Superoxide release from contracting skeletal muscle in pulmonary TNF-α overexpression mice

Combined cytotoxicity of polystyrene nanoplastics and phthalate esters on human lung epithelial A549 cells and its mechanism

Awareness of risks posed by widespread presence of nanoplastics (NPs) and bioavailability and potential to interact with organic pollutants has been increasing. Inhalation is one of the more important pathways of exposure of humans to NPs. In this study, combined toxicity of concentrations of polystyrene NPs and various phthalate esters (PAEs), some of the most common plasticizers, including dibutyl phthalate (DBP) and di-(2-ethyl hexyl) phthalate (DEHP) on human lung epithelial A549 cells were investigated. When co-exposed, 20 μg NPs/mL increased viabilities of cells exposed to either DBP or DEHP and the modulation of toxic potency of DEHP was greater than that of DBP, while the 200 μg NPs/mL resulted in lesser viability of cells. PAEs sorbed to NPs decreased free phase concentrations (C_free) of PAEs, which resulted in a corresponding lesser bioavailability and joint toxicity at the lesser concentration of NPs. The opposite effect was observed at the greater concentration of NPs, which may result from the dominated role of NPs in the combined toxicity. Furthermore, our data showed that oxidative stress and inflammatory reactions were mechanisms for combined cytotoxicities of PAEs and NPs on A549 cells. Results of this study emphasized the combined toxic effects and mechanisms on human lung cells, which are helpful for assessing the risk of the co-exposure of NPs and organic contaminants in humans.

The mechanism and prevention of mitochondrial injury after exercise

With the development of society, physical activity has come to be an effective means by which people pursue good health to improve the quality of life. However, with the increase of intensity and the passage of time, exercise injury has become a hazard that can no longer be ignored. It is imperative to find effective ways to inhibit or reduce the negative effects of exercise. Mitochondria are important organelles involved in exercise and play an important role in exercise injury and prevention. Studies have found that exercise preconditioning and increased mitochondrial nutrition can effectively decrease mitochondrial damage after exercise. Against this background, some of the newest developments in this important field are reviewed here. The results discussed indicate that exercise preconditioning and supplement mitochondrial nutrition need to be increased to prevent exercise-related injuries.

Effects of electrotactic exercise and antioxidant EUK-134 on oxidative stress relief in Caenorhabditis elegans

Antioxidant uptake and regular exercise are two well-acknowledged measures used for rejuvenation and oxidative stress elimination. Previous studies have revealed that moderate exercise mildly increases intracellular signaling oxidant levels and strengthens the ability of an organism to deal with escalating oxidative stress by upregulating antioxidant enzymes, such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase. Antioxidant supplementation directly scavenges intracellular reactive oxygen species (ROS) to reduce oxidative stress. However, research to understand the impacts of these enzymes on mitigating oxidative stress from the perspective of simple animals is limited. Herein, we show that exercise combined with antioxidant supplementation ameliorates the physiological phenotypes and markers of aging in wild-type and SOD/CAT-deficient Caenorhabditis elegans. We discovered that treated wild-type and gene-deficient worms show better survivorship, reproduction, and motility compared with their control counterparts. Assays of biochemical indices revealed that variations in sod-3 expression under different stress levels imply an inducible enzyme response resulting from exercise training and antioxidant supplementation. In addition, induced ROS resistance obtained from any type of treatment could persist for several days even after treatment cessation, thus suggesting a potential long-term antioxidative stress effect. Our findings confirm that exercise, antioxidant supplementation, and their combination could significantly improve the ability of C. elegans to withstand adverse stress. Our observations provide promising insights into future therapies of anti-oxidative stress in higher animals.

In vitro renal toxicity evaluation of copper-based metal-organic framework HKUST-1 on human embryonic kidney cells

HKUST-1 is currently studied for a very diverse range of applications. Despite its exciting potential, significant concerns remain regarding the safety of HKUST-1. Therefore, human embryonic kidney 293 (HEK293) cells were used to verify the renal toxicity of HKUST-1. In this study, HKUST-1 induced concentration-dependent cytotoxic effects in HEK293 cells. The depolarization of mitochondrial membrane potential and formation of apoptotic bodies and autophagic vesicles were observed in HKUST-1-treated HEK293 cells. Oxidative (oxidative stress and haem oxygenase-1 activation) and inflammatory responses (NF-κB and NLRP3 activation) in HEK293 cells were induced by HKUST-1 exposure. In addition, the observed reduction in NAD(P)H levels in HKUST-1-treated HEK293 cells may be attributable to PARP-1 activation following DNA single- and double-strand breaks. The HKUST-1-induced depletion of zonula occludens proteins in HEK293 cells might lead to altered renal barrier integrity. The variations of α1-antitrypsin, oxidised α1-antitrypsin and NLRP3 protein expression in HEK293 cells suggested that HKUST-1 increases the risk of chronic kidney diseases. However, most of these adverse effects were significantly induced only by high HKUST-1 concentration (100 μg/mL), which do not reflect the actual exposure. Thus, the toxic risk of HKUST-1 appears to be negligible.

