Plasmacytoid dendritic cells (pDCs) play essential roles in directing immune responses. These cells may be particularly important in determining the nature of immune responses to viral infections in patients with allergic asthma as well those with other atopic diseases. The purposes of this study were 1) to compare the functional capacity of pDCs in patients with one type of allergic disorder, allergic asthma, and controls; 2) to determine whether IgE cross-linking affects antiviral responses of influenza-exposed pDCs; and 3) to determine whether evidence of counterregulation of FcεRIα and IFN-α pathways exists in these cells. pDC function was assessed in a subset of asthma patients and in controls by measuring IFN-α production after exposure of purified pDCs to influenza viruses. FcεRIα expression on pDCs was determined by flow cytometry in blood samples from patients with allergic asthma and controls. pDCs from patients with asthma secreted significantly less IFN-α upon exposure to influenza A (572 versus 2815; p = 0.03), and secretion was inversely correlated with serum IgE levels. Moreover, IgE cross-linking prior to viral challenge resulted in 1) abrogation of the influenza-induced pDC IFN-α response; 2) diminished influenza and gardiquimod-induced TLR-7 upregulation in pDCs; and 3) interruption of influenza-induced upregulation of pDC maturation/costimulatory molecules. In addition, exposure to influenza and gardiquimod resulted in upregulation of TLR-7, with concomitant downregulation of FcεRIα expression in pDCs. These data suggest that counterregulation of FcεRI and TLR-7 pathways exists in pDCs, and that IgE cross-linking impairs pDC antiviral responses.

Multidimensional cancer genome analysis and validation has defined Quaking (QKI), a member of the signal transduction and activation of RNA (STAR) family of RNA-binding proteins, as a novel glioblastoma multiforme (GBM) tumor suppressor. Here, we establish that p53 directly regulates QKI gene expression, and QKI protein associates with and leads to the stabilization of miR-20a; miR-20a, in turn, regulates TGFβR2 and the TGFβ signaling network. This pathway circuitry is substantiated by in silico epistasis analysis of its components in the human GBM TCGA (The Cancer Genome Atlas Project) collection and by their gain- and loss-of-function interactions in in vitro and in vivo complementation studies. This p53–QKI–miR-20a–TGFβ pathway expands our understanding of the p53 tumor suppression network in cancer and reveals a novel tumor suppression mechanism involving regulation of specific cancer-relevant microRNAs.

Diesel exhaust particles (DEP) have been shown to alter pulmonary immune responses to bacterial infection. Exposure of rats to 100 mg/m(3) DEP for 4 h was found to aggravate Listeria monocytogenes(Listeria) infection at 3 days postinfection, but the bacteria were largely cleared at 7 days postinfection due to the development of a strong T cell-mediated immunity. In the present study, we examined the effects of repeated DEP exposure at lower doses on pulmonary responses to bacterial infection. Brown Norway rats were exposed to DEP by inhalation at 20.62 +/- 1.31 mg/m 3 for 4 h/day for 5 days, followed by intratracheal inoculation with 100,000 Listeria at 2 h after the last DEP exposure. DEP-exposed rats showed a significant increase in lung bacterial load at both 3 and 7 days postinfection. The repeated DEP exposure was shown to suppress both the innate, orchestrated by alveolar macrophages (AM), and T cell-mediated responses to Listeria. DEP inhibited AM production of interleukin- (IL-) 1beta, tumor necrosis factor- (TNF-) alpha, and IL-12 but enhanced Listeria-induced AM production of IL-10, which has been shown to prolong the survival of intracellular pathogens such as Listeria. DEP exposure also suppressed the development of bacteria-specific lymphocytes from lung-draining lymph nodes, as indicated by the decreased numbers of T lymphocytes and their CD4(+) and CD8(+) subsets. Furthermore, the DEP exposure markedly inhibited the Listeria-induced lymphocyte secretion of IL-2 at day 7, IL-10 at days 3 and 7, and interferon- (IFN-) gamma at days 3 to 10 postinfection when compared to air-exposed controls. These results show a sustained pattern of downregulation of T cell-mediated immune responses by repeated low-dose DEP exposure, which is different from the results of a single high-dose exposure where the acute effect of DEP aggravated bacteria infection but triggered a strong T cell-mediated immunity.

