The Effect Of Expression Of Cyclins And CDKs On The Apoptosis Of Ischemic Neurons

Objective: 1. To observe the effects of radix salviae miltiorrhizae (RSM) and Flavopiridol on the expression of cyclin Dl, cyclin G1, cdk4 protein and neuronal apoptosis in different intervals following permanent focal cerebral ischemia in rats. 2. To observe the effects of radix salviae miltiorrhizae (RSM) on the expression of cyclin Dl mRNA. Methods: 1. 315 male adult Sprague-Dawley rats were randomly divided into sham- operated group, ischemia group, RSM group, FH (high dose Flavopiridol) group and FL (low dose Flavopiridol) group. The RSM group of rats were treated 30 minutes before and 24h, 48h after the operation in a dose of lOg/kg weight with RSM,; The FH group were treated 30 minutes before and 24h, 48h after the operation in a dose of 2>( 1 0mol/kg weight with Flavopiridol by the intracerebroventricular injection, and the FL group in a dose of 1 ×1 0^-4 mind/kg weight. 2. A model of the middle cerebral artery occlusion (MCAO) in rats was performed with intraluminal filament occlusion. The inimunobistochemistry and TUNEL staining was respectively used to observe the distribution and quantities of cyclin Dl, cyclin G1, cdk4 protein and neuronal apoptosis in the brain tissues in every group. RT-PCR was used to study the expression of cyclin Dl mRNA at ischemic hemisphere. Result: 1. The significant increase in cyclin G 1, cyclin Dl and cdk4 immunostaining and TIJNEL positive staining was detected at lh, 6h, 12h and 12h after MCAO in the neurons of the ischemia penumbra respectively. They were most marked at 3h, 48h, 48h and 72h after MCAO respectively. The RSM could decrease the expression of cyclin Dl, cdk4 protein and TUNEL positive staining significantly. But the express of cyclin G1 protein could be increased by RSM at 1 2h after MCAO significantly. In FH and FL groups, the decrease of expression of cyclin Dl and cdk4 protein was significant, and the significant decrease of TUNEL positive staining was observed at every time-point of FL group, but only at 24h time-point of FH group. 2. The significant increase in cyclin Dl mRNA was observed at 6h after MCAO, and was most marked at 72h after MCAO. The difference among the ischemia group and the RSM group was significant. Conclusion: 1. The induction of cyclin Dl protein, mRNA and cdk4 protein at the ischemia penumbra indicated they might involve in the mechanism of neuronal apoptosis. RSM and Flavopiridol might reduce the neuronal apoptosis through down - regulating or inhibit the expression of cyclin Dl and cdk4, but Flavopiridol itself could induce apoptosis of normal neuron. 2. There was no relationship between the increase expression of cyclin Gl protein after neural ischemia and the neural apoptosis. Maybe it might participate in the DNA repairing mechanisms and an adaptive response to cellular stress induced by focal cerebral ischemia. RSM could protect the ischemic neurons by up- regulating the expression of cyclin 01 protein.