Sum-Yee Leung

Allergen-induced inflammation and airway epithelial and smooth muscle cell proliferation: role of Jun N-terminal kinase.

Chronic cellular inflammation and airway wall remodelling with subepithelial fibrosis and airway smooth muscle (ASM) cell hyperplasia are features of chronic asthma. Jun N‐terminal kinase (JNK) may be implicated in these processes by regulating the transcriptional activity of activator protein (AP)‐1. We examined the effects of an inhibitor of JNK, SP600125 (anthra [1,9‐cd] pyrazole‐6 (2 H)‐one), in a model of chronic allergic inflammation in the rat. Rats sensitised to ovalbumin (OA) were exposed to OA‐aerosol every third day on six occasions and were treated with SP600125 (30 mg kg−1 b.i.d; 360 mg in total) for 12 days, starting after the second through to the sixth OA exposure. We measured eosinophilic and T‐cell inflammation in the airways, proliferation of ASM cells and epithelial cells by incorporation of bromodeoxyuridine (BrdU), and bronchial responsiveness to acetylcholine. SP600125 significantly reduced the number of eosinophils (P<0.05) and lymphocytes (P<0.05) in bronchoalveolar lavage fluid, suppressed eosinophilic (P<0.05) and CD2+ T‐cell (P<0.05) infiltration within the bronchial submucosa, and the increased DNA incorporation in ASM (P<0.05) and epithelial cell incorporation (P<0.05). SP600125 did not alter bronchial hyper‐responsiveness observed after chronic allergen exposure. Pathways regulated by JNK positively regulate ASM cell proliferation and allergic cellular inflammation following chronic allergen exposure.

Effect of an inhibitor of Jun N-terminal protein kinase, SP600125, in single allergen challenge in sensitized rats

Jun N‐terminal kinase (JNK) has been implicated in the pathogenesis of inflammatory diseases including asthma. We examined the effect of SP600125 (anthra [1,9‐cd] pyrazol‐6 (2H)‐one), a novel inhibitor of JNK in a model of asthma. Brown‐Norway rats were sensitized to ovalbumin and treated with SP600125 intraperitoneally (90 mg/kg in total). SP600125 inhibited allergen‐induced, increased activity of phosphorylated c‐jun but not of phosphorylated‐MAPKAPK2, indicative of activation of p38 MAPK, in the lung. SP600125 inhibited macrophage (P < 0·04), lymphocyte (P < 0·05), eosinophil (P < 0·04) and neutrophil (P < 0·005) numbers in bronchoalveolar lavage. Eosinophil and T‐cell accumulation in the airways, mRNA expression for interleukin‐1β, tumour necrosis factor‐β, interleukin‐3, interleukin‐4 and interleukin‐5, serum levels of allergen‐specific immunoglobulin E and bronchial hyperresponsiveness were not affected by SP600125. Selective inhibition of JNK reduced inflammatory cell egress into the airway lumen after single allergen exposure. The role of JNK mitogen‐activated protein kinase activation may be limited in the pathogenesis of bronchial hyperresponsiveness after single allergen exposure.

Role of cathepsin S in ozone-induced airway hyperresponsiveness and inflammation

Ambient ozone has been linked to the worsening of symptoms of patients with obstructive diseases such as chronic obstructive pulmonary disease (COPD) and asthma. We investigated the role of cathepsin S on ozone-induced airway hyperresponsiveness (AHR) and inflammation, using the selective cathepsin S inhibitor, Compound A. Balb/c mice were exposed to ozone at a concentration of 3 ppm or air for 3 h, following administration by gavage of Compound A or vehicle. Bronchoalveolar lavage (BAL) was performed 3 h and 20-24 h following exposure, AHR was measured at 20-24 h only. Ozone exposure, compared to air exposure increased BAL cathepsin S levels, AHR and BAL inflammatory cells. Compound A (30 mg kg(-1) p.o.) dosing compared to vehicle dosing inhibited ozone-induced AHR (-logPC100 vehicle: -0.70+/-0.12, n=8 vs. cathepsin S inhibitor: -1.30+/-0.06, P<0.001, n=8) at 20-24 h and BAL neutrophilia at 3 h and 20-24 h (P<0.05, n=6). Ozone exposure increased levels of BAL cytokines IL-6, TNF-alpha and IFN-gamma. Compound A reduced IL-6 at 3 h and 20-24 h (P<0.05, n=5) and TNF-alpha, at 20-24 h (P<0.05, n=6). These data indicate an important role for cathepsin S in the regulation of ozone-induced AHR and neutrophil cell recruitment and suggest that cathepsin S may be a target in the treatment of oxidative stress-induced AHR and inflammation.

