Modulation of TLR signaling by multiple MyD88-interacting partners including leucine-rich repeat Fli-I-interacting proteins

The clinical significance and oncogenic function of LRRFIP1 in pancreatic cancer

PURPOSE

Pancreatic cancer is a lethal malignancy with a grim prognosis. Previous studies have proven that Leucine Rich Repeat of Flightless-1 Interacting Protein 1 (LRRFIP1) plays a pivotal role in cell biological processes, while its clinical significance and function in pancreatic cancer remain to be elucidated. Hence, we aimed to explore the roles and mechanisms of LRRFIP1 in pancreatic cancer.

METHODS

The expression of LRRFIP1 in pancreatic cancer tissues and its clinical significance for pancreatic cancer were analyzed by immunohistochemistry assay and bioinformatic analysis. The influences of LRRFIP1 on the proliferation and migration of pancreatic cancer cells were assessed in vitro. The underlying mechanisms of LRRFIP1 in pancreatic cancer progression were explored using gene set enrichment analysis (GSEA) and molecular experiments.

RESULTS

The results showed that LRRFIP1 expression was significantly upregulated in pancreatic cancer tissues compared to the normal tissues, and such upregulation was associated with poor prognosis of patients with pancreatic cancer. GSEA revealed that LRRFIP1 upregulation was significantly associated with various cancer-associated signaling pathways, including PI3K/AKT signaling pathway and Wnt pathway. Furthermore, LRRFIP1 was found to be associated with the infiltration of various immune cells. Functionally, LRRFIP1 silencing suppressed cell proliferation somewhat and inhibited migration substantially. Further molecular experiments indicated that LRRFIP1 silencing inactivated the AKT/GSK-3β/β-catenin signaling axis.

CONCLUSION

Taken together, LRRFIP1 is associated with tumorigenesis, immune cell infiltration, and prognosis in pancreatic cancer, which suggests that LRRFIP1 may be a potential biomarker and therapeutic target for pancreatic cancer.

A Novel Cargo Delivery System-AnCar-ExoLaIMTS Ameliorates Arthritis via Specifically Targeting Pro-Inflammatory Macrophages

Macrophages are heterogenic phagocytic cells that play distinct roles in physiological and pathological processes. Targeting different types of macrophages has shown potent therapeutic effects in many diseases. Although many approaches are developed to target anti-inflammatory macrophages, there are few researches on targeting pro-inflammatory macrophages, which is partially attributed to their non-s pecificity phagocytosis of extracellular substances. In this study, a novel recombinant protein is constructed that can be anchored on an exosome membrane with the purpose of targeting pro-inflammatory macrophages via antigen recognition, which is named AnCar-ExoLaIMTS . The data indicate that the phagocytosis efficiencies of pro-inflammatory macrophages for different AnCar-ExoLaIMTS show obvious differences. The AnCar-ExoLaIMTS3 has the best targeting ability for pro-inflammatory macrophages in vitro and in vivo. Mechanically, AnCar-ExoLaIMTS3 can specifically recognize the leucine-rich repeat domain of the TLR4 receptor, and then enter into pro-inflammatory macrophages via the TLR4-mediated receptor endocytosis pathway. Moreover, AnCar-ExoLaIMTS3 can efficiently deliver therapeutic cargo to pro-inflammatory macrophages and inhibit the synovial inflammatory response via downregulation of HIF-1α level, thus ameliorating the severity of arthritis in vivo. Collectively, the work established a novel gene/drug delivery system that can specifically target pro-inflammatory macrophages, which may be beneficial for the treatments of arthritis and other inflammatory diseases.

Stress-induced pseudokinase TRB3 augments IL1β signaling by interacting with Flightless homolog 1

Interleukin-1β is one of the most potent inducers of beta cell inflammation in the lead-up to type 1 diabetes. We have previously reported that IL1β-stimulated pancreatic islets from mice with genetic ablation of stress-induced pseudokinase TRB3(TRB3KO) show attenuated activation kinetics for the MAP3K MLK3 and JNK stress kinases. However, JNK signaling constitutes only a portion of the cytokine-induced inflammatory response. Here we report that TRB3KO islets also show a decrease in amplitude and duration of IL1β-induced phosphorylation of TAK1 and IKK, kinases that drive the potent NF-κB proinflammatory signaling pathway. We observed that TRB3KO islets display decreased cytokine-induced beta cell death, preceded by a decrease in select downstream NF-κB targets, including iNOS/NOS2 (inducible nitric oxide synthase), a mediator of beta cell dysfunction and death. Thus, loss of TRB3 attenuates both pathways required for a cytokine-inducible, proapoptotic response in beta cells. In order to better understand the molecular basis of TRB3-enhanced, post-receptor IL1β signaling, we interrogated the TRB3 interactome using coimmunoprecipitation followed by mass spectrometry to identify immunomodulatory protein Flightless homolog 1 (Fli1) as a novel, TRB3-interacting protein. We show that TRB3 binds and disrupts Fli1-dependent sequestration of MyD88, thereby increasing availability of this most proximal adaptor required for IL1β receptor-dependent signaling. Fli1 sequesters MyD88 in a multiprotein complex resulting in a brake on the assembly of downstream signaling complexes. By interacting with Fli1, we propose that TRB3 lifts the brake on IL1β signaling to augment the proinflammatory response in beta cells.

Epithelioid fibrous histiocytoma: three diagnostically challenging cases with novel ALK gene fusions, unusual storiform growth pattern, and a prominent spindled morphology

Epithelioid fibrous histiocytoma (EFH) is a distinctive cutaneous neoplasm with a relatively variable morphological appearance. Recently, it has been shown that this tumor is molecularly characterized by ALK gene fusions. We report three EFHs with unusual histological presentation represented by a prominent/predominant spindle cell proliferation arranged in a variably storiform/whirling architectural pattern with or without stromal sclerosis. One of the cases closely resembled cellular fibrous histiocytoma. All three cases were immunohistochemically ALK-positive and were analyzed for ALK gene rearrangements using a next-generation sequencing-based assay (FusionPlex Sarcoma Kit, ArcherDx). Three novel fusions, namely AP3D1::ALK, COL1A::ALK, and LRRFIP2::ALK, were detected and further confirmed by FISH in all 3 cases and RT-PCR in 1 case. All patients were elderly (62-63 years) and presented with a solitary polypoid lesion on the extremities. The awareness of these morphological variants is important since it entertains a wide and slightly different differential diagnosis than conventional EFH. We also presented evidence that a clear separation of EFH from BFH in all cases may not be as straightforward as previously thought. The consistent ALK immunoexpression and the continually expanding scale of ALK gene rearrangements provide a useful tool to distinguish EFH from its histologic mimics.

Flightless I Negatively Regulates Macrophage Surface TLR4, Delays Early Inflammation, and Impedes Wound Healing

TLR4 plays a pivotal role in orchestrating inflammation and tissue repair. Its expression has finally been balanced to initiate the early, robust immune response necessary for efficient repair without excessively amplifying and prolonging inflammation, which impairs healing. Studies show Flightless I (Flii) is an immunomodulator that negatively regulates macrophage TLR4 signalling. Using macrophages from Flii^+/−, WT, and Flii^Tg/Tg mice, we have shown that elevated Flii reduces early TLR4 surface expression, delaying and reducing subsequent TNF secretions. In contrast, reduced Flii increases surface TLR4, leading to an earlier robust TNF peak. In Flii^+/− mice, TLR4 levels peak earlier during wound repair, and overall healing is accelerated. Fewer neutrophils, monocytes and macrophages are recruited to Flii^+/− wounds, leading to fewer TNF-positive macrophages, alongside an early peak and a robust shift to M2 anti-inflammatory, reparative Ym1⁺ and IL-10⁺ macrophages. Importantly, in diabetic mice, high Flii levels are found in plasma and unwounded skin, with further increases observed in their wounds, which have impaired healing. Lowering Flii in diabetic mice results in an earlier shift to M2 macrophages and improved healing. Overall, this suggests Flii regulation of TLR4 reduces early inflammation and decreases the M2 macrophage phenotype, leading to impaired healing.

