Reactive oxygen species and tissue remodeling regulators, such as metalloproteinases (MMPs) and their inhibitors (TIMPs), are thought to be involved in the development of pulmonary fibrosis. We investigated these factors in the fibrotic response to bleomycin of p47phox -/- (KO) mice, deficient for ROS production through the NADPH-oxidase pathway.
Mice are administered by intranasal instillation of 0.1 mg bleomycin. Either 24 h or 14 days after, mice were anesthetized and underwent either bronchoalveolar lavage (BAL) or lung removal.
BAL cells from bleomycin treated WT mice showed enhanced ROS production after PMA stimulation, whereas no change was observed with BAL cells from p47phox -/- mice. At day 1, the bleomycin-induced acute inflammatory response (increased neutrophil count and MMP-9 activity in the BAL fluid) was strikingly greater in KO than wild-type (WT) mice, while IL-6 levels increased significantly more in the latter. Hydroxyproline assays in the lung tissue 14 days after bleomycin administration revealed the absence of collagen deposition in the lungs of the KO mice, which had significantly lower hydroxyproline levels than the WT mice. The MMP-9/TIMP-1 ratio did not change at day 1 after bleomycin administration in WT mice, but increased significantly in the KO mice. By day 14, the ratio fell significantly from baseline in both strains, but more in the WT than KO strains.
These results suggest that NADPH-oxidase-derived ROS are essential to the development of pulmonary fibrosis. The absence of collagen deposition in KO mice seems to be associated with an elevated MMP-9/TIMP-1 ratio in the lungs. This finding highlights the importance of metalloproteinases and protease/anti-protease imbalances in pulmonary fibrosis.
Background: Corticosteroids are routinely used in patients with pulmonary fibrosis. The timing for initiation of treatment is likely to be crucial for corticosteroids to exert an antifibrotic effect. Experimental studies in animals have examined the effect of corticosteroid treatment starting before or at the time of lung injury. However, this is not representative of the human condition as treatment only begins after disease has been established. We examined the effect of a short course corticosteroid treatment starting 3 days after bleomycin induced lung injury on the development of pulmonary fibrosis.
Methods: Bleomycin (1.5 mg/kg) was instilled intratracheally into rats to induce pulmonary fibrosis. The effect of a 3-day course of dexamethasone (0.5 mg/kg) initiated 3 days after bleomycin induced lung injury on cell proliferation and collagen deposition was examined by analysing bronchoalveolar lavage (BAL) fluid and lung tissue.
Results: Treating bleomycin exposed animals after injury with dexamethasone for 3 days inhibited lung collagen deposition compared with animals exposed to bleomycin without dexamethasone treatment (15.2 (2.2) mg collagen/lung v 22.5 (2.1) mg/lung; p<0.05). Dexamethasone treatment reduced pulmonary parenchymal cell proliferation in bleomycin exposed rats but did not influence BAL fluid mitogenic activity for lung fibroblasts or alter the BAL fluid levels of the fibrogenic mediators transforming growth factor-ß1, platelet derived growth factor-AB, and thrombin.
Conclusions: A 3 day course of dexamethasone treatment initiated 3 days after bleomycin induced lung injury reduces lung cell proliferation and collagen deposition by mechanisms other than through reduction of transforming growth factor-ß1, platelet derived growth factor-AB, and thrombin levels in BAL fluid. We propose that an early short course treatment with dexamethasone may be useful in inhibiting pulmonary fibrosis.
The angiotensin system has a role in the pathogenesis of pulmonary fibrosis. This study examines the antifibrotic effect of losartan, an angiotensin II type 1 receptor antagonist, in bleomycin induced lung fibrosis and its possible implication in the regulation of prostaglandin E2 (PGE2) synthesis and cyclooxygenase‐2 (COX‐2) expression.
Rats were given a single intratracheal instillation of bleomycin (2.5 U/kg). Losartan (50 mg/kg/day) was administrated orally starting one day before induction of lung fibrosis and continuing to the conclusion of each experiment.
Losartan reduced the inflammation induced by bleomycin, as indicated by lower myeloperoxidase activity and protein content in the bronchoalveolar lavage fluid. Collagen deposition induced by bleomycin was inhibited by losartan, as shown by a reduction in the hydroxyproline content and the amelioration of morphological changes. PGE2 levels were lower in fibrotic lungs than in normal lungs. Losartan significantly increased PGE2 levels at both 3 and 15 days. A reduction in COX‐2 expression by bleomycin was seen at 3 days which was relieved by losartan.
