Protective Effect And Mechanism Of Probiotics On Toxic Substance-induced Injury In Mice

Toxic substance exposure,especially the intake of environmental pollutants or toxic foods,aggravates the burden of human tissues and organs,resulting in a series of diseases and seriously threatening human health.Phthalate esters(PAEs)are generally recognized as environmental endocrine disruptors or reproductive toxins.In the environment,diethylhexyphthalate(DEHP)is the most common component of PAEs pollution.DEHP,with the lowest tolerable daily intake value of 20 ?g/kg/d in common plasticizer,is the most toxic of PAEs and induces testicular injury.In addition,alcohol is a recognized carcinogenic agent,directly resulting in liver injury.Alcoholic liver disease(ALD)is a leading cause of severe morbidity and mortality,and drinking has become a global public health and social problem.Environmental pollutants and alcohol exposure directly or indirectly interact with the gut microbiota and alter the composition of gut microbiota,leading to gut dysbiosis.Increasing evidence has confirmed that gut dysbiosis plays a key role in the development of various diseases.Probiotics have the characteristics of anti-oxidation,anti-inflammatory,anti-tumor,regulation of gut microbiota,which effectively prevent and treat many diseases.However,the protective mechanism is still not clear.In the present study,taking DEHP and alcohol exposed mice as examples,probiotics were used to prevent DEHP-induced testicular injury and ALD,and explore the relationship between gut microbiota and diseases and the protective mechanism of probiotics.The main contents and results in this paper are listed as follows:1.DEHP,acting as an environmental endocrine disruptor,disturbed reproductive health,especially testicular injury in mammals,and there is no effective treatment at present.The effect of Lactobacillus planturum TW1-1(LTW1-1)on DEHP-induced testicular injury in adult male mice was studied in this work.Results showed that LTW1-1 pretreatment significantly increased testicular weight and the ratio of testis to body weight,elevated the serum testosterone concentration,enhanced the semen quality,and attenuated gonad development defects in DEHP-exposed mice.LTW1-1 effectively alleviated DEHP-induced oxidative stress by reducing the concentration of malondialdehyde(MDA)and lipid peroxidation,and increasing the level of glutathione(GSH)and the activity of superoxide dismutase(SOD)and catalase(CAT)in the serum,testis and colon.LTW1-1 also obviously inhibited inflammation through decreasing the concentration of inflammatory factors such as tumor necrosis factor-?(TNF-?),interleukin(IL)-6,IL-1? in the serum and the gene expressions of these inflammatory factors in testis and colon in DEHP-exposed mice.Furthermore,LTW1-1 significantly reduced DEHP-induced intestinal hyper-permeability and serum lipopolysaccharide levels,and alleviated metabolic endotoxemia.Gut microbiota diversity analysis revealed that LTW1-1 regulated DEHP-disrupted gut microbiota in mice to normal state.At phylum level,LTW1-1 reversed DEHP-induced Bacteroidetes increase and Firmicutes decrease,and restored the relative abundance of Deferribacteres in DEHP-exposed mice.At genus level,LTW1-1 decreased the relative abundance of Prevotella,and increased Lactobacillus,Oscillospira,Paraprevotella,Coprococcus,Ruminococcus and Mucispirillum in DEHP-exposed mice.In addition,correlation analysis showed that the ratio of Firmicutes to Bacteroidetes(Firm/Bac ratio)was negatively correlated with testicular damage and inflammation.Key bacteria in the gut microbiota,Prevotella and unclassified Bacteroides were obviously and positively correlated with testicular injury,and S24?7,Lactobacillus,Ruminococcus,Paraprevotella,Mucispirillum,Oscillospira,Coprococcus and unclassified Lachnospiraceae were obviously and negatively correlated with it.These findings suggest that gut micorbiota plays an important role in DEHP-induced testicular injury in mice,and LTW1-1 could prevent DEHP-induced testicular damage via modulating gut microbiota.This study provides a new idea for the prevention and treatment of reproductive diseases induced by environmental pollutants.2.In the present study,a natural probiotic Bifidobacterium breve ATCC15700(ATCC15700)was used to evaluate the protective effects on the liver of long-term heavy alcohol exposed mice.In vitro and in vivo,results showed that ATCC15700 had the ability to resist alcohol and acid,and could colonize in the intestinal racts of mice.Although ATCC15700 did not participate in the metabolism of alcohol,it reduced the content of acetaldehyde in serum by increasing the expression of aldehyde dehydrogenase in the liver in alcohol-exposed mice.ATCC15700 significantly reduced activities of serum alanine aminotransferase and aspartate aminotransferase and liver accumulation of triglyceride,and decreased the expression of TNF-?,IL-6,IL-1?,and IL-17 in both serum and liver in alcohol-exposed mice.Additionally,ATCC15700 markedly inhibited liver injury and inflammation via regulating the ratio of Treg cells to Th17 cells in spleen and improving immunity.ATCC15700 also effectively alleviated alcohol-induced oxidative stress by reducing the concentration of MDA and increasing the level of GSH and the activities of SOD and CAT in the liver.The histopathological study of liver sections confirmed that ATCC15700 ameliorated alcoholic fatty liver and hepatocellular carcinoma.Furthermore,ATCC15700 promoted intestinal barrier function by stimulating the expressions of tight junction proteins,thereby decreasing intestinal permeability and endotoxemia in alcohol-exposed mice.Moreover,analysis of gut microbiota showed that ATCC15700 significantly increased the relative abundance of Bacteroidetes and decreased Firmicutes and Deferribacteres in acohol-exposed mice,normalized the structure and composition of the alcohol-disrupted gut microbiota.Correlation between gut microbiota and liver injury parameters revealed that Firm/Bac ratio was positively correlated with alcoholic liver injury.Key bacteria in the gut microbiota,including S24?7,unclassified Clostridiales,Butyricicoccus,Oscillospira,Ruminococcus,Mucispirillum and unclassified Lachnospiraceae,were predominantly associated with ALD.The data indicate that ATCC15700 protects alcohol-exposed mice against liver injury via modulating gut micobiota.Hence,gut microbiota has been identified as a key player in the development of ALD.Targeting gut microbiota with probiotics intervention will be an effective approach to prevent and treat ALD.