To investigate the role of remote limb ischemic postconditioning in mitigation of focal cerebral ischemia-reperfusion injury in rats via mitochondrial autophagy.

Totally 105 adult male Sprague-Dawley rats were divided into a sham operation group, a ischemia-reperfusion group (A group), a ischemia-reperfusion + remote ischemic postconditioning group (B group), a ischemia-reperfusion + remote ischemic postconditioning + isotonic NaCl solution group (C group) and a ischemia-reperfusion + remote ischemic postconditioning + mitochondrial division inhibitor-1 (Mdivi-1) group (D group), 21 rats in each group. The right carotid artery was exposed and freed in the sham operation group, while a model of focal cerebral ischemia-reperfusion injury was prepared by middle cerebral artery blockade in the A, B, C and D groups. Then 10 min of ischemia/10 min of reperfusion were performed for three cycles in the B, C and D groups, and an equal volume of isotonic NaCl solution and 3 mg/kg of Mdivi-1 were injected intraperitoneally in the C and D groups 5 min before ischemia respectively. The neurological deficit score (NDS), percentage of cerebral infarction volume, and apoptosis rate, microtubule-associated protein 1 light chain 3 (LC3)-Ⅱ/Ⅰ ratio, superoxide dismutase (SOD), malondialdehyde and 15-F_2t-Isoprostane of cerebral ischemic semidark cells were compared.

No neurological deficit and cerebral infarction occurred in the sham operation group. The NDS [(2.8 ± 0.6), (1.6 ± 0.4), (1.6 ± 0.5), (2.5 ± 0.5) scores] and percentage of cerebral infarction volume [(48 ± 3)%, (28 ± 4)%, (28 ± 4)%, (41 ± 3)%] were statistically significantly different in the A, B, C and D groups (F = 39.237, 53.278; both P < 0.001). Moreover, they were significantly lower in the B and C groups than in the A and D groups (all P < 0.05). The apoptosis rate [(2.3 ± 0.8)%, (54.6 ± 5.2)%, (29.3 ± 3.1)%, (29.8 ± 3.3)%, (51.2 ± 4.5)%], LC3-Ⅱ/Ⅰ ratio [(0.13 ± 0.03), (0.32 ± 0.05), (0.53 ± 0.06), (0.48 ± 0.08), (0.35 ± 0.06)], SOD [(168 ± 19), (92 ± 13), (162 ± 21), (165 ± 23), (94 ± 15) U/mg], malondialdehyde [(4.22 ± 0.28), (8.41 ± 0.42), (5.14 ± 0.27), (5.26 ± 0.31), (7.93 ± 0.44) nmol/mg] and 15-F_2t-Isoprostane [(179 ± 86), (389 ± 105), (208 ± 89), (215 ± 85), (364 ± 103) mg/g] of cerebral ischemic semidark cells were statistically significantly different in the sham operation, A, B, C and D groups (F = 54.658, 32.358, 59.677, 46.195, 193.962; all P < 0.001). Further pairwise comparison showed that the apoptosis rate, LC3-Ⅱ/Ⅰ ratio, malondialdehyde and 15-F_2t-Isoprostane in the A, B, C and D groups were significantly higher than those in the sham operation group, while the SOD expression level in the A and D groups was significantly lower than that in the sham operation group (all P < 0.05). Compared with the A and D groups, the LC3-Ⅱ/Ⅰ ratio and SOD expression level of rats in the B and C groups significantly increased, and the apoptosis rate, malondialdehyde and 15-F_2t-Isoprostane significantly decreased (all P < 0.05).

Remote limb ischemia postconditioning may reduce focal cerebral ischemia-reperfusion injury in rats by increasing the mitochondrial autophagy level and inhibiting the oxidative stress response.