Insight into mechanisms of pig lncRNA FUT3-AS1 regulating E. coli F18-bacterial diarrhea

Escherichia coli F18 is a common conditional pathogen that is associated with a variety of infections in humans and animals. LncRNAs have emerged as critical players in pathogen infection, but their role in the resistance of the host to bacterial diarrhea remains unknown. Here, we used piglets as animal model and identified an antisense lncRNA termed FUT3-AS1 as a host regulator related to E. coli F18 infection by RNA sequencing. Downregulation of FUT3-AS1 expression contributed to the enhancement of E. coli F18 resistance in IPEC-J2 cells. FUT3-AS1 knockdown reduced FUT3 expression via decreasing the H4K16ac level of FUT3 promoter. Besides, the FUT3-AS1/miR-212 axis could act as a competing endogenous RNA to regulate FUT3 expression. Functional analysis demonstrated that target FUT3 plays a vital role in the resistance of IPEC-J2 cells to E. coli F18 invasion. A Fut3-knockout mice model was established and Fut3-knockout mice obviously improved the ability of resistance to bacterial diarrhea. Interestingly, FUT3 could enhance E. coli F18 susceptibility by activating glycosphingolipid biosynthesis and toll-like receptor signaling which are related to receptor formation and immune response, respectively. In summary, we have identified a novel biomarker FUT3-AS1 that modulates E. coli F18 susceptibility via histone H4 modifications or miR-212/FUT3 axis, which will provide theoretical guidance to develop novel strategies for combating bacterial diarrhea in piglets.

LRRFIP1, an epigenetically regulated gene, is a prognostic biomarker and predicts malignant phenotypes of glioma

Aims

Glioblastoma (GBM) is the most common malignant brain tumor with an adverse prognosis in the central nervous system. Traditional histopathological diagnosis accompanied by subjective deviations cannot accurately reflect tumor characteristics for clinical guidance. DNA methylation plays a critical role in GBM genesis. The focus of this project was to identify an effective methylation point for the classification of gliomas, the interactions between DNA methylation and potential epigenetic targeted therapies for clinical treatments.

Methods

Three online (TCGA, CGGA, and REMBRANDT) databases were employed in this study. T‐test, Venn analysis, univariate cox analysis, and Pearson's correlation analysis were adopted to screen significant prognostic methylation genes. Clinical samples were collected to determine the distributions of LRRFIP1 (Leucine Rich Repeat of Flightless‐1 Interacting Protein) protein by immunohistochemistry assay. Kaplan–Meier survival and Cox analysis were adopted to evaluate the prognostic value of LRRFIP1. Nomogram model was used to construct a prediction model. GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway were performed to explore functions and related mechanisms of LRRFIP1 in gliomas.

Results

Our results showed that 16 genes were negatively connected with their methylation level and correlated with clinical prognosis of GBM patients. Among them, LRRFIP1 expression showed the highest correlation with its methylation level. LRRFIP1 was highly expressed in WHO IV, mesenchymal, and IDH wild‐type subtype. LRRFIP1 expression was an independent risk factor for OS (overall survival) in gliomas.

Conclusion

LRRFIP1 is an epigenetically regulated gene and a potential prognostic biomarker for glioma. Our research may be beneficial to evaluate clinical efficacy, assess the prognosis, and provide individualized treatment for gliomas.

Differential gene expression reveals host factors for viral shedding variation in mallards (Anas platyrhynchos) infected with low-pathogenic avian influenza virus

Intraspecific variation in pathogen shedding impacts disease transmission dynamics; therefore, understanding the host factors associated with individual variation in pathogen shedding is key to controlling and preventing outbreaks. In this study, ileum and bursa of Fabricius tissues of wild-bred mallards (Anas platyrhynchos) infected with low-pathogenic avian influenza (LPAIV) were evaluated at various post-infection time points to determine genetic host factors associated with intraspecific variation in viral shedding. By analysing transcriptome sequencing data (RNA-seq), we found that LPAIV-infected wild-bred mallards do not exhibit differential gene expression compared to uninfected birds, but that gene expression was associated with cloacal viral shedding quantity early in the infection. In both tissues, immune gene expression was higher in high/moderate shedding birds compared to low shedding birds, and significant positive relationships with viral shedding were observed. In the ileum, expression for host genes involved in viral cell entry was lower in low shedders compared to moderate shedders at 1 day post-infection (DPI), and expression for host genes promoting viral replication was higher in high shedders compared to low shedders at 2 DPI. Our findings indicate that viral shedding is a key factor for gene expression differences in LPAIV-infected wild-bred mallards, and the genes identified in this study could be important for understanding the molecular mechanisms driving intraspecific variation in pathogen shedding.

Multifunctional Roles of the Actin-Binding Protein Flightless I in Inflammation, Cancer and Wound Healing

Flightless I is an actin-binding member of the gelsolin family of actin-remodeling proteins that inhibits actin polymerization but does not possess actin severing ability. Flightless I functions as a regulator of many cellular processes including proliferation, differentiation, apoptosis, and migration all of which are important for many physiological processes including wound repair, cancer progression and inflammation. More than simply facilitating cytoskeletal rearrangements, Flightless I has other important roles in the regulation of gene transcription within the nucleus where it interacts with nuclear hormone receptors to modulate cellular activities. In conjunction with key binding partners Leucine rich repeat in the Flightless I interaction proteins (LRRFIP)1/2, Flightless I acts both synergistically and competitively to regulate a wide range of cellular signaling including interacting with two of the most important inflammatory pathways, the NLRP3 inflammasome and the MyD88-TLR4 pathways. In this review we outline the current knowledge about this important cytoskeletal protein and describe its many functions across a range of health conditions and pathologies. We provide perspectives for future development of Flightless I as a potential target for clinical translation and insights into potential therapeutic approaches to manipulate Flightless I functions.

Novel LRRFIP2-RAF1 fusion identified in an acral melanoma: A review of the literature on melanocytic proliferations with RAF1 fusions and the potential therapeutic implications

A small subset of cutaneous melanomas harbor oncogenic gene fusions, which could potentially serve as therapeutic targets for patients with advanced disease as novel therapies are developed. Fusions involving RAF1 are exceedingly rare in melanocytic neoplasms, occurring in less than 1% of melanomas, and usually arise in tumors that are wild type for BRAF, NRAS, and NF1. We describe herein a case of acral melanoma with two satellite metastases and sentinel lymph node involvement. The melanoma had a concomitant KIT variant and LRRFIP2-RAF1 fusion. This constellation of molecular findings has not been reported previously in melanoma. We review the existing literature on melanocytic neoplasms with RAF1 fusions and discuss the potential clinical implications of this genetic event.

Integrated analysis of RNA-binding proteins in human colorectal cancer

Background

Although RNA-binding proteins play an essential role in a variety of different tumours, there are still limited efforts made to systematically analyse the role of RNA-binding proteins (RBPs) in the survival of colorectal cancer (CRC) patients.

