Genome-wide identification of toll-like receptors in Octopus sinensis and expression analysis in response to different PAMPs stimulation.

Toll-like receptors (TLRs) are one of the extensively studied pattern recognition receptors (PRRs) and play crucial roles in the immune responses of vertebrates and invertebrates. In this study, 14 TLR genes were identified from the genome-wide data of Octopus sinensis. Protein structural domain analysis showed that most TLR proteins had three main structural domains: extracellular leucine-rich repeats (LRR), transmembrane structural domains, and intracellular Toll/IL-1 receptor domain (TIR). The results of subcellular localization prediction showed that the TLRs of O. sinensis were mainly located on the plasma membrane. The results of quantitative real-time PCR (qPCR) showed that the detected TLR genes were differentially expressed in the hemolymph, white bodies, hepatopancreas, gills, gill heart, intestine, kidney, and salivary gland of O. sinensis. Furthermore, the present study investigated the expression changes of O. sinensis TLR genes in hemolymph, white bodies, gills, and hepatopancreas in different phases (6 h, 12 h, 24 h, 48 h) after stimulation with PGN, poly(I: C) and Vibrio parahaemolyticus. The expression of most of the TLR genes was upregulated at different time points after infection with pathogens or stimulation with PAMPs, a few genes were unchanged or even down-regulated, and many of the TLR genes were much higher after V. parahaemolyticus infection than after PGN and poly(I:C) stimulation. The results of this study contribute to a better understanding of the molecular immune mechanisms of O. sinensis TLRs genes in resistance to pathogen stimulation.

LL-37-dsRNA Complexes Modulate Immune Response via RIG-I in Oral Keratinocytes.

Recognition of nucleic acids as pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) promotes an inflammatory response. On the other hand, LL-37, an antimicrobial peptide, is a multifunctional modulator of immune response, though whether it modulates inflammatory responses induced by nucleic acids in oral keratinocytes is unknown. In this study, we firstly investigated the effect of LL-37 on CXCL10 induced by DAMPs and PAMPs in immortalized oral keratinocytes, RT7. Furthermore, the effects of LL-37 on translocation of exogenous nucleic acids into cytoplasm as well as cytosolic receptor, RIG-I on immune responses mediated by LL-37-nucleic acid complexes were examined. From these results, LL-37 enhanced necrotic cell supernatant (NCS)-induced CXCL10 expression in RT7, while the response was decreased by RNase. Complexes of LL-37 and double-stranded (ds) RNA, Poly(I:C) enhanced CXCL10 expression in comparison with each alone, which were associated with NF-κB activation. Furthermore, LL-37 was shown to bind with ds nucleotides and translocate into cytoplasm. Knockdown of RIG-I decreased expression of CXCL10 induced by LL-37-Poly(I:C) complexes, and RIG-I were co-localized with Poly(I:C) entered by LL-37 in cytoplasm. LL-37 modulates dsRNA-mediated inflammatory response via RIG-I in oral keratinocytes, which may play an important role in the pathogenesis of oral inflammatory diseases.

Transcriptome analysis reveals the diverse response of pearl oyster Pinctada fucata martensii after different PAMP stimulation.

Bivalves have evolved effective strategies to combat different pathogens in the environment. They rely on innate immunity to deal with the invasion of various bacteria, viruses, and other microorganisms. However, the molecular mechanisms underlying the responses remain largely unknown. Herein, we constructed 21 transcriptomes of the hemocytes after lipopolysaccharide (LPS), peptidoglycan (PGN) and polyinosinic-polycytidylic acid (poly(I:C)) stimulation to investigate the molecular mechanisms underlying adaptations and plastic responses to different pathogen-related molecular patterns (PAMPs) in pearl oyster Pinctada fucata martensii. Transcriptome analysis revealed 1986-3427 responsive genes enriched in the major immune and cell cycle-related pathways at different times after PAMP stimulation, and the expression patterns of genes under these pathways are complex and diverse. Moreover, "lysosomes" were enriched 6 h after LPS and PGN stimulation, while "peroxisomes" were only enriched in poly(I:C) group. These results suggest different response strategies of pearl oyster to different PAMPs. Furthermore, we identified 261 pattern-recognition receptors (PRRs) including 4 retinoic acid-inducible gene I-like receptors, 38 NOD-like receptors, 83 Toll-like receptors, and 136 C-type lectins in the genome of P. f. martensii. The diverse expression patterns of these PRRs after different PAMP stimulation indicated that pearl oyster evolved complex and specific recognition systems due to tandem repeat and diverse domain combination, which may help pearl oyster cope with the different pathogens in the environment. The present study improved our understanding of the molecular response of pearl oyster to different PAMP stimulation.

sEH promotes macrophage phagocytosis and lung clearance of Streptococcus pneumoniae.