The antifibrotic effect of losartan appears to be mediated by its ability to stimulate the production of PGE2. Losartan, which is already widely used clinically, could be assessed as a new treatment in lung fibrosis.
pulmonary fibrosis; cyclo‐oxygenase; COX‐2; angiotensin II; losartan; prostaglandin E2
Stromal cell–derived factor-1 (SDF-1) participates in mobilizing bone marrow–derived stem cells, via its receptor CXCR4. We studied the role of the SDF-1/CXCR4 axis in a rodent model of bleomycin-induced lung injury in C57BL/6 wild-type and matrix metalloproteinase (MMP)-9 knockout mice. After intratracheal instillation of bleomycin, SDF-1 levels in serum and bronchial alveolar lavage fluid increased. These changes were accompanied by increased numbers of CXCR4+ cells in the lung and a decrease in a population of CXCR4+ cells in the bone marrow that did not occur in MMP-9−/− mice. Both SDF-1 and lung lysates from bleomycin-treated mice induced migration of bone marrow–derived stem cells in vitro that was blocked by a CXCR4 antagonist, TN14003. Treatment of mice with TN14003 with bleomycin-induced lung injury significantly attenuated lung fibrosis. Lung tissue from patients with idiopathic pulmonary fibrosis had higher numbers of cells expressing both SDF-1 and CXCR4 than did normal lungs. Our data suggest that the SDF-1/CXCR4 axis is important in the complex sequence of events triggered by bleomycin exposure that eventuates in lung repair. SDF-1 participates in mobilizing bone marrow–derived stem cells, via its receptor CXCR4.
bone marrow–derived stem cells; pulmonary fibrosis; SDF-1; CXCR4
Metabolites of arachidonic acid such as prostacyclin (PGI2) have been shown to participate in the pathogenesis of pulmonary fibrosis by inhibiting the expression of pro-inflammatory and pro-fibrotic mediators. In this investigation, we examined whether iloprost, a stable PGI2 analogue, could prevent bleomycin-induced pulmonary inflammation and fibrosis in a mouse model.
Mice received a single intratracheal injection of bleomycin with or without intraperitoneal iloprost. Pulmonary inflammation and fibrosis were analysed by histological evaluation, cellular composition of bronchoalveolar lavage (BAL) fluid, and hydroxyproline content. Lung mechanics were measured. We also analysed the expression of inflammatory mediators in BAL fluid and lung tissue.
Administration of iloprost significantly improved survival rate and reduced weight loss in the mice induced by bleomycin. The severe inflammatory response and fibrotic changes were significantly attenuated in the mice treated with iloprost as shown by reduction in infiltration of inflammatory cells into the airways and pulmonary parenchyma, diminution in interstitial collagen deposition, and lung hydroxyproline content. Iloprost significantly improved lung static compliance and tissue elastance. It increased the expression of IFNγ and CXCL10 in lung tissue measured by RT-PCR and their levels in BAL fluid as measured by ELISA. Levels of TNFα, IL-6 and TGFβ1 were lowered by iloprost.
Iloprost prevents bleomycin-induced pulmonary fibrosis, possibly by upregulating antifibrotic mediators (IFNγ and CXCL10) and downregulating pro-inflammatory and pro-fibrotic cytokines (TNFα, IL-6, and TGFβ1). Prostacyclin may represent a novel pharmacological agent for treating pulmonary fibrotic diseases.
Pulmonary fibrosis is characterized by excessive deposition of extracellular matrix in the interstitium resulting in respiratory failure. The role of remodeling mediators such as metalloproteinases (MMPs) and their inhibitors (TIMPs) in the fibrogenic process remains misunderstood. In particular, macrophage metalloelastase, also identified as MMP-12, is known to be involved in remodeling processes under pathological conditions. However, MMP-12 involvement in pulmonary fibrosis is unknown. Here we investigated fibrotic response to bleomycin in MMP-12 deficient mice.
Materials and methods
C57BL/6 mice, Balb/c mice and MMP-12 -/- mice with a C57BL/6 background received 0.3 mg bleomycin by intranasal administration. 14 days after, mice were anesthetized and underwent either bronchoalveolear lavage (BAL) or lung removal. Collagen deposition in lung tissue was determined by Sircol™ collagen assay, MMP activity in BAL fluid was analyzed by zymography, and other mediators were quantified in BAL fluid by ELISA. Real time PCR was performed to assess gene expression in lung removed one or 14 days after bleomycin administration. Student t test or Mann & Whitney tests were used when appropriate for statistical analysis.
