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

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.

MicroRNA-155 is essential for T(H)2-mediated allergen-induced eosinophilic inflammation in the lung.

BACKGROUND: Allergic asthma is a chronic disease of the conducting airways characterized by T(H)2 inflammation and tissue remodeling after exposure to inhaled allergens. Although the T(H)2 profile is undisputed, the underlying molecular mechanisms leading to this abnormal T(H)2 profile remain largely unclear. MicroRNAs (miRNAs) are short noncoding RNAs that are important regulators of gene expression in the immune system. However, the role of miRNAs, specifically miR-155, in the regulation of allergic airway inflammation is unexplored. OBJECTIVES: We sought to assess the contribution of miR-155 in a mouse model of allergic airway inflammation. METHODS: To investigate a role for miR-155 in the regulation of allergic inflammation in vivo, we used miR-155 knockout (KO) and wild-type (WT) mice sensitized and exposed to ovalbumin. RESULTS: miR-155 deficiency resulted in diminished eosinophilic inflammation and mucus hypersecretion in the lungs of allergen-sensitized and allergen-challenged mice compared with WT control animals. This was supported by a reduction in T(H)2 cell numbers and airway T(H)2 cytokine levels and complete abrogation of allergen-induced airway eotaxin-2/CCL24 and periostin levels in miR-155 KO mice. Intranasal instillation of eotaxin-2/CCL24 before allergen challenge partially restored airway eosinophilia in miR-155 KO mice, and adoptive transfer of CD4(+) T cells resulted in a similar degree of airway eosinophilia in miR-155 KO and WT mice. Furthermore, the transcription factor PU.1, a negative regulator of T(H)2 cytokine production, was upregulated in the airways of allergen-challenged miR-155 KO mice compared with WT mice. CONCLUSIONS: Our data provides evidence that miR-155 contributes to the regulation of allergic airway inflammation by modulating T(H)2 responses through the transcription factor PU.1.

MicroRNA in exosomes isolated directly from the liver circulation in patients with metastatic uveal melanoma.

BACKGROUND: Uveal melanoma is a tumour arising from melanocytes of the eye, and 30 per cent of these patients develop liver metastases. Exosomes are small RNA containing nano-vesicles released by most cells, including malignant melanoma cells. This clinical translational study included patients undergoing isolated hepatic perfusion (IHP) for metastatic uveal melanoma, from whom exosomes were isolated directly from liver perfusates. The objective was to determine whether exosomes are present in the liver circulation, and to ascertain whether these may originate from melanoma cells. METHODS: Exosomes were isolated from the liver perfusate of twelve patients with liver metastases from uveal melanoma undergoing IHP. Exosomes were visualised by electron microscopy, and characterised by flow cytometry, Western blot and real-time PCR. Furthermore, the concentration of peripheral blood exosomes were measured and compared to healthy controls. RESULTS: The liver perfusate contained Melan-A positive and RNA containing exosomes, with similar miRNA profiles among patients, but dissimilar miRNA compared to exosomes isolated from tumor cell cultures. Patients with metastatic uveal melanoma had a higher concentration of exosomes in their peripheral venous blood compared to healthy controls. CONCLUSIONS: Melanoma exosomes are released into the liver circulation in metastatic uveal melanoma, and is associated with higher concentrations of exosomes in the systemic circulation. The exosomes isolated directly from liver circulation contain miRNA clusters that are different from exosomes from other cellular sources.

Exosome-mediated transfer of mRNAs and microRNAs is a novel mechanism of genetic exchange between cells.

