title: Precursor of advanced glycation end products mediates ER-stress-induced caspase-3 activation of human dermal fibroblasts through NAD(P)H oxidase 4.
abstract: BACKGROUND
  The precursor for advanced glycation end products, 3-deoxyglucosone (3DG) is highly upregulated in skin explants of diabetic cutaneous wounds, and has been shown to negatively impact dermal fibroblasts, which are crucial in wound remodeling. 3DG induces apoptosis however; the mechanisms involved in the apoptotic action of 3DG in the pathogenesis of diabetic chronic wounds are poorly understood. Therefore, we sought to delineate novel mechanisms involved with the 3DG-collagen induced apoptosis.
  
  
  RESULTS
  Using human dermal fibroblasts, we demonstrated that 3DG-modified collagen induces oxidative stress and caspase-3 activation. Oxidative stress was found to be dependent on the upregulation of NAD(P)H oxidase 4 (Nox4), a reactive oxygen species (ROS) Nox homologue, triggering endoplasmic reticulum (ER) stress, as assessed by the ER stress-induced apoptosis marker Growth Arrest and DNA Damage-inducible gene 153 (GADD153). We demonstrated that 3DG-collagen activated GADD153 via phosphorylation of p38 mitogen activated protein kinase (MAPK), and this was dependent on upstream ROS. Inhibition of ROS and/or p38 MAPK abrogated 3DG-collagen induced caspase-3 activation. Our investigations also demonstrated that 3DG-collagen-induced caspase-3 activation did not signal through the canonical receptor for advanced glycation end products (RAGE) but through integrin alpha1beta1. To further verify the role of integrins, neutralization of integrins alpha1beta1 prevented 3DG-collagen-induced upregulation of ROS, GADD153, and caspase-3 activation; suggesting that 3DG-collagen signaling to the fibroblast is dependent on integrins alpha1beta1.
  
  
  CONCLUSIONS
  Taken together, these findings demonstrate for the first time that a RAGE independent mechanism is involved in 3DG-collagen-induced apoptosis. Moreover, the ER stress pathway through activation of Nox4 by integrins alpha1beta1 plays a key role in 3DG-collagen-induced caspase-3 activation, which may play an important role in the pathogenesis of diabetic wounds.
authors.affiliation: Microbiology and Immunology, Drexel University College of Medicine, Philadelphia, Pennsylvania, United States of America.
authors.forename: Danielle T
authors.initials: DT
authors.lastname: Loughlin
authors.forename: Carol M
authors.initials: CM
authors.lastname: Artlett
mesh_terms: D053148:Caspase 3 / Q000378:metabolism*; D003094:Collagen / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D004789:Enzyme Activation; D005347:Fibroblasts / Q000166:cytology*; D017127:Glycation End Products, Advanced; D006801:Humans; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases / Q000378:metabolism*; D018384:Oxidative Stress; D010766:Phosphorylation; D012867:Skin / Q000166:cytology / Q000378:metabolism*; D051742:Transcription Factor CHOP / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: C497249:DDIT3 protein, human; D017127:Glycation End Products, Advanced; D051742:Transcription Factor CHOP; D003094:Collagen; D000074663:NADPH Oxidase 4; D019255:NADPH Oxidases; C498910:NOX4 protein, human; D048051:p38 Mitogen-Activated Protein Kinases; D053148:Caspase 3