Effects of irradiation on cumulative mortality in mice: shifting toward a younger age of death.

Recently, the question of whether cancer risk is only accelerated but not increased by radiation exposure has been raised. To explore this matter, we analyzed whether the cumulative mortality of irradiated mice could be explained by x-axis (age) shifted cumulative mortality of nonirradiated mice. We reanalyzed publicly available data on observed cumulative mortality or prevalence in irradiated female B6C3F1 mice that lived their entire lifespan. The results showed that the irradiated curve was well matched to uniformly shifted nonirradiated curve for the cumulative mortality of all causes of death but not for the cumulative mortality of all solid tumors and prevalence of ovarian tumors as is. After adjusting lifetime mortalities, it was also well matched for all solid and ovarian tumors. The shifted days by irradiation were 71-116 days for all causes of death, 56-135 days for all solid tumors, and 41-140 days for ovarian tumors in the 1.9 Gy-irradiated group. The response was switched between irradiation at 35 and 105 days consistently for all the above indexes, supporting the hypothesis that radiation sensitivity differs between juvenile and adults. The shifted days of all causes of death showed a tendency of linear response to dose. This concept of shifting the age of death can be applied not only for all cause of death but also for mortality of all solid tumors after adjusting the magnitude. These findings contribute to the discussion on the application of the 'shifting age of death' concept to radiation protection.

The effects of transpositions of functional I retrotransposons depend on the conditions and dose of parental exposure.

PURPOSE: Transposable elements (TEs) cause destabilization of animal genomes. I retrotransposons of Drosophila melanogaster, as well as human LINE1 retrotransposons, are sources of intra- and interindividual diversity and responses to the action of internal and external factors. The aim of this study was to investigate the response to irradiation for the offspring of Drosophila melanogaster with the increased activity of inherited functional I elements. MATERIALS AND METHODS: The material used was dysgenic Drosophila females with active I retrotransposons obtained as a result of crossing irradiated/non-irradiated parents of a certain genotype. Non-dysgenic females (without functional I elements) were used as controls. The effects of different conditions (irradiation of both parents simultaneously or separately) and doses (1-100 Gy) of parental irradiation have been assessed by analyzing SF-sterility, DNA damage and lifespan. The presence of full-size I retrotransposons was determined by PCR analysis. RESULTS: The maternal exposure and exposure of both parents are efficient in contrast with paternal exposure. Irradiation of mothers reduces the reproductive potential and viability of their female offspring which undergo high activity of functional I retrotransposons. Though I retrotranspositions negatively affect the female gonads, irradiation of the paternal line can increase the lifespan of SF-sterile females. Radiation stress in the range of 1-100 Gy increases DNA fragmentation in both somatic and germ cells of the ovaries with high I-retrotransposition. CONCLUSIONS: These results allow for the specificity of the radiation-induced behavior of I retrotransposons and their role in survival under conditions of strong radiation stress.

COMBINED ANALYSIS OF CANCER INCIDENCE AND LIFESPAN IN MICE EXPOSED TO CHRONIC LOW DOSE RATE RADIATION.

The authors performed a combined analysis using the data obtained from continuous low dose rate irradiation experiments on mice conducted at the Institute for Environmental Sciences, namely, cancer incidence data and lifespan data. They estimated the length of cancer progression period, which is difficult to assess experimentally. The combined analysis showed that the mean cancer progression period is 173 d in the control group and 103 d in the irradiated group.

Accumulation of Glycogen and Upregulation of LEA-1 in C. elegans daf-2(e1370) Support Stress Resistance, Not Longevity.

