Protective effect of α-tocopherol on oxidative stress in experimental pulmonary fibrosis in rats

Phœnix dactylifera, L. seed oil alleviates Bleomycin-induced pulmonary fibrosis and oxidative stress in Wistar rats

OBJECTIVE

Idiopathic pulmonary fibrosis (IPF) is the most serious form of interstitial lung disease. We aimed to investigate the effect of Phœnix dactylifera, L. seed oil (DSO) on a murine model of IPF induced by bleomycin (BLM).

METHODS

Male Wistar rats were treated with a single intra-tracheal injection of BLM (4 mg/kg) and a daily intraperitoneal injection of DSO (75, 150 and 300 mg/kg) for 4 weeks.

RESULTS

Our phytochemical results showed that DSO has an important antioxidant activity with a high content of polyphenols and flavonoids. High-Performance Liquid Chromatography (HPLC) and Gas chromatography/mass spectrometry (GC-MS) analysis revealed a high amount of oleic and lauric acids and a large quantity of vitamins. Histological examination showed a significant reduction in fibrosis score and collagen bands in the group of rats treated with 75 mg/kg of DSO compared to the BLM group. DSO (75 mg/kg) reversed also the increase in catalase and malondialdehyde (MDA) levels while higher doses (150 and 300 mg/kg) are ineffective against the deleterious effects of BLM. We revealed also that DSO has no renal or hepatic cytotoxic effects.

CONCLUSION

DSO can play antioxidant and antifibrotic effects on rat models of pulmonary fibrosis at the lowest dose administered.

Vitamin E stabilizes iron and mitochondrial metabolism in pulmonary fibrosis

Introduction: Pulmonary fibrosis (PF) is a fatal chronic lung disease that causes structural damage and decreased lung function and has a poor prognosis. Currently, there is no medicine that can truly cure PF. Vitamin E (VE) is a group of natural antioxidants with anticancer and antimutagenic properties. There have been a few reports about the attenuation of PF by VE in experimental animals, but the molecular mechanisms are not fully understood. Methods: Bleomycin-induced PF (BLM-PF) mouse model, and cultured mouse primary lung fibroblasts and MLE 12 cells were utilized. Pathological examination of lung sections, immunoblotting, immunofluorescent staining, and real-time PCR were conducted in this study. Results: We confirmed that VE significantly delayed the progression of BLM-PF and increased the survival rates of experimental mice with PF. VE suppressed the pathological activation and fibrotic differentiation of lung fibroblasts and epithelial-mesenchymal transition and alleviated the inflammatory response in BLM-induced fibrotic lungs and pulmonary epithelial cells in vitro. Importantly, VE reduced BLM-induced ferritin expression in fibrotic lungs, whereas VE did not exhibit iron chelation properties in fibroblasts or epithelial cells in vitro. Furthermore, VE protected against mitochondrial dysmorphology and normalized mitochondrial protein expression in BLM-PF lungs. Consistently, VE suppressed apoptosis in BLM-PF lungs and pulmonary epithelial cells in vitro. Discussion: Collectively, VE markedly inhibited BLM-induced PF through a complex mechanism, including improving iron metabolism and mitochondrial structure and function, mitigating inflammation, and decreasing the fibrotic functions of fibroblasts and epithelial cells. Therefore, VE presents a highly potential therapeutic against PF due to its multiple protective effects with few side effects.

GGA (geranylgeranylacetone) ameliorates bleomycin-induced lung inflammation and pulmonary fibrosis by inhibiting apoptosis and oxidative stress

BACKGROUND

Fibrosis is a response to ongoing cellular injury, disruption, and tissue remodeling, the pathogenesis of which is unknown, and is characterized by extracellular matrix deposition. The antifibrotic effect of Geranylgeranylacetone (GGA), as an inducer of Heat shock protein 70 (HSP70), in liver, kidney and pulmonary fibrosis has been supported by multiple preclinical evidence. However, despite advances in our understanding, the precise roles of HSP70 in fibrosis require further investigation. The purpose of this study was to investigate whether GGA could participate in the progression of pulmonary fibrosis in mice through apoptosis, oxidative stress and inflammation.