Epoxyeicosatrienoic acids (EETs) have potent antiinflammatory properties. Hydrolysis of EETs by soluble epoxide hydrolase/ epoxide hydrolase 2 (sEH/EPHX2) to less active diols attenuates their antiinflammatory effects. Macrophage activation is critical to many inflammatory responses; however, the role of EETs and sEH in regulating macrophage function remains unknown. Lung bacterial clearance of Streptococcus pneumoniae was impaired in Ephx2-deficient (Ephx2-/-) mice and in mice treated with an sEH inhibitor. The EET receptor antagonist EEZE restored lung clearance of S. pneumoniae in Ephx2-/- mice. Ephx2-/- mice had normal lung Il1b, Il6, and Tnfa expression levels and macrophage recruitment to the lungs during S. pneumoniae infection; however, Ephx2 disruption attenuated proinflammatory cytokine induction, Tlr2 and Pgylrp1 receptor upregulation, and Ras-related C3 botulinum toxin substrates 1 and 2 (Rac1/2) and cell division control protein 42 homolog (Cdc42) activation in PGN-stimulated macrophages. Consistent with these observations, Ephx2-/- macrophages displayed reduced phagocytosis of S. pneumoniae in vivo and in vitro. Heterologous overexpression of TLR2 and peptidoglycan recognition protein 1 (PGLYRP1) in Ephx2-/- macrophages restored macrophage activation and phagocytosis. Human macrophage function was similarly regulated by EETs. Together, these results demonstrate that EETs reduced macrophage activation and phagocytosis of S. pneumoniae through the downregulation of TLR2 and PGLYRP1 expression. Defining the role of EETs and sEH in macrophage function may lead to the development of new therapeutic approaches for bacterial diseases.

Two Sides to Every Question: Attempts to Activate Chicken Innate Immunity in 2D and 3D Hepatic Cell Cultures.

The liver with resident tissue macrophages is the site of vivid innate immunity, activated also by pathogen-associated molecular patterns (PAMPs) leaking through the intestinal barrier. As gut-derived inflammatory diseases are of outstanding importance in broiler chickens, the present study aimed to establish a proper hepatic inflammatory model by comparing the action of different PAMPs from poultry pathogens on chicken 2D and 3D primary hepatocyte-non-parenchymal cell co-cultures, the latter newly developed with a magnetic bioprinting method. The cultures were challenged by the bacterial endotoxins lipopolysaccharide (LPS) from Escherichia coli, lipoteichoic acid (LTA) from Staphylococcus aureus and by enterotoxin (ETxB) from Escherichia coli, Salmonella Typhimurium derived flagellin, phorbol myristate acetate (PMA) as a model proinflammatory agent and polyinosinic polycytidylic acid (poly I:C) for mimicking viral RNA exposure. Cellular metabolic activity was assessed with the CCK-8 test, membrane damage was monitored with the lactate dehydrogenase (LDH) leakage assay and interleukin-6 and -8 (Il-6 and -8) concentrations were measured in cell culture medium with a chicken specific ELISA. Both LPS and LTA increased the metabolic activity of the 3D cultures, concomitantly decreasing the LDH leakage, while in 2D cultures ETxB stimulated, PMA and poly I:C depressed the metabolic activity. Based on the moderately increased extracellular LDH activity, LTA seemed to diminish cell membrane integrity in 2D and poly I:C in both cell culture models. The applied endotoxins remarkably reduced the IL-8 release of 3D cultured cells, suggesting the effective metabolic adaptation and the presumably initiated anti-inflammatory mechanisms of the 3D spheroids. Notwithstanding that the IL-6 and IL-8 production of 2D cells was mostly not influenced by the endotoxins used, only the higher LTA dose was capable to evoke an IL-8 surge. Flagellin, PMA and poly I:C exerted proinflammatory action in certain concentrations in both 2D and 3D cultures, reflected by the increased cellular IL-6 release. Based on these data, LTA, flagellin, PMA and poly I:C can be considered as potent candidates to induce inflammation in chicken primary hepatic cell cultures, while LPS failed to trigger proinflammatory cytokine production, suggesting the relatively high tolerance of avian liver cells to certain bacterial endotoxins. These results substantiate that the established 3D co-cultures seemed to be proper tools for testing potential proinflammatory molecules; however, the remarkable differences between 2D and 3D models should be addressed and further studied.

