Increase Of Mouse Melanoma Morbidity By Imbalanced Intestinal Microbiota And Reduction By Probiotics Treatment

Antibiotics can help human effectively kill a lot of bacteria,viruses,fungi and other microorganism,which poses a great threat to human and animal life.However,the abuse of antibiotics,sometimes even leads to bad situation,causing neurotoxicity,toxicity of kidney and liver,intestinal bacteria imbalance and a series of health problem [1].And intestinal flora is closely related to human health.Studies have shown that intestinal flora imbalance can cause all kinds of harmful effect on human health.Intestinal makes up the biological barrier of human body,when it is normal,it can effectively prevent toxic and harmful substances,which can also regulate the immune system.When people use antibiotics for a long time,there will be a lack of vitamins,and intestinal flora imbalance will appear,too.At this time,the intestinal flora can not continue to complete the role of immune defense,even decrease immunity.Currently,a healthy diet and micro ecological preparation,including yogurt and synbiotics,which contains lactobacillus,bifidobacterium addicted to lactobacillus and probiotics can improve the immunity of the human body.However,how to provide a direct evidence that antibiotics can reduce immunity and probiotics improve immunity,will help to study the mechanism further.Based on this idea,this paper intends to explore the effects of antibiotics and probiotics on intestinal microflora,and the tumor incidence reflects their effects on immunity.Objective: Our aim of the experiments of this project is to establish a melanoma model of mouse,and we use the incidence of tumor as a objective indicator to show how the disorder of intestinal flora promote the tumorigenesis,and provide direct evidence that probiotics can make intestinal flora healthy to inhibit tumor through the repair of the intestinal flora.Methods: Levofloxacin,which belongs to the category of quinolone antibiotics,has strong antibacterial effect.This experiment adopts the C57BL/6 mice by intragastric administration of oral antibiotics,to build a antibiotic intestinal dysbacteria model.In order to establish the tumor model in mice by subcutaneous injection of melanoma cells,to determine the minimum number of solid tumors,the tumor cell number can be tumor threshold.When the number of transplanted tumor cells is lower than the threshold value,the solid tumor appears,which means a low level of immunity.We extracted total DNA of fecal bacteria of stool of mice from the control group,antibiotic treatment group,treatment of probiotics recovery after use of antibiotic group,and bacterial 16 S rRNA was amplified by PCR.We used denaturing gradient gel electrophoresis(DGGE and DGGE)to analyse the intestinal flora changes.In order to determine the bacterial species changes,bacteria 16 S rRNA fragments were cloned and sequenced,then the database was used to determine these changes in the species of bacteria.Mice colon tissues were dissected and preparation of paraffin sections were observed to check whether the mice’s intestinal has changed in the internal morphology and expression of antibody of mice intestinal mucosal surface differences,so as to suggest a mechanism for the antibiotic and probiotic effect on immune function in mice.Results:After taking the injection of tumor cells,the tumor grow rate were 83.33% and 33.33% in antibiotics group and recovery group,respectively.Mice of probiotics group did not develop tumors.The changes of intestinal morphology in each group were not detected.The mice of the colonic mucosal surface of NF kappa B,and the expression of IL-6 and STAT-3 have different degrees of differences.NF kappa B in the probiotic group mice expressed lower than the other three groups;IL-1 beta in antibiotics group of mice was higher than that in the probiotic group,and in the probiotic group mice expressed lower than the other three groups.The expression of IL-6 and STAT-3 in antibiotic treated mice than control group.(p<0.05)Conclusion: Oral antibiotics can lead to decreased immunity in mice,mice immune ability can be gradually restored,and probiotic has good repairing effect of immunity.