Early and delayed reaction of the Hif-1α protein in the hippocampal fields on ischemia-reperfusion in rats with streptozotocin-induced diabetes mellitus

Abstract

Background. The role of the transcriptional hypoxia-inducible factor-1α (Hif-1α) in the pathogenesis of hypoxic damage and diabetes mellitus (DM) is proved, although molecular mechanisms underlying dysfunction of this factor, when DM is combined with ischemic-reperfusion damage of the brain, remain unknown. The purpose was to study the content of Hif-1α protein in the hippocampal neurons of rats with experimental DM in the dynamics of ischemic-reperfusion damage of the brain. Materials and methods. The study was performed on 6-month-old rats with DM modeled by single administration of 60 mg/kg weight streptozotocin (Sigma, USA). The cerebrovascular disorders were reproduced by occlusion of both carotid arteries for 20 minutes. The content of Hif1-α protein was determined by immunofluorescence method after 20-minute ischemia with one-hour reperfusion, and on the 12th day of the post-ischemiс period in the fields CA1, CA2, CA3, and CA4 of the hippocampus. Results. In rats without DM, 20-minute ische­mia with one-hour reperfusion increases the content of Hif-1α protein in all the fields of the hippocampus. On the 12th day of ischemic-reperfusion period, the values of certain examined indices of transcriptional Hif-1α activity continue to increase in the hippocampal fields CA2-CA4, and in СА1 field they normalize or approach to the values of animals in the control group. In rats with DM during early post-ischemic period, there are no changes of Hif-1α protein content in CA1 field, in CA2 field there are signs of its reduced activity, in CA3 field they are limited by the reaction of one index, in CA4 field they are similar to those of the control rats under experimental conditions. On the 12th day of ischemic-reperfusion period, all the indices of transcriptional Hif-1α activity in CA1 field increase exceeding the corresponding indices in animals of the control group by absolute values under the same experimental conditions. In СА2 and СА3 fields, changes of the examined parameters are limited as compared to those in animals from the control group, in CA4 field, the values that were increased in the control group decrease. Conclusions. DM restricts the reaction of Hif-1α protein on ischemia-reperfusion in the neurons of СА1-СА3 fields in the early ischemic-reperfusion period and in the neurons of СА2-СА4 fields — on the 12th day of observation.

Keywords

• diabetes mellitus
• cerebral ischemia-reperfusion
• Hif-1α protein