Cells Of Mononuclear Phagocyte System Research Articles

Unifying considerations and evidence of macrophage activation mosaicism through human CSF1R and M1/M2 genes

Addressing the mononuclear phagocyte system (MPS) and macrophage M1/M2 activation is important in diagnosing hematological disorders and inflammatory pathologies and designing therapeutic tools. CSF1R is a reliable marker to identify all circulating MPS cells and tissue macrophages in humans using a single surface protein. CSF1R permits the quantification and isolation of monocyte and dendritic cell (DC) subsets in conjunction with CD14, CD16, and CD1c and is stable across the lifespan and sexes in the absence of overt pathology. Beyond cell detection, measuring M1/M2 activation in humans poses challenges due to response heterogeneity, transient signaling, and multiple regulation steps for transcripts and proteins. MPS cells respond in a conserved manner to M1/M2 pathways such as interleukin-4 (IL-4), steroids, interferon-γ (IFNγ), and lipopolysaccharide (LPS), for which we propose an ad hoc modular gene expression tool. Signature analysis highlights macrophage activation mosaicism in experimental samples, an emerging concept that points to mixed macrophage activation states in pathology.

Single-cell transcriptomic landscape and the microenvironment of normal adjacent tissues in hypopharyngeal carcinoma.

The cellular origin of hypopharyngeal diseases is crucial for further diagnosis and treatment, and the microenvironment in tissues may also be associated with specific cell types at the same time. Normal adjacent tissues (NATs) of hypopharyngeal carcinoma differ from non-tumor-bearing tissues, and can influenced by the tumor. However, the heterogeneity in kinds of disease samples remains little known, and the transcriptomic profile about biological information associated with disease occurrence and clinical outcome contained in it has yet to be fully evaluated. For these reasons, we should quickly investigate the taxonomic and transcriptomic information of NATs in human hypopharynx. Single-cell suspensions of normal adjacent tissues (NATs) of hypopharyngeal carcinoma were obtained and single-cell RNA sequencing (scRNA-seq) was performed. We present scRNA-seq data from 39,315 high-quality cells in the hypopharyngeal from five human donors, nine clusters of normal adjacent human hypopharyngeal cells were presented, including epithelial cells, endothelial cells (ECs), mononuclear phagocyte system cells (MPs), fibroblasts, T cells, plasma cells, B cells, mural cells and mast cells. Nonimmune components in the microenvironment, including epithelial cells, endothelial cells, fibroblasts and the subpopulations of them were performed. Our data provide a solid basis for the study of single-cell landscape in human normal adjacent hypopharyngeal tissues biology and related diseases.

Aryl hydrocarbon receptor activation alters immune cell populations in the lung and bone marrow during coronavirus infection.

Respiratory viral infections are one of the major causes of illness and death worldwide. Symptoms associated with respiratory infections can range from mild to severe, and there is limited understanding of why there is large variation in severity. Environmental exposures are a potential causative factor. The aryl hydrocarbon receptor (AHR) is an environment-sensing molecule expressed in all immune cells. Although there is considerable evidence that AHR signaling influences immune responses to other immune challenges, including respiratory pathogens, less is known about the impact of AHR signaling on immune responses during coronavirus (CoV) infection. In this study, we report that AHR activation significantly altered immune cells in the lungs and bone marrow of mice infected with a mouse CoV. AHR activation transiently reduced the frequency of multiple cells in the mononuclear phagocyte system, including monocytes, interstitial macrophages, and dendritic cells in the lung. In the bone marrow, AHR activation altered myelopoiesis, as evidenced by a reduction in granulocyte-monocyte progenitor cells and an increased frequency of myeloid-biased progenitor cells. Moreover, AHR activation significantly affected multiple stages of the megakaryocyte lineage. Overall, these findings indicate that AHR activation modulates multiple aspects of the immune response to a CoV infection. Given the significant burden of respiratory viruses on human health, understanding how environmental exposures shape immune responses to infection advances our knowledge of factors that contribute to variability in disease severity and provides insight into novel approaches to prevent or treat disease.NEW & NOTEWORTHY Our study reveals a multifaceted role for aryl hydrocarbon receptor (AHR) signaling in the immune response to coronavirus (CoV) infection. Sustained AHR activation during in vivo mouse CoV infection altered the frequency of mature immune cells in the lung and modulated emergency hematopoiesis, specifically myelopoiesis and megakaryopoiesis, in bone marrow. This provides new insight into immunoregulation by the AHR and extends our understanding of how environmental exposures can impact host responses to respiratory viral infections.

