AIF-1 and RNASET2 Play Complementary Roles in the Innate Immune Response of Medicinal Leech

Dynamic relationship among extracellular matrix and body wall cells in Hirudo verbana morphogenesis

A great bulk of recent experimental evidence suggests the key role of the complex crosstalk between the extracellular matrix (ECM) and the cellular component of tissues during morphogenesis and embryogenesis. In particular, remodeling of the ECM and of its physical interactions pattern with surrounding cells represent two crucial processes that might be involved in muscle development. However, little information is available on this topic, especially on invertebrate species. To obtain new insights on how tuning the ECM microenvironment might drive cellular fate during embryonic development, we used the invertebrate medicinal leech Hirudo verbana as a valuable experimental model, due to its simple anatomy and the recapitulation of many aspects of the basic biological processes of vertebrates. Our previous studies on leech post-embryonic development have already shown the pivotal role of ECM changes during the growth of the body wall and the role of Yes-associated protein 1 (YAP1) in mechanotransduction. Here, we suggest that the interactions between stromal cell telocytes and ECM might be crucial in driving the organization of muscle layers during embryogenesis. Furthermore, we propose a possible role of the pleiotropic enzyme HvRNASET2 as a possible modulator of collagen deposition and ECM remodeling not only during regenerative processes (as previously demonstrated) but also in embryogenesis.

Identification of allograft inflammatory factor-1 suppressing the progression and indicating good prognosis of osteosarcoma

BACKGROUND

Osteosarcoma is one of the most common cancers worldwide. Intense efforts have been made to elucidate the pathogeny, but the mechanisms of osteosarcoma are still not well understood. We aimed to investigate the potential biomarker, allograft inflammatory factor-1 (AIF1), affecting the progression and prognosis of osteosarcoma.

METHODS

Three microarray datasets were downloaded from GEO datasets and one was obtained from the TCGA dataset. The differentially expressed genes (DEGs) were identified. GO and KEGG functional enrichment analyses of overlapped DEGs were performed. The PPI network of overlapped DEGs was constructed by STRING and visualized with Cytoscape. Overall survival (OS) and Metastasis free survival (MFS) were analyzed from GSE21257. Finally, the effect of the most relevant core gene affecting the progression of osteosarcoma was examined in vitro.

RESULTS

One hundred twenty six DEGs were identified, consisting of 65 upregulated and 61 downregulated genes. Only AIF1 was significantly associated with OS and MFS. It was found that AIF1 could be enriched into the NF-κB signaling pathway. GSEA and ssGSEA analyses showed that AIF1 was associated with the immune invasion of tumors. Cell experiments showed that AIF1 was underexpressed in osteosarcoma cell lines, while the malignant propriety was attenuated after overexpressing the expression of AIF1. Moreover, AIF1 also affects the expression of the NF-κB pathway.

CONCLUSION

In conclusion, DEGs and hub genes identified in the present study help us understand the molecular mechanisms underlying the carcinogenesis and progression of osteosarcoma, and provide candidate targets for diagnosis and treatment of osteosarcoma.

The Potential Role of the T2 Ribonucleases in TME-Based Cancer Therapy

In recent years, there has been a growing interest in developing innovative anticancer therapies targeting the tumor microenvironment (TME). The TME is a complex and dynamic milieu surrounding the tumor mass, consisting of various cellular and molecular components, including those from the host organism, endowed with the ability to significantly influence cancer development and progression. Processes such as angiogenesis, immune evasion, and metastasis are crucial targets in the search for novel anticancer drugs. Thus, identifying molecules with "multi-tasking" properties that can counteract cancer cell growth at multiple levels represents a relevant but still unmet clinical need. Extensive research over the past two decades has revealed a consistent anticancer activity for several members of the T2 ribonuclease family, found in evolutionarily distant species. Initially, it was believed that T2 ribonucleases mainly acted as anticancer agents in a cell-autonomous manner. However, further investigation uncovered a complex and independent mechanism of action that operates at a non-cell-autonomous level, affecting crucial processes in TME-induced tumor growth, such as angiogenesis, evasion of immune surveillance, and immune cell polarization. Here, we review and discuss the remarkable properties of ribonucleases from the T2 family in the context of "multilevel" oncosuppression acting on the TME.