DAF-16-dependent activation of a dauer-associated genetic program in the C. elegans insulin/IGF-1 daf-2(e1370) mutant leads to accumulation of large amounts of glycogen with concomitant upregulation of glycogen synthase, GSY-1. Glycogen is a major storage sugar in C. elegans that can be used as a short-term energy source for survival, and possibly as a reservoir for synthesis of a chemical chaperone trehalose. Its role in mitigating anoxia, osmotic and oxidative stress has been demonstrated previously. Furthermore, daf-2 mutants show increased abundance of the group 3 late embryogenesis abundant protein LEA-1, which has been found to act in synergy with trehalose to exert its protective role against desiccation and heat stress in vitro, and to be essential for desiccation tolerance in C. elegans dauer larvae. Here we demonstrate that accumulated glycogen is not required for daf-2 longevity, but specifically protects against hyperosmotic stress, and serves as an important energy source during starvation. Similarly, lea-1 does not act to support daf-2 longevity. Instead, it contributes to increased resistance of daf-2 mutants to heat, osmotic, and UV stress. In summary, our experimental results suggest that longevity and stress resistance can be uncoupled in IIS longevity mutants.

Increased Frequency of Copy Number Variations Revealed by Array Comparative Genomic Hybridization in the Offspring of Male Mice Exposed to Low Dose-Rate Ionizing Radiation.

There is very little information on the transgenerational or genetic effects of low dose-rate ionizing radiation. We report the detection of the transgenerational effects of chronic low dose-rate irradiation in mice, at the molecular level in the whole genome, using array comparative genomic hybridization technology. We observed that the number of the mice with de novo copy number variations (specifically, deletions) was significantly increased in the offspring of C57BL/6J male mice exposed to 20 mGy/day gamma-rays for 400 days (total dose: 8000 mGy), as compared to non-irradiated controls. We did not detect any difference in the size of the de novo deletions between the irradiated and the non-irradiated groups. An analysis of the life span of the offspring suggested a possibility that de novo copy-number variations may be associated with shorter life spans.

Effects of an electric field on sleep quality and life span mediated by ultraviolet (UV)-A/blue light photoreceptor CRYPTOCHROME in Drosophila.

Although electric fields (EF) exert beneficial effects on animal wound healing, differentiation, cancers and rheumatoid arthritis, the molecular mechanisms of these effects have remained unclear about a half century. Therefore, we aimed to elucidate the molecular mechanisms underlying EF effects in Drosophila melanogaster as a genetic animal model. Here we show that the sleep quality of wild type (WT) flies was improved by exposure to a 50-Hz (35 kV/m) constant electric field during the day time, but not during the night time. The effect was undetectable in cryptochrome mutant (cryb) flies. Exposure to a 50-Hz electric field under low nutrient conditions elongated the lifespan of male and female WT flies by ~ 18%, but not of several cry mutants and cry RNAi strains. Metabolome analysis indicated that the adenosine triphosphate (ATP) content was higher in intact WT than cry gene mutant strains exposed to an electric field. A putative magnetoreceptor protein and UV-A/blue light photoreceptor, CRYPTOCHROME (CRY) is involved in electric field (EF) receptors in animals. The present findings constitute hitherto unknown genetic evidence of a CRY-based system that is electric field sensitive in animals.

60Co-γ Radiation Alters Developmental Stages of Zeugodacus cucurbitae (Diptera: Tephritidae) Through Apoptosis Pathways Gene Expression.

Radiation is considered as a promising insect pest control strategy for minimizing postharvest yield losses. Among various techniques, irradiation is a method of choice as it induces lethal biochemical or molecular changes that cause a downstream cascade of abrupt physiological abnormalities at the cellular level. In this study, we evaluated the effect of 60Co-γ radiation on various developmental stages of Zeugodacus cucurbitae Coquillett and subsequent carry-over effects on the progeny. For this purpose, we treated eggs with 30- and 50-Gy radiation doses of 60Co-γ. We found that radiation significantly affected cellular antioxidants, insect morphology, and gene expression profiles. Our results indicate that in response to various doses of irradiation reactive oxygen species, catalase, peroxidase, and superoxide dismutase activities were increased along with a significant increase in the malondialdehyde (MDA) content. We observed higher mortality rates during the pupal stage of the insects that hatched from irradiated eggs (50 Gy). Furthermore, the life span of the adults was reduced in response to 50 Gy radiation. The negative effects carried over to the next generation were marked by significantly lower fecundity in the F1 generation of the irradiation groups as compared to control. The radiation induced morphological abnormalities at the pupal, as well as the adult, stages. Furthermore, variations in the gene expression following irradiation are discussed. Taken together, our results signify the utility of 60Co-γ radiation for fruit fly postharvest management.