Nano‐bio interactions between 2D nanomaterials and mononuclear phagocyte system cells

AbstractTwo‐dimensional (2D) nanomaterials, known for their unique atomic arrangements and exceptional physicochemical properties, have garnered significant attention in biomedical applications, particularly in the realms of immunotherapy for tissue engineering and tumor therapy. These applications necessitate a thorough assessment of the potential influence of 2D nanomaterials on immune cells. Notably, the mononuclear phagocyte system (MPS) cells, which play pivotal roles in both innate and adaptive immunity, are essential for maintaining organismal homeostasis. MPS cells with phagocytic capability contribute to the prevention of foreign body invasion and the elimination of dead or senescent cells. Furthermore, MPS cells, including macrophages and dendritic cells, serve as vital bridges between innate and adaptive immune responses. Therefore, understanding the nano‐bio interactions between 2D nanomaterials and MPS cells is imperative. These nano‐bio interactions including cellular uptake, cytocompatibility, and immunological impact are invaluable for the purposeful design of 2D nanomaterials. Herein, we provide an overview of the latest advancements in understanding the nano‐bio interactions between 2D nanomaterials and MPS cells, and discuss the current challenges and future prospects of employing 2D nanomaterials in the field of nanomedicine.

The Current Pathogenicity and Potential Risk Evaluation of Marburg Virus to Cause Mysterious "Disease X"-An Update on Recent Evidences.

The World Health Organization (WHO) defined Disease X as an upcoming disease with the potential to cause a pandemic. Pathogen X is responsible for Disease X. Marburg virus disease (MVD) is one of the diseases from the priority disease list published by WHO. Marburg virus is a filamentous, negative-sense RNA virus that belongs to the same filovirus family as the lethal Ebola virus. Since the first discovery of this virus in 1967, 17 outbreaks occurred sporadically till 2023. Rousettus aegyptiacus acts as the natural reservoir of the virus. With an average incubation period of 5 to 10 days, its first target is the mononuclear phagocytic system cells. It is highly contagious and can be easily transmitted from animal to human and human to human via direct contact with blood or body fluid, feces, and semen of the infected host. Although Marburg disease has a high case fatality rate of close to 90%, unfortunately, there is no approved vaccines or treatments are available. The most recent outbreak of Marburg virus in Equatorial Guinea and Tanzania in 2023 caused an alert for global health. However, based on the last global pandemic of COVID-19 and the sudden re-emerging of monkeypox around the world, we can assume that the Marburg virus has the potential to cause a global pandemic. Our modern world depends on globalization, which helps the virus transmission among countries. The Marburg virus can easily be transmitted to humans by fruit bats of the Pteropodidae family. This virus causes severe hemorrhagic disease, and there are no specific vaccines and treatments available to combat it. Therefore, community engagement and early supportive care for patients are keys to successfully controlling MVD.

Mutant PIK3CA is a targetable driver alteration in histiocytic neoplasms

AbstractLangerhans cell histiocytosis (LCH) is an inflammatory myeloid neoplasm characterized by the accumulation of clonal mononuclear phagocyte system cells expressing CD1a and CD207. In the past decade, molecular profiling of LCH as well as other histiocytic neoplasms demonstrated that these diseases are driven by MAPK activating alterations, with somatic BRAFV600E mutations in >50% of patients with LCH, and clinical inhibition of MAPK signaling has demonstrated remarkable clinical efficacy. At the same time, activating alterations in kinase-encoding genes, such as PIK3CA, ALK, RET, and CSF1R, which can activate mitogenic pathways independent from the MAPK pathway, have been reported in a subset of histiocytic neoplasms with anecdotal evidence of successful targeted treatment of histiocytoses harboring driver alterations in RET, ALK, and CSF1R. However, evidence supporting the biological consequences of expression of PIK3CA mutations in hematopoietic cells has been lacking, and whether targeted inhibition of PI3K is clinically efficacious in histiocytic neoplasms is unknown. Here, we provide evidence that activating mutations in PIK3CA can drive histiocytic neoplasms in vivo using a conditional knockin mouse expressing mutant PIK3CAH1047R in monocyte/dendritic cell progenitors. In parallel, we demonstrate successful treatment of PIK3CA-mutated, multisystemic LCH using alpelisib, an inhibitor of the alpha catalytic subunit of PI3K. Alpelisib demonstrated a tolerable safety profile at a dose of 750 mg per week and clinical and metabolic complete remission in a patient with PIK3CA-mutated LCH. These data demonstrate PIK3CA as a targetable noncanonical driver of LCH and underscore the importance of mutational analysis–based personalized treatment in histiocytic neoplasms.

