Harold Hamm Oklahoma Diabetes Center and Section of Endocrinology and Diabetes, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA.
Diabetes. 2010 Jun;59(6):1528-38. doi: 10.2337/db09-1057. Epub 2010 Mar 23.
Oxidative stress is a key pathogenic factor in diabetic retinopathy. We previously showed that lovastatin mitigates blood-retinal barrier (BRB) breakdown in db/db mice. The purpose of this study is to determine the mechanisms underlying the salutary effects of lovastatin in diabetic retinopathy.
Expression of NADPH oxidase (Nox) 4, vascular endothelial growth factor (VEGF), and hypoxia-inducible factor (HIF)-1alpha; production of reactive oxygen species (ROS); and retinal vascular permeability were measured in cultured retinal capillary endothelial cells (RCECs) and in db/db mice treated with lovastatin.
Expressions of Nox4 and VEGF were significantly increased in retinas of db/db mice and reduced by lovastatin treatment. In cultured RCECs, hypoxia and high glucose upregulated mRNA and protein expression of Nox4, ROS generation, and VEGF level. These changes were abrogated by pretreatment with lovastatin or NADPH oxidase inhibitor diphenyleneiodonium chloride. Overexpression of Nox4 increased basal level of ROS generation, HIF-1alpha, and VEGF expression in RCECs. In contrast, blockade of Nox4 activity using adenovirus-expressing dominant-negative Nox4 abolished hypoxia- and high-glucose-induced ROS production and VEGF expression. Moreover, inhibition of Nox4 attenuated hypoxia-induced upregulation of HIF-1alpha and high-glucose-elicited phosphorylation of STAT3. Finally, depletion of Nox4 by adenovirus-delivered Nox4 small interfering RNA significantly decreased retinal NADPH oxidase activity and VEGF expression and reduced retinal vascular premeability in db/db mice.
Activation of Nox4 plays an important role in high-glucose- and hypoxia-mediated VEGF expression and diabetes-induced BRB breakdown. Inhibition of Nox4, at least in part, contributes to the protective effects of lovastatin in diabetic retinopathy.
氧化应激是糖尿病性视网膜病变的一个关键致病因素。我们之前的研究表明，洛伐他汀可减轻 db/db 小鼠的血视网膜屏障（BRB）破坏。本研究的目的是确定洛伐他汀在糖尿病性视网膜病变中的有益作用的机制。
在培养的视网膜毛细血管内皮细胞（RCEC）和用洛伐他汀治疗的 db/db 小鼠中测量 NADPH 氧化酶（Nox）4、血管内皮生长因子（VEGF）和缺氧诱导因子（HIF）-1α的表达；活性氧（ROS）的产生；以及视网膜血管通透性。
db/db 小鼠视网膜中 Nox4 和 VEGF 的表达显着增加，而洛伐他汀治疗则降低了它们的表达。在培养的 RCEC 中，缺氧和高葡萄糖增加了 Nox4 的 mRNA 和蛋白表达、ROS 的产生以及 VEGF 水平。这些变化被洛伐他汀或 NADPH 氧化酶抑制剂二苯乙烯碘氯预处理所阻断。Nox4 的过表达增加了 RCEC 中 ROS 生成、HIF-1α和 VEGF 表达的基础水平。相反，使用表达显性负性 Nox4 的腺病毒阻断 Nox4 活性消除了缺氧和高葡萄糖诱导的 ROS 产生和 VEGF 表达。此外，抑制 Nox4 可减弱缺氧诱导的 HIF-1α上调和高葡萄糖引起的 STAT3 磷酸化。最后，用腺病毒递送的 Nox4 小干扰 RNA 耗尽 Nox4 可显着降低 db/db 小鼠的视网膜 NADPH 氧化酶活性和 VEGF 表达，并减少视网膜血管通透性。
Nox4 的激活在高葡萄糖和缺氧介导的 VEGF 表达以及糖尿病引起的 BRB 破坏中起重要作用。抑制 Nox4 至少部分有助于洛伐他汀在糖尿病性视网膜病变中的保护作用。
