Angiotensin II antagonism fails to ameliorate bleomycin-induced pulmonary fibrosis in mice

Impact of angiotensin II type 1 and G-protein-coupled Mas receptor expression on the pulmonary performance of patients with idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a severe interstitial disease with a mean survival of about 2.5-5 years after diagnosis. Its pathophysiology is still a major challenge for science. It is known that angiotensin II (Ang-II) binds AT1 receptor (AT1R) and its overactivation induces fibrosis, inflammation and oxidative stress. In contrast, activation of the Mas receptor (Mas-R) by angiotensin 1-7 opposes the harmful effects induced by Ang-II. Thus, our innovative objective was to analyze, in patients' lung with IPF, the balance between AT1R and Mas-R expression and their possible association with pulmonary spirometric parameters: forced expiratory volume in the first second (FEV1%) and forced vital capacity (FVC%). One cubic centimeter of lung tissue was obtained from IPF patients (n = 6) and from patients without IPF (n = 6) who underwent bronchial carcinoma resection. Receptor expression was quantified using western blot. AT1R expression was significantly higher (34 %) in patients with IPF (P = 0.006), whereas Mas-R was significantly less expressed (54 %) in these patients' lungs (P = 0.046). There was also a positive correlation between Mas-R expression and FEV1% (r = 0.62, P = 0.03) and FVC% (r = 0.58, P = 0.05). Conversely, AT1R expression was negatively correlated with FEV1% (r = 0.80, P = 0.002) and FVC% (r = 0.74, P = 0.006). In conclusion, our results demonstrated an increased expression of AT1R and reduced expression of Mas-R in the lung of patients with IPF. The dominance of AT1R expression is associated with reduced lung function, highlighting the role of the renin-angiotensin system peptides in the pathophysiology of IPF.

The dietary antioxidant quercetin reduces hallmarks of bleomycin-induced lung fibrogenesis in mice

BACKGROUND

Idiopathic pulmonary fibrosis (IPF) is a chronic, lethal disease of which the etiology is still not fully understood. Current treatment comprises two FDA-approved drugs that can slow down yet not stop or reverse the disease. As IPF pathology is associated with an altered redox balance, adding a redox modulating component to current therapy might exert beneficial effects. Quercetin is a dietary antioxidant with strong redox modulating capacities that is suggested to exert part of its antioxidative effects via activation of the redox-sensitive transcription factor Nrf2 that regulates endogenous antioxidant levels. Therefore, the aim of the present study was to investigate if the dietary antioxidant quercetin can exert anti-fibrotic effects in a mouse model of bleomycin-induced pulmonary fibrogenesis through Nrf2-dependent restoration of redox imbalance.

METHODS

Homozygous Nrf2 deficient mice and their wildtype littermates were fed a control diet without or with 800 mg quercetin per kg diet from 7 days prior to a single 1 μg/2 μl per g BW bleomycin challenge until they were sacrificed 14 days afterwards. Lung tissue and plasma were collected to determine markers of fibrosis (expression of extracellular matrix genes and histopathology), inflammation (pulmonary gene expression and plasma levels of tumor necrosis factor-α (TNFα) and keratinocyte chemoattrachtant (KC)), and redox balance (pulmonary gene expression of antioxidants and malondialdehyde-dG (MDA)- DNA adducts).

RESULTS

Mice fed the enriched diet for 7 days prior to the bleomycin challenge had significantly enhanced plasma and pulmonary quercetin levels (11.08 ± 0.73 μM versus 7.05 ± 0.2 μM) combined with increased expression of Nrf2 and Nrf2-responsive genes compared to mice fed the control diet in lung tissue. Upon bleomycin treatment, quercetin-fed mice displayed reduced expression of collagen (COL1A2) and fibronectin (FN1) and a tendency of reduced inflammatory lesions (2.8 ± 0.7 versus 1.9 ± 0.8). These beneficial effects were accompanied by reduced pulmonary gene expression of TNFα and KC, but not their plasma levels, and enhanced Nrf2-induced pulmonary antioxidant defences. In Nrf2 deficient mice, no effect of the dietary antioxidant on either histology or inflammatory lesions was observed.

