Oxidant-antioxidant imbalance as a potential contributor to the progression of human pulmonary fibrosis

Oxidative Stress and Lung Fibrosis: Towards an Adverse Outcome Pathway

Lung fibrosis is a progressive fatal disease in which deregulated wound healing of lung epithelial cells drives progressive fibrotic changes. Persistent lung injury due to oxidative stress and chronic inflammation are central features of lung fibrosis. Chronic cigarette smoking causes oxidative stress and is a major risk factor for lung fibrosis. The objective of this manuscript is to develop an adverse outcome pathway (AOP) that serves as a framework for investigation of the mechanisms of lung fibrosis due to lung injury caused by inhaled toxicants, including cigarette smoke. Based on the weight of evidence, oxidative stress is proposed as a molecular initiating event (MIE) which leads to increased secretion of proinflammatory and profibrotic mediators (key event 1 (KE1)). At the cellular level, these proinflammatory signals induce the recruitment of inflammatory cells (KE2), which in turn, increase fibroblast proliferation and myofibroblast differentiation (KE3). At the tissue level, an increase in extracellular matrix deposition (KE4) subsequently culminates in lung fibrosis, the adverse outcome. We have also defined a new KE relationship between the MIE and KE3. This AOP provides a mechanistic platform to understand and evaluate how persistent oxidative stress from lung injury may develop into lung fibrosis.

Tobacco smoking is associated with combined pulmonary fibrosis and emphysema and worse outcomes in interstitial lung disease

Tobacco smoking is an established cause of pulmonary disease whose contribution to interstitial lung disease (ILD) is incompletely characterized. We hypothesized that compared with nonsmokers, subjects who smoked tobacco would differ in their clinical phenotype and have greater mortality. We performed a retrospective cohort study of tobacco smoking in ILD. We evaluated demographic and clinical characteristics, time to clinically meaningful lung function decline (LFD), and mortality in patients stratified by tobacco smoking status (ever vs. never) within a tertiary center ILD registry (2006-2021) and replicated mortality outcomes across four nontertiary medical centers. Data were analyzed by two-sided t tests, Poisson generalized linear models, and Cox proportional hazard models adjusted for age, sex, forced vital capacity (FVC), diffusion capacity of the lung for carbon monoxide (DLCO), ILD subtype, antifibrotic therapy, and hospital center. Of 1,163 study participants, 651 were tobacco smokers. Smokers were more likely to be older, male, have idiopathic pulmonary fibrosis (IPF), coronary artery disease, CT honeycombing and emphysema, higher FVC, and lower DLCO than nonsmokers (P < 0.01). Time to LFD in smokers was shorter (19.7 ± 20 mo vs. 24.8 ± 29 mo; P = 0.038) and survival time was decreased [10.75 (10.08-11.50) yr vs. 20 (18.67-21.25) yr; adjusted mortality HR = 1.50, 95%CI 1.17-1.92; P < 0.0001] compared with nonsmokers. Smokers had 12% greater odds of death for every additional 10 pack yr of smoking (P < 0.0001). Mortality outcomes remained consistent in the nontertiary cohort (HR = 1.51, 95%CI = 1.03-2.23; P = 0.036). Tobacco smokers with ILD have a distinct clinical phenotype strongly associated with the syndrome of combined PF and emphysema, shorter time to LFD, and decreased survival. Smoking prevention may improve ILD outcomes.NEW & NOTEWORTHY Smoking in ILD is associated with combined pulmonary fibrosis and emphysema and worse clinical outcomes.

Nintedanib Ameliorates Bleomycin-Induced Pulmonary Fibrosis, Inflammation, Apoptosis, and Oxidative Stress by Modulating PI3K/Akt/mTOR Pathway in Mice

Idiopathic pulmonary fibrosis (IPF) seriously threatens human life and health, and no curative therapy is available at present. Nintedanib is the first agent approved by the US Food and Drug Administration (FDA) in order to treat IPF; however, its mechanism of inhibition of IPF is still elusive. According to recent studies, nintedanib is a potent inhibitor. It can antagonize platelet-derived growth factor (PDGF), basic fibroblast growth factor (b-FGF), vascular endothelial growth factor (VEGF), etc., to inhibit pulmonary fibrosis. Whether there are other signaling pathways involved in IPF remains unknown. This study focused on investigating the therapeutic efficacy of nintedanib in bleomycin-mediated pulmonary fibrosis (PF) mice through PI3K/Akt/mTOR pathway. Following the induction of pulmonary fibrosis in C57 mice through bleomycin (BLM) administration, the mice were randomized into five groups: (1) the normal control group, (2) the BLM model control group, (3) the low-dose Nintedanib administration model group, (4) the medium-dose nintedanib administration model group, and (5) the high-dose nintedanib administration model group. For lung tissues, morphological changes were found by HE staining and Masson staining, ELISA method was used to detect inflammatory factors, alkaline water method to estimate collagen content, and western blotting for protein levels. TUNEL staining and immunofluorescence methods were used to analyze the effect of nintedanib on lung tissue and the impacts and underlying mechanisms of bleomycin-induced pulmonary fibrosis. After 28 days, bleomycin-treated mice developed significant pulmonary fibrosis. Relative to bleomycin-treated mice, nintedanib-treated mice had markedly reduced degrees of PF. In addition, nintedanib showed lung-protective effects by up-regulating antioxidant levels, down-regulating inflammatory protein expression, and reducing collagen accumulation. We demonstrated that nintedanib ameliorated bleomycin-induced lung injury by inhibiting the P13K/Akt/mTOR pathway as well as apoptosis. In addition, significant improvement in pulmonary fibrosis was seen after nintedanib (30/60/120 mg/kg body weight/day) treatment through a dose-dependent way. Histopathological results further corroborated the effect of nintedanib treatment on remarkably attenuating bleomycin-mediated mouse lung injury. According to our findings, nintedanib restores the antioxidant system, suppresses pro-inflammatory factors, and inhibits apoptosis. Nintedanib can reduce bleomycin-induced inflammation by downregulating PI3K/Akt/mTOR pathway, PF, and oxidative stress (OS).

Tanshinone IIA Regulates Keap1/Nrf2 Signal Pathway by Activating Sestrin2 to Restrain Pulmonary Fibrosis

Tanshinone IIA (Tan-IIA) is a major component extracted from the traditional herbal medicine Danshen, which has shown antipulmonary fibrosis by suppress reactive oxygen species-mediated activation of myofibroblast. However, the exact mechanism of Tan-IIA against pulmonary fibrosis (PF) remains unclear. This work aimed to explore the underlying mechanism of the protective effects of Tan-IIA on PF. By using high-throughput RNA-Seq analysis, we have compared the genome-wide gene expression profiles and pathway enrichment of Tan-IIA-treated NIH-3T3 cells with or without transforming growth factor beta 1 (TGF-[Formula: see text]1) induction. In normal NIH-3T3 cells, Tan-IIA treatment up-regulated 181 differential expression genes (DEGs) and down-regulated 137 DEGs. In TGF-[Formula: see text]1-induced NIH-3T3 cells, Tan-IIA treatment up-regulated 709 DEGs and down-regulated 1075 DEGs, and these DEGs were enriched in extracellular matrix organization, collagen fibril organization, cell adhesion, ECM-receptor interaction, PI3K-Akt signaling pathway and P53 signaling pathway. Moreover, there were 207 co-expressed DEGs between Tan-IIA treatment vs. the Control and TGF-[Formula: see text]1 plus Tan-IIA treatment vs. TGF-[Formula: see text]1 alone treatment, some of which were related to anti-oxidative stress. In both normal and TGF-[Formula: see text]1-induced NIH-3T3 cells, protein-protein interaction network analysis indicated that Tan-IIA can regulate the expression of several common anti-oxidant genes including Heme oxygenase 1 (Ho-1, also known as Homx1), Sestrin2 (Sesn2), GCL modifier subunit (Gclm), GCL catalytic subunit (Gclc) and Sequestosome-1 (Sqstm1). Quantitative Real-time polymerase chain reaction analysis confirmed some DEGs specifically expressing on Tan-IIA treated cells, which provided new candidates for further functional studies of Tan-IIA. In both in vitro and in vivo PF models, the protein expression of Sesn2 was significantly enhanced by Tan-IIA treatment. Overexpression and knockdown experiments showed that Sesn2 is required for Tan-IIA against TGF-[Formula: see text]1-induced myofibroblast activation by reinforcing nuclear factor-erythroid 2-related factor 2 (Nrf2)-mediated anti-oxidant response via downregulation of kelch-like ECH-associated protein 1 (Keap1). These results suggest Tan-IIA inhibits myofibroblast activation by activating Sesn2-Nrf2 signaling pathway, and provide a new insight into the essential role of Sesn2 in PF.

