Pioglitazone restores phagocyte mitochondrial oxidants and bactericidal capacity in chronic granulomatous disease.

BACKGROUND: Deficient production of reactive oxygen species (ROS) by the phagocyte nicotinamide adenine dinucleotide (NADPH) oxidase in patients with chronic granulomatous disease (CGD) results in susceptibility to certain pathogens secondary to impaired oxidative killing and mobilization of other phagocyte defenses. Peroxisome proliferator-activated receptor (PPAR) γ agonists, including pioglitazone, approved for type 2 diabetes therapy alter cellular metabolism and can heighten ROS production. It was hypothesized that pioglitazone treatment of gp91(phox-/-) mice, a murine model of human CGD, would enhance phagocyte oxidant production and killing of Staphylococcus aureus, a significant pathogen in patients with this disorder. OBJECTIVES: We sought to determine whether pioglitazone treatment of gp91(phox-/-) mice enhanced phagocyte oxidant production and host defense. METHODS: Wild-type and gp91(phox-/-) mice were treated with the PPARγ agonist pioglitazone, and phagocyte ROS and killing of S aureus were investigated. RESULTS: As demonstrated by 3 different ROS-sensing probes, short-term treatment of gp91(phox-/-) mice with pioglitazone enhanced stimulated ROS production in neutrophils and monocytes from blood and neutrophils and inflammatory macrophages recruited to tissues. Mitochondria were identified as the source of ROS. Findings were replicated in human monocytes from patients with CGD after ex vivo pioglitazone treatment. Importantly, although mitochondrial (mt)ROS were deficient in gp91(phox-/-) phagocytes, their restoration with treatment significantly enabled killing of S aureus both ex vivo and in vivo. CONCLUSIONS: Together, the data support the hypothesis that signaling from the NADPH oxidase under normal circumstances governs phagocyte mtROS production and that such signaling is lacking in the absence of a functioning phagocyte oxidase. PPARγ agonism appears to bypass the need for the NADPH oxidase for enhanced mtROS production and partially restores host defense in CGD.

Plasma antioxidants are associated with impaired lung function and COPD exacerbations in smokers.

Low molecule weight antioxidants such as uric acid (UA), glutathione (GSH), and ascorbate (ASC) counter the effects of oxidants produced by cigarette smoke. Although dietary intake of foods rich in antioxidants has been associated with a reduced risk of smokers developing chronic obstructive pulmonary disease (COPD), the association between plasma antioxidants and COPD is less clear. In this cross-sectional study we investigated the relationship among plasma antioxidants and COPD phenotypes (severity of airflow obstruction on spirometry and history of exacerbations) in 136 smokers with normal lung function and 367 smokers with COPD. In the multivariate analysis, a lower plasma UA was associated with more severe COPD (P < 0.002) and a lower GSH was associated with a history of COPD exacerbations (P = 0.03); ASC was not associated with any COPD phenotypes. This suggests that antioxidant balance is impaired in smokers with obstruction on spirometry or a history of COPD exacerbations.

Spatial environmental heterogeneity affects plant growth and thermal performance on a green roof.

Green roofs provide ecosystem services, including stormwater retention and reductions in heat transfer through the roof. Microclimates, as well as designed features of green roofs, such as substrate and vegetation, affect the magnitude of these services. Many green roofs are partially shaded by surrounding buildings, but the effects of this within-roof spatial environmental heterogeneity on thermal performance and other ecosystem services have not been examined. We quantified the effects of spatial heterogeneity in solar radiation, substrate depth and other variables affected by these drivers on vegetation and ecosystem services in an extensive green roof. Spatial heterogeneity in substrate depth and insolation were correlated with differential growth, survival and flowering in two focal plant species. These effects were likely driven by the resulting spatial heterogeneity in substrate temperature and moisture content. Thermal performance (indicated by heat flux and substrate temperature) was influenced by spatial heterogeneity in vegetation cover and substrate depth. Areas with less insolation were cooler in summer and had greater substrate moisture, leading to more favorable conditions for plant growth and survival. Spatial variation in substrate moisture (7%-26% volumetric moisture content) and temperature (21°C-36°C) during hot sunny conditions in summer could cause large differences in stormwater retention and heat flux within a single green roof. Shaded areas promote smaller heat fluxes through the roof, leading to energy savings, but lower evapotranspiration in these areas should reduce stormwater retention capacity. Spatial heterogeneity can thus result in trade-offs between different ecosystem services. The effects of these spatial heterogeneities are likely widespread in green roofs. Structures that provide shelter from sun and wind may be productively utilized to design higher functioning green roofs and increase biodiversity by providing habitat heterogeneity.