METHODS AND RESULTS

B-cell lymphoma-2(Bcl-2) and Bcl2-Associated X (Bax) are two proteins related to apoptosis. Anti-apoptotic factor Bcl-2 and pro-apoptotic factor Bax are often involved in the apoptotic process in the form of dimer. Immunofluorescence and Western blot results showed that bleomycin (BLM) and transforming growth factor-β (TGF-β) inhibited Bcl-2 expression and promoted Bax expression in vitro and in vivo, respectively. In contrast, GGA treatment reverses this change. Reactive oxygen species (ROS), Malondialdehyde (MDA) and superoxide dismutase (SOD) are markers of oxidative stress, which often reflect oxidative injury of cells. The detection of ROS, MDA and SOD expression showed that TGF-β and BLM treatment could significantly promote oxidative stress, while GGA treatment could alleviate oxidative stress damage. In addition, BLM significantly elevated Tumor necrosis factor-α(TNF-α), Interleukin1β (IL-1β) and Interleukin 6 (IL-6), while scutellarin reversed the above alterations except for that of GGA.

RESULTS

Taken together, GGA suppressed apoptotic, oxidative stress and inflammation in BLM-induced pulmonary fibrosis.

Geranylgeranylacetone, an inducer of heat shock protein 70, attenuates pulmonary fibrosis via inhibiting NF-κB/NOX4/ROS signalling pathway in vitro and in vivo

Idiopathic pulmonary fibrosis (IPF) is a devastating and progressive pulmonary disease which is characterized by epithelial cell damage and extracellular collagen deposition. To date, the therapeutic options for IPF are still very limited, so the relevant mechanisms need to be explored. Heat shock protein 70 (HSP70), which has protective versus antitumor effects on cells under stress, is a member of the heat shock protein family. In the current study, qRT-PCR, western blotting, immunofluorescence staining, and migration assays were used to explore the Epithelial-mesenchymal transition (EMT) process in BEAS-2B cells. Moreover, the role of GGA in the process of pulmonary fibrosis was detected by HE, Masson staining, pulmonary function test and immunohistochemistry in C57BL/6 mice. Our results indicated that GGA, as an inducer of HSP70, enhanced the transformation of BEAS-2B cells from epithelial to mesenchymal cells through the NF-κB/NOX4/ROS (reactive oxygen species) signalling pathway and could significantly reduce apoptosis of BEAS-2B cells induced by TGF-β1(Transforming growth factor β1) in vitro. In vivo studies demonstrated that HSP70-inducing drugs, such as GGA, attenuated pulmonary fibrosis progression induced by bleomycin (BLM). Collectively, these results suggested that overexpression of HSP70 attenuated pulmonary fibrosis induced by BLM in C57BL/6 mice and EMT process induced by TGF-β1 through NF-κB/NOX4/ROS pathway in vitro. Thus, HSP70 might be a potential therapeutic strategy for human lung fibrosis.

Role of Ferroptosis in Fibrotic Diseases

Ferroptosis is a unique and pervasive form of regulated cell death driven by iron-dependent phospholipid peroxidation. It results from disturbed cellular metabolism and imbalanced redox homeostasis and is regulated by various cellular metabolic pathways. Recent preclinical studies have revealed that ferroptosis may be an attractive therapeutic target in fibrotic diseases, such as liver fibrosis, pulmonary fibrosis, kidney fibrosis, and myocardial fibrosis. This review summarizes the latest knowledge on the regulatory mechanism of ferroptosis and its roles in fibrotic diseases. These updates may provide a novel perspective for the treatment of fibrotic diseases as well as future research.

Treatment of chronic airway diseases using nutraceuticals: Mechanistic insight

Respiratory diseases, both acute and chronic, are reported to be the leading cause of morbidity and mortality, affecting millions of people globally, leading to high socio-economic burden for the society in the recent decades. Chronic inflammation and decline in lung function are the common symptoms of respiratory diseases. The current treatment strategies revolve around using appropriate anti-inflammatory agents and bronchodilators. A range of anti-inflammatory agents and bronchodilators are currently available in the market; however, the usage of such medications is limited due to the potential for various adverse effects. To cope with this issue, researchers have been exploring various novel, alternative therapeutic strategies that are safe and effective to treat respiratory diseases. Several studies have been reported on the possible links between food and food-derived products in combating various chronic inflammatory diseases. Nutraceuticals are examples of such food-derived products which are gaining much interest in terms of its usage for the well-being and better human health. As a consequence, intensive research is currently aimed at identifying novel nutraceuticals, and there is an emerging notion that nutraceuticals can have a positive impact in various respiratory diseases. In this review, we discuss the efficacy of nutraceuticals in altering the various cellular and molecular mechanisms involved in mitigating the symptoms of respiratory diseases.

