Transforming growth factor-beta-induced collagen synthesis by human liver myofibroblasts is inhibited by alpha(2)-macroglobulin

[摘要] Background: Transforming growth factor-beta (TGF beta) plays a central role in the stimulation of matrix production during liver fibrosis. The action of TGF beta in different systems has been shown to be influenced by alpha(2)-macroglobulin (alpha(2)M), a serum protein with strong protease-scavenging and cytokine-binding properties, Aims: In the present study alpha(2)M derived from normal human plasma has been tested for its ability to modulate the TGF beta-induced collagen production by human liver fat-storing cells (FSC), which had transformed into alpha-smooth muscle actin-expressing myofibroblasts in culture. Methods: alpha(2)M has been tested after activation with methylamine (alpha(2)M-Me), an in vitro equivalent of protease activated alpha(2)M. The binding of I-125-TGF beta 1 to activated forms of alpha(2)M was demonstrated by rate electrophoresis, Collagen synthesis was examined in human liver myofibroblast cultures obtained from three different human livers by incorporation of H-3-proline into TCA-precipitable, specific collagenase degradable proteins, Uptake of alpha(2)M was studied by means of immunofluorescence. Results: TGF beta (1 ng/ml) significantly stimulated collagen synthesis of controls in the absence of TGF beta. alpha(2)M-Me reduced this TGF beta-induced collagen synthesis dose-dependently, reaching significant inhibition from 10 mu g/ml alpha(2)M-Me onward. Upon addition of 100 mu g/ml alpha(2)M-Me the effect of TGF beta was reduced by 60% to 128 +/- 31% (mean +/- SD) of control values in the absence of TGF beta, Human liver myofibroblasts endocytosed alpha(2)M-Me added to the cultures as detected by immunofluorescence, Accordingly, reduction of TGF beta-activity by alpha(2)M-Me may be explained by receptor-mediated clearance of alpha(2)M-TGF beta complexes by the cells. Conclusions: TGF beta-induced collagen formation by human liver myofibroblasts obtained from three different livers is reduced in vitro by activated alpha(2)M. From these results, we hypothesize that alpha(2)M may have an antifibrogenic effect in vivo by interference with TGF beta-induced matrix synthesis during liver fibrosis.

[发布日期] 1997-06-01

[关键词] alpha(2)-macroglobulin;collagen;fat-storing cell;fibrosis;human;liver;myofibroblast;TGF beta