title: Aminoacetone, a putative endogenous source of methylglyoxal, causes oxidative stress and death to insulin-producing RINm5f cells.
abstract: Aminoacetone (AA), triose phosphates, and acetone are putative endogenous sources of potentially cytotoxic and genotoxic methylglyoxal (MG), which has been reported to be augmented in the plasma of diabetic patients. In these patients, accumulation of MG derived from aminoacetone, a threonine and glycine catabolite, is inferred from the observed concomitant endothelial overexpression of circulating semicarbazide-sensitive amine oxidases. These copper-dependent enzymes catalyze the oxidation of primary amines, such as AA and methylamine, by molecular oxygen, to the corresponding aldehydes, NH4(+) ion and H2O2. We recently reported that AA aerobic oxidation to MG also takes place immediately upon addition of catalytic amounts of copper and iron ions. Taking into account that (i) MG and H2O2 are reportedly cytotoxic to insulin-producing cell lineages such as RINm5f and that (ii) the metal-catalyzed oxidation of AA is propagated by O2(*-) radical anion, we decided to investigate the possible pro-oxidant action of AA on these cells taken here as a reliable model system for pancreatic beta-cells. Indeed, we show that AA (0.10-5.0 mM) administration to RINm5f cultures induces cell death. Ferrous (50-300 microM) and Fe(3+) ion (100 microM) addition to the cell cultures had no effect, whereas Cu(2+) (5.0-100 microM) significantly increased cell death. Supplementation of the AA- and Cu(2+)-containing culture medium with antioxidants, such as catalase (5.0 microM), superoxide dismutase (SOD, 50 U/mL), and N-acetylcysteine (NAC, 5.0 mM) led to partial protection. mRNA expression of MnSOD, CuZnSOD, glutathione peroxidase, and glutathione reductase, but not of catalase, is higher in cells treated with AA (0.50-1.0 mM) plus Cu(2+) ions (10-50 microM) relative to control cultures. This may imply higher activity of antioxidant enzymes in RINm5f AA-treated cells. In addition, we have found that AA (0.50-1.0 mM) plus Cu(2+) (100 microM) (i) increase RINm5f cytosolic calcium; (ii) promote DNA fragmentation; and (iii) increase the pro-apoptotic (Bax)/antiapoptotic (Bcl-2) ratio at the level of mRNA expression. In conclusion, although both normal and pathological concentrations of AA are probably much lower than those used here, it is tempting to propose that excess AA in diabetic patients may drive oxidative damage and eventually the death of pancreatic beta-cells.
authors: Departamento de Bioquimica, Instituto de Quimica, Universidade de Sao Paulo, SP, Brazil.
authors: Adriano
authors: A
authors: Sartori
authors: Humberto M
authors: HM
authors: Garay-Malpartida
authors: Maria F
authors: MF
authors: Forni
authors: Robert I
authors: RI
authors: Schumacher
authors: Fernando
authors: F
authors: Dutra
authors: Mari C
authors: MC
authors: Sogayar
authors: Etelvino J H
authors: EJ
authors: Bechara
mesh_terms: D000096:Acetone / Q000031:analogs & derivatives* / Q000737:chemistry / Q000494:pharmacology; D000111:Acetylcysteine / Q000494:pharmacology; D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002374:Catalase / Q000494:pharmacology; D016923:Cell Death / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003300:Copper / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D051379:Mice; D015394:Molecular Structure; D041681:NIH 3T3 Cells; D018384:Oxidative Stress / Q000187:drug effects*; D012333:RNA, Messenger / Q000378:metabolism; D013482:Superoxide Dismutase / Q000494:pharmacology; D014306:Trioses / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D007328:Insulin; D012333:RNA, Messenger; D014306:Trioses; D000096:Acetone; D003300:Copper; D002374:Catalase; D013482:Superoxide Dismutase; D000111:Acetylcysteine; C006495:aminoacetone