Cockroach exposure is a major risk factor for the development of asthma; however, the early immune events induced by cockroach leading to the Th2 response are not fully understood. Exposure of naïve mice to German cockroach (GC) feces (frass) was sufficient to induce dendritic cell (DC) recruiting and activating chemokines C-C motif ligand 20, granulocyte macrophage colony-stimulating factor, granulocyte colony-stimulating factor and macrophage inflammatory protein-1α into the airways. This corresponded with an increase in myeloid DCs (mDCs) in the airways as well as increased expression of CD80 and CD86 on the mDCs. Plasmacytoid DCs in the lung were unchanged. Levels of IL-5, IL-17A and IL-6 cytokines in whole lung cultures were significantly increased 18 h following GC frass exposure demonstrating the early development of a mixed Th2/Th17 response. In addition, GC frass stimulated the production of IL-23, IL-6 and IL-12p70 from bone marrow-derived mDCs. Adoptive transfer of GC frass-pulsed mDCs induced airway reactivity, airway inflammation as well as eosinophilia and induced a strong Th2/Th17 response in the lung. MyD88-deficient bone marrow-derived mDCs did not respond to GC frass treatment, suggesting a functional Toll-like receptor pathway was important to induce the Th2/Th17 response. Together, our data show that GC frass activated the innate immune response to augment DC recruitment and activation of mDCs which promoted robust T cell-skewing cytokines and ultimately drive the development of airway inflammation.
Chemokines; Cytokines; Immune response; Pathogen associated-molecular patterns; Toll-like receptor; Dendritic cell; Airway inflammation; Cockroach
Exaggerated levels of VEGF (vascular endothelial growth factor) are present in persons with asthma, but the role(s) of VEGF in normal and asthmatic lungs has not been defined. We generated lung-targeted VEGF165 transgenic mice and evaluated the role of VEGF in T-helper type 2 cell (TH2)-mediated inflammation. In these mice, VEGF induced, through IL-13–dependent and –independent pathways, an asthma-like phenotype with inflammation, parenchymal and vascular remodeling, edema, mucus metaplasia, myocyte hyperplasia and airway hyper-responsiveness. VEGF also enhanced respiratory antigen sensitization and TH2 inflammation and increased the number of activated DC2 dendritic cells. In antigen-induced inflammation, VEGF was produced by epithelial cells and preferentially by TH2 versus TH1 cells. In this setting, it had a critical role in TH2 inflammation, cytokine production and physiologic dysregulation. Thus, VEGF is a mediator of vascular and extravascular remodeling and inflammation that enhances antigen sensitization and is crucial in adaptive TH2 inflammation. VEGF regulation may be therapeutic in asthma and other TH2 disorders.
Reduced frequencies of myeloid and plasmacytoid dendritic cell (DC) subsets (mDCs and pDCs, respectively) have been observed in the peripheral blood of HIV-1-infected individuals throughout the course of disease. Accumulation of DCs in lymph nodes (LNs) may partly account for the decreased numbers observed in blood, but increased DC death may also be a contributing factor. We used multiparameter flow cytometry to evaluate pro- and antiapoptotic markers in blood mDCs and pDCs from untreated HIV-1-infected donors, from a subset of infected donors before and after receiving antiretroviral therapy (ART), and from uninfected control donors. Blood mDCs, but not pDCs, from untreated HIV-1-infected donors expressed lower levels of antiapoptotic Bcl-2 than DCs from uninfected donors. A subset of HIV-1-infected donors had elevated frequencies of proapoptotic caspase-3+ blood mDCs, and positive correlations were observed between caspase-3+ mDC frequencies and plasma viral load and CD8+ T-cell activation levels. Caspase-3+ mDC frequencies, but not mDC Bcl-2 expression, were reduced with viral suppression on ART. Apoptosis markers on DCs in blood and LN samples from a cohort of untreated, HIV-1-infected donors with chronic disease were also evaluated. LN mDCs displayed higher levels of Bcl-2 and lower caspase-3+ frequencies than did matched blood mDCs. Conversely, LN pDCs expressed lower Bcl-2 levels than their blood counterparts. In summary, blood mDCs from untreated HIV-1-infected subjects displayed a proapoptotic profile that was partially reversed with viral suppression, suggesting that DC death may be a factor contributing to blood DC depletion in the setting of chronic, untreated HIV disease.
