Role of connective tissue proteases in the pathogenesis of chronic inflammatory lung disease

Role of venlafaxine in prevention of cyclophosphamide-induced lung toxicity and airway hyperactivity in rats

Cyclophosphamide (CP) is a drug used in chemotherapy and management of neoplastic diseases. This study aimed to investigate the prophylactic impacts of venlafaxine against CP-induced lung toxicity in rats. Rats were assigned randomly into 3 groups; control, CP (150 mg/kg) and CP/venlafaxine (50 mg/kg). On the end day, rats were sacrificed then bronchoalveolar fluid (BALF) and lungs were harvested. CP produced significant decrease in animal body weights and significant increase in lung/body weight ratio; levels of LDH, total protein, total and differential cell counts in BALF in comparison with control group. Moreover, significant elevation incontents of MDA, NOx, TNF-α and IL-1β and significant decline in GSH, SOD activities were observed in lung tissues. CP increased the response of tracheal zigzag to ACh. Histopathological results showed that CP increased inflammation and fibrosis in lung tissues. Venlafaxine restored most parameters to the normal levels. This protective effect of venlafaxine could be linked to its ability to reduce oxidative stress and inflammation.

Semaphorin 4A enhances lung fibrosis through activation of Akt via PlexinD1 receptor

Semaphorin 4A plays a regulatory role in immune function and angiogenesis. However, its specific involvement in controlling lung fibrosis, a process that is closely related to angiogenesis and inflammation is still poorly understood. In the present study, we show that treatment of Sema4A on normal lung fibroblasts induces expression of proteins that contribute to a contractile phenotype, including alpha-smooth muscle actin (alpha-SMA), ezrin, moesin, and paxillin. We confirm that Sema4A enhances the ability of lung fibroblasts to contract collagen gel. Sema4A treatment led to resistance to apoptosis in normal lung fibroblasts. Relative to normal lung fibroblasts, fibroblasts cultured from scars of patients with the fibrotic disease Systemic Sclerosis (SSc) showed elevated Sema4A secretion, enhanced alpha-SMA, ezrin, moesin, and paxillin expression, and high ability to induce collagen gel contraction. Using neutralizing antibody against Sema4A receptor, PlexinD1, we found that endogenous Sema4A signalling in SSc fibroblast was through PlexinD1 receptor. We then identified the signalling mechanism through which Sema4A-PlexinD1 promotes the ability of normal fibroblasts to contract a collagen gel matrix. Western blot analysis showed that Sema4A activated the Akt pathway in lung fibroblasts, and the specific inhibitor of Akt pathway, Akt inhibitor III, blocked the ability of Sema4A to promote the ability of lung fibroblasts to contract a collagen gel matrix. Thus, blocking Sema4APlexinD1- Akt cascades might be beneficial in reducing pulmonary fibrosis.

Role of the KATP channel in the protective effect of nicorandil on cyclophosphamide-induced lung and testicular toxicity in rats

This study is the first to investigate the role of the KATP channel in the possible protection mediated by nicorandil against cyclophosphamide-induced lung and testicular toxicity in rats. Animals received cyclophosphamide (150 mg/kg/day, i.p.) for 2 consecutive days and then were untreated for the following 5 days. Nicorandil (3 mg/kg/day, p.o.) was administered starting from the day of cyclophosphamide injection with or without glibenclamide (5 mg/kg/day, p.o.). Nicorandil administration significantly reduced the cyclophosphamide-induced deterioration of testicular function, as demonstrated by increases in the level of serum testosterone and the activities of the testicular 3β- hydroxysteroid, 17β-hydroxysteroid and sorbitol dehydrogenases. Furthermore, nicorandil significantly alleviated oxidative stress (as determined by lipid peroxides and reduced glutathione levels and total antioxidant capacity), as well as inflammatory markers (tumour necrosis factor-α and interleukin-1β), in bronchoalveolar lavage fluid and testicular tissue. Finally, the therapy decreased the levels of fibrogenic markers (transforming growth factor-β and hydroxyproline) and ameliorated the histological alterations (as assessed by lung fibrosis grading and testicular Johnsen scores). The co-administration of glibenclamide (a KATP channel blocker) blocked the protective effects of nicorandil. In conclusion, KATP channel activation plays an important role in the protective effect of nicorandil against cyclophosphamide-induced lung and testicular toxicity.

Addition of immunosuppressive treatment to hemoperfusion is associated with improved survival after paraquat poisoning: a nationwide study

Paraquat poisoning associates very high mortality rate. Early treatment with hemoperfusion is strongly suggested by animal and human studies. Although the survival benefit of additional immunosuppressive treatment (IST) in combination with hemoperfusion is also reported since 1971, the large-scale randomized control trials to confirm the effects of IST is difficult to be executed. Therefore, we designed this nationwide large-scale population-based retrospective cohort study to investigate the outcome of paraquat poisoning with hemoperfusion and the additional effects of IST combined with hemoperfusion. This nationwide retrospective cohort study utilized data retrieved from the National Health Insurance Research Database (NHIRD) of Taiwan. A total of 1811 hospitalized patients with a diagnosis of paraquat poisoning who received hemoperfusion between 1997 and 2009 were enrolled. The mean age of all 1811 study subjects was 47.3 years. 70% was male. The overall survival rate was only 26.4%. Respiratory failure and renal failure were diagnosed in 56.2% and 36% patients. The average frequency of hemoperfusion was twice. IST was added in 42.2% patients. IST significantly increases survival rate (from 24.3% to 29.3%, P<0.001). The combined IST with methylprednisolone, cyclophosphamide and dexamethasone associates with the highest survival rate (48%, P<0.001). Moreover, patients younger than 45 years of age in the IST group had the best survival (41.0% vs. 33.7%, p<0.001). Our results support the use of IST with hemoperfusion for paraquat-poisoned patients. The best survival effect of IST is the combination of methylprednisolone, cyclophosphamide and daily dexamethasone, especially in patients with younger age.

