Inhibition of poly(I:C)–induced matrix metalloproteinase expression in human corneal fibroblasts by triptolide

PURPOSE Triptolide is a major component of the herb Tripterygium wilfordii Hook f, extracts of which are used in traditional Chinese medicine, and it has been found to possess immunosuppressive and anti-inflammatory properties. Viral infection of the cornea can lead to corneal ulceration and perforation as a result of collagen degradation in the corneal stroma. We have now examined the effect of triptolide on the expression of matrix metalloproteinases (MMPs) induced by polyinosinic-polycytidylic acid [poly(I:C)], a synthetic analog of viral double-stranded RNA, in cultured human corneal fibroblasts. METHODS Human corneal fibroblasts were cultured in the absence or presence of poly(I:C) or triptolide. Secretion of MMPs as well as the phosphorylation of mitogen-activated protein kinases (MAPKs) and the NF-κB-inhibitory protein, IκB-α, were examined by immunoblot analysis. The abundance of MMP mRNAs was determined by reverse transcription and real-time polymerase chain reaction analysis. RESULTS Poly(I:C) induced the secretion of MMP-1 and MMP-3 from corneal fibroblasts in a concentration-dependent manner as well as increased the intracellular abundance of MMP-1 and MMP-3 mRNAs. Triptolide inhibited these effects of poly(I:C) on MMP expression in a concentration-dependent manner. The poly(I:C)-induced secretion of MMP-1 and MMP-3 was also attenuated by synthetic inhibitors of MAPK and NF-κB signaling pathways. Triptolide inhibited the poly(I:C)-induced phosphorylation of IκB-α but did not affect that of the MAPKs, Extracellular Signal-Regulated Kinase (ERK), p38MAPK, and c-Jun N-Terminal Kinase (JNK). CONCLUSIONS Triptolide inhibited the poly(I:C)-induced production of MMP-1 and MMP-3 by human corneal fibroblasts. Triptolide therefore warrants further investigation as a potential treatment for corneal ulceration associated with viral infection.