Inhibition of AIF-1 alleviates laser-induced macular neovascularization by inhibiting endothelial cell proliferation via restrained p44/42 MAPK signaling pathway

Age-related macular degeneration (AMD) is a leading blinding disease worldwide, and macular neovascularization (MNV) is a common complication encountered in the advanced stages of AMD. While the underlying causes of MNV remain elusive, aberrant multiplication of choroidal endothelial cells (CECs) and increased vascular endothelial growth factor (VEGF) are thought to play significant roles in the occurrence and development of MNV. Allograft inflammatory factor-1(AIF-1) is a crucial regulatory factor of vascular tubular structure formation and growth, involving the proliferation and migration of vascular endothelial cells and various tumor cells. This study aimed to understand how AIF-1 effects the proliferation of CECs and the subsequent progression of MNV. To study this, a mouse MNV model was established through laser injury, and the AIF-1 expression levels were then measured using western blot and immunohistochemistry. AIF-1 siRNA was intravitreally injected to silence AIF-1 gene expression. Western blot and choroidal flat mount were performed to measure the progression of MNV and proliferation of the CECs. These results showed that the protein expression of AIF-1 was significantly elevated in the laser-induced mouse MNV model, and the expression trend was consistent with VEGF. The protein level of AIF-1 was significantly decreased after the intravitreal injection of AIF-1 siRNA, the damage range of laser lesions was significantly reduced, and the proliferation of endothelial cells was inhibited. Knockdown of the AIF-1 gene significantly inhibited the expression of mitogen-activated protein kinase p44/42 in MNV lesions. In summary, this research demonstrates that AIF-1 promoted MNV progression by promoting the proliferation of CECs and that silencing AIF-1 significantly ameliorates MNV progression in mouse models, which may act through the p44/42 MAPK signaling pathway. AIF-1 could be a new potential molecular target for MNV.

Response of Sabella spallanzanii to multiple stressors. The combined effect of infection and copper sulphate

The aim of this work is to study the immune responses of the polychaete Sabella spallanzanii after exposure to copper sulphate, an immunomodulating agent in marine organisms, and the multiple stresses caused by Escherichia coli infection, to validate the species as a model organism in marine-coastal biomonitoring programmes. Polychaetes were housed in laboratory and divided into five experimental groups: 1. Control (no microinjected), 2. filtered seawater + TBS injection (control of point 3), 3. filtered seawater + E. coli injection (control of point 4), 4. CuSO₄ + TBS injection (control of point 5), and 5. CuSO₄ + E. coli injection. The immune variables, esterase and alkaline phosphatase activity, cytotoxicity and detoxifying/antioxidant enzymes such as glutathione peroxidase were evaluated in total body extracts of the animals. Moreover, toll-like receptor, allograft inflammatory factor-1, lysozyme and haemagglutinating activity were investigated to highlight possible interactions. Indeed, the results of this work demonstrate the immunomodulating effect of copper sulphate on S. spallanzanii total body extracts related to oxidative stress and inflammatory markers.

Spatio-Temporal Changes of Extracellular Matrix (ECM) Stiffness in the Development of the Leech Hirudo verbana

The invertebrate leech Hirudo verbana represents a powerful experimental animal model for improving the knowledge about the functional interaction between the extracellular matrix (ECM) and cells within the tissue microenvironment (TME), and the key role played by ECM stiffness during development and growth. Indeed, the medicinal leech is characterized by a simple anatomical organization reproducing many aspects of the basic biological processes of vertebrates and in which a rapid spatiotemporal development is well established and easily assessed. Our results show that ECM structural organization, as well as the amount of fibrillar and non-fibrillar collagen are deeply different from hatching leeches to adult ones. In addition, the changes in ECM remodelling occurring during the different leech developmental stages, leads to a gradient of stiffness regulating both the path of migratory cells and their fates. The ability of cells to perceive and respond to changes in ECM composition and mechanics strictly depend on nuclear or cytoplasmic expression of Yes-Associated Protein 1 (YAP1), a key mediator converting mechanical signals into transcriptional outputs, expression, and activation.

