Prostaglandin E2 promotes M2 polarization of macrophages via a cAMP/CREB signaling pathway and deactivates granulocytes in teleost fish

Decoding Macrophage Subtypes to Engineer Modulating Hydrogels for the Alleviation of Intervertebral Disk Degeneration

A major pathological basis for low back pain is intervertebral disk degeneration, which is primarily caused by the degeneration of nucleus pulposus cells due to imbalances in extracellular matrix (ECM) anabolism and catabolism. The phenotype of macrophages in the local immune microenvironment greatly influences the balance of ECM metabolism. Therefore, the control over the macrophage phenotype of the ECM is promising to repair intervertebral disk degeneration. Herein, the preparation of an injectable nanocomposite hydrogel is reported by embedding epigallocatechin-3-gallate-coated hydroxyapatite nanorods in O-carboxymethyl chitosan cross-linked with aldehyde hyaluronic acid that is capable of modulating the phenotype of macrophages. The bioactive components play a primary role in repairing the nucleus pulposus, where the hydroxyapatite nanorods can promote anabolism in the ECM through the nucleopulpogenic differentiation of mesenchymal stem cells. In addition, epigallocatechin-3-gallate can decrease catabolism in the ECM in nucleus pulposus by inducing M2 macrophage polarization, which exists in normal intervertebral disks and can alleviate degeneration. The nanocomposite hydrogel system shows promise for the minimally invasive and effective treatment of intervertebral disk degeneration by controlling anabolism and catabolism in the ECM and inhibiting the IL17 signaling pathway (M1-related pathway) in vitro and in vivo.

Comparable Response Following Exposure to Biodiesel and Diesel Exhaust Particles in Advanced Multicellular Human Lung Models

Biodiesel is considered to be a sustainable alternative for fossil fuels such as petroleum-based diesel. However, we still lack knowledge about the impact of biodiesel emissions on humans, as airways and lungs are the primary target organs of inhaled toxicants. This study investigated the effect of exhaust particles from well-characterized rapeseed methyl ester (RME) biodiesel exhaust particles (BDEP) and petro-diesel exhaust particles (DEP) on primary bronchial epithelial cells (PBEC) and macrophages (MQ). The advanced multicellular physiologically relevant bronchial mucosa models were developed using human primary bronchial epithelial cells (PBEC) cultured at air-liquid interface (ALI) in the presence or absence of THP-1 cell-derived macrophages (MQ). The experimental set-up used for BDEP and DEP exposures (18 µg/cm² and 36 µg/cm²) as well as the corresponding control exposures were PBEC-ALI, MQ-ALI, and PBEC co-cultured with MQ (PBEC-ALI/MQ). Following exposure to both BDEP and DEP, reactive oxygen species as well as the stress protein heat shock protein 60 were upregulated in PBEC-ALI and MQ-ALI. Expression of both pro-inflammatory (M1: CD86) and repair (M2: CD206) macrophage polarization markers was increased in MQ-ALI after both BDEP and DEP exposures. Phagocytosis activity of MQ and the phagocytosis receptors CD35 and CD64 were downregulated, whereas CD36 was upregulated in MQ-ALI. Increased transcript and secreted protein levels of CXCL8, as well as IL-6 and TNF-α, were detected following both BDEP and DEP exposure at both doses in PBEC-ALI. Furthermore, the cyclooxygenase-2 (COX-2) pathway, COX-2-mediated histone phosphorylation and DNA damage were all increased in PBEC-ALI following exposure to both doses of BDEP and DEP. Valdecoxib, a COX-2 inhibitor, reduced the level of prostaglandin E2, histone phosphorylation, and DNA damage in PBEC-ALI following exposure to both concentrations of BDEP and DEP. Using physiologically relevant multicellular human lung mucosa models with human primary bronchial epithelial cells and macrophages, we found BDEP and DEP to induce comparable levels of oxidative stress, inflammatory response, and impairment of phagocytosis. The use of a renewable carbon-neutral biodiesel fuel does not appear to be more favorable than conventional petroleum-based alternative, as regards of its potential for adverse health effects.

Two ACTH analogs exert differential effects on monocytes/macrophages function regulation in ayu (Plecoglossus altivelis)

Adrenocorticotropic hormone (ACTH), a bioactive peptide of the family of melanocortins, is generated from pro-opiomelanocortin (POMC). So far, the research on the specific functions of ACTH in the immune system of teleosts is limited. We determined two complementary DNA (cDNA) sequences of POMC in ayu (Plecoglossus altivelis), termed PaPOMC-A and PaPOMC-B. PaPOMCs transcripts occurred in all examined tissues, and their expression in immune tissues changed following experimental infection with Vibrio anguillarum. PaACTH-B, but not PaACTH-A, suppressed the phagocytosis of monocytes/macrophages (MO/MФ). Two isoforms of PaACTH increased the bactericidal capacity of MO/MФ. PaACTH-A increased anti-inflammatory cytokine expression, while PaACTH-B decreased pro-inflammatory cytokine expression in MO/MФ. Compared with PaACTH-B treatment, the PaACTH-A treatment improved survival rate and reduced the bacterial load in V. anguillarum-infected ayu through interleukin (IL)-10. Our results indicate that the two PaACTH isoforms exert different effects in the host defense against bacterial infection.