Lipid Peroxidation, GSH Depletion, and SLC7A11 Inhibition Are Common Causes of EMT and Ferroptosis in A549 Cells, but Different in Specific Mechanisms

Epithelial-mesenchymal transition (EMT) induced by transforming growth factor-β1 (TGF-β1) is thought to be involved in the pathogenesis of pulmonary fibrosis. Emerging evidence suggested that there are some common causes between ferroptosis and pulmonary fibrosis. The interaction of EMT and ferroptosis and its mechanism were investigated by detecting the expression levels of α-smooth muscle actin (α-SMA), E-cadherin, solute carrier family 7 member 11 (SLC7A11), and glutathione peroxidase 4 (GPX4) and measuring the contents of reactive oxygen species (ROS), malondialdehyde (MDA), and glutathione (GSH). The cellular morphology and ultrastructure of mitochondria were studied by microscope and transmission electron microscope (TEM), respectively. The results showed that ferroptosis in A549 cells was induced by Erastin, which decreased the expression levels of E-cadherin (E-Ca), α-SMA, and SLC7A11, accompanied with ROS and MDA increase, as well as GSH decrease. TGF-β1 promoted ultrastructure variation of mitochondria similar to ferroptosis and mesenchymal changes in morphology during EMT of A549 cells, accompanied with reduced GSH content and expression of SLC7A11, as well as ROS and MDA increase. Ferrostatin-1 (Fer-1) recovered ferroptosis induced by Erastin, but had no effect on the morphological change caused by TGF-β1. Furthermore, Fer-1 reduced ROS and MDA production, and increased SLC7A11 expression in the early subsequently increased GSH. However, the effects of Fer-1 on above indicators were different in time. The expression of GPX4 had no significant change during EMT induced by TGF-β1 and ferroptosis induced by Erastin in A549 cells. It is indicating that Erastin promoted the de-epithelialization of lung epithelial cells, but inhibited the process of myofibroblast differentiation; Fer-1 could partially inhibit EMT induced by TGF-β1, but reverse ferroptosis induced by Erastin. TGF-β1 could delay the ferroptosis, but could not prevent it. Lipid peroxidation, GSH depletion, and SLC7A11 inhibition are common causes of EMT and ferroptosis in A549 cells, but different in specific mechanisms. The exact effects of GPX4 involved in EMT and ferroptosis in A549 cells need further study.

Epidemiological risk factors for adrenocortical carcinoma: A hospital-based case-control study

Adrenocortical carcinoma (ACC) is a rare malignancy whose risk factors are unclear. We explored the association of ACC risk with exposure to selected environmental factors, with a focus on cigarette smoking. We conducted a hospital-based case-control study at The University of Texas MD Anderson Cancer Center. Cases (n = 432) patients with ACC treated at MD Anderson, and controls (n = 1,204) were healthy and genetically unrelated spouses of patients at MD Anderson who had cancers not associated with smoking. Information on the subjects' demographic features and selected risk factors was collected using a structured, validated questionnaire and medical records review. Unconditional logistic regression was used to calculate adjusted odds ratios (AORs) via the maximum-likelihood method. Cases had a younger mean (± standard deviation) age than did controls (47.0 ± 0.7 and 60.0 ± 0.3 years, respectively), and the majority of cases were female (60.6%) and non-Hispanic white (82.4%). We found a markedly increased risk of ACC among male cigarette smokers, with an AOR = 1.8 (95% confidence interval [CI] =1.2-2.9), but not among female smokers (AOR = 1.1, 95% CI = 0.7-1.6). Family history of cancer was associated with increased risk of ACC (AOR = 2.8, 95% CI 1.9-4.3) and in both men and women, whereas alcohol consumption was associated with reduced risk in men (AOR = 0.2, 95% CI = 0.1-0.3) but not women (AOR = 0.7, 95% CI = 0.5-1.1). Understanding these risk factors and their underlying mechanisms may help prevent ACC in susceptible individuals and eventually identify new therapeutic options for ACC.

