Fibronectin stimulates endothelin-1 synthesis in rat hepatic myofibroblasts via a Src/ERK-regulated signaling pathway.
OBJECTIVE
Liver injury serves as an excellent model of wound healing, characterized by increased synthesis of various cytokines and peptides, including the vasoactive peptide endothelin-1. In the liver, wound healing is mediated by effector cells such as hepatic stellate cells, which cause tissue contraction. Endothelin-1 has autocrine effects on stellate cells and induces their contractile activities. We explored the role of various extracellular matrix components, particularly of fibronectin, in regulating endothelin-1 production during liver injury.


METHODS
Hepatic stellate cells were isolated from normal and injured rats. Real-time polymerase chain reaction immunoblot and enzyme-linked immunosorbent assay analyses were used to measure specific variables, including endothelin-1 production. Preproendothelin-1 promoter activity was determined by a luciferase assay. Stellate cell contraction was measured by a gel contraction assay.


RESULTS
Fibronectin stimulated transcription of preproendothelin-1 messenger RNA and expression of endothelin through an integrin-dependent pathway in activated hepatic stellate cells. In these cells, fibronectin induced phosphorylation/activation of extracellular signal-regulated kinase (ERK) through a Shc- and Src-dependent mechanism; ERK activation was required for fibronectin-induced endothelin-1 expression. Fibronectin stimulation by stellate cells induced expression of smooth muscle alpha-actin and endothelin-1-mediated autocrine stellate cell contraction. Stellate cells isolated from injured livers of rats exhibited increased basal phosphorylation levels of Src, Shc, and ERK, as well as increased endothelin-1 synthesis.


CONCLUSIONS
Fibronectin stimulates activated stellate cells to produce endothelin-1 and contract, via an ERK-dependent signaling pathway. The resulting autocrine functional effects of endothelin-1 are likely to be important in the wound-healing process in injured liver.
Zhan
Shuxin
S
Division of Digestive and Liver Diseases, University of Texas Southwestern Medical Center, Dallas, Texas 75390-8887, USA.
Chan
Che-Chang
CC
Serdar
Berrin
B
Rockey
Don C
DC
D000704:Analysis of Variance; D000818:Animals; D002478:Cells, Cultured; D004195:Disease Models, Animal; D019332:Endothelin-1 / Q000187:drug effects / Q000378:metabolism*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000187:drug effects / Q000378:metabolism*; D005353:Fibronectins / Q000494:pharmacology*; D055166:Hepatic Stellate Cells / Q000187:drug effects / Q000378:metabolism; D015151:Immunoblotting; D008099:Liver / Q000293:injuries*; D008297:Male; D010766:Phosphorylation; D011336:Probability; D012333:RNA, Messenger / Q000032:analysis; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects* / Q000502:physiology; D019061:src-Family Kinases / Q000187:drug effects / Q000378:metabolism*
D019332:Endothelin-1; D005353:Fibronectins; D012333:RNA, Messenger; D019061:src-Family Kinases; D048049:Extracellular Signal-Regulated MAP Kinases