[The effects of preconditioning and postconditioning with isoflurane on focal cerebral ischemi/reperfusion injury in rats].

Objective: To investigate the effects of preconditioning and postconditioning with isoflurane on pro-inflammatory cytokines and lipid peroxidation in focal cerebral ischemic/reperfusion (I/R) injury in rats.

Methods: Thirty-two Sprague-Dawley (SD) rats were randomly divided into four groups: control group, model group, isoflurane preconditioning group and isoflurane postconditioning group, with 8 rats in each group. Rats in control group did not receive any challenge. In rats of model group right middle cerebral artery occlusion (MCAO) was conducted for 90 minutes. Rats in isoflurane preconditioning group received 2% isoflurane exposure for 30 minutes 24 hours before MCAO for 90 minutes. Rats in isoflurane postconditioning group were given 60-minute 2% isoflurane exposure after reperfusion of right MCAO. Twenty-four hours after the procedure, all rats were anesthetized with isoflurane, and blood sample taken from the heart was centrifuged, and the pro-inflammatory cytokines, including interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α), and lipid peroxidation products such as malonaldehyde (MDA) and superoxide dismutase (SOD) were determined. The mRNA and protein expression levels of matrix metalloproteinase (MMP-2, MMP-9), tight junction protein Calaudin-5 and Occludin were determined by reverse transcription-polymerase chain reaction (RT-PCR) and Western Blot.

Results: Compared with control group, serum levels of IL-1β, TNF-α and MDA were elevated and activity of SOD decreased in rats of model group (IL-1β: 76.81±11.14 ng/L vs. 52.43 ± 8.86 ng/L, TNF-α: 64.93 ± 10.81 ng/L vs. 33.64 ± 7.94 ng/L, MDA: 8.63 ± 1.42 μmol/L vs. 4.14 ± 0.98 μmol/L, SOD: 0.95 ± 0.21 U/L vs. 2.36 ± 0.80 U/L, all P<0.05). After isoflurane preconditioning and postconditioning, compared with model group, the levels of IL-1β, TNF-α and MDA were lowered, while activity of SOD was increased (IL-1β: 54.37 ± 9.06 ng/L, 56.82 ± 8.67 ng/L vs. 76.81 ± 11.14 ng/L, TNF-α: 43.72 ± 6.16 ng/L, 39.49 ± 9.34 ng/L vs. 64.93 ± 10.81 ng/L, MDA: 5.65 ± 0.83 μmol/L, 5.82 ± 0.78 μmol/L vs. 8.63 ± 1.42 μmol/L, SOD: 1.64 ± 0.47 U/L, 1.71 ± 0.52 U/L vs. 0.95 ± 0.21 U/L, all P<0.05). Focal cerebral I/R injury could lead to an increased expression of MMP accompanied with a decreased expression of tight junction protein. Compared with model group, after isoflurane preconditioning and postconditioning, it was found that there were decreased mRNA and protein expression of MMP-2 and MMP-9 (MMP-2 mRNA: 1.25 ± 0.08, 1.32 ± 0.12 vs. 2.48 ± 0.26, MMP-2 protein: 1.56 ± 0.09, 1.50 ± 0.08 vs. 2.12 ± 0.11; MMP-9 mRNA: 1.26 ± 0.13, 1.20 ± 0.12 vs. 2.74 ± 0.28, MMP-9 protein: 1.53 ± 0.04, 1.51 ± 0.05 vs. 2.23 ± 0.09, all P<0.05) and increased levels of Calaudin-5 and Occludin (Claudin-5 mRNA: 0.40 ± 0.08, 0.38 ± 0.06 vs. 0.28 ± 0.03, Claudin-5 protein: 0.80 ± 0.06, 0.81 ± 0.07 vs. 0.39 ± 0.02; Occludin mRNA: 0.54 ± 0.07, 0.50 ± 0.08 vs. 0.26 ± 0.06, Occludin protein: 0.64 ± 0.06, 0.69 ± 0.05 vs. 0.49 ± 0.02, all P<0.05).

Conclusions: Preconditioning and postconditioning with isoflurane can lower the levels of pro-inflammatory cytokines and the degree of lipid peroxidation, and lower the hydrolytic activity of MMP to the tight junction protein in cerebral tissue, thereby decrease the loss of tight junction protein and alleviate I/R injury.