Protective mechanisms of Mg-gluconate against oxidative endothelial cytotoxicity.
The potential anti-radical properties and cytoprotective effects of Mg-gluconate were studied. When microsomal membranes were peroxidized by a *O2- driven, Fe-catalyzed oxy-radical system (R* = dihydroxyfumarate + Fe2+), Mg-gluconate inhibited lipid peroxidation (TBARS formation) in a concentration-dependent manner with IC50 being 2.3 mM. For the entire range of .25-2 mM, MgSO4 or MgCl2 were < or = 20% effective compared to Mg-gluconate. When cultured bovine aortic endothelial cells were incubated with the R* for 50 min. at 37 degrees C, 56% loss of total glutathione occurred. Pre-treatment (10 min.) of the cells with 0.25-4 mM Mg-gluconate before R* exposure significantly (p<0.05) prevented the GSH loss to varying degrees; the EC50 was 1.1 mM. In separate experiments, with 30 min. of free radical incubation of endothelial monolayers (approximately 65% confluent), cell survival/proliferation determined by the tetrazolium salt MTT assay, decreased to 38% of control at 24 hrs; Mg-gluconate concentration-dependently attenuated the lost cell survival with EC50 of approximately 1.3 mM. For comparison, the effects provided by MgSO4 or MgCl2 were significantly lower and were < or = 1/3 as potent as that produced by Mg-gluconate. In a Fenton-reaction system consisting of Fe(II)+ H2O2, Mg-gluconate but not other Mg-salts, significantly inhibited the formation of OH radicals as determined by the ESR DMPO-OH signal intensity. Mg-gluconate also dose-dependently inhibited the 'Fe-catalyzed' deoxyribose degradation suggesting that Mg-gluconate could displace Fe from 'catalytic sites' of oxidative damage. These data suggest that Mg-gluconate may serve as a more advantageous Mg-salt for clinical use due to its additional anti-radical and cytoprotective activities.
Mak
I T
IT
Department of Physiology and Experimental Medicine, The George Washington University Medical Center, Washington, DC 20037, USA. itmak@gwu.edu
Komarov
A M
AM
Kramer
J H
JH
Weglicki
W B
WB
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D001011:Aorta / Q000187:drug effects; D002417:Cattle; D002455:Cell Division / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003497:Cyclic N-Oxides / Q000494:pharmacology; D003855:Deoxyribose / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects*; D005609:Free Radicals; D005942:Gluconates / Q000494:pharmacology*; D005978:Glutathione / Q000494:pharmacology; D020128:Inhibitory Concentration 50; D015636:Magnesium Chloride / Q000378:metabolism; D008278:Magnesium Sulfate / Q000378:metabolism; D008297:Male; D018384:Oxidative Stress; D010100:Oxygen / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D019097:Spin Trapping; D013696:Temperature; D017392:Thiobarbituric Acid Reactive Substances; D013997:Time Factors
D000975:Antioxidants; D003497:Cyclic N-Oxides; D005609:Free Radicals; D005942:Gluconates; D017392:Thiobarbituric Acid Reactive Substances; D015636:Magnesium Chloride; D003855:Deoxyribose; C069977:2,2-dimethyl-5-hydroxy-1-pyrrolidinyloxy; D008278:Magnesium Sulfate; D005978:Glutathione; C030691:gluconic acid; D010100:Oxygen