Resveratrol has gained tremendous interest owing to multiple reported health-beneficial effects. However, the underlying key mechanism of action of this natural product remained largely ...controversial. Here, we demonstrate that under physiologically relevant conditions major biological effects of resveratrol can be attributed to its generation of oxidation products such as reactive oxygen species (ROS). At low nontoxic concentrations (in general <50µM), treatment with resveratrol increased viability in a set of representative cell models, whereas application of quenchers of ROS completely truncated these beneficial effects. Notably, resveratrol treatment led to mild, Nrf2-specific gene expression reprogramming. For example, in primary epidermal keratinocytes derived from human skin this coordinated process resulted in a 1.3-fold increase of endogenously generated glutathione (GSH) and subsequently in a quantitative reduction of the cellular redox environment by 2.61mVmmol GSH per g protein. After induction of oxidative stress by using 0.78% (v/v) ethanol, endogenous generation of ROS was consequently reduced by 24% in resveratrol pre-treated cells. In contrast to the common perception that resveratrol acts mainly as a chemical antioxidant or as a target protein-specific ligand, we propose that the cellular response to resveratrol treatment is essentially based on oxidative triggering. In physiological microenvironments this molecular training can lead to hormetic shifting of cellular defense towards a more reductive state to improve physiological resilience to oxidative stress.
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•RSV generates oxidation products under physiologically relevant conditions.•Oxidation products of RSV are causative for an increased cell viability.•Cellular response to RSV depends on the redox-sensitive transcription factor Nrf2.•Nrf2 induces cellular defense pathways and increased reducing equivalents.•Oxidation of RSV results in a slight, hormetic shift of cellular redox-environment.•Hormetic shift protects cells against additional (oxidative) stress.
Retinoic acid (RA) induces cell cycle arrest and differentiation of human neuroblastoma (NB) cells. Typically, NB cells differentiate along the neuronal lineage, but quiescent, "flat" cell types ...frequently have been described after treatment with differentiating agents. Two indistinguishable subclones of the cell line SK-N-SH, SK-N-SH-N (SH-N) and SK-N-SH-F (SH-F), display dramatically different responses to RA. In SH-N, RA induces neuronal differentiation, but in SH-F it transforms the small neuroblastic cells into large, flattened, epithelium-like cells. Here we analyze the mechanistic basis for the different effects of RA in the two NB subclones. First, we show that the flattened RA-treated SH-F expresses markers of cells undergoing replicative senescence. Inhibition of DNA synthesis by RA is significantly more rapid in SH-F than in SH-N. SH-F, which expresses basal amounts of p16INK4A, responds to RA with elevation of p18INK4C, marked down-regulation of cyclin D1, and swift inhibition of cyclin D-dependent kinases (cdks). Conversely, after addition of RA, SH-N retains cell cycling due to high expression of cyclin D1, the absence of Ink4 inhibitors, and accumulation of p21Cip1. These changes result in sustained cdk activity. Accordingly, overexpression of p21Cip1but not p16INK4Ainduces neuronal differentiation of untreated NB cells. We propose that rapid inhibition of cdks by RA in NB leads to early cell cycle arrest, prevents neuronal differentiation, and results in a senescence-like state.
We show here if under physiologically relevant conditions resveratrol (RSV) remains stable or not. We further show under which circumstances various oxidation products of RSV such as ROS can be ...produced. For example, in addition to the widely known effect of bicarbonate ions, high pH values promote the decay of RSV. Moreover, we analyse the impact of reduction of the oxygen partial pressure on the pH-dependent oxidation of RSV. For further interpretation and discussion of these focused data in a broader context we refer to the article “Hormetic shifting of redox environment by pro-oxidative resveratrol protects cells against stress” (Plauth et al., in press) 1.
SIRT1 is likely to play a role in the extension in healthspan induced by dietary restriction. Actions of SIRT1 are pleiotropic, and effects on healthspan may include effects on DNA methylation. ...Polycomb group protein target genes (PCGTs) are suppressed by epigenetic mechanisms in stem cells, partly through the actions of the polycomb repressive complexes (PRCs), and have been shown previously to correspond with loci particularly susceptible to age-related changes in DNA methylation. We hypothesised that SIRT1 would affect DNA methylation particularly at PCGTs. To map the sites in the genome where SIRT1 affects DNA methylation, we altered SIRT1 expression in human intestinal (Caco-2) and vascular endothelial (HuVEC) cells by transient transfection with an expression construct or with siRNA. DNA was enriched for the methylated fraction then sequenced (HuVEC) or hybridised to a human promoter microarray (Caco-2).
The profile of genes where SIRT1 manipulation affected DNA methylation was enriched for PCGTs in both cell lines, thus supporting our hypothesis. SIRT1 knockdown affected the mRNA for none of seven PRC components nor for DNMT1 or DNMT3b. We thus find no evidence that SIRT1 affects DNA methylation at PCGTs by affecting the expression of these gene transcripts. EZH2, a component of PRC2 that can affect DNA methylation through association with DNA methyltransferases (DNMTs), did not co-immunoprecipitate with SIRT1, and SIRT1 knockdown did not affect the expression of EZH2 protein. Thus, it is unlikely that the effects of SIRT1 on DNA methylation at PCGTs are mediated through direct intermolecular association with EZH2 or through effects in its expression.
