Autophagy activation is involved in neuroprotection induced
by hyperbaric oxygen preconditioning against focal cerebral
ischemia in rats
, Haopeng Zhang
, Xiaoguang Bai, Yan Lu, Hailong Dong, Lize Xiong
Department of Anesthesiology, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, China
ARTICLE INFO ABSTRACT
Accepted 20 May 2011
Available online 27 May 2011
Our previous studies have demonstrated that hyperbaric oxygen (HBO) preconditioning
induces tolerance to focal cerebral ischemia. The present study aimed to investigate
whether autophagy is involved in the neuroprotection elicited by HBO preconditioning in a
rat model of transient focal cerebral ischemia. Twenty-four hours after the completion of
HBO preconditioning (2.5 atm absolute in 100% oxygen for 60 min per day for 5 consecutive
days), male Sprague–Dawley rats were subjected to focal cerebral ischemia by middle
cerebral artery occlusion (MCAO) for 120 min. The neurobehavioral score and infarct volume
were used to evaluate cerebral ischemic injury. An intracerebroventricular injection of the
autophagy inhibitor 3-methyladenine (3-MA) or the autophagy inducer rapamycin was
administered before HBO preconditioning or MCAO. We found that after reperfusion the
protein expression of LC3-II and Beclin 1 and the formation of autophagosomes were
increased by HBO preconditioning or ischemia, but the increase following HBO
preconditioning was higher than the increase following ischemia. 3-MA suppressed the
increases in LC3-II and Beclin 1 induced by HBO preconditioning and attenuated the
neuroprotection of HBO preconditioning against cerebral ischemia. Furthermore, 3-MA
treatment before MCAO aggravated subsequent cerebral ischemic injury. In contrast,
pretreatment with rapamycin up-regulated LC3-II and Beclin 1 after reperfusion and
mimicked the neuroprotective effect of HBO preconditioning. These results indicate that
HBO preconditioning elevates autophagic activity, which elicits a neuroprotective effect
against ischemic injury in the brain, and suggest a novel mechanism of HBO
preconditioning-induced tolerance against transient focal cerebral ischemia.
© 2011 Elsevier B.V. All rights reserved.
BRAIN RESEARCH 1402 (2011) 109– 121
⁎ Corresponding author at: Department of Anesthesiology, Xijing Hospital, Fourth Military Medical University, Xi'an 710032, Shaanxi
Province, China. Fax: +86 29 83244986.
E-mail address: email@example.com (L. Xiong).
Abbreviations: ANOVA, analysis of variance; ATA, atmospheres absolute; CBF, cerebral blood flow; HBO, hyperbaric oxygen; i.c.v.,
intracerebroventricular; IPC, ischemic preconditioning; LC3, microtubule-associated protein 1 light chain 3; 3-MA, 3-methyladenine;
MCAO, middle cerebral artery occlusion; mTOR, mammalian target of rapamycin; PI3K, phosphatidylinositol 3-kinase; RAP, rapamycin;
ROS, reactive oxygen species; TTC, 2,3,5-triphenyltetrazolium chloride
These authors contributed equally to this work.
0006-8993/$ – see front matter © 2011 Elsevier B.V. All rights reserved.
available at www.sciencedirect.com