Regulation of PDGF production and ERK activation by estrogen is associated with TSC2 gene expression.

Mechanisms that regulate the growth response to estrogen (17beta-estradiol, E2) are poorly understood. Recently, loss of function of the tuberous sclerosis complex 2 (TSC2) gene has been associated with E2-related conditions that are characterized by benign cellular proliferation. We examined the growth response to E2 in vascular smooth muscle cells (VSMCs) that possess wild-type TSC2 and compared them with ELT-3 smooth muscle cells that do not express TSC2. In TSC2-expressing VSMCs, growth inhibition in response to E2 was associated with downregulation of platelet-derived growth factor (PDGF), PDGF receptor (PDGFR), and limited activation of extracellular signal-regulated kinase (ERK). In contrast, the growth-promoting effect of E2 in TSC2-null ELT-3 cells was associated with induction of PDGF, robust phosphorylation of PDGFR, and sustained activation of ERK. Furthermore, in ELT-3 cells, cellular growth and ERK activation by E2 were inhibited by the PDGFR inhibitor tyrphostin AG 17 and by PDGF-neutralizing antibody. These results demonstrate that autocrine production of PDGF and augmentation of the ERK pathway leads to estrogen-induced cellular proliferation in TSC2-null cells, a pathway that was downregulated in cells that express TSC2. Understanding the mechanisms that regulate the diverse responses to the steroid hormone estrogen could lead to novel approaches to the treatment of estrogen-related diseases that are characterized by aberrant cell proliferation.

Transforming growth factor-beta 1-induced activation of the ERK pathway/activator protein-1 in human lung fibroblasts requires the autocrine induction of basic fibroblast growth factor.

Transforming growth factor-beta (TGF-beta) is involved in multiple processes including cell growth and differentiation. In particular, TGF-beta has been implicated in the pathogenesis of fibrotic lung diseases. In this study, we examined regulation of the mitogen-activated protein kinase pathway by TGF-beta1 in primary human lung fibroblasts. TGF-beta1 treatment resulted in extracellular signal-regulated kinase (ERK) pathway activation in a delayed manner, with maximal activity at 16 h. ERK activation occurred concomitantly with the induction of activator protein-1 (AP-1) binding, a nuclear factor required for activation of multiple genes involved in fibrosis. AP-1 binding was dependent on ERK activation, since the MEK-1 (mitogen-activated protein kinase kinase) inhibitor PD98059 inhibited TGF-beta1-induced binding. Induction of the receptor tyrosine kinase-linked growth factor, basic fibroblast growth factor (bFGF) protein expression temporally paralleled the activation of ERK/AP-1. Induction of AP-1 by TGF-beta1-conditioned medium was observed at 2 h, similar to AP-1 induction in response to exogenous bFGF. Dependence of ERK/AP-1 activation on bFGF induction was demonstrated by inhibition of TGF-beta1-induced ERK/AP-1 activation when conditioned medium from TGF-beta1-treated cells was incubated with bFGF-neutralizing antibody. Together, these results demonstrate that TGF-beta1 regulates the autocrine induction of bFGF, resulting in activation of the ERK mitogen-activated protein kinase pathway and induction of AP-1 binding.

Serotonin stimulates mitogen-activated protein kinase activity through the formation of superoxide anion.

Our previous studies have shown that, through an active transport process, serotonin (5-HT) rapidly elevates O(-)(2). formation, stimulates protein phosphorylation, and enhances proliferation of bovine pulmonary artery smooth muscle cells (SMCs). We presently show that 1 microM 5-HT also rapidly elevates phosphorylation and activation of the mitogen-activated protein (MAP) kinases extracellular signal-regulated kinase (ERK) 1 and ERK2 of SMCs, and the enhanced phosphorylation is blocked by the antioxidants Tiron, N-acetyl-L-cysteine (NAC), and Ginkgo biloba extract. Inhibition of MAP kinase with PD-98059 failed to block enhanced O(-)(2). formation by 5-HT. Chinese hamster lung fibroblasts (CCL-39 cells), which demonstrate both 5-HT transporter and receptor activity, showed a similar response to 5-HT (i.e., enhanced mitogenesis, O(-)(2). formation, and ERK1 and ERK2 phosphorylation and activation). Unlike SMCs, they also responded to 5-HT receptor agonists. We conclude that downstream signaling of MAP kinase is a generalized cellular response to 5-HT that occurs secondary to O(-)(2). formation and may be initiated by either the 5-HT transporter or receptor depending on the cell type.

