Stefania Raimondo

Exosomes as Intercellular Signaling Organelles Involved in Health and Disease: Basic Science and Clinical Applications

Cell to cell communication is essential for the coordination and proper organization of different cell types in multicellular systems. Cells exchange information through a multitude of mechanisms such as secreted growth factors and chemokines, small molecules (peptides, ions, bioactive lipids and nucleotides), cell-cell contact and the secretion of extracellular matrix components. Over the last few years, however, a considerable amount of experimental evidence has demonstrated the occurrence of a sophisticated method of cell communication based on the release of specialized membranous nano-sized vesicles termed exosomes. Exosome biogenesis involves the endosomal compartment, the multivesicular bodies (MVB), which contain internal vesicles packed with an extraordinary set of molecules including enzymes, cytokines, nucleic acids and different bioactive compounds. In response to stimuli, MVB fuse with the plasma membrane and vesicles are released in the extracellular space where they can interact with neighboring cells and directly induce a signaling pathway or affect the cellular phenotype through the transfer of new receptors or even genetic material. This review will focus on exosomes as intercellular signaling organelles involved in a number of physiological as well as pathological processes and their potential use in clinical diagnostics and therapeutics.

Evidence that autophagy, but not the unfolded protein response, regulates the expression of IL-23 in the gut of patients with ankylosing spondylitis and subclinical gut inflammation

Objectives Interleukin (IL)-23 has been implicated in the pathogenesis of ankylosing spondylitis (AS). The aim of the study was to clarify the mechanisms underlying the increased IL-23 expression in the gut of AS patients. Methods Consecutive gut biopsies from 30 HLA-B27+ AS patients, 15 Crohns disease (CD) patients and 10 normal subjects were obtained. Evidence for HLA-B27 misfolding was studied. Unfolded protein response (UPR) and autophagy were assessed by RT-PCR and immunohistochemistry. The contribution of UPR and autophagy in the regulation of IL-23 expression was evaluated in in vitro experiments on isolated lamina propria mononuclear cells (LPMCs). Results Intracellular colocalisation of SYVN1 and FHCs but not a significant overexpression of UPR genes was observed in the gut of AS patients. Conversely, upregulation of the genes involved in the autophagy pathway was observed in the gut of AS and CD patients. Immunohistochemistry showed an increased expression of LC3II, ATG5 and ATG12 but not of SQSTM1 in the ileum of AS and CD patients. LC3II was expressed among infiltrating mononuclear cells and epithelial cells resembling Paneth cells (PC) and colocalised with ATG5 in AS and CD. Autophagy but not UPR was required to modulate the expression of IL-23 in isolated LPMCs of AS patients with chronic gut inflammation, CD patients and controls. Conclusions Our data suggest that HLA-B27 misfolding occurs in the gut of AS patients and is accompanied by activation of autophagy rather than a UPR. Autophagy appears to be associated with intestinal modulation of IL-23 in AS.

Potential involvement of IL-22 and IL-22-producing cells in the inflamed salivary glands of patients with Sjögren's syndrome

Objectives In chronic inflammatory disorders, interleukin (IL)-22 may act either as a protective or as a pro-inflammatory cytokine. At mucosal sites, IL-22 is mainly produced by CD4+ T cells and by a subset of mucosal natural killer (NK) cells expressing the receptor NKp44 (NKp44+ NK cells). The aim of this study was to investigate the IL-22 expression in the salivary glands of patients with primary Sjögrens syndrome (pSS). Methods Minor salivary gland biopsies were obtained from 19 patients with pSS and 16 with non-specific chronic sialoadenitis. Quantitative gene expression analysis by TaqMan real-time PCR and immunohistochemistry for IL-17, IL-22, IL-23 and STAT3 (signal transducer and activator of transcription) was performed on salivary glands from patients and controls. The cellular sources of IL-22 among infiltrating inflammatory cells were also determined by fluorescence-activated cell sorting analysis and immunohistochemistry. Results IL-22, IL-23 and IL-17 were significantly increased at both protein and mRNA levels in the inflamed salivary glands of patients with pSS. STAT3 mRNA and the tyrosine phosphorylated corresponding protein were also significantly increased in pSS. Th17 and NKp44+ NK cells were the major cellular sources of IL-22 in patients with pSS. Conclusions Our results suggest that, together with IL-17 and IL-23, IL-22 may play a pro-inflammatory role in the pathogenesis of pSS.

Exosome-mediated crosstalk between chronic myelogenous leukemia cells and human bone marrow stromal cells triggers an interleukin 8-dependent survival of leukemia cells.