Novel aspects of urokinase function in the injured lung: role of α2-macroglobulin

The level of active urokinase (uPA) is decreased in lung fluids of patients with acute lung injury/acute respiratory distress syndrome (ALI/ARDS) whereas α(2)-macroglobulin (α(2)-M), a plasma proteinase inhibitor, is a major component of these fluids. Since there have been reports describing the ability of α(2)-M to form complexes with uPA in vitro, we hypothesized that α(2)-M may interact with uPA in the lung to modulate its biological activity. Pulmonary edema fluids and lung tissues from patients with ALI/ARDS were evaluated for the presence of uPA associated with α(2)-M. Complexes between α(2)-M and uPA were detected in alveolar edema fluids as well as in lungs of patients with ALI/ARDS where they were located mainly in close proximity to epithelial cells. While uPA bound to α(2)-M retains its amidolytic activity towards low-molecular-weight substrates, it is not inhibited by its main physiological inhibitor, plasminogen activator inhibitor 1. We also investigated the functional consequences of formation of complexes between uPA and α(2)-M in vitro. We found that when α(2)-M:uPA complexes were added to cultures of human bronchial epithelial cells (BEAS-2B), activation of nuclear factor-κB as well as production of interleukin-6 and -8 was substantially suppressed compared with the addition of uPA alone. Our findings indicate for the first time that the function of uPA in patients with ALI/ARDS may be modulated by α(2)-M and that the effects may include the regulation of the fibrinolytic and signaling activities of uPA.

Conformational properties of the disease-causing Z variant of α1-antitrypsin revealed by theory and experiment

The human serine protease inhibitor (serpin) α-1 antitrypsin (α1-AT) protects tissues from proteases of inflammatory cells. The most common disease-causing mutation in α1-AT is the Z-mutation (E342K) that results in an increased propensity of α1-AT to polymerize in the ER of hepatocytes, leading to a lack of secretion into the circulation. The structural consequences of this mutation, however, remain elusive. We report a comparative molecular dynamics investigation of the native states of wild-type and Z α1-AT, revealing a striking contrast between their structures and dynamics in the breach region at the top of β-sheet A, which is closed in the wild-type simulations but open in the Z form. Our findings are consistent with experimental observations, notably the increased solvent exposure of buried residues in the breach region in Z, as well as polymerization via domain swapping, whereby the reactive center loop is rapidly inserted into an open A-sheet before proper folding of the C-terminal β-strands, allowing C-terminal domain swapping with a neighboring molecule. Taken together, our experimental and simulation data imply that mutations at residue 342 that either stabilize an open form of the top of β-sheet A or increase the local flexibility in this region, may favor polymerization and hence aggregation.

c-Kit is essential for alveolar maintenance and protection from emphysema-like disease in mice

RATIONALE

Previously, we demonstrated a candidate region for susceptibility to airspace enlargement on mouse chromosome 5. However, the specific candidate genes within this region accounting for emphysema-like changes remain unrecognized. c-Kit is a receptor tyrosine kinase within this candidate gene region that has previously been recognized to contribute to the survival, proliferation, and differentiation of hematopoietic stem cells. Increases in the percentage of cells expressing c-Kit have previously been associated with protection against injury-induced emphysema.

OBJECTIVES

Determine whether genetic variants of c-Kit are associated with spontaneous airspace enlargement.

METHODS

Perform single-nucleotide polymorphism association studies in the mouse strains at the extremes of airspace enlargement phenotype for variants in c-Kit tyrosine kinase. Characterize mice bearing functional variants of c-Kit compared with wild-type controls for the development of spontaneous airspace enlargement. Epithelial cell proliferation was measured in culture.

MEASUREMENTS AND MAIN RESULTS

Upstream regulatory single-nucleotide polymorphisms in the divergent mouse strains were associated with the lung compliance difference observed between the extreme strains. c-Kit mutant mice (Kit(W-sh)/(W-sh)), when compared with genetic controls, developed altered lung histology, increased total lung capacity, increased residual volume, and increased lung compliance that persist into adulthood. c-Kit inhibition with imatinib attenuated in vitro proliferation of cells expressing epithelial cell adhesion molecule.

CONCLUSIONS

Our findings indicate that c-Kit sustains and/or maintains normal alveolar architecture in the lungs of mice. In vitro data suggest that c-Kit can regulate epithelial cell clonal expansion. The precise mechanisms that c-Kit contributes to the development of airspace enlargement and increased lung compliance remain unclear and warrants further investigation.

Differences in acute lung response to elastase instillation in two rodent species may determine differences in severity of emphysema development

Elastase intratracheal instillation induces early emphysema in rodents. However, Syrian Golden hamsters develop more severe emphysema than Sprague-Dawley rats. We have reported species differences in oxidant/antioxidant balance modulating antiprotease function early after instillation. We now hypothesize that other components of the initial lung response to elastase might also be species-dependent. Sprague-Dawley rats and Syrian Golden hamsters received a single dose of pancreatic elastase (0.55 U/100 g body wt) to study acute lung injury biomarkers. Using serum, lung, and bronchoalveolar lavage fluid (BALF) samples, we evaluated changes in alveolar-capillary permeability, alpha 1-antitrypsin (α(1)-AT) concentration and activity, glutathione content, and proinflammatory cytokines. Rats showed a large increase in alveolar-capillary permeability and few hemorrhagic changes, whereas hamsters exhibited large hemorrhagic changes (P < 0.01) and mild transendothelial passage of proteins. Western blots showed a 30-fold increase in BALF α(1)-AT concentration in rats and only a 7-fold increase in hamsters (P < 0.001), with [α(1)-AT-elastase] complexes only in rats, suggesting differences in antiprotease function. This was confirmed by the α(1)-AT bioassay showing 20-fold increase in α(1)-AT activity in rats and only twofold increase in hamsters (P < 0.001). In rats, results were preceded by a 3-, 60-, and 20-fold increase in IL-6, IL-1β, and TNF-α respectively (P < 0.001). In hamsters, only IL-1β and TNF-α showed mild increases. All parameters studied were back to baseline by 4 days. In conclusion, several components of the initial lung response showed species differences. Cytokine release pattern and functional inhibition of α(1)-AT were the most significant components differing among species and could account for differences in susceptibility to elastase.