Hot water extract of Pleurotus pulmonarius stalk waste enhances innate immune response and immune-related gene expression in red hybrid tilapia Oreochromis sp. following challenge with pathogen-associated molecular patterns.

In aquaculture, commercial fish such as red hybrid tilapia are usually raised at high density to boost the production within a short period of time. This overcrowded environment, however, may cause stress to the cultured fish and increase susceptibility to infectious diseases. Antibiotics and chemotherapeutics are used by fish farmers to overcome these challenges, but this may increase the production cost. Studies have reported on the potential of mushroom polysaccharides that can act as immunostimulants to enhance the immune response and disease resistance in fish. In the current study, hot water extract (HWE) from mushroom stalk waste (MSW) was used to formulate fish feed and hence administered to red hybrid tilapia to observe the activation of immune system. Upon 30 days of feeding, the fish were challenged with pathogen-associated molecular patterns (PAMPs) such as lipopolysaccharides (LPS) and polyinosinic:polycytidylic acid (poly (I:C)) to mimic bacterial and viral infection, respectively. HWE supplementation promoted better feed utilisation in red hybrid tilapia although it did not increase the body weight gain and specific growth rate compared to the control diet. The innate immunological parameters such as phagocytic activity and respiratory burst activity were significantly higher in HWE-supplemented group than that of the control group following PAMPs challenges. HWE-supplemented diet also resulted in higher mRNA transcription of il1b and tnfa in midgut, spleen and head kidney at 1-day post PAMPs injection. Tlr3 exhibited the highest upregulation in the HWE fed fish injected with poly (I:C). At 3-days post PAMPs injection, both ighm and tcrb expression were upregulated significantly in the spleen and head kidney. Results showed that HWE supplementation enhances the immune responses of red hybrid tilapia and induced a higher serum bactericidal activity against S. agalactiae.

Interferon-Independent Restriction of RNA Virus Entry and Replication by a Class of Damage-Associated Molecular Patterns.

Mammalian cells detect microbial molecules known as pathogen-associated molecular patterns (PAMPs) as indicators of potential infection. Upon PAMP detection, diverse defensive responses are induced by the host, including those that promote inflammation and cell-intrinsic antimicrobial activities. Host-encoded molecules released from dying or damaged cells, known as damage-associated molecular patterns (DAMPs), also induce defensive responses. Both DAMPs and PAMPs are recognized for their inflammatory potential, but only the latter are well established to stimulate cell-intrinsic host defense. Here, we report a class of DAMPs that engender an antiviral state in human epithelial cells. These DAMPs include oxPAPC (oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine), PGPC (1-palmitoyl-2-glutaryl phosphatidylcholine), and POVPC [1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphatidylcholine], oxidized lipids that are naturally released from dead or dying cells. Exposing cells to these DAMPs prior to vesicular stomatitis virus (VSV) infection limits viral replication. Mechanistically, these DAMPs prevent viral entry, thereby limiting the percentage of cells that are productively infected and consequently restricting viral load. We found that the antiviral actions of oxidized lipids are distinct from those mediated by the PAMP Poly I:C, in that the former induces a more rapid antiviral response without the induction of the interferon response. These data support a model whereby interferon-independent defensive activities can be induced by DAMPs, which may limit viral replication before PAMP-mediated interferon responses are induced. This antiviral activity may impact viruses that disrupt interferon responses in the oxygenated environment of the lung, such as influenza virus and SARS-CoV-2.IMPORTANCE In this work, we explored how a class of oxidized lipids, spontaneously created during tissue damage and unprogrammed cell lysis, block the earliest events in RNA virus infection in the human epithelium. This gives us novel insight into the ways that we view infection models, unveiling a built-in mechanism to slow viral growth that neither engages the interferon response nor is subject to known viral antagonism. These oxidized phospholipids act prior to infection, allowing time for other, better-known innate immune mechanisms to take effect. This discovery broadens our understanding of host defenses, introducing a soluble factor that alters the cellular environment to protect from RNA virus infection.

