Ifty rahman - Academia.edu (original) (raw)
Papers by Ifty rahman
Idiopathic pulmonary fibrosis (IPF) is characterized by an increased oxidant burden and by a defi... more Idiopathic pulmonary fibrosis (IPF) is characterized by an increased oxidant burden and by a deficiency of glutathione, a major antioxidant, in the lung epithelial lining fluid (ELF). Therefore, a rational therapeutic approach is to reverse the imbalance between oxidants and antioxidants in the lung by enhancing the antioxidant screen. With this background, the aim of our study was to evaluate oral N-acetylcysteine (NAC) as a strategy to augment lung glutathione levels in patients with IPF Concentrations of total glutathione in bronchoalveolar lavage fluid (BALF) were quantified spectrophotometrically, before and following oral therapy with 3 x 600 mg NAC per day for 5 days, in 17 nonsmoking patients with biopsy-proven IPF The volume of ELF recovered by BAL was determined using the urea method. Pretherapy, total glutathione levels in ELF in IPF patients were significantly less than normal (187+36 vs 368+60 1y/), in contrast to levels in BALF (0.99+0-12 vs 1.18+ 19,uM). Following therapy with oral NAC, glutathione levels in BALF were 1.54 + 0.24 jiM (a significant increase compared to pretherapy), whereas the increase in ELF levels (319+ 92,M) did not reach significance. The therapy was well-tolerated, and all routine clinical and bronchoscopic parameters remained unchanged. It is thus feasible and safe to augment deficient lung glutathione levels in patients with IPF; thereby, potentially augmenting pulmonary antioxidant protection.
We studied asbestos, vitreous fiber (MMVF10), and refractory ceramic fiber (RCF1) from the Therma... more We studied asbestos, vitreous fiber (MMVF10), and refractory ceramic fiber (RCF1) from the Thermal Insulation Manufacturers' Association fiber repository regarding the following: free radical damage to plasmid DNA, iron release, ability to deplete glutathione (GSH), and activate redox-sensitive transcription factors in macrophages. Asbestos had much more free radical activity than any of the man-made vitreous fibers. More Fe3+ was released than Fe2+ and more of both was released at pH 4.5 than at pH 7.2. Release of iron from the different fibers was generally not a good correlate of ability to cause free radical injury to the plasmid DNA. All fiber types caused some degree of oxidative stress, as revealed by depletion of intracellular GSH. Amosite asbestos upregulated nuclear binding of activator protein 1 transcription factor to a greater level than MMVF1 0 and RCF1; long-fiber amosite was the only fiber to enhance activation of the transcription factor nuclear factor icB (NFKcB). The use of cysteine methyl ester and buthionine sulfoximine to modulate GSH suggested that GSH homeostasis was important in leading to activation of transcription factors. We conclude that the intrinsic free radical activity is the major determinant of transcription factor activation and therefore gene expression in alveolar macrophages. Although this was not related to iron release or ability to deplete macrophage GSH at 4 hr, GSH does play a role in activation of NFOcB.
The development of an oxidant/antioxidant imbalance in lung inflammation may activate redox-sensi... more The development of an oxidant/antioxidant imbalance in lung inflammation may activate redox-sensitive transcription factors such as nuclear factor-kappa B (NF-kappa B) and activator protein-1 (AP-1), which regulate the genes for proinflammatory mediators and protective antioxidant genes. GSH, a ubiquitous tripeptide thiol, is a vital intra- and extracellular protective antioxidant against oxidative stress, which plays a key role in the control of proinflammatory processes in the lungs. The rate-limiting enzyme in GSH synthesis is gamma-glutamylcysteine synthetase (gamma-GCS), which consists of a catalytic heavy and a regulatory light subunit. The promoter regions of the human gamma-GCS subunits contain AP-1, NF-kappa B, and antioxidant response elements and are regulated by oxidants, growth factors, inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha), and anti-inflammatory agent (dexamethasone) in lung cells. TNF-alpha depletes intracellular GSH, concomitant with an increase in oxidised glutathione levels in alveolar epithelial cells. TNF-alpha also induces the activation of NF-kappa B and AP-1 and the subsequent increase in gamma-GCS heavy subunit transcription in these cells. Dexamethasone depleted both basal and TNF-alpha-stimulated GSH levels by down-regulating the gamma-GCS-heavy subunit transcription via a mechanism involving AP-1 (c-Jun). The existence of this fine tuning between the redox GSH levels and the activation of transcription factors may determine the balance of transcription for proinflammatory and antioxidant gamma-GCS genes in inflammation. More studies are required to understand the signalling mechanism of the redox regulation of NF-kappa B and AP-1 and gene transcription in inflammation. This could lead to the development of therapeutic strategies based on the pharmacological manipulation of the production of this important antioxidant in inflammation.
The airway epithelium is injured by oxidants inhaled as atmospheric pollutants or produced during... more The airway epithelium is injured by oxidants inhaled as atmospheric pollutants or produced during inflammatory responses. We studied the effect of modulating the antioxidant intracellular glutathione, both using thiol compounds and by the adaptive effect of hyperoxia, on oxidant-induced injury and activation of the nuclear factor-kappaB (NF-B) in two cell lines: the human bronchial (16HBE) and type II alveolar epithelial cells (A549). The thiol antioxidants glutathione (GSH) and glutathione monoethyl ester (GSH-MEE) [2 mM] increased GSH levels (nmol/mg protein) in A549 cells (GSH 383 Ϯ 26 and GSH-MEE 336 Ϯ 23 vs control 171 Ϯ 13, P Ͻ 0.001) and in 16HBE cells (GSH 405 Ϯ 33, GSH-MEE 362 Ϯ 37 vs control 198 Ϯ 12, P Ͻ 0.001, N ϭ 3). Treatment of hyperoxia (95% oxygen) also increased GSH levels between 4 and 24 hr exposure compared with control (P Ͻ 0.01). Hydrogen peroxide (H 2 O 2) (0.01 mM) induced NF-B activation, whereas hyperoxia exposure did not affect NF-B activation in either cell line. Pretreatment with DL-buthionine (SR)sulfoximine, which decreased intracellular glutathione, increased NF-B binding induced by H 2 O 2 and increased lactate dehydrogenase (LDH) release (P Ͻ 0.001). Pretreatment with the thiol compounds and hyperoxia totally inhibited H 2 O 2-induced NF-B binding and cell injury as measured by LDH release. These data indicate the importance of intracellular glutathione and inhibition of NF-B in both protection/tolerance against oxidant-induced epithelial cell injury, and NF-B activation in response to oxidative stress which may be important in lung inflammation. Thus, increasing intracellular glutathione may be of therapeutic relevance if able to modulate NF-B activation and hence attenuate inflammation.
