The correlation between mRNA and protein expression of bax and bcl-xL follo wing fluid percussion brain injury in rats / 第二军医大学学报

ABSTRACT

Objective: To investigate the alterations of bcl-2 gene family in the rat brain and the molecular mechanism of neuronal apoptosis follow ing traumatic brain injury (TBI). Methods: Male Sprague-Dawley rats were subjected to lateral fluid percussion brain injury(FPBI) of moderate severity. bax and bcl-xL mRNA and protein expression was detected by RT-PCR an d immunohistochemistry. In addition to morphological evidence of apoptosis, TUNE L histochemistry was used to identify DNA fragmentation in situ under both l ight and electron microscope, whereas characteristic internucleosomal DN A fragm entation of apoptosis was demonstrated by DNA gel electrophoresis. Resul ts bcl-xL mRNA and protein decreased in the ipsilateral hemisphere t o the impact site as early as 6 h post-injury［(67.42±7.54)% and (85.85±5.72)% r espectively］. The decrease in bcl-xL mRNA and protein preceded apoptosis was observed 12 h post-injury. And this was the main cause of up-regulation of the ratio of bax to bcl-xL in the acute period(minutes-hours) followin g FPBI. bax mRNA and protein were observed to rise slowly, doubled 3 d post- injury, returned to sham level slowly. The delayed cell death (days-weeks) migh t associated with the up-regulation of pro-apoptotic gene bax. Conclusio n The expression of bcl-xL and bax coincide with apoptosis following TBI. The reg ulation of bax and bcl-xL by TBI occur before transcription. The balance of bax/bcl-xL ratio determines the neurocytes to survive or die following FPBI.