The development of pulmonary fibrosis in "fibrosis prone" (C57BL/6) mice was associated with prominent MMP-12 expression in lung, whereas MMP-12 expression was weak in lung tissue of "fibrosis resistant" (Balb/c) mice. MMP-12 mRNA was not detected in MMP-12 -/- mice, in conformity with their genotype. Bleomycin elicited macrophage accumulation in BAL of MMP-12 -/- and wild type (WT) mice, and MMP-12 deficiency had no significant effect on BAL cells composition. Collagen content of lung was increased similarly in MMP-12 -/- and WT mice 14 days after bleomycin administration. Bleomycin elicit a raise of TGF-β protein, MMP-2 and TIMP-1 protein and mRNA in BAL fluids and lung respectively, and no significant difference was observed between MMP-12 -/- and WT mice considering those parameters.
The present study shows that MMP-12 deficiency has no significant effect on bleomycin-induced fibrosis.
CXC chemokine receptor 4 (CXCR4), which binds the stromal cell-derived factor-1 (SDF-1), has been shown to play a critical role in mobilizing the bone marrow (BM)-derived stem cells and inflammatory cells. We studied the effects of AMD3100, CXCR4 antagonist, on a murine bleomycin-induced pulmonary fibrosis model. Treatment of mice with AMD3100 in bleomycin-treated mice resulted in the decrease of SDF-1 in bronchoalveolar lavage (BAL) fluids at an early stage and was followed by the decrease of fibrocytes in the lung. AMD3100 treatment decreased the SDF-1 mRNA expression, fibrocyte numbers in the lung at an early stage (day 3) and CXCR4 expression at the later stage (day 7 and 21) after bleomycin injury. The collagen content and pulmonary fibrosis were significantly attenuated by AMD3100 treatment in later stage of bleomycin injury. AMD3100 treatment also decreased the murine mesenchymal and hematopoietic stem cell chemotaxis when either in the stimulation with bleomycin treated lung lysates or SDF-1 in vitro. In BM stem cell experiments, the phosphorylation of p38 MAPK which was induced by SDF-1 was significantly blocked by addition of AMD3100. Our data suggest that AMD3100 might be effective in preventing the pulmonary fibrosis by inhibiting the fibrocyte mobilization to the injured lung via blocking the SDF-1/CXCR4 axis.
bleomycin; chemokine CXCL12; chemotaxis; JM 3100; pulmonary fibrosis; receptors, CXCR4
BACKGROUND—Erythromycin has been reported to have
an inhibitory effect on chronic inflammatory airway disease and chronic
infiltration of neutrophils into the airway. Bleomycin (BLM) often
induces interstitial lung fibrosis following acute lung injury. A study was undertaken to investigate the effects of erythromycin (EM) on
experimental bleomycin-induced acute lung injury in rats.
METHODS—Bleomycin-induced lung injury
was assessed by light microscopic examination, measurement of
neutrophil elastase activity and of the interleukin 8 (IL-8) content in
bronchoalveolar lavage (BAL) fluid. The potential inhibitory effect of
erythromycin was assessed by overall comparison of erythromycin
untreated (BLM alone), concurrently treated (BLM + EM), and
pretreated (BLM +pre-EM) groups.
RESULTS—The neutrophil count and concentration of
neutrophil-derived elastase in BAL fluid were significantly different
in the three groups. The morphological changes of lung injury were also
less extensive in rats pretreated with erythromycin. However, these protective effects were not marked in the group concurrently treated with erythromycin. Moreover, the concentration of IL-8 in the BAL
fluid tended to be less in the erythromycin treated groups; however,
there were no significant differences between the bleomycin-treated groups.
CONCLUSION—Erythromycin exhibits a prophylactic
effect on acute lung injury induced by intratracheal administration of
bleomycin, which is possibly associated with a downregulation of
IL-13 potently stimulates eosinophilic and lymphocytic inflammation and alveolar remodeling in the lung, effects that depend on the induction of various matrix metalloproteinases (MMPs). Here, we compared the remodeling and inflammatory effects of an IL-13 transgene in lungs of wild-type, MMP-9–deficient, or MMP-12–deficient mice. IL-13–induced alveolar enlargement, lung enlargement, compliance alterations, and respiratory failure and death were markedly decreased in the absence of MMP-9 or MMP-12. Moreover, IL-13 potently induced MMPs-2, -12, -13, and -14 in the absence of MMP-9, while induction of MMPs-2, -9, -13, and -14 by IL-13 was diminished in the absence of MMP-12. A deficiency in MMP-9 did not alter eosinophil, macrophage, or lymphocyte recovery, but increased the recovery of total leukocytes and neutrophils in bronchoalveolar lavage (BAL) fluids from IL-13 transgenic mice. In contrast, a deficiency in MMP-12 decreased the recovery of leukocytes, eosinophils, and macrophages, but not lymphocytes or neutrophils. These studies demonstrate that IL-13 acts via MMPs-9 and -12 to induce alveolar remodeling, respiratory failure, and death and that IL-13 induction of MMPs-2, -9, -13, and -14 is mediated at least partially by an MMP-12–dependent pathway. The also demonstrate that MMPs-9 and -12 play different roles in the generation of IL-13–induced inflammation, with MMP-9 inhibiting neutrophil accumulation and MMP-12 contributing to the accumulation of eosinophils and macrophages.