CONCLUSION

Quercetin exerts anti-fibrogenic and anti-inflammatory effects on bleomycin-induced pulmonary damage in mice possibly through modulation of the redox balance by inducing Nrf2. However, quercetin could not rescue the bleomycin-induced pulmonary damage indicating that quercetin alone cannot ameliorate the progression of IPF.

Balance and circumstance: The renin angiotensin system in wound healing and fibrosis

The tissue renin angiotensin system (tRAS) is a locally-acting master-modulator of tissue homeostasis and regeneration. Through these abilities, it is emerging as an attractive target for therapies aiming to restore tissue homeostasis in conditions associated with disturbed wound healing. The tRAS can be divided into two axes - one being pro-inflammatory and pro-fibrotic and one being anti-inflammatory and anti-fibrotic. However, the division of the axes is fuzzy and imperfect as the axes are codependent and the outcome of tRAS activation is determined by the context. Although the tRAS is a local system it shares its key enzymes, ligands and receptors with the systemic RAS and is consequently also targeted by repurposing of drugs developed against the systemic RAS to manage hypertension. With a focus on the skin we will here discuss the tRAS, its involvement in physiological and pathological wound healing, and the therapeutic aptitude of its targeting to treat chronic wounds and fibrosis.

Angiotensin-converting enzyme defines matrikine-regulated inflammation and fibrosis

The neutrophil chemoattractant proline-glycine-proline (PGP) is generated from collagen by matrix metalloproteinase-8/9 (MMP-8/9) and prolyl endopeptidase (PE), and it is concomitantly degraded by extracellular leukotriene A₄ hydrolase (LTA₄H) to limit neutrophilia. Components of cigarette smoke can acetylate PGP, yielding a species (AcPGP) that is resistant to LTA₄H-mediated degradation and can, thus, support a sustained neutrophilia. In this study, we sought to elucidate if an antiinflammatory system existed to degrade AcPGP that is analogous to the PGP-LTA₄H axis. We demonstrate that AcPGP is degraded through a previously unidentified action of the enzyme angiotensin-converting enzyme (ACE). Pulmonary ACE is elevated during episodes of acute inflammation, as a consequence of enhanced vascular permeability, to ensure the efficient degradation of AcPGP. Conversely, we suggest that this pathway is aberrant in chronic obstructive pulmonary disease (COPD) enabling the accumulation of AcPGP. Consequently, we identify a potentially novel protective role for AcPGP in limiting pulmonary fibrosis and suggest the pathogenic function attributed to ACE in idiopathic pulmonary fibrosis (IPF) to be a consequence of overzealous AcPGP degradation. Thus, AcPGP seemingly has very divergent roles: it is pathogenic in its capacity to drive neutrophilic inflammation and matrix degradation in the context of COPD, but it is protective in its capacity to limit fibrosis in IPF.

ACE degrades the collagen-derived matrikine, acetylate proline–glycine–proline, to limit pulmonary inflammation and promote repair.

Cardiovascular and antacid treatment and mortality in oxygen-dependent pulmonary fibrosis: A population-based longitudinal study

BACKGROUND AND OBJECTIVE

Severe idiopathic pulmonary fibrosis is associated with an increased risk of cardiovascular disease and gastro-oesophageal reflux, which may influence prognosis. We evaluated associations between cardiovascular and antacid medications, and mortality, in oxygen-dependent pulmonary fibrosis (PF) of unknown cause.

METHODS

Prospective population-based study of adults starting long-term oxygen therapy (LTOT) for PF in Sweden 2005-2009. PF of unknown cause was defined by excluding patients with known or probable secondary PF. Time-dependent associations between medications and all-cause mortality were analysed using extended Cox regression, adjusting for potential confounders including age, sex, vital capacity, blood gases, body mass index, performance status, comorbidity and concurrent medications.