Therapeutic effects of eperisone on pulmonary fibrosis via preferential suppression of fibroblast activity

Although the exact pathogenesis of idiopathic pulmonary fibrosis (IPF) is still unknown, the transdifferentiation of fibroblasts into myofibroblasts and the production of extracellular matrix components such as collagen, triggered by alveolar epithelial cell injury, are important mechanisms of IPF development. In the lungs of IPF patients, apoptosis is less likely to be induced in fibroblasts than in alveolar epithelial cells, and this process is involved in the pathogenesis of IPF. We used a library containing approved drugs to screen for drugs that preferentially reduce cell viability in LL29 cells (lung fibroblasts from an IPF patient) compared with A549 cells (human alveolar epithelial cell line). After screening, we selected eperisone, a central muscle relaxant used in clinical practice. Eperisone showed little toxicity in A549 cells and preferentially reduced the percentage of viable LL29 cells, while pirfenidone and nintedanib did not have this effect. Eperisone also significantly inhibited transforming growth factor-β1-dependent transdifferentiation of LL29 cells into myofibroblasts. In an in vivo study using ICR mice, eperisone inhibited bleomycin (BLM)-induced pulmonary fibrosis, respiratory dysfunction, and fibroblast activation. In contrast, pirfenidone and nintedanib were less effective than eperisone in inhibiting BLM-induced pulmonary fibrosis under this experimental condition. Finally, we showed that eperisone did not induce adverse effects in the liver and gastrointestinal tract in the BLM-induced pulmonary fibrosis model. Considering these results, we propose that eperisone may be safer and more therapeutically beneficial for IPF patients than current therapies.

Anti-Inflammatory, Antioxidant, and Antifibrotic Effects of Gingival-Derived MSCs on Bleomycin-Induced Pulmonary Fibrosis in Mice

BACKGROUND

Mesenchymal stem cell (MSC) intervention has been associated with lung protection. We attempted to determine whether mouse gingival-derived mesenchymal stem cells (GMSCs) could protect against bleomycin-induced pulmonary fibrosis.

METHODS

Mice were divided into three groups: control (Con), bleomycin (Bl), and bleomycin + MSCs (Bl + MSCs). Mice were treated with 5 mg/kg bleomycin via transtracheal instillation to induce pulmonary fibrosis. We assessed the following parameters: histopathological severity of injury in the lung, liver, kidney, and aortic tissues; the degree of pulmonary fibrosis; pulmonary inflammation; pulmonary oedema; profibrotic factor levels in bronchoalveolar lavage fluid (BALF) and lung tissue; oxidative stress-related indicators and apoptotic index in lung tissue; and gene expression levels of IL-1β, IL-8, TNF-α, lysophosphatidic acid (LPA), lysophosphatidic acid receptor 1 (LPA1), TGF-β, matrix metalloproteinase 9 (MMP-9), neutrophil elastase (NE), MPO, and IL-10 in lung tissue.

RESULTS

GMSC intervention attenuated bleomycin-induced pulmonary fibrosis, pulmonary inflammation, pulmonary oedema, and apoptosis. Bleomycin instillation notably increased expression levels of the IL-1β, IL-8, TNF-α, LPA, LPA1, TGF-β, MMP-9, NE, and MPO genes and attenuated expression levels of the IL-10 gene in lung tissue, and these effects were reversed by GMSC intervention. Bleomycin instillation notably upregulated MDA and MPO levels and downregulated GSH and SOD levels in lung tissue, and these effects were reversed by GMSC intervention. GMSC intervention prevented upregulation of neutrophil content in the lung, liver, and kidney tissues and the apoptotic index in lung tissue.

CONCLUSIONS

GMSC intervention exhibits anti-inflammatory and antioxidant capacities. Deleterious accumulation of neutrophils, which is reduced by GMSC intervention, is a key component of bleomycin-induced pulmonary fibrosis. GMSC intervention impairs bleomycin-induced NE, MMP-9, LPA, APL1, and TGF-β release.

Modulation of COX-2 and NADPH oxidase-4 by alpha-lipoic acid ameliorates busulfan-induced pulmonary injury in rats

Aims

This study aimed to explore the potential protective effect of α-lipoic acid on busulfan-induced pulmonary fibrosis in rats.

Main methods

Eighteen adult male rats were divided into 3 groups; control, busulfan, and busulfan plus α-lipoic acid groups. Lung index ratio, serum level of proinflammatory cytokine were assessed. The activities of antioxidant enzymes and lipid peroxidation products were estimated in the lung tissues in addition to the histopathological analyses. The deposition of the collagen in the lung tissues was evaluated by Sirius red staining. The expressions of α-smooth muscle actin (α-SMA), TNF-α, and Caspase 3 were determined immunohistochemically. The pulmonary expression of COX-2 and NOX-4 mRNA was assessed using qRT-PCR.

Key findings

Administration of ALA significantly protect the lung against BUS-induced pulmonary fibrosis, besides the upregulation of antioxidants, and downregulation of pro-inflammatory cytokines. Also, it reduced collagen deposition that associated with a decreased expression of α-SMA, TNF-α, and Caspase 3 in the lung tissues. Moreover, ALA significantly upregulated the expression of COX-2 concomitant with the downregulation of elevated NOX-4.

Significance

ALA attenuates the lung cytotoxicity of busulfan through its anti-inflammatory, anti-apoptotic, and antifibrotic effects that may be mediated by upregulation of COX-2 and downregulation of NOX-4.

Aerosol Delivery of Surfactant Liposomes for Management of Pulmonary Fibrosis: An Approach Supporting Pulmonary Mechanics

Excessive architectural re-modeling of tissues in pulmonary fibrosis due to proliferation of myofibroblasts and deposition of extracellular matrix adversely affects the elasticity of the alveoli and lung function. Progressively destructive chronic inflammatory disease, therefore, necessitates safe and effective non-invasive airway delivery that can reach deep alveoli, restore the surfactant function and reduce oxidative stress. We designed an endogenous surfactant-based liposomal delivery system of naringin to be delivered as an aerosol that supports pulmonary mechanics for the management of pulmonary fibrosis. Phosphatidylcholine-based liposomes showed 91.5 ± 2.4% encapsulation of naringin, with a mean size of 171.4 ± 5.8 nm and zeta potential of −15.5 ± 1.3 mV. Liposomes with the unilamellar structure were found to be spherical and homogeneous in shape using electron microscope imaging. The formulation showed surface tension of 32.6 ± 0.96 mN/m and was able to maintain airway patency of 97 ± 2.5% for a 120 s test period ensuring the effective opening of lung capillaries and deep lung delivery. In vitro lung deposition utilizing Twin Stage Impinger showed 79 ± 1.5% deposition in lower airways, and Anderson Cascade Impactor deposition revealed a mass median aerodynamic diameter of 2.35 ± 1.02 μm for the aerosolized formulation. In vivo efficacy of the developed formulation was analyzed in bleomycin-induced lung fibrosis model in rats after administration by the inhalation route. Lactate dehydrogenase activity, total protein content, and inflammatory cell infiltration in broncho-alveolar lavage fluid were substantially reduced by liposomal naringin. Oxidative stress was minimized as observed from levels of antioxidant enzymes. Masson’s Trichrome staining of lung tissue revealed significant amelioration of histological changes and lesser deposition of collagen. Overall results indicated the therapeutic potential of the developed non-invasive aerosol formulation for the effective management of pulmonary fibrosis.

You Say You Want a Resolution (of Fibrosis)

In pathological fibrosis, aberrant tissue remodeling with excess extracellular matrix leads to organ dysfunction and eventual morbidity. Diseases of fibrosis create significant global health and economic burdens and are often deadly. Although fibrosis has traditionally been thought of as an irreversible process, a growing body of evidence demonstrates that organ fibrosis can reverse in certain circumstances, especially if an underlying cause of injury can be removed. This body of evidence has uncovered more and more contributors to persistent and nonresolving tissue fibrosis. Here, we review the present knowledge on resolution of organ fibrosis and restoration of near-normal tissue architecture. We emphasize three critical areas of tissue homeostasis that are necessary for fibrosis resolution, namely, the elimination of matrix-producing cells, the clearance of excess matrix, and the regeneration of normal tissue constituents. In so doing, we also highlight how profibrotic pathways interact with one another and where there may be therapeutic opportunities to intervene and remediate pathological persistent fibrosis.

Nutraceuticals as potential therapeutics for vesicant-induced pulmonary fibrosis

Exposure to vesicants, including sulfur mustard and nitrogen mustard, causes damage to the epithelia of the respiratory tract and the lung. With time, this progresses to chronic disease, most notably, pulmonary fibrosis. The pathogenic process involves persistent inflammation and the release of cytotoxic oxidants, cytokines, chemokines, and profibrotic growth factors, which leads to the collapse of lung architecture, with fibrotic involution of the lung parenchyma. At present, there are no effective treatments available to combat this pathological process. Recently, much interest has focused on nutraceuticals, substances derived from plants, herbs, and fruits, that exert pleiotropic effects on inflammatory cells and parenchymal cells that may be useful in reducing fibrogenesis. Some promising results have been obtained with nutraceuticals in experimental animal models of inflammation-driven fibrosis. This review summarizes the current knowledge on the putative preventive/therapeutic efficacy of nutraceuticals in progressive pulmonary fibrosis, with a focus on their activity against inflammatory reactions and profibrotic cell differentiation.

