Leukotriene C4 upregulates collagenase expression and synthesis in human lung fibroblasts

Lipids - two sides of the same coin in lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is characterized by progressive extracellular matrix deposition in the lung parenchyma leading to the destruction of lung structure, respiratory failure and premature death. Recent studies revealed that the pathogenesis of IPF is associated with alterations in the synthesis and the activity of lipids, lipid regulating proteins and cell membrane lipid transporters and receptors in different lung cells. Furthermore, deregulated lipid metabolism was found to contribute to the profibrotic phenotypes of lung fibroblasts and alveolar epithelial cells. Consequently, several pharmacological agents, targeting lipids, lipid mediators, and lipoprotein receptors, was successfully tested in the animal models of lung fibrosis and entered early phase clinical trials. In this review, we highlight new therapeutic options to counteract disturbed lipid hemostasis in the maladaptive lung remodeling.

Parameters of lung inflammation in asthmatic as compared to healthy children in a contaminated city

Background

The impact of air pollution on the respiratory system has been estimated on the basis of respiratory symptoms and lung function. However; few studies have compared lung inflammation in healthy and asthmatics children exposed to high levels of air pollution. The aim of the study was to elucidate the modulatory effect of air pollution on Cysteinyl-leukotrienes (Cys-LTs) levels in exhaled breath condensate (EBC) among healthy and asthmatic children.

Methods

We performed a cross-sectional comparative study. Children between 7–12 years of age, asthmatics and non-asthmatics, residents of a city with high levels of PM₁₀ were included. In all cases, forced spirometry, Cys-LTs levels in EBC, and the International Study of Asthma and Allergies in Childhood questionnaire were evaluated. We also obtained average of PM₁₀, CO, SO₂ and O₃ levels during the period of the study by the State Institute of Ecology.

Results

We studied 103 children (51 asthmatics and 52 non-asthmatics). Cys-LTs levels were higher in asthmatics than in non-asthmatics (77.3 ± 21.6 versus 60.3 ± 26.8 pg/ml; p = 0.0005). Also, Cys-LTs levels in children with intermittent asthma were lower than in children with persistent asthma (60.4 ± 20.4 versus 84.7 ± 19.2 pg/ml; p = 0.0001). In the multiple regression model, factors associated with levels of Cys-LTs were passive smoking (β = 13.1, p 0.04) and to be asthmatic (β = 11.5, p 0.03).

Conclusions

Cys-LTs levels are higher in asthmatic children than in healthy children in a contaminated city and its levels are also associated with passive smoking.

Exposure of human astrocytes to leukotriene C4 promotes a CX3CL1/fractalkine-mediated transmigration of HIV-1-infected CD4⁺ T cells across an in vitro blood-brain barrier model

Eicosanoids, including cysteinylleukotrienes (cysLTs), are found in the central nervous system (CNS) of individuals infected with HIV-1. Few studies have addressed the contribution of cysLTs in HIV-1-associated CNS disorders. We demonstrate that conditioned medium from human astrocytes treated with leukotriene C4 (LTC4) increases the transmigration of HIV-1-infected CD4(+) T cells across an in vitro blood-brain barrier (BBB) model using cultured brain endothelial cells. Additional studies indicate that the higher cell migration is linked with secretion by astrocytes of CX3CL1/fractalkine, a chemokine that has chemoattractant activity for CD4(+) T cells. Moreover, we report that the enhanced cell migration across BBB leads to a more important CD4(+) T cell-mediated HIV-1 transfer toward macrophages. Altogether data presented in the present study reveal the important role that LTC4, a metabolite of arachidonic acid, may play in the HIV-1-induced neuroinvasion, neuropathogenesis and disease progression.