Polystyrene microplastic particles: In vitro pulmonary toxicity assessment

Microplastics (MPs) have become a global environmental concern. Recent studies have shown that MPs, of which the predominant type is often polystyrene (PS; known as PS-MPs), can extend to and affect remote, sparsely inhabited areas via atmospheric transport. Although exposure to inhaled MPs may induce lung dysfunction, further experimental verification of the pulmonary toxic potential of MPs and the mechanism underlying the toxicity is needed. Here we used normal human lung epithelial BEAS-2B cells to clarify the association between pulmonary toxicity and PS-MPs. Results revealed that PS-MPs can cause cytotoxic and inflammatory effects in BEAS-2B cells by inducing reactive oxygen species formation. PS-MPs can decrease transepithelial electrical resistance by depleting zonula occludens proteins. Indeed, decreased α1-antitrypsin levels in BEAS-2B cells suggest that exposure to PS-MPs increases the risk for chronic obstructive pulmonary disease, and high concentrations of PS-MPs can induce these adverse responses. While low PS-MP levels can only disrupt the protective pulmonary barrier, they may also increase the risk for lung disease. Collectively, our findings indicate that PS-MP inhalation may influence human respiratory health.

Hypoxic Preconditioning Attenuates Reoxygenation-Induced Skeletal Muscle Dysfunction in Aged Pulmonary TNF-α Overexpressing Mice

Aim: Skeletal muscle subjected to hypoxia followed by reoxygenation is susceptible to injury and subsequent muscle function decline. This phenomenon can be observed in the diaphragm during strenuous exercise or in pulmonary diseases such as chronic obstructive pulmonary diseases (COPD). Previous studies have shown that PO₂ cycling or hypoxic preconditioning (HPC), as it can also be referred to as, protects muscle function via mechanisms involving reactive oxygen species (ROS). However, this HPC protection has not been fully elucidated in aged pulmonary TNF-α overexpressing (Tg⁺) mice (a COPD-like model). We hypothesize that HPC can exert protection on the diaphragms of Tg⁺ mice during reoxygenation through pathways involving ROS/phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/extracellular signal regulated kinase (ERK), as well as the downstream activation of mitochondrial ATP-sensitive potassium channel (mitoK_ATP) and inhibition of mitochondrial permeability transition pore (mPTP).

Methods: Isolated Tg⁺ diaphragm muscle strips were pre-treated with inhibitors for ROS, PI3K, Akt, ERK, or a combination of mitoK_ATP inhibitor and mPTP opener, respectively, prior to HPC. Another two groups of muscles were treated with either mitoK_ATP activator or mPTP inhibitor without HPC. Muscles were treated with 30-min hypoxia, followed by 15-min reoxygenation. Data were analyzed by multi-way ANOVA and expressed as means ± SE.

Results: Muscle treated with HPC showed improved muscle function during reoxygenation (n = 5, p < 0.01). Inhibition of ROS, PI3K, Akt, or ERK abolished the protective effect of HPC. Simultaneous inhibition of mitoK_ATP and activation of mPTP also diminished HPC effects. By contrast, either the opening of mitoK_ATP channel or the closure of mPTP provided a similar protective effect to HPC by alleviating muscle function decline, suggesting that mitochondria play a role in HPC initiation (n = 5; p < 0.05).

Conclusion: Hypoxic preconditioning may protect respiratory skeletal muscle function in Tg⁺ mice during reoxygenation through redox-sensitive signaling cascades and regulations of mitochondrial channels.

Redox correlation in muscle lengthening and immune response in eccentric exercise

This study was designed to examine the potential involvement of reactive oxygen species in skeletal muscle dysfunction linked with stretching in a mouse model and to explore the effects of combined antioxidant intake on peripheral leukocyte apoptosis following eccentrically-biased downhill runs in human subjects. In the mouse model, diaphragmatic muscle was stretched by 30% of its optimal length, followed by 5-min contraction. Muscle function and extracellular reactive oxygen species release was measured ex vivo. In human models, participants performed two trials of downhill running either with or without antioxidant supplementation, followed by apoptotic assay of inflammatory cells in the blood. The results showed that stretch led to decreased muscle function and prominent ROS increase during muscle contraction. In human models, we observed an elevation in circulating leukocyte apoptosis 24-48 hours following acute downhill runs. However, there is an attenuated leukocyte apoptosis following the second bout of downhill run. Interestingly, the combination of ascorbic acid (vitamin C) and α-tocopherol (vitamin E) supplementation attenuated the decrease in B-cell lymphoma 2 (Bcl-2) at 24 hours following acute downhill running. These data collectively suggest that significant ROS formation can be induced by muscle-lengthening associated with eccentric exercise, which is accompanied by compromised muscle function. The combination of antioxidants supplementation appears to have a protective role via the attenuation of decrease in anti-apoptotic protein.