Drugs and Targets in Fibrosis

Fibrosis contributes to the development of many diseases and many target molecules are involved in fibrosis. Currently, the majority of fibrosis treatment strategies are limited to specific diseases or organs. However, accumulating evidence demonstrates great similarities among fibroproliferative diseases, and more and more drugs are proved to be effective anti-fibrotic therapies across different diseases and organs. Here we comprehensively review the current knowledge on the pathological mechanisms of fibrosis, and divide factors mediating fibrosis progression into extracellular and intracellular groups. Furthermore, we systematically summarize both single and multiple component drugs that target fibrosis. Future directions of fibrosis drug discovery are also proposed.

Reduced Glutathione Level Promotes Epithelial-Mesenchymal Transition in Lens Epithelial Cells via a Wnt/β-Catenin-Mediated Pathway: Relevance for Cataract Therapy

The epithelial-mesenchymal transition (EMT) process plays a pivotal role in the pathogenesis of posterior capsular opacification because of remnant lens epithelial cell proliferation, migration, and transformation after cataract surgery. The latter, we hypothesize, may result in posterior capsule wrinkling and opacification because of a profound change in the lens growth environment via a 1000-fold reduction of extracellular glutathione (GSH) levels. To test this hypothesis, we investigated the EMT process in cell culture and GSH biosynthesis deficiency mouse models. Our data indicate a dramatic increase of pro-EMT markers, such as type I collagen, α-smooth muscle actin, vimentin, and fibronectin, under conditions of lens GSH depletion. Further study suggests that decreased GSH triggers the Wnt/β-catenin signal transduction pathway, independent of transforming growth factor-β. Equally important, the antioxidants N-acetyl cysteine and GSH ethyl ester could significantly attenuate the EMT signaling stimulated by decreased GSH levels. These findings were further confirmed by mock cataract surgery in both gamma glutamyl-cysteine ligase, catalytic subunit, and gamma glutamyl-cysteine ligase, modifier subunit, knockout mouse models. Remarkably, increased EMT marker expression, β-catenin activation, and translocation into the nucleus were found in both knockout mice compared with the wild type, and such increased expression could be significantly attenuated by N-acetyl cysteine or GSH ethyl ester treatment. This study, for the first time we believe, links oxidative stress to lens fibrosis and posterior capsular opacification formation via EMT-mediated mechanisms.

Treatment effects of the traditional Chinese medicine Shenks in bleomycin-induced lung fibrosis through regulation of TGF-beta/Smad3 signaling and oxidative stress

Pulmonary fibrosis is a kind of devastating interstitial lung disease due to the limited therapeutic strategies. Traditional Chinese medicine (TCM) practices have put forth Shenks as a promising treatment approach. Here, we performed in vivo study and in vitro study to delineate the anti-fibrotic mechanisms behind Shenks treatment for pulmonary fibrosis. We found that regardless of the prophylactic or therapeutic treatment, Shenks was able to attenuate BLM-induced-fibrosis in mice, down regulate extracellular matrix genes expression, and reduce collagen production. The aberrantly high Smad3 phosphorylation levels and SBE activity in TGF-β-induced fibroblasts were dramatically decreased as a result of Shenks treatment. At the same time, Shenks was able to increase the expression of antioxidant-related genes, including Gclc and Ec-sod, while reduce the transcription levels of oxidative-related genes, such as Rac1 and Nox4 demonstrated by both in vivo and in vitro studies. Further investigations found that Shenks could decrease the oxidative productions of protein (3-nitrotyrosine) and lipid (malondialdehyde) and increase GSH content both in bleomycin treated mouse lungs and TGF-β stimulated fibroblasts, as well as inhibit the production of ROS stimulated by TGF-β to fight against oxidative stress. Overall, Shenks inhibited fibrosis by blocking TGF-β pathway and modulating the oxidant/antioxidant balance.

