Proteolytic Activity Present in House-Dust-Mite Extracts Degrades ENA-78/CXCL5 and Reduces Neutrophil Migration.

Background. Bronchial smooth muscle cells (BSMC) are a major source of proinflammatory and proangiogenic cytokines and chemokines, including VEGF and CXC-chemokines. CXC-chemokines act primarily on neutrophils, mediating their recruitment to and activation at the site of inflammation. In humans, house-dust mite (HDM) allergens can cause asthmatic exacerbations and trigger an inflammatory response through protease-dependent mechanisms. Objective. We investigated the effect HDM extract on the release of pro-angiogenic and proinflammatory cytokines from BSMC. Methods. Human primary BSMC were stimulated with HDM extract in the absence or presence of fetal calf serum (FCS). Twenty angiogenic cytokines were detected by a specific antibody array and modified protein levels were confirmed by ELISA. Neutrophil migration was measured using a 96-well Boyden chamber. Results. ENA-78/CXCL5 protein levels in conditioned medium of BSMC stimulated with HDM extract were significantly reduced (n = 10, P < 0.05) but restored in the presence of 5% FCS. HDM extracts did not affect ENA-78/CXCL5 mRNA levels. Recombinant ENA-78/CXCL5 was degraded after incubation with HDM extracts (n = 7, P < 0.05) but restored after the addition of the serine protease AEBSF. Neutrophil migration towards recombinant ENA-78/CXCL5 was also reduced in the presence of HDM extract. Conclusion. HDM proteases degrade ENA-78/CXCL5. Thus exposure to HDM allergens may alter ENA-78/CXCL5 levels in the lungs and may affect angiogenesis and the inflammatory response in the airways of asthma patients.

Hypoxia exerts dualistic effects on inflammatory and proliferative responses of healthy and asthmatic primary human bronchial smooth muscle cells.

BACKGROUND: For oxygen supply, airway wall cells depend on diffusion though the basement membrane, as well as on delivery by micro-vessels. In the asthmatic lung, local hypoxic conditions may occur due to increased thickness and altered composition of the basement membrane, as well as due to edema of the inflamed airway wall. OBJECTIVE: In our study we investigated the effect of hypoxia on proliferation and pro-inflammatory and pro-angiogenic parameter production by human bronchial smooth muscle cells (BSMC). Furthermore, conditioned media of hypoxia-exposed BSMC was tested for its ability to induce sprout outgrowth from endothelial cells spheroids. METHODS: BSMC were cultured in RPMI1640 (5% FCS) under normoxic (21% O2) and hypoxic (1% and 5% O2) conditions. Proliferation was determined by cell count and Western blot analysis for cyclin E and Proliferating Cell Nuclear Antigen (PCNA). Secretion of IL-6, IL-8, ENA-78 and VEGF-A was analyzed by ELISA. BSMC conditioned medium was tested for its angiogenic capacity by endothelial cell (EC)-spheroid in vitro angiogenesis assay. RESULTS: Proliferation of BSMC obtained from asthmatic and non-asthmatic patients was significantly reduced in the presence of 1% O2, whereas 5% O2 reduced proliferation of asthmatic BSMC only. Hypoxia induced HIF-1α expression in asthmatic and non-asthmatic BSMC, which coincided with significantly increased release of IL-6, IL-8 and VEGF-A, but not ENA-78. Finally, endothelial sprout outgrowth from EC spheroids was increased when exposed to hypoxia conditioned BSMC medium. CONCLUSION: Hypoxia had dualistic effects on proliferative and inflammatory responses of asthmatic and non-asthmatic BSMC. First, hypoxia reduced BSMC proliferation. Second, hypoxia induced a pro-inflammatory, pro-angiogenic response. BSMC and EC may thus be promising new targets to counteract and/or alleviate airway wall remodeling.

Tiotropium sustains the anti-inflammatory action of olodaterol via the cyclic AMP pathway.

Mesenchymal cells (fibroblasts) of the airway wall respond to cholinergic stimulation by releasing pro-inflammatory and chemotactic cytokines and may thus contribute to chronic inflammation of the lung. Here, we studied the anti-inflammatory potential of olodaterol, a long acting ß2-adrenergic receptor agonist, and tiotropium, a long-acting muscarinic receptor antagonist, and whether they interact at the level of the cyclic AMP dependent signaling pathway. Pulmonary fibroblasts of asthmatic (n = 9) and non-asthmatic (n = 8) subjects were stimulated with the muscarinic receptor agonist carbachol and interleukin-1ß (IL-1 beta) in presence or absence of tiotropium or olodaterol alone, or their combination. We also measured cAMP levels and phosphorylation of the cAMP response element binding protein (CREB). As single components, carbachol, olodaterol and tiotropium did not affect IL-6 and IL-8 release. Carbachol concentration-dependently enhanced the production of IL-1ß-induced IL-6 and IL-8, which was blocked by the simultaneous addition of tiotropium. The combination of olodaterol plus tiotropium further reduced IL-6 and IL-8 release. Olodaterol induced cAMP and the phosphorylation of CREB, an effect counteracted by carbachol, but rescued by tiotropium. We conclude that olodaterol plus tiotropium cooperate to decrease the inflammatory response in pulmonary fibroblasts in vitro.