Matrix metalloproteinases (MMPs) may have pro and antifibrotic roles within the lungs, due to its ability to modulate collagen turnover and immune mediators. MMP-8 is a collagenase that also cleaves a number of cytokines and chemokines.
Methodology and Principal Findings
To evaluate its relevance in lung fibrosis, wildtype and Mmp8−/− mice were treated with either intratracheal bleomycin or saline, and lungs were harvested at different time points. Fibrosis, collagen, collagenases, gelatinases, TGFβ and IL-10 were measured in lung tissue. Mmp8−/− mice developed less fibrosis than their wildtype counterparts. This was related to an increase in lung inflammatory cells, MMP-9 and IL-10 levels in these mutant animals. In vitro experiments showed that MMP-8 cleaves murine and human IL-10, and tissue from knockout animals showed decreased IL-10 processing. Additionally, lung fibroblasts from these mice were cultured in the presence of bleomycin and collagen, IL-10 and STAT3 activation (downstream signal in response to IL-10) measured by western blotting. In cell cultures, bleomycin increased collagen synthesis only in wildtype mice. Fibroblasts from knockout mice did not show increased collagen synthesis, but increased levels of unprocessed IL-10 and STAT3 phosphorylation. Blockade of IL-10 reverted this phenotype, increasing collagen in cultures.
According to these results, we conclude that the absence of MMP-8 has an antifibrotic effect by increasing IL-10 and propose that this metalloprotease could be a relevant modulator of IL-10 metabolism in vivo.
Background: Matrix metalloproteinases (MMPs) are involved in the remodelling and degradation of extracellular matrix and may play a role in pulmonary tissue destruction in cystic fibrosis (CF).
Methods: Bronchoalveolar lavage (BAL) fluid levels of MMP-8, MMP-9, and their natural inhibitor TIMP-1 were measured on two occasions within 18 months in 23 children with mild CF, 13 of whom were treated with DNase.
Results: MMP-8 (39.3 (6.8) v 0.12 (0.01) ng/ml), MMP-9 (58.0 (11.4) v 0.5 (0.02) ng/ml), and the molar ratio of MMP-9/TIMP-1 (0.36 (0.05) v 0.048 (0.01)) were significantly higher in patients with CF than in control children without lung disease. Gelatine zymography showed the typical banding pattern of neutrophil derived MMP-9, including 130 kDa NGAL-MMP-9 complex and 92 kDa latent MMP-9 bands; 85 kDa bands (corresponding to active MMP-9) were seen in all patients. There was a close correlation between BAL fluid concentrations of MMPs and α2-macroglobulin, a marker of alveolocapillary leakage. After 18 months MMP levels were increased in untreated patients and decreased in patients treated with DNase.
Conclusions: Uninhibited MMPs may contribute to pulmonary tissue destruction even in CF patients with mild lung disease that may be positively affected by treatment with DNase.
To determine the role of matrix metalloproteinase-8 (MMP-8) in acute lung injury (ALI), we delivered LPS or bleomycin by the intratracheal route to MMP-8−/− mice versus WT mice or subjected the mice to hyperoxia (95% O2) and measured lung inflammation and injury at intervals. MMP-8−/− mice with ALI had greater increases in lung PMN and macrophage counts, measures of alveolar capillary barrier injury, lung elastance, and mortality than WT mice with ALI. Bronchoalveolar lavage fluid (BALF) from LPS-treated MMP-8−/− mice had more macrophage inflammatory protein-1α (MIP-1α) than BALF from LPS-treated WT mice, but similar levels of other pro- and anti-inflammatory mediators. MIP-1α−/− mice with ALI had less acute lung inflammation and injury than WT mice with ALI, confirming that MIP-1α promotes acute lung inflammation and injury in mice. Genetically deleting MIP-1α in MMP-8−/− mice abrogated the increased lung inflammation and injury and mortality in MMP-8−/− mice with ALI. Soluble MMP-8 cleaved and inactivated MIP-1α in vitro, but membrane-bound MMP-8 on activated PMNs had greater MIP-1α-degrading activity than soluble MMP-8. High levels of membrane-bound MMP-8 were detected on lung PMNs from LPS-treated WT mice, but soluble, active MMP-8 was not detected in BALF samples. Thus, MMP-8 has novel roles in restraining lung inflammation and in limiting alveolar capillary barrier injury during ALI in mice by inactivating MIP-1α. In addition, membrane-bound MMP-8 on activated lung PMNs is likely to be the key bioactive form of the enzyme that limits lung inflammation and alveolar capillary barrier injury during ALI.
rodent; neutrophil; inflammation; knockout mice; chemokine
Neutrophil products like matrix metalloproteinases (MMP), involved in bacterial defence mechanisms, possibly induce lung damage and are elevated locally during hospital- acquired pneumonia (HAP). In HAP the virulence of bacterial species is known to be different. The aim of this study was to investigate the influence of high-risk bacteria like S. aureus and pseudomonas species on pulmonary MMPconcentration in human pneumonia.
