Prevention of cultured rat stellate cell transformation and endothelin-B receptor upregulation by retinoic acid.
1 Physiologically, perisinusoidal hepatic stellate cells (HSC) are quiescent and store retinoids. During liver injury and in cell culture, HSC transform into proliferating myofibroblast-like cells that express alpha-smooth muscle actin (alpha-sma) and produce excessive amounts of extracellular matrix. During transformation (also known as activation), HSC are depleted of the retinoid stores, and their expression of the endothelin-1 (ET-1) system is increased. ET-1 causes contraction of transformed HSC and is implicated in their proliferation and fibrogenic activity. In order to understand the association between retinoids, ET-1 and the activation of HSC, we investigated the effect of 13-cis-retinoic acid on the transformation of cultured HSC and the expression of ET-1 system. 2 HSC derived from normal rat liver were maintained for 10-12 days in a medium supplemented with 5% serum and containing 2.5 micro M retinoic acid without or with 50 nM ET-1 (ETA+ETB agonist) or sarafotoxin S6c (ETB agonist). In another set of experiments, cells treated for 10-12 days with vehicle (ethanol) or retinoic acid were challenged with ET-1 or sarafotoxin S6c, and various determinations were made at 24 h. 3 Retinoic acid inhibited transformation and proliferation of HSC as assessed by morphological characteristics, expression of alpha-sma, bromodeoxyuridine incorporation and cell count. Retinoic acid also prevented upregulation of ETB receptors without affecting ET-1 or ETA expression. Total protein synthesis ([(3)H]leucine incorporation), collagen alpha types I mRNA expression and collagen synthesis ([(3)H]proline incorporation) were lower in retinoic acid-treated cells. Although ET-1-treated cells were morphologically similar to the control cells, their expression of alpha-smooth muscle actin was significantly inhibited. The presence of retinoic acid in the medium during treatment with ET-1 caused further reduction in the expression of alpha-smooth muscle actin. ET-1 and sarafotoxin S6c stimulated total protein synthesis in vehicle- and retinoic acid-treated cells, but collagen synthesis only in the latter. 4 These results showing prevention of HSC activation and negative regulation of ETB receptor expression in them by retinoic acid may have important pathophysiologic implications.
Chi
Xuedong
X
Department of Surgery, Thomas E. Starzl Transplantation Institute, University of Pittsburgh, E-1540 BST, 200 Lothrop Street, Pittsburgh, PA 15213, USA.
Anselmi
Kristin
K
Watkins
Simon
S
Gandhi
Chandrashekhar R
CR
D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects*; D002455:Cell Division; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis / Q000235:genetics; D003593:Cytoplasm / Q000648:ultrastructure; D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1 / Q000187:drug effects / Q000378:metabolism; D005109:Extracellular Matrix / Q000378:metabolism; D016326:Extracellular Matrix Proteins / Q000235:genetics / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D022781:Hepatocytes / Q000187:drug effects* / Q000378:metabolism; D051381:Rats; D044023:Receptor, Endothelin B / Q000187:drug effects* / Q000235:genetics; D017466:Receptors, Endothelin; D016212:Transforming Growth Factor beta / Q000096:biosynthesis / Q000235:genetics; D014212:Tretinoin / Q000378:metabolism / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects* / Q000235:genetics
D065131:Endothelin B Receptor Antagonists; D019332:Endothelin-1; D016326:Extracellular Matrix Proteins; D044023:Receptor, Endothelin B; D017466:Receptors, Endothelin; D016212:Transforming Growth Factor beta; D014212:Tretinoin; D003094:Collagen