Carnosine and Lung Disease

Carnosine (β-alanyl-L-histidine) is a small dipeptide with numerous activities, including antioxidant effects, metal ion chelation, proton buffering capacity, and inhibitory effects on protein carbonylation and glycation. Carnosine has been mostly studied in organs where it is abundant, including skeletal muscle, cerebral cortex, kidney, spleen, and plasma. Recently, the effect of supplementation with carnosine has been studied in organs with low levels of carnosine, such as the lung, in animal models of influenza virus or lipopolysaccharide-induced acute lung injury and pulmonary fibrosis. Among the known protective effects of carnosine, its antioxidant effect has attracted increasing attention for potential use in treating lung disease. In this review, we describe the in vitro and in vivo biological and physiological actions of carnosine. We also report our recent study and discuss the roles of carnosine or its related compounds in organs where carnosine is present in only small amounts (especially the lung) and its protective mechanisms.

Baicalin alleviates bleomycin‑induced pulmonary fibrosis and fibroblast proliferation in rats via the PI3K/AKT signaling pathway

Baicalin is an important flavonoid compound THAT is isolated from the Scutellaria baicalensis Georgi Chinese herb and plays a critical role in anti‑oxidative, anti‑inflammatory, anti‑infection and anti‑tumor functions. Although baicalin can suppress the proliferation of tumor cells, the underlying mechanisms of baicalin in bleomycin (BLM)‑induced pulmonary fibrosis remain to be elucidated. Thus, the aim of the present study was to determine the role of baicalin in pulmonary fibrosis and fibroblast proliferation in rats. Hematoxylin and eosin (H&E) and Masson staining were used to measure the morphology of pulmonary fibrosis, ELIASA kits were used to test the ROS and inflammation, and western blotting and TUNEL were performed to study the apoptosis proteins. In vitro, MTT assay, flow cytometry, western blotting and immunofluorescence were performed to investigate the effects of baicalin on proliferation of fibroblasts. The most significantly fibrotic changes were identified in the lungs of model rats at day 28. Baicalin (50 mg/kg) attenuated the degree of pulmonary fibrosis, and the hydroxyproline content of the lung tissues was decreased in the baicalin group, compared with the BLM group. Further investigation revealed that baicalin significantly increased glutathione peroxidase (GSH‑px), total‑superoxide dismutase (T‑SOD) and glutathione (GSH) levels, whilst decreasing that of serum malondialdehyde (MDA). TUNEL‑positive cells were significantly decreased in rats treated with baicalin group, compared with the model group. Furthermore, it was found that BLM promoted fibroblasts viability in a dose‑dependent manner in vivo, which was restricted following treatment with different concentrations of baicalin. Moreover, BLM promoted the expression levels of cyclin A, D and E, proliferating cell nuclear antigen, phosphorylated (p)‑AKT and p‑calcium/calmodulin‑dependent protein kinase type. BLM also promoted the transition of cells from the G0/G1 phase to the G2/M and S phases, and increased the intracellular Ca2+ concentration, which was subsequently suppressed by baicalin. Collectively, the results of the present study suggested that baicalin exerted a suppressive effect on BLM‑induced pulmonary fibrosis and fibroblast proliferation.

Idebenone has preventative and therapeutic effects on pulmonary fibrosis via preferential suppression of fibroblast activity

Alveolar epithelial injury induced by reactive oxygen species (ROS) and abnormal collagen production by activated fibroblasts (myofibroblasts) is involved in the onset and exacerbation of idiopathic pulmonary fibrosis (IPF). Compared with alveolar epithelial cells, lung fibroblasts, especially myofibroblasts, exhibit an apoptosis-resistance phenotype (apoptosis paradox) that appears to be involved in IPF pathogenesis. Thus, we screened for chemicals eliciting preferential cytotoxicity of LL29 cells (lung fibroblasts from an IPF patient) compared with A549 cells (human lung alveolar epithelial cell line) from medicines already in clinical use. We identified idebenone, a synthetic analogue of coenzyme Q10 (CoQ₁₀, an antioxidant) that has been used clinically as a brain metabolic stimulant. Idebenone induced cell growth inhibition and cell death in LL29 cells at a lower concentration than in A549 cells, a feature that was not observed for other antioxidant molecules (such as CoQ₁₀) and two IPF drugs (pirfenidone and nintedanib). Administration of idebenone prevented bleomycin-induced pulmonary fibrosis and increased pulmonary ROS levels. Importantly, idebenone also improved pulmonary fibrosis and lung function when administered after the development of fibrosis, whereas administration of CoQ₁₀ similarly prevented bleomycin-induced pulmonary fibrosis, but had no effect after its development. Administration of idebenone, but not CoQ₁₀, suppressed bleomycin-induced increases in lung myofibroblasts. In vitro, treatment of LL29 cells with idebenone, but not CoQ₁₀, suppressed TGF-β–induced collagen production. These results suggest that in addition to antioxidant activity, idebenone exerts inhibitory activity on the function of lung fibroblasts, with the former activity being preventative and the latter therapeutic for bleomycin-induced fibrosis. Thus, we propose that idebenone may be more therapeutically beneficial for IPF patients than current treatments.

Catalase prevents myeloperoxidase self-destruction in response to oxidative stress

Catalase (CAT) and myeloperoxiase (MPO) are heme-containing enzymes that have attracted attention for their role in the etiology of numerous respiratory disorders such as cystic fibrosis, bronchial asthma, and acute hypoxemic respiratory failure. However, information regarding the interrelationship and competition between the two enzymes, free iron accumulation, and decreased levels of non-enzymatic antioxidants at sites of inflammation is still lacking. Myeloperoxidase catalyzes the generation of hypochlorous acid (HOCl) from the reaction of hydrogen peroxide (H₂O₂) and chloride (Cl^-). Self-generated HOCl has recently been proposed to auto-inhibit MPO through a mechanism that involves MPO heme destruction. Here, we investigate the interplay of MPO, HOCl, and CAT during catalysis, and explore the crucial role of MPO inhibitors and HOCl scavengers in protecting the catalytic site from protein modification of both enzymes against oxidative damage mediated by HOCl. We showed that CAT not only competes with MPO for H₂O₂ but also scavenges HOCl. The protective role provided by CAT versus the damaging effect provided by HOCl depends in part on the ratio between MPO/CAT and the affinity of the enzymes towards H₂O₂ versus HOCl. The severity of such damaging effects mainly depends on the ratio of HOCl to enzyme heme content. In addition to its effect in mediating protein modification and aggregation, HOCl oxidatively destroys the catalytic sites of the enzymes, which contain porphyrin rings and iron. Thus, modulation of MPO/CAT activities may be a fundamental feature of catalysis, and functions to down-regulate HOCl synthesis and prevent hemoprotein heme destruction and/or protein modification.

Melittin Exerts Beneficial Effects on Paraquat-Induced Lung Injuries In Mice by Modifying Oxidative Stress and Apoptosis

Melittin (MEL) is a 26-amino acid peptide with numerous biological activities. Paraquat (PQ) is one of the most widely used herbicides, although it is extremely toxic to humans. To date, PQ poisoning has no effective treatment, and therefore the current study aimed to assess for the first time the possible effects of MEL on PQ-induced lung injuries in mice. Mice received a single intraperitoneal (IP) injection of PQ (30 mg/kg), followed by IP treatment with MEL (0.1 and 0.5 mg/kg) twice per week for four consecutive weeks. Histological alterations, oxidative stress, and apoptosis in the lungs were studied. Hematoxylin and eosin (H&E) staining indicated that MEL markedly reduced lung injuries induced by PQ. Furthermore, treatment with MEL increased superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx) activity, and decreased malonaldehyde (MDA) and nitric oxide (NO) levels in lung tissue homogenates. Moreover, immunohistochemical staining showed that B-cell lymphoma-2 (Bcl-2) and survivin expressions were upregulated after MEL treatment, while Ki-67 expression was downregulated. The high dose of MEL was more effective than the low dose in all experiments. In summary, MEL efficiently reduced PQ-induced lung injuries in mice. Specific pharmacological examinations are required to determine the effectiveness of MEL in cases of human PQ poisoning.

Therapeutic effects of the rhSOD2-Hirudin fusion protein on bleomycin-induced pulmonary fibrosis in mice

Idiopathic pulmonary fibrosis (IPF) is a disease with a poor prognosis and high mortality, posing a major threat to human health. Increased levels of inflammatory cytokines, reactive oxygen species and coagulation cascade have been extensively reported in IPF. We previously fused Hirudin and human manganese superoxide dismutase (hSOD2) to generate a dual-feature fusion protein, denoted as rhSOD2-Hirudin fusion protein. In this study, 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) and Hydroxyproline (HYP) assays were used to investigate the effects of rhSOD2-Hirudin protein on thrombin-induced fibroblast proliferation and collagen accumulation in vitro. Subsequently, the mice model of pulmonary fibrosis induced by bleomycin was used for evaluating the anti-inflammatory and anti-fibrotic effects of rhSOD2-Hirudin protein in vivo. Results showed that rhSOD2-Hirudin protein could inhibit the proliferation of fibroblasts and reduce the HYP production in vitro by inhibiting the activity of thrombin. In vivo experiments showed that lung inflammation and fibrosis were significantly decreased in rhSOD2-Hirudin protein-treated mice. Furthermore, rhSOD2-Hirudin protein treatment reduced profibrotic protein and gene expression while reducing the number of inflammatory cells in the lung. In conclusion, rhSOD2-Hirudin protein can effectively attenuate pulmonary fibrosis in vitro and in vivo, mainly by inhibiting the activity of thrombin meanwhile increasing SOD2 levels prevent cells from being damaged by reactive oxygen species, thereby mitigating IPF progression. This study provided important information on the feasibility and efficacy of rhSOD2-Hirudin protein as a novel therapeutic agent for IPF.