Methods

Analysis of CRC transcriptome data collected from the TCGA database was conducted, and RBPs were extracted from CRC. R software was applied to analyse the differentially expressed genes (DEGs) of RBPs. To identify related pathways and perform functional annotation of RBP DEGs, Gene Ontology (GO) function and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were carried out using the database for annotation, visualization and integrated discovery. Protein-protein interactions (PPIs) of these DEGs were analysed based on the Search Tool for the Retrieval of Interacting Genes (STRING) database and visualized by Cytoscape software. Based on the Cox regression analysis of the prognostic value of RBPs (from the PPI network) with survival time, the RBPs related to survival were identified, and a prognostic model was constructed. To verify the model, the data stored in the TCGA database were designated as the training set, while the chip data obtained from the GEO database were treated as the test set. Then, both survival analysis and ROC curve verification were conducted. Finally, the risk curves and nomograms of the two groups were generated to predict the survival period.

Results

Among RBP DEGs, 314 genes were upregulated while 155 were downregulated, of which twelve RBPs (NOP14, MRPS23, MAK16, TDRD6, POP1, TDRD5, TDRD7, PPARGC1A, LIN28B, CELF4, LRRFIP2, MSI2) with prognostic value were obtained.

Conclusions

The twelve identified genes may be promising predictors of CRC and play an essential role in the pathogenesis of CRC. However, further investigation of the underlying mechanism is needed.

Proximity Labeling To Map Host-Pathogen Interactions at the Membrane of a Bacterium-Containing Vacuole in Chlamydia trachomatis-Infected Human Cells

Many intracellular bacteria, including the obligate intracellular pathogen Chlamydia trachomatis, grow within a membrane-bound bacterium-containing vacuole (BCV). Secreted cytosolic effectors modulate host activity, but an understanding of the host-pathogen interactions that occur at the BCV membrane is limited by the difficulty in purifying membrane fractions from infected host cells.

Many intracellular bacteria, including the obligate intracellular pathogen Chlamydia trachomatis, grow within a membrane-bound bacterium-containing vacuole (BCV). Secreted cytosolic effectors modulate host activity, but an understanding of the host-pathogen interactions that occur at the BCV membrane is limited by the difficulty in purifying membrane fractions from infected host cells. We used the ascorbate peroxidase (APEX2) proximity labeling system, which labels proximal proteins with biotin in vivo, to study the protein-protein interactions that occur at the chlamydial vacuolar, or inclusion, membrane. An in vivo understanding of the secreted chlamydial inclusion membrane protein (Inc) interactions (e.g., Inc-Inc and Inc-eukaryotic protein) and how these contribute to overall host-chlamydia interactions at this unique membrane is lacking. We hypothesize some Incs organize the inclusion membrane, whereas other Incs bind eukaryotic proteins to promote chlamydia-host interactions. To study this, Incs fused to APEX2 were expressed in C. trachomatis L2. Affinity purification-mass spectrometry (AP-MS) identified biotinylated proteins, which were analyzed for statistical significance using significance analysis of the interactome (SAINT). Broadly supporting both Inc-Inc and Inc-host interactions, our Inc-APEX2 constructs labeled Incs as well as known and previously unreported eukaryotic proteins localizing to the inclusion. We demonstrate, using bacterial two-hybrid and coimmunoprecipitation assays, that endogenous LRRFIP1 (LRRF1) is recruited to the inclusion by the Inc CT226. We further demonstrate interactions between CT226 and the Incs used in our study to reveal a model for inclusion membrane organization. Combined, our data highlight the utility of APEX2 to capture the complex in vivo protein-protein interactions at the chlamydial inclusion.

Flightless I exacerbation of inflammatory responses contributes to increased colonic damage in a mouse model of dextran sulphate sodium-induced ulcerative colitis

Ulcerative colitis (UC) is a chronic inflammatory bowel disease characterized by cytokine driven inflammation that disrupts the mucosa and impedes intestinal structure and functions. Flightless I (Flii) is an immuno-modulatory protein is a member of the gelsolin family of actin-remodelling proteins that regulates cellular and inflammatory processes critical in tissue repair. Here we investigated its involvement in UC and show that Flii is significantly elevated in colonic tissues of patients with inflammatory bowel disease. Using an acute murine model of colitis, we characterised the contribution of Flii to UC using mice with low (Flii+/-), normal (Flii+/+) and high Flii (FliiTg/Tg). High levels of Flii resulted in significantly elevated disease severity index scores, increased rectal bleeding and degree of colon shortening whereas, low Flii expression decreased disease severity, reduced tissue inflammation and improved clinical indicators of UC. Mice with high levels of Flii had significantly increased histological disease severity and elevated mucosal damage with significantly increased inflammatory cell infiltrate and significantly higher levels of TNF-α, IFN-γ, IL-5 and IL-13 pro-inflammatory cytokines. Additionally, Flii overexpression resulted in decreased β-catenin levels, inhibited Wnt/β-catenin signalling and impaired regeneration of colonic crypts. These studies suggest that high levels of Flii, as is observed in patients with UC, may adversely affect mucosal healing via mechanisms involving Th1 and Th2 mediated tissue inflammation and Wnt/β-catenin signalling pathway.

Varroa destructor parasitism has a greater effect on proteome changes than the deformed wing virus and activates TGF-β signaling pathways

Honeybee workers undergo metamorphosis in capped cells for approximately 13 days before adult emergence. During the same period, Varroa mites prick the defenseless host many times. We sought to identify proteome differences between emerging Varroa-parasitized and parasite-free honeybees showing the presence or absence of clinical signs of deformed wing virus (DWV) in the capped cells. A label-free proteomic analysis utilizing nanoLC coupled with an Orbitrap Fusion Tribrid mass spectrometer provided a quantitative comparison of 2316 protein hits. Redundancy analysis (RDA) showed that the combination of Varroa parasitism and DWV clinical signs caused proteome changes that occurred in the same direction as those of Varroa alone and were approximately two-fold higher. Furthermore, proteome changes associated with DWV signs alone were positioned above Varroa in the RDA. Multiple markers indicate that Varroa activates TGF-β-induced pathways to suppress wound healing and the immune response and that the collective action of stressors intensifies these effects. Furthermore, we indicate JAK/STAT hyperactivation, p53-BCL-6 feedback loop disruption, Wnt pathway activation, Wnt/Hippo crosstalk disruption, and NF-κB and JAK/STAT signaling conflict in the Varroa–honeybee–DWV interaction. These results illustrate the higher effect of Varroa than of DWV at the time of emergence. Markers for future research are provided.

Multidisciplinary Roles of LRRFIP1/GCF2 in Human Biological Systems and Diseases

Leucine Rich Repeat of Flightless-1 Interacting Protein 1/GC-binding factor 2 (LRRFIP1/GCF2) cDNA was cloned for a transcriptional repressor GCF2, which bound sequence-specifically to a GC-rich element of epidermal growth factor receptor (EGFR) gene and repressed its promotor. LRRFIP1/GCF2 was also cloned as a double stranded RNA (dsRNA)-binding protein to trans-activation responsive region (TAR) RNA of Human Immunodeficiency Virus-1 (HIV-1), termed as TAR RNA interacting protein (TRIP), and as a binding protein to the Leucine Rich Repeat (LRR) of Flightless-1(Fli-1), termed as Flightless-1 LRR associated protein 1 (FLAP1) and LRR domain of Flightless-1 interacting Protein 1 (LRRFIP1). Subsequent functional studies have revealed that LRRFIP1/GCF2 played multiple roles in the regulation of diverse biological systems and processes, such as in immune response to microorganisms and auto-immunity, remodeling of cytoskeletal system, signal transduction pathways, and transcriptional regulations of genes. Dysregulations of LRRFIP1/GCF2 have been implicated in the causes of several experimental and clinico-pathological states and the responses to them, such as autoimmune diseases, excitotoxicity after stroke, thrombosis formation, inflammation and obesity, the wound healing process, and in cancers. LRRFIP1/GCF2 is a bioregulator in multidisciplinary systems of the human body and its dysregulation can cause diverse human diseases.