Maladaptive, Th2-polarized inflammatory responses are integral to the pathogenesis of allergic asthma. As regulators of T cell activation, dendritic cells (DCs) are important mediators of allergic asthma, yet the precise signals which render endogenous DCs “pro-asthmatic”, and the extent to which these signals are regulated by the pulmonary environment and host genetics, remains unclear. Comparative phenotypic and functional analysis of pulmonary DC populations in mice susceptible (A/J), or resistant (C3H) to experimental asthma, revealed that susceptibility to airway hyperresponsiveness is associated with preferential myeloid DC (mDC) allergen uptake, and production of Th17-skewing cytokines (IL-6, IL-23), whereas resistance is associated with increased allergen uptake by plasmacytoid DCs. Surprisingly, adoptive transfer of syngeneic HDM-pulsed bone marrow derived mDCs (BMDCs) to the lungs of C3H mice markedly enhanced lung IL-17A production, and rendered them susceptible to allergen-driven airway hyperresponsiveness. Characterization of these BMDCs revealed levels of antigen uptake, and Th17 promoting cytokine production similar to that observed in pulmonary mDCs from susceptible A/J mice. Collectively these data demonstrate that the lung environment present in asthma-resistant mice promotes robust pDC allergen uptake, activation, and limits Th17-skewing cytokine production responsible for driving pathologic T cell responses central to the development of allergen-induced airway hyperresponsiveness.
Neuropilin 1 (NP1) is a part of essential receptor complexes mediating both semaphorin3A (SEMA3A) and vascular endothelial growth factor (VEGF) which is one of important mediators involved in the pathogenesis of asthma. Therefore, it is possible that SEMA3A plays a role in the pathogenesis of asthma through attenuation of VEGF-mediated effects. In the present study, we aimed to evaluate expression levels of SEMA3A and NP1 using induced sputum of asthmatics and a murine model of asthma. Firstly, SEMA3A and NP1 expressions in induced sputum of asthmatics and SEMA3A and NP1 expression on bronchoalveolar lavage (BAL) cells and lung homogenates of asthmatic mice were determined. Then we evaluated the immunolocalization of VEGF receptor 1 (VEGFR1), VEGF receptor 2 (VEGFR2), and NP1 expressions on asthmatic mice lung tissue and their subcellular distributions using fibroblast and BEAS2B cell lines. Sputum SEMA3A and NP1 expressions were significantly higher in asthmatics than controls. Similarly, SEMA3A and NP1 expressions on BAL cells and lung homogenates were significantly elevated in asthmatic mice compared to control mice. Immunohistochemical analysis showed that VEGFR1, VEGFR2, and NP1 expressions were also uniformly increased in asthmatic mice. Our observations suggest that SEMA3A and NP1 may play important roles in the pathogenesis of asthma.
Asthma; Neuropilin; Semaphorin-3A (SEMA3A); Vascular Endothelial Growth Factor
To determine the role of plasmacytoid dendritic cells (pDC) and myeloid dendritic cells (mDC) in priming effector T cells to induce allergy, and to evaluate the effect of immunostimulatory sequences (ISS, TLR9 agonist) on dendritic cells.
Cultured mDC and pDC with/without ISS were injected intratracheally into sensitized Balb/C mice. Mice were sacrificed, and then pulmonary function tests, bronchoalveolar lavage (BAL), cell counts, and cytokine levels were evaluated. Migration of dendritic cells was also evaluated after ISS administration.
In mice injected with mDC, airway hyperresponsiveness, eosinophil counts, and Th2 cytokine levels in BAL increased with increasing numbers of mDC injected. However, in mice injected with pDC, none of these changed, suggesting poor priming of T cells by pDC. In addition, mDC pulsed with ISS inhibited asthmatic reactions, and ISS administration inhibited migration of DC to the lung.
We suggest that pDC played a limited role in priming T cells in this asthma model and that mDC played a major role in inducing asthma. In addition, ISS inhibited migration of DC to the lung.
Plasmacytoid dendritic cell; myeloid dendritic cell; allergy; immunostimulatory sequence; TLR9; migration
The role of plasmacytoid dendritic cells (PDC), the major producers of alpha interferon upon viral infection, in the nasal mucosa is largely unknown. Here we examined the presence of PDC together with myeloid dendritic cells (MDC) in the nasal epithelia of healthy individuals, of asymptomatic patients with chronic nasal allergy, of patients undergoing steroid therapy, and of patients with infectious rhinitis or rhinosinusitis. Considerable numbers of PDC and MDC could be detected in the nasal epithelium. Furthermore, we demonstrate the expression of SDF-1, the major chemoattractant for PDC, in the nasal epithelium. PDC levels were significantly lower for patients with allergies than for healthy individuals. Interestingly, PDC and MDC were almost absent from patients who received treatment with glucocorticoids, while very high numbers of PDC were found for patients with recent upper respiratory tract infections. Our results demonstrate for the first time a quantitative analysis of PDC and MDC in the healthy nasal epithelium and in nasal epithelia from patients with different pathological conditions. With the identification of PDC, the major target cell for CpG DNA or immunostimulatory RNA, in the nasal epithelium, this study forms the basis for a local nasal application of such oligonucleotides for the treatment of viral infection and allergy.