Opsin 3 expression in human Langerhans cell histiocytosis and its mediation of ELD-1 cellular function.

Langerhans cell histiocytosis (LCH) is a type of -histiocytic disorder characterized by aberrant function, differentiation or proliferation of mononuclear phagocyte system cells, however, the pathogenesis is not fully understood. Opsin 3 (OPN3) plays an important role in regulating cell function. We aimed to investigate OPN3 expression in LCH and Langerhans cells and evaluate its possible regulation of cellular function in a Langerhans cell-like cell line (ELD-1). Expression of OPN3 in LCH and paired adjacent healthy skin tissue was determined using microscopic tools (immunohistochemical and immunofluorescence staining) and RNA scope. OPN3 protein and mRNA levels in primary dendritic cells and ELD-1 were measured by real-time quantitative PCR and western blotting, respectively. The effects of reduced or over-expressed OPN3 mRNA level, via a lentiviral vector, were examined on ELD-1 proliferation, migration, cell cycle and apoptosis using the Cell Counting Kit 8, EdU-594 kit, Transwell assays and Cell Cycle Analysis Kit and Annexin V-PE apoptosis kit, respectively. Lastly, the signalling pathway mediating these functions was investigated via RNA sequencing and western blotting. OPN3 was highly expressed in human LCH tissue compared to healthy tissue, and was expressed in primary dendritic cells and ELD-1. Knockdown of OPN3 in ELD-1 inhibited cell proliferation, the cell cycle, and cell migration, while over-expression reversed these processes. These functions correlated with induction of the MAPK (p38/JNK/ERK) signalling pathway. Our results provide insight into the role of OPN3 in LCH which may become a molecular target for the clinical treatment of LCH.

Inflammatory and tolerogenic myeloid cells determine outcome following human allergen challenge.

Innate mononuclear phagocytic system (MPS) cells preserve mucosal immune homeostasis. We investigated their role at nasal mucosa following allergen challenge with house dust mite. We combined single-cell proteome and transcriptome profiling on nasal immune cells from nasal biopsies cells from 30 allergic rhinitis and 27 non-allergic subjects before and after repeated nasal allergen challenge. Biopsies of patients showed infiltrating inflammatory HLA-DRhi/CD14+ and CD16+ monocytes and proallergic transcriptional changes in resident CD1C+/CD1A+ conventional dendritic cells (cDC)2 following challenge. In contrast, non-allergic individuals displayed distinct innate MPS responses to allergen challenge: predominant infiltration of myeloid-derived suppressor cells (MDSC: HLA-DRlow/CD14+ monocytes) and cDC2 expressing inhibitory/tolerogenic transcripts. These divergent patterns were confirmed in ex vivo stimulated MPS nasal biopsy cells. Thus, we identified not only MPS cell clusters involved in airway allergic inflammation but also highlight novel roles for non-inflammatory innate MPS responses by MDSC to allergens in non-allergic individuals. Future therapies should address MDSC activity as treatment for inflammatory airway diseases.

NATRIURESIS INDUCED BY ACUTE INTRAVENOUS SALINE INFUSION IN MICE IS MEDIATED BY TUMOR NECROSIS FACTOR-ALPHA (TNF) - EVIDENCE FOR PHYSIOLOGICAL ROLE OF THIS CYTOKINE IN KIDNEY

