Expression Of Starvation On Cerebral Cortical Apoptosis And Its Related Factors In Rats

Objectives To study the changes of cortical apoptosis-related factors as Bcl-2, Bax and Caspase-3 expression after starvation in rats.Methods Ninety adult male SD rats were divided randomly into 6 groups: blank control group, 3d, 5d, 7d, 9d and 11 d starvation groups, 15 rats in each group. And each group were subdivided randomly into three subgroups I, II, III, 5 rats in each subgroup. Subgroup I was used to detect the apoptosis of rat cortex by HE staining morphological comparison and TUNEL method; subgroup II to detect cortex Bcl-2, Bax, Caspase-3 m RNA and protein expression by RT-PCR and Western blot method; subgroup III to detect the water content of the brain using dry wet weight ratio method.Results 1 General behavior: The rats were not changed in 3d and 5d starvation groups,but the rates in 7d, 9d and 11 d starvation group were extreme weak and unresponsive to stimulation. 2 The changes of body weight: There were no significant differences in body weight among the groups before starvation(P>0.05). Along with the starvation time prolonged, the body weight of rats gradually reduced. 3 HE staining of cortex neurons: The neurons of cortex region were arranged in order, with deep cytoplasmic staining and plenty of nerve fibers in normal control group, 3d and 5d starvation groups, but were arranged disordered, with widened intercellular space, decreased number of cells and light cytopasmic staining in 7d, 9d and 11 d starvation groups. 4 TUNEL-positive neurons in cortex region: No significant difference in percentage of TUNEL-positive neurons in cortex region were observed between normal control group and 3d starvation group(P>0.05). The percentage of TUNEL-positive neurons in cortex region were relatively increased in the 5d starvation group(P<0.05) and were significantly increased in 7d, 9d and11 d starvation groups compared with normal control group(P<0.01). The results implied that the neuron apoptosis in cortex region became more and more serious along with the period of starvation prolonged. 5 RT-PCR method to detect the rat cortex Bcl-2, Bax,Caspase-3 m RNA expression results: Bax and Caspase-3 expression in cerebral cortex were significantly raised in all four starvation groups(P<0.01). Bcl-2 expression was raised in 3d, 5d and 7d starvation groups, compared with controls(P<0.01), with the heighest expression in 5d group. Bcl-2 expression decreased in 9d, 11 d starvation groups(P<0.01), with the lowest expression in 11 d starvation group. 6 Western blot method to detect the rat cortex Bcl-2, Bax, Caspase-3 protein expression results: Bax and Caspase-3 expression in cerebral cortex were significantly raised in all four starvation groups(P<0.05 in 5d, P<0.01 in 7d, 9d, 11 d groups). Bcl-2 expression was raised in 3d,5d and 7d starvation groups, compared with controls(P<0.01), with the heighest expression in 5d group. Bcl-2 expression decreased in 9d, 11 d starvation groups(P<0.01),with the lowest expression in 11 d starvation group. 7 The experimental results of dry/wet weight method: Compared with the normal controls, there was no obvious increase in brain tissue water content in 3d starvation group, but increased in 5d starvation group(P<0.01),and decreased in 7d, 9d and 11 d groups(P< 0.01).Conclusions 1 The apoptosis of rat cortex begin to increase from the 5th day of starvation. 2 Short-term starvation stress may have certain brain protection function, and long-term starvation stress may cause severe cortical cell apoptosis and lead to brain damage. 3 Bcl-2,Bax and Caspase-3 play the important role in apoptosis regulation during starvation stress.