Age and sensitivity to oxygen in the flour beetle, Tribolium confusum

Low-dose ionizing radiation as a hormetin: experimental observations and therapeutic perspective for age-related disorders

Hormesis is any kind of biphasic dose-response when low doses of some agents are beneficial while higher doses are detrimental. Radiation hormesis is the most thoroughly investigated among all hormesis-like phenomena, in particular in biogerontology. In this review, we aimed to summarize research evidence supporting hormesis through exposure to low-dose ionizing radiation (LDIR). Radiation-induced longevity hormesis has been repeatedly reported in invertebrate models such as C. elegans, Drosophila and flour beetles and in vertebrate models including guinea pigs, mice and rabbits. On the contrary, suppressing natural background radiation was repeatedly found to cause detrimental effects in protozoa, bacteria and flies. We also discussed here the possibility of clinical use of LDIR, predominantly for age-related disorders, e.g., Alzheimer's disease, for which no remedies are available. There is accumulating evidence that LDIR, such as those commonly used in X-ray imaging including computer tomography, might act as a hormetin. Of course, caution should be exercised when introducing new medical practices, and LDIR therapy is no exception. However, due to the low average residual life expectancy in old patients, the short-term benefits of such interventions (e.g., potential therapeutic effect against dementia) may outweigh their hypothetical delayed risks (e.g., cancer). We argue here that assessment and clinical trials of LDIR treatments should be given priority bearing in mind the enormous economic, social and ethical implications of potentially-treatable, age-related disorders.

Longevity in the red flour beetle Tribolium castaneum is enhanced by broccoli and depends on nrf-2, jnk-1 and foxo-1 homologous genes

Diet is generally believed to affect the aging process. The effects of complex foods on life span can be investigated using simple models that produce rapid results and allow the identification of food-gene interactions. Here, we show that 1 % lyophilized broccoli, added to flour as a dietary source, significantly increases the life span of the red flour beetle (Tribolium castaneum) under physiological conditions (32 °C) and under heat stress (42 °C). The beneficial effects of broccoli could also be reproduced by supplementing flour with the isothiocyanate sulforaphane at concentrations found in the broccoli-supplemented diet. We identified stress-resistant genes responsible for these effects on longevity by microinjecting pupae with double-stranded RNA to induce RNA interference (RNAi). The knockdown of transcripts encoding homologs of Nrf-2, Jnk-1 and Foxo-1 reduced the life span of beetles and abrogated the beneficial effects of broccoli, whereas the knockdown of Sirt-1 and Sirt-3 had no impact in either scenario. In conclusion, T. castaneum is a suitable model organism to investigate food-gene interactions that affect stress resistance and longevity, and RNAi can be used to identify functionally relevant genes. As a proof of principle, we have shown here that broccoli increases the longevity of beetles and mediates its effect through signaling pathways that include key stress-resistant factors such as Nrf-2, Jnk-1 and Foxo-1.

Ageing and parental age effects in Tribolium (review)

The experimental suitability of the flour beetles of the genus Tribolium has attracted ecologists, nutritionists, radiation biologists and geneticists for decades. I have, recently, evaluated their importance to gerontologists. This paper deals with age-related changes and parental age effects which were not included in a previous review. I have, first, discussed the known aspects of age-related changes in morphological, physiological, biochemical, behavioural and pathological parameters as well as on radiation-sensitivity and susceptibility to insecticides. Pre-adult biochemical and physiological changes have also been included, because of the important inter-relationship between growth and ageing. This is followed by an evaluation of parental age effects on physiological and genetic characteristics and of proposed areas for possible research.

Radiation-enhanced resistance to oxygen: a possible relationship to radiation-enhanced longevity

Shortly after gamma-irradiation, flour beetles (Oklahoma strain of Tribolium confusum) exhibited a decline in resistance to oxygen toxicity. Beginning about two weeks after irradiation, however, the LD50 exposure time in pure oxygen was much greater than that of nonirradiated beetles, and this enhanced resistance persisted for about 6 months. The magnitude of the enhancement was a function of dose, and decreased with increasing age at irradiation. These characteristics of a radiation-enhanced resistance to a stress are comparable to the characteristics of radiation-enhanced longevity in Tribolium, in that after irradiation mortality rate is less than that of controls for about 6 months, the magnitude of the effect is dose-dependent, and older beetles are refractory to the effect. Irradiation under anoxic conditions reduced the development of oxygen resistance to the same degree that it reduced acute radiation lethality, suggesting that the amount of biological damage is the critical factor. These results are discussed in terms of the "induced repair" theory of radiation-enhanced longevity of insects.