Beneficial effects of Oltipraz, nuclear factor - erythroid - 2 - related factor 2 (Nrf2), on renal damage in unilateral ureteral obstruction rat model

Introduction:

We investigated whether Oltipraz (OPZ) attenuated renal fibrosis in a unilateral ureteral obstruction (UUO) rat model.

Materials and Methods:

We randomly divided 32 rats into four groups, each consisting of eight animals as follows: Rats in group 1 underwent a sham operation and received no treatment. Rats in group 2 underwent a sham operation and received OPZ. Rats in group 3 underwent unilateral ureteral ligation and received no treatment. Group 4 rats were subjected to unilateral ureteral ligation plus OPZ administration. Transforming growth factor beta-1 (TGF-β1), E-cadherin, nitric oxide (NO) and hydroxyproline levels were measured. Histopathological and immunohistochemical examinations were carried out.

Results:

TGF-β1, NO and E-cadherin levels in the UUO group were significantly higher than the sham group and these values were significantly different in treated groups compared to the UUO group. In rats treated with UUO + OPZ, despite the presence of mild tubular degeneration and less severe tubular necrosis, glomeruli maintained a better morphology when compared to the UUO group. Expressions of α-SMA in immunohistochemistry showed that the staining positivity decreased in the tubules of the OPZ-treated group.

Conclusions:

While the precise mechanism of action remains unknown, our results demonstrated that OPZ exerted a protective role in the UUO-mediated renal fibrosis rat model highlighting a promising therapeutic potency of Nrf2-activators for alleviating the detrimental effects of unilateral obstruction in kidneys.

Beneficial effects of ascorbic acid to treat lung fibrosis induced by paraquat

Paraquat (PQ) is one of the most widely employed herbicides that is used worldwide and it causes severe toxic effects in humans and animals. A PQ exposition can lead to pulmonary fibrosis (PF) and the mechanisms seem to be linked to oxidative stress, although other pathways have been suggested. Antioxidants can be useful as a therapy, although interventions with this kind of system are still controversial. Hence, this study has investigated the role of ascorbic acid (vitamin C) post-treatment on PQ-induced PF in male C57/BL6 mice. Pulmonary fibrosis was induced by a single PQ injection (10mg/kg; i.p.). The control group received a PQ vehicle. Seven days after the PQ or vehicle injections, the mice received vitamin C (150 mg/kg, ip, once a day) or the vehicle, over the following 7 days. Twenty-four hours after the last dose of vitamin C or the vehicle, the mice were euthanized and their bronchoalveolar lavage fluid (BALF) and their lungs were collected. The data obtained showed that vitamin C reduced the cellular recruitment, the secretion of IL-17 –a cytokine involved in neutrophils migration, TGF-β–a pro-fibrotic mediator and the collagen deposition. Moreover, vitamin C elevated the superoxide dismutase (SOD) and catalase levels, both antioxidant enzymes, but it did not alter the tracheal contractile response that was evoked by methacholine. Therefore, the researchers have highlighted the mechanisms of vitamin C as being non-invasive and have suggested it as a promising tool to treat lung fibrosis when it is induced by a PQ intoxication.

Reducing protein oxidation reverses lung fibrosis

Idiopathic pulmonary fibrosis is characterized by excessive deposition of collagen in the lung, leading to chronically impaired gas exchange and death1-3. Oxidative stress is believed to be critical in this disease pathogenesis4-6, although the exact mechanisms remain enigmatic. Protein S-glutathionylation (PSSG) is a post-translational modification of proteins that can be reversed by glutaredoxin-1 (GLRX)7. It remains unknown whether GLRX and PSSG play a role in lung fibrosis. Here, we explored the impact of GLRX and PSSG status on the pathogenesis of pulmonary fibrosis, using lung tissues from subjects with idiopathic pulmonary fibrosis, transgenic mouse models and direct administration of recombinant Glrx to airways of mice with existing fibrosis. We demonstrate that GLRX enzymatic activity was strongly decreased in fibrotic lungs, in accordance with increases in PSSG. Mice lacking Glrx were far more susceptible to bleomycin- or adenovirus encoding active transforming growth factor beta-1 (AdTGFB1)-induced pulmonary fibrosis, whereas transgenic overexpression of Glrx in the lung epithelium attenuated fibrosis. We furthermore show that endogenous GLRX was inactivated through an oxidative mechanism and that direct administration of the Glrx protein into airways augmented Glrx activity and reversed increases in collagen in mice with TGFB1- or bleomycin-induced fibrosis, even when administered to fibrotic, aged animals. Collectively, these findings suggest the therapeutic potential of exogenous GLRX in treating lung fibrosis.

F2-isoprostanes can mediate bleomycin-induced lung fibrosis

F₂-isoprostanes (F₂-IsoPs) have been considered markers of oxidative stress in various pulmonary diseases, but little is known about their possible role in pulmonary fibrosis. In this study, we have investigated the potential key role of F₂-IsoPs as markers and mediators of bleomycin (BLM)-induced pulmonary fibrosis in rats. During the in vivo study, plasma F₂-IsoPs showed a peak at 7 days and remained elevated for the entire experimental period. Lung F₂-IsoP content nearly tripled 7 days following the intratracheal instillation of BLM, and by 28 days, the value increased about fivefold compared to the controls. Collagen deposition correlated with F₂-IsoP content in the lung. Furthermore, from day 21 onwards, lung sections from BLM-treated animals showed α-smooth muscle actin (α-SMA) positive cells, which were mostly evident at 28 days. In vitro studies performed in rat lung fibroblasts (RLF) demonstrated that either BLM or F₂-IsoPs stimulated both cell proliferation and collagen synthesis. Moreover, RLF treated with F₂-IsoPs showed a significant increase of α-SMA expression compared to control, indicating that F₂-IsoPs can readily activate fibroblasts to myofibroblasts. Our data demonstrated that F₂-IsoPs can be mediators of key events for the onset and development of lung fibrosis, such as cell proliferation, collagen synthesis and fibroblast activation. Immunocytochemistry analysis, inhibition and binding studies demonstrated the presence of the thromboxane A₂ receptor (TP receptor) on lung fibroblasts and suggested that the observed effects may be elicited through the binding to this receptor. Our data added a new perspective on the role of F₂-IsoPs in lung fibrosis by providing evidence of a profibrotic role for these mediators in the pathogenesis of pulmonary fibrosis.

Protective and therapeutic effect of felodipine against bleomycin-induced pulmonary fibrosis in mice

Idiopathic pulmonary fibrosis (IPF) involves alveolar epithelial injury and abnormal collagen production caused by activated fibroblasts; transforming growth factor (TGF)-β1 is implicated in this activation. In this study, we screened for chemicals capable of inhibiting TGF-β1-induced collagen production in cultured fibroblasts from medicines already in clinical use. We selected felodipine based on its extent of collagen production inhibition, clinical safety profile, and other pharmacological activity. Felodipine is a dihydropyridine Ca²⁺ channel blocker that has been used clinically to treat patients with high blood pressure. Felodipine suppressed collagen production within LL29 cells in the presence of TGF-β1, but not in its absence. Intratracheal administration of felodipine prevented bleomycin-induced pulmonary fibrosis, alteration of lung mechanics and respiratory dysfunction. Felodipine also improved pulmonary fibrosis, as well as lung and respiratory function when administered after fibrosis development. Furthermore, administration of felodipine suppressed a bleomycin-induced increase in activated fibroblasts in the lung. We also found other dihydropyridine Ca²⁺ channel blockers (nifedipine and benidipine) inhibited collagen production in vitro and partially prevented bleomycin-induced pulmonary fibrosis, alteration of lung mechanics and respiratory dysfunction in vivo. We propose that these Ca²⁺ channel blockers may be therapeutically beneficial for IPF patients.