Increases in the levels of environmental particulate matter with a diameter of Ͻ10 m diameter (PM... more Increases in the levels of environmental particulate matter with a diameter of Ͻ10 m diameter (PM 10) in the air are associated with a variety of adverse health effects, particularly chronic lung and cardiovascular diseases. The expression of many inflammatory genes involves the remodeling of the chromatin structure provided by histone proteins. Histone acetylation causes the unwinding of chromatin structure, therefore allowing transcription factor access to promoter sites. Acetylation is reversible and is regulated by histone acetyltransferases (HATs), which promote acetylation, and deacetylases, which promote deacetylation. PM10 and H2O2 increased IL-8 protein release from A549 cells after 24-h treatment, and this was enhanced by histone deacetylase inhibition by trichostatin A (cotreatment). PM10 and H2O2 treatment also increased HAT activity as well as the level of acetylated histone 4 (H4). PM10 enhanced H4 acetylation that was mediated by oxidative stress as shown by thiol antioxidant inhibition. Acetylation of H4 mediated by PM10 was associated with the promoter region of the IL-8 gene. These data suggest that remodeling of chromatin by histone acetylation plays a role in PM10-mediated responses in the lungs.
Neutrophil apoptosis represents a major mechanism involved in the resolution of inflammation. Sin... more Neutrophil apoptosis represents a major mechanism involved in the resolution of inflammation. Since hypoxia induces apoptosis in several cell lines and is of particular relevance in many disease states, we studied the effect of oxygen concentration on neutrophil survival in vitro. Hypoxia caused a dramatic decrease in neutrophil apoptosis (% apoptosis 20 h: 78.7 +/- 2.2% in 21% O2, 61.4 +/- 6.5% in 2.5% O2, 23.1 +/- 3.2% in 0% O2, n = 5). This was additive to the effect of GM-CSF (50 U/ml), not associated with induction of bcl-2 expression, and was not mimicked by methionine (5 mM), superoxide dismutase (200 micrograms/ml) or Trolox (10 mM) but was mimicked by catalase (250 micrograms/ml). Hence, hypoxia has a bcl-2-independent effect on neutrophil apoptosis that may adversely affect the clearance of these cells from an inflammatory focus.
We studied the acute effects of cigarette smoke condensate (CSC), H2O2, and tumor necrosis factor... more We studied the acute effects of cigarette smoke condensate (CSC), H2O2, and tumor necrosis factor (TNF)-alpha on the glutathione (GSH) redox system in a human type II epithelial cell line (A549) in vitro. CSC, in vitro and in vivo after intratracheal instillation of CSC in the rat, produced a depletion of intracellular soluble GSH, concomitant with GSH-conjugate formation, without significant elevation of oxidized GSH (GSSG), protein-GSH mixed disulfides (PrSSG), nor any GSH efflux from the cells. By contrast, H2O2 (500 microM) after 5-min exposure to A549 cells caused significant depletion of intracellular GSH associated with an efflux of GSSG and a significant increase in the formation of PrSSG. TNF-alpha, in concentrations of 100 U/ml and 1,000 U/ml, produced a significant depletion of GSH in A549 cells after 4- and 24-h exposure, with an associated elevation of GSSG. The activities of glutathione peroxidase, gamma-glutamylcysteine synthetase, and glucose-6-phosphate dehydrogenase were significantly decreased in epithelial cells and in rat lungs after CSC exposure, without change in glutathione S-transferase and glutathione reductase activities. By contrast, H2O2 and TNF-alpha did not alter these enzyme activities in epithelial cells. Thus GSH depletion and alteration in enzyme activities in alveolar epithelial cells by CSC, H2O2, and TNF-alpha occur by different mechanisms.
Macrophage migration inhibitory factor (MIF) is a potent proinflammatory mediator that has been s... more Macrophage migration inhibitory factor (MIF) is a potent proinflammatory mediator that has been shown to potentiate lethal endotoxemia and to play a potentially important regulatory role in human acute respiratory distress syndrome (ARDS). We have investigated whether eosinophils are an important source of MIF and whether MIF may be involved in the pathophysiology of asthma. Unstimulated human circulating eosinophils were found to contain preformed MIF. Stimulation of human eosinophils with phorbol myristate acetate in vitro yielded significant release of MIF protein. For example, eosinophils stimulated with phorbol myristate acetate (100 nM, 8 h, 37 Њ C) released 1,539 Ϯ 435 pg/10 6 cells of MIF, whereas unstimulated cells released barely detectable levels (Ͻ 142 pg/10 6 cells, mean Ϯ SEM, n ϭ 8). This stimulated release was shown to be (a) concentration-and time-dependent, (b) partially blocked by the protein synthesis inhibitor cycloheximide, and (c) significantly inhibited by the protein kinase C inhibitor Ro-31,8220. In addition, we show that the physiological stimuli C5a and IL-5 also cause significant MIF release. Furthermore, bronchoalveolar lavage fluid obtained from asthmatic patients contains significantly elevated levels of MIF as compared to nonatopic normal volunteers (asthmatic, 797.5 Ϯ 92 pg/ml; controls, 274 Ϯ 91 pg/ml). These results highlight the potential importance of MIF in asthma and other eosinophil-dependent inflammatory disorders. (J.