Children with allergic asthma have more frequent and severe human rhinovirus (HRV)-induced wheezing and asthma exacerbations through unclear mechanisms.
To determine whether increased high-affinity IgE receptor (FcεRI) expression and cross-linking impairs innate immune responses to HRV, particularly in allergic asthmatic children.
Peripheral blood mononuclear cells (PBMC) were obtained from 44 children and surface expression of FcεRI on plasmacytoid dendritic cells (pDCs), myeloid dendritic cells (mDCs), monocytes, and basophils was assessed using flow cytometry. Cells were also incubated with rabbit anti-human IgE to cross-link FcεRI, followed by stimulation with HRV-16, and interferon (IFN)-α and -λ1 were measured by Luminex. The relationships among FcεRI expression and cross-linking, HRV-induced IFN-α and -λ1 production, and childhood allergy and asthma were subsequently analyzed.
FcεRIα expression on pDCs was inversely associated with HRV-induced IFN- α and IFN-λ1 production. Cross-linking FcεRI prior to HRV stimulation further reduced PBMC IFN-α (47% relative reduction, 95% confidence interval [CI], 32–62%, p<0.0001) and IFN-λ1 (81% relative reduction, 95% CI, 69–93%, p<0.0001) secretion. Allergic asthmatic children had higher surface expression of FcεRIα on pDCs and mDCs when compared to non-allergic non-asthmatic children. Further, after FcεRI cross-linking, allergic asthmatic children had significantly lower HRV-induced IFN responses than allergic non-asthmatics (IFN-α, p=0.004; IFN-λ1, p=0.02) and non-allergic non-asthmatics (IFN-α, p=0.002; IFN-λ1, p=0.01).
Allergic asthmatic children have impaired innate immune responses to HRV that correlate with increased FcεRI expression on pDCs and are reduced by FcεRI cross-linking. These effects likely increase susceptibility to HRV-induced wheezing and asthma exacerbations.
asthma; allergic; rhinovirus; interferon; FcεRI; IgE receptor; plasmacytoid dendritic cells
We evaluated Toll-like receptor (TLR) function in primary human dendritic cells from 104 young (age 21–30) and older (≥ 65 years) individuals. We used multicolor flow cytometry and intracellular cytokine staining of myeloid (mDC) and plasmacytoid (pDC) DCs and found substantial decreases in older, compared to young individuals in TNF-α, IL-6 and/or IL-12 (p40) production in mDCs and in TNF-α and IFN-α production in pDCs in response to TLR1/2, TLR2/6, TLR3, TLR5, and TLR8 engagement in mDCs and TLR7 and TLR9 in pDCs. These differences were highly significant after adjustment for heterogeneity between young and older groups (e.g. gender, race, body mass index [BMI], number of comorbid medical conditions) using mixed effect statistical modeling. Studies of surface and intracellular expression of TLR proteins, and of TLR gene expression in purified mDCs and pDCs revealed potential contributions for both transcriptional and post-transcriptional mechanisms in these age-associated effects. Moreover, intracellular cytokine production in the absence of TLR ligand stimulation was elevated in cells from older, compared to young individuals, suggesting a dysregulation of cytokine production that may limit further activation by TLR engagement. Our results provide evidence for immunosenescence in dendritic cells; notably, defects in cytokine production were strongly associated with poor antibody response to influenza immunization, a functional consequence of impaired TLR function in the aging innate immune response.
Placental Plasmodium falciparum infection affects birth outcomes and sensitizes fetal lymphocytes to parasite antigens. We assessed the influence of maternal P. falciparum infection on fetal myeloid dendritic cells (mDC) and plasmacytoid dendritic cells (pDC), analyzing the cord blood of offspring of Gabonese mothers with different infection histories. Cord blood from newborns of mothers with malarial infection at delivery had significantly more mDC than that from nonexposed newborns (P = 0.028) but mDC and pDC HLA-DR expression was unrelated to maternal infection history. Independently of these findings, cord blood mDC and pDC numbers declined significantly as a function of increasing maternal age (P = 0.029 and P = 0.033, respectively). The inducible antigen-specific interleukin-10-producing regulatory-type T-cell population that we have previously detected in cord blood of newborns with prolonged in utero exposure to P. falciparum may directly reflect the altered DC numbers in such neonates, while the maintenance of cord blood DC HLA-DR expression contrasts with that of DC from P. falciparum malaria patients.