The Role of Nucleic Acid Sensing in Controlling Microbial and Autoimmune Disorders

Innate immunity, the first line of defense against invading pathogens, is an ancient form of host defense found in all animals, from sponges to humans. During infection, innate immune receptors recognize conserved molecular patterns, such as microbial surface molecules, metabolites produces during infection, or nucleic acids of the microbe's genome. When initiated, the innate immune response activates a host defense program that leads to the synthesis proteins capable of pathogen killing. In mammals, the induction of cytokines during the innate immune response leads to the recruitment of professional immune cells to the site of infection, leading to an adaptive immune response. While a fully functional innate immune response is crucial for a proper host response and curbing microbial infection, if the innate immune response is dysfunctional and is activated in the absence of infection, autoinflammation and autoimmune disorders can develop. Therefore, it follows that the innate immune response must be tightly controlled to avoid an autoimmune response from host-derived molecules, yet still unencumbered to respond to infection. In this review, we will focus on the innate immune response activated from cytosolic nucleic acids, derived from the microbe or host itself. We will depict how viruses and bacteria activate these nucleic acid sensing pathways and their mechanisms to inhibit the pathways. We will also describe the autoinflammatory and autoimmune disorders that develop when these pathways are hyperactive. Finally, we will discuss gaps in knowledge with regard to innate immune response failure and identify where further research is needed.

Recombinant Leucine-Rich Repeat Flightless-Interacting Protein-1 Improves Healing of Acute Wounds through Its Effects on Proliferation Inflammation and Collagen Deposition

Wound healing is an increasing clinical problem involving substantial morbidity, mortality, and rising health care costs. Leucine-rich repeat flightless-interacting protein-1 (LRRFIP-1) regulates toll-like receptor (TLR)-mediated inflammation, suggesting a potential role in the healing of wounds. We sought to determine the role of LRRFIP-1 in wound repair and whether the exogenous addition of recombinant LRRFIP-1 (rLRRFIP-1) affected healing responses. Using a model of full-thickness incisional acute wounds in BALB/c mice, we investigated the effect of wounding on LRRFIP-1 expression. The effect of rLRRFIP-1 on cellular proliferation, inflammation, and collagen deposition was also investigated. LRRFIP-1 was upregulated in response to wounding, was found to directly associate with flightless I (Flii), and significantly increased cellular proliferation both in vitro and in vivo. rLRRFIP-1 reduced Flii expression in wounds in vivo and resulted in significantly improved healing with a concurrent dampening of TLR4-mediated inflammation and improved collagen deposition. Additionally, decreased levels of TGF-β1 and increased levels of TGF-β3 were observed in rLRRFIP-1-treated wounds suggesting a possible antiscarring effect of rLRRFIP-1. Further studies are required to elucidate if the mechanisms behind LRRFIP-1 action in wound repair are independent of Flii. However, these results identify rLRRFIP-1 as a possible treatment modality for improved healing of acute wounds.

Relative and Absolute Quantitation in Mass Spectrometry-Based Proteomics

Mass spectrometry-based quantitative proteomics is a powerful tool for gaining insights into function and dynamics of biological systems. However, peptides with different sequences have different ionization efficiencies, and their intensities in a mass spectrum are not correlated with their abundances. Therefore, various label-free or stable isotope label-based quantitation methods have emerged to assist mass spectrometry to perform comparative proteomic experiments, thus enabling nonbiased identification of thousands of proteins differentially expressed in healthy versus diseased cells. Here, we discuss the most widely used label-free and metabolic-, enzymatic-, and chemical labeling-based proteomic strategies for relative and absolute quantitation. We summarize the specific strengths and weaknesses of each technique in terms of quantification accuracy, proteome coverage, multiplexing capability, and robustness. Applications of each strategy for solving specific biological complexities are also presented.

Microbial recognition and danger signals in sepsis and trauma

Early host recognition of microbial invasion or damaged host tissues provides an effective warning system by which protective immune and inflammatory processes are initiated. Host tissues responsible for continuous sampling of their local environment employ cell surface and cytosolic pattern recognition receptors (PRRs) that provide redundant and overlapping identification of both microbial and host alarmins. Microbial products containing pathogen-associated molecular patterns (PAMPs), as well as damage-associated molecular patterns (DAMPs) serve as principle ligands for recognition by these PRRs. It is this interaction which plays both an essential survival role in response to infection and injury, as well as the pathologic role in tissue and organ injury associated with severe sepsis and trauma. Elucidating the interaction between ligands and their respective PRRs can provide both a better understanding of the host response, as well as a rational basis for therapeutic intervention. This article is part of a Special Issue entitled: Immune and Metabolic Alterations in Trauma and Sepsis edited by Dr. Raghavan Raju.

Cytoskeletal protein Flightless I inhibits apoptosis, enhances tumor cell invasion and promotes cutaneous squamous cell carcinoma progression

Flightless I (Flii) is an actin remodeling protein that affects cellular processes including adhesion, proliferation and migration. In order to determine the role of Flii during carcinogenesis, squamous cell carcinomas (SCCs) were induced in Flii heterozygous (Flii+/-), wild-type and Flii overexpressing (FliiTg/Tg) mice by intradermal injection of 3-methylcholanthrene (MCA). Flii levels were further assessed in biopsies from human SCCs and the human SCC cell line (MET-1) was used to determine the effect of Flii on cellular invasion. Flii was highly expressed in human SCC biopsies particularly by the invading cells at the tumor edge. FliiTg/Tg mice developed large, aggressive SCCs in response to MCA. In contrast Flii+/- mice had significantly smaller tumors that were less invasive. Intradermal injection of Flii neutralizing antibodies during SCC initiation and progression significantly reduced the size of the tumors and, in vitro, decreased cellular sphere formation and invasion. Analysis of the tumors from the Flii overexpressing mice showed reduced caspase I and annexin V expression suggesting Flii may negatively regulate apoptosis within these tumors. These studies therefore suggest that Flii enhances SCC tumor progression by decreasing apoptosis and enhancing tumor cell invasion. Targeting Flii may be a potential strategy for reducing the severity of SCCs.

A novel 72-kDa leukocyte-derived osteoglycin enhances the activation of toll-like receptor 4 and exacerbates cardiac inflammation during viral myocarditis

Background

Viral myocarditis can severely damage the myocardium through excessive infiltration of immune cells. Osteoglycin (OGN) is part of the small leucine-rich repeat proteoglycan (SLRP) family. SLRP’s may affect inflammatory and fibrotic processes, but the implication of OGN in cardiac inflammation and the resulting injury upon viral myocarditis is unknown.

Methods and results

This study uncovered a previously unidentified 72-kDa variant of OGN that is predominant in cardiac human and mouse samples of viral myocarditis. Its absence in mice significantly decreased cardiac inflammation and injury in Coxsackievirus-B3-induced myocarditis. It also delayed mortality in lipopolysaccharide-induced endotoxemia going along with a reduced systemic production of pro-inflammatory cytokines. This 72-kDa OGN is expressed in the cell membrane of circulating and resident cardiac macrophages and neutrophils. Co-immunoprecipitation and OGN siRNA experiments revealed that this 72-kDa variant activates the toll-like receptor-4 (TLR4) with a concomitant increase in IL-6, TNF-α, IL-1β, and IL-12 expression. This immune cell activation by OGN occurred via MyD88 and increased phosphorylation of c-jun. Finally, the 72-kDa chondroitin sulfate is the result of O-linked glycosylation of the 32-kDa protein core of OGN. In contrast, the 34-kDa dermatan sulfate-OGN, involved in collagen cross linking, was also the result of O-linked glycosylation.

