Hyperthermia aggravates focal cerebral ischemiareperfusion injury in rats by up-regulating cathespin L expression

Abstract

Objective To investigate the effect of hyperthermia on expression of cathespin L(CTSL) in focal cerebral ischemia-reperfusion injury of rats and its mechanism in ischemia injury. Methods A total of 100 male Sprague-Dawley rats were randomly divided into sham-operated group(n=20), normothermia group (n=40) and hyperthermia group (giving constant temperature heating for 39 ℃, n=40); rats in the sham-operated group and normothermia group were given constant temperature heating for 37.5 ℃. Models of middle cerebral occlusion reperfusion in the later two groups were induced by intraluminal suture method. Both the normothermia and hyperthermia groups were sub-divided into 3 time point groups: ischemia for one h and reperfusion for 3, 6 and 24 h (n=10, 10 and 20). At 24 h after reperfusion, the neurological deficit scores, volume of infarction and brain water content were assessed. At 3, 6, and 24 h after reperfusion, the expression of CTSL in ischemic brain tissues was measured by Western blotting and immunohistochemical staining. Results At 24 h after reperfusion, the mean neurological deficit scores, volume of infarction and brain water content in the hyperthermia groups were significantly higher than those in the normothermia groups (3 h: 3.37±0.48 vs. 2.20±0.42, 6 h: 59.08%±0.98% vs. 24 h: 37.96%±0.16% and 84.82%±1.79% vs. 82.18%±0.45%, P< 0.05). Western blotting showed that CTSL expression did not change at each time point in the normothermia group, while the CTSL expression in the hyperthermia group was significantly higher than that in the normothermia group at each time point, respectively (P<0.05). CTSL expressed in neuron and glia of sham-operated group delected by immunohistochemistry, especially in glia. As compared with that in the sham-operated group, glia CTSL integrated optical density/accumulated positive cell area (IOD/area) began to decrease in the normothermia group at 24 h after reperfusion; neuron CTSL IOD/area began to increase at 3 h, reached to the summit at 6 h, and then, decreased at 24 h (P<0.05). At each time point, neuron CTSL IOD/area in the hyperthermia group was significantly higher than that in the normothermia group (P< 0.05). Conclusion Hyperthermia can probably worsen the brain edema and damage by up-regulating CTSL expression after ischemia/reperfusion. Key words: Cerebral ischemia; Hyperthermia; Cathespin L; Middle cerebral artery occlusion