The Effects Of Chronic Arsenic Exposure And Taurine On Intestinal Microbiota Of Mice

Background:Arsenic is a common toxic metalloid in the nature,which distribution in rock,soil,water and air.Chronic arsenic poisoning can cause multiple organ system diseases,and also lead to bladder cancer,liver cancer,kidney cancer,lung cancer and other diseases.There are a lot of bacteria to colonize in the human gut,which involve in many human normal physiological activities and maintaining the internal and external homeostasis balance,and intestinal microbiota is easy to be affected by toxic substances,food,bacteria,viruses,antibiotics,and external environment.Intestinal microbiota involves in redox reaction and metabolism of harmful substances to reduce the damages.The current studies of arsenic metabolism in the gastrointestinal tract are not entirely clear.High-throughput sequencing technology is a method that reflect the full community structure information and an overview of taxonomic composition and relative abundance,which only need a target gene or genomes to be sequenced.High-throughput sequencing technologies is applied to determination of gut microbiome taxonomy.Some anaerobic bacteria cannot be isolated by the traditional bacterial isolation and identification method,high-throughput sequencing technologies can overcome this problem.Ars1 operon is indispensable in the arsenic oxidation reaction process.The two different Acr3 anti-porters encoded by acr3 genes in two disparately located ars operons.Therefore,we speculate that acr3-1 and acr3-2 genes may be related to arsenic resistance in intestinal microbiota.Taurine is a beta amino acids with simple structure,some researches suggest that taurine as a precursor involved in metabolic activity,antioxidant effect,xenobiotic conjugation,etc.Using the anti-oxidation character of taurine to explore if it can affect arsenic oxidation damages.Some researches show that taurine increases the content of short chain fatty acids,reduces the content of harmful intestinal bacteria and concentration of lipopolysaccharide.Consequently,we assume that taurine may be able to relieve the negative impact of the arsenic.Objective:To explore the effects of chronic arsenic exposure on intestinal microbiota of mice and the influence of taurine on intestinal microbiota.Methods:1.20 adult male kunming mice,18-22 g,were randomly divided into four groups,5 for each group.The mice in the control group drank water only,the arsenic exposed group received water with arsenic trioxide(4mg/L),the taurine treated group water was given a gavage of taurine(150mg/kg body weigh)two times a week,the mice in arsenic with taurine group drank water with arsenic trioxide and given a gavage of taurine two times a week.2.After four months,stool samples were collected,then extracted total bacteria genomic DNA.The purity and the integrity of DNA were checked.3.PCR was used to amplify 16 s rDNA V4 region genome.4.High-throughput sequencing was used to analysis taxonomy and abundance of intestinal microbiota.5.Real-time quantification PCR was used to detect the relative copy number of acr3.Results:1.The arsenic group,the arsenic with taurine group,and the taurine group had no significant differences compared with the control group in community diversity and richness of intestinal microorganism.Percentage of Bacteroidetes increased in arsenic group,taurine group,and arsenic with taurine group,while taurine group increased the most.Among three treated groups,the percentages of Firmicutes were decreased,while taurine treated group was reduced the most.The percentages of Proteobacteria were decreased in all treated groups,and the arsenic with taurine group decreased the most,this might be attributed to combined effects of both arsenic and taurine.The percentage of Lachnospiraceae was decreased with arsenic exposure.In arsenic exposed group,the percentage of Staphylococcus,Dorea,Saccharopolyspora,Granulicatella,Turicibacter,and Treponema significantly decreased,while in taurine group and arsenic with taurine group they recovered.The percentage of Oscillospira significantly decreased in taurine group and arsenic with taurine group.The percentage of Desulfovibrio significantly decreased in taurine group.The percentage of Flavobacterium significantly increased in arsenic exposed group,and restored in arsenic with taurine group.The functional diversity of the majority bacterial phyla was not significantly different.2.acr3-2 gene copy number significantly decreased in arsenic exposed group compared with control group.acr3-1 gene copy number had no significant difference among four groups.Conclusions:1.The bacterial diversity and richness did not vary significantly between control and other three treated groups.2.The percentages of Staphylococcus,Dorea,Saccharopolyspora,Granulicatella,Turicibacter,and Treponema significantly decreased in arsenic exposed group,and taurine had restored effects on them.3.Taurine reduced the percentage of intestinal pathogenic bacteria Desulfovibrio.4.Chronic arsenic exposure led to acr3-2 gene copy number decreased significantly,and taurine treatment returned acr3-2 gene copy number to normal levels.