The emerging role of microplastics in systemic toxicity: Involvement of reactive oxygen species (ROS)

Plastic pollution is one of the most pressing environmental threats the world is facing currently. The degradation of macroplastics into smaller forms viz. microplastics (MPs) or Nanoplastics (NPs) is a potential threat to both terrestrial and marine ecosystems and also to human health by directly affecting the organs and activating a plethora of intracellular signaling, that may lead to cell death. There is accumulating evidence that supports the serious toxicity caused by MP/NPs at all levels of biological complexities (biomolecules, organelles, cells, tissues, organs, and organ systems) and the involvement of the reactive oxygen species (ROS) in this process. Studies indicate that MPs or NPs can accumulate in mitochondria and further disrupt the mitochondrial electron transport chain, cause mitochondrial membrane damage, and perturb the mitochondrial membrane potential or depolarization of the mitochondria. These events eventually lead to the generation of different types of reactive free radicals, which can induce DNA damage, protein oxidation, lipid peroxidation, and compromization of the antioxidant defense pool. Furthermore, MP-induced ROS was found to trigger a plethora of signaling cascades, such as the p53 signaling pathway, Mitogen-activated protein kinases (MAPKs) signaling pathway including the c-Jun N-terminal kinases (JNK), p38 kinase, and extracellular signal related kinases (ERK1/2) signaling cascades, Nuclear factor erythroid 2-related factor 2 (Nrf2)-pathway, Phosphatidylinositol-3kinases (PI3Ks)/Akt signaling pathway, and Transforming growth factor-beta (TGF-& beta;) pathways, to name a few. As a consequence of oxidative stress caused by the MPs/NPs, different types of organ damage are observed in living species, including humans, such as pulmonary toxicity, cardiotoxicity, neurotoxicity, nephrotoxicity, immunotoxicity, reproductive toxicity, hepatotoxicity, etc. Although presently, a good amount of research is going on to access the detrimental effects of MPs/NPs on human health, there is a lack of proper model systems, multi-omics approaches, interdisciplinary research, and mitigation strategies.

Automated summary

Plastic pollution is a significant environmental threat that can cause detrimental effects on terrestrial and marine ecosystems as well as human health. The degradation of macroplastics into microplastics or nanoparticles can lead to organ damage and activation of intracellular signaling, resulting in cell death. Accumulating evidence supports the serious toxicity of microplastics/nanoparticles at various biological levels, and their involvement in oxidative stress and reactive oxygen species production. These particles can accumulate in mitochondria, disrupt the electron transport chain, and generate reactive free radicals that induce DNA damage, protein oxidation, lipid peroxidation, and compromise antioxidant defense. Moreover, microplastic-induced oxidative stress triggers multiple signaling cascades, leading to organ damage such as pulmonary toxicity, neurotoxicity, and hepatotoxicity. Despite ongoing research, there is a lack of proper models, interdisciplinary approaches, and mitigation strategies to fully understand and address the detrimental effects of microplastics/nanoparticles on human health.