Chemokines and their role in airway hyper-reactivity

Airway hyper-reactivity is a characteristic feature of many inflammatory lung diseases and is defined as an exaggerated degree of airway narrowing. Chemokines and their receptors are involved in several pathological processes that are believed to contribute to airway hyper-responsiveness, including recruitment and activation of inflammatory cells, collagen deposition and airway wall remodeling. These proteins are therefore thought to represent important therapeutic targets in the treatment of airway hyper-responsiveness. This review highlights the processes thought to be involved in airway hyper-responsiveness in allergic asthma, and the role of chemokines in these processes. Overall, the application of chemokines to the prevention or treatment of airway hyper-reactivity has tremendous potential

NUDT2 Disruption Elevates Diadenosine Tetraphosphate (Ap4A) and Down-Regulates Immune Response and Cancer Promotion Genes.

Regulation of gene expression is one of several roles proposed for the stress-induced nucleotide diadenosine tetraphosphate (Ap4A). We have examined this directly by a comparative RNA-Seq analysis of KBM-7 chronic myelogenous leukemia cells and KBM-7 cells in which the NUDT2 Ap4A hydrolase gene had been disrupted (NuKO cells), causing a 175-fold increase in intracellular Ap4A. 6,288 differentially expressed genes were identified with P < 0.05. Of these, 980 were up-regulated and 705 down-regulated in NuKO cells with a fold-change ≥ 2. Ingenuity® Pathway Analysis (IPA®) was used to assign these genes to known canonical pathways and functional networks. Pathways associated with interferon responses, pattern recognition receptors and inflammation scored highly in the down-regulated set of genes while functions associated with MHC class II antigens were prominent among the up-regulated genes, which otherwise showed little organization into major functional gene sets. Tryptophan catabolism was also strongly down-regulated as were numerous genes known to be involved in tumor promotion in other systems, with roles in the epithelial-mesenchymal transition, proliferation, invasion and metastasis. Conversely, some pro-apoptotic genes were up-regulated. Major upstream factors predicted by IPA® for gene down-regulation included NFκB, STAT1/2, IRF3/4 and SP1 but no major factors controlling gene up-regulation were identified. Potential mechanisms for gene regulation mediated by Ap4A and/or NUDT2 disruption include binding of Ap4A to the HINT1 co-repressor, autocrine activation of purinoceptors by Ap4A, chromatin remodeling, effects of NUDT2 loss on transcript stability, and inhibition of ATP-dependent regulatory factors such as protein kinases by Ap4A. Existing evidence favors the last of these as the most probable mechanism. Regardless, our results suggest that the NUDT2 protein could be a novel cancer chemotherapeutic target, with its inhibition potentially exerting strong anti-tumor effects via multiple pathways involving metastasis, invasion, immunosuppression and apoptosis

Mechanisms of interleukin 1β-induced human airway smooth muscle hyporesponsiveness to histamine: Involvement of p38 MAPK and NF-κB

We have investigated the effect of IL-1β on histamine H 1-receptor (H 1R)-mediated inositol phosphate (IP) accumulation in human airway smooth muscle cells (HASMC) and on histamine-induced contraction of human bronchial rings. Stimulation of HASMC for 24 h with IL-1β resulted in significant loss of histamine-induced IP formation, which was associated with a reduction of histamine-induced contraction of IL-1β-treated human bronchial rings. An inhibitor of NF-κB activation, pyrrolidine dithiocarbamate, and a p38 MAPK inhibitor, blocked the IL-1β-induced H 1R desensitization, whereas anisomycin, an SAPK/JNK and p38 MAPK activator, mimicked the effect of IL-1β. IL-1β has been demonstrated to induce cox-2 expression and PGE 2 synthesis. In our study, indomethacin a cox antagonist, completely inhibited the effect of IL-1β on H 1R, whereas exogenously added PGE 2 was able to desensitize H 1R. Furthermore, H-89, a selective PKA inhibitor, antagonized the effect of IL-1β. Here, we have demonstrated that IL-1β desensitizes H 1R, which involves the activation of p38 MAPK and NF-κB, leading to the expression of cox-2 and the synthesis of PGE 2. PGE 2 increases intracellular cAMP resulting in PKA activation, which phosphorylates and functionally uncouples H 1R. Our results suggest that IL-1β protects airway smooth muscle against histamine-induced contractile responses and that bronchial hyperreactivity to histamine is not associated with proinflammatory cytokine-induced enhancement in H 1R signaling.link_to_subscribed_fulltex

