Mitochondrial dysfunction in airways and quadriceps muscle of patients with chronic obstructive pulmonary disease.

BACKGROUND: Mitochondrial damage and dysfunction have been reported in airway and quadriceps muscle cells of patients with chronic obstructive pulmonary disease (COPD). We determined the concomitance of mitochondrial dysfunction in these cells in COPD. METHODS: Bronchial biopsies were obtained from never- and ex-smoker volunteers and COPD patients (GOLD Grade 2) and quadriceps muscle biopsies from the same volunteers in addition to COPD patients at GOLD Grade 3/4 for measurement of mitochondrial function. RESULTS: Decreased mitochondrial membrane potential (ΔΨm), increased mitochondrial reactive oxygen species (mtROS) and decreased superoxide dismutase 2 (SOD2) levels were observed in mitochondria isolated from bronchial biopsies from Grade 2 patients compared to healthy never- and ex-smokers. There was a significant correlation between ΔΨm and FEV1 (% predicted), transfer factor of the lung for carbon monoxide (TLCOC % predicted), 6-min walk test and maximum oxygen consumption. In addition, ΔΨm was also associated with decreased expression levels of electron transport chain (ETC) complex proteins I and II. In quadriceps muscle of Grade 2 COPD patients, a significant increase in total ROS and mtROS was observed without changes in ΔΨm, SOD2 or ETC complex protein expression. However, quadriceps muscle of GOLD Grade 3/4 COPD patients showed an increased mtROS and decreased SOD2 and ETC complex proteins I, II, III and V expression. CONCLUSIONS: Mitochondrial dysfunction in the airways, but not in quadriceps muscle, is associated with airflow obstruction and exercise capacity in Grade 2 COPD. Oxidative stress-induced mitochondrial dysfunction in the quadriceps may result from similar disease processes occurring in the lungs.

Oxidative Stress in Ozone-Induced Chronic Lung Inflammation and Emphysema: A Facet of Chronic Obstructive Pulmonary Disease.

Oxidative stress plays an important role in the pathogenesis of chronic obstructive pulmonary disease (COPD) caused by cigarette smoke and characterized by chronic inflammation, alveolar destruction (emphysema) and bronchiolar obstruction. Ozone is a gaseous constituent of urban air pollution resulting from photochemical interaction of air pollutants such as nitrogen oxide and organic compounds. While acute exposure to ozone induces airway hyperreactivity and neutrophilic inflammation, chronic ozone exposure in mice causes activation of oxidative pathways resulting in cell death and a chronic bronchial inflammation with emphysema, mimicking cigarette smoke-induced COPD. Therefore, the chronic exposure to ozone has become a model for studying COPD. We review recent data on mechanisms of ozone induced lung disease focusing on pathways causing chronic respiratory epithelial cell injury, cell death, alveolar destruction, and tissue remodeling associated with the development of chronic inflammation and AHR. The initial oxidant insult may result from direct effects on the integrity of membranes and organelles of exposed epithelial cells in the airways causing a stress response with the release of mitochondrial reactive oxygen species (ROS), DNA, and proteases. Mitochondrial ROS and mitochondrial DNA activate NLRP3 inflammasome and the DNA sensors cGAS and STING accelerating cell death pathways including caspases with inflammation enhancing alveolar septa destruction, remodeling, and fibrosis. Inhibitors of mitochondrial ROS, NLRP3 inflammasome, DNA sensor, cell death pathways, and IL-1 represent novel therapeutic targets for chronic airways diseases underlined by oxidative stress.

Pathophysiological regulation of lung function by the free fatty acid receptor FFA4.