Exosomes are vesicles of endocytic origin released by many cells. These vesicles can mediate communication between cells, facilitating processes such as antigen presentation. Here, we show that exosomes from a mouse and a human mast cell line (MC/9 and HMC-1, respectively), as well as primary bone marrow-derived mouse mast cells, contain RNA. Microarray assessments revealed the presence of mRNA from approximately 1300 genes, many of which are not present in the cytoplasm of the donor cell. In vitro translation proved that the exosome mRNAs were functional. Quality control RNA analysis of total RNA derived from exosomes also revealed presence of small RNAs, including microRNAs. The RNA from mast cell exosomes is transferable to other mouse and human mast cells. After transfer of mouse exosomal RNA to human mast cells, new mouse proteins were found in the recipient cells, indicating that transferred exosomal mRNA can be translated after entering another cell. In summary, we show that exosomes contain both mRNA and microRNA, which can be delivered to another cell, and can be functional in this new location. We propose that this RNA is called "exosomal shuttle RNA" (esRNA).

Local proliferation and mobilization of CCR3(+) CD34(+) eosinophil-lineage-committed cells in the lung.

Emerging evidence suggests that haematopoietic CD34(+) progenitor cells migrate from bone marrow (BM) to sites of allergen exposure where they can undergo further proliferation and final maturation, potentially augmenting the degree of tissue inflammation. In the current study we used a well-characterized mouse model of allergen-induced airway inflammation to determine the role of CCR3 receptor-ligand interactions in the migration and function of CD34(+) cells. Allergen exposure significantly increased BM, blood and airway CD34(+) CCR3(+) cells as well as airway CD34(+) CCR3(+) stem cell antigen-1-positive (Sca-1(+) ) and CD34(+) CD45(+) interleukin-5 receptor-α-positive (IL-5Rα(+) ) cells. A portion of the newly produced CD34(+) CCR3(+), Sca-1(+) CCR3(+) and IL-5Ralpha(+) lung cells showed a significant proliferative capacity in response to allergen when compared with saline-treated animals. In addition, in vitro colony formation of lung CD34(+) cells was increased by IL-5 or eotaxin-2 whereas eotaxin-2 had no effect on BM CD34(+) cells. Furthermore, both eotaxin-1 and eotaxin-2 induced migration of BM and blood CD34(+) CCR3(+) cells in vitro. These data suggest that the CCR3/eotaxin pathway is involved in the regulation of allergen-driven in situ haematopoiesis and the accumulation/mobilization of eosinophil-lineage-committed progenitor cells in the lung. Hence, targeting both IL-5 and CCR3-mediated signalling pathways may be required to control the inflammation associated with allergen-induced asthma.

Effects of tobacco smoke on IL-16 in CD8+ cells from human airways and blood: a key role for oxygen free radicals?

Chronic exposure to tobacco smoke leads to an increase in the frequency of infections and in the number of CD8(+) and CD4(+) cells as well as the CD4(+) chemoattractant cytokine IL-16 in the airways. Here, we investigated whether tobacco smoke depletes intracellular IL-16 protein and inhibits de novo production of IL-16 in CD8(+) cells from human airways and blood while increasing extracellular IL-16 and whether oxygen free radicals (OFR) are involved. Intracellular IL-16 protein in CD8(+) cells and mRNA in all cells was decreased in bronchoalveolar lavage (BAL) samples from chronic smokers. This was also the case in human blood CD8(+) cells exposed to water-soluble tobacco smoke components in vitro, in which oxidized proteins were markedly increased. Extracellular IL-16 protein was increased in cell-free BAL fluid from chronic smokers and in human blood CD8(+) cells exposed to water-soluble tobacco smoke components in vitro. This was not observed in occasional smokers after short-term exposure to tobacco smoke. A marker of activation (CD69) was slightly increased, whereas other markers of key cellular functions (membrane integrity, apoptosis, and proliferation) in human blood CD8(+) cells in vitro were negatively affected by water-soluble tobacco smoke components. An OFR scavenger prevented these effects, whereas a protein synthesis inhibitor, a ß-adrenoceptor, a glucocorticoid receptor agonist, a phosphodiesterase, a calcineurin phosphatase, and a caspase-3 inhibitor did not. In conclusion, tobacco smoke depletes preformed intracellular IL-16 protein, inhibits its de novo synthesis, and distorts key cellular functions in human CD8(+) cells. OFR may play a key role in this context.

Human saliva, plasma and breast milk exosomes contain RNA: uptake by macrophages.

