Effect of Polystyrene Microplastics on the Antioxidant System and Immune Response in GIFT (Oreochromis niloticus)

SIMPLE SUMMARY: This study determined the levels of IL-1ß, TNF-α, ROS, and SOD in the brain, gills, liver, and intestine of tilapia exposed to different sizes of polystyrene microsphere microplastics (MPs) with or without the existing Chlorella. MPs may induce excessive ROS production and affect the antioxidative enzyme system, with the highest observed in the brain being 750 μm. A total of 750 μm of MPs may cause the over expression of brain IL-1ß and TNF-α. Chlorella may suffer oxidative stress caused by the presence of MPs. ABSTRACT: Recent studies have revealed a significant presence of microplastics (MPs) in freshwater ecosystems, raising concerns about their potential negative impacts on the growth and development of freshwater organisms. The present study was conducted to examine the effects of chronic sub-lethal doses of polystyrene microsphere MPs on the oxidative status (ROS, SOD) and the immune response (IL-1ß, TNF-α) of genetically improved farmed tilapia (a kind of tilapia hereafter referred to as GIFT). GIFT juveniles (5.1 ± 0.2 g) were exposed to different concentrations of substances. The experimental groups were as follows: group A (control, no exposure), group B (exposed to a concentration of 75 nm), group C (exposed to a concentration of 7.5 μm), group D (exposed to a concentration of 750 μm), group E (exposed to a combination of 75 nm, 7.5 μm, and 750 μm), and group F (exposed to a combination of 75 nm and Chlorella). The ROS contents in the brain and gills were significantly decreased in group F, while a significant increase was observed in group D following a 14-day exposure. SOD activities in the intestine showed an elevation in group F, as did those in the brain and gills in group D, while the SOD levels in the gills generally decreased over time in groups B and F. Notably, the highest ROS and SOD were observed in the brain of group D, whereas the lowest were in the intestines at the same concentration. The activity of IL-1β in the liver was significantly up-regulated in all of the exposure groups. IL-1β was significantly up-regulated in the brain of group B and in the gills of group D. Similarly, TNF-α was significantly up-regulated in the brain of groups B/D/E, in the liver of groups B/C/D, in the intestine of group B, and in the gills of group D. Notably, the highest levels of IL-1β and TNF-α activities were recorded in the brain, while the lowest were recorded in the intestine of group D. Overall, this study revealed that GIFT’s immune response and antioxidant system can be affected by MPs.