Vascular endothelial growth factor (VEGF) is a potent stimulator of vascular angiogenesis, permeability, and remodeling that also plays important roles in wound healing and tissue cytoprotection. To begin to define the roles of VEGF in diseases like asthma and COPD, we characterized the effects of lung-targeted transgenic VEGF165 and defined the innate immune pathways that regulate VEGF tissue responses. The former studies demonstrated that VEGF plays an important role in Th2 inflammation because, in addition to stimulating angiogenesis and edema, VEGF induced eosinophilic inflammation, mucus metaplasia, subepithelial fibrosis, myocyte hyperplasia, dendritic cell activation, and airways hyperresponsiveness via IL-13–dependent and -independent mechanisms. VEGF was also produced at sites of aeroallergen-induced Th2 inflammation, and VEGF receptor blockade ameliorated adaptive Th2 inflammation and Th2 cytokine elaboration. The latter studies demonstrated that activation of the RIG-like helicase (RLH) innate immune pathway using viral pathogen–associated molecular patterns such as Poly(I:C) or viruses ameliorated VEGF-induced tissue responses. In accord with these findings, Poly(I:C)-induced RLH activation also abrogated aeroallergen-induced Th2 inflammation. When viewed in combination, these studies suggest that VEGF excess can contribute to the pathogenesis of Th2 inflammatory disorders such as asthma and that abrogation of VEGF signaling via RLH activation can contribute to the pathogenesis of viral disorders such as virus-induced COPD exacerbations. They also suggest that RLH activation may be a useful therapeutic strategy in asthma and related disorders.
asthma; chronic obstructive pulmonary disease; virus; RIG-like helicase; mitochondrial antiviral signaling molecule
Vascular endothelial growth factor (VEGF), a substance that stimulates new blood vessel formation, is an important survival factor for endothelial cells. Although overexpressed VEGF in the lung induces pulmonary edema with increased lung vascular permeability, the role of VEGF in the development of acute lung injury remains to be determined.
To evaluate the role of VEGF in the pathogenesis of acute lung injury, we first evaluated the effects of exogenous VEGF and VEGF blockade using monoclonal antibody on LPS-induced lung injury in mice. Using the lung specimens, we performed TUNEL staining to detect apoptotic cells and immunostaining to evaluate the expression of apoptosis-associated molecules, including caspase-3, Bax, apoptosis inducing factor (AIF), and cytochrome C. As a parameter of endothelial permeability, we measured the albumin transferred across human pulmonary artery endothelial cell (HPAEC) monolayers cultured on porous filters with various concentrations of VEGF. The effect of VEGF on apoptosis HPAECs was also examined by TUNEL staining and active caspase-3 immunoassay.
Exogenous VEGF significantly decreased LPS-induced extravascular albumin leakage and edema formation. Treatment with anti-VEGF antibody significantly enhanced lung edema formation and neutrophil emigration after intratracheal LPS administration, whereas extravascular albumin leakage was not significantly changed by VEGF blockade. In lung pathology, pretreatment with VEGF significantly decreased the numbers of TUNEL positive cells and those with positive immunostaining of the pro-apoptotic molecules examined. VEGF attenuated the increases in the permeability of the HPAEC monolayer and the apoptosis of HPAECs induced by TNF-α and LPS. In addition, VEGF significantly reduced the levels of TNF-α- and LPS-induced active caspase-3 in HPAEC lysates.
These results suggest that VEGF suppresses the apoptosis induced by inflammatory stimuli and functions as a protective factor against acute lung injury.
Non-human primates such as Chinese rhesus macaques (Ch Rhs) provide good animal models for research on human infectious diseases. Similar to humans, there are two principal subsets of dendritic cells (DCs) in the peripheral blood of Ch Rhs: myeloid DCs (mDCs) and plasmacytoid DCs (pDCs). In this study, two-color fluorescence-activated cell sorting (FACS) analyses were used to identify the main DC subsets, namely CD1c+ mDCs and pDCs from Ch Rhs. Then, the apoptosis and immunophenotype changes of DCs subsets were first described during the acute phase of SIVmac239 infection. Both the DCs subsets showed decreased CD4 expression and enhanced CCR5 expression; in particular, those of pDCs significantly changed at most time points. Interestingly, the plasma viral loads were negatively correlated with CD4 expression, but were positively correlated with CCR5 expression of pDCs. During this period, both CD1c+ mDCs and pDCs were activated by enhancing expressions of co-stimulatory molecules, accompanied with increase in CCR7. Either CD80 or CD86 expressed on CD1c+ mDCs and pDCs was positively correlated with the plasma viral loads. Our analysis demonstrates that the pDCs were more prone to apoptosis after infection during the acute phase of SIVmac239 infection, which may be due to their high expressions of CD4 and CCR5. Both DCs subsets activated through elevating the expression of co-stimulatory molecules, which was beneficial in controlling the replication of SIV. However, a mere broad immune activation initiated by activated DCs may lead to tragic AIDS progression.