BACKGROUND: Exosomes are 30-100 nm membrane vesicles of endocytic origin produced by numerous cells. They can mediate diverse biological functions, including antigen presentation. Exosomes have recently been shown to contain functional RNA, which can be delivered to other cells. Exosomes may thus mediate biological functions either by surface-to-surface interactions with cells, or by the delivery of functional RNA to cells. Our aim was therefore to determine the presence of RNA in exosomes from human saliva, plasma and breast milk and whether these exosomes can be taken up by macrophages. METHOD: Exosomes were purified from human saliva, plasma and breast milk using ultracentrifugation and filtration steps. Exosomes were detected by electron microscopy and examined by flow cytometry. Flow cytometry was performed by capturing the exosomes on anti-MHC class II coated beads, and further stain with anti-CD9, anti-CD63 or anti-CD81. Breast milk exosomes were further analysed for the presence of Hsc70, CD81 and calnexin by Western blot. Total RNA was detected with a Bioanalyzer and mRNA was identified by the synthesis of cDNA using an oligo (dT) primer and analysed with a Bioanalyzer. The uptake of PKH67-labelled saliva and breast milk exosomes by macrophages was examined by measuring fluorescence using flow cytometry and fluorescence microscopy. RESULTS: RNA was detected in exosomes from all three body fluids. A portion of the detected RNA in plasma exosomes was characterised as mRNA. Our result extends the characterisation of exosomes in healthy humans and confirms the presence of RNA in human saliva and plasma exosomes and reports for the first time the presence of RNA in breast milk exosomes. Our results also show that the saliva and breast milk exosomes can be taken up by human macrophages. CONCLUSIONS: Exosomes in saliva, plasma and breast milk all contain RNA, confirming previous findings that exosomes from several sources contain RNA. Furthermore, exosomes are readily taken up by macrophages, supporting the notion that exosomal RNA can be shuttled between cells.

IL-17-producing T lymphocytes in lung tissue and in the bronchoalveolar space after exposure to endotoxin from Escherichia coli in vivo--effects of anti-inflammatory pharmacotherapy.

Interleukin (IL)-17 may play a critical role for the innate immune response in mammals. However, little is known about its production in T lymphocytes in comparison with other cells, in lung tissue and in the bronchoalveolar space in vivo. Even less is known about the effects of anti-inflammatory pharmacotherapy on this IL-17 production. In this study on mice we show that one single, intranasal exposure to endotoxin from Escherichia coli increases extracellular IL-17 protein in bronchoalveolar (BAL) samples during 3 days, and is accompanied by a local increase in neutrophils and other inflammatory cells. This endotoxin exposure also elevates IL-17 mRNA in lung tissue samples. Moreover, after endotoxin exposure, the absolute number of CD3-positive cells containing intracellular IL-17 protein is increased as well; from a moderate cell number in lung tissue samples and from virtually none in BAL samples; with the number in lung tissue exceeding that observed in BAL samples. Notably, we also demonstrate that among the cells that contain intracellular IL-17 protein after endotoxin exposure, the percentage of CD3-positive cells is similar to that of CD3-negative cells in lung tissue. In contrast, CD3-negative cells dominate among IL-17-containing cells in BAL samples. A high systemic dose of a glucocorticoid receptor agonist attenuates the endotoxin-induced increase in extracellular IL-17 protein in BAL samples, IL-17 mRNA in lung tissue samples, and in IL-17-containing CD3-positive cells in BAL and lung tissue samples. This is also true for the endotoxin-induced accumulation of neutrophils and other inflammatory BAL cells in vivo. A systemic dose of a calcineurin phosphatase inhibitor exerts a less complete and more selective effect on the endotoxin-induced increase in extracellular IL-17 protein and on neutrophils in BAL samples. In vitro, endotoxin also increases extracellular IL-17 protein in a co-culture of CD3-positive spleen cells and adherent mononuclear BAL cells; an increase that was inhibited by a glucocorticoid as well as by a calcineurin phosphatase inhibitor. In conclusion, endotoxin-induced IL-17 production and release from T lymphocytes originates from cells that reside in lung tissue and from cells that have been recruited to the bronchoalveolar space. In both compartments, there is also a substantial number of cells other than T lymphocytes that contain IL-17 after endotoxin exposure. The sustained IL-17 production from T lymphocytes and the associated neutrophil accumulation may be inhibited non-selectively through glucocorticoid receptor stimulation and more selectively through calcineurin phosphatase inhibition.