RESULTS

Of 462 included patients, 329 (71%) died under observation. No patient was lost to follow-up. Angiotensin-converting enzyme inhibitors or angiotensin receptor blockers (ACEI/ARB) were associated with reduced adjusted mortality (HR 0.63; 0.47-0.85) and antiplatelet drugs with increased mortality (HR 1.49; 1.11-2.00), largely driven by higher mortality in women. There were no associations with mortality for antacid treatments, β-blockers, diuretics or statins.

CONCLUSION

In oxygen-dependent PF, treatment with ACEI/ARB was associated with improved survival, antiplatelet drugs with decreased survival, whereas there was no association between antacid, β-blocker, diuretic or statin treatment and survival.

Angiotensin II type 1 and 2 receptors and lymphatic vessels modulate lung remodeling and fibrosis in systemic sclerosis and idiopathic pulmonary fibrosis

OBJECTIVE

To validate the importance of the angiotensin II receptor isotypes and the lymphatic vessels in systemic sclerosis and idiopathic pulmonary fibrosis.

METHODS

We examined angiotensin II type 1 and 2 receptors and lymphatic vessels in the pulmonary tissues obtained from open lung biopsies of 30 patients with systemic sclerosis and 28 patients with idiopathic pulmonary fibrosis. Their histologic patterns included cellular and fibrotic non-specific interstitial pneumonia for systemic sclerosis and usual interstitial pneumonia for idiopathic pulmonary fibrosis. We used immunohistochemistry and histomorphometry to evaluate the number of cells in the alveolar septae and the vessels stained by these markers. Survival curves were also used.

RESULTS

We found a significantly increased percentage of septal and vessel cells immunostained for the angiotensin type 1 and 2 receptors in the systemic sclerosis and idiopathic pulmonary fibrosis patients compared with the controls. A similar percentage of angiotensin 2 receptor positive vessel cells was observed in fibrotic non-specific interstitial pneumonia and usual interstitial pneumonia. A significantly increased percentage of lymphatic vessels was present in the usual interstitial pneumonia group compared with the non-specific interstitial pneumonia and control groups. A Cox regression analysis showed a high risk of death for the patients with usual interstitial pneumonia and a high percentage of vessel cells immunostained for the angiotensin 2 receptor in the lymphatic vessels.

CONCLUSION

We concluded that angiotensin II receptor expression in the lung parenchyma can potentially control organ remodeling and fibrosis, which suggests that strategies aimed at preventing high angiotensin 2 receptor expression may be used as potential therapeutic target in patients with pulmonary systemic sclerosis and idiopathic pulmonary fibrosis.

Endothelin-converting enzyme-1 gene ablation attenuates pulmonary fibrosis via CGRP-cAMP/EPAC1 pathway

Endothelin-1 (ET-1) has been shown to be involved in human pulmonary fibrosis. However, recent clinical trials targeting the ET-1 pathway with ET-1 receptor antagonists failed to achieve beneficial outcomes. Another strategy opposing the actions of ET-1 involves the inhibition of endothelin-converting enzyme-1 (ECE-1). We hypothesize that ECE-1 inhibition exerts beneficial effects on pulmonary fibrosis. Pulmonary fibrosis was induced by instilling bleomycin intratracheally into ECE-1 heterozygous knockout mice (ECE-1(+/-)) and their wild-type control mice (ECE-1(+/+)). Lung inflammation and fibrosis were assessed on Days 7, 14, and 28 after bleomycin instillation. The activity of ECE-1 and the concentrations of its related peptides, ET-1, bradykinin, atrial natriuretic peptide (ANP), and calcitonin gene-related peptide (CGRP), were determined. ECE-1(+/-) mice demonstrated less lung inflammation and limited fibrosis compared with control mice. ECE-1 activity was half-reduced in ECE-1(+/-) mice, and this activity also altered ET-1 and CGRP concentrations, but not concentrations of bradykinin and ANP. ET-1 concentrations were found to be lower in ECE-1(+/-) mice after the development of fibrosis, in contrast to the unaltered concentrations during inflammation. Reduced ECE-1 activity resulted in higher CGRP concentrations, which altered the pathological functionality of the lung, indicating the activation of the CGRP pathway involving cyclic adenosine monophosphate (cAMP)/exchange protein directly activated by cAMP and cAMP/protein kinase A in ECE-1(+/-) mice. Bleomycin instillation on Day 14 induced the accumulation of M2 macrophages expressing CGRP receptors in ECE-1(+/-) mice. Our results emphasize that the in vivo ECE-1-mediated degradation of CGRP promotes the transition from lung inflammation to fibrosis. Further, our study identified M2 macrophages as the target cells of CGRP action during this transition.

