Activation Of Murine Macrophages Research Articles

Extracts of Allium species suppress activation of the NLRP3 and AIM2 inflammasomes and formation of radiation-induced micronuclei

AbstractAllium is a plant genus with high medicinal and dietary value, which encompasses commonly used culinary herbs such as scallion, garlic, and onion. In this study, we investigated whether Allium extracts exert protective effects on radiation-induced chromosomal damage in BALB/c mice. The mice were orally administered 200 mg kg−1 Allium extracts (scallion, garlic, and onion) for 6 weeks and exposed to 2 Gy gamma radiation 1 day after the final feeding. Haematological parameters and the number of micronucleated bone marrow polychromatic erythrocytes (MnPCEs) were evaluated. Additionally, we analysed the effects of Allium extracts on inflammasome activation in lipopolysaccharide-primed murine bone marrow-derived macrophages. The Allium extracts increased the numbers of peripheral white blood cells, lymphocytes, neutrophils, and red blood cells; significantly decreased the number of MnPCEs; and suppressed the maturation of interleukin-1β by blocking activation of the NLRP3 and AIM2 inflammasomes.In conclusion, Allium extracts protected the hematopoietic function of bone marrow, reduced radiation-induced formation of micronuclei, and suppressed activation of the NLRP3 and AIM2 inflammasomes. Further research is needed to explore the molecular mechanisms of these effects of Allium.

Alveolar and Bone Marrow-derived Macrophages Differ in Metabolism and Glutamine Utilization.

Changes in metabolic activity are key regulators of macrophage activity. Pro-inflammatory macrophages upregulate glycolysis, which promotes an inflammatory phenotype, whereas pro-repair macrophages rely upon oxidative metabolism and glutaminolysis to support their activity. Work to understand how metabolism regulates macrophage phenotype has been done primarily in macrophage cell lines and bone marrow-derived macrophages (BMDM). Our study sought to understand changes in metabolic activity of murine tissue-resident alveolar macrophages (AM) in response to LPS stimulation and to contrast them to BMDM. These studies also determined the contribution of glutamine metabolism using the glutamine inhibitor, DON. We found that compared to BMDM, AM have higher rates of oxygen consumption and contain a higher concentration of intracellular metabolites involved in fatty acid oxidation. In response to LPS, BMDM but not AM increased rates of glycolysis. Inhibition of glutamine metabolism using DON altered the metabolic activity of AM but not BMDM. Within AM, glutamine inhibition led to increases in intracellular metabolites involved in glycolysis, the TCA cycle, fatty acid oxidation, and amino acid metabolism. Glutamine inhibition also altered the metabolic response to LPS within AM but not BMDM. Our data reveal striking differences in the metabolic activity of AM and BMDM.

Urea Suppresses the Alternative Activation of Murine Macrophages

Urea Suppresses the Alternative Activation of Murine Macrophages

Synthesis and pharmacological properties of novel guanidine derivatives of quinazoline-2,4(1H,3H)-dione

Introduction: Na+/H+ exchanger type 1 (NHE-1) is a validated drug target for the treatment of cardiovascular and ophthalmic diseases due to the cytoprotective, anti-ischemic and anti-inflammatory properties of NHE-1 inhibitors. This article presents data on the synthesis and pharmacological activity studies of novel guanidine derivatives of quinazoline-2,4(1H,3H)-dione 6-11 and reference drugs amiloride, rimeporide, zoniporide, dexamethasone, aminoguanidine, and acetylsalicylic acid. Materials and Methods: Pharmacological properties were assessed using pH-dependent platelets deformation assay, anti-inflammatory activity assay on LPS-stimulated peritoneal macrophages, antiglycation assay, analysis of platelet aggregation in vitro and measurement of intraocular pressure in vivo. Results: Several compounds combine NHE-1 inhibition with antiglaucomic and antiplatelet activity. Compound 11 significantly inhibits pro-inflammatory activation of murine macrophages (IC50 15.64 μM) and effectively suppresses the formation of glycated proteins (38.1±2.6% in C 1 mM). Conclusion: The investigated compounds represent a promising scaffold for development of agents for the treatment of cardiovascular pathologies, glaucoma, excessive inflammation, and late diabetic complications including retina diabetics and thrombosis.

