The Toxicity of (Nano)Microplastics on C. elegans and Its Mechanisms

Microplastics (MPs) and nanoplastics (NPs) are respectively defined as plastic debris with sizes of <5 mm and <100 nm. In recent years, (nano)microplastics (N/MPs) have been widely detected in air, water, soil, and other environmental matrices. Despite knowledge gap of the risks of N/MPs, more and more researchers pay attention to the adverse effects of this type of fine plastic items on biota. Caenorhabditis elegans (C. elegans) is an ideal model organism for toxicology study on N/MPs. In this chapter, we have reviewed research progress in the toxicity of N/MPs and its mechanism basing on this model. At the individual level, N/MPs can cause lethality on nematodes and the inhibition of growth and reproduction. The alteration of locomotion behavior has been demonstrated in nematodes after N/MPs exposure. Moreover, the behavioral toxicity was revealed to be involved in the especial neurotoxicity, including damages of GABAergic and cholinergic neurons. In addition, intestine damages and oxidative stress were found in nematodes exposed to N/MPs. Several studies proved that the N/MPs-induced effects might be closely dependent on the size and dose of N/MPs. Recent studies showed that the toxicity of N/MPs was mediated by the insulin signaling pathway and p38 signaling; the intestinal signaling cascade of PMK-1-ATF-7-XBP-1 and PMK-1-SKN-1-XBP-1/GST-5 could regulate the responses to nanopolystyrene particles in nematodes. Although the toxicity of N/MPs has been largely investigated basing on C. elegans, the toxic mechanisms are still unclear. Moreover, current studies are most relying on a special type of pure polystyrene sphere, which might not be the representative of all N/MPs types. Therefore, more researches on environmental (nano)microplastics with different chemical compositions and shapes need to be done in the future.