In the lungs of cystic fibrosis patients, overproduction of mucus leads to morbidity and mortality by obstructing airflow and shielding bacteria from antibiotics. Here we demonstrate that overproduction of mucus is a direct result of the activation of mucin gene expression by Gram-positive bacteria. Bacterial lipoteichoic acid activates the platelet-activating factor receptor, which is G protein-coupled. This results in activation of a disintegrin and metalloproteinase (ADAM10), kuzbanian, cleavage of pro heparin-binding epidermal growth factor and activation of the epidermal growth factor receptor. Unlike responses in macrophages, the epithelial-cell response to lipoteichoic acid does not require Toll-like receptor 2 or 4.

Cells dividing at the time of carcinogen exposure are at particular risk for neoplasia. Tobacco smoke contains numerous carcinogens, and we find that smoke, in the absence of exogenous growth factors, is capable of stimulating cell proliferation. The smoke-triggered mechanism includes the generation of oxygen radicals, which in turn stimulate tumor necrosis factor ␣-converting enzyme (a disintegrin and metalloproteinase (ADAM) 17) to cleave transmembrane amphiregulin, a ligand for the epidermal growth factor receptor (EGFR). The binding of amphiregulin to EGFR then stimulates proliferation of lung epithelial cells. These results shed light on the pathogenesis of lung cancer, suggest novel drug targets for the reduction of cancer risk in smokers, and provide insight into how EGFR integrates responses to diverse noxious stimuli.

In smokers' lungs, excessive mucus clogs small airways, impairing respiration and promoting recurrent infection. A breakthrough in understanding this pathology was the realization that smoke could directly stimulate mucin synthesis in lung epithelial cells and that this phenomenon was dependent on the cell surface receptor for epidermal growth factor, EGFR. Distal steps in the smoke-triggered pathway have not yet been determined. We report here that the predominant airway mucin (MUC5AC) undergoes transcriptional up-regulation in response to tobacco smoke; this is mediated by an AP-1-containing response element, which binds JunD and Fra-2. These transcription factors require phosphorylation by upstream kinases JNK and ERK, respectively. Whereas ERK activation results from the upstream activation of EGFR, JNK activation is chiefly EGFR-independent. Our experiments demonstrated that smoke activates JNK via a Src-dependent, EGFRindependent signaling cascade initiated by smoke-induced reactive oxygen species. Taken together with our earlier results, these data indicate that the induction of mucin by smoke is the combined effect of mutually independent, reactive oxygen species activation of both EGFR and JNK.The primary cause of morbidity in chronic bronchitis is mucin overproduction, a phenomenon for which the molecular pathogenesis is unknown. Inflammatory cells are abundant in smokers' airways (1-3) and are capable of stimulating mucin production (4 -7), suggesting that at least some of the excessive mucin in smokers' lungs is secondary to inflammation.In addition, however, smoke itself can induce mucin synthesis in lung cells (8,9). The question of how this occurs is complex in that smoke, a composite of irritant molecules including acetaldehyde, hydroquinone, formaldehyde, benzo-[a]pyrene, cresol, nicotine, catechol, acrolein, coumarin, anthracene, nitrogen oxides, and heavy metals (10, 11) may act on lung epithelial cells in diverse ways. For example, the induction of cytochrome P450 by tobacco smoke (12) is mediated by binding of the aryl hydrocarbon nuclear receptor to a dioxin response element in the 5Ј-flank of the gene, but the induction of the ␥-glutamylcysteine synthetase heavy subunit (␥-GCS-HS) gene is mediated by the binding of a c-Jun/c-Jun homodimer to an AP-1-like response element (13).Previous reports have implicated the receptor for epidermal growth factor (EGFR) 1 in the induction of mucin gene MUC5AC by smoke (9). Consistent with a role for EGFR in mucin induction, an EGF response element has been identified 200 bp upstream of the MUC5AC gene (14). The response of this element to EGFR ligands EGF and transforming growth factor-␣ is mediated by Sp1. One might predict from these data that the induction of MUC5AC by smoke would depend on interaction between the EGF response element at Ϫ200 bp and Sp1.In contrast, in the present study we show that MUC5AC is controlled principally by a smoke response element ϳ3 kb upstream of the EGF response element. This element is AP-1-dependent and is bound by Ju...

In order to assess inflammatory features related to severe asthma as compared with mild asthma, we investigated the secretion of 92 kDa gelatinase matrix metalloproteinase (MMP-9) in bronchial lavages of six patients undergoing mechanical ventilation (MV) for status asthmaticus (SA) and in six patients with mild asthma. Ten healthy nonventilated patients and four patients under MV without preexisting respiratory disease were also investigated. Patients with SA were characterized by prominent neutrophilic inflammation (82 +/- 4% versus 10% in mild asthma). On the basis of enzymatic and immunological analysis, results showed an acute 10- to 160-fold increase of 92 kDa gelatinase (MMP-9) concentration in epithelial lining fluid (ELF) from patients with SA, together with activated forms (46 and 26 kDa) of stromelysin-1 matrix metalloproteinase (MMP-3) and detectable concentration of free metallogelatinolytic activity (1-5 micrograms gelatin hydrolyzed/48 h/ml ELF). Concomitant elevated level of tissue inhibitor of metalloproteinase-1 (TIMP-1) was shown only in patients with SA, thus counterbalancing, at least partially, excess of activated 92 kDa gelatinase. Acutely enhanced albumin levels were only observed in patients with SA; in addition, 92 kDa gelatinase and albumin levels were significantly and positively correlated (r = 0.96, p < 0.0001), suggesting that 92 kDa gelatinase may account for increased bronchial permeability in patients with SA. Several arguments support that 92 kDa gelatinase during SA originates both from numerous activated chemoattracted neutrophils and from activated bronchial epithelial cells in response to in situ lung injury. The fact that no relevant change in ELF, albumin, MMP-9, MMP-3, TIMP-1, or laminin degradation products was observed during mild asthma, strongly supports that the mechanism of airway inflammation in SA is quite distinct from that observed in mild asthma.