Relationship between TGF-β 3/Smad3 signaling pathway and neuronal apoptosis during reduction of focal cerebral ischemia-reperfusion injury by isoflurane postconditioning in rats / 中华麻醉学杂志

ABSTRACT

Objective:To evaluate the relationship between transforming growth factor beta-3 (TGF-β 3)/mammalian homologs of the drosophila mad gene 3 (Smad3) signaling pathway and neuronal apoptosis during reduction of focal cerebral ischemia-reperfusion (I/R) injury by isoflurane postconditioning (ISO) in rats. Methods:Sixty clean-grade healthy male Sprague-Dawley rats, aged 6-8 weeks, weighing 210-230 g, were randomly divided into 5 groups ( n=12 each) sham operation group (group S), cerebral I/R group (group I/R), cerebral I/R plus isoflurane postconditioning group (group I/R+ ISO), cerebral I/R plus pirfenidone group (group I/R+ P), and cerebral I/R plus isoflurane postconditioning plus pirfenidone group (group I/R+ ISO+ P). Local cerebral I/R was produced by middle cerebral artery occlusion for 1.5 h followed by 24-h reperfusion in anesthetized rats.Pirfenidone 5 μg/kg was injected into the lateral ventricle at 30 min before ischemia in I/R+ P and I/R+ ISO+ P groups.In I/R+ ISO and I/R+ ISO+ P groups, 1.5% isoflurane was inhaled for 1 h starting from the time point immediately after onset of reperfusion.Neuro-functional deficit was assessed using neurologic deficit scores (NDS) at the end of reperfusion.Then the animals were sacrificed, and brain tissues were removed for determination of the neuronal damage rate (by Nissl staining), neuronal apoptosis rate (by TUNEL), expression of TGF-β 3 (using immunofluorescence), and expression of TGF-β 3, phosphorylated Smad3 (p-Smad3), caspase-3, Bax and Bcl-2 (by Western blot). Results:Compared with group S, the NDS, neuronal damage rate and apoptosis rate of neurons were significantly increased, the expression of TGF-β 3, caspase-3 and Bax was up-regulated, and the expression of p-Smad3 and Bcl-2 was down-regulated in group I/R ( P<0.05). Compared with group I/R, the NDS, neuronal damage rate and apoptosis rate of neurons were significantly decreased, the expression of TGF-β 3, p-Smad3 and Bcl-2 was up-regulated, and the expression of caspase-3 and Bax was down-regulated in group I/R+ ISO, and the NDS, neuronal damage rate and apoptosis rate of neurons were significantly increased, the expression of TGF-β 3 and p-Smad3 was down-regulated, and the expression of caspase-3 was up-regulated in group I/R+ P ( P<0.05). Compared with group I/R+ ISO, the NDS, neuronal damage rate and apoptosis rate of neurons were significantly increased, the expression of TGF-β 3, p-Smad3 and Bcl-2 was down-regulated, and the expression of caspase-3 and Bax was up-regulated in group I/R+ ISO+ P ( P<0.05). Conclusion:Isoflurane postconditioning can inhibit neuronal apoptosis by activating the TGF-β 3/Smad3 signaling pathway, thus reducing focal I/R injury in rats.