Diagnostic and therapeutic potential of RNASET2 in Crohn's disease: Disease-risk polymorphism modulates allelic-imbalance in expression and circulating protein levels and recombinant-RNASET2 attenuates pro-inflammatory cytokine secretion

Ribonuclease T2 gene (RNASET2) variants are associated in genome wide association studies (GWAS) with risk for several autoimmune diseases, including Crohn's disease (CD). In T cells, a functional and biological relationship exists between TNFSF15-mediated enhancement of IFN-γ production, mucosal inflammation and RNASET2. Disease risk variants are associated with decreased mRNA expression and clinical characteristics of severe CD; however, functional classifications of variants and underlying molecular mechanisms contributing to pathogenesis remain largely unknown. In this study we demonstrate that allelic imbalance of RNASET2 disease risk variant rs2149092 is associated with transcriptional and post-transcriptional mechanisms regulating transcription factor binding, promoter-transactivation and allele-specific expression. RNASET2 mRNA expression decreases in response to multiple modes of T cell activation and recovers following elimination of activator. In CD patients with severe disease necessitating surgical intervention, preoperative circulating RNASET2 protein levels were decreased compared to non-IBD subjects and rebounded post-operatively following removal of the inflamed region, with levels associated with allelic carriage. Furthermore, overexpression or treatment with recombinant RNASET2 significantly reduced IFN-γ secretion. These findings reveal that RNASET2 cis- and trans-acting variation contributed regulatory complexity and determined expression and provide a basis for linking genetic variation with CD pathobiology. These data may ultimately identify RNASET2 as an effective therapeutic target in a subset of CD patients with severe disease.

AIF-1 and RNASET2 are involved in the inflammatory response in the Mediterranean mussel Mytilus galloprovincialis following Vibrio infection

Filter-feeding bivalves, such as the Mytilus species, are exposed to different types of bacteria in the surrounding waters, in particular of the Vibrio genus. Mussels lack an adaptive immune system and hemocytes can recognize pathogen-associated molecular patterns (PAMPs) via pattern recognition receptors (PRRs) to activate intracellular signaling pathways to trigger the antimicrobial effectors synthesis. Among the areas of bivalve immunity that deserve study include the role of hemocyte subpopulations. Since little information are available on immune responses at the tissue level to human pathogenic vibrios commonly detected in coastal waters involved in seafood-borne diseases, in this work, immunological parameters of the hemocytes from the Mediterranean mussel M. galloprovincialis were evaluated in response to in vivo challenge with Vibrio splendidus. The histological approach has been first used in order to identify the hemocytes recruitment at the infection site and the morphological change of muscular fibers. In addition, using immunolabeling with specific antibody we detected the production of molecules involved in the inflammatory activated cascade: Toll-like receptors 4 (TLR4), the myeloid differentiation factor 88 (MyD88), the Allograft inflammatory factor-1 (AIF-1) and the ribonucleases RNASET2, belonging to the T2 family, that in vertebrates are involved in the recruitment and activation of macrophages. Our results indicate the activation of TLR4 during bacterial infection preparatory to the recruitment of the MyD88 adapter with a putative role in recognition and intracellular signalling. Furthermore, the data presented in this work suggest that challenging with Gram-negative bacteria causes a massive migration of AIF-1⁺ hemocytes and that the ribonuclease RNASET2 could play a key role in the recruitment of these activated hemocytes. Our approach is useful for further understanding the complex molecular defence mechanisms of the host in invertebrates, especially in relation to the need to develop methods to evaluate the immunological response of bivalve molluscs used in aquaculture.

Hirudo verbana as a freshwater invertebrate model to assess the effects of polypropylene micro and nanoplastics dispersion in freshwater