A novel prostacyclin agonist protects against airway hyperresponsiveness and remodeling in mice

Airway remodeling in bronchial asthma results from chronic, persistent airway inflammation. The effects of the reversal of airway remodeling by drug interventions remain to be elucidated. We investigated the effects of ONO-1301, a novel prostacyclin agonist with thromboxane inhibitory activity, on the prevention and reversibility of airway remodeling in an experimental chronic asthma model. Mice sensitized and challenged to ovalbumin (OVA) three times a week for 5 consecutive weeks were administered ONO-1301 or vehicle twice a day from the fourth week of OVA challenges. Twenty-four hours after the final OVA challenge, airway hyperresponsiveness (AHR) was assessed, and bronchoalveolar lavage was performed. Lung specimens were excised for staining to detect goblet-cell metaplasia, airway smooth muscle, and submucosal fibrosis. Mice administered ONO-1301 showed limited increases in AHR compared with mice administered the vehicle. The histological findings of airway remodeling were improved in ONO-1301-treated mice compared with vehicle-treated mice. Presumably, these therapeutic effects of ONO-1301 are attributable to the up-regulation of production of hepatocyte growth factor (HGF) in lung tissue, because the neutralization of HGF by antibodies prevented the effects of ONO-1301 on AHR and airway remodeling. Mice administered ONO-1301 showed similar levels of AHR and airway remodeling as mice administered montelukast, a cysteinyl-leukotriene-1 receptor antagonist, and lower levels were observed in mice administered dexamethasone. These data suggest that ONO-1301 exerts the effect of reversing airway remodeling, at least in part through an elevation of HGF in the lungs, and may be effective as an anti-remodeling drug in the treatment of asthma.

5-Lipoxygenase-activating protein (FLAP) inhibitor MK-0591 prevents aberrant alveolarization in newborn mice exposed to 85% oxygen in a dose- and time-dependent manner

Bronchopulmonary dysplasia is characterized by prolonged oxygen dependency due to compromised gas-exchange capability. This is attributable mainly to inadequate and aberrant alveolarization resulting from insults like hyperoxia. Leukotrienes are associated with hyperoxia-induced inhibition of alveolarization. We hypothesized that a 5-lipoxygenase-activating protein (FLAP) inhibitor given while newborn mice were exposed to 85% oxygen would prevent aberrant alveolarization in a dose- and time-dependent manner. Newborn mice were exposed to either room air or hyperoxia for 14 days. Pups were treated with either vehicle or MK-0591 10, 20, or 40 mg/kg subcutaneously daily for days 1-4, 5-9, or 10-14. On day 14, the lungs were inflated, fixed, and stained for histopathological and morphometric analyses. Hyperoxia groups treated with MK-0591 20 or 40 mg/kg during days P1-P4 or P10-P14 showed alveolarization that resembled that of room air controls while untreated hyperoxia groups showed definite evidence of aberrant alveolarization but no inflammation. In a hyperoxia-exposed newborn mice model, a FLAP inhibitor given during critical window periods may prevent aberration of alveolarization in a dose- and time-dependent manner.

Retinoic acids exhibit anti-fibrotic activity through the inhibition of 5-lipoxygenase expression in scleroderma fibroblasts

The pathogenesis of systemic sclerosis (SSc) is not fully understood and there is no effective treatment for this disease. Retinoic acid (RA) can modulate connective tissue metabolism, exhibit anti-fibrotic activity, and improve the clinical symptoms of SSc. However, the mechanisms by which RA elicits its anti-fibrotic actions remain to be determined. The aim of this study was to elucidate the underlying mechanisms by which RA exerts beneficial effects on scleroderma. Cultured skin fibroblasts from patients with scleroderma were treated with RA and their effect on the expression of 5-lipoxygenase (LOX), transforming growth factor (TGF)-β1, connective tissue growth factor (CTGF), type I and type III collagen was tested by reverse transcription polymerase chain reaction (RT-PCR) and western immunoblotting. The effect of MK886, a 5-LOX-specific inhibitor, on the expression of TGF-β1, CTGF, type I and type III collagen was also examined by RT-PCR. In cultured scleroderma fibroblasts, the expression of 5-LOX was elevated compared with normal human dermal fibroblasts. RA significantly inhibited the expression of 5-LOX and of TGF-β1, CTGF, type I and type III collagen. We further found that the expression of TGF-β1, CTGF and type I and type III collagen mRNA was inhibited by MK886 in scleroderma fibroblasts. In vitro, RA reduced 5-LOX expression in scleroderma fibroblasts and downregulated TGF-β1 and CTGF expression, leading to the inhibition of type I and type III collagen synthesis. Our results indicate that the clinical effects of RA on scleroderma are, at least in part, attributable to the reduction of 5-LOX expression and the subsequent suppression of TGF-β1 and CTGF expression that results in the blockade of collagenogenesis.

