Glutathione regulates transforming growth factor-beta-stimulated collagen production in fibroblasts

The historical background of hereditary cystatin C amyloid angiopathy: Genealogical, pathological, and clinical manifestations

Hereditary cystatin C amyloid angiopathy (HCCAA) is an Icelandic disease that belongs to a disease class called cerebral amyloid angiopathy, a group of heterogenous diseases presenting with aggregation of amyloid complexes and deposition predominantly in the central nervous system. HCCAA is dominantly inherited, caused by L68Q mutation in the cystatin C gene, leading to aggregation of the cystatin C protein. HCCAA is a very progressive and severe disease, with widespread cerebral and parenchymal cystatin C and collagen IV deposition within the central nervous system (CNS) but also in other organs in the body, for example, in the skin. Most L68Q carriers have clinical symptoms characterized by recurrent hemorrhages and dementia, between the age of 20-30 years. If the carriers survive the first hemorrhage, the frequency and severity of the hemorrhages tend to increase, resulting in death at average of 30 years with mean number of major hemorrhages ranging from 3.2 to 3.9 over a 5-year average life span. The pathogenesis of the disease in carriers is very similar in the CNS and in the skin based on autopsy studies, thus skin biopsies can be used to monitor the progression of the disease by quantifying the cystatin C immunoreactivity. The cystatin C deposition always colocalizes with collagen IV and fibroblasts in the skin are found to be the main cell type responsible for the deposition of both proteins. No therapy is available for this devastating disease.

Advances in the Use of N-Acetylcysteine in Chronic Respiratory Diseases

N-acetylcysteine (NAC) is widely used because of its mucolytic effects, taking part in the therapeutic protocols of cystic fibrosis. NAC is also administered as an antidote in acetaminophen (paracetamol) overdosing. Thanks to its wide antioxidative and anti-inflammatory effects, NAC may also be of benefit in other chronic inflammatory and fibrotizing respiratory diseases, such as chronic obstructive pulmonary disease, bronchial asthma, idiopathic lung fibrosis, or lung silicosis. In addition, NAC exerts low toxicity and rare adverse effects even in combination with other treatments, and it is cheap and easily accessible. This article brings a review of information on the mechanisms of inflammation and oxidative stress in selected chronic respiratory diseases and discusses the use of NAC in these disorders.

Protective role of baicalin in the dynamic progression of lung injury to idiopathic pulmonary fibrosis: A meta-analysis

BACKGROUND AND PURPOSE

The pathological progression of lung injury (LI) to idiopathic pulmonary fibrosis (IPF) is a common feature of the development of lung disease. At present, effective strategies for preventing this progression are unavailable. Baicalin has been reported to specifically inhibit the progression of LI to IPF. Therefore, this meta-analysis aimed to assess its clinical application and its potential as a therapeutic drug for lung disease based on integrative analysis.

METHODS

We systematically searched preclinical articles in eight databases and reviewed them subjectively. The CAMARADES scoring system was used to assess the degree of bias and quality of evidence, whereas the STATA software (version 16.0 software) was used for statistical analysis, including a 3D analysis of the effects of dosage frequency of baicalin in LI and IPF. The protocol of this meta-analysis is documented in the PROSPERO database (CRD42022356152).

RESULTS

A total of 23 studies and 412 rodents were included after several rounds of screening. Baicalin was found to reduce the levels of TNF-α, IL-1β, IL-6, HYP, TGF-β and MDA and the W/D ratio and increase the levels of SOD. Histopathological analysis of lung tissue validated the regulatory effects of baicalin, and the 3D analysis of dosage frequency revealed that the effective dose of baicalin is 10-200 mg/kg. Mechanistically, baicalin can prevent the progression of LI to IPF by modulating p-Akt, p-NF-κB-p65 and Bcl-2-Bax-caspase-3 signalling. Additionally, baicalin is involved in signalling pathways closely related to anti-apoptotic activity and regulation of lung tissue and immune cells.

CONCLUSION

Baicalin at the dose of 10-200 mg/kg exerts protective effects against the progression of LI to IPF through anti-inflammatory and anti-apoptotic pathways.

Ferroptosis: a double-edged sword mediating immune tolerance of cancer

The term ferroptosis was put forward in 2012 and has been researched exponentially over the past few years. Ferroptosis is an unconventional pattern of iron-dependent programmed cell death, which belongs to a type of necrosis and is distinguished from apoptosis and autophagy. Actuated by iron-dependent phospholipid peroxidation, ferroptosis is modulated by various cellular metabolic and signaling pathways, including amino acid, lipid, iron, and mitochondrial metabolism. Notably, ferroptosis is associated with numerous diseases and plays a double-edged sword role. Particularly, metastasis-prone or highly-mutated tumor cells are sensitive to ferroptosis. Hence, inducing or prohibiting ferroptosis in tumor cells has vastly promising potential in treating drug-resistant cancers. Immunotolerant cancer cells are not sensitive to the traditional cell death pathway such as apoptosis and necroptosis, while ferroptosis plays a crucial role in mediating tumor and immune cells to antagonize immune tolerance, which has broad prospects in the clinical setting. Herein, we summarized the mechanisms and delineated the regulatory network of ferroptosis, emphasized its dual role in mediating immune tolerance, proposed its significant clinical benefits in the tumor immune microenvironment, and ultimately presented some provocative doubts. This review aims to provide practical guidelines and research directions for the clinical practice of ferroptosis in treating immune-resistant tumors.

Targeting Oxidative Stress as a Therapeutic Approach for Idiopathic Pulmonary Fibrosis

Idiopathic pulmonary fibrosis (IPF) is a chronic interstitial lung disease characterized by an abnormal reepithelialisation, an excessive tissue remodelling and a progressive fibrosis within the alveolar wall that are not due to infection or cancer. Oxidative stress has been proposed as a key molecular process in pulmonary fibrosis development and different components of the redox system are altered in the cellular actors participating in lung fibrosis. To this respect, several activators of the antioxidant machinery and inhibitors of the oxidant species and pathways have been assayed in preclinical in vitro and in vivo models and in different clinical trials. This review discusses the role of oxidative stress in the development and progression of IPF and its underlying mechanisms as well as the evidence of oxidative stress in human IPF. Finally, we analyze the mechanism of action, the efficacy and the current status of different drugs developed to inhibit the oxidative stress as anti-fibrotic therapy in IPF.

Histone methyltransferase SETDB1 inhibits TGF-β-induced epithelial-mesenchymal transition in pulmonary fibrosis by regulating SNAI1 expression and the ferroptosis signaling pathway

The epithelial-mesenchymal transition (EMT) is an important pathological process in the occurrence of pulmonary fibrosis. Changes in histone methylation modifications of key genes play an important role in this process. As a histone methyltransferase, the regulatory mechanism and role of SET domain bifurcated 1 (SETDB1) in pulmonary fibrosis remain unclear. We found that SETDB1 inhibited EMT and that cells attenuated the expression of SETDB1 to relieve this inhibition during transforming growth factor-β (TGF-β)-induced EMT. Silencing SETDB1 expression significantly enhanced the mesenchymal phenotype induced by TGF-β and the expression and deposition of fibronectin and significantly reduced the expression of E-cadherin. The decrease in E-cadherin expression and the induction of EMT led to increased lipid reactive oxygen species (ROS) and ferrous ions, which induced ferroptosis. Chromatin immunoprecipitation (ChIP) results showed that SETDB1 regulates the expression of Snai1 by catalyzing the histone H3 lysine 9 trimethylation (H3K9me3) of Snai1, the main transcription factor that initiates the process of EMT, and thus, indirectly regulates E-cadherin. Surprisingly, when examining the effect of overexpressed SETDB1 on EMT, we found that overexpressed SETDB1 alleviated EMT and also caused ferroptosis. We suggest that the overexpression of SETDB1 partially reverses the mesenchymal phenotype to an epithelial state, while those cells that fail to reverse are depleted by ferroptosis. In conclusion, the histone methylase SETDB1 regulates Snai1 epigenetically, driving EMT gene reprogramming and ferroptosis in response to TGF-β. However, there are unexplored links between the epigenetic reprogramming and transcriptional processes that regulate EMT in a TGF-β-dependent manner.