Response mechanism of ♀ Epinephelus fuscoguttatus × ♂ Epinephelus lanceolatus under low-temperature and waterless stresses using TMT proteomic analysis

♀Epinephelus fuscoguttatus × ♂Epinephelus lanceolatus, a hybrid grouper created from artificial breeding, has been widely developed over the past decades. However, the study focusing on lukewarm high-protein-content fish species using advanced techniques has rarely been reported. In this work, the TMT (tandem mass tag)-assisted technique was employed to explore its differentially expressed proteins and response mechanisms under low-temperature dormant and waterless stresses. Our findings suggest that 162 and 258 differentially expressed proteins were identified under low-temperature dormant and waterless stresses, respectively. The waterless preservation treatment further identifies 93 differentially expressed proteins. The identified proteins are categorized and found to participate in lipid metabolism, glycometabolism, oxidative stress, immune response, protein and amino acid metabolism, signal transduction, and other functions. Accordingly, the factors that affect the response mechanisms are highlighted to provide new evidences at protein level.

Production of NOS2 and inflammatory cytokines is reduced by selected protein kinase inhibitors with partial repolarization of HL-60 derived and human blood macrophages

JAK/STAT pathway plays a well-known role in macrophage polarization, but other signaling routes may also be involved. The aim of this study was to identify new signaling pathways and repolarize macrophages by selected protein kinase inhibitors. HL-60 derived macrophages were chosen as model cells and human blood macrophages were used for comparison. M1 and M2 polarization of HL60 derived and human blood macrophages was promoted by LPS + IFNγ (LIF) and IL-4 treatments, respectively. In HL-60 derived macrophages, M1 polarization was mediated by Erk1/2 and p38 phosphorylation, while HSP27 phosphorylation was involved in M2 polarization. The inhibition of both MAPK and JAK/STAT pathways reduced the expression of NOS2, IP-10 and TNFα, IL-8 production was decreased by the inhibition of AMPK and PKD, the upstream kinase of HSP27. HSP27 phosphorylation was inhibited by NB 142, a PKD inhibitor. The expression of CD80 (M1 marker) was reduced by MAPK and JAK/STAT inhibitors, without increasing CD206 (M2 marker). On the other hand, CD206 was reduced by PKD and AMPK inhibitors, without increasing CD80 marker. Phagocytic capacity of HL-60 derived macrophages was higher in M1 macrophages and decreased by trametinib and a p38 inhibitor, while in human blood macrophages, where AT 9283, a JAK/STAT inhibitor also caused a significant decrease in M1 polarized macrophages, no difference was observed between M1 and M2 macrophages. Our results suggest that the repolarization of macrophages cannot be achieved by inhibiting their signaling pathways; nevertheless, the expression of certain polarization markers was decreased, therefore a "depolarization" could be observed both in M1 and M2 polarized cells. Selected protein kinase inhibitors of M1 polarization, decreasing NOS 2 and inflammatory cytokines may be potential candidates for therapeutical trials against inflammatory diseases.

Full-Length Transcriptome: A Reliable Alternative for Single-Cell RNA-Seq Analysis in the Spleen of Teleost Without Reference Genome

Fish is considered as a supreme model for clarifying the evolution and regulatory mechanism of vertebrate immunity. However, the knowledge of distinct immune cell populations in fish is still limited, and further development of techniques advancing the identification of fish immune cell populations and their functions are required. Single cell RNA-seq (scRNA-seq) has provided a new approach for effective in-depth identification and characterization of cell subpopulations. Current approaches for scRNA-seq data analysis usually rely on comparison with a reference genome and hence are not suited for samples without any reference genome, which is currently very common in fish research. Here, we present an alternative, i.e. scRNA-seq data analysis with a full-length transcriptome as a reference, and evaluate this approach on samples from Epinephelus coioides-a teleost without any published genome. We show that it reconstructs well most of the present transcripts in the scRNA-seq data achieving a sensitivity equivalent to approaches relying on genome alignments of related species. Based on cell heterogeneity and known markers, we characterized four cell types: T cells, B cells, monocytes/macrophages (Mo/MΦ) and NCC (non-specific cytotoxic cells). Further analysis indicated the presence of two subsets of Mo/MΦ including M1 and M2 type, as well as four subsets in B cells, i.e. mature B cells, immature B cells, pre B cells and early-pre B cells. Our research will provide new clues for understanding biological characteristics, development and function of immune cell populations of teleost. Furthermore, our approach provides a reliable alternative for scRNA-seq data analysis in teleost for which no reference genome is currently available.

Prostaglandin E3 attenuates macrophage-associated inflammation and prostate tumour growth by modulating polarization

Alternative polarization of macrophages regulates multiple biological processes. While M1‐polarized macrophages generally mediate rapid immune responses, M2‐polarized macrophages induce chronic and mild immune responses. In either case, polyunsaturated fatty acid (PUFA)‐derived lipid mediators act as both products and regulators of macrophages. Prostaglandin E₃ (PGE₃) is an eicosanoid derived from eicosapentaenoic acid, which is converted by cyclooxygenase, followed by prostaglandin E synthase successively. We found that PGE₃ played an anti‐inflammatory role by inhibiting LPS and interferon‐γ‐induced M1 polarization and promoting interleukin‐4‐mediated M2 polarization (M2a). Further, we found that although PGE₃ had no direct effect on the growth of prostate cancer cells in vitro, PGE₃ could inhibit prostate cancer in vivo in a nude mouse model of neoplasia. Notably, we found that PGE₃ significantly inhibited prostate cancer cell growth in a cancer cell‐macrophage co‐culture system. Experimental results showed that PGE₃ inhibited the polarization of tumour‐associated M2 macrophages (TAM), consequently producing indirect anti‐tumour activity. Mechanistically, we identified that PGE₃ regulated the expression and activation of protein kinase A, which is critical for macrophage polarization. In summary, this study indicates that PGE₃ can selectively promote M2a polarization, while inhibiting M1 and TAM polarization, thus exerting an anti‐inflammatory effect and anti‐tumour effect in prostate cancer.

