Endotoxin increases ascorbate recycling and concentration in mouse liver.
Sublethal exposure to Escherichia coli endotoxin [lipopolysaccharide (LPS)] attenuates the lethal effects of subsequent insults associated with oxidative stress, such as higher LPS dose, septic peritonitis, and ischemia. Because administration of the antioxidant ascorbate protects against these same insults and injection of dehydroascorbic acid (DHAA) protects against ischemia, the hypothesis that sublethal LPS increases endogenous ascorbate concentration and recycling (i.e., synthesis from DHAA) was tested. Injection of LPS [5 x 10(6) endotoxin units/kg body weight, i.p.] in mice caused a temporary inhibition of food intake, which was significant by 20 h and recovered within 3 d. LPS increased ascorbate concentration in adrenal gland, heart, kidney, and liver. LPS had similar effects in wild-type and Slc23a2+/- mice despite the latter's deficiency in the ascorbate transporter SVCT2. In liver, the ascorbate response to LPS was not accompanied by change in glutathione concentration. LPS decreased gulonolactone oxidase activity, which is rate-limiting for de novo synthesis of ascorbate from glucose, but increased the rate of DHAA reduction to ascorbate. In conclusion, sublethal endotoxin increases ascorbate recycling in liver and ascorbate concentration in liver, adrenal gland, heart, and kidney. The enhanced rate of ascorbate production from DHAA may protect these organs against the reactive oxygen species produced by subsequent, potentially lethal challenges.
Kuo
Shiu-Ming
SM
Department of Exercise and Nutrition Sciences, University at Buffalo, Buffalo, NY, USA.
Tan
Chee-Ho
CH
Dragan
Magdalena
M
Wilson
John X
JX
D000311:Adrenal Glands / Q000378:metabolism; D000818:Animals; D001205:Ascorbic Acid / Q000097:blood / Q000493:pharmacokinetics*; D001692:Biological Transport / Q000187:drug effects; D005978:Glutathione / Q000378:metabolism; D007668:Kidney / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008099:Liver / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009206:Myocardium / Q000378:metabolism; D029363:Organic Anion Transporters, Sodium-Dependent / Q000235:genetics / Q000378:metabolism; D060347:Sodium-Coupled Vitamin C Transporters; D013154:Spleen / Q000378:metabolism; D027981:Symporters / Q000235:genetics / Q000378:metabolism; D014815:Vitamins / Q000097:blood / Q000493:pharmacokinetics*
D008070:Lipopolysaccharides; D029363:Organic Anion Transporters, Sodium-Dependent; C555165:Slc23a2 protein, mouse; D060347:Sodium-Coupled Vitamin C Transporters; D027981:Symporters; D014815:Vitamins; D005978:Glutathione; D001205:Ascorbic Acid