Regulatory role of CD8+ T lymphocytes in bone marrow eosinophilopoiesis.

BACKGROUND: There is a growing body of evidence to suggest that CD8+ T lymphocytes contribute to local allergen-induced eosinophilic inflammation. Since bone marrow (BM) responses are intricately involved in the induction of airway eosinophilia, we hypothesized that CD8+ T lymphocytes, as well as CD4+ T lymphocytes, may be involved in this process. METHODS: Several approaches were utilized. Firstly, mice overexpressing interleukin-5 (IL-5) in CD3+ T lymphocytes (NJ.1638; CD3IL-5+ mice) were bred with gene knockout mice lacking either CD4+ T lymphocytes (CD4-/-) or CD8+ T lymphocytes (CD8-/-) to produce CD3IL-5+ knockout mice deficient in CD4+ T lymphocytes (CD3IL-5+/CD4-/-) and CD8+ T lymphocytes (CD3IL-5+/CD8-/-), respectively. Secondly, CD3+, CD4+ and CD8+ T lymphocytes from naïve CD3IL-5+ and C57BL/6 mice were adoptively transferred to immunodeficient SCID-bg mice to determine their effect on BM eosinophilia. Thirdly, CD3IL-5+, CD3IL-5+/CD8-/- and CD3IL-5+/CD4-/- mice were sensitized and allergen challenged. Bone marrow and blood samples were collected in all experiments. RESULTS: The number of BM eosinophils was significantly reduced in CD3IL-5+/CD8-/- mice compared to CD3IL-5+ mice and CD3IL-5+/CD4-/- mice. Serum IL-5 was significantly higher in CD3IL-5+/CD4-/- mice compared to CD3IL-5+ mice but there was no difference in serum IL-5 between CD3IL-5+/CD4-/- and CD3IL-5+/CD8-/- mice. Adoptive transfer of CD8+, but not CD4+ T lymphocytes from naïve CD3IL-5+ and C57BL/6 mice restored BM eosinophilia in immunodeficient SCID-bg mice. Additionally, allergen challenged CD3IL-5+/CD8-/- mice developed lower numbers of BM eosinophils compared to CD3IL-5+ mice and CD3IL-5+/CD4-/- mice. CONCLUSION: This study shows that CD8+ T lymphocytes are intricately involved in the regulation of BM eosinophilopoiesis, both in non-sensitized as well as sensitized and allergen challenged mice.

Interleukin-16-producing NK cells and T-cells in the blood of tobacco smokers with and without COPD.

BACKGROUND: Long-term exposure to tobacco smoke causes local inflammation in the airways that involves not only innate immune cells, including NK cells, but also adaptive immune cells such as cytotoxic (CD8+) and helper (CD4+) T-cells. We have previously demonstrated that long-term tobacco smoking increases extracellular concentration of the CD4+-recruiting cytokine interleukin (IL)-16 locally in the airways. Here, we hypothesized that tobacco smoking alters IL-16 biology at the systemic level and that this effect involves oxygen free radicals (OFR). METHODS: We quantified extracellular IL-16 protein (ELISA) and intracellular IL-16 in NK cells, T-cells, B-cells, and monocytes (flow cytometry) in blood samples from long-term tobacco smokers with and without chronic obstructive pulmonary disease (COPD) and in never-smokers. NK cells from healthy blood donors were stimulated with water-soluble tobacco smoke components (cigarette smoke extract) with or without an OFR scavenger (glutathione) in vitro and followed by quantification of IL-16 protein. RESULTS: The extracellular concentrations of IL-16 protein in blood did not display any substantial differences between groups. Notably, intracellular IL-16 protein was detected in all types of blood leukocytes. All long-term smokers displayed a decrease in this IL-16 among NK cells, irrespective of COPD status. Further, both NK and CD4+ T-cell concentrations displayed a negative correlation with pack-years. Moreover, cigarette smoke extract caused release of IL-16 protein from NK cells in vitro, and this was not affected by glutathione, in contrast to the decrease in intracellular IL-16, which was prevented by this drug. CONCLUSION: Long-term exposure to tobacco smoke does not markedly alter extracellular concentrations of IL-16 protein in blood. However, it does decrease the intracellular IL-16 concentrations in blood NK cells, the latter effect involving OFR. Thus, long-term tobacco smoking exerts an impact at the systemic level that involves NK cells; innate immune cells that are critical for host defense against viruses and tumors - conditions that are overrepresented among smokers.