Exhaled nitric oxide and bronchoalveolar lavage nitrite/nitrate in active pulmonary sarcoidosis.

Increased exhaled nitric oxide (NO) may reflect respiratory tract inflammation in untreated asthmatics. We compared exhaled NO and bronchoalveolar lavage (BAL) nitrate/nitrite (NO3-/NO2-) in 10 patients who had untreated, active pulmonary sarcoidosis with those of normal control subjects. Exhaled NO concentrations, determined by chemiluminescence, were similar in patients and control subjects (peak NO concentration of patients [mean +/- SD]: 13.6 +/- 5.9 parts per billion [ppb], peak NO concentration of control subjects: 11.2 +/- 5.7 ppb, p = 0.32; mean alveolar NO concentration of patients: 7.8 +/- 4.4 ppb, mean alveolar NO concentration of control subjects: 7.1 +/- 4.2 ppb, p = 0.70; end-tidal NO concentration of patients: 6.9 +/- 4.5 ppb, end-tidal NO concentration of control subjects: 6.6 +/- 4.0 ppb, p = 0.60). BAL NO2- was assayed using a modified Griess reaction after reduction of NO3- to NO2-. There was no significant difference in mean BAL NO2- concentrations, expressed as nanomoles per milliliter of epithelial lining fluid (patients: 544 nmol/ml, control subjects: 579 nmol/ml, p = 0.81) or as nanomoles per milliliter of BAL fluid (patients: 6.7 nmol/ml, control subjects: 5.7 nmol/ml, p = 0.41). These data suggest that excess NO generation does not accompany the respiratory tract inflammation of pulmonary sarcoidosis.

Matrix metalloproteinase expression and production by alveolar macrophages in emphysema.

The aim of this study was to examine the hypothesis that alveolar macrophages represent a significant source of matrix-degrading proteinases in the emphysematous lung. Macrophages from bronchoalveolar lavage fluid of 10 patients with emphysema and 10 normal volunteers were maintained in vitro for 24 h and assessed semiquantitatively for mRNA transcript levels of the matrix metalloproteinases (MMPs) gelatinases A and B, macrophage metalloelastase (MME), and interstitial collagenase. Release of these MMPs into the culture medium and secretion of neutrophil elastaselike activity was also assessed. Elevated levels of mRNA transcripts for gelatinase B (p < 0.0005) and interstitial collagenase (p < 0.0005) were observed in macrophages from emphysematous patients. Increased collagenase (p < 0.01) and neutrophil elastaselike activities (p < 0.001) were also measured in conditioned medium from patient macrophages. With gelatinase B, complexed forms of the enzyme were secreted by patient but not by control macrophages. No difference in transcript levels of gelatinase A or MME was observed between patient and control samples, and neither enzyme was detected in macrophage-conditioned media from either group. These results directly demonstrate that alveolar macrophages from the emphysematous lung produce elevated quantities of matrix-degrading enzymes with both elastolytic and collagenolytic activities.

Elevated levels of matrix metalloproteinases in bronchoalveolar lavage fluid of emphysematous patients.