SIRT1 affects DNA methylation across the genome, but particularly at PCGTs. Although the mechanism through which SIRT1 has these effects is yet to be uncovered, this action is likely to contribute to extended healthspan, for example under conditions of dietary restriction.
Abstract
An injury to the epidermis can result in a micro-wound, characterized by its localization above the dermal–epidermal junction and an absence of vessel damage. Re-epithelialization is driven ...by keratinocytes, which organize into overlapping migrating and proliferating zones to ensure faithful micro-wound closure. Although still relatively unexplored, keratinocyte-mediated cytokine secretion is thought to be a feature of the micro-wound re-epithelialization response. A failure to re-epithelize, also characteristic of chronic wounds, can lead to reoccurring infections and hyperpigmentation. Although wound healing has been extensively researched, there are gaps in our understanding of the cellular mechanisms involved in the onset and completion of re-epithelization, leading to a scarcity of available enhanced micro-wound healing compounds (MHCs). To investigate the utility of a panel of putative MHCs, a new high-throughput scratch assay method was devised. A guide for multichannel pipette scratches was produced by three-dimensional printing an autoclavable 96-well plate lid with custom-made lengthwise slits. Using an immortalized keratinocyte cell line (N/TERT), the rate of scratch healing was characterized. Critical re-epithelization time points have been determined, and markers of migration are being explored within the identified periods. Moreover, known keratinocyte migration-inducing compounds are being tested to serve as a positive control for enhanced MHC screening. Any putative MHC hits will be further explored using proteomic approaches to elucidate the signalling pathways involved in the onset and completion of re-epithelization. This analysis will assist in the identification of novel enhanced MHC targets and further our understanding of keratinocyte re-epithelization.
Kaposi sarcoma in South African children Stefan, Cristina; Stones, David; Wainwright, Linda ...
Infectious agents and cancer,
10/2010, Letnik:
5, Številka:
S1
Journal Article
Recenzirano
Odprti dostop
From: 12th International Conference on Malignancies in AIDS and Other Acquired Immunodeficiencies (ICMAOI) Bethesda, MD, USA 26-27 April, 2010 Author details 1-Department of Paediatrics and Child ...Health, Tygerberg Hospital and Stellenbosch University, Tygerberg, Cape Town, South Africa EMPTY 2-Department of Paediatrics and Child Health University of Free State Universitas Hospital, Bloemfontein, South Africa EMPTY 3-Department of Paediatrics and Child Health Chris Baragwanath Hospital, University of the Witwatersrand, Johannesburg, South Africa EMPTY 4-Epidemiology and Genetics Unit, Department of Health Sciences, University of York, York, UKEMPTY Supplemental Information: Aim To examine retrospectively a series of 70 HIV-positive children with Kaposi sarcoma, from several centers in South Africa, in order to describe the usual clinical presentation as well as the management and its impact on the course of the disease.
Aim: This paper presents a 20-year review of retinoblastoma in Johannesburg, South Africa, aiming to better characterize the disease in this sub-Saharan setting. Methods: The study represents a ...retrospective case series of retinoblastoma patients presenting to Charlotte Maxeke Johannesburg Academic Hospital and Chris Hani Baragwanath Academic Hospital between January 1, 1992, and December 31, 2011. Results: The total number of cases identified was 282, with 245 meeting the study inclusion criteria. Retinoblastoma comprised 6.9% of the total pediatric oncology presentations; 65.3% were unilateral, 34.3% bilateral, and 0.4% trilateral. The overall male-to-female ratio was 1.08. The mean age at presentation overall was 32.6 months (median 28.0), in the unilateral group 39.4 months (median 33.0), and in the bilateral group 19.7 months (median 17.0). The mean delay to presentation overall was 7.0 months (median 4.0). The most frequent presenting symptoms were leukocoria (37.1%) and proptosis (34.7%). The distribution of disease stages at presentation (International Retinoblastoma Staging System) was 1.6% stage 0, 24.1% stage I, 27.8% stage II, 16.3% stage III, and 25.3% stage IV. 26.5% defaulted care. The 5-year Kaplan-Meier survival estimate was 57.7% overall. Conclusion: This study shows that delayed presentation and refusal of therapy remains a significant barrier to effective treatment in this African setting.
The rapidity with which molecular sequence data are gathered continues to grow. The result is that, for many workers, it is increasingly difficult to keep abreast of the current state of play of ...molecular cloning, even for those genes that encode proteins of special interest. The clear success of the various worldwide genome projects has made this even more apparent, and by the end of 1996 the complete determination of the nucleotide sequences of the genomes of two eukaryotes, Saccharomyces cerevisiae and Caenorhabditis elegans, will have either been completed or will be nearing completion. This article is an attempt to provide, in an easily accessible format, a compilation of genes and cDNAs that have been sequenced and deposited in GenBank that encode transferase enzymes involved in eukaryotic glycoprotein or glycolipid biosynthesis. The full sequence information can be easily retrieved from a databank, e.g. GenBank, using the relevant accession number(s).
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