Effects Of Antioxidants On Immune Functions Of Animals And The Molecular Mechanisms Underlying It

Objective: The experiments are to study the effects of micro-derived antioxidantand N-acetylcysteine on growth performance, antioxidant ability and immunefunctions of animals, and also to investigate the molecular mechanisms thatantioxidants regulate antioxidant ability and immune functions of animals underoxidative stress. By this way, we would provide a theoretical evidence to establishnew methods of enhancing immune functions based on free radical theory.Method: Experiment1: Sixty Kunming female mice with body weight between18-22g were randomly divided into4groups,15mice of each group. The controlgroup was fed basal diet, and the experimental groups were fed microbe-derivedantioxidant with the dose of0.5g/kg bw （L-MA）,1.0g/kg bw （M-MA） and1.5g/kgbw （H-MA） on the basis of basal diet for once a day respectively. The experimentperiod was30days. At the end of the experiment, samples were collected fordetermining.Experiment2: Eighty-one21-day-old weaned piglets were randomly divided into3groups, with3replicates of9piglets each replicate. The control group was fed basaldiet and experimental group A and B were respectively fed basal diet supplementedwith5000mg/kg microbe-derived antioxidant and500mg/kg N-acetylcysteine. At theend of the experiment, samples were collected for determining.Experiment3: One hundred new-born piglets were used for two stageexperiments. On the first stage,5litters new-born piglets with10piglets each litter were fed basal diet from7-day-old.On21-day-old,10piglets which selected randomlyfrom each litter with2piglets each litter were weaned and fed basal diet （weaninggroup）, and the other piglets were breast-fed until25-day-old （nursing group）.On25-day-old,10piglets were selected from weaning group and nursing group with1piglet each litter for samples collecting.One the second stage, the same5littersnew-born piglets were fed basal diet supplemented with500mg/kg N-acetylcysteine7-day-old.On21-day-old, all the piglets were weaned and fed basal diet supplementedwith NAC. On25-day-old,5piglets were selected with1piglet each litter for samplescollecting.Result: Experiment1: The result showed that1.0g/kg bw of microbe-derivedantioxidant increased the enzyme activity of GSH-Px （P<0.01） and T-SOD （P<0.05）in serum of mice, and reduced the content of MDA （P>0.05）. While1.5g/kg bw ofmicrobe-derived antioxidant increased the content of IgA （P<0.01） and the level ofIL-2（P<0.01）, and increased lymphocyte proliferation by ConA （P<0.01） and thelevel of IL-6（P<0.05）.Experiment2: Compared to control group, ADG of experimental group A and Bincreased by1.92%and14.95%（P>0.05）, and F/G reduced by14.89%（P<0.05） and22.34%（P<0.05）. The enzyme activity of GSH-Px of experimental group A and Bincreased by6.80%（P>0.05） and26.97%（P<0.05） and the content of MDA reducedby18.35%（P<0.05） and16.51%（P<0.05）.At the same time, the content of NOreduced by15.24%（P>0.05） and19.48（P>0.05） and the content of H₂O₂reduced by5.56%（P>0.05） and30.34%（P<0.05）. The content of IgM increased by39.21%（P<0.01） and9.03%（P>0.05）, IL-2by19.92%（P <0.1） and18.22%（P <0.1）, andIL-6reduced by23.56%（P<0.05） and7.85%（P>0.05）.Experiment3: Compared to control group, the enzyme activity of GSH-Px andSOD in weaning group decreased by8.74%（P>0.05） and11.35%（P<0.05）.Thecontent of MDA increased by34.58%（P<0.05）, NO and H₂O₂by72.42%（P<0.01） and67.14%（P<0.01）. At the same time, the content of serum IgM in NAC groupdecreased by18.42%（P>0.05）, and the content of serum IL-6, IL-1β and82-αrespectively increased by39.39（P<0.05）,4.87%（P>0.05） and759.59%（P<0.01）.Compared to weaning group, the enzyme activity of GSH-Px and SOD in NAC groupincreased by14.44%（P<0.05） and28.30%（P<0.01）. The content of MDA decreasedby37.15%（P<0.01）, NO and H₂O₂by8.86%（P>0.05） and18.90%（P<0.05）.Thecontent of serum IgM in NAC group increased by33.31%（P<0.05）, and the contentof serum IL-6, IL-1β and82-α respectivel decreased by5.56%（P>0.05）,4.88%（P>0.05） and5.99%（P>0.05）.In addition, compared to control group, relativeexpression levels of IL-2, IL-6, TNF-α and I-κBα mRNA of spleen in weaning groupwere respectively0.54,2.06,3.26and1.05times, and NAC group were4.55,0.82,2.89and2.88times. There was a significant difference of IL-2, IL-6, I-κBα m62Aexpression between weaning group and NAC group （P<0.05）.Conclusion: The oxidative stress induced by weaning can lead to a large numberof free radicals and inflammatory cytokines release, but micro-derived antioxidant andNAC all can scavenge free radicals and decrease the release of inflammatorycytokines, thus to enhance antioxidant ability and immune functions. The regulationfunction of NAC to immune system may have a closely relation to NF-κB signal path.