Formoterol attenuates increased oxidative stress and myosin protein loss in respiratory and limb muscles of cancer cachectic rats

Muscle mass loss and wasting are characteristic features of patients with chronic conditions including cancer. Therapeutic options are still scarce. We hypothesized that cachexia-induced muscle oxidative stress may be attenuated in response to treatment with beta₂-adrenoceptor-selective agonist formoterol in rats. In diaphragm and gastrocnemius of tumor-bearing rats (108 AH-130 Yoshida ascites hepatoma cells inoculated intraperitoneally) with and without treatment with formoterol (0.3 mg/kg body weight/day for seven days, daily subcutaneous injection), redox balance (protein oxidation and nitration and antioxidants) and muscle proteins (1-dimensional immunoblots), carbonylated proteins (2-dimensional immunoblots), inflammatory cells (immunohistochemistry), and mitochondrial respiratory chain (MRC) complex activities were explored. In the gastrocnemius, but not the diaphragm, of cancer cachectic rats compared to the controls, protein oxidation and nitration levels were increased, several functional and structural proteins were carbonylated, and in both study muscles, myosin content was reduced, inflammatory cell counts were greater, while no significant differences were seen in MRC complex activities (I, II, and IV). Treatment of cachectic rats with formoterol attenuated all the events in both respiratory and limb muscles. In this in vivo model of cancer-cachectic rats, the diaphragm is more resistant to oxidative stress. Formoterol treatment attenuated the rise in oxidative stress in the limb muscles, inflammatory cell infiltration, and the loss of myosin content seen in both study muscles, whereas no effects were observed in the MRC complex activities. These findings have therapeutic implications as they demonstrate beneficial effects of the beta₂ agonist through decreased protein oxidation and inflammation in cachectic muscles, especially the gastrocnemius.

Real-time monitoring of superoxide anion radical generation in response to wounding: electrochemical study

Background

The growth and development of plants is deleteriously affected by various biotic and abiotic stress factors. Wounding in plants is caused by exposure to environmental stress, mechanical stress, and via herbivory. Typically, oxidative burst in response to wounding is associated with the formation of reactive oxygen species, such as the superoxide anion radical (O₂^•−), hydrogen peroxide (H₂O₂) and singlet oxygen; however, few experimental studies have provided direct evidence of their detection in plants. Detection of O₂^•− formation in plant tissues have been performed using various techniques including electron paramagnetic resonance spin-trap spectroscopy, epinephrine-adrenochrome acceptor methods, staining with dyes such as tetrazolium dye and nitro blue tetrazolium (NBT); however, kinetic measurements have not been performed. In the current study, we provide evidence of O₂^•− generation and its kinetics in the leaves of spinach (Spinacia oleracea) subjected to wounding.

Methods

Real-time monitoring of O₂^•− generation was performed using catalytic amperometry. Changes in oxidation current for O₂^•− was monitored using polymeric iron-porphyrin-based modified carbon electrodes (φ = 1 mm) as working electrode with Ag/AgCl as the reference electrode.

Result

The results obtained show continuous generation of O₂^•− for minutes after wounding, followed by a decline. The exogenous addition of superoxide dismutase, which is known to dismutate O₂^•− to H₂O₂, significantly suppressed the oxidation current.

Conclusion

Catalytic amperometric measurements were performed using polymeric iron-porphyrin based modified carbon electrode. We claim it to be a useful tool and a direct method for real-time monitoring and precise detection of O₂^•− in biological samples, with the potential for wide application in plant research for specific and sensitive detection of O₂^•−.

Effects of Ionizing Irradiation on Mouse Diaphragmatic Skeletal Muscle

Undesirable exposure of diaphragm to radiation during thoracic radiation therapy has not been fully considered over the past decades. Our study aims to examine the potential biological effects on diaphragm induced by radiation. One-time ionizing irradiation of 10 Gy was applied either to the diaphragmatic region of mice or to the cultured C2C12 myocytes. Each sample was then assayed for muscle function, oxidative stress, or cell viability on days 1, 3, 5, and 7 after irradiation. Our mouse model shows that radiation significantly reduced muscle function on the 5th and 7th days and increased reactive oxygen species (ROS) formation in the diaphragm tissue from days 3 to 7. Similarly, the myocytes exhibited markedly decreased viability and elevated oxidative stress from days 5 to 7 after radiation. These data together suggested that a single dose of 10-Gy radiation is sufficient to cause acute adverse effects on diaphragmatic muscle function, redox balance, and myocyte survival. Furthermore, using the collected data, we developed a physical model to formularize the correlation between diaphragmatic ROS release and time after irradiation, which can be used to predict the biological effects of radiation with a specific dosage. Our findings highlight the importance of developing protective strategies to attenuate oxidative stress and prevent diaphragm injury during radiotherapy.