Precursor B Cells Increase in the Lung during Airway Allergic Inflammation: A Role for B Cell-Activating Factor.

BACKGROUND: B cells, key cells in allergic inflammation, differentiate in the bone marrow and their precursors include pro-B, pre-B and immature B cells. Eosinophil progenitor cells increase in the lung after allergen exposure. However, the existence and possible role of B cell precursors in the lung during allergic inflammation remains elusive. METHODS: A BALB/c mouse model of allergic airway inflammation was utilized to perform phenotypic and quantification analyses of pro-B and pre-B cells in the lung by flow cytometry. B cell maturation factors IL-7 and B cell-activating factor (BAFF) and their receptors (CD127 and BAFFR, BCMA, TACI, respectively) were also evaluated in the lung and serum. The effect of anti-BAFF treatment was investigated both in vivo (i.p. administration of BAFF-R-Ig fusion protein) and in vitro (colony forming cell assay). Finally, BAFF levels were examined in the bronchoalveolar lavage (BAL) of asthmatic patients and healthy controls. RESULTS: Precursor pro and pre-B cells increase in the lung after allergen exposure, proliferate in the lung tissue in vivo, express markers of chemotaxis (CCR10 and CXCR4) and co-stimulation (CD40, CD86) and are resistant to apoptosis (Bax). Precursor B cells express receptors for BAFF at baseline, while after allergen challenge both their ligand BAFF and the BCMA receptor expression increases in B cell precursors. Blocking BAFFR in the lung in vivo decreases eosinophils and proliferating precursor B cells. Blocking BAFFR in bone marrow cultures in vitro reduces pre-B colony formation units. BAFF is increased in the BAL of severe asthmatics. CONCLUSION: Our data support the concept of a BAFF-mediated role for B cell precursors in allergic airway inflammation.

Increase in net activity of serine proteinases but not gelatinases after local endotoxin exposure in the peripheral airways of healthy subjects.

We tested the hypothesis that activation of the innate immune response induces an imbalance in the proteolytic homeostasis in the peripheral airways of healthy subjects, towards excess serine or gelatinase proteinase activity. During bronchoscopy, 18 healthy human subjects underwent intra-bronchial exposure to endotoxin and contra-lateral exposure to vehicle. Bronchoalveolar lavage (BAL) samples were harvested 24 or 48 hours (h) later. We quantified archetype proteinases, anti-proteinases, inflammatory BAL cells, and, importantly, total plus net proteinase activities using functional substrate assays. As expected, endotoxin exposure increased the concentrations of polymorphonuclear leukocytes (PMN's) and macrophages, of proteinases and the anti-proteinases tissue inhibitor of metalloproteinase-1, α-1-antitrypsin and, to a lesser extent, secretory leukoproteinase inhibitor, at both time points. Notably, at these time points, endotoxin exposure substantially increased the quantitative NE/SLPI ratio and the net serine proteinase activity corresponding to neutrophil elastase (NE). Endotoxin exposure also increased the total gelatinase activity corresponding to matrix metalloproteinase (MMP)-9; an activity dominating over that of MMP-2. However, endotoxin exposure had no impact on net gelatinolytic activity at 24 or 48 h after exposure. Thus, local activation of the innate immune response induces an imbalance towards increased net serine proteinase activity in the proteolytic homeostasis of the peripheral airways in healthy subjects. Hypothetically, this serine proteinase activity can contribute to tissue remodelling and hypersecretion via NE from PMN's, if it is triggered repeatedly, as might be the case in chronic inflammatory airway disorders.

