The selective MMP-12 inhibitor, AS111793 reduces airway inflammation in mice exposed to cigarette smoke.

BACKGROUND: Macrophage elastase (MMP-12) is involved in the inflammatory process of chronic obstructive pulmonary disease (COPD). The aim of this study was to investigate in mice the effect of MMP-12 inhibition on the inflammatory process induced by cigarette smoke (CS) or by lipopolysaccharide (LPS) exposure of the airways. EXPERIMENTAL APPROACH: C57BL/6 mice were given, orally, either the selective MMP-12 inhibitor AS111793 (3, 10, 30 and 100 mg kg(-1)), the PDE-4 inhibitor roflumilast (3 mg kg(-1)) or vehicle, then exposed to CS (for 3 days) or to LPS (100 microg mL(-1), 30 min). Subsequent to the last smoke or LPS exposure, bronchoalveolar lavages (BAL) were performed and lungs were removed and homogenized to analyze various markers of inflammation at appropriate times. KEY RESULTS: Inhibition of MMP-12 by AS111793 (10 and 30 mg kg(-1)) was associated with a reduction of the increase in neutrophil number in BAL fluids after 4 days and of macrophages after 11 days. On day 4, AS111793 also significantly reduced all the inflammation markers that had increased after CS exposure, including soluble TNF receptors I and II, MIP-1gamma, IL-6 and pro-MMP-9 activity in BAL fluids, and KC/CXCL1, fractalkine/CX3CL1, TIMP-1 and I-TAC/CXCL11 in lung parenchyma. In contrast, inhibition of MMP-12 did not reduce neutrophil influx, pro-MMP-9 activity or KC/CXCL1 release in BAL fluids of mice exposed to LPS. CONCLUSION: Inhibition of MMP-12 with AS111793, reduced the inflammatory process associated with exposure of mice to CS, strongly suggesting a specific involvement of MMP-12 in lung inflammation following CS exposure.

TIMP-1 is a key factor of fibrogenic response to bleomycin in mouse lung.

Pulmonary fibrosis is characterized by the 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. We investigated MMP-9, MMP-2, TIMP-1, TIMP-2 and TIMP-3 in the fibrotic response to bleomycin of fibrosis prone C57BL/6J and fibrosis resistant BALB/c mice. Mice were administered with 0.1 mg bleomycin by intranasal administration. Either 24 h or 14 days after, the mice were anesthetized and underwent either bronchoalveolear lavage (BAL) or lung removal. Collagen deposition in lung tissue was determined by hydroxyproline measurement, MMP activity was analyzed by zymography, and other mediators were analyzed by ELISA. TIMP-1 was localized in lung sections by immunohistochemistry and real time PCR was performed to gene expression in lung. Non parametric Mann-Whitney and Spearman tests were used for statistical analysis. Fourteen days after bleomycin administration, hydroxyproline assay and histological study revealed that BALB/c mice developed significantly less fibrosis compared to C57BL/6J mice. At day 1, bleomycin enhanced TIMP-1, MMP-2 and MMP-9 protein levels in BALF, and induced corresponding genes in lung tissue of both strains. The rise of Timp-1, Mmp-9 and Mmp-2 gene levels were significantly stronger in lungs of C57BL/6J, whereas gelatinase activities of MMP-2 and MMP-9 were similar. Immunohistochemistry revealed that TIMP-1 macrophages and epithelial cells were prominent TIMP-1 producers in both strains. At day 14, neither MMP-2 nor MMP-9 levels exhibited strain-dependent protein level or gene expression, although TIMP-1 was strongly associated with fibrosis. Interestingly, bleomycin induced neither Timp-2 nor Timp-3 in lung tissue at any time of the study. The present study shows that early altered regulation of TIMP-1 following bleomycin administration may be involved in bleomycin-induced pulmonary fibrosis.