Elastase modifies bleomycin-induced pulmonary fibrosis in mice

Pulmonary fibrosis (PF) is characterized by excessive accumulation of collagen in the lungs. Emphysema is characterized by loss of the extracellular matrix (ECM) and alveolar enlargement. We studied the co-participation of elastase-induced mild emphysema in bleomycin-induced PF in mice by analyzing oxidative stress, inflammation and lung histology. C57BL/6 mice were divided into four groups: control; bleomycin (0.1U/mouse); elastase (using porcine pancreatic elastase (PPE)+bleomycin (3U/mouse 14 days before 0.1U/mouse of bleomycin; PPE+B); elastase (3U/mouse). Mice were humanely sacrificed 7, 14 and 21 days after treatment with bleomycin or vehicle. PF was observed 14 days and 21 days after bleomycin treatment but was observed after 14 days only in the PPE+B group. In the PPE+B group at 21 days, we observed many alveoli and alveolar septa with few PF areas. We also observed marked and progressive increases of collagens 7, 14 and 21 days after bleomycin treatment whereas, in the PPE+B group, collagen deposition was observed only at 14 days. There was a reduction in activities of the antioxidant enzymes superoxide dismutase (p<0.05), catalase (p<0.01) and glutathione peroxidase (p<0.01) parallel with an increase in nitrite (p<0.01) 21 days after bleomycin treatment compared with the control group. These endpoints were also reduced (p<0.05, p<0.05 and p<0.01, respectively) and increased (p<0.01) in the PPE+B group at 21 days compared with the control group. Interleukin (IL)-1β expression was upregulated (p<0.01) whereas IL-6 was downregulated (p<0.05) in the PPE+B group at 21 days compared with the control group. PF and emphysema did not coexist in our model of lung disease and despite increased levels of oxidative stress and inflammatory markers after combined stimulus (elastase and bleomycin) overall histology was improved to that of the nearest control group.

Reciprocal regulation of TGF-β and reactive oxygen species: A perverse cycle for fibrosis

Transforming growth factor beta (TGF-β) is the most potent pro-fibrogenic cytokine and its expression is increased in almost all of fibrotic diseases. Although signaling through Smad pathway is believed to play a central role in TGF-β's fibrogenesis, emerging evidence indicates that reactive oxygen species (ROS) modulate TGF-β's signaling through different pathways including Smad pathway. TGF-β1 increases ROS production and suppresses antioxidant enzymes, leading to a redox imbalance. ROS, in turn, induce/activate TGF-β1 and mediate many of TGF-β's fibrogenic effects, forming a vicious cycle (see graphic flow chart on the right). Here, we review the current knowledge on the feed-forward mechanisms between TGF-β1 and ROS in the development of fibrosis. Therapeutics targeting TGF-β-induced and ROS-dependent cellular signaling represents a novel approach in the treatment of fibrotic disorders.

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TGF-β1 is the most potent ubiquitous profibrogenic cytokine.

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TGF- β 1 induces redox imbalance by ↑ ROS production and ↓ anti-oxidant defense system

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Redox imbalance, in turn, activates latent TGF-β1 and induces TGF-β1 expression.

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Redox imbalance also mediates many of TGF-β1’s profibrogenic effects

The role of catalase in pulmonary fibrosis

BACKGROUND

Catalase is preferentially expressed in bronchiolar and alveolar epithelial cells, and acts as an endogenous antioxidant enzyme in normal lungs. We thus postulated epithelial damage would be associated with a functional deficiency of catalase during the development of lung fibrosis.

METHODS

The present study evaluates the expression of catalase mRNA and protein in human interstitial pneumonias and in mouse bleomycin-induced lung injury. We examined the degree of bleomycin-induced inflammation and fibrosis in the mice with lowered catalase activity.

RESULTS

In humans, catalase was decreased at the levels of activity, protein content and mRNA expression in fibrotic lungs (n = 12) compared to control lungs (n = 10). Immunohistochemistry revealed a decrease in catalase in bronchiolar epithelium and abnormal re-epithelialization in fibrotic areas. In C57BL/6J mice, catalase activity was suppressed along with downregulation of catalase mRNA in whole lung homogenates after bleomycin administration. In acatalasemic mice, neutrophilic inflammation was prolonged until 14 days, and there was a higher degree of lung fibrosis in association with a higher level of transforming growth factor-β expression and total collagen content following bleomycin treatment compared to wild-type mice.

