Periodic Reporting for period 1 - NARESICA (Mechanisms linking stress and ageing in two avian species exhibiting contrasted natural resistance to stress (NAtural REsistance to Stress-Induced Cellular Ageing))
Periodo di rendicontazione: 2021-09-01 al 2023-08-31
The evolution of our modern society is increasingly exposing animals and human to stressful stimuli being linked for instance to the increasing urbanization and human-density, but also to pollution. Previous research has identified stress exposure as a key factor influencing health state and ageing rate. The overall aim of the proposed project is to investigate the precise mechanisms linking stress exposure to accelerated cellular ageing (using telomere length as a biomarker of ageing), and to identify potential mechanisms allowing some species or individuals to better prevent stress-induced ageing than others. To this aim NARESICA used two avian species (Japanese quail and king penguin) to investigate (1) if chronic stress affects telomere shortening differently between species or individuals exhibiting contrasted stress resistance, (2) if glucocorticoid ‘stress’ hormones are directly responsible of the stress-induced alterations in telomere dynamics and (3) by which mechanisms (i.e. alterations of mitochondrial function, oxidative stress and DNA damage, impaired mTOR cellular signaling or telomere maintenance) stress exposure is accelerating telomere shortening.
The project has been terminated before its planned end date (17 months instead of 24) since the recipient obtained a permanent researcher position at the CNRS (France). Since there was no option being administratively possible to postpone the start date further at the CNRS and no option to conduct both tasks as part-time due to French and EU regulation, this leaves NARESICA project in an unfinished state (i.e. shortage of funding for laboratory analyses on collected samples).
NARESICA employed experimental approaches manipulating stress exposure and glucocorticoid hormones in captive Japanese quail and wild king penguins and measured the resulting impact on growth rate, telomere shortening and its potential cellular drivers (mitochondrial function, oxidative stress, mTOR cellular signaling).
In wild king penguins, we used subcutaneous implants of glucocorticoid hormone (or placebo) in chicks and measured the impact on their growth, behavior, physiology and survival over ca. 150 days. While our experimental manipulation was successful in raising circulating glucocorticoid levels, we did not detect any significant deleterious impact on growth, survival or physiology, including telomere length, a biomarker of ageing. Specifically, chicks implanted with glucocorticoid grew slightly faster than placebo ones, experienced less oxidative damage to DNA and had preserved telomere length, partly owing to the up-regulation of genes involved in telomere maintenance. These results have been presented at the CEPA meeting in Montpellier (2021) and at the Society for Experimental Biology annual meeting (2022). The manuscript is close to submission, waiting for available funding to re-analyze part of the samples for telomere length using an alternative technique following reviewer’s comments.
In captive Japanese quails, the initial plans of NARESICA have been up-graded thanks to the collaboration of INRAE (Tours), which provided individuals coming from artificial selection lines that have been selected for low or high sensitivity to stress based on behavioral response. Individuals from both lines were splitted in three experimental groups: 1. Control, 2. Treated with glucocorticoid hormone through drinking water, 3. Submitted to a chronic stress protocol involving 5 stressor types rotated every weekday. We measured body mass growth, behavior and multiple physiological indicators during the 50 days of treatment. Lines differed markedly in their response to the experimental treatments, with the sensitive line exhibiting a clear drop in body mass growth in response to glucocorticoid supplementation, and a milder reduction in response to chronic stress. In-vitro work on freshly isolated mitochondria from heart demonstrated that the sensitive line showed an improved mitochondrial efficiency in response to chronic stress and glucocorticoid treatments, while this was not the case for the less sensitive line. This could theoretically lead to increased ROS production, oxidative stress and telomere shortening. Laboratory measurements of telomere length, gene expression, oxidative stress and circulating glucocorticoids are ongoing as part of a MSc internship. The preliminary results have been presented at the University of Glasgow in January 2023, for an invited talk in the group of Profs Pat Monaghan and Neil Metcalfe. One manuscript on the effects of the line*treatment interaction on body mass and mitochondrial bioenergetics is in preparation, and another one will be once laboratory results will be obtained for telomeres, gene expression and oxidative stress.
NARESICA employed experimental approaches manipulating stress exposure and glucocorticoid hormones in captive Japanese quail and wild king penguins and measured the resulting impact on growth rate, telomere shortening and its potential cellular drivers (mitochondrial function, oxidative stress, mTOR cellular signaling).
In wild king penguins, we used subcutaneous implants of glucocorticoid hormone (or placebo) in chicks and measured the impact on their growth, behavior, physiology and survival over ca. 150 days. While our experimental manipulation was successful in raising circulating glucocorticoid levels, we did not detect any significant deleterious impact on growth, survival or physiology, including telomere length, a biomarker of ageing. Specifically, chicks implanted with glucocorticoid grew slightly faster than placebo ones, experienced less oxidative damage to DNA and had preserved telomere length, partly owing to the up-regulation of genes involved in telomere maintenance. These results have been presented at the CEPA meeting in Montpellier (2021) and at the Society for Experimental Biology annual meeting (2022). The manuscript is close to submission, waiting for available funding to re-analyze part of the samples for telomere length using an alternative technique following reviewer’s comments.
In captive Japanese quails, the initial plans of NARESICA have been up-graded thanks to the collaboration of INRAE (Tours), which provided individuals coming from artificial selection lines that have been selected for low or high sensitivity to stress based on behavioral response. Individuals from both lines were splitted in three experimental groups: 1. Control, 2. Treated with glucocorticoid hormone through drinking water, 3. Submitted to a chronic stress protocol involving 5 stressor types rotated every weekday. We measured body mass growth, behavior and multiple physiological indicators during the 50 days of treatment. Lines differed markedly in their response to the experimental treatments, with the sensitive line exhibiting a clear drop in body mass growth in response to glucocorticoid supplementation, and a milder reduction in response to chronic stress. In-vitro work on freshly isolated mitochondria from heart demonstrated that the sensitive line showed an improved mitochondrial efficiency in response to chronic stress and glucocorticoid treatments, while this was not the case for the less sensitive line. This could theoretically lead to increased ROS production, oxidative stress and telomere shortening. Laboratory measurements of telomere length, gene expression, oxidative stress and circulating glucocorticoids are ongoing as part of a MSc internship. The preliminary results have been presented at the University of Glasgow in January 2023, for an invited talk in the group of Profs Pat Monaghan and Neil Metcalfe. One manuscript on the effects of the line*treatment interaction on body mass and mitochondrial bioenergetics is in preparation, and another one will be once laboratory results will be obtained for telomeres, gene expression and oxidative stress.
By using innovative experimental approaches, NARESICA shows that variation in stress sensitivity, both at the intra and inter-specific level, is a key factor influencing how stress or glucocorticoid exposure is affecting cellular ageing rate. The outputs of the project have been hindered by its early termination and the associated lack of funding for conducting part of the laboratory analyses on collected samples. Yet, NARESICA paves the way towards the identification of cellular mechanisms underlying the inter-individual or inter-species differences in the sensitivity to stress-induced ageing. The identification of such mechanisms should enable targeting those pathways to prevent stress-induced ageing in future projects.