title: Mechanism of hyperhomocysteinemia-induced vascular endothelium dysfunction - possible dysregulation of phosphatidylinositol-3-kinase and its downstream phosphoinositide dependent kinase and protein kinase B.
abstract: Imbalance of l-arginine/endothelial nitric oxide synthatase (eNOS) activity is the hallmark of vascular endothelium dysfunction. Hyperhomocysteinemia (Hhy) has been identified as a potential risk factor for vascular endothelium dysfunction that leads to cardiovascular disorders. Phosphatidylinositol-3 kinase (PI3K) is a ubiquitous enzyme involved in plethora of cell signaling including the endothelial cells and it has been reported that signaling through this enzyme and its downstream pathway viz phosphoinositide-dependent kinase (PDK)/protein kinase B (Akt) and eNOS is impaired in diseased conditions. Thus present study was designed to investigate the role of PI3K and PDK/Akt in vascular endothelium dysfunction produced by Hhy. Hhy was produced by administering l-methionine (1.7%w/w, p.o). After four weeks of l-methionine administration, vascular endothelium dysfunction was assessed in terms of attenuation of acetylcholine-induced endothelium dependent relaxation (Isolated aortic ring preparation), a decrease in serum nitrite level, mRNA expression of eNOS (rtPCR) and disruption of integrity of vascular endothelium (Electron microscopy). Administration of insulin (0.6 IU/kg/day, s.c), YS-49 (1.6 mg/kg/day, i.p), DAQB1 (5mg/kg/day, i.p) and atorvastatin (30 mg/kg/day, p.o) significantly improved acetylcholine-induced endothelium-dependent relaxation, serum nitrate/nitrite level, mRNA expression of eNOS and integrity of vascular endothelium. This ameliorative effect of insulin was blocked by wortmannin (inhibitor of PI3K), UCN-01(PDK inhibitor), API-2 (Akt inhibitor) and l-NAME (eNOS inhibitor). Thus, it may be concluded that activation of PI3K and its downstream pathways viz. PDK/Akt and eNOS improve Hhy-induced vascular endothelium dysfunction and that therapeutic interventions designed for these pathways may provide potential therapeutic strategies to combat vascular complications.
authors.affiliation: Department of Pharmacology, I.S.F. College of Pharmacy, G.T. Road, Moga 142001, Punjab, India.
authors.forename: Saurabh
authors.initials: S
authors.lastname: Sharma
authors.forename: Manjeet
authors.initials: M
authors.lastname: Singh
authors.forename: Pyare Lal
authors.initials: PL
authors.lastname: Sharma
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases / Q000378:metabolism*; D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D004730:Endothelium, Vascular / Q000187:drug effects / Q000201:enzymology* / Q000473:pathology*; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006710:Homocysteine / Q000097:blood; D020138:Hyperhomocysteinemia / Q000097:blood / Q000201:enzymology* / Q000473:pathology* / Q000503:physiopathology; D008297:Male; D009566:Nitrates / Q000097:blood; D052250:Nitric Oxide Synthase Type III / Q000235:genetics; D009573:Nitrites / Q000097:blood; D009599:Nitroprusside / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D014664:Vasodilation / Q000187:drug effects
chemical_list: D009566:Nitrates; D009573:Nitrites; D012333:RNA, Messenger; D006710:Homocysteine; D009599:Nitroprusside; D052250:Nitric Oxide Synthase Type III; D019869:Phosphatidylinositol 3-Kinases; D064413:3-Phosphoinositide-Dependent Protein Kinases; D051057:Proto-Oncogene Proteins c-akt; D000109:Acetylcholine
keywords: Hyperhomocysteinemia; Protein tyrosine phosphatase; Vascular endothelium dysfunction; eNOS (Endothelial nitric oxide synthatase)