Asthma and chronic obstructive pulmonary disease (COPD) are inflammatory lung diseases that are c... more Asthma and chronic obstructive pulmonary disease (COPD) are inflammatory lung diseases that are characterized by systemic and chronic localized inflammation and oxidative stress. Sources of oxidative stress arise from the increased burden of inhaled oxidants, as well as elevated amounts of reactive oxygen species (ROS) released from inflammatory cells. Increased levels of ROS, either directly or via the formation of lipid peroxidation products, may play a role in enhancing the inflammatory response in both asthma and COPD. Moreover, in COPD it is now recognized as the main pathogenic factor for driving disease progression and increasing severity. ROS and lipid peroxidation products can influence the inflammatory response at many levels through its impact on signal transduction mechanisms, activation of redox-sensitive transcriptions factors, and chromatin regulation resulting in pro-inflammatory gene expression. It is this impact of ROS on chromatin regulation by reducing the activity of the transcriptional co-repressor, histone deacetylase-2 (HDAC-2), that leads to the poor efficacy of corticosteroids in COPD, severe asthma, and smoking asthmatics. Thus, the presence of oxidative stress has important consequences for the pathogenesis, severity, and treatment of asthma and COPD. However, for ROS to have such an impact, it must first overcome a variety of antioxidant defenses. It is likely, therefore, that a combination of antioxidants may be effective in the treatment of asthma and COPD. Various approaches to enhance the lung antioxidant screen and clinical trials of antioxidant compounds are discussed.
The spectrophotometric/microplate reader assay method for glutathione (GSH) involves oxidation of... more The spectrophotometric/microplate reader assay method for glutathione (GSH) involves oxidation of GSH by the sulfhydryl reagent 5,5'-dithio-bis(2-nitrobenzoic acid) (DTNB) to form the yellow derivative 5'-thio-2-nitrobenzoic acid (TNB), measurable at 412 nm. The glutathione disulfide (GSSG) formed can be recycled to GSH by glutathione reductase in the presence of NADPH. The assay is composed of two parts: the preparation of cell cytosolic/tissue extracts and the detection of total glutathione (GSH and GSSG). The method is simple, convenient, sensitive and accurate. The lowest detection for GSH and GSSG is 0.103 nM in a 96-well plate. This method is rapid and the whole procedure takes no longer than 15 min including reagent preparation. The method can assay GSH in whole blood, plasma, serum, lung lavage fluid, cerebrospinal fluid, urine, tissues and cell extracts and can be extended for drug discovery/pharmacology and toxicology protocols to study the effects of drugs and toxic compounds on glutathione metabolism.
Reactive oxygen species (ROS), either directly or via the formation of lipid peroxidation product... more Reactive oxygen species (ROS), either directly or via the formation of lipid peroxidation products, such as 4-hydroxy-2-nonenal, acrolein and F2-isoprostanes, may play a role in enhancing inflammation through the activation and phosphorylation of stress kinases (JNK, ERK, p38) and redox-sensitive transcription factors such as NF-kappaB and AP-1. This increases the expression of genes regulating a battery of distinct pro-inflammatory mediators. Acetylation by histone acetyltransferase (HAT) of specific lysine residues on the N-terminal tail of core histones, results in uncoiling of the DNA and increased accessibility to transcription factor binding. In contrast, histone deacetylation by histone deacetylase (HDAC) represses gene transcription by promoting DNA winding thereby limiting access to transcription factors. Oxidative stress activates NF-kappaB resulting in expression of pro-inflammatory mediators through the activation of intrinsic HAT activity on co-activator molecules. In addition, oxidative stress also inhibits HDAC activity and in doing so enhances inflammatory gene expression which leads to a chronic inflammatory response. Oxidative stress can also increase complex formation between the co-activator CBP/p300 and the p65 subunit of NF-kappaB suggesting a further role of oxidative stress in chromatin remodeling. The antioxidant and/or anti-inflammatory effects of thiol molecules (glutathione, N-acetyl-L-cysteine and N-acystelyn), dietary polyphenols (curcumin-diferuloylmethane and resveratrol), the bronchodilator theophylline and glucocorticoids have all been shown to play a role in either controlling NF-kappaB activation or chromatin remodeling through modulation of HDAC activity and subsequently inflammatory gene expression in lung epithelial cells. Thus, oxidative stress regulates both signal transduction and chromatin remodeling which in turn impacts on pro-inflammatory responses in the lungs.
Inflammatory lung diseases are characterized by chronic inflammation and oxidant/antioxidant imba... more Inflammatory lung diseases are characterized by chronic inflammation and oxidant/antioxidant imbalance, a major cause of cell damage. The development of an oxidant/antioxidant imbalance in lung inflammation may activate redox-sensitive transcription factors such as nuclear factor-kB, and activator protein-1 (AP-1), which regulate the genes for pro-inflammatory mediators and protective antioxidant genes. Glutathione (GSH), a ubiquitous tripeptide thiol, is a vital intra-and extracellular protective antioxidant against oxidative/nitrosative stresses, which plays a key role in the control of pro-inflammatory processes in the lungs. Recent findings have suggested that GSH is important in immune modulation, remodelling of the extracellular matrix, apoptosis and mitochondrial respiration. The rate-limiting enzyme in GSH synthesis is c-glutamylcysteine synthetase (c-GCS). The human c-GCS heavy and light subunits are regulated by AP-1 and antioxidant response elements and are modulated by oxidants, phenolic antioxidants, growth factors, and inflammatory and anti-inflammatory agents in lung cells. Alterations in alveolar and lung GSH metabolism are widely recognized as a central feature of many inflammatory lung diseases such as idiopathic pulmonary fibrosis, acute respiratory distress syndrome, cystic fibrosis and asthma. The imbalance and/or genetic variation in antioxidant c-GCS and pro-inflammatory versus antioxidant genes in response to oxidative stress and inflammation in some individuals may render them more susceptible to lung inflammation. Knowledge of the mechanisms of GSH regulation and balance between the release and expression of pro-and anti-inflammatory mediators could lead to the development of novel therapies based on the pharmacological manipulation of the production as well as gene transfer of this important antioxidant in lung inflammation and injury. This review describes the redox control and involvement of nuclear factor-kB and activator protein-1 in the regulation of cellular glutathione and c-glutamylcysteine synthetase under conditions of oxidative stress and inflammation, the role of glutathione in oxidant-mediated susceptibility/tolerance, c-glutamylcysteine synthetase genetic susceptibility and the potential therapeutic role of glutathione and its precursors in protecting against lung oxidant stress, inflammation and injury.