The molecular, functional and phylogenetic characterization of PGE2 receptors reveals their different roles in the immune response of the teleost fish gilthead seabream (Sparus aurata L.)

Prostaglandin E₂ (PGE₂) plays an important role in immune activities in teleost fish, including seabream. However, receptors involved in PGE₂ signaling, as well as the pathways activated downstream, are largely unknown. In this study, one ortholog of mammalian PTGER1, PTGER3 and PTGER4, and two of PTGER2 (Ptger2a and Ptger2b) were identified and characterized in gilthead seabream. In silico analysis showed that all these receptors possessed the organization domain of G protein-coupled receptors, with the exception of Ptger2b. The corresponding in vivo studies revealed that they were expressed in all the tissues examined, the highest mRNA levels of ptger1 and ptger3 being observed in the spleen and of ptger2a and ptger4 in the blood. Bacterial infection induced higher mRNA levels of ptger2a, ptger3 and ptger4 in peritoneal exudate (the site of bacterial injection). In addition, head kidney acidophilic granulocytes and macrophages displayed different ptger1, ptger2a, ptger3 and ptger4 expression profiles. Furthermore, in macrophages the expression of the receptors was weakly affected by stimulation with bacterial DNA or with PGE₂, while in acidophilic granulocytes stimulation resulted in the upregulation of ptger2a and ptger4. Taken together, these results suggest different roles for seabream PGE₂ receptors in the regulation of the immune responses.

Cortisol Metabolism in Carp Macrophages: A Role for Macrophage-Derived Cortisol in M1/M2 Polarization

Macrophages are crucial not only for initiation of inflammation and pathogen eradication (classically polarized M1 macrophages), but also for inflammation inhibition and tissue regeneration (alternatively polarized M2 macrophages). Their polarization toward the M1 population occurs under the influence of interferon-γ + lipopolysaccharide (IFN-γ + LPS), while alternatively polarized M2 macrophages evolve upon, e.g., interlukin 4 (IL-4) or cortisol stimulation. This in vitro study focused on a possible role for macrophage-derived cortisol in M1/M2 polarization in common carp. We studied the expression of molecules involved in cortisol synthesis/conversion from and to cortisone like 11β-hydroxysteroid dehydrogenase type 2 and 3. (11β-HSD2 and 3) and 11β-hydroxylase (CYP11b), as well as the expression of glucocorticoid receptors (GRs) and proliferator-activated receptor gamma (PPARγ) in M1 and M2 macrophages. Lastly, we analyzed how inhibition of these molecules affect macrophage polarization. In M1 cells, upregulation of gene expression of GRs and 11β-HSD3 was found, while, in M2 macrophages, expression of 11β-hsd2 was upregulated. Moreover, blocking of cortisol synthesis/conversion and GRs or PPARγ induced changes in expression of anti-inflammatory interleukin 10 (IL-10). Consequently, our data show that carp monocytes/macrophages can convert cortisol. The results strongly suggest that cortisol, via intracrine interaction with GRs, is important for IL-10-dependent control of the activity of macrophages and for the regulation of M1/M2 polarization to finally determine the outcome of an infection.

17β-Estradiol affects the innate immune response in common carp

Inflammation is the evolutionary conserved immune response to harmful stimuli such as pathogens or damaged cells. This multistep process acts by removing injurious stimuli and initiating the healing process. Therefore, it must be tightly regulated by cytokines, chemokines, and enzymes, as well as neuroendocrine mediators. In the present work, we studied the immunoregulatory properties of 17β-estradiol (E2) in common carp. We determined the in vitro effects of E2 on the activity/polarization of macrophages and the in vivo effects during Aeromonas salmonicida-induced inflammation. In vitro, E2 reduced the lipopolysaccharide (LPS)-stimulated expression of pro- and anti-inflammatory mediator genes but did not change the gene expression of the estrogen receptors and of aromatase CYP19. In contrast, in vivo in the head kidney of A. salmonicida-infected fish, E2-treated feeding induced an upregulation of gene expression of pro-inflammatory (il-12p35 and cxcb2) and anti-inflammatory (arginase 1, arginase 2, il-10, and mmp9) mediators. Moreover, in infected fish fed with E2-treated food, a higher gene expression of the estrogen receptors and of the aromatase CYP19 was found. Our results demonstrate that estrogens can modulate the carp innate immune response, though the in vitro and in vivo effects of this hormone are contrasting. This implies that estradiol not only induces a direct effect on macrophages but rather exerts immunomodulatory actions through indirect mechanisms involving other cellular targets.