Arachidonic acid increases matrix metalloproteinase 9 secretion and expression in human monocytic MonoMac 6 cells

Background

Dietary fatty acids may modulate inflammation in macrophages of the atherosclerotic plaque, affecting its stability. The n-6 polyunsaturated fatty acid (PUFA) arachidonic acid (AA) generally promotes inflammation, while the PUFAs of the n-3 series eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) and docosahexaenoic acid (DHA) are considered anti-inflammatory. We determined how these PUFAs influence MMP-9 expression and secretion by the human monocytic cell line (MonoMac 6) at baseline and after 24-hour exposure. MMP-9 protein was measured by zymography and relative levels of MMP-9 mRNA were determined using quantitative real time PCR.

Results

Supplementation with AA (but not the n-3 fatty acids) increased, in a dose-dependent manner, expression of MMP-9 protein. This stimulation was regulated at the mRNA level. MMP-9 secretion started after 1 h of incubation and could not be prevented by simultaneous presence of n-3 series fatty acids. Finally, the secretion could be attenuated by LY 294002, a specific phosphatidylinositol-3-kinase (PI3K) inhibitor and by SH-5, a selective Akt inhibitor, suggesting that activation of PI3K by AA leads to augmented and sustained MMP-9 production.

Conclusion

This study shows that of the PUFA studied, AA alone influences the expression of MMP-9, which might have implications in MMP-9 induced plaque rupture.

Structural changes in airway diseases: characteristics, mechanisms, consequences, and pharmacologic modulation

In airway diseases such as asthma and COPD, specific structural changes may be observed, very likely secondary to an underlying inflammatory process. Although it is still controversial, airway remodeling may contribute to the development of these diseases and to their clinical expression and outcome. Airway remodeling has been described in asthma in various degrees of severity, and correlations have been found between such features as increase in subepithelial collagen or proteoglycan deposits and airway responsiveness. Although the clinical significance of airway remodeling remains a matter of debate, it has been suggested as a potential target for treatments aimed at reducing asthma severity, improving its control, and possibly preventing its development. To date, drugs used to treat airway diseases have a little influence on airway structural changes. More research should be done to identify key changes, valuable treatments, and proper interventional timing to counteract these changes. The potential of novel therapeutic agents to reverse or prevent airway remodeling is an exciting avenue and warrants further evaluation.

Exhaled breath condensate cysteinyl leukotrienes and airway remodeling in childhood asthma: a pilot study

Background

It has been suggested that cysteinyl leukotrienes (cysLTs) play an important role in airway remodeling. Previous reports have indicated that cysLTs augment human airway smooth muscle cell proliferation. Recently, cysLTs have been measured in exhaled breath condensate (EBC). The aim of this study was to evaluate the relationship between cysLTs in EBC and another marker of airway remodeling, reticular basement membrane (RBM) thickening, in endobronchial biopsies in children.

Methods

29 children, aged 4–15 years, with moderate to severe persistent asthma, who underwent bronchoscopy as part of their clinical assessment, were included. Subjects underwent spirometry and EBC collection for cysLTs analysis, followed by bronchoscopy and endobronchial biopsy within 24 hours.

Results

EBC cysLTs were significantly lower in asthmatic children who were treated with montelukast than in those who were not (median (interquartile range) 36.62 (22.60–101.05) versus 249.1 (74.21–526.36) pg/ml, p = 0.004). There was a significant relationship between EBC cysLTs and RBM thickness in the subgroup of children who were not treated with montelukast (n = 13, r = 0.75, p = 0.003).

Conclusion

EBC cysLTs appear to be associated with RBM thickening in asthma.

