JNK pathway may be involved in isoflurane-induced apoptosis in the hippocampi of neonatal rats

Previous studies have demonstrated that isoflurane, a commonly used volatile anesthetic, can induce widespread apoptosis in the neonatal animal brains and result in persistent cognitive impairment. Isoflurane-induced cytosolic Ca2+ overload and activation of mitochondrial pathway of apoptosis may be involved in this neurodegeneration. The c-Jun N-terminal kinase (JNK) signaling can regulate the expression of the Bcl-2 family members that modulates mitochondrial membrane integrity. Therefore, we hypothesize that JNK signaling pathway activation contributes to isoflurane-induced apoptosis in the brain. In this study, Sprague-Dawley neonatal rats at postnatal day 7 were exposed to 1.1% isoflurane or air for 4 h. The JNK inhibitor SP600125 at 5 μg, 10 μg, 20 μg, 30 μg or the vehicle was intraventricularly administered before the exposure. Neuronal apoptosis in the hippocampi of neonatal rats was detected by TUNEL 6 h after isoflurane or air exposure. The protein expression of phospho-JNK, phospho-c-Jun, and caspase-3 as well as the antiapoptotic protein Bcl-xL and Akt/glycogen synthase kinase (GSK)-3β pathway was detected by Western blotting. Isoflurane significantly increased apoptotic cells in the hippocampal CA1, CA3, and DG regions. The JNK inhibitor SP600125 dose-dependently inhibited isoflurane-induced neuronal apoptosis and increase of caspase-3 and phospho-JNK. SP600125 also attenuated isoflurane-induced down-regulation of Bcl-xL and maintained the activated Akt level to increase the phosphorylation of GSK-3β at Ser9. Our results indicate that JNK activation contributes to isoflurane-induced neuroapoptosis in the developing brain. Maintaining Bcl-xL and Akt activation may be involved in the neuroprotective effects of SP600125.