Aromatic Cytokinin Arabinosides Promote PAMP-like Responses and Positively Regulate Leaf Longevity.

Cytokinins are plant hormones with biological functions ranging from coordination of plant growth to the regulation of biotic and abiotic stress-related responses and senescence. The components of the plant immune system can learn from past elicitations by microbial pathogens and herbivores and adapt to new threats. It is known that plants can enter the primed state of enhanced defense induced by either natural or synthetic compounds. While the involvement of cytokinins in defense priming has been documented, no comprehensive model of their action has been provided to date. Here, we report the functional characterization of two aromatic cytokinin derivatives, 6-benzylaminopurine-9-arabinosides (BAPAs), 3-methoxy-BAPA and 3-hydroxy-BAPA, that proved to be effective in delaying senescence in detached leaves while having low interactions with the cytokinin pathway. An RNA-seq profiling study on Arabidopsis leaves treated with 3-methoxy-BAPA revealed that short and extended treatments with this compound shifted the transcriptional response markedly toward defense. Both treatments revealed upregulation of genes involved in processes associated with plant innate immunity such as cell wall remodeling and upregulation of specific MAP kinases, most importantly MPK11, which is a MAPK module involved in stress-related signaling during the pathogen-associated molecular patterns (PAMPs) response. In addition, elevated levels of JA and its metabolites, jasmonate/ethylene-driven upregulation of PLANT DEFENSIN 1.2 (PDF1.2) and other defensins, and also temporarily elevated levels of reactive oxygen species marked the plant response to 3-methoxy-BAPA treatment. Synergistic interactions were observed when plants were cotreated with 3-hydroxy-BAPA and the flagellin-derived bacterial PAMP peptide (flg22), leading to the enhanced expression of the PAMP-triggered immunity (PTI) marker gene FRK1. Our data collectively show that some BAPAs can sensitively prime the PTI responses in a low micromolar range of concentrations while having no observable negative effects on the overall fitness of the plant.

The Synergism of PGN, LTA and LPS in Inducing Transcriptome Changes, Inflammatory Responses and a Decrease in Lactation as Well as the Associated Epigenetic Mechanisms in Bovine Mammary Epithelial Cells.

Mastitis is usually caused by a variety of pathogenic bacteria that include both Gram-positive and Gram-negative bacteria. Lipopolysaccharide (LPS) is the pathogen-associated molecular pattern (PAMP) of Gram-negative bacteria, and peptidoglycan (PGN) and lipoteichoic acid (LTA) are those of Gram-positive bacteria. The effects of LPS, PGN and/or LTA on inflammatory response and lactation in bovine mammary epithelial cells (BMECs) are well studied, but the epigenetic mechanisms of their effects received less attention. Furthermore, since the three PAMPs are often simultaneously present in the udder of cows with mastitis, it has implications in practice to study their additive effects. The results show that co-stimulation of bovine mammary epithelial cells with PGN, LTA, and LPS induced a higher number of differentially expressed genes (DEGs) and greater expressions of inflammatory factors including interleukin (IL)-1ß, IL-6, IL-8, tumor necrosis factor-α (TNF-α), chemokine (C-X-C motif) ligand (CXCL)1, and CXCL6. In addition, co-stimulation further increased DNA hypomethylation compared with sole LPS stimulation. Co-stimulation greatly decreased casein expression but did not further decrease histone acetylation levels and affect the activity of histone acetyltransferase (HAT) and histone deacetylase (HDAC), compared with sole LPS stimulation. Collectively, this study demonstrated that PGN, LTA, and LPS had an additive effect on inducing transcriptome changes and inflammatory responses in BMECs, probably through inducing a greater decrease in DNA methylation. Co-stimulation with PGN, LTA, and LPS decreased casein expression to a greater degree, but it might not be linked to histone acetylation and HAT and HDAC activity.