Implicit mechanistic role of the collagen, smooth muscle, and elastic tissue components in strengthening the air and blood capillaries of the avian lung

To identify the forces that may exist in the parabronchus of the avian lung and that which may explain the reported strengths of the terminal respiratory units, the air capillaries and the blood capillaries, the arrangement of the parabronchial collagen fibers (CF) of the lung of the domestic fowl, Gallus gallus variant domesticus was investigated by discriminatory staining, selective alkali digestion, and vascular casting followed by alkali digestion. On the luminal circumference, the atrial and the infundibular CF are directly connected to the smooth muscle fibers and the elastic tissue fibers. The CF in this part of the parabronchus form the internal column (the axial scaffold), whereas the CF in the interparabronchial septa and those associated with the walls of the interparabronchial blood vessels form the external, i.e. the peripheral, parabronchial CF scaffold. Thin CF penetrate the exchange tissue directly from the interparabronchial septa and indirectly by accompanying the intraparabronchial blood vessels. Forming a dense network that supports the air and blood capillaries, the CF weave through the exchange tissue. The exchange tissue, specifically the air and blood capillaries, is effectively suspended between CF pillars by an intricate system of thin CF, elastic and smooth muscle fibers. The CF course through the basement membranes of the walls of the blood and air capillaries. Based on the architecture of the smooth muscle fibers, the CF, the elastic muscle fibers, and structures like the interparabronchial septa and their associated blood vessels, it is envisaged that dynamic tensional, resistive, and compressive forces exist in the parabronchus, forming a tensegrity (tension integrity) system that gives the lung rigidity while strengthening the air and blood capillaries.

Biophysical characterisation of fibulin-5 proteins associated with disease

FBLN5 encodes fibulin-5, an extracellular matrix calcium-binding glycoprotein that is essential for elastic fibre formation. FBLN5 mutations are associated with two distinct human diseases, age-related macular degeneration (AMD) and cutis laxa (CL), but the biochemical basis for the pathogenic effects of these mutations is poorly understood. Two missense mutations found in AMD patients (I169T and G267S) and two missense mutations found in CL patients (G202R and S227P) were analysed in a native-like context in recombinant fibulin-5 fragments. Limited proteolysis, NMR spectroscopy and chromophoric calcium chelation experiments showed that the G267S and S227P substitutions cause long-range structural effects consistent with protein misfolding. Cellular studies using fibroblast cells further demonstrated that these recombinant forms of mutant fibulin-5 were not present in the extracellular medium, consistent with retention. In contrast, no significant effects of I169T and G202R substitutions on protein fold and secretion were identified. These data establish protein misfolding as a causative basis for the effects of G267S and S227P substitutions in AMD and CL, respectively, and raise the possibility that the I169T and G202R substitutions may be polymorphisms or may increase susceptibility to disease.

Tissue elasticity and the ageing elastic fibre

The ability of elastic tissues to deform under physiological forces and to subsequently release stored energy to drive passive recoil is vital to the function of many dynamic tissues. Within vertebrates, elastic fibres allow arteries and lungs to expand and contract, thus controlling variations in blood pressure and returning the pulmonary system to a resting state. Elastic fibres are composite structures composed of a cross-linked elastin core and an outer layer of fibrillin microfibrils. These two components perform distinct roles; elastin stores energy and drives passive recoil, whilst fibrillin microfibrils direct elastogenesis, mediate cell signalling, maintain tissue homeostasis via TGFβ sequestration and potentially act to reinforce the elastic fibre. In many tissues reduced elasticity, as a result of compromised elastic fibre function, becomes increasingly prevalent with age and contributes significantly to the burden of human morbidity and mortality. This review considers how the unique molecular structure, tissue distribution and longevity of elastic fibres pre-disposes these abundant extracellular matrix structures to the accumulation of damage in ageing dermal, pulmonary and vascular tissues. As compromised elasticity is a common feature of ageing dynamic tissues, the development of strategies to prevent, limit or reverse this loss of function will play a key role in reducing age-related morbidity and mortality.

Fibrillin-1 staining anomalies are associated with increased staining for TGF-beta and elastic fibre degradation; new clues to the pathogenesis of emphysema

We recently demonstrated aberrant staining of fibrillin-1 in lung tissue specimens with emphysematous lesions. In this study, we have extended this observation by an elaborate analysis of the elastic fibre. Using domain-specific antibodies to fibrillin-1, and to other elastin fibre-associated molecules, lung tissue derived from patients without obvious clinical emphysema, but harbouring various degrees of microscopical emphysematous lesions, was analysed. In addition, the fibrillin-regulated growth factor TGF-beta was studied. Electron microscopy and biochemical analysis of desmosine (a marker for elastin) were also performed. Results were compared with lung tissue derived from patients with clinical emphysema. Domain-specific antibodies recognizing the C-terminal, N-terminal, and middle part of fibrillin-1 showed aberrant staining patterns associated with increasing degrees of microscopical emphysema. Staining for elastin, emilin-1, and fibulin-2 was, however, not aberrant. TGF-beta staining was markedly increased. On the electron microscopic, but not light microscopical, level, initial elastic fibre degradation was noticed in specimens with microscopical emphysema. Lung specimens from patients with clinical emphysema also displayed fragmented fibrillin-1 staining and, in addition, displayed extensive degradation of the elastic fibre. The results suggest that fibrillin-1 anomalies and TGF-beta overexpression are associated with initial events occurring during the emphysematous process. Based on these and other data, a mechanism for emphysematogenesis is proposed.

