Kewu Huang

Effects of leptin deficiency on postnatal lung development in mice

Leptin modulates energy metabolism and lung development. We hypothesize that the effects of leptin on postnatal lung development are volume dependent from 2 to 10 wk of age and are independent of hypometabolism associated with leptin deficiency. To test the hypotheses, effects of leptin deficiency on lung maturation were characterized in age groups of C57BL/6J mice with varying Lep(ob) genotypes. Quasi-static pressure-volume curves and respiratory impedance measurements were performed to profile differences in respiratory system mechanics. Morphometric analysis was conducted to estimate alveolar size and number. Oxygen consumption was measured to assess metabolic rate. Lung volume at 40-cmH(2)O airway pressure (V(40)) increased with age in each genotypic group, and V(40) was significantly (P < 0.05) lower in leptin-deficient (ob/ob) mice beginning at 2 wk. Differences were amplified through 7 wk of age relative to wild-type (+/+) mice. Morphometric analysis showed that alveolar surface area was lower in ob/ob compared with +/+ and heterozygote (ob/+) mice beginning at 2 wk. Unlike the other genotypic groups, alveolar size did not increase with age in ob/ob mice. In another experiment, ob/ob at 4 wk received leptin replacement (5 microg.g(-1) x day(-1)) for 8 days, and expression levels of the Col1a1, Col3a1, Col6a3, Mmp2, Tieg1, and Stat1 genes were significantly increased concomitantly with elevated V(40). Leptin-induced increases in V(40) corresponded with enlarged alveolar size and surface area. Gene expression suggested a remodeling event of lung parenchyma after exogenous leptin replacement. These data support the hypothesis that leptin is critical to postnatal lung remodeling, particularly related to increased V(40) and enlarged alveolar surface area.

Direct comparison of the dynamics of IL‐25‐ and ‘allergen’‐induced airways inflammation, remodelling and hypersensitivity in a murine asthma model

Interleukin‐25 has been implicated in the pathogenesis of asthma from studies on human asthmatics and in murine asthma models.

Resistin-like molecule-β is a human airway remodelling mediator

Though implicated in vascular remodelling, a role for the resistin-like molecule (RELM)-&bgr; in human airway remodelling remains unexplored. We hypothesised that RELM-&bgr; expression is increased in the airways of asthmatics and regulates airways epithelial cell function. Expression of RELM-&bgr; in the bronchial mucosa and its concentrations in bronchoalveolar lavage (BAL) fluid from asthmatics and controls were measured by immunohistochemistry and ELISA, respectively. Proliferation assays, Western blotting, ELISA and real-time PCR were employed to detect effects of RELM-&bgr; on airways epithelial cells. RELM-&bgr; expression was increased in the bronchial mucosa and BAL fluid of asthmatics compared with controls. In the asthmatics, the numbers of mucosal RELM-&bgr;+ cells correlated inversely with forced expiratory volume in 1 s (r=-0.531, p=0.016), while the numbers of epithelial RELM-&bgr;+ cells correlated positively with those of mucin (MUC)5AC+ cells. In vitro, interleukin-13 enhanced RELM-&bgr; expression by primary human airways epithelial cells, while RELM-&bgr; itself acted on these cells to induce proliferation, expression of MUC5AC, extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase (MAPK)-phosphatidylinositol 3-kinase (PI3K)/Akt phosphorylation and elevated expression of transforming growth factor-&bgr;2, epidermal growth factor and vascular endothelial growth factor. RELM-&bgr; has the potential to contribute to airway remodelling in diseases such as asthma by acting on epithelial cells to increase proliferation, mucin and growth factor production, at least partly via ERK/MAPK-PI3K/Akt signalling pathways.

Age-induced augmentation of p38 MAPK phosphorylation in mouse lung.