Vascular endothelial growth factor (VEGF)-D, a member of the VEGF family, induces both angiogenesis and lymphangiogenesis by activating VEGF receptor-2 (VEGFR-2) and VEGFR-3 on the surface of endothelial cells. Transforming growth factor (TGF)-β1 has been shown to stimulate VEGF-A expression in human lung fibroblast via the Smad3 signaling pathway and to induce VEGF-C in human proximal tubular epithelial cells. However, the effects of TGF-β1 on VEGF-D regulation are unknown. To investigate the regulation of VEGF-D, human lung fibroblasts were studied under pro-fibrotic conditions in vitro and in idiopathic pulmonary fibrosis (IPF) lung tissue. We demonstrate that TGF-β1 downregulates VEGF-D expression in a dose- and time-dependent manner in human lung fibroblasts. This TGF-β1 effect can be abolished by inhibitors of TGF-β type I receptor kinase and Jun NH2-terminal kinase (JNK), but not by Smad3 knockdown. In addition, VEGF-D knockdown in human lung fibroblasts induces G1/S transition and promotes cell proliferation. Importantly, VEGF-D protein expression is decreased in lung homogenates from IPF patients compared with control lung. In IPF lung sections, fibroblastic foci show very weak VEGF-D immunoreactivity, whereas VEGF-D is abundantly expressed within alveolar interstitial cells in control lung. Taken together, our data identify a novel mechanism for downstream signal transduction induced by TGF-β1 in lung fibroblasts, through which they may mediate tissue remodeling in IPF.
APC dysfunction has been postulated to mediate some of the parasite-specific T cell unresponsiveness seen in patent filarial infection. We have shown that live microfilariae of Brugia malayi induce caspase-dependent apoptosis in human monocyte-derived dendritic cells (DCs) in vitro. This study addresses whether apoptosis observed in vitro extends to patent filarial infections in humans and is reflected in the number of circulating myeloid DCs (mDCs; CD11c−CD123lo) in peripheral blood of infected microfilaremic individuals. Utilizing flow cytometry to identify DC subpopulations (mDCs and plasmacytoid DCs [pDCs]) based on expression of CD11c and CD123, we found a significant increase in numbers of circulating mDCs (CD11c+CD123lo) in filaria-infected individuals compared with uninfected controls from the same filaria-endemic region of Mali. Total numbers of pDCs, monocytes, and lymphocytes did not differ between the two groups. To investigate potential causes of differences in mDC numbers between the two groups, we assessed chemokine receptor expression on mDCs. Our data indicate that filaria-infected individuals had a lower percentage of circulating CCR1+ mDCs and a higher percentage of circulating CCR5+ mDCs and pDCs. Finally, live microfilariae of B. malayi were able to downregulate cell-surface expression of CCR1 on monocyte-derived DCs and diminish their calcium flux in response to stimulation by a CCR1 ligand. These findings suggest that microfilaria are capable of altering mDC migration through downregulation of expression of some chemokine receptors and their signaling functions. These observations have major implications for regulation of immune responses to these long-lived parasites.
Gene expression in murine dendritic cells (DCs) infected with green fluorescent protein-expressing Salmonella enterica serovar Typhimurium BRD509 was studied by mRNA differential display. Infected DCs were sorted from uninfected cells by flow cytometry. The mRNA expression patterns of infected and uninfected cells revealed a number of differentially expressed transcripts, which included the macrophage-derived chemokine (MDC). Up-regulation of MDC transcription in infected DCs was confirmed by Northern blotting, and the kinetics of MDC expression was examined by real-time reverse transcription-PCR, with which 31- and 150-fold increases were detected at 2 and 6 h postinfection, respectively. The increased release by DCs of MDC into culture media was detected by an enzyme-linked immunosorbent assay. The biological activity of MDC was investigated in in vitro and in vivo assays. In vitro, supernatants from S. enterica serovar Typhimurium-infected DCs were chemoattractive to T cells, and neutralization of MDC in these supernatants inhibited T-cell migration. Passive transfer of anti-MDC antibody to mice infected with BRD509 revealed that neither growth of the bacterium nor resistance of the mice to reinfection was affected and that in vivo inhibition of MDC did not affect T-cell responses, as measured by the gamma interferon ELISPOT method 3 days after challenge infection.