Osteoarthritis of the ankle: bridging concepts in basic science with clinical care

Trends in science are beginning to suggest that cartilage degeneration may be related to a chronic imbalance in extracellular matrix metabolism. In cartilage, a combination of biomechanical, biochemical, and matrix-related signaling pathways regulates the equilibrium between cartilage anabolism and catabolism. A potential limitation of many current treatments of osteoarthritis is that they may not comprehensively restore regulation of a balance between cartilage anabolism and catabolism.

Do we need molecular tomography of a cell and how can it be achieved?

1. The spatial relationship between intracellular molecules and their local concentrations are two critical parameters required for a better understanding of protein-protein interactions in the cell. 2. Determination of the local concentration of proteins in individual cells using more sophisticated techniques and determination of the spatial relationship between a molecular platform and its partners is essential for allow us to obtain more convincing and concrete scientific conclusions. 3. As a reasonable goal, development of molecular tomography of the cell is proposed.

Aberrant fibrillin-1 expression in early emphysematous human lung: a proposed predisposition for emphysema

Parenchymal destruction, airspace enlargement, and loss of elasticity are hallmarks of pulmonary emphysema. Although the basic mechanism is unknown, there is a consensus that malfunctioning of the extracellular matrix is a major contributor to the pathogenesis of emphysema. In this study, we analyzed the expression of the elastic fiber protein fibrillin-1 in a large number (n=69) of human lung specimens with early-onset emphysema. Specimens were morphologically characterized by the Destructive Index, the Mean Linear Intercept, and the Panel Grading. We observed a strong correlation (P<0.001) of aberrant fibrillin-1 staining with the degree of destruction of lung parenchyma (r=0.71), airspace enlargement (r=0.47), and emphysema-related morphological abnormalities (r=0.69). There were no obvious correlations with age and smoking behavior. Staining for three other extracellular matrix components (type I collagen, type IV collagen, and laminin) was not affected. The aberrant fibrillin-1 staining observed in this study is similar to that observed in Marfan syndrome, a syndrome caused by mutations in the gene encoding fibrillin-1. Strikingly, emphysema is noticed in a number of Marfan patients. This, together with the notion that disruption of the fibrillin-1 gene in mice results in emphysematous lesions, makes fibrillin-1 a strong candidate to be involved in the etiology and pathogenesis of emphysema.

Paraquat poisonings: mechanisms of lung toxicity, clinical features, and treatment

Paraquat dichloride (methyl viologen; PQ) is an effective and widely used herbicide that has a proven safety record when appropriately applied to eliminate weeds. However, over the last decades, there have been numerous fatalities, mainly caused by accidental or voluntary ingestion. PQ poisoning is an extremely frustrating condition to manage clinically, due to the elevated morbidity and mortality observed so far and due to the lack of effective treatments to be used in humans. PQ mainly accumulates in the lung (pulmonary concentrations can be 6 to 10 times higher than those in the plasma), where it is retained even when blood levels start to decrease. The pulmonary effects can be explained by the participation of the polyamine transport system abundantly expressed in the membrane of alveolar cells type I, II, and Clara cells. Further downstream at the toxicodynamic level, the main molecular mechanism of PQ toxicity is based on redox cycling and intracellular oxidative stress generation. With this review we aimed to collect and describe the most pertinent and significant findings published in established scientific publications since the discovery of PQ, focusing on the most recent developments related to PQ lung toxicity and their relevance to the treatment of human poisonings. Considerable space is also dedicated to techniques for prognosis prediction, since these could allow development of rigorous clinical protocols that may produce comparable data for the evaluation of proposed therapies.

Constitutive ALK5-independent c-Jun N-terminal kinase activation contributes to endothelin-1 overexpression in pulmonary fibrosis: evidence of an autocrine endothelin loop operating through the endothelin A and B receptors

The signal transduction mechanisms generating pathological fibrosis are almost wholly unknown. Endothelin-1 (ET-1), which is up-regulated during tissue repair and fibrosis, induces lung fibroblasts to produce and contract extracellular matrix. Lung fibroblasts isolated from scleroderma patients with chronic pulmonary fibrosis produce elevated levels of ET-1, which contribute to the persistent fibrotic phenotype of these cells. Transforming growth factor beta (TGF-beta) induces fibroblasts to produce and contract matrix. In this report, we show that TGF-beta induces ET-1 in normal and fibrotic lung fibroblasts in a Smad-independent ALK5/c-Jun N-terminal kinase (JNK)/Ap-1-dependent fashion. ET-1 induces JNK through TAK1. Fibrotic lung fibroblasts display constitutive JNK activation, which was reduced by the dual ETA/ETB receptor inhibitor, bosentan, providing evidence of an autocrine endothelin loop. Thus, ET-1 and TGF-beta are likely to cooperate in the pathogenesis of pulmonary fibrosis. As elevated JNK activation in fibrotic lung fibroblasts contributes to the persistence of the myofibroblast phenotype in pulmonary fibrosis by promoting an autocrine ET-1 loop, targeting the ETA and ETB receptors or constitutive JNK activation by fibrotic lung fibroblasts is likely to be of benefit in combating chronic pulmonary fibrosis.