Plastics are a heterogeneous class of synthetic compounds that, due to their unique characteristics find numerous applications both in industrial and civil fields. However, despite the great advantages that these materials brought in everyday life, the plastic wastes resulting from their massive use represent one of the main environmental problems at the global level. Once released, plastics persist for a long time and are subjected both to biotic and abiotic processes leading to the formation of small particles, known as micro and to nanoplastics, that interact with organisms, accumulating inside tissues and risking to enter in the trophic chain. Among the different types of plastic, polypropylene (PP) is one of the diffused, widely exploited in food and textile industries for disposable packaging and to produce surgical masks. Owing to the huge distribution and the resultant abundant presence of PP waste products, it results necessary investigate the possible toxicity on living organisms. For these reasons, here we analyzed the effects of PP micro and nanoplastics dispersed in freshwater, using the medicinal leech Hirudo verbana as invertebrate model. To better follow the plastics fate, fluorescent particles, labeled with a fluorophore, have been used. Animals were examined at various timings after plastics exposure and results were analyzed by means of microscopy, immunofluorescent and molecular biology analyses. After assessing the entrance of PP fragments into leech tissues, the activation of the innate immune response was evaluated. The results show that the presence of micro and nanoplastics induces an initial physical protection that consists in the secretion of mucus, followed by an increase of blood vessels and the recruitment of immune cells, in particular macrophages. Moreover, macrophages were directly involved in both phagocytic and encapsulation processes, as demonstrated by acid phosphatase (ACP) histoenzymatic and Thioflavin-T assays, expressing specific pro-inflammatory factors, such as HvRNASET2 and HmAIF-1, as demonstrated by immunolocalization and qPCR experiments. Finally, the expression levels of genes related to oxidative stress-induced enzymes have been investigated, in order to evaluate the possible increase in reactive oxygen species (ROS), due to the entry into the leech tissues of PP micro and nanoplastics. This work allows deepening the current knowledge of the possible harmful effects on human health deriving from micro and nanoplastics dispersion, leading new insight about freshwater ecosystems that often represent the first environments interested in plastic pollution.

Searching for antimicrobial photosensitizers among a panel of BODIPYs

In recent years, antimicrobial Photodynamic Therapy (aPDT) gained increasing attention for its potential to inhibit the growth and spread of microorganisms, both as free-living cells and/or embedded in biofilm communities. In this scenario, compounds belonging to the family of boron-dipyrromethenes (BODIPYs) represent a very promising class of photosensitizers for applications in antimicrobial field. In this study, twelve non-ionic and three cationic BODIPYs were assayed for the inactivation of Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans. As expected, S. aureus showed to be very sensitive to BODIPYs and mild conditions were sufficient to reach good rates of photoinactivation with both neutral and monocationic ones. Surprisingly, one neutral compound (named B9 in this study) resulted the best BODIPY to photoinactivate P. aeruginosa PAO1. The photoinactivation of C. albicans was reached with both neutral and mono-cationic BODIPYs. Furthermore, biofilms of the three model microorganisms were challenged with BODIPYs in light-based antimicrobial technique. S. aureus biofilms were successfully inhibited with milder conditions than those applied to P. aeruginosa and C. albicans. Notably, it was possible to eradicate 24-h-old biofilms of both S. aureus and P. aeruginosa. In conclusion, this study supports the potential of neutral BODIPYs as pan-antimicrobial PSs.

Comparison of body wall histologic structure of two medicinal leeches Hirudo sulukii and Hirudo verbana (Hirudinida: Hirudinidae)

In this study, it was aimed to determine secretory cell types using histochemical properties of secretory cells and epidermis histology in the body wall of two medicinal leech species, Hirudo verbana and Hirudo sulukii. In addition, areas of epidermis epithelial cells, secretory cell types, and secretion areas of secretory cells stained with histochemical stains were statistically compared in both species. Epidermis is composed of single layer of cylindrical epithelium and secretory cells. The cuticle layer covers the epithelial layer. Some Type 1 cells within and close to the epidermis were determined as pear-shaped secretory cells. Type 2a and Type 2b secretory cells were found in large groups in the inner parts of the body wall, especially around muscles. While Type 1 cells were stained weakly with PAS and AB, Type 2b cells were stained darker than Type 2a cells. Statistical calculations showed that areas of epithelial and secretory cells were generally larger in H. sulukii than in H. verbana. Therefore, H. sulukii was thought to be a more resistant species compared to H. verbana. As secretion areas of secretory cells reacting with PAS and AB stains were generally larger in H. sulukii, it was concluded that mucus composition between the two species has different concentration.