Apoptosis signal-regulating kinase 1 in leukotriene D(4)-induced activator protein-1 activation in airway smooth muscle cells

Cysteinyl leukotrienes (LTs) are involved in allergic disorders including bronchial asthma. Transcription factor activator protein-1 (AP-1) activation is essential for cell proliferation and differentiation. LTD(4) is shown to promote human airway smooth muscle cell proliferation; however, the effect of LTD(4) on AP-1 activation in airway smooth muscle cells and the molecular mechanism in regulating AP-1 activation have not been determined. We examined the effect LTD(4) on AP-1 activation in human airway smooth muscle cells and analyzed a role of apoptosis signal-regulating kinase1 (ASK1), an upstream kinase kinase of c-Jun-NH(2)-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK) in LTD(4)-induced AP-1 activation to clarify the signaling molecule regulating AP-1 activation. The results showed that LTD(4) induced AP-1 activation determined by AP-1-dependent luciferase gene activity and ASK1 phosphorylation. Transient transfection of the dominant negative form of ASK1 attenuated LTD(4)-induced AP-1 activation. In addition, LTD(4)-induced AP-1 activity was depressed in the dominant negative form of ASK1-stably transfected porcine artery endothelial cells compared to that in the parental porcine artery endothelial cells. These results indicate that LTD(4) is capable of inducing AP-1 activation and ASK1 regulates AP-1 activation in LTD(4)-stimulated airway smooth muscle cells.

[Drug treatments for idiopathic pulmonary fibrosis]

Idiopathic pulmonary fibrosis is a disease of unknown cause characterized by cough, progressive dyspnea, restrictive respiratory disorder, a typical honeycomb aspect on the high-resolution CT-scan, and usual interstitial pneumonia at histological examination of the lung biopsy. Most patients die 3 to 8 years after diagnosis. Current treatment is based on a combination of corticosteroids and immunosuppressants, but the efficacy of treatment remains a matter of debate. New therapeutics currently under evaluation in controlled clinical trials include interferon-gamma, pirfenidone, N-acetylcysteine, etanercept (anti-TNFalpha), bosentan (endothelin receptor antagonist), imatinib (tyrosine-kinases inhibitor of the PDGF receptor), etc. At the same time, new compounds showing efficacy in experimental models of fibrosis and the development of new pathophysiological concepts open new perspectives both in terms of concept and clinical practice.

Montelukast in early childhood asthma. Predict value of IgG in clinical reply in children 2 to 5 years old?

BACKGROUND

According to current knowledge, asthma is basically an inflammatory process. Its causes and physiopathological mechanisms are various. The final result is a recurrent obstructive bronchial process, with sibilants and/or dypnea, which causes an upset in functional respiratory tests, among which the maximum respiratory peak flow meter diminished for the age, sex, and height of patient.

AIMS

Our aim is to evaluate if response to treatment with Montelukast has any link with immnuloglobin values (IgG, IgA, IgM, IgE) at start of treatment.

MATERIALS AND METHODS

Included in the study were 32 children, of whom 2 did not begin and 1 who did not provide personal data. There were 29 patients in total, 11 girls and 18 boys. Each made three visits: first where they were instructed, together with their parents, in how to manage the meter and where they received the peak flow meter, Vitalograph, and personal data sheet, where personal and family medical history were noted. The second visit was after 4 weeks, for a clinical assessment and the third visit after 8 weeks. The value register of the PEF would be made morning and night, noting the highest value of three measurements. IgG, IgA, IgM, IgA values were quantified before treatment began. The statistic package STATA 2001 was used in the treatment of data statistics.

RESULTS

Our between the value reached by the PEF after treatment and the IgG values at the beginning of treatment (0.712). In lesser measurement for IgA values (0.660). For each 100 mg/ml of increase in the value of IgG, an increase of 10 l/min in the PEF measurement before and following treatment with Montelukast was produced.

CONCLUSIONS

IgG values increase with age. Children with a greater IgG value at the beginning of treatment reached higher PEF values after same. It is not known if the results would be similar with another type of treatment and the way in which IgG influences the results. What appears to be confirmed by available studies is that this relation is found in a group of small children, the aim of our study.

