Micro/nanoplastic threats to human and animal health: mitigation strategies with melatonin

Micro/nanoplastics (MNPs) are major contaminants in water, food, and air. Plastic residues are formed by long-term deterioration of discarded products, leading to a rise in the environmental toxin load in all ecosystems. Once MNPs enter an organism, they become permanent residents with the amount of internalized plastic debris accumulating with age. MNPs are taken in during the consumption of fluids and food, and in the air we breathe. The ragged shards physically damage cells and induce oxidative stress and stimulate inflammation. Additionally, plastic additives such as phthalates leach into consumables from plastic products and compromise cellular physiology by damaging mitochondria, resulting in increased reactive oxygen species production and inflammatory cytokine release. While the damaging effects of phthalates linger, they are detoxified in the liver and conjugated, usually to glucuronic acid, allowing for their urinary excretion. Although several means of mitigating the toxic effects of MNPs are being investigated, the methods used have not been entirely successful. Melatonin is an endogenously produced multifunctional agent which reduces oxidative stress and inflammation. Melatonin and its metabolites have widespread radical scavenging activities, preventing the formation of the highly reactive hydroxyl radical by chelating transition metals, and markedly upregulating antioxidant enzymes. Due to these multiple antioxidative actions, it is a worthy candidate to be tested for its use against the toxicity of microplastics and their residues, and may counter MNPs and phthalate toxicity. It is safe and can be administered by any route including in nano encapsulated formulations.