An HECT domain ubiquitin ligase CgWWP1 regulates granulocytes proliferation in oyster Crassostrea gigas

Ubiquitination is involved in the regulation of granulocyte proliferation in vertebrate, and E3 ubiquitin ligase WWP1 has been reported to play an essential role in this process. In the present study, an HECT type E3 ubiquitin ligase (CgWWP1) was identified from oyster Crassostrea gigas, which contained a N-terminal C2 domain, four WW domains, and a C-terminal HECT domain. CgWWP1 was able to bind the activated ubiquitin (Ub) and formed CgWWP1-Ub complex in vitro. The mRNA transcripts of CgWWP1 were expressed in granulocytes, semi-granulocytes and agranulocytes, with the highest expression level in granulocytes. The expressions of potential granulocyte markers CgSOX11 (0.18-fold, p < 0.05) and CgAATase (0.2-fold, p < 0.01) in haemocytes were significantly down-regulated at 24 h after the treatment with Indole-3-carbinol (I3C), a WWP1 inhibitor. The proportions of EdU⁺ granulocytes reduced significantly at 12 h (8.1% ± 1.4%) and 24 h (9.7% ± 2.8%) after I3C treatment, which were significantly lower than that in the sterile seawater treatment (SW) group at 12 h (15.8% ± 4.2%) and 24 h (17.6% ± 0.8%), respectively. Meanwhile, the green EdU signals observed by confocal scanning microscopy in granulocytes of oysters treated by I3C became weaker compared to that in the SW group. These results indicated that CgWWP1 was involved in the regulation of granulocyte proliferation as a ubiquitin-protein ligase.

HvRNASET2 Regulate Connective Tissue and Collagen I Remodeling During Wound Healing Process

Several studies have recently demonstrated that the correct regeneration of damaged tissues and the maintaining of homeostasis after wounds or injuries are tightly connected to different biological events, involving immune response, fibroplasia, and angiogenetic processes, in both vertebrates and invertebrates. In this context, our previous data demonstrated that the Hirudo verbana recombinant protein rHvRNASET2 not only plays a pivotal role in innate immune modulation, but is also able to activate resident fibroblasts leading to new collagen production, both in vivo and in vitro. Indeed, when injected in the leech body wall, which represents a consolidated invertebrate model for studying both immune response and tissue regeneration, HvRNASET2 induces macrophages recruitment, fibroplasia, and synthesis of new collagen. Based on this evidence, we evaluate the role of HvRNASET2 on muscle tissue regeneration and extracellular matrix (ECM) remodeling in rHvRNASET2-injected wounded leeches, compared to PBS-injected wounded leeches used as control. The results presented here not only confirms our previous evidence, reporting that HvRNASET2 leads to an increased collagen production, but also shows that an overexpression of this protein might influence the correct progress of muscle tissue regeneration. Moreover, due to its inhibitory effect on vasculogenesis and angiogenesis, HvRNASET2 apparently interfere with the recruitment of the myoendothelial vessel-associated precursor cells that in turn are responsible for muscle regeneration during wound healing repair.

Cigarette smoke extract promotes DNA methyltransferase 3a expression in dendritic cells, inducing Th-17/Treg imbalance via the c-Jun/allograft inflammatory factor 1 axis

Chronic obstructive pulmonary disease (COPD) is a chronic respiratory disorder. Although numerous studies on COPD have been conducted, therapeutic strategies for COPD are limited, and its pathological mechanism is still unclear. The present study aimed to explore the role of DNA methyltransferase 3a (DNMT3a) in dendritic cells (DCs) and the possible role of the Th-17/Treg cell balance in COPD. Immature DCs (iDCs) were induced and cocultured with CD4⁺ T cells. An in vitro COPD model was established by treatment with cigarette smoke extract (CSE). DNMT3a or allograft inflammatory factor 1 (AIF1) and c-Jun N-terminal kinase (JNK) were inhibited and overexpressed, respectively, by transfection with sh-DNMT3a or sh-AIF1 and JNK overexpression plasmids. The 3- (4,5-cimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay was used to measure cell viability. The Th17/Treg cell ratio was determined by flow cytometry. The expression levels of DNMT3a, c-Jun and AIF1 were measured using RT-qPCR or western blotting. Chromatin immunoprecipitation (CHIP) was used to confirm the interaction between c-Jun and the AIF1 promoter region. CSE stimulation promoted the expression of DNMT3a, and AIF1, and the ratio of p-c-Jun/c-Jun in iDCs. Besides, the iDC-mediated differentiation of Th17 cells was in a dose-dependent manner. However, knockdown of DNMT3a or AIF1 reversed the above effects caused by CSE. Inhibition of c-Jun signaling by treatment with the JNK inhibitor SP600125 also suppressed the iDC-mediated differentiation of Th17 cells, which was promoted by CSE. CHIP analysis showed that c-Jun could bind to the promoter region of AIF1. DNMT3a could regulate the iDC-mediated Th17/Treg balance by regulating the c-Jun/AIF1 axis.