Repeated allergen exposure reduce early phase airway response and leukotriene release despite upregulation of 5-lipoxygenase pathways.

BACKGROUND: Allergen induced early phase airway response and airway plasma exudation are predominantly mediated by inflammatory mast cell mediators including histamine, cysteinyl leukotrienes (cysLTs) and thromboxane A2 (TXA2). The aim of the present study was to evaluate whether repeated allergen exposure affects early phase airway response to allergen challenge. METHODS: A trimellitic anhydride (TMA) sensitized guinea pig model was used to investigate the effects of low dose repeated allergen exposure on cholinergic airway responsiveness, early phase airway response and plasma exudation, as well as local airway production of mast cell derived cysteinyl leukotrienes and thromboxane B2 (TXB2) after allergen challenge. RESULTS: Repeated low dose allergen exposure increased cholinergic airway responsiveness. In contrast, early phase airway response and plasma exudation in response to a high-dose allergen challenge were strongly attenuated after repeated low dose allergen exposure. Inhibition of the airway response was unspecific to exposed allergen and independent of histamine receptor blocking. Furthermore, a significant reduction of cysteinyl leukotrienes and TXB2 was found in the airways of animals repeatedly exposed to a low dose allergen. However, in vitro stimulation of airway tissue from animals repeatedly exposed to a low dose allergen with arachidonic acid and calcium ionophore (A23187) induced production of cysteinyl leukotrienes and TXB2, suggesting enhanced activity of 5-lipoxygenase and cyclooxygenase pathways. CONCLUSIONS: The inhibition of the early phase airway response, cysteinyl leukotriene and TXB2 production after repeated allergen exposure may result from unresponsive effector cells.

Immunophenotyping of circulating T helper cells argues for multiple functions and plasticity of T cells in vivo in humans--possible role in asthma.

BACKGROUND: The immune process driving eosinophilic and non-eosinophilic asthma is likely driven by different subsets of T helper (Th) cells. Recently, in vitro studies and animal studies suggest that Th cell subsets displays plasticity by changing their transcription factor or by expressing multiple transcription factors. Our aim was to determine whether individuals with asthma and elevated circulating eosinophils express signs of different regulatory immune mechanisms compared with asthmatics with low blood eosinophils and non-asthmatic control subjects. In addition, determine the relationship between eosinophilia and circulating Th cell subsets. METHODOLOGY/PRINCIPAL FINDINGS: Participants were selected from a random epidemiological cohort, the West Sweden Asthma Study. Immunophenotypes of fresh peripheral blood cells obtained from stable asthmatics, with and without elevated eosinophilic inflammation (EOS high and EOS low respectively) and control subjects, were determined by flow cytometry. No differences in the number of Th1 (T-bet), Th2 (GATA-3), Th17 (RORγt) or Treg (FOXP3) cells were observed between the groups when analysing each subset separately. However, in all groups, each of the Th subsets showed expression of additional canonical transcription factors T-bet, GATA-3, RORγt and FOXP3. Furthermore, by in vitro stimulation with anti-CD3/anti-CD28 there was a significant increase of single expressing GATA-3(+) and co-expressing T-bet(+)GATA-3(+) cells in the EOS high asthmatics in comparison with control subjects. In addition, T-bet(-)GATA-3(+)RORγt(+)FOXP3(+) were decreased in comparison to the EOS low asthmatics. Finally, in a group of control subjects we found that the majority of proliferating Th cells (CD4(+)CD25(+)Ki67(+)) expressed three or four transcription factors. CONCLUSIONS: The ability of human Th cells to express several regulatory transcription factors suggests that these cells may display plasticity in vivo.