Conclusion

The current study discovered a novel 72-kDa chondroitin sulfate-OGN that is specific for innate immune cells. This variant is able to bind and activate TLR4. The absence of OGN decreases cytokine production by both circulating and cardiac leukocytes upon (systemic) LPS exposure, and reduces cardiac inflammation and injury in viral myocarditis.

Electronic supplementary material

The online version of this article (doi:10.1007/s00018-016-2423-7) contains supplementary material, which is available to authorized users.

Flightless I Expression Enhances Murine Claw Regeneration Following Digit Amputation

The mammalian digit tip is capable of both reparative and regenerative wound healing dependent on the level of amputation injury. Removal of the distal third of the terminal phalange results in successful regeneration, whereas a more severe, proximal, amputation heals by tissue repair. Flightless I (Flii) is involved in both tissue repair and regeneration. It negatively regulates wound repair but elicits a positive effect in hair follicle regeneration, with Flii overexpression resulting in significantly longer hair fibers. Using a model of digit amputation in Flii overexpressing (FIT) mice, we investigated Flii in digit regeneration. Both wild-type and FIT digits regenerated after distal amputation with newly regenerated FIT claws being significantly longer than intact controls. No regeneration was observed in wild-type mice after severe proximal amputation; however, FIT mice showed significant regeneration of the missing digit. Using a three-dimensional model of nail formation, connective tissue fibroblasts isolated from the mesenchymal tissue surrounding the wild-type and FIT digit tips and cocultured with skin keratinocytes demonstrated aggregate structures resembling rudimentary nail buds only when Flii was overexpressed. Moreover, β-catenin and cyclin D1 expression was maintained in the FIT regenerating germinal matrix suggesting a potential interaction of Flii with Wnt signaling during regeneration.

Cytoskeletal Regulation of Inflammation and Its Impact on Skin Blistering Disease Epidermolysis Bullosa Acquisita

Actin remodelling proteins regulate cytoskeletal cell responses and are important in both innate and adaptive immunity. These responses play a major role in providing a fine balance in a cascade of biological events that results in either protective acute inflammation or chronic inflammation that leads to a host of diseases including autoimmune inflammation mediated epidermolysis bullosa acquisita (EBA). This review describes the role of the actin cytoskeleton and in particular the actin remodelling protein called Flightless I (Flii) in regulating cellular inflammatory responses and its subsequent effect on the autoimmune skin blistering disease EBA. It also outlines the potential of an antibody based therapy for decreasing Flii expression in vivo to ameliorate the symptoms associated with EBA.

Silencing of LRRFIP1 reverses the epithelial-mesenchymal transition via inhibition of the Wnt/β-catenin signaling pathway

The canonical Wnt/β-catenin signaling pathway has been shown to promote the epithelial-mesenchymal transition (EMT), which is a crucial process in multiple embryonic developmental processes and the progression of carcinomas. We recently provided evidence that leucine-rich repeat flightless-1-interacting protein 1 (LRRFIP1) promotes cancer metastasis and invasion. In the present study, we identified the signaling elements targeted by LRRFIP1 for promotion of the EMT in pancreatic and lung cancer. LRRFIP1 silencing reversed the EMT, as shown by increased expression of E-cadherin (an epithelial marker) and decreased expression of vimentin (a mesenchymal marker). Silencing of LRRFIP1 up-regulated phosphorylation of β-catenin and decreased its nuclear localization by targeting the β-catenin destruction complex. The expression of β-catenin and E-cadherin in the plasma membrane fraction was increased in LRRFIP1 silenced cancer cells, and the migration and invasion capabilities were strongly inhibited. In addition, this protein was highly expressed at the invasion front of malignant tissue collected from pancreatic cancer patients. Consequently, our data strongly suggested that LRRFIP1 played an important role in the invasion of carcinoma cells. Our data provide experimental evidence that LRRFIP1 is an attractive candidate for targeted therapy in human cancers.

Controlling the origins of inflammation with a photoactive lipopeptide immunopotentiator

Inflammatory immune responses are mediated by signaling molecules that are both produced by and recognized across highly heterogeneous cell populations. As such, the study of inflammation using traditional immunostimulants is complicated by paracrine and autocrine signaling, which obscures the origin of a propagating response. To address this challenge, we developed a small-molecule probe that can photosensitize immune cells, thus allowing light-mediated inflammation. This probe was used to control the origin of inflammation using light. Following this motif, inflammation was initiated from fibroblasts or dendritic cells. The contributions of fibroblasts and dendritic cells in initiating inflammation in heterogeneous co-culture are reported, thus providing insights into the future development of vaccines and treatment of inflammation.

Flightless-I (FliI) is a potential negative regulator of the Toll pathway in Litopenaeus vannamei

Flightless-I (FliI) is a protein negatively modulates the Toll-like receptor (TLR) pathway through interacting with Myeloid differentiation factor 88 (MyD88). To investigate the function of FliI in innate immune responses in invertebrates, Litopenaeus vannamei FliI (LvFliI) was identified and characterized. The full-length cDNA of LvFliI is 4, 304 bp long, with an open reading frame (ORF) encoding a putative protein of 1292 amino acids, including 12 leucine-rich repeat (LRR) domains at the N-terminus and 6 gelsolin homology (GEL) domains at the C-terminus. The LvFliI protein was located in the cytoplasm and LvFliI mRNA was constitutively expressed in healthy L. vannamei, with the highest expression level in the muscle. LvFliI could be up-regulated in hemocytes after lipopolysaccharide (LPS), poly I:C, CpG-ODN2006, Vibrio parahaemolyticus, Staphylococcus aureus, and white spot syndrome virus (WSSV) challenges, suggesting a stimulation response of LvFliI to bacterial and immune stimulant challenges. Upon LPS stimulation, overexpression of LvFliI in Drosophila Schneider 2 cells led to downregulation of Drosophila and shrimp antimicrobial peptide (AMP) genes. Knockdown of LvFliI by RNA interference (RNAi) resulted in an increase of the expression of three shrimp AMP genes (PEN2, crustin, and Lyz1). However, the mortality rates of LvFliI-knockdown shrimp in response to V. parahaemolyticus, S. aureus or WSSV infections were not significantly different from those of the control group. Taken together, all the results suggested that LvFliI may play a negative role in TLR signaling response in L. vannamei.

Integrating phosphoproteome and transcriptome reveals new determinants of macrophage multinucleation

Macrophage multinucleation (MM) is essential for various biological processes such as osteoclast-mediated bone resorption and multinucleated giant cell-associated inflammatory reactions. Here we study the molecular pathways underlying multinucleation in the rat through an integrative approach combining MS-based quantitative phosphoproteomics (LC-MS/MS) and transcriptome (high-throughput RNA-sequencing) to identify new regulators of MM. We show that a strong metabolic shift toward HIF1-mediated glycolysis occurs at transcriptomic level during MM, together with modifications in phosphorylation of over 50 proteins including several ARF GTPase activators and polyphosphate inositol phosphatases. We use shortest-path analysis to link differential phosphorylation with the transcriptomic reprogramming of macrophages and identify LRRFIP1, SMARCA4, and DNMT1 as novel regulators of MM. We experimentally validate these predictions by showing that knock-down of these latter reduce macrophage multinucleation. These results provide a new framework for the combined analysis of transcriptional and post-translational changes during macrophage multinucleation, prioritizing essential genes, and revealing the sequential events leading to the multinucleation of macrophages.

