title: HIF-1alpha and HIF-2alpha play a central role in stretch-induced but not shear-stress-induced angiogenesis in rat skeletal muscle.
abstract: Angiogenesis, which is essential for the physiological adaptation of skeletal muscle to exercise, occurs in response to the mechanical forces of elevated capillary shear stress and cell stretch. Increased production of VEGF is a characteristic of endothelial cells undergoing either stretch- or shear-stress-induced angiogenesis. Because VEGF production is regulated by hypoxia inducible factors (HIFs), we examined whether HIFs play a significant role in the angiogenic process initiated by these mechanical forces. Rat extensor digitorum longus (EDL) muscles were overloaded to induce stretch, or exposed to the dilator prazosin to elevate capillary shear stress, and capillaries from these muscles were isolated by laser capture microdissection for RNA analysis. HIF-1alpha and HIF-2alpha transcript levels increased after 4 and 7 days of stretch, whereas a transient early induction of HIF-1alpha and HIF-2alpha transcripts was detected in capillaries from prazosin-treated muscles. Skeletal muscle microvascular endothelial cells exposed to 10% stretch in vitro showed an elevation in HIF-1alpha and HIF-2alpha mRNA, which was preceded by increases in HIF-binding activity. Conversely, HIF-1alpha and HIF-2alpha mRNA were reduced significantly, and HIF-alpha proteins were undetectable, after 24 h exposure to elevated shear stress (16 dyn cm(-2) (16 x10(-5) N cm(-2)). Given the disparate regulation of HIFs in response to these mechanical stimuli, we tested the requirement of HIF-alpha proteins in stretch- and shear-stress-induced angiogenesis by impeding HIF accumulation through use of the geldanamycin derivative 17-DMAG. Treatment with 17-DMAG significantly impaired stretch-induced, but not shear-stress-induced, angiogenesis. Together, these results illustrate that activation of HIF-1alpha and HIF-2alpha contributes significantly to stretch- but not to shear-stress-induced capillary growth.
authors.affiliation: School of Kinesiology and Health Sciences, York University, Toronto, Ontario, Canada.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Milkiewicz
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Doyle
authors.forename: Tomasz
authors.initials: T
authors.lastname: Fudalewski
authors.forename: Eric
authors.initials: E
authors.lastname: Ispanovic
authors.forename: Maliheh
authors.initials: M
authors.lastname: Aghasi
authors.forename: Tara L
authors.initials: TL
authors.lastname: Haas
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D016227:Benzoquinones / Q000494:pharmacology; D002196:Capillaries / Q000201:enzymology / Q000378:metabolism; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000201:enzymology / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D005786:Gene Expression Regulation; D018841:HSP90 Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism*; D007211:Indoles / Q000494:pharmacology; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D008297:Male; D008465:Mechanoreceptors / Q000378:metabolism*; D040542:Mechanotransduction, Cellular; D018482:Muscle, Skeletal / Q000098:blood supply*; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000235:genetics; D010766:Phosphorylation; D011224:Prazosin / Q000494:pharmacology; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D011758:Pyrroles / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D013997:Time Factors; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D014664:Vasodilation / Q000187:drug effects / Q000235:genetics; D014665:Vasodilator Agents / Q000494:pharmacology; D000099162:Endothelial PAS Domain-Containing Protein 1
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D016227:Benzoquinones; D048049:Extracellular Signal-Regulated MAP Kinases; D018841:HSP90 Heat-Shock Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D007211:Indoles; D047029:Lactams, Macrocyclic; D011224:Prazosin; D047428:Protein Kinase Inhibitors; D011758:Pyrroles; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D040301:Vascular Endothelial Growth Factor Receptor-2; D014665:Vasodilator Agents; D000099162:Endothelial PAS Domain-Containing Protein 1; C517608:3-((2,4-dimethyl-3-(ethoxycarbonyl)pyrrol-5-yl)methylidenyl)indolin-2-one; C497444:Hif1a protein, rat; C467498:vascular endothelial growth factor A, rat; C448659:17-(dimethylaminoethylamino)-17-demethoxygeldanamycin