Effects Of Vitamin C On Endotoxin-induced Oxidative Damage In Mice

Objective Using Endotoxin-induced two different oxidative damage models, to observethe effects of two different dose of vitamin C on the models, and preliminary discuss themechanism.Methods Part1: The acute hepatic injury model for the mice was administered with asingle dose of LPS (4mg/kg, i.p.), the mice were pretreated with two different doses ofVC(100mg/kg or500mg/kg, i.g.) at30min before LPS administration and sacrificed at8h and24h after LPS administration. Serum was analyzed for the activity of alanineaminotransferase (ALT) and aspertate aminotransferase (AST), livers were dissected formeasurements of oxidative glutathione (GSSG) contents, reduced glutathione (GSH)contents, malondialdehyde (MDA) contents, pathological change, and the proteinexpressions of3-NT by western blotting and calculate the ratio of GSSG/GSH. Part2:The premature birth and intrauterine fetal death models for the mice were administeredwith a single dose of LPS (300μg/kg, i.p.) on the gestation day15(GD15), the micewere pretreated with two different doses of VC(100mg/kg or500mg/kg, i.g.) at30minbefore LPS administration, a part of the mice was observed the incidence rate ofpremature birth and intrauterine fetal death, average time of delivery, and the rest ofmice were sacrificed at8h and14h after LPS administration, livers and placentas weredissected for measurements of oxidative glutathione (GSSG) contents, reducedglutathione (GSH) contents, the protein expressions of3-NT by western blotting andcalculate the ratio of GSSG/GSH, placentas also was dissected for pathological change. Results Part1: Compared with the controlled group, LPS significantly up regulatedserum ALT and AST activity, the value was10.37±3.42(U/L) vs.53.90±20.34(U/L) and62.40±46.40(U/L) vs.106.17±10.69(U/L), significantly increased MDA contents, was2.86±0.62(μmol/g Pro) vs.4.33±1.32(μmol/g Pro) and increased the ratio of liverGSSG/GSH(0.59±0.20vs.0.93±0.41), the protein expressions of3-NT was upregulated, and a aggravated liver pathological change was observed in this study.Compared with the model group, the VC(100mg/kg) improved part of the pathologicalchanges caused by LPS, showing lower serum ALT and AST activity, was37.41±9.42(U/L) and65.68±31.06(U/L), lower MDA contents, was3.18±0.57(μmol/gPro) and lower protein expressions of3-NT, increased GSSG/GSH ratio(was0.59±0.063), the pathological changes were improved as well; But the VC(500mg/kg)group did not presented a significantly change compared with model group. Part2:Compared with the control group, LPS significantly up regulated the rate of prematurebirth and intrauterine fetal death (0%vs.100%;0%vs.100%), significantly shortedthe average time of delivery (72h vs.11h) and increased the GSSG/GSH ratio of liverand placenta (0.78±0.22vs.2.61±1.73;0.36±0.19vs.2.61±1.73), the proteinexpressions of3-NT was also upregulated, and a aggravated liver pathological changewas observed in this study. Compared with the model group, VC ameliorated part of thechanges was caused by LPS; but the effect of VC(500mg/kg) was better thanVC(100mg/kg). Showing a lower rate of preterm birth (45%vs.56%), a lower ratio ofGSSG/GSH in liver (1.35±0.62vs.1.62±0.90) and placenta (1.20±0.81vs.2.44±1.64),a shorter protein expressions of3-NT and a longer average time of delivery(53h vs.40h), the pathological changes was improved as well. In the VC(500mg/kg) group, theradio of GSSG/GSH in live fetal placenta was0.55±0.30, in dead fetal placenta was1.41±0.49, and the protein expression of3-NT in live fetal placenta was lower than deadfetal placental. Comparing of two models, In the model2, the GSSG/GSH ratio oflivers and placentas were both higher than the ratio of model1, which presents that theeffects of higher VC(500mg/kg) were better than the lower one. Conclusion In part1, VC(100mg/kg) can protect against LPS-induced liver damagevia counteracting LPS-induced oxidative damage, and VC(500mg/kg) is no effect onLPS-induced oxidative stress and liver damage. In part2，VC can protect against LPS-induced premature birth and intrauterine fetal death via counteracting LPS-inducedoxidative damage, the effect of VC(500mg/kg) is better than VC(100mg/kg). Therefore,oxidative stress is involved in the models of acute liver injury and premature birth andintrauterine fetal death induced by LPS, the effects of different doses of VC weredifferent, its role of antioxidant and protection were depend on the dosage and theoxidative stress level of body. In a word, VC should be used rationally.