Hypoxic stimulation of vascular endothelial growth factor expression in activated rat hepatic stellate cells.
The tissue repair response to hypoxic stimuli during wound healing includes enhanced production of angiogenic factors, such as vascular endothelial growth factor (VEGF). Hepatic stellate cells are oxygen-sensing cells, capable of producing VEGF. We hypothesized that hypoxia-stimulated signaling in activated stellate cells mediate VEGF secretion during liver injury. The specific aim was to evaluate the effect of hypoxia on the gene expression of VEGF in HSC-T6 cells, an immortalized rat hepatic stellate cell line, and in rat primary cultures of stellate cells. Hypoxic induction of VEGF mRNA was dose- and time-dependent. The hypoxic stimulation of VEGF messenger RNA (mRNA) correlated with the secretion of VEGF protein in conditioned media by hypoxic T6 cells. S-Nitroso-N-acetyl-D, L-penicillamine (SNAP), a nitric oxide (NO) donor, and desferrioxamine (DFx) and cobalt chloride, mimics of cellular hypoxia, similarly stimulated VEGF mRNA expression and secretion. Four previously described splice variants of the VEGF mRNA (VEGF-120, 144, 164, 188) were detected in both normoxic- or hypoxic-activated stellate cells. There was differential expression of the VEGF receptors, Flt-1 and Flk-1, in hypoxic T6 cells. Hypoxic conditions selectively stimulated Flt-1 mRNA expression, whereas Flk-1 mRNA remained unchanged. Hypoxic induction of VEGF was also demonstrated in primary stellate cell cultures and after in vivo injury. Hypoxia stimulates cell signaling in stellate cells, culminating in the rapid induction of VEGF and Flt-1 mRNA expression and VEGF secretion. The hypoxic induction of VEGF is mimicked by NO and may be of mechanistic importance in the pathogenesis of hepatic wound healing and hepatocarcinogenesis.
Ankoma-Sey
V
V
Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine, University of Texas Health Science Center/Medical School - Houston, TX 77030, USA. vankomas@heart.med.uth.tmc.edu
Wang
Y
Y
Dai
Z
Z
D017398:Alternative Splicing; D000818:Animals; D002251:Carbon Tetrachloride / Q000494:pharmacology; D015687:Cell Hypoxia / Q000502:physiology*; D002478:Cells, Cultured; D016228:Endothelial Growth Factors / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D007700:Kinetics; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D008222:Lymphokines / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010100:Oxygen / Q000008:administration & dosage; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics; D017978:Receptors, Growth Factor / Q000235:genetics; D040262:Receptors, Vascular Endothelial Growth Factor; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D008222:Lymphokines; D020030:Nitric Oxide Donors; D012333:RNA, Messenger; D017978:Receptors, Growth Factor; C110881:S-nitro-N-acetylpenicillamine; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; D002251:Carbon Tetrachloride; D020794:Receptor Protein-Tyrosine Kinases; D040262:Receptors, Vascular Endothelial Growth Factor; D010396:Penicillamine; D010100:Oxygen