S. Kagami et al., DUAL EFFECTS OF ANGIOTENSIN-II ON THE PLASMINOGEN PLASMIN SYSTEM IN RAT MESANGIAL CELLS/, Kidney international, 51(3), 1997, pp. 664-671
Previous studies indicate that angiotensin II (Ang II) stimulates extr
acellular matrix synthesis through induction of transforming growth fa
ctor-beta (TGF-beta) expression. Here we investigate Ang II effects on
the plasmin protease system. Plasmin both degrades extracellular matr
ix itself and activates metalloproteinases which then degrade collagen
s. Plasmin production is determined by the balance between plasminogen
activators (PA) and their inhibitors (PAI-1,2). The data presented he
re indicate that Ang II treatment of mesangial cells in culture marked
ly increases PAI-1 gene transcription and PAI-1 mRNA levels but does n
ot change the half life of PAI-1 mRNA. Increased PAI-1 protein was det
ected 24 hours after Ang II stimulation with a concomitant decrease of
PA activity. To determine whether these effects were mediated by TGF-
beta, cells were coincubated with Ang II and neutralizing antibody to
TGF-beta. Induction of PAI-1 at four hours was not altered but the pro
longed effect of Ang II on PAI-1 protein synthesis was markedly dimini
shed. Thus, Ang II acts both through rapid, direct transcriptional up-
regulation of the PAI-1 gene and through induction of TGF-beta, provid
ing sustained changes in the PAI-1/PA system, which would favor extrac
ellular matrix accumulation by inhibiting turnover. These data provide
further evidence that Ang II can act as a potent fibrogenic molecule
independent of its effects on blood pressure.