In 37 patients with HAP and 16 controls, MMP-8, MMP-9 and tissue inhibitors of MMP (TIMP) were analysed by ELISA and MMP-9 activity using zymography in bronchoalveolar lavage (BAL).
MMP-9 activity in mini-BAL was increased in HAP patients versus controls (149 ± 41 vs. 34 ± 11, p < 0.0001). In subgroup analysis, the highest MMP concentrations and activity were seen in patients with high-risk bacteria: patients with high-risk bacteria MMP-9 1168 ± 266 vs. patients with low-risk bacteria 224 ± 119 ng/ml p < 0.0001, MMP-9 gelatinolytic activity 325 ± 106 vs. 67 ± 14, p < 0.0002. In addition, the MMP-8 and MMP-9 concentration was associated with the state of ventilation and systemic inflammatory marker like CRP.
Pulmonary MMP concentrations and MMP activity are elevated in patients with HAP. This effect is most pronounced in patients with high-risk bacteria. Artificial ventilation may play an additional role in protease activation.
Background: The proteolytic enzyme matrix metalloproteinase (MMP)-9 can degrade structural compounds such as the extracellular matrix and the basement membrane in the airways and lungs. MMP-9 has therefore been implicated in remodelling of the airways and lungs during severe asthma and chronic obstructive pulmonary disease (COPD).
Methods: The effect of the T lymphocyte derived proinflammatory cytokine interleukin (IL)-17 on MMP-9 protein release and activity in the airways was studied in vivo and in vitro.
Results: In vivo, intranasal stimulation of mice with IL-17 induced the release of the precursor molecule proMMP-9 in bronchoalveolar lavage (BAL) fluid, associated with a pronounced local accumulation of neutrophils that stained positive for MMP-9. Stimulation with IL-17 also increased the concentration of free soluble MMP-9 that was proteolytically active as determined by a gelatinase substrate assay. The concentration of MMP-9 in BAL fluid had a strong positive correlation with the number of neutrophils; the amount of MMP-9 per neutrophil was not increased by IL-17 stimulation. In vitro, stimulation of mouse neutrophils with IL-17 did not increase the concentration of proMMP-9 in the conditioned medium.
Conclusion: Local stimulation with IL-17 increases the concentration of biologically active MMP-9 as well as its precursor molecule in mouse airways in vivo. This increase in proteolytic load is probably mainly due to an increased number of neutrophils and not to an increase in the release of MMP-9 from each neutrophil. These findings indicate a link between the T lymphocyte cytokine IL-17 and increased proteolytic load in the airways which may be relevant for chronic inflammatory airway diseases such as severe asthma and COPD.
The role of the receptor for advanced glycation end-products (RAGE) has been shown to differ in two different mouse models of asbestos and bleomycin induced pulmonary fibrosis. RAGE knockout (KO) mice get worse fibrosis when challenged with asbestos, whereas in the bleomycin model they are largely protected against fibrosis. In the current study the role of RAGE in a mouse model of silica induced pulmonary fibrosis was investigated.
Wild type (WT) and RAGE KO mice received a single intratracheal (i.t.) instillation of silica in saline or saline alone as vehicle control. Fourteen days after treatment mice were subjected to a lung mechanistic study and the lungs were lavaged and inflammatory cells, protein and TGF-β levels in lavage fluid determined. Lungs were subsequently either fixed for histology or excised for biochemical assessment of fibrosis and determination of RAGE protein- and mRNA levels. There was no difference in the inflammatory response or degree of fibrosis (hydroxyproline levels) in the lungs between WT and RAGE KO mice after silica injury. However, histologically the fibrotic lesions in the RAGE KO mice had a more diffuse alveolar septal fibrosis compared to the nodular fibrosis in WT mice. Furthermore, RAGE KO mice had a significantly higher histologic score, a measure of affected areas of the lung, compared to WT silica treated mice. A lung mechanistic study revealed a significant decrease in lung function after silica compared to control, but no difference between WT and RAGE KO. While a dose response study showed similar degrees of fibrosis after silica treatment in the two strains, the RAGE KO mice had some differences in the inflammatory response compared to WT mice.
