Clearance of neurotoxic peptides and proteins by meningothelial cells

Meningothelial cells (MECs) are the cellular component of the meninges that provide physical protection to the central nervous system (CNS). Their main function is the formation of a barrier enclosing the brain including the cerebrospinal fluid (CSF). Further, MECs are involved in maintaining CSF homeostasis by clearing CSF from bacteria and apoptotic cells. Furthermore, secretion of pro- and anti-inflammatory cytokines and chemokines involves MECs in immunological processes in the CNS. We demonstrated that meningothelial Ben-Men-1 cells ingest neurotoxic peptides amyloid-β (Aβ^1-40) and protein α-synuclein up to about 10-fold more efficiently compared to neuronal-like SH-SY5Y cells. Aβ^1-40 and α-synuclein are mainly taken up via macropinocytosis. Caveolar endocytosis in addition contributes to α-synuclein ingestion. Upon uptake, both are trafficked towards lysosomal degradation. While production of reactive oxygen species (ROS) following exposure to Aβ^25-35 and α-synuclein was similar between Ben-Men-1 and SH-SY5Y cells, mitochondrial function in Ben-Men-1 was significantly more robust to Aβ^25-35 treatment compared to neuronal-like SHSY5Y cells. Similarly, Ben-Men-1 were significantly less susceptible to Aβ^25-35-induced cell death than neuronal-like cells. Furthermore, co-culture with Ben-Men-1 offered significant protection to neuronal-like cells against Aβ^25-35-induced apoptosis. This study reveals for the first time the function of MECs as scavengers of neurotoxic Aβ and α-synuclein, thereby connecting these cells to neuroprotective processes and suggesting a new mechanism and pathway for clearing neurotoxic substances from the CSF.