p35 and p25 expressions and Cdk5 kinase activity in primary cultured rat hippocampal neurons with X-ray exposure

Objective To study the expressions of p35 and p25 and Cdk5 kinase activity in cultured rats hippocampal neurons following X-ray exposure to provide experimental evidence for prevention and treatment of radiation encephalopathy.Methods The hippocampal neurons cultured for 12 days were subjected to a single-dose X-ray exposure of 30 Gy.Western blotting was used to detect the p35 and p25 protein levels,and the effect of pretreatment with roscovitine,a Cdk5 inhibitor,on the apoptosis of the hippocampal neurons following the exposure was examined with 4',6-diamidino-2-phenylindole(DAPI) staining.Results The protein level of p35 increased significantly 3.5 and 4 h after the irradiation by 1.51±0.13 and 1.45±0.14 folds in comparison with the control level,respectively(P0.01),and the p25 level increased significantly 6 h after irradiation by 1.62±0.28 folds(P0.05).Nuclear condensation occurred in(24.8±3.97)% of the neurons 24 h after 30 Gy X-ray exposure,a rate significantly higher than that in the nonexposed cells [(1.82±1.08)%,P0.01) and that in roscovitine-pretreated neurons [(7.74±2.27)%,P0.01).Conclusion X-ray exposure activates Cdk5 by increasing the p35 and p25 expressions in rat hippocampal neurons,and inhibition of Cdk5 activity with roscovitine can significantly protect the neurons from apoptosis.