Aside from the difference in the fibrotic pattern, these studies showed no indicators of RAGE having an effect on the severity of pulmonary fibrosis following silica injury.
Idiopathic pulmonary fibrosis (IPF) is a fatal disease characterized by excessive deposition of extracellular matrix (ECM).
We investigated the regulation of matrix metalloproteinases (MMPs) and their inhibitors (TIMPs) in lung fibrosis.
MMP and TIMP expression, collagenolytic activity and collagen content was assessed in IPF (n=16) versus donor (n=6) lung homogenates and accomplished by in-situ-zymography for gelatinolytic and collagenolytic activities, combined with MMP antigen detection. Role of MMP13 was assessed employing the bleomycin model of lung fibrosis in MMP-13-/- versus wild-type mice.
Measurements and Main Results
In IPF, MMPs-1, 2, 7, 9 and 13, but not MMP-8, were significantly upregulated, whereas none of the TIMPs (1–4) were significantly altered. Collagen content was slightly increased and collagenolytic activity was most prominent in the airways and co-localized with MMP-13. We observed an exaggerated early inflammatory response and an augmented lung fibrosis in bleomycin-challenged MMP-13-/- versus wild-type mice, with elevated lung collagen content 28d after bleomycin challenge in the MMP-13-/- mice.
Our data suggest that i) collagen deposition in IPF lungs is not primarily due to excessive TIMP production, but rather due to overwhelming ECM production in face of an overall increased, but spatially imbalanced collagenolytic activity, ii) preferential distribution of collagenolytic activity, largely MMP-13, in the airways offers an explanation for the development of honeycomb cysts and iii) despite an overall increase in inflammatory cell content the presence of MMP-13 seems to limit the overall extent of ECM deposition in lung fibrosis.
Methods: Zndtp (10 µmol/kg) was administered subcutaneously twice daily to mice 1 week following the intratracheal instillation of 0.025 U bleomycin. Animals were killed 10 or 21 days after bleomycin instillation and indices of lung damage and fibrosis were evaluated.
Results: Bleomycin treatment induced pulmonary cytotoxicity, increased levels of active transforming growth factor ß (TGF-ß), enhanced lung collagen accumulation, and decreased glutathione content. Zndtp administration significantly attenuated these indices.
Conclusions: Administration of Zndtp in the bleomycin model resulted in appreciable alveolar cytoprotection and amelioration of pulmonary fibrosis. This molecule and its analogues may warrant further consideration in the treatment of acute lung injury and fibrotic lung disorders.
In a model of pulmonary inflammation and fibrosis induced by the antineoplastic antibiotic, bleomycin, we previously demonstrated that TGF-beta was markedly elevated within 7 d of bleomycin administration. At the time of maximal TGF-beta production, TGF-beta 1 was localized by immunohistochemistry to be present almost exclusively in alveolar macrophages. In this study, we have demonstrated that alveolar macrophages stimulated by bleomycin-induced injury secrete large quantities of biologically active TGF-beta 1 when explanted into tissue culture. However, alveolar macrophages from normal saline-treated rats secrete small quantities of biologically inactive TGF-beta. In contrast, splenic macrophages secrete large quantities of inactive TGF-beta and are unaffected by the intratracheal bleomycin treatment. High doses of the corticosteroid methylprednisolone given intramuscularly before and concomitantly with bleomycin administration prevented the influx of alveolar macrophages into the lungs, diminishing both the number of macrophages present in the alveoli and the total lung content of TGF-beta. However, the rate of secretion of TGF-beta by alveolar macrophages recovered from the alveoli was unchanged after corticosteroid treatment. When activated alveolar macrophages were cultured in the presence of several concentrations of dexamethasone that completely suppressed IL-1 secretion, little effect on TGF-beta secretion was observed. The findings in this study demonstrate that during bleomycin-induced injury, alveolar macrophages not only secrete large quantities of active TGF-beta 1, but are a predominant source of the enhanced TGF-beta response seen in this model. Furthermore, the alveolar macrophage secretion of TGF-beta is not inhibited by the presence of high concentrations of corticosteroids.
Fourteen-membered ring macrolides have been effective in reducing chronic airway inflammation and also preventing lung injury and fibrosis in bleomycin-challenged mice via anti-inflammatory effects. EM703 is a new derivative of erythromycin (EM) without the bactericidal effects. We investigated the anti-inflammatory and antifibrotic effects of EM703 in an experimental model of bleomycin-induced lung injury and subsequent fibrosis in mice.
