Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA.
Diabetes. 2012 Jan;61(1):104-13. doi: 10.2337/db11-0990. Epub 2011 Dec 6.
IGF-I-stimulated sarcoma viral oncogene (Src) activation during hyperglycemia is required for propagating downstream signaling. The aim of the current study was to determine the mechanism by which hyperglycemia enhances IGF-I-stimulated Src activation and the role of NADPH oxidase 4 (Nox4) and protein kinase C ζ (PKCζ) in mediating this response in vascular smooth muscle cells (VSMCs). Nox4 expression was analyzed in VSMCs exposed to hyperglycemia. The role of Nox4-derived reactive oxygen species (ROS) in IGF-I-stimulated Src activation was investigated via knockdown of Nox4. Different isoforms of PKC were screened to investigate their role in hyperglycemia-induced Nox4. The oxidation of Src was shown to be a prerequisite for its activation in response to IGF-I during hyperglycemia. Hyperglycemia induced Nox4, but not Nox1, and p22 phagocyte oxidase (p22phox) expression and IGF-I stimulated Nox4/p22phox complex formation, leading to increased ROS generation. Knockdown of Nox4 prevented ROS generation and impaired the oxidation and activation of Src in response to IGF-I, whereas knockdown of Nox1 had no effect. PKCζ was shown to mediate the hyperglycemia-induced increase in Nox4 expression. The key observations in cultured VSMCs were confirmed in the diabetic mice. Nox4-derived ROS is responsible for the enhancing effect of hyperglycemia on IGF-I-stimulated Src activation, which in turn amplifies IGF-I-linked downstream signaling and biological actions.
高血糖症会刺激 IGF-I 刺激的肉瘤病毒癌基因(Src)激活,从而传播下游信号。本研究的目的是确定高血糖增强 IGF-I 刺激的 Src 激活的机制,以及 NADPH 氧化酶 4(Nox4)和蛋白激酶 C ζ(PKCζ)在介导血管平滑肌细胞(VSMCs)中的这种反应中的作用。分析了高血糖症暴露的 VSMCs 中的 Nox4 表达。通过敲低 Nox4 研究了 Nox4 衍生的活性氧(ROS)在 IGF-I 刺激的 Src 激活中的作用。筛选了不同的 PKC 同工型,以研究它们在高血糖诱导的 Nox4 中的作用。研究表明,Src 的氧化是其对高血糖症下 IGF-I 反应的激活的前提条件。高血糖症诱导 Nox4,但不诱导 Nox1 和吞噬细胞氧化酶 p22(p22phox)的表达,并刺激 IGF-I 刺激的 Nox4/p22phox 复合物形成,导致 ROS 生成增加。敲低 Nox4 可防止 ROS 生成,并损害对 IGF-I 的 Src 氧化和激活,而敲低 Nox1 则没有影响。PKCζ 介导了高血糖诱导的 Nox4 表达增加。在培养的 VSMCs 中的关键观察结果在糖尿病小鼠中得到了证实。Nox4 衍生的 ROS 负责增强高血糖症对 IGF-I 刺激的 Src 激活的作用,从而放大 IGF-I 相关的下游信号和生物学作用。