Objective: Chronic high salt (HS) intake in diet is associated with exacerbation of inflammation as well as hypertension. HS intake, through ‘osmoreceptor function’, induces an immune mechanism that activates the mononuclear phagocyte system (MPS) cells in the myeloid tissues which then circulated and infiltrated in many organs including the kidney. These infiltrated MPS cells release TNF that appears in the circulation in its soluble form (sTNF). We hypothesize that the intravenous saline infusion can also induce the production of sTNF from MPS cells due to an increase in salt content in immune tissues and this sTNF influences saline induced natriuretic response in the kidney. Design and method: To examine this hypothesis, we measured the changes in sTNF levels in plasma and urinary excretion rate (UTNFV) during intravenous infusion of isotonic saline (0.9% NaCl), first at euvolemic conditions (3 μL/min for 60 min; Baseline period) and then at an enhanced infusion rate (12 μL/min for 90 min; saline volume infusion period) in anesthetized mice (n = 5). The concentration of sTNF in plasma and urine samples were determined using ELISA kit (Ebioscience, Woburn, MA) for measuring this cytokine. Results: Baseline level of plasma sTNF was undetectable, however, the level was increased to 3.7±1.3 pg/mL during saline volume infusion period. Baseline UTNFV level was 0.01±0.002 pg/min/g of kidney wt, which was increased to 0.11±0.03 pg/min/g (P<0.05) during volume infusion period. In another group of mice (n = 5) pretreated with a TNF inhibitor, etanercept (0.5 mg/kg intraperitoneally once daily for 3 days prior to the experiment day), it was observed that this increase in UTNFV during saline volume infusion period was markedly attenuated (0.003±0.002 to 0.006±0.004 pg/min/g; P = n.s.). The usual natriuretic response (0.5±0.2 to 3.8 ±1.1 μmol/min/g; P<0.05) to saline volume infusion observed in control mice was seen markedly attenuated (0.4±0.1 to 0.8±0.3 μmol/min/g; P = n.s.) in etanercept pretreated mice. Conclusions: These findings demonstrate for the first time that an intravenous saline volume infusion resulted an increase in sTNF level in plasma and in urine. These results strongly suggest a physiological role for sTNF in regulating renal excretory function during saline volume expansion.

The Role of Mononuclear Phagocytes in the Testes and Epididymis

The mononuclear phagocytic system (MPS) is the primary innate immune cell group in male reproductive tissues, maintaining the balance of pro-inflammatory and immune tolerance. This article aims to outline the role of mononuclear macrophages in the immune balance of the testes and epididymis, and to understand the inner immune regulation mechanism. A review of pertinent publications was performed using the PubMed and Google Scholar databases on all articles published prior to January 2021. Search terms were based on the following keywords: 'MPS', 'mononuclear phagocytes', 'testes', 'epididymis', 'macrophage', 'Mφ', 'dendritic cell', 'DC', 'TLR', 'immune', 'inflammation', and 'polarization'. Additionally, reference lists of primary and review articles were reviewed for other publications of relevance. This review concluded that MPS exhibits a precise balance in the male reproductive system. In the testes, MPS cells are mainly suppressed subtypes (M2 and cDC2) under physiological conditions, which maintain the local immune tolerance. Under pathological conditions, MPS cells will transform into M1 and cDC1, producing various cytokines, and will activate T cell specific immunity as defense to foreign pathogens or self-antigens. In the epididymis, MPS cells vary in the different segments, which express immune tolerance in the caput and pro-inflammatory condition in the cauda. Collectively, MPS is the control point for maintaining the immune tolerance of the testes and epididymis as well as for eliminating pathogens.

The mononuclear phagocyte system in hepatocellular carcinoma.

The mononuclear phagocyte system (MPS) consists of monocytes, dendritic cells and macrophages, which play vital roles in innate immune defense against cancer. Hepatocellular carcinoma (HCC) is a complex disease that is affected or initiated by many factors, including chronic hepatitis B virus infection, hepatitis C virus infection, metabolic disorders or alcohol consumption. Liver function, tumor stage and the performance status of patients affect HCC clinical outcomes. Studies have shown that targeted treatment of tumor microenvironment disorders may improve the efficacy of HCC treatments. Cytokines derived from the innate immune response can regulate T-cell differentiation, thereby shaping adaptive immunity, which is associated with the prognosis of HCC. Therefore, it is important to elucidate the function of the MPS in the progression of HCC. In this review, we outline the impact of HCC on the MPS. We illustrate how HCC reshapes MPS cell phenotype remodeling and the production of associated cytokines and characterize the function and impairment of the MPS in HCC.

Rapid Biotransformation of Luminescent Bimetallic Nanoparticles in Hepatic Sinusoids.