Pyranopyran-1,8-dione, an Active Compound from Vitices Fructus, Attenuates Cigarette-Smoke Induced Lung Inflammation in Mice

Previously, we isolated and identified pyranopyran-1,8-dione (PPY) from Viticis Fructus, as a bioactive compound possessing anti-inflammatory properties. The present study was aimed to evaluate the preventive benefit of PPY on cigarette-smoke (CS)-induced lung inflammation. C57BL/6 mice were exposed to CS for 2 weeks while PPY was administrated by oral injection 2 h before CS exposure. To validate the anti-inflammatory effects of PPY, the numbers of immune cells in the bronchoalveolar lavage fluid were counted. Proinflammatory cytokines (Tumor necrosis factor-α: TNF-α, IL-6) and keratinocyte chemokine (KC/CXCL1) were also measured. Histopathologic analysis and cellular profiles showed that inflammatory cell infiltrations were significantly decreased in peribronchial and perivascular area by PPY treatment. The alveolar destruction by CS was markedly ameliorated by PPY treatment. In addition, the TNF-α, IL-6, and KC levels were declined in the PPY groups. These observations suggest that PPY has a preventive potential for lung inflammatory diseases.

Effects of a simple prototype respiratory muscle trainer on respiratory muscle strength, quality of life and dyspnea, and oxidative stress in COPD patients: a preliminary study

Background

The aim of this study was to evaluate the efficiency of a simple prototype device for training respiratory muscles in lung function, respiratory muscle strength, walking capacity, quality of life (QOL), dyspnea, and oxidative stress in patients with COPD.

Methods

Thirty COPD patients with moderate severity of the disease were randomized into three groups: control (n=10, 6 males and 4 females), standard training (n=10, 4 males and 6 females), and prototype device (n=10, 5 males and 5 females). Respiratory muscle strength (maximal inspiratory pressure [PImax] and maximal expiratory pressure [PEmax]), lung function (forced vital capacity [FVC], percentage of FVC, forced expiratory volume in 1 second [FEV₁], percentage of FEV₁ [FEV₁%], and FEV₁/FVC), 6-minute walking distance (6MWD), QOL, and oxidative stress markers (total antioxidant capacity [TAC]), glutathione (GSH), malondialdehyde (MDA), and nitric oxide (NO) were evaluated before and after 6 weeks of training. Moreover, dyspnea scores were assessed before; during week 2, 4, and 6 of training; and at rest after training.

Results

All parameters between the groups had no statistical difference before training, and no statistical change in the control group after week 6. FVC, FEV₁/FVC, PImax, PEmax, QOL, MDA, and NO showed significant changes after 6 weeks of training with either the standard or prototype device, compared to pre-training. FEV₁, FEV₁%, 6MWD, TAC, and GSH data did not change statistically. Furthermore, the results of significant changes in all parameters were not statistically different between training groups using the standard and prototype device. The peak dyspnea scores increased significantly in week 4 and 6 when applying the standard or prototype device, and then lowered significantly at rest after 6 weeks of training, compared to pre-training.

Conclusion

This study proposes that a simple prototype device can be used clinically in COPD patients as a standard device to train respiratory muscles, improving lung function and QOL, as well as involving MDA and NO levels.

Metabolic Disorder in Chronic Obstructive Pulmonary Disease (COPD) Patients: Towards a Personalized Approach Using Marine Drug Derivatives

Metabolic disorder has been frequently observed in chronic obstructive pulmonary disease (COPD) patients. However, the exact correlation between obesity, which is a complex metabolic disorder, and COPD remains controversial. The current study summarizes a variety of drugs from marine sources that have anti-obesity effects and proposed potential mechanisms by which lung function can be modulated with the anti-obesity activity. Considering the similar mechanism, such as inflammation, shared between obesity and COPD, the study suggests that marine derivatives that act on the adipose tissues to reduce inflammation may provide beneficial therapeutic effects in COPD subjects with high body mass index (BMI).

