[ ABSTRACT] AIM:To investigate the effect of tripterygium hypoglaucum Hutch ( THH) on collagen-induced ar-thritis ( CIA) in rats and its possible mechanism.METHODS:SD rats were randomly divided into normal group and CIA group.The rat model of type II CIA was successfully established and the model rats were randomly divided into 4 different groups:model group, dexamethasone group, THH (200 mg/kg) group, and THH (400 mg/kg) group.The contents of IL-12, IL-23 and IL-37 in the serum and foot paws of the CIA rats were detected by ELISA.The histopathological changes of the skin of the food paws were observed by HE staining.The protein expression of MMP-13 was determined by Western blot.The MMP-13 activity in the foot paws was detected by fluorescence labeling method.RESULTS:Compared with CIA group, THH at dose of 400 mg/kg significantly reduced the weight loss in typeⅡCIA rats ( P<0.01 ) .THH at dose of 400 mg/kg obviously decreased the contents of IL-12 by 28.31%, IL-23 by 41.57%in the serum and IL-12 by 30.78%, IL-23 by 39.46%in the foot paws, while IL-37 was significantly increased by 79.43% in the serum and 75.78% in the foot paws ( P<0.01) .The pathological changes of the subcutaneous tissues were improved by treating with THH (400 mg/kg).The protein expression of MMP-13 was significantly decreased by 31.82%(P<0.01), and the MMP-13 activity was also reduced.THH at dose of 200 mg/kg had no obvious improvement on the above indexes.CONCLUSION:THH has significant inhibitory effect on rat CIA by reducing the content of proinflammatory cytokines IL-12 and IL-23, increasing the content of anti-inflammatory factor IL-37, inhibiting inflammatory cell infiltration and vascular proliferation, and attenuating the protein expression of MMP-13 and MMP-13 activity in rats.