scholarly journals Thimerosal-Derived Ethylmercury Is a Mitochondrial Toxin in Human Astrocytes: Possible Role of Fenton Chemistry in the Oxidation and Breakage of mtDNA

2012 ◽  
Vol 2012 ◽  
pp. 1-12 ◽  
Author(s):  
Martyn A. Sharpe ◽  
Andrew D. Livingston ◽  
David S. Baskin
Keyword(s):  
Hydrogen Peroxide ◽  
Caspase 3 ◽  
Permeability Transition ◽  
Fold Increase ◽  
Hydrogen Peroxide Production ◽  
Fenton Chemistry ◽  
Human Astrocytes ◽  
Mitochondrial Toxin ◽  
Normal Human

Thimerosal generates ethylmercury in aqueous solution and is widely used as preservative. We have investigated the toxicology of Thimerosal in normal human astrocytes, paying particular attention to mitochondrial function and the generation of specific oxidants. We find that ethylmercury not only inhibits mitochondrial respiration leading to a drop in the steady state membrane potential, but also concurrent with these phenomena increases the formation of superoxide, hydrogen peroxide, and Fenton/Haber-Weiss generated hydroxyl radical. These oxidants increase the levels of cellular aldehyde/ketones. Additionally, we find a five-fold increase in the levels of oxidant damaged mitochondrial DNA bases and increases in the levels of mtDNA nicks and blunt-ended breaks. Highly damaged mitochondria are characterized by having very low membrane potentials, increased superoxide/hydrogen peroxide production, and extensively damaged mtDNA and proteins. These mitochondria appear to have undergone a permeability transition, an observation supported by the five-fold increase in Caspase-3 activity observed after Thimerosal treatment.

scholarly journals A Functional NADPH Oxidase Prevents Caspase Involvement in the Clearance of Phagocytic Neutrophils

2007 ◽  
Vol 75 (7) ◽  
pp. 3256-3263 ◽  
Author(s):  
Rachel P. Wilkie ◽  
Margret C. M. Vissers ◽  
Mike Dragunow ◽  
Mark B. Hampton
Keyword(s):  
Nadph Oxidase ◽  
Caspase 3 ◽  
Caspase Activity ◽  
Wild Type ◽  
Caspase Activation ◽  
Effector Caspases ◽  
Nadph Oxidase Complex ◽  
Normal Human ◽  
Active Caspase

ABSTRACT Neutrophils play a prominent role in host defense. Phagocytosis of bacteria leads to the formation of an active NADPH oxidase complex that generates reactive oxygen species for bactericidal purposes. A critical step in the resolution of inflammation is the uptake of neutrophils by macrophages; however, there are conflicting reports on the mechanisms leading to the apoptosis of phagocytic neutrophils. The aim of this study was to clarify the role of effector caspases in these processes. Caspase activity was measured by DEVDase activity assays or immunofluorescence detection of active caspase-3. With normal human and wild-type murine neutrophils there was no caspase activation following phagocytosis of Staphylococcus aureus. However, caspase activity was observed in phagocytic neutrophils with a defective NADPH oxidase, including neutrophils isolated from X-linked gp91phox knockout chronic granulomatous disease mice. These results indicate that a functional NADPH oxidase and the generation of oxidants in the neutrophil phagosome prevent the activation of the cytoplasmic caspase cascade.

Integrin β3 prevents apoptosis of HL-1 cardiomyocytes under conditions of oxidative stressThis article is one of a selection of papers published in a Special Issue on Oxidative Stress in Health and Disease.

2010 ◽  
Vol 88 (3) ◽  
pp. 324-330 ◽  
Author(s):  
Lee J. Shewchuk ◽  
Sean Bryan ◽  
Marina Ulanova ◽  
Neelam Khaper
Keyword(s):  
Oxidative Stress ◽  
Hydrogen Peroxide ◽  
Flow Cytometry ◽  
Gene Silencing ◽  
Cardiac Remodeling ◽  
Caspase 3 ◽  
Annexin V ◽  
Fold Increase ◽  
Cardiomyocyte Apoptosis ◽  
Active Caspase

Integrin receptors are essential in the regulation of vital cardiac functions, and impaired integrin activity has been associated with cardiac remodeling. Oxidative stress is known to be involved in apoptosis and cardiac remodeling and thus may profoundly influence cardiac function via integrin modulation. The aim of this study was to determine the expression pattern and functional role of integrins in HL-1 cardiomyocytes under conditions of oxidative stress. Gene expression was studied by end-point and real-time PCR; surface protein expression was studied by flow cytometry; integrin knockdown was accomplished by siRNA gene silencing; and apoptosis was studied by annexin V staining and active caspase-3/7 using flow cytometry. Among the various subunits under study (αv, α5, α6, and β1, β3, β4, and β5), the expression of β3 integrin was significantly increased at both the mRNA and protein levels in cardiomyocytes exposed to 100 µmol/L hydrogen peroxide for 3 h. Gene silencing of β3 integrin by using siRNA resulted in a 2-fold increase in cardiomyocyte apoptosis upon treatment with hydrogen peroxide. This increase in apoptosis, as measured by annexin V staining, correlated with an increase in active caspase-3/7. Integrin β3 plays a vital role in preventing cardiomyocyte apoptosis under conditions of oxidative stress.

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