Circadian autophagy drives iTRF-mediated longevity.

Time-restricted feeding (TRF) has recently gained interest as a potential anti-ageing treatment for organisms from Drosophila to humans1-5. TRF restricts food intake to specific hours of the day. Because TRF controls the timing of feeding, rather than nutrient or caloric content, TRF has been hypothesized to depend on circadian-regulated functions; the underlying molecular mechanisms of its effects remain unclear. Here, to exploit the genetic tools and well-characterized ageing markers of Drosophila, we developed an intermittent TRF (iTRF) dietary regimen that robustly extended fly lifespan and delayed the onset of ageing markers in the muscles and gut. We found that iTRF enhanced circadian-regulated transcription and that iTRF-mediated lifespan extension required both circadian regulation and autophagy, a conserved longevity pathway. Night-specific induction of autophagy was both necessary and sufficient to extend lifespan on an ad libitum diet and also prevented further iTRF-mediated lifespan extension. By contrast, day-specific induction of autophagy did not extend lifespan. Thus, these results identify circadian-regulated autophagy as a critical contributor to iTRF-mediated health benefits in Drosophila. Because both circadian regulation and autophagy are highly conserved processes in human ageing, this work highlights the possibility that behavioural or pharmaceutical interventions that stimulate circadian-regulated autophagy might provide people with similar health benefits, such as delayed ageing and lifespan extension.

Review of Biological Effects of Acute and Chronic Radiation Exposure on Caenorhabditis elegans.

Knowledge regarding complex radiation responses in biological systems can be enhanced using genetically amenable model organisms. In this manuscript, we reviewed the use of the nematode, Caenorhabditis elegans (C. elegans), as a model organism to investigate radiation's biological effects. Diverse types of experiments were conducted on C. elegans, using acute and chronic exposure to different ionizing radiation types, and to assess various biological responses. These responses differed based on the type and dose of radiation and the chemical substances in which the worms were grown or maintained. A few studies compared responses to various radiation types and doses as well as other environmental exposures. Therefore, this paper focused on the effect of irradiation on C. elegans, based on the intensity of the radiation dose and the length of exposure and ways to decrease the effects of ionizing radiation. Moreover, we discussed several studies showing that dietary components such as vitamin A, polyunsaturated fatty acids, and polyphenol-rich food source may promote the resistance of C. elegans to ionizing radiation and increase their life span after irradiation.

Irradiation-induced sterility in an egg parasitoid and possible implications for the use of biological control in insect eradication.

Classical biological control is a pest control tool involving the release of imported natural enemies. The Sterile Insect Technique (SIT) comprises releasing sexually sterile insects of a pest into the wild population for suppression or eradication. Both these approaches are environmentally friendly and their combination can result in a synergistic impact on pest populations and improve eradication. However, stringent regulation surrounding the introduction of biological control agents limits their use in eradication owing to the perceived risk of effects on non-target organisms. We investigated the irradiation biology of the egg parasitoid Trissolcus basalis to ascertain whether sterile parasitoids could mitigate the risk of potential sustained non-target impacts. Mated female T. basalis were gamma-irradiated at doses between 120 and 150 Gy and exposed to egg masses of their host Nezara viridula throughout their lifespans. This resulted in host mortality, despite a substantial reduction in developing parasitoid offspring, which followed a negative dose-response. There was no emergence of parasitoid offspring at 140 Gy and above. Irradiation did not affect oviposition behaviour but caused an increase in longevity. Consequently, sterile parasitoids could possibly alleviate concerns regarding the irreversibility of biological control release, which promotes further investigation of their potential role in eradication.

H3K4me2 regulates the recovery of protein biosynthesis and homeostasis following DNA damage.