Endothelin-1 promotes myofibroblast induction through the ETA receptor via a rac/phosphoinositide 3-kinase/Akt-dependent pathway and is essential for the enhanced contractile phenotype of fibrotic fibroblasts

The endothelins are a family of endothelium-derived peptides that possess a variety of functions, including vasoconstriction. Endothelin-1 (ET-1) is up-regulated during tissue repair and promotes myofibroblast contraction and migration, hence contributing to matrix remodeling during tissue repair. Here, we show that addition of ET-1 to normal lung fibroblasts induces expression of proteins that contribute to a contractile phenotype, including alpha-smooth muscle actin (alpha-SMA), ezrin, moesin, and paxillin. We confirm that ET-1 enhances the ability of lung fibroblasts to contract extracellular matrix, a function essential for tissue repair, through induction of de novo protein synthesis. Blockade of the Akt/phosphoinositide 3-kinase (PI3-kinase) pathway with LY294002 and wortmannin prevents the ability of ET-1 to induce alpha-SMA, ezrin, paxillin, and moesin and to promote matrix contraction. Dominant negative rac and Akt blocked the ability of ET-1 to promote formation of alpha-SMA stress fibers. Using specific ET-1 receptor inhibitors, we show that ET-1 induces collagen matrix contraction through the ETA, but not the ETB, receptor. Relative to normal pulmonary fibroblasts, fibroblasts cultured from scars of patients with the fibrotic disease systemic sclerosis (scleroderma) show enhanced ET-1 expression and binding. Systemic sclerosis lung fibroblasts show increased ability to contract a collagen matrix and elevated expression of the procontractile proteins alpha-SMA, ezrin, paxillin, and moesin, which are greatly reduced by antagonizing endogenous ET-1 signaling. Thus, blocking ET-1 or the PI3-kinase/Akt cascades might be beneficial in reducing scar formation in pulmonary fibrosis.

Induction and Regulation of Macrophage Metalloelastase by Hyaluronan Fragments in Mouse Macrophages

Although the metalloproteinase murine metalloelastase (MME) has been implicated in lung disorders such as emphysema and pulmonary fibrosis, the mechanisms regulating MME expression are unclear. Low m.w. fragments of the extracellular matrix component hyaluronan (HA) that accumulate at sites of lung inflammation are capable of inducing inflammatory gene expression in macrophages (Mφ). The purpose of this study was to examine the effect of HA fragments on the expression of MME in alveolar Mφ. The mouse alveolar Mφ cell line MH-S was stimulated with HA fragments over time, total RNA was isolated, and Northern blot analysis was performed. HA fragments induced MME mRNA in a time-dependent fashion, with maximal levels at 6 h. HA fragments also induced MME protein expression as well as enzyme activity. The induction of MME gene expression was specific for low m.w. HA fragments and dependent upon new protein synthesis; it occurred at the level of gene transcription. We also examined the effect of HA fragments on MME expression in inflammatory alveolar Mφ from bleomycin-injured rat lungs. Although normal rat alveolar Mφ did not express MME mRNA in response to HA fragments, alveolar Mφ from the bleomycin-treated rats responded to HA fragment stimulation by increasing MME mRNA levels. Furthermore, baseline and HA fragment-induced MME gene expression in alveolar Mφ from bleomycin-treated rats was inhibited by IFN-γ. These data suggest that HA fragments may be an important mechanism for the expression of MME by Mφ in inflammatory lung disorders.

Biochemical and connective tissue changes in cyclophosphamide-induced lung fibrosis in rats

The present investigation was designed to characterize the biochemical and connective tissue components and to correlate the significance of morphological and biochemical perturbations in cyclophosphamide (CP)-induced lung fibrosis in rats. Lung fibrosis was induced in male Wistar rats by intraperitoneal injection of 20 mg/100 g body weight of CP, and their pneumotoxic derangements were characterized during an early destructive phase followed by a proliferative and synthetic phase. Serum angiotensin-converting enzyme (ACE) activity was higher in CP-treated rats at days 2, 3, 5, 7, and 11, but there was a significant decrease in lung ACE activity during the same time period. Elevated levels of beta-glucuronidase activity were observed in the lung lavage fluid of CP-administered rats days 2, 3, 5, and 7. Lung myeloperoxidase activity was higher in CP rats. Of significance was the presence of collagenase and collagenolytic cathepsin in the lavage fluid of CP rats, when compared with the barely detectable levels in controls. A similar increase in these enzyme activities was also noticed in the lung tissue of CP rats during the same experimental period. Lavage fluid hydroxyproline content was higher in CP rats when compared with controls. Similarly, lung protein and DNA levels were elevated significantly after treatment with CP. The pulmonary histamine and serotonin contents were significantly higher in CP rats. The incorporation of [3H]thymidine into lung total DNA, [3H]proline into lung hydroxyproline, and [35S]sulphate into lung glycosaminoglycan, measured as indicators of lung DNA, collagen, and glycosaminoglycan synthesis, respectively, was also higher in CP groups. Increased levels of hydroxyproline, elastin, hexosamine, total hexose, fucose, sialic acid, and uronic acid in the lungs of rats 14, 28, and 42 days after CP insult were characterized as biomarkers of CP-induced interstitial changes. These findings indicate that CP-induced lung fibrosis results in alterations not only in collagen synthesis and accumulation, but also in glycosaminoglycan and glycoprotein content.