Seven-week-old male ICR mice were used. All experiments used eight mice/group, unless otherwise noted in the figure legends. Bleomycin was administered intravenously to the mice on day 0. EM703 was orally administered daily to mice. All groups were examined for cell populations in the bronchoalveolar lavage (BAL) fluid and for induction of messenger RNA (mRNA) of Smad3 and Smad4 in the lung tissues by reverse transcriptase (RT)-polymerase chainreaction (PCR) on day 7. Fibroblastic foci were assessed histologically, and the hydroxyproline content was chemically determined in the lung tissues on day 28. We performed assay of proliferation and soluble collagen production, and examined the induction of mRNA of Smad3 and Smad4 by RT-PCR in murine lung fibroblast cell line MLg2908. We also examined Smad3, Smad4 and phosphorylated Smad2/3 (p-Smad2/3) protein assay by western blotting in MLg2908.
Bleomycin-induced lung fibrosis, and the infiltration of macrophages and neutrophils into the airspace were inhibited by EM703. The expression of Smad3 and Smad4 mRNA was clearly attenuated by bleomycin, but was recovered by EM703. EM703 also inhibited fibroblast proliferation and the collagen production in lung fibroblasts induced by Transforming growth factor-beta (TGF-β). The expression of Smad3 and Smad4 mRNA in murine lung fibroblasts disappeared due to TGF-β, but was recovered by EM703. EM703 inhibited the expression of p-Smad2/3 and Smad4 protein in murine lung fibroblasts induced by TGF-β.
These findings suggest that EM703 improves bleomycin-induced pulmonary fibrosis in mice by actions of anti-inflammation and regulation of TGF-β signaling in lung fibroblasts.
Clearance of recruited immune cells is necessary to resolve inflammatory reactions. We show here that matrix metalloproteinase 2 (MMP2), as part of an interleukin 13 (IL-13)–dependent regulatory loop, dampens inflammation by promoting the egress of inflammatory cells into the airway lumen. MMP2−/− mice showed a robust asthma phenotype and increased susceptibility to asphyxiation induced by allergens. However, whereas the lack of MMP2 reduced the influx of cells into bronchoalveolar lavage (BAL), numerous inflammatory cells accumulated in the lung parenchyma. BAL of MMP2−/− mice lacked normal chemotactic activity, whereas lung inflammatory cells from the same mice showed appropriate chemotactic responses. Thus, MMP2 establishes the chemotactic gradient required for egression of lung inflammatory cells and prevention of lethal asphyxiation.
While idiopathic pulmonary fibrosis (PF) is a devastating lung disease, the management of PF including effective monitoring of disease progression remains a challenge. Herein, we introduce a novel, fast and ultra-sensitive metalloproteinase (MMP) activatable optical probe, named MMP-P12, to non-invasively monitor PF progression and response to PF treatment. A bleomycin (BLM)-induced mouse PF model was subjected non-invasively to optical imaging at various time points after BLM treatment. Mouse PF model developed fibrosis during 21 days of experimental period, and the progression of PF was well correlated with the step-wise increase of MMP-2 expression as examined by quantitative RT-PCR and western blot analysis on the 7-, 14-and 21-day post-BLM administration. On these days, MMP-activated fluorescence images were acquired in vivo and ex vivo. Signal quantification showed time-dependent lung-specific incremental increases in fluorescence signals. As a treatment for PF, secretoglobin 3A2 was daily administered intravenously for five days starting day seven of BLM administration, which resulted in reduced MMP-2 activity and reduction of PF as previously demonstrated. Importantly, the fluorescence signal that reflected MMP activity also decreased in intensity. In conclusion, MMPs may play an important role in PF development and MMP-P12 probe could be a promising tool for PF detection, even at an early stage of the disease as well as an indicator of therapy response.
Pulmonary fibrosis; Matrix metalloproteinase; Optical imaging; Activatable probe; Secretoglobin 3A2
Humoral molecules can trigger injury on mechanically stressed and damaged tissue. We have studied the role of complement 3 (C3) in a mouse model of ventilator-induced lung injury (VILI). Compared with sham-treated wild type (WT) mice, ventilated WT mice have reduced total bronchoalveolar lavage (BAL) cells; and elevated activities of thrombin and matrix metalloproteinases (MMPs), such as gelatinase/collagenase in the BAL fluid. In contrast, these parameters in ventilated C3 null mice are not significantly different from sham-treated WT and C3 null mice. In mechanically ventilated mice, thrombin activity and MMPs are lower in C3 null mice than in WT mice and are inversely correlated with total single BAL cells. C3 activation is associated with MMP activation in vitro. Pretreatment of WT mice with humanized cobra venom factor, which inactivates C3, reduces C3 deposition in the lung and increases total BAL cells in VILI. We propose that C3 is involved with VILI and inhibition of complement activation may be a potential therapeutic strategy.