Reactive Oxygen Species in COPD-Related Vascular Remodeling

The pathogenesis of chronic obstructive pulmonary disease (COPD) is a multifaceted process involving the alteration of pulmonary vasculature. Such vascular remodeling can be associated with inflammation, shear stress, and hypoxia-conditions commonly seen in patients with lung diseases. Particularly, the overproduction of reactive oxygen species (ROS) in the diseased lungs contributes greatly to pulmonary vascular remodeling. ROS play an important role in vascular homeostasis, yet excessive ROS can alter pulmonary vasculature and impair lung function, as implicated in COPD at all stages. Increased inflammatory cell infiltration and endothelial dysfunction both correspond to the severity of COPD. As a byproduct of vascular remodeling, pulmonary hypertension negatively affects the long-term survival rate of COPD patients. While there is currently no cure for COPD, several treatment options have focused on alleviating COPD symptoms. Interventions such as long-term oxygen therapy, endothelium-targeted treatment, and pharmacological therapies show promising results in improving the life span of COPD patients and attenuating the progression of pulmonary hypertension. In this chapter, we aim to discuss the contributing factors of pulmonary vascular remodeling in COPD with an emphasis on the ROS, as well as potential redox treatments for COPD-related vascular remodeling.

Redox Mechanism of Reactive Oxygen Species in Exercise

It is well known that regular exercise can benefit health by enhancing antioxidant defenses in the body. However, unaccustomed and/or exhaustive exercise can generate excessive reactive oxygen species (ROS), leading to oxidative stress-related tissue damages and impaired muscle contractility. ROS are produced in both aerobic and anaerobic exercise. Mitochondria, NADPH oxidases and xanthine oxidases have all been identified as potential contributors to ROS production, yet the exact redox mechanisms underlying exercise-induced oxidative stress remain elusive. Interestingly, moderate exposure to ROS is necessary to induce body's adaptive responses such as the activation of antioxidant defense mechanisms. Dietary antioxidant manipulation can also reduce ROS levels and muscle fatigue, as well as enhance exercise recovery. To elucidate the complex role of ROS in exercise, this review updates on new findings of ROS origins within skeletal muscles associated with various types of exercises such as endurance, sprint and mountain climbing. In addition, we will examine the corresponding antioxidant defense systems as well as dietary manipulation against damages caused by ROS.

Central Nervous System Injury - A Newly Observed Bystander Effect of Radiation

The unintended side effects of cancer treatment are increasing recognized. Among these is a syndrome of long-term neurocognitive dysfunction called cancer/chemotherapy related cognitive impairment. To date, all studies examining the cognitive impact of cancer treatment have emphasized chemotherapy. Radiation-induced bystander effects have been described in cell culture and, to a limited extent, in rodent model systems. The purpose of this study was to examine, for the first time, the impact of non-brain directed radiation therapy on the brain in order to elucidate its potential relationship with cancer/chemotherapy related cognitive impairment. To address this objective, female BALB/c mice received either a single 16 gray fraction of ionizing radiation to the right hind limb or three doses of methotrexate, once per week for three consecutive weeks. Mice were sacrificed either 3 or 30 days post-treatment and brain injury was determined via quantification of activated astrocytes and microglia. To characterize the effects of non-brain directed radiation on brain glucose metabolism, mice were evaluated by fluorodeoxygluocose positron emission tomography. A single fraction of 16 gray radiation resulted in global decreases in brain glucose metabolism, a significant increase in the number of activated astrocytes and microglia, and increased TNF-α expression, all of which lasted up to 30 days post-treatment. This inflammatory response following radiation therapy was statistically indistinguishable from the neuroinflammation observed following methotrexate administration. In conclusion, non-brain directed radiation was sufficient to cause significant brain bystander injury as reflected by multifocal hypometabolism and persistent neuroinflammation. These findings suggest that radiation induces significant brain bystander effects distant from the irradiated cells and tissues. These effects may contribute to the development of cognitive dysfunction in treated human cancer patients and warrant further study.

Regulation of NADPH oxidases in skeletal muscle

The only known function of NAD(P)H oxidases is to produce reactive oxygen species (ROS). Skeletal muscles express three isoforms of NAD(P)H oxidases (Nox1, Nox2, and Nox4) that have been identified as critical modulators of redox homeostasis. Nox2 acts as the main source of skeletal muscle ROS during contractions, participates in insulin signaling and glucose transport, and mediates the myocyte response to osmotic stress. Nox2 and Nox4 contribute to skeletal muscle abnormalities elicited by angiotensin II, muscular dystrophy, heart failure, and high fat diet. Our review addresses the expression and regulation of NAD(P)H oxidases with emphasis on aspects that are relevant to skeletal muscle. We also summarize: i) the most widely used NAD(P)H oxidases activity assays and inhibitors, and ii) studies that have defined Nox enzymes as protagonists of skeletal muscle redox homeostasis in a variety of health and disease conditions.