Thymic stromal lymphopoietin (TSLP) has been reported to activate myeloid dendritic cells (mDCs) to induce Th2 T lymphocyte responses. Its effect on plasmacytoid dendritic cells (pDCs) with TLR ligands has not yet been studied. We investigated the effects of TSLP and TLR ligands on mDCs and pDCs subsets.
Myeloid dendritic cells (mDC) and plasmacytoid dendritic cells (pDC) were stimulated by TLR ligands (mDC with TLR1/2 LTA, TLR2 PGN, TLR3 poly I: C, TLR4 LPS, TLR5 Flagellin) (pDC with TLR9 CpG2006, CpG 2216, TLR7 loxoribine) in the presence or absence of TSLP. Supernatants from mDCs and pDCs were analyzed for cytokine production. mDCs and pDCs were collected and cultured with allogeneic naïve T cells and after 7 days of co-culture. DC-primed CD4+ T cells were washed and restimulated with PMA and ionomycin. Cytokine production in supernatants from restimulated cells - IL-4, IL-5, IL-10, IL-13, TNF-α was analyzed by Luminex.
TSLP alone induced the expression of maturation markers on mDCs and increased their ability to polarize lymphocytes into the Th2 phenotype. We demonstrated that pDCs also have the capacity to become even more potent inducers of Th2 immune responses, but only after combined treatment with TSLP and TLR ligands, particularly with TLR9 ligand CpG 2006.
TSLP plays a major role in Th2 polarization of immune response mediated by myeloid DCs. Here, we demonstrate that plasmacytoid DCs, exposed to TSLP together with TLR ligands, acquire significant potential towards Th2 polarization.
dendritic cell; T cell; allergy; TLR ligand
Prostaglandin I2 (PGI2) analog is regarded as a potential candidate for treating asthma. Human myeloid dendritic cells (mDCs) play a critical role in the pathogenesis of asthma. However, the effects of PGI2 analog on human mDCs are unknown. In the present study, circulating mDCs were isolated from six healthy subjects. The effects of PGI2 analogs iloprost and treprostinil on cytokine production, maturation and T-cell stimulatory function of human mDCs were investigated. Tumor necrosis factor (TNF)-α and interleukin (IL)-10 were measured by enzyme-linked immunosorbent assay. The expression of costimulatory molecules was investigated by flow cytometry. T-cell stimulatory function was investigated by measuring interferon (IFN)-γ, IL-13 and IL-10 production by T cells cocultured with iloprost-treated mDCs. Intracellular signaling was investigated by Western blot and chromatin immunoprecipitation. We found that iloprost and treprostinil induced IL-10, but suppressed TNF-α production in polyinosinic-polycytidylic acid (poly I:C)-stimulated mDCs. This effect was reversed by the I-prostanoid (IP), E-prostanoid (EP) receptor antagonists or intracellular free calcium (Ca2+) chelator. Forskolin, an adenyl cyclase activator, conferred a similar effect. Iloprost and treprostinil increased intracellular adenosine 3′,5′-cyclic monophosphate (cAMP) levels, and iloprost also increased intracellular Ca2+. Iloprost suppressed poly I:C-induced mitogen-activated protein kinase (MAPK) phospho-p38 and phospho–activating transcription factor (ATF)2 expression. Iloprost downregulated poly I:C-induced histone H3K4 trimethylation in the TNFA gene promoter region via suppressing translocation of histone 3 lysine 4 (H3K4)-specific methyltransferases MLL (mixed lineage leukemia) and WDR5 (WD repeat domain 5). Iloprost-treated mDCs inhibited IL-13, IFN-γ and IL-10 production by T cells. In conclusion, PGI2 analogs enhance IL-10 and suppress TNF-α expression through the IP/EP2/EP4 receptors–cAMP and EP1 receptor–Ca2+ pathway. Iloprost suppressed TNF-α expression via the MAPK-p38-ATF2 pathway and epigenetic regulation by downregulation of histone H3K4 trimethylation.
