A comprehensive approach to how hospital effluents lead to oxidative stress and shift the gene expression in target organs of Danio rerio

Hospital effluents represent a threat to the environment owing to the content of toxic substances capable of altering the structure and function of ecosystems. Despite the available information about the impact of hospital effluents on aquatic organisms, the molecular mechanism underlying this process has received little or no attention. The present study aimed to evaluate the oxidative stress and gene expression induced by different proportions (2 %, 2.5 %, 3 % and 3.5 %) of hospital effluent treated by hospital wastewater treatment plant (HWWTP) in liver, gut, and gills of Danio rerio at different exposure times. Significant increases in the levels of protein carbonylation content (PCC), hydroperoxides content (HPC), lipoperoxidation level (LPX) and superoxide dismutase (SOD) and catalase (CAT) activity were observed in most of the organs evaluated at the four proportions tested with respect to the control group (p < 0.05). It was found that at longer exposure times there is a lower response in SOD activity, suggesting catalytic depletion due to the oxidative environment at the intracellular level. The lack of complementarity between SOD and mRNA activity patterns indicates that the activity itself is subordinated to post-transcriptional processes. Upregulation of transcripts related to antioxidant processes (sod, cat, nrf2), detoxification (cyp1a1) and apoptosis (bax, casp6, and casp9) was observed in response to oxidative imbalance. On the other hand, the metataxonomic approach allowed the characterization of pathogenic bacterial genera such as Legionella, Pseudomonas, Clostridium XI, Parachlamydia and

Automated summary

Hospital effluents containing toxic substances can cause oxidative stress and changes in gene expression in aquatic organisms. This study evaluated the effects of different proportions of hospital effluent treated by a wastewater treatment plant on the liver, gut, and gills of Danio rerio. Significant increases in oxidative stress markers and antioxidant enzyme activity were observed, and gene expression related to antioxidant processes, detoxification, and apoptosis was upregulated. Additionally, pathogenic bacterial genera were identified using a metataxonomic approach.