1,25(OH)D vitamin D promotes NOS2 expression in response to bacterial and viral PAMPs in primary bovine salivary gland fibroblasts.

OBJECTIVES: The faecal-oral route is a predominant mode of infectious disease transmission and yet the immunology of the bovine oral cavity is poorly understood. The objectives of this study were to develop an in vitro cell model of bovine salivary gland cells and to characterize the role of vitamin D on the expression of innate immune genes induced by stimulation with bacterial and viral pathogen-associated molecular patterns (PAMPs). METHODS: Submandibular glandular tissue was excised post-mortem, processed, cells isolated and cultured until confluency after which cells were incubated with the active form of vitamin D (1,25(OH)D) for 18 h before stimulation with lipopolysaccharide (LPS µg/ml), lipoteichoic acid (LTA µg/ml) or polyinosinic:polycytidylic acid (poly I:C-20 µg/ml) PAMPs for 6 h and immune gene expression was assessed by Quantitative Real-Time PCR (RT-qPCR). RESULTS: RT-qPCR analysis of vimentin expression in cells derived from the bovine submandibular gland shows that cultured cells were fibroblast in origin. These cells significantly induce the pro-inflammatory cytokine IL1B, ß-defensin and cathelicidin genes but these were not significantly altered in response to 1,25(OH)D. In contrast, 1,25(OH)D significantly up-regulates the expression of the NOS2 gene encoding iNOS in bovine submandibular stromal cells compared to EtOH (vehicle) control and this is a maintained response to all three bacterial and viral ligands. We have developed a new in vitro model to allow detailed investigations of mechanisms to enhance oral immunity in cattle. We show that these cells are fibroblast in nature, immunologically competent and vitamin D responsive. Their vitamin D-mediated enhancement of NOS2 expression warrants further investigation in saliva as a potential mechanism to boost oral immunity against infectious agents.

Pathogen-Associated Molecular Pattern-Induced TLR2 and TLR4 Activation Increases Keratinocyte Production of Inflammatory Mediators and is Inhibited by Phosphatidylglycerol.

Skin serves not only as a protective barrier to microbial entry into the body but also as an immune organ. The outer layer, the epidermis, is composed predominantly of keratinocytes, which can be stimulated to produce proinflammatory mediators. Although some inflammation is useful to defend against infection, excessive or persistent inflammation can lead to the development of inflammatory skin diseases, such as psoriasis, a common skin disorder affecting approximately 2% of the US population. We have previously found that phosphatidylglycerol (PG) derived from soy can inhibit inflammation in a contact irritant ear edema mouse model. Here, we investigated the ability of soy PG to inhibit inflammatory mediator expression in response to activators of the pattern recognition receptors, toll-like receptor-2 (TLR2) and -4 (TLR4). We found that in epidermal keratinocytes, soy PG inhibited TLR2 and TLR4 activation and inflammatory mediator expression in response to a synthetic triacylated lipopeptide and lipopolysaccharide, respectively, as well as an endogenous danger-associated molecular pattern. However, at higher concentrations, soy PG alone enhanced the expression of some proinflammatory cytokines, suggesting a narrow therapeutic window for this lipid. Dioleoylphosphatidylglycerol (DOPG), but not dioleoylphosphatidylcholine, exerted a similar inhibitory effect, completely blocking keratinocyte inflammatory mediator expression induced by TLR2 and TLR4 activators as well as NFκB activation in a macrophage cell line (RAW264.7); however, DOPG was not itself proinflammatory even at high concentrations. Furthermore, DOPG had no effect on NFκB activation in response to a TLR7/8 agonist. Our results suggest that DOPG could be used to inhibit excessive skin inflammation. SIGNIFICANCE STATEMENT: Although inflammation is beneficial for clearing an infection, in some cases, the infection can be excessive and/or become chronic, thereby resulting in considerable tissue damage and pathological conditions. We show here that the phospholipid phosphatidylglycerol can inhibit the activation of toll-like receptors 2 and 4 of the innate immune system as well as the downstream inflammatory mediator expression in response to microbial component-mimicking agents in epidermal keratinocytes that form the physical barrier of the skin.

Stimulation of Mytilus galloprovincialis Hemocytes With Different Immune Challenges Induces Differential Transcriptomic, miRNomic, and Functional Responses.