3D Reconstruction of HvRNASET2 Molecule to Understand Its Antibacterial Role

Recent studies performed on the invertebrate model Hirudo verbana (medicinal leech) suggest that the T2 ribonucleic enzyme HvRNASET2 modulates the leech's innate immune response, promoting microbial agglutination and supporting phagocytic cells recruitment in challenged tissues. Indeed, following injection of both lipoteichoic acid (LTA) and Staphylococcus aureus in the leech body wall, HvRNASET2 is expressed by leech type I granulocytes and induces bacterial aggregation to aid macrophage phagocytosis. Here, we investigate the HvRNASET2 antimicrobial role, in particular assessing the effects on the Gram-negative bacteria Escherichia coli. For this purpose, starting from the three-dimensional molecule reconstruction and in silico analyses, the antibacterial activity was evaluated both in vitro and in vivo. The changes induced in treated bacteria, such as agglutination and alteration in wall integrity, were observed by means of light, transmission and scanning electron microscopy. Moreover, immunogold, AMPs (antimicrobial peptides) and lipopolysaccharide (LPS) binding assays were carried out to evaluate HvRNASET2 interaction with the microbial envelopes and the ensuing ability to affect microbial viability. Finally, in vivo experiments confirmed that HvRNASET2 promotes a more rapid phagocytosis of bacterial aggregates by macrophages, representing a novel molecule for counteracting pathogen infections and developing alternative solutions to improve human health.

The impact of blood-processing time on the proteome of human peripheral blood mononuclear cells

Human peripheral blood mononuclear cells (PBMC) are key to several diagnostics assays and basic science research. Blood pre-analytical variations that occur before obtaining the PBMC fraction can significantly impact the assays results, including viability, composition, integrity, and gene expression changes of immune cells. With this as motivation, we performed a quantitative shotgun proteomics analysis using Isobaric Tag for Relative and Absolute Quantitation (iTRAQ 8plex) labeling to compare PBMC obtained from 24 h-stored blood at room temperature versus freshly isolated. We identified a total of 3195 proteins, of which 245 were differentially abundant (101 upregulated and 144 downregulated). Our results revealed enriched pathways of downregulated proteins related to exocytosis, localization, vesicle-mediated transport, cell activation, and secretion. In contrast, pathways related to exocytosis, neutrophil degranulation and activation, granulocyte activation, leukocyte degranulation, and myeloid leukocyte activation involved in immune response were enriched in upregulated proteins, which may indicate probable granulocyte contamination and activation due to blood storage time and temperature. Examples of upregulated proteins in the 24 h-PBMC samples are CAMP, S100A8, LTA4H, RASAL3, and S100A6, which are involved in an adaptive immune system and antimicrobial activity, proinflammatory mediation, aminopeptidase activities, and naïve T cells survival. Moreover, examples of downregulated proteins are NDUFA5, TAGLN2, H3C1, TUBA8, and CCT2 that are related to the cytoskeleton, cell junction, mitochondrial respiratory chain. In conclusion, the delay in blood-processing time directly impacts the proteomic profile of human PBMC, possibly through granulocyte contamination and activation.

Allograft Inflammatory Factor-1 in Metazoans: Focus on Invertebrates

Simple Summary

During their life, all living organisms defend themselves from pathogens using complex strategies. Vertebrates and invertebrates share mechanisms and molecules that guarantee their overall bodily integrity. Allograft inflammatory factor-1 (AIF-1) is a protein extensively studied in vertebrates, and especially in mammals. This factor, generally involved in inflammation events occurring upon pathogenic infection or tissue injury, is linked to several important human diseases. This review collects data on the presence and role of AIF-1 in invertebrates, which are still poorly investigated organisms. Multiple alignment and phylogenetic analysis reveal that AIF-1 is conserved in vertebrates and invertebrates, suggesting similarity of functions. In some invertebrate species, the expression of AIF-1 increases considerably after a bacterial challenge, indicating that it plays a key role during the immune responses. This review highlights the importance of studying this protein in invertebrates as a way to improve our knowledge of innate immunity mechanisms and to better understand inflammatory regulation events in mammals.

