Approved Abstracts

Effects of chronic exposure of microplastics and nanoplastics on oxidative stress level, behavior and mitochondrial function of adult zebrafish (Danio rerio)

Author(s): Peixoto F; Carreira P; Félix ;
Presenter: Francisco Peixoto

Plastic pollution has been a growing problem throughout the last few decades, currently a major worldwide environmental issue. Microplastics are one of the main concerns, as their actual concentrations on the environment and their effects on the organism are still unclear.
This study was performed to enlighten a little more about the dangers and characteristics of these particles. We evaluated the effects caused by the chronic exposure to microplastics on the liver and brain of adult zebrafish. The exposure lasted for 21 days using two different concentrations of microplastics – 0,1 mg/L (LMP) and 1 mg/L (HMP). The microplastics used were obtained by blending day-to-day objects, with the final product consisting predominantly of a polypropylene and poly(ethylene-co-propylene) mixture, with particles of irregular shape and sizes between 79 and 220 nm.
The analysis of the effects of these particles was mainly focused on the metabolism of the mitochondria – membrane potential, mitochondrial respiration and electron transport chain (ETC) complexes activity – but behavioural tests and analysis of several enzymes and metabolites associated with oxidative stress were also performed – ROS, SOD, CAT, GPx, GR, GST, CarE, GSH, GSSG, OSI, LPO, AChE, LDH.
In the brain, some biomarkers showed that animals suffered from environmental stress. Nevertheless, the lack of significant alterations in tested animals' behavior and neurotoxicity indicate an adequate response to the microplastics.
On the liver, the signs of toxicity were more prominent, with significant inhibition of the mitochondrial membrane potential on both experimental groups, in addition to a reduction of the state 3 respiration rate and several changes in oxidative stress parameters inhibition of GPx, GR and GST, and an increase of GSSG. The inhibition of Carboxylesterase, Acetylcholinesterase and Lactate dehydrogenase also support that damages have occurred on this organ. All of these are clear signs of toxicity on this organ. However, ROS levels dropped significantly in both experimental groups, indicating that oxidative stress was not the cause. Uncoupling of the ETC or inference of ETC's mobile components are suggested causes to these alterations, but only subsequent tests could determine the definite mechanism and the true nature of the damages caused on the tested organs.
In conclusion, microplastics had detrimental effects on the physiology of the tested animals, especially on the liver. Therefore, microplastics lead to health complications and threaten the subject's survival, worrying given microplastics" worldwide presence and persistence in the environment. However, the mechanism through which these damages have occurred is unclear, and subsequent studies would be necessary.

Keywords: Microplastics; Biomarkers; Zebrafish




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