Thorax, 2000
BACKGROUND It has been suggested that oxidative stress is an important factor in the pathogenesis... more BACKGROUND It has been suggested that oxidative stress is an important factor in the pathogenesis of chronic obstructive pulmonary disease (COPD). We have shown that an oxidant/antioxidant imbalance occurs in the distal air spaces of smokers and in patients with COPD which is ...
Objective To investigate the cardioprotective efficacy of remote ischaemic preconditioning (RIPC)... more Objective To investigate the cardioprotective efficacy of remote ischaemic preconditioning (RIPC) in cardiac surgery. Design We have performed a systematic search of MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials to identify randomized controlled trials involving RIPC. Setting Randomized controlled trials of RIPC in open cardiac surgery patients. Main outcome measures Meta-analysis was performed with the primary outcome the standardized mean difference between intervention and control groups in 12 hour postoperative troponin concentration. Heterogeneity was examined by fixed effects meta-regression. Results Ten studies with a total of 693 participants were included in the meta-analysis. RIPC reduced troponin levels 12 hours after surgery compared with control. The fixed and random effects differences were 0.35 (95% CI 0.19 to 0.51) and 0.53 (95% CI 0.18-0.88) respectively. However, important heterogeneity was present. Fixed effects metaregression partially accounted for heterogeneity based on whether studies had full blinding, comprising blinding of patients, surgeons, anaesthetists and investigators. Studies with incomplete or no blinding demonstrated a larger estimate of effect, 0.74 (95% CI 0.47 to 1.00) compared to those with full blinding, 0.13 (95% CI-0.07 to 0.33). Conclusions Although our analysis suggests RIPC may result in cardiac protection during cardiac surgery, the effect was most marked in studies without full blinding, with a smaller and statistically nonsignificant effect in fully blinded studies. We propose that further double blind randomized controlled trials investigating the cardioprotective effects of RIPC in cardiac surgery are required to resolve the current clinical uncertainty.
FEBS letters, 1996
Increased levels of glutathione (GSH) occur in the epithelial lining fluid (ELF) of chronic cigar... more Increased levels of glutathione (GSH) occur in the epithelial lining fluid (ELF) of chronic cigarette smokers. Therefore we investigated the effect of cigarette smoke condensate solution (CSC) on GSH synthesis and the regulation of gamma-glutamylcysteine synthetase (gammaGCS) in human type II alveolar epithelial cells (A549). CSC exposure increased GSH levels, gammaGCS activity and gammaGCS heavy subunit (HS) mRNA, as well as increasing DNA binding of the activator protein-1 (AP-1) and the human antioxidant response element (hARE). Transfection of deletion constructs of the gammaGCS-HS promoter in a chloramphenicol acetyl transferase (CAT) reporter system revealed that an hARE, present within promoter, is not required for the CSC mediated induction. We conclude that CSC induction of gammaGCS-HS expression is associated with AP-1/AP-1-like responsive elements.
Biochemical and …, 1996
We studied the regulation of glutathione (GSH) synthesis and characterised the 5'-promote... more We studied the regulation of glutathione (GSH) synthesis and characterised the 5'-promoter region of the gamma-glutamylcysteine synthetase-heavy subunit (gammaGCS-HS) gene in human alveolar type II cells (A549) following exposure to menadione (MQ) and hydrogen peroxide (H2O2). Both MQ (100 microM) and H2O2 (100 microM) exposure increased intracellular GSH levels associated with increased gammaGCS activity. This was concomitant with enhanced expression of gammaGCS-HS mRNA. Transfection of deletion constructs of the gammaGCS-HS promoter (-1050 to +82 bp) in a chloramphenicol acetyl transferase (CAT) reporter system revealed that an human antioxidant response element (hARE), present within the proximal region of the promoter (-1050 to -818 bp), is not required for oxidant-mediated gene induction. We conclude that oxidant stress-induced gammaGCS-HS mRNA expression is associated with AP-1 or AP-1 like responsive elements (-817 to +45 bp).
Clinical & experimental …, 2008
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Survey of ophthalmology, 2003
Visually impaired patients may experience complex visual hallucinations, a condition known as the... more Visually impaired patients may experience complex visual hallucinations, a condition known as the Charles Bonnet Syndrome. Patients usually possess insight into the unreality of their visual experiences, which are commonly pleasant but may sometimes cause distress. The ...
American Journal of Respiratory and Critical Care Medicine, 1994
Airspace epithelial permeability is known to increase in cigarette smokers. To study the role of ... more Airspace epithelial permeability is known to increase in cigarette smokers. To study the role of the antioxidant reduced glutathione (GSH) in this phenomenon, we used an in vitro model of the epithelial permeability of a monolayer of human type II alveolar epithelial cells (A549 cell line). Both whole (WSC) and vapor (VSC) smoke condensates induced a recoverable, concentration-dependent increase in epithelial permeability to 125iodine-labeled bovine serum albumin (125IBSA), associated with a profound fall in intracellular GSH. Buthionine sulfoximine (BSO), a GSH synthesis inhibitor, decreased GSH levels in A549 epithelial cells, significantly increased A549 epithelial cell permeability, and enhanced both WSC and VSC-induced A549 epithelial cell permeability. Co-culturing epithelial cells and GSH (500 microM) reduced WSC-induced, but not VSC-induced A549 epithelial cell permeability. Increasing intracellular GSH also ameliorated the smoke-induced increased epithelial permeability. Concentrations of cigarette smoke condensate of < 20% increased A549 epithelial cell permeability without associated cell detachment and lysis, which was also the case with BSO-induced increased epithelial permeability. WSC and VSC, instilled intratracheally, significantly increased rat lung epithelial permeability to 125IBSA, 6 h postinstillation, associated with a significant recruitment of neutrophils into the airspaces. This was associated with a small increase in GSH in the lung tissue of VSC-treated rats. However, both WSC and VSC markedly reduced GSH in bronchoalveolar lavage (BAL) fluid. Reduction in lung GSH to 95% but not to 68% of control values by BSO increased lung epithelial permeability in vivo. However, there was no additive effect on epithelial permeability of WSC and BSO.(ABSTRACT TRUNCATED AT 250 WORDS)
Idiopathic pulmonary fibrosis (IPF) is characterized by an increased oxidant burden and by a defi... more Idiopathic pulmonary fibrosis (IPF) is characterized by an increased oxidant burden and by a deficiency of glutathione, a major antioxidant, in the lung epithelial lining fluid (ELF). Therefore, a rational therapeutic approach is to reverse the imbalance between oxidants and antioxidants in the lung by enhancing the antioxidant screen. With this background, the aim of our study was to evaluate oral N-acetylcysteine (NAC) as a strategy to augment lung glutathione levels in patients with IPF Concentrations of total glutathione in bronchoalveolar lavage fluid (BALF) were quantified spectrophotometrically, before and following oral therapy with 3 x 600 mg NAC per day for 5 days, in 17 nonsmoking patients with biopsy-proven IPF The volume of ELF recovered by BAL was determined using the urea method. Pretherapy, total glutathione levels in ELF in IPF patients were significantly less than normal (187+36 vs 368+60 1y/), in contrast to levels in BALF (0.99+0-12 vs 1.18+ 19,uM). Following therapy with oral NAC, glutathione levels in BALF were 1.54 + 0.24 jiM (a significant increase compared to pretherapy), whereas the increase in ELF levels (319+ 92,M) did not reach significance. The therapy was well-tolerated, and all routine clinical and bronchoscopic parameters remained unchanged. It is thus feasible and safe to augment deficient lung glutathione levels in patients with IPF; thereby, potentially augmenting pulmonary antioxidant protection.
