Isoflurane preconditioning induces neuroprotection by attenuating ubiquitin-conjugated protein aggregation in a mouse model of transient global cerebral ischemia.
BACKGROUND
In this study, we sought to clarify the role of inhibiting ubiquitin-conjugated protein aggregation in the formation of a neuroprotective effect after isoflurane preconditioning using a transient global cerebral ischemia-reperfusion injury mouse model.


METHODS
C57BL/6 mice were randomly assigned to 3 groups (isoflurane preconditioning [IsoPC] group, control [Con] group, and sham group, n = 24 in each group). Mice in the IsoPC group and sham group were placed in a chamber and pretreated with isoflurane (1.2% isoflurane, 98% O(2), 1 hour/day) for 5 days. Mice in the Con group were placed in the same chamber but pretreated with oxygen only (98% O(2), 2% N(2), 1 hour/day) for 5 days. Twenty-four hours after the last preconditioning day, bilateral common carotid artery occlusion was performed as a model of global cerebral ischemia for 20 minutes in the IsoPC group and Con group. The total motor scores, number of viable neurons in the CA1 region of the hippocampus, and expression levels of conjugated ubiquitin or free ubiquitin were assessed by neurological assessment, immunohistochemistry, and Western blotting (at 24 and 72 hours) after reperfusion, respectively.


RESULTS
The total motor scores in the IsoPC group were better than the Con group (P < 0.05). Morphological observations showed that the IsoPC group had better neuron structure than in the Con group. The numbers of viable neurons in the CA1 region were significantly increased by isoflurane preconditioning compared with those in the Con group (P < 0.05). The numbers of TUNEL-positive neurons in the CA1 region were significantly decreased after isoflurane preconditioning. The density of conjugated ubiquitin staining in the CA1 region of the IsoPC group was significantly lower than in the Con group (P < 0.05) and the expression of conjugated ubiquitin in the IsoPC group was lower than in the Con group (P < 0.05).


CONCLUSIONS
Inhibition of ubiquitin-conjugated protein aggregation may have an essential role in inducing cerebral ischemic tolerance by isoflurane preconditioning in a transient global cerebral ischemia-reperfusion injury mouse model.
Zhang
Hao-Peng
HP
Department of Anesthesiology, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, Shaanxi, China.
Yuan
Li-bang
LB
Zhao
Rui-ni
RN
Tong
Li
L
Ma
Rui
R
Dong
Hai-long
HL
Xiong
Lize
L
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D015153:Blotting, Western; D056547:CA1 Region, Hippocampal / Q000098:blood supply / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D002470:Cell Survival; D002560:Cerebrovascular Circulation / Q000187:drug effects; D004195:Disease Models, Animal; D015536:Down-Regulation; D004334:Drug Administration Schedule; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D002546:Ischemic Attack, Transient / Q000188:drug therapy* / Q000378:metabolism / Q000503:physiopathology; D007530:Isoflurane / Q000008:administration & dosage*; D017078:Laser-Doppler Flowmetry; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009043:Motor Activity / Q000187:drug effects; D009460:Neurologic Examination; D018696:Neuroprotective Agents / Q000008:administration & dosage*; D011499:Protein Processing, Post-Translational; D017966:Pyramidal Cells / Q000187:drug effects* / Q000378:metabolism / Q000473:pathology; D012039:Regional Blood Flow / Q000187:drug effects; D015427:Reperfusion Injury / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D013997:Time Factors; D057149:Ubiquitinated Proteins / Q000378:metabolism*; D054875:Ubiquitination
D018696:Neuroprotective Agents; D057149:Ubiquitinated Proteins; D007530:Isoflurane