Tdp2: A Means to Fixing the Ends

Tdp2: A Means to Fixing the End

A human 5'-tyrosyl DNA phosphodiesterase that repairs topoisomerase-mediated DNA damage

Topoisomerases regulate DNA topology and are fundamental to many aspects of chromosome metabolism1, 2. Their activity involves the transient cleavage of DNA, which, if it occurs near sites of endogenous DNA damage or in the presence of topoisomerase poisons, can result in abortive topoisomerase-induced DNA strand breaks3, 4, 5. These breaks feature covalent linkage of the enzyme to the DNA termini by a 3'- or 5'-phosphotyrosyl bond and are implicated in hereditary human disease6, 7, 8, chromosomal instability and cancer4, 9, and underlie the clinical efficacy of an important class of anti-tumour poisons3, 9, 10. The importance of liberating DNA termini from trapped topoisomerase is illustrated by the progressive neurodegenerative disease observed in individuals containing a mutation in tyrosyl-DNA phosphodiesterase1 (TDP1), an enzyme that cleaves 3'-phosphotyrosyl bonds6, 7, 8. However, a complementary human enzyme that cleaves 5'-phosphotyrosyl bonds has not been reported, despite the effect of DNA double-strand breaks containing such termini on chromosome instability and cancer6, 7, 8. Here we identify such an enzyme in human cells and show that this activity efficiently restores 5'-phosphate termini at DNA double-strand breaks in preparation for DNA ligation. This enzyme, TTRAP, is a member of the Mg2+/Mn2+-dependent family of phosphodiesterases. Cellular depletion of TTRAP results in increased susceptibility and sensitivity to topoisomerase-II-induced DNA double-strand breaks. TTRAP is, to our knowledge, the first human 5'-tyrosyl DNA phosphodiesterase to be identified, and we suggest that this enzyme is denoted tyrosyl DNA phosphodiesterase-2 (TDP2)

Ca²⁺-signaling in airway smooth muscle cells is altered in T-bet knock-out mice

<p>Abstract</p> <p>Background</p> <p>Airway smooth muscle cells (ASMC) play a key role in bronchial hyperresponsiveness (BHR). A major component of the signaling cascade leading to ASMC contraction is calcium. So far, agonist-induced Ca²⁺-signaling in asthma has been studied by comparing innate properties of inbred rat or mouse strains, or by using selected mediators known to be involved in asthma. T-bet knock-out (KO) mice show key features of allergic asthma such as a shift towards T_H2-lymphocytes and display a broad spectrum of asthma-like histological and functional characteristics. In this study, we aimed at investigating whether Ca²⁺-homeostasis of ASMC is altered in T-bet KO-mice as an experimental model of asthma.</p> <p>Methods</p> <p>Lung slices of 100 to 200 μm thickness were obtained from T-bet KO- and wild-type mice. Airway contraction in response to acetylcholine (ACH) was measured by video-microscopy and Ca²⁺-signaling in single ASMC of lung slices was assessed using two-photon-microscopy.</p> <p>Results</p> <p>Airways from T-bet KO-mice showed increased baseline airway tone (BAT) and BHR compared to wild-type mice. This could be mimicked by incubation of lung slices from wild-type mice with IL-13. The increased BAT was correlated with an increased incidence of spontaneous changes in intracellular Ca²⁺-concentrations, whereas BHR correlated with higher ACH-induced Ca²⁺-transients and an increased proportion of ASMC showing Ca²⁺-oscillations. Emptying intracellular Ca²⁺-stores using caffeine or cyclopiazonic acid induced higher Ca²⁺-elevations in ASMC from T-bet KO- compared to wild-type mice.</p> <p>Conclusion</p> <p>Altered Ca²⁺-homeostasis of ASMC contributes to increased BAT and BHR in lung slices from T-bet KO-mice as a murine asthma model. We propose that a higher Ca²⁺-content of the intracellular Ca²⁺-stores is involved in the pathophysiology of these changes.</p