Toward a comprehensive map of the effectors of rab GTPases

The Rab GTPases recruit peripheral membrane proteins to intracellular organelles. These Rab effectors typically mediate the motility of organelles and vesicles and contribute to the specificity of membrane traffic. However, for many Rabs, few, if any, effectors have been identified; hence, their role remains unclear. To identify Rab effectors, we used a comprehensive set of Drosophila Rabs for affinity chromatography followed by mass spectrometry to identify the proteins bound to each Rab. For many Rabs, this revealed specific interactions with Drosophila orthologs of known effectors. In addition, we found numerous Rab-specific interactions with known components of membrane traffic as well as with diverse proteins not previously linked to organelles or having no known function. We confirm over 25 interactions for Rab2, Rab4, Rab5, Rab6, Rab7, Rab9, Rab18, Rab19, Rab30, and Rab39. These include tethering complexes, coiled-coiled proteins, motor linkers, Rab regulators, and several proteins linked to human disease.

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Proteomic screen identifies effectors of Drosophila Rabs with a human ortholog

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Specific hits include orthologs of numerous known effectors of mammalian Rabs

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Validated effectors include traffic proteins and those of unknown function

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Orthologs of disease genes CLEC16A, LRRK2, and SPG20 are validated as effectors

Circulating tumor cells exhibit a biologically aggressive cancer phenotype accompanied by selective resistance to chemotherapy

With prostate cancer (PCa), circulating tumor cells (CTCs) and disseminated tumor cells (DTCs) portend a poor clinical prognosis. Their unknown biology precludes rational therapeutic design. We demonstrate that CTC and DTC cell lines, established from mice bearing human PCa orthotopic implants, exhibit increased cellular invasion in vitro, increased metastasis in mice, and express increased epithelial to mesenchymal transition biomarkers. Further, they are selectively resistant to growth inhibition by mitoxantrone-like agents. These findings demonstrate that CTC formation is accompanied by phenotypic progression without obligate reversion. Their increased metastatic potential, selective therapeutic resistance, and differential expression of potential therapeutic targets provide a rational basis to test further interventions.

Anti-inflammatory effect of Natterins, the major toxins from the Thalassophryne nattereri fish venom is dependent on TLR4/MyD88/PI3K signaling pathway

Here we evaluated whether Natterins affect the leukocyte-endothelial cell interaction, hampering leukocyte mobilization and extravasation. Leukocyte-endothelial cell interactions were evaluated in venules of mouse cremaster muscle using intravital microscopy. We reported that low doses of Natterins interfere with the cell capturing, inhibiting the interaction of blood neutrophils with the post-capillary venules induced by the TLR4 agonist LPS, or the chemokine KC. Using endotoxemic mice challenged with LPS, we confirmed that Natterins reduce neutrophil accumulation in the peritoneum exudates. The rolling of leukocytes induced by KC or LPS was not impaired in Natterins-treated TLR2, MyD88 deficient or TLR4 mutant mice, indicating that TLR2- or TLR4-MyD88-mediated signals are required for the anti-inflammatory effect of Natterins. The inhibitory effect was not influenced by endogenous regulators of inflammation such as IL-10, corticosteroids, the HO-1 or the antagonist of the receptor of IL-1, nor by the disruption of their proteolytic activity. However, it was completely dependent on the activation of serine/threonine phosphatases and the PI3K signaling pathway, but independent on increased proteasome activity. This work started asking how the main toxins in the T nattereri venom contributes for the deficient influx of inflammatory leukocytes, which consequently drive to the delayed inflammatory reaction finalization in injured tissue; and finished demonstrating that Natterins can control the leukocyte-endothelial wall interactions in a mechanism dependent on negative signals derived from TLR2-TLR4/Myd88 signaling cascade. Interestingly, we confirmed that the antagonist effect of Natterins is mediated by the activation of serine/threonine phosphatases and by the key signaling PI3K molecule.

LRRFIP2 negatively regulates NLRP3 inflammasome activation in macrophages by promoting Flightless-I-mediated caspase-1 inhibition

The NLRP3 inflammasome is the most characterized inflammasome activated by cellular infection or stress, which is responsible for the maturation of proinflammatory cytokines IL-1β and IL-18. The precise molecular mechanism for negative regulation of NLRP3 inflammasome activation needs to be further defined. Here we identify leucine-rich repeat Fli-I-interacting protein 2 (LRRFIP2) as an NLRP3-associated protein and an inhibitor for NLRP3 inflammasome activation. LRRFIP2 binds to NLRP3 via its N terminus upon NLRP3 inflammasome activation, and also interacts with Flightless-I, a pseudosubstrate of caspase-1, via its Coil motif. Knockdown of Flightless-I significantly promotes NLRP3 inflammasome activation. LRRFIP2 enhances the interaction between Flightless-I and caspase-1, facilitating the inhibitory effect of Flightless-I on caspase-1 activation. Furthermore, silencing of Flightless-I abrogates the inhibitory effect of LRRFIP2 on NLRP3 inflammasome. These data demonstrate that LRRFIP2 inhibits NLRP3 inflammasome activation by recruiting the caspase-1 inhibitor Flightless-I, thus outlining a new mechanism for negative regulation of NLRP3 inflammasome.

Inflammasomes promote the maturation of inflammatory cytokines in response to signals associated with damage and infection, but it remains unclear how these signals are attenuated. Here, the authors show that the NLRP3 inflammasome is inhibited by LRRFIP2 through recruitment of the protein Flightless I.

Characterization of Gcf2/Lrrfip1 in experimental cerebral ischemia and its role as a modulator of Akt, mTOR and β-catenin signaling pathways

Leucine-rich repeat in Flightless-1 interaction protein 1 (Lrrfip1) is an up-regulated protein after cerebral ischemia whose precise role in the brain both in healthy and ischemic conditions is unclear. Different Lrrfip1 isoforms with distinct roles have been reported in human and mouse species. The present study aimed to analyze the Lrrfip1 transcriptional variants expressed in rat cortex, to characterize their expression patterns and subcellular location after ischemia, and to define their putative role in the brain. Five transcripts were identified and three of them (Lrrfip1, CRA_g and CRA_a' (Fli-I leucine-rich repeat associated protein 1 - Flap-1)) were analyzed by quantitative real-time polymerase chain reaction (qPCR). All the transcripts were up-regulated and showed differential expression patterns after in vivo and in vitro ischemia models. The main isoform, Lrrfip1, was found to be up-regulated from the acute to the late phases of ischemia in the cytoplasm of neurons and astrocytes of the peri-infarct area. This study demonstrates that Lrrfip1 activates β-catenin, Akt, and mammalian target of rapamycin (mTOR) proteins in astrocytes and positively regulates the expression of the excitatory amino acid transporter subtype 2 (GLT-1). Our findings point to Lrrfip1 as a key brain protein that regulates pro-survival pathways and proteins and encourages further studies to elucidate its role in cerebral ischemia as a potential target to prevent brain damage and promote functional recovery after stroke.

Noncoding RNAs and LRRFIP1 regulate TNF expression

Noncoding RNAs have been implicated in the regulation of expression of numerous genes; however, the mechanism is not fully understood. We identified bidirectional, long noncoding RNAs upstream of the TNF gene using five different methods. They arose in a region where the repressors LRRFIP1, EZH2, and SUZ12 were demonstrated to bind, suggesting a role in repression. The noncoding RNAs were polyadenylated, capped, and chromatin associated. Knockdown of the noncoding RNAs was associated with derepression of TNF mRNA and diminished binding of LRRFIP1 to both RNA targets and chromatin. Overexpression of the noncoding RNAs led to diminished expression of TNF and recruitment of repressor proteins to the locus. One repressor protein, LRRFIP1, bound directly to the noncoding RNAs. These data place the noncoding RNAs upstream of TNF gene as central to the transcriptional regulation. They appear to serve as a platform for the assembly of a repressive complex.