We studied asbestos, vitreous fiber (MMVF10), and refractory ceramic fiber (RCF1) from the Therma... more We studied asbestos, vitreous fiber (MMVF10), and refractory ceramic fiber (RCF1) from the Thermal Insulation Manufacturers' Association fiber repository regarding the following: free radical damage to plasmid DNA, iron release, ability to deplete glutathione (GSH), and activate redox-sensitive transcription factors in macrophages. Asbestos had much more free radical activity than any of the man-made vitreous fibers. More Fe3+ was released than Fe2+ and more of both was released at pH 4.5 than at pH 7.2. Release of iron from the different fibers was generally not a good correlate of ability to cause free radical injury to the plasmid DNA. All fiber types caused some degree of oxidative stress, as revealed by depletion of intracellular GSH. Amosite asbestos upregulated nuclear binding of activator protein 1 transcription factor to a greater level than MMVF1 0 and RCF1; long-fiber amosite was the only fiber to enhance activation of the transcription factor nuclear factor icB (NFKcB). The use of cysteine methyl ester and buthionine sulfoximine to modulate GSH suggested that GSH homeostasis was important in leading to activation of transcription factors. We conclude that the intrinsic free radical activity is the major determinant of transcription factor activation and therefore gene expression in alveolar macrophages. Although this was not related to iron release or ability to deplete macrophage GSH at 4 hr, GSH does play a role in activation of NFOcB.
The development of an oxidant/antioxidant imbalance in lung inflammation may activate redox-sensi... more The development of an oxidant/antioxidant imbalance in lung inflammation may activate redox-sensitive transcription factors such as nuclear factor-kappa B (NF-kappa B) and activator protein-1 (AP-1), which regulate the genes for proinflammatory mediators and protective antioxidant genes. GSH, a ubiquitous tripeptide thiol, is a vital intra- and extracellular protective antioxidant against oxidative stress, which plays a key role in the control of proinflammatory processes in the lungs. The rate-limiting enzyme in GSH synthesis is gamma-glutamylcysteine synthetase (gamma-GCS), which consists of a catalytic heavy and a regulatory light subunit. The promoter regions of the human gamma-GCS subunits contain AP-1, NF-kappa B, and antioxidant response elements and are regulated by oxidants, growth factors, inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha), and anti-inflammatory agent (dexamethasone) in lung cells. TNF-alpha depletes intracellular GSH, concomitant with an increase in oxidised glutathione levels in alveolar epithelial cells. TNF-alpha also induces the activation of NF-kappa B and AP-1 and the subsequent increase in gamma-GCS heavy subunit transcription in these cells. Dexamethasone depleted both basal and TNF-alpha-stimulated GSH levels by down-regulating the gamma-GCS-heavy subunit transcription via a mechanism involving AP-1 (c-Jun). The existence of this fine tuning between the redox GSH levels and the activation of transcription factors may determine the balance of transcription for proinflammatory and antioxidant gamma-GCS genes in inflammation. More studies are required to understand the signalling mechanism of the redox regulation of NF-kappa B and AP-1 and gene transcription in inflammation. This could lead to the development of therapeutic strategies based on the pharmacological manipulation of the production of this important antioxidant in inflammation.
The airway epithelium is injured by oxidants inhaled as atmospheric pollutants or produced during... more The airway epithelium is injured by oxidants inhaled as atmospheric pollutants or produced during inflammatory responses. We studied the effect of modulating the antioxidant intracellular glutathione, both using thiol compounds and by the adaptive effect of hyperoxia, on oxidant-induced injury and activation of the nuclear factor-kappaB (NF-B) in two cell lines: the human bronchial (16HBE) and type II alveolar epithelial cells (A549). The thiol antioxidants glutathione (GSH) and glutathione monoethyl ester (GSH-MEE) [2 mM] increased GSH levels (nmol/mg protein) in A549 cells (GSH 383 Ϯ 26 and GSH-MEE 336 Ϯ 23 vs control 171 Ϯ 13, P Ͻ 0.001) and in 16HBE cells (GSH 405 Ϯ 33, GSH-MEE 362 Ϯ 37 vs control 198 Ϯ 12, P Ͻ 0.001, N ϭ 3). Treatment of hyperoxia (95% oxygen) also increased GSH levels between 4 and 24 hr exposure compared with control (P Ͻ 0.01). Hydrogen peroxide (H 2 O 2) (0.01 mM) induced NF-B activation, whereas hyperoxia exposure did not affect NF-B activation in either cell line. Pretreatment with DL-buthionine (SR)sulfoximine, which decreased intracellular glutathione, increased NF-B binding induced by H 2 O 2 and increased lactate dehydrogenase (LDH) release (P Ͻ 0.001). Pretreatment with the thiol compounds and hyperoxia totally inhibited H 2 O 2-induced NF-B binding and cell injury as measured by LDH release. These data indicate the importance of intracellular glutathione and inhibition of NF-B in both protection/tolerance against oxidant-induced epithelial cell injury, and NF-B activation in response to oxidative stress which may be important in lung inflammation. Thus, increasing intracellular glutathione may be of therapeutic relevance if able to modulate NF-B activation and hence attenuate inflammation.
