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Electron microscopic detection of morphological changes in hypothalamic mitochondria in response to endocrine disruptors As, Zea and BPA
Valkovszki Vivien - year 6
University of Veterinary Medicine Budapest, Department of Physiology and Biochemistry
Supervisors: Dr. Dávid Sándor Kiss, Dr. Attila Zsarnovszky

Abstract:

The goal of our research was to investigate morphological changes at the cellular level caused by endocrine disruptors (ED) in an in vivo mouse model. EDs are able to modify hormonal signalling pathways, even in very small doses, which determine processes related to development, reproduction, energy balance and stress tolerance, thus influencing homeostasis at the cellular level. Previous research has already demonstrated the direct cellular effects of bisphenol-A, zearalenone and arsenic, such as the induction of oxidative stress, mitochondrial DNA damage, apoptosis, membrane potential reduction. However, it is still unclear whether these EDs can also in acute form induce mitochondrial damage, and in particular whether this manifests at the ultrastructural level, in the neurons of the hypothalamic melanocortin system that plays an important role in the regulation of energy balance and homeostasis, and that is directly exposed to EDs due to the special ‘leakage’ of the blood-brain barrier at this location.

In our experiment, the above-mentioned EDs were administered by single intraperitoneal injection to juvenile mice of both sexes, in three different doses (40 µg, 5 mg and 10 mg). Sampling took place 6 hours after the treatment, and the hypothalamus was isolated. AgRP and POMC neurons, characteristic cells of the melanocortin system, were labelled by immunohistochemistry and examined by transmission electron microscopy. The examined morphological parameters were the following: average area of mitochondria (nm2), average number (pc), crista ratio compared to the area of mitochondria (%), number of mitochondria-endoplasmic reticulum connections (pc), average distance between them (nm), and the occurrence of closely contacting or fused mitochondria-endoplasmic reticulum.

Considering the results, the effect of ED on mitochondria can be deduced on all parameters examined. There is an increase in the average area of mitochondria and in the proportion of cristae, there is a decrease in the number of mitochondria and in the number of connections with the endoplasmic reticulum, while also an increase in the distance between the two organelles. Differences in the AgRP and POMC neuron groups, as well as the individual active substances and their different doses, were also presented.

The ultrastructural changes caused by EDs are crucial in their mechanism of action. Based on our results, we can state that in order to unveil the ED’s effects, processes at the cellular level, and particularly mitochondrial morpho-function is of utmost importance considering its fundamental impact on the energy balance at the cellular level, protein metabolism, and the proper signal transmission between neurons, through all of these it affects the whole organism.



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