Reactive Oxygen Species via Redox Signaling to PI3K/AKT Pathway Contribute to the Malignant Growth of 4-Hydroxy Estradiol-Transformed Mammary Epithelial Cells

The purpose of this study was to investigate the effects of 17-β-estradiol (E2)-induced reactive oxygen species (ROS) on the induction of mammary tumorigenesis. We found that ROS-induced by repeated exposures to 4-hydroxy-estradiol (4-OH-E2), a predominant catechol metabolite of E2, caused transformation of normal human mammary epithelial MCF-10A cells with malignant growth in nude mice. This was evident from inhibition of estrogen-induced breast tumor formation in the xenograft model by both overexpression of catalase as well as by co-treatment with Ebselen. To understand how 4-OH-E2 induces this malignant phenotype through ROS, we investigated the effects of 4-OH-E2 on redox-sensitive signal transduction pathways. During the malignant transformation process we observed that 4-OH-E2 treatment increased AKT phosphorylation through PI3K activation. The PI3K-mediated phosphorylation of AKT in 4-OH-E2-treated cells was inhibited by ROS modifiers as well as by silencing of AKT expression. RNA interference of AKT markedly inhibited 4-OH-E2-induced in vitro tumor formation. The expression of cell cycle genes, cdc2, PRC1 and PCNA and one of transcription factors that control the expression of these genes – nuclear respiratory factor-1 (NRF-1) was significantly up-regulated during the 4-OH-E2-mediated malignant transformation process. The increased expression of these genes was inhibited by ROS modifiers as well as by silencing of AKT expression. These results indicate that 4-OH-E2-induced cell transformation may be mediated, in part, through redox-sensitive AKT signal transduction pathways by up-regulating the expression of cell cycle genes cdc2, PRC1 and PCNA, and the transcription factor – NRF-1. In summary, our study has demonstrated that: (i) 4-OH-E2 is one of the main estrogen metabolites that induce mammary tumorigenesis and (ii) ROS-mediated signaling leading to the activation of PI3K/AKT pathway plays an important role in the generation of 4-OH-E2-induced malignant phenotype of breast epithelial cells. In conclusion, ROS are important signaling molecules in the development of estrogen-induced malignant breast lesions.

Redox Regulation of Ras Proteins in Dictyostelium discoideum

Reactive oxygen species are a normal consequence of life in an aerobic environment. However when they deviate from the narrow permissible range in cells, oxidative damage can occur. Dictyostelium discoideum is a model organism ideal for the study of cell signaling events such as those affected by oxidative stress. It was previously shown that Ras signaling in Dictyostelium is affected by genetic inactivation of the antioxidant enzyme Superoxide dismutase C (SodC) and in vitro data suggests that the NKCD motif of Ras is the redox target of superoxide. The main objective of this project was to determine the mechanism of superoxide mediated Ras regulation in vivo. To accomplish the main objective, we cloned, and in some cases, mutated different Ras proteins and later determined their activity in wild type and sodC- cells. RasC and RasD showed normal activation in sodC- cells, however RasG and RasS displayed high Ras activity. These last two Ras proteins contain the NKC118D motif inside the nucleotide binding region. A mutation of cysteine118 to alanine in RasG rendered the protein less active in sodC- than the wild type RasG protein and a mutation alanine118 to cysteine in RasD conferred redox sensitivity to this small GTPase. Additionally, the propensity of RasG to be targeted by superoxide was evident when the environment of wild type cells was manipulated to induce the internal generation of superoxide through changes in the extracellular ion levels mainly magnesium. Lack of magnesium ions increased the intracellular level of superoxide and severely hampered directional cell migration. Chemotaxis of cells expressing RasG was negatively impacted by the absence of magnesium ions; however rasG- cells did not seem to be affected in their ability to perform chemotaxis. The last experiment implies that RasG is an important mediator of cell signaling during oxidative stress, responsible for preventing cells from continuing their developmental program. Our study suggests that the cysteine residue in the NKCD motif is essential for mediating the redox sensitivity of Ras proteins in Dictyostelium and that RasG is an essential mediator of the response to oxidative stress in this organism.

Effect of support redox character on catalytic performance in the gas phase hydrogenation of benzaldehyde and nitrobenzene over supported gold

Peer reviewed

Redox regulation of ET-1-induced activation of ERK1/2, PKB and Pyk2 signaling in A-10 vascular smooth muscle cells

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Protection of primary cultures of mouse hepatocytes against fas-induced apoptosis : role of EGF receptor intrinsic activity and intracellular redox state

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

La nutrition parentérale modifie le statut et le potentiel redox du glutathion hépatique chez le modèle néonatal du cochon d'Inde

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

La signalisation redox en hypertension artérielle

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Therapeutically targeting mitochondrial redox signalling alleviates endothelial dysfunction in preeclampsia

Aberrant placentation generating placental oxidative stress is proposed to play a critical role in the pathophysiology of preeclampsia. Unfortunately, therapeutic trials of antioxidants have been uniformly disappointing. There is provisional evidence implicating mitochondrial dysfunction as a source of oxidative stress in preeclampsia. Here we provide evidence that mitochondrial reactive oxygen species mediates endothelial dysfunction and establish that directly targeting mitochondrial scavenging may provide a protective role. Human umbilical vein endothelial cells exposed to 3% plasma from women with pregnancies complicated by preeclampsia resulted in a significant decrease in mitochondrial function with a subsequent significant increase in mitochondrial superoxide generation compared to cells exposed to plasma from women with uncomplicated pregnancies. Real-time PCR analysis showed increased expression of inflammatory markers TNF-α, TLR-9 and ICAM-1 respectively in endothelial cells treated with preeclampsia plasma. MitoTempo is a mitochondrial-targeted antioxidant, pre-treatment of cells with MitoTempo protected against hydrogen peroxide-induced cell death. Furthermore MitoTempo significantly reduced mitochondrial superoxide production in cells exposed to preeclampsia plasma by normalising mitochondrial metabolism. MitoTempo significantly altered the inflammatory profile of plasma treated cells. These novel data support a functional role for mitochondrial redox signaling in modulating the pathogenesis of preeclampsia and identifies mitochondrial-targeted antioxidants as potential therapeutic candidates.