Macrophage polarization in innate immune responses contributing to pathogenesis of chronic kidney disease

Chronic kidney disease (CKD) is characterized by inflammation, injury and fibrosis. Dysregulated innate immune responses mediated by macrophages play critical roles in progressive renal injury. The differentiation and polarization of macrophages into pro-inflammatory 'M1' and anti-inflammatory 'M2' states represent the two extreme maturation programs of macrophages during tissue injury. However, the effects of macrophage polarization on the pathogenesis of CKD are not fully understood. In this review, we discuss the innate immune mechanisms underlying macrophage polarization and the role of macrophage polarization in the initiation, progression, resolution and recurrence of CKD. Macrophage activation and polarization are initiated through recognition of conserved endogenous and exogenous molecular motifs by pattern recognition receptors, chiefly, Toll-like receptors (TLRs), which are located on the cell surface and in endosomes, and NLR inflammasomes, which are positioned in the cytosol. Recent data suggest that genetic variants of the innate immune molecule apolipoprotein L1 (APOL1) that are associated with increased CKD prevalence in people of African descent, mediate an atypical M1 macrophage polarization. Manipulation of macrophage polarization may offer novel strategies to address dysregulated immunometabolism and may provide a complementary approach along with current podocentric treatment for glomerular diseases.

Blame the signaling: Role of cAMP for the resolution of inflammation

A complex intracellular signaling governs different cellular responses in inflammation. Extracellular stimuli are sensed, amplified, and transduced through a dynamic cellular network of messengers converting the first signal into a proper response: production of specific mediators, cell activation, survival, or death. Several overlapping pathways are coordinated to ensure specific and timely induction of inflammation to neutralize potential harms to the tissue. Ideally, the inflammatory response must be controlled and self-limited. Resolution of inflammation is an active process that culminates with termination of inflammation and restoration of tissue homeostasis. Comparably to the onset of inflammation, resolution responses are triggered by coordinated intracellular signaling pathways that transduce the message to the nucleus. However, the key messengers and pathways involved in signaling transduction for resolution are still poorly understood in comparison to the inflammatory network. cAMP has long been recognized as an inducer of anti-inflammatory responses and cAMP-dependent pathways have been extensively exploited pharmacologically to treat inflammatory diseases. Recently, cAMP has been pointed out as coordinator of key steps of resolution of inflammation. Here, we summarize the evidence for the role of cAMP at inducing important features of resolution of inflammation.

Transcriptome Analysis of Paralichthys olivaceus Erythrocytes Reveals Profound Immune Responses Induced by Edwardsiella tarda Infection

Unlike mammalian red blood cells (RBCs), fish RBCs are nucleated and thus capable of gene expression. Japanese flounder (Paralichthys olivaceus) is a species of marine fish with important economic values. Flounder are susceptible to Edwardsiella tarda, a severe bacterial pathogen that is able to infect and survive in flounder phagocytes. However, the infectivity of and the immune response induced by E. tarda in flounder RBCs are unclear. In the present research, we found that E. tarda was able to invade and replicate inside flounder RBCs in both in vitro and in vivo infections. To investigate the immune response induced by E. tarda in RBCs, transcriptome analysis of the spleen RBCs of flounder challenged with E. tarda was performed. Six sequencing libraries were constructed, and an average of 43 million clean reads per library were obtained, with 85% of the reads being successfully mapped to the genome of flounder. A total of 1720 differentially expressed genes (DEGs) were identified in E. tarda-infected fish. The DEGs were significantly enriched in diverse Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, especially those associated with immunity, disease, and infection. Ninety-one key DEGs involved in 12 immune-related pathways were found to form extensive interaction networks. Twenty-one genes that constituted the hub of the networks were further identified, which were highly regulated by E. tarda and involved in a number of immune processes, notably pathogen recognition and signal transduction, antigen processing and presentation, inflammation, and splicing. These results provide new insights into the immune role of flounder RBCs during bacterial infection.

Reparative macrophage transplantation for myocardial repair: a refinement of bone marrow mononuclear cell-based therapy

Reparative macrophages play an important role in cardiac repair post-myocardial infarction (MI). Bone marrow mononuclear cells (BM-MNCs) have been investigated as a donor for cell therapy but with limited clinical success. These cells, however, may be utilized as a source for reparative macrophages. This translational study aimed to establish a robust in vitro protocol to produce functional reparative macrophages from BM-MNCs and to establish pre-clinical evidence of the efficacy of reparative macrophage transplantation for the treatment of MI. Mouse BM-MNCs were treated with M-CSF plus IL-4, IL-10, TGF-β1 or combinations of these in vitro. The concomitant administration of M-CSF and IL-4 produced the highest rate and largest number of CD11b+F4/80+CD206+ reparative macrophages. Expression and secretion of tissue repair-related factors including IGF-1, TGF-β1, VEGF and IL1-ra were remarkably enhanced in reparative macrophages compared to BM-MNCs. These cells were transplanted in a mouse MI model, resulting in evident improvement in cardiac function recovery, compared to BM-MNC transplantation. Histological studies showed that reparative macrophage transplantation enhanced myocardial tissue repair including augmented microvascular formation, reduced cardiomyocyte hypertrophy and attenuated interstitial fibrosis. Moreover, survival of reparative macrophages in the heart post-transplantation was increased compared to BM-MNCs. Reparative macrophage transplantation also increased host-derived reparative macrophages in part through TGF-β secretion. In conclusion, concomitant M-CSF + IL-4 treatment effectively produced reparative macrophages from BM-MNCs in vitro. Transplantation of produced reparative macrophage achieved a superior therapeutic efficacy, compared to BM-MNC transplantation, through the enhanced quantity and quality of donor cell engraftment. Further development of this advanced cell-based therapy is warranted.