Reactive oxygen species formation and bystander effects in gradient irradiation on human breast cancer cells

Ionizing radiation (IR) in cancer radiotherapy can induce damage to neighboring cells via non-targeted effects by irradiated cells. These so-called bystander effects remain an area of interest as it may provide enhanced efficacy in killing carcinomas with minimal radiation. It is well known that reactive oxygen species (ROS) are ubiquitous among most biological activities. However, the role of ROS in bystander effects has not been thoroughly elucidated. We hypothesized that gradient irradiation (GI) has enhanced therapeutic effects via the ROS-mediated bystander pathways as compared to uniform irradiation (UI). We evaluated ROS generation, viability, and apoptosis in breast cancer cells (MCF-7) exposed to UI (5 Gy) or GI (8-2 Gy) in radiation fields at 2, 24 and 48 h after IR. We found that extracellular ROS release induced by GI was higher than that by UI at both 24 h (p < 0.001) and 48 h (p < 0.001). More apoptosis and less viability were observed in GI when compared to UI at either 24 h or 48 h after irradiation. The mean effective doses (ED) of GI were ~130% (24 h) and ~48% (48 h) higher than that of UI, respectively. Our results suggest that GI is superior to UI regarding redox mechanisms, ED, and toxic dosage to surrounding tissues.

Copper Deficiency in the Lungs of TNF-α Transgenic Mice

Tumor necrosis factor (TNF)-α is a well-known pro-inflammatory cytokine. Increased expression of Tnf-α is a feature of inflammatory lung diseases, such as asthma, emphysema, fibrosis, and smoking-induced chronic obstructive pulmonary disease (COPD). Using a mouse line with lung-specific Tnf-α overexpression (SPC-TNF-α) to mimic TNF-α-associated lung diseases, we investigated the role of chronic inflammation in the homeostasis of lung trace elements. We performed a quantitative survey of micronutrients and biometals, including copper (Cu), zinc (Zn), and selenium (Se), in the transgenic mice tissues. We also examined the expression of Cu-dependent proteins in the inflammatory lung tissue to determine whether they were affected by the severe Cu deficiency, including cuproenzymes, Cu transporters, and Cu chaperones. We found consistent lung-specific reduction of the metal Cu, with a mean decrease of 70%; however, Zn and Se were unaffected in all other tissues. RT-PCR showed that two Cu enzymes associated with lung pathology were downregulated: amine oxidase, Cu containing 3 (Aoc3) and lysyl oxidase (Lox). Two factors, vascular endothelial growth factor (Vegf) and focal adhesion kinase (Fak), related with Cu deficiency treatment, showed decreased expression in the transgenic inflammatory lung. We concluded that Cu deficiency occurs following chronic TNF-α-induced lung inflammation and this likely plays an essential role in the inflammation-induced lung damage. These results suggest the restoration of lung Cu status as a potential strategy in both treatment and prevention of chronic lung inflammation and related disorders.

Recent advances and long-standing problems in detecting oxidative damage and reactive oxygen species in skeletal muscle

An increasingly sophisticated array of approaches are now available for the study of the activities of reactive oxygen species and oxidative modifications in skeletal muscle, but the most up-to-date techniques are not readily available to many researchers in this field due to their requirement for sophisticated mass spectrometry, imaging or other high cost technologies. Most papers published therefore rely on a number of established approaches although the choice of approach is also clearly dependent upon the experimental model and access to skeletal muscle that is available to the investigator, how much detail is required and the overall question to be addressed. Numerous reports have described the problems associated with some of the popular approaches that are widely followed, including measurement of thiobarbituric acid substances and the sole use of fluorescence-based probes such as dichlorodihydrofluorescein. This brief review reports the areas in which methods are improving to allow valid assessments to made in this area and indicates some of the more recent developments that provide alternative ways to assess the activity of individual species and endpoints in the various experimental models that may be examined.

Redox Characterization of Functioning Skeletal Muscle

Skeletal muscle physiology is influenced by the presence of chemically reactive molecules such as reactive oxygen species (ROS). These molecules regulate multiple redox-sensitive signaling pathways that play a critical role in cellular processes including gene expression and protein modification. While ROS have gained much attention for their harmful effects in muscle fatigue and dysfunction, research has also shown ROS to facilitate muscle adaptation after stressors such as physical exercise. This manuscript aims to provide a comprehensive review of the current understanding of redox signaling in skeletal muscle. ROS-induced oxidative stress and its role in the aging process are discussed. Mitochondria have been shown to generate large amounts of ROS during muscular contractions, and thus are susceptible to oxidative stress. ROS can modify proteins located in the mitochondrial membrane leading to cell death and osmotic swelling. ROS also contribute to the necrosis and inflammation of muscle fibers that is associated with muscular diseases including Duchenne muscular dystrophy. It is imperative that future research continues to investigate the exact role of ROS in normal skeletal muscle function as well as muscular dysfunction and disease.