Redox regulation of ET-1-induced activation of ERK1/2, PKB and Pyk2 signaling in A-10 vascular smooth muscle cells

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

Protection of primary cultures of mouse hepatocytes against fas-induced apoptosis : role of EGF receptor intrinsic activity and intracellular redox state

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

La nutrition parentérale modifie le statut et le potentiel redox du glutathion hépatique chez le modèle néonatal du cochon d'Inde

Mémoire numérisé par la Direction des bibliothèques de l'Université de Montréal.

La signalisation redox en hypertension artérielle

Thèse numérisée par la Direction des bibliothèques de l'Université de Montréal.

Left to right: Dan Bond, Kim de Mutsert and Edward Castaneda measuring porewater salinity, redox, and hydrogen sulfide in dwarf mangroves, Taylor Slough

This material is based upon work supported by the National Science Foundation through the Florida Coastal Everglades Long-Term Ecological Research program under Cooperative Agreements #DBI-0620409 and #DEB-9910514. This image is made available for non-commercial or educational use only.

Mean redox potential values in surface sediments along the transect D in the Cretan Sea (Table 1)

The seasonal, spatial and bathymetric changes in the distribution of chloroplastic pigments (Chl a, phaeopigments and CPE), TOC, TON, ATP, bottom water nutrient content and the main biochemical classes of organic compounds (lipids, proteins and carbohydrates) were recorded from May 1994 to September 1995 over the continental margin of northern Crete. The concentration of chloroplastic pigment equivalents (CPE) was always low, dropping dramatically along the shelf-slope gradient. Microbial activity (ATP) also dropped sharply beyond the continental shelf following a distribution pattern similar to TOC and TON. Lipid, protein and carbohydrate concentrations, as well as biopolymeric carbon were comparable to those reported for other more productive areas, however, the quality of the organic matter itself was rather poor. Thus, carbohydrates, the dominant biochemical class, were characterised by being highly (80-99%) refractory, as soluble carbohydrates represented (on annual average) only 6% of the total carbohydrate pool. Protein and lipid concentrations strongly decreased with depth, indicating depletion of trophic resources in the bathyal zone. Proteins appeared to be the more degradable compounds and indeed the protein to carbohydrate ratios were found to decrease strongly in the deeper stations. Organic matter content and quality decreased both with increasing distance from the coast and within the sediment. All sedimentary organic compounds were found to vary between sampling periods, with the changes being more pronounced over the continental shelf. The different temporal patterns of the various components suggest a different composition and/or origin of the OM inputs during the different sampling periods. The amount of material reaching the sediments below 540 m is extremely low, suggesting that most of the organic material is decomposed and/or utilised before reaching the sea floor. In conclusion, the continental shelf and bathyal sediments of the Cretan Sea can be considered, from a trophic point of view, as two different subsystems.

Can emerging biomarkers of myocardial remodelling identify asymptomatic hypertensive patients at risk for diastolic dysfunction and diastolic heart failure?

AIMS: Hypertension is one of the main drivers of the heart failure (HF) epidemic. The aims of this study were to profile fibro-inflammatory biomarkers across stages of the hypertensive heart disease (HHD) spectrum and to examine whether particular biochemical profiles in asymptomatic patients identify a higher risk of evolution to HF.

METHODS AND RESULTS: This was a cross-sectional observational study involving a population of 275 stable hypertensive patients divided into two different cohorts: Group 1, asymptomatic hypertension (AH) (n= 94); Group 2, HF with preserved ejection fraction (n= 181). Asymptomatic hypertension patients were further subdivided according to left atrial volume index ≥34 mL/m(2) (n= 30) and <34 mL/m(2) (n= 64). Study assays involved inflammatory markers [interleukin 6 (IL6), interleukin 8 (IL8), monocyte chemoattractant protein 1 (MCP1), and tumour necrosis factor α], collagen 1 and 3 metabolic markers [carboxy-terminal propeptide of collagen 1, amino-terminal propeptide of collagen 1, amino-terminal propeptide of collagen 3 (PIIINP), and carboxy-terminal telopeptide of collagen 1 (CITP)], extra-cellular matrix turnover markers [matrix metalloproteinase 2 (MMP2), matrix metalloproteinase 9 (MMP9), and tissue inhibitor of metalloproteinase 1 (TIMP1)], and the brain natriuretic peptide. Data were adjusted for age, sex, systolic blood pressure, and creatinine. Heart failure with preserved ejection fraction was associated with an increased inflammatory signal (IL6, IL8, and MCP1), an increased fibrotic signal (PIIINP and CITP), and an increased matrix turnover signal (MMP2 and MMP9). Alterations in MMP and TIMP enzymes were found to be significant indicators of greater degrees of asymptomatic left ventricular diastolic dysfunction.

CONCLUSION: These data define varying fibro-inflammatory profiles throughout different stages of HHD. In particular, the observations on MMP9 and TIMP1 raise the possibility of earlier detection of those at risk of evolution to HF which may help focus effective preventative strategies.