In humans and animals, steroid hormones are naturally occurring compounds, involved in development, reproduction and in maintaining hormonal balance. Apart from the naturally present steroid hormones, different hormonal therapies also include synthetic analogs. Due to increased use in pharmaceutical and animal industry, the occurrence of steroid hormones in the environment is inevitable. On account of bioaccumulation, humans are re-exposed to steroid hormones mostly through seafood consumption. Moreover, steroid hormones in the environment are subjected to transformation and degradation processes. The resulting transformation or degradation products can in certain cases become more (eco)toxic or have higher endocrine potential as the parent compound; however, very little research has been conducted in this regard. This prompted us to explore this field more thoroughly in this Master´s thesis. The potential endocrine activity, the environmental impact and the acute ecotoxicity of nine steroid hormones from the estrogen, androgen, progestin and glucocorticoid families and their transformation products were determined by utilizing in silico tools, including Endocrine Disruptome and VegaNIC. Based on the results obtained, the steroid hormones were classified as the most and the least (eco)toxic. The endocrine toxicity of compounds was evaluated on their probability to bind to 13 nuclear receptors. The results obtained with Endocrine Disruptome indicate that steroid hormones bind mainly to the following five nuclear receptors: AR, AR an, ER α, ER ß in ER ß an. In addition, the calculated clogP values, the bioconcentration factor (BCF) and LC50 were included in the toxicity profile construction. The higher the value of clogP, the greater the possibility for the compound accumulation in the fatty tissue of organisms, their bioaccumulation in the environment (in the organic substance of the sediment) and their potential (eco)toxic impact on the organisms. Furthermore, high BCF values are yet another indicator of bioaccumulation potential. In the final toxicity screening, the calculated LC50 values were included to predict the acute toxicity of compounds towards aquatic organisms. The lower the LC50 values of compounds, the higher their acute toxicity and the greater the hazardous effects on aquatic organisms. Some in silico predictions differ from the experimental results. Nonetheless, the final toxicity profiling was performed to elucidate compounds with the highest and the lowest (eco)toxicity. Progesterone (including its degradation product PR-RP4) was predicted to be highly (eco)toxic and to have the highest potential to act as an endocrine disruptor. On the other hand, glucocorticoids display the lowest (eco)toxic effect and the lowest endocrine potential, in particular prednisolone and its degradation product PRED-RP3. According to in silico BCF predictions pertaining to the selected steroid hormones researched and their degradation products (except EE2-RP3), the compounds have been classified as non-bioaccumulative. It should be noted that certain degradation products have been predicted with higher endocrine potential compared to those of their parent compounds.
This emphasizes the need for further research in the field and, at the same time, guides the prioritization of ensuing in vitro and in vivo studies.
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