Glycoconjugates of Gram-negative bacteria and parasitic protozoa - are they similar in orchestrating the innate immune response?

Innate immunity is an evolutionarily ancient form of host defense that serves to limit infection. The invading microorganisms are detected by the innate immune system through germline-encoded PRRs. Different classes of PRRs, including TLRs and cytoplasmic receptors, recognize distinct microbial components known collectively as PAMPs. Ligation of PAMPs with receptors triggers intracellular signaling cascades, activating defense mechanisms. Despite the fact that Gram-negative bacteria and parasitic protozoa are phylogenetically distant organisms, they express glycoconjugates, namely bacterial LPS and protozoan GPI-anchored glycolipids, which share many structural and functional similarities. By activating/deactivating MAPK signaling and NF-κB, these ligands trigger general pro-/anti-inflammatory responses depending on the related patterns. They also use conservative strategies to subvert cell-autonomous defense systems of specialized immune cells. Signals triggered by Gram-negative bacteria and parasitic protozoa can interfere with host homeostasis and, depending on the type of microorganism, lead to hypersensitivity or silencing of the immune response. Activation of professional immune cells, through a ligand which triggers the opposite effect (antagonist versus agonist) appears to be a promising solution to restoring the immune balance.

Streptococcus agalactiae Induces Placental Macrophages To Release Extracellular Traps Loaded with Tissue Remodeling Enzymes via an Oxidative Burst-Dependent Mechanism

Streptococcus agalactiae, also known as group B Streptococcus (GBS), is a common pathogen during pregnancy where infection can result in chorioamnionitis, preterm premature rupture of membranes (PPROM), preterm labor, stillbirth, and neonatal sepsis. Mechanisms by which GBS infection results in adverse pregnancy outcomes are still incompletely understood. This study evaluated interactions between GBS and placental macrophages. The data demonstrate that in response to infection, placental macrophages release extracellular traps capable of killing GBS. Additionally, this work establishes that proteins associated with extracellular trap fibers include several matrix metalloproteinases that have been associated with chorioamnionitis. In the context of pregnancy, placental macrophage responses to bacterial infection might have beneficial and adverse consequences, including protective effects against bacterial invasion, but they may also release important mediators of membrane breakdown that could contribute to membrane rupture or preterm labor.

Streptococcus agalactiae, or group B Streptococcus (GBS), is a common perinatal pathogen. GBS colonization of the vaginal mucosa during pregnancy is a risk factor for invasive infection of the fetal membranes (chorioamnionitis) and its consequences such as membrane rupture, preterm labor, stillbirth, and neonatal sepsis. Placental macrophages, or Hofbauer cells, are fetally derived macrophages present within placental and fetal membrane tissues that perform vital functions for fetal and placental development, including supporting angiogenesis, tissue remodeling, and regulation of maternal-fetal tolerance. Although placental macrophages as tissue-resident innate phagocytes are likely to engage invasive bacteria such as GBS, there is limited information regarding how these cells respond to bacterial infection. Here, we demonstrate in vitro that placental macrophages release macrophage extracellular traps (METs) in response to bacterial infection. Placental macrophage METs contain proteins, including histones, myeloperoxidase, and neutrophil elastase similar to neutrophil extracellular traps, and are capable of killing GBS cells. MET release from these cells occurs by a process that depends on the production of reactive oxygen species. Placental macrophage METs also contain matrix metalloproteases that are released in response to GBS and could contribute to fetal membrane weakening during infection. MET structures were identified within human fetal membrane tissues infected ex vivo, suggesting that placental macrophages release METs in response to bacterial infection during chorioamnionitis.

Molecular characterization of a tissue factor gene from ayu: A pro-inflammatory mediator via regulating monocytes/macrophages

Tissue factor (TF) plays an important role in the host's immune system as the principal initiator of coagulation. However, the precise function of TF in teleosts remains unclear. We determined the cDNA sequence of TF from ayu Plecoglossus altivelis (PaTF). The PaTF transcript was expressed in all tested tissues, and changes in expression were observed in tissues and monocytes/macrophages (MO/MФ) upon infection with Vibrio anguillarum. PaTF was prokaryotically expressed and purified to prepare anti-PaTF antibodies. Western blot analysis revealed that native PaTF was glycosylated in thrombocytes, but not in ayu MO/MФ. Microparticles could transfer PaTF to thrombocytes. PaTF neutralization or knockdown led to anti-inflammatory status in ayu MO/MФ upon V. anguillarum infection. PaTF neutralization reduced the apoptosis of ayu MO/MФ and improve survival rate in V. anguillarum-infected ayu. Our results indicate that PaTF plays a role in ayu immune response against bacterial infection as a pro-inflammatory mediator.

