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Given a passage with a context and an answer, construct a question on the basis of the information present in the passage. Construct the question in such a way that (i) it is unambiguous, (ii) it is answerable from the passage, (iii) its answer is unique (iv) it answer uses text phrases from the passage. Avoid creating questions that (i) can't be answered correctly without actually understanding the passage and (ii) uses the same words or phrases given in the passage.

Context: Cilostazol, a selective inhibitor of PDE3, has a protective effect on endothelium after ischemic vascular damage, through production of nitric oxide (NO). The purpose of the present study was to clarify the molecular mechanisms underlying the preventive effect of treatment with cilostazol on oxidative stress-induced premature senescence in human endothelial cells.', 'Prematurely senescent human umbilical vein endothelial cells (HUVECs) were induced by treatment with hydrogen peroxide (H(2)O(2)) as judged by senescence-associated beta-galactosidase assay (SA-betagal), cell morphological appearance, and plasminogen activator inhibitor-1 (PAI-1) expression. Treatment with H(2)O(2) caused 93% of the cells to be SA-betagal positive, whereas 46% of cilostazol (100 micromol/L)-treated cells were positive. HUVECs treated with other cAMP-elevating agents and DETA-NO showed a reduction of SA-betagal-positive cells as well. Cilostazol increased phosphorylation of Akt at Ser(473) and of endothelial nitric oxide synthase (eNOS) at Ser(1177), with a dose-dependent increase in Sirt1 expression. Moreover, the effect of cilostazol on premature senescence was abrogated through inhibition of Sirt1.
Answer: Our results indicated that cilostazol exerted protective effects against endothelial senescence and dysfunction, and enhancement of NO production is a key mediator in upregulation of Sirt1.
Output:
Does cilostazol inhibit oxidative stress-induced premature senescence via upregulation of Sirt1 in human endothelial cells?