Leukotriene receptors in rhinitis and sinusitis

Cysteinyl leukotrienes (CysLTs) mediate their biologic activities through interactions with the CysLT1 and CysLT2 receptors. CysLT1 receptors are prominently expressed on smooth muscle cells and lung fibroblasts, whereas CysLT2 receptors are expressed on heart Purkinje fiber cells, adrenal chromaffin cells, and endothelial cells. Both receptors are expressed on eosinophils and mast cells, but CysLT1 receptors alone are on neutrophils. Antigen-presenting cells more prominently express the type 2 receptor. CysLT1 receptors are uniquely important for bronchospasm, whereas CysLT2 receptors can stimulate endothelial cell adherence, myofibroblast proliferation, and chemokine production by mast cells. Comprehensive inhibition of the proinflammatory activities of CysLTs might require either combination CysLT1 and CysLT2 receptor antagonists or inhibitors of the CysLT synthesis pathway.

Characterization of interleukin-4-stimulated nasal polyp fibroblasts

Chronic hyperplastic eosinophilic sinusitis is an inflammatory disease that results in the accumulation of eosinophils, fibroblasts, mast cells, and goblet cells at the site of injury. A common feature of this disease is the presence of nasal polyposis (NP). The current studies were designed to assess the contribution of interleukin (IL)-4 to fibroblast-mediated inflammation in chronic hyperplastic eosinophilic sinusitis/NP. In addition, we hypothesized that cysteinyl leukotrienes (CysLT) may directly influence fibroblast-mediated fibrotic and remodeling pathways in this disorder. Fibroblasts were isolated from NP tissue. All fibroblast lines expressed the IL-4 receptor. IL-4 induced changes in mRNA and protein expression of fibrotic (transforming growth factor-beta1 and -beta2) and inflammatory cytokines and chemokines (IL-6 and CCL11) by fibroblasts as measured by semiquantitative and quantitative polymerase chain reaction, RNase protection assay, and enzyme-linked immunosorbent assay. The expression of CysLT and other proinflammatory lipid receptors on fibroblasts was evaluated. CysLT1 and CysLT2 receptors were not expressed on fibroblasts; however, LPA(1) receptor was constitutively expressed and LPA(2) receptor expression was upregulated by IL-4. The metabolic cascade involved in CysLT synthesis was not expressed in fibroblasts and could not be induced by IL-4 treatment.

Elevated levels of leukotriene B4 and leukotriene E4 in bronchoalveolar lavage fluid from patients with scleroderma lung disease

OBJECTIVE

The leukotrienes are a family of arachidonic acid-derived lipid mediators with proinflammatory and profibrotic properties. The aim of this study was to analyze the role of leukotriene B(4) (LTB(4)) and LTE(4) in the pathogenesis of scleroderma lung disease (SLD).

METHODS

Nineteen systemic sclerosis (SSc) patients with SLD, 11 SSc patients without SLD, and 10 healthy controls were studied. Bronchoalveolar lavage (BAL) fluid was obtained during routine bronchoscopy of the right middle lobe in all study subjects. Levels of LTB(4) and LTE(4) were measured using enzyme immunoassay kits.

RESULTS

Levels of LTB(4) and LTE(4) were significantly higher in SSc patients with SLD (251 +/- 170 pg/ml and 479 +/- 301 pg/ml, respectively), than those in patients without SLD (114 +/- 86 and 159 +/- 149 pg/ml) and those in normal controls (86 +/- 49 and 110 +/- 67 pg/ml). In the total group of patients with SSc, levels of both leukotrienes correlated positively with the total number of cells in the BAL fluid and correlated negatively with the forced vital capacity. After intravenous pulse therapy with cyclophosphamide in 6 patients, there was a significant reduction in the concentration of LTB(4) (from 380 +/- 196 pg/ml to 155 +/- 123 pg/ml) but no significant difference in the levels of LTE(4) (from 697 +/- 325 pg/ml to 418 +/- 140 pg/ml).

CONCLUSION

Our findings show that LTB(4) and LTE(4) levels are elevated in SSc patients with SLD and correlate with parameters of inflammation in the lungs. These results indicate that leukotrienes may contribute to the pathogenesis of SLD and may represent a new therapeutic target.