Role of matrix metalloproteinases in the development of airway inflammation and remodeling

Matrix metalloproteinases (MMPs) are a major group of proteases known to regulate extracellular matrix (ECM) turnover and so they have been suggested to be important in the process of lung disease associated with tissue remodeling. This has led to the concept that modulation of airway remodeling including excessive proteolysis damage to the tissue may be of interest for future treatment. Within the MMP family, macrophage elastase (MMP-12) is able to degrade ECM components such as elastin and is involved in tissue remodeling processes in chronic obstructive pulmonary disease including emphysema. Pulmonary fibrosis has an aggressive course and is usually fatal within an average of 3 to 6 years after the onset of symptoms. Pulmonary fibrosis is associated with deposition of ECM components in the lung interstitium. The excessive airway remodeling as a result of an imbalance in the equilibrium of the normal processes of synthesis and degradation of ECM components could justify anti-protease treatments. Indeed, the correlation of the differences in hydroxyproline levels in the lungs of bleomycin-treated mice strongly suggests that a reduced molar pro-MMP-9/TIMP-1 ratio in bronchoalveolar lavage fluid is associated with collagen deposition, beginning as early as the inflammatory events at day 1 after bleomycin administration. Finally, these observations emphasize that effective treatment of these disorders must be started early during the natural history of the disease, prior to the development of extensive lung destruction and fibrosis.

Role of matrix metalloproteinases in the development of airway inflammation and remodeling.

Matrix metalloproteinases (MMPs) are a major group of proteases known to regulate extracellular matrix (ECM) turnover and so they have been suggested to be important in the process of lung disease associated with tissue remodeling. This has led to the concept that modulation of airway remodeling including excessive proteolysis damage to the tissue may be of interest for future treatment. Within the MMP family, macrophage elastase (MMP-12) is able to degrade ECM components such as elastin and is involved in tissue remodeling processes in chronic obstructive pulmonary disease including emphysema. Pulmonary fibrosis has an aggressive course and is usually fatal within an average of 3 to 6 years after the onset of symptoms. Pulmonary fibrosis is associated with deposition of ECM components in the lung interstitium. The excessive airway remodeling as a result of an imbalance in the equilibrium of the normal processes of synthesis and degradation of ECM components could justify anti-protease treatments. Indeed, the correlation of the differences in hydroxyproline levels in the lungs of bleomycin-treated mice strongly suggests that a reduced molar pro-MMP-9/TIMP-1 ratio in bronchoalveolar lavage fluid is associated with collagen deposition, beginning as early as the inflammatory events at day 1 after bleomycin administration. Finally, these observations emphasize that effective treatment of these disorders must be started early during the natural history of the disease, prior to the development of extensive lung destruction and fibrosis.

Interactions of tachykinin receptor antagonists with lipopolysaccharide-induced airway inflammation in mice.

1. Several observations suggest that tachykinins are involved in the pathogenesis of bronchopulmonary alterations. We have investigated the effect of antagonists for tachykinin NK1 (SR 140333), NK2 (SR 48968) or NK3 (SR 142801) receptors on inflammatory cell recruitment, tumour necrosis factor (TNF)-alpha and interleukin (IL)-6 release and matrix metalloproteinase (MMP)-9 activity in the bronchoalveolar lavage fluid (BALF) of mice exposed to lipopolysaccharide (LPS; 100 microg/mL aerosol for 30 min). 2. Treatment of mice with a combination of SR 140333 and SR 48968 (10(-6) mol/L, aerosol) significantly reduced the increase in the number of total cells and neutrophils and MMP-9 activity in the BALF of mice 2.5 h after LPS exposure. Treatment with the NK3 antagonist SR 142801 (10(-6) mol/L, aerosol) did not inhibit the influx of neutrophils, but markedly reduced the increase in TNF-alpha and IL-6 levels at 2.5 h and MMP-9 activity at 20 h. 3. These results show that the three tachykinin receptor antagonists may interfere with the development of airway inflammation, namely neutrophilia, TNF-alpha release or MMP-9 activity in the BALF of mice exposed to LPS and suggest that not only NK1 and NK2 receptors, but also NK3 receptors are involved in the modulation of the inflammatory response and airway remodelling.