Protective effect of Launaea procumbens (L.) on lungs against CCl4-induced pulmonary damages in rat

BACKGROUND

Launaea procumbens (L.) is traditionally used in the treatment of various human ailments including pulmonary damages. The present study was arranged to evaluate the role of Launaea procumbens methanol extract (LME) against carbon tetrachloride (CCl4) induced oxidative pulmonary damages in rat.

METHODS

36 Sprague-Dawley male rats (170-180 g) were randomly divided into 06 groups. After a week of acclamization, group I was remained untreated while group II was given olive oil intraperitoneally (i.p.) and dimethyl sulfoxide (DMSO) orally, groups III, IV, V and VI were administered CCl4, 3 ml/kg body weight (30% in olive oil i.p.). Groups IV, V were treated with 100 mg/kg, 200 mg/kg of LME whereas group VI was administered with 50 mg/kg body weight of rutin (RT) after 48 h of CCl4 treatment for four weeks. Antioxidant profile in lungs were evaluated by estimating the activities of antioxidant enzymes; catalase (CAT), peroxidase (POD), superoxide dismutase (SOD), glutathione-S-transferase (GST), glutathione reductase (GSR), glutathione peroxidase (GSH-Px), quinone reductase (QR) and reduced glutathione (GSH). CCl4-induced lipid peroxidation was determined by measuring the level of thiobarbituric acid reactive substances (TBARS) with conjugation of deoxyribonucleic acid (DNA) damages, argyrophilic nucleolar organizer regions (AgNORs) counts and histopathology.

RESULTS

Administration of CCl4 for 6 weeks significantly (p < 0.01) reduced the activities of antioxidant enzymes and GSH concentration while increased TBARS contents and DNA damages in lung samples. Co-treatment of LME and rutin restored the activities of antioxidant enzymes and GSH contents. Changes in TBARS concentration and DNA fragmentation were significantly (p < 0.01) decreased with the treatment of LME and rutin in lung. Changes induced with CCl4 in histopathology of lungs were significantly reduced with co-treatment of LME and rutin.

CONCLUSION

Results of present study revealed that LME could protect the lung tissues against CCl4-induced oxidative stress possibly by improving the antioxidant defence system.

Quantitative measurement of bleomycin-induced lung fibrosis in rabbits using sequential in vivo regional analysis and high-resolution computed tomography: correlation with pathologic findings

RATIONALE AND OBJECTIVES

To examine the feasibility of quantitative high-resolution computed tomography (HRCT) findings to monitor the stage of bleomycin-induced pulmonary fibrosis in rabbits by correlating HRCT and pathologic scores and analyzing sequential changes on HRCT images using regional volume histograms.

MATERIALS AND METHODS

Lung fibrosis was induced by injecting bleomycin intratracheally into 23 Japanese white rabbits. Rabbits were randomly separated into seven groups depending on follow-up period (12-hour, 24-hour, 3-day, 7-day, 14-day, 21-day, and 28-day). Four-row HRCT examinations were performed at any of the seven time points in each follow-up period and just after bleomycin administration in addition to pre-bleomycin administration as the baseline scan. Scores of consolidation, homogenous ground-glass opacity (GGO), inhomogeneous GGO, reticulolinear shadow, and honey-comb formation were recorded as ratio of affected area to total cross-section in four transaxial planes. Inflammatory and fibrous changes were scored histopathologically. Correlations between HRCT and pathologic findings were assessed. Sequential changes on HRCT images in areas with pathologically confirmed fibrosis were assessed on volume histograms of cubic regions of interest (ROI) using quantitative parameters.