In vivo administration of taurine and niacin modulate cyclophosphamide-induced lung injury

The antiinflammatory, antioxidant activity of taurine and niacin against cyclophosphamide-induced early lung injury in rats was investigated. A single intraperitoneal injection of cyclophosphamide markedly altered the levels of several biomarkers in bronchoalveolar lavage fluid: total protein, albumin, angiotensin converting enzyme, lactate dehydrogenase, lactate, N-acetyl-beta-D-glucosaminidase, alkaline phosphatase, acid phosphatase and lipid peroxidation product were significantly elevated. In contrast, decreased levels of total reduced glutathione (GSH) and ascorbic acid were observed. Cyclophosphamide significantly increased malondialdehyde levels in serum and lung. Significant increases in lung content of lipid hydroperoxides were seen that paralleled the decreased levels of total reduced glutathione and total sulfhydryl groups. Pretreatment of rats with daily intraperitoneal injection of taurine plus niacin 7 days prior to and 2 days after cyclophosphamide insult significantly inhibited the development of lung injury, prevented the alterations in lavage fluid biomarkers associated with inflammatory reactions, with less lipid peroxidation and restoration of antioxidants. In conclusion, our results suggest that taurine and niacin in combination is efficient in blunting cyclophosphamide-induced pulmonary damage.

Matrix metalloproteases and lung disease

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Inhibition of the human leukocyte endopeptidases elastase and cathepsin G and of porcine pancreatic elastase by N-oleoyl derivatives of heparin

N-oleoyl-heparin derivatives differing in their oleic acid and sulfate contents were synthesized and studied for their abilities to inhibit human leukocyte elastase (HLE), human leukocyte cathepsin G (CatG) and porcine pancreatic elastase (PPE) at pH 8.0, ionic strength 0.05 M and 37 degrees. Heparin (Hep) as well as N-oleoyl-heparins behaved as tight-binding, hyperbolic noncompetitive inhibitors of HLE (KiHep = 75 pM) and CatG (KiHep < 25 pM). The main driving force for the interaction between enzymes and glycosaminoglycans was electrostatic in nature. Under the condition [enzyme] >> Ki, the stoichiometries of the interaction with Hep were 1:2 (Hep:HLE) and 1:4 (Hep:CatG). Coupling one oleic acid residue to three disaccharide units of partially N-desulfated Hep, Ol1:3Hep, lowered HLE inhibition (Ki = 0.3 nM) and the stoichiometry of binding was reduced to 1:1. Re-N-sulfation of a similar derivative, Ol1:5Hep(SO4), containing one fatty acid residue for five disaccharide units, led to a substance with similar HLE inhibitory characteristics as Hep (Ki = 92 pM) and stoichiometry 1:2. Ol1:5Hep(SO4) was also a more efficient inhibitor of CatG (Ki < 33 pM) than Ol1:3Hep (Ki = 9.5 nM). The residual activities of N-oleoyl-Hep complexes with CatG were much lower than the corresponding activities in the presence of Hep. While oleate and Hep could not inhibit PPE, N-oleoyl-Hep, independently of fatty acid substitution and sulfate content, could inhibit this enzyme with Ki congruent to 60 nM and low residual activity. The efficient endopeptidase inhibitory characteristics of N-oleoyl-Hep derivatives, together with their non-anticoagulant properties and their capacity to interact with elastin, may be therapeutically useful in connective tissue degenerative diseases.

Activation of blood neutrophils in acute episodes of farmer's lung

Farmer's lung often presents clinically as recurring acute episodes several hours after exposure to moldy hay. During these episodes the blood neutrophil count increases. Because activated neutrophils release toxic oxygen metabolites and proteinases, we hypothesized that the pulmonary reaction in farmer's lung may be induced by the secretory products of activated neutrophils. To evaluate this concept, we quantified the respiratory burst of separated blood neutrophils from patients with farmer's lung (n = 12) during standardized exposure tests with moldy hay. The respiratory burst of these cells was evaluated by measuring zymosan-stimulated and lucigenin-amplified chemiluminescence (CL). Asymptomatic farmers (n = 12) and normal volunteers with no prior exposure to moldy hay (n = 15) were used as control subjects. As expected, following exposure in the group of patients with farmer's lung, striking changes in VC, TLCO, and PaO2 were observed, whereas there were only minor changes in these parameters in both control groups. In all three groups a considerable increase in the blood leukocyte count was observed. The CL response of the blood neutrophils from patients with farmer's lung 6 h after exposure was significantly higher than before or 1 h after exposure (p < 0.05 for both comparisons), whereas there was no significant change in the CL response in either control group during the observation period. Our results indicate that antigen inhalation induces an increase in the number of circulating neutrophils in patients and controls, but in patients with an acute episode of farmer's lung the neutrophils are primed for an enhanced respiratory burst and may thereby damage the lung.

The protease-antiprotease balance within the human lung: implications for the pathogenesis of emphysema

Critical elements of the mechanisms of emphysema remain to be clarified. However, taken together, the existing evidence supports the concept that alveolar matrix destruction ensues as the regulatory interplay between oxidant and protease expression is subverted. The final common pathway of matrix destruction links the inherited and acquired forms of emphysema through the ultimate expression of unimpeded neutrophil elastase.

Pulmonary disease progress in sarcoid patients with and without bronchoalveolar lavage collagenase

To assess the usefulness of bronchoalveolar lavage (BAL) collagenase measurement in gauging disease severity and outcome in sarcoidosis, we analyzed BAL fluids from 84 patients with sarcoidosis for collagenase and monitored disease progress in these patients for a minimum of 12 months. Twenty patients (24%) were found to have BAL collagenase activity on initial evaluation (collagenase-positive group). Compared with patients without BAL collagenase (collagenase-negative group), the collagenase-positive group had (1) a higher proportion of BAL suppressor T cells (p less than 0.03); (2) a lower helper-suppressor T-cell ratio (p less than 0.002); (3) lower mean percent predicted FEV1, FVC, and DLCO levels (p less than 0.05); and (4) a higher proportion of patients with advanced (Stage 4) disease on chest roentgenogram (p less than 0.001). Significant differences were also observed between the collagenase-positive and collagenase-negative groups during follow-up. A higher proportion (55%, n = 11) of collagenase-positive patients required corticosteroid therapy than did collagenase-negative patients (26%; n = 17; p less than 0.025). Of those who remained untreated, pulmonary function tended to decrease in the collagenase-positive group, whereas mean pulmonary function levels actually improved in the collagenase negative group (p less than 0.05). Of those who required therapy, mean percent predicted FVC and DLCO levels improved significantly after treatment in the collagenase-negative group (p less than 0.01 and p less than 0.05, respectively), whereas an improvement in percent predicted FVC levels only (p less than 0.01) was observed in the collagenase-positive group.(ABSTRACT TRUNCATED AT 250 WORDS)

