Triptolide mediates Wnt/β-catenin signalling pathway to reduce cerebral ischemia-reperfusion injury in rats

Introduction
Triptolide, extracted from Chinese medicinal materials Tripterygium wilfordii Hook F (TwHF), has immunosuppressive, anti-inflammatory and anti-tumour effects. The purpose of this study was to examine whether triptolide has the neuroprotective effect on cerebral ischemia-reperfusion (I/R) injury and to explore its possible mechanism.

Material and methods
The rat model of focal cerebral I/R was established by the suture-occluded method. The SD rats were randomly divided into five groups: sham operation group (Sham group), ischemia-reperfusion model group (I/R group), low concentration of triptolide group (12.5 mg/kg, TL-L group), medium concentration of triptolide group (25 mg/kg, TL-M group) and high concentration of triptolide group (50 mg/kg, TL-H group). The neurological function of the rats was scored, the degree of brain oedema was detected by the dry-wet method, and the cerebral infarction area was determined by TTC staining. Nissl staining was used to detect neuronal damage. The contents of reactive oxygen species (ROS), malondialdehyde (MDA) and superoxide dismutase (SOD) were also detected. Meanwhile, the expression level of proteins related to Wnt/-catenin signalling pathway was measured by Western blot.

Results
Compared with the I/R group, cerebral oedema, infarct volume, neurological impairment, the contents of MDA and ROS were reduced, while the SOD level was increased in the TL-L, TL-M, and TL-H groups. The results of Nissl staining showed that triptolide could reduce the nerve cell injury caused by cerebral I/R. In addition, the results of Western blot confirmed that the expression of Wnt1, -catenin, c-Myc, and Cyclin-D1 were down-regulated after triptolide intervention, that is, inhibited the activation of Wnt/-catenin signalling pathway.

Conclusions
Triptolide mediates Wnt/-catenin signalling pathway to alleviate cerebral I/R injury in rats. This study provides ideas and experimental basis for the treatment of ischemic stroke patients.