Mediterranean mussels (Mytilus galloprovincialis) are marine bivalve molluscs with high resilience to biotic and abiotic stress. This resilience is one of the reasons why this species is such an interesting model for studying processes such as the immune response. In this work, we stimulated mussel hemocytes with poly I:C, ß-glucans, and LPS and then sequenced hemocyte mRNAs (transcriptome) and microRNAs (miRNome) to investigate the molecular basis of the innate immune responses against these pathogen-associated molecular patterns (PAMPs). An immune transcriptome comprising 219,765 transcripts and an overview of the mussel miRNome based on 5,175,567 non-redundant miRNA reads were obtained. The expression analyses showed opposite results in the transcriptome and miRNome; LPS was the stimulus that triggered the highest transcriptomic response, with 648 differentially expressed genes (DEGs), while poly I:C was the stimulus that triggered the highest miRNA response, with 240 DE miRNAs. Our results reveal a powerful immune response to LPS as well as activation of certain immunometabolism- and ageing/senescence-related processes in response to all the immune challenges. Poly I:C exhibited powerful stimulating properties in mussels, since it triggered the highest miRNomic response and modulated important genes related to energy demand; these effects could be related to the stronger activation of these hemocytes (increased phagocytosis, increased NO synthesis, and increased velocity and accumulated distance). The transcriptome results suggest that after LPS stimulation, pathogen recognition, homeostasis and cell survival processes were activated, and phagocytosis was induced by LPS. ß-glucans elicited a response related to cholesterol metabolism, which is important during the immune response, and it was the only stimulus that induced the synthesis of ROS. These results suggest a specific and distinct response of hemocytes to each stimulus from a transcriptomic, miRNomic, and functional point of view.

A novel calreticulin-related molecule that interacts with bacteria and enhances host resistance against bacterial infection in black rockfish, Sebastes schlegeli.

Calreticulin (CRT) is a highly conserved and multi-functional protein with diverse localizations. CRT has lectin-like properties and possesses important immunological activities in mammalian. In teleost, very limited studies on CRT immunologic function have been documented. In the present study, a CRT homologue (SsCRT) was cloned, identified and characterized from black rockfish, Sebastes schlegeli, an important aquaculture species in East Asia. The full length of SsCRT cDNA is 2180 bp and encoded a polypeptide of 425 amino acids. SsCRT contains a signal peptide, three distinct structural and functional domains (N-, P- and C-domains), and an endoplasmic reticulum (ER) retrieval signal sequence (KDEL). The deduced amino acid sequence of SsCRT shares 89-92% overall sequence identities with the CRT proteins of several fish species. SsCRT was distributed ubiquitously in all the detected tissues and was highly expressed in the spleen, muscle and liver. After the infection of fish extracellular bacterial pathogen Vibrio anguillarum and intracellular bacterial pathogen Edwardsiella tarda, the mRNA transcripts of SsCRT in spleen, liver, and head kidney were significantly up-regulated. The expression patterns were time-dependent and tissue-dependent. Recombinant SsCRT (rSsCRT) exhibited apparent binding activities against different bacteria and PAMPs. In vivo studies showed that the expressions of multiple immune-related genes such as TNF13B, IL-1ß, IL-8, SAA, Hsp70, and ISG15 in head kidney were significantly enhanced when black rockfish were treated with rSsCRT. Furthermore, rSsCRT reduced pathogen dissemination and replication in fish kidney and spleen. These results indicated that SsCRT served as an immune receptor to recognize and eliminate the invading pathogens, which played a vital role in the immune response of Sebastes schlegeli. These findings provide new insights into understanding the roles of CRT proteins in immune response and pathogen infection in teleost.

A PAMP-triggered MAPK cascade inhibits phosphatidylinositol 4,5-bisphosphate production by PIP5K6 in Arabidopsis thaliana.