Lung collagenase inhibitors and spontaneous and latent collagenase activity in idiopathic pulmonary fibrosis and hypersensitivity pneumonitis

In order to analyze the mechanisms involved in the decreased collagenolytic activity previously observed in interstitial lung fibrosis, we studied the inhibitory collagenase activity and the latent activable collagenase in lung samples from five patients with IPF, six with HP, and three control subjects. Our results showed that in both diseases, the inhibitor levels were significantly higher than in control subjects. Findings suggest that in IPF low amounts of collagenase plus excessive enzyme-inhibitors may be operating to decrease collagen catabolism. In contrast, HP lungs seem to contain adequate amounts of the enzyme but higher levels of inhibitors play a role in the abnormal degradation observed in some patients.

Cathepsin G degrades denatured collagen

Neutrophils are known to contain several metalloproteinases that can damage collagen, a major structural component of the extracellular matrix. Here a neutrophil serine proteinase secreted from activated neutrophils was shown to cleave denatured collagen (gelatin). This serine proteinase was not inhibited by synthetic inhibitors of elastase (elastatinal or Me-O-suc-Ala-Pro-Val-CH2Cl). However, a synthetic inhibitor of cathepsin G (Z-Gly-Leu-Phe-CH2Cl) was able to inhibit the serine proteinase having gelatinolytic activity, indicating that cathepsin G, a major serine proteinase, from neutrophils is responsible for cleaving gelatin. Purified cathepsin G was also shown to degrade gelatin. In further experiments, oxidized glutathione was able to enhance the gelatinolytic activity of cathepsin G. These results show that cathepsin G is capable of cleaving denatured collagen, and its activity is enhanced or stabilized in the presence of glutathione. The data support the concept that cathepsin G released from neutrophils could play a major role in degrading collagen during inflammation and may in part account for the degradation of extracellular matrix during inflammation.

Serum type III procollagen peptide in asbestos workers: an early indicator of pulmonary fibrosis

Serum type III procollagen peptide (PIIIP) concentrations were determined in 36 male workers exposed to asbestos fibres in the production of asbestos cement items and in 13 healthy male controls. Mean (SD) PIIIP serum concentrations were 9.3 (1.5) ng/ml (range 7-12) in the controls and 13.7 (3.5)ng/ml (range 7.5-20) in the asbestos workers; the difference was statistically significant (p less than 0.01). The exposed workers were subdivided according to presence or absence of radiological signs of asbestosis and intensity and duration of exposure. PIIIP serum values of workers with asbestos related interstitial fibrosis were the highest of the groups at 14.6 (2.3) ng/ml. In workers with heavy exposure the PIIIP values were significantly related to duration of exposure (r = 0.95; p less than 0.01). PIIIP serum values may be a useful index for the early diagnosis of asbestos induced pulmonary fibrosis and its use should be considered as part of the biological monitoring of exposed workers.

Collagen metabolism in experimental lung silicosis. A trimodal behavior of collagenolysis

In spite of several studies, both in vivo and in vitro, the pathogenesis of silicosis remains unclear, mainly in those mechanisms related to fibrogenesis. In this study, we analyzed the concentration, biosynthesis, and degradation of collagen in silica-treated rats 7, 15, 30, 45, and 60 days after instillation. Our results showed a significant increase in collagen content and biosynthesis from the 15th day onward. However, our most remarkable finding was related to collagenolytic activity. In this sense, the silicotic rats presented a trimodal behavior: some animals showed an increased degradation, others had similar values to those of the controls, and others exhibited a decrease of collagenolytic activity. Altogether, these results suggest that collagen deposition in silicotic lungs is due to a rise in biosynthesis and, at least in some animals, to a decrease in degradation. Nevertheless, the steps of collagenolysis must be studied in more detail.

Lung collagen metabolism and the clinical course of hypersensitivity pneumonitis

We studied lung collagen metabolism in 18 patients with hypersensitivity pneumonitis to determine if changes at this level could explain the different clinical courses followed by these patients. Collagen concentration, biosynthesis and degradation were measured in lung tissue samples obtained before treatment. Four patients healed, eight improved and six did not improve or worsened. All patients who healed showed an important increase in collagenolysis; patients who improved had normal or high values, but significantly less than those obtained in patients who healed. Finally, five out of the six patients who did not improve or worsened had a significant decrease in degradation. These findings support the notion that a diminution of local collagenolysis may play a role in the progression to fibrosis in some patients with hypersensitivity pneumonitis and can also be a useful tool to predict the prognosis of this disease.