Liver sequestration, mainly resulting from the phagocytosis of mononuclear phagocyte system (MPS) cells, is a long-standing barrier in nanoparticle delivery, which severely decreases the disease-targeting ability, leads to nanotoxicity, and inhibits clinical translation. To avoid long-term liver sequestration, we elaborately designed luminescent gold-silver bimetallic nanoparticles that could be rapidly transformed by the hepatic sinusoidal microenvironment rich in glutathione and oxygen, significantly different from monometallic gold nanoparticles that were rapidly sequestrated by Kupffer cells due to the much slower biotransformation. We found that the rapid sinusoidal biotransformation induced by the synergistic reactions of glutathione and oxygen with the reactive silver atoms could help bimetallic nanoparticles to avoid MPS phagocytosis, promote fast release from the liver, prolong blood circulation, enhance renal clearance, and increase disease targeting. With the fast biotransformation in sinusoids, liver sequestration could be turned into a beneficial storage mechanism for nanomedicines to maximize targeting.

In vivo detection of urokinase-type plasminogen activator receptor (uPAR) expression in arterial atherogenesis using [64Cu]Cu-DOTA-AE105 positron emission tomography (PET)

Background and aimsUrokinase-type plasminogen activator receptor (uPAR) is associated with extracellular matrix (ECM) degradation and cancer aggressiveness. Its role in arterial atherogenesis as a molecular imaging target is not well-established. The aim of this study was to non-invasively visualize uPAR expression in atherosclerosis by a novel uPAR-targeting positron emission tomography (PET) tracer [64Cu]Cu-DOTA-AE105. MethodsWe used molecular biology to investigate uPAR expression by analyzing human atherosclerotic plaques and cultured cells. A retrospective analysis was performed on patients, who underwent combined PET/CT (n = 10) to measure [64Cu]Cu-DOTA-AE105 uptake in five large arteries, divided into a high and low-risk group based on coronary artery calcium score (CAC score). ResultsThe in vitro assay for THP-1 monocytes displayed a significantly upregulated uPAR expression upon stimulation (5.2-fold upregulation, p < 0.0001 by a one-way ANOVA followed by Tukey's test) by single-cell flowcytometric analysis. Freshly excised human atherosclerotic plaques underwent flow cytometric and microarray analyses manifesting 73.9 ± 2.9% of mononuclear phagocyte system (MPS) cells expressing uPAR and had a greater than 7-fold higher gene expression of plasminogen activator urokinase receptor (PLAUR, p = 0.002), integrin subunit alpha X (ITGAX, p = 0.0008), and cluster of differentiation 163 (CD163, p < 0.0001). The tissue-to-background ratios (TBRmax) in five large arteries showed a higher [64Cu]Cu-DOTA-AE105 uptake in the group with high CAC score compared to the group with low CAC score (2.4 ± 0.1 vs 1.7 ± 0.1, p = 0.057), significantly higher in the ascending aorta (2.7 ± 0.1 vs 2.0 ± 0.1, p = 0.038) and the abdominal aorta (3.2 ± 0.2 vs 2.0 ± 0.2, p = 0.038) by a non-parametric Mann-Whitney test. ConclusionsuPAR is abundantly expressed by MPS cells in atherosclerotic plaques and can be visualized by the novel PET tracer [64Cu]Cu-DOTA-AE105 that may non-invasively detect extracellular matrix remodeling during atherogenesis.

Orbital presentation of Langerhans cell histiocytosis

AbstractPurposeTo analyze and review an ophthalmic manifestation of an uncommon pathology such as Langerhans cell histiocytosis (LCH).MethodsSingle‐patient case report.ResultsLCH is an uncommon disorder produced by mononuclear phagocyte system cell proliferation, resulting in antigen‐presenting cells similar to Langerhans cells invading bone, skin, bone marrow, lymphatic nodes, liver, spleen and central nervous system (CNS). The number and location of affected organs is key in treatment and prognosis. In this case report, a 16‐year‐old girl presented 10 day‐long superoexternal orbital pain associated with palpebral edema, making acute dacryoadenitis and preseptal cellulitis the most common differential diagnoses. After poor response to antibiotic and anti‐inflamatory oral treatment, CT scan was ordered, showing an osteolytic frontal mass at the superoexternal orbital roof, expanding to extraconal space and anterior cranial fossa. With a differential diagnosis of LCH, osteomyelitis, hematologic disease or vascular malformation, among others, a biopsy was performed, confirming the LCH diagnosis. An extension exam was performed, excluding new tumors, reaching a diagnosis of a monostotic bone form of LCH. Chemotherapy with prednisone and visblastine was advised due CNS affectation risk because of the tumor’s location, with evident but incomplete response after six‐week induction and complete response after a second six‐week induction cycle. The patient is currently ongoing consolidation chemotherapy.ConclusionsOrbital tumors are not frequent in pediatric ages, but they must be included in the differential diagnosis of orbital cellulitis, since that can be the first manifestation of these tumors.