Smoking and COPD increase sputum levels of extracellular superoxide dismutase.

Extracellular superoxide dismutase (ECSOD) is the major superoxide-scavenging enzyme in the lung. Certain ECSOD polymorphisms are protective against COPD. We postulated that smokers and COPD subjects would have altered levels of ECSOD in the lung, airway secretions, and/or plasma. Lung tissue ECSOD was evaluated from nonsmokers, smokers, and subjects with mild to very severe COPD by Western blot, immunohistochemistry, and ELISA. ECSOD levels in plasma, bronchoalveolar lavage fluid (BALF), and induced-sputum supernatants were analyzed by ELISA and correlated with smoking history and disease status. Immunohistochemistry identified ECSOD in extracellular matrix around bronchioles, arteries, and alveolar walls, with decreases seen in the interstitium and vessels of severe COPD subjects using digital image analysis. Plasma ECSOD did not differ between COPD subjects and controls nor based on smoking status. ECSOD levels in induced sputum supernatants were elevated in current smokers and especially in COPD subjects compared to nonsmokers, whereas corresponding changes could not be seen in the BALF. ECSOD expression was reduced around vessels and bronchioles in COPD lungs. Substantial increases in sputum ECSOD in smokers and COPD is interpreted as an adaptive response to increased oxidative stress and may be a useful biomarker of disease activity in COPD.

Endogenous enzymes (NOX and ECSOD) regulate smoke-induced oxidative stress.

Chronic obstructive pulmonary disease (COPD) is the fourth leading cause of death in the United States and the incidence is increasing as the population ages. Cigarette smoking is the primary risk factor; however, only a minority of smokers develop the disease. Inhalation of cigarette smoke introduces an abundance of free radicals into the lungs, causing oxidative stress and inflammation. We hypothesized that after the initial burst of oxidative stress associated with cigarette smoke exposure, a sustained source of endogenous free radical production is modulated by the antioxidant enzyme extracellular superoxide dismutase (ECSOD) and the superoxide-generating complex NADPH oxidase (NOX). Primary mouse macrophages exposed to cigarette smoke extract exhibited increased oxidative stress as indicated by fluorogenic dyes and isoprostane concentration, which was suppressed in the presence of both a superoxide dismutase mimetic and a NOX inhibitor. Similarly, primary macrophages isolated from ECSOD-overexpressing mice or NOX-deficient mice showed reduced oxidative stress in response to cigarette smoke treatment. In addition, both reduced glutathione and cytokines (MIP2 and IFNγ) were increased in bronchoalveolar lavage fluid of wild-type mice exposed to cigarette smoke but not in ECSOD-overexpressing or NOX-deficient mice. These data suggest that the mechanisms underlying the host defense against cigarette smoke-induced oxidative damage and subsequent development of COPD may include endogenous oxidases and antioxidant enzymes.

Extracellular superoxide dismutase and oxidant damage in osteoarthritis.

OBJECTIVE: To use human cartilage samples and a mouse model of osteoarthritis (OA) to determine whether extracellular superoxide dismutase (EC-SOD) is a constituent of cartilage and to evaluate whether there is a relationship between EC-SOD deficiency and OA. METHODS: Samples of human cartilage were obtained from femoral heads at the time of joint replacement surgery for OA or femoral neck fracture. Samples of mouse tibial cartilage obtained from STR/ort mice and CBA control mice were compared at 5, 15, and 35 weeks of age. EC-SOD was measured by enzyme-linked immunosorbent assay, Western blotting, and immunohistochemistry techniques. Real-time quantitative reverse transcription-polymerase chain reaction was used to measure messenger RNA for EC-SOD and for endothelial cell, neuronal, and inducible nitric oxide synthases. Nitrotyrosine formation was assayed by Western blotting in mouse cartilage and by fluorescence immunohistochemistry in human cartilage. RESULTS: Human articular cartilage contained large amounts of EC-SOD (mean +/- SEM 18.8 +/- 3.8 ng/gm wet weight of cartilage). Cartilage from patients with OA had an approximately 4-fold lower level of EC-SOD compared with cartilage from patients with hip fracture. Young STR/ort mice had decreased levels of EC-SOD in tibial cartilage before histologic evidence of disease occurred, as well as significantly more nitrotyrosine formation at all ages studied. CONCLUSION: EC-SOD, the major scavenger of reactive oxygen species in extracellular spaces, is decreased in humans with OA and in an animal model of OA. Our findings suggest that inadequate control of reactive oxygen species plays a role in the pathophysiology of OA.