Toxic effects on enzymatic activity, gene expression and histopathological biomarkers in organisms exposed to microplastics and nanoplastics: a review

Microplastics (MPs) and nanoplastics (NPs) have become an important global environmental issue due to their widespread contamination in the environment. This review summarizes existing literature on the effects of MPs/NPs on three important biomarkers including enzymatic activity, gene expression, and histopathology in various organisms from 2016 to 2021 and suggests a path forward for future research. Application of enzymatic activity, gene expression, and histopathology biomarkers are increasingly used in experimental toxicology studies of MPs/NPs because of their early signs of environmental stress to organisms. Between 2016 to 2021, 70% of published studies focused on aquatic organisms, compared to terrestrial organisms. Zebrafish were widely used as a model organism to study adverse impacts of MPs/NPs. Polystyrene (PS) were the most important polymer used in experimental toxicology studies of MPs/NPs. Fewer studies focused on the histopathological alterations compared to studies on enzymatic activity and gene expression of different organisms exposed to MPs/NPs. There is a growing need to better understand toxic effects of environmentally relevant concentrations of MPs/NPs on enzymatic activity, gene expression, and histopathology biomarkers of both aquatic and terrestrial organisms.