Treg Cells Attenuate Neuroinflammation and Protect Neurons in a Mouse Model of Parkinson's Disease

Regulatory T cells (Tregs), which secrete transforming growth factor (TGF)-β and interleukin (IL)-10, have essential role in anti-inflammatory and neurotrophic functions. Herein, we explore the neuroprotection of Tregs in Parkinson's disease (PD) by adoptive transfer of Tregs. Tregs, isolated by magnetic sorting, were activated in vitro and then were adoptively transferred to 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP)-treated mice. Neuroinflammation, dopaminergic neuronal loss and behavioral changes of PD mice were evaluated. Live cell imaging system detected a dynamic contact of Tregs with MN9D cells that were stained with CD45 and galectin-1, respectively. Tregs prevented MPTP-induced dopaminergic neuronal loss, behavioral changes, and attenuated the inflammatory reaction in the brain. When blockade the LFA-1 activity in Tregs or the ICAM-1 activity in endothelial cells, the percentage of Tregs in substantia nigra (SN) decreased. CD45 and galectin-1 were expressed by Tregs and MN9D cells, respectively. CD45-labeled Tregs dynamically contacted with galectin-1-labeled MN9D cells. Inhibiting CD45 in Tregs impaired the ability of Tregs to protect dopaminergic neurons against MPP⁺ toxicity. Similarly, galectin-1 knockdown in MN9D cells reduced the ability of Tregs neuroprotection. Adoptive transfer of Tregs protects dopaminergic neurons in PD mice by a cell-to-cell contact mechanism underlying CD45-galectin-1 interaction. Graphical Abstract.