Adipose-derived stem cells ameliorate colitis by suppression of inflammasome formation and regulation of M1-macrophage population through prostaglandin E2

Inflammatory bowel disease (IBD) is an idiopathic disease caused by a dysregulated immune response to intestinal microbes in an individual with a genetic predisposition. Therefore, alleviation of inflammation is very important to treat IBD. Mesenchymal stem cells (MSCs) have been highlighted as new candidates for treating autoimmune disease based on their immunomodulatory properties. In this study, we investigated the anti-inflammatory mechanism and therapeutic effects of adipose tissue-derived MSCs (ASCs) using THP-1 macrophages and dextran sodium sulfate (DSS)-induced mice with chronic colitis. LPS-treated THP-1 cells expressed mRNA of CD11b, an M1 macrophage marker, at day 2. However, THP-1 co-cultured with ASCs expressed mRNA of CD206, CD68, CCL18, legumain, and IL-10, markers of M2 macrophages. In THP-1 cells co-cultured with ASCs, precursor (pro)-IL-1β, Cox-2, and NLRP3 increased dramatically compared to LPS-treated THP-1 cells. Secretion of IL-1β and IL-18 was significantly inhibited by ASCs, but PGE2 production was highly increased in co-culture conditions of THP-1 and ASCs. IL-18 secretion was inhibited by PGE2 treatment, and PGE2 inhibited inflammasome complex (ASC/Cas-1/NLRP3) formation in THP-1 cells. In the DSS-induced chronic colitis model, ASCs ameliorated colitis by decreasing the total number of macrophages and the M1 macrophage population. Our results suggest that ASCs can suppress the inflammatory response by controlling the macrophage population, and ASCs may be therapeutically useful for the treatment of IBD.

Sodium valproate modulates immune response by alternative activation of monocyte-derived macrophages in systemic lupus erythematosus

The anti-inflammatory role of macrophages in apoptotic cells (ACs) clearance is involved in Systemic Lupus Erythematosus (SLE) pathogenesis. The efferocytic capability of macrophages is altered by M1/M2 polarization. Histone deacetylase inhibitors (HDACi) are proposed to enhance the expansion of M2 macrophages. Sodium valproate (VPA) is an HDACi with different anti-inflammatory properties. Here, we aimed to investigate the effects of HDACi by VPA on the polarization of monocyte-derived macrophages (MDMs) and regulating the expression of anti-inflammatory cytokines in SLE. We studied the ex vivo alterations of MDMs among 15 newly diagnosed SLE patients and 10 normal subjects followed by ACs and VPA treatments. M1/M2 polarization was assessed by expression of CD86/CD163, IL1-β, IDO-1, and MRC-1 among treated and non-treated MDMs. We also evaluated the production of IL-10, IL-12, TGF-β1, and TNF-α cytokines in the cell culture supernatants. CD163 was overexpressed upon VPA treatment, while CD86 showed no significant change. IL1-β and IDO-1 genes were significantly downregulated, and the mRNA expression of MRC-1 was increased among VPA-treated MDMs of SLE patients. The anti-inflammatory cytokines (IL-10 and TGF-β1) were overproduced while TNF-α level was decreased in response to VPA. The population of classically activated macrophages was more prevalent among SLE patients and efferocytosis was defected. VPA could successfully enhance the anti-inflammatory immune response through alternative activation of MDMs in SLE patients.

Prostaglandins in teleost ovulation: A review of the roles with a view to comparison with prostaglandins in mammalian ovulation

Prostaglandins are well known to be central regulators of vertebrate ovulation. Studies addressing the role of prostaglandins in mammalian ovulation have established that they are involved in the processes of oocyte maturation and cumulus oocyte complex expansion. In contrast, despite the first indication of the role of prostaglandins in teleost ovulation appearing 40 years ago, the mechanistic background of their role has long been unknown. However, studies conducted on medaka over the past decade have provided valuable information. Emerging evidence indicates an indispensable role of prostaglandin E₂ and its receptor subtype Ptger4b in the process of follicle rupture. In this review, we summarize studies addressing the role of prostaglandins in teleost ovulation and describe recent advances. To help understand differences from and similarities to ovulation in mammalian species, the findings on the roles of prostaglandins in mammalian ovulation are discussed in parallel.

Novel mechanisms of Collagenase Santyl Ointment (CSO) in wound macrophage polarization and resolution of wound inflammation

Collagenases are useful in enzymatic wound debridement. Clostridial collagenase, marketed as Collagenase Santyl Ointment (CSO), is FDA approved for such use. Building on the scientific premise that collagenases as well as collagen degradation products may regulate immune cell function, we sought to investigate the potential role of CSO in wound inflammation. We tested the hypothesis that in addition to enacting debridement, CSO contributes to the resolution of persistent wound inflammation. Wound macrophages were isolated from PVA sponges loaded with CSO or petrolatum and implanted in mice. Significant increase in pro-reparative and decrease in pro-inflammatory polarization was noted in macrophages of acute as well as diabetic wounds. Wound macrophages from CSO-treated group displayed increased production of anti-inflammatory cytokines IL-10 and TGF-β, and decreased levels of pro-inflammatory cytokines TNF-α and IL-1β. The active ingredient of CSO, CS-API, induced the expression of mϕ^heal /M(IL-4) polarization markers ex vivo. CS-API treatment attenuated transactivation of NF-κB and significantly induced STAT6 phosphorylation. A significant role of a novel PGE2-EP4 pathway in CS-API induced STAT6 activation and the mϕ^heal /M(IL-4) polarization was identified. Taken together, findings of this work reposition CSO as a potential agent that may be effective in resolving wound inflammation, including diabetic wounds.