The phosphoinositide kinase PIP5K6 has recently been identified as a target for the mitogen-activated protein kinase (MAPK) MPK6. Phosphorylation of PIP5K6 inhibited the production of phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2 ), impacting membrane trafficking and cell expansion in pollen tubes. Here, we analyzed whether MPK6 regulated PIP5K6 in vegetative Arabidopsis cells in response to the pathogen-associated molecular pattern (PAMP) flg22. Promoter-ß-glucuronidase analyses and quantitative real-time reverse transcription polymerase chain reaction data show PIP5K6 expressed throughout Arabidopsis tissues. Upon flg22 treatment of transgenic protoplasts, the PIP5K6 protein was phosphorylated, and this modification was reduced for a PIP5K6 variant lacking MPK6-targeted residues, or in protoplasts from mpk6 mutants. Upon flg22 treatment of Arabidopsis plants, phosphoinositide levels mildly decreased and a fluorescent reporter for PtdIns(4,5)P2 displayed reduced plasma membrane association, contrasting with phosphoinositide increases reported for abiotic stress responses. Flg22 treatment and chemical induction of the upstream MAPK kinase, MKK5, decreased phosphatidylinositol 4-phosphate 5-kinase activity in mesophyll protoplasts, indicating that the flg22-activated MAPK cascade limited PtdIns(4,5)P2 production. PIP5K6 expression or PIP5K6 protein abundance changed only marginally upon flg22 treatment, consistent with post-translational control of PIP5K6 activity. PtdIns(4,5)P2 -dependent endocytosis of FM 4-64, PIN2 and the NADPH-oxidase RbohD were reduced upon flg22 treatment or MKK5 induction. Reduced RbohD-endocytosis was correlated with enhanced ROS production. We conclude that MPK6-mediated phosphorylation of PIP5K6 limits the production of a functional PtdIns(4,5)P2 pool upon PAMP perception.

Different origins of paralogues of salmonid TNR1 and TNFR2: Characterisation and expression analysis of four TNF receptor genes in rainbow trout Oncorhynchus mykiss.

Mammalian TNFR1 and TNFR2 bind TNFα and TNFß, and provide key communication signals to a variety of cell types during development and immune responses that are crucial for cell survival, proliferation and apoptosis. In teleost fish TNFß is absent but TNFα has been expanded by the third whole genome duplication (3R WGD) and again by a 4R WGD in some lineages, leading to the four TNFα paralogues known in salmonids. Two paralogues for each of TNFR1 and TNFR2 have been cloned in rainbow trout in this study and are present in other salmonid genomes. Whilst the TNFR2 paralogues were generated via the 4R salmonid WGD, the TNFR1 paralogues arose from a local en bloc duplication. Functional diversification of TNFR paralogues was evidenced by differential gene expression and modulation, upstream ATGs affecting translation, ATTTA motifs in the 3'-UTR regulating mRNA stability, and post-translational modification by N-glycosylation. Trout TNFR are highly expressed in immune tissues/organs, and other tissues, in a gene- and tissue-specific manner. Furthermore, their expression is differentially modulated by PAMPs and cytokines in a cell type- and stimulant-specific manner. Such findings suggest an important role of the TNF/TNFR axis in the immune response and other physiological processes in fish.

Scavenger receptor class B type I (SR-BI) in Ruditapes philippinarum: A versatile receptor with multiple functions.

In the present study, a scavenger receptor class B type I (designed as RpSR-BI) was cloned and characterized from manila clam Ruditapes philippinarum. The full-length cDNA of RpSR-BI was of 2000 bp, containing an open reading frame (ORF) of 1515 bp. Multiple alignments and phylogenetic analysis strongly suggested that RpSR-BI was a member of the scavenger receptors family. The mRNA transcript of RpSR-BI was constitutively expressed in all tested tissues, and mainly expressed in hepatopancreas and hemocytes. Generally, Vibrio anguillarum or Micrococcus luteus challenge induced the expression of RpSR-BI transcripts in hemocytes of manila clams. Recombinant protein of RpSR-BI (rRpSR-BI) could bind lipopolysaccharides, peptidoglycan and glucan, but not chitin in vitro. Coinciding with the PAMPs binding assay, a broad agglutination spectrum was displayed by rRpSR-BI including Gram-positive bacteria and Gram-negative bacteria. Moreover, rRpSR-BI could enhance the phagocytosis and chemotaxis of hemocytes. These results showed that RpSR-BI functioned as a pattern recognition receptor (PRR) with distinct recognition spectrum, and also as an opsonin involved in the innate immune response of R. philippinarum.