Enhancement of gelatinase activity during development of subepithelial fibrosis in a murine model of asthma.

BACKGROUND: Chronic asthma is characterized by inflammatory cell infiltration and tissue remodelling leading to subepithelial fibrosis. Metalloproteinases (MMPs) are involved in degradation of extracellular matrix in most chronic inflammatory diseases. OBJECTIVE: The aim of this study was to investigate the expression of MMPs in the development of inflammatory processes associated or not with the concomitant development of subepithelial fibrosis in an experimental model of asthma. METHODS: Sensitized BP2 mice were challenged with ovalbumin (OA) every 2 weeks during 8 months. Several mice were removed once a month and bronchoalveolar lavages (BAL) or lung biopsies were performed. RESULTS: Lung sections stained with picrosirius and hydroxyproline measurements showed a significant collagen deposition after 16 weeks of OA challenge, demonstrating the development of subepithelial fibrosis. Pulmonary inflammation was present from the first OA challenge and was consistent throughout the 8 months of the study. Moreover, an up-regulation and activation of MMP-9 and, to a less extent, MMP-2 were observed in BAL fluid from challenged mice. The level of tissue inhibitor of metalloproteinases (TIMP)-1 increased after 12 weeks of OA challenge vs. control mice. CONCLUSION: This study reveals that a decrease in the activation of the MMP-9 due to the increase in TIMP-1, could contribute to excessive collagen deposition following repeated antigen challenge in sensitized mice.

Involvement of gelatinases (MMP-2 and MMP-9) in the development of airway inflammation and pulmonary fibrosis.

Pulmonary fibrosis has an aggressive course and is usually fatal an average of 3 to 6 years after the onset of symptoms. Pulmonary fibrosis is associated with deposition of extracellular matrix (ECM) components in the lung interstitium. Matrix metalloproteinases (MMPs) are a major group of proteinases known to regulate the ECM remodeling and so they are hypothesized to be important in the process of lung fibrosis. These led to the concept that modulation of airway remodeling including excessive proteolytic damage of the tissue may be of interest for future treatment. The excessive airway remodeling as a result of an imbalance in the equilibrium of the normal processes of synthesis and degradation of extracellular matrix components could argue in favor of antiprotease treatments. Moreover, these observations emphasize that effective therapies for these disorders must be given early in the natural history of the disease, prior to the development of expensive lung destruction and fibrosis.

Increased release of matrix metalloproteinase-9 in the plasma of acute severe asthmatic patients.

BACKGROUND: Matrix metalloproteinases (MMPs) are likely to be relevant mediators of the extracellular matrix (ECM) degradation and airway remodelling. OBJECTIVE: We have compared the levels of MMPs, eotaxin and soluble interleukin 2 receptor (IL-2R) in the plasma of healthy subjects, atopic patients and asthmatic patients. METHODS: The asthmatic patients were separated into two groups, either well controlled on inhaled therapy or acute severe asthma. Patients with acute severe disease had all received systemic corticosteroids from 12 to 48 h before the blood was taken. Blood was recovered in EDTA tubes, incubated with either f MLP, PMA or vehicle for 10 min and centrifuged. MMP-9, TIMP-1, IL-2R and eotaxin levels were measured in the plasma by ELISA. Moreover, the activity of MMPs was also evaluated by zymography. RESULTS: An increased basal level of MMP-9 and IL2-R was observed in acute severe asthma. Following stimulation with f MLP and PMA there was an enhanced production of MMP-9 in the plasma of all groups of patients. However, the MMP-9 level was significantly enhanced in acute severe asthma, compared with the others. No difference was found for the TIMP-1 level between the patients. The eotaxin level in plasma was found to be significantly lower in acute severe asthmatics compared with the others groups. Zymography technique showed a significant increased activity of MMP-9 (92 kDa) but not MMP-2 (66 kDa) in the plasma of patients with acute asthma. CONCLUSION: The increased in MMP-9 production and activity observed in the present study suggests a process of extracellular matrix degradation in acute severe asthmatic patients and proposes MMP-9 as a non-invasive systemic marker of inflammation and airway remodelling in asthma.

