title: Endogenous oxidative stress, but not ER stress, induces hypoxia-independent VEGF120 release through PI3K-dependent pathways in 3T3-L1 adipocytes.
abstract: OBJECTIVE
  Expressions of vascular endothelial growth factor (VEGF) are increased in obese adipocytes and is secreted from obese adipose tissue through hypoxia-independent pathways. Therefore, we investigated the hypoxia-independent mechanism underlying increased expression and release of VEGF in obese adipocytes.
  
  
  METHODS
  We compared signal transduction pathways regulating VEGF with those regulating monocyte chemoattractant protein-1 (MCP-1), which is increased in obese adipocytes, in an in vitro model of artificially hypertrophied 3T3-L1 adipocytes preloaded with palmitate, without the influence of hypoxia.
  
  
  RESULTS
  Palmitate-preloaded cells exhibited significantly enhanced oxidative stress (P < 0.01) and showed increased VEGF120 and MCP-1 release (P < 0.01, respectively), while endoplasmic reticulum (ER) stress was not induced. Increased VEGF120 release was significantly decreased with PI3K inhibitor LY294002 (P < 0.01). In addition, antioxidant N-acetyl-cysteine (NAC) markedly diminished not only VEGF120 secretion (P < 0.01) but also augmented Akt phosphorylation on Ser473 (P < 0.01). In contrast, increased MCP-1 release was suppressed with JNK inhibitor SP600125 and p38 MAPK inhibitor SB203580 (P < 0.01).
  
  
  CONCLUSIONS
  VEGF120 release from hypertrophied adipocytes can be enhanced through PI3K pathways activated by oxidative stress but not by ER stress, suggesting that VEGF120 secretion is regulated through oxidative stress-dependent pathways distinct from those involved in MCP-1 release through either JNK or p38 MAPK activation.
authors.affiliation: Third Department of Internal Medicine, Kyorin University School of Medicine, Mitaka, Tokyo, Japan.
authors.forename: Kazuto
authors.initials: K
authors.lastname: Takahashi
authors.forename: Kaoru
authors.initials: K
authors.lastname: Miyokawa-Gorin
authors.forename: Keiko
authors.initials: K
authors.lastname: Handa
authors.forename: Atsuko
authors.initials: A
authors.lastname: Kitahara
authors.forename: Rie
authors.initials: R
authors.lastname: Moriya
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Onuma
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Sumitani
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Tanaka
authors.forename: Hidenori
authors.initials: H
authors.lastname: Katsuta
authors.forename: Susumu
authors.initials: S
authors.lastname: Nishida
authors.forename: Katsuhiko
authors.initials: K
authors.lastname: Yoshimoto
authors.forename: Hideki
authors.initials: H
authors.lastname: Ohno
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Ishida
mesh_terms: D041721:3T3-L1 Cells; D000111:Acetylcysteine / Q000494:pharmacology; D017667:Adipocytes / Q000166:cytology / Q000378:metabolism; D000818:Animals; D015687:Cell Hypoxia; D018932:Chemokine CCL2 / Q000378:metabolism; D002867:Chromones / Q000494:pharmacology; D059865:Endoplasmic Reticulum Stress / Q000502:physiology*; D007093:Imidazoles / Q000494:pharmacology; D051379:Mice; D009025:Morpholines / Q000494:pharmacology; D018384:Oxidative Stress / Q000502:physiology*; D010168:Palmitates / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D015398:Signal Transduction; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D002867:Chromones; D007093:Imidazoles; D009025:Morpholines; D010168:Palmitates; D011725:Pyridines; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; D019869:Phosphatidylinositol 3-Kinases; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; C093642:SB 203580; D000111:Acetylcysteine