title: Losartan improves aortic endothelium-dependent relaxation via proline-rich tyrosine kinase 2/Src/Akt pathway in type 2 diabetic Goto-Kakizaki rats.
abstract: In diabetic states, endothelial dysfunction is related to vascular complications. We hypothesized that insulin-induced relaxation and the associated proline-rich tyrosine kinase 2 (Pyk2)/Src/Akt pathway would be abnormal in aortas from the Goto-Kakizaki (GK) type 2 diabetic rat, which exhibits hyperglycemia/insulin resistance, and that losartan treatment of such rats (25 mg·kg(-1)·day(-1) for 2 wk) would correct these abnormalities. Endothelium-dependent relaxation was by measuring isometric force in helical strips of aortas from four groups, each of 30 rats: normal Wistar (control), GK (diabetic), losartan-treated normal, and losartan-treated GK. Pyk2, Src, and Akt/endothelial nitric oxide synthase (eNOS) signaling-pathway protein levels and activities were assayed mainly by Western blotting and partly by immunohistochemistry. In GK (vs. age-matched control) aortas, various insulin-stimulated levels [nitric oxide production and the phosphorylations of eNOS at Ser(1177), of Akt at Thr(308), of phosphoinositide-dependent kinase-1 (PDK1) at Ser(241), of Src at Tyr(416), and of Pyk2 at Tyr(579)] were all significantly decreased and unaffected by either Src inhibitor (PP2) or Pyk2 inhibitor (AG17), while the insulin-stimulated levels of insulin receptor substrate (IRS)-1 phosphorylation at Ser(307), total-eNOS, and total-Akt were significantly increased. Losartan treatment normalized these altered levels. The insulin-stimulated phosphorylation levels of Src/PDK1/Akt/eNOS, but not of Pyk2, were decreased by PP2 in control and losartan-treated GK, but not in GK, aortas. These results suggest that in the GK diabetic aorta increased phospho-IRS-1 (at Ser(307)) and decreased Pyk2/Src activity inhibit insulin-induced stimulation of the PDK/Akt/eNOS pathway. The observed increase in phospho-IRS-1 (at Ser(307)) may result from increased angiotensin II activity.
authors.affiliation: Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University, Shinagawa-ku, Tokyo, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Nemoto
authors.forename: Tsuneo
authors.initials: T
authors.lastname: Kobayashi
authors.forename: Kumiko
authors.initials: K
authors.lastname: Taguchi
authors.forename: Takayuki
authors.initials: T
authors.lastname: Matsumoto
authors.forename: Katsuo
authors.initials: K
authors.lastname: Kamata
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D000804:Angiotensin II / Q000378:metabolism; D047228:Angiotensin II Type 1 Receptor Blockers / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects* / Q000201:enzymology / Q000503:physiopathology; D015153:Blotting, Western; D003924:Diabetes Mellitus, Type 2 / Q000188:drug therapy* / Q000201:enzymology / Q000503:physiopathology; D003925:Diabetic Angiopathies / Q000188:drug therapy* / Q000201:enzymology / Q000209:etiology / Q000503:physiopathology; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000201:enzymology / Q000503:physiopathology; D051418:Focal Adhesion Kinase 2 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D007150:Immunohistochemistry; D007328:Insulin / Q000378:metabolism; D055504:Insulin Receptor Substrate Proteins / Q000378:metabolism; D007333:Insulin Resistance; D019808:Losartan / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D058539:Phosphatidylinositol 3-Kinase / Q000378:metabolism; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D014664:Vasodilation / Q000187:drug effects*; D014665:Vasodilator Agents / Q000494:pharmacology; D019061:src-Family Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D047228:Angiotensin II Type 1 Receptor Blockers; D007328:Insulin; D055504:Insulin Receptor Substrate Proteins; C526296:Irs1 protein, rat; D047428:Protein Kinase Inhibitors; D014665:Vasodilator Agents; D000804:Angiotensin II; D009569:Nitric Oxide; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat; D058539:Phosphatidylinositol 3-Kinase; D051418:Focal Adhesion Kinase 2; C496054:Ptk2b protein, rat; D019061:src-Family Kinases; D064413:3-Phosphoinositide-Dependent Protein Kinases; C578579:Pdpk1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D019808:Losartan