Impact of 12/15-Lipoxygenase on Brain Injury After Subarachnoid Hemorrhage.

Background and Purpose- Subarachnoid hemorrhage (SAH) is a devastating form of stroke. Oxidative stress contributes to brain injury, but the mechanisms have been poorly studied. Here, we evaluated the role of 12/15-lipoxygenase (12/15-LOX), an enzyme known to cause cell death in ischemic stroke, on brain injury in a mouse model of SAH. Methods- C57Bl6 wild-type mice and Alox15 knockout mice were subjected to SAH using a direct blood injection technique. In SAH wild-type mice, half received the 12/15-LOX inhibitor ML351 and half received vehicle. Immunohistochemistry, brain edema, blood-brain barrier leakage and functional outcomes were assessed 1 and 3 days after SAH induction. Results- SAH led to increased 12/15-LOX in macrophages of the brain parenchyma, adjacent to the subarachnoid blood. Neuronal cell death after SAH was reduced by ML351 and in Alox15 knockout mice. Similarly, SAH induced brain edema, which was 12/15-LOX dependent. Finally, Alox15 gene knockout and inhibitor treatment in wild-type mice with SAH led to an improved behavioral outcome. Conclusions- 12/15-LOX is overexpressed in macrophages after SAH in mice, and inhibition of the 12/15-LOX pathway decreases brain injury and improves neurological outcome. This study suggests 12/15-LOX as a novel therapeutic target to limit brain injury after SAH.