Attenuation of flightless I improves wound healing and enhances angiogenesis in a murine model of type 1 diabetes

AIMS/HYPOTHESIS

Skin lesions and ulcerations are severe complications of diabetes that often result in leg amputations. In this study we investigated the function of the cytoskeletal protein flightless I (FLII) in diabetic wound healing. We hypothesised that overexpression of FLII would have a negative effect on diabetic wound closure and modulation of this protein using specific FLII-neutralising antibodies (FnAb) would enhance cellular proliferation, migration and angiogenesis within the diabetic wound.

METHODS

Using a streptozotocin-induced model of diabetes we investigated the effect of altered FLII levels through Flii genetic knockdown, overexpression or treatment with FnAb on wound healing. Diabetic wounds were assessed using histology, immunohistochemistry and biochemical analysis. In vitro and in vivo assays of angiogenesis were used to assess the angiogenic response.

RESULTS

FLII levels were elevated in the wounds of both diabetic mice and humans. Reduction in the level of FLII improved healing of murine diabetic wounds and promoted a robust pro-angiogenic response with significantly elevated von Willebrand factor (vWF) and vascular endothelial growth factor (VEGF)-positive endothelial cell infiltration. Diabetic mouse wounds treated intradermally with FnAb showed improved healing and a significantly increased rate of re-epithelialisation. FnAb improved the angiogenic response through enhanced formation of capillary tubes and functional neovasculature. Reducing the level of FLII led to increased numbers of mature blood vessels, increased recruitment of smooth muscle actin-α-positive cells and improved tight junction formation.

CONCLUSIONS/INTERPRETATION

Reducing the level of FLII in a wound may be a potential therapeutic approach for the treatment of diabetic foot ulcers.

Identification and function of leucine-rich repeat flightless-I-interacting protein 2 (LRRFIP2) in Litopenaeus vannamei

Leucine-rich repeat flightless-I-interacting protein 2 (LRRFIP2) is a myeloid differentiation factor 88-interacting protein with a positive regulatory function in toll-like receptor signaling. In this study, seven LRRFIP2 protein variants (LvLRRFIP2A-G) were identified in Litopenaeus vannamei. All the seven LvLRRFIP2 protein variants encode proteins with a DUF2051 domain. LvLRRFIP2s were upregulated in hemocytes after challenged with lipopolysaccharide, poly I:C, CpG-ODN2006, Vibrio parahaemolyticus, Staphylococcus aureus, and white spot syndrome virus (WSSV). Dual-luciferase reporter assays in Drosophila Schneider 2 cells revealed that LvLRRFIP2 activates the promoters of Drosophila and shrimp AMP genes. The knockdown of LvLRRFIP2 by RNA interference resulted in higher cumulative mortality of L. vannamei upon V. parahaemolyticus but not S. aureus and WSSV infections. The expression of L. vannamei AMP genes were reduced by dsLvLRRFIP2 interference. These results indicate that LvLRRFIP2 has an important function in antibacterials via the regulation of AMP gene expression.

Protein phosphatase 2A catalytic subunit α plays a MyD88-dependent, central role in the gene-specific regulation of endotoxin tolerance

MyD88, the intracellular adaptor of most TLRs, mediates either proinflammatory or immunosuppressive signaling that contributes to chronic inflammation-associated diseases. Although gene-specific chromatin modifications regulate inflammation, the role of MyD88 signaling in establishing such epigenetic landscapes under different inflammatory states remains elusive. Using quantitative proteomics to enumerate the inflammation-phenotypic constituents of the MyD88 interactome, we found that in endotoxin-tolerant macrophages, protein phosphatase 2A catalytic subunit α (PP2Ac) enhances its association with MyD88 and is constitutively activated. Knockdown of PP2Ac prevents suppression of proinflammatory genes and resistance to apoptosis. Through site-specific dephosphorylation, constitutively active PP2Ac disrupts the signal-promoting TLR4-MyD88 complex and broadly suppresses the activities of multiple proinflammatory/proapoptotic pathways as well, shifting proinflammatory MyD88 signaling to a prosurvival mode. Constitutively active PP2Ac translocated with MyD88 into the nuclei of tolerant macrophages establishes the immunosuppressive pattern of chromatin modifications and represses chromatin remodeling to selectively silence proinflammatory genes, coordinating the MyD88-dependent inflammation control at both signaling and epigenetic levels under endotoxin-tolerant conditions.

The influence of Flightless I on Toll-like-receptor-mediated inflammation in a murine model of diabetic wound healing

Impaired wound healing and ulceration represent a serious complication of both type 1 and type 2 diabetes. Cytoskeletal protein Flightless I (Flii) is an important inhibitor of wound repair, and reduced Flii gene expression in fibroblasts increased migration, proliferation, and adhesion. As such it has the ability to influence all phases of wound healing including inflammation, remodelling and angiogenesis. Flii has the potential to modulate inflammation through its interaction with MyD88 which it an adaptor protein for TLR4. To assess the effect of Flii on the inflammatory response of diabetic wounds, we used a murine model of streptozocin-induced diabetes and Flii genetic mice. Increased levels of Flii were detected in Flii transgenic murine wounds resulting in impaired healing which was exacerbated when diabetes was induced. When Flii levels were reduced in diabetic wounds of Flii-deficient mice, healing was improved and decreased levels of TLR4 were observed. In contrast, increasing the level of Flii in diabetic mouse wounds led to increased TLR4 and NF- κ B production. Treatment of murine diabetic wounds with neutralising antibodies to Flii led to an improvement in healing with decreased expression of TLR4. Decreasing the level of Flii in diabetic wounds may therefore reduce the inflammatory response and improve healing.

Learning from the messengers: innate sensing of viruses and cytokine regulation of immunity - clues for treatments and vaccines

Virus infections are a major global public health concern, and only via substantial knowledge of virus pathogenesis and antiviral immune responses can we develop and improve medical treatments, and preventive and therapeutic vaccines. Innate immunity and the shaping of efficient early immune responses are essential for control of viral infections. In order to trigger an efficient antiviral defense, the host senses the invading microbe via pattern recognition receptors (PRRs), recognizing distinct conserved pathogen-associated molecular patterns (PAMPs). The innate sensing of the invading virus results in intracellular signal transduction and subsequent production of interferons (IFNs) and proinflammatory cytokines. Cytokines, including IFNs and chemokines, are vital molecules of antiviral defense regulating cell activation, differentiation of cells, and, not least, exerting direct antiviral effects. Cytokines shape and modulate the immune response and IFNs are principle antiviral mediators initiating antiviral response through induction of antiviral proteins. In the present review, I describe and discuss the current knowledge on early virus–host interactions, focusing on early recognition of virus infection and the resulting expression of type I and type III IFNs, proinflammatory cytokines, and intracellular antiviral mediators. In addition, the review elucidates how targeted stimulation of innate sensors, such as toll-like receptors (TLRs) and intracellular RNA and DNA sensors, may be used therapeutically. Moreover, I present and discuss data showing how current antimicrobial therapies, including antibiotics and antiviral medication, may interfere with, or improve, immune response.

Lysosomal secretion of Flightless I upon injury has the potential to alter inflammation

Intracellular Flightless I (Flii), a gelsolin family member, has been found to have roles modulating actin regulation, transcriptional regulation and inflammation. In vivo Flii can regulate wound healing responses. We have recently shown that a pool of Flii is secreted by fibroblasts and macrophages, cells typically found in wounds, and its secretion can be upregulated upon wounding. We show that secreted Flii can bind to the bacterial cell wall component lipopolysaccharide and has the potential to regulate inflammation. We now show that secreted Flii is present in both acute and chronic wound fluid.

