The mitogenic activity of the liver growth factor is mediated by tumor necrosis factor alpha in rat liver.
OBJECTIVE
Liver growth factor (LGF) is a hepatic mitogen, however, the hepatic stimulation pathway remains to be characterized. The aim of this study was to determine whether tumor necrosis factor alpha (TNF-alpha) stimulation constitutes a step in the mitogenic pathway of LGF.


METHODS
Rats were injected with 4.5 microg LGF/rat, and LGF activity was measured both by liver DNA synthesis stimulation and "proliferating cell nuclear antigen (PCNA)-positive" hepatocytes in rats injected with LGF or +anti-TNF-alpha. TNF-alpha expression was evaluated by reverse-transcription polymerase chain reaction. TNF-alpha-producing cells were immunodetected. Human endothelial cells (HUVEC) were stimulated by LGF. TNF-alpha was detected in the supernatant, and the expression of intercellular adhesion molecule-1 (ICAM-1) and vascular endothelial adhesion molecule-1 (VCAM-1) by flow cytometry analysis.


RESULTS
LGF-injected rats showed higher intrahepatic TNF-alpha expression. DNA synthesis and PCNA-positive hepatocytes induced by LGF were inhibited by anti-TNF-alpha, PCNA-positive hepatocytes being especially abundant around the central vein when LGF was injected alone, but TNF-alpha exhibited increased signal intensity in endothelial cells of the portal vein. LGF stimulated TNF-alpha secretion in HUVEC, but did not stimulate ICAM-1 or VCAM-1 up-regulation.


CONCLUSIONS
The mitogenic cascade initiated by LGF in rat liver in vivo depends, at least in part, on TNF-alpha stimulation. Portal vein endothelial cells seem to be a source of TNF-alpha.
Díaz-Gil
Juan J
JJ
Servicio de Bioquímica Experimental, Clínica Puerta de Hierro, S. Martín de Porres 4, Madrid 28035, Spain. jdiaz.hpth@salud.madrid.org
Majano
Pedro L
PL
López-Cabrera
Manuel
M
Sánchez-López
Vicente
V
Rúa
Carmen
C
Machín
Celia
C
Trilla
Carolina
C
García-Cañero
Rafael
R
Moreno-Otero
Ricardo
R
D000818:Animals; D001663:Bilirubin / Q000494:pharmacology*; D001706:Biopsy; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D022781:Hepatocytes / Q000737:chemistry / Q000187:drug effects*; D006801:Humans; D008099:Liver / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008934:Mitogens / Q000494:pharmacology*; D011169:Portal Vein / Q000378:metabolism; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis; D051381:Rats; D017208:Rats, Wistar; D012709:Serum Albumin / Q000494:pharmacology*; D000075462:Serum Albumin, Human; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism*; D014471:Umbilical Veins / Q000166:cytology
D008934:Mitogens; D018809:Proliferating Cell Nuclear Antigen; D012333:RNA, Messenger; D012709:Serum Albumin; D014409:Tumor Necrosis Factor-alpha; C053498:albumin-bilirubin complex; D001663:Bilirubin; D000075462:Serum Albumin, Human