Myeloid and plasmacytoid dendritic cells (mDCs, pDC) are crucial to the immune system, detecting microorganisms and linking the innate and adaptive immunity. pDC are present in small quantities in tissues that are in contact with the external environment; mainly the skin, the inner lining of the nose, lungs, stomach and intestines. They produce large amounts of IFN-α after stimulation and are pivotal for the induction of antiviral responses. Chronic obstructive pulmonary disease (COPD) patients are known to be more susceptible to viral infections. We have demonstrated that exposure of mDC to cigarette smoke extract (CSE) leads to the release of chemokines, however, not much is known about the role of pDC in COPD. In this study, we addressed several key questions with respect to the mechanism of action of CSE on human pDC in an in vitro model. Human pDCs were isolated from normal healthy volunteers and subjected to fresh CSE and the levels of IL-8, TNF-α, IP-10, IL-6, IL-1, IL-12 and IL-10 and IFN-α were studied by both ELISA and real time PCR methods. We observed that CSE augmented the production of IL-8 and suppressed the release of TNF-α, IL-6 and IFN-α. Moreover, CSE suppressed PI3K/Akt signalling in pDC. In conclusion, our data indicate that CSE has both the potential to diminish anti-viral immunity by downregulating the release of IFN-α and other pro-inflammatory cytokines while, at the same time, augmenting the pathogenesis of COPD via an IL-8 induced recruitment of neutrophils.
Rationale: Dendritic cells (DCs) have not been well studied in chronic obstructive pulmonary disease (COPD), yet their integral role in activating and differentiating T cells makes them potential participants in COPD pathogenesis.
Objectives: To determine the expression of maturation molecules by individual DC subsets in relationship to COPD stage and to expression of the acute activation marker CD69 by lung CD4+ T cells.
Methods: We nonenzymatically released lung leukocytes from human surgical specimens (n = 42) and used flow cytometry to identify three DC subsets (mDC1, mDC2, and pDC) and to measure their expression of three costimulatory molecules (CD40, CD80 and CD86) and of CD83, the definitive marker of DC maturation. Spearman nonparametric correlation analysis was used to identify significant correlations between expression of DC maturation molecules and COPD severity.
Measurements and Main Results: Expression of CD40 by mDC1 and mDC2 and of CD86 by mDC2 was high regardless of GOLD stage, but CD80 and CD83 on these two DC subsets increased with disease progression. pDC also showed significant increases in expression of CD40 and CD80. Expression of all but one of the DC molecules that increased with COPD severity also correlated with CD69 expression on lung CD4+ T cells from the same patients, with the exception of CD83 on mDC2.
Conclusions: This cross-sectional study implies that COPD progression is associated with significant increases in costimulatory molecule expression by multiple lung DC subsets. Interactions with lung DCs may contribute to the immunophenotype of CD4+ T cells in advanced COPD.
Clinical trial registered with www.clinicaltrials.gov (NCT00281229).
human; flow cytometry; B70 costimulatory molecules; CD69 antigen; CD4+; T lymphocytes
Plasmacytoid dendritic cells (pDC) have both stimulatory and regulatory effects on T cells. pDCs are a major CNS-infiltrating DC population during experimental autoimmune encephalomyelitis (EAE), but unlike myeloid DCs (mDC) have a minor role in T cell activation and epitope spreading. We show that depletion of pDCs during either the acute or relapse phases of EAE resulted in exacerbation of disease severity. pDC depletion significantly enhanced CNS but not peripheral CD4+ T cell activation, as well as IL-17 and IFN-γ production. Moreover, CNS pDCs suppressed CNS mDC-driven production of IL-17, IFN-γ and IL-10 in an IDO-independent manner. The data demonstrate that pDCs play a critical regulatory role in negatively regulating pathogenic CNS CD4+ T cell responses highlighting a new role for pDCs in inflammatory autoimmune disease.
Autoimmune disease; T lymphocytes; dendritic cells; T cell activation; antigen presentation; immunoregulation
Vascular endothelial growth factor (VEGF) is a main angiogenic factor which is known to be upregulated in lung cancer. In the present study, it was demonstrated that sanguinarine, an alkaloid obtained from the bloodroot plant, markedly repressed the VEGF-induced tube formation of human microvascular endothelial cells (HMVECs) and the migration of human A549 lung cancer cells. Furthermore, sanguinarine decreased VEGF secretion and expression in HMVECs and A549 lung cancer cells in a dose- and time-dependent manner. Additionally, sanguinarine inhibited the activation of serum starvation- and hypoxia-induced VEGF promoter activity. Sanguinarine also inhibited the VEGF-mediated Akt and p38 activation, as well as VE-cadherin protein phosphorylation. To the best of our knowledge, this is the first study demonstrating that VEGF inhibition appears to be an important mechanism involved in the antiangiogenic and anti-invasive activities of sanguinarine in lung cancer treatment.
