RESUMO
Early Life Stress (ELS) can critically influence brain development and future stress responses and thus represents an important risk factor for mental health and disease. Neuropeptide Y (NPY) is discussed to be a key mediator of resilient vs. vulnerable adaptations and specifically, the NPY-Y2 receptor (Y2R) may be involved in the pathophysiology of depression due to its negative regulation of NPY-release. The present study addressed the hypotheses that ELS and adult stress (AS) affect the expression of hippocampal Y2R and that exposure to ELS induces an epigenetically mediated programming effect towards a consecutive stress exposure in adulthood. The specific aims were to investigate if (i) ELS or AS as single stressors induce changes in Y2 receptor gene expression in the hippocampus, (ii) the predicted Y2R changes are epigenetically mediated via promoter-specific DNA-methylation, (iii) the ELS-induced epigenetic changes exert a programming effect on Y2R gene expression changes in response to AS, and finally (iv) if the predicted alterations are sex-specific. Animals were assigned to the following experimental groups: (1) non-stressed controls (CON), (2) only ELS exposure (ELS), (3) only adult stress exposure (CON+AS), and (4) exposure to ELS followed by AS (ELS+AS). Using repeated maternal separation in mice as an ELS and swim stress as an AS we found that both stressors affected Y2R gene expression in the hippocampus of male mice but not in females. Specifically, upregulated expression was found in the CON+AS group. In addition, exposure to both stressors ELS+AS significantly reduced Y2R gene expression when compared to CON+AS. The changes in Y2R expression were paralleled by altered DNA-methylation patterns at the Y2R promoter, specifically, a decrease in mean DNA-methylation in the CON+AS males compared to the non-AS exposed groups and an increase in the ELS+AS males compared to the CON+AS males. Also, a strong negative correlation of mean DNA-methylation with Y2R expression was found. Detailed CpG-site-specific analysis of DNA-methylation revealed that ELS induced increased DNA-methylation only at specific CpG-sites within the Y2R promoter. It is tempting to speculate that these ELS-induced CpG-site-specific changes represent a "buffering" programming effect against elevations of Y2R expression induced by AS.
RESUMO
BACKGROUND: There is no study of whether the dysplastic changes in the ovarian surface epithelium of X-ray-exposed rats during hysterosalpingography (HSG) decrease or not with the use of Lipiodol and melatonin given both intraperitoneally (i.p.) and into the suspensorium ovarii. OBJECTIVES: We investigated the restorative effects of melatonin and Lipiodol administration during the HSG procedure on the dysplastic changes in the ovarian surface epithelium of X-ray-exposed rats. MATERIAL AND METHODS: A total of 50 Wistar rats with regular estrous cycles were randomly divided into 5 groups. Group 1 was the control group. In other groups, X-ray was applied (group 2), 0.1 mL Lipiodol was applied to each uterine horn (group 3), 20 mg/kg intraperitoneal melatonin application was followed by 0.1 mL Lipiodol administration to each uterine horn after 15 min (group 4), and 20 mg/kg melatonin was administered to the ligamentum suspensorium ovarii, followed by 0.1 mL Lipiodol application to each uterine horn after 15 min (group 5). The rats in groups 2-5 were exposed to whole body radiation 3 times. After 3 h, the abdomens of all rats were reopened and left oophorectomy was performed. RESULTS: The presence of nucleoli and mitosis values were found similar among the groups. All other parameters were significantly higher in group 2 compared to other groups, except for the presence of nucleoli and mitosis values (p < 0.05). The presence of hyperchromasia and the total score were found to be the highest in group 2, followed by group 3, when compared to other groups (p < 0.05). It was detected that the detrimental effects of X-ray exposure diminished with Lipiodol use, and were further reduced by the use of melatonin in combination. CONCLUSIONS: We suggest that the use of melatonin and Lipiodol during HSG may prevent the carcinogenic changes exerted by radiation on the ovarian surface epithelium.