Sulforaphane prevents bleomycin‑induced pulmonary fibrosis in mice by inhibiting oxidative stress via nuclear factor erythroid 2‑related factor‑2 activation

Lung fibrosis is associated with inflammation, apoptosis and oxidative damage. The transcription factor nuclear factor erythroid 2-related factor-2 (Nrf2) prevents damage to cells from oxidative stress by regulating the expression of antioxidant proteins. Sulforaphane (SFN), an Nrf2 activator, additionally regulates excessive oxidative stress by promoting the expression of endogenous antioxidants. The present study investigated if SFN protects against lung injury induced by bleomycin (BLM). The secondary aim of the present study was to assess if this protection mechanism involves upregulation of Nrf2 and its downstream antioxidants. Pulmonary fibrosis was induced in C57/BL6 mice by intratracheal instillation of BLM. BLM and age-matched control mice were treated with or without a daily dose of 0.5 mg/kg SFN until sacrifice. On days 7 and 28, mice were assessed for induction of apoptosis, inflammation, fibrosis, oxidative damage and Nrf2 expression in the lungs. The lungs were investigated with histological techniques including haematoxylin and eosin staining, Masson's trichrome staining and terminal deoxynucleotidyl transferase UTP nick end labeling. Inflammatory, fibrotic and apoptotic processes were confirmed by western blot analysis for interleukin-1β, tumor necrosis factor-α, transforming growth factor-β and caspase-3 protein expressions. Furthermore, protein levels of 3-nitro-tyrosine, 4-hydroxynonenal, superoxide dismutase 1 and catalase were investigated by western blot analysis. It was demonstrated that pulmonary fibrosis induced by BLM significantly increased apoptosis, inflammation, fibrosis and oxidative stress in the lungs at days 7 and 28. Notably, SFN treatment significantly attenuated the infiltration of the inflammatory cells, collagen accumulation, epithelial cell apoptosis and oxidative stress in the lungs. In addition, SFN treatment increased expression of the Nrf2 gene and its downstream targets. In conclusion, these results suggested that SFN treatment of pulmonary fibrosis mouse models may attenuate alveolitis, fibrosis, apoptosis and lung oxidative stress by increasing the expression of antioxidant enzymes, including NAPDH quinone oxidoreductase, heme oxygenase-1, superoxide dismutase and catalase, via upregulation of Nrf2 gene expression. Thus, the results from the present study may facilitate the development of therapies for BLM-toxicity and pulmonary fibrosis.

Transforming growth factor β1 (TGFβ1)-induced CD44V6-NOX4 signaling in pathogenesis of idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is a progressive clinical syndrome of fatal outcome. The lack of information about the signaling pathways that sustain fibrosis and the myofibroblast phenotype has prevented the development of targeted therapies for IPF. Our previous study showed that isolated fibrogenic lung fibroblasts have high endogenous levels of the hyaluronan receptor, CD44V6 (CD44 variant containing exon 6), which enhances the TGFβ1 autocrine signaling and induces fibroblasts to transdifferentiate into myofibroblasts. NADPH oxidase 4 (NOX4) enzyme, which catalyzes the reduction of O₂ to hydrogen peroxide (H₂O₂), has been implicated in the cardiac and lung myofibroblast phenotype. However, whether CD44V6 regulates NOX4 to mediate tissue repair and fibrogenesis is not well-defined. The present study assessed the mechanism of how TGF-β-1-induced CD44V6 regulates the NOX4/reactive oxygen species (ROS) signaling that mediates the myofibroblast differentiation. Specifically, we found that NOX4/ROS regulates hyaluronan synthesis and the transcription of CD44V6 via an effect upon AP-1 activity. Further, CD44V6 is part of a positive-feedback loop with TGFβ1/TGFβRI signaling that acts to increase NOX4/ROS production, which is required for myofibroblast differentiation, myofibroblast differentiation, myofibroblast extracellular matrix production, myofibroblast invasion, and myofibroblast contractility. Both NOX4 and CD44v6 are up-regulated in the lungs of mice subjected to experimental lung injury and in cases of human IPF. Genetic (CD44v6 shRNA) or a small molecule inhibitor (CD44v6 peptide) targeting of CD44v6 abrogates fibrogenesis in murine models of lung injury. These studies support a function for CD44V6 in lung fibrosis and offer proof of concept for therapeutic targeting of CD44V6 in lung fibrosis disorders.

Tissue remodelling in pulmonary fibrosis

Many lung diseases result in fibrotic remodelling. Fibrotic lung disorders can be divided into diseases with known and unknown aetiology. Among those with unknown aetiology, idiopathic pulmonary fibrosis (IPF) is a common diagnosis. Because of its progressive character leading to a rapid decline in lung function, it is a fatal disease with poor prognosis and limited therapeutic options. Thus, IPF has motivated many studies in the last few decades in order to increase our mechanistic understanding of the pathogenesis of the disease. The current concept suggests an ongoing injury of the alveolar epithelium, an impaired regeneration capacity, alveolar collapse and, finally, a fibroproliferative response. The origin of lung injury remains elusive but a diversity of factors, which will be discussed in this article, has been shown to be associated with IPF. Alveolar epithelial type II (AE2) cells play a key role in lung fibrosis and their crucial role for epithelial regeneration, stabilisation of alveoli and interaction with fibroblasts, all known to be responsible for collagen deposition, will be illustrated. Whereas mechanisms of collagen deposition and fibroproliferation are the focus of many studies in the field, the awareness of other mechanisms in this disease is currently limited to biochemical and imaging studies including quantitative assessments of lung structure in IPF and animal models assigning alveolar collapse and collapse induration crucial roles for the degradation of the lung resulting in de-aeration and loss of surface area. Dysfunctional AE2 cells, instable alveoli and mechanical stress trigger remodelling that consists of collapsed alveoli absorbed by fibrotic tissue (i.e., collapse induration).

Bach1 siRNA attenuates bleomycin-induced pulmonary fibrosis by modulating oxidative stress in mice

Oxidative stress plays an essential role in inflammation and fibrosis. Bach1 is an important transcriptional repressor that acts by modulating oxidative stress and represents a potential target in the treatment of pulmonary fibrosis (PF). In this study, we knocked down Bach1 using adenovirus-mediated small interfering RNA (siRNA) to determine whether the use of Bach1 siRNA is an effective therapeutic strategy in mice with bleomycin (BLM)‑induced PF. Mouse lung fibroblasts (MLFs) were incubated with transforming growth factor (TGF)-β1 (5 ng/ml) and subsequently infected with recombined adenovirus-like Bach1 siRNA1 and Bach1 siRNA2, while an empty adenovirus vector was used as the negative control. The selected Bach1 siRNA with higher interference efficiency was used for the animal experiments. A mouse model of BLM-induced PF was established, and Bach1 siRNA (1x109 pfu) was administered to the mice via the tail vein. The results revealed that the Bach1 mRNA and protein levels were significantly downregulated by Bach1 siRNA. Furthermore, the MLFs infected with Bach1 siRNA exhibited increased mRNA and protein expression levels of heme oxygenase-1 and glutathione peroxidase 1, but decreased levels of TGF-β1 and interleukin-6 in the cell supernatants compared with the cells exposed to TGF-β1 alone. Bach1 knockdown by siRNA also enhanced the expression of antioxidant factors, but suppressed that of fibrosis‑related cytokines in mice compared with the BLM group. Finally, the inflammatory infiltration of alveolar and interstitial cells and the destruction of lung structure were significantly attenuated in the mide administered Bach1 siRNA compared with those in the BLM group. On the whole, our findings demonstrate that Bach1 siRNA exerts protective effects against BLM-induced PF in mice. Our data may provide the basis for the development of novel targeted therapeutic strategies for PF.

Earthworm extract attenuates silica-induced pulmonary fibrosis through Nrf2-dependent mechanisms

Silicosis is an occupational pulmonary fibrosis caused by inhalation of silica (SiO₂) and there are no ideal drugs to treat this disease. Earthworm extract (EE), a natural nutrient, has been reported to have anti-inflammatory, antioxidant, and anti-apoptosis effects. The purpose of the current study was to test the protective effects of EE against SiO₂-induced pulmonary fibrosis and to explore the underlying mechanisms using both in vivo and in vitro models. We found that treatment with EE significantly reduced lung inflammation and fibrosis and improved lung structure and function in SiO₂-instilled mice. Further mechanistic investigations revealed that EE administration markedly inhibited SiO₂-induced oxidative stress, mitochondrial apoptotic pathway, and epithelial-mesenchymal transition in HBE and A549 cells. Furthermore, we demonstrate that Nrf2 activation partly mediates the interventional effects of EE against SiO₂-induced pulmonary fibrosis. Our study has identified EE to be a potential anti-oxidative, anti-inflammatory, and anti-fibrotic drug for silicosis.

Long-term treatment with royal jelly improves bleomycin-induced pulmonary fibrosis in rats

This study investigated the anti-fibrotic potential of royal jelly (RJ) powder against bleomycin-induced pulmonary fibrosis in rats. The rats were given RJ orally (25, 50, and 100 mg/kg per day) for 7 consecutive days before the administration of single intratracheal instillation of bleomycin (BLM) at 7.5 IU/kg. RJ doses were continued for 21 days after BLM exposure. Fibrotic changes in the lungs were studied by cell count and analysis of cytokine levels in the bronchoalveolar lavage fluid (BALF), histopathological examination, and assaying oxidative stress biomarkers in lung tissue. The results showed that BLM administration significantly increased the fibrotic changes, collagen content, and levels of malondialdehyde and decreased total thiol and glutathione peroxidase antioxidant contents in the rats' lung tissue. An increase in the level of cell counts and pro-inflammatory and pro-fibrotic cytokines such as TNF-α and TGF-β in BALF was observed. Also, it significantly decreased IFN-γ, an anti-fibrotic cytokine, in BALF. However, RJ (50 and 100 mg/kg) reversed all of these biochemical indices as well as histopathological alterations induced by BLM. The present study demonstrates that RJ, by its antioxidant and anti-inflammatory properties, attenuates oxidative damage and fibrosis induced by BLM.