RESULTS

Consolidation and inhomogeneous GGO exhibited fair correlations with inflammation scores (r = 0.273, P = .009, and r = 0.393, P < .001); reticulolinear shadow and inhomogeneous GGO had a fair and good correlation, respectively, with fibrous scores (r = 0.327, P = .001, and r = 0.579, P < .001). Inhomogeneous GGO was hardly detected on regional images at 21 and 28 days after bleomycin administration. As to mean computed tomography attenuation, skewness, and kurtosis, inhomogeneous GGO differed from reticulolinear shadow and consolidation.

CONCLUSION

Using appropriate ROI settings, quantitative assessment of inhomogeneous GGO with regional volume histograms enables us to monitor the progression of lung fibrosis by sequential observations.

Angiotensin-converting enzyme N-terminal inactivation alleviates bleomycin-induced lung injury

Bleomycin has potent anti-oncogenic properties for several neoplasms, but drug administration is limited by bleomycin-induced lung fibrosis. Inhibition of the renin-angiotensin system has been suggested to decrease bleomycin toxicity, but the efficacy of such strategies remains uncertain and somewhat contradictory. Our hypothesis is that, besides angiotensin II, other substrates of angiotensin-converting enzyme (ACE), such as the tetrapeptide N-acetyl-seryl-aspartyl-lysyl-proline (AcSDKP), play a significant role in controlling fibrosis. We studied bleomycin-induced lung injury in normotensive mice, termed N-KO and C-KO, which have point mutations inactivating either the N- or C-terminal catalytic sites of ACE, respectively. N-KO, but not C-KO mice, have a marked resistance to bleomycin lung injury as assessed by lung histology and hydroxyproline content. To determine the importance of the ACE N-terminal peptide substrate AcSDKP in the resistance to bleomycin injury, N-KO mice were treated with S-17092, a prolyl-oligopeptidase inhibitor that inhibits the formation of AcSDKP. In response to bleomycin injection, S-17092-treated N-KO mice developed lung fibrosis similar to wild-type mice. In contrast, the administration of AcSDKP to wild-type mice reduced lung fibrosis due to bleomycin administration. This study shows that the inactivation of the N-terminal catalytic site of ACE significantly reduced bleomycin-induced lung fibrosis and implicates AcSDKP in the mechanism of protection. These data suggest a possible means to increase tolerance to bleomycin and to treat fibrosing lung diseases.

Angiotensin II signaling through the AT1a and AT1b receptors does not have a role in the development of cerulein-induced chronic pancreatitis in the mouse

The intraorgan renin-angiotensin system (RAS) plays an important role in the pathophysiology of a variety of diseases and has been implicated in fibrogenesis. The role of RAS in the development of chronic pancreatitis is not well established. The blockade of RAS in rat models with angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor 1 (AT1) blockers (ARBs) mostly have reduced pancreatic inflammation and fibrosis with a few exceptions. At the same time, the use of ACEi and ARBs in humans is associated with a modest risk of acute pancreatitis. The aim of this study was to elucidate the effect of the AT1 signaling pathway in the development of pancreatitis using AT1a- and AT1b-deficient mice as well as the ARB losartan. Chronic pancreatitis was induced by repetitive cerulein administration in C57BL/6J wild-type (WT) and AT1a- and AT1b-deficient mice (AT1a-/- and AT1b-/-), and pancreatic injury was assessed at day 10. Pancreatic weight of cerulein treated groups was significantly reduced. There was severe parenchymal atrophy and fibrosis assessed by histological examination. Fibrosis was accompanied by activation of pancreatic stellate cells (PSC) evaluated by Western blot analysis for alpha-smooth muscle actin. No differences were seen between cerulein-treated WT, AT1a-/- , AT1b-/- mice, or losartan treated-WT mice with regards to morphological or molecular alterations induced by cerulein. Our results demonstrate that AT1a and AT1b receptor pathways do not seem to be essential for the development of pancreatitis in the mouse model of pancreatitis induced by repetitive cerulein injury.

