The Possible Protective Effect of Losartan on Bleomycin-Induced Pulmonary Fibrosis in Albino Rats: A Histological And Immunohistochemical Study (original) (raw)
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Lung Fibrosis and Fibrosis in the Lungs: Is It All about Myofibroblasts?
Biomedicines
In the lungs, fibrosis is a growing clinical problem that results in shortness of breath and can end up in respiratory failure. Even though the main fibrotic disease affecting the lung is idiopathic pulmonary fibrosis (IPF), which affects the interstitial space, there are many fibrotic events that have high and dangerous consequences for the lungs. Asthma, chronic obstructive pulmonary disease (COPD), excessive allergies, clearance of infection or COVID-19, all are frequent diseases that show lung fibrosis. In this review, we describe the different kinds of fibrosis and analyse the main types of cells involved—myofibroblasts and other cells, like macrophages—and review the main fibrotic mechanisms. Finally, we analyse present treatments for fibrosis in the lungs and highlight potential targets for anti-fibrotic therapies.
Fibroblast growth factor (FGF) signaling has been implicated in the pathogenesis of pulmonary fibrosis. Mice lacking FGF2 have increased mortality and impaired epithelial recovery after bleomycin exposure, supporting a protective or reparative function following lung injury. To determine whether FGF2 overexpression reduces bleomycin-induced injury, we developed an inducible genetic system to express FGF2 in type II pneumocytes. Double-transgenic (DTG) mice with doxycycline-inducible overexpression of human FGF2 (SPC-rtTA;TRE-hFGF2) or single-transgenic controls were administered intratracheal bleomycin and fed doxycycline chow, starting at either day 0 or day 7. In addition, wild-type mice received intratracheal or intravenous recombinant FGF2, starting at the time of bleomycin treatment. Compared to controls, doxycycline-induced DTG mice had decreased pulmonary fibrosis 21 days after bleomycin, as assessed by gene expression and histology. This beneficial effect was seen when FGF2 overexpression was induced at day 0 or day 7 after bleomycin. FGF2 overexpression did not alter epithelial gene expression, bronchoalveolar lavage cellularity or total protein. In vitro studies using primary mouse and human lung fibroblasts showed that FGF2 strongly inhibited baseline and TGF1-induced expression of alpha smooth muscle actin (SMA), collagen, and connective tissue growth factor. While FGF2 did not suppress phosphorylation of Smad2 or Smad-dependent gene expression, FGF2 inhibited TGF1-induced stress fiber formation and serum response factor-dependent gene expression. FGF2 inhibition of stress fiber formation and SMA requires FGF receptor 1 (FGFR1) and downstream MEK/ERK, but not AKT signaling. In summary, overexpression of FGF2 protects against bleomycin-induced pulmonary fibrosis in vivo and reverses TGF1-induced collagen and SMA expression and stress fiber formation in lung fibroblasts in vitro, without affecting either inflammation or epithelial gene expression. Our results suggest that in the lung, FGF2 is antifibrotic in part through decreased collagen expression and fibroblast to myofibroblast differentiation.
Losartan attenuates bleomycin induced lung fibrosis by increasing prostaglandin E2 synthesis
Thorax, 2006
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.
