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This Article Full Text Full Text (PDF) All Versions of this Article: 293/3/E681    most recent 00584.2006v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (4) Citing Articles via Google Scholar Google Scholar Articles by Artwohl, M. Articles by Baumgartner-Parzer, S. M. Search for Related Content PubMed PubMed Citation Articles by Artwohl, M. Articles by Baumgartner-Parzer, S. M.

R-(+)--lipoic acid inhibits endothelial cell apoptosis and proliferation: involvement of Akt and retinoblastoma protein/E2F-1

¹Department of Internal Medicine III, Division of Endocrinology and Metabolism, Medical University of Vienna; ²Division of Molecular Microbiology and Development of Genetic Diagnostics, Children's Cancer Research Institute; ³Center for Biomolecular Medicine and Pharmacology, Institute of Vascular Biology and Thrombosis Research; ⁴Department of Surgery, Division of Vascular Surgery; ⁵Department of Ophthalmology; ⁶Clinical Institute of Pathology; and ⁷Center for Biomedical Techniques and Physics, Medical University of Vienna, Vienna, Austria

Submitted 3 November 2006 ; accepted in final form 8 June 2007

Lipoic acid was recently demonstrated to improve endothelial dysfunction or retinopathy not only in rats but also in diabetic patients. We tested the hypothesis that R-(+)--lipoic acid (LA) directly affects human endothelial cell (EC) function (e.g., apoptosis, proliferation, and protein expression), independent of the cells' vascular origin. Macrovascular EC (macEC), isolated from umbilical (HUVEC) and adult saphenous veins and from aortae, as well as microvascular EC (micEC) from retinae, skin, and uterus, were exposed to LA (1 µmol/l–1 mmol/l) with/without different stimuli (high glucose, TNF-, VEGF, wortmannin, LY-294002). Apoptosis, proliferation, cell cycle distribution, and protein expression were determined by DNA fragmentation assays, [³H]thymidine incorporation, FACS, and Western blot analyses, respectively. In macro- and microvascular EC, LA (1 mmol/l) reduced (P < 0.05) basal (macEC, –36 ± 4%; micEC, –46 ± 6%) and stimulus-induced (TNF-: macEC, –75 ± 11%; micEC, –68 ± 13%) apoptosis. In HUVEC, inhibition of apoptosis by LA (500 µmol/l) was paralleled by reduction of NF-B. LA's antiapoptotic activity was reduced by PI 3-kinase inhibitors (wortmannin, LY-294002), being in line with LA-induced Akt phosphorylation (Ser⁴³⁷, +159 ± 43%; Thr³⁰⁸, +98 ± 25%; P < 0.01). LA (500 µmol/l) inhibited (P < 0.001) proliferation of macEC (–29 ± 3%) and micEC (–29 ± 3%) by arresting the cells at the G₁/S transition due to an increased ratio of cyclin E/p27^Kip (4.2-fold), upregulation of p21^WAF-1/Cip1 (+104 ± 21%), and reduction of cyclin A (–32 ± 11%), of hyperphosphorylated retinoblastoma protein (macEC: –51 ± 7%; micEC: –50 ± 15%), and of E2F-1 (macEC: –48 ± 3%; micEC: –31 ± 10%). LA's ability to inhibit apoptosis and proliferation of ECs could beneficially affect endothelial dysfunction, which precedes manifestation of late diabetic vascular complications.