Increases in the levels of environmental particulate matter with a diameter of Ͻ10 m diameter (PM... more Increases in the levels of environmental particulate matter with a diameter of Ͻ10 m diameter (PM 10) in the air are associated with a variety of adverse health effects, particularly chronic lung and cardiovascular diseases. The expression of many inflammatory genes involves the remodeling of the chromatin structure provided by histone proteins. Histone acetylation causes the unwinding of chromatin structure, therefore allowing transcription factor access to promoter sites. Acetylation is reversible and is regulated by histone acetyltransferases (HATs), which promote acetylation, and deacetylases, which promote deacetylation. PM10 and H2O2 increased IL-8 protein release from A549 cells after 24-h treatment, and this was enhanced by histone deacetylase inhibition by trichostatin A (cotreatment). PM10 and H2O2 treatment also increased HAT activity as well as the level of acetylated histone 4 (H4). PM10 enhanced H4 acetylation that was mediated by oxidative stress as shown by thiol antioxidant inhibition. Acetylation of H4 mediated by PM10 was associated with the promoter region of the IL-8 gene. These data suggest that remodeling of chromatin by histone acetylation plays a role in PM10-mediated responses in the lungs.
Neutrophil apoptosis represents a major mechanism involved in the resolution of inflammation. Sin... more Neutrophil apoptosis represents a major mechanism involved in the resolution of inflammation. Since hypoxia induces apoptosis in several cell lines and is of particular relevance in many disease states, we studied the effect of oxygen concentration on neutrophil survival in vitro. Hypoxia caused a dramatic decrease in neutrophil apoptosis (% apoptosis 20 h: 78.7 +/- 2.2% in 21% O2, 61.4 +/- 6.5% in 2.5% O2, 23.1 +/- 3.2% in 0% O2, n = 5). This was additive to the effect of GM-CSF (50 U/ml), not associated with induction of bcl-2 expression, and was not mimicked by methionine (5 mM), superoxide dismutase (200 micrograms/ml) or Trolox (10 mM) but was mimicked by catalase (250 micrograms/ml). Hence, hypoxia has a bcl-2-independent effect on neutrophil apoptosis that may adversely affect the clearance of these cells from an inflammatory focus.
We studied the acute effects of cigarette smoke condensate (CSC), H2O2, and tumor necrosis factor... more We studied the acute effects of cigarette smoke condensate (CSC), H2O2, and tumor necrosis factor (TNF)-alpha on the glutathione (GSH) redox system in a human type II epithelial cell line (A549) in vitro. CSC, in vitro and in vivo after intratracheal instillation of CSC in the rat, produced a depletion of intracellular soluble GSH, concomitant with GSH-conjugate formation, without significant elevation of oxidized GSH (GSSG), protein-GSH mixed disulfides (PrSSG), nor any GSH efflux from the cells. By contrast, H2O2 (500 microM) after 5-min exposure to A549 cells caused significant depletion of intracellular GSH associated with an efflux of GSSG and a significant increase in the formation of PrSSG. TNF-alpha, in concentrations of 100 U/ml and 1,000 U/ml, produced a significant depletion of GSH in A549 cells after 4- and 24-h exposure, with an associated elevation of GSSG. The activities of glutathione peroxidase, gamma-glutamylcysteine synthetase, and glucose-6-phosphate dehydrogenase were significantly decreased in epithelial cells and in rat lungs after CSC exposure, without change in glutathione S-transferase and glutathione reductase activities. By contrast, H2O2 and TNF-alpha did not alter these enzyme activities in epithelial cells. Thus GSH depletion and alteration in enzyme activities in alveolar epithelial cells by CSC, H2O2, and TNF-alpha occur by different mechanisms.
Macrophage migration inhibitory factor (MIF) is a potent proinflammatory mediator that has been s... more Macrophage migration inhibitory factor (MIF) is a potent proinflammatory mediator that has been shown to potentiate lethal endotoxemia and to play a potentially important regulatory role in human acute respiratory distress syndrome (ARDS). We have investigated whether eosinophils are an important source of MIF and whether MIF may be involved in the pathophysiology of asthma. Unstimulated human circulating eosinophils were found to contain preformed MIF. Stimulation of human eosinophils with phorbol myristate acetate in vitro yielded significant release of MIF protein. For example, eosinophils stimulated with phorbol myristate acetate (100 nM, 8 h, 37 Њ C) released 1,539 Ϯ 435 pg/10 6 cells of MIF, whereas unstimulated cells released barely detectable levels (Ͻ 142 pg/10 6 cells, mean Ϯ SEM, n ϭ 8). This stimulated release was shown to be (a) concentration-and time-dependent, (b) partially blocked by the protein synthesis inhibitor cycloheximide, and (c) significantly inhibited by the protein kinase C inhibitor Ro-31,8220. In addition, we show that the physiological stimuli C5a and IL-5 also cause significant MIF release. Furthermore, bronchoalveolar lavage fluid obtained from asthmatic patients contains significantly elevated levels of MIF as compared to nonatopic normal volunteers (asthmatic, 797.5 Ϯ 92 pg/ml; controls, 274 Ϯ 91 pg/ml). These results highlight the potential importance of MIF in asthma and other eosinophil-dependent inflammatory disorders. (J.
