title: p16ink4a Expression Is Increased through 12-Lipoxygenase in High Glucose-Stimulated Glomerular Mesangial Cells and Type 2 Diabetic Glomeruli.
abstract: OBJECTIVE
  Arachidonic acid-metabolizing enzyme, 12-lipoxygenase (12-LO), is involved in the glomerular hypertrophy of diabetic nephropathy (DN), in which cyclin-dependent kinase inhibitors (CKIs) play important roles. However, it is unclear whether 12-LO regulates the expression of the CKI p16(ink4a) in DN.
  
  
  METHODS
  Primary glomerular mesangial cells (MCs) and glomeruli isolated from rats were used in this study. The rats were fed a high-fat diet and given low-dose streptozotocin to induce type 2 diabetes. The 12-LO product, 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), was infused through an osmotic minipump. Enzyme-linked immunosorbent assay, Western blot, and morphometric analyses were performed.
  
  
  RESULTS
  High glucose (HG) increased the p16(ink4a) protein expression in MCs, but this increase was prevented by the 12-LO inhibitor, cinnamyl-3,​4-dihydroxy-α-cynanocinnamate (CDC). The levels of p-p38MAPK and p16(ink4a) in MCs were significantly elevated after the 12(S)-HETE treatment, whereas the p38MAPK inhibitor SB203580 prevented these increases. Compared with levels in control MCs, marked increases in p38MAPK activation and p16(ink4a) expression were observed in MCs plated on collagen IV, while the CDC treatment prevented these changes. Subcutaneous injection of CDC did not affect glucose levels, but completely attenuated the diabetes-related increases in the 12(S)-HETE content, p16(ink4a) expression, p-p38MAPK levels, glomerular volume, and the kidney/body weight ratio. Compared with levels in controls, p16(ink4a) and p-p38MAPK in the glomeruli derived from 12(S)-HETE-treated rats were significantly higher.
  
  
  CONCLUSIONS
  12-LO-p38MAPK mediates the upregulation of p16(ink4a) in HG-stimulated MCs and type 2-diabetic glomeruli, and new therapies aimed at 12-LO inhibition may prove beneficial in ameliorating diabetes-induced glomerular hypertrophy.
authors.affiliation: Department of Nephrology, The First Hospital of Jilin University, Changchun, China.
authors.forename: Yuan-yuan
authors.initials: YY
authors.lastname: Zhang
authors.forename: Qiao-yan
authors.initials: QY
authors.lastname: Guo
authors.forename: Mei-yan
authors.initials: MY
authors.lastname: Wu
authors.forename: Chong-sen
authors.initials: CS
authors.lastname: Zang
authors.forename: Fu-zhe
authors.initials: FZ
authors.lastname: Ma
authors.forename: Tao
authors.initials: T
authors.lastname: Sun
authors.forename: Wan-ning
authors.initials: WN
authors.lastname: Wang
authors.forename: Li-ning
authors.initials: LN
authors.lastname: Miao
authors.forename: Zhong-gao
authors.initials: ZG
authors.lastname: Xu
mesh_terms: D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid / Q000008:administration & dosage; D000818:Animals; D001092:Arachidonate 12-Lipoxygenase / Q000378:metabolism*; D002478:Cells, Cultured; D024141:Collagen Type IV / Q000378:metabolism; D019941:Cyclin-Dependent Kinase Inhibitor p16 / Q000378:metabolism*; D003924:Diabetes Mellitus, Type 2 / Q000201:enzymology / Q000378:metabolism*; D003928:Diabetic Nephropathies / Q000201:enzymology / Q000378:metabolism*; D005920:Glomerular Mesangium / Q000187:drug effects* / Q000201:enzymology / Q000378:metabolism; D005947:Glucose / Q000008:administration & dosage*; D051381:Rats; D017207:Rats, Sprague-Dawley; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
chemical_list: D024141:Collagen Type IV; D019941:Cyclin-Dependent Kinase Inhibitor p16; D019377:12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; D001092:Arachidonate 12-Lipoxygenase; D048051:p38 Mitogen-Activated Protein Kinases; D005947:Glucose