Invisible threats of microplastics induced toxicity: Oxidative and inflammatory pathways in the CNS and retina

The global spread of microplastics has become a serious public health concern. Once thought to be inert, microplastics are now recognized as biologically active agents capable of accumulating in the body and causing toxic effects across organ systems. This review summarizes current evidence on their oxidative and inflammatory effects in the central nervous system (CNS) and the eye. Studies show that microplastics can cross biological barriers such as the blood-brain barrier (BBB) and blood-retinal barrier (BRB), where they are taken up by cells, impair mitochondria, and trigger inflammation. Microplastics have been found in cerebrospinal fluid, brain tissue, and ocular structures, raising concern about their link to neurodegenerative and retinal diseases, including Alzheimer's, Parkinson's, macular degeneration, and other disorders. Mechanistic data indicate activation of NF-κB and TGF-β1 pathways, promotion of protein aggregation, and disruption of neural signaling. In the eye, microplastics have been linked to oxidative stress, corneal thinning, and photoreceptor damage. However, human studies are limited due to challenges in detecting tiny particles and lack of microplastic-free controls. Research is further hindered by inconsistent definitions, particle diversity, and non-physiological exposure models. We highlight the need for standardized methods, multi-omics tools, and long-term studies to better understand exposure impacts. Given the rise in neurological and ocular diseases, clarifying the role of microplastics is essential for effective public health strategies.