COMPARATIVE TOXICITY AND IMMUNE DYSFUNCTION IN AFRICAN CATFISH, CLARIAS GARIEPINUS (BURCHELL 1822) EXPOSED TO BISPHENOL A AND ITS ANALOGUES

Abstract

Bisphenol A (BPA), has been frequently identified in aquatic environments and biota. It is an anthropogenic industrial chemical, which is widely used as a monomer or additive in the production of polycarbonates, epoxy resins, and other polymeric materials. The public concern and governmental regulations on BPA stimulated the development and production of alternative substances to replace BPA in a myriad of applications. Over the past two decades, more than 20 new structural analogues of BPA have been manufactured for different purposes. However, not much is known about their toxic effects on aquatic organisms. This study is therefore aimed at determining the comparative toxicities and immune dysfunction in the African catfish, C. gariepinus exposed to BPA and its two analogues (Bisphenol AP (BPAP) and Bisphenol P (BPP). Juveniles of African catfish were exposed to sublethal concentrations (70 and 140 μg/L) of Bisphenols A, AP, and P for 7, 14, or 21 days after which various endpoints which are indicative of cytotoxicity (lactate dehydrogenase (LDH) activity and percentage fragmented DNA), oxidative stress (levels of reduced glutathione (GSH) and thiobarbituric acid reactive substances (TBARS), and activities of catalase (CAT) and superoxide dismutase (SOD), haematological parameters such as red blood cells count, haematocrits, white blood cells count, and differential white blood cells count and innate immune parameters (levels of nitric oxide, respiratory burst and phenoloxidase activity) were determined in the liver homogenates or blood plasma. The exposure to bisphenol A and its analogues caused significant cytotoxic effects evidenced by significant increased activity of LDH and percentage fragmented DNA in comparison to the control. Similarly, exposure to these bisphenols resulted in significant redox imbalance (elevated levels of TBARS, reduced levels of GSH, and increased activities of CAT and SOD) and altered the haemato-immune parameters of the fish (decreased RBC, haematocrits and lymphocytes, increased WBCs and neutrophils, increased levels of nitric oxide, increased respiratory burst, and increased activity of phenoloxidase). The toxic effects elicited by the bisphenols was both concentration- and duration-dependent. Generally, BPA exerted more toxic effects on the fish, followed by BPAP while BPP exerted the least toxic effect effects to C. gariepinus. Summarily, the findings indicated that BPA and its two analogues studied in the research are capable of causing cytotoxicity, oxidative stress and immune dysfunction in C. gariepinus. It is, therefore, concluded that the analogues are not entirely safe to aquatic organisms as widely assumed.