de Dios S T, Hannan K M, Dilley R J, Hill M A, Little P J
Cell Biology of Diabetes Laboratory, Baker Medical Research Institute, P.O. Box 6492, Victoria, Melbourne 8008, Australia.
J Diabetes Complications. 2001 May-Jun;15(3):120-7. doi: 10.1016/s1056-8727(01)00141-6.
Diabetes is associated with a high level of mortality due to cardiovascular disease resulting from accelerated coronary artery atherosclerosis. A current focus for investigation of atherosclerotic mechanisms is the vascular endothelium since physical or functional injury may represent an initiating step for atherogenesis. Thiazolidinediones (TZDs) are the newest class of drugs for the treatment of insulin resistance and its metabolic consequences; they are peroxisome proliferator-activating receptor (PPAR)-gamma ligands that act as insulin-sensitizing agents. We are interested in the contribution of direct vascular actions to the clinical utility of these agents. We investigated the effect troglitazone and rosiglitazone on endothelial cell proliferation in low- and high-glucose media and further explored their action on the ubiquitous membrane transport system, the Na/H exchanger (NHE), which has been implicated in regulating the growth of vascular cells. Experiments were conducted in cultured bovine aortic endothelial cells (BAECs). Cell proliferation was assessed by cell counting, and NHE activity was determined in cells loaded with the pH-sensitive fluorescent dye, 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein, acetoxymethyl ester (BCECF-AM). Troglitazone caused a dose-dependent inhibition of endothelial cell proliferation with approximately 50% inhibition at 10 microM. Troglitazone inhibited endothelial cell proliferation with similar potency under low- (5 mM) and high-glucose (25 mM) concentrations. Rosiglitazone had no significant effect on endothelial cell proliferation at concentrations of up to 100 microM under low- or high-glucose concentrations. The NHE inhibitor, 3-metlylsulfonyl-4-piperidinobenzoyl guanidine (HOE 694), caused dose dependent inhibition of BAEC proliferation, which was independent of the media glucose concentration. Acute exposure of cells to troglitazone (10 microM) and rosiglitazone (30 microM) during recovery from acidosis showed slight but significant (P<.05) inhibition of NHE activity by troglitazone, but no significant (P>.05) effect by rosiglitazone. Exposure of cells to either drug for 24 h revealed no chronic regulation of NHE activity. Our data demonstrate that troglitazone has similar actions in endothelial cells as in vascular smooth muscle. The absence of rosiglitazone effects, a more potent PPAR-gamma activator, suggests that the observed actions of troglitazone may be at least partially independent of PPAR-gamma. The effects of troglitazone and rosiglitazone on endothelial cell proliferation and NHE activity, although contrasting, are consistent with a central signalling role of this transporter in cell proliferation.
糖尿病与因冠状动脉粥样硬化加速导致的心血管疾病高死亡率相关。目前对动脉粥样硬化机制的研究重点是血管内皮，因为物理或功能损伤可能是动脉粥样硬化发生的起始步骤。噻唑烷二酮类药物（TZDs）是治疗胰岛素抵抗及其代谢后果的最新一类药物；它们是过氧化物酶体增殖物激活受体（PPAR）-γ配体，起胰岛素增敏剂的作用。我们感兴趣的是直接血管作用对这些药物临床效用的贡献。我们研究了曲格列酮和罗格列酮在低糖和高糖培养基中对内皮细胞增殖的影响，并进一步探讨了它们对普遍存在的膜转运系统——钠/氢交换体（NHE）的作用，该交换体与调节血管细胞生长有关。实验在培养的牛主动脉内皮细胞（BAECs）中进行。通过细胞计数评估细胞增殖，并使用对pH敏感的荧光染料2',7'-双（2-羧乙基）-5-（和-6）-羧基荧光素乙酰氧基甲酯（BCECF-AM）加载细胞来测定NHE活性。曲格列酮引起内皮细胞增殖的剂量依赖性抑制，在10 microM时约有50%的抑制率。在低（5 mM）和高糖（25 mM）浓度下，曲格列酮以相似的效力抑制内皮细胞增殖。在低糖或高糖浓度下，罗格列酮在高达100 microM的浓度下对内皮细胞增殖无显著影响。NHE抑制剂3-甲基磺酰基-4-哌啶苯甲酰胍（HOE 694）引起BAEC增殖的剂量依赖性抑制，这与培养基葡萄糖浓度无关。在酸中毒恢复过程中，细胞急性暴露于曲格列酮（10 microM）和罗格列酮（30 microM）显示，曲格列酮对NHE活性有轻微但显著（P<0.05）的抑制作用，而罗格列酮无显著（P>0.05）影响。细胞暴露于任何一种药物24小时均未显示对NHE活性的慢性调节。我们的数据表明，曲格列酮在内皮细胞中的作用与在血管平滑肌中的作用相似。更有效的PPAR-γ激活剂罗格列酮无作用，这表明曲格列酮观察到的作用可能至少部分独立于PPAR-γ。曲格列酮和罗格列酮对内皮细胞增殖和NHE活性的影响虽然不同，但与该转运体在细胞增殖中的核心信号作用一致。