Characterization of mRNA and microRNA in human mast cell-derived exosomes and their transfer to other mast cells and blood CD34 progenitor cells.

BACKGROUND: Exosomes are nanosized vesicles of endocytic origin that are released into the extracellular environment by many different cells. It has been shown that exosomes from various cellular origins contain a substantial amount of RNA (mainly mRNA and microRNA). More importantly, exosomes are capable of delivering their RNA content to target cells, which is a novel way of cell-to-cell communication. The aim of this study was to evaluate whether exosomal shuttle RNA could play a role in the communication between human mast cells and between human mast cells and human CD34(+) progenitor cells. METHODS: The mRNA and microRNA content of exosomes from a human mast cell line, HMC-1, was analysed by using microarray technology. Co-culture experiments followed by flow cytometry analysis and confocal microscopy as well as radioactive labeling experiments were performed to examine the uptake of these exosomes and the shuttle of the RNA to other mast cells and CD34(+) progenitor cells. RESULTS: In this study, we show that human mast cells release RNA-containing exosomes, with the capacity to shuttle RNA between cells. Interestingly, by using microRNA microarray analysis, 116 microRNAs could be identified in the exosomes and 134 microRNAs in the donor mast cells. Furthermore, DNA microarray experiments revealed the presence of approximately 1800 mRNAs in the exosomes, which represent 15% of the donor cell mRNA content. In addition, transfer experiments revealed that exosomes can shuttle RNA between human mast cells and to CD34(+) hematopoietic progenitor cells. CONCLUSION: These findings suggest that exosomal shuttle RNA (esRNA) can play a role in the communication between cells, including mast cells and CD34(+) progenitor cells, implying a role in cells maturation process.

Expansion of CD4(+) CD25(+) and CD25(-) T-Bet, GATA-3, Foxp3 and RORγt cells in allergic inflammation, local lung distribution and chemokine gene expression.

Allergic asthma is associated with airway eosinophilia, which is regulated by different T-effector cells. T cells express transcription factors T-bet, GATA-3, RORγt and Foxp3, representing Th1, Th2, Th17 and Treg cells respectively. No study has directly determined the relative presence of each of these T cell subsets concomitantly in a model of allergic airway inflammation. In this study we determined the degree of expansion of these T cell subsets, in the lungs of allergen challenged mice. Cell proliferation was determined by incorporation of 5-bromo-2'-deoxyuridine (BrdU) together with 7-aminoactnomycin (7-AAD). The immunohistochemical localisation of T cells in the lung microenvironments was also quantified. Local expression of cytokines, chemokines and receptor genes was measured using real-time RT-PCR array analysis in tissue sections isolated by laser microdissection and pressure catapulting technology. Allergen exposure increased the numbers of T-bet(+), GATA-3(+), RORγt(+) and Foxp3(+) cells in CD4(+)CD25(+) and CD4(+)CD25(-) T cells, with the greatest expansion of GATA-3(+) cells. The majority of CD4(+)CD25(+) T-bet(+), GATA-3(+), RORγt(+) and Foxp3(+) cells had incorporated BrdU and underwent proliferation during allergen exposure. Allergen exposure led to the accumulation of T-bet(+), GATA-3(+) and Foxp3(+) cells in peribronchial and alveolar tissue, GATA-3(+) and Foxp3(+) cells in perivascular tissue, and RORγt(+) cells in alveolar tissue. A total of 28 cytokines, chemokines and receptor genes were altered more than 3 fold upon allergen exposure, with expression of half of the genes claimed in all three microenvironments. Our study shows that allergen exposure affects all T effector cells in lung, with a dominant of Th2 cells, but with different local cell distribution, probably due to a distinguished local inflammatory milieu.

RNA-containing exosomes in human nasal secretions.

