Detoxication Of Oral Exposure To Benzo(a)pyrene By Lactobacillus Plantarum CICC 23121 In Mice

Benzo(a)pyrene(Bap)is a carcinogenic substance that is found in various substances used in daily life.In vitro studies have shown that Bap can be adsorbed and removed by Lactobacillus.To investigate the detoxification effect of Lactobacillus strains in vivo,Lactobacillus plantarum CICC 23121(Lp121),which adsorbs Bap effectively,was used as a material to establish a model of oral exposure to Bap-Lp121 in mice for 28 days.Rescue of BaP by Lp121 strains was monitored by assessing changes in body weight and intake of feed or water,measuring changes in fecal content of Bap and short chain fatty acid(SCFA)(using High performance liquid chromatography),detecting oxidative stress in the liver,evaluating the effect of Bap on DNA in hemocytes(using Single cell gel electrophoresis),and analyzing the gene expression of CYP1A1 in the liver(using qRT-PCR and western blotting).16S rDNA amplicon sequencing and metagenomics were performed to analyze the effect of Bap on intestinal microflora balance and the KEGG pathway.Histological sections of ileum and colon were examined for pathological changes.The aim was to determine if Lpl21 could mitigate the effects of Bap toxicity in vivo.The following results were obtained:1.Oral exposure to Lp121 or Bap had no effect on the body weight or diet intake of mice.2.Oral exposure to Lpl21 accelerated the speed and amount of Bap excreted in feces.The reduction of intestinal propionic acid,and DNA damage of hemocytes caused by Bap was relieved by strain Lp121.In addition,Lp121 could enhance the antioxidant capacity of the liver.However,the expression of mRNA and protein of CYP1A1 gene were not consistent.3.16S rDNA amplicon sequencing indicated that oral exposure to Bap increased the relative abundance of Proteobacteria,and reduced butyric acid-and acetic acid-producing bacteria.Additionally,the chaol index and beta-diversity were reduced,indicating the reduced production of new species of intestinal microflora in mice.The negative effect could be attenuated by oral exposure to Lp121,which increased the alpha-and beta-diversities.Although species richness in each group fluctuated during the trial,no biomarkers were identified.4.Next generation sequencing(metagenomics)data showed that the intestinal microflora species and genes in the same cluster were similar to the control after oral exposure to Lp 121.This led to an unbalance of the CYP450 metabolic pathway,oxidative stress pathway,SCFA metabolic pathway,apoptosis,insulin,and glucagon metabolic pathways,and other related pathways following oral exposure to Bap.Lp121 tended to normalize these metabolic pathways.5.Oral exposure to Bap caused a significant increase in goblet cells in the ileum,intestinal hemorrhage,lymphocyte infiltration in ileum mucosa,desquamation of colonic mucosa along with lymphocytes,and local necrosis of colonic myometrium.However,Lp121 in the intestinal tract had a protective effect on the formation of intestinal mucosal barrier by producing goblet cells.