Reversal of redox-dependent inhibition of diacylglycerol kinase by antioxidants in mesangial cells exposed to high glucose
Reversal of redox-dependent inhibition of diacylglycerol kinase by antioxidants in mesangial cells exposed to high glucose
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DOI：
10.3892/mmr.2011.524
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发表时间：
2011-09-01
影响因子：
3.4
通讯作者：
Koya, Daisuke
中科院分区：
文献类型：
--
作者：
Atsumi, Hisanari;Kitada, Munehiro;Koya, Daisuke
二酰甘油（DAG）-蛋白激酶C（PKC）通路的激活是糖尿病肾病的病理机制之一。我们之前报道过，众所周知的抗氧化剂 d-α-生育酚可增强二酰甘油激酶 (DGK) 活性，从而减少链脲佐菌素诱导的糖尿病大鼠肾小球中过量 DAG 积累和 PKC 激活。然而，d-α-生育酚对 DGK 活性的影响是否是通过其抗氧化作用发挥的，仍有待确定。在正常（5.5 mM）或高葡萄糖（27.5 mM）条件下，在存在或不存在两种抗氧化剂（50 μM d-α-生育酚和普罗布考）的情况下，测量培养的人肾小球系膜细胞的 DAG 含量、PKC 和膜 DGK 活性。在存在或不存在300 U/ml过氧化氢酶的情况下将系膜细胞暴露于过氧化氢（H2O2）（10-1000，μM），然后测量DGK活性。两种抗氧化剂都能恢复高葡萄糖诱导的 DGK 活性降低，从而减少高葡萄糖诱导的 DAG-PKC 通路激活。系膜细胞暴露。在不同浓度的H2O2中，DGK活性以剂量依赖性方式降低。向细胞中添加抗氧化酶过氧化氢酶逆转了 H2O2 介导的 DGK 活性下调。总之，在高葡萄糖条件下培养的人系膜细胞中，DGK 活性因氧化应激而降低。抗氧化剂，包括 d-α-生育酚和普罗布考，可以通过增强 DGK 活性来改善高血糖诱导的 DAG-PKC 激活。
Activation of the diacylglycerol (DAG)-protein kinase C (PKC) pathway is one of the pathomechanisms of diabetic nephropathy. We previously reported that d-alpha-tocopherol, well known as an antioxidant, enhances diacylglycerol kinase (DGK) activity, leading to the reduction of excess DAG accumulation and PKC activation in the glomeruli of streptozotocin-induced diabetic rats. However, it remains to be determined whether the effect of d-alpha-tocopherol on DGK activity is exerted through its antioxidative action. DAG contents, PKC and membranous DGK activity were measured in cultured human glomerular mesangial cells under normal (5.5 mM) or high glucose (27.5 mM) conditions in the presence or absence of two antioxidants (50 mu M d-alpha-tocopherol and probucol). Mesangial cells were exposed to hydrogen peroxide (H2O2) (10-1000,mu M) in the presence or absence of 300 U/ml catalase, followed by measurement of DGK activity. Both antioxidants restored the high glucose-induced decrease in DGK activity, resulting in the reduction of high glucose-induced activation of the DAG-PKC pathway. In mesangial cells exposed. to H2O2 at various concentrations, DGK activity decreased in a dose-dependent manner. The addition of antioxidative enzyme catalase to the cells reversed the H2O2-mediated down-regulation of DGK activity. In conclusion, DGK activity is reduced by oxidative stress in human mesangial cells cultured under high glucose conditions. Antioxidants, including d-alpha-tocopherol and probucol may improve hyperglycemia-induced DAG-PKC activation by enhancing DGK activity.