

Neuroimmune nexus in the pathophysiology and therapy of inflammatory disorders: Role of α7 nicotinic acetylcholine receptors.

The α7-nicotinic acetylcholine receptor (α7nAChR) is a key protein in the cholinergic anti-inflammatory pathway (CAP) that links the nervous and immune systems. Initially, the pathway was discovered based on the observation that vagal nerve stimulation (VNS) reduced the systemic inflammatory response in septic animals. Subsequent studies form a foundation for the leading hypothesis about the central role of the spleen in CAP activation. VNS evokes noradrenergic stimulation of ACh release from T cells in the spleen, which in turn activates α7nAChRs on the surface of macrophages. α7nAChR-mediated signaling in macrophages reduces inflammatory cytokine secretion and modifies apoptosis, proliferation, and macrophage polarization, eventually reducing the systemic inflammatory response. A protective role of the CAP has been demonstrated in preclinical studies for multiple diseases including sepsis, metabolic disease, cardiovascular diseases, arthritis, Crohn's disease, ulcerative colitis, endometriosis, and potentially COVID-19, sparking interest in using bioelectronic and pharmacological approaches to target α7nAChRs for treating inflammatory conditions in patients. Despite a keen interest, many aspects of the cholinergic pathway are still unknown. α7nAChRs are expressed on many other subsets of immune cells that can affect the development of inflammation differently. There are also other sources of ACh that modify immune cell functions. How the interplay of ACh and α7nAChR on different cells and in various tissues contributes to the anti-inflammatory responses requires additional study. This review provides an update on basic and translational studies of the CAP in inflammatory diseases, the relevant pharmacology of α7nAChR-activated drugs and raises some questions that require further investigation.

IL-10 Promotes CXCL13 Expression in Macrophages Following Foot-and-Mouth Disease Virus Infection.

Foot-and-mouth disease (FMD) is one of the most contagious livestock diseases in the world, posing a constant global threat to the animal trade and national economies. The chemokine C-X-C motif chemokine ligand 13 (CXCL13), a biomarker for predicting disease progression in some diseases, was recently found to be increased in sera from mice infected with FMD virus (FMDV) and to be associated with the progression and severity of the disease. However, it has not yet been determined which cells are involved in producing CXCL13 and the signaling pathways controlling CXCL13 expression in these cells. In this study, the expression of CXCL13 was found in macrophages and T cells from mice infected with FMDV, and CXCL13 was produced in bone-marrow-derived macrophages (BMDMs) by activating the nuclear factor-kappaB (NF-κB) and JAK/STAT pathways following FMDV infection. Interestingly, CXCL13 concentration was decreased in sera from interleukin-10 knock out (IL-10-/-) mice or mice blocked IL-10/IL-10R signaling in vivo after FMDV infection. Furthermore, CXCL13 was also decreased in IL-10-/- BMDMs and BMDMs treated with anti-IL-10R antibody following FMDV infection in vitro. Lastly, it was demonstrated that IL-10 regulated CXCL13 expression via JAK/STAT rather than the NF-κB pathway. In conclusion, the study demonstrated for the first time that macrophages and T cells were the cellular sources of CXCL13 in mice infected with FMDV; CXCL13 was produced in BMDMs via NF-κB and JAK/STAT pathways; and IL-10 promoted CXCL13 expression in BMDMs via the JAK/STAT pathway.

A Preliminary Study of Mild Heat Stress on Inflammasome Activation in Murine Macrophages.

Inflammation and mitochondrial-dependent oxidative stress are interrelated processes implicated in multiple neuroinflammatory disorders, including Alzheimer's disease (AD) and depression. Exposure to elevated temperature (hyperthermia) is proposed as a non-pharmacological, anti-inflammatory treatment for these disorders; however, the underlying mechanisms are not fully understood. Here we asked if the inflammasome, a protein complex essential for orchestrating the inflammatory response and linked to mitochondrial stress, might be modulated by elevated temperatures. To test this, in preliminary studies, immortalized bone-marrow-derived murine macrophages (iBMM) were primed with inflammatory stimuli, exposed to a range of temperatures (37-41.5 °C), and examined for markers of inflammasome and mitochondrial activity. We found that exposure to mild heat stress (39 °C for 15 min) rapidly inhibited iBMM inflammasome activity. Furthermore, heat exposure led to decreased ASC speck formation and increased numbers of polarized mitochondria. These results suggest that mild hyperthermia inhibits inflammasome activity in the iBMM, limiting potentially harmful inflammation and mitigating mitochondrial stress. Our findings suggest an additional potential mechanism by which hyperthermia may exert its beneficial effects on inflammatory diseases.