The Effect Of Gut Microbiota And Lead-intolerant Microbes Against Lead Toxicity In Mice

Foodborne lead(Pb)pollution has become a serious public health problem.It causes irreversible damages to blood,liver,kidney and other organs.Both the whole digestive tract,especially the gut,a main absorption and excretion site of Pb and its inhibitors,gut microbiota were inevitably exposed to Pb and influenced by it.At the same time,gut microbiota might also have an influence on the absorption,distribution,excretion and toxicity of Pb.Therefore,this study aimed to investigate the interaction between gut microbiota and Pb toxicity.Firstly,antibiotic-treated gut microbiota depleted mice were used to investigate the effect of its existence on Pb contents in different tissues and toxicity.The results showed that Pb levels were significantly increased in liver,kidney,brain and blood of antibiotic-treated mice when compared to normal mice.The Pb contents in feces had a completely opposite result.All of these results indicated the role of gut microbiota in reduce the absorption and accumulation of Pb.In order to investigate the influence of acute and chronic Pb exposure on the gut microbiota composition,high-throughput sequencing technology of 16 S rRNA was adopted.Results showed that both acute and chronic Pb exposure led to a significant reduction of intestinal microbial diversity.The relative abundance of facultative anaerobes such as Enterobacter,Pseudomonas was increased and the relative abundance of Adlercreutzia,Ruminococcus,S24-7__unclassified and Allobaculum was declined after acute Pb exposure.After chronic Pb exposure,the ratio of intestinal Firmicutes and Bacteroidetes in Pb-exposed mice increased significantly,and the number of uncultured and unclassified members of Ruminococcaceae and Lachnospiraceae,Rikenellaceae_RC9_gut_group,Lachnoclostridium,Oscillibacter,and Akkermansia decreased significantly.And there were no significant up-regulated genera.Besides,the damages of acute and chronic Pb exposure to gut were also investigated.The results demonstrated that Pb exposure caused an oxidative stress in the intestinal as shown by the increasing malondialdehyde(MDA)and decreasing superoxide dismutase(SOD)and glutathione(GSH).As for total contents of short chain fatty acids(SCFA),both acute and chronic Pb exposure mice also had a decreased content.Moreover,acute Pb exposure mice also had an increased gut permeability indicated by more detectable dextran-4000-fluorescein isothiocyanate(DX-4000-FITC)in serum.Chronic Pb exposure disturbed the expression of intestinal tight junction protein genes concerning ZO-1,ZO-2,Occludin and Claudin.These results suggested that both acute and chronic Pb exposure impaired the balance of gut microbiota composition as well as gut function.Further investigation aimed to determine whether supplement of specific Pb intolerant species in the gut could restore the disorder of gut micro-environment,Akkermansia.muciniphila ATCC BAA-835,Faecalibacterium prausnitzii A2-165 and Oscillibacter ruminantium GH1 and their mixtures were selected.Their effects on Pb contents and toxicity in mice model were evaluated.Lactobacillus plantarum CCFM8661,which has been demonstrated to be effective in alleviating Pb toxicity,was used as a positive strain.The intervention of L.plantarum CCFM8661,F.prausnitzii A2-165,O.ruminantium GH1 and mixtures significantly decreased Pb level in liver,kidney and blood,promoted the gene expression of tight junction proteins and the production of short chain fatty acid by colonic microbiota,and showed protective effect on liver and kidney toxicity.However,A.muciniphila failed to reduc Pb toxicity,even though it made an influence on the disorder of gut microbiota caused by Pb exposure.In-vitro experiment was conducted to compare their tolerance to Pb as well as their binding ability.The results showed that all tested strains had a good binding ability to Pb while A.muciniphila ATCC BAA-835,F.prausnitzii A2-165 and O.ruminantium GH1 were sensitive to Pb,which was similar to the previous results.In conclusion,the interaction between Pb and intestinal gut microbiota limited the absorption and accumulation of Pb in different tissues.And Pb exposure did harm to intestine tissue and gut microbiotia.What's more,microorganisms such as F.prausnitzii A2-165 and O.ruminantium GH1 that could reduce Pb accumulation and alleviate Pb toxicity were found,indicating the potentials of intervening gut microbiota through diet to reduce heavy metal toxicity.