Redox mechanisms in age-related lung fibrosis

Redox signaling and oxidative stress are associated with tissue fibrosis and aging. Aging is recognized as a major risk factor for fibrotic diseases involving multiple organ systems, including that of the lung. A number of oxidant generating enzymes are upregulated while antioxidant defenses are deficient with aging and cellular senescence, leading to redox imbalance and oxidative stress. However, the precise mechanisms by which redox signaling and oxidative stress contribute to the pathogenesis of lung fibrosis are not well understood. Tissue repair is a highly regulated process that involves the interactions of several cell types, including epithelial cells, fibroblasts and inflammatory cells. Fibrosis may develop when these interactions are dysregulated with the acquisition of pro-fibrotic cellular phenotypes. In this review, we explore the roles of redox mechanisms that promote and perpetuate fibrosis in the context of cellular senescence and aging.

Pathophysiology of gadolinium-associated systemic fibrosis

Systemic fibrosis from gadolinium-based magnetic resonance imaging contrast is a scourge for the afflicted. Although gadolinium-associated systemic fibrosis is a rare condition, the threat of litigation has vastly altered clinical practice. Most theories concerning the etiology of the fibrosis are grounded in case reports rather than experiment. This has led to the widely accepted conjecture that the relative affinity of certain contrast agents for the gadolinium ion inversely correlates with the risk of succumbing to the disease. How gadolinium-containing contrast agents trigger widespread and site-specific systemic fibrosis and how chronicity is maintained are largely unknown. This review highlights experimentally-derived information from our laboratory and others that pertain to our understanding of the pathophysiology of gadolinium-associated systemic fibrosis.

Lung extracellular matrix and redox regulation

Pulmonary fibrosis affects millions worldwide and, even though there has been a significant investment in understanding the processes involved in wound healing and maladaptive repair, a complete understanding of the mechanisms responsible for lung fibrogenesis eludes us, and interventions capable of reversing or halting disease progression are not available. Pulmonary fibrosis is characterized by the excessive expression and uncontrolled deposition of extracellular matrix (ECM) proteins resulting in erosion of the tissue structure. Initially considered an 'end-stage' process elicited after injury, these events are now considered pathogenic and are believed to contribute to the course of the disease. By interacting with integrins capable of signal transduction and by influencing tissue mechanics, ECM proteins modulate processes ranging from cell adhesion and migration to differentiation and growth factor expression. In doing so, ECM proteins help orchestrate complex developmental processes and maintain tissue homeostasis. However, poorly controlled deposition of ECM proteins promotes inflammation, fibroproliferation, and aberrant differentiation of cells, and has been implicated in the pathogenesis of pulmonary fibrosis, atherosclerosis and cancer. Considering their vital functions, ECM proteins are the target of investigation, and oxidation-reduction (redox) reactions have emerged as important regulators of the ECM. Oxidative stress invariably accompanies lung disease and promotes ECM expression directly or through the overproduction of pro-fibrotic growth factors, while affecting integrin binding and activation. In vitro and in vivo investigations point to redox reactions as targets for intervention in pulmonary fibrosis and related disorders, but studies in humans have been disappointing probably due to the narrow impact of the interventions tested, and our poor understanding of the factors that regulate these complex reactions. This review is not meant to provide a comprehensive review of this field, but rather to highlight what has been learned and to raise interest in this area in need of much attention.

The Protective Effect of Naringin against Bleomycin-Induced Pulmonary Fibrosis in Wistar Rats

The aim of the current study was to investigate the protective effect of naringin on bleomycin-induced pulmonary fibrosis in rats. Twenty-four Wistar rats randomly divided into four groups (control, bleomycin alone, bleomycin + naringin 40, and bleomycin + naringin 80) were used. Rats were administered a single dose of bleomycin (5 mg/kg; via the tracheal cannula) alone or followed by either naringin 40 mg/kg (orally) or naringin 80 mg/kg (orally) or water (1 mL, orally) for 14 days. Rats and lung tissue were weighed to determine the lung index. TNF-α and IL-1β levels, hydroxyproline content, and malondialdehyde (MDA) levels were assayed. Glutathione peroxidase (GSH-Px) and superoxide dismutase (SOD) activities were determined. Tissue sections were stained with hematoxylin-eosin, Masson's trichrome, and 0.1% toluidine blue. TNF-α, IL-1β, and MDA levels and hydroxyproline content significantly increased (p < 0.01) and GPx and SOD activities significantly decreased in bleomycin group (p < 0.01). Naringin at a dose of 80 mg/kg body weight significantly decreased TNF-α and IL-1β activity, hydroxyproline content, and MDA level (p < 0.01) and increased GPx and SOD activities (p < 0.05). Histological evidence supported the results. These results show that naringin has the potential of reducing the toxic effects of bleomycin and may provide supportive therapy for conventional treatment methods for idiopathic pulmonary fibrosis.

Decreased VEGF Level Is Associated with Elevated Ferritin Concentration in Bronchoalveolar Lavage Fluid of Children with Interstitial Lung Diseases

BACKGROUND

A decreased level of vascular endothelial growth factor (VEGF) was previously described in bronchoalveolar lavage fluid (BALF) of adults with interstitial lung diseases (ILD) due to bronchial epithelial cell apoptosis and its proteolytic degradation. Elevated intrapulmonary ferritin was produced by alveolar cells that promoted oxidative injury in such patients.

OBJECTIVES

In this study, we analyzed the concentrations of VEGF and ferritin in BALF samples of ILD children and studied the relationship between their levels and the degree of inflammation.

METHODS

BALF and serum concentration of VEGF as well as ferritin and albumin in BALF samples were measured using enzyme-linked immunosorbent assay in children with idiopathic interstitial pneumonia (n = 16), hypersensitivity pneumonitis (n = 11) and idiopathic pulmonary hemosiderosis (n = 3). Twenty-four age- and gender-matched subjects with suspicious foreign body aspiration served as a control group.

RESULTS

VEGF per albumin levels in BALF were significantly decreased in ILD children compared to controls (1,075 [784-1,415] pg/mg albumin vs. 2,741 [1,131-4,660] pg/mg albumin, p = 0.0008). These values showed a significant negative correlation with inflammatory markers of total immune cell count in BALF (r = -0.411, p = 0.002) and serum C-reactive protein (r = -0.367, p = 0.006). Although serum VEGF was augmented in ILD children versus controls, no difference was observed among the ILD groups. In addition, BALF ferritin/albumin level (688 [188-1,571] ng/mg albumin vs. 256 [178-350] ng/mg albumin, p = 0.022) was significantly higher than normal in ILD individuals, especially in idiopathic pulmonary hemosiderosis.

CONCLUSION

Depressed VEGF and increased ferritin in BALF may reflect the severity of chronic pulmonary inflammation in altered respiratory epithelium of childhood ILD.

Total Glucosides of Danggui Buxue Tang Attenuate BLM-Induced Pulmonary Fibrosis via Regulating Oxidative Stress by Inhibiting NOX4

Pulmonary fibrosis (PF) is a serious chronic lung disease with unknown pathogenesis. Researches have confirmed that oxidative stress which is regulated by NADPH oxidase-4 (NOX4), a main source of reactive oxygen species (ROS), is an important molecular mechanism underlying PF. Previous studies showed that total glucosides of Danggui Buxue Tang (DBTG), an extract from a classical traditional Chinese herbal formula, Danggui Buxue Tang (DBT), attenuated bleomycin-induced PF in rats. However, the mechanisms of DBTG are still not clear. We hypothesize that DBTG attenuates PF through regulating the level of oxidative stress by inhibiting NOX4. And we found that fibrosis indexes hydroxyproline (HYP) and type I collagen (Col-I) were lower in DBTG groups compared with the model group. In addition, the expression of transforming growth factor-β1 (TGF-β1) and expression of alpha smooth muscle actin (α-SMA) were also much more decreased than the model group. For oxidative stress indicators, DBTG blunted the decrease of superoxide dismutase (SOD) activity, total antioxidant capacity (T-AOC), and the increase in malondialdehyde (MDA), 8-iso-prostaglandin in lung homogenates. Treatment with DBTG restrained the expression of NOX4 compared to the model group. Present study confirms that DBTG inhibits BLM-induced PF by modulating the level of oxidative stress via suppressing NOX4.

Naja naja atra venom ameliorates pulmonary fibrosis by inhibiting inflammatory response and oxidative stress

BACKGROUND

Naja naja atra venom (NNAV) displays diverse pharmacological actions including analgesia, anti-inflammation and immune regulation.In this study, we investigated the effects of NNAV on pulmonary fibrosis and its mechanisms of action.

