Experimental Models for the Study of Pulmonary Fibrosis: Current Usefulness and Future Promise

Mangiferin attenuates bleomycin-induced pulmonary fibrosis in mice through inhibiting TLR4/p65 and TGF-β1/Smad2/3 pathway

Objectives

Investigating the antipulmonary fibrosis effect of mangiferin from Mangifera indica and the possible molecular mechanism.

Methods

In vivo, bleomycin (BLM)-induced pulmonary fibrosis experimental model was used for evaluating antipulmonary fibrosis effect of mangiferin. Histopathologic examination and collagen deposition were investigated by HE and Masson staining as well as detecting the content of hydroxyproline. The expression of transforming growth factor-β1 (TGF-β1), α-smooth muscle actin (α-SMA), TLR4 and p-P65 in lung tissue was analysed through immunofluorescence. Leucocytes and inflammatory cytokines including IL-1β, IL-6, TNF-α and MCP-1 in bronchoalveolar lavage fluid were detected by cell counting and enzyme-linked immunosorbent assay. In vitro, TGF-β1-induced A549 epithelial–mesenchymal transition (EMT) cell model was used for investigating the possible molecular mechanism. Reactive oxygen species (ROS) generation was detected by DCFH-DA assay. Expression of all proteins was examined by Western blot.

Key findings

Oral administration of mangiferin could attenuate the severity of BLM-induced pulmonary fibrosis through increasing the survival rate, improving histopathological lesion and body weight loss as well as decreasing pulmonary index visibly. Pulmonary hydroxyproline content, TGF-β1, and α-SMA levels were reduced significantly. The molecular mechanism of mangiferin for inhibiting pulmonary fibrosis is that it could obviously inhibit the occurrence of inflammation and the secretion of inflammatory cytokine through inhibiting activation of TLR4 and phosphorylation of p65. Meanwhile, EMT process was suppressed obviously by mangiferin through blocking the phosphorylation of Smad2/3 and reducing MMP-9 expression. Besides, mangiferin could significantly inhibit the process of oxidant stress through downregulating the intracellular ROS generation.

Conclusions

Mangiferin attenuates BLM-induced pulmonary fibrosis in mice through inhibiting TLR4/p65 and TGF-β1/Smad2/3 pathway.

A Profibrotic Phenotype in Naïve and in Fibrotic Lung Myofibroblasts Is Governed by Modulations in Thy-1 Expression and Activation

Lung fibrosis is characterized by abnormal accumulation of Thy-deficient fibroblasts in the interstitium of the alveolar space. We have previously shown in bleomycin-treated chimeric Thy1-deficient mice with wild-type lymphocytes that Thy1-deficient fibroblasts accumulate and promote fibrosis and an “inflammation-free” environment. Here, we aimed to identify the critical effects of Thy1, or the absence of Thy1, in lung myofibroblast profibrotic functions, particularly proliferation and collagen deposition. Using specific Thy1 siRNA in Thy1-positive cells, Thy1 knockout cells, Thy1 cDNA expression vector in Thy1-deficient cells, and Thy1 cross-linking, we evaluated cell proliferation (assessed by cell mass and BrdU uptake), differentiation (using immunofluorescence), and collagen deposition (using Sircol assay). We found that myofibroblast Thy1 cross-linking and genetic manipulation modulate cell proliferation and expression of Fgf (fibroblast growth factor) and Angtl (angiotensin) receptors (using qPCR) that are involved in myofibroblast proliferation, differentiation, and collagen deposition. In conclusion, lung myofibroblast downregulation of Thy1 expression is critical to increase proliferation, differentiation, and collagen deposition.

A critical assessment of the scientific basis, and implementation, of regulations for the safety assessment and marketing of innovative tobacco-related products