Linoleic acid-derived diol 12,13-DiHOME enhances NLRP3 inflammasome activation in macrophages.

12,13-dihydroxy-9z-octadecenoic acid (12,13-DiHOME) is a linoleic acid diol derived from cytochrome P-450 (CYP) epoxygenase and epoxide hydrolase (EH) metabolism. 12,13-DiHOME is associated with inflammation and mitochondrial damage in the innate immune response, but how 12,13-DiHOME contributes to these effects is unclear. We hypothesized that 12,13-DiHOME enhances macrophage inflammation through effects on NOD-like receptor protein 3 (NLRP3) inflammasome activation. To test this hypothesis, we utilized human monocytic THP1 cells differentiated into macrophage-like cells with phorbol myristate acetate (PMA). 12,13-DiHOME present during lipopolysaccharide (LPS)-priming of THP1 macrophages exacerbated nigericin-induced NLRP3 inflammasome activation. Using high-resolution respirometry, we observed that priming with LPS+12,13-DiHOME altered mitochondrial respiratory function. Mitophagy, measured using mito-Keima, was also modulated by 12,13-DiHOME present during priming. These mitochondrial effects were associated with increased sensitivity to nigericin-induced mitochondrial depolarization and reactive oxygen species production in LPS+12,13-DiHOME-primed macrophages. Nigericin-induced mitochondrial damage and NLRP3 inflammasome activation in LPS+12,13-DiHOME-primed macrophages were ablated by the mitochondrial calcium uniporter (MCU) inhibitor, Ru265. 12,13-DiHOME present during LPS-priming also enhanced nigericin-induced NLRP3 inflammasome activation in primary murine bone marrow-derived macrophages. In summary, these data demonstrate a pro-inflammatory role for 12,13-DiHOME by enhancing NLRP3 inflammasome activation in macrophages.

Glucomannan is a promising isoniazid's enhancer that inducing macrophage phagocytosis.

Isoniazid (INH) is a frontline antituberculosis agent effective against Mycobacterium tuberculosis (Mtb), but the increasing challenge of avoiding multidrug-resistant tuberculosis, including INH resistance, necessitates innovative approaches. This study focused on enhancing macrophage phagocytosis to overcome INH resistance. Glucomannan, an immunomodulatory polysaccharide, emerged as a potential macrophage activator. Our objective was to characterize the glucomannan-INH mixture and assess its impact on INH efficacy and macrophage activity. Detailed examination of the glucomannan from Amorphophallus muelleri (0.05%-0.2%) was performed in several methods. INH sensitivity tests were carried out with the Mtb strain H37RV on Löwenstein-Jensen medium. Murine macrophage (RAW264.7) viability and activity were evaluated through MTT and latex bead phagocytosis assays. Ultraviolet-wavelength spectrophotometry was used to analyze chemical structure changes. Glucomannan (0.05%-0.2%) significantly enhanced murine macrophage viability and activity. When glucomannan was combined with INH, the IC50 value was greater compared to INH only. Phagocytosis assays revealed heightened macrophage activity in the presence of 0.05% and 0.1% glucomannan. Importantly, glucomannan did not compromise INH efficacy or alter its chemical structure. This study underscores the potential of glucomannan, particularly with a lower molecular weight, as a promising enhancer of INH, boosting macrophage phagocytosis against INH-resistant Mtb. These findings challenge the assumptions about the impact of glucomannan on drug absorption and prompt potential reevaluation. While specific receptors for glucomannan in macrophage phagocytosis require further exploration, the complement receptors are proposed to be potential mediators.

