Optimal time window selection in hyperbaric oxygen treatment for rat transient global cerebral ischemia on the basis of neuron-specific enolase bioactivity changes

Tianhui LIU; Rui CHEN; Yanguo TAN

ABSTRACT

BACKGROUND:

The level of blood neuron-specific enolase may help predict the severity of brain damage.

OBJECTIVE:

To define the optimal time window of hyperbaric oxygen(HBO) treatment for brain ischemia based on the dynamical changes in plasma neuron-specific enolase bioactivity.

DESIGN:

Factorial design.

SETTING:

Department of Biochemistry and Molecular Biology of Capital University of Medical Sciences.

PARTICIPANTS:

The experiment was conducted in the Laboratory of the Department of Hyperbaric Oxygen, Beijing Chaoyang Hospital Affiliated to Capital University of Medical Sciences in June 2002. Totally 54 adult female SD rats were randomized into 3 groups, namely sham operation group(n=6), ischemia-reperfusion (IR) group (n=24), and HBO group (n=24), the latter 2 groups further divided into 4 groups according to the reperfusion time of 6, 24, 48 and 96 hours, with 6 rats in each subgroup.

METHODS:

[1] Rat models of IR was prepared by occlusion of the 4 arteries for 20 minutes followed by reperfusion for different time. [2] The rats in the sham operation received the same operation without blocking the arteries. The rats in HBO group were subjected to HBO treatment (0.2 MPa,pure oxygen for 45 minutes), which was given after a 3-hour reperfusion inthe 6-hour subgroup and scheduled once daily at the same time point in the other 3 subgroups until blood sampling. The rats in IR group and sham operation group were kept under normal pressure without additional oxygen.MAIN OUTCOME

MEASURES:

Blood samples were collected at the specified time points in IR and HBO groups and at 24 hours of reperfusion in the sham operation group. Enzyme-linked immunosorbent assay (ELISA)was used to determine the activity of plasma neuron-specific enolase.

RESULTS:

Totally 54 rats enter result analysis after supplementary.Plasma neuron-specific enolase level was significantly lower in the sham operation group (1.97±0.09) μg/L than in 6 and 96-hour subgroups in the IR group [(2.80±0.26), (2.40±0.19) μg/L, respectively, P ＜ 0.05],and was obviously lower in 6-hour HBO subgroup than the 6-hour IR group [(2.04±0.27) μg/L, P ＜ 0.05], which was slightly increased at 24hours after HBO treatment but the difference was of no statistical significance (P ＞ 0.05).

CONCLUSION:

IR injury may lead to increment of plasma neuron-specific enolase level, which occurred at 6 and 96 hours respectively in IR group, possibly due to acute neuronal necrosis during brain ischemia and subsequent delayed neuronal apoptosis. HBO treatment promotes the recovery of neuron-specific enolase level, with 6 hours of reperfusion as the optimal therapeutic time window.