Roles of cysteinyl leukotrienes in airway inflammation, smooth muscle function, and remodeling

A new paradigm for asthma pathogenesis is presented in which exaggerated inflammation and remodeling in the airways are a consequence of abnormal injury and repair responses arising from a subject's susceptibility to components of the inhaled environment. An epithelial-mesenchymal trophic unit becomes activated to drive pathologic remodeling and smooth muscle proliferation through complex cytokine interactions. Histamine, prostanoids, and cysteinyl leukotrienes (CysLTs) are potent contractile agonists of airway smooth muscle (ASM). The CysLTs appear to play a central role in regulating human ASM motor tone and phenotypic alterations, manifested as hypertrophy and hyperplasia in chronic severe asthma. The CysLTs augment growth factor-induced ASM mitogenesis through activation of CysLT receptors. Although they mediate their contractile effects by increasing phosphoinositide turnover and inducing increased cytosolic calcium, new data suggest that part of the contractile effect may be independent of calcium mobilization. Prostaglandin E(2), the predominant eicosanoid product of the airway epithelium, is a potent inhibitor of mitogenesis, collagen synthesis, and mesenchymal cell chemotaxis and therefore can suppress inflammation and fibroblast activation. The capacity of the epithelium for CysLT synthesis is inversely related to its ability to make PGE(2). The ASM is capable of expressing both leukotriene-synthesizing enzymes and CysLT receptors, and cytokines upregulate the receptor expression. This may be an explanation for the CysLTs promoting airway hyperresponsiveness in asthma. The CysLTs play an important role in the airway remodeling seen in persistent asthma that includes increases of airway goblet cells, mucus, blood vessels, smooth muscle, myofibroblasts, and airway fibrosis. Evidence from a mouse model of asthma demonstrated that CysLT(1) receptor antagonists inhibit the airway remodeling processes, including eosinophil trafficking to the lungs, eosinophil degranulation, T(H)2 cytokine release, mucus gland hyperplasia, mucus hypersecretion, smooth muscle cell hyperplasia, collagen deposition, and lung fibrosis.

The biochemistry and medical significance of the flavonoids

Flavonoids are plant pigments that are synthesised from phenylalanine, generally display marvelous colors known from flower petals, mostly emit brilliant fluorescence when they are excited by UV light, and are ubiquitous to green plant cells. The flavonoids are used by botanists for taxonomical classification. They regulate plant growth by inhibition of the exocytosis of the auxin indolyl acetic acid, as well as by induction of gene expression, and they influence other biological cells in numerous ways. Flavonoids inhibit or kill many bacterial strains, inhibit important viral enzymes, such as reverse transcriptase and protease, and destroy some pathogenic protozoans. Yet, their toxicity to animal cells is low. Flavonoids are major functional components of many herbal and insect preparations for medical use, e.g., propolis (bee's glue) and honey, which have been used since ancient times. The daily intake of flavonoids with normal food, especially fruit and vegetables, is 1-2 g. Modern authorised physicians are increasing their use of pure flavonoids to treat many important common diseases, due to their proven ability to inhibit specific enzymes, to simulate some hormones and neurotransmitters, and to scavenge free radicals.

A role for cysteinyl leukotrienes in airway remodeling in a mouse asthma model

Airway inflammation and remodeling in chronic asthma are characterized by airway eosinophilia, hyperplasia of goblet cells and smooth muscle, and subepithelial fibrosis. We examined the role of leukotrienes in a mouse model of allergen-induced chronic lung inflammation and fibrosis. BALB/c mice, after intraperitoneal ovalbumin (OVA) sensitization on Days 0 and 14, received intranasal OVA periodically Days 14-75. The OVA-treated mice developed an extensive eosinophil and mononuclear cell inflammatory response, goblet cell hyperplasia, and mucus occlusion of the airways. A striking feature of this inflammatory response was the widespread deposition of collagen beneath the airway epithelial cell layer and also in the lung interstitium in the sites of leukocytic infiltration that was not observed in the saline-treated controls. The cysteinyl leukotriene(1) (CysLT(1)) receptor antagonist montelukast significantly reduced the airway eosinophil infiltration, mucus plugging, smooth muscle hyperplasia, and subepithelial fibrosis in the OVA-sensitized/challenged mice. The presence of Charcot-Leyden-like crystals in airway macrophages and the increased interleukin (IL)-4 and IL-13 mRNA expression in lung tissue and protein in BAL fluid seen in OVA-treated mice were also inhibited by CysLT(1) receptor blockade. These data suggest an important role for cysteinyl leukotrienes in the pathogenesis of chronic allergic airway inflammation with fibrosis.