We have previously demonstrated that exposure to diesel exhaust particles (DEP) prior to ovalbumin (OVA) sensitization in rats reduced OVA-induced airway inflammation. In the present study, Brown Norway rats were first sensitized to OVA (42.3 +/- 5.7 mg/m3) for 30 min on days 1, 8, and 15, then exposed to filtered air or DEP (22.7 +/- 2.5 mg/m3) for 4 h/day on days 24-28, and challenged with OVA on day 29. Airway responsiveness was examined on day 30, and animals were sacrificed on day 31. Ovalbumin sensitization and challenge resulted in a significant infiltration of neutrophils, lymphocytes, and eosinophils into the lung, elevated presence of CD4+ and CD8+ T lymphocytes in lung draining lymph nodes, and increased production of serum OVA-specific immunoglobulin (Ig)E and IgG. Diesel exhaust particles pre-exposure augmented OVA-induced production of allergen-specific IgE and IgG and pulmonary inflammation characterized by marked increases in T lymphocytes and infiltration of eosinophils after OVA challenge, whereas DEP alone did not have these effects. Although OVA-sensitized rats showed modest response to methacholine challenge, it was the combined DEP and OVA exposure that produced significant airway hyperresponsiveness in this animal model. The effect of DEP pre-exposure on OVA-induced immune responses correlated with an interactive effect of DEP with OVA on increased production of reactive oxygen species (ROS) and nitric oxide (NO) by alveolar macrophages (AM) and alveolar type II (ATII) cells, NO levels in bronchoalveolar lavage fluid, the induction of inducible NO synthase expression in AM and ATII cells, and a depletion of total intracellular glutathione (GSH) in AM and lymphocytes. These results show that DEP pre-exposure exacerbates the allergic responses to the subsequent challenge with OVA in OVA-sensitized rats. This DEP effect may be, at least partially, attributed to the elevated generation of ROS in AM and ATII cells, a depletion of GSH in AM and lymphocytes, and an increase in AM and ATII cell production of NO.

Exposure to diesel exhaust particles (DEP) was shown to increase the susceptibility of the lung to bacterial infection in rats. In this study, the effects of DEP on alveolar macrophage (AM) phagocytic and bactericidal functions and cytokine secretion by AM and lymphocytes in response to Listeria monocytogenes infection were investigated in vitro and the roles of different DEP components in these processes were compared. Exposure to DEP or the organic extracts of DEP (eDEP) significantly decreased the phagocytosis and killing of L. monocytogenes by AM obtained from normal rats. Washed DEP (wDEP) also decreased AM phagocytosis and bacterial killing to a lesser extent, whereas carbon black (CB) reduced AM phagocytosis but had no significant effect on AM bactericidal activity. DEP or eDEP concentration-dependently suppressed L. monocytogenes-induced secretion of tumor necrosis factor-alpha, interleukin (IL)-1beta, and IL-12 by AM and of IL-2 and interferon-gamma by lymphocytes obtained from L. monocytogenes-infected rats, but augmented the AM secretion of IL-10. wDEP or CB, however, exerted little or no effect on these L. monocytogenes-induced cytokines. These results provide direct evidence that DEP, through the actions of organic components, suppresses AM phagocytic and bactericidal functions in vitro. Inhibition of AM phagocytic function and alterations of AM and lymphocyte cytokine secretion by DEP and DEP organic compounds may be implicated in the diminished AM bactericidal activity and the lymphatic arm of the host immune system, thus resulting in an suppressed pulmonary clearance of L. monocytogenes and an increased susceptibility of the lung to bacterial infection.