Targeting the angiotensin pathway in idiopathic pulmonary fibrosis

BACKGROUND

The angiotensin pathway is involved in the pathogenesis of many fibrotic diseases and in idiopathic pulmonary fibrosis an innate overexpression of angiotensin II, a potent TGF-beta1 inductor has been demonstrated. Angiotensin II therapeutic blockade could be therefore a promising antifibrotic approach.

OBJECTIVE

Discussion of the results of a preclinical study assessing the antifibrotic efficacy of olmesartan and PD123319 in an experimental lung fibrosis.

METHODS/RESULTS

This study demonstrated that in belomycin-induced pulmonary fibrosis both compounds had significant anti-inflammatory and antifibrotic activities.

CONCLUSION

Targeting the angiotensin pathway with specific blocking agents could represent a promising antifibrotic treatment.

Angiotensin II type 2 receptor antagonist reduces bleomycin-induced pulmonary fibrosis in mice

Background

The role of angiotensin II type 2 receptor (AT2) in pulmonary fibrosis is unknown. To evaluate the influence of angiotensin II type 1 receptor (AT1) and AT2 antagonists in a mouse model of bleomycin (BLM)-induced pulmonary fibrosis.

Methods

We examined effects of the AT1 antagonist (AT1A) olmesartan medoxomil (olmesartan) and the AT2 antagonist (AT2A) PD-123319 on BLM-induced pulmonary fibrosis, which was evaluated by Ashcroft's pathological scoring and hydroxyproline content of lungs. We also analyzed the cellular composition and cytokine levels in bronchoalveolar lavage fluid (BALF).

Results

With olmesartan, the lung fibrosis score and hydroxyproline level were significantly reduced, and lymphocyte and neutrophil counts and tumor necrosis factor (TNF)-α levels in BALF were reduced on day 7. On day 14, macrophage and lymphocyte counts in BALF were reduced, accompanied by a reduction in the level of transforming growth factor (TGF)-β₁. With PD-123319, the lung fibrosis score and hydroxyproline level were reduced. On day 7, macrophage, lymphocyte, and neutrophil counts in BALF were reduced, accompanied by reductions in TNF-α and monocyte chemoattractant protein (MCP)-1 levels. On day 14, macrophage, lymphocyte, and neutrophil counts in BALF were also reduced, accompanied by a reduction in the level of macrophage inflammatory protein (MIP)-2 level but not TGF-β₁.

Conclusion

Both AT1 and AT2 are involved in promoting interstitial pneumonia and pulmonary fibrosis via different mechanisms of action.

The angiotensin II receptor 2 is expressed and mediates angiotensin II signaling in lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a severe interstitial lung disease unresponsive to currently available therapies. In IPF, initial alveolar epithelial cell damage leads to activation of fibroblast-(myo)fibroblasts, which deposit an increased amount of a collagen-rich extracellular matrix. Angiotensin II (ANGII) signaling, mediated via angiotensin II receptor type 1 (AGTR1) or type 2 (AGTR2), controls tissue remodeling in fibrosis, but the relevance of AGTR2 remains elusive. In the present study, we demonstrated increased expression of AGTR1 und AGTR2 in human and rodent lung tissues from patients with IPF and mice subjected to bleomycin-induced fibrosis, respectively. Both AGTR1 und AGTR2 localized to interstitial fibroblasts. Quantitative analysis of cell surface expression in primary mouse fibroblasts revealed a significant increase of AGTR2 surface expression in fibrotic fibroblasts, whereas AGTR1 surface expression levels remained similar. ANGII treatment of normal fibroblasts led to enhanced migration and proliferation, which was abrogated after pretreatment with losartan (LOS), an AGTR1 inhibitor. In contrast, in fibrotic fibroblasts, migration and proliferation was modified only by AGTR2, but not AGTR1 inhibition (using PD123319). ANGII-induced effects were mediated via phosphorylation of the mitogen-activated protein kinases p38 and p42/44, which was blocked via LOS and PD123319, respectively. Similar effects of AGTR1 and AGTR2 inhibition were observed using conditioned media of alveolar epithelial cells, a prominent source of ANGII in the lung in vivo. In summary, we conclude that ANGII signaling occurs primarily via AGTR1 in normal fibroblasts, while AGTR2-mediated effects are dominant on activated (myo)-fibroblasts, a receptor switch that may perturb epithelial-mesenchymal interaction, thereby further perpetuating fibrogenesis.

