RESUMO
Objective To study the effect and mechanism of endoplasmic reticulum stress on hippocampal neuron apoptosis and cognitive impairment in type 1 diabetic rats. Methods Ten rats were randomly selected as normal control group (Con group) from thirty Wistar rats, and the remaining twenty rats were intraperitoneally injected with streptozotocin to prepared for type 1 diabetic rat model. The successful model rats were randomly divided into diabetic group (DM group) and diabetic +Salubrinal group (DM+Sal group). Rats of DM+Sal group were injected by lateral ventricle with Salubrinal ( 75μmol/L, 1μL). Rats of Con group and DM group were given the equal volume of normal saline. The rat cognitive function was assayed by Morris water maze test. The hippocampal neuron apoptosis was detected by TUNEL and flow cytometry methods. The protein levels of endoplasmic reticulum stress markers, GRP78, CHOP and Caspase12, and the mRNA levels of GRP78 and CHOP, were examined by Western blot assay and Real-time PCR, respectively. Results Compared with the Con group, the cognitive function was significantly decreased in DM group, and the apoptotic rate of hippocampal neurons was increased. The protein levels of endoplasmic reticulum stress markers GRP78, CHOP and Caspase12 were significantly increased (P<0.05), and the mRNA levels of GRP78 and CHOP were also higher in DM group (P<0.05). After the injection with Salubrinal, the cognitive function was improved and hippocampal neuron apoptotic rate was decreased in DM+Sal group compared with those of DM group. Moreover, the protein levels of GRP78, CHOP and Caspase12 were significantly decreased (P<0.05) and the mRNA levels of GRP78 and CHOP were also lowered in DM+Sal group (P<0.05). Conclusion The cognitive impairment and the higher apoptotic rate appear in the diabetic rats, and endoplasmic reticulum stress may play an important role in it.