Asthma and chronic obstructive pulmonary disease (COPD) are inflammatory lung diseases that are c... more Asthma and chronic obstructive pulmonary disease (COPD) are inflammatory lung diseases that are characterized by systemic and chronic localized inflammation and oxidative stress. Sources of oxidative stress arise from the increased burden of inhaled oxidants, as well as elevated amounts of reactive oxygen species (ROS) released from inflammatory cells. Increased levels of ROS, either directly or via the formation of lipid peroxidation products, may play a role in enhancing the inflammatory response in both asthma and COPD. Moreover, in COPD it is now recognized as the main pathogenic factor for driving disease progression and increasing severity. ROS and lipid peroxidation products can influence the inflammatory response at many levels through its impact on signal transduction mechanisms, activation of redox-sensitive transcriptions factors, and chromatin regulation resulting in pro-inflammatory gene expression. It is this impact of ROS on chromatin regulation by reducing the activity of the transcriptional co-repressor, histone deacetylase-2 (HDAC-2), that leads to the poor efficacy of corticosteroids in COPD, severe asthma, and smoking asthmatics. Thus, the presence of oxidative stress has important consequences for the pathogenesis, severity, and treatment of asthma and COPD. However, for ROS to have such an impact, it must first overcome a variety of antioxidant defenses. It is likely, therefore, that a combination of antioxidants may be effective in the treatment of asthma and COPD. Various approaches to enhance the lung antioxidant screen and clinical trials of antioxidant compounds are discussed.
The spectrophotometric/microplate reader assay method for glutathione (GSH) involves oxidation of... more The spectrophotometric/microplate reader assay method for glutathione (GSH) involves oxidation of GSH by the sulfhydryl reagent 5,5&amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-dithio-bis(2-nitrobenzoic acid) (DTNB) to form the yellow derivative 5&amp;amp;amp;amp;amp;amp;amp;amp;amp;#39;-thio-2-nitrobenzoic acid (TNB), measurable at 412 nm. The glutathione disulfide (GSSG) formed can be recycled to GSH by glutathione reductase in the presence of NADPH. The assay is composed of two parts: the preparation of cell cytosolic/tissue extracts and the detection of total glutathione (GSH and GSSG). The method is simple, convenient, sensitive and accurate. The lowest detection for GSH and GSSG is 0.103 nM in a 96-well plate. This method is rapid and the whole procedure takes no longer than 15 min including reagent preparation. The method can assay GSH in whole blood, plasma, serum, lung lavage fluid, cerebrospinal fluid, urine, tissues and cell extracts and can be extended for drug discovery/pharmacology and toxicology protocols to study the effects of drugs and toxic compounds on glutathione metabolism.
Reactive oxygen species (ROS), either directly or via the formation of lipid peroxidation product... more Reactive oxygen species (ROS), either directly or via the formation of lipid peroxidation products, such as 4-hydroxy-2-nonenal, acrolein and F2-isoprostanes, may play a role in enhancing inflammation through the activation and phosphorylation of stress kinases (JNK, ERK, p38) and redox-sensitive transcription factors such as NF-kappaB and AP-1. This increases the expression of genes regulating a battery of distinct pro-inflammatory mediators. Acetylation by histone acetyltransferase (HAT) of specific lysine residues on the N-terminal tail of core histones, results in uncoiling of the DNA and increased accessibility to transcription factor binding. In contrast, histone deacetylation by histone deacetylase (HDAC) represses gene transcription by promoting DNA winding thereby limiting access to transcription factors. Oxidative stress activates NF-kappaB resulting in expression of pro-inflammatory mediators through the activation of intrinsic HAT activity on co-activator molecules. In addition, oxidative stress also inhibits HDAC activity and in doing so enhances inflammatory gene expression which leads to a chronic inflammatory response. Oxidative stress can also increase complex formation between the co-activator CBP/p300 and the p65 subunit of NF-kappaB suggesting a further role of oxidative stress in chromatin remodeling. The antioxidant and/or anti-inflammatory effects of thiol molecules (glutathione, N-acetyl-L-cysteine and N-acystelyn), dietary polyphenols (curcumin-diferuloylmethane and resveratrol), the bronchodilator theophylline and glucocorticoids have all been shown to play a role in either controlling NF-kappaB activation or chromatin remodeling through modulation of HDAC activity and subsequently inflammatory gene expression in lung epithelial cells. Thus, oxidative stress regulates both signal transduction and chromatin remodeling which in turn impacts on pro-inflammatory responses in the lungs.
Inflammatory lung diseases are characterized by chronic inflammation and oxidant/antioxidant imba... more Inflammatory lung diseases are characterized by chronic inflammation and oxidant/antioxidant imbalance, a major cause of cell damage. The development of an oxidant/antioxidant imbalance in lung inflammation may activate redox-sensitive transcription factors such as nuclear factor-kB, and activator protein-1 (AP-1), which regulate the genes for pro-inflammatory mediators and protective antioxidant genes. Glutathione (GSH), a ubiquitous tripeptide thiol, is a vital intra-and extracellular protective antioxidant against oxidative/nitrosative stresses, which plays a key role in the control of pro-inflammatory processes in the lungs. Recent findings have suggested that GSH is important in immune modulation, remodelling of the extracellular matrix, apoptosis and mitochondrial respiration. The rate-limiting enzyme in GSH synthesis is c-glutamylcysteine synthetase (c-GCS). The human c-GCS heavy and light subunits are regulated by AP-1 and antioxidant response elements and are modulated by oxidants, phenolic antioxidants, growth factors, and inflammatory and anti-inflammatory agents in lung cells. Alterations in alveolar and lung GSH metabolism are widely recognized as a central feature of many inflammatory lung diseases such as idiopathic pulmonary fibrosis, acute respiratory distress syndrome, cystic fibrosis and asthma. The imbalance and/or genetic variation in antioxidant c-GCS and pro-inflammatory versus antioxidant genes in response to oxidative stress and inflammation in some individuals may render them more susceptible to lung inflammation. Knowledge of the mechanisms of GSH regulation and balance between the release and expression of pro-and anti-inflammatory mediators could lead to the development of novel therapies based on the pharmacological manipulation of the production as well as gene transfer of this important antioxidant in lung inflammation and injury. This review describes the redox control and involvement of nuclear factor-kB and activator protein-1 in the regulation of cellular glutathione and c-glutamylcysteine synthetase under conditions of oxidative stress and inflammation, the role of glutathione in oxidant-mediated susceptibility/tolerance, c-glutamylcysteine synthetase genetic susceptibility and the potential therapeutic role of glutathione and its precursors in protecting against lung oxidant stress, inflammation and injury.
