title: Diglycolic acid, the toxic metabolite of diethylene glycol, chelates calcium and produces renal mitochondrial dysfunction in vitro.
abstract: BACKGROUND
  Diethylene glycol (DEG) has caused many cases of acute kidney injury and deaths worldwide. Diglycolic acid (DGA) is the metabolite responsible for the renal toxicity, but its toxic mechanism remains unclear.
  
  
  OBJECTIVE
  To characterize the mitochondrial dysfunction produced from DGA by examining several mitochondrial processes potentially contributing to renal cell toxicity.
  
  
  METHODS
  The effect of DGA on mitochondrial membrane potential was examined in normal human proximal tubule (HPT) cells. Isolated rat kidney mitochondria were used to assess the effects of DGA on mitochondrial function, including respiratory parameters (States 3 and 4), electron transport chain complex activities and calcium-induced opening of the mitochondrial permeability transition pore. DGA was compared with ethylene glycol tetraacetic acid (EGTA) to determine calcium chelating ability. DGA cytotoxicity was assessed using lactate dehydrogenase leakage from cultured proximal tubule cells.
  
  
  RESULTS
  DGA decreased the mitochondrial membrane potential in HPT cells. In rat kidney mitochondria, DGA decreased State 3 respiration, but did not affect State 4 respiration or the ADP/O ratio. DGA reduced glutamate/malate respiration at lower DGA concentrations (0.5 mmol/L) than succinate respiration (100 mmol/L). DGA inhibited Complex II activity without altering Complex I, III or IV activities. DGA blocked calcium-induced mitochondrial swelling, indicating inhibition of the calcium-dependent mitochondrial permeability transition. DGA and EGTA reduced the free calcium concentration in solution in an equimolar manner. DGA toxicity and mitochondrial dysfunction occurred as similar concentrations.
  
  
  CONCLUSIONS
  DGA inhibited mitochondrial respiration, but without uncoupling oxidative phosphorylation. The more potent effect of DGA on glutamate/malate respiration and the inhibition of mitochondrial swelling was likely due to its chelation of calcium.
  
  
  CONCLUSIONS
  These results indicate that DGA produces mitochondrial dysfunction by chelating calcium to decrease the availability of substrates and of reducing equivalents to access Complex I and by inhibiting Complex II activity at higher concentrations.
authors.affiliation: a Louisiana State University Health School of Medicine-Shreveport , Shreveport , LA , USA ;|b Department of Pharmacology, Toxicology, and Neuroscience , Louisiana State University Health Sciences Center , Shreveport , LA , USA ;
authors.forename: Taylor
authors.initials: T
authors.lastname: Conrad
authors.affiliation: b Department of Pharmacology, Toxicology, and Neuroscience , Louisiana State University Health Sciences Center , Shreveport , LA , USA ;
authors.forename: Greg M
authors.initials: GM
authors.lastname: Landry
authors.affiliation: c Department of Molecular and Cellular Physiology , Louisiana State University Health Sciences Center , Shreveport , LA , USA.
authors.forename: Tak Yee
authors.initials: TY
authors.lastname: Aw
authors.affiliation: b Department of Pharmacology, Toxicology, and Neuroscience , Louisiana State University Health Sciences Center , Shreveport , LA , USA ;
authors.forename: Royce
authors.initials: R
authors.lastname: Nichols
authors.affiliation: b Department of Pharmacology, Toxicology, and Neuroscience , Louisiana State University Health Sciences Center , Shreveport , LA , USA ;
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: McMartin
mesh_terms: D058186:Acute Kidney Injury / Q000139:chemically induced / Q000473:pathology*; D000818:Animals; D002118:Calcium / Q000737:chemistry*; D002478:Cells, Cultured; D002614:Chelating Agents / Q000737:chemistry / Q000633:toxicity*; D004533:Egtazic Acid / Q000737:chemistry; D005026:Ethylene Glycols / Q000737:chemistry / Q000633:toxicity*; D018698:Glutamic Acid / Q000378:metabolism; D006016:Glycolates / Q000737:chemistry / Q000633:toxicity*; D006801:Humans; D007668:Kidney / Q000166:cytology / Q000187:drug effects / Q000473:pathology; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000187:drug effects / Q000473:pathology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008293:Malates / Q000378:metabolism; D008297:Male; D008928:Mitochondria / Q000187:drug effects*; D033681:Mitochondrial Membrane Transport Proteins / Q000187:drug effects; D000083162:Mitochondrial Permeability Transition Pore; D010085:Oxidative Phosphorylation / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar
chemical_list: D002614:Chelating Agents; D005026:Ethylene Glycols; D006016:Glycolates; D008293:Malates; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D018698:Glutamic Acid; D004533:Egtazic Acid; C013484:diethylene glycol; C030298:malic acid; D007770:L-Lactate Dehydrogenase; C571256:diglycolic acid; D002118:Calcium
keywords: Calcium chelation; diethylene glycol; diglycolic acid; mitochondrial toxicity