Razao Issa

Role of c-jun N-terminal kinase in the induced release of GM-CSF, RANTES and IL-8 from human airway smooth muscle cells

Human airway smooth muscle cells (HASMC) contribute to airway inflammation in asthma by virtue of their capacity to produce several inflammatory mediators including IL‐8, GM‐CSF and RANTES. The intracellular signal pathway underlying the production of these cytokines in HASMC is not entirely elucidated. We examined the role of the mitogen‐activated protein kinase (MAPK) c‐jun N‐terminal kinase (JNK) in TNFα‐ and IL‐1β‐induced GM‐CSF, RANTES and IL‐8 production in HASMC by using a novel specific inhibitor for JNK (SP600125). Confluent HASMC were treated with TNFα or IL‐1β (10 ng ml−1) for 24 h in the presence or absence of SP600125 (1–100 μM). JNK activity was determined by a kinase assay. Phosphorylation of JNK, p38 MAPK and ERK was examined by Western blotting. Culture supernatants were assayed for GM‐CSF, RANTES and IL‐8 content by ELISA. Maximum TNFα‐ or IL‐1β‐induced phosphorylation of JNK in HASMC occurred after 15 min and returned to baseline levels after 4 h. SP600125 inhibited TNFα‐ and IL‐1β‐induced JNK activity in HASMC as shown by the reduced phosphorylation of its substrate c‐jun. Furthermore, GM‐CSF, RANTES and to a lesser extent IL‐8 release from HASMC treated with TNFα and IL‐1β was inhibited dosedependently by SP600125. JNK activation is involved in TNFα‐ and IL‐1β‐induced GM‐CSF, RANTES and IL‐8 production from HASMC. JNK may therefore represent a critical pathway for cytokine production in HASMC.

Corticosteroid Inhibition of Growth-Related Oncogene Protein-α via Mitogen-Activated Kinase Phosphatase-1 in Airway Smooth Muscle Cells

Expression of the inflammatory chemokine, growth-related oncogene protein-α (GRO-α), from airway smooth muscle cells (ASMC) is regulated by pathways involving NF-κB and MAPK activation. We determined the effects of dexamethasone on GRO-α induced by IL-1β or TNF-α with respect to the role of MAPK pathways and of MAPK phosphatase-1 (MKP-1). Human ASMC were studied in primary culture at confluence. Dexamethasone (10−8–10−5 M) partially inhibited GRO-α expression and release induced by IL-1β and TNF-α; this was associated with an inhibition of JNK, but not of p38 or ERK phosphorylation. Together with IL-1β or TNF-α, dexamethasone rapidly induced mRNA and protein expression of MKP-1, which dephosphorylates MAPKs. Using MKP-1 small interfering RNA (siRNA) to block the expression of IL-1β- and dexamethasone-induced MKP-1 by 50%, JNK phosphorylation was doubled. The inhibitory effect of dexamethasone on GRO-α release was partially reversed in ASMC treated with MKP-1 siRNA compared with those treated with scrambled siRNA. In contrast, overexpression of MKP-1 led to a reduction in IL-1β-induced release of GRO-α, but the inhibitory effects of dexamethasone were preserved. Nuclear translocation of the glucocorticoid receptor was increased in ASMC exposed to dexamethasone and IL-1β. Using chromatin immunoprecipitation assay, glucocorticoid receptor binding to the MKP-1 promoter was increased by IL-1β and dexamethasone compared with either alone. Glucocorticoids and IL-1β or TNF-α modulate GRO-α release partly through the inhibition of JNK pathway, resulting from an up-regulation of MKP-1 expression.

Induction and regulation of matrix metalloproteinase-12in human airway smooth muscle cells

BackgroundThe elastolytic enzyme matrix metalloproteinase (MMP)-12 has been implicated in the development of airway inflammation and remodeling. We investigated whether human airway smooth muscle cells could express and secrete MMP-12, thereby participating in the pathogenesis of airway inflammatory diseases.MethodsLaser capture microdissection was used to collect smooth muscle cells from human bronchial biopsy sections. MMP-12 mRNA expression was analysed by quantitative real-time RT-PCR. MMP-12 protein expression and secretion from cultured primary airway smooth muscle cells was further analysed by Western blot. MMP-12 protein localization in bronchial tissue sections was detected by immunohistochemistry. MMP-12 activity was determined by zymography. The TransAM AP-1 family kit was used to measure c-Jun activation and nuclear binding. Analysis of variance was used to determine statistical significance.ResultsWe provide evidence that MMP-12 mRNA and protein are expressed by in-situ human airway smooth muscle cells obtained from bronchial biopsies of normal volunteers, and of patients with asthma, COPD and chronic cough. The pro-inflammatory cytokine, interleukin (IL)-1β, induced a >100-fold increase in MMP-12 gene expression and a >10-fold enhancement in MMP-12 activity of primary airway smooth muscle cell cultures. Selective inhibitors of extracellular signal-regulated kinase, c-Jun N-terminal kinase and phosphatidylinositol 3-kinase reduced the activity of IL-1β on MMP-12, indicating a role for these kinases in IL-1β-induced induction and release of MMP-12. IL-1β-induced MMP-12 activity and gene expression was down-regulated by the corticosteroid dexamethasone but up-regulated by the inflammatory cytokine tumour necrosis factor (TNF)-α through enhancing activator protein-1 activation by IL-1β. Transforming growth factor-β had no significant effect on MMP-12 induction.ConclusionOur findings indicate that human airway smooth muscle cells express and secrete MMP-12 that is up-regulated by IL-1β and TNF-α. Bronchial smooth muscle cells may be an important source of elastolytic activity, thereby participating in remodeling in airway diseases such as COPD and chronic asthma.