Molecular characteristics of Echinococcus multilocularis FABP1 and its regulatory functions on murine macrophages

Fatty acid binding proteins (FABPs) have emerged as attractive vaccination candidates for several platyhelminth species. To explore the physiological functions of Echinococcus multilocularis (E. multilocularis) FABP, the molecular characteristics of EmFABP1 were analyzed by online software, and the regulatory roles of rEmFABP1 protein in murine macrophages were further investigated. The emfabp1 gene encodes 133 amino acids with the characteristic β-barrel shape of the cytoplasmic FABP family. Natural EmFABP1 protein is predominantly expressed in protoscoleces tegument and germinal layer cells and is also detected in cyst fluid and exosomes of E. multilocularis. rEmFABP1 protein demonstrated a notable suppression of phagocytic activity and nitric oxide production in murine macrophages. Additionally, the protein was observed to promote apoptosis and regulate cytokine expression in macrophages. These findings suggested that E. multilocularis FABP1 is critical in modifying macrophage physiological processes and that this protein may have immunomodulatory roles during infection.

Activation of murine macrophages by membrane proteins from Tritrichomonas foetus grown on iron- and calcium-rich conditions.

Tritrichomonas foetus is a protozoan parasite that causes a venereal disease in cattle limiting reproduction by abortions and sterility. The immune response against this parasite is poorly understood. Since the iron and calcium ions are important regulators of the microenvironment of the urogenital tract in cattle, we decided to evaluate the role of these divalent cations on the antigenicity of membrane proteins of T. foetus on macrophage activation as one of the first inflammatory responses towards this pathogen. Colorimetric methods and ELISA were used to detect the nitric oxide and oxygen peroxide production and expression of cytokines in culture supernatant from macrophage incubated with membrane proteins from T. foetus cultured in iron- and calcium-rich conditions. qRT-PCR assays were used to evaluate the transcript expression of genes involved in the inflammatory response on the macrophages. The membrane proteins used for in vitro stimulation caused the up-regulation of the iNOS and NOX-2 genes as well as the generation of NO and H2 O2 in murine macrophages on a dependent way of the metal concentrations. Additionally, after stimulation, macrophages showed a considerable rise in pro-inflammatory cytokines and a downregulation of anti-inflammatory cytokines, as well as up-regulation in the transcription of the TLR4 and MyD88 genes. These data suggest that membrane proteins of T. foetus induced by iron and calcium can activate an inflammatory specific macrophage response via TLR4/MyD88 signalling pathway.

Anti-inflammatory effects of yeast-derived vacuoles on LPS-induced murine macrophage activation.

Saccharomyces cerevisiae is a single-celled fungal microorganism. S. cerevisiae-derived vacuoles are closely related to mammalian lysosomes, which play a role in the degradation of macromolecules by various hydrolytic enzymes. This study evaluated the anti-inflammatory efficacy of S. cerevisiae-vacuoles by inhibiting inflammatory mediators induced by lipopolysaccharide (LPS). The results showed that treatment with 5, 10, and 20 µg/mL of S. cerevisiae-derived vacuoles almost completely inhibited the LPS-induced expression of iNOS protein and mRNA. Moreover, vacuoles significantly reduced the mRNA expression of tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL-1β), and interleukin 6 (IL-6) in LPS-stimulated macrophages compared to the control cells. The immunofluorescence analysis confirmed that S. cerevisiae-derived vacuoles inhibited the translocation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in LPS-stimulated cells. Taken together, the treatment with S. cerevisiae-derived vacuoles alone activated macrophages, but LPS-activated macrophages modulated pro-inflammatory mediators by downregulating the NF-κB pathway. These results suggest that S. cerevisiae-derived vacuoles may have therapeutic potential in the treatment of inflammatory diseases. In conclusion, our study provides new insights into the immunomodulatory effects of S. cerevisiae-derived vacuoles and their potential as a novel anti-inflammatory agent. IMPORTANCE This study investigates the potential of using vacuoles derived from the yeast Saccharomyces cerevisiae as a new anti-inflammatory therapy. Inflammation is a natural response of the immune system to invading pathogens, but when it is dysregulated, it can lead to chronic diseases. The researchers found that treating macrophages with vacuoles significantly reduced the production of pro-inflammatory cytokines and iNOS, markers of inflammation when they were stimulated with lipopolysaccharide. The study also showed that vacuoles inhibited the NF-κB signaling pathway, which is involved in the induction of pro-inflammatory cytokines in macrophages. These findings suggest that S. cerevisiae-derived vacuoles may have potential as a new therapeutic agent for regulating the inflammatory response in various diseases. Further studies are needed to evaluate the efficacy and safety of vacuoles in vivo and to elucidate the underlying mechanisms of their anti-inflammatory effects.