Amiodarone pulmonary toxicity. Recognition and pathogenesis (Part 2)

The pulmonary toxicity associated with amiodarone therapy is clinically complex and likely reflects underlying mechanisms of lung injury that result from direct toxic effects of the drug (or its metabolites) as well as indirect inflammatory and immunologic processes induced by the drug therapy (Fig 2). A role for the direct toxicity of the drug is likely because (a) toxicity in part is related to dosage and duration of therapy, (b) many patients with amiodarone pulmonary toxicity have no evidence of an inflammatory or immune response in the lung, (c) in vitro studies indicate that amiodarone can be directly toxic to cultured lung cells or perfused isolated lung tissue, and (d) recent studies suggest plausible biochemical mechanisms that may explain in part the mechanism(s) of direct toxicity of the drug. A role for indirect inflammatory or immune processes within the lung of some patients with APT is supported by: (a) variable relationship of pulmonary toxicity to amiodarone dosages and blood levels, (b) preliminary studies suggest altered immunologic markers in the blood and lungs of some patients with APT, and (c) the cellular findings of bronchoalveolar lavage indicating a CD8 lymphocytosis with or without influx of polymorphonuclear leukocytes, which is consistent with previous studies of hypersensitivity reactions. As our understanding of the biochemical and cellular mechanisms of APT improve, a number of key clinical issues may be clarified: (1) risk factor assessment for APT, (2) criteria for early diagnosis of APT, and (3) improved therapeutic approach to patients with APT.

Biochemical quantitation and histochemical localization of cathepsin B, dipeptidyl peptidases I and II, and acid phosphatase in pulmonary granulomatosis and fibrosis in rats

The purpose of this study was to quantitate biochemically and to localize histochemically the proteases cathepsin B (Cath B), dipeptidyl peptidase I (DPP I), and dipeptidyl peptidase II (DPP II) in experimental pulmonary granulomatosis and fibrosis. These were compared to the prototypical lysosomal hydrolase acid phosphatase (AP). Granulomatosis was induced by the intravenous injection of complete Freund's adjuvant (CFA, 0.2 ml) and fibrosis was induced by the intratracheal instillation of bleomycin sulfate (1 unit) in rats (Wistar, 200 g). Total Cath B, DPP I, and AP activities were markedly elevated over control values five days following both treatments when expressed as activity per lung or as specific activity per milligram protein or milligram DNA. By 14 and 28 days, total activity was elevated for all three enzymes, and activity per milligram DNA remained elevated for Cath B following both treatments and for DPP I 28 days following CFA treatment. Total lung activity of DPP II was significantly elevated at 28 days for both treatments. Histochemical staining indicated that these changes are due, in part, to the influx of inflammatory monocytes and their maturation to macrophages. This study provides a basis for examining the role of these proteases in connective tissue matrix injury during inflammatory processes in the lungs.

Degradation of connective tissue components by lung derived leucocytes in vitro: role of proteases and oxidants

Inflammatory leucocytes are implicated in connective tissue damage during chronic inflammatory lung disease. In an investigation of the role of leucocytes in connective tissue derangements in the lung, inflammatory leucocytes were generated in rat lungs by intratracheal instillation of inflammatory agents and retrieved by bronchoalveolar lavage. The proteolytic activities of control macrophages and of two inflammatory cell populations were compared; iodinated collagen, laminin, and fibronectin matrices were used. The inflammatory cells caused consistently and substantially more degradation of the matrices than the controls on a per cell basis. The oxidant scavengers superoxide dismutase and catalase did not inhibit matrix degradation, but alpha 1 protease inhibitor and alpha 2 macroglobulin were inhibitory. It is concluded that matrix damage in this assay is enhanced by inflammatory cells and is mediated principally by serine protease activity.

Pharmacologic suppression of the neutrophil component of the alveolitis in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial lung disease of unknown etiology characterized by inflammation of the lower respiratory tract and injury and fibrosis of the lung parenchyma. Neutrophils are a significant component of the alveolitis of IPF, and are known to have a potent armamentarium of mediators capable of damaging the lung parenchyma. To evaluate the ability of 2 pharmacologic agents, corticosteroids and cyclophosphamide, to suppress the neutrophil component of the inflammation of IPF, bronchoalveolar lavage was used to monitor those patients with active disease (greater than 10% neutrophils recovered by lavage). Those patients treated with corticosteroids alone showed no suppression in the neutrophil component of the alveolitis after 3 months and at 6 months of therapy (p greater than 0.8, both compared to before therapy). In marked contrast, patients treated with cyclophosphamide, alone or with corticosteroids, showed a significant reduction in the neutrophil alveolitis at 3 months (cyclophosphamide alone, p less than 0.01; cyclophosphamide and corticosteroids, p less than 0.02; both compared to before therapy) and at 6 months (cyclophosphamide alone, p less than 0.01; compared to before therapy). Pulmonary function tests at the beginning and end of the study were not different in any of the treatment groups. Thus, cyclophosphamide, alone or in combination with corticosteroids, is much more effective than corticosteroids alone in suppressing the neutrophil component of the inflammation of IPF. Whether or not this effect of cyclophosphamide will result in overall stabilization or improvement of the disease will require a larger, likely multicenter, trial.

Elastase inhibitors of sputum sol phase: variability, relationship to neutrophil elastase inhibition, and effect of corticosteroid treatment

The concentrations of three known elastase inhibitors (alpha 1 proteinase inhibitor, antileucoprotease, and alpha 2 macroglobulin) have been determined in the sputum of six patients with obstructive bronchitis over five consecutive days. Antileucoprotease was the major inhibitor measured and potentially could provide more than 80% of the elastase inhibition, whereas the contribution of alpha 2 macroglobulin was less than 0.2%. Comparison with the inhibitory capacity of the secretions active against human neutrophil elastase showed that the inhibitors could account for only about half of the inhibition measured. This suggests the presence of a substantial amount of unrecognised inhibitor. Corticosteroid treatment in 10 patients reduced the mean alpha 1 proteinase inhibitor concentration (p less than 0.025) from 18.6 micrograms/ml (SD 22.5) to 9.8 (6.6). Antileucoprotease, however, increased (p less than 0.05) from 20.5 micrograms/ml (24.3) to 39.3 (23.4). These changes were associated with an increase in elastase inhibition (p less than 0.025) from 180 (160) micrograms elastase/ml secretion to 310 (130), suggesting a beneficial effect of steroid treatment on the antielastases in lung secretions.