Basic & Clinical Pharmacology & Toxicology, 2008
Lung fibrosis is a common side effect of the chemotherapeutic agent, bleomycin. Current evidence suggests that reactive oxygen species may play a key role in the development of lung fibrosis. The present study examined the effect of mesna on bleomycin-induced lung fibrosis in rats. Animals were divided into three groups: (1) saline control group; (2) Bleomycin group in which rats were injected with bleomycin (15 mg/kg, i.p.) three times a week for four weeks; (3) Bleomycin and mesna group, in which mesna was given to rats (180 mg/kg/day, i.p.) a week prior to bleomycin and daily during bleomycin injections for 4 weeks until the end of the treatment. Bleomycin treatment resulted in a pronounced fall in the average body weight of animals. Bleomycin-induced pulmonary injury and lung fibrosis was indicated by increased lung hydroxyproline content, and elevated nitric oxide synthase, myeoloperoxidase, platelet activating factor, and tumor necrosis factor-a in lung tissues. On the other hand, bleomycin induced a reduction in reduced glutathione concentration and angiotensin converting enzyme activity in lung tissues. Moreover, bleomycin-induced severe histological changes in lung tissues revealed as lymphocytes and neutrophils infiltration, increased collagen deposition and fibrosis. Co-administration of bleomycin and mesna reduced bleomycin-induced weight loss and attenuated lung injury as evaluated by the significant reduction in hydroxyproline content, nitric oxide synthase activity, and concentrations of myeoloperoxidase, platelet activating factor, and tumor necrosis factor-a in lung tissues. Furthermore, mesna ameliorated bleomycin-induced reduction in reduced glutathione concentration and angiotensin activity in lung tissues. Finally, histological evidence supported the ability of mesna to attenuate bleomycin-induced lung fibrosis and consolidation. Thus, the findings of the present study provide evidence that mesna may serve as a novel target for potential therapeutic treatment of lung fibrosis. D
2007
The emergence of the myofibroblast phenotype (characterized by a-smooth muscle actin expression) in wound healing and in tissues undergoing fibrosis is thought to be responsible for the increased contractility of the affected tissues. In bleomycin-induced pulmonaryfibrosis, the myofibroblast is also responsible for the observed increase in collagen gene expression. To evaluate further these phenotypic changes in lung fibroblasts, contractile and other phenotypic properties of fibroblasts isolated from lungs of rats with bleomycin-inducedfibrosis were compared with those of normal rats using in vitro models. Pulmonaryfibrosis was induced in rats by endotracheal injection on day 0, and 7 and 14 days later the animals were sacrificed and lungfibroblasts isolated. Using immunofluorescence, <10% of fibroblasts from control animals express a-smooth muscle actin when cultured as a monolayer. In contrast, 19% and 21% of ceUs from day 7 and day 14 bleomycin-treated animals, respectively, ...
Epithelial Cell Apoptosis by Fas Ligand–Positive Myofibroblasts in Lung Fibrosis
American Journal of Respiratory Cell and Molecular Biology, 2007
The Fas/Fas ligand (FasL) apoptotic pathway has been shown to be involved in bleomycin-induced lung fibrosis. We examined the hypothesis that myofibroblasts from fibrotic lungs possess a cytotoxic phenotype that causes apoptosis of epithelial cells via the Fas/FasL pathway. We show in vivo epithelial cell apoptosis and associated upregulation of Fas and apoptotic Fas pathway genes in epithelial cells of lungs with bleomycin-induced fibrosis. In addition, we show that FasL surface molecules are overexpressed on ␣-SMA-positive cells in mice with bleomycin-induced fibrosis, and in humans with idiopathic pulmonary fibrosis. This enables the molecules to kill Fas-positive epithelial cells. In contrast, FasL-deficient myofibroblasts lose this myofibroblast cytotoxic phenotype, both in vivo and in vitro. In vivo, there was no bleomycin-induced epithelial cell apoptosis, as assessed by specific M30 staining in chimeric FasLdeficient mice that lacked FasL-positive myofibroblasts. In vitro, FasLpositive, but not FasL-negative myofibroblasts, induce mouse lung epithelial cell apoptosis. Thus myofibroblast cytotoxicity may underlie the absence of re-epithelialization, resulting in persistent lung fibrosis.
