Effects of isoflurane postconditioning on angiogenesis during cerebral ischemia-reperfusion in rats and the role of Shh signaling pathway

Abstract

Objective To evaluate the effects of isoflurane postconditioning on angiogenesis during cerebral ischemia-reperfusion (I/R) in rats and the role of Shh signaling pathway. Methods Thirty-two clean-grade healthy male Sprague-Dawley rats, aged 6-8 weeks, weighing 220-280 g, were divided into 4 groups (n=8 each) by a random number table method: sham operation group (Sham group), I/R group, isoflurane postconditioning group (ISO group), and isoflurane postconditioning plus Shh signaling pathway specific inhibitor cyclopamine group (ISO + CYC group). Cerebral ischemia was produced by inserting a 3-0 nylon thread with a rounded tip into the internal jugular vein. The nylon thread was threaded cranially until resistance was met. Occlusion was maintained for 1.5 h followed by 24 h reperfusion. Neurological deficit was scored at 24 h of reperfusion. Rats were then sacrificed, and brains were removed for determination of cerebral infarct volume (by TTC) and expression of glioma-associated oncogene homolog 1 (Gli1), vascular endothelial growth factor (VEGF) and transmembrane phosphoglycoprotein protein (CD34) in cerebral cortex (by Western blot) and for examination of the pathological changes (by Nissl staining). Results Compared with Sham group, the neurological deficit score and cerebral infarct volume were significantly increased, and the expression of Gli1, VEGF and CD34 in the cerebral cortex was up-regulated in I/R and ISO groups (P 0.05). Compared with ISO group, the neurological deficit score and cerebral infarct volume were significantly increased, and the expression of Gli1, VEGF and CD34 in the cerebral cortex was down-regulated in ISO+ CYC group (P<0.05). Conclusion The mechanism by which isoflurane post-conditioning attenuates cerebral I/R injury is related to activating Shh signaling pathway and promoting angiogenesis in rats. Key words: Isoflurane; Ischemic postconditioning; Reperfusion injury; Brain; Hedgehog proteins; Angiogenesis