Urokinase plasminogen activator (uPA) stimulates cholesterol biosynthesis in macrophages through activation of SREBP-1 in a PI3-kinase and MEK-dependent manner


      Urokinase plasminogen activator (uPA) is expressed in human atherosclerotic lesions, predominantly in macrophages, and contributes to atherosclerosis progression. Since atherogenesis is characterized by the formation of cholesterol-loaded macrophage foam cells, we questioned whether uPA atherogenicity may involve macrophage cholesterol accumulation, and by what mechanisms. uPA increased cellular cholesterol content by 44% (mainly unesterified cholesterol) in THP-1 macrophages, and this effect was inhibited by statins. This effect was associated with 172% elevated cholesterol biosynthesis, which required the binding of uPA to its receptor. An upregulation of HMGCoA reductase (HMGCR) expression (protein and mRNA) was noted. Since HMGCR expression is controlled by sterol regulatory element-binding proteins (SREBPs), we next analyzed this issue. Indeed, treatment of macrophages with uPA increased SREBP-1 processing, and mature SEREBP-1 content (by 5.7-fold) in the nucleus. These latter effects were mediated by uPA-induced activation of the mitogen-activated protein kinase/extracellular signal-regulated kinase (MEK). Finally, uPA was found to activate MAP-kinase through PI3 kinase (PI3K), as PI3K inhibition abrogated both uPA-induced ERK phosphorylation and cholesterol biosynthesis.
      In conclusion, uPA-induced macrophage cholesterol accumulation is a novel pathway by which uPA may contribute to accelerated atherosclerosis development. These findings provide new insight into the atherogenicity of uPA and may suggest new novel therapeutic means.


      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to Atherosclerosis
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Ross R.
        Atherosclerosis—an inflammatory disease.
        N Engl J Med. 1999; 340: 115-126
        • Krieger M.
        The best of cholesterols, the worst of cholesterols: a tale of two receptors.
        Proc Natl Acad Sci USA. 1998; 14: 4077-4080
        • Keidar S.
        • Attias J.
        • Heinrich R.
        • Coleman R.
        • Aviram M.
        Angiotensin II atherogenicity in apolipoprotein E deficient mice is associated with increased cellular cholesterol biosynthesis.
        Atherosclerosis. 1999; 146: 249-257
        • Brown M.S.
        • Goldstein J.L.
        A receptor-mediated pathway for cholesterol homeostasis.
        Science. 1986; 232: 34-47
        • Carmeliet P.
        • Moons L.
        • Lijnen R.
        • et al.
        Urokinase-generated plasmin activates matrix metalloproteinases during aneurysm formation.
        Nat Genet. 1997; 17: 439-444
        • Cozen A.E.
        • Moriwaki H.
        • Kremen M.
        • et al.
        Macrophage-targeted overexpression of urokinase causes accelerated atherosclerosis, coronary artery occlusions, and premature death.
        Circulation. 2004; 109: 2129-2135
        • Waltz D.A.
        • Fujita R.M.
        • Yang X.
        • et al.
        Nonproteolytic role for the urokinase receptor in cellular migration in vivo.
        Am J Respir Cell Mol Biol. 2000; 22: 316-322
        • Kienast J.
        • Padro T.
        • Steins M.
        • et al.
        Relation of urokinase-type plasminogen activator expression to presence and severity of atherosclerotic lesions in human coronary arteries.
        Thromb Haemost. 1998; 79: 579-586
        • Lupu F.
        • Heim D.A.
        • Bachmann F.
        • et al.
        Plasminogen activator expression in human atherosclerotic lesions.
        Arterioscler Thromb Vasc Biol. 1995; 15: 1444-1455
        • Padro T.
        • Emeis J.J.
        • Steins M.
        • Schmid K.W.
        • Kienast J.
        Quantification of plasminogen activators and their inhibitors in the aortic vessel wall in relation to the presence and severity of atherosclerotic disease.
        Arterioscler Thromb Vasc Biol. 1995; 15: 893-902
        • Clowes A.W.
        • Clowes M.M.
        • Au Y.P.
        • Reidy M.A.
        • Belin D.
        Smooth muscle cells express urokinase during mitogenesis and tissue-type plasminogen activator during migration in injured rat carotid artery.
        Circ Res. 1990; 67: 61-67
        • More R.S.
        • Underwood M.J.
        • Brack M.J.
        • de Bono D.P.
        • Gershlick A.H.
        Changes in vessel wall plasminogen activator activity and smooth muscle cell proliferation and activation after arterial injury.
        Cardiovasc Res. 1995; 29: 22-26
        • Kanse S.M.
        • Benzakour O.
        • Kanthou C.
        • et al.
        Induction of vascular SMC proliferation by urokinase indicates a novel mechanism of action in vasoproliferative disorders.
        Arterioscler Thromb Vasc Biol. 1997; 17: 2848-2854
        • Plekhanova O.
        • Parfyonova Y.
        • Bibilashvily R.
        • et al.
        Urokinase plasminogen activator augments cell proliferation and neointima formation in injured arteries via proteolytic mechanisms.