Evidence of 5-lipoxygenase overexpression in the skin of patients with systemic sclerosis: a newly identified pathway to skin inflammation in systemic sclerosis

OBJECTIVE

Leukotrienes are a family of arachidonic acid derivatives with potent proinflammatory and profibrotic properties, and 5-lipoxygenase (5-LOX) catalyzes two key steps in the leukotriene biosynthetic pathway. Since inflammatory cell infiltrates and excessive fibrosis are hallmarks of systemic sclerosis (SSc) skin lesions, we undertook the present study to investigate the expression of 5-LOX in skin biopsy specimens from patients with SSc.

METHODS

Expression of 5-LOX in skin sections from 10 SSc patients and 8 healthy controls was examined by in situ hybridization with specific riboprobes and by immunohistochemistry analysis with 5-LOX monoclonal antibodies. Synthesis of 5-LOX by cultured dermal fibroblasts from 7 patients with SSc and 4 controls was measured by fluorescence-activated cell sorter analysis. In addition, concentrations of leukotriene B4 (LTB4) and LTE4 in fibroblast supernatants after stimulation were determined using enzyme immunoassays.

RESULTS

Expression of 5-LOX was found in all skin sections from SSc patients as well as from controls. However, the number and percentage of 5-LOX-positive cells were significantly higher in SSc skin sections compared with control sections. Expression of 5-LOX was seen in cells within perivascular inflammatory infiltrates as well as in fibroblasts throughout the skin. The experiments with cultured skin fibroblasts revealed that 5-LOX was constitutively expressed in these cells, which resulted in the production of leukotrienes after cell stimulation. Whereas no difference was found for LTE4, SSc fibroblasts produced significantly higher amounts of LTB4 after stimulation, compared with healthy control fibroblasts.

CONCLUSION

The results of this study suggest that the 5-LOX pathway may be of significance in the pathogenesis of SSc and may represent a target for new treatment strategies.

Surfactant components modulate fibroblast apoptosis and type I collagen and collagenase-1 expression

During lung injury, fibroblasts migrate into the alveolar spaces where they can be exposed to pulmonary surfactant. We examined the effects of Survanta and surfactant protein A (SP-A) on fibroblast growth and apoptosis and on type I collagen, collagenase-1, and tissue inhibitor of metalloproteinase (TIMP)-1 expression. Lung fibroblasts were treated with 100, 500, and 1,000 microg/ml of Survanta; 10, 50, and 100 microg/ml of SP-A; and 500 microg/ml of Survanta plus 50 microg/ml of SP-A. Growth rate was evaluated by a formazan-based chromogenic assay, apoptosis was evaluated by DNA end labeling and ELISA, and collagen, collagenase-1, and TIMP-1 were evaluated by Northern blotting. Survanta provoked fibroblast apoptosis, induced collagenase-1 expression, and decreased type I collagen affecting mRNA stability approximately 10-fold as assessed with the use of actinomycin D. Collagen synthesis and collagenase activity paralleled the gene expression results. SP-A increased collagen expression approximately 2-fold and had no effect on collagenase-1, TIMP-1, or growth rate. When fibroblasts were exposed to a combination of Survanta plus SP-A, the effects of Survanta were partially reversed. These findings suggest that surfactant lipids may protect against intraluminal fibrogenesis by inducing fibroblast apoptosis and decreasing collagen accumulation.

Acidic fibroblast growth factor induces an antifibrogenic phenotype in human lung fibroblasts