Po2 cycling protects diaphragm function during reoxygenation via ROS, Akt, ERK, and mitochondrial channels

Po2 cycling, often referred to as intermittent hypoxia, involves exposing tissues to brief cycles of low oxygen environments immediately followed by hyperoxic conditions. After experiencing long-term hypoxia, muscle can be damaged during the subsequent reintroduction of oxygen, which leads to muscle dysfunction via reperfusion injury. The protective effect and mechanism behind Po2 cycling in skeletal muscle during reoxygenation have yet to be fully elucidated. We hypothesize that Po2 cycling effectively increases muscle fatigue resistance through reactive oxygen species (ROS), protein kinase B (Akt), extracellular signal-regulated kinase (ERK), and certain mitochondrial channels during reoxygenation. Using a dihydrofluorescein fluorescent probe, we detected the production of ROS in mouse diaphragmatic skeletal muscle in real time under confocal microscopy. Muscles treated with Po2 cycling displayed significantly attenuated ROS levels (n = 5; P < 0.001) as well as enhanced force generation compared with controls during reperfusion (n = 7; P < 0.05). We also used inhibitors for signaling molecules or membrane channels such as ROS, Akt, ERK, as well as chemical stimulators to close mitochondrial ATP-sensitive potassium channel (KATP) or open mitochondrial permeability transition pore (mPTP). All these blockers or stimulators abolished improved muscle function with Po2 cycling treatment. This current investigation has discovered a correlation between KATP and mPTP and the Po2 cycling pathway in diaphragmatic skeletal muscle. Thus we have identified a unique signaling pathway that may involve ROS, Akt, ERK, and mitochondrial channels responsible for Po2 cycling protection during reoxygenation conditions in the diaphragm.

Curcumin ameliorates skeletal muscle atrophy in type 1 diabetic mice by inhibiting protein ubiquitination

NEW FINDINGS

What is the central question of this study? We sought to examine whether curcumin could ameliorate skeletal muscle atrophy in diabetic mice by inhibiting protein ubiquitination, inflammatory cytokines and oxidative stress. What is the main finding and its importance? We found that curcumin ameliorated skeletal muscle atrophy in streptozotocin-induced diabetic mice by inhibiting protein ubiquitination without affecting protein synthesis. This favourable effect of curcumin was possibly due to the inhibition of inflammatory cytokines and oxidative stress. Curcumin may be beneficial for the treatment of muscle atrophy in type 1 diabetes mellitus. Skeletal muscle atrophy develops in patients with diabetes mellitus (DM), especially in type 1 DM, which is associated with chronic inflammation. Curcumin, the active ingredient of turmeric, has various biological actions, including anti-inflammatory and antioxidant properties. We hypothesized that curcumin could ameliorate skeletal muscle atrophy in mice with streptozotocin-induced type 1 DM. C57BL/6 J mice were injected with streptozotocin (200 mg kg(-1) i.p.; DM group) or vehicle (control group). Each group of mice was randomly subdivided into two groups of 10 mice each and fed a diet with or without curcumin (1500 mg kg(-1) day(-1)) for 2 weeks. There were significant decreases in body weight, skeletal muscle weight and cellular cross-sectional area of the skeletal muscle in DM mice compared with control mice, and these changes were significantly attenuated in DM+Curcumin mice without affecting plasma glucose and insulin concentrations. Ubiquitination of protein was increased in skeletal muscle from DM mice and decreased in DM+Curcumin mice. Gene expressions of muscle-specific ubiquitin E3 ligase atrogin-1/MAFbx and MuRF1 were increased in DM and inhibited in DM+Curcumin mice. Moreover, nuclear factor-κB activation, concentrations of the inflammatory cytokines tumour necrosis factor-α and interleukin-1β and oxidative stress were increased in the skeletal muscle from DM mice and inhibited in DM+Curcumin mice. Curcumin ameliorated skeletal muscle atrophy in DM mice by inhibiting protein ubiquitination, inflammatory cytokines and oxidative stress. Curcumin may be beneficial for the treatment of muscle atrophy in type 1 DM.

Six-minute walk test in Chinese adults with clinically stable bronchiectasis: association with clinical indices and determinants

BACKGROUND

The profiles of 6-minute walk distance (6MWD) in adults with clinically stable bronchiectasis in Chinese adult patients with bronchiectasis are unclear.

OBJECTIVES

To delineate the 6MWD by stratification of clinical indices, and to investigate the factors associated with reduced 6MWD in Chinese adults with clinically stable bronchiectasis.

METHODS

We recruited 141 adult bronchiectasis patients (mean age: 44.3 ± 13.9 years). Demography, radiology, spirometry, diffusing capacity, etiology, sputum bacteriology, modified Medical Research Council dyspnea scale (MMRC) and quality of life were assessed. The safety profile of the measurement was also examined.