        Atherosclerosis. 2001; 159: 297-306
        • Eierman D.F.
        • Johnson C.E.
        • Haskill S.J.
        Human monocyte inflammatory mediator gene expression is selectively regulated by adherence substrates.
        J Immunol. 1989; 142: 1970-1976
        • Vassalli J.D.
        • Belin D.
        Amiloride selectively inhibits the urokinase-type plasminogen activator.
        FEBS Lett. 1987; 214: 187-191
        • Xu X.X.
        • Tabas I.
        Lipoproteins activate acyl-coenzyme A: cholesterol acyltransferase in macrophages only after cellular cholesterol pools are expanded to a critical threshold level.
        J Biol Chem. 1991; 266: 17040-17048
        • Small D.M.
        • Bond M.G.
        • Waugh D.
        • Prack M.
        • Sawyer J.K.
        Physicochemical and histological changes in the arterial wall of nonhuman primates during progression and regression of atherosclerosis.
        J Clin Invest. 1984; 73: 1590-1605
        • Feng B.
        • Tabas I.
        ABCA1-mediated cholesterol efflux is defective in free cholesterol-loaded macrophages Mechanism involves enhanced ABCA1 degradation in a process requiring full NPC1 activity.
        J Biol Chem. 2002; 277: 43271-43280
        • Li Y.
        • Schwabe R.F.
        • DeVries-Seimon T.
        • et al.
        Free cholesterol-loaded macrophages are an abundant source of tumor necrosis factor-alpha and interleukin-6: model of NF-kappaB- and map kinase-dependent inflammation in advanced atherosclerosis.
        J Biol Chem. 2005; 280: 21763-21772
        • Blasi F.
        • Carmeliet P.
        uPAR: a versatile signalling orchestrator.
        Nat Rev Mol Cell Biol. 2002; 3: 932-943
        • Nykjaer A.
        • Petersen C.M.
        • Moller B.
        • et al.
        Purified alpha 2-macroglobulin receptor/LDL receptor-related protein binds urokinase plasminogen activator inhibitor type-1 complex Evidence that the alpha 2-macroglobulin receptor mediates cellular degradation of urokinase receptor-bound complexes.
        J Biol Chem. 1992; 267: 14543-14546
        • Hoyer-Hansen G.
        • Behrendt N.
        • Ploug M.
        • Dano K.
        • Preissner K.T.
        The intact urokinase receptor is required for efficient vitronectin binding: receptor cleavage prevents ligand interaction.
        FEBS Lett. 1997; 420: 79-85
        • Degryse B.
        • Orlando S.
        • Resnati M.
        • Rabbani S.A.
        • Blasi F.
        Urokinase/urokinase receptor and vitronectin/alpha(v)beta(3) integrin induce chemotaxis and cytoskeleton reorganization through different signaling pathways.
        Oncogene. 2001; 20: 2032-2043
        • Horton J.D.
        • Goldstein J.L.
        • Brown M.S.
        SREBPs: activators of the complete program of cholesterol and fatty acid synthesis in the liver.
        J Clin Invest. 2002; 109: 1125-1131
        • Vallett S.M.
        • Sanchez H.B.
        • Rosenfeld J.M.
        • Osborne T.F.
        A direct role for sterol regulatory element binding protein in activation of 3-hydroxy-3-methylglutaryl coenzyme A reductase gene.
        J Biol Chem. 1996; 271: 12247-12253
        • Brown M.S.
        • Goldstein J.L.
        A proteolytic pathway that controls the cholesterol content of membranes, cells, and blood.
        Proc Natl Acad Sci USA. 1999; 96: 11041-11048
        • Brown M.S.
        • Goldstein J.L.
        The SREBP pathway: regulation of cholesterol metabolism by proteolysis of a membrane-bound transcription factor.
        Cell. 1997; 89: 331-340
        • Roth G.
        • Kotzka J.
        • Kremer L.
        • et al.
        MAP kinases Erk1/2 phosphorylate sterol regulatory element-binding protein(SREBP)-1a at serine 117 in vitro.
        J Biol Chem. 2000; 275: 33302-33307
        • Eberle D.
        • Hegarty B.
        • Bossard P.
        • Ferre P.
        • Foufelle F.
        SREBP transcription factors: master regulators of lipid homeostasis.
        Biochimie. 2004; 86: 839-848
        • Castoreno A.B.
        • Wang Y.
        • Stockinger W.
        • et al.
        Transcriptional regulation of phagocytosis-induced membrane biogenesis by sterol regulatory element binding proteins.
        Proc Natl Acad Sci USA. 2005; 102: 13129-13134
        • Demoulin J.B.
        • Ericsson J.
        • Kallin A.
        • et al.
        Platelet-derived growth factor stimulates membrane lipid synthesis through activation of phosphatidylinositol 3-kinase and sterol regulatory element-binding proteins.
        J Biol Chem. 2004; 279: 35392-35402
        • Pillay V.
        • Dass C.R.
        • Choong P.F.
        The urokinase plasminogen activator receptor as a gene therapy target for cancer.
        Trends Biotechnol. 2007; 25: 33-39