METHODS

To determine if Naja naja atra venom (NNAV) can produce beneficial effects on pulmonary fibrosis, two marine models of pulmonary fibrosis were produced with bleomycin (BLM) and lipopolysaccharide (LPS). NNAV (30, 90, 270 μg/kg) was orally administered once a day started five days before BLM and LPS until to the end of experiment. The effects of NNAV treatment on pulmonary injury were evaluated with arterial blood gas analysis, hydroxyproline (HYP) content assessment and HE/Masson staining. The effects of NNAV treatment on inflammatory related cytokines, fibrosis related TGF-β/Smad signaling pathway and oxidative stress were examined.

RESULTS

The results showed that NNAV improved the lung gas-exchange function and attenuated the fibrotic lesions in lung. NNAV decreased IL-1β and TNF-α levels in serum in both pulmonary fibrosis models. NNAV inhibited the activation of NF-κB in LPS-induced and TGF-β/Smad pathway in BLM-induced pulmonary fibrosis. Additionally, NNAV also increased the levels of SOD and GSH and reduced the levels of MDA in BLM-induced pulmonary fibrosis model.

CONCLUSIONS

The present study indicates that NNAV attenuates LPS- and BLM-induced lung fibrosis. Its mechanisms of action are associated with inhibiting inflammatory response and oxidative stress. The study suggests that NNAV might be a potential therapeutic drug for treatment of pulmonary fibrosis.

Plasminogen activator inhibitor 1, fibroblast apoptosis resistance, and aging-related susceptibility to lung fibrosis

Idiopathic pulmonary fibrosis (IPF) is a fatal lung disorder with unknown cause and no effective treatment. The incidence of and mortality from IPF increase with age, suggesting that advanced age is a major risk factor for IPF. The mechanism underlying the increased susceptibility of the elderly to IPF, however, is unknown. In this study, we show for the first time that the protein level of plasminogen activator inhibitor 1 (PAI-1), a protease inhibitor which plays an essential role in the control of fibrinolysis, was significantly increased with age in mouse lung homogenate and lung fibroblasts. Upon bleomycin challenge, old mice experienced augmented PAI-1 induction and lung fibrosis as compared to young mice. Most interestingly, we show that fewer (myo)fibroblasts underwent apoptosis and more (myo)fibroblasts with increased level of PAI-1 accumulated in the lung of old than in young mice after bleomycin challenge. In vitro studies further demonstrate that fibroblasts isolated from lungs of old mice were resistant to H2O2 and tumor necrosis factor alpha-induced apoptosis and had augmented fibrotic responses to TGF-β1, compared to fibroblasts isolated from young mice. Inhibition of PAI-1 activity with a PAI-1 inhibitor, on the other hand, eliminated the aging-related apoptosis resistance and TGF-β1 sensitivity in isolated fibroblasts. Moreover, we show that knocking down PAI-1 in human lung fibroblasts with PAI-1 siRNA significantly increased their sensitivity to apoptosis and inhibited their responses to TGF-β1. Together, the results suggest that increased PAI-1 expression may underlie the aging-related sensitivity to lung fibrosis in part by protecting fibroblasts from apoptosis.

A translational preclinical model of interstitial pulmonary fibrosis and pulmonary hypertension: mechanistic pathways driving disease pathophysiology

Idiopathic pulmonary fibrosis (IPF) is a chronic progressive interstitial lung disease, in which a decline in patient prognosis is frequently associated with the onset of pulmonary hypertension (PH). Animal models exhibiting principle pathophysiological features of IPF and PH could provide greater insight into mechanistic pathways underlying disease progression and a means for evaluating novel therapeutic approaches for intervention. Here, we describe an in vivo disease model, in which animals develop progressive interstitial pulmonary fibrosis and associated PH, as defined by the presence of fibrotic foci adjacent to areas of alveolar injury and remodeling of the pulmonary vasculature. Associated changes in physiological parameters included a decline in lung function and increase in mean pulmonary arterial pressure (mPAP) >25 mmHg. The early fibrotic pathology is associated with a profibrogenic microenvironment, elevated levels of the matrix metalloproteases, MMP-2, MMP-7, and MMP-12, TIMP-1, the chemoattractant and mitogen, PDGF-β, and the chemokines CCL2 and CXCL12, that are associated with the recruitment of macrophages, mast cells, and fibrocytes. Principle mechanistic pathways associated with disease pathogenesis are upregulated in the lungs and pulmonary arteries, with sustained increases in gene transcripts for the profibrotic mediator TGF-β1 and components of the TGF-β signaling pathway; PAI-1, Nox-4, and HIF-1α. Therapeutic treatment with the ALK-5/TGF-β RI inhibitor SB-525334 reversed established pulmonary fibrosis and associated vascular remodeling, leading to normalization in clinically translatable physiological parameters including lung function and hemodynamic measurements of mPAP. These studies highlight the application of this model in validating potential approaches for targeting common mechanistic pathways driving disease pathogenesis.

The mitochondrial cardiolipin remodeling enzyme lysocardiolipin acyltransferase is a novel target in pulmonary fibrosis

RATIONALE

Lysocardiolipin acyltransferase (LYCAT), a cardiolipin-remodeling enzyme regulating the 18:2 linoleic acid pattern of mammalian mitochondrial cardiolipin, is necessary for maintaining normal mitochondrial function and vascular development. We hypothesized that modulation of LYCAT expression in lung epithelium regulates development of pulmonary fibrosis.

OBJECTIVES

To define a role for LYCAT in human and murine models of pulmonary fibrosis.

METHODS

We analyzed the correlation of LYCAT expression in peripheral blood mononuclear cells (PBMCs) with the outcomes of pulmonary functions and overall survival, and used the murine models to establish the role of LYCAT in fibrogenesis. We studied the LYCAT action on cardiolipin remodeling, mitochondrial reactive oxygen species generation, and apoptosis of alveolar epithelial cells under bleomycin challenge.

MEASUREMENTS AND MAIN RESULTS

LYCAT expression was significantly altered in PBMCs and lung tissues from patients with idiopathic pulmonary fibrosis (IPF), which was confirmed in two preclinical murine models of IPF, bleomycin- and radiation-induced pulmonary fibrosis. LYCAT mRNA expression in PBMCs directly and significantly correlated with carbon monoxide diffusion capacity, pulmonary function outcomes, and overall survival. In both bleomycin- and radiation-induced pulmonary fibrosis murine models, hLYCAT overexpression reduced several indices of lung fibrosis, whereas down-regulation of native LYCAT expression by siRNA accentuated fibrogenesis. In vitro studies demonstrated that LYCAT modulated bleomycin-induced cardiolipin remodeling, mitochondrial membrane potential, reactive oxygen species generation, and apoptosis of alveolar epithelial cells, potential mechanisms of LYCAT-mediated lung protection.

CONCLUSIONS

This study is the first to identify modulation of LYCAT expression in fibrotic lungs and offers a novel therapeutic approach for ameliorating lung inflammation and pulmonary fibrosis.

Passion fruit peel extract attenuates bleomycin-induced pulmonary fibrosis in mice

Idiopathic pulmonary fibrosis is a progressive fatal lung disease characterized by excessive collagen deposition, with no effective treatments. We investigated the efficacy of natural products with high anti-inflammatory activity, such as passion fruit peel extract (PFPE), in a mouse model of bleomycin-induced pulmonary fibrosis (PF). C57BL/6J mice were subjected to a single intratracheal instillation of bleomycin to induce PF. Daily PFPE treatment significantly reduced loss of body mass and mortality rate in mice compared with those treated with bleomycin. While bleomycin-induced PF resulted in elevated total numbers of inflammatory cells, macrophages, lymphocytes, and neutrophils in bronchoalveolar lavage fluid on both days 7 and 21, PFPE administration significantly attenuated these phenomena compared with bleomycin group. On day 7, the decreased superoxide dismutase and myeloperoxidase activities observed in the bleomycin group were significantly restored with PFPE treatment. On day 21, enhanced hydroxyproline deposition in the bleomycin group was also suppressed by PFPE administration. PFPE treatment significantly attenuated extensive inflammatory cell infiltration and accumulation of collagen in lung tissue sections of bleomycin-induced mice on days 7 and 21, respectively. Our results indicate that administration of PFPE decreased bleomycin-induced PF because of anti-inflammatory and antioxidant activities.