Abstract

Allograft inflammatory factor-1 (AIF-1) is a calcium-binding scaffold/adaptor protein often associated with inflammatory diseases. Originally cloned from active macrophages in humans and rats, this gene has also been identified in other vertebrates and in several invertebrate species. Among metazoans, AIF-1 protein sequences remain relatively highly conserved. Generally, the highest expression levels of AIF-1 are observed in immunocytes, suggesting that it plays a key role in immunity. In mammals, the expression of AIF-1 has been reported in different cell types such as activated macrophages, microglial cells, and dendritic cells. Its main immunomodulatory role during the inflammatory response has been highlighted. Among invertebrates, AIF-1 is involved in innate immunity, being in many cases upregulated in response to biotic and physical challenges. AIF-1 transcripts result ubiquitously expressed in all examined tissues from invertebrates, suggesting its participation in a variety of biological processes, but its role remains largely unknown. This review aims to present current knowledge on the role and modulation of AIF-1 and to highlight its function along the evolutionary scale.

RNase T2 in Inflammation and Cancer: Immunological and Biological Views

The RNase T2 family consists of evolutionarily conserved endonucleases that express in many different species, including animals, plants, protozoans, bacteria, and viruses. The main biological roles of these ribonucleases are cleaving or degrading RNA substrates. They preferentially cleave single-stranded RNA molecules between purine and uridine residues to generate two nucleotide fragments with 2'3'-cyclic phosphate adenosine/guanosine terminus and uridine residue, respectively. Accumulating studies have revealed that RNase T2 is critical for the pathophysiology of inflammation and cancer. In this review, we introduce the distribution, structure, and functions of RNase T2, its differential roles in inflammation and cancer, and the perspective for its research and related applications in medicine.

Antimicrobial Role of RNASET2 Protein During Innate Immune Response in the Medicinal Leech Hirudo verbana

The innate immune response represents a first-line defense against pathogen infection that has been widely conserved throughout evolution. Using the invertebrate Hirudo verbana (Annelida, Hirudinea) as an experimental model, we show here that the RNASET2 ribonuclease is directly involved in the immune response against Gram-positive bacteria. Injection of lipoteichoic acid (LTA), a key component of Gram-positive bacteria cell wall, into the leech body wall induced a massive migration of granulocytes and macrophages expressing TLR2 (the key receptor involved in the response to Gram-positive bacteria) toward the challenged/inoculated area. We hypothesized that the endogenous leech RNASET2 protein (HvRNASET2) might be involved in the antimicrobial response, as already described for other vertebrate ribonucleases, such as RNase3 and RNase7. In support of our hypothesis, HvRNASET2 was mainly localized in the granules of granulocytes, and its release in the extracellular matrix triggered the recruitment of macrophages toward the area stimulated with LTA. The activity of HvRNASET2 was also evaluated on Staphylococcus aureus living cells by means of light, transmission, and scanning electron microscopy analysis. HvRNASET2 injection triggered the formation of S. aureus clumps following a direct interaction with the bacterial cell wall, as demonstrated by immunogold assay. Taken together, our data support the notion that, during the early phase of leech immune response, granulocyte-released HvRNASET2 triggers bacterial clumps formation and, at the same time, actively recruits phagocytic macrophages in order to elicit a rapid and effective eradication of the infecting microorganisms from inoculated area.