Chronic myelogenous leukemia (CML) is a myeloproliferative disorder characterized by the Bcr-Abl oncoprotein with constitutive tyrosine kinase activity. Exosomes are nanovesicles released by cancer cells that are involved in cell-to-cell communication thus potentially affecting cancer progression. It is well known that bone marrow stromal microenvironment contributes to disease progression through the establishment of a bi-directional crosstalk with cancer cells. Our hypothesis is that exosomes could have a functional role in this crosstalk. Interleukin-8 (IL 8) is a proinflammatory chemokine that activates multiple signalling pathways downstream of two receptors (CXCR1 and CXCR2). We demonstrated that exosomes released from CML cells stimulate bone marrow stromal cells to produce IL 8 that, in turn, is able to modulate both in vitro and in vivo the leukemia cell malignant phenotype.

IL-34 is overexpressed in the inflamed salivary glands of patients with Sjögren’s syndrome and is associated with the local expansion of pro-inflammatory CD14brightCD16+ monocytes

OBJECTIVES To investigate the expression of IL-34 in labial salivary glands (LSGs) of patients with primary SS (p-SS) and its role in inducing a pro-inflammatory monocyte phenotype. METHODS LSG biopsies were obtained from 20 patients with p-SS and 10 patients with non-Sjögrens sicca syndrome (n-SS). The expression of IL-34, IL-1β, TNF-α, IL-17 and IL-23 was assessed by real-time PCR. IL-34 expression was also investigated in LSGs by immunohistochemistry. The frequencies of subpopulations of CD14(+) monocytes were evaluated by flow cytometry among isolated mononuclear cells from peripheral blood and salivary glands from both patients and controls. The role of recombinant IL-34 on isolated peripheral blood mononuclear cells was also evaluated. RESULTS IL-34 m-RNA was overexpressed in the inflamed salivary glands of p-SS and associated with increased expression of TNF-α, IL-1β, IL-17 and IL-23p19. The increased expression of IL-34 was confirmed by immunohistochemistry in paraffin-embedded salivary glands from p-SS patients. IL-34 expression was accompanied by the expansion of pro-inflammatory CD14(bright)CD16(+) monocytes in the salivary glands. In vitro stimulation of peripheral blood mononuclear cells with IL-34 induced the expansion of both CD14(+)CD16(-) cells and CD14(bright)CD16(+) cells in p-SS and non-SS subjects. CONCLUSION IL-34 seems to be involved in the pathogenesis of salivary gland inflammation in p-SS.

IL-33 is overexpressed in the inflamed arteries of patients with giant cell arteritis

Objective To study the expression of interleukin (IL)-33 and to evaluate its relationship with macrophage polarisation in artery biopsy specimens from patients with giant cell arteritis (GCA). Methods IL-33, ST2, p-STAT-6 and perivascular IL-1 receptor-associated kinase 1 (p-IRAK1) tissue distribution was evaluated by immunohistochemistry. Inducible nitric oxide synthase and CD163 were also used by immunohistochemistry to evaluate the M1 and M2 polarisation, respectively. Quantitative gene expression analysis of IL-33, T-helper (Th)2-related transcription factor STAT6, Th2 cytokines (IL-4, IL-5, IL-25) and interferon (IFN)-γ was performed in artery biopsy samples obtained from 20 patients with GCA and 15 controls. Five additional patients who had received prednisone when the temporal artery biopsy was performed were also enrolled. Results IFN-γ and IL-33 were significantly overexpressed in the inflamed arteries of GCA patients. IL-33 overexpression was not accompanied by a concomitant increase of Th2 cytokines. Neovessels scattered through the inflammatory infiltrates were the main sites of IL-33 expression. The expression of IL-33 receptor ST2 and of p-IRAK1 was also increased in GCA patients. Arteries from glucocorticoid-treated patients had a lower expression of IL-33. IL-33 was accompanied by the expression of p-STAT6 and a clear M2 macrophages polarisation. Conclusions A role for IL-33 in the inflammation of GCA patients is supported by these findings.

carboxyamidotriazole-orotate inhibits the growth of imatinib resistant chronic myeloid leukaemia cells and modulates exosomes-stimulated angiogenesis