Relaxin as an anti-fibrotic treatment: Perspectives, challenges and future directions

Fibrosis refers to the scarring and hardening of tissues, which results from a failed immune system-coordinated wound healing response to chronic organ injury and which manifests from the aberrant accumulation of various extracellular matrix components (ECM), primarily collagen. Despite being a hallmark of prolonged tissue damage and related dysfunction, and commonly associated with high morbidity and mortality, there are currently no effective cures for its regression. An emerging therapy that meets several criteria of an effective anti-fibrotic treatment, is the recombinant drug-based form of the human hormone, relaxin (also referred to as serelaxin, which is bioactive in several other species). This review outlines the broad anti-fibrotic and related organ-protective roles of relaxin, mainly from studies conducted in preclinical models of ageing and fibrotic disease, including its ability to ameliorate several aspects of fibrosis progression and maturation, from immune cell infiltration, pro-inflammatory and pro-fibrotic cytokine secretion, oxidative stress, organ hypertrophy, cell apoptosis, myofibroblast differentiation and ECM production, to its ability to facilitate established ECM degradation. Studies that have compared and/or combined these therapeutic effects of relaxin with current standard of care medication have also been discussed, along with the main challenges that have hindered the translation of the anti-fibrotic efficacy of relaxin to the clinic. The review then outlines the future directions as to where scientists and several pharmaceutical companies that have recognized the therapeutic potential of relaxin are working towards, to progress its development as a treatment for human patients suffering from various fibrotic diseases.

A metabolomic approach to elucidate the inhibitory effects of baicalin in pulmonary fibrosis

CONTEXT

Baicalin, a major flavonoid extracted from Scutellaria baicalensis Georgi (Lamiaceae), has been shown to exert therapeutic effects on pulmonary fibrosis (PF).

OBJECTIVE

To use serum metabolomics combined with biochemical and histopathological analyses to clarify anti-PF mechanisms of baicalin on metabolic pathways and the levels of potential biomarkers.

MATERIALS AND METHODS

Forty male Sprague-Dawley rats were randomly divided into the control, PF model, prednisolone acetate-treated (4.2 mg/kg/day) and baicalin-treated (25 and 100 mg/kg/day) groups. A rat model of PF was established using a tracheal injection of bleomycin, and the respective drugs were administered intragastrically for 4 weeks. Histomorphology of lung tissue was examined after H&E and Masson's trichrome staining. Biochemical indicators including SOD, MDA and HYP were measured. Serum-metabonomic analysis based on UPLC-Q-TOF/MS was used to clarify the changes in potential biomarkers among different groups of PF rats.

RESULTS

Both doses of baicalin effectively alleviated bleomycin-induced pathological changes, and increased the levels of SOD (from 69.48 to 99.50 and 112.30, respectively), reduced the levels of MDA (from 10.91 to 5.0 and 7.53, respectively) and HYP (from 0.63 to 0.41 and 0.49, respectively). Forty-eight potential biomarkers associated with PF were identified. Meanwhile, the metabolic profiles and fluctuating metabolite levels were normalized or partially reversed after baicalin treatment. Furthermore, baicalin was found to improve PF potentially by the regulation of four key biomarkers involving taurine and hypotaurine metabolism, glutathione metabolism, and glycerophospholipid metabolism.

CONCLUSIONS

These findings revealed the anti-fibrotic mechanisms of baicalin and it may be considered as an effective therapy for PF.

Antifibrotic effects and mechanisms of mesenchymal stem cell-derived exosomes in a systemic sclerosis mouse model: Possible contribution of miR-196b-5p

BACKGROUND

Systemic sclerosis (SSc) is a connective tissue disorder characterized by the development of fibrosis in the skin and internal organs. Increasing evidence suggests that mesenchymal stem cells (MSCs) can be used to a treatment for fibrotic diseases. Recent studies have demonstrated that some of the biological effects of MSCs are due to the secretion of exosomes. However, the precise mechanisms underlying MSCs-derived exosomes in skin fibrosis are not well understood.

OBJECTIVE

We aimed to elucidate the effect of MSCs-derived exosomes on skin fibrosis in SSc and the mechanism underlying their inhibitory action on fibrosis.

METHODS

Exosome was collected from MSCs by ultracentrifugation method. We examined the suppressive effect of MSCs-derived exosome on skin fibrosis in bleomycin-induced SSc mouse model. Skin samples from the injected site were collected for further examination, and micro-RNA analysis of MSCs-derived exosome was performed.

RESULTS

Injection of MSCs-derived exosomes significantly inhibited bleomycin-induced dermal fibrosis in mice. MSCs-derived exosomes significantly reduced the amount of collagen and the number of α-SMA⁺ myofibroblasts and CD68⁺ macrophages in lesional skin. They also reduced the expression of type I collagen and TGF-β receptor 1 in fibroblasts in vitro. Moreover, micro-RNA analysis revealed that several microRNAs in MSCs-derived exosomes have antifibrotic potential. We confirmed that overexpression of miR-196b-5p in fibroblasts significantly suppressed collagen type I alpha 2 expression.

CONCLUSION

This study demonstrated that inhibition of collagen type I expression by miR-196b-5p in exosomes might be one of the mechanisms by which MSCs suppress skin fibrosis in an SSc mouse model.

Impacts of n-acetyl cysteine on gibberellic acid-induced hepatorenal dysfunction through modulation of pro-inflammatory cytokines, antifibrotic and antioxidant activity

The extensive usage of gibberellic acid (GA3) in agriculture and plant growth is generally associated with enormous human and public health hazards. The present research assesses the impact of n-acetyl cysteine (NAC) on the hepatorenal injury persuaded by GA3 for this purpose, After two weeks of adaptation twenty-four rats allocated into four groups (6 rats/group) as follows: control group, supplied with saline only; n-acetyl cysteine (NAC) group, provided with 150 mg/kg/bw by stomach tube (orally) dissolved in saline; Positive GA3 group, received GA3 (55 mg/kg/bw) orally; Protective group received NAC (150 mg/kg/bw) and GA3 (55 mg/kg/bw) as in NAC and GA3 groups. Rats received their treatments for consecutive 3 weeks. On day 22, rats were anesthetized, then euthanized. Blood and tissue samples were obtained for biochemical, antioxidants markers analysis, gene expression, and histopathological examination. Our results revealed significant changes in serum AST, ALT, urea, uric acid, total protein, and albumin levels with a substantial rise of MDA and NO concentration in GA3 treated rats along with a considerable decrease of the GSH and overexpression of the inflammatory hepatic and renal cytokines (IL-10, TNF-α, NOS) and fibrotic gene expression TGF-β1, and α-SMA, with boost expression of nuclear factor-kappa (NF_k B). NAC co-administered with GA3 significantly normalized the kidney and liver function and the antioxidant state, besides normal histological structure of both liver and kidney tissue and downregulated expression of the pro-inflammatory cytokines as well as, fibrogenic gene expression. PRACTICAL APPLICATIONS: The current study confirmed that GA3 induced hepto-renal dysfunction that was ameliorated by NAC administration. Moreover, our findings confirmed the antioxidant capability of n-acetyl cysteine and afford robust evidence about the ameliorative effect of the n-acetyl cysteine to attenuate the hepatorenal injury induced by gibberellic acid through modulation of the antioxidant defense system fibrogenic, and pro-inflammatory cytokines expression.

Dynamic thiol/disulphide homeostasis in patients with hypertrophic cardiomyopathy

BACKGROUND

In addition to the genetic complexity of hypertrophic cardiomyopathy (HCM), there must be other disease-modifying factors that contribute to its highly variable clinical and phenotypic expression. The authors aimed to investigate serum thiol/disulphide homeostasis as a proxy for oxidative stress using a novel automated assay in patients with HCM.