Effects of PDE4 inhibitors on lipopolysaccharide-induced priming of superoxide anion production from human mononuclear cells.

AIMS: Phosphodiesterase 4 (PDE4) inhibitors have been described as potent anti-inflammatory compounds, involving an increase in intracellular levels of cyclic 3',5'-adenosine monophosphate (AMP). The aim of this study was to compare the effects of selective PDE4 inhibitors, rolipram and RP 73-401 with the cell permeable analogue of cyclic AMP, dibutyryl-cyclic AMP (db-cAMP) and the anti-inflammatory cytokine interleukin-10 (IL-10) on superoxide anion production from peripheral blood mononuclear cells preincubated with lipopolysaccharide (LPS). MAJOR FINDINGS: We report that, after incubation of the cells with LPS, a large increase in superoxide anion production was observed. Rolipram or RP 73-401 (10(-8) to 10(-5) M) induced significant reductions of fMLP-induced superoxide anion production in cells incubated with or without LPS. The db-cAMP (10(-5) to 10(-3) M) also elicited dose-dependent inhibitions of the fMLP-induced superoxide anion production. In contrast, IL-10 (1 or 10 ng/ml) did not elicit a reduction in fMLP-induced superoxide anion production in both conditions. PRINCIPAL CONCLUSION: These results suggest that the inhibitory activity of PDE4 inhibitors on fMLP-induced production of superoxide anion production is mediated by db-cAMP rather than IL-10.

Inhibition of inflammatory cell recruitment by the tachykinin NK(3)-receptor antagonist, SR 142801, in a murine model of asthma.

Several observations suggest that tachykinins (substance P, neurokinin A and neurokinin B) are involved in the pathogenesis of pulmonary diseases and elicit several airway responses such as bronchoconstriction and neurogenic inflammation via interactions with specific receptors denoted NK(1), NK(2) and NK(3). We have investigated the effect of a selective antagonist for tachykinin NK(3) receptor, SR 142801 ((R)-(N)-(1-(3-(1-benzoyl-3-(3,4-dichlorophenyl)piperidin-3-yl)propyl)-4-phenylpiperidin-4-yl-N-methylacetamide), on the inflammatory cell recruitment in ovalbumin-sensitized and -challenged mice used as a model of allergic asthma. Twenty hours after the two-ovalbumin challenges, differential cell counts were calculated and indicated that SR 142801 caused a significant decrease in the number of neutrophils and eosinophils. Forty hours after the last ovalbumin exposure, SR 142801 induced a significant decrease in the recruitment of eosinophils. These results suggest that tachykinins and tachykinin NK(3) receptors can interfere with cell recruitment in inflammatory response.

Modulation of airway remodeling-associated mediators by the antifibrotic compound, pirfenidone, and the matrix metalloproteinase inhibitor, batimastat, during acute lung injury in mice.

Matrix metalloproteinases (MMPs) are potent to degrade basement membrane collagen associated with acute lung injury in inflammatory processes. We have investigated effects of pirfenidone, antifibrotic agent, and batimastat, inhibitor of MMPs, on gelatinase activities, on release of tumor necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta (TGF-beta), as well as on recruitment of inflammatory cells in bronchoalveolar lavage (BAL) fluid after aerosol administration of lipopolysaccharide (LPS) in mice. Pretreatment with pirfenidone reduced neutrophil recruitment, TNF-alpha and TGF-beta levels, and MMP-9 secretion. In contrast, pretreatment with batimastat (30 or 60 mg/kg, i.p.) only reduced TNF-alpha and TGF-beta levels. Batimastat did not reduce MMP secretion in BAL fluid but inhibited MMP-9 activity. The increase in tissue inhibitor of matrix metalloproteinase (TIMP)-1 induced by LPS was not modified by the two drugs. These findings demonstrate that the two drugs can inhibit the in vivo increase in MMP induced by LPS, batimastat with a direct inhibitor effect on MMP activity and pirfenidone as a consequence of its antiinflammatory effect.