DNA damage causes cancer, impairs development and accelerates aging. Transcription-blocking lesions and transcription-coupled repair defects lead to developmental failure and premature aging in humans. Following DNA repair, homeostatic processes need to be reestablished to ensure development and maintain tissue functionality. Here, we report that, in Caenorhabditis elegans, removal of the WRAD complex of the MLL/COMPASS H3K4 methyltransferase exacerbates developmental growth retardation and accelerates aging, while depletion of the H3K4 demethylases SPR-5 and AMX-1 promotes developmental growth and extends lifespan amid ultraviolet-induced damage. We demonstrate that DNA-damage-induced H3K4me2 is associated with the activation of genes regulating RNA transport, splicing, ribosome biogenesis and protein homeostasis and regulates the recovery of protein biosynthesis that ensures survival following genotoxic stress. Our study uncovers a role for H3K4me2 in coordinating the recovery of protein biosynthesis and homeostasis required for developmental growth and longevity after DNA damage.

Nobiletin Delays Aging and Enhances Stress Resistance of Caenorhabditis elegans.

Nobiletin (NOB), one of polymethoxyflavone existing in citrus fruits, has been reported to exhibit a multitude of biological properties, including anti-inflammation, anti-oxidation, anti-atherosclerosis, neuroprotection, and anti-tumor activity. However, little is known about the anti-aging effect of NOB. The objective of this study was to determine the effects of NOB on lifespan, stress resistance, and its associated gene expression. Using Caenorhabditis elegans, an in vivo nematode model, we found that NOB remarkably extended the lifespan; slowed aging-related functional declines; and increased the resistance against various stressors, including heat shock and ultraviolet radiation. Also, NOB reduced the effects of paraquat stressor on nematodes and scavenged reactive oxygen species (ROS). Furthermore, gene expression revealed that NOB upregulated the expression of sod-3, hsp-16.2, gst-4, skn-1, sek-1, and sir-2.1, which was suggested that anti-aging activity of NOB was mediated most likely by activation of the target genes of the transcription factors including dauer formation (DAF)-16, heat-shock transcription factor (HSF)-1, and skinhead (SKN)-1. In summary, NOB has potential application in extension of lifespan, and its associated healthspan and stress resistances.

Gamma-Irradiation Reduces Survivorship, Feeding Behavior, and Oviposition of Female Aedes aegypti.

Aedes aegypti is a prominent disease vector that is difficult to control through traditional integrated vector management due to its cryptic peridomestic immature-stage habitat and adult resting behavior, increasing resistance to pesticide formulations approved by the US Environmental Protection Agency, escalating deregistration of approved pesticides, and slow development of new effective chemical control measures. One novel method to control Ae. aegypti is the sterile insect technique (SIT) that leverages the mass release of irradiated (sterilized) males to overwhelm mate choice of natural populations of females. However, one potential liability of SIT is sex sorting errors prior to irradiation, resulting in accidental release of females. Our goal in this study was to test the extent to which irradiation affects female life-history parameters to assess the potential impacts of releasing irradiated females accidentally sorted with males. In this study, we determined that a radiation dose ≥30 Gy-a dose sufficient to sterilize males while preserving their mating competitiveness-may substantially impact longevity, bloodfeeding, oviposition, and egg hatch rate of female Ae. aegypti after being irradiated as pupae. These findings could reduce public concern for accidental release of females alongside irradiated males in an operational Ae. aegypti SIT control program.

Influence of green light illumination at night on biological characteristics of the oriental armyworm, Mythimna separata (Lepidoptera: Noctuidae).

The oriental armyworm, Mythimna separata is an important crop pest in eastern Asia. Nocturnal insects, including nocturnal moths, have phototactic behavior to an artificial light source. Phototactic behavior in insects is species-specific in response to different wavelengths of light sources. Our previous study showed that green (520 nm) light emitting diode (LED) light resulted in a significantly higher phototactic behavior in M. separata moths compared to the other wavelength LED lights. The goal of the present study is to investigate the influence of green light illumination on biological characteristics of different developmental stages in M. separata. Our results revealed that when different developmental stages of M. separata were exposed to the green light illumination in a dark period, several biological characteristics in all developmental stages except for egg stage were positively changed, but those of F1 generation M. separata which are next generation of the adults exposed to the green light did not significantly change compared with the control level. These findings suggest that green light illumination at night (or dark period) has a positive effect on the development and longevity of M. separata.

The role of DNA repair genes in radiation-induced adaptive response in Drosophila melanogaster is differential and conditional.