Cyclic AMP Pathway Suppress Autoimmune Neuroinflammation by Inhibiting Functions of Encephalitogenic CD4 T Cells and Enhancing M2 Macrophage Polarization at the Site of Inflammation

Although it has been demonstrated that cAMP pathway affect both adaptive and innate cell functions, the role of this pathway in the regulation of T-cell-mediated central nervous system (CNS) autoimmune inflammation, such as in experimental autoimmune encephalomyelitis (EAE), remains unclear. It is also unclear how cAMP pathway affects the function of CD4 T cells in vivo at the site of inflammation. We found that adenylyl cyclase activator Forskolin besides inhibition of functions autoimmune CD4 T cells also upregulated microRNA (miR)-124 in the CNS during EAE, which is associated with M2 phenotype of microglia/macrophages. Our study further established that in addition to direct influence of cAMP pathway on CD4 T cells, stimulation of this pathway promoted macrophage polarization toward M2 leading to indirect inhibition of function of T cells in the CNS. We demonstrated that Forskolin together with IL-4 or with Forskolin together with IL-4 and IFNγ effectively stimulated M2 phenotype of macrophages indicating high potency of this pathway in reprogramming of macrophage polarization in Th2- and even in Th1/Th2-mixed inflammatory conditions such as EAE. Mechanistically, Forskolin and/or IL-4 activated ERK pathway in macrophages resulting in the upregulation of M2-associated molecules miR-124, arginase (Arg)1, and Mannose receptor C-type 1 (Mrc1), which was reversed by ERK inhibitors. Administration of Forskolin after the onset of EAE substantially upregulated M2 markers Arg1, Mrc1, Fizz1, and Ym1 and inhibited M1 markers nitric oxide synthetase 2 and CD86 in the CNS during EAE resulting in decrease in macrophage/microglia activation, lymphocyte and CD4 T cell infiltration, and the recovery from the disease. Forskolin inhibited proliferation and IFNγ production by CD4 T cells in the CNS but had rather weak direct effect on proliferation of autoimmune T cells in the periphery and in vitro, suggesting prevalence of indirect effect of Forskolin on differentiation and functions of autoimmune CD4 T cells in vivo. Thus, our data indicate that Forskolin has potency to skew balance toward M2 affecting ERK pathway in macrophages and indirectly inhibit pathogenic CD4 T cells in the CNS leading to the suppression of autoimmune inflammation. These data may have also implications for future therapeutic approaches to inhibit autoimmune Th1 cells at the site of tissue inflammation.

A comparative study: Difference in omega-6/omega-3 balance and saturated fat in diets for Atlantic salmon (Salmo salar) affect immune-, fat metabolism-, oxidative and apoptotic-gene expression, and eicosanoid secretion in head kidney leukocytes

The aim of this study was to compare how different dietary vegetable oil n-6/n-3 ratios affect gene responses involved in inflammation, signaling pathways, fatty acid synthesis and oxidation, oxidation and apoptosis as well as eicosanoid production in salmon head kidney tissues and isolated head kidney leukocytes. Salmon smolts (200 g) were fed four different diets where the main lipid components were palm oil (n-6/n-3 ratio = 0.7), rapeseed oil (n-6/n-3 ratio = 0.9), and soybean oil (n-6/n-3 ratio = 2.4) and a high soybean oil diet with an n-6/n-3 ratio = 4. Both head kidney tissue and leukocytes isolated from head kidneys were sampled from the four diets, but from different fish. Leukocytes isolated from the head kidneys were seeded into culture wells and added lipopolysaccharide (LPS) to induce inflammatory responses. Controls without LPS were included. Head kidney leukocytes and the tissues should have the same phenotype reflecting the different diets. Interleukin 1β (IL-1β) transcription was elevated in head kidney tissue and especially in LPS treated leukocytes isolated from soybean oil (n-6/n-3 = 2.4) fed salmon, which confirmed the suitability of the in vitro model in this experiment. Leukocytes, treated with LPS, and isolated from salmon fed the soybean oil diet (n-6/n-3 = 2.4) also upregulated tumor necrosis factor alpha (tnf-α), cyclooxygenase (cox2), prostaglandin D and E synthase (ptgds, ptges), fatty acyl synthase (fas), 5 and 6 desaturases (5des, 6 des) and a fatty acid translocase protein (cd36) when compared to the other diets. The results suggest that diets with a specific n-6/n-3 ratio influence the transcription of pro-inflammatory genes and may be cross-linked to transcription of selected fatty acid metabolism genes. Salmon fed the palm oil diet (n-6/n-3 = 0.7) showed a lower expression of inflammatory genes. Instead, peroxisome proliferator activated receptor β1 (pparβ1), acyl coenzyme A (aco), apoptosis regulator (bax) and superoxide dismutase (sod) were upregulated in leukocytes in vitro, while head kidney tissue transcription of a dendritic marker (cd83) was lower than measured in tissues from fish fed the other diets. The concentration of LTB4 (10-20 ng/mL) were relatively constant in leukocyte supernatants, all diets. Head kidney leukocytes from soybean oil (n-6/n-3 = 2.4) fed fish produced LPS induced PGE2 (mean 0.5 ng/mL) while leukocytes isolated from palm oil diet (n-6/n-3 = 0.7) secreted very high amounts of LTB5 (50-70 ng/mL). In addition, equal amounts of LPS induced PGE2 and PGE3 (mean 0, 5 ng/mL) were produced, indicating that the n-6/n-3 ratio of this saturated fatty acid may have a specific impact on eicosanoid production in the head kidney of salmon.