Complement; Coagulation; Matrix metalloproteinase; Complement; Acute lung injury; Humanized cobra venom factor
In patients with ventilator associated pneumonia (VAP), Pseudomonas aeruginosa type III (TTSS) secreting isolates have been li nked to poor clinical outcomes. Differential expression of matrix metalloproteinases (MMPs) induced by type III effector proteins may herald an irreversible lung injury.
Serial bronchoalveolar lavage fluids collected from 41 patients with P. aeruginosa at onset of VAP, day 4, and day 8 after antibiotic therapy were assayed for MMP-8, MMP-9, tissue inhibitor of metalloproteinase-1 (TIMP-1), and α-2 macroglobulin levels.
At the onset of VAP, isolates secreting ExoU had the highest MMP-9 levels. The response to antimicrobial therapy showed a differential drop in MMPs with significant decrease in MMP-8 and MMP-9 levels on days 4 and 8 in patients with TTSS− compared to TTSS+ phenotype. The ratio of MMP-9/TIMP-1 was significantly associated with α-2 macroglobulin at end of therapy (r=0.4, p=0.02). Patients who survived had a lower MMP-9/TIMP-1ratio than those who died (p=0.003).
VAP linked to P. aeruginosa Type III phenotype portrays a divergent antibiotic treatment response in regards to the concentrations of metalloproteinases in the alveolar space. The imbalance between MMP-9 and TIMP-1 may determine the intensity of alveolocapillary damage and ultimate outcome of Pseudomonas aeruginosa VAP.
Pseudomonas aeruginosa; exotoxin; metalloproteinases; ventilator associated pneumonia
Rationale: The insulin-like growth factor-I (IGF-I) pathway is an important determinant of survival and proliferation in many cells. However, little is known about the role of the IGF-I pathway in lung injury. We previously showed elevated levels of IGF-I in bronchoalveolar lavage fluid from patients with acute respiratory distress syndrome. Furthermore, immunodepletion of IGF from acute respiratory distress syndrome bronchoalveolar lavage increased fibroblast apoptosis.
Objectives: We examined the effect of blockade of type 1 IGF tyrosine kinase receptor (IGF-IR) in a murine model of bleomycin-induced lung injury and fibrosis.
Methods: Mice were treated with a monoclonal antibody against the IGF-I receptor (A12) or vehicle after intratracheal bleomycin instillation.
Measurements and Main Results: Mice treated with A12 antibody had significantly improved survival after bleomycin injury compared with control mice. Both groups of mice had a similar degree of fibrosis on days 7 and 14, but by Day 28 the A12-treated group had significantly less fibrosis. Delayed treatment with A12 also resulted in decreased fibrosis. A12-treated mice had significantly decreased apoptotic cells on Day 28 compared with control mice. We confirmed that A12 treatment induced mouse lung fibroblast apoptosis in vitro. In addition, IGF-I increased lung fibroblast migration. The primary pathway activated by IGF-I in lung fibroblasts was the insulin receptor substrate-2/phosphatidylinositol 3-kinase/Akt axis.
Conclusions: IGF-I regulated survival and migration of fibrogenic cells in the lung. Blockade of the IGF pathway increased fibroblast apoptosis and subsequent resolution of pulmonary fibrosis. Thus, IGF-IR may be a potential target for treatment of lung injury and fibrosis.
insulin-like growth factor; lung injury; lung fibrosis
Clearance of allergic inflammatory cells from the lung through matrix metalloproteinases (MMPs) is necessary to prevent lethal asphyxiation, but mechanistic insight into this essential homeostatic process is lacking. In this study, we have used a proteomics approach to determine how MMPs promote egression of lung inflammatory cells through the airway. MMP2- and MMP9-dependent cleavage of individual Th2 chemokines modulated their chemotactic activity; however, the net effect of complementing bronchoalveolar lavage fluid of allergen-challenged MMP2−/−/MMP9−/− mice with active MMP2 and MMP9 was to markedly enhance its overall chemotactic activity. In the bronchoalveolar fluid of MMP2−/−/MMP9−/− allergic mice, we identified several chemotactic molecules that possessed putative MMP2 and MMP9 cleavage sites and were present as higher molecular mass species. In vitro cleavage assays and mass spectroscopy confirmed that three of the identified proteins, Ym1, S100A8, and S100A9, were substrates of MMP2, MMP9, or both. Function-blocking Abs to S100 proteins significantly altered allergic inflammatory cell migration into the alveolar space. Thus, an important effect of MMPs is to differentially modify chemotactic bioactivity through proteolytic processing of proteins present in the airway. These findings provide a molecular mechanism to explain the enhanced clearance of lung inflammatory cells through the airway and reveal a novel approach to target new therapies for asthma.