METHODS

This cross-sectional study was conducted on 119 patients with HCM and 52 without HCM. The methods used to measure dynamic thiol/disulphide homeostasis as calorimetric and duplex quantities were developed in 2014.

RESULTS

Median serum native thiol levels were significantly lower in patients with HCM than in those without (312.5 μmol/L [285-370 μmol/L] vs 421 μmol/L [349-469.5 μmol/L]; p < 0.001). Serum total thiol levels and disulphide levels were considerably lower than those in the control group ([844.68 ± 195.99 μmol/L vs 1158.92 ± 243.97 μmol/L; p < 0.001], [259.13 ± 65.66 μmol/L vs 375.02 ± 79.99 μmol/L; p < 0.001], respectively). Serum disulphide/native thiol ratios and disulphide/total thiol ratios were significantly lower in HCM patients than in controls (0.80 ± 0.09 vs 0.92 ± 0.05; p < 0.001 and 0.31 [0.30-0.32] vs 0.32 [0.32-0.33]; p < 0.001). Finally, reduced thiol ratios were higher and oxidized thiol ratios were significantly lower in patients with HCM than in controls.

CONCLUSIONS

Despite the fact that antioxidant capacity was impaired, the extracellular environment remained in a reducing state by keeping serum disulphide/native thiol ratios low. Therefore, the authors speculate that HCM may behave similarly to tumours with respect to serum thiol-disulphide levels.

LRRC8/VRAC channels exhibit a noncanonical permeability to glutathione, which modulates epithelial-to-mesenchymal transition (EMT)

Volume-regulated anion channels (VRAC) are chloride channels activated in response to osmotic stress to regulate cellular volume and also participate in other cellular processes, including cell division and cell death. Recently, members of the LRRC8 family have been identified as the main contributors of VRAC conductance. LRRC8/VRAC is permeable to chloride ions but also exhibits significant permeability to various substrates that vary strongly in charge and size. In this study, we explored the intriguing ability of LRRC8/VRAC to transport glutathione (GSH), the major cellular reactive oxygen species (ROS) scavenger, and its involvement in epithelial-to-mesenchymal transition (EMT), a cellular process in which cellular oxidative status is a crucial step. First, in HEK293-WT cells, we showed that a hypotonic condition induced LRRC8/VRAC-dependent GSH conductance (P_GSH/P_Cl of ~0.1) and a marked decrease in intracellular GSH content. GSH currents and GSH intracellular decrease were both inhibited by DCPIB, an inhibitor of LRRC8/VRAC, and were not observed in HEK293-LRRC8A KO cells. Then, we induced EMT by exposing renal proximal tubule epithelial cells to the pleiotropic growth factor TGFβ1, and we measured the contribution of LRRC8/VRAC in this process by measuring (i) EMT marker expression (assessed both at the gene and protein levels), (ii) cell morphology and (iii) the increase in migration ability. Interestingly, pharmacologic targeting of LRRC8/VRAC (DCPIB) or RNA interference-mediated inhibition (LRRC8A siRNA) attenuated the TGFβ1-induced EMT response by controlling GSH and ROS levels. Interestingly, TGFβ1 exposure triggered DCPIB-sensitive chloride conductance. These results suggest that LRRC8/VRAC, due to its native permeability to GSH and thus its ability to modulate ROS levels, plays a critical role in EMT and might contribute to other physiological and pathophysiological processes associated with oxidative stress.

Regulation of Transforming Growth Factor-β/Smad-mediated Epithelial-Mesenchymal Transition by Celastrol Provides Protection against Bleomycin-induced Pulmonary Fibrosis

The respiratory disease pulmonary fibrosis (PF), which is characterized by scar formation throughout the lung, imposes a serious health burden. No effective drug without side effects has been proven to prevent this fatal lung disease. In this context, this study was undertaken to elucidate the protective effect of celastrol, a quinine methide pentacyclic triterpenoid from a Chinese medicinal plant 'thunder god vine' against bleomycin (BLM)-induced PF. We also attempted to study how the cytokine transforming growth factor-β (TGF-β) stimulates fibrosis through the induction of epithelial-mesenchymal transition (EMT) and the role of celastrol in regulating EMT. TGF-β (5 ng/ml) was administered to human alveolar epithelial adenocarcinoma A549 cells to induce fibrotic response in cells. Induction of EMT was analysed in cells through morphological analysis and expression of epithelial and mesenchymal markers by Western blotting. Bleomycin at a concentration of 3 U/Kg b.w was used to induce fibrosis in adult male rat lungs. Celastrol (5 mg/kg b.w) was given to rats twice a week after BLM administration for a period of 28 days. Western blot and immunofluorescence analyses were performed with lung tissue sample to find out the potential of celastrol in regulating EMT during the progression of fibrosis. TGF-β induces EMT in A549 cells as demonstrated by changes in epithelial cell morphology and expression of epithelial and mesenchymal marker proteins. The expressions of epithelial marker proteins E-cadherin and claudin were found to be reduced in the BLM-induced group of rats. Expression of mesenchymal markers, such as N-cadherin, snail, slug, vimentin and β-catenin, was enhanced in BLM-induced rat lungs. Celastrol reverts these cellular changes in rat lungs, and it was found that celastrol regulates EMT through the inhibition of heat shock protein 90 (HSP 90). Together, the results indicate that EMT is a crucial phenomenon for the progression of fibrosis, and celastrol provides protection against PF through the regulation of EMT.

TGF-β1 stimulates HDAC4 nucleus-to-cytoplasm translocation and NADPH oxidase 4-derived reactive oxygen species in normal human lung fibroblasts

Myofibroblasts are important mediators of fibrogenesis; thus blocking fibroblast-to-myofibroblast differentiation (FMD) may be an effective strategy to treat pulmonary fibrosis (PF). Previously, we reported that histone deacetylase 4 (HDAC4) activity is necessary for transforming growth factor-β1 (TGF-β1)-induced human lung FMD. Here, we show that TGF-β1 increases NADPH oxidase 4 (NOX4) mRNA and protein expression in normal human lung fibroblasts (NHLFs) and causes nuclear export of HDAC4. Application of the NOX family inhibitor diphenyleneiodonium chloride reduces TGF-β1-induced HDAC4 nuclear export, expression of the myofibroblast marker α-smooth muscle actin (α-SMA), and α-SMA fiber formation. Inhibition of HDAC4 nucleus-to-cytoplasm translocation using leptomycin B (LMB) had little effect on α-SMA expression but blocked α-SMA fiber formation. A coimmunoprecipitation assay showed that HDAC4 associates with α-SMA. Moreover, LMB abolishes TGF-β1-induced α-SMA fiber formation and cell contraction. Relevant to human pulmonary fibrosis, idiopathic PF specimens showed significantly higher NOX4 RNA expression and scant HDAC4 staining within nuclei of fibroblast foci myofibroblasts. Taken together, these results indicate that reactive oxygen species promote TGF-β1-mediated myofibroblast differentiation and HDAC4 nuclear export. The physical association of HDAC4 with α-SMA suggests that HDAC4 has a role in regulating the α-SMA cytoskeleton arrangement.

GGsTOP increases migration of human periodontal ligament cells in vitro via reactive oxygen species pathway

GGsTOP is a novel and selective inhibitor of gamma-glutamyl transferase (GGT), a cell-surface enzyme that has a key role in glutathione homeostasis and the maintenance of cellular reactive oxygen species (ROS). ROS are essential for wound healing. However, little is known about the molecular mechanisms underlying the inhibition of GGT by GGsTOP in human periodontal ligament cells (hPLCs). The present study assessed GGT expression in mouse periodontal ligament tissues, GGT activity in hPLCs, and the potential physiological effect of GGsTOP on hPLC migration. Immunohistochemical analysis confirmed that GGT was widely expressed in mouse periodontal ligament tissue. Treatment with GGsTOP was associated with greater proliferation and migration of hPLCs, and higher levels of cellular ROS compared with untreated hPLCs. However, the increase in intracellular ROS was attenuated in hPLCs co-cultured with the anti-oxidant N-acetylcysteine (NAC), a precursor of glutathione. The higher ROS levels associated with GGsTOP treatment were in parallel with increases in the levels of type I collagen and alpha smooth muscle actin, which was inhibited in hPLCs co-cultured with NAC. Thus, GGsTOP may promote hPLC migration and participate in the maintenance of the periodontal ligament apparatus via the ROS pathway.