Thorax, 2000
BACKGROUND It has been suggested that oxidative stress is an important factor in the pathogenesis... more BACKGROUND It has been suggested that oxidative stress is an important factor in the pathogenesis of chronic obstructive pulmonary disease (COPD). We have shown that an oxidant/antioxidant imbalance occurs in the distal air spaces of smokers and in patients with COPD which is ...
Objective To investigate the cardioprotective efficacy of remote ischaemic preconditioning (RIPC)... more Objective To investigate the cardioprotective efficacy of remote ischaemic preconditioning (RIPC) in cardiac surgery. Design We have performed a systematic search of MEDLINE, EMBASE and Cochrane Central Register of Controlled Trials to identify randomized controlled trials involving RIPC. Setting Randomized controlled trials of RIPC in open cardiac surgery patients. Main outcome measures Meta-analysis was performed with the primary outcome the standardized mean difference between intervention and control groups in 12 hour postoperative troponin concentration. Heterogeneity was examined by fixed effects meta-regression. Results Ten studies with a total of 693 participants were included in the meta-analysis. RIPC reduced troponin levels 12 hours after surgery compared with control. The fixed and random effects differences were 0.35 (95% CI 0.19 to 0.51) and 0.53 (95% CI 0.18-0.88) respectively. However, important heterogeneity was present. Fixed effects metaregression partially accounted for heterogeneity based on whether studies had full blinding, comprising blinding of patients, surgeons, anaesthetists and investigators. Studies with incomplete or no blinding demonstrated a larger estimate of effect, 0.74 (95% CI 0.47 to 1.00) compared to those with full blinding, 0.13 (95% CI-0.07 to 0.33). Conclusions Although our analysis suggests RIPC may result in cardiac protection during cardiac surgery, the effect was most marked in studies without full blinding, with a smaller and statistically nonsignificant effect in fully blinded studies. We propose that further double blind randomized controlled trials investigating the cardioprotective effects of RIPC in cardiac surgery are required to resolve the current clinical uncertainty.
FEBS letters, 1996
Increased levels of glutathione (GSH) occur in the epithelial lining fluid (ELF) of chronic cigar... more Increased levels of glutathione (GSH) occur in the epithelial lining fluid (ELF) of chronic cigarette smokers. Therefore we investigated the effect of cigarette smoke condensate solution (CSC) on GSH synthesis and the regulation of gamma-glutamylcysteine synthetase (gammaGCS) in human type II alveolar epithelial cells (A549). CSC exposure increased GSH levels, gammaGCS activity and gammaGCS heavy subunit (HS) mRNA, as well as increasing DNA binding of the activator protein-1 (AP-1) and the human antioxidant response element (hARE). Transfection of deletion constructs of the gammaGCS-HS promoter in a chloramphenicol acetyl transferase (CAT) reporter system revealed that an hARE, present within promoter, is not required for the CSC mediated induction. We conclude that CSC induction of gammaGCS-HS expression is associated with AP-1/AP-1-like responsive elements.
Biochemical and …, 1996
We studied the regulation of glutathione (GSH) synthesis and characterised the 5'-promote... more We studied the regulation of glutathione (GSH) synthesis and characterised the 5'-promoter region of the gamma-glutamylcysteine synthetase-heavy subunit (gammaGCS-HS) gene in human alveolar type II cells (A549) following exposure to menadione (MQ) and hydrogen peroxide (H2O2). Both MQ (100 microM) and H2O2 (100 microM) exposure increased intracellular GSH levels associated with increased gammaGCS activity. This was concomitant with enhanced expression of gammaGCS-HS mRNA. Transfection of deletion constructs of the gammaGCS-HS promoter (-1050 to +82 bp) in a chloramphenicol acetyl transferase (CAT) reporter system revealed that an human antioxidant response element (hARE), present within the proximal region of the promoter (-1050 to -818 bp), is not required for oxidant-mediated gene induction. We conclude that oxidant stress-induced gammaGCS-HS mRNA expression is associated with AP-1 or AP-1 like responsive elements (-817 to +45 bp).
Clinical & experimental …, 2008
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Survey of ophthalmology, 2003
Visually impaired patients may experience complex visual hallucinations, a condition known as the... more Visually impaired patients may experience complex visual hallucinations, a condition known as the Charles Bonnet Syndrome. Patients usually possess insight into the unreality of their visual experiences, which are commonly pleasant but may sometimes cause distress. The ...
American Journal of Respiratory and Critical Care Medicine, 1994
Airspace epithelial permeability is known to increase in cigarette smokers. To study the role of ... more Airspace epithelial permeability is known to increase in cigarette smokers. To study the role of the antioxidant reduced glutathione (GSH) in this phenomenon, we used an in vitro model of the epithelial permeability of a monolayer of human type II alveolar epithelial cells (A549 cell line). Both whole (WSC) and vapor (VSC) smoke condensates induced a recoverable, concentration-dependent increase in epithelial permeability to 125iodine-labeled bovine serum albumin (125IBSA), associated with a profound fall in intracellular GSH. Buthionine sulfoximine (BSO), a GSH synthesis inhibitor, decreased GSH levels in A549 epithelial cells, significantly increased A549 epithelial cell permeability, and enhanced both WSC and VSC-induced A549 epithelial cell permeability. Co-culturing epithelial cells and GSH (500 microM) reduced WSC-induced, but not VSC-induced A549 epithelial cell permeability. Increasing intracellular GSH also ameliorated the smoke-induced increased epithelial permeability. Concentrations of cigarette smoke condensate of < 20% increased A549 epithelial cell permeability without associated cell detachment and lysis, which was also the case with BSO-induced increased epithelial permeability. WSC and VSC, instilled intratracheally, significantly increased rat lung epithelial permeability to 125IBSA, 6 h postinstillation, associated with a significant recruitment of neutrophils into the airspaces. This was associated with a small increase in GSH in the lung tissue of VSC-treated rats. However, both WSC and VSC markedly reduced GSH in bronchoalveolar lavage (BAL) fluid. Reduction in lung GSH to 95% but not to 68% of control values by BSO increased lung epithelial permeability in vivo. However, there was no additive effect on epithelial permeability of WSC and BSO.(ABSTRACT TRUNCATED AT 250 WORDS)