Publications by authors named "Ken Raj"

10 Publications

  • Page 1 of 1

Epigenetic clock and methylation studies in elephants.

Aging Cell 2021 Jul 12;20(7):e13414. Epub 2021 Jun 12.

Department of Biostatistics, Fielding School of Public Health, University of California, Los Angeles, CA, USA.

Age-associated DNA-methylation profiles have been used successfully to develop highly accurate biomarkers of age ("epigenetic clocks") in humans, mice, dogs, and other species. Here we present epigenetic clocks for African and Asian elephants. These clocks were developed using novel DNA methylation profiles of 140 elephant blood samples of known age, at loci that are highly conserved between mammalian species, using a custom Infinium array (HorvathMammalMethylChip40). We present epigenetic clocks for Asian elephants (Elephas maximus), African elephants (Loxodonta africana), and both elephant species combined. Two additional human-elephant clocks were constructed by combining human and elephant samples. Epigenome-wide association studies identified elephant age-related CpGs and their proximal genes. The products of these genes play important roles in cellular differentiation, organismal development, metabolism, and circadian rhythms. Intracellular events observed to change with age included the methylation of bivalent chromatin domains, and targets of polycomb repressive complexes. These readily available epigenetic clocks can be used for elephant conservation efforts where accurate estimates of age are needed to predict demographic trends.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/acel.13414DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8282242PMC
July 2021

Epigenetic clock and methylation study of oocytes from a bovine model of reproductive aging.

Aging Cell 2021 05 2;20(5):e13349. Epub 2021 Apr 2.

Department of Human Genetics, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.

Cattle are an attractive animal model of fertility in women due to their high degree of similarity relative to follicle selection, embryo cleavage, blastocyst formation, and gestation length. To facilitate future studies of the epigenetic underpinnings of aging effects in the female reproductive axis, several DNA methylation-based biomarkers of aging (epigenetic clocks) for bovine oocytes are presented. One such clock was germane to only oocytes, while a dual-tissue clock was highly predictive of age in both oocytes and blood. Dual species clocks that apply to both humans and cattle were also developed and evaluated. These epigenetic clocks can be used to accurately estimate the biological age of oocytes. Both epigenetic clock studies and epigenome-wide association studies revealed that blood and oocytes differ substantially with respect to aging and the underlying epigenetic signatures that potentially influence the aging process. The rate of epigenetic aging was found to be slower in oocytes compared to blood; however, oocytes appeared to begin at an older epigenetic age. The epigenetic clocks for oocytes are expected to address questions in the field of reproductive aging, including the central question: how to slow aging of oocytes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1111/acel.13349DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8135012PMC
May 2021

Chronic irradiation of human cells reduces histone levels and deregulates gene expression.

Sci Rep 2020 02 10;10(1):2200. Epub 2020 Feb 10.

Wellcome/Cancer Research UK Gurdon Institute and Department of Biochemistry, University of Cambridge, Cambridge, CB2 1QN, UK.

Over the past decades, there have been huge advances in understanding cellular responses to ionising radiation (IR) and DNA damage. These studies, however, were mostly executed with cell lines and mice using single or multiple acute doses of radiation. Hence, relatively little is known about how continuous exposure to low dose ionising radiation affects normal cells and organisms, even though our cells are constantly exposed to low levels of radiation. We addressed this issue by examining the consequences of exposing human primary cells to continuous ionising γ-radiation delivered at 6-20 mGy/h. Although these dose rates are estimated to inflict fewer than a single DNA double-strand break (DSB) per hour per cell, they still caused dose-dependent reductions in cell proliferation and increased cellular senescence. We concomitantly observed histone protein levels to reduce by up to 40%, which in contrast to previous observations, was not mainly due to protein degradation but instead correlated with reduced histone gene expression. Histone reductions were accompanied by enlarged nuclear size paralleled by an increase in global transcription, including that of pro-inflammatory genes. Thus, chronic irradiation, even at low dose-rates, can induce cell senescence and alter gene expression via a hitherto uncharacterised epigenetic route. These features of chronic radiation represent a new aspect of radiation biology.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-020-59163-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7010678PMC
February 2020

Rapamycin retards epigenetic ageing of keratinocytes independently of its effects on replicative senescence, proliferation and differentiation.

Aging (Albany NY) 2019 05;11(10):3238-3249

Radiation Effects Department, Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Chilton, Didcot, Oxfordshire OX11 0RQ, United Kingdom.

The advent of epigenetic clocks has prompted questions about the place of epigenetic ageing within the current understanding of ageing biology. It was hitherto unclear whether epigenetic ageing represents a distinct mode of ageing or a manifestation of a known characteristic of ageing. We report here that epigenetic ageing is not affected by replicative senescence, telomere length, somatic cell differentiation, cellular proliferation rate or frequency. It is instead retarded by rapamycin, the potent inhibitor of the mTOR complex which governs many pathways relating to cellular metabolism. Rapamycin, however, is also an effective inhibitor of cellular senescence. Hence cellular metabolism underlies two independent arms of ageing - cellular senescence and epigenetic ageing. The demonstration that a compound that targets metabolism can slow epigenetic ageing provides a long-awaited point-of-entry into elucidating the molecular pathways that underpin the latter. Lastly, we report here an assay, validated in humans, that recapitulates human epigenetic ageing that can be used to investigate and identify potential interventions that can inhibit or retard it.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.18632/aging.101976DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6555449PMC
May 2019

Ionising radiation increases permeability of endothelium through ADAM10-mediated cleavage of VE-cadherin.