RESULTS

Lower levels of 6MWD were associated with older age (>50 years), higher HRCT total score, presence of cystic bronchiectasis, bilateral bronchiectasis, reduced diffusing capacity, higher MMRC score, and higher SGRQ scores. Correlation coefficients between 6MWD and spirometry and quality of life scores were different in patients with 6MWD higher and lower than lower limit of normal. DLCO being less than 80% predicted (OR = 3.13, 95% CI: 1.32-7.43, P = 0.01) and MMRC scale between 1 and 4 (OR = 6.42, 95% CI: 2.27-18.18, P < 0.01) were the factors associated with 6MWD being less than the lower limit of normal (80% predicted value). No severe adverse events were reported.

CONCLUSION

The 6MWD could be safely measured in adult patients with bronchiectasis and is poorly associated with clinical parameters. DLCO less than 80% predicted and higher MMRC scale are independent predictors of 6MWD below the lower limit of normal. Our findings will provide a reference for management of bronchiectasis patients in mainland China.

Characterization of reactive oxygen species in diaphragm

Reactive oxygen species (ROS) exist as natural mediators of metabolism to maintain cellular homeostasis. However, ROS production may significantly increase in response to environmental stressors, resulting in extensive cellular damage. Although several potential sources of increased ROS have been proposed, exact mechanisms of their generation have not been completely elucidated. This is particularly true for diaphragmatic skeletal muscle, the key muscle used for respiration. Several experimental models have focused on detection of ROS generation in rodent diaphragm tissue under stressful conditions, including hypoxia, exercise, and heat, as well as ROS formation in single myofibres. Identification methods include direct detection of ROS with confocal or fluorescent microscopy and indirect detection of ROS through end product analysis. This article explores implications of ROS generation and oxidative stress, and also evaluates potential mechanisms of cellular ROS formation in diaphragmatic skeletal muscle.

PO2 cycling reduces diaphragm fatigue by attenuating ROS formation

Prolonged muscle exposure to low PO₂ conditions may cause oxidative stress resulting in severe muscular injuries. We hypothesize that PO₂ cycling preconditioning, which involves brief cycles of diaphragmatic muscle exposure to a low oxygen level (40 Torr) followed by a high oxygen level (550 Torr), can reduce intracellular reactive oxygen species (ROS) as well as attenuate muscle fatigue in mouse diaphragm under low PO₂. Accordingly, dihydrofluorescein (a fluorescent probe) was used to monitor muscular ROS production in real time with confocal microscopy during a lower PO₂ condition. In the control group with no PO₂ cycling, intracellular ROS formation did not appear during the first 15 min of the low PO₂ period. However, after 20 min of low PO₂, ROS levels increased significantly by ∼30% compared to baseline, and this increase continued until the end of the 30 min low PO₂ condition. Conversely, muscles treated with PO₂ cycling showed a complete absence of enhanced fluorescence emission throughout the entire low PO₂ period. Furthermore, PO₂ cycling-treated diaphragm exhibited increased fatigue resistance during prolonged low PO₂ period compared to control. Thus, our data suggest that PO₂ cycling mitigates diaphragm fatigue during prolonged low PO₂. Although the exact mechanism for this protection remains to be elucidated, it is likely that through limiting excessive ROS levels, PO₂ cycling initiates ROS-related antioxidant defenses.

Interrelated role of cigarette smoking, oxidative stress, and immune response in COPD and corresponding treatments

Cigarette smoking (CS) can impact the immune system and induce pulmonary disorders such as chronic obstructive pulmonary disease (COPD), which is currently the fourth leading cause of chronic morbidity and mortality worldwide. Accordingly, the most significant risk factor associated with COPD is exposure to cigarette smoke. The purpose of the present study is to provide an updated overview of the literature regarding the effect of CS on the immune system and lungs, the mechanism of CS-induced COPD and oxidative stress, as well as the available and potential treatment options for CS-induced COPD. An extensive literature search was conducted on the PubMed/Medline databases to review current COPD treatment research, available in the English language, dating from 1976 to 2014. Studies have investigated the mechanism by which CS elicits detrimental effects on the immune system and pulmonary function through the use of human and animal subjects. A strong relationship among continued tobacco use, oxidative stress, and exacerbation of COPD symptoms is frequently observed in COPD subjects. In addition, therapeutic approaches emphasizing smoking cessation have been developed, incorporating counseling and nicotine replacement therapy. However, the inability to reverse COPD progression establishes the need for improved preventative and therapeutic strategies, such as a combination of intensive smoking cessation treatment and pharmaceutical therapy, focusing on immune homeostasis and redox balance. CS initiates a complex interplay between oxidative stress and the immune response in COPD. Therefore, multiple approaches such as smoking cessation, counseling, and pharmaceutical therapies targeting inflammation and oxidative stress are recommended for COPD treatment.