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Bruce R Pitt

Publications and source records attributed to Bruce R Pitt.

6 recordsLinked to original sources
PubMed2003

Multimodal optical imaging.

The recent resurgence of interest in the use of intravital microscopy in lung research is a manifestation of extraordinary progress in visual imaging and optical microscopy. This review evaluates the tools and instrumentation available for a number of imaging modalities, with particular attention to recent technological advances, and addresses recent progress in use of optical imaging techniques in basic pulmonary research.1 Limitations of existing methods and anticipated future developments are also identified. Although there have also been major advances made in the use of magnetic resonance imaging, positron emission tomography, and X-ray and computed tomography to image intact lungs and while these technologies have been instrumental in advancing the diagnosis and treatment of patients, the purpose of this review is to outline developing optical methods that can be evaluated for use in basic research in pulmonary biology.

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PubMed2002

The catabolic fate of nitric oxide: the nitric oxide oxidase and peroxynitrite reductase activities of cytochrome oxidase.

Stimulation of cardiomyocytes to endogenously evolve nitric oxide is shown by microsensor measurements on single cells to lead to transient nitric oxide concentrations of a few hundred nanomolar. At these submicromolar concentrations, no evidence could be found for the expected reaction between nitric oxide generated and the oxymyoglobin present in the cells: nitric oxide + oxymyoglobin --> nitrate + metmyoglobin. No metmyoglobin formation was detected by electron paramagnetic resonance spectroscopy, and microsensor measurements revealed near quantitative conversion of the nitric oxide to nitrite rather than nitrate ion. Moreover, the rate of nitrite formation is shown to be too rapid to be accounted for by non-enzymatic means. The essentially quantitative and rapid catabolism of nitric oxide to nitrite ion can plausibly be explained on the basis of a cycle of reactions catalyzed by cytochrome c oxidase. It is demonstrated with the purified hemoproteins in vitro that the terminal oxidase can outcompete oxymyoglobin for available nitric oxide. It is proposed that under normal physiological and most pathological (non-inflammatory) conditions, reaction with cytochrome c oxidase is the major route by which NO is removed from mitochondria-rich cells.

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PubMed2002

Redox sensor function of metallothioneins.

In summary, the redox conversions of MT cysteines are likely to be the principal mechanisms for regulation of metal binding and release by this protein. Oxidative and/or nitrosative challenges can serve to promote metal ion release from MT to render their delivery to specific target proteins. It is tempting to consider the potential roles of MTs as redox sensors because of their high sensitivity to cysteine modification, as well as their potential to amplify signals by releasing multiple metal ions. In other words, MTs may act early in a biological signaling cascade that triggers metal-dependent biochemical and cellular responses. Alternatively, uncontrolled release of metals by excessive oxidative stress may contribute to metal toxicity. Because oxidative and nitrosative signaling is ubiquitous within cells, the physiological function of MT demands that efficient recycling of modified cysteines be operative. Little is known regarding the potential mechanisms for the regeneration of MT after oxidative/nitrosative modification, but they may involve endogenous dithiols, such as thioredoxin, and pharmacologically relevant dithiols, such as dihydrolipoate.

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PubMed2002

Contribution of glutathione and metallothioneins to protection against copper toxicity and redox cycling: quantitative analysis using MT+/+ and MT-/- mouse lung fibroblast cells.

Glutathione (GSH) and metallothioneins (MT) are believed to play important roles in protecting cells against high copper (Cu) concentrations. Little is known, however, about their specific intracellular interactions and the coordination of protective functions. We investigated contributions of GSH and MT to protection against Cu toxicity in fibroblasts derived from wild-type (MT+/+) and knockout (MT-/-) mice that were challenged with cupric nitrilotriacetate (Cu-NTA). Endogenous levels of GSH and MT were manipulated using an inhibitor of gamma-glutamylcysteine synthetase, buthionine sulfoximine (BSO, 5 microM), as GSH depletor and ZnCl(2) (100 microM) as inducer of MT expression. BSO pretreatment markedly decreased cellular GSH levels in MT+/+ and MT-/- cells, by 65% and 70%, respectively, which resulted in Cu cytotoxicity accompanied by its elevated redox-cycling activity and enhanced Cu-induced membrane phospholipid peroxidation. BSO-pretreated MT-/- cells were markedly more sensitive to Cu despite the fact that the residual levels of GSH were similar in both BSO-pretreated MT+/+ and MT-/- cells. Zn pretreatment resulted in more than 10-fold induction of MT in MT+/+ cells but not in MT-/- cells. Accordingly, Zn pretreatment afforded significant protection of MT+/+ cells against Cu cytotoxicity, likely associated with MT-dependent suppression of Cu redox-cycling activity and phospholipid peroxidation, but it exerted no protection in MT-/- cells (as compared to naive cells). To determine whether MT functions specifically in Cu regulation or rather acts as a nonspecific Cu-binding cysteine-rich nucleophile, experiments were performed using MT+/+ and MT-/- cells pretreated with both BSO and Zn. BSO pretreatment did not affect Zn-induced MT expression in MT+/+ cells. As compared with BSO pretreatment alone, exposure to Cu of MT+/+ cells after Zn/BSO pretreatment resulted in the following: (i) a significantly higher viability; (ii) attenuated Cu-dependent redox-cycling activity; and (iii) a lower level of phospholipid peroxidation. In BSO/Zn-pretreated MT-/- cells, the redox-cycling activity of Cu and the level of phospholipid peroxidation remained remarkably higher than in naive cells and were not significantly different from those in cells pretreated with BSO alone. Cu-induced toxicity was remarkably higher in BSO/Zn-pretreated MT-/- cells than in naive or Zn-pretreated cells, although slightly lower than in the MT-/- cells pretreated with BSO alone.

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PubMedDate not supplied

Nitric oxide decreases the sensitivity of pulmonary endothelial cells to LPS-induced apoptosis in a zinc-dependent fashion.

We hypothesized that: (a) S-nitrosylation of metallothionein (MT) is a component of pulmonary endothelial cell nitric oxide (NO) signaling that is associated with an increase in labile zinc; and (b) NO mediated increases in labile zinc in turn reduce the sensitivity of pulmonary endothelium to LPS-induced apoptosis. We used microspectrofluorometric techniques to show that exposing mouse lung endothelial cells (MLEC) to the NO-donor, S-nitrosocysteine, resulted in a 45% increase in fluorescence of the Zn2+-specific fluorophore, Zinquin, that was rapidly reversed by exposure to the Zn2+ chelator, NNN'N'-tetrakis-(2-pyridylmethyl)ethylenediamine; TPEN). The absence of a NO-mediated increase in labile Zn2+ in MLEC from MT-I and -II knockout mice inferred a critical role for MT in the regulation of Zn2+ homeostasis by NO. Furthermore, we found that prior exposure of cultured endothelial cells from sheep pulmonary artery (SPAEC), to the NO-donor, S-nitroso-N-acetylpenicillamine (SNAP) reduced their sensitivity to lipopolysaccharide (LPS) induced apoptosis. The anti-apoptotic effects of NO were significantly inhibited by Zn2+ chelation with low doses of TPEN (10 microM). Collectively, these data suggest that S-nitrosylation of MT is associated with an increase in labile (TPEN chelatable) zinc and NO-mediated MT dependent zinc release is associated with reduced sensitivity to LPS-induced apoptosis in pulmonary endothelium.

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