Regulation of human lung epithelial cell numbers by diesel exhaust particles

Particulate air pollution is associated with respiratory morbidity and has cytotoxic and pro-inflammatory effects. The effects of diesel exhaust particles (DEP) on proliferation and apoptosis of A549 lung epithelial cells were examined. When deprived of serum (serum starvation), epithelial cell numbers fell, but DEP (5–200 µg·mL−1) prevented this. Using flow cytometric analysis of propidium iodide (PI) staining, DEP (10 µg·mL−1) increased cells in the S phase of cell cycle from 12.85 to 18.75% after 48 h, reversing serum starvation-induced G0/1 arrest. DEP also reduced the increase in apoptotic cells, as defined by double expression of annexin V/PI, observed after serum starvation (from 28.35 to 15.46%). The antioxidants, N-acetylcysteine (NAC; 33 mM) and AEOL10113 (10–100 µM), the N-terminal c-jun kinase inhibitor, SP600125 (33 µM), and nuclear factor-κB inhibitor, SN50 (33 µM), inhibited DEP-induced cell number increase. NAC inhibited DEP-induced reduction of G0/1 and increase in cells in the S and G2/M phases. Expression of p21CIP1/WAF1 mRNA and protein seen with serum starvation was reduced by DEP. In conclusion, diesel exhaust particles prevented serum starvation-led decreases in A549 epithelial cells by inducing cell cycle progression and preventing apoptosis, processes involving oxidative stress, inhibition of p21CIP1/WAF1 expression and stimulation of N-terminal c-jun kinase and nuclear factor-κB. Therefore, low-dose diesel exhaust particle exposure may lead to lung epithelial cell hyperplasia.

Attenuation of Ozone-Induced Airway Inflammation and Hyper-Responsiveness by c-Jun NH2 Terminal Kinase Inhibitor SP600125

Ozone has potent oxidizing properties, and exposure to ozone causes airway hyper-responsiveness (AHR) and lung inflammation. We determined the importance of c-Jun NH2 terminal kinase (JNK), a member of the mitogen-activated protein kinase pathway, in ozone-induced AHR and inflammation. SP600125 [anthra[1,9-cd] pyrazol-6 (2H)-one], a specific JNK inhibitor (30 mg/kg) or vehicle, was administered by intraperitoneal injection before and after ozone exposure (3 ppm for 3 h). SP600125 significantly reduced total cells, and neutrophils in bronchoalveolar fluid recovered at 20 to 24 h after exposure and inhibited ozone-induced AHR. Ozone exposure induced activation of JNK in the lung as measured by the expression of phosphorylated-c-Jun, an effect abolished by SP600125. Gene-microarray analysis revealed that ozone increased the expression of over 400 genes by more than 2-fold, including interleukin-6 (IL-6), CXCL1 (keratinocyte cytokine), and CCL2 (monocyte chemoattractant protein-1). SP600125 modulated the expression of a subset of 29 ozone-induced genes; IL-6 and CCL2 expression were further increased, whereas the expression of metallothionein 1, hemopexin, and mitogen-activated 3 kinase 6 was decreased in SP600125-treated ozone-exposed mice. Changes in mRNA for IL-6, CXCL1, and CCL2 were confirmed by real-time polymerase chain reaction. Ozone also decreased the expression of over 500 genes, with the most potent effect on angiopoietin-1. SP600125 modulated the expression of 15 of these genes, and in particular, SP600125 reversed ozone-induced decrease in expression of the redox-sensitive transcription factor, hypoxia-induced factor-1α. This study highlights an important role for JNK in response to oxidative stress through modulation of specific inflammatory and redox mediators. Inhibition of JNK with small molecule kinase inhibitors may be a means of reducing ozone-induced inflammation and AHR.

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.

Differential regulation of CCL-11/eotaxin-1 and CXCL-8/IL-8 by Gram-positive and Gram-negative bacteria in human airway smooth muscle cells

BackgroundBacterial infections are a cause of exacerbation of airway disease. Airway smooth muscle cells (ASMC) are a source of inflammatory cytokines/chemokines that may propagate local airway inflammatory responses. We hypothesize that bacteria and bacterial products could induce cytokine/chemokine release from ASMC.MethodsHuman ASMC were grown in culture and treated with whole bacteria or pathogen associated molecular patterns (PAMPs) for 24 or 48 h. The release of eotaxin-1, CXCL-8 or GMCSF was measured by ELISA.ResultsGram-negative E. coli or Gram-positive S. aureus increased the release of CXCL-8, as did IL-1β, LPS, FSL-1 and Pam3CSK4, whereas FK565, MODLys18 or Poly I:C did not. E. coli inhibited eotaxin-1 release under control conditions and after stimulation with IL-1β. S. aureus tended to inhibit eotaxin-1 release stimulated with IL-1β. E. coli or LPS, but not S. aureus, induced the release of GMCSF.ConclusionGram-positive or Gram-negative bacteria activate human ASMC to release CXCL-8. By contrast Gram-negative bacteria inhibited the release of eotaxin-1 from human ASMCs. E. coli, but not S. aureus induced GMCSF release from cells.Our findings that ASMC can respond directly to Gram-negative and Gram-positive bacteria by releasing the neutrophil selective chemokine, CXCL-8, is consistent with what we know about the role of neutrophil recruitment in bacterial infections in the lung. Our findings that bacteria inhibit the release of the eosinophil selective chemokine, eotaxin-1 may help to explain the mechanisms by which bacterial immunotherapy reduces allergic inflammation in the lung.