Our scientific, logistical, ethical and animal welfare-related concerns about the latest US Food and Drug Administration (FDA) regulations for existing and so-called 'new' tobacco products, aimed at reducing harmful exposures, are explained. Such claims for sales in the USA now have to be based on a wide range of information, a key part of which will increasingly be data on safety and risk. One of the pathways to achieve marketing authorisation is to demonstrate substantial equivalence (SE) with benchmark products, called predicates. However, the regulations are insufficiently transparent with regard to: a) a rationale for the cut-off date for 'old' and 'new' products, and for exempting the former from regulation; b) the scientific validity and operation of SE; c) options for product labelling to circumvent SE; d) the experimental data required to support, and criteria to judge, a claim; and e) a strategy for risk assessment/management. Scientific problems related to the traditional animal methods used in respiratory disease and inhalation toxicology, and the use of quantitative comparators of toxicity, such as the No Observed Adverse Effect Level, are discussed. We review the advantages of relevant in vitro, mechanism-based, target tissue-oriented technologies, which an advisory report of the Institute of Medicine of the US National Academy of Sciences largely overlooked. These benefits include: a) the availability, for every major site in the respiratory tract, of organotypic human cell-based tissue culture systems, many of which are already being used by the industry; b) the accurate determination of concentrations of test materials received by target cells; c) methods for exposure to particulate and vapour phases of smoke, separately or combined; d) the ability to study tissue-specific biotransformation; and e) the use of modern, human-focused methodologies, unaffected by species differences. How data extrapolation, for risk assessment, from tissue culture to the whole animal, could be addressed, is also discussed. A cost (to animal welfare)-benefit (to society, including industry and consumers) analysis was conducted, taking into account the above information; the potential for animal suffering; the extensive data already available; the existence of other, less hazardous forms of nicotine delivery; the fact that much data will be generated solely for benchmarking; and that many smokers (especially nicotine-dependents) ignore health warnings. It is concluded that, in common with policies of several tobacco companies and countries, the use of laboratory animals for tobacco testing is very difficult, if not impossible, to justify. Instead, we propose and argue for an integrated testing scheme, starting with extensive chemical analysis of the ingredients and by-products associated with the use of tobacco products and their toxicity, followed by use of in vitro systems and early clinical studies (involving specific biomarkers) with weight-of-evidence assessments at each stage. Appropriate adjustment factors could be developed to enable concentration-response data obtained in vitro, with the other information generated by the strategy, to enable the FDA to meet its objectives. It is hoped that our intentionally provocative ideas will stimulate further debate on this contentious area of regulatory testing and public safety.

Evaluation of the antifibrotic effect of fenofibrate and rosiglitazone on bleomycin-induced pulmonary fibrosis in rats

Idiopathic pulmonary fibrosis is the most prevalent chronic fibrosing lung disease. Peroxisome proliferator-activated receptors-gamma agonists provide potential therapy for fibrotic diseases of the lung. Peroxisome proliferator-activated receptors-alpha agonists may be helpful in the treatment of lung inflammatory diseases, however their therapeutic potential on the "fibro-proliferative" process and extracellular matrix accumulation in idiopathic pulmonary fibrosis has been less well studied. So, the present study was conducted to evaluate the anti-fibrotic effects of fenofibrate (peroxisome proliferator-activated receptors-alpha agonist) alone and in combination with rosiglitazone (peroxisome proliferator-activated receptors-gamma agonist) on lung injury induced by bleomycin administration. Oral administration of either rosiglitazone (5 mg/kg/d) or fenofibrate (100 mg/kg/d) for 14 days, attenuated the severity of bleomycin-induced lung injury and fibrosis through decreasing lung water contents, lung fibrotic grading, lung hydroxyproline contents and lung transforming growth factor-beta1 levels; with no significant difference between them. Combined low doses of rosiglitazone (1 mg/kg/d) and fenofibrate (30 mg/kg/d) provided more benefits than full separate doses of each on the deleterious effects accompanied bleomycin administration. These findings suggested the potential use of peroxisome proliferator-activated receptors-alpha ligands as anti-fibrotic agents in lung fibrosis. Additionally, the concurrent administration of fenofibrate and rosiglitazone in low doses has synergistic effect and enhanced the beneficial effects afforded by either fenofibrate or rosiglitazone.

[Liver growth factor improves pulmonary fibrosis secondary to cadmium administration in rats]

INTRODUCTION

Liver growth factor (LGF) is a liver mitogen with regenerating and anti-fibrotic activity even at extrahepatic sites. We used LGF in a lung fibrosis model induced by cadmium chloride (CdCl(2)), to study its antifibrotic capacity.

METHODS

Forty-two male Wistar rats were administered a single dose of 0.5ml/rat of CdCl2 0.025% (n=21) or the same volume of saline (control group, n=21). After 35 days, once a lesion was established, we started a 3 week treatment with LGF, after which we determined lung function--inspiratory capacity (IC), lung compliance (LC), forced vital capacity (FVC) and expiratory flow at 75% (FEF75%)-, lung morphometry--alveolar internal area (AIA), mean linear intersection (LM)-, and collagen (both by Sirius red and hydroxyproline residues) and elastin contents.

RESULTS

Pulmonary fibrosis in CdCl(2) rats was characterized by a marked decrease in pulmonary function with respect to healthy controls -reductions of 28% in IC, 38% in CL, 31% in FVC, and 54% in FEF75%- which was partially recovered after LGF injection -18% IC, 27% CL, 19% FVC and 35% FEF75%-; increase in collagen and elastin contents -165% and 76%, respectively, in CdCl2 rats, versus 110% and 34% after LGF injection-; and increases in AIA and LM, partially reverted by LGF.

CONCLUSIONS

Together, these data seem to demonstrate that LGF is able to improve lung function and partially reverts the increase in lung matrix proteins produced by CdCl(2) instillation.