The Bcr/Abl kinase has been targeted for the treatment of chronic myelogenous leukaemia (CML) by imatinib mesylate. While imatinib has been extremely effective for chronic phase CML, blast crisis CML are often resistant. New therapeutic options are therefore needed for this fatal disease. Although more common in solid tumors, increased microvessel density was also reported in chronic myelogenous leukaemia and was associated with a significant increase of angiogenic factors, suggesting that vascularity in hematologic malignancies is a controlled process and may play a role in the leukaemogenic process thus representing an alternative therapeutic target. Carboxyamidotriazole-orotate (CTO) is the orotate salt form of carboxyamidotriazole (CAI), an orally bioavailable signal transduction inhibitor that in vitro has been shown to possess antileukaemic activities. CTO, which has a reduced toxicity, increased oral bioavailability and stronger efficacy when compared to the parental compound, was tested in this study for its ability to affect imatinib-resistant CML tumor growth in a xenograft model. The active cross talk between endothelial cells and leukemic cells in the bone marrow involving exosomes plays an important role in modulating the process of neovascularization in CML. We have thus investigated the effects of CTO on exosome-stimulated angiogenesis. Our results indicate that CTO may be effective in targeting both cancer cell growth and the tumor microenvironment, thus suggesting a potential therapeutic utility for CTO in leukaemia patients.

Interleukin‐9 Overexpression and Th9 Polarization Characterize the Inflamed Gut, the Synovial Tissue, and the Peripheral Blood of Patients With Psoriatic Arthritis

To investigate the expression and tissue distribution of Th9‐related cytokines in patients with psoriatic arthritis (PsA).

Interleukin-36α axis is modulated in patients with primary Sjögren's syndrome.

The aim of this study was to investigate the expression of the interleukin (IL)‐36 axis in patients with primary Sjögrens syndrome (pSS). Blood and minor labial salivary glands (MSG) biopsies were obtained from 35 pSS and 20 non‐Sjögrens syndrome patients (nSS) patients. Serum IL‐36α was assayed by enzyme‐linked immunosorbent assay (ELISA). IL‐36α, IL‐36R, IL‐36RA, IL‐38, IL‐22, IL‐17, IL‐23p19 and expression in MSGs was assessed by reverse transcription–polymerase chain reaction (RT–PCR), and tissue IL‐36α and IL‐38 expression was also investigated by immunohistochemistry (IHC). αβ and γδ T cells and CD68+ cells isolated from MSGs were also studied by flow cytometry and confocal microscopy analysis. IL‐36α was over‐expressed significantly in the serum and in the salivary glands of pSS. Salivary gland IL‐36α expression was correlated with the expression levels of IL‐17, IL‐22 and IL‐23p19. IL‐38, that acts as inhibitor of IL‐36α, was also up‐regulated in pSS. αβ+ CD3+ T cells and CD68+ cells were the major source of IL‐36α in minor salivary glands of pSS. γδ T cells were not significantly expanded in the salivary glands of pSS but produced more IL‐17, as their percentage correlated with the focus score. Higher expression of IL‐36α and IL‐36R was also demonstrated in γδ T cells isolated from pSS compared to controls. In this study we demonstrate that a significant increase in circulating and tissue levels of IL‐36α occurs in pSS patients.

Two distinct extracellular RNA signatures released by a single cell type identified by microarray and next-generation sequencing.

ABSTRACT Cells secrete extracellular RNA (exRNA) to their surrounding environment and exRNA has been found in many body fluids such as blood, breast milk and cerebrospinal fluid. However, there are conflicting results regarding the nature of exRNA. Here, we have separated 2 distinct exRNA profiles released by mast cells, here termed high-density (HD) and low-density (LD) exRNA. The exRNA in both fractions was characterized by microarray and next-generation sequencing. Both exRNA fractions contained mRNA and miRNA, and the mRNAs in the LD exRNA correlated closely with the cellular mRNA, whereas the HD mRNA did not. Furthermore, the HD exRNA was enriched in lincRNA, antisense RNA, vault RNA, snoRNA, and snRNA with little or no evidence of full-length 18S and 28S rRNA. The LD exRNA was enriched in mitochondrial rRNA, mitochondrial tRNA, tRNA, piRNA, Y RNA, and full-length 18S and 28S rRNA. The proteomes of the HD and LD exRNA-containing fractions were determined with LC-MS/MS and analyzed with Gene Ontology term finder, which showed that both proteomes were associated with the term extracellular vesicles and electron microscopy suggests that at least a part of the exRNA is associated with exosome-like extracellular vesicles. Additionally, the proteins in the HD fractions tended to be associated with the nucleus and ribosomes, whereas the LD fraction proteome tended to be associated with the mitochondrion. We show that the 2 exRNA signatures released by a single cell type can be separated by floatation on a density gradient. These results show that cells can release multiple types of exRNA with substantial differences in RNA species content. This is important for any future studies determining the nature and function of exRNA released from different cells under different conditions.