Increased prevalence of inflammatory airway diseases including asthma and chronic obstructive pulmonary disease (COPD) together with inadequate disease control by current frontline treatments means that there is a need to define therapeutic targets for these conditions. Here, we investigate a member of the G protein-coupled receptor family, FFA4, that responds to free circulating fatty acids including dietary omega-3 fatty acids found in fish oils. We show that FFA4, although usually associated with metabolic responses linked with food intake, is expressed in the lung where it is coupled to Gq/11 signaling. Activation of FFA4 by drug-like agonists produced relaxation of murine airway smooth muscle mediated at least in part by the release of the prostaglandin E2 (PGE2) that subsequently acts on EP2 prostanoid receptors. In normal mice, activation of FFA4 resulted in a decrease in lung resistance. In acute and chronic ozone models of pollution-mediated inflammation and house dust mite and cigarette smoke-induced inflammatory disease, FFA4 agonists acted to reduce airway resistance, a response that was absent in mice lacking expression of FFA4. The expression profile of FFA4 in human lung was similar to that observed in mice, and the response to FFA4/FFA1 agonists similarly mediated human airway smooth muscle relaxation ex vivo. Our study provides evidence that pharmacological targeting of lung FFA4, and possibly combined activation of FFA4 and FFA1, has in vivo efficacy and might have therapeutic value in the treatment of bronchoconstriction associated with inflammatory airway diseases such as asthma and COPD.

Mesenchymal stem cells alleviate oxidative stress-induced mitochondrial dysfunction in the airways.

BACKGROUND: Oxidative stress-induced mitochondrial dysfunction can contribute to inflammation and remodeling in patients with chronic obstructive pulmonary disease (COPD). Mesenchymal stem cells protect against lung damage in animal models of COPD. It is unknown whether these effects occur through attenuating mitochondrial dysfunction in airway cells. OBJECTIVE: We sought to examine the effect of induced pluripotent stem cell-derived mesenchymal stem cells (iPSC-MSCs) on oxidative stress-induce mitochondrial dysfunction in human airway smooth muscle cells (ASMCs) in vitro and in mouse lungs in vivo. METHODS: ASMCs were cocultured with iPSC-MSCs in the presence of cigarette smoke medium (CSM), and mitochondrial reactive oxygen species (ROS) levels, mitochondrial membrane potential (ΔΨm), and apoptosis were measured. Conditioned medium from iPSC-MSCs and transwell cocultures were used to detect any paracrine effects. The effect of systemic injection of iPSC-MSCs on airway inflammation and hyperresponsiveness in ozone-exposed mice was also investigated. RESULTS: Coculture of iPSC-MSCs with ASMCs attenuated CSM-induced mitochondrial ROS, apoptosis, and ΔΨm loss in ASMCs. iPSC-MSC-conditioned medium or transwell cocultures with iPSC-MSCs reduced CSM-induced mitochondrial ROS but not ΔΨm or apoptosis in ASMCs. Mitochondrial transfer from iPSC-MSCs to ASMCs was observed after direct coculture and was enhanced by CSM. iPSC-MSCs attenuated ozone-induced mitochondrial dysfunction, airway hyperresponsiveness, and inflammation in mouse lungs. CONCLUSION: iPSC-MSCs offered protection against oxidative stress-induced mitochondrial dysfunction in human ASMCs and in mouse lungs while reducing airway inflammation and hyperresponsiveness. These effects are, at least in part, dependent on cell-cell contact, which allows for mitochondrial transfer, and paracrine regulation. Therefore iPSC-MSCs show promise as a therapy for oxidative stress-dependent lung diseases, such as COPD.

BET proteins are a key component of immunoglobulin gene expression.

AIM: BET proteins have been shown to regulate gene expression including inflammatory genes. METHODS: In order to investigate the role of the BET proteins in immunoglobulin production we treated the human B-cell line CLNH11.4 and primary human B cells and ozone-exposed mice with BET inhibitors (JQ1 or IBET151). RESULTS: Both proliferation and IgG production were reduced by JQ1 in a concentration-dependent manner. JQ1 significantly reduced immunoglobulin gene transcription. In vivo treatment of ozone-exposed mice with the BET inhibitor IBET151 similarly inhibited ozone-induced immunoglobulin production. JQ1 did not reduce the protein levels of Brd4 or Oct2 per se but reduced the ability of Brd4 and Oct2 to co-immunoprecipitate and of Oct2 to bind to immunoglobulin gene promoters. CONCLUSION: Our results indicate that BET proteins including Brd4 play a crucial role regulation B-cell-specific gene expression and immunoglobulin production.