Targeting of Gamma-Glutamyl-Cysteine Ligase by miR-433 Reduces Glutathione Biosynthesis and Promotes TGF-β-Dependent Fibrogenesis

AIMS

Glutathione (GSH) is the main antioxidant against cell damage. Several pathological states course with reduced nucleophilic tone and perturbation of redox homeostasis due to changes in the 2GSH/GSSG ratio. Here, we investigated the regulation of the rate-limiting GSH biosynthetic heterodimeric enzyme γ-glutamyl-cysteine ligase (GCL) by microRNAs (miRNAs).

RESULTS

"In silico" analysis of the 3'- untranslated regions (UTRs) of both catalytic (GCLc) and regulatory (GCLm) subunits of GCL enabled an identification of miR-433 as a strong candidate for the targeting of GCL. Transitory overexpression of miR-433 in human umbilical vein endothelial cells (HUVEC) showed a downregulation of both GCLc and GCLm in a nuclear factor (erythroid-derived 2)-like 2 (Nrf2)-independent manner. Increases in pro-oxidant stimuli such as exposure to hydrogen peroxide or GSH depletion in endothelial and hepatic cells caused an expected increase in GCLc and GCLm protein expression and abrogation of miR-433 levels, thus supporting a cross-regulation of these pathways. Treatment of HUVEC with miR-433 resulted in reduced antioxidant and redox potentials, increased S-glutathionylation, and reduced endothelial nitric oxide synthase activation. In vivo models of renal and hepatic fibrosis were associated with transforming growth factor β1 (TGF-β1)-related reduction of GCLc and GCLm levels that were miR-433 dependent.

INNOVATION AND CONCLUSION

We describe for the first time an miRNA, miR-433, capable of directly targeting GCL and promoting functional consequences in endothelial physiology and fibrotic processes by decreasing GSH levels.

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

Association of Nrf2 with airway pathogenesis: lessons learned from genetic mouse models

Nrf2 is a key transcription factor for antioxidant response element (ARE)-bearing genes involved in diverse host defense functions including redox balance, cell cycle, immunity, mitochondrial biogenesis, energy metabolism, and carcinogenesis. Nrf2 in the airways is particularly essential as the respiratory system continuously interfaces with environmental stress. Since Nrf2 was determined to be a susceptibility gene for a model of acute lung injury, its protective capacity in the airways has been demonstrated in experimental models of human disorders using Nrf2 mutant mice which were susceptible to supplemental respiratory therapy (e.g., hyperoxia, mechanical ventilation), cigarette smoke, allergens, virus, environmental pollutants, and fibrotic agents compared to wild-type littermates. Recent studies also determined that Nrf2 is indispensable in developmental lung injury. While association studies with genetic NRF2 polymorphisms supported a protective role for murine Nrf2 in oxidative airway diseases, somatic NRF2 mutations enhanced NRF2-ARE responses, and were favorable for lung carcinogenesis and chemoresistance. Bioinformatic tools have elucidated direct Nrf2 targets as well as Nrf2-interacting networks. Moreover, potent Nrf2-ARE agonists protected oxidant-induced lung phenotypes in model systems, suggesting a therapeutic or preventive intervention. Further investigations on Nrf2 should yield greater understanding of its contribution to normal and pathophysiological function in the airways.

Effects of N-acetylcysteine on the cardiac remodeling biomarkers and major adverse events following acute myocardial infarction: a randomized clinical trial

AIMS

The aims of this study were to evaluate the effects of N-acetylcysteine (NAC) on cardiac remodeling and major adverse events following acute myocardial infarction (AMI).

METHODS

In a prospective, double-blind, randomized clinical trial, the effect of NAC on the serum levels of cardiac biomarkers was compared with that of placebo in 98 patients with AMI. Also, the patients were followed up for a 1-year period for major adverse cardiac events (MACE), including the occurrence of recurrent myocardial infarction, death, and need for target vessel revascularization.

RESULTS

In patients who received NAC, the serum levels of matrix metalloproteinase (MMP)-9 and MMP-2 after 72 h were significantly lower than those in the placebo group (p = 0.014 and p = 0.045, respectively). The length of hospitalization in patients who received NAC was significantly shorter than that in the placebo group (p = 0.024). With respect to MACE, there was a significant difference between those who received NAC (14 %) and those patients on placebo (25 %) (p = 0.024). Re-infarction took place in 4 % of patients in the NAC group as compared with 16.7 % in patients who received placebo (p = 0.007).

CONCLUSION

NAC can be beneficial in preventing early remodeling by reducing the level of MMP-2 and MMP-9. Moreover, NAC decreased the length of hospital stays in patients after AMI. By decreasing MACE, NAC could possibly be introduced as a 'magic bullet' in the pharmacotherapy of patients with AMI. Further studies are needed to elucidate NAC's role in this population.

Lycopene, a powerful antioxidant, significantly reduces the development of the adhesion phenotype

Postoperative adhesions are a common medical complication of gynecologic and other pelvic surgeries resulting in persistent pelvic pain, obstruction of the intestines, and even infertility. The molecular mechanisms of postoperative adhesion development remain to be elucidated. We have recently described a role for reactive oxygen species, specifically superoxide, in the development of postoperative adhesions. In this study, we sought to determine whether lycopene, a potent antioxidant, reduces markers characteristic of the adhesion phenotype. Primary fibroblast cultures from normal peritoneum and adhesion tissues were utilized to determine mRNA levels of adhesion phenotype markers type I collagen, transforming growth factor-beta 1 (TGF-β1), and vascular endothelial growth factor (VEGF) in response to lycopene (24 hours, 10 μM) treatment. There was a 2 (p < 0.003), 4.7 (p < 0.004), and 1.6 fold (p < 0.004) increase in mRNA levels of type I collagen, TGF-β1, and VEGF, respectively, in adhesion as compared to normal peritoneal fibroblasts. Lycopene treatment led to a 6.8 and a 12.4 fold decrease in type I collagen mRNA levels, in normal peritoneal and adhesion fibroblasts, respectively (p < 0.005). Lycopene treatment led to a 4.2 (p < 0.03) and a 4.6 (p < 0.05) fold decrease in VEGF mRNA levels, in normal peritoneal and adhesion fibroblasts, respectively. Lycopene treatment led to a 7.0 fold decrease in TGF-β1 mRNA levels, in adhesion fibroblasts (p < 0.03). A 1.9 fold decrease in TGF-β1 mRNA was observed in normal peritoneal fibroblasts in response to treatment, although it was not significant. Lycopene substantially reduced levels of adhesion phenotype markers in normal peritoneal and adhesion fibroblasts and whether it will reduce postoperative adhesions needs to be further investigated.

Regulation of ion transport by oxidants

Ion channels perform a variety of cellular functions in lung epithelia. Oxidant- and antioxidant-mediated mechanisms (that is, redox regulation) of ion channels are areas of intense research. Significant progress has been made in our understanding of redox regulation of ion channels since the last Experimental Biology report in 2003. Advancements include: 1) identification of nonphagocytic NADPH oxidases as sources of regulated reactive species (RS) production in epithelia, 2) an understanding that excessive treatment with antioxidants can result in greater oxidative stress, and 3) characterization of novel RS signaling pathways that converge upon ion channel regulation. These advancements, as discussed at the 2013 Experimental Biology Meeting in Boston, MA, impact our understanding of oxidative stress in the lung, and, in particular, illustrate that the redox state has profound effects on ion channel and cellular function.

