Plasminogen activator activity increases during reversal of hepatic fibrosis in murine schistosomiasis

After specific chemotherapy, granulomatous fibrosis undergoes a marked reversal in liver of Schistosoma mansoni-infected mice. We have previously shown that this fibrosis reversal was related to a high proportion of the active form of the interstitial collagenase. In vitro, plasmin has been described as a physiological activator of interstitial procollagenase. Moreover, plasmin itself degrades directly matrix components such as proteoglycans and fibronectin. We have thus followed the course of the plasminogen activator, which converts plasminogen zymogen to plasmin, in liver of S. mansoni-infected mice treated with praziquantel, as schistosomicidal drug. It was found that plasminogen activator activity in the liver increases rapidly until 5 days after treatment as compared to nontreated infected mice and then diminishes gradually. Increased plasminogen activator activity appears to be one of initial events leading to this fibrosis reversal.