A new experimental model of acid- and endotoxin-induced acute lung injury in rats.

The majority of the animal models of acute lung injury (ALI) are focused on the acute phase. This limits the studies of the mechanisms involved in later phases and the effects of long-term treatments. Thus the goal of this study was to develop an experimental ALI model of aspiration pneumonia, in which diffuse alveolar damage continues for 72 h. Rats were intratracheally instilled with one dose of HCl (0.1 mol/l) followed by another instillation of one dose of LPS (0, 10, 20, 30, or 40 µg/g body weight) 2 h later, which models aspiration of gastric contents that progresses to secondary lung injury from bacteria or bacterial products. The rats were euthanized at 24, 48, and 72 h after the last instillation. The results showed that HCl and LPS at all doses caused activation of inflammatory responses, increased protein permeability and apoptosis, and induced mild hypoxemia in rat lungs at 24 h postinstillation. However, this lung damage was present at 72 h only in rats receiving HCl and LPS at the doses of 30 and 40 µg/g body wt. Mortality (∼50%) occurred in the first 48 h and only in the rats treated with HCl and LPS at the highest dose (40 µg/g body wt). In conclusion, intratracheal instillation of HCl followed by LPS at the dose of 30 µg/g body wt results in severe diffuse alveolar damage that continues at least 72 h. This rat model of aspiration pneumonia-induced ALI will be useful for testing long-term effects of new therapeutic strategies in ALI.

A haplotype of cyclooxygenase-2 gene is associated with idiopathic pulmonary fibrosis.

BACKGROUND: Cyclooxygenase-2, a key regulatory enzyme in the synthesis of the antifibrotic agent prostaglandin E2, is downregulated in lung tissue from patients with idiopathic pulmonary fibrosis. OBJECTIVE: To investigate the association between COX2.3050 (G --> C), COX2.8473 (C --> T) and COX2.926 (G --> C) single nucleotide polymorphisms (SNP) and the susceptibility to idiopathic pulmonary fibrosis and the progression of the disease. DESIGN: Genetic polymorphisms were analyzed in 121 out of 225 available control subjects and in all of 174 patients with idiopathic pulmonary fibrosis by real time polymerase chain reaction. Logistic regression analysis of covariance and chi-squares test were used for statistical analysis. RESULTS: While analysis of disease development did not find any significant association with single SNP genotype, a haplotype analysis revealed a strong association between the disease development and one haplotype [GC] at loci COX2.3050 and COX2.8473, and suggested a recessive genetic effect of this haplotype. Further analysis concluded that subjects having two copies of [GC] haplotype, or equivalently (GG/CC) genotype at the two SNPs, had an increased risk after adjusting for age and sex. Due to the interaction, this elevated risk increased slowly with age, and the estimated odds ratio (OR) decreased with age from OR = 1.4 at age 30 to OR = 1 at age 74 and OR = 0.96 at age SO. The OR was significantly greater than 1 up to age 66, and not significant for age older than 66. Therefore, the recessive effect of [GC] haplotype increased the risk of IPF of subjects younger than 66 years, but its effect diminished for seniors older than 66. One hundred and forty-nine patients with idiopathic pulmonary fibrosis were followed up for 33.7 +/- 2.1 months. Further analysis of disease progressions, defined by the changes in pulmonary function tests, did not reveal any association with either SNP genotypes or haplotypes. CONCLUSIONS: The carriage of double homozygote (GG/CC) at the SNP loci of COX2.3050 and COX2.8473 polymorphisms may increase the susceptibility to idiopathic pulmonary fibrosis, by approximately 1.4 folds at age 30 and by a smaller fold greater than 1 up to age 66 years, but not the progression of the disease. These findings may help to improve our understanding of idiopathic pulmonary fibrosis pathogenesis and may lead to the development of new therapeutic strategies.

Single and repeated bleomycin intratracheal instillations lead to different biomechanical changes in lung tissue.

Single dose of bleomycin induces acute alveolitis followed by a reparative process whilst a repeated dose results in progressive fibrosis, which may lead to distinct lung tissue biomechanical changes. To test this hypothesis, rats were intratracheally instilled with saline (N=11) or bleomycin (2.5U/kg) once (SD, N=8) or three times (RD, N=9) one week apart, and sacrificed 28 days after challenge. Forced oscillatory mechanics as well as the amount of collagen fibre and myeloperoxidase content (MPO(L)) were studied in lung tissue strips. Both elastic modulus (H), tissue damping (G), and MPO(L) increased only in RD-challenged rats. Although fibroblast focus was found in RD, collagen fibre content increased in both challenged groups. However, the amount of collagen fibre in SD group was not enough to induce lung tissue mechanical changes. In conclusion, repeated doses of bleomycin induce inflammatory and fibrogenic behaviour with biomechanical changes mimicking interstitial lung disease in humans.