Nimodipine rescues N-methyl-N-nitrosourea-induced retinal degeneration in rats

Background:

That nimodipine (NMD) is potentially useful for ophthalmic treatment. However, the effect of NMD is unknown on retinal degenerative diseases.

Objective:

The purpose of the present study was to investigate the effect of NMD on N-methyl-N-nitrosourea (MNU)-induced retinal degeneration (RD) and elucidate its possible mechanisms.

Materials and Methods:

Morphological observation of NMD on MNU-induced RD was evaluated by light microscopy and electron microscopy. Nonenzymatic antioxidant glutathione (GSH) was measured by a colorimetric method. Transforming growth factor-beta (TGF-β) was measured by enzyme-linked immunosorbent assay (ELISA). Telomerase was detected by reverse transcriptase polymerase chain reaction (RT-PCR).

Results:

The significantly protective effect of NMD on MNU-induced RD was demonstrated morphologically. NMD increased the content of GSH and decreased the level of TGF-β in rat retina. RT-PCR analysis demonstrated that NMD treatment significantly decreased mRNA level of telomerase.

Conclusion:

These data suggest that NMD inhibit MNU-induced RD in rats. The expressions of TGF-β, telomerase and GSH contents might partially contribute to its protective effects on MNU-induced RD.

Reactive oxygen species-targeted therapeutic interventions for atrial fibrillation

Atrial fibrillation (AF) is the most common arrhythmia that requires medical attention, and its incidence is increasing. Current ion channel blockade therapies and catheter ablation have significant limitations in treatment of AF, mainly because they do not address the underlying pathophysiology of the disease. Oxidative stress has been implicated as a major underlying pathology that promotes AF; however, conventional antioxidants have not shown impressive therapeutic effects. A more careful design of antioxidant therapies and better selection of patients likely are required to treat effectively AF with antioxidant agents. Current evidence suggest inhibition of prominent cardiac sources of reactive oxygen species (ROS) such as nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and targeting subcellular compartments with the highest levels of ROS may prove to be effective therapies for AF. Increased serum markers of oxidative stress may be an important guide in selecting the AF patients who will most likely respond to antioxidant therapy.

Transforming growth factor β suppresses glutamate-cysteine ligase gene expression and induces oxidative stress in a lung fibrosis model

The concentration of glutathione (GSH), the most abundant intracellular free thiol and an important antioxidant, is decreased in the lung in both fibrotic diseases and experimental fibrosis models. The underlying mechanisms and biological significance of GSH depletion, however, remain unclear. Transforming growth factor β (TGF-β) is the most potent and ubiquitous profibrogenic cytokine and its expression is increased in almost all fibrotic diseases. In this study, we show that increasing TGF-β1 expression in mouse lung to a level comparable to those found in lung fibrotic diseases by intranasal instillation of AdTGF-β1(223/225), an adenovirus expressing constitutively active TGF-β1, suppressed the expression of both catalytic and modifier subunits of glutamate-cysteine ligase (GCL), the rate-limiting enzyme in de novo GSH synthesis, decreased GSH concentration, and increased protein and lipid peroxidation in mouse lung. Furthermore, we show that increasing TGF-β1 expression activated JNK and induced activating transcription factor 3, a transcriptional repressor involved in the regulation of the catalytic subunit of GCL, in mouse lung. Control virus (AdDL70-3) had no significant effect on any of these parameters, compared to saline-treated control. Concurrent with GSH depletion, TGF-β1 induced lung epithelial apoptosis and robust pulmonary fibrosis. Importantly, lung GSH levels returned to normal, whereas fibrosis persisted at least 21 days after TGF-β1 instillation. Together, the data suggest that increased TGF-β1 expression may contribute to the GSH depletion observed in pulmonary fibrosis diseases and that GSH depletion may be an early event in, rather than a consequence of, fibrosis development.

Molecular and cellular mechanisms of pulmonary fibrosis

Pulmonary fibrosis is a chronic lung disease characterized by excessive accumulation of extracellular matrix (ECM) and remodeling of the lung architecture. Idiopathic pulmonary fibrosis is considered the most common and severe form of the disease, with a median survival of approximately three years and no proven effective therapy. Despite the fact that effective treatments are absent and the precise mechanisms that drive fibrosis in most patients remain incompletely understood, an extensive body of scientific literature regarding pulmonary fibrosis has accumulated over the past 35 years. In this review, we discuss three broad areas which have been explored that may be responsible for the combination of altered lung fibroblasts, loss of alveolar epithelial cells, and excessive accumulation of ECM: inflammation and immune mechanisms, oxidative stress and oxidative signaling, and procoagulant mechanisms. We discuss each of these processes separately to facilitate clarity, but certainly significant interplay will occur amongst these pathways in patients with this disease.

Therapeutic value of small molecule inhibitor to plasminogen activator inhibitor-1 for lung fibrosis

Fibrosis is a final stage of many lung diseases, with no effective treatment. Plasminogen activator inhibitor-1 (PAI-1), a primary inhibitor of tissue-type and urokinase-type plasminogen activators (tPA and uPA, respectively), plays a critical role in the development of fibrosis. In this study, we explored the therapeutic potential of an orally effective small molecule PAI-1 inhibitor, TM5275, in a model of lung fibrosis induced by transforming growth factor-β1 (TGF-β1), the most potent and ubiquitous profibrogenic cytokine, and in human lung fibroblasts (CCL-210 cells). The results show that an intranasal instillation of AdTGF-β1(223/225), an adenovirus expressing constitutively active TGF-β1, increased the expression of PAI-1 and induced fibrosis in murine lung tissue. On the other hand, treating mice with 40 mg/kg of TM5275 for 10 days, starting 4 days after the instillation of AdTGF-β1(223/225), restored the activities of uPA and tPA and almost completely blocked TGF-β1-induced lung fibrosis, as shown by collagen staining, Western blotting, and the measurement of hydroxyproline. No loss of body weight was evident under these treatment conditions with TM5275. Furthermore, we show that TM5275 induced apoptosis in both myofibroblasts (TGF-β1-treated) and naive (TGF-β1-untreated) human lung fibroblasts, and this apoptosis was associated with the activation of caspase-3/7, the induction of p53, and the inhibition of α-smooth muscle actin, fibronectin, and PAI-1 expression. Such an inhibition of fibrotic responses by TM5275 occurred even in cells pretreated with TGF-β1 for 6 hours. Together, the results suggest that TM5275 is a relatively safe and potent antifibrotic agent, with therapeutic potential in fibrotic lung disease.

Therapeutic potential and anti-amyloidosis mechanisms of tert-butylhydroquinone for Alzheimer's disease

Alzheimer's disease (AD) is a major cause of dementia in the elderly with no effective treatment. Accumulation of amyloid-β peptide (Aβ) in the brain, one of the pathological features of AD, is considered to be a central disease-causing and disease-promoting event in AD. In this study, we showed that feeding male AβPP/PS1 transgenic mice, a well established mouse model of AD, with a diet containing phenolic antioxidant tert-butylhydroquinone (TBHQ) dramatically reduced brain Aβ load with no significant effect on the amounts of alpha- and beta-C-terminal fragments or full-length AβPP. Further studies showed that TBHQ diet inhibited the expression of plasminogen activator inhibitor-1 (PAI-1), a protease inhibitor which plays a critical role in brain Aβ accumulation in AD, accompanied by increases in the activities of tissue type and urokinase type plasminogen activators (tPA and uPA) as well as plasmin. Moreover, we showed that TBHQ diet increased the expression of low density lipoprotein related protein-1, a multi ligand endocytotic receptor involved in transporting Aβ out of the brain, and plasma Aβ(40) and Aβ(42) levels. We also showed that TBHQ diet increased the concentration of glutathione, an important antioxidant, and suppressed the expression of NADPH oxidase 2 as well as lipid peroxidation. Collectively, our data suggest that TBHQ may have therapeutic potential for AD by increasing brain antioxidant capacity/reducing oxidative stress level and by stimulating Aβ degradation/clearance pathways.