Growth, blood health, antioxidant status and immune response in juvenile yellow catfish Pelteobagrus fulvidraco exposed to α-ethinylestradiol (EE2)

Triplicate groups of juvenile yellow catfish Pelteobagrus fulvidraco were exposed to three levels of α-ethinylestradiol (EE2) (0, 0.1 and 1 ng L^-1) for 56 days. Fish survival rate (>93.33%) was not different among experimental groups. Weight gain and specific growth rate of fish exposed to EE2 were higher than those of control fish. Hepatosomatic index of fish exposed to 1 ng L^-1 EE2 was the highest. Serum total protein, albumin, globulin, alanine aminotransferase, aspartate transaminase, cholesterol and triglyceride increased with increasing EE2 exposure levels. Liver total anti-oxidative capacity, malondialdehyde content and lysozyme activity of fish exposed to EE2 were higher than those of control fish. Phagocytic indices of fish exposed to 1 ng L^-1 EE2 was lower than that of control fish. This study indicates that although EE2 exposure can promote the growth of yellow catfish in short-term, EE2 exerts its toxic effects by inducing reactive oxygen species generation and malondialdehyde accumulation, leading to blood deterioration and interfering with immune response.

The resolution of acute inflammation induced by cyclic AMP is dependent on annexin A1

Annexin A1 (AnxA1) is a glucocorticoid-regulated protein known for its anti-inflammatory and pro-resolving effects. We have shown previously that the cAMP-enhancing compounds rolipram (ROL; a PDE4 inhibitor) and Bt₂cAMP (a cAMP mimetic) drive caspase-dependent resolution of neutrophilic inflammation. In this follow-up study, we investigated whether AnxA1 could be involved in the pro-resolving properties of these compounds using a model of LPS-induced inflammation in BALB/c mice. The treatment with ROL or Bt₂cAMP at the peak of inflammation shortened resolution intervals, improved resolution indices, and increased AnxA1 expression. In vitro studies showed that ROL and Bt₂cAMP induced AnxA1 expression and phosphorylation, and this effect was prevented by PKA inhibitors, suggesting the involvement of PKA in ROL-induced AnxA1 expression. Akin to these in vitro findings, H89 prevented ROL- and Bt₂cAMP-induced resolution of inflammation, and it was associated with decreased levels of intact AnxA1. Moreover, two different strategies to block the AnxA1 pathway (by using N-t-Boc-Met-Leu-Phe, a nonselective AnxA1 receptor antagonist, or by using an anti-AnxA1 neutralizing antiserum) prevented ROL- and Bt₂cAMP-induced resolution and neutrophil apoptosis. Likewise, the ability of ROL or Bt₂cAMP to induce neutrophil apoptosis was impaired in AnxA-knock-out mice. Finally, in in vitro settings, ROL and Bt₂cAMP overrode the survival-inducing effect of LPS in human neutrophils in an AnxA1-dependent manner. Our results show that AnxA1 is at least one of the endogenous determinants mediating the pro-resolving properties of cAMP-elevating agents and cAMP-mimetic drugs.

CXCR3.1 and CXCR3.2 Differentially Contribute to Macrophage Polarization in Teleost Fish

The study of multiple copies of chemokine receptor genes in various teleosts has long appealed to investigators seeking to understand the evolution of the immune system. The CXCR CXCR3 gene has two isoforms, CXCR3.1 and CXCR3.2, which are both expressed in macrophages. The distinct roles of teleost CXCR3s have not been identified previously. In this article, we found that CXCR3.1 and CXCR3.2 differentially contributed to macrophage polarization in the teleosts: ayu (Plecoglossus altivelis), grass carp (Ctenopharyngodon idella), and spotted green pufferfish (Tetraodon nigroviridis). In ayu macrophages, the P. altivelis CXCR3.1 (PaCXCR3.1) gene was constitutively expressed, whereas the P. altivelis CXCR3.2 (PaCXCR3.2) gene was induced postinfection with Escherichia coli Upon E. coli infection, PaCXCR3.1⁺ and PaCXCR3.2⁺ macrophages showed an M1 and an M2 phenotype, respectively. CXCL9-11-like proteins mediated M1 and M2 polarization by interacting with the PaCXCR3.1 and PaCXCR3.2 proteins on macrophages, respectively. The transcription factors P. altivelis STAT1 and P. altivelis STAT3 were activated in PaCXCR3.1⁺ and PaCXCR3.2⁺ macrophages, respectively. Furthermore, the prognosis of septic ayu adoptively transferred with PaCXCR3.2⁺ macrophages was improved. Our data reveal a previously unknown mechanism for macrophage polarization, suggesting that redundant genes may regulate crucial functions in the teleost immune system.

Hofbauer Cells: Placental Macrophages of Fetal Origin

Pregnancy complications such as preterm birth, miscarriage, maternal and/or neonatal morbidities, and mortality can be manifestations of underlying placental pathology. Hofbauer cells refer to a heterogeneous population of fetal macrophages that reside within the functional unit of the placenta known as the chorionic villus. Hofbauer cells can be detected within the connective tissue matrix of the placenta as early as 4 weeks post-conception and are present throughout pregnancy. These cells are implicated in a wide array of functions important for a successful pregnancy including placental morphogenesis, immune regulation, control of stromal water content, and the transfer of ions and serum proteins across the maternal-fetal barrier. Derangements in Hofbauer cell homeostasis are associated with placental pathologies involving infection, inflammation, and inadequate placental development. Despite a growing body of evidence that these cells are important, our knowledge about Hofbauer cell function in both normal and dysfunctional pregnancy is rudimentary. The goal of this chapter is to provide an overview of what is known about Hofbauer cell origins and their potential roles in normal and complicated pregnancy. We also review established and emerging methodologies available for the study of Hofbauer cells during in vitro and in vivo conditions.