title: LKB1 deficiency in Tie2-Cre-expressing cells impairs ischemia-induced angiogenesis.
abstract: LKB1 is a tumor suppressor protein whose loss leads to HIF1alpha-mediated activation of a proangiogenic program in intestinal polyps. LKB1 is also protein kinase regulator of AMP-activated protein kinase (AMPK) signaling, which is essential for endothelial cell responses to tissue ischemia. To discern whether LKB1 signaling is either pro- or antiangiogenic, we investigated ischemia-induced revascularization in mice that were deficient for LKB1 in Tie2-Cre-expressing cells. Whereas homozygous deletion of LKB1 led to embryonic lethality, heterozygous LKB1-knock-out (KO) (Lkb1(flox/+);Tie2(Tg/+)) mice were viable. Unchallenged heterozygous LKB1-KO mice displayed normal capillary density, but the revascularization of hind limb following ischemic surgery was significantly impaired as evaluated by laser Doppler flow and capillary density measurements. Reduction of LKB1 in cultured endothelial cells, using either small interfering RNA or an adenovirus expressing nonfunctional kinase-dead LKB1 protein, attenuated endothelial proliferation, migration, and differentiation into network structures on Matrigel that was accompanied by diminished AMPK phosphorylation at Thr-172. Conversely, adenovirus-mediated LKB1 overexpression (Ad-LKB1) augmented network structure formation, and this was associated with elevated AMPK phosphorylation. The augmented differentiation of endothelial cells into network structures induced by Ad-LKB1 was abrogated by the co-transduction of a dominant negative mutant of AMPK. These observations suggest that the LKB1-AMPK signaling axis in endothelial cells is a positive regulator of the revascularization response to tissue ischemia.
authors.affiliation: Molecular Cardiology/Whitaker Cardiovascular Institute, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
authors.forename: Koji
authors.initials: K
authors.lastname: Ohashi
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Ouchi
authors.forename: Akiko
authors.initials: A
authors.lastname: Higuchi
authors.forename: Reuben J
authors.initials: RJ
authors.lastname: Shaw
authors.forename: Kenneth
authors.initials: K
authors.lastname: Walsh
mesh_terms: D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases / Q000378:metabolism; D000818:Animals; D002469:Cell Separation; D042783:Endothelial Cells / Q000201:enzymology* / Q000473:pathology; D006579:Heterozygote; D006801:Humans; D019426:Integrases / Q000378:metabolism*; D007511:Ischemia / Q000150:complications* / Q000201:enzymology; D051379:Mice; D018345:Mice, Knockout; D009389:Neovascularization, Pathologic / Q000201:enzymology / Q000209:etiology*; D017346:Protein Serine-Threonine Kinases / Q000172:deficiency* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D042787:Receptor, TIE-2; D015398:Signal Transduction; D014471:Umbilical Veins / Q000166:cytology
chemical_list: D034741:RNA, Small Interfering; D020794:Receptor Protein-Tyrosine Kinases; D042787:Receptor, TIE-2; C079086:Tek protein, mouse; D017346:Protein Serine-Threonine Kinases; C109790:STK11 protein, human; C491654:Stk11 protein, mouse; D000091162:AMP-Activated Protein Kinase Kinases; D055372:AMP-Activated Protein Kinases; C045073:Cre recombinase; D019426:Integrases