Oncotarget 2017 Oct 30;8(47):82049-82063. Epub 2017 May 30.

Radiation Effects Department, Centre for Radiation, Chemical and Environmental Hazards, Public Health England, Chilton, UK.

The association between ionising radiation (IR) exposure and risk of cardiovascular diseases (CVD) is well documented, but the underlying mechanism is still poorly understood. As atherosclerotic plaques are the most common cause of CVD, we investigated the effects of IR on one of the critical parameters for atherosclerotic plaque formation - endothelium permeability to macromolecules. We used endothelial cells from human coronary artery as a model of the endothelial layer. Our results show that exposure of this endothelial layer to IR increased its permeability to macromolecules of various sizes in a dose-dependent manner. Immunofluorescence analysis revealed disruption of cell junctions caused by decreased amounts of two junction proteins, one of which is vascular endothelial cadherin (VE-cadherin). The reduction in the level of this protein was not due to diminished transcription but to protein processing instead. We observed a radiation dose-dependent increase in the cleavage of VE-cadherin by ADAM10. This was not mediated through the canonical VEGF route but was instead accompanied by intra-cellular calcium release. Importantly, inhibition of ADAM10 activity rescued IR-induced permeability. Our observations demonstrate that exposure to IR activates ADAM10 to cleave VE-cadherin leading to augmented endothelium permeability; a feature that can lead to the development of atherosclerotic plaques and increase the risk of cardiovascular disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.18632/oncotarget.18282DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5669869PMC
October 2017

Ultraviolet Radiation-Induced Production of Nitric Oxide:A multi-cell and multi-donor analysis.

Sci Rep 2017 09 11;7(1):11105. Epub 2017 Sep 11.

Radiation Effects Department, Centre for Radiation, Chemical and Environmental Hazards,Public Health England (PHE), Chilton, Oxfordshire, OX11 0RQ, United Kingdom.

Increasing evidence regarding positive effects of exposure to sunlight has led to suggestions that current advice may be overly weighted in favour of avoidance. UV-A has been reported to lower blood pressure, possibly through nitric oxide (NO) production in skin. Here, we set out to investigate effects of UV-A and solar-simulated radiation on the potential source of dermal NO, the effective doses and wavelengths, the responsiveness of different human skin cells, the magnitude of inter-individual differences and the potential influence of age. We utilised isogenic keratinocytes, microvascular endothelial cells, melanocytes and fibroblasts isolated from 36 human skins ranging from neonates to 86 years old. We show that keratinocytes and microvascular endothelial cells show greatest NO release following biologically relevant doses of UV-A. This was consistent across multiple neonatal donors and the effect is maintained in adult keratinocytes. Our observations are consistent with a bi-phasic mechanism by which UV-A can trigger vasodilatory effects. Analyses of NO-production spectra adds further evidence that nitrites in skin cells are the source of UV-mediated NO release. These potentially positive effects of ultraviolet radiation lend support for objective assessment of environmental influence on human health and the idea of "healthy sun exposure".
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-017-11567-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5593895PMC
September 2017

Radiation-Induced Endothelial Inflammation Is Transferred via the Secretome to Recipient Cells in a STAT-Mediated Process.

J Proteome Res 2017 10 14;16(10):3903-3916. Epub 2017 Sep 14.

Helmholtz Zentrum München - German Research Center for Environmental Health GmbH, Institute of Radiation Biology , D-85764 Neuherberg, Germany.

Radiation is the most common treatment of cancer. Minimizing the normal tissue injury, especially the damage to vascular endothelium, remains a challenge. This study aimed to analyze direct and indirect radiation effects on the endothelium by investigating mechanisms of signal transfer from irradiated to nonirradiated endothelial cells by means of secreted proteins. Human coronary artery endothelial cells (HCECest2) undergo radiation-induced senescence in vitro 14 days after exposure to 10 Gy X-rays. Proteomics analysis was performed on HCECest2 14 days after irradiation with X-ray doses of 0 Gy (control) or 10 Gy using label-free technology. Additionally, the proteomes of control and radiation-induced secretomes, and those of nonirradiated HCECest2 exposed for 24 h to secreted proteins of either condition were measured. Key changes identified by proteomics and bioinformatics were validated by immunoblotting, ELISA, bead-based multiplex assays, and targeted transcriptomics. The irradiated cells, their secretome, and the nonirradiated recipient cells showed similar inflammatory response, characterized by induction of interferon type I-related proteins and activation of the STAT3 pathway. These data indicate that irradiated endothelial cells may adversely affect nonirradiated surrounding cells via senescence-associated secretory phenotype. This study adds to our knowledge of the pathological background of radiation-induced cardiovascular disease.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1021/acs.jproteome.7b00536DOI Listing
October 2017

Proteome analysis of irradiated endothelial cells reveals persistent alteration in protein degradation and the RhoGDI and NO signalling pathways.

