title: Activation of intracellular angiotensin AT₂ receptors induces rapid cell death in human uterine leiomyosarcoma cells.
abstract: The presence of angiotensin type 2 (AT₂) receptors in mitochondria and their role in NO generation and cell aging were recently demonstrated in various human and mouse non-tumour cells. We investigated the intracellular distribution of AT₂ receptors including their presence in mitochondria and their role in the induction of apoptosis and cell death in cultured human uterine leiomyosarcoma (SK-UT-1) cells and control human uterine smooth muscle cells (HutSMC). The intracellular levels of the AT₂ receptor are low in proliferating SK-UT-1 cells but the receptor is substantially up-regulated in quiescent SK-UT-1 cells with high densities in mitochondria. Activation of the cell membrane AT₂ receptors by a concomitant treatment with angiotensin II and the AT₁ receptor antagonist, losartan, induces apoptosis but does not affect the rate of cell death. We demonstrate for the first time that the high-affinity, non-peptide AT₂ receptor agonist, Compound 21 (C21), penetrates the cell membrane of quiescent SK-UT-1 cells, activates intracellular AT₂ receptors and induces rapid cell death; approximately 70% of cells died within 24 h. The cells, which escaped cell death, displayed activation of the mitochondrial apoptotic pathway, i.e. down-regulation of the Bcl-2 protein, induction of the Bax protein and activation of caspase-3. All quiescent SK-UT-1 cells died within 5 days after treatment with a single dose of C21. C21 was devoid of cytotoxic effects in proliferating SK-UT-1 cells and in quiescent HutSMC. Our results point to a new, unique approach enabling the elimination non-cycling uterine leiomyosarcoma cells providing that they over-express the AT₂ receptor.
authors.affiliation: *Department of Nuclear Medicine, Molecular Imaging, Diagnostics and Therapy, University Hospitals of Schleswig-Holstein, Campus Kiel, 24105, Kiel, Germany.
authors.forename: Yi
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: *Department of Nuclear Medicine, Molecular Imaging, Diagnostics and Therapy, University Hospitals of Schleswig-Holstein, Campus Kiel, 24105, Kiel, Germany.
authors.forename: Ulf
authors.initials: U
authors.lastname: Lützen
authors.affiliation: †Institute of Immunology, University Hospitals of Schleswig-Holstein, Campus Kiel, 24105, Kiel, Germany.
authors.forename: Jürgen
authors.initials: J
authors.lastname: Fritsch
authors.affiliation: *Department of Nuclear Medicine, Molecular Imaging, Diagnostics and Therapy, University Hospitals of Schleswig-Holstein, Campus Kiel, 24105, Kiel, Germany.
authors.forename: Maaz
authors.initials: M
authors.lastname: Zuhayra
authors.affiliation: †Institute of Immunology, University Hospitals of Schleswig-Holstein, Campus Kiel, 24105, Kiel, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Schütze
authors.affiliation: ‡Department of Cardiovascular and Renal Research, Institute of Molecular Medicine, 5000 Odense, Denmark.
authors.forename: Ulrike M
authors.initials: UM
authors.lastname: Steckelings
authors.affiliation: §Cardiovascular Research Institute Maastricht, 6229 ER Maastricht, The Netherlands.
authors.forename: Chiara
authors.initials: C
authors.lastname: Recanti
authors.affiliation: §Cardiovascular Research Institute Maastricht, 6229 ER Maastricht, The Netherlands.
authors.forename: Pawel
authors.initials: P
authors.lastname: Namsoleck
authors.affiliation: §Cardiovascular Research Institute Maastricht, 6229 ER Maastricht, The Netherlands.
authors.forename: Thomas
authors.initials: T
authors.lastname: Unger
authors.affiliation: ║Institute of Experimental and Clinical Pharmacology, University Hospitals of Schleswig-Holstein, Campus Kiel, 24105, Kiel, Germany.
authors.forename: Juraj
authors.initials: J
authors.lastname: Culman
mesh_terms: D000970:Antineoplastic Agents / Q000378:metabolism / Q000494:pharmacology* / Q000633:toxicity; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D049109:Cell Proliferation; D005260:Female; D006801:Humans; D007890:Leiomyosarcoma / Q000378:metabolism* / Q000473:pathology; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D010539:Permeability; D044139:Receptor, Angiotensin, Type 2 / Q000819:agonists* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D013997:Time Factors; D014594:Uterine Neoplasms / Q000378:metabolism* / Q000473:pathology
chemical_list: D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; D044139:Receptor, Angiotensin, Type 2