Bronchial smooth muscle cells of asthmatics promote angiogenesis through elevated secretion of CXC-chemokines (ENA-78, GRO-α, and IL-8).

BACKGROUND: Airway wall remodelling is a key pathology of asthma. It includes thickening of the airway wall, hypertrophy and hyperplasia of bronchial smooth muscle cells (BSMC), as well as an increased vascularity of the sub-epithelial cell layer. BSMC are known to be the effector cells of bronchoconstriction, but they are increasingly recognized as an important source of inflammatory mediators and angiogenic factors. OBJECTIVE: To compare the angiogenic potential of BSMC of asthmatic and non-asthmatic patients and to identify asthma-specific angiogenic factors. METHODS: Primary BSMC were isolated from human airway tissue of asthmatic and non-asthmatic patients. Conditioned medium (CM) collected from BSMC isolates was tested for angiogenic capacity using the endothelial cell (EC)-spheroid in vitro angiogenesis assay. Angiogenic factors in CM were quantified using a human angiogenesis antibody array and enzyme linked immunosorbent assay. RESULTS: Induction of sprout outgrowth from EC-spheroids by CM of BSMC obtained from asthma patients was increased compared with CM of control BSMC (twofold, p < 0.001). Levels of ENA-78, GRO-α and IL-8 were significantly elevated in CM of BSMC from asthma patients (p < 0.05 vs. non-asthmatic patients). SB 265610, a competitive antagonist of chemokine (CXC-motif) receptor 2 (CXCR2), attenuated the increased sprout outgrowth induced by CM of asthma patient-derived BSMC. CONCLUSIONS: BSMC isolated from asthma patients exhibit increased angiogenic potential. This effect is mediated through the CXCR2 ligands (ENA78, GRO-α and IL-8) produced by BSMC. IMPLICATIONS: CXCR2 ligands may play a decisive role in directing the neovascularization in the sub-epithelial cell layers of the lungs of asthma patients. Counteracting the CXCR2-mediated neovascularization by pharmaceutical compounds may represent a novel strategy to reduce airway remodelling in asthma.

Pathomechanistic characterization of two exonic L1CAM variants located in trans in an obligate carrier of X-linked hydrocephalus.

Mutations in the gene encoding the neural cell adhesion molecule L1CAM cause several neurological disorders collectively referred to as L1 syndrome. We report here a family case of X-linked hydrocephalus in which an obligate female carrier has two exonic L1CAM missense mutations in trans substituting amino acids in the first (p.W635C) or second (p.V768I) fibronectin-type III domains. We performed various biochemical and cell biological in vitro assays to evaluate the pathogenicity of these variants. Mutant L1-W635C protein accumulates in the endoplasmic reticulum (ER), is not transported into axons, and fails to promote L1CAM-mediated cell-cell adhesion as well as neurite growth. Immunoprecipitation experiments show that L1-W635C associates with the molecular ER chaperone calnexin and is modified by poly-ubiquitination. The mutant L1-V768I protein localizes at the cell surface, is not retained in the ER, and promotes neurite growth similar to wild-type L1CAM. However, the p.V768I mutation impairs L1CAM-mediated cell-cell adhesion albeit less severe than L1-W635C. These data indicate that p.W635C is a novel loss-of-function L1 syndrome mutation. The p.V768I mutation may represent a non-pathogenic variant or a variant associated with low penetrance. The poly-ubiquitination of L1-W635C and its association with the ER chaperone calnexin provide further insights into the molecular mechanisms underlying defective cell surface trafficking of L1CAM in L1 syndrome.

L1 syndrome mutations impair neuronal L1 function at different levels by divergent mechanisms.

Mutations in the human L1CAM gene cause neurodevelopmental disorders collectively referred to as L1 syndrome. Here, we investigated cellular pathomechanisms underlying two L1 syndrome mutations, R184Q and W1036L. We demonstrate that these mutations cause partial endoplasmic reticulum (ER) retention of L1, reduce L1 cell surface expression, but do not induce ER stress in neuronal NSC-34 cells. We provide evidence that surface trafficking of mutated L1 is affected by defective sorting to ER exit sites and attenuated ER export. However, in differentiated neuronal cultures and long-term cultured hippocampal slices, the L1-R184Q protein is restricted to cell bodies, whereas L1-W1036L also aberrantly localizes to dendrites. These trafficking defects preclude axonal targeting of L1, thereby affecting L1-mediated axon growth and arborization. Our results indicate that L1 syndrome mutations impair neuronal L1 function at different levels, firstly by attenuating ER export and secondly by interfering with polarized neuronal trafficking.