Studies in human and mammalian cell cultures have shown that induction of DNA repair mechanisms is required for the formation of stimulation effects of low doses of ionizing radiation, named "hormesis". Nevertheless, the role of cellular defense mechanisms in the formation of radiation-induced hormesis at the level of whole organism remains poorly studied. The aim of this work was to investigate the role of genes involved in different mechanisms and stages of DNA repair in radioadaptive response and radiation hormesis by lifespan parameters in Drosophila melanogaster. We studied genes that control DNA damage sensing (D-Gadd45, Hus1, mnk), nucleotide excision repair (mei-9, mus210, Mus209), base excision repair (Rrp1), DNA double-stranded break repair by homologous recombination (Brca2, spn-B, okr) and non-homologous end joining (Ku80, WRNexo), and the Mus309 gene that participates in several mechanisms of DNA repair. The obtained results demonstrate that in flies with mutations in studied genes radioadaptive response and radiation hormesis are absent or appear to a lesser extent than in wild-type Canton-S flies. Chronic exposure of γ-radiation in a low dose during pre-imaginal stages of development leads to an increase in expression of the studied DNA repair genes, which is maintained throughout the lifespan of flies. However, the activation of conditional ubiquitous overexpression of DNA repair genes does not induce resistance to an acute exposure to γ-radiation and reinforces its negative impact.

Deleterious effects of electron beam irradiation on development and reproduction of tomato/potato psyllids, Bactericera cockerelli.

The potato/tomato psyllid Bactericera cockerelli causes serious damage to several solanaceous crops by direct feeding and vectoring Candidatus Liberibacter solanacearum, a bacterial pathogen. Electron beam (eBeam) irradiation is an environmentally friendly, chemical-free alternative method that is increasing in use for disinfestation of insect pests. We hypothesize that this irradiation technology will have detrimental effects on potato psyllid and thus impede its disease vectoring. To this end, we explored the effects of eBeam treatment ranging from 50 to 500 Gy on survival, development and reproduction of this pest. Impact on psyllids was apparently dose-dependent. When irradiated at 350 Gy, eggs could not hatch, 1st instar nymphs failed to emerge, and although a small portion of irradiated 5th instar nymphs survived, the emerged adults were mostly deformed. Abnormality in eclosed adults suggests harmful effects of eBeam on metamorphosis. Reproduction was seriously impaired when female psyllids were exposed to eBeam at the 5th instar nymphal or young adult stage, presumably due to inability to form oocytes. In addition, reciprocal crosses between irradiated and untreated psyllids indicated that female psyllids were more radiosensitive than males to eBeam. Taken together, these findings indicate that eBeam negatively impacted potato psyllid development and reproduction, which would inevitably compromise its disease transmission capacity. A dose of 350 Gy can be considered as a reference dose for effective control of potato psyllids.

Automated lifespan determination across Caenorhabditis strains and species reveals assay-specific effects of chemical interventions.

The goal of the Caenorhabditis Intervention Testing Program is to identify robust and reproducible pro-longevity interventions that are efficacious across genetically diverse cohorts in the Caenorhabditis genus. The project design features multiple experimental replicates collected by three different laboratories. Our initial effort employed fully manual survival assays. With an interest in increasing throughput, we explored automation with flatbed scanner-based Automated Lifespan Machines (ALMs). We used ALMs to measure survivorship of 22 Caenorhabditis strains spanning three species. Additionally, we tested five chemicals that we previously found extended lifespan in manual assays. Overall, we found similar sources of variation among trials for the ALM and our previous manual assays, verifying reproducibility of outcome. Survival assessment was generally consistent between the manual and the ALM assays, although we did observe radically contrasting results for certain compound interventions. We found that particular lifespan outcome differences could be attributed to protocol elements such as enhanced light exposure of specific compounds in the ALM, underscoring that differences in technical details can influence outcomes and therefore interpretation. Overall, we demonstrate that the ALMs effectively reproduce a large, conventionally scored dataset from a diverse test set, independently validating ALMs as a robust and reproducible approach toward aging-intervention screening.