Repeated endotoxin exposure induces interstitial fibrosis associated with enhanced gelatinase (MMP-2 and MMP-9) activity.

BACKGROUND: Dysregulation of matrix metalloproteinases (MMPs) has been implicated in lung injury associated with inflammatory disorders and several lung diseases such as pulmonary fibrosis. OBJECTIVE: We studied a murine model of lipopolysaccharide (LPS)-induced chronic inflammation in order to analyse the relationship between MMP activity in bronchoalveolar lavage fluid and collagen deposition in lung tissue. BP2 mice were exposed to repeated aerosols of LPS of E. coli for 8 months. RESULTS: The inflammatory reaction induced by LPS increased throughout the time of exposure and was associated after 10 weeks with collagen deposition in the alveolar walls. Meantime, we observed in BAL fluid from LPS-exposed mice an early induction of MMP-9 correlated with neutrophil recruitment. MMP-2 increased during the early inflammatory phase, and also during the development of the fibrotic phase. CONCLUSION: Repeated exposure of mice to an aerosol of LPS can lead to pulmonary interstitial fibrosis and MMPs seem to be associated with this process.

Inhibition of bleomycin-induced pulmonary fibrosis in mice by the matrix metalloproteinase inhibitor batimastat.

Bleomycin-induced pulmonary fibrosis is known to be associated with the increased activity of two gelatinases, matrix metalloproteinase (MMP)-2 and MMP-9, in bronchoalveolar lavage (BAL). This study has investigated the effect of a synthetic inhibitor of MMP, batimastat, on the development of pulmonary fibrosis induced by bleomycin administration in mice. Animals were intranasally instilled with saline or bleomycin (0.5 mg in 100 microl per mouse). Batimastat (30 mg/kg) or vehicle alone was administered by intraperitoneal injection 24 h and 1 h before saline or bleomycin instillation, and then daily at the same dosage until the end of the study. Fifteen days after bleomycin administration, BAL was performed and the lung was removed. Treatment of mice with batimastat significantly reduced bleomycin-induced lung fibrosis, as shown in the lung by histopathological examination and by a decrease in hydroxyproline levels. Batimastat also prevented the increase in BAL macrophage and lymphocyte numbers, whereas it did not show any effect on the increased expression of active transforming growth factor-beta (TGF-beta) in BAL. Batimastat treatment was effective in reducing MMP-2 and MMP-9 activity as well as the tissue inhibitor of metalloproteinase-1 (TIMP-1) level in BAL. These results suggest that administration of the MMP inhibitor batimastat is useful in preventing experimental pulmonary fibrosis induced by bleomycin and raises the possibility of a therapeutic approach to human pulmonary fibrotic disease.

Reduction of matrix metalloproteinase-9 activity by the selective phosphodiesterase 4 inhibitor, RP 73-401 in sensitized mice.

Matrix metalloproteinases are particularly potent in degrading basement membrane collagen and other extracellular matrix components. We have investigated the effects of a selective phosphodiesterase 4 inhibitor, RP 73-401 [N-(3, 5-dichloropyrid-4-yl)-3-cyclopentyloxy-4-methoxybenzamide], on gelatinase (matrix metalloproteinase-2 and matrix metalloproteinase-9) activity in ovalbumin-sensitized and -challenged mice. Twenty-four hours after the last challenge, matrix metalloproteinase activity was evaluated in the bronchoalveolar lavage fluids by a zymography technique, and a significant increase in matrix metalloproteinase-9, but not matrix metalloproteinase-2, activity was noted. When administered orally (0.3-3 mg/kg) 1 h before each ovalbumin challenge, the selective phosphodiesterase 4 inhibitor, RP 73-401, significantly reduced this increased matrix metalloproteinase-9 activity in bronchoalveolar lavage fluids. Our data suggest that RP 73-401 may modulate tissue remodelling associated with lung inflammatory processes including asthma.

Role of gelatinases MMP-2 and MMP-9 in tissue remodeling following acute lung injury.