BACKGROUND: Matrix degradation in emphysema has long been attributed to the action of neutrophil elastase (NE). More recently a role for other proteases, particularly the matrix metalloproteinases (MMPs), in the pathogenesis of this disease has been proposed. To date, however, the presence of MMPs in the lungs of patients with emphysema has not been demonstrated. METHODS: Samples of bronchoalveolar lavage (BAL) fluid from 10 patients with emphysema and from control subjects matched for sex and current smoking status were assessed for collagenase, gelatinase, and NE activity. Pulmonary function tests and computed tomographic (CT) scans were carried out on all study subjects. RESULTS: Collagenase activity was detected in BAL fluid samples from all emphysematous patients but in only one smoking control (p < 0.001). Gelatinase B was present in six patients and in two smoking controls (p < 0.03). The concomitant presence of gelatinase B in complex with lipocalin (NGAL) in the gelatinase positive samples suggests that the neutrophil is a significant source of the gelatinase B observed. NE was detected in six of the 10 patients with emphysema and in two smoking controls (p < 0.01), indicating that collagenase was more useful in discriminating between disease and control groups than either NE or gelatinase B. No relationship was observed between any of the enzymes measured and pulmonary function or CT density score. CONCLUSIONS: This study demonstrates, for the first time, the presence of increased levels of matrix metalloproteinases in the lungs of patients with emphysema and suggests that, in BAL fluid, collagenase activity may be a better indicator of the presence of emphysema than elastase.

Elastin and collagen remodeling in emphysema. A scanning electron microscopy study.

The relationship between elastin degradation and emphysema is well known. Recent evidence suggests that a complex process of pulmonary remodeling occurs within the emphysematous lung. The aim of this study was to assess the extent of extracellular matrix remodeling in emphysema by ultrastructural examination of elastin and collagen templates in an animal model of emphysema and in human emphysematous lungs. Emphysema was induced in rats by the intratracheal administration of porcine pancreatic elastase. Human lung samples were obtained at surgical resection for lung carcinoma. Emphysema was confirmed morphometrically and quantitated using the mean linear intercept. Matching sections were treated with sodium hydroxide and formic acid to expose collagen and elastin templates, respectively. Scanning electron microscopy with stereo-pair imaging allowed three-dimensional visualization of the exposed templates. In emphysematous lungs from both sources, sheets of elastin were disrupted and perforated with multiple fenestrations. In elastase-induced emphysema, this disintegration was accompanied by a marked increase in thickness of collagen fibrils, which contrasted with the fine fibrillar network of control lungs. Similarly, a pattern of thickened fibrils and disorganized deposition of collagen was observed in human lungs. In conclusion, these findings support the novel concept of increased collagen deposition and aberrant collagen remodeling in the pathogenesis of emphysema.

Effect of nebulised recombinant DNase on neutrophil elastase load in cystic fibrosis.

BACKGROUND: DNA released by degenerating inflammatory neutrophils contributes to mucous plugging of airways in patients with cystic fibrosis. Neutrophil elastase, a major effector of tissue destruction in the lungs of patients with cystic fibrosis, is a highly cationic molecule which is bound and inhibited by negatively charged polyanions such as mucin and DNA in purulent sputum. Thus, the solubilisation of DNA in the airways by aerosolised recombinant DNase may remove a source of neutrophil elastase inhibition, effectively increasing elastase load. The aim of this study was to assess the effect of rhDNase therapy on neutrophil elastase load in patients with cystic fibrosis. METHODS: Blood and sputum were collected from 15 patients with cystic fibrosis before initiation of nebulised DNase therapy and at 12 weeks following therapy. The long term effects of continuous rhDNase administration were evaluated at 52 weeks for 11 of these patients. Plasma was analysed for neutrophil elastase, interleukin (IL)-8 and neutrophil elastase in complex with alpha 1-protease inhibitor (alpha 1PI). Sputum was assessed for neutrophil elastase, IL-8, and active elastase. At each visit spirometric measurements were carried out. RESULTS: Sputum elastase activity decreased at 12 weeks and was maintained at 52 weeks when a decline in total plasma elastase was also observed. Although, as expected, there was a correlation between plasma levels of total elastase and neutrophil elastase/alpha 1PI complex, the decrease in the levels of the complex at 52 weeks did not reach statistical significance. CONCLUSIONS: This study indicates that prolonged daily administration of rhDNase results in a reduction in elastase load in patients with cystic fibrosis.