Int J Radiat Biol 2017 09 11;93(9):920-928. Epub 2017 Jul 11.

a Institute of Radiation Biology , Helmholtz Zentrum München, German Research Center for Environmental Health GmbH , Neuherberg , Germany.

Purpose: Epidemiological studies indicate that radiation doses as low as 0.5 Gy increase the risk of cardiovascular disease decades after the exposure. The aim of the present study was to investigate whether this radiation dose causes late molecular alterations in endothelial cells that could support the population-based data.

Materials And Methods: Human coronary artery endothelial cells were irradiated at 0.5 Gy (X-ray) and radiation-induced changes in the proteome were investigated after different time intervals (1, 7 and 14 d) using ICPL technology. Key changes identified by proteomics and bioinformatics were validated by immunoblotting and ELISA.

Results: The radiation-induced alteration of the endothelial proteome was characterized by sustained perturbation of Rho GDP-dissociation inhibitor (RhoGDI) and nitric oxide (NO) signalling pathways. At later time-points, this was accompanied by reduced proteasome activity, enhanced protein carbonylation indicating augmented oxidative stress, and senescence.

Conclusions: These molecular changes are indicative of long-term premature endothelial dysfunction and provide a mechanistic framework to the epidemiological data showing increased risk of cardiovascular disease at 0.5 Gy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/09553002.2017.1339332DOI Listing
September 2017

Low-dose radiation differentially regulates protein acetylation and histone deacetylase expression in human coronary artery endothelial cells.

Int J Radiat Biol 2017 02 21;93(2):156-164. Epub 2016 Oct 21.

a Institute of Radiation Biology, Helmholtz Zentrum München , German Research Center for Environmental Health , Neuherberg , Germany.

Purpose: Ionizing radiation induces cardiovascular disease, the endothelium being the main target. The exact mechanism of the damage is unclear but the involvement of multiple signaling pathways is probable. Reversible lysine acetylation is a posttranslational protein modification that regulates activity across a broad range of signaling pathways. The aim of this study was to determine if a low radiation dose results in acetylome alteration in endothelial cells.

Materials And Methods: Human coronary artery endothelial cell line was irradiated with Cs-137 gamma-rays (0.5 Gy) and proteomics analysis was performed using enriched acetylated peptides and all peptides. Data were validated using immunoblotting, deacetylase activity assay, and RhoA activity assay.

Results: Nearly a hundred proteins were found to have an altered acetylation status 24 h after irradiation, primarily due to an overall decrease in acetylation. The expression of specific deacetylases was significantly increased, coinciding with an enhancement in global deacetylase activity. Proteins changed in their acetylation status belonged to several pathways including protein synthesis, cytoskeleton-related processes, protein folding and calcium signaling. The predicted changes in the RhoA/actin cytoskeleton pathway were validated by immunoassay.

Conclusions: This study shows that protein acetylation is an important mediator of radiation responses in human cardiac coronary endothelial cells. Increased knowledge of the endothelial response to radiation is crucial for the development of normal tissue-sparing modalities during radiation therapy.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1080/09553002.2017.1237059DOI Listing
February 2017

Low-dose ionising radiation and cardiovascular diseases--Strategies for molecular epidemiological studies in Europe.

Mutat Res Rev Mutat Res 2015 Apr-Jun;764:90-100. Epub 2015 Apr 3.

BfS, Federal Office for Radiation Protection, Department Radiation Protection and Health, Neuherberg, Germany.

It is well established that high-dose ionising radiation causes cardiovascular diseases. In contrast, the evidence for a causal relationship between long-term risk of cardiovascular diseases after moderate doses (0.5-5 Gy) is suggestive and weak after low doses (<0.5 Gy). However, evidence is emerging that doses under 0.5 Gy may also increase long-term risk of cardiovascular disease. This would have major implications for radiation protection with respect to medical use of radiation for diagnostic purposes and occupational or environmental radiation exposure. Therefore, it is of great importance to gain information about the presence and possible magnitude of radiation-related cardiovascular disease risk at doses of less than 0.5 Gy. The biological mechanisms implicated in any such effects are unclear and results from epidemiological studies are inconsistent. Molecular epidemiological studies can improve the understanding of the pathogenesis and the risk estimation of radiation-induced circulatory disease at low doses. Within the European DoReMi (Low Dose Research towards Multidisciplinary Integration) project, strategies to conduct molecular epidemiological studies in this field have been developed and evaluated. Key potentially useful European cohorts are the Mayak workers, other nuclear workers, uranium miners, Chernobyl liquidators, the Techa river residents and several diagnostic or low-dose radiotherapy patient cohorts. Criteria for informative studies are given and biomarkers to be investigated suggested. A close collaboration between epidemiology, biology and dosimetry is recommended, not only among experts in the radiation field, but also those in cardiovascular diseases.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.mrrev.2015.03.002DOI Listing
August 2015
-->