title: Hyperglycemia enhances IGF-I-stimulated Src activation via increasing Nox4-derived reactive oxygen species in a PKCζ-dependent manner in vascular smooth muscle cells.
abstract: 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.
authors.affiliation: Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, North Carolina, USA.
authors.forename: Gang
authors.initials: G
authors.lastname: Xi
authors.forename: Xinchun
authors.initials: X
authors.lastname: Shen
authors.forename: Laura A
authors.initials: LA
authors.lastname: Maile
authors.forename: Christine
authors.initials: C
authors.lastname: Wai
authors.forename: Katherine
authors.initials: K
authors.lastname: Gollahon
authors.forename: David R
authors.initials: DR
authors.lastname: Clemmons
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002478:Cells, Cultured; D004789:Enzyme Activation / Q000187:drug effects; D006943:Hyperglycemia / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000378:metabolism*; D010084:Oxidation-Reduction / Q000187:drug effects; D011493:Protein Kinase C / Q000378:metabolism / Q000502:physiology*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism*; D000099221:Protein Kinase C zeta
chemical_list: D000975:Antioxidants; D007334:Insulin-Like Growth Factor I; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; D011493:Protein Kinase C; D016392:Proto-Oncogene Proteins pp60(c-src); D017382:Reactive Oxygen Species; D000099221:Protein Kinase C zeta; C422943:Nox4 protein, mouse