Catherine Méplan

Bio: Catherine Méplan is an academic researcher from Newcastle University. The author has contributed to research in topics: Selenoprotein & Selenoprotein P. The author has an hindex of 26, co-authored 45 publications receiving 2516 citations. Previous affiliations of Catherine Méplan include International Agency for Research on Cancer & Wageningen University and Research Centre.

Metalloregulation of the tumor suppressor protein p53: zinc mediates the renaturation of p53 after exposure to metal chelators in vitro and in intact cells.

Abstract: The tumor suppressor p53 is a transcription factor which binds DNA through a structurally complex domain stabilized by a zinc atom. Zinc chelation disrupts the architecture of this domain, inducing the protein to adopt an immunological phenotype identical to that of many mutant forms of p53. In this report, we used 65Zn to show that incorporation of zinc within the protein was required for folding in the 'wild-type' conformation capable of specific DNA-binding. Using a cellular assay, we show that addition of extracellular zinc at concentrations within the physiological range (5 microM) was required for renaturation and reactivation of wild-type p53. Among other divalent metals tested (Cd2+, Cu2+, Co2+, Fe2+ and Ni2+), only Co2+ at 125 microM had a similar effect. Recombinant metallothionein (MT), a metal chelator protein, was found to modulate p53 conformation in vitro. In cultured cells, overexpression of MT by transfection could modulate p53 transcriptional activity. Taken together, these results suggest that zinc binding plays a regulatory role in the control of p53 folding and DNA-binding activity.

Genetic polymorphisms in the human selenoprotein P gene determine the response of selenoprotein markers to selenium supplementation in a gender-specific manner (the SELGEN study)

Abstract: Selenium (Se), a micronutrient essential for human health, is incorporated into at least 25 selenoproteins including selenoprotein P (SePP), which transports Se within the body. This research identified two single nucleotide polymorphisms (SNPs) in the SePP gene, one in the coding region (position 24731, causing an Ala to Thr change) and one in the 3′untranslated region (position 25191). Their frequency was similar in Caucasian, Chinese, and South Asian populations. Prospectively genotyped volunteers were supplemented for 6 wk with 100 μg sodium selenite/day. Blood samples were analyzed for plasma Se and selenoprotein biomarkers at baseline, after supplementation, and during a washout period. Plasma Se, SePP, and glutathione peroxidase 3 (GPx3) levels increased with supplementation. Baseline plasma Se content depended on both SePP genotypes and body mass index. Presupplementation SePP concentration was associated with gender and genotype at SNP 24731 and postsupplementation concentration with SNP 25191. B...

Two common single nucleotide polymorphisms in the gene encoding β-carotene 15,15′-monoxygenase alter β-carotene metabolism in female volunteers

Abstract: The key enzyme responsible for beta-carotene conversion into retinal is beta-carotene 15,15'-monoxygenase (BCMO1). Since it has been reported that the conversion of beta-carotene into vitamin A is highly variable in up to 45% of healthy individuals, we hypothesized that genetic polymorphisms in the BCMO1 gene could contribute to the occurrence of the poor converter phenotype. Here we describe the screening of the total open reading frame of the BCMO1 coding region that led to the identification of two common nonsynonymous single nucleotide polymorphisms (R267S: rs12934922; A379V: rs7501331) with variant allele frequencies of 42 and 24%, respectively. In vitro biochemical characterization of the recombinant 267S + 379V double mutant revealed a reduced catalytic activity of BCMO1 by 57% (P<0.001). Assessment of the responsiveness to a pharmacological dose of beta-carotene in female volunteers confirmed that carriers of both the 379V and 267S + 379V variant alleles had a reduced ability to convert beta-carotene, as indicated through reduced retinyl palmitate:beta-carotene ratios in the triglyceride-rich lipoprotein fraction [-32% (P=0.005) and -69% (P=0.001), respectively] and increased fasting beta-carotene concentrations [+160% (P=0.025) and +240% (P=0.041), respectively]. Our data show that there is genetic variability in beta-carotene metabolism and may provide an explanation for the molecular basis of the poor converter phenotype within the population.

Cellular response to oxidative stress: signaling for suicide and survival.

Abstract: Reactive oxygen species (ROS), whether produced endogenously as a consequence of normal cell functions or derived from external sources, pose a constant threat to cells living in an aerobic environment as they can result in severe damage to DNA, protein, and lipids. The importance of oxidative damage to the pathogenesis of many diseases as well as to degenerative processes of aging has becoming increasingly apparent over the past few years. Cells contain a number of antioxidant defenses to minimize fluctuations in ROS, but ROS generation often exceeds the cell's antioxidant capacity, resulting in a condition termed oxidative stress. Host survival depends upon the ability of cells and tissues to adapt to or resist the stress, and repair or remove damaged molecules or cells. Numerous stress response mechanisms have evolved for these purposes, and they are rapidly activated in response to oxidative insults. Some of the pathways are preferentially linked to enhanced survival, while others are more frequently associated with cell death. Still others have been implicated in both extremes depending on the particular circumstances. In this review, we discuss the various signaling pathways known to be activated in response to oxidative stress in mammalian cells, the mechanisms leading to their activation, and their roles in influencing cell survival. These pathways constitute important avenues for therapeutic interventions aimed at limiting oxidative damage or attenuating its sequelae.

Food, Nutrition, Physical Activity, and the Prevention of Cancer : a Global Perspective : 食物、栄養、身体活動とがんの予防 : 世界的展望(後篇)

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Molecular mechanisms of N-acetylcysteine actions.

Abstract: Oxidative stress generated by an imbalance between reactive oxygen species (ROS) and antioxidants contributes to the pathogenesis of arthritis, cancer, cardiovascular, liver and respiratory diseases. Proinflammatory cytokines and growth factors stimulate ROS production as signaling mediators. Antioxidants such as N-acetylcysteine (NAC) have been used as tools for investigating the role of ROS in numerous biological and pathological processes. NAC inhibits activation of c-Jun N-terminal kinase, p38 MAP kinase and redox-sensitive activating protein-1 and nuclear factor kappa B transcription factor activities regulating expression of numerous genes. NAC can also prevent apoptosis and promote cell survival by activating extracellular signal-regulated kinase pathway, a concept useful for treating certain degenerative diseases. NAC directly modifies the activity of several proteins by its reducing activity. Despite its nonspecificity, ability to modify DNA and multiple molecular modes of action, NAC has therapeutic value for reducing endothelial dysfunction, inflammation, fibrosis, invasion, cartilage erosion, acetaminophen detoxification and transplant prolongation.