Effect of losartan on early liver fibrosis development in a rat model of nonalcoholic steatohepatitis

BACKGROUND AND AIM

Nonalcoholic steatohepatitis (NASH) is a metabolic disorder of the liver that may evolve into fibrosis or cirrhosis. Recent studies have shown reduction of experimental liver fibrosis with the use of angiotensin-converting-enzyme inhibitors or angiotensin-receptor antagonists. The aim of this study was to determine whether losartan can influence the early phase of fibrogenesis in an animal model of NASH.

METHODS

To induce NASH, a choline-deficient diet (CDD) was given to Sprague-Dawley rats for 12 weeks. These animals were then compared with a control group receiving choline-supplemented diet (CSD) and a group fed a CDD plus losartan (10 mg/kg/day). Biochemical (serum levels of alanine aminotransferase and aspartate aminotransferase) and histological evaluation of fatty liver was performed by conventional techniques. Hydroxyproline content in liver tissue was assayed by spectrophotometry. In addition, mRNA levels of procollagen I and transforming growth factor (TGF)-beta were assessed by semiquantitative RT-PCR and stellate cell activation by alpha-actin immunofluorescence stain.

RESULTS

After 12 weeks CDD induced a marked elevation of serum aminotranferases, a severe fatty liver infiltration with mild histological inflammation and fibrosis. These findings correlated with a significant increase in mRNA levels of both procollagen I and TGF-beta and significant increased liver hydroxyproline content. No differences were seen between rats receiving CDD alone and rats receiving CDD plus losartan with regard to the biochemical, morphological or molecular alterations induced by the CDD.

CONCLUSION

Losartan does not seem to influence liver injury and fibrogenic events in the CDD model of NASH.

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.

Losartan Attenuates Bleomycin-Induced Pulmonary Fibrosis in Rats

BACKGROUND

In addition to regulating blood pressure and body fluid homeostasis, the renin-angiotensin system is also involved in lung fibrogenesis.

OBJECTIVE

To study the effect of losartan, an angiotensin II antagonist, on bleomycin-induced pulmonary fibrosis in rats and its possible mechanism.

METHODS

Pulmonary fibrosis was induced in SD rats by intratracheal instillation of bleomycin (5 mg x kg(-1)). Subsequently, the rats received daily losartan (3, 9 and 27 mg x kg(-1)) or prednisone (20 mg x kg(-1)) orally. Six rats in each group were sacrificed 14 and 21 days after intratracheal instillation. Hydroxyproline, superoxide dismutase (SOD), and malondialdehyde (MDA) levels in lung tissues were determined by spectroscopy. The levels of TGF-beta1 in serum were measured by ELISA. Histological changes in the lungs were evaluated by hematoxylin-eosin stain, and scored.

RESULTS

Rat body weight evidently decreased while the indices of lung and hydroxyproline contents in lung tissue were significantly increased 14 and 21 days after intratracheal bleomycin instillation. Inflammatory cell infiltration and fibrotic scores were more prominent in the model group compared to the sham group. Losartan (3, 9 and 27 mg.kg(-1), i.g.) apparently attenuated the degree of pulmonary fibrosis. Further study showed that losartan significantly increased SOD levels while it decreased MDA contents in lung homogenates. Serum TGF-beta1 levels of pulmonary fibrosis rats were also decreased by losartan.

CONCLUSIONS

Losartan had an inhibitory effect on bleomycin-induced pulmonary fibrosis, and its effect may be associated with its anti-free radicals and the reduction in TGF-beta1.