Mapping physiological G protein-coupled receptor signaling pathways reveals a role for receptor phosphorylation in airway contraction.

G protein-coupled receptors (GPCRs) are known to initiate a plethora of signaling pathways in vitro. However, it is unclear which of these pathways are engaged to mediate physiological responses. Here, we examine the distinct roles of Gq/11-dependent signaling and receptor phosphorylation-dependent signaling in bronchial airway contraction and lung function regulated through the M3-muscarinic acetylcholine receptor (M3-mAChR). By using a genetically engineered mouse expressing a G protein-biased M3-mAChR mutant, we reveal the first evidence, to our knowledge, of a role for M3-mAChR phosphorylation in bronchial smooth muscle contraction in health and in a disease state with relevance to human asthma. Furthermore, this mouse model can be used to distinguish the physiological responses that are regulated by M3-mAChR phosphorylation (which include control of lung function) from those responses that are downstream of G protein signaling. In this way, we present an approach by which to predict the physiological/therapeutic outcome of M3-mAChR-biased ligands with important implications for drug discovery.

The MIF Antagonist ISO-1 Attenuates Corticosteroid-Insensitive Inflammation and Airways Hyperresponsiveness in an Ozone-Induced Model of COPD.

INTRODUCTION: Macrophage migration inhibitory factor (MIF) is an inflammatory cytokine associated with acute and chronic inflammatory disorders and corticosteroid insensitivity. Its expression in the airways of patients with chronic obstructive pulmonary disease (COPD), a relatively steroid insensitive inflammatory disease is unclear, however. METHODS: Sputum, bronchoalveolar lavage (BAL) macrophages and serum were obtained from non-smokers, smokers and COPD patients. To mimic oxidative stress-induced COPD, mice were exposed to ozone for six-weeks and treated with ISO-1, a MIF inhibitor, and/or dexamethasone before each exposure. BAL fluid and lung tissue were collected after the final exposure. Airway hyperresponsiveness (AHR) and lung function were measured using whole body plethysmography. HIF-1α binding to the Mif promoter was determined by Chromatin Immunoprecipitation assays. RESULTS: MIF levels in sputum and BAL macrophages from COPD patients were higher than those from non-smokers, with healthy smokers having intermediate levels. MIF expression correlated with that of HIF-1α in all patients groups and in ozone-exposed mice. BAL cell counts, cytokine mRNA and protein expression in lungs and BAL, including MIF, were elevated in ozone-exposed mice and had increased AHR. Dexamethasone had no effect on these parameters in the mouse but ISO-1 attenuated cell recruitment, cytokine release and AHR. CONCLUSION: MIF and HIF-1α levels are elevated in COPD BAL macrophages and inhibition of MIF function blocks corticosteroid-insensitive lung inflammation and AHR. Inhibition of MIF may provide a novel anti-inflammatory approach in COPD.

Klotho expression is reduced in COPD airway epithelial cells: effects on inflammation and oxidant injury.

COPD (chronic obstructive pulmonary disease) is associated with sustained inflammation, excessive injury, and accelerated lung aging. Human Klotho (KL) is an anti-aging protein that protects cells against inflammation and damage. In the present study, we quantified KL expression in the lungs of COPD patients and in an ozone-induced mouse model of COPD, and investigated the mechanisms that control KL expression and function in the airways. KL distribution and levels in human and mouse airways were measured by immunohistochemistry and Western blotting. The effect of CSE (cigarette smoke extract) on KL expression was detected in human bronchial epithelial cells. Moreover, the effect of KL on CSE-mediated inflammation and hydrogen peroxide-induced cellular injury/apoptosis was determined using siRNAs. KL expression was decreased in the lungs of smokers and further reduced in patients with COPD. Similarly, 6 weeks of exposure to ozone decreased KL levels in airway epithelial cells. CSE and TNFα (tumour necrosis factor α) decreased KL expression and release from airway epithelial cells, which was associated with enhanced pro-inflammatory cytokine expression. Moreover, KL depletion increased cell sensitivity to cigarette smoke-induced inflammation and oxidative stress-induced cell damage. These effects involved the NF-κB (nuclear factor κB), MAPK (mitogen-activated protein kinase) and Nrf2 (nuclear factor erythroid 2-related factor 2) pathways. Reduced KL expression in COPD airway epithelial cells was associated with increased oxidative stress, inflammation and apoptosis. These data provide new insights into the mechanisms associated with the accelerated lung aging in COPD development.

