The Effect Of Preconditioning With Lithium On The Living Neuron Density And The Expressions Of HSP70 And Bcl-2 Proteins In Gerbil After Global Ischemia

Objective To investigate the effect of preconditioning with lithium on the living neuron density in hippocampus and the expressions of HSP70 and Bcl-2 proteins in gerbil after global ischemia. Methods The transient ischemia model of gerbil global was established by clamping the bilateral common carotid arteries for 5 mm. 72 gerbils were randomly divided into group A (n=36) and group B (n=36). Gerbils in group A were injected intraperitoneally with lithium, 5mmol/kg, once a day for 5 consecutive days. Normal saline was used instead of lithium in group B as vehicle control. Both group A and B were further divided into 6 subgroups (n=6, in each subgroup). The subgroups in group A were: Aisl, underwent ischemia and killed 1 day after operation; Ashl, sham-operated and killed 1 day after operation; Ais3, underwent ischemia and killed 3 days after operation; Ash3, sham-operated and killed 3 days after operation; Ais7, underwent ischemia and killed 7 days after operation; Ash7, sham-operated and killed 7 days after operation. Treated as those in group A, the subgroups in groupB were: Bisl, Bshl, Bis3, Bsh3, Bis7 and Bsh7, with 6 gerbils each. All gerbils were perfusion-fixed and the brainswere made into 3 sets of paraffin sections. One set was stained by hematoxylin and eosin to determine the density of neurons in the hippocampal CAl region under light microscopy blindly. The other two sets were used for immunohistochemistry against HSP70 and Bcl-2. The results were analyzed with computerized image analysis system. All data were expressed as mean + SD. Statistical analysis was performed using SPSS10.0 and P value <0.05 was considered significant.Results (1) Histopathologically, the density of the pyramidal cells in the CAl region was decreasing time-dependently in an order of subgroups Aisl and Bisl>Ais3 and Bis3>Ais7 and Bis7. The living neuron density in the CAl region of subgroup Aisl was significantly higher than that of subgroup Bisl (P<0.01). Similarly the living neuron density of subgroup Ais3 and Ais7 was significantly higher than that of Bis3 and Bis7 (P<0.01).The numbers of the pyramidal cells(cells/mm2) in the CAl region were 470.59?127.02in Aisl, 395.14 + 82.74 in Ais3, 338.54+130.61 in Ais7, 370.82+92.85in Bisl, 295.19+114.50 in Bis3, 33.11+23.14 in Bis7 respectively. (2) HSP70 expression was seen in both the hippocampus and the cortex in subgroups Aisl and Bisl. Compared with the vehicle control, the HSP70 expression was decreased in the hippocampus CA1(P<0.05) but increased in the cortex(P<0.01) in lithium-treated group. The Bcl-2 expression was upregulated in the cortex(P<0.05) in all of the lithium-treated groups. Conclusions (1) Preconditioning with lithium may attenuate the delayed neuron death after global forebrain in gerbil. (2) HSP70 is a indirectly injury marker. (3) Upregulation of the protein of Bcl-2 is one of the mechanisms underlying the neuroprotective effect of lithium.