Acute lung injury is characterized by a severe disruption of alveolo-capillary structures and includes a variety of changes in lung cell populations. Evidence suggests the occurrence of rupture of the basement membranes and interstitial matrix remodeling during acute lung injury. The dynamic equilibrium of the extracellular matrix (ECM) under physiological conditions is a consequence of the balance between the regulation of synthesis and degradation of ECM components. Matrix metalloproteinases (MMPs) represent a group of enzymes involved in the degradation of most of the components of the ECM and therefore participate in tissue remodeling associated with pathological situations such as acute lung injury. MMP activity is regulated by proteolytic activation of the latent secreted proenzyme and by interaction with specific tissue inhibitors of metalloproteinases. This review details our knowledge of the involvement of MMPs, namely MMP-2 and MMP-9, in acute lung injury and acute respiratory distress syndrome.

Anti-inflammatory activities of a new series of selective phosphodiesterase 4 inhibitors derived from 9-benzyladenine.

Adenine derivatives substituted in position 9 have been demonstrated to have potent phosphodiesterase (PDE) inhibition properties with high selectivity toward PDE4. We compared the effects of various compounds derived from 9-benzyladenine with those of the selective PDE4 inhibitor RP 73401 on the inhibition of PDE4 isolated from bovine aorta, arachidonic acid, and tumor necrosis factor-alpha release by mononuclear cells from healthy subjects. The rank order of potency of the various compounds for in vitro activities on arachidonic acid release is RP 73401 > NCS 613 > NCS 630 > NCS 632 > BWA 78U = NCS 631. The most effective compounds in vitro (RP 73401 and NCS 613) were further investigated in vivo. Both PDE inhibitors dose dependently (1, 10, and 30 mg/kg per os) inhibited the recruitment of neutrophils in the bronchoalveolar lavage fluid of mice exposed to endotoxin via aerosol. Significant differences were observed with 10 and 30 mg/kg RP 73401 and 30 mg/kg NCS 613. In rats, RP 73401, but not NCS 613, significantly increased basal acid secretion at 30 mg/kg i.v. and pentagastrin-stimulated acid secretion at 0.3, 1, and 10 mg/kg. These results demonstrate that the compounds derived from 9-benzyladenine, namely NCS 613, elicit anti-inflammatory activities. It is also suggested that their activities have been mediated through the inhibition of PDE4 isoenzyme. The fact that NCS 613 did not stimulate the gastric acid secretion suggests that this compound may produce fewer gastrointestinal side effects than second-generation PDE4 inhibitors, such as RP 73401.

Endotoxin-induced acute lung injury in rats. Role of insulin.

Reduced inflammatory responses are frequently associated with diabetes mellitus. In order to investigate the influence of diabetes mellitus on the activation of bronchoalveolar cells, diabetic Wistar rats (alloxan, 40 mg/kg, iv, 30 days) and matched controls were exposed to an aerosol of endotoxin (lipopolysaccharide, LPS) or saline. Bronchoalveolar lavage (BAL) was performed 4 h thereafter. Compared with saline, aerosol administration of LPS significantly increased the number of neutrophils in the BAL fluid of control and diabetic rats. Number of mononuclear cells did not change and eosinophils were absent. A marked increase in luminol-dependent chemiluminescence (LDCL) was observed in control group after stimulation of the cells in vitro with zymosan. In contrast, tests performed with cells from diabetic rats showed a 50% reduction in LDCL generation. Full recovery of cell behaviour to match control values was observed after treatment of diabetic animals with insulin, administered before LPS exposure. Furthermore, relative to controls, level of TNF-alpha in the BAL supernatant of diabetic rats was significantly reduced. Values returned to control levels after treatment of diabetic rats with insulin, prior exposure to LPS. In conclusion, data presented suggest that insulin might regulate superoxide generation and TNF-alpha release by leukocytes upon exposure to LPS in vivo.

Comparative effects of betamethasone, cyclosporin and nedocromil sodium in acute pulmonary inflammation and metalloproteinase activities in bronchoalveolar lavage fluid from mice exposed to lipopolysaccharide.