Poly(ADP-ribose) polymerase 1 is indispensable for transforming growth factor-β Induced Smad3 activation in vascular smooth muscle cell

Background

Transforming growth factor type-β (TGF-β)/Smad pathway plays an essential role in vascular fibrosis. Reactive oxygen species (ROS) generation also mediates TGF-β signaling-induced vascular fibrosis, suggesting that some sort of interaction exists between Smad and redox pathways. However, the underlying molecular mechanism is largely unknown. This study aims to investigate the influence of poly(ADP-ribose) polymerase 1 (PARP1), a downstream effector of ROS, on TGF-β signaling transduction through Smad3 pathway in rat vascular smooth muscle cells (VSMCs).

Methods and Results

TGF-β1 treatment promoted PARP1 activation through induction of ROS generation in rat VSMCs. TGF-β1-induced phosphorylation and nuclear accumulation of Smad3 was prevented by treatment of cells with PARP inhibitor, 3-aminobenzamide (3AB) or N-(6-oxo-5,6-dihydrophenanthridin-2-yl)-2-(N,N-dimethylamino)acetami (PJ34), or PARP1 siRNA. TGF-β1 treatment promoted poly(ADP-ribosy)lation of Smad3 via activation of PARP1 in the nucleus. Poly(ADP-ribosy)lation enhanced Smad-Smad binding element (SBE) complex formation in nuclear extracts and increased DNA binding activity of Smad3. Pretreatment with 3AB, PJ34, or PARP1 siRNA prevented TGF-β1-induced Smad3 transactivation and expression of Smad3 target genes, including collagen Iα1, collagen IIIα1 and tissue inhibitor of metalloproteinase 1, in rat VSMCs.

Conclusions

PARP1 is indispensable for TGF-β1 induced Smad3 activation in rat VSMCs. Targeting PARP1 may be a promising therapeutic approach against vascular diseases induced by dysregulation of TGF-β/Smad3 pathway.

Factors influencing oxidative imbalance in pulmonary fibrosis: an immunohistochemical study

Background. Idiopathic Pulmonary Fibrosis (IPF) is a fatal lung disease of unknown etiology characterized by interstitial fibrosis determining irreversible distortion of pulmonary architecture. Reactive oxygen species (ROS) and markers of oxidative stress play a pivotal role in human IPF pathology, possibly through induction of epithelial-mesenchymal transition (EMT). Methods. We investigated by immunohistochemistry, in UIP and COP tissue samples, the expression of most relevant markers of the molecular interplay involving RAGE, oxidant/antioxidant balance regulation, tissue nitrosylation, and mediators of EMT. Results. In both UIP and COP, the degree of RAGE expression was similarly high, while SODs and i-NOS, diffusely present in COP endoalveolar plugs, were almost absent in UIP fibroblast foci. A lower degree of tissue nitrosilation was observed in UIP than in COP. Conclusions. Fibroblast lesions of UIP and of COP share a similar degree of activation of RAGE, while antioxidant enzyme expression markedly reduced in UIP.

The combination of selenium and vitamin E inhibits type I collagen formation in cultured hepatic stellate cells

This study investigated the effects of sodium selenite (Se) and of vitamin E (D-α-tochopherol) on the deposition of type I collagen by human LX-2 stellate cells. The cultured cells were treated with or without Se or vitamin E and with or without transforming growth factor β1 (TGFβ1). The combination of Se and vitamin E, but not either alone, protected against hepatic fibrosis by decreasing TGFβ1-mediated collagen secretion and accumulation by the stellate cells. This protective effect is due to a combination of decreased formation, decreased stability and increased degradation of the collagen. Effects of Se and vitamin E in decreasing α(1)(I) collagen mRNA and increasing apoptosis of stellate cells indicate decreased formation of collagen, while decreases in transglutaminase 2, which catalyze cross-linking of collagen, lead to decreased stability of the secreted collagen. Effects of Se and vitamin E on reducing tissue inhibitor metalloproteinase 1 (TIMP-1) are associated with increased degradation. The combination of Se and vitamin E decreased lipid peroxidation, while Se alone increased the activity of the antioxidant enzyme thioredoxin reductase. In conclusion, the combination of Se and vitamin E protected against TGFβ1-mediated hepatic fibrosis by decreasing TGFβ1-mediated type I collagen accumulation by stellate cells. This effect is due to a combination of decreased formation, decreased stability and increased degradation of the collagen.

Glucose Oxidase Incorporated Collagen Matrices for Dermal Wound Repair in Diabetic Rat Models: A Biochemical Study

Impaired wound healing in diabetes is a well-documented phenomenon. Emerging data favor the involvement of free radicals in the pathogenesis of diabetic wound healing. We investigated the beneficial role of the sustained release of reactive oxygen species (ROS) in diabetic dermal wound healing. In order to achieve the sustained delivery of ROS in the wound bed, we have incorporated glucose oxidase in the collagen matrix (GOIC), which is applied to the healing diabetic wound. Our in vitro proteolysis studies on incorporated GOIC show increased stability against the proteases in the collagen matrix. In this study, GOIC film and collagen film (CF) are used as dressing material on the wound of streptozotocin-induced diabetic rats. A significant increase in ROS ( p < 0.05) was observed in the fibroblast of GOIC group during the inflammation period compared to the CF and control groups. This elevated level up regulated the antioxidant status in the granulation tissue and improved cellular proliferation in the GOIC group. Interestingly, our biochemical parameters nitric oxide, hydroxyproline, uronic acid, protein, and DNA content in the healing wound showed that there is an increase in proliferation of cells in GOIC when compared to the control and CF groups. In addition, evidence from wound contraction and histology reveals faster healing in the GOIC group. Our observations document that GOIC matrices could be effectively used for diabetic wound healing therapy.

Targeting maladaptive glutathione responses in lung disease

The lung is unique being exposed directly to the atmospheric environment containing xenobiotics, pathogens, and other agents which are continuously inhaled on a daily basis. Additionally, the lung is exposed to higher ambient oxygen levels which can promote the formation of a complex number of reactive oxygen and nitrogen species. Due to this constant barrage of potential damaging agents, the lung has developed a high degree of plasticity in dealing with ever changing conditions. In the present commentary, we will focus on glutathione (GSH) as a key antioxidant in the lung airways and discuss mechanisms by which the lung uses GSH to adapt to its rapidly changing environment. We will then examine the evidence on how defective and inadequate adaptive responses can lead to lung injury, inflammation and disease. Lastly, we will examine some of the recent attempts to alter lung GSH levels with therapies in a number of human lung diseases and discuss some of the limitations of such approaches.

Glutamine prevents fibrosis development in rats with colitis induced by 2,4,6-trinitrobenzene sulfonic acid

We investigated the effects of glutamine on the development of colonic fibrosis and on the expression of the major fibrogenic factors in a rat model of experimental colitis. Colitis was induced in one-half of the male Wistar rats by intracolonic administration of 30 mg of 2,4,6-trinitrobenzene sulfonic acid (TNBS). L-glutamine (25 mg/kg) was administered rectally to one-half of the controls and one-half of the colitic rats. The control, control+glutamine, TNBS, and TNBS+glutamine groups were studied at d 2 and 7 after colitis induction. Glutamine induced a significant decrease in the area of colon fibrosis and in the staining of alpha-smooth muscle actin positive cells within areas of extracellular matrix deposits in the submucosa. Collagen synthesis was stimulated following TNBS administration, with a significant increase in procollagen IV, collagen III, and collagen Ialpha2 mRNA levels in the colon by d 2 after TNBS instillation. Tissue inhibitor of metalloproteinase, connective tissue growth factor, transforming growth factor-beta, platelet-derived growth factor, and phosphorylated Smad3 were overexpressed in the colon of TNBS-treated rats. These effects were significantly abrogated in the colitic rats treated with glutamine. Our findings suggest that glutamine treatment not only attenuates the outcome of TNBS-induced colitis by reducing the inflammatory response but also by downregulating the increased expression of several gene pathways that contribute to the accumulation of matrix proteins. This molecule may be an interesting candidate for reducing the risk of fibrosis and stricture formation in inflammatory bowel disease.

