title: Ras activation modulates methylglyoxal-induced mesangial cell apoptosis through superoxide production.
abstract: OBJECTIVE
  While previous studies have demonstrated that diabetic nephropathy is attributable to glucose-derived dicarbonyl compounds, methylglyoxal (MGO)-inducing apoptosis in renal mesangial cells, the molecular mechanism of upper stream redox signaling modulation, has not been fully elucidated.
  
  
  METHODS
  Rat mesangial cells pretreated with or without superoxide dismutase, diphenyloniodium, SB203580, and manumycin A were cultured in methylglyoxal stress-induced apoptosis. Signaling protein expression, flow cytometry, and morphological features of apoptotic cell death were assessed.
  
  
  RESULTS
  Methylglyoxal decreased cell viability in mesangial cells. Superoxide mediated methylglyoxal-induced caspase 3 cleavage. Pretreatment with diphenyloniodium, SB203580, and manumycin A reduced methylglyoxal augmentation of superoxide synthesis and caspase-3 activation. Methylglyoxal rapidly enhanced Ras activation and progressively increased cytosolic P38 and nuclear c-Jun activation. Scavenging of superoxide by superoxide dismutase or diphenyloniodium, inhibiting P38 by SB203580, and inhibiting Ras with manumycin A successfully reduced the promoting effect of methylglyoxal on P38 and c-Jun phosphorylation (activation). Furthermore, pretreatment with superoxide dismutase, diphenyloniodium, SB203580, and manumycin A significantly attenuated methylglyoxal induction of apoptosis on the basis of Annexin-V assay and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labelling (TUNEL) staining.
  
  
  CONCLUSIONS
  This study has shown that methylglyoxal increased Ras modulation of superoxide-mediated P38 activation and c-Jun activation, which resulted in increased apoptosis.
authors.affiliation: Chiayi Campus, Chang Gung Institute of Technology, Pu-tzu City, Chiayi, Taiwan.
authors.forename: Wei Jan
authors.initials: WJ
authors.lastname: Huang
authors.forename: Chun Wu
authors.initials: CW
authors.lastname: Tung
authors.forename: Cheng
authors.initials: C
authors.lastname: Ho
authors.forename: Jen Tsung
authors.initials: JT
authors.lastname: Yang
authors.forename: Min Li
authors.initials: ML
authors.lastname: Chen
authors.forename: Pey Jium
authors.initials: PJ
authors.lastname: Chang
authors.forename: Pei Hsien
authors.initials: PH
authors.lastname: Lee
authors.forename: Chun Liang
authors.initials: CL
authors.lastname: Lin
authors.forename: Jeng Yi
authors.initials: JY
authors.lastname: Wang
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D053148:Caspase 3 / Q000378:metabolism; D002395:Catecholamines / Q000494:pharmacology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D004789:Enzyme Activation; D007093:Imidazoles / Q000494:pharmacology; D048288:Imidazolines / Q000494:pharmacology; D020287:In Situ Nick-End Labeling; D010766:Phosphorylation; D011090:Polyenes / Q000494:pharmacology; D053284:Polyunsaturated Alkamides / Q000494:pharmacology; D016755:Proto-Oncogene Proteins c-jun / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D011765:Pyruvaldehyde / Q000494:pharmacology*; D051381:Rats; D013481:Superoxides / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism; D018631:ras Proteins / Q000378:metabolism*
chemical_list: D002395:Catecholamines; D007093:Imidazoles; D048288:Imidazolines; D011090:Polyenes; D053284:Polyunsaturated Alkamides; D016755:Proto-Oncogene Proteins c-jun; D011725:Pyridines; D013481:Superoxides; D011765:Pyruvaldehyde; C011775:(3,4-dihydroxyphenylamino)-2-imidazoline; D048051:p38 Mitogen-Activated Protein Kinases; D053148:Caspase 3; D018631:ras Proteins; C054474:manumycin; C093642:SB 203580