Rainbow Trout Maintain Intestinal Transport and Barrier Functions Following Exposure to Polystyrene Microplastics

Abstract

Ingestion has been proposed as a prominent exposure route for plastic debris in aquatic organisms, including fish. While the consequences of ingestion of large plastic litter are mostly understood, the impacts resulting from ingestion of microplastics (MPs) are largely unknown. We designed a study that aimed to assess impacts of MPs on fish intestinal physiology and examined integrity of extrinsic, physical and immunological barriers. Rainbow trout were exposed to polystyrene (PS) MPs (100–400 μm) via feed for a period of 4 weeks. Fish were fed four types of diets: control, diets containing virgin PS particles, or particles exposed to two different environmental matrices (sewage or harbor effluent). Extrinsic barrier disturbance in intestinal tissue was evaluated via histology. The paracellular permeability toward ions and molecules was examined using Ussing chambers and mRNA expression analysis of tight junction proteins. Active transport was monitored as transepithelial potential difference, short-circuits current and uptake rate of amino acid 3H-lysine. Immune status parameters were measured through mRNA expression level of cytokines, lysozyme activity, and hematological analysis of immune cells. We could not show that PS MPs induced inflammatory responses or acted as physical or chemical hazards upon ingestion. No measurable effects were exerted on fish intestinal permeability, active transport or electrophysiology.

An end to the controversy over the microscopic detection and effects of pristine microplastics in fish organs

“…Regarding progressive changes, in our study, the number and size of goblet cells did not show significant differences among the test groups. Likewise, a study conducted on Onchorhyncus mykiss fed PS MPs showed no significant changes in the numbers of goblet cells observed 58 . Although prior studies 95,118 have mentioned mucous hypersecretion, none of the photomicrographs provided showed a significant presence of mucous secretion.…”

“…In contrast, Asmonaitè et al . found limited impacts on gut integrity in Oncorhynchus mykiss exposed to MP particles for 4 weeks 58 . Jovanovic et al .…”

“…In the same species, Lu et al 48 reported signs of inflammation and lipid accumulation in the liver after exposure to MPs. In contrast, Asmonaitè et al found limited impacts on gut integrity in Oncorhynchus mykiss exposed to MP particles for 4 weeks 58 . Jovanovic et al concluded that dietary exposure of S. aurata for 45 days to different types of MPs did not cause any damage in the studied tissues 47 .…”

Toxicity of Microplastics and Nanoplastics in Mammalian Systems

“…An important general phenomenon to note is that toxicological responses typically arise from smaller plastic particles. Larger PS particles at around 100 µm or above were shown not to have any significant effect in a number of studies [65][66][67]. MP/NP feeding can result in behavioral abnormalities in terms of feeding and movement of adults and larvae [35,[68][69][70][71][72][73][74], as well as reproduction in adults [75][76][77].…”

Impacto de la ingesta de residuos plásticos en peces

“…Estos resultados contrastan a los obtenidos previamente por Alomar et al (2017), quienes no obtuvieron evidencia del estrés oxidativo y daño celular en el hígado de M. surmuletus; sin embargo, también visualizaron el aumento de la enzima GST, lo que sugiere la inducción del sistema de detoxificación del pez. Esta falta de evidencia podría sustentarse según Ašmonait et al (2018), quienes emplearon a Oncorhynchus mykiss «trucha arcoiris» para estudiar los efectos de los microplásticos tras un periodo de ingesta de 4 semanas, sin embargo, los resultados obtenidos no pudieron detectar ningún efecto significativo sobre la barrera intestinal, por lo cual concluyeron que los efectos nocivos de los microplásticos en peces dependen de su especie y el periodo de exposición.…”