Inhibition by triptolide of IL-1-induced collagen degradation by corneal fibroblasts.
OBJECTIVE
Extracts of the herb Tripterygium wilfordii hook f, the major component of which is triptolide, have been used in traditional Chinese medicine for the treatment of rheumatoid arthritis. Triptolide also exerts many other biological actions both in vitro and in vivo. The effect of this agent on collagen degradation by cultured corneal fibroblasts was examined.


METHODS
Rabbit corneal fibroblasts were cultured in three-dimensional gels of type I collagen and in the absence or presence of interleukin (IL)-1beta or triptolide. The extent of collagen degradation was determined by measurement of the amount of hydroxyproline generated by acid-heat hydrolysis of the culture supernatants. The activities of matrix metalloproteinase (MMP)-1 and plasmin were measured with the specific substrates thiopeptolide and S-2251, respectively. The release of MMPs into the culture supernatant was assessed by immunoblot analysis and gelatin zymography, and the abundance of MMP mRNAs in the cells was determined by reverse transcription and real-time polymerase chain reaction.


RESULTS
Triptolide inhibited the IL-1beta-induced degradation of collagen by corneal fibroblasts in a dose- and time-dependent manner. Neither the activity of purified recombinant MMP-1 nor that of plasmin in culture supernatants was affected by triptolide. The IL-1beta-induced expression of MMP-1, -2, -3, and -9 by corneal fibroblasts was inhibited by triptolide at the protein or mRNA level.


CONCLUSIONS
Triptolide inhibits collagen degradation by corneal fibroblasts by inducing downregulation of the production of MMPs, without directly affecting the collagenolytic activity of these enzymes.
Lu
Ying
Y
Department of Biomolecular Recognition and Ophthalmology, Yamaguchi University School of Medicine, 1-1-1 Minami-Kogushi, Ube City, Yamaguchi 755-8505, Japan.
Fukuda
Ken
K
Seki
Keisuke
K
Nakamura
Yoshikuni
Y
Kumagai
Naoki
N
Nishida
Teruo
T
D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology*; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism*; D017364:Collagenases / Q000235:genetics / Q000378:metabolism; D003315:Cornea / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004224:Diterpenes / Q000494:pharmacology*; D004852:Epoxy Compounds; D005341:Fibrinolysin / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D006909:Hydroxyproline / Q000096:biosynthesis; D015151:Immunoblotting; D007375:Interleukin-1 / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D008297:Male; D010616:Phenanthrenes / Q000494:pharmacology*; D011817:Rabbits; D020133:Reverse Transcriptase Polymerase Chain Reaction; D029757:Tripterygium / Q000737:chemistry
D000894:Anti-Inflammatory Agents, Non-Steroidal; D004224:Diterpenes; D004852:Epoxy Compounds; D007375:Interleukin-1; D010616:Phenanthrenes; C001899:triptolide; D003094:Collagen; D005341:Fibrinolysin; D017364:Collagenases; D006909:Hydroxyproline