Angiotensinogen gene G-6A polymorphism influences idiopathic pulmonary fibrosis disease progression.

Angiotensin II is a growth factor that plays a key role in the physiopathology of idiopathic pulmonary fibrosis (IPF). A nucleotide substitution of an adenine instead of a guanine (G-6A) in the proximal promoter region of angiotensinogen (AGT), the precursor of angiotensin II, has been associated with an increased gene transcription rate. In order to investigate whether the G-6A polymorphism of the AGT gene is associated with IPF development, severity and progression, the present study utilised a case-control study design and genotyped G-6A in 219 patients with IPF and 224 control subjects. The distribution of G-6A genotypes and alleles did not significantly differ between cases and controls. The G-6A polymorphism of the AGT gene was not associated with disease severity at diagnosis. The presence of the A allele was strongly associated with increased alveolar arterial oxygen tension difference during follow-up, after controlling for the confounding factors. Higher alveolar arterial oxygen tension changes over time were observed in patients with the AA genotype (0.37+/-0.7 mmHg (0.049+/-0.093 kPa) per month) compared to GA genotype (0.12+/-1 mmHg (0.016+/-0.133 kPa) per month) and GG genotype (0.2+/-0.6 mmHg (0.027+/-0.080 kPa) per month). G-6A polymorphism of the angiotensinogen gene is associated with idiopathic pulmonary fibrosis progression but not with disease predisposition. This polymorphism could have a predictive significance in idiopathic pulmonary fibrosis patients.

Inflammatory related changes in lung tissue mechanics after bleomycin-induced lung injury.

The impact of lung remodelling in respiratory mechanics has been widely studied in bleomycin-induced lung injury. However, little is known regarding the relationship between the amount of lung inflammation and pulmonary tissue mechanics. For this purpose, rats were intratracheally instilled with bleomycin (n=29) or saline (n=8) and sacrificed at 3, 7, or 15 days. Forced oscillatory mechanics as well as indices of remodelling (elastic fibre content and hydroxyproline) and inflammation (myeloperoxidase content, total cell count, alveolar wall thickness, and lung water content) were studied in lung tissue strips. Tissue resistance increased significantly at day 15, while hysteresivity was significantly higher in bleomycin group compared to control at all time points. Elastic fibres, hydroxyproline and myeloperoxidase contents augmented after bleomycin at days 7 and 15. Tissue resistance and hysteresivity were significantly correlated with myeloperoxidase, elastic fibre and lung water content. In conclusion, inflammatory structural changes and elastogenesis are the main determinants for hysteretic changes in this 2-week bleomycin-induced lung injury model.

In vivo antioxidant treatment protects against bleomycin-induced lung damage in rats.

1. This study examines the activity of the antioxidant N-acetylcysteine on bleomycin-induced pulmonary fibrosis in rats with emphasis on the early inflammatory phase. 2. Rats receiving N-acetylcysteine (300 mg kg(-1) day(-1), intraperitoneal) had less augmented lung wet weight, and lower levels of proteins, lactate dehydrogenase, neutrophil and macrophage counts in bronchoalveolar lavage fluid and lung myeloperoxidase activity with a betterment of histological score at 3 days postbleomycin. 3. A diminished lung GSH/GSSG ratio and augmented lipid hydroperoxides were observed 3 days postbleomycin. These changes were attenuated by N-acetylcysteine. Alveolar macrophages from bleomycin-exposed rats released augmented amounts of superoxide anion and nitric oxide. N-Acetylcysteine did not modify superoxide anion generation but reduced the increased production of nitric oxide. 4. N-Acetylcysteine suppressed the bleomycin-induced increased activation of lung NF-kappaB (shift assay and immunohistochemistry), and decreased the augmented levels of the early inflammatory cytokines, tumour necrosis factor-alpha, interleukin-beta, interleukin-6 and macrophage inflammatory protein-2 observed in bronchoalveolar lavage fluid at 1 and 3 days postbleomycin exposure. 5. At 15 days postbleomycin, N-acetylcysteine decreased collagen deposition in bleomycin-exposed rats (hydroxyproline content: 6351+/-669 and 4626+/-288 micro g per lung in drug vehicle- and N-acetylcysteine-treated rats, respectively; P<0.05). Semiquantitative histological assessment at this stage showed less collagen deposition in N-acetylcysteine-treated rats compared to those receiving bleomycin alone. 6. These results indicate that N-acetylcysteine reduces the primary inflammatory events, thus preventing cellular damage and the subsequent development of pulmonary fibrosis in the bleomycin rat model.

