Crossing barriers – tracking micro- and nanoplastic pathways into the human brain

Nano- and microplastic (NMP) has been detected in human post mortem (PM) brain homogenates. It is still a matter of debate, if NMP can cross brain barriers and reach neurofluids and the brain parenchyma. To track putative pathways, we have investigated in vitro endocytosis of NMP using human stimulated monocytes exposed to plain 1 μm and 100 nm polystyrene beads in vitro by transmission electron microscopy TEM (N=5) and EDX spectroscopy. NMP was localized after 10 min incubation time in endocytic vesicles and adjacent and inside degenerating mitochondria inducing mitophagy and lipofuscin accumulation. To track corresponding in vivo pathways, we have performed TEM of randomly accessed human PM choroid plexus (N=5) and subventricular tissue (N=5) as well as of leukocytes prepared from CSF cell pellets from geriatric patients (N=6). NMP remnants were detected in all autopsy cases (mean 75.6 yrs.) inside endothelia and epithelial cells as well as inside CSF leucocytes, localized adjacent to lipofuscin and Biondi bodies together with Aß fibrils. These preliminary results in a monocyte cell line, postmortem brain tissue and CSF cells localized accumulation of NMP remnants after crossing the barriers between blood and the human brain.