Recombinant HvRNASET2 protein induces marked connective tissue remodelling in the invertebrate model Hirudo verbana

The RNASET2 ribonuclease, belonging to the highly conserved RH/T2/s RNase gene family, has been recently shown to modulate inflammatory processes in both vertebrates and invertebrates. Indeed, the RNASET2 protein acts as a chemoattractor for macrophages in both in vitro and in vivo experimental settings and its expression significantly increases following bacterial infections. Moreover, we recently observed that injection of human recombinant RNASET2 protein in the body wall of the medicinal leech (a consolidated invertebrate model for both immune response and tissue regeneration) not only induced immune cell recruitment but also apparently triggered massive connective tissue remodelling as well. Based on these data, we evaluate here a possible role of leech recombinant RNASET2 protein (rHvRNASET2) in connective tissue remodelling by characterizing the cell types involved in this process through histochemical, morphological and immunofluorescent assays. Moreover, a time-course expression analysis of newly synthesized pro-collagen1α1 (COL1α1) and basic FGF receptor (bFGFR, a known fibroblast marker) following rHvRNASET2 injection in the leech body wall further supported the occurrence of rHvRNASET2-mediated matrix remodelling. Human MRC-5 fibroblast cells were also investigated in order to evaluate their pattern of collagen neosynthesis driven by rHvRNASET2 injection.Taken together, the data reported in this work provide compelling evidence in support of a pleiotropic role for RNASET2 in orchestrating an evolutionarily conserved crosstalk between inflammatory response and regenerative process, based on macrophage recruitment and fibroblast activation, coupled to a massive extracellular reorganization.

Role of allograft inflammatory factor-1 in pathogenesis of diseases

Allograft inflammatory factor-1 (AIF-1) is a 17 kDa calcium-binding protein produced by monocytes, macrophages, and lymphocytes; its synthesis is induced by INF-γ. The AIF-1 gene is located in the major histocompatibility complex (MHC) class III region on chromosome 6p21.3, surrounded by surface glycoprotein genes and complement cascade protein genes as well as TNF-α, TNF-β, and NF-κB genes. Increased expression of AIF-1 was observed in several diseases, including endometriosis, breast cancer, atherosclerosis, rheumatoid arthritis, and fibrosis. In this review, we summarise the role of AIF-1 in allograft rejection and the pathogenesis of diseases.

Innate Immune Response Regulation by the Human RNASET2 Tumor Suppressor Gene

The link between cancer development or progression and immune system dysregulation has long been established. Virtually every cell type belonging to both the innate and adaptive immune system has been reported to be involved in a complex interplay that might culminate into either a pro- or anti-tumorigenic response. Among the cellular components of the innate immune system, cells belonging to the monocyte/macrophage lineage have been consistently shown to play a key role in the tumorigenic process. The most advanced human tumors are reported to be strongly infiltrated with Tumor-Associated Macrophages (TAMs) endowed with the ability to contribute to tumor growth and dissemination. However, given their widely acknowledged functional plasticity, macrophages can display anti-tumor properties as well. Based on these premises, experimental approaches to promote the in vivo macrophage shift from pro-tumor to anti-tumor phenotype represent one of the most promising research field aimed at developing immune system-mediated tumor suppressive therapies. In this context, the human RNASET2 oncosuppressor gene has emerged as a potential tool for macrophage-mediated tumor suppression. A growing body of experimental evidence has been reported to suggest a role for this gene in the regulation of macrophage activity in both in vitro and in vivo experimental models. Moreover, several recent reports suggest a role for this gene in a broad range of cell types involved in immune response, pointing at RNASET2 as a putative regulator of several functional features within the immune system.

The medicinal leech as a valuable model for better understanding the role of a TLR4-like receptor in the inflammatory process

Despite extensive investigation focused on both the molecular characteristics and the expression level of Toll-like receptors (TLRs) during the inflammatory response in vertebrates, few data are available in the literature on the role of these proteins in invertebrate's immune response. Here, we propose the medicinal leech as a valuable model to better elucidate the role of TLR4 and its related products, such as tumor necrosis factor (TNF-α), after activation of the leech peripheral immune system with the endogenous medicinal leech recombinant allograft inflammatory factor-1 (rHmAIF-1) or with an exogenous stimulus, such as lipopolysaccharide (LPS). Our results indicate that activated macrophages (HmAIF-1⁺) and granulocytes (CD11b⁺) express both TLR4 and its coreceptor CD14. Moreover, functional studies performed by injecting a cyanobacterium selective TLR4 antagonist CyP demonstrated that only the TLR4 pathway was blocked, while the immune response caused by lipoteichoic acid (LTA) treatment is not affected. These results are consistent with literature on vertebrates, indicating that TLR4 functions as a LPS receptor while the recognition of LTA may involve other pathways.