Effects of Repetitive Ischemic Preconditioning on the Phosphorylation of Akt and Expression of HSP72 and HSP90 in the Rat Tibialis Anterior and Soleus Muscles

Seo, Youn Kyoung; Seo, Dae Yong; Jeon, Su Kyoung; Park, Hyun Joo; Paik, Doo Jin

Abstract

Akt, heat shock protein (HSP72)72, and HSP90 induced by ischemic preconditioning protect cells from the ischemic injury. The purpose of this study was to examine the alterations of the level of phospho-Akt, HSP72, and HSP90 in the rat tibialis anterior and soleus muscles after cyclic episodes of ischemic preconditioning. Sprague-Dawley rats aged 35 weeks were divided into control and ischemic preconditioning (IP) groups. The IP group was divided into 3 subgroups based on cycles of IP. Left common iliac artery was occluded 3, 6, and 10 times for 5 minutes, followed by 5 minutes reperfusion. The experimental animals were sacrificed at 0, 3, 6, 24, and 72 hours after reperfusion, and left tibialis anterior and soleus muscles were removed. The expression of phospho-Akt, HSP72, and HSP90 were examined with immunohistochemical methods and Western blot analysis. The results were as follows; 1. In the 3 and 6 times of IP groups, the expression of phospho-Akt (p-Akt) was increased at 0 and 3 hours after reperfusion, compared with control group. The expression of p-Akt in the 10 times of IP group was lower than that in 3 and 6 times of IP groups. At 72 hours after reperfusion, the expression of p-Akt showed no difference among the IP groups. The expression of p-Akt was higher in Soleus than that in Tibialis anterior. 2. The expression of HSP72 in 3 times of IP group increased at 0 and 3 hours after reperfusion, compared with 6 and 10 times of IP groups. The expression of HSP72 in the 10 times of IP group was lower than that in 3 and 6 times of IP groups. At 72 hours after reperfusion, the expression of HSP72 showed no difference among the IP groups. The expression of HSP72 was higher in Soleus than that in Tibialis anterior. 3. In the 3 and 6 times of IP groups, the expression of HSP90 increased at 0 and 3 hours after reperfusion, compared with control group. The expression of HSP90 in the 10 times of IP group was lower than that in 3 and 6 times of IP groups. At 24 hours after reperfusion, the expression of HSP90 showed no difference with increasing episode of IP. The expression level of HSP90 was higher in Soleus than that in Tibialis anterior. These findings suggest that ischemic preconditioning increases the expression of p-Akt, HSP72 and HSP90 at early phase after reperfusion in the rat tibialis anterior and soleus muscles. However, increased cycles of ischemic preconditioning may not induce the expression of them.