Role of p38 mitogen-activated protein kinase in ozone-induced airway hyperresponsiveness and inflammation

Ozone is a potent oxidant and causes airway hyperresponsiveness and neutrophilia. To determine the role of p38 mitogen-activated protein kinase (MAPK) activation, we studied the effect of a p38alpha inhibitor SD-282 (Scios Inc, Fremont, CA USA) on ozone-induced airway hyperresponsiveness and neutrophilia. Balb/c mice received SD-282 (30 or 90 mg/kg i.p) or vehicle 1 h before exposure to either ozone (3 ppm, 3 h) or air. Three hours after exposure, lungs were analysed for cytokine levels and bronchoalveolar lavage was performed. Another set of mice were dosed 6 h after exposure and 1 h before assessing airway hyperresponsiveness. SD-282 (90 mg/kg) significantly inhibited ozone-induced airway hyperresponsiveness (-LogPC(150): SD-282: -1.73+/-0.14 vs. vehicle: -0.99+/-0.15, P<0.05). Bronchoalveolar lavage neutrophil numbers were time-dependently increased in vehicle-dosed, ozone-exposed mice, greatest at 20-24 h after exposure. SD-282 (30 and 90 mg/kg) significantly inhibited ozone induced neutrophil numbers at 3 h and 20-24 h after ozone SD-282 significantly inhibited ozone-induced increases in phosphorylated p38 MAPK expression, and in cyclooxygenase-2 (COX-2), interleukin-6 (IL-6) and IL-1beta but not MIP-1alpha gene expression. We conclude that p38 MAPK is involved in ozone-induced airway hyperresponsiveness and lung neutrophilia. Inhibition of p38 MAPK with small molecule kinase inhibitors may be a means of reducing ozone-induced inflammation and airway hyperresponsiveness.

Modulation of ozone-induced airway hyperresponsiveness and inflammation by interleukin-13

The present study aimed to determine whether the T-helper cell type 2-derived cytokines, interleukin (IL)-4 and -13, can modulate the lung response to ozone exposure. IL-13-/-, IL-4/13-/- and IL-13-overexpressing transgenic (Tg) mice were exposed to ozone (3 ppm; 3 h) or air. Wild-type (Wt) Balb/c mice and transgenic-negative littermates (IL-13Wt) were used as controls for gene-deficient and IL-13Tg mice, respectively. IL-4/13-/- and IL-13-/- mice developed a lesser degree of ozone-induced airway hyperresponsiveness (AHR) while IL-13Tg mice developed a greater degree of AHR compared with ozone-exposed wild-type or IL-13Wt mice, respectively. Ozone caused a time-dependent increase of bronchoalveolar lavage (BAL) neutrophils and macrophages in wild-type mice, maximal at 20–24 h, which was attenuated in the IL-13-/- and IL-4/13-/- mice. In IL-13Tg mice, there was a greater increase in BAL neutrophils after ozone exposure compared with IL-13Wt mice. Using quantitative real-time PCR, ozone-induced mRNA expression for IL-6 and keratinocyte chemokine was further enhanced in IL-13-/- and IL-4/13-/- mice, and was inhibited in IL-13Tg mice. Macrophage inflammatory protein (MIP)-3α/CCL20 expression was enhanced after ozone exposure in wild-type mice, inhibited in IL-13-/- and IL-4/13-/- mice, while in IL-13Tg mice it was enhanced. A similar pattern of expression was observed with lipopolysaccharide-induced cytokine (LIX/CXCL5/ENA-78) expression. In conclusion, interleukin-13 augments ozone-induced airway hyperresponsiveness and neutrophilic inflammation, possibly through modulation of certain cytokines induced by ozone exposure.

Resolution of allergic airways inflammation but persistence of airway smooth muscle proliferation after repeated allergen exposures

Background Chronic inflammation in asthmatic airways can lead to characteristic airway smooth muscle (ASM) thickening and pathological changes within the airway wall.

Matrix metalloproteinases in airways inflammation of asthma and chronic obstructive pulmonary disease

Matrix metalloproteinases (MMPs) are produced in the respiratory tract from different inflammatory and structural cells and are involved in wound healing, inflammatory cell trafficking and tissue remodelling and repair. MMPs are tightly regulated and their effects are counterbalanced by their physiological inhibitors, tissue inhibitors of MMPs (TIMPs). Increased secretion and expression of MMPs have been reported in asthma and chronic obstructive pulmonary disease (COPD), which are chronic inflammatory lung diseases that lead to chronic airflow obstruction associated with significant mortality and morbidity. Cytokines and growth factors which are involved in these inflammatory processes interact directly with MMPs, leading to a regulation of their expression or changes in their biological activities through enzymatic cleavage. Different MMPs play a specific role with variations in different lung diseases. In COPD, MMP 1, MMP 9 and MMP 12 from lung macrophages play an important role in degradation of matrix leading to emphysema. MMPs may represent relevant therapeutic targets for many diseases. However, their contribution is potentially complex since MMPs may have both beneficial as well as deleterious effects. Thus, some actions may lead to pro-inflammatory effects, while others may also cause anti-inflammatory effects. Therefore, the precise role of these MMPs in airways disease with airflow obstruction need to be clarified carefully before selective MMP inhibitors are tried for therapeutic aims in these diseases.