BV2 Microglial Cell Activation/Polarization Is Influenced by Extracellular Vesicles Released from Mutated SOD1 NSC-34 Motoneuron-like Cells

Microglia-mediated neuroinflammation is a key player in the pathogenesis of amyotrophic lateral sclerosis (ALS) as it can contribute to the progressive degeneration of motor neurons (MNs). Here, we investigated the role of mSOD1 NSC-34 MN-like cell-derived extracellular vesicles (EVs) in inducing the activation of BV2 microglial cells. NSC-34-released EVs were isolated by culture medium differential ultracentrifugation to obtain two fractions, one containing small EVs (diameter < 200 nm) and the other containing large EVs (diameter > 200 nm). BV2 cells were incubated with the two EV fractions for 12, 24, and 48 h to evaluate 1) the state of microglial inflammation through RT-PCR of IL-1β, IL-6, IL-4, and IL-10 and 2) the expression of proteins involved in inflammasome activation (IL-β and caspase 1), cell death (caspase 3), and glial cell recruitment (CXCR1), and presence of the TGFβ cytokine receptor (TGFβ-R2). The obtained results suggest a mSOD1 type-dependent polarization of BV2 cells towards an early neurotoxic phenotype and a late neuroprotective status, with an appearance of mixed M1 and M2 microglia subpopulations. A significant role in driving with an appearance of mixed M1 and M2 microglia subpopulations. A significant role in driving microglial cell activation is played by the TGFβ/CX3CR1 axis. Therefore, targeting the dysregulated microglial response and modulating neuroinflammation could hold promise as a therapeutic strategy for ALS.