Isoflurane delays the development of early brain injury after subarachnoid hemorrhage through sphingosine-related pathway activation in mice

Objective: Isoflurane, a volatile anesthetic agent, has been recognized for its potential neuroprotective properties and has antiapoptotic effects. We examined whether isoflurane posttreatment is protective against early brain injury after subarachnoid hemorrhage and determined whether this effect needs sphingosine-related pathway activation. Design: Controlled in vivo laboratory study. Setting: Animal research laboratory. Subjects: One hundred seventy-nine 8-wk-old male CD-1 mice weighing 30-38 g. Interventions: Subarachnoid hemorrhage was induced in mice by endovascular perforation. Animals were randomly assigned to sham-operated, subarachnoid hemorrhage vehicle, and subarachnoid hemorrhage+2% isoflurane. Neurobehavioral function and brain edema were evaluated at 24 and 72 hrs. The expression of sphingosine kinase, phosphorylated Akt, and cleaved caspase-3 was determined by Western blotting and immunofluorescence. Neuronal cell death was examined by terminal deoxynucleotidyl transferase mediated uridine 5'-triphosphate-biotin nick end-labeling staining. Effects of a sphingosine kinase inhibitor N, N-dimethylsphingosine or a sphingosine 1 phosphate receptor inhibitor VPC23019 on isoflurane's protective action against post-subarachnoid hemorrhage early brain injury were also examined. Measurements and Main Results: Isoflurane significantly improved neurobehavioral function and brain edema at 24 hrs but not 72 hrs after subarachnoid hemorrhage. At 24 hrs, isoflurane attenuated neuronal cell death in the cortex, associated with an increase in sphingosine kinase 1 and phosphorylated Akt, and a decrease in cleaved caspase-3. The beneficial effects of isoflurane were abolished by N, N-dimethylsphingosine and VPC23019. Conclusions: Isoflurane posttreatment delays the development of post-subarachnoid hemorrhage early brain injury through antiapoptotic mechanisms including sphingosine-related pathway activation, implying its use for anesthesia during acute aneurysm surgery or intervention. (Crit Care Med 2012; 40:1908-1913)