Nanoplastic Impact on the Gut-Brain Axis: Current Knowledge and Future Directions

Abstract

The widespread usage of plastic places a significant burden on the environment and impacts numerous aquatic and terrestrial species. Humans in particular can be affected by plastic pollution, predominantly via inhalation and ingestion, as well as trophic transfer along the food chain. Under natural conditions synthetic materials undergo degradation into micro- and nanoparticles, especially prone to interact with biological systems. Organisms exposed to nanoplastic accumulate it in multiple tissues, including the gut and the brain. This phenomenon raises a question about the impact of nanoparticulate plastics on the communication pathways between these organs. The aim of this review is to explore an unsettling possibility of the influence of nanoplastic on the gut-brain axis and provide a comprehensive summary of available data regarding this subject. The scarce but consistent evidence shows that exposure to plastic nanoparticles can indeed affect both the digestive and the nervous system. Reported outcomes include microbiota alterations, intestinal barrier permeability, oxidative stress, inflammation, neurotoxicity and behavioral disturbances. Taking into consideration these alarming observations and the ubiquitous presence of plastics in human environment, more research is urgently needed in order to identify any potential threats that nanoplastic exposure can pose to the functioning of the gut-brain axis.

Keywords: inflammation; intestinal barrier permeability; microbiome; nanoplastic accumulation; neurotoxicity; oxidative stress.

Figure 1

Possible human exposure level to plastics originating from different sources. MPs, microplastic particles; MNPs, micro- and nanoplastic particles. Designed using elements by ©Canva, sparklestroke, Pixeden, iconsy, OpenClipart-Vectors via Canva.com ( access date: 18 November 2021, version used Canva 2.0).

Figure 2

Impact of nanoplastic exposure on the gut-brain axis. HPA axis, hypothalamic-pituitary-adrenal axis; ENS, enteric nervous system; SCFA, short-chain fatty acids. Designed using elements by ©HaticeEROL, sparklestroke, sketchify, Twemoji, Sketchify Edu, Clker-Free-Vector-Images, iconsy via Canva.com ( access date: 18 November 2021, version used Canva 2.0).