Role of LCN2 in a murine model of hindlimb ischemia and in peripheral artery disease patients, and its potential regulation by miR-138-5P

Background and aimsPeripheral arterial disease (PAD) is a leading cause of morbimortality worldwide. Lipocalin-2 (LCN2) has been associated with higher risk of amputation or mortality in PAD and might be involved in muscle regeneration. Our aim is to unravel the role of LCN2 in skeletal muscle repair and PAD. Methods and resultsWT and Lcn2−/− mice underwent hindlimb ischemia. Blood and crural muscles were analyzed at the inflammatory and regenerative phases. At day 2, Lcn2−/− male mice, but not females, showed increased blood and soleus muscle neutrophils, and elevated circulating pro-inflammatory monocytes (p < 0.05), while locally, total infiltrating macrophages were reduced (p < 0.05). Moreover, Lcn2−/− soleus displayed an elevation of Cxcl1 (p < 0.001), and Cxcr2 (p < 0.01 in males), and a decrease in Ccl5 (p < 0.05). At day 15, Lcn2 deficiency delayed muscle recovery, with higher density of regenerating myocytes (p < 0.04) and arterioles (αSMA+, p < 0.025). Reverse target prediction analysis identified miR-138-5p as a potential regulator of LCN2, showing an inverse correlation with Lcn2 mRNA in skeletal muscles (rho = -0.58, p < 0.01). In vitro, miR-138-5p mimic reduced Lcn2 expression and luciferase activity in murine macrophages (p < 0.05). Finally, in human serum miR-138-5p was inversely correlated with LCN2 (p ≤ 0.001 adjusted, n = 318), and associated with PAD (Odds ratio 0.634, p = 0.02, adjusted, PAD n = 264, control n = 54). ConclusionsThis study suggests a possible dual role of LCN2 in acute and chronic conditions, with a probable role in restraining inflammation early after skeletal muscle ischemia, while being associated with vascular damage in PAD, and identifies miR-138-5p as one potential post-transcriptional regulator of LCN2.

A suspension of inactivated bacteria used for vaccination against recurrent urinary tract infections increases the phagocytic activity of murine macrophages.

Urinary tract infections are a major cause of the consumption of antibiotics in humans. We studied the effect of a vaccine (StroVac®, containing inactivated bacteria and used to prevent recurrent urinary tract infections) licensed in Germany on the release of pro-inflammatory cytokines and the phagocytosis of Escherichia (E.) coli in primary murine macrophages and the macrophage cell line J774A.1. StroVac® increased the release of the cytokines TNF-α, IL-6, IL-12/23 p40, and IL-1β and stimulated the phagocytosis of E. coli in a dose-dependent manner. This effect was independent of LPS as shown by the use of macrophages isolated from LPS-resistant C3H/HeJ mice. At concentrations up to 30 mg/l it was not toxic to bacteria or eukaryotic cells. StroVac® does not only act via the adaptive but also by stimulating the innate immune system. This stimulation may help to build trained innate immunity against bacterial pathogens involved in recurrent urinary tract infections.

Interaction of Iron Oxide Nanoparticles with Macrophages Is Influenced Distinctly by "Self" and "Non-Self" Biological Identities.