Acidic fibroblast growth factor (FGF-1), a prototype member of the heparin-binding growth factor family, influences proliferation, differentiation, and protein synthesis in different cell types. However, its possible role on lung extracellular matrix (ECM) metabolism has not been evaluated. In this study we examined the effects of FGF-1 and FGF-1 plus heparin on type I collagen, collagen-binding stress protein HSP47, interstitial collagenase (matrix metalloproteinase [MMP]-1), gelatinase A, and tissue inhibitor of metalloproteinase (TIMP)-1 and TIMP-2 expression by normal human lung fibroblasts. Heparin was used because it enhances the biologic activities of FGF-1. Fibroblasts were exposed either to 20 ng/ml FGF-1 plus 100 micrograms/ml heparin for 48 h or to FGF-1 or heparin alone. Messenger RNA (mRNA) expression was analyzed by Northern blot. Collagen synthesis was evaluated by digestion of [3H]collagen with bacterial collagenase, MMP-1 by Western blot, and gelatinolytic activities by zymography. Our results show that FGF-1 induced collagenase mRNA expression, which was strongly enhanced when FGF-1 was used with heparin. Likewise, both FGF-1 and FGF-1 plus heparin reduced by 70 to 80% the expression of type I collagen transcript, in part through effect on pro-alpha1(I) collagen mRNA stability. A downregulation of HSP47 gene expression was also observed. Synthesis of collagen and collagenase proteins paralleled gene expression results. FGF-1 activities were abolished with genistein, a tyrosine kinase inhibitor. Neither FGF-1 nor FGF-1 plus heparin affected the expression of TIMP-1, TIMP-2, and gelatinase A. These findings demonstrate that FGF-1, mostly in the presence of heparin, upregulates collagenase and downregulates type I collagen expression that might have a protective role in avoiding collagen accumulation during lung ECM remodeling.

Collagenase-3 induction in rat lung fibroblasts requires the combined effects of tumor necrosis factor-alpha and 12-lipoxygenase metabolites: a model of macrophage-induced, fibroblast-driven extracellular matrix remodeling during inflammatory lung injury

The mechanisms responsible for the induction of matrix-degrading proteases during lung injury are ill defined. Macrophage-derived mediators are believed to play a role in regulating synthesis and turnover of extracellular matrix at sites of inflammation. We find a localized increase in the expression of the rat interstitial collagenase (MMP-13; collagenase-3) gene from fibroblastic cells directly adjacent to macrophages within silicotic rat lung granulomas. Conditioned medium from macrophages isolated from silicotic rat lungs was found to induce rat lung fibroblast interstitial collagenase gene expression. Conditioned medium from primary rat lung macrophages or J774 monocytic cells activated by particulates in vitro also induced interstitial collagenase gene expression. Tumor necrosis factor-alpha (TNF-alpha) alone did not induce interstitial collagenase expression in rat lung fibroblasts but did in rat skin fibroblasts, revealing tissue specificity in the regulation of this gene. The activity of the conditioned medium was found to be dependent on the combined effects of TNF-alpha and 12-lipoxygenase-derived arachidonic acid metabolites. The fibroblast response to this conditioned medium was dependent on de novo protein synthesis and involved the induction of nuclear activator protein-1 activity. These data reveal a novel requirement for macrophage-derived 12-lipoxygenase metabolites in lung fibroblast MMP induction and provide a mechanism for the induction of resident cell MMP gene expression during inflammatory lung processes.

Lung alveolar epithelial cells synthesize interstitial collagenase and gelatinases A and B in vitro

Type II pneumocytes are multifunctional alveolar epithelial cells that play a major role in the maintenance of lung structure and function. Recent evidence supports that these cells can synthesize a variety of extracellular matrix components in vitro, suggesting an active participation in connective tissue remodeling. However, their possible role in extracellular matrix degradation is unknown. In this study the production of matrix metalloproteinases (MMPs) was examined in primary cultures of rat alveolar type II pneumocytes after 2 and 7 days in culture. Under basal conditions, at both periods type II cells expressed interstitial collagenase mRNA. The immunoreactive protein was detected both in the cells and in conditioned media, and collagenolytic activity was revealed after trypsin activation. Gelatinolytic activity was detected by zymography showing a relative molecular mass of approximately 72 and 92 kDa (gelatinases A and B). Phorbol treatment increased collagenase and gelatinase activities. In addition, three alveolar epithelial cell lines were analysed for MMP production: MLE-12 (mice), L2 (rat), and A549 (human). The cell lines A549 and MLE-12 revealed collagenase and gelatinase A and B activities whereas the L2 cell line only exhibited gelatinase A activity, even after PMA induction. These findings demonstrate that alveolar epithelial cells synthesize in vitro several MMPs that confer on them the ability to degrade extracellular matrix and basement membrane components, a capacity of considerable importance for the remodeling of the stromal/epithelial interface.