Triptolide for cerebral ischemia/reperfusion injury

　BACKGROUND: Studies have demonstrated that triptolide has good anti-inflammatory and immunosuppressive effects. However, the effect of triptolide on cerebral ischemia/reperfusion injury is still unclear. OBJECTIVE: To observe the effects of triptolide on neurologic function, infarct volume, water content of brain tissue, neutrophil number in microvascular wall and interleukin-1β(IL-1β) expression in rat models of local ischemia/reperfusion, and analyze the mechanism of triptolide for protecting brain. DESIGN: Randomized controlled experiment. SETTING: Department of Pathology, Medical School of Ningbo University; Department of Forensic Medicine, Tongji Medical College of Huazhong University of Science and Technology. MATERIALS: Sixty Wistar rats of either gender, aged 4 months old, weighing from 200 to 250 g, were provided by the Experimental Animal Center, Tongji Medical College, Huazhong University of Science and Technology. Triptolide was purchased from Fujian Institute for Medical Science (purity 99.98%; Batch No. 2000215). It was dissolved in 20 g/L propanediol, and filtered with 200-mesh filter for later use. METHODS: This experiment was carried out in the laboratory of Forensic Medicine, Tongji Medical College of Huazhong University of Science and Technology, Department of Pathology, Medical School of Ningbo University between January 2001 and September 2004. ① Sixty Wistar rats were randomized into 4 groups: sham-operation group, model group, low-dose triptolide group and high-dose triptolide group. Rats in each group, except for sham-operation group, were developed into rat models of cerebral ischemia/reperfusion according to the method of Longa et al. In the first 3 days of modeling, rats in the low- and high-dose triptolide groups were intraperitoneally injected with 0.2 and 0.4 mg/kg triptolide respectively, once a day, 3 days in total. ② At ischemia 1 hour and reperfusion 24 hours, infarct volume, neurologic deficit (five-point scale, higher scores indicated poor neurologic function), water content of brain tissue, neutrophil number in microvascular wall in the middle cerebral artery occlusive side of rats were detected, meanwhile, brain tissue injury degree and IL-1βimmunohistochemical staining changes in brain-derived nerve cells were observed under the optical microscope. MAIN OUTCOME MEASURES: Neurologic deficit, infarct volume percentage, water content of brain tissue, neutrophil number in microvascular wall and positive rate of IL-1β immunoreaction. RESULTS: Sixty rats were all involved in the final analysis. ① Neurologic deficit scores of rats in the low- and high-dose triptolide groups were (1.96±0.14) and (1.75±0.16)points respectively , which were both significantly lower than those in model group [(2.58±0.11)points,P < 0.05,0.01]. ② Infarct volume percentages of rats in low- and high-dose triptolide groups were significantly lower than that in model group separately (P < 0.05, 0.01). ③Water content of brain tissue of rats in model group was significantly higher than that in the sham-operation group [(82.35±1.26)% vs. (76.65±1.17)%,P < 0.01]; Water content of brain tissue of rats in the low- and high-dose triptolide groups was respectively(80.15±1.43)%,(78.23± 1.15)%, which was significantly lower than that in the model group (P < 0.05, 0.01). ④Pathological changes of brain tissue of rats: Under the optical microscope, infarct focus was not found in the brain tissue of rats in the sham-operation group, while clear infarct focus could be found in the brain tissue of rats in the model group; Although infarct focus was found in the brain tissue of rats in the low- and high-dose triptolide groups, the whole infarct area was contracted as compared as that in the model group. ⑤Neutrophil number in microvascular wall of brain tissue of rats in the low- and high dose triptolide groups was 10.60± 2.12,8.11±1.21 respectively, which was significantly less than that in model group(16.25±1.96,P < 0.05, 0.01). ⑥Positive rate of IL-1βimmunoreaction in the brain tissue of rats in model group was significantly higher than that in the sham-operation group (P < 0.01); and positive rate of IL-1β immunoreaction in the brain tissue of rats in low- and high-dose triptolide groups was significantly lower than that in the model group (P < 0.05, 0.01), but higher than that in the sham-operation group, withoutsignificant difference (P > 0.05). CONCLUSION: Triptolide protects against cerebral ischemia/reperfusion injury of rats that may be related with anti-inflammations. Triptolide inhibits IL-1β expression in brain tissue and reduces the attachment and aggregation of neutrophils in blood capillary, and further inhibits the infiltration of blood white cells, thus, it will lessen cerebral injury, contract cerebral infarct and improve cerebral function.