Pathology and Pathogenesis of Lassa Fever: Novel Immunohistochemical Findings in Fatal Cases and Clinico-pathologic Correlation.

Lassa fever is a zoonotic, acute viral illness first identified in Nigeria in 1969. An estimate shows that the "at risk" seronegative population (in Sierra Leone, Guinea, and Nigeria) may be as high as 59 million, with an annual incidence of all illnesses of 3 million, and fatalities up to 67 000, demonstrating the serious impact of the disease on the region and global health. Histopathologic evaluation, immunohistochemical assay, and electron microscopic examination were performed on postmortem tissue samples from 12 confirmed Lassa fever cases. Lassa fever virus antigens and viral particles were observed in multiple organ systems and cells, including cells in the mononuclear phagocytic system and other specialized cells where it had not been described previously. The immunolocalization of Lassa fever virus antigens in fatal cases provides novel insightful information with clinical and pathogenetic implications. The extensive involvement of the mononuclear phagocytic system, including tissue macrophages and endothelial cells, suggests participation of inflammatory mediators from this lineage with the resulting vascular dilatation and increasing permeability. Other findings indicate the pathogenesis of Lassa fever is multifactorial and additional studies are needed.

Network analysis of transcriptomic diversity amongst resident tissue macrophages and dendritic cells in the mouse mononuclear phagocyte system.

The mononuclear phagocyte system (MPS) is a family of cells including progenitors, circulating blood monocytes, resident tissue macrophages, and dendritic cells (DCs) present in every tissue in the body. To test the relationships between markers and transcriptomic diversity in the MPS, we collected from National Center for Biotechnology Information Gene Expression Omnibus (NCBI-GEO) a total of 466 quality RNA sequencing (RNA-seq) data sets generated from mouse MPS cells isolated from bone marrow, blood, and multiple tissues. The primary data were randomly downsized to a depth of 10 million reads and requantified. The resulting data set was clustered using the network analysis tool BioLayout. A sample-to-sample matrix revealed that MPS populations could be separated based upon tissue of origin. Cells identified as classical DC subsets, cDC1s and cDC2s, and lacking Fcgr1 (encoding the protein CD64) were contained within the MPS cluster, no more distinct than other MPS cells. A gene-to-gene correlation matrix identified large generic coexpression clusters associated with MPS maturation and innate immune function. Smaller coexpression gene clusters, including the transcription factors that drive them, showed higher expression within defined isolated cells, including monocytes, macrophages, and DCs isolated from specific tissues. They include a cluster containing Lyve1 that implies a function in endothelial cell (EC) homeostasis, a cluster of transcripts enriched in intestinal macrophages, and a generic lymphoid tissue cDC cluster associated with Ccr7. However, transcripts encoding Adgre1, Itgax, Itgam, Clec9a, Cd163, Mertk, Mrc1, Retnla, and H2-a/e (encoding class II major histocompatibility complex [MHC] proteins) and many other proposed macrophage subset and DC lineage markers each had idiosyncratic expression profiles. Coexpression of immediate early genes (for example, Egr1, Fos, Dusp1) and inflammatory cytokines and chemokines (tumour necrosis factor [Tnf], Il1b, Ccl3/4) indicated that all tissue disaggregation and separation protocols activate MPS cells. Tissue-specific expression clusters indicated that all cell isolation procedures also co-purify other unrelated cell types that may interact with MPS cells in vivo. Comparative analysis of RNA-seq and single-cell RNA-seq (scRNA-seq) data from the same lung cell populations indicated that MPS heterogeneity implied by global cluster analysis may be even greater at a single-cell level. This analysis highlights the power of large data sets to identify the diversity of MPS cellular phenotypes and the limited predictive value of surface markers to define lineages, functions, or subpopulations.

Abstract P147: Attenuation Of Diuretic And Natriuretic Responses To Acute Saline Volume Expansion In Mice Pre-treated With Tumor Necrosis Factor-alpha (TNFα) Inhibitor, Etanercept.

