mRNA expression of bcl-2, bax, p53, and interleukin-1 beta hydroxylase in rat brain following repeated high positive acceleration exposure

Hongjin LIU; Qing CAI; Shuqiang JIANG; Jiandong JIANG

ABSTRACT

BACKGROUND:

Brain injury can be induced by repeated high positive acceleration ( + Gz) exposure, but the mechanism was still unclear.

OBJECTIVE:

To investigate the role of apoptosis in higher + Gz exposures induced brain injury by observing the changes of mRNA expression of bcl-2,bax, p53, and interleukin-1β(IL-1β) hydroxylase in rat brain.

DESIGN:

Randomized control experimental study based on experimental SD rat model.

SETTING:

Aviation medicine research center of a hospital.MATERIALS Twenty-six healthy male SD rats, weighed from 180 to 220 g,were randomly divided into control group(4 rats) and + Gz exposure group (22 rats).

INTERVENTIONS:

Rats were fixed on the rotating arm of animal centrifuger with their heads towards axis. Rats in + Gz exposure group were exposed to + 14 Gz for three times, each for 45 seconds with 30 minutes interval in between. Rats in control group were subject to the same experiment in + 1 Gz. The rat brains were taken 30 minutes, 6 hours, 24 hours and 48 hours after the last centrifuge run, and then fixed and embedded. Changes of bcl-2, bax, p53, and IL-1β hydroxylasein mRNA expressions in rat brain were measured with semi-quantitative reverse transcription polymerase chain reaction(RT-PCR) . Apoptotic cells were detected by terminal deoxynucleotide(correction of deoxynuleotide) transferase-mediated dUTP nick end labeling(TUNEL) technique.MAIN OUTCOME

MEASURES:

The changes of bcl-2, bax, p53, and IL-1 β hydroxyalse mRNA expressions at each time points.

RESULTS:

After repeated + Gz exposures for 6 hours, bcl-2 mRNA expression in rat brain tissue(0. 32 ± 0. 08) was found significantly lower than in control group(0. 69 ± 0. 15), while mRNA expressions of bax, p53, and interleukin-1β converting enzyme(ICE) 0.55 ±0. 09, 0. 48 ±0. 12, 0.79 ±0. 12were significantly higher than in control group 0.33 ±0. 09, 0. 31 ±0.05,0.51 ± 0.09 ( P ＜ 0. 01 ) . After 24 hours of exposure, mRNA expression of bcl-2 in rat brain tissue (0. 28 ± 0.05) was significantly lower than in control group, while the mRNA expressions of bax, p53, and ICE 0.61 ±0. 15,0.54 ± 0. 07, 0. 84 ± 0. 15 were significantly higher than in control group ( P ＜ 0.01); but the difference of brain bcl-2, bax, p53 and ICE mRNA expressions had no statistical significance when exposed for 0.5 hour and 48 hours( P ＞ 0.05). Partly apoptotic cells were observed at exposure for 6 hours and 24 hours.

CONCLUSION:

Changes of bcl-2, bax, p53 and ICE mRNA expressions, as well as apoptosis in rats brain can be induced by repeated + Gz exposures and may be involved in the molecular mechanisms of brain injury.