Upon contact with biological fluids like serum, a protein corona (PC) complex forms on iron oxide nanoparticles (IONPs) in physiological environments and the proteins it contains influence how IONPs act in biological systems. Although the biological identity of PC-IONP complexes has often been studied in vitro and in vivo, there have been inconsistent results due to the differences in the animal of origin, the type of biological fluid, and the physicochemical properties of the IONPs. Here, we identified differences in the PC composition when it was derived from the sera of three species (bovine, murine, or human) and deposited on IONPs with similar core diameters but with different coatings [dimercaptosuccinic acid (DMSA), dextran (DEX), or 3-aminopropyl triethoxysilane (APS)], and we assessed how these differences influenced their effects on macrophages. We performed a comparative proteomic analysis to identify common proteins from the three sera that adsorb to each IONP coating and the 10 most strongly represented proteins in PCs. We demonstrated that the PC composition is dependent on the origin of the serum rather than the nature of the coating. The PC composition critically affects the interaction of IONPs with macrophages in self- or non-self identity models, influencing the activation and polarization of macrophages. However, such effects were more consistent for DMSA-IONPs. As such, a self biological identity of IONPs promotes the activation and M2 polarization of murine macrophages, while a non-self biological identity favors M1 polarization, producing larger quantities of ROS. In a human context, we observed the opposite effect, whereby a self biological identity of DMSA-IONPs promotes a mixed M1/M2 polarization with an increase in ROS production. Conversely, a non-self biological identity of IONPs provides nanoparticles with a stealthy character as no clear effects on human macrophages were evident. Thus, the biological identity of IONPs profoundly affects their interaction with macrophages, ultimately defining their biological impact on the immune system.

ADP as a novel stimulus for NLRP3-inflammasome activation in mice fails to translate to humans

The NLRP3-inflammasome is a cytosolic multiprotein complex that triggers an inflammatory response to certain danger signals. Recently adenosine diphosphate (ADP) was found to activate the NLRP3-inflammasome in murine macrophages via the P2Y1 receptor. Blockade of this signaling pathway reduced disease severity in a murine colitis-model. However, the role of the ADP/P2Y1-axis has not yet been studied in humans. This present study confirmed ADP-dependent NLRP3-inflammasome activation in murine macrophages, but found no evidence for a role of ADP in inflammasome activation in humans. We investigated the THP1 cell line as well as primary monocytes and further looked at macrophages. Although all cells express the three human ADP-receptors P2Y1, P2Y12 and P2Y13, independent of priming, neither increased ASC-speck formation could be detected with flow cytometry nor additional IL-1β release be found in the culture supernatant of ADP stimulated cells. We now show for the first time that the responsiveness of monocytes and macrophages to ADP as well as the regulation of its purinergic receptors is very much dependent on the species. Therefore the signaling pathway found to contribute to colitis in mice is likely not applicable to humans.

SAT-386 - CXCL9 does not ameliorate murine macrophage activation syndrome hepatitis

SAT-386 - CXCL9 does not ameliorate murine macrophage activation syndrome hepatitis

Optimized assay for the measurement of caspase‐1 expression, release, and activity in murine macrophages

AbstractCaspase‐1 is a central component of the cellular inflammatory response, in particular with respect to its key role in the activation of the NLRP3 inflammasome pathway. Activation of caspase‐1 ensures the cleavage and release of the pro‐inflammatory cytokines interleukin (IL)‐1β and IL‐18, as well as the initiation of pyroptosis, that is a distinct form of programmed cell death. Hence, a wide‐ranging analysis of caspase‐1 in cellular systems is of special interest. To meet this requirement, we improved a commercial luminescence‐based caspase‐1 activity assay and combined it with the determination of the expression and release of caspase‐1 protein, using murine J774A.1 macrophages as a model system for in vitro studies. The presented assay procedure offers additional options over commercially available caspase‐1 activity assays as it allows for: (i) The simultaneous analysis of caspase‐1 activity and protein expression (both intracellular as well as secreted protein in supernatant) out of the same cell sample. (ii) A more economical use of valuable compounds and materials and improves the informative value of each measurement, since all results are generated from the same cell sample. Our optimized assay is therefore suitable for an efficient and reliable screening of modulatory effects of compounds of interest at various regulatory stages of the caspase‐1 system.