A variant in the LRRFIP1 gene is associated with adiposity and inflammation

Inflammation is an important factor linking abdominal obesity with insulin resistance and related cardiometabolic risk. A genome-wide association study of adiposity-related traits performed in the Quebec Family Study (QFS) revealed that a single-nucleotide polymorphism (SNP) in the LRRFIP1 gene (rs11680012) was associated with abdominal adiposity (P = 4.6 × 10(-6)).

OBJECTIVE

The objective of this study was to assess the relationship between polymorphisms in LRRFIP1 gene and adiposity (BMI, fat mass (FM), waist circumference (WC), and computed tomography-derived areas of total, subcutaneous and visceral abdominal adipose tissue) and markers of inflammation (C-reactive protein (CRP) and interleukin-6 (IL-6)).

DESIGN AND METHODS

Using Sequenom, 16 tag SNPs in the LRRFIP1 gene, capturing 78% of the genetic variation, were genotyped in 926 participants of the QFS.

RESULTS

Eight SNPs (rs7575941, rs3769053, rs11689421, rs3820808, rs11680012, rs3806505, rs6739130, and rs11686141) showed evidence of association with at least two adiposity phenotypes and plasma levels of one marker of inflammation. The strongest evidence of association was observed with rs11680012, which explained 1.8-3.4% of the variance in areas of abdominal adiposity and 2.0% of the variation in CRP levels. Carriers of the rare allele of rs11680012 had ≈ 30% more abdominal adiposity (P values between 2.7 × 10(-4) and 3.8 × 10(-6)) and 75% higher CRP levels (P = 1.6 × 10(-4)) than the common allele in age and sex adjusted data. Rs11680012 is a G/C SNP converting an arginine into a threonine and this amino acid substitution may potentially alter exonic splicing.

CONCLUSION

This gene may therefore represent a potential interesting target to investigate in further functional studies on adiposity and inflammation.

Topically applied flightless I neutralizing antibodies improve healing of blistered skin in a murine model of epidermolysis bullosa acquisita

Epidermolysis bullosa (EB) is a chronic inheritable disease that leads to severe blistering and fibrosis. Previous studies have shown that the actin cytoskeletal protein flightless I (Flii) impairs wound healing associated with EB. Using a mouse model of EB acquisita (EBA), the effect of "mopping up" Flii using Flii-neutralizing antibodies (FnAbs) before, during, and after blister formation was determined. FnAbs, incorporated into a cream vehicle and applied topically to the skin, penetrated into the basal epidermis and upper papillary dermis but were not detected in serum or other organs and did not alter neutrophil or macrophage infiltration into the blistered skin. Histological assessment of blister severity showed that treatment of early-stage blisters with FnAb cream reduced their severity and improved their rate of healing. Treatment of established blisters with FnAb cream also improved healing and restored the skin's tensile strength toward that of normal skin. Repeated application of FnAbs to EBA skin before the onset of blistering reduced the severity of skin blistering. Independent of when the FnAbs were applied, skin barrier function and wound healing were improved and skin fragility was reduced, suggesting that FnAbs could potentially improve healing of patients with EB.

Regulation of TLR7/9 signaling in plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs), also known as type I interferon (IFN)-producing cells, are specialized immune cells characterized by their extraordinary capabilities of mounting rapid and massive type I IFN response to nucleic acids derived from virus, bacteria or dead cells. PDCs selectively express endosomal Toll-like receptor (TLR) 7 and TLR9, which sense viral RNA and DNA respectively. Following type I IFN and cytokine responses, pDCs differentiate into antigen presenting cells and acquire the ability to regulate T cell-mediated adaptive immunity. The functions of pDCs have been implicated not only in antiviral innate immunity but also in immune tolerance, inflammation and tumor microenvironments. In this review, we will focus on TLR7/9 signaling and their regulation by pDC-specific receptors.

Flii neutralizing antibodies improve wound healing in porcine preclinical studies

Wound healing is an important area of widely unmet medical need, with millions of procedures carried out worldwide which could potentially benefit from a product to improve the wound repair process. Our studies investigating the actin-remodeling protein Flightless I (Flii) show it to be an important regulator of wound healing. Flii-deficient mice have enhanced wound healing in comparison to Flii overexpressing mice which have impaired wound healing. For the first time, we show that a Flightless I neutralizing monoclonal antibody (FnAb) therapy is effective in a large animal model of wound repair. Porcine 5 cm incisional and 6.25 cm(2) excisional wounds were treated with FnAb at the time of wounding and for two subsequent days. The wounds were dressed in Tegaderm dressings and left to heal by secondary intention for 7 and 35 days, respectively. At the relevant end points, the wounds were excised and processed for histological analysis. Parameters of wound area, collagen deposition, and scar appearance were analyzed. The results show that treatment with FnAb accelerates reepithelialization and improves the macroscopic appearance of early scars. FnAbs have the potential to enhance wound repair and reduce scar formation.

A major locus on chromosome 3p22 conferring predisposition to human herpesvirus 8 infection

Infection with human herpesvirus 8 (HHV-8), the etiological agent of Kaposi's sarcoma, has been shown to display strong familial aggregation, in countries in which HHV-8 infection is endemic. We investigated 40 large families (608 subjects aged one to 88 years) living in an isolated area of Cameroon in which HHV-8 is highly endemic. We performed a two-step genetic analysis for HHV-8 infection status (HHV-8+/HHV-8- determined by immunofluorescence) consisting of an initial segregation analysis followed by a model-based genome-wide linkage analysis. Overall HHV-8 seroprevalence was 60%, increasing with age. Segregation analysis provided strong evidence for a recessive major gene conferring predisposition to HHV-8 infection. This gene is predicted to have a major effect during childhood, with almost all homozygous predisposed subjects (∼7% of the population) becoming infected by the age of 10. Linkage analysis was carried out on the 15 most informative families, corresponding to 205 genotyped subjects. A single region on chromosome 3p22 was significantly linked to HHV-8 infection (LOD score=3.83, P=2.0 × 10(-5)). This study provides the first evidence that HHV-8 infection in children in endemic areas has a strong genetic basis involving at least one recessive major locus on chromosome 3p22.

Flightless, secreted through a late endosome/lysosome pathway, binds LPS and dampens cytokine secretion

Flightless (Flii) is upregulated in response to wounding and has been shown to function in wound closure and scarring. In macrophages intracellular Flii negatively modulates TLR signalling and dampens cytokine production. We now show that Flii is constitutively secreted from macrophages and fibroblasts and is present in human plasma. Secretion from fibroblasts is upregulated in response to scratch wounding and LPS-activated macrophages also temporally upregulate their secretion of Flii. Using siRNA, wild-type and mutant proteins we show that Flii is secreted via a late endosomal/lysosomal pathway that is regulated by Rab7 and Stx11. Flii contains 11 leucine rich repeat (LRR) domains in its N-terminus that have nearly 50% similarity to those in the extracellular pathogen binding portion of Toll-like receptor 4 (TLR4). We show secreted Flii can also bind LPS and has the ability to alter macrophage activation. LPS activation of macrophages in Flii depleted conditioned media leads to enhanced macrophage activation and increased TNF secretion compared to cells activated in the presence of Flii. These results show secreted Flii binds to LPS and in doing so alters macrophage activation and cytokine secretion, suggesting that like the intracellular pool of Flii, secreted Flii also has the ability to alter inflammation.