Regulation of hepatic stellate cell proliferation and collagen synthesis by proteinase-activated receptors.
OBJECTIVE
Thrombin and MC tryptase, which are agonists for proteinase-activated receptors-1 and -2, respectively, are both increased in injured liver. We have examined if rat stellate cells express these receptors and if receptor agonists influence stellate cell activation.


METHODS
Expression of mRNA for proteinase activated receptors-1 and -2 were examined by RT-PCR and Northern blotting in lysates of cultured stellate cells and receptor protein examined by Western blotting. The effects of receptor agonists on cell proliferation and collagen synthesis were examined by 3H-thymidine and 3H-proline incorporation assays, respectively.


RESULTS
Rat stellate cells activated by culture on plastic showed a progressive increase in expression of proteinase-activated receptor-1 and -2 mRNA and proteinase-activated receptor-2 protein as they transformed to a myofibroblastic phenotype. Proteinase-activated receptor-1 agonists thrombin and the peptide SFFLRN, and proteinase-activated receptor-2 agonists tryptase and the peptide SLIGRL induced stellate cell proliferation and the rapid phosphorylation of 44 and 42 kDa mitogen-activated protein kinases. PD98059, an inhibitor of these kinases, inhibited this proliferative response. Both tryptase and SLIGRL increased collagen secretion by stellate cells.


CONCLUSIONS
This study indicates that the natural proteinase-activated receptor agonists thrombin and MC tryptase might sustain liver fibrosis by promoting stellate cell proliferation and collagen synthesis.
Gaça
Marianna D A
MD
Liver Research Group, University Division of Infection, Inflammation and Repair, Southampton General Hospital, SO16 6YD, Southampton, UK.
Zhou
Xiaoying
X
Benyon
R Christopher
RC
D016475:3T3 Cells; D000818:Animals; D002455:Cell Division / Q000502:physiology; D003094:Collagen / Q000096:biosynthesis*; D015870:Gene Expression / Q000502:physiology; D006490:Hemostatics / Q000494:pharmacology; D022781:Hepatocytes / Q000166:cytology* / Q000378:metabolism*; D008103:Liver Cirrhosis / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008407:Mast Cells / Q000378:metabolism; D051379:Mice; D008934:Mitogens / Q000494:pharmacology; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin / Q000819:agonists / Q000235:genetics* / Q000378:metabolism*; D012697:Serine Endopeptidases / Q000494:pharmacology; D012867:Skin / Q000166:cytology; D013917:Thrombin / Q000494:pharmacology; D053802:Tryptases
D006490:Hemostatics; D008934:Mitogens; D012333:RNA, Messenger; D044463:Receptor, PAR-1; D044464:Receptor, PAR-2; D018179:Receptors, Thrombin; C509190:Tpsb2 protein, mouse; D003094:Collagen; D012697:Serine Endopeptidases; D013917:Thrombin; C509222:Tpsab1 protein, mouse; C509223:Tpsab1 protein, rat; C509221:Tpsb2 protein, rat; D053802:Tryptases