Toxicological evaluation of combined exposure to bisphenol A and diethyl hexyl phthalate and investigation of possible protective effect of carnosic acid

DEHP and BPA, the main components of plastic products, are the important endocrine-disrupting chemicals which can mimic or disrupt the actions of estrogen by inhibiting normal functions of the body. Because of this widespread usage of DEHP and BPA, not only alone exposure but also combined exposure is considered as an important issue. Nowadays, researches are increased related to the effects on neurological functions instead of endocrine disrupting effects. This study aims to investigate combined exposure of DEHP and BPA and the possible protective effect of carnosic acid as an antioxidant. In this study, C-57BL/6 mice aged 16 weeks (25 g to 35 g of body weight) were randomly divided into 15 groups (6 mice/group) as BPA (16, 5, 1.6 mg/kg), DEHP (16, 5, 1.6 mg/kg), 20 mg/kg CA, BPA+DEHP (16, 5, 1.6 mg/kg) and BPA+DEHP+20 mg/kg CA (16, 5, 1.6 mg/kg). Chemical exposure was assessed for subacute toxicity and application was made for 28 days by oral gavage. The animals were sacrificed 24 h after the last administration. Before and after drug administration passive avoidance and accelerated rotarod tests were conducted to examine the effects on behavior. And also, level of MDA, GSH-Px, CAT and SOD activities in the cortex were analyzed. Then Bcl-2, Bax, BACE and p-tau levels in the cortex were detected by western blot. There was not observed any change in passive avoidance and rotarod tests. The SOD activity of all dosage of BPA+DEHP and BPA+DEHP+20CA significantly decreased according to control. In CAT activity, while combined administration of 5 and 16 BPA+DEHP significantly increased as compared with control, combined administration of 1.6 and 16 BPA+DEHP+20CA significantly decreased as compared with 16 BPA and 1.6 DEHP. The same changes were observed in GSH-Px activity levels of BPA+DEHP+20CA and BPA+DEHP groups like CAT activity. Although there were no significant changes observed in BPA and DEHP groups, combined administration of BPA+DEHP caused a significant decrease in MDA levels according to control. While Bcl-2 and Bax levels were significantly increased at combined administration of BPA+DEHP, addition of CA to BPA+DEHP combination caused significantly decrease as compared to BPA+DEHP administration. Although the level of BACE enzyme expression significantly increased in combined administration of BPA+DEHP, BACE levels were significantly decreased in the combined administration of BPA+DEHP+20CA. However, there was an opposite effect between dose and response. And also, in our studies, no relevance was observed in the caspase-3, APP and amyloid beta tests. While p-tau levels of BPA+DEHP groups were significantly lower than other groups, p-tau levels of BPA+DEHP+20CA groups significantly increased compared to combined administration of BPA+DEHP groups. In conclusion, when BPA and DEHP used together, they damaged the cortex in terms of neurodegeneration by oxidative stress and also carnosic acid has been shown protection by radical scavenging properties.