An inhibitor of NADPH oxidase-4 attenuates established pulmonary fibrosis in a rodent disease model

Idiopathic pulmonary fibrosis is a chronic progressive disease of increasing prevalence for which there is no effective therapy. Increased oxidative stress associated with an oxidant-antioxidant imbalance is thought to contribute to disease progression. NADPH oxidases (Nox) are a primary source of reactive oxygen species within the lung and cardiovascular system. We demonstrate that the Nox4 isoform is up-regulated in the lungs of patients with IPF and in a rodent model of bleomycin-induced pulmonary fibrosis and vascular remodeling. Nox4 is constitutively active, and therefore increased expression levels are likely to contribute to disease pathology. Using a small molecule Nox4/Nox1 inhibitor, we demonstrate that targeting Nox4 results in attenuation of an established fibrotic response, with reductions in gene transcripts for the extracellular matrix components collagen 1α1, collagen 3α1, and fibronectin and in principle pathway components associated with pulmonary fibrosis and hypoxia-mediated vascular remodeling: transforming growth factor (TGF)-β1, plasminogen activator inhibitor-1, hypoxia-inducible factor, and Nox4. TGF-β1 is a principle fibrotic mediator responsible for inducing up-regulation of profibrotic pathways associated with disease pathology. Using normal human lung-derived primary fibroblasts, we demonstrate that inhibition of Nox4 activity using a small molecule antagonist attenuates TGF-β1-mediated up-regulation in expression of profibrotic genes and inhibits the differentiation of fibroblast to myofibroblasts, that is associated with up-regulation in smooth muscle actin and acquisition of a contractile phenotype. These studies support the view that targeting Nox4 may provide a therapeutic approach for attenuating pulmonary fibrosis.

Comparative proteome analysis of lung tissue from patients with idiopathic pulmonary fibrosis (IPF), non-specific interstitial pneumonia (NSIP) and organ donors

Among the idiopathic interstitial pneumonias (IIP), the two entities IPF and NSIP seem to be clinically related, but NSIP has a better outcome. The proteomic signatures which distinguish NSIP from IPF remain still elusive. We therefore performed comparative proteomic analysis of peripheral lung tissue from patients with sporadic IPF (n=14) and fibrotic NSIP (fNSIP, n=8) and organ donors (Controls, n=10), by using the 2-dimensional DIGE technique and MALDI-TOF-MS. The study revealed that the proteomic profiles of IPF and fNSIP were quite similar. Among the upregulated proteins in IPF and fNSIP were stress-induced genes involved in the ER stress-pathway, whereas downregulated proteins in IPF and fNSIP included antiapoptotic factors and antifibrotic molecules. The comparison fNSIP versus IPF indicated upregulation of subunits of the proteasome activator complex and antioxidant enzymes of the peroxiredoxin family. We conclude, that only few protein expression changes exist between IPF and fNSIP, and that epithelial ER- and oxidative stress play a major role in the pathogenesis of both diseases. In contrast to IPF, intracellular clearance of ROS and misfolded protein carbonyls seem to be enhanced in fNSIP due to enhanced expression of antioxidant acting proteins, and may explain the better outcome and survival in patients with fNSIP.

BIOLOGICAL SIGNIFICANCE

IPF and fibrotic NSIP (fNSIP) belong to the idiopathic interstitial pneumonias and are usually fatal, but fNSIP has a better outcome. In order to identify molecular mechanisms and differences between IPF and fNSIP, we herein present results of a comparative proteome analysis of IPF, fNSIP and control lung tissue. Our data including validation experiments suggest that ER stress and a general stress-response as well as the decline of antioxidant capacity in alveolar epithelium is key in the pathogenesis of IPF and fNSIP. In addition, we could observe a signature of an increased alveolar epithelial protection against oxidative and ER-stress in fNSIP as compared to IPF, which could help to explain the better outcome of fNSIP patients.

Nuclear factor erythroid 2-related factor 2 nuclear translocation induces myofibroblastic dedifferentiation in idiopathic pulmonary fibrosis

AIMS

Oxidants have been implicated in the pathophysiology of idiopathic pulmonary fibrosis (IPF), especially in myofibroblastic differentiation. We aimed at testing the hypothesis that nuclear factor erythroid 2-related factor 2 (Nrf2), the main regulator of endogenous antioxidant enzymes, is involved in fibrogenesis via myofibroblastic differentiation. Fibroblasts were cultured from the lungs of eight controls and eight IPF patients. Oxidants-antioxidants balance, nuclear Nrf2 expression, and fibroblast phenotype (α-smooth muscle actin and collagen I expression, proliferation, migration, and contraction) were studied under basal conditions and after Nrf2 knockdown or activation by Nrf2 or Keap1 siRNA transfection. The effects of sulforaphane (SFN), an Nrf2 activator, on the fibroblast phenotype were tested under basal and pro-fibrosis conditions (transforming growth factor β [TGF-β]).

RESULTS

Decreased Nrf2 expression was associated with a myofibroblast phenotype in IPF compared with control fibroblasts. Nrf2 knockdown induced oxidative stress and myofibroblastic differentiation in control fibroblasts. Conversely, Nrf2 activation increased antioxidant defences and myofibroblastic dedifferentation in IPF fibroblasts. SFN treatment decreased oxidants, and induced Nrf2 expression, antioxidants, and myofibroblastic dedifferentiation in IPF fibroblasts. SFN inhibited TGF-β profibrotic deleterious effects in IPF and control fibroblasts and restored antioxidant defences. Nrf2 knockdown abolished SFN antifibrosis effects, suggesting that they were Nrf2 mediated.

INNOVATION AND CONCLUSION

Our findings confirm that decreased nuclear Nrf2 plays a role in myofibroblastic differentiation and that SFN induces human pulmonary fibroblast dedifferentiation in vitro via Nrf2 activation. Thus, Nrf2 could be a novel therapeutic target in IPF.

Thiol-redox antioxidants protect against lung vascular endothelial cytoskeletal alterations caused by pulmonary fibrosis inducer, bleomycin: comparison between classical thiol-protectant, N-acetyl-L-cysteine, and novel thiol antioxidant, N,N'-bis-2-mercaptoethyl isophthalamide

Lung vascular alterations and pulmonary hypertension associated with oxidative stress have been reported to be involved in idiopathic lung fibrosis (ILF). Therefore, here, we hypothesize that the widely used lung fibrosis inducer, bleomycin, would cause cytoskeletal rearrangement through thiol-redox alterations in the cultured lung vascular endothelial cell (EC) monolayers. We exposed the monolayers of primary bovine pulmonary artery ECs to bleomycin (10 µg) and studied the cytotoxicity, cytoskeletal rearrangements, and the macromolecule (fluorescein isothiocyanate-dextran, 70,000 mol. wt.) paracellular transport in the absence and presence of two thiol-redox protectants, the classic water-soluble N-acetyl-L-cysteine (NAC) and the novel hydrophobic N,N'-bis-2-mercaptoethyl isophthalamide (NBMI). Our results revealed that bleomycin induced cytotoxicity (lactate dehydrogenase leak), morphological alterations (rounding of cells and filipodia formation), and cytoskeletal rearrangement (actin stress fiber formation and alterations of tight junction proteins, ZO-1 and occludin) in a dose-dependent fashion. Furthermore, our study demonstrated the formation of reactive oxygen species, loss of thiols (glutathione, GSH), EC barrier dysfunction (decrease of transendothelial electrical resistance), and enhanced paracellular transport (leak) of macromolecules. The observed bleomycin-induced EC alterations were attenuated by both NAC and NBMI, revealing that the novel hydrophobic thiol-protectant, NBMI, was more effective at µM concentrations as compared to the water-soluble NAC that was effective at mM concentrations in offering protection against the bleomycin-induced EC alterations. Overall, the results of the current study suggested the central role of thiol-redox in vascular EC dysfunction associated with ILF.

Protective roles of Cordyceps on lung fibrosis in cellular and rat models

ETHNOPHARMACOLOGICAL RELEVANCE

Cordyceps sinensis is a fungus used in traditional Chinese medicine as a tonic to soothe the lung for the treatment of fatigue and respiratory diseases. Idiopathic pulmonary fibrosis is a chronic, irreversible and debilitating lung disease showing fibroblast/myofibroblast expansion and excessive deposition of extracellular matrix in the interstitium leading to breathing difficulty. Our previous observation revealed a partial relief of lung fibrosis in patients suffering from severe acute respiratory syndrome (SARS). We hypothesize that Cordyceps has beneficial effects on lung fibrosis and the objective of this study is to explore the target(s) of Cordyceps in the relief of lung fibrosis in animal and cell models and to gain insight into its underlying mechanisms.

MATERIAL AND METHODS

A rat model of bleomycin (BLM)-induced lung fibrosis and a fibrotic cell model with transforming growth factor beta-1 induction were employed in the studies.

RESULTS

Reduction of infiltration of inflammatory cells, deposition of fibroblastic loci and collagen, formation of reactive oxygen species, and production of cytokines, as well as recovery from imbalance of MMP-9/TIMP-1, were observed in fibrotic rats after treatment with Cordyceps in preventive (from the day of BLM administration) and therapeutic (from 14 days after BLM) regimens. In a fibrotic cell model with transforming growth factor beta-1 induction, the human lung epithelial A549 acquired a mesenchymal phenotype and an increase of vimentin expression with a concomitant decrease of E-cadherin. This epithelial-mesenchymal transition could be partially reverted by cordycepin, a major component of Cordyceps.

CONCLUSION

The findings provide an insight into the preventive and therapeutic potentials of Cordyceps for the treatment of lung fibrosis.