High salt intake induces an immune response that activates the mononuclear phagocyte system (MPS) cells to produce TNFα. We have previously demonstrated that intravenous infusion of TNFα in mice induces diuresis and natriuresis by inhibiting renal tubular sodium reabsorption. We hypothesize that the intravenous saline infusion can also induce the production of TNFα from MPS cells and such increase in TNFα influences saline induced natriuresis in the kidney. To examine this hypothesis, we measured the changes in TNFα levels in plasma and in urinary excretion rate (U TNFα V) during intravenous infusion of isotonic saline (0.9% NaCl), first at euvolemic condition (3 μL/min for 60 min; Baseline period) and then at an enhanced infusion rate (12 μL/min for 90 min; Volume expansion period) in anesthetized mice (n=5). Renal blood flow (RBF) and glomerular filtration rate (GFR) were measured by PAH and inulin clearances respectively. TNFα concentration in plasma and urine samples were determined using ELISA kit (Ebioscience, Woburn, MA). TNFα level in plasma collected during baseline period was undetectable, however, TNFα was increased to 3.7±1.3 pg/mL during volume expansion (VE) period. Baseline U TNFα V level was 0.01±0.002 pg/min/g (kidney wt), which was increased to 0.11±0.03 pg/min/g (P&lt;0.05) during VE period. VE increased urine flow (V, 5.4±0.5 to 22.0±5.1 μL/min/g; P&lt;0.05) and sodium excretion (U Na V; 0.54±0.19 to 4.84 ±1.16 μmol/min/g; P&lt;0.05) without significant changes in RBF (7.1±1.0 to 6.0±1.8 mL/min/g) and GFR (1.18±0.11 to 0.94±0.28 mL/min/g). Interestingly, the diuretic and natriuretic responses to VE were markedly attenuated in mice (n=5) pretreated with a TNFα inhibitor, etanercept (ETN; 0.5 mg/kg intraperitoneally once daily for 3 days prior to the experiment day). VE induced changes in ETN treated mice are as follows: V, 5.9±0.65 to 7.9 ±1.6 μL/min/g; U Na V, 0.43±0.6 to 1.1±0.28 μmol/min/g; RBF, 5.4±0.4 to 6.6±0.9 mL/min/g and GFR, 0.87±0.09 to 0.98±0.13 mL/min/g. These findings demonstrate for the first time that an intravenous saline volume infusion resulted an increase in TNFα level in plasma and in urine. These results strongly suggest a physiological role for TNFα in regulating renal excretory function during saline volume expansion.

Replication in the Mononuclear Phagocyte System (MPS) as a Determinant of Hantavirus Pathogenicity.

Members of different virus families including Hantaviridae cause viral hemorrhagic fevers (VHFs). The decisive determinants of hantavirus-associated pathogenicity are still enigmatic. Pathogenic hantavirus species, such as Puumala virus (PUUV), Hantaan virus (HTNV), Dobrava-Belgrade virus (DOBV), and Sin Nombre virus (SNV), are associated with significant case fatality rates. In contrast, Tula virus (TULV) only sporadically causes mild disease in immunocompetent humans and Prospect Hill virus (PHV) so far has not been associated with any symptoms. They are thus defined here as low pathogenic/apathogenic hantavirus species. We found that productive infection of cells of the mononuclear phagocyte system (MPS), such as monocytes and dendritic cells (DCs), correlated well with the pathogenicity of hantavirus species tested. HTNV (intermediate case fatality rates) replicated more efficiently than PUUV (low case fatality rates) in myeloid cells, whereas low pathogenic/apathogenic hantavirus species did not produce any detectable virus titers. Analysis of PHPUV, a reassortant hantavirus derived from a pathogenic (PUUV) and an apathogenic (PHV) hantavirus species, indicated that the viral glycoproteins are not decisive for replication in MPS cells. Moreover, blocking acidification of endosomes with chloroquine decreased the number of TULV genomes in myeloid cells suggesting a post-entry block for low pathogenic/apathogenic hantavirus species in myeloid cells. Intriguingly, pathogenic but not low pathogenic/apathogenic hantavirus species induced conversion of monocytes into inflammatory DCs. The proinflammatory programming of MPS cells by pathogenic hantavirus species required integrin signaling and viral replication. Our findings indicate that the capacity to replicate in MPS cells is a prominent feature of hantaviral pathogenicity.