A novel LRR and Ig domain-containing protein could function as an immune effector in Crassostrea gigas.

A variety of combinations of leucine-rich repeat (LRR) and immunoglobulin-like (Ig) domains have been found and discovered in invertebrates and vertebrates, but the functions remain largely unexplored. In the present study, a novel LRR and Ig domain-containing protein (LRRIG), CgLRRIG-3, was identified and characterized from oyster Crassostrea gigas. It contained two typical LRR motifs, a LRRNT motif and an Ig domain and PSI-BALST and phylogeny analysis revealed that the sequence of CgLRRIG-3 was most related with leucine-rich repeat neuronal 1 proteins from vertebrate. Its mRNA transcripts were constitutively expressed in muscle, gill, hepatopancreas, mantle, gonad and hemocytes with the highest level in hepatopancreas. The mRNA expression level of CgLRRIG-3 in hemocytes could respond to the stimulations of variety PAMPs including lipopolysaccharide (LPS), peptidoglycan (PGN), glucan (GLU) and polyinosinic-polycytidylic acid (poly I:C). The recombinant proteins exhibited a wide PAMP binding repertoire to four typical PAMPs and could significantly induce the expression of CgTNF-1 and CgIL17-5 as well as increase phagocytosis in primary cultured oyster hemocytes. In hepatopancreas, CgLRRIG-3 was mainly distributed in the basolateral membrane of digestive tubule and the hemocoel sinusoid between the digestive tubules. And in hemocytes, the positive signal was mainly distributed in a special group of granulocytes. These results collectively indicated that CgLRRIG-3 could not only function as an immune effector.

Synthetic CpG oligonucleotides as potential modulators of neutrophil survival in PAMP-associated inhibition of apoptosis.

We studied the effects of a synthetic CpG oligonucleotide (CpG ODN2006) on polymorphonuclear leukocyte (PMNL, neutrophil) survival and oxidant status. CpG ODN2006 showed a dose-dependent effect on the apoptosis of resting neutrophils. Without affecting the viability of resting cells, low concentrations of CpG ODN2006 interfered with Salmonella typhimurium-mediated viability prolongation and increased neutrophil apoptosis to control levels. CpG ODN2006 stimulated neutrophil apoptosis by enhancing ROS generation. Even small doses of ODN could induce the production of intracellular superoxide anions. The high superoxide reactogenicity, including with respect to nitrogen oxide, led to increased levels of intracellular ROS and RNS, which ultimately caused apoptosis. The pro-oxidant effect of low concentrations of CpG ODN2006 was not sufficient to trigger irreversible pro-apoptotic mechanisms. However, the sensitivity of PMNLs to ODN2006, a modulator of apoptosis, increased significantly under conditions of infectious inflammation. Inactivated S. typhimurium proved to be suitable for simulating inflammatory conditions in vitro.

Danger signals in oral cavity-related diseases.

The oral cavity is a unique environment containing teeth juxtaposed with soft tissues, all of which are constantly bathed in microbial products and host-derived factors. While microbial dysbiosis in the oral cavity clearly leads to oral inflammatory disease, recent advances find that endogenous danger-associated molecular patterns (DAMPs) released from oral and salivary tissue also contribute to the progression of inflammatory and autoimmune disease, respectively. In contrast, DAMPs produced during oral fungal infection actually promote the resolution of infection. Here, we present a review of the literature suggesting a role for signaling by DAMPs, which may intersect with pathogen-associated molecular pattern (PAMP) signaling, in diseases that manifest in the oral cavity, specifically periodontal disease, oropharyngeal candidiasis, and Sjögren's syndrome.

The role of CNS macrophages in streptococcal meningoencephalitis.

In the healthy brain, microglia and other CNS macrophages are the most abundant immune cell type. Thus, they form the natural immune cell interface with streptococci, which are the leading cause of bacterial meningitis and encephalitis in infants and young children. In homeostasis, the blood-brain barrier allows for very limited access of immune cells circulating in the periphery. During bacterial meningoencephalitis, however, origin and fate of CNS macrophages are massively altered. This review summarizes the emerging knowledge on the sequence of reciprocal events between streptococci and CNS macrophages leading to host resistance, acute inflammation, changes in resident innate immune cells of the brain, and long-term neuronal damage.