Inhibition of neutral sphingomyelinase 2 reduces extracellular vesicle release from neurons, oligodendrocytes, and activated microglial cells following acute brain injury

Extracellular Vesicles (EVs) are implicated in the spread of pathogenic proteins in a growing number of neurological diseases. Given this, there is rising interest in developing inhibitors of Neutral Sphingomyelinase 2 (nSMase2), an enzyme critical in EV biogenesis. Our group recently discovered phenyl(R)-(1-(3-(3,4-dimethoxypheny1)-2,6-dimethylimidazo[1,2-b]pyridazin-8-yepyrrolidin-3-yecarbamate (PDDC), the first potent, selective, orally-available, and brain-penetrable nSMase2 inhibitor, capable of dose-dependently reducing EVs release in vitro and in vivo. Herein, using multiplexed Surface Plasmon Resonance imaging (SPRi), we evaluated which brain cell-derived EVs were affected by PDDC following acute brain injury. Mice were fed PDDC-containing chow at doses which gave steady PDDC brain exposures exceeding its nSMase2 IC50. Mice were then administered an intra-striatal IL-1 beta injection and two hours later plasma and brain were collected. IL-1 beta injection significantly increased striatal nSMase2 activity which was completely normalized by PDDC. Using SPRi, we found that IL-1 beta-induced injury selectively increased plasma levels of CD171 + and PLP1 + EVs; this EV increase was normalized by PDDC. In contrast, GLAST1 + EVs were unchanged by IL-1 beta or PDDC. IL-1 beta injection selectively increased EVs released from activated versus non-activated micmglia, indicated by the CD11b+/IB4 + ratio. The increase in EVs from CD11b + micmglia was dramatically attenuated with PDDC. Taken together, our data demonstrate that following acute injury, brain nSMase2 activity is elevated. EVs released from neurons, oligodendrocytes, and activated microglial are increased in plasma and inhibition of nSMase2 with PDDC reduced these IL-1 beta-induced changes implicating nSMase2 inhibition as a therapeutic target for acute brain injury.

Automated summary

A new nSMase2 inhibitor, PDDC, was found to reduce EV release and normalize IL-1 beta-induced EV increase after acute brain injury. This suggests that nSMase2 inhibition may be an effective therapeutic target for acute brain injury.