Isotonic saline infusion increases plasma and urinary levels of tumor necrosis factor‐alpha (TNFα) in mice; evidence for a physiological role of this cytokine in regulating renal function during saline volume expansion.

Although TNFα is considered to play its role in many pathological conditions, the physiological role of this cytokine in regulating many organs’ function including the kidney is increasingly recognized in recent days. Chronic high salt (HS) intake in diet induces an immune response that activates the mononuclear phagocyte system (MPS) cells to release TNFα that appears in the circulation in its soluble form (sTNFα). It has been shown that HS (4% NaCl) diet alone for 2 weeks increased MPS cell infiltration in the renal tissue in mice and this is associated with increases in the circulating sTNFα level in the plasma (Singh et al‐2013). It was also demonstrated that 1% salt added to the drinking water for 3 days in mice increases the urinary excretion rate of sTNFα indicating that its release in the kidney from the infiltrated MPS cells occur even at the early stage of HS intake (Hao et al‐2013). We have previously demonstrated that intravenous infusion of recombinant TNFα in mice induces natriuretic response by inhibiting tubular sodium reabsorption (Shahid et al‐2008; Majid‐2011). We hypothesize that the intravenous saline infusion can also induce the production of sTNFα from activated MPS cells due to an increase in salt content in immune tissues and such increase in sTNF influences saline induced natriuretic response in the kidney. To examine this hypothesis, we measured the changes in sTNFα levels in plasma and urinary excretion rate (UTNFαV) during intravenous infusion of isotonic saline (0.9% NaCl), first at euvolemic conditions (3 μL/min for 60 min; Baseline period) and then at an enhanced infusion rate (12 μL/min for 90 min; saline volume infusion period) in anesthetized mice (n=5). The concentration of sTNFα in plasma and urine samples were determined using ELISA kit (Ebioscience, Woburn, MA) for measuring this cytokine. Baseline level of plasma sTNFα was undetectable, however, the level was increased to 3.7±1.3 pg/mL during saline volume infusion period. Baseline UTNFαV level was 0.01±0.002 pg/min/g of kidney wt, which was increased to 0.11±0.03 pg/min/g (P&lt;0.05) during volume infusion period. In another group of mice (n=5) pretreated with a TNFα inhibitor, etanercept (0.5 mg/kg intraperitoneally once daily for 3 days prior to the experiment day), it was observed that this increase in UTNFαV during saline volume infusion period was markedly attenuated (0.003±0.002 to 0.006±0.004 pg/min/g; P=n.s.). The usual natriuretic response (0.5±0.2 to 3.8 ±1.1 μmol/min/g; P&lt;0.05) to saline volume infusion observed in control mice was seen markedly attenuated (0.4±0.1 to 0.8±0.3 μmol/min/g; P=n.s.) in etanercept pretreated mice. These findings demonstrate for the first time that an intravenous saline volume infusion resulted an increase in sTNFα level in plasma and in urine. These results strongly suggest a physiological natriuretic role for sTNFα in regulating renal excretory function during saline volume expansion.

Capturing the Fantastic Voyage of Monocytes Through Time and Space.

Monocytes are a subset of cells that are categorized together with dendritic cells (DCs) and macrophages in the mononuclear phagocyte system (MPS). Despite sharing several phenotypic and functional characteristics with MPS cells, monocytes are unique cells with the ability to function as both precursor and effector cells in their own right. Before the development of hematopoietic stem cells (HSCs) in utero, monocytes are derived from erythro-myeloid precursors (EMPs) in the fetal liver that are important for populating the majority of tissue resident macrophages. After birth, monocytes arise from bone marrow (BM)-derived HSCs and are released into the circulation upon their maturation, where they survey peripheral tissues and maintain endothelial integrity. Upon sensing of microbial breaches or inflammatory stimuli, monocytes migrate into tissues where their plasticity allows them to differentiate into cells that resemble macrophages or DCs according to the environmental niche. Alternatively, they may also migrate into tissues in the absence of inflammation and remain in an undifferentiated state where they perform homeostatic roles. As monocytes are typically on the move, the availability of intravital imaging approaches has provided further insights into their trafficking patterns in distinct tissue compartments. In this review, we outline the importance of understanding their functional behavior in the context of tissue compartments, and how these studies may contribute towards improved vaccine and future therapeutic strategies.