Transcriptomic signatures reveal a shift towards an anti-inflammatory gene expression profile but also the induction of type I and type II interferon signaling networks through aryl hydrocarbon receptor activation in murine macrophages.

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor that regulates a broad range of target genes involved in the xenobiotic response, cell cycle control and circadian rhythm. AhR is constitutively expressed in macrophages (Mϕ), acting as key regulator of cytokine production. While proinflammatory cytokines, i.e., IL-1β, IL-6, IL-12, are suppressed through AhR activation, anti-inflammatory IL-10 is induced. However, the underlying mechanisms of those effects and the importance of the specific ligand structure are not yet completely understood. Therefore, we have compared the global gene expression pattern in activated murine bone marrow-derived macrophages (BMMs) subsequently to exposure with either benzo[a]pyrene (BaP) or indole-3-carbinol (I3C), representing high-affinity vs. low-affinity AhR ligands, respectively, by means of mRNA sequencing. AhR dependency of observed effects was proved using BMMs from AhR-knockout (Ahr-/-) mice. In total, more than 1,000 differentially expressed genes (DEGs) could be mapped, covering a plethora of AhR-modulated effects on basal cellular processes, i.e., transcription and translation, but also immune functions, i.e., antigen presentation, cytokine production, and phagocytosis. Among DEGs were genes that are already known to be regulated by AhR, i.e., Irf1, Ido2, and Cd84. However, we identified DEGs not yet described to be AhR-regulated in Mϕ so far, i.e., Slpi, Il12rb1, and Il21r. All six genes likely contribute to shifting the Mϕ phenotype from proinflammatory to anti-inflammatory. The majority of DEGs induced through BaP were not affected through I3C exposure, probably due to higher AhR affinity of BaP in comparison to I3C. Mapping of known aryl hydrocarbon response element (AHRE) sequence motifs in identified DEGs revealed more than 200 genes not possessing any AHRE, and therefore being not eligible for canonical regulation. Bioinformatic approaches modeled a central role of type I and type II interferons in the regulation of those genes. Additionally, RT-qPCR and ELISA confirmed a AhR-dependent expressional induction and AhR-dependent secretion of IFN-γ in response to BaP exposure, suggesting an auto- or paracrine activation pathway of Mϕ.

The Anti-Atopic Dermatitis Effects of Mentha arvensis Essential Oil Are Involved in the Inhibition of the NLRP3 Inflammasome in DNCB-Challenged Atopic Dermatitis BALB/c Mice.

The NLRP3 inflammasome is upregulated by various agents, such as nuclear factor-kappa B (NF-κB), lipopolysaccharide (LPS), and adenosine triphosphate (ATP). The NLRP3 inflammasome facilitations the maturation of interleukin (IL)-1β, a proinflammatory cytokine that is critically involved in the pathogenesis of atopic dermatitis (AD). Although the NLRP3 inflammasome clearly exacerbates AD symptoms such as erythema and pruritus, drugs for AD patients targeting the NLRP3 inflammasome are still lacking. Based on the previous findings that Mentha arvensis essential oil (MAEO) possesses strong anti-inflammatory and anti-AD properties through its inhibition of the ERK/NF-κB signaling pathway, we postulated that MAEO might be capable of modulating the NLRP3 inflammasome in AD. The aim of this research was to investigate whether MAEO affects the inhibition of NLRP3 inflammasome activation in murine bone marrow-derived macrophages (BMDMs) stimulated with LPS + ATP in vitro and in a murine model displaying AD-like symptoms induced by 2,4-dinitrochlorobenzene (DNCB) in vivo. We found that MAEO inhibited the expression of NLRP3 and caspase-1, leading to the suppression of NLRP3 inflammasome activation and IL-1β production in BMDMs stimulated with LPS + ATP. In addition, MAEO exhibited efficacy in ameliorating AD symptoms in a murine model induced by DNCB, as indicated by the reduction in dermatitis score, ear thickness, transepidermal water loss (TEWL), epidermal thickness, and immunoglobulin E (IgE) levels. Furthermore, MAEO attenuated the recruitment of NLRP3-expressing macrophages and NLRP3 inflammasome activation in murine dorsal skin lesions induced by DNCB. Overall, we provide evidence for the anti-AD effects of MAEO via inhibition of NLRP3 inflammasome activation.