sanguinarine; vascular endothelial growth factor; human microvascular endothelial cells; lung cancer cells
Vascular endothelial growth factor (VEGF) produced by tumor cells plays a central role in stimulating angiogenesis required for tumor growth. Humanized monoclonal anti-VEGF antibody (bevacizumab, Avastin®), approved as a treatment for non-squamous, non-small cell lung cancer, requires administration every 3 wk. We hypothesized that an intrapleural administration of an adeno-associated virus (AAV) vector expressing an anti-VEGF-A antibody equivalent of bevacizumab would result in sustained anti-VEGF-A localized expression within the lung and suppress metastatic tumor growth. The AAV vector AAVrh.10αVEGF encodes the light chain and heavy chain cDNAs of monoclonal antibody A.4.6.1, a murine antibody that specifically recognizes human VEGF-A with the same antigen-binding site as bevacizumab. A metastatic lung tumor model was established in SCID mice by intravenous administration of human DU145 prostate carcinoma cells. Intrapleural administration of AAVrh.10αVEGF directed long term expression of the anti-human VEGF-A antibody in lung, as demonstrated by sustained, high level anti-human VEGF titers in lung epithelial lining fluid for 40 wk, the duration of the study. In the AAVrh.10αVEGF-treated animals, tumor growth was significantly suppressed (p<0.05), the numbers of blood vessels and mitotic nuclei in the tumor was decreased (p<0.05), and there was increased survival (p<0.05). Thus, intrapleural administration of an AAVrh.10 vector encoding a murine monoclonal antibody equivalent of bevacizumab, effectively suppresses the growth of metastatic lung tumors, suggesting AAV-mediated gene transfer to the pleura to deliver bevacizumab locally to the lung as a novel alternative platform to conventional monoclonal antibody therapy.
Alpha/beta interferons (IFN-α/β) are key mediators of innate immunity and important modulators of adaptive immunity. The mechanisms by which IFN-α/β are induced are becoming increasingly well understood. Recent studies showed that Toll-like receptors 7 and 8 expressed by plasmacytoid dendritic cells (pDCs) mediate the endosomal recognition of incoming viral RNA genomes, a process which requires myeloid differentiation factor 88 (MyD88). Here we investigate the requirements for virus-induced IFN-α/β production in cultures of bone marrow-derived murine myeloid DCs (mDCs). Using recombinant Semliki Forest virus blocked at different steps in the viral life cycle, we show that replication-defective virus induced IFN-α/β in mDCs while fusion-defective virus did not induce IFN-α/β. The response to replication-defective virus was largely intact in MyD88−/− mDC cultures but was severely reduced in mDC cultures from mice lacking IFN regulatory factor 3. Our observations suggest that mDCs respond to incoming virus via a pathway that differs from the fusion-independent, MyD88-mediated endosomal pathway described for the induction of IFN-α/β in pDCs. We propose that events during or downstream of viral fusion, but prior to replication, can activate IFN-α/β in mDCs. Thus, mDCs may contribute to the antiviral response activated by the immune system at early time points after infection.
Dendritic cells (DCs) are professional antigen-presenting cells that play a crucial role in the initiation and modulation of immune responses. Human circulating blood DCs are divided into two major subsets: myeloid DCs (mDCs); and plasmacytoid DCs (pDCs). Furthermore, mDCs are subdivided into two subsets: Th1-promoting mDCs (mDC1s); and Th2-promoting mDCs (mDC2s). Although CD1a, CD1c, and CD141 are generally used for classifying mDC subsets, their adequacy as a specific marker remains unclear. We performed this study to compare circulating mDC, pDC, mDC1, and mDC2 subsets between Th1- and Th2-mediated diseases using CD1a and CD141, and to analyze the adequacy of CD1a and CD141 as a marker for mDC1s and mDC2s, respectively.
Thirty patients with sarcoidosis, 23 patients with atopic diseases, such as atopic bronchial asthma, and 23 healthy subjects as controls were enrolled in this study. Peripheral blood DC subsets were analyzed with flow cytometry according to expressions of CD11c, CD123, CD1a, and CD141. For functional analysis, we measured interleukin (IL) 12p40 levels produced by the sorted mDC subsets.
The sarcoidosis group showed decreased total DC (P < 0.05) and mDC counts (P < 0.05) compared to controls. The atopy group showed decreased CD1a+mDC count (P < 0.05), and increased CD1a-mDC count (P < 0.05) compared to controls. CD141+mDC count in the atopy group was higher than controls (P < 0.05). Sorted CD1a+mDCs produced higher levels of IL-12p40 than CD1a-mDCs (P = 0.025) and CD141+mDCs (P = 0.018).
We conclude that decreased count of CD1a+mDC and increased count of CD141+mDC may reflect the Th2-skewed immunity in atopic diseases. The results of IL-12 levels produced by the sorted mDC subsets suggested the adequacy of CD1a and CD141 as a marker for mDC1 and mDC2, respectively, in vivo.
Dendritic cells; Peripheral blood; Sarcoidosis; Myeloid DC (mDC); CD1a; CD141