Oxidative stress-induced mitochondrial dysfunction drives inflammation and airway smooth muscle remodeling in patients with chronic obstructive pulmonary disease.

BACKGROUND: Inflammation and oxidative stress play critical roles in patients with chronic obstructive pulmonary disease (COPD). Mitochondrial oxidative stress might be involved in driving the oxidative stress-induced pathology. OBJECTIVE: We sought to determine the effects of oxidative stress on mitochondrial function in the pathophysiology of airway inflammation in ozone-exposed mice and human airway smooth muscle (ASM) cells. METHODS: Mice were exposed to ozone, and lung inflammation, airway hyperresponsiveness (AHR), and mitochondrial function were determined. Human ASM cells were isolated from bronchial biopsy specimens from healthy subjects, smokers, and patients with COPD. Inflammation and mitochondrial function in mice and human ASM cells were measured with and without the presence of the mitochondria-targeted antioxidant MitoQ. RESULTS: Mice exposed to ozone, a source of oxidative stress, had lung inflammation and AHR associated with mitochondrial dysfunction and reflected by decreased mitochondrial membrane potential (ΔΨm), increased mitochondrial oxidative stress, and reduced mitochondrial complex I, III, and V expression. Reversal of mitochondrial dysfunction by the mitochondria-targeted antioxidant MitoQ reduced inflammation and AHR. ASM cells from patients with COPD have reduced ΔΨm, adenosine triphosphate content, complex expression, basal and maximum respiration levels, and respiratory reserve capacity compared with those from healthy control subjects, whereas mitochondrial reactive oxygen species (ROS) levels were increased. Healthy smokers were intermediate between healthy nonsmokers and patients with COPD. Hydrogen peroxide induced mitochondrial dysfunction in ASM cells from healthy subjects. MitoQ and Tiron inhibited TGF-ß-induced ASM cell proliferation and CXCL8 release. CONCLUSIONS: Mitochondrial dysfunction in patients with COPD is associated with excessive mitochondrial ROS levels, which contribute to enhanced inflammation and cell hyperproliferation. Targeting mitochondrial ROS represents a promising therapeutic approach in patients with COPD.

Inhibitory effect of hydrogen sulfide on ozone-induced airway inflammation, oxidative stress, and bronchial hyperresponsiveness.

Exposure to ozone has been associated with airway inflammation, oxidative stress, and bronchial hyperresponsiveness. The goal of this study was to examine whether these adverse effects of ozone could be prevented or reversed by hydrogen sulfide (H2S) as a reducing agent. The H2S donor sodium (NaHS) (2 mg/kg) or vehicle (PBS) was intraperitoneally injected into mice 1 hour before and after 3-hour ozone (2.5 ppm) or air exposure, and the mice were studied 24 hours later. Preventive and therapeutic treatment with NaHS reduced the ozone-induced increases in the total cells, including neutrophils and macrophages; this treatment also reduced levels of cytokines, including TNF-α, chemokine (C-X-C motif) ligand 1, IL-6, and IL-1ß levels in bronchial alveolar lavage fluid; inhibited bronchial hyperresponsiveness; and attenuated ozone-induced increases in total malondialdehyde in bronchoalveolar lavage fluid and decreases in the ratio of reduced glutathione/oxidized glutathione in the lung. Ozone exposure led to decreases in the H2S production rate and in mRNA and protein levels of cystathionine-ß-synthetase and cystathionine-γ-lyase in the lung. These effects were prevented and reversed by NaHS treatment. Furthermore, NaHS prevented and reversed the phosphorylation of p38 mitogen-activated protein kinase and heat shock protein 27. H2S may have preventive and therapeutic value in the treatment of airway diseases that have an oxidative stress basis.