Rotating magnetic field delays human umbilical vein endothelial cell aging and prolongs the lifespan of Caenorhabditis elegans.

The biological effects of magnetic fields are a research hotspot in the field of biomedical engineering. In this study, we further investigated the effects of a rotating magnetic field (RMF; 0.2 T, 4 Hz) on the growth of human umbilical vein endothelial cells (HUVECs) and Caenorhabditis elegans. The results showed that RMF exposure prolonged the lifespan of C. elegans and slowed the aging of HUVECs. RMF treatment of HUVECs showed that activation of adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK) was associated with decreased mitochondrial membrane potential (MMP) due to increased intracellular Ca2+ concentrations induced by endoplasmic reticulum stress in anti-aging mechanisms. RMF also promoted the health status of C. elegans by improving activity, reducing age-related pigment accumulation, delaying Aß-induced paralysis and increasing resistance to heat and oxidative stress. The prolonged lifespan of C. elegans was associated with decreased levels of daf-16 which related to the insulin/insulin-like growth factor signaling pathway (IIS) activity and reactive oxygen species (ROS), whereas the heat shock transcription factor-1 (hsf-1) pathway was not involved. Moreover, the level of autophagy was increased after RMF treatment. These findings expand our understanding of the potential mechanisms by which RMF treatment prolongs lifespan.

Complex and interactive effects of ocean acidification and warming on the life span of a marine trematode parasite.

Human activities have caused an increase in atmospheric CO2 over the last 250 years, leading to unprecedented rates of change in seawater pH and temperature. These global scale processes are now commonly referred to as ocean acidification and warming, and have the potential to substantially alter the physiological performance of many marine organisms. It is vital that the effects of ocean acidification and warming on marine organisms are explored so that we can predict how marine communities may change in future. In particular, the effect of ocean acidification and warming on host-parasite dynamics is poorly understood, despite the ecological importance of these relationships. Here, we explore the response of one himasthlid trematode, Himasthla sp., an abundant and broadly distributed species of marine parasite, to combinations of elevated temperature and pCO2 that represent physiological extremes, pre-industrial conditions, and end of century predictions. Specifically, we quantified the life span of the free-living cercarial stage under elevated temperature and pCO2, focussing our research on functional life span (the time cercariae spend actively swimming) and absolute life span (the period before death). We found that the effects of temperature and pCO2 were complex and interactive. Overall, increased temperature negatively affected functional and absolute life span, e.g. across all pCO2 treatments the average time to 50% cessation of active swimming was approximately 8 h at 5 °C, 6 h at 15 °C, 4 h at 25 °C, and 2 h at 40 °C. The effect of pCO2, which significantly affected absolute life span, was highly variable across temperature treatments. These results strongly suggest that ocean acidification and warming may alter the transmission success of trematode cercariae, and potentially reduce the input of cercariae to marine zooplankton. Either outcome could substantially alter the community structure of coastal marine systems.

Life-Shortening Effect of Chronic Low-Dose-Rate Irradiation in Calorie-Restricted Mice.

Calorie restriction is known to influence several physiological processes and to alleviate the late effects of radiation exposure such as neoplasm induction and life shortening. However, earlier related studies were limited to acute radiation exposure. Therefore, in this study we examined the influence of chronic low-dose-rate irradiation on lifespan. Young male B6C3F1/Jcl mice were divided randomly into two groups, which were fed either a low-calorie (65 kcal/ week) or high-calorie (95 kcal/week) diet. The latter is comparable to ad libitum feeding. The animals in the irradiated group were continuously exposed to gamma rays for 400 days at 20 mGy/day, resulting in a total dose of 8 Gy. Exposure and calorie restriction were initiated at 8 weeks of age and the diets were maintained for life. The life-shortening effects from chronic whole-body irradiation were compared between the groups. Body weights were reduced in calorie-restricted mice irrespective of radiation treatment. Radiation induced a shortened median lifespan in both groups, but to a greater extent in the calorie-restricted mice. These results suggest that calorie restriction may sensitize mice to chronic low-dose-rate radiation exposure to produce a life-shortening effect rather than alleviating the effects of radiation.