Small Molecule Myeloperoxidase (MPO) Inhibition Prevents Delayed Cerebral Injury (DCI) After Subarachnoid Hemorrhage (SAH) in a Murine Model.

Background: Delayed cerebral injury (DCI) after aneurysmal subarachnoid hemorrhage (SAH) is a preventable injury that would improve patient outcomes if an effective treatment can be developed. The most common long-term disability in patients with SAH is cognitive dysfunction. Contrary to the common theory that damage from DCI originates solely from ischemia caused by cerebral vasospasm, inflammation has been shown to be an important independent mediator of DCI.

Methods: Neutrophil infiltration of the meninges is a critical step in developing late spatial memory deficits in a murine model of SAH and may serve as a surrogate marker for disease progression. Importantly, myeloperoxidase (MPO) null mice do not develop meningeal neutrophilia and are protected from spatial memory deficits.

Results: In this study, wildtype mice administered a single dose of the MPO inhibitor (MPOi) AZD5904 at peak neutrophil entry day have a higher percentage of neutrophils that remain in the meningeal blood vessel 6 days after the hemorrhage suggesting neutrophil extravasation into the meninges is inhibited (79 ± 20 vs. 28 ± 24, p < 0.01). Interestingly, the intraperitoneal route of administration has a larger effect than the intrathecal route suggesting that MPO inhibition is best administered systemically not in the central nervous system. Second, mice administered AZD5904 intraperitoneal for 4 consecutive days starting 2 days after the hemorrhage do not develop delayed spatial memory dysfunction (two-way analysis of variance, p > 0.001 F [2, 22] = 10.11).

Conclusions: Systemic MPOi prevents neutrophil entry into the meninges and prevents spatial memory dysfunction. MPOi is a promising strategy for translation to patients with aneurysmal SAH.