Objective  To investigate the effect of magnesium sulfate on neuron apoptosis and expression of caspase-3，bax and bcl-2 after cerebral ischemia/reperfusion injury.

Methods  Thirty six gerbils were randomly divided into three groups: ischemia/reperfusion Group (I/R, n=12), the bilateral common carotid arteries were occluded with aneurysm clips for 10 min, then the clips were removed for blood reperfusion; magnesium sulfate group (Ms, n=12), magnesium sulfate(2g/kg) was injected intraperitoneally 30 min before arterial occlusion; Sham-operation group (So, n=12), gerbils were operated on without occluding the arteries. The neuron apoptosis was assessed by TUNEL assay. The protein expression of caspase-3, bax and bcl-2 was detected by immunohistochemisty stain.

Results  Apoptotic neurons and the expression of caspase-3 and bax in groups I/R and Ms were significantly higher than those in group So(P<0.01). However, apoptotic neurons and expression of bax and caspase-3 in group Ms were greatly less than those in group I/R(P<0.01). There was no significant difference in the bcl-2 expression lever among three groups(P>0.05).

Conclusions  Magnesium sulfate could reduce neuron apoptosis through suppression of the expression of caspase-3 and bax genes after cerebral ischemia/reperfusion injury.

Apoptosis, or programmed cell death, is a normal component of the development and health of multicellular organisms. Neuronal apotosis, which plays an essential role in secondary neuronal loss after acute brain injury, is mediated by apoptosis-specific genes, certain oncogens and tumour suppressor genes. It is well known that the expression of bax, bcl-2 and caspase-3 plays important roles during apoptosis. In the present study, we investigated the effect of magnesium sulfate on neuron apoptosis and expression of caspase-3，bax and bcl-2 after cerebral ischemia/reperfusion injury.

MATERIAL AND METHODS

Animals and grouping

Thirty six gerbils weighting 50～60g were randomly divided into three groups: Sham-operation group (So, n =12), ischemia/reperfusion Group (I/R, n =12) and magnesium sulfate group (Ms, n =12).

Anesthesia and surgical procedures

Gerbils were anesthetized with sodium pentobarbital(45mg/kg) through intraperitoneal injection. The rectal temperature of the animals was monitored and maintained at 37± 1℃. The bilateral common carotid arteries of the gerbils were isolated. In group I/R, the bilateral common carotid arteries were occluded with aneurysm clips for 10 min. The clips were then removed for blood reperfusion. In group Ms, magnesium sulfate(2g/kg) was injected intraperitoneally 30 min before arterial occlusion. And in group So, gerbils were operated on without occluding the arteries. All the gerbils were anesthetized with sodium pentobarbital again, and their brains were collected 12h, 24h and 48h, respectively, after reperfusion.

TUNEL assay

The neuron apoptosis was detected by TUNEL[the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-fluorescence nick end labeling] method through which DNA fragmentation of apoptotic cells can be assessed in situ in tissue sections by incorporating fluorescein-12-dUTP at the 3’-OH ends of the DNA. Apoptotic cells were counted under fluorescence microscope.