Cerebral ischemia reduces expression of Hs1-associated protein X-1 (Hax-1) in mouse brain.

Hax-1, a multi-functional protein, recently was found to be involved in apoptosis and nerve system development. The purpose of this study was to detect the effect of cerebral ischemia on Hax-1 expression. We have detected the expression of Hax-1 in normal brain tissue and in ischemic brain tissue. Hax-1 was expressed in all brain regions detected with a level similar to the level of β-actin. There were no differences in the expression of Hax-1 in different brain regions detected. The confocal images confirmed that neurons expressed Hax-1. The results of ischemic stroke in vivo indicated that Hax-1 level was significantly reduced at 24h after ischemia in the ischemic hemisphere, which was only 37%±4.8 of healthy hemisphere (p<0.05), and there was a strong reverse correlation between the level of Hax-1 and infarct size indicated by the regress analysis (R(2)=0.84). The expression of Hax-1 was also reduced in the cells subjected to oxygen/glucose deprivation (OGD) (p<0.01). The expression of Hax-1 was 87%±4.6, 78%±4.9 and 54%±8.2 of control in the murine brain endothelial cell (bEND5 cell) at 1h, 2h and 16h OGD, respectively. The Hax-1 level was 82%±7.3 and 61%±8.1 of control in neuronal cell line (neuro-2a cells) at 5h and 12h OGD, respectively. The percentage of neuro-2a cell death was 40%±11 induced by a 5h of OGD compared to only 10%±4.2 cell death in the control group (p<0.01). Our present study provides preliminary evidence of the effect of cerebral ischemia on Hax-1 expression. The expression of Hax-1 in normal brain tissue and reduction of Hax-1 in ischemic brain tissue indicate its possible involvement in pathophysiological functions in the brain.