Oxidative modification of nuclear mitogen-activated protein kinase phosphatase 1 is involved in transforming growth factor beta1-induced expression of plasminogen activator inhibitor 1 in fibroblasts

Transforming growth factor beta (TGF-beta) stimulates reactive oxygen species (ROS) production in various cell types, which mediates many of the effects of TGF-beta. The molecular mechanisms whereby TGF-beta increases ROS production and ROS modulate the signaling processes of TGF-beta, however, remain poorly defined. In this study, we show that TGF-beta1 stimulates NADPH oxidase 4 (Nox4) expression and ROS generation in the nucleus of murine embryo fibroblasts (NIH3T3 cells). This is associated with an increase in protein thiol modification and inactivation of MAPK phosphatase 1 (MKP-1), a nuclear phosphatase. Furthermore, knockdown of MKP-1 using small interfering RNA enhances TGF-beta1-induced phosphorylation of JNK and p38 as well as the expression of plasminogen activator inhibitor 1 (PAI-1), a TGF-beta-responsive gene involved in the pathogenesis of many diseases. Knockdown of Nox4 with Nox4 small interfering RNA, on the other hand, reduces TGF-beta1-stimulated ROS production, p38 phosphorylation, and PAI-1 expression. TGF-beta also increased the nuclear level of Nox4 protein as well as PAI-1 expression in human lung fibroblasts (CCL-210 cells), suggesting that TGF-beta may induce PAI-1 expression by a similar mechanism in human lung fibroblasts. In summary, in this study we have identified nuclear MAPK phosphatase MKP-1 as a novel molecular target of ROS in TGF-beta signaling pathways. Our data suggest that increased generation of ROS by Nox4 mediates TGF-beta1-induced PAI-1 gene expression at least in part through oxidative modification and inhibition of MKP-1 leading to a sustained activation of JNK and p38 MAPKs.

Treating IPF--all or nothing? A PRO-CON debate

The Idiopathic Pulmonary Fibrosis (IPF) is a progressive fibrotic lung disease with poor prognosis. It is distinct from other idiopathic interstitial pneumonias by its histopathological pattern of usual interstitial pneumonia which is characterized by accumulation of fibroblasts, extracellular matrix and honeycombing. Inflammation is only scarce in true IPF. The use of anti-inflammatory therapy is still part of guidelines for IPF management, although not specifically recommended, because convincing evidence showing beneficial effects of this approach is lacking. This review provides a summary of important arguments PRO and CON using anti-inflammatory and anti-oxidant therapy for patients with IPF in form of a debate with a concluding statement of both positions at the end.

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.

Experimental therapies in hypertrophic cardiomyopathy

The quintessential clinical diagnostic phenotype of human hypertrophic cardiomyopathy (HCM) is primary cardiac hypertrophy. Cardiac hypertrophy is also a major determinant of mortality and morbidity including the risk of sudden cardiac death (SCD) in patients with HCM. Reversal and attenuation of cardiac hypertrophy and its accompanying fibrosis is expected to improve morbidity as well as decrease the risk of SCD in patients with HCM.The conventionally used pharmacological agents in treatment of patients with HCM have not been shown to reverse or attenuate established cardiac hypertrophy and fibrosis. An effective treatment of HCM has to target the molecular mechanisms that are involved in the pathogenesis of the phenotype. Mechanistic studies suggest that cardiac hypertrophy in HCM is secondary to activation of various hypertrophic signaling molecules and, hence, is potentially reversible. The hypothesis is supported by the results of genetic and pharmacological interventions in animal models. The results have shown potential beneficial effects of angiotensin II receptor blocker losartan, mineralocorticoid receptor blocker spironolactone, 3-hydroxy-3-methyglutaryl-coenzyme A reductase inhibitors simvastatin and atorvastatin, and most recently, N-acetylcysteine (NAC) on reversal or prevention of hypertrophy and fibrosis in HCM. The most promising results have been obtained with NAC, which through multiple thiol-responsive mechanisms completely reversed established cardiac hypertrophy and fibrosis in three independent studies. Pilot studies with losartan and statins in humans have established the feasibility of such studies. The results in animal models have firmly established the reversibility of established cardiac hypertrophy and fibrosis in HCM and have set the stage for advancing the findings in the animal models to human patients with HCM through conducting large-scale efficacy studies.

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.

Improving the cadmium-induced centriacinar emphysema model in rats by concomitant anti-oxidant treatment

1. The aim of the present study was to perform an evolutionary analysis of the morphometrical, biochemical and functional parameters of centriacinar emphysema induced by cadmium chloride (CdCl2) in rats and to determine the effects of concomitant N-acetylcysteine (NAC) administration. 2. Male Wistar rats were instilled orotracheally with either CdCl2 (n = 24) or saline (n = 24). One group of rats, consisting of both CdCl2- and saline-treated rats, was fed a normal diet (n = 24), whereas the other group received NAC (n = 24). 3. Changes in inspiratory capacity (IC), lung compliance (CL), expiratory flow at 75% (F75), forced vital capacity (FVC) and hydroxyproline content were assessed 2, 8, 21 and 45 days after instillation. Polymorphonuclear cells were evaluated 2 and 8 days after instillation and the mean linear intercept (Lm) was determined at 21 and 45 days. 4. Over time, CdCl2 instillation causes several changes that are bound up with centriacinar emphysema. The concomitant administration of NAC to CdCl2-treated rats partially reversed Lm at 21 days compared with CdCl2 alone (115 +/- 2 vs 127 +/- 2, respectively; P < 0.05). However, 45 days after instillation, NAC improved lung function in CdCl2-treated rats compared with that in the saline-treated control group (IC 14.64 vs 15.25, respectively (P = 0.054); FVC 16.94 vs 16.28, respectively (P = 0.052), F75 31.41 vs 32.48, respectively (P = 0.062)). In addition, 45 days after instillation, NAC reduced lung collagen content in both the saline-treated control (100 vs 81% alone and in the presence of NAC, respectively) and CdCL2-treated groups (213 vs 161% alone and in the presence of NAC, respectively). In addition, although the results were not significant, NAC tended to reduce Lm and enhance CL in NAC + CdCl2-treated rats. 5. In conclusion, NAC partially improved emphysematous changes and reduced collagen deposition, which diminished the CdCl2-induced fibrotic component of centriacinar emphysema.

N-acetyl-L-cysteine inhibits TGF-beta1-induced profibrotic responses in fibroblasts

BACKGROUND

Excessive production of TGF-beta(1) plays a key role in the tissue remodeling or fibrotic process observed in bronchial asthma, chronic pulmonary disease (COPD), and idiopathic pulmonary fibrosis (IPF). TGF-beta(1) has been reported to decrease the intracellular glutathione level and stimulate the production of reactive oxygen species.

OBJECTIVES

The aim of this study was to evaluate whether the antioxidant N-acetyl-l-cysteine (NAC) can affect TGF-beta(1)-mediated tissue remodeling in fibroblasts or modulate the production of fibronectin and vascular endothelial growth factor (VEGF) which are believed to be important mediators of tissue repair and remodeling.

METHODS

To accomplish this, human fetal lung fibroblasts (HFL-1) were used to assess the effect of NAC on the TGF-beta(1)-mediated contraction of floating gels and the TGF-beta(1)-induced mediator production. In addition, the effect of NAC on the TGF-beta(1)-induced differentiation to myofibroblasts was evaluated by assessing alpha-smooth muscle actin (alpha-SMA) expression.

RESULTS

NAC significantly abolished the TGF-beta(1)-augmented gel contraction (at 3mM, gel size 63.4+/-2.6% vs. 39.1+/-4.1%; p<0.01) compared with control in a concentration-dependent manner. NAC also significantly inhibited the TGF-beta(1)-augmented fibronectin (p<0.01) and VEGF (p<0.01) production in the media of both the three-dimensional gel and monolayer culture. Furthermore, NAC reversed the TGF-beta(1)-stimulated alpha-SMA expression (p<0.01).