The p38 mitogen-activated protein kinase (p38 MAPK) pathway is a key regulator of pro-inflammatory cytokine biosynthesis, which may contribute to the chronic low-grade inflammation observed with aging. We hypothesize that aging up-regulates the activation of p38 MAPK as well as the pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) in mouse lung, and is accompanied by disturbances in oxidant-antioxidant status. In addition, the elevated protein levels of phosphorylated active form of p38 MAPK (phospho-p38 MAPK) with age are tissue-specific. To test this hypothesis, protein levels of phospho-p38 MAPK were determined using Western blot analysis in isolated lung, brain, heart, spleen, kidney and muscle of young (2-month-old) and aged (20-month-old) male C57BL/6J mice. Results show that phospho-p38 MAPK protein levels, not total-p38 MAPK, increased significantly (p<0.01, n=8) in lung and brain of 20-month-old mice. The activation of p38 MAPK in other tissues was not altered with age. Immunostaining showed that epithelial cells and alveolar macrophages in lung parenchyma were the major cellular sources of phospho-p38 MAPK immunity. As measured by enzyme-linked immunosorbent assay (ELISA), TNF-α, IL-1β and IL-6 in lung homogenates were elevated significantly with age, but there were no differences with age in serum levels except for IL-6. In addition, IL-1β and IL-6 were increased notably while TNF-α was not different with age in bronchoalveolar lavage fluid (BALF). Furthermore, the oxidant-antioxidant status was evaluated by measuring pro-oxidant malondialdehyde (MDA) levels and the activity of reactive oxygen species scavenging enzymes (i.e. superoxide dismutase (SOD) and glutathione (GSH)) in lung homogenates. The results showed that SOD and GSH decreased with age, while MDA did not change. In conclusion, our data demonstrate that p38 MAPK is activated during lung aging with a corresponding increase in pro-inflammatory cytokines and decrease in antioxidant capacity.

Interleukin-25 promotes basic fibroblast growth factor expression by human endothelial cells through interaction with IL-17RB, but not IL-17RA.

Unlike other IL‐17 family members, the Th2‐derived cytokine IL‐25 (IL‐17E) induces (promotes) Th2 responses. One or both of the two receptors for IL‐25 (IL‐17RA, IL‐17RB) is expressed on inflammatory cells and tissue structural cells, suggesting that in addition to promoting Th2‐type inflammation IL‐25 may also act on structural cells at sites of Th2‐type inflammation such as in the asthmatic bronchial mucosa to promote remodelling changes.

Asthma COPD Overlap Syndrome on CT Densitometry: A Distinct Phenotype from COPD

Abstract Patients with asthma COPD overlap syndrome (ACOS) are an important but poorly characterized group. This study sought to explore the distinct characteristics of ACOS on CT densitometry. The study population was randomly selected from communities via questionnaires. All participants underwent low-dose volumetric chest CT both before and after bronchodilator administration. Each CT scan was performed at full-inspiration and full-expiration for CT densitometry. Emphysema index (EI), air trapping (AT), mean lung density (MLD) and total lung volume (TLV) were measured and compared between the ACOS and COPD groups. The distributions of both EI and AT were compared between patients with ACOS and COPD. The variations between the pre- and post-BD measurements observed in patients with ACOS were compared with those in patients with COPD. A total of 71 patients completed the study, including 32 patients with COPD and 39 patients with ACOS. The patients with ACOS exhibited lower EI and more upper-zone-predominant EI distributions, compared with the patients with COPD. No significant differences were exhibited in AT and its distribution. Following bronchodilator administration, the variations in AT and expiratory MLD were greater in patients with ACOS than in patients with COPD. No differences were observed in the variations of EI and inspiratory MLD. Our results indicate that patients with ACOS have lower extent of emphysema and different emphysema distribution, as well as greater post-BD variations in air trapping, compared with patients with COPD. These findings suggest that CT densitometry characterizes ACOS as a distinct phenotype from COPD.

Chinese response to allergy and asthma in Olympic athletes.