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.

IL-18 Binding Protein-Producing Cells Attenuate Anemia in Murine Macrophage Activation Syndrome.

IL-18 is a pleiotropic immunoregulatory cytokine of the IL-1 family. IL-18 has been identified as a potent IFN-γ inducer in synergy with IL-12 and IL-15 and thus as a powerful Th1 cell-polarizing cytokine. IL-18 activity is regulated by its naturally occurring soluble inhibitor IL-18 binding protein (IL-18BP), the production of which is stimulated by IFN-γ in a negative feedback loop. Circulating levels of IL-18BP are elevated, and unbound bioactive free IL-18 is thus not detectable in the circulation in physiologic conditions. However, emerging evidence indicates that the IL-18/IL-18BP balance could be dysregulated in macrophage activation syndrome (MAS), as mirrored by the presence of free IL-18 in the circulation of patients with MAS. Herein, we sought to identify IL-18BP-producing cells in a murine CpG-induced MAS model using IL-18BP knock-in tdTomato reporter mice. Endothelial cells, tissue-resident macrophages, and neutrophils appeared as major cellular sources of IL-18BP. We also identified extramedullary and medullary early erythroid progenitors as IL-18BP-producing cells in an IFN-γ-dependent manner. This finding suggests a novel regulation of IL-18 activity by erythroid precursors, which are likely involved in the prevention of the negative effects of IL-18 on erythropoiesis. Indeed, coherent invivo and invitro results indicate that IL-18 indirectly impairs erythropoiesis while favoring myelopoiesis and thus contributes to anemia associated with MAS and potentially with other IL-18-driven inflammatory diseases. In conclusion, IL-18BP production by endothelial cells, neutrophils, macrophages, and erythroid precursors attenuates the anemia associated with murine CpG-induced MAS.

P22-Based Nanovaccines against Enterohemorrhagic Escherichia coli.

Enterohemorrhagic Escherichia coli (EHEC) is an important causative agent of diarrhea in humans that causes outbreaks worldwide. Efforts have been made to mitigate the morbidity and mortality caused by these microorganisms; however, the global incidence is still high, causing hundreds of deaths per year. Several vaccine candidates have been evaluated that demonstrate some stability and therapeutic potential but have limited overarching effect. Virus-like particles have been used successfully as nanocontainers for the targeted delivery of drugs, proteins, or nucleic acids. In this study, phage P22 nanocontainers were used as a carrier for the highly antigenic T3SS structural protein EscC that is conserved between EHEC and other enteropathogenic bacteria. We were able to stably incorporate the EscC protein into P22 nanocontainers. The EscC-P22 particles were used to intranasally inoculate mice, which generated specific antibodies against EscC. These antibodies increased the phagocytic activity of murine macrophages infected with EHEC in vitro and reduced bacterial adherence to Caco-2 epithelial cells in vitro, illustrating their functionality. The EscC-P22-based particles are a potential nanovaccine candidate for immunization against EHEC O157:H7 infections. IMPORTANCE This study describes the initial attempt to use P22 viral-like particles as nanocontainers expressing enterohemorrhagic Escherichia coli (EHEC) proteins that are immunogenic and could be used as effective vaccines against EHEC infections.