Induction of c-fos messenger RNA by 3-(N-phenylamino)-1,2-propanediol esters, compounds related to Toxic Oil Syndrome.

The Toxic Oil Syndrome (TOS) was a toxic epidemic disease, related to the consumption of rapeseed oil denatured with aniline that affected more than 20,000 people in Spain and resulted in more than 330 deaths after its sudden appearance in 1981. It has been reported that the fatty acid esters of 3-(N-phenylamino)-1,2-propanediol (PAP) have shown a strong association with TOS. These PAP-esters could be absorbed and metabolized in a similar way than phospholipids. This is of interest because some products of phospholipid metabolism are important mediators in downstream pathways involved in the regulation of different nuclear factors. In particular, phospholipase D activity is involved in the activation of c-fos. Thus, we have investigated the effect of different PAP-esters in the induction of c-fos in lung fibroblasts. Results indicate that PAP-esters rapidly induced the expression of c-fos in a dose-dependent manner. In addition, both butanol and propranolol prevent this induction pointing to the involvement of phospholipase D in this activation. These results suggest that deregulation of some nuclear factors such as AP-1 could be involved in the pathogenesis of TOS.

Losartan attenuates bleomycin induced lung fibrosis by increasing prostaglandin E2 synthesis.

BACKGROUND: 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 E(2) (PGE(2)) synthesis and cyclooxygenase-2 (COX-2) expression. METHODS: 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. RESULTS: 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. PGE(2) levels were lower in fibrotic lungs than in normal lungs. Losartan significantly increased PGE(2) 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. CONCLUSIONS: The antifibrotic effect of losartan appears to be mediated by its ability to stimulate the production of PGE(2). Losartan, which is already widely used clinically, could be assessed as a new treatment in lung fibrosis.

Oral N-acetylcysteine reduces bleomycin-induced lung damage and mucin Muc5ac expression in rats.

Oxidative stress is involved in the pathogenesis of pulmonary fibrosis, therefore antioxidants may be of therapeutic value. Clinical work indicates that N-acetylcysteine (NAC) may be beneficial in this disease. The activity of this antioxidant was examined on bleomycin-induced lung damage, mucus secretory cells hyperplasia and mucin Muc5ac gene expression in rats. NAC (3 mmol x kg(-1) x day(-1)) or saline was given orally to Sprague-Dawley rats for 1 week prior to a single intratracheal instillation of bleomycin (2.5 U x kg(-1)) and for 14 days postinstillation. NAC decreased collagen deposition in bleomycin-exposed rats (hydroxyproline content was 4,257+/-323 and 3,200+/-192 microg x lung(-1) in vehicle- and NAC-treated rats, respectively) and lessened the fibrotic area assessed by morphometric analysis. The bleomycin-induced increases in lung tumour necrosis factor-alpha and myeloperoxidase activity were reduced by NAC treatment. The numbers of mucus secretory cells in airway epithelium, and the Muc5ac messenger ribonucleic acid and protein expression, were markedly augmented in rats exposed to bleomycin. These changes were significantly reduced in NAC-treated rats. These results indicate that bleomycin increases the number of airway secretory cells and their mucin production, and that oral N-acetylcysteine improved pulmonary lesions and reduced the mucus hypersecretion in the bleomycin rat model.

P-selectin upregulation in bleomycin induced lung injury in rats: effect of N-acetyl-L-cysteine.

BACKGROUND: A number of adhesion molecules are involved in the process of neutrophil infiltration into the lung. P-selectin is one of these neutrophil-endothelial cell adhesion molecules. A study was undertaken to examine the involvement of P-selectin in the development of bleomycin induced inflammation and the ability of N-acetyl-L-cysteine to reduce the potential expression of this selectin in rats. METHODS: N-acetyl-L-cysteine (3 mmol/kg po) was administered daily for seven days prior to bleomycin administration (2.5 U/kg). The kinetics of P-selectin expression and the effect of N-acetyl-L-cysteine after bleomycin treatment were measured using radiolabelled antibodies. P-selectin localisation was evaluated by immunohistochemistry and neutrophil infiltration was assessed by myeloperoxidase activity. RESULTS: Bleomycin administration resulted in an upregulation of P-selectin at 1 hour, returning to baseline at 3 hours. Myeloperoxidase activity showed a significant increase at 6 hours after bleomycin administration that lasted for 3 days. N-acetyl-L-cysteine treatment completely prevented these increases. CONCLUSION: Upregulation of P-selectin in the lung is associated with neutrophil recruitment in response to bleomycin. The beneficial effect of N-acetyl-L-cysteine on bleomycin induced lung injury may be explained in part by the prevention of neutrophil recruitment in the inflammatory stage of the disease.