CONCLUSIONS

Taken together, these findings demonstrate diminished catalase expression and activity in human pulmonary fibrosis and suggest the protective role of catalase against bleomycin-induced inflammation and subsequent fibrosis.

Oxidative stress and glutathione in TGF-beta-mediated fibrogenesis

Transforming growth factor beta (TGF-beta) is the most potent and ubiquitous profibrogenic cytokine, and its expression is increased in almost all the fibrotic diseases and in experimental fibrosis models. TGF-beta increases reactive oxygen species production and decreases the concentration of glutathione (GSH), the most abundant intracellular free thiol and an important antioxidant, which mediates many of the fibrogenic effects of TGF-beta in various types of cells. A decreased GSH concentration is also observed in human fibrotic diseases and in experimental fibrosis models. Although the biological significance of GSH depletion in the development of fibrosis remains obscure, GSH and N-acetylcysteine, a precursor of GSH, have been used in clinics for the treatment of fibrotic diseases. This review summarizes recent findings in the field to address the potential mechanism whereby oxidative stress mediates fibrogenesis induced by TGF-beta and the potential therapeutic value of antioxidant treatment in fibrotic diseases.

Nrf2 protects against airway disorders

Nuclear factor-erythroid 2 related factor 2 (Nrf2) is a ubiquitous master transcription factor that regulates antioxidant response elements (AREs)-mediated expression of antioxidant enzyme and cytoprotective proteins. In the unstressed condition, Kelch-like ECH-associated protein 1 (Keap1) suppresses cellular Nrf2 in cytoplasm and drives its proteasomal degradation. Nrf2 can be activated by diverse stimuli including oxidants, pro-oxidants, antioxidants, and chemopreventive agents. Nrf2 induces cellular rescue pathways against oxidative injury, abnormal inflammatory and immune responses, apoptosis, and carcinogenesis. Application of Nrf2 germ-line mutant mice has identified an extensive range of protective roles for Nrf2 in experimental models of human disorders in the liver, gastrointestinal tract, airway, kidney, brain, circulation, and immune or nerve system. In the lung, lack of Nrf2 exacerbated toxicity caused by multiple oxidative insults including supplemental respiratory therapy (e.g., hyperoxia, mechanical ventilation), cigarette smoke, allergen, virus, bacterial endotoxin and other inflammatory agents (e.g., carrageenin), environmental pollution (e.g., particles), and a fibrotic agent bleomycin. Microarray analyses and bioinformatic studies elucidated functional AREs and Nrf2-directed genes that are critical components of signaling mechanisms in pulmonary protection by Nrf2. Association of loss of function with promoter polymorphisms in NRF2 or somatic and epigenetic mutations in KEAP1 and NRF2 has been found in cohorts of patients with acute lung injury/acute respiratory distress syndrome or lung cancer, which further supports the role for NRF2 in these lung diseases. In the current review, we address the role of Nrf2 in airways based on emerging evidence from experimental oxidative disease models and human studies.

Antioxidants as potential therapeutics for lung fibrosis

Interstitial lung disease encompasses a large group of chronic lung disorders associated with excessive tissue remodeling, scarring, and fibrosis. The evidence of a redox imbalance in lung fibrosis is substantial, and the rationale for testing antioxidants as potential new therapeutics for lung fibrosis is appealing. Current animal models of lung fibrosis have clear involvement of ROS in their pathogenesis. New classes of antioxidant agents divided into catalytic antioxidant mimetics and antioxidant scavengers are being developed. The catalytic antioxidant class is based on endogenous antioxidant enzymes and includes the manganese-containing macrocyclics, porphyrins, salens, and the non-metal-containing nitroxides. The antioxidant scavenging class is based on endogenous antioxidant molecules and includes the vitamin E analogues, thiols, lazaroids, and polyphenolic agents. Numerous studies have shown oxidative stress to be associated with many interstitial lung diseases and that these agents are effective in attenuating fibroproliferative responses in the lung of animals and humans.