Matrix metalloproteinases (MMPs) are particularly potent in degrading basement membrane collagen associated with lung injury in inflammatory processes. We have investigated the effects of betamethasone, cyclosporin, and nedocromil on MMP2 and MMP9 activities, on TNF-alpha and IL-10 release, as well as on the recruitment of inflammatory cells in the bronchoalveolar lavage (BAL) fluid after aerosol administration of lipopolysaccharide (LPS) in mice. When mice were pretreated with betamethasone (5 mg/kg, po), MMP2 and MMP9 activities, TNF-alpha in BAL fluids, and the enhanced neutrophil number of LPS-exposed mice were reduced, whereas the level of IL-10 was increased. Pretreatment of mice with cyclosporin (10 mg/kg, po) did not significantly reduce MMP activities, but cyclosporin inhibited neutrophil recruitment, inhibited increase TNF- alpha and inhibited IL-10 decrease. Nedocromil sodium (30 mg/kg, ip) had no influence on the LPS-induced MMP activities, on neutrophil recruitment, or on IL-10 level, but this drug elicited a significant inhibition of TNF- alpha level. These results showed that treatment with the antiinflammatory drugs cyclosporin and nedocromil sodium did not lead to reduction of MMP release. However, since betamethasone reduced the LPS-induced pulmonary inflammation and production of MMPs, these results suggest that corticosteroids may decrease tissue remodelling associated with acute lung injury.

Effects of interleukin-10 and modulators of cyclic AMP formation on endotoxin-induced inflammation in rat lung.

The aim of this study was to investigate the effects of IL-10, a cell permeable analogue of cyclic AMP, dibutyryl-cAMP (db-cAMP), modulators of intracellular cyclic AMP such as phosphodiesterase (PDE) inhibitors and a beta 2-adrenoceptor agonist, salmeterol, on pulmonary inflammation following acute lung injury induced by endotoxin exposure in rats. Pulmonary inflammation was induced in adult Wistar rats by a 60-min exposure to endotoxin (lipopolysaccharide, LPS, 100 micrograms/mL). 4 h later bronchoalveolar lavage (BAL) was performed. The PDE inhibitors, rolipram (3 and 5 mg/kg) and theophylline (30 and 100 mg/kg) inhibited neutrophil recruitment, TNF-alpha release and cellular activation in BAL. Salmeterol (0.5 mg/mL) and IL-10 (0.1 microgram) only inhibit TNF-alpha increase in the BAL fluid and db-AMPc (2.5 micrograms/rat) was ineffective. The present data show that the selective PDE4 inhibitor, rolipram, and the non-selective PDE inhibitor, theophylline, markedly reduced the pulmonary inflammation associated with acute lung injury in the rat. These effects may be mediated in part by IL-10 rather than by cyclic AMP, as demonstrated by the potent inhibitory activity of exogenous IL-10 on the increase in TNF-alpha release in BAL fluid of rats exposed to LPS.

Reduced airway hyperresponsiveness by phosphodiesterase 3 and 4 inhibitors in guinea-pigs.

The aim of the present study was to compare the effects of selective phosphodiesterase (PDE) 3, 4 and 5 inhibitors on antigen-induced airway hyperresponsiveness in sensitized guinea-pigs. When the sensitized guinea-pigs were orally pre-treated with the selective PDE4 inhibitor, Ro 20-1724 (30 mg/kg), and studied 48h after OA, a significant reduction (P<0.01) of the leftward shift of the dose-response curve to ACh was noted, whereas it was ineffective at the lower dose (10 mg/kg). Administration of the selective PDE3 inhibitor, milrinone (30 mg/kg) also elicited a significant reduction (P<0.01) of the airway hyperresponsiveness, whereas the PDE5 inhibitor zaprinast (30 mg/kg) was ineffective. These results show that both PDE3 and PDE4 inhibitors are able to inhibit the antigen-induced airway hyperresponsiveness in sensitized guinea-pigs and support the potential utility of selective PDE inhibitors in the treatment of asthma.