An Experimental Model to Induce Homogeneous and Progressive Pulmonary Fibrosis in Rats
Indian Journal of Pharmaceutical Education and Research, 2021
Background: This study aims to develop a new experimental model of pulmonary fibrosis (PF) as an alternative to conventional bleomycin model to overcome its limitations and effectively screened the therapeutic agents. Similarity of new experimental model to human lung fibrosis particularly as uniform and continuous progression has encouraged us to evaluate the usefulness of this system by assessment of anti-fibrotic drug pirfenidone parallel with bleomycin induced PF. Materials and Methods: In new model, ovalbumin (OVA) related asthma induced rats were set to inhaled nebulized formaldehyde solution (0.5% v/v, 30 min) subsequent with cigarettes smoke exposure twice daily for 14, 28 or 42 days and designated as AFC treated rats. However, bleomycin (BLM) treated rats were administered (5 IU/kg) single dose intratracheal injection. The pulmonary associated effects were assessed through cells permeation study, biochemical evaluation, physical and physiological parameters, survival analysis and histopathological examination. Results: Overall, pulmonary associated effects induced by new as well as conventional bleomycin model exhibited almost similar results. Though, new model developed homogeneous and time dependent advancement in pulmonary severity with enhanced survival ratio as compared to bleomycin model. Comparatively, new model also represented low extent of normalization with pirfenidone treatment due to establishment of progressive fibrosis. Conclusion: This study reflects the role of formaldehyde and cigarette smoke in reinforcement of PF particularly during the lung inflammatory condition. Also, it provides novel idea to induce homogeneous and progressive PF in rats, which could resembles human lung fibrosis more specifically than conventionally induced by intratracheal bleomycin instillation.
Experimental mouse model of Bleomycin-induced Pulmonary Fibrosis
2020
Pulmonary fibrosis is a pathologic chronic lung disorder characterized by the deposition of extracellular matrix and damage to lung architecture. Models of pulmonary fibrosis were developed in several animal species. However, murine models are more common due to their low costs, availability and well characterized immune systems. Indeed, these murine models play an important role in understanding the biology of the diseases, deciphering the cellular and molecular mechanisms mediating pulmonary pathobiology and to explore novel therapeutic approaches. Although the majority of these models mimic certain characteristics of human idiopathic pulmonary fibrosis, most of them do not mimic other features especially those related to the progressive and irreversible nature of this disease. The present protocol describes the induction of a pulmonary fibrosis model in mice with bleomycin, which is a risk factor for human lung fibrosis. Specifically, we described the methodology of intratracheal...
DARU-JOURNAL OF FACULTY OF PHARMACY
Background and the purpose of the study: Recent studies have indicated the role of apoptosis and angiotensin in the pathogenesis of bleomycin induced-pulmonary fibrosis. Losartan, an angiotensin type 1 receptor (AT 1 R) antagonist, has ameliorated apoptosis and fibrosis from bleomycin. In this study, alterations in the expression of apoptosis-regulatory genes (bcl-2 and bax) were investigated in different cells of lung tissue of mice treated with bleomycin in the presence of losartan. Methods: Losartan (10 mg/kg, i.p.) was given to mice two days before administration of bleomycin (3 U/kg) and throughout the test period. After two weeks, lung tissues of mice were evaluated for fibrosis by biochemical measurement of collagen deposition and semiquantitative analysis of pathological changes of the lung. The expression of bcl-2 and bax was assessed by immunohistochemical assay using biotin-streptavidin staining method on paraffin-embedded lung tissues. Results and major conclusion: Pre-treatment with losartan significantly (P < 0.05) reduced the increase in lung collagen content and also inhibited the histological changes induced by bleomycin. Immunohistochemical studies showed that losartan significantly (P < 0.05) reduced the bax/bcl-2 expression ratio in the alveolar epithelial cells, lymphocytes, macrophages and interstitial myofibroblasts. Losartan also inhibited the bcl-2 upregulation which was educed by bleomycin in neutrophils. By reduction of bax/bcl-2 ratio as a determinant of susceptibility of a cell to apoptosis, losartan exerted protective effects on the alveolar epithelial cells that may be important in the amelioration of pulmonary fibrosis. These results may help to better understanding of the role of angiotensin II and apoptosis in pulmonary fibrosis.