A comprehensive analysis of oxidative stress in the ozone-induced lung inflammation mouse model.

Ozone is an oxidizing environmental pollutant that contributes significantly to respiratory health. Exposure to increased levels of ozone has been associated with worsening of symptoms of patients with asthma and COPD (chronic obstructive pulmonary disease). In the present study, we investigated the acute and chronic effects of ozone exposure-induced oxidative stress-related inflammation mechanics in mouse lung. In particular, we investigated the oxidative stress-induced effects on HDAC2 (histone deacetylase 2) modification and activation of the Nrf2 (nuclear factor erythroid-related factor 2) and HIF-1α (hypoxia-inducible factor-1α) signalling pathways. Male C57BL/6 mice were exposed to ozone (3 p.p.m.) for 3 h a day, twice a week for a period of 1, 3 or 6 weeks. Control mice were exposed to normal air. After the last exposure, mice were killed for BAL (bronchoalveolar lavage) fluid and lung tissue collection. BAL total cell counts were elevated at all of the time points studied. This was associated with increased levels of chemokines and cytokines in all ozone-exposed groups, indicating the presence of a persistent inflammatory environment in the lung. Increased inflammation and Lm (mean linear intercept) scores were observed in chronic exposed mice, indicating emphysematous changes were present in lungs of chronic exposed mice. The antioxidative stress response was active (indicated by increased Nrf2 activity and protein) after 1 week of ozone exposure, but this ability was lost after 3 and 6 weeks of ozone exposure. The transcription factor HIF-1α was elevated in 3- and 6-week ozone-exposed mice and this was associated with increased gene expression levels of several HIF-1α target genes including Hdac2 (histone deacetylase 2), Vegf (vascular endothelial growth factor), Keap1 (kelch-like ECH-associated protein 1) and Mif (macrophage migration inhibitory factor). HDAC2 protein was found to be phosphorylated and carbonylated in nuclear and cytoplasm fractions, respectively, and was associated with a decrease in DNA-binding activity and protein expression of HDAC2. Decreased HDAC2 activity, most likely a direct result of protein modification, in combination with the loss of the antioxidative stress response and activation of the HIF-1α pathway, contribute to the inflammatory response and emphysema observed in ozone-exposed mice.

Hepatic VLDL production in ob/ob mice is not stimulated by massive de novo lipogenesis but is less sensitive to the suppressive effects of insulin.

Type 2 diabetes in humans is associated with increased de novo lipogenesis (DNL), increased fatty acid (FA) fluxes, decreased FA oxidation, and hepatic steatosis. In this condition, VLDL production is increased and resistant to suppressive effects of insulin. The relationships between hepatic FA metabolism, steatosis, and VLDL production are incompletely understood. We investigated VLDL-triglyceride and -apolipoprotein (apo)-B production in relation to DNL and insulin sensitivity in female ob/ob mice. Hepatic triglyceride (5-fold) and cholesteryl ester (15-fold) contents were increased in ob/ob mice compared with lean controls. Hepatic DNL was increased approximately 10-fold in ob/ob mice, whereas hepatic cholesterol synthesis was not affected. Basal rates of hepatic VLDL-triglyceride and -apoB100 production were similar between the groups. Hyperinsulinemic clamping reduced VLDL-triglyceride and -apoB100 production rates by approximately 60% and approximately 75%, respectively, in lean mice but only by approximately 20% and approximately 20%, respectively, in ob/ob mice. No differences in hepatic expression of genes encoding apoB and microsomal triglyceride transfer protein were found. Hepatic expression and protein phosphorylation of insulin receptor and insulin receptor substrate isoforms were reduced in ob/ob mice. Thus, strongly induced hepatic DNL is not associated with increased VLDL production in ob/ob mice, possibly related to differential hepatic zonation of apoB synthesis (periportal) and lipid accumulation (perivenous) and/or relatively low rates of cholesterogenesis. Insulin is unable to effectively suppress VLDL-triglyceride production in ob/ob mice, presumably because of impaired insulin signaling.