BACKGROUND: Exosomes are nanovesicles of endocytic origin released by cells and present in human body fluids such as plasma, breast milk, and bronchoalveolar lavage fluid. These vesicles take part in communication between cells. Recently, it was shown that exosomes contain both mRNA and microRNA. This RNA can be shuttled between cells (exosomal shuttle RNA), which is a new route of communication between cells. The aim of this study was to determine whether nasal secretions harbor exosomes and furthermore, whether these exosomes contain RNA. METHODS: Human nasal lavage fluid (NLF) underwent centrifugation and filtration to discard cells and debris, followed by a final ultracentrifugation at 120,000 × g to pellet the exosomes. Exosomes were detected using electron microscopy (EM), flow cytometry, and Western blot. RNA was extracted and analyzed using a Bioanalyzer. RESULTS: Exosomes were visualized as 40-80 nm, CD63(+) vesicles using EM. Flow cytometry of exosomes using anti-major histocompatibility complex class II beads revealed exosomes positive for the tetraspanins CD9, CD63, and CD81. Western blot confirmed the presence of exosomal protein and absence of proteins from the endoplasmic reticulum (ER), because the exosomes were positive for Tsg101, but negative for the ER marker, calnexin. Bioanalyzer analysis revealed that, these exosomes contain RNA. CONCLUSION: This study shows for the first time that NLF contains exosomes and that these exosomes contain RNA. Further characterization of the exosomal RNA and proteins may provide important information about communication in the nose and potentially provide a source of biomarkers for upper airway diseases.

Exosomes communicate protective messages during oxidative stress; possible role of exosomal shuttle RNA.

BACKGROUND: Exosomes are small extracellular nanovesicles of endocytic origin that mediate different signals between cells, by surface interactions and by shuttling functional RNA from one cell to another. Exosomes are released by many cells including mast cells, dendritic cells, macrophages, epithelial cells and tumour cells. Exosomes differ compared to their donor cells, not only in size, but also in their RNA, protein and lipid composition. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we show that exosomes, released by mouse mast cells exposed to oxidative stress, differ in their mRNA content. Also, we show that these exosomes can influence the response of other cells to oxidative stress by providing recipient cells with a resistance against oxidative stress, observed as an attenuated loss of cell viability. Furthermore, Affymetrix microarray analysis revealed that the exosomal mRNA content not only differs between exosomes and donor cells, but also between exosomes derived from cells grown under different conditions; oxidative stress and normal conditions. Finally, we also show that exposure to UV-light affects the biological functions associated with exosomes released under oxidative stress. CONCLUSIONS/SIGNIFICANCE: These results argue that the exosomal shuttle of RNA is involved in cell-to-cell communication, by influencing the response of recipient cells to an external stress stimulus.

Functional relevance of the IL-23-IL-17 axis in lungs in vivo.

It is known that interleukin (IL)-23, an IL-12-family cytokine, can be released by certain antigen-presenting cells in response to bacterial pathogens. Recent in vitro studies indicate that this cytokine stimulates a unique subset of CD4 cells, the T helper cell (Th)17 subset, to produce and release the proinflammatory cytokine IL-17. However, it has not been known whether this is an action of IL-23 per se that has bearing for the early innate response in lungs in vivo and whether there is an IL-23-responsive population of IL-17-producing CD4 cells in the bronchoalveolar space. We now present evidence that IL-23 can be involved in the early innate response to both gram-negative and gram-positive bacterial products in the lungs: Recombinant IL-23 protein per se accumulates inflammatory cells in the bronchoalveolar space in part via endogenous production of IL-17, and this IL-17 production occurs locally in IL-23-responsive CD4 cells. This IL-17 response to IL-23 occurs without any pronounced impact on Th1/Th2 polarization. Moreover, recombinant IL-23 protein increases the local MMP-9 activity, which is generated by neutrophils mainly. CD4 cells in the lungs may thus respond to IL-23 from antigen-presenting cells exposed to gram-negative and gram-positive pathogens and thereby reinforce the early innate response. These findings support that IL-23 and IL-17 form a functionally relevant "immunological axis" in the lungs in vivo.