Single and Combined Effects of Bisphenol A Exposure and Schistosoma mansoni Infection: Biochemical and Histological Implications on Biomphalaria alexandrina Snails

Plastic production is a huge industry all over the world. However, their release into the environment can cause unexpected impacts on the biological levels of the freshwater systems. Thus, the present study aimed to investigate the impact of bisphenol A (BPA) exposure on oxidative stress markers, sex hormones, neurotransmitters, and histology of the digestive gland in the snail, Biomphalaria alexandrina (infected and non-infected with Schistosoma mansoni). Snails were exposed to 0.1 and 1 mg L^-1 BPA for up to 4 weeks. After a sequential period of exposure (24h, 2 and 4 weeks), oxidative stress markers such as catalase (CAT), lipid peroxidase (MDA), and sex hormones (testosterone and 17β-estradiol) were determined in the ovotestis of the snails. Neurotransmitters (dopamine; DA and serotonin; 5-HT) were measured in the central nervous system (CNS) of the snails. In addition, a histological examination was done in the digestive gland after 2 and 4 weeks of infection/exposure. CAT activity, sex hormones, and neurotransmitter concentrations were significantly decreased in both exposed and infected-exposed groups, compared to the control and infected groups at all-time points. Nevertheless, MDA was markedly increased after exposure/infection at all time intervals. Histological symptoms such as the appearance of fat droplets, fibrous tissues, and vacuolization were observed in the digestive gland of exposed and/or infected-exposed snails. The present data demonstrated the risks of sublethal exposure to BPA on the snails, B. alexandrina as a biomonitor of freshwater contamination. In conclusion, the implications of BPA as a chemical stressor dominated the biological effect of infection alone or in combination.