title: Key role of endothelial importin-α in VEGF expression and gastric angiogenesis: novel insight into aging gastropathy.
abstract: Recent in vivo studies demonstrated that aging gastric mucosa has impaired angiogenesis and reduced expression of vascular endothelial growth factor (VEGF). Angiogenesis is triggered by hypoxia and VEGF gene activation, and the latter requires transport of transcription factor(s) into endothelial cell nuclei. We focused on gastric mucosal endothelial cells (GMEC), which are key targets and effectors of gastric angiogenesis, and determined whether and to what extent importin-α, a nuclear transport protein, regulates VEGF gene activation and gastric angiogenesis and the possible role of importin-α in aging gastropathy. GMEC were isolated from rats 3 and 24 mo of age, young (YGEC) and aging (AGEC), respectively. We examined in these cells 1) in vitro angiogenesis, 2) expression of VEGF and importin-α, 3) nuclear transport of hypoxia-inducible factor (HIF)-1α by importin-α, 4) binding of HIF-1α to the VEGF gene promoter, and 5) effects of importin-α silencing in YGEC and its upregulation in AGEC on angiogenesis and VEGF expression. AGEC exhibited significantly impaired in vitro angiogenesis by fourfold and decreased expression of VEGF, importin-α, and nuclear HIF-1α by 1.4-fold, 1.6-fold, and 2.9-fold, respectively, vs. YGEC. Upregulation of importin-α in AGEC significantly reversed all these abnormalities. In YGEC, knockdown of importins-α1 and -α3 significantly reduced in vitro angiogenesis by 93% and 73% and VEGF expression by 48% and 52%, respectively. The above findings demonstrate that importin-α is a novel and critical regulator of gastric angiogenesis. Its reduced expression in AGEC is the key mechanism for impaired angiogenesis and reduced VEGF.
authors.affiliation: Medical and Research Services, Veterans Affairs Long Beach Healthcare System (VALBHS) and Southern California Institute for Research and Education.
authors.forename: Amrita
authors.initials: A
authors.lastname: Ahluwalia
authors.forename: Michael K
authors.initials: MK
authors.lastname: Jones
authors.forename: Andrzej S
authors.initials: AS
authors.lastname: Tarnawski
mesh_terms: D021581:Active Transport, Cell Nucleus; D000367:Age Factors; D000375:Aging / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000378:metabolism* / Q000473:pathology; D005753:Gastric Mucosa / Q000098:blood supply*; D005786:Gene Expression Regulation; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D018919:Neovascularization, Physiologic; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D051381:Rats; D011916:Rats, Inbred F344; D015398:Signal Transduction; D013272:Stomach Diseases / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D014162:Transfection; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics / Q000378:metabolism*; D028901:alpha Karyopherins / Q000235:genetics / Q000378:metabolism*
chemical_list: C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D042461:Vascular Endothelial Growth Factor A; D028901:alpha Karyopherins; C467498:vascular endothelial growth factor A, rat
keywords: VEGF; aging; angiogenesis; gastric endothelial cells; hypoxia; hypoxia-inducible factor-1α; importin-α