Effect of polystyrene microplastics on the antioxidant system and immune response in GIFT (Oreochromis niloticus)

<title>Abstract</title> Recent investigations have reported large number of microplastics (MPs) in the freshwater environment, which may have adverse effects on growth and development of freshwater organisms. The present study was conducted to investigate the effects of chronic sub-lethal dose of MPs on the oxidative status (ROS, SOD) and immune response (IL-1ß, TNF-α) of the genetically improved farmed tilapia (GIFT). Juveniles of GIFT (5.1 ± 0.2 g) were exposed to concentrations of 0 (group A), 75 nm (group B), 7.5 µm (group C), 750 µm (group D), 75 nm + 7.5 µm + 750 µm (group E) and 75 nm + Chlorella (group F). ROS content in the brain and gills were significantly decreased in group F and significantly increased in group D after the 14 d exposure. SOD activities in the intestine showed an elevation in group F and in the brain and gills in group D, and that of the gills generally decreased over time in group B and F. The highest ROS and SOD levels were observed in the brain in group D with the lowest in the intestines at the same concentration. The activity of IL-1ß was significantly up-regulated in the liver across all the exposure groups. IL-1ß was significantly up- regulated in the brain of group B and in the gills of group D. TNF-α was significantly up- regulated in the brain of group B/D/E, in the liver of group B/C/D, in the intestine of group B and in the gills of group D. The highest IL-1ß and TNF-α activities were recorded in the brain and the lowest in the intestine in group D. Overall, the current study revealed that GIFT’s immune response and antioxidant system could be affected by MPs.