Neuroprotection and Enhanced Hemoglobin Excretion by Intrathecal Clazosentan in Mice With Subarachnoid Hemorrhage.

BACKGROUND: Intravenous administration of clazosentan, a selective endothelin receptor subtype A antagonist, has been used as an anti-vasospastic agent. This study aimed to investigate whether intrathecal administration of clazosentan prevents neuroinflammation and affects lymphatic clearance of hemoglobin in a mouse model of acute subarachnoid hemorrhage (SAH). METHODS: Male C57BL/6 mice (n=109) underwent prechiasmatic cisternal injection models of SAH or sham models. From 30 minutes post-modeling, mice randomly received a continuous intracerebroventricular infusion of saline or clazosentan (1, 0.2, and 0.04 μg in 192 μL of saline; defined as 50%, 10%, and 2% of the clinically achievable blood concentration, respectively) at a rate of 8 μL/h for 24 hours. The intervention effects were assessed by neurobehavioral testing, SAH grading, and immunohistochemical staining at 24 and 48 hours, and Western blotting at 24 hours post-modeling. RESULTS: Clazosentan treatment did not influence SAH grading but showed a dose-dependent trend toward improved survival in SAH mice. A comparison of saline treatment and 50% clazosentan treatment revealed that clazosentan significantly suppressed post-SAH neurological deterioration, hemoglobin infiltration into the brain, and induction of ionized calcium-binding adapter molecule 1 and tenascin-C in the brain, and significantly upregulated vascular endothelial growth factor receptor-3 in the brain without affecting vascular endothelial growth factor-C levels. When comparing the effects of different clazosentan doses, an inhibitory effect on neuroinflammation was observed up to 10% clazosentan. At 48 hours post-modeling, clazosentan administration dose-dependently inhibited neurological deterioration, hemoglobin infiltration into the brain and activation of perivascular macrophages and microglia, and increased hemoglobin deposition in the deep cervical lymph nodes of SAH mice without intracranial lymphatic vessel proliferation. CONCLUSIONS: This study first showed that intrathecal administration of clazosentan can suppress early brain injury in terms of neuroinflammation at cerebrospinal fluid concentrations one-tenth of the clinically achievable blood concentrations, associated with enhanced lymphatic drainage of hemoglobin.