CONCLUSION

These results suggest that NAC can affect the TGF-beta(1)-induced tissue remodeling or fibrotic process in vitro.

Resolution of established cardiac hypertrophy and fibrosis and prevention of systolic dysfunction in a transgenic rabbit model of human cardiomyopathy through thiol-sensitive mechanisms

BACKGROUND

Cardiac hypertrophy, the clinical hallmark of hypertrophic cardiomyopathy (HCM), is a major determinant of morbidity and mortality not only in HCM but also in a number of cardiovascular diseases. There is no effective therapy for HCM and generally for cardiac hypertrophy. Myocardial oxidative stress and thiol-sensitive signaling molecules are implicated in pathogenesis of hypertrophy and fibrosis. We posit that treatment with N-acetylcysteine, a precursor of glutathione, the largest intracellular thiol pool against oxidative stress, could reverse cardiac hypertrophy and fibrosis in HCM.

METHODS AND RESULTS

We treated 2-year-old beta-myosin heavy-chain Q403 transgenic rabbits with established cardiac hypertrophy and preserved systolic function with N-acetylcysteine or a placebo for 12 months (n=10 per group). Transgenic rabbits in the placebo group had cardiac hypertrophy, fibrosis, systolic dysfunction, increased oxidized to total glutathione ratio, higher levels of activated thiol-sensitive active protein kinase G, dephosphorylated nuclear factor of activated T cells (NFATc1) and phospho-p38, and reduced levels of glutathiolated cardiac alpha-actin. Treatment with N-acetylcysteine restored oxidized to total glutathione ratio, normalized levels of glutathiolated cardiac alpha-actin, reversed cardiac and myocyte hypertrophy and interstitial fibrosis, reduced the propensity for ventricular arrhythmias, prevented cardiac dysfunction, restored myocardial levels of active protein kinase G, and dephosphorylated NFATc1 and phospho-p38.

CONCLUSIONS

Treatment with N-acetylcysteine, a safe prodrug against oxidation, reversed established cardiac phenotype in a transgenic rabbit model of human HCM. Because there is no effective pharmacological therapy for HCM and given that hypertrophy, fibrosis, and cardiac dysfunction are common and major predictors of clinical outcomes, the findings could have implications in various cardiovascular disorders.

Oxidative and nitrosative stress and fibrogenic response

Uncontrolled production of collagen I is the main feature of liver fibrosis. Following a fibrogenic stimulus such as alcohol, hepatic stellate cells (HSC) transform into an activated collagen-producing cell. In alcoholic liver disease, numerous changes in gene expression are associated with HSC activation, including the induction of several intracellular signaling cascades, which help maintain the activated phenotype and control the fibrogenic and proliferative state of the cell. Detailed analyses for understanding the molecular basis of the collagen I gene regulation have revealed a complex process involving reactive oxygen species (ROS) as key mediators. Less is known, however, about the contribution of reactive nitrogen species (RNS). In addition, a series of cytokines, growth factors, and chemokines, which activate extracellular matrix (ECM)-producing cells through paracrine and autocrine loops, contribute to the fibrogenic response.

The antioxidant response element and oxidative stress modifiers in airway diseases

Redox balance is particularly important in the airways because they are the first points of contact with environmental pollutants such as ozone, particles, and cigarette smoke, as well as pathogens such as bacteria and viruses. However, an imbalance between toxicant-induced reactive oxygen (ROS) and nitrogen (RNS) species and the antioxidant defense system leads to oxidative stress, which has been implicated in the development and/or perpetuation of airway diseases, including malignancy. Various antioxidant enzymes and proteins are critical to maintaining the reducing environment of the cell and preventing the damage to various biomolecules that is elicited by ROS/RNS. Emerging evidence indicates that transcriptional activation of the antioxidant response element (ARE) plays a crucial role in modulating oxidative stress and providing cytoprotection against prooxidant stimuli. This review focuses on the regulation and functional roles of key effectors that bind to the ARE and differentially (up- or down-) regulate gene expression in lung tissue/cell types in response to respiratory toxicants. It also provides a perspective on whether boosting ARE-mediated gene expression with dietary plants and synthetic plant products will offer a better therapeutic strategy for mitigating oxidative stress and respiratory pathogenesis.

Oxidation of extracellular cysteine/cystine redox state in bleomycin-induced lung fibrosis

Several lines of evidence indicate that depletion of glutathione (GSH), a critical thiol antioxidant, is associated with the pathogenesis of idiopathic pulmonary fibrosis (IPF). However, GSH synthesis depends on the amino acid cysteine (Cys), and relatively little is known about the regulation of Cys in fibrosis. Cys and its disulfide, cystine (CySS), constitute the most abundant low-molecular weight thiol/disulfide redox couple in the plasma, and the Cys/CySS redox state (E(h) Cys/CySS) is oxidized in association with age and smoking, known risk factors for IPF. Furthermore, oxidized E(h) Cys/CySS in the culture media of lung fibroblasts stimulates proliferation and expression of transitional matrix components. The present study was undertaken to determine whether bleomycin-induced lung fibrosis is associated with a decrease in Cys and/or an oxidation of the Cys/CySS redox state and to determine whether these changes were associated with changes in E(h) GSH/glutathione disulfide (GSSG). We observed distinct effects on plasma GSH and Cys redox systems during the progression of bleomycin-induced lung injury. Plasma E(h) GSH/GSSG was selectively oxidized during the proinflammatory phase, whereas oxidation of E(h) Cys/CySS occurred at the fibrotic phase. In the epithelial lining fluid, oxidation of E(h) Cys/CySS was due to decreased food intake. Thus the data show that decreased precursor availability and enhanced oxidation of Cys each contribute to the oxidation of extracellular Cys/CySS redox state in bleomycin-induced lung fibrosis.

Hypoxia-generated superoxide induces the development of the adhesion phenotype

Adhesion fibroblasts exhibit higher TGF-beta1 and type I collagen expression as compared to normal peritoneal fibroblasts. Furthermore, exposure of normal peritoneal fibroblasts to hypoxia results in an irreversible increase in TGF-beta1 and type I collagen. We postulated that the mechanism by which hypoxia induced the adhesion phenotype is through the production of superoxide either directly or through the formation of peroxynitrite. To test this hypothesis, normal peritoneal and adhesion fibroblasts were treated with superoxide dismutase (SOD), a superoxide scavenger, and xanthine/xanthine oxidase, a superoxide-generating system, under normoxic and hypoxic conditions. Also, cells were treated with peroxynitrite. TGF-beta1 and type I collagen expression was determined before and after all treatments using real-time RT/PCR. Hypoxia treatment resulted in a time-dependent increase in TGF-beta1 and type I collagen mRNA levels in both normal peritoneal and adhesion fibroblasts. Similarly, treatment with xanthine oxidase, to endogenously generate superoxide, resulted in higher mRNA levels of TGF-beta1 and type I collagen in both normal peritoneal and adhesion fibroblasts. In contrast, treatment with SOD, to scavenge endogenous superoxide, resulted in a decrease in TGF-beta1 and type I collagen expression in adhesion fibroblasts to levels seen in normal peritoneal fibroblasts; no effect on the expression of these molecules was seen in normal peritoneal fibroblasts. Exposure to hypoxia in the presence of SOD had no effect on mRNA levels of TGF-beta1 and type I collagen in either normal peritoneal or adhesion fibroblasts. Peroxynitrite treatment alone significantly induced both adhesion phenotype markers. In conclusion, hypoxia, through the production of superoxide, causes normal peritoneal fibroblasts to acquire the adhesion phenotype. Scavenging superoxide, even in the presence of hypoxia, prevented the development of the adhesion phenotype. These findings further support the central role of free radicals in the development of adhesions.