China is going to host the Games of the XXIX Olympiad from 8–24 August 2008 in Beijing. The number of athletes and accompanying individuals expected to arrive at China for the Beijing Olympics is estimated at over 10u2003000 and among them at least 2u2003000 (20%) are suspected to suffer from respiratory allergies. It is important to monitor the pollen counts and improve air quality in Beijing because Olympic athletes would be exposed to airborne allergens and pollutants during competitions which could hinder peak performance. The main pollen and spore families in Beijing are Artemisia, Ambrosia, Chenopodiaceae and Gramineae. They can reach around 307u2003000 grains of pollen/1000u2003m3 of air in August. Economic development in China is usually linked with worsening of air quality. Due to the adoption of various control measures, the ambient air quality in a number of areas in Beijing has actually improved. The ambient air TSP and SO2 levels in Beijing have been decreasing in the last decade. However, ambient air NOx level has been increasing due to the increased number of motor vehicles. Nevertheless, dedicated medical facilities in Beijing will provide medical services to athletes and delegations from all over the world during the Beijing Olympic Games.

Characteristics of IL-25 and allergen-induced airway fibrosis in a murine model of asthma.

Interleukin (IL)‐25 has been implicated in the pathogenesis of human asthma by inducing a Th2 cytokine response, but its possible role in the development of airway remodelling is less clear.

IL-25 induces airways angiogenesis and expression of multiple angiogenic factors in a murine asthma model

BackgroundTh2-promoting cytokine IL-25 might contribute to bronchial mucosal vascular remodelling in asthma through its receptor expressed by vascular endothelial and vascular smooth muscle cells.MethodsBy utilising a newly established chronic asthma murine model induced by direct exposure of the airways to IL-25 alone, we examined effects of IL-25 on angiogenesis, vascular remodelling and expression of angiogenic factors, compared changes with those in a “classical” ovalbumin (OVA)-induced murine asthma model. IL-25 and OVA were intranasally instilled into the airways of BALB/c mice for up to 55xa0days. Airways vessels and angiogenic factors, including Von Willebrand Factor (vWF), amphiregulin, angiogenin, endothelin-1, transcription factor ERG, basic fibroblast growth factor (bFGF), epidermal growth factor (EGF), insulin-like growth factor (IGF-1) and vascular endothelial growth factor (VEGF) in lung sections, homogenates and BAL fluid were detected and quantified by immunostaining or enzyme linked immunosorbent assay (ELISA). An in house assay was also utilised to compare the effects of IL-25 and other Th2-cytokines on angiogenesis by human vascular endothelial cells.ResultsRepetitive intranasal challenge with IL-25 alone or OVA alone in OVA-presensitised animals significantly increased peribronchial vWF + vessels in the murine airways, which was associated with remarkably elevated expression of amphiregulin, angiogenin, endothelin-1, bFGF, EGF, IGF-1, VEGF and ERG. IL-25, but not Th-2-cytokines induced human angiogenesis in vitro.ConclusionsThe data suggest that chronic exposure of murine airways to IL-25 alone is able to reproduce a local angiogenic milieu. Thus, blocking IL-25 may attenuate vascular remodelling and improve outcomes in asthma patients.

Comprehensive attenuation of IL-25-induced airway hyperresponsiveness, inflammation and remodelling by the PI3K inhibitor LY294002

Existing in vitro and in vivo studies suggest that both IL‐25 and phosphoinositide 3‐kinases (PI3Ks) exhibit broad effects on the functions of immune cells implicated in the pathogenesis of asthma. Whether the blockade of PI3K signalling directly inhibits the asthma relevant pathogenetic changes induced by IL‐25 in an in vivo condition is still unclear. Using an established IL‐25‐induced murine model of asthma, we undertook a comprehensive evaluation of the effects of co‐administered LY294002, a pharmacological pan‐inhibitor of PI3K on IL‐25‐induced changes on this model, with particular regard to airway remodelling.