title: TGF-alpha increases human mesenchymal stem cell-secreted VEGF by MEK- and PI3-K- but not JNK- or ERK-dependent mechanisms.
abstract: Transforming growth factor-alpha (TGF-alpha) may be an important mediator of wound healing and the injury response. Human bone marrow mesenchymal stem cells (MSCs) release VEGF as a potentially beneficial paracrine response; however, it remains unknown whether TGF-alpha stimulates the production of VEGF from MSCs and, if so, by which mechanisms. We hypothesized that TGF-alpha would increase human MSC VEGF production by MAP kinase kinase (MAPKK/MEK), phosphatidylinositol 3-kinase (PI3-K)-, ERK, and JNK-dependent mechanisms. To study this, MSCs were cultured and divided into the following groups: 1) with vehicle; 2) with various stimulants alone: TGF-alpha, TNF-alpha, or TGF-alpha+TNF-alpha; 3) with individual kinase inhibitors alone (two different inhibitors for each of the following kinases: MEK, PI3-K, ERK, or JNK); and 4) with the above stimulants and each of the eight inhibitors. After 24-h incubation, a TGF-alpha dose-response curve demonstrated that low-dose TGF-alpha (500 pg/ml) suppressed MSC production of VEGF compared with vehicle (502 +/- 16 pg/10(5) cells/ml to 332 +/- 9 pg/10(5) cells/ml), while high-dose TGF-alpha (250 ng/ml) significantly increased MSC VEGF production (603 +/- 24 pg/10(5) cells/ml). High-dose TGF-alpha also increased TNF-alpha-stimulated release of VEGF from MSCs. MSCs exposed to TGF-alpha and/or TNF-alpha also demonstrated increased activation of PI3-K, JNK, and ERK. The TGF-alpha-stimulated production of VEGF by MSCs and the additive effect of TNF-alpha and TGF-alpha on VEGF production were abolished by MEK and PI3-K inhibition, but not ERK or JNK inhibition. Our data suggest that TGF-alpha increases VEGF production in MSCs via MEK- and PI3-K- but not ERK- or JNK-dependent mechanisms.
authors.affiliation: Department of Surgery, Indiana University School of Medicine, Indianapolis, Indiana, USA.
authors.forename: Yue
authors.initials: Y
authors.lastname: Wang
authors.forename: Paul R
authors.initials: PR
authors.lastname: Crisostomo
authors.forename: Meijing
authors.initials: M
authors.lastname: Wang
authors.forename: Troy A
authors.initials: TA
authors.lastname: Markel
authors.forename: Nathan M
authors.initials: NM
authors.lastname: Novotny
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Meldrum
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D002478:Cells, Cultured; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D006801:Humans; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D059630:Mesenchymal Stem Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D020929:Mitogen-Activated Protein Kinase Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D016211:Transforming Growth Factor alpha / Q000494:pharmacology*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*
chemical_list: D004791:Enzyme Inhibitors; D048049:Extracellular Signal-Regulated MAP Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D047428:Protein Kinase Inhibitors; D016211:Transforming Growth Factor alpha; D014409:Tumor Necrosis Factor-alpha; D042461:Vascular Endothelial Growth Factor A; C467484:VEGFA protein, human